GB2051628A

GB2051628A - Method of producing a corrugated impact-absorption member and a corrugated impact-absorption member produced by this method

Info

Publication number: GB2051628A
Application number: GB8022758A
Authority: GB
Original assignee: Benteler Deustchland GmbH
Current assignee: Benteler Deustchland GmbH
Priority date: 1979-07-12
Filing date: 1980-07-11
Publication date: 1981-01-21
Also published as: ES493306A0; ES252022Y; FR2460733A1; SE8003903L; ES8104926A1; DE2928103A1; ES252022U; DE2928103C2

Abstract

A method of producing a substantially tubular impact absorption member, especially for use in safety steering columns of automotive vehicles, mainly comprises the steps of stamping a circular disc from a sheet metal, drawing said disc into a pot-shaped member and subsequently reducing during a further drawing operation the wall thickness of the peripheral wall of the pot-shaped member to about one- third of that of the bottom thereof, and forming adjacent corrugations in the peripheral wall. The method may further include the steps of forming a central inwardly directed neck in the bottom in which the neck is provided at the inner surface thereof with longitudinally extending serrations for connecting the member to the steering shaft, and forming substantially rectangular serrations at the free edge of the peripheral wall for connecting the member to a steering wheel. <IMAGE>

Description

SPECIFICATION Method of producing a corrugated impactabsorption member and a corrugated impact-absorption member produced by this method The present invention relates to a method of producing a corrugated tubular impact-absoraption member as well as an impact-absorption member produced by this method and especially usable in connection with steering columns in automotive vehicles.

Corrugated impact-absorption members are used in the construction of steering shafts for automotive vehicles in order to absorb the impact energy during a collision and the resulting impact of the driver onto the steering wheel. Up till now, such corrugated impactabsorption members have been produced from tubes provided with successive corrugation of predetermined height.

This way of producing a corrugated impactabsorbing member has various advantages, which assure a uniform high quality of the member so that this method according to the prior art has extensive use.

Nevertheless, the known method of producing a corrugated impact-absorption member from a tubular blank has resulted in certain difficulties in incorporating the impact-absorption member thus produced into the steering column construction. These difficulties result substantially from the fact that the connection between the impact-absorption member, which is open at opposite ends (since formed from a tube), and the corresponding connection elements of the steering wheel become more or less complicated so that technically unsatisfactory and also expensive compromise solutions are necessary. Thus, for instance, bosses have been used for connecting the impact-absorbing member with the steering column and such bosses have been cast onto the impact-absorbing member.

According to the present invention, there is provided a method for the production of a substantive tubular impact absorption member provided with corrugations, especially for use in a safety steering column for automotive vehicles, comprising the steps of stamping a circular disc from sheet metal; drawing the disc into a pot-shaped member having a bottom and a cylindrical peripheral wall; reducing during a further drawing operation the thickness of the peripheral wall; and forming corrugations in said peripheral wall.

Due to the possibility of drawing a potshaped base member with a bottom from a circular disc an impact absorption member may be produced which, due to its bottom, provides for advantagesous conditions for a technically perfect and at the same time very economic connection with adjacent connecting elements. With this method according to the present invention it is unnecessary to additionally manufacture a bridging element to be connected with the impact-absorption member to thus avoid the up to now existing difficulties of connecting the impact-absorption member to the steering column.Thereby, all advantageous characteristics according to the prior art are maintained, due to the essentially cylindrical, possibly slightly conical peripheral wall of the pot-shaped body, in order to construct the thickness of the peripheral wall and the arrangement as well as the formation of the corrugations in dependence on the constructive requirements of such an impact absorption member.

In order to assure sufficient stability of the bottom of the pot-shaped body to comply with the requirements of the connection element for the steering column construction, the thickness of the peripheral wall of the potshaped body is, according to a further preferred feature of the present invention, reduced during the drawing operation to a thickness which is about one-third of the wall thickness of the bottom. The thickness of the peripheral wall may be the same the length thereof so that the deforming characteristic of the impact-absorption member will be determined only by the construction and arrangement of the subsequently formed corrugations.

Deviating therefrom, it may, however, be advantageous to draw the thickness of the peripheral wall of the pot-shaped body from the bottom thereof with increasing or decreasing thickness. This varying thickness of the peripheral wall therefore permits the deforming characteristic obtained by the construction and arrangement of the corrugations to vary in a desired manner.

An especially advantageous construction for the connection of the impact absorption member with the steering wheel column construction is obtained by forming at the bottom of the impact absorption member a central inwardly directed neck of frustoconical form.

