Note: Descriptions are shown in the official language in which they were submitted.
21~8~2~
Description
RotarY Actuator-o~erat~d Seat Bslt Pretensioner
Backqround of the Invention
The present invention relates to a pretensioner
for a seat belt system and, in particular, to a
pretensioner in which a seat belt take-up shaft is
rotat~d by a rotary actuator operat~d by gas pressure.
Pretensioners are increasingly being provided in
the seat belt systems of vehicles to tighten the belt,
which is loosely held in engagement with the vehicle
occupant, in an emergency such as vehicle collision and
to restrain the body of the occupant more effectively.
Various types of operating mechanisms for pretensioners
are known. One type of mechanism has a rotary actuator
operated by gas pressure in which a belt take-up shaft
or a take-up reel is rotated by a rotating mem~er o~
the actuator. Pre~ensioners of that type are disclosed
15 in U.S. Patent No. 4,455,000 ("Ref. 1"), Japanese
Patent Laid-Open Publication No. 58-195571
~corresponding to U.S. Patent No. 4,588,832, "Re~. 2"),
Japanese Patent Publication No. 59-15657 ~"Ref. 3"),
and Japanese Patent Laid Open Publication No. 60-45449
("Ref. 4"~.
When a seat belt retractor is used for a take-up
mechanism for pretensioning the ~elt, the prPtensioner
must not interfere with the normal belt-winding and
- pull-out operation of the retractor. Thus, the
rotating member of the pretensioner actuator is
separated from the seat belt take-up shaft or take-up
reel when not in operation, and is engaged with them
only during operation.
A clutch mechanism is needed for the separation,
but in each of the references referred to above, the
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--2--
clutch mechanism is complicated and costly, such as the
arranyements of Ref. 1, 2 and 4. Moreover, a take-up
shaft of greater length is required, because the clutch
mechanism is arranged in series with the rotating
member in the axial direction of the take~up sha~t. In
Ref. 3, a more reasonable arrangement, in which a pin
supported on a vane is operated by gas pressure, is
proposed. However, since the engaging part of the pin
is received in an axial hole in a flange of the take-up
reel, there is some restriction to the alignment pitch
of the hole with respect to hole diameter, and the
device cannot be made to have an accurate and precise
operation. this leads to the problem that there is
undesirable play with respect to when engagement
occurs. Also, because the engagement of the pin with
the hole is only achievable after the vane is rotated,
the engaging operation is not consistent.
SummarY of the Invention
To solve the above problems, it is an object of
the present invention to provide a pretensioner for
rotating a seat belt take-up shaft by a rotary actuator
in which the axial length of the seat belt take-up
shaft is kept small by improvements of the actuator and
clutch mechanism and the mounting positions of these
components in order to ensure more reliable and smooth
engaging operation between the rotating member o~ the
actuator and the seat belt take-up shaft.
In addition, it is another object of the present
invention to provide a rotary actuator-operated
pretensioner, wherein a sufficient winding stroke can
be maintained by inertial rotation of the take-up
shaft.
The foreyoing objects are attained, in accordance
with the present invention, by a rotary actuator-
operated seat belt pretensioner having a frame, a belt
_3_ 20~2~
take-up shaft rotatably mounted on the frame, a rotary
act-lator mounted on the frame and including a pressure
chamber, a rotating member and a gas generator for
supplying pressurized gas to the pres~ure chamber ts
impart rotation the rotating member, and a clutch
interposed between the rotating member and the take-up
shaft. The invention is characterized in that the
pressure chamber of the actuator is annular and
includes an inner wall defining a space within the
chamber, and the clutch is received in the space within
the chamber.
By the above arrangement, a space for the clutch
engagement is provided by the use of dead space inside
the annular actuator, and the size in the axial
direction of the entire pretensioner unit can be kept
small hy mounting the clutch means in the dead space.
In some embodiments, the clutch includes a driving
engagement member movably carried by the rotating
member and a driven engagement me~ber mounted on the
take-up shaft, and the driving engagement member has a
pressure-receiving portion facing the pressure chamber
so as to be moved into engagement with the driven
engagement member by a force due to gas pressure
supplied by the pressure generator to the pressure
chamber acting on the pressure-receiving portion. In
other embodiments, the clutch has a driven engagement
member mounted on the take-up shaft and a driving
engagement member mounted on the rotating member and
engaged ~y rotation of the rotating member with the
driven engagement member.
Advantageously, the driven engagement member of
the clutch may be a ratchet wheel mounted on the take-
up reel and the driving engagement member of the clutch
may include a clutch key movably carried by the
rotating member for movement into engagement with the
ratchet wheel along an axis of movement that intersects
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a portion of the ratchet wheel and is substantially
orthogonal to the axis of rotation of the take-up reel
shaft. It is desirable, as explained below, that the
axis of movement of the clutch key and the axis of
rotation of the take up shaft be spaced apart by a
predetermined offset distance.
In the pretensioner, according to the invention,
the gas generator is operated by a signal from an
electrical or mechanical sensor that responds to
acceleration. When the operating gas is supplied to
the pressure chamber of the actuator, the pressure of
the gas acts on the rotating member and also on the
pressure-receiving portion of the clutch key. the
clutch key i9 pushed toward the ratchet wheel, which is
situated in a spaced defined within the inner wall of
the actuator and is engaged by the key. The rotating
member is connected to the take-up shat, and the
rotating force o~ the rotating member is transmitted to
the seat belt take-up shaft through the clutch means.
As the result of the shaft rotation, the belt is
pretensioned by winding up of a belt segment on the
belt reel~ By operation of this ratchet-type
mechanism, it is possible to ensure reliable engagement
between the rotating member and the seat belt take-up
shaft.
