US2290320A

US2290320A - Circuit breaker mechanism

Info

Publication number: US2290320A
Application number: US235608A
Authority: US
Inventors: Duffing Paul
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1937-11-10
Filing date: 1938-10-18
Publication date: 1942-07-21
Anticipated expiration: 1959-07-21
Also published as: FR873902A; NL50549C; US2198491A; BE431038A; US2249006A; DE708320C; CH214263A; DE758052C

Description

J y 1, 19 2- P. DUFFING CIRCUIT BREAKER MECHANISM Filed Oct. 18, 1938 2 Sheets-Sheet l INVENTOR Pal/Z Dllffiflg.

BY @W WITNESSES:

Patented July 21, 1942 2,290,320 CIRCUIT BREAKER MECHANISM Paul Dufiing, Berlin-Siemensstadt, Germany, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 18, 1938, Serial No. 235,608

. In Germany November 10, 1937 22 Claims.

The invention relates to electrical switching apparatus in general, and more particularly to operating mechanism of the hydraulic type for actuating high voltage circuit breakers or switches.

In electrical switching apparatus of the polyphase type it is important that the circuit opening and closing operations of the individual phases take place simultaneously or in an accurately determined sequence. Attempts have been made to actuate the switching devices by air pressure. This method has not proven entirely satisfactory because of the fact that the elasticity of the pressure medium makes it very difficult to attain the desired timed relationship of the switching process at the individual phases with any degree of accuracy; It has therefore been preferred in most cases where air pressure actuation is used, to provide a common air pressure actuating device and to connect the individual switching devices to the actuating device by means of mechanical bars to provide for simultaneous actuationof the switching devices. This construction, however, has certain disadvantages. For high voltages the insulation problem is very diflicult; and for high voltage where the spacing between the individual switching device is very large the mechanical bars have to be very large and long.

An object of the invention is the provision of an improved mechanical operating means for electrical switching apparatus comprising a separate actuating device for each individual switching member, and a common control means for simultaneously operating the actuating devices.

Another object of the invention is the-provision of an improved operating means as previously described in which the separate actuating devices consist of oil pressure operated pistons which are connected by oil pressure conductors to a common control pumpfor operation by the pump.

Another object of the invention is the provision of an operating mechanism for an electrical switch, comprising an oil pressure operated actuating piston connected to the switch and a control pump electrically isolated from the switch and connected to the piston by an oil pressure conducting means for operating the piston.

Another object of the invention is the provision of an operating means as previouslydescribed in which, according to one embodiment, the actuating piston is moved in one direction by oil pressure against the action of actuating spring or according to another embodiment, the piston is moved in both directions by oil pressure.

Another object of the invention is the provision of a hydraulic actuating device for an electric switch, embodying a cylinder having a piston therein connected to the switch by a rod which extends through one end of the cylinder, with an improved means for preventing leakage of oil through the rod opening of the cylinder when the piston is adjacent either of its end positions.

Another object of the invention is the provision of a hydraulic operating means for an electrical switch embodying a double acting actuating piston and control pump for operatingthe piston, and a means for connecting a source of oil under pressure to the last impinged on side of the actuating piston to maintain it in its final position.

Another object of the invention is the provision of a hydraulic operating means as previously described with a means for collecting oil which leaks past the actuating piston and restoring it to the oil pressure system.

Another object of the invention is the provision of a hydraulic operating means for an electric switch as previously described with a means for damping the quick motion of the actuating piston as it approaches either of its end positions.

Another object of the invention is the provision of a hydraulic operating system for electrical switching apparatus which is operable to quickly actuate the switching apparatus.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention 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 several embodiments thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a fragmentary view, partly in section, of a circuit breaker and an oil pressure operating means therefor constructed in accordance with the invention,

Figs, 2 and 3 are fragmentary views, partly in section, showing slightly modified forms of the oil pressure operating means for the circuit breaker,

Fig. 4 is a fragmentary sectional view of the actuating cylinder and actuating piston provided with the means for preventing leakage of oil through the rod opening in the cylinder.

