GB2177356A - Mobile crane - Google Patents

Abstract

A mobile crane is in the form of a tractor having a body which is pivotally mounted at its front end on an axle 2. A pedestal 11 is mounted on one side of the tractor engine 1 and carries a crane 12 which can be rotated continuously through 360 DEG . Hydraulic rams 19 are mounted above the front axle 2 and pistons 21 of the rams bear on stop plates 22 on the axle housing to lock the tractor against pivotal movement on the axle 2 when the crane 12 is in use. The rear wheel 3a on the side of the crane 12 is offset to enhance the stability of the tractor when the crane is in use. Hydraulic operation of the pistons 21 enables them to be controlled remotely from inside the tractor cab 6 whilst the position of the crane to one side enables the driver to see past the crane. <IMAGE>

Description

SPECIFICATION Mobile crane The present invention relates to mobile cranes, in particular the invention relates to tractor mounted cranes.

The front axle of a tractor attached to the tractor engine is mounted to pivot about an axis extending longitudinally of the tractor.

A first aspect of the present invention provides a tractor mounted crane in which the crane is mounted on a pedestal attached to a chassis or body of the tractor and an axle of the tractor is mounted to pivot about an axis longitudinal of the body, wherein hydraulically operated rams are provided on either side of the longitudinal axis to limit the pivoting movement of the axle.

The rams are mounted on the axle or the tractor body and are each arranged to abut a stop provided on the tractor body or axle respectively. Accordingly the axle can be locked in position relative to the tractor body during a lifting operation and be released, by withdrawal of the rams, for normal travel of the tractor. By hydraulically operating the rams the rams can be activated from within a cab of the tractor and also it is possible to allow automatically for lean of the tractor body relative to the axle when on sloping ground.

Another aspect of the invention provides a tractor mounted crane comprising a crane mounted on a pedestal attached to the tractor body, wherein the crane is positioned to one side of a central vertical plane extending longitudinally of the tractor. Preferably the crane can be rotated through a continuous 360" arc.

By positioning the crane to one side it is possible to allow for an approved safety or quiet cab to be mounted on the tractor, the tractor and crane being driven and operated from within the cab. preferably the pedestal is to one side of the engine.

Very preferably a wheel of the tractor on the side of the crane, preferably at least a rear wheel is mounted further from the central plane of the tractor than the corresponding opposite wheels. In a preferred embodiment both a front and a rear wheel are offset. By outwardly offsetting the wheel(s) on the side of the crane the stability is enhanced during lifting operations.

In a preferred embodiment a fuel tank of the tractor is mounted under a footplate of the tractor.

The invention will be further described with reference to the accompanying drawings, in which: Fig. 1 is a perspective view from one side of a tractor mounted crane in accordance with the invention; Fig. 2 is a detailed view from the other side of the tractor of Fig. 1; and Fig. 3 is a plan view of the embodiment of Fig. 1.

The drawings illustrate in outline a tractor mounted crane according to the invention.

A tractor body comprises an engine 1 and transmission 4, the tractor body being pivotally mounted at its front end on a front axle 2 and attached at its rear end to the transmission 4 which is mounted on and drives a rear axle driving rear wheels 3. Front axle 2 carries front wheels 5,5a which are steerable. Front axle 2 pivots about an axis A-A which is longitudinal of the tractor, as is known.

A safety cab 6 is mounted over the transmission 4 to the rear of the engine 1 which is covered by a bonnet 7.

Chassis members are attached to the engine 1 and transmission 4 and comprises a member 8 extending horizontally and longitudinally along the left and right side of the engine, when viewed from the cab 6. Member 8 projects ahead of the bonnet 7 and carries a box 9 in which weights may be carried to adjust the balance of the tractor. A member 10 (Fig.

2) extends parallel to the member 8 from the front of the engine 1, on the right side. A guard 30 protects the front of the bonnet 7 which may carry headlamps etc. (not shown).

To the right side of the engine a pedestal 11 is mounted and carries a hydraulically operated crane 12 shown schematically in Fig. 1.

Pedestal 11 is mounted on q vertical box section member 13 which is in turn mounted on vertical triangular plates 14, plates 14 being welded to the box member 13 and a back plate 15. Back plate 15 and box member 13 are attached to the tractor, for example by bolts. A triangular plate 18 provides additional support for pedestal 11 on box member 13.

