GB2084000A - Seat belt mechanism - Google Patents

Abstract

A seat belt for a vehicle passes over a roller 1 rotatably mounted within a housing which swivels on vehicle structure such as a door post. A sensing unit mounted above the housing includes a circular pendular mass 17. The mass is supported by a stalk having a part spherical upper end 15 carried in a vertical tubular guide 14. The mass sits on an inverted cone 18 located within an oppositely tapered recess in the under part of the mass, the tip of the cone seating in a "dimple" in the housing. Displacement of the mass as by acceleration due to impact of the vehicle causes it to rock about the upper edge of the cone which will raise the stalk upper end in the tubular guide. This in turn lifts a rod 21 connected to a pivoted quadrant 22 to trap the belt by engagement with serrations 24 in the quadrant surface pressing it into contact with a surface of the housing 4. <IMAGE>

Description

SPECIFICATION Strop securing means This invention relates to strop securing means which may be used for inhibiting undesirable movement of a load restrained by a strop.

In the event of an impact to a vehicle, there may be appreciable movement of a load due to the taking up of slack in, or extension of, a strop used to restrain the load. In particular, in safety harness as used in motor vehicles there is usually an appreciable length of webbing between an anchorage and the point of engagement with the wearer's body, and additionally an inertia reel, as commonly used, includes extra webbing to permit normal forward movement by the wearer. When impact occurs, the combined movement due to strop extension and the tightening of coils on an intertia reel can be sufficient to permit contact with parts of vehicle structure.

Prior co-pending European application No 80301011.5 is directed to the provision of securing means at an intermediate point on a strop whereby the amount of undesirable movement may be limited and discloses strop securing means comprising a housing containing a roller and means for displacing the roller so that a strop passing round the periphery of the roller will be pressed between the roller and a part of the housing.

The prior invention is utilised in the present case but with an impact sensor and a locking arrangement for the strop whereby normal movement of the wearer is permitted without the need for an inertia reel device.

Strop securing means according to the present invention comprises a housing containing a roller, means for guiding a strop into the housing and around the roller and an impact sensor arranged to operate means for inhibiting free movement of the strop through the housing.

In a preferred embodiment the impact sensor acts to operate means contacting the strop to increase frictional forces therein; in one form the means contacting the strop can urge it into contact with a part of the housing.

An embodiment of the invention will now be described by way of example, with reference to the accompanying drawing which is a side elevation of a strop securing mechanism according to the invention in partial section.

Referring to the drawing, a roller 1 (shown in dotted lines) freely revolving about its axis is carried in a housing comprising two side plates 2 (one shown) which are spaced apart and depend from the ends of a horizontal cross-member 3.

A curved support plate 4 extends between the side plates 2 of the housing towards the lower portion thereof and a guide plate 5 having a lip 6 extends between the side plates 2 at the upper portion of the housing opposite to the support plate 4 with respect to the axis of the roller. A slot defined by a plate 7 spaced above the cross-member 3 by end pieces serves to receive one arm of a bracket 8 which is retained by a pin 9, the housing being thereby adapted for swivel-mounting on a structure such as a door pillar of a motor car.

A strop 10, which may be of webbing material, enters the housing over the inner surface of the curved support plate 4 before changing direction to pass around the roller 1 and emerge beneath the guideplate 5. The lower end 11 of the strop 10 includes additional webbing stored in a storage device of known type (not shown), either linear or rotating, from which it may be paid out or drawn in according to movement of a wearer.

The outer end 12 of the strop 10 forms part of load restraining equipment such as a safety belt or harness for use by an occupant of a motor car. Normally the strop can move easily through the housing, the roller revolving freely to permit this, to facilitate the tying down of a load, or the assumption and adjustment of a belt or harness by a vehicle occupant. The roller is supported in the housing by a displaceable arrangement (not shown) such as is described in the prior specification already mentioned whereby the roller may be dislodged and supported on cam lobes which engage circumferentially-spaced teeth formed in the ends ofthe roller.

When used as a car safety belt the outer end 12 of the strop (or belt) 10 should desirably extend substantially horizontally as shown in dotted lines to pass over the wearer's shoulder, the lip 6 acting to ensure that the strop is gently guided into its desired alignment. For the smooth passage of a safety belt through the mechanism the angle of the mounting bracket 8 can be important, since the axis of the swivel pin 9 should pass through the belt anchorage point (or the exit point of an inertial reel housing).

