US3855902A

US3855902A - Cylinder piston unit for a power operated revolving chuck

Info

Publication number: US3855902A
Application number: US00337126A
Authority: US
Inventors: R Kirst
Original assignee: Hofmann & Co KG W
Current assignee: Hofmann & Co Kg dt; Hofmann & Co KG W
Priority date: 1972-11-21
Filing date: 1973-03-01
Publication date: 1974-12-24
Anticipated expiration: 1991-12-24
Also published as: FR2207248B3; DE2256933A1; DE2256933C3; FR2207248A1; DE2256933B2; IT980833B

Abstract

A pressurized fluid actuated cylinder piston unit for power operated lathe chucks and the like in which safety means are provided to prevent pressure drop in the pressurized cylinder chamber in case of a pressure source failure, each cylinder chamber being provided with a check valve as safety device, the valves being resilient rings surrounding the piston rod bilaterally of the piston and covering radial bores in communication with the pressure source, the ring in the chamber to be vented being mechanically expanded by a pressure responsive member.

Description

United States Patent [191 Kirst [11] 3,855,902 Dec. '24, 1974 CYLINDER PISTON UNIT FOR A POWER OPERATED REVOLVING CHUCK Inventor: Rudi Kirst, I-iilden, Germany Hofmann & Co. KG, Haan, Germany Filed; Mar. 1, 1973.

Appl. No.: 337,126

Assignee:

[30] Foreign Application Priority Data Nov. 21, 1972 .Germany..... 2256933 US. Cl 91/420, 92/106, 251/DIG. 1, 279/4 Int; Cl. FlSb 1 1/08, F15b 13/04 Field of Search 91/420; 279/41, 4; 92/106; 251/DIG. 1

References Cited UNITED STATES PATENTS 2/1964 Leduc 91/422 X 4/1964" Hohwart 92/l06 X 8/1971 9 Benjamin et al 9l/420 8/1971 Rohm ..9l/420 Primary Examiner-Irwin C. Cohen Assistant Examiner-Abraham Hershkovitz Attorney, Agent, or FirmH. Dale Palmatier ABSTRACT A pressurized fluid actuated cylinder piston unit for power operated lathe chucks'and the lilgein which safety means are provided to prevent pressure drop in the pressurized ,cyIinder chamber in case of apressure source failure, each cylinder chamber being provided with a check valve as safety device, the valves being resilient rings surrounding the piston rod bilaterally of the piston and covering radial bores in communication with the pressure source, the ring in the chamber to be vented being mechanically expanded by'a pressure responsive member. v

7 Claims, 2 Drawing Figures 18.1b I? 32 u T 1 ml \\W 1 I 1- 26 8 48 I5 CYLINDER PISTON UNIT FOR A POWER OPERATED REVOLVING CHUCK BACKGROUND OF THE INVENTION The invention relates to a pressurized fluid actuated rotating cylinder piston unit for power operated chucks, in particular, for lathes, milling machines, grinding machines and the like in which the tool or the blank is held in a jaw chuck.

For safety reasons, check valves are provided to prevent-pressure drop in the actually pressurized cylinder chamber in case of the pressure supply being shut down unintentionally, due to a pressure tube defect or another leakage. When reversing the pressure under normal operating condition, however, the respective chamber is to be vented, i.e., the respective check valve must be disabled, or rendered out of function.

German published patent specification German Offenlegungsschrift, published Oct. 7, 1971, No. 2 011 996 shows certain aspects of such a unit.

German Patent Specification 1 006 236 granted Oct. 10, 1957 discloses a cylinder piston unit for similar purposes and is likewise provided with a radially movable actuating piston. In this known design, the check valves are of the plug type with an extension engaged by the piston. The non-symmetrical disposition of the piston is a serious drawback because it may, under the effect of centrifugal forces, unintentionally render the safety device out of service. A further drawback is the complex shape of the valves. V

Similarly, the radially movable flap valves actuated by a radially movable auxiliary pistonas provided in the unit disclosed in German published patent specification German Offenlegungsschrift 1,918,428 is extremely expensive to manufacture.

German utility model DT-GM 1 985 828 registered May 22, 1968 discloses a cylinder unit in which one of the valves is a disc valve while the other is a flap valve. ln this design which is apparently quite expensive, an individual actuating piston is provided for each valve. This unit, nevertheless, has the technical advantage that all moving parts are disposed symmetrically with respect to the unit-axis; however, it is not possible to provide a hollow machine spindle extending through the unit and serving as blank supply channel for the check, as is often desired for lathes.

