Abstract:
The invention proposes a method for the integral molding of a flange ( 5 ) onto the end of a round or oval pipe ( 11 ) of thin-walled sheet metal. This method takes place in two stages. In a first stage, for the purpose of accumulating material, a sectionally circular or spiral-shaped bead ( 17 ) is molded on by means of a pre-forming roller tool ( 9 ), comprising a combination of rollers ( 13  to  15 ) (Figure a). In a second stage, the molded-on bead is compacted with the aid of a final-forming roller tool ( 18 ), comprising the rollers ( 19 ) and ( 20 ), to produce an at least partly solid flange ( 5 ) (Figure b).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a §371 National Phase of PCT/EP2006/006311, filed Jun. 29, 2006, the entirety of which is hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     Pipes made of thin-walled sheet metal are typically composed of sub-sections that are connected to one another. The method of connection crucially influences how economically the sub-sections can be produced and assembled. This also applies to pipe-shaped devices or devices comprising pipe-shaped connections, which must frequently be integrated in such pipes, and to pipe-shaped apparatuses comprising sub-sections. 
     With respect to the methods of connection, a differentiation is made between plug connections, which are predominantly used for smaller diameter pipes comprising sub-sections, and flanged connections. For these flanged connections, in general separate flanges are produced, which are screwed, riveted, welded or otherwise attached to the pipe end. 
     The flanges are produced by forming of the pipe end only in some cases. 
     The simplest way of an integrally formed flange is the stay flange, which is obtained by folding the edge of the pipe end at a right angle. In addition, crimpings are known, which are produced by rolling the pipe end into a bead that is substantially circular in its cross-section. 
     To connect these flanges configured as stay flanges or crimpings, tensioning rings having a U- or V-shaped cross-section are used, the clearance width of these rings being adjusted to the cross-section of the flanges bearing on one another. The tensioning rings must be considerably rigid because neither the stay flange nor the crimping sufficiently brace the pipe at the end in the radial direction. Higher radial rigidity is achieved with such integrally formed flanges that are created by folding up the pipe end twice at a right angle. Flanges of this type are used primarily for device housings, particularly the housings of radial fans. The flanges are connected to one another mostly be screws that are distributed across the circumference. 
     One of the more recent publications includes a method known from DE 100 47 310 A1 for integrally forming a flange to the end of a thin-walled pipe, which is first bent upward by 150° and then by 90°, thus creating a flange with a conical outer surface. The flanges bearing on one another on the abutment site of two pipe pieces can be connected by means of a tensioning ring having a V-shaped cross-section. 
     Due to drastically increased requirements with respect to tightness and smooth inside surfaces, particularly for the air ducts in ventilation, air conditioning and exhaust technology, increasingly pipes with integrally formed flanges are used. The disadvantage, however, is that the strength of the material forming the flange automatically only corresponds to the pipe wall thickness, which is frequently not sufficient for the required stability. To reinforce the flange, it has therefore been proposed, for example according to DE 102 15 112 C1, to slide a reinforcing ring on the end of the pipe section used for forming the flange, the ring doubling the wall thickness of the flange. 
     Frequently, however, even this type of reinforcement is not sufficient and not satisfactory. 
     It is therefore the object of the present invention to provide a method and a device for the integral forming of a flange to the end of a round or oval pipe made of thin-walled sheet metal, which allow a considerably stronger and considerably more stable flange to be produced. Such an object is achieved in that in a first stage, for the purpose of accumulating material, the end of an axial sub-section of the pipe is formed into a bead, while axially advancing a pre-forming roller tool at the same time, whereupon in a second stage the bead is compressed by means of a final-forming roller tool to produce a solid flange. 
     SUMMARY OF THE INVENTION 
     With this method, which can be performed using comparatively simple tools, solid or partly solid flanges being considerably thicker than the wall thickness of the pipe can be produced. 
     In the simplest case, the pre-forming roller tool is advanced enough that a bead having a substantially circular cross-section and at least one layer is produced, which is formed into a partly solid flange in the second stage. 
     If, the pre-forming roller tool is advanced so far that a bead having a substantially spiral-shaped cross-section and at least two layers is produced, in the second stage this bead can be compressed into a substantially solid flange. 
