US2194999A - Thermostat - Google Patents

Description

March 26, 1940. E. K. CLARK THERMOSTAT med oct. 21, 193s kEar/ A. C/ar/f.

' ATTbRNEY Patented Mar. 26, 1940 UNITED STATES THERMOSTAT Earl K. Clark, Mansfield, Ohio, asslgnor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 21, 1938, Serial No. 236,226

' 'f Claims.

My invention relates to thermostats and more particularly to a high-wattage, bimetallic snapacting thermostat.

An object of my invention is to provide a bi` 6 metallic thermostat having a resilient adjusting member engaging the bimetallic member and exterior adjusting means so as to eliminate any back-lash between the exterior adjusting means and the bimetallic member to ensure critical ad- 10 justments therebetween.

A further object of my invention is to provide a range-oven thermostat which may be directly associated with the oven and the power supply therefor without the use of additional relays and 15 controlling mechanisms.

A still further object of my invention is to provide a bimetallic thermostat having a movable contact assembly rigidly attached to, and insulated from, the bimetallic member, a heater being I provided which permits the thermostat to handle at least 4,000 watts and further enables such thermostat to operate with a two to one ratio and temperature amplitude, or less, from the center of' the oven to the bimetallic member.

Another object of my invention is to provide a simple, rugged, inexpensive, sensitive, directoperating range-oven thermostat which will carry the complete oven load and maintain an oven temperature diii'erential oi substantially 30 F. u throughout the complete oven temperature range.

Other objects of my invention will either be pointed out specifically in the course of the following description of the device embodying my invention or will be apparent from such descripu tion. g

In the accompanying drawing:

Figure l is a top plan view of a device embodying my invention, with the top cover thereof removed;

Fig. 2 is a partial side sectional view of the device embodying my invention with the cover thereof in place;

Fig. 3 is an enlarged top view of the bimetallic member included in the device shown in Figs. 45 1 and 2;

Fig. 4 is a side elevational view of the bimetallic member shown in Fig. 3 with an attaching bracket rigidly attached thereto;

Fig. 5 is a partial sectional view taken along" the line V--V of Fig. 2;

Figs. 6, 7 and 8 are top, end and side views, respectively, of thev adjusting member included in the device shown in Figs. l and 2, Fig. 6 being taken in a plane at right angles to ngers 68;

55 F18. 9 is an enlarged view taken along the line IX-IX of Fig. 2; and

Fig. 10 is a perspective view of the adjusting member of Figs. 6, 7 and 8.

Referring to the accompanying drawing, I

y show a bimetallic range oven thermostat It (Cl. o-122) Il operatively associated with the supporting 5.

structure I2 and engaging the adjusting member IB, an exterior adjusting means 20 operatively associated with the supporting structure I2 and the arm I8 for adjusting the bimetallic member I4, movable contact assembly 22 including U- l" shaped bracket 24 actuated by bimetallic member I4, contact plate 28 and heater 28 in thermal communication with the bimetallic member I4, and stationary contacts 30 positioned on, and insulated from, the supporting structure I2. 15

The casing or supporting structure I2 comprises in this instance a box-like base 32 and a removable cover 34. The base 32 is preferably formed from light sheet metal into an elongated parallelopiped having an open-top. lA plurality 20 of elongated slots 38 are formed within the bottom surface and adjacent side portions of the box 22 located at one end thereof to permit free passage of heated air therethrough. 'Ihe box 32 may be constructed in any suitable fabricated manner; however, it is to be understood that such structure must be formed so as to adequately support the bimetallic structure, as hereinafter described.

A removable top 34, adapted to be readily placed upon the support I2, consists primarily of an elongated sheet metal strip having a downwardly extending flange 28 at one end and a plurality of upwardly extending lugs 40 at the other end thereof. A boss 42 is located on the depending flange 38 to cooperate with the supporting structure and to retain the cover thereon. The removable top 34 is positioned upon and attached to the box 32 by inserting the lugs 40 within suitable slots 44 in the upper end of structure 32, and by snapping the inwardly extending boss 42 located upon the depending end portion 38 into the cooperating aperture 48 at the other end of the structure 22. Suitable slots 30a, in addition to slots 36, are also positioned a vwithin one end of the cover 34 to further permit passage of heated air through the supporting structure I2.

