A DEVICE FOR COUNTERACTING THE OCCURRENCE OF WHIPLASH INJURIES

Abstract: A device for counteracting whiplash injuries which can occur at a rapid motion change of a vehicle, e.g., a collision from the rear. The device includes means, allowing a controlled displacement of the entire seat and the person sitting thereon backwards against the direction of travel along control elements at a motion change, whereby the seat is arranged to remain in a backward position after the motion change. Said means includes at least one braking means (2) for retarding the seat (20) and the person sitting thereon, along said control element (1). The braking means (2) is so designed that a part of its braking force is a function of the weight of the person. The braking means is arranged to give a low braking froce during the initial motion of the seat backwards, applying an increasing braking force during the continued motion of the seat so that the motion velocity of the seat successively decreases in relation to the chassis of the vehicle, until the motion substantially has stopped before the seat and the person reach the maximal rear position of the braking means.

Description: A device for counteracting the occurrence of whiplash injuries The present invention relates to a device for counteracting the occurrence of whiplash injuries at a rapid motion change by a vehicle, e.g., a collision from the rear, the device including means, which allows a controlled change of position of the seat and the person sitting thereon backwards in relation to the direction of movement along the control element at the motion change, whereby the seat is arranged to remain in a rear position after the motion change. The background of the invention and the problem A whiplash injury is a soft tissue injury which can occur on account of violent acceleration and/or deceleration applied to the cervical spine. This kind of injuries occur i. a. when sitting in a car which is subjected to a rear-end impact. Whiplash injury at rear-end impact in a car is a large and a well known problem in today's cars. This kind of injury has increased while other injuries have decreased. There are a number of theories about how whiplash injuries occur at rear-end impacts. Some of them are shortly described below. 1. The cervical spine is subjected to a special movement in the early phase of the collision due to the neck being pressed forwards at the same time as the head and the back part move into the back rest of the seat. This happens because the back rest is considerably more stiff at the top portion due to the beam connecting the right and left side of the back rest. 2. The cervical spine assumes a S-shaped curve, which is an abnormal movement, during the early phase of the collision when the head moves backwards in relation to the shoulder part before the head starts to pivot. 3. There is a pressure increase in the spinal channel due to the decrease of the volume of the spinal channel in a very short period of time when the head is tilted backwards. 4. The cervical spine is subjected to shear stresses as the entire head wants to move backwards in relation to the shoulder part. 5. A rebound occurs in the late phase of the collision and the body is thrown into a stiff car belt due to the elastic energy of the back rest of the chair. The neck then makes a movement which passes its normal end position. 6. Since the acceleration of the chair at a rear-end impact is reciprocally proportional to the weight of the person, this means that the chair moves different distances backwards, when persons having different weights is subjected to the acceleration. The risk is then that a heavy person moves to the end position of the sliding track, which gives a major impact with successive rebound, which may be worse than a corresponding impact at a fixedly mounted chair. However, a light person e.g., a child can not achieve a force sufficient for the chair ack rest to begin to move backwards in the car. Independently of the reason for the occurrence of whiplash injuries, a common factor for all the above theories is a too high acceleration affecting the body in one way or another in such a manner that the injury occurs. Geiger, et al, showed in human trials 1995, that no whiplash injuries arise if the acceleration was reduced to below 4 g - 5 g (Geiger, B. C, Steffen, H., "Comparison of head neck kinematics during rear end impact between standard hybrid III, RID neck, volunteers and PMTO's", IRCOBI, 1995). The invention is based on a device described in WO98/40238 and including means, which at a motion change allows a controlled change of position of the entire seat backwards in relation to the travel direction. The seat is provided with control elements arranged to provide the seat and the person thereon, an essentially simultaneous movement against the travel direction and /or an essentially pivoting movement. Further, the seat is arranged to remain in a rearward position after the motion change. The object of the invention and the solution of the problem The basis for the