SAFETY-BELT ARRANGEMENT

Abstract: The invention relates to a safety belt arrangement in vehicles, comprising a retractor device (2) for a seatbelt strap (3), a guiding device (10) about which the strap (3) may run, means (6, 11, 13) for displacing the guiding device (10) in relation to the retractor (2) from an initial position to a second position, whereby the strap (3) is tightened, and an activation device (11) for activating said means (6, 11, 13). The invention is characterized in that said means (6, 11, 13) comprises energy-absorbing means (17, 18; 11) for reducing the force exerted upon the guiding device (10) by the strap (3) during a return movement from said second position. By means of the invention, an integrated arrangement for safety belts is provided, which arrangement provides height adjusting, pretensioning and force-limiting operation.

Description: TITLE: Safety-belt arrangement. TECHNICAL FIELD: The present invention relates to a safety belt arrangement for vehicles, according to the preamble of appended claim 1. In particular, the invention can be applied in the field of safety belts which are provided with a pretensioning device. BACKGROUND OF THE INVENTION: In the field of motor vehicles, it is common to use safety belts comprising a retractor device which is fixed to the floor of the vehicle or in the so-called B-post (i.e. the post which is formed by the bodywork to the side of each front seat), and a seatbelt strap running from the retractor device and across the body of the user. Normally, a guiding device for the strap is arranged at the same level as the shoulder portion of the user. The safety belt is locked in an anchoring on the vehicle's floor. In safety belts of the so called three-point type, the strap is also guided about the anchoring, allowing it to run across the waist of the user. As regards the operation of a safety belt, certain demands and requirements exist. Firstly, it is important that the guiding device is arranged so that the strap is guided in a position which is close to the shoulder portion of the user, i.e. in a position which is adapted to the height of the user. In this manner, optimum protection can be provided in the event of a collision. Furthermore, there is a need for a guiding device which provides height adjustment, i.e. which allows individual setting of the position of the guiding point. In particular, there is a demand for an automatic height adjustment device, relieving the user from having to adjust any control or the like in order to set the guiding device in a correct manner. Furthermore, there is often a requirement that the safety belt should comprise some type of pretensioning device which, in a known manner, is adapted to tension the belt in the event of a collision. In this regard, the strap is intended to be tightened against the upper torso of the user immediately after the collision, i.e. before the user is urged forwards due to his weight. In this manner, the pretensioning device can prevent or reduce personal injuries in connection with collisions. A device for pretensioning a strap by means of a pyrotechnic pretensioner is previously known from EP-A-0138507. Furthermore, there is a demand for a force-limiting operation of the safety belt in the event of a collision. This means that the safety belt should not be completely unyielding. Instead, it should absorb part of the energy which is developed when the user is urged forwards during heavy retardation. In recent years, safety belts have been developed in which both the retractor and the guiding device are integrated in the backrest of the vehicle seat (so-called "belt-in-seat"- devices), i.e. the retractor of the safety belt is not fixed to the body of the vehicle but instead in the vehicle seat. Such systems provide improved comfort and protection since the strap will always be in the same position in relation to the user, independently of the position of the vehicle seat. Furthermore, a simplified design for the B- post can be provided, as regards the technological demands, the space available and the design, since in this case the B-post does not have to be provided with any belt retractor and guiding device. Finally, a shorter strap can be used, which lowers the costs and decreases the risk for a "film- reel" effect to occur in the retractor. This means that a small amount of the strap is fed out due to the fact that it is packed on the retractor, in spite of the fact that the strap is locked. Several types of height adjustment devices, pretensioning devices and force-limiting devices are previously known. However, a problem in connection with today's