US2736295A - Circuit breaker with fluid motor having fluid admission varied during stroke - Google Patents

Description

Feb. 28, 1956 K 2,736,295

CIRCUIT BREAKER WITH FLUID MOTOR HAVING FLUID ADMISSION VARIED DURING STROKE Filed Jan. 23, 1955 SOURCE OF FL U/D UNDER PRESS URE 87 .2 WM, Aw.

A9 5 MONK/1% United States Patent CIRCUIT BREAKER WITH FLUID MOTOR HAVING FLUID ADMISSION VARIED DURING STRQKE Henry L. Peek, Boston, Mass, assignor to Ants-Chalmers Manufacturing Company, Milwaukee, Wis.

Application January 23, 1953, Serial No. 332,877 Claims. (Cl. 121-38) This invention relates to circuit breakers, and more particularly to pneumatically operated high speed circuit breakers.

Circuit breakers for electrical power systems which are designed to interrupt heavy currents usually employ strong springs to operate the arcing contacts between closed and opened positions. These springs are placed under tension by the circuit breaker pneumatic operator when the arcing contacts are closed. The pneumatic operator has a dual function to perform, in circuit breaker operation, namely to return the contacts to their closed position and to reset the circuit breaker tripping mechanism. In closing the contacts the pneumatic operator must overcome the extremely high spring and magnetic forces encountered near the end of its contact closing operation, and to come to rest at the end of its closing stroke Without an excessive amount of kinetic energy which must be absorbed by the circuit breaker structure.

Modern high speed circuit breaker structures are required to open and reclose a power circuit without noticeable power interruption. To accomplish high speed interruption, attempts were made to reduce the Weight of the tripping devices to reduce the kinetic energy resulting from the movement thereof, however, the tripping devices could not stand the force transmitted to it from the contact springs.

In order to achieve rapid contact separation and reengagement, a new and improved arrangement is provided for controlling the closing velocity of oil circuit breakers. Thisarrangement employs a pneumatic operator which is provided with a small air flow during the first part of its contact closing stroke followed by a greatly increased air flow near the end of its closing stroke when the extremely high spring and magnetic forces are encountered. This new and improved arrangement and device makes possible the limitation of final closing velocity of a pneumatically operated circuit breaker to any predetermined value by air flow control.

It is, therefore, one object of the present invention to provide a new and improved control arrangement for controlling the closing velocity of the movable contacts of a circuit breaker.

Another object of this invention is to provide a new and improved control arrangement for limiting the closing velocity of a pneumatically operated circuit breaker to any predetermined value.

A further object of this invention is to provide a new and improved pneumatic operator which controls the closing velocity of an oil circuit breaker.

A still further object of this invention is to provide an improved circuit breaker operating mechanism employing a trip free linkage in which the velocity of a pneumatic operator for closing a circuit breaker is varied during its closing operation 'to any degree by air flow control.

Other objects and advantages of the invention will become apparent from the following description when read in connection with the accompanying drawing, in which: i

Fig. '1 is a diagrammatic view, partly in section, of a circuit breaker operating system embodying the present invention; and

Fig. 2 illustrates a modification of the operating system shown in Fig. 1.

Referring more particularly to the drawing by characters of reference, Fig. 1 illustrates a pneumatic motor 1 of the cylinder and piston type operatively connected by a linkage 2 of the trip free type to a circuit breaker 3.

As diagrammatically shown, the circuit breaker 3 comprises a pair of. stationary contact members 4 and a movable contact member '5. The circuit breaker is biased to open circuit position by means of accelerating spring 6. The movable contact member 5 is supported by a breaker rod 7 which, in turn, is supported by lever 3 pivoted at 9. Lever 8 is connected to bell crank 10 by means of operating rod 11. Bell crank 10 is pivoted at 57 and forms part of linkage 2.

