US2401008A - Circuit interrupter - Google Patents

Description

May 28 1946.

L. R. LUDWIG ET AL 8,

CIRCUIT INTERRUPTER I;

Filed March 9, 1940 3 Sheets-Sheet 2 INVENIORS Leon 1?! Ludwg and Sen/gnu)? a/(er f? ATTORN y 6- 1.. R. LUDWIG ET AL 2,401,008

CIRCUIT INTERRUPTER Filed March 9, 1940 3 Sheets-Sheet 3 INVENT ORS Lean/P. Ludw/y and fienjgmgfifiaken q ATTQRNE? WITNESSES: 6 1 7% WM 5 Patented May 28, 1946 CIRCUIT INTERRUPTER Leon R. Ludwig, Forest Hills, and Benjamin P. Baker, Turtle Creek, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 9, 1940, Serial No. 323,214

26 Claims.

This invention relates to improvements in circuit interrupters, and more particularly to operating mechanisms for interrupters of the fluid operated type.

In the patent of A. H. Bakken, No. 2,282,154, issued May 5, 1942, and assigned to the assignee of this application, is shown and described a circuit interrupter of the gas-blast type utilizing compresed gas, such as air, to extinguish the arc and also to actuate appropriate mechanism for operating the contact structure to open and closed circuit positions. The instant invention is di rected more specifically to the mechanical operation of a circuit interrupt r of the aforesaid type, although the particular operating mechanism disclosed is not necessarily limited in its use in connection with an interrupter of the airblast type, and may with equal advantage be used in connection with air breakers other than that disclosed and also breakers of the liquid-immersed type.

The main object of our invention is to provide an improved operating mechanism of the fluid pressure actuated type that is simple and rugged in construction and capable of efiicient and reliable operation.

A further object of our invention is to provide a fluid pressure actuated operating mechanism for circuit interrupter-s that is capable of effecting high-speed opening and closing of the interrupter contacts without subjecting the contact structure and associated mechanism to severe shocks and strains.

It is also an object of our invention to provide a gas pressure actuated operating mechanism for circuit interrupters that possesses a high degree of flexibility in operation, so as to render the interrupter trip-free on overload, and in any other respect make it equivalent to trip-free mechanical mechanisms, but without the use of mechanical latches or mechanical trip-free devices.

Other objects and advantages relate to the various parts of the operating mechanism, as the operating piston, control valves, gas pressure supply and the arrangement thereof, and will appear more fully in the following description when read in connection with the accompanying drawings, in which:

Figure 1 is a front elevation View of a gas-blast circuit interrupter embodying the principles of our invention;

Fig. 2 is aside elevation View, partially in section, showing the circuit interrupter illustrated in Fig. 1;

Fig. 3 is a cross-sectional view taken through one of the auxiliary gas storage tanks at III-III of Fig. 2;

Fig. 4 is a further sectional view of a portion of one of the auxiliary gas storage tanks taken along the line IV-IV of Fig. 3; and

Fig. 5 is an elevation view, partially in section, of the operating cylinder of the operating mechanism and the control valves therefor.

Referring to the drawings, the reference numeral 6 designates the main tank for storing gas, such as air, under pressure. Extending from the top of the tank 6 are three flanged conduits 8 which, in turn, carry a metallic valve casing it. Mounted upon the upper end of each valve casing I9 is a tubular insulator I2 which, in turn, has secured to its upper end an arc chute support M also of insulating material. The support It has mounted thereon a stationary contact 16 provided with an external circuit terminal I8. A throat-like gas passage 20 extends through the support [4, and is preferably coextensive with the passage through the tubular insulator l2. This throat-like passage 20 opens into an arc chute structure 22 mounted upon the support l4 and secured thereto by bolts 24.

The forward side of each arc chute 22 is more clearly shown in Fig. 1, and is provided with a rectangular slot 25 at the lower end thereof through which a blade-like movable contact 28 may operate into and out of engagement with the stationary contact 16. The movable contact 28 is preferably of inverted L-shaped blade construction having a bifurcated arm 30', the two legs of which are pivoted at 32 a conducting bracket 34 clamped about the tubular insulator l2. The pivotal connection- 32' is of the highpressure type, so that good electrical connection is maintained at all times between the contact arm- 30 and the bracket 34. The right-hand side of the bracket 34 is provided ,with an external circuit terminal 36'. Thus when the interrupter is in the closed circuit position, as shown, an electrical circuit is made therethrough from the terminal it, the stationary contact [6, moving contact 28, contact arms 30, bracket 34' to the terminal 35.

