Abstract:
A detachable plug connection including a tubular insert part having a retaining projection on its outer circumference, a sleeve-shaped receiving part, and a connecting element connected to the receiving part with an inwardly directed, upwardly pivotable retaining edge that engages behind the retaining projection after pushing in the insert piece. A sleeve-shaped locking element surrounds the connecting element in a sliding manner and can be displaced between a release position, in which the axial sliding movement is transformed into an opening movement of the retaining edge(s) oriented transversally thereto, and a locking position, in which it surrounds the connecting element preventing upward bending in the region of the retaining edge(s) and the connecting element projects above the locking element, in an intermediate or coupling position of the locking element such that the retaining edge(s) can be bent upwards when the retaining projection on the insert piece is pushed in.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to a detachable plug connection having a tubular insert part which carries at least one retaining projection on its outside circumference, having a sleeve-shaped receiving part, the interior of which is intended for the insertion of the tubular insert piece and having a connecting element which is connected to the receiving part and on which at least one inwardly directed retaining edge is held so it can be bent up or pivoted up, which retaining edge engages behind the retaining projection once the insert part has been pressed in, wherein there is provided a locking element which engages around the connecting element displaceably in such a manner that the locking element can be displaced between a release position and a locking position, in which locking position the locking element engages around the connecting element in such a manner that a bending up of the connecting element in the region of the retaining edge(s) is prevented. 
       BACKGROUND 
       [0002]    EP 605 801 B1 has already previously made known a detachable plug connection of the type mentioned in the introduction which serves as a hose coupling for the connection of two line portions of a liquid line. The previously known plug connection comprises a sleeve-shaped receiving part, into the sleeve interior of which is insertable a tubular insert part which carries on its outside circumference a retaining projection which is realized as a circumferential annular flange. In the coupling position of the previously known plug coupling, the retaining projection, once the insert part has been pressed into the receiving part, is engaged behind by inwardly directed and elastically sprung retaining edges of a connecting element. The retaining edges of the connecting element, which are produced from hard elastic material, are connected together by means of spring webs, which are combined in a V-shaped manner, and can be elastically sprung as a result of a pressure acting on the combined web end regions of the spring webs in such a manner that the retaining edges are disengaged from the retaining projection. In order to lock the position of the connecting element, plate-shaped press buttons, which in the operating position protrude in each case through a complementarily realized reach-through opening in the circumferential wall of the connecting element, are integrally formed on the combined web end regions. It can be a particular advantage for the connecting element which is connected to the one line portion, the insert part which cooperates with the other line portion and the connecting elements to be able to be realized as plastic material injection molding parts. The production of said plastics material molding parts which are matched to one another, however, is connected to considerable expenditure. Above and beyond this, there is the risk that excessive loads which act on the connecting element and/or the insert part transversely with respect to the longitudinal extension thereof result in a break in at least one of said plastics material parts and in unwanted leakages. 
         [0003]    WO 02/079684 A1 has already made known a detachable plug connection, which has a tubular insert part which carries at least one retaining projection on its outside circumference and which comprises a sleeve-shaped receiving part, the interior of which is intended for the insertion of the tubular insert part. The previously known plug connection also has a connecting element which is connected to the receiving part and on which at least one inwardly directly retaining edge is held so as to be able to be bent up or pivoted up, which retaining edge engages behind the retaining projection once the insert part has been pressed in. The previously known plug connection also comprises a locking element which consists of two side walls which encompass the connecting element on both sides as well as a transverse wall which holds them in a U-shaped manner and which (locking element) carries an end plate on the end face. Insert faces, by means of which the locking element is guided on the connecting element so as to be transversely displaceable, are integrally molded on the end edges of the side walls which are remote from the end plate of the locking element. The locking element, which is guided on the connecting element so as to be transversely displaceable, is transversely displaceable between a release position and a locking position. Whereas in the release position a recess, which is provided on the end plate of the locking element, is in alignment in such a manner with the interior of the sleeve-shaped receiving part that the insert part is able to be inserted into the receiving part, in the locking position the locking element engages around the connecting element which is provided on the receiving part in such a manner that a bending up of the connecting element in the region of the retaining edges is prevented. 
