US1873271A - Thermal relay - Google Patents

Description

Aug. 23, 1932. EL BLETZ 1,873,271

THERMAL RELAY Filed March 12, 1929 wan/[mare aid. 43 W 4; 4/

| 39 Orr may 423-14.

| l 1 I W INVENTOR ATTORNEY Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE EDWARD'BLETZ, OF LEXINGTON, OHIO, ASSIGNOR TO WESTINGHQUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OFPENNSYLVANIA THERMAL RELAY App1ication filed March 12, 1929. Serial No. 346,393.

My invention relates to circuit-controlling devices and particularly to adjustable thermal relays. r t

An object of my invention is to provide a relatively simple and adjustable thermostaticv switch.

Another object of my invention is to pro vide a snap-acting thermostatic switch that shall be adjustable, within a predetermined temperature range, to vary the temperature while maintaining a substantially constant temperature differential. '1

In practicing my invention, I provide a cupped bimetallic disc adjustably held at its central portion on a suitable base provided with cooperating contact members and provided, in addition thereto, with stop members for limiting the outward dish of the cupped disc when actuated from its normal position in which the cooperating contact members are in engagement.

. In the single sheet of drawing, 1 Figure 1 is a top plan view of a thermal relay embodying my invention, one element thereof being omitted,

Fig. 2 is a view, partially in side eleva tion and partially in radial section, taken on the line 11-11 of Fig. 1,

Fig. 3 is a View, in side elevation, of the,

assembled device, a part thereof being bro ken away to show the internal construction,

Fig. 4 is a schematic view, partially in section and partially in side elevation, showing one adjustment of the bimetallic disc;

Fig. 5 is a View, similar to Fig. 4. showingI another adjustment of the bimetallic disc, anc I Fig. 6 is a set of curves showing the op erati on of the device embodying my'invention.

A substantially circular base for the device 11 comprises two metal discs 12 and 13. The disc 13 is provided with three symmetrically-spaced openings 14 therethrough which are of double-oval or hour-glass shape and in which there are located suitably shaped pieces 16 of insulating material, such as H1103. A substantially circular sheet 17 of mica 18 located against the outer surface of sheet 12, and a plurality of contact members 18, 19,

21 and 22 are located against the outer surface of the sheet 17.

The cont- act members 18 and 19, are held in their proper operative positions by two rivets 23. Each of the rivets 23 is provided witha relatively large head 24, as shown more particularly in Fig. 1 of the drawing, in order that the mica immediately under the head may not be damaged when the other end is headed over one of the contact members, as shown more particularly in Fig. 2 of the drawing.

Terminal posts 26 and'27 are located in certain of the openings 16 and have reduced portions extending through the two plates constituting the base and the mica plate 17 and into the terminal members 21 and 22, respectively, the outer ends of which are headed over, as shown at 28 in Figs. 2 and 3 of the drawing. Small screws 29 are rovided on the terminal posts 26 and 2. to

permit of connecting suitable supply circuit conductors thereto (not shown).

A tubular member 31' is provided with a reduced portion to fit into central openings in the plates 12 and 13 and extend slightly beyond the plate of mica 17, the outer end of this portion being headed over, as shown at 32 in Fig.2 of the drawing, in order to hold the two plates 12 and 13 and the mica plate 17 in proper operative positions and tightly against one another.

The member 31 is provided with internal I screw threads, as shown at 33, and has a shoulder portion 34 which is of substantially semi-annular extent and is provided for a purpose to be hereinafter set forth in dewill move suddenly from one limiting posi- 7 tion to another.

A plurality of contact-bridging members 37 are insulatedly mounted on-the disc near the periphery thereof and are uniformly peripherally spaced on the disc, the location of the terminal members 18, 19, 21 and 22 being such that certain of the spaces between these members will be bridged by the members 37 when the disc is in the position shown in Fig. 3 of the drawing. The bridging members 37 are mounted on the disc on insulated pins 38 on which they have some movement, in order that the bridging members may adapt themselves to different adjustments of the disc.

