US1801049A - Valve - Google Patents

Description

whereby the ,close fit of the operating Patented Apr.V 14, 1931 onEsrEa w. Lama, or rmmmmnu, PENNSYLVANIA VALVE Application le-d June 5, 1926. Serial No. 113,854.

This inventionl relates to valve mechanisms and more particularly to improved controlling means therefor. f

An object of my invention is to provide particularly for a valve of the plunger type improved hydraulic controlling means thereior whereby the plunger may be controlled and actuated by iuid pressure, and when the pressure on the plunger nose is suddenly reduced the plunger will be prevented from jumping to its seat.

A further object is to provide an improved combination of Huid operatin chambers and fluid controlling means thereir whereby the primary plunger moving force is created in one chamber and if this does not suiice for effecting plunger movement, fluid pressure in another chamber may be suitably controlled so as to produce a supplementary closing force. The first chamber is normally suiicient for closing the plunger.

A. further object is to provide an improved dashpot and operating cylinder arrangement dashpot is' connected to the plunger and is elfective thereon at the instant the dashpot action commences.V In this respect a more specific object is to provide improved means for maintaining a positive operating force and at the same time having effective dashpot action.

A further and more specific object of the invention is to rovide in combination with the plungervanclD operating piston and cylinder therefor an improved control valve arrangement which may be disposed;l either within or without the plunger valve mechanism. In either case, however, the valve controls a suitable port whereby pressure within and outside of the plungercmay be equalized, and it is one of the objects of this invention to so control'the said valve mechanism that normally communication will constantly occur between the inner and cuter sides of the plunger.

Still another object lis to provide an improved means for'connecting the operating piston to the plunger so thatia relatively may be had without danger of undue stresses when the piston and plunger are connected.

piston and cylinder` In addition to the foregoing objects, other objects and advantages will appear from the following description of the accompanying drawings,

in which Figs. 1 and 2 are sectional views of the Valve mecha-nism tions respectlvely;

in open and closed posi- Fig. 3 is a modification with a part of the control valve 4mechanism disposed outside,

and

Fig. 4 is a sectional view of a further modifi'cation showing the control valve mechanism disposed entirely outside of the plunger valve mechanism.

er 1 telescoping therewith. The plunger seat is preferably disposed so as to provide an external plunger surface which will be subjected to fluid pressure in the upstream pipe when the plunger is seated, thereby obtaining an opening Thesplunger val force by this fluid pressure. ve is provided with an auxiliary cylinder 5 connected by asolid partition to the internal casing 4'. Cylinder 5 is fitted with a piston 6 mountedlon a hollow rod 7, which is lugs 8 of segmental form corresponding spaces connected to plunger 1 by passing throughv between lugs 9 on the plunger. By means of this arrangement the rod 7 is inserte d axially into the position shown and locked against axial motion by turning around posite each other looseness is provided plunger 1, thus yment of piston 6 in cylinder 4.

until lugs 8 and 9 are op- A certain amount of radialy between rod 7 and permitting `separate align- 1n cylinder 5 and plunger 1 This is important inasmuch as the fit around cylinder 6 would in practice be closer than.

A hollow 'pilo at both ends,

the fit around plunger 1.

t valveQ is provided. closed but arranged with ports 10, 11

and 12. Pilot valve 2 is moved in an axial direction by a gear rack' 13 engaging with a pinion 14 mounted on a shaft 15, which latter passes through thebody of the valve and is operated by any usual and appropriate mechanism. ,Y Dt

her means of moving pilot of cylinder 5. The

valve 2 could be equally Well employed, such as a screw gear, bell crank, piston and cylin- ,der or other methods common in the art.

A chamber 16 is provided at the back end of the internal casing communicating with the chamber 18 within the latter by means of port 17. Port 17 is closed by plunger 2 when the latter has been moved to the left as far as it is possible to go, as shown in Fig. 1. At all other times chambers 16 and 18 are in free communication.

A drain pipe 19 is connected to chamber 16 and leads to some region of atmospheric pressure or of pressure substantially lower than the pressure of the pipe line. A valve 20 is provided in pipe 19 to cut oil the exhaust and prevent leakage when plunger 1 is closed, or at any other time when it might for some special reason be desirable. Ordinarily, valve 20 is always open except when plunger 1 is closed.

