US2668889A

US2668889A - Snap-action thermostatic switch

Info

Publication number: US2668889A
Application number: US203597A
Authority: US
Inventors: Albert E Baak
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-12-30
Filing date: 1950-12-30
Publication date: 1954-02-09
Anticipated expiration: 1971-02-09

Description

Feb. 9, 1954 BAAK SNAP ACTION THERMOSTATIC SWITCH 5 Sheets-Sheet 1 Filed Dec. 50, 1950 /NVENTOR. ALBERT E. 5mm

BYDHIS HTTORNEYS. l5, K/EcH, FosTaR & HARRIS Ham? 6v Feb. 9, 1954 A. E. BAAK SNAP ACTION THERMOSTATIC SWITCH 5 Sheets-Sheet 2 Filed Dec. 30, 1950 92 48 6/ "mag -571W,"

\UNI 2 NEwm wm w 5 WEMF I Feb. 9, 1954 A, E BAA 2,668,889

SNAP ACTION THERMOSTA'LIC SWITCH Filed Dec. 30, 1950 5 Sheets-Sheet 4 I4! a lNVENTOR. /Z/'' ALBERT 5.5HHK I44 I43 I42 BY HIS HTTORNEYS.

HARE/5, K/ECH, F05 7-5/2 & HARRIS Patented Feb. 9, 1954 stasis SNAK AGTION THERMOSTATIG SWITCH Albert E. naak, iacifi'c Palisades, Calif assignor to Paul Henry, Los Angeles, Calif.

Application December 30, 1950, Serial No. 203,597

20 Claims.

The present invention relates to mechanisms operating with a snap action and, more particularly, to a snap-action switch for opening and closing electrical circuits. The snap-action switch may be operated by thermostatic means responsive to temperature variations so as to open and close electrical circuits in response to such temperature variations.

A primary object of the invention is to provide ani-mproved snap-action switch and thermostatic operating means therefor.

More particularly, an object of the invention is to provide a snap-action switch having a switch member which is pivotable between two operating positions with a snap action by the resultant of a substantially constant force applied thereto and a variable input force applied thereto, the input force being variable with temperature variations, for example.

Another object is to provide a snap-action switch wherein the included angle between the substantially constant force and the variable input force is greater than and less than 180 so that the resultant of the two forces swings from one side of the pivot axis of the switch member to the other to move the switch member air-om one of its operating positions to the other, depending upon the magnitude of the variable input force.

Another object is to apply the substantially constant force to the switch member by means of a coil spring acting along a line in close proximity to the pivot axis of the switch member so that the length of the spring is substantially unchanged by pivotal movement of the switch memher through a limited angle, whereby to maintain the force applied by the spring substantially constant.

An important object of the invention is to apply the substantially constant spring .force and the variabl input force to a pivoted actuating member which is operatively connected to the switch member with a lost-motion connection so that the actuating member does not move the switch member until a predetermined pivotal 'movement of the-actuatingmember has occurred,

whereby the actuating member applies an impact force to the switch member to move the switch member suddenly. This insures a clean break pivotal axis. A related object in connection with one embodiment of the invention is to provide asnap-action switch wherein the actuating member and the switch member are independently pivotally connected to the supporting structure, but by the same pivot means. A further object in connection with such embodiment is to PTO? vide a lateral offset between the actuating membar and the switch member so that the ends of the actuating member are spaced from the switch member when the actuating member is in an intermediate position with respect to the switch member, whereby to .provide a lostmotion connection between the two members.

An object in connection with another embodiment of the invention is to provide a switch memher which is carried by the actuating member and which is .operatively connected thereto by a lost-motion connection.

Another important object is to provide a snapaction switch having wiping means comprising two relatively slidable elements for absorbing any kinetic energy tending to cause a contact .means of the switch member to bounce off stationary contact means carried by the supporting structure upon engagement of the contact means of the switchinember with the stationary contact means. A related object in connection with one embodiment of the invention is to provide such a wiping means which is completely independent of the contact means so that the wiping action which absorbs the kinetic energy does not take place between the two contact means. Thus, the energy absorption of the wiping means re- .mains constant and is unaffected by pitting of the contact means, which is an important feature.

Another object is to provide such a wiping means operating independently of the contact means which includes an element connected to and movable with the actuating member and sl'idably engaging a surface of the switch member so that the energy-absorbing wiping action takes place between such element and the switch element intermediate its ends, the fulcrum means including a second adjusting screw. A related object is to provide a fulcrum means which in-- cludes, in addition to such second adjusting screw, a fulcrum element engaging the bimetallic element, the fulcrum element and the second adjusting screw engaging opposite sides of the bimetallic element.

Another important object is to provide means for preventing any unusual forces applied to the bimetallic element from excessively stressing the bimetallic element. A related object is to provide a construction wherein the aforementioned fulcrum element is carried by one end of a leaf spring so that the fulcrum element may yield in response to unusual forces applied to the bimetallic element.

Another object is to provide a structure wherein one of the adjusting screws has a pointer connected thereto which is movable over a dial, the pointer having a detent element thereon which is engageable with indicia-forming detent elements on the dial to retain the pointer in various predetermined positions. Thus, the detent elements on the dial also serve as indicia for indicating the position of the pointer relative to the dial, which is an important feature.

Another object is to provide a snap-action switch which includes a minimum number of parts and which includes parts, that may be assembled readily. In this connection, an object is to provide a pivot means for the actuating member which merely includes an element having edges disposed in notches in the actuating member.

The foregoing objects and advantages of the present invention, together with various other objects and advantages thereof which will become evident, may be attained with the exemplary embodiments of the invention illustrated in the accompanying drawings and described in detail hereinafter. Referring to the drawings:

Figs. 1 to 4, inclusive, are views diagrammatically illustrating the structure and operation of the snap-action mechanism of one embodiment of the snap-action thermostatic switch of the invention;

Fig. 5 is a front elevation showing the actual construction of the embodiment diagrammatically illustrated in Figs. 1 to 4;

Fig. 6 is an enlarged sectional view taken along the arrowed line 6-6 of Fig. 5;

Fig. 7 is a sectional view taken as indicated by the arrowed line l'! of Fig. 6;

Figs. 8 and 9 are enlarged sectional views respectively taken along the arrowed lines 8-8 and 9-9 of Fig. 5;

Fig. 10 is a sectional view on a reduced scale taken along the arrowed line l0-l0 of Fig. 6;

Fig. 12 is a view similar to Fig. 9, but showing a modification of the embodiment illustrated in Figs. 1 to 11;

Figs. 13 to 16, inclusive, are views similar to Figs. 1 to 4 and illustrate diagrammatically the structure and operation of the snap-action mechanism of another embodiment of a snapaction thermostatic switch of the invention;

Fig. 1'7 is a sectional view which is similar to Fig. 8, but which illustrates the actual construction of the snap-action mechanism shown diagrammatically in Figs. 13 to 16, Fig. 17 being taken as indicated by the arrowed line l'I--l'l of Fig. 18;

Fig. 18 is a sectional view taken as indicated by the arrowed line I8l8 of Fig. 17; and,

Figs. 19 and 20 are sectional views taken along the arrowed lines iii-l9 and 2G2ll, respectively, of Fig. 18.

