WO1999010118A1

WO1999010118A1 - Method and device for producing an essentially v-shaped double spoke comprising a connection rod by means of a bending cold forging technique and using this method for the production and application of the double spoke

Info

Publication number: WO1999010118A1
Application number: PCT/EP1998/005396
Authority: WO
Inventors: Volker Müller; Manfred Fehn; Hans Sommer; Richard Langbein; Karl-Heinz Koburger
Original assignee: C.M.T.M. Dr. Müller Verfahrenstechnik Gmbh
Priority date: 1997-08-27
Filing date: 1998-08-25
Publication date: 1999-03-04
Also published as: AU9436898A

Abstract

The invention relates to a method and device for producing an essentially v-shaped double spoke comprising a connection rod by means of bending a wire using a cold forging technique. According to the invention, the v-shape is obtained in one free bending step without interlocking tension or clamping of the wire by means of a v-shaping bending punch (6), said bending punch being guided and pressed against a bending forging die (7) which is complementary to the bending punch, whereby the limbs are configured with varying lengths. A directed pintle (13) which is guided inside said forging die (7) and faces the bending base is engaged in a second step. The pintle (13) contains a bending segment (15) arranged with respect to an eccentrical axis of rotation and is connected to the pintle (13). Said bending segment (15) swivels around the rotational axis. The bending segment (15) rotates and comes in contact with the lower limb segment located in the bending base. During rotation of the bending segment (15), the limbs which are provided in a direction of rotation and are staggered in relation to opposite lying edges preferably pertaining to the forging die in order to form the connecting rod which is inclined with respect to the axis of the limbs come to a stop. Whereby, during a second bending step, the longer limb withdraws or shortens in line with the free step height of the stop allocated thereto and, according to the dimensions of the bending segment (15), is substantially identical to the limb which was originally shorter until it fully comes to rest on the edge allocated thereto.

Description

Method and device for producing an essentially V-shaped double spoke having a connecting web by means of cold bending and forming, and double spoke produced according to this method, and use of the double spoke

description

The invention relates to a method and a device for producing an essentially V-shaped double spoke having a connecting web by means of bending and cold forming, as well as a double spoke produced by this method and the use thereof.

From the German patent application DE 35 15 939 AI a spoke wheel is known which has spokes that have a double offset. The legs of the spokes emanating from the known double bend enclose a predetermined angle which results from a desired crossing scheme, the number of spokes and the height of the flange on the wheel hub. Both ends of the spokes are each provided with a thread for screwing on fasteners. The double spoke described in DE 35 15 939 AI is to be produced by means of bending, the bending radius of the cranks being adapted to the requirements of the material or the embodiment of the bores in the wheel hub and their countersinking.

With the double spoke in accordance with German utility model 70 29 373.1, a central bend in the form of a hairpin is necessary, the essential bending radius for this leading to considerable bending forces and undesirable changes in texture in the spoke wire. The same applies to the spokes of the spoke wheel according to DE 40 36 340 AI, the eyelet or U-shaped loop necessary there for fastening to the hub correspondingly requiring complex deformation steps and a high manufacturing outlay associated therewith. With regard to the spoke material, galvanized carbon steel is widely used, but tends to corrode after a certain period of use or under certain conditions. These difficulties do not exist with standard stainless steel spokes on the market, although in comparison to carbon steel, spoke breaks occur more frequently due to signs of fatigue. These undesirable spoke breaks are due to the vibration load and the resulting structural changes in the stainless steel, which increase the brittleness of the material. The bending point on the usual spoke head is predestined for this fracture, which is already preloaded due to the shape during the manufacture of the spoke.

