Method and Device for Relieving Actuation Forces

During Heavy Retardations.

The present invention generally relates to a method and a device for relieving actuation forces during heavy decelerations (=retardations), e.g. in collisions, particularly relieving of actuation forces of persons, who are strapped by car or safety belts in motor vehicles, or of strapped objects, or relieving of actuation forces of parts, for instance of deformation zones of a vehicle. More particularly the invention relates to such a method and such a device, by means of which the person or the object which is strapped by the safety belt or car belt, is protected both against injuries caused if the person or the object is thrown against hard objects in the vehicle and caused by the strapping belts being elastically elongated or said belts being too loosely tightened, and also against pressure injuri.es and decelerations (retardation) injuries, so called G-injuries, which may be caused by the safety belts being too tightly tightened and a subsequent too heavy deceleration of the seated person.

In the following the invention will mainly be described in connection to strapping of car safety belts arranged in a car for the driver and the passenger but it is obvious that the invention is as well useful in other types of vehicles, for tightening of strapped objects or for relieving of forces internally in a car, or in many other situations in which people, animals or objects may be injured due to heavy retardations.

The invention is based on the insight, that during many car emergency situations, e.g. in a collision, an initial strong tightening of the safety belt may be warranted, since the safety belt usually is relatively loosely applied and also is slightly elastic, the tightening resulting in a compensation both of the always existing elasticity of the safety belt and also the elongation of the active part of the car safety belt, which results because of a tightening of the rolled portion of a roll belt (the roll effect.)* and also the successive compression which the human body or the object is subjected to during the

deceleration. This tightening of the safety belt is important, particularly in combination with auto aticly inflatable safety cushions or balloons, which can be mounted in optional positions in front of and beside the driver and the passengers in a vehicle. The invention also is based on the knowledge that the injury effects on persons or objects can be reduced by extending in time the actuation force appears during the collision.

Without the above mentioned initial tightening of the safety belt the strapped person may be thrown forwards and be injured by the wheel, the instrument panel, the wind shield or other hard objects in the vehicle. Also, as is well known, a very tightly strapped person may, during a heavy deceleration, e.g. in a collision, be subjected to very heavy so called G- forces, and besides, this person can be subjected to heavy pressures caused by the safety belt enough to cause serious bodily harm, merely by the influence of the safety belt.

Many various known devices provide a tightening of the safety belt in connection with a collision. Some of these known devices are mechanical in nature and other are pyrotechnical in nature. The latter devices are advantageous, because they react very quickly and within just one or a few hundredths of a second they accomplish the required tightening of the safety belt.

For instance the Swedish laid out patent application No. 379,934 or the German laid out patent publication No. DE-A 3,220,498 relates to a device designed to tighten a safety belt by means of a pyrotechnical charge in case of an emergency. In these two cases the object is to effect an invariable tightening of the safety belt, which tightening eventually can be done in two successive steps. Such an invariable tightening of the safety belt will, if the vehicle is decelerated abruptly, result in a similar heavy deceleration of the strapped person, what may be injurious per se, and besides, a heavy tightening of the safety belt may lead to pressure injuries and other injuries to the strapped person. The present invention is based on the discovery, that it is

possible to strongly lower the risk of injuries due to strong decelerations by attaining a strong tightening of the safety belt in an initial step, after which, preferably in several, maybe in a large number of successive relieving steps, a certain force relieving of the body is attained or even the body is allowed to move an insignificant distance forwards, followed by a stop or some minor renewed tightening of the safety belt.

This can be achieved by means of a pyrotechnical stretching device, namely by the detonation of an initial comparatively strong pyrotechnical charge, primarily tightening the safety belt without locking the belt in this position, after which several, preferably a large number of successive detonations of weaker pyrotechnical charges ensue, between which the safety belt is allowed to slacken somewhat, the strapped person being relieved somewhat or, due to the gravity against the safety belt, being allowed to move an insignificant distance forwards, before the next detonation results in a stop of this movement or attains a renewed minor retightening of the safety belt. By this series of short, quick and comparatively weak, so to speak "jerking" detonations, instead of one or two strong unilaterally operating actuation forces, the generated G-force will be extended somewhat in time, which results in a considerably reduced risk of injuries to the strapped person.