Considering first the embodiment of the invention which is illustrated in Figs. 1 to 11, the general structure and operation of this embodiment will be considered in connection with Figs. 1 to 4 prior to considering the detailed structure thereof. It is thought that this procedure will make the disclosure of the detailed structure much easier to follow.

Referring particularly to Figs. 1 to 4 of the drawings, the snap-action switch illustrated therein is of the double-pole, double-throw type in the particular embodiment under consideration and includes a supporting structure indicated generally by the numeral 2|. Included in the supporting structure 2| is a support to which an actuating member 23 and an actuated or switch member 2 are pivotally connected by a common pivot means 25. Thus, the actuating member 23 and the switch member 24 may pivot relative to the supporting structure about the axis of the pivot means 25. It will be noted that the actuating member and the switch member 24 are offset laterally with respect to each other so that the actuating member 23 may pivot relative to the switch member 24 through a limited angle, the ends 26 and 2'! of the actuating member being adapted to engage the switch member 24 to limit pivotal movement of the actuating member relative to the switch member. Thus, it will be apparent that there is a lost-motion connection between the actuating member and the switch member, the actuating member being adapted to pivot through a limited angle befor one or the other of the

ends

26 and 21 thereof engages the switch member. As will be pointed out in more detail hereinafter, this lost-motion connection between the actuating member 23 and the switch member 2 1 is an important feature of the invention.

The switch member 24 includes a pair of contact means 39 and 3| respectively adapted to engage stationary contact means 32 and 33 carried by the supporting structure 2i. In the particular construction illustrated, the contact means 30 and 3| of the switch member 24 are contact bars and the stationary contact means 32 and 33 respectively comprise paired contacts which are spaced apart and which are adapted to be bridged by the contact bars, respectively. Also, as will be apparent, the two stationary contact means 32 and 33 serve as stop means for limiting the pivotal movement of the switch member 24 about the pivot axis provided by the pivot means 25. The paired contacts of the stationary contact means 32 and 33 may be connected in any desired electrical circuit or circuits.

accuses cussed in more detailhereinafter, the means for applying th substantially constant force 33 to the actuating member includes a coil spring acting in tension, the coil spring being diagrammatically represented by the broken line 31. As will be noted, the spring '31 is indicated as being connected to the end .2! of the actuating member 23 and as being connected to the supporting structure 2| at a point 38. It will also be noted that the spring 31 extends along a line in close proximity to the axis of the pivot means 25.

Consequently, as the actuating member 23 pivots :2

about the axis of the pivot means 25, the end 21 of the actuating member 23 moves substantially on an are having as its center the point 33 or connection of the spring 37 to the supporting structure 2|. Thus, the length of the spring 31 remains substantially constant as the actuating member 23 pivots so as to maintain the spring force '36 substantially constant, which is an important feature.

Also acting on, the actuating member 23 is a :1

variable input force, represented by the arrow 4|. It will be noted that the input force 4| is applied to the end 23 of the actuating member '23 in a direction such that it tends to pivot the actuating member in a direction opposite to that in which the spring force 35 tends to pivot the actuating member so that the two forces oppose each other, the input force 4| tending to pivot the actuating member in the clockwise direction as viewed in Figs. 1 to 4 of the drawings. it will be seen that the spring force 36 tends to open the contact means '38 and 32 and close the contact means 3! and 33, while the variable input forc 4| tends to close the contact means 30 and. 32 and to open the contact means 3| and 33.

In the particular "construction illustrated, the input force 4| is applied to the actuating member 23 by a thermostatic means 42, shown as including a bimetallic element 43 connected to the supporting structure 2| at 44.

Considering the general operation or the switch embodiment diagrammatically illustrated in Figs. 1 to l of the drawings the position of the switch member 24 is determined solely by the magnitude or" the variable input force 4| since the spring force 36 is substantially constant. Thus, the magnitude of the input force 4| determines whether the contact means 32! and 32 are closed, or whether the contact means 3| and 33 are closed. A a starting point, it will be assumed that the input force 4| is small so that theresultant of the spring force 35 and the input force 4| acts to bias the actuating member 23 and the switch member 24 in the counterclockwise direction, as viewed in Figs. 1 to 4 of the drawings, soas to close the contact means 3| and 33.

Now assume that the bimetallic element 43 in creases the input force 46 applied to the actuating member 23 to a value such that the resultant of Thus,

as LAW 6 ing due, for example, to an increase in the ternperature of the bimetallic element. This condition is illustrated. in Fig. 1 of the drawings, the resultant of the spring force '35 and the input force 4| being represented by the arrow 45. as

will be apparent, the resultant force 45 acts the clockwise direction so as to close the contact.

means so and 32 and to open the contact means 3| and 33. Thus, as soon as the input force-41 increases sufficiently to swing the resultant force across the axis of the pivot means 25 into the position occupied by the resultant force 45 in Fig. 1 of the drawings, the actuating member '23 starts to rotate in the clockwise direction, as viewed inFi'gs. l to 4 of the drawings; Because of the lost-motion connection between the actuating member 23 and the switch member 2 the latter member remains stationary until it is engaged'by the end 26 of the actuating member. Thus, the contact means 3| and 33 rem in closed until the end '23 of the actuating member '23 engages the switch member 24, whereupon the impact of the end 26 of the actuating member on the switch member opens the contact means 3| and '33 suddenly. This sudden breaking or "the contact means 3| and 33 minimizes arcing, which is an important feature of the invention.

Thus, as soon as the input'force 4| increases to a value sufficient to swing the resultant force across the axis of the pivot means 25 into the position occupied by the resultant force 45 in Fig. 1, the various components of the device move from the positions occupied thereby in Fig. 1 to the positions occupied thereby in Fig. 2. As will e be noted by comparing Figs. 1 and '2 of the drawings, even though the input force 4| decreases in magnitude somewhat as the stress in the bimetallic element 43 is relieved in response to movement of the various components from the positions shown in Fig. 1 to those shown in Fig. 2, the distance of the resultant force 45 from the axis of the pivot means 25 increases as the various components move towardthe positions shown in Fig. 2. Thus, the effective force applied to the various components increases as they move toward the positions shown in Fig. '2. This insures operation of the device with a sna action, which is an important'feature.