       SUMMARY 
       [0004]    Consequently, the object, in particular, is to create a plug connection of the type mentioned in the introduction which can be produced at reduced expenditure, by way of which it is possible to produce a connection which is lockable, sturdy and loadable, but at the same time is also easy to detach. 
         [0005]    The solution according to the invention to said object in the case of the plug connection of the type mentioned in the introduction is, in particular, that the locking element is developed in sleeve-shaped manner and engages around the connecting element in an axially displaceable manner, that in the release position the axial pushing movement of the locking element can be converted into an opening movement, oriented transversely thereto, of the retaining edge(s) and that the connecting element, with the locking element in an intermediate or coupling position, protrudes at least in regions in such a manner over the locking element that the retaining edge(s) can be bent up when the retaining projection which is provided on the insert part is pressed in. 
         [0006]    The plug connection according to the invention comprises a tubular insert part which carries at least one retaining projection on the outside circumference. The insert part is insertable into the sleeve interior of a sleeve-shaped receiving part. The receiving part is connected to a connecting element which, once the insert part has been pressed into the sleeve interior, has to lock the releasable connection between the receiving part and the insert part. Once the insert part has been pressed in, the retaining projection which is provided on the insert part is engaged behind by at least one inwardly directed retaining edge which is held on the connecting element so as to be able to bend up or pivot up. The plug connection according to the invention comprises a sleeve-shaped locking element which engages displaceably around the connecting element in such a manner that the locking element is displaceable between a release position and a locking position. Whereas in the release position the axial pushing movement of the locking element can be converted into an opening movement, oriented transversely thereto, of the retaining edge (s), which moves the retaining edge(s) out of engagement with the retaining projection on the insert part, in the locking position the locking element engages around the connecting element at least in a bend or pivot region in such a manner that a bending up of the connecting element in the region of the retaining edge(s) is prevented with certainty and the retaining edge(s) engage fixedly behind the retaining projection even under a heavy load. Even if pressure acts upon the locking element in a non-controlled manner in the radial direction, the locking element is able to lock the fixed connection, which is highly loadable in the axial direction, between the insert part and the receiving part. In a center or coupling position which is provided along the axial sliding path of the locking element between the locking position and the release position, the connecting element protrudes at least in regions in such a manner over the locking element that the retaining edge(s) is/are able to be bent up when the retaining projection which is provided on the insert part is pressed in and is/are able to engage behind the retaining projection on the insert part. In said center or coupling position, the plug connection according to the invention is already operationally reliable. As the plug connection according to the invention is formed of few components that can be produced at little expenditure, it is able to be produced in a comparatively cost-efficient manner. 
         [0007]    A preferred further development according to the invention provides that the plug connection is developed as a detachable hose connection, that a connecting piece for pushing on a hose end of a flexible hose line is provided at least on the tubular insert part or at least on the sleeve-shaped receiving part and that the receiving part as well as the insert part can be connected together in a liquid-tight manner. In the case of said further-developing embodiment, the insert part or the receiving part can be held immovably on the inflow side or on the consumer side, whilst the respective other component is connected to a flexible hose line. A preferred embodiment, however, provides that both the receiving part and the insert part are connected to a hose portion of a flexible hose line and that, where required, said flexible hose line can be interrupted in the region of the plug connection. 
         [0008]    In order to be able to seal in a liquid-tight manner an annular gap which possibly remains between the outside circumference of the insert part and the inside circumference of the receiving part, a preferred embodiment according to the invention provides that at least one annular groove, in which annular groove an annular seal is arranged, is provided at least on the outside circumference of the insert part or at least on the inside circumference of the receiving part. 
         [0009]    So that the retaining edges are able to engage behind the retaining projection on the insert part in a secure and fixed manner, it is advantageous when the connecting element has at least one retaining strip which is oriented transversely with respect to the pressing-in direction and on which a retaining edge is provided. 
         [0010]    The connection between the receiving part and the insert part can be locked in a particularly good manner and so as to be highly loadable when the connecting element has at least one pair of retaining strips which are provided on opposite sides of the receiving part. 