A connection 21 is also provided leading from the pipe line or some other source of pressure supply and connected to both ends ports 22 and 23, however, leadin to the interior of cylinder 5 are considera ly smaller than supply pipe 21 so that without providingany means of port 12.

pressure`may be exhausted from either end of cylinder 5 without materially reducing the pressure simultaneously supplied to the other end of the cylinder.: By this means the cylinder 5 is automatically supplied with operating pressureLand at the same time either`side of the pistonmay be exhausted shutting off the pressure supply.

The operation of the valve is as follows: Assuming plunger 1 to be open, and pilot valve 2 seated against port 17 as shown in Fig. 1, the pressures throughout chambers 18, 5 and 24 will be substantially equalized and equal to the pressure in the waterway 25, this being due to leakage through the its between the various moving parts. There will be no leakage out of the valve itself, however, inasmuch as the exhaust port 17 is closed.

To close plun er 1 pilot valve 2 is moved towards the riglgat. This opens port 17 and reduces thepressure in duction of pressure being communicated to the inside o pilot valve 2 through port 10. The movement Vof pilot valve 2 gradually cuts otI` port 11 and simultaneously opens This builds up pressure behind piston 6 and drops the pressure in front of piston 6, thus developing a closing force which is applied to plunger 1.

It will be observed that the size and location of ports 11 -and 12 are such that by the `time port 11 is completely closed port 12 is completely open, and at the same time pilot valve 2 has advanced only approximately half of its stroke towards its seat 26. .As a result of the latter condition the port 27 is chamber 18, this rex the drawing,

still fully open, providing free conmlunication from the waterway to chamber 24 through ports 28; and consequently the static pressures behind and in front of plunger- 1 are substantially equalized.- The equalization of static pressures leaves the forces developed on piston 6 free to overcome only the dynamic reaction of the iowin water on the nose of the plun er and the rictionof the moving parts. t is obvious, however, that if, as in the case of a valve discharging into the atmosphere at high velocity, the reaction developed against the nose of the plunger should be greater than the propelling force which could be applied to piston 6, then the pilot valve 2 will move still further forward relative to the plunger, gradually approaching its seat 26 and cutting oi the passage 27. This will prevent the exhaust of pressure from chamber 24 and will ermit pressure therein to build up, thus ad ing to the closing force developed on piston 6. Pilot valve 2 will continue to cut off passage 27 until the plunger starts to move. Thus it will be seen that the action of pilot valve 2 is cumulative. It first develops all of the force which it is possible to apply to piston 6 and if thisl is insuiicient to move the plunger it goes further and develops a supplementary force in chamber 24 until the plunger moves. The pressure in chamber 24 is automatically supplied either by leakage aroundl plunger 1 or else by an independent source of pressure supply, which, however, is of restricted size as compared with the exhaust port 27 so that chamber 24 may be exhausted regardless of the incomingpressure supply.

After plunger 1 has been seated at 33 as shown in Figure 2, pilot valve 2 continues its motion until it seats at 26, thusicutting off all iiow through the valve. .If it is desirable to stop leakage through pipe 19, valve 20 is then closed.

In opening the valve, pilot Yvalve 2. is moved in the opposite direction. Its first effect is to open port 27, thus equalizing the pressures upstream and downstream of the plunger seat. If the diameter of plunger 1 is the same as seat 28 no immediate movement of plunger plunger is larger than its seat as shown by then the pressure of the pipe line on the shoulder 29 will tend to open the plunger. Further movement of pilot valve 2 towards the left `will build up pressure in front of piston 6 and exhaust pressure fromf behind it, thus developing a force to open plunger 1. Any tendency of plunger 1 to drift relative to pilot valve 2 will be automatically corrected by the resultant opening or closing of ports 11, 12 and 27 It therefore results that plunger 1 will follow automatically the movement of pilot valve 2 until the plunger is completely open, after which a 1 will occur, but if the l further movement of the pilot valve closes port 17 and stops all leakage out of the operating chambers. It is desirable that this leakage should be cut off' when the plunger is open without closing valve 2O because if valve 20 were closed the entire control mechanism would be inoperative and the valve would not' be in condition for emergency closing by remote control.

