Patent GB-967212-A (GB)
Title: Method and apparatus for controlling moving members
IPC: B23Q5/40
Filed: 1961-07-11
Abstract: 967,212. Boring machine details. R. L. CARLSTEDT. July 11, 1961, No. 25034/61. Heading B3C. [Also in Division F2.] An arrangement for controlling the relative speed of a pair of members movable in opposite directions by an hydraulic motor comprises a screw axially fixed in one of the members, and a co-operating nut axially fixed in the other member, the nut and/or screw being rotatable relative to its supporting member, and control means independent of the motor for controlling the rate of relative rotation, whereby the screw threaded elements constitute the sole speed controlling means for the members. A deep hole boring machine 10, Fig. 1, comprises a rotating work spindle 12, a work clamp 14 and a boring slide 18 carrying a boring tool 20 which extends through clamp 14. Slide 18 is traversed by a fluid operated ram 22 connected thereto and the feed rate is controlled by a nut and screw assembly 34, 32, Fig. 2. Nut 34 is rotatably mounted in ram 22 by needle bearings 36 and a thrust bearing 38, and has a conical clutch surface 40 for co-operation with a clutch surface 42 on ram 22. When the ram moves rightwardly, Fig. 2, the clutch engages and holds the nut against rotation, and when the ram moves leftwardly the clutch is disengaged thus allowing rotation of the nut. A sprocket 50 is rotatably mounted on screw 32 and is adapted for driving engagement by a spring urged clutch 52 splined to screw 32 at 54. A chain 56, Fig. 3, passes over sprocket 50 and also over a second sprocket 58 driven by an electric motor 60, and a roller 61 carried by a lever engages the chain so that as the chain is tightened adjacent the roller, a limit switch LS1 is actuated. In operation a switch 70, Fig. 4, is closed, solenoids S1, A, B, are energized and fluid is supplied by a pump 80 to conduit 28 and ram 22 advances slide 18 at high speed. A cam 72 connected to slide 18 opens switch LS1, solenoid S1 is deenergized and clutch 52 engages sprocket 50 thus rotating screw 32 at a controlled speed to control the speed of advance of slide 18. At the end of the slide advance the latter engages a switch LS2, to de-energize solenoid A thus shifting valve 74 to exhaust fluid through conduit 28. Slide 18 will retract rapidly and nut 34 is de-clutched from ram 22 and spins freely on screw 32. Cam 72 opens switch LS4 to de-energize solenoid B the fluid is pumped back to reservoir 84 and the system stops. The screw and nut assembly may be of the ball bearing type, and the nut may be fixed to ram 22 with screw 32 being allowed to rotate during retraction. In a modification, Fig. 6, the screw is connected to a governor shaft 100 having balls 102 which move a plate 106 upwardly to engage an adjustable plate 108 to form a brake. In a further modification, Figs. 7, 8, a member 112 is moved by a double-acting ram 114, mounted on a slide 118, and carries a rod 134 having cams 136, 138 thereon which actuate a switch LS5 to control a motor 122. The speed of traverse of member 112 is controlled by a screw 142 driven by a motor 154 which engages a nut 148 in a fixed member 146. In operation a valve 132 is actuated to supply fluid to the left side of ram 114 and member 112 is moved to the right at a speed controlled by nut and screw 148, 142. Switch LS5 is actuated by cam 136, and motor 122 is started to drive a pinion 126, thus moving slide 118 to the right while member 112 carries on at the controlled speed. Switch LS5 is actuated by cam 138, and motor 122 and slide 118 are stopped, but member 112 continues at the controlled speed. When the control screw is long, sagging of the screw is eliminated by supporting it by mercury directly or by first supporting it on a flexible tube which floats on the liquid. In another modification member 220, Figs. 15-17, is moved by a double-acting ram 222, and control screw 230 co-operates with a nut 234 driven by a motor 240. Screw 230 passes through stationary member 232, and carries a collar 242 which co-operates with a spring-urged cup 244, which also engages a spring-urged block 248. When screw 230 is tensioned and block 248 moves to the left a switch LS6 is closed to indicate that the predetermined tension is being applied. A second switch LS7 is opened by collar 242 when screw 230 moves to the right thus indicating that the rod is being fed through nut 234 faster than member 220 is being advanced. The relative speed of screw 230 and feed of member 220 are controlled to produce the required tension in screw 230. In a still further modification, Fig. 19, member 300 is moved by rams 302, 304, each having a control screw and nut 306, 308 interconnected by chain and sprockets 310.