WO2005066001A1

WO2005066001A1 - A pretensioner with chain-like actuating bodies and a method of pretensioning

Info

Publication number: WO2005066001A1
Application number: PCT/IB2003/006327
Authority: WO
Inventors: Bijon Nag; Sudarsanam Rangarajan; Vijay Krishnappa Shetty
Original assignee: Autoliv Ifb India Pvt Limited
Priority date: 2003-12-23
Filing date: 2003-12-23
Publication date: 2005-07-21
Also published as: CN1980823A; AU2003288685A1; MY141100A; TW200528321A

Abstract

The present invention provides a pretensioner device for seat belts. The present invention further provides a pretensioner device with actuating bodies forming a chain on actuation to provide a drive for the retraction of seat belt and said actuating bodies getting detached as individual units on completion of the pretensioning of the seat belt. The present invention also provides a method of pretensioning by using chain-like actuating bodies.

Description

A PRETENSIONER WITH CHAIN-LIKE ACTUATING BODIES AND A METHOD OF PRETENSIONING

Technical field The present invention relates to a pretensioner device for seat belts. The present invention particularly relates to a pretensioner device with actuating bodies forming a chain on actuation, to provide a drive for the retraction of seat belt. The present invention also provides a method of pretensioning by adopting chain-like actuating bodies. Background and prior art Seat belt devices of automobiles having pretensioning devices are used to restrain the occupant to the seat in a vehicle in the event of a sudden impact or an accident. A pretensioning device applies tension to the seat belt, on sudden deceleration of a vehicle, by rapidly rotating the shaft of the pretensioning device on which the web of the seat belt is wound, thereby restraining the occupant to the seat. In order to provide a high ratio pretensioning for seat belt devices, a pyrotechnical charge is detonated in the event of sudden impact of a vehicle, to provide energy for actuating the driving means that are generally selected from a series of balls, gears, chain etc. for rapid rotation of the webbing of a seat belt. US Patent 4,444,010 disclose a pretensioner with bullet shaped actuating bodies to turn a drive member after activation. The spindle connected to the drive member is turned backwards and to retract the belt into the retractor. The transfer of the energy from the actuating body to the drive member occurs by friction. The efficiency of this system is not advantageous, because the jammed acceleration bodies have to be removed by the wedge shaped baffle after use. That takes a part of the energy away. Another alternative driving means in the form of balls is also disclosed in this patent. The following are some of the known disadvantages of spherical bodies used as driving means. When the actuating bodies are in the form of balls, one of the main factors to be considered is that the contact area from ball to ball is only a point. Further, on actuation the balls are pressed very hard to one another thereby causing plastic deformation of balls. As a result, the axle base of the balls in relation to the circular pitch of the toothed drive wheel is affected. Further, the impact of the balls (deformed) into the space of the drive wheel is not 100% synchronized anymore thereby leading to a loss of efficiency of the drive. A special drive wheel for retracting the seat belt is shown in US Patent 3,552,222, which is complicated to produce and therefore expensive. Similarly, US Patent 5,590,295 discloses a drive member, combined out of two drive wheels having semi-spherical recesses. A relatively good transfer of energy from actuating body to drive mechanism can be arranged with a chain, as shown in DE 3220498 and WO 97/13661(PCT/US96/16577). This patent further discloses a flexible chain located within the drive housing including a plurality of interconnected chain links for driving the gear wheel. But in case of chain driven pretensioning device, the main disadvantage is that actuating bodies are fixed to each other to form a chain. A chain thus formed cannot not be stored in a small container (reservoir) of a pretensioning device, as a single part after pretensioning of the seat belt, which is possible when balls are used as driving means. Therefore, there is a need for a big reservoir or a channel in a pretensioning device to store the chain subsequent to pretensioning of the seat belt. As a result, a compact design for a pretensioning device is not possible.

