US3898604A

US3898604A - Control device having automatic switch opening means and method of making the same

Info

Publication number: US3898604A
Application number: US441413A
Authority: US
Inventors: Donald F Weekes; James Sim
Original assignee: Robertshaw Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1974-02-11
Filing date: 1974-02-11
Publication date: 1975-08-05
Anticipated expiration: 1992-08-05
Also published as: CA1049116A

Abstract

A control device having an electrical switch and a condition responsive fluid operated unit for opening the switch when the fluid operated unit senses a certain condition. A lever is arranged in the control device to cause the switch to automatically open should the fluid operated unit lose a certain amount of its fluid.

Description

United States Patent [191 Weekes et al.

[ Aug. 5, 1975 CONTROL DEVICE HAVING AUTOMATIC SWITCH OPENING MEANS AND METHOD OF MAKING THE SAME [75] Inventors: Donald F. Weekes, Weston; James Sim, Oakville, both of Canada [73] Assignee: Robertshaw Controls Company,

Richmond, Va.

[22] Filed: Feb. 11, 1974 [21] Appl. No.: 441,413

[52] U.S. Cl. 337/322 [51] Int. Cl. HOlh 37/42 [58] Field of Search 337/322, 323, 320, 321;

ZOO/81.8

[56] References Cited UNITED STATES PATENTS 3,665,362 Hild et al. 337/322 3,678,758 7/1972 Lawrence ZOO/81.8 X

Primary Eraml'nerR. N. Envall, Jr. Attorney, Agent, 0r Firm-candor, Candor & Tassone 5 7 ABSTRACT A control device having an electrical switch and a condition responsive fluid operated unit for opening the switch when the fluid operated unit senses a certain condition. A lever is arranged in the control device to cause the switch to automatically open should the fluid operated unit lose a certain amount of its fluid.

10 Claims, 6 Drawing Figures CONTROL DEVICE HAVING AUTOMATIC SWITCH OPENING MEANS AND METHOD OF MAKING THE SAME This invention relates to an improved control device as well as to a method of making such a control device or the like.

It is well known that control devices have been provided wherein electrical switch means thereof are controlled by condition responsive fluid operated means.

For example, the U.S. Pat. No. 3,665,362, to Hild et al., discloses and claims such a control device wherein a plurality of electrical switches are controlled by the same fluid operated means, one of the electrical switches controlling the high temperature burn-off cleaning operation of an oven of a cooking apparatus whereby the fluid operated means will open the electrical switch when the temperature of the oven exceeds the preset high burn-off temperature and will close the switch when the oven temperature falls below such preset burnoff temperature.

However, it has been found according to the teachings of this invention, that should such condition responsive fluid operated means completely lose its fluid because of a fast leak of fluid therefrom during such high temperature burn-off cleaning operation, the electrical switch will remain closed and a run away temperature operation might exist in the oven and thereby cause an adverse situation.

Also, should a slow leak of fluid from the condition responsive fluid operated means occur over a period of time, the control device will begin to experience an upward drift or shift in the actual oven temperature being maintained thereby for each temperature setting thereof. However, when the loss of fluid has reached a certain amount, such as would cause a 70F shift in oven temperature, the control device of this invention has means that will automatically prevent the use of the control device for oven operation as will be apparent hereinafter so that such defective fluid operated means must be replaced.

Accordingly, it is a feature of this invention to provide means that will automatically open such electrical switch when the condition responsive fluid operated means loses a certain amount of its fluid.

In particular, one embodiment of this invention provides a pivotally mounted lever between a movable contact means of the electrical switch and the switch engaging means of the condition responsive fluid operated means so that when the fluid operated means loses a certain amount of its fluid and thereby causes the engaging means to be moved away from the movable contact means of the switch, such movement of the engaging means of the condition responsive fluid operated means will cause the lever to pivot and thereby act on the movable contact means of the electrical switch to move that movable contact means out of contact with its cooperable contact means ofthe switch so that the switch will remain in an open condition until the control device is replaced or repaired.

Accordingly, it is an object of this invention to provide an improved control device having one or more of the novel features set forth above or hereinafter shown or described.

Another object of this invention is to provide a method for making such a control device or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIG. 1 is an exploded perspective view of the improved control device of this invention.

FIG. 2 is an enlarged view of part ofthe conrol device illustrated in FIG. 1 and is taken in the direction of the arrows 22 of FIG. 1.

FIG. 3 is a cross-sectional view taken on line 33 of FIG. 2.

