US1957512A - Phonograph reproducer with superaudible frequency - Google Patents

Description

Patented May 8, 1934- PATENT OFFICE PHONOGRAPH REPRODUCER WITH SUPER- AUDIBLE FREQUENCY Julius Weinberger, New York, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application October 27,

10 Claims.

The invention concerns a phonograph reproducer and has for its principal object to provide a reproducer particularly adapted for playing phonograph records on which the markings correspond to super-audible frequency vibrations modulated at the frequencies of the sounds to be reproduced.

A further object of the invention is to provide a reproducer for such modulated high frequency records having a natural resonant frequency corresponding to the frequency of the carrier wave or the high frequency oscillations recorded on the record.

In a copending application, Ser. No. 60,369, filed Oct. 5, 1925, I have disclosed and described a phonograph record on which the markings corresponding to the sounds to be reproduced are in the nature of engravings of super-audible frequency vibrations modulated at audio frequencies. In making these records, a high frequency oscillator of constant frequency has its output modulated at audio frequencies and the record is engraved by a stylus vibrated at these modulated high frequencies. It is obvious that in playing such a record, if it is rotated at a constant speed, high frequency vibrations of constant frequency will be imparted to the reproducing stylus.

I propose according to the present invention to provide a reproducer having a natural resonant frequency equal to that of the carrier or superaudible frequency used on the records. A reproducer made in this way will naturally tend to vibrate at the carrier frequency and will easily and readily follow the markings on the grooves. Such reproducers may be made either of the piezo-electric crystal type using a crystal having the required natural frequency or electromagnetic or electro-static reproducers whose vibrating elements have the required natural frequency.

The invention is illustrated by way of example in the accompanying drawing in which,

Fig. 1 shows a reproducer of the piezo-electric crystal type.

45: Fig. 2 shows a condenser reproducer. and

Figs. 3 and 4 show sectional views at right angles to each other of an electro-magnetic reproducer. the section of Fig. 4 being taken along the line 44 of Fig. 3.

Figure 5 is an enlarged view of a portion of a record for which my improved reproducer is especially adapted, and,

Figure 6 is a diagrammatic sketch of a turntable, record and reproducer.

Referring to Fig. 1 a piezo-electric crystal of 1925, Serial No. 65,135

the required frequency characteristics is shown at l and is fastened at its ends to two extended bases 4 and 5. The crystal is provided on opposite sides with sheets of insulating material 2 overlaying which are a pair of metal plates 3 to which the connecting wires of the device may be attached. The crystal with its base pieces is placed in a generally cylindrical container 7, the latter being provided at one end with an internally extending flange 8 serving as an abutment to hold the base member 5 in place. A resilient member 43 may be provided between the flange and the base member to permit vibrations of the latter. The base member 4 rests against an annular shoulder in the opposite end of the container 7 and is held in place by a cap 6 having screw threaded engagement with the container. A lever arm 9 pivoted at 10 on a lug integral with the container 7, is fastened at one end to the central portion of the base member 5 and is provided at its opposite end with the stylus carrier 11. As the stylus follows the groove of the record it will have vibrations impressed upon it of the natural frequency of the crystal 1 and therefore in reproducing the record the crystal will vibrate at its natural frequency.

Fig. 2 shows a modification of the invention making use of a condenser reproducer. The plates of the condenser comprise the block 12 and the thin metallic diaphragm 13, of which the former is mounted on a block of insulation 4 and supported against an annular collar in the supporting ring 15, being retained in place by the retaining ring 16. The diaphragm 13 is clamped at its edges between co-acting annular serrations 20 in clamping rings 15. and 17 and these rings are fastened together by suitable bolts 21. The thin diaphragm 13 naturally has a high natural period of vibration and means are provided in the present case for stretching the diaphragm until its natural frequency corresponds to that of the carrier wave on the record. In the present case, the stretching means consists of a ring 18 bearing against the edge portion of the diaphragm between the annular support 117, forming part of the ring 17, and the clamp consisting of the serrations 20. The position of the ring 18 can be adjusted by the screws 19 and by tightening or loosening these screws the proper tension can be applied to the diaphragm. The stylus carrier 24 is mounted on one end of a lever 22, pivoted at 23 and having its opposite end secured to the middle portion of the diaphragm 13. When the stylus vibrates in following the markings on the record,

the diaphragm 13 will be caused to vibrate at its natural frequency in which case the capacity of the condenser formed by the diaphragm and blocl: 12 will change in accordance with the vibrations.

