US2436190A - Electric circuit breaker - Google Patents

Description

Feb. 17,, 1948.

A. c. BOISSEAU ETAL 2.436,190

ELECTRIC CIRCUIT BREAKER Filed Nov. 7, 1944 2 Sheets-Sheet 1 Fig}.

Insulation 44 5 0 I Inventors:

Alexander C. Boisseau, J 2 9 Rahah E. Sold,

- Patented Feb. 17, 1948 UNITED STATES PATENT OFFICE ELECTRIC cmcurr BREAKER 7 Application November 7, 1944, Serial No. 562,296

8 Claims. (Cl. 200 -82) Our invention relates to electric circuit break ers and more particularly to operating mechanisms for electric circuit breakers of the' fluid operated type. Specifically, our invention is an improvement on the circuit breaker operating system disclosed and claimed in United States Letters Patent 2,315,991, 'I'humin, granted April 6, 1943, and assigned to the same assignee as the present application.

Fluid operated circuit breakers have been used quite extensively within the last several years, particularly since the advent of the air blast circuit breakers. Since an air blast circuit breaker requires a source of air under pressure, it is usualiy advantageous to also utilize this source of air as the source of energy for operating the circuit breaker.

Heretofore, operating mechanisms for fluid p: erated circuit breakers and particularly fluid operated, fluid blast circuit breakers have been very complicated and expensive.

It is an object of the present invention to provide a new and improved operating mechanism for electric circuit breakers.

it is another object of our invention to provide an operating mechanism for electric circuit breakers which is simple and compact and requires only a fraction of the space and material required by the operating mechanisms used heretofore.

It is another object of our invention to provide an operating mechanism for electric circuit breakers which is simple and compact and which furthermore provides all the functions of retarding, accelerating and operating associated apparatus such as switches, blast valves, and the like.

Further objects and advantages of our inven tion will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of our invention, reference may be had to the accompanying drawings in which Fig. 1 is a schematic diagram, partly in section, of an electric circuit breaker and operating mechanism therefor with the circuit breaker shown in the closed circuit position; Fig. 2 is a view similar to Fig. 1 showing the circuit breaker in the open circuit position; Fig. 3 is an elevational view, partly in section, of a commercial embodiment of our invention schematically shown in Figs. 1 and 2 with minor modiflcations; and Fig. 4 is a portion of the embodiment shown in Fig. 3 viewed from the left hand side. I

Although our invention is particularly applicable to polyphase circuit breakers, as will become apparent from the description of Figs. 3 and 4 included hereinafter, we have illustrated our invention schematically in Figs. 1 and 2, as applied to a circuit breaker I, which is illustrated as a single phase circuit breaker of the cross gas blast type. Circuit breaker I. comprises a stationary contact 2 and a movable contact 3 arranged to be operated so as to draw an arc in arc chute 8, Contacts 2 and 3 are arranged to be connected with suitable line terminals schematically shown at 5 and '8, respectively. The fixed contact 2 is provided with spring pressed contact fingers l and longer arcing contact fingers 8, while movable contact 3 is provided with an arcing tip 9 so that when the contacts separate an arc occurs between arcing fingers 8 and arcing tip 9. Immediately after the separation of the contacts one terminal of the arc is transferred by a blast of fluid, such as air, flowing in conduit 1-, from contact fingers 8 to a contact I l which is provided with a tip of arc resistantmetal. The fluid blast from conduit l0 upon opening of the circuit breaker l drives the arc into the arc chute 4 against the edges of a plurality of partitions or baflles i2,

which partitions are transverse to the arc gap and the ends of which extend close to the path of movement of the arcing tip 9 of movable contact 3. The circuit breaker is illustrated by way oi example only order to describe our new and improved operating and control arrangement. This circuit breaker i, briefly described above,

is not our invention but is described and claimed in United States Letters Patent 2,28%,842, granted June 21, 1942, and assigned to the same assignee as the present application.

In view of the fact that we have illustrated ch":- cuit breaker i as a fluid blast circuit breaker of the cross air blast type, it is necessary to provide a source of fluid under pressure which is illustrated at l3. Conduit ID is connected to source I3 through a-blast valve l4 having a reciprocally movable valve member l5 fastened to a suitable valve stem ii. A spring I! normally biases valve member l5 to the closed position indicated in Fig. 1.