     If the advancement of the pre-forming roller tool occurs after the bead has been formed, the wall of the bead is compressed, thus creating a flange with higher density during the subsequent final-forming step. 
     According to this method, a round or oval pipe made of thin-walled sheet metal comprising an integrally formed, at least partly solid flange can be produced, which, is thicker than the wall thickness of the pipe and preferably has a rectangular, square, triangular or trapezoidal cross-section with rounded edges. 
     For example, it is possible to produce a flange for a pipe having a wall thickness in the range of 0.5 to 5 mm, the mean thickness of this flange measured in the axial direction of the pipe corresponding to two to ten times the thickness of the pipe wall. 
     So as to perform the method, a device is proposed, which comprises a pre-forming roller tool for producing the bead, a final-forming roller tool for producing the solid flange as well as a clamping device for the pipe. The roller tools are disposed non-rotatably, but radially and axially displaceably, and the motor-driven clamping device for the pipe is disposed rotatably, but axially non-displaceably on a mount. 
     In this device, the pipe to be provided with a flange revolves, while the roller tools are advanced axially in relation to the pipe. 
     In another exemplary embodiment, the roller tools are disposed jointly on a motor-driven, rotatably mounted rotary table such that they are radially and axially displaceable, while the clamping device for the pipe is provided on the mount such that it is not axially displaceable and not rotatable. 
     During the production of the flange using the device, the roller tools revolve around the braced pipe, while being axially advanced at the same time. 
     The configuration of the pre-forming roller tool is described herein. 
     The final-forming roller tool is also described herein. 
     Further design details of the roller tools are disclosed herein. 
     For clamping of the pipe, a clamping device is suited, in which radially displaceable jaws rest against the inside pipe wall in a force-fit manner. 
     In another embodiment, an elastic spring-loaded disk can be used for clamping, the tensioning finger of the disk likewise engaging the inside wall of the pipe in a force-fit manner. 
     Design measures, for example for actuating the clamping device or the drive of the tensioning device are characterized herein. 
     A pressure ring is proposed herein for clamping relatively thin-walled pipes. 
     To make production even more economical, a device is suited, which simultaneously molds flanges onto both pipe ends, as is described in detail herein. 
     The inventive device for producing pipes from sheet metal comprising integrally formed flanges according to the present invention is particularly suited for fully automatic production. For this purpose, a programmable circuit is required for controlling the drive mechanisms, valves and similar units based on defined manufacturing procedures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Details of the method as well as of the device for the integral forming of a flange to the end of a round or oval pipe as well as the pipes produced by this method are described hereinafter with reference to the exemplary embodiments illustrated in the figures, wherein: 
         FIG. 1  to  FIG. 4  are longitudinal sectional views of the pipe with comprising the integrally formed flange, 
         FIG. 5  to  FIG. 12  are longitudinal sectional views of the pre-forming roller tool with the end of the pipe to be provided with a flange in various processing stages, 
         FIGS. 10   a ,  11   a  are enlarged details according to  FIG. 10  and  FIG. 11 , 
         FIG. 13  to  FIG. 17  are longitudinal sectional views of the final-forming roller tool with the end of the pipe to be provided with a flange in various processing stages, 
         FIG. 18  is an axial section of a complete device for the integral forming of a flange according to the first exemplary embodiment, 
         FIG. 19  is a top view of the device according to  FIG. 18 , 
         FIG. 20  is a perspective illustration of a device for the integral forming of flanges at both ends of a pipe, 
         FIG. 21  is an axial section of a complete device for the integral forming of a flange according to the second exemplary embodiment, 
         FIG. 22  is a top view of the device according to  FIG. 21 , 
         FIG. 23  is a perspective illustration of a pressure ring, 
         FIG. 24  is a perspective illustration of a spring-loaded disk, 
         FIG. 25  is a perspective illustration of a clamping device inserted in the end of a pipe comprising the elements according to  FIGS. 23 and 24 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 to 4  illustrate four different possibilities of solid flanges that can be produced according to the invention. As the figures show, flanges  5  to  8  are integrally formed on the pipe walls  1  to  4  of a pipe, which is not shown in detail, the flanges being partly solid or solid depending on the compression. These flanges may have nearly arbitrary cross-sectional shapes. Preferred are flanges with a trapezoidal cross-section  5 ,  6  or  8 , or flanges with a rectangular cross-section  7 , which are particularly suited for an assembly with tensioning rings. The material accumulation in the flange profile produces extraordinarily high radial and axial flange rigidity. 
