U.S. patent application number 09/777388 was filed with the patent office on 2001-10-18 for seat belt pretensioner.
Invention is credited to Adamini, Chris A., Stevens, Bruce A..
Application Number | 20010030254 09/777388 |
Document ID | / |
Family ID | 26876138 |
Filed Date | 2001-10-18 |
United States Patent
Application |
20010030254 |
Kind Code |
A1 |
Stevens, Bruce A. ; et
al. |
October 18, 2001 |
Seat belt pretensioner
Abstract
A pretensioner 10 for a seat belt 12 utilizes a strap 34 coiled
about a clutch assembly 46 wherein the clutch assembly 46 is in
normal operation of a vehicle, rotatable about a portion of a
webbing reel shaft 16. The pretensioner 10 contains a first passage
20 and a second passage 22 for the respective containment of the
clutch assembly 46 and an actuator 32, wherein each passage is
formed perpendicular and in volumetric intersection with the other.
The pretensioner 10 also contains a gas generant composition 30 in
combustive communication with the actuator 32. Upon ignition, the
gas pressure produced by the pyrotechnic 30 propels the actuator 32
into the strap 34, thereby effecting rotary advancement of the
clutch assembly 46 and the shaft 16, and thus pretensioning the
seat belt 12 wound about a spool 13 of a seat belt retractor 14,
wherein the spool 13 is rotatably engaged with a second portion of
the shaft 16 and thus provided in coaxial relation with the clutch
assembly 46.
Inventors: |
Stevens, Bruce A.; (Oakland,
MI) ; Adamini, Chris A.; (Shelby Township,
MI) |
Correspondence
Address: |
Laurence C. Begin
Dinnin & Dunn, P.C.
Suite 2100
755 West Big Beaver
Troy
MI
48084
US
|
Family ID: |
26876138 |
Appl. No.: |
09/777388 |
Filed: |
February 5, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60180270 |
Feb 4, 2000 |
|
|
|
60180271 |
Feb 4, 2000 |
|
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Current U.S.
Class: |
242/374 |
Current CPC
Class: |
B60R 22/4633 20130101;
B60R 22/4619 20130101; B60R 22/4628 20130101; B60R 2022/468
20130101 |
Class at
Publication: |
242/374 |
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
the 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 a first end and a second end, the second end extending
across and past the diameter of the first passage; a clutch
assembly fixed within the first passage wherein said webbing reel
shaft axially extends through said clutch assembly; a strap having
a first end fixed to said housing, a portion extending across a
section of said second passage, and a second end coiled about and
fixed to said clutch assembly; an actuator positioned within the
first end of said second passage for tensioning said strap upon
pretensioner activation; and a gas generant composition, ignitable
to release sufficient force to drive the actuator through said
second passage to the second end thereof, thereby effecting a
tensioning of the strap and a peripheral force about the clutch
assembly, and then a simultaneous rotary advancement of the clutch
assembly, the webbing reel shaft, and the webbing reel, and thus
winding the reel and tensioning the seatbelt webbing thereon.
2. The pretensioner of claim 1 wherein said actuator is a one-piece
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 and thereby also functions as a gas
generator.
5. The pretensioner of claim 1 further comprising a resilient
cylindrical liner extending up to the circumference 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
the 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 end
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 clutch assembly fixed within the first passage wherein
said webbing reel shaft axially extends through said clutch
assembly; a strap having a first end fixed to said housing, a flat
portion extending across a section of said second passage, and a
second end coiled about and fixed to said clutch assembly; an
actuator positioned within said circular cylindrical sleeve for
acting upon the flat portion of the strap and tensioning said strap
upon pretensioner activation; a gas generant composition positioned
intermediate of the actuator and the first end of said cylindrical
sleeve; 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, wherein 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 to
the second end thereof, thereby effecting a tensioning of the strap
and actuation of the clutch assembly, and then a simultaneous
rotary advancement of the clutch assembly, the webbing reel shaft,
and the webbing reel, thus winding the reel and tensioning the
seatbelt webbing thereon.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. Nos. 60/180,270 and 60/180,271, each filed on Feb.
4, 2000.
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.
[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 often 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, sometimes injuring 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 therefore complicating 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.
SUMMARY OF THE INVENTION
[0010] The aforesaid problems are solved, in accordance with a
preferred constructed embodiment of the present invention, by a
seat belt pretensioner that utilizes a flat strap as a motion
multiplier and a linear channel for movement of a pretensioner
actuator, thereby reducing the load or force lost to friction in
certain known pretensioners. Given the ease of sealing, the present
design also inhibits retractor and occupant exposure to the gases
and solids formed upon combustion of a pyrotechnic composition
contained within the pretensioner.
