US3446362A

US3446362A - Derrick for ships

Info

Publication number: US3446362A
Application number: US655715A
Authority: US
Inventors: William L Banks Jr
Original assignee: TESTING ASSOCIATES Inc
Current assignee: TESTING ASSOCIATES Inc
Priority date: 1967-07-10
Filing date: 1967-07-10
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27

Description

May 27, 1969 w. L. BANKS, JR

DERRICK FOR SHIPS Sheet I Filed July 10. 1967 JNVE'NTUR B W/Z LIA/7 L. BANKj'J/P.

AGENT May 27, 1969 w. L. BANKS, JR

DERRICK FOR SHIPS Sheet Filed July 10, 1967 May 27, 1969 w. L. BANKS, JR

7 DERRICK FOR SHIPS Sheet Filed July 10. 1967 7, 1969 w. L. BANKS, JR 3,446,362

DERRICK FOR SHIPS Filed July 10, 1967 JNVE/V TOR WILL/Al? L. BANK-5J1? en M AGENT United States Patent US. Cl. 212-3 8 Claims ABSTRACT OF THE DISCLOSURE upon turning winch drums afiixed on deck or below deck,

said derrick providing a lifting movement of the boom and said turntable mounted around the base of the mast to support the lower end of the boom and permit a rotation of the base of the boom around the mast.

This invention relates to a derrick or cargo hoisting device for ships and more particularly to an improved hoist and the manner of rigging the boom and hoist to produce the necessary positioning and movement of the boom in lifting and swinging the cargo in a rotary movement into a desired position.

This invention is related to my issued Patents 2,830,710 issued April 15, 1958 and 2,944,680 issued July 12, 1960.

In the operation of a single boom of a derrick due to the hazardous conditions that exist on shipboard whether the ship is docked or at sea, it has been necessary to provide guy ropes so that a definite control of the swinging movement of the boom is retained at all times. Likewise in burtoning gear where two booms are utilized, guy ropes are provided for each boom so that the cargo handled between booms can be very carefully positioned and an absolute control of the swinging movement of both booms is retained at all times. In the present invention the rigging of the boom has been changed to provide the same degree of control on the swinging movement of the boom without the use of guy ropes.

It is an object of this invention to provide a derrick for a ship in which the rigging is comprised of a double topping lift to produce the necessary lifting movement of the boom and a controlled swinging range of the boom over 360.

It is a further object of this invention to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at the free end and is connected to a pair of swinging swivel elements that are spaced apart and attached to the top of the mast at either side thereof.

It is a further object of this invention to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at the free end and is connected to a pair of swinging swivel elements that are connected to the top of the mast and positioned either side of the boom and in which a topping lift may swing through 90 to a null point and be forced through its null point to swing an additional 90".

It is a further object of this invention to provide a derrick for a ship in which the boom is mounted at its base on a turntable whose center is the mast center and in which the pivotal supporting attachment for the rigging is positioned either side of the mast and in which the rigging includes a double topping lift to produce the necessary lifting movement of the boom and a controlled swinging range in an arc of 360.

It is a further object of this invention to provide a derrick for a ship in which the boom is mounted at its base on a turntable that is positioned about the mast center and in which the pivotal supporting attachment for the rigging is positioned either side of the mast and in which the rigging includes a double topping lift to produce the necessary lifting movement of the boom and a controlled swinging range in an arc of 360.

It is a further object of this invention to provide a derrick for a ship in which the boom is mounted at its base on a turntable whose center is the mast center and in which the pivotal supporting attachment for the rigging is a pair of swivel elements that are positioned either side of the boom and attached to the top of the mast and in which this rigging is a double topping lift to produce the necessary lifting movement of the boom and a controlled swinging range in an arc of 360.

