Excavator for making a substantially vertical slot in the ground

A cutter assembly for an excavator for excavating a substantially vertical slot in the ground, said cutter assembly comprising:

• a frame;
• a substantially vertical planar support shield extending downwardly from said frame and consisting of a solid plate;
• a tubular housing fixed on said support shield and having an axis extending generally perpendicular to said support shield with respective tubular portions lying to opposite sides of a plane of said support shield;
• a respective cutting wheel surrounding each of said tubular portions so that said cutting wheels axially overlap said tubular portions and lie close to opposite sides of said shield, the thickness of said plate determining the axial spacing of said cutting wheels;
• respective annular covers on opposite axial ends of said housing for closing same;
• a respective hub on each of said cutting wheels extending axially into said housing through the respective cover;
• a common shaft engaged in both of said hubs for angularly coupling said hubs for joint rotation;
• respective bearing means journaling each hub in and on the respective cover;
• an internally toothed hollow wheel keyed to one of said hubs in said housing;
• a motor-support plate fixed in said housing between said portions in the plane of the support shield, said shaft passing with clearance through a hole in said motor-support plate;
• a plurality of drive motors mounted on said support plate, spaced around said axis and having respective drive gears meshing with said hollow wheel for driving same and thereby driving said cutting wheels, said bearing means including a conical bearing journaling each hub in the respective core, said shaft having splines on opposite ends and said hubs having splines interfitting with the splines of said ends of said shaft, said motors being hydraulic motors mounted on said motor-support plate and having shafts extending through and journaled in said motor-support plate and carrying said drive gears for meshing with said internally toothed hollow wheel on a side of said motor-support plate opposite that on which said motors are mounted.