AU2021106220B4

AU2021106220B4 - Compensator for fifth-wheel couplings

Info

Publication number: AU2021106220B4
Application number: AU2021106220A
Authority: AU
Inventors: Kinh-Luan Viet Mai; Hans Prem
Original assignee: Mech System Dynamics Pty Ltd; Mechanical System Dynamics Pty Ltd
Current assignee: Mechanical System Dynamics Pty Ltd
Priority date: 2020-02-20
Filing date: 2021-08-20
Publication date: 2021-12-09
Anticipated expiration: 2029-08-20
Also published as: AU2021223659A1; WO2021163764A1; AU2021106220A4

Abstract

A compensator for a fifth-wheel coupling is disclosed. The compensator comprises mounting structure for connecting the compensator to a towing vehicle unit, a first support comprising a first mounting pivot and a first coupling pivot, and a second support comprising a second mounting pivot and a second coupling pivot. The mounting pivots are each pivotally connected to the mounting structure. The coupling pivots are each pivotally connected to the fifth-wheel coupling. The compensator further comprises a limit assembly configured to restrict movement of the supports by (i) engaging with the support between the mounting pivot and the coupling pivot; or (ii) engaging with the coupling pivot. A first axis extends through the first mounting pivot and the first coupling pivot, and a second axis extends through the second mounting pivot and the second coupling pivot. In use, the first and second supports are pivotally connected to the fifth-wheel coupling to support and allow movement of the fifth-wheel coupling relative to the mounting structure. In use, an intersection of the first and second axes defines a roll centre about which the fifth-wheel coupling moves relative to the mounting structure. In use, the first and second supports are aligned respective to each other such that the fifth-wheel coupling is positioned between the roll centre and the mounting structure.

Description

"Compensator for fifth-wheel couplings"

Technical Field

[1] The present disclosure relates generally to compensation mechanisms for a fifth-wheel coupling (alternately referred to as a turntable) for connecting one vehicle unit to another vehicle unit in goods-carrying freight or road vehicles having a rigid truck or a prime mover towing a trailer or a set of trailers.

Background

[2] Fifth-wheel couplings are used to connect a towed vehicle unit to a towing vehicle unit, such as a semi-trailer to a prime mover, a semi-trailer to another semi trailer, or a semi-trailer to a converter dolly, for example in a freight or combination vehicle such as a B-double, B-triple or A-double. The fifth-wheel coupling has a connecting or coupling part which comprises a typically semi-circular table plate, also referred to as a top plate or coupler plate, wherein the coupler plate defines a central hole and a vee section cut-out which in use is oriented towards the towed unit. A pair of coupling jaws is attached to the underside of the coupler plate and the jaws are configured to engage and retain a middle section of a kingpin, wherein the middle section is narrower than a lower section of the kingpin. The kingpin is usually mounted on the front underside of a towed vehicle unit, such as a semi-trailer, on a skidplate. To connect the towed vehicle unit to the towing vehicle unit, the kingpin is guided through the vee section into the central hole, which causes the narrow middle section of the kingpin to engage the coupling jaws and retain the kingpin. The towed vehicle unit is then lowered so that the skidplate rests on and is supported by the top surface of the coupler plate.

[3] When executing a turn on a road or highway, or when traversing uneven roadways or terrain, a freight vehicle as a whole may undergo a roll rotation. Roll rotation is largely in the vertical-transverse plane about a longitudinal axis nominally aligned with the direction of travel. During turns the fifth-wheel coupling connects adjacent vehicle units and effectively prevents the two connected units from rolling relative to each other. As the vehicle travels over uneven ground or goes around a corner executing a turn, in some designs these loads and the resulting stresses can lead to increased and excessive wear, and to failures in some cases, in couplings and in immediately adjacent areas, particularly in freight vehicles that feature semi-trailers with load carrying structures that are very stiff in torsion about the roll axis. Freight vehicles that fall into this class include road tankers designed to carry liquids, powders and other materials in bulk.

[4] Allowing a limited amount of roll to be transferred between towing and towed vehicle units spreads the overturning rolling moment along the vehicle to the suspensions and may improve the vehicle's stability. Some fifth-wheel couplings are designed to accommodate a limited amount of roll by having some clearance in the connection between the kingpin and the coupler plate and the jaws that retain the kingpin in place. The clearance in the connection between the kingpin, coupler plate and its jaws allows limited upward vertical movement of the kingpin relative to the coupler plate before the lower section of the kingpin engages with the jaws; this movement is referred to as lash. The lash in fifth-wheel couplings may allow a maximum relative roll angle between connected towed and towing units, for example, in the range of about 1.5 to 3 degrees. The lash may generally increase with wear of mating parts. In this arrangement, when the lash is fully taken up, the resulting forces from the overturning rolling movement may significantly stress the fifth-wheel coupling together with its supports and the adjoining structures. More importantly, the presence of lash in fifth wheel couplings is known to be the cause of significant reduction in vehicle rollover stability as reflected in the vehicle's static rollover threshold, which is the level of lateral acceleration that a vehicle can sustain without rolling over during a turn.

[5] It is desired to address or ameliorate one or more shortcomings or disadvantages associated with prior fifth-wheel couplings and compensators, or to at least provide a useful alternative thereto.

Summary

[6] Some embodiments relate to a compensator for a fifth-wheel coupling, the compensator comprising: mounting structure for connecting the compensator to a towing vehicle unit; a first support comprising a first mounting pivot and a first coupling pivot, and a second support comprising a second mounting pivot and a second coupling pivot, the mounting pivots each pivotally connected to the mounting structure, and the coupling pivots each configured to be pivotally connected to the fifth-wheel coupling; and a limit assembly configured to exert a force or moment on at least one of the first and second supports to restrict movement of the supports; wherein a first axis extends through the first mounting pivot and the first coupling pivot, and a second axis extends through the second mounting pivot and the second coupling pivot; so that when in use, thefirst and second supports are pivotally connected to the fifth-wheel coupling to support and allow movement of thefifth-wheel coupling relative to the mounting structure, an intersection of the first and second axes defines a roll centre about which the fifth-wheel coupling moves, and the first and second supports are aligned respective to each other such that the fifth-wheel coupling is positioned between the roll centre and the mounting structure, so that movement of the first and second supports reduces the rotation transferred to the mounting structure.

[7] A mounting axis may extend through the first and second mounting pivots. The mounting axis may define a first support angle with the first axis, and may define a second support angle with the second axis, and wherein moving the first and second supports moves the first and second axes to vary the location of the roll centre.

[8] The limit assembly may comprise a first elastically deformable limit member, and wherein an applied force causing movement of each of the supports may move the supports so that at least one of the supports engages with the first elastically deformable limit member to direct at least part of the applied force through thefirst elastically deformable limit member.

[9] The limit assembly may comprise a second elastically deformable limit member, the second elastically deformable limit member connected to the first elastically deformable limit member so that at least part of the applied force transmitted through the first elastically deformable limit member may be transmitted through the second elastically deformable limit member.

[10] The first and second elastically deformable limit members may be connected in series or in parallel. When connected in series the second elastically deformable limit member may be connected to the towing vehicle unit. When connected in parallel both the first and second elastically deformable limit members may be connected to the towing vehicle unit. The first elastically deformable limit member may be a spring, and the second elastically deformable limit member may be a bushing. The first and second elastically deformable limit members may be configured to dampen the applied force transmitted through to the towing vehicle unit.

[11] The compensator may further comprise an adjustment mechanism, wherein the top portion of the fifth-wheel coupling comprises a top surface, and wherein the adjustment mechanism allows a roll centre distance between the top surface and the roll centre to be varied by adjusting a spacing between the first and second mounting pivots. The roll centre distance may be greater than 0.5 metre.

[12] The top portion of the fifth-wheel coupling may comprise a flat top surface, and an angle between the top surface and a mounting platform of the towing vehicle unit may define a roll angle of the fifth-wheel coupling, wherein the roll angle may have a maximum value of approximately 7 degrees.

[13] The compensator as described above may further comprise: a first trunnion pivotally connected to the first support at thefirst coupling pivot; and a second trunnion pivotally connected to the second support at the second coupling pivot; wherein the first and second trunnions are pivotally connected to the fifth- wheel coupling at respective first and second pitch pivots; wherein the first and second pitch pivots are coaxial, and perpendicular to the first and second coupling pivots; and wherein the limit assembly indirectly exerts the force or moment through the first and second trunnions on to thefirst and second supports respectively to restrict movement of the supports.

[14] The first and second trunnions may comprise respective first and second connectors disposed adjacent to the respective first and second coupling pivots. The first and second connectors may each comprise a connector body defining a connector aperture. The connector aperture may be configured to receive a pin or bolt for connecting the connector aperture to a rod end bearing of the first elastically deformable limit member.

[15] The first elastically deformable limit member may comprise a damper. The damper may be or include: (i) a hydraulic damper; or (ii) a pneumatic piston. The damper may be or include: (i) a magnetic damper; or (ii) an electromagnetic damper.

[16] The first elastically deformable limit member may comprise a first end portion disposed at a first end of the damper, wherein thefirst end portion pivotally connects the damper to a base mount connected to the mounting structure. The first elastically deformable limit member may further comprise a second end portion disposed at an opposite second end of the damper, wherein the second end portion pivotally connects the damper to at least one of the coupling pivots via the trunnion.

[17] The second elastically deformable limit member may be a spring. The spring may comprise an elastically deformable material which is wound in a helix to define a lumen within the helix, and wherein the damper is disposed in the helix.

[18] Some embodiments relate to a compensated fifth-wheel coupling, comprising: a compensator as described above; and a fifth-wheel coupling configured to connect a towing vehicle unit and a towed vehicle unit; wherein the compensator reduces the rotation transferred from the towed vehicle unit to the towing vehicle unit.

[19] Some embodiments relate to an articulated vehicle comprising a towing vehicle unit and a towed vehicle unit, the articulated vehicle comprising a fifth-wheel coupling and the compensator as described above, wherein the roll centre of the fifth wheel coupling and a suspension roll centre of the towed vehicle unit define a towed vehicle unit roll axis adjacent to or above a centre of gravity of the towed vehicle unit.

