US3573410A

US3573410A - Snap action pressure sensitive switch with snap disc resiliently supported between legs of a terminal

Info

Publication number: US3573410A
Application number: US858832A
Authority: US
Inventors: Tadeusz Budzich; Frederick D Keady
Original assignee: Weatherhead Co
Current assignee: Weatherhead Co
Priority date: 1969-09-17
Filing date: 1969-09-17
Publication date: 1971-04-06
Anticipated expiration: 1988-04-06

Abstract

A pressure-operated switch is disclosed in which one switch contact is supported by an elongated bistable snap element. The snap element is mounted on cantilever springs urging the ends of the element toward each other causing the element to bend with a single node. The spring loading is insufficient to produce multinode bending during movement of the snap element between its two positions. Several of the elements perform more than one function thereby reducing the number of elements required for the assembled device. For example, one terminal element functions to support the snap element, limit the plunger travel in one direction, and provide support for the diaphragm. Similarly, a spring functions to connect the other terminal to one contact element and to resiliently bias the plunger in one direction.

Description

United States Patent [72} Inventors Tadeusz Budzich Moreland Hills; Frederick D. Keady, Cleveland Heights, Ohio [211 Appl. No. 858,832 [22] Filed Sept. 17, 1969 [45] Patented Apr. 6,1971 [7 3] Assignee The Weatherhead Company Cleveland, Ohio [54] SNAP ACTION PRESSURE SENSITIVE SWITCH WITH SNAP DISC RESILIENTLY SUPPORTED BETWEEN LEGS OF A TERMINAL 1] Claims, 3 Drawing Figs.

[52] U.S. Cl 200/83P, 200/67DB, 200/76, 200/166CT [SI] Int. Cl H0lh 35/34, H01hl3/38,I-I0lh13/48 [50] Field of Search 200/67 (D2), 76, 83.9, 83, 166(ICTS), 67D (Inquired) [56] References Cited UNITED STATES PATENTS 2,040,181 5/1936 Mekelburg 200/83.9X 2,84l,66l 7/l 958 Wintle ZOO/76X Primary ExaminerRobert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney- McNenny, F arrington, Pearne and Gordon ABSTRACT: A pressure-operated switch is disclosed in which one switch contact is supported by an elongated bistable snap element. The snap element is mounted on cantilever springs urging the ends of the element toward each other causing the element to bend with a single node. The spring loading is insufficient to produce multinode bending during movement of the snap element between its two positions. Several of the elements perform more than one function thereby reducing the number of elements required for the assembled device. For example, one terminal element functions to support the snap element, limit the plunger travel in one direction, and provide support for the diaphragm. Similarly, a spring functions to connect the other terminal to one contact element and to resiliently bias the plunger in one direction.

SNAP ACTION PRESSURE SENSITIVE SWITCH WITI-I SNAP DISC RESILIEN'ILY SUPPORTED BETWEEN LEGS OF A TERMINAL BACKGROUND OF INVENTION AND PRIOR ART This invention relates generally to pressure-operated switching devices and more particularly to a pressure switch constructed and arranged to minimize the number of parts required, to reduce manufacturing and assembly costs, and to improve reliability and durability.

The copending application of Eugene Bauniuk, Ser. No. 701,439, filed Jan. 26, 1968, assigned to the assignee of the present invention, discloses a pressure-operated switch which is particularly adapted for use in refrigeration systems or the like to prevent system operation when the pressure of the refrigerant is below a predetermined pressure.

A pressure-operated switch in accordance with the present invention is suitable for use in similar installations and is constructed and arranged to minimize manufacturing costs while maintaining reliability and durability.

SUMMARY OF INVENTION In the illustrated embodiment of this invention, the various elements of the combination are arranged so that a single element, in many instances,-performs a dual function in the combination. For example, a coil spring functions to bias the plunger in one direction and also provides the electrical connection between one terminal and the switch. A mounting ring functions to support one of the terminals, seal the diaphragm and guide the plunger assembly. Similarly, one of the terminal elements is arranged to function as a terminal connector, a support for a snap element, and to provide a surface for the support of the diaphragm to prevent damage thereof when the diaphragm is subjected to high pressure. With the illustrated structure, the number of parts is minimized, assembly is simplified, and the switch provides reliability and durability.

The snap action and the differential pressure of operation of the switch is provided by a bistable element, This element is an end-loaded column which is buckled into one node of a sine wave by a pair of cantilever springs which are integral parts of one terminal and act as the supports and locators of the snap element. The column end load applied to the snap element by the cantilever springs is sufficient to bend the snap element into a single node, but is insuflicient to bend it into two nodes, or an S curve. With this structure greater operating accuracy is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation in longitudinal section illustrating the assembled switch device in the switch open position;

FIG. 2 is a longitudinal section taken at right angles to the section of FIG. 1 illustrating the switch mechanism in the switch closed position; and

FIG. 3 is a fragmentary perspective view illustrating the structure of the snap element and its supporting terminal.