Objects of the invention The main object of the present invention is to provide a compact pretensioning device with actuating bodies acting as chain only under pressure during activation. An object of the present invention is to provide a wider surface contact area between the pinion (the receives drive from actuating bodies) and the actuating bodies for an effective transfer of energy from actuating bodies to pinion for rotating the shaft on which seat belt webbing is wound. Another object of the present invention is to provide a compact pretensioning device with actuating bodies are positioned loosely adjacent to each other in the channel when the device is not in use. Yet another object of the present invention is to provide a compact pretensioning device where the actuating bodies are cylindrical in shape. Further object of the present invention is to provide a compact pretensioning device having a reservoir to store the unchained actuating bodies after use. Still another object of the present invention is to provide a less expensive pinion (drive wheel) to drive the spindle on which seat belt webbing is wound. It is also an object of the present invention to provide a method of pretensioning where chain-like actuating bodies are used.

Summary of the invention Generally, a pretensioning device for a seat belt is connected to an emergency locking retractor (ELR) consisting of a frame and a spindle rotatably supported in the frame. One end of the seat belt is connected to the spindle. A pinion (driven member) is connected to the spindle. A housing connected to the frame has a channel extending in the plane parallel to the radial plane of the pinion and extending at least partially about a circumference of the pinion. In the present invention, actuating bodies having cylindrical shapes are positioned loosely adjacent to each other in the channel, to act as chain on activation to provide rotary drive to the pinion. The rotary drive of the pinion turns the spindle in a backward rotation and pull in the webbing, so that the occupant of a seat is secured by a tightened seatbelt. On pretensioning the chain-like actuating bodies get detached and stored in a reservoir of the pretensioner. The present invention also provides a method of pretensioning by adopting chain-like actuating bodies.

