US2328318A - Circuit breaker contact - Google Patents

Description

Aug. 31, 1943. J. D. WOOD CIRCUIT BREAKER CONTACT Filed April 5, 1942 INVENTOR z/sa x/ d flaaa Au, ATTORNEY Patented Aug. 31, 1943 CIRCUIT BREAKER CGNTACT Joseph D. Wood, Bethlehem, assigncr to Roller- Smith York Company, a. corporation OfNEW Application April 3, 1942, Serial No. 437,503

'3 Claims.

This invention relates to improved contacts for circuitbreakers and the like which may be manually or otherwise operated and is applicable to many various forms and types of circuit breakers.

The main object of the invention is to provide an improved construction of the arcing contacts at which the circuit is finally broken and wherein the electrodynamic' action will tend to maintain the contacts closed and also tend to iorce the are away from the adjoining parts of the switch. Another object is to accomplish this purpose with contacts ofa comparatively simple form which may be conveniently and economically manufactured. Another object is to prolong the durability or life of the contact parts. Another object is to-reduce the amount of care and attention required for maintaining them in proper operable condition. Other objects and advantages will be understood from the following description and accompanying drawing illustrating preferred embodimentsthereof.

Fig. l is a side view of a conventional form of circuit breaker showing one form of the improved contact incorporated therewith; Fig.2 is an enlarged sectional View of the contact; Fig. 3 is a rear view of the contact; and Fig. 4 is a side View of a modified form of contact.

The prior so-called inverted type of contact has the advantage that the electrodynamic forces tend to force the contacts together which aids in maintaining good electrical connection between them. However, it has the objection that when the contacts are separated, the arc is blown inwardly toward other portions of the circuit breaker instead of being blown outwardly and away from the circuit breaker parts whereby the arc may be more efiectively extinguished. Thus the so-called inverted type although desirable for maintaining good contact engagement, is objectionable with reference to extinguishment of the arc and protection of the adjoining parts. In the prior type of switch having non-inverted arcing contacts, the opposite conditions occurbecause the electrodynamic forces tend to separate the contacts. This not only decreases the contact pressure but results in the electrodynamic forces separating the contacts before the mov able element of the breaker has moved sufliciently to insure the are being formed at the most desirable portions of the contacts for the formation of the arc. On the other hand, the non-inverted type of contacts ha the advantage of tending to force the arc outwardly and away from the adjoining portionsof the breaker. The present invention obtains the advantages over each of these prior forms and likewise overcomes their objections.

In Fig. 1, a supporting panel loot insulating material is shown which supports a pair of forwardly extending brackets 2 011 the face thereof. A movable conducting member in theform of a pair of contact arm 3 are pivotally mounted on the pin 4 carried by the brackets Between the contact arms and at their inner portions is carried a conducting contact plate 5 engaged by the spring pressed contacts 6 which are in turn electrically connected with and mounted upon the leads 7 and la respectively. These leads are connected to the circuit controlled by the breaker. A flexible lead 3 is connected between the contact plate 5 and the lead id for maintaining good electrical connectionbetween the lead in and the contact arms when the breaker is opened. The breaker may be closed or opened by any means desired and in the present case manual means is indicated. This is in the form of a pair of plates E3 pivotally mounted on a pin 9a supported by the brackets 2. The arms 9 carry between them a roller 9bwhich isadapted to engage a roller carried between the arms 3. An insulated handle Hi issecured to the arms 9 for forcing the contact arms by a downward movement of the handle to the closed position by a common form of toggle and locking action. When the handle it is moved upwardly the contact arms are free to move outwardly for interrupting the circuit.

