Apparatus for use in subterranean excavation

Claim 1

In an apparatus for excavation and lining of subterranean tunnels including a shield assembly having multiple sections including a forward section of rectangular configuration in cross section including a top wall, right angle side walls and a base wall, and terminating forwardly in leading edges, an inclined plate mounted on the base wall rearwardly of the leading edge of the same and including an elevated discharge end to direct material rearwardly from the open end of said forward section, and conveyor means operatively associated with the elevated discharge end of said inclined plate to further move excavated material rearwardly within said apparatus, an excavation assembly within the shield, including digging apparatus movably mounted for excavation forwardly of the shield, and means for advancing the shield comprising a jack system contained within the shield and effective to force movement of the shield in one direction, the improvement comprising: a shield upper bonnet of inverted U-shape including a roof plate overlying completely the top wall of the shield and side plates depending therefrom and overlying the side walls of said shield forward section, the roof plate having a sharp leading Edge and a top angle plate extending inwardly from said leading edge, side angle plates on the leading edge of said side plates, each of said forward section side walls having a longitudinally extending slot therein and the top wall having a pair of laterally spaced slots formed therein, the respective slots being laterally coaligned and being coextensive in length, lugs extending from horizontal and vertical positions of the structural members and slidably engaged in respective slots of said shield top and side wall to captively hold said bonnet relative to said shield but allow longitudinal sliding of the same, a pair of push brackets on the upper bonnet, each comprising an L-shaped structural member with a horizontal portion and a vertical portion, the horizontal portion being secured to the top angle plate and the vertical portion being secured to the respective side angle plate, said shield including intermediate bulkheads and extensible and retractable hydraulic cylinders secured to the intermediate bulkhead and to the push bracket to effect advance of the bonnet under control of said lugs within said slot during extension of said cylinder.