Motor 1 comprises a main casting 12 defining the lateral wall of the operating cylinder of the motor, a top element 13 and a base element 14. Piston 15 of motor 1 is biased downward by any suitable means such as a helical spring 16 of which one end rests against top element 13 while its other end rests against piston 15. Base element 14 defines a passage 83 which is connected to a suitable sources of fluid under pressure (not shown). The flow of fluid under pressure from the source to the cylinder of motor 1 is controlled by a solenoid operated valve '90 and a fluid operated valve 91. Upon admission of fluid under pressure to motor 1, piston 15 is moved upward against the bias of spring 16. Piston 15 is provided with a ram 13 adapted to cooperate with a roller 19 forming part of linkage 2. Upon raising of piston 15, the parts by which linkage 2 is constituted are moved to their position shown in Fig. l, which causes engagement of contacts 4 and 5 of circuit breaker 3. Linkage 2 is then latched in by latch ing means which are fully described below, and thus linkage 2 restrains circuit breaker 3 in the closed position thereof against the bias of accelerating spring 6. When circuit breaker 3 is closed, piston 15 and ram 18 are free to move to their initial position shown in Fig. 1 under the combined action of gravity and spring 16.

Linkage 2 includes a bell crank 20 pivoted at 21 and connected by pin 22 to a toggle link 23. Lever 2t} and toggle link 23 form a toggle 20, 23 which is slightly off center in the closed position of the breaker as shown in Fig. 1 and which may be caused to collapse. The center pin 22 of toggle 20, 23 supports the above referred to roller 19 adapted to be acted upon by the ram 18 on piston 15. The right endof link 23, as viewed in Fig. 1, is pivoted at 24 on a floating lever 25. Link 26 interconnects floating lever and bell crank 10.

The main latch 27 is pivotally supported at 28 by stationary bracket 29 and acted upon by compression spring 30 of which one end bears against the main latch 27, while the other end bears against bracket 29. The lower end of main latch 27 is adapted to engage a latch plate 31 forming an integral part of hell crank 20. The upper end of main latch 27 constitutes an abutment 32 adapted to be engaged by a cooperating abutment 33 on latch 34. Latch 34 is pivoted at 35 and acted upon by a compres- 'sion spring 36 tending to pivot it clockwise about pin 35. As viewed in Fig. 1, the right side of latch 34 is provided with a cam surface 37 adapted to engage a roller 33 carried by floating lever 25 by means of pin 39.

Upon release of roller 38 by cam surface 3?, floating lever 25 is free to move under the action of lifI spring 6, and this permits separation of contacts and 5 of circuitbreaker 3. When roller 38 has been released by cam surface 37, pin 39 moves from left to right along substantially straight path defined by guiding means Latch '34 is also provided with a straight cam surface 54 adapted to engage roller 38 during the interruptin greases process of the circuit breaker, as will more clearly be seen as the description progresses.

An upper cam surface 41 on latch 34 rests against a latch 42 pivoted at 43 and acted upon by biasing spring 44 tending to pivot it counterclockwise about pin 43. Latch 42 is held in position by a latch 45 engaging pin 46 on latch 42. Latch 45 is pivoted at 47 and biased counterclockwise by spring 48. The left arm of latch 45 is adapted to be pulled upward by a solenoid 49, thus causing latch 45 to pivot clockwise about pin 47. Lever St) is pivotally mounted on pin 51 and adapted to engage lever 52 which is pivotally mounted on pin 53. Lever 52 is spring biased clockwise. Upon pivoting of lever 59 clockwise about pin 51 (which may be effected manually), lever 52 is pivoted against the action of its biasing spring counterclockwise about pin 53. This causes latch 45 to be pivoted clockwise about pin 47, releasing latch 42. Latch 42 then pivots counterclockwise about pin 43, which releases latch 34 and roller 38 on floating lever 25, which, in turn, initiates separation of contacts 4 and under the action of accelerating spring 6. V

The separation of contacts 4, 5 may be initiated and effected in a similar way by energizing the solenoid 49 in response to the occurrence of a fault in the system into which the breaker is connected or in response to manual operation of an auxiliary switch.

