US2859882A - Oscillating system for derrick booms - Google Patents

Description

Nov. 11, 1958 M. J. PURETIC 2,859,882

OSCILLATING SYSTEM FOR DERRICK BOOMS Filed July 2, 1957 2 Sheets-Sheet 1 ivy- INVENTOR Mane/ 0 J PMQEr/O ATTORNEY Nov. 11, 1958 M. J. PURETIC OSCILLATING SYSTEM FOR DERRICK BO OMS 2 Sheets-Sheet 2 Filed July 2, 1957 INVENTOR MAP/0 J. PueET/c ATTORNEY My 5 W.

limited State OSCILLATHNG SYSTEMFQR DEICK 'BOOMS Mario J; Puretic, Torrance, Calif.

Application July 2, 1957, Serial No. 669,620

10 Claims. (Cl. 212-66) This invention relates to hoisting apparatus primarily for use on shipboard and more particularly to a mechanism for automatically providing an oscillating movement to the boom of such hoisting apparatus in order to move the same back and forth through a predetermined are, such swinging movement being continuous and automatic.

Whilethe. apparatus of. this invention may be utilized in any installation whereit is desired to continuously and automatically oscillate the boom of a derrick through a predetermined arc, the primary purpose of this invention ,is to provide an apparatus for use in facilitating fishing operations in which a relatively long net, commonly called a seine, must be hoisted from the water and stacked on the deck of the fishing vessel. Heretofore, it has been customaryto hoist the seine from the water and to manually lay the same in folds on the deck of the vessel as the seine is lowered by the derrick, but since such seines are relatively heavy, considerable manual exertion is required on the part of severalmen and consequently, any apparatus which will perform this operation automatically thereby eliminating the necessity of manual operations will materially reduce the cost of such fishing operation.

It is accordingly an object of the invention to provide an automatic oscillating system for derrick booms which may be conveniently applied to existing equipment without material-modification thereof or which may be con veniently and economically included during the manufacture of such equipment.

A further object of the invention is the provision of an automatic oscillating system for derrick booms in whichthe are through which the boom oscillates may be conveniently adjusted andwith the center of such oscilla- 'tion disposed at any desired angular position.

A still further object of the invention is the provision of an automatic oscillating system for derrick booms in which fluid pressure maybe utilized to swing a boom to and fro through a predetermined arc and over any desired portion of the deck of a vessel or the surface below the boom.

Another object of the invention is the provisionof an automatic oscillating system for derrick booms in which double acting fluid pressure operated cylinders are utilized to swing the boom to and fro and in which the operation of such cylinders are automatically controlled by a simple atent o 2 ing the oscillating system of this invention andlfurther showing the arrangement of the cables utilized to swing the derrick boom from one side to the other;

Fig. 2 a side elevational viewshowinga portion of a derrick mast and boom, together with the oscillating systern of this invention .and the manner in which the sarne is installed;

Fig. 3 a sectional view taken. substantially on;.the line 33 of Fig. 2 andshowingthe valveactuating lever shifting'members disposed in position to maintain the boom substantially in a fore and aft position;

Fig. 4 a sectional view .taken substantially on .the' line d-4 of Fig. 2 and showing the valve actuating lever shifting members disposed in position to cause oscillationof the derrick boom through a predetermined arc and showing in dotted lines the extrerne positi onof the boom and shifting members prior to reversal of the oscillating mechanism;

Fig. 5 a fragmentary sectional view taken substantially on the line 5.-5 of Fig. 4 and showing the mechanism utilized to lock the shifting members in adjusted position; and

Fig. 6 a fragmentary sectional view taken substantially on the line 6-6 ,of Fig. 4 and showing the ,yieldable actuating lever engaging means on the shifting members.

With continued reference to thedrawing, th'ere is shown a derrick mast 10 upon which may bempunted atiany desired location a collar 11 which serves to pivotally support a king pin 12 for movementabout a vertical axis. King pin '12, may be provided at the upper end thereof with spaced ears 13 and a pivot pin 14extending,thro ugh the ears 13 serves topivotally mount the lower end j15 of a boom 16 for movement about a horizontal axis.

