US3822371A - Snap-action switch - Google Patents

Abstract

A switch exhibiting snap-action is disclosed in which the switch contact elements can assume one of their opposite states responsively to plural positionings of the switch actuator and hence plural input conditions.

Description

O United States Patent 1 1 1 1 3,822,371 Welsh 1 1 July 2, 1974 SNAP-ACTION SWITCH 2,840,662 6/1358 Iliussell 337/320 2,846,53 8 l 58 a er 0 I60 [75] Inventor: James welsh Summlt, Ni 3,200,213 8/1965 Mu rphy, Jr 200/67 B 3,294,931 12/1966 Lanza 200/67 B [73] Asslgnee i ggfi ggg g iw 3,449,538 6/1969 Long ZOO/I60 22 F1 d: t. 18 1972 1 1e 0c Primary ExaminerDavid Smith, Jr. PP 298,524 Attorney, Agent, or FirmWatson Leavenworth Kelton & Taggart [52] US. Cl. 200/160, 200/67 B, ZOO/67 D, 337/320 51 1111.01. H0lh 3/28, l-lOlh 13/64 [57] ABSTRACT [58] Search ZOO/67 g g A switch exhibiting snap-action is disclosed in which the switch contact elements can assume one of their opposite states responsively to plural positionings of [56] References the switch actuator and hence plural input conditions.

UNITED STATES PATENTS 2,486,033 10/1949 Kaminky 200/67 D 4 Claims, 4 Drawing Figures 1 SNAP-ACTION SWITCH FIELD OF THE INVENTION This invention pertains generally to improved electrical switches of the type having contact elements engaged and disengaged in snap-action manner in accordance with the movement of the switch actuator into one or another position.

BACKGROUND OF THE INVENTION In presently known switches of the snap-action type, contact elements are maintained in a first state while the switch actuator is disposed in a first position or is moved therefrom through a range of positions to a second position at which time the contact elements are snapped into their alternate state. The contact elements are maintained in such alternate state while the actuator is disposed in this second position or is moved therefrom through a range of positions from the second position to the first position at which time the contact elements return in snap-action manner to their first state.

An inherent operational limitation of such known switches, confronted by applicant in efforts concurrent with those of the subject invention and discussed below, is that they respond to only one input condition in assuming each contact element state. Specifically, considering the first contact element state to be one wherein the contact elements are in engagement and provide for the passage of current to a utilization device, current flow is interrupted in such known switches only on condition that the actuator be moved to its second position, as might be occasioned by excess heating of the utilization device. Evidently, such known switches do not lend themselves to use in applications requiring switches exhibiting snap-action and responsive to multiple conditions in assuming a single contact element state.

In the course of applicants invention of certain apparatus and methods, disclosed in his application filed concurrently herewith and entitled Method and Apparatus for Heat Detection and Control, and further disclosed in pertinent part below, applicant developed the need for the foregoing type of an electrical switch providing the desired performance benefits of snapaction switches and yet having actuator-responsive capabilities expanded over those of known snap-action switches. Specific unfulfilled need arose for a switch adapted to provide for the energization of a baseboard heater on the fundamental condition that associated heat detection apparatus be functioning properly and on the further condition that the heater be at a temperature below a preselected temperature. In this need, snap-action switch operation was required in respect of the latter condition.

SUMMARY OF THE INVENTION The present invention has as an object the provision of an electrical switch exhibiting snap-action and responsive to multiple conditions in assuming at least one contact element state thereof.

In the efficient attainment of the foregoing and other objects, the invention provides a switch incorporating means biasing the switch actuator to a position exteriorly of the first and second positions at which contact element snap-action occurs. In such biased position thereof, the actuator maintains the switch contact elements in a state converse to the contact element state occurring when the actuator is in its snap-action position nearest to such biased position. On disposition of the actuators in its biased position and movement therefrom successively into its snap-action positions, the contact elements may thereby be successively disengaged, engaged and disengaged, thus providing plural conditions for effecting the disengaged contact element state.

