Abstract:
A Device for transferring a vibrating movement to a rigid pipe for letting it penetrate into or removing it from a bed in upright or inclined position, comprises a clamping member for clampingly holding the upper end of the pipe for transfer of the vibrating movements thereto. The clamping members can be biased away from each other for clampingly engaging—exclusively—the inner surfaces of the pipe. The device further comprises a body to be attached to a vibrator block. The clamping members form a rigid unity with the body, considered in the axial direction of the pipe.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a pipe clamp for either rams or blocks for removal, working with vibrations. 
     2. Description of the Related Art 
     It is known to ram or remove foundation pipes into or from a waterbed in a more or less straight up position by means of a vibrator block placed on the upper end of the pipe. Such pipes are used to secure a structure to the waterbed. To that end the structure, for instance a so-called “template”, a “jacket” or a “frame” is provided at the corners with guide bushes for the foundation pipes which can be accommodated in there more or less fitting. With the help of a vibrator block each pipe is forced into the bed through the guide bush concerned and attached to the guide bush, with its upper end. 
     Known vibrator blocks are provided at their lower ends with at least two pairs of hydraulic operable clamping jaws which always clamp the upper end of the pipe wall between them at opposite locations. The clamping jaws engaging the outer side of the pipe result in a local enlargement of the diameter of the assembly pipe-clamp, as a result of which the pipe cannot entirely be lowered into the guide bush with its upper end. 
     However, it is often a requirement that the pipes have their upper ends flush with the upper edge of the guiding bushes concerned, so that the protruding upper portions of the pipes have to be cut off. For that purpose a special tool has to be lowered or divers have to be used, which entails high costs. 
     SUMMARY OF THE INVENTION 
     It is, an object of the invention to improve on this and to that end, from one aspect, provides a device for transferring a vibrating movement to a rigid pipe for letting it penetrate into or removing it from a bed in upright position, comprising clamping means for clampingly holding the upper end of the pipe for transfer of the vibrating movements thereto and biassing means for the clamping means, which clamping means comprise at least two clamping members that can be biassed away from each other by means of the biassing means, for clampingly engaging the -particularly opposite- inner surfaces of the pipe. 
     Because the pipe wall itself provides the counter clamping force and the pipe is exclusively engaged on—particularly opposite—inner surfaces, no clamping members that extend outside of the pipe wall are present. As a result the pipe can be rammed entirely into the guide bush, without the follow-up treatment of cutting off the upper end being necessary. 
     In a further development of the device according to the invention it comprises a body with means for attachment to a vibrator block, the clamping members forming a rigid unity with the body in pipe direction. The vibration forces (alternatingly upwards and downwards) are transferred here from the vibrator block, via the clamping members, to the pipe according to a direct force path. 
     Preferably the clamping means comprise one or more wedge members that can be moved in the direction of the pipe by the biassing means, which wedge members under tension press the clamping means radially outwards. 
     For reasons of constructive simplicity it is preferred if there is one central wedge member, which is active to several sides. 
     According to a further development the wedge members are provided with at least one wedge plane, of which the normal has a directional component in the direction towards the lower end of the pipe. Considered from another aspect the biassing means are active to move the wedge members in downward direction for biassing the clamping members. In this way the biassing means can be active from above and room is provided to the wedge members and the clamping members, so that they can be designed strong enough for nearly all purposes. 
     It is preferred here that the biassing means comprise a cylinder/piston assembly, the piston being situated above the clamping means, so that the space next to the clamping members is entirely available to the wedge members. If the device is further provided with a stop plate for the upper end of the pipe, it is preferred that the piston is situated above the stop plate. Furthermore also the cylinder of the cylinder/piston assembly is preferably situated entirely above the clamping means. 
     A further simplified construction and reliable working is realized when the piston rod of the cylinder/piston assembly is directly attached to the wedge members at the end which faces away from the piston. 
     The taking up of space in radial direction is kept small according to a further development of the device according to the invention when the wedge members are provided with a series of wedge planes which are arranged saw-toothed in the pipe direction. The taking up of space in radial direction here can even be independent from the engagement length of the clamping members in the pipe direction. 
     This saved space can for instance be used for making the clamping members two-pieced, the clamping members being assembled from an inner clamping part, which for wedge activity abuts the wedge member concerned, and an outer clamping part, which is detachably arranged on the inner clamping member. Thus the device can be used for various very different pipe diameters, by changing the outer clamping members. 
