Chairs and seats – Body or occupant restraint or confinement – Safety belt or harness; e.g. – lap belt or shoulder harness
Reexamination Certificate
1998-10-21
2001-06-26
Cuomo, Peter M. (Department: 3624)
Chairs and seats
Body or occupant restraint or confinement
Safety belt or harness; e.g., lap belt or shoulder harness
C280S806000, C060S638000, C297S480000
Reexamination Certificate
active
06250720
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a tensioner for a safety belt, with a piston/cylinder unit, which comprises a cylinder and a piston arranged in its interior, with a compressed gas source on the activation of which the piston is displaced, with a belt engaging means which engages on the safety belt, with a traction transfer means which connects the piston with the belt engaging means, and with a damping means for the absorption of energy on deceleration of the belt engaging means, the cylinder having a first end closer to the belt engaging means and a second end further away from it, the damping means having a first part connected with the traction transfer means, surrounding the traction transfer means at least partially and arranged outside the cylinder in the non-actuated state of the tensioner, and having a second part connected with the cylinder and provided on the end wall, the parts being moved towards each other on tensioning and providing for the damping.
BACKGROUND OF THE INVENTION
Tensioners for safety belts must be constructed to be as small as possible due to the small amount of space available in the vehicle. Inside or outside the cylinder, a damping means is usually provided, influencing the axial length of the tensioner in a negative manner, which damping means brakes the piston at the end of the tensioning path and in so doing absorbs energy, whereby stress peaks are reduced. Owing to the length of tensioning path and damping path which were necessary hitherto, known tensioners have such an axial overall length that they can not be installed in the vehicle without cable deflectors.
U.S. Pat. No. 4,458,921 discloses a generic tensioner having a damping member in the form of a sleeve which surrounds the traction cable and adjoins a deflector fitting connected to the traction cable. At the end of the tensioning process, this damping part cuts into a sealing member provided on the end face in the cylinder end wall and is caught therein. This process serves for the damping at the end of the tensioning path. However, the damping path is extremely short by design, so that great stresses occur during damping.
SUMMARY OF THE INVENTION
The invention provides a tensioner which with the same tensioning path is distinctly shorter in axial direction compared with known tensioners, without this being achieved at the expense of a poorer damping effect. This is achieved in a tensioner of the type initially mentioned in that the first part displaces the second part at least partially into the interior of the cylinder during the damping process. In tensioners known hitherto, the damping means is either arranged completely inside or completely outside the cylinder or one damping means is provided inside the cylinder and one outside the cylinder. When the damping means is outside the cylinder, the shape of the cylinder remains unchanged after the tensioning process. In contrast to this, the invention makes provision that at least one of the parts of the damping means penetrates into the interior of the cylinder at the end of the tensioning process. The displacement or deformation of the end wall of the cylinder is used in a specific manner for damping. The tensioning process is not negatively impaired by the change in shape of the cylinder, and the entire tensioner can be installed in the vehicle without a cable deflector, owing to the axially shorter type of construction due to the principle.
When the first part strikes onto the second part, according to a preferred embodiment, the second part can be displaced into the interior of the cylinder by the striking of the first part.
Furthermore, it is also possible that the first part penetrates into the second part and in so doing displaces the second part into the interior of the cylinder.
A third possibility consists in that the first part penetrates into the second part and the first part moves into the interior of the cylinder. This is able to be achieved for example in that the first part penetrates so deeply into the second part that it projects into the interior of the cylinder.
To simplify the manufacture, the second part is at least a section of the end wall of the cylinder at the first end. As a purposeful deformation and/or displacement of the second part on striking of the first part is desired, the second part is constructed as a separate part which is fastened to the cylinder and which is released from its fastening by the first part. Thereby, the forces acting between the first and second parts on deceleration of the belt articulation member can be kept in close, predetermined limits.
A simple possibility for the technical development of the second part consists in constructing this as a seal which separates the interior of the cylinder from its exterior and has an opening through which the traction transfer means extends. The second part thereby has a dual function, on the one hand acting for damping and on the other hand acting as a seal.
The damping effect can come about through various effects which can occur individually or in combination. On the one hand, by the purposeful plastic deformation of the first and/or of the second part on striking of the parts on each other a damping effect can be achieved, on the other hand it can be achieved by the penetrating of the first or second part into the interior of the cylinder and the resultant reduction in volume of the working space inside the cylinder. In the latter case, the cylinder acts like a pneumatic shock absorber, because on penetration of the first or of the second part into the interior of the cylinder, work is carried out against the remaining compressed gas situated in the working space.
The plastic deformation can be achieved by the provision of members between the first and the second part or, according to a preferred embodiment, in that the second part has a sleeve-shaped section which extends substantially outside the cylinder in the non-actuated state of the tensioner. In the actuated state of the tensioner, the first part deforms the sleeve-shaped section.
The previously described mode of operation of a hydraulic shock absorber can be achieved in that inside the cylinder a working space is provided for the gas which is released and also a stop is provided for the piston. The position of the first and second part, of the piston and of the stop are coordinated with each other such that after the striking of the piston onto the stop, the first and/or second part penetrates into the interior of the cylinder and leads to the reduction of the volume of the working space.
In order to prevent too much compressed gas from escaping from the working space via the end wall at the first end of the cylinder on reduction of the volume of the working space, a damping piston is provided which is arranged in the region of the first end in the non-actuated state of the tensioner. The damping piston is displaced in the direction of the piston by the first part and thereby reduces the volume of the working space. The second part can be coupled with the damping piston or can be integrally connected therewith, forming one piece.
A radial gap between the damping means and the inner wall of the cylinder can become increasingly smaller with an increasing distance covered by the damping piston, so that less gas emerges from the piston and the resistance for the damping piston increases.
According to a preferred embodiment, a fastening means is provided which connects the traction transfer means and the piston with each other, and which is constructed so that the traction transfer means is uncoupled from the piston on deceleration of the piston. Thereby, two units are produced which are separate from each other, namely on the one hand the piston and on the other hand the traction transfer means with the belt articulation member. These two units can be braked separately from each other and chronologically one after the other, if necessary with two separate damping means.
In order to save further structural space, the compressed gas source can be arranged inside th
Cuomo Peter M.
Tarolli, Sundheim, Covell Tummino & Szabo L.L.P.
TRW Occupant Restraint Systems GmbH & Co. KG
Vu Stephen
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