US3569887A

US3569887A - Time delay switch

Info

Publication number: US3569887A
Application number: US865014A
Authority: US
Inventors: Horace D Brown
Original assignee: MONTEC CORP
Current assignee: MONTEC CORP
Priority date: 1969-10-09
Filing date: 1969-10-09
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09

Abstract

A switch having a bimetal latch for locking a resilient contact in a closed circuit position, and a heating coil for activation of the latch to release the contact. An integral ambient temperature responsive switch energizes the coil periodically to stabilize the temperature of the bimetal.

Description

United States Patent [72] Inventor [5 6] References Cited UNITED STATES PATENTS 3,123,686 3/1964 Leichsenrin Horace D. Brown Miami, Fla. [21] AppLNo. 865,014

337/127(X) 337/56(X) 337/92(X) 337/75(X) 337/75(X) 3,087,146 4/1963 Boudouris......... 2,894,098 7/1959 Ludwig.......

2,584,673 2/1952 Cole.......

2,558,908 7/1951 Paige.......... 1,952,040 3/1934 Frank et [22] Filed Oct. 9, 1969 [45] Patented Mar. 9, 1971 [73] Assignee Montec Corporation Miami, Fla.

[54] TIME DELAY SWITCH Primary Examiner-Bernard A. Gilheany 7 Claims, 4 Drawing g Assistant Examiner-Dewitt M. Morgan Mt. a

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[50] Field 337/51, 55, for activation of the latch to release the contact. An in tegral ambient temperature responsive switch energizes the coil periodically to stabilize the temperature of the bimetal.

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, 7 e 9 a m I V w i ivlem 2 i I llW- MA a @554? uuuuuflm mmV/d a V: l m M 4M38 B 2 TIME DELAY SWITCH Numerous time delay devices have been patented which utilize the heat responsive flexing motion of a bimetal element to open an electric circuit. A coil of resistence wire is commonly used in these switches as a source of heat for flexing the bimetal. The means normally provided for manual operation of the switch do not function directly to open the circuit, but rather to close a second switch which connects the heating coil to a source of current. As a result, current flows through the coil and generates heat which is transferred to the bimetal, causing it to bend. The time required for the bimetal to heat and flex sufficiently to deactivate the switch provides a delayed action interval after the switch is manually turned off.

The previously patented switches of this type have a comrnon disadvantage: the temperature of the bimetal varies in conformity with the environmental temperature, which, in some operating circumstances, may range from sub zero winter to extremely hot summer conditions. Consequently, the bimetal is almost always in some degree of stress, depending on the temperature, and is thereby preflexed to some extent at the instant operating current is applied to the heating coil. As a result, the amount of flexure needed to operate the switch varies, and therefore the time required for heating is inconsistent.

The main object of the present invention is to provide a time delay switch which is consistent in the length of its time delay interval, and one which is unaffected by its environmental temperature.

A further object is to provide a time delay switch which is of simple structure, and one which is both foolproof in operation and economically feasible.

The objects and advantages of this improvement will be fully apparent from the following specification when taken in conjunction with the annexed drawing, in which:

FIG. l is a sectional side view showing the switch in its closed circuit position.

FIG. 2 is taken on the same plane as FIG. 1 and shows the toggle in its OFF position, but with the switch contacts locked in the closed circuit position by the time delay device.

FIG. 3 shows the toggle in its overriding position manually disengaging the delay device.

FIG. 4 is a top view with the cover plate and toggle removed.

Referring to the drawing in greater detail, in which like numerals indicate like parts throughout the several views, the numetal 24, FIG. 1, represents a nonconductive plastic case with its sidewall 37 partly cutaway to reveal the arrangement of the switch components. A section of the wall 37 is shown, illustrating a slotted opening 25, into which the switch terminal 22 is rigidly fitted. Similar slotted openings 26and 27 are provided in the two ends of case 24, into which

terminals

13 and 19 are rigidly fitted.

Terminal screws

14, 6, and 21, are pro vided in the

terminals

13, 22, and I9, respectively, for conv enience in connecting external circuit wires to the switch.

The terminal strip 19 bends 90, ,32, and extends horizontally in case 24 to engage the latch 34 on the bimetal element 1. The horizontal portion of terminal strip 19 is twisted 90, 17, resulting in the section 18 being flexible vertically, which permits the blade to pivot from its normally spring biased open circuit position shown in FIG. 3 to the closed circuit position shown in FIGS. I and 2.

The shaft 31 of toggle 28 is cradled in the two bearings 38 in case 24, and permits said toggle to pivot from the OFF position illustrated in FIG. 2 to the ON position shown in FIG. 1. A cam 29 on toggle 28 engages blade 15. When said toggle is manually rotated to the ON position, F IG.' 1, cam 29 rotates against blade 15 and forces it downward, causing extension 16 to electrically engage contact 23.

The terminal 13 is rigidly supported in the slotted opening 26 in case 24, and is riveted to a nonconductive terminal mounting block 10 within said case. The bimetal element I is also riveted at one end 11 to the mounting block 10. A latch 34 is an integral part of the bimetal element 1, and is situated in the path of movement of the end 7 of blade 15.

