Abstract:
A coupling part for a plug connector arrangement is provided. The coupling part having a coupling body comprising a receptacle into which a plug-in part can be plugged into in the direction of a longitudinal axis of the receptacle, in order to produce a fluid-tight connection. The coupling part has two spaced-apart locking elements which, in a locking position, penetrate laterally, opposite one another, into the receptacle in order to engage behind the plug-in part and which can be moved into a release position in order to release the plug-in part. A spring element is integrally formed with and connects the locking elements together. In order to develop the coupling part so that it is easier to handle, the coupling part is provided with an actuating element which is adapted to be moved relative to the coupling body. Movement of the actuating element causes the locking elements to be moved out of the locking position into the release position, in which they are spaced apart from one another to a greater extent than in the locking position.

Description:
This application is a continuation of international application number PCT/EP2006/011084 filed on Nov. 18, 2006. 
   The present disclosure relates to the subject matter disclosed in international application number PCT/EP2006/011084 of Nov. 18, 2006 and German application number 10 2006 002 565.2 of Jan. 5, 2006, which are incorporated herein by reference in their entirety and for all purposes. 

   BACKGROUND OF THE INVENTION 
   The invention relates to a coupling part for a plug connector arrangement. 
   Releasable plug connector arrangements having a coupling part and a plug-in part, which can be plugged one into the other, are used for connecting pipes and hoses, for example in lines for liquid or compressed air. By virtue of the plug-in part being plugged into the receptacle of the coupling part, it is possible to produce a fluid-tight connection between the plug-in part and the coupling part, and locking elements are used in order to secure the plug-in part in the receptacle. Utility Model DE 86 24 767 U1, in this context, proposes the use of a locking plug having two legs and a cross-piece connecting the two legs. The locking plug can be introduced laterally into the receptacle through slots in the coupling part and, in a locking position, it engages behind undercuts of the plug-in part and thus secures the latter axially in the receptacle. If the plug-in part is to be released then a screwdriver or some other suitable tool is used to grip the locking plug in the region of the cross-piece and pull it laterally out of the receptacle. As a result, the legs of the locking plug spread apart and thus release the plug-in part. 
   A disadvantage with the known coupling part is that it is difficult to handle, since it requires the use of an additional tool. Moreover, for the purpose of moving the locking elements into their release position, a sufficient amount of space has to be available in the lateral direction in order for the locking elements, in the form of the legs of the locking plug, to be pulled laterally out of the receptacle. 
   U.S. Pat. Nos. 2,823,934 and 3,709,528 disclose coupling parts for plug connector arrangements, the coupling parts each having an actuating element which can be moved relative to the coupling part. By virtue of the actuating element being moved, locking elements can be moved, counter to a resilient restoring force, into a release position, in which they are spaced apart from one another to a greater extent than in the locking position. These coupling parts have a comparatively complicated construction. 
   It is an object of the present invention to develop a coupling part of the type mentioned in the introduction so that it has a simple construction and is easy to handle. 
   SUMMARY OF THE INVENTION 
   The object is achieved by a coupling part in accordance with the present invention. The coupling part has a coupling body comprising a receptacle into which a plug-in part of the plug connector arrangement can be plugged into in the direction of a longitudinal axis of the receptacle, in order to produce a fluid-tight connection. The coupling part also has two spaced-apart locking elements which, in a locking position, penetrate laterally, opposite one another, into the receptacle in order to engage behind the plug-in part and which can be moved into a release position in order to release the plug-in part. The coupling part also has an actuating element which is adapted to be moved relative to the coupling body. Movement of the actuating element causes the locking elements to be moved counter to a resilient restoring force from a locking position into a release position. A spring element is integrally formed with and connects the locking elements together. 