     The production of these flanges occurs by forming the pipe end  10  of the pipe  11  in a two-stage process: 
     In the first stage, which is explained based on  FIGS. 5 to 12 , first the end  10  of the pipe  11  is formed into a bead  17  by means of a special rolling method. 
     In a second stage, which is explained based on  FIGS. 13 to 17 , this preformed bead is compressed into the desired shape of the solid or partly solid flange using a special milling method. 
     To produce the bead, the pre-forming roller tool  9  is used, which comprises the rollers  13  and  15 , which are disposed axially parallel, and the roller  14 , which is disposed with the axis  14   b  thereof perpendicular to the axes  13   c  and  15   d . The roller  13  is shaped such that it comprises at the upper end thereof a substantially cylindrical section  13   a  and connected thereto a likewise cylindrical section  13   b  having a smaller diameter. 
     The profiled roller  15  at the upper end thereof likewise comprises a cylindrical section  15   a  and connected thereto an annular groove  15   b  having a quarter-circle cross-section and connected thereto a cylindrical section  15   c  having a smaller diameter. 
     The third roller of the roller combination  9  disposed in T-shape is provided and dimensioned such that it engages the space between the cylindrical sections  13   b  and  15   c . This roller  14  has an annular groove  14   a  with a semi-circular cross-section. As the figure shows, the annular grooves  14   a  and  15   b  together with the cylindrical section  13   a  form a formed groove  16  with a circular cross-section, wherein the diameters of the sections  13   a  and  15   a  are dimensioned such that a receiving gap  12  remains between the rollers  13  and  15 , the clearance width of the gap corresponding to the thickness of the pipe wall  1 . 
     So as to produce the bead in the first stage of the method, the pipe  11  is rotated in relation to the pre-forming roller tool  9  or the pre-forming roller tool  9  in relation to the pipe  11 , wherein the pre-forming roller tool  9  or the pipe  11  is displaced in the axial direction A toward the pipe  11  or the pre-forming tool  9 . The wall  1  is inserted in the gap  12  between the rollers  13  and  15  until it comes in contact with the semi-circular formed groove  14   a  of the roller  14 , which is shown in  FIG. 6 . 
     During further advancement of the pre-forming roller tool  9  or of the pipe  11 , the outer edge  10  of the pipe wall  1  is beaded by means of the annular groove  14   a  of the roller  14  into a substantially semi-circular bead  17 , which is shown in  FIG. 7 . During further advancement of the roller tool  9  in the direction A or of the pipe  11 , the outer edge  10  of the pipe  11  is inserted in the annular groove  15   b  of the roller  15 , the groove having a quarter-circle cross-section, thus forming the edge  10  into a bead having a circular cross-section. This stage of the method is illustrated in  FIG. 8 . 
     If the advancement of the roller tool  9  is continued in the direction of the arrow A or of the pipe  11 —of course with continued relative rotation of the roller tool and pipe  11 —the bead  17  initially having a substantially circular cross-section becomes a bead  17  having a substantially spiral-shaped cross-section, as is illustrated in  FIGS. 9 ,  10  and  10   a.    
     This bead per se is already suited for the production of a partly solid flange in the second stage. 
     If higher material density for a solid flange is to be achieved, the axial advancement of the pre-forming roller tool  9  in the direction of the arrow A or of the pipe  11  is continued from the position shown in  FIGS. 10 and 10   a . Since no further crimping occurs due to the higher rolling resistance, the outer windings of the bead  17  are compressed due to the containment in the formed groove  16 , which prevents the material from giving way, so that the material thickness of the bead windings increases, as  FIGS. 11 and 11   a  show. 
     The advancement of the pre-forming roller tool  9  or of the pipe  11  is ended when a sufficient amount of material of the outer edge  10  of the pipe has been formed and compressed to achieve the necessary rigidity of the flange. 