         [0011]    In order to be able to bend up or pivot up the at least one retaining edge slightly both in the center position or the coupling position and in the release position, it is advantageous when the at least one retaining strip is held on at least one connecting arm of the connecting element, which connecting arm is developed so as to be bendable or pivotable up in a bend or pivot region. 
         [0012]    The high level of functionality and the secure connection which can be achieved with the plug connection according to the invention is promoted when the at least one retaining strip is held on two connecting arms, which connecting arms cooperate with the strip end regions of the retaining strip with which they are associated. 
         [0013]    It is possible for the receiving part and the insert part to be developed, for example, as a result of non-round cross sections in such a manner that the insert part is only able to be pressed into the receiving part in one relative position which is fixed in the circumferential direction. The handling of the plug connection according to the invention is made considerably easier, however, when the insert part which is located in the receiving part is freely rotatable, but is held securely and fixedly in the axial direction; in the case of the last-mentioned design, it is advantageous when a circumferential retaining projection which is developed preferably in the manner of an annular flange is provided on the outside circumference of the insert part. 
         [0014]    When the insert part is pressed into the receiving part, the retaining strips can be surmounted particularly well by the retaining projection until the retaining projection is engaged behind by the retaining edges when a run-up inclination, which converts a pressing-in movement of the insert part into a bending up or pivoting up movement of the at least one connecting arm, is provided on each retaining strip. 
         [0015]    It is advantageous when there is provided a sliding guide which converts an axial pushing movement of the locking element into a bending up or pivoting up movement, oriented transversely thereto, of the retaining edges, and when the sliding guide has at least one sliding projection which is provided on the inside circumference of the locking element and which interacts with at least one sliding path which is associated therewith on the connecting element. In this case, uniform bending up or pivoting up of the retaining strips and easy releasing of the retaining edges from the retaining projection on the insert part is promoted when a sliding path is provided in each case on the adjacent connecting arms of at least two retaining strips which are provided on opposite sides of the receiving part and when the sliding paths interact with a sliding projection which is associated therewith. In this case, a preferred embodiment according to the invention which is particularly simple to handle provides that a sliding projection is provided in each case on opposite sides of the inside circumference of the locking element and when said sliding projections interact in each case with a pair of sliding paths which are associated with one another. 
         [0016]    In order to signal in particular the locking position clearly to the user, it is advantageous when the retaining strips have on the outside in each case an impression, into which impressions in each case at least one associated latching projection, which is provided on the inside circumference of the locking element, locks on the outside. So that the locking of the latching projection in the impression is particularly clearly detectable and so that, for this purpose, the impression is also able to be developed sufficiently deeply without weakening a larger amount of the material of the retaining strips, it is expedient when the retaining strips comprise on their outside surface, at least no more than in regions, a curvature which is oriented transversely with respect to the pressing-in direction, and when the impression of the retaining strip is preferably provided centrally in the region of the curvature(s). 
         [0017]    In order to be able to fasten the connecting element on the receiving part in a particularly solid and loadable manner, a preferred embodiment according to the invention provides that the connecting arms are connected preferably in an integral manner at their arm ends remote from the retaining strips to a retaining ring, which retaining ring is held in an impression on the outside circumference of the receiving part so as to be immovable in particular in an axial direction. 
         [0018]    The locking element can be guided displaceably particularly well on the receiving part as well as on the connecting element connected thereto when the locking element has a substantially rectangular cross section at least on the side of the inside circumference and when the connecting element defines a substantially rectangular envelope circle on the side of the outside circumference, the form of which envelope circle is adapted to the rectangular inside cross section of the locking element. 
         [0019]    In order to be able to signal in an easily recognizable manner that the plug connection according to the invention is not yet situated in its locking position, it is advantageous when the connecting element in the intermediate or coupling position protrudes at least in regions visibly over the locking element, and when said protruding part region of the connecting element carries a marking, in particular is colored in a signaling color. If the user is able to recognize the signal color on the connecting element, he is also able to recognize that the plug connection is currently only in its intermediate or coupling position and, where required, still has to be moved into the locking position. 
