Patent Publication Number: US-2002009350-A1

Title: Retaining device for a connection element

Description:
[0001] The invention relates to a retaining device of the type outlined in the preamble of claim  1 .  
       [0002] A connection system is known from DE 197 50 658 C1, consisting of a sleeve with a screw, displaceable in an axial direction, captively retained therein by means of a retaining device. The screw has a head joined to a cylindrical shank extending in an axial direction, the end region of which is provided with a thread at a distance from the head, the external diameter of the thread being larger than a diameter of the shank. An internal thread pitch in the region of the insertion orifice of the sleeve is shaped by mechanical action once the screw is inserted, so that the screw is captively retained in the sleeve, but the need to provide an internal thread represents an additional production process.  
       [0003] Another assembly unit is known from DE 196 53 226 A1, consisting of a sleeve insertable in an assembly component and a screw. The screw is captively retained by an annular ridge projecting from a screw shank and by a fixing ridge projecting into the internal diameter of the sleeve in the direction of a neck of the screw shank. This design requires a complex screw structure, often preventing the use of less expensive standard screws.  
       [0004] Finally, a fixing assembly is known from EP 0 272 642 B1, essentially consisting of a washer with a sleeve-type collar in which is inserted a fixing screw having ridges upstanding in a radial direction on its shank, and an internal diameter of the collar at the end for inserting the screw has a smaller diameter than a major diameter of the ridges, whereby the screw is captively retained. This design also requires a complex process to produce a screw with ridges on the shank.  
       [0005] The objective of the invention is to provide a retaining device for captively receiving a fixing means in a tubular sleeve, which is simple and, hence inexpensive, to manufacture and assemble.  
       [0006] This objective is achieved by the invention as a result of the features outlined in the characterising part of claim  1 . The surprising advantage of this arrangement is that a tubular sleeve can be made by simple tooling and a standard bolt-design fixing means can be captively retained in a simple assembly step by sheathing the fixing means with an elastically returnable, deformable retaining element, thereby producing an axial compensation, which simplifies the use of connection systems for which a retaining device of this type is used.  
       [0007] The embodiment defined in claim  2  is also of advantage, because the assembled parts have sufficient play to guarantee the requisite manufacturing tolerances.  
       [0008] The advantage of an embodiment of the type described in claim  3  is that it produces an accurate vertical axial alignment of the sleeve on a component or alternatively of a damping element between a component and the flange enclosing the sleeve disposed.  
       [0009] Another advantageous embodiment is described in claim  4 , which securely anchors the sleeve in a component, in particular a plastics component.  
       [0010] Another possible embodiment is that defined in claim  5 , whereby a simple tool structure can be used to make the sleeve, thereby keeping costs to a minimum.  
       [0011] Another advantageous embodiment is described in claim  6 , which produces a secure retaining fit even if subjected to axial forces.  
       [0012] The advantageous embodiment defined in claim  7  enables the use of standard initial products, materials, etc..  
       [0013] Claim  8  defines another possible embodiment, which obviates the need to prefabricate and individually insert the retaining element.  
       [0014] Another advantageous embodiment is defined in claim  9 , wherein an upstanding section of the bolt-design fixing means, in other words proud of the end region of the tubular sleeve, is avoided, thereby making it easier to align a component on a part of the device prior to assembly.  
       [0015] Claim  10  defines another advantageous embodiment, which permits a longitudinal displacement of the fixing means in the retaining element in a predetermined displacement path.  
       [0016] As a result of the advantageous embodiment outlined in claim  11 , the fixing means is securely, i.e. captively, retained in the sleeve.  
       [0017] Other possible embodiments are defined in claims  12  and  13 , which enable the fixing means to be detachably retained in the retaining element so that the fixing means is prevented from standing proud of the end region or an end face of the sleeve from projecting out through the fixing means.  
       [0018] Finally, claim  14  defines an advantageous embodiment which enables adjustments to be made to meet different requirements. 
