US2402212A - Operation controlling means for pressure fluid actuated tools - Google Patents

Description

June 18, 1946. sHAFF 2,402,212

OPERATION CONTROLLING MEANS FOR PRESSURE FLUID AGTUATED TOOLS Filed Aug. 12,1942. 2 Sheets-Sheet 1 fizvelzzfor" JE rrzesifishafi June 18, H.

SHAFF 2,402,212

OPERATION CONTROLLING MEANS FOR PRESSURE FLUID ACTUATED TOOLS Filed Aug. 12, 1942 2 Sheets-Sheet 2 jdorvzga.

id initiate the cycle.

Pmm'd Jui1e 18, 1946- 2,402,212

' I im 1 lea-X15101? pressureflllidjactuatadttnls dndis; pliessedinthe ppended claimsw, f pyrticularly 1ccxice-rrm-ui:with valvemechaniamior The pl8sure fluid actuated i001 selectedfor conigxolling the working cycle or 1.9. pneumatic tool Purp s of; illustration; inconnection xwit'h l suph :as a piston; flfltliatBd-QQMD riveterv 5" invgntion is l a compression riveterv (mg.-,:1)# em y A z n qlm bje ct oi -the inventionisitoinprovide r bodying in this instance-aan elongated cylinders novel me hwi adapted wwmaticallyf s 1 arr l "having at one end ammu projeczm m a p u fluid t d. W r'f r sinzl riveting yoke ill; thereto through .an cyglqwithqiltl'filliring any;manipulativeact-oh thezeotjapchqred risi ltlbetwe'enrspacewparallel" eav t.,o -t e u e other thana momentary l a ls 12 9n. e b r el-.1 he outersend or the yoke 1, 7. I carries an adjustable atationary anvil orrivetlet Another object is to provide novel pressure fluid ",1 attachedgon bqpsearm: 0i vthe yoke hams. WW r h n mutof-t is ki-ndwhichisenecev; bore Min it s iorward n servingasca bearing tivejo vaziably cgntrpl the operapiyq, movements. guide fqrp rlelpngated reciprocal compression 1 thQ -i ,;.,trz J wall llqm wingg rlygt act li f lfhe-ramhaslanzinnerv; Anothgr. ObjQQQ pf the inventi n is; to provide end bz basg sectign l'l pr efe r ably ot angularlcrosa new and improved mecl amgm fpr-ggoyeming 3 the l sqtidg; Which/5181a; within; a alliim biev forwardly. f

L k ns'cy le 0 1a st n q a lpneum tic tool openin recess l8 rbr'mea ma r gucgd lzmntnew;

\ of parallel bores 81 and 38 therein in which, re-

into the chamber or cylinder 28 ahead of the pis-- ton 24. Exhaust of this end of the cylinder also takes place through this passage and port.

Control means for tools of this character or for others which are generally similar is provided 5 which in a number of respects materially improve tool operation. Thus, the present control mechanism embodies means by which'the user need only initiate operation of the tool by a momentary act to produce a movement of the tool through one complete cycle ofworking stroke and return. The control mechanism is eifective at the transition points between work and return strokes, to automatically reverse the pressure fluid connections and, at the end of the return stroke, to automatically reset itself to its initial or starting position. The control mechanism has a further feature in that it embodies means conveniently adjustable to a predetermined setting for automatically controlling the maximum forc exerted upon the work.

Referring first to Fig. 1. the control mechanism ispreferably disposed within the elongated boss 38on the barrel end wall 8|. The boss has a pair spectively, a throttle valve assembly 39 and soontrol valve assembly 48 (Fig. 3) are mounted. The throttle valve assembly-embodies means for controlling the admission of pressure fluid to the device and under certain conditions for controlling the exhaust of expended pressure fluid therefrom.

The control valve assembly embodies means for directing pressure fluid to drive the piston assembly. in one. direction or the other. It also embodies adiustable means for determining the end of the working' stroke and thereupon automatically effecting a'return of the assembly to its initial position to complete the cycle.

