GB2155763A - Safety belt emergency locking retractor - Google Patents

Abstract

An emergency locking retractor for a vehicle safety belt comprising a pair of mutually parallel frame members (14, 16) and a spool (20) having a belt-receiving shaft (22) and a respective disc (24, 26) adjacent to each end of the shaft (22), each disc (24, 26) having uniformly spaced locking teeth on its outer periphery. The spool (20) is mounted on the frame members (14, 16) in bearings (52, 66) arranged to permit limited movement relative to the frame members (14, 16) in a direction perpendicular to the axis of rotation, between a position in which said teeth engage with complementary teeth (18) on the frame members (14, 16) to inhibit rotation of the spool (20) and a position of disengagement. A respective spring (58, 68) associated with each frame member (14, 16) is arranged to bias the spool (20) into its position of disengagement, and actuating means (43) operative on one end of the spool (20), are arranged to cause movement of the spool (20) into its engaged position. Each spring (58, 68) has two interconnected U-shaped limbs (100, 101), one arm of one U-shape being connected to the corresponding arm of the other U-shape. <IMAGE>

Description

SPECIFICATION Safety belt emergency locking retractor This invention relates to an emergency locking retractor for a vehicle safety belt of the type comprising a pair of mutually parallel frame members and a spool having a belt-receiving shaft and a respective disc adjacent to each end of the shaft, each disc ahving uniformly spaced locking teeth on its outer periphery, the spool being mounted on the frame members in bearings arranged to permit limited movement relative to the frame members in a direction perpendiculartothe axis of rotation, between a position in which said teeth engage with complementary teeth on the frame members to inhibit rotation of the spool and a position of disengagement, a respective spring associated with each frame member being arranged to bias the spool into its position of disengagement, and actuating means operative on one end of the spool, being arranged to cause movement of the spool into its engaged position. A retractor of this type is disclosed in our Patent Specification Nos.

EP-A-01 12032 and EP-A-01 12033.

According to the invention, in an emergency locking retractor of the foregoing type, the spring associated with each frame member is formed with two interconnected limbs, each of which is arranged to exert a biasing force on the spool.

Preferably each limb of the spring is U-shaped, one arm of one U-shape being connected to the corresponding arm of the other U-shape. The point of interconnection may then be received in a locating formation associated with the frame member while the free ends of both limbs engage with a respective bearing of the spool.

The spring is preferably formed of material of rectangular cross-section so that it is of uniform thickness in the direction in which it is flexed in use, thereby maximising its resistance to fatigue.

In order to ensure that the locking teeth on both discs come into full engagement with the complementary teeth on the frame members when the spool moves into its engaged position, the spring on the same side of the frame members as the actuating means is preferably arranged to exert a stronger force than the spring on the other side of the frame members. For example, the force exerted by the latter resilient means may be between one quarter and three quarters of that exerted by the resilient means on the same side of the frame as the actuating means. Thus, although the actuating force is applied on one side of the spool, both sides move into engagement together.

Figure 1 is an exploded perspective view of an emergency locking retractor in accordance with an embodiment of the invention; Figure 2 is a plan view of one of the springs which biases the spool into its disengaged position; Figure 3 is an end view, from the frame, of the end member of the cassette containing the re-wind spring and one of the sliding bearings of the embodiment shown in Figure 1; Figure 4 is a cross-sectional view taken on the line 4--4 in Figure 2; Figure 5 is an end view, similar to Figure 2, of the corresponding end member of the cassette containing the actuating means; and Figure 6 is a fragmentary cross-sectional view taken on the line 66 in Figure 5.

The retractor illustrated in Figure 1 has a generally U-shaped frame 10, the base portion of which 9 is provided with a hole 12 whereby the frame 10 may be secured to the body of a motor vehicle. The side limbs of the U-shape constitute substantially identical frame members 14 and 16 each of which contains an aperture which is generally circular but somewhat enlarged in the vertical direction and which has a respective toothed segment 18 forming part of its upper periphery.

A spool 20 is mounted in the frame 10. The spool 20 comprises a central shaft portion 22, on which a safety belt may be wound, two toothed discs 24 and 26, for engagement with the toothed segments 18 on the frame members 14 and 16 respectively, and two projecting stub axles 28 and 30.

A distance bar 32 having perpendicularly projecting side limbs 34 and 36, extends between notches 38 and 39 in the outer edges of the frame members 14 and 16 so as to maintain the required spacing therebetween. The end limbs 34 and 36 project beyond the edges of the openings in the frame members 14 and 16 so as to overlap the toothed discs 24 and 26 of the spool and prevent axial displacement thereof. In addition, the distance bar 32 has respective hook formations 40 and 41 on its two ends which serve to retain a retractor spring cassette 42 in engagement with the outer side face of the frame member 16 and a locking mechanism cassette 43 in engagement with the outer side face of the frame member 14.

