US2307356A - Thermal control switch - Google Patents

Description

Jan. 5, 1943. H. w. BIRK THERMAL CONTROL SWITCH Filed Oct. 51, 1940 f i j Patented Jan. 5, 1943 UNITED STATES PATENT OFFICE THERMAL CONTROL SWITCH Harold w. mu, East Hartford, em, assignor to The Kart Manufacturing Company, Hartford, Conn., a corporation of Connecticut Application October 31, 1940, Serial No. 363,660

Claims. (Cl. 200- 142) The present invention relates generally to temperature control devices and more specifically to an improved electric circuit breaker, including one or more normally closed electric switches and an automatically operable breaker member for opening the switches when the temperature of a thermo-responsive element reaches a predetermined allowable maximum. When utilizing automatic circuit breakers of this type, it is customary to locate the thermo-responsive element within or adjacent to a heated chamber, as, for example, a hot water tank, so that the temperature of the element is always substantially that of the liquid within the chamber. In order to limit the temperature of the liquid to the allowable maximum, the switches of the circuit breaker are included in the electric circuit which energizes or otherwisecontrols the unit supplying heat to the chamber.

It is an object of the present invention to provide a circuit breaker for this purpose, having a thermo-responsive element including a fusible metal locking member which normally secures the automatic breaker member in an inoperative position against the action of a tensioned spring. When the temperature of the thermo-responsive element reaches the allowable maximum, the metal locking member quickly fuses, whereupon the breaker is actuated by the tensioned spring and operates to open the switches.

It is a further object of the invention to provide a circuit breaker of the type indicated, wherein'the action of the spring upon the breaker member in its inoperative position doe not impose a sumcient load to deform or produce partial failure of the fusible locking member before the predetermined allowable maximum temperature is reached. 4

A still further object of the invention is to provide a circuit breaker having the features and advantages indicated, which can be easily and inexpensively manufactured and assembled, and which can be reset following actuation thereof without the replacement of any part such as the fusible metal lock. Other objects will be input obvious and in part pointed out more in detail hereinafter.

The invention accordingly consists in the feeswitch made in accordance with the present invention;

Figure 2 isa profile view of the switch shown in Figure 1, and illustrates clearly one way in which a switch may be operatively attached to a device, the temperature of which 'is to be controlled;

Figure 3 is a view similar to Figure 1 with the front wall of the casing cut away;

Figure 4 is a cross-sectional view of the switch taken along line 4-4 of Figure l and shows the switch mounted on a slightly different fitting from the one shown in Figure 2;

Figure 5 is a rear view of the switch with the back cover removed;

Figure 6 is a perspective view of the manually operable member of the switch and the coopcrating positioning member therefor; and

Figure l is a perspective view of the temperature responsive elements of the switch partially broken away to show the parts thereof Referring to the embodiment of the invention illustrated in the drawing, there is provided a box-like casing C having side walls I2 and a front wall i4 which are integrally formed of a moldable plastic or similar non-current conducting material. A back cover It is secured to the free edges of the side walls I2 and provided an enclosure within which there is operably supported a pair of electric switches l0 and a spring actuated contact breaker B for opening the switches. A thermo-responsive element, indicated generally by the letter D, is supported in a centrally disposed opening 20 in the back cover It and normally restrains the breaker B in an inoperative position. I

More specifically, the front wall l4 of the casing C is provided at the four corners with suitable recesses 28 within which are secured terminals 30 and 32 for the electric switches ll. Each of the terminals 30 and 32 includes a terminal screw 33 by means of which the switches l0 may be connected into the electric wiring cirbreaker. In the embodiment shown in the drawing, the switch terminals 30 are located at diagonally opposite corners of the casing C, and support suitable resilient switch arms 34 which extend in opposite directions toward the terminals 32. An inwardly extending contact button is secured to the free end of each arm 34 and normally resiliently engages a similar button 38 carried by each terminal 32. The front wall [4 is Figure 1 is a plan view of one embodiment of a further provided with a centrally disposed circular hole 39 in which the forward end of the contact breaker B is rotatably journalled. As illustrated in Figure 5, the contact breaker B- is a substantially cylindrical member, provided along diametrically opposite elements with a pair or outwardly extending camLning lugs 48 for forcing the switch arms 34 away from the center of the casing C and thereby break the engagement of the contacts 36 and 38. In assembled position, the forward ends 4| of the lugs 48 bear against the rear surface of the front wall l4 so that the forward portion of the breaker B protrudes from and is journalled in the casing C.

To journal the other end of the breaker, there is provided a shaft 42 having its forward end received in a centrally disposed internal breaker bearing 44 and extending rearwardly therefrom through the central opening 28 in the back wall I6.