SUMMARY OF THE INVENTION lt is the object of the invention to provide a pressurized fluid actuated cylinder piston unit for power operated chucks and the like in which the advantages of the known units are maintained while their drawbacks are avoided. In other words, the check valves should have the form of simple O-rings, flat rings, quad rings or the like because these require but a minimum of space within the cylinder. Likewise, the actuating means are to be simple, small, and should be insensitive against centrifugal forces. Finally, the unit should permit hollow spindles to extend therethrough.

- According to the invention, there is provided a cylinder piston unit in which the fluid (preferably pressurized air) is supplied to the cylinder chambers bilaterally of the piston via channels extending axially through the piston rod and communicating each with one of the chambers via series of bores extending radially through the piston rod, each series being disposed at one side of the piston. The bores open into a circumferential groove in which an O-ring or other radially resilient ring is disposed. In case of the pressure within the channel drops unintentionally, the ring closes the bores and prevents rapid pressure drop within the respective cylinder. In case of the pressure being intentionally decreased or switched off, the other channel will be subjected to pressure. This permits provision of an actuating member to lift or radially expand the ring in response to pressure increase in the other chamber. Preferably, the actuating means comprises plungers slidingly received within some, but not all of the bores and pushed outwardly by a slider or auxiliary piston moved under the pressure which is supplied to the opposite chamber.

DESCRIPTION OF THE PREFERRED EMBODIMENT The accompanying drawings show in FIG. 1, an axial section view of a cylinderpiston unit according to the invention; and

FIG. 2 is a detail section, partly broken away, and taken at line 22 in FIG. 1.

The drawings show a pneumatic cylinder unit but it will be understood that the invention will be likewise applicable to hydraulic cylinders.

In a cylinder 10, a piston rod 18 carrying a piston 20 is axially movable and sealed against the cylinder by sealing

rings

12, 14 and 16. The piston 20 separates the

cylinder chambers

22 and 24. I e

The piston rod 18 has an elongate hollow interior 18.1, and a central sleeve or tube 26 extends from the rod end remote from the cylinder (lefthand in FIG. 1)

to a point adjacent the front 28 of the cylinder. It will be apparent to those skilled in the art that the cylinder front 28 will be connected to a chuck body while the piston rod extending therethroug h will be connected to the jaw actuating member mounted in said body; the chuck body andits associated parts, however, are not shown in the drawing because they do. not form part of the invention nor do the connection means, provided at the cylinder front 28 and the piston rod and not shown either for the same reason. v p

The interior or duct 29 of sleeve or tube 26 communicates, via axial bore '30 of the piston rod anda radial aperture 32 thereof with a first supply opening 34 of a supply sleeve 36 and also communicates with one end 18.1a of the hollow interior 18.1 of the rod. Opening 34, aperture 32, bore 30 and the interior 29 of sleeve 26 define a first fluid medium channel.

A second channel leads from a second supply opening 38 of supply sleeve 36 to asecond radial aperture 40 of piston rod 18 to the annular duct or passage 42 remaining between the outer circumference of sleeve 26 and inner wall of bore 30, and then to the other end 18.1b of the hollow interior 18.1 of the piston rod.

It will be apparent to those skilled in the art that supply sleeve 36 will be fixed while the assembly consisting in the piston rod with piston and cylinder may revolve relative thereto. Therefore, in the interior of supply sleeve 36 circumferential grooves are provided into which the

apertures

32 and 40 open, the grooves assuring permanent communication between the supply openings and the aligned apertures. It is a matter of it will be understood that

openings

34 and 38 are each connected to one output of a fluid main valve (not shown) by which either opening 34 or 38 is connected to a source of pressurized air while simultaneously the other opening is vented to the atmosphere. In case of a hydraulic cylinder, the other opening would be connected to a fluid tank.

Returning again to the drawings, an auxiliary piston or actuating slider 44 is slidably received between sleeve 26 and bore 30 about at the axial position of the piston 20. The slider is sealed at its interior and its exterior and has the shape of a double cone with a central cylindrical portion.

