BACKGROUND ART Straddle carriers are known in the art and are used at shipping ports to convey shipping containers and to load shipping containers onto a truck, or unload shipping containers from a truck.

These known straddle carriers have an extremely strong and heavy horizontal chassis on which or in which a shipping container can locate. A pair of inverted U- shaped tower assemblies are fixed to, or are part of the horizontal chassis and straddle the shipping container

(hence the name straddle carrier) . Ground engaging wheels are fixed to the chassis and an operator's cabin is located underneath the chassis but above the ground and usually between the front and rear wheels.

The existing straddle carriers suffer from a number of disadvantages. Firstly, the straddle carriers carry shipping containers at least 1.5m above the ground surface. Therefore, together with the tower assembly, the height of the straddle carrier is such that it cannot be easily manoeuvred in and out of storage sheds.

Another disadvantage with existing straddle carriers is that by having the shipping container fairly high above the ground, the centre of gravity of the straddle carrier is also fairly high which requires an extremely strong and heavy chassis.

Yet another problem with existing straddle carriers is that the carriers are not readily adapted to accommodate shipping containers of various lengths. That is, shipping containers are known to have lengths of between 20 - 50ft., and it is dangerous for a short length straddle carrier to carry a long shipping container due to the overhang of the container from each

end of the straddle carrier.

An attempt has been made to overcome the length disadvantage by making the chassis of the straddle carrier telescopic but this adds to the weight and greatly increases the cost of the straddle carrier.

Another type of known container support device is a Container Load Trailer, or CLT. The CLT comprises two separate wheel bogies which can be attached to the front and rear ends of a container. When attached, the container can be towed by a truck. A first main disadvantage with the CLT system is that the bogies are attached to the front and rear of the containers, and as each bogie is about 3m long, the two bogies add about 6m to the length of the container. This make manoeuvring and turning of the container extremely difficult.

The second main disadvantage with the CLT system is that it is extremely difficult to load a container to the back of a truck. Typically, the container is loaded lengthwise on the truck, but as the bogies are attached to the front and the end of the container, the truck must reverse sideways under the container and then by a process of repeated forward and rearward movements, manoeuvre itself such that the container is approximately lengthwise on the truck. The bogies can then be decoupled, but it is found that often the locking slots on the container do not line up with the locking pins on the truck.

The CLT bogies can also be used for sidelifting a container, which allows a truck to move lengthwise underneath the container, overcoming the above disadvantage, but once the truck has left, the bogies need to be decoupled and re-positioned to the front and the end of the container to allow the container to be towed. A further disadvantage with existing straddle carriers is that the straddle carriers are too large to be portable. That is, a conventional straddle carrier does not fit inside a shipping container. In poorer

countries, aid or other goods are shipped in containers for security purposes. The poorer countries rarely have the required straddle carriers or other lifting devices to allow the containers to be readily transported away from the port.

The CLT is designed to fit inside a shipping container, but requires a great amount of assembly and attachment to the container to make it useful.

The present invention is directed to a simple, efficient straddle carrier which can lift and transport shipping containers of any length and which has a low height profile making it more suitable for manoeuvring in and out of storage sheds.

OBJECT OF THE INVENTION It is an object of the invention to provide a straddle carrier which may overcome the abovementioned disadvantages or provide the public with a useful or commercial choice.

In one form, the invention resides in a straddle carrier for lifting and transporting shipping containers, the straddle carrier comprising separate front and rear towers, each tower being of a generally inverted U shaped configuration and having a pair of ground wheel assemblies which can be spaced apart sufficiently to allow a container to locate between the assemblies, each tower including attachment means to attach the tower to the container, each tower having lifting means to lift the container.

By having separate front and rear towers (as opposed to a chassis arrangement of existing straddle carriers) , the straddle carrier according to the invention can be simply attached to each corner of a container of any length. Thus, the straddle carrier can be used on containers having lengths of 20ft., 40ft. and 50ft., and can also handle containers without side walls or front or back walls which are also called flat beds or flat racks.

Each tower can, in use, extend adjacent each

side and over the top of a container. Thus, each tower may have a pair of side vertical members interconnected by an upper horizontal member. The vertical members and the horizontal member may comprise posts which are typically formed from steel box section.

