U.S. patent application number 09/871342 was filed with the patent office on 2002-03-14 for pretensioner drive.
Invention is credited to Stevens, Bruce A..
Application Number | 20020030396 09/871342 |
Document ID | / |
Family ID | 26903172 |
Filed Date | 2002-03-14 |
United States Patent
Application |
20020030396 |
Kind Code |
A1 |
Stevens, Bruce A. |
March 14, 2002 |
Pretensioner drive
Abstract
A pretensioner 10 for a seat belt 12 utilizes a perforated strap
34 loosely coiled about a hub 38 wherein the hub 38 is, in normal
operation of a vehicle, rotatable with a webbing reel shaft 40. A
plurality of protrusions 42 are circumferentially spaced about the
hub and mesh with the perforated strap 34 upon activation of the
pretensioner 10. The pretensioner 10 contains a first passage 44
and a second passage 46 for the respective containment of the hub
38 and an actuator 20, wherein each passage is formed perpendicular
and in volumetric intersection with the other. The pretensioner 10
also contains a gas generant composition 22 in combustive
communication with the actuator 20. Upon ignition, the gas pressure
produced by the pyrotechnic 22 propels the actuator 32 into the
strap 34, thereby effecting rotary advancement of the hub 38 and
the shaft 40, and thus pretensioning the seat belt 12 wound about a
spool 11 of a seat belt retractor 14, wherein the spool 11 is
rotatably engaged with a second portion of the shaft 40 and thus
provided in coaxial relation with the hub 38.
Inventors: |
Stevens, Bruce A.; (Oakland
Township, MI) |
Correspondence
Address: |
DINNIN & DUNN, P.C.
SUITE 2100
755 WEST BIG BEAVER
TROY
MI
48084
US
|
Family ID: |
26903172 |
Appl. No.: |
09/871342 |
Filed: |
May 31, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09871342 |
May 31, 2001 |
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09777388 |
Feb 5, 2001 |
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60208403 |
May 31, 2000 |
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Current U.S.
Class: |
297/480 |
Current CPC
Class: |
F15B 15/19 20130101;
B60R 22/4628 20130101; B60R 22/4633 20130101; B60R 2022/468
20130101; B60R 22/4619 20130101 |
Class at
Publication: |
297/480 |
International
Class: |
B60R 022/46 |
Claims
We claim:
1. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, that upon activation pretensions
seatbelt webbing associated therewith, the pretensioner comprising:
a housing having a first circular cylindrical passage
volumetrically intersecting a second rectangular cylindrical
passage, said passages formed perpendicular to each other, wherein
said webbing reel shaft extends through said first passage and said
second passage has a first end and a second end, the second passage
extending across and past the diameter of the first passage; a
cylindrical hub fixed to said webbing reel shaft and contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a first end fixed to said housing, a flat portion
extending from said first end and across said second passage, a
second flat portion arranged about a portion of said hub, and a
second end freely extending from said second flat portion such that
the hub rotates independently of said strap prior to pretensioner
activation; an actuator positioned within the first end of said
second passage for tensioning said strap upon pretensioner
activation; a gas generant composition, ignitable to activate the
pretensioner and release sufficient force to drive the actuator
through said second passage; and an initiator within said housing
and ignitably communicating with said gas generant composition for
igniting said gas generant composition, whereby upon ignition of
said gas generant, tensioning of the strap and mating of the
perforated strap and the plurality of protrusions is thereby
effected, resulting in an essentially simultaneous rotary
advancement of the hub, the webbing reel shaft, and the webbing
reel, thereby winding the reel and tensioning the seatbelt webbing
thereon.
2. The pretensioner of claim 1 wherein said actuator is a one-piece
cylindrical piston.
3. The pretensioner of claim 1 wherein said actuator is a segmented
bellows.
4. The pretensioner of claim 1 wherein said actuator contains a gas
generant composition that upon ignition propels the actuator.
5. The pretensioner of claim 1 further comprising a resilient
cylindrical liner within said second passage and extending up to
the circumference of but not within the diameter of the first
passage, for strengthening the first end of the second passage.