     
    
    
     [0019] To provide a clearer understanding, the invention will be described in more detail with reference to the embodiments illustrated in the appended drawings.  
     [0020] Of these:  
     [0021]FIG. 1 illustrates the retaining device proposed by the invention for a tubular sleeve and a fixing means projecting therethrough, seen in section;  
     [0022]FIG. 2 shows the sleeve with the fixing means and retaining element, in a head-on view, in a section along lines II-II of FIG. 1;  
     [0023]FIG. 3 illustrates how a component is fixed onto a part of the device together with the sleeve in conjunction with the retaining element and an additional damping element, seen in section from a front view;  
     [0024]FIG. 4 illustrates another embodiment of the tubular sleeve captively secured to the fixing means by the retaining element, seen in section from a front view. 
    
    
     [0025] Firstly, it should be pointed out that the same parts described in the different embodiments are denoted by the same reference numbers and the same component names and the disclosures made throughout the description can be transposed in terms of meaning to same parts bearing the same reference numbers or same component names. Furthermore, the positions chosen for the purposes of the description, such as top or bottom, relate to the drawing specifically being described and can be transposed in terms of meaning to a new position when another position is being described. Individual features or combinations of features from the different embodiments described may be construed as independent inventive solutions in their own right.  
     [0026] FIGS.  1  to  3  illustrate a connection system  1  consisting of a bolt-design fixing means  2 , in particular a screw  3 , and a tubular sleeve  4  enclosing the latter. A retaining device  5  consists of a retaining element  6  disposed between the sleeve  4  and the screw  3 . The retaining device  5  captively restrains the screw  3  when it is inserted through the retaining element  6  to project into the sleeve  4 .  
     [0027] In a preferred embodiment, the sleeve  4  is a deep-drawn component with a flange  7  and the collar  8  extending out from the plane of the flange  7  in an axial direction.  
     [0028] The bolt-design fixing means  2 , in particular the screw  3 , has a head  9  from which a shank  10  extends in an axial direction, having a cylindrical shank region  11  with no thread adjacent to the head  9  adjoined by a threaded region  12 . An external diameter, i.e. an external diameter  13  of the threaded region  12 , is bigger than an external dimension, e.g. a diameter  14  in the thread-free shank region  11 . A cross-section dimension, e.g. an internal diameter  15 , of the collar  8  or sleeve  4  has a larger dimension than a dimension of the diameter  14  of the thread-free shank region  11  as well as the external diameter  13  of the threaded region  12 .  
     [0029] The retaining device  5 , consisting of the retaining element  6 , is placed in the sleeve  4  at an insertion region  16  of the screw  3 , the retaining element  6  being made from an annular, elastically returnable, deformable material encasing the shank  10  of the fixing means  2 , in which the shank  10  is longitudinally slidably mounted in the direction of the longitudinal median axis  17  and which is supported on the shank  10  and an internal surface  18  of the sleeve  4 . Due to the fact that the retaining element is made from an elastically returnable material, being of a thickness  19  such that an external diameter is slightly larger than the internal diameter  15  of the sleeve  4 , a radial pre-tension is exerted between the shank  10  and the sleeve  4  and the retaining element  6 , once inserted in the sleeve  4 , conforms to the diameter  14  of the shank  10 , which is smaller than the external diameter  13  of the threaded region  12 , causing the retaining device  5  to come into play so that the fixing means  2  is captively retained in the sleeve  4 .  
     [0030] The connection system  1  is assembled, in a first step, by pushing the elastically returnable, deformable retaining element  6  over the threaded region  12 , enclosing the fixing means  2 , as far as the thread-free shank region  11 . Then, in a second step, the fixing means  2  encased in the retaining element  6  is inserted in the sleeve  4  and pressed into the sleeve  4  by means of a tension surface  20  applied by the head  9  of the fixing means  2 . The fixing means  2  or the screw  3  can then be pulled back out of the sleeve  4  in an axial direction following arrow  21  against the pre-tensioning force exerted by the retaining element  6  across a length  22  of the thread-free region  11  less a height  23  of the retaining element  6 , against the retaining force applied by the pre-tensioning force, so that the screw  3  does not project beyond an end face  24  bounding the sleeve  4  in an end region  25  opposite the flange  7 . Due to the action of the pre-tensioning force, the screw  3  is retained in this position by a standard manipulation and can only be changed by applying a force in the direction of arrow  26  for the purpose of an assembly process, i.e. a tightening the screw.  