Referring to the structure of the throttle valve as shown in Fig. 3, the bore 81 has a throttle valve 40 casing 4|sec'ured therein as by a driven fit. The casing extends beyond ,one end of the boss for screw threaded engagement by a nipple 42 arranged i'or connection with aconduit (not shown) from a suitable source of pressure fluid. The casing has an internal bore 43. the central portion 44 of which'is of restricted diameter to provide outwardly facing valve seats 45 and 48. The valve seat'facing toward the nipple 42 (in this instance the seat 45) is normally closed by a throttle valve 41 urged thereagainst by a spring 48 hearing between the valve and the inner end of the nipple 42. The other valve seat 45 is closed by an exhaust valve 49 and the two valves are. connected by a stem 58 so arran ed that they have an alternating o en and closed relationship.

The end of the throttle valve casing 4| o posite the ressure fluid inlet ni ple 42 is spaced in- Wardlv of the end of the boss 38 toprovide a chamber 5| in which a hollow piston 52 is mounted with its closed end 53 o pose to a. plu 54 screwedinto the end of the boss 36. The. iston 52 has an axial stem 55 for abuttin en agement with the end face 01' the exhaust valve 49 so hat, hen pressu e fluid is admitted to the cha ber 5| between the piston and the nine 54 the oiston will move to close the exhaust valve 49 and o en the throttle valve 41 against the force exerted the eon by the sorlnz 48.

The throttle valve housin 4| has a lateral has sage 58 therein openin into the restricted cantral portion 44 of the internal bore. 4.1 and leading to a port 51 formed in the. boss 98 between he bores 31 and 38 therein. Seated in the bore 88 is a control valve casing 58 held in place by right and left hand plugs 59 and 59, respectively (as shown in Fig. 3). The casing 59 has an ini sage 86 therein leading from th internal space at one end of the valve casing 58. Further, the valve casing has a port 91 communicating with the port 29 which leads to the recess 30 in the end wall of the cylinder 28 behind the piston 24 and a longitudinally spaced port 88 (Fig. 1) communicating with the passage 34 leading to the side of the cylinder 28 ahead of the piston 24.

A control valve 59 of the spool type, slidably mounted in the casing 58, has annular pressure fluid conducting grooves 18, therein arranged for constant communication respectively with the ports 51, 88. In the sliding movement of the valve, the annular grooves 18 and II are arranged alternately to place either the port 28 or passage 84 in communication with the pressure fluid inlet port 8| while connecting the other with exhaust through port 82 and opening 84 or port 88 and opening 85. The valve also has an intermediate position in which an annular rib 12 between the grooves 10 and II closes the intake port 5| and disposes the annular grooves 18 and II between and out of communication with both exhaust port (see Fig. 4)

The control valve has a deep recess 18 in one end thereof (in this instance the end which faces toward the plug 58) to receive one end of a spring I4. The other end of the spring bears against the flanged end-of a stud 15 which extends axially through and has screw threaded engagement, as at 15, with the plug 59. The outer end of the stud carries a manipulating head I1. By employing screw threads of relatively fine pitch manipulation of the head 11 will eifect adjustment of the tension of the spring 14 with a high degree of accuracy.

The spring normally urges the control valve toward the plug 60 and at this end of the valve the plug and the control valve casing form a chamber 18 (Fig. 5) for pressure fluid which acts on the adjacent end face of the control valve as a piston for shifting the control valve against the force of the spring 14. This end face of the control valve has a recess 19 therein to slidably receive what may-be termed an auxiliary piston 88. The end of the auxiliary piston within the control valve recess 19 has a peripheral groove and the inner end of the recess 19 is also grooved to provide a chamber 8| (Fig. 3) between the auxiliary piston and the control valve when the former is fully seated in the latter as shown in Fig. 1.

