US3456230A - Electrical switch apparatus - Google Patents

Description

July 15,1969 a. H MATTHEWS T AL ELECTRICAL SWITCH APPARATUS Original Filed Aug. 23, 1965 5 Sheets-Sheet 1 July 15; 1-969, 5 a. H. MATTHEWS ET-AL 3,456,230

ELECTRICAL SWITCH APPARATUS Original Filed Aug. 2a, 1965 s Sheets-Sheet 2 July 15, 1969 a. H. MATTHEWS ET 3,456,230

ELECTRICAL SWl'lCI-I APPARATUS Original Filed Aug. 23, 1965 5 Sheets-Sheet 5 United States Patent US. Cl. 338--200 3 Claims ABSTRACT OF THE DISCLOSURE A combination electric switch and resistor speed control is used to regulate the speed of a power tool. An activating trigger is slidable on an insulative base for switching a resistor in the circuit with the tool motor and selectively decreasing the amount of resistance in the circuit as the trigger is depressed. The resistance element and switching contacts are fixed to a surface of the trigger and the wiper means is fixed to the support.

This application is a division of Ser. No. 481,564 filed Aug. 23, 1965 and now Patent No. 3,389,365 issued June 18, 1968.

This invention relates to electrical switch apparatus which has a movable switch contact assembly that includes a slidable bridging switch contact operable between bridging and non-bridging positions to connect and disconnect respectively, a source of electrical energy to a circuit input, and a second contact assembly which includes a rheostat assembly having a slidably actuated rheostat element operable to adjust said rheostat and regulate the magnitude of electrical energy to said circuit in ut.

it is therefore one of the objects of the present invention to provide electrical switch apparatus of the type above defined, and further which can be miniaturized in its structure so that it can be readily inserted into the housing of a portable tool such as an electric drill, saw or the like and which may be operable by the conventional finger actuated trigger of said tool to control the speed of the drive motor of said tool.

Additional objects and advantages of the electrical switch apparatus of the present invention will be apparent to one skilled in the art to which it pertains and upon reference to several preferred embodiments thereof as are described herein and illustrated in the accompanying drawings wherein:

FIG. 1 is a side view of the electrical switch apparatus of the present invention disposed in its operative position within the handle of a portable electric tool or the like;

FIG. 2 is an end view looking in the direction generally indicated by the arrows 2-2 shown in FIG. 1;

FIG. 3 is a plan view of the electrical switch apparatus removed from its tool housing;

FIG. 4 is a plan view taken 44 shown in FIG. 1;

FIG. 5 is a sectional view taken approximately on the plane as indicated by the lines 5-5 shown in FIG. 1;

FIG. 6 is a sectional view taken approximately on the line 6-6, as shown in FIG. 1;

FIG. 7 is a schematic wiring diagram of a typical electrical control circuit of an electrical portable tool or the like and incorporating the switch apparatus of the present invention;

FIG. 8 is a longitudinal sectional view taken approximately on the line 8-8 shown in FIG. 2;

FIG. 9 is a similar longitudinal section taken on line 9-.-9 of FIG. 2;

- FIG. 10 is a longitudinal sectional view similar to FIG.

approximately on the line 3,456,230 Patented July 15, 1969 8 but with the movable rheostat actuating element shown in an intermediate position with respect to the fixed or stationary rheostat element;

FIG. 11 is a longitudinal sectional view similar to FIG. 9 and showing the electrical switch bridging member in a first bridging position with respect to the fixed or stationary switch contacts and occurring at the instant the rheostat actuating element is moved to the FIG. 10 position;

FIGS. 12 and 13 are longitudinal sectional views similar respectively to FIGS. 10 and 11, but with the rheostat actuating element and bridging switch contact of the movable contact assembly in their fully actuated position;

FIG. 14 is a fragmentary perspective view of the rheostat assembly;

FIG. 15 is a plan view of a second embodiment of switch housing assembly and showing the stationary or fixed switch and rheostat elements of said assembly;

FIG. 16 is a plan view of the movable switch'contact assembly incorporated in the second embodiment of switch apparatus of the present invention;

FIG. 17 is a longitudinal sectional view of the modified rheostat assembly shown in its off position;

FIG. 18 is a view similar to FIG. 17 but with the movable rheostat element moved to an intermediate position; and,

FIG. 19 is a view also similar to FIG. 17 but with the movable rheostat element moved to its full on position.