     After completion of the axial advancement of the pre-forming roller tool  9  or of the pipe  11  as well as the relative rotation between the pre-forming roller tool  9  and the pipe  11 , the roller  15  is moved radially away from the pipe  11  in the direction of the arrow B and braced to complete this first stage. Thereafter, the rollers  13  and  14  are pulled back, together with the roller  15 , in the opposite direction of the advancement direction and parallel to the axis of the pipe  11 , which is to say in the direction of the arrow C, into the starting position where they remain until the next pipe is processed. 
     It is not until during the next processing operation that the roller  15  is again retracted radially in the opposite direction of the arrow B, is braced and then axially advanced, together with the rollers  13  and  14 , in the opposite direction of the arrow C. 
     So as to produce the bead for pipes made of sheet metal having a wall thickness of 0.5 mm to 5 mm, a speed in the range 0.1 to 2 mm per pipe revolution has proven advantageous for the axial advancement of the pre-forming tool  9  or of the pipe  11 . 
     The second stage until the completion of the partly solid or solid flange will be explained with reference to  FIGS. 13 to 17 . 
     The final-forming roller tool  18  comprises two profiled rollers  19  and  20 , which are angularly displaceable in relation to one another and with respect to the wall  1  of the pipe  11  from the position shown in  FIG. 13  such that ultimately they assume the final position shown in  FIG. 16 . 
     The rollers  19  and  20  comprise annular grooves having a substantially V-shaped cross-section, the grooves being limited by the annular surfaces  19   a  and  19   b  or  20   a  and  20   b , which are disposed at an angle in relation to one another. 
     These annular surfaces are disposed and dimensioned such that they form a space that corresponds to the desired cross-section of the flange  5  as well as a required receiving gap  21  for the pipe wall  1  in the final position of the forming rollers  19  and  20 , which is shown in  FIG. 16 . 
     In the finishing stage of the flange, the rollers  19  and  20  are displaced jointly from their position shown in  FIG. 13  toward the bead  17  of the pipe  11 , initially parallel to the pipe axis in the direction of the arrow D, until the roller  19  with the annular surface  19   b  thereof comes in contact with the lower edge of the bead  17 , which is shown in  FIG. 14 . Then, the roller  20  is displaced obliquely in the direction of the arrow E, which is to say against the pipe wall  1  and the bead  17 , until it comes in contact with the annular surface  20   c  thereof with the wall  1  and with the annular surface  20   b  with the top of the bead  17 , which is shown in  FIG. 15 . The bead is hereby deformed to form the inner beveled surface of the flange. The roller  20  is locked in this position. The continued forming of the flange occurs by means of the forming roller  19 , which is now obliquely displaced from the position shown in  FIG. 15  in the direction of the arrow F against the locked roller  20  until the annular surface  19   a  thereof comes in contact with the inside of the pipe wall and has compressed the bead by means of the annular surface  19   b  into the flange  5  shown in  FIG. 16 . 
     Depending on the dimensions of the annular surfaces  19   a  and  19   b  or  20   a  and  20   b , flanges with different profiles and different dimensions can be produced. 
     After the flange  5  has been completed, the rollers are retracted from the position shown in  FIG. 16 , initially in the directions of the arrows G and H, as is shown in  FIG. 17 . 
     The rollers  19  and  20  of the final-forming roller tool  18  can now be jointly retracted in the opposite direction of the advancement direction parallel to the pipe axis in direction of the arrow I into the starting position. They are ready for another finishing operation. 
     For the advancement directions E and F an angle of approximately 45° has proven advantageous. Angles in the range of 45°±3° are also still practical. For angles outside of this range, however, the material forming result is inadequate. 
     As in the first stage, in the second stage the rollers are not driven, instead they revolve freely. 
     They must be mounted both radially and axially such that they tolerate high stresses. For this, in particular tapered roller bearings are suited. 
     The speed for the axial advancement of the final-forming roller tool  18  or of the pipe  11  advantageously ranges between 0.1 and 2 mm per revolution of the pipe or the tool  18 . 
     The dimensions of the rollers of the pre-forming roller tool and of the rollers of the final-forming roller tool as well as the axial advancement during the pre-forming operation must be matched such to each other that partly solid or solid flanges with rounded edges are produced. 
