Method for producing a shock absorber and shock absorber thus obtained
The method includes providing a planar sheet part; forming the planar sheet part by drawing or conical spinning to the shape of a partially formed part made up of a plate and a provisional hollow portion extending from the plate with a revolution shape with respect to an axis perpendicular to the plate, and an end wall closing an end of the provisional hollow portion opposite to the plate; and elongating a section of the provisional hollow portion by cylindrical or conical spinning. The shock absorber is integral with a plate and an elongated hollow portion extending from the plate with a revolution shape. A section of the elongated hollow portion has a thickness that is thinner than the thickness of the plate.
1. A method for producing a shock absorber for being used as a vehicle bumper crossbeam support, comprising the steps of:
providing a planar sheet part having an initial thickness and an initial outline;
forming by using a drawing technique said planar sheet part into a partially formed part having a general thickness that is substantially the same as said initial thickness, said partially formed part comprising a plate, a provisional hollow portion extending from said plate, and an end wall closing said provisional hollow portion at one end thereof opposite to the plate, the provisional hollow portion having a revolution shape with respect to an axis perpendicular to the plate, and comprising a first section connected to the plate and having a first average diameter, a second section connected to said end wall and having a second average diameter that is less than said first average diameter, and a transition section connecting said first and second sections, said transition section being configured to act as a deformable configuration intended to bring about a controlled deformation in the event that an axial force above a predetermined threshold is applied; and
elongating by using a spinning technique involving material flowing at least part of said second section of the provisional hollow portion of the partially formed part until obtaining a formed part with an elongated hollow portion having an elongated second section which is longer than the second section of the partially formed part, and at least part of which has a final thickness that is thinner than the initial thickness, said formed part being the shock absorber.
2. The method according to claim 1 , wherein the step of forming the planar sheet part into the partially formed part by using the drawing technique further comprises cutting one or more openings in the plate and/or in said end wall.
3. The method according to claim 1 , wherein the step of forming the planar sheet part into the shape of the partially formed part by using the drawing technique comprises forming the second section of the provisional hollow portion as substantially cylindrical second section.
4. The method according to claim 3 , wherein the step of forming the planar sheet part into the shape of the partially formed part by using the drawing technique comprises forming the first section of the provisional hollow portion as substantially cylindrical first section.
5. The method according to claim 1 , wherein the step of forming the planar sheet part into the shape of the partially formed part by using the drawing technique comprises forming the transition section as an annular step with a planar portion parallel to the plate between the first section and the second section.
6. The method according to claim 1 , wherein the step of forming the planar sheet part into the shape of the partially formed part by using the drawing technique comprises forming the transition section as an annular step defining an annular wave between the first section and the second section.
7. The method according to claim 1 , wherein the step of forming the planar sheet part into the shape of the partially formed part by using the drawing technique comprises forming rounded transition edges between the plate and the first section, between the first section and the transition section, between the transition section and the second section, and between the second section and the end wall.
8. The method according to claim 1 , wherein said spinning technique is a direct cylindrical spinning technique with a flow of material.
9. The method according to claim 1 , wherein said spinning technique is a reverse cylindrical spinning technique with a flow of material.
10. The method according to claim 1 , wherein said planar sheet part is provided having said initial outline according to a final outline of a plate of a shock absorber to be obtained.
11. The method according to claim 1 , wherein the step of forming the planar sheet part into the partially formed part using a the drawing technique further comprises cutting said initial outline to obtain a final outline for the plate.
12. The method according to claim 1 , further comprising a step of cutting the elongated second section of the elongated hollow portion transverse to the axis in order to eliminate said end wall.