Patent GB-543491-A (GB)
Title: Drilling machines
IPC: B23B47/22
Filed: 1940-06-24
Abstract: 543,491. Drilling-machines. GOLDBERG, H. June 24, 1940, No. 10810. Convention date, March 13. [Class 83 (iii)] A drilling or like machine has pneumatic drill feed mechanism and dashpot means adapted to retard the feed movement, when the hole is nearly completed, to avoid breakage of the drill. The hollow bed 25 has a front guide 25b for an adjustable work table 27 carrying the work piece 28. The drill 35 is carried in a pressure head 80 movable in a cylinder block 37 carrying the dashpot valve block 38. A motor 40 mounted in the hollow part 25c of the frame is connected by change speed pulleys and a belt 61 to a sleeve 64 carried in ball bearings 69 in a central bore 37a of the cylinder block and having a spline connection with the drill spindle which is mounted in ball bearings in the pressure head. The latter is connected to the piston rods 90 of a pair of parallel pneumatic cylinders which are closed by plugs 94, the pistons being normally retained in their raised position, Fig. 4, by means of constantly acting pressure supplied from a casing 45 through pressure regulator 47a, gauge 48a and line 54, Fig. 3. The casing 45 also supplies fluid through a second pressure regulator 47, and gauge 48 to a line 49 leading to a pedal operated valve 50. When the central spring- supported plunger 105, Fig. 16, of this valve is depressed by the pedal 51 the line 49 is connected to a line 52 leading to a fitting 95 secured to the valve block 38. Passages lead from this fitting to the space above the pistons 93 to feed the drill downwards. Each pressure regulator, Fig. 20, comprises a casing consisting of two parts 112, 113, between which is clamped a diaphragm 114 supported on one side by an adjustable spring 116. A disc 120 on the other face of the diaphragm is connected to a spring seated valve 122 controlling admission of fluid to the chamber 113a of the diaphragm. Compressed air is admitted through port 112b to the inlet side of valve 122 and the back pressure in the line 49 acts through a port 112d on the diaphragm. When the back pressure falls as the result of flow to the valve block 38, the valve 122 is opened by spring 116 thereby admitting additional fluid to chamber 113a until the valve 122 is again closed. By adjustment of the springs 116, 124, any desired pressure may be maintained in the supply line to the valve 50 and a suitable lower pressure in the line 54 leading to the lower ends of the cylinders 37c, the pressures being read on the dials 47, 47a. The downward movement produced by opening the foot valve 50 is cushioned by dashpot mechanism, carried by the valve block 38, and comprising a cylindrical cut-away member 130a, Figs. 8 and 12 having an upper sleeve-like portion 130c fitted with a dashpot plunger 131 terminating in a flange 131a and co-acting with a cup member 136 secured to a rod 135. The plunger is normally held by a spring 132 in an upward position limited by a cross pin 133. The cylinder 38c is partly filled with oil and the part 130 has a slightly tapered bore receiving the plunger 131. When the plunger moves downwards it forces oil from the part 130e until it is finally brought to rest at the moment when the hole is completely formed. The rod 135 carries nuts 139 which are entrained by a sleeve 80e secured to the drill head to cushion and retard the drill movement as the drill breaks through the work. The sleeve 80e engages a collar 137 on the rod 135 to return the rod independently of the return action of the spring 132 in the dashpot cylinder. When the drill comes to rest the pedal 51 is released so that the drill is returned to its upper position. The cutting oil is circulated by a pump 43, Fig. 17, having an impeller shaft 145 driven by a motor 42 and carrying the impeller 148. Oil is drawn through ports 141b and passes between the casing 140 and the sleeve 144 to a delivery pipe 143 and nozzle 57. The work table 27 has a channel from which oil flows back to the well in the housing 25.