US2261925A - Pressure fluid servomotor for high potential switches - Google Patents

Description

A. SALZER Nov. 4, 1941.

PRESSURE FLUID SERVOMOTOR FOR HIGH POTENTIAL SWITCHES 2 Sheeis-Sheet 1 Filed Feb. 24, 1959 u a W a a 5 :Inesses la s I Patented Nov. 4, 1941 PRESSURE FLUID SERVOMOTOR FOR HIGH POTENTIAL SWITCHES Albert St'tlzcr, Geisweid, Germany Application February 24, 1939, Serial No. 258,314

In Germany February 28, 193

8 Claims.

In the compressed air actuation of switches in electric power plants, it is of great importance that, on the one 'hand, every switching operation once commenced should be carried out with complete security to the end of the operation, even when the impulse given for example by a push knob or other device is only very short and ceases before the switching operation is terminated. On the other hand, it is of prime importance to exclude the possibility of the switching operation becoming suspended during its movement, for example by the dropp of the driving pressure, since thereby permanent arcs could occur, leading to the destruction of the switches, machines and the like.

Safety devices preventing non-completion of a switching operation when only very short operating impulses are adopted are already known. One such device adopts the insertion of an intermediate valve between the compressed air cylinder which carries out the switching process and a preliminary control valve excited only temporarily, the intermediate valve being controlled by the preliminary control valve and shifted in both directions by the pressure medium, and also in its position of rest connecting the working space of the switch cylinder with atmosphere. whilst in the opposite terminal position it connects it with the pressure medium pipe. This device has the disadvantage that the intermediate valve is continuously under the full pressure of the working agent and consequently it is diflicult to keep continuously tight. Leakages which could cause a sluggish switching action and all the dangers attaching thereto are consequently not impossible.

Another device has already been proposed for the same purpose in which the cylinder of the control piston connected with the inlet valve for the compressed air supply to the working cylinder after ceasing its charging with compressed air efiected by the key switch, is regularly emptied and the compressed air acting on the inlet valve only brings this inlet valve into the closed position (and thus cuts off the delivery of compressed air to the working cylinder) when the compressed air which is above the control piston in the control cylinder has all escaped to atmosphere.

Further, in order to prevent a switching operation once commenced not being carried to its termination owing to insufficient pressure, and thus causing a permanent arc, it has already been proposed to provide a spring-loaded subsidiary piston which opens a subsidiary path for .eration when the switching stroke has commenced. It is, however, diflicult to provide so wide an outlet conduit that the air escaping immediately after the beginning of the switching stroke, escapes sufliciently rapidly for the working piston to be stopped before reaching the arcing limit.

The present invention avoids these drawbacks by means which ensure that the pressure me dium is only supplied to the working cylinder carrying out the switching stroke when the tension of this is so high that the terminal position of the switch will be attained under any circumstances. This result is attained by an intermediate valve device, specially constructed for this purpose, between the key valve and the working cylinder. A piston of this intermediate valve device is subject, on the one side, to the working pressure and is supported on the other side by an adjustable spring. It is, furthermore, infiuenced by a 'pair of auxiliary springs located transversely to the piston axis and arranged on the pressure medium side, which auxiliary springs act, by means of two oscillatable toggles aiiording a snap-over action.

In order that this invention may be clearly understood and readily carried into eilect two sheets of drawings are appended hereto illustrating embodiments thereof, and wherein:

Fig. 1 shows in sectional elevation a device for switching in power switches, the switchedou or preparatory switching position being shown.

Fig. 2 is a sectional elevation but showing the relative positions of the parts at the instant of attaining the terminal switched-in position.

Fig. 3 is a sectional elevation of a modification which embodies means for switching in either direction, e. g. for circuit breakers, and,

Fig. 4 is a detailed sectional elevation view of a further modification.

