Abstract:
A method for producing a windshield wiper bracket ( 10 ) with a U-shaped cross section, with two through holes ( 12 ) disposed in the legs ( 11 ) of the bracket ( 10 ), through which a rivet ( 13 ) extends, wherein the method includes the following steps: 
     production of through holes ( 12 ) in a flat bracket blank ( 14 ); 
     insertion of a rivet slug ( 15 ) into one of the through holes ( 12 ); 
     folding of the legs ( 11 ) to produce the U-shaped profile and to thereby position the rivet slug ( 15 ) in a position aligned with the other through hole ( 12 ); 
     sliding of the rivet slug ( 15 ) into the position extending through both of the through holes ( 12 ), and 
     riveting of the rivet slug ( 15 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method for producing a windshield wiper bracket of U-shaped cross section, with two through holes disposed in the legs of the bracket, through which a rivet extends. 
     The invention also relates to an apparatus for producing windshield wiper bracket of U-shaped cross section, where the apparatus includes folding means for producing a U-shaped profile from a flat bracket blank provided with two through holes, a positioning mechanism for sliding a rivet slug into the through holes, which are aligned with each other after production of the U-shaped profile, and deformation means for producing at least one rivet head on the rivet slug, according to the preamble to claim  8 . 
     Methods for producing a windshield wiper bracket of U-shaped cross section are known. With these known methods, a U-shaped bracket, whose two legs are provided with through holes that are aligned with each other, is formed in a first station. In a second station, a rivet slug is inserted through the two mutually aligned through holes in the U-shaped bracket in such a way that a free end of the rivet slug protrudes out from the corresponding through hole of the bracket. Then in a separate work cycle, the respective end of the rivet slug is wobbled to form a rivet head. This method for producing a U-shaped bracket with a rivet is relatively complex and time-consuming. 
     It is also known to provide a bracket, which is U-shaped and suitably embodied, with a roll rivet. In order to produce a roll rivet, the legs of the U-shaped bracket are disadvantageously weakened by means of suitable excisions so that an undesirable fracture of the roll rivet connection on the bracket can occur during operation of the windshield wiper. The roll rivet breaking off from the bracket like this can, for example, be caused by an occurrence of material fatigue. This known method for producing a U-shaped bracket while forming a roll rivet is also disadvantageously complex and time-consuming. 
     SUMMARY OF THE INVENTION 
     The method according to the invention includes the following steps: 
     production of through holes in a flat bracket blank; 
     insertion of a rivet slug into one of the through holes; 
     folding of the legs to produce the U-shaped profile and to thereby position of the rivet slug in a position aligned with the other through hole; 
     sliding of the rivet slug into the position extending through both of the through holes, and 
     riveting of the rivet slug. 
     By inserting a rivet slug into one of the two through holes of a flat bracket blank before the folding of the legs, it is possible to bring the rivet slug into the desired position aligned with regard to the two through holes while simultaneously producing the bracket with the U-shaped cross section. It is also possible to execute the sliding of the rivet slug into the position that extends through both through holes, together with the folding of the legs and the positioning of the rivet slug in one continuous work step by means of a single, suitably embodied tool. The production of a bracket with a U-shaped cross section while forming a rivet can consequently take place in a single manufacturing or processing station. 
     Preferably, the rivet slug is fixed in position in the bracket blank. This assures that the rivet slug is disposed in a definite position before and during the folding of the legs to produce the U-shaped profile of the bracket. Is also possible to use preassembled flat bracket blanks, each provided with the rivet slug fixed in position, in order to produce brackets with U-shaped cross sections for windshield wipers. 
     In order to fix it in position, the rivet slug is advantageously pressed into the through hole of the flat bracket blank, forming a press fit. A position fixing of the rivet slug in one of the two through holes of the bracket blanks by means of a press fit can be produced simply and reliably from a production engineering standpoint. The strength of the press fit between the rivet slug and bracket blank can be adapted with relative ease to each intended application, i.e. depending on the wall thickness of the bracket blank and the diameter of the rivet slug. As a result, in particular the method steps of sliding and riveting of the rivet slug can be controlled and/or adjusted in a reliable and effective manner. Furthermore, using a press fit to fix the position of the rivet slug assures that after the folding of the legs and during the sliding of the rivet slug, it aligns exactly with the other through hole and no shifting of the rivet slug in relation to the through holes occurs, which would hinder the sliding of the rivet slug. 
