GB2356604A

GB2356604A - Belt force limiter for a safety belt

Info

Publication number: GB2356604A
Application number: GB0028558A
Authority: GB
Inventors: Robert Kopetzky
Original assignee: Takata AG
Current assignee: Takata AG
Priority date: 1999-11-23
Filing date: 2000-11-23
Publication date: 2001-05-30
Anticipated expiration: 2020-11-23
Also published as: DE10058001A1; GB2356604B; GB0028558D0

Description

I 2356604 T 3196 Belt Force Limiter

The invention relates to a belt force limiter for a safety belt. Such belt force limiters are basically known in the prior art and serve to convert kinetic energy into a different energy form in order to keep the belt forces which arise during an accident below a specific level.

Known belt force limiters are integrated into the belt reeling mechanisms of three-point safety belts and predominantly restrict the force acting on the shoulder belt. It is, however, also desirable to limit the force acting on the pelvic belt in the event of an accident. Moreover it is desirable to provide a belt force limiter which can be installed in simple manner and which can be fitted retrospectively.

Accordingly, it is the object of the present invention to provide a belt force limiter for a safety belt which is simple to install and with which existing safety belts can be retrospectively equipped in simple manner.

This object is satisfied by the features of claim 1.

In accordance with the invention the belt force limiter is so designed that the belt band is introduced through the inlet into the belt spindle and can be led through the outlet out of the belt spindle, whereby it is possible to couple the spindle to the belt band in simple manner and to "loop" the belt force limiter into an existing belt system. The belt band is thus not secured directly to the spindle at a free end, so that the possibility exists of 2 retrospectively equipping existing belt systems with the belt force limiter of the invention. In this way an additional component results which can be manufactured at favourable cost and is easy to install, and with which an effective limiting of the belt forces which arise can be achieved, in par- ticular for pelvic belts or pelvic belt sections of a three-point safety belt.

Advantageous embodiments of the invention are described in the description, the drawings and also in the subordinate claims.

A particularly small constructional size results when the energy absorbing element is a torsional element, for example, a torsion bar, since in this case a compact design of the belt force limiter is possible.

A torque pick up around which the belt band can be at least partly wrapped is preferably provided at the belt force limiter and prevents a rotation of the belt force limiter when a tensile force is exerted on the belt band. A torque pick up of this kind can have the form of a pin or connection element around which the belt band is at least partly wrapped when a tensile force is applied to the belt band, so that the torque is taken up which is transferred from the belt band to the coupling-device and from there to the torsion bar or to the frame. In this way, on applying a tensile force to the belt band it is not the frame which is turned, but rather the torsion element is twisted after reaching a particular force threshold.

In order to achieve a particularly simple matter of construction the frame can have two side cheeks which are connected to one another via a connection element, for example, via a pin and also a torsion bar. In this way only four components which are simple to manufacture are required for 3 the belt force limiter of the invention, which have to be connected together. For example, the two-side cheeks can be connected to one another with the aid of the pin and - optionally with the aid of further connection elements - with a torsion bar being rigidly connected at its one end to one side cheek and being rotatably connected at its other end to the opposite side cheek.

It is advantageous to arrange the belt force limiter in the region of an anchorage of the belt band to the vehicle chassis. It is also possible to sur- round the belt force limiter by a housing, for example, a plastic or rubber housing. A housing of this kind can also be designed so that it cooperates in covering over the anchorage of the belt band at the vehicle chassis.

In accordance with a further advantageous embodiment the frame of the belt force limiter can have an edge region extending parallel to the axis of the belt spindle and when bent around, preferably by 90% so that it points away from the axis. In this embodiment no seperate torque pick up is provided. On the contrary an edge region of the frame serves as the torque pick up. In order to preclude any form of damage to the belt band this edge region is preferably bent around so that it points away form the axis of rotation of the belt spindle of this embodiment, so that a rounded contact surface is provided for the belt band.

In accordance with a further preferred embodiment the belt force limiter is provided with a belt band which at least partly surrounds the belt spindle in a winding direction, with the belt band subsequently being guided through the inlet into the interior of the belt spindle and through the outlet out of the belt spindle. Thereafter the belt band which emerges from 4 the outlet is wrapped around the belt spindle opposite to the winding direction, so that at least two layers of the belt band located above one another can simultaneously be rolled onto the belt spindle and unrolled from the belt spindle. In this manner a simple attachment of the belt band to the belt spindle is provided without attachment means having to be provided by which the belt band is fixed directly to the belt spindle.