   By virtue of the actuating element being moved coaxially, the locking elements can be moved out of their locking position into a release position, in which they are spaced apart from one another to a greater extent than in the locking position. By changing the position of the actuating element relative to the coupling body, it is thus possible to widen the locking elements transversely to the longitudinal direction of the receptacle and thus to release the receptacle to the extent where the plug-in part plugged into the receptacle can be readily pulled out of the receptacle. The coupling part according to the invention is consequently very easy to handle. 
   The coupling part according to the invention has a simple construction since the only components necessary are a coupling body, with the receptacle into which the plug-in part can be plugged, and also the locking elements and the actuating element. The coupling part according to the invention is thus distinguished by the use of only a small number of components, and is therefore not particularly susceptible to malfunctioning. 
   The locking elements are adapted to be moved into the release position counter to a resilient restoring force. This has the advantage that they transfer automatically into their locking position provided that the locking elements are not subjected to any actuating force. The locking elements can be transferred out of their locking position into their release position counter to the resilient restoring force. It may be provided that the locking elements are adapted to be arrested in their release position. 
   In respect of a design of the coupling part which is as simple as possible, it is particularly advantageous if the locking elements are connected to one another via a spring element. The spring element thus forms a connecting element for the two locking elements and can therefore serve as a retaining element for the locking elements. In addition, the locking elements are subjected, via the spring element, to a restoring force in the direction of the locking position of the locking elements. 
   The coupling part according to the invention can be produced particularly cost-effectively in that the spring element and the locking elements are connected integrally to one another. The spring element and locking elements may be formed, for example, as a single-piece U-shaped wire portion in the form of two legs which are connected to one another via a cross-piece and at the free end of which there is a respective locking element which is angled in relation to the respective leg. The locking element is preferably formed as a locking pin which is oriented perpendicularly to the respective leg. 
   It is preferably possible for the actuating element to be displaced coaxially in relation to the longitudinal axis of the receptacle, or to be rotated about the longitudinal axis of the receptacle. It may be provided, for example, that the locking elements are adapted to be moved into their release position by virtue of the actuating element being displaced coaxially. 
   It is advantageous if the locking elements are configured as locking pins which pass laterally through the receptacle. The locking pins can penetrate into the receptacle transversely to the longitudinal axis of the receptacle in order to lock the plug-in part which has been plugged into the receptacle. The locking pins may be configured, for example, as wire pins. 
   It is advantageous if the locking pins are in each case oriented parallel to one another in the locking position and in the release position. During transfer from their locking position into their release position, the locking pins are thus changed merely in respect of their spacing apart from one another, without being bent or having their mutual orientation changed in any other way. 
   It has proven particularly advantageous if the spring element is of U-shaped configuration and has two legs which are oriented parallel to the longitudinal axis of the receptacle and are connected to one another via a cross-piece. The spring element can define, with the two legs and the cross-piece, a plane which is oriented parallel to the longitudinal axis of the receptacle. The cross-piece may be curved in the form of an arc of a circle. 
   In the case of an advantageous embodiment, the cross-piece forms the actuating element, which is adapted to be gripped by the user. This has the advantage that the spring element can be moved directly in order to transfer the locking elements into their release position. 
   The two locking elements are each connected to a leg of the spring element and, by virtue of the two legs being spread apart, the locking elements can be transferred out of their locking position into their release position. 
   The spring element is preferably disposed on the outside of the coupling body. This can simplify the assembly of the coupling part according to the invention and, moreover, in the case of such an embodiment, the coupling part is distinguished by a very small size. 
   The configuration of the actuating element has not been discussed specifically up until now. In the case of an advantageous embodiment, the actuating element encloses the coupling body in the circumferential direction. It is thus possible, in a constructionally straightforward manner, for the actuating element to be retained in captive fashion on the coupling body and, for example by virtue of the annular actuating element being displaced or rotated, the locking elements can be transferred out of their locking position into their release position. 
   The actuating element may be configured, for example, as a sleeve which encloses the coupling body and the spring element in the circumferential direction. The sleeve thus forms the outside of the coupling part according to the invention, and the spring element is adapted to be positioned between the sleeve and the coupling part. 
