Winding – tensioning – or guiding – Reeling device – With spring motor
Reexamination Certificate
2000-02-25
2002-07-16
Jillions, John M. (Department: 3653)
Winding, tensioning, or guiding
Reeling device
With spring motor
Reexamination Certificate
active
06419176
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to a pre-tensioner which rapidly rotates a take-up shaft of a seat belt retractor in the belt take-up direction, the pre-tensioner being incorporated in the seat belt device for restraining an occupant to a seat of a vehicle. More particularly, the present invention relates to a pre-tensioner which can securely impart pre-tension on the belt. The present invention also relates to a pre-tensioner which can effectively use pressure developed by a gas generator or to a pre-tensioner which can be constructed in a compact form as a whole and have lighter weight.
2. BACKGROUND OF THE INVENTION
Among seat belt devices installed in vehicles such as automobiles, a seat belt device of a type having a pre-tensioner has been multiplied these days. Such a pre-tensioner rapidly rotates a reel (take-up shaft), on which a seat belt is wound, in the belt take-up direction when a vehicle comes into collision in order to cancel the loosening on the wound belt and impart tension on the belt. In a typical pre-tensioner, powder is ignited according to a signal outputted in the event of the vehicle collision and a reeling mechanism is driven by gas pressure developed by the ignition.
One of such conventional pre-tensioners is disclosed in Japanese Patent Unexamined Publication No. 05-162614.
The pre-tensioner is provided with a pinion fixed to a belt take-up shaft. The pinion has external teeth formed on the outer periphery thereof.
A ring-like pulley separately from the pinion is arranged outside the external teeth of the pinion. The pulley has internal teeth formed on the inner periphery. The internal teeth of the pulley are capable of engaging the external teeth of the pinion. The pulley is accommodated in a housing and is held by pins within the housing. In a state where the pulley is held by the pins, a predetermined clearance between the internal teeth of the pulley and the external teeth of the pinion is ensured. The terminal end of a rope is attached to the outer periphery of the pulley. The rope near the terminal end is wound on the outer periphery of the pulley for several full circles. The start end of the rope is secured to a piston of a power source (gas generator). The piston slides within a cylinder extending straight outside of the housing when the gas generator ignites the powder.
The operation of the conventional pre-tensioner is as follows.
Before the operation of the pre-tensioner, the pulley is held by the fixed pins in a position within the housing where the internal teeth of the pulley and the external teeth of the pinion are not engaged. Therefore, the take-up shaft can freely rotate. As the gas generator is actuated in this state, however, the piston is pushed by gas generated from the gas generator and thus slides within the cylinder, so the rope secured to the piston is pulled. As the rope is pulled, force is exerted on the pulley so as to shear the fixed pins, thereby canceling the holding of the pulley. As a result of this, the pulley on which the rope is wound starts to rotate and move so that the internal teeth of the pulley engages the external teeth of the pinion. Because of this engagement, the rotation of the pulley is transmitted to the pinion and the take-up shaft rotates at the same time as the rotation of the pinion, thereby imparting pre-tension on the belt.
However, the aforementioned pre-tensioner has the following problems:
(1) Since the rope is employed as a member for pulling the pulley, the casing and cylinder must have openings for introducing the rope. There is a problem that the force for biasing the piston becomes weaker because a part of gas from the gas generator leaks through the openings.
(2) Since the cylinder for pulling the rope extends straight outside the casing, the size and weight of the pre-tensioner as a whole are increased.
Another conventional example will be explained.
FIG.
17
(
a
) is an exploded perspective view of the pre-tensioner disclosed in PCT International Publication No. WO95/27638 and FIG.
17
(
b
) is a perspective view showing the details of a drive wheel.
The pre-tensioner comprises a pair of drive wheel halves
103
,
104
attached to a take-up shaft
101
for a seat belt as shown in FIG.
17
(
a
). The drive wheel half
104
is secured to the take-up shaft
101
. The drive wheel half
103
is assembled to the take-up shaft
101
via the gear
106
. Both the drive wheel halves
103
,
104
form together a drive wheel
105
as shown in FIG.
17
(
b
) by arranging them to confront to each other. The drive wheel halves
103
,
104
are provided with a plurality of concavities
103
a
,
104
a
circumferentially formed in the respective confronting surfaces. When the drive wheel halves
103
,
104
are arranged to confront to each other, the concavities
103
a
,
104
a
form cup-like (hemispheric) concavities
100
. Also formed between the drive wheel halves
103
and
104
is a groove
110
.
Disposed between the drive wheel halves
103
,
104
is a sword box
114
. The sword box
114
is attached to a retractor housing (not shown) as well as a cup (casing)
112
. The sword box
114
is provided with projecting guide plates
116
,
117
. The guide plates
116
,
117
are positioned in the groove
110
of the drive wheel
105
.
Disposed inside the cup
112
is a U-like tube
118
. The tube
118
is positioned to surround the sword box
111
. The tube
118
has a notch-like opening
118
a
formed therein to confront a space between the guide plates
116
,
117
. Parts of the periphery of the drive wheel
105
enter into the opening
118
a.
Disposed on one end (proximal end) of the tube
118
, the right upper end in the drawing, is a gas generator
115
. The other end (distal end) of the tube
118
is fitted in a throat portion
119
formed in the cup
112
. Accommodated in the tube
118
are mass balls
120
for driving the drive wheel
101
. The mass balls
120
are a plurality and series of spheres. The mass balls
120
have a piston
121
on the proximal side (the side near the gas generator
115
).
The works and problems of the aforementioned pre-tensioner will be described with reference to FIGS.
16
(
a
) through
16
(
c
).
FIGS.
16
(
a
) through
16
(
c
) are front views schematically showing portions surrounding the drive wheel
105
of the conventional pre-tensioner of FIG.
17
(
a
). FIG.
16
(
a
) is a view showing the state before the actuation of the pre-tensioner, FIG.
16
(
b
) is a view showing the state of the normal actuation of the pre-tensioner, and FIG.
16
(
c
) is a view showing the state of the abnormal actuation of the pre-tensioner.
In the state shown in FIG.
16
(
a
) (before the actuation), the head mass ball
120
is not in contact with the drive wheel
105
so that the drive wheel
105
and the take-up shaft
101
can freely rotate. Therefore, no clutch mechanism is required between the drive wheel
105
and the take-up shaft
101
.
As the gas generator
115
(FIG.
17
(
a
)) is actuated in the event of an emergency, generated gas presses the mass balls
120
in the tube
118
toward the bottom in the drawing. Thus, the head mass ball
120
advances to the opening
118
a
and comes in contact with the side of one of the teeth
105
a
of the drive wheel
105
which is entered into the opening
118
a
. At this point, the mass ball
120
exerts force in a direction of arrow C, rotating the drive wheel
105
.
Since each concavity
105
b
between the adjacent teeth
105
a
is formed hemispheric corresponding to the dimension of the mass balls
120
, the concavities
105
b
and the mass balls
120
are engaged in regular order so that the drive wheel
105
rotates. At the same time as the rotation of the drive wheel
105
, the take-up shaft
101
rotates to wind up the belt in the belt take-up direction.
In this pre-tensioner, however, the rotation of the drive wheel
105
and the take-up shaft
101
is sometimes not secured. That is, as shown in FIG.
16
(
c
), there is a possibility that the mass ball
120
pressed from the tube
118
collide
Jillions John M.
Takata Corporation
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