         [0020]    In this connection it can be advantageous when the connecting element, with the locking element in the locking position, is covered and engaged around at least extensively and preferably completely by the locking element. As soon as the locking element covers and engages around the connecting element at least almost completely, unintentional releasing of the locking element from said locking position is avoided. At the same time, the protruding part region of the connecting element, which carries a marking, is also covered in such a manner that no incorrect information concerning the current position of the locking element is given to the user. 
         [0021]    As the locking element, which engages around the connecting element in the locking position, is able to protrude laterally slightly over the outside contour of the hose line, there is possibly the risk of the locking element unintentionally getting caught on an obstacle by way of its protruding end-face edge and being moved from its locking position into the coupling position or even into the release position. In order to counter said risk effectively and in order to prevent unintentional displacement of the locking element, which is situated in the locking position, into the coupling position or even into the release position, a particularly advantageous further development according to the invention provides that a locking cap is held on the insert part, that the locking cap protrudes at least in regions over the outside circumference of the locking element, and that the locking cap is arranged in the locking position adjacent to the locking element. As in the case of said further-developing embodiment the locking cap is held on the insert part, and as the locking cap protrudes at least in regions over the outside circumference of the adjacent locking element, the locking element is prevented effectively from getting caught and from being displaced unintentionally even into the release position. 
         [0022]    In this case, a particularly simple embodiment according to the invention which is easy to produce provides that the locking cap is developed as a ring disk which protrudes over the outside circumference of the locking element at least in regions. 
         [0023]    In order to prevent at all times unintentional release of the connection which is realized with the insert part according to the invention, it can be expedient when the locking cap has an outside contour which is adapted to the outside circumference of the locking element and protrudes on all sides over the outside circumference of the locking element. 
         [0024]    In this case, a preferred embodiment according to the invention provides that, in the locking position, the locking cap engages over the adjacent end face edge region of the locking element by way of a circumferential edge which is angled in the direction of the locking element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Further developments according to the invention are produced from the drawing in conjunction with the claims and the description. The invention is described below by way of a preferred exemplary embodiment, in which, in more detail: 
           [0026]      FIG. 1 : shows an axial longitudinal section of a detachable plug connection which is developed as a hose connection, the one hose portion being held on an insert part, whilst the other hose portion being connected to a receiving part and said component parts of the plug connection being shown separately from one another in an exploded position, 
           [0027]      FIG. 2 : shows the plug connection from  FIG. 1  in a center or coupling position when the tubular insert part is being pressed into the sleeve interior of the sleeve-shaped receiving part, 
           [0028]      FIG. 3 : shows the plug connection from  FIGS. 1 and 2  in the center or coupling position after the insert part has been pressed in such a manner into the receiving part that a retaining projection which is provided on the insert part is engaged behind by the retaining edges of a connecting element which is connected to the receiving part, 
           [0029]      FIG. 4 : shows a longitudinal section of the plug connection from  FIGS. 1 to 3  in a locking position in which a sleeve-shaped locking element engages around the connecting element in such a manner that a bending up or pivoting out of the retaining edges provided on the connecting element is prevented, 
           [0030]      FIG. 5 : shows the plug connection from  FIGS. 1 to 4  in a release position, in which release position the axial pushing movement of the locking element can be converted into a bending up or pivoting up movement, oriented transversely thereto, of the retaining edges, 
