A SHOCK ABSORBING BOX

Abstract: Shock absorbing rectangular boxes (16, 17) are mounted between each one of the two structural side beams (14, 15) of a vehicle and the bumper beam (11). The boxes are deep drawn from a steel sheet and their side walls have deformation guides (35) so that the boxes will deform in a controlled manner during a crash.

Description: A shock absorbing box Technical field This invention relates to a shock absorbing deep drawn rectangular open box between a bumper beam and a vehicle body, having a bottom, side walls and a flange. Background of the invention and prior art Nowadays, bumper beams for passenger cars are usually adapted to absorb impact energy by being deformed plastically. In small cars, the beam can be arranged to absorb enough energy. In bigger cars, energy absorbing elements need to be arranged between the side beams of the car and the bumper beam. DE-19537186-A shows such elements in the form of deep drawn rectangular boxes. US-3,998,485-A shows circular, stepped tubes as extensions of the side beams of a car. Object of the invention It is an object of the invention to provide a comparatively short shock absorbing element between a bumper beam and a vehicle body, which element will have a high energy absorption and a high and comparatively even resistance force while being deformed during a crash. Summary of the invention This object is fulfilled in principle in that the sides of an element in the form of an open deep drawn rectangular box with a side flange at its opening has different inclination of the part of its side walls adjacent the bottom and the part of its side walls adjacent the flange so that a deformation guide is formed between the two parts of each side wall of the box. To this end, the invention has been given the characteristics stated in the claims. Brief description of the drawings The invention will be described with reference to the accompanying drawings which show a shock absorbing box as an example of the invention. • Figure 1 is a transparent perspective view of the shock absorbing mounting box. • Figure 2 is a view of the box shown in figure 1 seen as indicated by the arrows 2-2 in figure 3. • Figure 3 is a section through the mounting element shown in figures 1 and 2 and it is taken along the line 3-3 in figure 2. • Figure 4 is a top plan view of a bumper beam mounted to the side beams of a vehicle by means of mounting boxes of the kind shown in the figures 1 and 2. • Figures 5 and 6 are two sections, at right angle to each other, through a somewhat modified design of the mounting box shown in figures 3 and 4. Description of the preferred embodiments In figure 4 is shown a bow-formed bumper beam of formed sheet steel. It has two flat mounting areas 12, 13 adjacent the structural side beams 14,15 of the vehicle. Between the side beams 14, 15 and the areas 12,13, there are two mounting elements 16, 17 by the intermediate of which the bumper beam is mounted to the side beams. Such a mounting element is shown in the figures 1 -3. It comprises a box deep drawn from one piece of sheet steel and it has a bottom 22, four side walls 23 and a flange 24. The bottom 22 has a central hole 25 and the mounting areas 12,13 of the bumper beam have corresponding holes so that the boxes can be mounted to the bumper beam by means of screw and nut fasteners. The flange 24 of the boxes has four holes 28-31 and the ends of the side beams have flanges or plates 32,33 with corresponding holes so that the boxes 16,17 can be fastened to the side beams 14,15 by screw and nut fasteners. Suitably, the boxes can be deep drawn from high carbon cold forming steel so that they do not need to be hardened after the forming Such a hardening process could not be carried out without a fixture and would therefore be an expensive operation. The boxes 16,17 are rectangular with rounded corners and they taper off slightly towards their bottoms. All four side walls 23 comprise a part 37 adjacent the bottom and a part 36 adjacent the flange and the two parts 36,37 have different inclination relative to the centreline of the box so that they form an obtuse angle in the line 35 in which they meet and the walls are thus concave. This line 35 between the two wall parts 36,37 form a guide for bending when the box is subjected to a load as will be described. The side wall part 36 adjacent the flange should preferably be shorter than the side wall part 37 adjacent the bottom and it could advantageously be less than 1/3 of the entire wall. The side wall parts 36,37 are preferably flat or substantially flat as shown. At a car crash, the bumper beam 1 1 should be deformed first and then its mounting elements, that is, the boxes 16, 17. Then, if the load is heavy, the load should be taken up by the side beams 14, 15. The lines 35 form guides for bending and the side walls 23 bend in these lines so that the parts 36 rotate inwards and upwards in figure 3 until they stop against the end plates of the side beams 14, 15. The parts 37 of the side walls will then have a slight S-form and they are inclined inwards. The corners of the upper part 36 have folded in more than one fold. Then, the initial bend in line 35 will roll inwards toward the centre of the box and the corners will continue to fold in several folds. This pattern of movement is efficient as to the energy absorption because a great part of the material will be plastically deformed and thereby take up energy. The resistance force will have no spikes and will be comparatively constant during the entire deformation and it will not have a spike at the end of the elastic deformation before the plastic deformation starts. A curve of the resistance force related to the deformation will thus be comparatively flat which is desirable but difficult to achieve when the distance available for deformation is small. In a box without the guides for bending 35, the resistance force before the plastic deformation would be much higher, but the total energy take-up much lower. Figures 5 and 6 show a modified box. Two opposite side walls 23 are concave as can be seen in figure 5 but the other two side walls 26 are convex as can be seen in figure 6. This modified design provides for a still better total energy take-up, probably because a more efficient folding of the corners.

Claims: Claims 1. A shock absorbing deep drawn rectangular open box between a bumper beam and a vehicle body, having a bottom (22), sides walls (23,26) and a flange (24), characterised in that the side walls (23,26) comprise one part (37) adjacent the bottom (22) and one part (36) adjacent the flange (24) and the two parts have different inclination so that a deformation guide (35) is formed between them. 2. A shock absorbing box according to claim 1 , characterised in that said part (36) adjacent the flange (24) is shorter than said part (37) adjacent the bottom (22). 3. A shock absorbing box according to claim 1 or 2, characterised in that all four side walls (23) are concave. 4. A shock absorbing box according to claim 1 or 2, characterised in that two opposite side walls (23) are concave and the other two side walls (26) are convex. 5. A shock absorbing box according to any one of the preceding claims, characterised in that the flange (24) is fixed to the structural side beam (14,15) of the vehicle body. 6. A shock absorbing box according to claim 5, characterised in that the flange (24) is fixed to an end plate (32,33) of the side beam (14,15).

Inventors: JONSSON MARTIN, NILSSON JOHAN, JONSSON, MARTIN, NILSSON, JOHAN
Applicants: JONSSON MARTIN, NILSSON JOHAN, SSAB HARDTECH AB, JONSSON, MARTIN, NILSSON, JOHAN
Application year: 2000
Main classification: B60R19
IPC codes: B60R19