The illustrated embodiment of this invention includes a metallic body element formed with an axially extending bore 11 defining a switch cavity 12. The body is provided with an end wall 13 and a threaded nipple section 14 arranged so that the switch body can be threaded into the associated system. A flow passage 16 extends through the nipple section and the end wall 13.

A flexible diaphragm 17 is positioned in the switch cavity 12 adjacent to the end wall 13. The diaphragm 17 is proportioned to fit within a bore extension 18 in the body 10 and a central recess 19 is formed in the body 10 adjacent to one side of the diaphragm 17 which cooperates with the diaphragm to form a chamber 21 on one side of the diaphragm open to the passage 16.

A mounting ring 22 formed of a nonconductive material such as a phenolic resin is positioned within the bore 11 and is axially located with respect to the body 10 by a radial shoulder 23. The mounting ring 22 and the body 10 are formed with annular projections 24 and 26, respectively, which press into the diaphragm surface to insure that the diaphragm seals with the body around its periphery.

The mounting ring 22 is engaged at its upper end by a closure member 27 which is also formed of a nonconductive material such as a phenolic resin. The body 10 is formed with a skirt 28 which is deformed at 29 overa shoulder 31 in the cap member 27 to hold the cap member 27 against the mounting ring 22, in turn, hold the mounting ring 22 against the shoulder 23.

A pair of

terminal elements

32 and 33 extends through the closure member 27 to provide external connecting portions by which the switch can be connected to an electrical system. As best illustrated in FIG. 2, the terminal member 32 is L-shaped and is provided with a laterally projecting portion 34 positioned within a mating recess 36 in the closure member 27. The upstanding portion of the terminal 32 extends through an opening 37 to the exterior of the device. The closure member is formed with a lateral shoulder 38 in the opening 37 into which a locking projection 39 extends to lock the tenninal 32 in the closure member 27 The terminal 33 is provided with a ring portion 41 at its lower end and three upstanding projecting

portions

42, 43, and 44. The projecting portion 44 extends upwardly through an opening 45 in the closure member 27 to provide one of the external terminal connections for the device. The other two projecting

portions

42 and 43 are located on opposite sides of the ring portion 41 and extend up through openings 46 in the mounting ring 22 as best illustrated in FIG. 1. The two projecting

portions

42 and 43 are formed with openings 47 and adjacent V-notches 48. A metallic snap element 49 is provided with tabs 51 at its ends which extend into the openings 47 and lateral edges 52 which seat in the V-notches 48. This connection provides a simple, substantially friction free mounting of the snap element 49 between the two projecting

portions

42 and 43.

Located within the mounting ring 22 and guided thereby is a plunger assembly 53. The plunger assembly includes an outer cup-shaped member 54 formed of a nonconductive material such as a phenolic resin, and an inner metallic cup-shaped member 56. The two

members

54 and 56 are proportioned so that the cup-shaped member 56 extends down into the cupshaped member 54 with its end wall 57 engaging the end wall 58 of the member 54. The upper end of the element 56 is provided with a radial flange 59 which serves as one of the contacts of the switch mechanism. The snap element 49 is formed with a central opening 61 best illustrated in FIG. 3 through which the upper end of the plunger assembly 53 projects with clearance. The snap element 49 is provided with a contact 60 on each of its legs which are movable into engagement with the flange 59 as illustrated in FIG. 2 to provide an electrical connection therebetween.

The mounting ring 22 is provided with an inwardly extending flange 62, the inner surface of which guides the plunger assembly 53. The cup-shaped member 54 is provided with a radially extending flange 63 positioned below the flange 62 and engageable therewith to limit upward movement of the plunger assembly. Downward movement of the plunger assembly is limited by engagement between the flange 63 and the end 64 of the ring portion 41 of the terminal 33. The ring portion 41 is formed with a conical extension 66 extending upwardly and inwardly from a reverse bend at 67. The conical extension 66 is proportioned to provide a smooth transition between the end wall 58 of the member 54 and the reverse bend 67 so that the diaphragm 17 is provided with smooth support when the chamber 21 is pressurized to a relatively high pressure. With this structure, the entire diaphragm is supported against damage resulting from high pressures.

The plunger assembly 53 is urged in a downward direction toward the diaphragm 17 by a metallic coil spring 68 which extends between the lateral portion 34 of the terminal 33 and the end wall 57 of the cup-shaped member 56. The spring 68 performs a dual function of urging the plunger assembly 53 toward the diaphragm and also providing an electrical connection between the cup-shaped member 56 and the terminal 33.

