GB2059371A

GB2059371A - A towing stabilizer

Info

Publication number: GB2059371A
Application number: GB7933850A
Authority: GB
Original assignee: Sterckeman M A
Current assignee: Sterckeman M A
Priority date: 1979-09-29
Filing date: 1979-09-29
Publication date: 1981-04-23

Abstract

A towing stabilizer for ensuring the travelling stability of a trailer (2) such as a caravan, is characterised in that it comprises at least one damper member (24, 18) of a type able to undergo a variation in length by traction or compression by providing resistance to said traction and/or to said compression. The stabilizer is intended to be universally mounted (21, 25, 22, 26) on the trailer (2) and on a towing vehicle (1). The stabilizer is intended to oppose swaying or rocking movements of the trailer (2) as well as opposing the dipping of the rear of the towing vehicle (1). The damper member may be harder to extend than to compress. <IMAGE>

Description

SPECIFICATION A towing stabilizer The present invention relates to a towing stabilizer.

It is known that this is the general name given to a device intended to ensure the travelling stability of a trailer such as a caravan, by tending to oppose oscillations of the trailer with respect to its towing vehicle, in the form of sideways swaying or swinging movements, naturally without prejudicing the possibilities of cornering the vehicles and driving them over rough ground, where the wheels of the trailer and those of the vehicle do not necessarily rest on the ground along one plane.

Currently known devices use leaf-springs which are subject to bending stress and pivotally connected to supports of adjustable length.

This type of device has the drawback of being very complicated, which is particularly noticeable at the time of assembly and adjustment, which drawback is all the more troublesome since each operation for uncoupling the caravan, which also requires dismantling of the device, requires that the leaf-springs be reieased previously, i.e. altering the adjustment of the adjustable pivoted supports. This adjustment must consequently be made at the time of each re-coupling operation, depending on the criteria for tensioning the springs, which criteria are very precise and difficult to respect.

Another drawback of these devices resides in the considerable number of moving parts.

Finally, this type of device has the drawback that when it operates, it imposes repeated torsional stress on the towing vehicle, which may result in a deformation of the chassis. The same is true for the A-frame of the trailer.

One of the objects of the present invention is to propose a towing stabilizer which overcomes these drawbacks and opposes the sideways swaying or swinging movements of a trailer.

This stabilizer uses telescopic damping members which are subject to tensile and/or compressive stress, in an approximately horizontal direction, between the trailer and the towing vehicle on which they are pivoted in any direction.

Another embodiment of the device according to the invention makes it possible to slow down and thus to reduce the dipping of the back of an overloaded towing vehicle, for example when passing over an open gutter or when travelling over rough ground.

Generally, in orderto reduce the tendency of the back of the towing vehicle to dip when passing over an open gutter or a bump in the road, one uses means for reinforcing the suspension of the towing vehicle, but this solution has the drawback of being permanent, since the means for reinforcing the suspension cannot be fitted and dismantled each time the trailer is coupled or uncoupled respectively.

When the vehicle is used on its own, reinforcing means of this type are detrimental to the shockabsorbing capacity of the latter and thus make its comfort and road holding mediocre. Furthermore, means for reinforcing the suspension which are mounted permanently on the vehicle, cannot be removed for the purpose of re-use when the vehicle is changed.

By way of contrast, one of the objects of the present invention is to propose a stabilizer device comprising a damper member which is subject to tensile and/or compressive stress, tending to oppose a dipping movement of the coupled vehicles. This device may be put in position and removed easily and quickly, each time the trailer is coupled or uncoupled. Thus, after uncoupling, the towing vehicle travelling alone recovers the shock-absorbing characteristics provided by the manufacture.

The stabilizer according to the invention which is intended to ensure the travelling stability of a trailer such as a caravan, is characterised in that it comprises at least one damper member of a type able to undergo a variation of length due to traction or compression, by providing resistance to said traction and/or said compression, which is pivoted in any direction respectively on the trailer and on the towing vehicle.

