Abstract:
Disclosed is a pressing device for compressingly joining pipe-shaped workpieces, particularly a pipe end and a fitting mounted thereon. At least one of the workpieces is plastically deformed by several press members which are movable along a central longitudinal axis of the workpieces for performing the compression. In order to produce a pressing device with several compression jaws that are comparatively easy to mount and allow the press members to be engaged as centrally as possible during compression, at least two press members are pivotally connected to each other by means of two articulated levers embodied as angle levers for applying compression force. The angle levers pressingly lean on a (first) press member, and both angle levers are train-connected to the same (second) press member.

Description:
CROSS-REFERENCE AND INCORPORATION BY REFERENCE 
       [0001]    This patent application is a divisional of U.S. patent application Ser. No. 10/498,023, filed Jun. 4, 2004, and entitled “Pressing Device”. U.S. patent application Ser. No. 10/498,023 is a National Stage of IB application number PCT/EP02/13948, filed Dec. 9, 2002, published as WO 03/049883 on Jun. 19, 2003. IB application number PCT/EP02/13948 claims priority from German Patent Application No. 101 60 349.5, filed Dec. 8, 2001, and German Patent Application No. 101 64 028.5, filed Dec. 28, 2001. Each of these applications are hereby incorporated by reference herein in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a pressing device for the press-joining of tubular workpieces, in particular of a tube end, on the one hand, to a fitting slipped onto it, on the other hand, with plastic deformation of at least one of the workpieces, having a plurality of press members, it being possible for the press members to be moved toward a central longitudinal axis of the workpieces in order to carry out the pressing. 
       BACKGROUND OF THE INVENTION 
       [0003]    A pressing device of this type is known, for example, from U.S. Pat. No. 3,662,450. An advantage of this known pressing device is that the individual press members can be moved centrally toward the longitudinal axis of the workpieces which are to be joined. However, this known pressing device is complex in that the individual press members each have to be actuated individually by hydraulic means. 
         [0004]    Furthermore, reference is to be made, in connection with the prior art, to U.S. Pat. No. 2,211,008. An advantage of this known pressing device, which has three pressing jaws connected to one another to form a pressing chain, is that the pressing force is applied in a mechanically simple way, by a lever transmission. However, in this case too there is still a significant circumferential component in the movement of the press members during the pressing operation. 
       SUMMARY OF THE INVENTION 
       [0005]    Working on the basis of the prior art cited in the introduction, the invention is based on the object of providing a pressing device having a plurality of pressing jaws, which combines a relatively simple structure with an optimally central approach of the press members during the pressing operation. 
         [0006]    This object is achieved by the subject matter of claim  1  in which it is provided that at least two press members, in order to apply pressing force, are pivotably connected to one another via two pivot levers formed as angle levers, the angle levers being supported pressing on a first press member, and both angle levers being connected in tension to the same second press member. The angle levers supported pressing on the first press member enable the first press member to move centrally toward the longitudinal axis of the workpieces to be pressed during a pressing operation. As a result of the second pressing jaw being pulled by means of the angle levers, it is also possible for this second pressing jaw at the same time to be pulled centrally toward the longitudinal axis of the workpieces. There is practically no movement of the press members in the circumferential direction. 
         [0007]    In a refinement, it is also provided that the angle levers are each connected, in the style of a toggle lever, to a pivot lever which transmits tensile force. In this respect, the angle lever can also be referred to as one of the two pivot levers of a toggle pivot, which is indeed predominantly addressed below. 
         [0008]    The introduction of force into a pivot lever also preferably takes place outside an outer pivot. The pivots of the toggle-lever-like arrangement which are connected to a press member are outer pivots. As an expedient refinement, it is possible for the first and second press members to be disposed opposite one another with respect to the pressing cross section. 
         [0009]    The press members being disposed opposite one another is in this context preferably to be understood as meaning that the ends of two press members are positioned mirror-symmetrically opposite one another with respect to a reference line running within the pressing cross-section plane. Furthermore, it is preferable for the two pairs, formed in this way, of ends, which are to face one another in the circumferential direction, of the first and second press members each to have an associated toggle lever, the ends of one pair in each case being connected to an outer pivot of the associated toggle lever. In this context, it is in particular also possible for the toggle levers to be disposed mirror-symmetrically with respect to a reference line which runs within a pressing cross-section plane and is perpendicular to the abovementioned axis of symmetry. This allows force to be introduced into the pressing device at two further locations, i.e. a total of four locations. Furthermore, depending on the number of press members, it is, of course, also possible to use a greater number of toggle levers, in which case it is possible, in terms of the way in which they are disposed, to employ various symmetries in order for force to be introduced as uniformly as possible. 
