US3564183A

US3564183A - Thermostat adjusting means

Info

Publication number: US3564183A
Application number: US777831A
Authority: US
Inventors: Robert W Eshelman
Original assignee: King Seeley Thermos Co
Current assignee: King Seeley Thermos Co
Priority date: 1968-11-21
Filing date: 1968-11-21
Publication date: 1971-02-16
Anticipated expiration: 1988-02-16

Abstract

A switch assembly having a pair of mateable contacts for controlling a heater in response to a sensed temperature condition wherein the relationship of the contacts is preset by means of a cam member to select the operating temperature at which the contacts will open or close. The calibration of the switch is effected by means of a calibrating screw threadedly received in a bore formed in the cam member.

Description

United States Patent Inventor Appl. No. Filed Patented Assignee THERMOSTAT ADJUSTING MEANS Primary Examiner-H. 0. Jones Attorney-Harness, Dickey & Pierce ABSTRACT: A switch assembl havi a air of matable 8 Claims 6 Drawmg Figs contacts for controlling a heatefi r i resp gse tg a sensed i511;- U.S. Cl 2110/166; perature condition wherein the relationship of the contacts is 337/319 preset by means of a cam member to select the operating tem- Int. Cl H0lh 1/34 perature at which the contacts will open or close. The calibra- Field of Search 200/166 tion of the switch is effected by means of a calibrating screw threadedly received in a bore formed in the cam member.

BAGKGROUND AND SUMMARY OF THE INVENTION of the sensed condition. In the form selected for illustration,

the switch is adapted to sense the-temperature of an oven. This sensed temperature is translated into movement of the movable arm either by heating the movable arm in the case of a bimetal type switch or by mechanically moving the arm in the case of a hydraulic sensor assembly. For purposes of this disclosure, a hydraulic type of controlswitch is illustrated. However, it is to be understood that the invention may be applicable to a thermally actuated or bimetal type of switch, both types including a set temperature contact and a sensed temperature contact. I

In order to select the temperature to be maintained by the environmental heating element, for example the oven heater, an adjustment means is provided which conveniently takes the fomi of a cam arranged to resiliently displace one contact through engagement with the other contact, this displacement and contact engagement being commonly described as contact overclosure. The angular position of the cam is indicated by a dial, or the like, including indicia legends on the face of the switch assembly. The accuracy of these legends, as indicators of the temperature level selected, depends upon the calibration of the switch. Basically, this calibration is accomplished by initially adjusting the contact overclosure for any given temperature selected. This initial calibration normally takes place at the time of manufacture of the switch assembly. However, it is also desirable to permit the calibration of the switches at the time of installation of the switch in the appliance to be controlled.

In accordance with the present invention, this initial calibration is accomplished by means of an adjusting screw threaded into an internal bore of the cam assembly whereby rotational movement of the adjustment screw causes the cam to move either in or out and thus increase or decrease the amount of contact overclosure for a particular selected temperature. The adjustment screw is readily accessible. from the exterior of the switch after the switch has been assembled and provides an extremely fine degree of control of the contact overpressure.

Accordingly, it is one object of the present invention to provide an improved cam actuated switch assembly. It is another object of the present invention to provide an improved assembly for calibrating cam actuated switch assemblies.

It is a further object of the present invention to provide a calibration assembly which may be readily utilized either at the time of manufacture of the switch assembly or upon assembly of the switch into the appliance to be controlled.

It is still a further object of the present invention to provide an improved cam actuated switch assembly and an apparatus for initially calibrating the switch assembly which is inexpensive to manufacture, reliable in use and simple in operation.

' Further objects, features and advantages of this invention will become apparent from a consideration of the following description, the appended claims and the accompanying drawings in which:

FIG. I is a plan view of the switch assembly incorporating the features of the present invention,.with the cover of the switch assembly removed; I

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 and particularly illustrating the calibration assembly of the present invention;

. FIG. 3 is another cross-sectional view of FIG. 1 taken along line 3-3 thereof; I

FIG. 4 is another cross-sectional'view of FIG. 1 as taken along4-4thereof;

FIG. 5 is still another cross-sectional view of FIG. 1 as taken along line 5-5 thereof; and

FIG. 6 is a bottom view of the switch assembly taken in the direction of arrow A of FIG. 2.

Referring now to the drawings, there is illustrated a switch 10 which is preferably enclosed in a hollow housing 12, the housing 12 being a boxlike enclosure having an open side and various element supporting appendages integrally formed therewith. The housing may be composed, for example, of a rigid phenolic resin which is molded into the desired shape. A cover plate 14 closes the open side of the housing and is held in place by suitable fastening means 16(see FIG. 6). Extending through the cover plate and across the switch housing to a suitable bearing is a shaft assembly 20, the outer end of which is secured to a knob (not shown) and a dial (also not shown), the legend being utilized to indicate the selected temperature level.