The tightening and the following successive relieving also can be attained mechanically, hydraulically, pneumatically or in other ways, but for the sake of clearness the invention is to be explained in connection to the accompanying drawings only in a pyrotechnical and in the form of a mechanical solution of the identified problems. A mechanical apparatus can comprise a strong, pre-stressed pressure spring, which in a certain situation provides a heavy momentary (immediate) spring actuation, for instance a tightening of a car safety belt, whereupon follows a stepwise releasing of the pressure provided by said spring, for instance by means of any known type of ratchet system, a free wheel

coupling or a similar device.

The invention will now be described in more detail, reference being made to the accompanying drawings. In the drawings Fig. 1 diagrammatically shows a longitudinal section of a pyrotechnical load-relieving device according to the invention. Figure 2 is a diagram illustrating how an apparatus according to the invention can be arranged to operate. Figure 3 illustrates two other tightening and releasing curves, whereby the curve A relates to a special function of an pyrotechnical apparatus, and the fragmentary illustrated curve B illustrates a successive force releasing according to the invention in a vehicle during a collision. Fig. 4 shows a device according to the invention, connected to a three-point safety belt. Fig. 5 fragmentarily shows a detail of the system according to Fig.4, and Fig.6 shows a phase of the functioning of the device according to the invention. Figure 7 shows a mechanical apparatus according to the invention prior to the releasing and the successive tensioning Of the safety belt, and figure 8 shows the same apparatus during the releasing moment. Figure 9 shows an alternative embodiment of a mechanical tensioning and releasing unit. Figure 10 shows an apparatus similar to that of figure 9 but adapted for force relasing in some part of a vehicle. Figure 11 shows a further embodiment of a mecanical apparatus according to the invention having a releasing unit.

The pyrotechnical load-relieving device or valve shown in Fig. 1 is, in the illustrated embodiment, designed as a piston- cylinder-device having a cylinder body 1, in which a piston 2 is displaceable from a normal bottom position, shown in Fig.1, adjacent a pyrotechnical sequential charge 3, and a projected position, in which piston 2 is removed from said bottom position. In the shown upper end of cylinder 1 a cylinder head or a so called piston catcher 4 is provided, which suitably is a separate portion, which is screwed in on cylinder 1. Sequential charge 3 comprises a number of, preferably a large number of,

elementary charges 5 having the same or preferably a different force potentional, e.g. a first heavy charge and next a large number of weak charges. Said sequential charge is designed to be initiated to a detonation by means of a diagrammatically shown ignition device 6, which can be a mechanical or an electric device and of known construction and which in its turn is connected to a trigger activator, e.g. a mechanical or electronic deceleration sensor 7.

Said sequential charge 3 can be designed as a replaceable shell 8, which e.g. jointly with a bottom plate 9 is fixed against the bottom of cylinder 1 by means of a nut 10.

The length and the shape of cylinder 1 can vary depending on what function it will have. Cylinder head 4 and the head of piston 2 are dome-shaped. The underside of piston 2 may have a recess and be adapted to the shape and size of the upper part of sequential charge 3. Cylinder head 4 is, in the shown embodiment, provided with a small exhaust port 11 designed to exhaust the air-cushion when the piston is pushed upwards in the cylinder, and the cylinder is, at a few places close to the bottom of the cylinder, designed with one or several through exhaust ports 12 to discharge possible surplus gas and to allow a withdrawal of piston 2 a larger or smaller distance between the detonation of the elementary charges and subsequent to the detonation of all the charge 3 respectively. Exhaust port 11 and/or exhaust ports 12 possibly are provided with (not shown) single-acting or double-acting spring-loaded valves in order to allow a limited free flow of the gas out of and/or in through said exhaust ports.