Means for supporting the disc adjustably, relatively to the base structure hereinbefore described, includes a rod 39 having a reduced end portion 41 at one end thereof for fitting loosely into a central opening in the disc 36 to permit the disc to change its shape in accordance with temperature variations to which the device may be subjected. A nut, or washer 42 may be located on the portion 41 in order to insure that the material of the disc and of the end of the rod 39'shall not be strained beyond its permissible limit, either in the assembly or in adjustable operation of the regaly.

cans for turning the rod 39, which is provided intermediate it ends with external screw threads cooperating with the screw threads 33 in the member 31, comprises a handle 43 which may be made ofa molded material and which has an insert 44 therein of metal having internal recesses extending longitudinally thereof and cooperating with a reduced end portion 46 of the member 39 which is cooperatingly grooved to provide interfitting portions of the two parts. The end portion 46 is provided with an axial hole therein which may be screw-threaded to receive the body of a holding bolt 47 to prevent disengagement of the handle member 43 from the rod 39 after assembly thereof.

A cupped bimetallic disc of this kind may have the upper operating temperature of the disc, namely, that at which it moves into the limiting position, substantially as shown in the broken lines of Figs. 4 and 5, varied to some degree by varying the position of the central portion of the disc relatively to the base and the contact members thereof.

It is not ossible, however, to vary simultaneously th operating temperatures with a device of this kind and, in order to obtain temperatures, I provide a plurality of stop screws 48 which will be operatively engaged by the periphery of the disc when it has been actuated to the other of its limiting positions, namely, that one in which it is curved away from the base.

When the disc is located relatively to its supporting base, as shown in Fig. 4 of the drawing, in which the amount of dish thereof is relatively large, it is obvious that a relatively large change of temperature must occur before the disc will snap over to the position 49 shown in broken lines. Let it be assumed that a device of this kind is to operate upon an increaseof temperature and that the disc is cupped a relativelylarge amount initially, and that the amount of this cupping is not reduced appreciably when adjusted to the position shown in Fig. 4 of "the drawing, it is evident that the increase of temperature necessary before the disc will snap over to its other position must be relatively large, that is, the disc will not be operated until the temperature has been increased to 'arelatively high value, say, for purposes of illustration, 600 F. If it then snaps over to the position shown by the broken lines in Fig. 4, it, and particularly the central portion of it, will be located relatively close to the plane of the heads of the rigid stop screws 48 and, therefore, it will be impossible for the reverse dished disc to have as much dish as it did originally. This means that the stop members 48 operate in the same manner as would an initial drop in temperature and this means that only a relatively small reduction in temperature is necessary to cause the disc to snap back to its original position. If the disc snap over at a temperature value of approximately 600 F., it has been found that, in one type of disc and with a certain adjustment of the stop members 48, the disc will snap back at about 500 F. In other words, the disc operates with a temperature differential of about 100 F.

Referring now to Fig. 5 of the drawing, the disc 36 is there shown as having been drawn downwardly against the base so that it has a relatively small amount of dishing only, and, in line with the statements made hereinbefore, the disc will now snap over at a much smaller temperature increase or at a relatively lower temperature than set forth in connection with the position shown in Fig. 4 of the drawing. Let it be assumed that this upper temperature limit is now 400.

Reference to Fig. 5 of the drawing, shows that the reverse dishing of the disc is now substantially the same as was shown for the' initial dishing of the disc in Fig. 4 of the drawing and, therefore, it is necessary that the temperature be reduced to a value much lower than 500 F. at which it was found that a disc of this kind would snap back when in the position shown in Fig. 4 of the drawing. Actualtests have shown that it is pos- 5 sible to obtain a substantially constant temperature differential between the two operating temperatures of the disc by the adjustment hereinbefore described, in which the stop members 48 are provided in cooperation with the other elements of the device.