safety belts resides in the fact that they do not allow a plurality of functions to be integrated in the same construction. This problem implies that today's systems often become space- consuming as well as costly. In particular, this is a problem in connection with the so-called "belt-in-seaf- devices. SUMMARY OF THE INVENTION: A main object of the present invention is thus to provide an improved device in connection with safety belts for motor vehicles, in which a plurality of functions can be integrated and which also constitutes a simple, compact and low-cost unit. This object is accomplished by means of an arrangement as initially mentioned, the characterizing features of which will be apparent from claim 1. The invention constitutes a combined guiding, pretensioning and force-limiting arrangement, which preferably is integrated with the vehicle seat. In this manner, a high degree of comfort and protection for the user can be provided. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will be described in greater detail in the following with reference to the annexed drawings, in which Fig. 1 is a front view of a combined guiding, pretensioning and force-limiting arrangement according to the present invention, Fig. 2 is a side view of the arrangement according to Fig. 1, Fig. 3 is a schematic view showing the arrangement according to the invention in a first operating position. Fig. 4 is a schematic view showing the arrangement according to the invention in a second operating position, Fig. 5 is a schematic view showing the arrangement according to the invention in a third operating position, and Fig. 6 shows an arrangement for force limitation according to a particular embodiment of the invention. PREFERRED EMBODIMENT: Figs. 1 and 2 show a front view and a side view, respektively, of an arrangement according to the present invention. According to a preferred embodiment, the arrangement is arranged in a vehicle seat 1, preferably on its backrest. The arrangement comprises a retractor 2 onto which a strap 3 of a safety belt can be wound. The retractor 2, which is of conventional type per se, is spring-biased so that the strap 3 is wound automatically when not in use. Furthermore, the retractor 2 comprises a shaft 4 which is mounted in corresponding holes in a fitting in the form of a mounting bracket 5. The retractor 2 is pivotally arranged in relation to the shaft 4. The mounting bracket 5 is fixed on the vehicle seat 1. A drum 6 is arranged on the mounting bracket 5, which drum constitutes a guiding device for the strap 3. The guiding drum 6 comprises two essentially circular plates or discs 7, 8 which are arranged on a through shaft 9. The shaft 9 protrudes a certain distance out of the respective discs 7, 8 and through corresponding holes in the mounting bracket 5. In this manner, the drum 6 is rotatably arranged within the mounting bracket 5. Furthermore, the drum 6 comprises a transverse guiding pin 10 which is mounted between the discs 7, 8. The guiding pin 10 is preferably attached on a point of the respective disc 7, 8 which is close the outer edge of the respective disc 7, 8. Preferably, the guiding pin 10 is pivotally arranged between the discs 7, 8, but may also be rotationally fixed. The disc 6 is arranged so that it can be rotated in both directions about the axis of symmetry which is defined by its through shaft 9. The strap 3 is arranged so that, during use, it is guided about the guiding pin 10 and is wound about the retractor 2 (see particularly Fig. 2). A pretensioning device 11 is arranged in connection with the drum 6. The pretensioning device 11 is preferably enclosed and fixed in the backrest of the seat 1, and according to the embodiment it is of the pyrotechnic type, which is a type of pretensioner which is known per se. A piston 12 is arranged inside the pretensioner 11, which piston 12 is connected to a connecting element 13, which is preferably constituted by a wire or a strap. One of the ends of the wire 13 is fixed in the piston 12, whereas its other end is fixed on one of the end discs 8 of the drum 6, preferably on the periphery thereof. An explosive charge (not shown) is arranged in the pretensioner 11 and can be ignited by means of a trigger device (not shown). In this manner, the piston 12 will be forced to be displaced in the downward direction, which in turn forces the wire 13 to be pulled downwards. Furthermore, the trigger device of the pretensioner 11 is connected to a sensor device 14 via a connector 15. The sensor 14 is preferably of the acceleration sensor type, which detects whether the vehicle is heavily retarded. Preferably, the sensor 14 is