Abstract:
The invention relates to a coaxial high-pressure coupling for hoses or pipelines, comprising a plug part ( 10 ) and a receptacle part ( 30 ) that accommodates the plug part in the coupled state, the plug part ( 10 ) and the receptacle part ( 30 ) each having a valve body ( 11, 31 ) having an inner channel ( 13, 33 ) and an outer channel ( 16, 36 ) concentric to the inner channel and the inner channels ( 13, 33 ) and the outer channels ( 16, 36 ) of the plug part ( 10 ) and of the receptacle part ( 30 ) being connected to each other in the coupled state, and in the inner channel ( 13 ) of the valve body ( 11 ) of the plug part ( 10 ) a closing cone ( 18 ) and in the outer channel ( 16 ) of the plug part ( 10 ) a closing sleeve ( 23 ) each being movable against spring action ( 21, 25 ) and being displaceable into the opening position thereof by the receptacle part ( 30 ) during the coupling process, is characterized in that a valve bore ( 61 ), which is connected to the inner channel ( 13 ) at one end and has a connection to the atmosphere at the other end and has a valve piston ( 62 ) movably arranged in the valve bore, is arranged inside the inner channel ( 13 ) formed by an inner pipe ( 14 ) and that the valve piston ( 62 ) is preloaded by spring action ( 63 ) into the blocking position of the valve piston, in which the connection between the valve bore ( 61 ) and the inner channel ( 13 ) is blocked, and can be displaced into a leakage position by an overpressure in the inner channel ( 13 ) that acts against the spring ( 63 ).

Description:
The invention relates to a coaxial high-pressure coupling for hoses or pipelines with a plug part and with a receptacle part that accommodates the plug part in the coupled state, wherein the plug part and the receptacle part each having a valve body with an inner channel and an outer channel arranged concentric thereto, wherein the inner channels and the outer channels of the plug part and of the receptacle part are connected to one another in the coupled state, wherein a closing cone can be moved against the force of a spring in the inner channel of the valve body of the plug part and a closing sleeve can be moved against the force of a spring in the outer channel of the plug part, and wherein the closing cone and the closing sleeve can be respectively displaced into their open position by the receptacle part during the coupling process. 
     BACKGROUND OF THE INVENTION 
     A high-pressure coupling with the aforementioned features is described in EP 0 853 743 B1. Couplings of this type with a plug part having an inner and an outer channel and with a correspondingly designed receptacle part are required, in particular, for connecting a hydraulic drive element to a hydraulically driven device, for example when a drive element in the form of a hydraulic pump is not only connected to a device in the form of a tool by means of a pressure line, but also by means of a return line. In such a high-pressure coupling, it is problematic that the fluid enclosed in the inner channel of the plug part by the closing cone may heat up in the decoupled state and therefore lead to such a pressure increase that it becomes difficult to couple the high-pressure coupling by inserting the plug part into the receptacle part because the closing cone in the inner channel of the plug part needs to be moved against the increased pressure. 
     SUMMARY OF THE INVENTION 
     In a correspondingly designed high-pressure coupling known from WO 2008/130311 A, it is proposed to solve the above-described problem by arranging a pressure relief valve in the closing cone that closes the inner channel of the plug part in the decoupled state, wherein said pressure relief valve is opened by a component of the receptacle part at the beginning of the coupling process such that the pressurized fluid in the inner channel of the plug part can flow off into the inner channel of the receptacle part, namely before the respective flow paths between the inner channels and the outer channels of the receptacle part and the plug part are released due to the respective position of the closing elements of the plug part and the receptacle part in the coupled state. However, this known solution has the disadvantage that a very high pressure may in the meantime be present in the plug part and that this high pressure may lead to a permanent high strain on the valve body with its seals and complicate the coupling process despite the pressure relief valve. 
     The invention therefore is based on the objective of realizing a coaxial high-pressure coupling of the initially cited type and with the above-described features in such a way that the disadvantageous consequences of a pressure increase in the plug part are prevented. 
     The solution to this objective as well as advantages embodiments and enhancements of the invention are defined in the claims that follow this description. 
     According to the basic idea of the invention, it is proposed that a valve bore, which is connected to the inner channel at one end and connected to the atmosphere at the other end and has a valve piston displaceably arranged therein, is arranged in the interior of the closing cone that can be moved in the inner channel formed by an inner pipe, and that the valve piston is prestressed into its blocking position, in which it blocks the connection between the valve bore and the inner channel, by the force of a spring and can be displaced into a leakage position by an overpressure in the inner channel that acts against the spring. 
     The invention provides the advantage that high pressure developing in the inner channel of the valve body of the plug part can be discharged into the atmosphere via the auxiliary valve, which is arranged in the interior of the closing cone and has the spring-loaded valve piston arranged in the valve bore of the closing cone, in that the fluid present in the inner channel acts upon the valve piston when the pressure increases and displaces this valve piston into a leakage position, in which the fluid can flow past the valve piston and escape into the atmosphere. Due to these features, high pressure can no longer develop in the plug part; in fact, this pressure is automatically reduced, namely when the limiting pressure defined by the force of the spring used for prestressing the valve piston is respectively reached. This means that the valve body of the plug part is not subjected to any undesirable pressure effects whatsoever and that the inventive coupling can also be easily coupled. 
     According to an embodiment of the invention, it is proposed that the valve bore is provided with an incremental cross-sectional widening in order to realize an effective leakage path between the inner channel and the atmosphere in the leakage position of the valve piston. 
     According to an embodiment of the invention, it is proposed that the cross-sectional widening is spaced apart from the valve piston situated in its blocking position by a clearance that needs to be traveled by the valve piston when it is acted upon with an overpressure, wherein this provides the additional advantage that the fluid initially can expand into the aforementioned clearance as the pressure in the plug part begins to increase without immediately causing the intended leakage and discharge of fluid from the plug part by displacing the valve piston. 
     According to an embodiment of the invention, it is proposed to insert a check valve between the closing cone arranged in the inner channel of the valve body of the plug part and a continuing line attached to the plug part. This limits the volume enclosed in the plug part or in its valve body after the high-pressure coupling has been decoupled because the fluid volume still present in the hose or pipeline attached to the plug part or a corresponding connector is respectively isolated from the valve body or the connector of the plug part by the check valve such that only the residual fluid present in the valve body or the connector can cause a pressure increase due to external influences. 
     Since a pressure increase in the outer channel of the plug part also cannot be entirely precluded in the decoupled state of the high-pressure coupling, an embodiment of the invention proposes to provide a hollow space, which is connected to the outer channel or to the connecting bore assigned thereto, in the plug part in order to prevent a pressure increase in its outer channel in the valve body or in the receptacle part, wherein a piston is movably arranged in said hollow space and prestressed into a position, in which it blocks the hollow space, by means of a spring, and wherein said piston can be displaced into the hollow space into a position, in which it unblocks the hollow space so as to realize a pressure compensation, due to an increasing pressure in the outer channel or in the connecting bore. In case a pressure increase occurs in the outer channel of the plug part, the motion of the piston in the hollow space provides an additional volume in the form of the unblocked portion of the hollow space, into which the fluid volume present in the outer channel can expand, such that an increasing pressure can be accordingly reduced. 
     In a coupling of the initially cited type, it shall furthermore be ensured that all four pipelines or hoses attached to the coupling parts are not simultaneously connected to one another when the coupling is coupled. In a correspondingly designed high-pressure coupling known from EP 1 789 717 B1, it is proposed to incorporate a bypass valve at least into the valve body structure of the receptacle part for this purpose, wherein said bypass valve on the one hand produces a connection between the inner channel and the outer channel of the receptacle part in the decoupled state in order to realize a pressure compensation and on the other hand closes this connection in the coupled state. 
     According to a practical embodiment of the invention, it is therefore proposed that an inner pipe forming the inner channel of the receptacle part has two bores that are arranged at an axial clearance from one another, and that a sleeve-shaped closing body, which can be displaced on the inner pipe in the outer channel surrounding the inner pipe, on the one hand closes the front bore of the inner pipe that faces the plug part and opens the rear bore as a bypass between the inner channel and the outer channel of the receptacle part in a closing position, in which the sleeve-shaped closing body is situated in the decoupled state, and on the other hand closes the rear bore of the inner pipe and opens the front bore in a position, in which the sleeve-shaped closing body is displaced into the interior of the valve body of the receptacle part due to the contact between the end face of the inner pipe of the plug part facing the receptacle part and the end face of the closing body of the receptacle part during the coupling process, such that the inner channel of the receptacle part is connected to the inner channel of the plug part via the front bore in the coupled state. 
     Since the closing body in the receptacle part is displaced into an open position for the front bore of the inner pipe of the receptacle part by the inner pipe of the plug part, the end face of which presses against the end face of the closing body during the coupling process when the plug part is inserted into the receptacle part, a potential flow path is formed between the contacting end faces of the inner pipe of the plug part and the closing body of the receptacle part such that the fluid can overflow from the inner channel of the receptacle part into the outer channel of the plug part via this flow path when a corresponding pressure difference exists between the inner channel of the receptacle part and the outer channel of the plug part. Since the coupling process cannot take place against an overpressure in the inner channel of the plug part due to the inventive design of the plug part with its overpressure relief, such a bypass connection between the inner channel of the receptacle part and the outer channel of the plug part is not provided during the coupling process and the end faces of the closing body and the inner pipe are sealed relative to one another in accordance with an embodiment of the invention in order to continuously seal the inner channel of the receptacle part relative to the outer channel of the plug part. 
     In alternative embodiments of the invention, it is proposed that the end faces are either sealed relative to one another by arranging a groove with a seal inserted therein in one of the two end faces or that the end faces are sealed relative to one another by processing at least one of the end faces such that a metallic seal is realized when the end faces contact one another. 
     According to an embodiment of the invention, however, it is also not excluded that such a bypass between the inner channel of the receptacle part and the outer channel of the plug part becomes effective in a certain stage of the coupling process, wherein it would be conceivable that the contacting end faces of the closing body of the receptacle part and of the inner pipe of the plug part allow a fluid passage of the type generally known from EP 1 789 717 B1 and the inner channel of the receptacle part is briefly connected to the outer channel of the plug part in an intermediate stage during the coupling process. 
     In this context, it is specifically proposed that a sliding ring of a material with sound sliding properties, which is respectively positioned on the outer ends of the sleeve-shaped closing body, as well as a spacer ring lying in between, are arranged in the interior of the sleeve-shaped closing body that can be displaced on the inner pipe, wherein the spacer ring covers the front bore of the inner pipe in the closed position of the closing body in the decoupled state and the two sliding rings are sealed relative to the closing body by means of ring seals arranged on their circumference. 
     In order to actuate the high-pressure coupling during the coupling and decoupling processes, aforementioned publication WO 2008/130311 A proposes that a rotatable outer actuating sleeve and an inner locking sleeve, which cooperates with the outer actuating sleeve and has driving projections that engage into screw-shaped grooves of the plug part, are arranged on the receptacle part. When the plug part is at the beginning of the coupling process inserted into the receptacle part to such an extent that the driving projections on the inner side of the locking sleeve engage into the screw-shaped grooves of the plug part, the coupling process can be carried out by rotating the actuating sleeve, whereby the driving projections sliding in the screw-shaped grooves of the plug part force the plug part to carry out an axial motion into the receptacle part until the receptacle part and the plug part are completely coupled. 
     Since a thusly designed high-pressure coupling can also be inadvertently decoupled due to a backward rotation of the actuating sleeve, the invention proposes to additionally secure the high-pressure coupling against unintentional decoupling in that the outer actuating sleeve can be displaced relative to the locking sleeve between a decoupled idle position, in which it is freely rotatable relative to the locking sleeve, and an engaged position with the locking sleeve, wherein the actuating sleeve is interlocked with the locking sleeve with the aid of an interlock means in the engaged position such that the locking sleeve is only rotationally driven due to a rotation of the actuating sleeve in the engaged position. Consequently, the high-pressure coupling can only be coupled and decoupled if the outer actuating sleeve initially is axially displaced into the engaged position with the locking sleeve, in which a rotation of the actuating sleeve is converted into a rotation of the locking sleeve. After the actuating sleeve has been released, it returns into its idle position, in which a rotation of the locking sleeve and therefore the coupling motion are precluded, under the influence of a correspondingly arranged spring. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are illustrated in the drawings and described in greater detail below. In these drawings: 
         FIG. 1  shows an individual illustration of the plug part of a high-pressure coupling in the form of a sectioned side view, 
         FIG. 2  shows the auxiliary valve according to the detail “X” in  FIG. 1 , which is arranged in the closing cone of the plug part, in the form of an enlarged partial view, 
         FIG. 3  shows an individual illustration of the corresponding receptacle part of the high-pressure coupling in the form of a sectioned side view, 
         FIG. 4  shows the high-pressure coupling with the plug part ( FIG. 1 ) and the receptacle part ( FIG. 3 ) in the coupled state, namely in the form of an illustration according to  FIGS. 1 and 3 , 
         FIG. 5  shows the high-pressure coupling with the plug part and the receptacle part during the coupling process, in which the inner channel of the receptacle part is sealed relative to the outer channel of the plug part, namely in the form of an enlarged illustration of the connecting region between the inner channels of the receptacle part and the plug part, as well as the outer channels of the receptacle part and the plug part, and 
         FIG. 6  shows a modified embodiment of the plug part according to  FIG. 1  that is provided with an additional overpressure relief for the outer channel. 
     
    
    
     DETAILED DESCRIPTION 
     The plug part  10  of a high-pressure coupling illustrated in  FIG. 1  has a valve body  11  and a connector  12  connected thereto. An inner channel  13  formed by an inner pipe  14  of the valve body  10  is provided in the valve body  11  and can be connected to a not-shown hose or pipeline attached to the connector  12  via a connecting bore  15  in the connector  12 . An outer channel  16 , which concentrically surrounds the inner channel  13 , is furthermore provided in the valve body  11  and connected to a connecting bore  17  in the connector  12  such that it is also connected to the hose or pipeline attached to the connector  12  by means of said connecting bore. 
     In the closed position of the plug part  10  shown, a closing cone  18  arranged in the inner pipe  14  is pressed against a conical seat  19  by a spring  21  that is supported on a spring abutment  22 ; in this case, the closing cone  18  is sealed relative to the inner wall of the inner pipe  14  by means of a seal  20 . 
     In order to close the outer channel  16 , a closing sleeve  23  is displaceably guided on the inner pipe  14  and pressed against a sealing seat  24  realized on the front end of the plug part  10  by a spring  25  that forms part of the valve body  11  and is supported on a spring abutment  26 . 
     Consequently, the inner channel  13  is sealed relative to the outside by the closing cone  18  and the outer channel  16  is sealed relative to the outside by the closing sleeve  23 . 
     In the embodiment shown, a check valve  27  in the connector  12 , which is prestressed by means of a supporting spring  28 , protrudes into the connecting bore  15  such that the inner channel  13  of the valve body  11  is sealed relative to the fluid present in the connector  12 , as well as in the hose or pipeline attached thereto, in the closed position of the check valve  27  illustrated in  FIG. 1 . 
     With respect to the coupling of the plug part  10  to the receptacle part yet to be described, a helical groove  29 , the function and effect of which are described in greater detail below, is arranged on the outer circumference of the plug part  10 . 
     In case the fluid volume enclosed in the inner channel  13  of the plug part  10  between the front closing cone  18  and the rear check valve  27  heats up in the decoupled state according to  FIG. 1 , for example due to heat exposure, and a corresponding pressure increase occurs, an auxiliary valve  60  for relieving the pressure is arranged in the closing cone  18  as illustrated in greater detail in  FIG. 2 . This auxiliary valve  60  consists of a valve bore  61  that extends through the closing cone  18  and is connected to the inner channel  13  with a conical widening on one side and has an outlet into the atmosphere on the opposite side. A valve piston  62  is arranged in the valve bore  61  such that it can be displaced against the force of a spring  63  and carries a seal  66  on its outer circumference. In order to realize a leakage path, the valve bore  61  is provided with a cross-sectional widening  64  that is spaced apart from the connection of the valve bore  61  to the inner channel by a clearance  65  and designed in such a way that the valve piston  62  is no longer sealed relative to the wall of the valve bore  61  or its cross-sectional widening  64  when the seal  66  of the valve piston  62  enters the cross-sectional widening  64  and fluid can flow from the inner channel  13  through the valve bore  61  and past the outside of the valve piston  62  with its seal  66  in order to ultimately escape into the atmosphere. In this context,  FIG. 2  shows the leakage position of the valve piston  62  in the valve bore  61 . In the closed state of the auxiliary valve  60 , the spring  63  ensures that the valve piston  61  with its seal  66  is situated within the predefined clearance  65 , in which the seal  66  correspondingly seals the valve bore  61 . 
       FIG. 3  shows the corresponding receptacle part  30  for the plug part  10  of the inventive high-pressure coupling that was described above with reference to  FIGS. 1 and 2 . The receptacle part  30  once again consists of a valve body  31  and a connector  32  connected thereto. An inner channel  33  is formed in the receptacle part  30  by a correspondingly arranged inner pipe  34  and once again connected to a connecting bore  35  in the connector  32 . Analogous to the design of the plug part, an outer channel  36  that concentrically surrounds the inner pipe is also provided in the receptacle part  30  and connected to a connecting bore  37  in the connector  32 . 
     In order to realize a corresponding flow path, the inner pipe  34  is provided with two radially circumferential rows of bores that are spaced apart from one another by an axial clearance, namely with front bores  38  on its end that faces the open end of the receptacle part  30  and therefore the plug part  10  to be inserted into the receptacle part  30  and with rear bores  39  that are spaced apart from the front bores by the axial clearance. 
     In order to close the outer channel  36  of the receptacle part  30 , a sleeve-shaped closing body  40  is furthermore guided on the inner pipe  34  of the receptacle part and prestressed into a front closing position, in which the sleeve-shaped closing body  40  covers and therefore seals the front bores  38  of the inner pipe  34 , by a spring  41  that is supported on a spring abutment  42 . For this purpose, the sleeve-shaped closing body  40  features in its interior a holding part  43  for fixing two sliding rings  44  that are respectively arranged on the two ends of the closing body  40  and a spacer ring  45  lying in between. According to the closed position of the receptacle part  30  illustrated in  FIG. 3 , the front bores  38  of the inner pipe  34  are covered by the spacer ring  45  of the sleeve-shaped closing body  40 . The corresponding seal of the front bores  38  is realized by sealing the two outer sliding rings  44 , which enclose the spacer ring  45  between one another, relative to the holding part  43  that holds these sliding rings and forms part of the closing body  40  with the aid of corresponding soft seals such that no fluid can escape from the inner pipe  34  toward the front. The rear bores  39  of the inner pipe  34 , in contrast, are not covered by the sleeve-shaped closing body  40  such that a connection between the inner channel  33  and the outer channel  36  of the receptacle part  30  is produced via the rear bores  39  in order to realize a pressure compensation of the type also described in aforementioned publication EP 1 789 717 B1. 
     Furthermore, a forwardly protruding locking sleeve  46  designed for accommodating the plug part  30  is arranged on the valve body  31  of the receptacle part  30  and carries driving projections  47  on its inner side. These driving projections  47  are designed for engaging into the helical grooves  29  of the plug part  10  inserted into the receptacle part  30  or its locking sleeve  46 , respectively, such that a rotation of the locking sleeve  46  causes the driving projections  47  to slide in the helical grooves  29  of the plug part  10  and to thereby axially pull the plug part into the receptacle part  30 , as well as to fix the plug part  10  and the receptacle part  30  relative to one another in the coupled state. A design of this type is described in aforementioned publication WO 2008/130311 A1. 
