GB2063055A - Locking device for seat belt retractor - Google Patents

Abstract

A locking seat belt retractor has a paw 6 pivoted at 7 and carrying on an extension a trip lever 11. When belt or vehicle acceleration reaches a predetermined level the trip lever is moved eg by a ball 10 into engagement with a ratchet wheel 5 on the reel shaft. Subsequent movement of the wheel causes pawl 6 to be pivoted into locking engagement with the ratchet wheel. The pawl is held in its inoperative position by a spring 8. <IMAGE>

Description

SPECIFICATION Locking device for seat belt retractor The invention relates two a locking device for a belt retractor for safety belts, in particular in motor vehicles, having a winding shaft and a ratchet wheel with locking teeth mounted thereon, with which, upon response of a sensor system, a movable pawl can be brought into locking engagement, the sensor system comprising a movable trip lever and responding to accelerations of the belt webbing extraction and/or of the vehicle in excess of limit value.

Such device is known from U.S. Pat. 3,918,658.

There, an inertia wheel with teeth is located on the outside of a flange of the belt retractor housing, and under it the trip lever is rotatably arranged so that its free end opposite the point of articulation can be brought into engagement with the teeth of the inertia wheel. This occurs when a threshold value is exceeded upon acceleration, deceleration or overturn of the vehicle. Upon rapid extraction of the belt webbing, the inertia wheel is thereby prevented from turning and rotates via two connected gears, so that via an actuating arm the pawl engages with the ratchet wheel.

In this known device one achieves a separation of pawl and trip lever, because these two parts have considerably different functions in the belt retractor.

The pawl must absorb the entire force via the teeth of the ratchet wheel at the moment of accident, while the trip lever should transmit only the accident signal given by the sensor system for triggering an engagement function.

At many motor vehicle manufacturers, narrow locking tolerances are demanded, i.e. the belt retractor must lock in a narrow and exact acceleration range. Frequently the meshing teeth of the ratchet wheels and the pawls are not ideally aligned, and it may happen that the tips of the teeth and the pawls hit, so that valuable time is lost while the winding shaft continues to turn and the belt webbing can be drawn further out of the belt retractor. After a delay the skipping tooth tips can finally engage in the counter-serration and lock the retractor. The uncertainty range from the state just before engagement in the counter-serrations to the final and complete engagement state is thereby increased.

The known belt retractor has disadvantageously, a rather complicated mechanism with an inertia wheel, gear train, lever transmissions, etc. Similarly complicated are also other known tripping devices which have very many interacting parts.

Known also is a synchronization disk of spring steel, which acts as return spring for the ratchet wheel in direction of rotation in such a way that in the normal case it is always maintained in its initial position, i.e. out of the locking position. In this form of realization, if the winding shaft is rotated in the normal case at a winding speed not exceeding a certain speed, the ratchet wheel will thus be in inoperative position out of locking engagement. Upon extraction of belt webbing at a high winding acceleration, the synchronization disk turns a distance, fasterthan the ratchet wheel, which through drivers turns a distance relative to the winding shaft in a sector-shaped recess.By ramp-type parts the synchronization disk is stretched and externally displaced so that the teeth of the synchronization disk present on the circumference engage with drivers of the pawl and in this manner cause the locking in the ratchet wheel. This device has several advantages, but like other known locking devices it has a plurality of sepa rate parts, in particular flywheel or a synchronization disk, which must first be rotated a distance before engagement with the next part. As a result, valuable time and extracted belt length are lost.

Important in all these devices is the rapid engagement and the complete engagement of the pawl in a tooth of the ratchet wheel.

The purpose of this invention therefore is an inter playofthe movementofthe rotating ratchetwheel and of the pawl better matched in time, in other words, a synchronization to make the locking device safer.