Piston 6 is provided with an extension or shoulder 30, having a close fit with a similar shoulder 31 on the cylinder head. When plunger l is closing these two shoulders lap at a point in the stroke of the plunger some distance from seat 28. The eiiiect of this is to cut o from the portion of cylinder 5 vwhich is being exhausted through port 23,

a chamber 32, which, having no outlet, acts asa dashpot to slow down the closing stroke of plunger 1. The water trapped in chamber-32 must be expelled entirely by leakage and this can only occur very slowly.

ln the modification -diagrammatically shown in Fig. 3 the pilot valve is left within the plunger while the remaining valve control is disposed outside. The elements of the outercontrol are given prime numbers corresponding to the numbers of the same elements in the preferred form. The rear exhaust passage feature of pilot valve 2 is formed in a member 2 which is actuated by any suitable means through a rack and pinion 13 and 14 respectively. Ports 11 and 12 have communication respectively with the rear and front ends ofcylinder 5 as through pipes 11a and 12a, ports in the sleeve 7 and chambers connecting said ports and pipes. The sleeves 7 is connected to plunger l by any usual rods or linkages so that all plunger movements will be copied by the sleeve. A. stationary valve controlled port 17 is provided by a telescopic connection between a hollow sleeve and-the rear of rod 2.

In the modilication diagrammatically shown in Fig. 4 the control valve mechanism including the pilot valve, is simply entirely removed to the exterior instead of being disposed within the plunger valve mechanism and the various chambers and ports are connected by pipes leading through the inner and outer casings. In this modified form the elements thereof corresponding to the elements in the preferred form are given corresponding double primed numbers. The hollow rod 7 which has a close sliding fit with the hollow pilot valve 2 is actuated by a pinion 14?; mounted upon the shaft 15 outside of the casing 3. This insures the member 7" to follow all movements of the plunger l justthe same as does the piston rod 7. A port 7 b is adapted to have communication with the port 12 to allow discharge of fluid from thefront end'o cylinder 5 to atmosphere as through ports 10 and 17". The ports 27 and 28 allow communication between the chamber 24 and the conduit just below the plunger seat as by the pipes 276 and 28?). Pipe 11b allows discharge of. 'fluid from the rear end of cylinder 5 as by ports 11, 10 and 17". To actuate the pilot`valve 2" for e'ectingv closing or open;

modified forms being identical to the pre-.

lerred form, description of the operation will not again be given.

It will thus be seen that in any of the above forms the effect of ports 27, 27', or 27 is merely supplementary to the effect of the auxiliary cylinder 5f The control of ports 27, 27 or 27 does not as heretofore produce the primary moving force for actuating the plunger and when the pilot valve does approach its seat or actually seats the supplementary force is not of a pure mechanical nature but rather hydraulic. Hence, any slight movement or'tendency `of the plunger to jump so as to cause relative movements between the pilot valve and the plunger will cause a 'substantially instantaneous reduction of the supplementary hydraulic` moving force. Such a mode of operation is particullarly important in those installations involving, for instance a hydraulic turbine, wherein when the turbine gates are closed the only flow in the penstock will be due to gate leakage. Y When the turbine gates are thus closed the plunger Valve will be closed in practicallystill water. Dueyto the small flow, pressure in the`downstream side of the plunger will not drop until the latter is very close to its seat. This sudden reduction of pressure will if the ports 27, 27 or 27 are not already open cause the plunger to jump forward and possibl `suddenl engage its seat. However, with t e constr ction herein disclosed the ports 27,27', or 27 will not be entirely closed and hence when the plunger approaches its seat and the downstream pressure drop occurs, such pressure drop will be instantly communicated to the plunger chamber 24 and reduce the supplementary closing force. There is no necessity for the plunger to move relative to the pilot valve to allow this communication of decreased pressure, hence plunger movement may be controlled to a nicety.

It is also to be noted that the ports 17, 17', or 17 close automatically when the plunger valve is wide open, thus cutting olf exhaust leakage, and which is accomplished in such mechanism for controllin between said internalcham er and the down-Q a way as not to put the valve out of operation as would be the case if valve 2() were closed. Valve 20 is closed when the main In fact, it is desirable that the valve should be arranged 'so that it cannot be opened from a distance. Otherwise, it might be opened too rapidly into an empty line or opened at a time when men were working in the pipe.

I claim:

1. In combination with a valve mechanism having inner and outer casings and a plunger cooperating with the inner casing to form an internal plunger fluid chamber, of means for moving said plunger comprising a piston and cylinder one of which is rigidly secured to said plunger for movement therewith, a movable control valve mechanism for controllino' fluid flow Vrelative to said cylinder whereby said plunger will substantially follow movements 'of said control valve, and

a means whereby said internal chamber is adapted, automatically in accordance with flow conditions through said casings, to have variable communication with the downstream side of said plunger during movement thereof by varying the flowarea of the communieating passage.

