Load engagement mechanism for a vehicle for transporting elongated loads

Abstract

A tractor unit is disclosed for transporting an elongated load such as a wind turbine blade or wind turbine tower segment. The unit comprises a tractor unit body with a longitudinal axis, a wheel set comprising at least three ground-engaging wheels, one or more of which is driven, said wheel set supporting, driving and steering the tractor unit body, and a load engagement mechanism for engaging with and supporting the elongated load, the load engagement mechanism being mounted on said tractor unit body. The load engagement mechanism is moveable along the longitudinal axis on the tractor unit body from a central location to a periphery of the tractor unit body. The load engagement mechanism is configured to be raised and lowered when positioned at the periphery of the tractor unit body.

Description

[0001] Load engagement mechanism for a vehicle for transporting elongated loads

[0002] Technical Field

[0003] This invention relates to a vehicle for lifting and transporting elongated loads such as a wind turbine blade or wind turbine tower segment.

[0004] Background Art

[0005] Elongated loads such as wind turbine blades or tower segments, or indeed other items of similar elongated dimensions, cannot be readily accommodated on conventional vehicles such as articulated lorries. The length of this kind of load brings significant challenges.

[0006] One of the preferred modes of transport involves a tractor unit and a trailer unit. The tractor unit is driven and steerable and mounts to an end of the load. The trailer unit supports the span of the load, usually in the rear half of the load but not at the rear end. The trailer unit is typically undriven, though it may be driven, and may or may not be steerable. The load itself provides the connection between the tractor and trailer units. The primary function of the trailer unit is to ensure the trailing end of the load is clear of the ground and supported for following the tractor.

[0007] While such an arrangement is useful, problems can still exist due to the lack of manoeuvrability of the tractor and / or trailer units. This is most evident when manoeuvring the load in confined spaces, where it must be steered sharply. United Kingdom Application No 1901106.3 is directed to addressing these issues. However, other issues remain with respect to attachment of the elongated load to the tractor unit. United Kingdom Application No 1901106.3 discloses a load engagement mechanism as does DE 20 2012 009 041 U1 and CN 102717745 A. However these prior art mechanisms suffer from some shortcomings.

[0008] FR3006958 Al describes a load transport machine comprising: - a motor comprising a first attachment module for the load, - an independent motorized chassis mounted on wheels and comprising a second attachment module for the load, said load being connected to the first and to the second attachment module, said first and second attachment modules comprising an attachment device for the load and a rotating support connecting said attachment device to the motorized chassis or to the motor, the rotating support of at least one of the first and second attachment modules comprising at least one slide perpendicular to the longitudinal axis of the attachment device on which said attachment device can slide. There are drawbacks with the limited movement and direction of movement of the attachment device of FR3006958 Al. This prior art document requires a large and heavy counterweight and the forces applied to the lifting mechanism are severe.

[0009] The present teachings are directed to addressing at least some of the shortcomings of the prior art.

[0010] Disclosure of the Invention

[0011] There is provided a tractor unit for transporting an elongated load such as a wind turbine blade or wind turbine tower segment, comprising a tractor unit body having a longitudinal axis, a wheel set comprising at least three ground-engaging wheels, one or more of which is driven, said wheel set supporting, driving and steering the tractor unit body, and a load engagement mechanism for engaging with and supporting the elongated load, the load engagement mechanism being mounted on said tractor unit body, wherein the load engagement mechanism is moveable on the tractor unit body having a longitudinal axis from a central location to a periphery of the tractor unit body, and wherein the load engagement mechanism is configured to be raised and lowered when positioned at the periphery of the tractor unit body.

[0012] By having the load engagement mechanism moveable from a central location to a periphery of the tractor unit a load can be engaged and lifted and then moved back to the central location for transport. This provides maximum stability and distributes the load evenly over all wheels of the tractor unit. A further advantage of this arrangement is avoiding the need for counter-balancing of the load. Furthermore the ability for the carriage to be positioned at the periphery of the chassis or tractor unit body for loading reduces the (push and pull) forces on the load being lifted, which for some relatively delicate long loads such wind turbine blade is a critical design factor.

[0013] Preferably the load engagement mechanism is configured to be raised and lowered only when positioned at the periphery of the tractor unit body.

[0014] Furthermore, the bad engagement mechanism may be configured to be held completely within the footprint of the tractor unit body when in the central position.

