GB2092672A - Improvements in lift-trucks - Google Patents

Abstract

A fork-lift truck has a fork carrier for forks mounted on a lifting carriage (not shown in Fig. 3) for hinging movement under the control of an hydraulic piston-and-cylinder assemblage (32, 33). A joint (34) connects the piston rod outer end to the carrier (5). The joint comprises a flanged bush (41) fixed in a hole (40) in the carrier (5) by bolts 43a, 43b, a transverse pin (44) carried by the bus and a headed rod (45) the head (50) of which is hinged on the pin (44) and the rod of which is screw threaded in a threaded hole in the end of the piston rod (33) and locked with a lock nut (47). The joint is assembled on the end of the piston rod and then fixed to the carrier (5). <IMAGE>

Description

SPECIFICATION Improvements in lift-trucks The invention relates to lift trucks having a lifting carriage mounted between two substantially vertical guide columns, the carriage comprising a carriage frame, a fork carrier for the forks of the fork-lift truck mounted on the carriage frame for pivoting about an axis transverse to the longitudinal axis of the guide columns, and at least one hydraulic piston-and-cylinder assemblage for controlling the inclination of the fork carrier, the piston-and-cylinder assemblage being connected between joints carried respectively by the fork carrier and the carriage frame.

Such a lifting carriage is known in practice wherein a joint between the piston rod of the piston-and-cylinder assemblage and the fork carrier is a ball-and-socket joint. For this purpose, the piston rod carries a ball head while a ball socket is provided on the fork carrier.

Since a ball-and-socket joint allows tilting and rotating movements, additional precautions must be taken in some circumstances to prevent the piston of the piston-and-cylinder assemblage from slowly turning in the cylinder during operation.

In addition, a ball-and-socket joint must be carefully sealed against the penetration of dust, particularly when working in a dusty environment, because in the known lifting carriage joints a considerable proportion of the surface of the ball is not covered by the ball socket.

In accordance with the invention, the fork carrier joint comprises a bush carried in an opening in the fork carrier, the bush having a transverse through bore in which a pin is fitted and a head received in the bush, the pin passing through a transverse bore in the head to hinge the head in the bush, said head being disposed coaxially with respect to the piston rod of said piston-and-cylinder assemblage and said pin extending parallel to the pivotal axis of the fork carrier.

This arrangement offers the advantage that rotating movements of the piston of the pistonand-cylinder assemblage are prevented.

Also, the joint is housed in an opening in the fork carrier so that the joint is largely protected and expensive sealing means can be dispensed with. Additionally, the joint does not increase the thickness of the fork carrier, at least substantially, and the joint is easily assembled.

Comparatively large pivotal angles of the head within the bush are possible with a relatively small difference in diameter between the head and the opening of the bush, and this is particularly so if the head has frusto conically chamfered end portions and an intermediate cylindrical portion as is preferred, the length of the cylindrical portion of the head, between its end portions, being somewhat greater than the diameter of the pin. In this way the cylindrical portion ensures a lateral guiding of the head on the pin, inside the bush.

The end position of the fork carrier can easily be adjusted if the head is formed at one end of a threaded bolt which is screwed into a corresponding threaded hole in the end of the piston rod and secured by a lock nut, as is also preferred.

In order to be able to transmit very great thrust forces to the fork carder, with simple mounting, the bush may have an attachment flange at its end face, at the end face adjacent the piston-and-cylinder assemblage, the length of the bush, without the flange, corresponding substantially to the thickness of the fork carrier.

Preferably also the pin is non-rotably received in the transverse through bore of the bush.

The length of the pin conveniently corresponds substantially to the external diameter of the bush so that no additional means is necessary to secure the pin against lateral displacement relative to the bush when the bush is close fitted in the opening in the fork carrier.

A specific embodiment of the invention will now be described by way of example and not by way of limitation with reference to the accompanying drawings in which: Figure 1 is a side view of a fork-lift truck according to the invention, with one guide column of its lifting mast removed; Figure 2 is a perspective view of the lifting carriage of the truck; Figure 3 is a side view of a first joint of the lifting carriage partially in section on the line Ill-Ill in Figure 4, and Figure 4 is a front view of the joint, disposed in the fork carrier as shown in Figure 3, with the fork removed.

With reference to the accompanying drawings, in Figure 1, a fork lift truck 1 is illustrated diagrammatically, at the front portion of which, two vertical guide columns are mounted which are spaced apart and form a lifting mast. For reasons of illustration, only one guide column 2 is illustrated. Both guide columns 2 have a U-shaped or C-shaped cross section and are so arranged that the open sides of the sections face one another.

Running between the two guide columns 2 is a lifting carriage 3 which is displaceable in height and which can be displaced in height by drive devices not illustrated, for example a chain and sprocket drive. The lifting carriage comprises a fork carrier 5, hinged on a carriage frame 4, the carrier having 'pushed-on' forks 6, and a pair of hydraulic piston-and-cylinder assemblages 7, which act between the fork carrier 5 and the carriage frame 4, to pivot the fork carrier 5 in relation to the carriage frame.

As illustrated in Figure 2, the carriage frame 4 comprises two side frame members 10 and 11 which are vertical and spaced apart and which are connected at their lower end by a lower transverse beam member 12 and, substantially in the upper half, by an upper transverse beam member 13, so that a stable frame construction results. The spacing of the members 10 and 11 corresponds substantially with that of the guide columns 2.

Mounted at the outside of the member 10 are three guide rollers 14, 1 5 and 16, the axes of rotation of which are perpendicular to the longitudinal axes of the guide columns 2 and which run in the U-section of the adjacent guide column 2, while correspondingly disposed guide rollers on the member 11, not visible for reasons of illustration, run in the other guide column 2.