Fig. is a schematic view, partly in section, of a complete hydraulic operating means and system for a polyphase switching apparatus, constructed in accordance with the invention, and

Fig. 6 is a fragmentary sectional view of the hydraulic operating means showing the novel means for damping the quick motion of the actuating piston at each end of its stroke.

Referring to Fig. 1 of the drawings, the reference numeral 3 designates generally a conventional circuit breaker having a movable bridging contact 5 which is connected to and movable by a rod 1 into and out of engagement with a pair of stationary contacts 9.

The breaker rod 1 is moved to open and closed circuit position by an actuating device H comprising an oil pressure operated piston 13 movable in an oil pressure cylinder IS. The cylinder I5 is closed at its upper end and is connected by an oil pressure conductor H to a suitable oil pressure control pump (not shown). The piston I3 is mechanically connected to the breaker actuating rod I through the agency of a piston rod l9. A compression spring 2| encircles the piston rod l9 and is disposed in the lower portion of the cylinder l5 between the lower side of the piston l3 and a fixed bearing support 22.

The control pump is operable to supply oil under pressure to the upper end of the cylinder l5 to efiect downward opening movement of the piston |3 against the force of the closing spring 2| to cause opening of the circuit breaker. The spring 2| acts to move the piston l3 upwardly when the oil pressure is removed from. the upper side of the piston by the pump to cause closing of the circuit breaker.

The control pump is located outside of the high tension region surrounding the circuit breaker and is electrically insulated from the circuit breaker by means of the oil pressure conductor which is preferably composed of insulating material, and by the oil in the conductor ll. It will thus be seen that the operating means of the present invention materially simplifies the insulation problem for the entire apparatus.

Two slightly modified forms of the operating means are illustrated in Figs. 2 and 3. In these figures similar reference characters have been used wherever applicable. In Fig. 2 the actuating piston I3 is connected to the breaker actuating rod 1 through the agency of a piston rod [9 and a lever 23. The lever-23 is pivoted intermediate its ends on a fixed support, one end of the lever being pivotally connected to the lower end of the piston rod l9 and the other end of the lever being pivotally connected to the upper end of the breaker rod 1. In this construction the piston I3 is moved downwardly by oil pressure against the force of the spring 2| to efiect closing of the circuit breaker, and the spring 21 supplies the force to move the piston upwardly to effect opening of the circuit breaker. The circuit breaker is releasably held in closed circuit position by means of latch 25 which is pivoted on a fixed support and biased by a compression spring 2'! to engage a notch 29 formed in the piston rod l9, when the circuit breaker is in closed position. v The latch 25 is connected by a rod 3| to a latch operating piston 33 which is movable in an oil pressure cylinder 35. When oil under pressure is supplied to the cylinder 35 through the liquid conductor 31, the piston 33 is moved upwardly to cause clockwise rotation of the latch 25 and release of the piston rod I9. The release of the piston rod l9 allows the spring 2| to move the actuating piston l3 upwardly to effect opening of the circuit breaker.

In Fig. 3, the actuating piston l3 which is biased upwardly by a circuit opening spring (not shown) is held in closed circuit position by means of the pivoted latch 25. The latch 25 in this embodiment of the invention is connected to a bellows 39 for actuation thereby. The bellows 39 is of resilient construction and is connected at its upper end by a liquid conductor 4| to the central portion of the actuating cylinder l5. The lower end of the bellows 39 is connected by a rod 43 to one arm of the latch 25. In this construction the circuit breaker is moved to closed circuit position when the control pump supplies oil under pressure to the upper end of the cylinder I5. The oil under pressure expands the bellows 39 and thus moves the latch 25 to latching position when the breaker reaches closed position. When the control pump is operated to remove the pressure from the upper side of the piston l3, the bellows 39 collapses and releases the latch 25 to allow the circuit opening spring to move the piston l3 upwardly and effect opening of the circuit breaker.