An annular groove 82 on the control valve communicates with the chamber 8| through a port 83. The groove 82 is arranged to communicate with a port 84 in the valve casing 58 (Figs. 2 and 3) in the starting position (see Fig. 3) and in the intermediate position.(see Fig. 4) of the control valve. The port 84, as shown in Fig. 2 opens to a passage 85 leading to the recess 88 at the end of the cylinder 29. The chamber 18 is normally vented to atmosphere only when the control valve is in its starting position by such means as an external longitudinal groove 88 in the valve. casing 58, opening through a port 81, into the chamber 18 and through a port 89 into the space 88 at the other end of the control valve.

5 The port 89 is disposed adjacent to the end of t the control valve to be closed thereby as it moves short distance from the end face of the plug 60.

Preferably the relationship is such that the control valve opens port SI just after it closes port 8!.

Manually manipulable means is provided for eiiecting initial opening of the throttle valve 41 and closing of the exhaust valve 49. This means in the present instance acts through the throttle valve piston 52 and may be a mechanical instrumentality of suitable character such as a lever or solenoid actuated plunger. It is preferred, however, to utilire pressure fluid as the motive power for opening the throttle valve and, to this end, .the plug 54 adjacent the piston 52 has an opening 82 therein to receive a coupling 93 for a conduit 94 connected with a suitable source of pressure fluid. Normally closed valve means, generally indicated at 95, having an operating lever 98 controls the admission of pressure fluid to the chamber ll behind the piston 52. Once the throttle valve has been opened by the inward movement of the piston 52, it is so held by pressure fluid from the cylinder 28 admitted to the chamber 5| through an open passage 91 (Fig. 2) between the chamber and the cylinder recess 30.

In discussing the operation of the present de-' vice, it will be considered that the parts are in their initial or starting positions as shown in Figs. 1 and 3 and that the'nipple l2 and conduit ll are connected with suitable sources of pressure fluid; To initiate operation of the device the user momentarily opens the valve 95 by manipulation of the lever 98 to admit pressure fluid to the chamber SI and cause piston 52 to open the throttle valve 41 and close exhaust valve 49. (This position of these parts is shown in Figs. 4 and 5). Pressure fluid thereupon flows to the ends of'the cylinders '21 and 28 behind the pistons 23' and 24 therein through internal bores 43, N, lateral passage 56, ports 51, 6|, groove 10, ports 81 and 20 to the recess at the end of cylinder 28 and thence through the bore 32 and the ports 31 in the piston rod 2! to the end of the cylinder 21. Pressure fluid thus admitted drives the pistons through their working stroke. At the same time, pressure fluid flows from the recess 30 through port 91 into the chamber it behind the piston 52 and exerts a holding force for maintaining the throttle valve open. This holding force is set up almost instantly after the throttle valve is; opened so that more than momentary manipulation of the valve 95 by the operator is unnecessary.

As the piston moves through its working stroke the end of the cylinder 28 in advance of its piston 24 is connected to exhaust to atmosphere through port 35. passage 14, port Bl, groove H, exhaust port 82 and openin 84. During the working stroke of the pistons the chamber H between the inner end of the auxiliary piston '80 and the control valve is subjected to the force of the pressure fluid in the cylinder 28 through the recess 3'. passage 88, port 8|, groove 82 and port ll. However, the force thus exerted in the chamber II will. during the working stroke, be insufficient to overcome the force exerted on the control valve by the spring 14.

As the pistons reach the end of their working stroke as determined by the-engagement of the rivet sets with the work and the exertion of a compression force thereon, the working pressure of the fluid behind the pistons will increase to a value such that the force exerted thereby in the chamber ll will overcome the force of the spring 14. Since the auxiliary piston 80 is seated against the plug '0 the control valve 69 will be shiftedaxially to its intermediate position (as shownin Fig. 4) where both of the annular grooves HI and H are out of communication with the inlet pressure fluid port ii and the exhaust passages 62, 64, and 63, 65. The initial movement of the control valve has, however, uncovered the port II to permit pressure fluid to flow from ports ll, ll through groove OI into the chamber II at the outer ends of the control valve and auxiliary piston whereby to continue the shifting movement of the control valve to its reversing position as shown in Fig.5. 1

As is best shown in Figs. 2 and 4, the pressure responsive area in the chamber 8i (represented by the base of the recess 1!) is substantially smaller than the comparable area of the chamber 18 (represented by the end face of the control valve It). Consequently the force exerted to overcome the spring force even at its maximum, will be less than the eilective force which will be exerted by the supply line pressure. The diflerential in the pressure responsive or piston areas therefore insures that the control valve will be shifted from itsintermediate to its reversing positions with a quick snap action or movement re gardless of such variables as fluctuations in supply line pressure, or the increase in the opposing force exerted by the spring as it is compressed or the adjustment of the device for heavy or light work.

