US2241810A - Circuit breaker - Google Patents

Description

May 13, 1941- R. c. DlcKlNsoN 2,241Q8l0 CIRCIT BREAKER Filed May 3l, 1938 2 Sheets-Sheet 1 WITNEssEs: lNvENToR i ZZ Cla/60.75022 WM" i Patented May 13, 1941 CIRCUIT BREAKEB Robert C. Dickinson, Wilkinsburg, Pa., assignor to Westinghouse Electric an Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 31, 1938, Serial No. 210,971

(Cl. v20o-446) l Claims.

'Ihe invention relates to circuit breakers in general and more particularly to contact means or systems for air circuit breakers of the highvoltage type.

Heretofore, it has been the usual practice to provide high-voltage air circuit breakers with a contact means for each pole comprising a movable contact arm pivoted at its lower end and carrying the main and arcing movable contacts at its free end for engaging the stationary main and arcing contacts. 'I'he pivotal mounting of the contact arm made it necessary-to provide a flexible shunt conductor of full load carrying capacity for connecting the movable contacts to the lower terminal of the breaker.v Flexibility of the contact means for predetermining the contact pressure was obtained by pivotally mounting the stationary contact and biasing it towards the movable contact by means of a spring. 'Ihe pivotal mounting of the stationary contact required the provision of a second ilexible shunt. conductor also of full load carrying capacity for connecting the stationary contact to the upper terminal of the breaker.

A contact system of the type 'described above. while fairly satisfactory as to operation, has a number of disadvantages. 'Ihel number of moving parts of the system are excessive and the current carrying exible shunts are large and subject to deterioration. In general, the system is complicated and expensive to manufacture.

An. object of the invention is the provision of a circuit breaker embodying an improved contact system which does not require any full load carrying capacity flexible shunts for connectin the contacts to the terminals of the breaker.

Another object of -the invention is the provision of an improved contact system for an air circuit breaker as described inthe preceding paragraph in which the stationary contacts are rigidly mounted and the movable contact assemblage carries a means for providing the required contact pressure.

Another object of the invention is the provision of an improved contact system as described above in which the movable contact is caused to roll on the stationary contact during circuit interruption so that onlythe arcing tips of the contacts are in engagement immediately before separation of the contacts.

Another object of the invention is the provision of an improved contact system, as described in the preceding objects, which is simple, has relatively few moving parts. and which is inexpensive to manufacture.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of a. preferred embodiment thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a fragmentary side elevational view, partly in section, of a circuit breaker embodying a contact system constructed in accordance with the invention, the contacts being shown in the closed position;

Fig. 2 is a view similar to Fig. l showing the contact system in the partly open position immediately following a tripping operation of the breaker;

Fig. 3 is a view'similar to Fig. 1 showing the contact system in the full open position; and

Fig. 4 is an enlarged sectional view taken substantially along the line IV-IV of Fig. l showing the connection of the operating rod to the switch arm and the mounting of the contact bridging bar.

"In the accompanying drawings, only those parts of the circuit breaker are shown which are considered necessary for a complete understanding of the invention.

Referring to the drawings, the reference numeral B designates a portion of a fabricated steel frame which serves to support the circuit breaker. A pair of insulating bushings 1 and 0 of strong insulating material extend through spaced openings provided therefor in theiframe 5, and are rigidly secured to the frame by means of the flanges Il carried by the bushings and the bolts I3. The bushings 1 and 9 serve to support a pair of spaced rigid terminal conductors Il and i1 which extend through the bushings and are insulated from the frame' thereby. These spaced terminal conductors i5 and I1 form the two terminals of the breaker.

A pair of stationary contact members i9 and 2| are rigidly mounted on the ends of the terminal conductors il and I1, and these contact members are adapted to be connected in the circuit controlled by the breaker by means of suitable terminal connections (not shown) at the opposite ends of the terminal members i5 and I1. The upper contact member Il which forms the stationary arcing contact of the breaker is provided with an arcing tip 2l of suitable arc resisting material. The lower contact member Il has a yoke-shaped extension it rigidly The invention secured thereto which serves to pivotally support a movable contact assemblage indicated generally at 21.

The movable contact assemblage comprises a U-shaped switch member 29 which is pivotally mounted on the extension 25 of the contact member 2|, and a bridging contact arm 3| of conducting material which is connected intermediate its ends to the switch member 29. The switch member 29 has a pair of spaced parallel side walls 33 connected by a transverse bight portion 35 which is provided with a semi-circular extension 31 having an inwardly extending edge 39. The extension 31 serves as a seat for one end of a spring means which will hereinafter be described. The switch member 29 is pivotally mounted on the extension 25 of the contact member 2| by means of a pivot pin 4| which extends through aligned openings provided therefor in the legs oi.' the extension 25 and in the lower ends of the side walls 33 oi' the switch member 29.