According to another embodiment of the invention, the actuation of the circuit breaker is effected by a double acting oil pressure piston so that the circuit closing movement, as well as the circuit opening movement of the breaker is carried out by oil pressure. An operating means of this construction is shown in Fig. 5 and will be described hereinafter. With this construction it is particularly important to provide a good packing at the exit position of the piston rod out of the cylinder in order to prevent leakage of oil. For this purpose, the end 49 (Fig. 4) of the actuating cylinder 61 through which the piston rod 45 extends is provided with a pair of packing rings 5| and 53 which are preferably composed of oil-proof rubber. The rings 5| and 53 are mounted in recesses provided in the opposite sides of the end 49 of the cylinder, and are disposed concentrically with respect to the piston rod 45. The ring 5| cooperates with an annular collar 55 formed integral with the piston 44 and disposed concentrically with respect to the piston rod 95. The ring 53 likewise cooperates with an annular collar 51 rigidly secured to the piston rod 45 outside of the cylinder. When the actuating piston 44 is moved in one direction to efiect actuation of the circuit breaker, the collar 55 is pressed into the rubber ring 5| adjacent the end of the stroke to prevent leakage of oil through the rod opening in the end of the cylinder. Similarly when the actuating piston 44 is moved in the opposite direction to eifect an opposite actuating of the breaker, the collar 51 is pressed into the rubber ring 53 at the end of the stroke to prevent leakage of oil through the rod opening in this end position of the piston.

A complete hydraulic operating mechanism for operating a three-phase circuit breaker is shown schematically in Fig. 5. In this figure, the various devices have been distorted out of their true positions relative to one another in order to simplify the drawings. Referring to Fig. 5, the three breaker actuating rods 7 are each connected to a separate actuating piston 44 through the agency of suitable levers (not shown) and the piston rods 45. The pistons 44 are movable in oil pressure cylinders 41 which have their one ends connected by a common oil pressure conductor 59 to one end of a common control cylinder BI. The opposite ends of the actuating cylinders 41 are connected by individual oil pressure conductors 63 to three

separate chambers

65, 61 and 69 of the control cylinder BI. A multiple difierential control piston II is movable in the control cylinder 6|. The multiple piston II is of the double acting type and is provided with three

integral portions

13, 15 and T! of difierent diameters which cooperate with the

chambers

65, 61 and 69. The portions 13, I and TI function in the manner of individual control pistons for forcing oil under pressure through the oil pressure conductors 63 to the left-hand ends of the three actuating cylinders 41.

The multiple control piston II is moved in either direction by an air pressure operated piston 8| disposed in an air pressure cylinder 83, the multiple piston II being connected to the air pressure piston 8| by a connecting rod 85.

The operation of the hydraulic operating means as thus far described is briefly as follows: When the control piston II is moved to the right, the oil in the right-hand end of the control cylinder BI is moved through the common oil pressure conductor 59 to the right-hand ends of the actuating cylinders 4'! and effects simultaneous movement of the actuating pistons 44 to the left to eilect simultaneous actuation of the three phases of the circuit breaker. When the control piston H is moved to the left, the "oil in the

chambers

65, 61 and 69 is moved through the individual oil pressure conductors 53 into the left-hand ends of the actuating cylinders 41 to efiect simultaneous movement of the actuating pistons 44 to the right to effect an opposite simultaneous actuation of the three phases of the circuit breaker.