This formation of the column in the bottom may be formed before or after forming the corrugations. This neck receives then the free end of the steering spindle, whereby the connection for simultaneous rotation of these two elements may be formed in different ways.

It is especially advantageous that the conically extending inner surface of the neck is provided with longitudinal extending serrations. In this case, corresponding serrations are provided at the free end of the steering spindle so that a perfect axial and radial connection between the impact absorption member and the steering spindle is obtainable.

It is further advantageous for the free edge of the peripheral wall of the impact absorption member to be provided with serrations which may be formed before or after producing the corrugations in the peripheral wall. Such serrations at the free end of the peripheral wall permit, for instance, the connection of the impact absorption member with a steering wheel for rotation therewith.

The present invention also provides an impact absorption member, especially for safety steering columns of automotive vehicles, comprising a pot-shaped member having a bottom provided with a central inwardly extending neck of frustoconical configuration for connecting the member to a steering wheel shaft, a peripheral wall having a thickness small than that of said bottom and provided with a plurality of axially spaced corrugations.

In order that the invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section of a pot-shaped base body for forming therefrom an impact absorption member according to the present invention; Figure 2 is a longitudinal cross-section through a finished impact absorption member; Figure 3 is a longitudinal cross-section showing the impact absorption member according to Fig. 2 incorporated into a steering column construction; Figures 4 to 6 are schematic longitudinal cross-sections through the tools necessary for forming a pot-shaped base member from a circular sheet metal disc; Figure 7 shows a detail of Fig. 6 at a slightly enlarged scale; Figure 8 is a longitudinal cross-section of the tools for reducing the peripheral wall of the pot-shaped member;; Figure 9 is a longitudinal cross-section through the modification of the tools shown in Fig. 8 in which the peripheral wall is drawn with a thickness slightly decreasing from the bottom of the pot-shaped member to the edge thereof; Figure 10 is a schematic longitudinal crosssection through punching tools for forming a central hole in the bottom of the pot-shaped member; Figure 11 is a partly sectioned schematic illustration of the tools for forming a central inwardly extending neck of frustoconical configuration in the bottom of the pot-shaped member; Figure 12 schematically illustrates in longitudinal cross-section a modification of the punching tool shown in Fig. 10; Figure 13 is schematic longitudinal crosssection through the tools for forming at the bottom a central outwardly extending neck thereof;; Figures 14 to 17 are schematic longitudinal cross sections through the tools for forming corrugations in the peripheral wall of the potshaped base member; Figure 18 is a schematic longitudinal crosssection through the tools for forming serrations or castellations at the free edge of the impact absorption member; and Figure 19 is a schematic top view of the tools shown in Fig. 18.

Fig. 1 shows in longitudinal cross-section a pot-shaped base member 1 for the production of a corrugated impact absorption member according to the present member. This potshaped base member 1 is drawn, as will be explained later, from a circular disc of sheet steel which is punched out from a sheet metal plate. The base member 1 has a bottom 2 and a cylindrical peripheral wall 3. The relationship of the thickness of the bottom 2 to the thickness of the peripheral wall 3 is about 3:1. The wall thickness of the peripheral wall 3 is shown in Fig. 1 the same over the whole length thereof, but as will be explained later, this wall thickness may, for instance, decrease from the bottom 2 to the free edge of the peripheral wall.

As shown in Fig. 2, the pot-shaped base member 1 is provided with successive corrugations 4 formed, as will be explained later, in the peripheral wall 3. As shown in Fig. 2, all of the corrugations 4 have the same height and are spaced the same distance from each other. The free edge 5 of the peripheral wall 3 is provided with rectangular serration or castellations 7 which form connecting elements to adjacent elements of a steering column construction.

The integration of a finish formed impact absorption member 6 into a steering column construction is illustrated in Fig. 3.

As shown therein, the bottom 2 of the impact absorption member 6 is additionally provided with a central inwardly extending frustoconically shaped neck 8. The conical inner surface of the neck 8 is provided with longitudinally extending serrations 9 which mesh with corresponding longitudinally extending serrations 10 on a conical section of the steering shaft 11 so that the impact absorption member 6 is connected to the shaft 11 for rotation therewith. The inner free end of the steering shaft 11 is provided with a screw thread 13 on which a nut 12 is screwed for positioning the impact absorption member 6 on the end portion of the shaft 11, whereby a washer 14 is sandwiched between the nut 12 and the inner free end of the neck 8 of the impact absorption member 6.

