GB2307844A - Safety belt retractor reel - Google Patents

Abstract

A pre-tensioning retractor comprises a shaft or spool (2) on which a safety belt (1) is to be wound. A sun gear (10) is connected for co-rotation with the shaft. The sun gear (10) is located within a housing (5) which defines a ring gear (7) which substantially surrounds the sun gear (10). A planet gear (17) is provided located between the ring gear (7) and the planet gear (10). A gas generator (9) is provided adapted to generate gas to drive the planet gear (17) around an arcuate path between the ring gear (7) and the sun gear (10). The exterior surface (18) of the sun gear (10) is not provided with teeth but is formed of a deformable material. On operation of the device, the planet gear (17) effectively cuts teeth in the deformable material forming the operative surface (18) of the sun gear (10). Alternatively the ring gear or the planet gear may be provided with the surface of deformable material.

Description

DESCRIPTION OF INVENTION "IMPROVEMENT8 IN OR RELATING TO A PRE-TEN8IONING RETRACTOR REEL" THE PRESENT INVENTION relates to a pre-tensioning retractor reel for use in a motor vehicle such as a motor car.

It has been proposed before to provide a pretensioning retractor reel, and such reels serve the function of taking up any slack that may exist in a seat belt, and tightening the seat belt across the lap and torso of the driver of or passenger in a motor vehicle, in the event that an accident should occur.

If a seat belt is not correctly and relatively tightly positioned across the lap and torso of the driver or occupant of a motor vehicle, in the event that an accident occurs that involves a rapid deceleration of the vehicle, the driver or occupant of the vehicle may move forwardly relative to their seat by a substantial distance before the safety belt even begins to retard their movement relative to the vehicle. A situation may thus develop where, even though a safety belt is being used, the driver or occupant collides with a relatively fixed part of the interior of the vehicle such as the steering wheel or the windscreen. It is thus desired to tighten the safety belt as soon as an accident is sensed in order to minimise the risk of this occurring.

Various proposals have been made for retractor reels adapted to pre-tension safety belts. Generally speaking the pre-tensioning mechanism must be disconnected from the spool of the retractor reel under ordinary circumstances to enable the seat belt to be used in the ordinary way, but must engage the spool of the retractor to wind in the safety belt when an accident occurs.

EP-0,581,288-A discloses a pre-tensioning seat belt retractor reel in which an extension of the spool comprises a toothed "sun" wheel that forms part of a planetary gear arrangement. The planetary gear arrangement comprises an outer ring gear which is fixed in position in such a way that the ring gear cannot rotate relative to the housing.

An intermediate planet gear has teeth adapted to engage the teeth on the sun gear and the teeth on the ring gear. A pyrotechnic charge is provided which is ignited in the event that an accident is sensed, and hot gas from the pyrotechnic charge drives the planet gear around an annular path that surrounds the sun gear. As the planet gear traverses this arcuate path, the sun gear is caused to rotate, thus drawing in any slack present on the seat belt and tightening the seat belt.

In the initial condition of the apparatus described in the European Specification, the planet gear engages the ring gear, but does not engage the sun gear. When the pyrotechnic charge has been ignited, the planet gear is moved from its initial position and is thus brought into contact with the sun gear. If the teeth of the planet gear are co-aligned with the spaces between the teeth of the sun gear, it is not envisaged that a problem will arise.

However, if the gears are brought into contact when the teeth on the planet gear are precisely aligned with the teeth on the sun gear, then the whole mechanism could jam.

The present invention seeks to provide an improved pre-tensioning retractor reel.

According to this invention there is provided a pre-tensioning retractor reel comprising a shaft or spool on which a safety belt is to be wound, and a gear arrangement comprising a sun gear, a housing containing the sun gear, the housing defining a ring gear which substantially surrounds the sun gear, and a planet gear located within the housing, one gear selected from the sun gear and the ring gear being connected for co-rotation with the shaft or spool, the other of said gears being fixed in position, gas generator means adapted to supply gas to cause the planet gear to follow a predetermined path between the ring gear and the sun gear, in engagement with the ring gear and the sun gear, thus rotating the shaft or spool on which the safety belt is wound, one gear selected from the sun gear being provided with an operative surface that is formed of a deformable material, the other gears being provided with operative surfaces that are formed with teeth.

