Patent GB-190803592-A (GB)
Title: Improvements in and relating to Electric servo-motor Systems.
Inventor: GRAMMONT ALEXANDRE
Filed: 1908-02-17
Granted: 1909-02-17
Abstract: 3592. Grammont, A., and Routin, J. L. Feb. 21,1907, [date applied for under Section 91 of Patents cEc. Act, 1907]. Motor control systems ; switches.-In an electric servo-motor system, the receiver of orders consists of an asynchronous motor, an auxiliary generator, and apparatus which determines the direction and duration of rotation of the servo - motor and the excitation of the auxiliary generator. The rotor 1 of the asynchronous motor at the transmitting- station and the rotor 3 at the raceiving-station are fed with single - phase current, while the stators 2, 4 are fed with three-phase current. When the rotor 1 is displaced, the rotor 3 is displaced to the same extent, thereby operating an arm 21 or 22 through the medium of worm-gearing 5, 6, a bevel-wheel 7, planet-wheel 9, bevel-wheel 10, shaft 8, and arm 20. This arm 20 carries contacts at its end which engage with .contacts on the arms 21, 22 when the arm is moved in a clockwise or an anti-clockwise direction. If the arm 20 is moved in a clcckwise direction, a contact 24<a> is removed from a contact 24, thereby removing a short-circuit about a resistance r<2> placed in parallel with an electro-magnet 26. The arm 16 is then attracted, connecting the motor armature 13 to the auxiliary generator 15, the shaft 12 of the motor 13 causing the arm 20 to be moved in an anti - clockwise direction until the shortcircuiting contacts 24, 24<a> engage, whereupon the magnet 26 is de-energized and the motor armature 13 is short-circuited to produce a braking effect. The field winding 18 of the auxiliary generator 15 is controlled by the movement of the arm 20 by the engagement of this arm 20 with the arm 22. The circuit of the winding 18 is then as follows : lead c<13>, winding 18, lead e<14>, ring 19, arms 20, 22, resistances r<3>, r<4>, r<5>, r<6>, ring 25, and lead c'‹. The continued movement of the arm 20 successively cuts out the resistances r', r<4>, r<5>, r<6>, thereby increasing the excitation of the field winding 18 and consequently the speed of the motor armature 13, so that movements due to large displacements of the arm 20 are executed at a high speed, while movements due to small displacements are executed slowly. If the arm 20 is moved in an anti-clockwise direction, the magnet 27 is energized, and the arm is turned in a clockwise direction by the motor 13. When it is desired .to stop the execution of the order, the switch 28 is opened, thereby deenergizing the magnet 26 or 27 and causing the armature 13 to be short-circuited to produce a braking effect. When the motor 13 is running at full speed, its back electromotive force is nearly equal to the pressure of the generator, so that, when the excitation of the generator is reduced by the movement of the arm 21 or 22, the motor 13 becomes a generator, and this continues while the speed of the motor gives a .higher pressure than that of the generator, thereby producing a progressive braking effect. In a modification, the levers 16, 17 may be dispensed with, in which case the field winding 18 is placed between the contacts 23b, 24b and a second fixed ring identical with the ring 19 for the contacts of the arms 21, 22. In this case, the movements of the arms 21, 22 reverse the excitation of the winding 18, and so reverse the direction of rotation of the armature 13. To obviate the effects of residual magnetism, a mechanical brake disengaged by the main current is employed, and, if necessary, a fixed resistance inserted in the circuit of the armatures 13, 15. A common wire may be used for conveying the single-phase current to the rotors 1, 3 and the stators 2, 4 ; while, if the receiving-station has no local source capable of supplying continuous current, two wires supplying continuous current, or a third wire which, combined with those feeding the rotors, allows of transmitting three-phase current, and a rotary converter are added. A non-reversible worm gear is placed between the shaft 12 and the - mechanism operated, while axial shocks due to stopping may be taken up by means of a series of Belleville disks placed at each end of the shaft.