US2502895A - Hydraulic hoist - Google Patents

Description

April 4, 1950 E. J. sHAFFER 2,502,895

HYDRAULIC HOIST April 4, 1950 E. J. sHAFFl-:R

HYDRAULIC noIsT 4 Sheets-Sheet 2,

Filed Oct. 26, 1944 E l: U- Ll INVENTOR Ems/f7 J.' .5f/#MR MMA.;

A rmx/c y E. J. SHAFFER HYDRAULIC) HOIST April 4, 195o 4 Sheets-Sheet 4 Filed Oct. 26. 1944 @il C 7' INVENTOR.

fbx/57 J. 5Min-fw? Patented Apr. 4, 1950 UNITED STATES PATENT oEEicE HYDRAULIC HOIST Ernest J. Shail'er, Tulsa, Okla., assigner of onehali' to Daniel W. Shaer, Hutchinson, Kans., and one-half to George W. Shatter. Jr., Tulsa.

Application October 26, 1944, Serial No. 560,436

15 Claims.

This invention relates to hydraulic hoisting apparatus and particularly to a hydraulic draw works system for well drilling rigs.

A principal object of this invention is the provision of a hydraulic apparatus adapted to operate for the raising or lowering of loads and which has a wide range of flexibility in its operative movements.

Another object is the provision of a simplified draw works system for well drilling rigs which is fully hydraulically operated, which is highly flexible and of greatly simpliiled construction, and which will replace the more conventional drilling rig draw works systems having wire lines, sheave blocks, cable drums, multispeed transmissions, braking mechanism and power connections commonly employed in such systems.

A further object is the provision of a system and apparatus which is easy to control by the operator, which is comparatively simple in construction and fool-proof in operation.

Still another object is the provision of a hydraulic draw works system for use with well drilling rigs which is largely self-contained and adapted for easy portability from place to place as a part of a complete drilling rig.

Other and more specilic objects and advantages of this invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings which illustrate a preferred form or embodiment in accordance with this invention. It will be understood that various Jmodiilcations and alterations of the details of this invention may be made within the scope of the appended claims, but without departing from the spirit of this invention.

In the drawings:

Fig. 1 is a side elevation of the hydraulic hoist device of this invention, shown in assembled relation as a part ol' a complete drilling rig and arranged therewith on a common base structure for purposes oi' ready portability;

Fig. 2 is a plan view of the base structure of the drilling rig showing the layout of the various elements of the rig on the common base;

Fig. 3 is a front elevation of the device of Fig. 1 showing particularly the arrangement of the parts of the hydraulic hoist and having some of the parts broken away for purposes of better illustration of rits details;

Fig. 4 is an enlarged cross-sectional view of a detail of the device taken along line 4-4 of Fie. 3;

Fig. 5 is a skeletonized or schematic view of the principal elements of the hydraulic device;

Fig. 6 is a side elevation o! the device as applied to a portable drilling rig, illustrating the manner of raising and lowering the hydraulic hoist members relative to the base structure; and

Figs. 7 and 8 are details o f the pivoted connection between the hoist device and the base structures.

Referring to the drawings, the hydraulic hoist device, in accordance with this invention, arranged for use with a well drilling rig. is designated generally by the numeral I, and is shown supported in a generally vertical position by a supporting frame, designated generally by the numeral 2. The supporting frame 2 includes a horizontally disposed base 3 of the skid type adapted for ready movement from place to place by a suitable transporting vehicle (not shown). Mounted on base 3 are the usual power supply engine I, mud pump I. and rotary table Ii normally employed in rotary drilling rigs. 'I'he rig also includes the usual power shaft 1, driven from engine 4 by a power connection 3, and drivingly connected to the mud pump 5 by a power connection 9 and to a cat-head shaft III, carrying a cathead Illa, by another power connection II. 'lll/1e rotary table drive shaft I2 is driven from the cathead shaft It by still another driving connection I3. vThese several driving connections are of the conventional types, such as sprocket-and-chain connections orl V-belt-andpulley drives. The usual clutches are also provided in proper relation to the various drive connectionsto provide for engagement and dis-engagement of the several driven units with the power source.