It is a still further object of this invention to provide a hoisting apparatus for a ship in which the boom is mounted at its base on a turntable whose center is the mast center and in which a pair of swivels are mounted at the top of the mast on either side thereof and in which the rigging and the swivels are the double topping lift and in which the double topping lift is connected to the boom at one end thereof and is connected to the pair of swivel elements that are spaced apart either side of the mast to swing through 360.

A still further object of this invention is to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at one end thereof and is connected to a pair of swinging swivel elements that are spaced apart either side of the mast and attached to a mast housing at the top of the mast and in which the double topping lift includes two lines to a turning drum affixed on deck and in which the two lines are rove on the winch drum in opposite directions so that the drum produces a shortening or lengthening of the lines to provide a bridling effect on the boom head.

A still further object of this invention is to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at one end thereof and is pivotally connected to a mast housing at the top of the mast and in which the double topping lift includes two lines to a turning drum afiixed on deck or in the hold and in which the two lines are rove on the winch drum in opposite directions so that the drum produces a shortening or lengthening of the lines to provide a bridling effect on the boom head.

It is a further object of this invention to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at one end thereof and is pivotally connected to a pair of swivel elements that are spaced apart either side of the mast at the top of the mast and in which the double topping lift includes two drums afiixed on deck or in the hold for the hauling operation and in which the two drums are operated on a shaft so that the boom may be topped or lowered while swinging and in which the hauling line also is rove on a winch drum in opposite directions so that the drum produces a shortening or lengthening of the lines to provide a swinging of the boom in either direction while being topped or lowered.

it is a further object of this invention to provide a hoistlng apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at one end thereof and is connected to a pair of swivel elements that are spaced apart either side of the mast and pivotally attached to a mast housing and in which the double topping lift includes two drums afiixed on deck for the houling operation and in which the two drums are operated on a single shaft so that the boom may be topped or lowered while swinging and in which the topping lift includes two lines that are rove on a winch drum in opposite directions so that the drum produces a shortening or lengthening of the lines to provide a swinging of the boom inboard either side of the outboard position.

It is a further object of this invention to provide a hoisting apparatus for ships in which the rigging is comprised of a double topping lift and in which the double topping lift is connected to the boom at one end thereof and is connected to a pair of swivel elements that are spaced apart either side of the mast and at the top of the mast and in which there are provided sheaves, two for each swivel arm, and in which the double topping lift includes two lines that are rove on a winch drum in opposite directions so that the drum produces a shortening or lengthening of the lines to provide a swinging of the boom in either direction.

A further object of this invention is to provide a derrick for a ship in which the rigging is comprised of a double topping lift on top of the mast to produce the necessary lifting movement of the boom and a controlled swinging range of the boom and in which all rigging lines are internal passing from below deck through the hollow center of the mast.

It is an object of this invention to provide a derrick for a ship in which the rigging is comprised of a double topping lift to produce the necessary lifting movement of the boom and a turntable mounted around the base of the mast to support the lower end of the boom and permit a rotation of the boom around the mast.

It is a still further object of this invention to provide a derrick for a ship in which the rigging is comprised of a double topping lift to produce the necessary lifting and slowing movement of the boom and in which the double topping lift includes two swivel arms that are spaced apart either side of the mast and at the top of the mast and in which said boom may be swung 90 either side of said mast with said slowing control to reach a null point which is the limit of the swinging or rotation by said control and in which auxiliary means are provided to carry the pivotally moving topping lift arm through the null point to allow said arm to drop in said next sector of rotary control and resume the slowing control.

