US2279929A

US2279929A - Thermostat

Info

Publication number: US2279929A
Application number: US323256A
Authority: US
Inventors: Mitchell J Schoumaker
Original assignee: JOSEPH G HAEG
Current assignee: JOSEPH G HAEG
Priority date: 1940-03-11
Filing date: 1940-03-11
Publication date: 1942-04-14
Anticipated expiration: 1959-04-14

Description

April 1942- M. J. SCHOUMAKER 2,279,929

THERMOSTAT Filed March 11, 1940 Aiiorne gs Patented Apr. 14 1942 THERMOSTAT Mitchell J. Schonmaker, Minneapolis, Minn, as-

signor of one-fourth to Joseph G. Haeg Application March 11, 1940, Serial No. 323,256

8Ciaims.

My invention relates to temperature responsive electric circuit controlling apparatus and particularly to a contact making thermostat. Various types of thermostats for use in connection with fire alarm systems and other control systems are available, but are mostly of construction which is relatively expensive.

An object of my invention is to provide a particularly compact and simple form of electrical contact making thermostat wherein duplicate pairs of contacts are connected in multiple.

Another object of my invention is to provide such a thermostat comprising a minimum of parts and including, other than fastening screws, only a single type of metallic part.

Still another object is to provide such a thermostat wherein a pair of identical bimetallic parts are so constructed that one portion of one such part cooperates with another portion of a duplicate part to .comprise a pair of electrical contacts and also wherein a pair of such parts provide for two pairs of electrical contacts.

A further object is to provide such a thermostat of light, compact, simple, rugged and inexpensive construction.

These and other objects and advantages of the invention will more fully appear from the following description made in connection with the accompanying drawing, wherein like reference characters refer to the same parts throughout the views, and, in which:

Fig. 1 is a top view of an embodiment of my invention with the cover thereof removed;

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1, as indicated by the arrows; and

Fig. 3 is a sectional View taken along the line 3-3 of Fig. 1, as indicated by the arrows.

Referring to the drawing I provide for the purpose of supporting and housing other parts of the particular embodiment of the invention which is illustrated, a relatively long and narrow open topped rectangular box 4 having at its lower side an outwardly projecting rectangular flange 4a in which are apertures 4b to accommodate means for attaching the flange 4a to a flat surface. The box' 4 includes end walls 4c and side walls 4d. and if desired the entire box inclusive of the flange 4a may be molded in one piece from plastic material. The primary requirement in regard to the material from which the box 4 is made is that this material be an electrical insulator.

Within the box 4 I provide a thermostat structure consisting of two bimetallic plates 5 which are placed against the inner sides of the longitudinal side walls 4d of the box 4. At the ends of the plates 5 blocks lie of insulating material may be placed between the corresponding end portions of the respective plates 5, as indicated in Figs. 1 and 2. The blocks 4e may be formed integrally with the box 4.

Each of the plates 5 is provided with a longitudinal slot 5a extending from one end of the plate 5 to a point short of the remaining end so as to divide the plate 5 into a mounting base portion 5b and a swingable arm portion which is connected by the unslotted end portion 5e of the plate 5. The two plates 5 are so arranged in the box 4 that the unslotted ends 5e of the respective plates 5 are at opposite ends of the box 4.

Each of the plates 5, in the attachment base portion 5b thereof, is apertured and internally screw threaded at points near the respective ends thereof and, in registration with these screw threaded portions of the plate 5, the longitudinal side walls 4d of the box 4 are provided with external bosses 4f and are apertured. Screws 5 of a headed type are inserted through the bossed and apertured portions of the box 4 and are screwed into the internally screw threaded portions of the plates 5 to secure the plates 5 to the longitudinal side walls 4d of the box 4. The screws 5 also constitute electrical terminal screws for the respective plates 5.

