Abstract:
In order to create a quick coupling for connecting at least two pressurised lines to a first coupling part that is connectable to a second coupling part so as to be pressure-proof, which quick coupling in a simple manner makes possible easy coupling while avoiding the mentioned disadvantages in all pressure ranges, it is provided for an externally arranged central pressure relief device ( 70 ) which is integrated in a second coupling part, or arranged on the second coupling part in an additional block ( 84 ), to be connectable to the pressurised lines (Lx) by way of pressure-relief connection lines ( 52 A to  52 D), and for the coupling parts to be able to be reversibly brought by a lever element ( 92 ) from a non-coupled position (P 1 ) to a coupled position (P 2 ), and to be lockable in place.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a quick coupling for connecting at least two pressurized lines to a first coupling part that is connectable to a second coupling part so as to be pressure-proof. 
     Quick couplings (rapid action couplings) of the generic type are well known. They are used to connect pressurised medium-conducting lines, and are used with liquids, for example with hydraulic oils, gases and other suitable media. Normally such quick couplings comprise two coupling parts, wherein a first coupling part is a plug-in part and a second coupling part is a socket part. To bring about coupling, the plug-in part can be pushed into the socket part. The generic quick coupling is also used to connect lines that are subjected to high media pressures. In such cases the connection has to be established one time under pressure in the socket part and another time under pressure in the plug-in part of the coupling. The connection can also be made with both coupling parts being either in the pressurised state or in the non-pressurised state. 
     In the case of quick couplings for high media pressures for example from 20 to 50 MPa in one of the two, or in both, coupling parts, pressure reduction elements are known for easier handling during the coupling process. By means of such pressure reduction elements it is possible to reduce the pressure in the coupling part by draining a small quantity of the medium to the face of the coupling part. Connection of the coupling parts of the quick coupling is facilitated in this way. Arranging pressure reduction elements in both coupling parts is also known. 
     From DE 41 01 001 A1 a coupling device is known in which a pressure reduction element is arranged and operated in the interior of at least one coupling part when the plug-in part is connected to a socket part. The pressure reduction element comprises a drain channel for the media pressure and a shut-off element which is arranged in the pressure reduction element and which can be operated by way of an operating element. When the pressure reduction element is operated the chambers of the coupling parts connected to said pressure reduction element form communicating vessels, as a result of which pressure equalisation takes place and the coupling can be closed with little physical effort. 
     Quick couplings are frequently associated with a problem in that the pressure reduction elements located in the coupling parts are of complex construction. Furthermore, impurities in the medium can lead to the pressure reduction elements clogging up and rendering the quick couplings heavy to operate. There is a further disadvantage in that depending on the type of the quick coupling the plug-in part or the socket part or both coupling parts have to comprise the complex pressure reduction elements. 
     To overcome this problem, quick couplings comprising two coupling parts, namely the plug-in part and the socket part, are known from DE 102 17 922 A1, which however comprise other pressure reduction options for the coupling process. In these quick couplings several plug-in parts of several pressurised lines are arranged in one connection block. The several socket parts which face the plug-in parts are accommodated in an additional connection block. A stud, which is centrally arranged in the connection block between the lines, is faced by a control piston between the socket parts, which control piston is centrally arranged in the connection block. The socket parts are connected to a pressure relief device. In an additional connection block (plug-in part) the elements of the pressure relief device are connected to the connection block (socket part). 
     Pressure-relief valve systems are integrated in the pressure relief device. Each line has its own pressure-relief valve system. The existing pressure-relief valve systems are connected to a shared pressure relief line by way of a pressure relief chamber. However, this arrangement, in which each line has its own pressure-relief valve system, is an expensive solution. 
     Furthermore, in most of the known quick couplings securing the coupling parts in relation to each other is problematic. Since quick couplings are also used in a very high-pressure range from 20 to 50 MPa, the requirements for firm connection between the coupling parts are very demanding. Apart from the actual design of the quick coupling, which in itself is very expensive and complicated, there is thus an additional need to integrate the locking elements in the housing of the quick coupling. 
     From DE 41 01 001 A1 locking elements such as clamp-type actuating springs and clamp-type ball fittings are known. These locking elements must be made to close tolerances to achieve a secure connection of the parts during the coupling action. The complex design and exacting requirements relating to the precision of the coupling part and to the additional locking parts pose considerable problems. 
     It is thus the object of the invention to provide a quick coupling of the generic type which in an easy way supports simple coupling while overcoming the above-mentioned disadvantages in all pressure ranges. 
