US2296445A - Thermal responsive switch - Google Patents

Description

Sept. 22, 1942. c. w. KUHN THERMAL RESPONSIVE SWITCH Filed Aug. 31, 1940 2 Sheets-Sheet l Sept. 22, 1942. c. w. Ku'HN 2,296,445

THERMAL RESPONSIVE SWITCH Filed Aug. 31, 1940 2 Sheets-Sheet 2 8&5 83 .6

2.7 50 3855575254 I0 Em saga llll I I as 3537 m 34 m ywm trol mechanism associated therewith.

' Patented Sept. 22, 1942 s PATENT OFFICE THERMAL RESPONSIVE SWITCH Clarence W. Kuhn, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application August 31, 1940, Serial No. 355,037

5 Claims. (01. zoo-s3) This invention relates to thermal responsive switches for controlling apparatus such as electric refrigerators.

Refrigerator control switches are usually provided with a thermal responsive operating mechanism including a loading spring which is manually adjustable by means of a rotatable cold control knob to maintain the cooling unit of the. refrigerator at selected refrigerating temperatures within a given normal range. In some instances such switches are also provided with a semi-automatic defrosting mechanism for controlling the loading spring to produce an automatically terminated defrosting period in the refrigerator during which period the temperature of the cooling unit is permitted to rise to a predetermined value substantially above the freezing point of water before normal refrigerating temperatures are again produced in the cooling unit of the refrigerator. g

The present invention has among its objects to provide a refrigerator control device of the aforesaid character having a simplified and generally improved semi-automatic defrosting con- Another object is to provide a refrigerator v control switch of the aforesaid type having a single adjusting knob for efiecting cold control and for also controlling the defrosting mechanism.

Another object is to provide a semi-automatic defrosting mechanism which comprises a relatively small .number of rugged and inexpensive parts which can be. readily manufactured and applied to existing types of refrigerator control switches withoutextensive modification of the latter.

Various other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate an em bodiment of the invention which will now be described, it being understood that various modifications may be made in the embodiment illustrated without departing from the spirit and scope of the appended claims.

In the drawings:

Figu're 1 is a side view of a thermal responsive switch embodying the invention, portions of the switchbeing broken away and shown in section;

Fig.2 is a fragmentary sectional view of certain of the switch parts shown in Fig. 1;

Fig. 3 is a sectional view taken substantially on line 3-3 of Fig. 1;

Figs. 4 and 5 are sectional views on line 4-4 of Fi 3 illustrating the defrosting mechanism 5 of the switch with the cold control knob in an intermediate position, and in an extreme off position;

Fig. 6 is a top elevational view illustrating the parts of the cold control mechanism with the cold control knob in an extreme off position;

Fig. 7 is a sectional view similar to that shown in Fig. 4 illustrating the defrosting mechanism in set position;

Fig. 8 is a fragmentary top elevational view of certain of the cold control parts with the defrosting mechanism set in the position shown in Fig. 7;

Fig. 9 is a sectional view on line 4-4 of Fig. 3 illustrating the defrosting mechanism in tripped position, and

Fig. 10 is an exploded perspective view'of certain of the parts of the defrosting mechanism illustrated in Figs. 1 and 3.

Referring to Fig. 1, the invention is shown in connection with a thermal responsive switch of the type disclosed in the patent to C. W. Kuhn, No. 2,158,824, of May 16, 1939. However, the

switch shown is merely selected to illustrate a practical application of the invention and it is apparent that the invention may be applied to switches of various other types having an adjustable loading spring associated therewith.

The control switch illustrated is mountedupon an elongated insulating base I and includes a movable bridging contact 2 which cooperates with a pair of stationary contacts 3. Stationary contacts 3 are mounted side by side adjacent the lower end of insulating base Lone of the same being shown in Fig. l, and bridging contact 2 is mounted upon a pivoted carrier 4 having a spring 5 associated therewith for biasing the same in a directionto hold bridging contact 2 in engagement with its cooperating stationary contacts 3. Contact carrier 4 is controlled by a fluid condition responsive device 6 through the medium of a snap operating mechanism including pivoted levers 'l and 8 and an over-center spring 9. v