A resetting compression spring 55 is arranged below the linkage and latch system 2 of the breaker and biases bell crank 26 clockwise. When the breaker is tripped the linkage and latch system 2 will be reset by the action of spring 55.

To close the breaker, fluid is admitted to fluid motor 1 through passage 83, thus causing piston and ram 18 to move upward. The closing force of motor 1 is applied to linkage 2 by engagement of ram 18 and roller 19. Toggle 2t 23, in moving up during a closing stroke of piston 15, rotates floating lever counterclockwise about pin 39. That rotary motion of lever 25 causes link 26 to be moved to the right. This, in turn, causes bell crank 19 to rotate clockwise about pin 57, pulling connecting rod 11 down and breaker rod 7 up, thereby closing the breaker against the action of accelerating spring 6.

As mentioned above, tripping may be initiated either mechanically by lifting the left end of lever 50, or electrically by energizing trip solenoid 49. In both instances the ensuing sequence of operation is about the same. When trip solenoid 49 is energized the armature thereof lifts latch against the bias of spring 48. The resulting clockwise rotation of latch 45 about pivot 47 releases pin 46 on latch 42. Thus, latch 42 is free to rotate counterclockwise under the action of spring 6 and against th action of spring 44, thereby sliding ofl the large latch 34. The large latch 34 is then free to rotate counterclockwise about pin 35 under the action of roller 38 which is acted upon by accelerating spring 6. The counterclockwise rotation of latch 34 against the. bias of spring 36 permits the top end of floating lever 25 to move to the right. As pin 39 on lever 25 moves to the right it slides in guiding means 40. That movement of lever 25 and pin 39 permits parts 7, 8 and 11 of breaker 3 to move to open circuit position.

Counterclockwise rotation of latch 34 about pin 35 causes abutment 33 to engage abutment 32 on main latch 27, thereby rotating main latch 27 clockwise about pin 28. Thus, main latch 27 becomes disengaged from latch plate 31 on bell crank 29.

Assuming now that at the end of the closing operation there is a main latch failure, i. e., that either the main latch 27 or the latch plate 31 is so badly damaged (either broken or worn out) that they fail to restrain the breaker in closed circuit position. The breaker then reopens under the action of accelerating spring 6, but its opening movement might be relatively slow on account of the decelerating action, or dash-pot action, of fluid motor 1. Even if the supply of compressed gas is shut off from motor 1 and the lower side of the motor 1 is being vented to atmosphere by prior art venting means, the decelerating efiect of motor 1 might be too large and the speed of separation of the contacts 4, 5 too small to achieve a safe interruption of the circuit controlled by the breaker. The dumping means shown in Fig. 1 is, however, so effective as to preclude any danger in case of complete failure of latching means 27 and 31. If the circuit breaker is closed on an overload, the downward movement of ram 18 is sufiiciently rapid to enable the linkage to have fully reset by the time the contacts 4, 5 have interrupted the current in the circuit, so that reclosure of the contacts may be initiated without further delay.

As shown in Fig. 1, dumping of gas under pressure previously admitted through passage 83 to cylinder 12 may be effected by a piston type valve which has been generally indicated by reference character 58. Dump valve 58 comprises a cylindrical valve body 59 and a valve element 60. Valve element 60 is movably arranged within valve body 59 and biased to closed position by means of helical spring 61. Valve element 619 is in the shape of a piston and one end of spring 61 rests against the inner side thereof, while the other end of spring 61 rests upon the base of valve body 59. Valve body 59 is provided with an intake opening 62 and an exhaust opening 63. Dumping tube 64 interconnects the base 14 of motor 1 with intake opening 62 of valve 58. The top of valve body 59 is provided with a screw threaded opening 65. Cylinder 12 of motor 1 is provided with an orifice 66 which is uncovered toward the end of each closing stroke of piston 15 so as to permit passage of compressed gas previously admitted to motor 1 through passage 83. Permanently open duct 67 interconnects orifice 66 with pilot opening 65.