Fig. 3 shows further that the castellations 7 at the free end 5 of the impact absorption member 6 engage into correspondingly formed serrations 15 of the spokes 16 of the steering wheel 17. In order to assure a perfect connection between the impact absorption member 6 and the steering wheel 17, the serrations 7 and 15 are welded to each other.

The region of the connection between the impact absorption member 6 and the steering wheel 17 is covered by a flat cap 18, prefera bly formed from plastic material and connected to the spokes 16 of the steering wheel in any convenient manner, for instance, by cementing.

The following Figs. 4 to 19 schematically illustrate the tools for producing the impact absorption member 6 as shown in Fig. 3.

More specifically, Figs. 4 to 17 illustrate the tools for forming a pot-shaped member from a circular disc of sheet metal 20, which is punched out in a conventional punch press from a flat sheet metal member. The circular flat disc 20 is placed into a corresponding cutout at the top face of an annular guide block 22 and subsequently the tool is closed by the annular drawing die 19. A stationary drawing mandrel 21 with a cutter edge 23 extends, closely guided in the guide block 22, through the central opening of the latter. It is to be understood that the tools shown in Fig.

4 are mounted in a standard press, the ram of which engages the upper surface of the annular drawing die 19. When the ram is now lowered, the drawing die 19 and the guide block supported by spring pressed columns 24 are moved downwardly as shown in Fig.

5, whereby the outer edge portion of the flat work piece 20 is squeezed between the annular drawing die 19 and the spring pressed guide block 22 and the adjacent portion of the work piece is squeezed into the clearance between the inner surface of the annular drawing die 19 and the outer surface of the drawing mandrel 21. Shortly before the members 19 and 22 reach their lowermost position, the cutting edge 23 on the drawing mandrel 21 will cut an annular surplus 25 from the work piece while a cut pot 26 remains on the drawing mandrel 21. Fig. 7 illustrates at a slightly enlarged scale the cut scrap 25 surrounding the enlarged portion of the drawing mandrel.Subsequently thereto, the press is opened and the annular drawing die is moved upwardly away from the guide block 22 and the cut pot 26 may be removed by hand from the upper end of the mandrel 21, whereas the remaining scrap 25 is removed from the guide block 22. It is also possible to form the drawing mandrel with a central bore therethrough in which a spring pressed stripper pin is located and corresponding stripper pins may also extend through the guide block 22 so that upon opening of the press the cut pot and annular scrap will be automatically ejected from the tools.

Fig. 8 schematically illustrates the drawing tools for reducing the thickness of the peripheral wall of the pot-shaped member 26 produced in the tools shown in Figs. 4 to 7.

The tools shown in Fig. 8 comprise a stationarily supported annular stretching or drawing die 28 and a stretching or drawing mandrel 27 cooperating therewith. It is to be understood that the tools shown in Fig. 8 are again mounted in a conventional press with the mandrel 27 connected to the press ram for movement in vertical direction relative to the drawing die 28 which is stationarily supported in the press. The pot-shaped member as produced by the tools shown in Figs. 4 to 7 is placed on the lower end portion of the mandrel 27 and as the ram of the press together with the mandrel 27 moves downwardly, the wall portion 29 of the pot 26 is thus reduced in its thickness while it is stretched in longitudinal direction.The edge or shoulder 30, formed between the large diameter portion and the reduced diameter portion of the mandrel, will assure that in the end position the upper edge of the reduced peripheral wall will be located in one plane parallel to the bottom. In this way, the peripheral wall of the pot-shaped member will be reduced to about one-third of the wall thickness of the bottom thereof.

Fig. 9 shows tool similar to that shown in Fig. 8 with the difference that the reduced diameter portion 31 of the drawing or stretching mandrel 27 tapers slightly towards the bottom face of the mandrel 27 so that the peripheral wall produced will have a thickness slightly decreasing toward the upper edge thereof.

Fig. 10 schematically illustrates the tools for forming a central hole in the bottom of the pot-shaped member produced in the tools shown in Figs. 8 or 9. These tools comprise a pressure plate 32 to be connected in any convenient manner to the ram of a punch press, a punch holder plate 34 connected in any convenient manner, for instance by screws or the like to the pressure plate 32 and carrying in its central bore thereof a punch 33 having a reduced end portion extending through a central bore of a stripper plate 36 placed on the inner surface of the bottom of the pot-shaped member and pressed by an annular compression spring 35 sandwiched between the punch holder plate 34 and the stripper plate 36 against this surface.The bottom of the pot-shaped member is located in an annular cutout formed at the upper surface of the stationary die 38 which is provided with a central slightly conical bore through which the end portion of the punch 33 extends during downward movement of the press ram to cut a central hole in the bottom of the pot-shaped member while the thus formed scrap 37 drops down through the central bore in the die 38.

