Machine for digging a trench beneath a submerged pipeline

An apparatus for digging a trench beneath a submerged pipeline comprising:

• a pair of substantially parallel spaced carrying axles,
• a fixed hood mounted at each end to the carrying axles, said hood having a circular cross-section open in the bottom portion and having circumferential guideways of a dovetailed configuration and axial guideways of a dovetailed configuration,
• first hydraulic drive means,
• a mantle having a larger sector engaging the circumferential guideways and coupled to the drive means for rotation about the hood and a narrower sector mounted atop the hood in the axial guideways,
• hydraulic drive means mounted on the hood to drive the narrower mantle sector axially to form a closed loop with the larger sector surrounding the pipeline, said sectors having front circular guides of a dovetail configuration.
• a disc engaging the front circular guides and having digging bits mounted thereon and a toothed portion thereabout.
• hydraulic drive means having a pinion engaging the toothed portion of the disc for rotational motion cuasing the digging bits to engage the trench,
• clamping means mounted on an intermediate portion of the axles to mount the apparatus to the submerged pipeline, and,
• a compressed air reservoir coupled to the axles and maintaining the apparatus at the desired level for digging a trench beneath the submerged pipeline.