In order to maintain the actuating pistons 44 in either their circuit closed or circuit opened positions, there is provided a separate oil container 8! which contains oil under static pressure. The separate oil container 81 is connected by liquid conductors 89, 9| and 93 with a pair of chambers 95 formed in the opposite ends of the control cylinder 6|. The chambers 95 communicate with the interior of the cylinder BI through passages which are normally closed by spring biased valves 91. The opposite ends of the multiple control piston 1| are provided with control members 99 which are adapted to open one of the alves 91 when the control piston 'II reaches either of its end positions. The actuating cylinders 41 are connected with each other at points intermediate their ends by a pair of pressure equalizing oil pressure conductors 70. When the actuating pistons 44 are at the left-hand ends of the cylinders 41, the right-hand ends of the cylinders 41 are all in communication with each other through the common oil pressure conductor 59 and the equalizing conductors HI. Similarly when the actuating pistons 44 are at the righthand ends of the cylinders 41, the left-hand ends of the cylinders are all in communication with one another through the pressure equalizing conductors III, the pistons 44 at this time being on the right-hand side of the points of connection of the conductors to the cylinders. From the above description, it will be seen that the separate oil container 81 is automatically connected to supply oil under static pressure to the last impinged on side of each of the actuating pistons 44 when the control piston reaches either end of its stroke, so that the actuating pistons are thus maintained either in their circuit open or circuit closed positions by static oil pressure. This arrangement also provides for replacement of any leakage oil past the pistons, the leakage oil in any part of the system being replaced by the oil from the container 81 so that every operation will commence with the correct length or volume of operating liquid. The arrangement also permits expansion or contraction of the operating liquid without altering the effective length or volume of the liquid columns when the control piston is in either end position.

In spite of good packing at the packing positions of the piston rods 45 and pistons 44, a certain amount of oil leakage exists. In order to prevent undue oil leakage at the packing positions and to suppress any undesired motions of the actuating pistons 44, there is provided an oil collecting container I03 which is connected by oil conductors I05, I01, I09 and III to the righthand ends of the

chambers

65, 6! and 69. By this arrangement any oil which leaks past the packing of the pistons 44 when the pistons 44 are at the left-hand ends of their movement is collected in the container I03, thus minimizing the possibility of oil leakage through the packing for the exit positions of the piston rods 45. The oil collected in the container I03 is returned to the separate oil pressure container 81 by means of a suitable pump H3. The pump Il3 may be arranged to be automatically operated whenever the oil in the collecting container I03 reaches a predetermined height; or the pump H3 may be arranged to be actuated at each actuation of the switching apparatus through a suitable oil pressure piston (not shown) which may be operated in conjunction with the control piston II. This arrangement in addition to compensating for oil leakage in the system also serves to compensate for changes in the volume of the oil due to temperature changes.

As has previously been pointed out, the various devices shown in Fig. 5 have been distorted out of their actual positions relative to one another in order to simplify the drawings. In the physical embodiment of the invention, the actuating cylinders 41, the control cylinder 6| and the leakage oil collecting container I03 are all mounted in substantially the same horizontal plane so that the level of the oil in all of these devices is the same. The separate oil container 81, however, is mounted in an elevated position in order to supply oil under static pressure to the system.

From the above description, it will be seen that oil leaking past the packing of the actuating pistons 44 is'collected in the container I93, pumped to the separate oil container 87, and returned to the system when the valves 97 are actuated,

In the above construction, the actuating cylinders and pistons may be spaced apart any desired distance in accordance with the spacing of the individual phases of the switching apparatus. The oil pressure conductors 59 and 53 are preferably formed of insulated material so that the control pump comprising the cylinder SI and the multiple piston H are electrically insulated from the switching apparatus. The control pump and all parts of the hydraulic operating system with the exception of the actuating cylinders and actua ng pistons ay b di p e remote from the switchi pparat s and outside of h hi h tension regicns rr unding h switflh l ppa atus.

In hydraulic operating means of the construction previously described, particularly in cases where the switching apparatus to be actuated is of the high voltage type, the actuating pistons are moved to open and closed positions at a very high speed. In such instances, it is desirable that the speed of the actuating piston be quickly and smoothly reduced or damped as the piston approaches either of its end positions. Fig. 6 shows a hydraulic operating mechanism for a single phase circuit breaker embodying a novel means for damping the quick motion of the actuating piston as it approaches either end of its stroke. Referring to Fig. 6, the circuit breaker operating rod H is connected to an actuating piston II! by a piston rod H8. The piston II], which is of the double acting type, is movable in an oil pressure cylinder H9. The ends of the cylinder II9 are connected by oil pressure conductors I23 to the opposite ends of a control cylinder I25. A control piston I2'I of the differential type is movable in the control cylinder I25 for operating the actuating piston II! in one direction or the other to operate the circuit breaker.

