Patent GB-759043-A (GB)
Title: Fluid pressure power feed mechanism for power driven tools
IPC: B23Q5/26
Filed: 1953-10-09
Abstract: 759,043. Drilling machine details. ROCKWELL MANUFACTURING CO. Oct. 9, 1953 [May 19, 1953], No. 27859/53. Class 83 (3). Fluid-pressure power-feed mechanism for effecting movements of one member relatively to another, e.g. the advance and retract movements of a tool-holder relatively to a workpiece, comprises a power - piston and one or more floating control - pistons, fluid under pressure being selectively applied to the power-piston or to the control-pistons to effect the advance and retract movements respectively, the advance movement being resisted by back-pressure due to the flow of liquid in a closed circuit interposed between the power and control-pistons, thereby to control the rate of the advance movement, the liquidcontrol-circuit including two paths in parallel, each path having an adjustable valve and a check or non-return valve, the two checkvalves allowing flow in opposite directions whereby the rates of advance and retraction of the power-piston are controllable independently. As applied to a drilling-machine, a quill 66, Fig. 8, is moved out of and into a housing 20 by a piston 56 slidable in a cylinder 40 under the control of a valve G and free-pistons 250, 272 slidable in cylinders 200, 202 respectively. Chambers 58, 256 and 276 of cylinders 40, 200, 202, respectively, are interconnected and contain hydraulic - fluid in a closed system. Valve G is reciprocable between two positions in a body C, having a compressedair inlet D and exhaust ports E, F, to control the supply and exhaust of lines A, B. Line A leads to chamber 60 of cylinder 40 and line B to chambers 254, 278 of cylinders 200, 202. Thus, to advance the quill from its innermost position, valve G is positioned as shown in full lines and air is supplied to chamber 60 and exhausted from chambers 254, 278. Piston 56 moves liquid from chamber 58 through line H, check valve 302, adjustable valve 320, and lines K, L, M into chamber 256 at a rate determined by the setting of valve 320, thus moving piston 250 until it abuts adjustable stop rod 260, and the quill is rapidly advanced. The remaining liquid is moved into chamber 276, to displace piston 272, from line K through adjustable valve 360, set to restrict flow to a greater extent than valve 320, whereby the quill is further advanced at a slower rate until stopped, e.g. by a shoulder 174 thereon abutting an adjustable stop 130, or the drill bit encounting an impenetrable obstruction. When this happens, the pressure in chamber 58 drops and causes, via line S, operation of a pressure-sensitive switch 292 to de-energize solenoid Q and thus allow spring U to move valve G to the position shown in broken lines. In this position chamber 60 is connected to exhaust, and air is supplied to chambers 254, 278 to move pistons 250, 272 and force liquid back into chamber 58. A ball-check valve 400 is provided in a line which by-passes valve 360 and, since pressures on opposite sides thereof are equal, the valve remains closed until piston 250 has transferred the liquid in chamber 256 via lines M, L, T, adjustable valve 322, check valve 300 and line H into chamber 58, thus retracting the quill at a rate determined by the setting of valve 322. After this, valve 400 opens and piston 272 ejects the liquid in chamber 276 via valve 322 into chamber 58, and thus retraction continues at the same rate, as is desirable when withdrawing a screwtap from the work. If the latter portion of the retraction is to be performed at a slower rate, e.g. for back spot-facing, the valve 400 is turned through 90 degrees to the position shown in Fig. 9. Thus when piston 272 moves, the liquid passes through valve 360, which is set to restrict flow to a greater extent than valve 322. When the quill is completely retracted, an extension 62 of piston 56 operates a plunger 293 to close switch 292 and energize solenoid Q, thus moving valve G to the full-line position and commencing the cycle again. Stop 130, Fig. 2, comprises an annular member, screwing in, threads 132 in a bore in the housing, the threads on the member being slotted to form gear teeth for engagement with an elongated pinion 140 rotatable in the housing by bevel gears 150, 154 and graduated-knob 164, to move the stop along threads 132. Cylinders 200, 202 are mounted side-by-side between end members 178, 180 bolted on top of housing 20 and provided with a cover 24, Fig. 1. Valves 320, 322, 360 and 400, Fig. 3, are mounted in member 178 and are externally adjustable as shown in Fig. 1, as is the stop-rod 260. Chamber 276 is used as a reservoir for the closed hydraulic system, since piston 272 does not use all of its available stroke. The quantity of liquid in the system is checked by removing a plug 283 from member 180 and inserting a calibrated-rod until it abuts a cap 280 on the piston 272. Liquid may be added through a fitting 297 and check valve 295, air escaping through a bore 349 after removing a plug 351. The control pistons and cylinders may be replaced by expansion chambers, e.g. bladders, bulbs or bellows. Spindle mountings. The quill supports a tool-spindle 104, Fig. 2, in preloaded bearings 90, 92 and is prevented from rotating by a rod, not shown, fixed to piston 56 and engaging a longitudinal bore in the housing. The spindle is rotated by a shaft 116 driven by an electric or hydraulic motor and connected to a member 112 splined to the spindle. Specifications 710,335, 719,846, 721,848, 723,337 and 723,871 are referred to.