     SUMMARY OF THE INVENTION 
     According to the invention this object is met by a quick coupling for connecting at least two pressurized lines to a first coupling part that is connectable to a second coupling part so as to be pressure-proof. By providing a central pressure relief device which is integrated in a second coupling part or externally arranged in an additional block on the second coupling part, wherein the pressure relief device can be connected, by way of pressure-relief connection lines, to the pressurised lines, and the coupling parts are reversibly movable from a non-coupled position to a coupled position by a lever element, and are lockable into place, a quick coupling is created for which a central pressure relief device is necessary for pressure relief during a coupling process. In an advantageous manner the lever element ensures that easy guidance in relation to each other, and safe coupling of the coupling parts in the coupled position are ensured. In the coupled position the coupling parts are safely locked into place. According to the invention, the solution provides a coupling which in an advantageous way provides a simpler design which in addition meets the safety requirements of quick couplings, in particular also in higher pressure ranges. 
     The first coupling part which forms the quick coupling is a plug-in part and the second coupling part is a socket part. The plug-in part is held together with a first guide pin (working ram) in a second connection block, which forms part of the plug-in part. The socket part is arranged in a first connection block. 
     In a preferred embodiment the quick coupling comprises a control device for the central pressure relief device. This control device is arranged in the first and second connection blocks or, in a further embodiment variant, in the first and second connection blocks, or in the first and second connection blocks and the additional block adjacent to the second coupling block. The connection blocks, or the additional block arranged adjacent to the first connection block of the second coupling part, result/results in a very compact design of the quick coupling according to the invention. 
     Furthermore, a preferred embodiment of the invention provides—as a control device—for a first guide pin, arranged in the plug-in part, in the coupled position to act on a control socket which is arranged in the first connection block, through which control socket a pressure-relief valve system of the central pressure relief device is operable in the first connection block, or in the first connection block and the additional block. 
     The central pressure relief device comprises the pressure relief valve system and an elimination valve with a pressure relief line. In addition a pressure chamber is arranged between the pressure-relief valve system and the pressure relief line of the elimination valve. 
     Another preferred embodiment of the invention further provides for several coupling pairs to be arranged in the quick coupling. 
     The characteristics according to the invention consist of several coupling pairs being designed so as to be pressure-relievable during the coupling action, by way of the pressure relief device, which is centrally arranged externally, i.e. arranged outside the plug-in part or the socket part. The central pressure relief device is connected to each of the pressurised lines, i.e. the respective coupling pair, by way of the pressure-relief connection lines. 
     In a further preferred embodiment of the invention each coupling pair in the pressure-relief connection lines is associated with at least one nonreturn valve by means of which valve pressure relief between the pressurised lines and the central pressure relief device is settable. 
     During coupling of the coupling pairs, the pressure-relief valve system that exists for all coupling pairs or for the associated pressurised lines of the central pressure relief device opens up depending on the arranged control device. The control device ensures that pressurised parts of the coupling pair are depressurised at the right point in time by way of the pressure relief device, as a result of which the medium flows into the pressure chamber and from there is evacuated into the pressure relief line of the elimination valve. 
     In a preferred embodiment of the invention, during the coupling process the control device makes possible synchronisation of the opening of the pressure-relief valve system with the coupling process corresponding to the control cam that is arranged on the control socket. 
     Thus, pressure equalisation of several coupling pairs takes place synchronously by way of the pressure-relief connection lines in the pressure relief device. The arranged nonreturn valves of the respective coupling pairs make it possible to set each pressurised line. 
     To achieve the shortest possible but synchronised opening of the pressure-relief valve system, the control socket is arranged such that the control cam is moved into, or out of, the pressure-relief valve system precisely at the point in time at which the respective sealing devices in the coupling parts open or close so that pressure relief takes place at a precisely predeterminable point in time. 
     In an advantageous embodiment an internal pressure reduction element is arranged in the interior of a coupling part. 
     In an advantageous way according to the invention the first and second coupling part are reversibly brought from a non-coupled position to a coupled position by a lever element, and are correspondingly locked in place in the coupled position. According to the invention to this effect the first connection block comprises a lever attachment for the lever element with its arranged lever arm. According to the invention the second connection block comprises an accommodation element which is engaged by a lever accommodation device of the lever element already in the non-coupled position. In this way, by operating the lever element the first coupling part (plug-in part) can be brought to the second coupling part (socket part) by swivelling the lever element, and in the coupled position can be secured by the lever element. In this coupling, which is supported from the outside by the lever element, the first guide pin (working ram) engages the control socket that is arranged in the first connection block, and together with the pressure relief device forms the control device for pressure relief of the quick coupling. 