More specifically contact carrier 4 and levers "l and 8 are carried by a horizontally arranged U-shaped bracket l0 mounted upon the front face of insulating base I. The side walls of. bracket III are drilled to receive horizontally arranged pivot pins II and H, the former pivot pin being located adjacent the under side of said bracket at a point midway between the ends thereof, and the latter pivot pin being arranged adjacent the upper side of said bracket at a point adjacent the rear end thereof. Contact carrier 4 and lever 1 are both pivotally mounted upon pivot pin II and lever 8 is pivotally mounted upon pivot pin I2. Contact carrier 4 has stop projections formed on opposite sides .thereof, one of which is shown at |4 in Fig. 1, and said stop projections are engageable with the under side of bracket ID to limit circuit opening movement of said contact carrier.

Lever 1 straddles contact carrier 4 and is movable with respect to said contact carrier between the stop projections I4 on the latter and an adjustable stop l5 carried by base I, said stop being illustrated in dotted lines ,in Fig. 1. Contact carrier 4 is provided with spaced side portions for receiving lever 8 therebetween and the free end of said lever projects forwardly through a recess in the front wall of bracket l0. Spring 9 is held under compression between a pair of cup washers and as shown in Fig. 2 the lower cup washer rides upon a pointed rivet I6 fixed to the lower end of lever 1, and the upper cup washer rides upon a pointed rivet |1 fixed to lever 8 and located below pivot pin I I.

As is apparent, upon counterclockwise rotation of lever 8 out of the position shown in Figs. 1 and 2 spring 9 assumes a position wherein the force thereof acts on a line located to the rear of pivot pin II and lever 1 then operates with a snap action to move contact carrier 4 and bridging contact 2 into circuit opening position against the action of spring 5. During return movement of lever 8 in a clockwise direction, spring 8 assumes a position wherein the axis thereof is located in front of pivot pin II and said spring then acts to move lever 1 with a snap-action into the position shown in Fig. 1 to permit closing movement of contact carrier 4 and its associated bridging contact 2 under the action of spring '5.

Lever 8 is controlled by the fluid condition responsive device 6, and in the embodiment illustrated said device comprises a bellows I 8 enclosed within a cup-shaped member I9. Bellows I8 is secured to the rear wall of cup member l3 and said cup member is fixed to the rear face of insulating base by screws 28 which also serve to secure bracket III to the front face of said insulating base. Bellows I8 is operatively connected to lever 8 so that upon expansion thereof the same moves said lever in a clockwise direction against the action of a loading spring 2|. Loading spring 2| is held under compression between lever 8 and a nut 22 which is held against rotation between the side arms of bracket Ill and is mounted upon a screw 23. Screw 23 is rotatably supported within an opening in the front wall of bracket I0 and is held against forward movement .by a shoulder 24 which engages the rear face of said front wall. As is apparent from Fig. 3 upon rotation of screw 23, nut 22 is moved axially thereon to vary the degree of compression of spring 2|.

.The above described control device may be used in connection with electric refrigerators to effect starting and stopping of the refrigerator upon predetermined temperatures in the food compartment thereof. For such service bellows l8 has a closed pipe extension 25 sealed to the rear wall a spacer 21. Spacer 21 is secured to an extension 28 on the front end of screw 23 by a cap screw 29 and said spacer is provided with an enlarged flange portion 30 having an axially extending cam projection 3| formed on the rear side thereof. Cam projection 3| cooperates with a stop .projection 32 on the front .wall of bracket |0to limit rotation of spacer 21 and its associated screw 23 in opposite directions between the extreme positions shown in Figs. 5 and 9, and said cam projection also acts upon movement into the extreme position shown in Fig. 5 to move operating lever 8 of the switch into circuit .opening position if the same is not already in such position.

