US2218797A - Electric circuit breaker - Google Patents

Description

Oct. 22, 1940. 1 UNEE ET AL 2,215,797

ELECTRIC CIRCUIT BREAKER Filed DGC. 22, 1939 Fig.1. 56

Inven tors: Lee on 21rd J. Lin ole,

Torild Aficlersen, b /e a/MA Their Attorfiey.

Patented Oct. 22, 1940 PATENT OFFIQE ELECTRIC CIRCUIT BREAKER Leonard J. Linde, Drexel Hill, and Torild Andersen, Yeadon, Pa assignors to General Electric Company, a corporation of New York Application December 22, 199, Serial No. 310,602

v 17 Claims. Our invention relates to electric circuit breakers and more particularly to improvements in electric circuit breakers or the gas blast type.

It is an object of our invention to provide an,

improved circuit breaker of the above type which has a high interrupting capacity and at the same time is-compact, durable and reliable in operation.

It is another object of our invention to provide an improved pneumatic operating mechanism for controlling the movement of the relatively mov able contacts of the breaker.

It is a further object of our invention to provide an improved means, coordinated with the contact actuating means, for controlling the admission of a gas blast to the arc gap formed upon separation of the contacts.

It is still another object of our invention to provide a circuit breaker of the fluid blast type including improved means for controlling the admission of the fluid blast to the arc chamber during both contact opening and contact closing operations.

Further objects and advantages of our invention will become apparent as the following description proceeds, reference being had to the accompanying drawing in which Fig. 1 is a partial elevational view in section of an electric circuit breaker embodying our invention: Fig. 2 isa plan view taken along the line 2-2 of Fig. 1; Fig. 3 is an'enlarged elevational view of the arrangement shown in Fig. 1 for operating the blast valve; and

Fig. 4 is an enlarged elevational view, partially in section, of a detail of the pneumatic operating system.

In the drawing we have shown our invention as embodied'in a three-phase circuit breaker in which the parts of the breaker are mounted in an enclosed metal framework to form a unit of the type that may readily be installed in a cubicle of metal-clad switch gear of the type now in extenslve use. A fixed contact l and a movable contact II are provided for each phase of the breaker and are arranged to separate within an interrupting unit comprising an insulating structure illustrated generally by the numeral l2. The fixed and movable contacts I0 and H are supported in insulated relation by insulating bushings l3 and the conductors l4 associated therewith. The insulating structure I 2 defines an arc chamber in which the arc is drawn when the contacts are separated-and also includes a plurality of barriers l5 which extend divergently from the arc chamber and form a plurality of passages into which the arc is driven and interrupted under the action of a gas blast from conduit it. An electric circuit breaker embodying interrupt- "ing units of this type is more fully described and claimed in the copending application of Prince et al., Serial No. 303,126, filed November 6, 1939, and assigned to the same assignee as the present application. I

A tank I! mounted at one end of the breaker structure provides a source of compressed air which is supplied to the interrupting units i2 of each of the phases through a conduit l8 under the control of a blast valve i9 which is normally biased to closed position by a spring Isa. The

conduit i8 is connected to the individual supply v conduits M5 by a manifold 20.

In accordance with the present invention an improved pneumatic operating mechanism is provided for moving the contact ll into and out of engagement with fixed contact H], which is capable of maintaining the desired speed of contact separation and which'also provides suitable cushioning at the end of the opening stroke so as to prevent destructive stresses from occurring in the movable parts of the breaker. As illustrated in Figs. 1 and 2, the movable contact ll of each phase is connected to a crankshaft 2i by means of insulating arms 22 which are secured to a flange 23 welded to the crankshaft. The crankshaft is rotatably supported from the breaker framework by suitable brackets 24. Thoconnection between the lower end of the insulating arm and the movable contact is accomplished through a pin and slot connection with a cros s-head 25 secured to the movable contact and slidably mounted on guide rods 26. It is ap arent that oscillation of the crankshaft will be effective to reciprocate the movable contact II and" move it into and out of engagement with fixed con-tact l0. As illustrated in the drawing, oscillation of the crankshaft is accomplished by means of a pair of operating pistons 21 and 28 which are connected to the crankshaft by means of piston rods 29 and 30. Two pairs of spaced flanges 3| and 32 secured to the crankshaft 2i form cranks to which the piston rods 29 and 30 are operatively connected by means of crank pins 33. The spaced flanges 3| are specially constructed to cooperate with a pivoted latch assembly illustrated generally by numeral 34 to control the operation of the blast valve l 9 in accordance with the position of the crankshaft 2|. This feature of the invention will be described more in detail at a later point in the specification.

