US2107050A - Sound recorder and reproducer - Google Patents

Description

Feb. 1, 1938. M. BENDER 2,107,050

SOUND RECORDER AND REPRODUCER Filed July 8, 1953 Qflj wu 4, 1/4 llllll lHlll l I I I [I I INVENTOR ATTORNEY Patented Feb. 1, 1938 UNITED STATES SOUND RECORDER AND REPRODUCER,

Max Bender, Astoria, N. Y., assignor, by mesne assignments, to United Acoustigraph Corporation, a corporation of Nevada Application July 8, 1933, Serial No. 679,465

1 Claim.

This invention relates to a recording and reproducing of sound, and has for its object an improved apparatus for recording sound in the form of a groove in relatively hard material, such for 5 example, as celluloid or motion picture film. A further object is toprovide an improved device which may be used alternately as a sound recorder and reproducer. A further object is to provide an improved form of cutting stylus.

Other objects and advantages of my invention will appear from the following description taken in connection with accompanying drawing, wherein;

Figure 1 is a top plan view of a sound recorder and reproducer embodying one form of my invention;

Figure 2 is a sectional view partly in elevation taken on the line 2--2 of Figure 1 and also 22 of Figure3, and showing in addition an anvil with a strip of film thereon;

Figure 3 is a sectional view taken on the line 3--3 of Figure 2; v

Figure 4 is a sectional view taken on the line 4-4 of Figure 2;

Figure 5 is an enlarged detail view showing the relative position of the movable, stylus operating, armature and the pole pieces between which the armature vibrates;

Figure 6 is a greatly enlarged side elevation of an improved form of a cutting stylus;

Figure 7 is a bottom plan view of the structure shown in Figure 6;

Figure 8 is a sectional view taken on the line 8-8 of Figure 6;

Figure 9 is a circuit diagram of the electrical connections through the armature operating coils; and

Fig. 10 is a plan view of an armature and stylus holder showing a modification.

Referring more particularly to Figures 2 to 4 inclusive, reference character l represents a permanent horse-shoe magnet which is adapted to be supported by a plate ll of brass or other non-magnetic material bolted or screwed at l2 to the ends of the poles of the magnet [0. Plate II is provided with elongated openings 3 by which the recorder may be adjustably secured in suitable support.

Secured to the sides of the permanent magnet H! by cement or any other suitable manner and extending inwardly therefrom are four coils, l4, l5, l6 and I1 respectively, arranged as shown in Figure 4. Each of the coils has an adjustable core l8, preferably of soft iron, forming at their inner ends two pairs of opposing pole pieces. The

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opposite end of each core is extended and screw threaded, and is adapted to be received in screw threaded opening 22 in the side of the permanent magnet l0, thus providing for the adjustment of the core.

Positioned between the pole pieces of each pair and adapted to vibrate on a vertical axis is an armature 25 of soft (Norway) iron. Armature 25 is supported by adjustable pivot bearings 21 and 28, secured respectively in the plate II and 10 in a brass plate 29 attached at opposite ends to the sides of the permanent magnet II], the armature preferably being provided pivot cups of hardened steel.

Plate II at opposite sides of the bearing 21 is 15 formed with openings 30 and 3| through which extend downwardly projecting parts 32 and 33 of the armature 25. The part or extension 32 of the armature carries at its lower end a recording stylus 34 and extension 33 of the armature may, 20 if desired, carry at its lower end reproducing stylus 35.

Mounted at one side of the permanent magnet l0 and extending inwardly therefrom at opposite sides of the pivotal axis of the armature are ad- 85 justable cushioning means, consisting of nonmagnetic screw threaded rods 40 received in screw threaded openings 4|, and adjustably held in place by lock nuts 42. The inner ends of the rods 40 are formed as cups 45 which contain rub- 80 her or other cushioning material 45a which extends outside of the cup and is constantly in contact with the side of the armature 25. It is to be noted that the armature in horizontal cross section is slightly tapered outwardly from its axis. 35 By forming the armature in this way, I find that I obtain more satisfactory contact of the armature with the pads and a more satisfactory operative relationship of the armature to the pole pieces, and at the same time provide sufiicient material at the center of the armature for its adequate support on the pivot bearings.

In Figure 2 I show an anvil 50 over which extends a strip of film 5|, which is adapted to be moved in the direction of the arrow 52 during the recording operation. After a record is made, it may be reproduced by adjusting the plate ll so that the reproducing stylus 34 rests in the groove of the film. Occasionally it is desired to record a groove on a film by moving the film in one direction, and then continue the recording by moving the film in the opposite direction. When this is done, I mount a recording stylus at the ends of both extensions of the armature as shown, for example, in Fig. 10, the stylu l6 carried by one extension 32 being adapted to record while the film is moved in the direction of the arrow 52 of Fig. 2 and the stylus carried at the end of the other extension being adapted to record when the film is moved in the opposite direction. 7

It will be noted from Figure 9 that the coils l4 to l1 are so wound as to tend to make oppo-. site poles of each pair of opposite sign, a north pole being opposite to a south pole and also corresponding poles of the two pair are of opposite faces 61, leaving between them a portion 68 of the original tapered surface 64. Theeflect ofgrinding or under-cutting to form surfaces 61 is to sharpen the curved edge 69 at opposite sides of the axis of the stylus where the upper surface 66 meets the lower surface of the stylus.

As the tapered surface 64 is conicalit is a comparatively simple operation to grind away this surface to a proper depth. The angle a between the upper surface 66 and the portion 68 of the tapered surface 64 should be between 25 and maximum. The angle b; as shown in Figure 8, between the surface 61 and the upper surface 66, should be between 20 and 30 maximum. I find that by forming the stylus in this manner, with the angles above given, I not only secure satisfactory cutting but there is sufiicient material back of the cutting edge to properly strengthen the stylus and minimize the breakage. In making a sound groove of the lateral type, the angle between the surface 68 and the tangent to the film at the cutting point should be approximately 25. 7

It will, of course, be understood that during the recording operation current which varies in The variation may be generated by a suitable monophone actuated by thesource of sound and the monophone current amplified by thermionic valves. ,In reproducing, the coils l4 to I! will be energized from a source of constant potential and the variations of current produced by vibrations of the armature 25. suitably amplifiedand reproduced as sound. The stylus as described makes a clean cut in the film, removing from the film a finethread of the film materiaL' Having now described my invention, what I claimand desire to secure by Letters Patent is:

In a device of the character described, a magnet having opposite poles, a fiat U shaped member of magnetic material pivotally supported at approximately the center of the bend of the U, and the, bend of the U being located between and under the influence of said poles, and a stylus secured directly in the end of each leg of the U.

- MAX BENDER.

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