CA1213665A - Shock hazard protection system - Google Patents
Shock hazard protection systemInfo
- Publication number
- CA1213665A CA1213665A CA000459278A CA459278A CA1213665A CA 1213665 A CA1213665 A CA 1213665A CA 000459278 A CA000459278 A CA 000459278A CA 459278 A CA459278 A CA 459278A CA 1213665 A CA1213665 A CA 1213665A
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- Canada
- Prior art keywords
- electrical
- source
- shock hazard
- load
- controlled rectifier
- Prior art date
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Abstract
SHOCK HAZARD PROTECTION SYSTEM
Abstract of the Disclosure:
The present invention teaches a new and novel system for protecting people and property against electrical shock. The invention includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems.
By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").
Abstract of the Disclosure:
The present invention teaches a new and novel system for protecting people and property against electrical shock. The invention includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems.
By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").
Description
~ 3 6 t~5 T-1375-6 SHOCK HAZARD PROTECTION SYSTEM
. This invention relates generally to electrlcal hazard preventlon, and more speclflcally to a shock hazard prevention sy~tem for di~connecting an electrical load from an electrical soul-ce when a shock hazard condltlon exi~ts withln the load.
Devices for protectlng human life and property agalnst electrical shock and damage re~ultlng from a shock hazard condltion within an electrlcal load are known. For example, the model No. 6199 ground fault circult interruptor (GFCI~
mar~eted by the assignee of the present invention is capable of senslng and responding to the lnadvertent grounding of the neutral conductor of an A-C electrical distrlbution system. It is noted, however, that in certain application~ the utilization of ~uch a GFCI is not practical.
In partlcular, the GFCI is a relatlvely expensive and complex device which requires the utilization of several transformers. In addition, the GFCI i5 often hardwired ln a wall outlet or receptacle and is neither portable nor readily disconnected. Thus, unless each outlet in which an electrical device such as, for example, an appliance is to be utilized 19 protected by a GFCI, the user of the appllance ïs sub~ect to possible injury if a shock hazard condition ~hould exist in con~unction with a non-protected outlet.
In addition, ln certain environment~ the utllization of a conventional GFCI would not afford any ~hock hazard protection to the user of an appliance. More specifically, a ~213665 conventional GFCI devlce of the type known to appllcants wlll not be effectlve or work ~f the user of an electrical appliance drops the appllance in a plastic insulated bathtub.
Another potential drawback, exl~t3 regarding the use of a GFCI for certaln types of portable electrical appliances such as, for example, a hair dryer. Although the owner of a halr dryer may have hls or her residence outlets adequately protected by GFCI devices, lt is possible that other places, such as hotels, the residence of relatives, friends, etc., where lt ls deslred to use the hair dryer may not be protected by such devices.
Accordingly, it is clear that what is needed is a shock hazard protector which i9 as~ociated with the appllance to be protected itself rather than with the elec~rical outlet ln which the appliance is plugged and energized. It is belleved that prior to the present invention, this need has gone unfulfilled.
A need exists for a shocX hazard protector which possesses attributes including having a minimum number of components, reliability, cost and portability.
It ls accordlngly a general object of thls invention to overcome the aforementioned limitations and drawbacks associated with the known devices and to fulfill the needs mentioned by provldin5 a hazard protection system having all of the desirable attributes noted above.
12~366S
It ls a particular object of the present lnvention to provide a shock hazard protector capable of disconnect~ng an electrical source from an electrlcal load in re~ponse to the detection of a shock hazard condltion wlthin the electrical load.
Another object of the present invention i9 to provide a shock hazard protector capable of detecting and responding to a -water-related shock hazard condition within an electrical appliance.
A ~urther object of the present invention is to provide a shock hazard protectlon system, as above, incorporating immer~ion detection circuitry.
A still further object of this invention is to provide a shock hazard protection system, as above, whereln a feature is provided for detecting a po~sible break or discontinuity ln a sensing or guard wire.
Yet another object of this invention is to provide a system, as above, wherein a solenoid-type electromechanical mechanism acts as a circuit breaking or interrupting means.
A further object is to provide such a sy~tem wherein a relay and associated clrcuitry and mechanical means enable the desired re~ult.
Yet a further ob~ect of this invention is to provide a detection system whlch detects or senses the presence of a conductive medium, and which causes an event in response thereto.
. - 3 -~Z13i~5 Another ob~ect of this invention ls to provlde a detectlon system whlch detects or sense~ the absence of the presence of ~ conductive medium, and whlch causes an event ln response thereto.
Other ob~ects will be apparent from the following deta~led de~cription and practice of the ~nvention.
The foregoing and other ob~ects and advantage~ which will be apparent in the follow~ng detailed descriptlon of the preferred embodlment, or in the practlce of the lnvention, are achleved by the invention disclosed hereln, which generally may be characterlzed as a hazard protector. The hazard protector includes detecting means associated with a load for detectlng a hazard conditlon within the load, an lnterrupting means associated with a source to which the load i5 operatively connected, and conducting means connected between the detecting mean3 and the interruptlng means. In response to the detection of a hazard condition within the load by the detecting means, the interruptlng means operatively disconnects the source from the load.
Serving to illustrate exemplary embodiments of the inventlon are the drawlngs, of which:
Fig. 1 i~ a perspectlve-type v~ew of a hair dryer and its assoclated cord set incorporatlng the system accordlng to the present invention;
~2~36~
Flg. 2 i~ a block dlagram of the shock hazard protector, in accordance with the present lnvention;
Fig. 3 is a ~chematic diagram of one embodlment of the shock hazard protector, in accordance with the present invention;
Fig. 4 is a schemat~c diagram of a second embodlment of the shock hazard protector, in accordance with the present invention;
Fig. 5 ls an enlarged partial sectlonal elevatlonal view taken through a cord set plug of a relay embodiment of the 10 present invention;
Fig. 6 is a partial fragmentary sectional plan view taken along the llne 6-6 of Fig. 5;
Fig. 7 is a schemat~c circ~it dlagram of the embodiment of the present invention as~ociated with Figs. 5 and 6;
Fig. 8 is an elevational vlew of the cord set plug illu~trated in Fig. 1 and taken along line 8-8 of that ~ame Fig. 1 depicting the assembled plug with its cover removed;
Fig. 9 is a partial sectional elevatlonal vlew taken along line 9-9 of Fig. 8;
Fig. 10 i~ a ~ectlonal view taken along llne 10-10 of Fig. 8;
Fig. 11 is a fragmentary sectional view taken along line 11-11 of Fig. 8; and Fig. 12 is an exploded-type perspect$ve view of components of the present inventlon illustrated in Fig. 8.
lZ13~65 Referrlng now in more detail to the drawlng~, F~g. 1 presented ln its form to lllustrate a halr dryer 12 and it~
associated cord set 14 a~ wholly containing and constitutlng or comprlsing the shock hazard protection system 10 of the present invention. It is applicants' intention and de~ire to emphasize -here the fact that this in~ention contemplates an electrical appliance, such as of the personal health care type (hair dryer~, etc.) which possesses all of the features and advantage~ of the invention. It is also an intention of appl~cants to provide the 10 system of the present invention in the form of an OEM product available for sale to manufacturers of such appliances.
A plug assembly 16 i9 illustrated in Flg. 1 as lncluding polarlzed blades 18 extending from housing 20. Whereas 15 commerclally avallable hair dryers, as an example of a personal health care appliance, normally include a c~rd set havlng two conductors or wire~, a third wire 22 ls lllustrated in the case of cord set 14 electrically communicatlng with a bare copper wire 24 whose path (in the example given in Fig. 1) includes proximity to and looped clrcuit near a dryer hou~ing opening through whlch an on-off switch a~sembly 26 extends, and thence upward to another loop proxlmate a dryer housing air inlet opening through which fan 28 driven by motor 30 pulls air to be heated by heatlng ccil 32 before exiting the dryer housing air outlet opening ln 1213~iS
which grill 34 i~ positioned. After leavlng the ~econd loop described as being ad~acent the alr inlet openlng, wire 22 extends to a thlrd loop ad~acent grill 34.
Slnce heater coil 32 carries and operates on current ln the "hot" or phase llne, and with the provi~lon of conductor or wire 24 wired a~ part of the neutral side of the line, the presence of a conductlve medlum such a~, bu~ not llmlted to, moisture or water between them wlll create a conductlve path ,contemplated by the invention as enabling lnterruption of current to the load 12. Thls embodiment is distinguishable from another embodiment of the present invention wherein a pair of conductor~, as opposed to a single guard or sensing conductor 24, are located at or near moisture/water hou~ing penetration points.
Configurations of one or more sen~ing or guard conductor~ other than those illu~trated herein are contemplated as coming wlthln the scope of this invention.
Referring to Fig. 2, a block dlagram of a shock hazard protector according to the present lnventlon ls illustrated. ~s shown therein, it comprises a source operatively connected to a load by first and second conductors 110 and 120, respectively, a detector 200 as~ociated with the load, a control circult 300 connected to the detector by a ~ensing or third conductor 130, and an interruptor circuit 400 as~ociated with the source and connected to the control circuit 300. In the case of an electrical A-C source, conductors 110 and 120 are tied to a phase and the neutral terminal, respectively, of the A-C source.
~Z~3~
In the normal mode of operation, that is, in the absence of a hazard condition withln the load, the control circuit 300, which changes from a flrst state to a second state in re~ponse to the detection of a hazard condltlon wlthln the load, remains ln the first state. Upon the detection by detector 200 of a predefined fault or hazard condition withln the load, the control circuit 300 changes from the first to the second state, whlch causes the interruptor circuit 400 to o~eratlvely disconnect the source from the load.
It is noted that the present lnventlon co~templates certain applications where the system sensitlvity;need not be accurately controlled, and the control circult 300 can be ellminated. In this situation the interruptor circuit 400 is connected to the detector 200 by the third conductor 130, and responds directly to the detection by detector 200 of a hazard condition within the load.
In either situation, the sensing or third conductor 130 communlcates the presense of the hazard conditlon wlthin the load to the control circuit 300 or the interruptor clrcuit 400.
Referring now to Flg. 3, a schematic dlagram of one embodiment of the invention particularly sultea for use ln con~unction with water-related shock hazard condltions wlthln an electrical appliance operatively connected to an A-C source (not shown) by electrical conductors 110, 120, respectively, ls illu~trated. As shown therein, detector 200 comprise~ a palr of ~Z136~i~
hazard or lmmerslon detection conductors 210 and 220, which are positloned in a non-contacting relationship and contalned withln the electrical load. A pair of immersion detectlon conductor~
210 and 220 are preferably located in proximity to each port of the appliance to be protected where water can enter.
