GB649453A - Improvements in and relating to rotary drills - Google Patents

Abstract

649,453. Drilling-machines. WERF C. EN STORK HIJSCH N.V. April 12, 1948, No. 10147. Convention date, April 30, 1947. [Class 83 (iii)] A drilling - machine for working in strata of varying hardness hav. ing means for controlling the pressure exerted on the drill bit and wherein the feed movement is effected by the differential rotation between a nut and a feedscrew, is characterised in that a coupling member transmitting the drive from the feed screw to the nut comprises a change-speed gear, the operating member for which is connected with the nut so that downward motion of the nut in a forward feed direction causes the circumferential velocity of the nut to be increased and vice versa. The drill rod 1 which carries a bit at its lower end is secured to a feed-screw 2 by a holder 3. A sleeve 5, slidably keyed to the feed-screw 2, is driven by gearing 6 to rotate the drill and at its upper end carries a bevel gear 19 engaging a bevel pinion 18 on the end of an adjustable friction drive gear 14, 16. The friction. wheel 16 is adjustable across the face of the disc 14 to vary the speed at which the latter drives, through gears 11, 12, the feed nut 8. Adjustment of the friction wheel 16 is effected by a yoke 21 secured to a link 22 connected to an arm 24 of a bell-crank lever, the other arm of which carries a yoke 26 engaging the feed nut. A spring 9, the compression of which is controlled by a hand wheel 10 screwed to the casing 7, bears on the nut and as the nut is moved downwardly in the feed direction the speed of rotation of the nut is automatically increased to give a faster feed rate. On encountering excessive drilling resistance, the nut is forced upwardly and the speed of rotation and hence the feed rate is automatically de. creased. When the nut rotates more slowly than the feed screw, the drill is withdrawn. The bell-crank lever may be moved by hand, utilizing the extension 27, if required.