Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Field of the Invention
The invention pertains to a device for tightening a safety belt of a motor
vehicle.
Background of the Invention
In a device of this type which is disclosed in German Offenlegungsschrift
No.2,249,786, a gas generator is disposed in a piston and the piston is driven
by means of a propellant generated by the gas generator. The piston is guided
in a guide pipe and can be connected with a safety belt of a motor vehicle via
a traction mechanism. A pressure chamber, from-which the propellant
generated in the interior of the piston is discharged via at least one outlet
opening, is disposed in the guide pipe.
Summary of the Invention
The invention is based on the objective of creating a device for
tightening a safety belt of a motor vehicle, which device has a more compact
construction and which requires a smaller number of components for assembly.
A guide pipe forms a pressure chamber on the end of a piston at which
propellant is discharged. In addition, a combustion chamber is formed in the
interior of the piston in which the final propellant that provides the driving
pressure is formed due to the
combustion of the propellant being discharged from the gas generator during
the ignition. On the side which is directed towards the interior of the piston
and/or the combustion chamber, the gas generator can be equipped for this
purpose with a bursting base as is, for example, described in German Patent
Application No. P 4228696.4 or European Patent Application No.
93/106542.9.
In addition, the gas generator can be constructed in such a way that the
gas is discharged from the gas generator in at least two stages, whereby the
gas discharged during the first stage applies a driving pressure onto the pistonwhich is lower as compared to the gas discharged during the ensuing second
stage and/or the ensuing stages. A pyrotechnic gas generator of this type is
disclosed in German Patent Application No. P 4228696.4. This measure
facilitates a controlled adaptation of the pressure profile as well as a reduced
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stress on the components to be moved. Initially, a pushing force is applied ontothe resting mass of the components to be moved during the first driving stage.
In the ensuing stage and/or stages, the final pressure is built up due to the
increased explosion speed. This results in a reduced stress on the part of the
safety belt to be moved during the acceleration process.
The drive mechanism can be used in any instance in which components
are moved from an initial position into a final position under a carefully applied
traction within a short period of time, e.g., within fractions of a second. Thisdevice can, for example, be used for moving safety shutters or components in
a motor vehicle
from a normal position into a retracted position. It is, for example, possible, to
retract a steering wheel, foot pedals or a safety belt.
An additional reduction of the individual parts to be assembled as well
as a reduction in the space requirement is achieved by arranging a return lock
on the piston which can be engaged with the inner wall of the guide pipe so
as to lock the movement of the piston opposite to the driving direction. This
means that the guide pipe fulfils an additional function, namely the function ofa deceleration pipe which cooperates with the return lock on its inner wall.
The return lock preferably is arranged on the end of the piston situated
in the driving direction. The traction mechanism preferably is rigidly connectedto the piston at this end of the piston, in particular via a cable pressing withwidened cross section. This measure allows forces acting upon the traction
mechanism to be transferred into the guide pipe which is fastened onto the
motor vehicle with a short power flux path
A preferred application of the invention is used for retracting a seat belt
lock of a safety belt. Through the retracting movement of the seat belt lock thesafety belt is tightened by the driven piston around the body of the motor
vehicle passenger, for example in an accident, via the traction mechanism
which preferably is constructed as a traction cable, so that the safety belt
tightener adjoins the body of the motor vehicle passenger. This prevents the
body of the motor vehicle passenger from being moved too far forward when
the safety belt is blocked in an accident.
Since the tightening movement of the seat belt lock must take place
within a few milliseconds, the lock is subject to a high acceleration force during
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the driving and the braking at the end of the tightening movement. To avoid
sudden braking, especially at the end of the tightening movements, an energy
absorber can be provided between the seat blet lock and the reversing
arrangement, through which the traction mechanism is led from the drive
5 piston to the seat belt lock; the energy absorber brakes the tightening
movement of the seat belt lock, especially at the end of the tightening
movement. This energy absorber can consists of an elastic material and can,
for example be in the form of a pipe. In particular, the material of the energy
absorber is softer than the material of the reversing arrangement. Braking can
10 be achieved by the softer material of the energy absorber being pushed into an
opening in the reversing arrangement at the end of the tightening movement,
through which the traction mechanism is led. In the process, the soft material
of the energy absorber is deformed and used up in braking the driving energy
of the seat belt lock..
Brief Description of the Figures
The invention is described in detail below with the aid of the
embodiments illustrated in the figures. The figures show:
Figure 1 is a cross-sectional view of a first embodiment of the drive
mechanism, and
Figure 2 is a view partly in cross-section of a second embodiment of the
drive mechanism.
