GB1261839A - Machine tool - Google Patents

Abstract

1,261,839. Machine tool details. ABEX CORP. 28 April, 1969 [13 Aug., 1968], No. 21598/69. Headings B3B and B3C. A machine for drilling vent holes in tyre moulds comprises two rotary indexable worktables 36, Figs. 2, 3, and two drill assemblies, each of which comprises an indexable head 44 carried by an arm 45 slidable on, and pivotable about a column 70 and a long drill 40 constantly supported by two bushings 200, 201, Fig. 10, and driven by a motor 42 secured to a carriage 230, Fig. 7, slidable along guide rods 210. Each of the tables 36 is indexed by a motor M through gears 35, 38. Each of the columns 70 is raised or lowered by a screw 81 driven by a reversible two 'speed motor through a chain and sprocket drive 83, Fig. 3, and is locked in the required position by an air cylinder 91 which actuates a pair of brake elements through a lever 92. Head 44 is indexed about a horizontal axis by a handle H, Figs. 15, 16, which rotates bevel gearing 121, 122, and a worm 125, which moves around a fixed worm-wheel 105, and is locked in the required position by a second handle H1, which moves a sleeve 100 to the right in Fig. 16 so as to lock the head against the worm-wheel. Bevel gears 121, 122, Fig. 15, may be disengaged, and bevel gears 133, 134 engaged by a handle H3, so that a pinion 161 rotates a nut 171, Fig. 16, and causes the drill support 55 to be freed from head 44 so that it may be indexed through 180 degrees. Motor carriage 230, Fig. 7, is moved along the guide rods 240 by a double acting fluid pressure cylinder 241, and a cam 51 carried by the rod 242R of a second cylinder 242 actuates a micro switch 295, Fig. 24, to control the rate of feed and retraction. The extreme positions of the drill are sensed by a linear potentiometer 50, Fig. 7, which operates a pair of servo valves so as to reverse the flow of fluid to cylinder 241. Cutting oil is automatically supplied to the drill in its fully retracted position, through passages 275, 270, 273, Fig. 10, and air for clearing away chips is supplied by passages (280-284), Fig. 9 (not shown). In operation, the rotational speed of the drill is sensed by a tachometer 48, Fig. 24, and the value is compared with a standard r.p.m. If the resistance to drilling increases, the comparator demands a slower drill feed rate, and a servo valve 330 is actuated so as to reduce the fluid supply to cylinder 241. If the drill seizes, the tachometer, and the servo valve 330 reach a predetermined minimum of speed and pressure, and the servo valve is reversed so as to retract the drill.