US2671143A - Thermostatic control switch - Google Patents

Description

March 2, 1954 w. STELZER ET AL 2,671,143

THERMOSTATIC CONTROL SWITCH Filed Sept. 11, 1952 '2 Sheets-Sheet l 5K. 2 I j INVENTORS.

March 2, 1954 w. STELZER ET AL 2,671,143 THERMOSTATIC CONTROL SWITCH Filed Sept. 11, 1952 2 Sheets-Sheet 2 'IIIII.

Patented Mar. 2, 1954 UNITED STATES PATENT OFFICE 2,671,143 THERMOSTATIC CONTROL SWITCH William-Stclzer, Summit, and Martin V. Groves, Hillside, N. J., assignors to Economy Faucet Company, Newark, N. J.

Application September 11, 1952,

8 Claims. 1

'The invention relates to thermostatic control switches and more particularly to a thermostatic control device using a bimetallic element and a manually reset snap'action mechanism releasable by said bimetallic element to actuate an electric switch.

Thermostatic control switches or cutouts used to protect equipment against overheating are well known since there are numerous difierent Serial No. 309,014

Fig. 4, a section taken on lines 44 of'Fig. 3;

Fig. 5, a section taken on lines 5-5 of Fig. 3}

Fig. 6, a sectional elevation showing a modified form of the invention;

Fig. 7, a section taken on lines '!-1 01 Fig. 6;

Fig. 8, a modification of Fig. 5, where the contacts are ordinarily open whereas in Fig. 5 they are ordinarily closed; and

Fig. 9, a perspective view of one ofthe links of constructions in use'today, where improvements 19 the snap action mechanism.

are usually of a minor nature. The present in- Before explaining the present invention in devention'contributes several improvements in detail, it is to be understood that the invention is vices for the purpose mentioned, resulting in a not limited in its application to the details of better construction as well as improved performconstruction and arrangement of partsillustrated ance. in the accompanying drawings, since the inven- The objectof the invention is'primarily' to provide-a very compact design so that the device canbe used with small or cumbrous equipment Where the'switch'must beconfi'ned to a small space, as'for'instance with electric motor-driven n hydraulic pumps where the thermostatic control switch servesto protect the pump against overheating that may have resulted from operation without pumping liquid, by interrupting the electric circuit of the motor after a certain temperature has been reached.

Another object of this invention'is to improve the'sensitivity of the device'or to decrease the temperature range within which the switch is operated;

A further objectis to mechamsm for instant operation of the switch so that it can be released or tripped in trigger fashion by the bimetallic element" to opcrate the switch.

Yet another object is to provide adjusting means not only for tripping the snap action mechanism ata certain temperature, but'also to set the snap action mechanism and to hold it'in aposition' where a minimum force is necessary to spring the device.

Other objects and advantages ofthis invention will. be apparent from the following description considered inconnection with theaccompanying drawings submitted for the purpose ofillustration and notto :definethescope. of the invention, reference being had for that purpose to the subjoined claims. Inthe drawings, wherein similar reference characters refer to similar parts throughout the several views:

Fig. 1 is aplan View ofthe novel thermostatic control switch;

Fig. 2', anelevation thereof;

tion'is'capable of other embodiments and of being practised or carried out in various ways. Also it is to be understood that the phraseology or terminology employed hereinis for the purpose of description and not limitation.