[20] The towing vehicle unit may be a prime mover, and the fifth-wheel coupling may be connected to a rear portion of the prime mover. Alternatively, the towing vehicle unit may be a semi-trailer, and the fifth-wheel coupling may be connected to a rear portion of the semi-trailer. The towing vehicle unit may also be or include a converter dolly. The fifth wheel coupling may be connected to the middle section of the converter dolly along the load supporting area of the chassis. The fifth-wheel coupling may alternatively be connected to a main load supporting area of the converter dolly.

[21] The first and second axes of the respective first and second supports may define the towed vehicle unit roll axis to be above the centre of gravity of the towed vehicle unit. The fifth-wheel coupling may be configured to engage a kingpin of the towed vehicle unit with a zero-clearance fit between the kingpin and thefifth-wheel coupling.

[22] Some embodiments relate to a towing vehicle unit including afifth-wheel coupling mounted at a rear of the towing vehicle unit, the fifth-wheel coupling including the compensator as described above.

[23] Some embodiments relate to a method of allowing for compensation of body roll transferred from a towed vehicle when connected to a towing vehicle, the method comprising: determining a maximum height of the centre of gravity of the towed vehicle unit; determining a location of a suspension roll centre of the towed vehicle unit; and mounting on the towing vehicle unit a fifth-wheel coupling that includes the compensator as described above; wherein the roll centre defined by the first and second axes of the compensated fifth-wheel coupling positions a towed vehicle roll axis above the maximum height of the centre of gravity, the towed vehicle unit roll axis being defined by the roll centre and the suspension roll centre.

[24] The fifth-wheel coupling as described in the above embodiments may be a non-separable fifth-wheel coupling. The non-separable fifth-wheel coupling may comprise pitch pivots connecting the towed vehicle unit to the compensator, and wherein the mounting structure may comprise a ballrace turntable.

Brief Description of Drawings

[25] Embodiments are described in further detail below, by way of example, with reference to the accompanying drawings, in which: Fig. 1A is a perspective view of a compensatedfifth-wheel coupling, comprising a fifth-wheel coupling attached to a compensator for controlling roll movements; Fig. 1B is a perspective view of the reverse side of the compensated fifth-wheel coupling of Fig. 1A, showing the coupler plate, vee opening and central hole for receiving a kingpin within the coupling jaws (not shown); Fig. 2 is an end view of the compensated fifth-wheel coupling of Figs. 1A and IB; Fig. 3A is an end view corresponding to the compensated fifth-wheel coupling as shown in Fig. 2, showing the instant roll-centre at a first height, HI; Fig. 3B is an end view showing the instant roll-centre at a second height, H2, the second height being lower than the first height shown in Fig. 3A; Fig. 3C is an end view showing the compensated fifth-wheel coupling in a first tilted position; Fig. 3D is an end view showing the compensated fifth-wheel coupling in a second tilted position, the second tilted position opposite to the first tilted position; Fig. 4 is an end view showing the compensated fifth-wheel coupling according to some embodiments, including a limit assembly for restricting the lateral or roll movement of the compensated fifth-wheel coupling; Fig. 5 is an end view showing the compensated fifth-wheel coupling according to some embodiments, including a further version of the limit assembly of Fig. 4; Fig. 6 is an end view showing the compensated fifth-wheel coupling according to some embodiments, including a further version of the limit assembly of Fig. 4; Fig. 7 is a schematic illustration in elevation view showing the compensated fifth-wheel coupling in the context of connecting a prime mover and semi-trailer, wherein the compensated fifth-wheel coupling controls some of the roll overturning movement of the semi-trailer transferred to the prime mover; Fig. 8 is a block diagram of a method of allowing for compensation of body-roll transferred from a towed vehicle unit when connected to a towing vehicle unit, using the compensated fifth-wheel coupling of any one of Figs. 1 to 6; Fig. 9A is a perspective view of the compensated fifth-wheel coupling, including a limit assembly for restricting the lateral or roll movement of the compensated fifth wheel coupling, according to some embodiments; Fig. 9B is an exploded view of the compensated fifth-wheel coupling of Fig. 9A; and Fig. 10 is an end view of the compensated fifth-wheel coupling, including a further embodiment of the limit assembly of Figs 9A and 9B.

Detailed Description

[26] Vehicles commonly feature a body/chassis (sprung mass) connected to and suspended above a set of axles or axle groups by a suspension system. The geometry of the vehicle's suspension sets a roll centre for each axle or axle group of the vehicle. The roll axis is a line or an axis extending through the roll centres of adjacent axles or axle groups. Roll refers to rotation about an axis, largely horizontal, and largely pointing in the direction of travel. The sprung mass of the vehicle has a centre-of gravity which is typically vertically offset from the roll axis. For a heavy goods vehicle comprising multiple vehicle units, each unit comprises one or more axles and associated suspensions, and each vehicle unit features a sprung mass. Vehicle units can include a rigid truck, prime mover, semi-trailer and converter dolly, and a combination vehicle can be made up of two or more of these vehicle units connected in series in some way leading with a rigid truck or a prime mover.

[27] The roll axis is the axis about which the sprung mass of the vehicle unit will tend to roll (rotate) when its centre of gravity moves laterally from its central position, for example as the vehicle travels over uneven ground or goes around a corner. Directional changes or travel over uneven terrain also causes each suspension to deflect in response to the changing under wheel conditions and changing loads, which may cause the location of the roll centres (and therefore the roll axis) to move very slightly.

[28] The distance between the centre of gravity and the roll axis affects the amount of roll, the roll stiffness of each suspension affects the distribution of the roll or overturning movement along the vehicle, which affects the stability of the vehicle. Increasing the total suspension roll stiffness increases the resistance to roll movement, and individual suspensions with the greatest roll stiffness will generally provide the greatest resistance to roll movement. Where there is a set of axles (two or more) forming an axle group, then the characteristics of each axle group will affect the stability of the vehicle. Roll and vertical movement of the sprung mass is generally undesirable and suspension systems are designed to absorb road surface unevenness as well as bumps and undulations when traversing uneven terrain. Disturbances that cause the sprung mass to roll will result in lateral movement of the sprung mass and a resultant further destabilising overturning moment. Accordingly, minimising the distance between the roll axis and the sprung mass centre of gravity has benefits for vehicle stability.

[29] The majority of articulated heavy goods freight vehicles operating on roads comprise a single semi-trailer connected to a prime mover by a fifth-wheel coupling. A road train is formed when further trailers are connected, through additional fifth-wheel couplings or a series of pin-type connections and fifth-wheel couplings to form a multi trailer combination. Examples include B-doubles, comprising a prime mover towing two semi-trailers each connected to the other through a fifth-wheel coupling, a B-triple or B-quad, where one and two additional semi-trailers, respectively, are connected through fifth-wheel couplings to the lead B-double semi-trailer set. The fifth-wheel coupling, referred to in industry as a B-type connection (hence the "B" in B-double), is designed to allow the connected vehicles to pitch and yaw but constrains the roll rotation between vehicle units. Vehicle units are said to be roll-coupled when a fifth wheel coupling is used to connect adjacent vehicle units.

[30] Roll-coupling through a fifth-wheel coupling connection transfers rolling movements and overturning loads between adjacent units. These loads are transmitted through fifth-wheel couplings and taken up in adjoining structural members, such as the chassis of the semi-trailer, and payload carrying structures such as decks and tanks. Accordingly, if the towed vehicle unit experiences a sufficiently large sideways force resulting in a large overturning moment leading to a rollover situation, the moment loading in roll through the fifth-wheel coupling connection will force the towing vehicle unit to follow the roll rotation of the towed vehicle unit, and vice-versa. This means that in a rollover situation, both the towed and towing vehicle units will rollover together.

[31] The connection between the kingpin and coupling jaws permits relative swivelling between the kingpin and the coupler plate and its jaws, thus allowing yaw movement between the connected towing and towed units when the freight vehicle executes a turn. For a stationary vehicle on a flat level surface, yaw is rotation largely about a vertical axis in the horizontal plane. When the vehicle executes a tight turn, articulation in yaw can be up to (and in some situations exceed) 90 degrees.

[32] Each side of the coupler plate is pivotally connected to the top of a support, allowing some pitching movement of the towed vehicle unit (usually a semi-trailer). Pitch rotation is largely in the vertical-longitudinal plane about a transverse horizontal axis. The support is attached to a base plate affixed to the rear of the towing vehicle unit. The support may be directly connected to the rear of the towing vehicle unit. In some configurations, the support may be directly connected to the rear of the towing vehicle through a ball bearing (ballrace) turntable. The fifth-wheel coupling is therefore pivotally connected to the rear of the towing vehicle unit (which may be another trailer, semi-trailer, converter dolly or the prime mover), allowing relative rotation in yaw and some rotation in pitch. When the support is directly connected to the rear of the towing vehicle through a ballrace turntable, swivelling between the kingpin/skidplate and the coupler plate is no longer required and is prevented from occurring by a skidplate locking key, which is a wedge shaped piece of steel bolted to the skidplate. The skidplate locking key fits snugly in the vee section opening in the rear of the coupler plate thus preventing any swivelling between the coupler plate and skidplate when engaged, so that articulation in yaw is through the ballrace turntable.

[33] By way of background, a pin-type connection, commonly referred to by industry as a Ringfeder or drawbar coupling, is designed to allow the connected vehicle units to pitch, yaw and roll relative to each other. Where a pin-type (Ringfeder) connection is used between adjacent vehicle units, complete and largely unconstrained rotation in roll can occur between adjacent vehicle units. A pin-type connection is referred to as an A-type connection and there is no roll-coupling between vehicle units when this type of connection is used. An example is an A-double combination, comprising a semi-trailer connected through a fifth-wheel coupling to a prime mover, which in turn is towing a trailer comprising a semi-trailer connected to a converter dolly through a fifth-wheel coupling. The trailer is connected to the rear of the lead semi-trailer through a drawbar which has at its towing point a pin-type connection. In a rollover situation the rear trailer of an A-double can rollover completely, rotating about the drawbar coupling, while the prime mover and lead semi-trailer remain upright. In a rollover scenario involving a B-double, B-triple or B-quad, the entire vehicle will rollover because all units in the vehicle are roll-coupled - if one semi-trailer tries to rollover, because all units are roll-coupled, all semi-trailers and the prime mover must rollover together for vehicle rollover to occur.

