Abstract:
A device for connecting two structural components, comprising:  
     a base part disposed at one structural component,  
     a spacer having a threaded portion in threaded engagement with the base part, said spacer being supported with one end thereof at the other structural component,  
     a connecting screw inserted frictionally engaged through the spacer,  
     a shoulder formed at one end of said threaded portion of the spacer, and  
     an abutment to be engaged by said shoulder and being formed at the base part,  
     wherein said abutment is arranged to become effective to limit, through engagement with said shoulder, a threading movement of the spacer in one direction relative to the base part only after the base part and the spacer have been assembled.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The invention relates to a device for connecting structural components, comprising a base part attached to one of said components, a spacer which is in-threaded engagement with the base part and has an end supported at the other structural component, and a connecting screw which is inserted frictionally engaged through the spacer.  
           [0002]    A known device of this type is described in U.S. Pat. No. 4,682,906 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.  
           [0003]    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.  
           [0004]    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, in which the spacer in this position is in contact with a stop and, in addition is held in position by a resilient tab. It must however be possible to overcome the resistance of this tab when the connecting screw is screwed in. Accordingly, it cannot be excluded 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. Another embodiment of a connecting device of this type is disclosed in applicant&#39;s co-pending U.S. patent application Ser. No. 09/920,201.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the invention to provide a device of the type indicated above, in which the spacer and the base part are held together so as to be prevented from getting lost.  
           [0006]    According to the invention, this object is achieved by the fact that the movement of the spacer relative to the base part in one direction is limited by a shoulder that is formed at an end of the threaded portion of the spacer and engages an abutment at the base part, which abutment becomes effective only after the spacer and the base part have been assembled.  
           [0007]    Thus, in the device according to the invention, it is possible that the spacer is initially screwed into the base part and then the abutment is made effective, so that the spacer can no longer be screwed out of the base part completely. If necessary, the movement of the spacer relative to the base part in the other direction may be limited by normal stops, so that it is not possible, neither, to screw the spacer completely through the base part. In this way, the spacer and the base part, once assembled, are held together so that the may not get lost.  
           [0008]    In one embodiment, the abutment, which becomes effective only after assembly, is formed by a spring member which projects radially inward from the base part, for example a spring member in the form of a resilient tab which retreats, when the spacer is screwed in, and which then locks behind the shoulder of the spacer.  
           [0009]    In another embodiment, the abutment is rigidly provided on a jacket into which a threaded sleeve is press-fitted. In this embodiment, the spacer is at first screwed into the threaded sleeve, and only then is the threaded sleeve pressed into the jacket of the base part, so that the abutment is made effective.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    In the following, embodiment examples of the invention are explained in conjunction with the drawings, in which:  
         [0011]    [0011]FIG. 1 shows an axial section through a connecting device and two structural components to be connected,  
         [0012]    [0012]FIG. 2 shows a connecting device according to another embodiment, and  
         [0013]    [0013]FIG. 3 shows a part of the connecting device of FIG. 2 in a front view. 
     
    
     DETAILED DESCRIPTION  
       [0014]    In FIG. 1, two plate-like 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  that is screwed into the base part  16 , and a connecting screw  20  which is inserted through the structural component  12  and into a central bore of the spacer  18  and, during the establishment of the connection, is screwed into a threaded bore  22  of the structural component  10 .  
         [0015]    The base part  16  has a threaded metal sleeve  24  which is supported at the component part  10  and has a knurled outer periphery onto which a plastic jacket  26  is pressed. The jacket  26  forms two claws  28  with which the base part  16  is non-rotationally clipped to the component part  10 .  
         [0016]    The spacer  18  is made of metal in its entirety. The threaded sleeve  24  of the base part and the spacer  18  are in threaded engagement with one another through a left-handed thread  30 . A spring collar  32  is pressed into a central bore of the spacer  18  and is in frictional engagement with the external thread of the connecting screw  20 .  
         [0017]    When the connecting screw  20  is screwed into the threaded bore  22  of the component part  10 , the spacer  18  is rotationally entrained, whereas the base part  16  is held non-rotatable by the claws  28 . Because of the left-handed thread, the spacer  18  is therefore screwed out of the base part  16 , so that it approaches the component part  12  which in turn is pressed against the spacer by the head of the connecting screw  20 .  
         [0018]    The left-handed thread  30  of the spacer  18  is limited at one end thereof, on the right side in FIG. 1, by a shoulder  34 . The inner peripheral surface of the jacket  26  is formed with an annular collar  36  at which one end of the threaded sleeve  24  is supported. A resilient tab  38  projects inwardly from the collar  36  at at least one location of the periphery of the latter. This tab  38  forms an abutment which cooperates with the shoulder  34  and thereby limits the maximum expansion stroke of the spacer  18 .  
