GB1360141A - Extendible boom - Google Patents

Abstract

1360141 Telescopic jib cranes NATIONAL CRANE CORP 29 Aug 1972 40043/72 Heading B8B [Also in Division E2] A telescopic boom with a winch 40 on its upper section 14 comprises a lower section 12 and sections 16, 18, 20. The boom is extended by a ram (28), Fig. 1 (not shown), and is provided with latch mechanisms 46 to ensure automatic, sequential extension and retraction of the sections. Each latch mechanism 46 includes a slide chamber 48 with a female latch member 50 in slide track 62 and additionally includes a male latch member or tang 52. As shown the sections are locked in their extended positions by end edges 70 of latch members 50 engaging in respective openings 90 covered by plates 92. When the boom is to be retracted the ram (28) is operated to retract moving section 14 to the left (as shown) so that its tang 52 enters the female latch member 50 in the slide chamber 48 attached to the section 20. Camming surface 74 on the member 50 is engaged by camming surface 86 on the tang 52 sliding the member 50, against the action of a friction bearing 80, out of the opening 90 to the dotted position shown so that sections 14 and 20 are locked together but are free to move jointly leftwise under the action of the ram (28). All the latch mechanisms 46 operate similarly. When the boom is extended the latch member 50 is forced into its associated opening 90 by the pulling force of the tang 52 acting on the latch member 50 through the oblique lateral walls of the slide track 62.