A separate oil container (not shown) containing oil under static pressure is connected to the control cylinder I25 at two points by oil conductors I29 and I3I. A pair of by-pass oil conductors I33 have their one ends connected to the control cylinder I25 at points in alignment with the points of connection of the conductors I29 and I3I, and their other ends connected to the oil pressure conductors I23. A pair of oil collecting conductors I35 are connected to the cylinder I25 adjacent the opposite ends thereof for collecting oil which leaks past the packing of the actuating piston I I1, and these conductors lead to an oil collecting container (not shown) similar to the container I93 of Fig. 5, and the leakage oil collected therein may be restored to the system in the same manner as shown and described in the Fig. 5 embodiment.

The control piston I2! is provided with an annular peripheral groove I31 intermediate its ends which is adapted to connect the static oil pressure conductors I29 and I3I with the by-pass conductors I33 when the control piston is in either of its end positions. The control piston I2I also serves to close off one of the oil collecting conductors I35 and open the other when the piston is at either end of its stroke. The control piston thus serves as a sliding valve to automatically connect the static oil pressure container to the last impinged on side of the actuating piston III, and to connect the opposite side or unimpinged side of the piston to the oil collecting container, when the control piston reaches either of its end positions.

In order to damp the quick motion of the actuating piston II! as it approaches either end of its stroke, the ends of the actuating cylinder I2I are extended a short distance beyond thepoints of connection of the oil pressure conductors I23 to the cylinder I2I. The extended ends I39 of the cylinder I2I form damping cylinders which cooperate with the opposite ends of the piston I I! and act in the manner of a dashpot to quickly and smoothly damp the quick movement of the actuating piston as it approaches either of its end positions. For this purpose, the ends of the piston are constructed to have a relatively loose ends of the piston which are biased to close the passages by means of a pair of springs I45. When oil under pressure is forced through either of the oil pressure conductors I23 to actuate the piston I I I, the oil pressure opens the corresponding valve I43 allowing the oil to enter the extended end portion I39 of the cylinder to initiate movement of the actuating piston III. The control piston I21 may be actuated by an air pressure operated piston as shown in Fig. 5.

While in all of the embodiments previously described, the actuating piston is connected by a direct mechanical connection to the breaker operating rod, it is to be understood that the .actuating pistons may be connected to the breaker operating rods through a suitable trip free connection if it is desired that the circuit breaker be trip free of the actuating piston.

In the case of high tension electrical systems a quick actuation of the circuit breakers is often necessary, and this quick movement requires a relatively largeexpenditure of energy. When the actuation of the circuit breakers is carried out hydraulically for example in the manner previously described, the time required for complete movement of the fluid should be made as small as possible in order to provide for quick actuation of the breakers.

In accordance with each of the embodiments of the invention the speed of actuation of the breaker is materially increased by constructing the diameter of the fluid conductor or conductors between the actuating piston and the control pump as large as possible and in particular at least larger'than one half of the diameter of the operating piston.

This arrangement is in conflict with known construction in which an attempt was made to maintain the mass of the fluid to be moved, small by using small cross section fluid conductor between the pump and the breaker operating piston, and in this manner attempting to maintain the energy necessary for moving the masses small. For a given amount of available energy this did not increase the speed of actuation of the breaker because the breaker actuating pis ton was moved at a speed many times slower than the speed of the fluid in the small cross section fluid conductors.

The basis of the present proposal is that although increasing the cross section of the fluid conductors increases the mass of fluid to be moved; yet the speed of the fluid in the conductors is made smaller so that less kinetic energy is used in moving the fluid.

This may be followed with reference to the following equations in which Dz is the diameter of the actuated piston, D1 the diameter of the liquid conducting tube, to the speed of the liquid in the conducting tube, e the specific weight of the liquid, and g the gravity acceleration.