'N'o'w assume'that, with the various components of the device in the position shown in Fig. 2 or the drawings, the temperature of the bimetallic element 43 decreases to an extent sufiicient to so reduce the input force 4| that the resultant of the spring force 36 and the input force 4| swings across the axis of the pivot means 25 in the opposite direction so that it tends to bias the actuating member 23 in the counterclockwise direction, as indicated by the position of the resultant force 45 in Fig. 3. As soon as the resultant force 45 crosses the pivot axis in this manner, it causes the actuating member 23 to pivot in the counterclockwise direction, the switch member 24 remaining stationary until the end 21 of the actuating member engages it with an impact force which breaks the

contacts

33 and 32 suddenly-to I minimize arcing. As shown in Fig. 4, even though the input force 4| increases somewhat as the bimetallic element 43 is stressed during pivoting of the various components into the positions .shown in Fig. 4, the resultant force 45 swings away from the pivot axis as the various components rotate into the positions shown in Fig. 4 sothat the efiective force acting to rotate the various components into the positions shown in Fig. 4 continually increases. Again, this causes ,being opened.

7 the device to operate with a snap action in this direction also.

Thus, the device operates with a snap action in both directions because of the fact that, as the various components of the device rotate toward their new positions when the resultant force 45 swings across the axis of the pivot means 25, the offset of the resultant force continually increases as the various components approach their new positions. Also, because of the lost-motion connection between the actuating member 23 and the switch member 24, the switch member 24 tends to remain stationary until the impact of the actuating member 23 thereon causes it to pivot,

thus insuring a clean break of the contact means Considerable kinetic energy is built up by the actuating member 23 during the interval that the lost-motion connection between the actuating member and the switch member 24 is being taken up so that the impact force applied to the switch member 24 is amply large to insure a clean break of the contact means being opened. which is an important feature of the invention. In order to maintain the contact means 30 and 3| in engagement with the respective stationary contact means 32 and 33 during the intervals that the lost motion in the connection between the actuating member 23 and the switch member 24 is being taken up, a small leaf spring 41 rigidly connected at its midpoint to the midpoint of the actuating member 23 is provided. This spring has ends 43 and 49 which bear against the switch member 24 on opposite sides of the axis of the pivot means 25. Thus, as the actuating member 23 pivots relative to the switch member 24 in pivoting from the position shown in Fig. 1 of the drawings to that shown in Fig. 2, the end 49 of the spring 41 biases the contact means 3| into engagement with the contact means 33 until such time as the lostmotion connection between the actuating member and the switch member is taken up, i. e., until such time as the end 26 of the actuating member strikes the switch member. Similarly, as the actuating member 23 pivots relative to the switch member 24 in pivoting from the position shown in Fig. 3 of the drawings to that shown in Fig. 4, the end 48 of the spring 41 biases the contact means 30 into engagement with the contact means 32 until such time as the lost-motion connection between the actuating member and the switch member is taken up by impact of the end 21 of the actuating member against the switch member.

Thus, irrespective of the direction of pivoting of the actuating member 23, the spring 41 maintains the two contact means which are about to be opened in positive engagement until the impact of the actuating member 23 on the switch member opens such contact means, insuring a clean break with a minimum of arcing. Thus, the spring 41 acts as a resilient means for biasing the two contact means which are about to be opened into positive engagement with each other until the instant they are opened by the actuating member 23.

In the embodiment presently under consideration, the spring 41 cooperates with the switch member 24 to provide a wiping means for absorbing any kinetic energy which tends to cause either of the contact means 38 Or 3| to bounce off the corresponding stationary contact means 32 or 33 as it makes contact therewith. As will be apparent, any tendency of one of the contact means 30 or 3| to bounce off its corresponding stationary contact means 32 or 33 requires pivotal movement or the switch member relative to the actuating member 23. Such pivotal movement of the switch member relative to the actuating member results in sliding movement of the

ends

48 and 49 of the spring 41 over a surface of the switch member 24, the kinetic energy tending to produce bouncing of either of the contact means 30 and 3| thus being 'frictionally absorbed. It will be noted that this energy-absorbing wiping action between the

ends

43 and 49 of the spring 41 and the switch member 24 is entirely independent of the contact means 3| to 33 so that it is not affected by pitting of the contact means. Thus, the energy-absorbing action of the wiping means formed by the spring 41 and the switch member 24 is a constant factor, which is an important feature of the invention.

It will be noted that the spring 41 applies a spring force to the switch member 24 which is in addition to the spring force 36 applied thereto by the spring 31 through the actuating member 23. However, the magnitude of the spring force applied by the spring 41 is so small, as compared to the magnitude of the spring force 36, that its effect on the resultant force 45 is negligible.

One more factor to be taken into consideration before discussing the detailed structure and operation of the embodiment in question is that the spring rate of the bimetallic element 43 must be such that the input force 4| applied to the actuating member 23 by the bimetallic element does not diminish excessively as the actuating element is pivoted from the position shown in Fig. 1 of the drawings to that shown in Fig. 2, and does not increase excessively as the actuating member is pivoted from the position shown in Fig. 3 to that shown in Fig. 4. In other words, the bimetallic element 43 must have a low spring constant. Otherwise, the offset of the resultant force 45 from the pivot axis might decrease in response to pivoting of the actuating member 23, in which case the device would not operate with as great a snap action, or the resultant force might re-cross the pivot axis, in which case the device would not operate at all.

The snap-action thermostatic switch hereinbefore generally described is illustrated in detail in Figs. 5 to 11 of the drawings. Referring thereto, the supporting structure 2| includes two housings GI and 62 secured together with screws 63. the housing 6| preferably being formed of electrical insulating material and enclosing the snapaction switch, and the housing 62 enclosing the bimetallic element 43 for operating the snapaction switch. The housings 5| and 62 respectively include

removable covers

65 and 66, as best shown in Fig. 6 of the drawings.

Considering first the detailed structure of the snap-action switch in the housing 6|, disposed in this housing is a resilient support 61 for the pivoted actuating and

switch members

23 and 24, the resilient support 61 having four legs 68 which bear against one wall 69 of the housing 3| which serves as a base on which the snapaction switch is mounted. The resilient support 61 is secured to the base wall 69 by a screw 10 extending through the base wall and threaded into the resilient support, as best shown in Fig. 6. As will be apparent, by varying the extent to which the screw 10 is threaded into the resilient support 61, the spacing between this resilient support and the base wall 69 may be varied. The paired contacts of the stationary contact means 32 and 33 are mounted on the base wall 69 so that varying the spacing between the resilient support 61 and the base wall 69 by means of the screw m in this manner serves to vary the gaps between the respective contact means 30 and SI of the switch member 24 and the stationary contact means 32 and 33 when the respective contact means are open. Thus, the resilient support at and the screw Iii provide a simple means or" sett' n the gaps between the respective contact means 30 and ill of the switch member 24 and the stationary contact means 32 and 33, which is an important feature of the invention.