A coil of resistence wire 2 encircles the bimetal element 1, and is connected at one end 12 to terminal 13. The opposite end 33 of said coil is connected to said bimetal at point 33. When end 7 engages latch 34, an electric circuit is completed from terminal 19, through coil 2, to terminal 13, and the resulting current flowing through said coil generates heat which causes the bimetal l to flex away from the end 7.

A cover plate 30 is shown, FIG. I, having conventional mounting ends 35, for installation in standard wall receptacle boxes.

To turn the switch on, the toggle 28 is manually moved from the OFF position shown in FIG. 2 to the ON position of FIG. 1. Movement of said toggle to the ON position rotates cam 29 against blade 15, forcing said blade downward, thereby causing extension 16 to electrically engage contact 23. Engagementof contact 16 with contact 23 completes an electric circuit between terminal 19 and terminal 22. As blade' 15 moves to the closed circuit position, end 7 moves downward against the angular surface 4 on latch 34 and displaces said latch from the path of movement of said end. When blade 15 reaches its fully closed positiori, FIG I, the bimetal l springs back to its normal position and places the detent 3 in the return path of movement of the end 7,. In the position of FIG. 1, cam 29 holds the spring biased blade 15 down far enough so that the end 7 does not engage the detent 3.

To turn the switch off, the toggle 28 is manually moved to the OFF position visible in FIG. 2. Movement of said toggle to the OFF position rotates cam 29 away from the blade 15 and permits said blade to pivot upward far enough to bring end 7 into engagement with the detent 3 on latch 34. Electrical continuity is established between terminal 19 and terminal 13 via engagement of end 7 with detent 3, causing current to flow through coil-2. The bimetal 1 flexes away from the end 7 as a result of heat generated by the current flowing through coil 2. A sliding contact is maintained between end 7 and detent 3 as the latch 34 is drawn away from the end 7 by the flexing of bimetal I. When sufficient heat has been generated to flex the bimetal l to the position shown in FIG. 3, the spring tension stored in section 18 of terminal strip I9 will cause the blade I5 to spring back to its normal open circuit position, also shown in FIG. 3. An interval of time elapses between the instant when the toggle 28 is manually moved to the OFF position and the instant when the blade 15 is released by latch 34. The length of the delay interval is determined by the time required for coil 2 to generate the necessary heat for flexing the bimetal element 1, and the degree of flexure needed to actuate the switch depends on the length of the detent 3. The time delay period, therefore, may be increased or decreased by a corresponding change in the length of the detent 3, or by altering the amperage through the coil 2.

Bimetal is commonly manufactured to various specifications for operation within many different environmental temperature conditions. By way of example only, we shall consider the bimetal element 1 shown in this disclosure to be designed for flexure within the temperature range of to [30 F. The position shown in FIG. 1 corresponds to a temperature of 101, and illustrates an open circuit between the end 7 and the contact surface 8 on latch 34. Assuming the environmental temperature of this example to be less than 100, the bimetal 1 will cool down and flex toward the end 7, causing contact surface 8 to engage end 7 of blade 15. The circuit thus completed by the engagement of blade 15 with latch 34 causes current to flow through coil 2 and generate heat, which raises the temperature of bimetal 1. As a result, the bimetal 1 will flex away from blade 15 and break connection between latch 34 and end 7, and thereby interrupt the current flow through coil 2. When the current flow ceases, coil 2 and bimetal 1 immediately begin to cool and flex again toward end 7 to reestablish connection between latch 34 and blade 15.

The natural cooling and flexing of the bimetal element 1 and the consequent energization of the heating coil 2 prevents the temperature of bimetal 1 from falling below 100, and the artificial heating and reversed flexing of bimetal 1 caused by energization of coil 2, followed by the automatic breaking of 5 connection between end 7 and latch 34, prevents the temperature of bimetal 1 from rising above 101. And since the environmental temperature of this example is less than 100, the bimetal 1 is kept in a preheated and preflexed state.

Because of the constant temperature maintained in the bimetal l, and the fixed length of the detent 3, the required heating and flexing time for bimetal 1 to move from the position shown in FIG. 2 to the fully flexed position demonstrated in FIG. 3, and thereby release blade 15, will always be the same, regardless of variations in the environmental temperature.

The delay period may be avoided and the switch may be instantly turned off if desired. To accomplish this the toggle 28 must be manually moved to the overriding position shown in F IG. 3. The projection 9 is shown in this view engaging the end 36 of bimetal element 1. Rotation of the toggle 28 to this position swings the projection 9 against end 36 and forces bimetal element 1 away from the end 7 of blade 15, and thereby releases the spring-biased blade to return to the open circuit position.

While only a preferred embodiment of the present invention has been shown and described, other embodiments are contemplated and numerous changes and modifications may be made herein without departing from the spirit of the invention as set forth in the following claims.