6. The pretensioner of claim 1 further comprising a gas generator
for containment of the gas generant composition.
7. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, that upon activation pretensions
seatbelt webbing associated therewith, the pretensioner comprising:
a housing having a first circular cylindrical passage
volumetrically intersecting a second rectangular cylindrical
passage, said passages formed perpendicular to each other, wherein
said shaft extends through said first passage and said second
passage has an open first end and a second end, the second passage
extending across and past the diameter of the first passage; a
resilient cylindrical sleeve having a closed first end and an open
second end, wherein the second end of the sleeve is fixed to and
axially aligned with the first end of the second cylindrical
passage; a cylindrical hub fixed to said webbing reel shaft and
contained within the first passage wherein said webbing reel shaft
axially extends through said hub; a plurality of protrusions
integral to and circumferentially spaced about said hub; a
perforated strap comprising a first end fixed to said housing, a
flat portion extending from said first end and across said second
passage, a second flat portion arranged about a portion of said
hub, and a second end freely extending from said second portion
such that the hub rotates independent of said strap prior to
pretensioner activation; an actuator positioned within said
circular cylindrical sleeve for acting upon the flat portion of the
strap upon pretensioner activation; a gas generant composition,
ignitable to activate the pretensioner and release sufficient force
to drive the actuator through said second passage; and an initiator
fixed within the first end of said cylindrical sleeve for igniting
said gas generant composition and closing the first end of the
cylindrical sleeve, whereby upon receipt of a signal to the
initiator, the gas generant composition is ignited to release
sufficient force to drive the actuator through said cylindrical
sleeve and through said second passage thereby tensioning the strap
and mating the perforated strap and the plurality of protrusions,
resulting in an essentially simultaneous rotary advancement of the
hub, the webbing reel shaft, and the webbing reel, thereby winding
the reel and tensioning the seatbelt webbing thereon.
8. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, that upon activation pretensions
seatbelt webbing associated therewith, the pretensioner comprising:
a housing having a first circular cylindrical passage
volumetrically intersecting a second rectangular cylindrical
passage, said passages formed perpendicular to each other, wherein
said webbing reel shaft extends through said first passage and said
second passage has a first end and a second end, the second passage
extending across and past the diameter of the first passage; a
cylindrical hub fixed to said webbing reel shaft and contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a first end fixed to said housing, a flat portion
extending from said first end and across said second passage, a
second flat portion arranged about a portion of said hub, and a
second end freely extending from said second flat portion such that
the hub rotates independently of said strap prior to pretensioner
activation; an actuator positioned within the first end of said
second passage for tensioning said strap upon pretensioner
activation; and a means for activating the pretensioner and driving
the actuator through the second passage; whereby upon activation of
the pretensioner, the strap is tensioned and the perforated strap
and the plurality of protrusions are meshed, thereby resulting in
an essentially simultaneous rotary advancement of the hub, the
webbing reel shaft, and the webbing reel, thus winding the reel and
tensioning the seatbelt webbing thereon.
9. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, that upon activation pretensions
seatbelt webbing associated therewith, the pretensioner comprising:
a housing having a first circular cylindrical passage
volumetrically intersecting a second rectangular cylindrical
passage, said passages formed perpendicular to each other, wherein
said webbing reel shaft extends through said first passage and said
second passage has a first end and a second end, the second passage
extending across and past the diameter of the first passage; a
cylindrical hub fixed to said webbing reel shaft and contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a plurality of apertures in an amount at least
corresponding to the plurality of protrusions, a first end fixed to
said housing, a flat portion extending from said first end and
across said second passage, a second flat portion arranged about a
portion of said hub, and a second end freely extending from said
second flat portion such that the hub rotates independently of said
strap prior to pretensioner activation, wherein said plurality of
apertures operatively engage said plurality of protrusions upon
pretensioner activation; an actuator positioned within the first
end of said second passage for tensioning said strap upon
pretensioner activation; a gas generant composition that upon
ignition combustively communicates with said actuator and releases
sufficient force to drive the actuator through said second passage;
and an initiator within said housing and ignitably communicating
with said gas generant composition for igniting said gas generant
composition, whereby upon ignition of said gas generant, the strap
tightens about the hub and the plurality of apertures and the
plurality of protrusions mate, resulting in an essentially
simultaneous rotary advancement of the hub, the webbing reel shaft,
and the webbing reel, and thereby winding the reel and tensioning
the seatbelt webbing thereon.
10. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, for pretensioning seatbelt webbing
associated therewith, the pretensioner comprising: a housing having
a first circular cylindrical passage and a second rectangular
passage, wherein said webbing reel shaft longitudinally extends
through said first passage and said second passage has a first end
and a second end; an annular circular cylindrical hub contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a plurality of apertures in an amount at least
corresponding to the plurality of protrusions, a first end fixed to
said housing, a first flat portion extending from said first end
and across said second passage, a second flat portion arranged
about a circumferential portion of said hub, and a second end
freely extending from said second flat portion such that the hub
rotates independently of said strap prior to pretensioner
activation, wherein said plurality of apertures operatively engage
said plurality of protrusions upon pretensioner activation; an
actuator positioned within the first end of said second passage for
tensioning said strap upon pretensioner activation; a gas generant
composition that upon ignition combustively communicates with said
actuator and releases sufficient force to drive the actuator
through said second passage; and an initiator within said housing
and ignitably communicating with said gas generant composition for
igniting said gas generant composition, whereby upon ignition of
said gas generant composition, the perforated strap translates
linear motion of the actuator to rotary movement of the hub and
thus pretensions the seatbelt in rotary communication with said
hub.
11. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, for pretensioning seatbelt webbing
associated therewith, the pretensioner comprising: a housing having
a first circular cylindrical passage and a second rectangular
passage, wherein said webbing reel shaft longitudinally extends
through said first passage and said second passage has a first end
and a second end; an annular circular cylindrical hub contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a plurality of apertures in an amount at least
corresponding to the plurality of protrusions, a first end fixed to
said housing, a first flat portion extending from said first end
and across said second passage, a second flat portion arranged
about a circumferential portion of said hub, and a second end
freely extending from said second flat portion such that the hub
rotates independently of said strap prior to pretensioner
activation, wherein said plurality of apertures operatively engage
said plurality of protrusions upon pretensioner activation; an
actuator positioned within the first end of said second passage for
tensioning said strap upon pretensioner activation; and a means for
activating the pretensioner and driving the actuator through the
second passage; whereby upon activation of the pretensioner, the
perforated strap translates linear motion of the actuator to rotary
movement of the hub and thus pretensions the seatbelt in rotary
communication with said hub.
12. A pretensioner cooperating with a webbing reel shaft of a
seatbelt retractor webbing reel, for pretensioning seatbelt webbing
associated therewith, the pretensioner comprising: a housing having
a first circular cylindrical passage and a second rectangular
passage, wherein said webbing reel shaft longitudinally extends
through said first passage and said second passage has a first end
and a second end; an annular circular cylindrical hub contained
within the first passage wherein said webbing reel shaft axially
extends through said hub; a plurality of protrusions integral to
and circumferentially spaced about said hub; a perforated strap
comprising a plurality of apertures in an amount at least
corresponding to the plurality of protrusions, a first end fixed to
said housing, a first flat portion extending from said first end
and across said second passage, a second flat portion arranged
about a circumferential portion of said hub, and a second end
freely extending from said second flat portion such that the hub
rotates independently of said strap prior to pretensioner
activation, wherein said plurality of apertures operatively engage
said plurality of protrusions upon pretensioner activation; an
actuator positioned within the first end of said second passage and
biased against said first flat strap portion for tensioning said
strap upon pretensioner activation; and a means for activating the
pretensioner and driving the actuator through the second passage;
whereby upon activation of the pretensioner, the perforated strap
translates linear motion of the actuator to rotary movement of the
hub and thus pretensions the seatbelt in rotary communication with
said hub.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/208,403 filed on May 31, 2000. This
application is also a continuation in part of co-pending U.S.
application Ser. No. 09/777,388 filed on Feb. 5, 2001.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to seat belt pretensioners
and, more specifically, to a seat belt pretensioner that
incorporates a motion multiplier thereby reducing the actuator
stroke requirement. Furthermore, the present invention provides
pretensioner drive mechanisms that substantially simplify the
pretensioner design as compared to known designs.