Normally when live pressure is admitted to the chamber 18, the auxiliary piston 80 will move into the recess 19 to the position shown in Fig. 5. When it will do so depends on the iit of the parts and to some extent on the pressure in the chamber 8|. If pressure fluid cannot leak from the chamber ll because of an extremely close flt, the piston may not change its relationship to the control valve as shown in Fig. 4 as the control valve moves to its reversing position (Fig. 5). This will not affect the operation of the device. However,

it is undesirable and usually impossible to obtain or preserve such a fit inasmuch as pressure iiuid leaking from the chamber II to chamber "will assist in the movement of the control valve to its intermediate position, this added force being quite effective where the opposing force of the spring increases rapidly as it is compressed. Such leakage, together with'leakase to the exhaust port 64 also vents the chamber ll after its communication with the port It is cut oil.

It will be noted (see Fig. 4) that the control valve during its movement, into and past its intermediate position; closes the port from the cylinder end substantially as the port'vsl is opened to admit active pressure fluid to the chamber 18.

There is. therefore. no indirect connection back to the cylinder end 28 by which cylinder pressure might be maintained or the active pressure connected to exhaust depending on the position of the control valve,

In the reversing position of the control valve. the end of the cylinder 28 behind the piston is connected to exhaust, the fluid trapped therein through the ports 28 and 61. groove 10, exhaust port 63 and opening 65. Pressure fluid is admitted to the end of the cylinder ahead of thepiston spring 48 because the volume of the cylinder ends behind the pistons 23 and 24 i relatively large as compared to the restricted area of the exhaust passage therefrom which includes the ports 20,

61, O3 and E in series relation. The pressure drop in the exhaust end of the cylinder is therefore relatively slow during this period. Thereafter the return movement of the piston maintains'sufflcientpressure in the end oi the cylinder being exhausted to hold the piston 52 advanced. The throttle valve will therefore be held open until the pistons return to their starting positions at which time the flnal escape of pressure fluid from behind the piston 28, 24 with the resultant drop of pressure in chamber allows the throttle valve to be closed by the force of its springto complete one cycle.

Closing of the throttle valve and the concurren opening of the exhaust valve 4! permits the pressure fluid trapped in the device by closing of the throttle valve to escape around the exhaust valve 40 throughchamber 5i and to exhaust through a port, in the boss 8 (see Fig. 3). Hence, the pressure fluid in the chamber II at. the end of the control-valve and auxiliary piston ll will exhaust allowing the spring 14 to return the control valve to its initial starting position. The cycle, it will be noted, will not repeat even though the. user should fail to release the lever It after initiating operation since pressure fluid will pass to the chamber I8 alter the control valve has reversed connections until the throttle valve has closed to allow. the control valve spring 14 to function.

The return movement of the control valve opens the port 89 immediately after port Ql kclosed to permit oi complete exhaustion otthe chamber 18 through port ll, groove 86, port 84, space control valve in its starting position. The shift of the control valve to its reversing position is determined by the increase of pressure in the cylinders 21, 28 at or near the end 0! the pistons working stroke, whichincrease is determined directly by the opposing force imposed by the work. This increased pressure acts directly on the 00 trol valve itself, thus avoiding indirect control of the reversing movement thereof. Therefore,. the transition point between the working and return strokes of the pistons may be accurately predetermined by adjustment of the tension exerted on the control valve by the spring 14. Since the increase oipressure in the piston cylinders'is a function oi the opposing force or resistance imposed on the tool at any point along the length of'the working stroke, adjustment of the force of the spring 14 will be eilective to determine the maximum iorce exerted on the work. Having predetermined by adjustment the cylinder pressure at which reversalis to take place.

increase in supply line pressure will not alter the operation of the device. Hence small rivets may be properly set and without difllculty from line pressure variations.

a It will be evident from the foregoing that a novel control'mechanism for a tool of this character has been provided which automatically produces one single complete cycle of operation alter the operator has, by manipulation of the lever I, opened the throttle valve. It requires only a momentary act to start the cycle" after which the user may release the lever.

