US1728811A

US1728811A - Thermostatic switch

Info

Publication number: US1728811A
Application number: US211054A
Authority: US
Inventors: Thomas Irvin Grey
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1927-08-06
Filing date: 1927-08-06
Publication date: 1929-09-17
Anticipated expiration: 1946-09-17

Description

Sept. 17, 1929. 1, THOMAS 1,728,811

THERMOSTATI C SWITCH Filed Aug. 6, 1927 INVENTOR fry/h 63 Thomas.

, ATCI'ORNEY Patented Sept. 17, 1929 UNITED STATES PATENT OFFICE mviN GREY THOMAS, or MANSFIELD, 0111c, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION or PENNSYLVANIA THEBMOSTATIC SWITCH Application filed August 6, 1927. Serial No. 211,054.

My invention relates to temperature-control devices and particularly to thermostatic switches of the quick-make-a-nd-break type.

An object of my invention is to provide a thermostatic switch that shall be simple in construction, compact, rugged and easily manfactured.

Another object of my invention is to pro-- vide a radiant heater for a snap-acting thermostatic member ofa thermostatic switch that shall be of simple construction and easily applied to the switch.

.And a further object of my invention 15 to provide a heater for a snap-acting thermostatic member that shall have a relatively small thermal capacity, and a relatively high radiant-heat capacity, in order that the disc may be caused to respond quickly to changes in energization of the heater. I

For a fuller understanding of my invention, reference may be had to the following description taken in conjunction with the accompanying drawings, in which:

Figure 1 is a top plan view of a switch-base structure embodied in my invention.

Fig. 2 is a view, partially in section, of an assembled thermostatic switch embodying my invention, and

Fig. 3 is a view of a radiant-heat-producing element for the-device illustrated in Figs. 1 and 2.

In Fig. 1 of the drawings is illustrated a base 11 having

washers

12 and 13 of insulating material mounted thereon, the washers being provided with openings at substantially the central portions thereof. In order that the washers may beheld in a relatively fixed position with respect to each other, an eyelet 14 is provided that clamps the two washers together. As shown, the washer 13 is of a smaller diameter than the washer 12 for a purpose to be hereinafter set forth.

A plurality of contacts 15 to 18, inclusive, and 19 are disposed circumferentially in spaced relation about the washer 13 and located on the washer 12 so as to be insulated from the base 11. The contacts being of arcuate-shape and located against the edge of the washer 13, turning or disarrangement of the contacts is prevented. The

contacts

15, 16

and 19 are secured to the base 11 by means of rivets 21 that extend through the base 11 and the contact members, the ends of the rivets belng peened over at 22. The rivets 21 may be lnsulated from the base 11 by washers 23 of suitable insulating material.

The contact members 17 and 18 may be secured to the base 11 by

rivet portions

24 and 25 of terminals 26 and 27, respectively, the ends of the rivets being peened over at 28 on to the contacts 17 and 18 in order to hold them securely in place. The terminals 26 and 27 may be insulated from the base 11 by washers 29 of suitable insulating material.

In order that an electric circuit may be completed between the terminals 26 and 27, adjacent ends 31 of the

contact members

16 and 17, 18 and 19, 19 and 15.are engaged by contact-bridging members or buttons 32 that are carried by a thermostatic bimetallic disc 33, the buttons being insulated from the disc by washers 34 of insulating material. The disc 33 is supported on the base by means of a stud-bolt 36 that has screw-thread engagc ment with the base 11 at 37, and cooperating nuts 38 between which the disc is.positioned. The pressure existing between the contact buttons 34 and the contacts 15 to 18, inclusive, and 19 may be adjusted, by means of the stud-bolt 36, to any desired value, after which the bolt may be held in the desired position by a lock washer 41 and a nut 42.