It is particularly preferred when the two layers which can be rolled up by the belt spindle and unrolled from the belt spindle are sewn together. In this connection a simple but reliable fixation of the belt band to the belt spindle can be provided.

In accordance with a further embodiment only one of the two layers can be guided around a deflector fixed relative to the frame. The deflector can, for example, be formed by a pin or the like. In this embodiment the advantage exists that the two layers can be tensioned prior to the sewing, whereby any loose belt is minimised. Furthermore, the deflector fixed relative to the frame can also serve as additional security should the torsion bar or the belt spindle break.

In a method in accordance with the invention, for the manufacture of the belt force limiter of the above named kind, one side cheek is first connected to the torsion bar and to a connector pin arranged spaced from and parallel to it. Then the belt band is pushed onto a spindle with two slots.

Thereafter the belt band is led out of the belt outlet, so that it at least partly wraps around the connector pin when a force is exerted. The belt band has now been introduced into the belt force limiter in an orderly manner so that the second side cheek can be connected to the free end of the torsion bar and to the free end of the connector pin.

Through the above described method a belt force limiter in accordance with the invention can be attached in a simple manner and also retrospectively to a belt band without having to dismantle the latter from the vehicle. The belt band, need also not be tediously introduced by its free end into the belt force limiter. On the contrary it is possible, by pushing the belt band onto the spindle, to achieve the desired passage of the belt 10 band through the belt force limiter in the simplest of manners.

In the following the present invention will be explained, purely by way example, with reference to advantageous embodiments and to the acompaning drawings which are shown:

Fig. 1 a perspective, partly sectioned view of a belt force limiter; Fig. 2 a sectional view, which is not to scale, through the belt force limiter of Fig. 1, Fig. 3 a partly sectioned view of the belt force limiter of Fig. I with the belt band inserted; Fig. 4 an illustration corresponding to Fig. 3 after an actuation of the belt force limiter; Fig. 5 the belt force limiter of Fig. 1 in the installed state; and 6 Fig. 6 a partly section side view further embodiment of a belt force limiter; Fig. 7 a section view of a further embodiment of a belt force limiter; Fig. 8 a sectioned view of a further embodiment of a belt force limiter in accordance with the line A-A Fig. 9, Fig. 9 a side view of the belt force limiter of Fig. 8; Fig. 10 a plan view of the belt force limiter of Figs. 8 and 9, and Figs. 11 and 12 in each case a side view of the belt force limiter of the Figs. 8 to 10.

The belt force limiter which is illustrated in Fig. I has a frame which consists of two parallel spaced apart side cheeks 10, 12 which are rigidly connected to one another by a connection pin 14. An energy absorbing element in the form of a torsion bar 16 is provided parallel to and spaced from the connection pin 14 and is rigidly, i. e. non-rotatably, connected to the side cheek 12 at its end 18 which is visible in Fig. 1. The oppositely disposed end 20 (Fig. 2) of the torsion bar is in contrast rotatably journalled in the side cheek 10, with the end of the torsion bar 16 which projects beyond the side cheek 10 being widened.

As Fig. 1 shows in paricular, the distance between the two side cheeks 10, 12 corresponds substantially to the width of the belt band 22 which passes through the belt force limiter.

7 As Fig. 2 shows, a coupling device, by means of which a tensile force which is exerted on the belt band 22 is transmitted to the torsion bar 16, is connected in one piece to the torsion bar 16 in the form of a spindle-like element 24, with the belt band 22 being wrapped around the spindle-like element. As Figs. 3 and 4 in particular show in this connection, the spindle-like element 24 corresponds to a cylindrical bobbin formed with slits at two oppositely disposed locations in order to enable the belt band 22 to enter into the interior of the bobbin through an inlet 26 and to leave the the interior of the bobbin through an outlet 28. In this way, two bobbin halves 30, 32 are formed in this embodiment.

The path of the belt band which is illustrated in Fig. 3 results in a simple way when the belt band is first inserted, as illustrated in Fig. 4, in such a manner that that it enters through the inlet 26 into the interior of the bobbin, is then led above the torsion bar 16 to the outlet 28 and from there out of the bobbin and then below the connection pin 14 out of the belt force limiter. By rotating the bobbin clockwise, i.e. opposite to the direction of rotation illustrated in Fig. 3, the band is then wound up until the wrapping position shown in Fig. 3 is reached. In this position the belt band has formed a loop which wraps around the bobbin half 30 and has a run which enters through the inlet 26 into the bobbin interior and leaves it again through the outlet 28. Two layers of the belt band then wrap around the bobbin half 32. The outwardly lying layer leads out of the belt force limiter or into the latter respectively and the inwardly disposed ply is then also wrapped, still counterclockwise, around the one run of the loop which is formed. This layer is then led further in the direction of the con- 8 nection pin 14 and emerges from the belt force limiter below this connection pin 14.

