Patent GB-340528-A (GB)
Title: Improvements in or relating to combined cinematographic and phonographic apparatus
IPC: G03B31/00
Filed: 1929-09-17
Abstract: 340,528. Stencil switches. CLIFFORD, E., 27, Worcester Street, and JOHNSON, R. B., Mulgrave House, London Road, both in Gloucester. Sept. 17, 1929, No. 28124. [Class 38 (v).] Pneumatic actuation.-For use with a volumecontrol device or " fader for sound-reproducing apparatus working synchronously with a kinematograph, a movable sheet or the equivalent is provided, operating in synchronism with the kinematograph and the sound-reproducing apparatus and having slots or the like therein, arranged in such a manner as to serve to effect automatically the requisite adjustments of the fader from time to time. In the arrangement shown in Fig. 8, a slotted sheet k driven by the kinematograph controls a set of pneumatically operated contacts 29 which are individually connected to the contacts 1c .. 15c of the fader b, Fig. 6. The pneumatic control device comprises a tracker-bar 17 over which the slotted sheet passes, a number of pipes 19 connecting ports in the bar to a corresponding number of bellows 27, each of which operates a contact, and a suction chamber 21 with valves 28, common to all the bellows. At any instant, the length of the resistance wire f of the potentiometer which is in circuit depends upon which particular contact finger has been brought into action by the slotted sheet k. The arrangement is shown as duplicated, the fader having two potentiometers for use respectively with two amplifiers A, A<1> (one for each of two sound-reproducers). Figs. 10 and 12 show apparatus whereby the contact-carrying spindle c of a fader may be automatically rotated in either direction to various positions, under the control of a fader sheet of the kind described above. The spindle c is geared through reduction gearing to a shaft 32 which can be clutched to one or other of the driving shafts 33<a>, 34<a> of two electromotors 33, 34, adapted to run in opposite directions. The clutching is effected by means of electromagnets 35, 36, fixed on opposite ends of the shaft 32. The armatures of the magnets are discs 35a, 36a, each splined on the respective motor shaft, and when either electromagnet is energized, its armature couples the shaft of the associated motor 33 or 34 to the shaft 32. The circuits of the magnets are selectively closed through slip rings and brushes D, D<1>, a fixed contact bar 38, Fig. 12, and a pair of movable contacts 37, 37<a>, the latter contacts being mounted on plungers of pistons 39 which slide in cylinders 39<a>, to which suction is applied through pipes 39b. A fader sheet k provided with two rows of appropriately disposed slots passes over and normally closes an inlet pipe 39c on the end of each cylinder. The arrangement is such that when a slot registers with one of the pipes 39<c>, the corresponding piston 39 is moved downwards, bringing its contact 37 or 37<a> against the bar 38. Thus, one of the magnets 35 or 36 is energized, and the corresponding motor 33 or 34 rotates the shaft 32, and thereby the fader spindle c, in one direction or the other, the extent of rotation depending on the length of the slot in the fader sheet which is then in action. A rotating disc, with controlling devices arranged concentrically thereon, may be used instead of a longitudinally moving sheet.