Abstract:
In a connecting device for connecting a first extruded hollow profile ( 10 ), having a profile channel and at least one undercut groove space on a longitudinal groove ( 20 ), to another such workpiece by a screw element or other member which passes through an opening ( 20 ) in the workpiece and can be inserted into the interior ( 22 ) of the other workpiece, there is fixed to the end face ( 14 ) of the hollow profile ( 10 ) a strip-like socket profile ( 34 ) which runs radially with respect to the profile channel ( 12 ) and has at least at one end a stepped face ( 35 ) for receiving the screw element, which screw element in the rest position lies inside the side contours of the socket profile ( 34 ) and in the connecting position projects beyond the socket profile at least on one side and engages in a retaining manner in the undercut space of the other hollow profile ( 10 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. divisional application of U.S. application Ser. No. 10/549,789 filed Jun. 19, 2005. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a connecting device for connecting a first extruded hollow profile—having a profile channel and at least one undercut groove space on a longitudinal groove—to another workpiece by means of a screw element or other connecting member. The invention also relates to a method for producing the device. 
         [0003]    DE 92 15 843 by the Applicant describes a connecting device for fixing in an undercut interior of a longitudinal groove of a hollow profile or other workpiece, with at least one dimension which exceeds the width of the narrow groove cross section for connecting a first workpiece, having the longitudinal grooves, to another workpiece, which is in turn provided with longitudinal grooves, the cross section of which opens towards the profile end face. This element is used in particular in the case of metallic hollow profiles, the interior of which is not accessible from outside; it is approximately square-shaped and has at least two opposite side walls which are inclined at an angle and also a spring member which at one end is fixed to one of the inclined side walls and at the other end engages with its free end over the narrower surface of the element. The latter is arranged at a distance from the element in the non-tensioned state of the spring. When the spring member is pressed against the nut element, the latter can readily be pushed—with its narrow side first—into the undercut groove. 
         [0004]    In another connecting member for fixing in an undercut groove space of a longitudinal groove of a hollow profile according to DE 198 40 057 A1 by the Applicant and for connecting the hollow profile to another workpiece which is in turn provided with corresponding longitudinal grooves, in each case at least one shaped portion which corresponds approximately to the width of a longitudinal groove forming the narrow groove cross section is provided on the surface of angled arms of an angled shaped piece as a fixing or connecting device, and there is fixed in the angled arm at least one screw which passes through said angled arm; the width of the angled arm exceeds the width of the longitudinal groove. Moreover, the cross section of the shaped portion tapers away from the surface of the angled arm. 
         [0005]    Knowing these conditions, the inventor set himself the aim of providing an operationally reliable possibility for fixing in particular extruded hollow profiles of polygonal—preferably rectangular—cross section which are to be connected to one another, especially at approximately right angles. In particular, a system is to be improved in which the profile end face of one workpiece bears against a longitudinal side of the other workpiece and is held thereon—as far as possible in a manner secured against twisting. Another aim of the inventor is to considerably simplify the connection procedure per se and above all to improve the handling of the connecting member by configuring the latter as one unit. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the invention, there is fixed to a hollow profile a strip-like socket profile which runs radially with respect to the longitudinal axis of the profile channel and has at least at one end a stepped face for receiving the screw element, which screw element in the rest position lies inside the side contours of the socket profile and in the connecting position projects beyond said socket profile at least on one side and engages in a retaining manner in the undercut space of the groove space of the other hollow profile. The socket profile is preferably fixed to the end face of the hollow profile. 
         [0007]    It has proven advantageous to provide the socket profile with a baseplate on a head strip which is of shorter length in longitudinal section than the length of the baseplate, so that part of the latter projects beyond the end side(s) of the head strip to form its surface as a stepped face. 
         [0008]    According to another feature of the invention, the screw element has a socket strip which is essentially rectangular in plan view, from the surface of which socket strip there projects a screw sleeve or socket sleeve for a screw passing axially through it, in particular for an Allen screw. The outer contour of this screw sleeve or socket sleeve is intended to have two corner edges which are arranged diagonally with respect to its interior and preferably issue from a longitudinal edge of the socket strip, from which corner edges a flat wall surface projects on either side as part of the sleeve wall; the latter merges into an arced area of the sleeve wall which is curved in cross section. This shaping improves the rotatability of the screw element when the latter is inserted in a longitudinal groove of a hollow profile. 