When the axis along which the clutch key moves to
~ngage the ratchet wheel is spaced apart (offset~ from
the axis of rotation o~ the take-up shaft by a
pretensioned spacing, the impact ~orce caused by a
collision of the clutch key against the ratchet wheel
when the clutch is engaged is mostly ~onverted to a
rotating force with respect to the ratchet wheel. The
impact bending load applied on the take-up shaft is
considerably reduced by that arrangement.
In particular, even when addenda o~ the ratchet
wheel and ths clutch key collide against each other,
_5_ 2~ 9~ 2 ~
the addenda are easily daviated, and this ensures
stable clutch-engaging operation at all times. By
offsetting the axis of movement of the clutch key, the
strength of shaft can be kept small because the impact
force of the clutch engagement exerts only a small
bending stress on the take-up shaft, and this makes it
possible to have a li~htweight shaft.
According to another aspect o~ the present
invention, a clutch key connector is provided ~or
sequence control of the movement of the clutch key into
engagement with the ratchet wheel and of the rotation
of the rotary member caused by the gas pressure
introduced into the pressure chamber by the gas
generator. With sequence control, the delivery of
operating gas pressure to the clutch key and the supply
of the operating gas to the pressure chamber for
imparting rotation to the operating member can be
controlled in sequence when the operating gas is
supplied to the pressure chamber of the actuator.
Therefore, by the transmission of gas pressure from the
key connector, the clutch key is initially moved toward
the ratchet wheel located in a space defined in the
inner ~ree space of the actuator, and the clutch key is
brought into contact with the ratchet wheel. Then, the
supply of the operating gas to the pressure chamber ~y
the key connector commences, and the rotating member
starts to rotate. Thus, the clutch key and the ratchet
wheel are engaged with each other, directly if they are
already in the engaging state, or along with the
rotation of the rotating member if they are in a
contact state, and the rotating force of the rotating
member is transmitted to the seat belt take-up shaft.
With the above arrangements, sequence control of
the key connector ensures initiation of rotor rotation
only after the clutch-engaging condition ha~ been
established, and even when addenda of the ratchet wheel
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and the clutch key collide against each other, the
addenda are easily deviated and are engaged with the
adjacent addenda. This contributes to stable operation
of the clutch at all times.
The clutch may be an overrunning clutch that
allows rotation of the take-up shaft by inertia beyond
the amount of rotation of the rotating member of the
actuator. With an overrunning clutch, even when the
rotating member of the actuator reaches the end of its
stroke and stops, ths take-up shaft, which has been
driven by the rotating member, continues its rotation
by inertia. Thus, the take-up shaft rotation exceeds
that of the rotating member, and the overrunning clutch
is released. As the result, the take-up shaft
lS continues to rotate and takes up the belt until the
moment of inertia reaches equilibrium with the belt
tension.
The invention makes it possible to minimize the
increase in the axial length of the seat belt take-up
shaft due to overlapping of the actuator and the clutch
mechanism in a direction transverse to the shaft axis.
It is also possible to maintain a sufficient winding
stroke, which may exceed that of the actuator.
For a better understanding of the invention,
reference may be made to the following description of
an exemplary embodiment, taken in conjunction with the
accompanying drawings.
Descri~tion of the Drawin~s
Fig. 1 is a perspective view of a first embodiment
of a rotary actuator-operated pret~nsioner according to
the present invention, showing the components partially
exploded;
Figs. 2A to 2C show step by st~p the operation of
the first embodiment;
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Fig. 3 is a schematic side elevational view of a
second embodiment with a modi~ied clutch means;
Figs. 4A and 4B are schematic side views of a
third embodiment, with a modified clutch means, showing
its opexation;
Fig. 5 is a schematic cross-~ectional view of a
fourth embodiment, also with a modified clutch means,
and a part of a belt retractor;
Fig. 6 is a side view of a cylinder portion of the
fourth embodiment;
Fig. 7 is a perspective view of a rotor of the
fourth embodiment;
Figs. 8A and 8B are schematic side views of a
fifth embodiment, showing two stages of its operation;
Fig. 9 is a transverse cross-sectional view,
showing a sixth embodiment of the present invention;
Fig. 10 is an exploded perspective view of the
sixth embodiment;
Figs. llA to 11~ show the oper~tion of the sixth
embodiment, step by step;
Figs. 12A to 12E are fragmentary views of the
sixth embodiment, showing how the clutch engages;
Fig. 13 is a transverse cross-sectional view of a
seventh embodiment;
2S Fig. 14 is a transverse cross-section~l view of an
eighth embodiment of the invention;
Fig. 15 is an exploded per~pective view showing
details of the clutch key and key connector of the
eighth embodiment;
Fig. 16 is an exploded perspective view of the
eight embodiment;
Figs. 17A to 17F show the operation of the eighth
embodiment, sequentially; and
Figs. 18A to 18D are fragmentary views of the
eighth embodiment, showin~ sequentially engagement of
the clutch.
,
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Description of the Embodiments
Xn the first embodiment of the invention (Figs. 1
and 2~, a pretensioner base 2 is shown in Fig. 1
rotated by 180 degree~ around the axis with respect to
the position shown in Fig 2. A rectangular portion
102 is formed on one end of a seat belt take-up shaft 1
~hereinafter referred to simply a~ the "take-up
shaft"~, which is rotatably supported on the
pretensioner base 2 that also serves as a retractor
frame. The rectangular shaft portion 102 is engaged in
a rectangular hole 514 formed on a ratchet wheel 51.
The ratchet wheel 51, constituting a driven engagement
member, is thereby mountPd on one end of the take-up
shaft l. The ratchet wheel 51 has inclined ratchet
teeth 511 on its periphery.
