GB2043028A - Lift trucks - Google Patents

Abstract

A lift truck comprises a drivable truck body (10) carrying a telescopic mast, having a fixed outer section (18, 19) and a movable inner section (17), a slide assembly (29, 30) movable up and down on the mast, the slide assembly having an arm (32) mounted thereon for traversing movements therealong, the arm (32) extending outwardly from the slide and having a load receiving device (34, 35, 36) pivotally mounted thereon, and an operator's cabin (14) forming an extension of said inner section (17) of the mast and thus moving therewith. A pair of chains (41, 42) extend over respective pairs of pulley wheels (37, 38, 39, 40) fixed to the inner section (17) of the mast, one end of each chain being secured to the slide assembly and the other end being secured to the outer section (18, 19) of the mast, so that movement of said inner section and thus the operator's cabin, through a predetermined distance and at a predetermined rate, causes corresponding movement of the slide on the mast, through a distance and at a rate greater than said predetermined distance and said predetermined rate. By this arrangement, the operator maintains a close view of the load lifted at all times. <IMAGE>

Description

SPECIFICATION Lift trucks This invention relates to lift trucks, in particular to lift trucks intended for narrow aisle operation, and has as its object the provision of such a lift truck in an effective and convenient form.

According to the invention there is provided a lift truck comprising a drivable truck body, a multiple section mast having a first section thereof fixed relative to the truck body and a further section thereof which can be elevated or lowered relative to the first section, a slide movable up and down on said mast, the slide extending transversely across the truck body and having an arm mounted thereon for traversing movement along it, the arm extending outwardly from the slide and having a load receiving device mounted thereon, an operator's cabin arranged to move up or down with said further section of the mast, and said slide being arranged so that, in use, upward or downward mbvement of said further section and thus said operator's cabin through a predetermined distance relative to said first section causes upward or downward movement of said slide on said mast, and thus of said load receiving device, through a distance greater than said predetermined distance.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a lift truck of the invention, with an operator's cabin and a slide being shown elevated, Figure-2 is a plan view thereof, and Figures 3 to 5 are schematic side views of the truck on a reduced scale, showing successive stages in elevating the slide to its fully raised position.

The truck illustrated comprises a rigid structural body including a chassis of generally rectangular configuration and indicated at 10 in the drawings.

Near two adjacent corners at the rear of the truck body there are provided wheels in the form of castors 11 Instead of castors 11, a pair of wheels could be provided, each wheel being capable of independent movement in a downward direction only from a reference position. Each wheel can return to said reference position after said downward movement, but it is prevented from moving upwardly from said reference position.

The other two corners are provided with fixed axle wheels 12. Under the chassis is a further, larger drive and steering wheel 13. This is disposed midway between the sides of the chassis and is swivelable about a vertical axis by means of steering gear controlled from an operator's cabin 14, to be described. The wheel 13 is sprung to maintain contact with the surface over which the truck travels. The four corners of the chassis carry resilient cushions 1 5 for co-operation, in use, with guiding means for steering the truck down narrow aisles.

The body of the truck also includes a superstructure 1 6 secured to the rear of the chassis and containing a power source and control apparatus for the control of various features of the truck.

Towards the front of the chassis but spaced therefrom, there is provided a dual section telescopic mast, which comprises an outer section fixed to the truck body and an inner section 1 7 slidable in the outer section which thus acts as guide means.

The outer section is in the form of the two vertical columns 1 8, 1 9 rising from opposite sides of the truck body. The inner mast section 1 7 is slidably disposed between the columns 1 8, 1 9 as best shown in Figure 2. The columns 18, 1 9 and the section 1 7 have co-operating parts which ensure the section can be raised or lowered in a stable manner without swaying.

The operator's cabin 14 is of generally rectangular form with an outer frame 25, and is constructed as an extension of the inner section 17 of the mast. As shown in Figure 2, the cabin has parallel, longitudinally extending frame pieces 20,21 extending from its rear, forwardly between the columns 1 8, 1 9, to the section 17where they join a transverse frame piece 22 of the section 17.

Further, strengthening pieces 23, 24 are also provided from the cabin to the piece 22. The cabin has a canopy over the operator area to protect the operator from objects which may fall from racks being served by the truck. The cabin has a seat for the operator, facing generally forwardly and disposed adjacent a control lever 25 and steering wheel 26. When the cabin 14 is in its lowermost position as shown in Figure 3, the operator eye level is, for example, approximately 2.5 metres above ground level and this gives the operator a good view of a load receiving device of the truck, which will be described hereinafter.