The pneumatic operating system for pistons 21 and 28 which are mounted in cylinders 35 and 35, respectively, will now be described. The pistons are operated by means of compressed air supplied to the cylinders and 35 through a conduit 31 under the control of a diverter valve illustrated generally by numeral 38. The valve may be of any desired construction and in the particular embodiment illustrated comprises a cylindrical casing 35 in which a double-ended piston member is slidably mounted. The piston is biased to central position by suitable springs 4|. Conduit 31 communicates at one end with the tank I1 and at the other end with the central portion of the valve casing 35. Conduits 42 and 43 communicate at one end with the opening end of cylinders 35 and 35, respectively, and at the other end with the interior of the casing 35 at a point spaced axially of casing 39 from conduit 31. A conduit 44 communicates with the opposite end of cylinder 35 and with the interior of the casing at a point on the opposite side of conduit 31 from the conduits 42 and 43. The piston member 45 of the valve may be shifted from one extreme position to the other by any suitable means such as a solenoid (not shown). When the piston member 40, as shown in Fig. 2, is moved to its uppermost position the conduit 31 is placed in communication with the conduits 42 and 43 so that air is admitted to the opening end of the cylinders 35 and 35 to move the pistons 21 and 25 to the right resulting in the separation of the contacts of the breaker. With the valve piston 40 in this position the conduit 44 i placed in communication with the atmosphere through the openings 45 in the lower end of the valve casing 39. Similar openings 45 are provided at the upper end of valve casing 33. The area of these openings 45 and 45 is suflicient to allow the free escape of air from the cylinders. 4

In accordance with one feature of the present invention, the opening movement of the circuit breaker is retarded by introducing air on the closing side of the piston 21 in cylinder 35 through a conduit 41 communicating at one end with the blast manifold 25, and at the other end with the closing end of the cylinder 35. The pressure in the manifold I5 is considerably less than the pressure in the tank I1 and therefore provides a desirable source of lower pressure air for retarding the opening movement of the contacts. As clearly shown in Fig. 4, conduit 41 is connected to the closing end of cylinder 35 by an elbow 43 in which a check valve 49 is provided. The check valve is normally biased to closed position by a spring 50 and is provided with a plurality of small openings 5| to provide for the gradual escape of air from the closing side of the piston as the breaker completes the opening movement of the contacts. If cushioning of the movin parts during contact closing is desired similar apertured check valves may be provided in conduits 42 and 43 to permit free flow of actuating fluid to the pistons 21 and 25for opening and gradual escape of fluid during closing.

The arrangement just described has proved very satisfactory for pneumatically operating the movable contacts of the breaker. The working surface of both pistons is available for moving the contacts to open circuit position and insures adequate separation of the movable contacts. The blast manifold has been found to be a very satisfactory source of air at a lower pressure for retarding the opening movement of the contacts. The use of one side of one of the pistons only for moving the contacts to closed position has been found to be entirely adequate. The double piston operating mechanism makes it possible to provide for fast speed of separation and cushioning of the movable parts with a'very compact mechanism.

In accordance with an important feature of the present invention the blast valve I5 is operated in accordance with the position of the crankshaft 2| to admit a blast of air to the interrupting unit l2 during both opening and closing of the contacts. The valve I3 is provided with a horizontally extending valve stem 52 which is supported in a suitable bearing 53 formed in the conduit I5, and by a depending guide arm 54. As previously stated, the blast valve is operated in accordance with the position of the crankshaft 2| by a pivoted assembly 34. The assembly 34 includes a pair of arms which are pivotally mounted on opposite sides of a supporting block 55. A pad 51' between the two arms 55 forms a bearing surface which engages the free end of the valve rod 52. A reenforcing member 53 extends between the spaced arms 55 and is provided with a recess for .the reception of a coiled spring' 55a which engages the lower surface of the supporting block 55 and biases the pivoted assembly against the end of the valve stem 52. A pin 53 extending between the spaced arms 55 supports a pivoted latching arm 50 and a roller 5|. The latching arm 55 is provided with an extension 52 which engages an adjustable stop 53. A spring 54 biases the latching member 55 against the stop. The spaced flange 3|, between which the piston rod 25 of piston 21 is connected, are also provided with arm'portions 55 between which a roller 55 is mounted. As shown in Figs. 1 and 2 the roller 55 forms a stop or thrust member and ages the end of the latching arm 50 in the closed circuit position of the breaker. One of the arms 55 is provided with an oflset cam portion 51' which cooperates with the roller 5| on the pivoted assembly 34 to open the blast valve during closing movement of the contacts.

