Drive unit for a belt pretensioner in vehicle safety belt systems

• US 5,411,291 A
• Filed: 03/03/1994
• Issued: 05/02/1995
• Est. Priority Date: 03/06/1993
• Status: Expired due to Fees

• Current Assignee: TRW Repa GmbH
• Original Assignee: TRW Repa GmbH
• Inventors: Fohl, Artur
• Primary Examiner(s): Rice, Kenneth R.
• Application Number:
  US08/206,599
• Time in Patent Office: 425 Days
• Field of Search: 280/805, 280/806, 188/371, 188/375
• US Class Current: 280/806
• CPC Class Codes: B60R 2022/4661 comprising venting means, e.g. for avoiding overpressure in case of fire or for allowing return motion with energy absorption
• CPC Class Codes: B60R 22/4619 Transmission of tensioning power by cable, e.g. using a clutch on reel side
• CPC Class Codes: B60R 22/4652 Mechanical triggering means therefor also adapted for air bag inflators B60R21/33
• CPC Class Codes: F16F 7/12 using plastic deformation of members F16F9/30 takes precedence; yieldable means for mounting bumpers on vehicles B60R19/26; yieldable or collapsible steering columns B62D1/192

Abstract

The invention relates to a belt pretensioner for vehicle safety belt systems comprising a pyrotechnic gas generator (12) and a piston and cylinder unit (16, 20) mounted in a housing block (14). The piston (20) of the piston and cylinder unit (16, 20) is arranged on a first end (161) of the cylinder (16) as well as being connected with a cable (22) and it is accelerated towards the second end (162), which has a constriction, of the cylinder (16) by the gas pressure produced by the gas generator (12). The piston and cylinder unit (16, 20) with the housing block (14) and the gas generator (12) mounted therein constitute a pivotally bearinged vehicle-sensitive inertial mass. In accordance with the invention a deformable member (46) is arranged on the piston (20) and on acceleration of the piston (20) is entrained towards the second end (162) of the cylinder (16) by the piston (20) and on impingement on the wall parts of the cylinder (16) constituting the constriction is plastically deformed.

Claims

1. A drive unit for a safety belt pretensioner, comprising a base adapted to be secured on a vehicle bodywork, a vehicle-sensitive trigger mechanism comprising an inertial mass, a housing pivotally mounted in said base, a cylinder having a first end fixed in said housing block and a second, tapered end, a piston slidingly received in the first end of said cylinder, a cable connected to said piston and a pyrotechnic gas generator accomodated in said housing block, said piston carrying a dampening member of a material which is plastically deformed upon impact of said dampening member on cylinder wall portions defining said tapered cylinder end, and said housing block with said cylinder, gas generator, piston and dampening member being part of said inertial mass.

2. The drive unit of claim 1, wherein said dampening member is of a material which has a fusion temperature above a self-ignition temperature of said gas generator.

3. The drive unit of claim 2, wherein said dampening member is of a metallic alloy.

4. The drive unit of claim 1, wherein said piston has a neck portion with reduced cross section on its side facing said tapered cylinder end, said dampening member being tubular and seated on said neck portion.

5. The drive unit of claim 1, wherein said dampening member has an outer surface provided with ridges and grooves alternating in a peripheral direction.

6. The drive unit of claim 4, wherein said dampening member has an inner surface provided with ridges and grooves alternating in a peripheral direction, said ridges engaging said neck portion of said cylinder.