As best shown in Fig. 9 of the drawings, the paired contacts of the stationary contact means 32 and 33 are pressed into openings in the base wall 69 of the housing 6|, these contacts being internally threaded to receive screws 13 for attaching electrical conductors thereto.

As best shown in Fig. 6, the resilient support '61 is provided with spaced cars It to which the actuating and switch members 23 and 2d are pivotally connected by the pivot means 25, the latter being a pivot pin carried by the ears M in the particular construction illustrated. The switch member 24 is preferably formed of electrical insulating material and has connected thereto by a rivet 15 a U-shaped bracket 16 having arms through which the pivot pin extends. The contact bars forming the contact means and 3| of the switch member 2 are loosely connected to the ends of the switch member 25, as by staples '11, to render the contact means 33 and 3I self-aligning with the stationary contact means 32 and 33.

The actuating member 23 is provided with ears 8| through which the'pivot pin 25 extends to pivotally mount the actuating member, as best shown in Fig. 6 of the drawings. It will be noted that the length of the ears SI of the actuating member 23 is greater than that of the arms of the U- shaped bracket it which supports the switch member 24, thereby offsetting the actuating member from the pivot pin 25 a greater distance than the switch member 24 to provide the lost-motion connection therebetween hereinbefore described.

As best shown in Figs. 7 and 8, the tension spring 3'! for biasing the actuating member 23 in one direction about the axis of the pivot pin 25 is connected to an arm 32 of the actuating member, the spring 31 being pivotally connected to such arm by being hooked through a hole there in. The other end of the spring 31 is hooked through a hole in a link 83, the latter having a hole therein which receives a reduced diameter portion of a pin as carried by the base wall 69 of the housing 65 and extending into such housmg.

The hereinbefore described leaf spring 41' for biasing one of the contact means 30 and 3i into engagement with the corresponding one of the stationary contact means 32 and 33 is secured to the actuating member 23 opposite the axis of the pivot pin as, as by a rivet 81. As best shown in Fig. 7 or the drawings, in order to increase the effective distances of the

ends

43 and 49 of the leaf spring t! from the point of connection of such spring to the actuating member 23, the spring is irreguiarly shaped, the shape of the spring being'approximately that of a block S As best shown in Fig. 6 of the drawings, it will. be noted that the pivot pin 25 is provided with portions of diiierent diameters which serve to maintain the actuating member 23 and the switch member 24 in their proper relative positions axially of the pivot pin. In the particular con- I struction illustrated, the pivot pin 25 is provided with portions of reduced diameter for engagement with the ears BI of the actuating member 23, and is provided with one portion of reduced diameter and one portion of larger diameter for engagement with the arms of the U-shaped bracket 16. to which the switch member 24 is connected. One of the arms of this U-shaped bracket is provided with a notch 2. .8 therein for application to a complementary reduced-diameter portion of the pivot pin 25.

Turning now to a consideration of the thermostatic means 42 and the manner in which it operates the snap-action switch, the bimetallic element 43 of the thermostatic means .is disposed in the housing 62 and is provided with a free end which bears against a pin 91 for applying the input force 4| to the actuating member 23. This pin extends through registering openings in the covers and 6B of the respective housings 6! and 62 and is seated in a socket 92, in the actuating member 23, as best shown in Fig. 11 of the drawings. The location of the socket 92 is, of course, such that the input force M applied to the actuating member 23 through the pin 9I acts in opposition to the tension spring 37, as hereinbefore discussed in detail. A leaf spring 93 riveted or otherwise secured to the cover 66 of the housing 52 bears against a shoulder 94 on the pin BI to keep the pin seated in the socket 92 even though the pin may be disengaged by the bimetallic element 43 under some temperature conditions. In order to provide the spring 93 with a relatively great effective length in a minimum of space, this spring is made approximately 'C-shaped, as best shown in Fig. 10 of the drawmgs.

Considering the supporting means for the bimetallic element 43 with particular reference to. Fig. 6 of the drawings, the end of the bimetallic. element opposite the free end thereof in engagement with the pin SI is supported by an adjusting or calibrating screw 96 threaded into a fitting 91 which is secured to the cover 66 of the housing 52. The calibrating screw 96 is provided with a stem 98 which extends through a hole in the bimetallic element, the latter being adapted to seat on a shoulder 99 at the junction of the stem 98 with the head of the calibrating screw. The bimetallic element 43 is supported intermediate its ends by a supporting structure which includes an adjustins screw I02 threaded through the cover 66 of the housing I52. and bearing against one side of the bimetallic element, the adjusting screw having a conical head to provide substantialiy point contact with the bimetallic element. Such supporting structure also includes a retaining element I03 which is adapted to engage the opposite side of the bimetallic element 43 between the adjusting screw I112 and the calibrating screw 96, the retaining element I63, being carried by the free end of a cantilever spring I04 riveted or otherwise secured to the cover 66 of the housing 62 at I05. It will be noted that the free end of the cantilever spring I04 is provided with a notch I06 therein which receives a reduced-diameter portion of the adjusting screw I02, the spring I04 being biased into engagement with a shoulder It? on the adjusting screw by its inherent resilience. The adjusting screw Hi2 carries a pointer I08 which is movable over a dial Hi9, Fig. 5, formed on the outer surface of the cover 56 of the housing 62. The dial I09 is provided with indicia lid and iscalibrated in terms of temperature.

Considering the operation of the supporting means for the bimetallic element 43, the pointer I03 may be positioned opposite that one of the indicia H corresponding to the temperature of the bimetallic element 43 at which the snapaction switch is to operate. Thereafter, the callbrating screw 36 may be adjusted independently of the adjusting screw I02 to vary the position of the free end or" the bimetallic element in such a manner as to cause the switch to open either the set of contact means and 32, or the set of contact means 3! and 33, at the temperature corresponding to the position of the pointer I08. After the initial calibration has been made in this manner by means of the calibrating screw 96, the lower end of the bimetallic element 43, as viewed in Fig. 6 of the drawings, is, for all practical purposes, pivotally connected to the supporting structure 2I by the supporting structure comprising the adjusting screw I02 and the retaining element I03. Thus, after the initial calibration has been made, adjusting the bimetallic elements 43 by means of the adjusting screw I02 changes the temperature at which the bimetallic element operates the snap-action switch.