2. In combination with a valve mechanism of the plunger type having inner and'outer casings and a plunger cooperating with the inner casing to form an internal chamber, of means for controlling the plunger including a piston and cylinder, one of which is normally immovably secured to said plunger so as to be movable therewith, and a pilot valve normally movable during movement of the plunger for controlling communication between said internal chamber and the downstream side of the plunger.

3. In combination with a valve mechanism of the plunger type having inner and outer casings and a plunger cooperating with the inner casing to form an internal chamber, of means for controlling the plunger including a piston and cylinder, one of which is normally immovably secured to saidy plunger so as to be movable therewith, and pilot valve communication stream side ofthe plunger and for also controlling fluid flow relative tosaid operating cylinder.

4. In combination with a valve mechanism of the plunger type having inner and outer casingsand a plunger cooperating with the inner casingl to form an internal chamber, of means for controlling the plunger including a piston and cylinder, one of which is norl mally immovably secured to said plunger soV as to be movable therewith, and a in ovable pilot valve for4 controlling communication -`between said internal-chamber and the downstream side of the plunger and having means for also controlling actuating fluid for said cylinder, whereby movement of'said valve is adapted to be substantially copied by the plunger, while communication between the internal chamber and the downstream side of the plunger is maintained.

5. The combination with a valveme'cha-y substantially by the plunger, and means autol matically controlled in accordance with plunger movement forpermitting communication between the downstream side of said plunger and said internal chamber through- 'out the closing stroke. of said plunger.

6. The combination with ya valve mechanism having inner and outer casings and a plunger cooperating with the inner chamber to form an internal fluid chamber, of means for controlling said plunger including Huid operated means, a movnble control valve adapted to control fluid to said operating means and to have its movements copied substantially by the plunger, means for permitting communication between the downstream side of said plunger and said internal chamber throughout the closing stroke of said plunger, and means including said control valve for closing said latter communication when said plunger is seated. Y

7. The combination with a valve mechanism having inner and outer casings, a plunger cooperating with the inner casing to form an internal fluid chamber, of means for controlling plunger movement includinga piston .and cylinder, one of which is movable and connected to the plunger, and a coinbined pilot and control valve whereby actuating fluid for said cylinder and piston and comternal chamber and the downstream side ofl the plunger are controlled, said combined valve being so arranged that said chamber l lil) and cylinder,

communication may be continually had durlng the closing plunger stroke.

9. The combination with a valve `mechanism having inner and outer casings and a plunger cooperating-with the inner casing to form an internal chamber, of means for controlling said plunger including a piston and cylinder, one of which is normally immovably connected to the plunger for movement therewith, means for controlling actuating Huid for said cylinder including a movable control valve adapted to have positive mechanical connection with said plunger for movement therewith and to effect opposite controlling characteristics of the fluid in the opposite ends of said plunger will be moved so longas said control valve is moving, and means permitting equalization of pressure between said chamber and the outer side of said plunger including a valve adapted to move with the plunger.

10. The combination with a valve mechanism having inner and outer casings and a plunger cooperating with one of said casings to form an internal fluid chamber, of'means for controlling the plunger including a piston ,and cylinder, means permitting a continual supply of operating fluid to opposite ends of said cylinder, and means for controlling exhaust of fluid from either of said cylinder ends including a movable control 'valve whereby said plunger will copy movements of said control valve.

11. The combination with a valve mechanism having inner and outer casings and a plunger cooperating with one of said casings to form an internal fluid chamber, of means for controlling the plunger including a' piston means permitting a continual supply of operating fluid to opposite ends of said cylinder, means for controlling exhaust of' fluid from either of said cylinder ends-including a movablecontrol valve whereby said plunger will copy movements of said control valve, and means for permitting constant communication between said internal chamber and the downstream side off said plunger durin the closing movement thereof until said p 'unger is seated. 1 v

12. The combination with a valvemechanism having innerand outer casings and a plunger cooperating with one of said casings to form an internal fluid chamber, of means for controlling the plunger including a pis-l ton and cylinder, means permitting a continual supply of operating Huid to opposite ends of said cylinder, means for controlling exhaust of fluid from either of' said cylinder ends including a movable control valve whereby said plunger will copy movements of said control valve, and means for preventing exhaust of fluid from said cylinder when the plunger is in open position.

