Abstract:
A device for connecting structural components ( 10, 12 ), with a base part ( 16; 116 ), which is disposed at the one structural component ( 10 ), a spacer ( 18;  on  118 ), which is in threaded engagement with the base part ( 16; 116 ) and is supported with one end at the other ( 12 ) structural component, and a connecting screw ( 20 ), which is inserted frictionally engaged through the spacer ( 18; 118 ), wherein the spacer ( 18; 118 ) is surrounded by any jacket ( 32; 126 ) of a softer material, preferably of a plastic which, at least in the state, in which the spacer and the base part together have the smallest axial dimension, is flush with the front surface of the spacer ( 118 ) or of the hard core ( 50 ) of the same or protrudes with respect to this front surface.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device for connecting structural components, with a base part, which is disposed at the one structural component, a spacer, which is in threaded engagement with the base part and is supported with one end at the other structural component, and a connecting screw, which is inserted frictionally engaged through the spacer. 
     A known device of this type is described in EP-B-0 176 663 and is used to connect two structural components, which are disposed at a particular distance from one another, with the help of the connecting screw without distorting the structural components as the connecting screw is tightened. The connecting screw is inserted, for example, through the structural component, which is to be supported at the spacer, and is then screwed into an internal thread of the other structural component, which is connected with the base part. During this screwing-in motion, the spacer is taken along by friction. The thread between the spacer and the base part is a left-handed thread, so that the spacer is screwed further out of the base part and approaches the structural component, which is held by the head of the connecting screw, until this component finally lies in contact with the front surface of the spacer. 
     However, if the distance between the structural components, which are to be connected, is greater than the maximum adjusting path of the spacer, it may happen that, as the connecting screw is screwed in, the spacer is screwed completely out of the base part. Since the spacer in this case is accessible only with difficulty, if at all, it is difficult to restore the threaded engagement between the spacer and the base part. 
     In the state of the connecting device as delivered, the spacer normally is screwed completely into the base part. From practice, a connecting device is known, for which the spacer in this position is in contact with a stop and, in addition is held in position by a spring-mounted latch. However, it must be possible to overcome the resistance of the latch when the connecting screw is being screwed in. Accordingly, it is not impossible that, because of improper handling or jarring, the spacer, before use of the connecting device, becomes detached completely from the base part, so that the parts of the connecting device fall apart and are lost. 
     For stability reasons, the base part and the spacer should consist of metal. In that case, however, the danger exists that the structural components, which are to be connected to one another, are scratched during the assembly by the spacer, which protrudes from the base part. This problem occurs, for example, in vehicle construction, when a cross member is to be fastened with the help of two such connecting devices between two body parts of the vehicle, which have already been painted. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention, to provide a device of the type mentioned above, with which damage by the spacer to one of the structural parts, which is to be connected, is avoided. 
     Pursuant to the invention, this objective is accomplished owing to the fact that the spacer is surrounded by a jacket of a softer material, preferably of plastic, and that the jacket, at least in the state, in which the spacer and the base part together have the smallest axial dimension, is flush with the front surface of the spacer or of the harder core of the latter or protrudes relative to this front surface. 
     Advantageous developments of the invention arise from the dependent claims. 
     A possible embodiment is characterized in that the spacer has a jacket, which overlaps the base part and in that stops are disposed at this jacket and at the base part, which limit the unscrewing movement of the base part and the spacer. In that case, the protective jacket is part of the spacer. 
     In the case of a different embodiment, the jacket is seated on the base part. Since the device, in the original state, before the start of the assembly work, is adjusted to the smallest possible axial dimension, the spacer lies protected in the jacket until the structural components, which are to be connected, are brought into position and the connecting screw is screwed in. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, an example of the invention is described in greater detail by means of the drawings, in which 
     FIG. 1 shows an axial section through a connecting device and two structural components, which are to be connected, 
     FIG. 2 shows two jackets, which belong to the connecting device, in a section in the plane II—II of FIG. 1, 
     FIG. 3 shows a side view of one of the jackets, 
     FIG. 4 shows the connecting device of FIG. 1 in the state during the establishment of the connection, 
     FIG. 5 shows a side view of the connecting device without the structural components, which are to be connected, in the state with the maximum axial dimension, 
     FIG. 6 shows an axial section through a connecting device of a different embodiment, 
     FIG. 7 shows a connecting device of a further embodiment and 
     FIG. 8 shows a part of the connecting device of FIG. 7 in a front view. 
