US3702454A

US3702454A - Ambient compensated time delay switch

Info

Publication number: US3702454A
Application number: US183513A
Authority: US
Inventors: Horace D Brown
Original assignee: MONTEC CORP
Current assignee: MONTEC CORP
Priority date: 1971-09-24
Filing date: 1971-09-24
Publication date: 1972-11-07
Anticipated expiration: 1989-11-07

Abstract

A switch having a bimetal latch for locking a movable spring contact in closed circuit with a second contact, and a heating coil for activating the latch to release the spring contact. A second bimetal element engages and opposes the bimetal latch and thereby counteracts the torque developed in the bimetal latch by changes in the ambient temperature.

Description

Ullitfld States I I i i 1151 3,702,454

Brown 1 51 Nov. 7, 1972 [s41 AMBIENT COMPENSATED TIME 3,559,140 1/1971 Brown ..337/7s DELAY SWITCH 3,496,509 2/1970 Metcalf ..337/77 x Inventor: Horace D. Brawn, Miami, Fla- LOl'CnZ X 31 Assisnee: Monm Corporation, Miami, Fla. Primary Examiner-Bernard A. Gilheany [22] Filed; Sept, 24, 1971 I Assistant Examiner-Dewitt M. Morgan [52] us. 01. .J ..337/77, 337/78, 337/81, A swim hams metal latch a mmbe 337/101 spring contact in closed circuit with a second contact, [511 1111. c1. "110111 61/013, 110111 71/16 a heating activating the release [53] n w 01 Search "337/37, 41, 56, 75 76, 77, the spring contact. A second bimetal element engages 7 7 31, 96, 99 101, 27 341, 5 and opposes the bimetal latch and thereby counteracts 37 the torque developed in the bimetal latch by changes in the ambient temperature. v

[56] References Citerl I 3Clai ms,6Drawing Flgures UNITED STATES PATENTS 3,569,887 3/1971. Brown; ..'.337/77 I VI I lmmcomsslmm DELAY'SWHEII This invention" relates tolls." Pat. No. 3,569,887. Its main object is to providea more; effective means of compensating for extreme changes inthe ambient temis adversely affected. t 4 A further object of the present" invention" isto properature, wherein the' length of the -tirne delay interval vide aydelayed' action switch of very simple structure,

v f FIG. 3 shows the relative position of the switch elementsintheON position.

- FIG; 4 is a detail view illustrating. the latching action of .the delay device after the switch has been manually turned to the OFF position. I

FIG; 5 demonstrates in anotherdetail view the overriding position bf the toggle whereby the latch is dis- A second birnetal element is riveted to-terminal block 10, in juxtaposition withbimetal blade 1. The free'end"1 =7of'bimetall5 extends and isbentat 18 to engagethe latch side of bimetal bladel. The purpose of-the bimetal element"15 will be? detailed'in the final paragraphsof this'specification. a

' A cover plate, or'mounting yolte 30 is shown, FIG. 1

I having conventionalrnountingends 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. 1 to the ON position of-FIG'. 3. Movement-of said toggleto the ONposition rotates cam 29. against spring 19 forcing said-springdownward; thereby causingextension 16 to electrically engage contact which is riveted at 5 to mounting block 10. Contact 23 is electrically connected' to terminal 22 (via means not shown) to complete an electric circuit between terminal spring 19 and terminal 22. As spring 19 moves to the closed;cir-

cuit position, end traverses the angular surface 4 on latch 34 and displaces said latch from the path of movement of said end. When the spring 19 reaches its fully closed position, FIG. 3, the ,bimetal Ispririgs back to its normal position and places latch 34 in the return path of movement :of end 7.In the fully ON position of FIG.

' cam'29 holds spring 19 down far enough so that the Placed and the delay. interval is circumvented to. in-

stantly turn the switch off.

I FIG. '6 is a detail side view of the switch elements showing the com ensating action of this invention.

Referring in greater detail to the drawing, in which like numerals indicate like parts throughout theseveral views, the numeral 24; FIG. 1", represents a nonconductive plastic case with its side will cut away to reveal the intemal arrangement .of .the switch components. The

case 24 supports three

terminals

13,22, and 19, in

slotted openings26, 25, and 27, respectively.

Binder head screws

14,6, and 21 providea'convenient means of attaching external circuit wires to the switch.

The terminal spring bends ninety degrees at 32, and extends through the case 24 to engage the latch 34 on r the bimetal blade 1. The flexible spring :19 pivots from the .open circuit position shown in FIG. '1 tothe closed circuit position visible in FIG..3.. 2

The shaft 3110f toggle 28 is cradled in the two bearings 38 in case 24, and pennits said toggle to pivot from thev position shown in FIGII to the position illustrated in FIG. 3. A cam 29 on toggle 28 engages spring 19.

The terminal 13 is rrigidly supported in the slotted opening 26 in case 24, and is riveted at 8 to a nonconend 7 "does not engage latch 34.

Totum the switch off, the toggle 28'is manually moved to the OFF position visible in FIG. 1. Cam '29 is thereby rotated. away from "spring 19, permitting said spring to pivot upward far-enough to bring .end 7 into engagement latch 34. Electrical continuity is established between: terminall9 .and terminal 13 via engagement'of end with latch 34, causing current to flow throughcoil '2. The binietal blade I flexes away from end 7 as a result of heat generated by the current flowing through coil 2. ,A sliding contact is'maintained between end 7-and latch 3.4 as said latch is drawn away from theend 7 by the flexingofblade l. When'sufficient heat has'been generatedto flex the bimetal-l to the position shown in FIG. 5, t he spring 1 9 will be ductivei terminal mounting block 10 within case.