~ or ease of description, lt will be assumed that the appliance to be protected only contalns one port or opening through which water may enter. For this ~ltuatlon, one end of ,one of the palr of immersion detection conductors 210 is operatively connected to the phase terminal of an A-C ~ource (not shown) via electrlcal ~conductor 110, and one end of the second of the pair of immersion detection conductors 220 is connected to the load end of the third electrlcal conductor 130. The other ends of lmmerslon detection conductors 210, 220 are unconnected and are maintained in a spaced-apart relatlonship, typically for example, not more than one inch.
Shock hazard or lmmersion detection conductors 210, 220 may comprise, for example, a pair of bare electrlcal conductors or a pair of conducting plated llnes on a printed circult board or other physical configurations that will enable a conductive path between the unconnected ends thereof.
Control clrcuit 300 comprises a solid state switching control circult and includes a first re~istor Rl connected in-line between the gate of a silicon controlled rectifier SCR
and the sour~e end of the third electrical conductor 130.
lZ13665 Resistor Rl limits the current applled to the gate of the SCR.
In addltion, control circuit 300 include~ a parallel network comprising reslstor R2, capacitor C and dlode D connected between the gate and cathode of the SCR. These components provide ~
measure of noi~e immunity and protection agalnst damage across the gate to cathode ~unction of the SCR.
Interruptor circult 400 compri~es an electromechanioal lnterrupting clrcuit and includes an energizing coll L and a flrst and second contact or switch Sl, S2 connected ln-line with the flrst and second electrical conduc}ors 110, 120, respectively. Switches Sl and S2 are responsive to th'e flow of current through energizing coil L and are closed when such current i5 not flowing. In response to the flow of such current they switch from the normall~ closed positlon to the shock hazard condltion open position. One end of energizing coil L is connected to the first electrical conductor 110 and the other end thereof is connected to the anode of the SCR. The cathode of the SCR is operatively connected to the second electrical conductor 120.
lZ~3~S
~ he exlstence of a water-related ~hock hazard condltlon within the electrical appliance is detected when both unconnected ends of the pair of lmmersion detection conductors 210, 220 are immersed in the water. More specifically, the immersion of both unconnected ends of the palr of immersion detection conductors 210, 220 causes the electr~cal A-C source to be operatively connected to the gate of the SCR via the path provided by the first electrical conductor 110, the first lmmersion detection ~onductor 210, the electrically conductlng path provlded by the water in which the unconnected ends of the first and second lmmersion detection conductors 210, 220 are immersed, the second immersion detection conductor 220, the third e~ectrical conductor 130, and resistor Rl. In response thereto, the SCR switches from the normally non-conducting ~tate to the shock hazard condition conducting state, thereby providing a path for current to flow through the energizlng coll L causing switches Sl and S2 to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting the A-C source from the electrical appliance.
To in~ure that the shock hazard protector ls operable prior to utilization of the appliance lt protects, a test clrcuit ~not shown) comprislng, for example, a resistor in series wlth a normally open switch connected between the pair of immersion detection conductors 210, 220 may be utilized. Closlng the normally open swltch causes the xesistor to be connected acros~
lZ136~S
the lmmerslon detectlon conductors and, if the shock haz~rd protect~r ~s operating, as descrlbed above, causes the A-C source ~o be operatively dlsconnected from the appliance. Preferably, the test circuit is contained within the electrical appliance.
In con~unction with said test clrcult, diode D could be replaced with a light-emitting-diode ~LED). If the LED is llluminated with the te~t switch ln the closed position it indicates that the shock hazard protector is not operating properly.
Preferablyl electrical conductors 110, 120 and 130 comprise a three wire conductor having an A-C source compatible plug at the source end, the control circuit 300 and interruptor circuit 400 are contalned in the plug, and the detector 200 i~
contained wlthin the appliance.
Thu~ in the case where the electrical appliance 15, is, for example, a hair dryer, the detector 200 would be located lnternally within the dryer and, as noted a~ove, ln proximlty to each port thereof where water can enter the dryer. It should be emphasizèd here that while water is given as the electrlcally conductive medium, this invention contemplates a response to any electrically conducting medium, such that the appliance is electrically disconnected from the A-C source in response to the presence of such a conductive medium.
Exemplary values for the circuit illustrated ln Figure 3 are as follow~: Rl-2000 ohms, R2-1000 ohms, C-0.1 microfarads, D-lN4004, SCR-2N5064.
Referring now to Figure 4, a schematic diagram of a second embodiment of the present invention particularly suited for u~e in conjunction with water-related shock hszard condltions withln an electrical appliance 1~ lllustrated. This embodlment provldes an add~tlonal feature not present in the first embodlment lllustrated ln Figure 3. In partlcular, the embodlment illustrated in Figure 3, provides shock hazard protection if any of e~ectrical conductor~ 110, 120, individually or in combination, are broken, but does not provlde shock hazard protection if electrical conductor 130 is broken. The embodlment illustrated in Flgure 4 provides an additional mea~ure of ~hock hazard protection by rendering the electrical appliance inoperative if any of electrical conductors 110, i20 and 130, individually or in combination, are broken.
Thls addltional measure of protection i8 provided by the additlon of a first diode Dl connected in series between the ~econd immersion detection conductor 220 and the thlrd electrical conductor 130, the replacement of the capacitor connected between the gate and cathode of the SCR wlth an approprlate charglng capacitor, the addition of a flrst charging circuit comprislng resist~r RN and diode DN connected between the first and third electrical conductors 110, 130, the addition of a zener diode in series with the diode connected between the gate and cathode of the SCR, the addltion of a second charging circuit comprlsing resistor Rp and diode Dp connected between the flrst electrlcal conductor 110 and the gate of the SCR, and the ellminatlon of resistor R2 connected between the gate and cathode of the SCR.
i2~ 6S
The operatlon of the clrcuit illu~trated in Figure 4 i9 as follows. Assuming that the senslng or third conductor 130, is ln tact, the appllance is not lmmersed in water and that it ls energized, during the negative half cycle of the A-C signal on electrical conductor llO a negative charging path via diode DN, reslstor RN, third conductor 13D, resistor Rl provides charge to-capacitor C, thereby charging it negatively. During the positlve half cycle diode DN blocks, however a po~itive charging path via resistor Rp and diode Dp provides charge to capacitor C, thereby charging it positively. Since the time constant of res1stsr RN
and capacitor C, is roughly 33 tlmes greater than;the time constant of resistor Rp and capacitor C, the capacitor C charges much faster in the negative sense, so that under steady state conditions a negatlve voltage exists on the gate of the SCR
thereby keeping it in a non-conducting state. In order to limit that negative voltage to a value that would not damage the ga~e to cathode junction of the SCR a three volt zener diode is added in serie~ with diode D2, also in parallel with capacitor C.
$he next condition to look at is a broken third conductor 130. Under this condition a negative charging path no longer exists for the negative voltage to be impressed on capacitor C, and, therefore during positive half cycles capicjtor C wlll dlscharge po~itively and eventually the voltage on the ~ate of the SCR will get high enough to trip the SCR, causlng it to switch to the conducting state thereby operatively dis-12136~5 connectlng the A-C ~ource from the appliance, puttlng you in a safe conditon. Exemplary values for the circuit illustratea ln Figure 4 are as follow~: Dl, D2, DN, Dp-lN 4004, RN-30,000 ohm~, Rp-l,000,000 ohms, Rl-2000 ohms, C-l microfarad,SCR-2N50~4, Z-3 volt zener diode.-Preferably, the component3 comprislng the flrstcharglng circui~ RN, DN and diode Dl are contained within the electrical appllance and are water proof, the components compri~ing the second charging circu~t Rp, Dp and the zener diode D are contained in the plug.
It is noted that with minor modifications the above described invention has many other appllcations. For example, in the situatlon where the electrical appliance comprlses a power tool, such as, a drlll, hav1ng an electrically conducting houslng the teachings of the present invention may be utilized by ellminating immer~lon detection conductor 220 and connecting the third electrical conductor 130 to the électrically conducting housing. The immersion ln water of the unconnected end of shock hazard detection conductor 210 provides an electrically conductive path between the shock hazard detectlon conductor and the electrically conducting hou~ing of the drill causing, a~
described above, the drill to be operatively disconneFted from the ~-C source.
12136~S
Referrlng now to an embodiment of the pre~ent inventlon whlch utilizes the ~pproach of a relay mechanism to accompllsh the circuit interruptlng goal of the lnvention, Flg. S
lllustrates a shock hazard protector embodlment of a plug assembly S10 ~ormed wlth a hou~ing wlth a base and cover body S halves 512 and 514, respectively, ~oined at a housing reference -line 516. A ~traln rellef 518 comprises part of cord 520 and, ln cooperative combination with the shape and contour of annulAr surfaces 522, 524, 526 and 528, serves as à mean~ for protecting the lntegrity of electrical connections dur~ng use.
Blades 530 extend outwardly from surfacé 532 of hou~ing hal~ 512 and serve the functlon of matingly and electrically engaging electrical contacts wlthln a receptacle (not shown) or electr~cal outlet in the home, for example. A fixed contact 534 is associated and integral wlth each of the blades 530, contacts 534 being fixed or stationary as opposed to movable when assembled.
A pair of movable contacts 536 are provlded and are integral with leaf springs 538 which, in turn, are anchored by means of eyelets 540 extending through openings ln an end portlon of the leaf ~pring~ 538 spaced from the movable contacts 536.
~hese eyelets further extend through openings through a printed circuit board 542 supported by ledges 544 and 546 ad~acent upstandlng wall~ 54~ and 550, as shown in Fig. 5.
12~36~ii5 A tab 552 assoclated with each leaf sprlng 538 further anchors the leaf springs to the prlnted circuit board in ~paced relatlon~hip with re~pect to the aforesaid eyelets, thereby serving an addltlonal function of preventing undesirable rotatlon of the leaf springs S38, assuring alignment and rel$ably repeated engagement between the fixed and movable contacts 534 and 536, respectively. Leaf springs 538 are conflgured to normally bias the movable contacts 536 away from the fixed contacts 534 when ln an unstressed condition, thereby normally interrupting an electrical path between these contacts. The ends of leaf springs 538 are formed with upstandlng flanges 554 to which conductors 556 are connected.
A plunger or core 558 is disposed vertically within a bobbin coil 560, as lllustrated in Fig. 5. A reset button 564 contacts the uppermost portions of plunger 558, while a butterfly cross bar 562 extends laterally across the plug housing and in contact with upper surfaces of leaf springs S38. The upward biasing forces of leaf springs 538 maintain the cross bar 562, plunger 558 and reset button 564 ln the positlons shown in Fig.