In all known devices with necessarily existing parts there are, of course, tolerances. If the chain of such tolerances is long, in other words, if there is a plurality of interengaging parts, the risk referred to above exists that an exact function is jeopardized, so that the locking device is not safe enough. One has tried, therefore, to keep the sum of the tolerances small, which of course necessitates high precision and hence expensive components.This is especially important in so-called automatics, i.e. belt retractors where the user can, in the normal case, pull out belt webbing slowly as desired and let it go back into the housing, i.e. carry out slow movements in the buckled state, while at the moment of accident prompt locking is demanded and has already been assured with more or less reliability in such a way that after locking the belt webbing can no longer be pulled out of the retractor, or hardly so.

To make the locking device of known design safer, this invention, therefore, proceeds from the idea to provide a complete and correct engagement between pawl and tooth of the ratchet wheel, in particularto let the pawl run against the flank of a tooth in the ratchet wheel when the gap between two teeth is arranged in the correct position next to the tip of the pawl. A further idea of the invention is the design of the device in such a way that there are only few parts, so that the necessarily existing tolerances cannot sum up to an undesirably high value.

The task of the invention therefore is the creation of a locking device of the initially explained kind with which, using a smaller number of components, a greater safety in locking is ensured by the fact that impingement of a tip or edge of the pawl on the tip of a tooth of the ratchet wheel is prevented and engagement always occurs when the matching parts are in the right position.

This problem is solved according to the invention in that the pawl is rotatable about a shaft secured to the housing, is spring-tensioned in inoperative position, and comprises a rear extension lever on which the trip lever is disposed in such a way that the pawl can be pressurized with a torque by the trip lever.

While in known locking devices the pawl tilts on a plate about an imaginary axis, driven by more or less many levers, according to the invention a pawl rotatable about a shaft secured on the housing is provided. Without external intervention, a mechani cal, pneumatic or electric system tensions the pawl in inoperative position, i.e. out of locking engage ment. The trip lever normally also secured on the housing in the known locking devices is disposes according to the invention on the rotatable pawl likewise in a movable and preferably pivotable man ner, namely on a rear extension lever, which open application of pressure or traction in a certain direction spaced from the rotary shaft provides that the pawl is turned counter to the spring tension out of the inoperative position and into the locking position.The trip lever, therefore, is advantageously used to "trigger" the locking process, in that a torque is exterted on the pawl and the latter is forced to rotate about the shaft. Despite the small number of components, in particular with elimination of flywheels, coupling systems, inertia partsorthe like, the initially mentioned separation between trip lever (of lighter and finer design) and pawl is nevertheless provided, which must transmit the full force at the moment of accident. The special advantage of the new system consists in the synchronizing of the movement of the pawl and that of the locking teeth, a timed adjustment of components relative to each other, which only upon engagement at the right instant show the full desired function and effect.

Also this safety is ensured with manufacturing tolerances according to the invention.

According to the invention it is further expedient if on the rear extension lever the sensor system responding to the acceleration of the vehicle is also disposed. It is, of course, quite conceivable to fix the sensor system on the retractor housing, e.g. on a lateral flange next to the pawl, because also in this case action of the sensor system on the trip lever pivotable on the pawl is possible and ensured. But it is especially advantageous to secure the sensor system on the rear extension lever because the synchronization is thereby favored and the construction as a whole is simplified. It is then favorable that the rear extension lever can be made longer, so that the lever effect becomes greater and the response time still shorter.

In advantageous further development of the invention the pawl is formed as a pressureabsorbing pushing member or as a tractionabsorbing hook-shaped member. The member act ing as pawl is, so to speak, the front lever, while the above explained extension lever is provided rearwardly of the shaft about which the entire pawl arrangement is rotatable. It is clearthat as the rear extension lever pivots, automatically a codirectional pivoting of the front pawl member occurs, while the entire pawl rotates about the shaft.According to the invention the construction is devised so that the trip lever pivots the rear extension leverwhen striking against a tooth counterto the spring tension in such a way that the pawl can likewise be moved in front of a locking tooth wheneverthe flank of the locking tooth has not yet been advanced too far against the tip of the pawl, so that tip-to-tip impingement is reli ably obviated. This is favored by the fact that approach of the flank of the locking tooth of the ratchet wheel against the pawl after entrance of the pawl into the preceding tooth gap can occur only after the ratchet wheel is turned by extraction of the belt. This turning will occur automatically at the moment of accident because the passenger to be protected exerts extraction of the belt out of the retractor during forward movement.Thereby impingement of pawl tip on tip of locking tooth is avoided with certainty.