The boom 16 may beprovided with lugs 17 and 18 extending from opposite sides thereof adjacenttheflower end 15 and fluid pressure operated cylinder 19 maybe provided at the lower end with spaced ears 20 which are received over the 111517 and a fastening member21 extending through the ears'20 and'lug 17 serves to secure the cylinder 19 at the lower end to the boom 16. In a similar manner, a second fluid pressure operated cylinder 22 may beprovided with spaced cars .23 which are received over the lug 18 and pivotallysecured theretof by suitable fastening means 24 in order to secure the cylinder 22 to the boom 16 adjacent the lower endthereof.

Cylinder 19 may be provided with a double actingpiston 25 to whichis connected a ram 26 projectingfrom. the upper end of the cylinder 19 and at the. upper end of the ram 26 there is'mounte'd a pulley 27. Inja similar manner, the cylinder 22 may be provided with a double acting piston to which is attached a ram 28 extending from the upper end of the cylinder 22 and at the upper end of the ram 28 there is mounted a pulley .29.

As best shown in Fig. 1, the boom 16 may be provided at the upper or head end thereof with head pulleys 30 and 31 disposed on opposite sides of the boom 16 and a flexible cable 32 of suitable material is trained over the head pulley 3t and downwardly around .the pulley 27 on the ram 26 with the adjacent end33 of the. cable 32Qbejing attached to the boom 16 outwardly-of ,the outermost point of travel of the ram 26. The opposite end.3.4. of the cable 32 is secured to a fixed member 35, whichqin the case of a marineinstallation, may be az partof the boat on which the apparatus is installed. In asimilar manner, a flexible-cable 36is trained overthe head pulley 31 and downwardly around pulley 29 'on-the ram.28 with the adjacent end 37 of the cable 36 being attached .to theboom 16 at a point outwardly of the outermost 451"Fluid pressure operated cylinder 19 may be connected to ,the control valve 40 through suitable flexible jcon'duits 4mm 47 and the operation of cylinder 19 may .j 'oecontrolled by the actuating member 42. In a similar r smay be provided with a hand engaging knob "niahner, fluid pressure operated cylinder 22 may be con- "nected to the emitter valve 40 through suitable flexible "conduits" 48 and '49 and cylinder 22'may be controlled .by'tlie valve actuating'lever 43. A fluid pressure supply "conduit 50 maybe connected to any suitable fluid presfsure'sourc'e, such as a pump and to the valve 40 and a .1 fluid pressure discharge conduit 51 may also'be connected 'to' the control valve 40 and to a fluid pressure supply tank or sump to which the fluid pressure pump may be connected. I Since" the fluid pressure operated cylinders 19 and 22 are double acting, it will be seen that upon actuation of the valve actuating levers 42 and 43 in either direction, that fluid pressure will be introduced to the cylinders 19 and '22 to either project-the rams 26 and 28 therefrom orto retract such rams within the cylinders. As will be seen from an inspection of Fig. 1, retraction of the ram I 26 and projection of the ram 28 will serve to shorten the cable. 32 and, at the same time, lengthen the cable 36 thereby swinging the boom 16 toward the fixed member 35 and operation of the rams 26 and'28 in the opposite directions will serve to swing the boom 16 in the opposite direction toward the fixed member 39. The length of the arc through which the boom 16 moves will, of course, be controlled by the length of travel of the r'ams26 and 28 in the cylinders 19 and 22. In order to provide automatic operation of the actuating levers 42 and 43 to provide continuous automatic I oscillation of the boom 16, a substantially semi-circular plate 52'may be fixed to the king pin 12 by means of a set screw 53 or other suitable fastening means for move- "me'ntwith the king pin 12 during swinging movement of the boom 16. The plate 52 may also be retained on the lower end of the king pin 12 by means of a nut or other, suitable'fastening means 54. Adjacent theperiphe'ry of the semi-circular plate 52 there may be pro- "vided an arcuate slot 55 and a suitable degree scale 56 maybe provided on the plate 52 adjacent the slot 55. Y Asubstantially semi-circular opening 57 is provided in the plate 52 and the actuating levers 42 and 43 of the reversing valve 40 project upwardly through the opening 57 to permit free oscillating movement of the plate 52.

