US3824358A

US3824358A - Calibratable pressure switch with adjustment means

Info

Publication number: US3824358A
Application number: US00359150A
Authority: US
Inventors: J Edwards; W Penland; J Warren
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1973-05-10
Filing date: 1973-05-10
Publication date: 1974-07-16
Anticipated expiration: 1991-07-16

Abstract

A casing for the switch has an internal cylindrical projection provided with a cavity for receiving a plunger-operated switch mechanism. A helical range spring surrounding the projection abuts an adjustable upper spring seat, and a diaphragm has a lower seat for the range spring and a switch plunger bonded to its inner side. The internal cylindrical projection has a pair of circumferentially spaced arcuate extensions extending from the cylindrical projection which serves as a stop means for the diaphragm and prevents undue movement of the plunger. The upper spring seat is generally annular but has generally radially protruding, parallel spaced end portions, which, when pressed together, permit the upper spring seat to be disengaged from the casing and raised or lowered relative to the casing. Upon release of the protruding end portions, circumferentially spaced projections on the outer periphery of the annular portion of the upper spring seat engage the inner wall of the casing to maintain the spring seat in a selected position.

Description

United States Patent [191 Edwards et a1.

[11] 3,824,358 51 July 16,1974

CALIBRATABLE PRESSURE SWITCH WITH ADJUSTMENT MEANS Inventors: Joseph L. Edwards, West Asheville;

William D. Penland, Weaverville;

James B. Warren, Skyland, all of NC.

Assignee: Square D Company, Park Ridge, 111. Filed: lYlay 10, 1973 Appl. No.: 359,150

US. Cl 200/83 S, 200/83 V Int. Cl. H01h'35/34 Field of Search....'.. 200/83 R, 83 P, 83 J, 83 S,

200/83 SA, 83 V, 83 W; 340/410 References Cited UNITED STATES PATENTS Primary Examiner-Robert K. Schaefer Assistant Examiner-Gerald P. Tolin,

Attorney, Agent, or Firm-Harold J. Rathbun; Richard T. Guttman; William H. Schmeling [57] ABSTRACT A casing for the switch has an internal cylindrical projection provided with a cavityfor receiving a plungercircumferentially spaced arcuate extensions extending from the cylindrical projection which serves as a stop means for the diaphragm and prevents undue movement of the plunger. The upper spring seat is generally annular but has generally radially protruding, parallel spaced end portions, which, when pressed together, permit the upper spring seat to be disengaged from the casing and raised or lowered relative to the casing. Upon. release of theprotruding end portions, circumvferentially spaced projections on the outer periphery of the annular portion of the. upper spring seat engage the inner .wall of the casing to maintain the spring seat in a selected position.

'10 Claims, 6 Drawing Figures 4- a2 74- r 7g a 52 6%; 78 69 76 72 PAIENIEDJUHBW 3824.358

sum 2 OF 2 FIG.6

CALIBRATAB LE PRESSURE SWITCH WITH ADJUSTMENT MEANS SUMMARY OF THE INVENTION This invention relates to a pressure responsive-electrical switch of the type commonly installed at the bottom of a bell attached to a sumppump, and more particularly to such a switch having an improved adjustable upper spring seat, switch mechanism, and diaphragm structure.

Switches of this type are sold in a highly competitive market and it is necessary, therefore, that the switches be capable of being manfactured, assembled, and calibrated at low cost while still being reliable in operation. Further, it is important that such switches be designed to permit them to be easily and rapidly calibrated during manufacture for operation at a wide range of operating pressures.

An object of this invention is to provide an improved pressure-responsive switch meeting the foregoing requirements.

Another object is to provide an improved pressure responsive switch comprising a casing having a slotted side wall through which end portions of a generally annular upper spring seat protrude to permit release of gripping projections on the upper spring seat which normally abut the inner side wall of the casing to retain the spring seat in position.

A more detailed object is to provide an improved pressure-responsive switch in which a flexible diaphragm closes an open end of a casing and is movable as a result of external pressure inwardly of the casing against the biasing force of a helical range spring thereby to operate a switch means, and an upper spring seat for the range spring which has a generally annular portion disposed within the casing and end portions protruding through a vertical slot in a side wall of the casing also has a plurality of circumferentially spaced gripping projections extending radially outwardly and obtusely from the said annular portion normally abutting the inner surface of said side walls, whereby pinching of the end portions toward each other permits release of the gripping projections to permit adjustment of the spring seat with respect to the casing for adjusting response of the switch to external pressure.