The features and advantages characterizing the circuitbreaker construction just described will become more apparent from a consideration of the operation thereof which will now be described. It, with the parts of the circuit breaker in the position shown in Figs. 1 and 2, piston 45 of control valve is moved to its uppermost position either bymanual operation or in response to an abnormal circuit condition, com-' pressed air will be admitted to the opening side of pistons 21 and 25 through conduit 31, valve casing 35 and conduits 42 and 43. As pistons 21 and 28 move to the right the crankshaft 2| will be rotated in counterclockwise direction as viewed in Fig. 1 and the movable contacts II will move to the right away from fixed contacts I5. As best shown in Fig. 1, the pivoted assembly 34 is latched to the crankshaft 2| by means of latch arm 53 and the roller 55 when the breaker is in closed position. As the crankshaft 2| rotates to separate contacts l0 and H, the pivoted assembly moves in a clockwise direction and results in an opening of the blast valve I5. Air flows from the tank I1 through conduit 5, manifold 25 and conduits I I5 to the individual interrupting units |2 until at a certain point in the separating movement of the contacts the roller 55 slips from the latching arm 50 and allows the pivoted assembly to swing in a counterclockwise direction under the action of the biasing spring |3a of the valve l3. It is apparent that the portion of the separating movement of the contacts .during which air is admitted to the interrupting units may be controlled by properly proportioning the parts of the pivoted assembly 34 and cooperating roller 86 and its supporting arms 65.

As soon as air is admitted to the blast manifold l9 air under pressure is conducted therefrom to the closing side of piston 21 through conduit 41 to retard the opening movement of the contact and reduce the shock to the moving parts of the breaker as they reach the end of the opening stroke. Since the air from the manifold acts upon only one piston and is initially at a lower .pressure than air on the opening side of the pistons 21 and 28, it is readily possible to get the desired cushioning efiect without retarding the speed of separation of the contacts to an undesirable extent, particularly at the beginning of the opening stroke. The relative positions of theparts of the pivoted assembly 34 and the cooperating parts carried by the crankshaft 2| when the breaker is in open circuit position are illustrated in Fi 3.

The breaker is closed by moving the control valve member to its lowermost position from that indicated in Fig. 2. This movement of the valve member 40 places the closing side of piston 28 in communication with the ,tank I! through conduits 3'I-and 44. Piston 21 is not utilized for closing the contacts of the breaker. The offset cam portion 61 on one of the supporting arms 65 carried by the crankshaft is arranged to engage the roller SI of the pivoted assembly to open the blast valve IQ for a brief interval just prior to the closing of the contacts. The length of time that the blast valve is open during closing of the breaker contact varies with the type of service to which the breaker is applied. The air blast during the closing movement of the contacts protects them from the action of the arc established upon circuit closing and also clears the interior of the interrupting unit of gases which may linger there from the prior circuit interrupting operation. If the breaker is apt to be subjected to repeated closures within short intervals it may be desirable to lengthen the blast during closing to cool the contacts and more effectively clear the interrupting unit of hot gases. It is apparent that the duration of the blast of air during closing movement of the contacts inay be readily varied by changing the length of cam portion 61. It is also seen that with the present construction the length of time during which the blast valve is open during contact separation is independent of the period during which the valve is open during the contact closing operation. This feature of the arrangement disclosed by applicants isvery desirable inasmuch as it makes possible the most emcient use of the compressed air. The broad idea of admitting a blast of fluid to the arc chamber during circuit interrupting operation of the breaker for a period of time which is independent of the period during .which the blast of fluid is admitted to the arc chamber during circuit closing operation, is not our invention and is embodied in a circuit breaker control system disclosed and claimed in the copend ing application of Thumin et al., Serial No.

317,564, filed February 6, 1940, and assigned to the same assignee as the present invention.

From the foregoing description it is seen that applicants have devised an improved pneumatic operating mechanism for electric circuit breakers which is coordinated with an improved arrangement for operating the blast valve during both circuit opening and closing movements of the breaker. The structure disclosed by applicants incorporates many desirable-features for air blast circuit breaker operation and at the same time is so compact that the entire breaker structure and operating mechanism is readily incorporated in a unit which may be placed in a metal-clad cubicle designed for oil breakers of similar rating.

While we have shown and described a particular embodiment of our invention, it will be apparent to those skilled in the art that many modifications thereof may be made Without departing from our invention, and we intend in the appended claims to cover all modifications falling within the true scope and spirit of our invention.