arranged in the passenger compartment of the vehicle. The occurrence of a collision will be detected by means of the sensor 14, causing the explosive charge to detonate. This causes the wire 13 to be pulled into the pretensioner 11, thereby rotating the drum 6 a certain amount in the clockwise direction. This is indicated by means of the arrow 16 in Fig. 2. It should be noted that the position of the pretensioner 11 and the length of the wire 13 are adapted so that during normal use (i.e. as long as no collision has occured) the drum 6 can be turned to such an angular position that the guiding pin 10 is set optimally according to the user of the seatbelt. To this end, the drum 6 is preferably spring- biased so as to be urged to be rotated in the counterclockwise direction when in an uninfluenced state. The arrangement preferably comprises a housing or a hood (not shown), which can be made of metal or hard plastic and which can be provided with a slit through which the safety belt 3 runs. Alternatively, the entire arrangement can be integrated in the upper portion of the backrest of the vehicle seat 1. The principle operation of the invention will now be described with reference to Figs. 3, 4 and 5. Initially, i.e. during normal use of the safety belt, the strap 3 runs about the guiding pin 10. Furthermore, the strap 3 is fixed to and arranged to be wound on the retractor 2. This initial condition is shown in Fig. 3. In the event of a collision, the pyrotechnic pretensioning mechanism 11 (not shown in Figs. 3-5) will be activated, causing the wire 13 to be tightened a small amount. This causes the drum 6 to be rotated a corresponding amount in the clockwise direction. The length of the wire 13 is preferably adapted so that rotation of the drum 6 slightly more than 180° is obtained after activation of the pretensioner 11. This rotation corresponds to a predetermined pretensioning of the strap 3. After the rotation, i.e. immediately after the collision, the drum 6 will consequently adopt the position shown in Fig. 4. When the body of the user is urged forwards due to the high retardation of the vehicle, the strap 3 will exert a force on the guiding pin 10, thereby causing the latter to affect the drum 6 to be rotated a further amount in the clockwise direction. During this continued rotation (which is shown in Fig. 5), a force-limitation takes place, i.e. the energy which is developed as a consequence of the high retardation will be absorbed to a certain extent. To this end, the drum 6 is adapted so as to provide rotational resistance during this phase of the rotation, which rotation occurs as a result of the strap 3 exerting a force upon the guiding pin 10. According to an alternative embodiment, this rotational resistance, which in turn gives rise to said energy- absorption, can be obtained by means of a force-limiting arrangement according to what is shown separately in Fig. 6. This drawing is a schematical side view showing that the drum 6 is provided with a pin or stud 17 which runs in a corresponding, essentially annular slot 18 in the mounting bracket 5. The pin 17 is positioned on the outside of the drum 6, i.e. on the side of the disc 8 which faces the mounting bracket 5. The slot 18 is preferably divided into two sections, 18a and 18b, respectively. The first section 18a extends in a manner which corresponds to the movement by the drum 6 during activation of the pretensioner 11, which is shown in detail in Figs. 3 and 4. This first section 18a is relatively wide, allowing the pin 17 to run freely during this pretensioning phase. During the force- limiting phase (cf. Fig. 5), the pin 17 will run in the second section 18b of the slot 18. This second section 18b is considerably narrower than said first section 18a. This menas that the slot will exert a force on the pin 17 during this force-limiting phase, thereby providing the energy- absorbing action of the drum 6. For the purpose of obtaining suitable energy absorption, the pin 17 is preferably manufactured from steel. The mounting bracket 5 is preferably manufactured from steel, alternatively from magnesium or corresponding material. According to an alternative embodiment, the invention can be used as follows. In the initial state, i.e. during normal use of the safety belt, the strap 3 runs about the guiding pin 10 in the same manner as shown in Fig. 3. In the event of a collision, the pyrotechnical pretensioning mechanism 11 will be activated, thereby tightening the wire 13. However, the wire will only be tightened so much that the drum 6 is rotated slightly less than 180° from the initial position. When the vehicle occupant