US2705745A - Thermal switch - Google Patents

Description

April 5, 1955 1. F. MATTHYSSE ET AL THERMAL SWITCH Filed Jan. 7, 1950 INVENTORS. Irwlng FMderic/(Matt/g/sas Henry HeluDuP e 2,705,745 THERMAL SWITCH Irving F. Matthysse, New York, and Henry Peter Dupre, Croton-on-Hudson, N. Y., assignors to Burndy Engineering Company, Inc., a corporation of New York Application January 7, 1950, Serial No. 137,328 3 Claims. (Cl. 200-137) Our invention relates to an electrical switch and more thermal switch whereby a dilferential rate of expansion of the metallic parts of the switch will circuit such as an alarm to temperature changes and which is relatively unaffected by external vibration and shock.

Furth in the following specification, particularly pointed out in the claims, and illustrated in the accompanying drawing, in which- Fig. 1 is a longitudinal cross sectional view of our thermal switch.

Fig. 2 is a cross sectional view taken along line 22 of Fig. 1.

Fig. 3 is a plan view of the contact member.

Fig. 4 isa side elevation view of the same.

Fig. 5 is a side elevation of a modified form of our contact member.

In the drawing, reference numeral designates generally our thermal switch comprising a housing 11 constructed of two hollow sleeves 12 and 13 positioned end-to-end, which house respectively a low expansion metal actuating member 14 and a contact unit 15. We prefer to construct the sleeves of stainless steel because excellent non-corrosive properties, but it 1s understood that there are other metals having a high coefiicient of expansion which may be used to practice this invention.

The inner end of sleeve 12 is brazed or welded at 16 to a triangularly shaped stainless steel mounting flange 3 is supporting plate 20 and is brazed or welded at 24 to the mounting flange 17. The supporting plate 20 is provided with a central aperture 25 to slidably receive and guide the actuating member as will be described later.

The actuating member 14, may be in the form of a switch through a copper sealing gasket 34.

The inner end of the actuating member 14 slidably extends through aperture 25 in the supporting plate 20 being guided therein to engage the contact unit 15. Op-

sliding movement therethrough.

he contact unit 15 comprises a resilient contact member illustrated in detail The free end of the contact member is provided with aperture 51 into which is riveted Threaded through insulating tion, which blocks are secured within an obtuse angle with respect to the body portion 41 when in an unattached position as shown in Fig. 4.

When the thermal switch is in the closed position, the body portion 41 containing the tongue portion 42 is substantially aligned along the longitudinal center line of the actuating member 14.

The thermal switch operates through the diiferential rate of expansion of the stainless steel sleeve 12 and actuating member 14. The distance that the contact buttons 52 and 53 are spaced apart as illustrated by the dashed position in Fig. 1 is in direct relation to the temperature range between the normal temperature and the operating temperatures for which the switch has been adjusted in any particular installation.

With the switch set at a given operating temperature, the normal position of the contact member 40 is shown in the dashed line pos'tion in Fig. 1 through the abutment of the adjusting member 14 with the tongue portion 42. The contacts are out of engagement and the circuit is open. The sleeve 12 is always mounted in a position where it is exposed to any temperature change. As the temperature rises above the normal operating conditions the sleeve 12 and actuating member 14 expand, but as the sleeve 12 expands at a faster rate than the actuating member, the actuating member withdraws from the sleeve 13, starting to release the pressure exerted on the tongue 42 of the contact member. When the temperature reaches the value to which the switch has been set, the actuating member has withdrawn to fully release the resilient contact member, permitting engagement of the contact buttons 52 and 53 to complete the electrical circuit. The actuating member is not in engagement with the contact member and the contact member is free of any external force thereon. The circuit may be wired to indicate a warning or set in alarm.

As the operating temperature lowers, the reverse operation occurs to break the electrical circuit and restore the switch to a normal open condition.

A different construction of our contact member is shown in Fig. in which the contact member 15a is provided with a modified tongue portion 42a offset or struck down from a position close to the contact button and at an acute angle with the body 41a of the contact member. The free end 35a of the actuating member may be provided with a groove 68 to receive the free end of the tongue portion 42a. With this construction a more accurate control of the contact member is obtained to minimize the vibration, and a larger ratio of movement of the contact member to that of the actuating member is achieved.

The switch may field. Removal of to the adjusting screw of the adjusting screw be adjusted at the factory or in the the sealing nut 32 will give access 26. A counterclockwise rotation will increase the operating temperature by extending the actuating member further into the sleeve 13, forcing the contact button 52 further out of engagement with the fixed contact button 53 and thus requiring a greater distance for the contact member 40 to return to the engaging position to make the circuit.

To increase the accuracy perature can be adjusted, we provide a on the adjusting screw 26. This is accomplished by using slightly different pitches on the internal and external threads of the adjusting screw. Thus a large angular adjustment of the screw 26 results in an extremely small longitudinal movement of the actuating member 14.

By the use of our thermal switch we obtain a contact unit that is simple, rugged and economically constructed, that is easily assembled, that is free from calibration difficulties which might be imposed by external vibration and shock; that has a design to permit a compact switch which is hermetically sealed, and which can be adjusted at the factory or in the field through a wide range of operating temperature.

We have thus described our invention, but we desire it understood that it is not confined to the particular forms or uses shown and described, the same being merely illustrative, and that the invention may be carried out .in other ways without departingfrom the spirit of our invention, and, therefore, we claim broadly the right to employ all equivalent instrumentalities coming within the scope of the appended claims, and by means of which, objects of our invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

We claim:

1. In a thermal switch having a chamber, a thermostatic element, a contact member, an intermediate contact member operable by said thermostatic element to engage the first contact member, said intermediate contact member comprising a flexible sheet metal stamping having a side with a fixed support and an oppositely positioned moving side provided with a contact, said intermediate member having a plurality of longitudinal slots extending from the side with the fixed support forming outside and intermediate tongues, the outer pair of which is attached to the fixed support, the intermediate tongue being bent to engage the end of the thermostat, causing the intermediate member to be flexed, said thermostatic element causing the intermediate member to open and close the circuit under varying thermal conditions.

2. The intermediate member of claim 1, wherein the free end and contact of the intermediate member extends linearly in the same direction as the longitudinal axis of i are engaged.

claim 1, wherein the intermediate tongue and the outer tongues are bent in opposite directions.

References Cited in the file of this patent UNITED STATES PATENTS

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