GB2156198A - Safety belt emergency locking retractor - Google Patents

Abstract

A retractor comprises a frame (10) and a spool (20) having a shaft (22) and a respective disc (24, 26) adjacent to each end of the shaft (22), each disc (24, 26) having locking teeth on its periphery. The spool (20) is mounted in bearings (52, 66) permitting limited movement relative to the frame (10) perpendicular to the axis between a position in which said teeth engage with teeth (18) on the frame (10) to inhibit rotation of the spool (20) and a position of disengagement. Resilient means (58, 68) are arranged to bias the spool (20) into disengagement, and arresting means (43) operative on one end of the spool (20), cause movement of the spool (20) into its engaged position due to belt tension. To ensure that the teeth on both discs come into full engagement with the teeth on the frame (10) either the resilient means (68) on the same side of the frame as the actuating means (43) is made stronger than the means (58) on the other side, or the teeth (18) on the opposite side of the spool (20) to the actuating means (43) are angularly displaced relative to the teeth (18) on the same side as the actuating means (43) in the belt retraction direction. In a future alternative, a cam device ensures slight rotation of the discs should the teeth approach in tip-to-tip relationship. <IMAGE>

Description

SPECIFICATION Safety belt emergency locking retractor This invenrion relates to an emergency locking retractorfor a vehicle safety belt of the type comprising a frame and a spool having a belt-receiving shaft and a respective disc adjacent to each end ofthe shaft, each disc having uniformly spaced locking teeth on its outer periphery, the spool being mounted on the frame in bearings arranged to permit limited movement relative to the frame in a direction perpendicular to the axis of rotation, between a position in which saidteeth engagewithcomplementaryteeth on the frame to inhibit rotation ofthe spool and a position of disengagement, resilient means being arranged to bias the spool into its position of disengagement, and actuating means operative on one end ofthe spool, being arranged to cause movement ofthe spool into its engaged position. A retractor of this type is disclosed in Patent Specification Nos. EP-A-0112032 and EP-A-01 12033.

According to the invention, in an emergency locking retractor of the foregoing type, means are provided for ensuring thatthe locking teeth on both discs come into full engagement with the complementary teeth on the frame when the spool moves into its engaged position.

In one form ofthe invention, the resilient means on the same side ofthe frame as the actuating means is arranged to exert a stronger force than the resilient means on the otherside ofthe frame. Forexample,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 ofthe frameastheactuating means. Thus, although the actuating force is applied on one side ofthe spool, both sides move into engagement together.

Alternatively, the complementary teeth on the frame on the opposite side ofthe spool to the actuating means may be angularly displaced relative to the teeth on the same side as the actuating means n the belt retraction direction. Thus, if the two sides of the spool move synchronously into engagement with the frame when webbing is being drawn off, the teeth on the same side asthe actuating means will come into engagement first.

The components ofthe bearings which move relative to the frame in a direction perpendicularto the axis of rotation are preferably constructed so asto resist axial displacement relative to the frame.

In anotherform ofthe invention, camming formations mounted in fixed locations relative to the frame are arranged to co-opartate with complementary formations on the discs ofthe spool to cause angular movement ofthe spool in the belt protraction direction if the teeth on the discs approach the complementary teeth on the frame in an orientation such as to come into tip-to-tip engagement. This ensures the necessary angular movementforthe teeth to come into full engagement even if the safety belt is substantially completely unwound from the spool.

In orderto ensure that the teeth on the spool come intocorrectaxial alignment with the complementary teeth on the frame, the former may be provided with an inclined outwardly extending flange on one side while the latter are provided with an inwardly extending inclined flange on the other.

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 plan view of one ofthe springs which biasesthespool into its disengaged position; Figure 3 is an end view, from the frame, ofthe end member ofthe cassette containing the re-wind spring and one of the sliding bearingsoftheembodinent shown in Figure 1; Figure4 is a cross-sectional view taken on the line 4 4in Figure 2; Figure 5 is an end view, similarto Figure 2, ofthe corresponding end member ofthe cassette containing the actuating means; and Figure 6 is a fragmentary cross-sectional view taken on the line 6 - 6 in Figure 5.

Figure7 isan end view of a modified form of the retractor shown in Figure 1; Figure 8 is a scrap view showing part of Figure 7 on an enlarged scale; Figure 9 is a scrap cross-sectional view taken on the line9-9in Figure7; and Figure 10 is a scrap cross-sectional view illustrating a further modification ofthe em bodiment shown in Figure 1.