FIG. 4 is a cross-sectional view taken on line 44 of FIG. 2 and illustrates the electrical switch means of the control device when the condition responsive means senses a condition below the switch opening condition thereof.

FIG. 5 is a view similar to FIG. 4 and illustrates the electrical switch when the condition responsive means is sensing the switch opening condition.

FIG. 6 is a view similar to FIG. 5 and illustrates the switch means when the fluid operated means has lost its fluid.

While the various features of this invention are hereinafter described and illustrated as being particularly adapted to provide a control device for controlling the heating means of a cooking apparatus, it is to be understood the various features of this invention can be utilized singly or in any combination thereof to provide a control device for other apparatus as desired.

Therefore, this invention is not to be limited to only the embodiment illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIGS. 1, 2 and 3 the improved control device of this invention is generally indicated by the reference numeral 10 and comprises a housing means 11 formed of a plurality of

parts

12, 13 and 14 suitably secured together to define a chamber 15 within the housing means 1 l for containing a plurality of electrical switch means respectively and generally indicated by the reference numerals l6, l7 and 18 to be controlled by a condition responsive fluid operated means carried by the housing plate 14 and being generally indicated by the reference numeral 19.

Such control device 10 is fully described and claimed in the aforementioned US. Pat. No. 3,665,362, to Hild et a1., and such patent is incorporated herein by reference as any desired information of the details and operation of the control device 10 can be obtained from such patent. However, in order to fully understand the features of this invention, sufficient structure of the control device 10 will now be described in order to better understand the features of this invention.

Each electrical switch means l6, l7 and 18 includes a first contact means 20 comprising a flexible blade 21 mounted in cantilevered fashion to the housing means 11 by having one end 22 thereof fixed to the housing means 11 and the other end 23 being provided with a contact 24 thereon. Each switch means I6, 17 and 18 also includes a movable contact means 25 that cooperates with the first Contact means 20 and comprises a flexible switch blade 26 having one end fixed to the 'housing means 11 so that the switch blade 26 is ment with each other, the switch blade 26 having a natural bias to tend to always move the contact 27 into contact with the contact 24 as illustrated in the drawings.

The condition responsive fluid operated means 19 includes a ribbon-like tubular member 29 arranged in spiral form with the inner end 30 of the tubular member 29 being interconnected with a crossbar 31 that is attached to the legs 32 of a yoke member 33 that carries an insulative switch engaging bar 34 on the upper end thereof, the switch engaging bar 34 being movable toward and away from the movable contact means 25 of the switch means 16, 17 and 18 depending upon the expansion and contraction of the fluid in the tubular member 29.

In particular, the tubular member 29 is fluidly interconnected by conduit means 35 to a bulb 36 which is adapted to be disposed in an oven (not shown) of a cooking apparatus (not shown) to sense the temperature thereof. As the temperature of the oven goes up, the fluid in the bulb 36 expands and, thus, causes the spiral tube 29 to tend to unwind and thereby move the switch engaging bar 34 toward the movable contact means 25 of the electrical switches l6, l7 and 18. Conversely, as the temperature of the oven goes down, the fluid in the bulb 36 contracts and thereby permits the tube 29 to tend to wind up by its natural resiliency and therby move the switch engaging bar 34 away from the movable contact means 25 of the switches l6, l7 and 18.

Therefore, it can be seen that the

electrical switches

16, 17 and 18 can each be so constructed and arranged that the switch contact bar 34 of the fluid operated means 19 will move the movable contact means 25 thereof away from the fixed contact means 20 thereof when the bulb 36 senses a certain temperature.

For example, the upper contact means 20 of the electrical switch 18 can be adjusted by a selector means 37 of the control device selecting a desired cooking temperature. In this manner, when that cooking temperature is reached in the oven and slightly exceeded, the bulb 36 has caused the engaging bar 34 to move toward the movable contact means 25 of the switch 18 in such a manner that the movable contact means 25 will be moved away from the contact means and thereby open the electrical switch means 18 which is controlling the heating means of the oven for that selected cooking operation, Thus, the electrical current to the heating means of the oven is terminated as long as the switch 18 is being held open by the bar 34. However, when the temperature in the oven falls slightly below the selected temperature, the fluid in the bulb 36 has contracted in such a manner that the bar 34 moves to the right in FIG. 3 to permit the movable contact means of the switch 18 to again make contact with the upper contact means 20 and thereby close the switch 18 so that the electrical current can again flow to the heating means for the oven. Accordingly, the switch 18 will be cycled on and of by the bar 34 to tend to maintain the temperature in the oven at the selected temperature.

