US2505810A

US2505810A - Hydraulic actuator mechanism and control therefor

Info

Publication number: US2505810A
Authority: US
Inventors: Ernest J Svenson
Original assignee: Odin Corp
Current assignee: Babcock and Wilcox Co; Odin Corp
Priority date: 1939-05-03
Filing date: 1946-11-07
Publication date: 1950-05-02
Anticipated expiration: 1967-05-02

Description

9 8* E. J. svENsoN 2,505,810

HYDRAULIC ACTUATOR MECHANISM AND CONTROL THEREFOR Original Filed May 5, 1939 5 Sheets-Sheet 1 II\'\ 'EXTOR.

, 1950 E. J. SVENSON 2,505,810

HYDRAULIC ACTUATOR MECHANISM AND CONTROL THEREFOR Original Filed Hay 3, 1939 5 Sheets-Sheet 2 PE 3 a Q 3 a as LE L T INVENTOR.

g 3 fined J'uewwz/ May 2, 1959 E. J. SVENSON 2,505,810

mmmuuc ACTUATOR MECHANISM AND CONTROL THEREFOR Original Filed May a, 1.959

5 Sheets-Sheet 3 '6 516 Ma A! 7 Z 6i F IHHI E. J. SVENSON HYDRAULIC ACTUATOR MECHANISM AND CONTROL. THEREFOR Original Filed May 3, 1939 5 Sheets-Sheet 4 E. J. SVENSON May 2, 1950 HYDRAULIC ACTUATOR MECHANISM AND CONTROL THEREFOR Original Filed May :5, 1939 5 Sheets-Sheet 5 MQQ Mwm wmw INVENTOR. Jj'uerw'am Patented May 2, 1959 I UNITED STATES PATENT OFF 2,505,810 ICE HYDRAULIC ACTUATOR MECHANISM AND CONTROL THEREFOR Illinois Original application May 3, 1939, Serial No.

Divided and this application Novemher 7, 1946, Serial No. 708,341

11 Claims. 1

This invention relates to hydraulic actuator mechanisms, and concerns particularly means and mechanisms for effecting the conjoint and interlocked control thereof in predetermined manner.

It is an object of the invention to provide control means for effecting the predetermined operation of a plurality of hydraulic actuator structures, of improved construction and improved operating characteristics.

More specifically stated, it is an object of the invention to provide an improved, simplified, and more reliable control means for plural hydraulic actuators for efiecting the operation theref, simultaneously or in predetermined operational sequence, the functioning of each actuator being dependent upon the position and functioning of the others so as to insure the proper relative coaction between all of the operated parts. The controlled hydraulic actuators may comprise, in each instance, a hydraulic actuator, a pump, and a reversible electric driving motor.

A further object of the invention is to provide improved control mechanism, of the type defined, wherein the operating means may be readily controlled by the operator, either directly or remotely, as by the manipulation of a push button, control knob, or the like; and wherein indicating means may be provided for indicating the position or positions of the parts. In accordance with the invention simple electrical means may be utilized for correlating and timing the movements of the actuators, thereby dispensing with complicated interlocking mechanisms.

This application is a division of my copending application, Serial No. 708,339, filed November 7, 1946, which is a continuation-in-part of my application now abandoned, Serial No. 271,444, filed May 3, 1939, entitled "Hydraulic actuator mechanism. This application is also a division of said application, Serial No. 271,444. The present case concerns particularly the means and mechanisms therein disclosed for controlling a Plurality of hydraulic actuators in predetermined manner or sequence.

Various objects, advantages and features of the invention other than those hereinbefore specifically referred to, will appear from the following specification when taken in connection with the accompanying drawings wherein certain preferred embodiments of the invention are illustrated.

In the drawings, wherein like reference numerals refer to like parts throughout:

Fig. 1 is a general assembly view, somewhat V diagrammatic in form, showing the invention in one of its embodiments as applied to the control of hydraulic actuators for shifting printing press rollers;

Fig. 2 is a view on an enlarged scale of one of the hydraulic actuator mechanisms, and associated parts, as embodied in the structure shown in Fig. 1;

Fig. 3 is a detail view of the actuating mechanism for the control or limit switch;

Fig. 4 is a detail view of the switch taken on the line 4-4 of Fig. 2;

Fig. 5 shows the wiring diagram for effecting the conjoint control of the several actuators of Fig. 1, in accordance with the invention;

. Fig. 6 illustrates a modified form or embodiment of the invention as applied to the operation of valves or the like;

Figs. 7 and 8 are sectional detail views, on an enlarged scale, of the actuator structures shown in Fig. 6, and taken on the lines 1-7 and 8-9, respectively, thereof;

Fig. 9 is a sectional view of a part of the switch mechanism as employed in the structures of Figs. 6, '7 and 8, taken as indicated by the line 9--9 of Fig. 7;

Figs. 10 and 11 are partial views showing the switch device of Fig. 9 in two of its operating positions; and

Fig. 12 is a wire diagram for the embodiment of the invention illustrated in Figs. 6-11.

In the drawings the invention has been shown applied to the actuation. and control of a plurality of actuators for effecting the operation of printing press rollers in Figs. 1-5, and for effecting the operation of valve structures in Figs.

6-12, as such installations are illustrative of' uses in which the principles of the invention may be employed. It is to be understood, however, that the invention may be used for efiecting the conjoint actuation and control of hydraulic actuators. of various types, and for ef fecting the operation of various machine parts, as may be desired.

Referring to the embodiment of the invention illustrated in Figs. 15. the structure shown comprises a machine diagrammatically indicated at i 9, which may be a printing press, paper handling machine or the like having three hydraulic actuator mechanisms indicated at I2, l4 and IE for shifting the printin or paper engaging cylinders. As best shown in Fig. 2, each of these hydraulic actuator mechanisms comprises in general a reversible electric motor I8.coup1ed to and adapted to drive a gear pump or the like 20 mounted within an oil reservoir 22. The intake and exhaust passages of the pump are hydraulically interconnected with a hydraulic actuator 24 having a reciprocable piston connected to a piston rod as indicated at 48 which, through a suitable mechanical linkage, shifts the roller or blanket cylinder 26 upwardly out of engagement with the pressure cylinder 39 or downward into engagement with said pressure cylinder 30 and the associated paper supporting web 3| as the occasion may require to eiTect the printing operation.

' from one pair of push button switches.

