GB2155764A - Safety belt emergency locking retractor - Google Patents

Abstract

An emergency locking retractor for a vehicle safety belt having a spool for receiving a strap (114) of a safety belt and locking means for obstructing rotation of the spool in the belt protraction direction. The spool is formed as a single casting or moulding having a belt-receiving shaft in the form of a hollow cylinder (100) having diametrically opposed radial webs (102, 104) coupled to a pair of transverse webs (106, 108) which bound a central slot (110) extending diametrically across the cylinder (100) for receiving the strap (114). The spool (20) has reinforcement means (122, 124) on the side of the slot (110) which is closer to the direction of belt withdrawal when the belt wound around the periphery of the cylinder (100) extends round less than ninety deg thereof. <IMAGE>

Description

SPECIFICATION Safety belt emergency locking retractor This invention relates to an emergency locking retractor for a vehicle safety belt of the type having a spool for receiving a strap of a safety belt and locking means for obstructing rotation of the spool in the belt protraction direction, the spool being formed as a single casting or moulding having a belt-receiving shaft comprising a hollow cylinder having diametrically opposed radial webs coupled to a pair of transverse webs which bound a central slot extending diametrically across the cylinder for receiving the strap. A retractor having a spool of this type is disclosed in Patent Specification No.

EP-A-01 1032.

In order to reduce the overall weight of the retractor, it is desirable for the various parts of the spool to be made as thin as possible. On the other hand, if the locking mechanism engages when the spool is oriented with its central slot perpendicular to the direction of belt withdrawal and the belt is almost completely protracted from the spool, the forces exerted on the parts of the spool on the side of the slot nearer to the direction of belt withdrawal are much greater than the forces exerted thereon when the spool is in any other orientation. It is an object of one aspect of the invention to provide a spool which can withstand these forces without being unduly heavy.

According to one aspect of the invention, in an emergency locking retractor of the type described above, the spool has reinforcement means on the side of the slot which is closer to the direction of belt withdrawal when the belt wound around the periphery of the cylinder extends round less than ninety deg thereof.

In one form of the invention, the reinforcement means comprises a reinforcement wedge inserted into one of the voids between the transverse web and the cylinder on the aforesaid side of the slot.

In another form of the invention, the reinforcement means comprises an increase in the thickness of the material forming the hollow cylinder on the aforesaid said of the slot.

According to another aspect of the invention, in an emergency locking retractor of the type described above where the locking means includes a ratchet wheel mounted on one end of the spool for rotation therewith, the means for mounting the ratchet wheel on the spool includes a hole in the spool extending from the surface of the spool against which the ratchet wheel abuts into one end of the central slot, together with a resilient finger secured to the ratchet wheel so as to project through said hole into the slot and having a formation adapted to engage with the edge of the said hole in said slot. This enables a visual inspection to be made to check that correct assembly has been achieved before the strap is fitted to the spool.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of an emergency locking retractor in accordance with an embodiment of the invention; Figure 2 is a longitudinal sectional view of a onepiece spool for use in the embodiment illustrated in Figure 1; Figure 3 is a cross-sectional view taken on the line 3-3 in Figure 2; Figure 4 is a cross-sectional view, similar to Figure 3, of an alternative form of spool for use with the embodiment illustrated in Figure 1; and Figure 5 is an enlarged longitudinal sectional view illustrating the connection of a ratchet wheel to the spool.

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 flanges 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 flanges 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 td 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 said face of the frame member 14.

The enclosure for the retractor spring cassette 42 comprises an end member 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 casssette 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 plate 74 which is subject to pn angular bias in the belt retraction direction by an extending limb 75 of the spring 68. A pawl 76 is pivotally mounted on the control plate 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 plate 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 plate 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 plate 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 belt-pullsensitive 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 flanges 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.

Figures 2 and 3 show the spool 20 formed as a single die casting. The shaft portion 22 comprises a hollow cylinder 100 having two dimetrically opposed radial webs 102 and 104 coupled to transverse webs 106 and 108 which bound a central slot 110 extending diametrically across the entire shaft portion 22 for receiving the inner end of the webbing of the safety belt. One end of the slot 110 has a broadened portion of rectangular crosssection for receiving a locking bar 112 of T-shaped cross-section (not shown) inserted through a loop formed in the end of the strap 114.

