Abstract:
A pretensioner for tightening an occupant restraint, such as a seatbelt, against an occupant on a vehicle. The pretensioner has a locking reel which is activated when a signal is sent by a crash sensing device. When such signal is sent, the pretensioner causes a rack to turn a pinion, which is attached to a reel which tightens the occupant restraint. The pinion is allowed to turn freely by holding the rack out of its sphere of movement until the piston, which controls the position of the rack, is caused to extend. The pinion turns a shaft which is connected to a locking reel through a connector which is movable between a connected configuration and a disconnected configuration.

Description:
BACKGROUND OF THE INVENTION 
     The field of the invention is occupant restraint systems for use in vehicles. It is especially adapted for use in fast moving vehicles, such as aircraft or race cars. Such vehicles can subject the occupants to large accelerations/decelerations during unexpected, undesirable events, such as a violent maneuver or a crash. These accelerations/decelerations can lead to large displacements of the occupant&#39;s body, which can result in the occupant&#39;s body or head contacting structure or objects within the vehicle. This can result in serious injuries or possibly death. Specially designed seats and restraint systems are typically used to restrain the occupant, however, excessive body displacement can still occur during the undesirable events due to the wide range of human body types and sizes. 
     Restraint systems include inertia reels that are designed to prevent movement of the body during normal operation of the vehicle—such as reaching with the arms and turning of the torso. The inertia reels are also designed to lock (preclude webbing payout from the housing) when large accelerations or decelerations are detected. This minimizes the displacement of the seated occupant&#39;s body to mitigate the potential for injury. Furthermore, the seated occupant is sometimes out of position or engaged in reaching or turning motions during the onset of an undesirable event. Even a securely restrained occupant seated firmly against the seatbelt with the restraint and inertia reel functioning perfectly, can still experience significant displacement (depending upon the severity of the event) and be seriously injured due to initial slack in the restraint, the compaction of the webbing on the inertia reel shaft, and induced stretch of the webbing material. 
     The device set forth below is intended to automatically retract the restraint webbing early in the event. By doing so, undesirable slack is removed and after the webbing is tightened, the occupant is held in the ideal upright seated posture, thereby minimizing the potential for serious injury. The device may be mounted directly to an existing inertia reel in the case of a retrofit, or configured as an integral feature of the inertia reel itself. Furthermore, the device is designed so that actuation will not injure the occupant it is intended to protect and ensure a safe exit from the vehicle after a crash. Also, non-crash, inadvertant actuation will not inhibit the occupant&#39;s ability to continue to safely operate the vehicle, which is particularly crucial in aviation applications. 
     Although the initial application is in aviation vehicles, the device is also applicable to land vehicles where fast actuation is desired due to the severity of potential undesirable events (e.g. crashes involving high speed racing vehicles). 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is for a pretensioner for tightening a restraint, such as a seatbelt, against an occupant upon the occurrence of a crash or other potential injury-causing acceleration or deceleration. The pretensioner has a locking reel to tighten the restraint when a signal directing such tightening is received. The pretensioner has a housing body with a cylinder having a rack with a piston end. The rack is held within the cylinder and includes an elongated arm having a piston at one end and a shaft extending toward a rack end of the cylinder. The shaft has a rack formed along a portion thereof and the rack is longitudinally movable within the cylinder. A pressure chamber is formed in the pretensioner body at the piston end of the cylinder. Means are provided for aligning the rack in the cylinder so that a longitudinal axis of the rack remains fixed during the movement of the rack. A pinion is held on a pinion shaft rotatably supported by the pretensioner body. The pinion shaft is connectable to the locking reel. A movable rack arm is held in a biased member against the terminus of the rack. This holds the rack so that the piston is nearest the piston end of the cylinder and the rack is out of contact with the pinion. In this way, the pinion can turn freely without contact with the rack until the rack is caused to move by pressure induced into the pressure chamber. The rack preferably has rack teeth along its upper surface and has a flat lower surface which rides on a shaft. As the rack moves, the movable rack arm, which is affixed to a shaft, causes a movable coupler arm to move. The movement of the movable coupler arm permits the release of a coupler, which is positioned between the pinion shaft and the locking reel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial perspective view of an air crew man wearing a safety harness that incorporates a webbing which is adapted to be pretensioned by the restraint pretensioner of the present invention. 