   In order to move the locking elements into their release position, it is provided, in the case of a preferred embodiment, that the coupling body and/or the actuating element have/has sliding surfaces which are oriented obliquely in relation to the longitudinal axis of the receptacle and along which the locking elements slide during transfer from the locking position into the release position. The sliding surfaces form guide members for the locking elements and, as the actuating element is moved, the locking elements slide along the sliding surfaces and are transferred out of their locking position into their release position. The sliding surfaces may be disposed on the coupling body, but as an alternative, or in addition, it may be provided that the actuating element has sliding surfaces. It is particularly advantageous if both the coupling body and the actuating element have associated sliding surfaces, since the locking elements can thus be moved particularly smoothly into their release position. 
   In the case of an advantageous embodiment, the coupling body has two apertures which are located diametrically opposite one another and have a wall surface which is oriented obliquely in relation to the longitudinal axis of the receptacle and forms a sliding surface, the locking elements each penetrating into an aperture. 
   The apertures may be configured, for example, as elongate holes which, offset laterally in relation to the center axis of the receptacle of the coupling body, extend through the latter. 
   As an alternative, it may be provided that the apertures are configured as slots which open out into an outer surface of the coupling body. The slots form a lateral through-passage in the coupling body and extend from the outer surface of the latter to the receptacle, so that the locking elements introduced into the slots penetrate laterally into the receptacle when they assume their locking position. 
   It is advantageous if the locking elements pass through the apertures, that is to say if each locking element has two end portions which project beyond the respective aperture. The projecting end portions may form engagement surfaces for the actuating element, so that the locking elements can be positioned against the actuating element by way of their end portions and can slide along the sliding surfaces of the apertures by virtue of the actuating element being moved relative to the coupling body. 
   In the case of a preferred configuration of the coupling part according to the invention, the actuating element encloses the coupling body in the circumferential direction and has at least two stop elements with a stop surface which is oriented obliquely in relation to the longitudinal axis and forms a sliding surface, it being possible for the locking elements to be positioned against the stop surface by way of an end portion which projects beyond the outer surface of the coupling body. In the case of such an embodiment, the actuating element, as the stop surfaces, has guide members for the locking elements, the guide members transferring the locking elements out of their locking position into their release position as the actuating element is moved. The guide members are configured in the form of the stop surfaces of the actuating element, and these are oriented obliquely in relation to the longitudinal axis of the receptacle of the coupling body. 
   It is advantageous if the actuating element, associated with each locking element, has two stop elements, and the respective locking element is adapted to be positioned against the stop surfaces of these two stop elements by way of first and second end portions which are directed away from one another. In the case of such a configuration, each locking element is gripped by two stop elements when the actuating element is moved, in particular displaced, relative to the coupling body. A first stop element forms a stop surface for a first end portion of the locking element and a second stop element forms a stop surface for the second end portion of the same locking element, the second end portion being directed away from the first end portion. The locking element is thus gripped by a respective stop element at its end regions and can therefore be transferred out of its locking position into its release position without bending. 
   The actuating element is preferably configured as a sleeve which encloses the coupling body in the circumferential direction and has a radially inwardly directed annular shoulder, on which the stop elements are integrally formed. The annular shoulder forms a narrowing of the sleeve and covers an intermediate space between the sleeve and the coupling body in the axial direction. The stop elements are integrally formed on the annular shoulders in the axial direction, and the locking elements can be positioned against these stop elements when the actuating element is moved. 
   A high level of ability to withstand mechanical loading can be given to the coupling part according to the invention in that the sleeve is retained on the coupling body such that it cannot be rotated about the longitudinal axis of the receptacle, but can be displaced coaxially in relation to the longitudinal axis. Such a configuration further simplifies the handling of the coupling part since, in order to actuate the coupling part, the user will intuitively displace the non-rotatable sleeve in the longitudinal direction. 