After a central hole is thus formed in the tool 10 in the bottom of the pot-shaped member, the latter is placed onto the cylindrical die 39 shown in Fig. 11, which is formed with a central conical cavity 40 extending from the bottom thereof into the latter. Cooperating with the die 39 is a stationary punch 43 having a central upwardly projecting frustoconical portion provided at the periphery thereof with longitudinally extending serrations 42 and having a conical end portion 41.

The die 39 is again connected in any convenient manner to the ram of a conventional punch press so that during lowering of the ram and the die 39 connected thereto, the conical end 31 will penetrate the hole punched in the bottom of the pot-shaped member to form during further lowering of the die an inwardly extending collar or neck 44 provided at the inner surface thereof with longitudinally extending serrations in the bottom of the pot-shaped member.

Fig. 12 shows tools similar to those shown in Fig. 10, for forming a central opening in the bottom of the pot-shaped member produced in the drawing or stretching tools shown in Figs. 8 or 9. The only difference between the tools shown in Figs. 12 and 10 is that the punch 33' shown in Fig. 12 has a larger diameter than the punch 33 shown in Fig. 10, and correspondingly the punch holder plate 34', the stripper plate 36' and the die 38' are formed with larger central bores than in Fig. 10. Of course, the punched out scrap 37' in Fig. 12 is also of larger diameter than the punched out scrap 37 shown in Fig. 10.

Fig. 13 schematically illustrates a tool for forming an outwardly extending annular collar or neck 45 on the bottom of the centrally punched pot-shaped member produced by the tools of Fig. 12.

The tools shown in Fig. 13 comprise a punch 46 to be connected in any convenient manner to the ram of a conventional punch press and the punch 46 has a lower reduced diameter portion 46' ending in a frustoconical end 48 and forming an edge or shoulder 49 and the punch 46 cooperates with a die 47 having a central bore 47' enlarged at its upper end. The die 47 is stationarily supported on the punch press so that during lowering of the punch 46 an outwardly extending collar or neck 45 is formed at the bottom of the pot-shaped member. The intermediate portion 46' of the punch 46 may also be provided at the outer periphery thereof with longitudinally extending serrations similar to the serrations 42 shown in Fig. 11 so that the downwardly extending neck 45 will be provided at the inner surface thereof with corresponding serrations.

Figs. 14 to 1 7 schematically illustrates the tools for forming corrugations in the peripheral wall of the pot-shaped member produced by the tools shown in Figs. 8 or 9. As mentioned before, these corrugations may be formed before or after the inwardly projecting neck 44, shown in Fig. 11, or the outwardly projecting neck 45, shown in Fig. 13, is produced in the bottom wall of the pot-shaped member. Figs. 14 to 17 illustrate an arrangement for forming the corrugations before the aforementioned necks are formed in the bottom wall.

As shown in Fig. 14, these tools for forming corrugations in the peripheral wall comprise an inner axially movable substantially cylindrical clamping jaw 53 formed with a central bore 53' therethrough, and a plurality of outer movable clamping jaws 52, movable radially and in axial direction for clamping the peripheral wall of the pot-shaped member 55 therebetween. The tools include further an inner stationarily arranged central mandrel 51 having a free end 51' of enlarged diameter and engaging the bottom of the pot 55. The stationary mandrel 51 is further formed with a central channel 54 having an end portion 54' extending normal thereto and ending at the periphery of the stationary central mandrel rearwardly of the enlarged end portion 51 t thereof.A plurality of movable forming jaws 50 cooperate with the end portion 51' of the inner stationary mandrel for clamping the peripheral wall of the pot 55 in the region adjacent to the bottom of the latter. As shown in Fig. 14, the movable clamping jaws 50 are provided at the inner ends thereof with cutouts 50'. In the position of the various elements as shown in Fig. 14, pressure fluid is fed through the channel 54 so that the peripheral wall of the pot 55 bulges slightly outwardly adjacent to the bottom thereof as shown at 55' in Fig. 14.

Subsequently thereto, the clamping jaws 52 and 53 are moved toward the forming jaws 50 until the left end of the clamping jaw 52 engages the right end face of the forming jaws 50, as shown in Fig. 15, while the pressure beneath the bulging portion 55' is maintained to thus form from this bulging portion a first corrugation 55". Subsequently thereto, the outer movable clamping jaws 52 are radially moved away from the inner clamping jaw 53 and both clamping jaws are moved in rial direction away from the forming jaws 50 for a distance equal to the width of the corrugation, plus the distance between two adjacent corrugations, as shown in Fig.

