GB1356517A - Light weight telescoping boom - Google Patents

Abstract

1356517 Telescopic jib cranes RUSTON-BUCYRUS Ltd 17 Aug 1972 [7 Sept 1971] 38371/72 Heading B8B [Also in Divisions E1 and F1] A truck mounted crane comprises a telescopic four section boom 1, 2, 3, 4. A ram 7 extends the section 2 and has its cylinder end pinned near the inner end of section 1 and its rod pinned near the outer end of section 2. A ram 8 for .extending the section 3 is pinned at the inner end of section 2 and at the outer end of section 3 while a ram 9 for extending the section 4 is similarly arranged with respect to sections 3 and 4. A bar 10 at the outer end of section 2 supports the underside of section 3 while a bar 1 similarly supports section 4. The section 3 is provided at its inner end with downwardly extending feet 12 which straddle the ram 7 while riding along the floor of the section 2. The section 4 is similarly provided with feet 13 which slide on the floor of section 3. The rams 7, 8, 9 are extended by fluid pressure from a pump P under the control of flowdivider valves 20, 23 the former of which sends one third of the fluid to the ram 7 and twothirds of the fluid to valve 23 which divides the entering fluid equally between the rams 8, 9 thus ensuring synchronized extension of the jib sections 2, 3, 4. Retraction of the sections 2, 3, 4 is by a cable 14 from an hydraulically driven winch 15, the flow divider valves 20, 23 acting to re-combine the fluid flows to synchronize the retraction of the sections. If the rams 7, 8, 9 become desynchronized due, for example, to leakage then pressure relief valves 31 enable all the rams to be bottomed-out to resynchronize their operation.