[34] Some fifth-wheel couplings incorporate a "compensator" mechanism allowing the coupler plate to roll relative to the fixed main support (base plate), such as by rocking side-to-side. These "compensated" fifth-wheel couplings typically allow a maximum roll angle, for example, up to 5 degrees, which is greater than uncompensated fifth-wheel couplings that rely on lash clearance. Typical compensator mechanisms may comprise an arrangement of springs, bushes, or stops, acting to control and limit the amount of rolling or rocking movement. These arrangements may reduce the forces being directed into thefifth-wheel coupling and fixed main supports. The moving parts in these arrangements typically comprise large, circular, sliding, load bearing surfaces requiring careful manufacture, frequent lubrication and maintenance to ensure smooth action and adequate operating life. Furthermore, these fifth-wheel couplings typically roll about a roll centre located at a single fixed height above the fifth-wheel coupling, and the roll axis is not considered. It is not possible to change the roll centre height in these conventional compensator designs without a costly major redesign.

[35] The present disclosure relates to a compensated fifth-wheel coupling comprising a mechanism that is interposed between the fifth wheel coupler plate and the base plate that is attached to a mounting area of the towing vehicle unit. This allows for limited and controlled lateral movement and tilting of the coupler plate in response to the relative rolling action between adjacent vehicle units when the vehicle is traversing uneven terrain, when negotiating a turn or when changing direction. Compensating for this rolling may lead to improvements in vehicle rollover stability. Compensating for this rolling may substantially reduce loads and stresses in combinations that feature stiff chassis and body structures, such as road tankers.

[36] Figs. 1A, 1B, and 2 show an embodiment of a fifth wheel coupling compensator 100 for compensating roll movement of the fifth-wheel coupling 104. The fifth wheel coupling 104 comprises a coupler plate 105 having a body defining a central hole 106A with jaws (not shown) for accommodating and retaining a kingpin 240 (Fig. 2) of a towed vehicle unit to be connected to coupler plate 105. The body of the coupler plate 105 further defines a vee-shaped cut-out or opening 106B which is arranged to guide the kingpin 240 towards the central hole 106A. The coupler plate 105 comprises a top surface 107 which in some embodiments is a substantially flat surface configured to align with another substantially flat surface (a skidplate) to which the kingpin is attached. The coupler plate 105 further comprises an underside portion 130 which is disposed opposite the top surface 107. The compensator 100 may comprise a mounting structure 108 for connecting the compensator 100 to a first body, such as a mounting platform 109 of a towing vehicle unit. The mounting structure 108 may comprise a foot mount load supporting arrangement, such as brackets 108A, 108B, which is attached to the mounting platform 109 and allows roll movement of the fifth wheel coupling 104 relative to the mounting platform 109. The mounting platform 109 is a rigid assembly connected to a towing vehicle unit, for example a steel plate coupled to a rear portion of a prime mover or semi-trailer, or the main load supporting area of a converter dolly. The mounting platform can also be existing chassis rails or any suitable supporting structure. For example, the Australian/New Zealand Standard 4968.2:2003 demonstrates various configurations of the mounting platform, such as a fixed base assembly configuration comprising a base plate coupled to angle sections (Fig. 3.3 of the Standard), a sliding base assembly configuration comprising a slider that is slidably connected to rails (Fig. 3.4 of the Standard), or a turntable base assembly configuration comprising a ball bearing turntable or slewing ring mounted to a base plate (Fig. 6.1 of the Standard) and including load distributor feet plates for the fifth-wheel coupling to be mounted to the ball bearing turntable and a skidplate locking key as described earlier. The loads associated with the roll rotation of coupler plate 105 can be reduced between the towed and towing vehicle units by the compensator 100.

[37] Herein, unless noted otherwise, reference to a towing vehicle unit refers to an articulated vehicle arrangement where the towing vehicle unit is connected to a towed vehicle unit via a fifth-wheel coupling. The towing vehicle unit may be a prime mover, or a semi-trailer to which another semi-trailer is connected. The towed vehicle unit is typically a semi-trailer for the transportation of liquids or materials in bulk. References herein to "towing vehicle unit" and "towed vehicle unit" are relative, in that when the combined articulated vehicle is travelling in a forward direction, the towing vehicle unit is the unit in front of (and towing) the towed vehicle unit. Unless noted otherwise, there is no requirement for the "towing vehicle unit" as described herein to be a source of drive power, such as a prime mover. Accordingly, a (unpowered) converter dolly may be a towing vehicle unit.

[38] The compensator 100 may further comprise a first support 110 comprising a first mounting pivot 112 and a first coupling pivot 114, and a second support 120 comprising a second mounting pivot 122 and a second coupling pivot 124, wherein the first and second supports 110, 120 are each pivotally connected to the mounting structure 108 at their respective mounting pivots 112, 122. The pivots 112, 114, 122, 124 are roll pivots, as they permit roll of the fifth-wheel coupling 104 relative to the mounting plate 109. The first coupling pivot 114 is rigidly connected to a first transverse coupling pivot 116, and the second coupling pivot 124 is rigidly connected and locked at right angles (when viewed from above) to a second transverse coupling pivot 126. The coupling pivots 116, 126 are pitch pivots, as they permit pitch of the fifth-wheel coupling 104 relative to the mounting plate 109. The coupling pivots 114, 116 together form a first roll-pitch spider 118. Similarly, the coupling pivots 124, 126 together form a second roll-pitch spider 128. As shown in Fig. 1A, the spiders 118, 128 each comprise a trunnion 140 which projects from the underside of the coupler plate 105. The trunnion 140 may be disposed at opposite lateral sides of the coupler plate 105. The trunnion 140 may be integrally formed with the coupler plate 105, or may be a separate component (such as shown in Fig 9B). The trunnion 140 defines apertures for receiving axles or pins 115, 125 to enable the coupler plate 105 to roll about the coupling pivots 114, 124. For the coupler plate 105 to roll as described, the apertures align the axles or pins 115, 125 so that their longitudinal axes are parallel with each other. The trunnion 140 further defines apertures for receiving axles or pins 117, 127 to enable the coupler plate 105 to pitch about the coupling pivots 116, 126. For the coupler plate 105 to pitch as described, these apertures are coaxial. The coupling pivots 116, 126 are each configured to be pivotally connected to the coupler plate 105. The coupling pivots 116, 126 give the coupler plate 105 freedom to rotate in pitch relative to roll coupling pivots 114, 124. The pitch rotation freedom of the coupler plate 105 through the coupling pivots 116, 126 described above is consistent with the operation of a conventional fifth-wheel coupling mounted on pedestal or foot mount supports.

[39] In some embodiments, the mounting structure 108 may comprise a single structure to which the first and second supports 110, 120 are connected, coupled, or linked. In some embodiments, such as shown in Fig. 1A and Fig. 1B, the mounting structure 108 may comprise separate bases, mounting structures, a ballrace (bearing) turntable, or the brackets 108A, 108B to which the first and second supports 110, 120 are respectively linked.

[40] In some embodiments, the compensator 100 as described herein is compatible with configurations of the articulated vehicle comprising the towed and towing vehicle units connected via a non-separable turntable. A non-separable turntable (or non separable fifth-wheel coupling) lacks the quick-release kingpin-and-jaw mechanism of conventional fifth-wheel couplings. In a non-separable turntable, the pitch pivots (116, 126) are integrally-mounted to the underside of the front end of the towed vehicle unit (usually a rear tipping semi-trailer). This may be achieved by fixedly connecting the coupler plate 105 to the underside of the towed vehicle unit, or by removing the coupler plate 105. Accordingly, in a non-separable fifth-wheel coupling, pitch occurs about an axis that is always perpendicular to the roll axis of the towed vehicle unit. The towed and towing vehicle units are configured to yaw (swivel) relative to each other via a ballrace (bearing) turntable mounted on the rear portion of the towing vehicle unit (a prime mover or semi-trailer, or middle section of the load carrying area of a converter dolly). In these configurations, the compensator 100 is installed to connect the ballrace turntable with the pitch pivots 116, 126. The coupler plate 105, kingpin and towed vehicle unit skidplate are not present in non-separable turntable configurations.

[41] Fig. 2 shows coupler plate 105 in a neutral position 200, wherein the towing unit (to which the fifth-wheel coupling compensator 100 is attached) and the towed unit are not rotated in roll relative to each other. This may be, for example, when the articulated vehicle is travelling in a straight line on a substantially flat and level road surface.

[42] A first reference line or first axis 210 extends through the first mounting pivot 112 and the first coupling pivot 114, and a second reference line or second axis 220 extends through the second mounting pivot 122 and the second coupling pivot 124. In some embodiments, the first and second supports 110, 120 are elongate members, and the first and second axes 210, 220 coincide with respective longitudinal axes of the first and second supports 110, 120. In some embodiments, the first and second supports 110, 120 are rigid so that roll movement of coupler plate 105 first occurs about the mounting pivots 112, 122 and/or the coupling pivots 114, 124. The first and second supports 110, 120 may be made of any suitable material, such as a metal or a non metal, such as a fibre-reinforced composite, or a combination thereof. A key consideration in the selection of materials is to reduce the weight of the compensator 100. Materials such as steel would be suitable, having mechanical properties similar to the properties currently found in coupler plates, pedestal and foot mounts, and pin-type couplings. Suitable steels would include Grade 350 mild steel having a minimum yield strength of 350MPa, for example. In some embodiments, high-strength aluminium alloys with comparable minimum yield strength to Grade 350 mild steel may be used. The materials selected should also allow the compensator 100 to accommodate vertical and lateral loads, and longitudinal fore-aft loading consistent with normal and also extreme multiple event acceleration and braking over a prolonged period, to reduce the likelihood of fatigue failure, serious maintenance or replacement of the compensator 100. The weight of the compensator 100 may also be kept low by choosing manufacturing techniques which have a high strength-to-weight ratio, such as forging. A forged steel part typically has a higher strength and lower weight compared to an equivalent part machined from a block of steel. However, in some embodiments of the compensator 100, machined steel parts or steel castings may still be used.