5, while a metal strap 566 extends about portions of coil 560 as shown. The cross sectional shape of reset button 564 ls polygonal, such as sguare, to prevent rotatlon thereof, while the cross sectional shape of core or plunger 558 $s round to provide maximum electromagnetic efficiency ln lts lnteraction with bobbln coil 560. Fig. 6 lllustrates ln a cross sectional view what , ~ .
12~3~
~pplicants refer to as the "butterflyl' wlth arm~ 5~8 belng ~played outwardly from a center rlvet member 570 aligned wlth plunger 558.
In operation, power for the printed clrcuit board electronic components is supplied by a copper path on the board vla pins 572 extending downwardly from the bobbln coil 560.
Prior to a shock hazard predetermined condition, the system of Flg. 5 ls "set" by means of depressing ~et or reset button 564 inwardly, which results ln movement of the plunger and the cro~
bar against the opposing biaslng force~ of leaf sprlngs 538.
This depression of the set or re3et button w~ll result in movement of the leaf springs until the movable contacts engage the flxed contact~, thereby completlng an electrlcal clrcuit.
The completion of the electrical clrcuit ~ust described re~ults in current flow to the bobbin coil whlch, ln turn, electromagnetically "keeps" and hold~ the plunger ln its d~pressed position until an lnterruption of such current flow.
The interengagement of the movable and fixed contacts further serves to enable the supply of power to the load or appliance with which the lnventlve assembly of Fig. 5 is assoclated, agaln, until an interruptlon in current flow to the bobbin coll.
In the event of the presence of a shock hazard condition, as a result of the operation of clrcultry of Fig. 7 described in detail below, current to the bobbin coll ls interrupted, wlth the result that the upward biasing force~ of ~Zi36~5 leaf springs 538 rapldly cau~e a separation of the movable contacts away from the fixed contact~, thereby in turn causing an interruption of power from the source through the blades t~ the load or appllance.
Referring now to Fig. 7 of the drawings, the aforesald circuitry assoclated with the devlce of Flg. 5 ls illustrated wlth like components ln Figs. S and 7 carrying like reference characters. Wlth the relay of Flg. 5 being fed wlth half wave ~ect$fled alternating current, or pulsating direct current, there is some current flow durlng the negative half cycle or the half cycle other than that when line current 1~ flowing. A free wheellng diode FWD contlnues current flow.
The main contacts Mc are normally open. When lt ls desired to turn on the appliance after plugging lt lnto a receptacle power source, pushlng a momentary double pull Dp wlth respect to the normally open swltch (set or reset button 564).
This applles half wave rectified direct current to the bobbln coil. Thls results in applying a voltage from the phase line through the double pole ~ingle throw switch DPST, through a diode Dl, thence through the bobb~n coil, w~th the other end of the coll going through another contact of the double pole switch to neutral. Thus, by pushing the swltch or re3et button, the coll is energized, and the maln contact Mc is closed.
.. ,, . i lZ136~5 Once the main contact M~ 1~ closed, a parallel path ~or the current i9 provided through another diode D2,~such that there ls current flow from phase through diode D2 through the coll wlth its free wheeling diode ln parallel wlth lt, thence through the collector of a transistor Ql~ the emitter of the translstor Ql being connected to neutral. The transistor is kept on by a resistor going from phase to the base. Rl 1~ the resistor between phase and the base.
Once the coil energizes itself as de~crlbed, the transistor 1~ turned on and then the momentary contact in the DPST is released and the coil is self-holdlng. Should the load or appllance be dropped lnto water, creating a shock hazard condition, the current ln a sense line is rectified by diode D3 and a reslstor R2 puts a negative voltage onto the base of the transistor. A capacitor Cl is provided between the transistor base and the emitter which will essentially store whatever voltage was ~resent to smooth it out. By setting the value of R2 relatively small with respect to the value of Rl, the time constant of the negative current is shorter than that of the positive curren~ and ln this way there is a negative charge turning off the transistor with the result that the movable contacts separate from the fixed contacts (Fig. 5).
lZ136~S
The reader is cautioned not to con~true the examples presented in thls speclficatlon, such a~ in de~crlbing halr dryers or other appllance~, as limlting the inventlon to these example~. Any electrical appllance or apparatus wlth whlch a shock hazard may be as~ociated is contemplated as being favorably affected by the advantages and features of the pre~ent lnven~lon.-Referrlng now to another embodlment of the pre~entinvention illustrated in Figs. 8-12, wherein a novel electro-jmechanical and electromagnetlc combination servles a circuit interrupting or breaklng function, as well as other functions. In Fig. 8 a plug assembly 600 of the type designated reference character 16 in Fig. 1 is shown wlth cover hou~ing half 602 removed to lllustrate base houslng half 604 wlth lts assembled subassemblles in place. A pair of movable contact arms 606 and lS 608 are each anchored at thelr respectlve angled depending legs 610 and 612 wlthln slot~ or rece~ses 614 and 616 of base houslng half 604. Near ends 618 and 620 of movable arms 606 and 608, respectively, remote from thelr ends 610 and 612, ~llver contacts 622 and 624 are rivoted to its arm.
Flexible conductors 626 are welded at 628 to depending legs 610 and 612 at one of thelr ends, and at thelr other end~
630 the flexible conductors are welded to plug insertlon blades 632. Blade~ 632 are conflgured with mountlng shoulders 634 so as to be held relatlvely integral with base 604 when assembled.
~;~136ti5 Movable contact arms 606 and 608 are normally blased ln the direction ~hown in phantom lines within FlgO 11 such t~at they bla~ the silver contacts 622 and 624 away from flxed sllver contacts 636 and 638 which are riveted to fixed contact term1nals 640 and 642, respectively. The flxed contact terminals 640 and 642 themselves are phy~ically and electrically connected to a printed circuit board 644 which carrles one of the eleckrical circuit embodiments described above and contemplated by the ,lnvention.
A latch member 646 formed with a tang 648 ls a~soclated with each movable contact arm and each i~ mounted and pivoted at its upper end on pivot points 650 formed on legs 652 of a set/reset button 654. At their lower ends 656, latches 646 are formed w$th downward bend or leg, as viewed in Fig. 11, these latter legs giving the latches structural stablllty for added rellability. The full lin~s of Fig. 11 illustrate latches 646 in their latched or set position, with tangs 648 holding the ends of mGvable contact arm5 606 and 608 such that movable silver contact~ 622 and 624 are in physical and electrlcal engagement with fixed silver contacts 636 and 638, thereby enabllng current flow through blades 632 ~rom a source such as an electrlcal receptacle to a load, such a~ hair dryer 12.
12~3~65 Reset button 654 ls normally biased ln a direction away from blades 632 by mean~ of helical compre~ion springs 658 shown in Figs. 9 and 12, for example. Springs 658 are held captive between and exert force~ against opposlng surfaces 660 and 662 of the underside of the reset button 654 and a metallic frame 664 (see Flg. 9). Set/reset button 654 ls vi~lble to the user through a window -668 formed within cover housing half 602 and preferably carries indicia of the type illustrated ln Flg. 8 to draw attention to lts functlon.
When the movable contact arms 606 and 608 are ln the posltions shown ln Fig. 11 in phantom outline, resting against a wall 666 formed ln base housing half 604, ~uch that the electrical circuit is in an interrupted ~tate wlth the movable and flxed contact~ spaced in opposition with respect to one another, the user of the present lnvention is able to close the clrcuit, assuming no hazard conditlon is present, by depressing with his or her flnger the set/reset button 654. This depression of the button 654 causes latches 646 to move ln the same dlrection as the movable button 654 and in sliding engagement with the ends of the movable contact arms 606 and 608 until and such that tangs 648 ride over these arm ends. Release of the formerly depressed button 654 results in its only partlally returning under the influence of springs 658 towards its original position, with a result~ng pulling of the movable contacts 622 lZ13~5 and 624 lnto engagement wlth thelr respective opposlng contact~
636 and 638 by latch tangs 648 again~t the undersides of the movable arm ends, there~y settlng the system and closing the clrcu~t. Latches 646 and thelr tang~ 648 hold the movable contacts in the last posltion ~ust descrlbed until a hazard conditlon is sensed or detected. In such an event, a plunger 67 shown ln Flgs. 8 and 9 as belng normally biased away from its assoclated windlng or coll 672 by means of a helical compresslon spring 674 is caused to rapidly approach the core of coll 672 as a result of its belng energized. Plunger 670 is formed with a neck 676 adjacent its end remote from coil 672, with which a clevis 678 of what will here by referred to as a banger 680 matingly engages. Banger 680 i8 further formed wlth pairs of trip and reset dogs 682 and 684 movable paths that coinclde wlth latch 646. Upon energization of coll 672, trip dogs 682 rapldly come into contact with and "bang" against the surfaces of latches -646 facing wall 666, forclbly disengaging the latches 646 and their tangs 648 from the movable contact arms, with the result that these arms return to thelr rest positions agalnst wall 666, and interrupt current flow through the movable and fixed contact~. Once the current is ~nterrupted, the compresslon forces within sprlng 674 cause the plunger 670 and lts lnterconnected banger 680 to return to the poslt1on illu~trated ln Fig. 9, with the reset dogs 684 comlng into contact wlth and blasing the latches 646 against the ends of the movable contact arms 606 and 608.
lZ136~S
Frame 664 compri~e~ part of the magnetic clrcult assoclated with an operating wlnding or coil 672, and for that purpo~e enclo~e~ a portlon of the coll. A straln rellef 686 formed in the lnsulation of a cord set 688 ls shown ln Figs. 8 and 9 held between oppo~ing annular walls 690 and 692, respectlvely, of housing halve~ 602 and 604 which, ln turn, are releasably ~ecured together by means of fasteners 694. Cord set 688 corresponds to the cord set 14 illustrated in Flg. 1.
Fig. 8 illustrates the printed circuit board 644 ln broken-line outline ln the position it occupie~ atop the banger a~embly and the fixed contacts. Fig. 8 further illustrates the three wires, phase/neutral 696 and the guard or sens~ng wire 698 whlch extend through and a~ part of cord set 688, through the strain relief 686, and into the conflnes of plug assembly 600.
Sensing wire 698 corresponds to the third wire 22 of Fig. 1 which electrically communicates with a sensing wire in the load, such as sensing wire 24 of Fig. 1, and wire 698 is coupled to the PC
board 644 while the phase and neutral lines are electrically secured to the fixed contact terminals 640 and 642. Terminals 640 and 642 are 90ft soldered to the PC board 644 by means of mountlng tabs 700.