A further object is to provide a method of calibrating a pressure switch comprising the steps of securing the pressure switch to a pressurized manifold, releasing an upper spring seat from engagement with a casing of the switch, raising or lowering the upper spring seat relative to the casing, and, when a switch means of the pressure switch operates, securing the upper spring seat to the casing.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent from the following description wherein reference is made to the drawings, in which:

FIG. 1 is a side view, partially in cross-section, showing a pressure-responsive switch in accordance with this invention in association with an electrically-driven sump pump;

FIG. 2 is a top view of the switch of FIG. 1;

FIG. 3 is a sectional view taken along the 3-3 of FIG. 2;

FIG. 4 is a bottom view of the switch of FIG. 1 with an annular sealing ring, a diaphragm, a lower spring and plunger seat, and a range spring removed;

FIG. 5 is a perspective view of an upper spring seat of the switch of FIG. 1; and

FIG. 6 is a schematic view showing how the switch of FIG. 1 maybe calibrated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, a pressure-responsive switch 10 in accordance with this invention is shown in combination with a pump 12 driven by a self-contained electric motor (not shown) and positioned to force liquid 14 from a sump 16 through a discharge pipe 18 until the liquid 14 reaches a predetermined low level, such as 20, as determined by operation of the switch 10. The switch 10 is shown in FIG. 1 as secured within a downwardly facing cylindrical bell 22 carried by an arm 26 attached to or integral with a housing of the pump 12. At the top of the bell 22 is an electric power supply cable construction 28 which permits two pairs of

electrical conductors

29a and 29b to enter the bell 22 in a liquid-tight manner.

The general construction so far described is well known, and further description thereof is unnecessary.

The switch 10 may be secured and sealed within the bell 22 by any suitable means. As shown in FIG. 1, a ring 30 is secured to the bottom of the bell 22 by a plurality of circumferentially spaced screws 32 and clamps a lower external flange 33 of the switch 10 against an annular shoulder 34 formed on the bell 22. A resilient seal ring 36 is interposed between the ring 30 and the flange 33 to assure liquid tightness.

As best shown in FIG. 3, the switch 10 comprises a generally cylindrical casing 44 preferably molded of plastic material, a plastic annular sealing ring 46, a flexible diaphragm 48, a lower spring and plunger seat 50 bonded securely and concentrically to the inner side of the diaphragm 48, a helical range spring 52, and an adjustable upper spring seat 53.

The casing 44 has a inwardly directed internal cylindrical projection 54, and is provided with a slot 55 extending upwardly from the flange portion 33 in a circumferential side wall of the casing 44 and partially into a top wall 56 of the casing 44. The top wall 56 is provided with three circumferentially spaced openings 58 (FIG. 2) which are used during calibration of the switch 10 as will be discussed in greater detail hereinafter.

The outer peripheral edge of the diaphragm 48 is clamped between the annular sealing ring 46 and an annular shoulder 62 formed internally of the casing 44 at the area of flange 33. The ring 46 may be secured to the inner peripheral wall of the casing 44 by ultrasonic welding.

A cavity 64 is provided within the projection 54 and receives a switching means 66. Four blade terminals 67 (FIG. 2) forming part of the switching means 66 pass through respective slots in the top wall 56 which are positioned respectively in four recesses 68. Each of the four blade terminals 67 is connected to a single lead of two pairs of

electrical conductors

29a and 29b comprising a portion of the electric power supply cable construction 28, which enters the bell 22 in a liquid- 3 tight manner. The terminals 67 are bent overat their inner end portions and each bent over portion is provided with a contact 69. Additional recesses 70 may be provided, if desired, for easier moldability.

Although any suitable switching means 66 having the requisite differential operating characteristics may be used, a preferred form is shown in US. Pat. No. 3,017,471 issued Jan. 16, 1962. Such a switching means has a pair of bridging contacts 71, a snap action spring 72 cooperating with a plunger 73, and a contact carrier 74 for the bridging contacts 71. When the plunger 73 is moved upwardly from the position shown in FIG. 3, the spring 72 exerts a snap action force so as to move the carrier 74 downwardly thus causing each bridging contact 71 to bridge a pair of the contacts 69. When the plunger 73 is released and returned downwardly by a return coil spring 75, the spring 72 exerts a snap action so as to lift the carrier 74 upwardly thus separating the bridging contacts 71 from the contacts 69.