Movement of the contact arm 36 about its pivot 32 to pen and closed circuit positions is accomplished by an operating mechanism generally indicated at 38. This operating mechanism' is'preferably a fluid: motor of the gas pressure opera-ted type, and includes a cylinder 40, a' piston "operative therein, and provided with a connecting rod 44' extending through the upper end of the cylinder 40. The connecting rod 44 is coupled by a pair of links 46 to a crank arm 48 secured to a cross-shaft 50. The crossshaft 50, for example, may be journaled in suitable brackets 52 secured to the side of the pressure tank 6.

The cross-shaft 50 is provided at spaced intervals with three crank arms 54 which, in turn, are coupled by an insulating operating rod 56 to the moving contact arms 30 of each respective pole unit. It will thus be seen that, if gas under pressure is admitted above the piston 42, the piston will be moved downwardly within the cylinder 40 and the connecting rod 44 will actuate crank arm 48 so as'to rock the crossshaft 50 in a counterclockwise direction as viewed in Fig. 2. Since the crank arms 54 are secured to the cross-shaft 50, rotation of the latter will also cause the crank arms 54 to be rotated in a counterclockwise direction, thereby moving the operating rods 56 downwardly so as to swin the contact arms 3|! about their pivotal points 32 towards the open-circuit position.

It should be noted that each crank arm 54 is provided with a cam surface 58 against which a roller 60 carried by the end of a bell crank 52 is adapted to ride. The bell crank 62 is pivoted upon a suitable support at 64, and has its other free end .nivotally coupled to a valve stem I35 carrying a valve 66 at its lower end which, in turn, is seated within the valve chamber Iii. The valve 68 normally seals the hollow air passage within the insulator I2 from the pressure tank 6. It is thus seen that, as the three crank arms 54 start to rotate in a counterclockwise direction as viewed in Fig. 2, the cams 58, by engaging the roller 60, will cause bell crank 62 to be rocked in a clockwise direction, thereby depressing the valve stem 66 to open the valve 68. As valves 68 are opened, blast of compressed air from the storage tank 6 rushes through each of the hollow insulators I2 through the throat-like passage 20 between the contacts l6 and 2B. The cam 58 of each pole unit is preferably so positioned with respect to the roller 60 that the valve 68 is o ened just prior to separation of the contacts l5 and 28, thereby insuring a blast of arc-extinguishing gas at the surface of the separating contacts when the arc is drawn. The are established between the contacts I6 and I8 is blown into the arc chute 22 by the blast of gas from the pressure tank 6 and extinguished in the arc chute. The air-blast control cams 58 on the crank arms 54 are so shaped that, when the moving contacts 28 have reached their full open circuit position. the airblast valves 68 are again permitted to close so to shut off the blast of arc-extinguishing gas.

It will be obvious that, upon the admission of gas under pressure on the lower side of piston 42, the piston will be driven upwardly within the cylinder 40, and the moving contacts 26 will be moved to the closed-circuit position in the reverse order above-described in connection with the opening operation. In moving to the closed circuit position the crank arms 54 are brought into engagement with stop members 55 so positioned that the crank arms 54 and their associated operating rods 56 form a slightly overcenter toggle arrangement, thereby maintaining the contacts 28 positively locked in the closed circuit position.

In order that the opening and closing operation of the circuit interrupter may be accomplished so as to meet the requirements of all operating conditions, two control valves I0 and I2 are provided. In general, these control valves control the flow of air from the storage tank 6 to the operating cylinder 4!] to eflect the opening and closing operations. The control valves "It and 12 are generally of the form broadly illustrated in the aforesaid patent to A. H. Bakken, and are secured to the operating cylinder 4%, as shown, to form a unit assembly.

As more fully disclosed in the aforesaid Bakken patent, this assembly rests upon and is secured to flanges I4 and 16 by two short conduit sections 18 and 86. The conduit sections I8 and 80, in turn, communicate respectively with relatively large conduits 82 and 84 extending through the side of the pressure tank 6 and terminating well within the interior thereof. Each of the conduits 82 and 84 is provided with a partition generally indicated at B6 in Fig. 2. and more specifically illustrated in Figs. 3 and 4. The partitions 86 are for the purpose of forming auxiliary gas storage compartments 83 and 85, respectively, for supplying the compressed gas used in opening and closing the interrupter. In order that the volume of the auxiliary tanks may be varied to meet certain conditions, we prefer a construction for the partitions 86 as more specifically shown in Figs. 3 and 4.