Similarly, the electrical switch means 16 can be utilized to control the operation of the heating means of the oven when a warmth retaining and non-cooking temperature in the oven is to be provided by the con trol device 10 whereby the movable contact means 25 of the switch 16 will always be moved away from the upper contact means 20 thereof by the bar 34 of the fluid operating means 19 when the temperature in the oven exceeds a certain preselected temperature, such as lF or the like, as preset by factory adjustments to the control device 10.

Similarly, the electrical switch means 17 can control the heating means of the oven for a high temperature burn-off cleaning operation wherein the switch means 17 will be opened by the fluid operating means 19 when the temperature of the oven exceeds the factory preset high burn-off temperature of approximately 900F or the like and will permit the switch means 17 to close when the temperature in the oven falls below that 900F.

However, as previously stated, one of the features of this invention is to provide means for automatically opening the switch 17 should the fluid operated means 19 completely lose its fluid because of a fast leak of fluid therefrom, such as by the bulb 36 breaking, etc., during a high temperature burn-off cleaning operation of the control device 10 so that the switch means 17 will terminate the high temperature burn-off cleaning operation of the oven.

Therefore, reference is now made to FIGS. 4, 5 and 6 wherein it can be seen that a pivotally mounted lever 38 of this invention is provided and has one end 39 thereof angularly bent and projecting through an opening 40 formed in the lower end 27 of the switch blade 26 of the movable contact means 25 of the switch means 17. The other end 41 of the lever 38 extends through an opening 42 passing through the insulative bar 34 of the fluid operated means 19 so as to be secured thereto.

The lever 38 engages a threaded adjusting member 43 carried by the housing means 11 intermediate its

ends

39 and 41 to thereby be pivotally mounted in the chamber 15 of the housing means 11 by the adjustable pivot member 43 to operate in a manner now to be described.

When the fluid operating means 19 is operating normally, the lever 38 does not impede the operation of the switch bar 34 acting on the movable contact means 25 of the switch 17 so that when the temperature of the oven is below the temperature that is desired for opening the switch 17, the bar 34 is to the right of the movable contact means 25 of the switch 17 in the manner illustrated in FIG. 4 whereby the natural bias of the switch blade 26 maintains its contact 27 in contact with the contact 24 of the upper switch blade 21 as illustrated in FIG. 4. However, when the temperature of the oven slightly exceeds such predetermined temperature, the fluid operated means 19 has moved the bar 34 to the left in FIG. 5 a sufficient distance to cause the movable contact means 25 of the switch means 17 to be moved out of contact with the upper contact means 20 to thereby open the electrical switch 17 for the purpose previously described.

Thus, the fluid operated means 19 cycles the electrical switch 17 between its opened and closed position to tend to maintain the temperature in the oven at the predetermined high burn-off cleaning temperature.

However, should the fluid operated means 19 completely lose its fluid, the natural resilience of the tubular member 29 is to move in a windup direction thereof and thereby move the contact bar 34 to the right in FIG. 6 away from the movable contact means 25 of the switch 17 whereby if the lever 38 of this invention were not utilized, the natural resilience of the movable contact means 25 would be to place the same into contact with the upper contact means 20 and thereby continuously operate the heating means through the closed switch 17 which situation might produce and adverse runaway heating condition.

Therefore, such large movement of the contact bar 34 to the right upon the complete loss of fluid from the fluid operated means 19 causes the lever 38 to pivot on the pivot member 43 in such a manner that the lever 38 moves in a clockwise direction and acts against the movable contact means 25 of the switch 17 to move the same to the left away from the contact means 20 in FIG. 6 and hold the movable contact means 25 out of contact with the contact means 20 whereby the switch means 17 will remain in an open condition and thereby terminate the operation of the heating means through the switch means 17 until the control device 10 is replaced or the fluid operating means 19 is repaired, as the case may be.

Therefore, it can be seen that the lever 38 of this invention automatically opens the switch 17 upon a complete loss of fluid of the fluid operated means 19 whether or not the control device 10 is being utilized for a high temperature burn-off cleaning operation at that time.

Also, the lever 38 of this invention will automatically open the switch 17 upon the loss of fluid of the fluid operated means 19 when such loss of fluid reaches a certain amount, which certain amount in this embodiment of the control device is less than the amount for a complete loss of fluid as previously described.

For example, it can be seen from the electrical circuit disclosed and described in the aforementioned US. Pat. No. 3,665,362 to Hild et al, that the switch 17 of the control device 10 is in series with the switch 18 so that during a normal baking operation being provided by the control device 10, the switch means 17 will be in a closed condition and the switch 18 will be cycled on and off in the manner previously described.

