GB2107281A

GB2107281A - A lifting mechanism

Info

Publication number: GB2107281A
Application number: GB08205619A
Authority: GB
Inventors: Ginka Simeonova Stoilova; Georgi Kirilov Stoilov; Angel Yossifov Mitov; Ivan Yordanov Petrov
Original assignee: INST ELEKTROKARI MOTOKARI
Current assignee: INST ELEKTROKARI MOTOKARI
Priority date: 1981-10-05
Filing date: 1982-02-25
Publication date: 1983-04-27
Also published as: DE3139758A1; FR2514336A1; NL8104518A; GB2107281B; FR2514336B3

Abstract

A lifting mechanism, for example for use on a fork-lift truck, comprises a carriage (3) which is lifted by hydraulic cylinders (4) acting through a chain and pulley mechanism (5, 6, 7, 8). Each lifting cylinder (4) is mounted on a respective upright (1) of a mast. Extension of each lifting cylinder (4) raises the pulley (7), around which the chain (5) runs. One end of the chain (5) is attached to the upright (1), and the other is attached to a column (2), so that lifting of the pulley (7) causes the column (2) to rise, taking with it the pulley (8). The chain (6) running over the pulley (8) is attached at one end to the upright (1) and at the other to the carriage (3), and lifting of the pulley (8) thus raises the carriage (3). The velocity ratio between the lifting cylinders (4) and the carriage (3) is 1:4. The cylinders (4) are mounted at the upper region of the mast, which enables wheels (9) of the truck to be positioned relatively close together. <IMAGE>

Description

SPECIFICATION.

A lifting mechanism This invention relates to a lifting mechanism, particularly, although not exclusively, a lifting mechanism for use on mechanical handling equipment, for example industrial electric or internal combustion engine driven vehicles such as fork-lift trucks.

A lifting mechanism for such purposes is known in which two lifting cylinders are mounted on the outboard sides of a mast comprising two uprights provided on the truck. The motion of the lifting cylinders is transmitted to a lifting carriage, on which, for example, the lifting forks may be mounted, through respective chain pulley mechanisms, each of which has a velocity ratio of 1:2. One end of each chain is fixed to the mast, and the other is fixed to the lifting carriage, while the pulley is mounted on the piston rod of the lifting cylinder.

A disadvantage of the known mechanism is that the stroke of the lifting cylinders must be very large to provide a satisfactory lifting height of the carriage. This stroke must be one half of the required maximum lift. The lifting cylinders thus extend over substantially the full height of the mast and significantly increase its total width for a given size of opening between the uprights to provide visibility for an operator. Since, in such trucks, the front wheels are frequently mounted one on each side of the mast, the track width of the vehicle is correspondingly large.

According to the present invention there is provided a lifting mechanism comprising a mast and a column which is movable upwardly and downwardly relatively to the mast, a lifting cylinder being mounted on the mast and arranged to raise and lower a first pulley over which runs a first elongate flexible member, one end of which is fixed to the mast and the other end of which is fixed to the column, a second pulley being mounted on the column, with a second elongate flexible member running over the second pulley, one end of the second elongate flexible member being fixed to the mast and the other end being fixed to a support for an article to be lifted by the mechanism.

The elongate members may be chains, and will be referred to as such from now on in this description.

Preferably, where the mast comprises two uprights, there is one of the hydraulic cylinders and an associated movable column on each upright, each provided with its own set of pulleys and chains.

The support for an article to be lifted is, in a practical embodiment of the invention, a carriage on which lifting forks may be fitted.

It will be appreciated that, by providing a double pulley arrangement for the or each lifting cylinder, a velocity ratio of 1:4 between the lifting cylinder and the support is achieved. This means that the lifting cylinders can be shorter than those of the known construction to obtain the same lifting height. By mounting such shorter cylinders towards the top of the mast, the space between the uprights can be enlarged while retaining a relatively small overall width at the bottom of the mast which enables the track width of a truck on which the lifting mechanism is mounted to be correspondingly small, since the lifting cylinders do not have to be accommodated between the wheels of the truck.