Supporting frame 2, of which only one side is shown, the other side being substantially identical in construction, includes upright leg members I4 disposed on opposite sides of base 3 and spaced rearwardly from the hydraulic hoist I. Suitable girts and braces I5 and I6, respectively, conneet leg members I4 to the members of the hydraulic hoist. The structure thus formed is pivotally supported upon a sub-base structure which is rigidly attached to base 3 and includes rear leg supports Il upon which the lower ends of leg members Il rest when in upright position. The sub-base structure also includes a pair of trunnion cradles It rigidly mounted on opposite sides of base 3 and adapted to rotatively cradle hollow trunnions I3 to which are attached the lower ends of hollow legs 2l and 20a, upon which the.

hydraulic hoist device is mounted. Upwardly and rearwardly extending angle braces ZI provide rigid bracing between trunnion cradles I8 and the upper ends of leg supports |1. Angle braces 22 connect hollow trunnions i9 to the lower ends or leg members I4 and are adapted to register with angle braces 2|, when the hoist device and supporting trame are in the upright position. Suitable removable connecting means, such as bolts 23, rigidly connect braces 2| and 22 when the device and supporting frame are in the upright position, and are adapted for removal when the superstructure is to be lowered to a transport position. When assembled in the upright position, the hydraulic hoist and the supporting frame including the sub-base structure form a derrick mast of the usual generally pyramid shape.

The hydraulic hoist comprises a pair oi vertically extending cylinders 24 and 24a, supported on hollow legs 20 and 20a, respectively, and constructed of heavy metal tube or pipe adapted to withstand high internal pressures and other stresses normally developed therein under operating conditions. Cylinders 24 and 24a have internal bores 25 and 25a, respectively, and are provided at their upper ends with caps 26. Bore 25 communicates with the interior of its supporting hollow leg 20 through a passageway 25h. A piston rod 21, carrying a piston 21a on one end thereof, is reciprocably mounted in each of the bores 25 and 25a, the opposite ends of rods 21 extending upwardly out of the cylinders 24 and 24a through suitable openings in caps 26. The upper ends of piston rods 21 carry brackets 28 in which the ends of a cross head 29 are rigidly connected. Extending rearwardly from brackets 28 are U- shaped slides 30 which slidingly engage with upwardly extending guide members 3|, which are `rigidly supported in their upright positions by vertical support columns 32 forming a part of the main support frame 2 by connection to leg members |4 by means of suitable girts and braces 33 and 34, respectively. A pinion shaft 35 extends transversely above cross head 29 between brackets 28 and the ends thereof are journalled in bearing supports 36 carried by brackets 28. A pinion 31 is mounted on pinion shaft 35 adjacent each end thereof and mesh with elongated racks 33 rigidly attached to the forward faces of guide members 3|. Co-action of pinions 31 with their respective racks 38 serves to keep the piston rods 21 moving in unison during reciprocation, and maintains even distribution of the load carried by the piston rods 21 under all hoisting conditions.

Mounted in the center of cross head 29 is a universal joint connection 39 from which is suspended a hydraulic cylinder 40, by means of a connection 4| which acts also as a closure'for the upper end of cylinder 40. A piston rod 42, carrying a piston 43, is reciprocably mounted in the bore of cylinder 40 and extends downwardly therethrough to the exterior of the cylinder through a bottom closure 44 connected to the lower end of the cylinder. A load connecting hook 46, of suitable and more or less conventional form, is hingedly attached to the lower end of piston rod 42 by means of a hinge pin connection 46. Hook 45 is adapted for connection to the drilling string or other loads to be raised and lowered in connection with drilling operations. As shown in Fig. 3, particularly, hook 45 is connected to the bail 41 of a water swivel 48 which, in turn, is connected in the usual manner to the Kelley rod 49 of a drilling string extending through rotary table l into the well beneath (not shown).