     If the ratios are not correct, flanges with sharp edges or even flanges with burrs or hollow flanges are produced. 
     In principle, if the tools are dimensioned correctly, nearly any flange cross-section can be produced regardless of the pipe wall thickness, with wall thicknesses in the range from 0.5 to 5 mm being preferred. As a result, the method can also be used for the production of flanges for pipe-like devices and apparatuses. 
     A first exemplary embodiment of a complete device for integrally forming a flange to a pipe  11  is illustrated in  FIGS. 18 and 19 . In this device, the roller tools  9  and  18 , which were explained in detail with reference to  FIGS. 5 to 17 , are provided radially displaceably on tool carriages  24  and  25  at the base plate  23  of a mount  37 . Adjusting spindles  32  serve the radial adjustment. The rollers  13  to  15  of the pre-forming roller tool  19  and the rollers  19  and  20  of the final-forming roller tool  18  are mounted axially and radially displaceably on the respective carriages  24  and  25  by means of advancing devices, which are not shown, in the manner explained with reference to  FIGS. 5 to 17 . 
     In the exemplary embodiment according to  FIG. 18 , the pipe  11  performs a rotary motion in relation to the mount  37  in order to produce the flange, while the carriages  24 ,  25  carrying the roller tools  9  and  18  are stationary. The carriages  24  and  25 , which are radially displaceable by means of the adjusting spindles  32  or optionally by means of pneumatic or hydraulic cylinders, are connected to the base plate  23  of the mount  37  by means of sufficiently stable and precise guide rails  36 . The freely revolving rollers  13  to  15  of the pre-forming roller tool  9  or  19  and  20  of the final-forming roller tool  18  are mounted in blocks provided on the carriages  24  and  25  and can be displaced by means of guides, which are not shown, in the manner explained with reference to  FIGS. 5 to 17 . Hydraulic or pneumatic cylinders integrated in the blocks, or threaded spindles with gear or servo motors, serve as the drive mechanisms, but are not shown. 
     For clamping the pipe  11 , a tensioning disk denoted with reference numeral  31  is used, which comprises a base disk  33  with tensioning segments  34  mounted radially displaceably thereon in a radial shape, which is shown in more detail in the top view according to  FIG. 19 . The base disk  33  is carried by a central hollow shaft  26 , which is mounted in the bearing block  27  attached to the bottom of the base plate  23 . The tapered roller bearings  27   a  of this bearing block  27  absorb the extremely high radial and axial loads. 
     So as to actuate the tensioning disk  31 , a pull rod  29  extending through the hollow shaft  26  is provided, at the upper end thereof a tensioning cone configured as a conical polygonal bolt  35  is attached, which rests against the inside jaw ends  34   a  of the jaws  34 . During the downward axial displacement of the pull rod  29  by means of a double-action cylinder  30 , the jaw segments  34  are consequently displaced radially outward and rest against the inside wall of the pipe  11  to be clamped in a force-fit manner. To detach the pipe  11 , the pull rod  29  is displaced in the opposite direction by means of the cylinder  30 . Return springs, which are not shown and are installed in the jaw segments  34 , ensure the return of the jaw segments  34 , so that the pipe  11  is released. 
     A drive motor  28  disposed in the mount  37  serves the rotary drive of the clamping device, the pinions  28   a  of the motor engaging a gear wheel  28   b  provided on the inner end of the hollow shaft  26 . 
     Instead of gear wheel drives also chain or toothed belt drives are suited. 
     Using the device according to  FIGS. 18 and 19 , the production process is as follows. 
     Before starting production, the pre-forming and final-forming roller tools  9  and  18  are adjusted by means of the carriages  24  and  25  to the diameter of the pipe section  11  to be provided with a flange and moved to the base position explained with reference to  FIGS. 5 to 17 . 
     The pipe  11  is pushed over the tensioning disk  31  such that the axial sub-section  11   a  required for the operation protrudes the bottom edge of the tensioning disk  31 . In this position, the pipe is clamped by spreading the jaw segments  34  and is then rotated at a rotational speed of between 20 and 300 rpm by means of the drive motor  28 . 