However, should the bulb 36 or other part of the fluid operated means 19 develop a slow leak, the same will cause an upward drift or shift in the temperature being maintained in the oven by the switch 18 for any temperature setting thereof and such upward shift of temperature would gradually increase over a relatively long period of time, such as several weeks or months whereby a housewife may not notice that her oven is 10, or 20 high and may simply lower her dial setting or reduce the cooking time the next time she uses the cooking apparatus for the same cooking operation. If she continues to use the oven, the oven will operate at progressively higher temperatures until the leak of the fluid operated means 19 has caused a shift of roughly 70F. At this time and when the bulb 36 is at room temperature, the loss of pressure in the fluid operated means 19 will have caused the bar 34 to move to the right, in substantially the manner illustrated in FIG. 6, a sufficient distance to cause the lever 38 to open the movable contact means away from the upper contact means 20 and thereby open the electrical switch 17 and prevent the control device 10 from even being utilized for normal cooking operations as a circuit cannot now be completed through the switch 18 even though the same is closed because the switch 17 is now being held open by the defective fluid operated means 19.

Thus, it can be seen that should the lever 38 of this invention not be provided, the housewife might notice originally that her oven was 25F high and might call a service man to have the thermostat recalibrated, time and time again, so that excessive calibration drift might be provided. However, with the lever 38 of this invention, even though the control device 10 is recalibrated in the above manner, such recalibration would only be a temporary measure and would not prolong the time when the loss of fluid in the fluid operated means 19 would cause the bulb 34 to operate the lever 38 to open the switch 17 when the bulb 36 was cool so that the control device 10 could not ever again turn on the heating means for the oven and such feature could not be altered by recalibration of the control device 10 whereby the defective device 19 and/or control device 10 must be replaced.

Therefore, it can be seen that the control device of this invention reacts to relatively small or slow leaks as well as to a complete loss of pressure of the fluid operated means to protect not only against a high temperature burn-off runaway operation, but also against other adverse high temperature operation of the control device 10 through a malfunctioning of the fluid operated means 19 after the same has lost a certain amount of its fluid.

Therefore, this invention not only provides an improved control device, but also this invention provides a method of making the same or the like.

While the form and method of this invention have been described and illustrated as required by the Patent Statute, it is to be understood that other forms and methods can be utilized and still come within the scope of the appended claims.

What is claimed is:

1. In a control device having electrical switch means and temperature responsive fluid operated means for opening said switch means when said fluid operated means senses a certain temperature or above the same and for closing said switch means when said fluid operated means senses a temperature below said certain temperature, the improvement comprising means operatively associated with said switch means and said fluid operated means for automatically opening said switch means when said fluid operated means loses a certain amount of its fluid.

2. In a control device as set forth in claim 1, said switch means including a fixed contact means and a movable contact means cooperable with said fixed contact means, said fluid operated means having engaging means for engaging said movable contact means to move said movable contact means out of contact with said fixed contact when said fluid operated means senses said certain condition.

3. In a control device as set forth in claim 2, said means for automatically opening said switch means including means engaging said movable contact means and said engaging means of said fluid operated means.

4. In a control device as set forth in claim 3, said engaging means of said means for automatically opening said switch means comprising a lever pivotally mounted between opposed ends thereof.

5. In a control device as set forth in claim 4, said lever having one of said ends thereof engaging said movable contact means.

6. In a control device as set forth in claim 5, said lever having the other end thereof secured to said engaging 9. In a control device as set forth in claim 8, said engaging means of said fluid operated means including an insulative bar having an opening passing therethrough, said other end of said lever extending into said opening of said bar to be secured thereto.

10. In a control device as set forth in claim 9, other electrical switch means carried by said device and being controlled by said bar of said fluid operated means.

Claims

6. In a control device as set forth in claim 5, said lever having the other end thereof secured to said engaging means of said fluid operated means to move in unison therewith.

7. In a control device as set forth in claim 6, said lever being pivoted against an adjustable pivot point of said device.

8. In a control device as set forth in claim 6, said movable contact means including a flexible switch blade mounted in cantilevered fashion and having a normal bias toward said fixed contact means, said blade having an opening therein, said one end of said lever having a tang disposed in said opening of said blade.

9. In a control device as set forth in claim 8, said engaging means of said fluid operated means including an insulative bar having an opening passing therethrough, said other end of said lever extending into said opening of said bar to be secured thereto.