The details of the gear pump and its interconnecting porting with the oil reservoir 22 and the actuator cylinder 24 are set forth in said companion application, Serial No. 708,339, to which reference may be made, if desired; sufllce to say that as the reversible electric motor 18 is operated in one direction or the other, the gear pump 20 will be similarly propelled in one direction or the other, which through its porting 1nterconnection withv the hydraulic actuator effects the propulsion of the piston rod 48 in one direction or the other, in proportion to the motor and pump movement.

The shifting of piston rod 48 effects the shifting of the blanket cylinder 26 through the action of an eccentric bushing 34 and a rack and gear mechanism 64-10 interconnecting the bushing and the piston rod 48, the details of such interconnecting means also being set forth in said companion application. As best shown in Fig. 3 part of this interconnecting means includes a link 32 extending between the spaced arms 54 of a vertically reciprocable yoke structure, the link being pivotally connected to the yoke structure as indicated at 56. and the yoke structure being vertically slidable within a frame bracket 50. One arm 54 of the yoke member is provided with spaced

lugs

16 and 18 for alternately engaging one arm of a bell-crank 80, the other arm of which engages the plunger 81 of a limit switch mechanism 82, it thus being evident that as the yoke member approaches the limit of its movement in either direction it will operate the limit switch mechanism. As seen in Fig. 4, the shaft of plunger 81 carries a spring-pressed lever 83 which abuts a pin 84 carried by a snap switch lever 85. As the plunger 81 is reciprocated, the lever 83 causes snap lever 85 to be shifted moving switch 244 into position to close either the

contacts

256 and 258 or the

contacts

408 and 410, the electrical functions of which will be presently described.

Any desired number of the described hydraulic actuating units may be controlled selectively For the purposes of illustration there is shown in Fig. 1 an installation comprising three

such units

12, 14 and 16. Fig. 5 illustrates the schematic electrical circuit for selectively controlling the three units of such installation from a single pair of push button switches. The motors 18 of these

units

12, 14 and 16 are schematically represented in Fig. 5 as three-phase electric motors 200, 202 and 204 respectively, although it is to be understood that it is within the contemplation of this invention to employ any suitable type of motor. either of alternating or direct current. Forward and

reverse switches

206 and 208 actuated by electromagnets 210 and 212, respectively, control the forward and reverse connection of the motor 200 to the

power supply lines

214, 216 and 218. Forward and reverse switches 220 and 222 actuated by'

magnets

224 and 226, respectively, control the.

forward and reverse connection of the motor 202 to the

power supply lines

214, 216 and 218. Similarly forward and

reverse switches

228 and 230 actuated by magnets 232 and 234, respectively, control the forward and reverse connection of the motor 204 to the

power supply lines

214, 216 and 218. One push button switch 236 is provided to initiate forward operation of all of the units and one push button switch 238 is provided to initiate the reverse operation of all of the units. The

units

14 and 16 are provided with disconnecting switches 240 and 242, respectively, to keep these units idle, if desired, when the push button switches 236 and 238 are operated. Thus switch 240 determines whether or not the motor 202 will operate and the switch 242 determines whether or not the motor 204 will operate.

Each hydraulic actuator unit includes a limit switch mechanism 82 as previously described. The limit switch mechanism of the actuator unit 12 includes the previously described switch 244 and similarly the

actuator units

14 and 16 include switches 246 and 248, respectively. The

switches

244, 246 and 248 are actuated by the lugs 16 and '18, Fig. 3, of the actuator unit with which the switches are associated, and as will be seen from Figs. 2 and 3, these limit switches, when tripped by one of the lugs, remain in tripped position until engaged by the companion lug of the pair when the actuator has been moved to its other limiting position.

For the purposes of description, it will be assumed that all of the actuating units are at the limit of their reverse movement and that the

limit switches

244, 246 and 248 have accordingly been moved to the positions shown in Fig. 5 to partially complete the circuit to the

actuating magnets

210, 224 and 232 of the forward control switches 206, 220 and 228. Accordingly upon actuation of the push button 236, assuming the main switch 213 to have been closed connecting the

supply lines

214, 216 and 218 to the main power lines 214a, 216a, and 218a, a c rcuit will be completed to the actuating magnet 210 from the supply line 214 through the

contacts

250 and 252 of the push button switch and wire 254, the

limit switch contacts

256 and 258, the wire 260 to the actuating magnet 210; and from this magnet through the wire 262, the wire 264, the wire 266, the contacts of overload relays 268, 210, 2'12, 2'14, 216 and 218, and wire 280 to the supply line 218. Similarly the closing of push button 238 completes a circuit for the actuating magnet 224 from the push button to the wire 282, to the wire 284, the wire 286, the

contacts

288 and 290 of the limit switch 246, and the wire 282 to the ac-- tuating magnet 224; and from the magnet 224 to the wire 294, the wire 296, the contacts of the disconnecting switch 240, the wire 238, the wire 300 and the wire 266, the overload relay switches 268 to 218 inclusive and the wire 280 to the supply line 218. The actuating magnet 232 is connected in parallel to the actuating magnet 224 between the

wires

284 and 300 by means of the wire 302, the

contacts

304 and 306 of the limit switch 248, the wire 308, the wire 310, the wire 312, the contacts of the disconnecting switch 242 and the wire 313. It will therefore be evident that the forward control switches 206, 220 and 228 will be simultaneously moved to closed positions by their

respective actuating magnets

210, 224 and 232, and this results in the energization of the motors 200, 2,02 and 204 and the completion of holding circuits as will now be'described.

