US2471924A - Thermal relay - Google Patents

Description

May 31, 1949.

J. D. BOLESKY THERMAL RELAY 3 Sheets-Sheet 1 Filed July 10, 1943 y 1949- J. D. BOLESKY 2,471,924

THERMAL RELAY Filed July- 10, 1943 3 She'ets-Sheat 2 y 1949. J. D. BOLESKY I 2 471 924 THERMAL RELAY Filed July 10, 3 Sheets-Sheet S k 26 a7 32 2/ 47 5/ f3 .35 H I 59 /7 l i Patented May 31, 1949 THERMAL RELAY John D. Bolesky, Attleboro, Mass., assignor to Metals 6; Controls Corporation,

Attleboro,

Mass, a corporation of Massachusetts Application July 10, 1943, Serial No. 494,173

Claims. (Cl. 6023) This invention relatesto thermal relays, and more specifically to an ambiently compensated thermostatic relay mechanism.

Among the several objects of the invention may be noted the provision of a simple and reliable snap-acting thermal relay mechanism which has a quick response from a remote control; the provision of apparatus of the class described in which no current flows except during relatively short periods; and the provision of apparatus of this class which is compensated for changes in ambient temperature. Other objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features oi. construction; and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention,

Fig. l is a view in elevation showing certain mechanical parts in one position, wiring being omitted;

Fig. 2 is a top plan view of Fig. 1;

Fig. 3 is a vertical section taken on line 3-3 of Fig. 2, but showing the parts in an alternate position;

Fig. 4 is a wiring diagram with parts according to their position shown in Fig. 1;

Fig. 5 is a wiring diagram with parts according to their position shown in Fig. 3;

Fig. 6 is a wiring diagram showing an alternative form of the invention; and,

Fig. 7 is a wiring diagram showing still another form of the invention.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Fig. 1, there is shown in general at numeral I a thermostatic relay unit. At numerals 3 are shown electrical insulating and heat resistant plates held together spacedly by spacing pillars 5 and 1, these being clamped together by studs 9 (see also Figs. 2 and 5).

The lower pillars 1 are grooved as shown at l l for loosely holding edges of thermostatic snapacting plates in the form of discs 43 and i5. These discs are what are known to the art as Spencer discs, each preferably consisting of a bimetallic snap-acting curved sheet. The upper disc I3 has its metal of high coeflicient of expansion H on the upper side and the metal of low coefllcient of expansion L on its lower side. The lower disc l5 has its metal of high coeillcient of expansion on the lower side and its metal of low coeilicient of expansion on the upper side. Thus the metals L are adjacent to one another and inside of the pair of discs, and the metals H are outside.

Centrally, the discs are provided with openings for loose reception in grooves l6 of a spacing pillar l1. Through pillar I1 is threaded a stem I! held in place by a lock nut l8. Stem l! carries at its top 20 an insulating bar 2 I. At its top .he stem is square 50 as to be guided without rotation in a square opening 23 in the middle plate 3.

The bar 2i is a switch actuating means. The switches operated thereby are carried on the upper insulating plate 3. These switches comprise terminals 25 and 26, from which extend cantilever springs 21 and 29 respectively. These springs carry at their ends movable contacts 3i and 32 respectively. The movable contact 32 of the spring 29 is normally biased downward to touch a fixed contact 31 carried on an underslung bracket 35 (Fig. 5). The movable contact II at the end of the spring 21 is engageable with a fixed contact 33, but normally stands in downwardly spaced relation to said contact 33 (Fig. 5). The contact 33 is wired to a lower heater coil M held on suitable insulating brackets on the lower plate 3, the other end of this coil 4| connecting with a line wire 53 at 45, as shown in Fig. 5. The contact 37 is wired into an upper heater M supported under the middle plate 8. The other end of the heater 4! is connected to said circuit 53, as shown in Fig. 5.

The terminals 25 and 26 are respectively con" nected to terminals 49 and 50 of a single-pole double-throw switch 5 l the single pole of which is connected to the other side of the energizing circuit 53.

The upper heater 41 'is adjacent to the highexpansion side (outside) of the upper disc l3 and the lower heater ii is adjacent the high-expansion side (outside) of lower disc l5. Thus the discs are respectively exteriorly heated by the respectively adjacent heaters.

