US3579284A - Reset and adjustment mechanism for a pressure-responsive switch - Google Patents

Abstract

A pressure-responsive switch assembly of the type used, for example, as a liquid level control in washing machines, including a slide means which is operable to automatically reset the diaphragm of the pressure-responsive switch when an adjustment is to be made of the operating point of the switch by advancing to a higher setting.

Description

United States Patent Anthony Mason Benton Harbor;

Clifton A. Cobb, St. Joseph, Mich. 741,763

July 1, 1968 May 18, 1971 Whirlpool Corporation Benton Harbor, Mich.

lnventors Appl. No. Filed Patented Assignee RESET AND ADJUSTMENT MECHANISM FOR A PRESSURE-RESPONSIVE SWITCH 6 Claims, 10 Drawing Figs.

US. Cl 200/83, 74/ 1 07 int. Cl H0lh 35/40 Field of Search ZOO/61.04,

61.2, 61.4, 81.9, 82, 83, 81 (H0), 83 (WM), 82.2, 83.1, 83.5, 83.9, 83.91; 74/107; 92/99; 337/318, 319

[56] Rel'erencesCited UNITED STATES PATENTS 2,636,093 4/1953 Clark et a1. 200/83(WM) 2,720,564 10/1955 Sorenget a1... 200/83(WM) 2,934,618 4/1960 Beller et a] 200/83(WM) 3,110,784 11/1963 Williams et a1. 200/83(WM) 3,291,932 12/1966 Main 74/107X 3,319,023 5/1967 Lake et a1. ZOO/83X 3,359,387 12/1967 Rhodes 200/83 Primary ExaminerRob'ert K. Schaefer Assistant Examiner.l. R. Scott Attorneys-Thomas E. Turcotte, James S. Nettleton, Donald W. Thomas, Burton H. Baker, Franklin C. l-larter, Gene A. Heth and Hill, Sherman, Gross & Simpson ABSTRACT: A pressure-responsive switch assembly of the type used, for example, as a liquid level control in washing machines, including a slide means which is operable to automatically reset the diaphragm of the pressure-responsive switch when an adjustment is to be made of the operating point of the switch by advancing to a higher setting.

Patented May 1 8, 1971.

3 Sheets-Sheet 2 INVENTORS ,4/v7w0/v 7 A44 s 011/ T FOR NE Y8 'IIIIH C4 /F70/V 4. C0

Patented May 18, 1971 3,579,284

3 Sheets-Sheet 5 llllll' I 1 N VENTORS u W @WTORNEYS RESET AND ADJUSTMENT MECHANISM FOR A PRESSURE-RESPONSIVE SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is in the field of pressure-responsive switch assemblies of the type in which a flexible diaphragm is exposed to the fluid pressure to be sensed, and a variable biasing force is applied to the opposite sides of the diaphragm. The flexure of the diaphragm operates a switch arm to move it between a pair of contacts, depending upon whether or not the fluid pressure is sufficient to overcome the biasing force.

In the present invention, means are provided to achieve resetting of this type of pressure switch and contemporaneous adjustment of the operating point of the switch, i.e., the biasing force, is part of the same operation so that there is an automatic resetting of the switch each time the biasing force is varied. The invention provides an operator acting on the biasing means, with a support ann supporting the operator, and slide means arranged to urge the operator against the biasing means with a force sufficient to move the switch arm from one contact to the other, thereby resetting the switch. Cam means are also provided which are engageable with the support arm to apply an adjustable force on the biasing means so that upon movement of the slide into the reset position, further lateral or rotative movement of the slide means is effective to change the biasing force which is applied to the diaphragm in normal operation of the pressure-responsive switch.

2. Description of the Prior Art US. Pat. No. 3,291,932 describes a pressure-responsive control reset structure, embodying several mechanisms for resetting a pressure switch of the diaphragm type. This patent describes push to reset and pull to reset mechanisms in which the resetting and the readjustment functions are performed separately.

Still another type of reset mechanism is disclosed in U.S. Pat. No. 3,319,023 which involves an overcenter snap switch which is reset in operation and which issepaiate and distinct from the adjustment of the level at which the pressure-responsive switch operates.

Reset mechanisms which are operated independently of the bias adjusting mechanism are not entirely satisfactory because it is difficult to educate the user of a washing machine that there is something more to setting a liquid level in the laundry tub than adjusting a dial. In many cases, the user will preselect a liquid level in the tub and find after the level has been reached that it is insufficient. When the user then attempts to move the liquid level on the dial on the washer to a higher level, and finds that nothing happens, the immediate reaction is that the controls are defective and a service man is called.

The present invention combines the reset and adjustment functions of the switch into a single operation so that the user is not able to adjust the operating point of the switch, i.e., the pressure level at which the switch is operative, without first going through a resetting operation. Consequently, there is no possibility that the user will attempt to change the water level in the tub without resetting the switch, since the resetting mechanism is interlocked with the adjusting mechanism so that the resetting always must precede the readjustment.