         [0009]    Advantageously, the socket strip projects beyond the sleeve wall in its longitudinal axis. The corner regions of this socket strip may be shaped as a segment of a circle in plan view, and a rounded corner region of the socket strip may be assigned to the corner edge of the sleeve wall. The socket profile is moreover intended to be passed through by an opening for a screw member, said opening being arranged approximately in the centre of its head strip, which screw member can be fixed in the profile channel of the hollow profile, the end face of which is intended to bear against the front face of the socket profile. 
         [0010]    It is within the scope of the invention that an upper or stepped face of the socket profile—or the two such faces thereof—run(s) at a distance from the end face of the hollow profile, which distance corresponds to the height of the end side of the head strip and/or to the sum of the thickness of shaped ribs—which cover the undercut space and delimit the longitudinal groove—and the thickness of the socket strip. 
         [0011]    It is moreover important according to the invention that the longitudinal axis of the socket strip of the screw member runs parallel to the longitudinal axis of the hollow profile in the inserted position and the socket strip is arranged such that it can be displaced in the longitudinal groove. According to the invention, in order to connect the two hollow profiles, the screw members of shaped ribs which in the connecting position cover the undercut space of one hollow profile are gripped from below in each case by the socket strips of said screw members, as a result of which the shaped ribs of one hollow profile are held firmly against the end face of the other hollow profile. In the connecting position the longitudinal axis of the socket strip is then transverse to the longitudinal axis of the associated hollow profile. 
         [0012]    In the context of the invention, there is to be used as the connecting element a sleeve which is inserted in the longitudinal groove, said sleeve having lateral outer ribs which can be inserted in radial grooves of the hollow profile. The sleeve is assigned a clamping screw which can be inserted coaxially into the sleeve interior, said sleeve interior optionally partially being provided with a polygonal cross section; the clamping screw is held by its sleeve on the hollow profile. 
         [0013]    The outer rib, which is approximately triangular in cross section at least in its free end region, merges with its rib faces into shaped channels of the sleeve peripheral surface, and the two rib faces preferably merge into a rib crest which may be designed as a sharp edge. 
         [0014]    Preferably, the outer rib has at one end a side edge which forms an angle of approximately 45° with a radial line placed approximately through the centre of the outer rib; the outer rib is upset at its inclined side edge. 
         [0015]    This sleeve has at least three groups of outer ribs which are parallel to its centre axis and are assigned to radial grooves in the fixing position; said radial grooves are formed in the groove bottom of the longitudinal groove of the hollow profile and also in facing surfaces of shaped ribs which delimit the longitudinal groove on the profile side face. It has proven advantageous if the side edges of a group of outer ribs are aligned with one another parallel to the centre axis. The inclined side edge of the outer rib advantageously forms a contact resistance between the sleeve and the associated radial grooves, which allows insertion of the outer ribs. 
         [0016]    The design of the abovementioned sleeve and its cooperation with the clamping screw assigned to it is of critical importance to the invention; the sleeve which is inserted in the longitudinal groove is—as has already been mentioned—provided with lateral outer ribs which project from its peripheral surface, said ribs being designed such that they can be inserted in radial grooves of the hollow profile. Moreover, the sleeve is assigned a clamping screw which can be inserted into its interior, with a round shaft being integrally formed on the screw head of said clamping screw. The round shaft merges into a coaxial screw shaft at a distance from the screw head. 
         [0017]    A shaft which is integrally formed on a screw head of the clamping screw and which is provided with the thread at a distance from the screw head has proven advantageous. A round portion of the shaft extends between the screw head and the thread, the length of which round portion corresponds approximately to two-thirds of the shaft length. 
