GB2170094A

GB2170094A - Safety belt reel

Info

Publication number: GB2170094A
Application number: GB08501136A
Authority: GB
Inventors: Artur Fohl
Original assignee: TRW Occupant Restraint Systems GmbH
Current assignee: TRW Occupant Restraint Systems GmbH
Priority date: 1985-01-17
Filing date: 1985-01-17
Publication date: 1986-07-30
Also published as: GB8501136D0; GB2170094B

Abstract

A safety belt reel comprises equipment for the locking of the belt (5) as well as a belt tightening device (7, 8, 9) which is triggered automatically in the event of danger. The locking equipment is associated with a control disc (12) which, when locked, is rotatable within limits relative to the belt spool (4) for actuation of a locking pawl. The control disc is connected with an inertia disc (16), which represents a trigger sensitive to the belt acceleration and which, when triggered, effects relative rotation of the spool (4) and control disc (12) through its inertia. The inertia disc (16) is so connected to the control disc (12) by a coupling element, such as a frangible pin, a slipping clutch, or a ratchet mechanism, that the inertia disc is rotatable relative to the control disc while overcoming the coupling force when a predetermined belt tightening acceleration is exceeded. <IMAGE>

Description

SPECIFICATION Safety belt reel The present invention relates to a safety belt reel.

In known safety belt reels, a control disc, consisting of for example plastics material, is mounted on a belt spool to be rotatable within limits set by abutment and serves to transmit a control movement from a sensor to a pawl-locking device and to effect a locking of the belt spool. In this case, it is known to provide, at the external circumference of the control disc, a toothing which co-operates with a deceleration and/or acceleration sensitive sensor, for example a ball sensor, so that the control disc is instantaneously locked by an appropriate pawl on the triggering of the sensor This causes a relative movement of the control disc and the spool provided with the pawl-locking device, which relative movement acts by way of a control can at the control disc to effect displacement of the locking pawl of the pawl-locking device into a stationary toothing.It is also known to firmly arrange at the control disc an inertia mass disc, for example of metal, which in the event of strongly accelerated belt withdrawal from the spool effects a relative rotation of the control disc and spool as a consequence of the mass disc inertia, which relative rotation is again utilised for displacement of the locking pawl. If a safety belt reel of that kind is now provided with a belt retightening device, for example a cable pulley coupled to the spool, a retightening cable, a drive piston and a pyrotechnic drive, then on triggering of the drive the spool is set into reverse rotation at a very high angular acceleration to effect tightening of the belt. This rotational direction is opposite to the normal dispensing direction of the belt.In the event of this extreme reverse rotation, the entire locking system is co-rotated, since the control disc is rotatable relative to the spool only through a certain angular travel, i.e. that determined by the abutment. On termination of the belt tightening process, the spool is braked abruptly when the belt comes to bear against the body of the person to be protected, while the masses loosely mounted thereon, for example the control disc and particularly the mass disc, exert a very high force on the downstream control elements. This can lead to destruction of these parts, particularly when the reel has a lightweight construction, i.e. the control elements and the like are made of a light plastics material.

It would thus be desirable to ensure that potentially destructive influences do not act on the belt spool locking equipment during the tightening phase, even in the case of a reel of lightweight construction.

According to the present invention there is provided a safety belt reel comprising a belt spool rotatable in one direction for spooling of a belt thereon and in the opposite direction for unspooling of such belt, a control element mounted to be rotatable with the spool, means to lock the control element against such rotation thereby to cause relative rotation of the control element and spool, means responsive to relative rotation of the control element and spool to lock the spool against rotation in said opposite direction, an inertia body connected to the control element to cause relative rotation of the control element and spool to take place when acceleration of the spool in said opposite direction of rotation exceeds a predetermined value, and belt tightening means operable to rotate the spool in said one direction of rotation, the inertia body being connected to the control element by coupling means arranged to permit relative rotation of the control element and inertia body when acceleration of the spool in said one direction of rotation exceeds a predetermined value.

Through the particular connection of the inertia body to the control element, when a predetermined belt tightening acceleration is exceeded, the firm coupling of the inertia body and control element is released and the inertia body can be freely rotatable relative to the control element so as to freely run on like a flywheel. In this manner, the forces emanating from the relatively large mass of the inertia body do not transfer to the remaining parts of the spool locking equipment so that a destruction of the same may be able to be avoided.

The coupling means can be a frangible element or a slipping clutch. Preferably, however, the coupling means is a ratchet detent coupling. In that case, the coupling function is maintained even after the over-coming of the coupling force, i.e.

driving of the control disc by the inertia body is possible directly after the belt tightening process.

