Abstract:
The invention relates to a device for forming an end area of a workpiece ( 2 ), especially for cold press-forming an end area of a pipe, comprising two force transmitting elements ( 7, 9 ) which are guided in a common housing ( 3 ). The device is characterised in that a first pressure chamber ( 26 ) is located between the two force transmission elements ( 7, 9 ) and in that a second pressure chamber ( 28 ) is allocated to the second force transmission element ( 9 ). When the first force transmission element ( 7 ) is in the bracing position, the second force transmission element ( 9 ) can be displaced in relation to the first force transmission element ( 7 ) in order to form the workpiece.

Description:
DESCRIPTION  
         [0001]    The invention relates to a device for shape-forming the end region of a workpiece, especially for cold-press shape-forming of a pipe end region. It is known to set in compression a workpiece by means of a first hydro-dynamically actuable force transmission element and to shape-form the end region via direct or indirect application of force thereagainst by a second hydrodynamically actuable force transmission element. The concept of hydro-dynamically actuable force transmission elements comprehends a body which is actuable in a hydraulic and/or pneumatic manner. In connection with the highest force which is required for the shape-forming of a workpiece, a hydraulic actuation is chosen specifically for this purpose.  
           [0002]    DE 195 11 447 A1 discloses a device adapted for shape-forming a pipe end region. This device includes a recess for exchangeable jaws operable to set the pipe in compression. By means of a first hydraulically actuable piston, the jaws are driven under pressure in order to compressively engage the pipe. The first piston comprises a central through opening in which a piston rod of a second hydraulically actuable piston is guidably disposed. The two pistons are in this manner coaxially movable within one and the same housing serially one behind the other.  
           [0003]    The piston rod of the second piston, which is provided with a shape-forming tool, can effect application of a force on the pipe end region, in view of the fact that the piston rod extends through the central, end-to-end continuously open, opening in the first piston, whereby the pipe end region is shape-formed in the axial direction. In this manner, the end region deforms in correspondence with the geometry of the shape-forming tool and the jaws.  
           [0004]    In a special configuration, the known device comprises a three-part housing. A first housing portion has a first bore in which the first, annularly shaped, piston is movably guided with its sleeve and has a second bore in which the second piston with its piston rod is movably guided. The second bore has a relatively smaller diameter than the first bore. In this manner, a stop or shoulder for engaging the sleeve of the first, annularly shaped, piston is formed which defines the maximum return position of the first piston. A hydraulic fluid can be introduced for actuating the first piston between the stop or shoulder and the piston sleeve. A further portion of the three-piece housing forms with the first housing portion a threadable housing end piece which comprises a cylindrical bore for guiding the end piece of the second piston. The first housing portion forms a stop or shoulder in the actuation direction of the second piston. A hydraulic medium can be introduced between the stop or shoulder and the second piston in order to effect a return movement of the second piston after the shape-forming of the pipe. The corresponding hydraulic space for receipt of the hydraulic fluid is sealed off relative to the first hydraulic space between the sleeve of the first piston and its rearward stop or shoulder. The third portion of the three-piece housing forms the receiving portion for the jaws and the forward portion of the first and the second pistons or, respectively, the shape-forming tool. The shape-forming tool is configured and connected with the forward end region of the piston rod of the second piston such that, during return movement of the second piston, the first piston is correspondingly brought along and the jaws are thus released from their compression position. In this connection, the central through opening of the first piston comprises a rearward stop or shoulder. The shape-forming process performed by the known device disclosed in DE 195 11 447 A1 is, to this extent, burdened with disadvantages in that a control of the course of the shape-forming process from the beginning to the end thereof as well as a monitoring of the tool and the pipe to be shape-formed before the beginning of the shape-forming process is neither provided for nor possible due to the coupling of the two pistons during their return movements.  
           [0005]    The invention provides a solution to the challenge of making available a device for shape-forming a workpiece end region which makes possible a better control of the shape-forming process.  
