US3149541A

US3149541A - Hydraulically controlled air leg structure

Info

Publication number: US3149541A
Application number: US295298A
Authority: US
Inventors: James F Hutter; Kelly Leonard
Original assignee: K and H Equipment Ltd
Current assignee: K and H Equipment Ltd
Priority date: 1963-07-12
Filing date: 1963-07-12
Publication date: 1964-09-22
Anticipated expiration: 1981-09-22

Description

Sept. 22, 1964 J, HLN-TER ETAL 3,149,541

` HYDRAULICALLY CONTROLLED AIR LEG STRUCTURE y I 5 Sheets-Sheet 1 Filed July 12, 1963 ATTORNEY sept. 22, 1964 3,149,541

HYDRAULCALLY CONTROLLED AIR LEG STRUCTURE J. F. HUTTER ET AL 5 Sheets-Sheet 2 Filed July l2, 1965 PATENT AGENT Spt. 22, 1964 J. F. HUTTER ET AL 3,149,541

HYDRAULICALLY CONTROLLED AIR LEG STRUCTURE Filed July l2, 1965 5l Sheets-Sheet I5 QN com. Nm@ mmm J www www uw (uw .N QN mmm o mm.

NNN @N mb N .llink PATENT AGENT Sept 22, 1964 J. F` HUTTl-:R ET AL HYDRAULICALLY CONTROLLED AIR LEG STRUCTURE 5 Sheets-Sheena?I 4 Filed July l2, 1963 Num@ PATENT AGENT J. F. HUTTER ET A L v3,149,541

5 Sl'xeetsf-S'heetv 5 T TOR BATNT AGENT Sept. 22, 1964 HYDRAULICALLY 'CONTROLLED AIR LEG STRUCTURE Filed July 12, 1963' United States Patent() 3,149,541 HYDRAUMCALLY CUNTROLLED All( LEG STRUCTURE Karnes F. Hutter and Leonard Kelly, Bancroft, Ontario, Canada, assignors to K d: H Equipment Limited, Toronto, ntario, Canada Filed `lruly 12, 1963, Ser. No. 295,298 1'7 Claims. (Cl. 91--422) This invention relates to fluid power actuators and, more particularly, to a hydraulically controlled air leg structure. This application is a continuation-in-part of copending application Serial Number 165,397, tiled January 10, 1962, now abandoned.

Long-stroke air cylinders or air or pusher legs are quite generally used to support and position rock drills, and supply the considerable force required for effective rock comminution by the percussive drill. In drifting or crosscutting, holes are drilled horizontally in a present pattern into the face for loading and blasting. The horizontal pressure and upward supporting force is supplied by an air leg, the piston of which is attached to the machine and may swivel in a vertical plane, while the cylinder itself slants backwards and downwards to a spike-like termination which is driven into the floor of the drift.

Apart from the difficulty of initially lining up the holes because of lack of precise control, there is a continual danger of the drill steel breaking once the hole is established and heavy pressure is being applied. Drill steel is subject to constant flexing and hammering, and eventually fatigues, fracturing suddenly. Relieved of restraint, the air leg explodes under full line pressure, pulling the drill operator towards the face and possible impalernent on the broken drill steel, unless his reactions are fast enough to Vrelease his grip on the machine.

lt is an object of this invention to provide an air leg structure which is subject to safe, convenient, controllable operation, and which has an increased effective life.

The invention will be described with reference to the accompanying drawing, in which FGURE l is a sectional side elevation of an air leg incorporating the structure of the present invention,

FlGURE 2 is a sectional side elevation of a modified forni of air leg structure,

FIGURE 3 is a sectional side elevation of a further modification of air leg stucture,

FIGURE 4 is an enlarged sectional elevation of a valve assembly employed in the modification of FIGURE 3,

FIGURE 5 is a sectional elevation of a modified form .of the valve assembly shown in FGURE 4,

FiGURE 6 is a sectional side elevation of another modified form of air leg structure, and

FIGURES 7 and 8 are sectional side elevations of additional modifications of air leg structures.

Referring to FIGURE l, a main air cylinder barrel 117 is terminated at one end by a blind end cap 118 in which an external ground spike 119 is screwed. A rod end cap 121i is screwed into the other end and forms the bearing through which a tubular air piston rod 121 extends and reti-acts, sealed by O-rin gs as shown and including a molded-rubber rod end wiper 122.

A standard rock drill fitting 123 is screwed into the external end of tubular air piston rod 121, and includes an air inlet and exhaust orifice 124, together with pressure Iand relief valves and swivel attachment to the rod drill (not shown). An air piston 125 is a pressure fit on the internal end of air piston rod 121, and slides in cylinder barrel 117 on O-ring seals as shown.

A tubular hydraulic piston rod 126 is screwed into blind end cap 118 and locked by a nut 127. Air piston 125 is centrally drilled, as shown, to allow sliding movement along hydraulic piston rod 126, and O-rings 128 3,149,541 Patented Sept. 22, 1964 ICC provide seal and wiping action. The other end of piston rod 12d-is terminated by a hydraulic piston seat 129. A hydraulic piston is held in contact with seat 129 by a light piston spring 131 reacting against a set collar 132 which is secured to piston rod 126.

