US3588395A

US3588395A - Fluid pressure responsive device

Info

Publication number: US3588395A
Application number: US763232A
Authority: US
Inventors: Harold E Hersey
Original assignee: Ranco Inc
Current assignee: Ranco Inc of Delaware
Priority date: 1968-09-27
Filing date: 1968-09-27
Publication date: 1971-06-28
Anticipated expiration: 1988-06-28

Abstract

AN ELECTRIC SWITCH ENCLOSED IN A HOUSING ADAPTED TO BE THREADED ONTO A FLUID LINE COUPLING IS ACTUATED BY A REVERSING FORM-TYPE SNAP DISC WHICH IS ENGAGED AND MOVED BY AN ANNULAR CORRUGATION ABOUT THE INTERMEDIATE SECTION OF A FLEXIBLE METAL DIAPHRAGM FIXED AT ITS EDGES AND CENTER AND SUBJECTED TO FLUID PRESSURE, THE CENTER OF THE DIAPHRAGM BEING ADJUSTABLY POSITIONED BY A SCREW AND NUT STRUCTURE TO ACCURATELY DETERMINE THE FLUID PRESSURES AT WHICH THE DIAPHRAGM CAUSES THE SNAP DISC TO REVERSE ITS FORM.

Description

United States Patent [72] Inventor Harold E. Hersey Columbus, Ohio [21] Appl. No. 763,232 [22] Filed Sept. 27, 1968 [45] Patented June 28, 1971 [73] Assignee Ranco Incorporated Columbus, Ohio 1 [54] FLUID PRESSURE RESPONSIVE DEVICE 5 China, 3 Drawing Figs.

[52] U.S.Cl 200/83, 92/101 [51] Int.Cl ..II0lh 35/40 [50] Field of Search 200/83,83 (.2); 29/622; 92/13, 101

[56] References Cited UNITED STATES PATENTS 1,183,486 5/1916 Pardue 92/101 1,684,530 9/1928 Bast 200/83(.2)X 2,381,835 8/1945 Moorhead ZOO/83(2) 3,302,269 2/1967 Cooper et a1. .1 29/622 3,365,557 1/1968 Cooper et a1. 200/83 3,367,244 2/1968 Charter 92/13 3,378,657 4/1968 Smith ZOO/83(2) Primary Examiner Robert K. Schaefer Assistant Examiner.l. R. Scott Attorney-Watts, Hoffmann, Fisher and Heinke PATENIED JUH28 29?: 588,395

SHEET 2 OF 2 INVISNTOK.

H A R OLD E. HERSEY ATTORNEY FLUID PRESSURE RESPONSIVE DEVICE BACKGROUND OF THE INVENTION The present invention relates to a pressure operated snap action control device, such as an electric switch of the general type shown in U.S. Pat. No. 3,177,313 in which an electric switch contained within a housing is snap actuated by the reversing of form of a distorted dish-shaped disc in response to changes in pressure applied thereto by a flexible diaphragm subjected to fluid pressure to which the switch is to respond. In the type of switch mentioned it is important that the control occupy a minimum of space which presents a problem in providing compact and yet accurate means for adjusting the fluid pressures at which the switch is actuated.

THE INVENTION The present invention provides a switch mechanism in a relatively compact housing which is adapted to be actuated in one direction by snap movement of a dish-shaped member acted upon by a flexible diaphragm subjected to fluid pressure to which the switch is to respond, the periphery and center portions of the diaphragm being fixedly supported and the annular intermediate section being corrugated and engaging and applying pressure to the curved surface of the snap disc, and the center of which diaphragm is accurately positioned by a screw and nut structure relative to the snap disc so that the annular corrugated portion of the diaphragm may be made to actuate the snap disc in response to attainment of a given fluid pressure against the diaphragm.

The invention provides a reliable and accurate pressure responsive switch mechanism which can be inexpensively manufactured in a compact housing and readily calibrated to provide accurate response to fluid pressures.

Other objects and advantages of the invention will be apparent from the following description of preferred forms thereof, reference being made to the accompanying drawings wherein: 1

FIG. 1 is a sectional view of a fluid pressure responsive switch embodying the invention;

FIG. 2 is a sectional view taken substantially along 2-2 of FIG. 1; and

FIG. 3 is a sectional view similar to FIG. 1, showing a modified form of the invention.