[0015] The load engagement mechanism may also be configured to be held partially outside the footprint of the tractor unit body when at the periphery of the tractor unit body.

[0016] Preferably, the load engagement mechanism is mounted on the tractor unit body by a tractor unit carriage which is configured to move laterally on the tractor unit body. The tractor unit body may comprise a track in which the tractor unit carriage is configured to move laterally.

[0017] Preferably the load engagement mechanism comprises a tractor unit carriage cylinder configured to move the tractor unit carriage laterally on the tractor unit body.

[0018] This configuration of the tractor unit carriage, track and cylinder allows the load engagement mechanism to move in a controlled manner on the tractor unit.

[0019] Preferably, the tractor unit carriage cylinder is configured to float so that it can freely extend and retract along the longitudinal axis to allow movement of the tractor unit carriage in response to an external force acting on the tractor unit carriage. The float condition of the cylinder allows it to function as a lateral suspension with respect to the load being carried. The tractor unit carriage can move laterally along the longitudinal axis in response to lateral movement of the load.

[0020] Preferably, the load engagement mechanism further comprises a mast attached to the tractor unit carriage. The mast may be attached to the tractor unit carriage by a slewing assembly configured to rotate relative to the tractor unit carriage and the tractor unit body about a vertical axis.

[0021] In addition, the mast may be configured to rotate with the slewing assembly relative to the tractor unit carriage and the tractor unit body about the vertical axis.

[0022] Preferably, the load engagement mechanism further comprises a triangular shaped mast carriage attached between the slewing assembly and the mast carriage, the mast carriage configured to allow the mast to be raised and lowered relative to the mast carriage.

[0023] A mast lifting cylinder attached to the mast carriage and the mast and configured to raise and lower the mast.

[0024] The mast carriage with the mast attached thereto is configured to be tilted relative to the tractor unit body.

[0025] The tractor unit may further comprise a mast carriage tilt cylinder attached between the slewing assembly and the mast carriage, configured to extend and retract to tilt the mast carriage.

[0026] Preferably, the mast carriage tilt cylinder is configured to float so that it can freely extend and retract to allow tilt of the mast carriage in response to an external force acting on the mast carriage. Optionally, the load engagement mechanism further comprises forks with fork catches configured to engage with fork pockets of the load.

[0027] There is also provided a system for transporting an elongated load such as a wind turbine blade or wind turbine tower segment, comprising two tractor units as previously described, such that the two tractor units are connected by the load itself.

[0028] In another independent aspect of the invention there is provided a mast for lifting an elongated load, such as a wind turbine blade or wind turbine tower segment, comprising a hollow top block at a distal end of the mast, the mast configured for attachment to a tractor unit at a proximal end, wherein the top block is configured to act as a spacer between the mast and the elongated load.

[0029] Preferably the top block is configured to be raised and lowered along a section of the mast.

[0030] The top block may include a load interface plate, parallel to the mast, the load interface plate having a plurality of slots therein.

[0031] Preferably, the plurality of slots are configured to accept bolts protruding from the load.

[0032] Brief Description of the Drawings

[0033] The invention will be further illustrated by the following description of embodiments thereof, given by way of example only with reference to the accompanying drawings, in which:

[0034] Fig. 1 is a side view of a tractor unit with a load engagement mechanism in a lowered position;

[0035] Fig. 2 is a perspective view of the Fig. 1 arrangement;

[0036] Fig. 3 is a side view of the tractor unit with the load engagement mechanism in a raised and centred position;

[0037] Fig. 4 is a perspective view of the Fig. 3 arrangement; Fig. 5 is a side view of tractor unit in accordance with the present teachings wherein the push and pull forces when lifting a load are shown;

[0038] Fig. 6 is a simplified side view of the load engagement mechanism in a lowered position; Figs. 7-8 show a top block of the load engagement mechanism at different positions;

[0039] Fig. 9 is another view of the top block; and

[0040] Fig. 10 is an overhead view of two tractor units operating as a system for transporting an elongated load.

