GB2338941A

GB2338941A - A safety tow-bar for trailers used on road vehicles

Info

Publication number: GB2338941A
Application number: GB9913141A
Authority: GB
Inventors: Michael Boel Olesen
Original assignee: Brenderup Trailers AS
Current assignee: Brenderup Trailers AS
Priority date: 1998-06-08
Filing date: 1999-06-08
Publication date: 2000-01-12
Anticipated expiration: 2019-06-08
Also published as: DE19927017A1; FR2779388B1; GB9913141D0; GB2338941B; FR2779388A1

Description

2338941 Safety tow-bar for trai ers The present invention concerns a

safety tow-bar, mainly for trailers of the kind which at least comprise a wheel- supported loading bed which via a tow-bar connection provided with a coupling mechanism can be coupled to a towing vehicle.

Tow-bars are known as V-shaped or straight tow-bars, the one end of which is secured to the chassis of the trailer and the other end of which comprises a standard coupling for cou- pling to a standard towing hook on a towing vehicle.

In the event of collision, it is very important to avoid the tow-bar system on the trailer from penetrating into the towing vehicle like a lance, with subsequent possibilities of personal injury.

If a collision occurs, the V-shaped tow-bar serves a safety function in that the impact forces arising from the collision are divided between the two bars, the free ends of which are mutually connected immediately in front of the coupling mechanism, the consequence being that the collision force first results in a deformation of the tow-bar system and the chassis before the tow-bar system bores its way into the rear end of the towing vehicle. This deformation will considerably suppress the influence of the force arising from the collision, so that in most cases said lance effect is avoided.

For further counteraction of the lance effect, from DK 156944 B there is known a V-shaped tow-bar arrangement for a single-axle or double-axle trailer, where deformations are provided on that half part of the Vshaped tow-bar which leads to the trailer coupling for controlling the deformation which arises with the collision. Said deformations do not, however, comprise any distinct weakening of the V-shaped tow bar, but merely ensure a bending-out in this area when the collision occurs.

With straight tow-bars, however, there are no systems known at present for the counteraction of said lance effect, and trailers with tow-bars of this type thus constitute a considerable risk for the users.

With the invention, the possibility has been achieved of counteracting the lance effect arising from a collision with trailers of the kind comprising a straight, tubular tow-bar, where the tow-bar in an area in between the coupling mecha- nism and the trailer has a collision zone in the form of a weakening of the deflection strength of the tow-bar, around which the tow-bar is deformed when the towing vehicle is involved in a frontal collision or collision from the rear.

It is hereby achieved that the tow-bar folds up (sideways of downwards) before the trailer coupling or the towing hook fails and the tow-bar possibly bores into the rear end of the towing vehicle.

The weakening of the deflection strength of the tow-bar can with advantage comprise cut-outs in the tubular material of the tow-bar at one or more selected places on the tow-bar.

With the cut-outs, a certain weakening of the strength of the tube is achieved, which ensures that in the event of a collision the tow-bar will be deformed precisely in the area of the cut-outs, so that under the force of the collision the tow-bar is bent outwards, which will result in a damping of the impact forces arising from the collision, and under all circumstances will counteract the lance effect. It should be noted that the collision zone achieved by weakening of the deflection rigidity of the tow-bar is possible without this having any significant effect on the nominal loading capacity of the trailer.

With regard to the controlling of the bending-out of the tow-bar in a desired direction in the event of collision, the cut-outs can with advantage be configured as two through- going cut-outs extending in parallel, the centre axes of which form an angle with the centre axis of the tow-bar.

In a second preferred embodiment of the safety tow-bar according to the invention, the weakening of the deflection strength of the tow-bar can consist of at least one weaker portion inserted in an area in between the coupling mechanism and the trailer. The advantage herewith is that the estab-lishing of the weakening of the tow-bar does not.;,result in the whole of the tow-bar having to be subject to working op- 3 erations, and that the weakened portions can be produced with specially adapted strength characteristics in accordance with the demands of the local authorities, without this having any influence on the production of the remaining parts of the trailer. Moreover, this embodiment gives the producer more scope with regard to the choice of material thickness etc. for the tube which is used for the production of the remaining parts of the tow-bar.