         [0018]    Moreover, for the sake of better fixing, the external diameter of the thread or of the screw shaft should be greater than the diameter of the sleeve interior or of an opening in a rear wall of the sleeve which delimits the sleeve interior and is passed through by the shaft. Since, according to the invention, the thread on the shaft forms an annular edge which faces towards the screw head, the latter serves as a stop member, the partner of which is the annular rear wall of the sleeve. According to a further feature of the invention, the clamping screw is arranged such that it can be displaced axially in the sleeve between its screw head and the annular edge; when the screw head of the clamping screw bears against the associated outer sleeve edge of the sleeve, the thread projects from the sleeve at the other end. 
         [0019]    Advantageously, a longitudinal portion of the interior of the sleeve should be designed as a polygonal cross section—in particular as a hexagonal cross section—and should bear against a cylindrical portion of the sleeve interior, the axis-parallel edges of said polygonal cross section being designed as notched channels. 
         [0020]    Advantageously, the axial length of the cylindrical portion of the sleeve interior corresponds approximately to the length of the thread of the clamping screw. 
         [0021]    It is also within the scope of the invention that an axial collar is integrally formed on the sleeve at its end remote from the rear wall, and the shaft can be displaced within said collar. This collar together with the peripheral surface of the sleeve delimits an annular zone of this sleeve, and moreover the height of the collar extends the contact length between sleeve and clamping screw. The preferred contact length is approximately 20.5 mm. 
         [0022]    According to the invention, the outer rib, which is approximately triangular in cross section at least in its free end region, merges with its lateral rib faces into shaped channels of the sleeve peripheral surface. The two rib faces merge into a rib crest which is preferably designed as a sharp edge. 
         [0023]    Preferably, the outer rib has at one end a side edge which forms an angle of approximately 45° with a radial line placed approximately through the centre of the outer rib; the outer rib is upset at its inclined side edge. 
         [0024]    Furthermore, a plate-like, flat, square body may be provided on a side edge of the outer rib in order to improve the seating position of the sleeve. This plate-like body engages axially over the outer ribs on their rib face remote from the collar. The inclined side edge of the outer rib forms a contact resistance between the sleeve and the associated radial grooves. The latter are formed in the groove bottom of the longitudinal groove of the hollow profile and also in facing surfaces of shaped ribs which delimit the longitudinal groove on the profile side face. 
         [0025]    Also within the scope of the invention is a method for producing the described device, in which the sleeve is pushed onto the round shaft of the clamping screw and the free end of the round shaft which projects coaxially from the sleeve interior is shaped to form a thread. This takes place in particular by means of rolling-shaping. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Further advantages, features and details of the invention emerge from the following description of preferred examples of embodiments and with reference to the drawing, in which: 
           [0027]      FIG. 1  shows the front view of an extruded hollow profile having longitudinal grooves, with connecting members for a second hollow profile of identical shape which is placed on the first hollow profile at right angles, said connecting members being pushed into two of the longitudinal grooves; 
           [0028]      FIG. 2  shows an exploded side view of a portion of the hollow profile in combination with an associated socket profile as part of a connecting member, said socket profile being shown in section; 
           [0029]      FIG. 3  shows the socket profile of  FIG. 2  on a smaller scale; 
           [0030]      FIG. 4  shows an enlarged detail from  FIGS. 3 and 14 , at the arrow IV therein; 
           [0031]      FIG. 5  shows the plan view of the socket profile; 
           [0032]      FIG. 6  shows an oblique view of the socket profile; 
           [0033]      FIGS. 7 ,  8  show a plan view and a side view of a screw element for the socket profile; 
           [0034]      FIG. 9  shows the plan view of a different embodiment of the screw element; 
           [0035]      FIG. 10  shows the front view of part of a hollow profile with the side view of an associated other hollow profile during the introduction of a screw element; 
