Belt retractor with force limitation

Details Belt retractor with force limitation Belt retractor with force limitation

1999-06-24

2001-03-27

Marcelo, Emmanuel M. (Department: 3653)

Winding, tensioning, or guiding

Reeling device

With spring motor

C280S805000, C297S470000

Reexamination Certificate

active

06206316

ABSTRACT:

BACKGROUND OF THE INVENTION
Conventional belt retractors comprise a frame, in which a belt spool is rotatably mounted, locking teeth and a locking catch which can be brought from an initial position into a locking position by a locking mechanism, whereby the belt spool is locked relative to the locking teeth.
In addition to the usual function of a belt retractor, namely making available a safety belt and blocking the unwinding of the belt webbing from the belt spool if required, many belt retractors nowadays also make available a so-called force-limiting function. The force-limiting function consists in making possible an unwinding of the belt webbing, despite the belt spool actually being locked, when the force acting in the belt webbing exceeds a predetermined value. The unwinding of the belt webbing which is then possible leads to an additional way being made available for decelerating the vehicle occupant, whereby the forces occurring due to the acting deceleration are reduced. In this way, the forces due to deceleration can be limited to a value where usually no injuries of any kind occur to the occupant of the vehicle.
The force-limiting function can be achieved for example by means of a torsion rod which acts between the belt spool and the locking teeth, which are arranged on the belt spool.
The object of the invention consists in providing a belt retractor in which the force-limiting function can be realized with a low expenditure in terms of construction. Additionally, the limit of the torque acting on the belt spool, from which up the force-limiting function starts becoming effective, can be adapted easily to the respective requirements.
SUMMARY OF THE INVENTION
For this purpose, a belt retractor for a vehicle safety belt is provided, which comprises a frame, a belt spool rotatably mounted in the frame, a locking catch arranged on the belt spool, a locking mechanism adapted to pivot the locking catch between an initial position and a locking position, a locking disc and a locking toothing. The locking toothing is arranged on the locking disc. The locking catch when in the locking position engages into the locking toothing of the locking disc so that the belt spool is locked with respect to the locking disc. The locking disc is connected to the frame by means of a holding device which allows a rotation of the locking disc relative to the frame only after a predetermined torque has been exceeded. So under normal conditions the holding device causes the locking disc and hence the locking teeth to be held non-rotatably. Only if the torque is exceeding a predetermined value, the locking disc can be rotated relative to the frame, owing to the torque transferred to it from the belt spool via the locking catch and the locking teeth, whereby an unwinding of the belt webbing from the belt spool is possible.
Preferably the holding device contains a traction cable which loops around the circumference of the locking disc. Owing to the looping friction such a traction cable provides a comparatively high holding torque with already comparatively small traction forces acting in the traction cable. In contrast to known belt retractors, in which a torsion rod is used to provide the force-limiting function, the use of a traction cable makes it possible for the belt spool to carry out an unlimited number of turns relative to the frame of the belt retractor, when the force-limiting function is effective. In belt retractors with a torsion rod, the number of relative turns is usually limited to one or to a maximum of two turns of the belt spool relative to the frame.
Advantageous developments of the invention will be apparent from the subclaims.


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patent: 4323205 (1982-04-01), Tsuge et al.
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patent: 5967442 (1999-10-01), Wier
patent: 5975451 (1999-11-01), Kawamoto
patent: 6029924 (2000-02-01), Ono et al.
patent: 6047914 (2000-04-01), Sasaki
patent: 29714583 (1998-01-01), None

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