Abstract:
A wiper bracket ( 10 ) with a hollow profile ( 64, 72, 74 ) is provided for fastening a wiper motor, via a motor receptable ( 24 ), and at least one wiper bearing ( 12, 14 ) for fastening a windshield wiper to a vehicle body. A longitudinally elastically resilient region ( 60, 62 ) is disposed between the motor receptacle ( 24 ) and the wiper bearing ( 12, 14 ).

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a wiper bracket for fastening a wiper motor and a wiper bearing for a windshield wiper to the body of a motor vehicle. 
     Motor vehicle wiper systems are secured to the body of a motor vehicle with a wiper bracket, or so-called elbow plate. The elbow plate has a wiper drive with a wiper motor, whose motor shaft, via connecting rods, drives cranks that are solidly connected to a drive shaft for each window wiper. The drive shaft is supported in a wiper bearing, whose bearing housing is secured to the elbow plate. The wiper bracket is secured directly to a vehicle body via the wiper bearings or via fastening eyelets that are formed onto the wiper bearing, the wiper bracket, and/or a motor bracket. 
     From German Utility Model DE-U 74 34 119, a wiper bracket is known that is made from a square pipe or tube to which a plate acting as a motor bracket is welded. Such wiper brackets, often also called tubular elbow plates or tubular frame systems, are distinguished by lightweight construction with great stability. For cost reasons, a straight tube is desired, because it requires no preliminary bending operation. The straight version of the tube has high rigidity in the axial direction, which does have a favorable effect in normal wiper system operation, but in the event of a blockage or when there is snow on the window has disadvantages, because the other components of the wiper system, such as the wiper bearings or wiper levers, are heavily loaded, because the tube has such low elasticity. These other components must therefore be reinforced. The attendant higher costs cancel out the cost advantage of the straight tube or make it even more expensive then the alternative. 
     A wi is also known from European Patent disclosure EP B1 0 409 944, in which tubular elements connect a motor bracket to the wiper bearings via positive-engagement connections. Noise-damping, frequency-filtering or noise absorbing adapters are inserted into the essentially straight tubular elements in order to damp noises that are transmitted from the wiper motor via the wiper bracket to the wiper bearings and then to the vehicle body. A variant shows that the tubular wiper bracket is perforated in one region and filled with a noise-absorbing material, which may be foam. In all these provisions, care must be taken not to reduce the stability of the bracket frame excessively. 
     A method for reshaping tubes into workpieces is also known from the journal “Werkstatt und Betrieb” Shop and Factory, Carl Hanser Verlag, Munich, 1995, pages 812-815, and the of print from the journal “Metallumformtechnik” Metal Reshaping Technology, Claus Dannert Verlag, 1994, entitled “Präzisions-Werkstücke in Leichtbauweise, hergestellt durch Innenhochdruck-Umformen” Lightweight precision workpieces, made by internal-high-pressure reshaping. This method, which is used above all for the automotive industry, employs high pressures. The tubular piece to be reshaped is placed in a split molding tool, into which the desired workpiece shape is machined. The molding tool, which is mounted in a press, is closed by a press slide that operates vertically. The ends of the tubular piece are closed by closing tools, through which a pressure medium is delivered that presses the walls of the tube against the internal tool shape. An axial pressure is exerted on the tube by horizontally acting slides, and this axial pressure is superimposed on the internal pressure. Thus the material that is required for the reshaping is taken not only from the wall thickness of the tubular piece but is also made available by the shortening of the tube. The closing tools are axially fed during the reshaping. Employing such a method for producing a tubular wiper bracket with different cross-sectional shapes is also the subject of an earlier patent application. 
     SUMMARY OF THE INVENTION 
     According to the invention, the wiper bracket has a longitudinally elastically resilient region between the motor receptacle and the wiper bearing; this region is expediently formed in that the hollow profile in this region has alternating portions with a smaller and a larger diameter. If the flexural strength of the wiper bracket is reduced by this provision, then this can be compensated for according to a feature of the invention in that the mean diameter in the elastically resilient region is increased compared with the diameter in the adjacent regions. The mean diameter is defined as the arithmetic mean between the larger and the smaller diameters. It is essential that the resistance moment, which is decisive for the flexural strength, be increased by an increased outer contour, but without increasing the wall thickness that is definitive for the axial elasticity. The same is true for tubular profiles with a nonround cross section as well. 