A cylinder 30 is mounted on the pretensioner base
2 by suitable fasteners, such as screws. The cylinder
30 has an annular operation sp~ce Q, one side o~ which
is open. The wall of the cylinder 30 facing the
pretensioner base 2 has a hole (only barely visible in
Fig. 1) to receive the ratchet wheel 51. A bulkhead
304 extends inwardly from a cylindrical peripheral wall
of the cylinder in an approximately radial direction.
A hole 300 in the peripheral wall near the bulkhead 304
serves as a gas inlet hole, as described below.
The cylinder 30 receives a rotor 31, which is
rotatably supported on the ratchet wheel 51. The rotor
31 comprises a ring segment 311, serving as a bearing
for rotatable support on the outer periphery of the
3Q ratchet wheel 51, and a vane 312, serving as a
pressure-receiving portion and extending outwardly in
approximately the radial direction with respect to the
ring segment 311. In cooperating with a bulkhead 304
of the cylinder 30 and with a cover 32, which serves as
an end wall closing the open side of the operating
space Q of the cylinder 30, the ring segment 311 and
9 ~ ~ 9 .3 2 ~
the vane 312 divide the space in the cylinder 30 into
an operating space Q and an engaging spare where the
ratchet wheel 51 is located. Also, the operating space
is divided by the vane into a pressure chamber C and a
back pressurn chamber.
To separate an inner bore space S of the cylinder
30 from the pressure chamber C, a clutch key 52 is
provided, which serves as a driving engagement member
and is supported on one side by the vane 312 of the
rotor 31 and by a guide member 316 on the opposite side
so that the clutch key can be displaced in the radial
direction. The clutch key 52 has a tip 522 shaped to
engage the teeth 511 of the ratchet wheel 51. A
rectangular hole 313 in the ring segment 311 o~ the
xotor 31 permits the clutch key to move inwardly and
engage the ratchet wheel 51.
A gas generator 4 i5 mounted outside the cylinder
30. The gas supply hole o~ the gas generator 4
communicates with the hole 300 in the peripheral wall
of the cylinder 30 that leads to the pressure chamber
C.
In the ratchet wheel 51 of the first embodiment,
the teeth 511 on the outer periphery are inclined
backwardly with respect to the rotating direction of
the ratchet wheel 51. The tip 522 o~ the clutch key 52
i~ also of inclined form to match the profile of the
rat~het teeth 511, thereby to prevent disengagement of
the pawl 522 from the outer tooth 511 and also to
ensure smooth engagement.
When not in operation, the rotor 31 is at the
position shown in Fig. 2A. The guide member 316 of the
rotor 31 contacts the bulkhead 304. Under this
condition, the pressure chamber C in the operating
space Q has its smallest volume, and the clutch key 52
is held positioned by suitable means, such as a shear
pin (not shown), so that it doe~ not engage the teeth
2 ~ 2 ~
--10--
511 of the ratchet wheel 51. Therefore, ~ven when the
belt take-up shaft of a belt retractor is used as the
take-up sha~t l of the pretensioner, the retractor can
function normally.
When the gas generator is operated, such as by an
electric signal, and generated gas is introduced into
the pressure chamber C through the supply hole and the
gas inlet hole 300, the clutch key 52 is displaced
toward the ratchet wheel 51 by the force of the gas
pressure applied on its radially outer end, and it is
moved to the position shown by solid lines in Fig. 2B.
In this case, the tip 522 seats in a space between two
teeth 511 of the ratchet wheel 51, and the rotor 31 is
engaged with the ratchet wheel 51 by the clutch key 52.
Meanwhile, gas pre~sure also acts on the vane 312,
pushing it circumferentially, and the rotor 31 is
rotated around the axis as shown by two-dot chain line
Fig. 2B. The rotating force i5 transmitted to the
take-up shaft 1 through the clutch key 52 and the
ratchet wheel 51.
Upon thP rotation of the take-up shaft 1, a
segment of the belt i5 wound onto the take-up shaft 1,
and pretension is imparted by tightening of the belt.
Finally, ~he rotor 31 reaches the position shown in
Fig. 3C, and the pretensivning operation i5 thus
completed.
In the second embodiment, shown in Fig. 3, the
driven engagement member and the driving engagement
member are modified~ The clutch key 52 is received in
a hole, i.e. the rectangular hole 313 on the ring
segment 311 of the rotor 31, so that it can be freely
displaced in the radial direction, and the clutch key
52 serves as a driving engagement member. on the inner
face of the clutch key 52 are engagement teeth 522A
that engage outer peripheral teeth 511A of a gear 51A.
In the example shown, both teeth 522A and 511A have
2~9~2~
normal gear teeth pro~iles~ but they may be formed as
ratchet teeth as in the first embodiment. The other
features of the arrangement of Fig. 3 are virtually the
same as the first embodiment. Thus, the same reference
numerals as in the f irst embodiment are given to
represent thP corresponding members or components, and
a detailed description is not given here. (The same
applies hereinafter.) The operation of this embodiment
is the same as that of the first embodiment.
Figs. 4A and 4B show a third embodiment, in which
the driven engagement member and the driving engagement
member are modified. In the ring seqment 311 of the
rotor 31 is a hole 313B having an outer portion o~
conical shape. A ball 52B is received in the hole 313B
15 50 as ~o be displaceable in the radial direction by gas
pressure. On the inner wall of the ring segment 311 of
the rotor 31 is a groove 317 that extends backwardly
relative to the rotating direction of the rotor from
inner end of the circular hole 313B. This groove 317
is a tapered groove, which is deeper on the side
connected to the circular hole 313B and becomes
gradually shallower toward its opposite side. On the
back of the ball 52B, a valve 53B of conical shape is
provided. A roller 51B without outer teeth serves as
the driven engagement member.