   In order to secure the sleeve in a non-rotatable manner on the coupling body, it is provided, in the case of an advantageous embodiment, that the sleeve has, on the inside, first guide elements, which interact with second guide elements disposed on the outside of the coupling body. 
   The first and/or second guide elements may be configured as guide ribs which are oriented parallel to the longitudinal axis of the receptacle. It may be provided, for example, that the sleeve, on the inside, has at least one guide-rib pair, into which penetrates a guide rib projecting from the outside of the coupling body. The coupling body preferably has a plurality of guide ribs which are spaced apart uniformly in the circumferential direction and each penetrate into a guide-rib pair of the sleeve. A converse arrangement may also be provided such that the coupling body has at least one guide-rib pair into which penetrates a guide rib disposed on the inside of the sleeve. 
   A preferred embodiment ensures a captive connection between the sleeve and the coupling body in that the sleeve is adapted to be latched to the coupling body. 
   It may be provided that the sleeve is adapted to be latched onto the coupling body in the axial direction. 
   For example, it may be provided that the sleeve carries, on the inside, two latching protrusions which are located diametrically opposite one another and each interact with a latching element disposed on the outside of the coupling body. 
   In the case of a particularly preferred embodiment, the receptacle of the coupling body forms a sealing portion and a locking portion, the sealing portion having a cross-section which is rotationally symmetrical in relation to the longitudinal axis of the receptacle and the locking portion having a cross-section which is rotationally asymmetrical in relation to the longitudinal axis of the receptacle, and the locking elements penetrating into the locking portion. By virtue of the rotationally symmetrical configuration of the sealing portion, the plug-in part can be connected in a fluid-tight manner to the coupling body in a constructionally simple manner, namely by means of a sealing ring and, by virtue of the rotationally asymmetrical configuration of the locking portion, into which the locking elements penetrate, it is possible to predefine the orientation of the plug-in part, which can be positioned in the locking portion by way of an undercut region, relative to the coupling body, and the plug-in part can be retained in a rotationally fixed manner by way of the rotationally asymmetrical configuration of the locking portion. Retaining the plug-in part in a rotationally fixed manner once again ensures that the mechanical loading to which the sealing ring, disposed on the plug-in part, is subjected is kept to a very low level. 
   The locking portion preferably comprises two flat wall portions which are located opposite one another and are connected to one another via two arcuate wall portions. In the case of such a configuration, the locking portion is distinguished by a substantially cylindrical construction comprising two mutually opposite flattened portions which are connected to one another via arcuate wall portions. The locking elements can penetrate into the locking portion in the region of the arcuate wall portions, and the flat wall portions constitute planar bearing surfaces for the plug-in part, which can be plugged into the receptacle. 
   The invention relates not just to a coupling part of the type mentioned above, but also to a plug connector arrangement having such a coupling part and having a plug-in part which is adapted to be plugged into the receptacle of the coupling body and, on the outside, has at least one undercut, which interacts with a locking element in order to lock the plug-in part in the receptacle. 
   The undercut preferably extends in the circumferential direction of the plug-in part merely over a sub-region. 
   It may thus be provided, for example, that the plug-in part has a sealing portion and a locking portion, the sealing portion carrying a circular annular groove, and the locking portion having a protrusion, for example in the form of an outer bead or of a wing or pin, which extends in the circumferential direction merely over a sub-region. The protrusion forms an undercut, behind which a locking element of the corresponding coupling part can engage. 
   The plug-in part preferably has two protrusions which are located diametrically opposite one another, extend circumferentially in each case over a sub-region and are connected to one another via lateral flattened portions. 
   In the case of an advantageous embodiment, the at least one protrusion has a conical end surface. This has the advantage that, when the plug-in part is plugged into the receptacle of the coupling body, the conical end surface of the protrusion can be positioned against a locking element and the latter can be pushed radially outward as the plug-in part is introduced further into the receptacle. 
