US3598946A

US3598946A - Pressure switch responsive to extra low pressure

Info

Publication number: US3598946A
Application number: US887898A
Authority: US
Inventors: Tore B Hanssen; Erich Kothe
Original assignee: Controls Company of America
Current assignee: Eaton Corp
Priority date: 1969-12-24
Filing date: 1969-12-24
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10
Also published as: CA933220A; DE7044915U

Abstract

In normal operation, the rising diaphragm raises the actuator and spring seat against the force of the reset spring. Just before reaching the trip point of the switch in one form, the seat engages the strip spring eyelet so the pressure is opposed by both springs, the force of the trip spring- and, hence, the operating pressure of the switch- being determined by the position of the plunger. As the pressure decreases under the diaphragm, the eyelet bottoms in the well before reset so the reset force on the diaphragm is determined by the reset spring only. At extra low level settings the plunger is allowed to rise until the spring lifter is picked up by the plunger- to cancel out the force of the trip spring- and lifted a little by the reset spring so the seat cannot engage the eyelet before the trip point. Therefore, at this setting the diaphragm is opposed only by the reset spring. The second modification differs in that the reset spring is affected by the trip spring adjustment.

Description

United States Patent [72] Inventors Torelllansen Roselle: Erich Kothe, Schiller Park, both of. Ill. [21] Appl No. 887,898 [22] Filed Dec. 24, 1969 [45] Patented Aug. 10. I97] [73] Assignee Controls Company of America Melroee Park, Ill.

83.9,83 WM. 166 M; 337/1 17,317,318. 319, 320

[56] References Cited UNITED STATES PATENTS 3,267,232 8/1966 Chapin 200/83 (WM) 3,315,053 4/1967 Bauer 200/83 (WM) 3,359,387 12/1967 Rhodes 200/83 (WM) FOREIGN PATENTS 598,382 5/1960 Canada ABSTRACT: In normal operation, the rising diaphragm raises the actuator and spring seal against the force of the reset spring. Just before reaching the trip point of the switch in one form, the seat engages the strip spring eyelet so the pressure is opposed by both springs, the force of the trip springand. hence, the operating pressure of the switchbeing determined by the position of the plunger. As the pressure decreases under the diaphragm, the eyelet bottoms in the well before reset so the reset force on the diaphragm is determined by the reset spring only. At'extra low level settings the plunger is allowed to rise until the spring lifter is picked up by the plungerto cancel out the force of the trip springand lifted a little by the reset spring so the seat cannot engage the eyelet before the trip point. Therefore, at this setting the diaphragm is opposed only by the reset spring. The second modification differs in that the reset spring is affected by the trip spring adjustment.

PRESSURE SWITCH RESPONSIVE TO EXTRA LOW PRESSURE BACKGROUND OF INVENTION Large capacity washing machines are now operated with mini" loads which call for very low water levels to be sensed. The practice has been to use two pressure switches-one operating at the normal range of water levels and the other designed to sense a very low level below the normal sensing capability of a normal pressure switchand a selector switch to select the pressure switch to control the program.

SUMMARY OF INVENTION The present invention provides a pressure switch which can perform the functions heretofore requiring two pressure switches and a selector switch as in the past practice. The construction described in the Abstract provides for opposing the diaphragm by a trip spring and a reset spring at the trip point and by only a reset spring and a reset spring at the trip point and by only a reset spring at the reset point. This conforms to past practice. But provision to eliminate the trip spring at the extra low setting so the diaphragm is opposed by only one spring at the trip point is the novel contribution. This extends the operating range of the pressure switch to embrace the functions of two pressure switches according to past practice. All versions are characterized by provision of means for leaving only one spring operative to oppose the pressure acting on the diaphragm. Let it be noted here that the weight of the diaphragm, the diaphragm pad, actuator, spring seat, etc. always act against the pressure but it is the spring forces which are of principal concern here and for that reason it is in terms of such forces that the invention will be described. The other forces obviously continue to act.

DESCRIPTION OF DRAWINGS FIG. I is a simplified vertical section.

FIG. 2 is an enlarged fragmentary section taken from the rightin FIG. 1.

FIG. 3 is a vertical section through a modified form of the pressure switch.