It is further expedient according to the invention if the trip lever comprises a trip arm as well as a first control arm and/or a second control arm. The configuration of the control lever depends on the particular form of the sensor system. For example, the trip arm of the trip lever alone suffices when compressed air issuing at the moment of accident pro videsforthe engagement of the trip lever with a tooth. The same applies when using a solenoid which causes a pivoting of the trip lever into the circle of moving tooth flanks at the moment of accident after excitation. Also a system responding to belt extraction is conceivable, which comes into engagement with the trip lever when a limit value of belt webbing acceleration is exceeded and which pushes the lever into the zone between rotating tooth flanks.In another conception a trip arm of the trip lever may be provided which rests on a metal ball contained in a shell and is pivoted upward at the moment of accident because the metal ball is moved from the lowest point of the shell upward to the edge due to its inertia. These and similar sensor systems determine the form of the respective trip lever.

The first control arm of the trip lever rests e.g. on the inertia body formed as a metal ball and is rigidly connected with the trip arm and at an angle thereto.

In this way the trip arm can be brought into a different position relative to the teeth. In a further form of realization, according to which the trip lever comprises in addition to the trip arm a first as well as a second control arm, the second control arm serves to bring the trip arm into engagement with a tooth when e.g. a system (responding to belt extraction) increases its diameter and these expanded parts then ride against the second control arm, pushing it away. In any case, the importantthing always is to impart a rotary movement to the trip lever, so that its trip arm engages with the teeth in the desired manner. Thereby the locking is then triggered.

In order to avoid advantageously in another embodiment of the invention that for instance also the tip of the trip lever collides with the tip of the locking member, although this is much less harmful than the impinging of the pawl on the locking tooth, one can further provide according to the invention that the trip arm of the trip lever can be brought into engagement with the pointed teeth of a trip cogwheel secured on the ratchet wheel. In this case, there is additionally provided a trip cogwheel dis posed on the ratchet wheel, which may be e.g. a thin plastic disk with pointed teeth on the periphery. The teeth of the trip cogwheel may e.g. be formed considerably more pointed than those of the ratchet wheel, because the trip cogwheel must transm it comparatively smaller forces.The term "pointed" means that the slowly entering trip arm of the trip lever is met by a slender tip of the tooth of the trip cogwheel. The probability of two tips impinging on each other is then negligibly small.

A further advantageous development of the invention is characterized in that the trip cogwheel is fastened to the ratchet wheel by means of two short axle ends and comprises elastic webs directed away from one another and separated by slots. Because of the low but yet not negligible weight of the pawl, so considerable an impact may possibly be exerted at the moment of accident by the trip lever onto the trip cogwheel that the latter would be damaged. In fact, in the instant of impingement of the trip lever the trip cogwheel is loaded by a strong torque, which the cogwheel evades by the fact that the elastic webs permit a slight elastic rotation of the trip cogwheel relative to the ratchet wheel. Usually this involves a rotation of only about 1" or similar small angle.

It is also advantageous according to the invention if the trip arm of the trip lever can be brought into engagement with a projection of a system responding to belt webbing extraction. It has been explained above that the sensor system is to respond also upon too rapid an extraction of the belt webbing, for which purpose one can use a centrifugal system or the like with known mechanisms. In the form of realization where the sensor system responds to excessive belt acceleration, the projection of the response system will then provide for the rotary movement of the trip lever, whereafterthe locking function is automatically reinitiated in the above described manner.

In another embodiment of the invention, the sensor system responding to acceleration of the vehicle and/orofthe belt webbing in excess of a limit value advantageously comprises a bearing part and an inertia body, a solenoid, a compressed air tube or the like.