In FIGS. 1 and 2 of the drawings, a pressure responsive switch device is shown which is particularly suitable for interrupting the circuit of the compressor motor of a refrigerating system, not shown, should the pressure of the refrigerant reach an undesirable relatively high value. The device 10 comprises a housing 11 which includes an assembly of an internally threaded coupling member 12, which is adapted to be threaded onto a pipe fitting in the appropriate section of the refrigerating system A collar 13, and a cap 14. A pair of switch terminal prongs 15,16 project from the cap 14 and provide a convenient electrical connection with a terminal plug in the compressor motor circuit of the refrigerating system.

The coupling member 12 is preferably formed of a short section of hexagonal brass stock and has a necked end which projects through an axial opening through the collar 13 and is hermetically attached to the collar by rolling a portion 17 of the necked end against the edges of the opening in the collar. Preferably, a solder joint 18 is formed in an undercut surrounding the abutting surfaces of the neck and collar. The member 12 has a bore 20 which is enlarged and threaded at 21 so that the member 12 can be easily attached to a refrigerating system by threading the member onto a standard connector provided in the piping circuit of the system.

The collar 13 has annular coaxial recessed portions of progressively larger diameters which provide a circular fluid chamber 22,

annular shoulders

23,24 respectively, and an annular lip 25 which is adapted to receive the open end of the cap 14 and to be turned against a sloping annular shoulder 26 formed on the cap to secure the cap to the collar.

The cap 14, which is preferably formed of a molded dielectric material, is generally cylindrical in shape and has a cavity 27 opening at one end of the cap. The

prongs

15,16 are embedded in the end wall 30 of the cap 14 and the inner ends project into the cavity 27. A leaf spring-type contact arm 33 is welded to the inner end of the terminal prong 16 and extends over a fixed contact member 34 attached to theend of a contact bar 35 projecting from the end of the terminal prong 15. The arm 33 carries a contact 36 and is biased to engage the contact 36 with the contact member 34 to complete a circuit between the terminal prongs.

The switch arm 33 is adapted to be moved to deflect contact member 36 from contact member 34 by a plunger 40 which is guided for longitudinal movement in a bushing 41 formed on a circular spacer plate 42. The lower end of the plunger 40, as viewed in FIG. 1, rests on the central portion of a snap disc 44, which, as explained more fully hereinafter, snaps upwardly and downwardly as viewed in the drawings to impart snap movements to the plunger 40 and cause it to move the contact arm 33 to open and close the

switch contacts

34,36 respectively.

The snap disc 44 is formed of a suitable sheet metal having the central portion distorted into a concave, dish shape and is internally stressed so that the central portion is urged to one side or the other ofa plane common to the peripheral portions of the disc. The disc 44 is formed to be inherently biased so that the central portion tends to bow downwardly as seen in FIG. 1.

The disc 44 is positioned in the housing 11 by the outer edges thereof being pressed to the annular shoulder 24 by a circular stop plate 46 having its peripheral edges overlying the edges of the disc and being pressed to the disc by staking as seen at 47. The stop plate 46 has a central opening through which the plunger 40 freely extends, and the central portion of the plate is bowed upwardly and forms a stop surface complementary to the disc to limit the upward switch opening snap movement of the central portion of the disc 44. The spacer plate 42 is positioned against the stop disc 46 and is retained in place by the ends of four ribs 50, formed on walls of the cavity 27, bearing against the rim of the spacer plate. Only these ribs 50 appear in the drawings.

The snap disc 44 is adapted to be moved from the position shown in FIG. 1 to engage the under side of stop disc-46 and move the plunger 40 to

open switch contacts

34,36 by a metallic flexible diaphragm 51, the outer edges of which are soldered to the annular shoulder 23 of the collar 16 so that the diaphragm forms a flexible end wall of the chamber 22. The diaphragm 51 is preferably formed of a thin sheet material, such as stainless steel or beryllium copper, and has two coaxial

annular corrugations

53,54 which are located axially relative to a threaded post 55 which extends through a central opening in the diaphragm and which has a head 56 soldered to the diaphragm in a rigid gastight connection. The post 55 is part of a structure by which the center of the diaphragm is restrained from movement so that changes in pressure against the underside of the diaphragm causes the

corrugated portions

53,54 to move laterally. The annular corrugation 54 is adapted to engage the dished portion of the snap disc 44 about an area concentric with the center of the disc and to cause the disc to snap move to the under side of the stop plate 46 when a certain pressure is applied to the under side of the diaphragm, as is explained more fully hereinafter.