In a further embodiment of the safety tow-bar according to the invention, the weakening of the deflection strength of the tow-bar consists of at least one hinge connection disposed in an area in between the coupling mechanism and the trailer, said hinge connection comprising overlaid parts which are secured with a lock mechanism, the breaking strength of which is less than a predetermined force, so that the lock mechanism breaks up in the event of frontal or rear collision, and the tow-bar is bent out in the same manner as earlier described and the lance effect is avoided. The lock mechanism can consist, for example, of a cotter pin or the like through holes in the overlaid parts and which is sheared over in the collision. The advantage herewith is that a minor collision does not give rise to the need for a major repair of the trailer, but merely the replacement of the cotter pin.

The lance effect can, however, also be avoided by a safety tow-bar of the kind disclosed, where the axial breaking strength of the tow-bar is weakened by a concentric tube piece on the tow-bar, said concentric tube piece being secured in overlaid parts of the tube piece and the tow-bar by locking mechanisms with a breaking strength which is less than a predetermined force, so that the locking mechanism breaks up in the event of frontal or rear collision. There is hereby achieved a reduction in the length of the tow-bar, corresponding to the effective length of the concentric tube piece, whereby the lance effect is avoided.

In a further advantageous embodiment o ' f the safety tow bar according to the invention, the safety tow-bar is dis placeable, mounted in fixed manner in the securing points on the trailer by locking mechanisms with a breaking strength 4 which is less than a predetermined force, so that the locking mechanism breaks up in the event of frontal or rear collision. In the event of collision, it is hereby achieved that by the breaking up of the locking mechanisms, the trailer will be displaced along the longitudinal axis of the safety tow-bar towards the towing vehicle, possibly until the leading end of the trailer collides with the rear end of the towing vehicle, whereby the lance effect is counteracted.

Practical tests have shown, however, that in the event of violent collisions, the weakening of the tow-bar in the collision zone can result in the breaking off of the tow-bar's foremost end with the coupling part, and herewith also the wire which is placed on the coupling part in accordance with the normal safety regulations to safeguard against loss of the trailer, and which by means of known securing means is connected with the towing gear of the towing vehicle.

With the view to avoiding the loss of trailers of the kind disclosed in the event of breakage of their tow-bars, the tow-bar according to the present invention can be pro- vided with a wire connection which is drawn inside the cavity in the tow- bar, where the one end of the wire is secured to the trailer behind the collision zone, and the other end of the wire is provided with means for securing to the towing vehicle and extends through the tow-bar and a part of the coupling part.

Security is hereby provided against loss of trailers provided with tubular tow-bars in the event of the tow-bar being broken over in the collision zone, in that the safety wire is secured to the trailer behind that area in which a possible breakage of the tow-bar will arise as a consequence of the weakening of the rigidity of the tow-bar in the collision zone.

With the view to protecting the cavity in the tow-bar against the ingress of foreign matter, including water, and to eliminate harmful effects of sharp edges in the cut-outs and to conceal the visual impression of a weakened tow-bar, in the collision area the tow-bar:can be provided with a tightly-fitting sleeve of flexible material.

In the following, the invention is explained with reference to the drawing, where fig. 1 is a perspective view of a trailer fitted with a tow-bar, where the tow-bar is provided with a collision zone according to the invention, fig. 2 is a detail side view of the collision zone established as cut- outs in the tow-bar, fig. 3 is a detail side view of the collision zone in the uncovered condition, fig. 4 shows the same as in fig. 3, but where the tow-bar is deformed in the collision zone, fig. 5 is a detail, partly side-section view of a second embodiment of the collision zone according to the invention, fig. 6 is a detail side view of a third embodiment of the collision zone according to the invention, fig. 7 is as shown in fig. 6, but with deformed collision zone, fig. 8 is a plan view of a fourth example embodiment of the safety tow-bar according to the invention, fig. 9 shows a perspective view of a fifth embodiment of the tow-bar according to the invention, and fig. 10 shows the same as in fig. 8 after a collision.

Fig. 1 shows a trailer 2 with a'tubular, straight tow-bar 4 according to the invention, the foremost end of which is provided with a coupling part 6 coupled to a standard towing hook 8 on a not-shown vehicle. The trailer comprises a bed 10 with a leading end 12. As will be seen from fig. 1, in an area of the tow-bar 4 in between the coupling part 6 and the leading end of the bed 12, there is a collision zone 16 covered by a rubber sleeve 14 where the deflection strength of the tow-bar is weakened. Fig. 2 is a detail view of the collision zone 16 covered with the rubber sleeve 14.

An example of how the deflection strength of the tow-bar is weakened is shown in fig. 3, which is a detail view of the collision zone 16 without the rubber sleeve 14. The collision zone 16 consists,of two elongated, oppositely-disposed, through-going cut-outs 18 in the sides of the tubular tow-bar 6 4. The cut-outs are further configured in such a way that their centrelines 20 form an angle V with the centreline 22 of the tow-bar'.

