US2046406A - Reclosing circuit breaker - Google Patents

Description

July 7, 1936. P. B. PARKS 'RECLOSING CIRCUIT BREAKER Filed Oct. 12, 1934 0M.- Unrmgus iii Gil

Patented July 7, 1936 UNITED STATES PATENT OFFICE RECLO SING CIRCUIT BREAKER Application October 12, 1934, Serial No. 748,096

4 Claims. (01. 175-4594) r This invention relates to certain new and useful improvements in reclosing circuit-breakers, and also to an improved safety circuit controlled by this circuit breaker so as to prevent the too prolonged flow of a destructive current through the circuit and thus protect electrically actuated devices in this circuit.

As is well known, the flow of an abnormal current in an electric circuit, caused by an overload or a short circuit may cause damage to the electrical apparatus in the circuit. Also some electrical devices are adapted to be actuated by a rather heavy current which flows only momentarily and is then cut off. If this current were allowed to flow for too long a time the apparatus would be injured. To prevent this, fuses or automatic circuit-breakers are often provided in the circuit. A fuse will burn out and must be replaced before the circuit can be reestablished. Many circuit breakers are of the type which must be manually reset before the circuit can be reestablished. According to the present invention, the improved circuit-breaker is of the type which is automatically re-closed at intervals, so that if the abnormal condition is only temporary the circuit will be automatically reestablished. An apparatus of this general type is disclosed and claimed in the patent to Parks et al. #1,922,452, granted August 15, 1933. The present invention relates to improvements in an apparatus of this type, as hereinafter set forth. Also, according to the present invention, the main operating circuit is not entirely broken, but a high-resistance signal device is thrown intothe circuit when the circuit-breaker is open. This high-resistance device functions to cut down the current flow to such an extent that the apparatus will not be injured, and at the same time gives a visible or audible signal so that the attendant will become aware of the abnormal condition and take steps to correct the same.

Briefly described, the controlling mechanism comprises a self-closing, normally closed circuitbreaker in the main circuit, and an electromagnetic device which will open the circuit breaker when energized. A heating element included in the main circuit is positioned adjacent a thermostatic device within a closed heating chamber. The prolonged passage of a heavy current through this heating element will affect the thermostatic device so as to close a switch which completes a circuit through the electromagnetic device thus opening the circuit breaker. The closing of the switch also completes an energizing circuit for an electromagnet which tends to hold the'switch closed so as to delay the re-closing of the main circuit for a more or less predetermined length of time.

The principal object of this invention is to provide an improved overload safety circuit of the type briefiy described hereinabove and disclosed more in detail in the specifications which follow.

Another object is to provide an improved reclosing circuit-breaker including electromagnetic means for opening the circuit and delaying the re-closing of the circuit.

Another object is to provide an improved means for automatically throwing a high-resistance signal device into a circuit so as to reduce the current flow and give an indication of the abnormal operating conditions.

Other objects and advantages of this invention will be more apparent from the following detailed description of one approved form of apparatus constructed and operating according to the principles of this invention.

The accompanying drawing is a diagrammatic illustration of the improved circuits and the improved safety mechanisms included therein.

The combination shown includes generally a source of electric power A (here shown by way of example as a battery), a pair of electrically operated valves B and B, a pair of relays C and C for controlling the actuating circuit for the valves B and B respectively, a pair of temperature responsive mechanisms D and D respectively controlling the relays C and C, the re-closing circuit breaker E, the assembly F for controlling the circuit-breaker, and the signal device G.

The valves B and B are similar and of the type commonly in use for controlling the flow of steam through the radiators of a railway car heating system. Each valve is controlled by a handle l, pivoted intermediately at 2, the valve being shown in the closed position. When handle l is swung to an oppositely inclined position at the other side of the vertical, the valve will be open. A pair of electric motor mechanisms 3 and i are provided for respectively moving the valves to open and closed position. As here shown these motors are in the form of solenoids 3 and 6 having their respective cores 5 and ii carried at the ends of an operating rod l having an intermediate yoke 8 which engages one arm of the handle or lever i. When solenoid 4 is energized, the handle will be swung to the position. shown in the drawing and the valve will be closed. When solenoid 3 is energized, the handle will be swung to an oppositely inclined position and the valve will be open. A snap-switch 9,

actuated by a yoke it on theopposite end of lever l, comprises a movable contact [ll adapted to engage alternatively with the fixed contacts i2 and I3. The purpose of this snap-switch is to break the operating circuit of solenoid 3 or 4 as soon as the valve movement has been com.- pleted. A rather heavy current is used in the motor, and if the flow of this current was allowed to persist for too long a time damage might be done to the electrical mechanism. This flow of current will normally be out ofi by the snap-switch 9 as soon as one of the valve movements has been completed, but in case the valve should stick or some other abnormal condition should arise, the snap-switch 9 might fail to break the circuit at this point and the continued flow of current might prove to be destructive. To prevent this, the safety mechanisms E, F and G, hereinafter described, are provided.