In a preferred construction, the first and second pulleys rotate about axes which are inclined to each other, preferably by 900.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 illustrates schematically the principle of a lifting mechanism; Figure 2 is a schematic rear view of a fork-lift truck having a lifting mechanism using the principle illustrated in Figure 1; Figure 3 is a schematic side view of the truck of Figure 2; and Figure 4 is a sectional view taken on the line lV-IV in Figure 2.

As shown in Figure 1, the lifting mechanism comprises a mast having two uprights 1.

Mounted on each of these uprights 1 is a column 2 which can move upwardly and downwardly relatively to its associated upright 1. A carriage 3, to which lifting forks (not shown) may be fitted, is suspended from the mast and the columns 2 by a pulley mechanism operated by lifting cylinders 4 which are mounted on supports 10 on the outboard side of each upright 1.

A first pulley 7 is mounted on the piston rod of each lifting cylinder 4. Over each pulley 7 runs a chain 5 which is connected at one end by a fitting 14 to the column 2 and at the other end by a fitting 13 to the upright 1. At the top end of the column 2 there is a further pulley 8 over which runs a chain 6. The chain 6 is connected at one end by the fitting 13 to the upright 1 and at the other end by a fitting 1 5 to the platform 3.

Although the pulleys 7 and 8 are shown in Figure 1 as being rotatable about parallel axes, they are, in the preferred embodiment as shown in Figures 2 to 4, mounted for rotation about axes which are perpendicular to each other.

As can be seen from Figure 2, each pulley 7 is supported between a limb of an L-shaped bracket 11 and a surface of the upright 1, and each pulley 8 is supported by a bracket 12. The two uprights 1 are interconnected by a cross-member. The truck to which the lifting mechanism is fitted is represented only by its front wheels 9.

In operation, fluid under pressure is fed to the hydraulic cylinders 4 which extend to raise the pulleys 7. This lifts the end of the chain 5 connected to the attachments 14, which in turn raises the column 2. The consequent rise of the pulley 8, acting through the chain 6, raises the carriage 3. It will be appreciated that the velocity ratio between the cylinders 4 and the carriage 3 is 1:4. Because the necessary lifting height can be achieved with cylinders 4 occupying only the space above the wheels 9, the wheels 9 can be placed relatively close together without reducing the space between the uprights 1, through which the operator must be able to see to manoeuvre the truck.

Claims

1. A lifting mechanism comprising a mast and a column which is movable upwardly and downwardly relatively to the mast, a lifting cylinder being mounted on the mast and arranged to raise and lower a first pulley over which runs a first elongate flexible member, one end of which is fixed to the mast and the other end of which is fixed to the column, a second pulley being mounted on the column, with a second elongate flexible member running over the second pulley, one end of the second elongate flexible member being fixed to the mast and the other end being fixed to a support for an article to be lifted by the mechanism.

2. A lifting mechanism as claimed in claim 1, in which the elongate flexible members are chains.

3. A lifting mechanism as claimed in claim 1 or 2, in which the first and second pulleys are rotatable about axes which are perpendicular to each other.

4. A lifting mechanism as claimed in any one of claims 1 to 3, in which the lifting cylinder is one of two lifting cylinders disposed symmetrically one on each side of the mast.

5. A lifting mechanism as claimed in any one of the preceding claims, in which the support comprises a carriage for receiving lifting forks.

6. A lifting mechanism as claimed in any one of the preceding claims, in which the velocity ratio between the lifting cylinder and the support is 1:4.

7. A lifting mechanism as claimed in any one of the preceding claims, in which the lifting cylinder is disposed at the upper region of the mast.

8. A lifting mechanism substantially as described herein with reference to and as shown in the accompanying drawings.

9. A vehicle provided with a lifting mechanism as claimed in any one of the preceding claims.

10. A vehicle as claimed in claim 9, in which wheels of the vehicle are disposed one on each side of the mast, the lifting cylinders being positioned above the level of the upper extremities of the wheels.