The two thermostatic discs l3 and I5 have the same strength and temperature-operating characteristics, but they are oppositely operative in response to a given temperature change, becauseof the opposite location of the metals of high and low coeillcients of expansion. The discs being coupled in tandem and located parallel to one another, when heated to the same temperature (as would be the case were they both in the same ambient heating medium),v there will be noactivity of the discs from a given position, such as shown in Fig. 4 or 5. That is to say, the pair of discs I3 and I may be placed either in the position shown in Fig. 4, or in the position shown in Fig. 5, and change in the ambient temperature will cause no activity of the discs.

It the upper heater 41 alone is heated sufllciently in the Fig. 5 position, then the discs I3 and I5 will snap from the positions shown in Figs. 3 and 5 to the upward positions shown in Figs. 1 and 4 and remain there even though the disc temperatures later equalize. If only the lower heater ll is heated in the Fig. 4 position, then the discs will snap from their upward positions shown in Figs. 1 and 4 to the downward positions shown in Figs. 3 and 5 and remain there even though the disc temperatures later equalize. The discs will retain a given up or down position which is stable at any value of ambient temperature around them as long as it is -sub-. stantially the same for both discs, for reasons given in United States Patent 2,203,558 (refer to Figs. 5 and 6 and accompanying description therein).

Operation is as follows, referring to Figs. 4 and 5:

The parts are stable in the Fig. 5 position. To operate, the selective control switch 5i is thrown over to the dotted-line position, that is, on point 50. This sends current through the thenclosed switch contacts 32, 31, heater t? and back to the line 53. The heater 4? heats the upper disc I3, and since the metal of high coeflicient of expansion is on top, the disc snaps up from the position shown in Fig. 5 to that shown in Fig. 4 (carrying along disc I5). Both discs then permanently hold the Fig. 4 position, even after the upper disc I3 cools down to the temperature of lower disc I5. This cooling will of course occur, since when the device moves from the Fig. 5 to the Fig. 4 position, the contacts 32, 3'8 are opened and the heater All is deenergized.

The above closes switch contacts 3i and 33 (Fig. 4), but since the control switch Si is at this time on point 50, as indicated by the solid line in Fig. 4, no current is available for either heater I or 41.

Now, if the control switch 5! be thrown from its solid-line to its dotted-line position (Fig. 4) to point 49, current will flow through contacts II, 33, lower heater II, and back to the line 53. This heats the lower disc I5, and since its metal of high coeflicient of expansion is below, this disc will snap down, carrying along with it the upper disc I3. This opens contacts 39, 33 and recloses the contacts 32, 3? as shown in Fig. 5. Since switch 5I is on point 49 all circuits are again broken through the heaters, and the parts maintain the Fig. 5 position until the switch 5| is again thrown to point 5Il.

The member I9 has a downward extension which is attached to means which it is desired to operate, such as for example an electric switch, valve or the like.

It will be seen that the invention provides a thermal relay which has a quick-acting forceful response. The metals H of high coemcient of expansion of the tandem discs I3 and I5 being -on the outside of the assembly of discs and the temperature with some delay caused by the time that it takes for heat to be transmitted through the outside component. Thus, the design is particularly eflective to bring about a quick and positive action.

Between operations no current is consumed, switch 5| being normally closed in connection with whichever oi the pairs of contacts 3|, 33 or :2. :1 is open.

As shown in Fig. 7 the heaters 41 and 4| may be dispensed with if it is desired to use the discs I3 and I5 per se as heating units. In such case the discs. will be made of material presenting proper electrical resistance to generate the required amount of heat for self -operation; or selfoperating current-conducting discs may be used with auxiliary heaters. Self-operated currentcarrying discs are shown in the patent to Vaughan et al. 2,207,422; and discs with auxiliary heaters are shown in my Patents 2,199,387 and 2,199,388.

The application of the circuit connections for v causing the discs to generate heat for self-enerinclude the respective discs I5 and I3, with (Fig.-

gization will be clear from said patents and from Figs. 6 and '7. I Thus the parallel circuit branches through the automatic switches 21 and 29, may

6) or without (Fig. 7) the heaters 4| and 41. In Fig. 6 the disc I I is connected in shunt around heater 4'! by lines 53 and GI. The disc I5 is con nected in shunt around heater II by lines 55 and 51. In Fig. '7 discs I3 and I5 are connected in their respective circuits by lines 59 and GI, and

55 and 51, but heaters 4| and 41 are omitted. Discs I3 and I5 therefore in both embodiments carry the current in their respective circuits and themselves serve as a heating means.