The thermostatic disc 33 is of the type disclosed in U. S. Patent 1,448,240 to J. A. Spencer. The disc there disclosed has the characteristic that, when heated to a temperature of a redetermined value, the curvature of the iso is in one direction and, when cooled to a temperature of a predetermined value, the curvature is caused to reverse in direction. Thus, the disc has two opposed limiting positions corresponding to two temperatures of predetermined values, the difference between which may be determined by the heat treatment and manufacturing processes applied to the disc.

Ordinarily, the difference between these temperatures is quite large, which difference may be designated the temperature differential of the disc. In some instances, for examof the contact buttons 33 from the contact members 15 to 18, illClllSiX'Q, and 19. In order to effect rcengagement of the contact members, the disc must be cooled to a temperature of say 400 F., in which case, the telnperature differential of the disc will be substantially 100 F.

If a thermostatic switch embodying the disc S3having a temperature differential of 100 F. is utilized for controlling a heating element in accordance with the temperature of a heated device; for example, the fiat iron, the temperature at the ironing surface thereof will vary between substantially two temperatures, the difference between which would be substantially 100 F. or more. In order that the temperature at the ironing surface of the flat iron may vary between say 400 F. and 450, the disc 33 must be caused to engage and be disengaged from the contact members thereof with greater rapidity. To accomplish this result, an auxiliary heating element 44 is provided.

The heating element 44 comprises a relatively short conductor of suitable resistance material, the terminals of which may be spotwelded either to the rivets 21 or to the

concontacts

15 and 16 in circuit with the terminals 26 and 27. In order that the conductor or resistance element 44 may not warp or bend to touch the disc 33, an eyelet 45 is provided in the washer 13 that loops over the heating element, thereby holding it in place.

The heating element 44 heats the disc 34 by radiant energy and causes the disc to respond quickly to current traversing the switch. Since the element is of small mass, it will cool quickly, when disengagement is effected between the contact members of the switch, and cause the disc to return to its circuit-making position or the position shown in Fig. 2 of the drawings.

The heat-generating capacity of the element 44 need not be sufficient to cause the disc to be actuated to its open-circuit position, in the absence of other sources of heat, but, if the switch illustrated in the drawings is utilized for controlling the temperature of a flat iron, for example, the heat-generating capacity of the element 44 may be suflicient to heat the disc 34 to the temperature of 500 F. when the temperature at the ironing surface of the fiat iron has reached a value of say 450 F. Since the heating element 44 has relatively small thermal capacity, the disc will cool quickly and will again cause the switch to return to its circuit-closing position when the temperature at the ironing surface of the flat iron has fallen to approximately 400 F.

The heating element 44 being located between the disc 33 and the base 11 in close proximity thereto, only a small amount of electric energy is required to increase the temperature of the disc to the value desired. The heating element is inexpensive, easily applied to the switch and e'liicient in its operation.

Various modifications may be made in the configuration and the structure of the device embodying my invention without departing from the spirit and scope thereof. 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 thermostatic switch comprising a base, spaced contact members carried thereby, a snap-acting thermostatic member secured to the base, contact members carried by the thermostatic member for bridging adj accnt ends of said contact members and radiant heating means secured to certain of said contact D1OI11- bers in electric circuit therewith for heating said thermostatic member.

2. The combination with a switch base, spaced contact members mounted thereon, a snap-acting thermostatic disc, contact members carried by said disc for engaging said spaced contact members, and means for supporting the disc from said base, of heating means disposed between said base and disc for heating said disc by radiant heat, and means for securing heating means to said spaced contact members and for connecting the heating means in circuit therewith.

3. A thermostatic switch comprising a base, contact members mounted on said base, a snap-acting thermostatic disc on said base for cooperation with said contact members and a radiant heat-producing element connected to said contacts and mounted between said base and said disc.

4. A thermostatic switch comprising a base, contact members mounted on said base, a snap-acting thermostatic disc on said base for cooperation with said contact members and a radiant heat-producing element connected to, and supported by, said contact members for heating said thermostatic disc.

In testimony whereof, I have hereunto subscribed my name this first day of August,

IRVIN GREY- THOMAS.