A pull rope 13 is fastened to the underside of piston 2 and designed to perform .the required safety operation. The purpose of pull rope 13 is both to effect a contraction of a safety belt and to limit the maximum push of piston 2 out from its bottom position in said cylinder, shown in Fig. 1. The length of rope 13 arrests the piston a distance from the cylinder head, but if the rope for some reasons breaks, then the cylinder head

will operate as a piston catcher 4 and stop the piston from being pushed out of the cylinder. Pull rope 13 extends through an axial hole in shell 8 and out through a central hole in nut 10. Alternatively or in combination with pull rope 13 said piston may on its upside be provided with a projecting actuation rod 14, which is shown in Fig. 1 and which rod directly actuates some safety device in the vehicle.

Elementary charges 5 are designed in a way known per se and are disposed in layers on top of each other or in a spiral and in such a way, that they are triggered in turn after each other, but within a preferably very brief period, say from one or a few thousandths of a second to some required longer period. In the shown embodiment the elementary charges are to be triggered from top to bottom, but obviously other solutions are possible. The elementary charges can e.g. be disposed in a cavity in the piston and be triggered from below and successively upwards. The elementary charges can be designed larger or smaller in such a way, that a certain required operation is obtained. Thus, the elementary charges can be designed in such a way, that the first detonating charge or charges has a larger power, while the subsequent detonations are weaker or successively weaker. Inversely, the elementary charges can be designed in such a way, that the power increases or fluctuates in a certain required and programmed way. Also, it is possible to provide a small power breake between each detonation to allow piston 2 to stop or even return a small distance towards its original poistion between each detonation. In this way piston 2 will step by step "cut" downwards or back to the original position, an improved result being obtained with a drawn-out deceleration and a stepwise load-releiving. By a. suitable design of the pyrotechnical sequential charge 3 almost any required operation can be achieved.

Figure 2 diagrammaticly shows how a pyrotechnical valve according to Fig. 1 will operate in practice. It is assumed in this embodiment that pull rope 13 with its free end is fastened

to some device, which is to be successively tightened and slackened, e.g. a safety belt. Also, it is assumed that sequential charge 3 comprises a large number of elementary charges disposed in a series and having different detonation power, in this embodiment designated a, b, c, d etc. In the diagram power is indicated along the vertical axis and time along the horizontal axis. It is shown that the first elementary charge "a" exerts a comparatively heavy power a during a certain small period of time. e.g. for a safety belt to be primarily tightened. The piston is allowed to move upwards unhindered, since the air cushion is exhausted through exhaust port 11. When this detonation a has ceased, the fastened body is slightly relieved before the next detonation "b" is ignited. The explosion gases are exhausted through exhaust ports 12. Detonation "b" is in the shown embodiment considerably weaker than detonation "a", and the safety belt is tightened only slightly, after which a certain relieving is done until the next detonation "c" effects a renewed minor tightening, etc. In this way the safety belt can be slackened stepwise, until it has returned to its original position, and consequently, the G-force on the strapped person has been extended in time and the maximum pressure, which the safety belt exerts on the person (or the object), has been gradually reduced. Actually, the total time for all the detonations can be as short as a few hundredths of a second and yet a most satisfactory result is obtained by the gradual "cutting" force and load-relieving.

In Fig. 3 curve A shows an alternative diagram is shown, in which the first primary tightening of the safety belt is achieved both by means of a first strong detonation "a" and also by a series of quick minor detonations "al", "a2" ..., which for a certain slight period of time keeps the safety belt unchangeably tightened. Subsequently, the above-mentioned gradual "cutting" power- and pressure-relieving is commenced. Curve B illustrates the power release of for instance a deformation zone of a vehicle as will be explained more closely

i connection fo figure 10.