''' lZ~3~6S
The pre~ent lnventlon thus provlde~ the user with a ~hock hazard protection 6ystem which: has a reponse time that conforms to Underwriters Laboratories requlrements; i~ trlp free;
possesses a double pole lnterrupting mechanism wlth an alr gap swltch; operates wlth reverse polarity; requlres only a 2 pole receptacle; operate~ ln an ungrounded environment, such as a plastlc tub; ls of a reasonable slze and cost; provldes the user with a vlsible trip indication; meets Underwriters Laboratorles ,overload, short circuit, and endurance requirements; po~sesses -electrical noise lmmunity so as to minimize false tripping;
provides protection in the event the cord is broken, wlth proper polarlty assumed; provides adequate stra~n relief; ls usable with a combinatlon swltch/receptacle; and provldes protectlon whether the load or appliance switches are on or off, or are at medium or hlgh settings.
The embodiments of the present invention herein described and d1sclosed are presented merely as examples of the lnvention. Other embodlment~, forms and structures coming wlthin the scope of this lnvention wtll readily suggest themselves to those ~kllled in the art, and shall be deemed to come withln the scope of the appended claims.
. This invention relates generally to electrlcal hazard preventlon, and more speclflcally to a shock hazard prevention sy~tem for di~connecting an electrical load from an electrical soul-ce when a shock hazard condltlon exi~ts withln the load.
Devices for protectlng human life and property agalnst electrical shock and damage re~ultlng from a shock hazard condltion within an electrlcal load are known. For example, the model No. 6199 ground fault circult interruptor (GFCI~
mar~eted by the assignee of the present invention is capable of senslng and responding to the lnadvertent grounding of the neutral conductor of an A-C electrical distrlbution system. It is noted, however, that in certain application~ the utilization of ~uch a GFCI is not practical.
In partlcular, the GFCI is a relatlvely expensive and complex device which requires the utilization of several transformers. In addition, the GFCI i5 often hardwired ln a wall outlet or receptacle and is neither portable nor readily disconnected. Thus, unless each outlet in which an electrical device such as, for example, an appliance is to be utilized 19 protected by a GFCI, the user of the appllance ïs sub~ect to possible injury if a shock hazard condition ~hould exist in con~unction with a non-protected outlet.
In addition, ln certain environment~ the utllization of a conventional GFCI would not afford any ~hock hazard protection to the user of an appliance. More specifically, a ~213665 conventional GFCI devlce of the type known to appllcants wlll not be effectlve or work ~f the user of an electrical appliance drops the appllance in a plastic insulated bathtub.
Another potential drawback, exl~t3 regarding the use of a GFCI for certaln types of portable electrical appliances such as, for example, a hair dryer. Although the owner of a halr dryer may have hls or her residence outlets adequately protected by GFCI devices, lt is possible that other places, such as hotels, the residence of relatives, friends, etc., where lt ls deslred to use the hair dryer may not be protected by such devices.
Accordingly, it is clear that what is needed is a shock hazard protector which i9 as~ociated with the appllance to be protected itself rather than with the elec~rical outlet ln which the appliance is plugged and energized. It is belleved that prior to the present invention, this need has gone unfulfilled.
A need exists for a shocX hazard protector which possesses attributes including having a minimum number of components, reliability, cost and portability.
It ls accordlngly a general object of thls invention to overcome the aforementioned limitations and drawbacks associated with the known devices and to fulfill the needs mentioned by provldin5 a hazard protection system having all of the desirable attributes noted above.
12~366S
It ls a particular object of the present lnvention to provide a shock hazard protector capable of disconnect~ng an electrical source from an electrlcal load in re~ponse to the detection of a shock hazard condltion wlthin the electrical load.
Another object of the present invention i9 to provide a shock hazard protector capable of detecting and responding to a -water-related shock hazard condition within an electrical appliance.
A ~urther object of the present invention is to provide a shock hazard protectlon system, as above, incorporating immer~ion detection circuitry.
A still further object of this invention is to provide a shock hazard protection system, as above, whereln a feature is provided for detecting a po~sible break or discontinuity ln a sensing or guard wire.
Yet another object of this invention is to provide a system, as above, wherein a solenoid-type electromechanical mechanism acts as a circuit breaking or interrupting means.
A further object is to provide such a sy~tem wherein a relay and associated clrcuitry and mechanical means enable the desired re~ult.
Yet a further ob~ect of this invention is to provide a detection system whlch detects or senses the presence of a conductive medium, and which causes an event in response thereto.
. - 3 -~Z13i~5 Another ob~ect of this invention ls to provlde a detectlon system whlch detects or sense~ the absence of the presence of ~ conductive medium, and whlch causes an event ln response thereto.
Other ob~ects will be apparent from the following deta~led de~cription and practice of the ~nvention.
The foregoing and other ob~ects and advantage~ which will be apparent in the follow~ng detailed descriptlon of the preferred embodlment, or in the practlce of the lnvention, are achleved by the invention disclosed hereln, which generally may be characterlzed as a hazard protector. The hazard protector includes detecting means associated with a load for detectlng a hazard conditlon within the load, an lnterrupting means associated with a source to which the load i5 operatively connected, and conducting means connected between the detecting mean3 and the interruptlng means. In response to the detection of a hazard condition within the load by the detecting means, the interruptlng means operatively disconnects the source from the load.
Serving to illustrate exemplary embodiments of the inventlon are the drawlngs, of which:
Fig. 1 i~ a perspectlve-type v~ew of a hair dryer and its assoclated cord set incorporatlng the system accordlng to the present invention;
~2~36~
Flg. 2 i~ a block dlagram of the shock hazard protector, in accordance with the present lnvention;
Fig. 3 is a ~chematic diagram of one embodlment of the shock hazard protector, in accordance with the present invention;
Fig. 4 is a schemat~c diagram of a second embodlment of the shock hazard protector, in accordance with the present invention;
Fig. 5 ls an enlarged partial sectlonal elevatlonal view taken through a cord set plug of a relay embodiment of the 10 present invention;
Fig. 6 is a partial fragmentary sectional plan view taken along the llne 6-6 of Fig. 5;
Fig. 7 is a schemat~c circ~it dlagram of the embodiment of the present invention as~ociated with Figs. 5 and 6;
Fig. 8 is an elevational vlew of the cord set plug illu~trated in Fig. 1 and taken along line 8-8 of that ~ame Fig. 1 depicting the assembled plug with its cover removed;
Fig. 9 is a partial sectional elevatlonal vlew taken along line 9-9 of Fig. 8;
Fig. 10 i~ a ~ectlonal view taken along llne 10-10 of Fig. 8;
Fig. 11 is a fragmentary sectional view taken along line 11-11 of Fig. 8; and Fig. 12 is an exploded-type perspect$ve view of components of the present inventlon illustrated in Fig. 8.
lZ13~65 Referrlng now in more detail to the drawlng~, F~g. 1 presented ln its form to lllustrate a halr dryer 12 and it~
associated cord set 14 a~ wholly containing and constitutlng or comprlsing the shock hazard protection system 10 of the present invention. It is applicants' intention and de~ire to emphasize -here the fact that this in~ention contemplates an electrical appliance, such as of the personal health care type (hair dryer~, etc.) which possesses all of the features and advantage~ of the invention. It is also an intention of appl~cants to provide the 10 system of the present invention in the form of an OEM product available for sale to manufacturers of such appliances.
A plug assembly 16 i9 illustrated in Flg. 1 as lncluding polarlzed blades 18 extending from housing 20. Whereas 15 commerclally avallable hair dryers, as an example of a personal health care appliance, normally include a c~rd set havlng two conductors or wire~, a third wire 22 ls lllustrated in the case of cord set 14 electrically communicatlng with a bare copper wire 24 whose path (in the example given in Fig. 1) includes proximity to and looped clrcuit near a dryer hou~ing opening through whlch an on-off switch a~sembly 26 extends, and thence upward to another loop proxlmate a dryer housing air inlet opening through which fan 28 driven by motor 30 pulls air to be heated by heatlng ccil 32 before exiting the dryer housing air outlet opening ln 1213~iS
which grill 34 i~ positioned. After leavlng the ~econd loop described as being ad~acent the alr inlet openlng, wire 22 extends to a thlrd loop ad~acent grill 34.
Slnce heater coil 32 carries and operates on current ln the "hot" or phase llne, and with the provi~lon of conductor or wire 24 wired a~ part of the neutral side of the line, the presence of a conductlve medlum such a~, bu~ not llmlted to, moisture or water between them wlll create a conductlve path ,contemplated by the invention as enabling lnterruption of current to the load 12. Thls embodiment is distinguishable from another embodiment of the present invention wherein a pair of conductor~, as opposed to a single guard or sensing conductor 24, are located at or near moisture/water hou~ing penetration points.
Configurations of one or more sen~ing or guard conductor~ other than those illu~trated herein are contemplated as coming wlthln the scope of this invention.
Referring to Fig. 2, a block dlagram of a shock hazard protector according to the present lnventlon ls illustrated. ~s shown therein, it comprises a source operatively connected to a load by first and second conductors 110 and 120, respectively, a detector 200 as~ociated with the load, a control circult 300 connected to the detector by a ~ensing or third conductor 130, and an interruptor circuit 400 as~ociated with the source and connected to the control circuit 300. In the case of an electrical A-C source, conductors 110 and 120 are tied to a phase and the neutral terminal, respectively, of the A-C source.
~Z~3~
In the normal mode of operation, that is, in the absence of a hazard condition withln the load, the control circuit 300, which changes from a flrst state to a second state in re~ponse to the detection of a hazard condltlon wlthln the load, remains ln the first state. Upon the detection by detector 200 of a predefined fault or hazard condition withln the load, the control circuit 300 changes from the first to the second state, whlch causes the interruptor circuit 400 to o~eratlvely disconnect the source from the load.
It is noted that the present lnventlon co~templates certain applications where the system sensitlvity;need not be accurately controlled, and the control circult 300 can be ellminated. In this situation the interruptor circuit 400 is connected to the detector 200 by the third conductor 130, and responds directly to the detection by detector 200 of a hazard condition within the load.
In either situation, the sensing or third conductor 130 communlcates the presense of the hazard conditlon wlthin the load to the control circuit 300 or the interruptor clrcuit 400.