         [0010]    In one expedient refinement, the toggle levers may for their part be movement- and/or force-coupled to one another so as to synchronize their movement sequences and/or to ensure an equal distribution of the introduction of forces, this coupling being effected, for example, by rigid or flexible transmission links, such as levers, pivot levers, tension cables or other expedient means. In principle, it is possible for ends of press members which are not connected by toggle levers to be connected, by single or double pivots, to a corresponding number of pivot bolts or, as is expanded upon below, to have displaceable guides. 
         [0011]    With regard to the toggle lever or levers, it is furthermore preferable for the two pivot levers of a toggle lever to be of different lengths, so that the toggle lever is at a different distance from the press links connected to the toggle lever. In particular, the length of one pivot lever may be a multiple of, preferably double or triple, the length of the second pivot lever connected thereto. 
         [0012]    If the two pivot levers are of unequal length, the advantageous situation may result, depending on the spacing of the outer pivots realized in the installed position at the pressing device, in the pressing position and if appropriate also even in an unstressed starting position of the pressing chain, in which a projection of the toggle pivot onto a straight line leading through the two outer pivots is located in the region of the outer pivot of the shorter pivot lever or even on the side which is remote from the other outer pivot. 
         [0013]    In the event of force being introduced into the, for example, shorter pivot lever, leading to a reduction in the spacing of the outer pivots, given a stationary center point of the pressing cross section, the shorter pivot lever results in the abovementioned compressive action on the press member which adjoins it, with a tensioning action being exerted via the longer pivot lever on the press member which adjoins it, which actions include components directed oppositely to one another. Introduction of force into a pivot lever outside an outer pivot, depending the position of the force engagement location on the pivot lever and depending on the direction of the force which is acting from, for example, a clamping device of the pressing device, offers further fundamental advantages, i.e. irrespective of the length ratio of the two pivot levers. In a preferred variant, it is provided that the location where force is introduced be located away from a straight line through the toggle pivot and the outer pivot of the pivot lever which is subject to the force, and that the force introduced have a component in the direction of this straight line. 
         [0014]    This means that the force introduced transmits a torque to the pivot lever, it being possible if necessary to step up or step down the movement or force transmitted to the ends, connected to the toggle lever, of the press members, depending on the outer pivot/location of force introduction and outer pivot/toggle pivot spacing ratio selected. In one expedient configuration, it is possible for an in relative terms shorter pivot lever of a toggle lever to have a force-introduction element positioned eccentrically with respect to the outer pivot of said toggle lever. The force-introduction element may, for example, be a bolt which is positively or nonpositively connected or cohesively joined to the pivot lever in the direction of movement of the latter. In particular in conjunction with the axially symmetrical positioning of two toggle levers as described above, consideration is preferably given to providing a force-introduction element at each of the mutually facing pivot lever ends of the two toggle levers. 
         [0015]    Corresponding pivot levers or angle levers may, for example, be triangular in form, with the outer pivot, the toggle pivot and the force-introduction element being distributed in the corner regions of the triangle, the corner regions having the force-introduction elements determining the shortest distance between the shorter pivot levers of two toggle levers. As an alternative or in combination with this, it is possible for the outer pivots of these two pivot levers to be pivotably fitted in the region of the two opposite ends of the same press member, so that there is a constant distance between these outer pivots. Proceeding from a starting position, in which there is no or no significant introduction of force into the force-introduction elements, the pressing chain can exert pressure so as to reduce the pressing cross section by the distance between the force-introduction elements of the toggle levers being further reduced until if appropriate the pressing movement or reduction in cross section is restricted by a stop, optionally a reciprocal stop, of the pivot levers in question. The reduction in the spacing of the force-introduction elements may expediently be effected using a clamping device, as disclosed, for example, by WO 98/40178 or DE 10010601 A1, the content of disclosure of which is hereby incorporated in its entirety in the present application, partly with a view to incorporating features in claims of the present application. The force-introduction elements may for their part be matched, with regard to their cross section and if appropriate further dimensions, to a force engagement of a pincer-like pressing jaw of a clamping device. 
