Shield for driving tunnels into unstable rock strata - has vertically pivoting spring loaded platforms for cut rock attached to horizontal knives

摘要

Shield for driving tunnels in loose and unstable rock strata includes a knife ring with vertically and horizontally projecting knives for breaking the rock and with horizontal platforms positioned against the horizontal knives. The platforms are so mounted that they change their position in a vertical plane to assume a position in which accumulated rock is removed from their surface. Each platform (7) is so preloaded by a spring force that when loaded with the cut rock it tips downwards in a vertical plane. With a certain weight of rock removed from the platform during the tipping movement the platform is returned by the spring force in its original horizontal position. The platform (7) is preloaded by leaf spring (14) attached at one end to the horizontal knife (5) to pivot in vertical plane and carrying a roller (15) at its other free end which is in contact with the platform (7) during its tipping movement. The middle part of the leaf spring is supported by a rod attached to the horizontal knife which limits the spring movement in the vertical plane.