     FIG. 2 is a perspective view partly in cross-section of the restraint pretensioner of the present invention taken from the rack side thereof. 
     FIG. 3 is a perspective view partly in cross-section taken near the pinion end thereof. 
     FIG. 4 is a cross-sectional view taken near the rack side thereof. 
     FIG. 4A is a cross-sectional view analogous to FIG. 4 except showing the rack extended. 
     FIG. 5 is a cross-sectional view similar to FIG.  3  and showing the intersection of the hex shaft and the drive shaft and showing the drive shaft in a coupled configuration. 
     FIG. 5A is a cross-sectional view analogous to FIG. 5 with the coupler in an uncoupled configuration. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The general environment in which the restraint pretensioner of the present invention is indicated in FIG.  1 . An occupant restraint, which typically includes a harness  16 , can be tightened by inertia reel  8  which is rigidly attached to the seat or some other portion of the vehicle structure. The pretensioner  6  may be an integral part of the inertial reel and a crash sensor  2  (similar to the one embodied in U.S. Pat. No. 6,299,102, which is incorporated by reference herein) is rigidly attached to the vehicle structure and located as close as possible to the occupant(s) to ensure accurate sensing of the accelerations (either positive or negative) actually experienced by the occupants. 
     Excessive acceleration detected by crash sensor  2  sends an activation signal to pretensioner  6 . The activation signal is received by electronic circuit board  22  (shown in FIG. 2) located within pretensioner  6 . Electronic circuit board  22  includes, among other components, electrical capacitors where sufficient electrical energy can be stored to initiate a pyrotechnic gas-dispensing cartridge contained within, or attached to, pretensioner  6 . Alternatively, such electrical energy can be used to open a valve which allows compressed gas to flow from a separate reservoir. In the embodiment shown in FIG. 2, the stored electricity from such capacitor is delivered to pyro  24  producing gas which flows into chamber  26 . The released gas pressurizes chamber  26  almost instantaneously, causing piston  28  to move rapidly within cylindrical hole  30  and housing  32 . An o-ring would normally be mounted in o-ring groove  34  in piston  28  to minimize leakage. 
     Piston  28  is elongated and equipped with an integral rack  36  with teeth  38 . As the teeth  38  engage the teeth  42  of pinion gear  40 , the linear displacement of piston  28  produces rotation of pinion gear  40 . Pinion gear  40  is directly coupled to the inertia reel&#39;s webbing shaft  20 , shown in FIG. 3, through drive shaft  46  and coupler  44 . Rotation of the inertia reel&#39;s webbing shaft  20 , in turn, forcibly back-drives the occupant restraint webbing  18  on shaft  20 , activating the inertia reel&#39;s automatic locking feature and maintaining the occupant in the optimum upright seated position to withstand the high acceleration of the event. 
     Prior to actuation, piston  28  and pinion gear  40  are disengaged—that is, piston  28  is initially prevented from movement by movable rack arm  50 , which is held in place by torsion spring  48 . Pinion gear  40  is able to rotate freely, as shown best in FIG.  4 . As the inertia reel&#39;s webbing shaft  20  turns, pinion gear  40  turns freely whenever the webbing  18  is retracted or “paid out.” That is, the teeth  38  of rack  36  are not in engagement with the teeth  42  of pinion gear  40  before mechanism actuation. Also the coupler  44  is in the coupled configuration as shown in FIG. 5 prior to actuation and during belt tensioning. 
     As piston  28  moves linearly, the lower surface of rack  36  is supported by pin  56 , which ensures proper alignment of the teeth  38  during engagement with teeth  42 . Note that rack  36  is prevented from moving before actuation by movable rack arm  50 . Movable rack arm  50  is keyed to and mounted on shaft  54 . Furthermore, a movable coupler arm  52  is also keyed to and mounted on shaft  54  and holds coupler  44  in the engaged position, as shown in FIG.  3 . The torsion spring  48  prevents shaft  54  from rotating prematurely. Thus, this mechanical sub-system prohibits piston  28  from moving prior to actuation by crash sensor  2 . The forced displacement of piston  28  both drives rack  36  and rotates shaft  54 , and movable rack arm  50  and movable coupler arm  52 . At the end of the stroke, piston  28  is stopped by pin  56  and prevented from rebounding by engagement between movable rack arm  50  and pocket  58  on the underside of piston  28 . 