Opposed actuating lever shifting members 58 and 59 are disposed on opposite sides of the actuating levers 42 and 43 and the inner ends 60 and 61 of the shifting members 58 and 59respectively are mounted for free pivotal 'movement on the king pin 12 above the semi-circular f plate 52. Shifting member 58 is provided adjacent the outer'en'd 62 thereof with clamp means comprising a "bolt" 63 extending downwardly through the slot 55 in the plate 52, there being provided at the lower end of the bolt 63 a head 64 and a washer 65 engaging the lower surface ofthe plate 52. A finger engaging knob 66 is threadedly received on the upper end of the bolt 63 and serves to clamp the shifting member 58 in adjusted angular position with relation to the semi-circular plate 52. In a similar manner, the shifting member 59 is provided adjacent the outer end 67 thereof with a bolt 68 I extending through the slot 55 in the plate 52 and a finger H engaging knob 69 threadedly engaging the upper end of the .;bolt 68 s erves to clamp the shifting member 59' in 4 I adjusted angular position with relation to the semi-circular plate 52.

Shifting member 58 may be provided with actuating lever engaging means 70 and 71, while shifting member 59 may be provided with actuating lever engaging means 72 and 73. Each of the actuating lever engaging means may be similarly constructed and as best shown in Fig. 6, such means may comprise a plunger 74 slidably received in a bore 75 in-the shifting members 58 and 59 and sliding movement of the plunger 74 may be restricted by a pin 76 disposed in a slot 77. Other means for restricting movement of the plunger 74 may, of course, be employed if desired. The plunger 74 may be yieldably urged to outer position by a compression spring 78 disposed in the bore 75 and engaging the plunger 74 and the tension of spring 78 may be conveniently controlled by a screw threaded member 79 threadedly received in the shifting members 58 and 59 and provided with a washer or other, suitable means 80 engaging the compression spring 78. The screw threaded member 79 may be provided with a wrench receiving portion 81 to permit convenient adjustment thereof.

In the operation of the apparatus of this invention, the shifting members 58 and 59 may be set at any desired angular position, as shown in full lines in Fig. 4, and it may be assumed that the valve actuating levers 42 and 43 are in neutral position and the boom 16 in a fore and aft position. It is also to be assumed that fluid pressure is supplied in the valve 40 through the conduit 50 and when it is desired to place the apparatus in operation, the hand engaging knobs 44 and on the actuating levers 42 and 43 may be moved in one direction to introduce fluid pressure to the cylinders 19 and 22 thereby resulting in swinging movement of the boom 16 in one direction. Assuming that the actuating levers 42 and 43 are moved toward the shifting member 59 as viewed in Fig. 4, this will result in movement of the boom 16 in a counter-clockwise direction until the actuating levers 42 and 43 are engaged by the means 72 and 73 on the shifting member 59 which will result in moving the actuating levers 42 and 43 to a position to'reverse the operation of the cylinders 19 and 22 thereby swinging the boom 16 in the opposite direction. The position at which movement of the actuating levers '42 and 43 takes place to reverse the swinging movement of the boom 16 is shown in dotted lines in Fig. 4. Upon completion of the movement of the boom 16 in the opposite or clockwise direction as shown in Fig. 4, the actuating I boom 16 in the opposite direction. This oscillating movement of the boom 16 will automatically continue until such time as the actuating levers 42 and 43 are manually moved to neutral position.

It will therefore be seen that a seine suspended from the head or upper end of the boom .16 and being continuously hoisted from the water and lowered toward the deck of the vessel will be laid in folds on the deck of the vessel and set in a uniform manner.

