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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on PCT Patent Application No. NO2007/000146, filed on Apr. 26, 2007, which was based on Norwegian Patent Application Nos. 20061861, filed on Apr. 27, 2006 and 20064321, filed on Sep. 25, 2006. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     This invention regards a wedge device. More particularly, it regards a wedge device for clamping of pipes and tools during petroleum production. The wedge device comprises an annular mounting element arranged to be connected to a deck or a rotary table, and a plurality of main wedges with associated clamps, displaceable with respect to the annular mounting element, and which encircle the vertical central axis of the wedge device. Each clamp is located on an auxiliary wedge displaceably coupled to the main wedge. 
     Traditionally, drill rigs of the type used in petroleum production use a wedge device to suspend pipes, typically in the rig drill floor. 
     According to prior art it is common to make use of so-called slips which are placed in a tapered ring, and which are arranged to grip a pipe when the pipe and the slips are displaced downward in the tapered ring. 
     It is also known to make use of hydraulically actuated clamps to suspend pipes. 
     A common feature of these known solutions is the frequent need, brought on by the uncertainty of the operation, for a safety clamp to grip the pipe in the event that the slips or the hydraulically pretensioned clamps slip along the pipe. Devices according to prior art are often adapted a relatively narrow range of pipe dimensions. Thus it is necessary to have access to a number of different components in order to be able to work for instance on pipes having different diameter. 
     It is also difficult for the slips to take up any torque before a significant vertical load has been placed on them. 
     The object of the invention is to remedy or reduce at least one of the drawbacks of prior art. The object is achieved, in accordance with the invention, through the characteristics stated in the description below and in the following claims. 
     (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     Not Applicable. 
     BRIEF SUMMARY OF THE INVENTION 
     A wedge device in accordance with the invention for clamping of pipes and tools during petroleum production, the wedge device comprising an annular mounting element arranged to be connected to a deck or a rotary table, and where a plurality of main wedges, with associated clamps and displaceable with respect to the annular mounting element, encircle the vertical central axis of the wedge device, is characterized in that the clamps are located on an auxiliary wedge displaceably or rotatably coupled relative to the main wedge. 
     Advantageously the main wedges are individually hydraulically actuable, and the angle between the central axis and the direction of displacement of the main wedge is selected so that the difference between the spacing of the clamps in the retracted, open position and the spacing of the clamps in the extended, closed position, is acceptable, while at the same time preventing inadvertent outward displacement of the main wedges in the event of a loss of hydraulic pressure to the hydraulic actuators. 
     The angle between the central axis and the direction of displacement of the auxiliary wedge is selected so as to ensure that the auxiliary wedges are pulled downwards in the main wedges by the weight of a pipe positioned in the clamps. 
     Thus the angle between the central axis and the direction of displacement of the auxiliary wedge is typically smaller than the angle between the central axis and the direction of displacement of the main wedge. 
     The angle between the central axis and the direction of displacement of the main wedge will have to be between 0 and 60 degrees, an angle of between 5 and 30 degrees between the central axis and the direction of displacement of the auxiliary axis showing good results, depending on the application. The angle between the central axis and the direction of displacement of the auxiliary wedge will have to be between 0 and 30 degrees, an angle of between 1 and 10 degrees between the central axis and the direction of displacement of the auxiliary axis showing good results, depending on the application. 
     A spring is connected between the auxiliary wedge and the main wedge. The spring is arranged to transfer vertical forces from the auxiliary wedge to the main wedge. Compressing the spring will displace the auxiliary wedge relative to the main wedge in the event of e.g. a loss of hydraulic pressure. Following disengagement of the clamps, the spring will displace the auxiliary wedge to its initial position with respect to the main wedge. 
     The constructional design of the wedge device means that the wedge device can operate within a relatively large range of pipe diameters without requiring a change-out of components in the wedge device. The design comprising double wedges in the form of main wedges and co-operating auxiliary wedges prevents the pipe from slipping in the wedge device in the event of a loss of hydraulic pressure. 
     Controlling the wedges interlocked and in groups will also ensure that the pipe is not inadvertently released, for instance when the pipe has a relatively low weight, thereby eliminating the need for an extra safety clamp around the pipe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following there is described a non-limiting example of a preferred embodiment illustrated in the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a wedge device according to the invention; 
         FIG. 2  is a vertical section III-III through the wedge device in  FIG. 3 , with the wedges in a retracted position; 
         FIG. 3  is a plan view of the wedge device in  FIG. 2 ; 
         FIG. 4  is a vertical section V-V through the wedge device in  FIG. 5 , with three of the wedges in a fully extended position; 
         FIG. 5  is a plan view of the wedge device in  FIG. 4 ; 
         FIG. 6  is a vertical section through a wedge assembly; 
         FIG. 7  is a section VI-VI through  FIG. 6 ; 
         FIG. 8  is a plan view of the wedge device, with three wedges pretensioned against three other wedges; and 
         FIG. 9  illustrates an alternative embodiment in which the auxiliary wedges are constituted by eccentrically supported pivoted wedges. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, reference number  1  denotes a wedge device positioned in a deck  2 , and which comprises an annular mounting element  4  and a plurality of main wedges  6  encircling the vertical axis  8  of the wedge device  1 . 