Hollow cross connections 50 and 5| provide communication between the lower and upper ends, respectively, of cylinders 24 and 24a, the points of communication being, respectively, below and above the limits of reclprocation of pistons 21a. The bore of hollow leg 20a which supports cylinder 24a communicates through a flexible hose 52 with the lower end of the bore of cylinder 40 below the point of maximum downward travel of piston 43, and a pipe 53, supported along side hollow leg 20, communicates by means of a ilexible hose 54 with the upper end of cylinder 40 above the point of maximum upward travel of piston 43. A second pipe 55, also supported along side hollow leg 20 communicates with cross connection 5|.

A high pressure pump 56, preferably of the multi-stage centrifugal type, is mounted on base 3 and is driven from power shaft 1 by means of a suitable driving connection 51. The suction of pump 56 is connected at 58 with a tank 59 containing a supply of a suitable hydraulic iluid. The hydraulic fluid is discharged by pump 56 through a pipe 60 to a hollow supply header 6I which communicates through a nipple 62 with the interior of hollow trunnions I9 and thence with the bore of leg 20. A four-way control valve 63 is interposed in pipe 60 and has a branch connection 64 communicating with the lower end of pipe 55 which leads to cross-connection 5|. A return pipe 65, for the return of fluid from the several hydraulic cylinders, is connected to another of the outlets of control valve 63 and leads back to tank 59. A second hydraulic fluid circuit includes a pipe 66 connected to discharge pipe 60 and to a second four-way control valve 61, from one outlet of which a pipe 66 connects to the lower end of pipe 53. Another outlet of valve 61 is connected by a pipe 69 to a second supply header 61a connected by a nipple 62a to the bore of hollow leg 20a, and a third outlet of control valve 61 connects through a branch pipe 16 with the return pipe 65. A pipe 1|, having a control check valve 12 interposed therein, provides a continuous by-pass connection between discharge pipe'60 and tank 59. An operating handle 12a is used to adjust the rate of flow through check valve 12 and by-pass 1| to regulate the pressure on the system and the volume of fluid passing through control valves 63 and 61. A stand-by pump 13. driven from power shaft 1 by a drive connection 14, has a suction connection 15 to tank 59 and a discharge connection 16 to discharge pipe 66. A valve 11 is interposed in discharge connection 16 between stand-by pump 13 and discharge pipe 60 to permit cutting-1n and out of pump 13 in the hydraulic supply circuit. Control valves 63 and 61 have their inlet and outlet connections and ports so arranged that at one position of their operating handles the valves connect one end of their connected cylinders to discharge pipe 60, while simultaneously connecting the opposite ends of the cylinders with return pipe 65.

With respect to the operation of the device, above described, reference should also be had to the schematic arrangement illustrated in Fig. 5, the more significant parts of which bear the same identifying numerals as are applied to the corresponding parts in the other figures.

Assume it is desired to withdraw the string of drilling tools from a well. Piston rods 21 and cross head 29 willfbe in the fully retracted position shown in solid outlines in Figs. 1 and 3. Piston rod 42 will be fully extended, as shown in solid lines in Fig. 5, it being assumed that the aaoaaos upper end of the drilling string is momentarily at its lowest point above rotary table 4. Y Fluid prssure may be applied beneath piston 43 by lon from pipe 4l through control valve l1. pipe i9, the bore of leg lla and connection I2. At the same time iiuid is released from above piston 43 through connection I4, pipe I3 and back through return line CI to tank, these operations being' effected by suitable manipulation of valve il. The application of pressure beneath piston 43 reti-acts piston 42 in cylinder 4I raising hook 4l and the drilling string connected thereto. When this movement is com-y pleted, the portion of the drilling string so withdrawn may be broken-out in the usual manner and swung from the derrlclr while still attached to hook 45. This pipe handling operation is possible because of the flexible connection between cylinder 4I and cross head 2! provided by universal joint connectionv 3l. These operations may then be repeated until the string is completely removed, or partially removed, as desired, from the well.

