DRILLING APPARATUS, PARTICULARLY WIRE LINE CORE DRILLING APPARATUS

摘要

This invention relates to a wire line core barrel inner tube assembly capable of travelling longitudinally within a drill string toward and away from a drill bit carried on the lower end of the string, the drill string having an annular landing shoulder therein. The inner tube assembly includes an elongated body having an annular landing shoulder adapted to co-operate with and seat on the landing shoulder of the drill string when in use. The body has a valve chamber defined therein and inlet and outlet ports leading from the valve chamber to the exterior of the body on opposite sides of the landing shoulder. These define a by-pass passage through which drilling liquid passing along the drill string must flow on its way toward the bit when the landing shoulder of said body is seated on the landing shoulder of the drill string. The valve chamber has a valve seat therein and a valve closure is located within the valve chamber. A biasing device urges the valve closure against the valve seat with a selected pre-loading force as to prevent flow of drilling liquid through the by-pass passage and toward the drill bit until the pressure differential across the valve closure is increased to a level sufficient to overcome the pre-loading force applied by the biasing device.