DESCRIPTION OF PREFERRED EMBODIMENTS The pressure switch includes the housing provided with a diaphragm l2 subjected to pressure variations in chamber I4 as transmitted through tube 16. The pressure varies in accordance with water level variations in the washing machine. As the diaphragm rises, it lifts diaphragm pad I8, actuator and spring seat 22. The tongue 24 of switch 26 engages the notches in the actuator and, when the tongue passes over center relative to blade 28, the blade contact will snap down to the lower fixed contact 30 (the full position) from contact 32 (empty). The point of snapping over is the trip point. Coming back, the snap point is the "reset point. The actuator 20 is provided with a shoulder on which the reset spring 34 seats. The spring is compressed between the seat and the underside of the inturned flange at the top of eyelet or bushing 36. The eyelet 36 seats on the inturned flange 38 of the spring lifter, being held thereagainst by trip spring 40 compressed between the underside of plunger 42 and the outturned flange at the bottom of the eyelet. The vertical position of the plungerand degree of compression of the trip spring 40-is determined by lever 44 acting on the plunger and controlled by any suitable means. The lifter has two opposed arms 46 which extend upward in the grooves 49 on the outside of the plunger 42 so the head 48 on each arm lies above the fingers S0 projecting into the grooves 49. In this way movement of the plunger away from the lifter is limited by engagement of the arms with the plunger. Normally the lifter tends to rest on the floor of the well 52 in the housing but may, by reason of slight inward bias of the arms, tend to follow the plunger until restrained by contact with the eyelet.

Flange 38 on the bottom of the lifter affords clearance for the seat to pass. The seat diameter-at the shoulder-is greater than the diameter of the inturned shoulder 54 in the eyelet. Therefore, the seat can engage the shoulder 54 and this happens just before the trip point is reached. At this moment the diaphragm is opposed by trip spring 40 as well as reset spring 34, which always opposes the diaphragm. After the switch trips and the diaphragm starts down, the eyelet will bottom" (seat on the well with the lifter between) or at least engage the lifter relative to the plunger to cancel out the effect of the trip spring. This happens before the reset point so at reset" only the reset spring 34 is effective.

If the plunger is allowed to rise to a high position, it will pick up the lifter and the effect of trip spring 40 is cancelled. A slight additional upward movement of the now unitized plunger-lifteFtrip spring, under influence of the reset spring 34, will move the eyelet shoulder high enough so the seat cannot engage it before the trip point is reached. Therefore, the trip point is now opposed only by the reset spring-which is also true at reset. This condition is achieved at the extra low level setting used in mini" loads as mentioned above. The effective force of the reset spring is slightly less than in the normal range by reason of the slight extension to lift the eyelet. The effective force is readily adjusted by the position of the plunger.

This construction, therefore, allows the trip spring to be removed from the operating considerations and the pressure switch can do the work of two under prior practice.

A variation of this arrangement reduces the vertical spacing between shoulder 54 and the seat 22 so the seat is engaged with the shoulder both at trip and at reset. With such an arrangement, the reset spring 34 is overcome by the stronger trip spring and it is the trip spring force which determines the trip and reset pressure.

FIG. 3 illustrates a variation in which the eyelet 136 is changed so that the reset spring I34 seats on the underside of the plunger 42. This arrangement results in the reset spring I34 being adjusted when the trip spring 40 is adjusted. Therefore, the reset pressure varies as the pressure switch is adjusted. In the first modification, the reset remains constant. When the FIG. 3 construction is set to "extra low," the trip spring is cancelled out (as in the FIG. I form) and the trip and reset value is determined by the compression of spring 134 as controlled by the vertical position of the plunger.

In both of the illustrated forms, the trip spring can be cancelled out or rendered inoperative at extra low" setting. In the FIG. I variation in which the eyelet is always engaged with the seat in the normal range, it is the reset springnot the trip sprng-which is rendered ineffective. Such an arrangement also results in higher reset values in the normal range simply because both springs are effective at the time of reset.

We claim:

I. In a pressure switch of the type including a housing divided into a pressure chamber and a switch chamber by a flexible diaphragm with a switch in the switch chamber moved from one position to another position at a trip point as the diaphragm moves with increasing pressure in the pressure chamber and returning to said one position at a reset point as the diaphragm returns as the pressure in the pressure chamber falls, the improvement comprising,

a reset spring means opposing diaphragm movement,

trip spring means positioned to become effective to oppose the diaphragm before the trip point is reached and to become ineffective before the reset point is reached upon return movement of the diaphragm,

means for adjusting the effective force of the trip spring means to vary the response characteristics of the pressure switch,

and means for rendering one of the spring means ineffective to oppose the diaphragm whereby only the other spring means opposes the diaphragm at both the trip point and reset point and the pressure switch responds to very low pressures in the diaphragm chamber.