Referring to the drawings the working cylinder a contains the working piston b with a switching rod 0 which is connected in any suitable manner with the switch contacts or contact levers not shown. In the cover of the working cylinder a through which the rod 0 passes is a compressed air inlet opening it through which the compressed air enters on the operation of an intermediate valve device e above the piston 1). Open- 2 a,oe1,eas

ings f are arranged in the lower part of the working cylinder a. through which openings the working air escapes to atmosphere when the piston b passes into the terminal switching position shown in Fig. 2.

The intermediate valve device e consists of the key valve device a and the safety snap valve device It controlled by the key valve 0, both being adapted for operation by compressed air. This air enters through a connection 13 in the cover i in a conduit is and the prelt .iinary chamher i, of the key valve and m of the safety valve h.

The key valve 0 consists oi the cylinder 1:, the key spindle o with main piston p and subsidiary piston q, and the valve cone 1', which under the pressure in the preliminary space 1 blocks the connection thereof with the valve cylinder 1: and the by-pass conduit s.

The safety valve h consists of the cylinder at in which is carried the step piston u, the upper reduced diameter portion 1) of which carries a valve plate cone in engaging a seating 20 so that in the position of rest this valve w closes the pressure preliminary space m. The valve 10 is furthermore provided with a circumferential recess a: in which engage two toggles l0 movable perpendicularly to the axis of the piston about the axes of hinges supported by slides 11 located in guides z. The hinge slides 11 are connected by tension springs 11 This valve carrying'part o of the piston 11. is in a preliminary space H of the cylinder t, and such space communicates with the by-pass conduit 8. The piston a has a concentric cylindrical hollow space l2 open downward and receiving one end of a compression spring I: interposed between the piston u and a disc I adjustable by a regulating screw IS in a cap it closing the cylinder t. i

Near the upper part of the cylinder t there is an annular surrounding space communicating with a conduit i8 extending into the working cylinder a. This in the position of rest is closed by the piston part 12.

The method of operation of the device is as follows:-

In the position of rest, the valves 1' and w of the intermediate valve device e are closed. There is pressure only in the connecting conduit is and the preliminary spaces 1 and m. The cylinder spaces n and t are relieved through the conduit 3 by the air pressure release opening [9 in the closing cap iii of the cylinder t. The piston b oi the working cylinder a is, as shown in Fig. 1, in its upper prepared position for the switching in.

For the switching in the free end of the key valve spindle o is forced upward by any electrical mechanical or manual actuation, and the upper piston p thereof lifts the valve cone 1' from its seat against the influence of a spring 1 and at the same time the lower piston q interrupts the connecting conduit 8 between cylinder preliminary space It and cylinder t. The compressed air passes through the seating of the valve 1' into the cylinder preliminary space i i and impinges on the upper annular surface u of the piston it which overcomes the influence of the main spring I! and the supporting force of the toggles ill arising from the tension of the pair of springs 3/ and with the compression of the main spring it forces the spring pivot slides 11 apart against the influence of the springs :1 until the toggles iii are perpendicular to the axis'of the piston. At this instant, the action all of the pair of springs 11 reverses and' supports the pressure of the air on the piston surface 1: against the main spring ii. The piston u now Jumps suddenly into its lowest position and leaves the passage i|--Il to the inlet opening (1 of the working cylinder a free. The piston b is brought suddenly into its lowest position (switched in position) as shown in Fig. 2. During this opera-- tion the air between the openings I and the bottom of the cylinder acts as a cushion, such air escaping slowly through the narrow conduits l in the bottom of the cylinder. Shortly before reaching this position, the piston b has left the openings J of the wall of the working cylinder 0 free, whereby the air pressure in the cylinder a and the cylinder preliminary space H issuddenly relieved. By that means the springs l3 move the piston u back, supported by the springs after passing of their toggles ll through their dead center, whereby the valve w is again closed against its seating w and the inner space II of the piston is brought by narrow bores |2a into communication with the conduit ll-ll, which now acts as an exhaust conduit. The valve 1' has previously been closed by its resetting spring 1' which thrusts back the key spindle 0 after the means that opened it had left holding. The

part of the conduit s. which was enclosed between the pistons q and v is freed from air through the cylinder t by the air discharge opening ii. In this way, the device is ready for a fresh switching-in operation.