     Preferably by means of an entry bevel in operational contact with a rivet edge, the rivet slug is pushed into the other through hole of the U-shaped bracket until the rivet slug protrudes out from the through holes with its ends. Because of the definite starting position (press fit) of the rivet slug in one of the through holes of the bracket blank, it is possible after the folding of the legs, to easily and reliably slide the rivet slug out of its initial position into the end position extending through both of the through holes. In this connection, it is particularly important that the rivet slug protrudes out from the through holes in the end position so that it is possible to produce rivet heads (riveting of the rivet slug). From a production engineering standpoint, an entry bevel is relatively easy and inexpensive to produce in a corresponding manufacturing tool. 
     According to a preferred embodiment, the ends of the rivet slug protruding out from the U-shaped bracket are plastically deformed by means of a wobbling process to form a respective rivet head. From a process engineering standpoint, it is particularly favorable to form rivet heads on the free ends of the rivet slug protruding out from the through holes of the bracket with the U-shaped cross section, preferably simultaneously by means of a wobbling process. As a result, the bracket with the U-shaped cross section, with the rivet slug disposed in the aligned position, can maintain its original position and does not have to be brought into a special and/or new working position for the formation of the rivet heads. A wobbling process for producing a rivet head is particularly advantageous with regard to a correct and controllable material deformation on the corresponding rivet slug end. The desired and/or necessary exertion of force and consequently the material deformation for producing the rivet head can be adapted to each intended application by suitably varying the wobbling process (deformation force, adjustment angle, wobbling speed). 
     Advantageously, the two ends of the rivet slug are plastically deformed simultaneously. The formation of both of the ends protruding out from the through holes of the bracket into respective rivet heads permits a rapid and effective rivet production on the bracket with the U-shaped cross section. 
     Advantageously, the rivet slug is stabilized in its shaft part between the legs during the plastic deformation of the two ends. This effectively prevents the rivet slug from buckling during the production of the rivet heads. It is consequently easily possible to produce a correct and particularly stable rivet connection between the legs of the bracket. 
     According to the invention, the apparatus is characterized in that the folding means, the positioning mechanism, and the deformation means are disposed in a single processing station. The production of a bracket with a U-shaped cross section and a rivet contained in it in a single processing station is particularly favorable from a production engineering standpoint because this eliminates the transport time and/or waiting time that would otherwise occur during the manufacturing process. Furthermore, a folding of the legs, and a sliding and riveting of the rivet slug in a single processing station permits a bracket to be produced with relative ease while fulfilling particularly high precision requirements since the manufacturing tolerances in the bracket and/or the rivet, which arise due to the use of a number of processing means working in various stations, can be completely or at least partially eliminated. Furthermore, the manufacturing means used can be disposed in a single station in a particularly space-saving manner. 
     Advantageously, the folding means are embodied as dies which can be moved toward and away from each other in a linear fashion. Dies are tools which are particularly well suited for folding the legs to produce a profile with a U-shaped cross section since they can be produced with relative ease and can be favorably adapted to various intended applications through corresponding geometric embodiments. 
     The positioning mechanism is advantageously embodied as an entry bevel on one of the dies. The die provided with the entry bevel therefore simultaneously has two different operating functions, namely folding the legs to produce the U-shaped profile and sliding the rivet slug into the position extending through both through holes. From a production engineering standpoint, it is particularly easy to produce an entry bevel on one of the dies. Furthermore, an entry bevel on a die permits a relatively exact and reliable sliding of the rivet slug into the desired final position in the bracket. 
     Preferably, the deformation means are embodied as movable deformation elements. Movable deformation elements permit a precise deformation of the ends of the rivet slug protruding out from the through holes into respective rivet heads and this deformation can be adapted to the respective intended application. 
     According to a preferred embodiment, the entry bevel is embodied as a linear, straight guide edge. Using a linear, straight guide edge as the entry bevel assures a continuous sliding of the rivet slug into the position extending through both through holes. In an alternative embodiment and depending on the respective intended application, the entry bevel can also be embodied as a curved guide edge. 