The pyrotechnical device or valve shown in Fig. 1 is adapted e.g. for tightening of a safety belt and it is shown in such an operation, one of several possible fields of application. The device is for this purpose provided with a roll 15, on which rope 13 from the piston is reeled and from which the rope is unreeeled, when the piston is pushed upwards in the cylinder. Roll 15 is mounted on a stationary shaft 16 and on the same shaft a second roll 17 is mounted. A rope 18 is fastened in second roll 17 and in its opposite end it is fastened to a pull guide 19 in order to shape a safety belt 20 into a loop, which will be explained in more detail with reference to Figs. 4-5. Ropes 13 and 18 are reeled in opposite directions on their rolls, rope 18 being reeled on roll 17, when rope 13 is being unreeled from its roll 15 in connection with the firing of serial charge 3. Rope 18 will then pull guide 19 downwards and shape the safety bel Into a loop, so that the belt will thereby be tightened around the strapped person, and simultaneously belt roll 28 is automatically locked. In an alternative embodiment of the device in Fig.1 a locking device is connected to the roll system 15-17, which device comprises a third roll 21, which also is mounted on shaft 6 and is connected by means of a freewheel locking device 22 and which over a rope 23 is connected to a fourth roll 24, on which rope 23 is reeled. By means of freewheel locking device 22 the rope 23 can be unreeled from roll 24 to roll 21, when pull rope 13 jointly with piston 2 travels in the opposite direction, i.e. when piston 2 travels downwards, and when rope 13 after the unreeling is reeled anew on roll 15. The advantage of this device is that the body never is allowed to move forwards a longer distance than what 1s equivalent to the unreeled length of rope 23, which 1s fastened to roll 24.

Fig. 4 shows the device according to the invention connected to a three-point roll safety belt 20 in a phase, when the deceleration force from the body of the passenger gradually

is relieved in several minor turns. The device also can be connected to different types of multi-point belts, and it is also possible to use two or several devices according to the invention for the same strapped person, e.g. one for the breast band portion and one for the hip band portion or to connect just one device to the breast as well as the hip band portion, and to connect a "central" device to two or more safety belts respectively. However, in Fig. 4, for the sake of simplicity, just one device is shown, which is connected to the breast band portion, Actually, 1t 1s easy to connect the described device also to already available safety belts. An electric contact is suitably provided, which prevents the pyrotechnical device from being triggered, if the belt lock is not connected.

Fig. 4 shows how belt 20 from a belt roll 28 runs though three different guides, namely two stationary guides 25 and 26 as well as the above-mentioned pull guide 19. According to Fig. 5 the pull guide is positioned in such a way, that the belt as a rule freely passes through the same and only slides over stationary guides 25 and 26. It is easy to disengage the pull guide from a holder 27, in which it may be mounted. Holder 27 lets the pull guide go, as soon as a charge 3 is triggered, the pull guide being pulled downwards and body 29 of the strapped person then being fastened against the seat in the car.

Fig.6 shows an alternative embodiment of the invention, in which the pyrotechnical valve is inversely mounted as compared to that of Fig. 1, said valve, by means of rope 13, directly actuating the pull guide in a phase, in which piston 2 stepwise "cuts" backwards towards its original position, namely the position before the collision. Figures 7 and 8 show a simple example of a mechanical apparatus according to the invention, comprising a cylinder 30 in which a piston 31 is displacable. Between the cylinder 30 and the piston 31 there is an annular space in which a strong spring 32 is mounted. The spring 32 is clamped between an upper collar of the cylinder 30 and a lower collar of the piston 31, so that

the spring 32 acts to press the piston 31 downwards in and through the cylinder 30. In its normal position the piston 31 is locked in the cylinder 30 with fully tensioned spring 32 by means of a lock 33, which can be actuated by means of a deceleration releasing means 34 which is of a type known per se and which is only shown diagramatically. During a heavy deceleration said releasing means 34 provides a release of the lock 33 from the piston 31, whereby the piston is being pressed in and through the cylinder 30 by the spring 32, and whereby a rope 13 pulls down the pull guide 19 from the holder 27, and whereby a sling of the safety belt is pulled down as shown in figure 8.

For providing, during a collision and after the safely belt has become tightened, a successive releasing of the deceleration force of the body in minor releasing steps and with a certain resting operation between each such releasing step the lower part of the piston 31 is formed with a barb-like ratchet shaft 35 having downwards widened cone portions 36 and flat bottom surfaces 37. Said ratchet shaft co-operates with a pair (or several pairs) of locking arms 38 having rolls 39 at their ends. One or more springs 40 having a predetermined spring force and mounted on a guiding shaft 41 act to press the locking arms 38 towards each other. Normally the locking arms 38 are kept locked in a released position for the ratchet shaft as shown in figure 7. hen the ratchet shaft 35 starts moving upwards and into the cylinder, 30 caused by the counter directed pulling of the rope 13 (see the arrow) depending on the gravity force of the body during the deceleration, a locking means (not shown) in the cylinder is released, whereby the locking arms 38 are being released and are pressed into contact with the ratchet shaft 35 as shown with the full lines in figure 8.