Referring now to Flg. 3, a schematic dlagram of one embodiment of the invention particularly sultea for use ln con~unction with water-related shock hazard condltions wlthln an electrical appliance operatively connected to an A-C source (not shown) by electrical conductors 110, 120, respectively, ls illu~trated. As shown therein, detector 200 comprise~ a palr of ~Z136~i~
hazard or lmmerslon detection conductors 210 and 220, which are positloned in a non-contacting relationship and contalned withln the electrical load. A pair of immersion detectlon conductor~
210 and 220 are preferably located in proximity to each port of the appliance to be protected where water can enter.
~ or ease of description, lt will be assumed that the appliance to be protected only contalns one port or opening through which water may enter. For this ~ltuatlon, one end of ,one of the palr of immersion detection conductors 210 is operatively connected to the phase terminal of an A-C ~ource (not shown) via electrlcal ~conductor 110, and one end of the second of the pair of immersion detection conductors 220 is connected to the load end of the third electrlcal conductor 130. The other ends of lmmerslon detection conductors 210, 220 are unconnected and are maintained in a spaced-apart relatlonship, typically for example, not more than one inch.
Shock hazard or lmmersion detection conductors 210, 220 may comprise, for example, a pair of bare electrlcal conductors or a pair of conducting plated llnes on a printed circult board or other physical configurations that will enable a conductive path between the unconnected ends thereof.
Control clrcuit 300 comprises a solid state switching control circult and includes a first re~istor Rl connected in-line between the gate of a silicon controlled rectifier SCR
and the sour~e end of the third electrical conductor 130.
lZ13665 Resistor Rl limits the current applled to the gate of the SCR.
In addltion, control circuit 300 include~ a parallel network comprising reslstor R2, capacitor C and dlode D connected between the gate and cathode of the SCR. These components provide ~
measure of noi~e immunity and protection agalnst damage across the gate to cathode ~unction of the SCR.
Interruptor circult 400 compri~es an electromechanioal lnterrupting clrcuit and includes an energizing coll L and a flrst and second contact or switch Sl, S2 connected ln-line with the flrst and second electrical conduc}ors 110, 120, respectively. Switches Sl and S2 are responsive to th'e flow of current through energizing coil L and are closed when such current i5 not flowing. In response to the flow of such current they switch from the normall~ closed positlon to the shock hazard condltion open position. One end of energizing coil L is connected to the first electrical conductor 110 and the other end thereof is connected to the anode of the SCR. The cathode of the SCR is operatively connected to the second electrical conductor 120.
lZ~3~S
~ he exlstence of a water-related ~hock hazard condltlon within the electrical appliance is detected when both unconnected ends of the pair of lmmersion detection conductors 210, 220 are immersed in the water. More specifically, the immersion of both unconnected ends of the palr of immersion detection conductors 210, 220 causes the electr~cal A-C source to be operatively connected to the gate of the SCR via the path provided by the first electrical conductor 110, the first lmmersion detection ~onductor 210, the electrically conductlng path provlded by the water in which the unconnected ends of the first and second lmmersion detection conductors 210, 220 are immersed, the second immersion detection conductor 220, the third e~ectrical conductor 130, and resistor Rl. In response thereto, the SCR switches from the normally non-conducting ~tate to the shock hazard condition conducting state, thereby providing a path for current to flow through the energizlng coll L causing switches Sl and S2 to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting the A-C source from the electrical appliance.
To in~ure that the shock hazard protector ls operable prior to utilization of the appliance lt protects, a test clrcuit ~not shown) comprislng, for example, a resistor in series wlth a normally open switch connected between the pair of immersion detection conductors 210, 220 may be utilized. Closlng the normally open swltch causes the xesistor to be connected acros~
lZ136~S
the lmmerslon detectlon conductors and, if the shock haz~rd protect~r ~s operating, as descrlbed above, causes the A-C source ~o be operatively dlsconnected from the appliance. Preferably, the test circuit is contained within the electrical appliance.
In con~unction with said test clrcult, diode D could be replaced with a light-emitting-diode ~LED). If the LED is llluminated with the te~t switch ln the closed position it indicates that the shock hazard protector is not operating properly.
Preferablyl electrical conductors 110, 120 and 130 comprise a three wire conductor having an A-C source compatible plug at the source end, the control circuit 300 and interruptor circuit 400 are contalned in the plug, and the detector 200 i~
contained wlthin the appliance.
Thu~ in the case where the electrical appliance 15, is, for example, a hair dryer, the detector 200 would be located lnternally within the dryer and, as noted a~ove, ln proximlty to each port thereof where water can enter the dryer. It should be emphasizèd here that while water is given as the electrlcally conductive medium, this invention contemplates a response to any electrically conducting medium, such that the appliance is electrically disconnected from the A-C source in response to the presence of such a conductive medium.
Exemplary values for the circuit illustrated ln Figure 3 are as follow~: Rl-2000 ohms, R2-1000 ohms, C-0.1 microfarads, D-lN4004, SCR-2N5064.
Referring now to Figure 4, a schematic diagram of a second embodiment of the present invention particularly suited for u~e in conjunction with water-related shock hszard condltions withln an electrical appliance 1~ lllustrated. This embodlment provldes an add~tlonal feature not present in the first embodlment lllustrated ln Figure 3. In partlcular, the embodlment illustrated in Figure 3, provides shock hazard protection if any of e~ectrical conductor~ 110, 120, individually or in combination, are broken, but does not provlde shock hazard protection if electrical conductor 130 is broken. The embodlment illustrated in Flgure 4 provides an additional mea~ure of ~hock hazard protection by rendering the electrical appliance inoperative if any of electrical conductors 110, i20 and 130, individually or in combination, are broken.
Thls addltional measure of protection i8 provided by the additlon of a first diode Dl connected in series between the ~econd immersion detection conductor 220 and the thlrd electrical conductor 130, the replacement of the capacitor connected between the gate and cathode of the SCR wlth an approprlate charglng capacitor, the addition of a flrst charging circuit comprislng resist~r RN and diode DN connected between the first and third electrical conductors 110, 130, the addition of a zener diode in series with the diode connected between the gate and cathode of the SCR, the addltion of a second charging circuit comprlsing resistor Rp and diode Dp connected between the flrst electrlcal conductor 110 and the gate of the SCR, and the ellminatlon of resistor R2 connected between the gate and cathode of the SCR.
i2~ 6S
The operatlon of the clrcuit illu~trated in Figure 4 i9 as follows. Assuming that the senslng or third conductor 130, is ln tact, the appllance is not lmmersed in water and that it ls energized, during the negative half cycle of the A-C signal on electrical conductor llO a negative charging path via diode DN, reslstor RN, third conductor 13D, resistor Rl provides charge to-capacitor C, thereby charging it negatively. During the positlve half cycle diode DN blocks, however a po~itive charging path via resistor Rp and diode Dp provides charge to capacitor C, thereby charging it positively. Since the time constant of res1stsr RN
and capacitor C, is roughly 33 tlmes greater than;the time constant of resistor Rp and capacitor C, the capacitor C charges much faster in the negative sense, so that under steady state conditions a negatlve voltage exists on the gate of the SCR
thereby keeping it in a non-conducting state. In order to limit that negative voltage to a value that would not damage the ga~e to cathode junction of the SCR a three volt zener diode is added in serie~ with diode D2, also in parallel with capacitor C.
$he next condition to look at is a broken third conductor 130. Under this condition a negative charging path no longer exists for the negative voltage to be impressed on capacitor C, and, therefore during positive half cycles capicjtor C wlll dlscharge po~itively and eventually the voltage on the ~ate of the SCR will get high enough to trip the SCR, causlng it to switch to the conducting state thereby operatively dis-12136~5 connectlng the A-C ~ource from the appliance, puttlng you in a safe conditon. Exemplary values for the circuit illustratea ln Figure 4 are as follow~: Dl, D2, DN, Dp-lN 4004, RN-30,000 ohm~, Rp-l,000,000 ohms, Rl-2000 ohms, C-l microfarad,SCR-2N50~4, Z-3 volt zener diode.-Preferably, the component3 comprislng the flrstcharglng circui~ RN, DN and diode Dl are contained within the electrical appllance and are water proof, the components compri~ing the second charging circu~t Rp, Dp and the zener diode D are contained in the plug.
It is noted that with minor modifications the above described invention has many other appllcations. For example, in the situatlon where the electrical appliance comprlses a power tool, such as, a drlll, hav1ng an electrically conducting houslng the teachings of the present invention may be utilized by ellminating immer~lon detection conductor 220 and connecting the third electrical conductor 130 to the électrically conducting housing. The immersion ln water of the unconnected end of shock hazard detection conductor 210 provides an electrically conductive path between the shock hazard detectlon conductor and the electrically conducting hou~ing of the drill causing, a~
described above, the drill to be operatively disconneFted from the ~-C source.
12136~S
Referrlng now to an embodiment of the pre~ent inventlon whlch utilizes the ~pproach of a relay mechanism to accompllsh the circuit interruptlng goal of the lnvention, Flg. S
lllustrates a shock hazard protector embodlment of a plug assembly S10 ~ormed wlth a hou~ing wlth a base and cover body S halves 512 and 514, respectively, ~oined at a housing reference -line 516. A ~traln rellef 518 comprises part of cord 520 and, ln cooperative combination with the shape and contour of annulAr surfaces 522, 524, 526 and 528, serves as à mean~ for protecting the lntegrity of electrical connections dur~ng use.
Blades 530 extend outwardly from surfacé 532 of hou~ing hal~ 512 and serve the functlon of matingly and electrically engaging electrical contacts wlthln a receptacle (not shown) or electr~cal outlet in the home, for example. A fixed contact 534 is associated and integral wlth each of the blades 530, contacts 534 being fixed or stationary as opposed to movable when assembled.
A pair of movable contacts 536 are provlded and are integral with leaf springs 538 which, in turn, are anchored by means of eyelets 540 extending through openings ln an end portlon of the leaf ~pring~ 538 spaced from the movable contacts 536.
~hese eyelets further extend through openings through a printed circuit board 542 supported by ledges 544 and 546 ad~acent upstandlng wall~ 54~ and 550, as shown in Fig. 5.
12~36~ii5 A tab 552 assoclated with each leaf sprlng 538 further anchors the leaf springs to the prlnted circuit board in ~paced relatlon~hip with re~pect to the aforesaid eyelets, thereby serving an addltlonal function of preventing undesirable rotatlon of the leaf springs S38, assuring alignment and rel$ably repeated engagement between the fixed and movable contacts 534 and 536, respectively. Leaf springs 538 are conflgured to normally bias the movable contacts 536 away from the fixed contacts 534 when ln an unstressed condition, thereby normally interrupting an electrical path between these contacts. The ends of leaf springs 538 are formed with upstandlng flanges 554 to which conductors 556 are connected.
