US1928777A - Thermostatic, electric, circuitcontroller - Google Patents

Description

1933- H. B. ACKERMAN THERMOSTATIC, ELECTRIC, CIRCUIT-CONTROLLER Filed April 2, 1932 1 a: mm 1 Z Patented Oct. 3, 1933 PATENT OFFICE THERMOSTATIC, ELECTRIC, CIRCUIT- CONTROLLER Howard B. Ackerman, Brooklyn, N. Y., assignor to Gold Car Heating & Lighting Company, Brooklyn, N. Y., a corporation of New York Application April 2, 1932. Serial No. 602,724

7 Claim.

This invention relates to improvements in thermostatic, electric, circuit-controlling devices, and, although well adapted for general application, is herein disclosed as applied to the thermostatic I control of an electric heating system.

It is an object of the invention to provide a thermostatically-controlled electric switch by which the switch terminals may be very quickly opened when the controlling circuit is broken 19 at the terminals of the thermostatand very quickly closed when the controlling circuit is closed at the terminals of the thermostat.

It is another object of the invention to provide a switch of the above-described character having a relatively powerful high-resistance electromotive device capable of quickly closing the switch in association with a relatively low resistance electromotive device capable of quickly opening the switch when the high-resistance electromotive device is de-energized, the circuits 7 being such that the two devices will be connected in parallel by the closing of the switch, thus causing the current through the high-resistance electromotive device to be quickly reduced to a strength no greater than that necessary to maintain the switch closed against the opposing effort of the low-resistance electromotive device with a reasonable factor of safety.

Still further objects of the invention are to make use of a part of the magnetic field of the low-resistance electromotive device as a means of extinguishing the are when the switch terminals are separated; to provide relatively movable mounting means for the switch terminals in order that their complementary surfaces may be brought into snug contact when closing the switch; and to line the part of the structure surrounding the switch terminals with insulating material in order to avoid arcing from said terminals to adjacent metal portions of the device when the terminals are separated.

In the accompanying drawing illustrating the preferred form of the invention:-

Figure 1 is a side view of a device embodying the invention, parts being conventionally represented in diagrammatic form and parts being broken away to more clearly indicate underlying, structure.

- Fig. 2 is a top view of the device illustrated in 1' 8. 1.

In the embodiment of the invention which has been selected for purposes of, illustration, represents an electric generator which may be of either the direct currentor alternating current type.v 21 represents the thermostaticallycontrolled switch and its operating mechanism as a whole. 22 is a conventional representation of a thermostat by which a controlling circuit of. the switch-operating mechanism may be opened and closed when the surrounding temperature rises above or falls below a predetermined standard. 23 is a conventional representation of electrical apparatus such, for example, as an electric heater in a circuit to be controlled by the thermostat. which may comprise an electric winding 25 surrounding a metal core 26 mounted in a metal support 2'7 secured in any appropriate manner to a base block 28 of insulating material. From the right end of the support 2'7 a pair of spaced supporting members 29 may be extended upwardly to provide spaced bearings 30 (Fig. 2) within which may be mounted a three-armed lever, one arm 31 of which may be provided with an armature 32 which may be moved into and out of contact with a pole-piece 33 at the upper end of the core 26 of the electromotive device by the rocking of the lever in the bearings 30. The metal core 26, support 27, supports 29, pintle 34 by which the lever is mounted in the bearings 30, arm 31, armature 32 and pole-piece 33 may all be made of iron or soft steel so as to comprise a complete, closed, magnetic circuit without airgap when the armature is in contact with the pole-piece.

A second electromotive device 35 comprising an electric winding 36 and a metal core 3'7 may preferably be mounted on the insulating block 28 in close association with the electromotive device 24. Preferably the electrical characteristics of the coil 36 will be such that its resistance will be relatively small compared with that of the coil 25, wherefore, as a matter of convenience, the electromotive device 24 will be referred to as a high-resistance electromotive device and the electromotive device 35 will be referred to as a low-resistance electromotive device.

In the preferred form herein disclosed the magnetic core 37 of the low-resistance electromotive device 35 is connected with a pair of pole-pieces 38, 39, and the core, coil and pole-pieces, as well as the parts of the high-resistance electromotive device, may be secured to the block 28 by appropriate fastening elements 40.

The core 37 and pole-pieces 38, 39 of the lowresistance electromotive device may be constructed of iron or soft steel so as to form a magnetic circuit of high reluctance because of the wide air-gap between the pole-pieces.

