US3555220A

US3555220A - Pressure switch

Info

Publication number: US3555220A
Application number: US719319A
Authority: US
Inventors: Charles G Wood
Original assignee: Essex International Inc
Current assignee: Lear Corp EEDS and Interiors
Priority date: 1968-04-08
Filing date: 1968-04-08
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12

Abstract

A switch responsive to fluid pressure includes a housing constructed of an electrically conductive material and a pair of chambers are formed within the housing separated by a flexible diaphragm. One of the chambers is adapted to be connected to a fluid pressure source and an electrically nonconductive cap seals the end of the other chamber and carries a stationary contact which extends into the other chamber. A resilient disc is disposed in the other chamber adjacent the diaphragm and includes a rim clamped between the housing and the cap, a resilient tab and a movable contact. The resilient tab is responsive to movement of the diaphragm which, in turn, is movable in response to pressure changes in the first chamber, to move the contact surface into and out of electrical contact with the stationary contact. The disc contacts the electrically conductive housing to complete the circuit.

Description

United States Patent [72] Inventor CharlesG. Wood Royal Oak, Mich. [211 Appl.No. 719,319 [22] Filed Apr.8,l968 [45] Patented Jan. 12,1971 [73] Assignee Essex lntemational,lnc.

Fort Wayne, Ind. a corporation of Michigan [54] PRESSURESWITCH 9 Claims, 7 Drawing Figs.

52 U.S.Cl 200/83 %511 Int.Cl ..H01h35/40 [50] FieldofSearch ZOO/61.12, 82.3,83,83.2,83.4,83.8,81

[56] References Cited UNITED STATES PATENTS 2,367,441 1/1945 Schwinn 200/61.12 2,562,286 7/1951 Wall 200/83(.2) 2,721,913 10/1955 Kent,.lr.. 200/83(.8) 2,762,895 9/1956 Throw 200/83(.2)x 2,817,727 12/1957 Schmeling. ZOO/83(2) 2,822,530 2/1958 Roten 200/83(.4)x

Primary Examiner-Robert K. Schaefer Assistant Examiner.l. R. Scott Att0rneyBair, Freeman & Molinare ABSTRACT: A switch responsive to fluid pressure includes a housing constructed of an electrically conductive material and a pair of chambers are formed within the housing separated by a flexible diaphragm. One of the chambers is adapted to be connected to a fluid pressure source and an electrically nonconductive cap seals the end of the other chamber and carries a stationary contact which extends into the other chamber. A resilient disc is disposed in the other chamber adjacent the diaphragm and includes a rim clamped between the housing and the cap, a resilient tab and a movable contact. The resilient tab is responsive to movement of the diaphragm which, in turn, is movable in response to pressure changes in the first chamber, to move the contact surface into and out of electrical contact with the stationary contact. The disc contacts the electrically conductive housing to complete the circurt.

PRESSURE SWITCH BACKGROUND OF THE INVENTION This, invention relates to a pressure switch and, more particularly, to a new and improved pressure switch, particularly adapted for use in an oil pressure warning circuit or the like.

Prior pressure switches, as used for sensing fluid pressure changes, suffered a number of disadvantages. In many of the prior switches, the electrical contact surfaces themselves were exposed to the fluid-stream. This exposure frequently resulted in an undesirable accummulation of foreign matter on the contact surfaces and erratic operation. Moreover, these switches could not be utilized where the pressure being sensed was that of an explosive fluid due to the disastrous consequences which would result from sparking of the contacts. Moreover, such prior switches frequently were constructed of numerous parts. Thus, their construction was rendered relatively complex and costly and the final structure was subjected to possible leaks and an increased probability of malfunction due to the failure of one of the many elemental parts.

In order to overcome many of the disadvantages of the aforementioned switches, various switches have been provided employing a diaphragm which separates the switch contact surfaces from the pressure fluid itself. These switches generally comprise a flexible diaphragm which is deformed in response to pressure variations of the fluid, the deformation of which operates a rigid movable contact carrying member or contact into and out of contact with a stationary contact member. These prior diaphragm switches uniformly employ a spring to urge the contact carrying member or the movable contact itself in at least one of the directions; the spring pressure being overcome by the deformation of the diaphragm. The spring is a necessary element since the movable contact carrying structure is rigid in the prior diaphragm switches. Thus, these diaphragm switches are also complex and require the use of a substantial number of elemental parts to complete their assembly. Such complexity again results in a relatively high cost of manufacture and/or repair and the probability of failure of anyone of the elements remains high.