[43] Use of the compensator 100 for compensating roll movement of the coupler plate 105 comprises the mounting structure 108 connected to the towing unit, for example to the mounting platform 109. The first and second supports 110, 120 are pivotally connected at the respective first and second mounting pivots 112, 122 to the mounting structure 108. For example, the first support 110 is pivotally connected at the first mounting pivot 112 to the bracket 108A, and similarly the second support 120 is pivotally connected at the second mounting pivot 122 to the bracket 108B. The first and second supports 110, 120 are pivotally connected to the coupler plate 105 to support and allow movement of the coupler plate 105 relative to the mounting structure 108. The first and second supports 110, 120 are aligned with respect to each other such that the first and second axes 210, 220 intersect at a point distant to the coupler plate 105. This point or intersection defines an instant roll centre 230 about which the coupler plate 105 may subsequently move laterally (transverse to the forward direction of travel of the vehicle) and rotate, for example in response to a force applied to the coupler plate 105 when the kingpin 240 is received and locked in the central position 106. The first and second supports 110, 120 are aligned respective to each other such that the coupler plate 105 effectively rotates about the roll centre 230 over a small range of angles. The roll movement of the coupler plate 105 results in rotation of the first and second supports 110, 120 about their respective pivots 112, 122.

[44] The nett effect for a sprung mass centre of gravity below the roll axis is a favourable change in the distribution of the overturning moment between the participating axle group suspensions. Without the compensator, as described above, the mismatch in roll stiffness between the drive and semi-trailer group suspensions leads to earlier wheel-lift at the semi-trailer axle group and a lower static rollover threshold value for the combination.

[45] Under normal vehicle operation, roll movement and loading in roll of the coupler plate 105 usually occurs through the skidplate mounted underneath the front of the semi-trailer. This occurs whenever there is a roll imbalance imposed on the vehicle due to travel over uneven roads or terrain, while executing a turn, or when performing transient manoeuvres, such as a lane change, or when changing direction. Under extreme conditions, typically when wheel lift has occurred on the semi-trailer axle group (which usually has greater roll stiffness than the prime mover axle group) and the vehicle is approaching rollover as the front of the semi-trailer continues to roll, the kingpin 240 may eventually be pulled upwards. The upward movement of the kingpin 240 transfers a vertical load to the centre of the coupler plate 105 where the kingpin 240 is connected to the coupling jaws, further increasing the overturning/rolling moment on the towing unit. The amount of rolling movement transferred from the kingpin 240 to the central hole 106A at the centre of the coupler plate 105 depends on the amount of vertical clearance between the kingpin 240 and the central hole 106A.

[46] Conventionally, some fifth-wheel couplings have a clearance between the kingpin and the central hole which allows limited movement (lash) of the kingpin 240 within the central hole 106A before the kingpin 240 engages with and transfers load to the surrounding body of coupler plate 105 which defines the central hole 106A. For uncompensated fifth-wheel couplings, the clearance between the kingpin and the central hole in the coupler plate allows a small amount of vertical movement. While this allows a small amount of relative roll movement across the fifth-wheel coupling between the towing and towed units, thereby relieving some structural loads due to roll, it has an adverse effect on the stability of the vehicle by reducing its rollover stability threshold. For the compensated fifth-wheel coupling 100, as described herein, a zero clearance fit between kingpin 240 and the central hole 106 in the coupler plate and skid-plate can be introduced thereby increasing vehicle rollover stability in prime mover and semi-trailer road tanker combinations.

[47] Movement of the kingpin 240 in the central hole 106A of the coupler plate 105 may include roll, pitch, and yaw movement. Yaw of the kingpin 240 and hence yaw of the towed unit may be measured relative to a global ground-fixed yaw axis 250. The global yaw axis 250 is a vertical axis that is perpendicular to the forward direction of travel. In some embodiments, the supports 110, 120 are positioned so that when the fifth-wheel coupling 104 is in the neutral position 200 as shown in Fig. 2, the roll centre 230 as defined by the intersection of the first and second axes 210, 220 intersects with the yaw axis 250.

[48] Clearance (lash) or free-play between the kingpin 240 and the coupler plate 105 may allow a small angle to be formed between the global yaw axis 250 and an axis aligned with a kingpin axis 260 of the kingpin 240. The kingpin axis 260 is collinear with the axis of revolution of the kingpin 240. As shown in Fig. 2, the axis 260 generally defines the axis along which the kingpin 240 may move vertically (vertical lash) before the kingpin 240 engages the coupler plate 105 through central hole 106A.

In some embodiments of the compensator 100, the supports 110, 120 may have a range of tilt movement which allows a zero-clearance fit between the kingpin 240 and the coupling jaws/coupler plate 105 through the central hole 106A. In some configurations, the zero-clearance fit may lead to practical difficulties for the prime mover to connect to the semi-trailer. If a zero-clearance fit is not practicable, a standard (snug) fit between the kingpin 240 and the coupling jaws/coupler plate 105 through the central hole 106A may be used, with a clamping arrangement put in place between the coupler plate 105 and kingpin 240 to effectively produce a zero-clearance fit when the prime move and trailer are connected. This clamping arrangement may be primarily mechanical, with other clamping mechanisms, such as pneumatic, hydraulic, electric, and/or electromagnetic mechanisms, being used to assist and/or actuate the clamping arrangement. The clamping arrangement may be automatically activated (e.g. by a control system carried by the vehicle 700) or manually activated. The zero clearance fit, or at least a snug fit, between the kingpin 240 and the coupling jaws/coupler plate 105, substantially eliminates lash. Non-separable couplings, as described earlier, are inherently equivalent to zero-clearance fit, no-lash, fifth-wheel couplings.

[49] In some embodiments, the supports 110, 120 are positioned so that when the coupler plate 105 is in the neutral position 200, kingpin axis 260 intersects with the roll centre 230 as defined by the intersection of the first and second axes 210, 220. Positioning kingpin axis 260 to be aligned or collinear with the roll centre 230 in the neutral position 200 may distribute the forces associated with the roll movement of the fifth-wheel coupling 104 more evenly between the supports 110, 120, compared to if the kingpin axis 260 was not aligned with the instant roll centre 230. That is, there is advantage to having kingpin axis 260 aligned or collinear with the global yaw axis 250, when the vehicle is on a flat level surface.

[50] For the purposes of kinematic analysis, the compensator 100 (with the first and second supports 110, 120 connected to a towing unit) may be represented or modelled as a planar four-bar linkage, comprising four links and four revolute joints. The supports 110, 120 each embody a link (two links in total), wherein each support 110,

120 (or link) has a revolute joint at each end, namely, at the mounting pivots 112, 122 and at the coupling pivots 114, 124, respectively. The coupler plate 105, which connects to the towed vehicle unit through the kingpin 240 and the kingpin's skidplate, forms a third link sharing the coupling pivots 114, 124 with the supports 110, 120, respectively. The fourth link is the mounting plate 109 which has the mounting pivots (revolute joints) 112, 122. Expressed in this way, the planar four-bar linkage defines a plurality of instant centres, wherein each instant centre is a point about which that link effectively rotates over a range of angles consistent with the neutral central starting position.

[51] In this kinematic analysis, modelling the mounting plate 109 as fixed in space and not moving relative to ground, then the first support 110 has its instant centre at the first mounting pivot 112 (when it tilts, its centre of rotation is the centre of the mounting pivot 112), and in the same way the second support 120 has its instant centre at the second mounting pivot 122. The coupler plate 105, which has at each end the coupling pivots 114, 124, has its instant centre at the roll centre 230 above the coupler plate 105 as shown in Fig. 2. That is, as the coupler plate 105 moves sideways (tilts) to the left or right, the motion of the coupler plate 105 is constrained to follow a circular arc prescribed by the rotation of the supports 110, 120 about each of their respective rotation centres (mounting pivots 112, 122). As such the instant centre of rotation of the coupler plate 105 is located at roll centre 230. For a range of roll/tilt angles the coupler plate 105 will rotate about a point very close to the original location of the roll centre 230. For this application the location of the coupler plate 105 instant centre 230 measured relative to mounting plate 109 can be considered fixed for sideways movement consistent with the coupler plate 105 roll/tilt angles between zero and at least seven degrees measured from the neutral or central position 200. For coupler plate 105 roll/tilt angles greater than seven degrees and up to about 10 degrees, the location of the instant centre 230 changes without fully changing or detracting from the performance benefits offered by the compensator 100.

[52] Turning now to Figs. 3A-3D, the location of the roll centre 230 may be expressed as a height H above the top surface 107 of the coupler plate 105. The height

H may be between approximately 0.25 m and approximately 4 m. In some embodiments, the height H is between approximately 1 m and approximately 3 m. In some embodiments, the height H is between approximately 1 m and approximately 2 m. The spacing of or distance between the mounting pivots 112, 122 may be expressed as a distance D. The distance D may be between approximately 0.5m, or less depending on the overall width (measured in the same direction as D) of the coupler plate 105, and approximately 2 m. In some embodiments, the distance D is between approximately 1 m and approximately 2 m. The distance D may be measured along a mounting axis 300, which connects the mounting pivots 112, 122. The mounting axis 300 defines a first support angle 310 with the first axis 210, and defines a second support angle 320 with the second axis 220. Fig. 3A shows the roll centre 230A (defined by the intersection of axes 21A, 220A) at a first height Hi above the top surface 107 of the coupler plate 105, which is in the central or neutral position 200. The height Hi may, for example, be approximately 1.5 m. Fig. 3A also shows the mounting pivots 112, 122 spaced apart at a distance D1. The distance D1 may, for example, be approximately 1I m. Similarly, Fig. 3B shows the roll centre 230B (defined by the intersection of axes 210B, 220B) at a second height H2 above the top surface 107 of the coupler plate 105 which is also in the central or neutral position 200. The height H2 may, for example, be approximately 1 m. Fig. 3B also shows the mounting pivots 112, 122 spaced apart at a distance D2. The distance D2 may, for example, be approximately 1.5 m. For a fixed distance between the coupling pivots 114, 124, the heights H1, H2 and distances D1, D2 are inversely proportional to each other; for example, reducing the height H requires an increase in the distance D. As shown, height Hi is larger than H2, distance D1 is smaller than D2, and in the neutral position 200, the angles 31GA, 320A are larger than the angles 31GB, 320B. For a set/fixed distance between the mounting pivots 112, 122, the height H of the roll centre 230 from the top surface 107 of the fifth-wheel coupling 104 may be adjusted by varying the spacing of or distance between the coupling pivots 114, 124.