A threaded shaft 83 is secured at its left-hand end, as viewed in Fig. 2, to the outer end of each of the conduits 82 and B4. Threaded to the shaft 88 is a metal collar 9i Surrounding the threaded rod 88 and held in contact with the metallic collar 90 is a flanged washer 92 of leather, rubber or other suitable material which is yieldingly urged into engagement with the inner ciroumference of the conduit 82 by a spring cupped washer 94. A nut 95 hearing against a washer 98 of smaller diameter serves to lock the assem' bly in position with respect to the threaded rod 88. The entire assembly is provided with a plu .rality of through passages or orifices I00 which serve to admit air under pressure from the tank 6 to the auxiliary tank Within the conduits 82 and 34. By enlarging the left-hand ends of the passages ID!) and providing the enla ged portions with threads, suitable plugs Ill? may be inserted for the purpose of closing part of the passage to the flow of gas when desi ed. Thus if a men rapid or a slower replacement of is d sired from the tank 5 to the am . rr tanks 83 and 85, some of the plugs Ill? are removed or replaced as the circumstances demand.

The valves I?! and 72, which respectively control the flow of air from the au ary tanks; 3 and 85, are similar in construction. The alve I0, which is shown in cross-section (omprises a valve casing I04, the lower face of which rests upon a flange 14 of conduit "8. The lower face of the casing I M is provided with a valve seat I05 which coacts with valve I08 of the poppet type. The valve M13 has a stem III! of usual construction provided at its end with a valve-lifting washer H2 coacting with a p g I I4 for normally holding the alve closed, The inner chamber or the valve casing Hi4 communicates, by passage II6, to the upper end of the cylinder 48. The side of the valve casing I04 is also provided with a bore or passage II! which communicates with the auxiliary chamber 83 and the valve chamber I20 within an auxiliary valve casing I22.

The auxiliary valve casing I22 has an elec tromagneticaly operated valve 624 which communicates, by passage I26, with a piston chamber I28 at the upper end of the valve casing I04.

The piston chamber Iithas. a piston: I3 3: operable therein which is normally held in. the raised position by a spring I32. The lower end: or skirt of the piston I30 extends to a plurality of ports or bleed passages I34 passing radially through theside of: the valve casing- I04. When the piston I 30 is in the raised position as shown in Fig. 5; the ports I3' iare-opened thereby con.- neoting the space in the operating cylinder 40 above the operating piston 42 with the atmosphere. It will be observed that upon movement of the piston I30 downwardly; the ports I34 will be: closed so as to seal the passage I I6 and the cylinder 404mm the atmosphere. The valve I 24 is actuated to the open position by an electromagnet I 38 which may be energizedby a suitable source of electrical potential (not shown), and is. moved tothe closed position by a spring I38;

When the interrupteris in the closed circuit position, the operating mechanism. including the operating piston 42 is in the position as shown in Fig. 5. When in this position, an overload occurs, or if it is desired for any other reason to open the-interrupter; electromagnet I'36-of the valve (0 is energized. The electromagnet I36 is preferably connected through and controlled by an auxiliary switch I40 mountedupon the tank 6', as shown in Fig. l, auxiliary switch I401 is of usual and well-known construction, further description thereofis deemed unnecessary for the purpose of understanding the present invention.

Upon energizing the electromagnet I36. valve I24 is opened to permit air underpressure Within the auxiliary tank 93 to flow through the passage H 8'; through the valve I24; the passage I26 into the piston chamber I281 The piston I-30isthereupon driven downwardly against the force of spring I32, thereby closing the vent ports I34. It will be notedthat the piston I 30 is 50 disposed with respect to the upper end of the valve stem I I0 that the ports I34 are substantially closed by the time the piston engages the upper end of the stem Ht. Further downward movement of thepiston I33 forces the valve stem H0 downwardly against the action of the valve spring I I4 toopenthe valve I08 and permit compressed air from the auxiliary tank 83 to liowthrough the passage H6 to the-space above theoperating piston42; The piston 42 will thereupon be moved downwardly to actuate breaker contacts 28' to the open circuit position in the manner previously described.