I claim as my invention:

1.,A pressure fluid actuated tool having, in

pressure fluid inlet, outlets communicating with said ports to the cylinder, and exhaust ports, a throttle valve and a control valve mounted in said housing in fluid pressure con'nnunication,

said valves being of the pressure fluid responsive piston type, spring means urging said throttle valve to closed position, manually controlled means for opening said throttle valve, spring means adjustable to urge said control valve toward one limit of movement with a prcdeter-' minable force opposed to the movement oi said. control-valve by pressure fluid, an. auxiliary pistom defining a chamber with said control valve,

- said control valve having es arranged at each or said limits to admit pressure fluid to a port for one end at said cylinder and connect the other port to exhaust, the pressure fluid bein admitted to drive the piston throughits working stroke when said control valve i in its spring urged limit position, said chamber being conneoted with the end of said cylinder under active pressure during the piston working stroke to shiit said control'valve initially when the pressure is sufllcient to overcome the opposing spring force,

the initial shift'moving said.valve to a position closing said passages,- a passage opened by said initial shift to subject said control valve and auxiliary piston to-pressure fluid to complete the said throttle valve is opened and closed for ex- *hausting the pressure fluid behind said throttle valve when closed.

2. A pressure fluid actuated tool having, in combination with a pressure fluid responsive driving piston, apiston cylinder having ports for admitting pressure fluid to the ends of said cylinder to move said piston through working and return strokes, a valve housing having a pressure fluid inlet, outlets communicating with said ports to the cylinder, and exhaust ports, a spring closed throttle valve in said housing, a control valve in said housing communicatingwith said throttle valve, said valves being or the pressure fluid responsive piston type, manuallycontrollcd means for opening said throttle valve, spring ward one limit or movement with a predeterminsble force primed to the movement of said control valve pressure one. an auxiliary piston deiining a chamber with said control valve, said control valve having passages arranged at each" or its limits to admit pressure fluid alternately to one or the other of said ports and to connect the opposite port to exhaust, the spring urged position said control valve establishing the connections i'or moving the piston through its working stroke, said chamber being connected with the cylinder end then under pressureto shirt said control valve initially when the cylinder pressure is suflicient to overcome the opposin: spring iorce, the initial shift being eil'ective to stop pressure fluid flow to said cylinder and to subject said control valve to pressure fluid to complete its movement against the spring force thereon to establish the alternate connections, and means for exhausting pressure fluid from behind said control valve when the return stroke of said piston is completed.

3. A pressure .fluid actuated tool having, in combination with a pressure fluid responsive driving piston, a piston cylinder having ports for admitting pressure fluid to the ends of said cylinder to move said piston through working and return strokes, a valve housing having a pressure fluid inlet, outlets communicating with said ports to the cylinder, and exhaust ports, a control valve mounted in said housing, spring means adjustable "to urge said control valve toward one limitoi movement with a predeterminable force, said control valve and housing torming a pressure fluid cylinder at one end 01' said control valve for effecting movement thereof as a piston against the force of said spring to an opposite limit, an auxiliary piston in said last mentioned cylinder movable in the same direction assaid control valve and providing an auxiliary chamber for pressure fluid therebetween, said control valve having passages arranged at each of said limits to admit pressure fluid alter- ,nately to one or'the other 01 said ports and to 9 l? the other of said ports to exhaust, said ,con'trol valve at its spring urged limit being arranged to eflect movement of said piston through its working stroke, passages for connecting said auxin, ary cylinder with the-end of s i D cylinder under active pressure fluid during said workingstroke to shift said control valve initially when the cylinder pressure increases sufllcientlyto overcome the opposing spring force on said control valve, the initial shiit positioning said control valve to close the pressure fluid passages and to open passages for admitting pressure fluid to the control valve cylinder to complete the movement or said control valve to its said opposite limit, valve means for controlling the flow of pressure fluid to said control valve, and means for closing said valve means and exhausting pressure fluid from said control valve cylinder at the end or one operative cycle.