Different cars will need differing shapes of bracket.

A C-section frame 13 supported on the plate 7 carries at its free end a sleeve, or hollow cylinder 14, aligned with its axis vertical. The sleeve 14 encloses the part spherical upper end 15 of a stalk 16 constituting an upward extension of a cylindrical mass 17 which has a co-axial frusto-conical recess formed in its under surface. The inner face of the recess sits on the base of an inverted metal cone 18 (ie the respective tapers of the recess and cone are in the opposite sense), the tip of which seats in a "dimple" 19 on the top of the plate 7. Thus, the cylindrical mass 17 is supported in an equilibrium position by the cone 18 and the sleeve 14, the part spherical upper end 15 of the stalk 16 being of substantially the same diameter as the bore of the sleeve.

A cylindrical plug, or follower, 20 is free to slide in the sleeve 17 on top of the part spherical upper end 15 and is connected by a rod 21 to a quadrant arm 22 which is carried on a pivot 23 disposed at the lower end of the roller housing opposite to the curved support plate 4. The outer end of the quadrant arm carries an arcuate surface 24 in which serrations have been made to form grooves to give a rough finish.

In the event of an impact such as would occur in a vehicle collision, resultant forces will act on the The drawing originally filed was informal and the print here reproduced is taken from a laterfiledformal copy.

cylindrical mass 17 and also on the metal cone 18 whereby the mass will be displaced as indicated in dotted lines at 17a and will rock about the circular upper edge of the cone 17. With the cone in the position indicated in dotted lines at 18a its conical surface will contact the side surface of the recess in the mass and the effect will beto raise the level of the part spherical upper end 15 within the sleeve 14 (which acts as a tubular guide). The cylindrical plug 20 will thus also rise up in the sleeve (as indicated in dotted lines at 20a) taking the rod 21 with it so asto rotate the quadrant arm 22 about its pivot. The arcuate surface 24 in turn will be moved into contact with the strop 10 where frictional interaction between the grooves and the strop material will act to restrain passage of the strop through the roller housing.At the limit of quadrant movement, the strop will be trapped between the arcuate surface 24 and the curved support plate 4.

The result of this and the impact on the person or load to which the strop is attached will be increased tension in the strop which will have the effect of displacing the roller in the manner described in the aforesaid prior specification when it will be supported on the cam lobes as previously mentioned so as to bear on the strop and secure it from further movement.

By virtue of the configuration of the strop within the housing, coefficient of friction between that portion of the circumference of the roller around which the strop passes (approximately 50%) and the strop itself will ensure an extended stress gradient in the strop acting to reduce the possibility of the strop parting underthe loads imposed. Roughness of the surface of the roller as by knurling can assist in this respect.

In this connection it is desirable that the diameter of the roller is such that friction will not hinder normal free movement of a seat belt wearer which could lead in turn to possible discomfort.

Claims (9)

1. Strop securing means comprising a housing containing a roller, means for guiding a strop into the housing and around the roller, and an impact sensor arranged to operate means for inhibiting force movement of the strop through the housing.

2. Strop securing means according to claim 1 in which the impact sensor acts to operate means contacting the strop to increase frictional forces therein.

3. Strop securing means according to claim 2 in which the means contacting the strop urges it into contact with a part of the housing.

4. Strop securing means according to claim 1, claim 2 or claim 3 in which the impact sensor comprises a pendular mass supported on a seating about which the mass can rock so as to move a surface into contact with the strop.

5. Strop securing means according to claim 4 in which the pendular mass is freely supported by an inverted cone cooperating with a frusto-conical recess in the underside of the mass and tapered in the opposite sense to the cone.

6. Strop securing means according to claim 4 or claim 5 in which a member extending upwardly from the pendular mass is carried in a vertical guide whereby rocking of the pendular mass can be transmitted to move the surface.

7. Strop securing means according to claim 4, claim 5 or claim 6 in which the surface is arcuate in form.

8. Strop securing means according to claim 7 in which the surface is a quadrant connected to be volated about a pivot through movement of the member extending upwardly from the pendular mass.

9. Strop securing means substantially as herein described with reference to the accompanying drawing.