[0011] In one embodiment of the invention, the pretensioner
contains a housing, a clutch assembly that in operation rotatably
and constrictively communicates with a webbing reel shaft of a
seatbelt retractor, a strap that constrictively exerts a
circumferential pressure about the clutch assembly upon
pretensioner activation, an actuator that communicates with and is
propelled against the strap upon pretensioner activation, a gas
generant or pyrotechnic that propels the actuator (or piston), and
an initiator that ignites the gas generant upon a signal from an
accelerometer or impact sensor, for example. Upon ignition of the
gas producing pyrotechnic, the actuator is driven forward in an
essentially linear path thereby tightening the strap about the
clutch assembly, and thus pretensioning the seat belt wound about a
spool in the retractor, wherein the spool and the clutch assembly
share the webbing reel retractor shaft as an axis in a preferred
embodiment.
[0012] Stated another way, a pretensioner 10 for a seat belt 12
utilizes a strap 34 coiled about a clutch assembly 46 wherein the
clutch assembly 46 is in normal operation of a vehicle, rotatable
about a portion of a webbing reel shaft 16. The pretensioner 10
contains a first passage 20 and a second passage 22 for the
respective containment of the clutch assembly 46 and an actuator
32, wherein each passage is formed perpendicular and in volumetric
intersection with the other. The pretensioner 10 also contains a
gas generant composition 30 in combustive communication with the
actuator 32. Upon ignition, the gas pressure produced by the
pyrotechnic 30 propels the actuator 32 into the strap 34, thereby
effecting rotary advancement of the clutch assembly 46 and the
shaft 16, and thus pretensioning the seat belt 12 wound about a
spool 13 of a seat belt retractor 14, wherein the spool 13 is
rotatably engaged with a second portion of the shaft 16 and thus
provided in coaxial relation with the clutch assembly 46.
[0013] After use, only the pretensioner and perhaps the retractor
shaft need be replaced, obviating the expense of also replacing the
retractor or other components of the seat belt retraction
mechanism.
[0014] Because expense heretofore associated with activation of a
pretensioner is significantly reduced, passengers can be given 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 permits the pretensioner to operate
less aggressively, reducing the possibility of injury caused by the
seat belt pretensioner itself.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a diagrammatic elevational view, partially in
cross-section, of a replaceable seat belt pretensioner prior to
activation, in accordance with the present invention.
[0016] FIG. 2 is a second diagrammatic elevational view of a second
embodiment, partially in cross-section, of a replaceable seat belt
pretensioner after activation;
[0017] FIG. 3 is a partially exploded view of the embodiment of
FIG. 1, in accordance with the present invention.
[0018] FIG. 4 is a cross-sectional view of the pretensioner of FIG.
1 taken along the line A-A.
[0019] FIG. 5 is a perspective view of a one-piece injection molded
clutch assembly or coupling mechanism, in accordance with the
present invention.
[0020] FIG. 6 is a top view of the clutch assembly of FIG. 5.
[0021] FIG. 7 is a side view of the clutch assembly of FIG. 5;
[0022] FIG. 8 is another embodiment of the present invention
wherein a resilient liner is utilized to strengthen a second
passage within the housing.
[0023] FIG. 9 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.
[0024] FIG. 10 is yet another embodiment of the present invention
containing a gas generator.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] Referring to the figures, a pretensioner 10 in accordance
with a preferred embodiment of the invention is employed to
pretension a seat belt 12 wound about a reel 13 of a conventional
seat belt retractor 14. "Pretensioning" is generally defined to
take up slack in the seat belt in the event of sudden deceleration,
or, a collision. A webbing reel retractor shaft 16 extends from the
retractor 14 into the pretensioner 10 and thereby cooperates with
the pretensioner 10 to tighten the seatbelt 12 in the event of an
accident. The pretensioner of the present invention has generic
application, for example only, in seatbelt assemblies having
seatbelt retractors as described in U.S. Pat. Nos. 4,558,832 and
4,597,546, herein incorporated by reference.
[0026] A housing 18 is formed from steel, aluminum, metal alloys,
plastic, and/or other known materials suitable for containment of
the components described below. The housing 18 is formed with a
first circular cylindrical passage 20 volumetrically intersecting a
second rectangular cylindrical passage 22, wherein each passage is
formed perpendicular to the other and second passage 22 is
substantially coextensive with the length of the housing 18. The
second passage 22 has a first end 24 and a second end 26. The
length of the second passage 22 preferably extends toward second
end 26 to permit at least one full turn of the webbing reel shaft
16. It should be noted that given the sealing means within the
first end 24, for example o-rings and/or a flared actuator 32, the
channel 22 could conceivably extend through the housing 18.
