Anchor pile hoisting device

Abstract

 In a anchor pile hoisting device, a hoisting cable (3) of which cooperates with a wire loop (5) wound around the anchor pile (6), the length of the wire loop is prescribed within narrow limits in order to prevent on the one hand slip of the wire loop with respect to the anchor pile (6) and on the other hand a too high tension in the wire loop (5).
In accordance with the invention the length of the wire loop (5) can be adjusted.

Description

[0001] The invention relates to an anchor pile hoisting device comprising.at least one hoisting cable co-operating with a wire loop wound around the anchor pile, said loop engaging the pile surface with sufficient friction, by being at an acute angle to a plane at right angles to the direction of the pile, under the influence of tractive force of the hoisting cable to loosen the pile from the ground and to subsequently hoist the same up.

[0002] Such a device is known. With the known type of anchor pile hoisting device hoisting or withdrawal of the anchor pile requires the extraction force to be transferrable to the pile. This is achieved by causing the wire loop to engage the pile wall with adequate frictional force. An extraction force in the hoisting cable equal to the sum of the adhesive force of the pile in the ground and the weight of the pile brings about an orthoganal force of the wire loop on the pile jacket which produces a lighter friction between the wire loop and the pile wall according as the angle between the wire loop and the plane at right angles to the pile is larger. With given dimensions and a given weight of the anchor pile and its adhesive force are thus associated a fixed length and section of the wire .and the wire loop angle. If the wire length increases, for example, due to elongation of the wire loop, the wire loop angle will also increase so that less friction will be produced and the wire loop may slip.

[0003] The known device of the kind set forth comprises a wire loop which is pre-stretched in order to avoid elongation so that with the wire loop load to be expected the resultant lengthening of the wire loop and hence the wire loop angle can be kept within permissible limits. However, in the rough dredging operations the wire will nevertheless lengthen after prolonged use. Therefore, in order to avoid catastrophes the known wire loops are replaced at regular intervals.

[0004] The invention has for its object to enhance the lifetime of the wire loop, whilst the length of the wire loop and hence the wire loop angle are kept within the predetermined narrow limits. To this end the anchor pile hoisting device according to the invention is characterized by adjusting means for setting the effective length of the wire loop.

[0005] An anchor pile hoisting device according to the invention in a preferred embodiment provides an improved guiding of the wire loop because the adjusting means comprise a stretching device journalled on a supporting ring surrounding the anchor pile.

[0006] A variant of the preferred anchor pile hoisting device is characterized in that the stretching device comprises at least one lifting screw.

[0007] In a further development of the anchor pile hoisting device according to the invention the wire loop has a smaller structural height, because the wire loop only partly surrounds the pile.

[0008] In order to permit of carrying out the post-adjustment operations in due time, a further development of the anchor pile hoisting device according to the invention comprises an angle feeler arranged on the supporting ring and measuring the wire loop angle.

[0009] In a still further developed embodiment of the anchor pile hoisting device according to the invention the stretching device comprises a leverage for adjusting the effective length during the hoisting operation.

[0010] The above-mentioned and further features of the invention will be described more fully hereinafter with reference to a drawing.

[0011] The drawing shows schematically in

Figures 1 to 3 each a play of forces for a wire loop engaging around a pile,

Figure 4 part of a suction dredger with an anchor pile hoisting device in accordance with the invention,

Figure 5 on an enlarged scale a detail V of Figure 4,

Figures.6,14 and 15 three variants of automatic stretching devices for further developments of the anchor pile hoisting device in accordance with the invention,

Figures 7,9,10,11,12 and 13 each a variant of the detail V of Figure 4 and

Figure 8 a side elevation of detail VIII of Figure 7.

[0012] A ground dredger 32 as shown in Figure 4, for example, a cutter head dredger, turns during operation around an anchor pile 6 lowered into the soil 9 and being movable up and down in guides 28 with respect to a floating body 1 on the water 33. Lifting of the anchor pile 6 is performed by means of an anchor pile hoisting device 31 as shown in Figure 14, comprising a lifting cylinder 2 standing on the floating body 1, a hoisting cable 3 passed around a disc 4 supported by the piston rod 27 of the lifting cylinder 2 and a wire loop 5 wound twice around the anchor pile 6, directly or indirect7y engaged by the hoisting cable 3. When the anchor pile 6 is lifted, the hoisting cable 3 draws the wire loop 5, which is thus drawn tightly around the anchor pile 6 and builds up a sufficient friction resistance w in order to overcome by a lifting force G' the sum of the weight G of the anchor pile 6 and the ground resistance G_g. Figures 1 to 3 illustrate this play of forces in a simplified manner.

[0013] Referring to Figure 1, the lifting force G' of the hoisting cable 3, which draws the wire loop 5 surrounding the anchor pile 6, produces in said wire loop 5 a stretching force K₁, whilst an angle a₁ is formed between the wire loop 5 and the plane 7 at right angles to the axis 8 of the pile.

[0014] The component N normal to the pile axis 8 is G' cotan a.

[0015] The frictional resistance w produced = f.N = f.G' cotan a.

[0016] Since the frictional resistance f between the wire loop 5 and the pile 6 is a constant, the cotan a and hence the angle a determine the lifting force G'.