Other objects of this invention may be apparent by reference to the accompanying detailed description and the drawings in which FIG. 1 is a side elevational view of the cargo hoisting device,

FIG. 2 is a front elevational view partially in cross section taken on line 2-2 of FIG. 1,

FIG. 3 is a plan view taken on line 3-3 of FIG. 1,

FIG. 4 is an enlarged exploded view partially in cross section of one side of the mast head housing and swivel arm taken on line 4-4 of FIG. 1,

FIG. 5 is an enlarged elevational view taken on line 5-5 of FIG. 1,

FIG. 6 is a plan view taken on line 6-6 of FIG. 5,

FIG. 7 is a side elevational view taken on line 7-7 of FIG. 6,

FIG. 8 is a schematic illustration of a further embodiment of the mast head housing,

FIG. 9 is a schematic illustration of the tackle cables in front elevation,

FIG. 10 is a side elevational view on line 10-10' of FIG. 6,

FIG. 11 is a schematic wiring diagram showing a motor drive clockwise, and

FIG. 12 is a schematic wiring diagram showing a motor drive counter-clockwise.

Referring to FIGS. 1, 2 and 3 there is illustrated a hol low ship mast 10 in which a mast housing 11 is mounted at the top of the mast. A turntable 12 is affixed in a stationary relationship at or near the base of the mast. The turntable 12 is provided with a rotatable ring 13 surrounding the mast and supported on rollers 12A on the turntable 12. The turntable ring 13 is provided with a pair of pivotal supports 14 on either side of the mast in aligned relationship for mounting the base of the boom 15, the boom 15 formed as a two pronged fork, each prong 14A provided with a clevis end 14B so that the end may be pivotally attached and supported on the pivotal supports 14 of the ring 13. This permits a rotation of the base of the boom 15 about mast 10 and with the pivotally supported heel or lower end of the boom permits a swinging and lifting movement of the boom in its normal operation. Boom 15 at its top end is provided with a yoke 16 that is pivotally attached to the end of the boom. Yoke 16 is comprised of two arms 16A and 16B that are pivotally movable about a pin 17. Each of the arms 16A and 16B are provided with

single blocks

18A and 18B. The boom 15 at its upper end is also provided with a single block 19. The mast housing 11 is permanently aflixed to the top of the mast 10. The mast housing 11 is formed boxlike with parallel sides 11A and 11B on either side of the mast. These sides 11A and 11B are used to mount a pair of topping lift arms 20 and 21 while the top of the housing 11 supports a single block 22 that is used to support the purchase cable 23 that passes through the center of the hollow mast 10 to a sheave 24 at the base or under mast 10 and in turn is mounted upon a takeup winch 25 that controls the lifting and lowering by the purchase cable 23. Purchase cable 23 extends from the top of the mast over the single block 19 in the boom to a double block which supports the cargo or derrick hook 31, the purchase cable extending from block 30 to a single block 18B and back down to be affixed to the supporting framework of 31 which supports block 30. Thus when winch 25 is rotated to take in the purchase cable, hook 31 will be raised. While, if winch 25 lets out cable 23, book 31 will drop. Another form of mounting the purchase cable when only 180 of travel is required is also shown in which the cable from winch 25 extends through the deck not through the mast passing over a pulley 70 that is mounted to turntable 12. Cable 23 may then extend parallel to the boom 15 passing over the block at 18B and extending down to the block 30 of the hook 31 and extending back up to block 18B. Thus when winch 25 takes up cable 23, it will lift hook 31 or when cable 25 is let out, it will drop hook 31. The mast housing 11 (FIGS. 4, 5, 6 and 7) is provided with rotary mounted supports 32 on either side 11A and 11B of the mast. The rotary support 32 extends through a bore 33 in the housing with a hollow stem 34 and is supported by a bearing 35 to be freely rotatable in the bore 33. To retain rotary support 32 in this relationship, there is a spacer 36 and a nut 37 threadably secured to the end of the stem 34. Element 32 can rotate 360. Element 32 is provided with a pivotal pin support 38 used to pivotally attach the topping lift arms 20 and 21, the topping lift arms 20 and 21 having a pin 39 that passes through support 38 'as well as two supports 40 and 41 on the topping lift arm. The rotary support 32 is also provided with a pair of supports 42 to support a pm 43. Pin 43 supporting a pair of