         [0016]    A further expedient configuration involves a further or in each case a further press member being disposed in the circumferential-angle region of the in relative terms longer pivot of one or both toggle pivots. For this purpose, it is possible to provide for a further press member of this type to have the pivot levers engaging around it in a pressing cross-section plane. As an alternative or in combination, the press member may also have recesses for the pivot levers to penetrate through. According to a further preferred configuration, it is possible for two adjacent press members to have, at ends which face one another in the circumferential direction, projections and recesses which correspond in the circumferential direction and have mutually associated sliding surfaces running in the circumferential direction. According to this aspect, which is also of independent importance in the present application, the press members of the pressing chain are thereby guided with respect to one another. This opens up the possibility in particular of individual, adjacent press members not being pivotably connected to one another yet nevertheless producing by means of the sliding guides a predetermined relative movement between the press members connected in this way when force is introduced into the pressing chain in order to reduce the size of the pressing cross section. By way of example, press members with pressing jaws which are recessed in the circumferential direction with respect to the ends of the press members and press members with pressing jaws which project in the circumferential direction with respect to the ends of the press members may be disposed alternately in the circumferential direction. In a more specific embodiment, it is possible for a pressing jaw which projects in the circumferential direction to have an outer-wall section which runs in the circumferential direction and faces radially outward, and for an adjacent press member, starting from a pressing jaw which is recessed in the circumferential direction, to have an inner-wall section which runs in the circumferential direction and faces radially inward, and for the inner-wall section and the outer-wall section to extend at substantially the same radial distance from the center of the pressing cross section and, from a starting position to a closed or pressing position of the pressing chain, to have an increasing coverage. In particular, sliding guidance of this type can be realized between all the adjacent press members of a pressing chain, so that in view of the coverage in the circumferential direction, the workpieces have a completely continuous coverage by the pressing chain over the entire circumference even before force is introduced. To position the device around the workpieces which are to be pressed together prior to a pressing operation, it is possible for the device to be opened, at virtually any desired pivot, by unscrewing the pivot bolt and to be closed again at the same location after the workpieces have been inserted. This means that in a device of this type, unlike with a pressing chain which is to be closed during a pressing operation, for example, there are no separately formed ends which constitute a possible weak point for the pressing operation. 
         [0017]    Furthermore, it is possible for a press member, which is disposed in the circumferential-angle region of a pivot lever, to be secured captively to the pivot lever. If the press member penetrates through the pivot lever, this can be realized by the pivot lever entering a recess in the press member, which is completely surrounded within a pressing cross-sectional plane, by means of a projection, for example a pin. The size of the recess is such that the press member is not impeded during the pressing operation during the movement which is predetermined by the sliding guides. 
         [0018]    One expedient configuration is also possible by virtue of a pressing jaw of a press member, in a cross section which is perpendicular with respect to the pressing cross section, having a semicircular recess which extends radially outward and is adjoined on one side by a pressure web which projects radially inward and is adjoined on the other side by locating pins which project radially inward. The locating pins may be formed as a plurality of cylindrical pins which are inserted into bores, extending radially from the pressing surface of the pressing jaw, in the pressing jaw. Whereas the recess, which is semicircular or at least comparable with regard to its cross section, is matched to a cross-sectional widening of the fitting for receiving a sealing element, for example an O ring, the locating pins are used to ensure that the pressing device can be closed in a predetermined orientation of the workpieces. If the workpieces are aligned correctly, it is then ensured that the radially inwardly projecting pressure web, during the pressing operation, leads to plastic deformation of overlapping regions of the workpieces which are to be pressed. Correctly positioned orientation of the workpieces is achieved by means of the locating pins, in that the latter are only supported against the cross-sectional widening of the pushed-on workpiece if the workpieces are oriented incorrectly, with the result that the pressing device, when it is placed onto the workpieces, cannot be reduced in size to the circumference required for insertion of a pivot bolt which has been removed. This is achieved, for example, by the workpiece which is pushed on, in the cross section perpendicular to the pressing cross section, having an asymmetrical bulge which enters the semicircular recess in the pressing jaw and the steeper flank of which does not form an obstacle to the locating pins, whereas the second, shallow flank of which leads to the said supporting of the locating pins. On the other hand, the pressing device can be fitted around the workpieces even when the latter are oriented incorrectly, but it cannot be closed. Even should one locating pin start to deteriorate in terms of its effect (spring) or become damaged (in particular in the case of a rigid design), the safety factor is not completely lost. It is also virtually impossible for any significant damage to be caused by any incorrect handling. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention is explained in more detail below with reference to the accompanying drawings, which merely illustrate exemplary embodiments and in which: 