An air transfer tube 133 is free to slide in tubular hydraulic piston rod 126 and through a central drilling in hydraulic piston seat 129, which is provided with O-ring seal 134. Transfer tube 133 is brazed to a floating oil reservoir cover 135 which may slide in tubular air piston rod 121 on O-ring seal, as shown. The arrangement described provides a rear oil chamber 136 in piston rod 121 between

pistons

125 and 130 and a forward oil chamber 137 between piston 13G and cover 135. A bleeder passage 13351 closed by a plug 138 is provided as an air bleed when filling rear oil chamber 136 and forward oil chamber 137 with oil. A sealed air passage is thus provided from the external supply via orifice 124 into an air inlet chamber 139 in piston rod 121 thence through transfer tube 133 into tubular hydraulic piston rod 126, and finally out of an orifice 140 in blined end cap 118 into main air pressure chamber 141 in main cylinder 117 between cap 118 and piston 125.

A controlled air passageway is provided in piston 125 from main air pressure chamber 141 to forward air chamber 142 in the main cylinder forwardly of piston 125. This passageway is provided by a shuttle valve arrange- 'ment in piston 125 and comprising an exhaust shuttle valve 143 slidingly mounted in a valve liner 144 fixed in a hole 145 drilled in the pressure chamber side of piston 125. A port 146 provides communication from the hole 145 to the chamber 142. A spring 147 urges valve 143 in one direction against a snap retaining ring 148 in liner f through transfer ports 149 formed in the valve via a transfer chamber 15d formed in hole 145 into transfer port 146.

Movement of valve 143 in the other direction is limited by a valve seat .51 provided in hole 145. It will be apparent that the valve 143 may be forced by air pressure Aagainst seat 151, thus breaking the connection between main pressure chamber 141 and forward air chamber 142.

A relief port 152 is provided in rod end cap 128 to connect forward air chamber 142 with a low pressure relief valve 153. A handle 154 is provided for moving and positioning the air leg.

The action of the air leg described is as follows:

Assume first that the air leg is in its fully retracted position, then air piston 125 is close to blind end cap 118, shuttle valve 143 is held against retaining ring 148 by spring 147, rear oil chamber 136 is at its maximum Volume, forward oil chamber 137 is at its minimum volume with hydraulic piston seat 129 located close to fioating oil reservoir cover 135, air inlet chamber 139 is at its minimium value, and low pressure relief valve 153 is closed.

If now compressed air is admitted at inlet 124, it is transmitted through transfer tube 133 and orifice 148 of hydraulic piston rod 126, into air pressure chamber 141. Orifice 141) is considerably larger than shuttle valve transfer ports 149, and furthermore, forward air chamber 142 is relieved at a few pounds above atmosphere by relief valve 153, consequently shuttle valve 143 closes against seat 161 when the differential pressure on opposite faces of the shuttle valve reach a certain value determined by spring 147.

The air pressure against the face of piston 125 tends to move it away from blind end cover 118, extending air piston rod 121 from the cylinder, However, the speed of movement is limited by the speed with which the pressurized oil in rear oil chamber 136 can leak past a predetermined clearance provided between piston 130 and the bore in piston rod 121. It will be apparent that a sealed piston with an internal leak orifice would be an alternative arrangement.

` As the piston rod 121 extends and hydraulic piston rod 126 is withdrawn from rear oil chamber 136, there is a net movement of reservoir cover 135 away from rock drill fitting 123 to compensate for the volume difference between piston rod 126 and air transfer tube 133. On this extension stroke, air is forced out of forward air chamber 142 through relief valve 153.

It is important to realize that it is very undesirable, in an atmosphere of abrasive rock dust, to allow outside air to be drawn anywhere into the cylinder on the retraction stroke, although this is common practice. A controlled air leak through the air piston may be used in an attempt to overcome this disadvantage but this is wasteful of air power. The combination of shuttle valve and low pressure relief valve in the arrangement described substantially eliminates dust contamination and air waste.

The action on retraction will now be described with orifice 124 exhausted to atmosphere through an external valve (not shown) under the control of the rock drill operator. As the pressure in main pressure chamber 141 drops to a certain pressure determined by spring 147, shuttle valve 143 opens, allowing the air to exhaust through port 146 into forward air chamber 142 as well as through orice 140. In this manner, no opposition is offered to the normal gravity retraction of the air piston by any vacuum effect in forward air chamber 142, and no air is drawn in from outside. At the same time, the expansion of rear oil chamber 136 behind hydraulic piston 130, lifts piston 131) off seat 129 against light spring 131, allowing oil to ow freely from forward oil chamber 137 as required, putting virtually no compressive force on hydraulic piston 130. Floating end cover 135 responds to the retraction stroke by moving towards rock drill fitting V123, as a consequence of the hydraulic piston rod moving into the rear oil chamber and replacing the effect of smaller diameter air transfer tube 133.

The safe controlled maximum speed of extension of this hydraulically controlled air leg is of major significance from the point of view of safety and convenience. However, an additional advantage derives from the full sealing provided in the structure described. The mechanism is completely isolated from the water and dust contaminated air, and, free of abrasion particles, the seals last their full rate life. This is many times greater than the life of seals working in the degrading conditions present in heretofore employed drill air legs.

Furthermore, inv this hydraulically controlled air leg, the high frequency vibrations caused by the percussive nature of the drill are substantially oil-damped, and taken up at the swivel joint rather than by movement of the air piston. This high frequency movement of the piston in the dust-contaminated cylinder of a standard air leg is the cause of the very high rate of wear in the leather seals employed. This Wear is so rapid that it is common practice to provide the miner with spare seals which he may change himself during the shift, at no small cost in downtime.