On both sides of piston 20 circumferential grooves 45 are machined in piston rod 18, and from the bottom of the grooves, bores 46 extend radially inwardly and open into axial bore 30 (see FIG. 2, too). An O-ring 48 is disposed in each of the circumferential grooves. In the embodiment shown, nine radial bores 46 are provided for each grooves and the nine bores consist of three groups of three bores each, the groups being equally angularly spaced. In the central bore of each group, a plunger 50 is slidably received, the outer end of each plunger abutting the inwardly facing side of the O-ring while the inner plunger and engages the conical surface of slider 44. It will be seen that each of the resiltion, such as to the right in FIG. 1, one set of the plungers 50 is urged radially outwardly as depicted in FIG.

2 so as to urge the resilient O-ring 48 out of the groove 45 and' allow the corresponding chamber 24 to be vented; and simultaneously, the left hand group of plungers 50 are allowed to move inwardly by the left hand conical camming surface of the slider 44 and the plungers 50 are urged radially inwardly and maintained in engagement with the slider 44 by the resilient O-ring 48 so as to allow the O-ring to seat into the groove 45 in a valving action, thereby permitting substantial fluid pressure to be confined in the chamber 22.

In order to explain the operation of the device, it may now be assumed that chamber 24 is under pressure while chamber 22 is vented and that the pressure supply be reversed. Thus, supply opening 34 will be vented and opening 38 connected to the source of pressurized air. Due to the pressure in channel 29, as compared to the pressure in chamber 24 the sealing ring 48 for chamber 24 is urged into the circumferential groove and prevents, at first, venting of cylinder chamber 24 as it is expected to do. Simultaneously, pressurized air will flow in passage 42 and into chamber 22 lifting its O-ring 48 out of groove 45, and due to the pressure differential across slider 44 the latter will move in a direction toward chamber 24 and to the right in FIG. 1 substantially to the position illustrated so that its conical surface urges the right hand plungers 50 outwardly toward chamber 24 for lifting sealing ring 48 in a camlike action. This instant is shown in FIG. 1, and FIG. 2 shows the deformation of the O-ring under the action of the plungers 50. It will be seen that the empty bores 46 adjacent each plunger are opened between passage 29 and chamber 24. Thus, the check valve formed by the O-ring asthe valve member and groove 45 plus empty bores 46 asthe valve seal has been actuated to vent the respective cylinder chamber 24.

Because of the changed pressure conditions in the

chambers

22 and 24, there is relative movement between the cylinder and piston rod 18 effectively en-' larging chamber 22 and diminishing chamber 24 to produce desired movement between the chuck body and the jaw actuating member of .the power operated chuck. While pressure is maintained in chamber 22,

and chamber 24' is vented, the pressure connections at ducts 34 and 38' may be reversed again so as to pressurize the duct 34 and vent the duct 38. Application of pressure at duct 34 causes pressure to be applied in the passage 29 and through the bores 46 and against the inside of the O-ring 48 which is disposed in the chamber .24, with the effect that the pressurized air urges the O- ring 48 outwardly to allow the air under pressure to be applied into chamber 24. Simultaneously, the pressurized air from passage 29 is applied against the righthand end of slider 44, tending to move the slider to the left.

' Because duct 38 has been vented, passage 42 is also vented and the air in passage 42 provides no resistance to the leftward movement of slider 44, and, accordingly, the slider 44 moves to the left until the slider is again stopped by the plungers 50. As theslider moves to the left, the plungers 50, associated with the O-ring 48 of chamber 24, are urged radially inwardly toward tube 26 so as to release the corresponding O-ring 48 and allow it to seat in the groove 45 of chamber 24 whenever a sufficient buildup of pressure in the chamber 24 stops the flowof air into this chamber. Because ofthe leftward movement of slider 44, the plungers 50 associated withchamber 22 and the corresponding 0- ring 48 are urged radially outwardly by theconical the power chuck and specifically the jaw actuating member thereof.

When this condition has occurred,.then the pressure conditions at

ducts

34 and 38 may be reversed again to produce the operation hereinbefore described when the duct 34 is ventedand the duct- 38 is pressurized.

' It will be appreciated that the venting of either

cylinder chamber

22 or 24 will be possible only in case no leakage has occurred in the pressurized air supply conduits, because pressure in the respective other channel will be required to actuate the slider 44. If a pressure drop occurs due to a leakage, slider 44 will not be moved and the sealing ring 48 subjected to the pressure in the respective chamber will prevent venting thereof. Thus, even in case of a sudden pressure drop there will be no risk that the chuck jaws release the tool or blank during the operation of the machine.