By the measures according to the invention, the pawl engages with the respective opposite tooth of the ratchet wheel in the desired manner in fitting position and with fitting length. The force or energy which regulates the rotation of the pawl and hence all necessary functions for initiating the locking process derives from the belt webbing pulled out at the moment of accident with necessarily great force.

Thus ample force is available without any great technical expense for bringing about the further necessary processes. Due to the simple measures for avoiding impingement of the tip of the pawl on the tip of the locking tooth, one no longer needs a complicated synchronization system, e.g. an electronic scanning system, using instead according to the invention an elegant and simple solution for rapid, good and correct locking.

It is here of great advantage that the trip lever rides against a rigid part, namely the locking tooth on the ratchet wheel rigidly secured on the winding shaft, or the tooth on the trip cogwheel also rigidly secured on the winding shaft. Evidently, therefore, the tripping function is considerably shorter and faster than is the case in the known devices where the tripping movement is first passed over a rotating wheel, i.e.

over relative displacements of flywheels or the like.

After the moment of accident, when the belt webbing is let go, the force of the return spring and of the pawl-tensioning spring is fully sufficient to rotate the pawl out of locking engagement, for practically only the friction of the pawl with the rotating shaft must be overcome. As the pawl abuts on the flank of the locking tooth at an abtuse angle, no other major force needs be overcome, so that after the accident the device according to the invention immediately comes out of locking engagement, so that the passenger has full mobility again.

Further advantages, features and possibilities of application of the present invention are evident from the following description in connection with the drawings, which show preferred embodiments of the invention. Specifically: Figure 1 showsschematicallya sectional view of a belt retractor according to the invention, wherein the pawl is in inoperative position.

Figure 2 is a similar view as Figure 1, but where the pawl is in locking engagement.

Figure 3 is an enlarged similar view as in Figures 1 and 2, but with a different embodiment of the pawl and the trip lever.

Figure 4 is a top view of a trip cogwheel.

Figure 5 is a similar view as in Figures 1 and 3, but where a system with a projection responding to belt extraction is shown.

Figure 6 is a similar view as Figure 3, where the sensor system comprises a solenoid.

Figure 7 is a similar view as Figure 6, where the sensor system shows a compressed air tube.

Figure 8 is a view of another form of the pawl, where the sensor system is fixed to the housing of the belt retractor.

Figure 9 is a broken off similar view as Figure 6 or 7, where another form of the trip lever is used.

The belt retractor comprises the winding shaft 2, in which the belt webbing 1 is wound. The arrow shown at the upper right in Figures 1 to 3 and 6 to 8 indicates the direction of extraction of the belt webbing 1. In the preferred embodiment shown, flanges 4 of housing 3 are disposed on the retractor housing 3 at right and left, that is, in the representations here selected behind and before the paper plane and parallel thereto. On the winding shaft 2 at least one ratchet wheel 5 with locking teeth 5a is provided, with which the pawl 6 can be brought into engagement, which is rotatable about shaft 7 and isten- sioned in inoperative position by spring 8. In Figures 1 to 5, the spring is a compression spring, but it may, of course, be also an extension spring, leaf spring, torsion spring or the like. In Figures 1,2 and 5, the rear extension lever 6a of pawl 6 is to the right of shaft 7, whereas in the forms according to Figures 6 to 9 it is to the left of shaft 7.

On this rear extension lever 6a, in the forms according to Figures 1 to 7 and 9, the sensor system is disposed, represented here schematically with bearing part 9 in the form of a cup and inertia body 10 in the form of a metal ball. Above the inertia body 10 the trip lever 11 makes contact. In the embodiment according to Figures 6 and 7, the sensor system is not shown with bearing part and inertia body.

Instead, according to Figure 6, a solenoid 15 is pro vided, while in Figure 7 a compressed air tube 1 6a is shown. In Figure 9 the sensor system is again shown with bearing part 9 and inertia body 10, here secured to the rear extension lever 6a, and according to Fig ure 8 fixed to the housing 3 or respectively to flange 4 of the belt retractor.