The motor lead 314 is connected by the switch arm 316 and the wires 318 and 320 to the supply line 218. Similarly the motor leads 322 and 324 are connected by the switch arms 326 and 328, and the wires 330 and 332 and the wires 334 and 336 to the

supply lines

216 and 214, respectively, The contact arm 838 of the forward control.

switch 206 completes a holding circuit forthe actuating magnet 210 from the supply line 214 through the wire 336, the wire 334, wire 340, contact arm 338 and the wire 282 to the wire 254:l 821382112111 the push button switch contacts 250 an Similarly. the

leads

842, 344 and 348 for the motor 202 are connected by the

arms

348, 358 and 362 of the forward control switch 220 to the

power supply lines

218, 216 and 214, respectively,

through

wires

354, 366, 368 and

wires

360, 362 and 364. The contact arm 366 of the forward control switch 220 completes a holding circuit for the magnet 224 from the supply line 214, by means of the wire 364 from the supply line, the wire 358, a wire 368, the arm 366, a wire 310, wire 284 and the wire 286, contact 288, switch 246, contact 280, wire 282, magnet 224, wire 284, wire 286, switch 240, wire 298, wire 300, wire 266, overload switches 268 to 216 and the wire 280 to the line wire 218. The leads 312, 314 and 316 for the motor 204 are similarly connected by the

arms

318, 380 and 382 of the forward control switch 228 to the

supply lines

218, 216

and 214 respectively through the wires 384, 386, i

368 and the

wires

390, 382 and 364. The contact arm 396 of the forward control switch 228 completes the holding circuit for the actuating magnet 232 from the supply line 214 through the wire 394, the wire 388, the wire 388, the arm 366, the wire 400, the wire 284, wire 302, contact 384, switch 248, contact 306, wire 308, magnet 232, wire 310, wire 312, switch 242, wire 313, wire 300, wire 266, overload switches 268 to 218 and wire 260 to the line wire 218. Any other desirable means may be employed in place of the contact arms 338, 366 and 396 for completing other conventional circuits for locking the actuating

magnets

210, 224 and 232 in their switch closing position.

From this description of the forward control circuits it will be evident that the disconnecting switches 246 and 242 being in their "on position, the momentary closing of the push button switch 236 results in the energization of all of the motors for operation in the forward direction. These motors 280, 202 and 204 drive their respective hydraulic pumps which in turn drive their hydraulically associated pistons in the forward direction. As each piston reaches its limit of movement in the forward direction, the limit switch associated therewith will be moved to its opposite position. For example, at the end of the upper stroke of the piston of the unit 12 the lug l8 will engage and operate the bell-crank 80 which in turn will move the plunger 81 to the right as seen in Figs. 2 and 3, thereby moving the switch 244, Fig. 4, to the right. This movement of the switch 244 breaks the circuit between

contacts

256 and 258, thereby breaking the holding circuit for the actuating magnet 218 which in turn allows the forward control switch to move to open position, breaking the circuit to the motor. Similarly the limit switches 246 and 248 when actuated break the holding circuits to the

actuating magnets

224 and 232, and these magnets in turn deenergize the circuits for the motors 202 and 204. It is to be noted that the holding circuits for the actuating

magnets

210, 224 and 232 are all arranged in parallel so that the breaking of any holding circuit deenergizes only its own associated actuating magnet.

The limit switches 244, 246 and 248 being in their reverse motor position, depression of the reversing push button 238 will complete circuits through these limit switches through the actuating magnets 21 2, 226 and 234 which operate the reverse control switches 208, 222 and 230. The depression of the push button switch 238 connects supply line 214 to actuating magnet 212 6 through the switch contacts 402 and 484, wire 4116, contacts 408 and 418 of the limit switch 244 and wire 412 to the actuating magnet 212. On the other side of the actuating magnet 212 the circuit is completed through the wire 414, the wire 262, wire 264, wire 266, overload relay contacts 268 to 218, and wire 280 to supply line 218. The circuit for the actuating magnet 226 is completed from the contact 404 of the switch 238 through the wire 416, wire 418, contacts 420 and 422 of the limit switch 246, wire 424, the actuating magnet 226, wire 426, the wire 286, the contacts of the disconnecting switch 240, the wire 298, the wire 300, wire 2'66 and overload relay switches 268 to 218 and wire 280 to the supply line 218. The circuit to the actuating magnet 234 is completed through the contact 404 of the switch 238 to the wire 416, wire 428, the contacts 430, 432 of the limit switch 248, wire 434, the actuating magnet 234, the wire 436, the wire 312, the contacts of the disconnecting switch 242, the wire 313, the wire 300, the wire 260, overload relay switches 268 to 218, and wire 280 to supply line 218.

Thus the closing of switch 238 causes the reversing

magnets

212, 226 and 234 to be energized and these magnets in turn operate the reverse control switches 208, 222 and 230 to cause reverse energization of the motors 200, 282 and 204. The operation of these motors in the reverse direction causes the hydraulic pump gears to be driven in the reverse direction to move the actuated pistons downward as seen in Figs. 1 to 3, Morespecifically, the

switch arms

438, 441i and 442 of the reverse control switch 288 connect the motor leads 314, 322 and 324 to the supply lines 244, 2i 6 and 216, respectively, through the wires 336, 332 and 320. It will be seen that the motor leads 314 and 324, which upon operation of the forward control switch 206 were connected to the

supply lines

218 and 214, respectively, are now connected by the reverse control switch 268 in opposite phase relation, the lead 314 being connected to the supply line 214 and the lead 324 being connected to the supply line 218. Hence, upon operation of the control switch 208, the motor will be energized for reverse rotation. The arm 444 of the reverse control switch 208 completes the holding circuit around the push button 238 from the supply line 214 through the wire 336, the wire 334, the wire 340, the arm 444, the wire 446, and the wire 416. This maintains a circuit to the actuating magnet 212 independent of the push button switch 238, the circuit to the magnet being established through wire 406 and

contacts

408 and 410, as previously described in reference to the actuation of the push button switch.

In like mannerthe switch

arms

448, 460 and 452 of the reverse control switch 222 connect the motor leads 342, 344 and 346 to the-

supply lines

214, 216 and 218, respectively, through the

wires

364, 362 and 360 so as to energize the motor for reverse rotation. The arm 454 of the reverse control switch 222 completes the holding circuit for the actuating magnet 226 around the push button switch 238, this holding circuit being completed from the supply line 214 through the wire 364, the wire 358, the wire 368, switch arm 454, wire 456, and wire 416, the circuit then continuing through wire 418, and contacts 420 and 422 to the magnet as previously described in reference to the operation of the push button switch 238.

In similar manner the

switch arms

458, 460 and 462 of the reverse control switch 230 connect the motor leads 312, 314 and 316 to the supply lines 2, M6 and H8, respectively, through the

wires

394, 392 and 390 so as to energize the motor 204 for reverse rotation. The arm 464 of the reverse control switch 230 completes the holding circuit from actuating magnet 234 around the push button switch 238, this circuit being completed from the supply line M4 to the wire 394, the wire, 388, wire 398, switch arm 464 and wire M6, and then through wire 428 and contacts 430 and 432 to the magnet as previously described.