The ring gear may be the gear provided with the operative surface of deformable material, but alternatively, the sun gear is the gear provided with the operative surface of deformable material.

The housing and the gears may be formed of metal, the surface of deformable material being formed of a deformable metal, such as aluminium.

Alternatively the housing and the gears may be formed of a plastics material, the deformable material comprising a foamed plastics material.

In one embodiment the sun gear is connected for corotation with the shaft, and is provided with the operative surface of deformable material.

Two gas generator means may be provided and preferably a first of the two gas generator means is adapted to provide gas initially to move the planet wheel and the second of the gas generator means is adapted to supply gas to move the planet wheel after the planet wheel has traversed a predetermined portion of its predetermined path.

In another embodiment the ring gear is connected for co-rotation with the shaft, and is provided with the operative surface of deformable material.

It is to be noted that, in the preferred embodiments of the invention, the planet gear, together with the gear that will remain stationary, are provided with teeth. The gear that will co-rotate with the shaft or spool is preferably provided with the deformable surface.

Initially, the planet gear is located in a position where it is in contact with the fixed toothed gear, but is separated from the gear that is provided with the deformable operative surface. When the planet gear moves, as a consequence of the gas generator generating gas, a planet gear is forced to rotate because it is in engagement with a fixed toothed gear. The toothed periphery of the planet gear then comes into contact with the deformable operative surface of the movable gear, deforming that surface and causing the movable gear to rotate, thus rotationally driving the shaft or spool.

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 an exploded perspective view of some of the principal parts of a pre-tensioning retractor reel, FIGURE 2 is a vertical sectional view taken transversely of the axis of the retractor reel of Figure 1, illustrating the arrangement when assembled, FIGURE 3 is a part elevational, part sectional view taken in a plane perpendicular to the plane of Figure 2 again further illustrating parts of the retractor reel in an exploded condition, FIGURE 4 is a sectional view, corresponding to Figure 2, illustrating an alternative embodiment of the invention, FIGURE 5 is another sectional view illustrating another modified embodiment of the invention, FIGURE 6 is another sectional view illustrating another modified embodiment of the invention, and FIGURE 7 is a view of a complete retractor, such ass the retractor of Figure 1.

FIGURE 8 is a sectional view taken on the line VIII-VIII of Figure 9, illustrating a further modified embodiment of the invention, and FIGURE 9 is a view taken on the line IX-IX of Figure 8.

Referring initially to Figures 1 to 3 of the accompanying drawings, a retractor reel incorporates various components, as illustrated. One end of a safety belt 1 is connected to a shaft or spool 2. One end of the shaft passes through an aperture 3 formed in a substantially circular end wall 4 of a housing 5. The housing 5 has a peripheral cylindrical wall 6. The interior of the cylindrical wall 6 is toothed to form a ring gear 7. The ring fear is not a complete ring, but extends over a substantial angle of arc.

A tubular extension 8 extends substantially tangentially from the cylindrical wall 6 of the housing 5, and contains a pyrotechnic gas generator 9.

A sun gear 10 is located within the housing 5 and is connected to the end of the spool or shaft 2 for rotation therewith. The sun gear 10 is substantially surrounded by the ring gear. The sun gear 10 carries an axially extending shaft 11 which terminates with a transverse slot 12. The shaft 11 is intended to pass through an aperture 13 provided in an end cover 14, the aperture 13 defining a bearing for the shaft 11. A helical spring 15 is provided having an inner end portion 16 adapted to engage the slot 12. The outer part of the helical spring is fixed in position (not shown). The spring 15 applies a winding force to the shaft 11, thus causing the spool 2 to apply tension to the seat belt 1.

A planet gear 17 is provided in the form of a toothed cylinder adapted to be located in position in engagement with the teeth 7 defining the ring gear within the housing 6 and also adapted to engage the sun gear 10.