In lieu of plungers 50, spheres or similar bodies may deformable resilient rings such as flat rings, quad rings or sealing rings of other section shape. An expert skilled in the art'will readily be capable of redesigning the axial support of the rings in accordance with the section shape concerned.

The sliding motion of slider 44 is limited by a shoulder 52 bilaterally provided of the cylindrical central portion of the slider, the shoulders serving as a stop means upon engagement at the plungers. Other stop means, of course, may be provided, and this will be compulsory if the plungers are replaced by spheres.

It will be appreciated that the centrifugal force acting upon the sealing rings will be negligible, and this will normally be assumed for the plungers, too. In case of extremely high speed of the chuck driven by the cylinder unit, the plungers may be replaced by link systems in which thecentrifugal force is counterbalanced; such systems are known to experts skilled in the art.

It will be appreciated that a hollow spindle may readily be disposed within the sleeve 26 extending through the entire length of the cylinder unit, and this is a very desirable feature as mentioned above. In such a design, the walls and diametersof the piston rod would have to be adapted.

Whatl claim is:

l. A revolving pressurized fluid actuated operator for a chuck and for use with fluid supply connections which are alternately pressurized and vented, comprising: v

a cylinder to confine a pressurized fluid,

a piston in the cylinder and dividing the cylinder into a pair of fluid chambers, and the piston having a rod movable with the piston and relative to the cylinder to operate the chuck, the piston rod having an elongate hollow interior with opposite ends adjacent the opposite sides of the piston,

. fluid supply means attachable to such alternately pressurized and vented fluid connections and includingradial bores in the piston rod at opposite sides of the piston to direct pressurized fluid to the chambers and to vent the chamberslalternately for controlling the piston movement in the cylinder and includingcheck valves'for each cylinder chamher to be opened and closed responsive to pressure reversal in the fluid supply means, said check valves comprising a pair of valve elements respectively disposed at opposite sides of the piston and on the piston rod and in obstructing relation with said radial bores to prevent release of fluid pressure in the chambers, said fluid supply means including duct means in the hollow piston rod defining and separating fluid channels from each other, said channels respectively communicating with opposite ends of the hollow interior of the piston rod to alternately vent and pressurize the ends of the hollow interior andbores,

operating means responsive to pressure reversal at such fluid supply connections to selectively lift the valve elements out of obstructing relation with the bores to alternately vent the chambers and including radially movable actuating members in the bores at both sides of the piston and acting on the valve elements to lift the valve elements out of obstructing relation and said actuating members also protruding into the hollow interior of, the piston rod, and an auxiliary fluid pressure-operated piston slidable in the hollow interior of the piston rod and sealably isolating said opposite ends of the hollow interior from each other, said auxiliary piston being exposed to different fluid pressures at opposite ends of the hollow interior of the piston rod and being moved endwise in the piston rod by the fluid pressure differentials, and said auxiliary piston being provided with cam faces engaging said actuating members for radially moving the actuating members in the bores. '2, A pressurized air actuated cylinder piston unit, comprising in combination: a hollow cylinder having a cylinder head at each end, a piston movable relative to I said cylinder and mounted on a piston rod extending through both cylinder heads, means'sealing said piston and piston rod against said cylinder, said piston rod having a-first and a second axially extending channel,

a sleeve being sealingly mounted about the piston rod v V end remote from said cylinder and provided withfirst and second axially spaced radial openings to be alternatively connected to a pressurized air source, each opening communicating with an internal circumferential groove within said sleeve, the first opening being via the respective groove and a radial aperture in the piston rod in communication with the first axially extending channel thereof and the second opening being via its groove and a radial aperture in the'piston rod in communication with the second axially extending channel thereof, saidsleeve and the assembly consisting of piston rod, piston, and cylinder being rotatable with respect to each other, a first set of radial passages extending from the first of said piston rod channels into a first cylinder chamber confined by the cyl'inder, the

