Patent GB-1151251-A (GB)
Title: Control Apparatus for Machine Tools
Inventor: BARLOW ERIC
IPC: B23Q5/54
Filed: 1966-02-12
Abstract: 1,151,251. Machine tool details. R. McIVOR & SONS (ENGS.) Ltd. 20 Jan., 1967 [12 Feb., 1966], No. 6307/66. Headings B3B, B3K, B3L and B3T. [Also in Division B5] A control apparatus for a machine tool having a cutting head which is required to move stepwise relative to a workpiece table by predetermined amounts comprises clutch means for connecting driving mechanism adapted to be driven in accordance with the relative movement to a rotary delay device, and switch means engageable by the delay device to stop the relative movement after the predetermined amount thereof and also to release the clutch means. The apparatus may be applied to the control of a lathe, milling machine, planing machine or other machine tool but, as described, is applied to a power-driven band saw machine in which foamed polyurethane material is carried on a horizontally reciprocable table for cutting into slices or sheets by a band saw carried by a vertically movable cutting head. A sprocket 1 is driven by the lifting mechanism of the cutting head and is rotatably mounted on, and coupled to, a shaft 3 through a lost-motion connection consisting of discs 4, 4a, 5, 6. A bevel 7 on the shaft meshes with a bevel gear 8 integral with a gear 11 and clutch ring 12 on a shaft 10, the gears 8, 11 and ring 12 being axially slidable when a solenoid E is actuated to engage gears 7 and 8 or engage the ring with a pulley 13 belt-driven from a motor D. Gear 11 meshes with a gear 14 on a shaft 15 of the rotary delay device which consists of a collar 16 splined to shaft 15 and adjustable along the shaft by a handle 23. The collar has pins 17 which are engageable with aperturss in plates 18 of which plate 18a is fixed to the shaft and plate 19 is fixed to an arm 20, all the plates, other than 18a being rotatable on the shaft and having stops on their opposed faces for transmitting drive therebetween. The arm 20 has a pin 21 that co-operates with an arm 24 which rocks a yoke 25 settable by a fine control selector 25 to actuate limit switches A, B, which can be held depressed by a trip lever 20a. The sprocket 1 is also integral with a gear 2 meshing with a gear 29 secured to a shaft 30 carrying a clutch mechanism actuated by a solenoid F so as to be connected with a pulley which is thereby driven to wind up a cord on a spring-loaded lever 36, the pulley also having a peg 37 for engaging a lever 38 of a microswitch C. In operation, the table of the machine is placed in its mid-position and the cutting head lowered to touch the top of a block of material to be cut. The thickness to be cut is then set by movement of handle 23 and arm 25, handle 23 engaging notches corresponding to 25 mm. thickness so that the pins 17 engage the corresponding number of plates 18. The table is then returned to its rearmost position and actuates a switch which lowers the cutting head and energizes solenoid E to engage bevel gears 7, 8. Rotation of sprocket 1 thus rotates shaft 15 which, when the determined lost motion between the plates 18 is taken up, drives arm 20 to cause pin 21 to actuate the micro-switches A, B, the movement of the arm 20 being determined by the setting of arm 25. One of the switches A or B stops the lowering of the cutting head and advances the table for the cutting stroke and the other starts motor D to return arm 20 to its initial position after solenoid E has disengaged bevel gears 7, 8, the return of the arm 20 releasing the trip 20a and switches A and B to stop motor D. At the end of the cutting stroke, solenoid F is energized to engage the clutch mechanism associated with gear 29 so that, as the cutting head is lifted, the rotation of sprocket 1, which, because of the lost motion connection 4, 4a, 5, 6 is not imparted to shaft 3, rotates the pulley against the spring-loaded lever 36 and causes peg 37 to actuate solenoid C to stop further lifting of the cutting head. Upon the return of the table, the micro-switch is again operated to lower the cutting head, the sprocket 1 not rotating shaft 3 until the lost motion connection is taken up. The spring- loaded lever 36 returns the pulley to its initial position when solenoid F is de-energized. The cycle is repeated until the head reaches its lowermost position.