Safety restraint

Abstract: A vehicle safety restraint seat belt incorporating a load limiting effect to allow a limited and controlled forward motion of the occupant after the retractor has locked to decrease the forces exerted by the belt on the occupant's torso. The webbing is attached to a structural part of the vehicle via a load limiting device, which comprises: a container defining a flow path for a fluid, an actuator arranged within the container and operable to act on the fluid, and a restriction in the flow path of the fluid, wherein the actuator is movable within the container under the action of load transmitted to the webbing from the vehicle occupant under extreme acceleration or deceleration conditions, to move the fluid through the restriction in the flow path thereby to dissipate a predetermined portion of the load on the webbing. A rotary paddle array, or forms of vane pumps or peristaltic pumps are used.

Description: The present invention relates to a safety restraint for use in a vehicle and particularly to a seat belt. Modern seat belts comprise a length of webbing arranged to pass diagonally across the torso of a vehicle occupant and generally horizontally across the hip region of the vehicle occupant (so-called lap portion of the belt). This is known as a three point belt system. One end of the belt webbing is firmly attached to a structural part of the vehicle such as the floor, and the other end is attached to the spool of a retractor which itself is firmly attached to a structural part of the vehicle, usually the side, B-pillar. The retractor automatically keeps any slack in the belt wound onto the spool and thus keeps a tension in the belt. Between the retractor and the other fixed point, a fastening element such as a metal tongue is fixed to the belt with which it can be fastened into a buckle which itself is attached to fixed part of the vehicle on the other side of the occupant seat. A clock spring in the retractor allows pay out of webbing under the influence of relatively gentle forwardly directed inertia of the vehicle occupant, for example to allow for normal movement of the occupant such as reaching forward to activate in car controls, glove compartments or door pockets. In the event of a crash the sudden high forward momentum of the occupant activates a crash sensor which locks the spool against rotation and prevents forward motion of the occupant to prevent him colliding with the internal fixtures of the vehicle such as the steering wheel, dashboard or windscreen. However it has been found in high velocity crashes that the sudden locking of the seat belt can itself cause injury to the occupant due to the sudden impact of the torso with the belt webbing. In recent years it has been proposed to introduce a load limiting effect into the seat belt system so as to allow a limited and controlled forward motion of the occupant after the retractor has locked. This decreases the forces exerted by the belt on the occupant's torso. Load limiting proposals are described in EP 0 297 537 wherein a plastically deformable member is used in the retractor, and particularly between the spool and inner most winding of the belt webbing. Alternative load limiting proposals are known in which crushable bushings or nuts or deformable torsion bars are placed in the retractor in the force path between the spool locking mechanism and belt webbing. These proposals are complex and expensive and require the retractor to be specially designed and constructed to incorporate them. US 2 680 476 shows a known hydraulic load limiting devices for seat belts according to the preamble of claim 1. The present invention proposes improved, simpler and more cost effective load limiting arrangements for seat belts. According to the present invention there is provided a vehicle safety restraint comprising: seat belt webbing for restraining a vehicle occupant, the webbing being attached to a structural part of the vehicle via a load limiting device, the load limiting device comprising: a container defining a flow path for a fluid, an actuator arranged within the container and operable to act on the fluid, and a restriction in the flow path of the fluid, wherein the actuator is movable within the container under the action of load transmitted to the webbing from the vehicle occupant under extreme acceleration or deceleration conditions, to move the fluid through the restriction in the flow path thereby to dissipate a predetermined portion of the load on the webbing, wherein the actuator comprises a rotary pump. This may for example take the general form of an eccentric vane pump or a peristaltic pump or a swash plate pump, though many other suitable forms of pump arrangement will be evident to those skilled in the art. In each case the fluid flow path within the pump housing is arranged with one or more restrictions to absorb some of the energy of a crash pulse. The restriction may comprise a feedback pipe external to the cylinder to feed fluid under pressure from the high pressure side of the piston to the low pressure side. This feedback pipe may have a further restriction or a valve. The valve may be adjustable to offer a predetermined resistance to fluid flow in dependence upon the force damping characteristics required for the particular seat belt. The valve may be actively controllable, for example in response to a gauge constantly monitoring the pressure of the fluid in the cylinder. In this way the load perceived by the vehicle occupant can be actively tailored, not only to the vehicle concerned, but also to the circumstances which generated the load: the severity of the crash pulse, the weight of the occupant and the activation of a secondary restraint such as an airbag, or the occurance of a second crash. 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: Figures 1a and 1b illustrate one embodiment of the present invention in perspective view in figure 1a and in cross-sectional view in figure 1b. Figures 2a and 2b illustrate another embodiment, again in perspective view in figure 2a and cross-sectional view in figure 2b. Figure 3 illustrates another embodiment, in perspective view in figure 3a and in part cross-sectioned view in figure 3b. Figures 1 to 3 illustrate load limiting arrangements using rotary motion of fluid. Like parts are referenced by like numerals. These load limiters work in a similar manner to the linear versions described above. They can be mounted at sill end or buckle end of a belt or to any position at which a rotatable member is present or could be introduced. For example a rod or spindle is mounted to a structural part of the vehicle and a few turns of webbing wound around it with the load limiter attached to the rod or spindle. Alternatively the load limiter could be connected to the retractor spool but in this case a clutch arrangement will be used to selectively connect the load limiter only in crash conditions. In each of the embodiments of figures 1 to 3 seat belt webbing 6 is wound on a rod or spool 30 which is mounted for rotation a frame 31 (which may be a retractor frame) . A load limiting device 40 is mounted at the spindle of the spool 30. The load limiting device is a fluid filled pump actuated by rotation of the spool spindle so that the fluid in the pump is driven though restrictions and/or compressed and absorbs some of the energy of the crash. In the embodiment of figure 1a and 1b the pump is an eccentric vane pump which has a rotor 41 attached to a spool spindle (not shown) and four rotating telescopic blades 42 mounted in a housing 43 defining the chamber filled with fluid 7. The blades 42 keep in constant contact with the inside wall of the housing 43 to maintain a good fluid seal. The housing 43 is eccentrically arranged compared to the spool spindle and the rotor 41. As the blades 42 rotate (anticlockwise in the example shown by the arrow in figure 11b) the eccentricity of the housing causes the effective chamber volumes between respective vanes to change in size; decreasing as the vanes 42 approach the upper part of the chamber and increasing as they approach the lower part. Thus the fluid is forced along an additional passage 44 and through a restrictor 45 (which could be programmable) arranged in this additional fluid passage 44. In figure 2 the pump is a peristaltic pump but the principle is similar. This comprises four rollers 47 which rotate forcing fluid 7 around the flexible channel 48 supported against the pump outer casing 49, and which has a soft inner wall 50. At the bottom of this channel 48 the fluid is forced through a restriction 45. The size of the restriction controls the force applied to the webbing. Figure 3a and 3b show a swash plate pump. The spool spindle has a swash plate 54 and an eccentric cam plate 50 which drives pistons 51 to pump fluid 7 around passages 52. Ball valves 53 are disposed in the passages 52 to restrict flow and thus absorb energy. The pistons 51 are biased to their return positions by springs 55 and ball valves 53 have springs 56 to control, the pressure required to force fluid past them. There are four sets of pistons and ball valves, ie four sets of pumps in the arrangement of figure 3a. Figure 3b illustrates one pump in more detail. As the swash plate 54 rotates, the eccentric cam plate 50 rotates and piston 51 is pushed in against the action of spring 55. This movement of the position forces fluid past the ball valve 53 against the action of spring 56, into fluid storage chamber 57. As the piston returns to its original position it creates a negative fluid pressure opening another ball valve 53 against action of spring 56 and allowing fluid in behind the piston 51. The cycle continues in this way and energy is absorbed by the fluid being forced through the restrictions of the ball valves.

