US2270736A - Circuit controlling device - Google Patents

Description

Jan; 20, 1942. c. w. KUHN Em. 2,270,736

CIRCUIT CONTROLLING DEVICE Filed NOV. 15, 1939 the aforementioned objection.

Patented Jan. 20, 1942 UNITED STATES PATENT OFFlCE 2,270,736 cmcm'r con'raomno nnvrca Clarence W. Kuhn and Robert 0. Perrine, Wauwatosa, Win, asslgnora to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application November 15, 1939, Serial No. 304,626

4 Claims. (CL-200-1 40) This invention relates to circuit controlling devices, and more particularly to thermo-responsive switches for controlling electric refrigerators.

Electric refrigerators are commonly controlled by a thermo-responsive switch which is manually adjustable to select temperatures within a given range known as the cold control range and to also provide an abnormally high temperature for defrosting. Such control switches are ordinarily provided with a gas filled temperature responsive operating bellows having a helical loading spring associated therewith which counteracts expansion of the bellows and is adjustable by means of a screw to vary the temperature values at which the refrigerator is started and stopped. The adjusting screw is usually of uniform pitch and has an adjusting knob or lever fixed thereto which cooperates with a stationary dial to indicate the temperature setting of the switch.

It is desirable in switches of the aforesaid type that the required range of cold control temperatures and also the relatively high defrosting temperature be obtained within one revolution of the adjusting screw. However, it has heretofore' been found dimcult, and in some cases im- .possible, to obtain such temperatures within a single revolution of the adjusting screw without narrowing to an objectionable degree the range of movement of the screw for effecting selection of the temperatures within the cold control range.

The'present invention has among its objects to'provide an improved adjusting mechanism for switches of the aforesaid type which overcomes Another object is to provide an improved adjusting mechanism for switches of the aforesaid .type which effects adjustment of the loading spring at an increasing rate upon movement of the adjusting knob from the cold end to the warm end ofits cold control range.

Another object is to provide an improved adjusting mechanism which can be readily applied to existing types of thermo-responsive switches without material modification of the, switch structure.

Another object is to provide an adjusting mechanism of the aforesaid type which is simple in construction and exceedingly positive and reliable-in operation.

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

The accompanying drawing illustrates an embodiment of the invention which will now be described, .it being understood that various modiflcations may be made in the embodiment illustrated without departing from the spirit and scope'of the appended claims.

In the drawing:

Figure. 1 is a side view of a thermorresponsive switch embodying the invention, the switch being shown in closed position and the enclosing casing therefor being shown in section;

Fig. 2 is a view similar to Fig. 1, illustrating the switch in circuit opening position, and also illustrating certain of the switch operating parts in section;

Fig. 3 is a front elevational view of certain of the operating parts of the adjusting mechanism shown in Figs. l and 2, and

Figs. 4 and 5 are diagrammatic views illustrating various settings of the operating parts shown in Fig. 3.

Referring to Figs. '1 and 2, the invention is shown inconnection with a thermc-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 as is apparent the invention may be applied to switches of various other types having a screw adjusting mechanism associated therewith.

The control switch illustrated in the drawing includes an elongated insulating base I which carries a switch mechanism including a pair of stationary contacts 2-2, and a cooperating bridging contact 3. Stationary contacts 22 are mounted side by side within openings adjacent the lower end of insulating base i and bridging contact I is mounted upon a pivoted insulating contact carrier 4 having a spring 5 associated therewith for biasing the same in a direction to hold said bridging contact in engagement with said stationary contacts. Contact carrier 4 is controlled by a fluid condition responsive device 6 through the medium of a snap operating mechanism including pivoted levers 1 and 8 and an over-center spring 9, and said fluid condition arranged adjacent the underside of said bracket and 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 8 are both pivotally mounted upon pivot pin it and lever I is pivotally mounted upon pivot pin i5. Contact carrier I is provided with spaced side arms l6 and said side arms are provided with stop rojections I! which are engageable with the underside of bracket I! to limit circuit openingmovement of said contact carrier beyond the position shown in Fig. 2.

Lever I is provided with spaced side arms for example which straddle contact carrier 4 and said lever is movable with respect to said contact carrier between the stop projections l? on the latter, and an adjustable screw stop i8 which is threaded into an opening in insulating base i. Lever l extends between the side arms of contact carrier 3 and the free end thereof projects forwardly through a recess in the front wall of bracket i2. Lever 8 has a pointed rivet i9 fixed to the lower end thereof which engages an indented cup washer 20, and lever i has apointed rivetiii fixed thereto at a point below pivot pin H which engages an indented cup washer 22. Spring of the snap operating mechanism is held under compression between the cup washers 2-0 and 22.

