US2357151A - Circuit breaker - Google Patents

Description

g 29, 1944. F. s. VON HOO-RN CIRCUIT BREAKER Filed April 10, 1943 His Attorney.

Inventor. Fred G. vgn Hoorn Patented Aug. 29, 1944 CIRCUIT BREAKER Fred G. von Hoorn. Nichols, Conn, assignor to General Electric Company, a corporation of New York Application April 10, 1943, Serial No. 482,605

7 Claims. (Cl. 200-416) My invention relates to circuit breakers, more particularly to manually operated thermal current responsive circuit breakers, and has ior its object means for manually holding the circuit breaker in its closed circuit position despite operation of the thermal current responsive means to open the breaker, and also means for shortcircuiting the thermal element.

In carrying out my invention in one form, I provide an auxiliary manually operable member for positively holding the circuit breaker in its closed circuit position, together with switch means operated by the thermostat when the thermostat is heated above a predetermined temperature and after the thermostat has released the switching means for opening movement for short-circuiting the thermostat thereby to prevent damage to the thermostat in the event that the switch is manually held closed when the current through the switch is higher than the maximum continuous current carrying capacity of the circuit breaker.

For a more complete understanding of my invention, reference should be had to the accompanying drawing in which Fig. 1 is a side elevation view with the casing showing the circuit breaker in its normal closed circuit position;

Fig. 2 is a view similar to Fig. 1 but showing the parts in their automatic current responsive open position; Fig. 3 is a view similar to Fig. 1 showing the parts in their manually held closed position with the thermostat short-circuited; Fig. 4 is a view in section taken along the line l4 of Fig. 1 looking in th direction of the arrows; Fig. 5 is a view taken along the line 55 of Fig. 2 looking in the direction of the arrows; while Fig. 6 is an exploded view showing parts of the apparatus.

I have shown my invention in one form as applied to a thermal current responsive manually operated trip-free circuit breaker of the type described and claimed in my Patent 2,184,372, issued on December 26, 1939, which patent is an improvement of my reissue Patent 22,218, issued November 3, 1942, original Patent 2,150,013, is-

sued on March 7, 1939. The device is provided with an electrically insulating casing ill in which is mounted a U-shaped metal support -ll fora floating contact or switch bar l2. The bar has a bearing pin i3 secured to it and extending through it so that its opposite ends are movable and guided in, slots l4 and i5 (Fig. 6) in the U-shaped supporting member ll. One end, as shown the left-hand end, of the floating bar I2 is normally held, as shown in Fig. 1, by a thermal current responsive member, shown .as a bimetallic thermostat I6. By means of a handle I! mounted on a pivot support Ila and bearing on a saddle member I6 carried by the bar, the righthand end of the bar carrying a movable contact is is movable between this closed circuit position of Fig. 1 and the open circuit position of Fig. 2.

The circuit through the circuit breaker may be traced from an external connection screw 20 through a lug 2| to a metal strap 22 extending upward in a shallow groove in one side wall of the casing, thence through an arm 23 on the bar 22 to the thermostat, and downward through the thermostat to a flexible conductor 24 secured to the lower end of the thermostat, thence through the conductor 24 to a point 25 where the end of the conductor is secured to the bar, then through the bar, contact i9 and its associated stationary contact, and lug 26 to th other external contact screw 21.

The upper end of the thermostat is secured, as by welding, to a bent over portion 26 of the arm 23, the thermostat being arranged so that when it flexes upon an increase in temperature, its lower end moves toward the left hand, as seen in the drawing. A screw 29 in the projection 28 bears on a lateral projection 30 on the strap 22 whereby the projection 28 can be adjusted somewhat to change the position, and therefore the current response, of the thermostat.

A helical spring 3| is provided for biasing ,the bar I2 upward against the handle, this spring having its upper end bearing against the righthand end of the saddle member [8 and its lower end bearing on an arm 31a secured to the U-shaped member ll. As shown in Fig. 6, the saddle member has two slots 32 and 33 through which the bar l2 extends, the bar having a slot 34 embracing the upper wall of the slot 32, whereby the saddle member is positioned lengthwise on the bar. The lower end wall 35 is bent closed to secure the bar after the bar has been inserted in the slots in the saddle member.

In the .closed position shown in Fig. l, a projection 36 on the handle has pressed the saddle member downward against the spring 3| until the lower edge of the slot 33 is spaced from the lower edge of the bar. Thus, the spring then applies a force through the saddle member, which acts as a lever with the projection 36 as a fulcrum, to the bar holding it downward against the stationary contact at its right-hand end and the latching projection 31 on the thermostat at its left-hand end. Also in this position the saddle member applies a force to the projection 36 tending to turn the handle counterclockwise thereby to hold the handle in its closed position shown.

