GB2323265A

GB2323265A - Seat belt retractor

Info

Publication number: GB2323265A
Application number: GB9705511A
Authority: GB
Inventors: Hossein Parvin
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1997-03-18
Filing date: 1997-03-18
Publication date: 1998-09-23
Anticipated expiration: 2017-03-18
Also published as: GB2323265B; GB9705511D0

Abstract

A retractor (1) incorporating load limiting means comprises a seat belt (10) attached to a spool (7) that is rotatably supported by trunnions (8, 9). A component (18) that forms a portion of the trunnion (9) extends into a recess (15) to define a substantially annular space within which two toothed cylindrical elements (23, 24) are provided. Should a very large predetermined force be applied to the safety belt (10) following actuation of locking means (13) then frangible pin (33) will break. This allows the main body (14) of the spool (7) to rotate relative to component (18) consequently rotating the cylindrical elements (23, 24) within the annular space. As the elements (23, 24) rotate they deform either the inner wall of the recess (15) or the component (18), thus allowing a length of seat belt (10) to be paid out in an energy absorbing manner.

Description

Description of Invention "Improvements In or Relating To A Seat Belt Retractor" THE PRESENT invention relates to a seat belt retractor and more particularly relates to a seat belt retractor incorporating a load limiter.

It has been proposed previously to provide a seat belt retractor in a vehicle, which, when the vehicle undergoes rapid deceleration or when the seat belt is withdrawn from the retractor at a velocity above a predetermined threshold, locks a spool of the retractor to prevent the seat belt from being extended further. This restrains an occupant of the vehicle wearing the seat belt from moving forwards relative to the vehicle due to their inertia.

It has also been proposed previously to provide a load limiter connected between the seat belt retractor and the vehicle frame so that, when the seat belt retractor locks the spool, the entire retractor mechanism may move in response to the force applied to the retractor by the seat belt when the force is above a predetermined threshold.

A seat belt retractor attached to a vehicle by a load limiter as described above provides some "give" in the seat belt when a vehicle decelerates extremely rapidly.

This is important because an occupant of a vehicle wearing such a seat belt during extremely rapid deceleration is pressed very strongly against the seat belt, which may result in injury. If the previously proposed load limiting mechanism is used then the occupant of a vehicle is allowed to move forward slightly relative to the vehicle so that he presses less strongly against the seat belt and the chances of injury are reduced.

A disadvantage of seat belt retractors attached to a vehicle via a load limiter as described above is that such a device takes up additional space in the vehicle. A number of documents disclose seat belt retractors that solve this problem by having the load limiter within the spool. The problem with these seat belt retractors is that they are quite complicated.

The present invention seeks to provide an improved seat belt retractor arrangement incorporating a load limiter.

According to this invention there is provided a seat belt retractor mechanism comprising a frame, a spool rotatably supported by at least one trunnion within the frame, a seat belt having one end attached to the spool and means to lock said at least one trunnion, there being provided load limiting means operatively connected between said at least one trunnion and the spool in order to permit limited movement of the spool relative to the trunnion with a load absorbing effect, said load limiting means comprising a recess formed in the spool, a component forming a portion of the trunnion and extending into said recess to define a substantially annular space, and at least one cylindrical element located within said space engaging the exterior of the component and the inner wall of the recess, one of the inner wall of the recess and the exterior of the component being toothed to engage said element, the other of said inner wall of the recess and said exterior of the component being of deformable material, the arrangement being such that when the locking means lock the trunnion and force is applied to the seat belt above a predetermined threshold, the load limiting means allow movement of the spool relative to the trunnion so that unwinding of the seat belt from the spook takes place.

The distance between the wall of the recess and the exterior of the component may be constant, or may vary, preferably with a tapering effect.

Conveniently the exterior of the component is toothed and the inner wall of the recess is made from a deformable material.

Alternatively the exterior of the component is made of deformable material and the inner wall of the recess is toothed.

Advantageously there is provided a seat belt retractor according to any one of the preceding claims wherein there is provided at least one stop extending at least partly across the annual space adjacent the position of the or each cylindrical element in normal use.

Conveniently the or each cylindrical element is a gear wheel.

Alternatively the or each cylindrical element is an elongate rod.

Preferably the trunnion is connected to said spool by a frangible pin in order to prevent rotation of the spool relative to the trunnion, the frangible pin being adapted to break when the locking means lock the trunnion and force is applied to the sat belt above a predetermined threshold, the breaking of the frangible pin allowing rotation of the spool relative to the trunnion.

