Patent GB-540721-A (GB)
Title: Improvements in and relating to screw cutting lathes
IPC: B23G1/04
Filed: 1940-04-10
Abstract: 540,721. Lathes. APPAREILLAGE GARDY SOC. ANON. April 10, 1940, Nos. 6476 and 6477. Convention dates, April 11, 1939, and May 26, 1939. [Class 83 (iii)] A screw cutting lathe has a tool carriage which is controlled by a single control member to perform a cycle of operations including repeated traverses and depth feed and final automatic stop. As diagrammatically shown in Fig. 1, the work-spindle 4 is driven from a power source S through change gears (not shown) spiral gears 5, 6 and clutch 8 operated by a lever 8a. The spindle 4 is connected through change gearing 10 to a gear 16 on a shaft 15 connected by a clutch 17 to a collinear shaft 15a which drives by gears 20 a screw 22. The shaft 15a also drives a cam shaft 26. The movable clutch part 17 is secured to a loose sleeve movable axially on a shaft 19 carrying a steep pitch screw 27 coacting with a fixed nut 91. Toothed sectors 28, 29 connect the shaft 19 to a clutch shaft 30 carrying another sector 31. The shaft 26 carries an axially fixed cam 32 and another cam 33 which moves axially with the shaft 26. Cam 32 co-acts with levers 34, 35 to operate a rock shaft 36 which carries a cam 51 transmitting movement to a frame 52 which acts through a lever 55, Fig. 4 to engage and disengage the nut segment 37 co-acting with the screw 22. The shaft 36 carries a lever 38 operated by cam 33 at the end of each traverse of the slide 3. A lever 101 pivoted to the slide 3 imparts axial movement to the shaft 26. Shaft 36 carries a lever 41 actuating ratchet mechanism to rotate a shaft 57 carrying a depth feed cam 60 and releasing plate 61. A shaft 45 connected to shaft 36 acts through a lever on a cam bar 47 slidable in a part 68 and engaged by a stop 67 on the part 66. The shaft 45 may be locked by a lever 48. The feed cam 60 is of spiral form, Fig. 3, and has a concentric part corresponding to full depth to allow a finishing traverse of the tool. The cam engages one of the tappets 65, 65a, on the part 66 according as internal or external threads are being cut. A lever 71 pivoted at 71a acts through a sleeve 72 on the cross slide 73, which carries an upper cross slide 68 and is mounted on a longitudinal slide 82. The lever 71 co-acts with levers 78, 79, Fig. 1, of which 78 is actuated from the release disc 61 through the rod 77. The lever 79 is released by a fixed stop 80 at the end of the traverse. A rack 81 transmits movement of cross slide to the stop shaft 30. The return of the longitudinal carriage after each movement is produced by a spring 90. For cutting multiple threads the spindle 4 carries a wheel 100 connected to a wheel 101. Geneva mechanism 103, and pinion 104 engaging the wheel 11 of the lead screw driving train. A rod 109 actuates a quick pitch screw 107 to rotate a shaft 111 driving a pinion 114 secured to the locking cam 118 of the Geneva mechanism. This cam has a notch coacting with a lever 121 which itself co-acts with a lever 123 carrying the locking pin 125. The machine is started by engaging the clutch 8. The spindle 4 drives the wheel 101 and through the Geneva mechanism operates the gear 104 and the lead screw driving train. By operation of lever 71 the cross slide is advanced to move the tool 95 up to the work, this movement also rotating the shafts 30 and 19 causing the latter shaft to move axially, engage the clutch 17 and initiate the drives of the lead screw and cam shaft 26. The cam 32 then actuates shaft 36 to engage the nut segment 37. At the same time the cam bar 47 is actuated to bring the stop 67 on to the higher part of the bar and move the tool into cutting engagement with the work. At the end of the operative travel lever 1011 causes the cam 33 to actuate the release lever 38 thus withdrawing the tool (through cam bar 47), disengaging the lead screw nut and allowing soring return of the longitudinal slide. The rod 109 is now actuated to cause actuation of the Geneva mechanism whereby a different thread is cut on the next traverse of the tool. After all the threads have had a first cut the mechanism 42 is actuated to impart a feed step to the cam 60. When the required depth of cut is reached the release cam 61 actuates rod 77 to disengage the trip lever 78 from the starting lever 71 so that when the second trip lever 79 is released by a stop 80 at the end of the last traverse, the starting lever is released and the cross slide 73 is returned thus disengaging the clutch 17 and stopping the lead screw.