GB2038259A - Device for damping snaking movements between towing vehicle and trailer vehicle - Google Patents

Abstract

A device for damping snaking movements between towing vehicle and trailer vehicle, with a coupling ball 2 on the towing vehicle and a coupling cup 16 on the trailer vehicle and with at least one mechanical pairing of friction surfaces, the common friction plane of which is horizontally disposed, and which is intended to prevent a yawing motion, whereby both surfaces are, through force transmitting elements, disposed to rotate about a common vertical axis through the centre of the coupling ball, characterised in that the coupling ball is rotationally rigidly mounted on the towing vehicle and in that between the coupling ball and its mounting there is or are mounted one or a plurality of rotary plates (8) which is or are adjacent the pairing of friction faces (6, 9; 7, 10) and operatively connected to the elements (11, 16) which transmit solely yawing motions to the pairings of friction surfaces. <IMAGE>

Description

SPECIFICATION Device for damping snaking movements between towing vehicle and trailer vehicle The invention relates to a device for damping snaking movements between towing vehicle and trailer vehicle with a coupling ball on the towing vehicle and a coupling cup on the trailer vehicle and with at least one mechanical pair of friction surfaces, the common friction plane of which is disposed horizontally and the pairing of friction surfaces being so constructed as to prevent yawing motion, both surfaces being disposed to rotate through force transmitting elements, about a common vertical axis and through the central point of the coupling ball.

Such a device is known from British Patent No. 892 952. In that case, however, in contrast to the object of the Application, the coupling ball is mounted to rotate in relation to its bracket on the towing vehicle.

The pair of friction surfaces is disposed in this swivel mounting or between the two parts. For transmitting yawing motions, a kind of open-end wrench is used which engages around the right and left-hand sides of the swivel mounting. This open-end wrench engages flats on the coupling ball. At the same time, these flats do however prevent the transmission of lurching movements. This means that in the event of lurching movements of a certain magnitude, the device may become distorted and no longer able to function properly.

Furthermore, a device for damping snaking movements is known from German laid-open specification No. 25 27 673. One surface of the pairing of friction surfaces is thereby disposed on the towing vehicle while the other surface is provided on the trailer vehicle. The surface provided on the towing vehicle consists of an arcuate portion which is furthermore hinged for movement about a horizontally disposed axis positioned transversely ofthe direction of travel of the towing vehicle. For practical purposes, the associated surface on the trailer vehicle consists of the pads of a disc brake; the pads are immovably - with the exception of application of their clamping force - disposed on the trailer vehicle.

Since the two surfaces which form the pairing of friction surfaces are mounted on different vehicle parts, in other words on the towing vehicle and on the trailer vehicle, in the event of yawing motions, there is no other possibility than for the resultant forces to be so transmitted between the pair of friction surfaces that the axis of such movement passes through the centre point of the coupling ball.

The question of whether the friction lining which is disposed on the towing vehicle, is of arcuate form or is semi-circular or the like is unaffected by this. This known device is suitable for counteracting purely yawing motion, in other words rotary movements about the vertical axis. Pitching movement, in other words purely movement of the trailer vehicle about a horizontal axis disposed transversely of the direction of travel, cannot be properly absorbed. Since, when pitching motion occurs, the two faces of the pair of friction surfaces rotate about different axes, there is the danger of tilting in the pair of friction surfaces which can only be prevented by the semi-circular friction lining and the adjacent parts also being flexion stressed, in other words distorted.While this inadmissible flexion stressing may in some circumstances be accommodated if the pitching movement is of negligible extent, the overall device becomes unacceptably distorted in the case of lurching movements, in other words pure slewing movements of the trailer vehicle about a horizontal axis located in the direction of travel. Since a snaking movement is understood as being a combined movement consisting of yawing, psitching and lurching, this known device is in itself not an antisnaking device and is therefore unsuitable for practical application.

DAS No. 1 253 590 shows a similar device with which it is intended also to prevent snaking movements although in this case too the movements prevented are first and foremost yawing movements. For this purpose, the two faces of the pair of friction surfaces are provided on the trailer vehicle and in fact at a corresponding distance from the vertical axis passing through the centre of the coupling ball. One face of the pair of friction surfaces is articulated on the towing vehicle via a linkage provided with a number of joints, so that with this device yawing movements about the vertical axis can be transmitted to the pair of friction surfaces through the centre of the coupling ball. This specification makes no mention of pitching and lurching movements.One of the two joints of the transmission linkage is intended however to be constructed as a ball joint in order in this way to provide more freedom in the movement to be transmitted and in order to counteract distortion of the linkage in the event of snaking movements. This known device cannot provide optimum counteraction of yawing movements, because forces resulting from the eccentric disposition of the pair of friction faces in respect of the vertical axis through the coupling ball are transmitted from the trailer vehicle to the towing vehicle at the coupling ball and lead to the particularly disadvantageous offset of the rear axle of the towing vehicle when snaking movements occur.