Accordingly, a pressure responsive switch constructed in accordance with the principles of my invention, contains no switch-contacting surfaces which are in contact with the pressurized fluid. Moreover, such a switch includes only a few structural elements thus simplifying its construction as well as its costs of manufacture and/or repair. Most of the elements of the switch constructed in accordance with the principles of my invention may be rapidly and inexpensively stamped from sheet material, thus further reducing the cost of manufacture and assembly. Since such switch has relatively few parts, the

In the course'of this description, reference will frequently be made to the attached drawings in which:

FIG. 1 is an elevation cross-sectioned view of a normally closed switch embodiment of a=switch-constructed in accordan'ce with the principles of my invention;

FIG. 2 is a plan view of the embodiment shown in FIG. I with the stationary contact removed;

FIG. 3 is an elevation view of the stationary contact;

FIG. 4 is a plan view of the disc; I

FIG. 5 is an elevation cross-sectioned view of the disc taken along line 5-5ofFIG. 4;

FIG. 6 is an end elevation view of the disc; and

FIG. 7 is an elevation cross-sectioned view of a normally open switch embodiment of a switch constructed in accordance with the principles of my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 1 Referring to FIG. 1, a generally cylindrical tubular housing 10 is provided which is preferably of onepiece construction. Disposed intermediate the 'e nds of the housing is an external shoulder portion 12 of hexagonal or other suitable shape for the purpose of accommodatingian,appropriate installation tool:;The lower extemalportion of the housing preferably carries threads for attaching the housing to an appropriate fluid-carrying conduit. The lower end-of the housing is closed by a wall 16 having an aperture or port 18 for communicating the interior of the housing with the fluid conduit.

A flexible diaphragm .20 is disposed within the housing intermediate its ends on anannular shoulder 22. The shoulder 22 carries an annular bead 24 upon its horizontal surface designed to engage a complimentary annular groove 26 in the diaphragm for holding the diaphragm in place. The diaphragm 20 sealingly separates the housing into a pair of

chambers

28 and 30. I I

The open end of chamber 30 is closed by a cap 32 composed of a nonconductive material, such as rubber or a synthetic polymeric material The cap carries a shoulder 33 and is held firmly in place on the housing by bending the housing 10 over the shoulder at 34. As shown in FIG. 2, a slot 35 is provided in the cap 32 and a stationary contact 36 is inserted probability of failure of a part of the switch is substantially reduced.

SUMMARY or THE INVENTION A fluid pressure responsive switch constructed in accordance with the principles of my invention, includes a housing having a pair of chambers therein. A flexible diaphragm sealingly separates the one chamber from the other chamber end of the other chamber and carries a stationary contact which extends into that chamber. A deformable resilient movable contact disc structure is positioned in the other chamber adjacent the diaphragm and carries a movable contact which is adapted to make and break an electrical circuit with the stationary contact. The resilient movable contact disc is arranged so as to be deformed by movement of the diaphragm in response to pressure changes in the first chamber.

These and other objects, features and advantages of the present invention will be more clearly understood through a consideration of the following detailed description.

through the slot. The stationary contact 36 is prevented from longitudinal movement in the slot by a pair of bent ears 38 overlying the external surface of the cap and a bent tang 40 underlying theinternal surface of the cap 32. One or both of I theears 38 or tang 40 may be bent after insertion of the contact is completed. Thestationary contact 36 also includes a terminal portion 42 extending externally of the cap 32 and an L-shaped switch contact'portion 44=disposed within chamber 30 and spaced above the diaphragm 20.