As Figs. 1 to 4 show, the belt force limiter in accordance with the invention has at its one end a belt inlet E and at its other, oppositely disposed end a belt outlet A, so that the belt band 22 can be passed through the belt force limiter.

For the installation of the described belt force limiter, and in particular for retrospectively equipping an existing safety belt with a belt force limiter of this kind, the connection pin 14 is first rigidly secured at its one end to the side cheek 10. At the same time the torsion bar 16, with the spindle 24 which is located on it, is secured in the side cheek 10 by turning over or flanging of the free end in such a manner that it can rotate about its axis. The belt band is then inserted as shown in Fig. 4, i.e. the belt band 22 is inserted through the inlet 26 and the outlet 28 and above the torsion bar 16 but below the connection pin 14. Now it is merely necessary to rotate the spindle 24 clockwise, so that the belt band 22 is wound up onto the spindle as is illustrated in Fig. 3. Then the second side cheek 12 is rigidly and rotationally fixedly connected to the free end of the connection pin 14 and the free end 18 of the torsion bar 16, through which the belt force limiter is completely installed and set-up.

In the event of an accident a large belt force is exerted on the belt band 22 and exerts a torque on the spindle 24 and thus on the torsion bar 16 which is taken up by the connection pin 14. After the belt force has exceeded a predetermined level, the torsion bar 16 begins to twist between the connection to the bobbin 24 and the rigid fixed end 18, through which 9 energy is dissipated. During this the bobbin 24 rotates in the direction of rotation which is illustrated in Fig. 3. If, in this situation, the belt band 22 is unrolled from the bobbin 24 by a distance S, then the belt force limiter moves by a distance S/2 in the unwinding direction. A maximum twisting is achieved when the state which is illustrated in Fig. 4 is present. In this state no further torque can be exerted on the bobbin 24 by a tension force acting on the belt band.

Fig. 5 shows the arrangement of the above described belt force limiter in the region of an anchorage of the belt band 22 to a vehicle body. In this the belt band end is sewn in the conventional manner to an anchoring plate 34 which is connected by a threaded bolt 36 to the vehicle chassis. In this arrangement a plastic housing 38, which is illustrated in broken lines, surrounds both the belt force limiter and the anchoring plate 34 with the threaded bolt 36.

Fig. 6 shows an alternative embodiment of a belt force limiter in which the same reference numerals have been used for the same parts. In this embodiment a flattened spindle embodiment has been provided in which the torsion bar 16 is connected in one piece to an elongated plate 40 with two pins 42 and 44 being secured to its two outer ends, and with the pins 42 and 44 corresponding functionally to the two bobbin halves 30 and 32. The manner of operation and installation correspond to that of the previously described first embodiment.

Fig. 7 shows a cross section of a further embodiment of a belt force limiter, with the same reference numerals being used for the same parts.

In this embodiment the frame is formed in one piece and consists of a Ushaped part with two-side cheeks 10 and a base plate 13. The design of the torsion bar 16 and also of the spindle 24 and the path of the belt band 22 is similar to that of the embodiment of Figs. 3 and 4. Instead of the torque pick up or torque reactor 14 provided in the embodiment of the Figs. 3 and 4 an edge region 15 of the base plate 13 is provided in the embodiment shovrn in Fig. 7, with the edge region extending parallel to the axis of the belt spindle 24. This edge region 15 is bent so that it points away from the axis (downwardly in Fig.7) and thereby forms a rounded roll-off edge. In the illustrated embodiment the edge region 15 is bent downwardly by an angle of approximately 90'. This reliably precludes the belt band being damaged at an edge on being tensioned.

Figs. 8 to 12 show a further embodiment of a belt force limiter in accordance with the invention. In this embodiment the frame is likewise formed in one piece and has a base plate 13 and also two side cheeks 10 and 12, with the two side cheeks 10 and 12 and the base plate 13 forming the limbs and the base of a U. Two bores are provided in the base plate 13 in order to fixedly install the belt force limiter in the vehicle.