           [0031]      FIG. 6 : shows a longitudinal section of the plug connection from  FIGS. 1 to 5  in the center or coupling position with the insert part and the receiving part pressed into one another, directly before the locking element is displaced axially into the locking position, 
           [0032]      FIG. 7 : shows a perspective longitudinal section of the connecting element and of the locking element, which is displaceably guided thereon, of the plug connection shown in  FIGS. 1 to 6 , 
           [0033]      FIG. 8 : shows a perspective longitudinal section rotated by 90° in the circumferential direction of the component parts from  FIG. 7 , 
           [0034]      FIG. 9 : shows a longitudinal section of the plug connection from  FIGS. 1 to 8  with the locking element in the locking position, 
           [0035]      FIG. 10 : shows a perspective longitudinal section of the connecting element and of the locking element of the plug connection shown in  FIGS. 1 to 9 , 
           [0036]      FIG. 11 : shows a perspective longitudinal section rotated by 90° in the circumferential direction of the component parts from  FIG. 10 , 
           [0037]      FIG. 12 : shows a longitudinal section of the plug connection from  FIGS. 1 to 11  in the release position, 
           [0038]      FIG. 13 : shows a longitudinal section of the plug connection from  FIGS. 1 to 12  in the release position shown in  FIG. 12 , 
           [0039]      FIG. 14 : shows a perspective longitudinal section rotated by 90° in the circumferential direction of the component parts from  FIG. 13 , 
           [0040]      FIG. 15 : shows a side view of the locking element of the plug connection shown in  FIGS. 1 to 14 , 
           [0041]      FIG. 16 : shows a side view rotated by 90° in the circumferential direction of the locking element from  FIG. 15 , 
           [0042]      FIG. 17 : shows a longitudinal section of the locking element from  FIGS. 15 and 16  through the cutting plane C-C from  FIG. 16 , 
           [0043]      FIG. 18 : shows a perspective top view of the locking element from  FIGS. 15 to 17 , 
           [0044]      FIG. 19 : shows a top view of the locking element from  FIGS. 15 to 18 , 
           [0045]      FIG. 20 : shows a side view of the connecting element of the plug connection shown in  FIGS. 1 to 14  on its own, 
           [0046]      FIG. 21 : shows a side view rotated by 90° in the circumferential direction of the connecting element from  FIG. 20 , 
           [0047]      FIG. 22 : shows a longitudinal section of the connecting element from  FIGS. 20 and 21  through the cutting plane D-D from  FIG. 21 , 
           [0048]      FIG. 23 : a side perspective view of the connecting element from  FIGS. 20 to 22 , 
           [0049]      FIG. 24 : a top view of the connecting element from  FIGS. 20 to 23 , 
           [0050]      FIG. 25 : shows a top view of the plug connections from  FIGS. 1 to 14 , the cutting plane A-A of the longitudinal sections according to  FIGS. 1 to 5  also being shown, 
           [0051]      FIG. 26 : shows a top view of the plug connections from  FIGS. 1 to 14 , the cutting plane B-B according to the longitudinal sections of  FIGS. 6 ,  9  and  12  also being shown, 
           [0052]      FIG. 27 : shows a further exemplary embodiment of the plug connection shown in  FIGS. 1 to 26 , the exemplary embodiment shown here in a part longitudinal section in the locking position having a locking cap which is held on the insert part so as to be immovable in the longitudinal direction, is developed here as an annular disk and counters unintentional catching and displacing of the locking element from the locking position into the coupling or even into the release position, 
           [0053]      FIG. 28 : shows a perspective top view of the exemplary embodiment of the plug connection shown in  FIG. 27 , 
           [0054]      FIG. 29 : also shows a part longitudinal section of a further exemplary embodiment of a plug connection which has a locking ring, the shape of which locking ring in this case, however, is adapted to the outside circumference of the locking element and protrudes laterally on all sides over the outside circumference of the locking element and 
