Patent ID: 8684851

Claim:
A sub tool for use with a top drive of a drilling rig, said sub tool comprising: (a) a housing having an upper end, a lower end, and a housing bore extending between an upper-end opening and a lower-end opening, and defining upper, middle, and lower intervals; (b) an upper member having an upper end, a lower end, and an upper-member bore having a cylindrical lower interval, and said upper member comprising: b.1 an upper section having a cylindrical outer surface slidably disposed within the upper-end opening of the housing; b.2 a middle section having a cylindrical outer surface in sealingly slidable engagement with the middle interval of the housing bore; and b.3 a lower section having a generally cylindrical outer surface with longitudinal splines; (c) a lower member having an upper end, a lower end, and a lower-member bore extending between the upper and lower ends of the lower member, and defining upper, middle, and lower intervals, with the upper interval of the lower-member bore having longitudinal splines matingly engageable with the splines on the lower section of the upper member; and wherein an upward-facing annular shoulder is formed at the juncture of the lower and middle intervals of the lower-member bore; and (d) an elongate stinger having an upper end, a lower end, and a cylindrical outer surface, said lower end of the stinger being sealingly and coaxially mounted to the annular shoulder on the lower member; wherein: (e) an upper portion of the lower member is disposed within and fixedly mounted to the lower interval of the housing bore such that: e.1 the upper end of the stinger is slidably and sealingly disposed within the lower interval of the upper-member bore; and e.2 the splines on the upper interval of the lower-member bore slidably engage the splines on the lower section of the upper member; and (f) the sub tool has: f.1 an upper annular chamber defined by the upper interval of the housing bore, the middle section of the upper member; the upper section of the upper member, and the middle interval of the housing bore; f.2 a middle annular chamber defined by the lower section of upper member, the middle section of the upper member, the upper end of the lower member, and the middle interval of the housing bore; and f.3 a lower annular chamber defined by the lower end of the upper member, the shoulder on the lower member, the middle interval of the lower-member bore, and the outer surface of the stinger; with the volumes of the upper, middle, and lower annular chambers being variable according to the axial position of the upper member; (g) the upper annular chamber is in fluid communication with the exterior of the housing; (h) the middle and lower annular chambers are in fluid communication; and (i) the sub tool includes regulator means for regulating pressure in the middle and lower annular chambers.