With lever l in the position shown in 2 spring 3 is positioned so that the force thereof acts on a line located to the rear of pivot pin M. Lever-'8 is thus biased to move forwardly into engagement with stop projections I! on contact carrier 4 to hold said contact carrier in open position, as shown in Fig. 2;. During forward movement of lever I from the position shown in Fig. 2 into the position shown in Fig. 1 spring 9 assumes a position wherein the force thereof acts on a line located in front of pivot pin I4. Lever 8 then snaps out of the position shown in Fig. 2 into engagement with stop I8, and contact carrier I is thus quickly moved into circuit closing position under the action of spring 5. During return movement of lever i from the position shown in Fig. i into the position shown in Fig. 2 spring 3 returns to a position wherein the force thereof acts on a line located to the rear of pivot pin I4. Lever 8 is then snapped into the position shown in Fig. 2, and during final movement thereof into such position the same engages stop projections I! on contact; carrier 4 to quickly move the latter into circuit opening position against the action of spring 5.

Lever 1 is controlled by the fluid condition responsive device 8 and in the embodiment. illustrated said device comprises a bellows 23 enclosed within a cup shaped member 24. Bellows 23 is secured to the rear wall of cup member 24 and said cup member is fixed tothe rear face of insulating base I by rivets 24 which also serve to secure the bracket I2 to the front face of said insulating base. The front end of bellows 23 has a pin 25 fixed thereto which extends through an opening in base I and is provided with a pointed end which engages a thrust member 26 fixed within an opening in lever 1. The front end of thrust member 26 engages a washer 21.and loading spring III is held under compression between said washer and a nut 23 mounted upon screw II. Nut 23 is held against rotation by en- Basement with bracket I2 and screw II is rotatably mounted within an opening in the front wall of said bracket and is provided with a shoulder for engaging the rear side of said wall. Thus upon rotation of screw I I nut 28 is moved axially thereon to vary the degree of compression of spring I I.

The above described control device may be used in connection with electric refrigerators to effect starting and stopping of the refrigerator upon given temperatures in the food com-partment thereof. For such service bellows 23 has a closed pipe extension 29 sealed to the rear end thereof to be arranged within the cooling compartment of the refrigerator. Pipe extension 29 and bellows 23 contain an expansible fluid, as methyl chloride, and upon tempera ture changes within the cooling compartment the a avogzso pressure of such fluid varies to effect operation of bellows 23.

Upon an increase in temperature within the cooling compartment bellows 23 expands and at a predetermined temperature determined by the opposing force of spring ill, lever l is operated to move contact carrier a into circuit closing position for starting of the refrigerator. Upon a given decrease in temperature within the cooling compartment bellows 23 contracts under the action of spring i0 and lever l is operated to move contact carrier i into circuit opening position for slppping of the refrigerator. As is apparent, screw ii is adjustable to vary the degree of compression of spring id for variation of the temperature values at which the refrigerator is started and stopped. [is hereinafter set forth, screw ii is adjustable within a given range known as the cold control" range to effect operation of the refrigerator at selected refrigerating temperatures, and said screw is also movable to a point beyond said range to effect operation of the refrigerator at an abnormally high temperature for defrosting.

In accordance with the present invention screw I I is adjustable by a knob 30 through the medium of a pair of elliptical spur gears 3i and 32. Gears 3! and 32 are of the same shape and size and each is mounted to revolve about one of its foci as a fixed center. Gear 3i is fixed to the front end of screw H and gear 32 is rotatably mounted upon the front wall of a cover member 33 which is removably secured to the from; face of insulating base I. Cover 33 is formed of molded insulating material and the front. wall thereof is provided with an opening for receiving gear 3 I.

Gear 3! is secured to the front end of screw Ii by a screw 34 and is held against turning with respect to said screw by a lock washer 35. As shown in dotted lines in Fig. 3, the rear face of gear 3! has a cam projection 36 formed. thereon which cooperates with a projection 31 on the front wall of bracket I2 to limit movement of said gear in opposite directions between extreme positions designated by reference characters 011" and 9 in Fig. 4. Cam projection 35 also cooperates with the front end of lever I and acts upon counterclockwise rotation of gear 3| into oif" position to move said lever into circuit opening position.

Gear 32 has a spindle 38 formed on the rear side thereof which is rotatably supported within an opening in the front wall 01 cover 33. Gear 32 is held in assembled position upon the front wall of cover 33 by a washer 33 secured to the rear end of spindle 38 and knob 30 is fixed to a projection 40 on the front face of gear 32. The

front face of knob 30 is provided with an arrow ll which cooperates with a. stationary dial plate shown in section in Fig. 1 to indicate the temperature setting of the switch.

Fig. 5 illustrates the various settings of knob 30 and its associated gear 32, and Fig. 4 illustrates corresponding settings of gear 3| and its associated screw II. With knob 33 in position 9 (Fig. 5) the gears 3| and 32 are positioned as shown in Fig. 3, cam projection 33 being in engagement with stop 3'! to prevent countersition shown in Fig. 5. With gear 31 and screw 9 (Fig. 4) the spring III is compressed to a degree to cause operation of the refrigerator at a low temperature such as is required for quick freezing.

