INERTIA REEL

Abstract: An inertia reel device for a vehicle safety belt has a gear wheel (22) coupled to its shaft (12). A ring (26), of greater internal diameter than the external diameter of the gear wheel (22) and having gear teeth on a central zone of its inner periph­ ery adapted to mesh with the teeth of the gear wheel (22), is supported on two part-spherical support surfaces (36) dis­ posed adjacent to, and one on each side of, the part of the edge of the gear wheel (22) which is uppermost when the reel device is in its normal orientation. Each part-spherical surface has a radius equal to that of the outer zones of the inner periphery of the ring (26) and is bounded by an edge such that the ring is supported on at least one of said surfaces when the reel is tilted at an angle relative to its normal orientation which does not exceed a predetermined tilt angle and that the ring is sup­ ported on said edge when said tilt angle is exceeded. Sensing means (42) is arranged to initate locking of the reel spindle against rotation in the unwinding direction when the ring (26) is supported on said edge out of contact with the rest of said support surfaces.

Description: Inertia Reel This invention relates to inertia reel devices for vehicle safety belts of the type in which a single element senses both vehicle accelaration (i.e. sudden retardation or lateral movement in any horizontal direction) and webbing accelaration (i.e. a sudden "snatch" on the safety belt harness). G.B. Specification No. 1329009 discloses an inertia reel device of this type in which the inertia sensor comprises a runner ring suspended from a perpendicular groove in one end of the reel spindle. The inner periphery of the ring is provided with gear teeth which mesh with the teeth of the gear. The effect of horizontal accelaration is to cause the ring to pivot on the spindle and, since relative angular movement is controlled by the gear teeth, the result is that the runner ring rises relative to the reel spindle. Similarly, sudden accelaration of the spindle, due to a "snatch" on the harness, causes the ring to lock behind the spindle with the result, once again, that the ring rises relative to the spindle. In either case this rising movement is sensed by wire loops which hang over the bottom of the ring so as to be lifted thereby. The various standard specifications for inertia reels specify both a minimum angle through which the entire reel device may be tilted relative to is orientation of normal use before locking takes place and a maximum angle of tilt before which locking must have taken place. It is therefore, desirable for the actual angle of tilt at which locking takes place to be substantially the same in all horizontal directions. The present invention is concerned with the provision of an inertia reel device in which this is achieved. According to the invention, an inertia reel device for a vehicle safety belt comprises a shaft on which part of the safety belt is wound, a gear wheel coupled to the shaft, a ring of greater internal diameter than the external diameter of the gear wheel and having gear teeth on a central zone of its inner periphery adapted to mesh with the teeth of the gear wheel, support means having two part-spherical support surfaces disposed adjacent to, and one on each side of, the part of the edge of the gear wheel which is uppermost when the reel device is in its normal orientation, each part-spherical surface having a radius equal to that of the outer zones of the inner periphery of the ring and being bounded by an edge such that the ring is supported on at least one of said surfaces when the reel is tilted at an angle relative to its normal orientation which does not exceed a predetermined tilt angle and that the ring is supported on said edge when said tilt angle is exceeded, the device further comprising sensing means for initiating locking of the reel spindle against rotation in the unwinding direction when the ring is supported on said edge out of contact with the rest of said support surfaces. Preferably, the sensing means is arranged to engage with the ring adjacent to said support surfaces. In one form of the invention the sensing means comprises a lever having one end resting on the outer periphery of said ring. An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which, Figure 1 is a longitudinal cross-sectional view of an inertia reel in accordance with the invention, Figure 2 is a cross-sectional view taken on the line 2 - 2 in Figure 1, Figure 3 is a cross-sectional view taken on the line 3 - 3 in Figure 1, and Figure 4 is a scrap perspective view of the support means for the sensing ring of the inertia reel shown in Figure 1, with the gear wheel and ring removed. Referring to the drawings, an inertia reel comprises a U-shaped support frame 10 having a spindle 12 journaled in holes in the limbs of the U-shape. The spindle 12 has a central bore 14 communicating with a slot 16 in the periphery thereof. In use, the loop formed in one end of the safety belt is inserted through the slot 16 and retained by a rod (not shown) inserted through the bore 14. One end of the spindle 12 is coupled to a conventional rewind spring 18. The other end of the spindle 12 carries a ratchet wheel 20 with which the main locking pawl engages, as will be explained hereinafter, and a gear wheel 22. As can best be seen from Figures 1 and 3, the teeth of the gear wheel 22 engage with a corresponding set of gear teeth formed on a central zone 24 of the inner periphery of a ring 26 which has a substantially greater internal diameter than the external diameter of the gear wheel 22. On each side of this central zone 24, the inner periphery of the ring 26 has two smooth side zones 28 and 30 which are supported on respective support surfaces 32 and 34, one on each side of the gear wheel 22. The support surfaces 32 and 34 are formed on respective members 36 and 38 which are mounted on the adjacent side limb of the frame 10. Referring to Figure 4, the surfaces 32 and 34 are curved both in the direction parallel to and the direction perpendicular to the axis of the spindle 12. The radius of curvature in both directions is equal to the radius of the outer zones 28 and 30 of the inner periphery of the ring 26. On all sides except that confronting the gear wheel 22, each of the surfaces 32 and 34 is bounded by a respective edge 40 which comprises the locus of the intersection of the surfaces 32 and 34 with a perpendicular line through the centre of curvature of the ring 26 when the inertia reel is first tilted to an angle at which locking is to be initiated and then rotated through 3600 about a vertical axis. Thus, until such tilt angle is reached, the centre of gravity of the ring 26 is directly below the support surfaces 32 and 34 and consequently the ring does not move relative to the support surfaces 32 and 34. On the other hand, when this tilt angle is exceeded, the ring 26 pivots on the edge 40 of one or both of the support surfaces 32 and 34 depending on the direction of the tilt. Turning now to Figure 2, a lever 42 is pivoted at 44 on the frame 10 and has one end 46 resting on the outer periphery of the ring 26 between the support surfaces 32 and 34. The other end 48 of the lever 42 engages with a projection 50 on one end of a pawl 52 which is supported by a pivot pin 54 in a slot 56 in the frame 10 (Figure 3). Thus, when the ring 26 pivots on one or both of the edges 40, the end 46 of the lever 42 is lifted so that the other end 48 thereof presses the projection 50 inwards, bringing an adjacent tooth 57 on the pawl 52 into engagement with the ratchet wheel 20. Rotation of the shaft 12 in the unwinding direction thus causes the ratchet wheel to lift the tooth 56 so that the pin 54 moves upwards in the slot 56 so that a plurality of main locking teeth 58 on the pawl 52 engage with the ratchet wheel 20 to lock the spindle 12. In use, when the ratchet is subject to horizontal accelsratior exceeding a predetermined threshold, the ring is displaced horizontally, pivoting on one or other of the edges 40 to initiate the abovedescribed locking action. Similarly, if the spindle 12 is subject to sudden acceleration in the unwinding direction due to a snatch on the safety belt, the ring 26 tends to lag behind the gear wheel 22 with the result that the point at which its teeth engage with those of the gear wheel is no longer coincident with the zone between the support surfaces 32 and 34. Consequently, the end 46 of the lever 42 is, once again lifted to initiate locking. As soon as the ring 26 swings back to its normal position, the pawl 52 is free to disengage when the tension in the safety belt is removed, allowing the spindle 12 to rotate in the retraction direction sufficiently to let the pin 54 move back to the bottom of the slot 56. Preferably, the lever 42 and the pawl 52 are balanced so that their centres of gravity are coincident with their respective pivot pins 44 and 54 in order to ensure that they are not themselves subject to the effects of acceleration in any direction.

