US1229543A - System and apparatus for controlling fluid-motors. - Google Patents

Description

N. W. STORER & A. J. HA LL. SYSTEM AND APPARATUS FOR CONTROLLING FLUID MOTORS.

2 SHEETS-SHEET I.

li it APPLICATION FILED ocr 5. 1912. Patentedhme 12 N. W. STORER & A. J. HALL. SYSTEM AND APPARATUS FOR CONTROLLING FLUID MOTORS.

M APPLICATION FILED OCT. 5,1912- LQQQ l -A Patented June 12, 1917.

2 SHEETS-SHEET 2.

INVENTURS NORMAN W. STORER, OF PITTSBURGH, AND ARTHURJ. HALL, OFWILKINSBURG, PENN- SYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC PANY, A CORPORATION OF PENNSYLVANIA.

AND MANUFACTURING COM- SYSTEM AND APPARATUS FOR CONTROLLING FLUID-MOTORS.

Specification of Letters Patent.

Application filed October 5, 1912. Serial No. 724,063.

Allegheny and State of Pennsylvania, have.

invented a new and useful Improvement in Systems and Apparatus for Controlling Fluid-Motors, of which the following is a specification.

paratus for controlling fluid motors, and-it has special reference to power-actuated drum controllers and systems embodying the same. One object of our invention is to provide a relatively simple and compact mechanism for actuating controllers of the drum type that shall be adapted to replace the usual cover and motormens handles of present manually operated railway controllers, and the operation of which is governed by a small master controller.

Another object of our invention is to provide a controller actuating device of the character above indicated which shall be.so

constructed and arranged as to permit of its may be positively actuated in a series ofdistinct and definite steps through the agency of an operating cylinder and a movable piston upon the opposite sides of which relatively high balanced pressures are nor mallymaintained for the purpose ofholding" the piston at rest, it being necessary only to reduce the pressure on one side of said piston in order to efl'ect an unbalancing of'pressures and a consequent movement of the piston in the one direction or-the other until balanced pressures are restored.

A well known type of controller for rail-' way motors comprises a main drum that is rotatable for the purpose of governing themotor circuits and the value of the accelerating resistance, and a reverse drum that is adapted to occupy the one or the other of two positions, according to the desired direction of rotation of the motor armatures.

The drums are provided with star Wheels and pawls. or similar devices for accentuating the various control positions, and the drum shafts extend through holes in the cover of the controller so that they may be turned by means of suitable handles. However, cars equipped with controllers of this character cannot be operated intrains and controlled from the front end only, since the controllers must be separately and man- Our invention relates to systems and approvide what We shall hereinafter term an operating head which constitutes a unitary structure that may be removably secured to any ordinary drum controller and is adapted to actuate the main drum of the controller either step-by-step or continuously, and also to operate the reverse drum. The controllers and their associated operating heads may be located under the cars, and the'operation thereof governed by means of a master controller and a suitable remotecontrol auxiliary system which may convenientlyv be of'the multiple-unit type.

In a co-pending application, Serial No. 724,065, filed October 5, 1912, by A. J. Hall and L. G. Riley, and assigned to the Westinghouse Electric and Manufacturing 00., a somewhat similar control system is disclosed which embodies a fluid-operated controller drum that is adapted'to be actuated through Patented June i2, 191?.

turn, governs the operation of a plurality of electro-magnetically controlled valves that are associated with the opposite ends of an operating cylinder. This fluid-actuated devloe, however, is so constructed and arranged as to be actuated by merely admitting an opcrating fluid to-one side of its movable pisfton, and its movement is arrested by releasing the operating fluid ahd thus permitting the reestablishment of balanced atmospheric pressures acting upon the piston. An appreciable time interval is necessarily required to effect the'exhaust .of operating fluid, during which period, the inertia of the moving piston and associated parts may cause it to over-shoot its proper position,

while the operating fluid released is entirely wasted. In order to resume the operation, a complete new charge of fluid is required which becomes effective only when a material pressure has been built up which consumes an appreciable element of time. Moreover,- 1n case 1t 15 desired to reverse the dlrection of operation, it becomes necessary to discharge ever, balanced pressures are normally main tained on both sides of the piston and, therefore, movement in either direction may be effected quickly merely by opening the exhaust valve on one side thereof topermit the escape or reduction in pressure of the operating fluid. As soon as the pressure on one side has been reduced a comparatively small amount, the unbalanced pressures acting upon the piston is suflicient to cause the movement thereof. Only a relatively small amount of operating fluid therefore is wasted, while the operation of the apparatus is quickly responsive. In order to arrest the movement of the piston, it is only necessary to supply a small additional amount of operating fluid to the low-pressure side, thereby establishing balanced-pressure relations and positively and definitely bringing the piston to rest. Our present invention, therefore. has the advantages of economy of opcrating fluid which is utilized at a relatively high average pressure and, therefore, serves to produce a quick and sensitive operation of the control drum which is positively stopped in any position and is substantially dead heat.

