VEHICLE SAFETY RESTRAINTS

Abstract: A vehicle passenger safety restraint arrangement in which a traditional belt restraint is used in combination with an airbag, comprises force limiting means to limit the force applied to an occupant by the belt under crash conditions if the airbag is deployed. This arrangement prevents the combined forces exerted by the airbag and the belt from exceeding safe limits and possibly causing injury to the occupant.

Description: VEHICLE .SAFETY RESTRAINTS This invention relates to vehicle passenger safety restraints and relates especially to safety restraints which are fitted with force limiting means. It has already been proposed to provide vehicle passenger safety belts with force limiting means which can limit the force exerted on the occupant by a belt during a crash whilst still sufficiently restraining movement of the occupant within the vehicle to avoid serious injury. By limiting the force exerted on the occupant the risk of injury by the belt itself is reduced. Such force limiting can be provided by means which permits controlled extension of the effective length of restraint when a predetermined reaction force tends to be exceeded and by thereby progressively absorbing energy from the occupant can limit the reactive force. A number of examples of force limiting devices are described in European Patent Specification No 0 568 327. Even when force limiting is provided in the foregoing manner, if the vehicle is additionally fitted with an inflatable restraint for one or more of the occupants such as is now known as an "air bag", it is possible that the combined forces exerted on an occupant by the "air bag" and the safety restraint will exceed safe limits and may as a consequence, result in injury to an occupant. The present invention therefore seeks to provide a passenger safety restraint in which such a shortcoming is reduced or overcome. According to the present invention there is provided a vehicle passenger safety restraint designed to constrain movement of an occupant relative to a vehicle during abnormal vehicle deceleration or acceleration such as may occur in a crash said safety restraint including force limiting means deployable in response to a signal indicative of deployment of a further restraint. Said safety restraint may be a seat belt and the force limiting means may be deployable by a catch or other device which is actuated by said signal indicative of deployment of a said further restraint such as an air bag. Said force limiting means may be arranged to be deployed by means of a device which capsizes a mechanical by-pass and where the mechanical by-pass includes a catch the by-pass may be arranged to come under tension only in the event of a predetermined force being exceeded. In order that the invention may be more clearly understood and readily carried into effect the same will now be further described in more detail with reference to examples given with reference to the accompanying drawings of which:- Fig. 1, illustrates a vehicle passenger safety restraint with a force limiter Fig. 2, illustrates a controlling mechanism for a safety restraint in accordance with the invention Figs. 3, 4, 5, 6 and 7, illustrate variants on a safety restraint in accordance with the invention. Referring to Fig. 1, the vehicle passenger restraint system includes a seat having a seat squab portion 1 and a seat back portion 2, the latter typically being manually tiltable in a conventional manner. Assuming the seat is installed as a front seat in a passenger car, the restraint webbing is fed out from an emergency locking type of webbing retractor, concealed in the "B" post of the car body at one side of the seat and exits via a shoulder height guide loop at 3 to pass diagonally, as at 4, downwards across the torso of an occupant and through a buckling tongue 5 engaged in a buckle 9 anchored on the other side of the seat. Webbing 6 coming away from the buckling tongue passes across the lap of the occupant to a connection to an anchoring means 7 on the same side as 3, nearest the viewer of the drawing. The anchoring means 7 incorporates a force limiting device 8 designed and constructed to submit in a controlled manner to a pre- determined limited force value by way of movement whilst sustaining force up to said value. Considering now the operation of the system, in the event of a frontal collision being encountered by the vehicle the emergency locking retractor senses a predetermined deceleration value of the vehicle and the retractor locks the webbing portion 4 against withdrawal movement via the guide 3. As the collision progresses the deceleration value increases as do the inertial forces exerted by the occupant on the belt portion 4 and the belt portion 6 of the restraint. When the tension in the portion 6 attains a predetermined force limit value (typically 5KN) the force limiting device 8 submits to such initial maximum force to the extent of permitting payout whilst maintaining no more than such force as a restraining force at the anchorage 7. Such payout allows a few centimetres of forward movement of the portion 4 and the occupant and since some sliding of the belt can occur at the buckle tongue 5, forward movement has the effect of transferring kinetic energy of the occupant progressively as power to the force limiting device and thereby limiting the level of the impulsive forces applied to the occupant by the safety restraint webbing and also thereby reducing the probability of head and neck injury occurring. In the drawing (Fig. 1), diagrammatic illustration is given of the extent of torso movement (A) of a seat occupant with a force limiting device fitted to the restraint