GB2494427A

GB2494427A - A linkage mechanism for operative association between a fifth wheel of a drive vehcile and at least one pair of steerable rear wheels of a traler unit

Info

Publication number: GB2494427A
Application number: GB201115466A
Authority: GB
Inventors: Gerald Muldoon
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-09-07
Filing date: 2011-09-07
Publication date: 2013-03-13
Anticipated expiration: 2031-09-07
Also published as: GB2494427B; GB201115466D0

Abstract

A linkage mechanism for operative association between a fifth wheel of a drive vehicle and at least one pair of steerable rear wheels 16 of a trailer unit 10 is provided. The linkage mechanism permits limited rotary movement of the fifth wheel by the incorporation of compressive components 30, 32 at the connection between a roller cam 24 and a plate 14, when the at least one pair of steerable rear wheels 16 arc in a straight ahead position without steering movement of the at least one pair of steerable rear wheels 16. Retaining means 22, 40, 42, 44 may also be provided for retaining the at least one pair of steerable wheels 16 in the straight ahead position during the limited rotary movement of the fifth wheel.

Description

Linkage mechanism for a trailer steering and a vehicle incorporating same The present invention relates to a linkage mechanism which is suitable for operative association between a FIfth wheel of a drive vehicle, for example a tractor unit, and a steerable rear axle of, for example, a trailer unit.

The term "steerable rear axle" is intended to embrace a rear axle/rear wheel assembly pivotable about a central vertical axis, as well as pivotable rear wheels connected to a rear axle steerable under the influence of a king pin steering system.

Articulated tractor-semi-trailer combinations are extensively uscd in the haulage industry to transport goods on thc road network. Semi-trailers having a trailer length of over 12 metres arc quite common. In addition, proposals have been made to permit the use of trailers even exceeding this length. When such long tractor-trailer combinations are used on motorways, no particularly significant problems are encountered, since the lanes are wide, and the curves are large radius curves. When the tractor-trailer combination, particularly for such long trailers, is operated on city streets and roundabouts. However, the relatively narrow width and tight radius of many streets and roundabouts makes it very difficult or impossible to manoeuvre the tractor-trailer through turns. The rear wheels of the trailer unit do not track the wheels of the tractor unit, but tend to be considerably offset, particularly in sharp turns, as the tractor manocuvrcs through a turn.

One way of alleviating this problem is to provide a steerable rear axle on the trailer, as disclosed inWO 98/21082, incorporated herein by reference.

However, even trailers 2 having such steerable rear axles 4 can encounter problems where trailer length exceeds 12 metres. When approaching a roundabout, a trailer over 15.5 metres long must be able to turn on either lock so that no part of it projects outside the area contained between two concentric circles of 5.3m and l2.5m radii. As can be seen from Figure 1, this is particularly difficult to achieve when the trailer 2 begins its turn in conjunction with the driving cab 1. The back end X of the trailer 2 easily protrudes the area as soon as the lorry begins its tum, a process known as "kickout".

An object of the present invention is to provide an improved linkage mechanism intended to alleviate such problem.

According to a first aspect of the invention there is provided a linkage mechanism for operative association between a fifth wheel of a drive vehicle and at least one pair of steerable rear wheels of a trailer unit, the linkage mechanism permitting limited rotary movement of the fifth wheel substantially when said at least one pair of steerable rear wheels are in a straight ahead position without steering movement of said at least one pair of steerable rear wheels.

Preferably retaining means are provided for retaining said at least one pair of steerable rear wheels in said straight ahead position during said limited rotary movement of said fifth wheel. Said retaining means may be adapted to retain said at least one pair of steerable rear wheels in said straight ahead position until a turning force applied to the at least one pair of steerable rear wheels by the linkage mechanism exceeds a predetermined minimum force required to overcome the retaining means.

In one embodiment said retaining means includes a retaining member moveable between an engaged position, wherein said retaining member retains the at least one pair of steerable rear wheels in said straight ahead position, and a disengaged position, wherein said at least one pair of steerable wheels are free to be steered. Preferable said retaining member is biased towards its engaged position by biasing means, such as a spring or ram.

In one embodiment said linkage mechanism includes a resilient linkage means acting between said fifth wheel and said at least one pair of steerable rear wheels, said resilient linkage means permitting said limited rotary movement of the fifth wheel substantially when the at least one pair of steerable rear wheels are in said straight ahead position. Preferably said resilient linkagc means enables said limited rotary movement of the fifth wheel without transmitting sufficient force to the at least one pair of steerable rear wheels to overcome said retaining means.