Disturbing influences, such as frictional or environmental influences, can be avoided.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic perspective view of a safety belt reel embodying the invention; Figures 2a and 2b are an exploded perspective view and a cross-sectional view, respectively, of the coupling between control disc and mass disc in a first safety belt reel embodying the invention; Figures 3a and 3b are an exploded perspective view and a cross-sectional view, respectively, of the coupling between control disc and mass disc in a second safety belt reel embodying the invention; and Figures 4a, 4b, and 4c are an exploded perspective view, a cross-sectional view and a sectional front view, respectively, of the coupling between control disc and mass disc in a third safety belt reel embodying the invention.

Referring now to the drawings, there is shown in Figure 1 the basic construction of a safety belt reel embodying the invention, the reel comprising a belt spool 4, on which is reeled a flexible belt 5 and which is rotatably mounted between the limbs 1 and 2 of a U-shaped frame 3. A spool return spring, a belt tightening device and a spool locking device (not shown) are disposed in engagement with the spool 4. One component of the tightening device is, for example, a cable pulley 6, which, when locking of the spool is to occur, is couplable with the spool 4 and on which is wound a cable 7.

The cable is connected with a piston within a cylinder 8, which at a pressure side thereof communicates with an electrically ignitable pyrotechnic drive set within a housing 9. On ignition of the drive set, the piston in the cylinder is moved upwardly (in Figure 1), in connection with coupling of the pulley 6 with the spool, rotation of the spool in the belt tightening direction, and tightening of the belt 5 until contact with the body of the person to be protected. The pulley 6, and possibly also the spool return spring, lie within a cover 10. Disposed on the other side of the frame 3, also largely within a cover 11, is a pawl-locking device comprising a locking pawl, which is pivotably mounted on, for example, a flange of the spool 4 and co-operates with a stationary locking toothing arranged at the limb 2 of the frame 3.A control disc 12, which has an external control toothing 13 and is arranged externally of the cover 11, is mounted on a shoulder of the spool 4 to be freely rotatable against the force of a spring (not shown) through a predetermined angular travel. The toothing 13 co-operates with a control lever 14 of a ball sensor 15 sensitive to deceleration and/or acceleration, in particular of a vehicle in which the reel may be mounted. Connected with the control disc 12, which may consist of plastics material, is a metallic mass disc 16, which represents a sensor sensitive to acceleration of the spool 4 on withdrawl of the belt. The sensor 15 reacts on a sudden vehicle deceleration or acceleration in such a manner that the control lever 14 engages in the toothing 13 and locks the control disc 12.As a result, a relative movement takes place between the spool 4, which still rotates, and the locked control disc 12. In that case a control projection, for example the projection 12a shown in Figure 2a, runs up against the control pawl in the interior of the cover 11 and resets this into the stationary locking toothing, whereby the spool 4 is also locked. As an alternative to this, locking of the spool 4 can be initiated by way of the sensor sensitive to spool acceleration, i.e. the mass disc 16, in that the rotational movement of the control disc 12 connected with the disc 16 lags behind that of the spool 4, due to the inertia of the disc 16, in the case of strongly accelerated withdrawl of the belt and the locking pawl is also displaced into the locking setting through the resulting relative movement of the control disc 12 and the spool.

Illustrated in Figures 2 to 4 are three different ways in which the control disc 12 and disc 16 can be coupled together so that the disc 16, on a predetermined belt tightening acceleration being exceeded, is rotatable relative to the control disc after overcoming of the coupling force between the disc 16 and control disc 12, which ensures that the forces emanating from the disc 16 do not act deleteriously on the associated parts, such as control disc, locking pawl and the like. As already mentioned, the control disc is so mounted on the spool 4 that it is capable of rotating against the force of a spring relative to the spool through a certain angular travel. In normal operation, the control disc 12 rotates together with the spool 4.In that case the control disc bears, for example through the force of the afore-mentioned spring, against an abutment, by which the control disc 12 is entrained during the belt spooling movement. On triggering of one of the sensors, the control disc 12 is either locked by means of the sensor 15 or braked by means of the inertia of the disc 16, so that the relative movement necessary for the actuation of the locking pawl takes place between the control disc 12 and the spool 4 which is rotating in the direction of arrow a (unspooling direction). During the belt tightening operation, the spool 4 rotates in the opposite direction b, i.e. the spool 4 during this movement entrains the control disc 12 and mass disc 16.The forms of coupling illustrated in Figures 2 to 4 have the effect that the mass disc 16 does not need to follow the rotational movement of the control disc 12 after the occurrence of the belt tightening pulse.