[0041] Detailed description of preferred embodiments

[0042] In figure 1 there is indicated, generally at 100, a tractor unit shown in accordance with the present teachings. The tractor unit 100 has a tractor unit body 101 with a longitudinal axis. Six wheel sets and ground engaging wheels are attached to the tractor unit body 101, three at each side of the tractor unit body 101 or longitudinal axis thereof. The wheels sets are configured for supporting, driving and steering the tractor unit body. A load engagement mechanism 102 for engagement with and for supporting an elongated load (not shown) is mounted on the tractor unit body. The load engagement mechanism 102 is moveable on the tractor unit body 101 along the longitudinal axis from a central location to a periphery of the tractor unit body. In figure 1, the load engagement mechanism is at a periphery of the tractor unit body 101. In this peripheral position the load engagement mechanism 102 can be raised and lowered. In figure 1 the load engagement mechanism 102 is lowered and ready for engagement with a load. It can be seen that when the load engagement mechanism 102 is at the periphery of the tractor unit body 101 it extends partially outside the footprint of the tractor unit body. That is, when the tractor unit 100 is viewed in plan view the tractor unit body 101 defines a rectangle and the load engagement mechanism 102 extends outside this rectangle when at the periphery of the tractor unit body 101.

[0043] Figure 2 shows the same arrangement as figure 1 in perspective view. It can be seen that the load engagement mechanism 102 is mounted on top of the tractor unit body 101. In addition the load engagement mechanism 102 is provided with a tractor unit carriage 103 which is configured to move laterally along the longitudinal axis on the tractor unit body 101. The tractor unit carriage 103 may be provided with wheels or skids which allows the tractor unit carriage 103 move across the surface of the tractor unit body 101. The load engagement mechanism 102 is also provided with a mast 104. In figures 1 and 2 the mast is in a lowered position ready for engagement with a load.

[0044] Figure 3 shows the tractor unit 100 with the load engagement mechanism 102 raised and moved along the longitudinal axis to a central location of the tractor unit body 101. It should be understood that in this central location the load engagement mechanism 102 is held completely within the footprint of the tractor unit body 101 i.e., the aforementioned rectangle when viewed in plan view. At the central location the load engagement mechanism is held fully above the height of tractor unit body 101. The load engagement mechanism can only be lowered below the height of tractor unit body 101 when at the periphery of the tractor unit body 101.

[0045] A mast cylinder 105 is provided to raise and lower the mast 104. In figure 3, the mast cylinder 105 is in a fully extended positon so that the mast is fully raised. The mast must be fully raised in order to move to the central location and the mast can only be lowered below the height of the tractor unit body 101 (for attachment to a load) when at the periphery of the tractor unit body 101. The load engagement mechanism is also provided with a slewing assembly 106. The slewing assembly is provided between the tractor unit carriage 103 and the mast 104 and is configured to rotate relative to the tractor unit carriage 103 and tractor unit body 101. That is, the slewing assembly rotates about an axis perpendicular to the top surface of the tractor unit body 101. In this manner the mast 104 (along with the mast cylinder 105 and other components) can rotate due to the rotation of the slewing assembly 106. The range of slewing is + / - 170° in each direction from the 0° position (shown in figures 3 and 4). However during operation the mast would rarely move past 90° in either direction.

[0046] The slewing is to allow turning around corners when the tractor unit 100 is travelling with a load. In addition, slewing aids alignment of forks 107 of the load engagement mechanism 102 with fork pockets on a load to be lifted. With a load attached the slewing assembly is free to rotate within the aforementioned operational range. The slewing assembly 106 allows the engagement mechanism to be mounted pivotally on the tractor unit body about a vertical axis.

[0047] The mast 104 can be pulled back in towards the tractor unit body 101 so that it rests against a bumper 108 that stabilises the mast from moving around. That is, the tractor unit carriage 103 can move laterally so that the mast, in a lowered position, engages with the bumper 108. This can be useful when the tractor unit 100 is driving around with the mast in a lowered position and without a load attached thereto. When it is desired to engage with a load (such as the aforementioned fork pockets of the load) the mast 104 can be moved away from the bumper to allow slewing. 150mm has been found to be a suitable distance but the skilled person can choose any appropriate distance. Turning back to figure 1, the mast can be seen in a lowered position and away from the bumper 108 i.e., ready for engagement with a load.

[0048] A locking pin (not shown) can be provided which is engaged for servicing the machine, i.e. to prevent the mast from turning / slewing when it is raised up over the tractor unit body 101 for inspections when no load is attached.

[0049] A top block 115 is also provided generally at the top or distal end of the mast. The main function of the top block 115 is as a spacer between the mast and the load i.e., to keep the top of the face of the load away from the mast 104. As will be explained in more detail hereinafter the top block is slides ble along the mast 104. That is, the top block 115 can be raised and lowered to a correct height for engagement with different load faces.