Describing Figs. 1-5, the thermostatic control switch comprises a metallic casing I having a threaded plug portion 2 for attachment to the particular equipment for which the control switch is intended, this type of connection being shown byway of example. A central bore 3 accommodates a bimetallic element or leaf 4 soldered or otherwise rigidly secured and supported in slot 5, the width of element 4 being smaller than the diameter of hole 3 and slightly smallerthan the diameter of bore 3 near the point of attachment to'prevent free movement of-element 4 in' here 3 in response to changes in heat transmitted from casing l to element 4. The upperportion of casing I has a stepped bore tin the lower part of which is housed a snap action switch operating mechanism and in the upper part an electric switch operatively connected'by the switch oper ating mechanism. The latter comprises a toggle action snap mechanism consisting of a semi-circuiar leaf spring 7 riveted or otherwise secured at its central portion to casing i by means of a hollow rivet 8, a pair of toggle links 9' pivotally held by the ends of leaf spring 1 and engaging vertical grooves 53 in the main body portion 'of operating member 5 i of dielectric material having a tapped hole containing a central adjusting screwiB engaging the upper offset movable end of bimetailic'eiement i. The latter has a hole in which stud 53 extending from screw i2 is slideable. Thus operating member i l at one endis carried by the bimetallic element and at the other by casing i as the button portion M of operating member ll passes throughand is. slideablein a hole in casing i diametrically opposite of hollow 3 rivet 8. Toggle links 9 at their outer extremeties have tabs 9 engaging a corresponding slot in the ends of spring I, while the inner ends which form the knee of the toggle may be provided with tabs 29 which do not engage groove it but extend above and below member H to keep the links in place. An upwardly pointing finger l5 forms another extension of operating member I l and serves to operate the electric switch mechanism. The elements of the latter are encased in an insulating socket l6 seated on the step of bore 6 and an insulating cap ll fitting inside of socket l6 and retained by the upper edge of casing i where it is peened over at id to firmly hold the cap in the desired position and prevent it from rotation. Socket it held in the proper position by a short tab it extending from the central portion of spring I into a small recess or slot in socket it. The latter has a rectangular opening it through which finger iii passes and in which it is guided, the end walls of the opening serving to limit the movement of operating member H in the direction of the axis of adjusting screw 52. While the button portion i4 is guided in the hole in casing l in which it slides, an additional bearing 2i extending from socket it may be provided.

The selection and construction of the electric switch is depending on and dominated by the different applications which occur in practice;

thus for instance it may be desired to open an electric circuit when a certain temperature is exceeded to disconnect a motor or other equipment, or a circuit may be closed to put an alarm system into operation. By way of example, an ordinarily closed switch is illustrated in Fig. 5, and a switch having the same elements but with the contacts ordinarily open is shown in Fig. 8. Insulator cap l'i supports a pair of spaced electrically conducting connector blades 22 adapted to be plugged into a conventional connector for connection with an electric circuit or device. The base portions or these connector blades are formed into brackets 23 secured to plug H by means of rivets 23. One of the brackets has secured to it acontact spring free end a contact point 25 positioned to contact another contact point 26 extending from the other bracket, contact spring 24 being biased into a contacting position where contact 25 is pressed against 26. Finger [5 of operating member H is positioned a certain distance away from spring 255 so that when operating member H is tripped it can be accelerated by the force of spring l to provide a hammer action against spring 2 and thereby break the contact instantbeen rotated 180 dely. In Fig. 8 cap H has grees so that operating member II when tripped acts toclose the contacts. Spring 2c is slightly bent back so that the contacts are ordinarily open, as shown. I

In the modification shown in Figs. 6 and 7 the improved thermostatic control switch comprises a casing 3B similar to casing l of the construction that already has been described. A straight bimetallic element 3| soldered or brazed in slot 5 extends upwardly through a clearance hole 32 in plate 33 seated at the bottom of bore 6 and serving as a bearing for operating member 34 whose button portion 35 slides in hole 35 of casing 39 and contains an adjusting screw 3'! extending into a cavity 38 so it can engage the upper and free end of element 3|, the latter being reduced in width to have ample clearance in hole 82 and cavity 38. Another adjusting screw 39 is held in a centrally threaded rivet 40 securing 2d carrying at its toggle spring I, the toggle links 9 being similar to the ones described. Adjusting screw 39 serves as an abutment for operating member 34 so that the latter can be set in a fixed position where the toggle'links 9 are nearly in alignment with each other and where the mechanism can be tripped with a light and predetermined force exerted by bimetallic element 3|. This eliminates any movement of member 34 except to operate the switch, and element 3i is free to move in response to any fluctuation in temperature within the normal and safe range. The elimination of the movements of member H and toggle links 9 eliminates wear in grooves It, and consequently eliminates a change in the setting of the device so that it will always be tripped at exactly the same temperature.