FIGURE 2 illustrates an air leg structure which permits rapid retraction of the main piston rod, if required. The main air cylinder barrel is indicated at 229 and is provided at one end with a blind end cap 230 and at the other end with a rod end cap 231. The cap 231 includes a sleeve 232 having a liner 233 and seal 234 through which extends a tubular air piston rod 235. An air piston 236 is mounted on the end of rod 235 and slides in barrel 229 on a sealing ring 237.

A tubular hydraulic piston rod 238 has one end fixed to blind end cap 230 and a hydraulic piston seat member V239 fixed to its other end. An air transfer tube 240 is free to slide in piston rod 238 and through member 239 which is provided with a sealing ring 241. Transfer tube 249 is fixed to a fioating oil reservoir cover 242 which may slide in air piston rod 235 on sealing ring 243.

A hydraulic piston 244 is slidingly mounted on piston rod 23S and, in conjunction with piston seat member 239, provides controlled communication between a rear oil chamber 245 in piston rod 235 and a forward oil chamber 246 in piston rod 235. Piston 244 has a closed position wherein it is in engagement with valve seat member 239 and an open position defined by engagement with retaining ring 247 on piston rod 23S wherein communication between

chambers

245 and 246 is provided through ports 248 and annular passage 249 in piston 244.

It will be apparent that in barrel 229 there is provided, by piston 236, a main air chamber 250 rearwardly thereof and a forward air chamber 251 forwardly thereof. Communication between air inlet chamber 252 forwardly of cover 242 and main air chamber 250 is provided through transfer tube 24?, hollow piston rod 238, and ports 253 in rod 238.

Controlled communication between chambers 25) and 251 is provided by an annular interior air transfer passage 254 surrounding piston rod 238 in the rearward end portion of piston 236, an annular exterior recess 255 in piston 236 adjoining the forward end thereof and forming an annular passage 256, and a plurality of radially extending ports 257 connecting

such passages

254 and 256 through a bore 258 in the piston 236. Slidably mounted in bore 258 and on piston rod 238 is a cylindrical valve 259 having sealing rings 260, 261. Bore 258 terminates in an annular shoulder 262 adjoining passage 254, such shoulder constituting a valve seat engageable by valve 259 to define the closed position thereof and wherein ports 257 are closed.

It will be observed that valve 259 controls the passageway between main air chamber 250 and forward air chamber 251 in response to the differential pressure between rear oil chamber 245 and main air chamber 250.

The compressed air admitted to the air piston rod 235 through the conventionaly provided control valve (not shown) transmits pressure almost instantaneously to the hydraulic fluid through the oating reservoir cover 242. Corresponding build-up or reduction of pressure in main air chamber 250 lags the controlled pressure because of the restrictive nature of the air transfer tube 240 and the capacity of the main air chamber 256.

Thus, when feed pressure -is applied, valve 259 closes against valve seat 262 and the pressure then builds up in main air chamber 250, extending the air leg. Once rvalve 259 is closed, ythe face area thereof exposed to the air presure in annular transfer passage 254 becomes smaller than the area exposed to the hydraulic pressure in chamber and the valve becomes overbalanced. Control air pressure on the hydraulic fluid must be reduced below the pressure in main air chamber 25@ before valve 259 will re-open, and again the restriction of transfer tube 240 and the capacity of chamber 2511 assists the speedy attainment of this required opening differential.

Once valve 259 shuttles open in response to a sharp reduction in control pressure, air in chamber 259 may exhaust freely through ports 257 into forward air chamber 251 which may be ported directly to atmosphere, as indicated at 263, or held at slight positive pressure by low pressure relief va-lves such as indicated at 153 in FIG- URE l. This rapid reduction in the pressure of main air chamber 250 allows rapid retraction of the main air piston rod 235 if required, or simply rapid pressure relief tosome intermediate control pressure since it will be observed that valve 259 will close whenever the pressure in chamber 251 has dropped to the set control pressure.

It will be apparent that the air pressure in inlet chamber 252 is transmitted almost instantaneously to the hydraulic fluid and that this pressure is virtually independent of the pressure/how conditions in the air chambers of the device itself. By using this hydraulic pressure to actuate the relief transfer valve 259 with high flow characteristic in the air piston, retraction can be accomplished with speed and ease.

There is also illustrated in FGURE 2, an improved blind end cover attachment. It is common prac-tice to secure the blind end cover to the cylinder barrel by screw threads. This is not entirely satisfactory because the cylinder barrel must be ordinarily of light metal, such as aluminum alloy, and all the hammering of the drill is transmitted through the threaded connection to the ground spike. Loosening of the blind end cap and destruction of the threads, with consequent scrapping of valuable tubing, is a common mishap.

As shown, the blind end cover 230 comprises anend member 25d having a recessed annular shoulder 265 engageable with the end of the barrel 229, and a compression plug 266 screw-threadedly mounted in a socket 267 in member 264 and having a sliding fit in the cylinder barrel 229. Plug 266 has an outer annular recess 268 and disposed in such recess is a compression collar 269, which is slidable on the plug within barrel 229 but is restrained from backward movement by a retaining ring 270 mounted in the barrel. A plurality of sealing rings 271, such as conventional C-rings are interposed ia recess 268 between the compression collar 26% and a shoulder 272 defining the termin-ation of the recess.

The rings 271i. provide a pressure sea-l and result in a vibration-proof lock washer effect by maintaining tension on the threads over several revolutions of the linal tightening of the cover member 26d. Shoulder 1F35 is under constant pressure against the end face of the cylinder barrel, and vibration is transmitted without wear, loosening, or hammer.

Further embodiments of 4the invention will now be described with particular reference to air legs incorporating power retraction means.