     By means of the pressure-relief connection lines arranged in the first connection block, or in a further embodiment variant arranged in the additional block, all arranged coupling pairs are thus depressurised at the same time within the quick coupling by way of the central pressure relief device. 
     Below, further preferred embodiments of the invention are described with reference to a coupling pair. 
     The embodiments correspondingly apply to each coupling pair, i.e. also in the case of designs involving several coupling pairs within the quick coupling according to the invention. 
     In a preferred embodiment of the invention the pressurised lines are coupled to each other, wherein at the same time axial displacement of the first guide pin (working ram) in the second connection block of the plug-in part in the direction of the first connection block of the socket part, or of the first connection block (coupling block) and the additional block takes place. The first guide pin (working ram) slides the control socket, which is arranged in the first connection block of the socket part or of the first connection block (coupling block) and of the additional block. First, the control cam of the control socket operates a pressure relief valve and opens a pressure-relief valve system and thus the pressure relief device. Pressure relief of a first medium channel in the socket part takes place. 
     In the quick coupling subsequently a fourth sealing device in the socket part is released, and further pressure equalisation takes place first from the first medium channel in the socket part to a chamber in the plug-in part. The pressure in the quick coupling is then relieved up to the chamber. 
     Also preferred is the opening of a first sealing device of the plug-in part after opening an additional pressure reduction element, after which the coupling pair of the quick coupling start to open completely. As a result of continued engagement of the control cam on the pressure relief valve of the control sleeve that has been pushed further into the pressure-relief valve system, the pressure-relief valve system is still open so that pressure relief is continued. 
     Finally, the first sealing device opens completely, as a result of which by further axial displacement of the coupling parts and of the first guide pin (working ram) the control cam of the control socket is led out of the pressure-relief valve system while releasing the pressure relief valve so that the pressure-relief valve system closes and the pressure in the quick coupling builds up. 
     In a preferred embodiment of the invention the control socket can comprise several control cams so that opening and closing the quick coupling is possible by multiple opening and closing of the pressure-relief valve system. In this case, pressure relief in the coupling parts of the quick coupling is possible at different points in time. 
     Further preferred embodiments of the invention are stated in the remaining characteristics provided in the subordinate claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Below, one embodiment of the invention is explained in more detail with reference to the associated drawings. The following are shown: 
         FIG. 1  an outside view of a quick coupling in the non-coupled state; 
         FIG. 2A  a perspective view of the quick coupling in the non-coupled state; 
         FIG. 2B  a section of the quick coupling in the non-coupled state; 
         FIG. 2C  a section of a pressure relief device in an additional block of the quick coupling in the non-coupled state; 
         FIG. 3  a section of the quick coupling in the partly coupled state in a first coupling step; 
         FIG. 4  a section of the quick coupling in the partly coupled state in a second coupling step; 
         FIG. 5  a section of the quick coupling in the partly coupled state in a third coupling step; 
         FIG. 6A  a perspective outside view of the quick coupling in the coupled state; 
         FIG. 6B  a section of the quick coupling in the coupled state according to a fourth coupling step; 
         FIG. 6C  a section of a pressure relief device in the additional block of the quick coupling in the coupled state; 
         FIG. 7  a perspective view of the machine-side connection of the additional block; 
         FIG. 8  a section of the additional block with a view of the pressure-relief connection lines and the nonreturn valves between the pressure lines and the pressure relief device; and 
         FIG. 9  a section, comprising several sectional planes, showing the pressure-relief connection lines, the nonreturn valves between the pressure lines, and the pressure relief device as well as the lever element and the machine-side connection adapters. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Below, reference is made to the figures, wherein in all figures identical parts are designated by identical reference characters. 
     The quick coupling, overall designated  100 , in  FIG. 1  shown in the non-coupled state P 1 , comprises a known basic design comprising two coupling parts  12  and  14 . In this arrangement the second coupling part is a plug-in part  12  and the first coupling part  14  is a socket part  14 . The special feature of the quick coupling  100  consists of several plug-in parts  12  of several pressurised lines L 1 , L 2  (Lx), which lines are to be connected to each other, being arranged in a second connection block  18 . 
     The several possible socket parts  14  which face several possible plug-in parts  12  are accommodated in a first connection block  16 .  FIG. 1  also shows the lines Lx (L 1 , L 2 ) that lead out of the socket parts  14 . Hereinafter a plug-in part  12  and a socket part  14  are designated a coupling pair. 