Other objects and features of the invention will be evident from the following detailed description of preferred embodiments thereof, disclosed in the abovementioned heat detection and control environment, and from the drawings wherein like reference numerals are employed to designate like parts throughout.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevational view, partly in section, of a first embodiment of a switch constructed in accordance with the invention shown in association with heat detecting apparatus.

FIG. 2 is a side elevational view taken along the lines ll--Il of FIG. 1.

FIG. 3 is a front elevational view, partly in section, of a second embodiment of a switch constructed in accordance with the invention.

FIG. 4 is a side elevational view of the FIG. 3 switch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, capillary protector 24 is a form of heat detector which provides a mechanical output, i.e., diaphragm movement, when the contents thereof expand volumetrically, as occurs in heating thereof. The protector comprises a hollow heat-conductive tube 26 containing vaporizable material 12, such as silicon oil, in exclusively liquid state. Tube 26 is provided with a closure member including a resilient portion in engagement with the contained material/In FIG. 1, such closure member includes a diaphragm 28 and a housing 30, the diaphragm margins being disposed in abutting relation with both tube 26 and housing 30. An extended marginal portion of diaphragm 28 abuts with housing 30 and is thus not deformable outwardly of the tube. The remaining expanse of diaphragm 28 interiorly of this marginal portion is unrestrained and hence is readily deformable both outwardly and inwardly of tube 26. By appropriate dimensioning of the readily deformable interior expanse of diaphragm 28, the diaphragm is caused to apply a continuing pressure to material 12 to exert thereon a force sufficient to maintain the material in exclusively liquid state when tube 26 is at temperatures below a preselected temperature of interest. The purpose for such pressurization is discussed in detail in the above-mentioned concurrently-filed patent application.

Housing 30 and its contents discussed below comprise a first embodiment of a switch constructed in accordance with the invention. In such arrangement, the switch is operatively responsive to diaphragm 28 in its illustrated position and positions which the diaphragm assumes in deforming ourwardly and inwardly of tube 26.

Housing 30 fixedly supports an electrical contact element 32 and a terminal 34 connected thereto. The housing supports a further electrical contact element 36 on movable support arm 38. Terminal 40 is provided with electrical continuity to movable contact element 36 by support arm 38 and a further support arm 42, arm 38 being pivotallysupported by arm 42 at its point of juncture therewith. Displacement of support arm 38 is controlled by actuator 44, also supported for pivotal movement by support arm 42, by coil spring 46, whose end loops respectively overlap support arm 38 and actuator 44, and by fail-safe linkage 48. Actuator 44 includes an arcuate portion 44a adapted for engagement with diaphragm 28. Housing 30 includes a recess 50 adapted to limit rightward movement of contact arm 38.

In its configuration shown in FIG. 2, diaphragm 28 is shown in engagement with material 12 under the conditions wherein tube 26 is effectively containing the material, i.e., has not been ruptured, wherein tube 26 is throughout its extent at a temperature below the preselected temperature and wherein material 12 is in exclusively liquid state. The illustrated configuration of diaphragm 28 provides a measure of the volume of material 12 under these conditions and contacts 32 and 36 are maintained in engagement by the diaphragm since the diaphragm exerts force on actuator 44 such that spring 46 forces support arm 38 into its illustrated position. Snap-action can occur at this actuator position, and the position may thus be considered to be the first actuator position discussed above. On the occurrence of the heating of an expanse of tube 26 to the preselected temperature or above, material 12 vaporizes in part and the deformable expanse of diaphragm 28 is urged Ieftwardly to rotate actuator 44 counterclockwise. Upon such rotation of actuator 44, spring 46 passes through an equilibrium condition and thereupon, in snap-action, drives support arm 38 into recess 50, thereby disengaging contacts 32 and 36. Under this condition the actuator may be said to be in the abovediscussed second position thereof at which snap-action can occur. Such deformation of diaphragm 28 provides a configuration thereof indicative of volumetric expansion of material 12 according with the occurrence of heating of tube 26 intended to be detected. This situation will persist until heat is removed from tube 26 and the void occasioned therein by the heating commences to diminish.