16. Subsequently thereto, the outer movable clamping jaws 52 are moved toward the inner clamping jaw 53 to again clamp a portion of the peripheral wall of the pot-shaped member therebetween while the forming jaws 50 are moved in radially outward direction away from the peripheral wall. Subsequently thereto, the clamping jaws 52 and 53 are moved in axial direction towards the position 51' of the inner mandrel 51 to the position shown in Fig. 14 to advance the pot-shaped member in axial direction toward the left, as viewed in Fig. 17.

Subsequently thereto, the movable forming jaws are moved radially inwardly to the position as shown in Fig. 14 and the abovedescribed cycle of operations is then repeated to form a plurality of axially spaced corrugations in the peripheral wall of the pot-shaped member.

It is mentioned that the various elements disclosed in Figs. 14 to 17 may be moved between the positions thereof in a manner similar to the manner as disclosed in the copending application Serial No. 40275 to Benteler et al.

Finally, Figs. 18 and 19 show the tools for forming serrations or castellations 7 at the free edge of the impact absorption member 6.

These tools comprise a stationary die 56, having a central upwardly projecting annular portion 56' formed intermediate the ends thereof with a plurality of circumferentially spaced openings 57 of rectangular cross-sections therethrough. A plurality of punches 58 of a cross-section corresponding to that of the openings 57 are arranged and guided for movement in axial direction in openings of an annular guide member 61 having an inner end spaced from the outer periphery of the die portion 56' so that the cylindrical end portion 6' of the corrugated impact absorption member 6 may be placed therebetween. Fluid operated cylinder and piston means 59 mounted on the guide member 61 serve to reciprocate the punches 58 in axial direction so that during inward movement of the punches serrations or castellations will be formed on the cylindrical end portion 6'.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of methods of producing a corrugated impact absorption member and a corrugated impact absorption member produced by this method differing from the types described above.

While the invention has been illustrated and described as embodied in a method of producting a corrugated impact absorption member for incorporation into a steering column construction of an automotive vehicle and a corrugated impact absorption member produced by this method, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Claims

1. A method for the production of a substantially tubular impact absorption member provided with corrugations, especially for use in a safety steering column for automotive vehicles, comprising the steps of stamping a circular disc from sheet metal; drawing the disc into a pot-shaped member having a bottom and a cylindrical peripheral wall; reducing during a further drawing operation the thickness of the peripheral wall; and forming corrugations in said peripheral wall.

2. A method according to claim 1, wherein the thickness of said peripheral wall is reduced in the additional drawing operation to about one-third of the wall thickness of the bottom.

3. A method according to claim 1, wherein the wall thickness of said peripheral wall is reduced during the additional drawing operation so that its thickness uniformly decreases from the bottom of the pot-shaped member.

4. A method according to claim 1, 2 or 3, including the step of forming in the potshaped member a central inwardly directed neck of frustoconical configuration.

5. A method according to claim 4, and including the step of forming longitudinally extending serrations on the inner surface of said neck.

6. A method according to any one of claims 1 to 5, and including the step of forming serrations at the free edge of the peripheral wall.

7. A method according to claim 6, wherein said serrations at the free edge of the peripheral wall are formed of substantially rectangular configuration.

8. An impact absorption member, especially for safety steering columns of automotive vehicles, comprising a pot-shaped member having a bottom provided with a central inwardly extending neck of frustoconical configuration for connecting the member to a steering wheel shaft, a peripheral wall having a thickness smaller than that of said bottom and provided with a plurality of axially spaced corrugations.

9. An impact absorption member according to claim 8, and including serrations on the free edge of said peripheral wall for connecting the latter to a steering wheel.

10. An impact absorption member according to claim 8 or 9, wherein the wall thickness of said peripheral wall gradually decreases from the bottom toward the free edge of the peripheral wall.

11. An impact absorption member according to claim 8, 9 or 10, wherein said corrugations are equally spaced from each other.

12. An impact absorption member according to claim 8, 9 or 10, wherein the distance between adjacent corrugations varies.

13. An impact absorption member according to any one of claims 8 to 12, wherein all of said corrugations have the same outer radius.

14. A method for the production of an impact absorption member substantially as hereinbefore described with reference to the accompanying drawings.

15. An impact absorption member substantially as hereinbefore described with reference to the accompanying drawings.

16. Any novel feature or combination of features herein described.