Figure 3 schematic view of a further embodiment of the invention in
normal operating position; and
Figure 4 the embodiment shown in Fig. 3 after the retracting movement
of the seat belt lock.
Detailed Description of the Preferred Embodiments
The drive mechanisms illustrated in the Figures includes a guide pipe 7
in which is guided a piston 2 that is driven by a propellant. A gas generator 1
is arranged in the interior of the piston so as to realize the drive of the piston
2. Viewed in the driving direction (arrow A) of the piston 2, the gas generator
1 is situated at the front end of the piston 2. The gas generator 1 can be
constructed in accordance with European Patent Application No. 93/106542.9,
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i.e., the gas generator 1 has a bursting base 20 at its propellant outlet side 3.
This base opens once the gas generator 1 ignites. Consequently, the propellant
can be discharged into an interior space 4 of the piston. This interior space 4
of the piston is constructed as a combustion chamber. The combustion of the
exploding propellant occurs in this combustion chamber.
It is also possible to construct the generator as a two-stage generator
as described in German Patent Application No. P 4228696.4, i.e., the gas
generator is equipped with explosives of different explosion speeds, whereby
the gas of the first stage can be formed primarily by one or more explosives of
the ignition device. The ignition preferably is carried out with the aid of an
electric ignition device 14 that has a power supply 22. It is also possible to
provide a mechanical ignition device.
The interior space 4 of the piston serving as the combustion chamber
simultaneously serves for accommodating a cable pressing 17 which has a
wider diameter than the diameter of the traction
cable that serves as the traction mechanism 15. The cable pressing 17 in
addition comprises a support ring 19 which firmly adjoins the inner side of the
piston base 18, namely also in the starting position (Figure 1). One or more
recesses 5 through which the propellant formed in the interior space 4 of the
piston can be discharged is (are) situated in the cable pressing 17, in particular
in the support ring 19. The propellants are discharged into a pressure chamber
6. The interior space 4 of the piston, which serves for accommodating the
cable pressing 17, simultaneously acts as a combustion chamber towards
which the propellant outlet side 3 of the gas generator 1 is directed.
A return lock 9 is situated at the rear end of the piston 2 viewed in the
driving direction A. The return lock 9 according to Figure 1 is equipped with anexpandable locking element 10 which consists in this embodiment of several
ring segments, e.g., three ring segments. However, it is also possible to
construct the locking element as a snap ring. This locking element 10 is guided
on a conical projection 11. The conical projection 11 is formed onto the outer
side of the piston base 18. The conical projection 1 1 is constructed in a hollow
fashion. Its interior is connected to the pressure chamber 6 via leakage
openings 23, whereby the outlet opening and/or outlet openings 5 are directed
towards said pressure chamber. In the starting position, the conical projection
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11 is braced on a closure element 8 of the guide pipe 7. This closure element
can be constructed as a plastic plug and can form a filter for combustion
residues. The other end of the pipe can also be equipped with such a closure
element. The locking element 10 can be guided on the conical projection 11
5 with the aid of a peripheral spring element 21 and adjoin a peripheral rubber
cushion 24.
The locking element 10 is constructed in such a way that it can be
moved freely along the inner wall of the guide pipe 7 in the driving direction A.
When moving the piston opposite to the driving direction A, the locking
10 element 10 is widened by the conical projection 1 1 and engages with the inner
wall of the guide pipe such that it locks the movement of the piston. For this,
the locking ring preferably is provided with a pointed tip 13. Additional
peripheral grooves 12 can be formed in the inner wall of the guide pipe so as
to supplement the engagement between the locking element 10 with the guide
15 pipe 7 to lock the movement of the piston. The cross section of these
peripheral grooves 12 is constructed in such a way that the pointed tip 13 can
engage with the locking element in a positive as well as non-positive fashion.
Viewed in the moving direction A, the locking element has a slanted peripheral
surface which originates at the peripheral tip 13. This measure facilitates the
20 free movability of the locking element in the moving direction A in the
illustrated embodiment.
The traction mechanism 15 which is constructed as a traction cable
extends toward the component to be moved through the closure element 8. A
narrowing 26 (Figure 2) is provided in the guide pipe 7 at the end of the pipe
25 in order to limit the movement of the piston 2. The piston 2 moves into this
narrowing 26 with its front
part 25 that is constructed in a conical fashion, whereby the piston
subsequently is decelerated and stopped. As explained previously, the
tightened condition is maintained by means of the return lock 9 that engages
30 with the inner wall of the guide pipe 7 so as to lock the movement of the
piston. The forces which act upon the traction mechanism 15 are absorbed by
the cable pressing 17 fastened onto the piston 2 and transferred into the pipe
7 over a short path via the piston base and the return lock 9. The pipe 7 is
mounted to be stationary, e.g., on the body of a motor vehicle.