Figure 1 of the accompanying drawings is a plan view, with the cover removed, of a controller operating head which forms a part of our invention. Fig. 2 is a view in side elevation and in section of the operat ing head of Fig. 1 and the upper portion of a controller with which the head is associated. Figs. 3 and 4 are sectional detail views, on a larger scale, of the valves which form parts of the operating head shown in the other figures. Fig. 5 is a diagrammatic view of the auxiliary control circuits of a system embodying our invention.

A preferred type of complete (main and auxiliarycircuit) control system is set forth and claimed in our co-pending divisional application, Serial No.-122,383, filed September 27, 1916, and in the present specification we will describe and explain only such control circuits and connections as are necessary to afford a thorough understanding of our present invention.

Referring toFigs. 1 to 4, inclusive, of the drawings, the structure here shown comprises an operatinghead 1, a controller of the well known type having a casing 2, a main drum 3, a reversing drum 4, and suitable control fingers associated with each drum.

The operating head 1 comprises a base plate 5, which constitutes the cover of the tromagnetically controlled valves 18 and 19 for controlling the supply of compressed air to the cylinders 13 and 14, and a pair of auxiliary or control drums 20 and 21 which are respectively coupled to the drums 3 and 4 of the controller and are provided with suitable contact fingers. The cylinders 6, 7, 13 and 14 may form a single casting or may be separately secured to the base plate upon which they are mounted, and the cylinder heads are preferably formed integral with the valve casings with which they are associatedf A yoke 22 is mounted on the cylinder casting and is provided with bearings 23 and 24 in which a shaft 25 of the auxiliary drum is rotatively supported. Another yoke 26 is secured to the cylinder casting and is provided with bearings 27 and 28 in which a shaft 29 of the aum'liary drum 21 is rotatively mounted.

The shafts and 29 are respectively in substantial alinement with shafts 30 and 31 of the drums'3 and 4, to which they are operatively connected by couplings 32 and 33. The coupling 33 is provided with a crank projection 34 which is operatively connected to the piston rod 17 by means of a link 35. The arrangement of parts is such that, when the actuating windings of the valves 18 and 19 are energized, compressed air is admitted through the *said' valves to the cylinders 13 and 14, and, when the said windings are deenergized, the cylinders are open to the atmosphere and the air pressure within them 7 is relieved.

The coupler 32 is provided with an annular toothed portion which constitutes a. pinion and meshes with the teeth of the rack upon one side of the connecting rod 10. The arrangement of parts is such that, when fluid pressure is: admitted through the valve 11 to the cylinder 6 and fluid pressure is exhaust-ed through the valve 12 from the cylin-- der 7, the pistons 8 and 9 and the connecting rod 10 are so actuated as to produce rotative movement of the main drum 3 and the auxiliary or control drum' 20.

The electromagnetically actuated valves 11, 18 and 19 are substantially alike and-each of them is constructed as shown in Fig. 3 of the drawings. The valve 12 is, however, constructed as shown in Fig. 4 of the drawings. Each. of the valves 11, 18 and 19 comprises a casting 39 having a vertically extending cylindrical chamber, a pair of apertured disks 37 and 38 having frusto-com'cal valve seats located and spaced apart within the said chamber, a valve stem 42 having frusto-conical plugs 40 and 41 adapted to engage said' seats, and a magnet comprising a coil 43, a stationary core member 44, which forms a part of the casting 39, and a movable core member or armature 45 which is secured to the valve stem 42.

The cylindrical chamber in which the disks 37 and 38 are located is dividedthereby into an exhaust chamber 46 having an exhaust port 47, an inlet chamber 48 having an inlet port 49, and a pressure chamber 50 with which a passage 51 leading to the cylin der communicates; The lower end of the valve stem 42 is enlarged to form a frustoconical spring seat 52, and a plug 53, which closes the lower end of the cylindrical chamher, is provided with an opposing conical projection 54, a helical spring 55, which tends to force the plug 41 against its seat and to raise the plug 40 from its seat, being interposed between the members 52 and 54. When the coil 43 is energized, the armature 45 is moved downwardly to cause the plug 40 to engage its seat and the plug 41 to' be released from its seat.