The invention will be better understood on referring to the ensuing description, relating to a nonlimiting embodiment and to the accompanying drawings which form an integral part of this description.

Figure 1 is a plan view of a towing stabilizer device according to the invention, mounted between the rear of a towing vehicle and the front of a trailer such as a caravan in two different embodiments.

Figure 2 is a side view of the device fitted in the second embodiment.

In a first arrangement of the damper member of the stabilizer according to the invention, the reference numeral 1 represents the rear of the vehicle and the reference numeral 8 represents the A-frame of the trailer. The reference numeral 5 designates a coupling part in the form of an angle iron connected to the vehicle and which is bolted for example in place of the traditional coupling part supporting the ball, which is integral with the chassis of the vehicle, in manner known per se. To this end, the coupling member 5 comprises a vertical arm 36 the general direction of which is horizontal and perpendicular to the mean general direction 3 of the vehicle, which coincides with that of the trailer in the relative position of the trailer and vehicle illustrated, which corresponds for example to travelling in a straight line.

The member 5 also comprises, projecting rearwards with respect to the vehicle, a horizontal arm 38 extending like the arm 36 symmetrically on either side of the mean direction 3, perpendicular to the latter. Seen in section through a transverse plane with respect to the general direction of the arms 36 and 38, one can see that the coupling member 5 has an L-shaped profile, which gives the latter good rigidity.

Along the axis of the vehicle, i.e. at its intersection with the direction 3, the arm 38 of the member 5 supports the traditional coupling bore 9 on its upper side which, when the coupling is engaged, is covered by a complementary part 7 integral with the front end of the A-frame 8, if necessary through the intermediary of a device which controls the braking of the trailer by inertia (not shown).

Symmetrically respectively on either side of the direction 3, the arm 38 of the coupling members supports on its upper side, in an integral manner, two identical balls 21 similar to the ball 6 but generally having a smaller diameter. Preferably, the two balls 21, located at the same transverse level with respect to the direction 3, are offset towards the front of the vehicle with respect to the ball 6, or located at the same transverse level as the latter. The following figures are given as a non-limiting example: good results have been obtained in tests by staggering the balls 21 towards the front with respect to the ball 6 by a distance d of between 0 and 25mm, the levels in question being those of the axes ofthe balls.

Symmetrically, respectively on either side of the mean general direction of the trailer which in this case coincides with the direction 3, the A-frame 2 in turn supports two balls 22 similarto the balls 21 and located outside the A-frame, on the upper side respectively of two securing brackets 23 connected to the A-frame by bolting for example. The two balls are located at the same transverse level with respect to the mean direction of the trailer, at the same horizontal level coinciding as well as possible with that of the balls 21 when the coupling is engaged on horizontal ground. In order to facilitate an adjustment in this direction, the brackets 23 are preferably designed so that they may be fixed without difficulty at several levels to the A-frame 8.

Each of the balls 21 and the corresponding balt 22, i.e. the ball located on the same side of the direction 3, are respectively intended to receive opposite ends of a damper piston and cylinder arrangement 24, or any other equivalent damper device able to undergo a variation in its length by traction or compression, thus providing resistance to this traction and/or to this compression.

To this end, at each of its ends corresponding respectively to the piston rod and to the body of the cylinder, the damper cylinder/piston 24 comprises a cup-like housing respectively 25, complementing the ball 21 and 26 complementing the ball 22, so that the two ends of the piston/cylinder are pivoted in all directions respectively to the coupling member 5 and to the securing bracket 23 on the A-frame.

Advantageously, the housings 25 and 26 may be lined internally with hard rubber, plastics material or other equivalent material, in order to reduce the wear of the parts in contact.

In order to allow the release of the piston/cylinder arrangements with respect to the balls 21 and 22 and their positioning on these balls, the housings 25 and 26 are retained on the balls 21 and 22 by clipping (not visible in the drawing), which makes it possible to disconnect them or connect them in several seconds.

