Seabed Plow Chassis Capable of Over-the-Stern Release and Retrieval in Any of Boulder Clearing, Trenching and Backfill Configurations

Abstract

A seabed plow capable of over-the-stern release and retrieval is usable in any of boulder clearing, trench cutting and backfill modes. In its boulder clearing mode, the plow uses its skid in torquing configuration followed by moldboards to push boulders out of the path to be trenched. In the trench cutting mode, the plow uses the skid in the same configuration with its share and moldboards for initial trench depth and the same share and moldboards with moldboard extensions for increasing trench depth in subsequent passes. In the backfill mode, the plow uses its skid in trench-straddling configuration following a blade with a passage designed to discharge fragmented spoil directly onto the pipe being covered. Thus, a single plow can be reconfigured for all modes for release and retrieval to and from a relatively small vessel without use of heavy lifting equipment.

What is claimed is: 
     
         1 . A seabed-plow chassis comprising:
 an elongated member;   one end of said elongated member being adapted for mounting a skid thereon for supporting said one end of said elongated member above the seabed; and   another end of said elongated member being adapted for mounting thereon a tool comprising moldboards for clearing boulders pushed by the skid outward of a path traveled by the skid further outward from its path as the skid leads the moldboards along the seabed.   
     
     
         2 . A seabed-plow chassis according to  claim 1 , said elongated member having a first transition surface configured to extend between the skid and the tool, said first transition surface being contoured to pivot about a fulcrum on a stern of a vessel contacting said first transition surface as a plow crosses the fulcrum during release of the plow from the vessel into the sea and during retrieval of the plow from the sea onto the vessel. 
     
     
         3 . A seabed-plow chassis according to  claim 2 , a shape of said first transition surface and a weight of said elongated member being coordinated to resist roll of said chassis about a longitudinal axis of said elongated member. 
     
     
         4 . A seabed-plow chassis according to  claim 2 , vertical longitudinal cross-sections of said first transition surface being concave. 
     
     
         5 . A seabed-plow chassis according to  claim 2 , the fulcrum being a roller and paths defined by continuous symmetrically opposite points of said first transition surface being contoured to maintain contact with the roller as the plow crosses the roller. 
     
     
         6 . A seabed-plow chassis according to  claim 1 , said another end of said elongated member being further adapted for mounting thereon a selected one of (a) said tool comprising moldboards and (b) a tool comprising a plow share and moldboards for sequentially cutting and moving outward and upward, respectively, spoil from the seabed to create a trench as the skid leads the plow share and moldboards along the seabed. 
     
     
         7 . A seabed plow chassis according to  claim 6 , said elongated member further having a second transition surface configured to extend between said skid and said tool comprising a plow share and moldboards, said second transition surface being contoured to pivot about the fulcrum on the stern of the vessel contacting said second transition surface as the plow crosses the fulcrum during release of the plow into the sea from the vessel and during retrieval of the plow from the sea onto the vessel. 
     
     
         8 . A seabed-plow chassis according to  claim 7  a shape of said second transition surface and said weight of said elongated member being coordinated to resist roll of the plow about a longitudinal axis of said elongated member. 
     
     
         9 . A seabed-plow chassis according to  claim 7 , the fulcrum being a roller and paths defined by continuous symmetrically opposite points of said second transition surface being contoured to maintain contact with the roller as the plow crosses the roller. 
     
     
         10 . A seabed-plow chassis according to  claim 1 , said another end of said elongated member being further adapted for mounting thereon a selected one of (a) said tool comprising moldboards and (b) a tool comprising a blade and moldboards cooperating as the blade and moldboards lead the skid along the seabed to sequentially collect, funnel inward and release downward into the trench spoil lying outside of the trench. 
     
     
         11 . A seabed-plow chassis according to  claim 10 , said elongated member having a first transition surface configured to extend between said skid and any selected one of (a) said tool comprising moldboards and (b) said tool comprising a blade and moldboards, said first transition surface being contoured to pivot about the fulcrum on the stern of the vessel contacting said first transition surface as the plow crosses the fulcrum during release of the plow from the vessel into the sea and during retrieval of the plow from the sea onto the vessel. 
     
     
         12 . A seabed-plow chassis according to  claim 11 , a shape of said first transition surface and a weight of said elongated member being coordinated to resist roll of the plow about a longitudinal axis of said elongated member. 
     
     
         13 . A seabed-plow chassis according to  claim 11 , longitudinal vertical cross-sections of said first transition surface being concave. 
     
     
         14 . A seabed-plow chassis according to  claim 11 , the fulcrum being a roller and paths defined by continuous symmetrically opposite points of said first transition surface being contoured to maintain contact with the roller as the plow crosses the roller. 
     
     
         15 . A-seabed plow chassis according to  claim 1 , said another end of said elongated member being further adapted for mounting thereon a selected one of (a) said tool comprising moldboards, (b) a tool comprising a blade and moldboards cooperating as the blade and moldboards lead the skid along the seabed to sequentially collect, funnel inward and release downward into the trench spoil lying outside of the trench and (c) a tool comprising a plow share and moldboards for sequentially cutting and moving outward and upward, respectively, spoil from the seabed to create a trench as the skid leads the plow share and moldboards along the seabed. 
     
     
         16 . A seabed-plow chassis according to  claim 15 , said elongated member having a first transition surface configured to extend between said skid and any selected one of (a) said tool comprising moldboards and (b) said tool comprising a blade and moldboards and a second transition surface configured to extend between said skid and said tool comprising a plow share and moldboards, said first and second transition surfaces being contoured to pivot about a fulcrum on a stern of a vessel contacting one of said first and second transition surfaces as the plow crosses the fulcrum during release of the plow from the vessel into the sea and during retrieval of the plow from the sea onto the vessel. 
     
     
         17 . A seabed-plow chassis according to  claim 16 , said shapes of each of said first and second transition surfaces and said weight of said elongated member being coordinated to resist roll of the plow about a longitudinal axis of said elongated member. 
     
     
         18 . A seabed-plow chassis according to  claim 16 , longitudinal vertical cross-sections of each of said first and second transition surfaces being concave. 
     
     
         19 . A seabed-plow chassis according to  claim 16 , the fulcrum being a roller and paths defined by continuous symmetrically opposite points of each of said first and second transition surfaces being contoured to maintain contact with the roller as the plow crosses the roller.