           [0006]    The solution to this challenge is revealed in the advantageous embodiments and further configurations of the invention as set forth in the patent claims which follow this description.  
           [0007]    In this connection, the invention initially provides, in a first embodiment, that, between the first force transmission element and the second force transmission element, a first pressure space is arranged communicated with a first pressure connector and that the second force transmission element has a second pressure space, communicated with a pressure connector, arranged relative thereto such that the introduction of a pressure medium into the second pressure space drives the second force transmission element in the compression and shape-forming direction. During the forward displacement of the second force transmission element to set the workpiece in compression, the pressure exerted by the pressure medium in the first pressure space is maintained via blockage of the first pressure connector, whereby, upon reaching a predetermined overpressure, the pressure medium is released from the first pressure space, so that the second force transmission element moves relative to the first force transmission element, which remains in its workpiece compressive engagement position, to thereby effect shape-forming of the workpiece and, after the shape-forming of the end region of the workpiece, the second force transmission element is moved rearwardly to its start position by a renewed introduction of a pressure medium in the first pressure space and, by means of a special drive, the first force transmission element is moved correspondingly therewith back into its start position.  
           [0008]    In this connection, the advantage is provided that, by reason of the pressure controlled release of the pressure medium in the first pressure space following the reaching of the overpressure during the forward displacement of the second force transmission element, the workpiece compressive engagement pressure is uniformly maintained at the required value. The required pressure need only be maintained so long as is necessary. In this manner, an unnecessarily high pressure, and an unnecessarily long time period for the maintained pressure and the therewith connected unnecessary loss of performance and high temperature development, are avoided in an advantageous manner. After completion of the shape-forming process, the second force transmission element is movable in an active manner back into its start position.  
           [0009]    In accordance with one embodiment of the invention, it is provided that a third pressure space with a connection to a third pressure connector is provided as a drive for the return movement of the first force transmission element. Alternatively, the drive for the return movement of the first force transmission element can, however, be additionally configured as a return spring.  
           [0010]    In accordance with an embodiment of the invention, it is provided that the start position of the first force transmission element is defined between the housing and a first force transmission element stop or shoulder. By fixedly positioning the first force transmission element in its start position as well as, also, by selection of the start position of the second force transmission element, the relative displacement movement path between the second and the first force transmission elements required for the shape-forming process is constructively laid out.  
           [0011]    In accordance with embodiments of the invention, sensors are provided which recognize the inserted workpiece as well as monitor the respective position of the first force transmission element to determine whether the first force transmission element has again been returned into its start position. In this connection, it is provided, in a case-by-case manner, that before the start of the shape-forming process, it can be automatically determined whether a suitable compression and/or shape-forming tool is available and/or is properly positioned, whereby the availability and/or the proper position of the shape-forming tool can be determined by a non-contact distance measurement effected by a sensor. Additionally, it can be provided that, via a sensor, the start position of the shape-forming tool and the position thereof during the shape-forming process can be sensed.  
           [0012]    In a further development of the inventive device, it can be provided that the required relative movement path for the shape-forming process between the first force transmission element and the second force transmission element—that is, the so-called shape-form length L—is adjustably settable in a first process step, such that the first force transmission element is movable away from the second force transmission element by introduction of a pressure medium into the first pressure space, whereby, via introduction of a pressure medium in the second pressure space, the compression process and the shape-forming process follow thereafter as described. A pressure medium is, accordingly, introduced into the first pressure space both for actuation of the first force transmission element as well as for releasing the second force transmission element, whereby there is obtained the advantage of a still further improved control possibility for the shape-forming process.  
           [0013]    In this connection, it can be provided that the length of the first pressure space between the first actuation surface and the second actuation surface is adjustably set before the shape-forming of the workpiece in order to set the desired defined work path. Following therefrom, the two force transmission elements can be moved while maintaining a constant relative position to one another until the workpiece has been set in compression. As a further consequence thereof, the second force transmission element is movable precisely along the predetermined length of the pressure space against the first force transmission element, so that the compressively engaged workpiece is shape-formed by a movement along this length. The shape-forming process is brought to an end in particular due to the engagement of the first actuation surface and the second actuation surface of the first pressure space with one another.  