sheaves

44 and 45 which is a double block arrangement to carry the topping lift cable. The topping lift includes a pair of arms 20 and 21. At the upper end of arms 20 and 21 there is provided a swivel support element 56, element 56 provided with a stem 57 that extends into arm 20 and is anchored within arm 20 by a block 58 and nut 59 that is threadably secured to stem 57. Element 56 at its outer end supports a double block consisting of two sheaves 54 and 60. If we refer to FIG. 9 and consider a single cable 46, we may assume that the cable 46 has been rove on the drum of the winch 48A. The cable may be passed around a lead sheave 62A up the mast through the further lead sheaves 61A, 44A and through the topping lift arm 20 through lead sheave 60A extending to the single block 18A at the top of the boom and from the block 18A the cable will go back over a lead sheave 54A and continue over a lead sheave 45A and continue over a lead sheave 50A and down the mast and pass in a clockwise direction around the drum of winch 65 for two or three or more turns and the cable 46 will extend from the drum of winch 65 up the mast over a lead sheave 50B over a second lead sheave 458 through the topping lift arm over a lead sheave 5413 up to the single block 18B at the top of the boom extending from block 18B down over a lead sheave 60B over lead sheave 44B and 61B and down through the mast to a lead sheave 628 to the drum of winch 4813 to be rove on this drum in the same direction as the cable is rove on drum 48A. This completes the tackle for operating the movement of the boom 15. It is apparent that the operation of the winch drums 48A and 48B in a clockwise direction will take up cable or line and thus produce a shortening of the topping lift which in turn produces a lifting of the boom 15 while operation of the winch drums 48A and 48B in a counter-clockwise direction will release cable 46 lengthening the topping lift and allowing boom 15 to drop. With the winch drums 48A and 48B stationary, it is apparent that operation of the winch drum 65 clockwise will affect a movement of cable 46 producing a pull on the one side of the topping lift to the boom while releasing the cable 46 on the opposite side of the topping lift to boom 15. This will therefore produce a swinging movement of boom 15 and the direction of movement will be based upon the direction of rotation of winch 65. A clockwise rotation may produce a swinging of the boom to the right of a center position while a counter-clockwise rotation may produce a swinging of the boom 15 to the left to center position. The degree of swinging movement of boom 15 is not limited due to the fact that, if the boom is swung to the right 90, it reaches a null point and the boom should be in a raised positioned at the null point. It is apparent that the base of the boom will likewise move to this position as it is free to rotate. With means to be described later, the boom may be carried past the null point. To continue rotation in a further 90 sector, the winches 48A and 488 must be reversed thus letting out cable on the one side to allow the boom to drop while continuing to swing in a rotation to the right while taking in cable on the opposite side of winch 65. Thus it is apparent that boom 15 may be controlled in its movement 90 either side of its starting position and the boom 15 may be raised on either side to its full 90 or null point and, by auxiliary means to be described, carried over the null point and due to the rotation of the base of the boom, it is in a new position to continue operation of the boom for 90 either side of the null point established. It is to be further noted that, although the boom may swing from a starting position 90 and reaching a null point, swing an additional 90, it is not intended that the boom continue to rotate in one direction about mast but rather that the boom may be swung either side of mast 10 to reach a position 180 from its starting position. It is to be noted, referring to FIG. 1, that the topping lift arms 20 and 21 may swing from a starting position in which the boom is dropped to its lowest horizontal position and in lifting boom either side of mast 10 to an upright vertical position and moving past the null point may be dropped on the opposite side dropping the boom to its lowermost horizontal position thus completing an arc with the boom of 180. The rotation of the base of the boom permits this operation without hindrance. The boom 15 may be rotated 180 as illustrated in FIG. 3 in a smaller are as illustrated in a dotted line YY. It is to be noted that the boom 15 is longer than the mast 10 thus it will extend in its raised position to a greater height than the top of the mast thus the pivotal mounting of the topping lift arms is most important. This pivotal connection permits the topping lift arms 20 and 21 to move in an arc shown by dotted lines ZZ, FIG. 1, so that the end of the boom may move from any position well above the end of the mast to a horizontal position that is parallel with the deck of a ship and in any position, the topping lift will produce a straight pull from the ends of the topping'lift arms. It is to be noted in FIG. 1 with the raising of the boom 15 when boom 15 rises, the swivel arms 20 and 21 are pivotally moved to provide a direct pull upon the end of the boom and since the boom is longer than the mast, as the boom continues to rise, the topping lift arms 20 and 21 continue to move counter-clockwise until the boom reaches a vertical position. However winch 65 must be operated to move the boom either to the left or to the right to reach the vertical position which is the null point on the operation of the boom and the limit of travel by