Brief description of the accompanied diagrams

Figure 1 depicts a sectional view of pretensioning device with loosely arranged actuating bodies prior to pretensioning. Figure 2 is a sectional view of a pretensioner with actuating bodies moving like a chain during pretensioning and the detachment of actuating bodies after pretensioning. Figure 3, 4 and 5 depict the cylindrical actuating bodies both as a single entity and in the form of chain. Figure 6 depicts a view of meshing arrangement of actuating bodies with the pinion of the pretensioner to provide an effective transfer of drive from the actuating bodies. Figure 7 shows the advantage of cylindrical shaped actuating bodies over the spherical actuating bodies. Detailed description of the invention Initially referring to Fig 1, a retractor 1 is mounted on a frame 12 of the vehicle body having a housing 8. The housing 8 is made up of die casting metal. A webbing of the seat belt 13 is wound on a spindle 3 of the retractor 1 (which is not shown in this figure), and is stretched towards webbing pull-out direction 14 whenever the user wears the belt while seated. The spindle 3 is connected to the pinion 4 of the pretensioning device 2 by means of clutch (not shown in fig). A channel 7 is provided which extends in the plane parallel to the radial plane of pinion 4. A gas generator 17 is disposed at one end of the channel 7, to provide a pyrotechnical charge on sudden impact. A gas inlet 18 is provided in the channel 7 to permit the gas to enter into channel 7. A plurality of actuating bodies 10 positioned loosely adjacent to each other in the channel when the device is not in use. The last actuating body 6 is disposed in the channel 7 in close proximity to the gas generator 17 to receive the pyrotechnical charge from the gas generator 17. The seal (not shown in fig) of the last actuating body 6 prevents the products of combustion (pyrotechnical charge) from escaping the channel 7. The channel 7 acts as a conduit to the actuating bodies 10 and further provides a rotary path to the chain of actuating bodies 10 when they are in rapid motion on receiving the drive as a result of the pyrotechnical charge generated by the gas generator 17 on sudden impact. The actuating bodies 10 are positioned in the channel 7 by abutting to one another and are held in position with the help of stopper 11 when they are in idle condition. The actuating bodies 10 that are disposed in the channel 7 are led around the pinion 4 to form an angle 5 so that always a pair of actuating bodies 10 is meshed with the teeth profile of the pinion 4 to ensure that transfer the energy generated by the moving chain of actuating bodies 10 is transferred onto the pinion 4 at a given point of time. The actuating bodies 10 on receiving a charge from the ignition of the gas generator 17 form a chain of actuating bodies 10 while rapidly moving along the channel 7, which extends in the plane parallel to the radial plane of pinion 4. The rotary movements of accelerated actuating bodies 10 turns the pinion 4, since the actuating bodies 10 are meshed with teeth profile the pinion 4. A spindle 3 is connected to the pinion 4 to receive the rotary drive from the pinion 4 to rapidly retract the belt 13 in the webbing pull-in direction 15. Now by referring to Figure 2, in addition to Fig 1, an embodiment wherein the movement of chain of actuating bodies 10 in the form of chain, in the channel 7 after receiving the drive from the pyrotechnical charge is shown. The actuating bodies 10 in the form of a chain provide a rapid rotary drive to the pinion 4 and the direction of rotation 28 as shown in Fig 2. During the process of pretensioning of seat belt 13, in the webbing pull-in direction 15, it is noticed here that the first actuating body 9 of the chain of actuating bodies 10 is already out of use and disconnected from the chain of actuating bodies 10 and is being eased out into the reservoir 16 as a single unit and gets accumulated one after the other. The single units of actuating bodies have to be secured after use in a safe chamber because their rapid movements are very substantial in nature. It is also observed here that the single units of actuating bodies act together under pressure like a chain and they are easily disconnected after use for simple storage in reservoir 16. Another embodiment of the present invention is as shown in Figure 3 wherein the cylindrical actuating body 10 comprising a working section 23 considered as the outer diameter of the actuating body. The present Figure also demonstrates the formation of chain of actuating bodies 10. The working section 23 is the outer diameter of the body, running in the channel 7 (Figs 1 &2). A pair of spindle shaped protuberances 22, one each on either side of the working section 23 of the actuating bodies is formed. Each of these spindle shaped protuberances 22 terminates with a rotator-cuff shaped head 19 on one side and as a stem 21 on the other side on the working section 23. A semi-circular inner contact surface in the form of a recess 20 on the stem side is carved out of the opposite ends of each of the actuating bodies. The rotator-cuff shaped heads 22 of one actuating body pivots into inner contact surfaces 20 of the next actuating body to form a consecutive chain of actuating bodies 10 on application of pressure generated by the pyrotechnical charge of gas generator 17. This chain of actuating bodies 10 provide a rotary drive to the pinion 4 which in turn rotates the spindle 3 having a clutch means, to effect a rapid retraction of the seat belt. The rotary drive of the pinion 4 is enabled by meshing the teeth profile of the pinion 4 with the intervening working areas 23 of two adjacent actuating bodies. Figure 4 is a disclosure of an alternate actuating body 24 resembling a dumbbell, wherein the outer diameter 25 is carved with a concave recesses 20 that come in contact with the outer contact surface 19 of the neighboring actuating body 24. The working section 23 has a smaller diameter than the outer diameter 25 to enable a good encompass of the teeth of the pinion 4. The rotary drive of the pinion 4 is enabled by meshing with the teeth profile of the pinion 4 with the intervening working areas 23 of two adjacent