A plunger or core 558 is disposed vertically within a bobbin coil 560, as lllustrated in Fig. 5. A reset button 564 contacts the uppermost portions of plunger 558, while a butterfly cross bar 562 extends laterally across the plug housing and in contact with upper surfaces of leaf springs S38. The upward biasing forces of leaf springs 538 maintain the cross bar 562, plunger 558 and reset button 564 ln the positlons shown in Fig.
5, while a metal strap 566 extends about portions of coil 560 as shown. The cross sectional shape of reset button 564 ls polygonal, such as sguare, to prevent rotatlon thereof, while the cross sectional shape of core or plunger 558 $s round to provide maximum electromagnetic efficiency ln lts lnteraction with bobbln coil 560. Fig. 6 lllustrates ln a cross sectional view what , ~ .
12~3~
~pplicants refer to as the "butterflyl' wlth arm~ 5~8 belng ~played outwardly from a center rlvet member 570 aligned wlth plunger 558.
In operation, power for the printed clrcuit board electronic components is supplied by a copper path on the board vla pins 572 extending downwardly from the bobbln coil 560.
Prior to a shock hazard predetermined condition, the system of Flg. 5 ls "set" by means of depressing ~et or reset button 564 inwardly, which results ln movement of the plunger and the cro~
bar against the opposing biaslng force~ of leaf sprlngs 538.
This depression of the set or re3et button w~ll result in movement of the leaf springs until the movable contacts engage the flxed contact~, thereby completlng an electrlcal clrcuit.
The completion of the electrical clrcuit ~ust described re~ults in current flow to the bobbin coil whlch, ln turn, electromagnetically "keeps" and hold~ the plunger ln its d~pressed position until an lnterruption of such current flow.
The interengagement of the movable and fixed contacts further serves to enable the supply of power to the load or appliance with which the lnventlve assembly of Fig. 5 is assoclated, agaln, until an interruptlon in current flow to the bobbin coll.
In the event of the presence of a shock hazard condition, as a result of the operation of clrcultry of Fig. 7 described in detail below, current to the bobbin coll ls interrupted, wlth the result that the upward biasing force~ of ~Zi36~5 leaf springs 538 rapldly cau~e a separation of the movable contacts away from the fixed contact~, thereby in turn causing an interruption of power from the source through the blades t~ the load or appllance.
Referring now to Fig. 7 of the drawings, the aforesald circuitry assoclated with the devlce of Flg. 5 ls illustrated wlth like components ln Figs. S and 7 carrying like reference characters. Wlth the relay of Flg. 5 being fed wlth half wave ~ect$fled alternating current, or pulsating direct current, there is some current flow durlng the negative half cycle or the half cycle other than that when line current 1~ flowing. A free wheellng diode FWD contlnues current flow.
The main contacts Mc are normally open. When lt ls desired to turn on the appliance after plugging lt lnto a receptacle power source, pushlng a momentary double pull Dp wlth respect to the normally open swltch (set or reset button 564).
This applles half wave rectified direct current to the bobbln coil. Thls results in applying a voltage from the phase line through the double pole ~ingle throw switch DPST, through a diode Dl, thence through the bobb~n coil, w~th the other end of the coll going through another contact of the double pole switch to neutral. Thus, by pushing the swltch or re3et button, the coll is energized, and the maln contact Mc is closed.
.. ,, . i lZ136~5 Once the main contact M~ 1~ closed, a parallel path ~or the current i9 provided through another diode D2,~such that there ls current flow from phase through diode D2 through the coll wlth its free wheeling diode ln parallel wlth lt, thence through the collector of a transistor Ql~ the emitter of the translstor Ql being connected to neutral. The transistor is kept on by a resistor going from phase to the base. Rl 1~ the resistor between phase and the base.
Once the coil energizes itself as de~crlbed, the transistor 1~ turned on and then the momentary contact in the DPST is released and the coil is self-holdlng. Should the load or appllance be dropped lnto water, creating a shock hazard condition, the current ln a sense line is rectified by diode D3 and a reslstor R2 puts a negative voltage onto the base of the transistor. A capacitor Cl is provided between the transistor base and the emitter which will essentially store whatever voltage was ~resent to smooth it out. By setting the value of R2 relatively small with respect to the value of Rl, the time constant of the negative current is shorter than that of the positive curren~ and ln this way there is a negative charge turning off the transistor with the result that the movable contacts separate from the fixed contacts (Fig. 5).
lZ136~S
The reader is cautioned not to con~true the examples presented in thls speclficatlon, such a~ in de~crlbing halr dryers or other appllance~, as limlting the inventlon to these example~. Any electrical appllance or apparatus wlth whlch a shock hazard may be as~ociated is contemplated as being favorably affected by the advantages and features of the pre~ent lnven~lon.-Referrlng now to another embodlment of the pre~entinvention illustrated in Figs. 8-12, wherein a novel electro-jmechanical and electromagnetlc combination servles a circuit interrupting or breaklng function, as well as other functions. In Fig. 8 a plug assembly 600 of the type designated reference character 16 in Fig. 1 is shown wlth cover hou~ing half 602 removed to lllustrate base houslng half 604 wlth lts assembled subassemblles in place. A pair of movable contact arms 606 and lS 608 are each anchored at thelr respectlve angled depending legs 610 and 612 wlthln slot~ or rece~ses 614 and 616 of base houslng half 604. Near ends 618 and 620 of movable arms 606 and 608, respectively, remote from thelr ends 610 and 612, ~llver contacts 622 and 624 are rivoted to its arm.
Flexible conductors 626 are welded at 628 to depending legs 610 and 612 at one of thelr ends, and at thelr other end~
630 the flexible conductors are welded to plug insertlon blades 632. Blade~ 632 are conflgured with mountlng shoulders 634 so as to be held relatlvely integral with base 604 when assembled.
~;~136ti5 Movable contact arms 606 and 608 are normally blased ln the direction ~hown in phantom lines within FlgO 11 such t~at they bla~ the silver contacts 622 and 624 away from flxed sllver contacts 636 and 638 which are riveted to fixed contact term1nals 640 and 642, respectively. The flxed contact terminals 640 and 642 themselves are phy~ically and electrically connected to a printed circuit board 644 which carrles one of the eleckrical circuit embodiments described above and contemplated by the ,lnvention.
A latch member 646 formed with a tang 648 ls a~soclated with each movable contact arm and each i~ mounted and pivoted at its upper end on pivot points 650 formed on legs 652 of a set/reset button 654. At their lower ends 656, latches 646 are formed w$th downward bend or leg, as viewed in Fig. 11, these latter legs giving the latches structural stablllty for added rellability. The full lin~s of Fig. 11 illustrate latches 646 in their latched or set position, with tangs 648 holding the ends of mGvable contact arm5 606 and 608 such that movable silver contact~ 622 and 624 are in physical and electrlcal engagement with fixed silver contacts 636 and 638, thereby enabllng current flow through blades 632 ~rom a source such as an electrlcal receptacle to a load, such a~ hair dryer 12.
12~3~65 Reset button 654 ls normally biased ln a direction away from blades 632 by mean~ of helical compre~ion springs 658 shown in Figs. 9 and 12, for example. Springs 658 are held captive between and exert force~ against opposlng surfaces 660 and 662 of the underside of the reset button 654 and a metallic frame 664 (see Flg. 9). Set/reset button 654 ls vi~lble to the user through a window -668 formed within cover housing half 602 and preferably carries indicia of the type illustrated ln Flg. 8 to draw attention to lts functlon.
When the movable contact arms 606 and 608 are ln the posltions shown ln Fig. 11 in phantom outline, resting against a wall 666 formed ln base housing half 604, ~uch that the electrical circuit is in an interrupted ~tate wlth the movable and flxed contact~ spaced in opposition with respect to one another, the user of the present lnvention is able to close the clrcuit, assuming no hazard conditlon is present, by depressing with his or her flnger the set/reset button 654. This depression of the button 654 causes latches 646 to move ln the same dlrection as the movable button 654 and in sliding engagement with the ends of the movable contact arms 606 and 608 until and such that tangs 648 ride over these arm ends. Release of the formerly depressed button 654 results in its only partlally returning under the influence of springs 658 towards its original position, with a result~ng pulling of the movable contacts 622 lZ13~5 and 624 lnto engagement wlth thelr respective opposlng contact~
636 and 638 by latch tangs 648 again~t the undersides of the movable arm ends, there~y settlng the system and closing the clrcu~t. Latches 646 and thelr tang~ 648 hold the movable contacts in the last posltion ~ust descrlbed until a hazard conditlon is sensed or detected. In such an event, a plunger 67 shown ln Flgs. 8 and 9 as belng normally biased away from its assoclated windlng or coll 672 by means of a helical compresslon spring 674 is caused to rapidly approach the core of coll 672 as a result of its belng energized. Plunger 670 is formed with a neck 676 adjacent its end remote from coil 672, with which a clevis 678 of what will here by referred to as a banger 680 matingly engages. Banger 680 i8 further formed wlth pairs of trip and reset dogs 682 and 684 movable paths that coinclde wlth latch 646. Upon energization of coll 672, trip dogs 682 rapldly come into contact with and "bang" against the surfaces of latches -646 facing wall 666, forclbly disengaging the latches 646 and their tangs 648 from the movable contact arms, with the result that these arms return to thelr rest positions agalnst wall 666, and interrupt current flow through the movable and fixed contact~. Once the current is ~nterrupted, the compresslon forces within sprlng 674 cause the plunger 670 and lts lnterconnected banger 680 to return to the poslt1on illu~trated ln Fig. 9, with the reset dogs 684 comlng into contact wlth and blasing the latches 646 against the ends of the movable contact arms 606 and 608.
lZ136~S
Frame 664 compri~e~ part of the magnetic clrcult assoclated with an operating wlnding or coil 672, and for that purpo~e enclo~e~ a portlon of the coll. A straln rellef 686 formed in the lnsulation of a cord set 688 ls shown ln Figs. 8 and 9 held between oppo~ing annular walls 690 and 692, respectlvely, of housing halve~ 602 and 604 which, ln turn, are releasably ~ecured together by means of fasteners 694. Cord set 688 corresponds to the cord set 14 illustrated in Flg. 1.
Fig. 8 illustrates the printed circuit board 644 ln broken-line outline ln the position it occupie~ atop the banger a~embly and the fixed contacts. Fig. 8 further illustrates the three wires, phase/neutral 696 and the guard or sens~ng wire 698 whlch extend through and a~ part of cord set 688, through the strain relief 686, and into the conflnes of plug assembly 600.