   A more specific explanation will be given by the following description of preferred embodiments of the invention in conjunction with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective illustration, in exploded form, of a first embodiment of a coupling part according to the invention; 
       FIG. 2  shows a perspective illustration, in exploded form, of a coupling body and of a locking device of the coupling part from  FIG. 1 ; 
       FIG. 3  shows a perspective illustration of the coupling part from  FIG. 1  in the assembled state; 
       FIG. 4  shows a sectional view of a sleeve of the coupling part along line  4 - 4  in  FIG. 1 ; 
       FIG. 5  shows a sectional view of the sleeve of the coupling part along line  5 - 5  in  FIG. 1 ; 
       FIG. 6   a  shows a partially cut-away plan view of the coupling part from  FIG. 1  prior to the insertion of a plug-in part; 
       FIG. 6   b  shows a longitudinally sectioned view of the coupling part from  FIG. 1  prior to the insertion of the plug-in part; 
       FIG. 7   a  shows a partially cut-away plan view of the coupling part from  FIG. 1  as the plug-in part is being inserted; 
       FIG. 7   b  shows a longitudinally sectioned view of the coupling part from  FIG. 1  as the plug-in part is being inserted; 
       FIG. 8   a  shows a partially cut-away plan view of the coupling part from  FIG. 1  with the plug-in part inserted; 
       FIG. 8   b  shows a longitudinally sectioned view of the coupling part from  FIG. 1  with the plug-in part inserted; 
       FIG. 9   a  shows a partially cut-away plan view of the coupling part from  FIG. 1  as the inserted plug-in part is being released; 
       FIG. 9   b  shows a longitudinally sectioned view of the coupling part from  FIG. 1  as the inserted plug-in part is being released; 
       FIG. 10  shows a sectional view corresponding to  FIG. 4 , but this time of an alternative embodiment of a sleeve of the coupling part; 
       FIG. 11  shows a sectional view corresponding to  FIG. 5 , this time of the alternative embodiment of the sleeve; 
       FIG. 12  shows a perspective illustration of an alternative configuration of a coupling body of the coupling part with the locking device assembled; 
       FIG. 13  shows a further alternative configuration of a coupling body with the locking device assembled; and 
       FIG. 14  shows a perspective illustration of a second embodiment of a coupling part and of an associated plug-in part. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 to 9   b  illustrate, schematically, a first embodiment of a coupling part for a plug connector arrangement, the coupling part being designated overall by the reference numeral  10 . The coupling part  10  has a coupling body  11  as well as a locking device  12  and a sleeve  13 . 
   The coupling body  11  is of substantially hollow-cylindrical configuration and has a receptacle  15  in the form of a stepped through-bore with a sealing portion  16  which widens, via a step, in the direction of a front side  17  of the coupling body  11  and merges into a locking portion  18 , which opens out into the front side  17  via a widening  19 . On its outside  21 , the coupling body  11  carries a plurality of guide ribs  23  which are spaced apart uniformly from one another in the circumferential direction and are oriented parallel to the longitudinal axis  22  of the receptacle  15 . In the region of the locking portion  18 , as seen along the longitudinal axis  22 , the coupling body  11  has two apertures, offset laterally from the longitudinal axis  22 , in the form of two elongate holes  24 ,  25  which pass through the coupling body  11 . The elongate holes  24  extend obliquely in relation to the longitudinal axis  22  and form a respective sliding surface  26 ,  27  by way of their wall surface which is directed toward the front side  17 . 
