Device for absorbing impact energy

(42) Date of commencement of the patent: 15. 7.1996 (45) Date of issue: 25. 2.1997

<td>(56) Documents:</td><td>(73) Patent owner:</td>

<td>DE 1755006A1 DE 2123944A1</td><td>EUROMDTIVE GES.MBH A-5282 RANSHOFEN, UPPER AUSTRIA (AT).</td>

<td></td><td>(72) Inventor:</td>

<td></td><td>GARNWEIDNER PETER LAMP RIGHT HOUSE, UPPER AUSTRIA (AT).</td>

(54) DEVICE FOR RECEIVING STOßENERG1E (57) Devices for absorbing impact energy, wherein in a collision two coaxially arranged, parallel to the impact direction tubes are pushed into each other, wherein one of the two tubes (1, 2) is either narrowed or widened, wherein a frusto-conical portion of the inner tube is enclosed by a frusto-conical portion of the outer tube and in this region a truncated cone-shaped intermediate layer (3) made of a material is arranged, which opposite to that of the two tubes, which is deformed during the impact, has a predictable within narrow limits friction.

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AT 402 186 Β

The invention relates to a device for absorbing impact energy.

The device is intended to be mounted between a shock absorbing member (a member to which the shock hits) and a member to be protected from the impact. Typically, the component that absorbs the impact may be the bumper of an automobile. The component to be protected from impact is then the frame construction of the automobile.

The device for absorbing impact energy allows in the case of a shock, a relative movement of the shock absorbing component to the protected before the shock component. It sets this relative movement but a resistance. Maximum protection is achieved when the resistance during the entire relative movement is as close as possible to the maximum force with which the component to be protected from the impact can be loaded without being damaged.

The force-displacement characteristic curve describing the abovementioned relative movement should therefore be as precisely predeterminable, horizontal as possible in terms of height.

Devices for absorbing impact energy are known, for example, from EP 486058 A1 and DE 4238631 A1. According to both documents, two metal tubes arranged coaxially with one another and parallel to the direction of impact are pushed into one another in the event of a collision.

Except for a truncated conical narrowed region at that end face with which the inner tube is inserted in the outer tube, the outer diameter of the inner tube is greater than the inner diameter of the outer tube. The part of the outer tube which encloses the frusto-conical tapered portion of the inner tube has a frusto-conical enlarged inner diameter matching the inner tube. When telescoping the two tubes, either the outer tube is widened or the inner tube is narrowed. The impact energy is dissipated by forming a tube and generating frictional heat at the sliding surface between the two tubes.

A disadvantage of these previously known embodiments that the amount of friction between the two tubes can be predicted only very inaccurate. It is heavily dependent on the extent and nature, of possible corrosion or contamination of the surfaces of the two tubes. In particular, when the surfaces of the tubes are torn at individual points in the relative movement, the friction can increase very sharply. This is a danger especially when using aluminum pipes, which is offered for many reasons.

The resulting force, which counteracts the telescoping of the two tubes, must under no circumstances be greater than that force which the component to be protected just barely withstands. The device for absorbing impact energy is therefore designed so that the resistance reaches as close as possible to the maximum permissible force only at maximum friction as desired. At mostly lower friction, the resistance and thus the absorbed impact energy and with this the protective effect is unsatisfactory low.

The object underlying the invention is that the known devices for absorbing impact energy namely those in which

- two coaxially arranged, parallel to the impact direction tubes are pushed into each other, wherein the relative to the outer tube relative to the rear part of the inner tube has a larger outer diameter than the inner diameter of the relative to the inner tube relative to the rear part of the outer tube, wherein the inner tube has an area in which its outer diameter narrows in a truncated cone, the smaller cross-sectional area of ​​this truncated cone being at the front relative to the direction of relative movement to the outer tube, wherein the outer tube has a region in which its inner diameter widens in a truncated cone, wherein the larger cross-sectional area of ​​the truncated cone is anterior with respect to the relative movement to the inner tube, and wherein the frusto-conical portion of the inner tube is enclosed by the frusto-conical portion of the outer tube,

- To improve so that the amount of the resulting force, which counteracts the telescoping of the two tubes, is more predictable.