The interior of the housing supports a switch assembly 24 which includes a pair of mating switches 26 (FIG. 4) and 28 (FIG. 5), each switch having a fixed contact and a movable contact. The movable contacts of the

switches

26, 28 are supported on a common resilient support member 30, one end of which is bifurcated to define movable contact arms 32, 34 which support at their respective ends movable contacts 36, 38. The support member 30 is fixed to the housing member 12 by means of rivet 40 which also secures a tenninal element 42 to the housing 12. The terminal element 42 provides a common terminal for the movable contacts 36, 38. The support element 30 also includes a follower portion 48 which cooperates with an actuator element to impart movement to the support element 30 in response to variations in sensed conditions, as will be more fully explained hereinafter.

Referring to FIG. 4, the movable contact 36 is adapted to be moved into engagement with a set of fixed contacts 50 which is mounted on a resilient arm assembly 52 secured to the housing by means of a rivet 54. The rivet 54 also secures a terminal element 56 to the housing, the element 56 providing a connection point for the fixed contact 50. The arm assembly 52 includes a resilient member 58 which is electrically and mechanically connected to the contact element 50 and a cam follower arm 60 which includes a cam follower portion 62 formed as'an integral part thereof. The cam follower portion 62 is positioned into engagement with a cam surface .64 on cam element 66, the portion of the cam surface 64 which is in contact with follower portion 62 varying in response to rotation of the stem 20 to a preselected position.

As is seen from the configuration of the cam surface 64, the cam follower element, and thus the contact 50, is moved to the right or left depending on the particular portion of the cam surface 64 which is positioned into engagement with the cam follower portion 62. In the position shown in FIG. '4, the cam 66 has been rotated into the off position such that the contacts 36, 50 are out of mating engagement. The contacts 36, 50 provide a selectable set temperature arrangement whereby the user may preselect a temperature at which the contacts will open to discontinue the supply of heat to the environment being sensed. This arrangement is shown purely for illustrative purposes and it is to be understood that the situation may be reversed whereby the contacts are closed to discontinue the supply of heat to the environment and/or the contacts may be closed in response to the positioning of the switch in the off position.

Referring now to FIG. 5, there is illustrated the second set of contacts 28 which are provided, in the illustrated arrangement, for presetting a particular hold temperature, independently of the set temperature selected through the rotation of the shaft 20. Specifically, the switch 28 includes the movable contact 38 and a fixed contact 70. The movable contact is controlled by means of the movable am 34 described above.

The hold temperature set by fixed arm 72 is selected by contacts 36, 70, are controlled by means of a heat responsive hydraulic assembly which is interconnected with the movable arms 32, 72 to move the arms toward'or away from fixed arms 52, 34 in response to variations in the sensed condition, for example, the temperature of an oven. In this situation, it is desired to control the temperature in the oven to maintain the temperature at'a preselected level.

The hydraulic sensor assembly includes a bellows member 92' which is in fluid communication with a sensor element 94, one end of which (not shown) includes a bulb containing an expansible fluid situated in the oven cavity and the other end 96v being connected with the bellows element 92. In the preferred embodiment, a rise in temperature in the oven cavity creates an increase inpressure in the hydraulic sensor 94 which increases the pressure within the bellows element 92. This increase in pressure is communicated to an expansion chamber 98 causing a portion of the expansion chamber 98 to move toward the right in FIG. 4 and toward the left in FIG. 5.

The described movement is communicated to the member 30, particularly'to the follower portion 48, by means of a ceramic followermemb er 100. It is to be noted that the support member 30 is spring biased toward the bellows element 92 tending to cause the contact 36 to move to the left in FIG. 4 and contact 38 to move to the right in H6. 5. The hydraulic assembly 90is supported on the housing 12 by means of a shoulder 102 which bears against an inner portion of the housing 12 anda spring biased washer element 104 fitted around a necked-down portion 106 of the hydraulic assembly.

. In operation, assuming that the cam element 66 is rotated to a position on the inclined portion of the cam surface 64, the follower arm 60 will permit contact 50 to engage contact 36 causing contact 36 to move away from the cam element 66. As described above, the degree of contact overclosure determines the temperature which the oven environment will achieve, this contact overclosure being created through the spring action of arm 30. Also,

contacts

38, 70 will bein engagement until such time as the oven heats up to the preselected hold temperature and the shoulder 86 engages the pin 78. In the system, the control of the oven is switched to the hold contacts'38, 70 when it is desired to maintain the hold temperature and not the set temperature.