     According to a further development the wedge member and the clamping member are connected to each other by means of a pin/slit connection, the slit extending in pipe direction. In this way the wedge member can slide in pipe direction with respect to the clamping member. 
     It is noted that from CH-A-400.023 a device is known for transferring forces to a pipe for letting it penetrate in a bed or removing it from it. This device comprises clamping means with a wall with filling pieces extending over the pipe and a centrally situated wedge member and further wedge members intended to engage the inner surface of the pipe attached around it extending within the pipe. In use fluid under pressure is supplied in order to force a piston which is operatively connected to the central wedge member, upwards and therewith force the further wedge members against the inner surface of the pipe. The intention here is to deform the pipe outwardly at that location so that it will closely abut the wall and/or filling pieces extending over the pipe. 
     From a further aspect the invention relates to an assembly of a device according to the invention and a vibrating block. 
     From yet another aspect the invention provides a method for transferring a vibrating movement on a rigid pipe for letting it penetrate into or removing it from a bed in upright position, the clamping means of the assembly according to the invention being inserted in the upper end of the pipe, the biassing means being activated to let the clamping means clampingly engage the inner surfaces of the pipe and keeping them clamped, without noticeable deformation of the circumference of the pipe at that location, and subsequently activating the vibrator block. 
     Preferably exclusively those circumferential surfaces of the pipe are clampingly engaged, which are situated on the inside of the pipe. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention will be elucidated on the basis of the exemplary embodiment shown in the attached drawings, in which: 
     FIG. 1 shows a schematical view on an arrangement for driving a pipe into a seabed with the aid of an exemplary embodiment of the device according to the invention; 
     FIG. 2 shows a combined cross-section and side view of the exemplary embodiment of the device according to the invention; 
     FIG. 3 shows a cross-section according to arrow III in FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 a vibrator block  1  is shown which is provided with a pulling head  9  and a vibrator member  10  with eccentric weights and hydro engine, the vibrator block  1  being connected to a hydraulic unit and operation means by means of a hydraulic lead  50  and at the bottom being provided with a clamping device  11  according to the invention. The clamping device  11  is inserted in the upper end of a pipe  8 , which pipe  8  extends downwards until in the seabed  4  from the water surface  3  of an aqueous body  2 . With the help of the pipe  8  a corner of a so-called template  5  comprising a frame  6  and on each corner a guide bush  7  is secured. 
     The clamping device  11  only extends into the upper end of the pipe  8  and not at its outer side. In this way with the help of the vibrator block  1  the upper end of the pipe  8  can actually be brought to the level S or below it, the upper edge of the pipe  8  being situated in one plane S with the upper edge of the guide bush  7 , or below it. After that with the help of suitable hoisting elements the vibrator block  1  can simply be hoisted out of the pipe  8  after the clamping means of the clamping device  11  have been deactivated. 
     In FIG. 2 on the left-hand side a vertical cross-section through the clamping device  11  is shown, and on the right-hand side a side view thereon. 
     The clamping device  11  comprises an upper plate  12 , which is provided with a series of holes  14  with which the upper plate  12  and therewith the clamping device  11  can be attached to the vibrator block  10 . A cylinder casing  13  defining a cylindrical space  60  is formed as a unity with the upper plate  12 . In the cylindrical space  60  an annular piston  15  is accommodated, which by means of sealing rings  16  sealingly abuts the inner surface of the casing  13 . Above the piston  15  a pressure chamber  18  is situated, which chamber by means of gate  17  communicates with a hydraulic pressure lead, not shown, to a hydraulic pressure source. The pressure in the lead is adjustable by means of means not further shown. The piston  1   5  is screwed to the upper end  20  of a piston rod  19 , which further comprises an intermediate part  21  and a lower end  22 . The piston rod  19 , in particular its intermediate part  21 , is sealingly and slidingly accommodated in block  23  with the help of sealing rings  24  and  25 , the block being attached to the casing  13  by means of bolts  26  and provided with radially protruding attachment studs  27 . 
     With the help of bolts  26  a stop plate  40  is also attached to the block  23  and thus to the casing  13 , which stop plate  40  serves as positioning means for the clamping device  11  on the upper edge of the pipe  8 . 