13. The combination with a valve mecha- .nism having inner and outer casings and a will copy movements cylinder whereby said plunger cooperating with one of said casings to form an internal fluid chamber, of means for controlling the plunger including a piston and cylinder, means permitting a continual ysupply of operating fluid to opposite ends of' said cylinder,v means for 'controlling exhaust of fluid from said cylinderends including a movable control valvewherebysaid plunger and means for preventing exhaust of fluid from said cylinder whenI the plunger is in open position and while said control valve is so positioned relative to said cylinder that normally it would permit exhaust of fluid therefrom.

14. The combination with a valve mechanism having inner and outer casings and a plunger cooperating with said inner casing to form a fluid chamber whereby a closing force on the plunger may be created, of means for controlling the plunger including piston and cylinder elements forming a unit spaced from but attached to the plunger and adapted to exert thereon a fluid operating force separate from the pressure in said chamber, a pilot valve controlled by said elemfents and means for effecting a positive dashpot action adapted when created to be instantly effective on the plunger.

15. The. combination with a valve mechanism of the plunger type having an internal chamber formed by the plunger whereby a closing force may be created, of means for controlling the plunger including piston and cylinder elements forming a unit spaced lfrom of said control valve,l

but attached to the plunger and adapted to` l forming aldashpot operative during a certain portion of the plunger movement to create a closed dashpot chamber, and means for constantly applying a fluid force in said cylinder while said dashpot action is effective.

16. The combination with a valve mechanism of the plunger type, of means for controlling the plunger including a piston rod and piston and cylinderV elements, one of which is movable and connected to the plunger by said piston rod, said elements having cooperating members spaced from said rod and disposed adjacent the cylinder walls to form a dashpotoperative during a, certain portion of the plunger stroke, and means permitting exhaust of fluid from said space adjacent said rod while said dashpot action is effective.

17. The combination with a valve mechanism'of the plunger type, of means for controlling the plunger including piston and cylinder elements, one of which is movable,

and means for connecting said movable element and plunger whereby said plunger and movable element are adapted to have relative l -lateral movement, and a controlling valve plunger,

' derand piston in said cylinder.

' cylinder and 19. The combination with a valvemechanism having inner and Outer casings and a plunger telescoping with said inner casing to form an internalfluid chamber, of means for controlling said plunger including a piston disposed within said chamber, a hollow rod connecting said piston and plunger, a sleeve valve disposed with- -in said hollow rod to control the operating fluid in said cylinder, and a pilot valve including a port formed in the plunger and a closure portion therefor carried on` said sleeve valve.-

20. The combination with a valve mechanism having inner and outer casings and a plunger telescoping with said inner casing to form an internal fluid chamber, of means for controlling said plunger including a cylinder and piston disposed within said c amber, a hollow rod connecting said piston and plunger, a sleeve valve disposed within said hollow rod to control the operating fluid in said cylinder, and'fa pilot valve including a port formed in the plunger and a closure portion therefor carried on said sleeve valve, said hollow rod having a passage therein whereby communication may be had between the internal chamber and the outside of said plunger through said plun r port.

21. The combination wit -a valve mechanism having inner and outer casings and a plunger telescoping with the inner casing to form an internal luid chamber, of means for controlling the plunger including a cyly inder and piston therein, a hollow rod connecting said piston and lplunger whereby' they are relatively longitudinally immovable, a hollow sleeve valve disposed within said rod and having ports adapted to communicate with opposite ends of said cylinder, and a valve mechanism for sealing the interior of said operating means Jwhen the plunger is in open position.

22. The combination with a valve mechanism having inner and outer casings and a plunger telesco'ping with the inner casing to form an internal Huid chamber, of means for controlling the plunger including a cylinder and piston therein, a hollow rod connecting said piston and plunger Whereb said piston and plunger are relatively longitudinally immovable, a hollow sleeve valve disposed within said rod and having ports adapted to communicate with opposite ends of said cylinder, and a valve mechanism for when the plunger is in open position, said latter valve means constituting an exhaust port through which fluid from said cylinder is discharged upon exhaust through said sleeve ports.

23. In combination, a valve mechanism comprising a movable valve member, means forming a and means for controlling said valve member, including a piston and a cylinder, one of which is movable with said valve member and immovable relative thereto, and a pilot fluid operating chamber therefor,

valve for controlling communication between said chamber and the downstream side of said valve mechanism and for also controlling fluid flow relative to said operating cylinder.

