Luffing And Slewing Jib Crane

Abstract

A ship's crane has a jib which is adapted for luffing and slewing movements, and from which is suspended a load-handling device, particularly for containers. The load-handling device is in two portions, with a motor to rotate the two portions relative to each other to position the load accurately. The crane has a single load cable which is reeved about the jib head and the upper of the two portions in such a way that, in addition to resisting reactionary rotation of the upper portion of the load-handling device, the device is enabled to maintain its horizontal position irrespective of the angle of elevation of the jib or list of the ship.

Description

This invention relates to luffing and slewing jib cranes and has particular reference to ship's and other cranes for handling loads in the form of goods containers and like heavy or bulky loads which can be referred to in general as "objects."

In known cranes which incorporate object-orienting means comprising two members so connected together as to be rotatable relative to each other about a vertical axis through the medium of power operated means, the lower of said members is attached to the object being handled and the upper member is adapted for suspension from the crane by load cable reaches which are reeved round around pulleys or sheaves provided on said upper member and which emanate from a trolley adapted to traverse a horizontal track on an overhead structure of the crane.

In these known cranes the aforesaid cable reaches, which are so disposed and spaced apart as to resist rotation of the upper member of the orienting means and also swinging of said means and the object attached thereto, are formed by a plurality of cables which are connected to winch means on the trolley or are guided from the trolley to winch means located elsewhere on the crane.

The above-mentioned cable arrangements, however, are inapplicable to luffing and slewing jib cranes, since the orienting means, and object attached thereto, would be constrained to tilt inwardly to or outwardly from the jib, accordingly as the jib is raised or lowered, this characteristic being due to the separate cables maintaining their length relationship to each other.

Such tilting of the orienting means and object would impose unequal strains in the separate cables, resulting in adverse effects on the rotation resisting characteristic and stability of the suspending cable reaches, which, coupled with the inclined axis of rotation of the orienting means and the object, would make satisfactory handling and orienting of the load very difficult.

According to the present invention there is provided a crane having a jib adapted for luffing and slewing movements, and incorporating object orienting means comprising two members so connected together as to be rotatable relative to each other about a vertical axis through the medium of power operated means, wherein supporting cable reaches are formed by reeving a single cable, connected to winch means, upward and downward between pulley means located on the free end of the jib and on both sides thereof and pulley means on the upper of said members, said pulley means comprising a plurality of pulleys so arranged as to space apart, at a suitable distance from each other, said supporting reaches.

IN this way, provided that, in accordance with usual practice, the object is balanced on the orienting means, i.e. with its center of gravity coincidental with the axis of rotation of said means, said means is enabled to be maintained substantially horizontally level irrespective of the angle of elevation of the jib, and in the case of ship's cranes, irrespective also of a ship's lists.

An example of the invention will now be described with reference to the accompanying drawing, which to some extent is diagrammatic, and in which:

FIG. 1 is a perspective view of a ship's crane embodying the invention and showing the load attachment with an object in the form of a container attached thereto.

FIG. 2 is a side elevation, to a larger scale than FIG. 1, showing the load attachment suspended from the jib head of the crane shown in FIG. 1, with the load attachment shown as a part section taken on the line 2-2 of FIG. 3.

FIG. 3 is an end elevational view of the structure of FIG. 2, showing an outside view of the load attachment.

FIG. 4 is a plan view taken on the line 4-4 of FIG. 2.

Referring to the drawing, and at first particularly to FIG. 1, the crane shown is in effect an adaptation of the crane described in my prior U.S. Pat. No. 3,191,779, and comprises a jib 1 which is pivotally mounted at 2 on a trunnion 3 secured to a ship's deck 4, with a bridgelike structure which provides an anchorage for the pulley blocks carrying the crane's various cables, and which consists of a cross member 5 disposed transversely of the deck above the trunnion 3 and supported by two columns 6 upstanding from the deck. The jib head 7 of the crane is provided with an outrigger 8 carrying a pulley block 9 at each of its ends, and two coaxial pulleys 10 are mounted at the end of the jib head, one on each side thereof. In addition, four coaxial pulleys are also mounted on the jib head, two of these pulleys, 11 and 12, being disposed in juxtaposition on each side of the jib head and located approximately midway between the outrigger and the pulleys 10. The crane also includes cargo, luffing and slewing winches, but only the two winding drums 13 of the first mentioned are shown, since the other winches referred to are irrelevant to the invention. The luffing and slewing cables, and pulley means associated therewith, are also irrelevant to the invention and, apart from the fragments thereof shown in chain-dotted lines at 14, are omitted from the drawing. The load cable of the crane comprises a single length of cable 15 having its ends wound in the same direction around the winding drums 13, wherefrom it is arranged in the manner hereinafter described.