If, however, it is desired to withdraw a greater length of the string than is eil'ected by the full stroke of piston rod 42. an additional length may be withdrawn after piston rod 42 has completed its retractive stroke, by then applying iluid pressure beneath pistons 21a in cylinders 25 and 25a and forcing the pistons and their connecting cross head upwardly for all or part of their stroke, cylinder 4I and its connected load being drawn up therewith for the additional distance represented by the stroke of piston rods 21. Fluid pressures for this operation will be supplied through the proper connections by suitable manipulation of control valve 63. Alternatively, if the shorter stroke only is desired, piston rod 42 may be left in extended position and pistons 21a moved to their extended positions, shown in dotted outlines in Fig. 3. Again, if the longer stroke is desired and the full power of all the hydraulic cylinders utilized at the same time, piston 43 may be retracted as described and pistons 21a extended, both operations being conducted simultaneously by suitable simultaneous manipulation of the control valv i3 and 61.

Any single one o'r any combination of these operations may be employed when running or pulling drill pipe, casing tubing or other tool strings. When drilling down, the operation may be begun by having pistons 21a in the fully extended positions and piston rod 42 in the fully retracted position, and allowing piston rod `42 to be extended and pistons 21a to be retracted under the weight of the string of drilling tools, pressure iluid being withdrawn simultaneously or sequentially from beneath the respective pistons during descent of the tools, or, if desired, pressure maybe applied above the several pistons if it is desired to drill down under pressure greater than that of the weight of the tools alone.

These and all other operations conventionally required about a drilling rig for hoisting and for some of the drilling operations may all be performed by suitable manipulation of the combination of hydraulic cylinders and pistons, arranged as described. It will be seen that great flexibility of operation is aiforded, and theA many advantages of smooth operation, close control of speeds, hoisting and braking prsures and other characteristics of hydraulic systems may be utilized to the fullest extent.

The nexible connection provided by the universal joint connection Il between the cross head member 2! and its depending cylinder 4l, which .is ordinarily the most actively used element of the cylinder will absorb all of the vibrational and I swaying movements normally incidentV to the various hoisting and drillingoperations about a drilling rig.

The provision of the rack-and-pinion connection between piston rods 21 and supported guides 3| is especially useful and important in insuring fully unified movement of the side pistons throughout all operations and even distribution of the load on the pistons. O therwise, unequal loading, for one reason or another, oi' the side pistons, might cause these pistons to move at unequal rates and result in destructive or injurious binding or jamming between the relatively moving parts.

The areas of the several pistons may be made of any suitable dimensions depending upon the loads to be handled and the manner of distribution desired. The areas of pistons 21a are ordinarily made equa1 to provide for equal distribution of the loads thereon, and their combined area will be suillcient to carry the full load for which the device is designed. Piston 43 is ordinarily made to have an area equal to the combined areas of pistons 11a, since in many operations, the cylinder 40 will be required to carry the full load on the device.

Cylinders 24 and 24a and hollow legs 24 and 20a constitute the front legs of the derrick structure in which much of the load, including the shock load ordinarily occurring during operation, is absorbed in the hydraulic cushion inside the cylinders on which the pistons are cushioned, thereby increasing the life of the structure and its members.