Sensing wire 698 corresponds to the third wire 22 of Fig. 1 which electrically communicates with a sensing wire in the load, such as sensing wire 24 of Fig. 1, and wire 698 is coupled to the PC
board 644 while the phase and neutral lines are electrically secured to the fixed contact terminals 640 and 642. Terminals 640 and 642 are 90ft soldered to the PC board 644 by means of mountlng tabs 700.
''' lZ~3~6S
The pre~ent lnventlon thus provlde~ the user with a ~hock hazard protection 6ystem which: has a reponse time that conforms to Underwriters Laboratories requlrements; i~ trlp free;
possesses a double pole lnterrupting mechanism wlth an alr gap swltch; operates wlth reverse polarity; requlres only a 2 pole receptacle; operate~ ln an ungrounded environment, such as a plastlc tub; ls of a reasonable slze and cost; provldes the user with a vlsible trip indication; meets Underwriters Laboratorles ,overload, short circuit, and endurance requirements; po~sesses -electrical noise lmmunity so as to minimize false tripping;
provides protection in the event the cord is broken, wlth proper polarlty assumed; provides adequate stra~n relief; ls usable with a combinatlon swltch/receptacle; and provldes protectlon whether the load or appliance switches are on or off, or are at medium or hlgh settings.
The embodiments of the present invention herein described and d1sclosed are presented merely as examples of the lnvention. Other embodlment~, forms and structures coming wlthin the scope of this lnvention wtll readily suggest themselves to those ~kllled in the art, and shall be deemed to come withln the scope of the appended claims.
Claims (49)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination with a load operatively connected to a source, hazard preventing means comprising:
detecting means associated with said load for detecting a hazard condition within said load;
interrupting means associated with said source;
conducting means connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said source from said load in response to the detection of a hazard condition within said load.
detecting means associated with said load for detecting a hazard condition within said load;
interrupting means associated with said source;
conducting means connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said source from said load in response to the detection of a hazard condition within said load.
2. In combination with an electrical load operatively connected to an electrical source, hazard preventing means comprising;
detecting means associated with said electrical load for detecting a hazard condition within said load;
control means;
conducting means connected between said detecting means and said control means;
interrupting means associated with said electrical source and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a hazard condition within said electrical load;
said interrupting means operatively disconnecting said electrical source from said electrical load in response to the changing of said control means from the first state to the second state.
detecting means associated with said electrical load for detecting a hazard condition within said load;
control means;
conducting means connected between said detecting means and said control means;
interrupting means associated with said electrical source and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a hazard condition within said electrical load;
said interrupting means operatively disconnecting said electrical source from said electrical load in response to the changing of said control means from the first state to the second state.
3. In combination with an electrical load operatively connected to an A-C source, hazard preventing means comprising:
detecting means associated with said electrical load for detecting a hazard condition within said load;
switching control means;
conducting means operatively connected between said detecting means and said switching control means;
interrupting means associated with said A-C source and connected to said switching control means;
said switching control means switching from a first state to a second state in response to the detection of a hazard condition within said electrical load;
said interrupting means operatively disconnecting said A-C
source from said electrical load in response to the switching of said switching control means from the first state to the second state.
detecting means associated with said electrical load for detecting a hazard condition within said load;
switching control means;
conducting means operatively connected between said detecting means and said switching control means;
interrupting means associated with said A-C source and connected to said switching control means;
said switching control means switching from a first state to a second state in response to the detection of a hazard condition within said electrical load;
said interrupting means operatively disconnecting said A-C
source from said electrical load in response to the switching of said switching control means from the first state to the second state.
4. The combination recited in Claim 3 wherein said detecting means is contained within said electrical load and comprises immersion means for detecting a water-related shock hazard condition within said load, said immersion means including a pair of shock hazard detection conductors maintained in a non-contacting relationship, one of said pair of shock hazard detection conductors being operatively connected at one end to said A-C source and the other of said pair of shock hazard detection conductors being operatively connected at one end to said conducting means, and the other ends of said pair of shock hazard detection conductors being maintained in a spaced-apart relationship.
5. The combination recited in Claim 4 wherein said electrical load comprises an electrical appliance.
6. The combination recited in Claim 5 wherein said electrical appliance is a hair dryer.
7. The combination recited in Claim 3 wherein said electrical load is contained within an electrically conducting housing, said detecting means is contained within said electrical load and comprises immersion means for detecting a water-related shock hazard condition within said load, said immersion means including a shock hazard detection conductor maintained in a non-contacting relationship with said electrically conducting housing, one end of said shock hazard detection conductor being operatively connected to said A-C source and the other end thereof being unconnected, and said electrically conducting housing being connected to said conducting means.
8. The combination recited in Claim 7 wherein said electrical load comprises an electrical appliance.
9. The combination recited in Claim 8 wherein said electrical appliance is a power tool.
10. The combination recited in Claim 5 or 8 further including testing means for selectively connecting impedance means across said immersion detecting means.
11. In combination with an electrical load operatively connected to an A-C source by a first and second electrical conductor having a source end and a load end, respectively, 8 shock hazard preventing circuit comprising;
a third electrical conductor having a source end and load end;
a first and second shock hazard detection conductor having a connected end and an unconnected end, respectively, positioned in a non-contacting relationship and contained within said load, the connected end of said first shock hazard detection conductor being connected to the load end of said first electrical conductor, the connected end of said second shock hazard detection conductor being connected to the load end of said third electrical conductor, and the unconnected ends of said first and second shock hazard detection conductors being maintained in a spaced-apart relationship;
an interrupting circuit including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operatively connected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected ends of said first and second shock hazard detection conductors provides an electrically conductive path between said first and second shock hazard detection conductors causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical load.
a third electrical conductor having a source end and load end;
a first and second shock hazard detection conductor having a connected end and an unconnected end, respectively, positioned in a non-contacting relationship and contained within said load, the connected end of said first shock hazard detection conductor being connected to the load end of said first electrical conductor, the connected end of said second shock hazard detection conductor being connected to the load end of said third electrical conductor, and the unconnected ends of said first and second shock hazard detection conductors being maintained in a spaced-apart relationship;
an interrupting circuit including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operatively connected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected ends of said first and second shock hazard detection conductors provides an electrically conductive path between said first and second shock hazard detection conductors causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical load.
12. The combination recited in claim 11 further comprising:
a first resistor connected in series between the gate of said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
a first resistor connected in series between the gate of said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
13. The combination recited in claim 12 wherein said electrical load comprises an electrical appliance.
14. The combination recited in claim 12 further comprising:
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the load end of said first electrical conductor and the load end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between the connected end of said second shock hazard detection conductor and the load end of said third electrical conductor.
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the load end of said first electrical conductor and the load end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between the connected end of said second shock hazard detection conductor and the load end of said third electrical conductor.
15. The combination recited in claim 14 wherein said diode circuit comprises a zener diode connected in series with a second diode, the anode of said zener diode being operatively connected to the gate of said silicon controlled rectifier, and the anode of said second diode being operatively connected to the cathode of said silicon controlled rectifier.
16. The combination recited-in claim 15 wherein:
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the load end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the load end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
17. The combination recited in claim 16 wherein said electrical load comprises an electrical appliance.
18. The combination recited in claim 17 wherein said first charging circuit and said first diode are contained within said electrical appliance.
19. The combination recited in claim 13 or 17 wherein said electrical appliance is a hair dryer.
20. The combination recited in claim 18 further including a test circuit operatively connected between said first and second shock hazard detection conductors and comprising a second resistor in series with a normally open switch.
21. The combination recited in claim 20 wherein said second diode comprises a light-emitting-diode.
22. In combination with an electrical load contained within an electrically conducting housing and operatively connected to an A-C source by a first and second electrical conductor having a source end and a load end, respectively, a shock hazard preventing circuit comprising;
a third electrical conductor having a source end and a load end;
a shock hazard detection conductor contained within said electrical load and maintained in a non-contacting relationship with said electrically conducting housing, one end of said shock hazard detection conductor being connected to the load end of said first electrical conductor and the other end of said shock hazard detection conductor being unconnected and maintained in a spaced-apart relationship with said electrically conducting housing, and said electrically conducting housing being connected to the load end of said third electrical conductor;
an interrupting circuit including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operativelyconnected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected end of said shock hazard detection conductor provides an electrically conductive path between said shock hazard detection conductor and said electrically conducting housing causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical load.
a third electrical conductor having a source end and a load end;
a shock hazard detection conductor contained within said electrical load and maintained in a non-contacting relationship with said electrically conducting housing, one end of said shock hazard detection conductor being connected to the load end of said first electrical conductor and the other end of said shock hazard detection conductor being unconnected and maintained in a spaced-apart relationship with said electrically conducting housing, and said electrically conducting housing being connected to the load end of said third electrical conductor;
an interrupting circuit including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operativelyconnected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected end of said shock hazard detection conductor provides an electrically conductive path between said shock hazard detection conductor and said electrically conducting housing causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical load.
23. The combination recited in claim 22 further comprising:
a first resistor connected in series between the gate of said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
a first resistor connected in series between the gate of said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
24. The combination recited in claim 23 wherein said electrical load comprises an electrical appliance.
25. The combination recited in claim 23 further comprising:
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the load end of said first electrical conductor and the load end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between said electrically conducting housing and the load end of said third electrical conductor.
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the load end of said first electrical conductor and the load end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between said electrically conducting housing and the load end of said third electrical conductor.
26. The combination recited in claim 25 wherein said diode circuit comprises a zener diode connected in series with a second diode, the anode of said zener diode being operatively connected to the gate of said silicon controlled rectifier, and the anode of said second diode being operatively connected to the cathode of said silicon controlled rectifier.
27. The combination recited in claim 26 wherein:
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the load end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the load end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
28. The combination recited in claim 27 wherein said electrical load comprises an electrical appliance.
29. The combination recited in claim 28 wherein said first charging circuit and said first diode are contained within said electrical appliance.
30. The combination recited in claim 24 or 29 wherein said electrical appliance is a power tool.
31. The combination recited in claim 29 further including a test circuit operatively connected between said shock hazard detection conductor and said electrically conducting housing and comprising a second resistor in series with a normally open switch.
32. In combination with an electrical appliance operatively connected to an A-C source by connecting means including first and second electrical conducting means and plug means compatible with said A-C source, hazard preventing means comprising:
detecting means contained within said electrical appliance for detecting a hazard condition within said appliance;
interrupting means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said A-C
source from said electrical appliance in response to the detection of a hazard condition within said electrical appliance.
detecting means contained within said electrical appliance for detecting a hazard condition within said appliance;
interrupting means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said A-C
source from said electrical appliance in response to the detection of a hazard condition within said electrical appliance.