subsequently is urged forwards, the strap 3 will exert a force upon the guiding pin 10 so that the guiding pin in turn forces the drum 6 to be rotated a certain amount in the counterclockwise direction. During this rotational phase, energy will be absorbed by means of the pretensioner. To this end, the pretensioner is provided with an energy- absorbing mechanism (not shown), for example a spring arrangement which absorbs energy arising due to the fact that the strap 3 exerts a force upon the guiding pin 10. The invention is not limited to the above-mentioned embodiments, but may be varied within the scope of the subsequent claims. For example, the invention can either be integrated in the vehicle seat 1 or arranged separately. Furthermore, the invention allows automatic height adjustment due to the fact that the guiding pin 10 is set according to the height of a user, i.e. the shoulder height of the user. The invention can be supplemented with a device for fixing the drum 6 in a predetermined angular position, thereby fixing the guiding pin 10 in a certain position in relation to the shoulder portion of the user. As regards the force-limiting operation of the invention, the resistance and thus also the energy-absorption can be affected through the choice of material of the pin 17 and the mounting bracket 5 (see Fig. 6). Furthermore, the slot 18 can be designed with a gradually diminishing width or with two or more section of different widths. The drum 6 can be dimensioned so that a high resistance is provided at the beginning of the rotational movement and a lower resistance towards the end of the rotational movement, or vice versa. Furthermore, the drum 6 may have another geometry than the circular one described above. For example, it may be excentrical, which implies that a varying pretensioning force can be obtained during the pretensioning phase. Instead of the pyrotechnic pretensioner 11 which has been described above, some other type of pretensioning device can be used in the invention. The invention can be used in connection with different types of vehicles, for example cars, trucks or buses.

Claims: CLAIMS : 1. Safety belt arrangement in vehicles, comprising a retractor device (2) for a seatbelt strap (3), a guiding device (10) about which the strap (3) may run, means (6, 11, 13) for displacing the guiding device (10) in relation to the retractor (2) from an initial position to a second position, whereby the strap (3) is tightened, and an activation device (11) for activating said means (6, 11, 13), c h a r a c t e r i z e d i n that said means (6, 11, 13) comprises energy-absorbing means (17, 18; 11) for reducing the force exerted upon the guiding device (10) by the strap (3) during a return movement from said second position. 2. Arrangement according to claim 1, c h a r a c t e ¬ r i z e d i n that said means for displacing the guiding device (10) comprises a rotatable drum (6) on which the guiding device (10) is arranged. 3. Arrangement according to claim 2, c h a r a c t e ¬ r i z e d i n that it comprises means (11, 13) for rotating the drum (6) during activation of the activation means (11). 4. Arrangement according to claim 2 or 3, c h a r a c t e ¬ r i z e d i n that the guiding device (10) extends essentially parallel to the centre axis (9) of the drum (6) and to the centre axis (4) of the retractor (2). 5. Arrangement according to any one of claims 2-4, c h a r a c t e r i z e d i n that said energy-absorbing means is constituted by a protruding pin (17) which is adapted to cooperate with a slot (18). 6. Arrangement according to claim 5, c h a r a c t e - r i z e d i n that the pin (17) is arranged on the drum (6) and the slot (18) is arranged in a bracket element (5) supporting the drum (6) and being fixed in the vehicle. 7. Arrangement according to any one of claims 2-6, c h a r a c t e r i z e d i n that the drum (6) is adapted for displacing the guiding device (10) essentially along a circular arc. 8. Arrangement according to any one of claims 1-7, c h a r a c t e r i z e d i n that the activation means (11) is adapted to be activated in the event of a vehicle collision. 9. Arrangement according to claim 8, c h a r a c t e - r i z e d i n that said activation means (11) comprises a pyrotechnic pretensioning device which is adapted to be activated by means of an acceleration sensor (14) arranged in the vehicle. 10. Vehicle seat comprising a safety belt arrangement according to any one of claims 1-9.

Inventors: OEHLUND ANDERS, OEHLUND, ANDERS
Applicants: OEHLUND ANDERS, VOLVO AB, AB VOLVO, OEHLUND, ANDERS
Application year: 1997
Main classification: B60R22
IPC codes: B60R22