Automatic seat belt retractors return a seat belt automatically back to its'original position after use. An automatic seat belt retractor should prevent catching in the otherwise slack seat belt located inside a vehicle when getting in and out, or loading and unloading, etc.

Seat belt retractor locking devices include a so- called vehicle-sensitive and/or webbing-sensitive locking or blocking device. Both blocking devices serve to prevent a forward movement of the person secured by the seat belt even during decelerations of the motor vehicle which are lower than the decelerations releasing the main locking means. As these blocking devices come into action before activation of the main locking means, they are frequently also described as pre-locking or pre- blocking devices. The respective pre-blocking device is able to lock the seat belt system to prevent further unwinding of the seat belt webbing also via the main locking means.

As the seat belt frequently secures not only a person but also child seats or other bulky objects transported inside the vehicle, a further pre-locking device is frequently provided in the known automatic seat belt retractors, in order to lock the automatic seat belt retractor against further extraction after

extraction of a predetermined length of seat belt webbing from the winding shaft. Although the seat belt can be retracted again until the child seat and/or the bulky object is firmly secured by the seat belt, the seat belt cannot be further extracted. This prevents the object secured in this way from moving during deceleration of the motor vehicle. This pre- locking device is frequently referred to as a child seat locking device.

EP 0 625 449 discloses an automatic seat belt retractor of the type mentioned at the outset with a child seat locking device in which a rotatably mounted securing lever is provided.

There is provided in accordance with claim 1 an automatic seat belt retractor of the type mentioned at the outset in which the child seat locking device has fewer components compared to those of the prior art.

Brief Description of the Drawings Fig. 1 is a schematic view of the front face of an automatic seat belt retractor according to the invention in which the child seat locking device is shown in its'rest position.

Fig. 2 is a view similar to Fig. 1 showing the child seat locking device in an intermediate position before attainment of the locking position.

Fig. 3 is a view similar to Fig. 1 showing the child seat locking device in the locked position.

Detailed Description of the Invention Further advantageous developments and an embodiment will be described hereinafter with reference to the accompanying drawings. The terms "top","bottom","right"and"left"used in conjunction with the description of the embodiments refer to the orientation of the drawings as viewed with a normally legible description of the figures.

Identical components are identified by identical reference numerals in the drawings.

Figs. 1 to 3 show an end face of an automatic seat belt retractor 5 according to the invention with a child seat blocking or child seat locking device.

The automatic seat belt retractor comprises a winding shaft 10 that is made of metal. The winding shaft is mounted in a metal frame of the automatic seat belt retractor (not shown in detail) that is rigidly connected to the vehicle chassis. Seat belt webbing (also not shown) of the seat belt system can be wound onto the winding shaft. In the embodiment shown in Figs. 1 to 3, the winding shaft 10 extends substantially horizontally and perpendicularly to the plane of the drawings. For the rotational driving of various components of the seat belt system, the winding shaft 10 is constructed as a serrated shaft.

For a compact construction of the automatic seat belt retractor the vehicle-sensitive pre-blocking device can comprise a carrier disc on which the intermediate element and optionally the securing

component are rotatably or pivotally mounted. It is in principle sufficient for either the actuating device or the intermediate element to be releasably lockable in the locking position of the pre-locking device or of the child seat locking device, in order to maintain this position.

The shaft end 10a, shown in Figs. 1 to 3, of the winding shaft 10 passes through a carrier disc 12, for example produced from a plastic material, of a vehicle-sensitive pre-blocking device 45. The carrier disc 12 is arranged concentric with the winding shaft 10 freely rotatably thereon and is secured axially and radially by a plurality of resilient clips 14, made for example of a plastic material. The clips 14, one of which is shown in Figs. 1 to 3, are arranged along the outer circumference of the carrier disc 12. The clips are shaped on a casing part made of a plastic material (which is not shown in detail) and is rigidly connected to the metal frame of the automatic seat belt retractor.

The vehicle-sensitive pre-blocking device 45 comprises an inertia body, for example a ball (not shown in detail) which is mounted movably in a casing- like receiver 16 shaped on the lower outer circumference of the carrier disc 12. A pre-blocking pawl 18 is a securing component that engages the teeth of a gear wheel that is non-rotatably connected to the winding shaft. The inertia body acts on the pre- blocking pawl 18 which is produced from a plastic material and is mounted pivotal about a pivot axis 20

extending parallel to the winding shaft 10 on the receiver 16 of the carrier disc 12. The pre-blocking pawl 18 is pivoted radially inward by the inertia body during a displacement of the inertia body in the receiver 16 owing to a corresponding deceleration of the motor vehicle. The pre-blocking pawl comes into engagement with a pre-blocking gear wheel 22 that is made of a plastic material and is arranged non- rotatably on the winding shaft 10 behind the carrier disc 12 in the axial direction of the winding shaft 10. The teeth of the pre-blocking gear wheel 22 are designed in the manner of saw teeth, the saw teeth 22a pointing in the unwinding direction of the seat belt webbing. The pivoting movement of the pre-blocking pawl 18 radially outward is limited by a stop 16a located on the receiver 16.

