US2200866A - Apparatus for recording sound on thin disks - Google Patents

Description

May 1 1940- 1.. THOMPSON APPARATUS FOR RECORDING SOUND ON THIN DISKS Filed Dec. 15, 1938 TFI.

K AMPL 07m IIH INVENTOR Lincoln Thompson jaw.

ATTORNEY Patented May 14, 1940 PATENT OFFICE REESE? E APPARATUS FOR RECORDING SOUND ON THIN DISKS Lincoln Thompson, Stamford, Conn.

Application December 15, 1938, Serial No. 245,944

2 Claims.

This invention relates to sound recording, and more particularly to an apparatus for recording sound on a thin disk record.

It has hitherto been considered impractical to 6 make sound recordings on a thin flexible disk due to the fact that the surface of said disk would become permanently deformed and would warp so badly that it would not play back with satisfaction, Even when relatively thick aluminum disks 10 of the orderof .030" thickness (#20 gauge) were embossed with sound grooves in the conventional recording machines, it was found that the disks showed some warpage after recording. This was due largely to the fact that the disk was mounted on a soft felt or yieldable rubber pad which permitted the heavy pressure of the embossing stylus (10 to 16 ounces) to bend the disk record into dish form. With thinner disks, this dishing or warping effect would naturally be greatly eg- 20 gravated.

By means of the present invention, the above and other disadvantages have been overcome, and it has been found possible to emboss sound grooves in an extremely thin flexible disk record v245 without appreciable warpage, using disks as thin as .006". This result has been accomplished by eliminating the soft felt or rubber pads previously used as a frictional foundation for the disk record, and in placing the record upon a solid 30 and rigid turntable or plate mounted on said turntable. The tendency to produce warpage is still further reduced by employing a lower embossing pressure on the stylus, whereby a more shallow groove or sound track will be produced. 35 At the same time, in order to drive the thin record without slippage, an interlocking connection is made between the record and the spindle of the turntable, .as by providing a-square driving recess in the center of the record for fitting over 40 a similarly shaped section on said spindle.

By the use of this construction the thin record is supported rigidly so that it cannot bend below the point of the embossing stylus, yet permitting the latter to form a spiral groove in the surface 45 of the record in a manner similar to the action of a plow.

One object of the present invention is to pro-- vide an apparatus by means ofwhich extremely thin disk records between .006" and .015" may 50 be readily embossed with sound grooves on both faces, without producing suilicient warpage as to interfere with the satisfactory playing back of.

the record.

A further object is to provide an apparatus by 65 means of which a bendable semi-rigid record disk may be recorded which will not buckle up during recording when positively driven by the center spindle and without the necessity of clamping the record on the turntable.

A still further object of this invention is to provide an apparatus for recording on a thin semirigid metal disk which will be relatively inexpensive to manufacture, simple in construction, ornamental in appearance, and very eflicient and durable in use.

With these and other objects in view, there have been illustrated on theaccompanying drawing two forms of sound recording apparatus in which the invention may be conveniently embodied in practice.

In the drawing:

Fig. 1 illustrates partly diagrammatically the first form. of improved sound recording apparatus embodying the present invention.

Fig. 2 is a top plan view of the thin disk record as it appears when interlocked with the turntable spindle, and with the embossing stylus in operating position,

Fig. 3 is an enlarged side view, partly in section, of the thin-disk record turntable and embossing stylus shown'in Fig. 2, taken on the line 3--3 of Fig. 2.

Fig. 4 is a greatly enlarged sectional view of the disk record, turntable and stylus in operating position.

Fig. 5 illustrates a fragmentary side view of a modified form of the invention employing a rigid record supporting plate resting on the usual turntable felt cushion.

Referring now to the drawing wherein like reference numerals denote like parts throughout the several views, the numeral l designates a turntable which is adapted to be rotated by an electric motor Ii in the conventional manner. The motor H is adapted to be energized by being connected to a source of electrical energy through main line conductors l2 and It, a plug ll, conductors l and. I6, and a switch ll.

The sound grooves are adapted to be embossed in the record by means of an electrically actuated recording head It arranged to swing over the turntable l0 and being driven in this swinging movement by power driven mechanism, not shown. A suitable mechanism for this purpose was disclosed in my prior patent, No. 2,133,596, dated October 18, 1938. The sound vibrations received by the apparatus are reproduced in the form of a spiral groove in the disk record 24 by means of an embossing" stylus l9 carried by the recording head it, the latter being responsive to n le rical circuit which includes a microphone p on s'that 20, a. pair of conductors 2|, a vacuum tube ampliwhen recording with either form of apparatus fler 22, and apair of conductors 23. The recordherein disclosed, the stylus l9 will emboss or ing head 18 is of a conventional type, and is plow a sound groove 25 in the surface of either 5 adapted to rest upon the surface of a disk record side of the disk record 24 without appreciable 6 24 with a pressure of about four ounces. warping.

The disk record 24 is preferably made from a In operation, the stylus l9 forces up a. pair of thin flexible metal, such as sheet aluminum, havlateral ribs 3! and 32, which define the side ing a thickness of less than .015", and preferably borders of the sound groove and mater allli re- 1; a t inforce the stiflness of the record 10 s'iredj he blank ds r y 4,; may have a ring-shapedmarking areal 33"etched upon its surface within the sound grooves for permitting the user to make any desired indicia or memorandagtheregn yvith a pencil. Three rectangular l5 aped marking portions 34, 35 and 36 may also etched on the record for receiving any other desired 'ndicia pertaining to the sounds recordedduring handling or recording Foraexample ylf I a disk .006" in thickness is use round that if desired, the op- 20 erator =may write directly across the sound .--J h; :a-: at smogthhe a i a 7'28 sthusgnreveniz n h whoss n z-ltr ci I a a ation,

In the modified form ofthe invention shown i Fig.:;5, insteadi'of- 'supportin'g'theiidislc record 24:

'; directlyioniithe turntable'zitop 128,?iascin :the:first.-3., arm lo ateda vew aidreq d n hav n r .form; aismooth rigidplate 29 iszemployedzand is cutting head for indenting 1aterally;.undu1at:ing

1 1 adapted ito restupon the xusualielt cushion pad rchelical: groovesgin saidrecord-withoutsubstantial whichi-is glued-ror cementedzto theqturntable :1 s-

a g w, L H

Images