Abstract: A rubber tube for dredging work embedded in and used in a pipe-line used for dredging work in the sea or river. This rubber tube has a tubular body made of rubber having a plurality of strengthening clothes embedded therein, and a plurality of metal rings axially arranged in a suitably spaced relation which are embedded in an inner peripheral surface of said tubular body and which inner peripheral surface forms a part of the inner peripheral surface of said tubular body. The metal rings have their joined surface with the tubular body placed in parallel to the axis and axial both ends thereof made thin in wall-thickness. Thereby, a contact area between the metal ring and the tubular body is increased to strengthen a bonding force and minimize a peeling off of the joined surface between both ends of the metal rings and the tubular body.

Abstract: In an apparatus in which cylindrical articles violently collide with one another as they roll down on the inclined skid rails, from the inlet to the outlet thereof, a control rail covered thick with a soft and elastic foamed substance is located. The control rail is positioned side by side in parallel to the skid rails, and frequently reciprocated vertically to brake the articles as they move downwards over the skid rails so that the maximum rolling speed is sufficiently reduced for restricting the noise of collision below an allowable level.