Shock absorbing system for suction dredgers

Claim 1

In a suction dredger having a suction pipe provided with a suction head which is adapted to be dragged along the bottom beneath a body of water, said suction head including a cutting tool pivotally mounted for movement from a cutting position to an inoperative position in response to a predetermined force exerted against the cutting tool, the improvement which comprises: piston/cylinder means for allowing said cutting tool rapidly to swing to said inoperative position upon compression thereof and slowly to return to said cutting position upon extension thereof, said means comprising a cylinder, a piston slidably received in said cylinder, and a piston rod connected to said piston and projecting from said cylinder, said piston separating the interior of said cylinder into a first fluid chamber and a second fluid chamber on opposite sides of said piston, the second fluid chamber being on the piston rod side of said piston, gas cushion means in said first chamber normally maintaining fluid pressure sufficient to extend said piston/cylinder means, passage means restricting flow of fluid from said second chamber to said first chamber to restrict the rate of extension of said piston/cylinder means, and means for by-passing said passage means to allow substantially unrestricted passage of fluid from said first chamber to said second chamber as said piston/cylinder means is compressed.