           [0036]      FIG. 11  shows the hollow profiles of  FIG. 10  in the position where they are fixed to one another; 
           [0037]      FIG. 12  shows an oblique view of a different embodiment of the socket profile; 
           [0038]      FIG. 13  shows the plan view of the socket profile of  FIG. 12 ; 
           [0039]      FIG. 14  shows the longitudinal section through  FIG. 13  along the line XIV-XIV therein; 
           [0040]      FIG. 15  shows the front view of another hollow profile with an integrated connecting element; 
           [0041]      FIG. 16  shows a side view of the partially cut-away hollow profile of  FIG. 15 ; 
           [0042]      FIG. 17  shows an enlarged plan view of the connecting element of  FIG. 15 ; 
           [0043]      FIG. 18  shows part of the connecting element in an enlarged and partially cut-away side view; 
           [0044]      FIG. 19  shows an enlarged detail from  FIG. 18 ; 
           [0045]      FIG. 20  shows a side view of a sleeve with a clamping screw associated axially therewith; 
           [0046]      FIG. 21  shows the partially cut-away pairing of  FIG. 20  in a different operating position; 
           [0047]      FIG. 22  shows an oblique view of the sleeve of  FIGS. 20 ,  21 ; 
           [0048]      FIG. 23  shows a front view of  FIG. 22 ; 
           [0049]      FIG. 24  shows an enlarged detail of  FIGS. 20 ,  29  at the part XXIV therein; 
           [0050]      FIGS. 25 ,  27  each show a diagram of a differently configured sleeve, corresponding more or less to the diagram in  FIG. 22 ; 
           [0051]      FIG. 26  shows a longitudinal section through the sleeve of  FIG. 25  with an associated clamping screw; 
           [0052]      FIG. 28  shows a front view of  FIG. 27 ; 
           [0053]      FIG. 29  shows a diagram of the sleeve of  FIG. 27  with a clamping screw associated axially therewith, said diagram corresponding to that of  FIG. 20 ; 
           [0054]      FIGS. 30 ,  31  each show the partially cut-away pairing of  FIG. 29  in a different operating position; 
           [0055]      FIG. 32  shows a cut-away region of  FIG. 22  in a different embodiment; 
           [0056]      FIG. 33  shows an enlarged oblique view of a detail of the sleeve of  FIG. 32 . 
       
    
    
     DETAILED DESCRIPTION 
       [0057]    A hollow profile  10  of square cross section having an outer side length a of in this case 45 mm with cross-sectional axes B, B 1  as axes of symmetry, said cross-sectional axes being placed through the centre Z of its end face  14  (the centre Z being defined by a profile channel  12  running in the profile longitudinal axis A), has a central column  11  of square cross section which contains the profile channel  12  and also, in each case in the centre of its profile side faces  16 , a longitudinal groove  20  of width b of for example 12 mm, said longitudinal groove being delimited on either side by shaped ribs  18  of thickness c of in this case 6 mm and merging towards the profile longitudinal axis A into a groove space  22  which is undercut in cross section. The shaped ribs  18  are provided with corner cut-outs  17  on the profile side face  16 . 
         [0058]    The undercut space or groove space  22  is delimited towards the centre Z of the end face by a bottom or groove bottom  24  and is shaped as a channel-like recess which is covered by said shaped ribs  18 , the channel-like recess having a height e of approximately 8 mm and a maximum width f of approximately 20 mm. The free end of each of the channel-like recesses forms a hexagonal end opening  25  in the end face  14  of the hollow profile  10 , and the longitudinal groove  20  forms an elongate opening in the profile side faces  16 . 
         [0059]    Assigned to the four outer faces of said central column  11  which form the groove bottoms  24 , respectively on either side of their cross section, is an arm-like rib  26  which runs in a manner inclined at an angle of 45° with respect to the cross-sectional axes B, B 1 , that is to say diagonally in the end face  14 . Each of these ribs  26  formed on the central column  11  merges into one of the corner regions  28  of the hollow profile  10 ; in each of these corner regions  28  there is—parallel to the profile longitudinal axis A—a corner channel  30  of almost square cross section, from which there issue narrow blind slots  32  of the shaped ribs  18 , which run in the latter in an axis-parallel manner. 
         [0060]    The upper hollow profile  10  in  FIG. 1  is gripped from below at one of its end faces  14  by a second hollow profile  10  of identical cross section which is associated therewith at right angles, and is connected by connecting members. The two hollow profiles  10  are preferably extruded from an aluminium alloy. 
