US2855486A - Thermostatic switches - Google Patents

Description

Oct. 7, 1958 v. WEBER arm.

THERMOSTATIC SWITCHES 2 Sheets-Sheet 1 Filed Aug. 15 1957 m Q w 1 w x g g 2 y g a g Q a am a 3 m a Km M; in L[ m m M w m m m w m H, m gw H M 1 0 m o X I m 2 w Ill/l7" INVENTORS'. Victor Weber and lVilb'amJ My: MM

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Oct. 7, 1958 v. WEBER arm. 2,855,486

THERMOSTATIC SWITCHES Fil-ed Aug. 15 1957 2 Sheets-Sheet 2 21 my 12 i 1a 1?? a as 2 1m 194 194 l I 1&9 1 L 189 INVENTORS. WtiarWrber and Sanders.

United States Patent THERMOSTATIC SWITCHES Victor Weber, Greensburg, and William J. Sanders, Mount Pleasant, Pa., assignors to Robertshaw-Fulton Controls Company, Greensburg, Pa., a corporation of Delaware Application August 15, 1957, Serial No. 678,366

9 Claims. (Cl. 200140) able bridge and the fixed contacts when the controlled 1:

circuit is broken is predetermined to conform to the operating differential of the switch. When the switch is in an inoperative position, there is no thermostatic cycling and the bridge is separated from the fixed contacts by the same air gap distance as mentioned above for the cycling operation. Since certain installations require a greater air gap between current carrying members and ground when the switch is in an inoperative position, conventional switches cannot perform this function and a separate operation interferes with the particular switch differential.

Accordingly, it is an object of this invention to maintain the Operating ditierential of a switch while increasing the air gap between current carrying members and ground when the switch is in an inoperative position.

It is another object of this invention to vary the air gap between the mating contacts of a switch without altering the operating differential of such switch.

Another object of this invention is to increase the air gap of a switch in its off position and to decrease such air gap for cycling operation when the switch is in an on position.

A further object of this invention is to increase the air gap of a switch automatically when the switch is moved to its 0 position.

An additional object of this invention is to so combine a switch arm actuator with a switch control that the switch arm is locked when the switch is in its otF position.

Other objects and advantages will become apparent from the following description in connection with the accompanying drawings wherein:

' Fig. l is a front elevation view of a thermostatic device with certain parts removed to illustrate this invention;

Fig. 2 is a longitudinal sectional view taken on line HIl of Fig. 1;

Fig. 3 is a sectional view taken on line IlI--III of Fig. 2;

Fig. 4 is an enlarged view of a detail of the cam and dial locking means of this device;

Fig. 5 is a longitudinal sectional view similar to Fig. 2 but showing a modification thereof;

. Fig. 6 is a sectional view taken on line Vl-VI of Fig. 5;

Fig. 7 is a sectional view taken on line VII- VII of Fig. 6; and

ill

2,855,486 Patented Oct. 7, 1958 "ice Fig. 8 is a partial perspective view of a detail of Fig. 1.

Referring to Figs. 1 and 2, there is shown a housing, indicated generally at 10, formed by a top member 12 of insulating material, a rear member 14 and a front cover 16, all held together by any suitable means into a generally rectangular configuration. Cover 16 is provided with a centrally disposed, internally threaded boss 18 for receiving a control rod in the form of an adjusting screw 28 which carries on its exterior D-shaped end the usual control knob 22 by means of which the adjusting screw 20 can be rotated.

An expansible and contractible diaphragm element 24 is carried on a connecting pin 26 which has a reduced portion 28 slidably supported in a bore provided in the interior end of adjusting screw 20. A thrust button 30 projects from the forward end of diaphragm element 24 and the arrangement is such that upon rotation of knob 22, the diaphragm 24 and button 30 will move axially. One end of a capillary tube 32 communicates with the interior of diaphragm 24 While its other end extends extcriorly of housing 10 for communication with the usual bulb element 34 appropriately positioned in a medium to be controlled thermostatically. As is well known in the art, the diaphragm 24, capillary tube 32 and bulb 34 form a temperature responsive means which is a closed system containing an expansible fluid whereby temperature variations sensed by bulb 34 causes axial movement of button 30.