[0050] Figure 4 shows the same arrangement as figure 3 in perspective view. The load engagement mechanism 102 is in a withdrawn position with the mast 104 raised. It can be seen that a tractor unit carriage cylinder 109 is provided with one end attached to the tractor unit body 101 and the other end attached to the tractor unit carriage 103. Extension of the tractor unit carriage cylinder 109 causes the tractor unit carriage 103 (as well as attached components such as the mast 104 etc.) to move towards the periphery of the tractor unit body 101. Retraction of the tractor unit carriage cylinder 109 causes the tractor unit carriage 103 (as well as attached components such as the mast 104 etc.) to move towards a central area on top of the tractor unit body 101.

[0051] It can also be seen from figures 4 as well as figure 2 that the tractor unit 100 includes a track on the tractor unit body 101. The tractor unit carriage 103 is configured to slide or move within the track when pulled or pushed by the tractor unit carriage cylinder 109. The track is defined by two parallel opposing rails 110 on the tractor unit body 101.

[0052] The tractor unit is also provided with a triangular shaped mast carriage 111 connected to the slewing assembly 106. The aforementioned mast cylinder 105 is mounted to the mast carriage 111 as well as the mast 104. A plurality of mast cylinders 105 may be used to raise and lower the mast 104 as is known in the art.

[0053] The capability for the tractor unit carriage 103 to be positioned at the periphery of the tractor unit body 101 for loading reduces the length or size of the triangular shaped mast carriage 111 required for the lifting operation. This in turn reduces the push / pull forces on the load being lifted, which for a wind turbine blade is a critical factor in the design of the blade.

[0054] By having the tractor unit carriage 103 movable along the length of the tractor unit body so that the load engagement mechanism 102 or mast 104 can be moved to the periphery of the vehicle only a relatively short triangular shaped mast carriage 111 is required. The moveable tractor unit carriage 103 allows the load engagement mechanism 102 to be moved to the rear of the tractor unit body for loading and unloading and then brought back to the centre of the tractor unit body to evenly distribute the load over all wheels when transporting the load in a forwards / backwards direction (along the length of the wind turbine blade). When transporting the load in this forwards / backwards direction the tractor unit carriage 103 is locked in this central position having the load centralised over all wheels. A relatively short triangular shaped mast carriage 111, when compared to the prior art, is possible since the tractor unit carriage 103 is moveable to the periphery of the tractor unit which reduces the push / pull forces needed for lifting the load. Figure 5 shows the importance of the capability to have the tractor unit carriage 103 moveable. A long load 500 is attached to the load engagement mechanism. This is exerting a push force at the top of the mast i.e., pushing against the top block and a pull force at the bottom of the mast i.e., pulling against the forks. The distance between the load 500 and the centre of the tractor unit carriage 103 is marked as X. The shorter that distance X can be kept the lower the push / pull forces will be on the load being lifted. This is a critical design feature when handling relatively delicate loads like wind turbine blades. If the tractor unit carriage 103 could not move the load engagement mechanism to the periphery of the tractor unit and remained the central location distance X would be much longer and the push / pull forces much greater. A larger triangular mast carriage 111 would be needed both to reach the periphery of the tractor unit and to handle the greater forces.

[0055] Turning back to figure 4, it can be seen that a mast carriage tilt cylinder 112 is also provided connected between the slewing assembly 106 and the mast carriage 111. The function of this mast carriage tilt cylinder 112 is to tilt the mast carriage relative to the slewing assembly 106 (and tractor unit body 101). It can be seen from figure 4 as well as figure 3 that the mast carriage is connected to the slewing assembly 106 at two pivot points 113 as well as being connected to the slewing assembly 106 via the mast carriage tilt cylinder 112. Extension and retraction of the mast carriage tilt cylinder 112 causes the mast carriage 111 to rotate about an axis defined by the two pivot points 113. That is, extension and retraction of the mast carriage tilt cylinder 112 causes the mast carriage 111 to tilt with respect to the slewing assembly 106 and tractor unit body 101. A mast carriage tilt cylinder 112 may be provided at either side or both sides of the mast carriage 111. The ability to tilt the mast 104 allows easier engagement with a load.

