Patent GB-468442-A (GB)
Title: Sound recording and reproducing
IPC: G11B3/00
Filed: 1935-12-05
Abstract: 468,442. Sound film apparatus. DEHN, F. B. (Ripley Corporation) Dec. 5, 1935, No. 33770. [Class 40 (ii)] Relates to a method of recording sound in which a vibratory recording stylus is brought into engagement with a record strip of permanently deformable material while the strip is passed over a support. According to the invention, the strip is passed over an arcuate support having one or more channels in its supporting surface, the support being stationary so as to produce a drag and hugging contact of the strip therewith and the stylus engaging the strip in line with the channel or one of the channels. A film 12, Fig. 1, is wound at its ends on two reels (not shown) and is provided near each end with a notch which operates suitable mechanism adapted to effect reversal of the film feed. The film passes from one reel around idler rollers 13, 14, 15, 16 and 16<a> to one side of the driving drum A from whence it passes over the idler roller 17 to the stationary recording drum or other arcuate anvil B after which it passes under a further idler roller 18, over the other side of the driving drum and around idler rollers 19, 20, 14 and 21 to the other reel. A recording head C, connected through an amplifier C<3> to a microphone C<2>, and a pick-up D, connected through an amplifier D<2> to a loud-speaker D<3> are so mounted adjacent the recording drum that either the recording stylus C<1> or the reproducing needle D<1> or both, can be brought into engagement with the film as it passes around the drum B, when both the stylus and needle are in engagement with the film an observer is able to check the recording while it is being done. The driving drum A, which is shown in section in Fig. 2, comprises a driven shaft 22 on which is keyed the driving drum 23 having an annular shoulder 25 and spaced rubber friction bands 24 which preferably extend slightly above the cylindrical surface of the drum. The film when pressed laterally against the shoulder 25 extends slightly beyond the opposite edge of the drum. A thin spring sheet metal disc 26 is pressed against a hub 23<a> on the drum 23 by a hub 27<a> on a nut 27 which is screwed on the outer end of shaft 22. The hub 23<a> projects slightly farther than the overhanging portion of the film so that when no pressure is applied to the disc it has a tendency to stand very slightly away from the film. A plate 28, which during recording is normally stationary, is journalled on the hub 27a and has along its upper edge a series of axial holes 29 in each of which is a spring- pressed plunger 30 carrying a small leather finger 31 adapted to press against the outer surface of disc 26. Two or more similar fingers 33 are provided at the opposite side of the plate 28. This plate is also provided with pins 35, 36 adapted, as shown in Fig. 1, to engage with a stop 37 carried by the front panel 11, the arrangement being such that, when the shaft 22 is rotated in a counterclockwise direction, the pin 35 engages with the upper side of the stop whilst, when the rotation of shaft 22 is reversed, the plate 28 is carried round through half a revolution until the pin 36 strikes the under side of the stop. Spring-pressed arcuate shoes 38, 39, adjustable by screws 39<a>, are mounted on hinge pins 40, 41 above and below the drum so as to prevent the film from buckling under the side pressure of the disc 26. The recording anvil 45, Fig. 6, is retained against a shoulder 44 on an eccentric sleeve 43 mounted on a stud 42 by means of a ring 46 which is held in place by screws 47 passing through the front panel 11. The sleeve 43 carries a shift lever 48 co-operating with an adjustable stop screw 48<a>. The member 45 comprises a thin annular anvil element 45<a> and a shoulder 45<b> against which one edge of the film bears. A heavy shoe 50 is pressed against the overhanging edge of the film by a spring 51 abutting against a split washer 52 seated in an annular slot 53 in the sleeve 43. On release of a lock-nut 54 threaded on the outer end of the stud 42, the sleeve 43 can be partially rotated by the lever 48 either to regulate the depth of the sound groove or so as to bring the film out of contact with the recording stylus. As shown in Fig. 5, the anvil element 45<a> is provided with a number of equally spaced V-section channels 45<a>, the width of which is sufficiently greater than that of the sound groove to accommodate the lateral shifting therein of the material embossed on the reverse side of the film by the laterally vibrating stylus. Preferably, each channel is made twice as wide as the sound groove. Each time the direction of feed of the film is reversed, the recording head C is stepped transversely of the film, being slidably mounted on a stationary guide 56 and carrying an indicator mechanism 57 which is movable beneath a pointer 58 to indicate the channel over which the recording stylus is operating. The pick-up D is carried by an arm 59 which is mounted on vertical pivots 60 and a horizontal pivot 60<a> and has a pin 61 in line with the needle D<1>, the pin engaging an arm 62 connecting the outer end of the arm 59 with the recording head C. The arm 59 can be raised and lowered by operation of the knurled nut on the screw 63 in order to bring the needle D<1> into and out of engagement with the sound groove. If desired, a second pick-up may be provided on the opposite side of the drum B to the pickup D. Specification 398,656 is referred to.