The field of the invention is submarine pipeline trenching apparatus.
Apparatus is presently known for digging a trench below a pipeline, examples of which are U.S. Pat. Nos. 3,429,131 and 3,429,132 granted to Charles F. Martin. With such prior patents it was necesary to pre-form or pre-dig a hole below the pipeline in the ocean bottom for receiving the cutter assembly or assemblies so that the apparatus could be mounted on the pipeline in its operable digging position. Additionally, difficulty was sometimes experienced in use due to shifting and other instability of the apparatus as it moved along the pipeline because of lateral bends and vertical undulations. Dragging of the lower ends of the cutters along the bottom of the trench often interfered with the cutting action and rapid longitudinal travel of the cutters relative to the pipeline.