Patent ID: 6070678
Filing Date: 2000-06-06
Classification: E21B

Abstract:
A percussion bit assembly for connection to a drill string for earth boring operations comprising:a substantially tubular housing having a lower end portion defining an opening;a substantially tubular chuck member having upper and lower portions and upper and lower ends, the upper portion of the chuck member being mountable to the lower end portion of the housing;a percussion bit having a shank and a head, wherein at least a part of the shank is disposed within the chuck member and the head is disposed below the lower end of the chuck member, the shank including a radially extending shoulder having an outside diameter;a substantially tubular bit retainer supported by the chuck member and having upper and lower ends and interior and exterior surfaces, said interior surface disposed around the shoulder of the bit and around the lower portion of the chuck member, and with the lower end of the interior surface being spaced from the bit below said shoulder; andmeans insertable through at least two locations at the exterior surface of the lower end of the retainer into said space between the retainer and the bit, said means when inserted thereby defining opposed ledges situated between the retainer and the bit shank, whereby in the event of breakage of the bit shank above the bit shoulder, the shoulder is retained between the lower end of the chuck member and the ledges.