Fig. 6 illustrates the manner in which the hydraulic cylinders may be employed, without assistance from outside agencies, for raising and lowering the hoist device and the supporting structure. To lower the structure from the upright position to the lowered position,shown in dotted outlines in Fig. 6, a wire loop 1l, or other similar connection, is suitably connected at one end to the rear of the sub-base Structure and the other end is hookedto hook 45, piston rod 42 being in its fully retracted position. Fluid pressure is then released from beneath piston 43 and applied above the piston, causing piston rod 42 to be extended. The mast may be constructed so that the center of gravity is forward of the trunnions i9, causing the structure to tilt forwardly about trunnions I9 as pivots. Or the structure may be manually pushed or pulled past its center of gravity in order to start it on its downward movement. The iluid pressures on the opposite sides of piston 43 are then controlled through suitable manipulation of control valve 61 to allow the structure to be lowered of its own weight by the controlled-extension of piston rod 42. The structure may be `raised back to its upright position by applying iluid pressure so as to retract piston rod 42, which acting through the anchorage of hook 45 to the sub-base structure, will hydraulically raise the structure to the upright positie asoaaos Any desired speeds of operation or nuid pressures may be employed in effecting the various operations performed by the hydraulic device in accordance with this invention, by suitable manipulation and adjustment of valves i3 and B1 and check valve 12. Any suitable type of hydraulic nuid may, of course, be employed, and many other and varied operations in addition to those specifically described, may be performed by the combination of hydraulic cylinders and pistons heretofore described.

From the foregoing it will be seen that this invention provides a simplified iorm of hydraulic hoist, which is particularly adapted for use with well drilling rigs, which is comparatively inexpensive to construct and operate, which is simple in operation, and which eliminates all of the many heavy, complicated and expensive hoisting mechanisms and devices employed in connection with conventional drilling rigs.

What I claim and desire to secure by Letters Patent is:

1. In'a well drilling rig, a hydraulic draw works system comprising, in combination with a base member, a pair of laterally spaced hydraulic lifts vertically supported on said base member, a cross connection between said pair of lifts reciprocable thereby, means operatively associated with said cross connection for synchronizing the reciprocating movements of said pair of lifts, a third hydraulic lift suspended between said pair of lifts from said cross connection, a load connecting member reciprocably supported by said third lift, and means to supply actuating fluid to all of said lifts, said synchronizing means comprising a rack and pinion guide for each one of said pair of lifts, said pinions being carried on a common shaft extending transversely between the pair of lifts and rotatively supported thereon.

2. In a well drilling rig, a hydraulic draw works system comprising in combination with a base member, a pair of laterally spaced hollow leg members pivotally supported on said base member, a pair of laterally spaced hydraulic lifts vertically supported on said hollow leg members, a cross connection between said lifts reciprocable thereby, a third hydraulic lift disposed between said pair of lifts and swingingly suspended from said cross connection, a load connecting member reciprocably supported by said third lift, an actuating fluld circuit connected to said pair of lifts and including one of said hollow leg members in the circuit, a separate actuating fluid circuit connected to said third lift and including the other of said hollow leg membersI in the circuit, a common source of supply of said actuating fluid for both said circuits, and independently oper-v able control means in each of said circuits.

3. In a well drilling rig, a hydraulic draw works system comprising in combination withv a base member, a pair of laterally spaced hydraulic cylinders vertically disposed on said base member and pivotally connected thereto, an elongated frame connected to said pair of cylinders and adapted to pivot therewith on said base member, pistons reciprocably mounted in said pair of cylinders, piston rods connected to said pistons and extending upwardly from the upper ends of said pair of cylinders, a cross head connecting the upwardly extending ends of said piston rods and reciprocable therewith, a shaft extending parallel to said cross head and rotatably supported thereon, a pinion mounted on each endI of said shaft, vertically disposed guide racks engaging with said pinions for constraining synchronized movement of said piston rods, a third cylinder swingingly suspended between said pair of cylinders from said cross head, a third piston reciprocably mounted in the third cylinder and having a third piston rod connected thereto and extending downwardly from the lower end of said third cylinder, a load connecting member carried by the extended end of said third piston, an actuating fluid circuit connected to opposite ends of said pair of cylinders, a second actuating fluid circuit connected to opposite ends of said third cylinder, independently operable control means in each of said circuits, each of said control means being operable in its circuit to effect movement of the pistons responsive thereto in either direction at will, and a common source of supply of said actuating fiuid for both said circuits.