When drilling horizontally with an air leg/drill combination, it is necessary for the operator to regularly advance the air leg, as the drill steel feeds into the rock, in order to maintain the correct angle and force components for optimum drilling. When non-retractable air legs are used, the feed pressure must be turned off, and the air leg pulled up and positioned manually each time a move is made.

Retractable air legs now in use are generally of the upside-down type, i.e., the cylinder is attached `to the drill, and the piston rod end presses against the sill. This orientation simplifies the positioning of the usual four-way extend/ retract valve, which should be at the blind end of the air leg cylinder to facilitate the plumbing to the front and rear air chambers, and must also be conveniently in reach of the operators hand on the drill. However, this inverted orientation has a disadvantage in that the elevation of the handle on the cylinder changes as the air leg extends, and while the power retraction does reduce the lift required, nevertheless, the leg must be guided and positioned manually. n high back holes, the handle m-ay be at chest level, which is not a convenient height for lifting.

Two versions of a right-way-up retractable air leg, incorporating hydraulic damping and a single valve control of extend-retract and pressure regulation, will now be described.

Referring to FGURES 3 and 4, 27?) is a main air cylinder barrel terminated at one end by a blind end cap 274i in which an external ground spike may be screwed. A rod end cap 275 is screwed onto the other end and supports a bearing 276 through which a tubular air piston rod 277 extends and rctracts. As shown, the bearing includes a replaceable liner 278, a rod end wiper 279, and a sealing O-ring 288.

It will be apparent that a standard rock drill fitting will be screwed onto the external end 281 of the piston rod 277, to connect the air leg to a drill, and to provide an air passageway into the piston rod 277 from the pressure control valve (not shown).

An air piston 282 is a tight screw lit on the internal end of air piston rod 277 and slides in the cylinder barrel 273 on O-ring seal 283, as shown.

One end of a tubular hydraulic piston rod 284 is screwed into a retainer 285 carried by a valve body 286 fixed to blind end cap 274i. Air piston 282 is centrally drilled at 287 to allow sliding movement along piston rod 284, an O-ring hydraulic seal 288 being provided. A hydraulic piston seat member 289 is mounted on the other end of piston rod 284. A hydraulic piston 290, slidable on .piston rod 28d, has a limited travel between a retaining ring 291 on the rod 284 and the seat 289. Hydraulic piston 29@ provides controlled communica-tion between rear oil chamber 292 and forward oil chamber 293 in piston rod 277. When piston 29d is in engagement with seat 289 (as during extension of the air leg) there is controlled oil transfer between

chambers

292 and 293 through an annular passage 2% in piston 290, a port 285 in piston 298 leading from chamber 292 to passage 284, and selfcleaning grooves 296 on the sealing face of piston 290. When piston 298 moves off seat 289, oil flow in the opposite direction is unrestricted through passage 294 and port 295 (as a retraction of the air leg).

An air transfer tube 2427 is free to slide in tubular hydraulic piston rod 284 and through a central drilling 298 in piston seat 289, which is provided with a sealing ring 229. A floating oil reservoir cover 380 is fixed to the forward end of transfer tube 297. Cover 300 is slidable in air piston rod 277 on sealing ring Stil.

Referring now more particularly to` FIGURE 4, valve body 286 houses a pressure sensitive four-way valve structure now to be described.

As shown, hydraulic piston rod retainer 285, which is provided with a seal 382, is retained in body 28d by means of a ring 283. Also mounted in the body between retainer 285 and a retaining ring 3nd is a valve liner 36S. Also mounted in the body between retaining ring 384 and another retaining ring 386 are a pair of spring housings 387 containing a spring 308, housings 307 being normally spaced apart under the influence of spring 308.

A shuttle valve member 369 is mounted in liner 385. Valve member 309 has has a pressure distribution chamber 315.8. Chamber Sill) has a port Sill leading to its forward face adjacent retainer 285, and communicating with the interior of piston rod 284 through opening 312 in retainer 285. Port 311 is normally closed by a check valve 313 under influence of a spring 31d. Chamber 3l@ has a small orifice Silla bypassing check valve 313.

An extension port 315 connects chamber Sill with a circumferential groove 326 in member 389 and a retraction port 3l7 connects chamber 318 with a circumferential groove SiS.

Member 389 also contains an exhaust passage 319 which is open rearwardly thereofV and which has a port 320 connecting with a circumferential exhaust groove 321 in member 389. Rings 322 provide pressure seals between the circumferential grooves, as shown.

Liner 385 has `a plurality of radially extending ports 323 leading inwardly from a circumferential extension groove 324 thereon and communicating with groove 321 Liner 395 also has a plurality of radially extending ports 325 leading inwardly from a circumferential retraction groove 326 thereon iand communicating with groove 318. Liner groove 32d communicates with extension ports 327 in valve body 286 and liner groove 326 communicates with retraction ports 328 in valve body 286.

A circumferential groove 329 in valve body 286 provides a passageway from retraction ports 32S to an eX- ternal transfer tube 33d which communicates with the forward air chamber 331 of the air leg through an annular recess 332 in the piston 282. Extension ports 327, separated by a sealing ring 333 from the retraction groove 329, lead directly into the main air chamber 334 via a circumferential recess 33S in body 285.

Preferably, the liner 3695 is formed of a plastic composition such as that known under the trade name Teflonamas-r1 The

circumferential grooves

324 and 326 therein are sealed by O-rings 336. Danger of O-ring damage or extrusion may be obviated by making the diameter of the @-ring greater than that of the

ports

323 and 325.