         [0061]    In  FIG. 2 , one end of the upper hollow profile  10  in  FIG. 1  is shown with a socket profile  34  for connecting members shown at  50  in  FIG. 1 , which socket profile is to be fixed to the end face  14  of the hollow profile. This socket profile  34 , the longitudinal axis of which is shown at E, has a baseplate  36  having for example a length g of 44 mm, a width b 1  of 10 mm and a height h of 5 mm, on which there is integrally formed a central head strip  38  having the same width b 1 , a shorter length g 1  of approximately 24 mm and a height h 1  of approximately 9 mm. The baseplate  36  respectively forms, on either side of the head strip  38  made in one piece therewith, a stepped face  35  which is parallel to its top face  40  and which adjoins the end side  39  of the head strip  38 . As shown in  FIG. 4 , bottom strips  41  having a height h 2  of 0.3 mm which are triangular in cross section may be integrally formed on the end sides  37  of the baseplate  36 . 
         [0062]    This socket profile  34  is fixed in the profile channel  12  by means of a screw, shown at  44  in  FIG. 2 , which passes through a central opening  42  having a diameter d of 8 mm, in such a way that the top face  40  of the head strip  38  of the socket profile  34  bears against the end face  14  of the hollow profile  10 . A depression having a diameter d 1  of 5 mm is shown at  46  on either side of the head strip  38  in the stepped or upper face  35  of the baseplate  36 ; screw holes  48  may also be provided instead of said depressions, as shown in  FIG. 12 . 
         [0063]    When the socket profile  34  is fixed on the end face  14  of the hollow profile  10 , the upper faces  35  offered by the two ends of the baseplate  36  run at a distance h 1  from the end face  14  and in each case serve to support a screw element  50 , by means of which the two hollow profiles  10  lying at right angles to one another are connected. 
         [0064]    This screw element  50 , which is made of a hard metal, comprises a rectangular socket strip  52 —having a length a 1  of approximately 16 mm, a thickness c 1  of approximately 3 mm and a width f 1  of approximately 9 mm—and a screw sleeve  54  which is integrally formed thereon. Said width f 1  of the socket strip  52  is also the width f 1  of the socket sleeve  54 , the length a 2  of which is approximately 9 mm, that is to say corresponds to the width f 1 . Between two corner edges  57  of the socket sleeve  54  which are diagonal to one another and are in each case formed by two wall surfaces  55  at the longitudinal edges  56  of the socket strip  52  which abut against one another at right angles in plan view, or between said wall surfaces  55 , the outer contour of the socket sleeve  54  is shaped like a segment of a circle in a 90° arc region  58  in plan view. An Allen screw  62  is seated in the cylindrical interior  60  of the socket sleeve  52 . 
         [0065]    In the embodiment of the screw element  50   a  which is shown in  FIG. 9 , two corner regions  53  of the socket strip  52   a  are rounded and lie opposite the corner edges  57  of the screw sleeve or socket sleeve  54 . 
         [0066]    When two hollow profiles  10  are joined together, as shown in  FIGS. 10 ,  11 , the socket strip  52  of the screw element  50  or  50   a —which is screwed onto a stepped face  35  of the baseplate  36  of the socket profile  34  fixed on the upper hollow profile  10  in the described manner—is placed on the baseplate  36  in such a way that it does not protrude laterally, wherein the longitudinal axis of the socket strip runs parallel to the longitudinal axis A of the hollow profile  10 . The screw element  50  can then be inserted into the longitudinal groove  20  of the hollow profile  10 . Once the end face  14  of the other hollow profile  10  is seated on the profile side face  16  of the first hollow profile, the screw element  50  or  50   a  is turned through 90° using an Allen key on the Allen screw  62 , so that the projecting regions of the socket strip  52  or  52   a  engage below the adjacent shaped ribs  18 . By virtue of a further screwing operation, the upper faces  51  of the socket strip  52  or  52   a  are drawn towards the lower faces  19  of the shaped ribs  18  and hold the hollow profiles  10  against one another in a clamped manner. 