           [0014]    In a further configuration of the device, the length of the pressure space is directly or indirectly measurable in order to adjustably set the length. In particular, the length is indirectly measurable via a distance sensor which is oriented toward a surface whose distance from the distance sensor varies as a function of the length of the pressure space. A surface of this type is, for example, configured as an outwardly expanding conical outer surface of the first force transmission element. It is advantageous if a non-contact measuring distance sensor is deployed.  
           [0015]    A non-contact measuring sensor is provided which emits a signal in dependence upon whether the workpiece to be shape-formed is in a start position in which it can be compressively engaged and/or shape-formed. The sensor is, in particular, a distance sensor which measures the distance in a measurement direction to the most closely adjacent object. Such sensors, including, for example, a laser emitting sensor, are known.  
           [0016]    In this event, the workpiece need only be disposed in the start position in order to produce the signal. In particular for controlling the compression process and/or the shape-forming process, a control is provided which is connected via a signal connection with the sensor. By means of the transmission of a signal to the control, especially, an automatic signal, the compression process and/or shape-forming process is initiated.  
           [0017]    In particular, non-contact measurement of a dimension of the workpiece to be shape-formed or, respectively, a measurement value, is performed which provides a clear measurement of the dimension of the workpiece to be shape-formed. If, for example, a pipe is to be shape-formed, the possibility is available to measure the pipe diameter. This permits, before the start of the compression process and/or the shape-forming process, a monitoring of whether a workpiece with the desired dimensions for shape-forming is standing ready. If the proper workpiece has not been brought into a start position or there is, in any event, no workpiece at all in the start position, a start signal is correspondingly also not produced. An unintended actuation of the shape-forming device or, respectively, the working of the workpiece with false dimensions can thus be avoided in this manner. An important advantage lies in the fact that security measures for protecting the operating personnel can be maintained in a simple manner and, at the same time, damage of the device such as through the disposition of too large a workpiece therein, can be prevented.  
           [0018]    Furthermore, it is suggested that, before the start of the compression process and/or the shape-forming process, that it be automatically determined whether a suitable compression and/or shape-forming tool is available and/or is properly positioned. In this connection, it is particularly suggested to provide a non-contact measuring sensor which generates a signal as a function of whether a suitable compression and/or shape-forming tool is available and/or is properly positioned. A shape-forming tool recognition in this manner can be combined with the above-described sensor to produce a start signal in order to achieve still greater assurance against false actuation and false functioning. In particular, the same sensor can be used for measuring the start position and for measuring the availability and/or the positioning of the shape-forming tool. In this event, the availability and/or the proper positioning of the shape-forming tool is, preferably, initially measured or, respectively, pre-set.  
           [0019]    Moreover, it is further suggested to provide a sensor which measures in a non-contact manner the progression or continuing movement of the shape-forming of the workpiece. In particular, a control can be further provided which receives a signal of the sensor, and which, after the shape-forming has been adequately performed, effects the end of the shape-forming process. 
       
    
    
       [0020]    The inventive device is described hereinafter in connection with two embodiments thereof; in this regard, the drawings show:  
         [0021]    [0021]FIG. 1 A longitudinal view through a shape-forming device in its start position,  
         [0022]    [0022]FIG. 2 the shape-forming device shown in FIG. 1 having a workpiece received therein in the start position,  
         [0023]    [0023]FIG. 3 the shape-forming device after the completion of the workpiece compressive engagement process,  
         [0024]    [0024]FIG. 4 the shape-forming device in its position at the end of the shape-forming process,  
         [0025]    [0025]FIG. 5 the shape-forming device in the intermediate position during return movement at a time at which the second force transmitting element has already been returned to its start position,  
         [0026]    [0026]FIG. 6 the shape-forming device in another embodiment thereof comprising a function for variable adjustment of the shape-form length (L), the shape-forming device being shown in the start position,  
         [0027]    [0027]FIG. 7 the subject matter shown in FIG. 6 with an inserted pipe end,  
         [0028]    [0028]FIG. 8 the shape-forming device as shown in FIG. 6 following setting of the shape-form length (L),  
         [0029]    [0029]FIG. 9 the shape-forming device as shown in FIG. 8 upon reaching the workpiece compressive engagement position of the first force transmitting element,  
         [0030]    [0030]FIG. 10 the shape-forming device as shown in FIG. 9 following completion of the shape-forming process. 