[53] In some embodiments, the mounting structure 108 may comprise an adjustment mechanism to allow variation of the distance D between the mounting pivots 112, 122. This allows the compensator 100 to adjust the height H of the roll centre 230 relative to the centre of gravity of the towed unit, thereby adjusting the amount of roll that the towed unit experiences when it changes direction or travels over an uneven surface. For example, if the towed unit is a load carrying semi-trailer, the centre of gravity of the semi-trailer may change position as goods are added, shift or move around, or removed. Furthermore, the height of the semi-trailer's load, its mass properties (centre of gravity height, mass distribution expressed as mass or polar moments of inertia) will depend on the semi-trailer's design and may differ across different makes and transportation of different freight commodities.

[54] The adjustment mechanism for setting compensator 100's roll centre height may comprise a structure with a plurality of pre-set positions to which the mounting structure 108 may be moved and rigidly secured to set the desired distance D between the mounting pivots 112, 122, and accordingly, change the height H of the roll centre 230. The adjustment mechanism may comprise a rack and/or an actuator to allow adjustment of the distance D. In some embodiments, the adjustment mechanism comprises a ratchet and pawl system to allow gradual adjustment in one direction, and quick adjustment in the opposite direction when the pawl is released from engagement with the ratchet. In some embodiments, the adjustment mechanism comprises slots or slotted bolt holes, which allow spacing of the brackets 108A, 108B to be adjusted before the brackets 108A, 108B are secured to the mounting plate 109.

[55] In some embodiments, the adjustment mechanism is configured to adjust a spacing of or distance between the coupling pivots 114, 124. The height H of the roll centre 230 may be adjusted by varying the spacing between the coupling pivots 114, 124 while the distance D between the mounting pivots 112, 122 is fixed. In some embodiments, the compensator 100 may comprise multiple adjustment mechanisms. Both the spacing between the coupling pivots 114, 124 and the distance D between the mounting pivots 112, 122 may be relatively adjusted by the adjustment mechanisms to achieve the desired height H of the roll centre 230.

[56] In some embodiments, the desired height H of the roll centre 230 may be adjusted by adjusting the distance between the mounting and coupling pivots connected by the first and second supports 110, 120, while the distance D between the mounting pivots 112, 122 is fixed. Specifically, by adjusting the distance between the mounting and the coupling pivots 112, 114 on the first support 110, and by making the same adjustment to the distance between the pivots 122, 124 on the second support 120. Adjusting the distances between the between the pivots 112, 114 and the pivots 122, 124 would also change the height of coupler plate 105 above base plate 109.

[57] Figs. 3C and 3D show the coupler plate 105 in tilted positions, wherein the coupler plate 105 has tilted or rotated away from the neutral position 200 about the neutral position roll centre 230A, for example in response to relative roll movement between the towing and towed units. As described above, the tilt or inclination of the coupler plate 105 relative to the towing vehicle unit may be quantified in terms of a roll or tilt angle 330. The roll or tilt angle 330 is the angle measured between the top surface 107 and the mounting platform 109. When the fifth-wheel coupling 104 is in the neutral position 200, the roll or tilt angle 330 is zero. The roll or tilt angle 330 may be measured between the global yaw axis 250 and the kingpin axis 260, as shown in Figs. 3C and 3D, if the towing vehicle unit is on a horizontal surface. Alternatively, if the top surface 107 and the mounting axis 300 are parallel in the neutral position 200, the roll or tilt angle 330 may be measured between the top surface 107 and the mounting axis 300. The roll or tilt angle 330 may be between zero and ten degrees.

[58] When the coupler plate 105 is tilted towards the left, as shown in Fig. 3C, the first and second supports 110, 120 rotate in an anticlockwise direction. The anticlockwise rotation of the first and second supports 110, 120 increases the size of the first support angle 31OC (measured between the first support 110 and the mounting axis 300) while decreasing the size of the second support angle 320C (measured between the second support 120 and the mounting axis 300). Meanwhile, the coupler plate 105 translates to the left, simultaneously rotating in a clockwise sense about instant roll centre 230A. Similarly, when the fifth-wheel coupling 104 is tilted towards the right, as shown in Fig. 3D, the first and second supports 110, 120 rotate in a clockwise direction. The clockwise rotation of the first and second supports 110, 120 decreases the size of the first support angle 31OC while increasing the size of the second support angle 320C. When the coupler plate 105 is tilted towards the right, all of the movements and rotations shown in Fig, 3C are exactly mirrored in Fig. 3D. Accordingly, the coupler plate 105 translates to the right, simultaneously rotating in an anti-clockwise sense about instant roll centre 230A.

[59] Turning now to Figs. 4, 5, and 6, the compensator 100 may further comprise a limit assembly configured to contact or exert a force on at least one of the first and second supports 110, 120 to restrict the movement of at least one of the supports 110, 120, and thereby limit the amount of roll movement of the coupler plate 105. For example, a void is defined underneath the coupler plate 105 and between the first and second supports 110, 120, so that movement of the supports 110, 120 is unimpeded and the compensator 100 may roll freely without obstruction. Accordingly, the limit assembly may be disposed between the first and second supports 110, 120 to limit the amount that the compensator 100 may roll. In some embodiments, the limit assembly comprises parts disposed outside of the first and second supports 110, 120. For example, the limit assembly may include components positioned to either lateral side outside of the first and second supports 110, 120.

[60] In some embodiments, the limit assembly comprises magnets (such as a permanent and/or coiled wired electromagnet) arranged to apply a repulsive magnetic force to a corresponding magnet having the same polarity on the supports 110, 120. The use of magnets, such as neodymium magnets which provide a strong magnetic force in a compact size, allow the limit assembly to limit the amount of movement of the supports 110, 120 without physically contacting the supports 110, 120. This may reduce wear and tear on the supports 110, 120 compared to a limit assembly which relies on physical contact to restrict movement. The use of magnets provides a hard stop when the rotation of the supports 110, 120 moves the opposing magnets into their respective magnetic field.

[61] In some embodiments, the limit assembly comprises a torsion bar installed in place of at least one of the mounting pivots 112, 122. The torsion bar may comprise a bearing fitted on a splined shaft to provide a limited amount of rotation at the mounting pivots 112, 122, with further rotation limited by the torsional strength of the torsion bar. The torsion bar may be used in combination with a hard stop (such as shown in Fig. 4) to physically limit free rotation of the supports 110, 120 beyond the allowable amount of torsion for the torsion bar. The torsion bar arrangement may provide a compact and an unobtrusive means of limiting the rotation of the supports 110, 120.

[62] Fig. 4 shows an embodiment of the compensator 100 with a first embodiment of the limit assembly 400, Fig. 5 shows an embodiment of the compensator 100 with a second embodiment of the limit assembly 500, and Fig. 6 shows an embodiment of the compensator 100 with a third embodiment of the limit assembly 600. The limit assembly 400, 500, 600 is disposed between the first and second supports 110, 120.

[63] In some embodiments, the limit assembly 400, 500, 600 comprises a first limit member 410, 510, 610. The first limit member 410, 510, 610 may be connected to the mounting platform 109 or to the mounting structure 108. The connection may be a rigid connection so that the first limit member 410, 510, 610 does not move relative to the towing unit when a force is applied. The first limit member 410, 510, 610 may be configured to directly or indirectly engage with one of the first or second supports 110, 120. For example, the first limit member 410, 510, 610 may directly contact or be connected to the first and/or second support 110, 120 to direct at least part of the forces from movement of the first and/or second support 110, 120 into the first limit member 410, 510, 610. The first limit member 410, 510, 610 may resist the movement of the first and/or second support 110, 120. The resistance provided by the first limit member 410, 510, 610 may be via an absorber or a progressively increasing resistive load which precisely controls the forces and moments transmitted through thefifth-wheel coupling acting between towing and towed vehicle units.

[64] In some embodiments, the first limit member 410, 510, 610 indirectly contacts the first and/or second support 110, 120 via a separate structure, for example a second limit member 420, 520, 620. The limit assembly 400, 500, 600 may comprise the second limit member 420, 520, 620. The second limit member 420, 520, 620 may directly contact or be connected to the first limit member 410, 510, 610 and to the first and/or second support 110, 120. In some embodiments, the first and second limit members 410, 420, 510, 520, 610, 620 are connected in series, so that movement of the first and/or second support 110, 120 deforms the first and/or second limit members 410, 420, 510, 520, 610, 620. In some embodiments, the first and second limit members 610, 620 are connected in parallel, as shown in Fig 6, so that movement of the first and/or second support 110, 120 initially deforms the first limit member 610 and then engages and deforms the second limit member 620 which provides a further resistive load.

[65] As shown in Fig. 4, the limit assembly 400 is spaced apart from the first and second supports 110, 120 when the coupler plate 105 is in the neutral position 200. This spacing allows some initial movement (for example, leftward or rightward movement) of the coupler plate 105 before one of the first or second supports 110, 120 contacts the limit assembly 400 so that further movement is substantially resisted or is substantially prevented. Movement of the coupler plate 105, for example towards the left, causes the second support 120 to compress and deform the adjacent first limit member 410. The leftward movement may also compress and deform the second limit member 420 connected in series to the first limit member 410. Similar compression and deformation of the limit members 410, 420 applies with rightward movement of the fifth-wheel coupling 104.

[66] In some embodiments, at least one of the first and second limit members 410, 420 may be elastically deformable to absorb kinetic energy when contacted by the first and/or second support 110, 120. For example, at least one of the first and second elastically deformable limit members 410, 420 may be a spring such as a coil spring or a torsion bar, a rubber block ("snubber block"), or a bushing such as a urethane bushing. The first elastically deformable limit member 410 may have the same spring constant as the second elastically deformable limit member 420 so that the limit members 410, 420 deform at the same rate for a given force. Alternatively, the first elastically deformable limit member 410 may have a different spring constant to the second elastically deformable limit member 420.

[67] In the embodiment of the limit assembly 400 shown in Fig. 4, the first limit member 410 is an elastically deformable snubber block and the second limit member 420 is a rigid (or substantially less elastically deformable) structure, for example made from steel and connected to the mounting platform 109. This configuration of the limit assembly 400 allows some initial free movement of the coupler plate 105, and a controlled non-linear hard stop when the coupler plate 105 reaches the limit of its travel as contact is made with limit assembly 400 as described earlier.

