Patent ID: 9404342
Filing Date: 2016-08-02
CPC Classification: E21B,Y10T

Claim Text:
1. A downhole percussion tool, comprising: a casing comprising a top end, a bottom end, and a casing passageway extending longitudinally from the top end to the bottom end; a top sub comprising a top sub passageway extending longitudinally therethrough and coupled to the top end of the casing; a drive sub coupled to the bottom end of the casing; a mandrel comprising a mandrel passageway extending longitudinally therethrough, the mandrel being supported within a lower portion of the casing and extending through the drive sub; a feed tube disposed within the casing passageway and comprising an inner wall defining a central channel extending the length of the feed tube, the central channel in fluid communication with the top sub passageway and the mandrel passageway; a choke coupled to a top end of the feed tube and comprising a choke passageway restricting the flow of a fluid from the top sub passageway through the central channel; and a check valve positioned in fluid communication with the choke, wherein the choke is accessible from the top sub through the top sub passageway without dismantling the top sub from the casing.