[0027] An initiator 28 is fixed (threadedly received, for example)
within the first end 24 of the passage 22. As shown in FIG. 1, the
initiator 28 ignitably communicates with a gas generant propellant
30 that may if desired be placed proximate to the initiator 28,
intermediate of the initiator 28 and the second end 26. An actuator
32, preferably made of a hard resilient material such as plastic,
steel, brass and metal alloys and flared at one end to provide a
sealing means, is also placed within the first end 24, intermediate
of the propellant 30 and the second end 26. The actuator 32 may be
formed as a one-piece slug, or as a plurality of segments although
other types of actuators may also be implemented. A strap 34,
preferably made from steel or some other hard and ductile metal or
alloy, is fixed to the housing 18 and passages through an
intermediate portion of the passage 22. A flat portion 36 of the
strap 34 traverses a cross-section of the passage 22 thus providing
a relatively large contact area for flush communication of a
leading portion 37 of the actuator 32.
[0028] In the embodiment shown in FIGS. 1 and 2, a clutch assembly
or coupling mechanism 46 is fixed about the retractor shaft 16
whereby the shaft 16 functions as an axis of rotation. As
illustrated, the clutch assembly 46 is fixed to a clip 48 that has
a circumference roughly equivalent to that of the first passage 20
and a key corresponding to a female counterpart in the channel 20.
Clip 48 is thus key-fitted within the first passage 20 thus
preventing rotation upon activation of the clutch assembly 46. The
clutch assembly 46 further includes a first segment 50 and a second
segment 52. A first shear pin 54 is press-fitted through an annulus
56 of the first segment 50. A second shear pin 58 is press-fitted
through an annulus 61 of the second segment 52, whereby shear pins
54 and 58 form slight protrusions through the respective upper and
lower surfaces of segments 50 and 52. The protrusions 60 thus
function to secure each segment to corresponding annuli in the clip
48. At the other end of the segments, the segments may be held in
place by annuli formed within the cover 59, or, another clip 48a
may be used to secure the segments from the coiled energy of the
strap 34 during normal vehicular operation. When the segments 50
and 52 are fixed in place, the retractor shaft 16 rotates freely of
the segments except when the pretensioner is activated.
[0029] FIGS. 5-7 illustrate an alternative one-piece injection
molding of a clutch assembly 46a. The clutch assembly includes
protrusions 60a integral to segments 50a and 52a thereby securing
the clutch 46a to clip 48. Segments 50a and 52a are joined together
by spring members 62 and 64.
[0030] In general, the clutch assemblies illustrated herein are
merely exemplary of the many known clutches useful in the art.
Accordingly, as used herein, the term "clutch assembly" is meant to
apply generically to any clutch component or combination of
components that are useful in the seatbelt retractor and
pretensioner art. Stated another way, a "clutch assembly" is any
component or combination of components that exert a rotatable and
circumferential force about the retractor shaft 16 and thus produce
a pretensioning or tightening of the belt 12 by winding the
associated webbing reel 13. U.S. Pat. Nos. 5,743,480 and 5,222,994,
herein incorporated by reference, illustrate known
alternatives.
[0031] The strap 34 is preferably wrapped at least twice around the
periphery of segments 50 and 52, and then hooked in place about an
edge of either segment 50 or 52. As the actuator 32 propels the
strap 34 to the second end 26 of passage 22, the strap 34 tightens
about the clutch assembly 46, shearing pins 54 and 58, and exerting
a peripheral force about the clutch assembly 46. The forward motion
of the actuator 32 thus results in compression and constriction of
the clutch segments 50 and 52 about the retractor axle 16. Rotary
movement of the clutch assembly 46 and the webbing reel shaft 16 is
thus effected as the associated teeth of the segments 50 and 52
mate with the associated teeth of the shaft 16. Clutch operation
therefore results in rotation of the webbing reel 13 of the
retractor 14 and tightening or pretensioning of the associated belt
webbing 12. Cover 59 encloses the passages 20 and 22 and the
components contained therein.
[0032] Thus, in accordance with the present invention, the linear
movement of the actuator 32 and the strap 34 thus provides a
multiplier effect similar to that provided by geared motion
multipliers. 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 actuator 32 stroke
requirement. Additionally, the substantially sealed housing largely
prevents the release of gas, noise, and flame.
