GB1375569A - - Google Patents

Abstract

1375569 Slewable lifting device MATTERSON Ltd 24 May 1972 [26 May 1971] 17219/71 Heading B8H A lifting device comprises a telescopic pillar 22 and a telescopic cantilever lifting arm 58 mounted on the upper section 54 of the pillar for vertical and rotary movement therewith. The pillar comprises a lower section 24 mounted on a base 20 and closed at its upper end by a plate 36 with a central aperture and a circular array of ports 40 closed by a valve member 46 mounted within the central aperture. A spindle 76 passes through the valve member and is secured at one end to the upper end plate 74 of the upper sections 54 whereby, when compressed air is fed into the upper section causing the same to rise, upon said upper section reaching a predetermined height the spindle lifts the valve member 46 to uncover the ports 40 and thereby prevent the upper section rising further. The upper and lower section having bearing sleeves 64 located therebetween to allow relative rotary motion therebetween. The lifting arm comprises a rear section 96 fixed to the pillar, and an intermediate section 102 movably received within one end of the rear section and mounting a pair of rollers 112, 130 which respectively engaged the upper and lower surfaces of the rear section. Bolts (120), (132), Fig. 5 (not shown), which secure the respective shafts 116, 124 for the rollers 112, 130, have heads which bear on the sides of the rear section to centralize the intermediate section within the rear section. A front section 104 of the boom is similarly mounted within the intermediate section by rollers 140, 150 and bolts (142), (148) Figs. 7, 8 (not shown), and mounts a loop 212 by which articles may be secured to the lifting arm. A pneumatic ram 106 is mounted parallel to the lifting arm and is connected between the rear section and the intermediate section to effect movement of the intermediate section relative to the rear section. A flat metal strip 160 secured at one end to the rear section, by a tensioning bolt 162, passes over an idler wheel 164 and is secured at its other end to the rear end of the front section by a bolt 166. A further metal strip 168 secured by a bolt 170 to the rear section passes over a roller 172 mounted on the rear of the intermediate section and is secured at its other end to the rear end of the front section. The strips ensure that movement of the intermediate section results in corresponding movement of the front section. A pair of valves 180, 182 respectively controlling the supply of air to the ram 106 and the upper section of the pillar are controlled by respective control rods 188, 190 coupled to a control lever 200 by a control box 192 mounted at the outer end of the intermediate section of the boom; whereby vertical movement of the lever results only in movement of the control rod 190 and hence vertical movement of the lifting arm and horizontal movement of the lever results only in movement of the control rod 188 and hence horizontal movement of the lifting arm. Rotation of the arm is effected by manual effect.