The cup-shaped member 54 is provided with a radial surface 69 opposed to and spaced from the flange 59. The various elements are proportioned so that movement of the plunger assembly 53 toward its upper position under the influence of fluid under pressure in the chamber 21 causes the shoulder 69 to engage the snap member 49 and move it through its midposition. The snap element then snaps on through until the contact 61 engages the flange 59 to close the switch. When the pressure of the fluid in the chamber 21 drops to a predetermined minimum pressure, the spring 68 causes the plunger assembly to move downwardly against the action of the snap element and the pressure in the chamber 21 until the snap element is carried past its midposition. When this occurs, the snap element snaps to the position of stability illustrated in FIG. 1 and the contact 60 snaps out of engagement with the flange S9.

The cup-shaped member 54 is preferably provided with an upstanding skirt 71 proportioned to extend up through the snap member 49 even when the snap member is in a closed position of FIG. 2. This insures that shorting will not occur between the snap element and the cup-shaped member 56.

The two

projections

42 and 43 which support the bistable snap element 49 function as cantilever springs to produce a resilient force urging the ends of a snap element 49 toward each other. Therefore, the snap element is bent with a single node toward its positions of stability. AS the plunger assembly engages the center part of the snap element it moves it toward the midposition and the two

projections

42 and 43 are deflected outwardly toward the phantom position illustrated in FIG. 1. The openings 46 are formed with clearance behind each of the

projections

42 and 43 to permit this deflection. Because the supporting

projections

42 and 43 are not rigid and can deflect outwardly as the snap element moves toward its midposition, the snap element can assume a straight condition at its midposition and it is not necessary for the snap element to assume a compound S-type curve having two nodes. Once the snap element passes through its midposition, however, sufficient force is provided by the supporting

projections

42 and 43 to cause the opposite bending and the snap element moves with snap motion to its other position of stability. The inner walls 50 of the openings 46 engage the associated

projections

42 and 43 to limit their inward movement and thereby limit the amount of bending of the snap element.

Because the snap element moves between its two positions with simple, single node bending, the operating characteristics of the snap element can be accurately predicted by relatively simple mathematical analysis. Therefore, this structure improves the predictability of the operating characteristics of the assembled device. Further, the structure, which is symmetrical, results in a straight line movement of the contacts 60 as they are carried by the snap element between its two positions of stability. Consequently, the contacts 60 move straight into engagement with the flange 59 without rocking movement when the switch closes. Similarly, the contacts 60 are moved away from the flange 59 with a substantially straight line movement when the switch opens. With this structure, arcing is minimized and contact life is improved.

With the disclosed structure, the terminal 33 serves three functions. First, it functions as one of the terminals of the switch. Second, it supports the snap member, and, third, it supports the diaphragm against damaging stress when the pressure of the fluid in the chamber reaches relatively high pressures. The spring 68 functions to urge the plunger assembly toward the diaphragm and also functions to provide an electrical connection between the terminal 32 and the cupshaped member 56. The entire assembly is held together without separate fastening means by a simple expedient of bending the skirt 28 over a mating flange on the closure member 27.

Although a preferred embodiment of this invention is illustrated, it is to be understood that various modifications and rearrangements may be resorted to without departing from the scope of the invention disclosed.

We claim:

1. A snap switch comprising a body assembly, a plunger mounted in said body assembly for reciprocation between first and second positions, a pair of opposed supports in said body assembly with one on each side of said plunger, a resilient snap element supported at its ends on said opposed supports and formed with a central opening through which said plunger assembly extends, said snap element providing a leg on each side of said plunger assembly, said supports urging the ends of said snap element toward each other and causing said snap element to bend with a single node so that said snap element is provided with two positions of stability, said plunger assembly providing opposed surfaces on opposite sides of said snap element engageable with said snap element substantially midway between its ends, one of said opposed surfaces being electrically conductive and in engagement with said snap element when said snap element is in its first position of stability and said plunger is in its first position, movement of said plunger to its second position causing said snap element to move through a position of instability and causing said snap element to move with snap motion out of contact with said conductive surface to its second position of stability, and a pair of terminals adapted to be connected to an external circuit, one of said terminals being electrically connected to said conductive surface and the other of said terminals being electrically connected to said snap element.

2. A snap switch as set forth in claim 1 wherein said supports resiliently urge the ends of said snap element toward each other with sufficient force to cause said snap element to bend with a single node and insufficient force to cause said snap element to bend with a double node.

3. A snap switch as set forth in claim 2 wherein said conductive surface engages both of said legs substantially midway between the two ends of said snap element.

4. A snap switch as set forth in claim 3 wherein a contact element is mounted on each of said legs substantially midway between the ends of said snap element.