Button 30 abuts a face of an actuating lever 36 of a snap-acting mechanism. Lever 36 is generally of T- shaped configuration and is provided at the end of its vertical leg with a knife edge 38 which is cooperable with a V-shapcd bearing groove in a bracket 40 extending from the housing rear member 14. A knife edge 42 is also provided on the horizontal end portion of T lever 36. A pair of coil springs 44 (only one being shown) are disposed on opposite sides of the levers vertical portion with one end of each spring being hooked around the knife edge 42.

A switch arm 46 has upper and lower strips joined by side legs to form a rectangular configuration. A knife edge 48 on the upper strip of switch arm 46 receives the opposite hooked ends of coil springs 44. The lower ends of the side legs of switch arm 46 are each provided with a knife edge 52 for cooperation with suitable V- shaped bearing groove 54 formed in the housing 10. An insulating plate 56 is attached to the upper strip of switch arm 46 by any suitable means, such as rivets 58.

A U-shaped contact bridge holder 60 extends from the front of insulating plate 56 and has a pair of opposed slots in the legs thereof for slidably receiving a contact bridge 62. A coil spring 64, compressed between bridge 62 and the bottom of holder 60, exerts a biasing force on bridge 64 and minimizes contact bounce when it is in position to form a current carrying bridge for a pair of fixed contacts 66 carried by the insulating top member 12 of housing 10. A rib member 68 projects from the rear of insulating plate 56 and extends between a second pair of fixed contacts 70 carried by the insulating top member 12 of housing 10.

A second U-shaped contact bridge holder 72 is fastened to housing 10 and has a pair of opposed slots in the legs thereof for slidably receiving a contact bridge 74. A coil spring 76 is compressed between the bottom of holder 72 and bridge 74 and urges the same toward fixed contacts 70 and rib member 68. Switch member 46 moves from its inoperative position to its controlling positions so that the contacts 66 and 70, controlling electrical circuits exteriorly of housing 10, are so arranged 7 that contacts 70 are closed to complete a first circuit and contacts 66 are subsequently closed to complete a second circuit. When the switch breaks these circuits, contacts 66 are opened first, followed by the opening of contacts 70.

As is illustrated in Fig. 2, the exterior of boss 18 is provided with a pair of ears 80 (only one being shown) having aligned apertures in which opposite ends of a pivot pin 82 are received. A generally L-shaped bracket 84 comprises a vertical leg 86 with a centrally disposed aperture 87 and a horizontal leg 88 and is pivotally mounted between ears 80 by means of an apertured flange 90 extending perpendicularly from the undersurface of horizontal leg 88 for mounting on pivot pin 82. The free end of horizontal leg 88 is formed with a generally V-shaped bearing surface 92 for a purpose to be described hereinafter.

A bracket, indicated generally at 94, has a mounting leg 96 rigidly fastened to the inner surface of front cover 16 and an offset leg 98 with an aperture 100 therethrough. An aperture 102 through front cover 16 is so positioned as to be in axial alignment with aperture 87 and aperture 100. Aperture 87 has a small diameter, aperture 102 an intermediate diameter, and aperture 100 a large diameter. A rod-like plunger 104 has a diameter slightly less than that of aperture 102, and is slidably mounted for reciprocation therethrough. The inner end of plunger 104 extends through aperture 100 with a loose fit therebetween to engage switch arm 46. The outer end of plunger 104 has a reduced portion 106 which extends through aperture 87 with a loose fit therebetween. An annular groove in reduced portion 106 receives a split retaining washer 108 which operatively connects plunger 104 to bracket 84 for movement therewith. A coil spring 110 is compressed between front cover 16 and vertical leg 86 and normally biases bracket 84 in a counterclockwise direction about pivot pin 82.

A circular cam plate 112 is formed with a D-shaped central opening 114 which receives the correspondingly shaped end of adjusting screw 20 for rotation therewith. A portion of the periphery of cam plate 112 is provided with a cam 116 which is engageable with bearing surface 92 on the horizontal leg 88 of bracket 84. A substantially square shaped slot 118 in cam plate 112 is inwardly displaced from the periphery thereof and is angularly spaced from cam 116.

An annular mounting bracket 120 has a central cutout which surrounds boss 18 and coil spring 110, and is secured to the front cover 16 by any suitable means, such as rivets (not shown). Extending radially from the secured portion of bracket 120 are two diametrically opposed tongues 122, 124 which are located in a plane ofiset from that of the secured portion. The angled portion of tongue 122 is formed with a T-shaped slot 126 and the opposed edges of the angled portion of tongue 124 are recessed at 128.

