Patent GB-875139-A (GB)
Title: Control mechanism for machine tools such as turret lathes
Inventor: KOZACKA ARTHUR GEORGE
IPC: B23B3/18
Filed: 1960-02-16
Abstract: 875,139. Turret lathes drilling; tapping. ACME INDUSTRIAL CO. Feb. 16, 1960, No. 5444/60. Class 83 (3). Control mechanism for a lathe having a reversible drive for advancing and retracting an indexible turret in a standard cycle of movement including advancing at traverse rate for a first distance, advancing at a feed rate for a second distance and then retracting at traverse rate to the initial position, is characterized in the provision of normally ineffective means for modifying said mechanism to produce a reciprocating drilling cycle of turret movement in which the turret is fed successively to more advanced positions and partially retracted after each feed movement and of means indexed in step with the turret for rendering said modifying means effective when the turret is in any selected indexed position. The indexible tool-turret 15, Fig. 1 is carried on a slide 16 which is reciprocated by a double-acting piston and cylinder device 20. The turret is indexed on full retraction by known means not described. A shaft 15a which effects the indexing, carries a pinion 37, Fig. 3 (plan), meshing with two further pinions 38, 39, secured to control-shafts 40, 41, respectively. The control-shaft 40 carries a trip 45 and adjustable stop 49, Fig. 2, for each indexed position of the turret. The trips 45 operate a switch 46, CS-FD which changes the limit-slide movement from fast approach to slow feed and the stops 49 operate switch 50 CS-R which reverses the movement and gives the turret a fast return. The rate of feed is changed automatically by dogs 35, Fig. 3, on a disc 36 secured to shaft 52 which is rotated with the turret by a splined connection with controlshaft 41. The dogs 35 engage the end of a rate control valve 30 which is held fully open for the fast approach by a solenoid S-RT, Fig. 7. This valve, when it is released by the solenoid and spring-pressed against one of the dogs 35, throttles the exhaust fluid from the cylinder 20. A switch CS-F, Fig. 2, is actuated by a stop 53 when the turret slide is fully retracted and conditions the circuitry to start a new cycle. The slide operations may be stopped by moving a hand lever CL, Fig. 1, which operates a valve 25, Figs. 2 and 7; to shut off the supply of pressing fluid, or, this may be effected automatically by a dog 55 inserted in one of a circular set of holes 56 in the control-shaft 40. Controls for dwell at the end of a feed. An electronic time delay of the resistance-capacitance type is incorporated in the control circuits and six adjustable resistors, equal to the number of turret positions are connected to switches DSTa-DSTf, Fig. 2. The switches are operated at the required times by dogs 65 inserted in holes in the peripheries of discs secured to the control sleeve 52, Figs. 3 and 4. The tool is thus made to dwell at the end of a feed movement to clean up the bottom of a hole &c. Back-feeding cycle. In some cases it is required that the tool be fed back to the end of the work at a slow rate to prevent marking the work; this may be effected by a further control disc D-BF on sleeve 52 operating a switch DS-BF, Fig. 2. Floating feed for screw-cutting. Tapping operations and screw-cutting with dies are performed by by-passing the pressure fluid for cylinder 20, Fig. 7, through a solenoid-operated valve 70. The limit slide is then only moved by the piston sufficient to pick-up the threads of the tap &c. This solenoid S-FL is controlled by a disc D-FL and switch DS-F, Fig. 2. Reciprocating cycle for long holes. Controls are provided for drilling long holes to give a rapid traverse up to the work, a slow cutting feed for a predetermined resistance, a rapid return to the outside of the work, a rapid reverse nearly to the bottom of the hole, a further slow feed deeper into the work, and so on until the hole is completed. This is brought into operation by a dog 82, Fig. 6, positioned in the periphery of a disc 80 provided on the longitudinally moving control-rod 41. The dog 82 contacts a depending part 84 of a sleeve 84a slidable on a hollow shaft 75. The sleeve 84a has a cam-portion which operates a switch CS-PO and, after a small " lost-motion " movement, contacts a cap 99 secured to shaft 75 and carries it forward to the desired first step depth of feed. The hollow shaft 75 is retained in each successive extended position by a ball clutch 85. When the hole is completed a solenoid S-BR moves a retaining sleeve 89 to the left to allow the clutch to slip and the sleeve 75 is retracted to its initial position by a spring 94.