GB2345048A

GB2345048A - Lift truck

Info

Publication number: GB2345048A
Application number: GB9930386A
Authority: GB
Inventors: Franz Hettegger
Original assignee: Palfinger Crayler Staplertechnik GmbH
Current assignee: Palfinger Crayler Staplertechnik GmbH
Priority date: 1998-12-23
Filing date: 1999-12-22
Publication date: 2000-06-28
Also published as: GB9930386D0; DE29922311U1

Abstract

A lift truck for lifting a load, including at least one counterweight (8) movably disposed within the confines of the truck for counterbalancing a load lifted by the lift truck. The counterweight may be movable backwards and forwards between the front and rear axles. In addition, the lift truck may include a mast (4), tiltable along the longitudinal axis of the lift truck, with the counterweight operatively coupled to the mast so as to be moved in conjunction therewith, and in a direction opposite to the direction of movement of the mast. The counterweight may move along a guide member (11) and be coupled to the mast by means of a chain or cable connecting element (13). The lift truck may feature two separate counterweight mechanisms and may be configured to be transportable on a goods vehicle.

Description

LIFT TRUCK The present invention relates to a lift truck, in particular a stacker such as a fork-lift truck.

When stacking heavy loads, the weight of the lift truck is generally not sufficient to counterbalance such loads. For this reason, most front-loading lift trucks are provided with a counterweight at the rear thereof to counterbalance a load lifted at the front thereof.

However, the provision of such counterweights at the rear of lift trucks leads to problems, notably in transportable lift trucks. Transportable lift trucks are distinguished from other lift trucks in being adapted to be carried on the back of heavy goods vehicles. Usually, a transportable lift truck is mounted to a vehicle by locating the lifting forks in guides located in the vehicle at a height corresponding to the loading surface and then causing the body of the lift truck to be raised from the ground by the action of lowering the lifting forks. With this arrangement, the principal factor limiting the size of the counterweight is the dimension and stability of the rear end of the vehicle. Ideally, the transport of a lift truck on a vehicle should be possible without requiring significant modification, such as by way of reinforcement, of the vehicle. The transport of larger lift trucks provided with heavier counterweights has, for this reason, only been possible to a very limited extent, as the centre of gravity of such lift trucks, in being located a long way beyond the back end of any vehicle to which it is mounted, leads to undesirable over-stressing of the rear end of the vehicle.

AT-B-241848 discloses a lift truck which includes a movable counterweight. By providing for movement of the counterweight, the counterweight can be moved forwards to a position closer the lifting forks for transporting the lift truck, in which position the centre of gravity of the lift truck is located closer to the vehicle to which it is mounted, resulting in reduced stressing of the rear end of the vehicle. Further, by moving the counterweight, different loading conditions of the lift truck can be accomodated.

A significant drawback of this known lift truck is, however, that moving the counterweight rearwards causes the counterweight to be moved a long distance beyond the rear end of the lift truck. The consequence of this arrangement is that the operator of the lift truck must be vigilant of the constantly changing external dimension of the lift truck. As will be appreciated, where the dimension of the lift truck is constantly changing, the danger of accidental collisions is increased significantly. Moreover, with the counterweight being extendable beyond the rear end of the lift truck, it is possible that the operator could extend the counterweight into a stationary object or worse still trap a person between the counterweight and a stationary object.

It is thus an aim of the present invention to provide a lift truck with improved operating safety.

Accordingly, the present invention provides a lift truck for lifting a load, including at least one counterwieight movably disposed within the confines of the lift truck for counterbalancing a load lifted by the lift truck.

By maintaining the counterweight entirely within the confines or footprint of the lift truck, the external dimension of the lift truck remains unchanged with the counterweight in any position.

Preferably, the at least one counterweight is movably disposed within the interior of the lift truck.

Preferably, the at least one counterweight is configured so as to be movable backwards and forwards in the direction of the central longitudinal axis of the lift truck.

Preferably, the lift truck includes front and rear axles, wherein the at least one counterweight is movable backwards and forwards in the region between the front and rear axles. By providing for the counterweight to be movable in the region between the front and rear axles of the lift truck, the counterweight can be moved substantially further forward than in the lift trucks of the prior art, whereby the lift truck can be better transported on vehicles.

Preferably, the lift truck includes a mast and at least one lifting element movably disposed thereto, wherein the mast is movable backwards and forwards in the direction of the central longitudinal axis of the lift truck and the at least one counterweight is operatively coupled to the mast such as in use to be moved in conjunction therewith. In one embodiment the at least one lifting element comprises lifting forks.

Preferably, the at least one counterweight is operatively coupled to the mast such as to be moved a direction opposite to the direction of movement of the mast.

In one embodiment the at least one counterweight is coupled to the mast by means of a connecting element guided by rollers.