winches

48A and 48B. From this null point the winches must be reversed to either drop the boom back in the same sector or having passed the null point, to drop the boom back in the next 90 sector. The topping lift arms can work together in their movement with a straight lift as in FIG. 3 from a horizontal position moving up, but when the boom is swung say counter-clockwise, the left hand lift 20 will pull while the right 'hand lift 21 lets out cable thus 20 will rise while 21 will lag or remain. The position of the boom when in the middle of the starting sector will be an equal pull by both topping lifts. If the boom is swung counter-clockwise, arm 20 pulls or takes in cable while arm 21 lets out an equal amount of cable. If the boom is rising while swinging, arm 20 will rise with the rise of the boom and will lift as shown in dotted lines but arm 21 will lag as it lets out cable for swinging and will not lift because it is letting out cable, thus arms 20 and 21 will not be aligned until the base of the boom moves to follow the swing and the arms again equalize their lift. With the topping of the boom when it reaches its 90 travel, it reaches a null point and the arm 20 cannot pull any further and the cable has reached the end of its pulling. At this point an additional force is required to carry the topping lift 20 past the null point. The additional force is provided by the mechanism shown in FIGS. 5, 6, 7, 10 and the circuit diagrams of FIGS. 11 and 12. If the arm or lift 20 is rotated until it reaches the null point, the winch must be reversed so that the cable is then payed out to allow the boom to fall into the next 90 sector for its swing. The base of the boom will rotate on the turntable following the swing of the boom, and finally both arms will be equalized in their supporting position.

Although the movement of the boom from horizontal to vertical is quite simple, the swinging of the boom 90 either side of a starting center presents problems. We find the upright dead center position much too sharp with an almost direct pull from the top of the mast. To improve upon this vertical plane of rotation of the base of the topping lift arms, the further embodiment shown in FIG. 8 may be utilized. With the faces 11A and 11B set at an angle to the centerline of the mast, that is spaced further apart at the top, the base of each topping lift will swing in a plane that is at an angle to the centerline of the mast. This keeps the topping lift when at its highest point out and away from the central pull of the cable coming out of the mast and improves the control.

