Field of the Invention

This invention relates to a straddle carrier for lifting and transporting shipping containers.

Background of the Invention

Straddle carriers are vehicles used in, for example, port terminals and intermodal yards for stacking and moving intermodal containers, also known as shipping containers or ISO containers.

Conventional straddle carriers typically have a strong and heavy horizontal chassis in which a shipping container is engaged using a spreader attachment suspended from the chassis by wire ropes or other flexible members. Conventional straddle carriers therefore comprise two main components corresponding to the main chassis and the spreader attachment. The wire ropes or flexible members lift and lower the spreader attachment to which a container may be engaged.

Conventional straddle carriers suffer from a number of disadvantages. Firstly, straddle carriers are often tall machines so that the height to which the spreader attachment may be raised is sufficient to be able to lift and stack a container on a number of already stacked containers. Therefore, the height of the straddle carrier is such that it cannot be easily manoeuvred in and out of storage sheds or awnings. Furthermore, when lifting and moving a shipping container at a height above the ground, the centre of gravity of the straddle carrier may be such that there is an increased risk that the straddle carrier may tip over. To mitigate this danger, straddle carriers are formed of a very strong and heavy chassis. However, a straddle carrier having a heavy chassis requires significant power to move the vehicle and to raise/lower containers.

Therefore the present invention has been developed with a view to mitigating the above-mentioned problems.

Summary of the Invention Accordingly, in one aspect, the invention provides a straddle carrier for lifting and transporting a shipping container, the straddle carrier comprising a spreader which is engageable with the shipping container, the spreader having a central elongated frame and an engagement mechanism at either end of the frame for engaging the container, the frame being mounted on a set of legs, the legs being extendable to raise and lower the frame. Optionally the engagement mechanism comprises a twistlock. Optionally the engagement mechanism is engageable with the top of the shipping container. Optionally the engagement mechanism is engageable with a corner casting located on the shipping container. Optionally the elongated frame comprises a substantially rectangular configuration. Optionally the elongated frame comprises a pair of longitudinal members. Optionally the longitudinal members run from one end of the frame to the other end of the frame. Optionally the elongated frame further comprises at least one transverse member perpendicular to the longitudinal members. Optionally the transverse member is connected to two extendable legs located at the opposing elongate sides of the frame. Optionally the frame is mounted to the transverse member. Optionally the frame is mounted directly to the extendable legs. Optionally the frame comprises extendable legs mounted at or towards the corners of the frame. Optionally the legs are mounted to the elongate sides of the frame with at least one leg proximate to each corner. Optionally the frame comprises at least four legs. Optionally, in use, the legs maintain the frame in a substantially horizontal position relative to the ground. To this end, the mechanism extending the legs preferably includes means to synchronise the extension (or contraction) of the legs.

Optionally each extendable leg comprises at least one ground wheel. Optionally, each leg further comprises a sleeve member, wherein the sleeve member is slidable along the leg. Optionally, each extendable leg further comprises a lifting means to slide the sleeve member relative to the leg.

Further optionally, the lifting means comprises at least one ram. Optionally, the ram is a hydraulic or pneumatic ram. Optionally at least two of said legs are steerable, each steerable leg having one or more steering cylinders operable to alter the direction of the respective ground wheel. Optionally the frame comprises at least one arm extendable from the frame. Optionally, in a retracted position, the arm is located within a sleeve portion of the frame. Optionally, the arm is slidable within the sleeve portion. Optionally, the frame comprises at least one pushing means to slide the arm relative to the sleeve portion. Further optionally, the pushing means comprises at least one ram. Optionally, the ram is a hydraulic or pneumatic ram. Optionally the frame comprises at least two extendable arms. Optionally the extendable arms are located at opposing ends of the frame.

Optionally the straddle carrier further comprises a power unit operable to provide power to the straddle carrier. Optionally the power unit is located on the frame of the spreader. Preferably the power unit comprises an engine powering a hydraulic circuit, with the hydraulic circuit driving the movement of the components of the carrier and driving hydraulic motors on the driven ground wheel(s). Alternatively, the power unit could be a generator supplying electrical power, a compressor supplying pneumatic power, an engine providing mechanical power, or any combination of these and other known power mechanisms. Optionally the straddle carrier further comprises a control station operable to control the straddle carrier. Optionally the control station is provided in an operator's cabin located on the straddle carrier. Further optionally the operator's cabin is located on the frame of the spreader. The straddle carrier may be suitably configured to engage with any desired container size, and in particular with conventional standard containers such as 20, 30, 40 or 45 foot containers. The container may also be composed of a number of individual modules rigidly affixed to one another, such as a pair of 20 foot containers which are connected together end-to-end to provide a single 40 foot long unit.

Brief Description of the Drawings

The embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG 1 is a perspective view of a straddle carrier according to the embodiment of the invention, in which the relative movement of the extendable portions of the frame and the extendable legs is indicted by double-headed arrows. FIG 2 is a front view of a straddle carrier according to the embodiment of the invention.

