WO2002016178A1

WO2002016178A1 - A pre-tensioner

Info

Publication number: WO2002016178A1
Application number: PCT/SE2001/001792
Authority: WO
Inventors: Leif Ennerdal; Lennart Haglund
Original assignee: Autoliv Development Ab
Priority date: 2000-08-25
Filing date: 2001-08-23
Publication date: 2002-02-28
Also published as: GB2366257B; GB0021082D0; GB2366257A

Abstract

In a pre-tensioner a gas generator (6) is provided which, when actuated, directs gas through a nozzle (8) to a support element (9) in the form of a membrane which forms the seal of a cylinder (16) containing a compressed gas. Gas from the gas generator (6) and from the cylinder (16) are directed towards a piston (20) contained within the cylinder (19) the piston being connected to a wire (23) which drives a spool (25) on which part of a safety-belt is wound. The piston is provided with means (21, 22) which enable the piston in the opposite direction. On actuation of the gas generator (6) the piston (20) moves to apply tension to the safety-belt. Gas from the bottle (16) maintains a high pressure on one face of the piston so that if any slack occurs in the safety-belt the piston will move further within the cylinder to take up the slack.

Description

"A PRE-TENSIONER"

THE PRESENT INVENTION relates to a pre-tensioner, and more paiticularly relates to a pre-tensioner adapted to pre-tension a safety-belt in a motor vehicle.

It has been proposed previously to provide a pre-tensioner to provide tension in a safety-belt in a motor vehicle. Typically such a pre-tensioner may incorporate a pyrotechnic device adapted to generate gas when an accident situation, or a potential accident situation is detected, that gas being directed to move a piston within a cylinder, the movement of the piston causing a rotation of a reel upon which part of the safety-belt is wound. Thus tension is applied to the safety-belt. Such pre-tensioners may provide a very beneficial effect, especially in a frontal impact situation.

A typical pre-tensioner includes a gas generator incorporating one pyrotechnic charge which gives a strong pre-tensioning of the safety-belt, although that pre-tensioning only lasts for a relatively brief period of time, which is typically less than one second.

It has been found that if a motor vehicle is involved in a roll-over situation, it would be desirable for a pre-tensioner to be able to provide tension to a safety-belt for a relatively long period of time, for example a time period of several seconds.

DE-A-2517539 discloses a pre-tensioner for pre-tensioning a safety-belt in which a piston unit is provided which can be driven axially within a cylinder by means of a pyrotechnic charge. A resilient spring arrangement is provided between the piston unit and an element connected to the safety-belt. The arrangement is very complicated and relatively weighty.

The present invention seeks to provide an improved pre-tensioner.

According to this invention there is provided a pre-tensioner for pre- tensioning a safety-belt, the pre-tensioner comprising means, responsive to a supply of gas, to provide tension to the safety-belt, the means responsive to a supply of gas being connected to receive gas from a pyrotechnic charge, and also to receive gas from a source of compressed gas, the source of compressed gas being provided with an opening mechanism to open a flow path from the source of compressed gas to the said means, the opening mechanism being adapted to be opened by a flow of gas from the pyrotechnic device.

Preferably the source of compressed gas comprises a gas bottle winch is sealed by a membrane, and the opening mechanism comprises an element moveable in response to a flow of gas from the pyrotechnic charge, movement of the element effecting the rupture of the membrane.

Conveniently the moveable element is an element that initially supports the membrane. Alternatively the moveable element is a piston having a piston rod located to penetrate the membrane.

Conveniently the piston rod is tubular to form a gas flow path for gas from the source of compressed gas.

Preferably means are provided to control the rate of release of gas from the gas bottle, said means comprising a gas flow regulating device.

Advantageously the gas flow regulating device is mounted inside the gas bottle.

Conveniently the gas flow regulating device comprises an element defining a hole, the arrangement being such that the stored gas has to pass through the hole before leaving the gas bottle.

Preferably the stored gas is an inert gas, such as mixture of argon and helium.

Conveniently the means responsive to a supply of gas comprise a piston contained within a hollow cylinder, and movable in response to a supply of gas, the piston being connected to an element which is directly or indirectly connected to the safety-belt.

Preferably means are provided to permit movement of the piston in one direction within the cylinder, and to prevent movement of the piston in the opposite direction. In one embodiment the source of compressed gas is a gas cylinder, which is parallel with said hollow cylinder.

In an alternative embodiment of the invention the source of compressed gas is a gas cylinder which is co-axial with the hollow cylinder, thus the hollow cylinder forms a hollow core for the gas cylinder.

