GB1287788A - Automatic control of the path of the end of the boom of a luffing crane - Google Patents

Abstract

1287788 Hydraulic circuits HOPPER Inc 21 Nov 1969 [27 Nov 1968] 57177/69 Heading F1P [Also in Division B8] - Fig. 1 -shows a crane with an inner boom 13 pivotally mounted at 14 on a base 10 on a horizontal bearing 12. An outer boom 15 is pivoted at 16 to the inner boom 13. The inner boom 13 is pivoted with respect to the base by an hydraulic cylinder 17 and the outer boom is pivoted with respect to the inner boom 13 by an hydraulic cylinder 22. As shown in the hydraulic circuit in Fig. 6 the cylinders 17, 22 are respectively independently operable by manually operated valves 44, 45. Operation of manually operable level buffing valve 42, e. g. to the right as shown, connects pressurized line 77 from pump 37 to lines 78, 55 and thus to port 56. Back pressure in the line 77 acts through lines 62, 61, 78 to cause pilot valve 79 to connect line 63 to line 74. The back pressure in line 55 acts through line 60 to open check valve 59. Accordingly, hydraulic fluid passes from cylinder 17 to cylinder 22 through port 57, line 63, valve 79, line 74 and port 71. The cylinder 17, 22 are so proportioned that they require the same volume of fluid during their respective strokes. The outer end of the outer boom 15 moves in an approximation to a horizontal straight line, load supporting hook 31 following path 81. A more exact horizontal line may be achieved by using a cam 84 fixed to the boom 13 and a follower roller 85 mounted on a rod 86 of an hydraulic cylinder 87 connected by a line 87 to the line 74. The varying volume of fluid in the cylinder 87 causes variations in the relative movement of piston rods 17r, 22r minimizing deviation of the path of the hook 31 from a true horizontal line. Inclined buffing can be achieved by tilting the bore 10. In a modification, Fig. 3 (not shown) an outer boom 15α is provided with a teles copic extension member (100). In the embodiment shown in Fig. 4 an inner boom 13b is buffed by a cylinder 17b and an outer, telescopic boom 15b is extended and retracted by a cylinder 22b. In this case approximate level-buffing of the load is shown by line "C".