FIG 3 is a side view of a straddle carrier according to the embodiment of the invention engaging a 40ft shipping container, in which the relative movement of the extendable portions of the frame is indicted by double-headed arrows.

FIG 4 is a side view of a straddle carrier according to the embodiment of the invention engaging a 20ft shipping container.

FIG 5 is a side view of a straddle carrier according to the embodiment of the invention which is positioned about a transport vehicle to place/lift a shipping container on/off the vehicle.

FIG 6 is a side view of a straddle carrier according to the embodiment of the invention which is positioned to place/lift a shipping container on/off the vehicle.

Description of Preferred Embodiments

With reference to Figures 1-2, a straddle carrier (10) of the invention may comprise a spreader (12) and four extendable legs (18). The spreader (12) may comprise an elongated frame (14) substantially rectangular in form. The frame (14) may further comprise at least one engagement mechanism (16) for engaging a container (C). The engagement mechanism (16) may be located on the frame (14), advantageously at the ends of the frame (14). The frame (14) may also comprise at least one extendable arm (20) at the end of the frame (14). In this configuration, the engagement mechanism (16) may be located on the arm (20). The engagement mechanism (16) may be any suitable coupling means that allows the frame (14) of the spreader (12) to engage a shipping container (C). The engagement mechanism may further comprise at least one guide to aid the alignment of the spreader (12) and engagement mechanism (16) with the container (C) and the corresponding engagement means on the container. Advantageously, the engagement mechanism (16) may comprise a twistlock. The twistlock may form a rotating connector with a corner casting of a container (C). As shown in Figures 3, 5 and 6, the engaging means (16) may engage the top of the container (C). When the engaging means (16) is a twistlock, the twistlock may engage a corning casting located on the top side of a container (C).

The elongated frame (14) of the spreader (12) may comprise, in plan, a substantially rectangular configuration. However, it will be appreciated by the skilled person that the frame (14) may have any suitable shape, for example, the frame (14) may be substantially square-shaped. The frame (14) may comprise a pair of longitudinal members (22) corresponding to the longitudinal or elongate sides of the rectangularly configured frame. Therefore, the longitudinal members (22) may run from one end of the frame to the other end of the frame. The frame (14) may further comprise at least one transverse member (24) arranged perpendicular to the longitudinal members (22). The transverse member (24) may be located proximate to the end of the frame. The transverse member (24) may be connected to a pair of extendable legs (18) located at the opposing elongate sides of the frame. The transverse member (24) and the two extendable legs (18) may form a U-shaped, or alternatively, a H-shaped configuration as seen in Figure 2. The frame (14) may be mounted to the transverse member (24). Alternatively, or additionally, the frame (14) may be mounted directly to the extendable legs (18). In particular the longitudinal members (22) of the frame (14) may be mounted to the transverse member (24) and/or to the extendable legs (18).

The extendable legs (18) may be mounted, that is, fixed, to the frame (14) at or towards the corners of the frame (14). Advantageously, the legs (18) may be mounted to the elongate sides of the frame (14) with at least one leg (18) proximate to each corner of the frame. The frame (14) may therefore comprise at least four legs (18). The legs (18) may be arranged substantially perpendicularly relative to the plane of the frame (14). Thus, in use, the legs (14) can maintain the frame (14) in a substantially horizontal position relative to the ground. In one embodiment, the frame (14) may comprise two transverse members (24), each transverse member (24) connected to a pair extendable legs (18) located at the opposing elongate sides of the frame (14). Each transverse member (24) and associated pair of legs (18) may be located proximate to a respective end of the frame (14) and the extending legs being operable to maintain the frame (14) in a substantially horizontal position relative to the ground as described further below.

Each leg (18) is extendable, preferably telescopic, thus allowing the length of the leg (18) to be adjusted. The length of the leg (18) may be adjusted by any suitable mechanism. In one embodiment, each leg may comprise a sleeve member (26). The sleeve member (26) may be arranged coaxially with the leg (18) and may be slidable along the leg (18). In a non-extended configuration, part or all of the leg (18) may be contained within the bore of the sleeve member (26). Each leg (18) may further comprise a lifting means (28) which is operable to exert force on the sleeve member (26) to slide the sleeve member (26) relative to the leg (18). In use, the lifting means (28) may be operated to cause the sleeve member (26) to slide along the leg (18) thus extending the leg (18). The lifting means (28) may be connected to a power unit (40) located on the straddle carrier (10). Advantageously, the lifting means (28) may comprise at least one ram. The ram may be a hydraulic or pneumatic ram. It will be appreciated that the frame (14) and/or the transverse member (24) may be mounted to the sleeve member (26) of the leg (18). In use, when the legs (18) are extended, the spreader (12) is raised, as is a container (C) if it is engaged by the spreader (12). The legs (18) may be extended, and therefore the spreader (12) may be raised, to a sufficient height that allows the straddle carrier (10) to place a container (C) on a transport vehicle and/or on a stack of one or more containers (C).