Conveniently said at least one cylindrical element is partly accommodated in a groove in the inner wall of said recess in normal use, the distance between the wall of the recess and the exterior of the component around the remainder of the recess being substantially less than the diameter of said cylindrical element.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a view of the principal parts of a seat belt retractor incorporating a load limiter in accordance with the invention with part cut-away, and with part shown diagrammatically, Figure 2 is a cross-section taken along the line A-A of Figure 1, Figure 3 is a cross-section, corresponding to Figure 2, but showing a modified embodiment of the invention, and Figure 4, is a cross-section, corresponding to Figure 2, but showing a further embodiment .of the invention.

Referring initially to Figure 1, a seat belt retractor mechanism 1 comprises a substantially U-shaped frame 2 having a base 3 and two forward-extending parallel spaced-apart side arms 4. Each side arm defines an aperture 5,6.

A spool 7 is provided, the spool having, at opposed ends thereof, trunnions 8,9 which are received, respectively, within the apertures 5,6. The spool is mounted in position so as to be rotatable. A seat belt 10 is provided having a terminal portion thereof wound as a spiral 11 on the exterior of the spool 7.

One trunnion 8 is associated with a helical "clock" spring 12 adapted to impart a rotational bias to the spool 7 to draw safety belt 10 onto the spool 7. The trunnion 9 is associated with a locking mechanism 13, which is illustrated schematically, which is adapted to lock the trunnion, and thus the spool, in response to predetermined parameters such as deceleration of the vehicle, in which the retractor mechanism 1 is mounted, in excess of the predetermined threshold or withdrawal of the seat belt 10 from the spool at a velocity in excess of a predetermined threshold.

It is to be observed, from Figure 1, that the spool 7 is not of a unitary construction, but instead, is formed of a plurality of components.

The spool, as illustrated in Figure 1, comprises a main body component 14. The main body component 14 defines a cylindrical exterior surface upon which the helical portion 11 of the seat belt 10 is wound.

The main body component 14 defines, in the end thereof remote from the trunnion 8, a recess 15. The recess 15 comprises a first portion 16 which is of circular section and of a first diameter. Formed in the base of the first portion 16 is a second portion 17 which is also of circular section but of reduced diameter which is coaxial with the first portion.

The spool 7 also comprises a second component 18.

The second component 18 defines the second trunnion 9 and also defines an inwardly directed cylindrical portion 20 which extends into the recess 15, the innermost end of the cylindrical portion 20 being received, as a sliding fit, within the smaller diameter second portion 17 of the recess 15. The second component 18 also comprises a radially outwardly directed flange 21 located adjacent the base of the trunnion 9, the inner surface of the flange 21 defining a lip 22 which engages as a sliding fit within the open mouth of the recess 15 provided at the end of the main body portion 14 remote from the trunnion 8. The cylindrical portion 20 of the second component and the wall of the first portion 16 of the recess 15 define between them an annular space. The distance between the wall of the recess and the cylindrical portion 20 is constant. A frangible pin 33 is optionally provided to connect the flange 21 to the wall of the first portion 16 of the recess 15. The frangible pin 33 has one end accommodated in a recess in the wall of the first portion 16 and the other end accommodated in a recess in the flange 21. The frangible pin 33 is adapted to break when the force applied to it exceeds a predetermined threshold.

As will become clear from the following description, the main body component 14 may rotate relative to the second component 18, once the frangible pin 33 has been broken (if provided).

Referring now additionally to Figure 2, it is to be observed that two cylindrical elements 23,24 are provided at diametrically opposed positions in the annular space formed in the first portion 16, of the recess 15, the elements 23, 24 being separated by the cylindrical portion 20 of the second component 18. Each cylindrical element 23, 24 has a toothed outer periphery.

Referring to Figure 2 it is to be observed that each cylindrical element is located adjacent a radially inwardly directed stop 25,26 extending inwardly at least partly across the annular space from the inner wall of the first portion 16 of the recess 15 and directed inwardly towards the cylindrical portion 20 of the second component 18.

In the embodiment illustrated, the outer surface of the cylindrical projection 20 within the first part 16 of the recess 15 is toothed 27, with the teeth engaging the toothed periphery of each of the cylindrical elements 23,24. The inner wall 28, 29 of the first portion 16 of the recess 15 as defined by the main body component 14 is formed of a deformable material. The diameter of each of the cylindrical elements 23,24 is selected so that the cylindrical elements are at least a tight fit between the toothed exterior 27, of the cylindrical projection 20 and the inner wall of the first portion 16 at the recess 15 as defined by the main body portion 14.