In one embodiment said resilient linkage means may comprise at least one compressible resilient member acting between a driving member and a driven member of said linkage mechanism to permit limited movement of said driving member relative to said driven member. Said at least one compressible resilient member is adapted to compress under the action of said driving member to accommodate said limited rotary movement of the fifth wheel, said retaining means retaining the at least one pair of steerable rear wheels in said straight ahead position during such compression of said at least one compressible resilient member. Subsequent rotary movement of the fifth wheel is transferred to the at least one pair of steerable rear wheels, overcoming the retaining force applied by the retaining means and causing steering movement of said at least one pair of steerable rear wheels.

Said resilient linkage means may comprise a pair of compressible resilient members located on either side of a driven member for transmitting a driving force between said driving member and said driven member while permitting limited movement of the driving member on either side of a straight ahead position without movement of the driven member while the at least one pair of steerable rear wheels are in said straight ahead position.

Said driving member may comprise a turntable or rotatable plate adapted to be operatively engaged with the fifth wheel of a drive vehicle, said driven member being coupled to said plate via said resilient linkage means.

Preferably said resilient linkage means acts between said driving member of said linkage mechanism operatively coupled to said fifth wheel and said driven member of said linkage mechanism operatively coupled to said at least one pair of steerable rear wheels, whereby said resilient linkage means permits limited movement of said driving member with respect to said driven member to allow limited rotational movement of said fifth wheel while said retaining means retains the at least one pair of steerable rear wheels in said straight ahead position.

Said at least one resilient member may comprise an elastomeric bush, spring or accumulator, preferably located bctwccn said driving and drivcn members.

In a further embodiment the linkage mechanism includes a hydraulic circuit for transferring a driving force between the fifth wheel and the at least one pair of steerable rear wheels, said hydraulic circuit including at least one accumulator or moveable wall or other compressible means, whereby said at least one accumulator, moveable wall or other compressible means enables limited movement of the fifth wheel without corresponding steering movement of the at least one pair of steerable rear wheels. Preferably said at least one pair of steerable rear wheels are retained in a straight ahead position by said retaining means during said limited movement of the fifth wheel, said at least one accumulator, moveable wall or other compressible means limiting thc force transmitted to the at least one pair of steerable rear wheels via the hydraulic circuit until the rotary movemcnt of said fifth wheel exceeds said limited rotary movement.

According to a second aspect of the invention there is provided a vehicle having at least one pair of steerable rear wheels and incorporating a linkage mechanism according to a first aspect of the invention.

Preferably, the vehicle comprises a drive vehicle and trailer unit assembly, the trailer unit having the at least one pair of the steerable rear wheels.

The term "trailer unit" is intended to embrace semi-trailers.

Linkage mechanisms in accordance with embodiments of the present invention will now be described, by way of example only, with reference to Figures 2 to 12 the accompanying drawings, in which:-Figure 2 is a plan view of a trailer unit incorporating a linkage mechanism in accordance with a first embodiment of the present invention; Figure 3 is detailed view ofa resilient linkage means of the linkage mechanism of Figure 2; Figure 4 shows the resilient linkage means of Figure 2 is when the tractor unit is steered approximately 5° to the left; Figure 5 shows the resilient linkage means of Figure 2 is when the tractor unit is steered approximately 5° to the right; Figure 6 is a perspective view of a rear part of the trailer unit of Figure 2; Figure 7 is a detailed view of the rear part of the trailer unit of Figure 2 showing a retaining means for retaining the rear steerable wheels of the trailer unit in a straight ahead position during initial turning of the tractor unit; Figure 8 is a perspective view of the rear part of the trailer unit with the rear steerable wheels steered to the left; Figure 9 is a detailed view of the rear part of the trailer unit of Figure 2 showing the retaining means in a disengaged position allowing the rear steerable wheels to be steered; Figure 10 is a perspective view of a trailer unit incorporating a linkage mechanism in accordance with a second embodiment of the present invention; Figure 11 is a detailed view of the linkage mechanism of Figure 10; and Figure 12 is a plan view of the trailer unit of Figure 10.

A general illustration of a typical tractor/trailer combination 10 is shown in Figure 1. The trailer unit 2 is pivotally connected to the tractor unit 1 at the junction of the fifth wheel 5 and the trailer kingpin, as generally known. The rearmost pair of wheels 4 of the trailer unit 2 are steerable by means of a linkage mechanism, such as that disclosed in WO 98/2 1082.

