GB725163A - Automatic speed control for electrically driven duplicating machines - Google Patents

Abstract

725,163. Operating clutches. NILES-BEMENTPOND CO. Feb. 9, 1953, No. 3626/53. Class 80 (2) [Also in Groups XXII and XXXVII] A lathe has a lead screw 7 driven by an electric motor 14 through a pair of magnetic clutches 10, 10a, so that the feed of the lead screw can be reversed by energizing one clutch or the other, and, by breaking the circuit of both clutches, the feed can be stopped. A cross-feed lead screw 20 is similarly driven through a pair of clutches 24 by an electric motor 26. The cross-feed slide 17 has a bracket arm 30 supporting an electrical tracer 31 which co-operates with a pattern 33. Thus, the tracer follows the pattern and controls the movements of the respective lead screws through the magnetic clutches, the lathe tool operating upon the work to reproduce the outline of the pattern. The tracer spindle 32a actuates a contact-carrying lever 39 which is pivoted at 40, and, when the tracer is in the normal position shown, contacts 42, 43 are closed to energize relay 64 and close contacts 65, so completing the circuit of one of the clutch coils 24 for feeding the cross-feed slide toward the pattern and work. As soon as the tool engages the work, it cuts in until the tracer engages the pattern and the contact lever 39 moves to close contacts 60, 62, so energizing relay 78. The clutch 10 or 10a is then energized, according to the position of the manual switch 84, so that the tool begins to move in the required longitudinal direction. A further motion of the tracer spindle will cause contacts 42, 43 to open and the tool will travel parallel to the axis of the spindle as long as the tracer is not subjected to increase or decrease of pressure against the pattern. If the tracer engages a high point in the pattern, a contact lever 39 will be thrown over to close contacts 50, 51, and energize relay 64. so closing contacts 66 and energizing the clutch coil for moving the cross slide outwardly in conformity with the shape of the pattern. If the pressure of the tracer against the pattern is very great, additional movement of the contact lever 39 opens contacts 60, 61, to de-energize the clutch 10 or 10a, and longitudinal movement of the tool is halted whilst the tool is withdrawn from the work until the excessive pressure is released. Accidental excess pressure causes the opening of contacts 53, 56 to stop all movement, the contact 53 being mounted on an arm 54,pivoted at the point 55. The armatures 107, 108 of the motors 14, 26 are supplied through separate rectifiers 109, 110, which are respectively controlled by transformer taps 114, 115, driven by A.C. pilot motors 125, 126. Each time one of the clutch coils 10 or 10a is energized, relay 94 is operated to reverse the pilot,motor 125 and to move the tap 114 towards its high-voltage position. Thus, the voltage of the-motor 14 is increased when the clutches 10, 10a are energized whilst the opposite operation takes place when the clutches are de-energized The control of the clutches 24 and the motor 26 are similarly related. The circuit of each of the relays 94, 92, and of the clutches connected thereto, is first completed through only a part of the relay winding, and, after a short delay, the circuit is made through the whole winding and a series resistor. After the initial energization, therefore, the clutch current is reduced to a holding-value which allows of ready disengagement when the clutch coil is to be de-energized. The overall movement of the pilot motors 125, 126 is restricted by means of limit switches. The field windings 105, 106 of the motors 14, 26 are supplied through rectifier 90 which is connected to adjustable resistor 101 and transformer winding 96. A rectifier 68 supplies the control circuits. Specification 609,819 is referred to.