[0056] In the exemplary embodiment shown in the figures, fork catches 114 are provided on the forks 107. These are useful when fork pockets are provided on the load. For example, an elongated load such as a wind turbine can be filled with a lifting bracket that has fork pockets. The engagement of the fork catches 114 with the fork pockets allows the forks to grip the load and ensures the load does not slide off the forks when the tractor unit carriage 103 is pulling the mast and load towards the centre of the tractor unit body 101. It will be appreciated by those skilled in the art that any other type of mechanism may be provided, in place of the forks 107 and fork catches 114, using some sort of hook type catch to allow the load engagement mechanism 102 to grip the load for the pulling portion of the lift.

[0057] Referring now to figure 6, this shows a simplified view of the load engagement mechanism 102 in accordance with the present teachings. The operation of the tractor unit will be explained in more detail with respect to figure 6.

[0058] It can be seen that the tractor unit carriage 103 is at the periphery of the tractor unit body i.e., the tractor unit carriage cylinder 109 is fully extended. This has the result of the mast being fully extended out past the end of the tractor unit body 101. That mast 104 can be raised and lowered using the hydraulic mast cylinder(s) 105 to get the required height for the forks 107 to enter the fork pockets of the load (not shown). Hydraulic mast carriage tilt cylinder(s) 112 can be used to adjust the tilt of the mast carriage 111 and simultaneously the mast 104. Slewing assembly 106 allows the mast carriage 111 and mast 104 to rotate freely about a vertical axis.

[0059] When the forks 107 enter the fork pockets on the load to be lifted the fork catch 114 on each fork 107 is hooked onto the back of the fork pocket by raising the mast 104. After the fork catch 114 is hooked in position and as the mast 104 is continued to be raised, the top block 115 comes in contact with the top face of the load being lifted. The top block 115 acts as an interface between the mast 104 and the load. When the load is wind turbine the top block 115 is configured such that it fits down over the blade's mounting stud bolts allowing the mast 104 to push against the main structure of the blade on the area between the mounting stud bolts so as to not damage the mounting stud bolts. This configuration is explained in more detail below with reference to figures 6 to 8. As the mast 104 is continued to be raised up the tractor unit begins to take the weight of the load and increase the pressure in mast carriage tilt cylinder 112. Once this increase in pressure is detected the tractor unit is configured to dump the oil at the mast carriage tilt cylinder 112 back to a tank to allow this cylinder 112 to float or operate in a float condition. As is known in the art a float condition permits a cylinder to freely extend or retract in response to external forces acting on the hydraulic cylinder. Allowing the mast carriage tilt cylinder 112 to float means the load engagement mechanism 102 can compensate for any changes in the orientation of the elongated load. Taking a wind turbine blade as an example, a second end distal to an end being engaged by the load engagement mechanism 102, may raise or lower in response to undulations in the ground over which the second end is travelling. Because of the floating condition of the mast carriage tilt cylinder 112 the mast 104 can tilt in a corresponding manner to compensate and reduce any strain that may be placed on the load engagement mechanism 102.

[0060] The load engagement mechanism 102 is further configured to continue to raise the mast 104 above the level of the tractor unit body 101. The tractor unit carriage 103 is then pulled back into the centre of the tractor unit body 101 after the mast 104 is raised i.e., the forks are raised above the height of the tractor unit body 101. The centring of the tractor unit carriage ensures even distributing of the weight of the load over all wheels.

[0061] The load engagement mechanism may also be configured to allow the tractor unit carriage cylinder 109 to float or operate in a float condition. That is, the tractor unit carriage 103 can freely move laterally within the track defined by two parallel opposing rails 110. The degree of lateral movement is limited by the length of the tractor unit carriage cylinder 109. The benefit of such an arrangement is described with respect to figure 10.

[0062] It should be noted that the specific means of how to make a cylinder (such as cylinders 109 and 112) float are known to the person skilled in the art and is not repeated here. Figures 6-8 show the top block 115 in more detail. In particular, figure 7 shows the top block 115 in a raised position on the mast while figure 8 shows the top block 115 in a lowered position. A stopper 601 is provided on the mast 115 to engage with the top block 115 in a raised position. The top block may take the form of a hollow square or rectangular block or any hollow shape suitable for the load being lifted. However, the top block shown in figures 6-8 is configured for use with a wind turbine blade 602 wherein the wind turbine blade has a plurality of bolts 603 protruding from the face thereof. In order to accommodate the stud bolts 603 of the blade 602 the top block 115 is provided with slots 604 into which the bolts 603 pass when the top block 115 is lowered. That is, the bolts are positioned within the hollow body of the top block.

