US 2113226 A
Description (OCR text may contain errors)
April 5, 1938.
C. J. YOUNG SOUND RECORDING AND REPRODUCING SYSTEM Filed May 8, 1935 INVENTOR CHARLES J. YOUNG ATTORNEY Patented Apr. 5, 1938 UNITED STATES PATENT OFFICE SYSTEM Charles J. Young, Haverford, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application May 8, 1935, Serial No. 20,326
This invention relates to sound recording and reproducing systems, and has for its principal obiect the provision of an improved apparatus and method of operation for continually maintaining the sound translation point of the record at a speed which is constant with respect to the sound recording or reproducing element.
Various means have been provided in the past for driving a sound record in a manner to ensure constancy of speed at the translation point where the sound is being recorded or reproduced. In connection with sound records of the disk type, such means have usually involved the use of friction gears or other mechanical elements which are constantly adjusted to increase the record speed as the cutter or reproducer approaches the center of the record. Such means have not proved altogether satisfactory for the reason that they are complicated in structure, can be accurately constructed only at very considerable expense and are likely to get out of adjustment.
In accordance with the present invention, these difllculties are avoided by recording sound at a speed which is substantially constant from one end of the sound track to the other and recording with the sound a control component of a frequency which is inaudible and which changes gradually along the record. During reproduction of sound from the record, this inaudible component is reproduced together with the sound, is separately amplified and is utilized to regulate the speed of the reproduced record.
Further objects of the invention are to provide an improved sound record on which is superimposed a control current record of inaudible frequency and to provide means whereby this control current may be utilized to maintain the speed of the sound translation point constant with respect to the pick-up device or reproducer.
The invention will be better understood from the following description when considered in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.
Referring to the drawing:
Fig. 1 is a diagrammatic showing of a sound recording system operable in accordance with the invention, and
Fig. 2 is a similar showing of a sound reproducing system.
The recording system of Fig. 1 includes a turntable III which has its rotational speed so controlled as to ensure that the point at which sound is recorded on a record blank always moves at a speed which is constant with respect to the cutter. Any suitable driving means may be utilized to ensure that the turntable speed is increased at the proper rate as the cutter moves from the periphery toward the center of the record.
Audio current is supplied to the cutter l2 from a microphone or other pick-up device through an amplifier, these elements being generally indicated at i3. Superimposed on theaudio current supplied to the cutter is the output current of an oscillation generator and amplifier generally indicated at H. For gradually varying the frequency at which current is delivered by the generator, the tuning element or elements of the generator are suitably geared to the shaft l of the turntable Ill. The record produced under these conditions contains a sound component and a control component of a frequency which gradually changes from one end of the record to the other. If a sub-audible control current frequency is utilized, the frequency may be ten cycles when the cutter is at a six inch radius and may gradually increase to thirty cycles when the cutter isg at a two inch radius. In other words, the control current frequency is preferably inversely proportional to the distance of the cutter from the center of the record.
A suitable type of apparatus for reproducing the record just described is illustrated by Fig. 2 wherein i is the record, 2 is the drive motor which may be of the induction disk type. and 3 is an inductor alternator rotor mounted on the turntable shaft together with the drive motor rotor. The inductor alternator includes a stator 4 upon which are wound a direct current winding 5 and an alternating current winding 2i connected through transformer 6 to the anode circuit of tubes 1.
Operatively associated with the record I is a pick-up device 8 which supplies acoustically modulated current through an amplifier 9 to a loud speaker l0. From the pick-up device 8, control current of gradually varying frequency is supplied through a transformer 21 to the input circuit of an amplifier tube 28 which has its output circuit coupled through a transformer 29 to the input circuits of tubes 1. With these connections, there is impressed on the grids of tubes 1 control potentials which are substantially in phase opposition. Condensers 30 and 31 are connected across the transformer secondary windings to facilitate the selection of the range of recorded control frequencies and a potential source [6 is arranged to bias tubes 1 to cut-off.
To operate the reproducer, the pick-up device 8 is placed on the record at its outer edge in the usual way. Even before the beginning of the selection to be played the sub-audible frequency, for example ten cycles, is transmitted through the amplifier to the tubes 7. These tubes thus act as a thermionic brake on the alternator and lock in the shaft of the phonograph at the correct speed. 'As the pick-up travels towards the center of the record, the recorded control frequency gradually increases and the alternator synchronizes the shaft at constantly increasing speeds. Thus, the pick-up moves with constant linear velocity over the record as in the original recording process.
It should be noted that the inductor alternator actually supplies power to the tubes 1 which act to brake the alternator and regulate the phonograph speed. While the phonograph may be driven by suitably regulated mechanical or electrical drive means, the induction disk motor type of drive is preferred. It is, of course, apparent that the inductor alternator may be geared to the phonograph drive shaft so as to run at high speed in cases where this is found desirable. The type of record described has the advantage that the playing time for a given record surface is more than doubled.
Having thus described my invention, I claim:
1. The combination with a combined sound and gradually varying frequency control current disc record, of means for driving said record, means for reproducing said record, and means responsive to the control current component of said record for regulating the speed of said driving means.
2. A constant linear speed system including means for reproducing a sound component and a control current component of variable frequency from a disc record, disc record driving means,
driving means in accordance with the frequency of said control current.
3. The method of producing constant linear speed at the translation point of a combined sound and variable frequency control current record which includes reproducing said disc record, and regulating the record speed in accordance with the frequency of said control current.
4. The method of producing constant speed at the translation point of a combined sound and gradually increasing frequency control current disc record, which includes reproducing said record, and increasing the rotational speed of said record in accordance with the increase in the frequency of said control current. 4
5. A constant linear speed system including means for reproducing a sound component and. a control current component of variable frequency from a disc record, disc record driving means, and means including an inductor generator operable to regulate the speed of said driving means in accordance with the frequency of said control current.
6. A constant linear speed system including means for reproducing a combined sound and variable frequency control current disc record, record driving means of the induction disk type, and means including an inductor alternator operable to regulate the speed of said driving means in accordance with the frequency of said control current.
CHARLES J. YOUNG.
.and means operable to regulate the speed of said