The respective positions of the centres of the balls 21 and of the centres of the balls 22 with respect to the centre of the swivel defined in a complementary manner by the coupling ball 21 and its counterpart 7, the coupling assumed to be engaged, are such that even when taking an acute bend, where, for example during a manoeuvre, the relative angle of the respective mean directions of the towing vehicle and of the trailer is of the order of 60 to 70 , the distance between the respective centres of a swivel 21 and of the swivel 22 located on the same side of the A-frame is never less than the minimum length of the compressed damper or greater than the maximum length of the extended damper.Consequently, a man skilled in the art will determine the optimum distance between the centres of the two balls 21 on the-one hand and between the respective centres of each ball 22 and of the swivel defined in a complementary manner by the coupling bore 9 and by its counterpart 7 on the other hand, depending on the characteristics of the dampers 24 used, i.e. their maximum length when extended, their maximum length when compressed and their possible clearance, i.e. the difference between these two lengths.

As a non-limiting example, good results have been obtained by adopting the following arrangements: the distance separating the centre of a ball 21 from the centre of the ball 22 located on the same side, the vehicle and the trailer being assumed to be coupledup, in line, was close to the maximum length of the damper measured from the centre of the housing 25 to the centre of the housing 26, less approximately half the possible clearance of this damper in its longitudinal direction and for example equal to the maximum length of the damper reduced by 50% of the clearance, plus or minus 3%, or even to the minimum length of the damper increased by 42% of the clearance, plus or minus 3%.The distance separating the centres of the two balls 11 was at least equal to the clearance of the damper, or of the order of 250 to 400mm and the distance separating the centres of the two balls 22 was of the order of 500 to 650mm, these figures also being given as nonlimiting examples. It should be noted that the more the movement of the trailer with respect to the towing vehicle results in a considerable deformation of the quadrilateral defined by the respective centres of the balls 21 and 22, the more effective the device.

Double-acting dampers 24 are preferably used, which are hard to draw out but easy to compress, for example in a ratio of between Sto 1 and 6to 1,these figures being given as a non-limiting example signifying that the damper is 5 to 6 times more resistant to drawing out than to compression, so that in the case of braking, dampers which are easy to compress allow the trailer to move towards the towing vehicle, thus preventing this forwards movement from being fierce, which allows the possible inertia braking system of the trailer to come into action smoothly.

The tendency of the trailer to sway is in turn counteracted by the damper which it attempts to place under tensile stress,i.e. which it attempts to draw out, at a given instant. Thus, for example, if the trailer tends to swing towards the left about the tow ball 6, referring to the positions illustrated in Figure 1, the left-hand piston/cylinder arrangement which is subject to compression does little to oppose this movement, but the right-hand piston/cylinder arrangement which is subject to traction, opposes the latter. The calibration of the dampers 14 is naturally such that the latter do not oppose cornering, i.e. a slow movement of greater or lesser amplitude of the trailer out of alignment with respect to the towing vehicle, but effectively retard the alternating disalignment of varying speed, which is a feature of the swaying movement.

The swivel-type mounting of each of the damper members respectively to the coupling member 5 integral with the vehicle and to the brackets 23 supported by the A-frame of the trailer allows these damper members to assume positions in which they are not located in the same approximately horizontal plane, as is the case when the coupled vehicles are stopped on flat ground. However, a movement of this type, characteristic of a tendency of the trailer to roll, causes the extension of the damper members 24, a movement which the piston/cylinder arrangements oppose most forcefully, which in other words means that the device according to the invention is also effective against rolling.

It should be noted that the dampers 24 continue to fulfil their function in the same way whatever their degree of extension or compression, which in other words means that they fulfil their function in the same way whether the coupled vehicles are travelling in a straight line or tasking a corner.