[0003] Seat belt pretensioners remove slack from a seat belt in the
event of a collision in order to minimize forward movement of the
passenger. While it is known to use pyrotechnic gas generators to
operate mechanisms which wind up or otherwise pull in slack in the
seat belt during a collision, such known pyrotechnic gas generators
are generally disposed internally of a seat belt retractor. Thus,
the vehicle owner is faced with a significant cost penalty in that
the entire pretensioner and retractor assembly must be replaced
after activation because of the inability to prevent degradation of
the retractor. High-temperature gases tend to abrade interior metal
surfaces and produce ash and clinkers that bind up the retraction
mechanism.
[0004] Another problem with known pretensioners is that they are
designed to activate only in severe accidents, for example,
accidents that exhibit "G" forces sufficient to activate the
vehicle airbags. Safety system designers generally choose such a
relatively high activation threshold due to the expense of
replacing the entire seat belt retractor and pretensioner assembly
after activation. As a result, seat belt pretensioners do not
protect passengers in less severe accidents.
[0005] A related problem with known pretensioners is that when the
pretensioner is activated only in severe accidents, activation is
relatively late in the crash sequence. Thus, the pretensioner must
rapidly take up slack in the seat belt thereby potentially
aggravating the passenger.
[0006] U.S. Pat. No. 5,967,440, herein incorporated by reference,
describes a pretensioner and a conventional retractor for a safety
belt system. When compared to the seatbelt retractor, the
pretensioner is relatively complex and large, thus increasing the
weight and spatial requirements of the seatbelt assembly.
[0007] U.S. Pat. No. 5,899,399, herein incorporated by reference,
describes a state of the art pretensioner. The pretensioner is
relatively complex and as such complicates the manufacturing
process.
[0008] U.S. Pat. No. 5,944,350, herein incorporated by reference,
describes a state of the art pretensioner. Again, the pretensioner
is relatively large, thus increasing the weight and spatial
requirements of the seatbelt assembly.
[0009] German Patent No. DE 10010379 A1, herein incorporated by
reference, describes a pretensioner having an arcuate path for a
multi-piece actuator (a plurality of cylinders) that drives a steel
cord wrapped around a webbing reel hub and thereby effects
pretensioning of an associated seat belt. The manufacturing of the
pretensioner is more complex given the multi-piece actuator and
given the arcuate channel that the actuator must traverse.
Uniformity in channel width and effective sealing becomes more
difficult with the use of an arcuate channel. Secondly, a noise
reduction means is employed to prevent rattling during normal
vehicle operation, thereby increasing manufacturing costs.
Furthermore, the joint use of the multi-piece actuator with the
steel cord results in a friction loss and a reduction in the load
applied to the steel cord by the forward-most cylinder of the
actuator. As a result, more force is required to drive the
multi-piece actuator and pretension the seatbelt. One solution is
described by the use of an intermediate element "43" for
facilitating the smooth movement of the rotating elements along the
arcuate channel. Consequently, without the use of the intermediate
element "43", a more robust pretensioner housing would be
necessitated to withstand the relatively greater combustion
pressure (produced by a greater amount of propellant) likely
necessary to pretension the seatbelt in accordance with customer
requirements.
[0010] Other pretensioner designs employ relatively complicated
clutch assemblies for clutching a seat belt retractor axle
associated therewith. Many known pretensioner drive systems are
also relatively complex. U.S. Pat. Nos. 6,042,041, 5,842,344,
5,794,876, and 5,699,976, herein incorporated by reference,
illustrate the complexity of known pretensioners. Simplification of
known designs, therefore, is desirable given a resultant
simplification of manufacturing requirements.