actuating bodies. Further by referring to Figure 5 an alternate actuating body 26 with an outer diameter in the shape of dumb-bell having contact surface 27 and the working section 23. However, this type of actuating body when compared with balls when used as actuating bodies is much more resistive to the deformation due to the enhanced contact area. The actuating bodies 24 and 26 as shown in Figure 4 and Figure 5 are alternate actuating bodies to the ones as disclosed in Figures 1-3. Now, referring back to Figures 1 & 2 the rotary drive of the pinion 4 is enabled by meshing with the teeth profile of the pinion 4 with the intervening working areas 23 of two adjacent actuating bodies. Figure 6 depicts an embodiment, wherein the loosely connected actuating bodies 10 are meshed with the gear profile of the pinion 4 to provide a rotary drive to pinion 4 on pretensioning. This figure clearly shows that at any given point of time a pair of actuating bodies is meshed with the gear profile of the pinion 4 to provide an effective transfer to drive the pinion 4. Another preferred embodiment of the present invention is described by referring to Figure 7, wherein the design of actuating bodies is similar to a chain, is described, wherein the diameter 'd' of the working section 23 is less than the axle base "a" (center distance or pitch between two working sections). As a result, the teeth of the pinion 4 can encompass the cylindrical working section 23 much more effectively and pre-dominantly when compared with the actuating bodies of spherical shapes having diameter "d" of the working section equal to the axle base "a". Therefore, the force F applied from the chain-like actuating body to the tooth of the pinion 4 is more in the line of the movement direction and influence a lower resultant force R onto the wall of the channel, resulting in less friction when compared with the actuating bodies that are in spherical shapes. The functional aspects of the pretensioning device of the present invention are described in the following embodiments Upon sensing an emergency condition, for instance in the case of sudden impact of the vehicle, the electric signal is sent to initiator of pyrotechnic charge to produce products of combustion (pyrotechnical charge), which propels the last actuating body 6, which in turn accelerate the other actuating bodies 10. The seal of the last mass body prevents the products of combustion from escaping from the chamber. Thereafter, the last actuating body 6 is propelled through the channel 7 and in doing so pushes the chain-like actuating bodies 10 thus formed as a result of drive generated through the channel 7. Primarily, the channel 7 guides the accelerated chain of actuating bodies 10. Each of the actuating bodies 10 moves past the outer gear profile of the pinion 4 by engaging the gear profile of the pinion 4, for short period of time. The engagement of working section 23 of the actuating bodies 10 with the gear profile of the pinion 4 provides a complimentary radial drive to the spindle 3. The webbing 13 wound on the spindle 3 retracts a determinable amount of webbing back to tighten the seat belt securely to the occupant. Accordingly, the present invention, provides a pretensioner for retracting the seat belt, having a detachable chain-like actuating bodies, said pretensioner comprising a pretensioner housing, a rotatable pinion with an outer gear profile mounted on a rotatable spindle is disposed in the pretensioner housing, a webbing of the seat belt wound on the spindle, a channel disposed in said housing to provide a guiding path for the rapid movement of said chain-like actuating bodies, the actuating bodies consisting of a working area and a pair of projections mounted on either side of their lateral outer edges, each of said projections having a stem and a head, a pair of concave sockets are carved out on the bottom ends of the stems of actuating bodies to form a semi-circular recesses, a chain formed with plurality of actuating bodies by loosely pivoting the head of one actuating body to the semi-circular recesses of adjacent actuating body, intervening gaps formed in the chain between two working areas of said actuating bodies are used as means to mesh with the gear profile of the pinion, said working area of the actuating bodies having a diameter less than the mean distance between the adjacent actuating bodies, and a reservoir to collect the detached individual actuating bodies after use. An embodiment of the present invention, wherein the actuating bodies having an outer diameter in the form of a cylinder comes in contact with the gear profile of the pinion on application of pressure. Another embodiment of the present invention, wherein the actuating bodies are positioned in an angle whereby two actuating members are simultaneously in contact with the outer teeth profile of the pinion even when the pretensioner is in idle position. Further, the intervening gap thus formed as a result of chain-like actuating bodies, is used to mesh with the outer gear profile of pinion. Yet another embodiment wherein optional actuating bodies are selected from cylindrical shaped bodies with circular outer diameter or an outer diameter with concave surfaces. It is also an embodiment of the present invention, wherein a method of pretensioning of seat belt is disclosed by using the pretensioner of the present invention said method comprising the steps of: powering the loosely connected actuating bodies to rapidly move and to form chain-like actuating bodies on pyrotechnical charge, driving the pinion mounted on the spindle by engaging the moving chain-like actuating bodies with the outer gear profile of the pinion, retracting the seat belt by rotating the spindle, detaching the actuating bodies automatically on pretensioning, and storing the detached actuating bodies in the reservoir. In an embodiment of the present invention, a method wherein the chain of actuating bodies is detachable automatically on pretensioning. It is also an embodiment of the present invention, wherein the force applied by the actuating body to the tooth of the pinion is more in the line of movement of the actuating bodies and thereby resulting in lower resultant resistance force and friction.