piston, and the piston rod, asecond set of radial passages extending from said second-piston rod channel into a second chamber confined by the cylinder, piston, and piston rod separated from the first chamber by the piston, radially resilient ring means surrounding the pis-- ton rod at the positionof said first and second sets of radial passages closing the respective passages to prevent pressure drop within the respective chamber, and actuating means to radially expand the ring means and to render communicating the respective chamber and channel in response to pressure increase in the respective other channel, said actuating means including radially movable plungers in said radial passages to lift the resilient ring means out of obstructing relation with the passages to release pressure in said cylinder chambers, said actuating means also including a slidable operator movable along the piston rod and having oblique cam surfaces engaging the plungers in said first and second set of radial passages for alternately opening said first and second passages as the operator is moved endwise of the piston rod, and means slidably mounting said operator within the piston rod between said first and second axially extending channels to facilitate movement of the operator under influence of the pressure reversal in said first and second axially extending channels to release the pressure in said'chambers as the fluid pressure is reversed at the radial openings of the sleeve,

3. A revolving pressurized fluid actuated operator for a chuck, comprising:

a cylinder to confine pressurized fluid, a piston in the cylinder and dividing the cylinder into to the cyla pair of fluid chambers, and the piston having a fluid supply means includingradial bores in the-piston rod to direct pressurized fluid to the chambers and to vent the chambers alternately for controlling the piston movement in the cylinder and including check valves for each cylinder chamber to be opened and closed responsive to pressure reversal in the fluid supply means, said check valves comprising a pair of deformable rings respectively disposed at opposite sides of the piston and on the piston rod and in obstructing relation with said radial bores, said fluid supply means including a sleeve in the hollow piston rod and defining and separating fluid channels from each other, an actuation member movably mounted in one of said bores to lift the check valve ring and provide venting of the respective cylinder chamber, and an auxiliary piston being slidably mounted on said sleeve and being provided with cam faces engaging said actuating member for radially moving the actuating member in the bore. 1 4. A fluid actuatedoperator as claimed in claim 3 wherein a plurality of said actuation members are movably mounted in bores at both sides of the piston to lift the deformable check valve rings for venting alternate chambers, and said auxiliary piston having tapered ends engaging said actuation members and alternately urge said actuation members outwardly.

5. An operator as claimed in claim 4 wherein said actuation members are plungers guided within said bores.

6. A revolving pressurized fluid actuated operator for a chuck, comprising:

adjacent the piston defining'a combined fluid passage and guideway, said piston rod also having a plurality of radial bores extending between said hollow interior and the exterior of the piston rod, said bores being disposed in at least two locations along the length of the piston rod adjacent each of said chambers so that certain of said bores provide communication between the hollow interior and one of the chambers, and the remaining bores provide communication between the hollow interior and the other of the chambers; releasable valve means at the exterior of said piston rod and obstructing said radial bores, and including a plurality of plungers extending inwardly through said bores and protruding into said hollow interior, said valve means being biased into boreobstructing position and being operable in response to outward movement of said plungers'to open the'valve means and release pressure from the chamber;

a fluid pressure operated slider in said hollow interior of the piston rod which defines the slideway for the slider, said slider traversing the hollow interior and sealing around the interior periphery of the slideway to obstruct fluid communication longitudinally along the hollow interior of the piston rod, said slider having oblique camming surfaces bearing outwardly against said plungers to restrain inward movement of-the plungers and produce radial outsaid piston rod having a pair of separate fluid passages each communicating with a respective end of the hollow interior of said piston rod to facilitate control of the fluid pressure applied to said bores and to the corresponding sides of the slider for simultaneously pressurizing one of the cylinder chambers and venting the other chamber as the fluid pressure moves the slider to operate the plungers and valve means. 4

7. A revolving pressurized fluid actuated operator for a chuck, comprising:

a cylinder to confine a pressurized fluid; 1

a piston in the cylinder and dividing the cylinder into a pair of fluid chambers, and the piston having a piston rod movable with the piston and relative to the cylinder to operate the chuck, the piston rod having a hollow interior adjacent the piston defining a combined fluid'passage and guideway, said piston rod also having a plurality of radial bores extending between said hollow interior and the exterior of the piston rod, said bores being disposed in at least two locations along the length of the piston rod adjacent each of said'chambers so that certain of said bores provide communication between the hollow interior and one of .the chambers, and the remaining bores provide communication between the hollow interior and the other of the chambers; 1

releasable valve means at the exterior of said piston rod and obstructing said radial bores, and including a plurality-0f plungers extending inwardly through said bores and protruding into said hollow interior, said valve means being biased into boreobstructing position and being operable in response to outward movement of said plungers to open the valve means and release pressure from the chamber;