[0033] In the embodiment shown in FIG. 2, a cup portion 38 may be
provided within the actuator 32 and may contain the propellant 30,
if desired. The propellant 30 is simply placed within the actuator
32 prior to installation thereof within passage 22, and then
ignitably connected to the initiator 28. A spring 39 may if desired
be placed between the initiator 28 (or first end 24) and the
actuator 32, thereby biasing the leading edge of the actuator 32
against the flat portion 36 of the strap 34.
[0034] In one aspect of the invention as shown in FIG. 8, a hard
and resilient cylindrical liner 27, steel for example, may if
desired be press fitted within the first end 24 to conform to the
inner surface of the passage 22, wherein the liner 27 extends up to
the circumference of the first cylindrical passage 20, but not in
intersecting relationship with the diameter of passage 20. Liner 27
thus enhances the strength of the combustion or pressure chamber 24
(first end 24) therefore permitting the use of lower strength
materials for the housing such as aluminum or certain plastics.
Material costs may thereby be reduced.
[0035] In another embodiment shown in FIG. 9, the steel sleeve
insert 27 may alternatively be threadedly received or otherwise
fixed to an opening in the exterior of housing 10 in axial
alignment with passage 22. The initiator 28 may be threadedly
received or otherwise fixed to an opposite end of the sleeve 27.
The propellant 30 and the actuator 32 would then be sequentially
positioned within the sleeve 27 between the initiator 28 and the
housing 10. At the second end of the sleeve 27, the strap 34 and
the leading edge of the actuator 32 would again be in flush
communication prior to activation of the pretensioner 10. In
contrast to the embodiment shown in FIG. 8, the use of the sleeve
27 outside of the second cylindrical passage 22 permits a reduction
in the size of the housing 10 and therefore a reduction in
materials and weight.
[0036] As shown in FIG. 10, a pretensioner of the present invention
may also utilize an initiator 28a in ignitable communication with a
propellant 30a within a gas generator 38, each contained within a
third cylindrical chamber 40. The third cylindrical chamber 40 runs
parallel to the first cylindrical chamber 20, and perpendicular to
the second cylindrical chamber 22. Gas produced from the gas
generator is forced through into the second cylindrical passage
22a, thus driving the actuator 32 forward.
[0037] In operation, electrical contacts 44 on the initiator 28
communicate with a sensor that signals actuation of the
pretensioner 10. Once the initiator 28 receives a signal, from an
accelerometer for example, the initiator 28 ignites the pyrotechnic
gas generant 30. The resultant gas pressure propels the piston or
actuator 32 against the strap portion 36, and then forces the
actuator 32 and the strap 34 from the first end 24 to the second
end 26. As the strap 34 advances, the clutch assembly 46 engages
the webbing reel shaft 16 and pretensions the belt 12. Linear
movement of the actuator 32 thus effects rotary movement of the
shaft 16 thereby pretensioning the seatbelt webbing 12 contained
and extending from the retractor 14.
[0038] The housing 18, the piston or actuator 32, and the clutch
assembly 46 may be die cast from aluminum, steel or suitable alloys
thereof. Or, they may be injection molded if plastic material is
used. In a preferred embodiment, the actuator 32 and the clutch
assembly 46 are formed from hard resilient plastic thereby reducing
the weight of the pretensioner 10. The gas generator 38, the gas
generant propellant 30, and the initiator 22 are all manufactured
or obtained by methods known to those of ordinary skill. The strap
34 may be cut from steel sheet metal for example.
[0039] 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. When utilized in conjunction with the linear
movement of the actuator 32, the strap 34 provides a multiplier
effect similar to that provided by geared motion multipliers. 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 actuator stroke requirement.
Manufacturing of the present pretensioner is also relatively simple
given the straight cylindrical passages. The employment of linear
passages not only simplifies manufacturing, but also reduces the
friction loss of the applied load on the actuator as compared to
arcuate passages, for example. Additionally, the use of linear and
cylindrical passages facilitates the sealing of the passages as
compared to other geometrically shaped passages. Finally, the
essentially sealed housing 10 substantially prevents the release of
gas, solids, noise, and flame. After activation of the pretensioner
10, therefore, only the pretensioner 10 need be replaced. In
general, all or most of the retractor mechanism 14 will be
salvageable after pretensioner use.
[0040] Gas generants useful in conjunction with the present
invention are gas generants well known to those of ordinary skill
in the art. For examples, see U.S. Pat. Nos. 5,035,757, 5,460,668,
5,756,929, and 5,872,329, herein incorporated by reference. These
compositions exemplify, but do not limit, useful gas generant
compositions.
[0041] While the foregoing examples illustrate and describe the use
of the present invention, they are 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.
* * * * *