When the piston 42- reaches the lower endof the cylinder 40, or. in other words, when the breaker has reached its full open circuit position, the auxiliary switch I40 actuated by suitable linkage I42 coupled. to the connecting rod 44 will interrupt the circuit energizing the electromagnet I36 to allow valve I 2 4 to close. Thus, when the pressure is removed from the upper end of piston I30, springs I14 and I 32 cause the piston I30 to move upwardly and'at the same time cause valve I08 to close. In order that the piston 42 may be moved downwardly at a very high rate of speed so as to efiect opening of the contacts of the interrupter as quickl as possible, a relatively high gas pressure is essential at the beginning of the opening stroke. We have discovered that if the operating pressure is maintained substantially constant upon the piston 42, it is dimcult to arrest the motion of the piston at the end of its stroke without injury to the operating mechanism or contact structure.

Inasmuch as the In orderto" eliminate shock at. the: end of the opening stroke, but without: sacrificing speed of operation, we have decreased the force acting upon the piston 42 as the movement of: the piston increases. This. has. been accomplished by pro viding the auxiliary tank 83 of: such volume as to produce the desiredv results. For example, if the airpressure within the maintank 6 is maintained at 1 50 pounds persquare inch, it is desirable to. provide the auxiliary. tank 83; of volume approximately one-half of' the volume of the operating cylinder 4.0. As the. operating piston 42 is moved. to the open-circuit position, the air pressure within the auxiliary tank 83 decreases to approximately 50- pounds per. square inch during the short interval of time required by the mechanism to reach the fullopen position. Thus, the average pressure supplied bythe auxiliary tank 83 to the: piston 42 is much less than would be supplied by the main tank 6. In order to meet these requirements, it is also necessary that a: very. small orifice or passage lilll in the partition 8.6. be employed so as to avoid substantial replacement of air within the auxiliary tank 83 from themaintank 6 during the opening operation. By providinga number of orifices or passages I00 and providing means, such as plugs I02, as. shown in. Fig. 4, the proper rate of flow of air from the main tank 6 into the auxiliary tank 83. may be obtained.

Theopening operation under conditions abovedescribed is similar to that obtained by purely mechanical: means, utilizing acompression. spring directly operative on the operating mechanism. Although, by using but a. limited quantity of air to-eflect the opening operation, the piston and operating mechanism may be brought to rest without substantial shock or impact, it is desirableto;provideshock-absorbing means of some form in order to maintain the requisite highspeed operation. It is, of course, obvious that unless. the space ahead: of the operating piston 4.2- within the operating cylinder 40 is freely vented, the gas. contained therein will be compressed during the opening stroke of the piston. By controlling thedischarge of air ahead of the piston 42- during the opening stroke. the degree ofi' compression, particularly at the end of the stroke, maybe controlled" and: utilized" to provide a shock-absorbing. cushion for arresting the motion. of the piston. and the associated moving parts. This control of the escape of air ahead of the piston; is provided: by the bleed passages or ports I231 through the side of the valve casing IM' of the control valven. It will be observed that the control valve 12 isv similar in construction to the control valve L0, and that when control valve 10 is. opened: for admitting air to the operating cylinder 4:0; to effect an opening operationi. the; control valve 12-, which normally admits; air; at the lower end of the cylinder 43, to effect the; closing; operation, will be closed.

In practice, it is. desirable to arrange the ports L34. oi: the control valve 12, both with respect to size and number so that the air ahead of the pision, 42 during the opening operationmay reach compr ssionof. from. 55150, pounds p square inch at the end of; the opening stroke. It, of course, follows that this condition of compression within the cylinder 45 ahead of the, piston 42* persists only for a short time, and that the air quickly bleeds from the cylinder 40 through the ports I34. Also, when the piston 42 reaches the full open-circuit position and the control valve is closed as a result of deenergization of the electromagnet I36, the air above the piston 42 quickly bleeds through the passage I I6 and ports I34 in the control valve I so as to permit a reclosing operation of the interrupter by the admission of air to the lower side of the piston 42 through the valve 12.

