Crane structure

A crane characterized in that it comprises a lower vertical boom (10) and an upper horizontal boom (12), mutually connected through a joint element (20), in that the lowest part of the vertical boom is connected through a pedestal (14), the pedestal further comprising a slew ring for rotating of the crane about a vertical axis (16), and a tension rod (22) is arranged between the pedestal and the joint element in a distance from the vertical boom and mainly parallel to this in a normal position of the crane.

RELATED CASES

This application claims priority on PCT/NO09/000,299 filed on 25 Aug. 2009 and Norway Application No. 20083654 filed on 25 Aug. 2008.

The present invention relates to an arrangement for a crane as indicated in the preamble of the following claim1.

There is a disadvantage in existing crane structures with fixed boom, bending boom and telescopic boom in that the load is raised or lowered in response to radial movements. In order to move the crane boom horizontally, i.e. when a load is to be positioned horizontally, several movements must be combined, or adjustment must be made by hoisting or slackening at the winch.

As concerns the prior art, reference will be made to what is known from DE 3,602,912, U.S. Pat. No. 3,884,359, Dutch publication NL-7410091 and GB patent 2,065,597.

The patent first mentioned discloses a lifting arrangement comprising a lower boom and an upper boom, which are connected with each other by way of an articulated piece. The lower boom is arranged pivoting in a swivel head for rotation of the cranes about a vertical axis. Hydraulic cylinders are used for control of the respective booms. A tension member is mounted between the articulated piece and the upper end of a swivel head element.

Objects of the Invention

It is an object of the invention to provide a crane construction which employs substantial movement from smallest to largest radius, outwardly from a central point.

It is an object of the invention to provide a crane construction enabling an approximately horizontal movement of the load over a complete working region, wherein vertical movement of the load is achieved with help of a winch.

It is therefore an object of the invention to provide a construction operating so that when the assembly of a vertical boom and a stay member is pivoted about a horizontal axis, a wire pulley at the end of the horizontal boom of the crane moves mainly along a straight line.

The Invention

The crane structure of the invention is characterized by the features appearing in the following independent patent claim1. Preferred embodiments are defined in the independent claims.

The crane structure is characterized in that it comprises a lower boom10and an upper horizontal boom12of predetermined length L which are mutually connected via an articulated member20. The boom10is at its bottom connected to a “crown”14, which in turn comprises a swivel head for use in rotating the crane about a vertical axis16, and a stay member22is arranged between the “crown” and the articulated member20at some distance from the boom10and substantially parallel with the latter in a normal position (vertical) of the crane.

Preferably, the stay member22is mounted on the “crown” at another level of height relative to the vertical boom10.

Preferably, the “crown” as seen in a side section, forms an approximately triangular design, in that a line L between the vertical boom (10) and the articulated member20(points A and C) mutually form an angle in a range of 30° to 60°, namely of about 45°.

Preferably the articulated member20is a triangular structure, in which (in the normal position of the crane,FIG. 1B) the vertical boom10and the stay member22respectively, are attached swivelingly or pivotably and spaced apart at substantially the same level of height.

Preferably the vertical boom10, the horizontal boom12and the stay member22respectively are supported at respective corners B-D-G in the articulated member.

Preferably the stay member22is shorter than the vertical boom10.

Compared to the state of art as represented by the aforementioned German patent DE-3.602.912, the following differences are pointed out in respect of the present invention.

According to the German patent, the wire runs over a curved pulley, whereas in the present invention a stay member22is used and connected to a point in an articulated element.

According to the German patent DE-3.602.912, the wire operates with a constant working radius, (the distance from a wire9to an axis6, according to the figure), whilst the stay member22will have a variable working radius (the distance from the stay member22to point B in the aforementioned solution, see the figure which is discussed later).

In the forward and rear positions of the crane, this radius will be smaller, and will be largest in its intermediate position. The reduction of the working radius results in the horizontal boom12being lifted to an extra degree, and in this manner compensates for the difference in height that arise during the pivot movement.

In the German patent DE-3.602.912, the pulley disc7and the loading arm8are disposed in a common axis6on the top of the outer assembly3(see the figure in the German patent). In the present construction the boom12is coupled to an axis G on the articulated member20and therefore does not have a common axis with the articulated member20which rotates about the axis B on the top of the vertical boom10.

It will be appreciated from the figures as discussed in the following that the anchoring points between the crown, the vertical boom10, the articulated member20and the stay member22forms a rectangle with corners A, B, C, D. The decisive feature for the crane to be able to maintain a constant height for the wire pulley J, relates to the geometry of this quadrangle. First and most the position that arises between positions A and C on the crown, and especially the angle they form in relation to the horizontal plane.

Secondly it relates to the relationship between the length of the vertical boom (A-B), the length of the stay elements (C-D), the distance (B-D) of the stay element and the distance (A-C) on the crown.

By adapting this geometry in a correct manner as described above and shown in the drawing figure, it is possible to achieve a result that the wire pulley J moves in a direct line (+/−2%) during the pivot actuation, for example pursuant to the curve shown inFIG. 2. It is also possible to define whether the lifting height is to rise or fall with increasing working radius, namely defining a slope of the straight line.

