Power plants – One shot explosion actuated expansible chamber type motor – Having latch – rupture or safety means resisting movement of...
Patent
1998-11-16
2000-08-01
Nguyen, Hoang
Power plants
One shot explosion actuated expansible chamber type motor
Having latch, rupture or safety means resisting movement of...
60638, F01B 2908
Patent
active
060949139
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a belt tensioner, more particularly a buckle tensioner for a vehicle occupant restraint system, comprising a housing, a gas generator, a working space into which the pressurized gas released in a restraint situation flows, a piston part which is displaceable in the working space by the pressurized gas, a belt engagement means in force-transmitting relationship with the buckled belt, and a traction transfer means which connects the belt engagement means with the piston part.
In a restraint situation, hot pressurized gas released by the gas generator flows into the working space to displace the piston part. The traction transfer means, normally a traction cable, is exposed in the process to high temperatures due to the immediate contact with the hot pressurized gas and may thereby be damaged. In the case of buckle tensioners, in addition to the thermal stress the traction transfer means is subjected to a high tensile load which is exercised by the vehicle occupant shifting forward. The traction transfer means has hitherto been overdimensioned to enable it to withstand the loads, which, however, makes the belt tensioner more expensive to manufacture and increases its weight.
The invention provides a belt tensioner in which the thermal stresses to which the traction transfer means is subjected are lower than in the case of belt tensioners known hitherto. This is achieved in a belt tensioner of the type mentioned at the outset in that in the working space a housing-fixed deflection means is provided which guides the stream of pressurized gas away from the traction transfer means and at least largely prevents the pressurized gas which flows out of the gas generator from directly impinging on the traction transfer means. Unlike in belt tensioners known hitherto, in the case of the belt tensioner in accordance with the invention the hot pressurized gas is prevented from directly impinging on the traction transfer means, whereas in belt tensioners known hitherto the pressurized gas stream is typically directed immediately to the traction transfer means via a radial bore, so that the high temperature--even though of short duration--in combination with a high flow rate may result in the damage to the traction transfer means as described above. Since the time period in which the hot pressurized gas flows into the working space is very short, it is sufficient to prevent the traction transfer means from being directly impinged.
The deflection means preferably guides the pressurized gas towards the housing wall at which the pressurized gas is cooled down significantly and from where it can then strike the traction transfer means without placing it under too great a thermal stress.
The deflection means need not necessarily be integrally connected as a one-piece part with the housing of the belt tensioner, it also being possible to design the deflection means as a separate part which is not displaced with the traction transfer means during the tensioning process. In accordance with a preferred embodiment, the deflection means may be a section of the gas generator housing. The gas generator housing is normally closed and is not opened until ignition of the propellant charge occurs. The pressure produced on activation causes the gas generator housing to be bent open in the fashion of a flap in the region of the section forming the deflection means, and the section projecting into the working space serves as deflection means and surrounds the traction transfer means.
Preferably, the gas generator housing is annular and is disposed in the interior of the housing of the belt tensioner. The section is formed by the end wall adjacent to the working space. The end wall may be provided with predetermined breaking lines defining sections which open like flaps upon activation of the belt tensioner. Since the end wall usually flips open radially inwards, its wall thickness is greater in radially inwardly located areas than it is in radially outer areas which are located further away from the traction transfer
REFERENCES:
patent: 3199288 (1965-08-01), Nahas
patent: 5519997 (1996-05-01), Specht
patent: 5553890 (1996-09-01), Buhr et al.
patent: 5927756 (1999-07-01), Wier
patent: 5956954 (1999-09-01), Schmid
Nguyen Hoang
TRW Occupant Restraint Systems GmbH & Co. KG
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