Referring to FIGS. 5, 6 and 7 there is illustrated one approach to provide the means to carry the topping lift arms 20 or 21 past the null point and in turn carry the boom past the null point for operation in the next 90 sector. The rotary supports 32 provide an additional func tion, they are formed in their periphery as a gear or gear segment 32A. A reversible motor 80 is mounted on top of the mast head housing 11. The reversible motor 80 is provided with a pair of centrifugal clutches 81 so that the motor drive produces engagement of the clutch and relaxing of the clutch with the motor drive stopping. Thus :motor 80 may drive a shaft 81 on either side of motor 80, shaft 81 being supported in a bearing 82, shaft 81 extending into a gear reduction housing 83, shaft 81 being afiixed to a pinion gear 84 within housing 83, pinion gear 84 meshing with a reduction gear 85 also within housing 83, gear 85 being mounted on a shaft 86, shaft 86 being supported in a bearing 87, shaft 86 having at its other end a pinion gear 88, gear 88 meshing with the periphery gear 32A thus providing the means of driving the rotary support 32 through an arc of rotation, that is, the actual drive is picked up at a selected point as illustrated in FIG. 10. With the rotation of the rotary support 32 clockwise, a pair of mechanically actuated switches A & C are provided and are mounted on the faces 11A and 11B while an actuating roller 90 is aflixed to the apron of the rotary suuport 32 to be rotated with the rotation of gear 32A. As the arm or 21 rises to ward the null point, it will reach a sector S-S which establishes the positioning points for switches A & C so that as the rotary support 32 rotates clockwise, roller 90 will contact switch A pivotally flipping switch A from its off position to its on position. This energizes motor 80 according to the circuit shown in FIG. 11, that is, with the motor 80 connected to a contact 92, switch A will move a contact arm 93 from its oif position to its on position closing the circuit through a line 94 through battery B to a ground. The opposite side of motor 80 is connected through switch C through a switch arm 95 to ground. The motor 80 when energized will operate and cause its centrifugal clutch 80A to engage and rotate shaft 81 and in turn gear 84 which rotates gear 85 at a reduced speed, gear 85 in turn rotating gear 88 which engages gear 32A of the rotary support thus carrying arm 20 or 21 as the case may be in a continued clockwise direction through the null point and after passing the null point, the roller 90 will contact switch C flipping or pivotally moving switch C from its on position or grounded position to its off position as shown in FIG. 11. When 95 is pivotally moved, it also moves an arm 96 which is connected to ground on one side and closes a circuit through contact 97 and line 98 to the winch motor 65M. The opposite side of winch motor 65M is connected through a line 99 to battery B and ground. Thus winch 65 may be operated after the arm 20 or 21 is carried through the null point to continue rotation and movement of the boom in the next sector of operation. If motor 80 is reversed, that is, if arm 20 or 21 is now to be rotated counter-clockwise, the rotary support 32 will rotate counter-clockwise under the drive of winch 65 and motor 65M. When roller 90 contacts switch C, it will pivotally move switch C from its off position to its on position closing arm 100 to contact 101 closing the circuit from motor 80 through the battery to ground, the opposite side of motor 80 being connected through a switch arm 102 to ground to rotate motor 80 in a counter-clockwise direction. Motor 80, through its centrifugal clutch 80A, will, as in the previous sequence, drive shaft 81, gear 84 to in turn drive gear 85 and gear 88 to in turn drive the gear 32A to move the arm 20 or 21 in its clockwise movement through the null point. When arm 20 or 21 moves through the null point, roller 90 will contact switch A pivotally moving switch A from its on position to its off position. When arm 102 is moved, it also moves an arm 103 which is connected to ground on one side and closes a circuit through contact 104 and line 105 to the winch motor 65M. The opposite side of winch motor 65M is connected to a line 99 to battery B and ground. Thus winch 65 may be operated after the arm 20 or 21 is carried through the null point to continue rotation and movement of the boom in a counter-clockwise movement in the next sector of operation. Thus the movement of arm 20 or 21 by means of winch 65 either clockwise or counter-clockwise reaches a range of operation in the proximity of the null point where the reversible motor 80 takes over and 65 reaches the limit of its control. And when the arm 20 or 21 is carried through the null point, the switches A or C out out motor and return the control to motor 65M of winch 65 to continue operation in the next 180 sector in which the boom has passed. A reversal of winch 65 will provide the operator with the same directional control, but the operator must about face to follow the boom in the new 180 of movement.

