US1637903A - Production of phonographic records - Google Patents

Description

0. A. HOXIE PRODUCTION OF PHONOGRAPHIC RECORDS Aug. 2,1927.

Filed Dec. 28. 1921 v Inventor: Charles A'Hoxie b W QM;

H LS Attorn ey.

records may be made by Patented Aug. 2, 1927.

UNITED LSTATES PATENT OFFICE.

cnannns A. noxm, or s'cnnnncrnmr, new YORK, ASSIGNQR r0 GENERAL nmic'rmc comrm, a conronarron or NEW YORK.

IPROD'U(i'lIONv OI PHONOGBAPHIG RECORDS.

Application filed December 28, 1921. 7 Serial lite. 525,862

My invention-relates to the production of phonograph records, particularly to the cutting of master records from which duplicate methods well known to the art.

The apparatus heretofore commonly employed forcutting master phonograph records may be described briefly as a diaphragm, upon which impinge the sound waves to berecorded, and a cutter having a cuttin tool mechanically connected with the diap ragm so as to be vibrated thereby as it'cuts a path on the surface of the wax disk or cylinder. It is well known, that sound waves representing the human-voice or those produced by I musical instruments are extremely complex in form and in the simplest case may comprise a fundamental tone upon which are superposed various overtones or harmonics by means ,of which the ear is able to distinguish one voice or instrument from another.- These harmonics often have frequencies many times that of the fundamental and may be comparatively weak and in order that they all may be faithfully recorded, all elements of the moving system including the diaphragm, the cutter tool and the connecting mechanism must be able to follow them without distortion. This ideal condition has been heretofore only partially realized with the result that reproduction of certain musical sounds has been far from perfect. Among the known contributing causes of imperfect reproduction may be mentioned the tendency of the moving; system to over-emphasize those vibrations which correspond to its natural period of vibration, the fact that the diaphragm is required to do considerable work in moving the cutting tool as it is dragged through the wax, the inertia effect of the moving system, and the effect of permitting the cutting tool to move with too great freedom, the latter being often recognizedin the reproduction by what is known as blasting.

An object of my invention therefore is to overcome or minimize the difliculties heretofore encountered whereby a greatly improved record may be produced.

Numerous other objects and advantages of my invention will appear from the following description taken in connection with the accompanying drawings, wherein Fig. 1 is a bottom plan view; Fig. 2 a side elevation; Fig. 3 a central section partly in elevation of a cutter embodying my invention; and

Fig. 4 is a diagrammatic view of one means employed for controlling said cutter.

Referring more particularly to Figs. 1 to 3, 10 represents a supporting plate provided with an upstanding lug 11 to which is pivoted a member or frame 12 having an openmg 13 across which extends avibratory strip or diaphragm 14. This strip is preferably composed of steel and is held at its endsin slots 15 in the sides of the member 12 by means of screws 16. Suitable means 17 are placed between the sides of the opening 13 and strip 14 to dampen the vibration I of the strip. Secured .to the strip 14 mid-.

way between'its ends is the jewel cutting point 18 which extends but a slight distance below the lower edge of the strip 14. The cutting point 18 is adapted to form a groove in the recorddisc 29 which is mounted for rotation about its center, suitable guiding means 60 being provided whereby the cutter may be move longitudinally by any convenient means, such ascords 61. Supported by the plate 10 .but movable relative thereto are two permanent magnets 20 and 21. The magnet 20 is held between members 22 and 23 by screws 24, the member 22 being held by a screw 25 which is adapted to move in a slot 26 formed in a plate 10. A feeding screw 27 which is threaded into member 22 and is rotatably supported in a member 28 secured to the supporting plate 10 serves to adjust the magnet 20 horizontally. The

magnet 21 is supported and adusted by similar means to those employe for the magnet 20.

Each of the magnets 20 and 21 are pro-v vided with pole pieces 30 having pole tips 31 arranged to extend in close proximity with the strip 14 upon opposite sides thereof and upon opposite sides of the cuttin point 18. The magnets are arrangedwit their poles in the positions indicated by the letters N and S in Fig. 4. 'Surroundin each pole piece 30 is a coil 32, the severa coils being connected in series and wound in the manner shown in Fig. 4. These windin' are such that if a current flowing throug the coils tends to strengthen,-say the north pole of magnet 20, it will likewise strengthen the south pole of the same magnet and weaken both poles of magnet 21. A reverse 7 current will weaken the poles of magnet 20 and strengthen the poles of magnet 21. It

. which is formed in the disc 29 when the latter is rotated. It will of course be understood that suitable means will be provided for advancing the cutter to form a continuous groove as the-record rotates.

Means is provided for raising and lowering the member 12. As here shown, this comprises a screw 34 which isthreaded into the member 12 at 35 and is rotatably mounted at 36 in a bracket 37 mounted upon a supporting plate. lBy movement of the screw 34 the member 12 is swung about its pivot.

If desired, the entire member 12 may be raised and lowered by providing for an ad justment by a screw similar to the screw 34 in place of the pivotal connection of the member 12 to the plate 10.

From the foregoing it will be seen that I have provided an electromagnetically operated cutter which is so constructed that the magnetic forces are applied in close proxcally arranged in respect thereto so that the point follows very closely the changes produced in the magnetic forces. In addition, the mass affected by these magnetic forces is small and there is therefore but a small distortion of the wave form due to the inertia of the moving parts.