The operative exterior surface 18 of the sun gear 10, which is to co-operate with the planet gear 17, is not toothed, but instead is formed of a deformable material.

When the illustrated components are initially assembled, the planet gear 17 is located in position adjacent the lower end of the tangential tubular extension 8, as shown in Figure 2. Teeth of the planet gear 17 engage teeth forming the ring gear 7. The planet gear 17 is spaced from the outer surface 18 of the sun gear 10. The planet gear may be maintained in this position by a small projection provided for that purpose on the cover 14 which, on actuation of the device, is intended to break.

In the event that an accident occurs, an appropriate sensor generates a signal which activates the pyrotechnic charge 9. A quantity of gas is generated. The gas moves the planet wheel 17 from the initial position illustrated in Figure 2. The planet wheel initially moves downwardly, and because the teeth of the planet wheel engage the ring gear 7, the planet wheel rotates in a counter-clockwise direction. After a brief movement the teeth of the planet wheel engage the outer surface 18 of the sun gear 10. Since the outer surface 18 of the sun gear 10 is formed of deformable material, the teeth of the planet gear deform that material and firmly grip the sun wheel.Continuing rotation of the planet wheel 17, caused by continuing movement of the planet wheel 17 along the arcuate path indicated by the dotted line 20, located between the interior of the ring gear 7 and the exterior of the sun gear 10, causes the sun gear 10 to rotate in the clockwise direction. Due to the relative size of the planet gear 7 and the sun gear 10, the sun gear will effect a plurality of revolutions by the time the planet gear has reached the end of the arcuate path 20, thus substantially tightening the seat belt.

As the planet gear 17 moves along the arcuate path 20, any gas present within the housing in front of the planet gear may be evacuated from the housing through an appropriate vent, such as vent 21 as shown in Figure 2.

In the embodiment of Figures 1 to 3, reference has been made to a pyrotechnic gas generator. The gas generated by such a pyrotechnic gas generator may be relatively hot. Consequently, the housing 5 is preferably made of a material such as steel, with the planet gear and the sun gear also being made of steel, the outer deformable surface of the sun gear being formed of a soft metal, such as aluminium. It is to be understood that in operation of the device the teeth of the planet gear 17 effectively cut or form co-operating teeth in the aluminium that forms the deformable outer surface 18 of the sun gear 10. Initially the outer surface 18 does not have any teeth, but the teeth are formed as the planet gear 17 moves round the sun gear 10.

Of course, other metals having the appropriate mechanical properties could be utilised.

Since a metal such as aluminum is not deformed elastically, the size of the sun gear is selected so that when the sun gear has effected almost one revolution, so that a deformed part of the outer surface again engages the planet gear, the teeth of the planet gear are substantially aligned with the recesses that have been formed in the outer surface of the sun gear.

In modified embodiments of the invention, instead of using a pyrotechnic gas generator, a supply of compressed gas in a bottle could be utilised as the gas generator, meaning that the gas would not be emitted at an elevated temperature. This would enable the use of alternative materials for the housing, the gear and for the sun wheel. All these components could, in such an embodiment, be made of an appropriate plastics material.

The deformable surface of the sun gear can be a permanently or non-elastically deformable material such as aluminium as mentioned above. However, the deformable surface could be resiliently deformable, and in an embodiment which does not utilise a pyrotechnic source of gas, the deformable material could comprise a foamed plastics material, preferably with a yieldable skin, or even a bristled or carpet-like material. The deformable surface should be such that it may be firmly gripped by the co-operating toothed gear member, to form a substantially gas-tight seal.

If an elastically deformable material is used the gears may be of any size, since there is no need to ensure that the teeth of the toothed gear should engage recesses already formed in the deformable surface.

In the embodiment of Figures 1 to 3, the sun gear has a deformable outer surface. However, it is to be appreciated that in a modified embodiment of the invention, the sun gear could have a toothed outer surface, with the planet gear initially being in contact with the sun gear, and the interior surface of the housing, that is to say, the surface that defines the ring gear in the embodiment of Figures 1 to 3, could be provided with the deformable surface.