One solution to the above problem is the production of spokes made of stainless steel-coated carbon steel. While the core wire made of carbon steel ensures mechanical resilience, the stainless steel sheath, which has an approx. 20% cross-section, offers sufficient corrosion protection. However, this corrosion protection is not provided on the cut surfaces of the spoke wire because the core wire is exposed there. The threaded end of a spoke made of such a composite material is largely protected against corrosion after assembly by the nipple into which the spoke is screwed. The spoke head always has a corrosion-sensitive area on the top. Locking this point permanently and corrosion-proof during spoke production is, however, very complex on the manufacturing side.

In principle, there is now the possibility of using the composite wire material mentioned in connection with the solutions described above for a double spoke. However, it has been found that, as already mentioned, the bending processes which have become known and used so far, ultimately also due to the necessary bending shape, lead to an undesirable change in structure and texture also in the composite material. However, this inhomogeneous texture of the spoke material, which results from known bending processes, gives rise to problems with the later load change stress, so that there is not sufficient long-term stability and reliability of the spoke.

It is therefore an object of the invention to provide a method and an apparatus for producing an essentially V-shaped double spoke having a connecting web by means of cold-bending a wire, the bending processes and thus the bending effort to be reduced and ensuring that disturbances of the homogeneous texture of the starting material can be largely avoided. In addition, the invention, in particular on the device side, is intended to provide a solution which makes it possible to reduce the manufacturing costs by reducing the effort for the tool. Ultimately, a double spoke is to be specified, which has a homogeneous texture of the material used and which can be used in conventional spoke wheels without any further structural changes.

The object of the invention is achieved with a method in its definition according to patent claim 1 and with a device according to the features of patent claim 3 and with reference to the double spoke according to patent claim 11. The respective subclaims include at least expedient refinements and developments of the invention.

According to a basic concept of the invention in terms of the process, a two-step bending process is used in the manufacture of the double spoke having a connecting web, a so-called free bending basically taking place, i.e. during bending, the workpiece, i.e. the spoke wire, no such force is applied that leads to material tension or a clamping in the bending tool.

In a first bending step, the V-shape of the double spoke is created by means of a punch and a bending die, the connecting web being formed in the second step. The first free bending step, which is carried out without positive clamping or clamping by means of a V-shaped bending punch, which is pressed against a bending die that is complementary to the bending punch, also ensures that the pretreated wire sections, which already have threads on the wire ends, are appropriately fed with material have, in their V-shape then legs of different lengths, so that the connecting web can be formed in the second bending step described below.

In the second, following the first free bending step, a pivot pin guided in the bending die and directed towards the base of the bending is used, the pivot pin having a bending segment which is arranged eccentrically to the axis of rotation of the bolt and is connected to the bolt. This bending segment can be pivoted together with the bolt about its axis of rotation, and when the bending segment is rotated it comes into operative connection with the lower leg portion of the spoke wire located in the bending base.

When the bending segment is rotated, the limbs come into abutment at edges which are offset in the direction of rotation and are offset and are preferably formed on or connected to the die, and the connecting web which is angled to the limb axis is formed. During the second bending step, the longer leg retracts to the essentially same length of the original shorter leg until it lies completely against the associated edge, in accordance with the free step height of the stop assigned to it and the dimensions of the bending segment.

In the second bending step, too, the workpiece, ie the spoke wire, is not clamped or clamped, but moves freely towards the stops or along the respective stop, so that the wire material can flow freely during the bending process without any changes in the texture or structure of the material. materials occur. According to one embodiment of the invention, in the second bending step, the bending die remains in the die without, however, clamping stresses or clamping forces being exerted on the V-shaped wire.

The basic concept of the device on the device side is to start from a bending die which has a V-shaped recess, the flanks of the recess enclosing a predetermined angle, for example in the range from 106 ° to 115 °. According to the invention, on the flanks of the bending die, a fixed and / or adjustable edge forming a workpiece stop is arranged opposite and offset by a lateral distance. These edges run essentially perpendicular to the V-shaped groove in the bending die.