           [0020]      FIG. 1  shows a perspective view of a pressing device according to the invention with workpieces which are to be pressed together inserted therein; 
           [0021]      FIG. 2  shows a perspective, exploded view of the individual parts of the pressing device according to the invention; 
           [0022]      FIG. 3  shows a perspective view of the pressing device shown in  FIG. 1  in an open position without workpieces; 
           [0023]      FIG. 4  shows a perspective view of the pressing device shown in  FIG. 1  in a pressing position without workpieces; 
           [0024]      FIG. 5  shows a side view of the pressing device shown in  FIG. 1  in an open position with workpieces which are to be pressed; 
           [0025]      FIG. 6  shows a sectional view on section line VI-VI in  FIG. 5 ; 
           [0026]      FIG. 7  shows a sectional view on section line VII-VII in  FIG. 5  with inserted closure bolt; 
           [0027]      FIG. 8  shows a sectional view with the closure bolt disengaged compared to  FIG. 7 ; 
           [0028]      FIG. 9  shows a side view of the pressing device shown in  FIG. 1  in the pressing position with workpieces to be pressed; 
           [0029]      FIG. 10  shows a simplified side view of the pressing device according to the invention with the device open; 
           [0030]      FIG. 11  shows a side view of the pressing device according to the invention with the device open but already fitted around the workpieces to be pressed; 
           [0031]      FIG. 12  shows a side view of the pressing device, in the fully locked position, but before a pressing operation commences; 
           [0032]      FIG. 13  shows a perspective view of the pressing device according to the invention in conjunction with pressing jaws of a clamping device; 
           [0033]      FIG. 14  shows a pressing device as shown in  FIG. 1 , but with the position of a further press member (auxiliary press member) predetermined by means of a spring; 
           [0034]      FIG. 15  shows the pressing device shown in  FIG. 14  in the pressing state; 
           [0035]      FIG. 16  shows a sectional view on XVI-XVI in  FIG. 5  with the workpieces oriented correctly; 
           [0036]      FIG. 17  shows a sectional view according to  FIG. 16  with the workpieces oriented incorrectly; 
           [0037]      FIG. 18  shows a sectional view with modified locating pins compared to  FIG. 16 ; 
           [0038]      FIG. 19  shows a side view of the pressing device fitted around a pipe with a fitting slipped onto it and locating pins in accordance with a second embodiment, closure of the pressing device not possible; 
           [0039]      FIG. 19   a  shows a cross section through the pressing device of  FIG. 19 ; 
           [0040]      FIG. 20  shows a side view of the pressing device corresponding to  FIG. 19  but with the pipe with the fitting inserted the other way round, allowing closure of the pressing device; 
           [0041]      FIG. 20   a  shows a cross section through the pressing device of  FIG. 20 ; 
           [0042]      FIG. 21  shows a side view of the pressing device as shown in  FIG. 20  after pressing has taken place; and 
           [0043]      FIG. 21   a  shows a cross section through the pressing device of  FIG. 21 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0044]      FIG. 1  shows a perspective view of a preferred embodiment of the pressing device  1  according to the invention with tubular workpieces which are to be pressed together inserted in it. These workpieces, as can be seen in conjunction with the following figures, are a pipe  2  which has been inserted into a fitting  3 . 
         [0045]    The workpieces have a common central longitudinal axis A. 
         [0046]    As can be seen in conjunction with  FIG. 2 , the pressing device  1 , in the exemplary embodiment shown, comprises four press members. In the context of the present invention, this means that a total of four press members interact in the operation of pressing of the workpieces, whereas—as explained further below—in the exemplary embodiment only two of the four press members are components which are connected by means of pivots which transmit tensile force. 
         [0047]    The pressing device  1  has firstly two press members  5 ,  6  which lie opposite one another in the circumferential direction and, in order to change a pressing cross section  7  (cf.  FIG. 3 ,  4 ), can be displaced with respect to one another by means of two toggle levers  10  which each include a pivot lever  8  formed as an angle lever and a pivot lever  9 . A pivot lever  8  is in each case connected to a pivot lever  9  by means of a toggle pivot  11 . The pivot lever  8  has an outer pivot  12  which is connected to the press member  5 . 