The component parts of the electric switch are similar to those already described so that Figs. 5 and 8 also may be referred to, though cap I! is replaced by a slightly different insulating cap 45 designed to eliminate socket IE. Cap 4| is keyed to tab it of spring 1' fitting into slot 42 in the skirt of cap it. There is another such slot diametrically opposite so that cap t! can be rotated degrees depending on whether a make or break switch is required. A thin insulating disc 43 with a rectangular hole 44 is held between cap 5! and the recess of bore 6, hole at serving as a guide for operating member 34 and limiting its movement after it has been tripped.

The operation of the thermostatic control device is self-explanatory. Adjustment of adjusting screw 52 or 3'! in a clockwise direction causes tripping of the toggle mechanism at a lower temperature, while turning the screw in the opposite direction to be further away from the bimetallic element causes release at a higher temperature. After release and after the temperature of the bimetallic element has fallen below maximum, the device may be reset by pushing in button [4 or 355 until the toggle links are reversed as shown in Fig. 4 or '7.

In the set position of the snap action means, as shown in Figs. 4 and '7, toggle links 9, whose outer ends are urged together by spring I; have their inner portions which form the knee of the toggle pointing'in a direction urging the operating member into a holding position. Assuming now that casing l or St is heated beyond the permissible maximum, the upper end or" the bimetallic element acts against and moves adjustingscrew i2 or 35 and the operating member to straighten out the toggle and then move it over its dead center whence the toggle snaps into a reverse position due to the force or" spring 1, causing the operating member to move rapidly towards the left, and to thereby operate the switch through figure 15. The button portion of the operating member then extends out of hole 38, giving a visual indication that the switch has been tripped.

It is obvious that the thermostatic control device can also be used to make or break a circuit when a certain minimum temperature is reached. For this it is merely necessary to turn bimetallic element t or 3! around 180 degrees so that the action relative to the toggle mechanism is reversed. 1

Having thus described our invention, we claim:

1. In a thermostatic control switch of the class described, a metal casing, a temperature sensitive bimetallic element having a movable end and another end rigidly supported in said casing; an electric switch. a dielectric switch operating member slideably housed within said casing and having a push button portion extending out of said casing, said operating member having a finger to operate said switch, an adjusting screw threaded into said push button portion into engageable apposition with said movable end of said bimetallic element, said operating member being movable codirectionally with said movable end of said bimetallic element, snap action means comprising a toggle having a pair of toggle links, the knee of said toggle being in engagement with said operating member, and spring means for pivotally securing the outer ends of said toggle links and for resiliently urging them towards each other, said toggle being positioned near dead center to be pushed over dead center by the movement of said movable end of said bimetallic element in response to a maximum temperature change to instantly operate said switch through the force of said spring means.

2. The construction as claimed in claim 1, and

by said casing, an electric switch,

it has been tripped, an adjusting screw threaded into said push button portion and serving as an intermediary between said bimetallic element and said operating member, and spring tended snap action means trip-pable by the movement of said 5. The construction as claimed in claim 4 where said snap action means comprises a toggle having a pair of links pivoted to said main portion of said operating member to form the knee of the toggle, and spring means pivotally holding the outer ends of said links to be fixed in the direction of movement of said knee and to urge the outer ends of said links towards each other.

6. The construction as claimed in claim 4, and an adjusting screw extending through said casing and arranged to serve as a stop for said operating member in a direction opposite to the direction of movement for actuating said switch.

7. The construction as claimed in claim 5, where tact, said switch being operated by said finger striking against said current conducting spring. switch end of said bimetallic element, intermediate said operating member movable end of said operating member is in engageable apposition with said WILLIAM STELZER. MARTIN V. GROVES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,037,024 Dezotell July 13, 1937 2,268,445 Drapeau Dec. 30, 1941 2,394,121 Ulanet Feb. 5-, 1946 2,463,891 Malone Mar. 8, 1949 2,499,208 Zimmer Feb. 28, 1950

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