Advantages

1. The actuating bodies of the present invention act as a chain under pressure to provide the desired force to the teeth profile of the pinion resulting in rotary movement.

2. The actuating bodies of the present invention act as a chain under pressure reduce the resultant force acting on the channel while in use, therefore providing a less frictional movement of the actuating bodies as compared with balls.

3. The pretensioning device of the present invention provides a simple storage area for storing the actuating bodies after their use. As a result no increase in the shape of the retractor.

4. The actuating bodies adopted in the present invention have a secured distance (axis base) to each other and an advantageous shape (cylindrical) for driving a simple and inexpensive drive wheel like a pinion.

Claims

What we claim is 1. A pretensioner for retracting the seat belt, having a detachable chain-like actuating bodies, said pretensioner comprising: (a) a pretensioner housing, (b) a rotatable pinion with an outer gear profile mounted on a rotatable spindle is disposed in the pretensioner housing, (c) a webbing of the seat belt wound on the spindle, (d) plurality of actuating bodies which forms a chain like structure on actuating, (e) a channel disposed in said housing to provide a guiding path for the rapid movement of said chain-like actuating bodies, (f) the actuating bodies consisting of a working area with a pair of projections mounted on either side of their lateral outer edges, each of said projections having a stem and a head, (g) a pair of concave sockets are carved out on the bottom ends of the stems of actuating bodies to form a semi-circular recesses, (h) a chain formed with plurality of actuating bodies by loosely pivoting the head of one actuating body to the semi-circular recesses of adjacent actuating body, (i) intervening gaps formed in the chain between two working areas of said actuating bodies are used as means to mesh with the gear profile of the pinion, and (j) a reservoir to collect the detached individual actuating bodies after use.

2. The pretensioner of claim 1, wherein the actuating bodies are cylindrical.

3. The pretensioner of claim 1, wherein the chain of actuating bodies having an outer diameter in the form of a cylinder comes in contact with the gear profile of the pinion on application of pressure.

4. The pretensioner of claim 1, wherein the actuating bodies are positioned in an angle whereby two actuating members are simultaneously in contact with the outer teeth profile of the pinion even when the pretensioner is in idle position.

5. The pretensioner of claim 1, wherein the intervening gap formed in chain of actuating bodies is used to mesh with the outer gear profile of pinion.

6. The pretensioner of claim 1, wherein optional actuating bodies are selected from cylindrical shaped bodies having a circular outer diameter or an outer diameter with concave surfaces.

7. The pretensioner of claim 1, wherein working area of the actuating bodies having a diameter less than the mean distance between the adjacent actuating bodies.

8. A method of pretensioning of seat belt by using the pretensioner of claim 1, said method comprising the steps of: (a) powering the loosely connected actuating bodies to rapidly move and to " form chain-like actuating bodies on pyrotechnical charge, (b) driving the pinion mounted on the spindle by engaging the moving chainlike actuating bodies with the outer gear profile of the pinion, (c) retracting the seat belt by rotating the spindle, (d) detaching the actuating bodies automatically on pretensioning, and (e) storing the detached actuating bodies in the reservoir.

9. The method of claim 1, wherein the chain of actuating bodies are detachable automatically on pretensioning.

10. The method of claim 1, wherein the force applied by the actuating body to the tooth of the pinion is more in the line of movement of the actuating bodies and thereby resulting in lower resultant resistance force and friction.