           [0055]      FIG. 30 : shows a perspective top view of the exemplary embodiment of the plug connection shown in  FIG. 29 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0056]      FIGS. 1 to 30  shows several exemplary embodiments of a detachable plug connection  1  and of the essential component parts thereof. Each of said plug connections  1  has a tubular insert part  2  which carries at least one retaining projection  3  on the outside circumference. The insert part  2  is insertable into the sleeve interior of a sleeve-shaped receiving part  4 . The receiving part  4  is connected to a connecting element  5  which has to produce the detachable connection between the receiving part  4  and the insert part  2  once the insert part  2  has been pressed into the sleeve interior. After the insert part  2  has been pressed into the receiving part  4 , the retaining projection  3  which is provided on the insert part  2  is engaged behind by inwardly directed retaining edges  6 ,  7  which are held on the connecting element  5  so as to be bendable up or pivotable up. The plug connection  1  comprises a sleeve-shaped locking element  8  which engages displaceably around the connecting element  5  in such a manner that the locking element  8  is displaceable between a release position which is shown in  FIG. 5  and a locking position which is depicted in  FIG. 4 . Whereas in the release position the axial pushing movement of the locking element  8  can be converted into a bending up movement or a pivoting up movement, oriented transversely thereto, of the retaining edges  6 ,  7 , which moves the retaining edges  6 ,  7  out of engagement with the retaining projection  3  on the insert part  2 , in the locking position the locking element  8  engages around the connecting element  5  in a bend or pivot region in such a manner that a bending up of the connecting element  5  in the region of the retaining edges  6 ,  7  is prevented with certainty and the retaining edges  6 ,  7  engage fixedly behind the retaining projection  3  even under a high load. Even if the locking element  8  is acted upon with force in a non-controlled manner in the radial direction, the locking element is able to lock the fixed connection between the insert part  2  and the receiving part  4 , which is highly loadable in the axial direction. In a center or coupling position shown in  FIGS. 2 and 3 , in which the connection is already operationally reliable and withstands operationally usual loads and which is provided along the axial pushing path of the locking element between the locking position and the release position, the connecting element  5  protrudes at least in regions in such a manner over the locking element  8  that the retaining edges  6 ,  7  are able to be bent up when the retaining projection  5  provided on the insert part  2  is pressed in and can engage behind the retaining projection  3  on the insert part  2 . The part regions of the connecting element  5 , which protrude over the locking element  8  and can be colored in a signal color, in this case signal that the plug connection  1  is not yet situated in its locking position. In this case, the surface center of gravity of the contact face of the retaining projection  3  on the one side and of the retaining edges  6 ,  7  on the other side are chosen such that no outwardly acting bending forces are generated in the connecting element  5  and in particular in its connecting arms  15 . As the plug connection  1  according to the invention consists of few component parts which can be produced at little expenditure, it can be produced in a comparatively cost-efficient manner. 
         [0057]    It is clear from  FIGS. 1 to 6 ,  9  and  12  that the plug connection  1  is realized as a detachable hose connection and that, for this purpose, both the receiving part  4  and the insert part  3  are connected to a hose portion  22  or  23  of a flexible hose line  10 . The hose portions  22  and  23  of the hose line are reinforced here by an external metal braid  11 . 
         [0058]    It can be seen in  FIGS. 1 to 5  that an annular groove, in which is arranged an annular seal  12  which seals the annular gap between the receiving part  4  and the insert part  2  inserted therein in a liquid-tight manner, is provided on the inside circumference of the receiving part  4 . 
         [0059]    The connecting element  5  of the plug connection  1  is shown in more detail in  FIGS. 20 to 24 . The connecting element  5 , which can also be produced, for example, from reinforced plastics material, where applicable, comprises a pair of retaining strips  13 ,  14  which are oriented transversely with respect to the pressing-in direction and on each of which a retaining edge  6 ,  7  is provided. The retaining strips  13 ,  14  are arranged on opposite sides of the receiving part  4  which can be seen in  FIGS. 1 to 6 ,  9  and  12 . The retaining strips  13 ,  14  are held in each case on two connecting arms  15  which cooperate with the strip end regions of the retaining strips  13 ,  14  associated therewith. On each retaining strip  13 ,  14  there is provided a run-up inclination  16  which converts a pressing-in movement of the insert part  2 , once it has been inserted into the receiving part  4 , into a bending up or pivoting up movement of the connecting arms  15 . In order to support the resetting movement of the connecting arms  15 , they are preferably developed so that they can be bent up or pivoted up in a spring elastic manner. 