In the event that it is desired to close the interrupter, the electromagnet I36 of the control valve 12 is energized through the auxiliary switch I40 so as to admit air under pressure from the auxiliary tank 85 to the lower side of the operating piston 42. Inasmuch as the valves 12 and III are identical in construction, further description of the closing operation need not be given, except that it may be stated that, during the closing operation, air above the piston 42 is compressed so as to provide an elastic cushion for arresting the motion of the operating mechanism upon reaching the full closed-circuit position, The degree of compression desired will, of course. be obtained by the particular selection of size and number of exhaust ports I34 provided in the control valve I0. Also upon reaching the closed circuit position, or at a predetermined time before, the auxiliary switch I40 will interrupt the control circuit to the electromagnet I36 of the control valve I2 so as to deenergize the electromagnet and permit the valve 12 to close in the manner above-described.

In the event that the circuit interrupter is closed while conditions of overload exist on the connected circuit, it becomes necessary to quickly reverse the motion of the piston 42 so as to actuate the interrupter to the open circuit position.

This operation becomes difiicult or, in fact, may

be impossible. unless provision is made to quickly relieve the pressure under the piston 42. It will be observed that, during the closing stroke, compressed air has been dmitted below the piston 42, and that, upon reaching the closed-circuit position when conditions of overload exist upon the breaker contacts, the piston would ordinarily have to be moved against the residual air pressure remaining under the piston at the end of the closing stroke.

In order that the piston 42 may be moved to the open-circuit position under the above conditions, a quick release valve is provided at the lower end of the cylinder 40, as more clearly shown in Fig. 5. This release valve, for instance, may comprise a valve member I44 carried by a stem I40 slidably operative through the lower end 01! the cylinder 40 and biased to the closed position by a spring I48 or other suitable means. The valve I44 may be moved to the open position by an operating rod I50 secured at its lower end to the valve I44 and at its upper end to the lower end of the connecting rod 44. More specifically, the upper end of rod I50 is provided with a circular head I52 slidable within the bore of the connecting rod 44 and adapted to be engaged at its lower shoulders by a packing and guide sleeve I54 threaded into the lower end of the connecting rod 44. The operating rod I 50 is preferably of a length such that when the piston 42 reaches the upper limit of its travel, valve I44 will be fully opened, thereby quickly exhausting the air below the piston 42 to atmosphere. Thus the piston 42 is free to move downwardly as under normal conditions of operation. It will be noted that only a short travel in the downward direction is required of the piston 42 before valve I44 is closed, thereby permitting the air under the piston 42 to be compressed for the purpose of cushioning the piston at the end of its opening stroke.

Inasmuch as the control valves 10 and I2 are electrically operated by their respective electromagnets I36, a condition may prevail whereinthe two electromagnets may become energized simultaneously. Thus, if equal forces were admitted on either side of the operating piston 42, the operating mechanism would become inoperative and no movement in either the opening or closing direction would take place. Since it is a prime requisite to provide overload protection for the connected circuit, it is desirable to insure opening operation even under such abnormal conditions of simultaneous energization of both control valves. The desired reliability of operation has been accomplished by making the auxiliary tank 83 larger than the auxiliary tank 85, so that in the event that valves I0 and I2 are simultaneously opened, even though each tank 83 and B5 is initially at the same pressure, the volume of tank 83 being larger will give a higher average pressure and exert a predominating force upon the piston 42 and cause it to be moved toward the open-circuit position. The auxiliary tanks 83 and 85 are so proportioned that sufllcient movement of the interrupter toward the open circuit position will be obtained to effectively interrupt the circuit. The volume of the auxiliary tanks 83 and 85 may readily be changed to suit operating conditions by adjusting the partition members 86 axially along the threaded rods in a manner previously described.

We have discovered that by utilizing an operating mechanism of the type above-described in a circuit interrupter capable of interrupting 1,500,000 kv.-a. at 15,000 volts, contact opening speeds in excess of 2'7 feet per second were obtainable. In spite of this high-speed contact movement, the operating mechanism was brought to rest at the end of its stroke without subjecting the mechanism or its associated parts to severe shocks 0r strains.

Furthermore, the above-described mechanism is in effect trip-free in that opening of the interrupter contacts immediately following a closure under conditions of overload on the connected circuit is obtained with the same degree of effectiveness as during a, straight opening operation. This trip-free effect, however, is obtained without the use of latches or mechanically-operated trip-free mechanisms.