The contact arms carry at their inner upper ends an arcing contact H which engages the arcing contact carried by a fixed conducting member or support I2 electrically connected with and supported by the lead 7 and extending upwardly or outwardly therefrom. This conducting metal member is provided with an upwardly or outwardly extending arcing horn 12a and with a cylindrical opening. Within this cylindrical opening is fitted a rotatable conducting cylinder it having fixed thereto and downwardly extending therefrom, or inwardly with refer ence to the breaker, a conducting metal plate it. This plate isbent on itself and then extends upwardly, or outwardly with reference to the breaker, in a portion Ma and terminates in an upwardly or outwardly extending horn Mb. The

portions 14 and Ma with their inner connected ends form a conducting element of general U form. On the front face of the side portion M0. is secured a plate 15 of arc-resisting metal which engages the, arcing contact I! carriedby the contact arms. This improved form of contact is more clearly shown in Figs. 2 and 3. The conducting plate side portion I4 is in good electrical connection through the cylinder I3 with the conducting member I2 which forms a pivotal support for the outer end of the portion 14 of the conducting element. A sheet of insulation 26 is introduced between the side portion or plate I4 and the side portion l4a of the U-shaped conducting elernent. An insulated screw bolt I1 is passed through the rear portion of the plate and through the insulation I6 and has a threaded engagement with the front portion Ma of this U- shaped contact finger for the purpose of holding hese parts firmly together. The arcing contact I5 is brazed or otherwise secured to the conducting portion I M. As shown in Fig. l, a spring I8 is supported by the bracket I2 and engages the head of the insulated bolt I1, being thereby insulated from the conductor I4. This spring forces the conductor l4 outwardly for assisting in maintaining good contact between the contact surfaces. The lower portion of the cylindrical opening is cut away to permit a rotary movement of the cylinder 13 and the pivoted conducting element, the outer face IZb of this opening serving as a stop to limit the outward movement of the element.

When the breaker is brought to the closed position shown in Fig. l by moving the handle l downwardly, the path of the current is from the lead la to the lower contacts 6 and plate and then to the upper contacts 6 and lead '1. In the opening movement of the breaker, the first eifect is to open the connection between the plate 5 and upper contacts 6. This causes the current to pass through a path from the lead la upwardly through the contact arms 3 of the breaker, through the arcing contacts II and i5 and then downwardly or inwardly through conducting portion Ma and then upwardly or outwardly through the conducting plate M to the cylinder l3 and downwardly or inwardly through the conducting member I2 to lead '1. As the contact arms move outwardly, the spring pressed conducting element moves outwardly on its pivot formed by the cylinder I3 following the contact face II and maintaining engagement therewith. During this action the contact area between the surfaces H and I 5' moves downwardly on ,the face of metal contact I5 and the current then passes inwardly to the lower portion of the contact i5 and then upwardly or outwardly through the conductor 25 to the cylinder I3 and downwardly or inwardly through the conducting member I2 to the lead 1. This forms a loop in which the current passes in opposite directions in the two sides of the loop formed by the conductor I2 and the conductor l4 creating an electrodynamic force against the conductor M which serves to force it towards the contact I I and thereby maintain good electrical contact therewith. This electrodynamic pressure is maintainedas long as any current passes through the breaker giving the advantage of the inverted contact in this respect.

When the contact I I is about to separate from the contact IS, the conductor M has engaged the stop formed by the surface I 22) and the parts are then in the first dotted line position shown.

he arc between the contacts II and I5 is now about to form and at this time the current passes upwardly or outwardly through the conducting member 3 to the arcing contact I2 and arcing contact l5 and then through the contact 15 and side portion Ma of the U shaped conducting element to the side portion I4. This creates a magnetic field localized at the arc tending to blow the arc outwardly from the current path and outwardly along the arcing contacts. This secures the advantage of non-inverted contacts in forcing the are away from the conducting parts of the breaker and outwardly. When the contacts separate, the arc is driven outwardly more and more as the separation continues and in the second dotted line position the arc will extend from the contact I l to the upper portion of the contact I5 and will be driven up the horn I 4b to the horn I 2a. The arcing is finally interrupted before the contact arm 3 reaches the third dotted line position which is the final open position.

