GB1253815A - Improvements relating to derrick cranes and like derrick hoists - Google Patents

Abstract

1,253,815. Telescopic jib cranes. W. F. VONK. 25 Nov., 1968 [28 Nov., 1967], No. 54144/67. Heading B8B. A crane includes a derricking jib 3 of four telescoping sections 21, 22, 23, 24, of successively increased square or triangular cross-sections, with a jib extension cable 30 to vary the jib length. As shown, the derricking cable comprises a fixed length 12 extending between the top of the jib 3 and a pulley 13, and a variable length portion 10 including a cable 14 passing over pulleys 13, 15, 42 and jib-telescoping winch 40 to become integral with the jib extension cable 30. The jib 3 may be raised or lowered by operating a derrick winch 17 to take in or pay out cable 16 attached at one end to the pulley 15, the three runs of the cable 14 between the pulleys 13, 15 giving a mechanical advantage. The jib 3 may be extended or contracted by operating the winch 40, the cable 30 between adjacent jib sections, e.g. sections 23, 24 as shown in Fig. 2, passing around pulleys 31 to 35, of which 32, 35 are fixed to the section 24 and 31, 33, 34 are attached to the section 23. Thus, if the cable 30 is taken up the three runs of cable respectively between pulleys 35, 34; 33, 32 and 32, 31 will all be shortened giving a mechanical advantage. As the cables 30 and 14 are integral the jib 3 may thus be extended or contracted by the winch 40, the change in length of the cable 30 being substantially commensurate with the change in length of the cable 14 without the necessity of operating the derricking winch 17.