US2926288A - Electrical protective apparatus - Google Patents

Description

Feb. 23, 1960 B. DOUVAN 2,926,288

ELECTRICAL PROTECTIVE APPARATUS Filed June 1, 1954 2 Sheets-Sheet 1 IN VEN T 0R.

Boris Douvon BY ATTORNEYS Feb, 23, 1960 B. DOUVAN 2,926,288

ELECTRICAL PROTECTIVE APPARATUS Filed June 1, 1954 2 Sheets-Sheet 2 JNVENTOR: 12 Boris Douvon BY 134 fiVMQ-n; M

ATTORNEYS United States Patent ELECTRICAL PROTECTIVE APPARATUS Boris Douvan, Bayonne, N.J., assignor of one-half to George J. Kupchik, New York, NY.

Application June 1, 1954, Serial No. 433,465 3 Claims. (Cl. 317-23) The present invention relates to electrical protective apparatus and more particularly to self-reclosing circuit breakers for overload protection.

It is an object of the present invention to provide acircuit breaker which is fully automatic, and which will reclose itself without any manual intervention whenever the fault or overload condition which caused the tripping is eliminated, or in other words, when the impedance of the load circuit is sufficiently high to preclude the occurrence of an overload condition, and in which the power consumption is substantially zero while the breaker is in its tripped condition.

Another object of the invention is the provision of an automatic self-reclosing circuit breaker of this character in which the danger of sparking during tripping is minimized.

Other objects will become apparent upon reading the following description and consideration of the accompanying drawings forming a part hereof.

Referring to the drawings:

Fig. 1 is a circuit diagram illustrating one embodiment of the invention;

Fig. 2 is a circuit diagram of a modification ofthe embodiment of the invention illustrated in Fig. 1;

Fig. 3 is an axial section through a screw plug circuit breaker constructed for operation in accordance with the circuit diagram of Fig. 2;

Fig. 4 is a cross-section taken on line IV-IV of Fig. 3;

Fig. 5 is a detail view showing certain parts in section taken on line VV of Fig. 4;

Fig. 6 shows a detail of the circuit breaker illustrated in Fig. 3 separately in a perspective View; and

Fig. 7 is a circuit diagram showing a variation of the circuits illustrated in Fig. 2.

Throughout the various figures, the same reference numerals are employed to denote corresponding circuit elements in the several circuits, respectively.

Referring now to the drawings and first to Fig. 1, the reference numeral 10 denotes a load connected to a neutral line 11 and energized from a line wire 12 through a circuit breaker constructed in accordance with the invention and designated generally by the reference nu-. meral 13.

The circuit breaker 13 comprises a series trip coil 14 and a pair of load interrupting contacts 15 which are normally bridged by movable contacts 16 to maintain a low impedance main circuit through circuit breaker 13 for normal energization of the load 10.

The movable contacts 16 are mounted on a crosspiece 17 of a vertical plungerrod 18 urged upward by a helical tension spring 19 and carrying at its upper end a magnetizable trip plunger 20. The trip plunger 20 extends into the solenoid trip coil 14 to be urged downwardly thereby against the yielding action of tension spring 19 when trip coil 14 is energized.

When the current in the circuit of load 10 exceeds a predetermined overload value, the trip coil 14 pulls the trip plunger 20 with the rod 18 and its crosspiece 17 and movable contacts 16 downwardly. This opens the main circuit at contacts 15 and closes stationary contacts 21 of a supervisory or holding circuit.

The vertical plunger rod 18 carries at its lower end a contact 21 is connected on the one hand to the load 10 and, on the other hand, to one end of reset coil 35, the other end of which is connected to neutral line 11.

When an overload current flows in the circuit of load 5 10, trip coil 14 opens the main circuit at contacts 15,

as described above. Latch member 29 moves downwardly and is engaged by latch member 30 which locks; rod 18 in its downward position, holding interrupting contacts 15 open and contacts 21 closed. Current flows through the capacitor 34, which may have an impedance value of, for instance, 100 ohms, and the circuit of load 10, thereby producing a voltage drop in the load circuit. The reset coil is connected in multiple with the load 10 as described above. When the load circuit impedance rises to a suitable value, as by removal of a short circuit,

then the voltage drop in the load circuit becomes suflicient to cause reset coil 35 to draw plunger 31 and rod 32 to the right, thereby disengaging latch members 30 and 29 and permitting rod 18 to rise under the action of Just 'as in Fig. 5, the trip plunger 20 projects into trip spring 19 and to reclose the main circuit at contacts 15.

In the embodiment shown in Fig. 2, the vertical rod 18 carries at its opposite ends two plungers, namely, a trip plunger 20 and a resetting plunger 36, respectively.

coil 14 which receives current from the energizing line 12 in a main circuit including a conductor 37 connecting energizing line 12 to one end of the trip coil 14, a con-: ductor 38 connecting the other end of trip coil 14 to a stationary interrupting contact 39, a movable contact 40 carried by a cross-member 41 pivotally connected near.

spark-suppressing action of capacitor 34. The resetting plunger 36 at the lower end of rod 18 cooperates with a resetting coil 46 having one end connected to a stationary contact 47 and the other end to the neutral line 11. The resetting coil 46 tends to restore the rod 18 to its upper position shown in Fig. 2 whenever it is connected to the load 10 through movable contact 40 in its lower position and stationary contact 47 and the impedance of the load circuit exceeds a predetermined value.