33. In combination with an electrical appliance operatively connected to an A-C source by connecting means including first and second electrical conducting means and plug means compatible with said said A-C source, hazard preventing means comprising:
detecting means contained within said electrical appliance for detecting a hazard condition within said appliance;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a hazard condition within said electrical appliance;
said interrupting means operatively disconnecting said A-C
source from said electrical appliance in response to the changing of said control means from the first state to the second state.
detecting means contained within said electrical appliance for detecting a hazard condition within said appliance;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a hazard condition within said electrical appliance;
said interrupting means operatively disconnecting said A-C
source from said electrical appliance in response to the changing of said control means from the first state to the second state.
34. In combination with an electrical appliance operatively connected to an A-C source by a cord set including a first and second electrical conductor and a plug compatible with said A-C source, a shock hazard preventing circuit comprising:
a shock hazard detector contained within said appliance;
a switching control circuit contained within said plug and including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state;
a third electrical conductor contained within said cord set and connected between said shock hazard detector and said switching control circuit;
an interrupting circuit contained within said plug and connected to said switching control circuit and including an energizing coil and a first and second switch responsive to the Flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
said silicon controlled rectifier switching from the normally non-conducting state to the shock hazard condition conducting state in response to the detection of a shock hazard condition within said electrical appliance;
said interrupting circuit operatively disconnecting said A-C
source from said electrical appliance in response to the switching of said silicon controlled rectifier from the normally non-conducting state to the conducting state.
a shock hazard detector contained within said appliance;
a switching control circuit contained within said plug and including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state;
a third electrical conductor contained within said cord set and connected between said shock hazard detector and said switching control circuit;
an interrupting circuit contained within said plug and connected to said switching control circuit and including an energizing coil and a first and second switch responsive to the Flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
said silicon controlled rectifier switching from the normally non-conducting state to the shock hazard condition conducting state in response to the detection of a shock hazard condition within said electrical appliance;
said interrupting circuit operatively disconnecting said A-C
source from said electrical appliance in response to the switching of said silicon controlled rectifier from the normally non-conducting state to the conducting state.
35. In combination with an electrical appliance operatively connected to an A-C source by a cord set including a first and second electrical conductor having a source end and an appliance end, respectively, and a plug compatible with said A-C
source, a shock hazard preventing circuit comprising:
a third electrical conductor having a source end and an appliance end and contained within said cord set;
a first and second shock hazard detection conductor having a connected end and an unconnected end, respectively, positioned in a non-contacting relationship and contained within said electrical appliance, the connected end of said first shock hazard detection conductor being connected to the appliance end of said first electrical conductor, the connected end of said second shock hazard detection conductor being connected to the appliance end of said third electrical conductor, and the unconnected ends of said first and second shock hazard detection conductors being maintained in a spaced-apart relationship;
an interrupting circuit contained within said plug and including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit contained within said plug and including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operatively connected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected ends of said first and second shock hazard detection conductors provides an electrically conductive path between said first and second shock hazard detection conductors causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical appliance.
source, a shock hazard preventing circuit comprising:
a third electrical conductor having a source end and an appliance end and contained within said cord set;
a first and second shock hazard detection conductor having a connected end and an unconnected end, respectively, positioned in a non-contacting relationship and contained within said electrical appliance, the connected end of said first shock hazard detection conductor being connected to the appliance end of said first electrical conductor, the connected end of said second shock hazard detection conductor being connected to the appliance end of said third electrical conductor, and the unconnected ends of said first and second shock hazard detection conductors being maintained in a spaced-apart relationship;
an interrupting circuit contained within said plug and including an energizing coil and a first and second switch responsive to the flow of current through said energizing coil, said first switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said first electrical conductor, and said second switch being operable between a normally closed position and a shock hazard condition open position and connected in-line with said second electrical conductor;
a switching control circuit contained within said plug and including a silicon controlled rectifier operable between a normally non-conducting state and a shock hazard condition conducting state, the gate of said silicon controlled rectifier being operatively connected to the source end of said third electrical conductor, the cathode of said silicon controlled rectifier being connected to the source end of said second electrical conductor, the anode of said silicon controlled rectifier being connected to one end of said energizing coil, and the other end of said energizing coil being connected to said first electrical conductor;
such that the immersion in water of the unconnected ends of said first and second shock hazard detection conductors provides an electrically conductive path between said first and second shock hazard detection conductors causing said A-C source to be operatively connected to the gate of said silicon controlled rectifier resulting in the switching of said silicon controlled rectifier from the normally non-conducting state to the shock hazard condition conducting state thereby providing a path for current to flow through said energizing coil and causing said first and second switches to switch from the normally closed position to the shock hazard condition open position and thus operatively disconnecting said A-C source from said electrical appliance.
36. The combination recited in claim 35 further comprising:
a first resistor connected in series between the gate or said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
a first resistor connected in series between the gate or said silicon controlled rectifier and the source end of said third electrical conductor; and a diode circuit connected between the gate and cathode of said silicon controlled rectifier.
37. The combination recited in claim 36 further comprising:
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the appliance end of said first electrical conductor and the appliance end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between the connected end of said second shock hazard detection conductor and the appliance end of said third electrical conductor.
a charging capacitor connected between the gate and cathode of said silicon controlled rectifier;
a first charging circuit connected between the appliance end of said first electrical conductor and the appliance end of said third electrical conductor;
a second charging circuit connected between the source end of said first electrical conductor and the gate of said silicon controlled rectifier; and a first diode connected in series between the connected end of said second shock hazard detection conductor and the appliance end of said third electrical conductor.
38. The combination recited in claim 37 wherein said diode circuit comprises a zener diode connected in series with a second diode, the anode of said zener diode being operatively connected to the gate of said silicon controlled rectifier, and the anode of said second diode being operatively connected to the cathode of said silicon controlled rectifier.
39. The combination recited in claim 38 wherein:
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the appliance end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
said first charging circuit comprises a first charging resistor connected in series with a first charging diode, the cathode of said first charging diode being operatively connected to the appliance end of said first electrical conductor; and said second charging circuit comprises a second charging resistor connected in series with a second charging diode, the cathode of said second charging diode being operatively connected to the gate of said silicon controlled rectifier.
40. The combination recited in claim 39 wherein said first charging circuit and said first diode are contained within said electrical appliance.
41. The combination recited in claim 40 wherein said electrical appliance is a hair dryer.
42. The combination recited in claim 41 further including a test circuit operatively connected between said first and second shock hazard detection conductors and comprising a second resistor in series with a normally open switch.
43. The combination recited in claim 42 wherein said second diode comprises a light-emitting-diode.
44. The combination recited in claim 43 wherein the value of said second charging resistor is at least ten times the value of said first charging resistor.
45. In combination with a hair dryer operatively connected to an A-C source by connecting means including first and second electrical conducting means and plug means compatible with said A-C source, hazard preventing means comprising:
detecting means contained within said hair dryer for detecting a hazard condition within said hair dryer;
interrupting means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the detection of a hazard condition within said hair dryer.
detecting means contained within said hair dryer for detecting a hazard condition within said hair dryer;
interrupting means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said interrupting means;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the detection of a hazard condition within said hair dryer.
46. In combination with a hair dryer operatively connected to an A-C source by connecting means including first and second electrical conducting means and plug means compatible with said A-C source, shock hazard preventing means comprising:
detecting means contained within said hair dryer for detecting a shock hazard condition within said hair dryer;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a shock hazard condition within said hair dryer;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the chaning of said control means from the first state to the second state.
detecting means contained within said hair dryer for detecting a shock hazard condition within said hair dryer;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a shock hazard condition within said hair dryer;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the chaning of said control means from the first state to the second state.
47. In combination with a hair dryer operatively connected to an A-C source by connecting means including first and second electrical conducting means and plug means compatible with said A-C source, shock hazard preventing means comprising:
immersion detecting means contained within said hair dryer for detecting a water-related shock hazard condition within said hair dryer;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said immersion detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a water-related shock hazard condition within said hair dryer;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the changing of said control means from the first state to the second state.
immersion detecting means contained within said hair dryer for detecting a water-related shock hazard condition within said hair dryer;
control means contained within said plug means;
third electrical conducting means contained within said connecting means and connected between said immersion detecting means and said control means;
interrupting means contained within said plug means and connected to said control means;
said control means changing from a first state to a second state in response to the detection of a water-related shock hazard condition within said hair dryer;
said interrupting means operatively disconnecting said A-C
source from said hair dryer in response to the changing of said control means from the first state to the second state.
48. The combination recited in claim 47 wherein said immersion detecting means comprises a pair of shock hazard detection conductors maintained in a non-contacting relationship, one of said pair of shock hazard detection conductors being operatively connected at one end to said A-C source and the other of said pair of shock hazard detection conductors being operatively connected at one end to said third electrical conducting means, and the other ends of said shock hazard detection conductors being maintained in a spaced-apart relationship.
49. The combination recited in claim 47 wherein said immersion detecting means comprises a shock hazard detection conductor maintained in a non-contacting relationship with a heating element of said hair dryer, one end of said shock hazard detection conductor being operatively connected to said A-C
source and the other end thereof being unconnected, and said heating element being connected to said third electrical conducting means.
source and the other end thereof being unconnected, and said heating element being connected to said third electrical conducting means.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US55826083A | 1983-12-05 | 1983-12-05 | |
| US558,260 | 1990-07-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1213665A true CA1213665A (en) | 1986-11-04 |
Family
ID=24228834
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000459278A Expired CA1213665A (en) | 1983-12-05 | 1984-07-19 | Shock hazard protection system |
Country Status (4)
| Country | Link |
|---|---|
| BR (1) | BR8407200A (en) |
| CA (1) | CA1213665A (en) |
| PH (1) | PH24839A (en) |
| ZA (1) | ZA849475B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4823225A (en) * | 1987-08-18 | 1989-04-18 | Associated Mills Inc. | Bipolar immersion detection circuit interrupter |
-
1984
- 1984-07-19 CA CA000459278A patent/CA1213665A/en not_active Expired
- 1984-12-04 PH PH31526A patent/PH24839A/en unknown
- 1984-12-05 ZA ZA849475A patent/ZA849475B/en unknown
- 1984-12-05 BR BR8407200A patent/BR8407200A/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4823225A (en) * | 1987-08-18 | 1989-04-18 | Associated Mills Inc. | Bipolar immersion detection circuit interrupter |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA849475B (en) | 1985-07-31 |
| PH24839A (en) | 1990-10-30 |
| BR8407200A (en) | 1985-11-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |