Patent Abstract:
A device for producing a pressure-tight pipe coupling with at least one pipe and comprises a bushing-type, rotationally symmetric base body. The base body is provided with at least one essentially cylindrical inner chamber, having toothed elements in order to receive the pipe end. The toothed elements are displaced radially into the pipe end arranged in the inner chamber by means of a pressing device which impinges upon the outer surface of the base body. A pressing device consisting of a shaping ring and a corresponding pair of shaping rings guarantee that the radial displacement potential is realized in the form of a radial displacement, resulting in significantly lower pressing power.

Full Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device for manufacturing a tube coupling of two tube ends, and in particular a tube coupling which at least comprises a basic body enclosing the tube end, and a press means enclosing the basic body wherein the basic body is radially urged into the surface of the tube by axially shifting the press means. 
     Pipe connections using this principle are known from the patent specifications U.S. Pat. Nos. 3,827,727, 3,893,720, 4,026,006, 4,061,367, 4,482,174 and 5,110,163. 
     The disadvantage of these pipe connections is in that they are functionally restricted in use regarding the size of the tube diameter, claims of quality on the tube to be connected, and the amount of pressure of the medium. Moreover, the constructional design of the displacing potentials formed in these tube couplings provides in addition to the intended radial crowding being absolutely necessary to obtain a pressure sealed connection, an axial crowding which does not contribute to the pressure sealed connection but influences the forces of pressure to be applied from the outside such that the forces of pressure exceed the dimension required for the radial crowding. Thus, from the start follows an oversizing of both the press tool and single elements of the tube coupling. 
     SUMMARY OF THE INVENTION 
     The invention is based upon the object to provide a pressure sealed pipe connection by axially pressing which ensures highest universality regarding the requirements of quality of the tubes to be connected. 
     Another object of the invention is in that to make a sealed connection in the high pressure range as well by the use of normal commercially available tubes, e.g. welded tubes made of most different materials, and the thus permissible tolerances regarding the mechanical properties and length related dimensions. 
     Further, it is an object of the invention to minimize the forces required for axially pressing on the press elements, and thus the force to be applied for penetrating into the tube surface at maximum penetrating depth. 
     These objects will be solved by a device according to the features of the first claim. 
     The device for manufacturing a pressure sealed tube coupling having at least one tube end comprises a sleeve shaped, rotationally symmetrical basic body wherein the basic body at least includes one substantially cylindrical interior space provided with teeth means for receiving the tube end, and the teeth means are radially displaced into the surface of the tube end received by the interior space by means of press means acting upon the outer surface of the basic body. 
     The basic body comprises a hollow cylinder shaped coupling sleeve having a wall thickness substantially remaining the same wherein at least two radially surrounding indentations are located on the inside of the coupling sleeve which are spaced to one another and recessed in comparison with the inner diameter of the coupling sleeve. On the outside of the coupling sleeve are formed radially surrounding flat locating features opposite the respective indentation which have a width corresponding to the width of the indentation. For it, a pressure ring concentrically slidable over the coupling sleeve is provided to cover the coupling sleeve in almost its total length wherein the pressure ring has radially surrounding projecting parts corresponding to the locating features on its inside, and an increasing cone shaped enlargement directed from each end of the pressure ring towards its centre, on its outside. 
     A press ring concentrically enclosing the pressure ring is associated to the pressure ring on each side, wherein each press ring on its inside has a cone shaped enlargement corresponding to the cone shaped enlargement of the pressure ring such that a radial displacement of the indentations into the surface of the tube received by the coupling sleeve by means of the projecting parts and the locating features corresponding to the projecting parts occurs during the axial shift of the press rings against each other from a spaced initial position into an almost final position without any distance. 
     Further features of the invention are cited in the dependent claims. 
     The invention will be explained in more detail according to an embodiment shown the associated drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal section through a tube coupling according to the invention performed on both sides wherein on the left hand of the axis of symmetry A—A a pre-pressed half, and on the right hand of the axis of symmetry A—A a pressed half of the tube coupling are illustrated; 
     FIG. 2 is a longitudinal section through the tube coupling according to FIG. 1 having an inserted supporting sleeve; 
     FIG. 3 is a longitudinal section through the upper half of the tube coupling according to FIG. 1 wherein the opposite press rings are shifted against each other by screws; 
     FIG. 4 is a longitudinal section through the upper half of a pressure ring having a stepped cone shaped formation of the surface; 
     FIG. 5 are two views of a pressure ring segmented by slots; 
     FIG. 6 is a longitudinal section through the upper half of another embodiment of the tube connection; 
     FIG. 7 is a longitudinal section through a tube coupling according to the invention in another embodiment which is performed on both sides; 
     FIG. 8 is a longitudinal section through a tube coupling according to FIG. 7 in which the pressure ring is divided; 
     FIG. 9 is a longitudinal section through the tube coupling according to the invention in another embodiment. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a longitudinal section through a tube coupling  1  according to the invention performed on both sides wherein on the left hand of the axis of symmetry A—A a pre-pressed and on the right hand of the axis of symmetry A—A a pressed half of the tube coupling  1  are illustrated. 
     The tube coupling  1  comprises a hollow cylinder shaped coupling sleeve  2  having axially opposite entering ends  3  into which the ends of the tubes  4  to be connected are inserted. The tube coupling  1  is constructed symmetrically with respect to the axis A—A, that is the subsequently described coupling elements and acting relations always relate to one half of the coupling sleeve  2 . In the present embodiment in which two tubes  4  having the same diameter are to be connected in a pressure sealed manner the constructional formation of the coupling elements on the one half of the coupling sleeve  2  is in symmetry to the axis A—A with that of the other half of the sleeve. Therefore, in the present case the structure and action of the tube coupling  1  will be described for one side only. 
     The coupling sleeve  2  is generally fabricated from a material which is identical with the material of the tubes  4 . 
     The coupling sleeve  2  is a hollow cylinder the wall thickness of which substantially remains constant over the length of the coupling sleeve  2 , and which is in relation to the outer diameter of the tube  4  and the wall thickness thereof. 
     The inside of the coupling sleeve  2  comprises radially surrounding indentations wherein one indentation  6  is located spaced in the proximity of the entering end  3  of the coupling sleeve  2 , and the second indentation  7  is located spaced to the first indentation  6  towards the axis A—A. In the present embodiment, the indentation  6 ,  7  comprises three juxtaposed teeth which are recessed in comparison with the inner diameter of the coupling sleeve  2  in the way such that the diameter measured in the area of the tooth tips equals the inner diameter or is greater than the inner diameter of the coupling sleeve  2 . As a result, it is avoided that the tooth tips are damaged with inserting the tube  4  into the interior space of the coupling sleeve  2 . 
     The tooth tips of the indentations  6 ,  7  are allowed to be differently formed according to the case of application. Thus, it is conceivable to flatten or round the tooth tip in order to thus influence the penetrating behavior of the indentation  6 ,  7  into the surface of the tube  4 . On the outside of the coupling sleeve  2  there are located locating features which represent as radially surrounding, flat grooves  8 ,  9  opposite the respective indentations  6 ,  7 . The function of these grooves  8 ,  9  will be dealt with in a later connection. 
     In a particular case of application, in the area of the axis of symmetry A—A, thus in the area wherein in the coupling position the ends of the tubes  4  are oppositely located the coupling sleeve  2  can be realized with an inner stepped neck portion which causes limiting the inserting depth of the inserted tube  4 . When the coupling sleeve  2  is not necked inside as in the present embodiment, thus it can be used as a shifting sleeve. 
     On the coupling sleeve  2  is located a pressing set  10  coaxially located therewith which comprises a pressure ring  11 , two press rings  12 ,  13  and a covering sleeve  14  as the case may be. 
     The pressure ring  11  is a rotationally symmetrical hollow cylinder which on the inside comprises locating features for fixing on the coupling sleeve  2 . These locating features represent radially surrounding projecting parts  15 ,  16  which are realized such that they correspond to the grooves  8 ,  9  on the outside of the coupling sleeve  2 . The axial position of the pressure ring  11  on the coupling sleeve  2  will be defined by the respective combination of the groove  8 ,  9 /projecting part  15 ,  16 . The diameters of the groove basic, on the one hand, and of the projecting part, on the other hand, will be selected such that between the two structural members a pre-pressed condition realized by means of a clearance fit is obtained which facilitates an assembly of the tube coupling  1 . 
     On the top surface of the pressure ring  11  are located cone shaped enlargements  17 ,  18  originating from the ends of the pressure ring  11  which increase evenly and continuously up to the axis of symmetry B—B. 
     Each cone shaped enlargement  17 ,  18  of the pressure ring  11  is associated to a press ring  12 ,  13 . The press rings  12 ,  13  represent rotationally symmetrical hollow cylinders which on their inside comprise a cone shaped enlargement  19 ,  20  directed towards the axis of symmetry B—B. This cone shaped enlargement  19 ,  20  of the press ring  12 ,  13  corresponds to the associated cone shaped enlargement  17 ,  18  of the pressure ring  11  by contacting the two structural members on the cone shaped surfaces. 
     In the pre-pressed condition of the tube coupling  1  the press rings  12 ,  13  are pushed on the respective enlargement  17 ,  18  of the pressure ring  11  so far that there is a sufficient distance between the press rings  12 ,  13  opposing each other which is measured, such that during carrying out the pressing action an axial motion of the press rings  12 ,  13  will be permitted to each other. 
     The top surface of each press ring  12 ,  13  comprises a pair of radially surrounding spaced grooves  21 ,  22  which receive a covering sleeve  14  acting as retaining element. The covering sleeve  14  comprises on its borders inwardly facing edges  24 ,  25  which will be engaged with the circumferential grooves  21 ,  22 . On that occasion, in the pre-pressed condition of the tube coupling  1 , the edges  24 ,  25  are engaged with the groove  21  nearest the axis of symmetry B—B, respectively, wherein in the pressed condition of the tube coupling  1 , the engagement of the edges  24 ,  25  merges to the adjacent grooves  22 . To facilitate this transition during the axial motion of the press rings  12 ,  13  to each other both the edges  24 ,  25  and the grooves  21 ,  22  comprise run-out bevels. 
     The covering sleeve  14  with the pre-pressed tube coupling  1  accomplishes the function to keep the individual elements of the press set  10  together in a condition in which they are capable of being assembled. 
     With the pressed tube connection  1  the object of the covering sleeve  14  is in that to actively oppose an unintentionally loosening of both press rings  12 ,  13 , and moreover to avoid soiling of the space  26  located between the press rings  12 ,  13 . 
     In the following, the action of producing the pressure sealed tube coupling  1  will be described. A press set  10  including a pressure ring  11  a pair of press rings  12 ,  13  and the covering sleeve  14  is pushed on the coupling sleeve  2 . On that occasion, the inwardly facing projecting parts  15 ,  16  of the pressure ring  11  lock into the respective groove  21 ,  22  located on the outside of the coupling sleeve  2  thus defining the place of the pressing set  10  on the coupling sleeve  2 . This assembly is allowed to be prefabricated and delivered to the assembly yard depending on the nominal width of the tubes  4  to be connected. On the assembly yard, the ends of the tubes  4  to be connected are inserted with a predetermined length into the coupling sleeve  2 . By means of suitable tools which are known per se and thus are not described, the press rings  12 ,  13  associated to a pair are axially shifted against each other. Then, the press rings  12 ,  13  slide over the cone shaped surfaces between the press ring  12 ,  13  and the pressure ring  11  and displace the material of the pressure ring  11  in the radial direction. The displacement primarily occurs through the projecting parts  15 ,  16  of the pressure ring  11  and is transferred to the indentations  6 ,  7  opposite the grooves  8 ,  9 . The indentations  6 ,  7  are radially urged into the surface of the inserted tubes  4  and ensure in this way a pressure sealed connection between the coupling sleeve  2  and the tube  4 . 
     Both, the axial force to be applied and the penetrating depth and supporting force as well of the circumferential indentation  6 ,  7  of the coupling sleeve  2  in the tube  4  to be connected can be influenced through the angle of the cone shaped enlargements of the press rings  12 ,  13  and the pressure ring  11 , and the path as well travelled during axially pushing together. 
     In FIG. 2 is shown the same tube coupling  1  as described in FIG.  1 . The difference is in that a supporting sleeve  27  will be inserted into the tube  4 , which in the area of the displacement provides for the tube  4  a resistance supporting the penetration of indentation  6 ,  7  into the surface of the tube  4 . The supporting sleeve  27  comprises radially surrounding asperities on its outer surface which balance the tolerances of the tube  4  during inserting it into the supporting sleeve  27 . 
     In FIG. 3 applying the axial shifting force upon the press rings  12 ,  13  by means of screws is shown. The press rings  12 ,  13  comprise bores axially located on a graduated circle  32  wherein the bore located within the press ring  12  is formed as a through hole  28 , and the bore axially opposite inside the press ring  13  is formed as a threaded hole  29 . Due to uniformly pulling the screws  23  the press rings  12 ,  13  are displaced against each other on the cone shaped surfaces. 
     As shown in FIG. 4 the top surface of the pressure ring  11  can be realized in a stepped way up to the axis of symmetry B—B wherein a conically increasing, plane formed section  30  is followed by an undercut section  31  which is formed as a cone shaped neck. This sequence repeats preferably four times up to the axis of symmetry B—B. These undercut sections  31  prevent mutually sliding in the pre-pressed and finish-pressed condition, respectively, with a complementary formation of the inside of the press rings  12 ,  13 . 
     In FIG. 5 the pressure ring  11  is shown in a partly segmented formation. The body of the pressure ring  11  is slotted except from the radially surrounding projecting parts  15  and  16 . As a result, the required axial forces of pressure are minimized with steady properties of the pressing set  10  and the radial displacement. The number and the width of the slots  34  are in a direct combination with the radial shortening of the pressure ring  11 . 
     In a modified form the pressure ring  11  can also be composed of single arcuate segments. 
     The form of the fixing area between the pressure ring  11  and the coupling sleeve  2  shown in FIG. 6 is allowed to be further modified. Thus, for example it is possible for the fixing area on the coupling sleeve  2  to be carried out in circumferential way. The circumferential ring grooves  33  serve as a balancing area for stresses in the structural members of the coupling becoming too strong which occur with pressing the tubes having a great range of tolerance when the tolerance of the outer tube diameter is in the upper limit range. 
     The forms of the bottom side of the pressure ring  11  shown in the embodiments are allowed to be further modified without thus being departed from the scope of protection of the patent. 
     The tube coupling will be described in another embodiment. The tube coupling  101  according to FIG. 7 comprises a hollow cylinder shaped coupling sleeve  102  having axially opposite entering ends  103  into which the ends of the tubes  104  to be connected are pushed in up to the axis of symmetry C—C. 
     The inside of the coupling sleeve  102  comprises radially surrounding indentations wherein one indentation  106  is located spaced in the proximity of the entering end  103  of the coupling sleeve  102 , and the second indentation  107  is located spaced towards the first indentation  106  in the direction of the axis C—C in the proximity of the tube end pushed in. Therefore, the ends of the tubes  104  will be positioned in the coupling sleeve  102  such that each tube end is associated to both an indentation  106  and indentation  107 . 
     On the coupling sleeve  102  is located a press set  110  coaxially mounted thereto which comprises the pressure ring  111 , and two press rings  112 ,  113 . 
     The pressure ring  111  is a rotationally symmetrical, hollow cylinder being substantially of the same length with the coupling sleeve  102 . The pressure ring  111  and the coupling sleeve  102  comprise on their ends axially effecting locating features which represent on the coupling sleeve  102  as a flat circumferential swelling  121  and on the pressure ring  111  as a flat groove  122  corresponding to the swelling  121 . These locating features define the axial position of the pressure ring  111  on the coupling sleeve  102 , and ensure in the pre-pressed condition an interlocking connection between the coupling sleeve, on the one hand, and the pressure ring, on the other hand. A high degree of prefabrication of the tube coupling is obtained by means of this cohesion of the single elements of the assembly. 
     On the top surface of the pressure ring  111  are located cone shaped enlargements  117 ,  118  originating from the ends of the pressure ring  111  which increase continuously and evenly up to the axis of symmetry C—C. A press ring  112 ,  113  is associated to each cone shaped enlargement  117 ,  118  of the pressing ring  111 . The press rings  112 ,  113  represent as rotationally symmetrical hollow cylinders which comprise a cone shaped enlargement  119 ,  120  directed towards the axis of symmetry C—C on its inside. These cone shaped enlargements  119 ,  120  of the press rings  112 ,  113  correspond to the associated cone shaped enlargements  117 ,  118  of the press rings  111  by contacting the two structural members each other on the cone shaped surfaces. 
     In the pre-pressed condition of the tube coupling  101  the press rings  112 ,  113  are pushed on the respective enlargement  117 ,  118  of the pressure ring  111  so far that between the opposite press rings  112 ,  113  a sufficient distance exists which is dimensioned such that an axial motion of the press rings  112 ,  113  to each other will be permitted during carrying out the pressing action. 
     The process of fabrication of the pressure sealed tube coupling  101  will be described below. A press set comprising the pressure ring  111  and a pair of press rings  112 ,  113  is pushed on the coupling sleeve  102 . According to the nominal width of the tubes  104  to be connected this assembly can be prefabricated and delivered to the assembly yard. On the assembly yard the ends of the tubes  104  to be connected are inserted with a predetermined length into the coupling sleeve  102  up to the axis of symmetry C—C. By means of suitable tools which are known per se and thus are not described the press rings  112 ,  113  associated to one pair are axially displaced against each other. On that occasion, the press rings  112 ,  113  slide over the cone shaped surfaces between the press ring  112 ,  113  and the pressure ring  111 , and displace the material of the pressure ring  111  in the radial direction. The displacement primarily occurs through the projecting parts  115 ,  116  of the pressure ring  111 , and will be transferred to the indentations  106 ,  107  opposite the projecting parts  115 ,  116 . The indentations  106 ,  107  are radially urged into the surface of the inserted tubes  104 , and ensure this way a pressure sealed connection between the coupling sleeve  102  and tube  104 . In this particular embodiment as well the cone shaped enlargements  117 ,  118  of the pressure ring  111  are designed in a stepped way. This means, that originating from the end of the pressure ring  111  a greater area of the cone shaped enlargement is followed by a cone shaped neck of less extent. This stepped formation repeats up to the axis of symmetry over the total cone shaped enlargement  117 ,  118 . Accordingly, the cone shaped enlargements  119 ,  120  of the press rings  112 ,  113  are complimentarily formed. 
     The functional effects of this stepped formation of the opposite surfaces are of importance in two respects. In the pre-pressed condition, the interlocking engagement between the pressure ring  111 , on the one hand, and the press rings  112 ,  113 , on the other hand, ensure a cohesion of the individual elements of the assembly, and thus a high degree of pre-fabrication of the tube coupling. In the pressed condition, the same formation ensures to avoid the press rings from sliding back from the pressure ring. Thus, the safety of the tube connection will be increased with most different loads. 
     In an embodiment formed as shown in FIG. 8 the pressure ring  111  is divided in its radial axis of symmetry D—D into the pressure ring portions  111 ′ and  111 ″. Both pressure ring portions  111 ′ and  111 ″ are coupled with each other by an axial intermediate ring  140 . Then, the intermediate ring  140  has the same inner diameter as the pressure ring portions  111 ′ and  111 ″ in order to push the pressure ring assembly formed of the pressure ring portions  111 ′ and  111 ″ and the intermediate ring  140  over the coupling sleeve  102  having the same length. 
     The intermediate ring  140  comprises two spaced surrounding flanges  141 ′ and  141 ″ on its outside which serve as a stop for the face directed towards the axis of symmetry D—D of the respective pressure ring portion  111 ′,  111 ″. Moreover, the intermediate ring  140  comprises each an area from the outside directed from the flange  141 ′,  141 ″, respectively, which terminates in an from the outside facing edge  142 ′,  142 ″. The end of the pressure ring portion  111 ′,  111 ″ associated to the edge  142 ′,  142 ″ comprises an area with a diameter which is increased in comparison with the inner diameter, in which a groove  143 ′,  143 ″ is machined which will be engaged with the edge  142 ′,  142 ″. This engagement ensures a pre-mounting state of the two pressure ring portions  111 ′,  111 ″. 
     The space located between the flanges  141 ′,  141 ″ serves for receiving a pressing tool not shown wherein the pressing tool supports on the flange, on the one hand, and on the outwardly directed face of the associated press ring. The advantage of this modification is in the diminution of the pressing path, and thus of extensive minimization of the pressing tool. The invention will be described according to another embodiment. In this embodiment, the device serves for the pressure sealed connection of two opposite tube ends of the same nominal width in alignment. The tube coupling  201  performed as shown in FIG. 9 restricts to the one side of the device since it is provided symmetrically to the axis A—A. 
     The tube end  204  will be pushed in from one side into the hollow cylinder shaped coupling sleeve  202  approximately up to its centre. The inner area of the coupling sleeve  202  is provided in the section receiving the tube end  204  with a plurality of radially surrounding teeth  206  being spaced to one another and recessed in comparison with the inner diameter of the coupling sleeve  202  which are directed against the surface of the tube end  204 . 
     Over this section of the coupling sleeve  202  is pushed a pressure ring  211  the inner diameter of which is slightly greater than the outer diameter of the coupling sleeve  202 . On its outside the pressure ring  211  comprises a cone shaped enlargement  217 ,  218  originating from each end and increasing to the centre of the pressure ring  211 . 
     The pressure ring  211  is associated on each side with a press ring  212 ,  213 . Each press ring  212 ,  213  is realized on its inside with a cone shaped enlargement  219 ,  220  which correspond to the cone shaped enlargements  217 ,  218 . In the not pressed position of the device which is characterized with the reference numeral  245  the press rings  212 ,  213  are pushed over the respective end area of the pressure ring  211  wherein the cone shaped enlargements ( 217 / 219 ,  218 / 220 ) are adjacent in these areas. 
     From the position  245  the press rings  212 ,  213  are shifted against each other over the cone shaped enlargements into the pressed position of the device as illustrated at  246  by means of a tool being not shown. On that occasion, the pressure ring  211  is radially urged into the coupling sleeve  202  which in turn results in a radial displacement of the teeth  206  into the surface of the tube end  204 . In this way, a pressure sealed, non-detachable tube coupling is formed. 
     A considerable feature of the invention is in that to pre-assemble the single elements of the tube coupling such as the coupling sleeve  202 , pressure ring  211  and press rings  212 ,  213  in order to provide them as a compact assembly on the assembly yard. With this, it is necessary for the single elements to be equipped with means which enables a defined positioning of the single elements to one another. 
     For this reason, the coupling sleeve  202  is formed with radially surrounding grooves  235  on the outside of the section which receives the tube end  204 . The pressure ring  211  on its inside comprises radially surrounding locating features formed as swellings and corresponding to the grooves  235 . The tolerance between the two elements is formed such that with pushing on the pressure ring  212  on the coupling sleeve  202  by means of manual force, the swellings  236  lock into the grooves  235 , and fix the position of the two elements to one another in the pre-pressed condition. 
     In a similar way, the pressure ring  211  on its outside and the press rings  212 ,  213  on its inside are equipped with respective means for positioning to one another. 
     The pressure ring  211  is equipped with a locating feature  237 ,  238  on its cone shaped enlargement  217 ,  218  in the proximity of its end, respectively, and with another locating feature  239 ,  240  in the proximity of its centre, and the respective press ring  212 ,  213  is provided with a locating feature  241 ,  242  on its end facing towards the pressure ring  211  on its cone shaped enlargement  219 ,  220  formed on the inside, and with another locating feature  243 ,  244  on the end facing off the pressure ring  211  . 
     The locating features correspond to each other in a different way according to the condition of the tube coupling  201 . In the not pressed condition of the tube coupling  201  the locating features  237 ,  238  formed on the pressure ring  211  correspond to the locating features  241 ,  242  of the press rings  212 ,  213 . As a result, all elements of the tube coupling  201  are assembled to a structural unit factory sided which in this compactness can be provided on the assembly yard. 
     With pressing the tube coupling  201  the engagement of the locating features acting between the pressure ring  211  and the press rings  212 ,  213  will be changed such that, on the one hand, the locating features  239  and  240  of the pressure ring  211  come into active relation with the locating features  241 ,  242  of the press ring  212 ,  213 , and on the other hand, the locating features  237  and  238  of the pressure ring  211  come into active relation with the locating features  243 ,  244  of the press ring  212 ,  213 . In this way, the press rings  212 ,  213  will be prevented from sliding back over the cone shaped formations after pressing and thus endangering the stability under load of the tube coupling  201 . 
     Another feature of the invention is the construction of the pressure ring  211 . The pressure ring  211  in its cross-section consists of single segments spaced to one another which uniformly enclose the coupling sleeve  202 . For it, the pressure ring  211  will be circumferentially slotted over its total wall thickness in the axial direction wherein preferably between the adjacent segments ridges are left which obtain the shape of the pressure ring  211 . The advantage of this construction is in that with pressing the tube coupling  201 , the work of deformation between the pressure ring  211  and the press rings  212 ,  213  will be minimized since the intended and required diminution of the diameter of the pressure ring  211  is firstly realized through closing the slots between adjacent segments, and not through a deformation of the pressure ring  211 . The diameter reduction of the pressure ring  211  by shifting the press rings  212 ,  213  against each other transfers to the section of the coupling sleeve  202  which has received the tube end  204  wherein the teeth  206  are urged into the surface of the tube end  204 , and thus ensuring a pressure sealed tube coupling  201 . 
     Another possibility of spacing the individual segments of the pressure ring  211  to one another in a defined way is in depositing a flexible distance mass between the segments which maintains a uniform distribution of the segments on the circumference of the pressure ring  211 . During pressing the tube coupling the distance mass between the adjacent segments will be pressed out. 
     The invention provides a tube coupling which ensures highest universality regarding the requirements to the quality of the tubes to be connected. It comprises a calculable behavior and is capable to ensure high pressure sealed tube couplings planewith great tolerances of outer tube diameters. 
     The solution according to the invention minimizes the forces required for axially pressing the press rings on the pressure ring and thus on the coupling sleeve. It is distinguished by a high stability in comparison with vibrations, axial tensile forces on the tube and extreme fluctuations of temperature. 
     The tube coupling comprises rotationally symmetrical components to be simply manufactured which enable optimum combinations with regard to the aspired properties of the tube coupling with regard to the functional selection of the employed materials having their specific properties. 
     The solution according to the invention enables the standardization of the design of the press set. 
     In connection with different coupling sleeves and embodiments, respectively, one and the same design of press set can be used. Thus, it is also possible to press different outer tube diameters only by constructive adaptation of the coupling sleeve in particular limits. 
     Although the present invention has been described according to some preferred embodiments which show the connection of two tube ends it will be readily appreciated for one skilled in the art that various modifications and changes can be made without departing from the scope of protection of the following claims. Thus, it can be seen that it is fallen back on the pressing connection carried out according to the invention on one side only, however, the other side is equipped with conventional connecting elements such as, e.g. threaded joints or flanges which merely represents a special embodiment of the invention.

Technology Classification (CPC): 5