In Fig. 4 I have illustrated the system comprising my invention whereby sound waves are converted into corresponding electrical waves, the electrical waves amplified without distortion and these in turn recorded on a phonograph record blank. The system comprises. essentially a transmitter, an amplifier and the recorder. The transmitter comprises a very small and light diaphragm held by a holderg41 and connected to a very small mirror 45 mounted on a delicate shaft held against jewel bearingsby the force of a magnet. A small beam of light from the source 42 is reflected by the mirror 45 into the photoelectric cell 43, the arrangement being such that as the mirror is'rocked by the vibration of the diaphragm more or less of the beam of light reflected by the mirror enters the photoelectric cell.

The construction of this transmitter is described and claimed in my United States Letters Patent No. 1,527,649, Feb. 24, 1925, and No. 1,549,550, August 11, 1925, both assigned to the same. assignee as the present application. Sound waves falling upon the diaphragm of the transmitter cause the mirror'45 to vibrate, which in turn causes the beam of light from the source 42 to vibrate 'imity to the cutting point and are symmetrimemos and by reason of the partial interception of the beam by a properly positioned screen causes the quantity of light entering the photo-electric cell 43 to vary in strict accordance with the vibration of the diaphragm. This cell is connected to the grid of the pliotron amplifier 44 and to a suitable source of current 47, the resistance 48 being interposed between the source 47 and the connection be current 51 and a resistance'5'2 across which is shunted through condensers 53 and 54 the coils of the cutter. The changes of potential of the grid 49 cause corresponding changes in the plate current with the result that impulses are sent through the coils of the cutter which likewise correspond to the changes in current. The condensers 53 and 54 are employed to prevent any direct current from flowing through the coils of the cutter. I s It will be seen that by the apparatus shown in Fig. 4 I have provided a means by which the cutter will be controlled in a manner which corresponds strictly to the form of sound waves falling uponv the diaphragm of the transmitter. The transmitter diaphragm and mirror as described in the aforesaid patents are extremely light, having a fundamental frequency which preferably is above the limits of audition and are 1051 constructed so as not to create loops within the body of the diaphragm or attached parts which would result in the formation of undesirable harmonics. The operative connection between the transmitter mirror and the photo-electric cell is without mass and therefore not liable to distortion because of its inertia. The contruction of the photo-electric cell as described in my aforesaid Patent No. 1,527,649 is such that the changes in current produced are in strict conformity with the changes of illumination, andthe connections of the pliotron are substantially free from inductance and capacity which would tend to produce a distortion of the current wave form.

. What I claim as new and desire to secure by Letters Patent of the United States, is

1. A I phonographic record cutter, com prising a vibratory. strip secured in a fixed position at its ends, a cutting point carried by said strip intermediate its ends and having its point of application in substantially; the plane of said strip. v

2. A phonographc record cutter comprismemos secured at its ends, a cutting point secured to said strip intermediate its ends andmeans for causinn said strip to move In accordancewith the sound which it is desired to record, said means comprising magnetic devices arranged to exert magnetic forces upon 'said strip at points along said strip at substantially equal distances on each side of said cutting point. p

4. A phonographic record cutter comprising a strip of magnetic material secured at its ends, a cutting point secured to said strip intermediate its ends, permanent magnets havingtheir pol-e pieces arranged in close proximity thereto and upon opposite sides of said strip and current coils arranged to alter the effect pr0duced,by said permanent magnets upon said stri whereby said strip may be caused to vibrate in accordance with changes produced in the current of said coils.

5. A nhonographic record cutter comprising a strip secured at its ends. a cutting point secured thereto intermediate its ends. magnets for controlling the movement of said strip and point arranged on opposite sides of said strip and means for adjusting said magnets relative to said strip.

6. In a phonographic record cutter, a supporting means, a movable frame secured thereto, a vibratory cutting strip secured to said frame, magnetic actuating means secured to said suppor means for adjusting said actuating means relative to said strip and means for moving said frame and stri relative to said magnetic means.

7. A phonographic record cutter comprising a support, a vibratory member secured at its ends to said support, a cutting member secured to said vibratory member intermediate its ends, and means arranged on opposite sides of said vibratory member for actuating the same.

8. A phonographic record cutter comprising a support, a vibratory strip secured at its ends to said support, a cutting member secured to said strip intermediate its ends, and electromagnetic means having poles arranged on opposite sides of said strip for vibrating the same.

9. A phonographic record cutter comprising a supporting frame, a vibratory strip secured thereto at its ends, a cutting member carried by said strip at an intermediate point thereof, and a magnet for vibrating said strip, said magnet having wound pole pieces positioned on the same side of said strip and on opposite sides of member.

10. A phonographic record cutter comprising a supporting frame, a magnetic visaid cutting bratory strip secured thereto at its ends, a

cutting member carried by said strip at an intermediate point thereof. a pair of permanent magnets, each of said magnets having pole pieces arranged on one side of saidstrip and on opposite sides of said cutting member, said pole pieces terminating close to said magnetic strip, and windings on said pole pieces. I

11. A phonogiaphic record cutter comprising a frame, a vibratory strip secured thereto at its ends, a cutting point carried by the strip intermediate its ends, and actuating means' comprising a plurality of pairs of magnet poles symmetrically arrangedon opposite sides of said strip.

In witness whereof, I- have hereunto set my hand this 27th day of December, 1921.

' CHARLES A. HOXIE.

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