When the plug 40 is raised, the cylinder with which the passage 51 communicates is exhausted through the port 47, and when the plug 41 is lowered, fluid pressure is supplied from any suitable source (not shown) through the inlet port 49. I

The magnet valve 12 shown in Fig. 4 differs from that of Fig. 3 in that its'exhaust passage is normally closed and its admission passage isnormally open. casting 56 having a stepped cylindrical chamber which is divided into an exhaust chamber 57, a pressure chamber 58 and an admission chamber 59 by means of apertured disks 60 and 61 having frusto conical valve seats. q

A frusto-conical plug 62 for the exhaust passage cooperates with the seat in the disk 60 and is normally held in engagement therewith by a spring 63, while another plug 64 is, by the same means, normally main tained in a raised position and out of engagement with the corresponding seat in the disk 61. The plugs62 and 64 are carried bv a valve stem 42 that is adapted to be actuated by an electromagnet similar to that shown in Figs. 2 and 3, the plug'62 It comprises a 1 being lowered away from its seat when the electromagnet is energized and the plug 64 being caused to engage its seat.

In view of the foregoing, it is evident that if the actuating electromagnets of the valves 18 and 19 are both deenergized, atmospheric pressure will exist in the cylinders 13 and 14, and, accordingly, no movement of the pistons 15'and 16 or of the reverser and Since the valves 11 and 12 are difierent in construction, that is, since the valve parts .in the one are in inverse relation-to those in the other, full pressure will normally exist in the cylinder 7, while pressure will be exhausted from the cylinder 6 when the actuatin windings of both magnets are deenergize and, therefore, the drum 3 and the control drum 20,will be moved into on held in their ofi positions.

In order to advance the said drums, it is only necessary to energize the actuating windings of both the valves 11 and 12,

thereby introducing-full pressure to the cylinder 6,'- and exhausting pressure from the cylinder 7. The drums may be stopped and held indefinitely in any 1 position jby merely dene'rgizing the actuating winding of the valve 12, while energy is supplied to the winding of the valve 11, or, in other words, by restoring full balanced pressure in the cylinders 6-and 7 The auxiliary or control drum 20, as hereinafter pointedout, is adapted to govern the venergization of the actuating windings for the valves '11 and 12, while the control drum '21 is adaptedto govern the energization of the windings of the reverservalves 18 and 19. Referring to Fig. 5 of the drawings, the control system here shown comprises aposi- I tive supiy circuit conductor 71, a negative line con uctor 72, a control circuit resistor 78, the auxiliary or control drum 20', which is preferably mounted on the same shaft as the main accelerating drum 3, 'as' fully set forth in our above-identified co pending application, the reversing auxiliary or control drum 21, a limit switch79i, anoverload trip relay switch 80, v and a reversing master s'witch-82.' v

The control circuitresistor 7 81 is connectmainmaster switch 81 ed directly between the supply. circuit conductors 7 land 72, when a pair of switches 83 and 84am closed. p .The master reverscr 82' adapted to ocswitch 81 is adapted to occupy an off position and a plurality of motor-operatingpositions 1 to 8, corresponding to the varlous positions of the main control-drum 3.

Assuming that the master reverser 82 is thrown to position :0 and that the master switch 81 is moved into position 1, a circuit is established from an intermediate tap 85 in the resistor 78, to a conductor 86, contact fingers 87 and 88, which are bridged by a contact member 89, a conductor 90, contact fingers 91 and 92 of the auxiliary reverser drum21 which arebridged by a contact member 93, actuating coil 94 of the valve 18, a conductor 95, contact fingers 96 and 97,

which are bridged by a contact member 98 of the master reverser 82, an emergency cutto the c coil 115 of valve out switch 99, a conductor 100, contact fingers 101, which are bridged by acontact member 102, and a conductor marked 0 to substantially the middle point in the control resistor 78. i i

The coil 94 of the valve 18 being now en ergized, causes fluid pressure to be admitted linder 13,with the result that the reverse drum 4 and the auxiliary drum 21 are moved to the position :0. tion, the finger 92 is disengaged from the contact member 93 and, consequently, the coil 94 is denergized so that fluid pressure is released from the cylinder 13 in order that the reverser may be ready for subsequent operation in the opposite direction.