   The locking device  12  is configured as a wire bracket and comprises a U-shaped spring element  29  with two legs  30 ,  31  which are oriented parallel to the longitudinal axis  22  and are connected integrally to one another via a semicircular cross-piece  32 . The free ends of the legs  30  and  31  are followed in each case by a locking element in the form of a respective locking pin  33 ,  34  which is oriented at right angles to the respective leg  30 ,  31 . As is clear, in particular, from  FIGS. 1 and 2 , the locking pins  33 ,  34  can be inserted laterally into the respective elongate holes  24  and  25 , the spring element  29  being positioned in a flattened region of the outside  21  of the coupling body  11  and accommodating a guide rib  23  between its legs. The locking pins  33 ,  34  pass through the respective elongate holes  24  and  25 , in which case they project beyond the respective elongate holes  24  and  25  by way of a first end region  35 , which is directed away from the spring element  29 , and by way of a second end region  36 , which is directed toward the spring element  29 . 
   The sleeve  13  forms an actuating element, by means of which the locking pins  33 ,  34  can be moved from a locking position into a release position. In the locking position, which is illustrated in  FIGS. 1 ,  6   a ,  6   b  and  8   a  and  8   b , the locking pins  33 ,  34  penetrate laterally into the locking portion  18  of the receptacle  15 . In the release position, which is illustrated in  FIGS. 7   a ,  7   b  and  9   a  and  9   b , the locking pins  33 ,  34  release the locking portion  18  of the receptacle  15  and are spaced apart from one another to a greater extent than in the locking position. 
   The sleeve  13  encloses the coupling body  11  and the spring element  29 , and also the locking pins  33 ,  34 , in the circumferential direction and, on a level with the front side  17  of the coupling body  11 , the sleeve  13 , on the inside, has an annular shoulder  39  with two arcuate shoulder portions  40 ,  41  which are located diametrically opposite one another and between which are disposed, likewise diametrically opposite one another, two elastically deformable latching protrusions  43 ,  44 . Directly adjacent to the latching protrusions  43 ,  44 , each shoulder portion  40 ,  41  has a respective stop element  46  with a stop surface  47  which is oriented obliquely in relation to the longitudinal axis  22  and is directed away from the front side  17 . 
   On the inside, the sleeve  13  carries two guide-rib pairs  49  located diametrically opposite one another. 
   In order to assemble the coupling part  10 , in first instance, the locking device  12 , with the spring element  29  and the locking pins  33 ,  34 , can be fitted on the coupling body  11 , as is illustrated in  FIG. 1 , and, thereafter, the sleeve  13  can be pushed onto the coupling body  11  in the axial direction. By virtue of this action, the latching protrusions  43 ,  44  engage at the front side  17  behind outer protrusions  51  disposed on the outside of the coupling body  11 , so that the sleeve  13  snaps onto the coupling body  11  and is then retained thereon such that it cannot be rotated, but can be displaced in the direction of the longitudinal axis  22 . If, starting from its rest position, which is illustrated in  FIG. 3  and in which the annular shoulder  39  is disposed on a level with the front side  17 , the sleeve  13  is displaced in the direction away from the front side  17 , then the stop surfaces  47  of the shoulder portions  40  and  41  engage against the respective first and second end regions  35 ,  36  of the locking pins  33 ,  34 . As the sleeve  13  is displaced further, the locking device  12  is displaced in the direction away from the front side  17 , the locking pins  33 ,  34  sliding along the respective sliding surfaces  26  and  27  of the elongate holes  24 ,  25 , and along the stop surfaces  47  of the annular shoulder  39 , and the U-shaped spring element  29  is spread apart, so that the locking pins  33 ,  34  are transferred from their locking position into their release position. 