Whilst such rear wheel steering arrangement enables the turning radius of the trailer 2 to closely mimic the turning radius of the tractor unit 1, such arrangement tends to cause the rearmost end X of the trailer unit 2 to kick out" during initial steering of the tractor unit into a tum, away from a straight ahead direction.

A trailer unit 10 incorporating a linkage mechanism in accordance with a first embodiment of the present invention is illustrated in Figures 2 to 9. The trailer unit 10 comprises an elongate chassis 12 having a having a rotatably mounted plate 14 at a forward end with a centrally mounted king pin 15 secured thereto for coupling with the saddle of a conventional fifth wheel of a tractor unit, such that a steering action of the tractor unit can be transmitted to the trailer unit via the fifth wheel and said plate 14 and be subsequently conveyed to a steering action of a rearmost set of steerable wheels 16 of the trailer unit 10 via the linkage mechanism. Two further pairs of non-steerable wheels 18,20 are provided ahead of said steerable wheels 16.

The rearmost pair of wheels 16 arc mounted a rear bogie 22 which is rotably mounted on the chassis 12 of the trailer unit 10 to be rotatable with respect to the chassis 12 about a vertical axis under the action of the linkage mechanism.

The fifth wheel of the tractor unit is provided with a wedge shaped socket adapted to receive a wedge shaped member extending from the plate of the trailer unit to rotatably couple the plate to the fifth wheel. A cam roller 24 is associated with the wedge shaped member to engage a bell erariJc 26, whereby rotary motion of the fifth whee' can be transmitted to a steering action of the rear wheels 16, as described in WO 98/21082. As described in WO 98/2 1082, the bell crank may be provided with an cam collar (not shown) within which is received the earn roller 24, the cam collar having a substantially obround section opening into a substantially elliptical section, whereby, as the tractor unit is steered so that the fifth wheel rotates up to approximately 40° from the longitudinal axis of the trailer, the cam roller 24 engages against the obround section of the cam collar, causing pivotally movement of the bell crank 26, which is in turn transmitted into a steering movement of the steerable rear wheels 16, via a hydraulic or mechanical connection between the bell crank 26 and the steerable rear wheels 16. As the fifth wheel rotates to a position grcater than 40° from the longitudinal axis of the trailer, the cam roller 24 moves into the elliptical section of the cam collar, such that further rotation of the fifth wheel with respect to the trailer unit can occur without further pivotal movement of the bell crank 26 and thus without further steering movement of the rear wheels 16 of the trailer unit 10.

The connection between the cam roller 24 and the wedge shaped member on the plate 14 incorporates compressive components 30,32 comprising blocks of compressive material on either side of the cam roller 24 to incorporate 5° flexibility in either direction from a central position of the cam roller 24. Such compressive components 30,32 (rubber bush, spring or ram attached to accumulator) on either side of the cam roller 24 provides a resilient connection between the cam roller 24 and the plate 14 such that the plate 14 can rotate with respect to the cam roller 24.

Figure 5 shows the similar situation when the fifth wheel is rotated approximately 50 to the right.

In the embodiment shown in Figure 2, the motion of the bell crank 26 is transmitted to the steerable rear wheels 16 via a hydraulic coupling. However, it is envisaged that such motion may be transmitted by a mechanical connection, such as rods or cables.

As shown in Figures 6 to 9, the steerable rear whe&s 16 are retained in a straight ahead position by means of a retaining member 40 engaging a recess 42 in the rear bogie 22 of the steerable wheels 16. The retaining member 40 is moveable between a retracted position (shown in Figure 9), wherein the retaining member 40 is spaced from the recess 42 in the rear bogie 22, allowing rotation of the rear bogie 22 with respect to the chassis 12, and an extended position, wherein a roller 44 provided at a distal end of the retaining member 40 engages the recess 42 in the rear bogie 22 to retain the steerable wheels 16 in a straight ahead direction. The retaining member 40 is biased towards its extended position by biasing means, in the form of a spring and/or a hydraulic or pneumatic actuator, possibly coupled to the hydraulic circuit of the linkage mechanism or an accumulator associated therewith.

The retaining member 40 retains the steerable rear wheels 16 in their straight ahead position until a steering force applied to the rear wheels 16 via the linkage mechanism overcomes the retaining force of the retaining member 40.

