Abstract:
The invention relates to a method for producing lamella packets ( 60, 70 ) of the type normally used in adjustable steering columns in automobiles and which comprise a soft lamella ( 71 ) made of soft sheet metal material and at least one layered hard lamella ( 71 ) placed on top of said material. The lamella ( 71, 74 ) are connected by at least one rivet made of soft lamella ( 71 ). The method is characterized by the use of presses ( 110, 120 ) positioned one after the other. A soft lamella ( 71 ) is formed and stamped out of a strip ( 111 ) of said softer material in the first press ( 110 ) at a rate dictated by the press ( 110 ). Soft lamella ( 71 ) produced in this matter are transported to the second press ( 120 ). At least one hard lamella ( 72, 74 ) is completely formed in a second press ( 120 ) from a band ( 121 ) of harder sheet material and then stamped. Said hard lamella is placed over a soft lamella ( 71 ) and a rivet connection is produced.

Description:
TECHNICAL FIELD 
     The present invention relates to a method for producing lamella packets of the type normally used in adjustable steering columns in automobiles, which prevent slippage and unintended adjustment of the steering column by means of a plurality of friction surfaces. The lamella packets comprise a soft lamella made of a relatively soft sheet metal material and at least one hard lamella placed thereon and made of a relatively hard sheet metal material. The lamellae in the packets are joined by at least one rivet, which is formed, respectively, from the soft lamella. 
     PRIOR ART 
     Such lamella packets are known in the art and comprise on the one hand packets with so-called longitudinal lamellae and on the other hand packets with so-called height lamellae. The individual lamellae within the packets are spaced apart by a distance corresponding approximately to their thickness. One packet of longitudinal lamellae and one packet of height lamellae, respectively, form an associated pair. The two packets of each pair are then pushed together such that longitudinal lamellae and height lamellae alternate in the stack. On their mutual contact surfaces, the lamellae are in part provided with specially structured friction surfaces. 
     A pair each of the aforementioned lamella packets is arranged on either side of a so-called guide box, which holds the bearings for the steering column. Each longitudinal lamella packet is fixed to the guide box by means of fastening eyes, while each height lamella pair is mounted to a support strap, which in turn is fixed to the chassis, also by means of fastening eyes. A tension bolt penetrates the guide box as well as all the lamellae. For this purpose, guide slots are provided on the lamellae. 
     The adjustability of the steering column is due to the fact that the mutually meshing lamella packets can be displaced as well as pivoted relative to one another. The displacement or pivoting range is limited by the length of the aforementioned guide slots in the lamellae. To fix the steering column in a desired position, the tension bolt is tightened so as to press together the aforementioned friction surfaces on the lamellae. 
     It goes without saying that—for a given tension force of the tension bolt—the resulting total friction force or holding force can be correlated with the number of lamellae in the lamella packets and adjusted in a simple manner by selecting this number. 
     To keep the lamellae in the prior art lamella packets spaced at the desired distance, some of them are provided with a collar that is formed out of the lamellar plane in the area of the aforementioned fastening eyes. The initially mentioned rivet by which the individual lamellae of each packet are held together is also formed by such a collar, which is shaped on one of the two outermost lamellae of each packet—the so-called soft lamella—at one of the fastening eyes, to the point where it is capable of penetrating the corresponding fastening eyes of the remaining lamellae. On the far side of the opposite outermost lamella, this collar is then shaped outwardly around the edge of the fastening eye of that lamella. 
     DESCRIPTION OF THE INVENTION 
     The invention, as described in the claims, defines a manufacturing concept (method) that permits efficient automatic production and assembly of the lamella packets of the described type. 
     According to claim  1 , this method is characterized, in particular, by the use of two successive presses. At a rate defined by the first press 
     a soft lamella is completely formed and stamped from a strip of the softer sheet metal material in the first press, 
     a soft lamella thus produced is transported to the second press, 
     at least one hard lamella is completely formed and stamped from a strip of the harder sheet metal material and placed over a soft lamella in the second press, and the riveted connection is produced. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     The invention will now be described in greater detail by means of an exemplary embodiment with reference to the drawing in which 
     FIG. 1 shows the core piece of an adjustable steering column in an automobile with a packet of longitudinal lamellae and a packet of height lamellae, 
     FIG. 2 shows the two lamella packets in cross section (I-I in FIG. 5 b ), 
     FIG. 3 is an enlarged detail (section line II-II in FIG. 2) of a lamella packet with a riveted connection, 
     FIG. 4 is a schematic representation of a system to implement the method according to the invention, and 
     FIG. 5 under a) and b) shows a top view onto a work holder used in the arrangement according to FIG. 4, with a packet of height lamellae and a packet of longitudinal lamellae. 
    
    
     METHODS FOR IMPLEMENTING THE INVENTION 
     FIG. 1 illustrates an arrangement of the above-described type.  10  identifies the axis of a steering column,  20  a guide box,  30  and  40  two bearings for the steering column inside the guide box,  50  a partially depicted support strap fixed to the chassis and arranged bridge-like over the guide box  20 , and  60  and  70  two lamella packets. Lamella packet  60  is fastened to support strap  50  by means of two eyes  65 ,  66  and lamella packet  70  to guide box  20  by means of two eyes  75  and  76 . A corresponding pair of lamella packets, not visible in FIG. 1, is arranged and fixed behind guide box  20  in the same manner as pair  60  and  70 . The lamellae of packet  60  have a vertically extending guide slot  67  for adjusting the height of the steering column and are therefore referred to as height lamella. A corresponding guide slot  77 , but substantially horizontal, is also provided in the lamellae of packet  70  and is used to adjust the steering column in longitudinal direction. The lamellae of packet  70  are therefore referred to as longitudinal lamellae. A tension bolt  80  that is held in the guide box penetrates the guide slots  67 ,  77  of lamella packets  60  and  70 , that is to say of both pairs in front of and behind guide box  20 . When tension bolt  80  is loosened, the longitudinal lamellae, and with them, via guide box  20 , the steering column can be displaced and pivoted in height and length relative to the height lamellae and thus, via support strap  50 , relative to the chassis. The adjustment range is defined and limited by guide slots  67  and  77 . The steering column can be locked in each desired position and pivot position of the adjustment range by tightening tension bolt  80 . This may be accomplished, for instance, by means of a schematically indicated locking lever  90 . Tightening causes the friction surfaces of the lamellae to be pressed together. 