     The bead is integrally formed by means of the pre-forming roller tool  9 , as is explained above with reference to  FIGS. 5 to 12 . This is followed by the second processing stage, namely the production of the partly solid or solid flange by means of the final-forming roller tool  18  without interrupting the rotation of the pipe  11 . This process is described above with reference to  FIGS. 14 to 17 . After finishing the flange, also the final-forming roller tool  18  is returned to the original position. The rotation is stopped. After loosening the tensioning disk  31 , the pipe  11  with the integrally formed flange according to  FIGS. 1 to 4  can be removed from the device. 
     Not shown in the figures are driving elements, valves and the similar units for the programmed control of the entire device, which enable a fully automatic production process based on predefined data. These units and the controller are preferably accommodated in a mount  37  covered with a sheet metal housing. 
     The device according to  FIGS. 18 and 19  is only suited for integrally forming a flange to one end of a pipe  11 . 
     For economical reasons, particularly in straight pipe sections, it may be advantageous to integrally form flanges on both end of the pipe section at the same time. 
     For this purpose, the device illustrated in  FIG. 20  is provided, wherein two forming units  38 , the design of which corresponds to the device according to  FIGS. 18 and 19 , are disposed horizontally in a pipe mount  39 , so that the tensioning disks  31  are disposed opposite from one another. 
     At least one of the two forming units  38  can be horizontally displaced in the support rails  41  in the direction of the double arrow K with the help of driven threaded spindles  40 . In this way, the distance of the two forming units  38  can be adjusted in accordance with the pipe length, wherein at least one forming unit  38  is axially displaceable for inserting and removing the pipe  11 . 
     Another variant for producing a flange that is integrally formed on the pipe, the variant being referred to as the forming unit  42 , is illustrated in  FIGS. 21 and 22 . 
     In this exemplary embodiment, which is particularly suited for processing non-rectilinear pipe sections, the pipe is stationary during processing, while the roller tools  9  and  18  are provided on a rotary table  43  driven by the gear motor  45  and rotating about the axis of the pipe  11 . 
     The device for clamping the pipe  11  is designed similar to that provided in the device according to  18  and  19 . Here as well, a tensioning disk  31  comprising jaw segments  34  serves the bracing of the pipe  11 , the segments being radially displaceable with the help of a polygonal bolt  35 , the pull rod  29  and the cylinder  30 . The base disk  33  carrying the jaw segments  34  is provided at the upper end of the hollow shaft  26  through which the pull rod  29  extends. Unlike in the device according to  FIGS. 18 and 19 , the hollow shaft  26  is firmly connected to the base plate  23  of the mount  37 . 
     The rotary table  43  is rotatably about the hollow shaft  26 . At the bottom thereof, it is provided with a rotating rim gear  44 , which is connected to the pinion  45   a  of the gear motor  45 . 
     On the rotary table  43 , the carriages  24  and  25  with the roller tools  9  and  18  are disposed, the carriages being radially displaceable by adjustment spindles  32 , wherein the design and configuration of the tools correspond to those according to  FIGS. 18 and 19 . 
     The forming unit  42  shown in  FIGS. 21 and 22  is above all suited for forming flanges on molded parts or awkwardly shaped pipes, since these do not require rotation during the flanging operation. 
     During the one-sided forming of a flange by means of the devices according to  FIGS. 18 and 19  or  21  and  22 , it is very important that the pipe  11  is clamped with extremely high stability by the tensioning disk  31  since the pipe  11  must not only be tensioned radially, but must also be braced against the impact of the axially displaceable roller tools  9  and  18 . Otherwise, complete and precise forming of the flanges is not possible. When simultaneously forming the flanges on both pipe ends of the device according to  FIG. 20 , clamping is less critical because the axially acting forces applied by the roller tools offset one another. 
     The clamping of relatively thin-walled pipes with one-sided integral flange formation is especially critical because the tensioning disk  31  to be inserted in the pipe, including the jaw segments  34  of said disk, can radially deform the pipe if the jaw segments apply a higher amount of pressure. The pressure acting in the radial direction, however, can be reduced only to a limited extent because the pipe during processing must be fixed in place non-rotatably by the friction force. 
