US2298195A - Thermostat - Google Patents

Description

. t- 1942- E. K. CLARK EIAL 2,298,195

THEHMOSTAT 2 Sheets-Sheet; 2

Fi led June 21, 1940 f6 msuumorq 4 30 Z 75 54 WITNESSES:

INVENTORS far/ K (702% and WM aa/A Lee.

A-TTORNEY Patented Oct. 6, 1942 UNITED STATES PATENT OFFICE THERMOSTAT Earl K. Clark and Paul R. Lee, Mansfield, Ohio,

assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 21, 1940, Serial No. 341,624 9 Claims. (01. 200-122) Our invention relates to snap-acting devices and more particularly to a snap-acting bimetallic thermostatic device.

An object of our invention is to provide a bimetallic thermostat having positive acting cooperating contacts which are free from any tendency to creep open or closed.

A further object of our invention is to provide an adjustable thermostat which has a small temperature differential, and which is capable of handling a large quantity of power, say, at least 2000 watts at 110 volts or 220 volts.

Another object of our invention is to provide a relatively low cost, rugged snap-acting thermostat which may be adjusted to any desired operating value and which has a switch action so that an operator can manually open the electrical circuit passing therethrough.

Other objects of our invention will either be pointed out specifically in the course of the following description, or will be apparent from such description.

In the accompanying drawings:

Figure 1 is a top plan view of the device embodying our invention;

Figs. 2 and 3 are side elevational views of the device shown in Fig. 1 in its closed or operative and its open or inoperative positions, respec tively;

Fig. 4 is a plan view of a portion of the device embodying our invention;

Fig. 5 is an end and partial sectional view of the device shown in Fig. 2;

Fig. 6 is a sectional view taken along the lines VIVI of Fig. 2; and

Fig. 7 is a sectional view taken along the line VII-VII of Fig. 1.

Referring to the accompanying drawings, in which like reference characters indicate like parts in the several figures, we show a thermostatic device ID comprising a supporting struc ture I2, a bimetallic heat responsive element M, a movable contact arm member IS, a hoolnlilre member I8 cooperating with the bimetallic element l4 and contact arm NS for moving such arm in response to the movements of such element [4, a radiant heating element 20. cooperative movable and stationary contacts 22 and 24, respectively, and an adjusting member 25 rotatably attached to the supporting structure l2 and engaging the bimetallic element l4 so as to adjust the movements thereof.

The supporting structure l2 comprises, in this instance, a substantially flat metallic platedike member which is adapted to support and maintain the various operating parts of the device embodying our invention. However, it is to be understood that any other suitable supporting structure may be used in lieu thereof. A plurality of upstanding posts 28 are positioned along a transverse line of the supporting structure [2 and are rigidly attached thereto by suitable rivet members 30. The posts 28 .and rivets 30 are adapted to support the bimetallic element 14, as hereinafter described. A relatively small post 32 is rigidly attached to the supporting structure near posts 28 and preferably along the longitudinal axis of the plate like member. Post 32 has an annular groove 34 formed within the upper portion thereof for receiving and flexibly or fulcrumly retaining one end of the contact arm 16, as hereinafter described. In addition, an internally threaded sleeve member 36 is rigidly attached to substantially the central portion of the supporting structure 12 for retaining the adjusting member 26 as hereinafter described. Furthermore, there is a small threaded aperture 38 positioned within the structure l2 for retaining an adjusting stop screw 40, see Figs. 6 and 7.

The bimetallic member i4 is, in this instance, an elongated strip-type member having a plurality of elongated longitudinally extending slots therethrough so as to form a three-legged member, deformations being formed in the outer legs only, thus providing a snap-acting member. This bimetallic member is more fully described and claimed in a copending application of P. R. Lee, Serial No. 250,538, filed January 12, 1939, now Patent No. 2,259,312, issued October 14, 1941, and assigned to the assignee of this application.

The bimetallic member l4 extends longitudinally along the supporting structure l2 and is retained above such structure by means of the posts 28. Such bimetallic member is located above the threaded sleeve 36 so as to permit the adjusting member 26 passing therethrough to cooperate with the central portion or leg of the member M, as hereinafter described.