present invention is a study based on crash tests with different kinds of dummies (Hybrid III and BIORID) and a mathematic model for simulation of the dynamics around whiplash injuries. After having achieved a good correlation between the mathematic model and the crash tests with the dummies, it can be noted that all values being considered having importance for the risk of acquiring a whiplash injury, have been reduced with 20 % till 70 % using the present invention. The purpose of the present invention is to reduce the acceleration of the person directly after the incidence of the collision, so that it not exceeds 4 g or 5 g, whereby whiplash injuries can be avoided or at least be significantly alleviated. This object has been solved by means of the features defined in the claims. Description of the drawings The invention will be further described below in a number of embodiments with reference to the drawings. Fig. 1 shows a cross section through a first embodiment of control and braking means forming part of the invention. Figs. 2, 3 and 5 show schematically three different embodiments of braking means providing a braking force utilizing plastification. Fig. 4 shows schematically a side view of a further embodiment of a braking means providing a braking force by means of friction and a resilient force. Fig.6 shows a side view of a person sitting on a seat and the forces influencing the same. Description of the embodiments The device to counteract the occurrence of whiplash injuries according to the invention includes specific means, which at the motion change of the vehicle allows a controlled change of position of the entire seat 20 backwards in relation to the direction of movement. The term seat means at least one sitting part 21, a back rest 22 and a neck rest 23, see fig. 6. The seat is provided with control elements 1, which are arranged to give the seat and the person thereon an essentially simultaneous, linear movement against the direction of travel and/or an essentially pivoting motion. Said means comprises braking means 2 to brake the seat and the person sitting thereon. The braking force of the braking means is related to the weight of the person in such a way that the braking force is higher for a person having a higher weight than for a person having a lower weight. Further, the braking force is arranged to increase during the movement backwards relative to the floor of the vehicle. The braking of the seat is as said, taken care of by the braking means 2 which is so designed that the velocity of the motion for the seat and the person relative to the floor of the vehicle decreases until the movement has stopped and this before the seat and the person reach the maximum rearward position of the braking means. It should be noted that this naturally only applies when the rear end impact is of the size and the extent that a risk for a whiplash injury is present. A first embodiment is shown in Fig. 1, in which 1 designates a control element provided with a braking means 2 in the form of three friction surfaces 2a between a seat part 3 and a chassis part 4. Suitably two control elements 1 are arranged between the seat and the chassis next to each other in the direction of movement at an impact. The chassis part 4 may be constituted by a sliding track and the seat part 3 of a slide adapted to cooperate with each other. The sliding track 4 may be shaped as an U-girder, in which the slide 3 is displaceable. The slide 3 and the sliding track 4 are arranged in friction contact with each other, so that the seat is braked during its movement backwards at a relative motion change. The friction coefficient for the contact surface 2 may be essentially constant along the control element 1, but may also be arranged to increase in the direction of movement of the seat. Using fundamental physical principles the friction coefficient can be calculated using a simple model as follows. Assuming that the seat exhibits two support points against the base, whereof one for reasons of simplicity is assumed to be zero, the seat and the person thereon apply a gravitation force F mg directed downwards. This gravitation force is compensated by two normal forces F ljZ and F 2 z directed upwards. In figure 6 the force situation is shown and by applying fundamental mechanical principles in a coordinate system in a suitable way, the following equations are obtained, where: Fx = the force in x-direction Fz = the force in z-direction m = the total mass of the chair and the person a stol = the acceleration of the chair g = gravitation μ = the ratio between Fx and Fz (friction coefficient) d = the distance in z-direction between Cg (the common centre of gravity) and the sliding track b = the distance in x-direction between the front and rear sliding point c = the distance in x-direction between the front sliding point and Cg Motion equation: ∑F X ~ nixa; F iχ +F 2x= mxa stol (1) Equilibrium equation: ∑F Z = 0; F )z +F 2z - mxg= 0 (2) Constitutive correlation (Coulumbs law): F lx = μxF lz (3) By utilizing the d'Alemberst force (mxa) in