    
    
     DETAILED DESCRIPTION 
     In FIG. 1, two plate-shaped structural components  10 ,  12  are shown, which are to be connected to one another at a distance from one another by a connecting device  14 . The connecting device  14  is formed by a base part  16 , which is held at the structural component  10 , a spacer  18 , which is screwed into the base part  16 , and a connecting screw  20 , which is inserted through the structural component  12  and inserted into a central borehole of the spacer  18  and, during the establishment of the connection, is screwed into a threaded borehole  22  of the structural component  10 . 
     The base part  16  has a metal core  24 , which is supported at the structural component  10  and, at the outer periphery, has a knurled collar, onto which the plastic jacket  26  is pressed. The jacket  26  forms two claws  28 , with which the base part  16  is clipped non-rotationally to the structural component  10 . 
     The spacer  18  also has a metal core  30 , which is surrounded by a plastic jacket  32 . The jacket  32  is pressed onto a knurled collar  34  of the core  30  and grips into an annular space between the core  24  and the jacket  26  of the base part  16 . 
     The cores  24 ,  30  of the base part and of the spacer engage one another by means of a left-handed thread  36 . In the central bore hole of the spacer  18 , a lock washer  38  is pressed, which brings about a non-positive connecting with the outer thread of the connecting screw  20 . 
     When the connecting screw  20  is screwed into the threaded borehole  22  of the structural component  10 , the spacer  18  is carried along in the direction of rotation, while the base part  16  is held non-rotationally by the claws  28 . Therefore, because of the left-handed thread  36 , the spacer  18  is screwed out of the base part  16 , so that it moves axially towards the structural component  12  which, in turn, is pressed by the head of the connecting screw  20  against the spacer. 
     At the opposite ends of the outer jacket  26  of the base part  16 , two cog-shaped stops  40 ,  42  are formed, which are offset by 180°, protrude towards the inside from the jacket  26  and, together with a further stop, which is formed by a rib  44  on the outer periphery of the jacket  32  of the spacer  18 , limit the adjusting path of this spacer in the screwing-in as well as in the screwing-out direction. As can be seen clearly in FIGS. 2 and 3, the rib  44  has the shape of a left-handed helix which, at the free end of the jacket  32 , runs almost completely around the jacket. The pitch of this helix is identical with the pitch of the left-handed thread  36 . The opposite ends  46 ,  48  of the rib  44  are opposite to one another at a distance, which is slightly larger than the peripheral length of the stops  40  and  42 . 
     In the state shown in FIGS. 1 and 2, the end  46  of the rib  44  lies against the stop  40  and thus prevents further rotation to the left of the spacer  18 . In this way, the screwing-in motion of the spacer is limited. However, if the spacer  18  is rotated to the right with the help of the connecting screw  20 , the opposite end  48  of the rib can move past the stop  40 . After a full revolution, the spacer  18  emerges from the base part  16  by the length of a thread pitch of the left-handed thread  36 , so that the end  46  of the rib  44  can then move past the stop  40 . 
     As the connecting screw  20  is screwed in further, the state, shown in FIG. 4, is then reached as an intermediate state, in which the spacer  18  has already moved some distance out of the base part  16 . If the connecting screw  20  is screwed in further, the structural component  12  is clamped tightly between the head of the connecting screw and the end of the spacer  18  and, with that, a stable connection is established between the structural components  10  and  12 . 
     If the distance between the structural components were larger and the connecting screw  20  were longer, the spacer  18  could be moved out further. The screwing-out movement of the spacer is, however, limited owing to the fact that the end  48  of the rib  44  comes up against the stop  42 , as shown in FIG.  5 . In this way, it is prevented that the spacer  18  can be screwed out completely from the base part  16 . 
     As can be seen in FIGS. 1 and 4, the jacket  32  of the spacer projects somewhat beyond the core  30  with its end facing the structural component  12 . Therefore, when the spacer comes up against the structural component  12 , there is frictional contact between the jacket  32  and the structural component  12 . Since the jacket  32  consists of plastic, damage to the surface of the structural component  12  is avoided. However, if a more stable support of the spacer  18  at the structural component  12  is desired, the end of the jacket  32  can also be offset back into a flush position, so that the spacer  18  is also supported with its metal core  30  at the structural component  12 . 