a plunger-operating slider in said hollow interior of the piston rod which: defines the slideway for the slider, said slider traversing the hollow interior and sealing around the interior periphery of the slideway to obstruct fluid communication longitudinally along the hollow interior of the piston rod, said slider having oblique camming surfaces bearing outwardly against said plungers to restrain inward movement of the plungers and produce radial outward movement of the plungers as the slider moves longitudinally along the piston rod for operating said valve means; and

said piston rod having a pair of separate fluid passages each communicating with a respective end of the hollow interior of said piston rod to facilitate control of the fluid pressure applied to said bores and to the corresponding sides of the slider for simultaneously pressurizing one of the cylinder chambers and venting the other chamber as the slider operates the plungers and valve means, wherein said piston rod includes a stationary tube extending longitudinally through said hollow inte rior andbeing connected to one of said fluid passages, and said slider being annular and having an interior periphery mounted upon and sliding along the exterior of said tube.

Claims

1. A revolving pressurized fluid actuated operator for a chuck and for use with fluid supply connections which are alternately pressurized and vented, comprising: a cylinder to confine a pressurized fluid, a piston in the cylinder and dividing the cylinder into a pair of fluid chambers, and the piston having a rod movable with the piston and relative to the cylinder to operate the chuck, the piston rod having an elongate hollow interior with opposite ends adjacent the opposite sides of the piston, fluid supply means attachable to such alternately pressurized and vented fluid connections and including radial bores in the piston rod at opposite sides of the piston to direct pressurized fluid to the chambers and to vent the chambers alternately for controlling the piston movement in the cylinder and including check valves for each cylinder chamber to be opened and closed responsive to pressure reversal in the fluid supply means, said check valves comprising a pair of valve elements respectively disposed at opposite sides of the piston and on the piston rod and in obstructing relation with said radial bores to prevent release of fluid pressure in the chambers, said fluid supply means including duct means in the hollow piston rod defining and separating fluid channels from each other, said channels respectively communicating with opposite ends of the hollow interior of the piston rod to alternately vent and pressurize the ends of the hollow interior and bores, operating means responsive to pressure reversal at such fluid supply connections to selectively lift the valve elements out of obstructing relation with the bores to alternately vent the chambers and including radially movable actuating members in the bores at both sides of the piston and acting on the valve elements to lift the valve elements out of obstructing relation and said actuating members also protruding into the hollow interior of the piston rod, and an auxiliary fluid pressureoperated piston slidable in the hollow interior of the piston rod and sealably isolating said opposite ends of the hollow interior from each other, said auxiliary piston being exposed to different fluid pressures at opposite ends of the hollow interior of the piston rod and being moved endwise in the piston rod by the fluid pressure differentials, and said auxiliary piston being provided with cam faces engaging said actuating members for radially moving the actuating members in the bores.

1. A revolving pressurized fluid actuated operator for a chuck and for use with fluid supply connections which are alternately pressurized and vented, comprising: a cylinder to confine a pressurized fluid, a piston in the cylinder and dividing the cylinder into a pair of fluid chambers, and the piston having a rod movable with the piston and relative to the cylinder to operate the chuck, the piston rod having an elongate hollow interior with opposite ends adjacent the opposite sides of the piston, fluid supply means attachable to such alternately pressurized and vented fluid connections and including radial bores in the piston rod at opposite sides of the piston to direct pressurized fluid to the chambers and to vent the chambers alternately for controlling the piston movement in the cylinder and including check valves for each cylinder chamber to be opened and closed responsive to pressure reversal in the fluid supply means, said check valves comprising a pair of valve elements respectively disposed at opposite sides of the piston and on the piston rod and in obstructing relation with said radial bores to prevent release of fluid pressure in the chambers, said fluid supply means including duct means in the hollow piston rod defining and separating fluid channels from each other, said channels respectively communicating with opposite ends of the hollow interior of the piston rod to alternately vent and pressurize the ends of the hollow interior and bores, operating means responsive to pressure reversal at such fluid supply connections to selectively lift the valve elements out of obstructing relation with the bores to alternately vent the chambers and including radially movable actuating members in the bores at both sides of the piston and acting on the valve elements to lift the valve elements out of obstructing relation and said actuating members also protruding into the hollow interior of the piston rod, and an auxiliary fluid pressure-operated piston slidable in the hollow interior of the piston rod and sealably isolating said opposite ends of the hollow interior from each other, said auxiliary piston being exposed to different fluid pressures at opposite ends of the hollow interior of the piston rod and being moved endwise in the piston rod by the fluid pressure differentials, and said auxiliary piston being provided with cam faces engaging said actuating members for radially moving the actuating members in the bores.