A substantially U-shaped bow type spring, indicated generally at 130, comprises a pair of legs 132, 134 joined at their upper ends by a cross piece 136. A T-shaped tongue 138 integral with cross piece 136 is received in T-shaped slot 126 in the angled portion of tongue 122. The free ends of legs 132, 134 are inserted in the recesses 128 in the angled portion of tongue 124 so that the spring 130 is fastened to bracket 120 in a bowed manner. As is shown in Figs. 1 and 2, each of the legs 132 and 134 have at their respective mid-points, curved humps 140, 142 which frictionally engage cam plate 112.

In its assembled position, the bow spring 130 is tensioned so as to provide a biasing force on cam plate 112 thus holding the same in contact with the outer surface of boss 18. A lug 144 on the curved hump 140 of leg 132 is received in slot 118 whenever cam plate 112 rotates the same into alignment with lug 144. Lug 144 and slot 118 are arranged to be aligned when knob 22 is rotated to an off position thereby providing a locked ofi position. The resiliency of leg 132 and curved hump 140 provides a friction lock with lug 144 so that knob 22 cannot be dislodged accidentally from its 05" position.

While this thermostatic device may control various types of external circuits, for the purpose of describing its sequence of operation, it will be assumed that contacts 70 control a power circuit and contacts 66 control a cycling circuit. When knob 22 is rotated to an 0115" position, the adjusting screw 20 and diaphragm 24 move inwardly axially. With removal of the thrust force on the snap mechanism, actuating lever 36 is pivoted counterclockwise about its knife edge 38 moving coil springs 44 through their overcenter positions, causing switch arm 46 to pivot clockwise about its knife edge 52 whereby bridges 62 and 74 are separated from their respective contacts 66 and 70 by appropriate air gaps therebetween.

Simultaneously with the rotation of knob 22, cam plate 112 is rotated so that cam 116 engages its follower bearing 92 on bracket 84 causing the same to pivot clockwise about pivot pin 82. By means of the pivotal bracket 84, the rotary motion of cam plate 112 is translated into reciprocating motion for plunger 104. Such pivotal movement causes vertical leg 86 to move against the bias of coil spring 110 and force inward movement of plunger 104 through aperture 102 and guiding aperture to a position where plunger 104 causes additional clockwise movement of switch arm 46 about its knife edge 52 to an inoperative position. This additional movement of switch arm 46 correspondingly moves bridges 62 and 74 so that a wider air gap separates the same from their respective contacts 66 and 70.

The position of cam plate 112 when the knob 22 is in an off position is apparent in Fig. 4 wherein the lug 144 on the curved hump 140 is in biased engagement with slot 118 on the cam plate 112. Inasmuch as slot 118 is angularly displaced 90 from cam 116, it cooperates with lug 144 to form a locked off position for knob 22 whereby switch arm 46 is retained in an inoperative position and the increased air gap is maintained as long as knob 22 is in its off position.

Assume now that knob 22 has been rotated to an on" position at a desired temperature setting corresponding to the radial position of cam plate 112 in Fig. l and that such a temperature has been sensed by bulb 34. The operating elements of the control device are now in their controlling positions shown in Fig. 2, i. e., cam 116 is not in engagement with its bearing follower 92 and coil spring has biased vertical leg 86 against split washer 108 causing outward movement of plunger 104 and counterclockwise pivotal movement of bracket 84. Movement of plunger 104 permits switch arm 46 to assume its cycling position in which bridge 74 engages contacts 70 to complete the power circuit and bridge 62 is separated from contact 66 by the smaller cycling air gap. As soon as bulb 34 senses a drop in temperature, the diaphragm 24 contracts and decreases the thrust of button 30 on actuating lever 36 until coil springs 44 are moved through their overcenter positions causing switch arm 46 to pivot counterclockwise. This brings bridge 62 into engagement with contacts 66 and completes the cycling circuit.

During the cycling operation, the rib member 68 moves between the pair of contacts 70 to engage and disengage bridge 74 successively. However, hridge 74 is not separated from contacts 70 because the size and design of coil spring 76 is sufficient to maintain bridge 74 in engagement with contacts 70 so that bridge 74 serves as a stop for rib member 68 to limit movement of insulating plate 56.