In the bending die, a pivot pin directed towards the bending base is also movably guided, the pivot pin interacting with a drive device. The surface directed towards the bending base of the pivot pin has a possibly interchangeable bending segment which is arranged eccentrically to the axis of rotation and which, during rotational movements, has a frictional or frictional engagement with the workpiece, i.e. the preformed spoke wire. When executing the preferably 90 ° rotating or pivoting movement of the pivot pin or. of the bending segment, the wire, which is located in the bending die, is then taken along by the bending segment and moved along the associated stop edge until the deformation and the web formation have been completed and the corresponding leg end lies completely against the assigned edge.

The bending punch forming the tool is designed to be complementary to the bending die in order to obtain the desired bent part workpiece shape, whereby it is alternatively possible to use the mentioned workpiece stops, i.e. to form the edges on the bending punch.

To ensure variable use of the tool even with different wire materials, wire diameters or wire To enable shapes, the bending segment is interchangeable and the pivot pin is axially guided and movably or adjustably arranged in the bending die.

According to the invention, the width of the connecting web results from the eccentric position and the dimensions of the bending segment in connection with the distance dimension and the position of the stop edges.

According to one embodiment of the invention, the bending segment can have a receiving slot, matched to the wire diameter, or the shape of a circular segment.

The double spoke manufactured with the method according to the invention described above thus has an angled spoke wire, two long legs provided with corresponding thread ends being connected to one another by a short web, and the long legs not running parallel to each of the functions of a single spoke. The web has a clear distance between the two legs in the size of the thickness of a conventional wheel hub flange. The wire material is preferably stainless steel coated steel wire. Due to the special design of the double spoke with the course and length of the angled connecting web, which can be changed by simple tool variation, the double spoke can be used without changes to conventional, well-known wheel hubs and wheel rims.

Due to the shape of the spokes and the described bending process, disturbances in the homogeneous texture of the spoke material are excluded from the outset, so that materials with a high modulus of elasticity, such as titanium, can also be used successfully. The mutual clamping of the spoke legs in a known hub, when used, brings about a harmonious application of force when subjected to load changes. Because the design of the spoke head is already impossible force impacts that are inherently harmful to the spoke wire material can also be prevented.

The invention will be explained in more detail below using an exemplary embodiment and with the aid of figures.

Here show:

Figure 1 is a side view of a wheel hub with double spokes according to the invention already retracted.

Fig. 2 is a front view of the wheel hub shown in Fig. 1 with

Partial sectional view to explain the arrangement of the connecting web in the holes in the hub;

3 shows a sectional view through a bending tool according to the invention; and

FIG. 4 shows a section through the bending tool along the line AA in FIG. 3.

As is clear from FIGS. 1 and 2, the double spoke according to the exemplary embodiment can be used with conventional wheel hubs 5, taking into account its special shape of the central bending point. Each leg of the double spoke 1, 2 forms a single spoke on the one hand and on the other hand fulfills the function of the spoke head in connection with the connecting web 3. A spoke can easily be spoked with the described double spokes instead of single spokes, with only every second hole in a conventional wheel hub flange 4 is being used. When wheels are spoked in, the number of spokes to be hooked into the hub flanges is halved, which means that the spokes themselves can be accelerated.

According to a preferred embodiment of a corrosion-protected double spoke, it can be made of stainless steel Carbon steel can be produced, since problems with the cut surface sealing caused by the spoke shape do not arise.

The preferably used stainless steel-clad steel wire has a core of low-alloy carbon steel with 0.1% to 0.5% C, preferably 0.2% to 0.3% C. The stainless steel-sheathed steel wire for the wheel spoke described is cold-formed, preferably drawn , followed by a heat treatment, preferably intermediate annealing. Of course, other combinations of austenitic sheathing material and ferritic carbon steel are also conceivable for the production of spoke wire.

The bending tool shown in principle in FIG. 3 consists of a bending punch 6 and a bending die 7, which is fixed in a corresponding receptacle (not shown).