In another embodiment of the invention, a second angle-iron 10 is provided on the towing vehicle, which angle-iron is advantageously secured to this vehicle by the same means as the angle-iron 5 and which comprises on a horizontal arm 11 projecting towards the rear of the vehicle, a coupling sphere 12 similar to the coupling balls 6 but generally of smaller dimensions. The centre 13 of this coupling sphere 12 is located in the same vertical plane including the direction 3 as the centre 9 of the swivel defined by the members 6 and 7, at a level less than that of this point 9, the difference in level between the points 9 and 13 preferably being as large as possible in view of the requirements of keeping the vehicle on the ground. Preferably, the respective vertical lines passing through the points 9 and 13 are close or coincide.For example, the point 13 is located slightly in front of the point 9 as illustrated, although other arrangements are equally possible.

At the rear of the counterpart of the coupling 7, at a level corresponding substantially to that of the horizontal arm 11 of the angle-iron 10, the A-frame 8 of the trailer supports a substantially horizontal plate 15 projecting forwards, which on its upper side comprises a ball and socket 14, whereof the centre 16 is preferably located in the vertical plane including the direction 4, substantially at the same level as the centre 13 of the ball and socket 12 so that a line joining the points 13 and 16 is approximately horizontal.

Thus, the points 9, 13, 16 define the three corners of a triangle, whereof two sides, respectively joining the points 9 and 13 and the points 9 and 16 have a fixed length and whereof the third side, joining the points 13 and 16 has a length which varies if the points 9, i.e. the rear of the towing vehicle and the front of the A-frame, tends to dip or to move away from the ground, i.e. if the respective floors of the towing vehicle and of the trailer, which are normally substantially parallel to the ground 17, come to assume an oblique position in opposite directions with respect to the latter, due to the clearance of the rear suspension of the towing vehicle.

According to the invention, the two ends of a damper member of a type able to undergo a variation of length due to traction or compression by providing resistance to said traction and/or said compression are pivoted respectively on the ball and socket 12 and on the ball and socket 14. This member is in this case constituted by a damper member 18, one end 19 of which corresponding to the body, for example constitutes the counterpart of the ball and socket 12 and the other end 20 of which, corresponding to the piston rod, constitutes the counterpart of the swivel 14sothattheends19and 20 of the damper are pivoted in any direction respectively on this swivel 12 and on this swivel 14.

Preferably, the damper member in this case constituted by the piston/cylinder arrangement 18 is chosen so that it provides resistance both to extension by traction and shortening by compression, so that it tends to oppose a sudden variation in the distance separating the points 13 and 16 whatever the cause of the latter and consequently reduces the amplitude of the vertical movement to which the point 9 is subjected when crossing an open gutter or passing over a bump, in that it damps this movement sufficiently in order that it has the time to continue solely over a short distance, for example of the order of 20mm instead of 100mm or more, depending on the calibration of the damper member 18.

Although positions of the member 18 which differ from that which has been described and illustrated, may be adopted, it will be noted that the position illustrated is advantageous in that it is possible to use a member 18 which is more difficult to extend than to compress, resulting in more effective damping when there is a tendency for the rear of the vehicle to dip and the total absence of any hindrance to the operation of the possible system for controlling braking of the trailer by inertia, since at the time of braking of the vehicle, the trailer is liable to move forwards with respect to the latter, which movement initiates the operation of the inertia braking system.

It will be noted that the damper member 18 thus fulfils the function of a regulator for controlling the braking by inertia, in that it prevents an excessively sudden movement of the trailer with respect to the vehicle, when the latter begins to brake and thus prevents jerky operation of the trailer brakes.

Various means may be provided for the detachable connection of the ends 19 and 20 of the member such as the damper 18 to the ball and socket 12 and 14 and in order to limit as far as possible the wear of the parts in contact at this level. For example, housings provided in the ends 19 and 20 of the member such as 18, complementing the ball and sockets 12 and 14, could be lined internally with materials such as hard rubber, plastics material or other equivalent material and they may be connected by clipping onto the balls 12 and 14, which makes it possible to connect or disconnect them in several seconds (these arrangements known to a man skilled in the art have not been shown in the drawing).