The electrical switch apparatus as herein disclosed is especially designed to be utilized with a motor control circuit for varying the speed of an electrical series motor of the type used in a portable electric tool such as a drill, saw or the like and is operable to provide a variable magnitude of electrical energy to said motor.

Referring momentarily to FIG. 7, a typical motor control circuit is schematically illustrated and shows a series motor with its armature and field connected in series with each other and across line conductors L and L to which is applied a source of alternating current voltage such as V. AC.

The electrical switch apparatus of the present invention as shown in its entirety at S is connected in series in either line L, or L For purposes of identification the switch assembly is provided with a pair of output leads L L, which connect respectively to line conductor L and to one side of the motor armature.

Likewise, as will be hereinafter more clearly described, the switch assembly is of such electrical configuration as to be incorporated into a plurality of motor control circuits. For example, as shown in FIG. 7 herein the bridging contact 33 may be connected to the movable rheostat element 62 by connecting terminal. points A and A together to enable the instant switch assembly to be used in the FIG. 7 configuration of motor control circuit. Likewise, by connecting terminal points A and A together in the manner shown in FIG. 7 the movable bridging contact 42 is also connected serially into the circuit eifective to control the application of electrical energy to said circuit and motor. Likewise, for use of the instant switch assembly in a motor control circuit of the type that is disclosed in copending application Ser. No. 354,957, the terminal points A and A are connected respectively to the base 0 of the SCRIS and to the conductor 22 of the circuit disclosed therein. As will be also obvious hereinafter, the electrical switch apparatus may be readily applicable to other configurations of motor control circuitry not herein specifically referred to.

With reference now directed to FIG. 1, the electrical switch apparatus of the present invention, as identified at 10, is sufficiently miniaturized so as to enable the same to be readily inserted into the housing of a portable hand tool 11 such as an electric drill, saw or the like, said apparatus having a somewhat rectangular housing 12 formed preferably of a plastic material or the like in which the switch elements are disposed. The housing 12 is seen to be suitably mounted in the handle part 110! of the tool housing, the usual trigger 13 extending outwardly therefrom and actuatable by the finger of the operator in the normal manner. By squeezing the trigger 13, the movable actuator 15 of the switch apparatus is slidably actuated as will be hereinafter described so as to connect and vary simultaneously the magnitude of electrical energy to the tool motor effective to vary its speed.

One embodiment of switch apparatus of the present invention is illustrated in FIGS. 1-6 and 8-14 and is seen to include the aforementioned housing 12 of rectangular configuration upon which is slidably mounted the movable actuator 15 which is in the form of a bar and which may be preferably integrally formed with the aforementioned tool trigger 13.

As best seen in FIGS. 1 and 2, the slide bar 15 is mounted on top of the housing 12, being secured to the latter as to be reversibly slidably movable longitudinally thereover by an inverted U-shaped clamp 17 which as seen in FIG. 2 has inwardly opposed fingers 19 provided at the ends thereof and which engage the switch housing 12 at recesses 20 located at the ends thereof being thus elfective to securely fasten said slide bar 15 thereto.

As seen in FIG. 8, the housing 12 is of rectangular configuration having upstanding end and side walls 22 and 23 respectively, preferably integrally formed with the housing base 24 to thereby define an open-ended boxshaped container having a chamber 25 of similar configuration formed therein.

A switch plate identified at 30 is disposed within the upper open end of the housing 12 being preferably slightly smaller in its dimensions so as to substantially completely close the housing chamber 25. The switch plate 30, as best seen in FIG. 5, has a set of fixed or stationary switch contacts 32, 33 and 34 mounted on its upper surface 30a which are secured to said plate in longitudinal spaced relation to each other. Spaced laterally therefrom a narrow elongated rheostat bar as identified at .36 is mounted on its one longitudinal edge on said plate and extends longitudinally therealong in parallel spaced relation to said contacts.