In ordinary use of the retractor mechanism as described with reference to Figures 1 and 2, the retractor mechanism will operate in a conventional manner. As the safety belt is pulled out from the retractor mechanism the spool 7 will rotate and tension will be applied to the helical clock spring 12. The frangible pin 33 prevents any rotation of the main body component 14 of the spool 7 relative to the second component 18. When the seat belt 10 is released the helical clock spring 12 will impart a rotation to the spool 7 tending to rewind the safety belt 10 back into the retractor mechanism. In the event of the vehicle in which the retractor mechanism is mounted should decelerate rapidly, or should the safety belt be withdrawn from the spool at a velocity in excess of a predetermined threshold, the locking mechanism 13 will operate to lock the trunnion 9 to prevent further rotation of the spool 14.

Should, however, a very large force be applied to the safety belt 10, following actuation of the locking mechanism 13, the frangible pin 33 may break and the main body portion 14 of the spool may rotate relative to the second component 18 of the spool. The end region of the cylindrical portion 20 received within the second portion 17 or the recess 15 and the lip 22 provided on the flange 21 received within the open end of the first portion 16 of the recess 15 remote from the trunnion 8 will act as bearings to permit this rotation whilst maintaining the integrity of the spool.

As the main body component rotates, relative to the second component 18, in the direction illustrated by the arrow 30, each cylindrical element 23,24 will rotate in the direction indicated by the arrows 31,32. As the toothed cylindrical elements 23,24 rotate the teeth will engage, and deform, the inner wall of the first portion 16 of the recess 15 as defined by the main body component 14, consequently absorbing energy.

Thus it is to be appreciated that in use of a retractor mechanism as described, the retractor mechanism will operate in a conventional manner under ordinary circumstances but should a load in excess of a predetermined threshold be applied to the safety belt 10 tending to withdraw the safety belt from the retractor mechanism following locking of the spool by the locking mechanism 13, the frangible pin 33 will break and the main body portion 14 of the spool is permitted to effect a further rotation against a limiting force, that limiting force being dependent upon the energy required to deform the inner wall of the first portion 16 of the recess 15 by the toothed outer peripheries of the cylindrical elements 23 and 24.

It should be appreciated that after a predetermined degree of rotation of the main body component 14 relative to the second component 18 of the spool, the cylindrical elements will engage the stops 25,26 located substantially diametrically opposite the initial positions of the cylindrical elements 23,24 thus preventing further rotation of the main body component of the spool. Thus, after a predetermined length of seat belt has been paid out, the main body component 14 of the spool will be finally locked preventing the withdrawal of further safety belt.

Figure 3 illustrates a modified embodiment of the invention in which the first portion 16 of the recess 15 formed in the main body component 14 of the spool 7 is not of uniform diameter. In the embodiment of Figure 3, on one side of the stop 25 the inner wall of the first portion 16 of the recess 15 is spaced from the toothed outer periphery of the cylindrical projection 20 that forms part of the second component of the spool 7 by a distance which is substantially equal to the diameter of the cylindrical element 24. The surface defined by the inner periphery of the first portion 16 of the recess 15, however, tapers radially inwardly, to a point adjacent the diametrically opposed stop 26, where the inner surface of the first portion 16 of the recess 15 is spaced from the toothed outer periphery of the cylindrical projection 20 by a distance which is substantially less than the diameter of the cylindrical element 24. Similarly, on the opposite side of the stop 26 the inner wall of the first portion 16 of the recess 15 is spaced from the cylindrical projection 20 by a distance substantially equal to the diameter of the cylindrical element 23, with that surface tapering inwardly to a point, adjacent the stop 25 where the distance between the inner wall of the first portion 16 of the recess 15 and the outer toothed periphery of the cylindrical projection 20 is much less than the diameter of the cylindrical element 23. Thus in this embodiment the distance between the inner wall of the first portion 16 of the recess and the exterior of the cylindrical projection varies.

It can be seen that, in this embodiment, when the frangible pin 33 is broken and the main body component 14 moves relative to the second component 18, the cylindrical elements 23,24 will move in such a way that they become embedded deeper and deeper in the deformable material forming the inner wall of the first portion 16 of the recess 15, thus meeting a greater and greater resisting force.

