GB783570A - Hydraulic control mechanism for machine tools - Google Patents

Abstract

783,570. Drilling long holes. LELANDGIFFORD CO. June 22, 1955, No. 18089/55. Classes 83 (2) and 83 (3). [Also in Group XXIX] A machine-tool comprises hydraulic piston- and-cylinder means for imparting a rapid advance to a tool-head to the point where the tool contacts the work, a slow feed during cutting, and a rapid reverse, an actuator 236, Fig. 16, to move a main control-valve 180 through a cycle, hydraulically-responsive means 206 to reverse the valve upon an increased pressure-demand to feed the piston, mechanical means 234 associated with the valve actuator to move the valve to slow-feed position, and means 260 on the head to move the mechanical and hydraulic means to cause the valve to supply pressure to advance the piston. A drilling machine comprises a vertically adjustable work-table 14, Fig. 1a, and a quill 130 adjusted vertically by a manually-rotated pinion 142, Fig. 2a, and clamped in position by a handle 32. A motor 26 balancing the drill-head rotates, through belt-gearing, the drill and an hydraulic pump 116. The head-casing 118 forms a reservoir having a fluid-retaining air outlet 120 at its upper end. A rod 154 on a piston-carrying sleeve 137, within which the quill is carried, engages a ball-catch 158 at an extreme upper position to hold the drill in place when pressure is released from the cylinder 150. In the rapidadvance condition of the main valve 180 in Fig. 13a, pressure fluid P passes to the top T of the feed cylinder, as does the exhaust fluid from the bottom B via passages 190, 192. A small proportion of exhaust fluid passes a metering valve 198 to balance the valve 180 at passage 200. In the feed condition of Fig. 13c, pressure fluid P passes to the top T via passages 186, 202, a balancing valve 182 and a passage 204. Exhaust fluid passes to the sump D by way of the metering valve 198, which controls the feed speed. When the feed pressure exceeds a value determined by a valve 208, a valve 206 is operated to move a plunger 250 to strike the actuator 236 and so cause a rapid return of the tool, the valves thus determining the depth of each step. In the rapid-return condition, pressure-fluid passes to the bottom B via the passage 186, and is exhausted through passages 194, 196. At the top of a return stroke a plate 143, Fig. 16, on the head strikes a plunger 260 which, through a rod 262, actuates a valve 264 to cause reversal of the fluid flow. The plunger 260 may be moved by a " STOP " lever 276 to a position where it registers with a recess 145 in the plate 143 and is rendered ineffective. The plate 143 then continues to rise until a peg 278 engages a rod 280 which, through the block 234, a bellcrank 228, 230 and the plunger 236, moves the valve 180 to neutral and stops the feed movements. In the downward movement, the point at which the rapid traverse changes to feed is determined by a stop 305. As the head moves downwardly a block 292 carried with it engages a lip on the block 234 to depress it, and the stop 305 engages a cam-plunger 304 to cause the block 292 to slip on its rod 294. On a subsequent feed movement, therefore, the feed speed is not introduced until the drill has reached the bottom of the previously-drilled hole. A cycle continues until a stop block 310 moves the block 234 to rapid-reverse position. A roller 313 on the block 310 also operates by disengaging a lever 344 from the rod 314 to allow a spring to turn the rod, and thus to position a block 312 in the path of the block 292. Consequently, as the head rises, the block 292 is moved down its rod 294 to its initial position. The block 312 is swung out of its operative position by a hand " reset " lever 316, or automatically by actuation of a plunger 318 and wedge 322 as the plate 143 on the head moves to its upper position. The head may be stopped after a shorter upward movement by attaching a pin 361, Fig. 18a, to the collar of the stop-lever 276 so that the pin 280 is actuated before the head can be reversed. Additionally, however, a lengthened pin 260a may be fitted so that reversal takes place at a lower position of the head. If the head at any time overruns in an upward direction, a lever 380 is moved to cut off the pump and to render solenoids 282, 284 inactive. The feed-rate valve 198 and the step-length adjustment 208 are of the form shown in Fig. 12 d, f, g. The adjusting knobs 207 (209) each carry a screwdriver member 418 engaging a slot 434 in a rotary plate 414 having an opening 432 co-operating with an opening 411, in a stationary plate 410. As the valve opens, fluid passes at first only through a V- notch 412, thus providing a fine adjustment. The valve parts are kept clean by fluid flowing through recesses 440 to lift the plate 414, against a spring 416, at each reversal of pressure. A hand-lever 220 connected to the bellcrank 228, 230 can be used to control the main valve 180 at any time. The operator can also start or reverse the feed piston at any time by actuating solenoids 282, 284. As a safety precaution, every surge of pressure in line 244 or 245 moves a rod 332 to the left to turn the " stop " lever, thus removing the pin 260 momentarily from the path of the head plate 143. In a modification, the machine is arranged with the drill 34, Fig. 1d, horizontal. Making valve-blocks. A valve-block containing oil channels may be made by casting three sections as shown in Figs. 1a-10c, clamping the sections together with sheets of a brazing material such as brass or German silver interposed, and heating them to produce a one-piece block, Fig. 10d.