Patent GB-913128-A (GB)
Title: Improvements in screw-threading machines
IPC: B23G5/12
Filed: 1960-09-20
Abstract: 913,128. Screw - cutting; thread - rolling. NATIONAL ACME CO. Sept. 20, 1960 [Sept. 24, 1959], No. 32304/60. Classes 83 (3) and 83 (4). A parallel or taper-tapping machine with means for progressively moving the tap parts e.g. chasers, inwardly to produce the taper, means for radially disengaging the chasers from the work after screwing, and means for allowing removal of the chasers for resharpening, comprises a spindle 18 rotatable in a frame 16, by a gear 19, a sleeve 20 slidably keyed to the spindle, having a member 24 slidably mounted therein, and a tool body 25 secured to the spindle, and slidable in a member 24, having a rod 37 secured thereto by a pin 81. A nose-piece 26 secured to body 25, carries dove-tailed slides 29 having chasers 30 secured thereto, the slides co-operating with a dovetailed wedge 27 axially adjustably secured to rod 37. A sleeve 36 is splined into rod 37, and a pin 35 splined in sleeve 36 carries wedge 27, which is adjusted axially by a screw and nut 39, 40. A lever 47 is pivoted in a yoke 43 at 51, and in sleeve 20 at 50, and a pin 52 is engageable in one of two bores 53, 54, in the lever, and extends into arms 55 mounted in transverse slots 56 in rod 37. The weight of the machine is supported by a plate 63 carried by cylinders 62, and a wear plate 64 is provided between the relatively rotating parts. A fluid distributer 68 fixed to frame 16 selectively supplies fluid to either side of a piston 74 secured to rod 37 and to the top of a piston 70 to produce axial movements of wedge 27, the fluid being supplied from a pressure source 85, through a valve 86, filter 87, pressure regulator 88, to a solenoid operated four-way valve 90, or to a pressure regulator 99, and thence to the pistons 70, 74, the solenoid 91 being actuated by dogs 104, 105, on the piston rod of the piston in cylinder 62. In operation, the non-rotating workpiece 12 engages plate 63 and is moved axially with spindle 18 rotating, thus moving sleeve 20 upwardly and pivoting lever 47 about point 51. Pin 52 moves rod 37 and therefore wedge 27 upwardly and chasers 30 are fed radially inwardly to produce a tapered thread 13. When pivot 50 moves to position 50A, the thread is completed and dog 104 actuates switch 103, thus moving valve 90 to supply fluid through conduit 94, and move piston 74 upwardly. Wedge 27 is moved to collapse chasers 30, lever 47 pivots about point 50A, and the work is retracted. Sleeve 20 moves downwardly by gravity until dog 105 actuates switch 103 to supply fluid to the opposite side of piston 74, which moves wedge 27 to reset the chasers. To remove the chasers at the end of a threading operation, when wedge 27 is in its upward position, regulator 99 is manually actuated to reduce the pressure above piston 70 and due to the diameter of piston 70 being greater than that of piston 74, piston 70 is moved upwardly and due to the reduced pressure, piston 74 moves along with piston 70 a further distance upwardly, pivots lever 47 about point 50A, and wedge 27 is disengaged completely from slides 29, and the chasers can then be removed.