As such void is' driven to nil by pressurization of material 12 by diaphragm 28, the diaphragm reassumes its illustrated disposition, actuator 44 reverts to its first position and a reverse snap-action occurs under the influence of spring 46 and contacts 32 and 36 are reengaged. In the event that tube 26 is ruptured in use, or otherwise leaks material therefrom, diaphragm 28 will deform inwardly of tube 26 and will be followed by actuator portion 44a under the influence of spring 46. On this occurrence, fail-safe linkage 48, which is secured to actuator 44, engages arm 38 and disengages the reengaged contacts 32 and 36. In this position, the actuator may be said to be in the above-discussed (third) position thereof exteriorly of the first and second positions thereof. More specifically, the actuator is in a further position, to which it is biased by spring 46, outside of the position range inclusive of the first and second positions and positions therebetween.

In usage of the apparatus of FIG. 2, one of terminals 34 and 40 is connected to a heating element and the other terminal is connected to one terminal of the power supply for such heating element. Electrical continuity between terminals 34 and 40 is provided exclusively where tube 26 is below the preselected temperature and is in material-containing condition.

In this exemplary application for switches of the invention and in the absence of malfunction in the structure of tube 26, actuator movement occurs only on the heating of the tube to the preselected temperature and subsequent cooling, i.e., movements between the first and second actuator positions. The extremes of these movements are accompanied, desirably so, by snapaction in contact element engagement and disengagement. The fail-safe feature, namely, contact disengagement on actuator movement from the first position in the direction of the third position, is not a snap-action function and is not required to be such since the same occurs, not repetitively as in normal functioning of the apparatus, but only on malfunction.

Referring to the alternate switch embodiment of FIGS. 3 and 4, housing 77 fixedly supports an electrical contact element 78 and a terminal 80 connected thereto. The housing supports further an electrical contact arm 82. Terminal 84 is provided with electrical continuity to contact arm 82 by support arm 86, arm 82 being pivotally supported by arm 86 at its point of juncture therewith. Displacement of contact arm 82 is controlled by actuator 88, also supported for pivotal movement by support arm 86 and by spring 90.

Unlike spring 46 above, which was a coil spring looped about and freely movable relative to arm 38 and actuator 44 (FIG. 1), spring is in strip metal or ribbon form including a planar section 90a rigidly secured by welding or the like to contact arm 82 and a folded section 90b extending to actuator 88 and securely engaging a rib 88a thereof. Actuator 88 includes an arcuate portion 88b adapted for engagement with a diaphragm or other switch controller. Housing 76 includes a post 92 adapted to limit rightward movement of contact arm 82.

In the illustrated configuration thereof, the switch contact elements are disengaged, actuator 88 being in its furthest clockwise disposition (third position) abutting stops 86b of support arm 86. In the switch embodiment of FIG. 1, the separation of contact elements with the actuator so disposed was effected by fail-safe link 48 and, in the absence of such link, the contact elements would have been engaged under the influence of coil spring 46. In the FIG. 7 switch embodiment, contact separation with actuator 88 in its furthest clockwise position is effected by spring 90 which, by reason of its disposition and non-rotative securement to contact arm 82 and its gripping securement with rib 88a, biases actuator 88 into such position and also lifts contact arm 82 away from contact element 78.

When a diaphragm or other member is placed in operative engagement with actuator portion 88b to rotate the actuator clockwise, the contacts are engaged. Snapaction disengagement and reengagement occur thereafter on actuator movement as discussed in the case of the FIG. 1 switch embodiment. Upon diaphragm or like failure, the switch assumes its illustrated configuration.