[68] Fig. 5 shows the second embodiment of the limit assembly 500 comprising first and second limit members 510, 520. The first and second limit members 510, 520 are functionally equivalent to the first and second limit members 410, 420, in that they act to restrain lateral movement of the first and second supports 110, 120. At least one of the first and second limit members 510, 520 may be elastically deformable, for example wherein the first limit member 510 is elastically deformable, and the second limit member 520 is a rigid (or substantially less elastically deformable) structure connected to the mounting platform 109 and/or to the mounting structure 108.

[69] Unlike the first embodiment 400, the second embodiment 500 of the limit assembly is not spaced apart from the first or second supports 110, 120. In some embodiments, the first limit member 510 is a coil spring having a first end 512 in contact with the first and/or second supports 110, 120 so that the first and/or second supports 110, 120 have no initial free movement, compared to the limit assembly 400. With the limit assembly 500, movement of the fifth-wheel coupling 104, for example towards the left, causes the second support 120 to compress and deform the right-sided first limit member 510. The spring 510 may comprise a second end 514 disposed opposite the first end 512, wherein the first end 512 is in contact with the first and/or second supports 110, 120, and the second end 514 is in contact with the second limit member 520, so that the second limit member 520 may be said to be connected in series to the first limit member 510. Accordingly, the leftward movement may compress and deform both the first limit member 510 and the right-sided second limit member 520 when connected in series.

[70] In some embodiments, the first limit member 510 is connected to the first and second supports 110, 120. As the first limit members 510 are connected to respective first and second supports 110, 120 and arranged as an opposed pair, movement of the fifth-wheel coupling 104, for example towards the left, compresses the right-sided first limit member 510 and extends the left-sided first limit member 510. The extension and compression of the pair of opposed first limit members 510 may provide an initial preload force which biases the coupler plate 105 to remain in the neutral position 200 until a lateral or roll force is applied. The preload force may bias the coupler plate 105 to return to the neutral position 200 when the lateral or roll force is reduced or removed.

[71] The resistance resulting from the extension and compression of the pair of opposed first limit members 510 may be approximately double the resistance provided by the arrangement where the first limit members 510 are not connected to the first and second supports 110, 120. For example, the first limit member 510 may not be attached to the first support 110, so that during said leftward movement the left-sided first limit member 510 is not stretched, and resistance to lateral movement of the coupler plate 105 is provided by only the right-sided first limit member 510. In some embodiments, the first limit member 510 may be attached to the first and/or second support 110, 120 so that both of the first limit members 510 may resist the lateral movement of the coupler plate 105.

[72] Fig. 6 shows the third embodiment of the limit assembly 600 comprising first and second limit members 610, 620. The first and second limit members 610, 620 are functionally equivalent to the first and second limit members 410, 420, 510, 520. The limit assembly 600 comprises elastically deformable first and second limit members 610, 620, wherein the second limit member 620 is nested within the first limit member 610 so that they may be said to be connected in parallel.

[73] The first limit member 610 comprises a first end 612 in contact with the first and/or second supports 110, 120 so that the first and/or second supports 110, 120 have no initial free movement, compared to the limit assembly 400. The second limit member 620 comprises a first end 622, which in some embodiments is in contact with the first and/or second supports 110, 120 so that the first and second limit members 610, 620 deform simultaneously. In some embodiments, the first end 622 is spaced apart from the first and/or second supports 110, 120 so that the first limit member 610 deforms before the second limit member 620. The first limit member 610 may be a coil spring, and the second limit member 620 may be a snubber block, for example.

[74] The limit assembly 600 comprises a third limit member 630, which may be a rigid structure such as a steel block attached to the mounting structure 108 or to the mounting platform 109. The first and second limit members 610, 620 comprise respective second ends 614, 624 disposed opposite respective first ends 612, 622. At least one of the second ends 614, 624 is in contact with the third limit member 630. In some embodiments, both of the second ends 614, 624 are in contact with the third limit member 630.

[75] Similar to the limit assembly 500, in some embodiments the first end 612 of both first limit members 610 are connected to the first and second supports 610, 620 to provide the preload force as discussed above. In some embodiments, the first end 612 and the first end 622 of both the first and second limit members 610, 620 are connected to the first and second supports 610, 620 to provide the preload force.

[76] Regardless of their composition or configuration, the function of the limit members 410, 420, 510, 520, 610, 620 should be understood to act to control roll movement and dampen the force transmitted from the coupler plate 105 between the towed and towing vehicle units. The various embodiments of the limit assembly 400, 500, 600 are examples of the possible customisation options of the compensator 100 to match the lateral and roll resistance characteristics of the compensated fifth-wheel coupling with the suspension of the articulated vehicle.

[77] In use, embodiments of the compensator 100 connect a towing unit and a towed unit to form an articulated vehicle. For example, in a prime mover and semi trailer example, the two units are connected to each other through afifth-wheel coupling. By changing the roll centre height of the coupler plate 105, the roll axis of the towed semi-trailer when the coupler plate 105 is in the neutral position 200 may be shifted relative to the centre of gravity of the towed semi-trailer. When the centre of gravity is below the roll-axis, improved compensation of roll-movements of the towed semi-trailer can be expected, compared to conventional compensated fifth-wheel couplings or uncompensated fifth-wheel couplings, when the articulated vehicle laterally changes direction or travels over an uneven surface.

[78] In Figs. 4 to 6, the limit members 410, 420, 510, 520, 610, 620 are shown to be in contact with the first and second supports 110, 120. Specifically, the limit members 410, 510, 610 are configured to be connected to or be in contact with the first support 110 at a point between the mounting pivot 112 and the coupling pivot 114, and/or connected to the second support 120 between the mounting pivot 122 and the coupling pivot 124. The resistance provided by the limit members 410, 420, 510, 520, 610, 620 imparts a lateral load on the supports 110, 120.

[79] In some embodiments of the limit assembly 400, 500, 600, the limit members 410, 510, 610 are instead configured to be connected to or be in contact with the first support 110 at or near the first coupling pivot 114, and/or connected to or be in contact with the second support 120 at or near the second coupling pivot 124. For example, the limit members 410, 510, 610 are connected to the supports 110, 120 at or near the coupling pivots 114, 124 via the trunnion 140. This provides an alternative load path for the forces causing the rolling/tilting of the coupler plate 105, and removes or at least reduces the aforementioned lateral loads from being directly applied to the supports 110, 120.

[80] Figs. 9A and 9B show an embodiment of a limit assembly 900 comprising a first elastically deformable limit member 910. Fig. 9B is an exploded view of Fig. 9A. The limit assembly 900 is disposed in the void defined underneath the coupler plate 105 and between the first and second supports 110, 120. The first elastically deformable limit member 910 may comprise a damper 912, such as a hydraulic damper or pneumatic piston. In some embodiments, the damper 912 is or includes a magnetic or electromagnetic damper. In some embodiments, the damper 912 is a linear damper that comprises a piston 914 and a damper body 916 defining a plurality of chambers (not shown) for containing a fluid or gas, such as hydraulic fluid or air. This fluid or gas may be compressible. In some embodiments, the damper 912 is or includes a non linear damper. The linearity of the damper may refer to the nature of the damping; for example, a linear damper provides a constant proportional relationship (damping coefficient) between the damping force and the speed of compression or extension of the piston 914, whereas a non-linear damper provides a varying damping coefficient. Compression or extension of the piston 914 moves the piston 914 relative to the damper body 916, thereby moving the fluid or gas between the chambers within the damper body 916. The movement of the fluid or gas provides resistance to the compression or extension of the piston 914.

[81] Rolling or tilting movement of the coupler plate 105 is thereby resisted by extension or compression of the damper 912. As shown in Figs. 9A and 9B, two of the first elastically deformable limit member 910 (damper 912) cooperates to control the tilting movement of the coupler plate 105, wherein when one of the damper 912 is compressed, the other one of the damper 912 is extended. In some embodiments of the compensator 100, only one of the limit members 910 (and optionally one damper 912) is present. Use of a single limit member 910 and damper 912 is possible since the same limit member 910 can be used to limit or resist movement of the first support 110 or the second support 120 in both lateral directions, since the limit member 910 is connected, coupled or anchored to both the support 110 or 120 and the mounting platform 109 (via base plate 932). Use of a single limit member 910 may take up less space overall than two limit members 910 and may involve lower cost, when considering the other components required for attaching the damper 912 to the coupler plate 105. However, the provision of two dampers 912 may allow each individual damper 912 to be smaller and shorter than a single larger and longer damper 912. The provision of two dampers 912 also provides redundancy in the event of failure of one of the dampers 912. Similarly, some embodiments of the limit assembly 500 and 600 may employ only a single limit member 510 or 610, where that limit member is suitably strong yet suitably deformable to resist roll of the coupler plate 105, and is connected, coupled or anchored to both the support 110 or 120 and/or the mounting platform 109.

[82] The limit assembly 900 may comprise a second elastically deformable limit member 920, such as a bump stop, which limits the compression of the damper 912. The bump stop 920 may be located at a distal end of the piston 914 so that it abuts the damper body 916 when the piston 914 is fully retracted into the damper body 916.

[83] The limit assembly 900 may comprise a third elastically deformable limit member 930, which may be a base mount. The base mount 930 may be a rigid structure attached to the mounting structure 108 or to the mounting platform 109. The base mount 930 comprises a base plate 932 and a flange 934 extending from the base plate 932. In some embodiments, the flange 934 defines a hole or aperture configured to receive a coupling pin 936 so that the first limit member 910 can be pivotally connected to the base mount 930. The flange 934 may define a plurality of holes to enable a plurality of the first limit member 910 to be pivotally connected to the base mount 930.

[84] In some embodiments, the first elastically deformable limit member 910 further comprises a first end portion 940. The first end portion 940 is disposed at a first end of the damper 912 and is configured to allow the damper 912 to be pivotally connected to the base mount 930. In some embodiments, the first limit member 910 further comprises a second end portion 950. The second end portion 950 is disposed at an opposite second end of the damper 912 and is configured to allow the damper 912 to be pivotally connected to (or near to) at least one of the coupling pivots 114, 124 via the trunnion 140, such as by pins 115, 125 at the pivots 114, 124. This may allow the damper 912 to indirectly exert, via the trunnion 140 and through pins 115, 125 at the pivots 114 and 124, a force or moment on at least one of thefirst and second supports 110, 120 to restrict their movement.