     
    
       [0031]    [0031]FIG. 1 shows a longitudinal view through a shape-forming device  1 . The shape-forming device  1  includes a base housing  3  having a central cylindrical bore such that a cylinder surface  4  is formed thereby. In the region of the open end of the base housing  3 , a receiving housing  5  is disposed for receipt of jaws  31  operable as compression jaws. The cylinder surface  4  is configured as a guide surface for guiding the movement of a first force transmission element configured as an outer ring piston  7  and for guiding the movement of a second force transmission element configured as an inner piston  9 . The inner piston  9  substantially completely fills the closed end of the cylindrical bore. A piston rod  11  of the inner piston  9  extends in the direction toward the open end of the cylinder bore. The piston rod  11  is received in a central cylindrical bore of the outer piston  7  and is fixedly coupled with an extension piece  11 ( a ) which is, in turn, connected to a compression tool  13 . The outer piston  7  thus forms a guide for guiding the movement of both the piston rod  11  and a rotation preventing device  15  which connects the piston rod  11  or its extension piece  11 ( a ) with a compression tool  13  operable as a shape-forming tool.  
         [0032]    The rotation preventing device  15  is operable in a manner similar to a bayonet lock. A locking projection  16  of the compression tool  13  is disposed, via a linear movement in the axial direction of the extension piece  11 ( a ) of the piston rod  11 , into a corresponding recess in the extension piece  11 ( a ) and is thereafter pivoted about the longitudinal axis of the piston rod  11  in order to lock the connection.  
         [0033]    The base housing  3  comprises a first pressure connection  25  through which a hydraulic medium can be introduced into the interior of the base housing  3  or, respectively, can be discharged from the base housing  3 . A first pressure space  26  in the base housing  3  is communicated with the first pressure connector  25 , the pressure space being disposed outside of the cylinder surface  4  and being limited, as well, by a first actuation surface  10  of the outer piston  7  and by a second actuation surface  12  of the inner piston  9 . The first pressure space  26  is configured as a relatively larger or smaller space as a function of the operational condition of the shape-forming device  1  and can be disposed in various positions relative to the first pressure connector  25  (see FIGS.  1 - 5 ). In each operational condition, however, the first pressure connector  25  is communicated with the first pressure space  26 .  
         [0034]    In particular, the first pressure space  26  expands outwardly in the radial direction, as the first actuation surface  10  and the second actuation surface  12  are each partially configured as conical surfaces.  
         [0035]    As can be seen in FIGS. 3 and 4, the first actuation surface  10  and the second actuation surface  12  each respectively comprise a further region which is annularly shaped and represents a stop or shoulder for the other piston  7 ,  9 .  
         [0036]    The first pressure space  26  is sealed off against the open end and the closed end of the cylinder bore of the base housing  3  by seals between the piston rod  11  and the inner surface of the outer piston  7 , by seals between the outer surface of the outer piston  7  and the cylinder surface  4 , and as well by seals between the outer surface of the inner piston  9  and the cylinder surface  4 . The seals are collectively designated with the reference numeral  21 .  
         [0037]    In the region of the closed end of the cylinder bore, there is additionally provided a second pressure space  28  in the base housing  3  which is communicated with a second pressure connector  27 . The second pressure space  28  has a variable volume which can be varied to a value of practically zero.  