When gas pressure is applied to the pressure
chamber C of this embodiment, the ball 52B is pushed
out o~ the hole 313B by gas pressure toward to the
roller 51B. Upon rotation of the rotor 31, the ball
52B moves backward in the groove 317. As shown in Fig.
2B, the ball ~inally enters into a gap between outer
periphery of the roller 51B and the groove 317, and the
rotor 31 is engaged with the roller 51B by a wedge
action. In the meantime, the valve 53B is seated in
the conical portion of the hole 313B and prevents
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-12-
leaking of excessive gas. The operation after this
stage is the same as in the first smbodiment.
Fig. 5 to Fig. 7 schematically illustrate a fourth
embodiment of the invention, where again the driven
engagement member and the driving engagement member arP
further modified. Whereas the driving engagement
member is moved by gas pressure and the two engagement
members are engaged in the rotating direction in the
above three embodiments, the driving engagement member
is operated by rotation of the rotor in this example,
and the two engagement members are engaged in a
direction perpendicular to the rotating direction.
As shown in the perspective view of Fig. 7, a
movable vane 52C serving as a driving engagement member
is pivotally mounted on the back of the vane 312 of the
rotor 31, and a friction plate 522C is mounted on inner
end of the movable vane 52C. The intermediate portion
of the movable vane 52C i5 inserted into an opening
313C of the rotor 31, and this prevents leakage of
excessive gas. A friction plate 51C mounted on an end
of the take-up shaft 1 and serving as the driving
engagement member is located face-to-face to the
~riction plate 522C. The upstream portion of the
op~rating space Q of the cylinder 30 has a tapered
surface 30C, and as shown in Fig. 5 and Fig. 6, this
surface is inclined with its outer portion wider and
narrowed down in the rotatin~ direction of the rotor,
terminating at a predetermined position. In this
example, the ring segment 311 of the rotor 31 has its
outer periphery supported in circular holes 300C and
320C of the cylinder 30 and the cover 32. In Fig. 5,
the reference numeral 22 represents the side wall of a
frame of the retractor, and 20 a winding spring unit of
the retractor.
In this pretensioner, the movable vane 52C
initially is biased clockwise around the pivot point by
-13- 2~
the weight of the friction plate 522C mounted on its
inner end, and the two friction plates 522C and 51C are
in a non-engaged state. When gas is supplied to the
actuator, gas pressure is applied on the backs of the
vane 312 and the movable vane 52C, and the rotor 31 is
rotated in the direction shown by the two-dot chain
line in Fig. 7. Upon rotation, the movable vane 52C
moves along the tapered surface 30C. The skew of the
movable vane 52C with respect to the vane 312 is
gradually decreased and is eliminated at the end of the
tapered plane 30C. The friction plate 522C mounted on
the inner end of the movable vane 52C is engaged with
the friction plate 51C of the take-up sha~t 1. Thus,
the rotor 31 and the take-up shaft 1 are engaged with
each o~her. The subsequent operation is the same as
the above-described embodiment.
Fig. 8 shows a fifth embodiment of the invention
in simplified form. The vane 312 of the rotor 31 is
pivotally mounted on the ring segment 311 and serves aC
a movable vane. The inner end of the vane 312 serves
as a driving engagement member.
The driven engagement member is a ratchet wheel
51, as in the first embodiment. The vane 312 of the
rotor 31 has an outer cylindrical surface 312D having
its axis at the pivot, a small diameter cylindrical
section 314D, and a concave inner cylindrical surface
315D in clearance from the teeth of the ratchet wheel
51. The surface 312D is in sliding contact with the
outer wall of the operating space of the cylinder, and
the small diameter cylindrical section 314D is
pivotally fixed on the ring segment 311 in the
cylindrical hole 313 formed on the ring segment 311 of
the rotor 31.
The vane 312 is tilted forward in th rotating
direction of the piston around the pivot axis when gas
pressure is applied. As the result, a projection 522D
-14- 2 ~ '2 ~
formed at the juncture of the section 314D with the
surface 315D is engaged with a tooth of the ratchet
wheel Sl. With this engaged state maintained by gas
pressure, the rotor 31 is rotated together with the
ratchet wheel 51. In this example, too, the subsequent
operation is the same as in the above-described
embodiments.
In the first embodiment, the clutch key is
arranged in such manner that its axis o~ movement and
the axis of the ratchet wheel cross each other on th~
same plane, whereas the clutch key 52 may be arranged
in such manner that its axis of movement X crosses the
axis Y of the ratchet wheel 51 with a certain spacing
D, as shown in Fig. 9. (Hereinafter, this condition is
referred to as "offset.") A sixth embodiment with such
an arrangement is shown in Figs. 9 to 12 and will now
be described.
The pretensioner of Figs. 9 to 12 comprises a
rotary actuator 3 mounted on a pretensioner base 2,
which also serves as a retractor frame as shown in Fig.
10 and supports a rotatable take-up shaft 1, a ~as
generator 4 for supplying operating gas to a pressure
chamber 3 of the actuator 3, and clutch means 5 for
connecting a rotor 31, serving as rotating output
member of the actuator 3, to the take-up shaft 1 by gas
pressure supplied to the pressure cha~ber C. The
actuator 3 has a chamber of annular form around a space
S, and clutch means 5 is disposed in the space S. The
clutch means 5 comprises a ratchet wheel 51 attached on
the take-up shaft 1 and a clutch key 52 movably
supported on the rotor 31. The clutch key 52 has an
axis of movement X directed in a direction to cross
the axis of rotation Y of the ratchet wheel 51 with a
certain spacing D (i~e., offset), and a pressure
receiving portion 521 faces toward the pressure chamber
C.