       FIG. 1  thus shows a quick coupling  100  with two coupling pairs that are associated with two pressurised lines L 1 , L 2 . One special feature of the embodiment shown consists of an additional block  84  being attached to the first connection block  16  (coupling block) in which, in this embodiment, there is a pressure relief device  70  (not shown in  FIG. 1 ). The following description and the associated figures explain the arrangement of the pressure relief device  70  and of a control device  10  (not shown in  FIG. 1 ) in the second connection block  18  (plug-in part  12 ) or on the first connection block  16  (coupling block/socket part  14 ) and an additional block  84  as an additional device that is associated with the first connection block  16  (coupling block). 
     However, the invention also relates to a design without an additional block  84 . In this case all the components that would otherwise be arranged in the additional block  84  are arranged in the first connection block (coupling block/socket part  14 ). 
       FIG. 1  shows a first guide pin (working ram)  42 , which is arranged beside the lines Lx in the second connection block  18 . In the first connection block  16  the first guide pin (working ram)  42  faces a control socket  44  ( FIG. 2 , but not visible in  FIG. 1 ) as part of the control device  10 . 
       FIG. 1  further shows a second guide pin  43 , which in the first connection block  16  faces a borehole  112  ( FIG. 9 ). In the second connection block  18  the second guide pin  43  is arranged as a centring aid in addition to the first guide pin  42 . Furthermore,  FIG. 1  shows an elimination valve  49  arranged on the additional block  84  beside the pressure lines Lx. This elimination valve  49  is used for pressure relief during the coupling procedure of the quick action coupling  100 . As shown in  FIG. 1 , according to the invention the quick coupling  100  comprises a lever element  92  which comprises a lever arm  94  and a lever accommodation device  96 . By way of a lever attachment  102 , the lever element  92  is rotatably held on the first connection block  16 . The lever element  92  forms a rotary axis  104  of the lever. On the second connection block  18  an accommodation element  98  is arranged, which, when the lever element  92  is fully lowered and when the plug-in part  12  is plugged into the socket part  14 , engages the lever accommodation device  96 . As a result of the lever element  92  the plug-in part  12  can be displaced in relation to the socket part  14  and due to the control curve in the lever accommodation device  96 , when the accommodation element  98  engages the lever accommodation device  96 , said plug-in part  12  can be moved to the socket part  14  and is lockable into place and securable in a non-coupled position P 1  (not shown). In a position P 1  that is not coupled in  FIG. 1 , the socket part  14  can be locked by a hinge able cover  124  so that the socket part  14  is protected from dirt and the like. The following figures show the coupling process and the additional functions of the quick coupling  100 . 
       FIG. 2A  again shows the quick coupling  100  in the non-coupled position P 1 , wherein the accommodation element  98  already accommodates a first contact in the lever accommodation device  96  of the lever element  92 . Unlike the perspective view of  FIG. 2A , which shows the same components as in the lateral view of  FIG. 1 ,  FIG. 2B  shows the quick coupling  100  in a sectional view. In this arrangement  FIG. 2B  shows a sectional view of a coupling pair  12 ,  14  (plug-in part and socket part) of the pressurised pressure line L 1 . Also shown is the control device  10  which comprises the working ram  42 , a control socket  44  and a pressure-relief valve system  50 . The pressure-relief valve system  50  forms part of the central pressure relief device  70 , which in addition comprises the elimination valve  49  and a pressure relief line  48 . The central pressure relief device  70  is shown in detail in  FIG. 2C  in a further sectional view that is analogous to the view in  FIGS. 2A ,  2 B in the non-coupled state P 1  of the quick coupling  100 . 
     In its home position the face  24  of the housing  22  of the plug-in part  12  rests against an axially displaceable second housing element  62  of the socket part  14 . Furthermore, the face  24  of a ram  28 , which ram  28  by way of a third sealing device  38  provides a seal on a second housing  22  of the plug-in part  12 , rests against a firmly held slide element  26 . 
     The slide element  26  is held in a slide element bearing  40 . The force of a first spring element  76  pushes the ram  28  that is axially guided in a ram bearing  86  against the third sealing device  38  and closes a chamber  34  off against the atmosphere. A first sealing device  30  on a seal seat  32  closes off the chamber  34  in the direction of a second medium channel  68  that conveys medium and is pressurised. 
     A pressure reduction element  56  can be arranged in the sealing device  30 . However, the function according to the invention of the quick coupling  100  according to the explanations below is available also without a pressure reduction element  56 . 
     The socket part  14  is integrated in the first connection block  16 . The socket part  14  seals an outer housing  20  off against the first connection block  16 . The outer housing  20  of the socket part  14  comprises the inner first housing element  23 , the outer third housing element  64  and the front second housing element  62 . 
