Patent GB-642593-A (GB)
Title: Improvements in or relating to a tractor mounted mast and a boom assembly
IPC: B66C23/74
Filed: 1947-06-24
Abstract: 642,593. Portable cranes. HYSTER CO. June 24, 1947, No. 16641. Convention date, Nov. 1, 1945. [Class 78 (iv)] [Also in Group XXI] A crane adapted to be detachably mounted on a tractor having endless flexibly mounted tracks, is of the kind provided with a crane boom mounted for slewing about an axis placed above a hoist unit, and having a mast mounted for swinging about a horizontal axis on the tractor and connected by backstay means to the track units and is characterized by the provision of a fairlead on the mast mounted substantially in alignment with the vertical axis and adapted to receive both the hoist cable and a boom suspension cable. The tractor 11, which is provided with a bulldozing blade 15 at the front is equipped at the rear with a hoist unit 26 which includes an operating seat 36 and a bull wheel 25, on which is pivotally mounted at 40 a boom 24. A mast 20 is pivotally supported at 32 adjacent the hoist unit and when erected is positioned with a fairlead 23 vertically above the hoist unit. The mast is retained in position by two back stays 21 of adjustable operative lengths whose lower ends are pivoted at 34 to brackets 33 on the endless track frames. The hoist unit comprises two drums 51 and 52, Fig. 3, from which run a hoist cable 46 and a second cable 47. The second cable may be used as a dragline scraper cable, Fig. 2, or for luffing when ordinary hoisting is carried out. In either case both cables pass over sheaves in the fairlead 23 but, when scraping, cable 47 passes down over a sheave 43 and fairlead rollers 44 in the boom 24. Luffing is in this case carried out by a hand winch 56 on the mast and the luffing cable 45, is preferably passed from the winch first down to a sheave 50, Fig. 3, in the hoist unit and then vertically up to fairlead 23. Fig. 5 shows the method of erecting the boom, which is detachable in three sections for transport, mast 20 and backstays 21 being also detachable for transport. The boom joints comprise brackets through which pins 61 are thrust. One pin of the first joint is left out for assembly allowing the boom to be dragged along the ground and the lower end to be positioned for engaging by operation of the hand winch 56 hauling a cable attached to one eye 63. The correct positioning is assured by providing a pair of hook members 42 adapted to engage a pivot 41 on the hoist unit. The cable from winch 56 is then removed to a position further along the boom to raise the open joint when the second pin 61 may be secured. The luffing cable 45 may then be passed over fairlead 23 and coupled to the winch or hoist drum 52 to raise the boom until openings 65 and 66 coincide when the main support pin can be inserted. For transport it is unnecessary to dismantle the boom and mast completely if a suitable lorry is available, since the boom may be lowered down on to a support on the lorry and the backstays 21 may be disconnected from the mast so that all can be laid flat on top of the boom. Alternatively, struts may be provided between the partly laid down backstays and the tractor frame so that the backstays act as a mast of low height to support the mast 20 by means of a cable joining them, the partly laid down mast in turn supporting the boom which now need not be supported by the lorry. Specification 592,499 is referred to.