2. A pressurized air actuated cylinder piston unit, comprising in combination: a hollow cylinder having a cylinder head at each end, a piston movable relative to said cylinder and mounted on a piston rod extending through both cylinder heads, means sealing said piston and piston rod against said cylinder, said piston rod having a first and a second axially extending channel, a sleeve being sealingly mounted about the piston rod end remote from said cylinder and provided with first and second axially spaced radial openings to be alternatively connected to a pressurized air source, each opening communicating with an internal circumferential groove within said sleeve, the first opening being via the respective groove and a radial aperture in the piston rod in communication with the first axially extending channel thereof and the second opening being via its groove and a radial aperture in the piston rod in communication with the second axially extending channel thereof, said sleeve and the assembly consisting of piston rod, piston, and cylinder being rotatable with respect to each other, a first set of radial passages extending from the first of said piston rod channels into a first cylinder chamber confined by the cylinder, the piston, and the piston rod, a second set of radial passages extending from said second piston rod channel into a second chamber confined by the cylinder, piston, and piston rod separated from the first chamber by the piston, radially resilient ring means surrounding the piston rod at the position of said first and second sets of radial passages closing the respective passages to prevent pressure drop within the respective chamber, and actuating means to radially expand the ring means and to render communicating the respective chamber and channel in response to pressure increase in the respective other channel, said actuating means including radially movable plungers in said radial passages to lift the resilient ring means out of obstructing relation with the passages to release pressure in said cylinder chambers, said actuating means also including a slidable operator movable along the piston rod and having oblique cam surfaces engaging the plungers in said first and second set of radial passages for alternately opening said first and second passages as the operator is moved endwise of the piston rod, and means slidably mounting said operator within the piston rod between said first and second axially extending channels to facilitate movement of the operator under influence of the pressure reversal in said first and second axially extending channels to release the pressure in said chambers as the fluid pressure is reversed at the radial openings of the sleeve.

4. A fluid actuated operator as claimed in claim 3 wherein a plurality of said actuation members are movably mounted in bores at both sides of the piston to lift the deformable check valve rings for venting alternate chambers, and said auxiliary piston having tapered ends engaging said actuation members and alternately urge said actuation members outwardly.

7. A revolving pressurized fluid actuated operator for a chuck, comprising: a cylinder to confine a pressurized fluid; a piston in the cylinder and dividing the cylinder into a pair of fluid chambers, and the piston having a piston rod movable with the piston and relative to the cylinder to operate the chuck, the piston rod having a hollow interior adjacent the piston defining a combined fluid passage and guideway, said piston rod also having a plurality of radial bores extending between said hollow interior and the exterior of the piston rod, said bores being disposed in at least two locations along the length of the piston rod adjacent each of said chambers so that certain of said bores provide communication between the hollow interior and one of the chambers, and the remaining bores provide communication between the hollow interior and the other of the chambers; releasable valve means at the exterior of said piston rod and obstructing said radial bores, and including a plurality of plungers extending inwardly through said bores and protruding into said hollow interior, said valve means being biased into bore-obstructing position and being operable in response to outward movement of said plungers to open the valve means and release pressure from the chamber; a plunger-operating slider in said hollow interior of the piston rod which defines the slideway for the slider, said slider traversing the hollow interior and sealing around the interior periphery of the slideway to obstruct fluid communication longitudinally along the hollow interior of the piston rod, said slider having oblique camming surfaces bearing outwardly against said plungers to restrain inward movement of the plungers and produce radial outward movement of the plungers as the slider moves longitudinally along the piston rod for operating said valve means; and said piston rod having a pair of separate fluid passages each communicating with a respective end of the hollow interior of said piston rod to facilitate control of the fluid pressure applied to said bores and to the corresponding sides of the slider for simultaneously pressurizing one of the cylinder chambers and venting the other chamber as the slider operates the plungers and valve means, wherein said piston rod includes a stationary tube extending longitudinally thRough said hollow interior and being connected to one of said fluid passages, and said slider being annular and having an interior periphery mounted upon and sliding along the exterior of said tube.