The switch 41 to be controlled by the thermo- 24 is an electromotive device.

magnetic circuit without air-gaps, is many times greater than the attractive force exerted between.

the armature and the pole-piece ii the two are even slightly separated, and this difference-is still zreaterii an additional air-gap is introduced into the magnetic circuit of the magnet. For the foregoing reasons it will be apparent that the electromagnetic characteristics of the high-reslstance el'ectromotive device and the low-resistonce electromotive device may readily be made such that the coil may cause the high-resistance electromotive device to hold the armature 32 in contact with the pole-piece 33 against the attractive force exerted against the plunger 49 by the magnetic field of the low-resistance electromotive device 35 even though the resistance of the respective branch circuits be such that a very T small current be caused to pass through the coil 25 as compared with that which passes through the coil 36 when the switch 41 is closed. This means that throughout the period during which the heater 23 is in use but a very small portion of, the current need pass through the high-resistance coil 25 and the coil 36 may be of relatively low resistance whereby but a small percentage of energy is consumed in the mechanism relied upon to control the circuit.

As soon as the temperature has been raised to a degree above the predetermined standard the terminals 80, 81 of the thermostat 22 will be caused to open, thus breaking the circuit through the energizing coil 25 of the high-resistance electromotive device 24, whereby said coil will be completely de-energized. When this happens the entire current supplied to the heating device 23 will pass through the coil 36 of the low-resistance electromotive device, thus increasing the attrac tive force on the plunger 49 at the time when the lame between the armature 32 and its pole-piece 33 has been reduced by de-energization of the coil 25. The electromagnetic characteristics of the two electromotive devices may readily be so 1 designed that under such conditions the plunger 49 will separate the armature 32 from the polepiece 33 and, through the three-armed lever 47 and link 51, cause the terminals 42, 44 of the switch 41 to be very suddenly opened.

The quick opening of the switch, which, as is well known, tends to reduce the destructive effect 01' the arcing between the terminals, is enhanced by the spring 53, which tends to impart an initial movement to the switch-opening mechanism as soon as the armature 32 separates from the polepiece 33. 7

It will be observed that the pole-pieces 38, 39 not only provide an air-gap adapted to produce a magnetic field adjacent the plunger 49 for the purpose already described, but also establish an air-gap adapted to produce a magnetic fiel across the space within which the switch contacts 42 and 44 are separated when the switch is opened. This magnetic field which exists at the time of the opening of the switch terminals is relied upon to serve as a so-called magnetic switch 41 the coil 36 of the low-resistance electromotive device is immediately de-energized, but before the coil loses its energy the coil 25 has been de-energized, the armature 32 has been separated from the pole-piece 33, the switch terminals have been separated, and the switch members 52, 45 and connected parts of the switchoperating mechanism 51, 47 have been set in rapid motion in their switch-opening directions, thus causing the switch to be thrown to its COilipletely opened position.

After the opening of the switch in the abovedescribed manner the circuit from the source of electromotive force 20 to the heater 23 remains open and both coils 25 and 36 remain deenergized until the temperature again falls below the predetermined standard and causes the contacts 80, 81 of the thermostat 22 to be again closed, thus completing the cycle of operations.

Although it is intended that the resistance of the coil 25 be materially greater than the resistance of the coil 36, it will be apparent that since the coil 25 is always short-circuited within a fraction of a second after its energizing circuit is closed by the shunting of the part of the circuit in which it is included by the lOdJ-IGSlSJdllCB coil 36, this coilmay be so designed to transmit a verymuch heavier current during its effective operation in closing the switch than it could safely transmit for any material length of time. This means either that the coil 25 may be of such electromagnetic characteristics as to a materially greater switch-closing capacity than one not inter-related with other parts of the mechanism in accordance with the teachings of this invention, or a high-resistance switch-clot ing electrcmotive device of the same swi nclosing capacity as one not embodying the in vent-ion may be constructed at a smaller expense because of the amount of copper whi h may be saved by reducing the current-carrying capacity and heat-dissipating capacity which would other wise have to be provided for.

Although the invention has been disclcsed in the alone relied upon to open the switch when the coil 25 is die-energized.

The invention is not intended to be limited in its application to use in a system supplied with energy by a direct current source or electromotive force, but if its magnetic circuits are suitably laminated in a manner and for reasons well known to those skilled in the art it is equally applicable for use in a circuit supplied with current from an alternating source of electromotive force.

Zhat is claimed is:-

l. A thermostatic, electric, circuit-controlling device comprising a switch, operating mechanism to open and close the terminals of said switch, a high-resistance electromagnet to control the switch-operating mechanism, a low-resistance coil, conductors connecting said coil and switch in a series relation, a thermostat to make and break an electrical connection in accordance with variations of temperature, conductors connecting said electromagnet and thermostat in a

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