         [0038]    On the side of the outer piston  7  turned away from the first pressure space  26 , a third pressure space  51  is formed in the compression and shape-forming device in front of the outer piston  7  between this piston and a housing insert  52 , the third pressure space being communicated with a third pressure connector  50 . This third pressure space  51  serves as a drive for the return movement of the outer piston  7  into its start position.  
         [0039]    The receiving housing  5  forms a receiving space for the jaws  31  which are operable through actuation of the pistons  7 , 9 —that is, through the movement of the pistons in the axial direction—to place a workpiece under compression. The jaws  31  are, for example, configured and actuated in the same manner as the jaws shown in DE 195 11 447 A1.  
         [0040]    The jaws  31  include, on the right hand back end thereof as viewed in FIGS.  1 - 5 , a shape-forming recess  33  which forms an encircling groove-type recess closing upon itself if a workpiece with a corresponding outer dimension is disposed under compression in the shape-forming device. The shape-forming recess  33  serves to shape-form the workpiece as will be described hereinafter in more detail. Alternatively or additionally, the shape-forming can also be effected by selection of the geometry of an alternative compression tool which is provided in lieu of the illustrated compression tool  13  and which is connectable with the piston rod  11 .  
         [0041]    The compression tool  13  comprises, on its free back end at which the compression tool has a smaller outer diameter than the area thereof axially behind this free back end, a measurement band  8 .  
         [0042]    The inner piston  9  comprises, in the region of the free end of its piston rod  11  or its respective extension piece  11 ( a ) which extends toward the jaws  31 , a conically shaped section  6  which forms the outer periphery of the extension piece  11 ( a ).  
         [0043]    Two bores are formed in the complete housing formed by the base housing  3  and the receiving housing  5 , the two bores extending in a radial direction to the central longitudinal axis of the shape-forming device  1 . A sensor S 1  or, respectively, S 2 , is arranged in each respective bore. The sensor S 1  serves to identify the compression tool  13  in that the sensor S 1  is oriented toward the measurement band  8  of the compression tool  13  and can identify the respective compression tool  13  as a function of the distance between the sensor S 1  and the measurement band  8 .  
         [0044]    The sensor S 2  serves to establish the base position of the inner piston  9  in that the sensor S 2  is oriented toward the conical surface  6  of the extension piece  11 ( a ) that is connected with the inner piston  9 , so that, via the determination of the position of the conical surface  6  or, respectively, the movement of the extension piece  11 ( a ) with the cylindrical peripheral surface relative to the sensor S 2 , the continuation of the movement of the inner piston  9  is sensed.  
         [0045]    An example of the operation of the shape-forming device  1  is hereinafter described:  
         [0046]    Starting from the position of the shape-forming device as shown in FIG. 1, initially, a workpiece such as, in particular, the end of a pipe  2 , is introduced into the shape-forming device until the inward end of the pipe is seated against the compression tool  13 , whereby the start position of the shape-forming device can be seen in FIG. 2. As can be seen in FIG. 3, the pressure space  28  is filled with a pressurized medium which leads to a displacement of the inner piston  9  to the left hand direction as seen in FIG. 3. Since the pressure connector  25  of the first pressure space  26  is closed during this first phase of the pressure filling of the second pressure space  28 , the feeding force of the inner piston  9  is transmitted via the pressure medium present in the first pressure space  26  to the outer piston  7  so that this piston is displaced in the same direction in coordination with the displacement of the inner piston  9 ; with continuing movement of the two pistons  7 ,  9 , the jaws  31  are pushed into position on the outer surface of the pipe  2  and place the pipe in compression, whereby the outer piston  7  pushes outwardly in a discharging manner the pressure medium present in the third pressure space  51 . Once the pipe  2  is placed in compression, the outer piston  7  can no longer be further moved and, in this manner, the pressure rises in the pressure medium in the first pressure space  26  until an overpressure corresponding to the desired compression force is reached. Upon reaching the overpressure, the pressure connector  25  is opened so that the pressure medium in the first pressure space  26  can flow out of the pressure space. In this manner, a continuation of the feed movement of the inner piston  9  is made possible, with the piston now being further displaced relative to the fixedly positioned outer piston  7  and thereby performing a compression working until the space between the annular surfaces of the inner pistons  9  and the outer piston  7 , which has been laid out as a function of the compression work to be exerted, has been exhausted.  
