Improvements in or relating to locking devices for lifting platforms

摘要

1,020,561. Catch gear for load lifting platforms. LEIPZIGER STAHLBAU UND VERZINKEREI VEB. Aug. 15, 1962, No.-31320/62. Headings B8H and B8L. A lifting platform 1, adapted to be raised by projections 30 on rods 7 suspended from a cross-member 29 on the piston rod 281 of a hydraulic ram 28, is supported in its uppermost position, Fig. 1, by pawls 2, 21 engaging notches 6, 61 in the platform and may be supported in other positions by engagement of the pawls with projections on the rods 7. Further pawls 23, 231 are adapted to engage notches 24, 241 in the platform in its uppermost position if the pawls 2, 21 fail to function correctly. The pawls 2, 21 are mounted, together with cams 3, 31 and toothed sectors 4 on rotatable shafts 5, 51 and, in their inoperative position shown in Fig. 2, a pressurized ram 8 maintains, through a bell-crank lever 15 and link 14, a Z-shaped member 13, pivotally mounted at 131, in the position shown in which it prevents rotation of the cams 3, 31 through the action of a link 12 and a weight 9 on a lever 10 which tends to rotate in a counterclockwise direction about a stop 11 on the platform 1 when the platform is in its uppermost position. On releasing the pressure in the ram 8, the lever 10 is free to pivot about the stop 11 and to rotate the pawls 2, 21 into engagement with the notches 6, 61. The pawls are disengaged from the notches by applying pressure to the ram 8. Simultaneously with the operation of the pawls 2, 21, pawls 23, 231 are swung outwardly into notches 24, 241 on the platform by means of a weight 17, a bell-crank lever 18 and a rod 19 which acts on levers 20, 21, Fig. 5, and drivers 22. A space is provided between the pawls 23, 231 and the notches 24, 241 whereby the pawls are effective only on failure of the pawls 2, 21. The pawls 23, 231 are released from the notches 24, 241 by applying pressure to a hydraulic ram.25. In positions other than the topmost position, the platform 1 is supported by the rods 7 and when the platform is lowered, together with the stop 11, the weight 9 causes a lever 101 to bear against a fixed stop 16, and rotates the cam 3 and pawl 2 in a counterclockwise direction to engage the pawl with the rod 7, provided the pressure is released from the ram 8. In operation, in the event of a failure in a ram 28, when the ram is lowered in relation to other lifting rams, the entire installation is halted through electrical control devices (not shown), whereby the ram 8 is automatically relieved of pressure and the weight 9 causes locking of the pawls 2, 21 with the rods 7.