A resilient-contact disc 46 is disposed upon the diaphragm 20 in chamberdt). The overall geometrical shape and surface area of the disc 46 is substantially the same as the geometrical shape and cross-sectional area of chamber 30. Referring to FIGS 4-6, a-resilient tab 48 is-formed in the disc leaving a rim 50. The rim 50 is firmly held down by thecap 32 and is in contact with the inner wall of the electrically conductive housing it). The surface of the tab 48 preferably constitutes the major portion of the surface area of the disc to render the disc readily responsive to deformation of the diaphragm 20 and is raised slightly above the surface of rim 50. The tab 48 is formed integral withthe rim 50 at its periphery by leg 52 I where it is bent upwardly from the rim. A contact surface 54 is facilitate bending of the tab from the rimand prevent progressive ripping of the leg 52 during. use. The disc 46 may be stamped or otherwise formed from sheet metal.

Referring again to FIG. 1, when assembling the pressure responsive switch of the present invention, the diaphragm 20 is inserted into the housing and placed upon the shoulder 22 such that its annular groove 26 aligns with the annular bead 24. The resilient disc 46 is next inserted into the housing 10 and placed upon and in parallel relationship with the diaphragm 20. The cap 32 containing the stationary contact 36 is then inserted into the open end of the housing 10 and the horizontal portion of the L-shaped contact 44 is moved beneath the contact surface 54 of the disc. The housing 10 is then bent at 34 over the shoulder portion 33 of the cap 32 and the lower edge of the cap is brought to rest firmly bearing against the rim 50 of the disc 46 urging the rim into electrical contact with the conductive housing 10 at its stepped shoulder 64. The

tabs

58 and 60 act as springs firmly urging the diaphragm into fixed engagement with the housing shoulder 22. N In operation, the fluid of which the pressure is desired to be sensed, enters the port or aperture 18 and fills chamber 28. If the fluid is not pressurized, the diaphragm 20 will be in a generally horizontal undeformed disposition and the tab 48 of the disc 46 will also be in a generally horizontal undeformed lowered position. Thus, the contact surface 54 of the disc will be in a lowered position and in contact with the upper surface of the L-shaped contact 44 of the stationary contact 36. Therefore, when the system is not pressurized, the switch will be in a normally closed position and an electrical circuit will be completed through the terminal 42, L-shaped contact 44, the contact surface 54, leg 56, tab 48, leg 52, rim 50 and since the rim is in contact with the conductive housing 10 at stepped shoulder 64, the circuit will be completed through the housing to ground. When pressure is exerted on the fluid, the pressure will be transmitted through the port or aperture 18 to the fluid contained in chamber 28. Since the pressure in chamber 30 remains substantially constant at atmospheric pressure, the diaphragm 20 will be deformed in an upward direction particularly at its center. When the diaphragm 20 is deformed, it contacts the tab'48 of the disc 46 deforming it in an upward direction. As the tab 48 is deformed upwardly, the contact surface 54 is moved upwardly and out of electrical contact with the upper'surface of the L-shaped contact 44 of the stationary contact 36. Thus, the electrical circuit is broken. If the fluid pressure again decreases, the diaphragm 20 will return to its generally horizontal position due to its resiliency. When the diaphragm returns to its horizontal position, it no longer is disposed in lifting relationship with the tab48 and since the tab is also resilient, it returns to its original horizontal position. When the tab 48 is lowered, the contact surface 54 is also lowered and again comes irito electrical contact with the stationary contact 36, again completing the circuit. If the switch is disposed in an indicator circuit of the type commonly utilized in oil low pressure warning systems, the loss of oil pressure will cause the L-shaped contact 44 and the contact surface 54 to close completing the warning circuit and energizing a suitable alarm or warning light.

Although the above described switch is a normally closed switch, a nonnally open switch is also contemplated. A normally open embodiment is shown in FIG. 7 in which like reference numerals are employed for like elements. As shown in that FlG., the previously described embodiment of switch I may be readily adapted to be normally open by locating a contact portion 66 above the disc contact surface 54 rather than below the contact surface. Thus, when the switch is in its unpressurized condition, the resilient diaphragm 20 and the disc 46 and its associated tab 48 will be relaxed and disposed in their lowermost position. When in their lowermost position, the contact surface 54 will be separated from the stationary contact 36 and its contact portion 66 and the circuit will be broken. When the chamber 28 is pressurized, the diaphragm 20 will be deformed upwardly at its center, thus deforming the tab 48 in an upward direction. Deformation of the tab 48, in turn. raises the contact surface 54 into engagement with the contact portion 66 of the stationary contact 36 completing the circuit.