The figures provide the crane which is formed of two main parts, namely a vertical boom10and a horizontal boom12. The vertical boom10is at its lower end coupled to a “crown” or socket component14which is operable to be turned about a vertical axis16on a bearing18at the top of the bottom socket or a swivel head19. The vertical boom10is moveable with help of a tilting cylinder (alternatively in two pieces)21which are mounted between the point B on the crown14and the point F on the vertical boom10. In the upper end of the vertical boom10, there is disposed an articulated member20at the point E. The articulated member20can be, seen from a side view, a triangular construction. The horizontal boom12is coupled at the point G at a distance from the point E.

The articulated member20is held up and guided by way of a stay member22which is coupled at its lower end to the “crown”14at the point C, and to a lower end of the articulated member20at the point D. The figure provides an illustration of the “crown”14which has a triangular form, with horizontal and vertical leg, in that the skewed hypotenuse defines a line between points A and C on the crown, respectively. This hypotenuse subtends an angle of 45° with the horizontal. The stay member22is attached to the crown14in a point C which is at a higher horizontal level than the position whereat the horizontal boom10is attached to the crown14at the point A, which in consequence of the crown14defining the aforementioned angle 45°. As seen in the vertical boom10position as shown inFIG. 1B, the distance between the points A-C on the crown14is larger than the distance between the points B-D, and that the stay element22is somewhat shorter than the vertical boom10. In this position, the stay element22and the vertical boom10are operable to be parallel.

The crane can rotate with help of the turning crown18on the foot19as is conventional.

The horizontal boom12is held up by assistance of a lifting cylinder24mounted between the point H on the articulated member20and the point I on the horizontal boom12. At a distal end of the horizontal boom12, there is attached a wire pulley J. This pulley guides a wire from the winch mounted onto or remote from the crane itself. As further seen inFIGS. 1A and 1B, lift cylinder24is pivotally coupled at its distal end to an intermediate point I on said upper boom12, and at its proximal end to articulated member20intermediate points G and H on said articulated member, and as shown in this embodiment, to said articulated member along a straight line between points G and H.

According to a simpler embodiment of the invention, the lifting cylinder24can be omitted. The horizontal boom12and the articulated member20form a interconnected boom. Regulation of the height of the wire pulley J as described in the following paragraph is not possible, although the load can be lifted and lowered using the winch.

In a situation that the tilting cylinder and the lifting cylinder have sufficient operating length, the crane can be folded together in a more compact position as illustrated inFIG. 1D.

Manner of Operation

The crane moves itself between a largest radius R1and a smallest radius R2(reaching distance) by way of the vertical boom10moving forwards and backwards in relation to the vertical starting position, by way of assistance from the tilting cylinder21. During such movement, the vertical boom10has as a main function to regulate the working radius of the crane. Thus, boom10is the lower boom, boom12is the upper boom, and boom10moves between rearward upward incline as seen inFIG. 1C, through a vertical position as seen inFIG. 1B, 2Aforward upward incline position as seen infigure 1A. The horizontal boom12is operable to compensate for the height difference which arises (at point B) under this movement, such that the block (point J) is held at constant height. This occurs without the lifting cylinder being actuated, and in consequence the horizontal boom12follows movement of the articulated member20. The stay member22steers this movement. By calculating optimal disposition of the points A, B, C and D, a compensation of movement is achieved which results in a substantially constant (horizontal) height for the wire pulley at point J. It is possible to achieve a height variation of approximately +/−2% of the radial movement.

By disposing the lifting cylinder24in another position, the height of the wire pulley J can be changed to approach a higher or lower position, simultaneously with it being possible to move the lifting moment closer to the centre of rotation of the crane.

This construction provides a series of advantages:1: the boom cannot fall down. For a fall to occur, there must be a physical break in the steel construction of the crane. Loss of hydraulic power does not have any significance. In an event that the hydraulic cylinder is removed, the crane can continue to be moved horizontally.2: the radial movement of the load is horizontal. This means that there is minimal force required for this horizontal movement, namely something which requires lower energy utilization as a consequence of employing a crane constructed pursuant to the present invention. Faster speed of operation is thereby possible in a similar manner to when the crane pivots around. This means that the load can be moved at high speed in all directions in a horizontal plane by way of rotation and radius adjustment.3: adjustment of crane movement in operation becomes simpler and more logical. Every movement is controlled by its corresponding hydraulic function: rotation (adjustment of angle), reaching range (adjustment of radius), lifting (change in working height) and winch (raising and lowering of loads). The functions do not influence one another.

FIG. 2is an illustration of how hook height (y-axis) in the horizontal boom12(at the wire pulley J) changes itself in relation to the crane's radial reaching distance or position (x-axis). As a result, the point J (wire pulley) holds itself stable at a height level of 21 to 22 metres over a given foundation level. As provided in the figures, the apex of the crane at point J is capable of a reaching range 40 metres to each side of the vertical axis16. The position x=0 on the x-axis corresponds to the tip of the boom J intersecting the axis16(FIG. 1B).