Now the locking arms 38 with their rolls 39 are relatively strongly pressed into contact with a first cone portion of the ratchet shaft 35, and when the ratchet shaft 35 is pulled further upwards by the action of the pulling rope 13 the locking

1 t

arms 38 with their rolls 39, which are rolling along the upwarly moving cone portions, become pressed apart against the action of the spring or the springs 40 whereby the safety belt is slightly slackened or elongated. When the rolls 39 of the locking arms 38 roll over the edge and into engagement with a flat bottom surface 37 of the ratchet shaft there appears a short resting pause, during which the safety belt is being slightly tensioned depending on a certain re-slackening until the rolls 39 of the locking arms 35 start rolling along the next cone portion and the safety belt is once again being slightly slackened or elongated.

During the short periods of time that the rolls 39 of the locking arms 38 roll along the cone portions 36 the human body, which previously had a free and almost unhindered possibility of moving forwardly, now gets a short period of braking and thereby looses a little amount of the total deceleration force developped or loaded with during the said collision. When the rolls 39 slide over the edge and into contact with a flat bottom portion 37 the human body once again gets the possibility of moving slightly forwards until the rolls 39 of the locking arms

38 start rolling along the next cone portion 36.

The above described force releasing should follow several times during a predetermined moving-time or a predetermined moving-distance, and whereby the strapped body does not become locked by the safety belt.

The ratchet shaft 35 acts as a kind of free wheel ratchet which allows a stepwise releasing of the tensioning force of the belt 20 in that the rolls 29 roll along the cone portions 36 which administrate the re-tensioning force for the spring 32 and which prevent a renewed release of the spring 32 after the rolls

39 have reached a position in contact with the flat bottom surface 37 of the ratchet shaft 35.

Alternatively to a ratchet shaft having cooperating locking arms the power release apparatus can be formed as illustrated in figure 9. In this embodiment the apparatus comprises a cylinder

30, and the lower end of the displacable piston 31 is formed as a sealing piston part 42. The lower end of the cylinder 30 is formed with a rotatable valve means 43 of the known type which allows a free displacement of the piston 31, 42 towards the inner of the cylinder, and which allows a successive re-pulling of the piston and the saftety belt 20 resp. via the rope 13 in a series of successive steps and intermediate resting pauses, in that the valve means 43 during its rotation in one moment closes and in the next moment opens one or more (not shown) valve openings at the bottom of the cylinder 30 outside the rotatable valve 43.

The apparatus can be formed with a bar 14 extending through the bottom of the cylinder 30 and which bar 14 is fixed connected to the sealing piston portion 42 as indicated with the dotted lines in figure 9. The bar 14 can be arranged to actuate a protection of a safety means of the vehicle, for instance a children's safety seat, or to provide a momentary (immediate) expelling of a protection cushion, which has in advance or automatically become inflated, thereby first preventing the person in. said seat from moving from its relatively safe sitting position, and then under completely controlled forms successively, in several small releasing steps, unloading the body from the deceleration force or the kinetic energy that the body is subjected to or is loaded with during a heavy collision. Thus, for instance the actuation bar 14 in the apparatus according to figure 1 or 9, or the ratchet shaft 35 of figure 7-8 can be connected to the wheel bar of an axially telescopic wheel having an inflatable protection cushion such that wheel bar with the protection cushion is being expelled towards the driver upon a heavy.deceleration, and so that the wheel bar thereafter, by the action of the deloading apparatus according to the invention is stepwise returned to its initial position during the deceleration step as previously described. In an alternative embodiment shown in figure 10 the apparatus is mirror symmetrical about a cross centre line, and

at cylinder bottom it is formed with a rotatable valve 43a, 43b and a projecting actuation bar 14a and 14b resp., each bar being fixedly connected to a sealing piston portion 42a, 42b. The pistons with the sealing piston portions 42a, 42b are telescopically introduced in each other and extend through a common pressure spring 32 which is kept pre-stressed and locked by a (not illustrated) catch 33a, 33b connected to the deceleration releasing means.

