Lock for securing covering grid of shaft - has rotating actuating knob on lock housing not accessible from outside

摘要

Vertical locking bar upper end is bent for hooking aweb of the grid. The lock cannot be released by reaching through grid opening with a tool. A lock (17) is held within protection housing (19) held firmly on shaft wall (10). The lock is actuated by rotating knob (21) for releasing the locking bar (13) whose lower end is held within housing. Upper end of this bar (13) clmps the grid firmly in position. The actuating knob has screwdriver slot and the knob must be rotated through more than half full turn so that it cannot be rotated by a tool passed through the grid.