The Film Daily (1929)

THE •swan DAILY Wednesday, July 10, 1929 24th Instalment, 'Sound Patent' Series ADD'L USES FOR MOTORS This is the twenty-fourth instalment in "Sound Patents," a series of articles dealing zvith the patent history of sound and synchronisation devices in the United States, England, France and Germany. Benjamin T. Rauber, New York patent attorney, is the author. In United States patent No. 941,891, issued to Pietro Pierini Nov. 30, 1909, and in corresponding British patent No. 10,396, issued to him on Aug. 13, 1909, a synchronous motor is used, not for the purpose of driving the phonograph, but to control the speed of an independently driven phonograph. This is accomplished by connecting the synchronous motor to the driving shaft of the phonograph. As the synchronous motor is driven at a speed proportional to that of the projection machine, it acts as a brake against any tendency of the phonograph drive to rotate at too rapid a speed and, on the other hand, tends to accelerate the phonograph drive if it should tend to lag. By thus removing the burden of driving the phonograph entirely from the synchronous motor the effects of friction or other retarding causes which might cause the motor to run more slowly than the projection machine are removed. The apparatus is shown diagrammatically in Figs. 1 and 2 of the patent, in which a motor (1) for driving the projection machine is mechanically Another use for synchronous motors in connection with sound. U. S. Patent No. 941,891 jfo K? £>3 Wiring arrangement illustrating in Higham system. connected through a belt (2) to a shaft (3) on which is mounted the alternating device or commutator for controlling the supply of current to the synchronous motor that control the speed of the phonograph. As shown in Fig. 2 this commutator device comprises three cylindrical segments (30, 31 and 32) insulated from each other and connected by wires to slip rings (33, 34 and 35) respectively. A battery (8) is connected to a pair of brushes (6 and 7) so positioned as to contact with two of the segments (30-32). As the shaft (3) rotates, the brushes (6 and 7) are successively connected to definite pairs of segments and thus, through the slip rings (33) and their respective brushes (18, 19 and 20) to corresponding pairs of wires (21, 22 and 23). Accordingly, with each rotation of the shaft (3) the current successively enters the wires (21, 22 and 23) and returns through another of the wires (21, 22 and 23). The wires (21, 22 and 23) are connected to the field poles of an induction motor (24) having nine field poles. In the winding of this field motor the wire (21) is connected successively to the first, fourth and seventh pole, the wire (22) to the second, fifth and eighth, and the wire (23) to the third, sixth and ninth poles, so that the respective sets of poles are successively energized with each revolution of the shaft (3). The effect of this arrangement is to cause the rotating armature (25) to advance the space of one field magnet pole with each change of the connection of the wires (21, 22 and 23) to the battery (8) or to advance a distance of three poles for each revolution of the shaft (3) or an entire revolution of the armature for each three revolutions of the shaft. This arrangement is a common expedient for decreasing the speed of a motor relative to the change of pha=p of the current supplied to it, the speed being inversely proportional to the number of poles. Synchronous motors and phase changing commutators have been how synchronous motor drives belt used U. S. Patent .... i u:>4,_uJ shown in connecting projection machine and phonograph in apparatus described in previous instalments, aUiamatre being that the projection machine and phonograp! could thereby be placed at any desired distance from each other inasmuch as they are connected by electric wiring rather than by mechanii ur.ve 1' or example in United States patent No. 941,211, issued to Franz E. Thormeyer on Nov. 23, 1909, an arrangement of a synchronous motor drive is substituted for the gear wheels (16 and 17) in the device of patent No. 989,207 described in the seventeenth instalment on May 2. In the apparatus of patent No. 941,211, the gear (16) on the shaft (11 ) for driving the projection machine is patent No. 989,207, is replaced by a commutator (5) which controls, in a manner similar to that of the previously described apparatus, a driving motor (6) of a projection machine (7). The brushes of the commutator may be shifted to speed up or retard the projection machine motor and to thus bring it into synchronism with the phonograph. This is accomplished by swinging the arms (5c) in one direction or the other. S-'milarly, the Higham patent No. 1,054,203 described in the seventh instalment on March 17, also shows ■n Fig. 8 an arrangement in which the belt drive is replaced by a synchronously driven motor and appropriate motor mechanism. The figure is merely a diagrammatic showing of the wiring arrangements, the mechanical construction being obvious from the wiring diagram. In this diagram a pair of rotating rings (57 and 58) and a split ring or commutator (59, 60) are shown side by side but in actual construction are to be mounted on a single shaft or on the phonograph mandrel. The rings (57 and 58) are connected by means of brushes (61, 62) to a battery or other source of electricity (63) and are also permanently connected to the rings (59 and 60) respectively. The three brushes (64, 65 and 66) also bear on the rings (59, 60) which are insulated from each other, in such a manner that with each rotation of the shaft on which the rings are mounted the ring (60) is in contact with one of the brushes (64, 65 and 66) and the ring (59) is in contact with the other. Each of the brushes (64, 65 and 66) is connected through a wire (67, 68 or 69) to the field magnet (70, 71 and 72) respectively. In the position of the apparatus shown in the figure, current from the battery (66), therefore, passes through the brush (61) rings (57) to the ring segment (60) and thence through the brush (65) and wire (68) to the field magnet (71) and thence to the frame of the motor and returns through t^e field magnets (70 and 72) and connecting wire (67 and 69) to the ring segment (59) and returns to the battery or source of electricity. The field magnet (71) is thereby energized in such a manner as to attract the rotor (12) of the motor. Upon the further rotation of the phonograph shaft or mandrel the brush (64) is brought in contact with the ring segment (60) and the field magnet (70) energized in such a manner as to rotate the rotor (12) still further and, through this succession of changes in current, the rotor (12) which is used to drive the projection machine is caused to rotate at a speed proportionate to the rotation of the phonograph. A curious use of a commutator is shown in Brtish patent No. 10,519 of June 26, 1913, and in United States patent No. 1,213.883, of Jan. 30, 1917. both granted to I. Kitsee, although neither shows the use of a synchronous motor. The commutator is used in the Kitsee apparatus to control the t:med admission of compressed air to a compressed air motor driving and projection machine. The arrangement of the apparatus is shown in Fig. 9 of the United States patent. In this apparatus the shaft or mandrel (67) of the phonograph cylinder (R) drives a commutator shaft (651 through a belt (66). The commutator shaft has a number of insulated contacts (49, 50) etc., each of which is insulated from the other and is electrically connected to a circular contact surface (47) which is, in turn, connected through a brush (46) to a generator (45). As the commutator is rotated each of the contacts (Continued on Page 8) Commutator figures importantly in Kitsee device, U. S. Patent No. 1,213,883