Figs. 3, 4, 5 and 6 illustrate the actual construction of a screw-in plug circuit breaker designed for operation. in accordance with the circuit diagram of Fig. 2. The

r circuit breaker here shown comprises a housing 48 of insulating material provided with an integral screw-- threaded portion 49 of reduced diameter which in turn is surrounded by a sleeve 50 of conducting metal con formed to the surface of the screw thread. The screw 4 threaded portion can be screwed into a standard fuse re' Patented Feb. 23, 1960 A capacitor 34 is In this arrange-. ment, the danger of sparking on opening of overload contacts 39, 40 of the load circuit, is minimized by the.

ceptacle where it will be connected to the ungrounded side of the usual load circuit. At its lower end the housing portion 49 projects beyond the sleeve 50 and tapers to a central point where it carries a conducting central terminal button 51 for cooperation with a corresponding terminal of the energizing line 12. Seated in the lower end of the screw-threaded plug portion 49 is a solenoid trip coil 52 havingmounted thereon a circuit breaker switch generally designated by the reference nu.- meral 53. Specifically, the switch 53 comprises a bracket 54 (see Fig. 6) including a generally U-shaped base plate 55 resting on the upper surface of coil 52, a stirrupshaped element 56 supported above the base plate 55 by means of a vertical arm 57 in a plane substantially parallel to that of the plate and a second vertical arm 58 pro jecting upwardly from one leg of the base plate 55. A

a rotary shaft 59 extends and is rotatably mounted between the ends of the stirrup member 56. Near one end thereoi the shaft 59 is provided with a flat-surfaced portion 60, for instance, of rectangular cross-section, which cooperates with an upstanding flat leaf spring 61 (see Fig. mounted on the base plate 55 of bracket 54. Near its opposite end the rotary shaft 59 carries a radially proj'ecting contact arm 62 adapted to engage selectively either a stationary contact 63 secured with insulation to the vertical arm 58 of bracket 54 or with a stationary contact 64 mounted on the base plate 55 of bracket 54. Due to the cooperation between the flat-surfaced portion 60 of shaft 5? and the leaf spring 61, the switch is always snapped to one or the other of these two positions. Between its ends the rotary shaft 59 is provided with a radially projecting actuating finger 65 which extends into a slot 66 of a vertical rod 67 of insulating material. The rod 67 projects from the lower threaded casing portion 49 through an insulating partition plate 68 into the upper part of casing 48 and carries at its upper end a resetting plunger 69 and'at its lower end a trip plunger 70, shown in Fig. 3 as projecting partially into trip coil 52. In Fig. 3 the upper solenoid plunger 69'is shown as being located within a resetting solenoid coil 71 arranged in the casing 48. An annular capacitor 72 is disposed peripherally on the inside of casing 48. The circuit connections are as follows:

Central terminal button 51 is connected by a conductor 73 to one end of solenoid coil 52, the other end of which is connected to the stationary contact 63 by means of conductor 74. Contact arm 62 is connected by conductor 75 to the screw threaded metal sleeve 50.

Terminal 51 is further connected by means of conductor 76 to one end of the capacitor 72, the other end of which is connected by means of conductor 77 to the metal sleeve 50. Finally, the stationary contact 64 is connected by means of conductor 78 to one end of the reset solenoid coil 71, the other end of which is connected by means of an insulated conductor 79 passing through the wall of casingAS to a spade terminal 80 adapted to be connected to the neutral wire, e.g. at a suitable screw terminal of the bus bar of a fuse box. The casing is closed by an insulating cover-81.

The device operates as follows:

Normally, a main circuit is closed from terminal 51 over conductor 73 through trip coil 52, conductor 74, forked contact 63, contact arm 62, conductor 75 and metal casing 50 to the load circuit. When the current in the load circuit rises above a predetermined maximum, the trip coil 52 becomes sufliciently energized to attract the trip plunger 76, thereby moving rod 67 downwardly. This. rotates shaft 59 in clockwise direction against the force of leaf spring 61, thus breaking the normal load circuit at contact 63. The load is then energized at a greatly reduced voltage from terminal 51 throughconductor 76, capacitor 72, conductor '77 sleeve 50 at a point corresponding to point '43 in the diagram of Fig. 2. After movement of shaft 59 through an angle of about '45", spring 61 passes the dead enter point and acts to snap shaft 59 to its second position in which, contact arm 62 engages the stationary contact 64. This establishes a control circuit from metal sleeve 50, parallel to the load circuit, to the neutral line through conductor 75, contact arm 62, stationary contact 64, conductor 78, resetting coil 71, conductor 79 and spade terminal 80.