Exhaust passage 319 communicates with atmosphere through openings 337 in spring housings 367, a space 338 between valve body 286 and the blind end cover 274, and ports 339 in the blind end cover.

The parts as shown inthe drawing are in their normal or retract position.

In operation, when it is desired to extend the air leg, air under pressure is admitted through air transfer tube 297 'and piston rod 28d to the forward end of valve member 309 and when the air pressure overbalances the force exerted by spring 308, valve member 309 will move rearwardly to its extend position. In this position, air under pressure is supplied to main air chamber 334i through

elements

311, 315, 316, 323, 327 and 335, while forward air chamber 331 is exhausted to `atmosphere through

elements

332, 339, 329, 325 and 321, to the ports 339.

If it is required to reduce the pressure of extension, this may be done by slowly backing off control pressure and relieving through by-pass 311:1.

On the other hand, if a quick relief of pressure is required to switch valve 309 to retraction position, the standard manual control valve may be closed rapidly. Check valve 313 then permits quick exhaust of pressure in hydraulic piston rod 234, valve 309 switches to retract position, and the large capacity of main air chamber 33d exhausts quickly through elements 323, 321, 32% and 319 and thence to ports 339. Thus, the check valve by-pass arrangement permits a rapid switch to retraction position, without waiting for the large capacity of the main air chamber 334 to bleed down to the switchover pressure. It will be recognized, however, that while the check valve is of substantial convenience, it is not essential to the fundamental operation.

The setting of the valve mechanism described may be such that power retraction occurs at pressures between say, to 30 p.s.i. Above, say, 30 p.s.i., the valve member 309 shuttles, exhausts the forward air chamber 331, and pressurizes the main air chamber 334 for rod extension at whatever pressure is set by means of the usual manual control valve.

Referring now to FIGURE 5, a valve arrangement is shown which permits use of a greater range of pressures in both the extension and retraction operations.

The embodiment of FIGURE 5 is substantially the same as that of FIGURES 3 and 4 but includes the provision of ball detents 356 mounted in valve body 236, and urged by springs 341 into engagement with the side wall of the forward spring housing 3137. The latter housing has a circumferential groove 342 therein arranged to receive the spring-loaded detents 340 when the housing is moved to extend position by the valve member 309.

By `appropriate choice of spring pressure and detent breakaway force, a Wide choice of overlapping extension and retraction ranges is available. Thus, the control valve 309 may be set to shuttle to extend position at a pressure greater than, say, 60 p.s.i., and the detents may be employed to hold it in this position until the pressure is reduced to, say, p.s.i., when it will flip back to retract position. Thus, once a particular extension mode has been selected, any pressure between l0 p.s.i., and full line pressure may be used for extension. Similarly, once the pressure is reduced below l0 p.s.i., any pressure between zero and 60 p.s.i., may be selected for retraction.

Briey, therefore, Valve return spring 308 determines the control pressure required to switch the valve to extend position, while the difference between the force of spring 358 and the detent restraining force, determines the switching pressure below which the valve will shuttle back to retrac position.

FIGURE 6 illustrates a further modilication of a hydraulically-controlled power-retractable air leg. It includes a main air cylinder barrel 343, a tubular air piston rod 344 extending slidably through a rod end cover 345, an air piston 345 fixed to the inner end of rod 344 and forming in barrel 343 a main air chamber 347 and a forward air chamber 343, and a tubular hydraulic piston rod 349 having one end xed to a blind end cover element 35u and a hydraulic piston 351 slidably mounted thereon between retaining ring 352 and piston seat 353 fixed to its other end. An air transfer tube 354 extending into hydraulic piston rod 349 and carrying a floating oil reservoir cover 355 provides communication between air inlet chamber 356 and main air chamber 347 through port 357. A drill titting 358 is connected to the forward end of air piston rod 344.

A thin-walled tube 359 is concentrically mounted within the air piston rod 3454 in radially spaced relation to the rod 344 and to the hydraulic piston rod 349. The rearward end of tube 359 extends into air piston 346 and is provided with a seal 35@ to seal the rear oil chamber 361 from an annular air passageway 362 formed between the tube and the air piston rod 344. The forward end of tube 359 is mounted on a boss 363 on tting 353 and is retained thereon by a retaining ring 364.

The passageway 362 connects the forward air chamber343 through port 365 with a retraction control port 356 in fitting 358. An extension control port 367 in fitting 353 communicates with air inlet chamber 356 and main air chamber 347 through the transfer tube 354 and hydraulic piston rod 349. The

ports

366 and 367 will be connected to conventional control valve mechamsm.

Communication between rear oil chamber 361 and forward oil chamber 368 in tube 359 is freely established in the retracted position of the air leg in which position piston 351 is spaced from seat 353, through an annular passageway 369 in piston 351 having ports 37d communicating with chamber 361 and the annular space 371 between seat 353 and the bore of tube 359. As piston rod 344 extends, piston 351 will tend to engage seat 353 to close passageway 369. Thereafter, the speed of movement of the piston rod is limited by the speed with which the pressurized oil in rear oil chamber 361 can leak past the meeting faces of piston 351 and seat 353. As in respect of FIGURE 3, one of these meeting faces may be provided with grooves such as 236.

It will be observed that the air leg modifications set forth herein have been described in relation to that orientation thereof wherein air is admitted through the piston rod and the blind end of the cylinder is to the ground. It will be apparent that the reverse orientation of the air legs may be provided by making minor obvious rearrangements of the parts thereof if such orientation were necessary or preferred.