In yet another modified embodiment of the invention, the sun gear and the ring gear could be provided with teeth and the planet gear could be provided with a deformable outer surface.

Since, in each of these arrangements, at least one gear does not initially have any teeth, the risk of jamming, as encountered in the arrangement of EP-0581288-A, is substantially eliminated.

Referring now to Figure 4, a modified embodiment of the invention is illustrated. In this embodiment, in addition to the pyrotechnic gas generator 9, as described in the embodiment of Figures 1 to 3, the tangential extension 8 accommodates a second pyrotechnic gas generator 29. The gas outlets of both of the gas generators are directed to drive the planet gear 17 around the arcuate path 20. The gas generators 9 and 29 may be activated simultaneously or, alternatively, one of the gas generators may be activated initially, with the other of the gas generators being activated after a brief delay.

In the embodiments of Figures 1 to 4, the gas generators extend substantially tangentially relative to the axis of the retractor. Figure 5 illustrates an alternative arrangement in which two gas generators 30,31 are provided which have axes which extend substantially parallel with the axis of the retractor. Consequently in Figure 5 only the outlet ports for the gas generators 30,31 are visible. These outlet ports communicate with a chamber 32, which subsequently directs the flow of gas from the gas generators 30 and 31 to the planet gear 17 to move the planet gear 17 around the arcuate path 20.

Figure 6 illustrates a further alternative arrangement in which two gas generators 33,34 are provided, these gas generators again being such that they have axes extending parallel to the axis of the retractor reel. The gas generator 33 is located to supply gas to the planet gear 17 to drive the planet gear 17 around the arcuate path 18. The gas generator 34, however, has its outlet connected to part of the arcuate path 20 which is spaced from the initial position of the planet gear 17. The arrangement shown in Figure 6 is thus intended to operate with the gas generator 33 initially providing gas which drives the planet gear 17 part way along the arcuate path 20, with the second gas generator 34 then generating gas to assist in the continual movement of the planet gear 17 around the arcuate path 20.

Figure 7 illustrates a complete retractor, such as the retractor of Figure 1. The housing 5, together with the tangential projection 8, carries an end cap 40, which covers the spring 15. The radially outer-most end of the spring 15 will be connected to the cap 40.

A cylindrical housing portion 41 extends from the other side of the housing 5, to define a cavity which receives the safety belt 1 when it has been wound on to the shaft or spool 2. A further end cap 42 is mounted on the housing 41. The end cap 42 defines a bearing which supports the end of the spool or shaft 2 remote from the housing 5. The end cap 42 also accommodates a locking mechanism adapted to lock the shaft or spool in the event that an accident is detected. Such locking mechanisms are conventional. The locking mechanism is adapted to permit safety belt to be wound on to the spool when the locking mechanism is locked, but to prevent safety belt being paid out from the spool.

A sensor 43 is provided which is adapted to activate the pyrotechnic gas generator 9. The sensor 43 may be an impact sensor.

Referring to Figures 8 and 9, a further modified embodiment of the invention is disclosed. Many of the details of the design are similar to or identical with the embodiments described above.

In the embodiments of Figures 8 and 9, the shaft or spool 50 on which the seat belt is wound is connected to a plate 51 which carries, at its outer edge, an upwardly extending flange 2 which carries the ring gear on its inner face. In this embodiment the inner face 53 of the flange 52 is formed of a deformable material.

A housing 54 is provided which totally surrounds the plate 51 and the flange 52. The shaft 50 emerges from the housing 54 through an appropriate aperture 55.

The wall 56 of the housing opposite the aperture 55 is provided with an inwardly directed boss 57, which has a toothed outer periphery 58 defining a sun gear. An axial bore 59 is defined in the boss 57 which contains a pyrotechnic charge 60.

A radially extending duct 61 is provided extending from the pyrotechnic charge 60, to the space between the sun gear and the ring gear.