The kinetic energy based on 1 square centimeter of the piston area is equal to e.1 D, 3 vis.)

The total energy For fast actuation of the circuit breaker, the weight of the liquid in the system should be maintained small; therefore, from a practical standpoint D 2 D 0.5D, or. 24

From this it Will be seen that in spite of the larger mass of fluid used when the cross section of the fluid conductor is increased, the speed of actuation of the breaker operating piston and breaker is considerably increased.

The advantage of the arrangement is also illustrated as follows. If the cross section of the fluid conductor tube is equal to that of the piston, the speed at which the piston will be moved is the same as the speed of the fluid in the tube; whereas if the cross section of the tube is smaller than that of the piston, then th speed of the piston will be smaller than the speed of the liquid in the tube.

In the embodiments of the invention shown in Figs. 1, 2 and 3 of the drawings the control or pump piston (not shown) may be operated by an air pressure operated piston by having the air pressure operated piston connected to the pump piston as shown in Fig. 5. In these embodiments the air pressure piston would obviously be operated by air pressure in one direction against the force of the biasing spring associated with the circuit breaker piston.

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 reasonableconstruction permissible in the light of the prior art.

I claim as my invention:

1. In combination, a circuit breaker movable to open and to closed circuit position, actuating means for said breaker comprising a liquid 'pressure operated piston movable in a cylinder and connected to said breaker for actuating said breaker to closed circuit position, spring means acting on said piston for actuating said breaker to open circuit position, latch means for releasably holding said breaker in. closed position, a control cylinder and a control piston in said cylinder for moving the operating liquid to move said liquid pressure operated piston in a closing direction, and a liquid conducting tube of insulating material connecting said cylinders for transmitting the operating liquid.

2. In combination, a circuit breaker movable to open and to closed circuit position, actuating means for said breaker comprising a liquid pressure operated piston connected to said breaker for actuating said breaker to closed circuit position, spring means acting on said piston for actuating said breaker to open circuit position, a latch for releasably holding said breaker in closed position, and means including a second liquid pressure operated device for operating said latch.

3. In combination, a circuit breaker, a hydraulic operating mechanism for said breaker comprising a liquid pressure system including a cylinder, a liquid pressure operated piston in said cylinder having a rod extending through a packed opening in one end of said cylinder and connected to said breaker for actuating said breaker, a control piston for moving the operating liquid to operate said first mentioned piston, and liquid pressure conducting means connecting said control piston to said cylinder, and means for collecting leakage liquid past said liquid pressure operated piston and restoring said leakage liquid to said system.

4. In combination, a multiple circuit breaker having a plurality of movable contact members, a hydraulic operating mechanism for said breaker comprising a liquid pressure system including a separate liquid pressure cylinder and double acting liquid pressure operated piston in said cylinder for each contact member, each piston being connected to its corresponding contact member by a rod extending through a packed opening at one end of its cylinder, a common double acting liquid pressure pump connected to each end or said cylinders by means of liquid pressure conductors of insulating material, and means operable to compensate for and minimize liquid leakage loss in said system and to compensate for volume variations of the liquid in said system.

5. In a circuit interrupter, a movable contact member, operating mechanism comprising an oil pressure system including a cylinder, a double acting piston in said cylinder having a rod extending through a packed opening at one end or said cylinder connected to said contact member, a control cylinder electrically isolated from said interrupter, a control piston in the cylinder, and a pair of oil pressure conductors connecting the ends of said cylinders, a leakage container connected to one of said cylinders for collecting oil leakage past said pistons and for minimizing leakage of liquid from said system, and means for restoring the leakage of oil past said pistons to said system.

6. In a circuit interrupter, a movable contact member, hydraulic operating mechanism comprising an oil pressure system including a cylinder, a double acting piston in said cylinder connected to said contact member, a control cylinder insulated from said interrupter, a control piston in the cylinder, and a pair of oil pressure conductors connecting the ends of said cylinders, said system having principal packing places to reduce oil leakage, a container connected to said system adjacent said principal packing places for collecting oil leakage through said places and means for restoring said leakage oil to said system.

