It is a well-known fact that, when a vehicle equipped with a frame hitch at its rear end projecting beyond the rear end of the vehicle to permit access to the towing <BR> <BR> <BR> <BR> ball of the frame hitch is involved in a collision from the rear or is influenced in some other way by a large force from the rear, a catapult-like effect is imposed on the occupants sitting in the vehicle, even if they are secured in place with a safety belt, because in the majority of cases a distance remains between the head-rests and the rear part of the occupants'heads.

When a modern vehicle is involved in a collision from the rear, and if a frame hitch is installed, the effect is catapult-like, that is to say the integral deformation zones of the vehicle are invalidated. The effect is more or less like driving into a rock. A vehicle with a frame hitch

which is involved in a collision from the rear, even at relatively high speeds, caR very often entirely escape damage to the bodysork at the rear. The whole of the force from the colliding vehicle is then absorbed by the frame hitch and its attachments, which are very often fixed to the frame of the vehicle, such as the chassis member system or the bottom plate, which are not included in the deformation zones in the same way.

Although frame hitches are previously disclosed in which the actual coupling component with its ball can be readily detached from the vehicle and stored in the luggage compartment, for example, the attachment for the frame hitch remains in place and projects beyond the rear extremity of the vehicle. It is this attachment which, in the event of a rear-end impact, transfers the impact forces from a vehicle colliding from the rear.

The risk of whiplash injuries is believed to increase significantly when this type of traditional frame hitch is installed, and the total cost of neck injuries in the EU is estimated at the equivalent of around 90 zhousand million Swedish kronor.

Also previously disclosed through SE 396 202 B and US 3 843 162 A are frame hitches of which the attachment is so arranged, for example in the event of an impact with the vehicle in question from the rear, as to be displaced in a forward direction. The aforementioned previously disclosed designs have not met with success in the vehicle industry, however, the reason for which is believed to be that the attachments that were app ied were excessively compllcat2d or were incapable of diverting fully the rigid force effect of the frame hitch in the normal direction of travel of the vehicle, with the result that the force of the colliding vehicle was transferred to the vehicle subject to the impact with an associated risk of neck injuries to the driver and passengers in the aforementioned impacted vehicle.

The principal object of the present invention is thus, in the first instance, to solve the aforementioned problems by simple and effectively functioning means in such a way that the harmful effect on the occupants of the impacted vehicle is reduced and, at least, is not aggravated due to the presence of a frame hitch on the vehicle in which they are travelling. That is to say, the object is to arrange the frame hitch so that it crumples or disappears in some other way under the rear part of the vehicle, for example in the event of a rear impact.

The aforementioned object is achieved by means of an arrangement in accordance with the present invention, which is characterized essentially in that the means for achieving the aforementioned possibility of free displacement of the frame hitch are formed by at least one of the following : a number of members exhibiting lattice construction so arranged, when subjected to an external influence, as to be deformed to produce a change in their length, whereby the aforementioned lattice beams are so arranged as to be attached on the underside of the vehicle to its frame and/or bottom plate so that they are influenced by pressure to bring about their compression; explosive means such as an exploding bolted joint, an exploding pin or some other exploding connection between the frame hitch and the vehicle in question; a telescope, in which a number of deformable devices are present between the constituent telescoping bars of the aforementioned telescope; a fluid device, such as a gas-filled or liquid- filled piston, which fluid-filled piston is so arranged for the purpose as to be emptied rapidly of its fluid medium when subjected to an external force in the aforementioned directions and as to be compressed ;

a shear plate constructed from two angled plates which are attached to one another at some point in the longitudinal extent of the hitch under the vehicle, both of which plates are set at an angle and are attached with bolts, which are so dimensioned as to shear when they are subjected to a given force in the event of an impact with the vehicle from the rear, in conjunction with which the hitch becomes detached from the vehicle and has no negative influence on the deformation zones of the vehicle; or a frame hitch bar mounted under the vehicle and restrained by a cable in both lateral directions, in conjuction with which both cables are so arranged as to absorb all tractive forces in the rearward direction, but are so arranged as to collapse when they are subjected to a given force in the forward direction.