SUMMARY OF THE INVENTION The present invention provides a pressure-responsive switch assembly particularly suitable for use in washing machines which includes a fluid pressure responsive diaphragm and a switch arm operated by movement of the diaphragm between a pair of contacts. As customary from the prior art, biasing means are provided for applying a variable biasing force on the diaphragm in opposition to the fluid pressure acting thereon, to thereby adjust the operating point at which the switch arm moves from one contact to the other.

In accordance with the present invention, an operator is provided which acts in conjunction with a slide means to provide enough force on the biasing means to move the diaphragm from a position in which the switch arm engages one of the contacts to a reset position in which it engages the other contact. Slide means also forms part of the adjustment mechanism so that upon attainment of the reset condition, the slide means is operative either by lateral movement or by rotary movement to effect the desired adjustment and raise the pressure level at which the diaphragm operated switch becomes operative.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a somewhat schematic view of a pressure-responsive switch assembly as it has been employed in prior art washing machine assemblies;

FIG. 2 is a wiring diagram illustrating more completely the function of the switch assembly;

FIG. 3 is a fragmentary view of the front of a washing machine employing a pressure-responsive switch according to the present invention;

FIG. 4 is a plan view of one form of a pressure-responsive switch which can be employed in accordance with the present invention;

FIG. 5 is a view similar to FIG. 4 but illustrating the condition of the elements during the resetting operation;

FIG. 6 is a side elevational view of the structure shown in FIGS. 4 and 5;

FIG. 7 is a side elevational view of a modified form of the present invention;

FIG. 8 is a rear elevational view of the structure shown in FIG. 7;

FIG. 9 is a fragmentary view of a pressure-responsive switch illustrating the normal position of the cam; and

FIG. 10 is a view similar to FIG. 9 but illustrating the position of the cam during the resetting operation.

' DESCRIPTION OF THE PREFERRED EMBODIMENTS In the schematic showing of FIG. 1, reference numeral 10 indicates generallya washing machine includingan imperforate tub in which there is disposed a perforate, rotatable basket 12. A centrally mounted agitator 13 is driven in an oscillatory fashion by means of a motor 14 acting through a transmission 15. A water inlet conduit 16 supplies water to the tub II and is under the control of a solenoid operated valve 17.

An outlet port I8 near the bottom of the tub I1 is connected by means of a flexible tube 19 to an inlet port 20 of a pressure-responsive switch assembly generally indicated at numeral 21. As the fluid level in the tub rises, air in the conduit 19 is compressed, and enters a chamber 22 where it acts upon a flexible diaphragm 23. A post 24 acts on the rear of the diaphragm 23 in opposition to the fluid pressure acting on the diaphragm in the chamber 22. A post 24 is biased against the diaphragm 23 by a compression spring 25. The spring 25 is preloaded by means of a plunger 26, the pressure thereon being determined by a follower screw 27 which engages the plunger 26 and is subjected to a varying pressure by engagement with a cam 28. The relative position of the plunger 26 within the switch assembly and hence the amount of preloading acting against the diaphragm 23 is determined by the relative position of the cam 28 and varies from a low point on the cam to a lobe 29 at which maximum pressure is exerted. The position of the cam 28 relative to the follower screw 27 is determined by a control knob 30 on the console of the washing machine, the control knob 30 being coupled to the cam 28 through a mechanical linkage generally indicated at numeral 31 in the drawings. Thus, if the control knob 30 is set at a high water level position, the cam 28 biases the plunger 26 to a low position, with a relatively high portion of the cam 28 riding on the follower 27. In this position, the spring 25 exerts a strong force on the diaphragm 23 by means of the post 24. It then requires a high degree of air compression in the chamber 22 to overcome the biasing force. At the other extreme, when the cam 28 engages the follower at its low point, a relatively small amount of air pressure in the chamber 22 will be effective to move the diaphragm 23.

The diaphragm 23 controls the position of a switch arm 32 which is mounted at one end in the switch housing. The switch am 32 is arranged to move between a pair of stationary con' tacts 33 and 34, depending upon the position of the diaphragm 23. A "C" spring 35 acts as a toggle spring, and has one end connected to a center tongie 36 of the switch arm 32. Upon movement of the post 24 caused by flexure of the diaphragm, the C" spring 35 is moved into an overcenter position, causing a toggle action to occur in moving the switch arm 32 from contact 33 to contact 34. The follower screw 27 is threaded into a movable support arm 27a.