     The upper end  20  of the piston rod  19  extends upwards to beyond the piston  15 , so that always some space remains left above the piston  15  and the hydraulic pressure means can easily get above the piston  15 . 
     A central wedge member  31  is screwed on the lower end  22  of the piston rod  19  which wedge member  31  at the—in this example four—sides is provided with wedge surfaces  32   a-d  arranged saw-toothed, which are each oriented obliquely downwards and to the outside and to below and merge into each other by means of horizontal steps  33   a - 33   c.    
     Inner clamping plates  30  are hung on the radial studs  27 , here four in number, with the help of annular upper ends  29 , which plates are kept in their places in axial direction of the pipe  8  with respect to block  23  by the studs  27 . The radial inner surface of the inner clamping plates  30  is saw-toothed, in order to suit the saw-toothed surface of the central wedge member  31 . At the upper side and the lower side each inner clamping plate  30  is provided with a vertical slit  39   a, b,  in which a pin  34   a, b  attached in the central wedge member  31  extends. 
     The radial outer surface of the inner clamping plates  30  is provided with a number of vertical teeth  36   a,    36   b  and  36   c,  with which the inner clamping plates  30  engage counter to axial sliding in corresponding teeth on outer clamping plates  37  placed against it. As can be seen in FIG. 3 the outer clamping plates  37  are tightened against the inner clamping plates  30  by means of a number of bolts  41 . Furthermore it can be seen that the outer clamping plates  37  are provided with two series of teeth  38   a,    38   b  that are inclined with respect to each other and separated from each other by a vertical slit  35 . The teeth  38   a,    38   b  can, as a result, be formed straight in horizontal direction and still be correctly oriented for an optimal engagement of the inner surface of the pipe  8 . 
     When the pipe  8  has to be vibrated into the bed  4  (both offshore and onshore) the clamping device  11  is attached to the vibrator block  1 , lowered in the upper end of the pipe  8 , until the plate  40  rests on the upper edge of the pipe  8 . Subsequently via gate  17  the space  18  is pressurized at a predetermined pressure, which is very high, for instance  320  bar,—adjusted to the radial outward pressure maximally to be taken by the tube, depending on the thickness of the wall and the kind of material—, as a result of which the piston  15  and thus the piston rod  21  is pushed downwards in the direction A with great force. In this way the central wedge member  31  will also be forced downwards in the direction A. The clamping plates  30  and  37 , however, remain in their places in axial direction with respect to the block  23 , by the engagement of the annular upper end  29  on the studs  27 . 
     During the downward movement of the central wedge member  31  the pins  34   a,    34   b  slide downwards within the slots  29   a,    29   b.  As a result of the oblique orientation of the surfaces  32   a - 32   d  and the inner clamping plates  30  remaining axially in their places, the inner clamping plates  30  will be forced radially to the outside in the direction B. The annular upper ends  29  here radially slide to the outside over the studs  27 , so that the clamping plates will not tilt. As a result of the connection between the inner clamping plates  30  and the outer clamping plates  37  the latter will also be forced to the outside in the direction B, and the teeth  38   a,    38   b  will be forced in the inner surface of the pipe  8  with great force. The clamping forces that can be reached here are large enough the maintain the engagement between the clamping device  11  and the pipe  8  when vibrating the pipe  8  into the bed and low enough to prevent deformation of the circumference of the pipe at that location. By way of example there could be a vibration frequency of 23 Hertz with a double amplitude of 25 mm and a maximal downward force in the order of 250 tons and a maximal upward force of a similar order of magnitude, with maximal accelerations in the order of 25 G. The vibrating forces here are directly passed on from the vibrator block  10 , via the upper plate  12 , the casing  13 , the block  23 , the studs  27 , the inner clamping plates  30  and the outer clamping plates  37  to the pipe wall. 
     As can be seen in FIG. 3 the clamping device  11  leaves a number of vertical passages  35  and  42  open, through which passages water can flow along the clamping device  11  in order to either enter the pipe  8  or to leave it. In this way an unwanted pressure build-up of the water in the pipe  8  during ramming is prevented. 
     The clamping device  11  is also suitable to be used in a similar manner during the removal of pipes from the bed. The possibly present guide bush does not impede the placing of the clamping device.