GB2336146A

GB2336146A - Fork-lift truck having individually height adjustable fork(s)

Info

Publication number: GB2336146A
Application number: GB9906180A
Authority: GB
Inventors: Sjoerd Meijer; Leeu Marinus Gerardus De; Graaf Folkert De
Original assignee: MEIJER MACHINEBOUW HOLDING BV; KOOI BV
Current assignee: MEIJER MACHINEBOUW HOLDING BV; KOOI BV
Priority date: 1998-04-06
Filing date: 1999-03-17
Publication date: 1999-10-13
Anticipated expiration: 2019-03-17
Also published as: NL1008813C2; GB9906180D0; GB2336146B; DE19915006A1

Abstract

A fork lift truck 1 includes a substantially upright mast 4, a carrier 6 eg a carriage connected for movement relative thereto and at least one fork 8 mounted on the carrier and extending substantially transversely thereof, whereby, said fork(s) is/are mounted for movement relative to said carrier in the direction of said mast. The fork(s) may be 'L' shaped and can be actuated for movement relative to said carrier by an hydraulic cylinder provided in a first leg of said 'L' which extends in a direction along the mast, said cylinder comprising a cylinder chamber (14 figs. 3 and 4) and piston (16 Figs. 3 and 4), the free end of the piston rod (17 Figs.3 and 4) being connected to the movable carrier. The fork(s) may further be hydraulically extendible eg telescopic in a direction transverse of the mast. In use, at least one fork can be adjusted in height relative to the carrier so as to allow the fork-lift truck to be positioned relative to an obliquely situated load. The carrier may further be used as a rest when lifting/lowering large loads. Extendible forks enable the fork-lift truck to reach loads set at a distance.

Description

1 FORK-LIFT TRUCK 2336146 The present invention relates to a fork-lift

truck of the type described in claim 1.

Such fork-lift trucks are generally known, wherein the fork or forks of the fork-lift truck are suspended from the carrier and the carrier is movable up and downward along the mast. In other known fork-lift trucks the forks extending transversely of the longitudinal direction of the mast are extensible in order to set down a load far from the fork-lift truck.

Particularly in the case of a fork-lift truck with two forks together defining a bearing surface, one drawback is that, when the fork-lift truck is standing obliquely relative to a load for lifting, the forks cannot be pushed under this load, or hardly so.

Another drawback of the known fork-lift trucks is that, in the case of the extending forks, an exceptionally heavy load which has to be set down far from the fork-lift truck causes such a high moment of force relative to the tilt line located through the front wheels of the fork-lift truck that there is the danger of the fork-lift truck tipping over.

The invention has for its object to obviate these drawbacks and a forklift truck is provided for this purpose which is distinguished by the characterizing properties of claim 1.

With a fork-lift truck according to the present invention one of the two forks of the fork-lift truck can be adjusted in height relative to the carrier so as to thus take up a position adapted to the position of a load for lifting. Loads in relation to which the fork-lift truck is obliquely positioned can be lifted without problem in this manner. When a heavy load has to be set down far from the fork-lift truck, the carrier can 2 moreover be used as rest. The carrier herein rests on the surface on which the heavy load has to be placed or from which it must be removed since the forks are brought into a raised position relative to the carrier. The tilt line, which normally runs through the front wheels of the forklift truck, is hereby displaced in forward direction to the position where the carrier rests on the above stated surface. The distance over which a load can be set down can hereby be increased, or the weight of the load can be increased.

Preferred embodiments are described in the subclaims. Relevant considerations here are the provision of a possible embodiment, keeping the configuration simple and so on. The different aspects will be made further apparent with reference to the following figure description, in which:

fig. 1 shows a perspective view of a fork-lift truck according to the present invention during operation; fig. 2 is a perspective view of a detail of the fork-lift truck shown in fig. 1 in another operating situation; and fig. 3 and 4 show partly cut-away perspective views of details of the forks of the fork-lift truck according to the present invention shown in fig. 1. 25 Fig. 1 shows a fork-lift truck 1 in perspective view in operation during loading of a load 2 onto the loading floor 3 of a vehicle. Fork-lift truck 1 comprises a vehicle 5 with a mast 4 thereon. Arranged on mast 4 is a carrier designed as a carriage 6 which is movable up and downward along mast 4 using a lifting mechanism 7. Arranged on carriage 6 are forks, of which the parts 8 extending transversely of mast 4 and therefore in horizontal direction are telescopic or otherwise extensible. The object hereof is to be able to place load 2 as far as possible away from fork-lift truck 1 onto loading floor 3. For this purpose parts 8 contain an extending mechanism (not shown) which 3 operates for instance hydraulically and for which purpose forks 9 are provided with hydraulic connections 10. These latter are connected to channels through forks 9 running to said hydraulic mechanism.

The parts of forks 9 running parallel to mast 4 pass through tubes 11 which form guides for the first legs of forks 9, i.e. the parts of forks 9 running vertically parallel to mast 4. The parts 8 of forks 9 running horizontally or transversely of the direction of the mast are defined as the second legs.

Tubes 11 form guides for forks 9, wherein the first legs of forks 9 are movable up and downward in tubes 11 which are mounted fixedly on carriage 6. Use is made for this purpose of a hydraulic drive system as will be further described hereinbelow.