4. In a well drilling rig, a hydraulic draw works system comprising, in combination with a base member and a derrick structure uprightly disposed on said base member, a pair of laterally spaced hydraulic lifts vertically supported in said derrick structure, a cross connection between said lifts reciprocable thereby, athird hydraulic lift disposed between said pair of lifts and swingingly suspended from said cross connection, a load connecting member reciprocably supported by said third lift, means to supply actuating fluid to all of said lifts, and independently operable means for controlling the actuating fluid to said third lift, whereby the latter may be actuated independently of the movements of said pair of lifts.

5. A hydraulic hoist comprising, a pair of laterally spaced hydraulic lifts, a cross connection between said lifts reciprocable by the joint movements thereof, a rack and pinion guide for each one of said pair of lifts associated with the cross connection, said pinions being carried on a common shaft extending .transversely between the pair of lifts and rotatably supported thereon, a third hydraulic lift disposed between said pair of lifts, a universal joint member between said cross connection and said third lift, a load connecting member reciprocably supported by said third lift, and means to supply actuating uid to all of said lifts, said means including separate control means for the fluid going to said pair of lifts and for the fluid going to said third lift to independently control the movement of the respective lifts.

6. In a well drilling rig, a hydraulic draw works system comprising in combination with a base member, a pair of laterally spaced hydraulic lifts vertically supported on said base member, a 'cross connection between said lifts reciprocable by the joint movements thereof, a third hydraulic lift suspended between said pair of lifts from said cross connection, a load connecting member reciprocably supported by said third lift, and means to supply actuating fluid to all of said lifts, said means including hollow cross connections between the lower and upper ends of said pair of lifts and control means for selectively actuating said pair of lifts and said third lift to independently control movement of the respective lifts.

7. In a well drilling rig, a hydraulic draw works system comprising, in combination with a base member, a pair of laterally spaced hydraulic lifts vertically supported on said base member, a cross connection between said pair of lifts reciprocable thereby, a third hydraulic lift disposed between said pair of lifts and swingingly suspended from said cross connection by a universal joint member, said universal joint closing the upper end of said lift, a load connecting member reciprocably supported by said third lift, and means to supply asoases actuating fluid to all of said lifts, said means including hollow connections between the lower and upper ends of said lifts.

8. In a well drilling rig, a hydraulic draw works system comprising in combinationfwlth a base member, an elongated frame pivotally mounted on the base member, a pair of laterally spaced hydraulic lifts vertically supported on said frame, a cross connection between said pair of lifts reciprocable thereby, means operatively associated with said cross connection for synchronizing the reciprocating movement of said pair of lifts, a third hydraulic lift suspended between said pair of lifts from said cross connection, a load connecting member reciprocably supported by said third lift, and means for supplying actuating fluid to all of said lifts whereby said lifts may be selectively operated.

9. In a well drilling rig, a hydraulic draw works system comprising in combination with a base member, an elongated frame pivotally mounted on the base member, said frame including hollow legs, av pair of laterally spaced hydraulic lifts vertically supported on said legs, a cross connection between said pair of lifts reciprocable thereby, means operatively associated with said cross connection for synchronizing the reciprocating movement of said pair of lifts, a third hydraulic lift attached to and suspended between said pair of lifts from saidcross connection, a load connecting member reciprocably supported by said third lift, means for supplying actuating fluid to said pair of lifts through said legs, vmeans for supplying an actuating fluid to the third lift whereby said lifts may be selectively operated.

10. In a well drilling rig, a hydraulic draw works system comprising in combination with a base member, a pair of laterally spaced hydraulic cylinders vertically disposed on said base member, an elongated frameconnected to said pair of cylinders and adapted to pivot therewith on said base member, pistons reciprocably. mounted in said pair of cylinders,` piston rods connected to said pistons and extending upwardly from the upper ends of said pair of cylinders, a cross head connecting the upwardly extending ends of said piston rods and reciprocable therewith, a shaft extending parallel to said cross head and rotatably supported thereon, means mounted on each end of said shaft for constraining synchronized movement of said piston rods, a third cylinder swingingly suspended between said pair of cylinders from said cross head, a third piston reciprocably mounted in the third cylinder and having a third piston rod connected thereto and extending downwardly from the lower end of said third cylinder, a load connecting member carried by the extended end of said third piston, an actuating fluid circuit connected to opposite ends of said pair of cylinders, a second actuating fluid circuit .A....... and cylinder elements,vv one ofwhich is 'connected with the cross member, load connecting means carried by the other-element of the third lift. laterally arranged guide means -on one of said members, laterally arranged rolling means on the other member and having engagement with said laterally arranged guide means, and means interconnecting said rolling means for synchronizing movement of said interconnected elements'of the pair of lifts to maintain parallel relationship of said lifts.