Also German laid-open specification No. 25 54679 shows a device having a pair of friction faces disposed eccentrically of the vertical axis through the centre of the coupling ball. In order to counteract disadvantageous distortion of the relevant parts of the device, attempts have in this case already been made to provide the necessary degree of freedom by a multiplicity of points of articulation and an additional longitudinally movable guiding of the linkage.

But also with this device it has been impossible to prevent transmission to the towing vehicle of forces resulting in the event of snaking movements and incipient damping and such as lead to the unfavourable lateral offset of the rear axle of the towing vehicle, already referred to. An even greater number of joints and a therefore further complicated device is shown in German laid-open specification No. 25 29262. Despite the multiplicity of these articulations, there occurs for example in the case of pure lurching movements and thus also in the event of every snaking movements which comprises a proportion of lurching movement, disadvantageous distortion between the individual parts of the device.For the rest, in the case of this known device, different pairings of friction surfaces are provided, including a pair of friction surfaces designed to counteract yawing motions and another pair of friction surfaces intended to prevent pitching.

The invention is based on the problem of provid ing a device for damping snaking movements of the type described at the outset in which, when snaking movements occur, the yawing motion component is damped while forces occurring in the case of lurching or pitching movements are kept away from the pair of friction surfaces, so that there is no inadmissible distortion of the parts of the device.

According to the invention, this is achieved in that the coupling ball is rotationally rigidly mounted on the towing vehicle and in that mounted between the coupling ball and its mounting one or a plurality of rotary plates is or are mounted adjacent to the pair of friction surfaces and operatively connected to ele ments transmitted solely yawing motions to the pairs of friction surfaces. First and foremost, what is essential is that both surfaces of the pair of friction surfaces are not provided on different parts of the vehicle, but instead that both are provided either on the towing vehicle only or on the trailer vehicle only, an additional condition being that both surfaces are, through force-transmitting elements, disposed to rotate about a common vertical axis through the centre of the coupling ball.In addition to the coupling ball and the mounting, a third part must be disposed on the towing vehicle, namely the rotary plate or plates which in turn must rotate about a vertical axis through the coupling ball, whereas the coupling ball itself must be non-rotatably i.e. rotationally rigidly, mounted on the towing bracket of the towing vehicle. This additional rotary plate which is not to be found in the state of the art, at the same time affords an opportunity of providing on its top and bottom faces two pairings of.friction surfaces in order to increase the transmissible moment.The elements transmitting the yawing motions to the rotary plate or rotary plates are however so constructed that they transmit only yawing motions, in other words exclusively yawing motions, whereas lurching movements and pitching movements of the trailer can take place without the friction damping responding. It is therefore necessary to achieve an entraining of the force-transmitting elements in the horizontal plane, in other words upon rotation about the vertical axis (yawing) while on the other hand the necessary freedom is provided in the other two spatial directions.

For the reproducible and rapid application or removal of the pretensioning force which acts in the pairing of friction surfaces, it is particularly advantageous to provide an eccentric lever. This measure is required in order that towing vehicle and trailer vehicle may be coupled and uncoupled in the various angular relationships one to the other. The eccentric lever can be locked in the tensioning position by a mechanical lock, so reliably preventing the tensioning pressure being removed in the pair ing of friction surfaces while the vehicles are travell ing.As is generally conventional with such mechanical pairings of friction surfaces, the force with which they are applied against each other is transmitted via a spring, for example a plate spring, which can be readjusted, in order so to counteract wear in the pairing of friction surfaces that the pretensioning force is more or less reproducible. In order to increase the acceptable torque of a yawing motion, a plurality of pairings of friction surfaces may be provided one above another, in other words for example in the form of a layered assembly, such as is also known in the case of multi-plate clutches. In this way, it is possible for the torque which can be accommodated by the hitherto known devices to be substantially increased or to be raised to a different magnitude.