         [0067]    The socket profile  34   a  of  FIGS. 12 to 14  has a protruding region of the baseplate  36   a  only at one end side of the head strip  38 , and thus only one stepped face  35 . The latter is provided with a screw hole  48  for receiving the Allen screw  62  of the screw element  50 ,  50   a  which is to be placed thereon. The connection operation takes place in the manner described above by turning the stepped face  35  below the lower face  19  of a shaped rib  18  and then pressing the two faces  19 ,  35  against one another. 
         [0068]    The hollow profile  10 , of  FIGS. 15 ,  16  has, on either side of the longitudinal grooves  20 , shaped ribs  18   a  which are hook-shaped in cross section. The hook ends  21  of the shaped ribs  18   a  are oriented towards the groove bottom  24  of the undercut groove space  22 . The corner channels  30  are in this case of almost square cross section. 
         [0069]    In the undercut space  22  located at the bottom in  FIG. 15 , there can be seen a sleeve  70  with a cylindrical interior  72 , from the peripheral surface  74  of which there project radial outer ribs  76  having a front width i of 5 mm; these form—in each case at a peripheral distance q from one another—three parallel rows of protrusions  80  which run parallel to the central axis M of the sleeve  70 , each of said rows containing in this case four outer ribs  76 . Said interior of the sleeve  70 —having a length y of 25 mm and an external diameter k of 10.2 mm and an internal diameter k 1  of 6.0 mm—merges at the upper sleeve end into a hexagonal region  73  having an axial length y 1  of 6 mm. In the region of the cylindrical area of the sleeve interior  72 , the aforementioned outer ribs  76  project from the peripheral surface  74  of the sleeve  70  with a protruding width i 1  of approximately 1 mm, at axial central spacings n of approximately 4 mm from one another. 
         [0070]    As shown in  FIG. 19 , the axis-parallel section of the outer ribs  76  is triangular; the two rib faces  78  issuing from the rib crest  77  define a cross-sectional angle w of almost 45°. These rib faces  78  respectively merge into a channel  75  formed in the peripheral surface  74 , said channel having a depth i 2  of 0.3 mm. As shown in  FIG. 17 , the two side edges  79 ,  79   a  of each of the outer ribs  76 —which are arranged in three axis-parallel rows or groups  80  of uniform peripheral spacing q—are inclined away from the peripheral surface  74  at different angles t and t 1  of respectively 15° and approximately 45° with respect to a radial line Q which crosses through the centre of the outer rib  76 ; the side edge  79  may also define an even smaller angle t 1 . The upset side edge  79   a  gives rise to a greater contact resistance upon rotation of the sleeve  70 , which will be perceived by the operator during the rotation operation and will terminate the rotation operation. Moreover, the length of said peripheral spacing q corresponds approximately to that of the front width i of the outer ribs  76 . 
         [0071]    The outer ribs  76  are inserted in a rotating manner into radial grooves  82  of the groove bottom  24  and of the hook ends  21 , and allow a firm seating of the sleeve  70  in the hollow profile  10   a . 
         [0072]    A clamping screw  84  may be embedded in the sleeve interior  72 ,  73 , the screw head  86  of which clamping screw has a hexagonal hole  87  for an Allen key (not shown), wherein the screw head  86  bears against the lower sleeve edge  68   t  in the clamped position. Adjoining the screw head  86  is a round shaft  88 , which merges into a screw shaft  90  as a threaded region. The latter protrudes beyond the upper sleeve edge  68  in  FIG. 18 . 
         [0073]    A different unit, consisting of a sleeve  70   a  and  71  respectively—having a length y of in this case 18 mm and 20.5 mm respectively and an external diameter k of 10.2 mm—of and a clamping screw  84   a  and  85  respectively which is inserted into said sleeve, is shown in  FIGS. 20 to 24  and  27  to  31  respectively, in  FIG. 29  as the connecting member  64 . The sleeve  70   a  or  71  likewise has three groups or rows  80  of in each case four outer ribs  76   a  and  76   n , which define an external diameter k 2  of 12 mm and the rib crest  77  of which tapers in cross section from a rib thickness n 1  of approximately 0.8 mm at an angle w 1  of 30°, as shown in  FIG. 24 . The lateral rib faces  78  which adjoin the rib crest  77   n  run parallel and inclined with respect to one another.  FIG. 33  in particular shows that one of the side edges  79  of the outer rib  76   n  is assigned a plate-like, flat, square body  81  of small height. Moreover, the axial spacing y 2  of the outer ribs  76   a  and  76   n  from one another is in this case 4 mm. 