system and the extent of torso movement (B) of an occupant restrained by a system without such a restraint fitted. In (A) the hips of an occupant are permitted to move in a controlled manner due to the limiter introducing slack to the lap portion of the belt. The upper torso then tends to move in a translational manner rather than pivoting excessively about the hips. Forward movement of the occupants head and chest is thereby less as also are the sustained belt forces. In a modern safety restraint system as indicated above it may be desirable to provide such a safety restraint in addition to an air bag in order to meet statutory requirements in various countries of the world. However deployment of a safety restraint such as that of Fig. 1 together with an air bag may result in excessive restraining forces being applied to the occupant in the event of a crash. With a view to avoiding this the seat belt is provided with force limiting means which when the air bag is deployed is operable at a force which is appreciably lower than the above described 5KN. Referring to Fig. 2, the force limiting device 8 associated with the seat belt anchorage 7 of Fig. 1 may comprise a deformable tube 21 such as described with reference to Fig. 8 of the above mentioned published European Patent Specification and a deforming member 22 which can be drawn along the tube when a predetermined belt tension is applied thereto by a cable 23. In accordance with one aspect of the invention, the member 22 is locked within the tube by a detent 24 which normally engages with an annular groove 25. This detent 24 is releasable by an electrical or pyrotechnically operable device 26 which is actuatable by an electric system for producing a release signal when the air bag is also deployed. By such means the force limiter is operable only on deployment of the passenger air bag. In order to provide force limiting at a higher value and which is effective when no air bag is present, additional force limiter means may be included in the anchorage 7 or alternatively it may be provided in the anchorage of buckle 9 located at the other side of the seat. If the buckle anchorage includes a buckle pretensioner, the force limiting means may also be incorporated in the pretensioner. Referring to Fig. 3, instead of employing a deformable tube to limit the force in the event of deployment of the further restraint or air bag the known concept of "tear-webbing" may be employed. In a force limiter employing tear-webbing a short section 33 of the seat belt webbing near the anchorage is folded back on itself and stitched in a manner to progressively capsize when a predetermined force is applied. In Fig. 3 the main body of webbing 31 terminates in an eye 32 which is attached to an anchorage bracket 36. This main body incorporates a force limiter in the form of the tear-webbing section 33 near the anchorage. As one with the main body 31 of webbing there is an inhibiter strop of webbing 34 which is normally not under tension, this stop being anchored to the bracket by a releasable electric catch 35. The catch 35 is normally under no tension and is thereby arranged to be readily and freely releasable by an electrical signal indicative of air bag deployment. However in the absence of such a signal as soon as the force attains 0 the force limiting value causing capsize of the tear-webbing to commence, the strop 34 comes under tension and inhibits any appreciable force limiting action by the tear-webbing 33. Again, if it is desired to include force limiting which is 5 operable at a higher limit value in the absence of air bag deployment such force limiting may be additionally included either in the anchorage 7 or in the buckle anchorage as referred to above. In the case of an arrangement such as Fig. 3, the strop 34 could include a tear-webbing section D which may operate additionally to the tear-webbing section 33. An alternative catch mechanism which may be readily adapted to replace the wedge or detent of Fig. 1 or indeed the catch 5 35 of Fig. 3, may comprise a locking pin device such as illustrated in Fig. 4. An electrically operable actuator 41 is connected to a pin 42 which passes through the housing or bracket 43 via the member 44 to be retained. On signalling of the actuator 41 upon deployment of an air bag, the actuator withdraws the pin 42 to release the member 44. A further alternative mechanism such as shown in Fig. 5 has a member 54 to be retained, provided with an annular groove 55 which is normally engaged by a key-hole plate 56 with a key-hole aperture 56a movable in its own plane by the actuator 57 to release the member 55 in response to a signal indicative of deployment of an air bag. A further mechanism such as shown in Fig. 6 has spring-loaded pivotally movable catch 61 shaped to normally hold a transverse pin 62 carried by the member 63 which is to be retained. The catch 61 is displaceable against the action of spring 64 by an electrically operable actuator 65 in response to a signal indicative of deployment of an air bag. Yet another mechanism which is particularly applicable to the force limiting mechanism of Fig. 2 is shown in Fig. 7. In this case the forming member 71 has an extension 72 with a head 73 which is retained in position axially by a pair of mutually outwardly spring-loaded pivotally carried jaws having inwardly projecting detents 75 which axially retain the head 73. The outer ends of jaws 74 are normally retained together against the spring 76 by a ring or yoke 77. The ring or yoke 77 is easily axially movable by an electrical actuator 78 allowing the jaws 74 to separate to release the head 73 and therefore the member 71, to enable the force limiter.

