Kelly seal

摘要

An earth boring machine is shown with an improved kelly seal. The machine includes a hydraulic cylinder and a kelly rotatably carried within the cylinder and axially movable with respect to the longitudinal axis of the cylinder. A rotary quill surrounds the kelly for supplying rotational force to the kelly. A packing assembly carried about the kelly within the hydraulic cylinder proximate and end thereof seals hydraulic fluid within the hydraulic cylinder. An improved retaining assembly connects the packing assembly to the rotary quill but allows limited relative rotational movement of the packing assembly with respect to the rotary quill about the longitudinal axis of the kelly. The limited movement provided by the retainer assembly isolates the packing assembly from drive torque which is transferred from the rotary quill to the kelly, thereby reducing the tendency of the packing assembly to drive the kelly.