-15 ~ 2 ~
Referring to Fig. 10, the take-up sha~t 1 is
integrated into a reel for taking up a belt webbing
(not shown~. The reel 11 is provided with a slit 1~
~or receiving an end of the belt webbing, and flanges
13 and 1~ on both end~. On one of the flanges 14 is an
annular collar 141 that slightly protrudes axially and
surrounds the periphery of the take-up shaft 1.
Internal teeth 142 on the collar 141 engage with outer
teeth 511 so that the inner end of the ratchet wheel
51, which is separate from the take-up shaft 1, can be
inserted, and this serves as a detent when the ratchet
wheel 51 is engaged with the take-up shaft 1.
The pretensioner base 2 is U-shaped and support~
the ends of the take-up shaft 1 and also acts as a
retractor frame. Holes 23 and 24 in the side walls 21
and 22 where the reel flanges 13 and 14 are
accommodated, have internal ratchet teeth 25 and 26
that are engaged by locking pawls 15 and 16 that are
operated by an emergency locking mechanism 18, and are
mounted on a connecting shaft 17 supported by the reel.
The retractor has a winding sprinq unit 20. A belt
guide 27 is affixed to the frame and guides the belt
webbing.
The actuator 3 comprises a cylinder 30
constituting its fixed member, a rotor 31 serving as
rotating member, and a cover 32 to close the open outer
end of the cylinder 30. The cylinder 30 consists of a
block, which has an operating space Q (Fig. 9) having
one end open that is defin~d by an annular inner wall
301, an outer peripheral wall 302 and an end wall 303,
and further includes a bulkhead 304 and a supply
chamber R that communicates with the operating space Q.
A gas-introducing groove 300 near one side of the
bulkhead 304 communicates the supply chamber R and the
operating space Q. Near the other side i~ an exhaust
hole 305, which passes through the outer peripheral
-16- 20$~2~
wall 302 from the operating space Q. A seal groove 306
is provided on the open end surface of the cylinder 30
around the outer periphery of the operating space Q and
the supply chamber R. ~n annular axial flange 321
5 protrudes from the inner end surface of the cover 32,
facing the inner peripheral wall 301 of the cylinder 30
with a certain spacing and serving as a bearing to
support the inner bore of the rotor 31.
The rotor 31 serves as the inner peripheral wall
10 of the operating space Q and comprises a ring seg~ent
311 to define the space S (Fig. 9) and a vane 312
extending îrom the ring segment 311 in the radial
direction and functioning as a pressure-receiving
portion. On the upstream side of the vane 312,
15 relative to its direction of rotation, a rectangular
hole 313 through the ring segment 311 receives the
clutch key 52. The hole 313 is in an offset position
relative to the axis of the take-up shaft 1. On the
inner side of the ring segment 311, a graded hole with
20 both ends enlarged is provided to receive the inner
peripheral wall 301 of the cylinder 30 and the axial
flange 321 of the cover 32.
The pressure-receiving surface of the vane 312 is
fitted with a sealing member 314 having a continuous
25 seal lip on both side edges and the outer peripheral
edge. This sealing member 314 is attached to the rear
surface o~ the vane 312 by engagement of hooks in
notches a~ the corners of the tip of the vane 312 and
prevents gas leakage from the pressure chamber C of the
30 operating space Q into the back pressure chamber wher
the rotor 31 is rotated.
The clutch key 52 of the clutch mechanism is
received in the hole 313 and is in sliding clearance so
that it can be freely displaced along its axis of
35 movement. The clutch key 52 comprises a pressure-
recaiving head to receive gas pressure and a tip 522
-17~ 2~52~
serving as the engaging means with the outer teeth 511
of the ratchet wheel Sl. The tip 522 is arranged to
face toward the ratchet wheel 51. On the rear surface
of the clutch ]cey 52, a stopping groove 523 is formed
perpendicularly to the moving direction of the clutch
key 52, as shown in Fig. 9. This groove 523 is engaged
with a ridge 309 provide face-to-face to the bulkhead
304 of the cylinder 30 and serves as a stopping means
for holding the clu~ch key 52 in its initial "set"
position.
A deep radial groove is formed on the bulkhead
304. A sealing member 307 accommodated in the groove
is pushed by a spring 308 inserted behind it and forms
a sliding seal with the outer peripheral surface of the
ring segment 311 of the rotor 31. On the front seal
surface of the sealing mem~er 307, an engagement groove
310 is formed parallel to the axis of the rotor 31, as
shown in Fig. 9, and a ridge 315 i5 formed on the outer
periphery of the ring segment 311 of the rotor 31
facing the groove 310. The ridge and groove engage
each other and s~rve as a releasable stop for holding
the rotor 31 at its initial set position.
An elastomer seal 33 is received in the seal
groove 306 that runs along the circumferences o~ the
supply chamber R and the operating space Q, protrudes
between them and toward the bulkhead, and fulfills a
sealing function between the cylinder 30 and the cover
32.
The gas generator 4 is of the type in which a
propellant in a case is ignit~d by a primer 41 and
burns. It is incorporated in the cylinder 30 in this
example. The gas generator 4 is received in a chamber
340 in the cylinder parallel to the take-up shaft axis.
A hole in the bottom of the chamber 340 allow~ a firing
pin to be propelled into the generator 4 when an
acceleration sensor 9 is operated to ignite the gas
-18- 2 ~ 2 ~
generator 4. A seal sleeve 42 with a collar is
inserted into the hole ~rom the ch~mber 340, and the
gas generator with the primer 41 attached to it is
inserted into the chamber 340 and is held in place by a
snap ring 43.