The object is achieved by arranging in the region between the two tubes, in which the frusto-conical region of the inner tube is surrounded by the frusto-conical region of the outer tube, an intermediate layer of a material which is at least opposite that of the two tubes, which at impact is deformed (narrowed or widened) has a predictable within narrow limits friction.

By "narrowly predictable friction, it is meant that the range of forces in which the frictional force between the liner and the tube being deformed can vary is substantially less than the range of forces in which the frictional force between the inner and outer tubes could vary if no liner would be used.

The invention will be more apparent from the drawings:

AT 402 186 Β

Fig. 1 shows a device according to the invention for absorbing impact energy in a sectional view from a shock.

The device is shown between the bumper and the frame of an automobile. The cutting plane is normal to the bumper beam and parallel to the thrust direction.

Fig. 2 shows the device of Fig. 1 after a shock also in a sectional view.

In the illustrated example, the inner tube 1 is connected via a bolt to the bumper beam 11. The outer tube '2. is connected to the vehicle frame 12, so with the component to be protected from the impact.

In this example, the inner tube is narrowed in the event of a shock. The outer tube 2 is not deformed. It therefore only needs to consist of a truncated cone-like part and a part to its attachment to the vehicle frame and not from a pipe section with a constant diameter.

As shown in FIG. 1, the inner tube is pushed through the outer tube 2 with one end before the impact. In the area in which the inner tube 1 is covered by the outer tube, it is narrowed in a truncated cone, that it rests on the truncated cone-shaped intermediate layer 3 on the interior of the outer tube 2 forming a truncated cone.

The end portion of the inner tube 1, which projects through the narrow end portion of the outer tube 2, is provided with an extension 5, that its outer diameter is larger than the adjoining inner diameter of the outer tube 2. Thus, the inner tube 1 is not out of outer tube 2 are pulled out.

In the case of a shock on the bumper beam 11, the inner tube 1 is moved by this to the vehicle frame 12 and thus pressed by the outer tube 2. In this case, the inner tube 1 slides on the truncated cone-shaped intermediate layer 3 and is reshaped so that its diameter is smaller and its length becomes larger.

The cutting lines of the truncated cones, which are formed by the tubes 1 and 2 and the truncated cone-shaped intermediate layer 3 with planes parallel to the axis, close with the tube axis at an angle of only a few degrees, for example 4 *, otherwise the force required to narrow the inner tube 3 would be too large, so that, for example, the inner tube would buckle.

Thus, the truncated cone-shaped intermediate layer 3 is not entrained in the impact of the inner tube 1, it is secured at its relative to the relative movement to the inner tube rear end acting as a stop diameter restriction 4 on the tube 2.

It is important that the friction between the truncated cone-shaped intermediate layer 3 and the inner tube 1 in a narrow range is predictable. An important condition for this is that this friction must not be so great that it can cause the rupture of the surface of the inner tube 1. If the impact were to be done safely within a short time after assembly, the truncated cone-shaped liner 3 could simply be formed by an oil or grease film. But if the device - as in the use for motor vehicles - years later after assembly and in different environmental conditions to work reliably, the use of chemically resistant solids is advisable. Highly suitable are chemically resistant, solid plastics, which have little friction on metals. Plastics that are "rubbery" are bad: as well as those containing adhesion additives. For example, polyethylene, polytetrafluoroethylene and polyamide are well suited. The modulus of elasticity of the material for the truncated cone-shaped intermediate layer 3 should be at least 1 kN / mm² be and in any case significantly lower than that of the material of the tube, which is to slide on the truncated cone-shaped intermediate layer 3. Favorable is a modulus of elasticity of the truncated cone-shaped intermediate layer 3 in the range between 1/20 and 1/5 of the modulus of elasticity of that tube which is to slide on it.

There are also embodiments within the invention in which the tubes used do not have annular cross-sectional areas, but elliptical or polygonal cross-sectional areas. Thus, there are also embodiments within the invention for which, starting from the present description, instead of the word "truncated cone", the word "truncated pyramid" would be more appropriate.