As'each actuated part or piston of the several hydraulic actuating units reaches its original position or lowermost position as seen in Figs. 1 to 3, the lug 16 of each actuating unit engages and actuates the bell-crank 86, Fig. 3, thereby moving the limit switches to their original position, as shown in Fig. 4, whereby the holding circuit for the actuating magnet 01 the reverse control switch is broken and the circuit to the actuating magnet of the forward control switch partially completed. Each limit switch controls only its own holding circuit, thereby insuring that the deenergization of each motor unit will be under the control of its own limit switch.

In a multiple unit system it is sometimes necessary to maintain the second and third units idle while the first unit operates, or to maintain either the second or third unit idle while the other two units operate. In such a case it is only necessary to manually operate the disconnecting switch 240 or the disconnecting switch 242 to an off position. The switch 240, when in ofi" position, breaks the circuit to both of the actuating

magnets

224 and 226 disconnecting the common wire 298 from the common wire 296. The switch 242, when in off position, disconnects both actuating magnets 232 and 234 by breaking the circuit between their common wires 3l3 and 3l2. Hence, when the switch 240 or the switch 242 is in off position, the motor 202 or the motor 204 will not be operated by the closing of either the push button 236 or the push button switch 238.

In Figs. 6-12 there is disclosed, as further illustrative of the principles of the present invention, a hydraulic actuator system for the control of valves or the like in a piping system, which may, for example, be a gasoline or oil refining process, such as the Houdry oil refining or cracking process described in Fortune Magazine, February, 1939, pages 56 and 58. In systems of this type the various valves in the installation must be opened and closed quickly and efficiently in a predetermined timed sequence, and each valve must be closed to a predetermined accurately controlled actuating pressure. These requirements are met by the control system provided by the present invention.

The multiple valve installation illustrated, and as will presently be described, includes simplified controls and interlocking means by which any number of the hydraulic valve actuators may be operated in sequence and in timed relation, the interlocking means preventing false operation of any unit if a unit which should be previously operated has failed to operate at' the proper time or to the proper position.

Referring more specifically to Fig. 6, the piping system shown may comprise a main pipe line 500 and

auxiliary pipe lines

502, 504 and 506 through which various treating agents may be introduced into the main pipe line or through which liquid or fluid therein may be withdrawn.

Valves 508, H0, H2 and 5 are provided in the pipe line to control the flow of fluid therethrough and to the various auxiliary pipes. These valves are provided with hydraulic actuating units Bil, M8, 520 and 522, respectively.

Each of the valve structures and its associated hydraulic actuating unit may be identical in construction. As shown, each valve comprises a valve stem 530, Fig. 7, the lower end of which is provided with a suitable gate valve (not shown) for controlling fluid fiow through the valve structure. Each valve further comprises a bonnet 532 arranged to support the hydraulic actuator unit for the valve, and through which the valve stem 530 extends.

As further shown in Fig. 7, the valve stem 530 is connected to the actuating piston rod 548 oi the hydraulic actuator unit by coupling means including a collar 552 having an integral arm 553 extending outwardly and which is adjustably connected at its outer end to the actuating rod 556 of a limit switch interlock mechanism 550. The switch mechanism 558 and the hydraulic actuator 560 are individually mounted upon a base plate 562 bolted to the valve bonnet frame. By this method of connecting the hydraulic actuator and the switch mechanism of each actuator unit to the valve structure, it is possible to remove either the hydraulic actuator 560 Or the switch mechanism 558 without disturbing the other which is of great importance in certain installations where a number of valves are interlocked together as in the Houdry cracking system previously noted.

The actuator unit comprises a main cylinder casting 566 containing two different size cylinder bores 568 and 510. The upper bore is arranged to receive a piston 512 secured to the piston rod 548, whereas the lower bore receives a floating or power piston 514, the function of which will be presently described. This latter piston is pro vided with a reduced head portion 516 extending upwardly into the smaller bore 568.

Each actuator unit further includes an electric motor 518, Fig. 8, a gear pump 580, a fiuid reservoir 582, and a pressure controlling switch mechanism- 586. v The pump is mechanically interconnected to the motor 518 by means of a coupling 590.

Ports or

passages

592 and 594 connect the inlet and

outlet ports

596 and 598 of the pump to the upper end of the cylinder bore 566 and to the lower end of the cylinder bore 510, the ports or

passages

592 and 594 being formed in the pump casting and within walls of the actuator cylinder. A fluid passage or port 600 extends through the cylinder casting from the upper end of the cylinder bore 568 to the lower bore 510. The enlarged central bore 602 of the piston head 516 provides a fluid passage about the piston rod 548 permitting the fiuid to pass from the under side of the piston 514 to the under side of the piston 512.

Assuming the valve to be closed as shown in Fig. '1. upon rotation of the motor in a direction to effect an upward movement of the valve stem 530, the pump 580 will draw fluid, preferably oil, from the cylinder'bore 568 above the piston head 512, and force fluid through the port 594 into the cylinder bore 510 below the piston 514. Piston 514 thereupon moves upwardly for a predetermined distance determined by the space 604, until the upper end of its head portion 516 strike: the lower wall of piston 512. The piston 517 thereupon moves upwardly by fluid supplied thereto by port 602. The. piston 514 moves upwardly only a predetermined distance and is then stopped by the upper wall oi. the cylinder bore 510.

As the piston 512 approaches its normal limit of movement in the upward direction, the switch rod 556 will cause the operation of the interlock and switch mechanism 558 to break the circuit to the motor 518 in a maner to be later described. After opening of the valve, the frictional resistance to movement of the parts, and the resistance to circulation of fluid through the several passages or ports may be relied upon to prevent the weight of the valve from moving it toward a closed position.

Upon energization of the motor 518 to effect a closing of the valve, fluid will be withdrawn from the cylinder chamber 568 beneath the piston 512 and from the cylinder chamber 510 beneath the piston 514 through the port 594 to the pump port 598, and forced under pressure through the pump port 596 and the port 592 into the cylinder chamber 568 above the piston 512. Fluid is also forced into the cylinder chamber 510 above the piston 514 from the cylinder chamber 568 through the port 600. This movement of the fluid, forces both the

pistons

512 and 514 downwardly to effect a closing of the valve.