Referring now to Figs. 5 and 6, there is shown a modification of the contact bridges and their related elements. In order to simplify the description of this modification, parts corresponding to similar parts in the first modification have been given the same reference numerals and will not be described further except as necessary for correlation.

- As is illustrated in Fig. 5, a single coil spring 44 has its upper end hooked to a cross piece of switch arm 46 which is located in a plane below that in which button 30 moves. An insulating plate 156 is attached to the upper portion of switch arm 46 by any suitable means, such as rivets 158. A first U-shaped contact bridge holder 160 extends from the front of insulating plate 156 and has a pair of opposed slots in the legs thereof which slidably receive a contact bridge 162. A coil spring 164, compressed between bridge 162 and the bottom of the holder 160, exerts a biasing force on bridge 162 and minimizes contact bounce when it is in position to form a current carrying bridge for a pair of fixed contacts 166 carried by the insulating top member 12 of housing 10.

A second U-shaped contact bridge holder 172 (Fig. 6) also extends from the front of insulating plate 156 in spaced relation to holder 160 and has a pair of opposed slots in the legs thereof which slidably receive a contact bridge 174. Similarly, a coil spring is compressed in holder 172 and biases bridge 174 to minimize contact bounce when it is in position to form a current carrying bridge for a second pair of fixed contacts 170 also carried by the insulating top member 12.

A U-shaped bracket 180 is fastened to housing and has a pair of spaced upstanding legs 182, 184 extending toward insulating plate 156. Each of legs 182, 184 is provided with a pair of opposed recesses 186 in their respective side edges. A second U-shaped bracket 188 has a pair of spaced upstanding legs 190, 192 which are engageable with the rear of insulating plate 156. The base portion of bracket 188 is provided with a slot 194 adjacent leg 192 and a slot 195 adjacent leg 190. A tongue 197 extends into slot 194 and is bent upward before inserting bracket 188 onto the upright legs 182 and 184 of bracket 180. After insertion, the tongue is bent down level with the base portion of bracket 188 whereby it will confine this bracket sidewise but will permit movement towards the rear member 14 of housing 10. A coil spring 196 is compressed between the facing surfaces of the respective bottom portions of brackets 180 and 188. Coil spring 196 exerts a biasing force on bracket 188 so that the free ends of legs 190, 192 act as a stop for the insulating plate 156.

The operation of the device shown in Figs. 5 and 6 is similar to that of the previously described modification except that the contact bridges 162, 174 move as a unit relative to their respective fixed contacts 166, 170 to control the external circuitry simultaneously. When the temperature reaches the desired setting as reflected by sensing bulb 34 to the diaphragm 24, the snap acting mechanism causes the insulating plate 156 and its attached holders to move to their positions illustrated in Figs. 5 and 6. Thus, bridges 162 and 174 are separated from contacts 166 and 170, respectively, by a small air gap required for the cycling operation. Inasmuch as coil spring 196 exerts a relatively large biasing force on bracket 188, the movement of insulating plate 156 is limited to prevent the small air gap from exceeding its designed distance.

When knob 22 is rotated to an 0 position, the plunger 104 moves inwardly as previously described and causes further movement of insulating plate 156 against the bias of coil spring 196. In this position, bridges 162 and 174 are separated from their respective contacts 166 and 170 by a larger air gap than that of the cycling air gap.

Since the operating differential of a switch is related to the air gap which separates its contacts, this invention makes it possible to vary the air gap without altering the operating differential. In both modifications the movement of the contact bridges is limited during the cycling operation to maintain the air gap and switch differential within their designed requirements, while additional movement is provided when the control knob is rotated to an off position to increase the air gap auto matically. This increased air gap is maintained during the ofi position by locking means and is automatically decreased to the cycling air gap by unitary rotation of cam plate 112 and knob 22 to an on" position.

Inasmuch as the details contained in the foregoing description of the drawings are subject to various changes, and features thereof may be embodied in other combinations, it is intended that such disclosures be interpreted as illustrative and not in a limiting sense.

We claim:

1. In a switch, the combination comprising a movable switch member having contacts separated by an air gap when said switch member is in an inoperative position and a controlling position wherein the maximum air gap separating said contacts is less than when the switch member is in the inoperative position, means to actuate said switch member to said controlling position, and means operable independently of said actuating means to move said switch member to its inoperative position.

2. The combination as recited in claim 1 wherein locking means cooperates with said last mentioned means to retain said switch member in inoperative position.