In one embodiment of the invention the pre-tensioner includes a reel on which the safety belt is wound, said means responsive to a supply of gas being adapted to rotate the reel. In such an embodiment of the invention the piston which is contained within a hollow cylinder, and which is movable in response to a supply of gas, may be connected to a wire, the wire being wound around a drum which is mounted to co-rotate with the spool.

In alternative embodiments of the invention the element associated with the piston may comprise a wire or a rigid element which is connected directly to the end of the safety-belt or which is connected to a loop through which part of the safety-belt passes.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a sectional diagrammatic view of a pre-tensioner in accordance with the invention,

FIGURE 2 is an enlarged view of part of Figure 1. FIGURE 3 is a sectional diagrammatic view of part of an alternative pre- tensioner in accordance with the invention.

FIGURE 4 is a perspective view of one sub-assembly forming part of the pre-tensioner of Figure 3.

FIGURE 5 is an enlarged view showing the position of components before deployment of the pre-tensioner.

FIGURE 6 is a view corresponding to Figure 5 showing the position of components during deployment of the pre-tensioner.

FIGURE 7 is a sectional diagrammatic view of part of a further embodiment of pre-tensioner in accordance with the invention.

FIGURE 8 is a diagrammatic sectional view of a component that can be used in a further embodiment of pre-tensioner.

A pre-tensioner in accordance with the present invention comprises a housing 1 of monolithic structure, which supports various further components. The housing 1 defines, within it, a generally annular gas flow passage 2 which communicates, by means of a transversely extending gas duct 3 to a chamber 4.

The gas flow passage 2 surrounds a bore 5 which extends through the housing. Received in one end of the bore 5 is a cartridge 6. The cartridge 6 contains a gas generating pyrotechnic charge 7. The charge 7 is contained within the cartridge 6 so that on ignition of the charge 7 gas from the cartridge 6 flows through a nozzle 8 at one end of the cartridge, and is directed towards a support element 9 which is located within the chamber 4. The support element 9, as will be described hereinafter, is intended to support a membrane sealing a gas bottle containing pressurised gas. The support element 9 is of generally "L"-shape cross-section and comprises a first arm 10, one end of which is received in a notch formed adjacent the nozzle 8, the arm 10 extending generally parallel with the direction of the flow of gas from the pyrotechnic charge 7. The other arm 12 extends perpendicularly to the first arm, and rests on a support region 13 that is again formed on part of the nozzle 8 that projects into the chamber 4. The side-wall defining the chamber 4 is provided with aperture 14 which lead to the annular gas flow passage 2, and a filter element 15 is provided, in the form of a band of porous filter material, which is located in position adjacent the inner wall of the chamber 4, to provide a filter for gas flowing through the apertures 14.

A gas bottle in the form of a cylinder 16 is provided containing a compressed gas which may, for example, be an inert gas which is preferably a mixture of argon and helium. The cylinder 16 is received in the other end of the bore 5. The open end of the gas cylinder 16 is directed towards the cartridge 6, and the open end is sealed by a breakable web or membrane 17. The membrane 17 is in contact with and supported by the second arm 12 of the support element 9. Located to the interior of the gas cylinder 16, adjacent the membrane 17, is a gas flow rate restrictor 18 in the form of a washer, the periphery of which is secured to the gas cylinder 16 in a gas-tight manner, the washer defining a relatively small aperture through which gas may flow.

Communicating with the chamber 4, defined within the housing 1, is a hollow cylinder 19 which contains a generally cylindrical piston 20, the piston 20 being a sliding, but substantially sealing fit within the cylinder 19. The exterior of the cylindrical side wall of the piston is provided with a recess 21 having a tapering portion. Surrounding the piston, within the recess, is an annular element 22 formed, for example, of a resilient material, the combination of the annular element and the conical part of the recess serving, as will be described hereinafter, to permit movement of the piston in one direction within the cylinder 19, but to prevent movement of the piston in the reverse direction.

The piston 20 is connected to a steel wire 23, which passes across the chamber 4 and exits the housing through a substantially gas-tight seal 24. The wire is wound around a drum 25 which is connected to co-rotate with a reel 26 upon which a seat-belt 27 is wound.

The pyrotechnic charge 7 is adapted to be ignited in response to a signal from a sensor, such as a sensor which senses a side impact or roll-over situation.

When the pyrotechnic charge is ignited, gas is generated. The gas leaves the cartridge 6 through the nozzle 8, the flow of gas is directed into a region between the arms 10 and 12 of the support element 9, and the gas dislodges the support element 9 from its initial position, thus moving the support element 9 to a position in which the arm 12 no longer supports the membrane 17. Because the membrane 17 is no longer supported, the membrane ruptures, due to the effect of the high pressure applied to the membrane by the gas within the gas cylinder 19.

