US2069003A - Electrical apparatus - Google Patents

Description

Jan. 26, 1937. R BEMAN 2,069,003

ELECTRI CAL APPARATUS Filed Feb. 18, 1955 INVENTOR.

Ply/mam hf Elem/w ATTORNEY Patented Jan. 26, 1937 ELECTRICAL APPARATUS Ransom H. Beman, Detroit, Mich assign'or to Kelvinator Corporation, Detroit, Mich., a corporation of Michigan Application February 18, 1935, Serial No. 7,104

5 Claims.

My invention pertains to time delay safety devices and more particularly to safety control devices for oil burner systems.

It is an object of my invention to provide a safety control device comprising an iron structure and means for heating the same by the hysteresis and eddy current losses induced therein by an alternating magnetic field set up by an initiated operation for actuating a thermally associated thermostatic device, a predetermined time thereafter and having means for opposing and neutralizing the magnetic field in response to a succeeding operation whereby the operation of the thermostatic device is avoided.

It is a further object of my invention to provide a time delay safety control device comprising a thermostatic switch heated by an electromagnetic solenoid comprising an iron core slidably disposed therein whereby the time characteristics and the impedance of the device in the controlled circuit may be adjusted.

It is also an object of my invention to provide a variable impedance time delay safety'device for use in alternating current circuits comprising a thermostatic device heated by variable impedance means energized in motor circuit and including opposing electromagnetic means which is adapted to be subsequently energized under normal operating conditions to prevent the continuation of the heating of the thermostatic element to deenergize the motor.

The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments, when read in conjunction with the accompanying drawing, in which:

Fig. 1 is an elevational view of an embodiment of my time delay safety control device partially in section; and

Fig. 2 is a diagrammatic view representing a system controlled by my safety device.

Referringmore particularly to Fig. 1 of the drawing my safety control device comprises a bobbin structure I of non-magnetic material, such rubber or brass for example, for supporting a pair of separately insulated solenoid windings 3 and 5 thereon. The coil supporting bobbin I maybe mounted upon a bracket 1 projecting from a. suitable instrument board or panel'S and it is of spool like conformation having an aperture I extending axially therethrough for slidably receiving a core member II ofsome magnetizable material such as iron. An adjusting screw I3 is threadably supported in a bracket l projecting from the panel 9 under the lower end of the core whereby its insertion into the bobbin I may be adjusted. The lower end of the core is preferably provided with a laterally projecting flange ll for positively limiting its insertion into the winding.

The upper end of the bobbin I is provided with upwardly projecting flanges I9 upon which a thermostat 2| comprising a bimetallic element is supported across the upper end of the core. The bimetallic element 2! may consist of a pair of connected flat strips of unlike metal, or if a quick snap action is desired, it may be composed of a pair of cup shaped discs of unlike metal firmly secured together. If the material of the solenoid bobbin is a poor heat conductor, such as rubber or a phenolic condensation product, the core receiving aperture I0 may be extended through the upper end thereof to permit the core I I to be elevated into intimate thermal coupled relation with the bimetallic element 2|. If the bobbin structure is of some non-magnetic metal such as brass or copper the entire structure will be heated from the iron core thereby heating the thermostatic element 2|. in

Although my safety control device may be utilized for regulating mechanical elements, it is especially suitable for controlling electrical apparatus which is accomplished by a pair of electrical contact members 23 and 25 supported in engageable relation on resilient metallic arms 21 and 29 mounted in electrically insulated relation on a bracket 3 la projecting from the panel board. The lower extended ends of the separate contact supporting arms 2'! and 29 are provided with rounded loops 3!! for smoothly engaging the adjacent end of a. wedge shaped actuating member 3I which is slidably mounted in a bracket 33 projecting from the panel. The contact actuator 3| 40 is disposed for free slidable movement through the bracket 33 and its lower end is provided with a smooth spherical terminal 35 for operatively engaging the bimetallic member. A compressional spring 36 may be concentrically disposed on the actuator 3| for reacting between the bracket I 33 and the flange of the spherical terminal 35 for continuously biasing it downwardly. When the actuator is elevated by distortion of the bimetallic member, its uppermost end spreads apart the contact supporting arms thereby disengaging the contacts and interrupting any electrical circuit associated therewith. It will be understood that a mechanical regulating mem- II is permanently connected through another conductor 42 to one end of the other separately insulated winding 5 on the bobbin l. The other terminal 43 is connected jointly to the other ends of the two windings by permanently connected conductors 44 and 45.