The retractor illustrated in Figure 1 has a generally U-shaped frame 10, the base portion of which is provided with a hole 12 whereby the frame 10 may be secured to the body of a motor vehicle. The side limbs ofthe U-shape constitute substantially identical frame membersl4and l6eachofwhichcontainsan aperturewhich is generally circular but somewhat enlarged in the vertical direction and which has a respective toothed segment 18 forming part of its upper periphery.

Aspool 20 is mounted intheframe 10. The spool 20 comprises a cental 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 14and 16 respectively, and two projecting stub axles 28 and 30.

A distance bar 32 having perpendicular projecting side limbs 34 and 36, extends between notches 38 and 39 in the outer edges of the frame members 14 and 16 so asto maintain the required spacing therebetween.

The end limbs 34 and 36 project beyond the edges of the openings in theframe members 14 and 16 so as to overlap the toothed discs 24 and 26 ofthe 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 faceoftheframememberl6andalocking machanism cassette 43 in engagement with the outer side face of Ine frame member 14.

The enclosure for the retractor spring cassette 42 comprises an end plate 44, which abuts the trame member 16 and is engaged by the hookformation 38, togetherwith a cover 46 wh ich carries a stop (not shown) to which the outer end of a retraction spring 48 is secured. The inner end ofthe spring 48 is secured to a plastics boss 50 having a cylindrical outer surface and a slotted opening for engagement with the flattened end ofthe stub axle 30 of the spool. The axial length of the boss 50 is greaterthan the width of the spring48 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 ofthe 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 enrage 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 ofthe frame men, 3r 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 elongateslot64and a sliding bearing 66, which is spring biased awayfrom the toothed segments 18 ontheend plate 14by a spring 68, in a similar mannerto the corresponding components ofthe 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 acylindrical outersurfaceforengagementinthe bearing 66 and a slot for engagement with the flattened end portion of the stub axle 28 ofthe spool 20.

The sliding bearing 66 is an integral part of a control member 74 which is subject two an annular bias in the belt retraction direction by an extended limb 75 ofthe spring 68. A pawl 76 is pivotally mounted on the control member74so that it can be moved into engagement with the teeth ofthe ratchet wheel 72 by a conventional ball-in saucer inertia sensing mechanism 78 mounted on the bottom ofthe 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 consists of an inertia disc 84which is pivotally mounted on the stub axle 70 ofthe ratchet wheel 72 and a pawl 86 which is pivotally mounted on a pin 88 secured to one side face ofthe ratchet wheel 72 adjacentto its periphery. The inertia disc84 has a pin 90 which engages in a slot in the pawl 86to cause the latterto move outwardly, if the inertia disc 84 lags behind the ratchet wheel 72, againstthe 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 ofthe spring 92 with the resultthatthe pawl 86 moves outwardly into engagementwith internal ratchet teeth 94formed on aflange projecting from the control members , -. s -, that the latter is thereby coupied to the ratchet wheel 72 just as if the inertia sensing mechansim 78 had been actuated.

When the control member74 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 74to 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 theteeth ofthe discs 24and 26 come into engagement with the toothed segments 18 on the frame members 14and 16. Once pivotal movement ofthe 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 ofthe safety belt, with the object of reducing noise generated by rattling ofthe inertia sensing mechanism.

The locking mechanism in the cassette 43, of course, acts on one end ofthe spool 20. The other end of the spool 20 is raised, when the locking mechanism is actuated, bytransversediagonal forces inthesafety belt strap attached thereto. In order to ensure that both discs 24 and 28 come into contact with their respective toothed segments 18 atthe same time, the strength of the spring 68 is arranged to be approximatelytwice 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 respectto the corresponding teeth on the other side of the spool 20so that the teeth on the disc 24 come into engagement first if the axis ofthe 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 ofteeth come into engagement together.

Referring nowto 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 ofthe 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 inwardlytowardsthe formation 102. Figure2showsthespring 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 Figures3 and 4, the recess 54 in the end plate 44 is generally T-shaped, having its stem parallel to the longer diamension ofthe slot 56. Each of the arms 1 03, 104 of the cross-bar of theT-shape accommodates a respective U-shaped fcrmation 100, 101 ofthe 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 servesto locate the spring 58. Thefree limbs of the two U-shapes 100 and 101 bear againstthe boss 57 ofthe 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 oftheT-shape furthest from the cross-bar thereof.The combined effect ofthe shoulders 106, 108 and 110 isto retainthe bearing plate 52 against displacement in the axial direction.

Turning nowto 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 andthatthe 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 mannerto the parts 102, 103 and 104 of Figure 3. As before, the boss 66 has a shoulder 115 under which the free ends ofthe spring 68 engage (similar to the shoulder 105 of Figure 5). However, since the boss 66 is an integral part ofthe 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 ofthe 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 partthereofwhich is beyond the normal range of movement of the boss 66 therein. During assembly, the projections 116 and 117 passthroughtheside openings 118 and 119 prior to insertion ofthe spring 68.