     The second housing element  62  is arranged on the interior wall of a borehole  120  ( FIG. 8 ). The second housing element  62  is axially displaceable in relation to the third housing element  64  as well as in relation to the first housing element  23  against the force of a first and second spring element  58 ,  60 . The first spring element  58  is arranged between the housing elements  62  and  64 , and the second spring element  60  is arranged between the housing elements  64  and  23 . By way of a fourth sealing device  88  the slide element  26  seals the socket part  14  against the axially displaceable third housing element  64  in the non-coupled state P 1 . 
     A first medium channel  66  is connected to the slide element  26 , which medium channel  66  is open towards the medium-conveying first pressure line L 1  of the socket part  14 . In the embodiment shown the first medium channel  66  is integrated in the additional block  84 . As mentioned above, where there is no additional block  84 , said medium channel  66  can also be completely arranged in the first connection block  16  (coupling block). 
     In the first connection block  16  and the additional block  84  a control socket borehole  78  is arranged so as to be spaced apart parallel in relation to the coupling pair  12 ,  14 . The control socket  44  is integrated in this control socket borehole  78 , which control socket, as shown in  FIG. 2B , is not yet engaged by the working ram  42  in the non-coupled position P 1 . The control socket borehole  78  guides the control socket  44  right into the additional block  84 , wherein within the control socket  44  a control socket spring  45  is arranged which not only rests against the inside of the control socket  44 , but is also arranged in an indentation of a pressure relief chamber  46 . The control socket  44  rests on the same axis as the working ram  42 , and in the non-coupled state P 1  forms a limit stop  80  in the control socket borehole  78 . 
     In the non-coupled state P 1  the working ram  42 , which forms part of the control device  10 , and at least one control cam  54  arranged on the working ram  42  do not engage the pressure-relief valve system  50 . 
     The pressure-relief valve system  50  which forms part of the control device  10  is a main component of the pressure relief device  70  which in  FIG. 2C  is shown in an enlarged view. The pressure-relief valve system  50  comprises a pressure relieve valve  72 , a spring control device  74  as well as a valve element  51 . In this arrangement the part  47  transfers the axial movement. Behind the pressure relief valve  72  ( FIG. 2C ) there is a pressure-relief connection line  52  or a system of pressure-relief connection lines  52 A to  52 D, byway of which the coupling pairs  12 ,  14  and thus the pressurised pressure lines Lx (L 1 , L 2 ) are vented by way of the central pressure-relief valve system  50  of the pressure relief device  70 . This requires that the pressure relief valve  72  opens at a particular point in time during the coupling procedure, thus making possible coupling of the coupling pairs without any pressure, i.e., pressure-proof. 
       FIGS. 3 ,  4  and  5  as well as  6 A to  6 C show the coupling procedure with which an incremental pressure relief of the quick coupling  100  in the plug-in part  12  and socket part  14  is achievable. In the following it is assumed that both coupling parts  12  and  14  in the medium-carrying channels  66 ,  68  are pressurised in the non-coupled state P 1 .  FIGS. 6A to 6C  show the completely coupled state P 2 , wherein again a perspective outside view, a section of the quick coupling  100  and a section of a pressure relief device  70 , shown in an enlarged view, of the quick coupling  100  are shown. 
     In principle, coupling takes place in four steps. In the first coupling step pressure relief of the first medium channel  66  takes place after opening the elimination valve  49 . Subsequently, in the second coupling step, opening of the fourth sealing device  88  and elimination of the pressure up to chamber  23  take place. In the third coupling step again, opening of a device, namely of the pressure reduction valve  56 , takes place, as a result of which, elimination of the pressure in the second medium channel  68  occurs, after which finally in the fourth coupling step complete opening of the plug-in part  12  takes place by lifting the first sealing device  30 . There is thus a constant sequence of the procedures of “opening-elimination-opening-elimination . . . ” and so forth. 
     Below, the function of further pressure relief is described in more detail. 
       FIG. 3  shows a section of the quick coupling  100  in the first coupling step. In this first coupling step, at first the elimination valve  49  is opened to relieve the pressure of the coupling parts  12 ,  14 . 
     The non-coupled quick coupling  100  of  FIG. 2  represents the starting position for opening the elimination valve  49 . By axial displacement of the second connection block  18  with the integrated plug-in part  12  and the first guide pin (working ram)  42  in the direction of the socket part  14 , the housing face  24  of the second housing  22  is pushed into the socket part  14 . 
     In the commencing coupling procedure the control socket  44  is pushed further into the pressure relief device  70  than is the case in the home position. 