Returning of the main piston b from the position of Fig. 2 to that of Fig. 1 is initiated by an element that has been excited by its going from the position of Fig. 1 to that of Fig. 2, e. g. by the resetting springs for maximum load of an electric switch.

Referring to the arrangement shown in Fig. 3, a device is shown for duplicate switching direction, as for circuit breakers and the like purposes. Inserted between the control valve e and the working cylinder a is a reversing device 2|. This comprises a cylinder 24 connected through an upper admission conduit 2| and a lower 0 e 22 and a connecting conduit 23 with the out et conduit it, formed in a connector d of the control valve device e. In the cylinder 24 moves an upper piston 25 and a lower one 28 which are connected together by a common rod 21. The upper end of this rod carries a disc 22 on which presses a spring 28 adapted to move the pistons 25 and 26 into their lower positions. In this lower position the bottom piston 26 closes a compressed air inlet 30 to the lower end 'of the working cylinder a but leaves free an exha t opening 3i slightly spaced above the inlet 0, whilstthe upper piston 25 leaves free the pass e from the compressed air inlet 2| to the upper compressed air conduit 32 of the working cylir'pder a and blocks the upper air release openi'nl'g 33. The air passing through the air release holes 3i or 33 escapes to atmosphere through the opening 34.

The openings 30 and SI, and also 32 and 32 are connected together each said pair by narrow conduits 35 or 36, which in the positions of rest permit of a slow equalisation of pressure even out of the blocked parts.

The intermediate valve device e in this embodiment for circuit breakers has a second key valve device 21. This consists of the cylinder 38, the keyrod I! with the pistons II, II and 42 and the key valve cone 43 which valve cone,

under the pressure in the preliminary space 44,-

is closed to cut ofl connection between the conduit k and the switch cylinder 38 and by-pass conduit 3. The cylinder 38 has two openings 45 and 48, the opening 45 being connected'by the pipe 41 with the lower end of the cylinder 24. of the reversing device 20. The opening 48 leads to atmosphere and serves to relieve the pipe 41 and the cylinder space 38 from air.

The method of operation of the device shown in Fig. 3 is as follows:

To close the circuit breaker, the free end of the key valve spindle o is pressed upward by any 25 of the cylinder space 24 and also the connecting conduit 32 above the piston b of the working cylinder a, and moves .the piston b into the lower position. In this position the piston b leaves the air outlet opening 3| free and the working air escapes by the cylinder 24 through the opening 34 to atmosphere. In this way, the conduits 23 and 32, as also the cylinders a and 24 are freed from air. The circuit breaker is now closed.

If it is now to be opened again, the key spindle 39 of the second key valve 31 is pressed upward by any suitable actuating device. The subsidiary piston 42 here interrupts the connecting conduit s between the cylinder preliminary space II and the cylinder t of the intermediate valve device e. At the same time, the upper piston 48 raises the valve cone 43 from its seating. The compressed air enters through the seating of this valve 43 and the connecting conduit s into the upper part of the cylinder space 38 freed by the raised piston 40. The lower piston 4|, has, on rising, closed the air release opening 46 leading to atmosphere. The compressed air now enters through the opening 45 and the pipe 41 underneath the reduced diameter lower extension 48 of the piston 25 of the reversing device 20, and forces the control rod 21 with the pistons 25 and 25 upward against the pressure of the spring 23. The upper piston 25 now closes the conduits 2| and 32 and opens the air release opening 33. The lower piston 26, on the contrary, frees the conduit 23 and the connecting opening 38 between the working cylinder (1 and the control cylinder 24 and closes the air release opening 3|. At the same time, the compressed air has passed from the valve 43 of the key valve 31 also into thepreliminary space H of the intermediate valve e. It there suddenly presses the piston u downward in the manner already described, so that the compressed air passes over the cylinder t and the outlet opening I1--I8 through the connecting conduit 23 and the opening 30 underneath the working piston -b which pressure spring 29 now returns the control rod 21 with the pistons 25 and 23 to the lower terminal position. The circuit breaker is now opened. The pipe 41 and the cylinder 38, after the passing of the key spindle 39 into the lower position, are relieved of air through the discharge opening 43. As the piston rod c is in this case connected with the contact lever of the circuit breaker, the piston b remains suspended in the upper position until the next impulse for the closing of the switch.