An important feature of the cantilever spring I04 with the retaining element I03 thereon is that it provides means for relieving excessive stresses in the bimetallic element 43, such stresses arising, for example, from temperatures in excess of the normal operating range for which the bimetallic element is designed. As will be apparent, referring particularly to Fig. 6 of the drawings, as the upper or free end of the bimetallic element 43 moves to the left in response to a temperature increase, for example, it acts through the pin 9i to apply the input force 4! to the actuating member 23. Also. the lower end of the bimetallic element 43, as viewed in Fig. 6, exerts a force to the left on the calibrating screw 93. Consequently, the bimetallic element exerts a force to the right on the retaining element I03 of the cantilever spring I04, the magnitude or" such force depending upon the temperature to which the device is subjected. Thus, the spring force which the spring I04 exerts to the left against the adjusting screw I02 may be so selected that as the force wh ch the bimetallic element exerts to the right on the retaining element I03 approaches a maximum value below the maximum permissible stress in the bimetallic element, the spring I04 begins to deflect to permit the retaining element I03 to move to the right so that the bimetallic element disengages the adjusting screw I02. In this manner, the spring I04 not only serves as a means of supporting the bimetallic element, but also serves as a means for relieving excessive stresses therein, due, for example, to excessive temperatures, which is an important feature of the invention.

As best shown in Fig. 6 of the drawings, the indicia IIO on the dial I09 are formed by depressions or indentations in the surface of the dial, i. e., in the outer surface of the cover 33 of the housing 62. The pointer I08 is provided with a projection or detent I I 3 thereon which is engageable with the detent elements provided by the indicia I I 0. Thus, the detent H3 and the indicia H0 serve as a detent means for retaining the pointer I03, and, consequently, the adjusting screw I02, in various predetermined positions, which is another important feature of the invention.

Referring now to Fig. 12 of the drawings, the

modification illustrated therein is substantially identical to the snap-action thermostatic switch hereinbefore described and will not be considered in detail. The switch illustrated in Fig. 12 is a single-pole, single-throw switch and differs principally from the switch described previously in the omission of the contact means 30 of the switch member 24 and the stationary contact means 32. In place of the contact means 30, the switch member 24 is provided with a button H6 which is engageable with a stop III to limit the pivotal movement of the switch member. Also, the end 48 of the leaf spring 41 for biasing the contact means 30 into engagement with the contact means 32 is omitted. In all other respects, the structure of the switch illustrated in Fig. 12 is identical to that described previously, and the operation is also identical.

In Figs. 13 to 20 of the drawings is illustrated a single-pole, single-throw, snap-action thermostatic switch which is similar in structure and operation to that described previously, the embodiment illustrated in Figs. 13 to 20 differing principally in that the structure of the snapaction mechanism is greatly simplified. As a matter of convenience, the general structure and operation of the embodiment of Figs. 13 to 20 will be considered first so that the detailed description of the structure thereof may be more readily understood.

Referring particularly to Figs. 13 to 16 of the drawings, the embodiment illustrated therein includes a supporting structure I2I for an actuating member I23 and a switch member I24, the actuating member I23 being pivotally mounted on the supporting structure I2I by a pivot means I25. The switch member I24 is carried by the actuating member I23 in the particular construction illustrated so that it pivots with the actuating member about the axis of the pivot means I25. The switch member I24 is diagrammatically shown as being disposed in a space I28 between two engaging surfaces of the actuating member I23 so as to provide a lost-motion connection between the actuating member and the switch member. The details of the connection between the actuating member and the switch member will be considered hereinafter.

The switch member I24 serves directly as a contact means in this embodiment, having the form of a contact bar which is adapted to bridge two contacts of a stationary contact means I33 carried by the supporting structure I2I. Since this embodiment is a switch of the single-pole, single-throw type, the end of the actuating member I23 opposite that which carries the switch member I24 merely engages a stop means I32 carried by the supporting structure I2I.

A tension spring, indicated diagrammatically by the broken line I31, applies a spring force I33 to the actuating member I23 in a direction to bias the switch member I24 into engagement with the contact means I33. The spring I3! is shown as connected to the actuating member I23 intermediate the pivot means I25 and the switch member I24, and as connected to the supporting structure II at a point I30. As in the embodiment previously described, the line of the spring I3! is in close proximity to the pivot means I25 so that the length of the spring is substantially unchanged by pivoting of the actuating member I23, whereby the spring force applied to the actuating member is substantially constant as the actuating member pivots be tween a position wherein one end thereof engages 13 the stop means I32 and a position wherein the switch member I25 engages the stationary contact means I33.

A variable input force "I is applied to the actuating member I23 ina direction such thatv it'tends to separate the switch member I24 and. the stationary contact means I33, the input force. being illustrated as applied by a thermostat means- I42 which includes. a bimetallic element: Hi3 con.- nected to the supporting structure I 2I at IM.

As in the embodiment previously described, the constant spring force and the variable input force may be regarded as a. resultant fierce applied to the actuating member I23, the resulting force being designated by the numeral I45: in Figs. 13 to 1d of the drawings. Referring particularly to Fig. 13, the magnitude of the. input force M-I has increased to such an extent that the resultant I45 has swung across the axis of. the pivot means I25 and biases the actuating member I23 in a direction to separate the switch member I218 from the stationary contact means I33. In Fig. 1 1- of the drawings, the actuating member is shown as having pivoted into its. other operative position in response to the action of the resultant force I45, the switch member I24 being separated from the stationary contact means I43. It will be noted that, as in the embodiment previously described, the offset of the resultant force I45 from the axis of the pivot means I25 increases as the actuating member I23 pivots, thereby insuring a snap action. Also, because of the lost-motion connection be.- tween the actuating member I23 and the switch member I24, the switch member remains in engagement with the stationary contact means until the actuating memb-crhas completed. part, of its pivotal movement so that the actuating member strikes the switch member I24 with an impact force, thereby insuring a clean break of the contacts with a minimum of arcing.

Referring to Figs. and 16, when the input force MI decreases sufliciently, the resultant force #45 recrosses the axis. of the pivot means I25 to restore the actuating member to its original position, thereby causing the switch member I24 to re-engage the stationary contact means I33. Again the offset of the resultant force I45 from the axis of the pivot means [25 increases asthe pivotal movement of the actuating member progresses so as to insure a snap action.

Thus, it will be. seen. that the operation of the embodiment of. the invention which is illustrated inFigs. 13 to is substantially identical to that described previously. As in the previous em- Q bodiment, it is necessary that the bimetallic element I43 have a relative low spring constant so as to minimize the effects of deflection of the bimetallic element on the input force MI.

