US3553402A

US3553402A - Pressure switch with improved diaphragm and snap action disc structure

Info

Publication number: US3553402A
Application number: US746903A
Authority: US
Inventors: Charles John Hire
Original assignee: Fasco Industries Inc
Current assignee: Fasco Controls Corp
Priority date: 1968-07-23
Filing date: 1968-07-23
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05

Abstract

Two male terminals project from the closed end of a cup-shaped, dielectric switch housing; and a flexible diaphragm is secured over the opposite, open end of the housing for operation by a fluid pressure system. A bowed metal disc in the housing engages the diaphragm, so that upon predetermined increase in pressure in the fluid pressure system, the disc is snapped suddenly by the diaphragm to cause a spring-loaded, dielectric plunger to move a metal contact into contact with the male terminals. The spring pressure on the plunger is adjustable by a screw to adjust the reset pressure of the switch after it has been tripped, or in some cases to adjust the range or differential switch.

Description

United States Patent Charles John Hire Pittsiord, N.Y.

July 23, 1968 Jan. 5, 1971 Fasco Industries, Inc. Rochester, N.Y.

a corporation of New York Inventor Appl. No. Filed Patented Assignee Field of Search 200/83(All), 16.1, 83.4

References Cited UNITED STATES PATENTS 4/1948 Cressey 4/1949 Katcheretal.

Primary Examiner-Robert K. Schaefer Assistant Examiner-J. R. Scott Attorney-B. Edward Shlesinger ABSTRACT: Two male terminals project from the closed end of a cup-shaped, dielectric switch housing; and a flexible diaphragm is secured over the opposite, open end of the housing for operation by a fluid pressure system. A bowed metal disc in the housing engages the diaphragm, so that upon predetermined increase in pressure in the fluid pressure system, the disc is snapped suddenly by the diaphragm to cause a spring-loaded, dielectric plunger to move a metal contact into contact with the male terminals. The spring pressure on the plunger is adjustable by a screw to adjust the reset pressure of the switch after it has been tripped, or in some cases to adjust the range or differential switch.

INVENTOR CHARLES JOHN HIRE PATENTED JAN 5197! mORNEY PRESSURE SWITCH WITII IMPROVED DIAPHRAGM AND SNAP ACTION DISC STRUCTURE This invention relates to electrical switches, and more particularly to a pressure-operated vacuum or differential pressure switch of the type containing a flexible diaphragm that is responsive to predetermined pressure or vacuum changes to open or close the switch.

An object of this invention is to provide an improved vacuum or differential pressure switch, which is substantially more compact, less expensive and more reliable than prior such switches.

Another object of this invention is to provide an improved pressure, vacuum or differential pressure switch, which has substantially fewer moving parts than prior such switches.

Another object of this invention is to provide an improved pressure, vacuum or differential pressure switch which can be readily calibrated.

Still another object of this invention is to provide a pressure, vacuum or differential pressure switch, which can be readily manufactured as either a normally open or a normally closed switch.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accom panying drawing.

In the drawing:

FIG. 1 is a plan view of a switch made in accordance with one embodiment of this invention;

FIG. 2 is a longitudinal sectional view of the switch taken along the line 2-2 in FIG. 1 looking in the direction of the arrows; and

FIG. 3 is a view similar to FIG. 2, but illustrating a modified switch.

Referring now to the drawing by numerals of reference, and first to the embodiment illustrated in FIGS. 1 and 2, .10

.denotes the switch generally. This switch comprises a hollow,

inverted, generally cup-shaped rigid plastic member 12, which is of enlarged diameter at its open end and has intennediate its ends'an external, circumferential shoulder 14, formed at the juncture of the closed end and its enlarged diameter portion. Secured in member 12, and projecting out of its closed end in spaced, parallel relation, are two, conventional maleprongs or

terminals

16 and 18. Withinbase 12 the prongs l6 and 18 are seated in diametrically opposed grooves or

slots

19 and 20, respectively, formed in the member 12 at diametrically opposite sides of its central recess 22. At its inner end each prong l6, 18 is bent at right angles radially inwardly as indicated at 23 and 24, respectively.

Seated over a boss 26, which projects from the underside of the closed end of base 12 into the recess 22 coaxially thereof, is a metal cap 28. An external annular flange 29 on the upper end-of cap 28 provides a seat for the upper end of a compression spring 30, which surrounds cap 28. The lower end of spring 30 engages the upper face of a movable, metal contact plate 32, which extends diametrially across recess 22, to overlie the

inner ends

23 and 24 of the prongs l6 and 18. Plate 32 may-be silver on copper or brass or Monel. 33 denotes the silver contact layer.