The deviceshown in Fig. 4 differs from the arrangements shown in Figs. 1, 2 and 3 by the working air instead of escaping to atmosphere out of the cylinder 58 at the end of the switching-in stroke of the working piston 53 in the cylinder 58, being carried through an opening 54 and a by- pa'ss 55, 51 terminating in the cylinder 1. under the control piston 11.. It also shows the mounting of the working cylinder directly underneath the regulator housing. r v

The method of operation of this device is as follows:

From the position of rest the valve cone 1 is lifted by the valve spindle 0 and the compressed air impinges on the upper annular surface u of the piston u and forces it down, as previously described, to open the passage from the preliminary space H to chamber l1, from which passages l8 lead to the cylinder 50. Thuscompressed air impinges on the working piston 53 throwing it suddenly into its lowest position.

As soon as the upper edge of the working piston 53 leaves the opening 54 free, working air passes through the by- pass 55, 51 in opening the return valve 58 in the housing 55 underneath the control piston u and counteracts the pressure of air acting on this piston u from the top, so that this piston is suddenly thrown into the closed position by the action of the spring l3.

At the lower end of the working cylinder 50 is provided an opening 5! through which air in front of the piston 53 can escape to atmosphere when the piston 53 moves down.

A resilient bufier ring 53 for the piston 53 is provided in the cover 52 of the working cylinder.

I claim:

1. In a pressure fluid servo-motor device an intermediate valve device between the pressure fluid su ply source and the motor, said valve device comprising a cylinder, a spring loaded piston 'in the said cylinder, a valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a reduced diameter part at said end of the piston carrying the valve to afford an exposed annular part on the piston to receive fluid pressure, a spring loaded snap action toggle device yieldingly opposing opening movement of said valve but adapted after a predetermined movement to accelerate full opening movement of said valve and piston, an inlet to the servo-motor-cylinder closed by said piston, and a key valve adapted to be moved to an opened position to admit pressure fluid to said cylinder to move the piston therein an extent to bring into efiect the snap over action of the spring loaded toggle device to impart an accelerated movement'to the valve-piston against the influence ofits spring load, to open the inlet to the servo-motor cylinder and to be secured'in the open position at one end of the piston for admitting pressure .fluid to the servo-motor.

2. In a pressure fluid servo-motor-device an intermediate valve device between the pressure fluid supply source and the motor, said valve device comprising a cylinder, 9. spring loaded piston in the said cylinder, a .valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a reduced diameter part at said end of the piston carrying the valve to 5 aflord an exposed annular part on the piston to receive fluid pressure, a spring loaded snap action tgogle device yieldingly opposing opening movement or said valve butadapted afterapretermined movement to accelerate full opening movement of said valve and piston, an inlet to the servomotor-cylinder closed by said piston but opened thereby when the valve is moved to the' open position, and a key valve adapted to be moved to an opened position to admit pressure fluid to said cylinder to move the piston therein an ex-- tent to bring into effect the snap over action of the spring loaded toggle device to impart an accelerated movement to the valve-piston against the influence of its spring load to open the inlet when ithas traversed nearly its full length under the action of the pressure fluid admitted by the beforesaid valve carrying piston so as to automatically relieve pressure of pressure fluid in the intermediate valve device to transmit the action of the pressure fluid to said valve carrying piston to move it to the closed position, whereby the main pressure fluid device is freed for moveunder the action of the pressure fluid admittedby the beioresaid valve carrying piston so as to automatically relieve pressure 0! pressure fluid in the intermediate valve device to transmit the action of the pressure fluid to said valve carrying piston to move it to the closed position,

, whereby the main pressure fluid device is freed for movement independently or the influence of pressure fluid.