     Preferably the deformation elements are embodied as cups which execute a wobbling motion. In this manner, it is possible for the ends of the rivet slug protruding out from the through holes to be plastically deformed into rivet heads by means of a wobbling process. In this connection, the wobbling motion of the cups, i.e. in particular the adjustment angle and the deformation force, can be adapted to the respective material and/or geometrical parameters of the rivet slug and/or the bracket with the U-shaped cross section. 
     The apparatus advantageously has a stabilization mechanism for the rivet part disposed between the legs of the U-shaped profile during the production of the rivet head. The stabilization mechanism prevents the rivet slug from buckling in its rivet part disposed between the legs of the U-shaped profile during the production of the rivet head due to the processing forces being exerted. 
     The dies are advantageously provided with a recess in the pivot region of the rivet slug. Providing a recess in the dies prevents the rivet slug that is inserted into one of the two through holes of the flat bracket blank from colliding with the die bodies during the folding of the legs to produce the U-shaped profile, since the rivet slug also necessarily executes a pivoting motion during the folding of the legs. 
     Preferably, the apparatus is operatively connected to a vibrator for supplying rivet slugs. Using a vibrator is a particularly reliable way to supply the apparatus with a large number of rivet slugs in succession, rapidly and in a definite position. 
     The apparatus advantageously has a reference element for the exact positioning of the flat bracket blank between the dies. In order to obtain a precise alignment of the two through holes after the production of the U-shaped profile, the flat bracket blank must be disposed in a correspondingly precise position with regard to the dies. In this connection, it is particularly advantageous to provide a reference element which comes into contact with a reference point or a reference line of the flat bracket blank and consequently permits an exact positioning of the flat bracket blank between the dies. A reference point or a reference line can be disposed on an edge of one of the through holes or another opening and/or edge of the flat bracket blank. 
     Other advantageous embodiments of the invention ensue from the description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in detail below in an exemplary embodiment in conjunction with accompanying drawings. 
     FIG. 1 is a schematic side view of an apparatus according to the invention, with a flat bracket blank; 
     FIG. 2 is a schematic side view of the apparatus according to FIG. 1, during the folding of the bracket blank; 
     FIGS. 3 and 4 are schematic side views of the apparatus according to FIG. 2, with continuing folding of the bracket blank; 
     FIG. 5 is a schematic side view of the apparatus according to FIG. 4, with an almost completed folding of the bracket blank; 
     FIG. 6 is a schematic side view of the apparatus according to FIG. 5, with a rivet slug in a position aligned with two through holes of the bracket blank; 
     FIG. 7 is a schematic side view of the apparatus during the riveting of the rivet slug; 
     FIG. 8 is a schematic side view of the apparatus during the riveting, which is rotated by 90° in relation to FIG. 5, and 
     FIG. 9 is a schematic top view of a detail of the flat bracket blank according to FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a flat bracket blank  14  which is provided with two through holes  12  that are spaced apart from each other. A rivet slug  15  is fixed in position in one of the two through holes  12 , by means of a press fit. The flat bracket blank  14  is secured by an apparatus  19 , which includes two upper dies  23  and one lower die  22 , in such a way that a central section of the bracket blank  14  rests against an end face of the lower die  22  and two lateral outer sections of the bracket blank  14  protrude beyond the end face of the lower die  22 . The upper dies  23  of the apparatus  19 , which are disposed opposite from the lower die  22  and laterally spaced apart from it, rest with their corresponding end faces against the lateral sections of the flat bracket blank  14 , which protrude out beyond the lower die  22 . The lower die  22  and the two upper dies  23  can be moved toward and away from each other in accordance with the arrows  24  and  25  simultaneously or successively in such a way that the flat bracket blank  14  disposed between the lower die  22  and the upper dies  23  can be deformed into a bracket  10  with a U-shaped cross section. In the vicinity of the rivet slug  15 , the lower die  22  and the corresponding upper die  23  are each provided with a suitable recess  26 ,  27  in order to prevent an undesirable collision of the rivet slug  15  with the dies  22 ,  23  resting against the bracket blank  14  during the deformation of the flat bracket blank  14  into a bracket  10  with a U-shaped cross section. 
