Abstract: In a tunneling machine including a hollow shield, a non-rotatable outer housing mounted in the shield for longitudinal movement, and inner housing rotatably mounted within the outer housing, an excavator including a boom and bucket pivotally mounted on the forward end of the inner housing, and a boom cylinder having a forward portion pivotally engaged with the boom and a rear portion mounted at the rearward portion of the inner housing.

Abstract: The articulated boom-dipper-bucket assembly is utilized in a tunnel boring machine of the type which includes a hollow cylindrical body with a front circular cutting edge and a central axis on which an excavator including the assembly is positioned. The assembly includes a base having a front face facing axially of the machine and being mounted on a bulkhead having siderails which are received in channels fixed to the body and extending parallel to the central axis. A piston and cylinder mechanism is associated with the bulkhead for reciprocating same in a direction parallel to the central axis. The assembly further includes a boom having one end pivotally mounted to the front face of the base at one side thereof and a second end positioned outwardly from the base, an elongate dipper member pivotally mounted at a first inner end to the second outer end of the boom, and a bucket-scoop having an inner edge and an outer cutting edge and being pivotally mounted to a second outer end of the dipper member.