The invention is described below with reference to the accompanying drawings, in which: Fig. 1 illustrates a passenger car equipped with a frame hitch ; Fig. 2 illustrates schematically the attachment or such a frame hitch to the rear part of the vehicle viewed from the side; Fig. 3 illustrates the attachment of the frame hitch as a plan view; Fig. 4 illustrates means for the frame hitch to enable it to be displaced from its position in the event of a rear-end collision; Fig. 5 illustrates an example of means to enable the aforementioned displacement; Fig. 6 illustrates another example of means to enable displacement of the frame hitch; Figs. 7-9 illustrate a further example of a frame hitch attachment functioning with attachment plates; and Fig. 10 illustrates an example of a frame hitch attachment with cables.

An arrangement 1 for a frame hitch 2 for a vehicle 3 comprising an attachment-component 4 to which the frame hitch 2 is attached for the purpose of securing the frame hitch 2 to the vehicle 3 on its underside 3A, in conjunction with which the ball 5 or a similar coupling component of the frame hitch is so arranged as to extend rearwards 6 beyond the rear part of the vehicle in a hitching position, comprises means 7 to enable the frame hitch to be displaced from its position if it is subjected to an external influence. More specifically, means 7 are provided between the frame hitch 2 and the vehicle 3 and are so arranged that, in the event of powerful influence of the frame hitch 2 in a direction from the rear 8 and/or at an angle from the rear 9, as to enable the hitch 2 and/or part of a rearward-projecting attachment component 10 for a detachable frame hitch ball 6 to be displaced freely from its rearward-projecting hitching position I and to be moved instead towards a detachable position in which the rear end 3B of the vehicle, preferably for instance the rear bumper 11 of the vehicle, is instead accessible to influence by an external force.

Means for achieving the aforementioned possibility of free displacement of the frame hitch 2 and/or its attachment component 10 are constituted in accordance with a preferred illustrative embodiment by a number of members 7~ exhibiting a lattice construction, for example as shown in Fig. 5, which are so arranged, when subjected to an external influence from the rear 8 and/or at an angle from the rear 9, as to be deformed to produce a change in their length, that is to say as to be compressed so that their effective length L is reduced and the frame hitch 2 is caused to be pushed in towards the inside of the vehicle and accordingly does not produce an injurious effect on the occupants. The aforementioned lattice beams are so arranged as to be attached on the underside 3A of the vehicle to its frame

and/or bottom plate 20 so that they are influenced by pressure to bring about their compression.

Other means for achieving the aforementioned possibility of free displacement are constituted by a weakened section 7-of the vehicle, for example a shear pin, a deformable plate or some other similar device that is so arranged, in the event of the vehicle 3 being subjected to an external effect from the rear 8, as to cause the frame hitch attachment to be weakened, for example as shown in Fig. 3, in a direction towards the front 12 of the vehicle 3. The expression towards the front 12 shall also be taken to denote at an angle, for example so that the frame hitch 2 is caused to fold upwards, downwards or sideways about an articulation 13, or so that it is attached by means of a pivot link which is locked in the hitching position, but is caused to pivot out of the way when subjected to an external influence.

The means for achieving the aforementioned possibility of free displacement are constituted by explosive means, such as an exploding bolted joint, a pin or some other exploding connection between the frame hitch 2 and the vehicle 3 in question.

The means for achieving the aforementioned possibility of free displacement can also be constituted by a spring device, for example which is so arranged as to be compressed in the event of its being subjected to severe compressive influence, and/or which is so arranged as to be extended when subjected to powerful tractive influence, and the aforementioned spring device is so arranged as to act between the frame hitch 2 and the vehicle 3, preferably at the attachment of the frame hitch to the vehicle 3 or at the attachment 10 between the frame hitch 2 and the vehicle 3.