SUMMARY OF THE INVENTION
[0011] The aforesaid concerns are resolved, in accordance with a
preferred constructed embodiment of the present invention, by a
seat belt pretensioner that utilizes a motion multiplier within an
essentially sealed housing thereby preventing retractor exposure to
combustion gases and clinkers. The present design also prevents
occupant exposure to the gases and solids formed upon combustion of
a pyrotechnic composition contained within the pretensioner.
[0012] In a preferred embodiment of the invention, the pretensioner
contains a housing, an annular hub having spaced circumferential
protrusions integral thereto, a retractor shaft axially disposed
within the annular hub thereby providing mechanical cooperation
between the pretensioner and a seat belt retractor, a perforated
strap having a plurality of apertures wherein each aperture at
least corresponds to a respective protrusion of the hub, a piston
that communicates with the strap upon pretensioner activation, a
gas generant or pyrotechnic that upon combustion propels the
piston, and an initiator that ignites the gas generant upon a
signal from an accelerometer, for example. Upon ignition of the gas
producing pyrotechnic, the piston is driven forward in an
essentially linear path thereby tightening the strap about the hub
as the perforations mesh with the hub protrusions. The seat belt
spooled about a second end of the retractor shaft within the seat
belt retractor is thus pretensioned.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a diagrammatic elevational view of a replaceable
seat belt pretensioner in a pre-activated condition, in accordance
with the present invention.
[0014] FIG. 2 is a second diagrammatic elevational view of the
present invention illustrating activation of the pretensioner.
[0015] FIG. 3 is a perspective view of the hub having a plurality
of circumferential protrusions integral thereto.
[0016] FIG. 4 is an elevational view of the perforated strap having
a plurality of perforations.
[0017] FIG. 5 is an elevational view of a pretensioner of the
present invention in cooperation with a state-of-the-art seat belt
retractor.
[0018] FIG. 6 is another embodiment of the present invention
wherein a resilient liner is utilized to strengthen a second
passage within the housing and a gas generator is also
employed.
[0019] FIG. 7 is yet another embodiment of the present invention
wherein a resilient sleeve exterior of the housing is fixed to the
second passage within the housing, in axial alignment
therewith.
[0020] FIG. 8 is yet another embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] Referring to the figures, a pretensioner 10 in accordance
with a preferred embodiment of the invention, comprises a gas
generator 16 adapted to pretension a seat belt 12 of a conventional
seat belt retractor 14. Exemplary seat belt retractors wherein the
pretensioner of the present invention has potential application are
described in U.S. Pat. Nos. 4,558,832 and 4,597,546, herein
incorporated by reference. In general, a pretensioner 10 in
accordance with the present invention may if desired replace many
pretensioners now employed in the art.
[0022] A housing 18 contains the gas generator 16. Upon
pretensioner activation, the gas generator 16 fluidly communicates
with a piston 20. The piston 20 is made from steel, brass,
aluminum, plastic, or other sufficiently rigid material. The gas
generator 16 contains a pyrotechnic material 22 used to actuate the
pretensioner 10. The gas generant 22 may comprise any known or
state of the art propellant now used in pretensioners, or
alternatively, it may comprise any known gas generant useful in
airbags for example. To illustrate, see U.S. Pat. No. 5,035,757
herein incorporated by reference. Alternatively, the gas generant
22 may be housed within the piston 20 wherein the piston also
functions as a gas generator thereby eliminating the need for a
separate generator 16.
[0023] Electrical contacts 24 on an initiator 26 communicate with
any known crash event sensor (not shown) that signals actuation of
the pretensioner 10. The initiator 26 is housed within an initiator
retainer 28. Once the initiator 26 receives a signal, from an
accelerometer for example, the initiator 26 ignites the pyrotechnic
gas generant 22. Stated another way, a means for activating the
pretensioner 10 and driving the actuator 20 includes the gas
generant 22 contained within the piston 20 (or provided in a
separate gas generator 16), the electrical contacts 24, and the
initiator 26.
[0024] Gas produced from combustion of the pyrotechnic gas generant
22 then propels the piston 20 into a flat portion 30 of a strap 34.
