Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2000-12-21
2003-06-17
Nguyen, John Q. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
C280S805000
Reexamination Certificate
active
06578786
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a seat belt retractor for accommodating a webbing in such a manner as to allow the webbing to be retracted and withdrawn, and more particularly, to a seat belt retractor with a torsion bar for absorbing load exerted on a webbing when an occupant wears the webbing and the webbing is stopped from being withdrawn in the event of emergency, such as a vehicle collision, at which large deceleration is exerted on the vehicle.
Conventionally, a seat belt device installed in a vehicle, such as an automobile, prevents an occupant from jumping out of a vehicle seat by restraining the occupant with a webbing or seat belt thereof, thereby protecting the occupant in the event of emergency as mentioned above.
Such seat belt device is provided with a seat belt retractor for accommodating the webbing. When the webbing is not used, the webbing is fully wound on a reel of the retractor. When an occupant wears the webbing, the webbing is withdrawn to hold the occupant on the seat. In the seat belt retractor, a locking mechanism is activated in the event of emergency as mentioned above to stop the rotation of the reel in a belt unwinding direction, thereby preventing the webbing from being withdrawn. Therefore, the webbing can securely restrain and thus protect the occupant.
However, the conventional seat belt retractor of the seat belt device has a problem. That is, when the webbing restrains and protects the occupant, a large deceleration is exerted on the vehicle, so that the occupant tends to move forward due to a large inertia force. Accordingly, a large load is exerted on the webbing, and the occupant receives a large impact load from the webbing. Though this impact load is not so severe for the occupant, it is better to absorb the impact load.
Accordingly, a seat belt retractor which has a torsion bar to absorb the load exerted on a webbing in the event of emergency when the webbing is worn has been developed.
FIG. 10
is a vertical sectional view showing an example of the conventional seat belt retractor having the aforementioned torsion bar. In the drawing, reference numeral
1
designates a seat belt retractor, reference numeral
2
designates a U-like frame, reference numeral
3
designates a webbing, reference numeral
4
designates a reel which is rotatably supported between side walls of the U-like frame
2
and on which the webbing
3
is wound, reference numeral
5
designates a deceleration sensing means which detects a large deceleration of the vehicle in case of emergency mentioned above, reference numeral
6
designates a locking mechanism which is activated by the deceleration sensing means
5
to prevent the reel
4
from rotating in the webbing unwinding or withdrawing direction, reference numeral
7
designates a torsion bar loosely fitted and inserted in the axial direction in the center of the reel
4
and rotatably connecting the reel
4
and the locking mechanism
6
, reference numeral
8
designates spring means for always biasing the reel
4
in the webbing winding direction through a bush
10
by the spring force of a spiral spring
9
, reference numeral
11
designates a pretensioner which is activated in the case of emergency mentioned above for producing webbing winding torque, and reference numeral
12
designates a bush for transmitting the webbing winding torque of the pretensioner
11
to the reel
4
.
The locking mechanism
6
includes a pawl holder
14
which can rotate together with a first torque transmitting portion
17
described later of the torsion bar
7
and pivotally holds a pawl
13
, and a lock gear
6
a
which rotates together with the torsion bar
7
in a normal state and stops according to the activation of the deceleration sensing means
5
to produce rotation relative to the torsion bar
7
in emergency and engages the pawl
13
with one of internal teeth
19
of the side wall of the frame
2
, thereby stopping the rotation of the pawl holder
14
, i.e. the rotation of the reel
4
in the webbing unwinding direction. The pawl holder
14
has an external thread portion
15
. Screwed onto the external thread portion
15
is a nut-like stopper member
16
which rotates together with the reel
4
.
The torsion bar
7
has the first torque transmitting portion
17
which is fitted to the pawl holder
14
for preventing the relative rotation, and a second torque transmitting portion
18
which is fitted to the reel
4
for preventing the relative rotation.
The reel
4
is always biased by the spring force of the spring means
8
in the webbing winding direction through the bush
10
, the torsion bar
7
, the second torque transmitting portion
18
of the torsion bar
7
, and the bush
12
. When the pretensioner
11
is activated, the webbing winding torque produced by the pretensioner
11
is transmitted to the reel
4
through the bush
12
, whereby the reel
4
winds up the webbing
3
for a predetermined amount.
In the conventional seat belt retractor
1
having the aforementioned structure, the webbing
3
is fully wound by the biasing force of the spring means
8
when it is not used. As the webbing
3
is withdrawn at a normal speed for wearing the webbing, the reel
4
rotates in the webbing unwinding direction, so that the webbing
3
is smoothly withdrawn. After a tongue (not shown) slidably fitted to the webbing
3
is inserted into and engaged with a buckle fixed to a vehicle body, an excess amount of the webbing
3
pulled outwardly is wound onto the reel
4
by the biasing force of the spring means
8
until the webbing
3
is fitted to the occupant's body without a feeling of oppression.
In the event of emergency as mentioned above, the webbing winding torque produced by the pretensioner
11
is transmitted to the reel
4
, so that the reel
4
winds up the webbing
3
for a predetermined amount, thus strongly restraining the occupant. On the other hand, the deceleration sensing means
5
is activated by large deceleration produced in the emergency to activate the locking mechanism
6
. That is, the activation of the deceleration sensing means
5
prevents the rotation of the lock gear
6
a
in the webbing unwinding direction and then the pawl
13
of the locking mechanism
6
pivots and engages one of the internal teeth
19
of the side wall of the frame
2
so as to stop the rotation of the pawl holder
14
in the webbing unwinding direction. As a result of this, the reel
4
rotates in the webbing unwinding direction relative to the pawl holder
14
while the torsion bar
7
is twisted. From this, the reel
4
rotates in the webbing unwinding direction while twisting the torsion bar
7
. By this twisting of the torsion bar
7
, the load applied to the webbing
3
is limited, thus absorbing the impact on the occupant.
Since the reel
4
rotates relative to the pawl holder
14
, the stopper member
16
rotates relative to the external thread portion
15
which is screwed into the stopper member
16
, whereby the stopper member
16
moves toward the pawl holder
14
. As the stopper member
16
comes to contact the pawl holder
14
, the stopper member
16
is prevented from further rotating, so that the reel
4
is also prevented from rotating and the torsion bar
7
is prevented from being twisted. In this manner, the withdrawal of the webbing
3
is stopped, whereby the occupant is restrained by the webbing
3
securely, and the maximum allowable twisting deformation of the torsion bar
7
is defined, thereby preventing the torsion bar
7
from being broken by further twisting.
In addition, in this conventional seat belt retractor
1
, the pawl holder
14
of the locking mechanism
6
rotates in the webbing unwinding direction relative to the lock gear
6
a
when the webbing is rapidly withdrawn. Also in this case, the pawl
13
of the locking mechanism
6
engages one of the internal teeth
19
of the side wall of the frame
2
so as to stop the rotation of the pawl holder
14
in the same manner as mentioned above. Therefore, the reel
4
is
Kanesaka & Takeuchi
Nguyen John Q.
Takata Corporation
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