Patent ID: 6408956
Filing Date: 2002-06-25
Classification: E21B

Abstract:
A rotary drill rig comprising:(a) a drill platform: (b) a derrick for carrying drill machinery, said derrick supported on said drill platform; (c) a rotary powerhead for moving and rotating a drill string; (d) a fixed pulley assembly on said derrick for supporting a flexible connector thereon; (e) a movable pulley assembly on said derrick for supporting said flexible connector thereon and for moving back and forth along said derrick to move said rotary powerhead back and forth along said derrick; and (f) a hydraulic cylinder rod assembly on said derrick for moving said movable pulley assembly back and forth, said cylinder assembly having at least one piston rod reciprocable within a cylinder casing, said cylinder casing immovably fixed to said derrick, whereby said piston rods are maintained in tension during operation thereof.