When the valve gate reaches the seating position, the pressure on the top of the piston 512 builds up to a predetermined value as determined or controlled by the pressure switch mechanism 586, and when the switch mechanism operates the motor 518 is deenergized. The pressure switch 586 may be of any suitable construction, and in the present instance comprises a pressure actuated plunger 608 and a set of switches 6l0 operated thereby which are actuated to closed position when a predetermined pressure condition exists within port or passage 592, the pressure switch structure being interconnected with said port through a passage 618. Return fluid from the pressure switch passes to reservoir 582 through a drain line 660, Fig. 8. The details of the particular pressure switch disclosed are fully set forth in said companion application Serial No. 708,339, to which reference may be made, if desired.

Referring to Figs. 9 to 11, the interlock switch mechanism 558 comprises in addition to the operating rod 556, a rod housing 666 welded to and depending from the supporting plate 562 and provided at its lower end with a bearing block 668 for the rod 556. A rod housing 669 welded to the dome of the detachable housing 618 forms a guide for a collar 612 secured to the upper end of the rod 556. The upper end of the rod 556 is threaded as shown to adjustably receive spaced collars 614 and 616 which form the means for actuating the interlock switch device 150, the collars 614 and 616 being retained in adjusted position by lock screws 680 and 682 respectively.

The switch device 150 comprises a plurality of sets or pairs of leaf springs carrying the sets of electrical contacts 152, 154, 156, 158 and 160 and mounted upon a common block or blocks of insulation 684 attached to brackets 686 carried by a mounting plate 688, the mounting plate 688 also carrying an elec rical panel board 690 which may be provided with the usual terminals permanently wired to the contacts of the switch device and by which the external connections to the switch may be varied as desired. The swi ch 150 comprises uouer and

lower parts

692 and 694 which are selectively operable by the roller 6,96

mounted on a crank arm 698 secured to a stud 100 carried by the mounting plate 688. The stud 100 also has fixed thereto a crank arm 102 provided at its outer end with a roller 104 lying in the path of movement of the actuating collars 614 and 616, and actuated thereby as the rod 556 approaches its upper and lower limits of movement. A counterweight '106 secured to the stud or to the crank arms 698 or 102 as desired, balances the arms allowing the parts to assume the position shown in Fig. 9 when the roller 104 is not engaged by either of the collars 614 and 616. Figs. 10 and 11 illustrate the diifer'ent positions to which the crank 698 and roller 696 and assoc ated switch parts are moved by the collars 614 and 616 on operation of the actuator. It will be seen that when the roller 104 is not engaged by either of the actuating col ars, the two sets of contacts 160 and 158 of the upper switch part 692 and the lower contacs 154 and 152 are open, while the other upper switch contacts 156 are in circuit closing position. As the gate valve approaches its closed position, the actuating collar 616 will engage the roller 104 and move the roller 696 downwardly, thereby moving the contacts 154 and 152 into circuit closing position (Fig. 11). As the gate valve reaches its normal limit of movement in the upward direct on. the actuating collar 614 will engage the roller 104 and move the roller 696 upwardly to eifect a closing of the two sets of contacts 160 and 158 of the switch part 692. but to break the circuit between the set of contacts 156 of this switch part, as seen in Fig. 10.

Fig. 12 discloses schematically the electrical control circuits for operating a system providing three of the hydraulic valve actuating units previously described, automatically in a predetermined sequence, or manually at will. For purposes of illustration the system is shown as comprising three-phase motors 108, N0 and 112, although it will be evident that any other alter- 'nating current motor may be used as well as any direct current motor, each of these motors being used as the motor 518 for driving the pump 580 of a hydraulic actuating unit. It is also obvious that the system may comprise any desired number of actuating units as the occasion may require.

In the manual operation of the system. the push button switches 114, 1| 6 and 118 individually control the actua ing magnets 120, 122 and 124 for the forward control switches 126. 128 and 130, while the push button switches 182, 184 and 136 individually control the actuating magnets 138, 148 and 142 of the reverse control switches 144, 146 and 148. For purposes of descri tion. it will be assumed that initially the first actuator is standing in the valve closed position. In this case its interlock switch 158 will be in the position shown in Fig. 11 in which the pairs of contacts 152 and 154 of the lower set are in circuit closed position as is also the contact pair 156 of the upper set, while the pairs of con acts 158 and 160 of the upper set are in circuit open position. The green indicating lamp 162 is thus energized through a circuit from the supply line L--l through a wire 164, the lamp 162, the wire 165, contacts 156 and the wires 166 and 168 to the supply line L-3. This lamp 162 indicates that its valve is in c osed position.

Upon de ression of the valve opening switch N4, the circuit to the actuating magnet is completed from the supply line L--3 throu h the 75 wire 168, the wire 110, the push button 1, the

11 wire 112, the actuating magnet I and the wire I64 to the supply line L-l. This magnet therefore actuates the forward control switch I26, the arms of which connect the motor leads I14, I18 and I18 to the supply lines Ll, L-2 and L-3, respectively, through the wires I84, I82 and 180, and wires I86, I88 and I68.

The arm I90 of the switch 126 completes a holding circuit for the actuating magnet I20, this circuit being completed from the supply line L-l through the wire I64, the actuating magnet 120, the wire I92, the arm 590, the wire I94, the interlock contact I58, wire I66 and wire I68 to the supply line L-B.

Simultaneously with the energization of the actuating magnet 120, the switch actuating magnet I96, which is connected in parallel with the magnet I20 is also energized and this magnet operates a switch I98 to complete a circuit for the red lamp 800 from the supply line L-t through the wire H64, the lamp tho, the wire 802, the switch I98, the wire 88% and the wire I68, to a supply line iii-3. The green lamp 182 and the red lamp 800 are now both lighted, thus indicating that the valve is betweenopen and closed positions; thus, if for any reason the valve should for failure of any cause remain between the opened and closed positions, the illumination of both lamps will indicate such fact. Also, these lamps may be used at a remote panel board for indicating the fact that the valve is moving.

As the valve actuator completes its normal opening stroke, the rod 55% operates the interlock switch 150; thus in the case of the first unit breaking the holding circuit for the actuating magnet I20 at the interlock contacts I56. The magnet I20 being thus deenergized, the forward control switch 126 is returned to open circuit position, breaking the motor circuit and the motor I08 stops rotating. The opening of the interlock contacts I56 also breaks the circuit to the green lamp I62 which is thus extinguished, but the circuit to the red lamp 800 remains energized through the switch I98 for the switch I88 is moved to its opposite positions only upon energizationof the magnet 198 or the magnet 806. The red lamp 800 therefore now indicates that the valve is standing in opened position.