Claims: CLAIMS 1. An inertia reel device for a vehicle safety belt comprises a shaft (12) on which part of the safety belt is wound, a gear wheel (22) coupled to the shaft (12), a ring (26) of greater internal diameter than the external diameter of the gear wheel (22) and having gear teeth on its inner periphery adapted to mesh with the teeth of the gear wheel (22), and sensing means (42) for initiating locking of the reel spindle when the ring (26) is displaced from the position in which the uppermost part of its inner periphery is in contact with the gear wheel (22) characterised in that support means (36,38) having two part-spherical support surfaces (32,34) are disposed adjacent to, and one on each side of, the part of the edge of the gear wheel (22) which is uppermost when the reel device is in its normal orientation, each part-spherical surface (32,34) having a radius equal to that of the outer zones of the inner periphery of the ring and being bounded by an edge (40) such that the ring is supported on at least one of said surfaces (32,34) when the reel is tilted at an angle relative to its normal orientation which does not exceed a predetermined tilt angle and that the ring is supported on said edge (40) when said tilt angle is exceeded, and the sensing means is arranged to initiate locking of the shaft (12) against rotation in the unwinding direction when the ring (26) is supported on said edge (40) out of contact with the rest of said support surfaces (32,34). 2. An inertia reel device according to claim 1, characterised in that the sensing means (42) comprises a follower (46) arranged to engage with the part of the outer periphery of the ring which is upermost when the reel device is in its normal orientation. 3. An inertia reel device according to claim 2, characterised in that the follower (46) comprises one arm of a two-arm lever, the other arm (48) of which is coupled to locking means (52) 4. An inertia reel device according to claim 3, characterised in that the locking means comprises a ratchet wheel (26) coupled to the shaft (12) and a pawl (52) with a plurality of teeth (57,58) supported on a pin-and-slot pivotal mounting (54,56) which is so arranged that, when the pawl has been pivoted by the second arm of the two-arm lever to bring one tooth (57) thereof into engagement with the ratchet wheel (20), further rotation of the ratchet wheel (20) in the direction restrained by the pawl brings the remaining teeth (58) into engagement.

Inventors: CUNNINGHAM, DOUGLAS JAMES
Applicants: BRITAX (WINGARD) LIMITED
Application year: 1983
Main classification: B60R22
IPC codes: B60R22