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

1. An electric circuit breaker of the fluid blast type comprising relatively movable contacts, an

operating mechanism for moving said contacts to open and closed circuit positions, and means including a plurality of pistons for controlling said operating mechanism, means for supplying fluid under pressure to one side of each of said pistons for moving said contacts to open circuit position, means for supplying fluid under pressure to the opposite side of one of said pistons during opening movement thereof to reduce the speed-of separation of said contacts, and means for supplying fluid to the opposite side of the other of said pistons for moving said contacts to closed circuit position.

2. An electric circuit breaker of the fluid blast type comprising relatively movable contacts, an operating mechanism for moving said contacts to open and closed circuit positions, and means including a plurality of pistons for controlling said operating mechanism, means for supplying fluid under pressure to one side of each of said pistons for moving said contacts to open circuit position, means responsive to movement of said operating mechanism for admitting fluid at a lower pressure to the opposite side of one of said pistons to reduce the speed of separation of said contacts, and means for supplying fluid to the opposite side of the other of said pistons for moving said contacts to closed circuit position.

3. An electric circuit breaker of the fluid blast type comprising relatively movable contacts, an operating mechanism for moving said contacts to open and closed circuit positions, and means including a plurality of pistons for controlling said operating mechanism, means for supplying fluid under pressure to one side of each of said pistons for moving said contacts to open position, means for supplying fluid under pressure to the opposite side of one of said pistons during opening movement of said contacts, and valve means constructed and arranged to allow fluid to flow freely to said other side of said piston to precharge the cylinder associated therewith for dashpot action during the remainder of the opening stroke of said piston and to permit the gradual escape of fluid from, said opposite side of said one piston during the remainder of the opening stroke of said" piston to provide the desired cushioning of the moving partsof said breaker.

4. An electric circuit breaker of the gas blast type com rising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source of gas under pressure, and an operating mechanism for moving said contacts to open and closed circuit positions comprising an operating member, a plurality of driving pistons for moving said operating member, means for supplying gas under pressure to one side of each of said pistons for moving said operating member in one direction to separate said relatively movable contacts, valve means for controlling the flow of arc extinguishing gas from said source to. said are chamber and operable in response to movement of said-operating member in said one direction, and means connected with the low pressure side of said valve means for supplying gas under premu're to the opposite side of one 01' said pistons to retard the opening movement of said contacts.

5. An electric circuit breaker oi the fluid blast type comprising means defining an. arc chamber, relatively movable contacts separable to draw an arcin said chamber, a source of fluid under pressure for supplying arc extinguishing fluid to said are chamber, an operating mechanism for said relatively movable contacts comprising an opersaid breaker for admitting an arc extinguishing blast of fluid to said are chamber, and means connected to the low pressure side of said valve means for supplying fluid under pressure to the Opposite sideoi said driving piston to decrease I the speed of separation of said contacts.

6. An electric circuit breaker cfthe gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, means for supplying a gas blast to said chamber, a valve for controlling the flow of gas to said chamber, an operating mechanism for moving said contacts including an operating member, a plurality of pistons for operating said member, means for supplying fluid under pressure to one side of each of said pistons for moving said contacts to open circuit position, meam for supplying fluid to the closing side of one of said pistons from the low pressure side of said blast valve during opening movement oi said contacts to retard the separation of said contacts, and a pivoted assembly interposed between said blast valve and said operating member and latched thereto for a portion oi the opening movement 01 said contacts to retain said blast valve in open position ior a predetermined period during the opening movement oi said contacts.

7. An electric circuit breaker of the mild blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source of fluid under pressure for supplying arc extinguishing fluid to said are chamber, an operating member for moving said relatively movable contacts comprising an operating member, a plurality of pistons for controlling the operation of said member, means for supplying fluid under pressure to one side of said pistons for moving said member in a direction to separate said contacts, valve means operable in response to movement of said operating member in said one direction to admit an arc extinguishing blast of fluid to saidarc chamber, means connected to the low pressure side of said blast valve for supplying fluid under pressure to the opposite side or one of said driving pistons-to decrease the speed oi separation of said contacts, and means for opening said blast .valveduring closing movement of said :movable contacts to admit a gas blast to said are chamber -for a period 01' timeduring the closing movement of assembly interposed between said operating means and said valve means for causing operation oi said valve means to open position for periods of independent length during both open-- ing and closing of said contacts.

9. An electric circuit breaker of the gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source of gas under pressure for supplying a gas blast to said are chamber, a valve for controlling the flow oi fluid from said source to said are chamber, operating means ior operating said contacts to open and closed circuit positions, and means responsive to the operation, of said operating means for operating said valve to admit ,a blast of gas to said are chamber during at least a portion of both opening and closing movement of said contacts,

said last mentioned means being efiective to maintain said valve open for a period of time and a portion of the contact travel during opening movement of said contacts which is independent 0! the period oi time and the portion of contact travel during which said valve is open during .closing movement of said contacts.