In accordance with my present invention, I provide a second manually actuable means for moving the bar to its closed circuit position, as shown in Fig. 3, this means comprisirga button 38 having its upper end extending through the casing of the circuit breaker and its lower end pivotally secured at 39 to the end of the bar. Shoulders 40 are provided on the button which engage the upper wall of the casing and limit the upward opening movement of the bar.

Thus, assuming the circuit breaker in the closed circuit position as shown in Fig. 1, when the thermostat releases the left-hand end of the bar, that end is first moved downward by the force applied by the spring 3| until the saddle turns on the projection 36 to a point where it applies a clockwise torque to the handle, whereupon the handle moves to its open circuit position shown in Fig. 2. During this movement of the handle, the spring forces the right-hand end of the bar and the button an upward until the shoulder 40 is brought to rest against the casing whereupon the'spring 3i applies a clockwise force to the bar, raising its left-hand end to the reset position shown in Fig. 2 ready to be'engaged by the thermostat when the thermostat has cooled. In case the spring 3i fails to raise the left-hand end of the bar, this end may be raised by moving the handle i1 clockwise, the projection 36 engaging a projection 40a on the bar to raise the left-hand end of the bar.

Another feature of my invention is the provision of switching means for short-circuiting the thermostat when the current is greater than a predetermined value, this short-circuit switching means being actuated by the thermostat itself.

As shown, this switching means comprises an arm 4| secured, as by rivets, in electrically con ducting relation to the strap 2! and extending in front of the thermostat, as seen in the drawing, to a position behind or to the left-hand side of the thermostat where it is provided with a downwardly extending switch arm 42 carrying at its end a stationary contact 43 in position to be engaged by a movable contact 44 on the left-hand side of the thermostat near its lower end.

It will be understood that the thermostat will be held closed by means of the button 38 only when the current through the circuit breaker is higher than the normal maximum permissible 43. The engagement of these two contacts, it will be observed, establishes a circuit directly from the conducting strap 22 through the arm 4|, arm 42, and contacts "and 44 to the flexible conducting strip 24 whereby the thermostat itself is shortcircuited. This short-circuiting of the thermostat prevents damage to the thermostat by these heavycurrents.

Of course, when the bar I! is held manually in its closed circuit position for any considerable interval with more than the normal currents flowing in it, the thermostat may 0001 sufiiciently to disengage the contact 44 from the contact 43 whereby the current will again flow through the thermostat. However, in that event, the thermostat will again be heated quickly and will re-engage the contacts to again short-circuit itself.

It is contemplated also that, in some cases at least, the thermostat will short-circuit itself during normal automatic opening of the circuit breaker in response to current, especially when the current is very high. The point in the movement of the thermostat at which it short-circuits itself may be adjusted by adjusting the position of the stationary contact 43 as by bending the arm 42. Thus the contact 43 may be positioned close enough to the thermostat so that the thermostat will short-circuit itself upon a slightcontinued movement of the thermostat toward the left after it has released the bar I 2.

This short-circuiting of the thermostat under automatic opening conditions is caused largely by the inertia of the .trip bar and mechanism in moving far enough to completely open the circuit by establishment of the arc. Thus the contact members remain in the closed circuit position after the thermostat has released the bar for a very short interval of time while the contact members are being accelerated by the spring from their normal closed circuit positions of rest to the positions in which the arc is broken. Consequently, the thermostat receives additional energy from the circuit after the bar is released up to the time the arc is extinguished.

Furthermore, the continued movement of the thermostat to short-circuit itself is due in part to the inherent inertia of the thermostat in bending in correspondence with the temperature to which it is heated.

This short-circuiting of the thermostat protects it against damage from very heavy short-circuit currents during the time that the contact bar and other parts require to open the circuit.

While I have shown a. particular embodiment of my invention, it will be understood, 0! course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended elaimsto cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A circuit breaker comprising a movably mounted contact member, a handle for moving said contact member between closed and open circuit positions, a thermostat normally securing a portion of said contact member during such movement by said handle but releasing said contact member in response to a predetermined current in said contact member for opening movement of said contact member independently of said handle, a second manually operated member operatively connected to said contact member for moving said contact member to said closed circuit position and for holding said contact member in-said closed circuit position when said contact member is released by said thermostat, and switching means for short-circuiting said thermostat operated by said thermostat to short-circuit said thermostat after said thermostat has released said contact member.

2. A circuit braker comprising a contact member, a thermostatic device normally securing pivotally one point of said contact member, electric connections connecting said thermostatic device in circuit with said contact member, a handle for moving said contact member between closed and open circuit positions about said point, a spring for biasing said contact member against said handle and for pivotal movement about said handle to an open circuit position when said point is released by said thermostatic device, a second manual operating means for moving said contact member to a closed circuit position independently of said handle, and electric switching means operated by said thermostatic device to reduce the current in said thermostatic device in response to an excessive current when saidbar is held in its closed circuit position by said second manual operating means.