12. A fluid hoist including mast and base members, a pair of hydraulic lifts each including a cylinder element and a piston element, an elongated frame connected to one element of each lift and adapted to pivot therewith on the base member, means interconnecting the other elements of said lifts including a cross member reciprocably responsive to movement of said elements, a third hydraulic lift including piston and cylinder elements, one of which is connected with the cross member, load connecting means carried by the other element of the third lift, laterally arranged guide means on one of the cross and mast members, laterally arranged rolling means on the other of said last named members and having engagement with said laterally arranged guide means, and means interconnecting said rolling means for synchronizing movement of said interconnected elements of the pair of lifts to maintain parallel relationship of said lifts.

13. A uid hoist including mast and base members, a pair of hydraulic lifts each including a cylinder element and a piston element, an elongated frame connected to one element of each lift and adapted to pivot on the base member, means ini to movement of said elements, a third hydraulic connected to opposite ends of said third cylinder,

member, means interconnecting the other elements of said pair of lifts including a cross member reciprocably responsive to movement of said elements, a third hydraulic lift including piston lift including piston and cylinder elements, one of which is connectedwith the cross member, the

cylinder of the third lift being of asize substantially equal to both of said pair of lifts, load connecting means carried by the other element of the third lift, laterally arranged guide means on one of the cross and mast members, laterally arranged rolling means on the other of said last named members and having engagement with said laterally arranged guide means, and means interconnecting said rolling means for synchronizing movement of lsaid interconnected elements of the pair of lifts to maintain parallel relationship of said lifts.

14. A fluid hoist including mast and base members, a pair of hydraulic lifts each including a cylinder element and a piston element, an elongated frame connected to one element of each lift and adapted to pivot on the base member, means interconnecting the other elements of said lifts including a cross member reciprocably responsive to movement of said elements, a third lift including piston and cylinder elements, one of which is pivotally suspended from the cross member, load connecting means carried by the other element of the last named fluid lift, laterally arranged guide means on,one of the cross and mast members, laterally arranged rolling means on the other of said last named members and having engagement with said laterally arranged guide means, and means interconnecting said rolling means for synchronizing movement of said interconnected elements of the pair of lifts to maintain parallel relationship of said lifts.

15. In a well drilling rig including a. derrick, a

hydraulic draw works system comprising, in comil bination Vwith a bese member. a pair of laterally spaced hydraulic lifts vertically supported by said base member. a cross connection between said pair of lifts reciprocable thereby, means operatively assoeiated with said cross connection for synchronixins the reciprocating movements of said pair of lifts, a third hydraulic lift suspended between said pair of lifts from said cross connection, a load connectinz member reeiprocably supported by said third lii't. and means to supply actuating uid t0 all 0f said lifts. said means to supply actuating fluid to all oi' said liits including separate control means for the iiuid going to said pair of lifts and for the fluid going to said third lift to independently control the move- 15 ments oi the respective lifts.

ERNIBT J. SHAFFER.

Remmers cnsn The following references are of record in the me of this patent:

UNITED STATES PATENTS Number Name Date 1,790,913 Grau et al Feb. 3, 1931 1,865,853 Granville July 5, 1932 1,884,752 Krueger Oct. 25, 1932 1,938,690 Burmist Dec. 12, 1933 2,179,557 Mason Nov. 14, 1939 2,334,312 Caldwell Nov. 16, 1943

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