Referring now particularly to FIGS. 2, 3 and 4 of the drawing, the load attachment comprises two main members of which the first, 16, is shown for simplicity as a horizontal rectangular plate having a centrally located bearing 17 for a vertical shaft 18. Two rows of pulley blocks are attached to the top of the member 16, one row being located near, and parallel to, each end of the member. These rows each comprise four pulley blocks which are symmetrically spaced on opposite sides of the plane coincidental with the line 2-2 of FIG. 3, the row nearer the jib 1 consisting of two inner blocks 19 and two outer blocks 20, and the row farther from the jib consisting of two inner blocks 21 and two outer blocks 22.

The second main member 23 of the load attachment is also shown in the drawing as a horizontal rectangular plate of the same size and proportions as the member 16. The shaft 18 passes through a central hole in the member 23 and is secured to the underside of the member by a flange 24 provided on the shaft. The shaft is also provided with a collar 25 at its upper end, adjacent the bearing 17.

An electric motor 26, with self-contained speed-reduction gearing, is mounted on the underside of the member 16, near a corner thereof, and is connected by a coupling 27 to the shaft of a worm 28 which engages a worm wheel 29 mounted on the shaft 18 adjacent the lower end of the bearing 17. The worm shaft is journaled, at each end of the worm, in bearings 30 which are adapted to withstand the thrust imposed on the worm by the power transmitting effort thereof.

Also mounted on the shaft, below the worm wheel, is a hub 31 which carries the inner ends of six equispaced and radially arranged axles 32, on the outer ends of which are rotatably mounted flanged rollers 33. The axles are secured to the member 23 by brackets 34 located adjacent the inner sides of the rollers. The rollers are adapted to rotate on a circular rail 35 concentric with the shaft 18, and the rail 35 is mounted on a carrier member 36 which extends outwardly from and around the rail and is connected to the member 16 by six vertically disposed round tubes or ties 37 which are equispaced concentrically with the shaft 18 outside the path of rotation of the rollers and worm wheel. For additional rigidity between the members 16 and 36, adjacent ties 37 may be connected together by crossbracing struts (not shown).

Eyes 38 are secured to the underside of member 23, at each corner thereof, for the attachment of chain or rope slings 39, which are connected to a lifting frame 40 fixed to the top of an object in the form of a container 41, as shown in FIG. 1.

The single load cable, previously referred to, is arranged in two runs whereof the ends are wound in the same direction around the winding drums 13. The runs pass from the winch to and around two pulley block 42 anchored to the crossmember 5, and thence to the sides of the jib head 7. Each run is then reeved, on the appropriate side of the jib head and member 16 of the load attachment, first around the pulley 11 on the jib head, then downward to and around the pulleys 19 and 21 on the member 16, then upward to and around the pulley 12 on the jib head, then to and around the pulley 10 at the end of the jib head, then downward to and around the pulleys 22 and 20 on the member 16, and finally upward to the outrigger 8, where both runs of the cable form a terminal loop 15a (see FIG. 3) reeved around and extending between the pulley blocks 9. With this arrangement the load attachment is suspended from the jib head by eight cable reaches which, between them, support the combined weight of the load and load attachment.

Although the lifting frame is shown in FIG. 1 as a simple rectangular structure, it may incorporate known means (not shown) adapted automatically to balance the objects attached to the crane, and, although not shown in the drawings, the electric motor 26 would be controlled by the crane driver from his operating station, or by another person assigned to this duty, by means of, for example, a control box suspended from the crane's boom. The motor would be connected to the crane's electric power supply and to the motor-controlling means by a flexible cable or cables suitably supported by the crane.

It should be understood that, although the members 16 and 23 of the load attachment are shown in the drawing and referred to hereinbefore as rectangular plates, this has been done for the sake of clarity. In practice, these members would be fabricated structures giving commensurate strength-to-weight ratios.

As in the case of the winch described in the aforementioned prior patent, the winch drums 13 are so arranged that both can be driven in unison, or one drum only driven while the other is held at rest, according to the weights of the objects being handled by the crane.

In the operation of the crane and load attachment just described, and when it is required to turn an object into position for stowing, loading, or otherwise being deposited, the motor 26 is operated in the appropriate rotational direction. The motor thereupon, through the medium of the worm 28, worm wheel 29 and shaft 18, causes the members 23 and 16, with the respective parts connected thereto, slowly to rotate in relation to each other, whereby the rollers 33 roll on the rail 35. At first, however, because of the disparity of weight between the load and the attachment, the member 16 will be constrained to react by rotating to some extent in the reverse direction, until the resistance to this rotation produced in the suspending cable reaches becomes sufficient to overcome the inertia of the load and parts rotatable therewith. The load thereupon will start to rotate towards the required position, and by stopping the motor in time to allow for the return rotation of the member 16, the load will rotate into a position approximating that required. Thereafter, adjustment of the load's position can be made by one or two men when the load is being finally lowered.