Claims: A vehicle safety restraint comprising: seat belt webbing (6) for restraining a vehicle occupant, the webbing (6) being attached to a structural part of the vehicle via a load limiting device (40), the load limiting device (40) comprising: a container (43) defining a flow path for a fluid (7), an actuator (41) arranged within the container (43) and operable to act on the fluid (7), and a restriction (45) in the flow path of the fluid (7), wherein the actuator is movable within the container (43) under the action of load transmitted to the webbing (6) from the vehicle occupant under extreme acceleration or deceleration conditions, to move the fluid (7) through the restriction in the flow path thereby to dissipate a predetermined portion of the load on the webbing (7), characterised in that the actuator comprises a rotary pump. A vehicle safety restraint according to claim 1 wherein the actuator (41) comprises a rotary paddle or vane member or an array of such members, mounted for rotation in a housing containing the fluid. A vehicle safety restraint according to claim 1 or claim 2 wherein the load limiting device (40) comprises an eccentric vane pump. A vehicle safety restraint according to claim 1 or claim 2 wherein the load limiting device (40) comprises a peristaltic pump. A vehicle safety restraint according to claim 1 or claim 2 wherein the load limiting device (40) comprises a swash plate pump. A vehicle safety restraint according to any one of the preceding claims wherein the restriction comprises a feedback pipe (44) external to the container (43) to feed fluid (7) under pressure from the high pressure side to the low pressure side. A vehicle safety restraint according to claim 6 wherein the feedback pipe (44) comprises a restriction (45) or a valve. A vehicle safety restraint according to claim 7 wherein the feedback pipe restriction (45) comprises a valve (53). A vehicle safety restraint according to claim 8 wherein the valve (53) is adjustable to offer a predetermined resistance to fluid flow in dependence upon the force damping characteristics required for the seat belt (6). A vehicle safety restraint according to claim 8 or claim 9 wherein the valve (53) is actively controllable. A vehicle safety restraint according to claim 10 comprising a gauge arranged to monitor the pressure of the fluid in the cylinder and connected to the valve to control the valve in dependence upon the monitored pressure. A vehicle safety restraint according to claim 10 or claim 11 wherein the valve (53) is connected to be controlled in dependence upon any one or any combination of features taken from the list of: the type of vehicle; the severity of the crash pulse; the weight of the occupant; the activation of a secondary restraint; and the occurance of a second crash.

Inventors: BLACKADDER DAVID, GORDON IAN ALEXANDER, HARTE JOSEPH PATRICK, PARK ANDREW, REES ELIZABETH, SMITHSON ALAN GEORGE, TAYLOR JOHN, BLACKADDER, DAVID, GORDON, IAN ALEXANDER, HARTE, JOSEPH PATRICK, PARK, ANDREW, REES, ELIZABETH, SMITHSON, ALAN GEORGE, TAYLOR, JOHN
Applicants: KEY SAFETY SYSTEMS INC, KEY SAFETY SYSTEMS, INC.
Application year: 1998
Main classification: B60R22
IPC codes: B60R22