Upon uncovering of orifice 66 by piston 15 compressed gas flowing through duct 67 depresses valve element 60 against the bias of spring 61. This efiects initial opening of valve 58, permitting compressed gas from motor 1 to enter through intake opening 62 into the body 59 of valve 58, tending to push valve element 69 farther down to uncover exhaust port 63. Upon uncovering of port 63, gas under pressure below piston 15 is free to flow through passage 64, intake opening 62, the space within valve 58 above valve element 60 and exhaust opening 63 to atmosphere.

When valve 58 has been opened wide by compressed gas admitted to it through passage 64, a high pressure zone forms on top of valve element 60 tending to maintain valve element 60 in its open position against the bias of spring 61. Thus, valve element 60 remains safely open when, as a consequence of the reversal of the movement of piston 15 under the action of spring 16, orifice 66 in cylinder 12 is reclosed or obstructed by piston 15 as it moves downward. In the position of valve 58 shown in Fig. 1, valve element 60 shuts off intake opening 62 from the inside of valve body 59 and, as long as this is the case, valve 58 cannot be opening by any pressure of gas in passage 64.

Cracking of valve 58 by compressed gas supplied through duct 67 and pilot port 65 to the top of valve element 69 occurs close to the end of each closing stroke of piston 15. There must be sufficient pressure behind piston 15 to insure engagement of main latch 27 and latch plate 31 before compressed gas can be dumped from fluid motor 1. The moment the breaker 3 is restrained in closed circuit position by engagement of latching means 27 and 31, any gas under pressure within the cylinder 12 of motor 1 can instantly completely be dumped. If the latch mechanism 27, 31 performs properly upon closing of circuit breaker 3 by fluid operated motor 1, the circuit breaker remains in closed circuit position (unless it should be tripped at that time either manually or automatically) but dumping of gas under pressure through passage 64, intake port 62, valve 58 and exhaust port 63 nevertheless occurs and results in substantially instantaneous high speed reversal of the movement of piston 15 to its position shown in Fig. l. Piston 15, upon having reached that position, is ready to perform another closing operation.

In order not to decelerate the closing stroke of piston 15 by formation of a cushion of compressed air in front of it, the top end or" fluid motor 1 is permanently vented to atmosphere by provision of one or more venting holes 13a in cover casting 13.

The connection between the motor 1 and the source of fluid under pressure is effected by a valve means comprising valves 90 and 91. The solenoid valve 90 which causes fluid under pressure to flow to motor 1 comprises a housing 92, a valve body 93 which is biased to valve closed position by a spring 93-, and an opening coil 95. Coil 95 may be connected to a source of electric current (not shown).

Fig 2 illustrates a way of mechanically operating valve 91 in response to movement of piston 15 of motor 1. In Fig. 2 the orifice 106 and duct 107 are omitted and a push rod 112 connected to hell crank of linkage mechanism 2 through a lost motion connection 113 is substituted therefor. When the arcing contacts 4, S are closed valve element 101 is held in valve open position by push rod 112. When the arcing contacts 4, 5 are opened push rod 112 is actuated upward by bell crank 10 causing spring 102 to move valve element 101 to valve closed position. During a circuit breaker opening opera- 'tion the pin in crank 10 which contacts the bottom of slotted link 113 to operate valve element 101 is required to move valve element 101 only far enough to crack valve 91, i. e., far enough for top of element 101 to uncover top of port 109. The pressure in port 109 will complete the opening of valve 91 once it is cracked.

Upon actuation of motor 1 in contact closing direction, and near the end of its stroke, rod 112 pushes valve ele ment 101 to the valve open position causing fluid under pressure to flow from passage 109 through cylinder 100, passage 104 to cylinder 12.

In accordance with the invention a new and improved pneumatically operated control valve 91 is provided for greatly increasing the cross sectional area of the compressed air intake at the time during the closing stroke of the circuit breaker contacts that the load upon the breaker operating fluid motor 1 is greatly increased.