The enclosure for the retractor spring cassette 42 comprises an end plate 44, which abuts the frame member 16 and is engaged by the hook formation 38, together with a cover 46 which carries a stop (not shown) to which the outer end of a retraction spring 48 is secured. The inner end of the spring 48 is secured to a plastics boss 50 having a cylindrical outer surface and a slotted opening for engagement with the flattened end of the stub axle 30 of the spool. The axial length of the boss 50 is greater than the width of the spring 48 so as to be long enough for one end thereof to project into an opening in a plastics bearing plate 52 which is slidably mounted in an elongate recess 54 in the surface of the end plate 44. Centrally disposed within the recess 54 is an elongate slot 56 through which project the stub axle 30 and a boss 57 on the bearing plate 52.The lengths of the recess 54 and the slot 56 are such that the bearing plate 52 can slide between a position in which the teeth on the disc 26 engage with the toothed segments 18 on the end plate 16 and a position in which they are clear of such engagement. A spring 58 engages with a formation on the bearing plate 52 to bias it into the disengaged position.

The locking mechanism cassette 43 is enclosed by an end plate 60, which abuts the outer face of the frame member 14 and is engaged by the hook formation 40 on the distance bar 32, together with a cover 62. The end plate 60 has an elongate slot 64 and a sliding bearing 66, which is spring biased away from the toothed segments 18 on the end plate 14 by a spring 68, in a similar manner to the corresponding components of the retractor spring cassette 42. However, in the locking mechanism cassette 43, the boss 50 is replaced by a stub axle 70 which is rigidly attached to a ratchet wheel 72, the stub axle 70 having a cylindrical outer surface for engagement in the bearing 66 and a slot for engagement with the flattened end portion of the stub axle 28 of the spool 20.

The sliding bearing 66 is an integral part of a control member 74 which is subject to an angular bias in the belt retraction direction by an extended limb 75 of the spring 68. A pawl 76 is pivotally mounted on the control member 74 so that it can be moved into engagement with the teeth of the ratchet wheel 72 by a conventional ball-in-saucer inertia sensing mechanism 78 mounted on the bottom of the end plate 60. The control member 74 also has a hole 80 by which it is pivotally mounted on a pin 82 secured to the end plate 60.

The locking mechanism cassette 43 also includes a belt-pull-sensitive actuating mechanism which is of conventional type. Briefly, the belt-pull-sensitive locking mechanism consists of an inertia disc 84 which is pivotally mounted on the stub axle 70 of the ratchet wheel 72 and a pawl 86 which is pivotally mounted on a pin 88 secured to one side face of the ratchet wheel 72 adjacent to its periphery. The inertia disc 84 has a pin 90 which engages in a slot in the pawl 86 to cause the latter to move outwardly, if the inertia disc 84 lags behind the ratchet wheel 72, against the action of a spring 92, when the belt is being withdrawn from the spool 20.If the belt is accelerated in the withdrawal direction, the disc 84 has sufficient inertia to overcome the action of the spring 92 with the result that the pawl 86 moves outwardly into engagement with internal ratchet teeth 94 formed on a flange projecting from the control member 74 so that the latter is thereby coupled to the ratchet wheel 72 just as if the inertia sensing mechanism 78 had been actuated.

When the control member 74 is coupled to the ratchet wheel 72, either by the pawl 76 of the inertia sensing mechanism or by the pawl 86 of the beltpull-sensitive mechanism, continued tension in the safety belt causes the control plate 74 to pivot about the pin 82, the bearings 52 and 66 sliding along the slots 56 and 64 against the action of the springs 58 and 68 until the teeth of the discs 24 and 26 come into engagement with the toothed segments 18 on the frame members 14 and 16. Once pivotal movement of the control plate 74 has commenced, the mechanism will move into and then remain in its fully locked position until tension in the safety belt is removed.

The ratchet wheel 72 has a hub (not shown) projecting from the opposite side to the stub axle 70.

A hold-off lever 112, formed from resilient wire has one end wrapped round this hub. Its other end is bent to engage with the pawl 76 and arranged to hold the latter out of engagement with the ratchet wheel except during protraction of the safety belt, with the object of reducing noise generated by rattling of the inertia sensing mechanism.

The locking mechanism in the cassette 43, of course, acts on one end of the spool 20. The other end of the spool 20 is raised, when the locking mechanism is actuated, by transverse diagonai forces in the safety belt strap attached thereto. In order to ensure that both discs 24 and 28 come into contact with their respective toothed segments 18 at the same time, the strength of the spring 68 is arranged to be approximately twice that of the spring 58.