On the side facing the observer, the carrier disc 12 is provided with internal teeth 12a. The internal teeth 12a are arranged on a carrier ring (not shown in detail) which is formed integrally with the carrier disc 12 and has a diameter which is smaller than the external diameter of the carrier disc. The carrier ring for the internal teeth projects axially from the carrier disc.

A tumbling disc 24 made of a plastic material is also provided on the side of the carrier disc 12 facing the observer. The tumbling disc 24 is arranged on the winding shaft 10 eccentrically to the axis A of the winding shaft. For rotational driving by the winding shaft the tumbling disc 24 is provided with a

bore-hole 24a of which the bore-hole axis (not shown in detail) extends parallel, but eccentrically to the axis of the winding shaft when assembled. With this bore-hole 24a, the tumbling disc 24 rests on a hub 10b which similarly has an external contour eccentric to the axis A of the winding shaft and is connected non- rotatably to the winding shaft. The tumbling disc 24 has a smaller diameter than the carrier disc 12. On its'exterior, the tumbling disc 24 has external teeth 24b which engage the internal teeth 12a of the carrier disc 12 and roll along the internal teeth 12a during rotation of the winding shaft 10. In principle, it would be conceivable for the actuating device to be actuated merely by a movement derived from the winding shaft. It is advantageous, however, if the actuating device is a reduction gear that is in direct rotational connection with the winding shaft. The external teeth 24b of the tumbling disc 24 and the internal teeth 12a of the carrier disc 12 together form a reduction gear which reduces the rotation of the winding shaft 10 toward the tumbling disc 24. The thickness of the tumbling disc 24 in the direction of the axis A of the winding shaft 10 roughly corresponds to the thickness of the carrier ring for the internal teeth 12a, so that the tumbling disc 24 is received in the carrier ring and ends flush with it.

Concentric with the axis A of the winding shaft 10 is an activating disc 26 made of a plastic material that is mounted to rotate freely on the winding shaft.

The diameter of the winding shaft 10 is greater than

that of the tumbling disc 24 but smaller than that of the carrier disc 12 that is also provided on the side of the tumbling disc 24 facing the observer. The activating disc 26 is secured in its'radial and axial position by a plurality of resilient clips 28 that are shaped integrally on the carrier disc 12 but do not prevent the rotational movement of the activating disc 26. The activating disc 26 has a circular depression (not shown in detail) which is directed toward the carrier disc 12 and has an internal diameter such that it overlaps the carrier ring for the internal teeth 12a. This depression has a depth roughly corresponding to the thickness of the carrier ring for the internal teeth 12a in the axial direction. Owing to the axial and radial fixing of the activating disc 26, the tumbling disc 24 is also secured axially and radially via the circular depression.

To enable the activating disc to actuate the intermediate element when the predetermined length of seat belt webbing is extracted, the activating disc can have an arcuate recess 26a which engages a driving pin non-rotatably connected to the tumbling disc. The activating disc 26 is provided with an arcuate recess 26a extending concentric to the winding shaft 10 over an angle that is smaller than about 180°. As shown in Figs. 1 to 3 the external radius of the recess 26a corresponds roughly to the internal radius of the internal teeth 12a of the carrier disc 12. A driving pin 24c formed integrally with the tumbling disc 24 engages in the recess 26a. Starting with completely

retracted seat belt webbing, initially the winding shaft, and therefore also the tumbling disc, are set into rotation as the seat belt webbing is extracted.

When a first predetermined extracted length is reached, the driving pin of the tumbling disc comes into contact with one edge of the arcuate recess of the activating disc and entrains the activating disc.

It has proven advantageous if the intermediate element comprises at least one cam portion that is in engagement with the actuating device, and one actuating portion which actuates the securing component triggering the pre-locking of the winding shaft. The cam portion of the intermediate element therefore slides on the control contour of the outer circumference of the activating disc and, after reaching the second predetermined extracted length, actuates the securing component of the pre-locking device.

An intermediate element 32 made of a plastic material is also mounted rotatably on the side of the carrier disc 12 facing the observer by means of an shaft 30 mounted rigidly on the carrier disc 12. The shaft 30 is made of a plastic material and extends substantially parallel to the axis A of the winding shaft 10 and is arranged on the carrier disc 12 at the bottom in the region of the vehicle-sensitive pre- blocking device 45. Only a single intermediate element is required for actuation of the securing components by the actuating device, with the solution according to the invention. Not only are the pure

material and production costs reduced as the number of components is diminished, but also the assembly costs are reduced, since only a single component has to be assembled in addition to the components already used in the past.