A circuit concurrently is completed from the conductor 90, through contact fingers 103 which are bridged by a contact member 104 when the controller 20 occupiesits off position, a conductor 105, a coil 106 of the line switch, the trip relay switch 80, a conductor 107, contact-fingers 108 and 109, which are bridged by a contact member 110 of the control reverser etc., to the, conductor 0. The line switch is thus closed and a holding circuit is established for the coil 106 from the conductor 90, through the interlocking contact members marked LS-in.

As soon as the line switch closes, a circuit is also established from conductor 1 90 through the interlocking contact members LS-in, actuating coil .115 of the'valve 11,

and the conductor 107, etc., to the 0 conductor.- By reason of the energization of the 11, fluid pressure is admitted to the cylinder 6. However, no movement of the pistons 8 and 9 occurs at this time because balanced pressures exist in the cylinders 6 and 7.

A connection is concurrently established from the conductor 90 through contact fingers111 and 112, which are bridged by a contact member 113 of the auxiliary drum 20, a conductor 114, the limit switch 79, the actuating coil 117 of the valve 12, and conmains in position 1, but if the In this posi- I 21, the conductor 95, 0

moved forward until the contact finger 111 becomes disengaged from the member 113. This occurs as soon as control drum 20 occupies position 1. Atthis point in the operation, the coil 117 of the valve 12 is deenergized, .thereby restoring balanced pressures in the cylinders 6 and 7 and holding the drums 3 and 20 in position 1.-

The initial series circuit connections of the governed motors are thereupon established by the 'main controller 3, as will be understood, and as fully set forth in'our above-identified divisional application.

The acceleration of the motors will not progress so long as the'master switch 81 remaster switch is moved successively through its positions 2, 3 and 4, the coil 117 of the valve 12 is alternately energized and deiinergized, and the drums 3 and 20 will move forward through the corresponding positions stepby-step, but dependent upon the action of. they limit switch 79, in accordance with a familiar and the valve 12 exhausts cylinder? and allows the piston 8 to advance the controller to its next step. Subsequently, the operation may proceed in accordance with circuit conditions and the will of the operator.

The controller 3 is adapted to effect a well known series-parallel control for the motors and need not be described in detail. As to the controller 20,-the contact member 113 is 'so subdivided and arranged as to interrupt the circuit established through the coil 117 of the magnet valve 12 as each control position is reached. Each successive forward movement is thus dependent both upon the limit switches and the position of the mastercontrollen- The contact member 102 is mounted on an drum of the master controller 81 by a friction clutch or similar connection and is limited'in its rotative movement by a stationary pin or stop 153 which permits it to move only into engagement with the fingers 101. The arrangement of parts is such that when the master switch is moved into its position 1, the friction clutch connection carries the contact me her 102 into engagement with.

120 insulating ring 152 that is connected to the s was es the fingers 101 and the stop 153 holds it in i this position as long as the master switch progresses forwardly, but any abackward movement of the master switch, whether it be from the osition 8 or from some intermediate position, will move the contact member 102 out of engagement of the fingers and will break the circuit at this point.

From the circuits above traced, it is evident that, as soon as the circuit is interrupted between the fingers 101, the line switch will be opened and the coils of the valve 11, 12, '18 and 19 will be de'e'nergized. While this will produce noimovement of the reverser'21, it will throw the drums 3 and 20 to their oft positions, as hereinbefore pointed out;

Obviously, the' circuit connections of the system may be varied considerably and the operating head may also be greatly modified as to its structural features and-may be. employed to operate any form of drum dontroller or regulator, withoutdeparting from the spirit and scope of our invention, and We, therefore, do not WlSll our invention l1m1ted to the specific details herein disclosed.

We clann as our invention a 1. The combination with a fluid actuator comprising a cylinder and a piston movable therein, of means for admitting fluid to one end of the cylinder and for releasing it at treme positions.

both ends of the cylinder to stop the other end to effect forward movements of the piston, and for admitting fluid to the said forward movement and to maintaln the piston stationary, said means being adapted to normally bias said piston to its initial posi-; tion. f 2. The combination with a fluid actuator comprising a cylinder and a'piston movable therein, of means for admitting fluid to one end of the cylinder and for releasing it at the other end to efl'ect'forward movements of the piston, and for admitting fluid to both ends of the cylinder to stop the said forward moveinent and to maintain the pis ton stationary, said means being caused to release fluid from one end of the cylinder and to admit fluid to the other end thereof in order to bias the piston to one .of its ex- 3. The combination with a fluid-actuator comprising a cylinder and a pistonmovable therein, of valves governing the admission and release of fluid to and from the respective ends of the cylinder, electromagnets for respectively actuating thesaid valves, and means governing the circuits of the electromagnets whereby one thereof is continuously energized to admit fluid to .one' end of the cylinder, and whereby the other is energized to release fluid from-the other end thereof to permit a forward movement of the piston and is deenergized to stop the said forward movement, both electromag-y ends of said container for arresting nets being deenergized to return the piston to its initial position.