The bimetallic member I4 omprises, in this instance, a unitary member having elongated slots 48 therein which form a central strip III and ltwo exterior strips 52 as well as end portions 54 manner hereinafter described. An aperture l2 is located in the end portion I4 of the bimetalllc member I4 to permit a supporting angular bracket SII to be rigidly attached thereto by means of a suitable rivet 62, substantially as shown in Fig. 4. 'I'his angular bracket is rigidly attached to the bimetalllc member I4 in line with the teachings of E. K. Clark and P. R. Lee in a copending application, Serial No. 225,354, filed August 1'7, 1938, and assigned to the assignee o! the present application.

The rivet B0 is rigidly attached to the bimetalllc member before the heat treatment thereof and may then be heat treated along with the bimetalllc member I4. The bimetalllc member I4 may thus be rigidly attached to the supporting structure I2 without altering the thermal characteristics thereof in any manner whatsoever. An aperture 64 is located within the second end portion 58 of the bimetalllc member I4 to permit the movable contact assembly 22 to be rigidly attached thereto, as hereinafter described.

The intermediate adjusting member It is preferably formed from a single sheet oi' resilient material and includes a main body portion il, two upwardly extending nngers il, positioned substantially normal to the main body portion, and an upwardly extending post 10 positioned intermediate the ilngers 0I. The body portion 66 has a plurality of apertures 1I) located in one end thereof to permit adjusting member Ii to be rigidly attached to the supporting structure I2 by means of rivets 12, as shown in Fig. 2. The iingers il have outwardly extending notches 14 positioned on their inner edge at substantially the upper end thereof to cooperate with the bimetalllc member I4. The exact shape of these fingers and the manner of cooperation with the bimetalllc member I4 is more fully described and is claimed in my copending application Serial No. 237,270, led October 27, 1938, and assigned to the assignee of the present application.

The fingers B2, being formed of resilient material, may be forced outwardly, so as to permit a snap-on resilient fulcruming engagement with the central strip Il of the bimetalllc member I4, as hereinafter more fully described.

The upwardly extending post 1| is substantially triangular with the vertex positioned above the main body portion 46 of the adjusting member I6. An elongated boss or ridge 1l is formed within the post to give it additional strength. Small triangular notches are cut within the vertex of the triangular post so as to form small ledges 19, one on either side of an upwardly extending tongue II. The ledges 12 and tongue 8i cooperate with lip 82 of the arm I2 to permit the adjusting movements thereof to be directly transmitted to the main body portion of the adjusting member Il without distorting the fingers 88.

The arm I8 comprises, in this instance, substantially a channel-like member, see Figs. l, 2 and 5, having a flat top portion 1l, downwardly extending side portions I! and an outwardly ex: tending lip l2 which is substantially in theplane of the top surface 'I8 and located at one end thereof. The arm I8 is fulcrumed to the casing or support I2 by means of a through-pin 24 which extends through the depending side por-L tions of the arm I8 and the side walls of the casing I2 to permit the arm Il to rotate about the pin 84. This action permits the arm Il to transmit the manually adjusted movements of the adjusting means 20 to the bimetalllc member I4, through the cooperative action of the intermediate adjusting member Il and lip I2. The lip l2 extends outwardly from the top surface I2 of the ann Il and is fitted over tongue II of post 'Il so as to transmit the movements of the arm Il to the fingers il, in a manner hereinafter more fully described. A large rectangularly-shaped aperture Il is positioned within substantially the left end portion of the arm Il to permit the movable contact assembly 22 to extend therethrough as shown in Figs. 1, 2 and 5, and as hereinafter described.

The adjusting means 2|, as shown in Fig. 2, includes in this instance a threaded shaft which extends through the bottom surface of the casing I2 and cooperates with an abutment Il located at substantially the right end of arm Il. The adjusting screw 2U is threadedly attached to the supporting structure I2 by means of an internally threaded bushing Il which is rigidly attached to such casing I2 by having its upper ends riveted over tightly against the inner surface of such structure.