As seen in FIGS. and 9, the set of switch contacts 32, 33 and 34 project upwardly above the surface 30a of the switch plate 30, fixed contact 32 having a rectangular fiat portion as indicated at 3211 and an upwardly projecting nipple-shaped camming portion 32b integrally formed on its end closely adjacent to contact 33. Switch contacts 33 and 34 in turn are each preferably circular in configuration.

As seen in FIGS. 5, 8 and 14, the upright rheostat bar 36 is composed of a suitable non-conducting base, as indicated at 36a, such as Bakelite and which is covered on its one side surface with two carbon tracks 37a and 37b forming a preselected value of resistance for example on the order of 100,000 ohms, the value depending upon the value of the components in the motor circuit to which it is connected. Track 37b on the inner end thereof connects to an intermediate metallic conductor plate 38. The opposite or remote end of the carbon track 37a is seen to connect with a similar metallic conductor plate 39. As best seen in FIGS. and 14, the carbon track 37a is terminated at its inner end at 370 to space said track from the conductor plate 38.

The slide bar 15, which is slidably mounted on top of the switch housing 12, carries a pair of contacts which are movable therewith into selective engagement with the stationary contacts 32, 33, 34 and the rheostat bar 36.

As best seen in FIG. 9, the slide bar is formed with a recess as indicated at 40 into which is disposed a metallic contact 42 being somewhat of inverted U- shaped configuration, coil spring 43 being disposed in 4 blind hole 45 formed in said bar 15 and effective to bias said contact 42 toward the switch plate 30.

Referring now to FIGS. 9, 11, and 13, by pressing the trigger 13 the slide bar 15 is slidable over the housing 12 from left to right causing the contact 42 to move from its FIG. 9 position thence to a plurality of intermediate positions as represented in its FIG. 11 position and finally to its FIG. 13 position.

As shown in FIG. 9, the contact 42 has a contacting end portion thereof as shown at 42a which, in the FIG. 9 or off position of the switch assembly has its bottom edge riding upon the top of the camming portion 32b of the fixed contact 32, being urged into contact therewith by the coil spring 43.

Said end portion 42a is formed with an angular wall 420 which extends outwardly and rearwardly therefrom to terminate with the main stem portion of the body of the contact 42.

The angular wall 420 of said movable contact 42 and the upwardly extending camming portion 320: of contact 32 are each of such related configuration that as the switch bar 15 is moved from its FIG. 9 toward its FIG. 11 position, said contact 42 is cammed so that its forward contact portion 42a is dropped directly onto the fixed contact 33 prior to and without any initial wiping action occurring between the said contacts 42 and 33.

With the slide bar 15 moved toward its FIG. 11 position contacts 32 and 33 are connected to each other by movable contact 42, said switch elements thus defining a closed contact or switch position for said assembly.

The closing of switch contacts 32, 33- by contact 42 is shown schematically in FIG. 7 to connect line conductor L to the switch apparatus S, and with the conductors A, and A connected together, said line conductor L is also connected to the adjustable element of the rheostat.

Thereafter, with the trigger 13 being additionally moved to the right to its FIG. 13 position, the contact 42 is moved therewith, its tail portion sliding along the rectangular fiat section 32a of the contact 32, whereupon its forward portion 42a rides over and partially onto the top of contact 34 thus bridging said contacts 33, 34 and connecting the same with contact 32.

The contacts 33, 34 being connected to each other and to the contact 32 by movable contact 42 is also shown schematically in FIG. 7 to connect line conductor L directly to the armature of the motor thus bypassing the rheostat assembly.

With reference directed now to FIGS. '8, 10 and 12, the slide bar 15 is also formed with a second rectangularshaped recess 60 which is spaced laterally from the recess 40. A contact 62 is disposed in said recess 60 and is formed of a suitable conductive material and has a plurality of depending fingers 63-67 disposed as best seen in FIG. 14 in longitudinal spaced relation along and projecting outwardly from the base of said contact.