As an alternative or in addition to the foregoing, the teeth on either the toothed segment 18 on the frame member 16 or the teeth on the disc 26 may be offset with respect to the corresponding teeth on the other side of the spool 20 so that the teeth on the disc 24 come into engagement first if the axis of the spool 20 remains parallel to its original orientation.

Since this does not, in practice happen because of the asymmetrical force exerted by the cassette 43, as described above, the aforesaid offsetting ensures that both sets of teeth come into engagement together.

Referring now to Figure 2, the lateral biasing spring 58 associated with the retractor spring cassette 42 is formed from spring steel of rectangular cross-section and has two side limbs 100 and 101, each of which is generally U-shaped, the ends of the limbs of the U-shapes facing one another. The two U-shapes 100 and 101 are interconnected by one limb, the point of interconnection 102 being displaced outwardly. The other ends of the two U-shapes 100 and 101 confront one another and are displaced inwardly towards the formation 102. Figure 2 shows the spring 58 in solid lines its partially stressed condition with the spool free to rotate, in dotted lines in its unstressed condition, and in chain-dotted lines in its fully stressed condition when the retractor is locked.

Turning to Figures 2 and 4, the recess 54 in the end plate 44 is generally T-shaped, having its stem parallel to the longer dimension of the slot 56. Each of the arms 103, 104 of the cross-bar of the T-shape accommodates a respective U-shaped formation 100, 101 of the spring 58. The recess 54 has an indentation 105 in its end wall opposite the stem of the T-shape which accommodates the interconnection 102 and thus serves to locate the spring 58. The free limbs of the two U-shapes 100 and 101 bear against the boss 57 of the sliding bearing and engage under a shoulder 106 formed thereon. On the opposite side to the spring 58, the bearing plate 52 includes a flange 107 which engages under shoulders 108 and 110 on each corner of the stem of the T-shape furthest from the cross-bar thereof. The combined effect of the shoulders 106, 108 and 110 is to retain the bearing plate 52 against displacement in the axial direction.

Turning now to Figures 5 and 6, it will be seen that the spring 68 is of substantially the same shape as the spring 58 of Figure 2 and that the slot 64 is formed in a T-shaped recess having pockets 111 and 112 and an indentation 113 for accommodating the spring 68 in similar manner to the parts 102,103 and 104 of Figure 3. As before, the boss 66 has a shoulder 115 under which the free ends of the spring 68 engage (similar to the shoulder 105 of Figure 5). However, since the boss 66 is an integral part of the control member 74, it does not have a flange equivalent to the flange 106. Instead, the boss 66 has projections 116 and 117 which overlap the surface of the end plate 60. The slot 64 is longer than the corresponding slot 56 in the end plate 54 and has side openings 118 and 119 in a part thereof which is beyond the normal range of movement of the boss 66 therein. During assembly, the projections 116 and 117 pass through the side openings 118 and 119 prior to insertion of the spring 68.

Claims (6)

1. An emergency locking retractor for a vehicle safety belt comprising a pair of mutually parallel frame members and a spool having a belt-receiving shaft and a respective disc adjacent to each end of the shaft, each disc having uniformly spaced locking teeth on its outer periphery, the spool being mounted on the frame members in bearings arranged to permit limited movement relative to the frame members in a direction perpendicular to the axis of rotation, between a position in which said teeth engage with complementary teeth on the frame members to inhibit rotation of the spool and a position of disengagement, a respective spring associated with each frame member being arranged to bias the spool into its position of disengagement, and actuating means operative on one end of the spool, being arranged to cause movement of the spool into its engaged position, the spring associated with each frame member being formed with two interconnected limbs, each of which is arranged to exert a biasing force on the spool.

2. An emergency locking retractor according to claim 1,wherein each limb of the spring is Ushaped, one arm of one U-shape being connected to the corresponding arm of the other U-shape.

3. An emergency locking retractor according to claim 2, wherein the point of interconnection is received in a locating formation associated with the frame member and the free ends of both limbs engage with a bearing of the spool.

4. An emergency locking retractor according to claim 1,2 or 3, wherein the spring is formed of material of rectangular cross-section of uniform thickness in the direction in which it is flexed in use.

5. An emergency locking retractor according to any preceding claim, wherein the spring on the same side of the frame members as the actuating means is arranged to exert a stronger force than the spring on the other side of the frame members.

6. An emergency locking retractor for a vehicle safety belt, substantially as hereinbefore described with reference to the accompanying drawings.