Various changes and modifications in the apparatus of the invention will be evident to those skilled in the art. Accordingly, the foregoing disclosed particular embodiments of the invention are intended in an illustrative and not in a limiting sense. The true spirit and scope of the invention is defined in the following claims. I

What is claimed is:

l. An electrical switch comprising a housing, a first contact fixedly supported in said housing, a support member fixedly positioned in said housing, a contact arm supported for movement by said support member, a second contact supported by said contact arm, an actuator supported by said support member for movement from a first position into second and third positions, spring means having a first end engaging said actuator and a second end engaging said contact arm, l for biasing said actuator into said first position, (2) for moving said contact arm to engage said first and second contacts on movement of said actuator from said first into said second position and (3) for moving said contact arm in snap-action manner to disengage said contacts on said movement of said actuator from said second position into said third position, and further means providing connection of said actuator and said contact arm when said actuator is moved to said first position for'moving said contact arm to disengage said first and second contacts.

2. The switch claimed in claim 1 wherein said support member supports said actuator for rotative movement, said actuator being positionable on unidirectional rotative movement thereof from said first position successively in said second and said third positions, said first and second contact elements being thereby successively disengaged, engaged and disengaged.

3. An electrical switch comprising a housing, a first contact fixedly supported in said housing, a support member fixedly positioned in said housing, a contact arm supported for movement by said support member, a second contact supported by said contact arm, an actuator supported by said support member for movement from a first position into second and third positions, strip metal or ribbon spring means having a first end engaging said actuator and a second end engaging said contact arm, l for biasing said actuator into said first position, (2) for moving said contact arm to engage said first and second contacts on movement of said actuator from said first into said second position and (3) for moving said contact arm in snap-action manner to disengage said contacts on said movement of said actuator from said second position into said third position, said spring means second end being nonrotatively secured to said contact arm whereby said spring means moves said contact arm to disengage said first and second contacts when said actuator is moved to said first position.

4. The switch claimed in claim 3 wherein said support member supports said actuator for rotative movement, said actuator being positionable on unidirectional rotative movement thereof from said first position successively in said second and said third positions, said first and second contact elements being thereby successively disengaged, engaged and disengaged.

Claims (4)

1. An electrical switch comprising a housing, a first contact fixedly supported in said housing, a support member fixedly positioned in said housing, a contact arm supported for movement by said support member, a second contact supported by said contact arm, an actuator supported by said support member for movement from a first position into second and third positions, spring means having a first end engaging said actuator and a second end engaging said contact arm, (1) for biasing said actuator into said first position, (2) for moving said contact arm to engage said first and second contacts on movement of said actuator from said first into said second position and (3) for moving said contact arm in snap-action manner to disengage said contacts on said movement of said actuator from said second position into said third position, and further means providing connection of said actuator and said contact arm when said actuator is moved to said first position for moving said contact arm to disengage said first and second contacts.

2. The switch claimed in claim 1 wherein said support member supports said actuator for rotative movement, said actuator being positionable on unidirectional rotative movement thereof from said first position successively in said second and said third positions, said first and second contact elements being thereby successively disengaged, engaged and disengaged.

3. An electrical switch comprising a housing, a first contact fixedly supported in said housing, a support member fixedly positioned in said housing, a contact arm supported for movement by said support member, a second contact supported by said contact arm, an actuator supported by said support member for movement from a first position into second and third positions, strip metal or ribbon spring means having a first end engaging said actuator and a second end engaging said contact arm, (1) for biasing said actuator into said first position, (2) for moving said contact arm to engage said first and second contacts on movement of said actuator from said first into said second position and (3) for moving said contact arm in snap-action manner to disengage said contacts on said movement of said actuator from said second position into said third position, said spring means second end being non-rotatively secured to said contact arm whereby said spring means moves said contact arm to disengage said first and second contacts when said actuator is moved to said first position.

4. The switch claimed in claim 3 wherein said support member supports said actuator for rotative movement, said actuator being positionable on unidirectional rotative movement thereof from said first position successively in said second and said third positions, said first and second contact elements being thereby successively disengaged, engaged and disengaged.

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