A small pin II is positioned close to the bushing 9| and is rigidly attached to the supporting structure I2. A stop lug I2 is positioned upon and adjustably attached to the screw 22. This lug is attached to the screw 2l so that it will contact the pin II and limit the rotational mov ment of such screw as it is rotated within the bushing Il. 'Ihe cooperation of the pin II and lug Il thus prevents the screw from being ac-v cidentally removed or from being run in so far as to injure the thermostat.

The movable contact assembly 22, more fully described in my above-identified copending application, comprises a U-shaped bracket 24, a contact plate 2l flexibly attached to the bracket 24, contacts 02 insulatedly attached to the contact plate 2l, and a radiant heater 2l bent into substantially U shape and rigidly attached to the contacts and to contact plate 2l and Insulated therefrom. The contact assembly 22 is rigidly attached to the free end of the bimetalllc member I4 by means of a rivet Il which extends rough the aperture I4 in the bimetallic mem- In assembling the thermostat embodying my invention, the resilient intermediate adjmting member Il is rigidly attached to the inner bottom surface of the box-like supporting structure I2 by means of rivets 'I2 as hereinabove described, whereupon the fingers l2 and post Il will extend substantially upwardly. The arm Il will now be positioned within the support I2 so that the aperture l2 in lip 22 will cooperate with the ledges 'Il andtonguell ofpostll of adjusting member I6 and the through-pin 24 will be insertedthroughthearm Il andthesidewallsof the casing I2 tov fulcrumly mount such arm thereabout. The arm II will then be operatively associated with the supporting structure I2 and the adjusting member Il through the cooperation oi the pin I4 and lip l2.

The bimetalllc member I4, having previously had the angular bracket il and movable contact assembly 22 rigidly attached thereto and .having been properly heat treated to its predetermined value, is positioned within the supporting structure I2 in such a manner that the central strip l0 thereof will cooperate with the upwardly extending fingers Il of resilient adjusting member I 2 (so that the notches Il located in central strip Il will cooperate with notches 14).

The bimetalllc member is then forced downwardu ly, whereupon the fingers I8 will expand outwardly, permitting a resilient snap-on fulcruming action therebetween. The angular bracket 60 is then forced downwardly permitting the screw 88 to be inserted within the end wall of Y the supporting structure I2 to cooperate with the threaded aperture in the bracket 80. Suitable bosses |0| may be formed within the end of the supporting structure, which, along with the slot |08 positioned in the bottom oi' the structure to receive tongue of bracket 80, maintains the bracket in alignment therewith. The bimetallic member I4 is then rigidly attached at one end thereof to the supporting casing |2 and engages the adjusting member i0 or, more specifically, the central strip of the bimetallic member |4- engages the adjusting member and cooperates with the arm Il through such member.

'I'he resilient adjusting member I8 biases the bimetallic member Il and the arm I8, at its left end, upwardly at all times due to its inherent characteristics and to the particular shape of its main body portion 88 thereof. 'I'he adjusting screw 28 is then threadediy inserted within the bushing 80 which has been rigidly attached to the supporting structure I2 so as to engage the abutment 88 which, due to the cooperative action of the resilient adjusting member I6. is biased in a downward direction. The adjusting screw 20 is, however, run into the supporting structure a considerable distance further so that the arm I0 is in a substantially horizontal position at the mid-point of the temperature range of the thermostat.

With the adjusting screw 20 holding the arm I8 in substantially a horizontal position and with resilient intermediate adjusting member I8 biasing the left end of the arm I8 upwardly or away from the horizontal position, it is apparent that there will be a positive action between the lip 82 and post 18 of resilient adjusting member I8, and between abutment 08 and adjusting screw 20 at all times. Accordingly, the back-lash in the threaded cooperation between the adjusting screw 20 and bushing 80 will be eliminated and a positive engagement between the resilient member |8 and arm |8 will be maintained at all times.