41 A pressure fluid actuated tool having, in combination with a pressure fluid response driving piston, a piston cylinder, ports for admitting pressure fluid to the ends of said cylinder to move said piston through working and return strokes,

a valve housing having a pressure fluid inlet, outlets communicating with said ports to the cylinder, and exhaust ports, a control valve mounted a in said housing, spring means adjustable to urge said control valve toward one limit of movement with a-predeterminable iorce, said control valve asoaais r 9 I 'Iiosns adjustable tonrse said control valve toi 10 having passages arranged at each oi said limits to admit pressure .fluid alternately to one or the other or said ports and to connect the other or said ports to exhaust, said control valve at its spring urged limit beingarranged to eflect movement of said piston through its working strokes, means responsive to the pressure in the end 0! said piston cylinder under active pressure fluid during said working stroke for shifting said control valve initially when the pressure increase is suflicient to overcome the opposing spring force on said control valve, the initial shift positioning said control valve to close the pressure fluid passages and to open passages for subjecting the control valve to pressure fluid to complete the movement of said control valve to its said opposite limit, and valve means for controlling the now of pressure fluid to and exhaust from said control valve.

5. In a pressure fluid actuated tool having a cylinder and piston actuator, means for'controlling the flow of pressure fluid to, and exhaust from opposite ends of said cylinder having, in combination, a valve housing having a manually controllable inlet for pressure fluid, passages leading to opposite ends of the cylinder, and exhaust ports, a control valve in said housing, adjustable means for urging said control valve to an initial position, pressure fluid responsive means for shifting said control valve to a reversing position, said control valve having passages adapted in each position to connect one end of said cylinder with pressure fluid and the opposite end with an exhaust port, and means responsive to the pressure in the cylinder end to, which pressure fluid is admitted when said control valve is in its initial position for shifting said control valve to an intermediate position, said control valve in said intermediate position preventing pressure fluid flow to said cylinder and establishing a connection for pressure fluid to said responsive, means for shifting said control valve to its reversing position.

6. In a pressure fluid actuated tool having a cylinder and piston actuator and passages for conducting and exhausting pressure fluid to and from the opposite ends of said cylinder, the, combination of valve housing means having a pressure fluid inlet, a normally closed throttle valve in said housing means controlling the flow of pressure fluid, a control valve having spring means urging it to a; starting position, passages effective when said control valve is in said starting position for connecting one end of said cylinder with the pressure fluid inlet, means responsive to an increase of pressure in said one end of the cylinder for overcoming the force of said spring means to shift said control valve to areversing position, pressure fluid responsive means for holding said control valve in its reversing position, passages effective when said control valve is in said reversing position for connecting the opposite end of said cylinder with the pressure fluid is closed for releasing the holding pressure fluid on said control valve.

7. In a pressure fluid actuated tool having a cylinder and piston'actuator and passages for conducting and exhausting pressure fluid to and from, the opposite ends oi said cylinder, the comaeoasia bination of valve housing means having a Pressure fluid inlet, a throttle valve in said housin means controlling the flow of pressure fluid. a control valve having spring means urilnl it to a starting position, passages eiieotive when said controlvalve is in'said starting position for connecting one end or said cylinder with the pressure fluid inlet and the opposite end thereof with exhaust, means responsive to an increase of pressure in said one end of the cylinder for overcoming the force of said spring means to shift said control valve to a reversing position, passages effective when said control valve is in said reversing position for connecting the opposite end of said cylinder with the pressure fluid inlet and said one end with exhaust, the exhaust passages from said one end being restricted to maintain pressure in said one end, a pressure fluid cylinder in said housing means, a piston in said cylinder responsive to pressure fluid to hold said throttle valve open, and an open passage between said one end and said last mentioned cylinder.