A plastic plug or bumper 35, which has a reduced diameter upper end 36, is secured in plate 32 so that plug 35 and the plate 32 move together. The head of plug 35 overlies the inner ends of the prongs l6 and 18. to limit the axial movement of the, plug and of plate 32.

Removably seated around its peripheral edge in a circumferentialnotch or counterbore formed in the open end of member 12 is a metal disc 42 made of Beryllium copper, or the like. The disc is preformed to slightly bow at its center downwardly as illustrated in FIG. 2.- A flexible, disc-shaped diaphragm 44 made of Mylar, or the like, is secured over disc 42 and the open end of base 12 by a resilient gasket or sealing ring 46. This sealing ring is interposed between diaphragm 44 and a metal coupling or bushing 48 Coupling 48 has a stern portion externally threaded as denoted at 53. It is thinner walled and of enlarged diameter above this stem portion as denoted at 50. Ring 46 seats on an internal, circumferential shoulder 49 formed in the bushing 48. The upper end 50 of bushing .48 is rolled or peened radi-.

ally inwardly over the shoulder 14 on memberl2 as at 52, securely to grip the marginal edge of diaphragm 44. The externally threaded portion 53 has an' axial bore communicating with the underside of diaphragm 44.

In use the switch 10 is connected by its threaded stem 53 with a source of fluid pressure. The prongs I6 and 18 are plugged or otherwise connected into an electrical circuit which is to be responsive to predetermined pressure changes in the associated pressure fluid system, Normally switch 10 is closed, and the prongs l6 and 18 are electrically connected to one another through engagement of contact 33 with the

inner ends

23 and 24 of the prongs. When the pressure in the external pressure system exceeds a predetermined value, the pressure of flexible diaphragm 44 will snap the disc 42 suddenly upwardly against the plug 35 to drive the latter upwardly against the resistance of the spring 30 a distance sufficient to effect disengagement of the contact 33 from the inner ends of the prongs I6 and 18. This instantaneously opens the circuit containing the switch 10. The switch 10 will remain open until the pressure on diaphragm 44 and disc 42 falls once again below a predetermined value. At such time the spring 30 will urge the plate 32 downwardly, once again to close the switch.

The disc 42 may be made to snap at one pressure, say 50 pounds, and to return to its normal position at say 20 pounds. The disc is made to have hysteresis differential.

To calibrate or otherwise adjust the selected pressure at which the switch 10 will be made to return from its open to its closed position, a setscrew 55 may be adjustably threaded into the member 12 to adjust cap washer 28, thereby to alter the tension in spring 30.

Plug 35 is mounted to be rotatable in plate '32 so as to change the locus of its contact with disc 42 to avoid wear.

Referring now to the embodiment illustrated in FIG. 3, wherein like numerals are employed to designate elements similar to those employed in the first embodiment, the

modified, normally open switch 60 comprises a rigid, plastic, hollow member 12, and which has its lower, open end secured sealingly in the upper end of coupling member 48 in a manner similar to that of the first embodiment. Instead of using an electrically conductive plate 32, however, the second embodiment employs as a seat for the lower end of spring 30 a dielectric bar 32, which is fixed to the upper end of plug 35 of the type shown in the first embodiment.

Secured to the reduced diameter upper end of theplug 35 and positioned beneath the dielectric bar 32' is a bar 31, which is made of copper, brass or the like, and which extends at opposite ends, thereof beneath and in registry with the inner ends of prongs l6 and 18. At opposite ends thereof, the upper surfaces of bar 31 have secured thereon silver contacts '33, which normally are held spaced beneath the inner ends of prongs l6 and 18 by the action of spring 30 on member 32'. Switch 60 is otherwise the same as the switch illustrated in FIGS. 1 and 2.

In use, switch 60 is connected by its nipple portionT53-to a fluid pressure system; and its prongs I6 and 18 are plugged or otherwise connected in a circuit, which is to be responsive to predetermined changes in the associated pressure system. Normally contacts 33' are spaced from the inner ends of the prongs l6 and 18, so that switch 60 is open, and hence sotoo is the circuit in which it is connected. However, when the pres- From the foregoing, it will be noted that applicant has developed a sturdy, compact, and relatively inexpensive pressure switch, which utilizes a minimum of moving parts, is securely sealed against accidental leakage of the pressure fluid, and will effect instantaneous operation of the switches or 60 for the slightest of pressure differentials. Moreover, the switch may be simply and readily calibrated.

