Patent GB-306426-A (GB)
Title: Improvements in and connected with sound reproducing apparatus for use with cinematograph films
IPC: G03B31/00
Filed: 1927-10-15
Abstract: 306,426. Stevens, A. Oct. 15, 1927. Sound-reproducing machines associated with kinematographs; tape machines; pickups, arranging and supporting; tape records; sound-grooves.- Relates to apparatus for reproducing sound simultaneously with the working of a kinematograph projector. According to the invention, a strip bearing sound-record grooves is driven alternately in opposite directions past a sound-reproducer such as an electric pick-up, the feed-mechanism for the strip being driven by one or other of a pair of electromotors, each of which serves also to drive one of a pair of picture-projecting machines. In the preferred construction, the record strip has a number of independent parallel soundgrooves running along its length. The arrange,- ment is such that when one picture projector is working, the sound-record strip is driven in one direction; at the end of the travel of the strip, the circuit of the operating motor is broken, and after the sound-reproducer has been shifted so as to coact with an adjacent track on the record, a control lever is moved, whereby the other picture projector is brought into action and its motor drives the record strip in the opposite direction. The record strip passes to and fro between two spools, and means are provided for keeping it taut during its travel. Sound-record strip and feed mechanism therefor :-The sound-record L, consisting of a perforated metal strip having molded thereon a composition which receives the parallel sound-grooves, is drawn from one to another of two spools J, J<1> by means of a sprocket wheel F. The sprocket is fixed on a spindle A' carrying a bevel wheel A, with which either of two wheels p, p<1> can be brought into gear by movement of a lever C. When the wheel p is in gear with the wheel A, the circuit of the driving motor M of a picture projector P is closed, as subsequently described, and as the motor drives the projector P it drives at the same time the record feed sprocket F through a shaft S and the wheels p, A. Shifting over the lever C, after the circuit of the motor M has been broken, brings the other projector P<1> into action, and at the same time causes its motor M<1> to reverse the driving movement of the sprocket F, by means of the shaft S' and wheels p<1>, A. Each spool J, J<1> is mounted between and in frictional engagement with a pair of rotatable plates g, g<2> or g<1>, g<3>. The plates g, g<1> are driven in opposite directions, as the strip travels, by chain and sprocket gearing G, G<1> and toothed wheels a, a<1>, a<2>, the wheel a<2> being fixed on the spindle A<1>, and the wheels a, a<1> being mounted on a pivoted carrier a<3> which is rocked by movement of the arm C so as to bring one or other of the wheels a, a<1> into gear with the wheel a<2>. By this means, the spool from which the strip is being unwound at any time always tends to rotate in the opposite direction to the take-up spool (the frictional mounting of the unwinding spool providing the necessary slip), and the strip is kept taut. Mounting sound-reproducing pick-up:-The reproducer, in the apparatus shown, is an electric pick-up, operating a loud-speaker R' through an amplifier R. The pick-up is mounted on a sleeve N<1>, fitted on to a support N<2>, Fig. 5, having a pin N<3> which is adapted to engage in any one of a series of staggered slots N<4> in the sleeve. This arrangement enables the pick-up to be moved when and as required, so that the needle can engage with any one of the sound-grooves on the record. When the pick-up is adjusted for any one groove, the slope of the needle is appropriate to the direction of travel of the strip whilst reproduction from that particular groove is occurring. Switching-arrangements for starting and stopping, and for changing-over :-Mounted on the framework of the sound-reproducing machine are a pair of insulated metal rollers O, O<1> which bear on the record strip. This is provided with contacts, one at each end, so that when the strip reaches the end of its travel in either direction, one of the rollers is connected through the frame to a battery T, Fig. 14. Two switches m, m<1> are also provided, each having three pairs of contacts 4, 3; 1, 2; 6, 7. These switches are constructed as shown in Fig. 12, the contacts referred to being mounted on a base u, and a slidable spring- pressed bar U<3> being provided, the bar carrying two bridging contacts 3<a>, 5. An electromagnet U or U<1> has an armature forming a detent which holds the bar U<3> when the contacts 6, 7 and 4, 3 are bridged, but which, when attracted, releases the bar and allows it to bridge the contacts 1, 2. The electromagnets U, U<1>, switches m, m<1>, rollers O, O<1> and battery T are connected as shown in Fig. 14. The lever C carries two contacts Q<1>, Fig. 13, connected to an electromagnet Q, which, when energized, holds in the inoperative position a brake (not shown) adapted to act on the spindle A<1>. When the arm C is moved to either of its extreme lateral positions, the contacts Q<1> engage contacts Q<3> or Q<5> arranged in the circuits of the motors M, M<1> as shown in Fig. 13, the contacts 6, 7 of the switches m, m<1> being included in these circuits; the main leads are shown at Z, Z<1>. Manual switches X, X<1> are also provided to enable the picture projectors to be run independently of the soundreproducing machine when desired. The action of the switching arrangements is as follows. Starting with the contacts in the switches m, m<1> connected as shown in Fig. 14, and the arm C so placed that the circuit of the motor M is closed at Q<5>, the record strip is driven until at the end of its travel in one direction one of the contacts on it closes the circuit from the battery T through the magnet U. Thereupon the bar U<3> of the switch m is released, disconnects its contacts 3, 4, closes its contacts 1, 2, and breaks the circuit of the motor M at 6, 7. The switch m<1> is then moved by hand to its other position (with its own contacts 1, 2 open and the other contacts bridged), and after the pick-up has been adjusted to engage the next record groove, the lever C is moved over to close the circuit of the motor M<1> at Q<3>, with the result that the record strip is driven in the reverse direction. Safety device.-To prevent risk of a picture film being ignited when it is stationary by heat from the lamp, the film gate may be automatically closed by a shutter, as soon as the film stops, the shutter being normally held up by a catch, but being released and allowed to drop when the catch is pushed aside by the movement of the adjacent switch-bar U<3>.