The bimetallic plates 5 are faced in such directions that the swingable arm portions 50 thereof will swing away from the corresponding box wall 4d responsive to change in temperature in a selected direction. For example, if the thermostat is to be used in connection with a fire alarm system the plates 5 are so faced that the swingable arms thereof will flex outwardly from the corresponding box walls 4d responsive to an increase in temperature.

The free ends of the swingable arm portions 5c are formed into electrical contact elements and in the embodiment illustrated this is done by bending the free end portion 5d of the swingable arrn 5c of each plate 5 toward the other plate 5, as indicated in Figs. 1 and 3. Preferably the free end portions 5d are tapered so that the ends thereof are relatively narrow. When the arms 50 flex responsive to temperature change each of the free ends 5d of the arms 50 will engage the unslotted portion 5e of the other plate 5,,whereby the respective plates 5 will become electrically interconnected. It should be apparent that the two contact elements 511 in cooperation with the two unslotted end portions 5e of the respective plates 5 comprise two pairs of electrical contacts which are connected in multiple and which will make contact responsive to the same variation in temperature. Should any foreign material interfere with engagement of one of these pairs of contacts a factor of safety is provided in that the other pair of contacts is available for closing the circuit.

A rectangular centrally apertured cover plate 1 is provided, the marginal portion of which is shouldered, as indicated in Fig. 2, to fit the upper edges of the end and side walls 40 and 4d of the box 4. The center of the upper side of the bottom wall 49 of the box 4 is provided with an upstanding recessed and internally screw threaded boss 4h into which a cover securing screw 8 projecting downwardly through the central aperture through the cover I may be screwed.

From the above described it will be seen that the slotted and apertured plates 5 are identical in construction and hence that only one type of metallic part other than the screws 6 and 8 is involved in the construction of my thermostat. It will further be seen that the screws 6 perform dual functions, that is they serve both to secure the plates 5 to the walls of the box 4 and as electrical terminals for the plates 5. In using the screws 6 as electrical terminals the screws may be loosened for insertion of the looped or hook shaped ends of wires under the heads thereof whereafter each loosened screw 6 may be again tightened to secure the wire and resume its function of securing the plate 5 to the box wall. In a two wire circuit connected to a plurality of thermostat units wires extending to the thermostat unit from one direction may be attached thereto by means of the screws 6 at one end of the thermostat unit, and wires extending from the thermostat unit in the other direction may be connected to the thermostat unit by means of the screws 6 at the remaining end of the thermostat unit so that the wire circuit will be connected to the thermostat unit and will be continued through the base portions of the plates 5 of the thermostat unit.

It is apparent that I have invented a novel and particularly simple, light, compact, reliable and inexpensive type of contact making thermostat unit.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the various parts without departing from the scope of my invention.

What is claimed is:

1. A thermostat comprising, a pair of relatively long, generally rectangular bi-metallic plates, each of said plates being longitudinally slotted from one end thereof to a point short of the remaining end thereof to divide the plate into a mounting base and a swingable arm interconnected by the unslotted end portion of the plate, a supporting structure to which the base portions of said plates are secured in mutually facing, parallel, spaced relation with the unslotted portions of said plates at opposite ends, said plates being so faced that the arm of each will flex toward the unslotted portion of the other responsive to a temperature change in a predetermined direction, the free end of the arm of each plate being formed into an electrical contact element for engagement with the unslotted end portion of the other plate, and electrical terminals connected to said respective plates.

2. A thermostat comprising, a pair of relatively long, generally rectangular bi-metallic plates, each of said plates being longitudinally slotted from one end thereof to a point short of the remaining end thereof to divide the plate into a mounting base and a swingable arm joined by the unslotted end portion of the plate, a supporting structure carrying said bases in spaced, parellel, mutually facing relation with the unslotted portions of said plates at opposite ends, said plates being so faced that the arm of each will flex toward the unslotted portion of the other responsive to a temperature change in a predetermined direction, the free end of the arm of each plate being bent toward the other plate and formed into an electrical contact for engagement with the unslotted portion of the other plate, and electrical terminals connected to said respective plates.

