LOCKBAR FOR A SEATBELT RETRACTOR

Abstract: A lockbar (5) for a seatbelt retractor has an elongate joining member (8) and two end pieces (7) joined to the joining member at opposite ends therefore. The end pieces are made of a higher strength material than the joining member. The joining member may be made by extrusion and may be tubular or may be formed as a hollow member. The end pieces (7) may be produced as forgings, die casting or plastic injection moldings or by other suitable methods. The end pieces can be produced from different materials and to different designs to suit the specification of the seatbelt retractor. Hence a single basic seatbelt retractor design can be employed for a variety of strength requirements by selecting appropriate end pieces and an appropriate joining member.

Description: LOCKBAR FOR A SEATBELT RETRACTOR The present invention relates to a seatbelt retractor, and specifically to a lockbar for a seatbelt retractor. A seatbelt generally comprises belt webbing that passes over a vehicle occupant's torso to restrain forward movement in a crash. The webbing is wound on a spool that is mounted in the retractor for rotation about its longitudinal axis to wind in or pay out webbing. The spool is biased in a winding in direction by a spiral spring. A sensor detects a crash, for example by detecting acceleration or deceleration above a predetermined level. The crash sensor activates a locking mechanism to lock the spool against rotation and prevent further pay out of webbing thus restraining the occupant against forward motion. The spool is locked by engagement of teeth on a ratchet wheel on the edge of the spool with a locking pawl . Often two locking pawls are used mounted at opposite ends of a bar extending the length of the spool so as to lock both ends simultaneously. Such a lockbar is traditionally made in one piece of a single type of material, for example as a metal die casting. However, die cast parts are inherently rather weak and the traditional U-shaped lockbar is complex to manufacture . There is provided in accordance with the appended claim 1 an improved lockbar for a seatbelt retractor and an improved method of manufacturing or assembling a lockbar. According to a preferred embodiment of the present invention, the lockbar comprises an elongate joining member and two end pieces joined to the joining member at opposite ends therefore, the end pieces being made of a higher strength material than the joining member Hence a single basic seatbelt retractor design can be employed for a variety of strength requirements by selecting appropriate end pieces and an appropriate joining member. Brief Description of the Drawings For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made by way of example to the accompanying drawings in which: FIG.l is an isometric view of a seatbelt retractor incorporating a lockbar according to one embodiment of the present invention; FIG.2 is an exploded isometric view of the lockbar shown in FIG.l; FIG.3 is an exploded isometric view of a second embodiment of a lockbar according to the present invention; FIG.4 is an exploded isometric view of a third embodiment of a lockbar according to the present invention; and FIG.5 is a cross-sectional view of the lockbar of FIG.4. Detailed Description of the Invention FIG.l shows a seatbelt retractor comprising a frame 1, with cut-outs in the sides 2 supporting a spool 3 for rotation about its longitudinal axis. Ratchet teeth 4 are arranged around the circumference of each end of the spool 3. A lockbar 5 extends across frame 1 and has locking teeth 6 to engage the ratchet teeth 4 in the locking position when a crash is indicated in known manner. As can be seen more clearly in FIG.2 and FIG.5, the lockbar 5 comprises two end pieces 7 on which the locking teeth 6 are formed, and a central elongate joining member 8. The end pieces generally comprise pin formations for guidance purposes that interact with features in the retractor mechanism to move the end pieces into locking positions. These may be formed as separate pieces and inserted or otherwise attached. They may be formed by pressing, semi- shearing, over molding, over casting, cold forging, friction welding or other suitable methods. The end pieces, being either generally flat or L-shaped are easier to manufacture than the traditional one piece U-shaped lockbar. The end pieces may be attached to the joining member in a variety of ways to suit the strength requirements and the materials from which the parts are made. The end pieces can be produced from different materials and to different designs to suit the specification of the seatbelt retractor. For example, forged aluminum or steel end pieces are envisaged. These materials have a higher mechanical strength and a better metallurgical microstructure than die cast parts. The joining member may be hollow along its whole length or at its end to accommodate projections on the end pieces in the form of bars or pins . Alternatively, extending pins on the ends of the joining member may fit into holes in the end pieces. The joints may be made stronger by pressing, spot welding, riveting, over molding, over casting and/or by using adhesive. The joining member may be made by extrusion and may be tubular or may be formed as a hollow member, for example, of prismatic form (i.e., with a triangular cross-section) . It is preferably designed to have relatively high torsional and axial stiffness but can be made of relatively low strength material such as aluminum or glass-filled plastic. In the lockbar of FIG.2, the end pieces 7 have holes 9 into which pins 10 fit extending from the ends of the elongate joining member 8 in a permanent manner. The pins may be glued, crimped, pressed or welded to fix the end pieces 7 to the joining member 8. Other methods of fixing can also be used as will be evident to persons skilled in the art depending upon the materials used and the strength and specification required. The longer pair of pins 10 are also used a pivot features for the rotational datum of the lockbar assembly. In the lockbar of FIG.3 the end pieces are again fixed by pins 10 extending through holes 9. Additionally, two further pins 11 are provided at each end of the joining member 8. These fit through cutouts 12 on each end piece 7 so as to extend, after assembly, beyond the end pieces 7 and provide the necessary mechanism by which the lockbar is pivoted to bring the teeth 6 into engagement with the ratchet teeth on the spool 3 in the event of a crash. The embodiment of the lockbar shown in FIG.4 and FIG.5 has a tubular prismatic joining member 8. Corresponding shaped extensions are formed at the end pieces 7 so as to fit into the ends of the joining member 8. The end pieces 7 are forged from aluminum and the joining member 8 is extruded aluminum.

Claims: Claims : 1. A lockbar (5) for a seatbelt retractor comprising an elongate joining member and two end pieces joined to the joining member at opposite ends therefore, the end pieces being made of a higher strength material than the joining member. 2. The lockbar (5) for a seatbelt retractor according to claim 1 wherein the end pieces (7) are of a generally -shaped form. 3. The lockbar (5) for a seatbelt retractor according to either of claims 1 or 2 wherein the joining member (8) is an extrusion. 4. The lockbar (5) for a seatbelt retractor according to claim 3 the joining member (8) is tubular. 5. The lockbar (5) for a seatbelt retractor according to claim 3 wherein the joining member (8) is hollow. 6. The lockbar (5) for a seatbelt retractor according to claim 5 wherein the joining member (8) has a triangular cross-section. 7. The lockbar (5) for a seatbelt retractor according to claim 1 wherein the end pieces (7) have projections and the joining member (8) is hollow at least at its ends and to accommodate said projections on the end pieces to attach the end pieces to the joining member 8. The lockbar (5) for a seatbelt retractor according to claim 1 wherein the joining member (8) has projections and the end pieces (7) have holes therein to accommodate said projections on the joining member to attach the end pieces to the joining member. 9. The lockbar (5) for a seatbelt retractor according to claim 1 wherein the end pieces (7) further comprise pin formations for guidance purposes that interact with features in a retractor mechanism to guide the end pieces into locking positions.

Inventors: BLACKADDER DAVID, BOWMAN PAUL, HARTE JOSEPH PATRICK, MITCHINSON NIGEL, SMITHSON ALAN GEORGE, TAYLOR JOHN, BLACKADDER, DAVID, BOWMAN, PAUL, HARTE, JOSEPH, PATRICK, MITCHINSON, NIGEL, SMITHSON, ALAN, GEORGE, TAYLOR, JOHN
Applicants: BREED AUTOMOTIVE TECH, BREED AUTOMOTIVE TECHNOLOGY, INC.
Application year: 2000
Main classification: B60R22
IPC codes: B60R22