When it is desired to secure the boom 16 in a fore and aft position upon completion of fishing operations or for any other purpose, the shifting members 58 and 59 may be disposed in the position shown in Fig. 3 in which, the actuating levers 42 and 43 are simultaneously engaged by the means 70 and 71, as well as the means 72 and 73 on both of the shifting members 58 and 59.

This, of course, will operate to maintain the levers 42 and 43 in neutral position.

4, the swinging movement of the boom 16 will be uniform about a fore and aft line, but, of course, if desired, the Q shi ting m m er 5% an 5 a b ag iv t s tq-gw a-swingingmovement centered about a linerat an angle to the fore and aft line of the vessel.

It will, therefore, be seen that the apparatus of this invention will operate to eflicien'tly stack a seine on the deck of a vessel in folds of any desired length and will thereby eliminate the necessity of manual handling of the net during recovery thereof from the water thereby materially reducing the cost of fishing operations.

While the apparatus of this invention has been described primarily for use on a fishing vessel, nevertheless,-it will be obvious that the same may be utilized for any installation where a continuous automatic or mauual oscillation of the boom of aderrick is required or advantageous and the apparatus of this invention is=of such nature, that the same may be conveniently installed on any-existing derrick, installation or,'of course, may be incorporated in new installations.

Itwill be obvious tothose skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown inthe sure cylinders mounted on opposite sides of said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to the upper end of said boom on opposite sides, a pair of cables trained over .said head pulleys and around the pulleys on said ram with the adjacent ends of said cables fixed to said boom outwardly of the outermost point of travel of said rams, the opposite ends of said cables beingfixedattransversely spaced points in alignment with said king pin, a reversing control valve for each cylinder, conduits connecting 'said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected 'to said valves, an actuating lever on each valve, a sub stantially semi-circular plate fixed to said king pin for movement therewith, an arcuate slot in said plate adjacent the periphery, a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means at the opposite end of each member extending through said slot for fixing each member in adjusted angular position and yieldableactuating lever engaging means on each member whereby said levers and control valves will be periodically actuated to alternately connect said fluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said members on said plate.

2. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom pivotally connected at the lower end to said king pin for movement about a horizontal axis, a pair of double acting fluid pressure cylinders mounted on opposite sides of said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to the upper end of said boom on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said 'boom outwardly of the outermost point of travel of said rams, :the opposite ends of said cables being fixed at :transversely spaced points in alignment with said king 6 pin, a reversing. control valve for each .cylinder, conduits connecting said cylindersand said valves, a fluid pressure supply conduit and a fluid pressure discharge .conduit connected to said valves, an actuating lever on each valve, a substantially semi-circular plate fixed to said king pin for movement therewith. an arcuate slotin said plate, a substantially semi-circular opening .insaid plate through which said actuating levers project, opposedtactuating levershifting members disposed on opposite'sides of said actuating levers, said members being vmounted at one end for free pivotal movement on "said kingpin, clamp means at the opposite :end of each member extending through said slot for fixing each :member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be periodically actuated toalternatelyconnectr said fluid pressure supply conduit to saidrcylinders to'lengthen and shorten said cables thereby continuously and 'automatically swinging said boom back and forththrough'an are determined by the position of said members onsaid plate.

3. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on opposite sides of said 'boom adjacent the lower end, a ram projecting fromthe upper end of each cylinder, a pulley on the upperend of each ram, a pair of head pulleys secured to "the upper end of said boom on opposite 'sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom outwardly of the outermost pointoftravel of said rams, the oppositeends of said cables'being fixed at transversely spaced points in alignment-with said kiug pin, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fiuidpressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating'lever on each valve, a substantially semi-circular plate fixed -to said king pin for movement therewith, an arcuate slot 'in' said plate, a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted-at one end for free pivotal movement on said king pin,

. clamp means at the opposite end of each member extending through said slot for fixing each member in adjusted angular position and actuating leverengagingmeans on each member'whereby said levers and control valves will be periodically actuated to alternately connect said'fiuid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forththrough an ail'c determined by the position of said members on said p ate.

4. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at'the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on opposite sides of said boom adjacent thelower end, a ram projecting fromthe upper end of each cylinder, a pulley onthe upper end of each ram, a pair of head pulleys secured to the upper end of said boom on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom outwardly of the outermost point of travel of said rams, the opposite ends of said cables being fixed at transversely spaced points, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and afluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a substantially semi-circular plate fixed to said king pin for movement therewith, an arcuate 7 slot in said plate, a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposlte sides of said actuating levers, said members being mounted at one end for free pivotal movement on said 'king pin, clamp means at the opposite ends of each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be periodically actuated to alternately connect said fluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said members on said plate.

5. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on opposite sides of said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to the upper end of said boom on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom outwardly of the outermost point of travel of said rams, the opposite ends of said cables being fixed at transversely spaced points, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate, a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means at the opposite end of each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be periodically actuated to alternately connect said fluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said members on said plate.

6. An automatic oscillating system for derrick booms,

said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid -.pressure cylinders mounted on opposite sides of said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to said boom on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent .ends of said cables fixed to said boom outwardly of the outermost point of travel of said rams, the opposite ends of said cables being fixed at transversely spaced points,-a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate, a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating levers shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means at the opposite end of each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will ,be periodicallyactuated to alternately connect saidfluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said members on said plate.

7. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on opposite sides of: said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to said boom on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom, the opposite ends of said cables being fixed at transversely spaced points, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate,'a substantially semi-circular opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means at the opposite end of each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be periodically actuated to ultimately connect said fluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said member on said plate.

8. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on opposite sides of said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on theupper end of each ram, a pair of head pulleys secured to said boom 1 on opposite sides, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom, the opposite ends of said cables being fixed at transversely'spaced points, a reversing control valvefor each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate, an opening in said 7 V plate through which said actuating levers project, op-

posed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means on each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be periodically actuated to alternately connect said fluid pressure supply conduit to said cylinders to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on said boom adjacent the i lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to said boom, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom, the opposite ends of said cables being fixed at transversely spaced points on opposite sides of said boom, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on said valves, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate, an opening in said plate through which said actuating levers project, opposed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin, clamp means on each member extending through said slot for fixing each member in adjusted angular position and actuating lever engaging means on each member whereby said levers and control valves will be actuated to alternately connect said fluid pressure supply conduit to said cylinders, to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an arc determined by the position of said members on said plate.

10. An automatic oscillating system for derrick booms, said system comprising a king pin mounted for pivotal movement about a vertical axis, a boom connected at the lower end to said king pin, a pair of double acting fluid pressure cylinders mounted on said boom adjacent the lower end, a ram projecting from the upper end of each cylinder, a pulley on the upper end of each ram, a pair of head pulleys secured to said boom, a pair of cables trained over said head pulleys and around the pulleys on said rams with the adjacent ends of said cables fixed to said boom, the opposite ends of said cables being fixed at transversely spaced points on opposite sides of said boom, a reversing control valve for each cylinder, conduits connecting said cylinders and said valves, a fluid pressure supply conduit and a fluid pressure discharge conduit connected to said valves, an actuating lever on each valve, a plate fixed to said king pin for movement therewith, an arcuate slot in said plate, an opening in said plate through which said actuating levers project, op osed actuating lever shifting members disposed on opposite sides of said actuating levers, said members being mounted at one end for free pivotal movement on said king pin and clamp means on each member extending through said slot for fixing each member in adjusted angular position whereby said levers and control valves will be periodically actuated to alternately connect said fluid pressure supply conduit to said cylinders, to lengthen and shorten said cables thereby continuously and automatically swinging said boom back and forth through an are determined by the position of said members on said plate.

References Cited in the file of this patent UNITED STATES PATENTS 400,798 Russell Apr. 2, 1889 497,216 Rogers May 9, 1893 665,684 Hetlesaeter Jan. 8, 1901 2,021,066 Huxford Nov. 12, 1935

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