In the load attachment described, the weight of the objects being handled is transferred from the member 16 to the member 23 through the medium of the rollers, circular rail and other parts associated therewith, thereby substantially relieving the shaft 18 of all but the torsional stresses produced by the motor-driven worm gearing.

With cranes as aforedescribed, objects can be rotated substantially in the required position while they are being raised, moved by slewing and luffing actions of the crane, and lowered, thereby appreciably accelerating the load-handling operations.

Also, owing to the arrangement of the suspending cable reaches, the objects being handled are maintained substantially in a level trim, even should the cranes be inclined, for example, on listing ships. This feature is due to the reeving of the single cable, which permits the suspending reaches thereof to be self-accommodating in their lengths.

Further, the arrangement of the reaches referred to above resists tendencies of the load and load attachment to swing.

Although the invention has been particularly described in relation to a jib crane, it is equally applicable to other cranes, for example, overhead traveling and gantry cranes, wherein the pulleys and pulley blocks mounted on the jib head of the crane hereinbefore described would instead be mounted on a traversing carriage which would also, as in usual practice, carry the cable-winding drum or drums. These and other modifications and variations can be resorted to without departing from the purview and scope of the present invention as defined by the appended claims.

Claims

I claim:

1. A crane having load cable means and a load attachment comprising a first member suspended from the crane by reaches of said load cable means, a second member, means for securing a load to said second member, means connecting said second member to said first member for rotation of said second member relative to said first member about a vertical axis, power-operated means for effecting said rotation, the said cable reaches being so spaced apart relative to the crane and said first member as to effect resistance to, and restrict, reactionary rotation of said first member resulting from the action of said power-operated means, pulley means on the crane and on said first member with which said load cable reaches cooperate in such a way that the load is substantially maintained in proper trim while being raised, moved, turned and lowered by the crane, said load cable reaches being formed by a single length of load cable so as to be self-accommodating in regard to their respective lengths, winch means for said cable, said cable having its ends connected to the winch means and passing in two runs to the pulley means on the crane, the said runs then being reeved upward and downward around and between said pulley means on the crane and said pulley means on said first member, said cable finally forming a terminal loop reeved around at least one pulley of said pulley means, said crane having a jib free at one end, an outrigger on the free end of the jib and extending to opposite sides thereof, said pulley means on the crane being located on the jib and on said outrigger, said load cable being reeved around the pulley means on said outrigger to form said terminal loop, said pulley means on the crane comprising a pulley mounted on each side of the jib adjacent the free end thereof, a pulley at each end of said outrigger, and two pulleys mounted on each side of the jib and located intermediate the end of the jib and said outrigger, the pulley means on said first member of the load attachment comprising a series of four pulleys connected at spaced intervals to said first member adjacent each end thereof, said load cable runs being reeved first around one of said intermediately located pulleys on each side of the jib, then downward to said first member and around the inner pulleys of the series of pulleys nearer to the jib and then to the series of pulleys remoter from the jib, then upward to and around the other said intermediately located pulleys on the jib, then to and around the pulleys adjacent the end of the jib, then downward to said first member and around the outer pulleys of the series of pulleys remoter from the jib and then around the series of pulleys nearer to the jib, and finally upward to said outrigger at which said runs form a terminal loop reeved around and extending between the pulleys at the end of said outrigger.

2. A crane having a jib, means mounting the jib for luffing and slewing movements, a single load cable, winch means for winding and unwinding said single cable, upper and lower members connected together for rotation relative to each other about a vertical axis to support an object from the crane and to orient said object relative to the crane, power means for rotating said upper and lower members relative to each other, said single cable being reeved upward and downward between pulley means located respectively on the free end of the jib and on both sides of the free end of the jib and on said upper member, an outrigger on the jib near the free end thereof and extending to opposite sides thereof, a pulley mounted on each side of the jib at the free end thereof, a pulley at each end of said outrigger, and two pulleys mounted on each side of the jib and located intermediate the end of the jib and said outrigger, the pulley means on said upper member comprising a series of four pulleys connected at spaced intervals to said member across each end thereof, said load cable having two runs which are reeved first around one of said intermediately located pulleys on each side of the jib, then downward to said upper member and around the inner pulleys of the series nearer to the jib and then of the series remoter from the jib, then upward to and around the other said intermediately located pulleys on the jib, then to and around the pulleys adjacent the end of the jib, then downward to said upper member and around the outer pulleys of the series of pulleys remoter from the jib and then of the series nearer the jib, and finally upward to said outrigger at which said runs form a terminal loop reeved around and extending between the pulleys at the ends of said outrigger.