The bimetal blade 1 is riveted at one end 1'1 to the mounting block 10, and a latch 34-is an integral partof said blade. Said latch 34 is situated in the path of movev rnent of. the end 7 on spring 19.

A coil of resistance wire 2 encircles the .bimetal 'l, and is connected at one end 12' to the terminal 13. The

opposite end 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 nonconductive sleeve 3 insulates bimetal 1 from coil 2.

released by latch and will return to the open circuit position of FIG. I. An interval of timelapses between the instant when the toggle 28 is manually moved to the OFF position and the instant when spring 19 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 blade 1 sufficiently to-remove thelatch 34 fromthe return path of movement of end 7.

Another factor, however, imposes an undesirable effect upon the-length of the delay interval: the constantly changing ambient temperature. When the surrounding temperature decreases, the bimetal blade 1 if not restrained, will flex toward the end 7, and if it is restrained from motion, it will build up force the direction of end 7 as a result of .the temperature drop.

The adverse flexure, or force build up, must first be counteracted, or overcome, before the desired directional motion can be obtained whereby the switch is actuated. Consequently, when the switch is functioning in a below normal temperature environment, the heat generated by coil 2 must first overcome the adverse torque already existing in blade 1 before its normal functionbegins. I

. To cancel the effect of this adverse flexure, a second bimetal element 15 is rigidly fixed to the terminal base at one end 36, and is oriented so that its temperature responsive flexure opposes that of bimetal l. The free end of bimetal is bent 17 to extend toward the free tion", the resulting opposite motion of the two units causes end 41 and end 18 to engage. A continued decrease in their common" temperature will serve to build up force in bothbimetal units, each one exerting force against the. other, and each unit thereby restraining the other against motion. The counteracting force of each ,bimetal unit against the other, due to the engagement of end 41 with end 18, neutralizes the pulling force that otherwise would cause the two ends of the respective bimetal units to flex away from each other.

In order to visualize the ambient temperature compensating action of this invention, let us assume that the environmental temperature is thirty degrees below zero F. When the toggle 28 is rotated to the OFF position, FIG. 4, the end '7 of spring 19 engages'latch 34, thereby energizing the coil 2. Because of the opposing stresses already developed in bimetal l and bimetal 15 by the extremely cold environment, end 18 and end 41 will be firmly pressed'together. The heat produced in bimetal l by the current flowing in coil 2 immediately begins to neutralize the torque existing in blade 1. No heat, however, is generated in bimetal 15. The counteracting pull of bimetal l5v is, therefore still present, and continues toexert itself against bimetal l. The heat generated by coil 2 functions to flexbimetal l and latch 34 in a "direction to release end -7, while the-low ambient temperature causes bimetal 15 to flex in the same direction. The continued pulling force of bimetal '15 against bimetal l], coupled with the heat flexture of bimetal 1, results in the two bimetal units bending in the same direction as shown in FIG. 6, thereby releasing end 7 to return to the open circuit position. A heat shielding sleeve 20 isolates bimetal 15 from the heat produced in coil 2.

The delay period may be avoided and the switch may be instantly turned off is desired. To accomplish this the toggle 28 must be manually moved to the overriding position shown in FIG. 5. The projection 9 is shown in this view engaging the latch 34. Rotation of toggle 28 7 4 a a pulling action against bimetal blade I. It will be obvious to anyone skilled in the art of bimetal design that a variety .of combination in bimetal types and configurations as well as the manner of cou lin the o in forces together, may be employed td pe or'm I e com pensating action described and claimed herein.

lclaim:

l. A switch mechanism comprising: supportmeans, fixed and movable contact means secured relative to said support means, anoperator means secured relative 7 said latch means being thermally responsive and having to this position swings the projection 9 against latch 34 heatgenerating means, ambient temperature responsive means secured to said support means in space relation to said latch means and engaging said latch means to counteract the adverse torque developed in said latch means by changes in the ambient temperature,

said heat generating means 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 contact means disengage.

2. A switch mechanism'comprising: support means, fixed and movablecontact 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 causessaid contact means to engage 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 saidsecond position out of engagement with said movable contact means, said latch means including a bimetal blade secured at one of its two ends to said support means and having heat generating means, a second bimetal element secured to said support meansin space relation to said bimetal blade and oriented so that its ambient temperature responsive flexure engages and opposes that of said bimetal blade and thereby counteracts the adverse forces developed in said bimetal blade by changes in the ambient temperature, said heat generating means 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 contact means disengage.

3. The switch as set forth in claim I wherein said operator means has a third position, said second position being between said first position and said third position, said operator means engaging said latch means when said-operator means is in said third-posi-

Claims

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 causes said contact means to engage each other, and latch means which hold said contact means in engagement with each other for a predetermined interval of time after said operator mans 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 having heat generating means, ambient temperature responsive means secured to said support means in space relation to said latch means and engaging said latch means to counteract the adverse torque developed in said latch means by changes in the ambient temperature, said heat generating means 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 contact means disengage.

2. 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 causes said contact means to engage 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 said second position out of engagement with said movable contact means, said latch means including a bimetal blade secured at one of its two ends to said support means and having heat generating means, a second bimetal element secured to said support means in space relation to said bimetal blade and oriented so that its ambient temperature responsive flexure engages and opposes that of said bimetal blade and thereby counteracts the adverse forces developed in said bimetal blade by changes in the ambient temperature, said heat generating means 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 contact means disengage.

3. The switch as set forth in claim 1 wherein said operator means has a third position, said second position being between said first position and said third position, said operator means engaging said latch means when said operator means is in said third position to displace said latch means from the path of movement of said movable contact means to permit said contact means to return to the open circuit position without the delay interval.