The post 55 is threaded into a nut 60 which is rotatably supported in an opening 61 formed in the upper end of the coupling member 12. The nut 60 is restrained against axial shifting by laterally projecting shoulders 62,63 formed at opposite ends of the nut and engaging opposite face edges of the opening 61. By rotation of the nut 60 the threaded post 55 is shifted axially and thereby adjustably positions the corrugated portion 51 of the diaphragm 51 relative to the snap disc 44. To increase the fluid pressure at which the snap disc 44 will be actuated by the diaphragm 51 to open the switch contacts, the nut 60 is adjusted to move the post 55 from the disc and to decrease this pressure the nut is adjusted to move the post towards the disc.

Fluid pressure is applied to the under side of the diaphragm 51 through a bored opening 64 formed in the upper end of the coupling 12 to provide a passage from the bore 20 to the chamber 22.

The device is assembled by joining the collar 13 with one end of the coupling member 12 as described, the nut 60 being assembled in the coupling prior to the joining of the coupling with the collar. The diaphragm 51 is then positioned on the shoulder 23 by threading the post 55 through the nut 60 and the edges of the diaphragm are then soldered to the shoulder 23, after which the snap disc 44 is placed over the diaphragm and against the annular shoulder 24. The stop and

spacer plates

46,42 are then positioned over the disc 44 in the order shown in FIG. 1 and the plunger 40 is inserted through the guide bushing 41. The cap 14, having the switch arm 33 attached to the terminal 31, as described, is then inserted into the open end of the collar 13 with the end surface 47 engaging the stop plate 46. The lip 25 of the member 12 is then rolled against the tapering shoulder 26 of the cap 14 to secure the cap to the collar.

The device 10 may then be calibrated by threading the coupling member 12 onto a fixture in which a given fluid pressure is maintained, and the nut 60 is then rotated one direction or the other to cause the disc 44 to be snapped against the plate 46 and

open switch contacts

34,36 through the action of plunger 40 on the arm 33. This arrangement provides a relatively easy and accurate calibration of the operating pressures of the device.

The device 10 as just described is operative to open the switch contacts in response to an increase in fluid pressure to a predetermined value. In some instances it is desirable to provide a switch mechanism which will open its switch contacts in response to a decrease in fluid pressure to a given value and in this event the switch mechanism of the device 10 can be modified as shown in FIG. 3 in which contact 36 is supported on the upper face of the arm 33 and contact 34 is attached to a laterally projecting part of the terminal 15 extending above the contact 36. The nut 60 is then adjusted so that the fluid pressure in excess of the pressure at which switch opening is desired causes the diaphragm to maintain the disc 44 in the position shown in FIG. 3. When the pressure falls to the value desired to cause opening of the switch, the diaphragm 51 collapses under the inherent bias of the disc 44 and causes the arm 33 to follow the plunger 40 and the disc downwardly to separate

contacts

34,36. Here again, accurate calibration of the switch opening pressure is easily obtained by adjustment of the nut 60 following assembly of the device.

Although but two forms of the invention have been described it will be apparent that other forms, modifications and adaptations thereof could be made, all falling within the scope of the claims which follow.

lclaim:

1. A pressure responsive control device comprising, means forming a housing having a cavity adapted to be placed in communication with a source of fluid pressure, a flexible diaphragm forming one end of said cavity, said diaphragm having an annular corrugation therein, means to secure said diaphragm to the sides of said cavity whereby said corrugated portion thereof may flex laterally of said diaphragm proper, means to adjustably position the portion of said diaphragm centrally of said annular corrugation to limit movement of said portion of said diaphragm at least in one direction to less than the movement of the corrugated portion of said diaphragm, and control means actuated by movement of said corrugated portion of said diaphragm in said one direction.

2. A pressure responsive control device as set forth in claim 1 in which said means to adjustably position said portion of said diaphragm comprises a threaded post attached to the center of said'diaphragm, a rotatable nut into which said post is threaded, and means for rotatably supporting said nut and preventing axial movement thereof.

3. A pressure responsive control device as set forth in claim 2 in which said housing comprises a coupling member having a threaded internal bore, said coupling member having a part rotatably supporting said nut in alignment with said threaded bore.

4. A pressure responsive control device comprising, means forming a housing having a movable switch member therein, a snap disc supported in said housing about its edges, the central portion ofsaid snap disc having a concave area therein, means interconnecting said concave area with said switch member, a flexible diaphragm in said housing and adapted to be subjected to fluid pressure, means securing said diaphragm about its edges to said housing, and means to fixedly position said central portion of said diaphragm against movement, the portions of said diaphragm intermediate its edges and center having an annular corrugation adapted to engage said concave area of said disc.

5. A pressure responsive control device as set forth in claim 4 further characterized by means to adjustably position said central portion of said diaphragm relative to said disc.