The relay C is normally energized through the following closed circuit: from positive main 04 through wires i5 and i6, resistance ill, relay coil i8, wire l 9, resistance 23, and wire M to the negative main 22. When so energized, the movable contact plate 23 will be pulled down into engagement with the pair of fixed contacts 24 and 25. The thermostatic mechanism D is adapted to short circuit this current around the coil it so as to deenergize the relay and permit the spring 26 to move the contact plate 23 into engagement with the pair of fixed contacts 27 and 28 (as shown in the drawing).

This thermostatic mechanism D is of a well known type comprising a plurality of mercury tube thermostats 29, 30 and 3!] adapted to function respectively at certain predetermined high, mediumv and low temperatures, the thermostat in control of the relay at any given time being determined by the positioning of the manually operated selectorlswitch 32. This switch comprises a movable contact arm 33, always in engagement at its lower end with the arcuate contact plate 34, and adapted to be moved selectively into engagement at its upper end with any one of the fixed contacts 35, 36 or 371. As shown in the drawing, the low temperature thermostat 30 is in control of the relay. When the mercury column 38 of this thermostat rises sufficiently tu engage the fixed contact 33, a shunt circuit around the relay coil 118 will be completed as follows: from one terminal of this relay coil through wire 40, thermostat 3|, wire 4|, fixed contact 3], movable contact arm 33, fixed contact 34, and wire 43 to the other terminal of coil W. This will deenergize the relay and permit spring 26 to move the contact plate 23 to the position shown in the drawing. When the temperature in the space whose temperature is to be controlled by the mechanism D falls below the predetermined temperature for which thermostat 3| is adjusted, the mercury column will break this circuit by moving down out of contact with the fixed contact member 39 so that this shunt circuit will be broken and the relay coil l8 will again be energized so as to draw the contact plate 23 down into engagement with the lower contacts 24 and 25. When the movable selector arm 33 is moved into a vertical position in engagement with the fixed contact 36, an exactly similar control circuit will be completed through the medium temperature thermostat 40, but at a somewhat higher temperature. When contact arm 33 is moved into engagement with the contact 35, the control circuit will be completed at a still higher temperature through Wire 40, thermostat 23, and wires 44 and 43 directly back to the relay coil.

The circuit-breaker E comprises the movable contact plate'45 which is normally held by spring 46 so as to bridge the two fixed contacts 4'! and 48. When the electromagnetic device 49 is energized, the movable contact plate 45 will be drawn down into engagement with the stops 59 so as to break the circuit between contacts 4'! and 48. The control mechanism F, which will be hereinafter described more in detail, includes a heating element 5! (usually a resistance coil) which will become rather highly heated when the normal operating current for the valves B or B flows therethrough for any unusual length of time.

Returning now to the operation of the valve mechanisms, the valve B is shown in the drawing as closed, the temperature in the space to be heated having risen to or above the predetermined temperature for which thermostat 3| is adjusted. When the temperature in this space falls below the predetermined. temperature, the shunt circuit through thermostat 3| will be broken and relay 0 will again be energized so as to pull down the contact plate 23, whereupon an operating circuit for opening the valve 3' will be completed as follows: from positive main M v through wires l5 and 52, relay contacts 24, 23

and 25, wire 53, solenoid 3, wire 54, snap-switch contacts l2 and H, wires 55, 56 and 57, circuitbreaker contacts 43, 45 and 47, wire 58, heating element 5| and wire 59 to the negative main 22. Solenoid 3 will now draw in the core 5 and move the valve to open position, and at the completion of this movement the actuating circuit will be broken by snap-switch 9 moving the contact it over into engagement with the other fixed contact l3. When the temperature again rises to the predetermined point, the shunt y'circuit through thermostat 3| will again be completed so as to deenergize the relay C, whereupon relay contact plate 23 will again be moved up into engagement with fixed contacts 27 and 28 thus completing an actuating circuit for valve motor 4 as follows: from positive main l4 through wires l5 and 60', relay contacts 27, 23 and 28, wire 6|, solenoid 4, wire 62, snap-switch contacts l3 and H, and thence as before through wires 55, 56 and 51 to and through the circuit-breaker E and heating element 5|. As soon as the valve has been moved to closed position, this circuit will be broken by snap-switch 9 moving contact ll back into engagement with contact l2, all as shown in the drawing.