- Reference to Fig. 6 of the drawing may be had, in which curve 51 shows the upper temperature limits at which a particular disc of this kind will snap over, that is, move from the position shown by the full lines in Figs. 4 and 5 to that shown by the broken lines in these figures. Curve 52 shows the temperatures at which the discwill snap from the shape shown by the broken lines in Figs. 4 and 5 to its initial position.

The horizontal base of these curves is indicated as having twenty-four divisions, and it has been found possible to obtain a reduction in the upper temperature limits of operation from 600 F. to 400 F. and a simultaneousreduction of the lower temperature limits from 500 F. to 300 F. with a total angular motion over twelve of these divisions and this limit is imposed by a in 53 which is properly located in the mem er 39, in order to engage the arcuate shoulder portion 34 at each end of its travel. The amount of turning movement of the rod 39 is somewhat less than 180 mechanical degrees and trary.

It may be noted that the intermediate portions of curves 51 and 52 are substantially straight and extend substantially parallel to each other and this means that it is possible to obtain a substantially uniform temperature differential over the desired operating range of temperatures, as set forth above.

The lower right-hand portion of curve 52 illustrates what happens when the stop mem bers 48 are so far away from the base as to be engaged by the disc 36 either very lightly or not at all. The same holds true with re- 5o 51 which indicates that the disc was so adto go "well beyond the twelve divisions and, still obtain a variation in the upper and the lengths of the divisions are purely arbi-' gard to the upper left-hand portion of curve.

lower temperatures with substantially constant temperature differential.

The device embodying my invention thus provides a thermal relay embodying a snapacting cupped disc, in which means are provided for ensuring adjustable operation of the thermostat over a wide range of temperature values, the temperature differential between the upper and the lower temperature limits remaining substantially constant. I

A device of this kind permits of operatively associating it with an electrically heated device and of controllin the energization of the heating unit thereof over a wide range of 7 temperature, while maintainin a substantially constant temperature di erential and an electric flat iron is one device which may be so controlled. Because of the variations in the operating conditions of an electric flat iron, a temperature diflferential of F; is not serious, and very successful operation of electric irons embodying a device of this kind has been obtained.

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 or are 'set forth in the appended claims.

vI claim as my invention: I l I 1. In a thermally-actuable switch having a base, contact members thereon, a snap-acting bimetallic disc, and contact members thereon cooperating with the contact members on the base to control a circuit, an internally-threadedtubular member secured to the base at one endthereof and coaxial therewith and having a shoulder portion at its other end, an externally-threaded rod extending through the tubular member and having the disc mounted at one of its ends, the screw threads on the rod and in the tubular member being in engagement, an adjusting lever on the otherend of the rod for turning the same in the tubular member to adjust the position of the central part of the disc relatively to the base, and a pin on the rod for engaging the shoulder portion of the tubular member to limit the adjusting movement of the rod and of thedisc.

2. In a thermally actuable switch having a circular base, contact members insulatedly fixed thereon at one side thereof, a cupped bimetallic disc at one side of the base, and contact members thereon cooperating with the contact members on the base, a plurality of stop screws projecting through the disc adj acentto its periphery and mounted in the base, an internally-threaded tubular member having one end secured to the base coaxially therewith'and having its other end provided with a shoulder portion, an externallythreaded rod in said tubular member having the disc mounted thereon at that end extending through the base to that side having the contact members secured thereto, the internal and external screw threads in the tubular member and on the rod being in engagement, an adjusting lever on the other end of the rod for turning the same to vary the position of the central portion of the iso relatively to the base and the outer ends of the sto screws, and a pin in said rod for engaging t e shoulder portion of the tubular member to limit the turning movement of the rod in either direction of movement.

In testimony whereof, I have hereunto subscribed my name this Fifth day of March,

EDWARD BLETZ.

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