         [0048]    At its opposite end, the pivot lever  9  has an outer pivot  13 , which is connected to the press member  6 . In view of the discernible axially symmetrical positioning of the two toggle levers  10 , here and below identical reference symbols are selected for corresponding elements. In the respective circumferential-angle region of a pivot lever  9 , which has a greater length than the pivot lever  8 , there is in each case a further press member  15 ,  16 , with the press members  15 ,  16  likewise lying opposite one another with respect to the pressing cross section. 
         [0049]    The press members  5 ,  6  are not connected to the press members  15 ,  16  by means of pivots, but rather are merely held captively at the pivot levers  9  and, as explained in more detail below, guided by means of sliding guides on the press members  5 ,  6 . This means that in the exemplary embodiment of the pressing device according to the invention described here, the press members surround the pressing cross section, or the workpieces to be pressed, uniformly over the entire circumference even before the pressing operation commences. 
         [0050]    The uniform surrounding, in contrast to conventional pressing chains, does not have any end links, which constitute a possible weak point, and consequently there is accordingly also no interruption in any circumferential region to the surrounding by press members which are by contrast at a greater distance from one another. 
         [0051]    Furthermore, according to the exemplary embodiment having the four press members, what is formed is not a conventional chain in the sense of “link on link”. Instead, just two of a total of four press members involved in the pressing operation carried out by the device are pivotably integrated into the device by means of force-transmission elements connected between them. Furthermore, in the exemplary embodiment described, the pressing cross section is formed by circumferentially alternating integrated press members and elements connected between them. 
         [0052]    The two press members which are provided as elements connected in between, which are also referred to as auxiliary members, are merely held captively at the force-transmission elements, in the present case the toggle levers, with additional guidance being made possible by means of bearing surfaces on the respectively adjacent integrated press members. The integrated press members are disposed so as to surround the auxiliary members in a positively locking manner—by means of the bearing surfaces—in such a manner that the auxiliary members, during a pressing operation, are prevented from yielding radially outward relative to the integrated press members. 
         [0053]    Whereas in the case of conventional pressing chains respectively adjacent press members are all connected, either directly or if appropriate by simple connecting elements, in such a manner that a tensile force is passed through all the press members in the circumferential direction, and consequently the pressing chain fails completely in the event of problems with any single press member, this is advantageously avoided in the exemplary embodiment described for the press members which are merely held captively. Accordingly, in the pressing device according to the invention there is no need for any circumferential pivot force transmitted in each case between circumferentially adjacent links, but rather a radially oriented introduction of force can be effected, by means of the toggle levers, at the two press members which are integrated in the manner of a chain and are spaced apart at the circumference, from where the pressing force introduced is transmitted, via the bearing surfaces described above, to adjacent press members which are not integrated in the pressing chain, predominantly as compressive and shear force. 
         [0054]    Furthermore, force-introduction elements  14  for introducing force outside the outer pivot are provided at the pivot levers  8 . In the exemplary embodiment shown, the press members  6 ,  15  and  16  and the pivot levers  8  each have four plate regions which are spaced apart from and parallel to one another, with parallel gaps located between them. By contrast, the press member  5  and the pivot levers  9  each have three comparable spaced-apart plate regions, which are dimensioned and spaced apart in such a manner that they can engage in the gaps in the press members  6 ,  15 ,  16  and the pivot lever  8 , so that mutual penetration of the links is enabled. With regard to the press members  5 ,  6 ,  15  and  16 , the plate regions are integrally connected to one another via pressing jaws  17 ,  18 ,  19 ,  20 , resulting in a stable configuration. At the same time, there are production advantages, in that the press members  6 ,  15  and  16  are obtained with equal dimensions and spacing of plate regions by cutting from a common semifinished product. 
         [0055]    The pivot connections between the press members  5 ,  6  and the pivot levers  8 ,  9  explained above are made through end bores which penetrate through one another in the assembled state and through which the cylindrical pins are fitted and held at their ends by securing rings. In the exemplary embodiment shown, it is provided that the pressing chain can be opened at the toggle pivot  11  of the upper toggle lever  10  by a coupling bolt  21  being removable. However, this is not an imperative choice, but rather as an alternative it would also be possible for the pressing chain to be opened by removal of, for example, a pivot bolt at one of the outer pivots and closed again after insertion of the workpieces to be pressed together. 