The inner mast section is raised and lowered relative to the columns 18, 19 by means of conventional lift cylinders 27, 28 respectively contained, as shown in Figure 2, within parts of the outer mast section columns. The lift cylinders can, for example, act on brackets fixed to the inner mast section 1 7 and operation thereof is controlled by the operator from the cabin 14.

Carried Orl the inner section 1 7 of the mast for vertical movement along it in the usual manner, is a transversely disposed slide assembly comprising two spaced, interconnected parallei horizontal rails 29, 30. The ends of the rails 29 are connected to the ends of the rail 30 respectively by plate members one of which 31 is best visible in Figure 1.

Carried by the rails 29, 30 is an arm 32 which extends outwardly and forwardly of the chassis.

The arm 32 extends over the chassis and beyond the front end thereof, the chassis being a low platform in this region, as shown in Figure 1, and Figures 3 to 5. The arm 32 carries guide means 33 for maintaining its position in relation to the rails but permitting lateral sliding movement of the arm across the rails of the slide assembly. Power operated control means are provided for producing the sliding movement, such control means not being illustrated but being carried by the superstructure 16. The guide means 33 are such that when the arm 32 occupies a position close to one end of the rails 22, 23 the arm will serve to stiffen the rail ends and prevent distortion under load. Additional stiffening could be provided, if required, but this should be minimised in order to allow good operator visibility.

Pivotally carried on the outer end of the arm 32 is a load receiving device in the form of a fork assembly comprising a pair of flat tines 34, 35 connected by a member 36. The member 36 is pivoted about a vertical axis at the end of the arm 32 and rigidly supports the tines. The arm contains a mechanism for swivelling the tines about said vertical axis. The tines are shown extending transversely of the truck but they can swivel through 180" from the positions shown. As can be seen from the figures, the tines, in their sidewardly extending, lowermost position, are disposed close to but beyond the front end of the chassis 1 0.

At its upper end thereof, the inner section 17 of the mast is provided, adjacent the interior surfaces of its opposite shorter sides respectively, with respective pairs of spaced pulley wheels 37, 38 and 39, 40. The pulley wheels are at the same height and are secured to the section 1 7 so that they move with it. Around the pairs of pulleys are respective chains 41,42. Each chain has its one end, which is adjacent the pulleys when the section 1 7 is in its lowermost position, fixed to a column of the outer mast section, as shown for the chain 41 at 43 in Figures 3 to 5. The other end of each chain is fixed to the bottom of the slide assembly, as shown at 44 in Figures 3 to 5.

With this arrangement of chains, there is in effect a linkage connection between the mast section 17 and the slide assembly. With the pulley arrangement shown and described there is a 2:1 relationship between movement of the slide assembly upwardly or downwardly on the mast section 1 7 and upward or downward movement of the mast section 1 7 by itself. Thus if the inner mast section 17, and thus the operator's cabin 14 which moves with it, moves through a predetermined distance 42 upwardly or downwardly relative to the fixed outer mast section, then the slide assembly moves a corresponding distance x upwardly or downwardly on the mast, and thus the tines 34, 35 move a distance x as they are raised or lowered with the arm 32 on the rails 29, 30 of the slide assembly.

The pulleys thus provide a mechanical advantage for lifting or lowering the slide, it associated arm and load receiving device.

By a suitable alternative linkage arrangement, using chains and pulleys or otherwise, the slide could be arranged to move by any chosen distance greater than the movement of the section 1 7, as required.

Figure 3 shows the slide and also the cabin in their respective lowermost positions, with the fork assembly able to pick up from the floor.

In operation, the truck is designed principally for serving shelves spaced apart by a relatively narrow aisle. The aisle width may be only slightly wider than the total width of the truck. To collect a load from a shelf at one side of the aisle, the truck is positioned with the tines within the width of the truck and directed to the side of the truck at which the load to be collected is disposed. The lift cylinders are then operated to raise the inner mast section 1 7 and cabin 14 and simultaneously and at twice and rate, to raise the slide assembly, arm 32 and tines 34, 35.

Figure 4 shows the slide and thus the fork assembly, in a slightly raised position, where the slide has reached the level of the cabin 14. The inner mast section 17 has been raised by a distance half that through which the slide has been raised.

The raising operation is continued until the tines coincide with the bottom of the load to be collected. The arm 32 is now moved transversely across the rails of the slide assembly so that the tines enter a space provided beneath the load.