         [0047]    Upon the completion of the compression working, the pressure connector  27  of the second pressure space  25  is moved into a release position and a pressure medium is introduced via the first pressure connector  25  into the first pressure space  26 ; in this manner, the inner piston  9  is moved in the right hand direction into its start position, as can been seen in FIG. 5. Thereafter, a pressure medium is introduced via the third pressure connector  50  into the third pressure space  51  and, thereby, the outer piston  7  is likewise moved in the right hand direction into its start position as can be seen in FIG. 1, or respectively, in FIG. 2. The end position of the outer piston  7  is thereby determined or given by a stop member (not shown) between the outer piston  7  and the housing.  
         [0048]    With respect to the embodiment of the shape-forming device shown in FIGS.  6 - 10 , there is performed, in addition to the functions performed by the embodiment described in accordance with FIGS.  1 - 5 , an additional function by which the shape-form length L required for the working of the workpiece is variably adjustable in a first functional step. Otherwise, the same components are designated with the same reference numerals.  
         [0049]    Thus, a receiving space  18  extends outwardly from the rotation preventing device  15  in the axial direction of the piston rod  11  toward the interior thereof, a compression spring  17  being received in the receiving space. The compression spring presses the compression tool  13  into a position in which a gap is created between the compression tool  13  and a surface  14  formed on the back end of the piston rod  11 . Correspondingly, a gap is also formed in the region of the rotation preventing device  15  between the compression tool  13  and the piston rod  11  which permits movement of the compression tool  13  against the piston rod  11  by the width of the gap.  
         [0050]    In addition to the seals  21  disposed between the respective moveable components, guide rings  19  are provided for guiding the movement of the pistons  7 ,  9 .  
         [0051]    Moreover, a sensor arrangement is variably configured in the embodiment shown in FIGS.  6 - 10 . In this connection, the jaws  31  include a measurement groove  35  which extends radially inwardly from the outer surface of the jaws  31 . In lieu of the measurement groove  35 , a measurement indentation can be provided which, unlike the groove shown in FIGS.  6 - 9 , does not extend in the circumferential direction around the jaws  31  but is, however, only a single indentation formed in one location or at several locations on the jaws. In this event, the proper positioning must be observed relative to a distance sensor, whose function is described in more detail hereinafter.  
         [0052]    The jaws  31  further include a measurement opening  29  extending in the radial direction which permits an electromagnet emission such as, in particular, a laser emission, to be directed from outside the jaws  31  interiorly onto a workpiece which is held in compression by the shape-forming device. The measurement opening  29  terminates on the inside of the shape-forming recess  33  so that, as will be described in more detail hereinafter, the progress of the shape-forming process can be measured.  
         [0053]    In a variation of the embodiment shown in FIGS.  1 - 5 , the conical surface  6  is configured on the free end of the outer piston  7  turned toward the jaws  31 , whereby the conical surface  6  defines the outer periphery of the outer piston  7 .  
         [0054]    In addition to the bores previously described with respect to the embodiment in FIGS.  1 - 5  for receipt of the sensors, both bores in the embodiment shown in FIGS.  6 - 10  each comprise a distance sensor  37 ,  39 . The distance sensors  37 ,  39  measure the distance to the most closely adjacent object lying in the radial direction inwardly or, respectively, the distance to the oversurface associated therewith. As schematically shown in FIG. 6, the first distance sensor is connected via a first signal lead  43  with a control  41 . Furthermore, the second distance sensor  39  is connected via a second signal lead  45  with the control  41 . The control  41  is, in turn, connected with a display device  47  which comprises six light emitting diodes  49 . The light emitting diodes  49  serve to display the operational phases and the measured operational conditions of the shape-forming device  1 .  