During a heavy collision the deceleration releasing means releases either of or both catches 33a, 33b, whereby the spring 32 expells the corresponding actuation bar 14a, 14b in either direction depending from which direction the deceleration forces appear in relation to the location of the apparatus. The actuation bar or bars can be expelled practically without any resistance from the valve 43a, 43b. Depending on the counter directed force against the bar 43a, 43b, for instance a deformation of some part of the vehicle, there is a tendency that the bar is pressed into the cylinder 30, but a free introduction is restricted by the rotatable valve 43a, 43b, which only allows short introduction distances with intermediate resting pauses, since the valve alternatingly opens and closes the valve openings of the cylinder bottom as illustrated diagram atically in figur 3, curve B.

Since the valve opening of the cylinder opens and closes resp. several times during the course of the collision, without having the actuation bar becoming locked, it is thereby possible to obtain an improved effect by a deceleration which is extended in time and a stepwise unloading of the force, and therefore the invention is suited also for being used as a dampening means included in the vehicle and arranged to provide a deformation or similar which follows in a controllable way.

The apparatus of figure 11 is a mechanical embodiment of the apparatus shown in figure 1 in combination with a the ratchet bar system of figures 7-8. In the apparatus of figure 11 the ratchet bar system is formed as a ratchet ring 44 having

3

14

conical ratchets 45, see figure lib and the partial evolvent picture of figure lid, and a cooperating ball ring 46 having several balls 47 beared is said ring, see figure lie. In its normal condition the ball ring 46 is locked, released from the ratchet ring 44 as indicated with the dotted lines of figure 11a, but it becomes engaged after the safety belt has becomed tensioned, and this is made in that a spring means (not shown) connected to the ball ring becomes released depending on the counter-directed force from the safety belt 20 and the pulling rope 13 (the gravity of the human body), which releases the ball ring 46, and said ring is then pressed into spring contact with the ratchet ring 44.

The ratchet means 44-47 thereby allows a stepwise slackening of the safety belt following the arrow 48 but prevents a further tensioning of the safety belt 20 depending on the cooperation between the balls 47 and the conically formed ratchets 45 of the ratchet wheel 44.

The apparatus Includes a tensioning means comprising a piston 30 which over a wire 49 is connected to a wire roll 50 which is fixed on a shaft 51. A belt roll 52 is mounted on the same shaft and a belt 53 is adapted to be reeled onto said roll 52. The belt is via the pulling rope 13 connected to the pull guide 19 for the safety belt 20.

When the piston 31 is released, by means -of a (not illustrated) deceleration releaser as previously mentioned, the spring 32 presses the piston 31 to a bottom position in the cylinder 30. Thereby the piston 31 brings the wire 49 which is thereby unreeled from the wire roll 50. At the same time the belt roll 52 is rotated, whereby the belt is reeled onto the roll 52 and tensions the safety belt 20.

Between the wire roll 50 and the belt roll 52 there may be a release coupling 54 which releases the wire roll 50 from the belt roll 52 when the piston has taken its position at the bottom of the cylinder 30. During a heavy deceleration the piston is immediately

released and is pressed downwards in the cylinder 30, and concurrently therewith the belt 53 is reeled onto the belt roll 54 and causes a sling of the safety belt to be pulled down. Due to the deceleration the human body is pressed to the safety belt 20 thereby providing a counter-directed pulling of the safety belt 53. Thereby the lock for the ball ring 46 is released and the ball ring is biassed by spring action to the ratchet wheel 44. Depending on the cooperation between the catches 45 of the ratchet wheel and the balls 47 of the ball ring the belt is thereafter being slacked in a controlled operation comprising a series of slacking steps and intermediate rest periods during which the safety belt is subjected to a certain elastic restretching as shown 1 figure 2. The stepwise slacking and restretching of the safety belt is made without locking of the safety belt and thereby without locking of strapped body during a collision, and hence the strapped body can move slightly forwards during the course of the deceleration. Thereby the deceleration process is extended in time and an improved effect is obtained in that the power relase is extended in time.