The embodiments according to Figure 1,2 and 5 involve a pawl formed as a pressure-absorbing, pushing part. It is seen that the rotating locking teeth 5a (incidentally, rotating counterclockwise in all forms of realization with the ratchet wheel 5 rotating upon belt extraction) bear with their flanks against pawl 6, exerting pressure. In the forms according to Figures 3 and 6 to 9, instead, pawl 6 is formed as a traction-absorbing, hook shaped part.

The hook, which is positioned on top in the embodiment shown, must be pivoted to the left for engagement, forwhich reason pawl 6turns counterclockwise in these embodiments, while in the embodiments according to Figures 1,2 and 5 pawl 6 is turned clockwise for locking engagement.

The operation is easy to explain with reference to Figures 1 and 2. In Figure 1, all parts are in inoperative position. Now if an acceleration, deceleration or overturn of the vehicle occurs, the vehicle sensitive sensor system here shown responds in such a way that the inertia body 10 is moved up out of the depression in the support 9 onto the edge, so that consequently the trip lever 11 moves upward into a gap between two locking teeth 5a of the ratchet wheel 5. If the ratchet wheel 5 would not be rotated further, nothing else would happen. But at the moment of accident, automatically there is a pull on the belt webbing 1 in the direction of the shown arrow due to movement of the passenger on the belt, so that ratchet wheel 5 rotates a little counterclockwise.Thereby the trip lever 11 is pushed to the right and exerts a torque on pawl 6, so that the latter assumes the position shown in Figure 2. Compression spring 8 is compressed, and the front tip of pawl 6 snaps into ratchet wheel 5. The length of trip lever 11 is arranged so that the tip of pawl 6 can with certainty enterthe gap between two locking teeth 5a and is pressed against the pressure-exerting flank of the respective locking tooth 5a only after ratchet wheel 5 has been rotated another distance counterclockwise due to further belt extraction. Figure 2 shows the locking position.

Figure 3 shows the other embodiment with the traction-absorbing, hook-shaped part as pawl 6. But here, to avoid the eventuality that the tip of the trip lever rides against the tip of a locking tooth 5a, additionally a trip cogwheel 12 is provided, which is cottered on the ratchet wheel 5 by means of axle ends 13a shown in Figure 4 which are secured thereon.

One sees the pointed teeth of the trip cogwheel 12.

Trip lever 11 has a corresponding angle configuration, to ensure perfect operation. At the moment of accident, the inertia body 10 drives the tip of the trip lever 11 between the pointed teeth of the trip cogwheel 12, whereby a torque occurs on the rear extension lever 6a of pawl 6 and a turning thereof counterclockwise about shaft 7 counter two the force of spring 8. Thus the hook of pawl 6 shown atthetop can enterthe gap between two successive locking teeth 5a and stop the ratchet wheel 5.

For the event that due to the pivoting of pawl 6, whose weight is not immaterial, at the suddenly occuring moment of accident a load by e.g. 30-fold forces due to an acceleration of 30 g is exerted on the trip cogwheel 12, slots 13 according to Figure 4 are provided, by which are formed elastic webs 13b directed away from one another. The trip cogwheel 12 is cotteredon the axle ends 13a secured on ratchetwheeL5 in the mannershown in Figure 4.

Should the above described load or respectively the not inconsiderable torque occur, then these elastic webs 13b cannot cause breaking of the trip cogwheel 12, which is preferably 2 mm thick and made of plastic, even when cold and brittleness of the material would present the other preconditions.

In Figure 5 is shown a system responding to belt extraction in the form of an inverted capsule 14. In it can be conceived a flywheel and a small pawl protruding outward therefrom. Alternatively a flywheel may be provided which increases its diameter, as already provided in sensor systems known in themselves. In any case it is thereby achieved that upon sudden acceleration the drum 14 rotates due to inertia counterclockwise as indicated by arrow by e.g. 5 to 10 , so that the projection 14a in the form of a finger again pushes the trip lever 11 in the above described manner against a pointed tooth of the trip cogwheel 12 or against a locking tooth 5a, after which the locking process is initiated.