To achieve greater security, however, the actuating device and the intermediate element can also be releasably lockable, independently of one another, in the locking position of the pre-locking device.

Catch pins for fixing the actuating device and the intermediate element can be provided on the carrier disc for this purpose. To prevent the pre-locking position from being released prematurely, it is preferably also proposed that the intermediate element have a locking portion for the releasable locking of the intermediate element in its'locking position.

This catching of the activating disc in the pre- locking position can be achieved by means of a catch lever 32b which is provided at the outer circumference of the activating disc and rests releasably on a catch pin which is stationary in the pre-locking position of the catch lever. This catch pin can in turn be provided on the vehicle-sensitive pre-locking device.

To enable the catch lever of the activating disc to be released from the catch pin on release of the pre- locking position, the catch pin can also have a contour that is such The intermediate element 32 possesses several functional portions that will be described hereinafter. Thus, the intermediate element 32 comprises a cam portion 32a, a catch lever portion

32b and an actuating lever portion 32f so that the catch lever is not blocked on the catch pin.

The cam portion 32a scans a control contour 34 that is provided on the outer circumference of the activating disc 26 and will be described in more detail hereinafter. The cam portion 32a rests on this control contour 34 during the entire actuation of the intermediate element 32 or of the activating disc 26 and has the form of a truncated cone projected into a plane.

The catch lever portion 32b arranged in a position about 90° in a clockwise direction relative to the cam portion 32a is designed as a radially resilient lever. The catch lever portion 32b is integrally connected at one end to the intermediate element 32 and initially extends radially outward and then, while maintaining a space 32c, in the circumferential direction of the intermediate element 32. At the free end, the catch lever portion 32c is provided with a radially inwardly extending triangular extension 32d in such a way that the space 32c is closed on all sides. The extension 32d preferably rests on the outer circumference of the intermediate element 32. On the projection 32d, the catch lever portion 32b is provided with a contact contour 32e that is directed in the circumferential direction of the intermediate element 32 and with which the catch lever portion 32 rests on a catch pin 36 in a locking position which will be described hereinafter. In the rest position of the intermediate element 32 shown in

Fig. 1 the catch lever portion 32b comprises the catch pin 36 which is preferably produced from a plastic material and is rigidly mounted on the carrier disc 12 in an orientation substantially parallel to the winding shaft 10.

The actuating lever portion 32f of the intermediate element 32 is provided roughly at an angle of 180° opposite the cam portion 32a. The actuating lever portion 32f is connected integrally to the intermediate element 32 at one end and projects roughly radially outward from the intermediate element. At its'free end, the actuating lever portion 32f has an S-shaped contour with a rounded end 32g. With this end 32g, the actuating lever portion acts on the pre-blocking pawl 18 of the vehicle- sensitive pre-blocking device 45 or on a lever extension 18a connected to the pre-blocking pawl.

The control contour 34 that is provided on the outer circumference of the activating disc 26 and is scanned by the cam portion 32a of the intermediate element 32 has a plurality of control regions 34a- 34c. The first control region 34a is formed by the unchanged outer contour of the activating disc 26 and can be described as a control region for the rest position of the intermediate element 32. The intermediate element is at rest while the cam portion 32a of the intermediate element scans this control region 34a. The control regions 34b, 34c, i. e. the second and third control regions adjoining the first control region 34a in the extraction direction of the

seat belt webbing are formed by the lateral edges of a substantially U-shaped recess 26b provided on the activating disc 26. During the scanning of these control regions 34b, 34c by the cam portion 32a of the intermediate element 32, the intermediate element is pivoted in a clockwise or anticlockwise direction in a manner which will be described hereinafter.

In the belt extraction direction, a resiliently designed catch lever 26c that directly adjoins the recess 26b is provided on the outer circumference of the activating disc 26. The lateral edge of the recess 26b forming the third control region 34c is identical to the outer edge of the catch lever 26c.

The catch lever 26c is connected integrally at one end to the activating disc 26, extends radially outward from there and then, while maintaining a space 38 in the belt extraction direction, in the circumferential direction of the activating disc. At its'free end the catch lever 26c is provided with a radially outwardly extending triangular extension 26d. With the side of the triangle facing in the belt extraction direction of the extension 26d, the catch lever 26c rests on a catch pin 40, made of a plastic material, in a locking position which will be described in more detail hereinafter. The catch pin 40 is mounted on the side of the carrier disc 12 facing the observer in an orientation extending substantially parallel to the winding shaft 10. The catch lever 26c is designed in such a way that it can deflect radially.

As already described hereinbefore, Fig. 1 shows the rest position of the child seat locking or pre- blocking device. Starting from this position, the automatic seat belt retractor according to the invention operates as follows.