The contact 62 is intended to engage the rheostat bar 36 being slidably actuated therealong so as to connect predetermined portions of the carbon tracks 37a and 37b thereof to the energy source being thereby operable as a variable resistance connected in series with the line conductor L effective to vary the magnitude of electrical energy delivered to the connected motor.

As seen in FIG. 14, the contact 62 is mounted on the top longitudinal edge 36a of the rheostat bar 36 whereby the end fingers 63 and 67 extend over and engage the carbon tracks 37b and 37a respectively, the centrally disposed finger 65 extending over and engaging the opposite side surface of said rheostat bar, the material forming said contact 62 being preferably resilient in characteristic whereby said engaging fingers act to resiliently hold the contact 62 thereon.

To provide additional stability to the movable contact 62 as it slides along the upper edge 36a of the bar 36, the intermediate fingers 64, 66 of said contact are seen to be shorter in their respective length so as to slidably engage the upper edge 36a of said bar.

As best seen in FIGS. 8 and 9, a connector bar 68 extends transversely across the underside of switch plate 30 and connects contact 34 and conductor plate 39 together.

With the slide bar 15 disposed in its FIG. 8 position corresponding to the off position for said switch the contact fingers 63 and 67 are in engagement with the carbon tracks 37a and 37b whereby a predetermined maximum value of resistance of said rheostat is connected serially in circuit with the terminal point A and line conductor L As the slide bar 15 is thereafter moved to the right by pressing upon the trigger '13 the contact 62 is slidably moved along the carbon tracks 37a and 37b simultaneously with the movement of bridging contact 42. As the slide bar 15 is moved to the right progressively toward its FIG. 10 and 12 positions, the value of the rheostat resistance is likewise progressively reduced until said slide bar is moved to its FIG. 12 position at which the contact fingers 63 and 67 engage the conductor plates 38 and 39 respectively, thus, connecting contacts 62 directly across the terminal point A and line conductor L to thereby short out the carbon tracks 37b, 37a whereby line conductor L of the motor circuit may be connected directly to the one side of the motor armature.

At this instant, as is aforementioned and as seen in FIG. 13, the trailing end of bridging contact 42 is in em gagement with the fixed contact 32 and its opposite end is in engagement with both contacts 33 and 34 thereby connecting the line conductor L through closed switch contacts 42, 34 to conductor L and to said one side of the motor armature to provide a. second conductor path to said armature.

Upon the operator releasing the trigger 13, the coil spring 75 interposed between the slide bar 15 and the end wall 17a of the bracket 17 as seen in FIG. 9 is operative to spring said bar and trigger to its oif position as shown in FIGS. 8 and 9. The instant switch apparatus is therefore seen to provide a first bridging switch assembly 32, 33, 34 and 42 which is operable to connect and disconnect respectively a source of electrical energy L to a circuit input (motor circuit) and a second variable rheostat assembly operable to vary the magnitude of electrical energy to said circuit input.

Further, in the instant switch assembly the actuation of the bridging switch (movable contact 42) and rheostat (rheostat contact 62) are carried by the slide bar 15 and slidably actuated simultaneously.

In FIGS. 15-19 a second embodiment of switch apparatus of the present invention is herein disclosed, and differs from the previous switch structure in the rheostat assembly.

With reference directed particularly to FIGS. 15 and 17, the switch plate 30' has the fixed or stationary contacts 32, 33 and 34 mounted therein and which function with the bridging or movable switch contact 42 in the same manner as in the previous switch assembly.

The modified rheostat assembly comprises a pair of metallic spring- like fingers 80, 81 securely fastened at one end to the switch plate 30 in longitudinal spaced relation to each other and extending angularly upwardly therefrom. Finger 80 is connected to one end of conductor A and [finger '81 is attached to bracket 68 to which is connected one end of conductor L As in the previous switch assembly, when using the switch apparatus in the motor control circuit as shown in FIG. 7, conductors A and A are connected together to thereby connect the stationary contact 33, the movable bridging contact 42 and finger 80 to each other.

Likewise, when using the switch apparatus in conjunction with the motor control circuit of the type disclosed in the aforesaid copending application Ser. No. 354,957 the conductors A and A are connected to fixed contact point d and to conductor 22, respectively.

