Importance

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Abstract

A rotary excavating head is provided with a plurality of peripherally spaced tool holders supporting respective picks, each pick having a shank which is rotatable about its own axis and limitedly shiftable within a socket formed by the respective tool holder. A space of variable volume, formed between the shank end and the bottom of the socket, communicates via a check valve with a source of water whose supply pressure urges the pick outward, this space opening onto a restricted passage that terminates at a nozzle through which the water is sprinkled onto a mine face or tunnel wall attacked by the head when the respective pick is forced back against the water pressure by its encounter with the mineral matter to be fragmented. The restricted passage may include a pressure-relief valve; the nozzle may be constituted by a narrow annular clearance separating the shank of the pick from the cylindrical wall of the socket.

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First Claim