     [0031]FIG. 3 illustrates one possible application of the connection system  1  for securing a component  27  onto a device part  28 , for example. There are multiple applications for a connection system  1  of this type in the automotive industry, where, as with the embodiment illustrated here, it is necessary to provide effective damping against vibrations, e.g. from engines.  
     [0032] In order to simplify the procedure of mounting the component  27  on the device part  28  on site, the component  27  is supplied ready-fitted with the connection system  1  and a damping element  29  enclosing the sleeve  4  is provided between the flange  7  and the component  27 .  
     [0033] The broken lines indicate the position of the fixing means  2  in which the fixing means  2  is not projecting beyond the end face  24  of the sleeve  4  and hence a surface  30  of the component  27  facing the device part  28 . This position is retained by the pre-tensioning force resulting from the pretension exerted by the retaining element  6  between the shank  10  and the internal face  18  of the sleeve  4 . Accordingly, the component  27  can be placed and positioned on the device part  28  with the pre-assembled connection system  1 —generally speaking a component  27  of this type has a number of such connection systems  1 —without the screws  3  projecting beyond the surface  30 . If, in spite of the positioning, there is a slight variance between the longitudinal median axis  17  of the screw  3  and the median axis  31  of a bore  33  with an internal thread  32  in the device part  28 , this can be compensated by the radial clearance afforded by the difference in diameter between the internal diameter  15  of the sleeve  4  and the external diameter  13  of the thread and can be so by pulling the screw  3  into an axially flush alignment.  
     [0034] By preference, fixing means of this type also have a locating tip at their end region, facilitating insertion in a thread, which is of particular advantage if using automated assembly processes, e.g. with robots.  
     [0035] A variance in the flush alignment between the longitudinal median axis  17  and the median axis  31  due to manufacturing tolerances can also be obtained as a result of the elastic deformability of the retaining element  6 .  
     [0036] In order to anchor the sleeve  4  in the component  27 —particularly if the latter is made from plastics—the sleeve  4  has a bead-shaped formed zone  34  at the end region  25 , for example, where an annular circumferential projection  36  extends beyond an external diameter  35  of the sleeve  4 .  
     [0037] In the embodiment illustrated as an example here, a length  37  of the collar  8  is placed against a thickness  38  of the component  27  and an optionally pre-tensioned thickness  39  of the damping element  29  and there is therefore no need to provide an additional packer when securing the component  27  to the device part  28  because the requisite fixing forces, acting in the form of pressure forces in the collar  8 , are absorbed thereby. This enables the screw to be duly tightened to predetermined clamping rates, in accordance with the screw specifications, to prevent the connection system  1  from working loose and necessary to secure the connection system  1  sufficiently firmly.  
     [0038] When pre-assembling the connection system  1 , the fixing means  2  is fitted with the retaining element  6 , e.g. a tube or hose section  40  made from plastics, rubber, etc., which is pushed onto the shank  10  until the head  9  lies against the tension surface  20 . The fixing means  2  is then inserted in the sleeve  4  and the head  9  displaced in the direction of the flange  7  so that the tension surface  20  pushes the retaining element  6  into the sleeve  4 . This process is facilitated by the rounding in the transition region between the flange  7  and the collar  8 . The retaining element  6  is therefore reduced from its originally larger external diameter to the internal diameter  15  of the sleeve  4 , thereby producing a press-fit mounting in the sleeve  4 . Due to the elasticity of the material of the retaining element  6 , this then causes a radial pre-tensioning force on the shank  10  of the fixing means  2  but still allows the threadless shank region  11  to be pushed into an initial position in which the fixing means  2  is not projecting beyond the end face  24  of the sleeve  4 . Since the external diameter  13  of the threaded region  12  is larger than the diameter  14  of the shank region  11 , the fixing means  2  can only be pulled out by force, destroying the assembly. In this initial position, the connection system  1  is inserted in the component  27 , optionally after pushing on a damping element  29  as with the example illustrated in FIG. 3.  