     Because the rigidity in the axial direction is reduced, the peak load in the wiper arm and wiper bearing in the event of blockage or snow on the window is reduced. This applies above all in the region of the parking position and the reversal point of the wiper arm, or the extended and covering position between the crank of the wiper motor and a connecting rod. Since the components subjected to less stress can be smaller in size, there are savings in terms of cost and weight. 
     Disadvantages that might possibly arise from reduced flexural strength of the axially elastically resilient region can also be overcome by providing that this region is disposed in a portion of the hollow profile that is subjected to only little bending stress. Such regions are formed by straight portions of the hollow profile, which extend essentially parallel to a connecting rod and thus above all absorb tensile and compressive forces. 
     As a rule, elastically resilient regions will be provided on both sides of the wiper motor. Often, however, it will suffice to dispose an axially elastic region on only the passenger side of the wiper motor. As a result, the wiping quality on the driver&#39;s side is not impaired by the axial elasticity, and nevertheless the components are largely protected against an overload. 
     The different diameters can expediently be achieved by means of a pressing operation or an internal-high-pressure reshaping process. By pressing, in general only indentations can be made, by which the mean diameter in this region is reversed, but by the internal-high-pressure reshaping process, the diameter of the high-profile can be widened, so that the hollow profile of the wiper bracket can be widened in the region of the alternating diameters and thus gains a higher resistance moment and at the same time a greater axial elasticity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages will become apparent from the ensuing drawing description. In the drawing, exemplary embodiments of the invention are shown. The drawing, description and claims include numerous characteristics in combination. One skilled in the art will expediently consider each of the characteristics individually as well and make appropriate further combinations of them. 
     Shown are: 
     FIG. 1, a perspective view of a wiper bracket; 
     FIG. 2, an enlarged longitudinal section through a longitudinally elastically resilient region II in FIG. 1; 
     FIG. 3, a variant of FIG. 2; 
     FIG. 4, a variant of FIG. 3; 
     FIG. 5, a fragmentary section through an opened pressing die for producing an elastically resilient region; 
     FIG. 6, a fragmentary section through a closed pressing die of FIG. 5; 
     FIG. 7, a fragmentary section through an opened molding tool for producing an elastically resilient region by the internal-high-pressure reshaping method; and 
     FIG. 8, a fragmentary section through a closed molding tool of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A wiper bracket  10 , in an embodiment with hollow profiles  64 ,  72 ,  74 , also known as a tubular elbow plate or tubular frame, joins together two wiper bearings  12 ,  14  secured to its ends and a motor bracket  22  disposed between them. On the wiper bearings  12 ,  14  and on the motor bracket  22 , fastening eyelets  16 ,  18 ,  20  are provided, with which the wiper bracket  10  is secured to a vehicle body, not shown in further detail. 
     A wiper drive, which essentially comprises a motor shaft  28 , cranks  34 ,  36 ,  38 , connecting rods  46 ,  48 , and drive shafts  30 ,  32  for a window washer, not shown, is schematically indicated by dashed lines. A wiper motor, to which the motor shaft  28  belongs, is held on the motor bracket  22  via a motor receptacle  24  and drives the connecting rods  46  and  48  by way of its motor shaft  28  and the cranks  34 . The connecting rods  46  and  48  are connected via a joint  44  to the crank  34  of the motor shaft  28  and via further joints  40  and  42  on the other ends to the cranks  36  and  38 , respectively, which are secured to the drive shafts  30  and  32 . The direction of rotation  50  of the motor shaft  28  and the swiveling directions  52 ,  54  are indicated by arrows. 
     During the wiping motion of the window wiper, tensile and compressive forces, which are supported via the wiper bracket  10 , act on the connecting rods  46 ,  48  in the force regions  56  and  58 . If the window wiper is blocked by snow or otherwise, considerable peak loads occur, which have to be absorbed by the components, such as the wiper bearings  12 ,  14  and the wiper arms, not shown, mounted on the drive shafts  30 ,  32 . These components must be dimensioned with special strength to suit the maximum loads to be expected. To reduce the peak loads, axially elastically resilient regions  60  and  62  are provided on both sides of the motor bracket  22 ; in the event of blockage, they deform axially elastically and thus reduce the peak load. The axially elastically resilient regions  60  and  62  are expediently disposed in straight regions of the wiper bracket  10  that experience only slight bending moments and that extend essentially parallel to the connecting rods  46 ,  48 . 