The valve mechanism 13' may be controlled in an exactly similar manner through relay C by means of the single thermostat D. It will be noted that all of these valve-actuating circuits pass through the circuit-breaker E and the heating element 5|. It will also be understood that the valve operating assemblies B and B, as well as their control mechanisms C and C and D and D are shown and described principally for the purpose of illustrating a type of electricallyoperated apparatus that may be protected by the improved safety mechanisms E, F and G.

The control assembly F comprises the casing 63 provided with closure 64 so as to completely A suitable thermostatic element is also iii heating element 5|, so as to respond quickly to temperature changes produced by the prolonged flow of current through the coil 5|. Preferably this thermost tic ele ent is in the form of a bimetallic bar 6 ored at one end 69 in the casing and in electrical connection with binding post 61. A movable contact 10 carried by the free end of bar 68 is adapted to engage with fixed contact II mounted in the casing wall so as to form a normally open switch. When the bar 68 is heated, it will warp downwardly so as to bring switch contact I into engagement with the fixed contact 'H. The armature 12 of an electromagnet 13 is mounted in the lower wall of casing 63 so as to be in position to attract and hold the bar 68 in its warped position when the electromagnet is energized. This magnet is not of sufiicient strength to permanently hold the thermostatic bar in this warped position, but it will resist the tendency of the bar to straighten out so that the thermostatic bar must cool considerably before it can move away from the magnet and break the switch contacts.

The signal device G is in the form of an electric lamp, or other visible or audible signal device of rather high resistance, connected through wires 14 and 15 in a branch of the main circuit in parallel with or shunted around the circuit closure contacts 47 and 48.

Assuming now that one of the valve mechanisms B or B should stick, or some other abnormal condition should arise so as to cause one of the heavy operating currents to persist for an abnormal length of time, the heating element will become heated sumciently to cause the thermostatic bar 68 to warp downwardly and close the switch contacts and H so that an energizing circuit for electromagnet 49 will be completed as follows: From positive main l4 through wire 14, electromagnetic device 49, wire I5, switch contacts H and Ill, thermostatic bar 68, binding post 61, and wire 59 to the negative main. This will energize the electromagnetic device 49 and draw down the contact plate 45 so as to break the main operating circuit between contacts 41 and 48. This main circuit will not be entirely broken but will now be shunted through the high resistance signal device G. This device G will now be illuminated or will give other indication to the attendant that some abnormal condition exists, and at the same time it will so cut down the current flowing in this main circuit that it will no longer be injurious to the valve-operating mechanism, nor will it be suiiiciently strong to highly heat the element 5| which will now begin to cool on. At the same time an energizing circuit for the holding magnet 13 will be completed as follows: From positive main l4 through wires 14 and 16, magnet 13, wire I3, switch contacts H and Ill, thermostatic bar 68, binding post 61, and wire 59 to the negative main. This magnet will tend to hold the switch in closed position, and will prevent chattering of the switch. As soon as the thermostatic bar 68 begins to cool off it will tend to straighten out and break the energizing circuit through the switch, but the magnet 13 will tend to hold the switch in closed position for a certain time before the thermostatic bar develops enough energy to break the switch contacts. Also the housing of the heating element 5| and thermostat 68 within the closedcasing tends to delay the loss of heat from these elements and thus delay the re-closing of the circuitbreaker and the main operating circuit, and cause the signal D to operate for a suitable length of time. After a certain time, the thermostat 68 will cool off sufficiently to overcome the attraction of magnet 13 and break the switch contact thereby deenergizing the electromagnets l3 and 49,

and the circuit-breaker will again be closed by v spring 46 thus short-circuiting the signal G and again completing the normal operating system. If by this time the abnormal condition in this operating circuit has ceased to exist or has been corrected, the devices E, F and G will remain in this normal position (as shown in the drawing), but if the main circuit is still closed the element 5| wil again heat up so as to cause another movement of the thermostatic bar and the operations previously described will be repeated so as to again open the circuit-breaker and cause the signal G to operate. This cycle of events will be continued indefinitely until the main operating circuit is broken at some other location, by the proper operation of the snap switches 9, or some equivalent operation in case other types of mechanism are positioned in this circuit.