Upon operation of the valve closing Push but ton switch 132 a circuit will be completed for the actuating magnet I38 01 the reverse control switch I, this circuit being completed from the supply line L-3 through the wire 808, the push button I32, the wire 806, the wire 8l0, the actuating magnet I38 and the wire M2 to the supply line L- l. Upon operation, the reverse control switch I connects the motor leads I14, I16 and 118 to'the supply lines L-3, L-2 and Ll, respectively, through the wires I88, I88 and 188. This completes the motor circuit and the motor begins to rotate in a valve closing direction. The holding circuit for the actuating magnet I38 is completed by the switch arm 8 from the supply line Li through the wire M2, the actuating magnet 138, the wire 8l8, the switch arm 8", the wire 8", the switch I98 which is in closed position, the wire 804 and the wire I88 to the pp y line L-3.

As the valve actuator starts to move in a closing direction, it allows the interlock switch to return to its neutral position, closing contacts I56 and opening contacts I58 and 180. The closing of the contacts I56 again completes the circuit to the green lamp I82 so that this lamp is re-lighted and both lamps are again burning in- 12 dicatlng to the operator that the valve actuator is in motion.

As the valve actuator completes its closing stroke, hydraulic pressure is built up in the cylinder of the pressure switch device 6I0, schematically represented in Fig. 12, thereby completing a circuit from the supply line L--l through the wire 184, the magnet 808, the contacts of the pressure switch M0, the wire 822 and the wire I68 to the supply line L3. The magnet 806 then moves the switch I88 to open circuit position, thereby breaking the holding circuit for the actuating magnet I38 stopping the motor and also breaking the circuit for the red lamp 800. The green lamp I82 remains energized, however, thus indicating that the valve has been brought to closed position. The valve actuator as it completes its closing stroke also actuates the lower part 884 of the interlock switch I80, as shown in Fig. 11, to close the contacts I50 and I52 for a purpose. which will presently appear in connection with automatic operation.

The manually contrdled circuits for the motors H0 and H2 for the second and third actuating units are identical to the manually controlled circuits for the motor I08 and need no further description other than to state that push button 6 initiates the operation of the second actuator unit in the valve opening direction, that push button switch Il8 initiates operation of the third operating unit in a valve opening direction, while push buttons I30 and I38 initiate operation of the respective actuating units in a valve closing direction. The interlock switches 824 and 828 for the second and third actuator units are operated by their respective units in the same manner as interlock switch I50 0! the first unit. Position indications are given for the second unit by

lamps

828 and 880, corresponding to the lamps I82 and 800 of the first actuator unit, and similarly,

lamps

882 and 83! provide position indications for the third unit. Pressure operated

switches

888 and 838 for the second and third actuating units, corresponding to the pressure operated switch 6 10 for the first unit, control the limit of movement 01' the second and third actuating units in the valve closing direction.

In many installations of valve actuators it is necessary that the valves which are controlled shall be operated in some predetermined sequence. and that this sequential operation shall be accomplished automatically when once initiated or in continuous repetitious cycles of operation. It is also often necessary for the successful operation of such a system that a valve be not operated unless others 0! the valves are in certain positions. For purposes oi illustration Fig. 12 discloses schematically one possible interlocking system as illustrative of the general principle of interlocking and controlling a system 0! such multiple actuating units in accordance with the invention, however, it is to be understood that by suitably varying the arrangement'and timing of the automatic operating devices, various desired specific types of interlock control may be obtained.

In the illustrative example it is assumed that the three units shown are to be operated continuously in numerical sequence and at equal intervals. For example, assuming all valves to be closed, it is assumed that it is desired to first open the valve of the first unit, then after a predetermined interval open the second valve, and after the lapse of a like interval, open the third valve; and that it is further then desired after the lapse of the same interval to close the first valve, and successively at equal intervals, then close the second and third valves. The cycle of operation will then continue in the same order with all time interval equal.

The illustrated interlocking system provides means for preventing any valve from being moved unless the other valves stand in the position that they should occupy at the time that the first mentioned valve should be moved. For example, the valve of the first unit may not be opened unless the valves of the second and third units are closed, nor may the valve of the first unit be closed unless the valves of the second and third units are opened. Similarly the valve of the second unit may not be opened unless the valve of the first unit is opened and the valve of the third unit is closed, nor may the valve of this second unit be closed unless the valve of the first unit is closed and the valve of the third unit is opened. In like manner the valve of the third unit may not be opened unless the valves of the first and second units are both open, nor may the valve of the third unit be closed unless the valves of the first and second units are both closed.

The time intervals between the movements of the valve actuators are provided by a multi-contact switch mechanism comprising a plurality of interconnected switches, of which the contacts are shown in Fig. 12 as 848, 842, 844, 846, 848 and 858, there being in the assumed illustration two sets of such contacts for each of the actuator units. These contacts are actuated by a series of synchronously operated cams 852 to 862 which may, if desired, be mounted on and driven by a single shaft, which shaft may be continuously rotated by some suitable clock mechanism or synchronous electric motor, such as the three-phase synchronous motor 864. Each cam is provided with a contact actuating projection on its periphery and these cam projections are angularly related to each other in such a way that they will operate the contacts in the desired order and after the desired predetermined intervals. In the illustrative example, a complete cycle of operation of the valves is effected in one revolution of the common cam shaft, and since all intervals between the actuation of the units are to be equal, the projections on each of the

cams

852, 856 and 868 which control the opening movement of the valve actuating units are displaced by the same angle of 60 degrees from the preceding cam, while each of the

cams

854, 858 and 862 which control the closing movements of the actuating units is similarly displaced from the preceding cam by an angle of 60 degrees.

It should further be noted that since in the assumed example, the cycle is to be repeated after a lapse of an interval equal to the interval between the actuation of each valve in the cycle, the projection on the opening control earn 852 is displaced from the projection on the closing cam 862 by an angle of 60 degrees.