A part of the boss 57 adjacent the duct 61 extends, in the form of a sealing arm 62 substantially across the space between the sun gear and the ring gear. The forwardly directed face of the arm 62, that is to say the face immediately adjacent the duct 61, carries a tangentially extending projection 63 which initially engages a planet gear 64 located between the ring gear and the sun gear, the peg 63 holding the planet gear 64 which has a toothed periphery in engagement with the toothed periphery of the sun gear, whilst keeping the toothed periphery of the planet gear slightly spaced from the inner surface 53 of the ring gear 52.

The rear face of the arm 62 defines a recess 65 adapted to accommodate the planet gear 64 when it has completed a predetermined motion, and a gas outlet vent 66 is provided to permit gas to be exhausted from the interface between the ring gear and the sun gear.

When the pyrotechnic charge 60 is activated, gas flows through the passage 61, directly impinging upon the planet gear 64. The planet gear then becomes disengaged from the peg 63. The toothed exterior of the planet gear 64 is in engagement with the toothed exterior of the sun gear 58, and as the planet gear begins to follow the arcuate path defined between the ring gear and the sun gear, the planet gear rotates, about is own central axis, in a counter-clockwise direction. The exterior of the planet gear engages the interior surface 53 of the flange 52 forming the ring gear, causing the ring gear to rotate.

The planet gear follows the arcuate path between the ring gear and the sun gear in a clockwise direction as shown in Figure 9. Any gas present in the inter-space between the ring gear and the sun gear becomes compressed by this movement of the planet gear, but the compressed gas escapes through the air vent 66. The planet gear 64 moves until it reaches the recess 65 formed in the radially extending arm 62.

Claims (16)

CLAIMS:

1. A pre-tensioning retractor reel comprising a shaft or spool on which a safety belt is to be wound, and a gear arrangement comprising a sun gear, a housing containing the sun gear, the housing defining a ring gear which substantially surrounds the sun gear, and a planet gear located within the housing, one gear selected from the sun gear and the ring gear being connected for co-rotation with the shaft or spool, the other of said gears being fixed in position, gas generator means adapted to supply gas to cause the planet gear to follow a predetermined path between the ring gear and the sun gear, in engagement with the ring gear and the sun gear, thus rotating the shaft or spool on which the safety belt is wound, one gear selected from the sun gear being provided with an operative surface that is formed of a deformable material, the other gears being provided with operative surfaces that are formed with teeth.

2. A retractor according to Claim 1 wherein the ring gear is the gear provided with the operative surface of deformable material.

3. A retractor according to Claim 1 wherein the sun gear is the gear provided with the operative surface of deformable material.

4. A retractor according to any one of the preceding Claims wherein the housing and the gears are formed of metal, the surface of deformable material being formed of a deformable metal.

5. A retractor according to Claim 4 wherein the said deformable metal comprises aluminium.

6. A retractor according to any one of Claims 1 to 3 wherein the housing and the gears are formed of a plastics material, the deformable material comprising a foamed plastics material.

7. A retractor according to any one of the preceding Claims wherein the sun gear is connected for co-rotation with the shaft, and is provided with the operative surface of deformable material.

8. A retractor according to any one of the preceding Claims wherein two gas generator means are provided.

9. A retractor according to Claim 8 wherein a first of the two gas generator means is adapted to provide gas initially to move the planet wheel and the second of the gas generator means is adapted to supply gas to move the planet wheel after the planet wheel has traversed a predetermined portion of its predetermined path.

10. A retractor according to any one of Claims 1 to 6 wherein the ring gear is connected for co-rotation with the shaft, and is provided with the operative surface of deformable material.

11. A pre-tensioning retractor substantially as herein described with reference to and as shown in Figures 1 to 3 and 7 of the accompanying drawings.

12. A pre-tensioning retractor substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings.

13. A pre-tensioning retractor substantially as herein described with reference to and as shown in Figure 5 of the accompanying drawings.

14. A pre-tensioning retractor substantially as herein described with reference to and as shown in Figure 6 of the accompanying drawings.

15. A pre-tensioning retractor substantially as herein described with reference to and as shown in Figures 8 and 9 of the accompanying drawings.

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