Although we have described a derrick with a single mast having a pair of topping lifts located at the top of the mast and connected to a boom it shall be understood that this arrangement shall apply to any framework or superstructure that may be utilized in place of a mast and although we have described a single mast and double topping lift for the operation of a boom, the principles involved shall also apply where two masts and the same components on each mast are utilized for a burtoning operation. Although we have described a particular physical structure for the arms of a topping lift, the shape, the size and the curvature of the arms may vary without departing from the spirit of this invention and although we have described a derrick that may operate either side of a center line, that is, if the center line is 90 to the axis of the ship, the boom may be operated fore and aft. And although we have described a means of rotating the boom from one sector of operation to the next sector of thus providing a complete 360 of operation, it is to be understood that the means of accomplishing this rotation may be varied without departing from the spirit of this invention. And although we have shown simplified circuits and components to produce the desired control during the rotation of the topping lift, it is to be understood that changes in these circuits may be made to assist in this operation without departing from the spirit of this invention. And although we have shown a means of rotating the base of the boom with respect to the rotation of the topping lift, changes may be made in the mounting and means of rotation of the base of the boom without departing from the spirit of this invention.

What is claimed is:

1. A derrick for a ship which includes a mast and boom, a pair of independently rotatable topping lift arms positioned either side of the mast at the head of the mast, a pair of topping lift winches and cable to haul and lift the boom, a purchase winch and cable to lift the cargo and a rotation winch and cable to rotate said boom, each of said topping lift arms supporting a sheave at its outer end and said boom supporting a sheave at its outer end, said cable from said topping lift winches rove through the sheaves and said topping lift winches to be movable in opposite directions to control the swing of said boom, one of said topping lift arms rotatable from a forward position with the lifting and swinging of the boom toward one side, the other topping lift arm rotatable only by the lifting of the boom, a turntable on said mast to support the base of said boom and retain said boom in an alignment with said mast during rotation of said boom about said mast, said boom swingable from a forward axis in front of the mast to 90 either side of the mast, said boom raised during its 90 swing to reach the limit of the topping lift winch travel and the limit of the cable pull to reach a null position, a reversible motor and drive mounted at the top of the mast and connected to each topping lift arm, means to rotate either of said topping lift arms to carry it past the null position and means to drop said boom away from the null position and move said boom into the next sector of rotation.

2. In a device according to claim 1 in which said mast is tubular and said cable from said winches passes through the center of the tubular mast.

3. In a device according to claim 1 in which said topping lift arms are also pivotally connected to the rotary mounting to move from a closed position on the rotary mounting to an open position according to the pull of the cable from the end of the boom.

4. In a device according to claim 1 in which said boom is swingable 90 either side of a center line and movable from a horizontal position to an approximately vertical position and in which said boom may be either lifted or lowered while rotating by controlling a single cable that is rove on both the topping lift winches and the rotation winch.

5. In a device according to claim 1 in which the topping lift arms rotate in an arc of 270 and in which one topping lift arm is in a closed position while the boom swings through the central portion of its arc of travel and the opposite topping lift arm is pivotally movable to an open position when the swing of the boom is to the side toward the arm that opens.

6. In a device according to claim 1 in which the boom is operative for lifting in one sector of 180 but is movable into a second sector of 180 that is 90 removed from its original sector and in which said boom is again movable into a new sector of 180 that is 90 removed from its second sector to provide 360 of rotation for operation of said boom.

7. In a device according to claim 1 in which the means to urge said boom to move through its null point of operation includes a reversible motor with automatic engaging clutches connected to reduction gears which are in turn connected to means to rotate said topping lift arms and a pair of switches that are actuated by the movement of said topping lift arms to control the on and off operation of said motor as well as the direction of rotation.

8. In a device according to claim 7 in which there is a reversible motor drive on said rotation winch and said switches also reverse the operation of said reversible motor to lower said boom while continuing to travel in the same rotation.

References Cited UNITED STATES PATENTS 2,830,170 4/1958 Banks 2123 FOREIGN PATENTS 1,020,170 11/1957 Germany.

1,094,617 12/1960 Germany.

RICHARD E. AEGERTER, Primary Examiner. HARVEY C. HORNSBY, Assistant Examiner.

U.S. Cl. X.R. 212--58, 144