Preferably, the connecting element is a chain or cable.

With this configuration, the counterweight can be located in a forward position adjacent the front axle when the mast is in the driving position and a rearward position when the mast is in the loading position, that is, extended forwards to take on or set down a load. This forward position of the counterweight would be the position of the counterweight in the transport of the lift truck on a vehicle. Further, where the lift truck includes a mast which is movable backwards and forwards, the counterweight can automatically be positioned to maintain the centre of gravity of the lift truck at an optimal position during use.

Preferably, the lift truck includes at least one guide member for guiding the movement of the at least one counterweight.

Preferably, the at least one counterweight is composed of steel. Preferably, the lift truck includes two separate counterweights configured so as to be movable in symmetrical relation.

In a preferred embodiment the lift truck is of the kind transportable on a heavy goods vehicle.

A preferred embodiment of the present invention will now be described hereinbelow by way of example only with reference to the accompanying drawings, in which: Figure 1 illustrates a partially cut away side view of a lift truck in accordance with a preferred embodiment of the present invention; and Figure 2 illustrates a partially cut away plan view of the lift truck of Figure 1.

The lift truck comprises a base framework 1 having disposed thereto first and second front wheels 2,2 and a rear wheel 3 by which the lift truck is driveable, and a mast 4 supporting conventional, vertically-movable lifting forks 5.

The mast 4 is coupled to a support member 6 about axles 7 so as to be movable in two principal directions. The support member 6 is movably disposed to the framework 1 by first and second hydraulic drive cylinders 8,8 which are arranged symmetrically in the framework 1 and when operated cause the support member 6 and hence mast 4 to be moved backwards and forwards in the direction of the central longitudinal axis of the lift truck. The mast 4 is further coupled to the support member 6 by first and second hydraulic pivot cylinders 9,9 which when operated cause the mast 4 to be pivoted about the axles 7.

The lift truck further comprises first and second counterweights 10,10 which are movable backwards and forwards in the direction of the central longitudinal axis of the lift truck. In this embodiment the first and second counterweights 10, 10 are located in respective ones of first and second housings 11,11 which are open at the top and include guide rails 12,12 for ensuring precise guidance of the counterweights 10,10. The first and second counterweights 10,10 are attached to respective ones of first and second pulling elements 13,13, in this embodiment cables or chains guided by means of rollers 14,14 mounted to the framework 1, to which respective ones of first and second transmission elements 15,15 on the support member 6 are also attached. With this configuration, the counterweights 10,10 are in use together moved in a direction opposite to the direction of movement of the mast 4. That is, when the mast 4 is moved forwards the counterweights 10,10 are moved backwards and vice versa. It will be understood that, as the positioning of the counterweights 10,10 is achieved by hydraulic drive cylinders 8,8, precise positioning of the counterweights 10,10 is possible.

Finally, it will be understood that the present invention has been described in its preferred embodiment and can be modified in many different ways without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS 1. A lift truck for lifting a load, including at least one counterwieight movably disposed within the confines of the lift truck for counterbalancing a load lifted by the lift truck.
2. A lift truck according to claim 1, wherein the at least one counterweight is movably disposed within the interior of the lift truck.
3. A lift truck according to claim 1 or 2, wherein the at least one counterweight is configured so as to be movable backwards and forwards in the direction of the central longitudinal axis of the lift truck.
4. A lift truck according to any of claims 1 to 3, including front and rear axles, wherein the at least one counterweight is movable backwards and forwards in the region between the front and rear axles.
5. A lift truck according to any of claims 1 to 4, including a mast and at least one lifting element movably disposed thereto, wherein the mast is movable backwards and forwards in the direction of the central longitudinal axis of the lift truck and the at least one counterweight is operatively coupled to the mast such as in use to be moved in conjunction therewith.
6. A lift truck according to claim 5, wherein the at least one lifting element comprises lifting forks.
7. A lift truck according to claim 5 or 6, wherein the at least one counterweight is operatively coupled to the mast such as to be moved a direction opposite to the direction of movement of the mast :
8. A lift truck according to any of claims 5 to 7, wherein the at least one counterweight is coupled to the mast by means of a connecting element guided by rollers.
9. A lift truck according to claim 8, wherein the connecting element is a chain or cable.
10. A lift truck according to any of claims 1 to 9, including at least one guide member for guiding the movement of the at least one counterweight.
11. A lift truck according to any of claims 1 to 10, wherein the at least one counterweight is composed of steel.
12. A lift truck according to any of claims 1 to 11, including two separate counterweights configured so as to be movable in symmetrical relation.
13. A lift truck according to any of claims 1 to 12, configured so as to be transportable on a goods vehicle.
14. A lift truck substantially as hereinbefore described with reference to the accompanying drawings.