8. In a pressure fluid actuated tool having a cylinder and piston actuator and passages for conducting and exhausting pressure fluid to and from the opposite ends of said cylinder, the combination of valve housing means having a pres-- sure fluid inlet, a throttle valve in said housing means controlling the flow of pressure fluid, a control valve in said housing means having spring means urging it to a starting position, passages eflective when said control valve is in said starting position for connecting one end of said cylinder with the pressure fluid inlet and the opposite end thereof with exhaust, means responsive to an increase of pressure in said one end of the cylinder for overcoming the force of said spring means to shift said control valve to a reversing position, passages efiective when said control valve is in said reversing position for connectin the opposite end 01' said cylinder with the pressure fluid inlet and said one end with exhaust, the exhaust passages from said one end being restricted to maintain pressure in said one end, and pressure fluid responsive means in open communication with said one end for holding said throttle valve open.

9. In a pressure fluid actuated tool having a cylinder and piston actuator and passages for conducting and exhausting pressure fluid to and from the opposite ends of said cylinder, the combination of a shiftable control valve having alternate positions for connecting one or the other of the ends of said cylinder with pressure fluid and the opposite end with exhaust to drive the piston through working and return strokes, a normally closed throttle valve controlling the flow of pressure fluid to said control valve, restricted exhaust passages from the end oi said cylinder exhausted during the return stroke of said piston effective to maintain pressure in said end, and means responsive to such maintained pressure for holding said throttle valve open.

10. In a pressure fluid actuated tool having a cylinder and piston actuator, means for controlling the flow of pressure fluid to and exhaust from opposite ends of said cylinder having, in combination, a reversingcontrol valve for directing pressure fluid flrst to one end and then to the opposite end of the cylinder, a throttle valve controlling the flow of pressure fluid to said control valve, means urging said throttle valve normally closed, a normally open exhaust valve for releasing pressure fluid from the control valve when the throttle valve is closed, said exhaust valve being movable with said throttle valve to close when said throttle valve opens. manually operable means for opening said throttle valve, and means responsive to the pressure in the end of the cylinder to which pressure fluid is first admitted for holding said throttle valve open.

11. In a pressure fluid actuated tool having a cylinder and piston actuator, means for controlling the flow oi pressure fluid to and exhaust from opposite ends of said cylinder having, in combination, a reversing control valve for directing pressure fluid first to one end and then to the opposite end of the cylinder, means urging said control valve to an initial position, a throttle valve controlling the flow of pressure fluid to said control valve, means urging said throttle valve normally closed, a normally open exhaust valve for releasing pressure fluid from the control valve when the throttle valve is closed and connected to move with said throttle valve to clme when said throttle valve opens, manually operable means for opening said throttle valve, and means responsive to the pressure in the end of the cylinder to which pressure fluid isflrst admitted for holding said throttle valve open and for moving said control valve out of its initial to its reversing position.

12. In a pressure fluid actuated tool having a cylinder and piston actuator, control means for conducting and exhausting pressure fluid alternately to and from the opposite ends of said cylinder, the combination of a valve for controlling the flow of pressure fluid to said control means, and means responsive to the pressure in one end of said cylinder when pressure fluid is admitted thereto and also responsive to the pressure of the fluid being exhausted therefrom for holding said valve open.

13. In a pressure fluid actuated tool having a cylinder and piston actuator, control means for conducting and exhausting pressure fluid alternately to and from the opposite ends of said cylinder and having a normal position in which pressure fluid is directed to one end of said cyiinder, the combination therewith of a valve controlling the flow of pressure fluid to said control means responsive to pressure in said one end of said cylinder for maintaining said valve open, and manipulable means for initially openingsaid valve momentarily at the start of the cycle to admit pressure fluid through the control means to said one end of said cylinder to actuate the pressure responsive means. i.

