GB1116101A - Extensible load lifting masts - Google Patents

Abstract

1,116,101. Lift trucks. CONVEYANCER FORK TRUCKS Ltd. 31 May, 1966 [29 April, 1965], No. 18101/65. Heading B8H. An extensible load-lifting mast 2 fitted to an industrial truck 1, by a tilting device comprises a generally upright outer mast member 3 with an inner mast member 4 slidedable within outwardly facing channellike openings in the outer mast member 3. The outer mast member 3 comprises two similar plates 9, 10, the sides of which are turned over to form flanges 11, Side plates 13, 14 are secured to the front and rear plates 9, 10 at stepped portions 12. The inner mast member 4 comprises two outwardly facing channel members 33, 34 secured at their upper ends by a capping plate 50, with a central cut-out portion 52 and two holes 50<SP>1</SP>. A load-lifting carriage 5 has a plate 35 with bearing roller assemblies 35<SP>1</SP>, secured to the plate 35 which assemblies 35<SP>1</SP> have upper and lower rollers 38 respectively bearing on the front and rear inner faces of the channel members 33, 34 and upper and lower rollers 39, 39<SP>1</SP> arranged in pairs to engage the outer side faces of the channel members 33, 34. The pairs of rollers 39<SP>1</SP> are mounted on eccentric spindles 43<SP>1</SP> to provide adjustment on assembly to eliminate excessive clearances between the outer side faces of the channel members 33, 34 and the rollers 39, 39<SP>1</SP>. A pulley 46 is mounted in a yoke 48 on a piston. rod 61 of a lift jack 6. A lifting chain (not shown) passes over the pulley 46 and has one end connected to the top of the cylinder of the lift jack 6 and the other end connected to the lift carriage 5. Application of hydraulic pressure to the jack 6 initially lifts the carriage 5 at twice the speed of jack extension. When the carriage 5 is lifted to the top of the channel members 33, 34, tapered pegs 35A on the roller assemblies 35<SP>1</SP> enter the holes 50<SP>1</SP> and are wedged therein, continued extension of the jack 6 lifting the channel members 33, 34. On release of pressure in the jack 6 the weight of the carriage 5 causes the jack 6 to close, allowing descent of the carriage 5, which pulls the inner mast member 4 with it due to the wedging action of the pegs 35A in the holes 50<SP>1</SP>. When the inner mast 4 is fully down, the taper angle of the pegs 35A is such as to allow the weight of the carriage to cause the pegs 35A to be released from the holes 50<SP>1</SP>. Alternatively the pegs 35A and holes 50<SP>1</SP> are omitted being replaced by an automatic latching rrangement (not shown). The mast tilting mechanism, Figs. 13, 14 (not shown), incorporates means for taking off torsion loads in the form of tubes 59 sliding in guides having trunnions mounted on brackets 62. In a modification the yoke (48) has sleeves (73), Figs. 15 to 17 (not shown), attached to it, which sleeves (73) slide in slots (69) in the channel members 33, 34 so that when the jack (6) extends the pulley (46) moves upwardly a short distance, lifting the carriage 5 alone, via the chain, until the sleeves (73) abut the top of the slots (69), whereupon continued extension of the jack (6) also lifts the inner mast member 4. The mast may be used with an overhead travelling crane (not shown).