The resilient connection between the cam roller 24 and the plate 14 by means of the compressive components 30,32 enables the fifth wheel and plate 14 to rotate through a limited angle with respect to the cam roller 24, during an initial steering movement of the tractor unit from a straight ahead position, during which time the retaining means 40 retains the steerable rear wheels 16 of the trailer unit 10 in a straight ahead position. Further rotary movement of the fifth wheel with respect to the trailer unit 10 is transferred directly to thc cam roller 24, causing the rear bogie 22 of the steerable rear wheels 16 to be rotated, forcing the retaining member 40 out of engagement with the recess 42 in the bogie 22.

In the position shown in Figure 3, both of the compressive components 30,32 are at filly extended positions, maintaining the cam roller 24 in a central position with respect to the plate 14. Figure 4 shows the condition where the fifth wheel is rotated approximately 5° to

B

the left with respect to the trailer unit. In such condition, the left hand compressive component 30 is fully compressed, while the cam roller 24 and bell crank 26 remain in their straight ahead position, movement of the cam roller 24 being resisted by the retaining member 40 retaining the bogie 22 of the steerable rear wheels 16 in its straight ahead position.

When the compressive component 30 has its maximum compressive state it will allow the linkage mechanism to override the retaining member 40 so that the retaining member 40 moves out of the recess 42 on the rear bogie 22, as shown in Figure 8 and 9. The wedge will return to its central location and the system will work as standard.

The effect of the improved Linkage mechanism is that it will allow the tractor unit to begin turning before the rear wheel steering system takes effect, therefore reducing initial kickout.

When a turn is initiated by the steering wheels of the tractor unit, one of the compressive components 30,32 compresses as the fifth wheel rotates. This compression of the respective compressive component allows a turn of up to approximately a 5 degree angle before the retaining member is forced out of its recess 42 in the rear bogie 22.

When turned in the other direction, the first compressive component 30 will return to its original state and the other compressive component 32 will compress.

When the retaining member 40 is forced out of the recess 42, the compressive components 30,32 revert back to their original state.

When the steering of the tractor unit causes the fifth wheel to rotate with respect to the trailer unit 20 beyond 5 degrees, the retaining member is forced out of the recess 42, thns rotating the rear bogic 22 and steering the rear wheels 16.

In straight forward position the system is inactive. At 2.5° the steering is not activated due to the compression of the compressive components 30,32. There is not enough pressure to override the retaining effect of the retaining member 40 on the rear bogie 22. At 5° the respective compressive component 30,32 has reached fts maximum compression point. The rear wheels 16 are still in a straight forward position at this point. The system will now be able to override the retaining member 40, releasing the retaining member from the recess 42 on the rear bogie 22, allowing the rear wheels 16 to turn. At such time, the compressive component 30,32 automatically decompresses, allowing the rear wheel steering system to rorlc as described in WO 98/21082.

In an alternative embodiment, shown in Figures 10 to 12, the compressive components 30,32 are replaced by accumulators 100 provided in the hydraulic circuit 104 between the bell crank 26 and the rear bogie 22. The accumulators 100 comprise a moveable wall 102 exposed to the hydraulic fluid within the hydraulic circuit 104, said moveable wall 102 being bounded by a compressible fluid, gas or a spring such that the accumulators absorb the initial hydraulic actuating force transmitted from the bell crank 26 to the rear bogie 22, allowing the fifth wheel to rotate through up to approximately 5° in either direction from a straight ahead position during initiation of a turn, without any corresponding movement of the rear steerable wheels 16 from the straight ahead position. The accumulators 100 may be set such that the moveable walls 102 therein moves to a preset limit, against such compressible fluid, gas or spring, such that the hydraulic circuit 1 04 transmits movement between the bell crank 46 and the rear bogie 22 once the rotary movement of the fflih wheel from its central position exceeds approximately 5° to 8°.

As with the first embodiment, the retaining member 40 engages a recess in the rear bogie 22 to retain the steerable rear wheels in a straight ahead position during such initial steering of the tractor unit. The retaining member 40 may be operated by an actuator connected to the hydraulic circuit such that the fluid pressure in the hydraulic circuit, once the accumulators have frilly extended, may urge the retaining member towards its retracted position.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