     As shown in FIG. 9, the flat bracket blank  14  has a central, longitudinal, slot-like through opening  21  and two transversal, slot-like through openings  34 . The longitudinal through opening  21  and the two transversal through openings  34  are directly connected to each other and combine to form an H-shape, where the two through holes  12  are disposed on a common transversal axis between the two transversal through openings and spaced equidistantly apart from the longitudinal through opening  21 . Both the through holes  12  and the through openings  21 ,  34  can be produced by being suitably punched out of the flat bracket blank  14 . Preferably, such a punch processing of the flat bracket blank  14  takes place in a processing station separate from the apparatus  19 . 
     According to FIG. 1, the apparatus  19  has a reference element  33 , which is disposed between the two upper dies  23  and protrudes with a free end into the central, longitudinal through opening  21  of the flat bracket blank  14  in order to assure an exact disposition of the flat bracket blank  14  symmetrical to the dies  22 ,  23 . In the current exemplary embodiment, the free end of the reference element  33  protrudes through the longitudinal through opening  21  into the recess  26  of the lower die  22 , where the reference element  33  is embodied in such a way that a collision between the bracket blank  14  and the reference element  33  is prevented while the flat bracket blank  14  is being deformed into a U-shaped bracket  10 . 
     FIGS. 2 to  5  show different phases of the folding of two legs  11  of the initially flat bracket blank  14  (see FIG. 1) in order to produce a desired U-shaped profile. To this end, the lower die  22  and/or the two upper dies  23  are moved toward one another according to the arrows  24 ,  25  so that as a result of the deformation force introduced into the bracket blank  14  by the deformation edges  28  of the lower die  22  and by the respective deformation edge  29  of the upper dies  23 , the legs  11  of the bracket  10  are plastically bent and pivoted in such a way that the originally flat bracket blank  14  (see FIG. 1) is formed into a bracket  10  with a U-shaped cross section (see FIG.  5 ). With this plastic deformation of the flat bracket blank  14  into a U-shaped profile, the rivet slug  15  that is fixed in position in one of the two through holes  12  is pivoted from an initial position (see FIG. 1) by preferably 90° in accordance with the movement of the legs  11  in such a way that it assumes a position that is aligned with the two through holes  12 . During the folding of the legs  11  to produce the U-shaped profile according to FIGS. 2 to  5 , an access opening  30  is unblocked (see FIG. 5) whose longitudinal span corresponds to that of the longitudinal through opening  21  and whose lateral span corresponds to the length of the transversal through opening  34 . As a result, the length of the transversal through openings  34  extends over the entire width of the top edge  31  of the bracket  10  with the U-shaped cross section. Because of an access opening  30 , which is embodied in this way and can be obtained through suitable preparation of the flat bracket blank  14  (through openings  21 ,  34 ), it is possible for the legs  11  of the bracket  10  not to be exposed to any plastic deformation in the vicinity of the rivet slug  15 , but instead to be pivoted as flat edges from a horizontal starting position shown in FIG. 1 into a vertical end position according to FIG.  6 . 
     Immediately after the folding of the legs  11  to produce the U-shaped profile and the positioning of the rivet slug  15  in a position that is aligned in relation to the two through holes  12 , further movement of the lower die  22  and/or the upper dies  23  toward one another according to the arrows  25 ,  24  causes the rivet slug  15 , which is fixed in position in one of the two through holes  12  by means of a press fit, to be slid toward the other through hole  12 . FIG. 6 shows the apparatus  19  and the U-shaped bracket  10  after the rivet slug  15  has been slid into the other through hole  12  of the bracket  10  with the U-shaped cross section. This sliding of the rivet slug  15  is caused by an entry bevel  16  on one of the upper dies  23 , which comes into operative contact with a contact edge  32  of the rivet slug  15  when there is a relative motion between the dies  22 ,  23  according to the arrows  24 ,  25 . With this operative contact, the entry bevel  16 , which is inclined in relation to the rivet slug  15  end face containing the contact edge  32 , transmits a corresponding compressive force onto the contact edge  32  with a sliding motion of the lower die  22  and/or the upper dies  23  according to the arrows  25 ,  24 . Because of this compressive force transmitted to the contact edge  32  by the entry bevel  16 , the rivet slug  15  is slid by means of the one through hole  12  (press fit) in such a way that its free end disposed inside the U-shaped profile enters into the second, aligned through hole  12  of the bracket  10 . As a result, the rivet slug  15  is slid, aligned with the through holes  12 , until both of its free ends protrude out from the two through holes  12  (not shown in FIG.  6 ). In the current exemplary embodiment, the entry bevel  16  is embodied as a linear, straight guide edge. 