As shown diagrammatically in Figs. 13 to 1.6,

quently, a sudden break of the contacts with a minimum of arcing is provided, which is an im pcrtant feature. As will be discussed in more detail hereinafter, the spring III! also produces a wiping, action between the switch member I24 and the stationary contact means I33 so as to absorb any kinetic energy tending. to. cause. the, switch member In to bounce oil the. contact means I33 upon closure.

Considering the structure of the embodiment. of Figs. 13 to 20 in more detail with particular reference to Figs. 1'7 to 20 of the drawings, the supporting structure i2I includes a. housing: I61 for the snap-action switch and a housing I62 for the thermostatic means I 4 2, the two housings being secured together by screws I63. The housi'ngs IBI and IE2 are provided with covers I65 and W6 arranged in face-tc-face relation.

The switch embodiment presently under consideration includes a resilient support I61. which corresponds to the previous resilient support 61' and which is provided with legs I68 bearing against a base wall I 69 of the housing lat, the resilient support being secured by a screw." I'IIl' which serves to vary the deflection of theresilient support so as to vary the gap between the switch member 524 and the stationary contact means I33 when separated. The stationary contact. means I33 is carried by the base wall I69 and comprises two contacts pressed into openings in the base wall, these contacts being internally threaded to receive screws I13 for electrical C011? sections to the switch.

The resilient support I6? is provided with ears I'M having openings therethrough which receive tabs I15 on the pivot means I25, the latter, as best shown in Fig. 19, having the form of a thin strip of sheet metal which extends between the ears I'M of the resilient support. The sheet metal strip forming the pivot means: I25 is generally channel-shaped to provide rigidity and, as best shown in Fig. 18, is. provided with a generally V-shaped opening I16 therethrough. The actuating member I23 is provided with a pair of flanges Ill and I78 which extend along the sides thereof, respectively, the flange Ill having a V-shaped notch I79 therein. The apex of the notch I'I9 bears against the edge of the V-shaped opening I16 at the apex thereof to provide a pivotal connection between the actuating member I23 and the sheet metal strip forming the pivot means I25. Another, axially aligned, pivotal connection there'between is provided by engagement of the apex of a V-shaped notch, I80 in the other flange i'it on the actuating member I23 with an edge of the sheet metal strip forming the pivot means I25. As best shown in Figs. 17 and 19, the two vshaped notches I199 and I80 face in opposite directions.

The foregoing pivotal connection between the actuating member I23 and the .pivot means I25 renders these elements very easy to assemble. All that is necessary is to insert a portion of the flange IlI of the actuating member through the v-shaped opening I'I'S until the apex of the notch I'IQ therein is in engagement with the apex of such opening, and to bring the apex of the notch I86} in the other flange into engagement with the corresponding edge of the sheet metal strip of the pivot means i255.

As best shown in Figs. 1'! and 19, the flanges Ill and I78 are provided with notches I 8| and IE2, respectively, for tabs 433 and IB l on the switch member 26, such tabs being best shown in Fig. As best shown in Fig. 17, when the switch member I 2-". is in engagement with the contact means I33, the tabs 83 and I84 are spaced from the bottoms of. the notches I8I. and I82. Consequently, as the actuating member I23. starts to pivot in a direction to separate the switch member I24 from the contact means I33,

the tabs I 83 and I84 on the switch member do not engage the bottoms of the notches i8I and I82 until the actuating member has pivoted through a. limited angle. Thus, the actuating member engages the switch member with an impact force to provide a sudden disengagement of the switch member from the contact means I 33, thereby minimizing arcing.

The spring M1 is generally rectangular, as best shown in Fig. 18, and is provided with tabs I8! and I88 which extend into and engage shoulders I89 and I98 in the notches I8I and I82, respectively, the tabs [8? and I88 also retaining the tabs I83 and I84 on the switch member 124 in the notches I8I and I82 to simplify construction and assembly. The spring I 41 is also provided with an intermediate arm I9i having an end I92 which engages the switch member I24, being seated in a socket I93 therein. Thus, the tabs I81 and I88 on the springs I l'i bear against the actuating member 2 23 while the end I92 of the arm I9I bears against the switch member I24 to bias the switch member toward the stationary contact means I33. Thus, the spring I47 serves to maintain the switch member I24 in engagement with the stationary contact means I33 until the lost motion in the connection between the switch member and the actuating member I23 is taken up, thereby insuring a clean break. Moreover, since the spring I4'I tends to maintain the switch member I24 in engagement with the stationary contact means I33, it produces a wiping action between the switch member and the contact means upon closure of the switch so that any kinetic energy tending to cause the switch member to bounce off the contact means is absorbed, which is an important feature.

The tension spring I31 acting on the actuating member I23 is pivotally connected thereby by hooking an end of the tension spring through a hole in an arm Hi6 of the actuating member. The other end of the spring I3! is hooked through a hole in a link I9! having another hole therein which receives a reduced-diameter portion of a pin I98 carried by the base wall I 69 of the housing I6I.

As in the embodiment previously discussed, the bimetalic element I43 is disposed in the housing I62 and acts on the actuating member I23 through a pin which applies the variable input force I4! produced by the bimetallic element to the actuating member. The pin 20| extends through holes in the covers I65 and I66 into a socket 282 in the actuating member I23, the socket being located on the opposite side of the axis of the pivot means I25 from the point of attachment of the spring I31 to the actuating member in the particular construction illustrated to cause the variable input force IM to oppose the spring force I46. The pin 20I is biased into the socket 202 by a spring 203 riveted or otherwise secured to the cover I66 of the housing I62 and seated against a shoulder 284 on the pin 28 I.

The bimetallic element I43 may be supported and adjusted in the same manner as the bimetallic element 43 hereinbefore described. Consequently, the means for supporting and adjusting the bimetallic element I43 are not illustrated in the drawings.

Although I have disclosed exemplary embodiments of my invention herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in the embodiment disclosed without departing from the spirit of the invention.

I claim as my invention: I

1. In a snap-action mechanism, the combina tion of supporting structure; an actuating member; pivot means providing a pivot axis and connecting said actuating member to said supporting structure for pivotal movement about said pivot axis; an actuated member mounted for pivotal movement relative to said supporting structure about said pivot axis so that both said actuating member and said actuated member are pivotable about the same said pivot axis; means operatively connecting said actuated member to said actuating member so that said actuating member pivots said actuated member upon pivotal movement of said actuating member about said pivot axis, said connecting means including a lost-motion connection between said actuated member and said actuating member so that said actuating member does not pivot said actuated member until a predetermined pivotal movement of said actuating member has occured, whereby said actuating member applies an impact force to said actuated member; means including a pair of stop means carried by said supporting structure for limiting pivotal movement of said actuating member; means for applying to said actuating member at a point spaced from said pivot axis a substantially constant force tending to produce pivotal movement of said actuating member about said pivot axis in one direction; and an element on said actuating member at a point spaced from said pivot axis and adapted to have applied thereto a variable input force tending to produce pivotal movement of said actuating member in the opposite direction, whereby said actuating member pivots in one of said directions or the other, depending on the magnitude of said variable input force.