Further raising of the tines with the arm and the rails lifts the load so that it is wholly supported by the truck. It can then be brought out of the shelf by returning the arm to its initial position. The load may be swivelled to the front or to the other side of the truck by pivoting the tines about the axis at the end of the arm 32, whilst the arm is traversed laterally of the truck along the rails of the slide assembly to the appropriate position.

With this arrangement, a load can be picked up from floor level since the tines may be lowered below the level of the chassis, as shown in Figure 1. However, the tine 35 is close to the front of the chassis so that a load carried by the tines, when the tines are above the level of the chassis, may at least partly overhang the low platform formed by the front of the chassis. When carrying a load at any position forwardly or laterally of the truck the truck is stable even though no heavy weight is provided as a counterbalance at the rear of the truck. The positioning of the superstructure at the rear of the chassis and the positioning of the front wheels up to, but not under, the tines in their sidewardly directed position ensures the stability of the truck.

The maximum amount by which the section 1 7 and thus the slide can be raised is shown in Figure 5, where the slide has passed the cabin 14. A safety stop ensures no further lifting of the section 17.

As it is fabricated to the inner mast section, the operator's cabin forms a reinforcing structure for the mast and the cabin is thus more stable at high lifts than conventional lifted cabins, since no chains and bearings are empioyed in supporting and guiding the cabin. As the slide assembly elevates at twice the rate of the inner mast section 17, the slide assembly will, as described, eventually pass the cabin. However, throughout the whole of the slide assembly elevation, the operator has a relatively clear unobstructed view of the load receiving and lowering/raising operation. Even at full elevation of the tines, the operator's eye level is no more than, for example, 2.5 metres below the tines. The construction of the outer mast as two columns, overcomes visibility problems often caused by bracings on conventional masts. As can be seen In Figure 1, the slide is largely open, so that as it passes the cabin, the operator's visibility is not greatly impaired.

Thus the truck of the invention allow the operator a relatively clear view of operating conditions at all times.

Claims (11)

1. A lift truck comprising a drivable truck body, a multiple section mast having a first section thereof fixed relative to the truck body and a further section thereof which can be elevated or lowered relative to the first section, a slide movable up and down on said mast, the slide extending transversely across the truck body and having an arm mounted thereon for traversing movement along it, the arm extending outwardly from the slide and having a load receiving device mounted thereon, an operator's cabin arranged to move up or down with said further section of the mast, and said slide being arranged so that, in use, upward or downward movement of said further section and thus said operator's cabin through a predetermined distance relative to said first section causes upward or downward movement of said slide on said mast, and thus of said load receiving device, through a distance greater than said predetermined distance.

2. A truck as claimed in Claim 1, wherein the slide is arranged to co-operate with said mast so that it moves simultaneously with and at a greater rate than the further section thereof.

3. A truck as claimed in Claim 2, wherein said slide co-operates with said mast by way of chain means, one end of which is fixed relative to the first section of the mast and the other end of which is fixed to the slide, the chain means passing over pulley means on the further section of the mast, so that as said further section moves upwardly or downwardly the chain means raise or lower said slide.

4. A truck as claimed in Claim 3, wherein said pulley means are a pair of pulley wheels at each side of said further section of the mast, and the chain means are a pair of chains passing over said pairs of pulley wheels respectively, one end of each chain being fixed to the slide and the other end of each chain being fixed to the first section of the mast.

5. A truck as claimed in Claim 3 or Claim 4, wherein said slide moves up and down, in use, on said further section of the mast and when moving upwardly can eventually pass said cabin.

6. A truck as claimed in any one of the preceding Claims, wherein the ratio of the movement of said slide to the movement of said further section is 2 1.

7. A truck as claimed in any one of the preceding Claims, wherein the operator's cabin is fabricated to and forms an extension of the further section of the mast, so as to move therewith in use.

8. A truck as claimed in any one of the preceding Claims, wherein the first section of the mast comprises two opposed columns rising vertically from the truck body with a substantially free space between them, in which said further section of the mast moves, in use.

9. A truck as claimed in any one of the preceding Claims, in which said arm extends over and beyond a front end of the truck body, so that, in use, with the slide in its lowermost position on the mast, said load receiving device can pick up a load from the level of the surface over which the truck is travelling.

10. A truck as claimed in any one of the preceding Claims, wherein said load receiving device is pivotaliy mounted on said arm, so that it can be directed, in use, to either side of the truck or to the front thereof.

11. A lift truck substantially as hereinbefore described with reference to and as shown in the accompanying drawings.