The movable contact arm member 16 is formed of a substantially flat metallic material. A notch 42, see Figs. 4 and '7, is formed within one end of the arm 16 to cooperate within the annular groove 34 of the relatively small post 32 as hereinafter described. A centrally located aperture 44 is positioned within the arm iii to permit the passage of the upper end of the adjusting member 26 therethrough. Such aperture is slightly larger than that portion of the adjusting member 26 which passes therethrough so as bracket-like member. member is attached'to the upper surface of the to permit the arm I6 to freely move or fulcrum about the post 32. An aperture 46 is positioned within the end portion of arm 16 opposite to that in which the notch 42 is located. Such aperture 46 is relatively larger than the adjustable stop screw 40 so as to permit the arm l6 to move relative thereto, as hereinafter described.

A resilient finger or arm 48 is rigidly attached to the upper surface of arm [6 by means of suitable rivets 50. The finger 48 is bent upwardlyfrom the arm I6 and has the free end thereof positioned above the aperture 46. An aperture 52 is positioned within the small or free end of the resilient finger 48 and is substantially coaxial with the aperture 46 in the arm l6. Such aperture 52 is substantially the size of the adjustable stop screw 40 so as to permit such screw to pass therethrough. The resilient finger 48 thus cooperates with the'stop screw 40 and is adapted to engage the head thereof so as to bias the arm 16 downwardly or into a contact-closed position, and to guide the movements of the arm I6 so as to prevent any binding action between the arm and the adjusting member 26 and stop screw 46.

The resilient member 48 in cooperation with the stop screw 40 keeps the contacts 22 mengagement with the stationary contacts 24, thus preventing any creeping action therebetween. However, when the bimetallic member I4 snaps to an upper or contact disengaged position, such resilient member in cooperation with-stop screw 36 limits the upward movements of the arm l6 and bimetallic member l4. i

The position of the head of adjustable stop screw 40 thus determines the temperature differential of the thermostatic device W.

A depending. J-shaped finger member 16 is rigidly attached to the lower portion of the arm 56. Such finger member '36 (see Figs. 3, 4 and is retained beneath the arm !6 by means of the rivets 50 which are used to attach the resilient member 48 to the upper surface of such arm. The finger i6 is adapted to be engaged .by a stop member 74 of general rectangular shape which has a notched end attached to the manually operable adjusting member 26. The cooperation of such member and finger is adapted to manually operate the thermostat as the adjusting member 26 is rotated to. an off position. The stop member 74 engages the finger 76, when rotated clockwise as viewed in Fig. 1, and forces it and the arm I6 upward so as to disengage the cooperating contacts, as hereinafter described. The degree of clockwise movemerit of stop member 74 is determined by pin or post 79.

I The hook-like member i8 is formed of a light metal and is bent into substantially a right-angle A portion of the hook-like arm i 6, say, by spot welding or the like. The second part of the angle member is then located substantially normal to the arm i6. An inwardly extending irregular shaped notch or aperture 54 (see Figs. 2 and 3) is formed within the inner edge of the upwardly extending portion of the member l8. Inwardly extending lips 56 are positioned within the notch or aperture 54 and are spaced apart, one above the other, a distance slightly greater than the thickness of the bimetallic member !4, for a purpose hereinafter described. The notched or irregularly shaped ill tion to another.

back of the notch 42.

formed within the inner portion of the memberof bimetallic member [4. The hook-like member 18, therefore, moves with the bimetallic member as such member snaps from one posi- The arm [6 being rigidly attached to the hook-like member l6 thus moves with the bimetallic member 14, through the cooperation of such hook-like member l8.

The movable contacts 22, being two in this instance, are insulatedly and rigidly attached to the free end of arm l6. Such movable contacts 22 are formed substantially in the shape of a rivet and pass through oversized apertures 58 in the arm I6, see Fig. 6. Suitable insulating members 66 are positioned about the contact members to adequately insulate them from the arm. A suitable washer 62 is ositioned on top of the arm and about the. upper end of the rivet-like contacts 22, permitting the upper end of such contacts to be spun over against the washer 62 to rigidly attach them to the arm l6.