Claims: CLAIMS 1. A vehicle passenger safety restraint arrangement comprising a sensor for detecting conditions indicative of a crash situation, a first safety restraint for constraining movement of a vehicle occupant relative to a vehicle, the first restraint being responsive to the sensor, force limiting means to limit the force exerted by the first restraint during constraint of an occupant, wherein the force limiting means is responsive to a signal indicative of deployment of a further restraint. 2. A vehicle passenger safety restraint arrangement according to claim 1 wherein the first restraint is a seat belt. 3. A vehicle passenger safety restraint arrangement according to claim 1 or claim 2 comprising a catch for deploying the force limiting means, which catch is actuated by the signal indicative of deployment of the further restraint. 4. A vehicle passenger safety restraint arrangement according to any one of claims 1 to 3 , wherein the further restraint is an airbag. 5. A vehicle passenger safety restraint arrangement according to any one of the preceding claims comprising a mechanical bypass and a device for capsizing the mechanical bypass for deploying the force limiting means in response to the signal indicative of deployment of the further restraint. 6. A vehicle passenger safety restraint arrangement according to claim 5 wherein the mechanical bypass includes a catch . 7. A vehicle passenger safety restraint arrangement according to claim 5 or claim 6 wherein the bypass is arranged to come under tension only in the event of a predetermined force being exceeded. 8. A vehicle passenger safety restraint arrangement according to any preceding claim wherein the force limiting means is deployed at a predetermined force of less than 5KN. 9. A vehicle passenger safety restraint arrangement according to any preceding claim wherein the force limiting means comprises a deformable tube and a deforming member mounted therein and arranged to deform the tube when a predetermined belt tension is applied. 10. A vehicle passenger safety restraint arrangement according to claim 9 wherein the force limiting means comprises a detent adapted to engage with an annular groove to lock the deforming member within the tube. 11. A vehicle passenger safety restraint arrangement according to claim 10 wherein the detent is releasable by an electrical or pyrotechnically operable device. 12. A vehicle passenger safety restraint arrangement according to any one of claims 2 to 11 wherein the force limiting means is associated with a buckle fastening point o f a three point seat belt. 13. A vehicle passenger safety restraint arrangement according to any preceding claim wherein the safety restraint comprising pretensioning means and the force limiting means is incorporated in the pretensioning means. 14. A vehicle passenger safety restraint arrangement according to any one of claims 2 to 8 wherein the force limiting means comprises a portion of the seat belt which is folded and stitched, which stitching is arranged to tear when subjected to a predetermined force.

Inventors: BELL JOHN, BLACKADDER DAVID, BELL, JOHN, BLACKADDER, DAVID
Applicants: ALLIEDSIGNAL LTD, BELL JOHN, BLACKADDER DAVID, ALLIEDSIGNAL LIMITED, BELL, JOHN, BLACKADDER, DAVID
Application year: 1995
Main classification: B60R22
IPC codes: B60R21, B60R22