Due to the apparent concave upwardly curvature of the bimetallic member I4 as shown in Fig. 4, after such member has been heat treated, it follows that with the cooperative action of the outwardly extending notches 14 oi fingers 68, such fingers retain the bimetallic member I4 in substantially a horizontal position at the midpoint of the temperature range. In addition there will be at all times a positive connection or engagement therebetween. Accordingly, it is obvious that due to the cooperative engagement between the adjusting member I8 and the arm I8 there will be a positive connection between the adjusting screw 20 and the bimetallic member Il, at all times, whereby any adjusting movements whatsoever of the adjusting screw 20 will be immediately transmitted to the bimetallic member I4 without any idle or lost motion.

'I'he contact assembly 22, rigidly attached to the free end of the bimetallic member I4 through the cooperation of rivet 98 with aperture 84,

f extends downwardly within the rectangular aperture 86 in arm. I8. The substantially U- shaped heater 28 then extends `along under the bimetallic member I4 away from the adjusting screw 20 so as 'to be in thermal communication with the bimetallic member Il. With the bimetallic member Il rigidly attached at one end thereof to the supporting structure I2, as hereinabove described, and with the movable contact assembly rigidly attached to the lower surface of the free end of the bimetallic member, it follows that such movable contact assembly 22 will positively engage with the stationary contacts 80 to afford a good electrical contact therewith as the bimetallic member Il is in its lower or operative position.

An angular bracket |02 or any other suitable structure is attached to the side wall of the supporting member I2 by means of screw |04 and extends out over the free end of the bimetallic member Il so asrto cooperate with the upper surface of the rivet 80. The angular bracket |02 thus limits the upward movement of the bimetallic member I4, whereas cooperation with the stationary contacts 80 limits the lower movement thereof. However, it is to be understood that the movements of the free end of the bimetallic member Il are to be very limited, being of the order of V100 of an inch.

In the manual adjustment of the thermostat embodying my invention, assuming that the bimetallic member is in an open or disengaged position, the free end of the bimetallic member Il and the movable contact assembly 22 will be in an upper position with the top portion of rivet 98 engaging the angular bracket |02. However, through the cooperative engagement of the central strip 50 with the fingers 88, the central portion of the bimetallic member Il will be retained in its predetermined position. The exact location of this position determines the opening and closing temperatures of the bimetallic member, inasmuch as the bimetallic member must snap about the fulcruming engagement between the fingers 08 and the central strip 50 in a manner described in my above-identified copending application.

Should it be desired to adjustably lower these operating temperatures with the bimetallic member Il, the adjusting screw 20 will be rotated so that the right end of the adjusting arm I8 is raised. inasmuch as he arm I8 is fulcrumed intermediate the ends thereof, the lip 82, located at the other end of the arm I8, will be lowered, causing the fingers 88 and post 'I8 which cooperate therewith, to be likewise lowered. The retained or engaged portion of the central strip 50 of the bimetallic member I4 will then, in a similar manner, be lowered with the fingers 68, thus lowering the "off and on operating temperature of the bimetallic member I l.

It is, therefore, obvious that the adjusting screw or adjusting means 20 operatively associated with the support I2, through the sleeve 90,

and the arm or second intermediate member I8, through abutment 88, adjusts the operation of the bimetallic mem-ber H through the cooperative action of the resilient intermediate adjusting member I 6 and its engagement with the bimetallic member I4.

When operating the thermostat embodying my invention within the oven of a range, the end of the casing in which the bimetallic member il is rigidly attached and in which the slots 38 and 86a are positioned, is located within the oven proper, whereas the end of the support I2 containing the adjusting screw 20 is located or positioned outside of the walls of the oven. The adjusting screw 28 is thus located outside of the heated oven so that such screw and cooperating sleeve 90 will be relatively cool with respect to the bimetallic end of the thermostat. Such arrangementwill prevent any galling action between such adjusting screw and sleeve.