2. In a snap-action switch, the combination of: supporting structure; an actuating member pivotally connected to said supporting structure for pivotal movement relative thereto about a pivot axis; a switch member mounted for pivotal movement relative to said supporting structure about the same pivot axis, said switch member being operatively connected to said actuating member so as to pivot therewith about said pivot axis upon pivotal movement of said actuating member about said pivot axis, there being a lostmotion connection between said switch member and said actuating member so that said actuating member does not pivot said switch member until a predetermined pivotal movement of said actuating member has occurred, whereby said actuating member applies an impact force to said switch member to pivot said switch member suddenly, said switch member including a contact means; means including a pair of stop means carried by said supporting structure for limiting pivotal movement of said actuating member and said switch member about said pivot axis, one of said stop means including stationary contact means engageable by said contact means of said switch member; means, including a spring connected to said supporting structure and connected to said actuating member at a point spaced from said pivot axis, for applying to said actuating member at said point a substantially constant force tending to produce pivotal movement of said actuating member about said pivot axis in one direction; and means engaging said actuating member at a point spaced from said pivot axis for applying to said actuating accuses member a "variable input force tending to 'produce pivotal movement oi said actuating member in the opposite direction, whereby said actuating member pivots in one of said directions or the other, depending upon the magnitude variable input force.

3-'. In a snap-action switch, the combination of: supporting structure; an actuating member pivotally connected to said supporting structure for pivotal movement relative thereto about a pivot axis; a switch member mounted for-pivotal movement relative to said supporting structure about the same pivot axis, said switch member being operatively connected to said actuating member so as to pivot therewith about said pivot axis upon pivotal movement of said actuating member about said pivot axis, there being a lostmotion connection between said switch member and said actuatingmembsr so that said actuating member does not pivot said switch member until a predetermined pivotal movement of said acturating member has occurred, whereby said actuating member applies an impact force to said switch member to pivot said switch 1 ember suddenly, said switch member including a contactmeans; means including a pair or stop means carried by said supporting structure for limiting pivotal movement of said actuating member and said Switch member about said pivot axis, one of said stopmeans including stationary contact means engageable by said contact means of said switch member; means, including a spring connected to said supporting structure and connected to said actuating member at a point spaced from said pivot axis, for applying to said actuating mem ber at said point a substantially constant force tending to produce pivotal movement of said actuating member about said pivot axis in one direction; and thermostatic means responsive to term perature variations and engaging said actuating member at a point spaced from said pivot axis for applying to said actuating member a variable input force tending to produce pivotal movement of said actuating member in the opposite direction, whereby said actuating member pivots in one of said directions or the other, depending on the magnitude or" said variable input force.

4. In a snap-action switch, the combination of: supporting structure; an actuating member pivotally connected to said supporting structure for pivotal movement relative thereto about a pivot axis; a switch member operatively connected to said actuating member so as to move there with about said pivot axis upon pivotal movement of said actuating member about said pivot axis, there being a lost-motion connection between said switch member and said actuating member so that said actuating member does'not move said switch member until a predetermined pivotal movement of said actuating member has oc curred, whereby said actuating member applies an impact force to said switch member to move said switch member suddenly, said switch member including a contact means; means including a pair of stop means carried by said supporting structure for limiting pivotal movement of said actuating member and said switch member about said pivot axis, one of said stop means including stationary contact means engageable by said con-- tact means of said switch member; means, including a spring connected to said supporting structure and connected to said actuating member at a point spaced from said pivot axis, for applying to said actuating member at said point a substantially constant force tending to produce 18 pivotal movement of said actuating member about said pivot axis in one direction; and thermostatic means responsive to temperature variations and engaging said actuating member at a point spaced from said pivot axis for applying to said actuat"- ing memberv a variable input force tending to produce pivotal movement of said actuating member in theopposite direction, the angle between said substantially constant force applied to said actuating member by said spring and said variable input force applied to said actuating member by said thermostatic means being greater than 0 and less than so that the resultant of said forces swings from one side of said pivot axis to the other with variations in said variable input force so as to pivot said actuating member in one of said directions or the other, depending upon the magnitude of said variable input force.

5. A snap-action switch as defined in claim 4 wherein said spring is a coil spring extending along a line which is in close proximity tosaid pivot axis so that the length of said spring re mains substantially constant during pivotal-movement of said actuating member about said pivot axis, whereby to maintain the force applied to said actuating member by said spring substantially' constant.

6. Ina snap-action switch, the combination of: supporting structure; an actuating member pivotally connected to said supporting structure for pivotal movement relative thereto about a pivot axis; a switch member operatively connected to said actuating member so as to move therewith about said pivot axis upon pivotal movement of said actuating member about said pivot axis, said actuating member being pivotally connected to said supporting structure for pivotal movement about said pivot axis by a pivot means and said switch memberbeing pivotally connected to said supporting structure for pivotal movement about said pivot axis by the same pivot means, there being a lost-motion connection between said switch member and said'actuating member so that said actuating member does not move said switch member until a predetermined pivotal movement of said actuating member has occurred, whereby said actuating member applies an impact force to said switch member to move said switch member suddenly, said switch meniber including a contact means; means including a pair or stop means carried by said supporting structure for limiting pivotal movement of said actuating member and said switch member about said pivot axis, one of said stop means including stationary contact means engageable by said contact means of said switch member; means, including a spring connected to said supporting structure and connected to said actuating member at a point spaced from said pivot axis, for applying to said actuating member at said point a substantiallyconstant force tending to produce pivotal movement of said actuating member about said pivot axis in one direction; and means engaging said actuating member at a point spaced from said pivot axis for applying to said actuating member a variable input force tending to produce pivotal movement of said actuating member in the opposite direction, whereby said actu' ating member pivots in one of said directions or the other, depending upon the magnitude of said variable input force.

7. A snap-action switch as defined in claim 6 wherein said actuating member and said switch member are offset laterally with respect to each other so that said actuating member may pivot relative to said switch member about said pivot axis so as to produce said lost-motion connection between said actuating member and said switch member, said actuating member having ends on opposite sides of said pivot axis which are adapted to engage said switch member after pivotal movement of said actuating member relative to said switch member through a limited angle to communicate pivotal movement of said actuating member to said switch member.