4:. The combinationwith a fluid-actuator comprising a cylinder and a piston movable therein, of valves governing the admission and release of fluid to and from the respective-ends of the cylinder, electromagnets for respectively actuating the said valves, and means governing the circuits of the electromagnets whereby one thereof is continuously energized to admit fluid to one end of the cylinder, and whereby the other is energized to release fluid from the other end thereof to permit a forward movement of the piston and is deenergized to stop the said forward movement.

comprising a cylinder and a cooperating movable. piston, of means for admitting fluid to one end of said cylinder and for releasing it from the other end thereof to effect a movement of said piston in one direction and for subsequently admitting fluid to the second end of said cylinder to arrest the movement of said piston, said means being adapted to bias said piston to'its initial position. v

6. The combination with fluid actuating means comprising a movable member and a container in which it is disposed, of means for admitting an operating fluid to one end of said container and for releasing it from the other end thereof for efl'ecting a movement of said movable-member in one direction, for admitting operating fluid to boflh t e movement of said piston and maintainlng it at rest, and for releasing operating fluid from the first end of said cylinder and ad-.

Initting it to the second end thereof for effecting a movement of said pietonin the opconnected with the rotatable member, a rack meshing with the pinion, and electro-pneumaillic actuating means for adJuStmg the rac y 8. The combination with a rotatable mem ber, of an operating head comprlsmg a control drum and a gear inion operatlvely connected with the rotata le member, a rack meshing with the pinion, a pair of pistons. secured to o posite ends of the rack, cylin ders in whic the pistons operate, and elec- M vtrically controlled valves for governing the admission of operating fluid to the cylinders.

9. The combination with a rotatable member, of a'fluid-operated head comprising a control drum, a gear pinion operatively connected with the rotatable member, a rack rat opposite ends of the rack, cylinders in which the pistons operate, and electro-magnet valves associated with the cylinders, one of said valves being closed when energized to exhaust fluid from its associatedcylmder and the other being open when energized to admit fluid to the cylinder with which it is associated. I

10. The combination with a casing, a roatable member and a shaft for said member extending, upwardly out of the casing, of means removably mounted on the casing, comprising a. pair of pistons, cylinders in which the pistons operate, an operative connection between the pistons and the shaft of the member, and electro-responsive means for governing the admission of operating fluid to the cylinders. V v

11. A fluid actuator comprising a cylinder and a piston movable therein, and means for admitting operating fluid to one end of the cylinder and for releasing it from the other end thereof to efl'ect movements of said piston and for admitting operating *fluid to both ends of said cylinder to arrest the movements thereof, said means being adapted to biassaid piston to a predetermined position.

' 12. The combination with fluid-actuated means comprising a cylinder and apiston movable therein, of valves for govermng the admission and release of operating fluid to and from the respective ends of the cylinder,

posed therein, and a plurality of valves severally associated with the opposite ends of said cylinder for governing the admission and release of operatin fluid to and from said cylinder, one of said valves being normally closed and the? other normally open whereby unbalanced pressures bias said piston to one of its extreme positions, of control means for opening said first valve to effect a balance of pressures acting upon said piston and for closing said second valve whereby the pressure in. the corresponding end of the cylinder is released andthe resultant unbalance of pressures upon the piston eflect's a movementthereof away from its initial position. I

14. The combination with fluid-operated means comprising a cylinder and a piston disposed therein, of a plurality of valves associated with the opposite ends of said; cylinder for governing the admission and release of operating fluid to and from the tion. 1 15. The combination with fluid-operated respective ends thereof and adapted to establish unbalanced pressures acting upon said piston to actuate said piston in a forward direction, to estabhsh balanced pressures to arrest the movement of said plston and to eflect reversed unbalanced premures' to actuate said piston in the opposite direcmeans comprisin'ga cylinder, and a piston disposed therein, of a plurality of valves associated with the opposite ends of said cylinder for governing. the admission and release of operating fluid to. and from the respective en'dsthereoflone of said valves being normally open and the other valve being normally closed, and control meansfor maintaining said second valve open and for intermittently closing said first valve to 'eflect step-'by-step movements of said piston.