The above described control switch is provided with a semi-automatic defrosting mechanism comprising a follower 34 associated with nut 22, a latch 35 for locking said nut follower in a predetermined position, and-a member 36 for tripping said latch. As shown in Figs. 3 and 6 nut follower 34 is interposed between nut 22 and the front end of loading spring 2|, and the same has a pair of forwardly extending prongs 31-31 formed on opposite sides thereof. Nut 22 is recessed on opposite sides to receive the prongs 31 and said prongs extend through openings in the front wall of bracket I8. Latch 35 is ring-shaped and the same is rotatably supported upon the front end of screw 23 and is held against axial movement between the front face of bracket l0 and a retaining member 38. Latch 35 is provided 0 with a forwardly extending projection 39 to be engaged by a radial projection 48 on the inner end of spacer 21 and said latch is also provided with oppositely disposed locking projections 4| and 42 for engaging the front ends of prongs 31. As shown in Fig. 10, locking projections 4| and 42 are provided with inclined projections 4| and 42 and the latter locking projection is provided with an arcuate extension 44 to be engaged by trip member 36. Trip member 38 is pivotally secured to the front. end of bracket ID by a pin 45, and said trip member is provided with a projection 46 for engaging extension 44 on latch 35 and is also provided with a tail piece 41 to be engaged by the front end of operating lever 8 of the switch operating mechanism. Retaining member 38 is ring shapedto receive the front end of screw 22 and is held in assembled position upon the front end of bracket It by the inner end of spacer 21. Said retaining member is recessed as shown at 48 to receive stop projection 32 on bracket l0 and the same is also provided with stop projections thereof to be arranged within the cooling compartment of the refrigerator. Pipe extension 25 and bellows 8 contain an expansible fluid, as for example methyl chloride, and upon temperature changes within the cooling compartment of the refrigerator the pressure of such fluid varies to effect operation of said bellows.

Upon an increase in temperature within the 49 and 50. Stop projection 49 cooperates with projection 42 on latch 35 to limit counterclockwise rotation of said latch beyond the position shown in Fig. 5. Stop projection 58 cooperates with the shoulder 5| formed on latch 35 to limit rotation of said latch in a clockwise direction beyond the position shown in Figs. 4 and 9.

The operation of the aforedescribed defrosting mechanism will now be more fully described. Screw 23 is adjustable within a given range known as the cold control range for selection of refrigerating temperatures, and said screw and its associated spacer 21 are movable beyond said range into an extreme position shown in Fig. 5. To effect a defrosting operation of the refrigerator knob 26 is first operated to move spacer 21 and its associated screw 23 into the extreme position shown in Fig. and is then operated to restore said spacer and said screw to a selected position within the cold control range. During movement of screw 23 and spacer 21 into the position shown in Fig. 5 cam 3i moves lever 6 into circuit opening position if the same is not already in such position, and nut 22 and its associated follower 34 are moved inwardly into the position shown in Fig. 6. With nut 22 and follower 34 in the position shown in Fig. 6 the front ends of the prongs 31 of said follower are flush with the front face of bracket 1..

The latch 35 is normally positioned as shown in Fig. 4. However, during final movement of spacer 21, into the position shown in Fig. 5 the radial projection 40 on said spacer engages projection 39 on latch 35 to move said latch into the position shown in Fig. 5. With latch 35 in the position shown in Fig. 5 the locking projections 4| and 42 thereof overlap the front ends of the prongs 31 to lock the nut follower 34 against forward movement out of the position shown in Fig. 6. Thus upon return of knob 26 to a position within its cold control range, nut 22 moves away from its associated follower 34, as shown in Fig. 8, and said follower maintains loading spring 2| compressed to a degree which prevents movernent of lever 8 out of circuit opening position until the temperature within the refrigerator rises to a predetermined value for defrosting. 7

Upon attainment of said predetermined defrosting temperature within the refrigerator, lever 6 is moved in a clockwise direction by bellows l8 against the action of the loading spring 2| to effect closure of the switch for starting of the refrigerator and during such movement of lever 8 the trip member 36 is moved upwardly to rotate latch 35 from the position shown in Fig. 7 into the position shown in Fig. 4. Movement of latch 35 out of the position shown in Fig. '1 effects release of nut follower 34, and said follower then snaps into engagement with nut 22 to restore loading spring 2| to a selected cold control setting determined by the position of knob 26.

The defrosting operation may be terminated manually at any time by moving knob 26 in a clockwise direction into an extreme position wherein cam projection 3i on spacer 21 engages the stop projection 32 on the front end of bracket II), as shown in Fig. 9. During clockwise movement of cam projection 3| into engagement with stop projection 32 the radial projection 40 on spacer 21 engages projection 39 on latch 35' to move said latch into released position, as shown in Fig. 9. The.nut follower 34 is thus released and moves into engagement with nut 22 to provide for operation of the refrigerator at a temperature setting determined by setting of knob 26.