3. A thermostat unit comprising, a relatively long and narrow, open topped box having parallel, spaced side walls, a pair of rectangular bimetallic plates secured in their lower portions to the inner sides of said respective side walls, said plates being longitudinally slotted from respectively opposite ends thereof to points short of the remaining ends thereof to divide each plate into a base portion and a swingable arm connected by the unslotted end of the plate, each of said plates being so faced that the arm portion thereof will flex toward the remaining plate responsive to a temperature change in a predetermined direction, and the free end of each of said arms being formed into an electrical contact element engageable with the unslotted end of the other plate responsive to flexure of the arm, and electrical terminals connected to the respective plates.

4. A thermostat unit comprising, a relatively long and narrow open-topped box having parallel, spaced side walls, a pair of rectangular bimetallic plates placed in said box against the inner sides of said respective side walls, said plates being longitudinally slotted from respectively opposite ends thereof to points short of the respective remaining ends thereof to divide each plate into an attachment base and a swingable arm joined together by the unslotted end portion of the plate, each of said plates being so faced that the arm portion thereof will flex toward the remaining plate responsive to a temperature change in a predetermined direction, the free end of the arm of each of said plates being formed into an electrical contact element engageable with the unslotted end portion of the other plate responsive to flexure of the arm, said side walls and said bases being apertured in registering portions thereof, and elements extending through said respective registering pairs of apertures to secure said bases to said side walls and to function as electrical terminals for said respective plates.

5. A thermostat unit comprising, a relatively long and narrow open-topped box having parallel, spaced side walls, a pair of rectangular bimetallic plates placed in said box against the inner sides of said respective side walls, said plates being longitudinally slotted from respectively opposite ends thereof to points short of the respective remaining ends thereof to divide each plate into an attachment base and a swingable arm joined together by the unslotted end portion of the plate, each of said plates being so faced that the arm portion thereof will flex toward the remaining plate responsive to a temperature change in a predetermined direction, the free end of the arm of each of said plates being formed into an electrical contact element engageable with the unslotted end portion of the other plate responsive to flexure of the arm, each of said bases being apertured and internally screw-threaded in longitudinally spaced portions thereof and respective registering portions of said side walls being apertured, and headed screws projecting through the apertured portions of said side walls and screwed into the screw-threaded portions of said bases to secure said bases to said side walls and to constitute electrical terminals for said respective plates accessible from the outside of said box.

6. A thermostat comprising, a relatively long bimetallic plate, said plate being longitudinally slotted from one end thereof to a point short of the remaining end thereof to divide the plate into a mounting base and a swingable arm interconnected by the unslotted end portion of the plate, a supporting structure upon which said plate is mounted, an electrical terminal secured to each end of said mounting base, a second plate of electrically conductive material mounted upon said supporting structure and comprising a contact element engageable by said swingable arm on said first plate upon flexing of said arm under temperature changes, and said second plate being substantially co-extensive with said first plate and having an electrical terminal connected to each end thereof.

7. A thermostat comprising, a pair of relatively long bi-metallic plates, each of said plates being longitudinally slotted from one end thereof to a point short of the remaining end thereof to divide said plate into a mounting base and a swingable arm interconnected by the unslotted end portion of the plate, a supporting structure upon which said plates are mounted in spaced relationship, said plates being so positioned that the arm of each will flex toward and engage a portion of the other plate responsive to a temperature change, the free end of the arm of each plate constituting an electrical contact element for engagement with the other plate and electrical terminals connected to said respective plates.

8. A thermostat comprising, a relatively long electrically conductive bi-metallic plate slotted from one end thereof to a point short of the other end thereof to divide the plate into an electrically conductive mounting base and a swingable contact arm joined together by the unslotted portion of said plate, a non-conducting supporting structure for said plate, an electrical terminal at each end of said mounting base portion of said plate, and an electrical contact element mounted on said structure in position for engagement by said contact arm as a result of flexing of said arm responsive to a temperature change.

MITCHELL J. SCHOUMAKER.