In the case of the embodiment according to Figures 2a and 2b, the control disc, as in the case of the remaining embodiments, has an axial bearing projection 12b by which it is rotatably mounted, limited by abutment, in the spool 4. The bearing projection 12b has a radially extending control projection 12a, through which the locking pawl co-operable therewith is driven in the event of relative movement of the spool and control disc. On the other side, the control disc 12 has a further bearing projection 12c, on which the mass disc 16, provided with a corresponding bearing opening 16a, is rotatably mounted. The disc 16 is held in axial direction against the disc 12 by a spring-like axial securing member 17 which engages in a groove 18 of the projection 12c.Eccentrically arranged on the control disc 12 is a shear pin 19 which is, for example, injection-moulded on the disc and which passes through an opening 20 in the disc 16, the pin 19 representing an entraining member for the disc 16 in the case of normal actuation of the reel.

On the occurrence of extreme angular acceleration during the belt tightening process, the pin 19 breaks and allows the disc 16 to freely rotate. The relatively heavy disc 16, for example of metal, therefore rotates due to the belt tightening pulse like an impelled flywheel.

In the embodiment according to Figures 3a and 3b, a slipping clutch in the form of a plate spring 21 is provided as the coupling between control disc 12' and mass disc 16. The spring 21 is mounted on the bearing projection 12c' of the control disc 12' and resiliently biassed relative to the mass disc 16 by the axial securing member 17.

Due to the frictional force exerted by the spring 21, the mass disc 16 is entrained by the control disc 12' in normal operation. The frictional force is overcome merely on the occurrence of an increased angular acceleration and the control disc 12' rotates without the mass disc 16. In this case, the coupling between the control disc 12' and mass disc 16 is maintained except in the case of the extreme angular acceleration, so that the sensor, sensitive to belt acceleration in the form of the disc 16 can become effective after the belt tightening process.

In the embodiment according to Figures 4a to 4c, the mass disc 16' is again rotatably mounted on a bearing projection 12c" of the control disc 12" and secured axially through the axial securing member 17. In this case, the opening 16a' of the disc 16' possesses an internal toothing 22. Disposed in the bearing projection 12c", i.e. in the bearing hub of the control disc 12', is a substantially tangential recess 23, into which is inserted and detented a ratchet leaf spring 24 constructed as spring platelet of metal or plastics material. The free end portion of the spring 24 resiliently engages in the toothing 22 of the disc 16' in such a manner that in the case of normal rotation of the spool 4 and in the case of the locking process, i.e. on rotation of the spool 4 in the direction of arrow a according to Figure 1 - a fixed coupling exists between the control disc 12" and the disc 16', i.e. both parts are connected with each other to be secure against relative rotation. Merely in the case of the extremely rapid rotation of the spool 4 in the direction b, i.e.

during the belt tightening process, is the force of the coupling engagement of the ratchet spring 24 overcome and the disc 16' freed from the control disc 12" so that it can rotate relative to the control disc and need not follow the rotational movement of the control disc. A ratchet coupling of the two parts is thus provided.

Claims

1. A safety belt reel comprising a belt spool rotatable in one direction for spooling of a belt thereon and in the opposite direction for unspooling of such belt, a control element mounted to be rotatable with the spool, means to lock the control element against such rotation thereby to cause relative rotation of the control element and spool, means responsive to relative rotation of the control element and spool to lock the spool against rotation in said opposite direction, an inertia body connected to the control element to cause relative rotation of the control element and spool to take place when acceleration of the spool in said opposite direction of rotation exceeds a predetermined value, and belt tightening means operable to rotate the spool in said one direction of rotation, the inertia body being connected to the control element by coupling means arranged to permit relative rotation of the control element and inertia body when acceleration of the spool in said one direction of rotation exceeds a predetermined value.

2. A safety belt reel as claimed in claim 1, the means to lock the spool comprising a pawl actuable by the control element when rotated relative to the spool.

3. A safety belt reel as claimed in either claim 1 or claim 2, the coupling means comprising a frangible element arranged to break when the spool acceleration in said one direction of rotation exceeds the respective predetermined value.

4. A safety belt reel as claimed in either claim 1 or claim 2, the coupling means comprising a slipping clutch arranged to slip when the spool acceleration in said one direction of rotation exceeds the respective predetermined value.

5. A safety belt reel as claimed in either claim 1 or claim 2, the coupling means comprising a ratchet detent coupling arranged to be overridden when the spool acceleration in and only in said one direction of rotation exceeds the respective predetermined value.

6. A safety belt reel as claimed in claim 5, wherein the ratchet detent coupling comprises a leaf spring mounted at one end portion in one of the control element and the inertia body and engaging at its other end portion in a toothing of the respective other one of the control element and the inertia body.

7. A safety belt reel substantially as hereinbefore described with reference to Figures 1, 2a and 2b of the accompanying drawings.

8. A safety belt reel substantially as hereinbefore described with reference to Figures 3a and 3b of the accompanying drawings.

9. A safety belt reel substantially as hereinbefore described with reference to Figures 4a, 4b and 4c of the accompanying drawings.