[0063] Preferably the top block 115 is raised up to a home position with a small hydraulic cylinder using a wire rope and pulley system although any suitable lifting means may be used. The top block 115 is left in a raised position as shown in figure 7 to allow an operator concentrate on locating the forks 107 into the fork pockets at the bottom of the load. Once the forks are positioned and hooked in the pockets the top block 115 it is lowered into position over the stud bolts 603 as shown in figure 8. As the lift is performed the top block 115 is pushed against the face of the blade 602 and a force is not placed on the stud bolts. With this configuration the stud bolts do not have to be removed for transport, which is a time consuming task due to the number of stud bolts present on each turbine blade. Without the use of a top block 115 with slots 604 therein a force would be applied to the bolts when lifting and they would be damaged or bent.

[0064] The home position of the top block can be manually adjusted in height to accommodate differently sized blades. For differently sized blades, different top block interfaces can be used as the diameter of the blade and stud bolt pattern is generally different for different blades.

[0065] Figure 9 shows a view of the top block 115 in a lowered position from the direction of the mast. The mast is not shown for increased visibility. It can be seen that a stud bolt 603 has entered each of the slots 604 of the top block 115 so they are held within the hollow top block 115. A load facing plate of the top block may be considered a load interface plate 801 and it is this plate 801 that is provided with the slots 604 allowing the bolts to enter the hollow top block 115 when the top block is lowered onto the bolts 603. Turning to figure 10, this shows the tractor unit 100 for transporting an elongated load in accordance with the present teachings configured to work in tandem with another tractor unit 100 positioned at an opposite end of the load. In figure 10, a system 900 is shown where two tractor units 100 are connected by the load 901 itself. White only one tractor unit 100 is shown turning but it should be appreciated that both tractor units can turn in conjunction with each other or independently as needed. In this tandem mode of operation the tractor unit carriage cylinder 109 (on one or both tractor units) is allowed to float, in order to accommodate and compensate for any change in distance between the tractor units 100 so as to not damage the load 901 being lifted.

[0066] It should also be appreciated that the tractor unit 100 for transporting an elongated load in accordance with the present teachings can function with a wheeled trailer unit such that the tractor unit and wheeled trailer unit are connected by the load itself. The trailer unit is typically undriven, though it may be driven, and may or may not be steerable.

[0067] It should be appreciated that one of main benefits of the load engagement mechanism in accordance with the present teachings is the ability to pick up a long-oversized load beyond the footprint of the tractor unit 100 without the need for counterbalance. The tractor unit carriage provides the ability to pull the oversized load back to the centre of the tractor unit body for maximum stability and to distribute the load evenly over all wheels of the tractor unit.

[0068] While the embodiments thus described have six wheels, the skilled person will appreciate that the disclosure can be extended to a three-wheeled embodiment or even to more than four wheels such as six, eight or twelve wheels if desired. The three-wheeled embodiment has been found to be particularly manoeuvrable. In this embodiment the aforementioned central location for the load engagement mechanism is the centre of a triangle defined by the three wheels. In this embodiment when the load engagement mechanism is at the periphery of the tractor unit body it also extends partially outside the footprint of the vehicles. That is, when the three wheel tractor unit is viewed in plan view the tractor unit body defines a triangle and the load engagement mechanism extends outside this triangle when at the periphery of the tractor unit body. Of course, the three wheel tractor unit can also have a rectangular shape in a similar manner as shown in the enclosed figures.

[0069] It should be appreciated that while the drawings show the tractor unit 100 with an operator cab and a front section adjacent to the cab the preferred embodiment does not include these elements. Rather, the tractor unit 100 is exclusivity remotely operated by a user standing and walking adjacent to the tractor unit. This provides an operator with a much better view during the loading and unloading procedure as well as during transport of the load.

[0070] In the exemplary embodiment the tractor unit is configured such that the tractor unit carriage moves longitudinally towards the rear of the tractor unit (the periphery of the tractor unit) to engage with a load. However, the present teachings are not limited to this and the track on which the tractor unit carriage moves can be positioned at any orientation on top of the tractor unit body. For example, at 90 degree to the longitudinal direction shown in the figures so that the load engagement mechanism engages a load at the side of tractor unit as opposed to the rear in the exemplary embodiment. The tractor unit could also be configured so that the load engagement mechanism is moved to the front of the tractor unit and lowered at that position to engage with a load.