The bending punch 6, as symbolized by the arrow, can be moved towards the bending die and back from it.

To obtain the desired workpiece shape, the bending die 7 has a V-shaped recess 8, which corresponds to the surface shape 9 of the punch 6.

The flanks 10 and 11 of the recess 8 enclose a predetermined angle, in the exemplary embodiment in the range from 106 ° to 115 °, preferably 110 °.

Fixed and / or adjustable edges 12 (see FIG. 4) each forming a workpiece stop are arranged on the flanks 10, 11 opposite and offset by a lateral distance.

In a section of the bending die 7 there is a pivot pin 13, which is directed towards the bending base and is movably guided. The pivot pin 13 interacts with a drive device 14. The surface facing the bending base of the pivot pin 13 has a possibly exchangeable bending segment 15 which is arranged eccentrically to the axis of rotation. The bending segment 15 is in a rotational movement, caused by the drive unit 14 in connection with the pivot pin 13, in force or frictional engagement with the workpiece 16, ie the preformed spoke wire 16. Here, the leg of the workpiece 16 recognizable on the right in FIG. 3 is deformed and while maintaining the connecting web up to the stop edge 12 (Fig. 4) moved or shortened during this deformation movement. The opposite, not shown stop edge forms a force counter bearing.

As can be seen from FIG. 4, dimension a represents the web width, which in turn can be predetermined by the distance between the edges forming a stop (only edge 12 is shown) in connection with the shape of the bending segment 15.

Due to the free sliding along when bending to form the connecting web on the associated edge 12 and the free mobility of the further leg on the stop edge, tensions in the workpiece, i.e. excluded in the spoke wire material during deformation, so that the original texture is largely preserved.

The function of the tool described with reference to FIGS. 3 and 4 will be explained in more detail below.

The workpiece, ie the wire for producing the double spoke, is suspended in a manner known per se and thread sections are applied to the respective wire ends. This semi-finished product is arranged between the punch 6 and the bending segment 7 in such a way that the desired V-shape of the wire and the legs of different lengths are formed during the bending process. In the second bending process, which follows the first bending step, the connecting web is then produced, which is done by bending the second, longer leg by engaging the bending segment in the bending base of the bending die. The width of the connecting web is determined by the dimension of the bending segment or bending bolt and the coordinated position of the stop for the second, longer leg. The execution of the individual bending steps is extremely gentle on the material used. Notches or injuries as well as structural changes in the region of the deformation section, in particular the double-spoke web, are prevented, as were previously unavoidable in the known prior art by upsetting or angling spoke heads.

During the bending process, the wire sections are not clamped positively, i.e. there is a free bending. This free bending is also maintained in the second bending step in that the angled wire interacts with the bending segment and the corresponding stop, but does not exert any tension forces or clamping forces that can prevent the material from migrating. By turning the pivot pin with the bending segment in the base of the bend around the axis of rotation with an angle of rotation of essentially 90 °, the longer spoke leg is shortened until it lies completely against the corresponding stop edge. As already explained, the width of the connecting web between the legs of the same length is determined by the dimensions or the shape of the bending segment and the position of the stop for the second, originally longer leg, which limits the free step height.

With the method presented and the associated device, undesired structural changes, in particular in the area of the connecting web, can be avoided. The free, particularly gentle bending in the two-step process shown also reduces unwanted work hardening effects that lead to material brittleness. adorns, so that the long-term stability and operational reliability of the double spoke thus produced increases.

In the described bending processes, only very low bending stresses occur, so that the fiber course is only slightly disturbed during the forming process and deviates little from the normal course. When the connecting web is formed, the wire material can yield elastically to the acting bending moment, so that the tensile and compressive loads in the second bending step either have little or no influence on the original texture.