Whilst the invention has been described with reference to the embodiments in which the cylindrical projection 20 is toothed and the inner wall of the first portion 16 and the recess 15 is formed of a deformable material it is to be appreciated that in modified embodiments of the invention the inner wall of the first portion 16 of the recess 15 may be toothed and the exterior of the cylindrical projection 20 may be formed of deformable material.

In embodiments of the invention the cylindrical elements may only have a short length, thus comprising gear wheels, or may have a greater length, thus comprising elongate rods.

It is to be appreciated that, in an alternative embodiment of the present invention, the main body component 14 of the spool 7 may be held relative to the second component 18 in normal use by means other than the frangible pin 33. For example, as shown in Figure 4, the cylindrical elements 23, 24 may each be partly accommodated in a respective groove 34, 35 in the inner wall 28, 29 of the first portion 16 of the recess 15, adjacent the stops 25, 26. The distance between the outer surface of the cylindrical projection 20 and the inner wall 28, 29 of the first portion 16 around the remainder of the recess 15 is selected to be substantially less than the diameter of the cylindrical elements 23, 24. Thus, in normal use each cylindrical element 23, 24 is held between its respective stop 25, 26 and the wall of its respective groove 34, 35 preventing rotation. Only when the force applied to the safety belt 10 is above a predetermined threshold, is the force on the main body component 14 sufficient to cause the cylindrical elements 23, 24 to deform the inner wall 28, 29 of the first portion 16 of the recess 15 and allow rotation of the main body component relative to the second component 18.

Claims

1. A seat belt retractor mechanism comprising a frame, a spool rotatably supported by at least one trunnion within the frame, a seat belt having one end attached to the spool and means to lock said at least one trunnion, there being provided load limiting means operatively connected between said at least one trunnion and the spool in order to permit limited movement of the spool relative to the trunnion with a load absorbing effect, said load limiting means comprising a recess formed in the spool, a component forming a portion of the trunnion and extending into said recess to define a substantially annular space, and at least one cylindrical element located within said space engaging the exterior of the component and the inner wall of the recess, one of the inner wall of the recess and the exterior of the component being toothed to engage said element, the other of said inner wall of the recess and said exterior of the component being of deformable material, the arrangement being such that when the locking means lock the trunnion and force is applied to the seat belt above a predetermined threshold, the load limiting means allow movement of the spool relative to the trunnion so that unwinding of the seat belt from the spool takes place.

2. A seat belt retractor according to Claim 1 wherein the distance between the wall of the recess and the exterior of the component is constant.

3. A seat belt retractor according to Claim 1 wherein the distance between the wall of the recess and the exterior of the component varies.

4. A seat belt retractor according to Claim 1, 2 or 3 wherein the exterior of the component is toothed and the inner wall of the recess is made from a deformable material.

5. A seat belt retractor according to Claim 1, 2 or 3 wherein the exterior of the component is made from a deformable material and the inner wall of the recess is toothed.

6. A seat belt retractor according to any one of the preceding claims wherein there is provided at least one stop extending at least partly across the annular space adjacent the position of the or each cylindrical element in normal use.

7. A seat belt retractor according to any one of the preceding claims wherein there are two diametrically opposed cylindrical elements.

8. A seat belt retractor according to any one of the preceding claims wherein the or each cylindrical element is a gear wheel.

9. A seat belt retractor according to any one of Claims 1 to 7 wherein the or each cylihdrical element is an elongate rod.

10. A seat belt retractor according to any one of the preceding claims wherein the trunnion is connected to said spool by a frangible pin in order to prevent rotation of the spool relative to the trunnion, the frangible pin being adapted to break when the locking means lock the trunnion and force is applied to the seat belt above a predetermined threshold, the breaking of the frangible pin allowing rotation of the spool relative to the trunnion.

11. A seat belt retractor according to any one of Claims 1 to 9 wherein said at least one cylindrical element is partly accommodated in a groove in the inner wall of said recess in normal use, the distance between the wall of the recess and the exterior of the component around the remainder of the recess being substantially less than the diameter of said cylindrical element.

12. A seat belt retractor substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.

13. A seat belt retractor substantially as herein described with reference to and as shown in Figure 3 of the accompanying drawings.

14. A seat belt retractor substantially as herein described with reference to and as shown in Figure 4.

15. Any novel feature or combination of features disclosed herein.