[85] The structure of the trunnion 140 is more clearly visible in the exploded view of Fig. 9B. The embodiment of the trunnion 140 shown in Fig. 9B is separate to the coupler plate 105, and may be attached thereto via mounting lugs 150 projecting from the underside 130 of the coupler plate 105.

[86] The trunnion 140 comprises a trunnion body 142, which defines a roll aperture 144 for receiving a roll axle or roll pin 115, 125 (not shown) to connect the trunnion 140 to the supports 110, 120 and thereby enable the coupler plate 105 to roll about the coupling pivots 114, 124. The trunnion body 142 may comprise a protrusion or boss 143, which extends away from the trunnion body 142 and further defines the roll aperture 144. The trunnion body 142 further defines a pitch aperture 146 for receiving a pitch axle or pitch pin 117, 127 (not shown) to connect the trunnion 140 to the coupler plate 105 (via the mounting lugs 150) to enable the coupler plate 105 to pitch about the coupling pivots 116, 126. The trunnion body 142 defines the roll aperture 144 and the pitch aperture 146 to be perpendicular to each other.

[87] The portion of the trunnion body 142 defining the roll aperture 144 (such as the boss 143) may be substantially cylindrical to facilitate the rolling movement of the coupler plate 105 when the trunnion 140 is connected to the supports 110, 120. The portion of the trunnion body 142 defining the pitch aperture 146 may be substantially cylindrical to facilitate the pitching movement of the coupler plate 105 when the trunnion 140 is connected to the mounting lugs 150.

[88] The trunnion body 142 further comprises a connector 152 for connecting the first elastically deformable limit member 910 to the trunnion 140. The connector 152 is disposed adjacent to the roll aperture 144 so that rolling movement of the supports 110, 120 is transferred into axial compression or extension of the first elastically deformable limit member 910.

[89] The connector 152 has a connector body that defines a connector aperture 154 for receiving a pin or bolt (not shown). When this pin or bolt is received in the connector aperture 154, the second end portion 950 (and thus the damper 912) is connected to the trunnion 140. When the limit members 910 (dampers 912), trunnions

140, and coupler plate 105 are connected, the connectors 152 are disposed adjacent to the respective first and second coupling pivots 114, 124.

[90] The second end portion 950 comprises a second rod end bearing (rose joint) 952 which allows multi-axis rotation. Similarly, the first end portion 940 comprises a first rod end bearing (rose joint) 942 which allows multi-axis rotation. The first and second rod end bearings 942, 952 may be identical.

[91] The first and second rod end bearings 942, 952 allow rolling or tilting movement of the coupler plate 105 to be resisted by the damper 912 while providing the rotational freedom necessary to enable the coupler plate 105 to move. The first and second rod end bearings 942, 952 each comprise a ball swivel that defines a hole for receiving a pin or bolt, such as the coupling pin 936 to connect to the flange 934 of the base mount 930. The ball swivel is rotatably contained within a housing. The housing may comprise a flange to allow the damper 912 to be connected thereto.

[92] The first and second rod end bearings 942, 952 allow the damper 912 to rotate its alignment in response to the sideways or tilting movement of the coupler plate 105. This allows the forces from the coupler plate 105 to be substantially transmitted along the longitudinal axis of the damper 912. In other words, movement of the coupler plate 105 is substantially translated into extension or compression of the damper 912 (pure axial loading), instead of being substantially translated into bending or torque along the longitudinal axis of the damper 912.

[93] Fig. 10 shows (in section view for clarity) an embodiment of the limit assembly 1000 comprising a first elastically deformable limit member 1010, second elastically deformable limit member 1020, and third elastically deformable limit member 1030. In some embodiments, the first elastically deformable limit member 1010 comprises the damper 912 and a coil spring 1012. The coil spring 1012 comprises an elastically deformable material which is wound in a helix to define a lumen 1014 within the helix. The damper 912 is positioned in the lumen 1014 and connected to the coil spring 1012 so that extension or compression of the coil spring

1012 can be resisted by extension or compression of the damper 912. Positioning the damper 912 in the lumen 1014 of the coil spring 1010 provides a more compact arrangement than positioning the damper 912 outside the coil spring 1012.

[94] The second elastically deformable limit member 1020 may be a bump stop 1020, which limits the compression of the damper 912 and/or the coil spring 1012. The bump stop 1020 may be largely identical to the bump stop 920. The third elastically deformable limit member 1030 may be the base mount 930.

[95] In some embodiments, the first elastically deformable limit member 1010 further comprises the first end portion 940. In the limit assembly 1000, the first end portion 940 is configured to allow the damper 912 and the coil spring 1012 to be pivotally connected to the base mount 930. In some embodiments, the first elastically deformable limit member 1010 further comprises the second end portion 950. The second end portion 950 is configured to allow the damper 912 and the coil spring 1012 to be pivotally connected to (or near to) at least one of the coupling pivots 114, 124 via the trunnion 140.

[96] Similar to the limit assembly 900, in the limit assembly 1000 the first and second end portions 940, 950 enable the damper 912 and the coil spring 1012 to rotate in response to the sideways or tilting movement of the coupler plate 105. This allows movement of the coupler plate 105 to be substantially translated into extension or compression of the damper 912 and the coil spring 1012, instead of being substantially translated into bending or torque along the respective longitudinal axes of the damper 912 and the coil spring 1012.

[97] In some embodiments, extension or compression of the damper 912 and the coil spring 1012 is simultaneous. In some embodiments, extension or compression of the damper 912 and the coil spring 1012 occurs independently; for example, the coil spring 1012 may accommodate a limited amount of extension or compression before the damper 912 is extended or compressed.

[98] Similar to the embodiment of the limit assembly 900 shown in Figs. 9A and 9B, a pair of the limit assembly 1000 may operate to control the tilting movement of the coupler plate 105, wherein when one of the limit assembly 1000 is compressed, the other one of the limit assembly 1000 is extended. On the left side of Fig. 10, one damper 912 and its coil spring 1012 is fully compressed, so that the damper 912 is abutting the bump stop 1020. Meanwhile, the other damper 912 and its coil spring 1012 is fully extended.

[99] In some embodiments of the compensator 100, only one of the limit members 1010 (and optionally one damper 912) is present. Use of a single limit member 1010 and damper 912 is possible since the same limit member 1010 can be used to limit or resist movement of the first support 110 or the second support 120 in both lateral directions, since the limit member 1010 is connected, coupled or anchored to both the support 110 or 120 and the mounting platform 109 (via base plate 932). Use of a single limit member 1010 may take up less space overall than two limit members 1010 and may involve lower cost, when considering the other components required for attaching the damper 912 to the coupler plate 105. However, the provision of two dampers 912 may allow each individual damper 912 to be smaller and shorter than a single larger damper 912. The provision of two dampers 912 also provides redundancy in the event of failure of one of the dampers 912.

[100] The resistance to roll/tilt may be adjusted by selection of the damper 912 and/or its coil spring 1012. For example, where slower movements and/or a greater resistance to sudden changes in roll/tilt is desired (when there is higher roll-velocity to control), a stiffer damper 912 can be interchanged, and/or a coil spring 1012 with greater stiffness interchanged when more resistance to roll/tilt angle is desired. Compared to the coil spring 1012, the dampers 912 may provide a finer degree of control and resistance to roll/tilt velocity (rate of change of roll/tilt angle) of the coupler plate 105. Conversely, the coil spring 1012 may provide an appropriate level of control and resistance in response to larger angular roll/tilt movements of the coupler plate 105.

[101] Fig. 7 shows an example of articulated vehicle 700. The articulated vehicle 700 comprises a prime mover 710 (the towing unit) connected to a semi-trailer 720 (the towed unit) using the fifth-wheel coupling 104. The coupler plate 105 may be operably integral to the compensator 100. The prime mover 710 has a first suspension roll centre 712 above the front steer axle, and a second suspension roll centre 714 above the rear driven axle, wherein a line joining the first suspension roll centre 712 and the second suspension roll centre 714 defines a prime mover roll axis 716. Similarly, the semi-trailer 720 has a third suspension roll centre 722 above the rear axle, and a fourth suspension roll centre 724 located on the prime mover roll axis 716 directly below the fifth-wheel coupling 104. A line joining the third suspension roll centre 722 and the fourth suspension roll centre 724 defines a semi-trailer roll axis 726.

[102] The fourth suspension roll centre 724 is idealised and assumes both the prime mover 710 sprung mass and the connection to the front of the semi-trailer 720 through the fifth-wheel coupling 104 is perfectly rigid, consistent with a conventional (uncompensated) fifth-wheel coupling that has no (lash) roll freedom. Under this assumption, the sprung mass of semi-trailer 720 rotates about the semi-trailer roll axis 726. With the introduction of the compensator 100, the roll centre 230 of coupler plate 105 provides the semi-trailer with further roll freedom. The height of the roll centre 230 is adjustable between positions 230A and 230B, as described above with reference to Figs. 3A and 3B, for example at 230AB.

[103] As shown in Fig. 7, by way of example, the location of the roll centre 230A designates the maximum height of the roll centre 230 of compensator 100 fifth-wheel coupling 104. The roll centres 230A and 722 define a roll axis 728A of the fifth-wheel coupling 104. By way of example, the location of the roll centre 230B designates the minimum height of the roll centre 230 of thefifth-wheel coupling 104 when installed on the mounting platform 109 located on a rear portion of the prime mover 710. The roll centres 230B, 722 define a roll axis 728B. The roll centre 230 of the fifth-wheel coupling 104 may also be adjusted to a position 230AB located between the highest roll centre 230A and the lowest roll centre 230B, wherein the roll centres 230AB, 722 define a roll axis 728AB. The location of the centre of gravity of the semi-trailer 720 may vary depending on the configuration of the chassis of the semi-trailer 720 and/or the goods transported on the semi-trailer 720. For example, the semi-trailer 720 when unloaded may have a centre of gravity 730A, and the semi-trailer 720 when loaded may have a centre of gravity 730B, wherein the centre of gravity 730A is located closer to the ground than 730B.