Each of the flanges 24 and 26 has a circular recess 113 from which apertures communicate with the cavities within the cylindrical shaft portion 22. Teeth 118 are formed on the peripheries of the flanges 24 and 26. Flanges 120 project outwardly beyond the teeth 118 and help to prevent axial movement of the spool 20 relative to the frame members when the spool 20 is in the locked position.

When the retractor locks with the spool 20 in the orientation illustrated in Figure 3, i.e. with the strap 114 almost completely unwound and the slot 110 between the webs 106 and 108 at right-angles to the direction of protraction of the strap 114, an excessively large load is imposed on the part of the cylinder 100 adjacent to the web 108. In order to make provision for this, reinforcing wedges 122 and 124 are inserted into the voids 126 and 128 on each side of the radial web 104. The reinforcing webs 126 and 128 both extend along the entire length of the spool 20 from the flange 24 to the flange 26; their ends being shown in Figure 2 as projecting into the recesses 113 although, in practice, any such projection would be minimal.A central semi-circular reinforcing web 116 is disposed one the other side of the central slot 110 and interconnects the cylinder 100 and the webs 102 and 106.

Figure 4 illustrates a modification to the spool shown in Figure 3. In place of the wedges 122 and 124, the web 104 is replaced byathickerweb 130 and the parts 132 and 134 of the walls of the cylinder 100 are made thicker than the corresponding parts 136 and 138thereof on the other side ofthe slot 110.

Figure 5 shows the connection of the stub axle 70 of the ratchet wheel 72 to the stub axle 28 of the spool 20. As mentioned above, the stub axle 28 has a flattened end portion (shown at 140 in Figure 5) which engages with a complementary flat in the slot 110 in the stub axle 70 of the ratchet wheel 72 so as to prevent relative rotation. In addition, the stub axle 28 has a bore 142 extending into communication with the slot 110 in the spool 20. A resilient finger 144, moulded integrally with the ratchet wheel 72, projects through the bore 142 and carries a locking formation 146 on its end which engages with the edge of the bore 142 in the slot 110. Thus, after assembly of the retractor but before the safety belt has been fitted thereto, it is possible to carry out a visual inspection to check whether the ratchet wheel 72 has been properly secured to the spool 20.

In order to impede entry of dust past the bearing surfaces 150 into the enclose formed by the end plate 60 and the cover 62, respective labyrinth seal formations 152 and 154 are provided on the control plate 74 and the flanges 24 of the spool 20.

Claims (5)

1. An emergency locking retractor for a vehicle safety belt having a spool for receiving a strap of a safety belt and locking means for obstructing rotation of the spool in the belt protraction direction, the spool being formed as a single casting or moulding having a belt-receiving shaft comprising a hollow cylinder having diametrically opposed radial webs coupled to a pair of transverse webs which bound a central slot extending diametrically across the cylinder for receiving the strap, the spool having reinforcement means on the side of the slot which is closer to the direction of belt withdrawal when the belt wound around the periphery of the cylinder extends round less than ninety deg thereof.

2. A retractor according to claim 1, wherein the reinforcement means comprises a reinforcement wedge inserted into one of the voids between the transverse web and the cylinder on the aforesaid side of the slot.

3. A retractor according to claim 1, wherein the reinforcement means comprises an increase in the thickness of the material forming the hollow cylinder on the aforesaid side of the slot.

4. A retractor according to claim 1,2 or 3, wherein the locking means includes a ratchet wheel mounted on one end of the spool for rotation therewith, and the means for mounting the ratchet wheel on the spool includes a hole in the spool extending from the surface of the spool against which the ratchet wheel abuts into one end of the central slot, together with a resilient finger secured to the ratchet wheel so as to project through said hole into the slot and having a formation adapted to engage with the edge of the said hole in said slot.

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