Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2002-08-06
2003-12-16
Jillions, John M. (Department: 3654)
Winding, tensioning, or guiding
Reeling device
With spring motor
C280S806000
Reexamination Certificate
active
06663037
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a technical field of a pretensioner (hereinafter, sometimes referred to as “PT”) which rotates a reel shaft of a seat belt retractor in a belt-winding direction by reaction gas at an early stage in emergency event such as a vehicle collision, thereby increasing the force of restraining an occupant by a seat belt and, more particularly, relates to a technical field of a pretensioner comprising a piston which receives gas pressure of reaction gas and thereby produces force, and a plurality of force transmitting members for transmitting the force produced by the piston to a reel shaft of a seat belt retractor.
Vehicles such as automobiles are equipped with seat belt devices. In recent years, various kinds of seat belt devices with pretensioners have been developed. A pretensioner is a device for rapidly removing slack of a seat belt and also applying tension to the seat belt to increase the force of restraining an occupant by rotating a reel shaft of a seat belt retractor in the belt winding direction by the reaction gas generated by a gas generator at an early stage in emergency event such as a vehicle collision.
As an example of conventional pretensioners, a pretensioner has been proposed in Japanese Patent Unexamined Publication No. 2001-63519 (incorporated by reference herein), which comprises a piston which receives gas pressure of reaction gas and thereby produces force, and a plurality of force transmitting members, composed of balls, for transmitting the force produced by the piston to a reel shaft of a seat belt retractor.
FIGS.
4
(
a
) and
4
(
b
) disclose a pretensioner disclosed in the aforementioned publication, wherein FIG.
4
(
a
) is a sectional view showing the pretensioner in non-operational state and FIG.
4
(
b
) is a sectional view similar to FIG.
4
(
a
) but showing the pretensioner during winding-up a seat belt.
FIGS.
4
(
a
) and
4
(
b
) disclose a pretensioner (PT)
1
, a pipe
2
having an open end
2
a
, a plurality of force transmitting members
3
which are movably disposed to be in contact with each other within the pipe
2
and are each composed of a metal ball made of iron, aluminum, or the like. A piston
4
is movably disposed within the pipe
2
to receive gas pressure of reaction gas and is composed of a ball made of material having sealing function such as silicone rubber and resin. A pressure vessel
5
having a pipe-like shape is connected to a proximal end
2
b
of the pipe
2
. A gas generator
6
is housed in the pressure vessel
5
. A ring gear
7
is positioned to enter into the pipe
2
through a cut-out portion
2
c
formed near the end of the pipe
2
. Levers
8
,
9
project from the outer periphery of the ring gear
7
. Internal teeth
10
are formed on the inner peripheral surface of the ring gear
7
. FIGS.
4
(
a
) and
4
(
b
) also disclose a reel shaft
11
of a seat belt retractor and a pinion
12
fixed to the outer periphery of the reel shaft
11
. External teeth
13
are formed on the outer periphery of the pinion
12
. A casing
14
is provided for receiving the force transmitting members
3
out of the pipe
2
. A gear holder
15
is provided for retaining the ring gear
7
in a home position where the internal teeth
10
of the ring gear
7
do not mesh with the external teeth
13
of the pinion
12
. A pair of pins
16
,
17
are studded on the gear holder
15
for holding levers
19
,
20
therebetween.
The pipe
2
forms a tube path curved in substantially flat oval shape. The force transmitting members
3
and the piston
4
housed in the pipe are guided to move along the tube path. Generally, the PT
1
is integrally installed in a frame of the seat belt retractor.
In the conventional PT
1
, the front-most force transmitting member
3
is held in a position where it is in contact with the lever
8
of the ring gear
7
as shown in FIG.
4
(
a
). The other force transmitting members
3
and the piston
4
are held in the illustrated state when the PT
1
is not operating (normal state). In addition, the levers
9
of the ring gear
7
are held between pairs of pins
16
,
17
of the gear holder
15
, respectively, in order to retain the ring gear
7
in the home position, shown in FIG.
4
(
a
). As a result, the internal teeth
10
of the ring gear
7
are held in a position in which they do not mesh with the external teeth
13
of the pinion
12
.
As the vehicle suffers an emergency event such as a collision, the event is sensed and the gas generator
6
is actuated to generate reaction gas into the pressure vessel
5
. The gas is introduced into the pipe
2
and directs toward the piston
4
as shown by an arrow A. The piston
4
receives the gas pressure of the gas so as to produce force pushing the force transmitting members
3
. The force is transmitted to the lever
8
of the ring gear
7
via the force transmitting members
3
which are in contact with each other.
The piston
4
is deformed easier than the force transmitting members
3
because the force transmitting members
3
are made of metal for achieving effective force transmission and the piston
4
is made of material such as resin for enabling the enlargement of the diameter of the piston
4
to seal the tube and prevent gas leak by. Therefore, during the force transmission, the piston
4
is deformed in the operational direction of gas pressure by the gas pressure and the reaction force from the force transmitting member
3
adjacent to the piston
4
. The diameter of the piston
4
is enlarged so that the pressure at the contact area of the piston
4
relative to the inner peripheral surface of the pipe
2
is increased, thereby creating the sealing function for sealing the gas pressure.
As the pushing force is transmitted to the lever
8
of the ring gear
7
, torque in the belt-winding direction B (the counter-clockwise direction in FIGS.
4
(
a
),
4
(
b
)) is produced on the ring gear
7
. The pins
16
,
17
holding the levers
19
,
20
are sheared by the torque so as to release the ring gear
7
from being retained in the home position by the gear holder
15
. Therefore, the ring gear
7
moves to substantially the right in the drawing, whereby the internal teeth
10
of the ring gear
7
are meshed with the external teeth
13
of the pinion
12
as shown in FIG.
4
(
b
).
The ring gear
7
rotates in the belt-winding direction (counter-clockwise direction) because the lever
8
is pushed through the force transmitting members
3
by the pushing force of the piston
4
receiving the gas pressure. Because of the rotation of the ring gear
7
, the pinion
12
starts to rotate in the same direction so that the reel shaft
13
starts to rotate in the same direction, thereby starting the winding-up operation of the seat belt.
The respective force transmitting members
3
and the piston
4
move in the counter-clockwise direction according to the rotation of the ring gear
7
due to the pushing force of the piston
4
receiving the gas pressure. The front-most force transmitting member
3
is positioned between the lever
8
and an adjacent lever
9
and the next two force transmitting members
3
are positioned between the lever
9
adjacent to the lever
8
and the next lever
9
. After that, subsequent two force transmitting members
3
fit in the space between subsequent two levers in the same manner. The force transmitting member
3
out of the engagement with the levers
8
,
9
is forced out from the end
2
a
of the pipe
2
and is received by the casing
14
.
Due to rotation of the reel shaft
13
, the seat belt is wound up, thereby removing slack of the seat belt and also applying tension to the seat belt to increase the force of restraining the occupant.
In the conventional seat belt retractor having such a pretensioner, the seat belt is wound up in a predetermined manner by the operation of the aforementioned pretensioner and subsequently the seat belt is also loaded to be withdrawn by inertia force of the occupant so that torque is applied to the reel shaft in the bel
Foley & Lardner
Jillions John M.
Takata Corporation
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