US1899671A - Thermostatic switch - Google Patents

Description

Feb. 28, 1933. K'CLARK 1,899,671

THERMOSTATIC SWITCH Filed July 18, 1930 INVENTOR Earl K Clarlf ATTORNEY Patented Feb. 28, 1933 UNITED STATES PATENT OFFICE EARL K. CLARK, OI IANBFIELD, OHIO, ASSIGNOR TO WETINGHOUSE ELECTRIC &

IANUFAGIUBING COKPANY, A CORPORATION OF PENNSYLVANIA TEE-RKOSTATIC SWITCH Application filed July 18, 1880. Serial N0. 468,854.

. My invention relatesto thermal devices and particularly to thermostatic swltches.

An object of my invention is to provide a relatively simple and compact thermal devlce which shall cause a plurality of movements 'ofone contact member relatively to a cooperating contact member.

Another object of my invention is to provide a relatively simple and inexpensive structure for the thermostatic control of heating elements which are to be operated at a plurality of different temperatures.

In practicing my invention, I provide a base member, of substantially bar shape, a movable contact bar structure, of substantlally U-shape, and a pair of substantially coextensive and spaced bimetal bars to actuate the contact structure of U-shape in aplurality of predetermined directions relatively to a fixed contact. member or members.

In the single sheet of drawings,

Figure 1 is a view, partially in side elevation and partially-in section, of a thermostatic switch assembly embodying my invention;

Fig. 2 is a view in end elevation thereof,

Fig. 3 is a top plan view of the device with the casing removed;

Fig. 4 is a view in side elevation with the cover shown in section of a modified form of device embodying m invention, and

' Fig. 5 is a view in en elevation thereof.

Referring more particularly to Figs. 1 to 3, inclusive, I have there illustrated a metal base plate 11 which is provided with an mtermediate inwardly bent portion 12. The right-hand end portion of the basemember 11 is provided with a recess 13 for receivmg therein a terminal-supporting member 14 of electric-insulating material. A plurality of adjustable contact members 16, 17 and 18 extend through the member 14 and may be locked in any adjusted position by nuts 19 thereon.

' A contact spring member 21, of substantially U-shape, has oiie -end portion thereof secured to the base, as by rivets 22 at the portion 12 of the base. A contact member 23 is secured to the other end of the member 21 closely adjacent to the end of the arm and in such position as to operatively engage contact terminal 16. A relatively thin metal plate 24 has one of its ends riveted to an intermediate portion of the upper part of the member 21 as by rivets 26. The other end of member 24 is slit so as to provide two arms 27 and 28, each of which arms are provided with contact members 29 and 31, respectively, so located as to operatively engage terminals 17 and 18.

A bimetallic strip 32 has one end thereof secured against the end portion of spring contact member 21 by the rivets 22 and extends toward the intermediate portion of member 21 the free end thereof being provided with a nt-outportion 33 which operative-ly engages the spring contact member 21. A second bimetal strip 34 has one end thereof secured to a resilient suppor 36 in the shape of a bar which has one end thereof secured by the rivets 22 to the intermediate portion 12. The other end of member 36 is suitably secured as by welding or by a rivet 37 to the substantially fixed end of bimetal bar 34. The other end of the bar 34 is adapted to engage the upper portion of spring contact arm 21, but initially there is a small clearance between the free end of the arm 34 and more particularly between the bent-out portion 38 and the inner face of arm 21, for a purpose to be hereinafter specified.

In order to permit of adjusting the switch assembly and thereby to vary the temperature at which the devicewill operate, a machine screw 41 extends through one part of the base plate 11 adjacent to one end and through the members 21 and 32 and engages rivet 37 and may be locked in any position by a lock nut 42.

A casing 43, of substantially U-shape, fits over the edge portions of base plate 11.

51 terial. with a plurality of terminals 53, 54

and 56 extending therethrough and held by ldck nuts 57. The spring contact member of substantially U-shape is here made in two portions including a portion 58 of substantially 1O U-shape and a bar 59 which has associated therewith a double arm contact element-61 as was hereinbefore set forth for the arm 24 shown in Fig. 1 of the drawing.

A bimetal strip 62 has one end secured to the base 51 as by rivets 63 and has its other end operatively engaging one leg portion of the member 58. A second bimetal bar 64 has one end thereof secured to a spring supporting member 66, the other end of WhlCll is secured to the base 51 by the rivets 63. The free end. of bimetal bar 62 is bent laterally first in one direction and then in the reverse direction from the plane of the rest of the bar to constitute a pocket of V-shape to receive the end of portion 67 of the arm 59 in abutting relation, the arm 59 and the member 58 constituting, in effect, a spring contact member of substantially U-shape.