     For the one-sided integral forming of flanges on thin-walled pipes therefore a modified clamping device is proposed, which is illustrated in  FIGS. 23 to 25 . 
     So as to prevent pipe expansion under the action of the tensioning disk, which is to say so as to produce counter-pressure, a pressure ring  46  is provided, which is attached at the height of the tensioning disk on the outside of the pipe  11 . For this purpose, the pressure ring  46  is configured in two pieces. The two parts  46   a  and  46   b  can be connected to one another after being slid onto the pipe  11 , for example by means of screw assemblies on  47 . Instead of a second screw assembly, it is also conceivable to provide an articulated connection of the parts  46   a  and  46   b , for example by means of a hinge or the like. 
     In this exemplary embodiment, a conical spring-loaded disk  48  configured as a disk spring is provided as the tensioning disk, which is divided into radially extending tensioning fingers  50  provided in a radial shape from the center bore  41  by means of radial slots  49 . This spring-loaded disk  48  sits on a pressure plate  53  to be inserted into the inside of the pipe, the plate being attached to the upper end of the hollow shaft  26 . Again, a pull rod  29  axially extending through the hollow shaft  26  and the pressure plate  53  serves the actuation of the spring-loaded disk  48 , the upper end of the rod penetrating the center bore  51  of the spring-loaded disk  48  and being connected thereto by a nut  54 . 
     If a pulling force is applied to the pull rod  29  by means of the cylinder, which is not shown, the tensioning fingers  50  are spread and rest against the inside wall of the pipe  11  in a force-fit manner, wherein they grab the pipe wall when an appropriate pulling force is applied. This is possible because the pressure ring  46  prevents radial evasion of the pipe wall, thus fixing the pipe  11  in place. The spring-loaded disk  48  allows the pulling force applied by the pull rod  29  to be multiplied, wherein as the cone angle of the spring-loaded disk  48  flattens the spreading force of the spring-loaded disk  48  increases. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Pipe wall
         1   a  Inner wall surface     1   b  Outer wall surface   
     
           2 ,  3 ,  4  Pipe wall 
           5 ,  6 ,  7 ,  8  Flange 
           9  Pre-forming roller tool 
           10  Outer rim or edge of the pipe end 
           11  Pipe
         11   a  Axial sub-section     11   b  Pipe axis   
     
           12  Receiving gap between rollers  13  and  15   
           13  Roller of the pre-forming roller tool  9 
         13   a  Cylindrical section     13   b  Cylindrical section     13   c  Axis   
     
           14  Roller of the pre-forming roller tool  9 
         14   a  Annular groove     14   b  Axis   
     
           15  Roller of the pre-forming roller tool  9 
         15   a  Cylindrical section     15   b  Annular groove     15   c  Cylindrical section     15   d  Axis   
     
           16  Formed groove 
           17  Bead 
           18  Final-forming roller tool 
           19  Forming roller
         19   a ,  19   b  Annular surfaces   
     
           20  Forming roller
         20   a ,  20   b ,  20   c  Annular Surface   
     
           21  Receiving gap 
           22  - - - 
           23  Base plate 
           25  Tool carriage 
           25  Tool carriage 
           26  Hollow shaft 
           27  Bearing block
         27   a  Tapered roller bearing   
     
           28  Drive motor
         28   a ,  28   b  Gear wheels   
     
           29  Pull rod 
           30  Dual-action cylinder 
           31  Tensioning disk 
           32  Adjusting spindles 
           33  Base disk 
           34  Jaw segments
         34   a  Inner jaw ends   
     
           35  Conical polygonal bolt, clamping cone 
           36  Guide rails 
           37  Mount 
           38  Forming unit 
           39  Pipe mount 
           40  Threaded spindles 
           41  Support rails 
           42  Forming unit 
           43  Rotary table 
           44  Rotating rim gear 
           45  Drive motor
         45   a  Gear wheel   
     
           46  Pressure ring
         46   a ,  46   b  Parts of the pressure ring  46     
     
           47  Screw assembly 
           48  Spring-loaded disk 
           49  Slot 
           50  Tensioning finger 
           51  Bore 
           52  Spring-loaded tensioning disk 
           53  Pressure plate 
           54  Nut 
         A to K Arrows to designate directions of movement