     As a rule, the elastic regions  60  and  62  are provided on both sides of the motor bracket  22 . In many cases, however, one elastic region  60  on one side of the motor bracket  22  will suffice. That region should then expediently be located on the passenger side of the vehicle, so as to preclude impairment of the wiping quality on the driver&#39;s side of the vehicle during normal operation that could possibly occur from the greater elasticity. 
     FIG. 2 shows a hollow profile  64  with the elastically axially resilient region  60 , in which portions with a smaller diameter  66  alternate with portions of a greater diameter  68 . The hollow profile is devoid of obstructions therein. The portions with the smaller diameter  66  are formed by beads  80  which are pressed into the hollow profile  84 . The portions with the larger diameter  68  correspond to the diameter  70  of the adjacent region, compared to which the mean diameter of the elastic region  60 , resulting from the larger diameter  68  and the smaller diameter  66 , is reduced. The upper part of FIG. 2 shows how the region  60  lengthens elastically, under the influence of a tensile force  56 , by a distance  98 , while the middle part undergoes an elastic shortening by a distance  100  under the influence of a compressive force  58 . The lower part shows the region  60  without any load. 
     In the versions of FIGS. 3 and 4, the elastically resilient regions  60  are formed by a corrugated tube; indentations  90  are pressed in (FIG. 3) or protuberances  26  are deformed outward (FIG.  4 ), in each case beginning at a diameter  70 . The beads  80  and the indentations  90  can be made in the hollow profiles  64 ,  74  in a simple way by a pressing process. FIG. 5 shows an opened pressing form with an upper pressing die  76  and a lower pressing die  78 . Under the influence of the pressing forces  82  and  84 , the pressing tool  76 ,  78  is closed (FIG.  6 ), and the beads  80  are thus formed into the hollow profile  64 . A corrugated tube can be made with a suitable tool in the same way. 
     If the protuberances  26  extend past the diameter  70  of the adjacent part of the hollow profile  72 , then an internal-high-pressure reshaping method is expediently employed. In it, the hollow profile  72  is placed in a molding tool  86 ,  88 , whose upper molding tool  86  and lower molding tool  88  are closed by closing forces  94  and  96  and then kept closed. In order to form the molding tool from the inside by means of compressive forces  92 , the hollow profile  72  is subjected to a pressure medium (FIG.  8 ). As a result, diameters  66 ,  68  can be obtained in the elastically deformable region that produce a larger mean diameter than the diameter  70  in the adjacent regions, so that a higher resistance moment with a greater flexural strength is attained. As a result, despite a greater axial elasticity, the flexural strength can be kept the same or even increased. 
     LIST OF REFERENCE NUMERALS 
       10  Wiper bracket 
       12  Wiper bearing 
       14  Wiper bearing 
       16  Fastening eyelet 
       18  Fastening eyelet 
       20  Fastening eyelet 
       22  Motor bracket 
       24  Motor receptacle 
       26  Protuberance 
       28  Motor shaft 
       30  Drive shaft 
       32  Drive shaft 
       34  Crank 
       36  Crank 
       38  Crank 
       40  Joint 
       44  Joint 
       46  Connecting rod 
       48  Connecting rod 
       50  Direction of rotation 
       52  Swiveling direction 
       54  Swiveling direction 
       56  Force direction 
       58  Force direction 
       60  Elastic region 
       62  Elastic region 
       64  Hollow profile 
       66  Small diameter 
       68  Large diameter 
       70  Diameter 
       72  Hollow profile 
       74  Hollow profile 
       76  Upper pressing die 
       78  Lower pressing die 
       80  Bead 
       82  Pressing force 
       84  Pressing force 
       86  Upper molding tool 
       88  Lower molding tool 
       90  Indentations 
       92  Compressive force 
       94  Closing force 
       96  Closing force 
       98  Distance 
       100  Distance