The extendable legs (18) may further comprise at least one ground wheel (30) located at the end of each leg (18). The ground wheels (30) may therefore maintain the legs (18) spaced apart from the ground and allow the straddle carrier (10) to move along the ground to transport a container (C) from one location to another. Each leg (18) may comprise one or more steering cylinders (32) which may be operated to alter the direction of the ground wheel (30) and therefore the direction in which the straddle carrier (10) moves. The steering cylinder (32) controls the rotation of a ground wheel (30) relative to the substantially vertical axis of the wheel (30). The steering cylinders (32) may be connected to the power unit (40) located on the straddle carrier and controlled from a control station as described further below.

The frame (14) may further comprise at least one arm (20) extendable from the frame.

Advantageously, the frame comprises at least two extendable arms (20). The extendable arms (20) may be located at opposing ends of the frame (14). In use, one arm (20) may be extended from one end of the frame (14) and a second arm (20) may be extended from the opposing end of the frame (14). As illustrated in Figure 1 , each arm (20) may be substantially U-shaped having two substantially parallel members (36) joined at one end by a cross member (38) arranged substantially perpendicularly relative to the parallel members (36). In a retracted position, the arm (20) may be located within a sleeve portion (34) of the frame (14). In the illustrated embodiment in Figure 1 , the parallel members (36) of the arm (20) may be located within sleeve portions (34) of the frame (14). The sleeve portion (34) may be formed by at least part of a longitudinal member (22) of the frame (14) having a bore for receiving the arm (20). Each sleeve portion (34) may be arranged coaxially with the arm (20), or parallel member (36) of the arm (20). The arm (20) may be slidable within the sleeve portion (34). The frame (14) may further comprise at least one pushing means (not shown) to exert force on the arm (20) to slide the arm relative to the sleeve portion (34). In use, the pushing means may be operated to cause the arm (20), or parallel member (36) of the arm (20), to slide within the sleeve portion (34) thus extending the arm (18) from the frame (14). The pushing means may be connected to the power unit (40) located on the straddle carrier (10). Advantageously, the pushing means comprises at least one ram. The ram may be a hydraulic or pneumatic ram. The arm (20) may be extended to various lengths. Advantageously the arms (20) may be extended to a length which allows the engagement mechanisms (16) located at the ends of the arms (20) to be aligned with and engage the corresponding engagement means on the shipping container (C). Shipping containers (C) are typically 20ft, 40ft, or 50ft in length (i.e. 6.1 m, 12.2m, or 15.2m, respectively).

The power unit (40) is operable to provide power to the straddle carrier (10). The power unit (40) may be located on the frame (14). The power unit (40) may be configured to provide pneumatic or hydraulic power to the lifting means (28), the steering cylinders (32) and/or the pushing means via a pneumatic or hydraulic circuit (not shown). The straddle carrier (10) may further comprise a pneumatic or hydraulic circuit connected to one or more drive motors for driving the ground wheels (30). The motor(s) and drive circuitry are not shown, but the manner of its implementation will be readily known to the skilled person.

The straddle carrier (10) may further comprise a control station operable to control the straddle carrier (10). Optionally the control station is contained in an operator's cabin (42) located on the straddle carrier (10), for example, on the frame (14) of the spreader (12). The straddle carrier (10) may be operated by an operator seated in the cabin (42). The power unit (40) may be operated from the control station in the cabin (42) and therefore the operator may control the actuation of the lifting means (28), the steering cylinders (32) and/or the pushing means for lifting and transporting shipping containers (C). In a further modification of the straddle carrier (10), the operator's cabin (42) may be removed and the straddle carrier (10) controlled remotely.

The main advantages of the straddle carrier (10) described above are:

1. The straddle carrier (10) of the invention is lighter than conventional straddle carriers since the spreader makes up part of the main chassis, therefore fewer components are required.

2. The straddle carrier (10) has lower fuel consumption than conventional straddle carriers due to the overall construction being lighter and, as a consequence, a smaller power unit can be used.

3. The straddle carrier (10) requires less maintenance than conventional straddle carriers since there are less moving components, e.g. wire ropes, pulleys, etc.

4. The straddle carrier (10) has a lower centre of gravity than conventional straddle carriers. When travelling unladen, the spreader which is the heaviest component can be lowered.

5. The straddle carrier (10) has a lower travelling height than conventional straddle carriers and can lift/place containers under awnings.

6. The straddle carrier (10) may comprise only four wheels since the carrier is lighter.

7. The straddle carrier (10) is cheaper to manufacture than conventional straddle carriers due to less components being required. The invention is not limited to the embodiment described herein but can be amended or modified without departing from the scope of the present invention.