The design of the belt spindle 24 and also of the torsion bar 16 is the same as in the previously named embodiments. However, in this embodiment, a deflector 46 in the form of a pin fixed to the frame is provided between the two side cheeks 10 and 12. The belt band 22 is wound as follows onto the belt force limiter:

The belt band 22 is first wound onto the belt spindle 24 (opposite to the clockwise sense in Fig. 8) and is subsequently pushed through the inlet 26 11 into the belt spindle 24. Thereafter the belt band is guided through the outlet 28 of the belt spindle 24 and turned around through about 180', so that the belt band can be wound opposite to the first winding direction (i.e. in the clockwise sense in Fig. 8) onto the belt spindle 24. After the outwardly disposed layer of the belt band 22 has been partly wrapped around the belt spindle 24 this outwardly disposed layer is guided around the deflector 46. Thereafter this layer is led back in the direction of the originally arriving belt band so that the incoming layer and also the layer emerging from the belt force limiter after deflector 46 can be sewn together by a searn 50. In this respect it is preferred for the two layers to be first tensioned prior to sewing them together and for them to be sewn together in the tension state. In this way the loose belt which arises is minimised. At the same time, this embodiment ensures that the deflector 46 also picks up the belt forces which arise when the belt band is fully unwound from the spindle or if the torsion bar or the spindle should break.

The belt force limiter shown in Figs. 8 to 12 can be installed in a simple manner at the end of a belt band and can subsequently be screwed to the vehicle. In this connection it is also possible, in distinction to the position shown in Fig. 8, for several layers or double layers of the belt band to be wound onto the belt spindle.

12 Reference numeral list 10, 12 side cheek 13 base plate 14 connector pin edge region 16 torsion bar 18 end of the torsion bar rigidly secured rotatably fixed end of the torsion bar 22 belt band 24 spindle-like element 26 inlet 28 outlet 30,32 halves of the spindle 34 anchoring plate 36 threaded bolt 38 housing plate 42,44 pin 46 pin seaxn E belt inlet A belt outlet 13

Claims

T 3196 Claims

1. Belt force limiter for a safety belt (22) comprising a frame (10, 12, 13, 14) on which a torsion element (16) is secured, the torsion ele ment having a belt spindle (24) with which a tension force exerpted on the belt band (22) is transmitted to the torsion element (16), with the belt spindle (24) having an inlet (26) and an outlet (28) for the belt band (22).

2. Belt force limiter in accordance with claim 1 wherein the belt spindle (24) has a passage for the belt band (22) with an inlet (26) into the interior of the belt spindle (24) and an outlet (28) out of the interior of the belt spindle (24).

3. Belt force limiter in accordance with claim 1, wherein the frame (10, 12, 13) has an edge region (15) extending parallel to the axis of the belt spindle (24) and bent around, preferably through approximately 900, to point away from the axis.

4. Belt force limiter in accordance with claim 1, wherein a torque pick up (14, 15) is provided around which the belt band (22) is at least partly wrapped in order to prevent a rotation of the belt force limiter when a tension force is exerted on the belt band (22).

5. Belt force limiter in accordance with claim 3 and claim 4, wherein the torque pick up is formed by the edge section (15).

14

6. Belt force limiter in accordance with claim 1, wherein a belt band (22) is at least partly wrapped around the belt spindle (24) in a winding direction, is subsequently led through the inlet (26) into the interior of the belt spindle (24) and through the outlet (28) of the belt spindle and is then at least partly wrapped around the belt spindle opposite to the winding direction, so that at least two layers of the belt band located above one another can simultaneously be rolled onto the belt spindle or unrolled from the belt spindle.

7. Belt force limiter in accordance with claim 6, wherein the two layers are sewn together.

8. Belt force limiter in accordance with claim 7, wherein only one of the two layers is guided around a deflector (46) fixed to the frame.

9. Safety belt having a belt force limiter in accordance with claim 8, wherein the deflector is formed by a pin (46).

10. Method of manufacturing a belt limiter in accordance with claim 6 in which method:

- the belt band (22) is partly wound up onto the belt spindle in a winding direction, is subsequently led through the inlet (26) into the interior of the belt spindle (24) and led out of the belt spindle through the outlet (28) and is then partly wound up onto the belt spindle (24) opposite to the winding direction, so that at least two layers of the belt band located above one another are simultane ously wound onto the belt spindle, - the outer wound layer of the belt band (22) is guided around the deflector (46) fixed to the frame and - the two layers of the belt band are subsequently led together again, are tensioned and thereafter sewn to one another.