In fig. 1 the forks 9 in tubes 11 are placed in the highest position thereof relative to carriage 6. The bottom part or heel 12 of carriage 6 hereby becomes available under the underside of forks 9. In the operating situation shown here, heels 12 of carriage 6 rest on loading floor 3. As a result the tilt line of fork-lift truck 1, which in the normal course of events runs through front wheels 13 thereof, is shifted in the direction of arrow A to the edge of loading floor 3. The reach, designated with arrow B, of the extensible parts 8 of forks 9 relative to carriage 6 is hereby correspondingly increased when a load 2 remains constant, the gravitational force exerted by this load being indicated schematically with arrow C.

It is possible per se,to arrange on carriage 6 a heel protruding permanently below the bottom of forks 9. However, load 2 can then never be set down on the loading floor 3 or on the surface over which vehicle 5 travels because of the height difference caused by heel 12. The realization of the greater reach, indicated with arrow B, is therefore directly associated in the embodiment shown 4 here with the provision of heels 12 on carriage 06 and the mobility of the forks relative to the carrier.

Fig. 2 shows a detail of the fork-lift truck 1 shown in fig. 1 in oblique position. That is, load 2 lies 5 obliquely relative to mast 4.

As can be seen in the situation shown here in fig. 2, forks 9 are displaceable independently of each other in tubes 11, whereby adapting to said oblique position of a fork-lift truck 1 according to the invention is possible. It is found that in the situation of fig. 2 the incline is 11'. The range of possible adaptation to the oblique position depends on the degree of freedom of movement of forks 9 relative to tubes 11 and the distance between tubes 11.

Fig. 3 and 4 show a detail of one of the forks 9 in a tube 11. Forks 9 are provided with hydraulic connections 10 which via a channel 13 through the length of fork 9 communicate with the hydraulic mechanism serving to extend the horizontally running parts 8 of forks 9. This is shown specifically in fig. 1.

In fig. 3 fork 9 is situated in the lowered position relative to tube 11, while in fig. 4 fork 9 is situated in the upward displaced position relative to tube 11. Displacement of fork 9 in tube 11 is realized using hydraulic mechanism which here takes a dual form.

Bores are arranged in fork 9 from the top side thereof in order to form cylinder chambers 14. These latter are closed by means of screw-caps 15 and pistons 16 with piston rods 17 mounted thereon are situated in cylinder chambers 14. Opposite screw-caps 15 the cylinder chambers are sealed round piston rods 17 by means of sealing bushes 18 through which piston rods 17 protrude. On the free end thereof piston rods 17 are provided with transverse pins 19 which are placed through slotted holes 20. Transverse pins 19 are further fixed on either side to the tube 11, for instance by means of a weld as indicated at 21.

Slotted holes 20 form an open connection between the outside and the boreholes in which cylinder chambers 14 are formed, but only under the position of the sealing bushes, so that sealing of the cylinder chambers is ensured. When the pressure in cylinder chambers 14 is increased above pistons 16, for 'Instance via pressure connection 22, pistons 16 will move downward from the position shown in fig. 3 to the position shown in fig. 4. As a result of the connection between pistons 16 and transverse pins 19 the fork 9 is herein pressed upward to effect displacement of fork 9 in tube 11.

In order to cause fork 9 to return from the position shown in fig. 4 to the position shown in fig. 3, the pressure supplied via pressure connection 22 can simply be removed, whereafter fork 9 will sink in tube 11 under the influence of its own weight. In the configuration shown here a second pressure line 23 is further provided which is connected to cylinder chambers 14 close to piston rods 17. Hydraulic fluid at the piston rods can thus be driven out through pressure connection 23 when pistons 16 move downward in cylinder chambers 14 and vacuum suction can be prevented by supplying hydraulic fluid to the piston rods when pistons 16 move upward. It is also possible to increase the pressure in the parts of cylinder chambers 14 corresponding with piston rods 17 when tube,11 fits closely round fork 9 such that some friction has to be overcome.

It is of course also possible to reverse the orientation of piston fods 17 relative to pistons 16, wherein the piston rods extend upward from pistons 16. In this alternative construction the fork is suspended from piston rods 17. Herein the fork as it were pulls itself up on piston rods 17 when hydraulic fluid is supplied under pressure. The advantage hereof is that in more favourable manner the piston rods are under strain of tension instead of pressure. Although mention is made in the foregoing of hydraulic fluid, other forms of medium 6 under pressure can also be applied. In addition, the present invention is not limited to the use of hydraulic mechanisms; the displaceability of the forks, and preferably of each fork individually, can for instance also be realized with a screw spindle or the like.

1

Claims

1. Fork-lift truck, comprising a vehicle with:

mast extending substantially upward; carrier connected to the mast and movable therealong; and - at least one fork arranged on the carrier and extending substantially transversely of the mast, wherein the fork is connected to the carrier for movement relative to the carrier in the direction of the mast.

2. Fork-lift truck as claimed in claim 1 with at least two forks, wherein the forks are individually movable along the mast relative to the carrier.

3. Fork-lift truck as claimed in claim 1 or 2, wherein the fork is extensible in the direction transversely of the mast.

4. Fork-lift truck as claimed in any of the foregoing claims, wherein the fork is substantially Lshaped with a first leg extending along the mast and a second leg extending transversely of: the mast, and wherein in the first leg is arranged at least one hydraulic cylinder with a cylinder chamber and an assembly of piston and piston rod movable herein in a direction corresponding with the mast, wherein the free end of the piston rod is fixedly connected to the carrier.

5. Fork-lift truck as claimed in claim 4, wherein the first leg comprises at least one elongate lateral passage in a direction corresponding with the mast, through which passage the carrier and the piston rod are mutua11v connected.

6. Fork-litEt truck, substantially as hereinbefore described with. reference to and as shown in the accompanying drawings.