It is further obvious that with the bimetallic member I4 located in the oven proper, as mentioned above, such bimetallic member will receive heat directly from the oven without the use of any additional relays or bimetallic thermostat. However, inasmuch as the bimetallic member H will be located substantially close to one wall or side of the oven, the temperature thereof would tend to be slightly lower than the central point of the oven. However, due to the thermal communication between the heater 28 and the bimetallic member H, the temperature of such bimetallic member Il will be maintained substantially the same as the temperature of the midpoint of the oven without an appreciable time lag. In other words, the bimetallic member Il responds jointly to the heat from the center of the oven and from the heater 28. Accordingly, the thermal amplitude or heat range of the oven will be greatly reduced by ensuring a relatively quick heating of the bimetallic member Il, when power is being supplied to the oven heaters (not shown). The thermostat embodying my invention will thus not only reduce the thermal amplitude of the oven during continued operation thereof, but will eliminate to a great extent the initia1 temperature overshoot" when the oven is first connected to the power supply (not shown) by an operator.

Inasmuch as the movable contact assembly 22 is formed in the manner hereinabove described, it follows that such thermostat may carry the total operating current of the oven without the need of additional power or current relays.

Various modifications may be made in the device embodying my invention without departing from the spirit and scope thereof, and I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art and the appended claims.

I claim as my invention:

1. A thermostat comprising, in combination, a supporting structure, a bimetallic member, an intermediate adjusting member having two spaced parts for resiliently engaging the bimetallic member, an arm operatively associated with the support and having one portion disposed between the parts of the intermediate member, and an adjusting means directly associated with the arm for adjusting the operations of the bimetallic member through the cooperative actions of the arm, intermediate member and bimetallic member.

2. A thermostat comprising, in combination, a supporting structure, a bimetallic member, an intermediate adjusting member having two spaced parts engaging the bimetallic member, an arm rockably attached to the support and engaging the adjusting member between said parts, and external adjusting means operatively associated with the support and arm for varying the operations of the bimetallic member.

3. A thermostat comprising, in combination, a supporting structure, a functionally integral bimetallic member having a central strip and two exterior strips, and an adjusting member attached at substantially one end to the 'support and having two spaced parts engaging the central strip of the bimetallic member at the other end, an arm attached to the support and engaging the adjusting member intermediate said parts thereof, and external adjusting means operatively associated with the support and arm for varying the operations of the bimetallic member.

4. A thermostat comprising, in combination, a supporting structure, a bimetallic member, a resilient intermediate adjusting member having lingers for yieldingly engaging the bimetallic member, an arm attached to the support and engaging the lingers, and external adjusting means operatively associated with the support and arm for varying the operations of the bimetallic member.

5. A thermostat comprising, in combination, a supporting structure, a bimetallic member, a resilient intermediate adjusting member rigidly attached to the support at one end and having iingers on the other end which fulcrumly engage the bimetallic member, a second intermediate member rockably attached to said structure and engaging the fingers, and adjusting means operatively associated with the support and second intermediate member for adiusting the operations of the bimetallic member.

6. A thermostat comprising, in combination, a supporting structure, a functionally integral bimetalic thermal responsive member having a central strip and two exterior strips rigidly attached at substantially one end to the support, a resilient intermediate adjusting member attached at one end to the support having fingers on the other end which resiliently engage the central strip of the bimetallic member, a second intermediate member operatively associated intermediate the ends thereof with the support and operatively associated at one end with the flngers, and adjusting means operatively associated with the support and the second end of the intermediate member for adjusting the operations of the bimetallic member through the cooperative actions of the second intermediate member, intermediate adjusting member and the central strip of the bimetallic member.

'7. A thermostat comprising, in combination, a supporting structure, a functionally integral bimetallic thermal responsive member having a central strip and two exterior strips rigidly attached at substantially one end to the support, a movable contact assembly attached to and movable with the free end of the bimetallic member including a contact plate, contacts insulatedly attached to the plate and a heater attached to the contacts and in thermal communication with the bimetallic member, a resilient intermediate adjusting member attached at one end to the support having fingers on the other end which resiliently engage the central strip of the bimetallic member, a second intermediate member operatively associated intermediate the ends thereof with the support and operatively associated at one end with the ilngers, and adjusting means operatively associated with the support and the second end of the intermediate member for adjusting the operations of the bimetallic member and movable contact assembly through the cooperative actions of the second intermediate member, intermediate adjusting member and the central strip of the bimetallic member.

IEARL K. CLARK.

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