     The procedure for producing the connecting device, described above, may be as follows. The core  30  of the spacer is screwed into the core  24  of the base part  16 , before these metal parts are connected with the associated plastic jackets. The screwing in therefore is not impeded by the stops  40 ,  42  and the rib  44 . The screwing-in depth can be adjusted to a particular value by inserting a suitable gauge in the space between the collar  34  of the spacer and the front surface of the core  24  of the base part. 
     The jacket  32  is then pushed from the left in FIG. 1 over the core  24  of the base past and pressed onto the collar  34  of the spacer. Subsequently, the jacket  26  of the base part is pushed, once again from the left in FIG. 1, over the jacket  32 . At the same time, the jacket  26  is held in an angular position, in which the stop  40  can enter the space between the ends  46 ,  48  of the rib  44 . In this position, the jacket  26  is then pushed onto the core  24 , until its front surface is a flush with the front surface of the core  24 . 
     The end position of the spacer  18 , in the screwed-in position shown in FIG. 1, can be defined precisely in this way. The adjusting path of the spacer is defined by the position of the stops  40  and  42 . Since these stops are diametrically opposite to one another in the example shown, the adjusting path of the spacer corresponds to (n+½) revolutions and accordingly amounts to (n+½) times the pitch of the left-handed thread  36  (n is a whole number). This adjusting path can also be varied infinitely by changing the angular offset between the stops  40  and  42 . 
     The end position of the spacer  18  in the screwed-in position preferably is selected so that the front surface of the spacer  18 , facing the structural component  10 , is recessed slightly from the front surface of the base part  16 . By these means, it is prevented that the spacer  18  becomes jammed, when the base part  16  is pressed against the structural component  10 . 
     FIG. 6 shows a connecting device  114  of a different embodiment. The connecting device  114  is formed by a base part  116 , which is held at the structural component  10 , a spacer  118 , which is screwed into the base part  116 , and the connecting screw  20 , which is inserted through the structural component  12  and into the central borehole of the spacer  118  and, during the establishment of the connection, is screwed into the threaded borehole  22  of the structural component  10 . 
     The base part  116  has a threaded metal bushing  124 , which is supported at the structural component  10  and, at the outer periphery, has a milled edge, onto which a plastic jacket  126  is pressed. The jacket  126  forms two claws  128 , with which the base part  116  is clipped non-rotationally to the structural component  10 . 
     The spacer  118  consists completely of metal. The threaded bushing  124  of the base part and the spacer engage one another by means of a left-handed thread  130 . A lock washer  132 , which establishes a non-positive connection with the external thread of the connecting screw  20 , is pressed into the central borehole of the spacer  118 . 
     When the connecting screw  20  is screwed into the threaded borehole  22  of the structural component  10 , the spacer  118  is carried along in the direction of rotation, while the base part  116  is held non-rotationally by the claws  128 . Therefore, because of the left-handed thread, the spacer  118  is screwed out of the base part  116 , so that it moves axially onto the structural component  12  which, in turn, is pressed by the head of the connecting screw  20  against the spacer. 
     The left-handed thread  130  of the spacer  118  is bounded at one end, on the right hand side in FIG. 6, by a shoulder  134 . At the inner peripheral edge, the jacket  126  forms a circulating collar  136 , at which one end of the threaded bushing  124  is supported. An elastic latch  138  protrudes inwards at least at one place on the periphery from this collar  136 . This latch  138  forms a stop, which interacts with the shoulder  134  and, in this way, limits the maximum extension path of the spacer  118 . 
     At the end facing the structural component  12 , the spacer  118  has a radially protruding flange  140 , which forms a stop surface for the structural component  12 , when the structural components  10  and  12  are clamped together by the connecting screw  20 . In the state shown in FIG. 6, in which the spacer  118  still is retracted completely in the base part  116 , the outer surface of the flange  140  concludes flush with the front surface of the jacket  126 . A projection  142 , starting out radially from the edge of the flange  140 , lies at an inwardly protruding stop  144  of the base part  116 . The stop  144  thus prevents the spacer  118  being rotated to the left in the screwing-in direction of the connecting screw  20 . Accordingly, the spacer  118  cannot be shifted beyond the position, shown in FIG. 6, in the direction of the structural component  10 . However, when the connecting screw  20  is screwed to the right into the threaded bushing  124 , the spacer  118  can rotate along to the right, since then the projection  142  is freed from the stop  144 . After a complete revolution of the spacer  118 , the projection  142  has already emerged to such an extent from the base part  116 , that it can move outside of the base part past the stop  144 . 