   A plug-in part  55 , as is illustrated in  FIGS. 6   a  to  9   b , can be readily introduced into the receptacle  15  of the coupling body  11 . The plug-in part  55  is in the form of a piece of tubing and, in the exemplary embodiment illustrated, a hose  56  has been plugged onto that end of the plug-in part  55  which is directed away from the front side  17  of the coupling body  11 . The plug-in part  55 , in the direction of the front side  17 , has a sealing region  58  with an annular groove  59  into which a sealing ring  60  is embedded. At a spacing from the annular groove  59 , the plug-in part  55  forms a locking region  57  comprising an annular bead  61  which runs all the way around in the circumferential direction and has a conical front face  62  and a rear face  63  which is oriented perpendicularly to the longitudinal axis  22  and forms an undercut, as seen with respect to the longitudinal axis  22 . In the case of that embodiment of the plug-in part  55  which is illustrated in  FIGS. 6   a  to  9   b , both the sealing region  58  and the locking region  57  are rotationally symmetrical, as seen with respect to the longitudinal axis  22 , and it is also the case that the locking portion  18  and the sealing portion  16  of the coupling body  11  have a corresponding rotationally symmetrical configuration. 
   If the plug-in part  55  is plugged into the receptacle  15  of the coupling body  11 , then the front face  62  engages against the locking pins  33 ,  34  and, as the plug-in part  55  is introduced further into the receptacle  15 , the locking pins  33 ,  34  are displaced, by the front face  62 , along the respective sliding surfaces  26  and  27  until the annular bead  61  can pass through between the locking pins  33 ,  34 , as is illustrated in  FIGS. 7   a  and  7   b . The sealing region  58  of the plug-in part  55  then assumes a position within the sealing portion  16  of the coupling body  11 , the sealing ring  60  engaging in a fluid-tight manner against the wall of the sealing portion  16 . 
   Once the annular bead  61  has been guided through between the locking pins  33 ,  34 , the latter automatically resume, on account of the resilient restoring force to which they are subjected by the spring element  29 , their locking position, in which they penetrate laterally into the locking portion  18  of the coupling body  11  and thus engage behind the annular bead  61 . The plug-in part  55  is thus arrested axially in the receptacle  15  of the coupling body  11 . In the case of the coupling part  10  which is illustrated in  FIGS. 1 to 9   b , there is no need, for the purpose of arresting the plug-in part  55 , for the sleeve  13  to be displaced in the axial direction. A user can thus insert the plug-in part  55  into the coupling part  10  using one hand. 
   In order to release the plug-in part  55 , the locking pins  33 ,  34  have to be pushed apart from one another. For this purpose, the user can displace the sleeve  13  axially until the stop surfaces  47 , as has already been explained above, butt against the end regions  35 ,  36  of the locking pins  33 ,  34  and then transfer the latter into their release position as the sleeve  13  is displaced further. In this position, as is clear from  FIGS. 9   a  and  9   b , the plug-in part  55  can readily be removed from the receptacle  15 . The user can subsequently release the sleeve  13 , which, on account of the spring force of the spring element  29 , is then displaced back, by the end regions  35 ,  36  of the locking pins  33 ,  34 , into its rest position, which is illustrated in  FIG. 3 . 
   In combination with the plug-in part  55 , the coupling part  10  forms a plug connector arrangement, by means of which for example two hoses or two sections of pipe can readily be connected to one another in a fluid-tight manner and, optionally, also separated from one another again. 
     FIGS. 10 and 11  illustrate an alternative embodiment of a sleeve which is designated overall by the reference numeral  73 . This sleeve is largely identical to the sleeve  13  explained above. In contrast to the latter, the sleeve  73 , however, does not have any stop elements  46  with stop surfaces  47  oriented obliquely in relation to the longitudinal axis  22 ; rather, the sleeve  73  comprises an annular shoulder  74  which is extended axially as compared with the annular shoulder  39  of the sleeve  13  and, by way of its rear side  75 , which is directed away from the front side  17 , forms a stop surface which runs in a plane oriented perpendicularly to the longitudinal axis  22 , that is to say, unlike the stop surfaces  47 , is not oriented obliquely to the longitudinal axis  22 . 