FIGURE 7 illustrates a form of the invention as applied to a pusher leg. The main tube or cylinder is indicated at 372 and is provided at one end with a blind end cap 373 and spike 374 and at the other end with a gland nut 375. A hollow push rod or air piston rod 376 extends through the gland nut into the cylinder and is provided with an air piston 377 fixed to its inner end and a suitable adaptor 378 on its outer end. The piston may be provided with a packer ring 379 engaging the inner wall of the cylinder.

Located within the air iston rod 376 is a floating hydraulic cartridge 335 comprising a tube 351 each end of which terminates inwardly of but closely adjacent the adjoining end or" the rod 376. The external diameter of the tube 331 is less than the internal diameter of rod 376 to provide a space 382 between the opposed wall surfaces of rod 376 and tube 381. As shown, the radial extent of space 332 may be relatively small. The inner end of tube 331 is closed by a sealing cover 333 having a portion extending into the tube provided with an O-ring 384. Cover 383 also has a portion extending outside 9 the tube, the end of which bears on a washer 385 Which in turn is seated on a ring 386 fixed within the end of rod 376.

The other end of tube 331 is closed by a floating reser- Voir cover 387 which extends into the tube and is provided with an O-ring seal 338. An air bleed passage 389 in the cover 337 is closed by a plug 3%. A spring 391 is interposed between the end of tube 331 and adapter 37S. The spring holds the cartridge assembly in place while permitting it to float. It eliminates any need for close tolerances on the tube length and prevents cartridge hammer during drilling operation.

A hydraulic piston rod 392 has one end fixed to blind end cap 373 and extends axially into piston rod 376 and tube 381. The rod 392 extends through cover 383, sealing means 393 therewith being provided. Mounted on the free end of piston rod 392 within tube 381 is a piston assembly 394 incorporating valve means operable during the extension and retraction strokes of the piston rod 376. The assembly 394 comprises a retraction valve member 395 and an extension valve member 395 each in the form of a collar fixed to the rod 332, and a tubular valve seat member 397 freely reciprocal between members 395 and 3%. Member 397 has an axial fiuid flow passage 397e therein and has sealing engagement, by means of seal 39717, with tube 381. Member 397 has, as shown, a bevelled seat 398 and one end for engagement with a complementary seat 399 on member 395 and a bevelled seat 4h@ at its other end for engagement with a complementary seat 491 on member 396. Member 3% has a relatively large slot or passage 402 therein which provides relatively unrestricted fluid flow therethrough during the retraction stroke, i.e., when member 397 is seated on member 395. Member 396 has a relatively smaller slot or passage 4l3 therein which provides controlled fluid flow therethrough during the extension stroke, i.e., when member 397 is seated on member 3%.

Air is supplied to the cylinder through an orifice 404 in adapter 37 thence through space 382 into an outer annular recess 4% in cover 383, ports 4416 and inner annular recess 407 in cover 383, central opening 408 in washer 335, and finally through ring 3% into main air pressure chamber 469. Flow of air out of forward air chamber 41h is around a spacer 411 (which may be provided as required) and through a groove 412, annular space 413, and ports 414 in the gland nut 375.

The cartridge tube 424 is filled with oil, in operation, and it will be apparent, as previously indicated, that, during the extension stroke of piston rod 376, restricted flow of oil through passage 493 occurs from the chamber on one side of the piston assembly 394 to the chamber on the other side of the piston assembly. During the retraction stroke, unrestricted flow of oil through passage 4&2 from one chamber to the other occurs.

The pusher leg described is a simplified and less expensive version of the invention in that it does not provide for power retraction. This single-acting leg eliminates the need for expensive honing.

FIGURE 8 shows an adaptation of the structure of FIG- URE 7 for use as a stopper. Main cylinder 415 is shown as mounted on a conventional stopper body 416. Holland push rod or air piston rod 417 extends through bearing 41% in the outer end of the cylinder. A plate 419 closes the inner end of the cylinder and provides an air inlet chamber 42@ adjacent the stopper body. A foot 421 closes the outer end of rod 417 and an air piston 422 is mounted on the inner end within the cylinder.

A hydraulic cartridge 423, adapted to receive a supply of oil, is disposed within the hollow piston rod 417 and comprises a tube 424, cover 425 closing the inner end thereof and floating reservoir cover 426 closing the outer end thereof, and positioning and retaining spring 427. The cartridge provides an air space 428 between its external wall and the internal wall of the rod 417. Cover 425 bears upon a collar 429 in rod 417.

A hydraulic piston rod 43? has one end fixed to plate l@ 419, as by

nuts

431 and 432, and extends axially into tube 424 through cover 425. A piston assembly 433 similar to piston assembly 394 is mounted on piston rod 429 within tube 424.

Chamber 42d has an air inlet 434 leading from a control valVe (not shown) and air flow is from chamber 420 through port 43S in plate 419, and into the end of piston rod 417 to move piston 422 and extend the rod. Air also flows through collar 42@ and space 428 to the outer end portion of the piston rod to permit axial movement of the floating reservoir cover 426 The operation of the device will be apparent from the foregoing description. Air is supplied, as described, to effect the extension stroke. For retraction, air transfers through the unsealed clearance of bearing 413 and piston rod 417.