         [0056]    It is clear from  FIG. 3  that as soon as the coupling bolt  21  has been inserted, and before the actual pressing operation commences, the pressing cross section  7  is completely encircled by press members  5 ,  6 ,  15  and  16 . It can also be seen that during a pressing operation, during which the distance between the force-introduction elements  14  is reduced, the force introduced is introduced via the toggle levers  10  at four locations distributed over the circumference of the pressing cross section  7 , namely the outer pivots  12  and  13 , which are in each case present in pairs. Prior to the pressing operation, spaces  22  between the pressing jaws, the delimiting walls of which come to bear against one another in the pressing position illustrated in  FIG. 4 , are in each case left between the press members  5 ,  6 ,  15  and  16 . The pressing position is in this case simultaneously defined by a stop for the pivot levers  8  in their corner regions produced by means of the force-introduction elements  14 . 
         [0057]      FIG. 5  shows a side view of the embodiment of the pressing device according to the invention illustrated in  FIGS. 1 to 4  in the position corresponding to  FIG. 3  with the pressing device  1  closed prior to commencement of the pressing operation. This figure once again reveals that the length of the pivot lever  8 , i.e. the distance between the toggle pivot  11  and the outer pivot  12 , is selected to be shorter than the distance of the pivot lever  9 , i.e. the distance between the toggle pivot  11  and the outer pivot  13 . It is also clear from this figure that the press members  5 ,  6  are configured with pressing jaws  17 ,  18  which are recessed in the circumferential direction with respect to their ends, and the press members  15 ,  16  are configured with pressing jaws  19 ,  20  which project in the circumferential direction with respect to their ends. 
         [0058]    The pressing jaws  19 ,  20  which project in the circumferential direction have a wall section  23  which runs in the circumferential direction and faces radially outward. By contrast, the adjacent press members  5 ,  6 , starting from a pressing jaw  17 ,  18  which is recessed in the circumferential direction, have an inner-wall section  24  which runs in the circumferential direction and faces radially inward, the inner-wall sections and the outer-wall sections extending at the same radial distance R from the center of the pressing cross section  7  and having an increasing coverage from the starting position illustrated in  FIG. 5  to the pressing or closed position which is shown by way of comparison in  FIG. 9 . 
         [0059]    These wall sections  23 ,  24 , which are in compressive engagement with one another during pressing, produce a positive lock in the radial direction. As a result, pressing force is transmitted from the first and/or second press member  5 ,  6  to a further press member  15 ,  16 . 
         [0060]    Furthermore, two means, which can be realized as alternatives or in combination with one another, for limiting the rotation of the pivot levers  8  are also provided in  FIG. 5 . The rotation limiting is in each case formed by a stop, which becomes active at a limit rotation angle, for an edge  42  of the pivot levers. One stop is in this case formed as an edge  43  of the press member  15  or  16 , which the edge  42  butts against at a preselected opening angle of the pivot levers  8 . In the variant, the stop is in each case formed by an end  44 , which protrudes beyond the press member, of a pin, in which case a stop is reached against the edge  42  likewise at a predetermined opening angle. The rotary limiting means described above may preferably be formed or disposed in such a way that it is only possible to reach a maximum opening angle of the pivot levers  8  at which the guide surfaces of the inner-wall sections and outer-wall sections, when the pressing chain is closed, still remain with a circumferential coverage with respect to one another, so that in any possible opening position of the pivot levers  8  unlimited rotation of the press members  15 ,  16  about the captive securing feature is prevented. 
         [0061]    In detail, the captive securing feature comprises a peg  44  (cf. in particular  FIGS. 14 ,  15 ), which is disposed on a pivot lever  9 . The peg  44 —are advantageously two pegs  44  formed opposite one another on a pivot lever  9 —projects into a recess  45  in a further press member  15 ,  16 . At the same time, the recess  45  limits the movability of the further press member  15 ,  16  relative to the pivot lever  9  (with the movability also being limited by the positively locking engagement with respect to the first or second press member  5 ,  6 ). 