     Coupler  44  serves several functions: (a) allows for simultaneous axial and radial misalignment between the male hex shaft  62  of pinion gear  40  and drive shaft  46 , (b) couples the pinion gear assembly to the webbing shaft  20 , and (c) decouples pinion  40  and drive shaft  46  after actuation is finished. The decoupled configuration is shown in FIG.  5 A. The input side of coupler  44  engages the output side of male hex shaft  62  of pinion gear  40 . The large end of drive shaft  46  is flared and enlarged for strength and engages the output side of coupler  44 . The smaller end of drive shaft  46  fits into, is keyed to, and drives webbing shaft  20  of inertia reel  8 . Coupler  44  stays engaged to both hex shaft  62  of pinion gear  40  and drive shaft  46 , and is constrained from separating by the presence of movable rack arm  50  until actuation is complete. After actuation is complete, the compression spring  60  moves coupler  44  axially away from the flared end of drive shaft  46 , disengaging hexagonal drive shaft  46  from webbing shaft  20 . The occupant is still confined within the occupant restraint  16  because inertia reel  8  is still locked. After the undesirable event is complete, the occupant can manually unlock the inertia reel via handle  12 , regaining complete freedom of movement and/or egress capability. 
     As an alternative to pyro  24 , a compressed gas system can be used. In another embodiment, pretensioner  6  could be equipped with a small pressure intensifier driven by electronic circuit board  22 . The pressure intensifier can refill a pressure reservoir after each actuation (opening the release valve) permitting the system to be “recyclable.” Recycling the system permits the use of lower actuation thresholds for the crash sensor, allowing system operation in “marginal” events without loss of capability or the primary objective (crash events). The pressure intensifier is a small, reciprocating, piston-type pump which draws in ambient air and forces it into the reservoir until the desired pressure is reached. Subsequent on/off cycles can be used to maintain the reservoir at the desired pressure negating the need for hermetic sealing, which would be particularly difficult for the release valve. 
     A critical, additional feature of this design shown in FIG. 4 is that the first tooth  63  of rack  36  is modified from the standard tooth profile by the removal of a portion  37  of the trailing surface. In the rare instance of a precise initial tip alignment of the first tooth  63  with a tooth (teeth  42 ) of pinion gear  40  (which could prevent the teeth from engaging), this feature ensures that the gear teeth do not lock as engagement is attempted. This could render the device inoperable and potentially trap the seated occupant in the occupant restraint system. In this case, the modified portion of the tooth will shear, allowing the remaining portion to align and complete the tooth engagement sequence. In addition, the tips of all teeth (teeth  38  and teeth  42 ) are smoothly contoured in order to maximize synchronous and smooth engagement. 
     A second critical feature of the present design is the addition of a means for venting the post-actuation chamber pressure. After the pretensioning event is completed, the internal gas pressure in chamber  26  can be vented through a spring loaded pressure relief valve  64 , shown in FIG.  4 . Alternatively, an optional small diameter orifice  65  can be used to relieve the pressure within chamber  26 . Venting or relieving the internal pressure effectively eliminates any forces between the teeth of rack  36  and pinion gear  40 , which could prohibit coupler  44  from decoupling once the pretensioning event is completed. As the rack is in the process of turning pinion gear  40 , torsional friction tends to hold drive shaft  46  in coupler  44 . When the rack has fully extended, the pinion gear  40  is free to move and thus any torsional friction is eliminated, decoupling the drive shaft  46  from the male hex shaft  62  of pinion gear  40 . 
     The pressure relief valve  64  is held in an open position by spring  64 ′. However, once the gas enters chamber  26 , this valve  64  is closed rapidly by such gas pressure during the pretensioning event. The pressure set point at which valve opens and closes can be varied using springs having different spring rates. The optional orifice  65  is best placed in the piston  28 , such that venting can occur regardless of the amount of linear displacement of piston  28  that has occurred. This feature eliminates the need for orifice  68  in the housing wall, which could possibly tear the o-ring mounted in groove  34  during traversal. 
     The pretensioner of the present invention is quite small in size and is readily added to or configured to be part of an existing occupant restraint system. 
     The present embodiments of this invention are thus to be considered in all respects as illustrative and not restrictive; the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.