The internal cylindrical projection 54 has a'pair of circumferentially spaced arcuate extensions 76 extending from an internal cylindrical projection which form a stop means for the diaphragm 48 and thus prevent the plunger 73 from being moved upwardly too far.

The lower spring and plunger seat 50 has an annular central raised portion 77 which defines a recess forming a seat for the plunger 73 of the switch means 66, and also has an outer upwardly turned flange 78 which holds the lower portion of the range spring 52 in place on the upper surface of the seat 50.

The axis of the range spring is normal to the diaphragm 48 and its upper end abuts the upper spring seat 53 which is shown most clearly in FIG. 5. The seat 53 is formed of resilient metal, is generally annular, and has generally radially protruding

end portions

79 and 80, for a purpose to be described, and a plurality of circumferentially spaced gripping projections 81 extending radially from outer periphery of said seat 53 and which normally abut an inner side wall 82 of the casing 44 to hold the seat 53 in position. Preferably, the projections 81 are arranged in groups of three on diametrically opposite sides of the axis of the generally annular body portion of the seat 53 and the outer two of each group are bent axially in a direction away from the spring 52 and at an obtuse angle to the main body portion while the remaining projection 81 of each group is similarly bent axially toward the spring 52.

A method of calibrating of the switch 10 is shown diagrammatically in FIG. 6. The switch 10 is initially secured to a manifold 83 and a scissors type clamping means 84 has its arms positioned against the radially protruding

end portions

79 and 80 of the upper spring seat 53 in position to force them together. Three rods 85 of an adjustment ram 86 are inserted in the three radially spaced openings 58 on the top wall 56 of the casing 44 with the ends of the three rods in contact with the upper spring seat 53.

During calibration, as shown in FIG. 6, the clamping means 84 is operated causing the radially protruding

end portions

79 and 80 to be pinched together resulting in a disengagement of the gripping projection 81 of the upper spring seat 53 from the inner side wall 82 of the manifold 83 is then pressurized to a predetermined activating level, and the ram 86 is retracted permitting the seat 53 to move upwardly in response to the pressure of the manifold 83 exerted through the diaphragm 48,the lower spring seat 77, and the range spring 52.

The adjustment ram 86 is retracted upwardly until the diaphragm 48 moves to a position causing the switch means 66 to operate. At this point, the protruding end portions 79 and of the upper spring seat 53 are released by the clamping means 84 and then the adjustment ram 86 is fully elevated. The manifold is then depressurized thereby allowing the diaphragm to move back to its normal position. Thus the switch 10 is calibrated to operate at the predetermined pressure of the manifold 83.

Alternatively, the switch may be calibrated in the following manner: The upper spring seat 53 is positioned abutting the range spring 52 when it is fully distended. The manifold 83 is pressurized to a predetermined level. Since the range spring is fully distended, the diaphragm 48 will be depressed and the switch means 66 will operate. The end portions 79 and- 80 are now pinched together and the rods 85 of the adjustment ram 86 are inserted as described above. The adjustment ram 86 is moved downwardly until the diaphragm 48 is moved to a position at which the switch means 66 again operates. The clamping means 84 is then disconnected and the manifold depressurized as described above.

.The first calibration method is preferred because it insures that the switch 10 will operate and commence operation of the pump 12 at the predetermined activating pressure. Since the switching means 66 has a differential characteristic which may not be a constant, calibrating the switch by the latter method does not provide as accurate a calibration as does the first method.

It is obvious to one skilled in the art that electric circuitry including the contacts of the switch may be employed to carry out either of the calibration methods described above, in being understood that the clamping means 84 and the ram 86 could be electrically powered.

In operation, the pressure responsive switch 10 is installed as previously described, and under normal conditions the diaphragm 48 does not experience pressure sufficient to cause it to be depressed sufficiently to operate the switching means 66. However, when the pressure on the diaphragm '48 reaches the predetermined level set by the calibration procedure, the diaphragm 48 and lower seat 50 are pressed upwardly against the range spring 52 and the switch plunger 73 sufficiently to move the plunger 73 far enough to cause the switch means 66 to operate and cause the bridging contacts 71 to bridge the pairs of contacts 69 completing an energizing circuit for the pump 12 through the conductor pairs 29a and 29b. As a result of the differential characteristic of the switching means 66, the bridging contacts 71 will remain closed and the pump 12 will continue to run until the pressure is reduced to a level below that which was required to initially activate the switching means 66 and close the contacts 71. When said lower level of pressure is reached the diaphragm moves back to its normal position causing the switching. means 66 to operate thus opening bridging contacts 71.