The slide bar '15 is formed with a recess 85 spaced laterally from the recess 40 and extending generally longitudinally along said bar in parallel spaced relation to said recess 40.

A rheostat bar 87 is disposed in the recess '85, being secured by any suitable means such as adhesive to the top wall 89 thereof.

As seen in FIG. 16, the underside of the rheostat bar 87 is provided with a somewhat L-shaped copper bus bar 91 which is disposed adjacent a somewhat similarly shaped carbon track 92 the surfaces of said bus bar and carbon track being preferably coplanar.

A flat spacer member 95 is seen to have a pair of slots 97 and 98 formed on opposite ends and adjacent the opposed longitudinal edges thereof and into which the curved ends of the fingers and 81 are disposed.

The spaced member 95 is preferably of such width as to enable it to be inserted into the recess and freely slidably movable therethrough.

With the slide bar 15 mounted over the switch plate 30', the fingers 80 and 81 project upwardly into recess 85 and are pressed against the rheostat bar 87.

As seen in FIGS. 16 and 17, with the slide bar 15 and trigger 13 in the off position for the switch apparatus, the curved end of finger 80 is intended to engage the carbon track 92 at approximately point b and in like manner at point a by finger 81. At this switch position the resistance of the carbon track 92 between points a and b represents the rheostat resistance connected between line conductors L and L in the motor control circuit shown in FIG. 7.

With the trigger 13 further depressed to a position such as illustrated in FIG. 18, whereby the fingers 80 and 81 engage the carbon track 92 at points at and b' respectively the resistance between said points a and b' has been progressively reduced to thereby provide a larger magnitude of electrical energy to the motor effective to increase the speed thereof to, for example, half speed.

As the trigger 13 is moved to its FIG. 19 position, the fingers 80 and 81 engage the copper bus bar 91 at points x and y respectively, whereby the rheostat resistance is zero and maximum energy is available to the motor to enable the same to attain full speed.

Having thus described several preferred embodiments of switch apparatus of the present invention it will be realized that the same is susceptible to various modifications, combinations and arrangements of parts thereof without departing from the inventive concepts as are defined in the claims.

What is claimed is:

1. In an electric switch, in combination, a switch base, at least a pair of stationary contacts mounted on said base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement with at least one of said stationary contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising resistance means carried by said actuator means, contact means connectable with said resistance means, terminal means on said switch base connecting with said contact means, and said actuator means while slidably moving over said base being operable to move said resistance means over said contact means effective to provide a plurality of resistance values between said terminal means.

2. In an electric switch, in combination, a switch base, at least a pair of stationary contacts mounted on said base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement with at least one of said stationary contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising re over said base to move said resistance means with respect to each said contacts effective to provide a plurality of resistance values between said terminals.

3. In an electric switch, in combination, a switch base, at least a pair of stationary contacts mounted on said base in spaced relation to each other, an electrically conductive bridging contact having contacting ends, actuator means supporting said bridging contact and mounted for sliding movement over said base between a non-bridging position where said bridging contact is out of engagement with at least one of said stationary 20 A. T. GRIMLEY, Assistant Examiner contacts and a bridging position where the contacting ends of said bridging contact engage said stationary contacts, respectively, a rheostat assembly comprising an elongated resistor element carried on said actuator means, a pair of terminals mounted on said base, a flexible cond-uctive contact secured to each terminal extending outwardly therefrom and engageable with said resistor element, and said actuator means being slidably movable over said base to move said resistor element with respect to each said contacts effective to provide a plurality of resistance values between said terminals.

References Cited UNITED STATES PATENTS 3,327,196 6/1967 Sahrbacker 318-345 1 3,328,613 6/1967 Gawron 310-68 X 3,329,842 7/1967 Brown 310-50 3,373,396 3/1968 Yungblut et a1. 338-183 2,740,029 3/1956 Kueser et a1. 3,381,254 4/1968 Campbell 338-179 2,999,994 9/1961 Bourns et a1. 338-183 X LEWIS H. MYERS, Primary Examiner US. Cl. X.R.

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