The heating element 20 is insulatedly attached to the arm l6 by means of the movable contacts 22. The element 26 is substantially in the shape of a U or horseshoe with the free ends thereof positioned about the contacts 22 and beneath the washers 62. It therefore follows that such heater 20 is electrically in series with the movable contacts and is rigidly attached to the arm I6 by such contacts. The inner or loop portion of the heating element 26 is retained slightly above the arm l6 by means of an insulating member 64, see Figs. 2, 3, 4 and 7. Such member-is rigidly attached to the arm 16 slightly in A groove or notch 66 is 64 for receiving the loop portion of the heating element 26. Such element is thus retained by the arm [6 and is adapted to move therewith.

The stationary contacts 24, being two in this instance, are independent members rigidly attached to and insulated from the supporting structure l2. The contacts 24 are, in this instance, the upper ends of suitable terminal members 68. Such members, including the stationary contacts 24, are insulated from the supporting structure by means of insulating members 16, in a well known manner.

The electrical passage through the thermostat thus is as follows: Power enters one of the terminals 68 and passes to a stationary contact 24, the cooperating movable contact 22; through the heating element 20, the second movable contact 22, the cooperating second stationary contact 24, and out through the second terminal 68.

The adjusting member 26 is, in this instance, an elongated shaft-like member which is adapted to be threadedly engaged with and retained by the bushing or sleeve 36. The adjusting member 26 comprises an elongated shaft member having a substantially reduced upper portion 12 (see Fig. 7) which is adapted to pass through the aperture 46 in arm [6 and to be attached to the central portion of bimetallic member M, in a well known manner. The adjustable member 26 may then be rotated by means of an operator and is adapted to arch or flex the central portion of the bimetallic member l4 in'response to the rotative movements thereof so as to adjust the operations of such bimetallic member I 4' in a well known manner. An annular groove or slot 21 (see Fig. '7) is formed within said member 26 a relatively small distance below the reduced upper portion 12 to receive the notched end of stop member 74,

aperture 55 is adapted to receive the free end in keep t es a s ed p e- The stop member 14, has a thickness slightly greater than the width 01' slot 21, and has'its notched end (see Fig. 1) rigidly attached to the shaft 26, by being driven or forced into said slot. The member 14 is located slightly above the supporting structure I2 for cooperating with the depending finger 16. The cooperation oi the portion of stop member 14 extending in the opposite direction from the notch, and finger I6 as the adjusting member 26 is rotated clockwise as viewed in Fig. l, is adapted to bodily move the finger I6 and arm I6 upwardly. This action is adapted to disconnect the contacts 22 and 24 so as to manually disconnect or interrupt the passage of current flowing through the thermostat as hereinafter described. As previously noted, movement or member 14 in said clockwise direc tion is stopped by pin or post 19.

When assembling the thermostat embodying our invention, the posts 28 are positioned upon the relatively flat supporting member I2 with the bimetallic element I4 placed thereon. The rivets 30 are passed-through the bimetallic member and posts 28 and structure I2, whereupon they are riveted over against the structure so as to rigidly attach the bimetallic element to such structure. However, the bimetallic member I4 may be attached to the structure I2 in any other desired manner. The relatively small post 32 is attached to the structure so as to retain the contact arm I6. Stop screw 40 is passed through the apertures 52 of resilient finger 46 and aperture 46 or arm I6. Such adjustable stop screw limits the movement of the contact arm at one end :by means 01' the resilient finger 48 while the notch 42 is resting within annular groove 34 of post 32, which retains the contact arm at the other end.

The adjusting member 26 is threadedly passed through the bushing or sleeve 36 and stop member 14 is pressed or driven into slot 21 in member 26 so as to rigidly attach said stop member 14 to the adjusting member 26. The upper portion 12 or member 26 passes through the aperture 44 in arm I6 and is loosely attached to the bimetallic member I4 by means of a suitable washer I8. The movable contacts insulatedly positioned upon the lower surface of the contact arm I6 may then cooperate with the stationary contacts and terminals insulatedly attached to the supporting structure I2.