Means for achieving the aforementioned possibility of free displacement through the influence of an external force F can also be constituted by a telescope, in which a number of deformable devices are preferably present between

the constituent telescoping bars of the aforementioned telescope, so that compression can take place after the aforementioned device has been deformed.

Means 7 for achieving the aforementioned possibility of free displacement can also be constituted by a fluid device, such as a gas-filled or liquid-filled piston, in conjunction with which a fluid-filled piston is so arranged as to be emptied rapidly of its fluid medium when subjected to an external force F in the aforementioned directions (8,9).

Means for the attachment of a frame hitch 2 to a <BR> <BR> <BR> <BR> Ver:ia?=:,'i:ti'-q.?_of,EC=:5:.'.2' a shear plate 50, which is situated ahead of the actual hitch ball, etc., 5 of the frame hitch viewed in the normal direction of travel 12 of the vehicle, i. e. forwards.

The shear plate 50 is constructed in such a way that two angled plates 50A, 50B are attached to one another at some point in the longitudinal extent of the hitch under 3A the vehicle 3.

The two plates are 50B are set at an angle and are attached, for example vits four bolts 51, with one bolt at each corner of the plates.

These bolts 51 are so dimensioned as to shear when they are subjected to a given force in the event of an impact with the vehicle from the rear, in conjuction with which the hitch 2 becomes detached, for example so that it falls to the ground, and thus has no negative influence on the deformation zones of the vehicle.

The invention is equally applicable to fixed frame hitches 2 and to detachable frame hitches.

The normal force imposed by a trailer attached to the vehicle via the hitch is so arranged as not to cause the aforementioned means for the displacement of the frame hitcn to release.

Finally, means for anchoring a frame hitch 2 to a vehicle 3 on its underside-3A at its rear end can comprise cabRes.

The design functions in such a way that a frame hitch bar 104 is mounted under 3A the vehicle 3. This frame hitch bar 104 is then restrained by a cable 175,176 in both lateral directions of the vehicle.

These two cables 175,176 then absorb all tractive forces in the rearward direction. In the event of the vehicle 3 being subjected to a rear-end collision, the actual frame hitch bar 104 will collapse when it is subjected to a given force F in the forward direction 12 together with the cables 175,176, which only give strength to the hitch in the rearward 6 direction.

Means for achieving the aforementioned possibility of free displacement of this kind are so arranged as to be controlled by a number of sensors 14,15, which, for the purpose of sensing the influence of the force F, for example, are so arranged as to activate the aforementioned means in order to permit the free displacement of the frame hitch 2 in a forward direction 12.

When the new frame hitch is installed in a vehicle, this will have the following implications in the event of a rear-end collision: A. The hitch and its attachments will disappear under the rear part of the vehicle and will accordingly not have a negative influence on the integral deformation zones of the vehicle, and the rear part will crumple as envisaged in order to provide a damping effect (shock-absorbing).

B. When this new frame hitch is installed in a vehicle, the risk of suffering a"worse"neck injury than otherwise permitted by the circumstances should be significantly less than if a traditional frame hitch were installed.

C. This new frame hitch should be of interest to many groups within society, such as:

Individuals The State Insurance companies Automobile manufacturers Its construction must withstand all tractive forces in the rearward direction, as well as certain loadings in the forward direction, such as in the event of heavy braking with a heavily laden trailer, when"thrusting"in a forward direction occurs.

Its construction with the various forces, both tensile and compressive, can be easily computer-simulated so that a factor balance between these various forces is known.

It can also be stated that a series of efficiently functioning measures (product development and patents) has been adopted with regard to the neck protection afforded by car seats, in particular in conjunction with rear-end collisions, and that these are very good. However, when a frame hitch of the previously disclosed kind is installed on the vehicle, these new functions are invalidated to some degree.

The nature and function of the invention should have been appreciated from the above description and the illustrations in the drawings, although the invention is not restricted to this and can be varied within the scope of the Patent Claims without departing from the idea of invention.