Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R22/00—Safety belts or body harnesses in vehicles
  • B60R22/34—Belt retractors, e.g. reels
  • B60R22/46—Reels with means to tension the belt in an emergency by forced winding up
  • B60R22/4628—Reels with means to tension the belt in an emergency by forced winding up characterised by fluid actuators, e.g. pyrotechnic gas generators
  • B60R22/4633—Linear actuators, e.g. comprising a piston moving along reel axis and rotating along its own axis
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
  • B60R22/00—Safety belts or body harnesses in vehicles
  • B60R22/34—Belt retractors, e.g. reels
  • B60R22/46—Reels with means to tension the belt in an emergency by forced winding up
  • B60R2022/468—Reels with means to tension the belt in an emergency by forced winding up characterised by clutching means between actuator and belt reel

Definitions

• 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.
• 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.
• 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.
• the pretensioner When compared to the seatbelt retractor, the pretensioner is relatively complex and large, thus increasing the weight and spatial requirements of the seatbelt assembly.
• 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.
• 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.
• 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.
• the piston 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.
• Fig. 1 is a diagrammatic elevational view of a replaceable seat belt pretensioner in a pre-activated condition, in accordance with the present invention.
• Fig. 2 is a second diagrammatic elevational view of the present invention illustrating activation of the pretensioner.
• Fig. 3 is a perspective view of the hub having a plurality of circumferential protrusions integral thereto.
• Fig. 4 is an elevational view of the perforated strap having a plurality of perforations.
• Fig. 5 is an elevational view of a pretensioner of the present invention in cooperation with a state-of-the-art seat belt retractor.
• 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.
• 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.
• Fig. 8 is yet another embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT
• a pretensioner 10 in accordance with a preferred embodiment of the invention, comprises a gas generator 1 6 adapted to pretension a seat belt 1 2 of a conventional seat belt retractor 14.
• a gas generator 1 6 adapted to pretension a seat belt 1 2 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. Patent Nos. 4,558,832 and 4,597,546, herein incorporated by reference.
• a pretensioner 10 in accordance with the present invention may if desired replace many pretensioners now employed in the art.
• a housing 1 8 contains the gas generator 1 6.
• the gas generator 1 6 fluidly communicates with a piston 20.
• the piston 20 is made from steel, brass, aluminum, plastic, or other sufficiently rigid material.
• the gas generator 1 6 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. Patent 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 1 6.
• an initiator 26 communicates 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 1 6), the electrical contacts 24, and the initiator 26.
• 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.
• the diameter of the perforations 36 is sized to be at least slightly larger than the diameter of the protrusions 42.
• 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.
• a first cylindrical channel 44 contains the hub 1 8.
• 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 1 8 at a point adjacent to the piston 20.
• the strap 34 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.
• the piston 20 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.
• 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 1 2.
• the present invention 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.
• the pretensioner 10 for the seat belt 1 2 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.
• 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 1 2 wound about a spool 1 1 of a seat belt retractor 14, wherein the spool or webbing reel 1 1 is rotatably engaged with a second portion of the shaft 40 and thus provided in coaxial relation with the hub 38.
• 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 1 8 such as aluminum or certain plastics. Material costs may thereby be reduced.
• 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 1 8.
• the strap portion 30 and the leading edge of the actuator would again be in flush communication prior to activation of the pretensioner 10.
• the use of the sleeve 62 outside of the second rectangular passage 46 permits a reduction in the size of the housing 1 8 and therefore a reduction in materials and weight.
• a pretensioner 10 of the present invention may also utilize an initiator 26 in ignitable communication with a propellant 22 within a gas generator 1 6, 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 1 6 is forced into the second passage 46, thus driving the actuator 20 forward.
• Fig. 8 illustrates a compact embodiment of the present invention.
• Pretensioning is generally defined to mean to take up slack in the seat belt.
• 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.
• the seat belt retractor is generally salvageable.
• 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.
• Resultant benefits include simplified manufacturing and retractor preservation.
• U.S. Patent No. 5,899,399 to Brown et al. also see U.S. Patent 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.
• gas ventilation ports as required in certain pretensioners are not required and therefore manufacturing is even further simplified.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Automotive Seat Belt Assembly (AREA)
• Storing, Repeated Paying-Out, And Re-Storing Of Elongated Articles (AREA)

Applications Claiming Priority (3)

Publications (2)

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• 2001
  • 2001-05-31 JP JP2001588120A patent/JP2003534985A/ja active Pending
  • 2001-05-31 WO PCT/US2001/017553 patent/WO2001092138A1/en not_active Application Discontinuation
  • 2001-05-31 EP EP01941726A patent/EP1284917A4/de not_active Withdrawn

Patent Citations (1)

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