Each ground wheel assembly may have a number of ground wheels, and the ground wheels are suitably arranged such that the tower is free-standing. Thus, it is preferred that each wheel assembly has front and rear in-line wheels extending forwardly and rearwardly of the vertical member.

The ground wheels may support a generally horizontal base plate or chassis and the vertical member may have a lower end attached to and supported by the base plate or chassis.

Each tower has attachment means to attach the tower to the container. The type of attachment means may depend on the type of container. For instance, if the container has ISO corner castings fitted to each corner of the container, the attachment means may comprise a pin which can insert into the casting.

It is preferred that each tower is attached to the side of the container as opposed to the front or rear ends of the container, thereby allowing the container to be more easily lifted onto or from the back of a truck.

The attachment means may be attached to a sleeve member, the sleeve member being slidable along each vertical member of the tower. A lifting means is provided which can facilitate sliding of the sleeve member thereby functioning to raise or lower a container. The lifting means may comprise one or more rams such as hydraulic or pneumatic rams.

There is an advantage in maximising the distance between the vertical members as this facilitates loading and unloading of shipping containers from the back of trucks. To facilitate this, the attachment means may be moveable between an extended and retracted position. The attachment means may comprise a insertable

pin which may be attached to a support member, and the support member may be moveably mounted to a bracket to allow it to move or rotate between the extended and retracted positions. The bracket may be moveable between an extended and retracted position relative to the vertical member. The bracket may be moveable by one or more hydraulic or pneumatic rams. The bracket may form part of a side shift mechanism. To make the straddle crane according to the invention compact, each vertical member may be collapsible as well as each horizontal member. Thus, the vertical members and the horizontal members may be telescopic. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described with reference to the following drawings in which

Figure 1 is a side view of a straddle carrier attached to a container and in the lowered transport position.

Figure 2 is an end view of the straddle carrier of Figure 1.

Figure 3 is a side view of the straddle carrier of Figure 1 with the container in the elevated position. Figure 4 is an end view of the straddle carrier of Figure 3.

Figure 5 is a side view of the straddle carrier of Figure 1 when not in use.

Figure 6 is a top view of the straddle carrier of Figure 5.

Figure 7 is a top view of a straddle carrier straddling a container.

Figure 8 is an end elevation view of a ground wheel assembly. Figure 9 is a plan view of the assembly of

Figure 8.

Figure 10 is an end elevation view of the wheel assembly of Figure 8 in the extended position.

Figure 11 is a plan view of the assembly of Figure 10.

Figure 12 is a close-up view showing the support member in a retracted position. Figure 13 illustrates the support member in a extended position.

Figure 14 illustrates a further attachment embodiment .

Figure 15 shows a ground wheel assembly in a totally collapsed state.

Figure 16 shows the ground wheel assembly of Figure 15 in a partially extended state.

Figure 17 shows the ground wheel assembly of Figure 15 is a fully extended state. Figure 18 shows a top horizontal member in a collapsed state.

Figure 19 shows the horizontal member of Figure 18 in an extended state.

Figures 20 and 21 show an alternative arm construction.

BEST MODE

Referring to the drawings and initially to

Figures 1 - 4, there is shown a staddle carrier for lifting and transporting shipping containers 11. The straddle carrier has a front tower 12 and a rear tower

13. Each tower 12, 13 is of a generally inverted U- shaped configuration (see Figures 2 and 4) . The generally inverted U-shape configuration consists of a pair of vertical members 14, 15 interconnected by an upper horizontal member 15A. Although Figures 2 and 4 illustrate rear tower 13, front tower 12 is similarly designed.

Each tower 12, 13 is free-standing, and this is achieved by a ground wheel assembly at the lower end of each vertical member. Figure 2 illustrates the pair of ground wheel assemblies 18, 19 on rear tower 13 while Figures 1 and 3 illustrate only one of the front ground wheel assemblies 16.

Each ground wheel assembly is itself formed from a leading wheel and trailing wheel which are in longitudinal alignment. Figures 6 and 7 which are plan views of the staddle carrier, show the wheel assemblies more clearly. Front wheel assemblies 16, 17 each have a front leading wheel 20, 22 and a rear trailing wheel 21, 23. Leading wheels 20, 22 are driven wheels and are also steering wheels while trailing wheels 21, 23 are swivel wheels. With the rear wheel assemblies 18, 19, each assembly has a leading swivel wheel 25, 26 and a trailing fixed wheel 27, 28.