<claim-text>Claims 1. A linkage mechanism for operative association between a fifth wheel of a drive vehicle and at least one pair of steerable rear wheels of a trailer unit, the linkage mechanism permitting limited rotary movement of the fifth wheel substantially when said at least one pair of steerable rear wheels are in a straight ahead position without steering movement of said at least one pair of steerable rear wheels.</claim-text> <claim-text>2. A linkage mechanism as claimed in claim I, wherein retaining means are provided for retaining said at least one pair of steerable rear wheels in said straight ahead position during said limited rotary movement of said fifth wheel.</claim-text> <claim-text>3. A linkage mechanism as claimed in claim 2, wherein said retaining means are adapted to retain said at least one pair of steerable rear wheels in said straight ahead position until a turning force applied to the at least one pair of steerable rear wheels by the linkage r mechanism exceeds a predetermined minimum force required to overcome the retaining means.</claim-text> <claim-text>14') 4. A linkage mechanism as claimed in claim 3, wherein said retaining means includes a 0 20 retaining member moveable between an engaged position, wherein said retaining member retains the at least one pair of steerable rear wheels in said straight ahead position, and a disengaged position, wherein said at least one pair of steerable wheels are free to be steered.</claim-text> <claim-text>5. A linkage mechanism as claimed in claim 4, wherein said retaining member is biased towards its engaged position by biasing means.</claim-text> <claim-text>6. A linkage mechanism as claimed in any of claims 2 to 5, wherein said linkage mechanism includes a resilient linkage means acting between said fifth wheel and said at least one pair of steerable rear wheels, said resilient linkage means permitting said limited rotary movement of the fifth wheel substantially when the at least one pair of steerable rear wheels are in said straight ahead position.</claim-text> <claim-text>7. A linkage mechanism as claimed in claim 6, wherein said resilient linkage means enables said limited rotary movement of the fifth wheel without transmitting sufficient force to the at least one pair of steerable rear wheels to overcome said retaining means.</claim-text> <claim-text>8. A linkage mechanism as claimed in claim 6 or claim 7, wherein said resilient linkage means comprise at least one compressible resilient member acting between a driving member and a driven member of said linkage mechanism to permit limited movement of said driving member relative to said driven member.</claim-text> <claim-text>9. A linkage mechanism as claimed in claim 8, wherein said at least one compressible resilient member is adapted to compress under the action of said driving member to accommodate said limited rotary movement of the fifth wheel, said retaining means retaining the at least one pair of steerable rear wheels in said straight ahead position during such compression of said at least one compressible resilient member.r 10. A linkage mechanism as claimed in claim 9, wherein said resilient linkage means comprise a pair of compressible resilient members located on either side of a driven member for transmitting a driving force between said driving member and said driven member while If) permitting limited movement of the driving member on either side of a straight ahead 0 20 position without movement of the driven member while the at least one pair of steerable rear wheels are in said straight ahead position.11. A linkage mechanism as claimed in any of claims 8 to 10, wherein said driving member comprises a turntable or rotatable plate adapted to be operatively engaged with the fifth wheel of a drive vehicle, said driven member being coupled to said plate via said resilient linkage means.12. A linkage mechanism as claimed in any of claims 8 to 11 said resilient linkage means acts between said driving member of said linkage mechanism operatively coupled to said fifth wheel and said driven member of said linkage mechanism operatively coupled to said at least one pair of steerable rear wheels, whereby said resilient linkage means permits limited movement of said driving member with respect to said driven member to allow limited rotational movement of said fifth whe& while said retaining means retains the at least one pair of steerable rear wheels in said straight ahead position.13. A linkage mechanism as claimed in any of claims 8 to 12, wherein said at least one resilient member comprises an elastomeric bush, spring or accumulator, preferably located between said driving and driven members.14. A linkage mechanism as claimed in any of claims 2 to 5, wherein the linkage mechanism includes a hydraulic circuit for transferring a driving force between the fifth wheel and the at least one pair of steerable rear wheels, said hydraulic circuit including at least one accumulator or moveable wall or other compressible means, whereby said at least one accumulator, moveable wall or other compressiblc means enables limited movement of the fifth wheel without corresponding steering movement of the at kast one pair of steerable rear wheels.15. A linkage mechanism as claimed in claim 14, wherein said at least one pair of steerable rear wheels are retained in a straight ahead position by said retaining means during said r limited movement of the fifth wheel, said at least one accumulator, moveable wall or other compressible means limiting the force transmitted to the at least one pair of steerable rear 0 wheels via the hydraulic circuit until the rotary movement of said fifth wheel exceeds said limited rotary movement.16. A vehicle having at least one pair of steerable rear wheels and incorporating a linkage mechanism according to any of claims 1 to 15.17. A vehicle as claimed in claim 16, wherein the vehicle comprises a drive vehicle and trailer unit assembly, the trailer unit having the at least one pair of the steerable rear wheels.18. A linkage mechanism substantially as described herein with reference to the accompanying drawings.</claim-text>