The clutch means 5 comprises a ratchet wheel 51,
serving as a take-up shaft-engaging means, and the
clutch key 52, serving as an actuator-engaging means.
The teeth 511 on the periphery of the wheel S1 are
tilted backward against the rotating direction o~ the
ratchet. To match them, the tip 522 of the clutch key
52 has an inclined tooth. The tilted teeth ensure
engagement of the tip 522 with the teeth 511 when the
ratchet wheel 51 is driven by the clutch key 52 and
permit disengagement of the tip 522 from the ratchet
wheel teeth 511 during reverse driving from the ratchet
wheel 51, thus making the clutch means 5 work as an
overrunning clutch.
These component parts are arranged on the frame by
the following procedure, although thP procedure is not
limited to this: First, an assembly in which the
locking mechanism 18 is assembled on one end of the
reel 11 is inserted into openings 23 and 24 on both
sides o~ the fame. The locking mechanism 18 is
centered and mounted when projections 190 are inserted
into mounting holes 210 of the ~rame 50 that a cover 19
having a take-up shaft support hole 191 covers the
locking mechanism 18. Next, the ratchet wheel 51 is
engaged with a large diameter portion 101 of the take-
up shaft 1, one end of which is supported as describedabove. In this case, the outer teeth 511 of the
ratchet wheel 51 are engaged with the inner teeth 142
so that it is not rotatable with respect to the take-up
shaft 1. Next, the cylinder 30 is fixed on the other
side wall 2 by a bolt. Further, the rotor 31
incorporat~d with the clutch key 52 and the sealing
-19- 2 ~
member 314 as well as a seal 33 are inserted from the
open end of the cylinder 30. After the sealing member
307 combined with a spring 308 is assembled, the lid 32
is affixed on the cylinder 30 by screws. Finally, the
spring unit 20 is installed by engaging a projection
201 on the spring unit into a mounting hole which
extends from the lid 32 to the cylinder 30. Thus, the
take-up shaft 1 has one end supported on one side of
the frame through the cover 19, and the other end
supported on the other side o~ the frame through the
spring unit 20.
Fig. 11 shows sequentially the operation of the
pretensioner of Figs. 9 to 12. When the pretensioner
is set and not operated, it is at the position of Fig.
llA in which the back o~ the clutch key 52 inserted
into ths rotor 31 touches the bulkhead 304. Under this
condition, the pressure chamber C has its smallest
volume, and the clutch key 52 is not enyaged with the
teeth 511 of the ratchet wheel 51 since the groove 523
in the rear of the clutch key is fitted to the ridge
309 of the cylinder bulkhead 304 (Fig. 9). Thus, the
take-up shaft 1 is completely separated from the
actuator 3 and is freely rotatable, and the normal
function of the retractor is maintained.
When an acceleration is detected and the firing
pin of the sensor 9 (Fig. 10) is operated, the primer
41 of the gas generator 4 is ignited (Fig. llB) t and
the gas generated by combustion o~ propellant is
introduced into the pressure chamber C through the
supply chamber R and the gas introducing groove 300
(Fig. llC). With gas pressure applied on its pressure
receiYing head 521, the clutch key 52 is pushed
inwardly along its offset axis of movement. The tip
522 enters a trough between two teeth 511 o~ the
ratchet wheel 51, and the rotor 31 is engaged with the
-20~ 2 ~
ratchet wheel 51 through the clutch key 52. Thus, the
take-up shaft ~ is now coupled to the actuator 3.
Gas pressure is also applied on the vane 312 of
the rotor 31 and the pressure force acts on the back of
the vane 312, whereby the rotor 31 is rotated
counterclockwise around the sha~t as shown in Fig. llD.
The pressure in the back pressure chamber of the
operating space Q (downstream from the vane) generated
by this rotation is released into the atmospheric air
through the exhaust hole 305, and this prevents
occurrence of resistance due to a pressure increase in
the back pressure chamber. As the result, the rotating
force of the rotor 31 is transmitted to the take-up
shaft 1 through the clutch key ~2 and the ratchet wheel
51.
Upon rotation of the take-up shaft 1, a segment of
the belt is wound onto the take-up shaft 1 and
pretension is imparted to it by tightening of the belt.
Finally, the rotor 31 reaches the position shown in
llE. When it is at this position, the pressure chamber
C is also opened to the atmospheric air, and the
remaining gas pressure is also discharged through the
exhaust hole 305. However, the take-up shaft 1 and the
reel continue rotation by inertia because the teeth Sll
of the ratchet wheel 51 push the clutch key 52 in it
disengaging direction. Thus, the take-up shaft 1 is
released from the rotor 31, and the rotation of the
take up shaft 1 is continued. The rotation by inertia
continues until the belt tension and the rotary moment
of i.nertia of the take-up shaft and reel reach
equilibrium. Belt pretension due to his rotation can
be set to about 1/2 of the pulling by rotor rotation,
although it depends upon the quantity of the propellant
loaded in the gas generator 4. Thus, the operation to
give pretension is completed. After this operation is
completed, the pulling out of the belt is blocked by
-212~$~
the engagement of the lock pawls 15 and 16, components
of the retractor locking mechanism, with the ratchet
teeth 25 and 26 in the frame.