4. In a pressure fluid servo-motor-device an intermediate valve device between the pressure fluid supply source and the motor, said valve device comprising a cylinder, a spring loaded piston in the said cylinder, a valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a snap action spring loaded toggle device engaging said piston and opposing opening movement of the said valve butadapted after a predetermined movement of the piston in the valve opening direction to accelerate the opening movement, and a key valve adapted to be moved to an opened position to admit pressure fluid to said cylinder to move the piston therein an extent to bring into eflect the snap over action of the spring loaded toggle device to impart an accelerated movement to the piston against the influence of its spring load to open the inlet to the servo-motor-cylinder and to be secured in the open position at one end of the piston for admitting pressure fluid to the servo-motor, a pressure fluid operated reversing device between the said piston and the servoment independently of the influence of pressure valve device comprising a cylinder, a spring 4 loaded piston in the said cylinder,'a valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a reduced diameter part at said end of the piston carrying the valve to afiord an exposed annular part on the piston to receive fluid pressure, a spring loaded snap action toggle device yieldingly opposing opening movement of said valve but adapted after a predetermined movement to accelerate full opening movement of said valve and piston, an inlet to the servo-motor-cylinder closed by said piston but opened thereby when the valve is moved to the open position, and a key valve adapted to be moved to an opened. position to admit pressure fluid to said cylinder to move the piston therein an extent to bring into eflect the snap over action of the spring loaded toggle device to impart an accelerated movement to the valve-piston against the influence of its spring load to open the inlet to the servo-motor-cylinder and to be secured in the open position at one end of the piston for admitting pressure fluid to the servo-motor, a preliminary pressure space containing the reduced diameter part of said valve motor adapted to reverse the direction of admission of pressure fluid to the motor-cylinder,

a conduit connecting said reversing device tothe pressure fluid source, means to open such conduit contemporaneously with the opening of the key valve to operate the reversing device one way to eflect a reversing action, and spring means to operate the reversing device the opposite way.

5. In a pressure fluid servo-motor an intermediate valve device between the pressure fluid supply source and the motor, said valve device 0 comprising a cylinder, a spring loaded piston in the said cylinder, a valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a reduced diameter part at said end of the piston carrying the valve to afford an 0 exposed annular part on the piston to receive carrying piston, a by-pass conduit connecting said space to the opposite end of the said piston, a slidable member to actuate said key valve, an auxiliary piston on said slidable member which blocks said by-pass when the key valve is opened, spring means to return the key valve piston when it has traversed nearly its full length fluid pressure, a spring loaded snap action toggle device yieldingly opposing opening movement of said valve but adaptedafter a predetermined movement to accelerate full opening movement of said valve and piston, an inlet to the servomotor closed by said piston but opened thereby when the valve is moved to the open position, and a key valve adapted to be moved to an opened position to admit pressure fluid to said cylinder to move the piston therein an extent to bring into efiect the snap over action of the spring loaded toggle device to impart an accelerated movement to the valve piston against the influence of its spring load to open the inlet to the servo-motor-cylinder and to be secured in the open position at one end of the piston for admitting pressure fluid to the servo-motor, a

preliminary pressure space containing the reduced diameter part of said valve carrying piston, a by-pass conduit connecting said space to the opposite end or the said piston, a slidable member to actuate said key valve, an auxiliary piston on said slidable member which blocks said by-pass when the key valve is opened, spring means to return the key valve to the closed position and to open the by-pass, said servo-motor comprising a main cylinder, a main piston therein, and a pressure fluid escape opening adapted to be uncovered by the main piston when it has traversed nearly its full length under the action of the pressure fluid admitted by the beforesaid valve carrying piston so as to automatically relieve pressure of pressure fluid in the intermediate valve device to transmit the action of the pressure fluid to said valve carrying piston to move it to the closed position, whereby the servo-motor is freed for movement independently of the influence of pressure fluid, a pressure fluid operated reversing device between said inlet and said main cylinder and comprising a rod, two axially spaced pistons on the rod, an inlet and exhaust opening at each end of the main cylinder, one pair being controlled by one of said pistons, and the other pair by the other of said pistons, spring means urging the rod and pistons in a direction to open an inlet at one and an outlet at the other end of the main cylinder, a conduit connecting said reversing device to said preliminary space to admit pressure fluid to the reversing device to reverse the opening and closing of said inlet and exhaust openings, a resetting valve and slidable member to operate it, a piston on the latter slidable member to open the conduit to the reversing device when opening the resetting valve, and another piston on the latter slidable member to open a fluid pressure exhaust to said latter conduit when the resetting valve is opened to allow said spring means of the resetting device to reverse the opening of said two pairs of inlet and exhaust openings.

