Patent GB-422380-A (GB)
Title: Improvements in and relating to automatic lathes
IPC: B23B7/12
Filed: 1934-04-07
Abstract: 422,380. Lathes. PRATT & WHITNEY CO., 436, Capitol Avenue, Hartford, Connecticut, U.S.A. April 7, 1934, Nos. 10593 and 10594. Convention dates, April 11, 1933 and Dec. 1, 1933. [Class 83 (iii)] A lathe is provided with magnetic clutches for controlling the forward and return movements of the carriage and cross-slide respectively, switches controlling the energizing of the clutches being operated by the carriage and cross-slide in such a way that the carriage and cross-slide movements follow in succession according to a definite cycle. The lathe comprises a headstock 4 and tailstock (not shown) for supporting a workpiece W, the spindle being driven from a motor 8<a> through bevel gear 8<c>, magnetic clutch 8<b> and spur gearing 8<g>. A brake magnet 8<h> is associated with this drive, a splined member on the shaft 8<f> being provided with clutch discs 8<e>, 8<k> which coact with the electromagnets 8<b>, 8<h> respectively to drive or brake the spindle. The main slide-rest 9 carries a cross-slide 10 in which one or more tools 12 may be mounted. The main slide may be actuated by a leadscrew 15 engaging a nut 16, and the crossslide is operated by a screw 18 driven through bevel gearing from a vertical shaft 20 driven from a longitudinal shaft 24. The rear of the lathe carries a slide bracket 25 which may be manually adjusted in the longitudinal direction and which carries a cross slide 27 driven by a lead-screw 29 connected through bevel gearing 32 and vertical shaft 33 to a longitudinal shaft 37. The worm shafts which operate the feeds are driven through magnetic clutches consisting of magnets which are rotated continuously from an independent motor 48<b> and which, when energized, engage clutch discs splined on the particular driven shaft. The motor 48<b> is connected through spur gearing to a shaft 48 which drives clutch magnet 54 on lead-screw 15. The opposite end of this shaft carries a clutch magnet 89 driven in the opposite direction and at a variable speed by a gear train from the shaft 48. Similarly the feed shaft 24 carries oppositely driven clutch magnets 55, 90, and the feed shaft 37 carries oppositely driven magnets 68, 104, all the magnets being driven through gearing from the shaft 48. The clutch magnets controlling the feed movements of the various slides are driven at lower speed than the magnets controlling the return movements. For energizing the respective clutch magnets to obtain automatic slide movements in accordance with a predetermined cycle the circuit shown in Fig. 2 is employed. Limit switches 107, 108, 109, which are normally closed by spring pressure are opened by means of projections such as 111 of insulating material when a slide reaches the end of its return movement to bring the slide to rest. These switches are adjustably mounted so that the starting position of each slide may be varied. For stopping the feed movements and initiating the succession, of movements of the cycle the slides operate contact lever switches 118-120 controlling relays which preferably operate in low potential auxiliary circuits. For example, switch 119 is opened at the end of the in-feed of the front cross slide by a lug 125 adjustably secured to the slide and other switches are operated by a lug 122 on the main slide and by a lug 128 on the rear cross slide. Six relays A-F are operated on a low potential circuit and are controlled from a starting relay G in a high potential circuit. The circuits of relays A and C are completed through contact switch 119 and the circuits of relays B and D are completed through contact switch 118. The relay E has two circuits, one of which includes contact switch 118 while the other includes a limit switch 108<a>. The operating circuit of relay F is completed through a contact switch 142<a>, which may be closed at any point of the forward run of the main slide by a bevelled end of a rod 17b. Another relay H controls the rotation of the spindle and a similar relay K, the actuation of the braking magnet. The various clutch magnets are energized by a 110 volt circuit including a main switch 145 and the motor 147 of the motor generator operating the low voltage circuit. In operation the motors 8<a> and 48b are started up and the main switch is moved to the right to start the motor 147. A branch circuit from line 146 closes the double contact switch 154. The main circuit from line 146 extends through relay coils G and H and starting switch arm 152, thus energizing relay G and breaking the low potential circuit and also through relay H breaking the circuit between lines 146<a> and H<2> so that the brake clutch 8<h> remains energized. At this time all slides are in their initial positions. The starting switch SS is now momentarily depressed thus breaking the circuit of relays G and H and energizing the relays A ... E. The spindle clutch magnet 8<b> is also energized to start the spindle while the breaking of the circuit K<2>, K<3> de-energizes the brake magnet. A circuit is now completed through the armatures 150, 161 and 167 to the clutch magnet 90 for the in-feed of the front cross-slide which continues until lever contact 119 is broken upon which armatures of relays A and C are released. The tool is now positioned for the longitudinal feed and the circuit for effecting this movement is completed through armatures 150, 161, 170 and 172 and clutch magnet 89. During this traverse the bar 17b causes the switch 142a to close, thus closing the circuit of relay F and completing the circuit of clutch magnet 104 to initiate the feed movement of the rear cross-slide. When the main slide reaches the end of its movement the contact lever 118 is actuated to de-energize relays B and D thus breaking the circuit of clutch magnet 89 and stopping the main slide. At the same time the circuit of clutch magnet 55 is energized to actuate the rapid return traverse of the front crossslide and when the initial position is reached the switch 108<a> is opened to break the circuit of relay E. The rear cross-slide continues its feed movement until contact lever 120 is actuated. When the relay E is de-energized the circuit of clutch magnet 54 is completed to effect the high speed return of the main slide. The rear cross slide is also returned to its starting position. On starting the return movements of the main slide and the rear cross-slide the magnet 8<b> is de-energized and magnet 8<h> energized to stop and brake the spindle. After inserting a fresh work piece the starting switch SS is depressed to repeat the above-described cycle. Manual switches S<1>-S<3> are provided to return the slides to their initial positions before completion of the cycle. The rear cross-slide may be eliminated from the cycle by disconnecting the bar 17b.