The illustrated thermostatic device is usually attached to say, a heating device, such as a roaster, flat-iron or the like, which in turn heats the bimetallic member I4 so as to operate it partially in response to the temperature of such heating device.

In addition, when operating the bimetallic thermostatic device embodying our invention, the terminals 68 are connected in series with a circuit (not shown) which it is desired to have the thermostat control. The power flowing through the circuit thus passes through the heating element as long as the bimetallic member I4 is in its lower or contact engaged position.(see Fig. 2). The current flowing through the circuit and thermostatic device will eventually cause the heating element 20 to produce suflicient heat, in conjunction with such heating device, so that the bimetallic element I4 in thermal communication therewith will flex upwardly with a snap action. As

the bimetallic element I4 moves upwardly with a snap action the free end of such member strikes the upper lip 56 within notch 54 of hook-like member I8 with an impact causing the hook-like member and contact arm I 6 to be moved up wardly with the bimetallic element without any creeping action. The movable contacts 22 sulatedly attached to the lower surface of the contact arm I6 will thus be moved upwardly from the stationary contacts 24 and therefore, the circuit passing through the thermostatic device and the heating device (not shown) will be interrupted.

With suificient passage of time the bimetallic element I4 will cool and will snap back to its original operative position. As the bimetallic element I4 moves downwardly with a snap acting action the free end thereof engages the lower lip 56 within notch 54 of hook-like member it with an impact suiiicient to cause such member and contact arm I6 to be moved downwardly with the bimetallic member. 22 will then reengage the and reconnect the circuit stat and heating device.

It therefore follows that the contact arm H5 is placed intermediate the bimetallic element I4 the supporting structure l2 and is adapted to move in response to the snap acting movements of the bimetallic member I4 through the cooperation of the hook-like member I8. Further, it is obvious that the heating element 20 is positioned intermediate the contact arm I6 and bimetallic member I4 and is adapted to furnish heat in direct response to the flow of power through the thermostatic structure. .Such heating element is thus adapted to cause the bimetallic element i to flex partially in response to the passage of current through such structure.

While we have shown our invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

We claim as our invention:

1. A thermostat comprising, in combination, a supporting structure, a snap-noting bimetallic member, a movable contact arm, m ans attached to such arm adapted to receive the member for moving the arm with such member, means tached to the supporting structure and cooperat" ing with the contact arm for limiting the move ments thereof, and resilient means attached to The movable contacts stationary contacts 24 through the thermcthe contact arm and engaging the last named means for biasing the arm into a closed position.

2. A thermostat comprising, a bimetallic heat responsive member, a movable arm member, movable contacts attached to such arm member, heating element insulatedly attached to such arm intermediate the arm and heat responsive mem ber, means attached to such arm adapted to cooperate with the heat responsive member so as to move the arm in response to the movements of such member, and manually adjustable means passing through the arm member and attached to the bimetallic member for selectively adjusting the operations of such member.

3. A thermostat comprising, a bimetallic responsive member, a movable arm member, movable contacts attached to such arm member, a heating element insulatedly attached to such arm intermediate the arm and heat responsive memher, means attached to such arm adapted to co operate with the heat responsive member so to move the arm in response to the movements of such member, manually adjustable means arm cooperating with the passing through the arm member and attached to the bimetallic member for selectively adjusting the operations of such member, and manually adjustable means for manually moving the arm member and disengaging the cooperating contacts.

4. A thermostat comprising, in combination, a supporting structure, a bimetallic member, means for attaching such member to the structure, c0- operating contacts including movable and stationary contacts, a contact arm, means for flexibly fulcrumingly supporting such arm at one end, an adjustable stop member engaging said structure, resilient means attached to the contact arm and cooperating with the stop member for biasing such arm into a contact-engaged position and for guiding the free end of such arm, and hook means attached to the free end of the bimetallic member for moving the arm in response to the movements of such member.