While the invention has been described in connection with a specific embodiment thereof, it will be understood that it is capable of further modification, and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention or the limits of the appended claims.

lclaim:

l. A pressure-responsive switch, comprising:

a dielectric, generally cup-shaped member open at one end and having a shallow counterbore in said open end to form an internal shoulder, and having a pair of electrically conductive terminals projecting from its closed end;

an electrical contact in said housing movable between first and second positions electrically to connect and disconnect, respectively, said terminals;

- a spring urging said contact to one of its two positions;

a flexible diaphragm secured around its marginal edge over the open end of said member;

a snap-action metal disc mounted on said shoulder between said contact and said diaphragm, said disc having its marginal edge movably seated on said shoulder, and being "normally bowed at its center outwardly away from said contact into engagement with the center of said diaphragm;

a coupling secured to said member to hold said diaphragm on said member and having an axial bore for admitting fluid under pressure against one side of said diaphragm, so that upon a predetermined increase in the pressure of said fluid, said diaphragm and said disc will be snapped suddenly inwardly in the direction of said contact; and

a plug interposed between said disc and said contact, and responsive to the sudden snapping of said disc to move said contact from said one to its other position.

2. A switch as defined in claim 1, wherein:

said plug is made of a dielectric material;

said contact is secured to said plug for movement therewith;

and

said spring is a compression spring mounted in said member between one end thereof and said plug, and is opcratively connected to said plug to urge the latter and said contact resiliently in the direction of said disc.

3. A switch as defined in claim 1, wherein:

said terminals are secured in said member with the inner ends thereof bent toward and spaced from one another;

said plug has a reduced diameter shank portion extending between the inwardly bent ends of said terminals, and an enlarged diameter head portion positioned between said disc and said inwardly bent ends and overlying the latter;

said contact is mounted on'said plug to extend transversely between said terminals with opposite ends thereof overlying, and registering with, said inner ends of said terminals; and

said plug is mounted for limited reciprocation by said spring and said disc between a closed position in which said contact thereon engages both said inner ends, and an open position in which said contact is disengaged from at least one of said inner ends.

4. A switch as defined in claim 3, wherein:

said plug has a transverse member secured thereto made of a dielectric material; and

said contact is secured to said enlarged head portion of said plug normally to be disposed in spaced, confronting relation to said terminals.

Claims

1. A pressure-responsive switch, comprising: a dielectric, generally cup-shaped member open at one end and having a shallow counterbore in said open end to form an internal shoulder, and having a pair of electrically conductive terminals projecting from its closed end; an electrical contact in said housing movable between first and second positions electrically to connect and disconnect, respectively, said terminals; a spring urging said contact to one of its two positions; a flexible diaphragm secured around its marginal edge over the open end of said member; a snap-action metal disc mounted on said shoulder between said contact and said diaphragm, said disc having its marginal edge movably seated on said shoulder, and being normally bowed at its center outwardly away from said contact into engagement with the center of said diaphragm; a coupling secured to said member to hold said diaphragm on said member and having an axial bore for admitting fluid under pressure against one side of said diaphragm, so that upon a predetermined increase in the pressure of said fluid, said diaphragm and said disc will be snapped suddenly inwardly in the direction of said contact; and a plug interposed between said disc and said contact, and responsive to the sudden snapping of said disc to move said contact from said one to its other position.

2. A switch as defined in claim 1, wherein: said plug is made of a dielectric material; said contact is secured to said plug for movement therewith; and said Spring is a compression spring mounted in said member between one end thereof and said plug, and is operatively connected to said plug to urge the latter and said contact resiliently in the direction of said disc.

3. A switch as defined in claim 1, wherein: said terminals are secured in said member with the inner ends thereof bent toward and spaced from one another; said plug has a reduced diameter shank portion extending between the inwardly bent ends of said terminals, and an enlarged diameter head portion positioned between said disc and said inwardly bent ends and overlying the latter; said contact is mounted on said plug to extend transversely between said terminals with opposite ends thereof overlying, and registering with, said inner ends of said terminals; and said plug is mounted for limited reciprocation by said spring and said disc between a closed position in which said contact thereon engages both said inner ends, and an open position in which said contact is disengaged from at least one of said inner ends.

4. A switch as defined in claim 3, wherein: said plug has a transverse member secured thereto made of a dielectric material; and said contact is secured to said enlarged head portion of said plug normally to be disposed in spaced, confronting relation to said terminals.