     The control cam  54  operates a valve element  51 , as a result of which an aperture between a pressure-relief connection line  52  and the pressure relief chamber  46  is opened in the pressure relief valve  72 . Because the pressure relief chamber  46  is connected to a non-pressurised pressure relief line  48 , according to the principle of communicating vessels, pressure relief in the socket part  14  can take place by way of the elimination valve  49 . In particular, the first medium channel  66  is thus relieved in the socket part  14  by way of the pressure-relief connection line  52 . 
     In a second coupling step according to  FIG. 4  the housing elements  62  and  64 —see FIG.  2 B—are further displaced in axial direction against the spring elements  58  and  60  in the direction of the channel  66 . 
     The ram  28  is fundamentally displaced axially against the force of the first spring element  76  due to the counterforce that emanates from the stationary slide element  26 , in the direction of the channel  68 . 
     As a result of this arrangement a fourth sealing device  88  of the slide element  26  on the third housing element  64  is released. Further axial displacement takes place by way of the first guide pin (working ram)  42  onward in the direction of the control socket  44 . 
     Pressure relief acts by way of the pressure-relief connection lines  52 C,  52 B,  52 A ( FIGS. 8 and 9 ) by way of the first medium channel  66  to chamber  34  by opening the sealing device  88  in the plug-in part  12 . As a result of this first described displacement the control socket  44  leaves its limit stop  80  in the control socket borehole  78  of the first connection block (coupling block)  16 . 
       FIG. 4  shows a sectional view of the quick coupling  100  in the partly coupled state P 2  according to the first and the second coupling steps. 
     The diagram shows that the fourth sealing device  88  is slowly released by axial displacement of the housing elements  62  and  64 , and comprises a connection to the chamber  34 . The first spring element  76  of the plug-in part  12  is already in a partly tensioned state. The pressure-relief valve system  50  is open and pressure equalisation by way of the first medium channel  66  and the pressure-relief connection line  52 C to  52 A right up to the chamber  34  takes place. 
     In continuation of the converging movement of the connection blocks  16  and  18  (coupling device) the control socket  44  enters further into the pressure-relief valve system  50 . 
       FIG. 5  shows that the cam  54  continues to engage the region of the pressure relief valve  72 . 
     In a third coupling step according to  FIG. 5  a pressure reduction element  56  makes possible a first pressure equalisation of the two coupling parts  12  or  14  beyond the chamber  34 . Pressure relief, or a first pressure equalisation, then takes place between the second medium channel  68  and the chamber  34 . To this effect the ram  28  with its side facing the first sealing device  30  touches a pressure pin integrated into the first sealing device  30 , which pressure pin releases a pilot flow in existing gaps of the first sealing device  30 . 
     However, during the generated pilot flow, which causes the first pressure equalisation between the chamber  34  and the second medium channel  68 , the first sealing device  30  still rests against the seal seat  32 . 
     In the further coupling process, a fourth coupling step, according to  FIG. 6B  the sealing device  30  is still further axially displaced in the direction of the channel  68  as a result of the action of the ram  28 . The seal seat  32  is released, and by way of the released chamber  34 , through the partly-open fourth sealing device  88 , the channel  68  is also completely relieved of pressure by the pressure relief device  70  and its pressure relief valve  72 . 
       FIG. 6B  further shows that the first guide pin (working ram)  42  of the control socket  44  is further displaced into the pressure relief device  70 . The end of the control cam  54  has been reached. The control cam  54  has run off the pressure relief valve  72 . As the control cam  54  runs off the pressure relief valve  72  the pressure relief valve system  50  closes and consequently the pressure relief chamber  46  and thus the elimination valve  49  close. 
     In the last phase of the coupling process of the connection blocks  16  and  18  the plug-in part  12  is completely slid into the socket part  14 . A second sealing device  36  provides sealing of a first phase  17  of the first connection block  16  and a second phase  19  of the second connection block  18 . This second sealing device  36  seals off the entire perimeter of the second connection block when it engages the first connection block. The quick coupling  100  has thus reached its coupled terminal position, and closing the elimination valve ensures pressure build-up. 
     This pressure relief function according to  FIGS. 3 to 6C  can be realised by arranging several pressure-relief connection lines  52 A, B, C ( FIGS. 8 and 9 ) right up to the pressure relief device  70  for any desired number of coupling pairs  12  and  14 . 
       FIGS. 6A  to C show the quick coupling  100  in its fully opened coupled state. In this arrangement  FIG. 6A  again shows a perspective view of the quick coupling in the completely coupled state;  FIG. 6B  shows a section of the quick coupling in the fully coupled state; and  FIG. 6C  shows a section of a pressure relief device in the additional block of the quick coupling in the fully coupled state. 