   The sleeve  73  also can be snapped onto the coupling body  11 . If the sleeve  73  is displaced in the direction away from the front side  17 , then the rear side  75  of the annular shoulder  74  engages against the end regions  35  and  36  of the locking pins  33  and  34 , which are then likewise displaced along the sliding surfaces  26 ,  27  of the elongate holes  24 ,  25  as the sleeve  73  is displaced further. 
     FIG. 12  illustrates an alternative embodiment of a coupling body which is designated overall by the reference numeral  81 . This coupling body is largely identical to the coupling body  11  explained above. In contrast to the latter, however, the coupling body  81 , rather than having any elongate holes, has lateral slots  82 ,  83  which are disposed in the region of the locking portion  18 , open out in the outside  21  of the coupling body  81  and extend into the region of the locking portion  18  of the coupling body  81 . In a manner corresponding to the elongate holes  24 ,  25 , the slots  82 ,  83  each accommodate a respective locking pin  33 ,  34  and each form, by way of a wall region, a respective sliding surface  84 ,  85  which is oriented obliquely in relation to the longitudinal axis  22  and along which the locking pins  33 ,  34  can slide as the sleeve  13  or the sleeve  73  is displaced. 
     FIG. 13  illustrates a further alternative embodiment of a coupling body which is designated overall by the reference numeral  91  and is largely identical to the coupling body  11  explained above. Unlike the latter, this coupling body, instead of the elongate holes  24 ,  25 , has lateral slots  92 ,  93 , which are oriented radially, open out into the outside  21  of the coupling body  91  and each accommodate a locking pin  33 ,  34 . In combination with the sleeve  13 , the coupling body  91  forms a coupling part according to the invention. The sleeve  13  can be snapped onto the coupling body  91  and, by virtue of the sleeve  13  being displaced, the locking pins  33 ,  34 , which are disposed in the slots  92 ,  93 , can be transferred out of their locking position, which is illustrated in  FIG. 13 , into a release position. The end regions  35 ,  36  of the locking pins  33 ,  34  slide along the stop surfaces  47  of the sleeve  13  and are thus pushed apart from one another. 
     FIG. 14  illustrates an alternative embodiment of a coupling part according to the invention which is designated overall by the reference numeral  100 .  FIG. 14  also illustrates an alternative embodiment of a plug-in part according to the invention, which is designated overall by the reference numeral  105 . 
   The coupling part  100  differs from the coupling part  10  explained above merely by the fact that the locking portion  18  of the receptacle  15  is rotationally asymmetrical, as seen with respect to the longitudinal axis  22 . It comprises two flat wall portions  101 ,  102  which are located diametrically opposite one another and are connected to one another via arcuate wall portions  103 ,  104 . 
   The plug-in part  105  is largely identical to the plug-in part  55  explained above. Unlike the latter, however, it has two outer beads  106 ,  107  which each extend circumferentially only over a sub-region, are located diametrically opposite one another and are connected to one another in each case via a lateral flattened portion  108 ,  109 . 
   It is also the case that the plug-in part  105 , adjacent to its free end, carries a rotationally symmetrical annular grove, which accommodates a sealing ring  110 . The plug-in part  105  can be inserted into the receptacle of the coupling part  100 , the rotationally asymmetrical configuration of the outer beads  106  and  107  and of the locking portion of the coupling part  100  ensuring that the plug-in part  105 , when inserted into the coupling part  100 , cannot be rotated. It is thus secured in the coupling part  100  both in the axial direction and in the radial direction. This avoids the situation where the sealing ring  110  is subjected to wear as a result of the plug-in part  105  rotating. Moreover, the plug-in part  105  can only be inserted into the coupling part  100  with predefined orientation. The plug-in part  105  is distinguished by a particularly small amount of material being used, and it can thus be produced in a particularly cost-effective manner. It is only in the region of the locking pins  33 ,  34  that the plug-in part  105  has corresponding undercuts in the form of the outer beads  106 ,  107 , whereas the regions between the locking pins  33 ,  34  are formed without any undercuts.