In Fig. 4 another form of arcing contact is shown which is supported by the downw rdly or inwardly extending fixed conducting member 20 which is electrically connected with and supported by the lead 1 of the former figures. A metal casting II is secured to the conductor 29 as by the bolt 2 I a and extends upwardly and forwardly with a downwardly extending hook Elb forming a cylindrical bearing Me. A conducting block 22 which may preferably be in the form of a series of plates mounted side by side, has its upper cylindrical end journaled in the bearing 2Ic. This block or series of plates extends downwardly and supports from its lower end an upwardly extending horn 23 or a plurality of horns side by side which pass in front of the hook 2Ib. A layer of insulation 24 i introduced between the main portion of the horn or horns 23 and the block or plates 22 but this may sometimes be omitted and the space left as an air space. The front lower portion of the horn or horns is faced with a strip or strips 25 of arc resisting metal. The conductor 22 or series of conducting plates is forced outwardly by one or more springs 23 seated between the casting 2! and the conductor 22 and insulated from the conductor 22. The arcing contact H of the Contact arm engages the contact 25 in the same manner as shown in Fig. l where it engages the contact I5. The action is similar to that described with reference to Fig. 1 when the breaker is opened, the electrodynamic forces serving to maintain good electrical contact between the surfaces of the engaging contacts up to the time of the separation of the contact II from the contact 25. The outward movement of the conductor 22 is limited by its engaging the inside of the hook Zlb and when the contacts separate, the electrodynamic action forces the arc upwardly and outwardly along the contact 25 and to the upper portion of the horn 23. The final interruption of the arc takes place bet-ween the contact II of the contact arm and the upper portion of the horn 23 before the contact arm arrives at its fully open position.

Although preferred embodiments of the invention have been described various modifications may be made without departing from the scope thereof.

I claim:

1. A circuit breaker comprising a movable con ducting member, a fixed conducting member, one of said members having an arcing contact surface, a conducting element of general U form having one side portion of the U extending inwardly with reference to the breaker and pivotally mounted at its end on the other of said members and the other side portion of the U extending outwardly with reference to the breaker and having an arcing contact surface engaged by said first named arcing contact'surface when the breaker is closed, the first named side portion forming a loop circuit with the member on which it is pivotally mounted for electrodynamically forcing said conducting element against said first named arcing surface when the breaker is closed and during its opening movement, and the second named side portion forming a circuit through said engaging contact surfaces for e1ectrodynamically forcing the arc outwardly along the contact surfaces upon the separation of said contacting surfaces.

2. A circuit breaker comprising a movable conducting member, a fixed conducting member, one of said members having an arcing contact surface, a conducting element of general U form having one side portion of the U extending inwardly with reference to the breaker and pivotally mounted at its end on the other of said members and the other side portion of the u extending outwardly with reference to the breaker and having an arcing contact surface engaged by said first named arcing contact surface when the breaker is closed, the first named side portion forming a loop circuit with the member on which it is pivotally mounted for electrodynam ically forcing said conducting element against said first named arcing surface when the breaker is closed and during its opening movement, and the second named side portion forming a circuit through said engaging contact surfaces for electrodynarnically forcing the arc outwardly along the contact surfaces upon the separation of said contacting surfaces, said second named side portion having an arcing horn extending outwardly with reference to the breaker from its contact surface.

3. A circuit breaker comprising a movable conducting member, a fixed conducting member, one of said members having an arcing contact surface, a conducting element of general U form having one side portion of the U extending inwardly with reference to the breaker and pivotally mounted at its end on the other of said members and the other side portion of the U extending outwardly with reference to the breaker and having an arcing contact surface engaged by said first named arcing contact surface when the breaker is closed, the first named side portion forming a loop circuit with the member on which it is pivotally mounted for electrodynamically forcing said conducting element against said first named arcing surface when the breaker is closed and during its opening movement, and the sec ond named side portion forming a circuit through said engaging contact surfaces for electrodynamically forcing the arc outwardly along the contact surfaces upon the separation of said con-- tacting surfaces, the said member which pivotally supports the conducting element having an arcing horn extending outwardly with reference to the breaker.

JOSEPH D. WOOD.

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