Naturally, numerous variations of the invention could be envisaged without diverging from the scope of the latter.

Claims

1. A towing stabilizer for ensuring the travelling stability of a trailer such as a caravan, characterised in that it comprises at least one damper member which is able to undergo a variation in length due to traction or compression by providing resistance to said traction and/orto said compression.

2. A stabilizer as claimed in Claim 1, in which the damper member is arranged at the side of an A-frame member of the stabilizer for use in an approximately horizontal position.

3. A stabilizer as claimed in Claim 1 or 2, in which the damper member provides resistance to both traction and compression.

4. A stabilizer as claimed in Claim 2 or 3 when dependent on Claim 2, in which two such damper members are provided arranged symmetrically respectively on each side of the A-frame and each of which is universally mounted to be pivotable independently in any direction respectively to a trailer and to a towing vehicle.

5. A stabilizer as claimed in Claim 3, in which the damper member is harder to extend than it is to compress.

6. A stabilizer as claimed in Claim 5, in which the damper member is five to six times more resistant to extension than to compression.

7. A stabilizer as claimed in Claim 4, in which a pivotal arrangement is provided for location along the longitudinal axis of the towing vehicle for attachment to the trailer thereto, the universal mountings of the two damper members on the towing vehicle being arranged at the same level symmetrically respectively on each side of said axis.

8. A stabilizer as claimed in Claim 7, in which the respective universal mountings of the damper members on the towing vehicle are arranged in front of the pivotal arrangement or in the same vertical plane of the latter.

9. A stabilizer as claimed in Claim 7 or 8, in which the distance separating the respective universal mountings of the two damper members on the towing vehicle is at least equal to the difference between the maximum length and the minimum length of one of said members.

10. A stabilizer as claimed in any one of Claims 7 to 9, in which the pivotal arrangement for connecting the trailer to the towing vehicle is also located along the longitudinal axis of the trailer, and in which the respective universal mountings of said damper members on the trailer are locted at the same level, symmetrically respectively on each side of said axis of the trailer.

11. A stabilizer as claimed in Claim 1, in which the damper member is adapted to be universally mounted on a towing vehicle and on a trailer at locations which are staggered with respect to a towing coupling for attachment of the trailer to the vehicle-and at least one of which locations is at a different horizontal level from the level of the towing coupling.

12. A stabilizer as claimed in Claim 11, in which the universal mounting of said damper member respectively on the towing vehicle and on the trailer is adapted to be located in the same longitudinal vertical plane, respectively of the vehicle and of the trailer, as the towing coupling.

13. A stabilizer as claimed in Claim 11 or 12, in which the universal mountings of said damper member respectively on the towing vehicle and on the trailer are located approximately at the same level and in which said member is adapted for use in an approximately horizontal position.

14. A stabilizer as claimed in Claims 11 to 13, in which the universal mounting of said damper member on the towing vehicle is adapted to be located in the vicinity of a vertical line passing through the towing coupling.

15. Astabilizeras claimed in any one of Claims 11 to 14, in which the universal mountings of said damper member respectively for the vehicle and for the trailer are adapted to be located at a level lower than that of the towing coupling.

16. A stabilizer as claimed in any one of Claims 11 to 15, in which said damper member provides resistance both to traction and to compression.

17. A stabilizer as claimed in Claim 16, in which the damping of the damper member is, in use, stronger in a direction of a deformation following a relative pivotal movement of the trailer and of the vehicle in the direction of a dipping movement of the towing coupling and weaker in the opposite direction.

18. A stabilizer as claimed in any one of Claim 15 to 17, in which the damper member is harder to extend than to compress.

19. A stabilizer as claimed in any one of the preceding Claims, in which the damper member is a damper cylinder/piston arrangement.

20. A towing stabilizer for ensuring the travelling stability of a trailer such as a caravan substantially as hereinbefore described with reference to the accompanying drawing.