US1478719A - Thermostatic switch - Google Patents

Description

Dec. 25, 1923.

H. J. SMITH wnsauosunc swrrcn Filed July 10 1920 2 Sheets-Sheet R mw EH m5 v P 0 1 A H "TO/ill s site irection, whereupon the opposite e enema Dec. 25, 1923.

UNITED STATES v 1,478,719 PATENT osncs.

men I. m 01' CHICAGO, ILLINOIS, ASSIGIOB, BY DIRECT. AID ml AIIIGI- ms, 01 ODD-IOU! TO WILLARD REID AID ONE-ml '10 ALFRED EAB'IIIGB M, BOTH OI SPRINGFIELD, IABSACHUBETIB.

THEBIOSTA'IIO Application filed July 10, 1990. lorlal Io. 808,424.

To all whom it may concern:

Be it known that I, HAZOR J. Surrn a citizen of the United States, residin at cisc o, in the county of Cook and tate of II mois, have invented certain new and useful Improvements in Thermostatic Switches, of which the following is a specification.

This invention relates to an automatic switch of the thermostat t pe whereby an electric circuitis com leted or interrupted due to a tern rature c ange.

The invention consists ntially in a bulb or container containing a medium, preferably volatile liquid, whose coeflicient of expansion is high or whose pressure increases rapidly with a comparatively small rise of temperature. A rise of temperature will exand the thermal medium where it will flow into an expansion elementwhich will change its length under the increased ressure exerted on it by the thermal me ium and this change of length will operate a leyer to make or break an electrical circuit. A lowerin of the temperature will cause a lessening o the pressure in the expansion element and consequently its shortening, and its shortenin is used to rotate the ever in the optpoect is had upon the electrical circuit. Interposed between the expansion element and the lever may be placed a balanced arm for bringing about an adjustable follow up of the action between the chan e of lengt of the expansion element and t e lever. The best embodiment of my invention of which I am at present informed is shown by way of illustration in the attached drawings in which Fi re 1 shows a side elevation of the switc part of the invention in open position;-

F1 2 shows a detail of the switch corresponding to Fig." 1 but in closed position;

Fig. 3 shows the wiring diagram;

Fig. 4 shows an end view of the switch with the thermostatic bulb, and

Fig. 5 shows a modification wherein a spring is substituted for a wei ht for adjusting the tension on the arm tween the expansion element and the lever.

In the drawings, the numeral 11 represents a thermostatic bulb adapted to contain a thermal medium 12 which should be any of the volatile liquids, provided that the temperature at which the device is to bc used is a the princi is" of operation of the switch is that the c anges in (pressure of a gas in the presence of its liqui are used to o erate the switch. In the resent device, app cant has found sulphur ioxide (S0,) very satisfactory because of its comparatively'straight pressure temperature line in the ra e from 20 to 40 F., it being understood t at the dev ce is excellentl constituted for use with refrigeration machines. If the device should be used to control a baking oven, the ressure of this gas would be unduly hig so in that case, some liquid having a boiling point much hlgher than sulphur dioxide would have to be used.

In the tube 11 is placed any suitable stopper means 13 adapted to prevent the escape of any of the gas and tube 14 is adapted to convey the gas rom the bulb 11 into the base 15 of the switch wherein it communi- .cates with the passage leading to a bellowslike expansion element 16 provided with an upper end late 1 which end late is equipped wit a knife edge 18. Upon the base 15 of the switch there extends a forked standard 19 adapted to carry plates 20 and 21 upon which plates are supported certain elements of the switch. 22 indicates a fulcrum carried by an upward extension 23 of the base 15.

Resting between the fulcrum 22 and the knife edge 18, is an arm 24 which extends between the legs of the forked standard 19 and 25 indicates a weight slidably mounted upon the arm 24 having a set screw 26 for holdlng it in adjusted position upon the arm. f desired this weight ma have substituted for it a springr27 (see ig. 5) with adjusting means 28. he arm 24 has portions thereof channeled at 29 and 30 to coact with the knife edges 18 and 22 respectively. Adjacent the channel 29 the arm 24 carries a trip rod 31 extending upwardly in the general ine of the center of the expansion element 16. The trip rod 31 carries at its upper end, an adjustable plate 32 from which depends a spring 33' and the lower end of the spring is attached to a bent extension 34 of lever or pivoted trip 35. The trip 35 is supported upon the points of two pivot screws 36 and 3 carried by the side plates 21 and 20 respectively. The plate 32 is made ove the boiling point of the liquid, for

adjustable to vary the tension of the s ring 33. The trip or lever 35 has an insu ating arm 38 from which de ends a bridging contact bar 39 preferably -shaped, having legs 40 and 41. 42 represents a stop pin for limiting the opening movement of the lever 35. 43 and 44 represent mercury cups adapted to be entered respectively by the legs 40 and 41 of the contact 39, and 45 and 46 respectively represent the terminals for the mercury cups. 47 represents a fuse block and 48 a fuse. 49 represents a canopy switch which may be included in the assembly for convenience of use.

In operation, the bulb 11 is partly filled with liquid S0 and all air exhausted from the tube 14 and diaphragm bellows or other expansion element 16 and then sealed. Now assume that the weight of the arm 24 and the weight 25 (orthe pressure of thespring 27) is greater than the pressure upon the head 17 of the expansion element 16 exerted by the gas due to the temperature of the bulb 11. The device will be in equilibrium and in the position shown in Figure 1. If the temperature of the bulb is raised, the pressure of the S0 will be increased along the line of its pressure temperature curve and the state of equilibrium will be altered. The pressure of the gas against the head 17 of the expansion element 16 will be sufficient to raise the head, the knife edge 18 and the arm 24, about its fulcrum. The raising of the lever 24'will throw the trip rod 31 across the center of support of the lever on trip 35 and the tension of the spring 33 will be exerted upon the opposite side of the center as shown in Fig. 2, whereupon the trip 35 will be pivotally moved and the connector 39 and its legs 40 and 41 will be plunged into the mercury cups 423 and 44 and the electric circuit completed that whatever is in the circuit, such as a motor driven compressor, will be set in operation.

If the bulb 2 is cooled the gas pressure will be reduced, the weighted arm 24 will overcome the pressure of the as in the bellows 16 and the trip rod 31 wil be thrown across to the opposite side of the center of support of the lever the tension of the spring 33 will raise the trip 35 until it strikes against the stop pin 42 and the connector 39 will be withdrawn from the mercury cups and the circuit opened with the consequent stoppage of the motor driven compressor or of a prime mover in the circuit.

What I claim as my invention is In a thermostatic switch of the type described, the combination of a thermal element containing an expansive gas, a balanced lever actuated b a change of pressure within the thermal e ement, and mounted for vertical and arcuate movement, a plate (32) adjustably carried at the upper end thereof, a spring (33) depending from said plate and attached to a bent extension (34) of a pivoted trip (35), said trip carrying contacts adapted to cooperate with mercury on s to make and break an electrical circuit.

11 testimony whereof I afiix my si ature.

HAZOR J. S TH. Witnesses:

- WnmnnRmn, H, Y. Slum.

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