A particularly simple embodiment of the device is achieved if the pairing of friction surfaces is disposed below the coupling ball on the towing vehicle and if the elements transmitting the forces comprise a towing bracket on the towing vehicle and a drive member associated with the trailer vehicle. The drive member engages laterally around the coupling cup in a longitudinal direction, so that only yawing motions of the trailer but not pitching motions or lurching motions of the trailer are transmitted into the pairing of friction surfaces. The drive member is thereby constructed to act in both directions of rotation and consists for example of a yoke for the coupling ball cup.

Also the reverse construction is possible in which therefore both surfaces of the pairing of friction surfaces are located on the trailer vehicle. Then, of course, the drive member must be operatively connected to the towing vehicle.

The invention permits of various constructions. It is explained in greater detail hereinafter with reference to examples of embodiment which are shown in the accompanying drawings, in which: Figure lisa partially sectional side view of the essential parts of the invention; Figure 2 is a view of the device according to Figure 1, seen from the rear; Figure 3 is a side view of a further embodiment of the device, and Figure 4 is a rear view of the device, partly in section.

Rotationally rigidly mounted on a two-part bracket 1 which is connected to the towing vehicle is a coupling ball 2 of a ball coupling. For this purpose, the stem 3 which passes through the bracket 1 has a milled surface 4 to prevent the stem 3 rotating in the bracket 1. The coupling ball has a widened diameter collar 5 on the underside of which is one face 6 of a pair of friction surfaces. A further face 7 is provided by the bracket 1. Between the two faces 6 and 7, a rotary plate 8 is mounted to rotate about the stem 3 of the coupling ball 2, the rotary plate 8 being provided on its two faces with friction surfaces 9 and 10 consisting of mechanical friction material. As can be seen, the pairing of friction surfaces 6, 9; 7, 10 is of dual construction. Rotationally rigidly connected to the rotary plate 8 is a drive member 11.

In order to apply the necessary pressure of application in the pairing of friction faces 6, 9; 7, 10, the stem 3 of the coupling ball 2 has on its end which protrudes from the bracket 1 a screwthread 12 with which a castle nut 13 secured by the cotter pin 14 is associated. Between the castle nut 13 and the bracket 1 there is yet another resilient element 15, for example a plate spring or the like which is suitable for compensating wear and tear arising in the pairings of friction surfaces 6, 9; 7, 10 after prolonged use. It will be appreciated that the contact force in the pair of friction surfaces 6, 9; 7, 10 is applied via the castle nut 13 and the spring element 15.

Figure 1 readily shows that the two or four faces of the pairing of friction surfaces 6, 9; 7, 10 are located on the towing vehicle, in fact in such a way that their axis about which movement can occur, passes through the centre of the coupling ball 2. This is essential insofar as it means that damping of yawing motions takes place where no resulting forces can be transmitted to the towing vehicle through the coupling ball 2.

On the trailer vehicle, the ball cup 16 is in known manner connected to the drawbar. Also, an overrun brake is provided in the usual way. The ball coupling consists in known manner of the coupling ball 2 and the ball cup 16, the details of how the coupling is opened and closed being omitted. Figures 1 and 2 do however show how the ball cup 16 engages over the coupling ball 2. The drive member 11 extends rearwardly by the amount necessary to transmit the torque arising in the case of a yawing motion and, in the manner shown in Figure 2, engages around the ball cup 16. The drive member 11 is constructed in two parts so that it is operatively employed in both directions of rotation. It is rotationally connected to the rotary plate 8, being for example welded or even manufactured in one piece therewith.Figure 2 furthermore clearly shows that only pure yawing motions can lead to moment transmission between the cup 16 and the drive member 11, while purely lurching motions or purely pitching motions cannot.

The last two mentioned types of motion - certainly in the extent to which they normally occur between a towing vehicle and a trailer vehicle - have no effect on the pairing of friction surfaces 6, 9; 7, 10. Purely pitching motions, since they result substantially in just a deflection of the rear axle of the towing vehicle, are not regarded as harmful, certainly insofar as they cannot bring about a lateral offset of the rear axle of the towing vehicle. A similar situation applies to purely lurching movements, in fact when the instantaneous centre of the lurching axis passes through the centre of the coupling ball 2.

It will be appreciated that in order to increase the torque which can be absorbed, the pairing of friction faces 6,9; 7, 10 may also be multiplied, on a basis similar to that known with regard to multiplate clutches. Assemblies of friction pads may be disposed both above as well as below the bracket 1. It is also possible to provide the pairings of friction surfaces on the trailer vehicle instead of the towing vehicle. In such a case the drive member 11 must be associated with the towing vehicle. Here, therefore, the construction is reversed.