Upon clockwise rotation of knob 30, gear 3; acts to drive gear'3| and screw H in a counterclockwise direction to increase the degree of compression of spring l and'thereby increase the temperature values at which the refrigerator is started and stopped. As is apparent tfrom Fig. 3, during clockwise rotation of knob 30 from position 9 to position 1 the pitch radius of gear 32at the point of contact with gear 3| increases, while the pitch radius of gear 3| at the point of contact with gear 32' decreases. Thus the degree of .angular movement of gear 3| and its associated screw I I per. degree of knob rotation increases during movement of said knob from position 9 to position .1. In theembodiment illustrated the cold control range of screw extends through an angle of 92 and as shown in Fig. 5 said screw is moved through said range by movement of the knob 30 and gear 32 through an angle of 118.

In practice it has been found that the operating characteristics of a gas filled bellows is such that a given degree of rotation of screw II at the cold end of its cold control range effects -a greater degree of variation in the temperature setting of the switch than is obtained by a corresponding degree of rotation of the adjusting screw at the warm end of said range. Gears 3| and 32 are designed to suit the operating characteristic of the bellows, the same being so proportioned and arranged as to effect adjustment of screw H for corresponding variations in the temperature setting of the switch upon substantially like degrees of adjustment of knob 30 at opposite ends of its cold control range.

Upon movement of knob 39 beyond its cold control range into the defrost position (Fig. 5) gear 3| and its associated screw ii are moved into defrost position (Fig. 4) to increase the loading effect of spring H) to a degree which provides for cycling of the refrigerator at a relatively high defrosting temperature. In the embodiment illustrated knob 30 moves through an angle of 142 from position 1 to its defrost position, whereas gear 3| and screw I l are moved through an angle of 178 from position "1. to the defrost position. Also in the embodiment illustrated movement of knob 30 through an angle of 52 from defrost position to off position ef fects a corresponding degree of movement of gear 3| and screw ll. Upon movement of gear 3| and I to move said lever into circuit opening position for stopping of the refrigerator.

In connection with the foregoing it should be noted that knob 30 is movable through a rela-. tively wide range for selection of coldcontrol temperatures, and is also adapted upon movement through a relatively small range to effect a wide change in the loading effect of spring I0 for defrosting. 7 J

In the embodiment illustrated spring I0 is of special design to provide a relatively high defrosting temperature upon movement of screw II and its associated gear'3l from position 1 to defrost position. As shown in Fig. 1, the end turns of spring II are of lesser pitch than the intermediate turns thereof. The arrangement is such that upon movement of gear 3| and screw II from position 1 into defrost" position the end turns of spring II are brought into engagement to effect a relatively wide increase in the loading effect of said spring.

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

1-. The combination with a temperature responsive refrigerator control switch including a loading spring and a screw for adjustingsaid spring to vary the temperature setting of said said screw through its cold control range, and

less than unity formovement of said screw beyond said cold control range into defrosting position.

2. The combination with a temperature responsive refrigerator control switch including a loading spring and a screw for adjusting said spring to vary the temperature setting of said switch, said screw being movable within a given cold control range for selection of refrigerating temperatures and being movable to a point beyond said range to provide a relatively high defrosting temperature, a rotatable manual adjusting knob for said screw and an elliptical gear drive between said knob and said screw, said gear drive acting upon movement of said knob in one direction out of a given extreme position to effect adjustment of said screw at an increasing rate from the cold end to the warm end of said cold control range.

3. The combination with ,a temperature responsive'refrigerator control switch including a loading spring and a screw for adjusting said screw H from the defrost position into off a position cam 36 engages the front end of lever spring to vary the temperature setting of said switch, said screw being movable within a given col-d control range for selection of refrigerating temperatures and being movable to a point beyond said range to provide a relatively high defrosting temperature, a rotatable adjusting knob for said sore and a gear drive between said knob and sai screw, said gear drive being of varying pitch radius to render the ratio of movement of said knob with respect to said screw greater than unity for movement of said screw through its cold control range, and less than unity for movement of said screw beyond said cold controlrange into defrosting position and said spring being of varying pitch to provide a relatively large increase in the loading efl'ect thereof upon movement of said screw beyond its cold control range into defrosting position.

4. The combination with a temperature responsive refrigerator control switch including a loading spring and a screw rotatable to adjust said spring for variation of the temperature setting of said switch, of a. rotatable manual adjusting member, a drive between said manual-adjusting member and said screw including adriving gear fixed to said manual adjusting member and a driven gear mounted upon said screw, said gears being of elliptical form to provide varying degrees of adjustment of said screw upon like angular movements of said rotatable adjusting member in different parts of its range and said screw being releasably connected to said driven gear to permit-adjustment of the angularposition of said. screw with respect to said drive.

CLARENCE W. KUHN. ROBERT 0. PERRINE.

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