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Once the piston 2 is decelerated, the cable pressing 17 with the traction
mechanism 15 connected thereon continues its movement in the driving
direction A of the piston due to its inert mass. In the embodiment shown, a
brake 16 in the form of a disk spring is arranged between the cable pressing
5 17 which produces the connection between the piston 7 and the traction
mechanism 15. The cable pressing 17 is decelerated by brake 16 during its
continued movement in the driving direction A. This measure facilitates a
double-stage deceleration at the end of the driving movement.
In the embodiment shown in Figure 2, the return lock 9 which also can
10 act as a return brake consists of roller bodies 27 which adjoin a ring 28 of
elastic material in their starting position. The roller bodies 27 are retained in a
tapered, annular space which encompasses the piston. The inner side of this
space has a slanted surface. This slanted surface is formed by hard shells 29
which encompass a piston part 30 that consists of a soft material, e.g.,
15 an aluminum alloy. The other annular limitation is formed by the inner surface
of the guide pipe 7.
When moving the piston in the direction of the arrow A, the remain in the
position shown in Figure 2. In a return of the piston 2, the roller bodies 27
roller bodies 27 order to prevent are displaced along the slanted surfaces of the
20 hard shells 29 and act as clamping bodies inside of the aforementioned tapered
space. It is also possible that the roller bodies are deformed on the inner wallof the pipe 7 and act as a brake.
The traction mechanism 15 which is constructed as a traction cable is
connected to a seat belt lock 31 of the seat belt in a motor vehicle which is
25 partially illustrated in the figures. The piston 2 facilitates that the seat belt lock
can, for example, be retracted by a distance of 80 mm so that the safety belt
is tightened around the body of the motor vehicle passenger.
Fig. 3 and 4 show a further embodiment of the invention. In this
embodiment, the example shown in Fig. 1 or Fig. 2 can be used as the drive
30 mechanism in guide pipe 7. As in the example shown in Fig. 2, the traction
mechanism 15 constructed as a traction cable is led through a reversing
arrangement 32 to seat belt lock 31 of a safety belt for a motor vehicle.
Traction cable 15 is led through a curved opening 36 in reversing arrangement
32. The reversing arrangement 32 is fastened to a fastening point 35 on a
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vehicle seat not shown in detail, or on the vehicle body. As explained above,
seat belt lock 31 can be retracted by a distance S of about 80 mm through a
tightening movement generated by the drive mechanism in guide pipe 7. This
tightens the safety belt to the body of the motor vehicle passenger.
Fig. 3 illustrates the situation while a motor vehicle is in normal driving
mode. Fig. 4 shows the situation after seat belt lock 31 has retracted. In this
position, seat belt lock 31 has retracted by a distance S (Fig. 3). To carry outthe retracting movement, the seat belt lock is subjected to a high-speed in
relation to the retracting movement. When this retracting movement is ended
suddenly, high acceleration forces are applied to seat belt lock 31 and the
associated parts of the seat belt loc, i.e. to forces which can move the lock
parts from their set positions. To prevent the abrupt or sudden end of the
tightening movement, the shown embodiment in the form of a pipe is provided
with an energy absorber 33. This is provided between the seat belt lock and
the reversing arrangement 32. In the embodiment shown, the energy absorber
33 in the form of a pipe is fastened to traction mechanism 15, for example by
means of clamping. On the underside of seat belt lock 31, a pushing element
34 in the form of a stop is provided. This stop or the pushing element can be
formed by the cable pressing with which the traction mechanism 15
constructed as a traction cable is connected. During the retracting movement,
seat belt lock 31 is moved along distance S (Fig. 3). The energy absorber 33
in the form of a pipe is inserted by means of the pushing element 34 into the
opening 36 of reversing arrangement 32. Since the material of the pipe-shaped
energy absorber 33 is softer than the material of reversing arrangement 32, the
energy absorber is deformed. The energy thus expanded reduces the kinetic
energy which is applied to seat belt lock 31 by the tightener drive in pipe 7.
This causes the energy absorber 33 to brake the retracting movement,
especially toward the end of this movement. This braking action means the
shock applied to seat belt lock 31 and its components is dampened, so that the
forces acting upon the lock components are relatively low, and the risk that
they may move from their locking position is reduced or eliminated.