The example of embodiment shown in Figures 3 and 4 demonstrates a constmcrion in which the pairings of friction faces 6,9 and 7, 10 zre provided above and below the bracket 1. Here, the drive member 11 is not rotationally rigidly connected, directly to a separate rotary plate 8 but directly to the collar 5 on the couling ball 2. In consequence, in the case of purely yawing motions, the coupling ball 2 with its stem 3 will co-rotate, i.e. rotate in relation to the bracket 1, so that in this case the stem 3 must be rotatably mounted. Beneath the bracket 1 is an additional similar collar 5' which is disposed so that it is rotationally rigid with the stem 3 but is axially displaceable.In this way, a rotary movement of the coupling cup 16 is transmitted via the drive member 11 to the two collars 5' and 5. The drive member 11 has lateral reinforcing ribs 17 and 18 as Figure 4 shows, in order to be able to accommodate the relatively high torque values. As can be seen, the drive member 11 is open at the bottom. The resilient element 15 is in this case interposed between the upper collar 5 and a collar 19 on the coupling ball 2.

As a result of the rotatonally rigid connection of the two collars 5, 5' to the stem 3, therefore, in the event of purely yawing motions, the entire coupling ball 2 rotates in the bracket 1.

In order to apply the contact pressure in the pairing of friction faces 6, 9; 7, 10, rotatably mounted at the bottom end of the stem 3 is an eccentric lever 20 which is used as a quick-action tensioning lock.

On the collar 5' is an extension 21 through which, in the tensioned position, a securing element 22 is passed and at the same time traverses the eccentric lever 20, maintaining this latter in the secured position. The eccentric lever 20 affords an opportunity of very easily and rapidly removing the contact pressure if for example a coupling operation is to be performed between towing vehicle and trailer vehicle. Since the relative angular position between towing vehicle and trailer vehicle which existed at the last uncoupling operation cannot as a rule be accurately respected during coupling up, it is after releasing the eccentric lever 20, possible very easily and quickly to restore an aligned location between the drive member 11 and the coupling cup 16 by turning the drive member 11 in the untensioned state. The eccentric lever 20 may also be constructed so that it is separable from the stem 3 so that after uncoupling the trailer vehicle, also the coupling ball 2 with the relevant component parts can be removed from the bracket 1 if the towing vehicle is to be driven without the trailer vehicle.

Claims (8)

1. A device for damping snaking movements between towing vehicle and trailer vehicle, with a coupling ball on the towing vehicle and a coupling cup on the trailer vehicle and with at least one mechanical pairing of friction surfaces, the common friction plane of which is horizontally disposed, and which is intended to prevent a yawing motion, whereby both surfaces are, through force transmitting elements, disposed to rotate about a common vertical axis through the centre of the coupling ball, characterised in that the coupling ball is rotationally rigidly mounted on the towing vehicle and in that between the coupling ball and its mounting there is or are mounted one or a plurality of rotary plates (8; 5, 5') which is or are adjacent the pairing of friction faces (6, 9; 7, 10) and operatively connected to the -elements (11, 5, 16) which transmit solely yawing motions to the pairings of friction surfaces.

2. Adevice according to Claim 1, characterised in that for reproducible and rapid application or remov al of the pretensioning force acting in the pairing of friction surfaces (6, 9; 7, 10), an eccentric lever (20) is provided.

3. A device according to Claim 2, characterised in that the eccentric lever (20) can be locked in the tensioned position by a mechanical lock (21, 22).

4. A device according to Claim 1, characterised in that to increase the torque of a yawing motion which can be absorbed, a plurality of pairings of friction surfaces (6, 9; 7, 10 etc.) are provided.

5. A device according to Claim 1 to 3, characte rised in that the pairing of friction surfaces (6,9; 7, 10) is disposed below the coupling ball (2) on the towing vehicle while the force transmitting elements consist of a bracket (1) on the towing vehicle and a drive member (11) associated with the trailer vehicle.

6. A device according to Claim 5, characterised in that the drive member (11) engages in a longitudinal direction laterally around the coupling cup (16).

7. A device according to Claim 5 and 6, characte rised in that the drive member (11), acting in both directions of rotation, is constructed as a yoke for the coupling cup (16).

8. A device for damping snaking movements between a towing vehicle and trailer vehicle sub stantially as described with reference to and as illustrated in the accompanying drawings.