Reference list

1, 2 double spoke legs

3 connecting bridge

4 wheel hub flange

5 wheel hub

6 bending punches

7 bending die

8 V-shaped recess

9 surface shape of the stamp 10, 11 flank

12 edge

13 pivot bolts

14 drive device

15 bending segment

16 workpiece or. Wire spoke

Claims

claims

1. A method for producing a substantially V-shaped, a connecting web having double spoke by means of bending and cold-forming a wire, characterized in that in a first, free bending step without positive tension or clamping force acting on the wire by means of a V-shaped punch, which against a bending die is formed which is complementary to the bending punch and is pressed, the V-shape is formed while maintaining legs of different lengths; in a second, downstream, also free bending step, a pivot pin guided in the bending die and directed towards the base of the pivot, containing a bending segment which is arranged eccentrically to the axis of rotation of the pivot pin and is connected to the bolt, is pivoted about the axis of rotation, when the bending segment is rotated in operative connection with the im The lower leg section of the longer leg, which is located at the bend, occurs; furthermore, when turning the bending segment, the legs come to abutment in the direction of rotation, offset opposite edges of the die, forming the connecting web angled to the leg axis, during the second bending step the longer leg corresponding to the free step height of the stop assigned to it and the dimensions of the Bends back to the substantially same length of the originally shorter leg until it is fully in contact with the associated edge.

2. The method according to claim 1, characterized in that during the second bending step the punch remains in the die, but without exerting clamping tensions or clamping forces on the preformed wire.

3. Device for producing an essentially V-shaped double spoke having a connecting web by means of cold-bending a wire, comprising a bending die that can be guided against a bending die, characterized in that the bending die (7) has a V-shaped recess (8), wherein the flanks (10, 11) of the recess (8) enclose a predetermined angle (α) and on the flanks (10, 11) opposite each other and offset by a lateral distance each forming a workpiece stop, fixed and / or adjustable edges

(12) are arranged so that in the bending die (7) a pivot pin (13) directed towards the bending base is movably guided, the pivot pin

(13) cooperates with a drive device (14), furthermore the surface facing the bending base of the pivot pin (13) has an optionally exchangeable bending segment (15) which is arranged eccentrically to the axis of rotation and which, when rotating, has a force or frictional engagement with the workpiece (16 ), whereby it is located in the bending die (7) in connection with the edges (12) to obtain the connecting web in a free bending step and that the bending punch (6) is complementary to the bending die (7) to obtain the desired bent part workpiece shape is.

4. The device according to claim 3, characterized in that the edges forming the workpiece stop (12) are alternatively formed on the bending punch (6).

5. Apparatus according to claim 3 or 4, characterized in that the predetermined angle (α) for obtaining the bent part workpiece shape is substantially in the range between 106 ° and 115 °.

6. Device according to one of claims 3 to 5, characterized in that the pivot pin (13) is axially guided and movably or adjustably arranged in the bending die (7).

7. Device according to one of claims 3 to 6, characterized in that the width of the connecting web (2) by the eccentric position and the dimensions of the bending segment (15) in connection with the distance dimension and the position or height of the stop edge (12) is specifiable for the longer leg.

8. The device according to claim 7, characterized in that the bending segment (15) has a receiving slot for the workpiece (16).

9. The device according to claim 7, characterized in that the bending segment (15) has the shape of a circular segment.

10. Device according to one of claims 3 to 9, characterized in that the bending segment (15) or the pivot pin (13) by means of the drive device (14) executes a bending rotary movement of substantially 90 °.

11. Double spoke, produced by a method according to claim 1 or 2, comprising the following features: the spoke wire is angled such that two long legs (1, 2) are connected to one another by a short web (3), the long legs (1 , 2) fulfilling the function of a single spoke each do not run parallel and the web (3) ensures a clear spacing of the two legs (1, 2) in the size of the thickness of a conventional wheel hub flange (4), the wire material preferably being stainless steel-coated steel wire.

12. Double spoke according to claim 11, characterized by their use on conventional, known, commercially available wheel hubs and wheel rims.