         [0055]    By use of the device shown in FIGS.  6 - 10 , the device measures the first distance via the first distance sensor  37  to the measurement band  8  of the compression tool  13 . The outer diameter at the measurement band  8  is a characteristic measure of the type of compression tool that the compression tool  13  is, especially with respect to its other measurements. Each compression tool connectable with the piston rod  11  or any other tool has, in any event, a measurement band which, however, has a different outer diameter. In accordance with the distance to the measurement band  8  and, correspondingly, the outer diameter of the compression tool  13 , the first distance sensor generates a measurement signal which is transmitted to the control  41 . The control  41  which is, in particular, configured as an intelligent microprocessor-configured control, recognizes the presence of the tool via the measurement signal.  
         [0056]    The second distance sensor  39  measures the distance to the bottom of the measurement groove  35  in the jaws  31 . The distance to the groove bottom is a representative measure of the type of jaws which the jaws  31  are. The second distance sensor  39  generates a corresponding measurement signal via the second signal lead  45  to the control  41 . The control  41  recognizes the jaws  31 .  
         [0057]    The jaws  31  and the compression tool  13  serve to shape-form a certain type of pipe—namely, the shape-forming of pipes with a predetermined outer diameter. From the information concerning which compression tool and which jaws are available, the control  41  determines what type of pipes can be shape-formed in combination with the workpieces.  
         [0058]    As shown in FIG. 7, if a pipe is received in a receiving opening  20  of the compression tool  13  and, as shown by the arrow pointing to the right, is impacted by a force, the shape-forming of the pipe  2  commences. If the force is sufficiently large in order to move the compression tool  13  so as to overcome the counter force of the spring  17  against the rod rear surface  14 , then the compression tool  13  is positioned at a spacing from the jaws  31 . As a result of this, the first distance sensor  37  can now measure the distance or spacing to the outer surface of the pipe  2 . The first distance sensor  37  transmits via the first signal lead  43  a corresponding measurement signal to the control  41 . The control  41  monitors whether the pipe  2  has the proper outer diameter or, respectively, whether the proper measurement signal was received. If this is the case, the control  41  starts the compression-and shape-forming process.  
         [0059]    In this connection, as can be seen in FIG. 8, the outer piston  7  is initially moved along the shape-form length L in the axial direction (in the illustration in FIG. 8, towards the left). In order to ensure that the movement is accomplished, a hydraulic medium is introduced through the first pressure connector  25  into the first pressure space  26 . During this procedure, the first distance sensor  37  measures the distance to the conical surface  6  of the outer piston  7  and continuously transmits a measurement signal to the control  41 . Once the distance between the annularly-shaped surfaces of the first actuation surface  10  and the second actuation surface  12  is the same as the shape-form length L, and the first distance sensor  37  has transmitted a corresponding measurement signal to the control  41 , the control  41  interrupts the introduction of the hydraulic medium into the first pressure space  26  so that the movement of the outer piston  7  is stopped.  
         [0060]    Thereafter, as best seen in FIGS. 9 and 10, the actual compression and shape-forming of the pipe  2  begins, as has been basically described with respect to the embodiment shown in FIGS.  1 - 5 , whereby the control  41  commences the introduction of a hydraulic medium through the second pressure connector  27  into the second pressure space  28 . Following this operational condition, which is shown in FIG. 9, the compression-and shape-forming work is completed as has already been described with respect to the embodiment shown in FIGS.  1 - 5 .  