My safety controller may be advantageously utilized for controlling a system wherein a certain operation must successfully follow an initiated operation and upon the failure thereof the initiated operation must be promptly terminated; Such a. system may comprise an oil burner control system, as shown in Fig. 2. In the operation of such a system the decrease of ambient temperature to a predetermined degree causes hill the energization of a blower motor M which throws a blast of oil spray into an associated furnace (not shown). Normally'the oil spray is successfully ignited by a continuous burning pilot flame or an electric spark, in a well known manner, and the oil spray is consumed as it enters the furnace. It is necessary however to provide for the contingency of failure of ignition which might be caused by extinction of the pilot flame or other conditions. For this purpose I provide a thermo responsive stack switch 56 which comprises a spiral bimetallic element 56 disposed in the stack, or closely associated therewith, for rotating a disc 53 operatively connected with anesible contact arm 55 carrying a contact 56 toward or away from a stationary contact 58 mounted adjacent thereto. The stack operated electric contacts and iii are electrically connected by conductors ill and $3 to the terminals di and so respectively connected to the separated ends of the separate windingson the safety control de vice.

in operation decreasing room temperature causes the room thermostat 6'! to close its contacts thereby completing-a circuit to energize the blower motor M from the alternating current service mains Li and L2. The motor energizing circuit may be traced from main line conducto? Ll through a conductor 59 to the contacts $59 of the room thermostat 51 and through a conductor 6! to terminal 39 on the safety controller thence to the winding 3 on the bobbin, and from the other end of the winding 3 by way of conductor 35 to the terminal connector 63, through a conductor 65 to the thermostatically controlled contacts 25 and 23 on the safety controller thence by way of a conductor 61 to the motor M and from the other terminal of the motor through a conductor 69 to the other main line conductor L2.

As the motor starts up it drives a suitable oil throwing blower or unit it which supplies a blast of oil spray to a furnace or other heating device (not shown).

In response to normal ignition of the flame the rising temperature variations afiect the stack switch to close its contacts and 58 within a very short time alter the blower motor M has started. This connects the two separate wind ings i3 and in parallel relntionior simultaneous energization in the motor circuit.

The separate windings 3 are coiled in opposing relation or are so connected into their respective circuits that their magneto-motive forces'oppose and neutralize, and when both are energized simultaneously the heating effects or? eddy currents andhysteresis losses in the core ii are eliminated. Hence, normally the ironcore structure is subjected to the heating effect of the alternating magnetic field for only a very short time until the subsequent energization of the second winding in opposed parallel relation neutralizes this effect.

When. the pilot flame fails, or other conditions arise which cause the flame failure when the blower motor starts, the stack switch will not receive heat and consequently will not close its thereby opening the motor circuit and stopping Q the blower. This operation prevents the danger ous and undesirable conditions which would he caused by continuously supplying unignited oil or gas to the furnace.

Although the thermostatic stack switch re sponds promptly to the rising temperature in the stack, an appreciable time interval must he cl lowed for this efiect to take place after the blower motor M has started... This is readily accomplished by adjusting the time intervals of operation the safety control device by'turning the adjus able stop screw it under the iron core ll As the core ii is projected upwardly into the winding, the heating efiect of the alternating magnetic held is increased, and the thermo coupling of core it with the bimetallic element 25 is also in= creased, thereby reducing the time interval re= ouired between the closing of the motor circuit by the room thermostat 5i and the reopening oi the circuit by the safety device. iii it is de sired to lengthen this time interval, this is r 1 lg; accomplished by adjusting the threaded stop member (13 to lower the iron core ll. metallic element it is of the quick snap acting type, it separates the electric contact members 23 and 25 quickly when the stack switch fails to close after a predetermined interval.

By adjusting the position of the iron core it within the windings 3 and 5 the impedance of the winding 3 in the motor circuit may also he varied to match the characteristics of the cir cuit. "lihis adjustment 'may also be utilized to vary the circuit characteristics, to compensate for various motor loads or to compensate for different alternating current frequencies. In manner my device may be adjusted in eccord-= ance with the particular installation in which the device is used.

it will be seen that I have provided a simple,

positive acting, time delay safety control device ill desire to limit the invention structions herein set forth;

I claim as my invention:

1. In combination a heat -responsive device, means actuated thereby, means for controlling said device comprising a member of magnetizable material, said material being in heat exchange relation with the heat responsive device, a source of magneto-motive force adjacent thereto, and a, source of opposing magneto-motive force for opposing and neutralizing the effect of said first source in the, vicinity of said member.

2. In combination a heat responsive device, means actuated thereby, heating means for controlling said device comprising a thermally coupled member of magnetizable material, said material being in heat exchange relation with the heat responsive device, an adjacent source of alternating magneto-motive force for heating said member by inducing eddy current and hysteresis losses therein, and means for varying the rate of heating said device.

3. In combination a heat responsive device, means actuated thereby, heating means for controlling said device comprising a thermally coupled member of magnetizable material, said material being in heat exchange relation with the heat responsive device, an adjacent source of alternating magneto-motive force for heating to the exact consaid member by inducing eddy current and hysteresis 1 losses therein, means for varying the rate of heating said device, and an opposing source oil alternating magneto-motive force for neutralizing and eliminating the effect of said first source in thevicinity of said member.

4. In combination in a, variable impedance time relay controller, a heat responsive actuator; control means actuated thereby; heating means for said actuator comprising a thermally coupled member of magnetizable material, an adjacent source of magneto-motive force, means for varying the rate of heating said actuator; and an opposed source of magneto-motive force for limiting the heating efiect of said first source in the vicinity of said member.

5. In combination in a variable impedance time delay controller, asnap acting heat responsive device comprising cupped discs of unlike metal, control means actuated thereby, heating means for operating said device comprising a thermally coupled member of magnetizable material, an adjacent source of alternating magneto-motive force, adjustable means for varying the rate of heating said device, and an opposing source of alternating magneto-motive force for neutralizing and eliminating the effect of said first source in the vicinity of said member.

RANSOM H. BEMAN.

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