We claim:

l. A hydraulically controlled air leg comprising a main cylinder barrel, an air piston rod extending axially into said barrel and having rear and forward hydraulic fluid chambers therein, an air piston fixed to said piston rod in said barrel, a hydraulic piston rod axially arranged in said barrel and fixedly connected thereto, said hydraulic piston rod extending through said air piston, a floating cover in said air piston rod defining one end of said forward hydraulic fluid chamber, a hydraulic piston on said hydraulic piston rod, said hydraulic piston separating said rear and forward hydraulic fluid chambers, and means providing an oil flow passage through said hydraulic piston from one of said chambers to the other.

2. A hydraulically controlled air leg as defined in claim 1, including a hydraulic piston seat fixed -to said hydraulic piston rod, said hydraulic piston having a first position defined by engagement thereof with said seat and a second position defined by disengagement thereof with said seat, means forming a restricted passageway leading from one of said chambers to the other through said hydraulic piston and said seat in said first position.

3. A hydraulically controlled air leg comprising a main cylinder barrel, an air piston rod extending axially into said barrel and having rear and forward hydraulic fluid chambers therein, an air piston fixed to said piston rod in said barrel, a hydraulic piston rod fixed to and axially arranged in said barrel, said hydraulic piston rod extending through said air piston, a floating cover in said air piston rod defining one end of said forward hydraulic fluid chamber, a hydraulic piston on said hydraulic piston yrod and having limited axial movement thereon, said hydraulic piston separating said rear and forward hydraulic fluid chambers, means providing an oil flow passage through said hydraulic pisten from one of said chambers to the other, and means controlling fluid flow through said passage.

4. A hydraulically controlled air leg as defined in claim 1, including a hydraulic piston seat fixed to said hydraulic piston rod, said hydraulic piston having a first position dened by engagement thereof with said seat and a second position defined by disengagement thereof with said seat, means forming a restricted passageway leading from one of said chambers to the other through said hydraulic piston and said seat in said first position, said chambers being in substantially unrestricted communication with each other in said second position.

5. A hydraulically controlled air leg comprising a main air cylinder ba-rrel having a blind end cap at one end thereof and a rod end cap at the other end thereof, a tubular air piston rod extending through said rod end cap into said barrel, an air piston fixed to said piston rod in said barrel, a hydraulic piston rod axially arranged in said air piston rod and having one end fixed to said blind end cap, a floating oil chamber cover in said air piston rod, a hydraulic piston on said hydraulic piston rod between said oil chamber cover and said air piston, said air piston rod having therein a rear oil chamber between said hydraulic piston and said air piston and a forward oil chamber between said hydraulic piston and said oil 'l l chamber cover, and means providing an oil flow passage from one of said chambers to the other.

6. A hydraulically controlled air leg comprising a main air cylinder barrel having a blind end cap at one end thereof and a rod end cap at the other end thereof, a tubular air piston rod extending through said rod end cap into said barrel, an air piston fixed to said piston rod in said barrel, a hydraulic piston rod axially arranged in said air piston rod and having one end fixed to said blind end cap, a floating oil chamber cover in said air piston rod, a hydraulic piston on said hydraulic piston rod between said oil chamber cover and said air piston, said air piston rod having therein a rear oil chamber be- -tween said hydraulic piston and said air piston and a forward oil chamber between said hydraulic piston and said oil chamber cover, means providing an oil iiow passage from one of said chambers to the other, and means controlling oil ow through said passage.

7. A hydraulically controlled air leg comprising a main air cylinder barrel having a rear end, a blind end cap thereon, a forward end, and a rod end cap on said rear end, a tubular air piston rod extending through said rod end cap into said barrel, an air piston yfixed to said piston rod in said barrel, a hydraulic piston rod axially arranged in said air piston rod and having one end fixed to said blind end cap, a hydraulic piston reciprocally mounted on said hydraulic piston rod, said hydraulic piston rod having a seat engageable by said hydraulic piston, means urging said hydraulic piston into seated position, a floating oil `reservoir cover in said air piston rod forwarding of said hydraulic piston, said air piston rod having therein an air inlet chamber forwardly of said reservoir cover, a forward oil chamber between said reservoir cover and said hydraulic piston, and a rear oil chamber between said hydraulic piston and said air piston, means forming a restricted passageway extending through said hydraulic piston and providing controlled communication between said forward and rear oil chambers, said hydraulic piston being movable from its seat to establish substantially unrestricted communication between said forward and rearward oil chambers, said barrel having therein a main air chamber between said air piston and said blind end capand a forward air chamber between said air piston and said rod end cap, means forming an air passage leading from said air inlet chamber to said main air chamber, and a relief valve-controlled air passage leading from said forward air chamber, including a valve-controlled air passage extending through said air piston from said main air chamber to said forward air chamber.

8. A hydraulically controlled air leg as defined in claim 7, including an air passage extending through said air piston from said main air chamber to said forward air chamber, a valve in said passage, a spring urging said valve into open position, said valve being movable to closed position in response to air pressure in said main valve chamber.

9. A hydraulically controlled air leg as defined in claim 1, said air piston rod having an air inlet chamber, said barrel having a main air chamber on one side of said air piston and a forward air chamber on the other side of said air piston, said floating cover dening one wall of said air inlet chamber and separating said forward hydraulic iiuid chamber and said air inlet chamber, means forming an air passageway leading from said air inlet chamber to said main air chamber, means forming an air passage leading through said air piston from said main air chamber to said forward air chamber, a valve axially movable on said hydraulic piston rod and having a first position closing said air passage and a second position opening said air passage, said valve having a face defining a wall of said rear hydraulic fluid chamber, said valve being movable to said second position in response to hydraulic uid pressure in said hydraulic fluid chambers transmitted by air pressure in said air inlet chamber on said floating cover.