An operating rod 43 oi.' strong insulating material has one of its ends pivotally connected to the switch member 29 by a yoke 45 (Fig. 4) secured to the end of the rod. The yoke 45 extends between and engages the inner ends of the sidel walls 33 of the switch member 29 and is pivotally connected to the switch member by means of a pivot pin 41. which extends through aligned openings in the legs of the yoke 45 and in the side walls of the switch member 29. The opposite end or the operating rod 43 is pivotally connected to a crank arm 49 secured to a rotatable operating shaft The shaft 5| has cylindrical ends which are rotatably mounted in a pair of bearings 53 carried by the frame 5, and a square portion 55 on which the crank arm 49 is mounted.

An operating crank 51 is also secured to the square portion 55 of the shaft 5|, and this crank is adapted to be connected to a suitable operating mechanism (not shown) for moving the switch member 29 to open and to closed circuit positions. The operating mechanism is not an important part of the present invention, and any standard mechanism of the type embodying an opening spring i'or biasing the switch member to open position, a closing means for moving the switch member to closed position, and a suitable tripping means for causing opening movement of the switch member may be used. One suitable form of operating mechanism which may be connected to the operating crank 51 for moving the switch member 29 to open and closed position is that disclosed in Patent No. 1,807,020, issued to R. C. Van Sickle. May 26, 1931, and assigned to the assignee of the present invention.

The contact arm 3| which is of conducting material serves to bridge the stationary contact members 9 and 2| in the closed position of the breaker to establish an electrical circuit therebetween, and is movable to open and closed circuit position b v the opening and closing movement of th-e switch member 29. The contact arm 3| is provided at its upper end with a movable arcing contact 59 for engaging the stationary arcing contact member I9. and at its opposite end with a movable contact 9| for engaging the stationary contact member 2|. The movable arcing contact 59 is provided with an arcing tip 93 oi' arc resisting material for cooperating with the arcing tip 23 of the contact member I9 during opening of the breaker.

The contact arm 3| is disposed between the legs oi' the yoke 45 and also between the side walls 33 ofthe switch member 29, and is connected to the switch member by a pin-and-slot connection comprising the pivot pin 41 and a slot 95 formed in the arm 3|, whichengages the pin 41. A pair of washers 91 (Fig. 4) are interposed between the sides of the contact arm 3| and the legs of the yoke 45 to prevent lateral displacement of the contact arm 3| during operation of the switch y member.

A spring means 99, comprising a pair of concentric coil springs 1| and 13, is interposed between the semi-circular extension 31 of the switch arm 29 and the contact arm 3|. 'I'he right-hand end of the spring means 99 seats against the semi-circular extension 31 of the switch arm 29 and the left-hand end engages a seat 15 secured to the contact arm 3| at a point intermediate the connecting pin 41 and the arcing contact 59. Lateral displacement of the springs 1| and 13 is prevented by a pair of studs 11 and 19 carried by the switch member 29 and the contact arm 3|, respectively. The spring means 99 serves to provide a predetermined contact pressure between the movable contacts 59 and 8| and their cooperating stationary contact members I9 and 2| when the breaker is in closed circuit position, and also causes the contact arm 3| to irst separate from the lower stationary contact member 2| and simultaneously rock on the arcing contact member 29 during the initial portion of the opening movement of the switch member 29, so that only the arcing tips 23 and 93 remain in engagement prior to movement of the contact arm 3| to open circuit position.

An adiusting screw 9| is threaded through the lower end of the bight portion 35 of the switch member 29 for engaging the lower end oi the contact arm 3| to limit the rocking movement of the arm as it rocks on the arcing contact member I9 during the initial portion of the opening movement of the switch member 29, as shown in Fig.2.

A relatively small flexible shunt conductor 93 electrically connects the lower stationary contact member 2| to the contact arm 3| to maintain the circuit between the lower contact member 2| and the contact arm 3| during circuit interruption. The shunt conductor 83 need only be of relatively small cross-section sufiicient to carry the current momentarily while the breaker is opening the circuit, since when the breakerI is closed the current flows directly from the stationary contact member 2| to the contact arm 3| through the movable contact 9|. The purpose oi' the shunt conductor 93 is to shunt the current around the contacts 2| and 9| when these Ycontacts separate during opening of the breaker until the circuit is nally interrupted by opening of the arcing contacts 23 and 53. Thus the shunt 93 prevents any arc between the contacts 2| and 9| during opening or closing of the breaker.