         [0062]      FIG. 6  shows a sectional view through the pressing device  1  on section line VI-VI in  FIG. 5 . It is clear from this figure that a pipe  2  and a fitting  3  which has been pushed over it have been inserted into the pressing cross section as workpieces. The fitting has a radial bulge  25  running in the circumferential direction, which in terms of its position is associated with a semicircular recess  26  which faces radially outward and likewise extends over the circumference in the pressing jaws. 
         [0063]      FIG. 7  shows a sectional view on section line VII-VII in  FIG. 5 , with the coupling bolt  21  inserted into bores within the pivot levers  8  and  9  in order to close the toggle joint  11 . In this position, the coupling bolt can also be fixed in place by a securing disk (not shown in the drawing) at the narrowed end. 
         [0064]      FIG. 9  shows a pressing position, in which the press members have been moved radially inward toward the longitudinal axis A of the workpieces. 
         [0065]      FIG. 8 , by contrast, shows a section in which the coupling bolt  21  has already been virtually completely pulled out of the bores for opening purposes. In this case, however, the coupling bolt  21  still intentionally projects into a holding plate  31  sufficiently for a holding element  33  to enter an annular groove  32 , so as to form a captive securing feature. The holding element  33  may, for example, be a grub screw, a cylindrical pin pressed resiliently against the annular groove or the like. 
         [0066]      FIGS. 10 to 12  show the successive movement sequence involved in closing the pressing device  1 , with a simplified illustration compared to the previous figures having been selected.  FIG. 10  in this respect describes a position which is open at the toggle pivot  11 , so that ends formed in this way are pulled apart for insertion or enclosing of the workpieces  2 ,  3 . 
         [0067]      FIG. 11  shows a further state which is passed through during the closure movement of the device  1 , shortly before the pivot levers  8  and  9  have been pivoted into the overlapping position which is required for insertion of the coupling bolt  21 . 
         [0068]      FIG. 12  shows the device in the required overlap, in which the coupling bolt  21  is to be inserted on account of the overlapping bores. 
         [0069]      FIG. 13  shows a perspective view of the pressing device  1  according to the invention, which is also illustrated in the preceding figures, in conjunction with pincer-like pressing jaws  34  and a clamping device  35 . The pressing jaws  34  are connected in a rotationally fixed manner to in each case a lever  37  by bolts  36 , the levers  37  being accommodated rotatably by pins  38  in two parallel straps  39 . The straps  39  have bores  40  for positionally fixed securing to the clamping device  35 , which is not otherwise illustrated in the drawing. During a pressing operation, the sliding bodies  41  illustrated are pressed toward the fixed point at the bore  40  by a pressure ram of the clamping device  35 , and consequently, on account of the shaping of the lever inner walls, the levers  37  are spread apart. This causes the distance between the pressing jaws  34  on the opposite side from the pins  38  to be reduced. These pressing jaws  34  are connected to the pivot levers  8  in a positively locking manner by means of the force-introduction elements  14 . During a pressing operation, therefore, the distance between force-introduction elements  14  is reduced, which leads, via rotation of the pivot levers or angle levers  8  and  9 , to the reduction in the pressing cross section  7  described above. 
         [0070]    Advantageous predetermining of the position of the further press members  15 ,  16  in the assembly of the pressing device is explained with reference to  FIGS. 14 and 15 . 
         [0071]    A further press member  15 ,  16  is preloaded into a circumferentially spaced position, cf. distance a in  FIG. 14 , with respect to a first or second press member  5 ,  6 . The preloading is realized by means of spring elements  46  ( FIGS. 14 and 15  in each case illustrate just one spring element  46 ; however, it will be understood that both further press members  15 ,  16  are each connected to a pivot lever  9  by means of at least one spring element  46 ). The preloading is limited by a positive lock with respect to the pivot lever  9 , as explained in more detail below. In this case, the limiting is provided in such a way that the circumferential spacing a with respect to the first or second press member  5 ,  6  is in each case identical. 
         [0072]    During the pressing operation, this circumferential section is reduced in size as a result of all the pressing jaws moving centrally inward, not as a result of the pressing jaws moving circumferentially. 
         [0073]    The positively locking movement restriction is achieved by virtue of a peg  44  bearing against a circumferential edge of the recess  45 , as illustrated in  FIG. 14 , in the starting state. Furthermore, the recess  45  is selected in such a way that, after pressing, the peg  44 , with a diagonal path through the slot-like recess, is located at a diagonally opposite edge section of the recess  45 . 