Claims

Claims1. A tractor unit for transporting an elongated load, comprising: a tractor unit body having a longitudinal axis; a wheel set comprising at least three ground-engaging wheels, one or more of which is driven, said wheel set supporting, driving and steering the tractor unit body; and a load engagement mechanism for engaging with and supporting the elongated load, the load engagement mechanism being mounted on said tractor unit body; wherein the load engagement mechanism is moveable on the tractor unit body along the longitudinal axis from a central location to a periphery of the tractor unit body; and wherein the load engagement mechanism is configured to be raised and lowered when positioned at the periphery of the tractor unit body.

2. A tractor unit according to claim 1, wherein the load engagement mechanism is configured to be raised and lowered only when at the periphery of the tractor unit body.

3. A tractor unit according to claim 1 or 2, wherein the load engagement mechanism is configured to be held completely within the footprint of the tractor unit body when in the central position.

4. A tractor unit according to any one of claims 1 to 3, wherein the load engagement mechanism is configured to be held partially outside the footprint of the tractor unit body when at the periphery of the tractor unit body.

5. A tractor unit according to any one of claims 1 to 4, wherein the load engagement mechanism is mounted on the tractor unit body by a tractor unit carriagewhich is configured to move laterally along the longitudinal axis on the tractor unit body.

6. A tractor unit according to claim 5, wherein the tractor unit body comprises a track in which the tractor unit carriage is configured to move laterally along the longitudinal axis.

7. A tractor unit according to claim 5 or 6, wherein the load engagement mechanism comprises a tractor unit carriage cylinder configured to move the tractor unit carriage laterally along the longitudinal axis on the tractor unit body.

8. A tractor unit according to claim 7 , wherein the tractor unit carriage cylinder is configured to float so that it can freely extend and retract to allow movement of the tractor unit carriage in response to an external force acting on the tractor unit carriage.

9. A tractor unit according to any one of claims 4 to 8, wherein the load engagement mechanism further comprises a mast attached to the tractor unit carriage.

10. A tractor unit according to claim 9, wherein the mast is attached to the tractor unit carriage by a slewing assembly configured to rotate relative to the tractor unit carriage and the tractor unit body about a vertical axis.

11. A tractor unit according to claim 10, wherein the mast is configured to rotate with the slewing assembly relative to the tractor unit carriage and the tractor unit body about the vertical axis.

12. A tractor unit according to any one of claims 9 to 11, wherein the load engagement mechanism further comprises a triangular shaped mast carriage attached between the slewing assembly and the mast, the mast carriage configured to allow the mast to be raised and lowered relative to the mast carriage.

13. A tractor unit according to claim 12, further comprising a mast lifting cylinder attached to the mast carriage and mast and configured to raise and lower the mast.

14. A tractor unit according to claim 12 or 13, wherein the mast carriage with the mast attached thereto is configured to be tilted relative to the tractor unit body.

15. A tractor unit according to claim 14, wherein tractor unit further comprises a mast carriage tilt cylinder attached between the slewing assembly and the mast carriage, configured to extend and retract to tilt the mast carriage.

16. A tractor unit according to claim 15, wherein the mast carriage tilt cylinder is configured to float so that it can freely extend and retract to allow tilt of the mast carriage in response to an external force acting on the mast carriage.

17. A tractor unit according to any one of claims 9 to 16 further comprising a hollow top block at a distal end of the mast, the mast being attached to the tractor unit carriage at a proximal end, wherein the top block is configured to act as a spacer between the mast and the load.

18. A tractor unit according to claim 17 wherein the top block is configured to be raised and lowered along the mast.

19. A tractor unit according to claim 18 wherein the top block includes a load interface plate, parallel to the mast, the load interface plate having a plurality of slots therein.

20. A tractor unit according to claim 19 wherein the plurality of slots are configured to accept bolts protruding from the load.

21. A tractor unit according to any one of claims 1 to 20, wherein the load engagement mechanism further comprises forks with fork catches configured to engage with fork pockets of the load.

22. A system for transporting an elongated load, comprising two tractor units according to any one of claims 1 to 21, such that the two tractor units are connected by the load itself.

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