By providing two solid stationary contacts connected respectively to the terminals of the breaker, and a solid bridging contact which is moved in the manner disclosing, the necessity of additional resiliently mounted arcing contacts and full load carrying capacity shunts has been eliminated. The shunt 93 which connects the lower stationary contact 2| to the movable bridg- 'ing contact 33 can be of relatively small size or cross-section as it only carries the current momentarilly during separation of the upper contacts, the contacts 2| and 9| serving to carry full load current when the breaker is closed. The purpose of the flexible shunt conductor 93 is ited by the adjustable stop screw 2|.

to prevent arcing from taking piace between the contacts 2| and il, and the purpose of the con-` type may be associated with the arcing contacts is and I9 of the breaker i'or extinguishing the arc drawn between these contacts during circuit interruption. One form oi arc extinguishing structure which may be associated with the arcing contacts of the breaker is that disclosed and claimed in Patent No. 2,080,611, issued to l". B. Johnson. May 18, 1937, and assigned to the assignee of the present invention.

'I'he operation of the circuit breaker is briey as follows: When the breaker is in closed circuit position, as shown in Fig. i, the latch oi' the 0D- erating mechanism (not shown) releasabiy holds the operating rod l2 and the switch member 22 in closed position, as shown in Fig. 1, against the force exerted by the breaker opening spring and the spring means 89, which is held in compres-` sion. In this position it will be noted that the connecting pin 41 is disposed intermediate the ends of the slot 66 since the switch member 2s has been moved slightly beyond the position necessary to cause the contact arm 2l vto bridge the stationary contact members Il and 2|. This position of the switch member 20 causes the spring I9 to be compressed and the reactive force of the springs '|I and 18 of the spring means 2l acting on the contact arm 2| provides a predetermined contact pressure of the contacts l2 and Il on the stationary contact members Il and 2|.

When the breaker is tripped, the operating rod 42 is moved towards the right by the force exerted on the operating crank l1 by the opening spring of the breaker mechanism. 'Ihe opening movement oi' the operating rod l2 and the reactive force of the spring means 2l causes the contact arm 2| to rock on the upper stationary contact member is to the position shown in Fig. 2. in which the movable contact il is separated from the lower stationary contact member 2|, and only the arcing tips 22 and I2 oi the upper pair of contacts remain in engagement. This rocking movement oi' the contact arm 2| is lim- 'I'he continued opening movement of the operating rod Il causes the contact arm 2| to be moved by the switch member 29 to the open circuit position shown in Fig. 3. Since the arcing tips 22 and l2 are the last portions of, the contact system to separate during opening of the breaker, the arc formed during circuit interruption is drawn only between these arcing tips.

In closing the breaker, substantially the reverse action takes place. I'he operating rod C2 is moved towards the left by the operating mechanism oi' the breaker to cause the switch member 2s to be rotated in a counter-clockwise direction about the pivot pin li. During the movement of the switch member 2l toward the circuit closin! position. tbe contact arm 2| is moved with the, switch member but remains in the canted Dosition relative to the switch arm. as shown in Fig. f

ary contact member |9 in a clockwise direction until the movable contact 6| engages the lower stationary contact member 2|. A slight further closing movement of the operating rod 4l before it is latched in closed position by the operating mechanism compresses the spring means 69 to provide a predetermined contact pressure between both sets oi' movable and stationary contacts of the circuit breaker.

It will thus be seen that the invention provides a simple and improved contact system for a circuit breaker which eliminates the necessity of any full-load carrying capacity shunts, and in which the means for providing contact pressure is entirely carried by the movable contact assemblage.

The current path through the breaker when the breaker is in closed position passes entirely through rigid conducting members and-rigidly mounted contacts, thus producing a much more eilicient and desirable contact system than the contact systems of the prior art devices which embodied resilient conducting members and contacts.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be .understood that various changes in the structural details thereof may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable construction permissible in the light of the prior art.

I claim as my in vention:

1. In a circuit breaker, a pair of rigidly mounted stationary contacts, a movable contact member of rigid conducting material for bridging said contacts, means for moving said member to first cause said member to separate from one of said contacts and then to separate from the other of said contacts, and means electrically connecting said contact member to the stationary contact from which it first separates providing a low resistance electrical connection therebetween.

2. In a circuit breaker, a pair of spaced rigidly mounted stationary contacts of rigid conducting material, a movable contact bar oi' rigid conducting material ior bridging said contacts to establish a circuit therebetween, means for moving said contact bar to open and to closed circuit position, said means being operable during an opening operation to cause said contact bar to ilrst separate from one o! said contacts and then to separate from the other of said contacts), and a exible shunt conductor connecting said liar to the contact from which it n rst separates providing a low resistance electrical connection therebetween.

3. In a circuit breaker, a pair of rigidly mounted stationary contacts, a movable contact arm for bridging said contacts to establish a circuit therebetween, means i'or moving said contact arm to open and to closed circuit position. said means being operable during an opening operation to cause said arm to ilrst separate from one of said contacts and simultaneously rock on the other of said contacts so as to engage only the tip portion thereof, and then to separate from said last mentioned contact, and a conductor electrically connecting said arm to the contact from which it first separates providing a low resistance electrical connection therebetween.

