874 



EXPLORATION GEOPHYSICS 



pump), the oil storage tank, the pressure release valves, and the control 

 valves for operating the various hydraulic features of the drill. To feed the 

 rods downward the oil under pressure is introduced at the top of the two 



Fig. 547. — Hydraulic feed type drill, (A) drill chuck; (B) 

 operating controls; (C) cat head; (E) mast; (F) hydraulic mast 

 raising cylinders; (I) mud pump; (J) hydraulic oil tank; (K) 

 hydraulic feed cylinder; (L) drive rod; (Q) drill pipe; (R) swivel 

 hose; (S) water swivel; (U) hoisting bail; (V) safety hook. 

 (Courtesy of Joy Manufacturing Company.) 



feed cylinders (K), the drive rod (L) is fed downward, and the oil in the 

 bottom of the cylinders below the pistons (T) flows back to the hydraulic 

 oil storage tank (J) at atmospheric pressure. When the process is reversed, 

 the tops of the cylinders are vented to the oil tank, the oil under pressure 