16. The combination with fluid-actuated means comprising a, cylinder and a movable controlled valves disposed at the respective endsof said cylinder for governing the ad- 1111581011 and release of operating fluid, one

- piston, of a'plurality'of electro-magnetically of said valves being open and the other closed when deenergized whereby unbalanced pressures act upon said movablepis.

ton'for biasing it to a predetermined position, and control means including means dependent .upon the position of said piston for continuously energizing the second electromagnetically controlled valveand intermittently energizing the first electro-magnetically controlled valve whereby a step-bystep movement of said piston is eflected.

17. The combination with fluid-actuated means comprising a cylinder and a movable plston associated therewith, of a plurality of electro-magnetically controlledvalves disposed at the respective ends of said cylinder for governing the admission and release of operating fluid, one of said valves being normally open and the other closed, of control means including an auxiliary controller mechanically associated with said piston and having interlocking control means adapted to make and break the energizing circuit of the firstelectromagnetically controlled'valve and also for maintaining the energization of saild second electro-magnetically controlled va ve.

18; The combination with a fluid-actuator comprising a fluid-containing member and a movable member disposed therein, of

valves for governing the admission and release of fluid to and from the respective ends of said containing member, electrically controlled means for actuating said valves, and means for governing the circuits of said electrically controlled means whereby one of said means is continuously energized to admit fluid to'one end of said contaming means and whereby the other is energized to release .to one side of the said piston, and means under the control of an operator for governing the admission of operating fluid to the other side of said piston in accordance with the position thereof for effecting a definite step-by-step movement thereof.

20. The combination with a fluid-actuated 'mechanism comprising a piston and a cylinder, of means for continuously admitting an operating fluid to one end of said cylinder and for admitting and releasing operating fluid to and from the oppositeend thereof, said means embodying means associated with said piston for effecting the successive admission and release of operating fluid to and from the last named end of said cylinder, whereby predetermined distinct steps in the movement of said piston are efl'ected.

21. The combination with a fluid-contain- .ing member and a movable member disposed therein, of controllable valves for governing the fluid pressure in the respective ends of said containing member, one of said valves being normally opened and the other closed whereby said movable member is biased to one position, and means for holding open the closed valve and intermittently closing the open valve to effect a step-by-step movement of said movable member in a forward direction.

22. The combination with a fluid-actuator comprising a fluid-containing member, a movable member disposed therein, and electrically-controlled valves for governing the admission and release of operating fluid to and from the respective ends of said containing member, of controlling means comprising a master controller and an auxiliary controller for governing the circuits of said electrically controlled valves, whereby one said forward movement, said auxiliary controller being connected in circuit with one of said electrically controlled valves for effecting a step-by-step movement of said movable member.

23. The combination with fluid-actuated means comprising a cylinder and a piston movable therein, of controllable valves'for governing the fluid pressure in the respective ends of said cylinder, means for holding open one of said valves to continuously admit operating fluid to one end of said cylinder, and for intermittently closing the other valve to release operating fluid from the other end thereof whereby said piston is actuated in a series of distinct steps.

24. The combination with fluid-actuated means comprising a cylinder and a piston disposed therein, of a plurality of valves associated with the opposite ends of said cylinder for governing the admission and release of relatively high-pressure operating:

fluid to and from the respective ends thereof, and adapted to normally admit highpressure fluid to one end of said cylinder to bias said piston to its ofl position, to admit high-pressure fluid to the other end of said cylinder and to release operating fluid from the first end thereof to effect a forward actuation of said piston, and to admit highpressure fluid to both ends of said cylinder to arrest movements thereof.

25 The combination with a fluid-actuator comprising a cylinder and a piston disposed therein, of means for normally establishing atmospheric pressure in one end of said cylinder and a relatively high pressure in the other end thereof to bias said piston to one extreme position, for establishing a reversed condition of relative pressures upon the respective sides of said piston for eflecting its actuation in the opposite direction and for establishing balanced high pressures in both ends of said cylinder to arrest movements thereof.

In testimony whereof, we have hereunto subscribed our names this 4th day of Oct, 1912.

'- NORMAN W. STORER.

-- ARTHUR J. HALL.

Witnesses:

0. Emma, 18. B. Hume.

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