the moment equation around point 2 is obtained: m x a stol χ d + m x g χ c - F lz x b = 0 (4) To simplify the calculations in this example, put: F 2x = 0 (5) (l) + (2) → m χ a stol = xF, z ; (4) = F lz = m x a stol x d + m x g x c / b From this follows: mx a stoI x b = m x μ x a stoI x d + m x μ x g x c a s t o i = μ x g xc / (b-μ)d From the above it is evident that a stoI is independent of the weight of the person. According to a second embodiment, shown in figure 2, the braking means may comprise a plasticizing means including at least one projecting seat part 5 and at least one chassis part including a rectangular opening or a groove 6. The groove is at least to a part 7 of its extension narrower than the first part. The seat part 5 is arranged for a relative motion change along the groove 6 under simultaneous plastification of one or both parts 5 and 6. The term plastification means a change of shape which does not reassume its earlier shape. One example of plastification is when one or both contact surfaces 2 are designed with a friction material, which may be serrations, toothing or the like or with a friction coating, e.g. of the type sand paper. The friction material or coating may be thinner in the beginning of the sliding track and increase towards the end of the track as to obtain an increased retarding effect. In figure 3 an alternative embodiment of the plastification is shown. Here the cross section of the seat part 3 is wedge-shaped, the converging surfaces 8 of which cooperates with the side surfaces 9 in a groovelO in the chassis part 4. The groove 9 is designed with a complementary form to the form of the wedge. The wedge-shaped seat part 3 is relieved by springs 11, so that the wedge 8 in the relieved state of the seat 20 is somewhat elevated relative to the bottom of the groove 10. Depending on the weight of the person a major or a minor part of the friction surfaces 8 and 9 to participate in the plastification. The arrow FI indicates the weight of the person and arrow F2 the collision force moving the chair in opposite direction. According to a fourth embodiment shown in figure 4, the braking means 2 comprise at least one resilient element 12, which is connected to a friction block 13, and which braking means is displaceable within two inclined friction surfaces 14. The spring 12 is arranged transversely against the direction of movement of the seat, in order to prevent the rebound of the seat from a rear end position and thereby to avoid the risk of injury associated with the rebound. The braking force is achieved by that the movement of the braking means 12, 13 continues in the wedge shaped groove 10, in the direction of which the groove taper. This leads to an increase of the braking force. It should be noted that the resilient element 12 also may comprise a part of the wedge shaped groove 14, i.e., that one or both side of the friction surfaces 14 of the wedge shaped groove 10 flexes back and thereby aids to retard the seat. An other alternative of utilizing plastification is shown in figure 5. The plastification means consists of a rectangular element, e.g., a rod, a plate 15 or the like, arranged between two loading points 16, 17, 18 situated in a triangular relation on both sides of the element 15. The point 17 may for example represent the seat part 3 and the points 16 and 18 the chassis part 4. The element 15 is suitably of a plastic material, which does not reassume its earlier shape after the deformation. For all the above described embodiments applies, that the seat or its back rest/ neck rest is brought to assume a forward leaning position, before the seat is set in a backwards motion, to place the neck rest in a forward' position. This localisation in advantageous in view of injury, since the neck rest is displaced in the direction towards the rear part of the head of the person in the incidence of collision and catches its backwards impact. The forward leaning position is achieved by means of a release mechanism, mechanically activating a spring, or pyrotechnically a powder charge or other suitable power, during a certain period of time, e.g., 10 - 50 ms. Thereafter the seat may be given a backwards tilted position, which eventually increases during the continued movement of the seat. In order to reduce the acceleration at a rear end impact, it may be suitable to arrange an acceleration measuring device, which applies the brakes of the vehicle when the acceleration exceeds a certain value and the velocity of the vehicle is below an other value. The collision velocity may then be reduced by between 0.5 and 1 g. It should be noted that it is possible to and may be advantageous to combine one or more of the described embodiments of braking means. Therefore it may be used a resilient, a secondary as well as a plastic change of shape one by one or in combination. The invention is not limited to the described embodiments but it would be obvious for the person skilled in the art, that several modifications and variants may be performed within the scope of the enclosed claims.