     The first spring element  76  ( FIG. 6B ) is now in its completely tensioned state. The ram  28  pushes against the stationary slide element  26 , as a result of which the first sealing device  30  lifts from the housing  22  of the plug-in part  12 . The pressure reduction valve  56  is fully open. The ram  28  is fully displaced in the direction of the socket part  14 . At the same time the fourth sealing device  88  is open so that it no longer rests against the third housing element  64  of the socket part  14 . The housing faces  24  of the plug-in part  12  and of the socket part  14  are pushed against the spring elements  58  and  60  by their housing elements  62  so that the fourth sealing device  88  of the slide element  26  fully releases the connection between the chamber  34  and the channel  66 . After completed coupling of the quick coupling  100 , pressure relief is no longer necessary. 
     The first guide pin (working ram)  42  has guided the control socket  44  further into the pressure relief device  70  so that the control cam  54  no longer engages the pressure relief valve  72 . The pressure relief valve  72  closes. The pressure relief function of the pressure relief device  70  is thus interrupted. In the quick coupling  100  the full medium pressure of the connected open coupling parts  12  and  14  builds up. 
       FIG. 6A  shows a perspective outside view of the quick coupling  100  in its fully coupled state. The coupled lines L 1  and L 2  between the connection blocks  16  and  18  are shown, as is the additional block  84 , which in this embodiment accommodates the pressure relief device  70 . 
     As shown in  FIG. 6C , the pressure relief device  70  leads by way of the pressure relief chamber  46 , which is not visible from the outside, to the common pressure relief line  48 . The pressure-relief valve systems  50 , which are arranged radially in relation to the pressure relief chamber  46 , which pressure-relief valve systems during the coupling procedure are opened and closed by way of the guide pin  42  and the control socket  44 , are only indicated by their closure elements. 
       FIG. 6A  is a perspective view of the quick coupling  100  as seen by the user. The cover  124  of the first connection block  16  is open, and the second connection block  18  is moved so that it is directly adjacent to the first connection block  16 . This coupling with the prescribed pressure relief is mechanically supported by the lever element  92  that has been provided. As already described in the context of  FIGS. 2A to 2C , the lever accommodation device  96  engages the accommodation element  98 , which is located on the second connection block  18 . The lever accommodation device  96  provides a type of control curve for the coupling procedure, because bringing together the connection blocks  16 ,  18  is predeterminable with the lever accommodation device  96 . This control curve of the lever accommodation device  96  thus makes it possible to determine the point in time at which the cam  54  of the control socket  44  ( FIG. 10 ) opens the pressure-relief valve system  50  of the pressure relief device  70  during closing or opening the quick coupling  100  for pressure relief. The other components of  FIG. 6A  are known from the description provided so far, in particular in the context of  FIGS. 2A to 2C . 
     Opening the quick coupling  100  takes place the other way round. 
     Corresponding to the coupling steps described in the context of  FIGS. 3 to 6C , when the quick coupling  100  is being closed, in reverse order, first the chamber  34 , which faces the second medium channel  68 , is closed by closing the first sealing device  30  (fourth coupling step) by means of pressure relief by way of the pressure relief device  70 . 
     Subsequently the pressure reduction valve  56  (third coupling step) in the plug-in part  12  also closes. 
     The force of the spring element  76  results in a further return of the ram  28  to its home position. The housing elements  23 ,  62  and  64  are also displaced back to their home positions (non-coupled position P 1 ) as a result of the force of the spring elements  58  and  60  so that the fourth sealing device  88  (second coupling step) of the slide element  26  again provides a seal on the third housing element  64 . 
     As a result of this, in the socket part  14  the first medium channel  66  is closed off against the chamber  34  or the plunger  28  while at the same time providing pressure relief by way of the pressure relief device  70 . 
     Finally, at the end of the uncoupling process the pressure relief device  70  and thus the elimination valve  49  close in that the control device  10  leaves the region of the pressure relief valve  72  of the pressure relief device  70  so that pressure equalisation is interrupted. Thus after separation of the connection blocks  16  and  18 , each coupling part  12  and  14  is sealed off both against the pressure-relief connection lines  52  and against the face. 
