HYDRAULICALLY OPERATED LOADING CRANE INCLUDING MEANS FOR LIMITTING THE MOMENT ARM LOADING OF THE BOOM THEREOF

摘要

1383586 Limiting moment arm load of crane booms HIAB-FOCO AB 28 April 1972 19767/72 Heading B8B A crane comprises a post 1 on which is pivotally mounted a loading boom 3 comprising inner and outer arm parts 4, 5, the arm part 4 being movable about pivot 2 by means of a ram 9. The arm part 5 is movable about pivot A by means of arm 12. The boom also includes an arm 6 in which a load hook 7 is mounted, this arm being movable by means of a ram 14, into and out of the arm 5. The rams 9,12, and 14, are connected respectively to operating valves 19- 21, each comprising an operating piston 28 movable in a valve housing 27 (Fig. 3) and having points of connection 31, 34, to the respective rams, and being in connection with an oil reservoir 17. In operation of the crane, if the liquid pressure in the line 22 to the ram 9 exceeds a predetermined, value, the pressure in the line 22 will rise, and the pressure in the line 23 willalso rise, and will propagate through a channel 51 in the piston 50 of a two way valve 24 causing the piston 50 to be displaced upwardly against the action of a biasing spring 60 allowing pressurized liquid to pass through line 25 to a cylinder 26 at the bottom of each valve 19-21. This results in the moving of a piston 45 upwardly to abut against and displace the oper ating piston 28 of the valves 19-21 from the position of Fig. 3 to that of Fig. 4 in which the valves are closed thus stopping the supply of oil to the cylinders 9, 12, and 14, thus stopping further increase in the value of the moment of loading. By the use of central levers (not shown), the pistons 28 may be moved to a position (Fig. 5) opposite to that shown in Fig. 3, in which supply of pressurized oil to the cylinders 9, 12, and 14, is in the opposite direction, thus retracting the loading beam 3 to decrease the moment of loading.