10. A hydraulically controlled air leg as defined in claim l, said barrel having a main air chamber on one side of said air piston and a forward air chamber on the other side of said air piston, a valve body mounted in said barrel adjoining said main air chamber, a valve reciprocally mounted in said body and having therein a first chamber communicating with said main air chamber and an exhaust chamber communicating with atmosphere, said first chamber having a pair of ports and said exhaust chamber having a port leadingv externally of said valve, said valve body having a first port and a passageway leading to said main air chamber and a second port and a pssageway leading to said forward air chamber, said valve having a first position placing said exhaust chamber port in registry with said first port to exhaust said main air chamber to atmosphere, and a second position placing said exhaust chamber port out of registry with said first port and in registry with said second port to exhaust said forward air chamber to atmosphere, and a spring acting upon one face of said valve to urge it in one direction towards said first position, said valve having an opposite face exposed to air pressure in said main air chamber for movement thereby in the opposite direction towards said second position.

1l. A hydraulically controlled air leg as defined in claim l0, including a check valve in said first chamber controlling communication therefrom to said main air chamber.

l2. A hydraulically controlled air leg as defined in claim l0, including a plastic composition liner mounted in said valve body, said valve being slidably mounted in said liner, said valve having a plurality of circumferentially extending annular grooves each communicating with one of said ports, said liner having a plurality of series of radially extending ports, each said series communicating with one of said passageway and arranged for communication with one of said annular grooves.

13. A hydraulically controlled air leg as dened in claim l0, including latch means defining said second position of said valve, said latch means being releasable in response to a predetermined degree of air pressure on said valve.

14. A hydraulically controlled air leg as defined in claim l0, including a housing for said spring reciprocally mounted in said valve body and engaged by said valve to compress said spring, and a spring-loaded detent engaging said housing, said housing having a recess for reception of said spring to define said second position of said valve.

15. A hydraulically controlled air leg comprising a main cylinder barrel, an air piston rod extending axially into said barrel and having rear and forward hydraulic fluid chambers therein, an air piston fixed to said piston rod in said barrel and providing therein a main air chamber on one side of said air piston and a forward air chamber on the other side of said piston, a tube concentrically arranged within said air piston rod in radially spaced relation thereto to provide an annular air passage therebetween, a hydraulic piston rod fixed to and axially arranged in said barrel, said hydraulic piston rod extending through said air piston, a floating cover in said tube defining one end of said forward hydraulic fluid chamber, a hydraulic piston on said hydraulic piston rod, said hydraulic piston separating said rear and forward hydraulic fluid chambers, means providing a hydraulic fluid flow passage through said hydraulic piston from one of said hydraulic fluid chambers to the other, and means controlling iiuid flow through said hydraulic iiuid flow passage, said annular air passage having a port communicating with said forward air chamber and an air inlet and outlet port, said main air chamber having an air inlet and outlet port.

16. A hydraulically controlled air leg comprising a main cylinder barrel, a hollow air piston rod extending axially into said barrel, an air piston fixed to said piston rod in said barrel and providing therein an air chamber on each side of said air piston, a floating hydraulic cartridge in said piston rod and having an external diameter less than the internal diameter of said piston rod to provide an air passage extending longitudinally through said piston rod, said cartridge comprising a tube, a cover closing one end of said tube, and a floating cover closing the other end of said tube, a hydraulic piston rod ixedly mounted Within said barrel and extending axially through said iirst cover into said tube, a hydraulic piston carried by said hydraulic piston rod Within said tube, and defining a hydraulic uid chamber on each side of said hydraulic piston, means providing a hydraulic uid passage extending through said hydraulic piston from one of said hydraulic fluid chambers to the other of said hydraulic uid chambers, said air passage having communication with one of said air chambers, and means forming an air supply passage communicating with said air passage.

14 17. A hydraulically controlled air leg as defined in claim 16, said hydraulic piston having valve means responsive to axial movement of said tube in each direction and controlling uid ow through said hydraulic fluid passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,364 Becker Apr. 27, 1937 2,132,519 Slater Oct. 11, 1938 2,193,736 Onions Mar. 12, 1940 2,564,790 Orlotf Aug. 21, 1951 2,679,827 Purdue June 1, 1954 2,813,515 Curtis Nov. 19, 1957 3,055,343 Kurt Sept. 25, 1962

Claims

1. A HYDRAULICALLY CONTROLLED AIR LEG COMPRISING A MAIN CYLINDER BARREL, AN AIR PISTON ROD EXTENDING AXIALLY INTO SAID BARREL AND HAVING REAR AND FORWARD HYDRAULIC FLUID CHAMBERS THEREIN, AN AIR PISTON FIXED TO SAID PISTON ROD IN SAID BARREL, A HYDRAULIC PISTON ROD AXIALLY ARRANGED IN SAID BARREL AND FIXEDLY CONNECTED THERETO, SAID HYDRAULIC PISTON ROD EXTENDING THROUGH SAID AIR PISTON, A FLOATING COVER IN SAID AIR PISTON ROD DEFINING ONE END OF SAID FORWARD HYDRAULIC FLUID CHAMBER, A HYDRAULIC PISTON ON SAID HYDRAULIC PISTON ROD, SAID HYDRAULIC FLUID CHAMBERS, AND MEANS PROVIDING AN OIL FLOW PASSAGE THROUGH SAID HYDRAULIC PISTON FROM ONE OF SAID CHAMBERS TO THE OTHER.