If the seat belt webbing is unwound from the winding shaft 10 in a clockwise direction, the pre- blocking gear wheel 22 also rotates in a clockwise direction. Owing to the eccentric arrangement of the tumbling disc 24 relative to the winding shaft 10 and owing to the engagement of the external teeth 24b of the tumbling disc 24 with the internal teeth 12a of the carrier disc 12, the tumbling disc 24 is simultaneously set into rotation in a counter clockwise direction.

After extraction of a first predetermined length of belt webbing, the driving pin 24c, which is non- rotatably connected to the tumbling disc 12 and which engages in the arcuate recess 26a of the activating disc 26, comes into contact with the face end of the recess 26a directed in a counter clockwise direction, as shown in Fig. 2.

Since the activating disc 26 is freely rotatable relative to the winding shaft 10, the activating disc is therefore engaged by the driving pin 24b during continued extraction of the seat belt webbing. The activating disc 26 is therefore rotated in a counter clockwise direction. The cam portion 32a scans the control contour 34 at the outer circumference of the activating disc and, after a the extraction of a

further predetermined length of the seat belt webbing, comes into engagement with the recess 26b, as shown in Fig. 2. The cam portion 32a comes into contact with the third control region 34c of the control contour 34 (see Fig. 2) so that, during further extraction of the seat belt webbing, the intermediate element 22 begins to pivot or rotate in a clockwise direction. Owing to this pivoting movement, the actuating lever portion 32f of the intermediate element 32 again comes into contact with the pre-blocking pawl 18 or the lever extension 18a of the vehicle-sensitive pre-blocking device 45. At the same time, the catch lever portion 32b of the intermediate element 32 begins to move past the catch pin 36 by pivoting radially outward.

Furthermore, the catch lever 26c of the activating disc 26 begins to move past the catch pin 40 mounted rigidly on the carrier disc 12, while pivoting radially inward owing to contact with the catch pin as shown in Fig. 2.

During further extraction of the seat belt webbing, the activating disc 26 is rotated further in a counter clockwise direction owing to the engagement of the driving pin 24b, so that the actuating lever portion 32f of the intermediate element 32 pivots the pre-blocking pawl 18 radially inward via the lever extension 18a of the vehicle-sensitive pre-blocking device 45, so that the pre-blocking device comes into engagement with the teeth 22a of the pre-blocking gear wheel 22 as shown in Fig. 3. At the same time, the catch lever portion 32b engages behind the catch pin

36 and the catch lever 26c behind the catch pin 40.

The locking position of the child seat locking device is thus achieved. Further extraction of seat belt webbing is prevented by the engagement of the blocking pawl 18 in the teeth 22a of the pre-blocking gear wheel 22, so that a forward movement of an object, for example a child seat, held by the seat belt webbing, is avoided. However, the seat belt webbing can be retracted again at any time as, in this case, the pre- blocking pawl 18 slips over the teeth 22a. Premature release of the locking position is prevented by the catch lever portion 32b and the catch lever 26c contacting the respective catch pin 36,40.

For releasing the locking position, the seat belt webbing is wound on the winding shaft 10 again by known measures. During this winding, the pawl 18 passes over the teeth 22a that are now rotating in a counter clockwise direction. After a predetermined length of seat belt webbing, the driving pin 24b comes into contact with the face end, directed in a clockwise direction, of the recess 26a of the activating disc 26. The activating disc is therefore rotated in a clockwise direction, the catch lever 26c disengaging from the catch pin 40 and the catch lever portion 32b disengaging from the catch pin 36. The intermediate element 32 is pivoted in a counter clockwise direction by the second control region 34b of the control contour 34, so that the actuating lever portion 32f disengages from the pawl 18. The pawl pivots from the path of movement of the pre-blocking

gear wheel 22 owing to gravity or a spring element (not shown in detail) so that the position shown in Fig. 1 is finally adopted again.

In summary the automatic seat belt retractor 5 of the present invention has at least one pre-locking device comprising the pre-blocking pawl 18, the pre- blocking gear wheel 22, the activating disc 26 and the intermediate element 32. That is to say the pre- locking device has an actuating device comprising the tumbling disc 24 and activating disc 26 which actuates at least one securing component in the form of the pre-blocking pawl 18 which is a component of the vehicle-sensitive pre-blocking device 45. An automatic seat belt retractor should prevent catching in the otherwise slack seat belt located inside a vehicle when getting in and out, or loading and unloading, etc. Of course the automatic seat belt retractor 5 of the present invention contains well known components that prevent a forward movement of a person secured by the seat belt when the motor vehicle is subjected to rapid deceleration. Any suitable well known locking device module that prevents unwinding of the seat belt in such cases may be used in the practice of the present invention to carry this out.

To distinguish from further locking devices which may be provided this module is referred to herein and in the appended claims as the main locking means.