     In order to increase the manipulation safety, an additional actuating sleeve  48  is displaceably arranged on the valve body  31  of the receptacle part  30  or on the locking sleeve  46  arranged thereon, respectively, and prestressed into its rear position by a correspondingly supported spring  49 . Furthermore, locking balls  50  are inserted into radial bores distributed over the circumference of the locking sleeve  46  such that they protrude over the circumference of the locking sleeve  46  with part of their cross section. In the rear idle position of the actuating sleeve  48  assumed due to the force of the spring  49 , correspondingly arranged recesses  52  in the actuating sleeve  48  are positioned above the locking balls  50  such that the actuating sleeve  48  is freely rotatable relative to the locking sleeve  46  in this idle position and the locking sleeve  46  is not set in rotation by rotating the actuating sleeve  48 . Ball receptacles  51  are furthermore provided on the inner side of the actuating sleeve  48  with an axial offset referred to the recesses  52 . When the actuating sleeve  48  is forwardly displaced away from the connector  32  against the force of the spring  49 , the ball receptacles  51  of the actuating sleeve  48  are moved above the locking balls  50  of the locking sleeve  46  such that an interlock means in the form of a positive fit between the actuating sleeve  48  and the locking sleeve  46  is realized in this forwardly displaced position of the actuating sleeve  48 . If the actuating sleeve  48  is rotated in this displaced position, the actuating sleeve  48  also drives the locking sleeve  46  during its rotation such that the coupling process or also a decoupling process is effectively initiated due to the engagement of the driving projections  47  into the helical grooves  49 . Once the coupling or decoupling process has been completed and the actuating sleeve  48  has been released, the spring  49  pushes the actuating sleeve back into its rear position facing the connector  32 , in which the actuating sleeve  48  is once again freely rotatable relative to the locking sleeve  46  and the high-pressure coupling cannot be inadvertently coupled or decoupled. 
     With respect to the preceding description of the plug part  10 , the receptacle part  30  and the auxiliary valve  60  with their corresponding individual components, it goes without saying that these individual components respectively need to be suitably sealed with the aid of separate seals, wherein the position of these seals is not discussed in greater detail if they are not directly related to the invention. 
     In the coupled state of the plug part  10  and the receptacle part  30  illustrated in  FIG. 4 , the valve body  11  of the plug part  10  is inserted into the receptacle part  30 , wherein the driving projections  47  of the locking sleeve  46  of the receptacle part  30  lie in the helical grooves  29  of the plug part  10  and therefore fix the plug part  10  relative to the receptacle part  30 . Due to the force of the spring  49 , the actuating sleeve  48  is in this case situated in its rear position, in which it is freely rotatable relative to the locking sleeve  46 , such that unintentional decoupling is precluded. In this case, the inner pipe  34  of the receptacle part  30  has displaced the closing cone  18  into the inner pipe  14  of the plug part  10  against the force of the spring  21  acting upon the closing cone such that the fluid arriving through the inner pipe  34  of the receptacle part  30  can flow into the inner channel  13  of the plug part  10  through the front bores  38 . Once the corresponding pressure is reached, the check valve  27  in the connecting bore  15  of the connector  12  subsequently opens such that the fluid can flow onward into the hose or pipeline attached to the connector  12 . At the same time, the front end of the inner pipe  14  of the plug part  10  has displaced the sleeve-shaped closing body  40  on the inner pipe  34  of the receptacle part  30  rearward against the force of the spring  41  prestressing the sleeve-shaped closing body such that the holding part  43  and the sliding ring  44  of the sleeve-shaped closing body  40  have opened the front bores  38  of the inner pipe  40  of the receptacle part  30  in order to realize the above-described flow path, but the rear bores  39  of the inner pipe  34  of the receptacle part  30  are already closed, such that the bypass realized at this location in the decoupled state is now blocked. The outer channel  16  of the plug part  10  and the outer channel  36  of the receptacle part  30  are at the same time connected to one another via an outer flow channel  55 . 