Each of the wheels is mounted to a shaft which is journalled into a wheel support plate 29 (see Figure 1) . Each of the wheel assemblies has a chassis or base plate 30 (see Figure 3) on which is supported the vertical members 14, 15.

A sleeve member 31, 32 is slidably attached to each vertical member 14, 15 and can slide between a lower retracted position as illustrated in Figure 2 and an upper extended position as illustrated in Figure 4.

A lower lifting bracket 33, 34 is attached to or forms part of the sleeve members 31, 32 and this is more clearly illustrated with reference to Figures 8 and 10.

Sleeve member 32 slides over vertical member 15, and rollers 35 are located within sleeve 32 to provide a smooth shifting movement of sleeve member 32 along its associated vertical member 15. Sleeve member 32 is moved between its extended position illustrated in Figure 4 and its retracted position illustrated in Figure 2 by a lifting means in the form a hydraulic ram 36. Ram 36 has a ram cylinder attached to lifting bracket 34 through a lift eye 37 (see Figure 8 and 10) , and has a ram piston 38 attached to base plate 30.

To attach each tower to shipping container 11, each tower is provided with two attachment means in the

form of locking pins 40 and which are illustrated in Figures 2, 4, 8 - 11. Locking pins 40 can be of a conventional type and are inserted into a corner casting on a shipping container. Of course, if the shipping container does not have a corner casting, the type of locking pin or attachment means may vary to suit. Locking pin 40 is attached to a steel angled support member 41. Support member 41 is mounted for rotation about a vertical axis to a bracket 42. In this manner, support member 41 and thus pin 40 can twist or rotate between an extended position shown in Figures 8 and 10 and a retracted position (not shown) where support member 41 is turned 90° either way. The ability to move pins 40 away from shipping container 11 maximises the distance between the vertical members 14, 15 thereby facilitating loading and unloading of containers.

Bracket 42 is itself mounted for movement between an extended position as shown in Figure 11 and a retracted position as shown in Figure 9. Rams 43 are used to extend or retract bracket 41. Extension of retraction of bracket 41 causes further extension or retraction of pin 40. Thus, when bracket 41 is retracted and support member 41 is rotated to a free position, there is sufficient room between container 11 and the tower to facilitate unloading and loading of the container. By having bracket 42 able to extend and retract, the arrangement provides a side shift mechanism to container 11. The side shift mechanism helps the operator to position the straddle carrier over the container and to fasten the twist locks. If the straddle is not in line with the container, an operator can side shift the twist lock arm towards the container and thus position the twist lock into the corner casting. The second reason for having the side shift mechanism is to enable the operator to correct the position of the container and to bring it ^" in line with the vehicle that awaits the loading. Thus, the side shift mechanism makes loading containers onto vehicles much faster and

efficient and avoids the vehicle driver having to correct his vehicle into the right position. That is, the side shift mechanism will do the corrections instead. The stroke of bracket 42 is suitably about 200mm. To avoid extreme forces on the twist lock arm should the container be out of line widthwise, the face plate that rests against the corner casting of the container, and the twist lock pin that locks the twist lock into the corner casting, both have a machined radius incorporated. This is illustrated in Figures 12 and 14. If the container is not level, the radius prevents unacceptable forces from being applied to the twist lock arm, the twist lock and the corner casting.

Figures 20 and 21 illustrate an alternative construction where a pendulum arm 70 is slidably attached to a vertical member 71 through nylon gliders 72. Pendulum arm 70 can move to and away from a container by two rams 73, 74. The free end of arm 70 is fitted with a twistlock 75. This alternative construction reduces forces on the apparatus.

In use, the straddle carrier initially has the two towers connected together as illustrated in Figure 5. The straddle carrier is self-propelled and has an engine 24 to power the drive wheels (which can be hydraulically driven and steered) , and which also provides hydraulic fluid to the various rams. The forward tower has a platform 45 provided with an operator's seat 46, and steering and other controls 47. When in the coupled arrangement as illustrated in Figure 5, the straddle carrier can be driven around. The coupling 48 can be of any convenient type but should be one which can be fairly easily decoupled.

