A story in the Globe and Mail this week reported on a project to harvest dead trees, including valuable teak and mahogany, from a man-made lake in Ghana. The total value of the wood is estimated at up to $3 billion. This isn't the first time that entrepreneurs have proposed recovering wood from the bottom of lakes and rivers. By some estimates, millions of logs were lost in North American rivers during log drives in the last century. Several small-scale recovery projects in BC and the State of Maine are underway. It made me wonder if anyone had patented technology for underwater logging.
Patents related to forestry are classified in ECLA classification A01G23. So a logical esp@cenet search strategy might be to combine A01G23 with the keywords "underwater" OR "submerg*". This retrieves six documents, including three by inventor Cyril Burton of Castlegar, BC. Burton's earliest patent was issued in 1973 for an "Underwater Saw for Stump and Tree Removal"; his most recent, a "Submersible Logging Device", was issued in 1999. A Canadian application published in 2003 (CA2635367) describes a "method and apparatus for underwater tree cutting and retrieval" that involves a remote-controlled submarine and inflatable airbags.