       FIG. 5  shows an intermediate position of the receptacle part  30  and the plug part  10  during the coupling process, in which the inner channel  33  of the receptacle part  30  also remains sealed relative to the outer channel  16  of the plug part  10  during this coupling process. For this purpose, a groove  81  with a seal  82  inserted therein is respectively arranged in the end face  80  of the closing body  40  or the holding part  43  held therein such that the two end faces  80  and  83  are sealed relative to one another once the end face  83  of the inner pipe  14  of the plug part comes in contact with the end face  80  of the closing body  40  during the coupling process. Consequently, the fluid already discharged from the front bores  38  of the inner pipe  34  of the receptacle part  30  during the coupling process cannot be admitted into the outer channel  16  of the plug part  10 . 
     Although not illustrated in detail, corresponding processing of either the end face  80  of the closing body  40  or the end face  83  of the inner pipe  14  may in an alternative embodiment of the invention ensure that a metallic seal is produced between the end faces  80 ,  83  when they contact one another during the coupling process. 
     In an alternative embodiment of the invention, the proposed design illustrated in  FIGS. 1 and 3  may in accordance with EP 1 789 717 B1 be realized such that the inner channel  33  of the receptacle part  30  is for a brief moment connected to the outer channel  16  of the plug part  10  during the coupling process, namely while the inner pipe  34  of the valve body  31  of the receptacle part  30  is inserted into the valve body  11  of the plug part  10  on the one hand and while the sleeve-shaped closing body  40  is pushed back by the front end face  83  of the inner pipe  14  of the plug part  10  in order to open the front bores  38  of the inner pipe  34  on the other hand. In this intermediate position, the clearance between the front bores  38  and the rear bores ensures that the bypass connection between the inner channel  33  and the outer channel  36  of the receptacle part  30  realized by means of the rear bores  39  is interrupted due to the predefined position of the sleeve-shaped closing body  40  in the instant, in which the inner channel  33  of the receptacle part  30  is connected to the outer channel  16  of the plug part  10  due to the contacting end faces  80  of the closing body  40  and  83  of the inner pipe  14 . 
     In order to decouple the coupling position illustrated in  FIG. 4 , the actuating sleeve  48  is displaced into the front position, in which the ball receptacles  51  of the actuating sleeve  48  interlock with the locking balls  50  of the locking sleeve  46  in order to realize the interlock means, against the force of the spring  49  such that a backward rotation of the actuating sleeve  48  also leads to a corresponding rotation of the locking sleeve  46  and the release of the plug part  10  from the receptacle part  30 . 
     According to  FIG. 6 , the plug part  10  described in detail above with reference to  FIGS. 1 to 4  may also be provided with an additional overpressure relief for the fluid volume present in its outer channel  16  and the connecting bore  17  connected thereto in the decoupled state of the high-pressure coupling. For this purpose, a hollow space  70 , which is connected to the connecting bore  17  by means of a connecting bore  71 , is provided in the receptacle part  12  and sealed in a fluid-tight fashion on its outer side by means of a drain plug  74 . A piston  72  provided with a circumferential outer seal is displaceably arranged in the hollow space  70  and prestressed into a position, in which it closes the connecting bore  71  leading to the connecting bore  17 , by means of a spring  73  that is supported on the drain plug  74 . If a pressure increase occurs in the outer channel  16  or in the connecting bore  17  when the high-pressure coupling is decoupled, the fluid volume present presses the piston  72  into the hollow space  70  against the force of the spring  73 , namely into a position, in which the hollow space  70  is accordingly unblocked and in which the unblocked hollow space  80  provides an additional volume, by means of which a corresponding pressure increase is prevented. 
     The characteristics of the object of this document disclosed in the preceding description, the claims, the abstract and the drawings may be essential to realizing the different embodiments of the invention individually, as well as in arbitrary combinations.