7. In a circuit interrupter, a movable contact member, hydraulic operating mechanism comprising a liquid pressure cylinder, a double actins operating piston in said cylinder connected to said contact member for actuating said interrupter, a control cylinder, a double acting control iston in said cylinder, a pair of liquid pressure conductors connecting the ends of said control cylinder to said first-mentioned cylinder, means for moving the control piston in either direction to actuate said operating piston and contact member, aliquid reservoir, and means operable by said control piston when it reaches either end of its movement for connecting said liquid reservoir with the side of the operating piston that is last impinged on.

8. In a circuit interrupter, a movable contact member, hydraulic operating mechanism comprising a; liquid pressure cylinder, a double acting operating piston in said cylinder. connected to said contact member for actuating said contact member, a control cylinder, a double acting control piston in said cylinder, a pair of liquid pressure conductors connecting the ends ofsaid control cylinder to said first-mentioned cy means for movingthecontrol piston in either direction toactuate saidoperating piston and contact member, a'liquid reservoir, and meansoper able by said control piston when it reaches either end of its movement for connectingsaid liquidreservoir with the side of the operatingpiston that is last impinged on, a liquid collecting container, means for connecting said collecting container to the unimpinged side of the operatin piston when said reservoir is connected to the opposite side of said operating piston.

9. In a circuit interrupter, a movabl contact member, hydraulic operating mechanism comprising an operating cylinder, at double acting A operating piston in said cylinder connected. to said contact member for actuating said contact member, a control cylinder, a double acting control piston in said cylinder, a pair of liquid pressure conductors connecting the ends-of said control cylinder to said first-mentioned cylinder, means for moving thecontrolpistonin either direction to actuate said operating piston and contact member, a liquid reservoir, meansr operable by said control piston at each end of its movement for connecting'said reservoir with the side of the operating piston that islast impinged on, a liquid collecting container, means for connecting said collecting container tothe unimpinged side of the operating piston when said reservoir isconnected tothe opposite side of said operating piston, and a liquid pump-for returning the liquid collected in the collecting container to the reservoir.

10, In a circuit interrupter, a movable contact member, hydraulic operating mechanism comprising a liquid pressure cylinder, a doubleacting operating piston in said cylinder connected to said contact member for actuating the same, a control cylinder, a double acting control piston in said cylinder, a pair'of liquid pressure conductors connecting the ends of said control cylinder to said first-mentioned cylinder, means for mov-- ing the control pistonin either direction to actuate said operating piston, a liquid reservoir, means operable by said control piston when it reaches either end of its movement for connecting said reservoir with the side or the operating piston that is last impinged on, a liquid collecting container, means for connecting said collecting container to the unimpinged side of the p-' erating piston when said reservoir is connected to the opposite side of said operating piston, a liquid pump operable at each actuation of the witching apparatus for returning the liquid collected in said collecting container to the reservolr.

11. A multiple circuit interrupter having a plurality of switch members, hydraulic operating mechanism therefor comprising a plurality of operating cylinders one for each pole of the interrupter, a double acting operating piston in each cylinder connected to one of the switch members for actuating the switch members, a common liquid control pump comprising a multiple chamber control cylinder, a multiple difierential control piston in said control cylinder and a plurality of liquid pressure conductors connecting the chambers of said control cylinder to the ends of said operating cylinders.

12. In a circuit interrupter, a movable contact member, hydraulic operating mechanism comprising a liquid pressure cylinder, a double acting liquid pressure operated piston in said cylinder connected to said contact member, a control cylinder, a piston in said control cylinder, a pair of liquid pressure conductors connecting the ends of said control cylinder with the ends of said first-mentioned cylinder and hydraulic damping means for damping the quick motion of the operated piston at each end of its stroke.