A plurality of apertures or perforations 36 are evenly or otherwise
spaced along the length of the strap 34. The strap 34 is loosely
arranged around a portion of the circumference of a hub 38. Hub 38
is press-fitted or otherwise fixed to a retractor axle 40 and
therefore rotatably communicates with the retractor axle 40. As
shown in FIG. 1, hub 38 freely rotates with the retractor axle 40
prior to pretensioner 10 activation. Hub 38 contains a plurality of
knobs or protrusions 42 evenly or otherwise spaced about the
circumference of hub 38 wherein each knob in the plurality 42
preferably corresponds to at least one aperture in the plurality
36. The distance from one respective perforation to another
respective perforation in the strap 34 is roughly equivalent to the
arcuate distance from one corresponding protrusion to another about
the hub 38. As shown in FIG. 4, the diameter of the perforations 36
is sized to be at least slightly larger than the diameter of the
protrusions 42. Alternatively, the perforations 36 may be
elliptically shaped or otherwise shaped to accommodate the smaller
sized protrusions 42. In essence, the perforations 36 are sized to
facilitate rapid engagement and meshing with the protrusions 42
once the pretensioner 10 is activated.
[0025] In accordance with one aspect of the invention, a first
cylindrical channel 44 contains the hub 18. A second rectangular
channel 46 has a first end 48 and a second end 50, and is formed in
perpendicular orientation and in volumetric intersection with the
first channel 44. The actuator 20 is housed in the first end 48,
prior to ignition of the propellant 22 and activation of the
pretensioner 10. A spring 52 may be used to bias the actuator 20
against the flat portion 30 of the strap 34 that crosses the
channel 46. Noise due to vibration is thereby inhibited. Strap 34
has a free first end 56 that extends from a second flat portion 58
of the strap 34 that is oriented about the circumference of the hub
38. A second end 54 of the strap 34 is secured to the housing 18 at
a point adjacent to the piston 20. When arranged in this manner,
the strap 34 provides a multiplier effect similar to that afforded
by the use of gearing style motion multipliers, but at a much lower
cost.
[0026] Upon activation of the pretensioner 10 and combustion of the
propellant 22, the piston 20 is propelled into the strap 34 wherein
the strap 34 then grips and tightens around the hub 38. Or, upon
combustion of the propellant 22 and upon rotation of the hub 38,
the plurality of knobs 42 are forcibly seated into respective
apertures within the plurality of apertures 36. The forward linear
motion of the piston 20 thus results in a rotary movement of the
hub 38 and the retractor axle 40, thereby tightening the belt 12.
The present invention, however, simplifies the design and
manufacturing of known motion multipliers and yet retains the
multiplier advantage of reducing the strap 34 or piston 20 stroke
requirement. Additionally, the essentially sealed housing 18
prevents the release of large quantities of gas, noise, and
flame.
[0027] Stated another way, the pretensioner 10 for the seat belt 12
utilizes a perforated strap 34 loosely coiled about the hub 38
wherein the hub 38 is, in normal operation of a vehicle, rotatable
with a webbing reel shaft 40 independent of strap 34. A plurality
of protrusions 42 are circumferentially spaced about the hub and
mesh with the perforated strap 34 upon activation of the
pretensioner 10. The pretensioner 10 contains a first passage 44
and a second passage 46 for the respective containment of the hub
38 and an actuator 20, wherein each passage is formed perpendicular
and in volumetric intersection with the other. The pretensioner 10
also contains a gas generant composition 22 in combustive
communication with the actuator 20. Upon ignition, the gas pressure
produced by the pyrotechnic 22 propels the actuator 32 into the
strap 34, thereby effecting rotary advancement of the hub 38 and
the shaft 40, and thus pretensioning the seat belt 12 wound about a
spool 11 of a seat belt retractor 14, wherein the spool or webbing
reel 11 is rotatably engaged with a second portion of the shaft 40
and thus provided in coaxial relation with the hub 38.