Thus it is apparent that there has been provided, in accordance with the invention, a pressure switch that fully satisfies the objects, aim, and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as full within the spirit and broad scope of the appended claims.

I claim: I

l. A pressure-responsive switch comprising a casing, a flexible diaphragm closing an open end of the casing and movable inwardly of the casing as a result of external pressure exerted on an outer face of the diaphragm, switch means in the casing operated in response to movement of the diaphragm, a helical spring in the casing opposing inward movement of the diaphragm, and an upper spring seat for the spring having a springy generally annular portion engaged by the spring and disposed within the casing, said upper spring seat having spaced end portions protruding outside the casing in parallel spaced relation through a slot in the casing, and the outer periphery of said annular portion engaging the inner surface of a wall of the casing hereby retaining the spring seat in a fixed position relative to the casing, whereby pinching of the end portions toward each other causes disengagement of the annular portion from the inner surface of the side wall to permit adjustment of the position of the spring seat with respect to the casing for adjusting response of the switch to external pressure.

2. A pressure-responsive switch as claimed in claim 1 wherein said outer periphery includes a plurality of circumferentially spaced gripping projections extending generally radially outwardly from the annular portion into tight engagement with the inner surface of said side wall for maintaining the spring seat in its adjusted position in the casing.

3. A pressure-responsive switch as claimed in claim 2 wherein the casing has a wall opposite the open end, said wall has a plurality of openings therethrough which are circumferentially spaced with respect to the annular portion of the spring seat and provide access to the spring seat for entry of a means for moving the spring seat with respect to the casing when end portions are pinched toward each other and the gripping projections are disengaged from said inner surface.

4. A pressure-responsive switch as claimed in claim 2wherein some of the gripping projections are inclined axially in a direction toward the spring and some are inclined axially in a direction away from the spring.

5. A pressure-responsive switch as claimed in claim 2 wherein the casing has at least one opening in addition to the slot providing access to the annular portion of said spring seat to facilitate moving the spring seat with respect to the casing when the end portions are pinched toward each other to cause disengagement of the gripping projections from said inner surface.

6. A pressure-responsive switch as claimed in claim 2 wherein the gripping projections are inclined axially of the spacing in a direction away from the diaphragm.

7. A pressure-responsive switch as claimed in claim 1 wherein a plunger is provided for operation of the switch means, and a lower seat for the spring and the plunger is bonded securely to the inner side of the diaphragm.

8. A pressure-responsive switch as claimed in claim 1 wherein the casing has an end wall opposite the open end and the switch means is disposed within a cavity of an inwardly directed internal projection of said end wall and the spring surrounds the projection.

9. A pressure-responsive switch as claimed in claim 8 wherein the internal projection and the casing are substantially cylindrical.

10. A pressure-responsive switch as claimed in claim 8 wherein a stop means for the diaphragm is provided and comprises an extension extending from the internal cylindrical projection toward the diaphragm.

Claims

1. A pressure-responsive switch comprising a casing, a flexible diaphragm closing an open end of the casing and movable inwardly of the casing as a result of external pressure exerted on an outer face of the diaphragm, switch means in the casing operated in response to movement of the diaphragm, a helical spring in the casing opposing inward movement of the diaphragm, and an upper spring seat for the spring having a springy generally annular portion engaged by the spring and disposed within the casing, said upper spring seat having spaced end portions protruding outside the casing in parallel spaced relation through a slot in the casing, and the outer periphEry of said annular portion engaging the inner surface of a wall of the casing hereby retaining the spring seat in a fixed position relative to the casing, whereby pinching of the end portions toward each other causes disengagement of the annular portion from the inner surface of the side wall to permit adjustment of the position of the spring seat with respect to the casing for adjusting response of the switch to external pressure.

4. A pressure-responsive switch as claimed in claim 2 wherein some of the gripping projections are inclined axially in a direction toward the spring and some are inclined axially in a direction away from the spring.