The effect of the collision zone 16 is that in the event of a collision, e.g. by the trailer being driven into from the rear, the tow-bar 4 is deformed around the out-outs 18, so that the tow-bar 4 is thus bent cf. fig. 4, and thus the tow-bar does not bore its way into the towing vehicle. By the bending of the two-bar at the moment of collision, a part of the impact forces from the collision is absorbed, whereby the influence of the towing vehicle is reduced.

As indicated, the tow-bar 4 is also provided with a wire connection 5 drawn inside the cavity of the tow-bar, in that the one end of the wire is secured to the trailer 2 at a point lying to the rear of the collision zone 16, and the other end of the wire is provided with means for fastening 7 to the towing vehicle, extending through the tow-bar and a part of the coupling part.

Security is hereby provided against loss of the trailer in the event of the tow-bar breaking over in the collision zone 16, in that the safety wire 5 is secured to the trailer to the rear of that area (collision zone) where a possible break in the tow-bar 4 will occur as a result of the weaken ing of the rigidity of the tow-bar.

In fig. 5 there is shown a second embodiment of the safety tow-bar 4, where instead of establishing a distinct cut-outs 18 (cf. fig. 3) in the collision zone 16, there is inserted an intermediate part 24 with a tensile strength which is reduced in relation to the tow-bar 4, whereby in the event of a collision the tow-bar will be deformed in the collision zone, and thus the lance effect is avoided. The advantage of establishing the intermediate part is that this provides the possibility of choosing different strength characteristics for the part 24, all depending on whatever demands are made by the authorities.

In figs. 6 and 7 there is shown a third embodiment of the safety tow-baraccording to the invention, where the collision zone 16 is configured with a hinge connection 26 on the 7 tow-bar 4, where through a part 28 in front of the pivot axis 30 of the hinge there is a pin 32 inserted into holes 34, 36 in the part 28 and the tow-bar 4 respectively. When a collision occurs, the safety tow-bar 4 turns around the pivot axis 30 as shown in fig. 7, in that at the moment of collision the pin 32 is cut over by the scissors effect which arises from the force of the collision which results in a turning of the part 28 in relation to the tow-bar 4.

Fig. 8 shows a fourth embodiment of the safety tow-bar according to the invention, where the weakening of the strength of the tow-bar consists of a concentric tube piece 38 on the tow-bar, said concentric tube piece being secured at overlaid parts 40 of the tube piece 38 and the tow-bar 4 by locking mechanisms 42 in the form of pins inserted through holes 41 in the tow-bar 4 and the concentric tube piece 28.

The breaking strength of the pins 42 is less than a predetermined force, so that the locking mechanism is broken up by a frontal or rear collision. With the collision, a cutting-over of the pins 42 occurs between the opposing surfaces of the tow-bar 4 and the tube piece 38, whereby the safety tow-bar is shortened sufficiently for the lance effect to be avoided.

In fig. 9 there is shown a fifth embodiment of the safety tow-bar 4 according to the invention. Here, the tow-bar 4 is fastened firmly but in a displaceable manner to the vehicle's cross member 44 and the bed 10 by means of mounting brackets 46. The mounting brackets 46 and the tow-bar 4 have throughgoing holes 48, 50 into which pins 52 are inserted, the tensile characteristics of said pins 52 being such that the pins can withstand ordinary conditions of use of the trailer, but such that they will be sheared over in the event of a frontal or rear collision.

In fig. 10 is seen the trailer shown in fig. 9 at the moment of collision, where the pins 52 have been sheared over (not shown), and the bed 10 and herewith the foremost end 12 of the trailer has been displaced forward3 in towards the rear end 54 of the towing vehicle. During the collision, the part of the tow-bar 4 extending in front of the foremost end 12 of the trailer has thus become shorter, while at the same 8 time the coupling 6 has remained sitting on the towing hook 8, and the lance effect is hereby avoided.

With the invention it will be obvious that the establishing of collision zones on tow-bars according to the invention can consist of configurations other than those which are shown in the embodiment examples described above. The cutouts 18 can thus be of other configurations which ensure that the trailer's tow-bar 4 is deformed in the collision zone in the event of collisions.

However, this does not alter the inventive aspect which consists in the recognition that an effective avoidance of the lance effect in the event of collision with trailers provided with straight bar- formed/tubular tow-bars is possible by establishing a collision zone in the form of a weakening of the deflection rigidity of the straight tow-bar, irrespective of whether this is done by weakening the tow-bar's deflection strength or by reducing the tow-bar's ability to absorb axial forces, which can be effected by modification of the fastening in between the tow-bar and the trailer or by modification of the tow-bar itself.