By inclosing the heating element 5| and thermostat 68 in close juxtaposition within the airtight casing 63, the heating element and bar will heat up quickly when subjected to an abnormal current flow, and also the slow dissipation of heat from this heating chamber 65 will help to delay mally closed circuit-breaker in this circuit, and an electromagnetic device adapted to open the circuit-breaker and thereby break the main circuit, a thermostatic-switch assembly comprising an electric-heating element, a thermostatic element positioned in close proximity to the heating element, a casing intimately enclosing the heating and thermostatic elements to form a closed heating chamber about these elements so as to expedite the transfer of heat therebetween and minimize the heat losses from the thermostat, a switch mounted in the casing and adapted to be closed by the thermostat when heated, electric terminals for the heating element and switch carried by the casing, the heating element being connected in the main circuit, an electro-magnetic device mounted on the casing and having an armature projecting through a wall of the casing into position to attract'the thermostatic element and hold the switch closed while the thermostat is heated, and energizing circuits for the two electromagnetic devices, both of'said circuits including the switch and being opened and closed thereby.

2. In combination with a main circuit, a normally closed circuit-breaker in this circuit, and an electromagnetic device adapted to open the circuit-breaker and thereby break the main circuit, the main circuit including a branch shunted around the circuit-breaker, and a high-resistance signal device in said branch circuit, a thermostatic-switch assembly comprising an electricheating element, a thermostatic element positioned in close proximity to the heating element, a casing intimately enclosing the heating and thermostatic elements to form a closed heating chamber about these elements so as to expedite the transfer of heat therebetween and minimize the heat losses from the thermostat, a switch mounted in the casing and adapted to be closed by the thermostat when heated, electric terminals for the heating element and switch carried by the casing, the heating element being lid connected in the main circuit, an electromagnetic device mounted on the casing and having an armature projecting through a wall of the easing into position to attract the thermostatic element and hold the switch closed while the thermostat is heated, and energizing circuits for the two electromagnetic devices, both of said circuits in== cluding the switch and being opened and closed thereby.

3. In combination with a main circuit, a nor= mally closed circuit-breaker in this circuit, and. an electromagnetic device adapted to open the circuit-breaker and thereby break the main circuit, a thermostatic-switch asernbly comprising a casing enclosing a shallow heating chamber, a heating element mounted within this chamber, a thermostatic bar anchored at one end in a wall of the casing and projecting into the chamber in proximity to the heating element, a movable switch contact carried by the free end portion of the bar, a second switch contact mounted in one wall of the casing in position to be engaged by the movable contact when the bar is heated, and terminals mounted in the casing and connected respectively with the ends of the heating element, the fixed end of the bar, and the fixed switch contact, the heating element being connected in the main circuit, an electromagnetic device mounted on the casing and having an armature projecting through a wall of the casing into position to attract the .bar and hold the switch closed while the bar is heated, and energizing circuits for the two elecaocaeoe tromagnetic devices, both of said circuits including the switch and being opened and closed thereby.-

4. In combination with a main circuit, a normally closed circuit-breaker in this circuit, and an electromagnetic device adapted to open the circuit-breaker and thereby break the main circuit, the main circuit including a branch shunted around the circuit-breaker, and a high-resistance signal device in said branch circuit, a thermostatic-switch assembly comprising a casing enclosing a shallow heating chamber, a heating element mounted within this chamber, a thermostatic bar anchored at one end in a wall of the casing and projecting into the chamber in proximity to the heating element, a movable switch contact carried by the free end portion of the bar, a second switch contact mounted in one wall of the casing in position to be engaged by the movable contact when the bar is heated, and terminals mounted in the casing and connected respectively with the ends of the heating element, the fixed end of the bar, and the fixed switch contact, the heating element being connected in the main circuit, an electromagnetic device mounted on the casing and having an armature projecting through a wall of the casing into position to attract the bar and hold the switch closed while the bar is heated, and

energizing circuits for the two electromagnetic,

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