To lift a container, the coupled straddle carrier is driven over the container which is initially on the ground. The rear tower 13 is positioned at the rear end of the container ^" and when in position, the pins are connected with the container corner casting. Each pin can be moved vertically by raising or lowering the

respective sleeve members 31, 32 and can be moved sidewardly by the side shift mechanism as illustrated in Figures 8 - 11. When the rear tower is locked in position, it is decoupled from the front tower and the front tower is driven forwardly to the front of the container where again it is locked to each corner of the container. The container can then be lifted approximately 300 or 400mm above the ground level as illustrated in Figure 1 and can then be driven to a desired area at about 5km p/hour. One of the advantages of the staddle carrier is that the container is only slightly lifted above the ground which provides the entire arrangement with a low centre of gravity. Also, the towers are coupled to the container and the container itself can be seen as forming part of the horizontal chassis .

When loading a shipping container onto a truck, the straddle carrier is driven into position with the container in the lower position as illustrated in Figure 1. The staddle carrier is then halted and container ll is lifted to an upper position as illustrated in Figure 3, the position being high enough to allow a truck to pass underneath the container. The container can then be lowered onto the back of a truck and the side shift mechanism as illustrated in Figures 8 - 11 can be used to ensure that the corner castings align with the locking pins on the back of the truck.

To position the straddle over a container, it is important to have as much space as possible between the container and the straddle. To make it easy for the operator to manoeuvre, the space between the inside of the staddle and the container should be about 600mm. The straddle carrier according to the invention makes this possible by having the locking pin 40 collapsible allowing for maximum clearance.

Figure 15 - 19 illustrate further embodiments of the straddle carrier to make if extremely compact and thus able to be driven into a container such that the

straddle carrier can be shipped with the container.

To provide a low height profile to the straddle carrier, the vertical members 14, 15 may themselves be telescopic. In Figure 15, the straddle carrier is collapsed such that the distance between horizontal member 15A and the ground is about 1.9m, while in the fully extended position shown in Figure 17, the distance between horizontal member 15A and the ground is 4.6m. In Figure 15, vertical member 15 is provided in two telescopic sections being outer telescopic section 15B and inner telescopic section 15C. The inner telescopic section 15C is attached to a lifting bracket 50. Vertical member 15 can be expanded and contracted through ram 51 and Figure 15 and 16 show how expansion of ram 51 causes vertical member 15 to extend upwardly. When in the extended position shown in Figure 16, ram 36 is operated which in turn lifts lifting bracket 50. To stabilise the system, a guide post 52 is attached to base plate 30 and extends to a position lower than the height of ram 36. A sleeve 53 is positioned about guide post 52 and lifting bracket 50 is guided along sleeve 53 through rollers 54.

It can be seen that upon operation of ram 36, lifting bracket 50 is raised upwardly and rolls along the outside of sleeve 53. The top of sleeve 53 has an abutment plate 56, and when rollers 54 strike abutment plate 56, further expansion of ram 36 will now cause sleeve 53 to move upwardly along guide post 52.

The overall effect is that the height of horizontal member 15A can be from 4.6m in the fully extended position shown in Figure 17 down to 1.9m in the fully retracted position shown in Figure 15.

Figures 18 and 19 show how the upper horizontal member 15A is itself telescopic and can move between a retracted position shown in Figure 18 where vertical members 14, 15 are about 2m apart to a fully extended position as illustrated in Figure 19 where vertical members 14, 15 are 4.5m apart. A three-stage ram 60 is

used to move horizontal member. The ram 60 is activated when the towers are slowly being moved on their wheels. The wheels will allow expansion and retraction without undue stresses. The collapsible straddle carrier as described above is of benefit to organisations wishing to transport the straddle carrier without dismantling it. The collapsed sides of the straddle carrier is such that it fits in a 8ft. high, 20ft. long ISO container. The collapsible straddle can be loaded within a container and can unload itself out of the container without the help of lifting equipment. When unloaded, the straddle carrier can then attach itself to the outside of the container and lift it to transport it and also to load it onto the back of a truck.

Some of the advantages of the straddle carrier is that the system is lighter than conventional straddle carriers, the straddle carrier has a very low working height of approximately 3.5m allowing it to work under awnings or inside buildings. The staddle carrier can handle any length of containers without modification.

It should be appreciated that various other changes and modifications may be made to the embodiment described without departing from the spirit or scope of the invention.