An electro-magnetic type of reproducer is shown in Figs. 3 and 4. The diaphragm 32 of this reproducer is clamped between serrations on the casing 30 and the retaining ring 31 and means are provided for varying the tension on the diaphragm, consisting of the ring 40 adjustable as to position by means of the adjusting screws il. This arrangement is entirely similar to that shown in Fig. 2. Within the casing 30 is provided a U-shaped magnet 36 having extensicns 37 fastened to its ends which extensions are provided with pole pieces 38, the end of these pole pieces being located in proximity to the center of the diaphragm. The operating coils 39 are wound on the extending pole pieces 38. It will be understood that in this case also, the diaphragm 32 will be properly tensioned to cause it to have a natural resonant frequency equal to the carrier wave frequency of the records to be reproduced; The lever 33 is pivoted at 35 and attached at one end to the center of the diaphragm 32. At its other end it carries the stylus carrier 34. As the diaphragm vibrates in response to the movements of the stylus, it will vary the air gap between the magnetic pole pieces 38 and cause a variation in the flux through the pole pieces corresponding to the vibrations of the diaphragm. This varying flux induces currents in the coils 39 which likewise correspond in frequency and amplitude to the original markings on the phonograph record.

Figure 5 is an enlarged view of a portion of a record 101 upon which modulated waves 151 have been engraved.

Figure 6 shows diagrammatically such a record upon a turn-table 103 in position for playing, I02 representing a reproducer which may be any one of the types shown in Figures 1 to 4.

While I have illustrated and described my invention with respect to several specific modifications, it will be obvious that various other adaptations will readily suggest themselves to those skilled in the art; for example, the vibrating elements of the condenser and magnetic reproducers need not be diaphragms but can be other elements having the requisite frequency characteristics.

I intend to be limited therefore only as indicated by th scope of the following claims:

1. A phonograph reproducer for reproducing phonograph records having modulated high frequency vibrations recorded thereon comprising an element adapted to be vibrated by said recorded vibrations, said element having a natural resonant frequency equal to the carrier wave frequency recorded on the record.

2. A phonograph reproducer for reproducing phonograph records having modulated high frequency vibrations recorded thereon comprising a piezo-electric crystal having a mechanical resonant frequency equal to the carrier wave frequency recorded on the record.

3. In combination, a record having a modulated wave engraved thereon, and a reproducer having an element whose natural period of oscillation is substantially equal to the period of the engraved wave.

4. In combination, a record having a wave of constant frequency modulated by a variable frequency recorded thereon, and an element actuated by said recorded wave, said element having a natural period substantially equal to the frequency of the constant frequency component of the wave on the record.

5. In combination, a phonograph record having a modulated wave recorded thereon and a reproducer comprising a piezo-electric crystal whose natural period equals that of the recorded wave.

6. In combination, a record having a wave of modulated inaudible frequency recorded thereon, and a reproducer having an element responsive to said recordings and whose natural period equals that of the recorded inaudible wave.

7. In combination, a uniformly rotatable member having recordings of modulated constant frequency thereon, and an element responsive to said recordings whose natural period substantially equals that of the recordings.

8. In combination, a record having a wave of constant frequency recorded thereon, and a piezoelectric crystal whose natural period of vibration equals that of the wave recorded on the record adapted to be actuated by said recorded wave.

9. In combination, an element having a wave of constant frequency recorded thereon, a piezo electric crystal whose natural period of vibration equals that of the constant frequency wave recorded on the element, and means for actuating said crystal by the constant frequency recordmg.

10. In combination, a movable element having recordings of a substantially constant frequency thereon, a piezo electric crystal whose natural period of vibration substantially equals that of the recording, and means adapted to be actuated by said recordings for mechanically vibrating said crystal.

JULIUS WEINBERGER.

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