13. In a circuit interrupter, a movable contact member, hydraulic operating mechanism therefor comprising an operating cylinder, a liquid pressure operated double acting operating piston in said cylinder connected to said contact member, a control pump comprising" a control cylinder, a control piston in said cylinder, a pair of liquid pressure conductors connecting the ends of said control cylinder to the ends of said operating cylinder, the ends of said operating cylinder extending beyond the points of connection of said liquid pressure conductors thereto and cooperating with said operating piston to damp the quick motion of said operating piston at each end of its stroke.

14. In a circuit interrupter, a movable contact member, hydraulic operating mechanism therefor comprising an operating cylinder, a double acting operating piston in said cylinder cOnnected to said contact member, a control cylinder and a control piston in said cylinder for actuating said operating piston, a pair of liquid pressure conductors connecting the ends of said control cylinder to the ends or said operating cylinder, the'ends of. said operating cylinder extending beyond the points of connection of said liquid pressure conductor thereto for damping the quick motion of's'aid operating piston at each end of its stroke", said operating" piston being provided with passages at each end which extend from the side of the piston through the end for conducting liquid under pressure from" said liquid pressure conductors to the extended ends of said operating cylinder to initiate movement of said operating piston from eitherof'its' end positions, and a pair Of valves on the ends of said operating piston biased by springs to closesaidpassages.

15. In a high voltage-circuit breaker, a movable contact member, a liquid pressure actuated device connected to said contact member, a liquid pressure control piston and cylinder disposed outside of the high tension region surrounding said breaker and electrically insulated from said breaker for actuating saidlliquidpressure actuated device, and an airpressure operating means connected to said control piston for operating said control piston.

16-. In a circuit breaker, amovable contact member, operating means comprising a piston connected to said contact member, and means for applying forces derived from air under pressure and transmitting said forces through two insulating columns of insulating liquid respectively to opposite sides of said piston for effecting opening and closing movements of said contact member.

17. In a circuit breaker, a movable contact member, operating mechanism comprising a liquid actuated piston connected to said contact member and means for applying a force to either side of said piston comprising two columns of insulating liquid and a hydraulic actuating piston, and an air pressure operated piston mechanically coupled to said hydraulic actuating piston for moving said hydraulic actuating piston.

18. In a multiple circuit breaker, a plurality of movable contact members, operating mechanism comprising a separate liquid actuated piston connected to each contact member, a common actuating means including a double acting hydraulic actuating piston and two insulating columns of insulating liquid for simultaneously transmitting forces to either side of each of said liquid actuated piston respectively for effecting simultaneous opening and closing movements of said contact members.

19. In a circuit breaker, a movable contact member, operating mechanism therefor comprising a liquid actuated piston connected to said contact member, means for transmitting forces through two insulating columns of insulating liquid respectively to opposite sides of said piston for efiecting opening and closing movements of said contact member, and means permitting free expansion and contraction of the liquid columns without altering their effective lengths when the movable contact member is at the end of an operating stroke.

20. In a circuit breaker, a movable contact member, operating mechanism comprising a liquid actuated piston connected to said contact member, means for transmitting forces through two columns of insulating liquid respectively to opposite sides of said piston for effecting opening and closing movements of said contact member, a liquid reservoir, and means actuated when said piston is at the end of its stroke for establishing communication at least in one direction of flow between one of the liquid columns and said liquid reservoir.

21. In a circuit breaker, a movable contact member, a hydraulic operating system therefor containing an insulating operating liquid and having a liquid actuated piston connected to said contact member for moving said contact member to closed position, latch means for holding the movable contact member in closed position after operation, said latch means being releasable by the operating liquid of said system.

22. In a circuit breaker, a movable contact member, hydraulic operating means therefor comprising a cylinder, a liquid pressure operated piston in said cylinder connected to said contact member, a control cylinder, a control piston in said control cylinder movable to effect operation of said liquid pressure operated piston, a liquid conduit of insulating material connecting said cylinders, an insulating operating liquid in said system, and means for hydraulically damping the quick motion of said liquid pressure operated piston at at least one end of its stroke.

PAUL DUFFING.