     [0039] Another embodiment of the connection system  1  with the retaining device  5  is illustrated in FIG. 4. In this case, the fixing means  2  is of a special structure and, as shown by way of illustration, the threadless shank region  11  is provided with an annular necking  41  at the transition to the threaded region  12 . A width  42  of the necking  41  corresponds approximately to the height  23  of the retaining element  6 . A diameter  43  is slightly smaller than the diameter  14  of the adjoining shank  10  running in the direction of the tension surface  20  of the head  9 . Accordingly, the retaining element  6  engages so that the fixing means  2  reaches a rest position and an additional initial position in the sleeve  4 . The length  22  of the threadless shank region  1   1  corresponds to the sum of the width  42  and a screwing depth  44 , as illustrated by broken lines. Furthermore, the fixing means  2  is provided with a locating tip  45  at its thread-side end region, which facilitates insertion in a thread if there is any axial deflection.  
     [0040] Another possible approach and design which may be used for the retaining element  6  is to use injection technology as a means of application, whereby a foaming plastics material is injected or poured into the gap between the threadless shank region  11  and the inner face  18  of the sleeve  4 , the shank region  11  being provided with a dividing means prior to applying the material in order to prevent any adhesion on the shank region  11 .  
     [0041] For the sake of good order, it should finally be pointed out that in order to provide a clearer understanding of the retaining device proposed by the invention, it and its constituent parts have been illustrated out of scale to a certain extent and/or on an enlarged and/or reduced scale.  
     [0042] The tasks underlying the independent inventive solutions can be found in the description.  
     [0043] Above all, subject matter relating to the individual embodiments illustrated in FIGS. 1, 2,  3 ;  4  can be construed as independent solutions proposed by the invention. The tasks and solutions can be found in the detailed descriptions relating to these drawings.  
     Reference Numbers  
     [0044] 1  Connection system  
     [0045] 2  Fixing means  
     [0046] 3  Screw  
     [0047] 4  Sleeve  
     [0048] 5  Retaining device  
     [0049] 6  Retaining element  
     [0050] 7  Flange  
     [0051] 8  Collar  
     [0052] 9  Head  
     [0053] 10  Shank  
     [0054] 11  Shank region  
     [0055] 12  Threaded region  
     [0056] 13  External diameter  
     [0057] 14  Diameter  
     [0058] 15  Internal diameter  
     [0059] 16  Insertion region  
     [0060] 17  Longitudinal median axis  
     [0061] 18  Face  
     [0062] 19  Thickness  
     [0063] 20  Tension surface  
     [0064] 21  Arrow  
     [0065] 22  Length  
     [0066] 23  Height  
     [0067] 24  End face  
     [0068] 25  End region  
     [0069] 26  Arrow  
     [0070] 27  Component  
     [0071] 28  Device part  
     [0072] 29  Damping element  
     [0073] 30  Surface  
     [0074] 31  Median axis  
     [0075] 32  Internal thread  
     [0076] 33  Bore  
     [0077] 34  Formed zone  
     [0078] 35  External diameter  
     [0079] 36  Projection  
     [0080] 37  Length  
     [0081] 38  Thickness  
     [0082] 39  Thickness  
     [0083] 40  Tube-or hose section  
     [0084] 41  Necking  
     [0085] 42  Width  
     [0086] 43  Diameter  
     [0087] 44  Screwing depth  
     [0088] 45  Locating tip