In the assumed example at the beginning of the cycle of operation, all valves are in closed position, and it is further assumed that the predetermined interval has elapsed since the closing of the third valve of the system. Therefore at this instant the opening cam 852 is in engagement with and closes the contacts 848.. A shunt circuit is completed around the contacts of the opening push button N4 of the first unit from the contact on one side of the push button through the wire 864, the contacts 848, the wire 866, the contacts152 of the interlock switch 158 which contacts are in closed position when the valve is closed (Fig. 11), the wire 868, the wire 818, the closed contacts812 of the interlock switch 824, the wire 814, the closed contacts 816 of the interlock switch 826, the wire 818 and the wire 888 to the supply line L3 to which the contact on the other side of the push button H4 is connected by the wires 168 and 118. The closing of the contact 848 therefore acts exactly as the closing of the push button switch 114, to complete an energizing circuit for the magnet 128 of the forward control motor switch 126, from line Ll through wire 164, coil 128 and wire 112 to wire 864 and the remainder of the shunt circuit just specified, and thus the opening of the first unit is initiated automatically. Closing of contacts 848 also energizes magnet 196 to close switch 198 so that the holding circuit for magnet 138 will be completed when 8l4 connects wires M6 and 818 upon subsequent closing of the circuit to 138.

This opening takes place, however, only if the second and third units are in valve closed position. If the valves of either of these second or third units are in open position or in partially open position, the

contacts

812 and 816 of the interlock switch 824 or the interlock switch 826 will be opened and the above described shunt circuit around the push'button 4 cannot be completed by the contacts 848.

As the cams continue to rotate the contact 848 will be reopened, but the motor 188 of the first actuating unit will continue in operation because of the holding circuit for the actuating magnet 128 completed by the arm 198 of the forward control switch 126 as previously described. The first actuating unit will be stopped at the end of its movement in the openin direction by the opening of the contacts 156 of the interlock switch 158 as previously described.

At the predeterm ned interval after the closing of the contacts 848 and the foregoing operations, the contacts 844 will be operated by the cam 856 and these contacts will complete a shunt circuit around the push button 116 of the second unit as well as closing the switch of this unit, the equivalent to switch 198 of the first unit. This circuit is completed from the one side of the push button 1l6 through the wire 882, the contacts 844, the wire 884, the now closed (Fig. 10) contacts 158 of the interlock switch 158, the wire 818, the closed contacts 812 of the interlock switch 824, the wire 814, the closed contacts 816 of the interlock switch 826, the wire 818 and the wire 888 to the supply line L3 to which line the other side of the push button H6 is connected by the

wires

888 and 886. Since this shunt circuit includes the contacts 158 of the interlock switch 158, it will be evident that the energizing circuit for the actuatin magnet 122 of the forward control switch 128 of the second actuator unit will not be completed unless the first actuator unit has completed its opening operation. This shunt circuit also includes the contacts 816 of the interlock switch 826, thereby preventing energization of the second actuator unit for movement in the opening direction unless the valve of the third unit is closed.

The holding circuit for the actuating magnet 122 of the second unit, which holding circuit is identical to the holding circuit for the actuating magnet 128 of the first unit maintains this unit active after the momentarily closed contacts 844 have been opened, and after the contacts 812 of the interlock switch have been opened by the movement of the second valve from its" closed position. On operation of the valve to its open position, the holding circuit for magnet I22 is broken and the contacts 898 are closed.

After the lapse of the predetermined interval, the contacts 848 are operated by the cam 888 to cause a shunt circuit around the push button H8 of the third unit. This shunt circuit is completed from one side of the push button H8 through the wire 898, the contacts 848, the wire 892, the wire 894, the now closed contacts 898 of the interlock switch 824, the wire 898, the closed contacts I88 of the interlock switch I58, the wire 988 and the wire I88 to the supply line L3 to which the other side of the push button H8 is connected by the wires 982 and 988. Thus it will be seen that the third unit will be energizedior movement in the opening directiononly if the valves of the first and second units are in opened position.

The next operation of the cycle is the closing of the valve of the first unit and hence when the predetermined interval has elapsed following the opening of the third valve, the cam 854 will engage and close the contacts 842 to complete a shunt circuit around the push button switch 832 of this unit. This circuit is completed from one side of the push button switch I32 through the wire 988, the wire 988, contact 842, the wire 9H8, the now closed contacts 912 of the interlock switch 826, the wire 9, the wire 894, the closed contacts 898 of the interlock switch 824, the wire 898, the closed contacts I88 of the interlock switch 158, the wire 988 and the Wire I88 to the supply line L-3 to which the other side of the push button I32 is connected by the wire 888. This shunt circuit energizes the coil I38 the same as if switch I32 were closed as previously described, but since this shunt circuit includes the contacts 898 and 9I2 of the interlock switches 824 and 828, it will be evident that the actuating magnet I38 for the reverse control switch I44 will not be energized unless the second and third valves are in their open position. Upon closure of the valve means of this unit, pressure will build up to operate the pressure switch 8| 8 to close the circuit through magnet 888 which will open switch 198 to break the holding circuit for magnet I38.

The closing cam 858 next operates its contacts 848 to complete a shunt circuit around the push button I34 of. the second unit, this circuit being completed from one side of the push button by the wire M8, the contacts 848, the wire 9l8, the wire 928, the closed contacts I54 of the interlock switch I58, the wire 922, the closed contacts 924 of the interlock switch 828, the wire 928, and the wire 888 to the supply line L3 to which the push button I34 is connected at its other side. Thus it will be'seen that the second actuator unit will be energized for closing movement the same as if push button I34 were operated, but only if contacts I54 of the interlock switch I88 and the contacts 924 of the interlock switch 828 of the third unit are in closed position. Since the contacts 184 will be closed only when the valve .of the first unit is closed, and the contacts 924 will be closed only when the valve of the third unit is in open position, it will be seen that the valve in the second unit will be energized for closing movement only if the valve of the first unit is closed and the valve of the third unit is open. Completion of the closing. movement of the valve of the second unit causes pressure switch838 to open the holding circuit for magnet I The cycle of operation is completed by the actuation of the contacts 888 by the cam 882. This completes a shunt circuit around the push button I38 of the third unit resulting in the actuation of coil I42 and in the closing of the third valve, the circuit being completed from one side of the push button through the wire 928, the wire 988, the contacts 858, the wire 932, the wire 934, the now closed contacts 938 of the interlock switch 824, the wire 938, the wire 928, the closed contact I84 of the interlock switch I88, the wire 922, the closed contacts 924 of the interlock switch 828, the wire 928 and the wire 888 to the supply line L-3 to which the other side of the push button is connected by the wire 948. Thus it will be seen that since this shunt circuit includes the contacts I84 of the interlock switch 158 and the contacts 938 of the interlock switch 828, the actuator of the third unit cannot be energized for movement in the closing direction if the valve of either the first or the second unit is opened or partially opened. Completion of the closing movement of the valve of the third unit causes pressure switch 838 to open the holding circuit for magnet I42.