It will be realised that complete engagement ofthe teeth on the discs 24 and 26 with the complementary teeth 18 on the frame 10 depends on the spool 20 rotating in the belt protraction direction as it is displaced laterally against the action ofthe springs 58 and 68. If the safety belt is completely withdrawn from the spool 20, this rotation may not take place, with the consequencethattheteeth on the spool 20 may merely come intotip-to-tip engagementwith the teeth on the frame 10. Figures 7to 9 illustrate a modification of the embodiment of the invention shown in Figure 1 which avoids this risk. The disc 24 of the spool 20 is formed with a peripheral rim 120 which has a series of inwardly extending projections 122 on its inner periphery, each ofthe projections 122 being aligned with a respecitve lockingtooth ofthe disc 24.As can be seen from Figure 8, the ratio of the width A of each of the projections 1 22to the gap B between adjacent projections is approximately 2:3.

The end plate 60 of the locking mechanism cassette 43 carries three projections 124 which are axially algined with the projections 122 on the disc 24 and which are located radially inwardly of such projections 122 when the spool 20 is in its normal released position, the projections 124 being diametrically opposite the central zone ofthe toothed segment 18 on the frame member 14.Each of the projections 124 has an inclined face 126 on its outer cornerfacing the approaching projections 122 on the disc 24 as the safety belt is protracted so asto cause a slight retraction ofthe safety belt if the projections 122 come into contact with thesefaces 126 asthe spool 20 moves into its engaged position. similar inclines' faces 128 are formed on tSe other outer corners of the projections 122.

Asimilararrangementto that described with reference to Figures 7 to 9 provided on the disc 26 own the other end of the spool 20.

Turning nowto Figure 10, it will be realised that if the retractor illustrated in Figure 1 was subject to a very large acceleration in the axial direction, partial misalignment ofthe locking teeth on the discs 24 and 26 with the complementary teeth 18 on the frame could occur, leading to excessive loads being imposed onthose parts ofthetooth faces which do engage. In order to avoid this, the disc 24 may be provided with a radially extending flange 130 on the axially inner side of the locking teeth thereof. The axially outer face 132 of such flange is inclined axially inwardly so that, if the tips of the complementary teeth 18 on the frame member14touchsuch surface 132 asthe spool 20 moves into its engaged position, it is displaced axially to bring the teeth into full alignment with one another.

The end plate 60 ofthe cassette 43 is provided with a similar inclined surface 134 which would engage with the outer edge 1 36 of the dise 24 in the event of axial misalignment. Corresponding arrangements (not shown) are provided on the disc 26 and frame member 16 to deal with axial misalignment in the other direction.

Claims (7)

1. An emergency locking retractor for a vehicle safety belt comprising a frame and a spool having a belt-receiving shaft and a respective disc adjacent to each end ofthe shaft, each disc having uniformly spaced locking teeth on its outer periphery, the spool being mounted on the frame in bearings arranged to permit limited movement relative to the frame in a direction perpendicularto the axis of rotation, between a position in which said teeth engage with complementaryteeth on the frame to inhibit rotation ofthe spool and a position of disengagement, resilient means 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, means being provided for ensuring thatthe locking teeth on both discs come into full engagement with the complementary teeth on theframe when the spool moves into its engaged position.

2. An emergency locking retractor according to claim 1, wherein the resilient means on the same side of the frame as the actuating means is arranged to exert a strongerforcethan the resilient means on the other side ofthe frame.

3. An emergency locking retractor according to claim 1, wherein the complementary teeth on the frame on the opposite side ofthe spool to the actuating means are angularly displaced relative to the teeth on the same side as the actuating means in the belt retraction direction.

4. An emergency locking retractor according to claim 1,2 or 3, wherein the components ofthe uearings which move relative to the frame in a direction perpendicular to the axis of rotation are constructed so as to resist axial displacement relative to the frame.

5. An emergency locking retractor according to any preceding claim,wherein camming formations mounted in fixed locations relative to the frame are arranged to co-operate with complementaryforma- tions on the discs ofthe spool to cause angular movement ofthe spool in the belt protraction direction if the teeth on the discs approach the complementary teeth on the frame in an orientation such as to come into tip-to-tip engagement.

6. An emergency locking retractor according to any preceding claim, wherein each disc ofthe spool has a respective inclined outwardly extending flange on one side of its teeth and each frame has a respective inwardly extending inclined flange on the other side of its teeth.

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