6. In a pressure fluid servo-motor-device, an intermediate valve device between the pressure fluid supply source and the motor, a pressure fluid operated reversing device, a spring loaded fluid pressure opened valve in the said valve device, a snap action spring loaded device opposing opening movement of the said valve but adapted after a predetermined movement of the valve in the valve opening direction to accelerate the opening movement, and akey valve adapted to be moved to an opened position to admit pressure fluid to open said first mentioned valve an extent to bring into eflect the snap over action of the spring loaded device to impart an accelerated movement to the said flrst mentioned valve against influence of its spring load, to secure it in the open position for admitting pressure fluid to the servo-motor, said reversing device comprising a valve, means to selectively open the valve, two spaced pairs of inlet and exhaust ports with the main operating device, two axially spaced pistons moving in unison controlling said two pairs of ports, spring means urging the pistons in a direction to open an inlet at one end and an outlet at the other end of the main operating device, a conduit connecting said reversing device to pressure fluid supply to reverse the opening and closing of said inlet and exhaust openings, a resetting valve and slidable member to operate, a piston on the latter slidable member to open the conduit to the reversing device when opening the resetting valve, and another piston on the latter slidable member to open a fluid pressure exhaust to said latter conduit when the resetting valve is opened to allow said spring means of the resetting device to reverse the opening of said two pairn of inlet and exhaust openings.

7. In a pressure fluid servo-motor-device an intermediate valve device between the pressure fluid supply source and the motor, said valve device comprising a cylinder, a spring loaded piston in the said cylinder, a valve at one end of the piston adapted under the spring load to close a pressure fluid inlet, a reduced diameter part at said end of the piston carrying the valve to afford an exposed annular part on the piston to receive fluid pressure, a spring loaded snap action toggle device yieldingly opposing opening movement of said valve but adapted after a predetermined movement to accelerate full opening movement of said valve and piston, an inlet to the motorcylinder closed by said piston but opened thereby when the valve is moved to the open position and has passed the dead centre of the snap action device, and a key valve adapted to be moved to an opened position to admit pressure fluid to said cylinder to move the piston therein an extent to bring into effect the snap over action of the spring loaded toggle device to impart an accelerated movement to the piston against the influence of its spring load to secure in the open position the valve at one end of the piston for admitting pressure fluid to the motor, said motor comprising a main cylinder, a main piston therein, and a pressure fluid escape opening adapted to be uncovered by the main piston when it has traversed nearly its full length under the action of the pressure fluid admitted by th beforesaid valve carrying piston so as to automatically relieve pressure of pressure fluid in the intermediate valve device to transmit the action of the pressure fluid to said valve carrying piston to move it to the.closed position, whereby the main pressure fluid device is freed for movement independently of the influence of pressure fluid, an exhaust opening in the main cylinder slightly beyond the working stroke end position, and a by-pass connecting said exhaust opening with the spring loaded side of said valve carrying piston.

8. In a pressure fluid servo-motor according to claim 1, such servo-motor comprising a main cylinder, a main piston therein, and a pressure fluid escape opening adapted to be uncovered by the main piston when it has traversed nearly its full length under the action of the pressure fluid admitted by the beioresaid valve carrying piston so as to automatically permit expansion of fluid pressure from the main cylinder and intermediate valve device, that the piston of the latter returns to its closed position, whereby the main pressure fluid device is freed for movement independently of the influence of pressure fluid.

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