[0017] From Figure 1 it will be apparent that in the case of a small angle a₁ a heavy force N₁ is exerted, which results in a heavy frictional resistance w₁ so that a high lifting force G' is prevailing. With a small angle a₁, however, the stretching force K₁ is found to be comparatively high so that the wire loop 5 must be made from a thick and hence expensive cable.

[0018] Referring to Figure 2 the angle a₂ appears to be chosen correctly, because it results in a reasonable stretching force K_2' whilst because of G' being equal to f.N₂ a sufficient lifting force is obtained.

[0019] The angle a3 of Figure 3 is too large and results in an inadequate lifting force G'.

[0020] In the simplest form illustrated in Figures 14 and 5 the hoisting cable 3 is connected by means of a fastening pin 29 with a wire loop 5 wound twice around the anchor pile 6. Through a stretching device 10 the wire loop 5 is automatically tightened until a sufficient lifting force G¹ is built up for drawing the pile 6.

[0021] Referring to Figure 14 the stretching device 10 comprises a wire eyelet 35 at one end 36 of the wire loop 5, through which the other end 37 of the wire .loop 5 is passed. Referring to Figure 5 the stretching device 10 comprises a steel eyelet 38 fastened to one end 36 of the wire loop and having a curved wire guide 39 for the other end 37.

[0022] In principle it is even possible to make the hoisting cable 3 and the wire loop 5 from a single length of wire.

[0023] The anchor pile hoisting devices of Figures 6 to 15 have each a supporting ring 11 surrounding the pile 6 and suspended by means of a fastening pin 29 to the hoisting cable 3.

[0024] Figure 6 shows that the supporting ring 11 is arranged around the pile 6 on which one end 36 of the wire loop 5 is journalled by means of a wire fastener 12. The effective length of the wire loop 5 is adjusted by means of a curved guide strip 13, which is fastened to the supporting ring 11.

[0025] Figures 7 to 10 illustrate a number of stretching devices adjustable in a different way.

[0026] The anchor pile hoisting device 31 according to the invention shown in Figure 7 comprises a stretching device 40 comprising an eccentric 14 rotatably journalled in the supporting ring 11 and fixable by means of a pin 41 in a hole selected from a plurality of holes 42. By selecting the correct position among the plurality of eccentric positions the effective length of the wire loop 5 and hence the angle a can be adjusted to the required value. If due to elongation of the wire loop 5 the angle a becomes larger, the wire loop 5 comes into contact with the angle feeler 17, which indicates that the effective length of the wire loop has to be shortened by readjustment of the eccentric 14.

[0027] Referring to Figure 9 the anchor pile hoisting device according to the invention comprises as a stretching device 40 a lifting screw 15, a nut 45 of which bearing on a console 44 fastened to the ring 11 engages a threaded rod 46, which is fastened to one end 36 of the wire loop 5, the other end 37 of which is fastened to a fixed pin (not shown) of the supporting ring 11.

[0028] Figure 10 differs from Figure 9 in that the lifting screw 15 is replaced by a pin 50 and a rod 48 having holes 49. The pin 50 is inserted into the console 44 and into a selected one of the holes 49.

[0029] Figure 11 shows an improved wire loop 5 made from a flat, for example, braided belt 18.

[0030] Figures 12 and 13 show each a wire loop structure of small height b. As shown in Figure 12 a single wire loop 20 partly surrounds the pile 6. Figure 13 shows a plurality of wire loops 20 journalled on a divided guide ring 21, the two halves 51 of which are supported each by means of two hoisting cables 3. The wire loops 20 are held at a distance from the guide ring 21 by spring stretchers 24, which provide the required distance and hence the required lifting force G'. The effective length of the wire loop 20 is adjusted, as shown in Figures 13 and 13, by means of a hydraulic post- stretcher 56.

[0031] Figure 15 shows a stretching device 10, which automatically stretches the wire loop 5 by means of a lever 22 in accordance with the lifting force G'. The lever 22 is pivotally journalled on the support 11 by means of a pivot 57 and has a cam 23, to which is fastened an arcuate cable saddle 60. The end 36 of the wire loop 5 extends above the cable saddle 60 towards a fastening pin 61. The higher the lever 22 turns upwards with a heavier force, the shorter becomes the effective length of the wire loop 5 and the smaller becomes the angle a.

Claims

1. An anchor pile hoisting device comprising at least one hoisting cable co-operating with a wire loop wound around the anchor pile and engaging the pile surface with adequate friction under the influence of the tractive force of the hoisting cable because of being at an acute angle to a plane normal to the longitudinal direction of the pile for loosening the pile from the ground and for subsequently hoisting the same up, characterized by adjusting means for setting the effective length of the wire loop.

2. A device as claimed in Claim 1 characterized in that the adjusting means comprise a stretching device journalled on a supporting ring surrounding the anchor pile.

3. A device as claimed in Claim 2 characterized in that the stretching device comprises at least one lifting screw.

4. A device as claimed in Claim 2 or 3 characterized in that in order to reduce the structural height of the loop around the pile the hoisting device comprises at least one wire loop post-adjustably connected with the ring and sur- irounding the pile only partly.

5. A device as claimed in Claim 2 or 3 characterized in that the stretching device comprises a leverage for adjusting the effective length during the hoisting operation.

6. A device as claimed in anyone of the preceding Claims characterized in that the wire loop is constructed in the form of a flat belt.

7. A device as claimed in anyone of Claims 2,3,5 or 6 characterized in that an angle feeler measuring the wire loop is arranged on the supporting ring.

Drawing