GB1191395A - Improvements in or relating to Cranes. - Google Patents

Abstract

1,191,395. Jib cranes. JONES CRANES Ltd. 23 Jan., 1969, No. 3663/68. Heading B8B. [Also in Division F1] A crane jib assembly includes a jib with four telescopic sections 54 to 57 of rectangular crosssection. The end section 54 is pivotally secured through a pair of bushes 58 to brackets 52 on a crane body 51 mounted for slueing on a lorry (50), Fig. 1 (not shown). A telescopic ram with sections 1 to 4 is also pivoted to a bracket 52 on the crane body 51 and connected by a bush 38 and boss 34 to the upper end of the jib section 57. Pairs of tie-ropes 61 are connected between flange 7 of ram section 2 and the end of the jib section 55 adjacent the crane body 51, tie-ropes 62 being similarly connected between flange 6 of the ram section 3 and the end of the jib section 56. Application of hydraulic pressure (by means not shown) to the ram initially extends the ram section 2, owing to its larger larger effective area and with it the jib section 55 with the jib sections 56, 57 inside until stop 59 on the jib section 54 is contacted by abutment flange 60 on the jib section 55. The jib sections 56, 57 are similarly extended, in order, the stops 59 and abutments 60 limiting the jib extension to a predetermined maximum. The tie ropes 61, 62, owing to the continuing pressure in the ram, pre-tension the jib sections, such pretensioning being increased by the application of a longitudinal load on the jib since such a load increases the pressure in the ram, which may have an hydraulic accumulator. The jib is luffed by a derricking rope and has an adjustable buffer (67) to act as a back stop. A fixed jib extension (68) may be secured to the upper end of the jib section 57.