At the side of the upper transverse beam 13 remote from the members 10 and 11 there are two brackets 20 and 21, having aligned bores 22 and 23, the axis of which extends perpendicular to the longitudinal axis of the guide columns 2.

Mounted on a pin journalled in the bores 22, 23 by means of arms 24, which receive the pin in corresponding bores is the fork carrier 5.

The fork carrier 5 is a substantially rectangular stiff plate having its upper and lower edges formed with rebates 25, 26 onto which complementary formations 27, 28 of the substantially L-shaped forks 6 are pushed.

Provided beside the members 10 and 11, on the upper transverse beam, are downwardly projecting fork-like extensions 30, 31 journalling hinge pins hinging the cylinders of the piston-andcylinder assemblages 7. The piston rods 33 of the assemblages 7 are connected to the fork carrier 5 each by means of a joint 34, in such a manner that the cylinders of the piston-and-cylinder assemblages lie substantially horizontally in the position of rest.

The joint 34 is shown in detail in Figures 3 and 4 and comprises a cylindrical bush 41 which is mounted in a corresponding bore 40 in the fork carrier 5. The bush has an attachment flange 42 at its end face adjacent the assemblage 7 which lies snugly against the fork carrier 5.

In order to transmit tensile forces from the bush 41 to the fork carrier 5, four circumferentially spaced apart bores are provided in the flange 42, through which four screw bolts 43a to 43d are engaged in correspondingly screw threaded holes in the fork carrier 5 to hold the flange 42 against the fork carrier 5.

Rotatably mounted on a pin 44 in the bush 41 is a head 50 formed on a threaded rod 45. The pin 44 is fixed in a corresponding transverse through bore in the bush 41, and has such a length equal to the outer diameter of the bush such that the pin does not project beyond the external dimensions of the bush 41. In order that pivotal movement may be effected between the head 50 and the pin 44, and not between the pin 44 and the bush 41, in an undesirable manner, the pin 44 is splined at one end as at 46, and is press fitted into the wall of the bush when the pin 44 is forced into the transverse through bore of the bush to prevent the rotation of the pin relative to the wall of the bush.

The head 50 has a substantially cylindrical shape and is formed with its cylindrical axes coincident with the longitudinal axis of the threaded rod 45.

The threaded rod 45 is screwed into a correspondingly screw threaded hole in the end of the piston rod 33 and secured by a lock nut 47.

The two end portions of the head 50 are chamfered substantially frustoconically so as to allow a relatively large pivotal movement of the head inside the bush. The difference in diameter between the cylindrical portion of the head 50 and the bore of the bush 41 is chosen to allow pivoting as required.

For the purpose of lubricating the bearing surfaces between the pin 44 and the head 50, a lubricating nipple 48 is provided at the side of the head adjacent the piston rod 33.

When assembling the joints 34, the threaded rod 45, carrying the lock nut 47 is first screwed far enough into the hole in the end of the piston rod 33. Then the bush 41 is pushed over the head 50 so that the transverse bore in the bush 41 is in alignment with the bore in the head and the pin 44 is inserted. Then the joint 34, thus previously assembled, is fitted into its opening 40 in the fork carrier 5 and fixed by means of the screws 43a to 43d.

In order to adjust the position of rest of the fork carrier 5, the piston rods 33 can subsequently be displaced forwards or backwards by turning the threaded rods 45 until the correct adjustment is reached, after which the lock nuts 47 are tightened.

As assembled, each joint 34 fits largely into the fork carrier 5 so that the carrier is of a very shallow structural depth. In addition, very high pushing and pulling forces can be transmitted via the pins 4.

Because of the clearance between the head 50 and the bore of the bush 41 in each case, a pivotal movement of the head 50 in the bush 41 sufficient for the desired inclination of the forks 6 is possible, and in addition, each head 50 can be displaced laterally on its pin 44 to accommodate manufacturing tolerances leading to misalignment between the openings 40 in the fork carrier 5 and the formations 30, 31 of the upper transverse beam 13.

Claims (7)

1. A fork-lift truck having a lifting carriage mounted between two substantially vertical guide columns, the carriage comprising a carriage frame, a fork carrier for the forks of the fork-lift truck mounted on the carriage frame for pivoting about an axis transverse to the longitudinal axis of the guide columns, and at least one hydraulic pistonand-cylinder assemblage for controlling the inclination of the fork carrier, the piston-andcylinder assemblage being connected between joints carried respectively by the fork carrier and the carriage frame, wherein the fork carrier joint comprises a bush carried in an opening in the fork carrier, the bush having a transverse through bore in which a pin is fitted and a head received in the bush, the pin passing through a transverse bore in the head to hinge the head in the bush, said head being disposed coaxially with respect to the piston rod of said piston-and-cylinder assemblage and said pin extending parallel to the pivotal axis of the fork carrier.

2. A fork-lift truck as claimed in Claim 1, wherein the head has frusto-conically chamfered end portions and an intermediate cylindrical portion the length of the cylindrical portion of the head being somewhat greater than the diameter of the pin.

3. A fork-lift truck as claimed in Claim 1 or 2, wherein the head is formed at one end of a threaded bolt which is screwed into a corresponding threaded hole in the end of the piston rod and secured by a lock nut.

4. A fork-lift truck as claimed in any preceding claim, wherein the bush has an attachment flange at its end face adjacent the piston-and-cylinder assemblage the length of the bush without the flange corresponding substantially to the thickness of the fork carrier.

5. A fork-lift truck as claimed in any preceding claim, wherein the pin is non-rotatably received in the transverse through bore of the bush.

6. A fork-lift truck as claimed in any preceding claim, wherein the length of the pin corresponds substantially to the external diameter of the bush.

7. A fork-lift truck having a fork carrier substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.