Next is a detailed description of the engaging
operation of the clutch means 5. Fig. 12 shows what
happens when the add~ndum of a tooth 511 of the ratchet
wheel 51 is initially struck by the addendum of the tip
522 of the clutch key 52 under the worst of the
possible engagement conditions. From the initial
state, as shown in Fig. 12A, pushing of the clutch key
52 by gas pressure and the rotation of the rotor 31 are
started at the same time, the rotor is rotated by an
angle aO, and an addendum collides against the tooth GO
as shown in Fig. 12B. In this case, it is supposed
that the distance in the offset direction between the
addendum and the inner periphery of the ring segment is
hO. Under this condition, the ratchet wheel 51 is
still stopped, and the rotor 31 continues to accelerat~
at a certain angular acceleration. The velocity of the
clutch key 52 in the offset direction is 0. Failing to
engage under this condition, the clutch key 52
continues rotation by a certain angle from this
position, and it is again accelerated from the velocity
O until the rotating angle reaches al and the next
outer tooth Gl i reached, as shown in Fig. 12C. The
sum hl of the moving distance in the offset direction
by this re-acceleration and the moving distance up to
the initial addendum collision is always long r than
the distance hOo In particular, when the rotor 31 and
the clutch key 52 are made of the same material, the
inertial mass of the clutch key 52 is far lower than
the inertial mass of the rotor 31. Thus, re-
acceleration occurs while the rotor 31 is accelerated
from the outer tooth GO to G1 and rotated by an angle
a2, and sufficient engagement allowance is obtained as
shown in (D) until tip of the pawl 522 finally hits the
22?~9520
next outer tooth G1. Therefore, the clutch key 52 is
engaged with the next outer tooth G1 even in the worst
case, regardless of the positional relationship with
the addendum of the outer tooth 511 o~ the ratchet
wheel 51. The rotor rotating angle a2 up to this
engagement is about 38 degrPes when the clutch key 52
and the rotor 31 are made of steel.
Studying the colliding condition of tha clutch key
52 against the outer tooth 511 of the ratchet wheel 51
when the clutch means 5 is in engaging operation, the
working point of the impact force is deviated from the
axial line Y by a distance D due to the o~fset. Most
of the impact force is turned to rotary moment around
the axial line Y, and the compon n~ in the direction of
the axial line Y becomes very low. As the result, the
bending load exerted on the take-up shaft 1 by clutch
engagement can be kept very small.
Fig. 13 shows a seventh embodiment in which the
interaxial distance (offset) is set to -D by setting
the offset direction of the clutch key 52 to the
direction opposite to that of the above embodiment.
Even in this arrangement, the same operation as in the
sixth embodiment can be achieved. However, when the
offset direction is set forward with respect to the
rotating direction of the ratchet wheel 51, it is no
longer certain that the force in the engaging direction
due to rotation of the rotor 31 is mechanically applied
on the clutch key 52. Thus, the pressure-receiving
surface 521 of the clutch key 52 must be of
suf~iciently large area to obtain the engaging force
from gas pressure acting on the clutch key.
Figs. 14 to 18 show an eighth embodiment in which
the clutch means is slightly modified from the sixth
embodiment. In this example, a key connector 53 is
added for sequence control of the transmission of the
operating gas pressure to the clutch key 52 and supply
2 ~
-23-
of the operating gas to the pressure chamber C. In
this case, the head 521 of the clutch key 52, serving
as a pressure-receiving portion to receive gas
pressure, also acts as a connection with the key
connector 53, and the key connector 53 ac~s as stopping
means for holding ~he clutch key 52 at the initial set
position.
As shown in Fig. 15, the clutch key is made of
steel and comprises a rectangular head 521, a guide 520
in form of rectangular column, and a tip 522.
Projections 523 extending toward the ends of thP head
are provid~d on both sides of the hea~ 521. The key
connector 53 is made of a polymeric material and
comprises a leg segment 531 ~for connection with the
clutch key 52) and a guide segment 530, forming an L-
shape as a whole. The leg segment 531 is provided with
a dovetail groove 53~ that engages the projection 523
of the clutch key 52. On the tip of the guide segment
530 to be fitted closely in a groove 300 (for gas
supply and key connector insertion) of the cylinder 30,
a control groove 534 is provided. On the forward end
of a wall, which defines said groove and is elastically
displaceable in the direction of the groove because of
its thinness, a hook 535 is formed outwardly with
respect to the groove.
The clu~ch key 52 and the key connector 53 are
connected with each other by engaging the projection
523 of the clutch key with the dovetail groove 532 of
the key connector. When combined, the clutch key has
its guide 520 engaged with a rectangular hole 313 of
the rotor 31, and the key connector has its guide
se~ment 530 engaged with the groove 300 of the cylinder
30 as shown in Fig. 14. In this case, the hook 535 is
engaged with a corner where the peripheral wall of the
supply chambPr R crosses the groove 300, and the
portion of the l~g segment 531 opposite to the dovetail
2~)9~2~
--2~--
groove touches the peripheral wall of the cylinder 30.
in this position, the guide segmenk 530 of the key
connector 53 virtually blocks the groove 300 over its
entire length and shuts off the supply chamber R from
the pressure chamber C. The ~ontrol groove 534 sets
the sealing distance from the inner end of the
peripheral wall of the cylinder to the bottom o~ ~he
control groove 534 so that it becomes equal to the
stroke until the addendum collision occurs between the
clutch key 52 and the ratchet wheel 51.
The features other than described above of this
eighth embodiment are the same as those of the sixth
embodiment. Thus, while the entire arrangement is
shown in Fig. 16, no detailed description is required
or given here.
Figs. 17A to 17F shows in stages the operation of
a pretensioner according to the eighth embodiment.
When not in operation, the rotor 31 is at the position
shown in Fig. 17A, in which the back o~ the clutch key
~0 52 inserted into the rotor touches the bulkhead 304.