The breaker B is further provided with a rearwardly disposed arm 46 which extends radially outward from the breaker at a 45 degree angle to the adjacent lug 48 and is engageable with a pair of stops 48 and 58 integrally formed with the casing C. As illustrated in Figure 5, the stops 48 and 58 limit the rotation of the breaker between the breaker position X, illustrated by solid lines, and the position Y, illustrated by broken lines. When the breaker is located in the closed switch position X, the lugs 48 are positioned midway between the switch arms 34, whereas when the breaker is in the position Y each of the lugs 48 cams one of the switch arms 34 outwardly so as to disengage the contacts 36 and 38. As previously indicated, the switch contacts are normally closed and to retain the breaker in the closed switch position X, it is operatively secured to the shaft 42 and the shaft, in turn, is normally held against rotation relative to the casing C by the thermo-responsive element D. To provide a satisfactory connection between the breaker and the shaft, a recess 66 is formed in the rear end of the breaker and the inner surface thereof (as indicated in Figure 6) is provided with a series of four radially disposed steps 68 located at 90 degrees to one another.

Positioned within the recess 56 and secured to the shaft 42. as by a non-rotatable bearing 68, is a central metal plate 66 having a pair of resiliently upset steps 68 which cooperate with the complementary steps 58 of the breaker to provide a uni-directional drive therebetween when the shaft 42 is free to rotate.

In order to retain the steps 68 in resilient engagement with the cooperating steps 58 of the breaker, the shaft 42 is provided with an annular groove 18 wherein there is located a horse-shoe shaped washer 12 which bears against the rear wall l6 of the casing to prevent rearward lateral movement of the shaft relative thereto.

As heretofore indicated, the shaft is normally held against rotation by the heat responsive element D. More particularly, the element D includes a hollow cylindrical sleeve 14 including an internal bearing 16 for rotatably supporting the shaft. The sleeve 14 is provided forwardly of the bearing 16 with a tongue-shaped support 18 which is non-rotatably secured in the opening of the back wall I6. Rearwardly of the running bearing 16 the sleeve is internally provided with an undercut annular ring 80 and an internally serrated cylindrical surface 82. Formed on the outer end of the shaft and inwardly spaced from 'the serrated surface 82 is a serrated cylinder 84 normally secured relative to the sleeve 14 and the casing C by a fusible material 86 The fusible material 86 may be formed of various low melting point metals, the proportions of which may be varied so that the mixture will fuse at any desired temperature.

An enclosure 88 seals the rear end of the cylindrical sleeve 14 and prevents the fusible metal in the molten condition from flowing from the cylinder.

The fusible metal 86 normally locks the shaft 42 relative to the frame or casing C and through the engagement of the step 68 with the cooperating steps 58 prevents rotation of the breaker B to the open switch position Y (Figure 5) However, the metal 86 will fuse if it is heated to the allowable maximum temperature, whereupon the shaft 42 is free to rotate relative to the casing.

In order to automatically rotate the breaker B to the open switch position Y, the breaker arm 46 is provided with an anchor pin 98 to which one end of a spring 92 is secured. The other end of the spring is secured and tensioned to the casing C by an anchor lug 84. As illustrated in Figures 3 and 4, the anchor lug 84 is upset from the back wall l6 and is located at the corner diagonally opposite from the corner in which the anchor pin 98 is located when the breaker is in the closed switch position X. In this position, the spring centrally engages the shaft 42 and is thereby thrown out of alignment with the axis of the breaker. component of the force exerted by the spring 82 on the breaker 'arm 46 in the open switch position X acts through the rotational axis of the breaker and does not tend to rotate the breaker. The minor or tangential component which tends to rotate the arm to open switch position X is relatively small, and consequently the load on the element D is not sufficiently great to cause partial failure or defamation of the fusible metal lock 86 before the lock reaches the fusing temperature. Following fusing of the lock 86 the tangential or rotating component 'of the force produced by the switch becomes increasingly larger as the breaker rotates from positionX to position Y. Thus the force produced by the spring is sufficient to cam the resilient switch arms 34 outwardly and insure positive opening of the contacts 36 and 38.

In order to rotate the breaker from the position Y to the position X following the fusing of the metal lock 86 and its subsequent solidification, thebreaker is provided with a reset handle H which is constructed so as to prevent manual rotation of the breaker from position X to position Y.

More specifically, the handle comprises a diametrically disposed rib 96, the side walls of which decrease in depth in opposite directions from end to end. In the embodiment illustrated, the recesses located on either side of the rib 96 decreases in a counter-clockwise direction with respect to the cylindrical axis of the breaker from a maximum to a negligible minimum depth. Thusthe side walls of the rib may be grasped by the fingers for rotation in a clockwise direction, but cannot be effectively grasped so as to enable an operator to manually rotate the breaker in a counterclockwise direction.