3. A circuit breaker comprising a floating contact bana thermostat normally securing pivotally one end of said bar, electric connections connecting said thermostat in circuit with said contact member, a handle for moving said bar between closedand open circuit positions about said one end, a spring for biasing said bar against said handle and for pivotal movement about said handle to an open circuit position irrespective of the position in which said handle may be held when said one end is released by said'thermostat, a second manual operating means for moving the other end of said bar to a closed circuit position, and electric switching means for shortcircuiting said thermostat operated by said thermostat to short-circuit said thermostat in response to an excessive current when said bar is held in its closed circuit position by said second manual operating means.

4. A circuit breaker comprising a support, a switch bar, means mounting said switch bar for pivotal movement about an intermediate point and for transverse bodily movement, a movable electric contact on a first end of said bar, a stationary contact on. said support arranged to be engaged by said movable contact, a thermostatic device normally iorming a pivotal support for the other second end of said bar, a handle cooperating with an intermediate portion of said bar, a spring for biasing said bar against said handle, said handle being movable to move said first end 01 said bar into and out of engagement with said stationary contact; said bar when released by said thermostatic' device being moved by said spring about said handle to its open circuit position irrespective of the position in which said handle may be held, a second manual operating member secured to said first end of said bar for moving said first end to its closed circuit position even though said second end is released by said thermostatic device, electrical connections for connecting said thermostatic device in series circuit relation with said bar and said contacts, and switching means operated by said thermostatic device for reducing the current in said thermostatic device in the event of an excessive current when said bar is held in its closed circuit position by said second manual operating memher.

5. A circuit breaker comprising a support providing an enclosure and provided with parallel slots in opposite walls, a switch bar, a pivot pin extending through said bar at an intermediate point thereof and having its ends extending into said slots whereby said switch bar is pivotally movable on said pin and movable bodily upon movement of said pin in said slots, a movable electric contact on a first end of said bar, a stationary contact on said support arranged to be engaged by said movable contact, a thermostat normally forming a pivotal support for the other second end of said bar, a pivoted handle cooperating with an intermediate portion oi said bar, a spring for biasing said bar against said handle, said handle being movable to move said first end of said bar into and out of engagement with said stationary contact, said bar when released by said thermostat being moved by said spring about said handle to its open circuit position irrespective of the position in which said handle may be held, a second manual operating member secured to said first end or said bar out of said enclosure for moving said first end to its closed circuit position even though said second end is released by said thermostat, stop means on said manual operating member for limiting the open circuit position of said first end whereby said second end is moved normally by said spring about said manual member as a pivot to a reset position after automatic opening by said thermostat, electrical connections for connecting said thermostat in series circuit relation with said bar and said contacts, and switching means operated by said thermostat for short-circuiting said thermostat in the event of an excessive current when said bar is held in its closed circuit position by said second manual operating member.

6. A circuit breaker comprising a movably mounted contact member, a manually operated member connected to said contact member for moving said contact member between closed and open circuit positions, means biasing said contact member to an open circuit position independently of said manually operated member when said contact member is held by said manually operated member in said closed circuit position, a latch for holding normally said contact member in said closed circuit position against said bias, actuating means for said latch responsive to the current in said contact member for releasing said contact member upon the occurrence of a predetermined high current therethrough for opening movement independently of said handle, a second manually operated member operatively connected to said contact member for moving said contact member to said closed circuit position irrespective of the position of said first manually operated member and for holding said contact member in said closed circuit position even though said latch is released by said actuating means in response to a predetermined high current, and means operated by'said actuating means in response to an excessive current through said contact member when said contact member is held in its closed circuit position by said second manually operated member for reducing the current in said actuating means.

'7. A circuit breaker comprisin a movably mounted contact member, a handle operatively connected to said contact member for movin said contact member between closed and open circuit positions, means biasing said contact member to an open circuit position independently of'said handle when said contact member is held by said handle in said closed circuit position. a latch for holdin normally said contact member in said closed circuit position against said bias when said handle is in said closed circuit position, a thermostat responsive to the current in said contact member for actuating said latch to release said contact member upon the occurrence of a predetermined hi h current therethrough for opening movement independently of said handle, a second handle operativelv connected to said contact member for moving said contact memberto said closed circuit position irrespective of the position of said first handle and for holding said contact member in said closed circuit position even though said latch is released by said thermostat in response to a predetermined high current,and a normally open switch operated by said thermostat to shortcircult said thermostat in response to an excessive current through said contact member when said 7,

contact member is held in its closed circuit position by said second handle.

FRI) G. von HOORN.

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