Since a source of air or fluid under pressure I3 is necessary for air blast circuit breaker I, it is desirable to utilize this same source of fluid under pressure to produce the energy for operating the circuit breaker to the open and closed positions. In accordance with our invention we have provided a simple and compact fluid operated operating mechanism generally indicated at l8. Operating mechanism l3 includes a fluid motor comprising a circuit breaker opening piston l9 and a circuit breaker closing piston 20 rigidly interconnected by a rack 2|. Piston I3 is reciprocal in a cylinder 22 while piston 20 is reciprocal in cylinder 23. Preferably these cylinders 22 and 23 are arranged as one continuous cylinder with a discontinuous portion so that a pinion 24 fixedly mounted on a rotatable shaft 25 may engage rack 2|. With this arrangement the rectilinear motion of the pistons of the fluid motor is translated into rotary motion of shaft 25.-

Cylinder 22 is connected to source l3 through schematically illustrated circuit breaker opening valve 26 and conduit 21. Similarly, cylinder 23 is connected to source l3 through circuit breaker closing valve 23 also schematically shown, and conduit 29. The circuit breaker opening and closing valves 26 and 23, respectively, may be controlled in any suitable manner well known to those skilled in the art and no further discussion thereof will be included herewith.

In order to provide accurate speed control of the fluid motor including pistons l9 and 20, we have provided another set of pistons 30 and 3| rigidly interconnected by a rack 32, which rack also engages pinion 24. Pistons 30 and 3| are mounted in cylinders 33 and 34, respectively, which like cylinders 22 and 23 are preferably arranged as one continuous cylinder, parallel with the continuous cylinder comprising cylinders 22 and 23. It will be obvious that with this arrangement, whenever pistons 83 and 2d are moved to the left, as viewed in Fig. 1, pistons 30 and. 3| will be moved to the right by virtue of pinion 23, whose teeth engage with both racks 2| and 32.

Pistons 3B and 3| provide a very desirable means for controlling the speed of operation of the operating mechanism is during an operating stroke of the circuit breaker and eliminate the requirement of any separate dashpots or retarding devices as was required in prior art arrangements. Pistons 30 and 3| therefore act as buffers or dashpots to retard the operating mechanism in any desired manner. A suitable spring loaded check valve 35 controls a passageway 36 between cylinders 22 and 33. Similarly, a spring loaded check valve 31 controls a passageway 38 interconnecting cylinders 23 and 34. The size of pas- 'sageways 36 and 38 and the spring loading of check valves 35 and 31 are arranged so as to charge the associated cylinders 33 and 36 during operating strokes of the circuit breaker to give the desired speed control as will be brought out in greater detail hereinafter. In order to improve the speed control, cylinder 33 is provided with a needle valve 39 leading to atmosphere and cylinder 34 is provided with a needle valve as, also lead ing to' atmosphere. Although in Figs. 1 and 2 we have illustrated pistons l3 and 23 as being larger than pistons 33 and 3!, it should be understood that these pistons may all be the same size as shown in Fig. 3 if desired.

From the description of the operating mechanism i8 above it is obvious that the fluid motor produces rotation of shaft 25 and it is obvious that shaft 25 may be connected to one or more sets of relatively movable contacts to produce relative movement between said contacts.

Rigidly fastened to shaft 25 and rotatable therewith is'a crank arm 4|. Preferably the free end of crank arm 4| is pivotally connected as inrollers 45, arranged two on either side of movable contact 3.

It will be observed that link 43 and crank arm 4| are arranged so as to provide a toggle arrangement so that with the circuit breaker in the closed position shown in Fig. 1, this toggle is in an overcenter position so that any force applied to the contacts tending to open the circuit breaker will have no effect, and fluid under pressure must be provided in cylinder 22 in order to rotate crank arm 4| slightly and move the toggle out of its locking position, or other means for rotating crank arm 4| must be provided.

It will be observed that when the circuit breaker is in the open position indicated in Fig. 2, link 43 and crank arm 4| again form an over-center toggle arrangement with the goose-neck 43" fitting around shaft 25. Any force applied to movable contact 3 tending to close the circuit breaker will be inefiective and the breaker is efiectively locked in the open position requiring movement of piston 1 20 to release the locking means. The rotation of shaft 25 from open to closed position is somewhat more than With our improved operating mechanism the blast valve it can readily be operated in response to relative movement of the contacts merely by providing a cam 66 on shaft 25 rotatable with shaft 25. Cam 3G- engages with a roller Elli -mounted on a bell crank 53 pivotally mounted at 69. Bell crank 38 has an extension 48 engageable with blast valve stem It. Upon rotation of haft 25 in a counter-clockwise direction as viewed in Fig. 1, blast valve i3 is opened to provide a blast of fluid under pressure adjacent rela= tively movable contacts 2 and 3 before these contacts separate sufficiently to draw an are therebetween. It should be noted that the lift of the blast valve during the opening stroke occurs while the locking toggle is being released and before force is applied to accelerate moving contact blades, thereby maintaining the force required to open the breaker at a minimum.

It should be understood that cutofi switches and the like can be controlled very simply with our new and improved operating mechanism merely by providing additional cams on shaft 25.