         [0061]    Insofar as the compression work of the jaws  31  is effected in a rapid manner, the continuing movement of the inner piston  9  in the axial direction towards the left ensures that no slippage of the pipe  2  through the jaws  31  occurs, once the inner piston  9  has reached its maximal extended position. If, for example, because of relatively low surface roughness of the pipe outer surface and/or the jaws  31 , a slippage of this type should occur, an adjustment of the distance between the actuation surfaces  10 ,  12  (see the operational phase shown in FIG. 8) can be implemented. In this event, the shape-form length L does not, in fact, exactly correspond to the actual path, in which the end of the pipe  2  is shape-formed in the axial direction. A precise pre-adjustment of the desired shape-form path is, however, possible. A further factor, which can lead to inequality between the shape-form length L and the actual shape-form path, is the yieldability or, respectively, the elasticity, of the material connection between the outer piston  7  and the jaws  31 . In particular, elastic material can be deployed such as, for example, a material to effect a damping of noise or to prevent a wearing away.  
         [0062]    As the end region of the pipe  2  is shape-formed via the application of force by the shape-form tool  13  in the axial direction, the second distance sensor  39  measures, through the measurement opening  29 , the distance to the bend or bulge  36  formed as a result of the shape-forming around the outer periphery of the pipe  2 . A corresponding signal is continuously provided by the second distance sensor via the second signal lead  45  to the control  41 . After the shape-forming of the pipe has ended by means of engagement of the shape-form tool  13  against the jaws  31 , the actual measurement value is compared with a desired value and it is determined whether the bulge  36  has achieved the desired outer diameter. Alternatively, the shape-forming can be ended once the control  41  determines that the bulge  36  has achieved the desired outer diameter and the control can thereby interrupt the shape-forming process. In this event, the shape-form length L serves to ensure that a sufficiently long shape-forming path is available.  
         [0063]    After the stroke movement of the inner piston  9  in the axial direction to the left has ended, the second pressure space  28  is released from its pressurized condition—that is, the hydraulic medium disposed therein is permitted to flow out through the second pressure connector  27 . Moreover, the pressure medium in the first pressure space  26  is flowed out via the first pressure connector  25 . In this manner, the inner piston  9  is moved under the influence of the pressure medium in the second pressure space  25  in the axial direction toward the right. Thereafter, via opening of the blocking valve, the hydraulic medium in the first pressure space  26  is released so that the hydraulic medium flows out of the pressure space  26 . The outer piston  7  is returned to its start position by means of spring force generated thereagainst by one or more not-illustrated springs to return to its start position as shown in FIG. 6. In this manner, the jaws  31  release the shape-formed pipe  2  so that this pipe can be removed.  
         [0064]    Once the heretofore described work steps, operational conditions and/or operational phases have been successfully concluded, the respective status is indicated by illumination of a respective one of the light emitting diodes  49 . In this connection, the control  41  controls the display device  47 . The meaning of the illumination of the in total six light emitting diodes  49  is, in connection with the serial passage of a successfully concluded shape-forming process, as follows:  
         [0065]    1. Light Emitting Diode: Compressive- and shape-forming tool correctly disposed,  
         [0066]    2. Light Emitting Diode: Pipe outer diameter is appropriate for the shape-forming tool,  
         [0067]    3. Light Emitting Diode: Forward movement of the outer piston and setting of the shape-forming length L concluded,  
         [0068]    4. Light Emitting Diode: Pipe set in compression,  
         [0069]    5. Light Emitting Diode: Pipe is shape-formed, shape-forming result is satisfactory,  
         [0070]    6. Light Emitting Diode: Return stroke is concluded, pipe can be removed.  
         [0071]    If a mistake occurs, this can be determined by reading the display device  47 , which indicates the respective operational phase or, respectively, operational condition, during which the mistake occurred. In particular, an additional, not-illustrated light emitting diode can be provided which displays or illuminates if there is an interruption of the shape-forming process. Alternatively or additionally, a mistake can be indicated by intermittent lighting of a light emitting diode to show the corresponding operational phase. Also, it can be additionally interpreted that, if, for example, a light emitting diode does not illuminate, yet a light emitting diode later in the series does illuminate, that a mistake has occurred.