5. A snap switch as set forth in claim 4 wherein said other terminal includes a terminal portion exterior of said body assembly and integrally formed cantilever spring portions providing said opposed supports, said snap element being mounted on the free ends of said cantilever spring portions.

6. A snap switch as set forth in claim 4 wherein contact elements are carried by said snap element for movement into and out of engagement with said conductive surface, said contact means moving with substantially straight line movement when said snap element moves between said first and second positions of stability.

7. A snap switch comprising a body assembly provided with a switch chamber, a pair of terminal members each having a terminal portion adapted to be connected to an external circuit, one of said terminal members providing opposed integrally formed cantilever spring portions, a resilient snap element mounted at its ends on the free ends of said cantilever spring portions, said spring portions urging the ends of said snap element toward each other to cause the snap element to bow with a single node and provide two positions of stability, a plunger assembly in said body assembly reciprocable between said first and second positions, contact means carried by said plunger assembly electrically connected to the other of said terminal members and operable to engage said snap element to provide an electrical connection between said terminal members, a spring operable to urge said plunger assembly toward its first position, a diaphragm mounted in said body assembly operably connected to said plunger assembly to overcome said spring and move said plunger assembly to its second position, said one terminal member providing a support section around said plunger assembly engageable with said diaphragm when said diaphragm moves said plunger assembly to said second position to cooperate with said plunger assembly and provide substantially complete support of said diaphragm.

8. A snap switch asset forth in claim 7 wherein said support section prevents movement beyond said first position in a direction away from said second position.

9. A snap switch as set forth in claim 8 wherein said spring provides the electrical connection between said contact means and said other terminal member.

10. A pressure responsive switching device comprising a body formed with a switch cavity having an apertured end wall, a flexible diaphragm positioned against said end wall, a nonconductive mounting ring in said body pressing said diaphragm into sealing engagement with said end wall, a first terminal element mounted on said mounting ring and provided with opposed support projections, a snap-acting contact mounted at its ends on said projections, a plunger assembly including a cup-shaped nonconductive plunger element axially movable along said mounting ring and a cup-shaped electrically conductive plunger element telescoping into said nonconductive plunger element, a closure element positioned against the end of said mounting ring pressed in a direction toward said mounting ring by said body, a second terminal on said closure element, a conductive spring extending between said second tenninal and said electrically conductive plunger element operating to electrically connect them and to urge said plunger assembly and said diaphragm toward said first position, fluid under pressure admitted to one side of said diaphragm through said apertured end wall operating to overcome said spring and move said plunger assembly to said second position when predetennined pressures exist, said plunger elements each providing a radially extending surface with one on each side of said snap-acting contact, said radial surfaces cooperating to engage said snap-acting contact to move it between said positions of stability when said plunger moves between said first and second positions, said snap-acting element engaging said radial surface of said electrically conductive plunger element when said plunger assembly is in one of said first and second positions to provide an electrical connection between said surfaces.

11. A pressure responsive switching device as set forth in claim 10 wherein said opposed support projections are resilient cantilever springs which urge the ends of said snapacting contact toward each other with sufficient force to bend said snap-acting contact with a single node and insufi'icient force to bend it with a multinode.

Claims

8. A snap switch as set forth in claim 7 wherein said support section prevents movement beyond said first position in a direction away from said second position.

10. A pressure responsive switching device comprising a body formed with a switch cavity having an apertured end wall, a flexible diaphragm positioned against said end wall, a nonconductive mounting ring in said body pressing said diaphragm into sealing engagement with said end wall, a first terminal element mounted on said mounting ring and provided with opposed support projections, a snap-acting contact mounted at its ends on said projections, a plunger assembly including a cup-shaped nonconductive plunger element axially movable along said mounting ring and a cup-shaped electrically conductive plunger element telescoping into said nonconductive plunger element, a closure element positioned against the end of said mounting ring pressed in a direction toward said mounting ring by said body, a second terminal on said closure element, a conductive spring extending between said second terminal and said electrically conductive plunger element operating to electrically connect them and to urge said plunger assembly and said diaphragm toward said first position, fluid under pressure admitted to one side of said diaphragm through said apertured end wall operating to overcome said spring and move said plunger assembly to said second position when predetermined pressures exist, said plunger elements each providing a radially extending surface with one on each side of said snap-acting contact, said radial surfaces cooperating to engage said snap-acting contact to move it between said positions of stability when said plunger moves between said first and second positions, said snap-acting element engaging said radial surface of said electRically conductive plunger element when said plunger assembly is in one of said first and second positions to provide an electrical connection between said surfaces.

11. A pressure responsive switching device as set forth in claim 10 wherein said opposed support projections are resilient cantilever springs which urge the ends of said snap-acting contact toward each other with sufficient force to bend said snap-acting contact with a single node and insufficient force to bend it with a multinode.