It will be evident when considering the aforementioned description of the preferred embodiments of my invention, that a pressure responsive switch constructed in accordance with the principles of my invention need include only a few elemental parts. Moreover, a major number of those parts may be easily stamped and fabricated from sheet metal. Thus, the manufacture and assembly of such switch is extremely inexpensive and simple and the probability of failure of any one of the elemental parts is substantially reduced. Also, since the switch contact surfaces themselves are not disposed in the fluid, the pressure of which is to be sensed, maintenance and malfunction is substantially reduced, and the environments in which the switch may be utilized become virtually unlimited.

It should be understood that the embodiments of the present invention which have been described are merely illustrative of a few applications of the principles of the invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention.

Iclaim:

1. A fluid pressure responsive switch including:

a housing defining first and second chambers each having,

an open end; I

a flexible diaphragm in said housing sealingly separating said first chamber from said second chamber;

said open end of said first chamber being adapted to communicate with a source of fluid pressure to movably flex said diaphragm;

a cap closing the open end of said second chamber;

stationary contact means carried by said cap and positioned in said second chamber;

the improvement comprising resilient movable contact means positioned in said second chamber adjacent said diaphragm, said resilient movable contact means being resiliently deformable in response to movement of said flexible diaphragm to a first position when a first pressure obtains in said first chamber and being movable to a second position by its own resiliency when a second pressure obtains in said first chamber, the degree of deformation of said resilient movable contact means between said positions being substantially equal to the degree of movement of said flexible diaphragm, said stationary and said movable contact means being in-electrical contact with each other in one of said positions.

2. The switch of claim 1 wherein said housing is electrically conductive and said resilient movable contact means is in electrical contact with said housing in said first and second positions.

3. The switch of claim 2 wherein said resilient movable contact means is clamped between said housing and said cap.

- 4. The switch of claim I wherein said cap is electrically nonconductive.

S. The switch of claim 1, said resilient movable contact means comprising a disc having a rim portion and a center tab of substantial surface area raised above the major part-ofthe surface of said rim, and a contact surface raised above the surface of said tab.

6. The switch of claim 5 wherein said disc and the cross sec- ILlOlfl of said second chamber are of substantially the same geometric shape and area.

7. The switch of claim 6 wherein said tab comprises a major portion of the surface area of said disc and said tab is resiliently deformed relative to said rim in response to the movement of said diaphragm.

8. The switch of claim 1 wherein said resilient movable contact means is in electrical contact with said stationary contact means when said resilient movable contact means is in said first portion and said electrical contact is broken when said resilient movable contact means is in said second position, said second pressure being greater than said first pressure.

9. The switch of claim 1 wherein said resilient movable contact means is in electrical contact with said stationary contact means when said resilient movable contact means is in said said second pressure being greater than said first pressure.

Claims

1. A fluid pressure responsive switch including: a housing defining first and second chambers each having an open end; a flexible diaphragm in said housing sealingly separating said first chamber from said second chamber; said open end of said first chamber being adapted to communicate with a source of fluid pressure to movably flex said diaphragm; a cap closing the open end of said second chamber; stationary contact means carried by said cap and positioned in said second chamber; the improvement comprising resilient movable contact means positioned in said second chamber adjacent said diaphragm, said resilient movable contact means being resiliently deformable in response to movement of said flexible diaphragm to a first position when a first pressure obtains in said first chAmber and being movable to a second position by its own resiliency when a second pressure obtains in said first chamber, the degree of deformation of said resilient movable contact means between said positions being substantially equal to the degree of movement of said flexible diaphragm, said stationary and said movable contact means being in electrical contact with each other in one of said positions.

4. The switch of claim 1 wherein said cap is electrically nonconductive.

5. The switch of claim 1, said resilient movable contact means comprising a disc having a rim portion and a center tab of substantial surface area raised above the major part of the surface of said rim, and a contact surface raised above the surface of said tab.

6. The switch of claim 5 wherein said disc and the cross section of said second chamber are of substantially the same geometric shape and area.

9. The switch of claim 1 wherein said resilient movable contact means is in electrical contact with said stationary contact means when said resilient movable contact means is in said second position and said electrical contact is broken when said resilient movable contact means is in said first position, said second pressure being greater than said first pressure.