Claims: Claims 1. Device for preventing the occurrence of whiplash injuries during a rapid motion change, e.g., a collision from the rear, the device including means allowing a controlled change of displacement of the seat and the person sitting thereon backwards in relation to the direction of movement at the motion change, whereby the seat is arranged to remain in a rearward position after the motion change, characterised in, that the device includes at least one braking means (2) for retarding the seat (20) and the person sitting thereon along said control element (1), that the braking means (2) is so designed that a part of its braking force is affected by the weight of the person, and that the braking means is arranged to give a low braking force during the initial motion of the seat backwards, and to apply an increased braking force during the continued motion of the seat so that the motion velocity of the seat successively decreases in relation to the chassis of the vehicle, until the motion substantially has stopped before the seat and the person reach the maximal rear position of the braking means. Device according to claim 1 , characterised in, that the braking means (2) is a friction brake, including at least one friction surface (2a) between a seat part (3) and a chassis part (4). Device according to claim 2, characterised in, that the friction coefficient of the contact surface (2a) essentially is constant along the braking means (2) of the control element (3). 4. Device according to claim 2, characterised in, that the friction coefficient of the contact surface (2a) is arranged to increase in the direction of movement of the seat. 5. Device according to claim 2, characterised in, that the contact surfaces (2a) of the braking means include or comprise plasticizing means, which are designed to provide a permanent deformation. 6. Device according to claim 1 , characterised in, that the chassis part (4) include at least one rectangular opening, groove (6) or the like, in which a seat part (5) is insertable, that the groove (6) and the seat part (3) cooperating with this are provided with or designed with friction surfaces, and that the opening, the groove (6) or the like, is narrowing along at least a part of its extension in the direction towards one end its rear diverging end so that an increasing braking effect is achieved between the parts (3, 4) during a relative motion change. 7. Device according to claim 1, characterised in, that the seat part (3) has a wedge-shaped cross section, the converging surfaces (8) of which are arranged to cooperate with the side surfaces (9) in a groove (10) or the like in a chassis part (4), that the groove (10) or the like are designed with a shape essentially complementary to the shape of the wedge, and that the wedge-shaped seat part (3) is vertically displaceable in the groove against the action of at least one spring (11). 8. Device according to claim 5, characterised in, that the plasticizing means is designed with increasing amounts of material for plastification in the direction of movement of the seat. 9. Device according to claim 1, characterised in, that the seat part (3) of the braking means (2) includes a braking block (13) acted upon by a resilient element (12), that the braking means (2) is arranged and displaceable in the space between two inclined surfaces (14) of the chassis part (4), and the flexing motion of the resilient element (12) is arranged transversely to the motion direction of the seat. 10. Device according to claim 1, characterised in, that the seat and/or its back rest /neck rest are provided with means arranged to bring the seat and/or its back rest /neck rest in a forward leaning position in the first phase of the collision movement, in order to meet the back head of the person. 11. Device according to claim 1, characterised in, that the seat and /or its back rest are provided with means which are arranged to during the motion of the seat backwards to bring this in a rearwardly inclined position relative to the floor of the vehicle. 12. Device according to claim 10, characterised in, that said means comprise a release mechanism, which mechanically activates a spring (11) or pyrotechnically a powder charge or other suitable power , during a certain period of time, e.g., 10-50 ms, during which the seat is tilted forwards. 13. Device according to claim 5, characterised in, that the plasticizing means comprise a rectangular element (15), e.g., a rod, plate or the like, which is arranged between the seat part (3) and the chassis part (4), that the rectangular element (15) is intended to receive bending forces at motion of the seat part (3) relative to the chassis part (4), and that the element (15) is of a plastic material, which does not resume its earlier shape after the deformation. 14. Device according to claim 1, characterised in, that an acceleration measuring device is arranged, which emits a signal at a rear end impact when the acceleration exceeds a certain value and the velocity of the vehicle is below an other value for activating the brakes of the vehicle.

Inventors: NILSSON KENT, NILSSON, KENT
Applicants: NILSSON KENT, NILSSON, KENT
Application year: 2000
Main classification: B60N2
IPC codes: B60N2