24. In combination with a valve mechanism having a movable valve member, means cooperating therewith to form afluid operating chamber therefor, piston and cylinder elements for controlling the valve member, whereby cylinder may be diierent from the unit pressure in said chamber, and means permitting constant communication between said chamber and the fluid conduit with which said valve mechanism is associated, said 'means being adapted to control automatically said communication in accordance with low conditions through said valve, land said cylinder. and piston elements bein adapted to exert a constant operating orce -on the plunger during control of the chamber pres.- sure.

25.' In combination, a valve mechanism comprising a movablevalve member, piston and cylinder elements for controlling operation thereof, a piston rod connecting one of said elements with said valve member and means forming a dashpot for controlling movement of said valve member and bein spaced from but surrounding said rod, sai dashpot means and piston and cylinder elements being formed in the same structure but operable independently of each other.

26. In combination, a valve mechanism comprising a movable valve member, piston' and cylinder elements for eiectmgl movement thereof, a piston rod connecting one of said elements with said valve member. means for supplying fluid to one end of said cylinder, andI means disposed within said cylinder end for formin a dashpot, said dashpot being operable in ependent y of the fluid supply to said cylinder end after the dashpot action has once been initiated. i

27. The combination in a valve mechanism comprising a conduit casing'having a seat, a second casing, a plunger telesco ically carried'by said casing and adapted or engagethe unit fluid pressure in said lill ment with said conduit seat, said plunger and second casingforming a fluid chamber, an orice formed in said plunger whereby communication may be had between said chamber and the conduit passage on the downstream side of the conduit seat, piston and cylinder elements disposed Within said second casing, a sleeve directly connected to said plunger and one of said elements, a hollow rod slidably disposed within said sleeve and carrying at one end a valve adapted to Icooperate with said orifice to control iiow therethrough and also having spaced from said valve a plurality of ports certain of which are adapted for communication with opposite ends of said cylinder, said sleevey having a port adapted to register with one of said other ports to allow communication with one end of said cylinder and a hollow portion of said rod, a discharge port formed in said second casing, means also carried by said rod to control said discharge port, and means for movingsaid rod axially.

28. The combination, in a valve mechanism, comprising inner and outer casings spaced to form a fluid passageway therebetween, a plunger telescoping with said inner casing to form an internal chamber therewith, an orifice in the nose of said plunger, a pilot valve for controlling said orifice, and a discharge passage leading from the rear end of said inner casing to the exterior of said cuter casing, said inner casing having a valve seat upon which the rear end of said pilot valve is adapted to seat to prevent substantially Huid flow through said discharge passage.

29. '.lhe combination, in a valve mechanism, comprising inner and outer casings spaced to form a relatively smooth passageway therebetween, a plunger telescoping with said inner casing, and means for operating said plunger including a piston and cylinder disposed within said inner casing, an orilice in the nose oi.E said plunger, a pilot valve for controlling said orifice, a discharge passage leading from the rearrend of said inner casing to the exterior of saidouter casing, and including a valve seat, means whereby fluid pressure acting upon atleast one side of said piston may be discharged through said discharge passage, and a valve carried by the rear end of said pilot valve for engaging said valve seat to prevent substantiall any discharge of duid through said disc arge passage..

3U. The combination, in a valve mechanism, comprising inner and outer casings spaced to form a relatively smooth annular duid passageway, a plunger telescoping with said inner casing to form an inner Huid chamber, and means for operating said plunger including a piston and 'cylinder disposed within said inner casing, means for discharging the pressure, acting upon at least one side of said piston, through the rear end of said inner casing, and means for preventing discharge of said Huid including a valve which is adapted to be closed upon rearward movement of said piston.

'm 31. 'lhe combination, 1n a valve mecha-- nism, comprising inner and outer casings spaced to form a relatively smooth annular fluid passageway, a plunger telescoping with said inner casing, and means for operating said plunger including piston and cylinder elements disposed within said inner casing, a discharge passage for the fluid pressure acting upon said piston and leading from the rear end of said inner casing and a valve adapted to close said passage while said plunger is in its open position.

32. The combination, in a valve mechanism, comprising inner and outer casings spaced to form a relatively smooth annular fluid passageway, a plunger telescoping with said inner casing to form an internal fluid chamber, and means for operating said plunger including a piston and cylinder disposed within said' inner casing','an orifice in the nose of said plunger, a'pilot valve for controlling said orifice, means for discharging fluid from the rear end of said inner casing including a discharge passage, iand a valve mechanism associated with the rear end of said pilot valve for controllingsaid discharge passage whereby fluid flow through said discharge passage is prevented when the pilot valve is in its rearmost position.

CHESTER 1W, LARNER.

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