     FIG. 7 shows deformation means  18  of the apparatus  19  for producing two rivet heads  17  on the rivet slug  15 . The deformation means  18  consequently execute the riveting of the rivet slug  15  and are embodied as movable deformation elements  18  in the form of cups which can execute a wobbling motion in relation to a longitudinal axis of the rivet slug  15 . The two ends of the rivet slug  15  protruding out from the through holes  12  are plastically deformed by the movable cups  18  of the apparatus  19 , each forming a respective rivet head  17 . The deformation of the ends of the rivet slug  15  preferably takes place by means of the wobbling process. To this end, the cups  18  execute an adjustable and controllable wobbling motion in relation to the ends of the rivet slug  15 . 
     FIG. 8 shows the apparatus according to FIG. 7 rotated by 90°. In order to prevent the rivet slug  15  from buckling during riveting, i.e. during the plastic deformation of the ends of the rivet slug  15  by means of the cups  18  executing a wobbling motion, the apparatus  19  has a core piece  20  (see FIG.  8 ). The core piece  20  stabilizes the shaft of the rivet slug  15  extending between the two legs  11  and consequently prevents an undesirable elastic and/or plastic deformation of the rivet slug  15  between the two legs  11 . In this manner, the core piece  20  functions as a stabilization mechanism for the rivet part disposed between the legs  11  during the production of the rivet heads  17 . Preferably, the core piece  20  extends over the entire shaft length of the rivet slug  15  between the legs  11  of the bracket  10  with the U-shaped cross section so that it rests in contact with the inside of the two legs  11  of the bracket  10  and consequently also effectively prevents undesirable elastic and/or plastic deformations of the legs  11  during the riveting of the rivet slug  15 . The core piece  20  has a receiving seat that encompasses the shaft of the rivet slug  15  by approximately 180°. 
     According to the embodiment shown in FIG. 7, the two ends of the rivet slug  15  are plastically deformed by the two movable cups  18  simultaneously in a double wobble riveting process. After the production of the rivet  13 , it is non-rotatably anchored in the through holes  12  of the legs  11  of the bracket  10  with the U-shaped cross section. 
     According to an embodiment that is not shown, the rivet slug  15  can also be already provided with a rivet head on one of its two ends, i.e. on the end which protrudes out from the bracket  10  after the legs  11  are folded to produce the U-shaped profile. According to this other embodiment, the entry bevel  16  of the corresponding upper die  23  comes into operative connection with the prefabricated rivet head and causes the rivet slug  15  to slide with its as yet unprocessed free end through the corresponding opposite through hole  12 . Consequently, in order to produce the rivet  13 , the rivet slug  15  is plastically deformed at only one end and only one movable cup  18  deforms the as yet unprocessed end of the rivet slug  15  to form a rivet head by means of a one-ended wobbling process. 
     The flat bracket blank  14  can be prefabricated in a separate section, i.e. punch-processed, or with a suitable embodiment of the apparatus  19  (additional disposition of corresponding punching tools), can also be pre-punched and then formed into a bracket  10  with a U-shaped cross section and a rivet  13  in a single station. 
     The cylindrical rivet slugs  15  can be rapidly and reliably supplied to the apparatus  19  in a vertical position by means of a vibrator that is not shown and can then be slid by means of suitable tools into one of the two through holes  12  of the rivet slug  15 , forming a press fit. 
     It is consequently advantageously possible to execute work steps which were previously carried out in separate processing stations (folding of the legs, sliding of the rivet slug, positioning of the rivet slug) in a single station. The folding of the legs  11  to produce the U-shaped profile and the sliding of the rivet slug  15  into position extending through both through holes  12  consequently take place in a single work step in which the dies  22 ,  23  are simply moved toward each other in the direction of the arrows  25 ,  24 . This represents a reduction in the number of work cycles and a simple, reliable, and rapid production of a bracket  10  with a U-shaped cross section and a rivet  13 . It is possible to produce a bracket  10  with a U-shaped cross section and a stable rivet connection in a single apparatus. In addition, through the use of the stabilizing mechanism  20  (core piece), it is possible to produce a bracket  10  with thinner walls while maintaining the same stability.