4. In a circuit breaker, a pair ot rigidly mounted stationary butt contacts, a movable contact arm for bridging said contacts to estab- .lish a circuit therebetween, means for moving said contact arm to open and to closed circuit position, said means being operable during an opening operation to cause said arm to rst separate from one of said contacts and simultaneously rock on the other of said contacts so as to engage only the tip portion thereof, and then to separate from said last mentioned contact, andu a flexible shunt conductor connecting said arm to the contact from which it ilrst separates providing a low resistance electrical connection therebetween, said means for moving said arm including yielding means for providing a predetermined contact pressure of said arm on said contacts.

5. In a circuit breaker, a pair of rigidly mounted stationary butt contacts, means for establishing and interrupting a circuit between said contacts comprising a movable switch arm, a movable bar of rigid conducting material for bridging said 'contacts movable with said arm and movable relative thereto, yielding means interposed between said bar and said switch arm for providing a predetermined contact pressure between said bar and said contacts when the breaker is closed and for causing said bar to first separate from one of said contacts and then to separate from the other contact during opening movement ofv said switch arm, and a shunt conductor connecting said bar tothe stationary contact from which it first separates providing a low resistance electrical connection therebetween.

6. In a .circuit breaker, a pair of rigidly mounted stationary butt contacts, a movable contact arm for bridging said contacts, means for moving said arm to opexrland to closed circuit position comprising a movable switch arm, a spring interposed between said contact arm and said switch arm for providing a predetermined contact pressure between said contact arm and said contacts when the breaker is closed and for causing said contact arm to separate from one of said contacts and simultaneously rock on the other contact so as to engage only the tip portion thereof before separating from said last mentioned contact during opening movement o! said switch arm; and a flexible shunt conductor connecting said contact arm to the stationary contact from which it first separates providing a low resistance electrical connection therebetween.

7. In a circuit breaker, a pair of rigidly mounted stationary butt contacts, a movable contact arm of rigid conducting material for bridging said contacts to establish a circuit therebetween, a movable switch arm for moving said contact arm to open and to closed circuit position, said contact arm being connected intermediate its ends to said switch arm by a pin and slot connection, a spring interposed between said contact arm and said switch arm for providing a predetermined contact pressure between said contact arm and said contacts when the breaker is closed and for causing said contact arm to first separate from one of said contacts and simulta-v shunt conductor connecting said contact arm the stationary contact from which it rst separates, providing a low resistance electrical connection therebetween.

8. In a circuit breaker, a pair of spaced terminal members, a pair of spaced rigid stationary contacts connected respectively to said terminal members, one of said stationary contacts having an arcing contact portion, a movable contact arm of rigid material for bridging said stationary contacts to complete a circuit between said ter-v minal members, and means for moving said contact arm to cause said arm to ilrst separate from one of said contacts and then to separate from the contact having the arcing contact portion, and conducting means of low electrical resistance connecting said arm to said one contact.

9. In a circuit breaker, a pair of spaced terminals, a pair of spaced rigidly mounted stationary contacts connected respectively to said terminals, one of said contacts having an arcing contact portion. a movable contact arm for bridging said contacts to establish a circuit between said terminals, said arm rigidly carrying a pair of contacts for engaging said stationary contacts, one of the movable contacts carried by said arm having an arcing contact portion for cooperating with the arcing contact portion o! theA stationary contact, means for moving said arm to open and to closed circuit position. said means being operable during an opening operation to first cause one of the movable contacts to separate from its stationary contact and to cause only the arcing contact portions of the other contacts to engage, and then to cause the other movable contact having the arcing contact portion to separate from the stationary contact having the arcing contact portion, yielding means for providing a predetermined pressure engagement of said contacts when the breaker is closed, and means providing a low resistance electrical connection between said contact arm and the stationary contact from which it ilrst separates for causing an arc to be drawn only between arcing contact portions of the stationary and movable contacts so equipped, during a circuit opening operation.

10. In a circuit breaker, a pair of spaced terminals, a pair of rigidly mounted stationary butt contacts connected respectively to said terminals, one of said contacts having a rigid arcing tip. movable contact means comprising a contact arm of rigid conducting material tor bridging said contacts to complete a circuit between said terminals, said arm rigidly carrying a pair of movable butt contacts for engaging said stationary contacts, means for moving said arm to first cause one of said movable contacts to separate from its cooperating stationary contact and the other movable contact to simultaneously rock on its cooperating stationary contact which has the arcing tip so that only the tip portions oi said last mentioned contacts engage, and to then cause movement of both of said contacts to an open circuit position away from said stationary contacts, and conducting means electrically connecting said contact arm to the stationary contact from which it first separates providing a low resistance electrical connection therebetween.

ROBERT C. DICKIN SON.

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