As is to be noted from the above description, the relative position of the cam surface selected, in the left and right direction in FIGS. 2, 4 and 5, in conjunction with the springiness of the arms 32, 34, will determine the amount of overclosure of the contact elements 36, 50. Thus, for a particular selected temperature, the surface of the cam for that particular temperature must be accurately positioned, left and right, in order to achieve that particular temperature. Accordingly, a calibration assembly 120 has been provided in order to ad- I just the relative position of the cam surface. The cam element 66 includes a reduced diameter portion 122 which is adapted to pass through an aperture 124 in the cover plate 14 and provide a bearing surface for the cam member 66 to restrict the movement thereof relative to the cover plate 14. Also, the bottom of the housing 12 is formed with an integral cup-shaped portion 126 to receive a lower shaft portion of the cam member 66 to form a second support point. The cam element ,66 is initially positioned within the cavity in the cup member 126 and a spring element 127 is positioned to bear against the cover 14 and tends to urge cam element 66 toward the bottom of "the housing member 12 (FIG. 2).

The central portion of the cam member 66 is provided with an interior bore 128, the bore 128 being fitted with a metal "bottom of the cam member 66, the insert 134 being formed with a flange portion 135 received in a countersunk recess in the bottom of the cam member '66. The lowermost portion of the sleeve 130 and the entirety of the sleeve 134 are internally threaded and adapted to receive an adjusting screw at the bottom of the cam member 66. The bottom of the adjusting screw 140 is dished to receive a spherical-shaped bearing element 142, the housing 12 also being dished at 144 to receive the element 142.

In order to calibrate the element 66 relative to the housing 12, the screw member 140 is advanced or retracted by means of a screwdriver placed into a screw slot 148 formed in the head of the screw 140. By advancing the screw element 140, the cam element 66 is moved to the right in FIG. 2 to move the cam surface 64 in the direction of the cover member 14. This calibration may be accomplished by any known method including placing the switch assembly 10 in an apparatus which simulates the selected temperature to be maintained and sensing the operation of the switch.

From the foregoing, it is seen that a simple calibration assembly has been provided which is readily accessible from the exterior of the switch after assembly and may be used to calibrate the switch during the initial manufacturing phases or after installation into the final appliance to be controlled. While it will be apparent that theembodiments of the invention herein disclosed are well calculated to fulfill the objects of the invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined trolled by the hydraulic actuator and a settable contact, a follower arm having one end fixedly supported relative to said base assembly and the other end supporting the settable contact, and a movable cam element having a cam surface engaged by a portion of the follower arm for selectively presetting the settable contact relative to the movable contact in response to rotational movement of the cam element, the improvement comprising calibration means for adjusting the preset condition of the cam surface in the absence of rota tional movement of the cam element including means forming a bore interiorly of the cam element, said bore being threaded, and plug means including a plug element engaging a portion of said base assembly having an exterior threaded portion threadedly engaging said bore, the rotation of said plug means moving the cam element toward and away from said portion of said base assembly for adjusting the preset position of said cam surface, said cam element and said plug element rotating as a unit in response to rotational movement of the cam element.

2. The improvement of claim 1 further including resilient means biasing said cam element toward said base assembly portion.

3. The improvement of claim 1 wherein said plug element is provided with exterior threads and said plug means includes a bearing element positioned between said base said plug element.

4. The improvement of claim 1 wherein the base assembly includes a generally circular annular bearing portion integrally formed in said base assembly, said cam element having a depending first shaft portion received within said bearing portion, said plug means being generally concentrically located relative to said bearing portion.

5. The improvement of claim 4 wherein said plug element is provided with exterior threads and said plug means includes a bearing element positioned between said base assembly and said plug element.

assembly and includes a tool receiving portion positioned within said bore and accessible from the hollow portion of said second shaft.

8. The improvement of claim 7 wherein said hollow portion of said second shaft is accessible exteriorly of said base assembly.

Claims

1. In a hydraulically controlled switch assembly having a base assembly, a condition responsive hydraulic actuator, a pair of mateable contacts including a movable contact controlled by the hydraulic actuator and a settable contact, a follower arm having one end fixedly supported relative to said base assembly and the other end supporting the settable contact, and a movable cam element having a cam surface engaged by a portion of the follower arm fOr selectively presetting the settable contact relative to the movable contact in response to rotational movement of the cam element, the improvement comprising calibration means for adjusting the preset condition of the cam surface in the absence of rotational movement of the cam element including means forming a bore interiorly of the cam element, said bore being threaded, and plug means including a plug element engaging a portion of said base assembly having an exterior threaded portion threadedly engaging said bore, the rotation of said plug means moving the cam element toward and away from said portion of said base assembly for adjusting the preset position of said cam surface, said cam element and said plug element rotating as a unit in response to rotational movement of the cam element.

3. The improvement of claim 1 wherein said plug element is provided with exterior threads and said plug means includes a bearing element positioned between said base assembly and said plug element.

6. The improvement of claim 5 wherein said plug element is within said first shaft portion and said cam element includes a second depending shaft portion extending in a direction opposite to said first shaft portion, said second shaft portion being substantially hollow between said plug element and the end of said second shaft.

7. The improvement of claim 6 wherein said plug element includes a tool receiving portion positioned within said bore and accessible from the hollow portion of said second shaft.