The operation of the arrangement disclosed in Figs. 1 and 2 will be obvious to those skilled in the art in view of the detailed description included above. If the circuit breaker opening valve 26 is opened, fluid under pressure enters cylinder 22 forcing piston is to the left, as viewed in Fig. 1. Since piston i9 is mechanically connected by racks 2i and 32 with piston 3d, piston 30 must move to the right. Bypass 36 permits air to enter in front of piston 33 which acts as a bufier or dashpot. B proper proportioning of the size of bypass 35 and the strength of the spring of spring-loaded check valve 33, the amount of precharging of cylinder 33 can be controlled whereby the motion of piston l9 can be controlled exactly by the pressure acting on piston 33. It is therefore possible to accelerate the operating mechanism at any reasonable rate and then by precharging cylinder 33, bring the mechanism to a stop without damaging or overstressing the parts. When the circuit breaker has attained its of said contacts. the rotary motion of said shaft extending through an angular travel of more than 180 degrees, said arm and link comprising a'toggle which at each limiting position of said shaft is in an overcenter position for holding said one of said relatively movable contacts in the open and the closed positions respectively,

3. In combination with an electric circuit breaker comprising a pair of relatively movable contacts, an operating mechanism for producing relative movement of said contacts comprising a force applying member adapted to have a substantially rectilinear motion, a rotatable shaft, mean-s for translating the rectilinear motion of said force applying member into rotary motion of said shaft, means including an arm on said shaft and a link connected to said arm for translating the rotary motion of said shaft into substantially rectilinear motion of one of said contacts, the rotary motion of said shaft extending through an angulartravel of more than 180 degrees, said arm and link comprising a toggle which at each limiting position of said shaft is in an overcenter position for holding said one of said relatively movable contacts in the open and the closed positions respectively, and means COoperating with said arm and said link for retarding both the rectilinearly and rotatably moving masses.

4. In combination with an electric circuit breaker comprising a pair of relatively movable contacts, a source of fluid under pressure, means center position for holding said one of said relatively movable contacts in the open and the closed positions respectively, the holding eifectof said toggle-being released upon initial movement of said force applying member prior to relative movement of said contacts, a source of fluid under pressure, means including a. blast valve for supplying a blast of fluid under pressure from said source adjacent said relatively movable contacts during a circuit opening operation of said circuit breaker, and means rotatable with said shaft to open said blast valve while the holding effect of said toggle is released preceding relative separation of said contacts.

6. In combination with an electric circuit breaker comprising a pair of relatively movable contacts, a tank containing fluid under pressure, means including a blast valve for supplying a blast of fluid from said tank adjacent said relatively movable contacts during a circuit opening operation, an operating mechanism for producing relative movement of said contacts comprisinga fluid motor connected to said source including a piston, a shaft rotatable in response to movement of said piston means for interconnecting said shaft and one of said contacts, meansfor manually applying a force to rotate said shaft, and means for preventing a manual force from being applied to said shaft unless substantially no fluid under pressure is present in said tank.

including a blast valve for supplying a blast of fluid adjacent said relatively movable contacts, an operating mechanism for producing relative movement of said contacts comprising a force applying member adapted to have a substantially rectilinear motion, a rotatable shaft means for translating the rectilinear motion of said force applying member into rotary motion of said shaft, means for translating the rotary motion of said shaft into substantially rectilinear motion of one of said contacts, the rotary motion of said shaft extending through an angular travel of more than 180 degrees, said last mentioned means comprising a toggle which at each limiting position of said shaft is in an overcenter position for holding said one of said relatively movable contacts in the open and the closed positions respectively, and means rotatable with said shaft to operate said blast valve.

5. In combination with an electric circuit breaker comprising a pairof relatively movable contacts, an operating mechanism for producing relative movement of said contacts comprising a force applying member adapted to have a substantially rectilinear motion, a rotatable shaft, means for translating the rectilinear motion of said force applying member into rotary motion 7. In combination with an electric circuit breaker comprisin a pair of relatively movable contacts, a tank containing fluid under pressure, an operating mechanism for producing relative movement of said contacts comprising a fluid motor connected to said source, means for manof said shaft, means for translating the rotary no motion of said shaft into substantially rectilinear motion of one of said contacts, the rotary motion of said shaft extending through an angular travel of more than 180 degrees, said last mentioned means comprising a toggle which at each limiting position of said shaft is in an overually applying a force to move said contacts, and means for rendering said last mentioned means ineffective to move said contacts unless substantially no fluid under pressure is present in said tank.

8. In combination with an electric circuit breaker comprising a pair of relatively movable contacts, a tank containing a fluid under pressure, an operating mechanism for producing relative movement of said contacts comprising a fluid motor connected tosaid source, means for manually applying a force to produce relative movement of said contacts, a blow-down cock on said tank, and means for rendering said last mentioned means ineffective unless said blowdown cock is in the open position.

ALEXANDER C. BOISSEAU. RALPH E. BOLD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Baker et a1. Nov. 21, 1944

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