This invention relates to load handling apparatus comprising a telescopic boom carrying a hydraulic unit for manipulating a load receiving device.

Such apparatus is already known in which the telescopic boom has three sections. The first section carries the hydraulic unit and is adapted to carry the load receiving device; a hydraulic ram acts between the second and third sections; synchronising means extend and retract the first section in synchronism with the second section; and the third section is tiltably mounted on a vehicle.

Using a fork as the load receiving device it is possible to unload containers up to 9 m long, by inserting the boom through one end of the container. However, longer containers (e.g. 12 m) raise the problem of achieving a telescopic boom which has a sufficiently long telescoping range. Increasing the length of the sections increases the retracted length of the boom. However, increasing the number of sections raises the problem of supplying hydraulic fluid to the hydraulic unit along the widely variable length of the telescopic boom.

The present invention provides load handling apparatus as set forth in claim 1. Preferred and optional features are set forth in claims 2 et seq.

The invention will be described, by way of example, with reference to the accompanying drawings, in which:-

Figure 1 is a side elevation of a vehicle equipped with load handling apparatus including a telescopic boom carrying a hydraulic unit for manipulating a load receiving device;

Figure 2 is a diagram showing means for extending and retracting the boom;

Figure 3 is a diagram showing means for supplying hydraulic fluid to the hydraulic unit for manipulating the load receiving device;

Figure . is a diagram showing means for supplying hydraulic fluid to a ram for extending part of the boom;

Figure 5 is a diagrammatic side view of the boom in a partly extended state;

Figure 6 is a diagrammatic side view of the boom in a fully extended state;

Figure 7 is a diagrammatic side elevation of the vehicle, showing various possible positions of the boom; and

Figures 8 to 11 show parts of a preferred embodiment of the telescopic boom, in vertical cross-section, with certain items omitted for the sake of clarity.

The vehicle 10 illustrated in Figure 1 has a telescopic boom 11 which is tiltably mounted on a chassis frame 12 and can be raised and lowered about a pivot 13 by means of a hydraulic ram (not shown) connected between the boom 1 and the frame 12. At the front end the boom 11 has a bracket 1. adapted to carry a load receiving device 16 which includes a fork 17 and which is tiltable about a pivot 18. The front end of the boom 11 also

carries a hydraulic unit 19 including a ram 21, for manipulating the load receiving device 16. In Figure 1 the vehicle 10 is shown in its travelling position, with the boom 11 fully retracted and stowed in its lowest tilting position, the load receiving device 16 being tilted to a median position, and the fork 17 being raised and folded backwards from its normal operating position on the load receiving device 16.

In Figure 1 the manipulating ram 21 projects from the boom 11 and is pivoted to a lug 22 on the load receiving device 16. Figures 10 and 11 show an alternative arrangement in which the ram 21 is housed in the boom 11 and is connected by a lever 23 and a link 2. to a lug 26 on the load receiving device 16.

The load receiving device 16 carries castor wheels 27 for supporting the device 16 on the ground when the extended boom 11 is tilted down and the device 16 is tilted backwards about the pivot 18.

The boom 11 has four sections 1 to . telescopically engaged in sequence and mounted so as to be slidable relative to one another. The first section 1 carries the bracket 1. and the hydraulic manipulating unit 19. The second section 2 accommodates the cylinder 28 of a first hydraulic ram 29 extending longitudinally of the boom 11. The rear end of the cylinder 28 is fixedly mounted on the rear end of the second section 2 and its front end carries a bracket 31 which bears slidingly on the first section 1 via a roller 32. The rear end of the hollow ram piston 33 is fixedly mounted on the rear end of

- - - the third section 3, the ram 29 being operable (by hydraulic fluid supplied to a connector 3^ on the piston 33) to move the second section 2 between a fully retracted position (Fig. 1) and a fully extended position (Figs. 5 and 6) relative to the third section 3-

The first section 1 is moved between a fully retracted position (Fig. 1) and a fully extended position (Figs. 5 and 6) relative to the second section 2 (in synchronism with the movement of the second section 2 relative to the third section 3) by a synchronising arrangement (Fig. 2) comprising a chain 3- (or other flexible element), which passes round a pulley 37 mounted on the bracket 31 and which has one end fixed to an anchorage 38 at the rear end of the third section 3 and the other end fixed to an anchorage 39 at the rear end of the section section 2, and a chain .0, which passes round a pulley -1 mounted on the rear end of the second section 2 and which has one end fixed to the anchorage 39 and the other end fixed to an anchorage .2 the front end of the third section 3.

A second hydraulic ram .3, extending longitudinally of the boom 11, has a cylinder -. fixed on the outside of the fourth section . of the boom 11 and has a piston .6 whose front end is connected to an external lug .7 at the front end of the third section 3- The ram .3 is operable (by hydraulic fluid supplied from a hydraulic control unit - not shown - to the cylinder .4) to move the third section 3 relative to the fourth section .

between a fully retracted position (Figs. 1 and 5) and a fully extended position (Fig. 6).

The hydraulic manipulating unit 19 is supplied with hydraulic fluid in the following way (Fig. 3). The ram 21 is connected by a hose .8 to the front end of a fixed pipe -9 extending along the first section 1 of the boom 11. A first rolling hose 51 communicates between the rear end of the pipe .9 and a first connector 52 mounted at the front end of the third section 3- A second rolling hose 53 communicates between the first connector 52 and a second connector 5^ mounted near the front end of the fourth section .. The second connector 5 ~i is connected to a pipe 56 which is connected in turn to the hydraulic control unit (not shown). The hoses 51,53 _? which roll between U-shaped and J-shaped configurations as the boom 11 is extended and retracted, are of sufficient length to allow full extension of the boom.

A third rolling hose 57 communicates between the connector 3*1 of the first ram 29 and a third connector 58 at the front end of the fourth section of the boom 11. The connector 58 is connected to a pipe 59 which is connected in turn to the hydraulic control unit (not shown).

The hydraulic control unit is operable to move the load bearing device 16 across the entire range of positions indicated in Figure 7. In particular the second ram .3 is only operable to extend the third section 3 if the first ram 29 is fully extended and the angle of elevation of the boom 11 is below an upper

limit. The manipulating ram 21 is controlled by the hydraulic control unit in dependence on the angle of elevation of the boom 11 so that the fork 17 is kept level.

The fully retracted boom 11 may have an overall length of about 6 m. When the first ram 29 is fully extended (Fig. 5) the boom length L may be about 13 m. When, in addition, the second ram -3 is fully extended (Fig. 6) the boom length L_ may be about 16 m.