2. The pressure switch according to claim I including,

means actuated by the diaphragm to transmit motion thereof to the switch,

said reset spring acting on the motion-transmitting means,

said motion-transmitting means normally engaging the trip spring means to be opposed thereby before the trip point is reached and being disengaged from the trip spring means before the reset point is reached after tripping,

said means for rendering the trip spring means ineffective being operative to move the trip spring means to a position in which the motion transmitting means in unable to engage the trip spring means.

3. The pressure switch according to claim 2 in which,

the trip spring means includes an eyelet and a plunger and a trip spring compressed therebetween,

said adjusting means acting on the plunger to vary the compression of the trip spring,

said motion-transmitting means engaging the eyelet.

4. The pressure switch according to claim 3 in which the eyelet and the motion-transmitting means have cooperating shoulders which are normally engageable and the means rendering the trip spring ineffective moves the eyelet to a position in which its shoulder is beyond the travel of the shoulder on the transmitting means at the trip point.

5. The pressure switch according to claim 4 in which the reset spring is compressed between the transmitting means and the eyelet.

6. The pressure switch according to claim 5 in which the means rendering the trip spring ineffective includes a lifter engageable with the eyelet.

said lifter being actuated when the plunger adjusting means is moved to a position corresponding to a low force on the trip spring.

7. The pressure switch according to claim 6 in which the plunger and the lifter become engaged when the trip spring is rendered ineffective whereby the only force acting on the transmitting means is the reset spring and the force of the reset spring is determined by the plunger position.

8. In a pressure switch of the type including a housing divided into a pressure chamber and a switch chamber by a flexible diaphragm with a switch in the switch chamber moved from one position to another position at a trip point as the diaphragm moves with increasing pressure in the pressure chamber and returning to said one position at a reset point as the diaphragm returns as the pressure in the pressure chamber falls, the improvement comprising,

two springs opposing the diaphragm,

and means for rendering one of the springs ineffective for very low pressures.

9. The pressure switch according to claim 8 including means for adjusting the effective force of one of the springs.

10. The pressure switch according to claim 8 including means for adjusting the effective force of both springs.

11. The pressure switch according to claim 8 including means for adjusting the force of the spring which is effective while the other is ineffective.

Claims

1. In a pressure switch of the type including a housing divided into a pressure chamber and a switch chamber by a flexible diaphragm with a switch in the switch chamber moved from one position to another position at a trip point as the diaphragm moves with increasing pressure in the pressure chamber and returning to said one position at a reset point as the diaphragm returns as the pressure in the pressure chamber falls, the improvement comprising, a reset spring means opposing diaphragm movement, trip spring means positioned to become effective to oppose the diaphragm before the trip point is reached and to become ineffective before the reset point is reached upon return movement of the diaphragm, means for adjusting the effective force of the trip spring means to vary the response characteristics of the pressure switch, and means for rendering one of the spring means ineffective to oppose the diaphragm whereby only the other spring means opposes the diaphragm at both the trip point and reset point and the pressure switch responds to very low pressures in the diaphragm chamber.

2. The pressure switch according to claim 1 including, means actuated by the diaphragm to transmit motion thereof to the switch, said reset spring acting on the motion-transmitting means, said motion-transmitting means normally engaging the trip spring means to be opposed thereby before the trip point is reached and being disengaged from the trip spring means before the reset point is reached after tripping, said means for rendering the trip spring means ineffective being operative to move the trip spring means to a position in which the motion transmitting means in unable to engage the trip spring means.

3. The pressure switch according to claim 2 in which, the trip spring means includes an eyelet and a plunger and a trip spring compressed therebetween, said adjusting means acting on the plunger to vary the compression of the trip spring, said motion-transmitting means engaging the eyelet.

6. The pressure switch according to claim 5 in which the means rendering the trip spring ineffective includes a lifter engageable with the eyelet, said lifter being actuated when the plunger adjusting means is moved to a position corresponding to a low force on the trip spring.

8. In a pressure switch of the type including a housing divided into a pressure chamber and a switch chamber by a flexible diaphragm with a switch in the switch chamber moved from one position to another position at a trip point as the diaphragm moves with increasing pressure in the pressure chamber and returning to said one position At a reset point as the diaphragm returns as the pressure in the pressure chamber falls, the improvement comprising, two springs opposing the diaphragm, and means for rendering one of the springs ineffective for very low pressures.