Assuming that the metal 86 has solidified and cooled subsequent to the actuation of the circuit breaker, the breaker may be reset to the closed switch position X by manual rotation of the handle in a clockwise direction (Figure 3). The breaker steps 58 will cam the resilient steps 68 of However, the major the plate '60 rearwardly until the proceeding steps 50 at 90 to the previously engaged steps are engaged thereby.

In order to secure the circuit breaker to a chamber, the temperature of which is to be controlled, there is provided outwardly at the back wall IS a pair of rearwardly extending resilient fingers 98 equally spaced from the cylindrical sleeve I4, as illustrated in Figure 2. The fingers 98 are adapted to secure the circuit breaker to acup-shaped mounting I and to position the element D within the well I02 formed therein. More particularly, the mounting I00 may be threaded into the wall I04 of a liquid chamber so as to allow the liquid in the chamber to surround the well I02. With this construction, the temperature of the element D is always substantially that of the liquid in the chamber.

Figure 4 shows a slightly different type of mounting I00, which may be secured by means of the strap I06 to the cylindrical surface of the wall I04. In this embodiment, the mounting I00 is provided with a cylindrical opening I02, which receives and positions elements D adjacent to the wall I04 of the chamber.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could' be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim as my invention:

1. An electric circuit breaker including a resilient closed switch, a rotatable switch opening member movable from a normal position when the switch is closed to a second position to positively open the switch, a fusible lock for normally holding said switch opening member in normal position, resilient means for moving said switch opening member to the second position when said lock fuses, said resilient means comprising a spring, means carried by the opening member to which one end of the spring is secured, fixed means for securing the other end of the spring, said spring holding means being diametrically opposite when the opening member is in normal position, and means aligned with the axis of the opening member for deflecting the spring out of a straight line when the switch opening member is in normal position whereby said spring will have a minimum rotational effect on said member in the normal position and a maximum effect in the second position.

2. An electric circuit breaker comprising a normally closed switch, a rotatable supporting shaft, a fusible lockdirectly engageable with the supporting shaft for normally holding said shaft against rotation, a switch opening member mounted on the shaft for rotation between a normal position where said switch is closed to a second position where it opens said switch, spring means normally tending to'rotate said shaft from normal to second position, and means on the shaft engageable with means on said switch opening member upon rotation of the opening member from normal position to second position and disengageable upon rotation from second to normal position.

3. An electric circuit breaker including a normally closed switch, a rotatably supported shaft, a cylindrical switch opening member journalled on the shaft for rotation between a normalposition when said switch is closed to a second position when it opens said switch, a fusible lock for normally holding the shaft against rotation, a uni-directional drive between the switch opening member and shaft engageable upon rotation of the opening member from normal position to second position and disengageable upon rotation from second position to normal position, a spring for rotating said opening member, said spring having one end secured to the opening member and its other end fixed at a point diametrically opposite the other end when said opening member is in normal position, said spring extending when said opening member is in normal position across said shaft and biased out of diametric alignment by said shaft to thereby have a minimum rotational effect on said opening member in its normal position and a maximum effect in the second position.

4. An electric circuit breaker comprising a casing, a normally closed switch mounted in the casing, a shaft rotatably supported in the casing,

a switch opening member journalled on the shaft between a normal position and a second position, said member having a handle portion extending out of the casing and manually engageable for rotation in one direction only, a lug on said opening member for camming the switch to open position when the member is in said second position, a fusible lock for normally holding the shaft against rotation, a uni-directional drive between the member and shaft engageabie upon movement of the member from normal to second position and disengageable upon movement from second to normal position, a spring having one end secured to the switch opening member and its other end to the casing at a point diametrically' opposite to its fixed end when the switch opening member is in normal position, said spring being slightly biased out of diametric alignment by said shaft to produce a minimum rotational effect on said switch opening member in normal position and a maximum effect in the second position.

5. An electric circuit breaker comprising a casing, a normally closed switch within the casing including a rotatable supporting shaft, 9. fusible lock normally holding said shaft against rotation, a switchopening member mounted on said shaft, interengaging means on said shaft and member allowing free rotation of the opening member in one direction and engagin said member with the shaft when rotated in the other direction, spring means normally tending to rotate said member to cause said interengaging means to engage, means carried by said opening member for securing one end of said spring, fixed means in said casing for securing the other end of the spring, the means for securing the ends of the spring being disposed to opposite sides of said shaft and in diametric' alignment with one another and said shaft when said switch is in normally closed position, whereby the intermediate portion of the spring will be biased out of alignment by said shaft.

HAROLD W. BIRK.

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