The chamber 4 is then supplied, simultaneously, with gas from the pyrotechnic charge 7 and gas from the cylinder 16. The gas passes, from the chamber 4, through the filter 15 into the annular gas flow passage 2, and thus passes through the transverse gas flow duct 3 into the chamber 4. The gas then enters the cylinder 19 and driving the piston 20 axially along the cylinder 19. As the piston moves, towards the right as shown, the annular element 22 moves towards the narrower end of the tapering portion of the piston. As the piston moves, the wire 23 is moved, together with the piston, and thus the drum 25 is rotated, consequently winding the seat-belt 27 on to the spool 26. When the seat-belt is tightened, movement of the piston terminates. If the piston then tends to move back towards the left, the annular element 22 will ride up the tapering portion of the body of the piston 20 and become firmly wedged between the body of the piston 20 and the interior of the cylinder 19, thus preventing movement of the piston towards the left.

After the membrane is ruptured, gas from the gas cylinder 16 may flow through the hole formed in the washer 18, which provides a flow rate regulating effect, past the cover 12 through the gas transfer passage 14 into the gas flow passage 2 and thus, via the gas flow duct 3 into the chamber 4. Thus, gas from the gas cylinder 15 maintains a steady pressure upon the piston 20. Should, for any reason, the seat-belt 27 become slack, this gas pressure will cause the piston 20 to move further towards the right within the cylinder 19, thus again causing a further part of the seat-belt 27 to be wound on to the spool 26.

It is to be understood that the piston effects a first movement when the pyrotechnic charge is activated, primarily as a response to the supply of gas from the pyrotechnic charge. The piston moves very swiftly after the pyrotechnic charge has been actuated, and, although the gas cylinder is opened during this movement, gas from the gas cylinder only makes a very minor contribution to the first movement of the piston 20. Subsequently gas from the gas cylinder 16, which passes through the hole formed in the washer 18 maintains the pressure applied to the piston 20 which will cause the piston 20 to move further towards the right within the cylinder 19 should there be any slack within the seat-belt 27. It is to be appreciated that in utilising the pre-tensioner as described, if any slack occurs in the safety-belt during a relatively long period of time (in the context of motor vehicle accidents) following the beginning of the accident, the seat-belt 27 will be wound on to the spool 26, thus maintaining the tensioning effect provided by the pre-tensioner.

It is preferred that the stored gas within the gas cylinder 16 should be an inert gas, to minimise the risk of the gas poisoning, in any way, the occupant of the vehicle, and preferably the inert gas is a mixture of argon and helium. It is preferred that the flow of gas from the gas cylinder 16 is regulated so that the effect of the gas may be extended to cover a relatively long period of time, in the context of a motor vehicle accident, such as a period of time of up to five seconds.

Figures 3 to 6 illustrate an alternative embodiment of the invention. Again, in this embodiment, a caitridge is provided containing a pyrotechnic charge and gas from the cartridge causes a piston to move to apply tension to a wire which rotates a reel upon which a seat-belt is wound.

Figure 3 illustrates only part of the complete pre-tensioner assembly.

Referring to Figure 3, the illustrated embodiment comprises a housing 30 of monolithic structure which supports various further components. The housing defines a first tubular passage 31 which receives a cartridge 32 which contains a pyrotechnic charge 33. The caitridge 32 seals the end of the passage 32. The housing 31 also receives a composite structure 34 which comprises a pressurised gas cylinder 35 which contains within it, adjacent one side wall, a hollow tube 36. The gas cylinder 35, is closed at one end by a closure plate 37 (see Figure 4). The closure plate 37 defines a first aperture 38 which is aligned with the hollow tube 36. Closure plate 38 defines a relatively small aperture 39 which communicates with a chamber defined within the gas cylinder 35 which contains pressured gas. The aperture 39 is initially sealed by means of a metal foil 40.

The closure plate 38 is mounted to the housing 31 to close a chamber 41 defined within the housing which communicates with the passage 31. A piston 42 is contained within the hollow cylinder 36, the piston 42 being connected to a wire 43 which passes across part of the chamber 41 and which then passes through a substantially gas tight seal 44 defined by the main housing 31.

An actuating element 45 is provided in the form of a piston element having a piston head 46 received in a terminal part of the passage 31 and having a hollow tubular piston rod 47 which extends across the chamber 41 and which is initially aligned with the aperture 39.

As can be seen most clearly in Figure 4 the head 46 of the piston 45 is provided with a plurality of radially outwardly directed resilient arms 48 which engage the side wall of the passage 31 to retain the actuating element 45 in the initial position shown in Figures 3 and 5. It is to be observed that the piston rod 47 is of hollow or tubular form thus defining part of a gas flow duct 48 which extends along the piston rod 47 and to the periphery of the head of the piston.