10. An electric circuit breaker oi the gas blast type comprising means deflning an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source or gas under pressure for supplying a gas blast to said arc chamber, valve means for controlling the flow of gas from said source to said are chamber, means for operating said contacts to open and closed circuit positions, and means for operating said valve means in accordance with the position of said relatively movable contacts to admit a blast at gas to said are chamber during both opening and closing movements 01' said contacts, said last mentioned means being constructed and arranged to open said blast valve for a period or time during the opening movement oi said contacts which is independent of the period oi time that said blast valve is open during closing movement oi said contacts.

11. An electric circuit breaker oi the fluid blast said latch arm being latched to said operating means vtor a predetermined portion 01' the movement of said operating means in the direction to separate said contacts, and-means carried by said operating means for engaging said roller for a predetermined portion of the movement of said operating means in a direction to close said contacts.

12. An electric circuit 555;; ot the fluid blast type comprising means defining an arc chamber,

relatively movable contacts separable to draw an means including a pivoted latch arm-ands rol-ler, i

are in said chamber, a source of fluid under pressure connected with said arc chamber, a valve for controlling the flow of fluid from said source to said are chamber, operating'means for moving said contacts to open and closed circuit positions, and means including a pivoted member for moving said valve to open position, said pivoted member being latched to said operating means and movable therewith for a predetermined portion of the opening movement of said contacts, and means carried by said operating means for engaging said pivotedmember when said operating means is moved in a direction to close said'contacts to open said blast valve for a predetermined time during the closing movement 01' said contacts.

13. An electric circuit breaker of the gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source of fluid under pressure for supplying la gas blast to said chamber, a rotatable operating member for moving said contacts to open and closed circuit positions, valve means for controlling the flow of gas to said arc chamber, said last mentioned means being latched to said rotatable operating memher and movable thereby to open said valve means for a predetermined portion of the movement oi. said operating member in a direction to separate said contacts.

14. An electric circuit breaker of the gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a source of gas under pressure for supplying a gas blast to said chamber, a rotatable operating member for moving said contacts to open and closed circuit positions, valve means for controlling the flow of. gas from said source to said are chamber in accordance with the position of said contacts, said last mentioned means comprising an assembly pivoted to a fixed support and including a pair of spaced pivotally mounted arms between which a pivoted latching arm and a roller are mounted, a stop member carried by said rotatable operating member for engaging said latch arm during a predetermined portion of the movement of said operating member in a direction to separate said contacts to 'admit a gas blast to said are chamber, and means carried by said operating member for engaging the roller of said pivoted assembly during a portion of the movement of said operating member in a direction toclose said contacts to admit a gas blast to said are a chamber during closing movement of said con- 15. An electric circuit breaker of the gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc in said chamber, a'source of gas under pressure connected with said are chamber, a rotatable operating member for moving said contacts to open and closed circuit positions, a blast valve forwcontrolling the flow of gas from said source to said are chamber in response to movement of said operating member, means controlling the operation of said blast valve comprising a member pivoted to a fixed support and engaging a portion of said blast valve, a latch arm pivoted on said first pivoted member and having a portion engaging a stop on said rotatable opera/ting member and eifective .to open said blast valve for a predetermined portion of the movement of said rotatable member in a direction to separate said relatively movable contacts, and means for limiting the pivotal movement of said latch to cause said latch to become disengaged from said stop at a predetermined point inthe opening operation of said breaker.

16. An electric circuit breaker of the gas blast type comprising relatively movable contacts separable to draw an arc, means for eiiecting operation of said contacts to open and closed positions, valve means for controlling the supply of arc extinguishing gas to said contacts, and means including a pivoted assembly operable in response to operation of said first mentioned means for operating said valve means to open. position during circuit interrupting and circuit closing operations of said breaker, the period of time during a which said valve means is open during circuit interrupting operation of said breaker being independent of the period of time during which said valve means is open during circuit closing operation of said breaker.

17. An electric circuit breaker of the gas blast type comprising means defining an arc chamber, relatively movable contacts separable to draw an arc insaid chamber, a source of gas under pressure for supplying a gas blast to said chamber, operating means for moving said contacts to open and closed circuit positions, valve means for controlling the flow of gas to said are chamber, latching means and means associated with said operating means cooperating with said latching means to positively drive said valve means for a predetermined portion of the movement of said operating means in a direction to separate said contacts to open said valve means for a predetermined portion of the move-' ment of said cperating means.

LEONARD J. LIN'DE. TORILD ANDERSEN.

Images