Nozzle assembly for an earth boring drill bit

A nozzle assembly for an earth boring drill bit of the type comprising a bit body having a threaded pin at its upper end adapted to be detachably secured to a drill string, and passaging therein for receiving drilling fluid under pressure from the drill string extending from an opening in the pin down to a nozzle bore in the lower end of the bit positioned closely adjacent to the well bore bottom when the bit is in engagement therewith for exit of the drilling fluid from the bit, the nozzle bore comprising inner and outer portions of generally circular section in coaxial alignment with each other, the outer portion extending up into the bit body from the underside thereof and being defined in part by a threaded side wall, the inner portion of the nozzle bore being defined in part by an inner end wall and carrying a seal member;

• said nozzle assembly comprising:
• a generally cylindrical nozzle member of an abrasion and erosion resistant material selected from a plurality of such members each being of the same outer diameter but having passaging therein of different sectional areas, the passaging extending generally along the central longitudinal axis of the respective nozzle member and tapering from a relatively large opening in one end thereof, constituting its inner end with respect to the nozzle bore, to a relatively small opening in its other end, constituting its outer end, the nozzle member being adapted to be fitted in the inner portion of the nozzle bore in sealing relationship with the seal member, thereby forming a first seal for the nozzle assembly;
• and
• a locknut separate from the nozzle member, for detachably securing the nozzle member in the nozzle bore formed at least in part of an abrasion and erosion resistant metal and having a body portion and a sleeve portion, said body portion including a first end, constituting its inner end, engageably with the outer end of the nozzle member, and a second end, constituting its outer end, generally closing the opening to the nozzle bore for preventing erosion of the bit body and the nozzle assembly by drilling fluid exiting the nozzle assembly and splashing back toward the assembly after impinging the well bore bottom;
• said sleeve portion extending inwardly beyond the inner end of said body portion to form a recess to receive the outer end of the nozzle member and including an outer side wall threadingly engageable with the threaded side wall of the nozzle bore for forming a second seal for the nozzle assembly, and an aperture therethrough in alignment with the passage in the nozzle member of larger sectional area than the opening in the outer face of the nozzle member for enabling a stream of high-velocity drilling fluid from the nozzle member to flow therethrough while acting to diffuse the stream, with the aperture for at least a substantial portion of its length being so configured in section as to receive a wrench for turning the locknut in one direction to thread it into the nozzle bore and in the other direction to remove it.