5. A thermostat comprising, in combination, a supporting structure, a snap-acting bimetallic member, means for attaching such member by one end thereof to the structure, a movable arm member, means for fulcrumly attaching such arm member to the structure intermediate the bimetallic member and such structure, cooperating contacts including a movabl contact insulatedly attached to the arm member and a stationary contact insulatedly attached to the supporting structure, an adjustable stop member movab1y attached to the supporting structure and passing through the arm member to limit the movements thereof, a resilient member attached to the arm member and cooperating with the stop member for guiding the free end of such arm and biasing such arm into a contact engaged position, and means attached to the arm for receiving the bimetallic member and moving the arm and movable contact in response to the movements of such bimetallic member.

6. A thermostat comprising, in combination, a supporting structure, a snap-acting bimetallic member, means for attaching such member by one end thereof to the structure, a movable arm member, means for iulcrumly attaching such arm member to the structure intermediate the bimetallic member and such structure, cooperating contacts including a movable contact insulatedly attached to the arm member and a stationary contact insulatedly attached to the supporting structure, an adjustable stop member movab1y attached to the supporting structure and passing through the arm member to limit the movements thereof, a resilient member attached to the arm member and cooperating with the stop member for guiding the free end of such arm and biasing such arm into a contact-engaged position, a radiant heater insulatedly attached to the arm member intermediate the arm and bimetallic member, said heater being electrically associated with the movable contacts so as to produce heat when the cooperating contacts are engaged, and

means attached to the arm for receiving the bimetallic member and moving the arm and movable contact in response to the movement of such bimetallic member.

'7. A thermostat comprising, in combination, a supporting structure, a snap-acting bimetallic member, means for attaching such member by one end thereof to th structure, a movable arm member, means for fulcruxnly attaching such arm member to the'structure intermediate the bimetallic member and such structure, cooperating contacts including a movable contact insulatedly attached to the arm member and a stationary contact insulatedly attached to the supporting structure, an adjustable stop member movab1y attached to the supporting structure and passing through the arm' member to limit the movements thereof, a resilient member attached to the arm member and cooperating with the stop member for guiding the free end of such arm and biasing such arm into a contact engaged position, a radiant heater insulatedly attached to the arm 'member intermediat the arm and bimetallic member, said heater being electrically associated with the movable contacts so as to produce heat when the cooperating contacts are engaged, means attached to the arm for receiving the bimetallic member and moving the arm and movable contact in response to the movements of such bimetallic member, and manually adjustable means passing through the arm member and attached to the bimetallic member for selectively adjusting the operations of such member.

8. A thermostat comprising, in combination, a supporting structure, a snap-acting bimetallic member, means for attaching such member by one end thereof to the structure, a movable arm member, means for fulcrumly attaching such arm member to the structure intermediate the bimetallic member and such structure, cooperating contacts including a movable contact insulatedly attached to the arm member and a stationary contact insulatedly attached to the supporting structure, an adjustable stop member movab1y attached to the supporting structure and passing through the arm member to limit the movements thereof, a resilient member attached to the arm member and cooperating with the stop member for guiding the free end of such arm and biasing such arm into a contact engaged position, a radiant heater insulatedly attached to th arm member intermediate the arm and bimetallic member, said heater being electrically associated with the movable contacts so as to produce heat when the cooperating contacts are engaged, and means attached to the arm for receiving the bimetallic member and moving the arm and movable contact inresponse to the movements of such bimetallic member, manually adjustable means passing through the arm member and attached to the bimetallic member for selectively adjusting the operation of such member, and

means cooperating with the arm member and manually adjustable means for manually moving the arm member and disengaging the cooperating contacts.

9. A thermostat comprising, in combination, a supporting structure, a heat-responsive member, a movable contact arm, means adapted to move the arm with such member, mean attached to the supporting structure and cooperating with the contact arm for limiting movement thereof, and a spring acting between said contact arm and said last-named means for biasing the arm into a predetermined position.

EARL K. CLARK. PAUL R. LEE.

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