The pyrotechnic charge 33 is again adapted to be ignited in response to a signal from a sensor, such as a sensor which senses a side impact or roll-over situation. When the pyrotechnic charge is ignited, gas is generated. The gas leaves the cartridge 6 and flows through the passage 31 acting on the piston head 46 of the actuating element 45. The resilient arms 48 yield to release the actuating element 45 which is driven forcibly towards the right, as shown in Figure 3. The piston rod 47 passes through the aperture 39 formed in the closure plate 37 thus rupturing the foil 40. The actuating element thus moves to the position shown in Figure 6. Gas from the chamber defined within the gas cylinder 35 may flow through the gas flow passage 48 constituted by the hollow tubular piston rod and a hollow part of the piston head into the chamber 41. The chamber 41 thus receives gas from the pyrotechnic charge 33 and also from the interior of the gas cylinder 35. The chamber 41 communicates with one face of the piston 42 and thus the gas within the chamber 41 acts on the piston 42 tending to move the piston 42 along the hollow tube 36 thus applying tension to the wire 43. The wire rotates the reel of the retractor, as described above.

Figure 7 illustrates an embodiment which, operatively, is the same as that of Figures 3 to 6 and wherein like parts are given like references. However, in this embodiment of the invention, the hollow tube 36 is not just parallel to the gas cylinder 35, as in the embodiments of Figures 3 to 6, but is mounted co-axially.

The material forming the gas cylinder 35 is welded or otherwise secured to the free end of the inner tube 36 at the terminal region 50 thereof.

Figure 8 illustrates a component that may be utilised in place of the separate pressure cylinder 35 and tube 36 of the embodiment of Figure 7. In this embodiment a single re-entrant tube 51 is utilised, the tube having a portion of a first relatively large diameter 52 which is inwardly or re-entrantly folded 53 back in upon itself to merge with a second portion 54 of slightly smaller diameter. An annular pressure chamber 55 is thus formed which surrounds a hollow cylindrical tubular space 56.

In the present specification "comprise" means "includes or consists of and "comprising" means "including or consisting of.

The features disclosed in the foregoing description, or the following Claims, or the accompanying drawing, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A pre-tensioner for pre-tensioning a safety-belt, the pre-tensioner comprising means, responsive to a supply of gas, to provide tension to the safety-belt, the means responsive to a supply of gas being connected to receive gas from a pyrotechnic charge, and also to receive gas from a source of compressed gas, the source of compressed gas being provided with an opening mechanism to open a flow path from the source of compressed gas to the said means, the opening mechanism being adapted to be opened by a flow of gas from the pyrotechnic device.

2. A pre-tensioner according to Claim 1 wherein the source of compressed gas comprises a gas bottle which is sealed by a membrane, and the opening mechanism comprises an element moveable in response to a flow of gas from the pyrotechnic charge, movement of the element effecting rupture of the membrane.

3. A pre-tensioner according to Claim 2 wherein the moveable element is an element that initially supports the membrane.

4. A pre-tensioner according to Claim 2 wherein the moveable element is a piston having a piston rod located to penetrate the membrane.

5. A pre-tensioner according to Claim 4 wherein the piston rod is tubular to form the gas flow path for gas from the source of compressed gas.

6. A pre-tensioner according to any one of the preceding Claims wherein means are provided to control the rate of release of gas from the gas bottle, said means comprising a gas flow regulating device.

7. A pre-tensioner according to Claim 6 wherein the gas flow regulating device is mounted inside the gas bottle.

8. A pre-tensioner according to Claim 6 or 7 wherein the gas flow regulating device comprises an element defining a hole, the arrangement being such that the stored gas has to pass through the hole before leaving the gas bottle.

9. A pre-tensioner according to any one of the preceding Claims wherein the stored gas is an inert gas.

10. A pre-tensioner according to Claim 9 wherein the stored gas is a mixture of argon and helium.

11. A pre-tensioner according to any one of the preceding Claims wherein the said means responsive to a supply of gas comprise a piston contained within a hollow cylinder, and movable in response to a supply of gas, the piston being connected to an element which is directly or indirectly connected to the safety- belt.

12. A pre-tensioner according to Claim 11 wherein means are provided to permit movement of the piston in one direction within the cylinder, and to prevent movement of the piston in the opposite direction.

13. A pre-tensioner according to Claim 11 or 12 wherein the source of compressed gas is a gas cylinder which is parallel with said hollow cylinder.

14. A pre-tensioner according to Claim 11 or 12 wherein the source of compressed gas is a gas cylinder which is co-axial with said hollow cylinder.

15. A pre-tensioner according to any one of the preceding Claims wherein the pre-tensioner includes a reel on which the safety-belt is wound, the said means responsive to a supply of gas being adapted to rotate the reel.