         [0074]    A further subject of the invention, which is of significance on its own or in combination with the features described above, is a pressing jaw  34  for a pressing device as described in detail here. In this context, it is significant that the pressing jaw  34  is formed by jaw elements  47  which are disposed covering and spaced apart from one another, cf. for example  FIG. 13 . At their free ends (with respect to the securing state at the pressing device, prior to connection to a pressing chain), the jaw elements  47  have through-bores which are aligned with one another. 
         [0075]    The jaw elements  47  are formed as flat parts. At their other end, which is connected to the clamping device, they are connected to a solid jaw foot  48 , specifically by means of the abovementioned bolts  36 . The jaw foot  48 , which is to this extent U-shaped in form, engages around the jaw elements  47 . 
         [0076]    Furthermore, the thickness of the jaw elements  47  is matched to the engagement distance between plate parts of the pivot levers  8 . 
         [0077]      FIG. 16  shows a sectional view on section line XVI-XVI in  FIG. 5 , but unlike in  FIG. 6  projecting locating pins are additionally provided on the radially inner wall of the pressing jaw  19 . In the exemplary embodiment shown, there are four locating pins  28  which are distributed at equal spacings over the circumference and are inserted into blind bores extending radially starting from the inner wall of the pressing jaws.  FIG. 16  shows a correctly positioned, i.e. desired orientation of the workpieces in the pressing device, in which the bulge  25 , which is asymmetrical in the plane of the drawing, is positioned with a steep flank to the side of the locating pin. 
         [0078]      FIG. 17 , by contrast, shows the opposite orientation of the workpieces, in which the locating pin  28 , when the pressing device is closed, comes to bear against a shallow flank of the bulge  25  before the pressing device can be completely closed (cf.  FIGS. 12 ,  19 ). The correct positioning of the workpieces ensures that the pressure web  27  is located in the region of a workpiece overlap in the region of which plastic deformation is to occur. By contrast, plastic deformation on the opposite side of the bulge  25  would be undesirable, since this would jeopardize secure engagement of a sealing ring which can be accommodated inside the bulge  25  but is not shown in the drawing. 
         [0079]      FIG. 18  shows a configuration of the locating pins which is modified with respect to  FIG. 16  and in which a pressure pin  29  is preloaded by a compression spring  30  in such a manner that the pressing chain, with the undesired orientation of the workpieces illustrated, likewise cannot be closed. As an alternative to this embodiment of the locating pins, this embodiment may also have threaded pins which can be adjusted as required in a radially extending bore by means of a threaded nut. 
         [0080]    The embodiment shown in  FIGS. 19-21  uses locating pins  28  which are also spring-mounted against a compression spring  30 , in a manner corresponding to  FIG. 18 . 
         [0081]    Whereas in the first embodiment the locating pins  28  are disposed so close to the recess  26  in the press jaw that if utilized incorrectly ( FIGS. 17 ,  18 ) they strike the inclined surface of the fitting, in the embodiment shown in  FIGS. 19-21  the locating pins  28  are disposed outside the pressing jaw and therefore at a distance from the recess  26  which is such that in the event of incorrect use they merely come into contact with the horizontal section of the fitting. Nevertheless, the pressing device described here cannot be closed if it is used incorrectly, as above ( FIG. 20 ). 
         [0082]    The locating pins  28  are accommodated in a holder  44 ″ fitted onto the outer side of the pressing jaws  17 ,  18 . 
         [0083]    A locating pin  28  is preloaded in its extended position, as illustrated in  FIGS. 19 and 20 , by the spring  30 . 
         [0084]    The preloading is so great that it cannot be overcome by normal manual force during fitting. It is, for example, 200 N per locating pin. 
         [0085]    The spring preloading, which is subsequently overcome by the pressing force used during the pressing, at the same time also means that the unaffected pipe also cannot be damaged. Accordingly, it is selected in such a way that it does not leave behind any or any significant imprint of pressing in the pipe. 
         [0086]    This spring preloading is correspondingly important by virtue of the fact that the locating pins can be disposed at the said distance from the recess  26 , and therefore protrude a corresponding distance onto the pipe, but at the same time cannot cause any damage during the pressing operation. 
         [0087]    All features disclosed are (inherently) pertinent to the invention. The disclosure content of the associated priority documents is hereby incorporated in its entirety in the disclosure of the application, partly with a view to incorporating features of these documents in claims of the present application.