The electrical circuit for the switch assembly is shown in FIG. 2 of the drawings. With the tub 11 empty, the switch arm 32 of the pressure switch engages the contact 33, thereby closing the circuit to the solenoid-operated valve 17 which, in turn, permits water to enter the tub through the inlet conduit 16. After the water level in the tub reaches a height determined by the setting of the control knob 30, the diaphragm 23 is deflected enough to cause the switch arm 32 to shift from contact 33 to contact 34, thereby energizing the motor 14 and deenergizing the solenoid-operated valve 17. Thus, water introduction is terminated and the agitator 13 begins to operate.

Nonnally, the control knob 30 will be set at some position which is intermediate the low and high level points. After the tub 11 has been filled to the predetermined level, further additions of water cannot be made until the switch arm 32 is reset so that it is in contact with the contact 33. To accomplish this, it is necessary to move the control knob 30 to the reset" position, whereupon the lobe 29 of the cam 28 engages the follower 27 forcing the plunger 26 to its extreme lowermost position, thereby flexing the diaphragm 23 to the bottom of the chamber. This amount of movement is sufficient to snap the spring 35 back over center and the switch arm 32 thereby moves from contact 34 to contact 33 permitting the solenoidoperated valve 17 to again become operative. Then, the operator can move the control knob to a higher position and change the maximum water level in the tub.

One type of improved reset and adjustment mechanism of the present invention is illustrated in FIGS. 4 to 6 of the drawings. The internal construction of the pressure-responsive switch may be exactly that shown in FIG. 1 and is generally indicated for purposes of convenience at numeral 21. The pressure-responsive switch 21 has its plunger 26 arranged to be engaged by an operator consisting of an adjustable screw 41. The latter is threadedly received within a pivotal support arm 42 at one end of which there is a pin 43 mounting the arm 42 for pivotal movement in a bifurcated portion 44 of the housing 45 in which the diaphragm and the switch arm are located as illustrated in FIG. 1. At its lower end, the support arm 42 has a vertically oriented extension 46 which is received within an elongated slot 47 formed within a resilient spring arm 48, and fonning a lost-motion connection therewith. One end of the spring arm 48 is secured to a mounting bracket 49 as by means of rivets 50.

The opposite end of the spring am 49 is formed into a pawl portion 51 (FIG. which is arranged to engage a series of serrations 52 to prevent movement of a bar slide 53 to the right as viewed in FIGS. 4 and 5. The bar slide 53 includes a pair of elongated slots 54 and 55 which permit sliding movement of the slide bar 53 relative to a pair of headed studs 56 and 57 which are secured to the bracket 49.

The amount of force which the screw 41 exerts on the plunger 26 is determined by the relative position of the extension 46 against a camming surface which takes the form of a triangular wedge 58 formed on the bar slide 53. Accordingly, when the pawl 51 is disengaged from the serrations 52, which occurs during the reset operation, shown in FIG. 5, the slide bar 53 is free to move to the right and thereby cause the extension 46 to engage a higher point on the wedge 58 at the new setting so that a greater fluid pressure is necessary to operate the pressure-responsive switch.

The reset operation is accomplished by movement of an inwardly moving slide member 61 which has an offset portion 62 on which there is mounted an operating lever 63. As seen in FIG. 3, the operating lever 63 is positioned on a console 64 of an automatic washing machine and extends through a slot 65 provided in that console. The slide 61 has an elongated slot 66 which permits sliding movement about a pair of shanks 67 and 68 which extend from a guide plate 69 and serve to secure the guide plate 69 to the slide bar 53. A spring 70 having one end secured to the slide bar 53 and its other end secured to the slide 61 provides a biasing force to return the slide 61 to the position shown in FIG. 4.

When it is desired to change the operating point of the pressure-responsive switch 21, the operator pushes in on the lever 63 so that the end of the slide 61 engages the extension 46 of the support arm 42 and moves it inwardly. Eventually, the extension 46 hits the back of the slot 47 as shown in FIG. 5 and the force then applied to the plunger 26 is sufficient to reset the switch arm 32 in the pressure-responsive switch. In this condition. the end of the spring arm 48 is lifted slightly so that the pawl 51 no longer engages the serrations 52, as shown in FIG. 5, and the slide bar 53 is free to move to the right as shown in FIG. 5 by the lateral movement of the operating lever 63. When the inward pressure on the operating lever 63 is released, the pawl 51 again engages the serrations 52 and restrains further movement of the slide bar 52 to the right. Thus, the adjustment to a higher water level takes place only after the reset operation has occurred, since the pawl 51 will not be disengaged from the serrations 52 until a sufficient biasing force has been applied on the plunger 26 to accomplish resetting.