         [0060]    It is clear from a comparison of  FIGS. 2 and 3  that for the coupling of the insert part  2  and the receiving part  4  first of all the insert part  2  has to be inserted into the sleeve interior of the receiving part  4  until the retaining projection  3 , which is provided on the insert part  2  and is realized here as a circumferential annular flange, abuts against the upper longitudinal edge of the retaining strips  13 ,  14  (cf.  FIG. 2 ). As a result of pressing the insert part  2  further in, the retaining projection  3  runs onto the run-up inclinations  16 —developed here as a longitudinally sectioned cone—in such a manner that the connecting arms  15  and the retaining edges  6 ,  7  which are connected to the connecting arms  15  by means of the retaining strips  13 ,  14  bend upward. As soon as the retaining edges  6 ,  7 , which are formed by the bottom longitudinal side of the retaining strips  13 ,  14 , engage behind the retaining projection  3 , the connection between the insert part  2  and the receiving part  4  is held in the axial direction, operational reliability of the connection already being achieved here (cf.  FIG. 3 ). 
         [0061]    As a result of the displacement of the locking element  8 , the plug connection can be moved into the locking position shown in  FIG. 4  in which the locking element  8  also engages around the connecting element  5  in the bend or pivot region of its connecting arms  15  in such a manner that a bending up of the connecting element  5  in the region of the retaining edges  6 ,  7  is prevented. In this locking position, the connection produced between the insert part  2  and the receiving part  4  is locked against unintentional release even in the case of the locking element,  8 , which, for example, is also produced, where applicable, from reinforced plastics material, being acted upon radially with a force. 
         [0062]    A sliding guide, which converts an axial pushing movement of the locking element  8  into a bending up or pivoting up movement, oriented transversely thereto, of the retaining edges  6 ,  7  is provided in order to be able to re-release the connection between the insert and receiving parts  2 ,  4  which are preferably produced from metal and in particular from brass. Here said sliding guide comprises two sliding projections  17 , which are provided on opposite sides on the inside circumference of the locking element  8  and interact on both sides in each case with a sliding path  18  which is formed by a wall portion which is integrally molded onto the connecting arms  15 . 
         [0063]    It is clear from a comparison between  FIGS. 12 to 14 , which show the plug connection  1  in the release position, that in the release position the locking element  8  is displaced back in such a manner that the sliding projections  17 , which interact with the sliding paths  18 , bend the connecting arms  15 , which protrude in regions over the locking element  8 , with the retaining strips  13 ,  14  integrally molded thereon, in such a manner up and outward that the retaining edges  6 ,  7  are disengaged from the retaining projection  3  and the plug connection  1  between the insert part  2  and the receiving part  4  is able to be released. 
         [0064]    It can be seen in  FIGS. 1 to 5  that the connecting arms  15  are integrally connected on their arm ends, which are remote from the retaining strips  13 ,  14  to a retaining ring  19 , which retaining ring  19  is held in an impression  20 , which is also realized, where applicable, as an annular groove, on the outside circumference of the receiving part  4 . In this case, said retaining ring  19  is clamped between the annular shoulder  21  of the impression  20  which faces the retaining strips  13 ,  15  and a press sleeve  22 , which press sleeve  22  holds the hose portion  23  on a portion of the receiving part  4  which is realized as a hose nipple. In this case, the receiving part  4  is pushed from the side of the connecting arms  15  through the retaining ring  19  until the retaining ring  19  strikes against the annular shoulder  21 . It can be seen from  FIGS. 15 to 19  that the locking element  8  has a substantially rectangular inside cross section at least on the side of the inside circumference. It can be seen from a comparison of  FIGS. 15 to 19 , on the one hand, and  20  to  24 , on the other hand, and from the top views shown in  FIGS. 25  and  26  that the connecting element  5  defines a substantially rectangular envelope circle on the outside circumference, the shape of which envelope circle is adapted to the rectangular inside cross section of the locking element  8 . This complementarily non-round development of the locking element  8  and the connecting element  5  ensures that the locking element  8  is guided on the connecting element  5  so as to be non-rotatable, but displaceable in the axial direction. 