Although we have shown and described a. specific circuit interrupter and a particular operating mechanism therefor, it is to be understood that the same is for the purpose of illustration and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

We claim as our invention:

1. In a circuit interrupter, separable contacts operating means for actuating said contacts to open and closed positions, said operating means including a fluid pressure actuated device, a main source of fluid under pressure, an auxiliary sourc: of fluid normally maintained under pressure derived from said main source, and valve means between said auxiliary source and said pressure actuated device for admitting iluid under pressure from said auxiliary source to said pressure actuated device, said auxiliary source having a capacity to operate said pressure actuated device completely and but once without replacement of fluid from said main source of fluid pressure.

2. In a circuit interrupter, separable contacts.

operating means for actuating said contacts to open and closed positions, said operating means including a fluid pressure actuated device, a main source of fluid under pressure, an auxiliary source of fluid under pressure derived from said main source, and valve means for admitting fluid under pressure from said auxiliary source to said pressure actuated device, said auxiliary source having a capacity to operate said pressure actuated device but once without replacement of fluid from said main source of fluid pressure, said auxiliary source of fluid pressure having a permanent connection with said main source, and means controlling the flow of fluid from said main source of pressur to said auxiliary source to prevent substantial replacement of fluid in said auxiliary source during a contact operation.

3. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a cylinder, a piston in said cylinder operatively coupled to at least one of said contacts, a main tank for storing fluid under pressure, an auxiliary tank deriving fluid and normally maintained under pressure from said main tank and supplying all of the fluid for operating said piston in one direction, and valve means for admitting fluid from said auxiliary tank to said cylinder to actuate said piston, the volume of said auxiliary tank being so proportioned with respect to the volume of said cylinder that the force exerted upon said piston decreases substantially with the distance traveled by said piston.

4. In a circuit interrupter, separabl contacts, operating means for actuating said contacts to open and closed positions, said operating means including a cylinder, a piston in said cylinder operatively coupled to at least one of said contacts, a main tank for storing fluid under pressure, an auxiliary tank deriving fluid under pressure from said main tank, and valve means between said auxiliary tank and cylinder for admitting fluid from said auxiliary tank to said cylinder to actuate said piston, and means disposed between said main tank and said auxiliary tank for controlling the rate of flow of fluid therebetween, said means admitting substantially no fluid into said auxiliary tank durin the operation of said operating means.

5. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, a source of gas under pressure, valve means for admitting gas from said source to at least one side of said piston for actuating said operating means, and means controlling the escape of gas from ahead of said piston during movement thereof in a given direction to provide a shock absorbing cushlon of gas for arrestin the motion of said piston at the end of its stroke.

6. In a circuit interrupter, contact means, operating means including a cylinder and a pist'on operative therein for moving said contact means to open and closed positions, a, source of gas under pressure, opening and closing valves for alternately admitting gas under pressure from said source to opposite sides of said piston to respectively cause said piston to move to open and closed circuit positions, and means operated in accordance with the position of said valves for controlling the escape of gas ahead of said piston during movement thereof in either the aircuit opening or closing direction, said last-named means enabling gas to be compressed ahead of said piston to assist in bringing said piston to rest at the end of its stroke.

7. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, a source of gas under pressure, opening and closing valves for alternately admitting gas under pressure from said source to opposite sides of said piston to respectively cause said piston to move to open and closed circuit positions, and means controlling the escape of gas ahead of said piston during movement thereof in either the circuit opening or closing direction to provide a shock absorbing cushion of gas for arresting the motion of said piston at the end of its stroke, and additional means for quickly exhausting the gas on the high pressure side of said piston at the end of its stroke to enable the piston to be reversed immediately without interference from excessive back pressure.

8. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, a source of gas under pressure, opening and closing valves for alternately admitting gas under pressure from said source to opposite sides of said piston to respectively cause said piston to move to open and closed circuit positions, means operated in accordance with the position of said valves for controlling the escape of gas ahead of said piston during movement thereof in either the circuit opening or closing direction to cause gas to be compressed ahead 'of said piston to assist in bringing said piston to rest at the end of its stroke, and means for quickly relieving the gas pressure on the high pressure side of said piston at the "end of its stroke to enable said piston to be reversed immediately free fromv back pressure.

9. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, means for selectively admitting gas under pressure to either side of said piston for causing said piston to move to open and closed circuit positions, valve means controlling the escape of gas ahead of said piston to provide an elastic cushion for bringing said piston to rest at the end of its stroke, and additional valve means operative at the end of the stroke of said piston for releasing the pressure on the high pressure side of said piston so as to enable said piston to be reversed without time delay.