Iclaim:

1. A switch mechanism comprising: support means, fixed and movable contact means secured relative to said support means, an operator means secured relative to said support means and having a first position wherein said operator means holds said contact means in engagement with each other, and latch means which hold said contact means in engagement with each other for a predetermined interval of time after said operator means is moved from said first position to a second position out of engagement with said movable contact means, said latch means being thermally responsive and including heat generating means, said heat generating means being periodically energized and deenergized by the making and breaking of electrical contact between the latch means and the contact means while said operator means is in said first position whereby the latch means is kept at a constant temperature regardless of the environmental temperature where the switch is located, said heat generating means also being energized when said operator means is moved from said first position to said second position to move said latch means out of engagement with said contact means whereby said contacts disengage.

2. The switch as set forth in claim 1 wherein said latch means includes a bimetallic member secured at one of its two ends to said support means, and said heat generating means includes a heating coil secured to said bimetallic member, said coil being energized when the free end of said bimetallic member is in electrical contact with said contact means, the energization of said coil heating said bimetallic member thereby causing said bimetallic member to move out of electrical contact with said contact means and thereby deenergize said coil, the deenergization of said coil allowing said bimetallic member to cool and thereby reestablish electrical contact with said contact means.

3. The switch as set forth in claim 1 wherein said fixed contact means is secured to said support means, said movable contact means comprises an elongated resilient contact blade means one end of which is secured to said support means, said operator means including .cam means, said cam means bearing on said blade means when said operator means is in said first position thereby holding said blade means in contact with said fixed contactmeans.

4. The switch as set forth in claim 3 wherein said latch means includes a latch scoured to the free end of said bimetallic means, said latch normally disposed in the path of movement of the free end of said blade means thereby preventing said blade means from disengaging from said fixed contact means when said operator means is moved from said first position to said second position, said latch holding said blade means in engagement with said fixed contact means until said bimetallic means is heated sufficiently to move the latch out of the path of movement of the free end of said blade means.

5. The switch as set forth in claim 4 wherein said operator means has a third position, said second position being between said first position and said third position, said operator means also including a second cam means, said bimetallic member including a projection on the free end thereof, said projection engaged by said second cam means when said operator is moved from said second position to said third position thereby moving said latch out of the path of movement of the free end of said contact blade whereby said blade means disengages said fixed contact means without any time delay interval.

6. A delayed action switch mechanism comprising support means, a contact means secured to said support means, a flexible contact blade secured at one of its two ends to said support means, operator means mounted relative to said support means and movable to a first position wherein it holds the free end of said blade means in contact with said contact means, and thermally responsive latch means secured relative to said support means, said latch means holding said blade means in engagement with said contact means only when said operator means is moved to a second position out of engagement with said blade means, said latch means including heating means which is energized when said latch means is in engagement with said blade means, the energization of said heating means causing'said latch means to disengage from said blade means and thereby deenergize said heating means, upon cooling said latch means moving back into engagement with said blade means so long as said operator means is in said first position whereby the temperature of said latch means remains approximately constant regardless of the temperature of the surrounding environment prior to the movement of said operator means to said second position.

7. An electric switch mechanism comprising housing means, a contact means secured to said housing means, a resilient contact blade means secured at one of its ends in said housing means, an operator means mounted on said housing means, said operator means having a first position in engagement with said blade means whereby said blade means is held in engagement with said contact means, and thermally responsive latch means secured in said housing means, said latch means including heat generating means, said heat generating means being energized periodically by intermittent electrical contact between said blade means and said latch means when said blade means is held in engagement with said contact means by said operator means whereby said latch means is kept at a preselected temperature regardless of the temperature of the surrounding environment, said heat generating means also being energized when said operator means is moved to a second position out of engagement with said blade means thereby permitting said latch means to hold said blade means in engagement with said contact means for a time delay period.

Claims

3. The switch as set forth in claim 1 wherein said fixed contact means is secured to said support means, said movable contact means comprises an elongated resilient contact blade means one end of which is secured to said support means, said operator means including cam means, said cam means bearing on said blade means when said operator means is in said first position thereby holding said blade means in contact with said fixed contact means.

4. The switch as set forth in claim 3 wherein said latch means includes a latch secured to the free end of said bimetallic means, said latch normally disposed in the path of movement of the free end of said blade means thereby preventing said blade means from disengaging from said fixed contact means when said operator means is moved from said first position to said second position, said latch holding said blade means in engagement with said fixed contact means until said bimetallic means is heated sufficiently to move the latch out of the path of movement of the free end of said blade means.

6. A delayed action switch mechanism comprising support means, a contact means secured to said support means, a flexible contact blade secured at one of its two ends to said support means, operator means mounted relative to said support means and movable to a first position wherein it holds the free end of said blade means in contact with said contact means, and thermally responsive latch means secured relative to said support means, said latch means holding said blade means in engagement with said contact means only when said operator means is moved to a second position out of engagement with said blade means, said latch means including heating means which is energized when said latch means is in engagement with said blade means, the energization of said heating means causing said latch means to disengage from said blade means and thereby deenergize said heating means, upon cooling said latch means moving back into engagement with said blade means so long as said operator means is in said first position whereby the temperature of said latch means remains approximately constant regardless of the temperature of the surrounding environment prior to the movement of said operator means to said second position.