The operation of the embodiment according to Figure 6 is that via the indicated electric lines the solenoid 15 is excited at the moment of accident, whereby the trip lever 11 is pushed in the direction of the arrow against a tooth 5a of ratchet wheel 5. Here, too, this tooth 5a then exerts via trip lever 11 a torque for turning pawl 6 about shaft 7 counterclockwise.

The same rotary movement occurs with the pawl 6 of Figure 7, after an appropriate control system expels compressed air through tube 16a against trip lever 11 according to the shown arrows 16, whereby the trip lever 11 is again pressed against a tooth 5a and the locking process is triggered.

The operation of the device according to Figure 8 is the same as in the above described embodiments of the locking device, even though the sensor system with support part 9 and inertia body 10 is secured on the housing 3 and not on the rotatable pawl 6. However, the form of the trip lever 11 is different here, for here the first control arm 11 b, which is rigidly connected with the trip arm 11 a at an angle, rests on the - inertia body 10. For the rest, the mode of operation is the same, so that it need not be repeated here Lastly Figure 9 shows a form very similar to Figure 3, except that another embodiment of the trip lever 11 is shown. Again the first control arm 11 b rests on the inertia body 10, and the trip arm 11 a is firmly connected with it at an angle; but in addition a second trip arm 1 1c projects on the right, which acts similarly to the trip lever 11 in Figure 5, that is, for examplethe projection not shown of a flywheel not shown, which increases its diameter at high acceleration, rides against the right upper edge of the sec ond control arm 11 c, so that trip arm 11 a is rotated into the engagement position shown in Figure 9.

Another possibility is to arrange the trip lever and/or the sensor system, not on the rear extension lever of the pawl, but on the front lever thereof. Then it is expedient to provide a hook at the outer end of the trip lever similar two the hook on pawl 6 according to Figure 3, so that triggering of the locking process occurs after application of tensile stress on the trip lever.

Claims (10)

1. Locking device for a bolt retractor for safety belts, in particular for use in motor vehicles, having a winding shaft and a ratchet wheel with locking teeth mounted thereon, with which, upon response of a sensor system, a movable pawl can be brought into locking engagement, the sensor system comprising a movable trip lever and responding to accelerations of the belt webbing extraction and/or of the vehicle in excess of a limit value, wherein the pawl is rotatable about a shaft secured to the housing, is pretensioned in operative position, and comprises a rear extension lever on which the trip lever is disposed in such a way that the pawl can be pressurized by the trip lever with a torque.

2. Device according to claim 1, wherein a sensor system responding to acceleration of the vehicle is also disposed on the rear extension even

3. Device according to claim 1 or2, wherein the pawl is formed as a pressure-absorbing pushing member or as a traction-absorbing hook-shaped member.

4. Device according to any one of claims 1 to 3, wherein the trip lever comprises a trip arm as well as a first control arm and/or second control arm.

5. Device according to any one of claims 1 to 4, wherein the trip arm of the trip lever can be brought into engagement with the pointed teeth of a trip cogwheel secured to the ratchet wheel.

6. Device according to claim 5, wherein the trip cogwheel is fastened to the ratchet wheel by means of two short axle ends and comprises elastic webs directed away from one another and separated by slots.

7. Device according to any one of claims 1 to 6, wherein the trip arm of the trip lever can be brought into engagement with a projection of a system responding to belt webbing extraction.

8. Device according to any one of claims 1 to 7, wherein the sensor system responding to acceleration of the vehicle and/orofthe belt webbing in excess of a limit value comprises a support part and an inertia body, a solenoid ora compressed airtube.

9. A locking device for safety belt retractor, such device being characterized and arranged to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

10. Asafety belt retractor embodying the locking device of any preceding claim.