[104] The roll characteristics of the prime mover 710 are different to the roll characteristics of the semi-trailer 720. The semi-trailer 720 carries a greater load and also has a higher sprung mass centre-of-gravity than the prime mover 710. The greater sprung mass of the semi-trailer 720 means that the suspension of the semi-trailer 720 is designed to have a greater roll-stiffness than the roll-stiffness of the suspension of the prime mover 710. The lower roll stiffness of the prime mover 710 allows the prime mover 710 to keep its wheels in contact with ground for steering and to provide good traction under a range of road conditions.

[105] The type of load carried by the semi-trailer 720 may also affect the location of the centre of gravity of the sprung mass, and thereby affect the roll characteristics of the semi-trailer 720. For example, if the semi-trailer 720 carries a tank of liquid (such as a bulk tank of petrol), the sloshing movement of the liquid results in movement of the centre of gravity of the semi-trailer 720, even with the presence of baffles. Reducing the distance between the centre of gravity and the roll axis reduces the amount of roll induced by the movement of the centre of gravity as the moment arm is shorter, which in turn improves the stability of the vehicle 700 when the vehicle 700 changes direction or travels over an uneven surface. A shorter moment arm means that a larger lateral force (from the movement of the centre of gravity of the sprung mass) would be required to induce the same amount of roll about the roll axis as would be induced by a smaller lateral force operating a longer moment arm.

[106] Notably, for embodiments where the compensator 100 allows for manual adjustment of the rest angles 310, 320 of the first and second supports, the compensator 100 allows for the position of the roll axis to be adjusted once the weight of the semi trailer 720 to be towed is determined. For example, knowing the weight of the semi- trailer 720 when loaded, the location of the loaded centre of gravity 730B can be determined, and the position of the roll centre 230 can be set to a position (such as corresponding to the roll centre 230A) to define a location of the roll axis 728A which reduces the moment arm of the centre of gravity 730B. This may also reduce maintenance costs; for example, the compensator 100 may absorb the rolling forces and thereby reduce the amount of rolling forces that would otherwise be transferred to the fifth-wheel coupling 104 or to the suspension of vehicle 700.

[107] The location of the sprung mass centre-of-gravity 730 (730A, 730B) with respect to the roll axis 728 (728A, 728AB and 728B) is relevant to proper setup and operation of the compensator 100 so as to obtain an appreciable improvement in rollover stability. If the centre-of-gravity is above the roll axis 728 (for example, as shown by 730B) then the overturning moment loading will be in a direction that is opposite that if the centre-of-gravity is below the roll axis 728 (for example, as shown by 730A). A compensator design which only considers the position of the centre of mass relative to roll centre 230, and does not factor in the location of the semi-trailer centre-of-gravity 730 relative to the semi-trailer roll axis 728, can lead to less than optimum improvements in rollover stability. For example, Fig. 7 shows that the centre of-gravity 730A is at the same height as roll centre 230B but it is above roll axis 728B. For the centre-of-gravity 730A a more favourable rollover stability outcome would be consistent with compensator roll centre at 230AB or 230A, which puts the roll axis 728AB and 728A above the centre-of-gravity 730A. In a similar way, the higher centre-of-gravity 730B would gain progressively increasing benefit from roll centres 230B, 230AB and 230A, respectively, consistent with a progressively increasing upward tilt of roll axis 728 and a decreasing moment (decreasing distance from the centre-of-gravity to the roll axis). These findings have been found to be consistent with the results of sophisticated whole-of-vehicle numerical modelling performed by the inventors.

[108] The further benefit of compensator 100 and favourable location of the centre of-gravity 730 relative to the roll axis 728, is the ability to redirect the overturning moment away from the suspension with the higher roll stiffness and distribute it more favourably between participating suspensions to improve rollover stability. This can be done in at least two ways, through optimisation of the location of the centre-of-gravity 730 relative to roll-axis 728, and by optimising the characteristics of components 400, 500, 600, 900 and 1000 described earlier and shown in Figs 4, 5, 6, 9A and 10.

[109] It is important to note that any free-play in the fit of the kingpin 240 in the coupler plate 105 introduces an additional amount of roll freedom, which may be effectively modelled as another roll centre (not shown in Fig. 7) at the point of connection between the kingpin 240 and the coupler plate 105. That is, for a conventional fifth-wheel coupling that has some lash, roll rotation of the semi-trailer sprung mass comprises two rotations, namely one about roll axis 726, and a second rotation about an axis running from 722 through the kingpin 240 to the coupler plate 105 roll centre 230. Rotation of the sprung mass 730 due to turntable lash has a destabilising effect, leading to a reduction in vehicle rollover stability. Therefore, when possible turntable lash should be removed entirely or reduced to a minimum. In some embodiments, the compensator 100 allows lash to be removed entirely while providing for sufficient roll freedom between the roll-coupled vehicle units to accommodate most in-service road and uneven terrain conditions encountered frequently by freight vehicles.

[110] Fig. 8 shows a method 800 of allowing for compensation of body-roll transferred from a towed vehicle unit when connected to a towing vehicle unit by a fifth-wheel coupling 104 using the compensator 100. The towed vehicle unit may be the semi-trailer 720, and the towing vehicle unit may be the prime mover 710, for example. The method 800 comprises the step of determining a maximum height of the centre of gravity of the towed vehicle unit, at 810. Determining the maximum height of the centre of gravity is determined based on the towed vehicle unit being maximally loaded with the material or cargo that it is designed to carry. In most cases, the towed vehicle unit will not be maximally loaded, so the actual height of the centre of gravity may be less than the maximum. If the roll axis is designed to be above the maximum height of the centre of gravity, then for lesser loads in the towed vehicle unit during use, the roll axis can be assured to be above the actual height of the centre of gravity.

[111] The method 800 further comprises the step of determining a location of a suspension roll centre of the towed vehicle unit, at 820. The suspension roll centre of the towed vehicle unit may be the third suspension roll centre 722. The method 800 further comprises the step of determining the absorptive or resistive characteristics of the limit assembly required to achieve the desired distribution of the overturning roll moment between the towing and towed vehicle units' participating axle groups, at 830. At least one of the steps 810, 820, 830 may involve numerical modelling or calculation. For example, the modelling or calculation for step 830 may comprise considering the spacing D of the pivots 112, 122, and the height H of the roll centre 230. The method 800 further comprises the step of mounting on the towing vehicle unit the compensated fifth-wheel coupling 104 with the desired roll centre and limit assembly characteristics, at 840. The roll centre 230 defined by the first and second axes 210, 220 of the compensated fifth-wheel coupling 104 is selected to position the towed vehicle unit roll axis 728 above the height of the maximum centre of gravity. The towed vehicle unit roll axis 728 is defined by the roll centre 230 and the suspension roll centre 722, as described above.

[112] The compensator 100 reduces the need for large amounts of lubrication as required for existing compensated fifth-wheel couplings and would be expected to have less maintenance and longer operating life. The compensator 100 provides means for adjusting the roll centre and therefore the roll axis, to better suit the load carried by the towed vehicle units, compared to existing compensated fifth-wheel couplings which have a roll centre at a fixed height, for example 1 m, and do not take into consideration the specific mechanical properties of the participating axle groups and location of the roll axis. The compensator 100 has few moving parts and a simple kinematic arrangement, which means a reduced risk of breakdown compared to existing compensated fifth-wheel couplings with complex configurations of moving parts. The compensator 100 provides roll compensation of the towed vehicle unit as the articulated vehicle travels at low speeds (speeds up to approximately 30 km/h) over uneven terrain. Furthermore, as the articulated vehicle travels at higher speeds (speeds greater than approximately 30 km/h), the stability of the towed vehicle unit against rollover is improved compared to conventional compensated fifth-wheel couplings or uncompensated fifth-wheel couplings.

[113] The aforementioned embodiments of the compensator 100 control the amount of roll transferred to the towing vehicle unit 710 via the fifth-wheel coupling 104 by having supports 110, 120 which move in response to the roll movement of the towed vehicle unit 720. The movement of the supports 110, 120 provides a passive roll compensation system wherein the compensator 100 is dependent on reacting to the movement of the suspension and/or the movement of the trailer 720.

[114] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each of the appended claims.

[115] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[116] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A compensator for a fifth-wheel coupling, the compensator comprising: mounting structure for connecting the compensator to a towing vehicle unit; a first support comprising a first mounting pivot and a first coupling pivot, and a second support comprising a second mounting pivot and a second coupling pivot, the mounting pivots each pivotally connected to the mounting structure, and the coupling pivots each pivotally connected to the fifth-wheel coupling; and a limit assembly configured to restrict movement of the supports by: (i) engaging with the support between the mounting pivot and the coupling pivot; or (ii) engaging with the coupling pivot; wherein a first axis extends through the first mounting pivot and the first coupling pivot, and a second axis extends through the second mounting pivot and the second coupling pivot; so that when in use, thefirst and second supports are pivotally connected to the fifth-wheel coupling to support and allow movement of thefifth-wheel coupling relative to the mounting structure, an intersection of the first and second axes defines a roll centre about which the fifth-wheel coupling moves relative to the mounting structure, and the first and second supports are aligned respective to each other such that the fifth-wheel coupling is positioned between the roll centre and the mounting structure.

2. The compensator of claim 1, wherein the limit assembly comprises at least one elastically deformable limit member, and wherein an applied force causing movement of each of the supports moves the supports and directs at least part of the applied force through the elastically deformable limit member.

3. A compensated fifth-wheel coupling, comprising: a compensator in accordance with claim 1 or claim 2; and a fifth-wheel coupling configured to connect a towing vehicle unit and a towed vehicle unit; wherein the compensator allows rotation between the towed vehicle unit and towing vehicle unit and vice versa.

4. An articulated vehicle comprising a towing vehicle unit and a towed vehicle unit, the articulated vehicle comprising a fifth-wheel coupling and the compensator of claim 1 or claim 2, wherein the roll centre of the fifth-wheel coupling and a suspension roll centre of the towed vehicle unit define a towed vehicle unit roll axis adjacent to or above a centre of gravity of the towed vehicle unit.

5. A towing vehicle unit including a fifth-wheel coupling mounted at a rear of the towing vehicle unit, the fifth-wheel coupling including the compensator of claim 1 or claim 2.

104 115 105 114 107 130 140 118 117 127 116 126 128 140 100 125 124 120 110

122 1/13

109 112

108B 108A

108

Fig.1A

104 107 106A

100 106B

117 118 116 115 114 120 2/13

110

122

108A 108B 112 108 109

Fig.1B