3. in a switch, the combination comprising a movable switch member having contacts separated by an air gap when said switch member is in an inoperative position and a controlling position wherein the maximum air gap separating said contacts is less than when the switch member is in the inoperative position, means to actuate said switch member to said controlling position, a control element movable between off and on positions and being operatively connected to said actuating means for controlling the actuation thereof, a movable member engageable with said switch member, cam means connected to said control element for movement therewith, and an operable connection between said cam means and said movable member for moving the same whereby said movable member moves said switch member to its inoperative position when said control element is moved to its oiF position.

4. The combination as recited in claim 3 wherein friction locking means engages said cam means when said control element is in its otF position to retain said switch member in its inoperative position.

5. In a switch, the combination comprising fixed contact means, a movable switch member having an inoperative position and a plurality of controlling positions, bridging means movable by said switch member and being located adjacent said fixed contact means for cooperation therewith, means to actuate said switch member between a first controlling position where said fixed contact means and said bridging means are engaged and a second controlling position where said fixed contact means and said bridging means are separated by an air gap. a control element operatively connected to said actuating means and being movable from an otF position to an on position where said actuating means places said switch member in one of its controlling positions, motion translating means operatively connected to said control element for operation independently of said actuating means when said control element is in its ofF position to move said switch member to its inoperative position where said fixed contacts and said bridging means are separated by a second air gap.

6. In a switch the combination comprising fixed contact means, a movable switch member, contact bridging means operable by said switch member into and out of engagement with said fixed contact means, means to actuate said switch member between a first controlling position where said bridging means is engaged with said fixed contact means and a second controlling position where said bridging means is separated from said fixed contact means by an air gap, a control element operatively connected to said actuating means and being movable between on and off positions, a reciprocating member engageable with said switch member, cam means operatively connected to said control element for movement therewith, and an operable connection between said cam means and said reciprocating member, said cam means being operated when said control element is moved to its off position to cause said reciprocating member to move said switch member to an inoperative position where said bridging means is separated from said fixed contacts by a larger air gap.

7. In a switch the combination comprising a housing, a movable switch member therein having an inoperative position and a plurality of controlling positions, circuit controlling means on said switch member, actuating means operatively connected to said switch member for moving the same between its controlling positions, a control element operable between off and on positions and being operatively connected to said actuating means causing the same to place said switch member in one of its controlling positions, a reciprocating member engageable with said switch member, cam means operatively connected to said control element for movement therewith, an operable connection between said cam means and said reciprocating member for moving the same when said control element is moved to its ofi position whereby said reciprocating member places said switch member in its inoperative position, a bow spring carried by said hous ing, and friction locking means on said bow spring engaging said cam means when said control element is in its 011" position to lock said switch member in its inoperative position.

8. In a switch the combination comprising a movable switch member having an inoperative position and a plurality of controlling positions, circuit controlling means on each side of said switch member, actuating means operatively connected to said switch member for moving the same between its controlling positions, a control element operable between off and on positions and being operatively connected to said actuating means causing the same to move said switch member to one of its controlling positions, a reciprocating member engageable with said switch member, cam means operatively connected to said control element for movement therewith, and an operable connection between said cam means and said reciprocating member for moving the same when said control element is moved to its off position whereby said reciprocating member places said switch member in its inoperative position.

9. In a switch the combination comprising a housing having first fixed contact means and second fixed contact means spaced therefrom, a movable switch member, first bridging means on one side of said switch member for cooperation with the first fixed contact means, second bridging means carried by said housing for cooperation with the second fixed contact means, a rib member extending from the other side of said switch member to engage said second bridging means, means to actuate said switch member between controlling positions whereby said first bridging means are moved into and out of engagement with the first fixed contact means, a control element operatively connected to said actuating means causing the same to move said switch member to a controlling position, and motion translating means operatively connected to said control element and being engageable with said switch member to move the same independently of said actuating means to an inoperative position whereby said first bridging means are separated from the first fixed contact means and said rib member moves said second bridging means to separate the same from the second fixed contact means.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,699 Henning Jan. 9, 1934 2,157,857 Lee May 9, 1939 2,322,161 Schleicher June 15, 1943 2,557,810 Bletz June 19, 1951 2,726,299 Carlson Dec. 6, 1955 2,759,068 Manecke Aug. 14, 1956

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