[0028] In one aspect of the invention as shown in FIG. 6, a hard
and resilient liner 60, steel for example, may if desired be press
fitted within the first end 48 to conform to the inner surface of
the passage 46, wherein the liner 60 extends up to the
circumference of the first cylindrical passage 44, but not in
intersecting relationship with the diameter of passage 44. Liner 60
thus enhances the strength of the combustion or pressure chamber 48
(first end 48) therefore permitting the use of lower strength
materials for the housing 18 such as aluminum or certain plastics.
Material costs may thereby be reduced.
[0029] In another embodiment shown in FIG. 7, a steel sleeve 62 may
alternatively be threadedly received or otherwise fixed to an
opening in the exterior of housing 18 in axial alignment with
passage 46. The initiator 26 may be threadedly received or
otherwise fixed to an opposite end of the sleeve 62. The propellant
22 and the actuator 20 are then sequentially positioned within the
sleeve 62 between the initiator 26 and the housing 18. At the
second end of the sleeve 62, the strap portion 30 and the leading
edge of the actuator would again be in flush communication prior to
activation of the pretensioner 10. In contrast to the embodiment
shown in FIG. 6, the use of the sleeve 62 outside of the second
rectangular passage 46 permits a reduction in the size of the
housing 18 and therefore a reduction in materials and weight.
[0030] As also shown in FIG. 6, a pretensioner 10 of the present
invention may also utilize an initiator 26 in ignitable
communication with a propellant 22 within a gas generator 16, each
contained within a third chamber 64. The third chamber 64
preferably runs parallel to the first cylindrical chamber 44, and
perpendicular to the rectangular chamber 46. Gas produced from the
gas generator 16 is forced into the second passage 46, thus driving
the actuator 20 forward.
[0031] FIG. 8 illustrates a compact embodiment of the present
invention.
[0032] To illustrate a retractor response based on pretensioner
operation, see U.S. Pat. No. 5,899,399 to Brown et al., herein
incorporated by reference. "Pretensioning" is generally defined to
mean to take up slack in the seat belt. In accordance with the
present invention, the gas produced by the gas generant propels the
piston 20 into the strap 34 and thus affects rotary advancement of
the hub 38 thereby tightening the slack in the seat belt 12.
[0033] After activation of the pretensioner 10, only the
pretensioner 10 or parts therein need be replaced. The seat belt
retractor is generally salvageable.
[0034] The housing 18, the piston 20, the hub 38, and the initiator
retainer 26 are preferably injection-molded, die cast and/or
machined from plastics, composites, and/or one or more metals such
as steel, a steel alloy, zinc, or aluminum. The gas generator 16,
the gas generant 22, the initiator 26 and the strap 34 are all
manufactured or obtained by methods known to those of ordinary
skill. Strap 34, for example, may be cut from sheet metal and then
stamped or punched to provide the plurality of apertures 36.
Companies such as Takata, Inc. of Japan, for example, may supply
the gas generator 16. The initiator 22 may be supplied by the
original equipment manufacturer or from companies such as Special
Devices Incorporated. The aforementioned references are
incorporated by reference and cited by way of example.
[0035] Resultant benefits include simplified manufacturing and
retractor preservation. For example, see U.S. Pat. No. 5,899,399 to
Brown et al. Also see U.S. Pat. No. 5,397,075 to Behr, herein
incorporated by reference, wherein complicated gear driving
mechanisms used to actuate the retractor axle can be replaced by
the present invention.
[0036] Because expense heretofore associated with activation of a
pretensioner is significantly reduced, passengers can be assured of
the protection of seat belt pretensioning in even minor accidents.
Moreover, a pretensioner that activates in minor collisions will
also activate earlier in a severe crash sequence. Earlier
activation of the pretensioner facilitates a less aggressive onset
of initial pretensioner operation, thereby reducing the possibility
of injury caused by the seat belt pretensioner.
[0037] Finally, gas ventilation ports as required in certain
pretensioners are not required and therefore manufacturing is even
further simplified.
[0038] While the foregoing illustrates and describes the use of the
present invention, it is not intended to limit the invention as
disclosed in certain preferred embodiments herein. Therefore,
variations and modifications commensurate with the above teachings
and the skill and/or knowledge of the relevant art, are within the
scope of the present invention as described herein and as stated in
the appended claims.
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