As long as the impedance of the circuit containing the load 10 remains below a predetermined value, the resetting coil 71 remains inactive, but whenever the overload condition is eliminated and the impedance of the load circuit again exceeds the predetermined value, reset coil 71 is energized and acts upon resetting plunger 69 to restore rod 67 upwardly to its original position shown in Fig. 3, thus re-establishing the normal load circuit through the series trip coil 52.

In Fig. 7 trip coil 14 is replaced by a bi-metallic thermo element 82 and resetting coil 46 is replaced by a bi-metallic thermo element 83. Otherwise, the circuit is substantially identical with that shown in Fig. 2. Thus, on occurrence of an overload, the tripping thermo element 82 is deformed downwardly as shown in dot and dash lines and moves the snap switch member 41 from its upper position to its lower position, thus establishing a circuit through the heating coil of the resetting thermo element 83. As long as the impedance of the load remains below the predetermined value, the resetting thermo element 83 is inactive, but when the impedance of the load circuit is restored to normal, thermo element 83 becomes deformed upwardly and restores the snap switch to its original position. 7

It will be seen that this arrangement requires a time interval sufiicient for the heating of the thermo element 83 before reclosure of the contacts of the energizing circuit. 7

Various modifications and adaptations of the invention will be apparent to those skilled in the art. It will therefore be understood that the invention is not limited to the particular embodiments described and illustrated above except as defined in the following claims.

What is claimed is:

1. Overload protection apparatus adapted for connection between an energizing circuit and a load circuit, including a substantially cylindrical insulating housing having a screw-threaded conducting sleeve adapted to be screwed into a fuse receptacle for connection to the load circuit and a central terminal button for connection to the energizing circuit connection in said receptacle, a trip coil and a re-setting coil 'coaxially arranged in said housing, a plunger rod axially slidable in said housing and carrying at its opposite ends a trip plunger and a re-setting plunger, respectively, said plunger cooperating respectively with said coils, a rotatable switch shaft having two contiguous flat-surfaced portions disposed at an angle to from said switch shaft, two fixed contacts, one in a normal circuit and the other in a control circuit, respectively, arranged for engagement by said contact arm in opposite terminal positions of said switch shaft, a current-limiting and spark-suppressing capacitor having the form of a cylindrical sleeve lining part of said housing, and a cable passing from the re-setting coil to the outside of thehousing and terminating in a terminal member adapted to be connected to abus bar, the normal circuit extending from the central terminal through the trip coil, one of theffixed contacts and the contact arm to the conducting sleeve,

the capacitor'being permanently connected between the central terminal and the conducting sleeve'in shunt with the normal circuit and the control Circuit extending from the conducting sleeve through the contact arm, the second fixed contact, the re-setting coil and the cable to the terminal member.

2. Overload protection apparatus adapted for connection between an energizing circuit and a load circuit, including a substantially cylindrical insulating housing having a screw-threaded conducting sleeve adapted to be screwed into a fuse receptacle for connection to the load circuit and a central terminal button for connection to the energizing circuit connections, respectively, in said receptacle, a trip coil and a resetting coil coaxially arranged in said housing, a plunger rod axially slidable in said housing and carrying at its opposite ends a trip plunger and a resetting plunger, respectively, said plungers cooperating respectively with said coils, a two-position snap switch in said housing, said switch being actuable by said rod between a normal position and a tripped position, a current-limiting and spark-suppressing capacitor disposed in said housing, a flexible conductor extending exteriorly of said housing and having a free end adapted for connection to the neutral terminal associated with said fuse receptacle, a normal circuit extending between said sleeve and said terminal button through said trip coil and said switch when said switch is in its normal condition, and a normally deenergized control circuit extending from said flexible conductor through the series combination of said resetting coil and said capacitor to said terminal button when said switch is in its tripped position, said capacitor being connected in shunt with respect to said switch, said resetting coil being operatively energized to actuate said switch from its tripped position to its normal position when the impedance of said load circuit exceeds a predetermined minimum value.

3. Apparatus according to claim 2, wherein said capacitor is of annular shape and is arranged coaxially with respect to said coils.

References Cited in the file of this patent UNITED STATES PATENTS 656,324 Holmes Aug. 21, 1900 1,644,525 Hoyler Oct. 4, 1927 1,644,527 Hoyler Oct. 4, 1927 1,643,4l5 Moore Sept. 27, 1927 1,689,836 Legg Oct. 30, 1928 1,733,817 Moranor Oct. 29, 1929 1,748,177 Hoyler Feb. 25, 1930 1,750,895 Heghausen Mar. 18, 1930 1,760,081 Parks May 27, 1930 2,008,174 Frank July 16, 1935 2,575,740 Warrington Nov. 20, 1951 2,620,382 Van Ryan Dec. 2, 1952 2,675,506 Erown et al. Apr. 13, 1954 FOREIGN PATENTS 676,476 France Nov. 28, 1929

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