10. In a circuit interrupter, con-tact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, said piston having a tubular connecting rod secured thereto, means for selectively admitting gas under pressure to either side of said piston for causing said piston to move to open and closed circuit positions, a gas escape valve for said cylinder, said valve having a stem extending through said cylinder and being slidably operative within said tubular connecting rod, and means for connecting said stem to said connecting rod for opening said valve upon movement of said conta'cts to the closed circuit position, said valve releasing the gas pressure ahead of said piston to enable said contacts to be moved without time delay to the open circuit position.

ll. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, means for selectively admitting gas under pressure to either side of said piston for causing said piston to move to open and closed circuit positions, a gas escape valve for said cylinder, and means disposed within said cylinder for operatively coupling said piston to said gas escape valve for opening said valve upon movement of said contacts to the closed circuit position, said valve releasing the gas pressure ahead of said piston to enable said contacts to be moved without time delay to the open circuit position.

12. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed .positions, said operating means including a fluid pressure actuated device, a main source of fluid under pressure, a first auxiliary source of fluid under pressure derived from said main source, a second auxiliary source of fluid under pressure also derived from said main source, valve means for admitting fluid under pressure from said first auxiliary source to said pressure actuated device for causing said device to be moved in one direction, and a second valve means for admitting fluid under pressure from said second auxiliary source to said pressure actuated device for causing said device to be moved in the reverse direction, one of said auxiliary sources of pressure having a larger capacity than the other auxiliary source to cause said pressure actuated device to be actuated always in the same direction when fluid is admitted thereto simultaneously from both auxiliary sources of pressure.

13. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a piston, means for supplying fluid under pressure to one side of said piston to move said contacts to one of said positions, and means for supplying fluid under pressure to the other side of said piston to move said contacts to the other position, the average pressure supplied by one of said pressure supply means being greater than the average pressure supplied by the other pressure supply means for causing said piston to be moved always in the same direction when fluid pressure is supplied simultaneously from both supply means to opposite sides of said piston,

14. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a piston, a main source of fluid under pressure, an auxiliary source of fluid under pressure derived from said main source, means for admitting fluid from said auxiliary source to one side of said piston to move said contacts to the open position, a second auxiliary source of fluid under pressure also derived from said main source, and means for admitting fluid from said second auxiliary source to the other side of said piston for moving said contacts to the closed position, said first auxiliary source having a fluid capacity capable of delivering fluid at a higher average pressure than said second auxiliary source to cause said piston to move said contacts to the open position when fluid is supplied to both sides of said piston from said respective sources.

15. In a circuit interrupter, contact means for opening and closing the circuit, a fluid motor for actuating said contact means, a source of fluid under pressure, a chamber containing a quantity said fluid under pressure suflicient to operate said fluid motor to actuate said contact means in one direction with a large reduction in pressure in said chamber, valve means for controlling the flow of fluid from said chamber to said fluid motor, and a connection from said chamber to said source of fluid under pressure automatically operable immediately upon said reduction in pressure in the chamber to begin restoring the pressure in the chamber to full value.

16. In a circuit interrupter, contact means for opening and closing the circuit, a fluid motor for actuating said contact means, a source of fluid under pressure, a chamber containing a quantity of said fluid under pressure, valve means for controlling the flow of fluid from said chamber to said fluid motor, a restricted passage from said source of fluid under pressure to said chamber, the size of said chamber and the size of said restricted passage being such that there is a large reduction in pressure in said chamber upon the actuation of said contact means by said fluid motor, and said restricted passage being open during actuation of said contact means to permit the restoration of full pressure in said chamber from said source.

17. In a circuit interrupter, contact means for opening and closing the circuit, a fluid motor for actuating said contact means, a source of fluid under pressure, and a control device between said fluid motor and said source of fluid under pressure operable to apply pressure to said fluid motor at substantially the full pressure of said source at the beginning of the operation of said contact means and to decrease the pressure during the operation of said contact means until only a much lower pressure is applied at the very end of the operation.

18. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means, a source of fluid under pressure, valve means for admitting fluid from said source to actuate said piston in one direction, and means for relieving said pressure to permit return movement of said piston by providing a large vent apart from said valve means for quickly relieving the pressure during the first part of the return movement and means apart from said large vent providing a restricted vent for relieving the pressure slowly and cushioning the later part of the return movement.

19. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a cylinder, a piston in said cylinder operatively coupled to at least one of said contacts, a main tank for storing fluid under pressure, an auxiliary tank deriving fluid under pressure from said main tank and normally maintained under sufficient pressure to actuate the piston, and valve means for admitting fluid from said auxiliary tank to said cylinder to actuate said piston, means disposed between said main tank and said auxiliary tank for controlling the flow of fluid therebetween, and the pressure exerted on said piston from said auxiliary tank being substantially unaffected by the pressure in the main tank during the period that the piston is being moved.

20. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a cylinder, a piston in said cylinder operatively coupled to at least one of said contacts, a main tank for storing fluid under pressure, an auxiliary tank deriving fluid under pressure from said main tank, means for caus ing a blast of fluid from said main tank to flow across said contacts as they separate to extinguish the arc, and valve means for admitting fluid from said auxiliary tank to said cylinder to actuate said piston, means disposed between said main tank and said auxiliary tank for controlling the flow of fluid therebetween, and the pressure exerted on said piston from said auxiliary tank being substantially unaffected by the pressure in the main tank during the period that the piston is being moved.

21. In an electric circuit breaker, a pair of relatively movable contacts separable to draw an arc therebetween, a fluid motor for producing relative movement between said contacts, a main source of fluid under pressure, means for introducing a blast of fluid driven by the pressure of said main source adjacent said contacts for arcextinguishing purposes, an auxiliary source of fluid under pressure supplied from said main source for operating said fluid motor to produce relative movement between said contacts, and said auxiliary source supplying substantially all of the fluid to operate said motor at an average pressure less than the pressure that would be supplied from said main source.

22. In an electric circuit breaker, a pair of relatively movable contacts separable to draw an arc therebetween, a source of fluid under pressure, means for introducing a blast of fluid from said source adjacent said contacts for arc-extinguishing purposes, a fluid motor, a second source of fluid under pressure connected to supply only said fluid motor, means for operating said motor from said second source to produce relative movement between said contacts, and the pressure supplied to the fluid motor from the second source being substantially unaffected by the pressure of said first-mentioned source during operation of the fluid motor.

23. In a circuit interrupter, contact, means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, a source of gas under pressure, valve means for admitting gas from said source to at least one side of said piston for actuating said operating means, means controlling the escape of gas from ahead of said piston during movement thereof in a given direction to provide a shock absorbing cushion of gas for arresting the motion of said piston at the end of its stroke, and valve controlled outlet means near one end of the cylinder operated to open widely and permit quick exhaust of gas only when the piston is near the other end of the cylinder to permit quick movement of the piston during at least the early part of its movement toward the end having said valve controlled outlet means.

24. In a circuit interrupter, contact means, operating means including a cylinder and a piston operative therein for moving said contact means to open and closed positions, a source of gas under pressure, valve means for admitting gas from said source to at least one side of said piston for actuating said operating means to close the contacts, means controlling the escape of gas from ahead of said piston during movement thereof in closing direction to provide a shock absorbing cushion of gas for arresting the motion of said piston at the end of its closing stroke, and valve controlled outlet means near the end of the cylinder toward which the piston moves during opening movement operated to open widely and permit quick exhaust of gas only when the piston is near the end of the cylinder Where the contacts are closed.

25. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a fluid pressure actuated device, a main source of fluid under pressure, an auxiliary source of fluid under pressure derived from said main source, and valve means for admitting fluid under pressure from said auxiliary source to said pressure actuated device, said auxiliary source having a capacity to operate said pressure actuated device completely and but once without replacement of fluid from said main source of fluid pressure, and another valve means for admitting fluid from said main source to blast through the are formed at said separable contacts to extinguish it independently of the pressure of said auxiliary source.

26. In a circuit interrupter, separable contacts, operating means for actuating said contacts to open and closed positions, said operating means including a cylinder, a piston in said cylinder operatively coupled to at least one of said contacts, a main tank for storing fluid under pressure, an auxiliary tank deriving fluid under pressure from said main tank and supplying all of the fluid for operating said piston in one direction, and valve means for admitting fluid from said auxiliary tank to said cylinder to actuate said piston, the volume of said auxiliary tank being so proportioned with respect to the volume of said cylinder that the force exerted upon said piston decreases substantially with the distance traveled by said piston, and a blast valve for admitting fluid from said main tank to extinguish the are formed at said separable contacts substantially independently of the pressure in said auxiliary tank.

LEON R. LUDWIG. BENJAMIN P. BAKER.

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