GB991082A - Improvements in or relating to feed mechanisms - Google Patents

Abstract

991,082. Screw-and-nut gearing. BIRFIELD ENGINEERING Ltd. April 16, 1964 [April 18, 1963], No. 15239/63. Heading F2Q. [Also in Division B3] A two-speed feed drive for a machine tool spindle in, e.g. a multi head drilling machine, comprises a pneumatically actuated piston 13 connected to the spindle for providing a rapid feed, and a screw and a bronze nut 20, 22 driven from a constant speed electric motor 10 through a planetary gear drive, for providing a slow feed. A pulley 3 is keyed to spindle 1 for relative axial movement, and has a spider 40 attached thereto. Two rods 39 carried by the spider pass through holes in a planet carrier 34 rotatably mounted on nut 22 so that the carrier is rotated at the same speed as spindle 1. The carrier supports a counter weight 38 and two planet pinions 36, 37 which mesh with sun gears 23, 24. Sun gear 24 is keyed to nut 24, and sun gear 23 is formed on a sleeve 26 rotatable on the nut. Sleeve 26 has a ring 28 secured thereto which carries teeth 27, for engagement with similar teeth 29 formed on a fixed ring 30. In operation, spindle 1 and carrier 34 are rotated, and air is supplied to cylinder 12. Piston 13 and spindle 1 are fed axially at a rapid rate, until dogs 27, 29 engage. Sun gear 23 is: held against rotation and sun gear 24 along with nut 22 is rotated in the opposite direction to spindle 1 thus allowing piston 13 to move forward at a slow rate. A stop 8 on spindle 1 abuts pulley 3, thus preventing further movement of the spindle but nut 22 continues to unscrew on screw 20 until dogs 27, 29 disengage a limit switch 44 is actuated by a cam rod 46 and reverses the air flow to move piston 13 rearwardly until a second limit switch is actuated to stop the air flow ready for the next cycle.