Under this condition, the pre sure chamber C has its
smallest volume, and the clutch key 52 is positioned by
the key connector 53 (Fig. 14) and is in clearance with
the teeth 511 of the ratchet wheel 51. Therefore, the
take-up shaft 1 is completely separated form the
actuator 3 and is freely rotatable, and the retractor
can function normally.
When accPleration is detected and the ~iring pin
of a sensor 9 (Fig. 16) is operated, the primer 41 of
the gas generator 4 is ignited ~Fig. 17B) and gas
generated by combustion o~ the propellant is applied on
the key connector 53 in ~he gas supply chamber R. The
engagement by the hook 535 (Fig. 15) is released, and
the key connector 53 is pushed along the groove 300.
The clutch key 52 is pushed by the key connector 53
inwardly in the o~fset direction, and the tip is moved
20~52a
-25-
to such position that it touches the top of a tooth 511
of the ratchet wheel 51. The bottom of the control
groove 534 of the key connectur 53 r~aches the outer
peripheral surface of the pressure chamber C, and the
supply of the operating gas into the pressura chamber C
commences.
As the result, ~as pressure is now also applied on
the vane 312 o~ the rotor 31 and pushes on the back
upstream surface of the vane 312. Thus, the rotor 31
starts to rotate counterclockwise around the shaft as
shown in Fig. 17C. Upon the rotation, the pressure in
the back pressure chamber in the oper~tion space Q is
released into the atmo~pheric air through the exhaust
hole 305 of the cylinder 30, and this prevents
occurrence of resistance due to pressure increase in
the back pressure chamber. on the other hand,
displacement of the clutch key 52 is continued. Soon,
the pawl 522 of the clutch key 52 is engaged with an
outer tooth 511 of the ratchet wheel 51, and the rotor
31 is engaged with the ratchet whe l 51 through the
clutch key 52. At this time, the take-up shaft 1 is
connected with the actuator 3. As shown in 17D, a
rotating force on the rotor 31 is transmitted to the
take-up shaft 1 through the clutch key 52 and the
ratchet wheel 51.
Upon rotation of the take-up shaft 1, a segment of
the belt is wsund onto the take-up shaft 1 and
pretension is imparted by tightening o~ th~ belt. When
the rotor reaches the position shown in Fig. 17E, the
pressure chamber C is also opened to the atmospheric
air, and the remaining gas pressure is discharged. Th~
take-up shaft 1 and the reel 11 continue to rotate
thereafter by inertia~ The subsequent operation is the
same as that of the sixth embodiment.
Figs. 18A to 18D show the engagement sPquence when
an addendum of a tooth 511 of the ratchet wheel 51 is
2~9~2~
initially struck by the addendum o the tip 522 of the
clutch key 52 in the worst of the possible engagement
conditions. First, ths key connector 53 is pushed by
gas pressure from the initial set state, as shown in
5 Fig. 18A, and pushing of the clutch key 52 is started.
~en pushing proceeds and the addendum of the tip 522
of tbe clutch key 52 collides against an addendum sf a
tooth 511 of the ratchet wheel 51, addendum collision
against tooth GO in Fig. 18B occurs. When this
10 happens, the bottom of the control groove 534 of the
key connector 53 reaches the outer pariphery of the
pressure chamber C. From this position, gas supply to
the pressure chamber C is started, and the rotor 31
begins to rotat~. It is supposed that the distance in
the offset direction between the addendum and inner
periphery of the ring segment is hO. Under this
condition, the ratchet wheel 5} is still stopped. The
rotor 31 starts acceleration at a certain angular
acceleration, and th2 velocity of the clutch key 52 in
the offset direction is 0.
Having failed to achieve engagement, the clutch
key 52 is rotated by a certain angle from this position
and is accelerated again from the velocity O until the
rotating angle becomes al and the next tooth Gl is
reached. The sum hl of the moving distance in the
offset direction obtained by this re-acceleration and
the moving distance up to initial addendum collision is
always longer than the distance hO. In particular,
when the rotor 31 and the clutch key 52 are made of the
same material, the inertial mass of the clutch key 52
is far lower than the inertial mass of the rotor 31.
Thus, re-acceleration occurs while the rotor 31 is
accelerated from the outer tooth GO to G1 and is
rotated by an angle a2. Until the tip 522 finally
collides against the next outer tooth G1, sufficient
engagement allowance is obtained as shown in Fig. 18D.
-27- ~ 5~a
Therefore, the clutch key 52 engages with the next
outer tooth G1, even in the worst case, regardless of
the positional relationship, with the addendum of a
tooth 511 of the ratchet wheel 51. When the clutch key
52 is made of steel and the rotor 31 is made of light
alloy, i.e. when the inertial mass of the rotor 31 i5
closer to the inertial mass of the clutch key 52 than
the case where these two are made of the same material,
the rotor rotating angle a2 up to the engagement is
still about 36.5 degrees.
During the clutch engagement processes shown in
Figs. 18B and 18C, most of the key connector 53 i5
withdrawn from the groove 300, and the leg segment is
pulled by the clutch key 52 when the rotation of the
rotor 31 is startedO Thus, the engagement at the
dovetail groove is released, and the key connector is
disengaged from the clutch key 52.
As an overrunning clutch in the present invention,
the following may be used instead of those of in the
above described embodiments: ~ dog clutch used in a
transmission device with serrated engaging teeth so
that it is released when driven in the reverse
direction; a device in which a ball or a roller is
pushed into a wedge-like space when driven in the
forward direction and is released when driven in the
reverse direction.
The em~odiments of the present invention described
above are intended to be merely exemplary, and numerous
variations and modifications of the embodiments will be
apparent to those skilled in the art without departing
from the spirit and scope of the invention. All such
variations and modifications are intended to be
included within the scope of the invention, as set
forth in the appended claims.