     The annular mounting element  4  connected to the drill floor  2  consists of two pieces and is provided with connecting bolts  10 . Thus the annular mounting element  4  is arranged to be opened if so required. 
     Each main wedge  6  is displaceably coupled to a mounting block  12 , typically by a main guide  14 . The main guide  14  makes an angle a with the central axis  8 , see  FIG. 6 . In this preferred exemplary embodiment, the angle a is 20 degrees. 
     A hydraulic cylinder  16  is connected in an articulated manner between the upper portion of the mounting block  12  and the main wedge  6 . The hydraulic cylinder  16  is connected to a hydraulic control system (not shown) by hose and pipe connections (not shown), and is arranged in a controlled and synchronous fashion to move the main wedge  6  along the main guide  14 , between a retracted, open position, see  FIG. 3 , and an extended, closed position, see  FIG. 5 . 
     An auxiliary wedge  18  is displaceably coupled to the main wedge  6  by an auxiliary guide  20 , the auxiliary guide making an angle b with the central axis  8 , see  FIG. 6 . In this preferred exemplary embodiment, the angle b is 5 degrees. 
     On the side facing the central axis  8 , the auxiliary wedge  18  is provided with a clamp  22 . The clamp  22  is shaped to firmly engage a pipe  24  located in the gripping device  1 , see  FIG. 5 . The clamp  22  may consist of a separate material, or it may be an integral part of the auxiliary wedge  18 . 
     Both the main guide  14  and the auxiliary guide  20  are designed to take up torque. 
     The main wedge  6  is provided with a compression spring  26  projecting essentially in parallel with the central axis  8 , against a shoulder  28  on the auxiliary wedge  18 . Thus the compression spring  26  transfers forces from the auxiliary wedge  18  to the main wedge  6 . 
     When the auxiliary wedge  18  is displaced in the direction of the spring  26  force, the shoulder  28  stops against a wedge lock  30  at the opposite side relative to the compression spring  26 . Thus the wedge lock  30  prevents the auxiliary wedge  18  from being displaced out of its auxiliary guide  20 . 
     The auxiliary wedge  18  is also prevented from displacing out of the auxiliary guide  20  in the downward direction. 
     The mounting block  12  is provided with a dovetail  32 , see  FIG. 7 , which is a complementary fit to a dovetail groove  34  in the annular mounting element  4 . 
     The mounting block  12 , the main wedge  6 , the auxiliary wedge  18  and the hydraulic cylinder  16  form parts of a wedge assembly  36  which is quite easily replaced by using the dovetail joint  32 ,  34 . This is particularly advantageous in connection with completion and intervention operations in a petroleum well. 
     In the preferred embodiment, the wedge device  1  is arranged to grip pipes ranging from a diameter of 60 mm (2⅜″) to a daylight opening of 330 mm (13″) without requiring a change of wedge assemblies  36 . Another set of wedge assemblies  36  covers the range from a diameter of 241 mm (9.5″) to a daylight opening of 483 mm (19″). 
     To grip a pipe  24 , three or six main wedges  6 , all depending on the pipe dimensions, are synchronously displaced towards the pipe  24  by respective hydraulic cylinders  16 , whereby the clamps  22  grip around the pipe  24 . The synchronous extension of the main wedges  6  causes the clamps  22  to clamp the pipe  24  in a central position in the wedge device  1 . 
     If the pipe  24  is of a relatively small diameter, there is only room for three clamps  22  up against the pipe  24 . The remaining main wedges  6  are still moved into abutment against the gripping main wedges. The control mechanism (not shown) is connected up in a manner such that an operating error will result in only three clamps being released, thus preventing inadvertent release of the pipe  24 , which could fall into e.g. a well (not shown). 
     In the event of a loss of hydraulic pressure to the cylinders  16 , the auxiliary cylinders  18  will still be pulled downwards in the main wedges  6  due to the weight of the pipe  24  suspended from the clamps  22 , thus gripping around the pipe  24  with an even stronger grip. 
     In an alternative embodiment the auxiliary wedge is constituted by an eccentrically supported pivot wedge  38  which can be rotated about a shaft  40 . The mode of operation of the pivoted wedge, relative to the main wedge  6 , is the same as that described above, the pitch of the pivot wedge  38  being indicated by reference c in  FIG. 9 . 
     The pivot wedge is provided with a gripping surface  42  arranged to grip the pipe  24 .  FIG. 9  does not show the pipe  24 . A downward force from the pipe  24  will seek to rotate the pivot wedge  38  into an even tighter engagement with the pipe  24 . The pivot wedge  38  can be made up of several coordinate plates.

Summary:
A wedge device for clamping of pipes and tools during petroleum production, this wedge device comprising an annular mounting element arranged for connection to a deck or a rotary table, where a plurality of man wedges, with associated clamps and displaceable with respect to the annular mounting element, encircle the vertical central axis of the wedge device, and where the clamp is located on an auxiliary wedge displaceably or rotatably coupled to the main wedge.