     In the case of the example shown, it is thus ensured that the spacer  118  cannot be screwed out of the base part  116  in the one or the other direction. 
     However, for assembling the connecting device, the spacer  118  can be screwed from the right side in FIG. 6 into the threaded bushing  124  of the base part. In so doing, the elastic latch  138  initially is bent towards the inside, so that it gives way to the spacer  118 . As the spacer is screwed in further, the latch  138  then slides along the outer threads of the spacer and finally slides over the shoulder  134 , so that it can spring back once again into its original position, in which it acts as a stop for the shoulder  134 . 
     FIGS. 7 and 8 show a further example of a connecting device  146 , for which the connecting screw  20  is screwed in from the opposite end. In this case, the structural component  10  has a keyhole-shaped opening  148  with two diametrically opposed protuberances  150  for accommodating the claws  128 . The circular inner part of the opening  148  is covered by a disc  152 , at which the head of the connecting screw  20  and the threaded bushing  124  of the base part  116  are supported. 
     The threaded bushing  124  and the spacer  118  in this case have a right-handed thread, so that the spacer  118  moves to the right in FIG. 7 in the direction of the structural component  12 , when the connecting screw  20  is turned to the right. 
     FIG. 7 shows the spacer  118  already in the extended state, in which the shoulder  134  has already almost reached the stop position. In this case however, the stop at the jacket  126  is formed by a rigid projection  154  and not by a spring-mounted latch. The flange  140 , which is formed at the spacer  118  and in this case has a smaller diameter, has a recess  156 , through which the projection  154  can pass axially, at one place of its periphery. 
     During the assembly of the connecting device  146 , initially the threaded bushing  124  and the spacer are screwed together, before the threaded bushing  124  is pressed into the jacket  126 . The spacer  118  can therefore be screwed from the right in FIG. 7 into the threaded bushing  124 , until it has reached approximately the screwed-in position shown in FIG.  7 . Subsequently, the spacer  118  and in the threaded bushing  114  are inserted jointly from the left side in FIG. 7 into the jacket  126 . In so doing, the spacer  118  is held at an angular position, in which the projection  154  can pass through the recess  156 . In the end phase of the insertion movement, the threaded bushing  124  is then pressed with its milled outer circumferential edge into the jacket  126 . Finally, the spacer  118  is screwed deeper into the threaded bushing  124 , until its opposite end faces are flush with the corresponding surfaces of the base part  116  and the jacket  126 , respectively. 
     In the state, in which the connecting device has the smallest possible axial dimension, the base part  116  is then clipped to the structural component  10  and the connecting screw  20  is inserted and screwed in, so that the spacer  118  can then be extended once again. 
     FIG. 8 shows a part of the front surface of the flange  140 , as well as a part of the collar  158 , which is formed at the jacket  126  and surrounds this flange  140 . In this state shown in FIG. 8, the recess  156 , which is formed at the edge of the flange  140 , is twisted with respect to the projection  154  of the base part. At the left flank of the recess  156  in the view of FIG. 8, a projection  160  is formed, which protrudes radially towards the outside from the edge of the flange  140 . A stop  162 , which protrudes towards the inside, and a bridge-like stop spring  164  are integrally molded to the inner peripheral surface of the collar  158 . As long as the flange  140  lies axially outside of the base part, as shown in FIG. 7, the spacer  118  can be turned to the right and, with that, screwed deeper into the base part  116 . During the last revolution, immediately before the minimum axial dimension is attained, the flange  140  enters the collar  158 . The projection  160  initially, overcoming a certain resistance, slides over the lock spring  164  and then comes into contact with the stop  162 . The further screwing-in movement of the spacer  118  is limited in this manner. The spacer is held by the stop spring  164  in the position attained with the minimum axial dimension and prevented from shifting because of vibrations. However, the force of the stop spring  164  is dimensioned, so that it can be overcome by the frictional resistance between the connecting screw  20  and the spacer, when the connecting screw  20  is being screwed in. During the screwing-in movement, the spacer  118  rotates to the left in the view of FIG. 8, so that the projection  160  distances itself from the stop  162 .