     FIG. 2 is a section along line I-I in FIG. 5 b ) through the two lamella packets  60  and  70 , shown here with four lamellae  61 - 64  and  71 - 74 , respectively. In principle, there could also be only two or three lamella, or possibly more. Nor does the number of lamellae in the two packets have to be the same. As may be seen, the individual lamellae  61 - 64  and  71 - 74  of the two packets  60  and  70  are spaced apart at a distance that corresponds approximately to their thickness. Thus, the packets can mesh such that a lamella of one packet is followed by a lamella of the other packet in the stack. The mutual distance of the lamellae is defined and maintained by collars, which are formed on three ( 61 - 63  and  71 - 73 ) out of the four ( 61 - 64  and  71 - 74 ) lamellae of each packet, as shown in FIG. 2, along the edges of eyes  75  and  78  (as well as  65  and  66 ). In the area of their mutual contact surfaces, the lamellae may be provided with some structuring, corrugation, or the like ( 78  in FIG. 1) to increase their mutual frictional resistance. The uppermost lamella  61  of packet  60  is also provided with a trough-like shaping  68  around guide slot  67 , which serves as a guide for head  81  of tension bolt  80 . 
     FIG. 3 shows the area of eye  75  of lamella packet  70  in cross section (II-II in FIG.  2 ). The aforementioned collars are clearly visible here. FIG. 3 further shows a rivet connection, which holds the lamella packet  70  together. To form this rivet connection, the material of the lowest lamella  71  is pulled up far enough that it penetrates all the remaining lamellae  72 - 74  and can be shaped around the topmost lamella  74 . A corresponding rivet connection is provided in eye  66  of packet  60 . 
     Due to the material deformation required to form the rivet connection, which can be quite substantial In part depending on the number of lamellae within the packet, the corresponding lamella, e.g. lamella  71 , is made from a sheet metal material that is slightly softer and can therefore be shaped more easily than the material used for the remaining lamellae. The latter material should be relatively hard so that the aforementioned corrugation or structuring of the friction surfaces is durable. For this reason, the individual lamella packets each comprise a soft and one or more hard lamellae. 
     FIG. 4 shows a system for implementing the method according to the invention, which permits efficient automatic production and assembly of lamella packets of the above-described type. 
     The system of FIG. 4 comprises two presses  110  and  120 , a handling station  130 , a packing station  140 , and a conveyor system  150  connecting all these elements in a closed circuit. A plurality of work holders, only one of which is identified as  160 , circulate within the-circuit in the direction of the arrows. The first press  110  is supplied with an endless strip  111  of a relatively soft sheet metal material to produce soft lamellae and the second press with an endless strip of a relatively hard sheet metal material  121  to produce hard lamellae. 
     In front of press  110  the work holders  160  are empty. At the rate dictated by the first press  110 , one empty work holder  160  is introduced into press  110 , while another that has just been loaded is removed therefrom and transported to the second press. In the first press  110 , two soft lamella (a height lamella and a longitudinal lamella) are stamped in parallel from sheet metal material  111  and completely shaped including the collar for the aforementioned rivet connection in several sequential steps (one step per cycle) by means of a so-called progressive die, and are placed side by side on the empty work holder present. Final separation from the strip takes place only in the last step. 
     At the rate determined by the first press  110 , a work holder carrying two soft lamellae side by side is introduced into the second press  120  one station downstream, while another that has just been loaded is removed therefrom and transported to the handling station  130 . In the second press  120 , essentially the same process takes place as in the first press  110 , except that here hard lamellae are produced from the harder sheet metal material  121  and are placed onto the work holder over the previously deposited soft lamellae. In the last step executed in the second press  120 , the rivet connection is produced by shaping the corresponding upwardly protruding collar on the soft lamella around the hard lamella. 
     If the lamella packets to be produced are intended to comprise several hard lamellae, the second press  120  must be operated at a correspondingly higher rate than the first press. A problem results from the fact that the hard lamellae of the same packet, as illustrated also in the example of FIG. 3, are shaped differently from one another, especially with respect to the spacer collar and possibly also with respect to their structuring on the friction surfaces. This can be resolved, however, by using a controlled progressive die, which is capable of executing different actions in the same position in consecutive steps. Consequently, if several hard lamellae are used, the collar on the soft lamella to produce the rivet connection can be shaped only when the last hard lamella is placed on the stack and not before. 
     In handling station  130 , the two lamella packets lying side by side on work holders  160  as illustrated in FIG. 5 a  are pushed together into their functional position on work holders  160  as shown in FIG. 5 b . To accomplish this without problems, a type of comb precisely determines the spacing of the lamellae. 
     In packing station  140 , the lamella packets, which are pushed together in this manner in pairs and thereby save space, are finally transferred from the work holders  160  onto prepared blister pack holders  170 . A single pack-holder can receive several lamella packets. The work holders  160  are then free to pick up new lamellae in the first press  110 .