         [0019]    The spacer  18  has, at its end facing the component part  12 , a radially projecting flange  40  which provides an engagement surface for the component part  12  when the component parts  10  and  12  are clamped together by the connecting screw  20 . In the condition shown in FIG. 1, in which the spacer  18  is still completely accommodated within the base part  16 , the outer end face of the flange  40  is flush with the end face of the base part  16 . A projection  42  which radially projects from the edge of the flange  40  engages an inwardly projecting stop  44  of the base part. The stop  44  thus prevents the spacer  18  from being rotated in the counterclock sense, as seen in the direction in which the connecting screw  20  is screwed in. Consequently, the spacer  18  cannot be displaced towards the component part  10  beyond the position shown in FIG. 1. When, however, the connecting screw  20  is screwed in clockwise direction into the threaded sleeve  24 , the spacer  18  can co-rotate in the clock sense, because the projection  42  is then lifted from the stop  44 . After one complete turn of the spacer  18 , the projection  32  has moved already out of the base part  16  to such an extent that it can now move past the stop  44  of the base part.  
         [0020]    It is thus assured in the shown embodiment that the spacer  18  cannot be screwed out of and removed from the base part  16 , neither in the one direction nor in the other.  
         [0021]    When the connecting device is being assembled, the spacer  18  can however be screwed into the threaded sleeve  24  of the base part from the right end in FIG. 1. Then, the elastic tab  38  is at first bent inwardly, so that it retreats from the spacer  18 . When the spacer is screwed-in further, the tab  38  slips over the external thread of the spacer, and it finally slips over the shoulder  34 , so that it returns elastically into its original position in which it acts as an abutment for the shoulder  34 .  
         [0022]    [0022]FIGS. 2 and 3 show, as another example, a connecting device  46  in which the connecting screw  20  is screwed-in from the opposite end. In this case, the component part  10  has an opening  48  shaped like a key hole and having two diametrically opposed extensions  50  for receiving the claws  28 . The circular inner part of the opening  48  is covered by a disk  52  at which the head of the connecting screw  20  and the threaded sleeve  24  of the base part  16  are supported.  
         [0023]    The threaded sleeve  24  and the spacer  18  have in this case right-handed threads, so that the spacer  18  is extended towards the component part  12 , to the right in FIG. 2, when the connecting screw  20  is turned clockwise.  
         [0024]    [0024]FIG. 2 shows the spacer  18  already in the extended condition, in which the shoulder  34  has almost reached the abutment position. However, the abutment at the jacket  26  is in this case not formed by a resilient tab but by a rigid projection  54 . The flange  40 , which is formed at the spacer  18  and which, in this case, has a smaller diameter, has, at one location of its periphery, a recess  56  through which the projection  54  may pass in axial direction.  
         [0025]    When the connecting device  46  is assembled, the threaded sleeve  24  and the spacer are first screwed together, before the threaded sleeve  24  is pressed into the jacket  26 . As a result, the spacer  18  can be screwed into the threaded sleeve  24  from the right side in FIG. 2, until it has approximately reached the screwed-in position shown in FIG. 2. Then, the spacer  18  and the threaded sleeve  24  are, together, inserted into the jacket  26  from the left side in FIG. 2. At this instant, the spacer  18  is held in an angular position in which the projection  54  can pass through the recess  56 . In a final phase of the insertion movement, the threaded sleeve  24  is then pressed into the jacket  26  with its knurled outer periphery. Finally, the spacer  18  is screwed deeper into the threaded sleeve  24 , until its opposite end faces are flush with the corresponding end faces of the base part  16 . In this condition, in which the connecting device has its smallest possible axial dimension, the base part  16  is then clipped to the component part  10 , and the connecting screw  20  is inserted and screwed-in, so that the spacer  18  is extended again.  
         [0026]    [0026]FIG. 3 shows a part of the end face of the flange  40  as well as a part of a boss  58  which is formed at the jacket  26  and surrounds the flange  40 . In the condition shown in FIG. 3, the recess  56  formed in the periphery of the flange  40  is angularly displaced from the projection  54  of the base part. Adjacent to the left flank, as seen in FIG. 3, of the recess  56 , there is formed a projection  60  which projects radially outwardly from the edge of the flange  40 . An inwardly projecting stop  62  and a bridge-shaped retaining spring  64  are molded to the internal peripheral surface of the boss  58 . As long as the flange  40  is in an axial position outside of the base part, as in FIG. 2, the spacer  18  can be rotated clockwise and hence be screwed deeper into the base part  16 . During the last turn, immediately before the smallest axial dimension is reached, the flange  40  enters into the boss  58 . The projection  60  slips at first over the retaining spring  64 , while overcoming a certain retaining resistance, and then abuts at the stop  62 . In this way, the spacer  18  is prevented from being screwed-in further. The retaining spring  64  retains the spacer in the then-reached position, which corresponds to the smallest axial dimension, and prevents the spacer from being misadjusted due to vibrations. However, the force of the retaining spring  64  is dimensioned such that it can be overcome by the frictional coupling between the connecting screw  20  and the spacer, when the connecting screw  20  is screwed in. During this operation of screwing-in the connecting screw, the spacer  18  turns left in the view shown in FIG. 3, so that the projection  60  moves away from the stop  62 .