In View of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above 4 constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A thermal relay comprising an ambienttemperature-compensated thermostatic means embodying two inherently snap-acting thermo static plates arranged so that snap movement of one opposes snap movement of the other, said plates being coupled for conjoint snap movement, a first electrical heating circuit including a first switch for heating one of said plates to snap both plates from a first position to a second position, a second electrical heating circuit including a second switch for heating the other plate to snap both plates i'rom their second position to their first position, and switch actuating means controlled by said thermostatic means adapted in the first position of said plates to close the first switch and open the second switch, and in the second position of said plates to close the second switch and open the first switch.

2. A thermal relay comprising an ambienttemperature-compensated thermostatic means embodying two inherently snap-acting thermostatic plates arranged so that snap movement of one opposes snap movement of the other, said plates being coupled for conjoint snap movement, a first circuit including a first switch and a first electrical heating element in heat-exchange relation to one of said plates for heating said one plate to snap both plates from a first position to a second position, a second circuit including a second switch and a second electrical heating element in heat-exchange relation to the other plate for heating it to snap both plates from their second to their first position, and switch actuating means controlled by said thermostatic means adapted in the first position of said plates to close the first switch and open the second switch, and in the second position of said plates to close the second switch and open the first switch.

3. A thermal relay comprising an ambienttemperature-compensated thermostatic means embodying two inherently snap-acting thermostatic plates arranged so that snap movement of one opposes snap movement of the other, said plates being coupled for conjoint snap movement, a first electrical heating circuit including a first switch and also including one of said plates as an electrical resistance heating element for heating said one plate to snap both plates from a first position to a second position, a second electrical heating circuit including a second switch and also including the other of said plates as an electrical resistance heating element for heating said other plate to snap both plates from their second to their first position, and switch actuating means controlled by said thermostatic means adapted in the first position of said plates to close the first switch and open the second switch, and in the second position of said plates to close the second switch and open the first switch.

4. A thermal relay comprising an ambienttemperature-compensated thermostatic means embodying two coaxial and parallel inherently snap-acting thermostatic bimetal dished discs coupled for conjoint snap movement with their respective low coefiicient of expansion sides adjacent one another. whereby snap movement of one disc opposes snap movement of the other, a first electrical resistance heating element adjacent the high expansion side of one disc for heatingsaid one disc to snap both discs from a first to a second position, said element being connected in a first circuit including a first switch, a second electrical resistance heating element adjacent the high expansion side of the other disc for heating said other disc to snap both discsfrom their second to their first position, said second heating element being connected in a second circuit including a second switch, and switch actuating means controlled by said thermostatic means adapted in the first position of said discs to close the first switch and open, the second switch, and in the second position or said discs to close the second switch and open the first switch.

5. A thermal relay comprising a support including a pair of spaced insulation plates held together by spacing members, a pair of snapacting thermostat bimetal dished discs edgemounted in grooves in the spacing members between the plates, said discs being mounted in coaxial spaced relation with their low coefficient of expansion sides facing one another, a stem centrally connecting the discs for conjoint snap movement, one end of the stem extending through an aperture in one of the plates and carrying a switch actuating member outward of the plate, a first electrical resistance heating element carried 6 by one of the plates in heat-exchange relation to the high coefiicient side of the disc adiacent that plate for heating said disc to snap both discs to a first position bowed toward said first heating element, a second electrical resistance heating element carried by the other plate in heat-exchange relation to the high coefilcient of expansion side of the other disc for heating said other disc to snap both discs to a second position bowed toward said second heating element, first and second switches carried by the support in P0511 tion for actuation by the switch-actuating member, the first switch being connected in a first circuit in series with the first heating element. the second switch being connected in a second circuit in series with the second heating element, said switch actuating member closing the first switch and opening the second switch in the first position of the discs, and closing the second switch and opening the first switch in the second position of the discs. 5

6. A thermal relay as-set forth in claim 1, turther'including a power supply circuit having a double-throw control switch adapted selectively to energize one or the other of said first and second heating circuits.

7. A thermal relay as set forth in claim 2, fur- I ther including a power supply circuit having a double-throw control switch adapted selectively to energize one or the other of said first and second circuits.

8. A thermal relay as set forth in claim 3, further including a power supply circuit having a double-throw control switch adapted selectively to energize one or the other of said first and second heating circuits.

9. A thermal relay as set forth in claim 4, further including a power supply circuit having a double-throw control switch adapted selectively to energize one or the other of said first and second circuits.

10. A thermal relay as set forth in claim 5, further including a power supply circuit having a double-throw control switch adapted selectively to energize one or the other of said first and secand circuits.

JOHN D. BOLESKY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS

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