Novel pyrotechnic tensioning device for use with safety belts

• US 3,917,031 A
• Filed: 07/22/1974
• Issued: 11/04/1975
• Est. Priority Date: 08/03/1973
• Status: Expired due to Term

• Current Assignee: Bernard E. Plantif, Bernard J. Doin, Jean F. Tillac
• Original Assignee: Bernard E. Plantif, Bernard J. Doin, Jean F. Tillac
• Inventors: Plantif, Bernard E., Doin, Bernard J., Tillac, Jean F.
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US05/490,382
• Time in Patent Office: 470 Days
• Field of Search: 188/1B,1C 280/15AB,15SB 297/386,388 74/492
• US Class Current: 188/375
• CPC Class Codes: B60R 22/1955 Linear actuators
• CPC Class Codes: B60R 22/28 incorporating energy-absorbing devices belt anchors provided with energy-absorbing means for protecting the occupants in case of physical contact therewith B60R21/055; belt retractors comprising energy-absorbing means B60R22/341, B60R22/4676

Abstract

A pyrotechnic tensioning device for a safety belt, comprising a piston slidably mounted in a cylinder, a piston rod projecting from one end of the cylinder, and a pyrotechnic charge for forcing the piston forwards along the cylinder to retract the piston rod and tension the safety belt, also includes damping means for damping movement of the piston in the reverse direction through the cylinder under the action of the tension in the safety belt. The damping means comprises elements, such as balls, located between the piston and cylinder and which cooperate with a conical surface to jam between the piston and cylinder during said reverse movement, whereby controlled damping is effected by the elements deforming or biting into the cylinder by a predetermined amount. A tube or ring may surround the cylinder with similar elements located therebetween, such that a similar damping effect is achieved when the cylinder is pulled out of the tube or ring. The device may include means for limiting the tension applied to the belt, comprising an ejectable member normally blocking passage of combustion gases from one side of the piston to the other, the member being retained in position by an element designed to fracture at a particular pressure.

Claims

1. A pyrotechnic tensioning device for use with a safety belt, comprising damping means comprising a cylinder having opposed ends, a piston slidably mounted within said cylinder, said cylinder and said piston having cooperating inner and outer surfaces, respectively, bottom and opposed side wall means defining an annular groove in the cooperating surface of one of said cylinder and said piston, said groove bottom wall having a conical bearing surface ending in one of said groove side walls which forms a path limiting stop, a circular row of elements located within the said groove, and having a radial dimension which is greater, by a predetermined amount, than the depth of the said groove adjacent the path limiting stop, whereby, in use, movement of the said piston relative to said cylinder in one direction of relative movement, is damped in a controlled manner by the said elements deforming or penetrating the said cooperating surface of the cylinder, said device further comprising a rod secured to said piston and projecting from one said end of said cylinder;

a pyrotechnic charge positioned adjacent the said piston, and surrounding the said rod, so that firing of the said charge causes the piston to move in a first direction relative to the said cylinder;

firing means for firing said pyrotechnic charge from externally of the said cylinder; and

wherein the said damping means is arranged to damp movement of the piston relative to the cylinder in a direction opposite the said first direction, the said groove being located in the surface of the piston.

2. A pyrotechnic tensioning device according to claim 1, wherein the said damping means includes a tubular member shaped as a surface of revolution and telescoped over the cylinder, a circular row of additional elements being provided in the said cylinder and the said tubular member, at the end of the cylinder opposite the said end through which the piston rod projects, the said additional elements having a radial dimension which is greater, by a predetermined amount, than the radial distance between the said tubular member and cylinder.

3. A pyrotechnic tensioning device according to claim 1, wherein the said damping means includes a ring having an inner surface surrounding the said end of the cylinder through which the piston rod projects, a circular row of additional elements is provided in the said inner surface of the said ring, the said additional elements having a radial dimension which is greater, by a predetermined amount, than the radial distance between the said ring and cylinder.

4. A pyrotechnic tensioning device according to claim 2, further comprising bottom and side wall means defining a circumferential groove in the external surface of the said cylinder, the said bottom wall of this groove including a conical bearing surface ending in one said side wall which forms a path limiting stop, said additional elements being disposed within said groove and having a radial dimension which is greater, by a predetermined amount, than the depth of the said groove adjacent said path limiting stop.

5. A pyrotechnic tensioning device according to claim 3, wherein bottom and side wall means define an annular groove in said inner surface of said ring, said bottom walL of the groove including a conical bearing surface ending in one said side wall which forms a path limiting stop, said additional elements being disposed within said groove and having a radial dimension which is greater, by a predetermined amount, than the depth of said groove adjacent the said path limiting stop.

6. A pyrotechnic tensioning device according to claim 1, wherein said elements are balls made of a very strong material, the controlled damping being effected by deforming and rolling out grooves in the wall of the cylinder, with the said balls.

7. A pyrotechnic tensioning device according to claim 1, wherein the said elements are conical ring segments having penetration means on their external faces made of a very strong material.

8. A pyrotechnic tensioning device according to claim 7, wherein the penetration means are cutting devices so arranged that the controlled damping is effected by gouging grooves in the surface of the said cylinder, with the said cutting devices.

9. A pyrotechnic tensioning device according to claim 2, wherein a U-shaped attachment clamp is pivotally mounted on the said tubular member.

10. A pyrotechnic tensioning device according to claim 3, wherein a U-shaped attachment clamp is pivotally mounted on the said ring.

11. A pyrotechnic tensioning device according to claim 2, wherein a base closes the said tubular member at the end thereof opposite the said end through which the piston rod projects and a seal is provided at the other end of the tubular member so that gases produced by the combustion of the pyrotechnic charge are retained inside the said tubular member.

12. A pyrotechnic tensioning device according to claim 2, wherein the tubular member has a variable internal diameter, and is so arranged that the controlled damping is effected by exerting a force of predetermined intensity opposing the relative movement, and which varies according to the shape of the internal generatrix of the tubular member.

13. A pyrotechnic tensioning device according to claim 2, wherein the said additional elements are radial fins provided on the external surface of the said cylinder.

14. A pyrotechnic tensioning device according to claim 2, wherein the said additional elements consist of balls located in a circular groove means or in hemispherical depression means provided in the external surface of the cylinder.

15. A pyrotechnic device according to claim 1 including means for limiting the tensile force exerted by the piston rod on a safety belt to which it is attached.

16. A pyrotechnic tensioning device according to claim 15, wherein the said device for limiting the tensile force comprises an ejectable plug and a frangible flange normally retaining the plug in position and arranged to fracture when the internal pressure exceeds a predetermined value, the said piston having a bore with an outlet normally sealed by the plug, and the bore connecting the said combustion chamber on one side of the piston with the space on the opposite side of the said piston when the plug is ejected.

17. A pyrotechnic tensioning device according to claim 15, wherein the device for limiting the tensile force comprises an ejectable annular piston and a retaining disc which normally retains the annular piston in position and is arranged to fracture when the internal pressure exceeds a predetermined value.