The cycle of operation is now completed and all valves are returned to closed position. However, in the illustrated example, this cycle of operation will be repeated automatically upon the elapsing of the predetermined interval.

It should be noted that each actuator unit may be manually operated regardless of the positions of the other units, for the holding circuits and the circuits completed by the manual operation of the push buttons-for each unit are independent or the interlocking circuits.

In the event that the automatic cycle of operations should be interrupted for any cause, the red and green signal lamps will indicate the positions of the several valves, whether open, closed or in intermediate position.

It is obvious that various changes may be made in the specific embodiments of the invention set forth for purposes of illustration without departing from the spirit thereof. Accordingly the invention is not to be limited to the precise embodiments heretofore shown and described, but only as indicated in the following claims.

The invention is hereby claimed as follows:

1. In a hydraulic actuator structure, a plurality of hydraulic actuator units each having its own power source, a fluid pump adapted to be actuated by the power source, a, reciprocable hydraulic actuator hydraulically connected with the pump for actuation thereby, a machine ele ment to be shifted, and means for connectin the machine element to the hydraulic actuator whereby to shift the element in accordance with the movements of the actuator, and means for controlling the units in a predetermined timed relation and sequence, said last named means including provisions for inhibiting the operation of any unit if the other unitsv are not in predetermined position.

2. In a hydraulic actuator structure, a plurality of hydraulic actuator units each having its own driving electric motor, a fluid pump adapted to be actuated by the electric motor, a reciprocable hydraulic actuator hydraulically connected with the pump for actuation thereby, a machine element to be shifted, means for connecting the machine element to the hydraulic actuator whereby to shift the element in accordance with the movements of the actuator, and electric control circuits for interlocking the electric motor power connections whereby to control the units in predetermined timed and sequential relation.

3. A hydraulic actuator mechanism compristuators individually to said elements, switch mechanisms controlled individually by the movements of the hydraulic actuators for terminating the operations of the motors individually, and a master control means to initiate the operations of all of said motors.

l. A hydraulic actuator system comprising a plurality of reversible electric motors, a plurality of reversible pumps adapted to be actuated by said motors, a plurality of reciprocable actuators adapted to be actuated by fluid from said pumps, a plurality of elements to be shifted in dividually connected to said actuators, and control circuits for said motors, said control circuits including a switch for initiating operation of a plurality of said motors, a plurality of motor cut-off switches controlled individually by the movements of the hydraulic actuators, and a plurality of switches individual to each motor named switch.

5. A hydraulic actuator system comprising a plurality of reversible electric motors, a plurality of reversible pumps adapted to be actuated by said motors, a plurality of reciprocable actuators adapted to be actuated by fluid from said pumps, a plurality of elements to be shifted individually connected to said actuators, and control means for effecting the operation of said actuators in predetermined timed relation and sequence, said control means including. mechanism for inhibiting the operation of one actuator when another actuator is not in predetermined position.

6. A hydraulic actuator system comprising a plurality of hydraulic actuator units, each unit comprising a power source, a fluid pump adapted to be actuated by the power source, and a hydraulic actuator hydraulically connected with the pump for actuation thereby, a plurality of machine elements to be shifted individually connected to each hydraulic actuator, and common control means for controlling the operation of the actuators in a, predetermined timed relation and sequence, said control means including a plurality of pressure switches individually actuated by pressure conditions within the actuators.

7. A hydraulic actuator system comprising a plurality of reversible electric motors, a plurality of reversible pumps adapted to be actuated by said motors, a plurality of reciprocable actuators adapted to be actuated by fluid from said pumps, a plurality of elements to be shifted individually connected to said actuators, control circuits for said motors, said control circuits including switch means for initiatingoperation of a. plurality of said motors, a plurality of motor cut-off switches controlled individually by the movements of the hydraulic actuators, and-indicator means for indicating the individual positioning of each actuator.

8. A hydraulic actuator system for valves comprising a plurality of reversible electric motors, a plurality of reversible pumps individually con- Number Name Date Re. 14,815 Horn Mar. 9, 1920 833,931 Johnson Oct. 23, 1906 1,616,841 Beebe Feb. 8, 1927 1,799,113 Miedbrodt Mar. 31, 1931 1,948,951 Walker Feb. 27, 1934 2,145,956 Stern Feb. 7, 1939 2,187,212 MacMillin Jan. 16, 1940 2,207,580 Daniels July 9, 1940 FOREIGN PATENTS Number Country Date 635,171 Germany Sept. 11, 1936 18 nected to said motors, a plurality of hydraulic actuators individually connected to said pumps, each of said actuators comprising a reciprocable cylinder and piston construction the operating element of which is adapted for connection to a valve to be actuated, and common control circuits for said motors, said control circuits including switch means for initiating operation of the motors, and a plurality of switches individually actuated by the actuators for disabling the movement of each valve when the valve reaches predetermined position.

9. A hydraulic actuator system for valves comprising a plurality of reversible electric motors, a plurality of reversible pumps individually connected to said motors, a plurality of hydraulic actuators individually connected to said pumps, each of said actuators comprising a reciprocable cylinder and piston construction the operating element of which is adapted for connection to a valve to be actuated, and common control circuits for said motors, said control circuits including switch means for initiating operation of the motors, and a plurality of pressure actuated switches respectively controlled by the pressure conditions within the actuators.

10. A hydraulic actuator system for valves comprising a plurality of hydraulic actuator units, each unit having its own power source, a fluid pump adapted to be actuated by the power source, and a reciprocable hydraulic actuator hydraulically connected with the pump for actuation thereby and having its shiftable element adapted for connection to a valve to be operated, and control means for controlling the operation of the actuators in a predetermined timed relation and sequence, said control means including a switch for each actuator operated thereby inaccordance with the actuator movements.

11. A hydraulic actuator system for valves comprising a plurality of hydraulic actuator units, each unit having its own power source, a fluid pump adapted to be actuated by the power source, and a reciprocable hydraulic actuator hydraulically connected with the pump for actuation thereby and having its shiftable element adapted for connection to a valve to be operated, and control means for controlling the operation of the actuators in a predetermined timed relation and sequence, said control means including a switch for each actuator operated thereby in accordance with the actuator movements and aswitch timer having a plurality of cam operated switches individual to each actuator.

ERNEST J. SVENSON.

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

UNITED STATES PATENTS