         [0065]    It is clear from  FIGS. 20 to 24  and in particular from  FIGS. 22 and 23  that the retaining strips  13 ,  14  have in each case on the outside an impression  25 , into which impression  25  in each case at least one associated latching projection  26 , which is provided on the inside circumference of the locking element, locks in the locking position (cf.  FIG. 4 ). So that the user is able to recognize the locking of the plug connection into its locking position in a particularly good manner and so that the impression  25  can be developed in a particularly deep manner without weakening the retaining strips  13 ,  14 , the retaining strips  13 ,  14  comprise on their outside surface at least in regions curvatures  27  which are oriented transversely with respect to the pressing-in direction. In this case, the impressions  25  of the retaining strips  13 ,  14  are provided approximately centrally in the region of the curvatures  27 . 
         [0066]    It can be seen in  FIGS. 3 and 4  that the locking element  8 , which engages around the connecting element  5  in the locking position, protrudes laterally slightly over the outside contour of the hose line  10 . In this case, there is the risk of the locking element  8  getting caught unintentionally by on an obstacle way of its protruding end face edge and being moved from its locking position into the coupling position or even into the release position. 
         [0067]    In order to counter this risk, the exemplary embodiments of the plug connection  1  shown in  FIGS. 27 to 30  comprise a locking cap  24  which is held so as to be immovable on the insert part  2  in the longitudinal direction thereof. This locking cap  24  protrudes at least in regions in such a manner over the outside circumference of the locking element  8  that the locking element  8  getting unintentionally caught and displaced in an unwanted manner from the locking position into the coupling position or even into the release position is countered. 
         [0068]    It can be seen in  FIGS. 27 and 29  that a shoulder  28  is provided on the insert part  2  at a spacing from the retaining projection  3 . Between the shoulder  28 , which is preferably developed as a circumferential annular shoulder, and a crimping sleeve  29 , which holds the hose end of the hose portion  22  on the insert part  2 , the locking cap  24  is held so as to be immovable in the longitudinal direction of the insert part  2 . 
         [0069]    In the case of the exemplary embodiment shown in  FIGS. 27 and 28 , the locking cap  24  is developed as an annular disk which protrudes at least in regions over the outside circumference of the adjacent locking element  8  and, in this case, is developed so as to be circularly round on the outside circumference. 
         [0070]    In contrast, the locking cap  24  of the exemplary embodiment shown in  FIGS. 29 and 30  comprises an outside contour, the shape of which is adapted to the preferably rectangular and, in this case, square outside circumference of the locking element  8  and protrudes on all sides over the outside circumference of the locking element  8 . In this case, the locking cap  24  of the exemplary embodiment shown in  FIGS. 29 and 30  engages over the adjacent end face end region of the locking element  8  by way of a circumferential edge  30  which is angled in the direction of the locking element  8  in such a manner that the locking element  8  is not able to become caught unintentionally and consequently also not able to be released from the locking position. 
         [0071]    For the rest, the exemplary embodiment of the plug connection  1  shown in  FIGS. 28 to 30  corresponds to the design which has already been described in  FIGS. 1 to 26 . 
       LIST OF REFERENCES 
       [0000]    
       
           1  Plug connection 
           2  Insert part 
           3  Retaining projection (on the insert part  2 ) 
           4  Receiving part 
           5  Connecting element 
           6  Retaining edge 
           7  Retaining edge 
           8  Locking element 
           9  Press sleeve 
           10  Hose line (with the hose portions  22  and  23 ) 
           11  Metal braid 
           12  Annular seal 
           13  Retaining strip 
           14  Retaining strip 
           15  Connecting arms 
           16  Run-up inclinations 
           17  Sliding projection (on the inside circumference of the locking element  8 ) 
           18  Sliding paths (on the connecting arms  15 ) 
           19  Retaining ring (of the connecting element  5 ) 
           20  Impression 
           21  Annular shoulder (of the impression  20 ) 
           22  Hose portion (on the insert part  2 ) 
           23  Hose portion (on the receiving part  4 ) 
           24  Locking cap (on the insert part  2 ) 
           25  Impression 
           26  Latching projection (on the circumferential side of the locking element  8 ) 
           27  Curvature 
           28  Shoulder (on the insert part  2 ) 
           29  Crimping sleeve (on the insert part  2 ) 
           30  Circumferential edge (on the locking cap  24  of the exemplary embodiment according to  FIGS. 29 and 30 )