8. A snap-action switch as defined in claim 2 wherein said switch member is connected to said actuating member by said lost-motion connection at a point spaced from said pivot axis.

9. A snap-action switch as defined in claim 2 including wiping means, comprising a pair of relative slidable elements, for absorbing any kinetic energy tending to cause said contact means of said switch member to bounce off said stationary contact means, said kinetic energy being frictionally absorbed by said relatively slidable elements.

0. A snap-action switch as defined in claim 9 wherein one of said elements of said wiping means is carried by said actuating member and slidably engages a surface of said switch member, said surface of said switch member forming the other of said elements of said wiping means. I

11. A snap-action switch as defined in claim 10 wherein said one element of said wiping means includes a leaf spring, rigidly connected to said actuating member and engaging said surface of said switch member, for biasing said contact means of said switch member toward said stationary contact means, said leaf spring maintaining said contact means of said switch member in engagement with said stationary contact means during pivotal movement of said actuating member in a direction to separate the two contact means until such time as the lost motion between said actuating member and said switch member is taken up.

12. A snap-action switch as defined in claim :2 including resilient means carried by said actuat ing member and engaging said switch member for biasing said contact means of said switch member toward said stationary contact means, whereby said resilient means maintains said contact means of said switch member in engagement with said stationary contact means during pivotal movement of said actuating member in a direction to separate the two contact means until such time as the lost motion between said actuating member and said switch member is taken up.

13. In a snap-action switch, the combination of: supporting structure; stationary contact means carried by said supporting structure; a

switch member movable relative to said supporting structure and including contact means errgageable with said stationary contact means; means movably connecting said switch member to said supporting structure, including pivot means providing a pivot axis about which said switch member is pivotable relative to said supporting structure; and wiping means, including an element slidably engaging said switch member, for absorbing any kinetic energy tending to cause said contact means of said switch member to bounce off said stationary contact means, said element of said wiping means comprising a leaf spring which is pivotally connected to said supporting structure by said pivot means and which is offset laterally from said switch member to provide a lost-motion connection therebetween, said leaf spring having an end in slidable engage- 20 ment with said switch member, said snap-action switch further including means for biasing said end of said leaf spring into slidable engagement with said switch member.

14. A snap-action switch as defined in claim 13 wherein said contact means of said switch member is disposed on one side of said switch member and wherein said end of said leaf spring engages the opposite side of said switch member adjacent said contact means thereof so that the leaf spring biases said contact means of said switch member toward said stationary contact means.

15. A snap-action switch according to claim 2 wherein said supporting structure includes a base which carries said stationary contact means and includes a resilient support which carries said actuating member and said switch member, said snap-action switch further including adjusting means engaging said base and said resilient support for flexing said resilient support to vary the gap between said stationary contact means and the contact means of said switch member when the two contact means are separated.

16. In a snap-action switch, the combination of: supporting structure including a base and a resilient and flexible support connected to said base; stationary contact means carried by said base; a switch member pivotally connected to said resilient support and including contact means engageable with said stationary contact means; means for pivoting said switch member between a position wherein the two contact means are separated and a position wherein the two are in engagement; and adjusting means engaging said base and said resilient support for flexing said resilient support to vary the gap between the two contact means when the two are separated.

17. A snap-action mechanism as defined in claim 1 wherein said actuating member is provided with oppositely facing notches therein along said pivot axis, said pivot means comprising an element having edges disposed in said notches, respectively.

18. In a snap-action mechanism, the combination of supporting structure; an actuating member; pivot means providing a pivot axis and connecting said actuating member to said supporting structure for pivotal movement about said pivot axis; an actuated member; means operatively connecting said actuated member to said actuating member so that said actuating member moves said actuated member upon pivotal movement of said actuating member about said pivot axis, said connecting means including a lost-motion connection between said actuated member and said actuating member so that said actuating member does not move said actuated member until a predetermined pivotal movement or" said actuating member has occurred, whereby said actuating member applies an impact force to said actuated member; means including a pair of stop means carried by said supporting structure for limiting pivotal movement of said actuating member; means for applying to said actuating member at a point spaced from said pivot axis a substantially constant force tending to produce pivotal movement of said actuating member about said pivot axis in one direction; and an element on said actuating member at a point spaced from said pivot axis and adapted to have applied thereto a variable input force tending to produce pivotal movement of said actuating member in the opposite direction, the angle between said substantially constant force applied to said actuating member and said variable input force applied thereto being greater than and less than 180 so that the resultant of said forces swings from one side of said pivot axis to the other with variations in said variable input force so as to pivot said actuating member in one of said directions or the other, depending upon the magnitude of said variable input force.

19. In a snap-action switch, the combination of: supporting structure; an actuating member pivotally connected to said supporting structure for pivotal movement relative thereto about a pivot axis; a switch member pivotally connected to said supporting structure for pivotal movement relative thereto about the same pivot axis, said switch member being operatively connected to said actuating member so as to pivot therewith about said pivot axis upon pivotal movement of said actuating member about said pivot axis, there being a lost-motion connection between said switch member and said actuating member so that said actuating member does not pivot said switch member until a predetermined pivotal movement of said actuating member has occurred, said switch member including a contact means; a stationary contact means carried by said supporting structure and engageable by said contact means of said switch member upon pivotal movement of said actuating member and said switch member in a direction to move said contact means of said switch member toward said stationary contact means; and wiping means, comprising a pair of relatively slidable elements, for absorbing any kinetic energy tending to cause said contact means of said switch member to bounce off said stationary contact means, one of said elements of said wiping means being carried by said actuating member and slidably engaging a surface of said switch member, said surface of said switch member forming the other of said elements of said wiping means.

20. A snap-action switch as defined in claim 19 wherein said one element of said wiping means includes a leaf spring, rigidly connected to said actuating member and engaging said surface of said switch member, for biasing said contact means of said switch member toward said stationary contact means, said leaf spring maintaining said contact means of said switch member in engagement with said stationary contact means during pivotal movement of said actuating member in a direction to separate the two contact means until such time as the lost motion between said actuating member and said switch member is taken up.

ALBERT E. BAAK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,667,020 Wendel Apr. 24, 1928 1,859,985 Riedel May 24, 1932 1,869,648 Ashworth Aug. 2, 1932 1,910,510 Warner May 23, 1933 1,913,617 Smith June 13, 1933 2,074,132 Rich Mar. 16, 1937 2,111,816 Shaw Mar. 22, 1938 2,216,032 Christiansen Sept. 24, 1940 2,414,961 Mason Jan. 28, 1947 2,529,785 Persons Nov. 14, 1950 FOREIGN PATENTS Number Country Date 580,302 Great Britain Sept. 3, 1946