The embodiment of the invention shown in FIGS. 7 to 10, inclusive, utilizes a rotary motion in combination with a slide mechanism to accomplish the adjustment of the operating point of the switch instead of the lateral motion of the previously described embodiment. Again, the invention is shown in conjunction with a conventional pressure-responsive switch 21 of the type which is illustrated in FIG. 1 of the drawings. In this instance, however, there is provided a screw follower 71 which engages the plunger 26 and is mounted on a resilient spring arm 72. The spring arm 72 is secured to a mounting bracket 73 by fastening means 74. A shaft 75 is journaled for rotation between the support bracket 73 and a plate 76 extending from the base of the support bracket 73. The shaft 75 carries a sector-type cam 77 having a plurality of teeth 78 formed therein.

As best illustrated in FIGS. 8 and 10, the support arm 72 has an arcuate forward end portion 79 and is split medially therealong to provide a flexible finger 80 which engages the 'teeth 78 on the cam 77 and prevents rotation of the cam in the normal position. When, however, a knob 81, located on the end of the shaft 75, is pushed inwardly, the lower surface of the sector cam 77 rides up along the arcuate surface 79 to the position shown in FIG. 10. This movement is sufficient to depress the screw follower 71 against the plunger 26 with sufficient force to reset the switch arm 32 in the pressure-responsive switch assembly. As the cam 77 rides along the arcuate surface 79, the teeth 78 are also disengaged from the resilient finger 80, and rotation of the knob 81 is then effective to rotate the cam 77 relative to the finger 80. Then, when axial pressure is released from the knob 81, the finger 80 will ride in a different tooth of the sector cam 77 and will provide a greater biasing force on the plunger 26, thereby changing the operating level of the pressure responsive switch. It should be noted, however, that the adjustment to a higher level cannot be made until such time as the follower 71 has acted with sufficient force against the plunger 26 to cause resetting to occur.

From the foregoing, it will be understood that the pressureresponsive switch assembly of the present invention provides an interlocked resetting and adjustment mechanism which provides for presetting prior to any adjustment to a higher operating point. Consequently, the combined operations of resetting and readjustment are accomplished automatically without the necessity of two separate operations.

It should be evident that various modifications can be made to the described embodiments without departing from the scope of the present invention.

We claim:

1. A pressure-responsive switch assembly comprising: 5

A flexible diaphragm,

means for communicating one side of said diaphragm to a source of fluid pressure,

a switch arm arranged to be moved by flexing of said diaphragm,

a pair of spaced contacts selectively engageable by said switch arm depending on the amount of flexing of said diaphragm,

biasing means acting on said diaphragm to set the pressure level at which said switch arm moves from one to the other of said contacts,

an operator acting on said biasing means,

a support arm supporting said operator,

slide means arranged to urge said operator against said biasing means with a force sufficient to flex the diaphragm sufficiently to move said switch arm from one contact to the other contact into a reset position, and inclined cam means engageable with said support arm to apply an adjustable force on said biasing means, said inclined cam means being positionable relative to said support arm upon movement of said slide means to cause movement, of said switch arm into said reset position and by additional movement of said slide means when said switch and arm are in said reset position.

2. The pressure-responsive switch assembly of claim 1 in which said additional movement is a lateral movement of said slide means.

3. The pressure-responsive switch assembly of claim 1 in which said additional movement is a rotary movement of said slide means.

4. The pressure-responsive switch assembly of claim 1 in which said support arm is a resilient spring arm.

5. The pressure-responsive switch assembly of claim 1 in which said cam means comprises a wedge acting on said support arm.

6. The pressure-responsive switch assembly of claim 1 in which said cam means comprises a rotary cam acting on said support arm.

Claims (6)

1. A pressure-responsive switch assembly comprising: A flexible diaphragm, means for communicating one side of said diaphragm to a source of fluid pressure, a switch arm arranged to be moved by flexing of said diaphragm, a pair of spaced contacts selectively engageable by said switch arm depending on the amount of flexing of said diaphragm, biasing means acting on said diaphragm to set the pressure level at which said switch arm moves from one to the other of said contacts, an operator acting on said biasing means, a support arm supporting said operator, slide means arranged to urge said operator against said biasing means with a force sufficient to flex the diaphragm sufficiently to move said switch arm from one contact to the other contact into a reset position, and inclined cam means engageable with said support arm to apply an adjustable force on said biasing means, said inclined cam means being positionable relative to said support arm upon movement of said slide means to cause movement of said switch arm into said reset position and by additional movement of said slide means when said switch and arm are in said reset position.

2. The pressure-responsive switch assembly of claim 1 in which said additional movement is a lateral movement of said slide means.

3. The pressure-responsive switch assembly of claim 1 in which said additional movement is a rotary movement of said slide means.

4. The pressure-responsive switch assembly of claim 1 in which said support arm is a resilient spring arm.

5. The pressure-responsive switch assembly of claim 1 in which said cam means comprises a wedge acting on said support arm.

6. The pressure-responsive switch assembly of claim 1 in which said cam means comprises a rotary cam acting on said support arm.

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