Patent GB-775713-A (GB)
Title: Improvements in and relating to machine tools, e.g. lathes, of which the work spindle is driven through a change speed transmission
IPC: B23Q5/14
Filed: 1955-04-07
Abstract: 775,713. Machine-tool details. NAAMLOOZE VENNOOTSCHAP NEDERLANDSCHE MACHINEFABRIEK ARTILLERIEINRICHTINGEN. April 7, 1955 [April 21, 1954], No. 10235/55. Class 83 (3). [Also in Group XXIV] A lathe &c. has the work-spindle driven through axially-shiftable sets of gears moved by two shifter-members reciprocated with constant strokes in opposite directions, and an independently-adjustable preselector for setting the distances through which gear sets are to be moved by the shifter-members, an electric locking-system being provided which prevents the work-spindle rotating at other than the preselected speed. A work-spindle 1, Fig. 1, is driven by toothedgearing from a pulley 17 rotated by an electricmotor 17a, Fig. 2. A driving-shaft 16, Fig. 1, is connected by electro-magnetic clutches 18, 19 respectively, either through forward-drive gears 11, 12, or reverse-drive gears 13- 15. A shaft 6 carrying four gears 7-10 is thus driven, and the gears are selectively used to drive the work-spindle by sliding the gearcluster 2-5 along a splined extension of the work-spindle 1. This is effected by a lever 21, connected at one end to a fork 23 which has a threaded connection with a sleeve 25 carrying a plate 29. The relative positions of the plate and fork are adjusted by a preselector knob 27 provided with speed-indicating means. The plate 29 is moved to effect the selected gear-change by fork-members 31, 32 which slide in with equal movement through rack-and-pinion connections 33-35. The rack 34 is connected to a pneumatic-piston 37 controlled by a solenoidoperated valve 40. Electrical control. The switch 47 is first closed to start the driving-motor 17a through the controller 49, and an auxiliary-contact 50 is closed at the same time. The preselectorknob having been previously set to give the desired spindle-speed, a press-button 45 is operated, closing contact 51 and opening contact 57. The circuit for the solenoid 44 operating the air-valve for the forks 31, 32 is thus moved and the gears are shifted to give the speed set by the preselector. The circuit for the solenoid 44 includes a centrifugal-switch 54 carried by the intermediate shaft 53, which opens as soon as the work-spindle rotates. The contact 57 opens the circuit for the electromagnetic brake 58 also carried by the shaft 53. When the piston 37, which moves the selectorforks together, reaches its extreme right-hand position, a switch 59 is closed, thus completing a circuit through electromagnet 56. This operates a holding-contact 60, closes contacts 61, 62, 65, and opens back-contact 55. Current is thus cut off from the solenoid 44 and the valve 40 and selector forks return to their initial positions. A switch 46 is provided to control contacts 65, 52, 71. This switch has a " neutral," and " forward " and " reverse " positions, and determines the direction in which the workspindle will rotate at the predetermined speed. The button 45 is pressed a second time to close a circuit to electromagnet 66 which closes a holding-contact 67, and contacts 68, 69. The latter are in the circuits of electromagnetic clutches 18, 19. The position of the contact 71, (controlled by switch 46), determines which of the clutches is operated and thus the direction of rotation of the spindle. Preselection of a different speed opens a switch 64 associated with the dial 28, which stops current flow to the electromagnet 56 and extinguishes an indicatorlamp 72 or 73 showing forward or reverse-speed correspondence of the spindle and dial setting. The switch 46 is moved into the " neutral " position to stop the spindle, button 45 is pushed to move the gears, switch 46 repositioned for " forward " or " reverse " drive and button 45 pushed a second time to restart the spindle. If no speed-change is required the spindle may be stopped by opening and closing the switch 46 and pushing the button 45 once. The electromagnetic clutches 18, 19 and the brake 58 and signal-lamps 72, 73 are fed with direct-current through a rectifier 75. The motor may be rotated at half or nominal speed, and conventional reduction-gears may be used additionally.