A small machine screw 68 extends through the base 51 and through openings in member 58 and bimetal bar 62 into operative engagement with the end of spring arm 66, in order to adjust the device, a nut 69 being provided on the screw 68 to lock it in any desired adjusted position. A casing 71 of U-shape, is adapted to slidingly fit over the edge portions of base member 51.

The device embodying my invention was designed particularly for use with Warming pads and one or more of these thermostatic switches may be located in the warming pad so as to control the temperature thereof.

The heating element of a warming pad or, in fact, of any electrically heated device, is represented by heating element 73 and a manually operable switch 74 is provided having a movable contact arm which may be moved selectively into engagement with fixed contact members 76, 77 or 78. The contact members 76, 77 and 78 are connected, by suitable conductors, to the terminals 16, 17 and 18 or in the device shown in Fig. 4 to terminals 53, 54 and 56.

Assuming that the device has been properly adjusted and that contact arm of switch 74 is in engagement with contact member 76, I have found it possible to maintain an average temperature in a warming pad on the order of 120 F. If contact member 77 is engaged, I have found that an average temperature of 150 F. may be maintained, while, if contact member 78 is engaged by the switch arm, an average temperature of 180 F. may be maintained. 1.

The movable contact structure, including As was hereinbefore stated, the movable end of bimetal bar 32 is in engagement with a part of spring contact member 21 before the free end of bar 34 is in engagement therewith. Upon sufiicient change of temperature to cause movement of the bar 32, it will move downwardly or toward the base 11, so that v the upper portion of the arm 21 will, in effect, be moved toward the left, whereby a scraping action is effected between the cooperating fixed and movable contact members. This, of course, will have the result of cleaning the cooperating contacts without breaking or interrupting the circuit. At a difierent predetermined temperature, the end 38 of bar 34 will engage the spring contact member 21 and will cause. dis-engagement of contact members 23 and 16, then the dis-engagement of contact members 29 and 17 and finally of contact members 31 and 18, it being assumed, of course, that the temperature varies a suflicient amount to cause such action.

Upon the reverse changes of temperature, the reverse sequence of operation will be effected, that is, the cooperating contact members will be moved into engagement and then will be caused to scrape one upon the other to efi'ect a cleaning of the contact members and, therefore, obtain a better engagement therebetween.

The device embodying my invention thus provides a means for effecting a plurality of movements in diiferent directions and in a predetermined sequence in a thermostatic switch embodying a bimetal actuating element. Also the first bimetal bar effects movecontact members, so that any radio devices.

operated in the neighborhood of a thermostat of this kind are not aflected to any appreciable extent.

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 contact member on the base, a sprin contact bar on said base and a plurality o bimetal members on said base for actuating the spring contact bar in sequence in different directions at right angles to each other relatively to the 10 fixed contact member.

2. In a thermostatic switch, a base, a fixed contact member on the base, a spring contact arm, of substantially U-shape, mounted on the base, and a plurality of bimetal bars located within the spring contact member and supported by the base for actuating the spring contact arm in sequence in different directions at right angles to each other relative to the fixed contact member.

3. In a thermosatic switch, a base, a fixed contact member on the base, a spring contact member, of substantially U-shape, supported by said base, a first bimetal bar mounted on the base and having its free end engaging the spring contact member to eflect a scraping movement between the engaged contact members and a second bimetal bar supported by said base and efiective to cause aseparating movement of'the contact members, upon a predeterminedchange of temperature. fi

4. In a thermostatic switch, a base, a contact member on the base, a spring contact member operatively supported on the base and spaced therefrom, a bimetal strip having one end mounted on the strip and its other end operatively engaging the spring contact members to effect scraping movement between the contact members, a second bimetal bar having one end resiliently supported on said base and having its other end engaging the spring contact member to cause separation of the contact members upon a predetermined variation of temperature, and means operativel engaging the resilientlysupported end 0 the second bimetal bar to vary the temperature at which separation of the contact members occurs.

5. A thermostatic switch including a base, a plurality of fixed contact members on the base, a resilient bar providing a plurality of contact arms of different rigidity cooperating with the fixed contact members and a plurality of bimetal bars on the base for actuat-ing the resilient bar in different directions at right angles to each other to effect disengagement between the cooperating contact members in sequence and at different temperatures. I

6. A thermostatic switch including a fixed contact, a spring contact arm cooperating with the fixed contact and a pair of bimetal bars engaging the spring contact arm, one of said bimetal bars effecting a scraping movement between the cooperating contact members and the second bimetal bar effecting se aration therebetween.

A thermostatic switch including a fixed contact, a spring contact arm cooperatin with the fixed contact and a pair of bimeta bars engaging the spring contact arm at different points along its len h and effective to actuate it in sequence in di erent directions at right angles to each other relatively to the fixed contact member.

In testimony whereof, I have hereunto subscribed my-name this 13 day of June, 1930. EARL K. CLARK.

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