14. In a pressure fluid actuated tool having a cylinder and piston power source in which the piston is driven in opposite directions by pressure fluid admitted alternately to opposite ends 0! the cylinder, the combination therewith of control means for effecting the alternation of pressure fluid flow including a, reversing valve yieldably urged to one position, said valve being pressure fluid responsive for movement to its reversing position and having differential pressure areas, and means for subjecting each of said areas to pressure fluid, the smaller of said areas being subjected to the lower pressure.

15. In a pressure fluid actuated tool having a cylinder and piston power source in which the piston is driven in opposite directions by pressure fluid admitted alternately to opposite ends of the cylinder, the combination therewith of control means for effecting the alternation of pressure fluid flow including a reversing valve yieldably urged to one position, said valve being pressure fluid responsive for movement to its re,-

of the cylinder, the combination therewith of control means for effectingv the alternation of pressure fluid flow including a reversing valve yieldably urged to one position and being pressure fluid responsive for movement to its reversing position, means for initially subjecting said valve to apressuresufflcient to move said valve against the force which yieldably urges it to said one position, and means for thereafter subjecting said valve to a higher pressure.

17. In a pressure fluid actuated tool, in combination, a cylinder and piston actuator, control means for effecting operation of said actuator in cycles each including forward and return strokes of said piston, said means including a control valve operable to direct pressure fluid alternately v to opposite ends of said cylinder to effect such forward and return strokes of said piston, a throttle valve controlling the supply of pressure fluid to said control valve, means yieldably urging said throttle valve to a closed position, manually controlled means for shifting said throttle valve to an open position to initiate the forward movement of said piston, means operable in response to the completion of the forward stroke of said Piston for shifting said control valve into a position to initiate the return stroke of said piston, 1 means operative to hold said throttle valve in said open position independently of said manually controlled means, said throttle valve normally returning to the closed position under the influence of said yieldable means upon the completion of the return stroke of said piston, and means operative to hold said control valve in its shifted positionand thereby prevent the initiation i ofanother operating cycle until said throttle valve has been closed.

'18. In a pressure fluid actuated tool, in combination, a cylinder and piston actuator, control means for eil'ecting operation of said actuator in cycles. each including forward and return strokes of said piston, said means including a control valve operable to direct pressurefluid alternately to opposite ends of said cylinder to eifect such forward and return strokes of said piston, a throttle valve controlling the supply of pressure fluid throttle valve to a closed position, manually conto said control valve, means yieldably urging said T" 14 trolled means for shifting said throttle valve to an open position to initiate the forward movement of said piston, and means providing a connection between said actuator and said throttle valve operative to hold said throttle valve in said open position independentl of said manually controlled means until said piston has completed its forward and return strokes, said throttle valve being released for return to closed position as an incident to the completion of the return strok of said piston.

19. In a pressure fluid actuated tool, in combination, a cylinder and piston actuator, cycling mechanism including, a control valve operable to direct Pressure fluid alternatel to opposite ends of said cylinder to eilect forward and return strokes of said piston, a throttle valve controlling the supply of ipressure fluid to said control valve, means yieldably urging said throttle valve to a closed-position, manually controlled means for shiftin said throttle valve to an open position to initiate the forward movement of said piston, and means including a pressure fluid connection from said cylinder efiectivfeto hold said throttle valve in said open position independently oi' said manually controlled means through a single cycle of said actuator comprising forward and return strokes of said piston.

20. In a pressure fluid actuated tool, in combination, a cylinder and piston actuator, a control valve including a shiftable valve plunger yieldably urged to a position to direct pressure fluid into one end of said cylinder, said valve plunger being shifted automatically to interrupt the flow of pressure fluid to said cylinder upon a predetermined increase in the pressure of the fluid in said cylinder, an auxiliary plunger operable to further shift said valve plunger to a position for directing pressure fluid to the other end oi said cylinder. and fluid passages controlled b said valve plunger for controlling the operation of said auxiliary plunger.

21. In a, pressure fluid actuated tool, in combination, a cylinder and piston actuator, a control valve including a shiftable valve plunger yieldably urged to a position to direct pressure

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