       FIGS. 7 to 9  show the additional block from the outside in a perspective view of the connection on the machine side and a section of the additional block showing the pressure-relief connection lines  52 A to  52 D as well as a section ( FIG. 9 ) with several sectional planes of the quick coupling.  FIG. 10  shows the connection options, on the machine side, of the additional block  84 , wherein apart from the pressure lines L 1 , L 2  an additional line (so-called outlet line) La is shown. So-called adapters  122  are associated with each line. In the lateral region of the additional block  84  a plug  118  is shown, which, as is also shown in the sectional view of  FIG. 8 , makes possible access to the pressure-relief connection lines  52  and in particular to a first nonreturn valve  114 . On the opposite side of the additional block  84  at another height there is also a plug  118  which provides access to a second nonreturn valve  116 . The respective nonreturn valves  114  and  116  make it possible to set the extent of pressure relief of the respective coupling pairs  12  and  14  (not visible in the drawing). 
     In  FIG. 8  the section view shows the corresponding boreholes  120  in which the pressure-relief connection lines  52  end. Starting from the borehole  120 , a first pressure-relief connection line  52 A is associated with the first pressure line L 1  and is connected to the pressure relief device  70  by way of the first nonreturn valve  114 . Analogously to this the second pressure line L 2  is connected to a third pressure relief line  52 C by way of a fourth pressure relief line  52 D, wherein in the third pressure relief line  52 C again a second nonreturn valve  116  for setting the extent of pressure relief is arranged. The third pressure-relief connection line  52 C again leads to the pressure relief device  70 . By way of the second pressure-relief connection line  52 B, the first pressure-relief connection line  52 A and the third pressure-relief connection line  52 C are interconnected so that each pressure line L 1 , L 2  can be routed to the pressure relief line  70  by way of a system of pressure relief connection lines  52 . 
       FIG. 9  shows the analogous arrangement of the pressure relief connection lines  52 A to  52 D and the arranged nonreturn valves  114 ,  116  in various sectional planes. In the boreholes  120 , the respective first, second and third connection adapters  106 ,  108  and  110  are shown. In addition, the section view in  FIG. 9  shows a socket borehole  112  which the second guide pin  43  of the quick coupling  100  engages during the coupling or decoupling procedure. The design illustrated in  FIG. 9  in particularly shows that a central pressure relief device  70 , even without the presence of an additional block  84 , can be arranged so as to be completely in the first connection block  16  of the socket part  14 . 
     Finally,  FIG. 9  diagrammatically shows the lever element  92 , which is arranged on the outside, which lever element  92  ensures mechanical securing and joining of the quick coupling. 
     LIST OF REFERENCES 
     
         
           100  Quick coupling 
           10  Control device 
           12  Plug-in part 
           14  Socket part 
           16  First connection block 
           17  First face (first connection block  16 ) 
           18  Second connection block (coupling block) 
           19  Second face (second connection block  18 ) 
           20  Housing (socket part  14 ) 
           22  Second housing (plug-in part  12 ) 
           23  First housing element 
           24  Housing face 
           26  Slide element 
           28  Ram 
           30  First sealing device (plug-in part  12 ) 
           32  Seal seat 
           34  Chamber 
           36  Second sealing device (faces  17 ,  19 ) 
           38  Third sealing device (second housing  22 ) 
           40  Slide element bearing 
           42  First guide pin (working ram) 
           43  Second guide pin 
           44  Control socket 
           45  Control socket spring 
           46  Pressure relief chamber 
           47  Part 
           48  Pressure relief line 
           49  Elimination valve 
           50  Pressure-relief valve system 
           51  Valve element 
           52 A First pressure-relief connection line 
           52 B Second pressure-relief connection line 
           52 C Third pressure-relief connection line 
           52 D Fourth pressure-relief connection line 
           54  Control cam 
           56  Pressure reduction element 
           58  First spring element 
           60  Second spring element 
           62  Second housing element 
           64  Third housing element 
           66  First medium channel 
           68  Second medium channel 
           70  Pressure relief device 
           72  Pressure relief valve 
           74  Spring control device 
           76  First spring element 
           78  Control socket borehole (in connection block  16 ) 
           80  Limit stop 
           84  Additional block 
           86  Ram bearing 
           88  Fourth sealing device 
           92  Lever element 
           94  Lever arm 
           96  Lever accommodation device 
           98  Accommodation element 
           102  Lever attachment 
           104  Rotary axis of the lever 
           106  First connection adapter 
           108  Second connection adapter 
           110  Third connection adapter 
           112  Socket borehole (in connection block  16 ) 
           114  First nonreturn valve 
           116  Second nonreturn valve 
           118  Plug 
           120  Boreholes 
           122  Adapter (on the machine side) 
           124  Cover 
         Lx Pressure lines 
         L 1  First pressure line 
         L 2  Second pressure line 
         La Outlet line 
         P 1  Non-coupled position 
         P 2  Coupled position