A tie bar 16 connects the box member 13 to the rear axle (not shown) of the tractor, and a member 17 extends diagonally from the box member 13 beside the engine 1 to connect with member 10.

Diagonal member 17, at the junction with member 10, and horizontal member 8 each carry a hydraulic ram 19 comprising a cylinder 20 and piston 21. The rams 19 are positioned above the axle 2 and stop plates 22 are welded to the housing of axle 2 below the pistons 21. Fig. 1 is drawn with the pistons 21 urged against the axle 2 to lock the axle 2 against pivotal movement relative to the tractor body 1. Fig. 2 is drawn with the pistons 21 withdrawn.

As seen in Fig. 3, the rear wheel 3a on the right side of the tractor is further from the longitudinal axis A-A than the left side wheel 3b to provide for enhanced stability when the crane 12 is in use.

When the crane 12 is to be used the hydraulic rams 19 are actuated, for example using a hydraulic power take off from the tractor, to urge the pistons 21 against the stop plate 22 on axle 2, thus locking the axle 2 relative to the tractor main body.

The hydraulic rams are operated from a lever within the cab and equal pressure is exerted through either ram regardless of the angle of the axle 2 relative to the tractor main body. When the operating lever is set into a neutral position a hydraulic lock value 25 on top of each ram locks each ram in the set position until such time as the operating lever in the cab is actuated and the locks released.

The crane 12 can then be used in the normal way. When the crane 12 is to be used the hydraulic rams for lifting and motors for slewing and winching are actuated by oil flow using a power take off from the tractor, the controls for the tractor and crane being housed within the safety cab 6. The driver is positioned over the central longitudinal axis A A of the tractor and so has a forward view past the crane 12.

The right side rear wheel 3a and front wheel 5a is offset further from axis A-A than wheel 3b or wheel 5 to provide enhanced stability.

The fuel tank of a tractor is usually mounted beneath the bonnet. In the present embodiment, as seen in Fig. 1, the fuel tank 23 is set beneath a footplate 24, thus providing for greater ease of access to engine components and the tractor battery which may be housed under the bonnet.

The hydraulically operated crane 12 incorporates an inbuilt hydraulically driven winch 12a within the boom section. The winch is provided with a steel cable running the length of the boom, over pulleys fitted with a lifting hook 12b. The winch and its wire in conjunction with the vertical movement of the boom create a versatile lifting/lowering capability of the crane.

Two visual indicators in the form of hydraulic gauges are mounted within the cab in view of the operator. One indicates lifting capacity of hydraulic rams and the other indicates lifting capacity on the wire of the inbuilt hydraulic winch. Both gauges are marked to indicate the maximum safe working load levels on the crane boom and winch wire.

Claims (11)

1. A mobile crane in which the crane is mounted on a pedestal attached to a chassis or body of a tractor and an axle of the tractor is mounted to pivot about a longitudinal axis of the body, wherein hydraulically operated rams are provided on either side of the longitudinal axis to limit pivoting movement of the axle.

2. A mobile crane as claimed in claim 1, wherein the rams are mounted on the tractor chassis or body and are extendable to bear on the axle.

3. A mobile crane as claimed in claim 2, wherein the rams bear on stop plates on a housing of the axle.

4. A mobile crane as claimed in claim 1, 2 or 3, wherein a hydraulic lock valve is provided to lock the rams in position, limiting the movement of the axle.

5. A mobile crane as claimed in any one of claims 1 to 4, wherein the crane is positioned to one side of a central vertical plane of the tractor.

6. A mobile crane as claimed in claim 5, wherein a wheel of the tractor on the side of the crane is offset from the vertical plane relative to the corresponding wheel on the other side of the plane.

7. A mobile crane as claimed in claim 6, wherein the rear wheel is offset.

8. A mobile crane as claimed in any one of claims 1 to 7, wherein a fuel tank is mounted under a footplate of the tractor.

9. A mobile crane as claimed in any one of claims 1 to 8, wherein the crane is continuously rotatable through 360 degrees.

10. A tractor mounted crane comprising a crane mounted on a pedestal attached to the tractor body, wherein the crane is positioned to the side of a central vertical plane extending longitudinally of the tractor.

11. A tractor mounted crane substantially as hereinbefore described with reference to the accompanying drawings.