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Claims

C L A I N S

Safety tow-bar (4), especially for trailers (2) and the like with one or two axles and of the kind which at least comprise a wheel-supported loading bed (10), which via a towbar connection consisting of a straight, tubular tow-bar (4) provided with a coupling mechanism (6) can be coupled to a towing vehicle, c h a r a c t e r i z e d in that in the area between the coupling mechanism (6) and the trailer (2), the tow-bar (4) has a collision zone (16) in the form of a weakening of the deflection strength of the tow-bar, around which the tow-bar (4) is deformed in the event of frontal collision or collision from the rear.
2. Safety tow-bar (4) according to claim 1, c h a- r a c t e r i z e d in that the weakening of the deflection strength of the tow-bar is achieved by providing cut-outs (18) in the tow-bar's tubular material at one or more selected places on the tow-bar (4).
3. Safety tow-bar (4) according to claim I or 2, c h a r a c t e r i z e d in that the cut-outs (18) are configured as two through-going, elongated cut-outs extending in parallel, the centre axes (20) of which form an angle V with the centre axis (22) of the tow-bar.
4. Safety tow-bar according to claim 1, c h a r a c- t e r i z e d in that the weakening of the deflection strength of the tow- bar comprises at least one weaker part inserted in an area between the coupling mechanism (6) and the trailer (2).
5. Safety tow-bar according to claim 1, c h a r a c- t e r i z e d in that the weakening of the deflection strength of the tow- bar comprises at least one hinge connection disposed in an area between the coupling mechanism (6) and the trailer (2), said hinge connection comprising overlaid parts which are secured with a locking mechanism, the breaking strength of which is less than a predetermined force, so that the locking mechanism breaks up in the event of frontal collision or collision from the rear.
6. Safety tow-bar, especially for trailers (2) with one or two axles and of the kind which at least comprise a wheelsupported loading bed (10), which via a tow-bar connection consisting of a straight, tubular tow-bar (4) provided with a coupling mechanism (6) can be coupled to a towing vehicle, c h a r a c t e r i z e d in that the tow-bar breaking strength for axial forces is reduced by a concentric tube piece (38) on the tow-bar, said concentric tube piece being secured in overlaid parts (4) of the tube piece (38) and the tow-bar (4) by locking mechanisms (42), the breaking strength of which is less than a predetermined force, so that the locking mechanism is broken up in the event of frontal collision or collision from the rear.
7. Safety tow-bar, especially for trailers (2) with one or two axles and of the kind which at least comprise a wheel- supported loading bed (10), which via a tow-bar connection consisting of a straight, tubular-tow-bar (4) provided with a coupling mechanism (6) can be coupled to a towing vehicle, c h a r a c t e r i z e d in that the tow-bar is fas- tened firmly but in a displaceable manner to the trailer by the securing brackets (46) with locking mechanisms (48, 50, 52), the breaking strength of which is less than a predeter mined force, so that the locking mechanism (52) is broken up in the event of frontal collision or collision from the rear.
8. Safety tow-bar according to claim 6 or 7, c h a r a c t e r i z e d. in that the locking mechanism consists of a pin (42, 52) inserted through holes (41, 48, 50) in the overlaid parts (40) or the securing brackets (46), and which is sheared over in the event of a frontal collision or colli- sion from the rear.
9. Safety tow-bar (4) according to any of the claims 1-8, c h a r a c t e r i z e d in that the tow-bar comprises a wire connection (5) drawn inside the cavity in the tow-bar and a part of the coupling part (6), in that the one end of the wire is fastened to the trailer (2) at a point lying behind the collision zone (16), and the other end of the wire is provided with means (7) for fastening to the towing vehicle.

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10. Safety tow-bar (4) according to any of the claims 1-9, c har act eri sed inthat thetow-bar (4) is provided with a tight-fitting sleeve (14) of flexible material in the collision area.
11. Safety tow-bar constructed and arranged substantially as described in relation to Figs 1-4.
12. Safety tow-bar constructed and arranged substantially as described in relation to Fig.5.
13. Safety tow-bar constructed and arranged substantially as described in relation to Figs. 6 and 7.
14. Safety tow-bar constructed and arranged substantially as described in relation to Fig.8.
15. Safety tow-bar constructed and arranged substantially as described in relation to Fig.9.