         [0074]    The sleeve  70   a  or  71  has a cylindrical sleeve interior  72  having an internal diameter k 1  of 6 mm, which merges into a hexagonal region  73   a  or  73   n  having an axial length y 1  of 6 mm. In the six corners thereof there run axis-parallel notched channels  66 , as shown in  FIG. 26 . The resulting outer internal diameter k 3  of the hexagonal region  73   a  or  73   n  is 6.9 mm. 
         [0075]    The clamping screw  84   a  or  85  consists here in the installed state of a screw head  86  having an axial length z of 6 mm—with a hexagonal hole  87  at the end for an Allen key (not shown)—and of a continuous round shaft  88  having a length z 1  of in this case  29  or 30 mm; the thread  89  or  90  is cut into the shaft  88  over a length z 2  of 9 mm—preferably by rolling-shaping—only once the sleeve  70   a  or  71  has been pushed onto the round shaft  88  until it comes to bear against the screw head  86 . The distance of the thread  89  from the screw head  86 , or the distance of an annular edge  92  of the thread  90  from the screw head  86  (said annular edge surrounding the shaft  88  in FIG.  30 )—and thus the length of a round portion  88   n  of the shaft  88 —is denoted z 3  and in this case is 20 mm. Upon axial displacement of the clamping screw  85  in the assembly or tightening direction x of  FIG. 31 , this annular edge  92  strikes the inner face of the rear wall  94  of the sleeve  71 , and this prevents removal of the clamping screw  86  from the sleeve  71 . The rear wall  94  contains an opening  83  for the round shaft  88 . 
         [0076]    In  FIG. 21 , for reasons of clarity the sleeve  70   a  is shown somewhat at a distance from the screw head  86 ; once the thread  89  has been formed, the clamping screw  86  can be displaced axially in the sleeve  70   a  but cannot be completely removed on account of the thread  89 ; the external diameter q 1  of the latter is greater than the adjoining internal diameter k 1  of the sleeve interior  72 . 
         [0077]    The sleeve  70   b  or  71  of  FIGS. 25 to 27  differs from the sleeve  70   a  of  FIG. 22  by a collar  96  which is formed at one end, said collar having a height h 3  of for example 2 mm and an external diameter k 4  which at 8 mm is smaller than the external diameter k of the sleeve  70   b  of 10.2 mm. This collar  96  increases the axial contact length g 3  of the sleeve  70   b  with the clamping screw  84  to in this case 20.5 mm. As can be seen, the thread  89  of the latter runs outside the sleeve  70   b . 
         [0078]    Moreover, in  FIG. 31 , for the sake of clarity, the clamping screw  85  is shown in its inner position in which it bears against the sleeve  71 ; the latter is again at a distance s of approximately 20 mm from the screw head  86 . Once the thread  90  has been formed, the clamping screw  85  can be displaced axially in the sleeve  71  but cannot be completely removed on account of the thread  90  and its annular edge  92 ; as already mentioned, the external diameter q 1  thereof is greater than the diameter k 4  of said opening  83 . 
         [0079]    A collar  96  is likewise integrally formed at the end of the sleeve  71  which is remote from said rear wall  94 , said collar  96  having a height h 3  of for example 2 mm and an external diameter k 5  which at 8 mm is smaller than the external diameter k of the sleeve  71  of 10.2 mm. As shown in  FIGS. 30 ,  31 ,  33 , this collar on one side delimits the peripheral surface  74  of the sleeve  71  and on the other side an annular zone  68  as sleeve edge; the collar  96  is made in one piece with the latter. This collar  96  increases the axial contact length y 3  of the sleeve  71  with the clamping screw  85  to in this case 20.5 mm.