When compressed air is delivered through directional valve 1 to cylinder 2, piston 3 moves to the left. Gear rack a on the piston rotates pinion 4 which meshes with rack d of spindle quill 5, feeding the quill and spindle to the right. Mounted on shaft O of pinion 4 are two more pinions, 6 (see lower drawing) and 7, which rotate together with pinion 4. Pinion 6 advances sleeve 8 with whose rack it meshes. When sleeve 8 reaches piston 9, the speed of travel of the spindle quill is considerably reduced due to the resistance of the hydraulic fluid under the piston. Fluid from cylinder 10 is forced out through pressure reducing valve 11 and flow-control valve 12 into the tank. By adjusting the clear opening in valve 12, the rate of fluid flow out of cylinder 10 can be varied, thereby varying the rate of feed of the spindle. Pressure reducing valve 11 maintains constant pressure before flow-control valve 12, providing for a constant rate of spindle feed. Rack 13, meshing with pinion 7, moves upward upon rotation of pinion 4 and, at the end of the spindle travel, contacts lever 14, turning about fixed axis A. Lever 14 depresses a member of pneumatic directional valve 1, connecting cylinder 2 to the atmosphere. Then spring 15 moves piston 3 to the right, retracting spindle quill 5. During quill and spindle withdrawal, sleeve 8 moves upward, first by itself and then, when it reaches nut 16, together with piston 9. As piston 9 moves upward, hydraulic fluid is drawn from the tank through ball check valve 17 and into cylinder 10. Regulating nut 16 sets the length of rapid approach of the spindle and regulating screws 18 and 19 set up the point of tool (spindle) withdrawal.
$4206$CHP,Dr$