The above described control switch may be provided with a cover member of the type disclosed in my aforementioned Patent No. 2,158,824.

Also if desired the front face of said cover mernber may be provided with dial markings for indicating the setting of knob 26.

What, I claim as new and desire to secure by Letters Patent is:

1. In a refrigerator control device, in combination, a control switch, thermoresponsive operating means therefor, a single loading spring associated with said thermoresponsive operating means, an adjustment control for said spring including a rotatable adjusting member movable within a given normal range to adjust said spring for operation of said switch at selected refrigerating temperatures, said adjusting member being also movable beyond said range into a given extreme position to effect a given setting of said spring for operation of said switch at a predetermined abnormal temperature, latching means for looking said spring in said given setting, said latching means being set upon movement of said adjusting member into said extreme position and acting to maintain said spring in said given setting upon return of said adjusting member to a position within said normal range, and means acting upon response of said switch at said abnormal temperature to trip said latching mechanism for restoration of said loading spring to control by said adjusting member.

2. In a refrigerator control device, in combination, a control switch, thermoresponsive operating means therefor, a single loading spring associated with said thermoresponsive operating means, a manual adjustment control for said spring including a rotatable adjusting member movable within a given normal range to adjust said spring for operation of said switch at selected refrigerating temperatures, said adjusting member being also movable beyond said range into a given extreme position to effect opening of said switch and to also effect a given setting of said spring for operation of said switch at a predetermined defrosting temperature, latching means for locking said spring in said given setting, said latching means being set upon movement of said adjusting member into said extreme position and acting to maintain said spring in said given setting upon positioning of said adjusting member within said normal range, and means acting upon response of said switch at said defrosting temperature to trip said latching mechanism. for restoration of said loading spring to control by said adjusting member.

3. In a refrigerator control device, in combination, a control switch, thermoresponsive operating means therefor, a single loading spring associated with said thermoresponsive operating means, a manual adjustment control for said spring including a rotatable adjusting member movable between given limits and acting in one of said limits to effect a given setting of said spring to prevent response of said switching mechanism under the action of said thermoresponsive operating means except upon a predetermined defrosting temperature, a latching mechanism for holding said spring in said given setting, said latching mechanism being set upon movement of said adjusting member into said limit and acting to'maintain said spring in said given setting upon return of said adjusting member to an intermediate position, tripping means associated with said switching mechanism and acting upon response thereof at said defrosting temperature to trip said latching mechanism for .restoration of said loading spring to control by said adjusting member, and tripping means associated with said adjusting member for tripping said latching mechanism upon movement of said I adjusting member into its other extreme position.

4. In a refrigerator control device, in combination, a control switch having an operating member movable in opposite directions between extreme circuit opening and circuit closing positions, thermoresponsive means for moving said operating member toward circuit closing position, a single loading spring associated with said control element for opposing movement thereof into circuit closing position, and adjustment control for said spring including a rotatable adjusting member movable within a given normal range to adjust said spring for operation of said switch at selected refrigerating temperatures, said adjusting member being also movable beyond said range into a given extreme position to move said operating element into circuit opening position and to also effect a given setting of said spring to prevent movement of said operating element out of circuit opening position exsaid latching mechanism for restoration of said loading spring to control by said adjusting member, and means associated with said adjusting member for tripping said latching mechanism at will.

5. In a refrigerator control device, in combination, a switch, thermoresponsive operating means therefor, a single loading spring associated with said thermoresponsive operating means, a screw mechanism for adjusting said spring to provide for operation of said switch at selected temperature values, said screw mechanism being movable in opposite directions between given extreme positions and acting in one extreme position to set said spring for operation of said switch at a predetermined defrosting temperature, a spring follower interposed between said screw mechanism and said spring, latching means for locking said follower to hold said spring in said given setting, said latching means being set upon movement of said screw mechanism into said extreme position and acting to maintain said spring in said given setting upon movement of said screw mechanism out of said given extreme position, and means acting upon responseof said switch at said defrosting temperature to trip said latching mechanism for restoration of said loading spring to control by said adjusting member.

CLARENCE W, KUHN.

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