Control valve 91 comprises a cylindrical valve body or casing 100 and a valve element 101. Valve element 101 is movably arranged within valve body 100 and biased to closed position by means of a helical spring 102. Valve element 101 is a piston and one end of spring 102 rests against the inner side thereof while the other end of spring 102 rests upon the base of valve body 100. Valve body 100 is provided with an intake opening 103 and an exhaust opening 10 Exhaust opening 104 is connected to passage 83 of motor 1. The top of valve body 100 is provided with a screw threaded opening 105. Cylinder 12 of motor 1 is provided with an orifice 106 which is uncovered toward the end of each closing stroke of piston 15 so as to permit passage of compressed gas or fluid previously admitted to motor 1 through passage 83. Permanently open duct 107 interconnects orifice 106 with pilot opening 105. A permanently open duct or passage 108 bypasses valve element 101 by connecting intake opening 103 with exhaust opening 104.

Valve element 10]. generally blocks the passage 104 from intake opening 109. With valve element 101 closed fluid under pressure passes through bypass 108 which has a controlled orifice 110. Orifice 110 limits the flow of fluid under pressure passing through passage 108 to fluid motor 1 to a predetermined value to control the contact closing speed of motor 1 to any desired value. When the linkage mechanism 2 starts to compress the heavy accelerator spring 6 near the end of the contact closing stroke piston 15 of motor 1 passes orifice 106 and fluid under pressure flows through orifice 106 to control valve 91. Fluid under pressure from passage 108 flowing through cylinder 12 into passage 107 cracks or depresses valve element 101 against the bias of spring 102. This effects initial opening of valve element 101, permitting compressed fluid from. the source to enter through intake valve through passage 109 into valve body of valve 91 tending to push valve element 101 farther down to uncover exhaust opening 104. Upon uncovering of opening 104, an increased flow of fluid under pressure may flow through the large passage 109, through valve bodyiitll), passage 83, and into cylinder 12 of motor 1, thereby providing a substantially unrestricted fluid flow to motor 1. Motor 1 now has the force behind it necessary to rapidly close the arcing contacts and to overcome the force of the accelerating spring 6 and the magnetic forces of the contact structure without an excessive amount of kinetic energy which would have to be absorbed by the circuit breaker structure.

lthough but two embodiments of the present invention have been illustrated and described, it will be an parent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

it is claimed and desired to secure by Letters Patent:

1. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein, source of fluid under pressure, a ram on said piston for reclosing said breaker, and means for controlling the flow of fluid under pressure to said cylinder to close said breaker, said controlling means comprising a permanently open passage for supplying fluid for actuating said piston in breaker closing direction and a normally closed passage, said normally closed passage being opened by the fluid under pressure from said first passage upon said piston reaching a predetermined position in breaker closing direction to actuate said breaker to closed position.

2. In an operatingmechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein, a source of fluid under pressure, a first means for admitting fluid under pressure from said source to said cylinder to actuate said breaker in contact closing direction, a second means for admitting fluid under pressure from said source to said cylinder to aid said first means in closing said breaker. said second means comprising a valve casing, a piston type valve element movably arranged in said casing, resilient means for biasing said valve element to a closed position, means defining a passage from said source to said cylinder, said casing forming an integral part of said passage, a pressure responsive surface provided on said valve element upon which the pressure of the fluid flowing through said passage acts to maintain said valve in an open position against the action of said biasing means, said second means being operative only upon cracking of said valve element, pilot means for cracking said valve element including means defining an orifice in said cylinder controlled by said piston, and means defining a per manently open duct for connecting said orifice to said second means, said first means providing the fluid for actuating said piston beyond said orifice in breaker closing direction and for providing fluid under pressure to flow through said orifice to crack said valve element, said second means providing the fiuid under pressure to aid said first means in actuating said piston to breaker closed position.

3. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein, a source of fluid under pressure, a ram on said piston for closing said breaker, and valve means for controlling the flow or fluid under pressure to said cylinder to close said breaker, said valve means comprising a first passage connecting said source to said cylinder, a valve casing, a piston type valve element movably arranged in said casing, resilient means for biasing said valve element to closed position, means defining a second passage from said source to said cylinder, said casing forming an integral part of said second passage, a pressure responsive surface provided on said valve element upon which the pressure of the fluid flowing through said second passage acts to maintain said valve in an open position against the action of said biasing means, said valve means being operative only upon cracking of said valve element, pilot means for cracking said valve element including means defining an orifice in said cylinder controlled by said piston, and means defining a permanently open duct for connecting said orifice to said valve, said first passage providing fluid under pressure for actuating said piston beyond said orifice in breaker closing direction and for providing fluid under pressure to flow through said orifice to crack said valve element, said second passage upon opening thereof providing the fluid under pressure to actuate said piston to breaker closed position.

4. In an operating mechanism for circuit breakers, a motor operable by fluid under pressure and comprising a cylinder and a piston movably arranged therein, a source of fluid under pressure, a ram on said piston for closing said breaker, and valve means for controlling the flow of fluid under pressure to said cylinder to close said breaker, said valve means comprising a first passage connecting said source to said cylinder, a valve casing, a piston type valve element movably arranged in said casing, resilient means for biasing said valve element to closed position, means defining a second passage from said source to said cylinder, said casing forming an integral part of said first and said second passages, a pressure responsive surface provided on said valve element upon which the pressure of the fluid flowing through said second passage acts to maintain said valve in an open position against the action of said biasing means, said valve means being operative only upon cracking of said valve element, pilot means for cracking said valve element including means defining an orifice in said cylinder controlled by said piston, and means defining a permanently open duct for connecting said orifice to said valve, said first passage providing fluid under pressure for actuating said piston beyond said orifice in breaker closing direction and for providing fluid under pressure to flow through said orifice to crack said valve element, said second passage upon opening thereof providing the fluid under pressure to actuate said piston to breaker closed position.

5. In an operating mechanism for circuit breakers, a motor operable by gas under pressure and comprising a cylinder and a piston movably arranged therein, a source of fluid under pressure, means for admitting fluid under pressure from said source to said cylinder to close the breaker, means for controlling said fluid admitting means, a spring for returning said piston to the initial position thereof upon closing of said breaker, a ram on said piston for reclosing the breaker, valve means for controlling the flow of fluid under pressure to said cylinder to close said breaker, said valve means comprising a first passage connecting said source to said cylinder, a valve casing, a piston type valve element normally arranged in said valve casing, resilient means for biasing said valve element to a closed position, means defining a second passage from said source to said cylinder, said casing forming an integral part of said second passage, a pressure responsive surface provided on said valve element upon which the pressure of the fluid flowing through said second passage acts to maintain said valve in an open position against the action of said biasing means, said valve means being operative only upon cracking of said valve element, pilot means for cracking said valve element including means defining an orifice in said cylinder controlled by said piston, and means defining a permanently open duct for connecting said orifice to said valve, said first passage providing fluid under pressure for actuating said piston beyond said orifice in breaker closing direction and for providing fluid under pressure to flow through said orifice to crack said valve element, said second passage upon opening thereof providing the fluid under pressure to actuate said piston to breaker closed position, and means for venting said cylinder to cause said spring to rapidly return said piston to said initial position thereof.

References Cited in the tile of this patent UNITED STATES EATENTS 1,641,131 Baker et al Aug. 30, 1927 1,877,102 Whitesell Sept. 13, 1932 2,159,879 Dewandre May 23, 1939 2,270,767 Platz Jan. 20, 1942 2,286,104 Platz June 9, 1942 2,296,071 Thumim Sept. 15, 1942 2,434,549 Cumming Jan. 13, 1948 2,524,114 Millat Oct. 3, 1950 2,578,204 Peek Dec. 11, 1951

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