US1994093A - Sound record - Google Patents

Description

March 12; 1935..l H. .1. BILLINGS A 1,994,093

soUND RECQRD l Filed July 17, 1929 /y i l I l Zi/yf.

Patented Mar. 12, 1935 UNITED STATES SOUND' RECORD Howard J. Billings, South Acton, Mass., assigner to Arthur D. Little, Incorporated, Cambridge, Mass., a `corporation of Massachusetts Application July 17, 1929, serial No. 378,893

11'c1a'ims. (o1. 181-483) 1 This invention relates to improvements in sound records and its chief object is to provide a sound record having a backing or core upon which is provided at one or both sides a record sheet consisting of a base ofv moldable compound in sheet form and a coating which forms the playing surface. In the preferred form of 'recordthe grooves are impressed into the base and are completely lined with the coating. A further object is to provide a method of making such a record.

A further object of this invention is to provide, in a sound record, a` recording sheet consisting of abase of molding compound in sheetform, comprising a thermoplastic binder and felted fibrous material intimately associated throughout the body f the compound, and a coating for vsaid base comprising a thermoplastic binder', a ller and an abrasive in approximately equal parts Another object of this invention is to provide, in a sound record, a core or backing consisting of a plurality of laminated sheets certain of said sheets being of moldable compound comprising a'thermoplastic binder and `a ller intimately associated throughout the body of the compound, and other of said sheets having less or no binder therein.

Other objects of this invention will appear from an examination of the following specification taken in'conne'ction with the accompanying drawing which forms a part thereof and'in which Fig. 1 is a diagrammatic view in section of a sound record embodying one -form of rthis invention prior to the formation of record groove therein, the several layers being sho-wn yseparated for clearness;

Fig. 2 is an enlarged sectional view of a portion of a record blank before the record grooves are formed therein;

Fig. 3 is an enlarged sectional view of a portion of the sound recordshownin Figs. l and 2 after the record grooves have been formed therein;

Fig. 4 is a sectional view similar to that shown in Fig. 2 of said record sheet alone; and

Fig. 5 is a sectional view'of a sound record embodying another form of `this invention.

VSound records produced in accordance with the methods now or formerly in use are generally frangible and unbendable so that they crack or break fairly readily when subjected tothe general course ofhandling or when Shipped through the mail. On-the'other hand reoords'made-according to this invention may be handled or shipped Without the Vnecessity of expensive packing, may be dropped upon the Iloor without injury to the playing surfaces and after being so treated regain their original condition without developing any surfacejcracks or hair lines in the playing surfaces which would have a deleterious effect upon their use as sound records.

I am well awareof the fact that there are now two ways of manufacturing sound records cfa flexible type which methods are brieiiy first, to coat or paint sheets of cardboardor paper with shellac, synthetic resin or othershellac-like material, and form ther record grooves in the coating, and second, to incorporate shellac in paper by repeated coatings or dippings and use the paper so treated as a record sheet.

Neither of these methods, however, producesy satisfactoryrecords. The coatingisalways liable to develop cracks'orvv hair 'lines ori bending ordropping if it be builtup to a thickness sufficient toreceive andiretai'n satisfactory'playing surface impressions, a .condition which cannot be avoided by providing a very thin coating of the resinous surface-becausesuch a coating would not receive .and retain a satisfactory playing surface and would not have the requisite surface strength to prevent the record from cracking if bent or'dropped.'

Sound recordspparticularly those of the disk type now almost universally used, made in accordance Awith this invention have a smoothl playing surfaceand the walls of the sound grooves are so strong that they will not under ordinary use break down and permit the needle to jump across from one groovev to' another, possess toughness, ilexibility without producing hair lines or cracks` in the playing surface',`can be made economically and when finished have a high glaze upon the outer surfaces. Moreover 1 the record :is .much lighter than the sound records commercially manufactured at the present time. Thus a ten-inch record of my invention weighs between threeand four ounces while the average commercial record of the'same diameter weighs not less than seven ounces.

As shown in the drawing the soundrecord 10 comprises a backing 'or core` l1, (Fig'l)` and a record' sheet 1,2. '.The" backing 11v in the first embodiment is a laminated structure comprising a plurality of combining sheets 15, preferably of a moldable compound, and iiilling sheets l6,.pref erably of paper. These sheets are preferably, though not necessarily, arranged alternately as shown in Fig. 1. The record sheet 12 comprises a base 20 consisting of an uncoatedsheet of moldable compound and a thin coating 21 upon the outer surface thereof. The record grooves 25 in the recording surface of the coating 2l are also impressed into the base 20, the coating 21 completely lining the grooves, whereby the walls or ridges 26 separating the grooves 25 are completely covered by the coating 21 and interiorly reinforced near the bottoms by the base 20, as is clearly shown in Fig. 3.

The combining sheets 15 and bases 2O (before coating) are preferably made by a process of pulping librous material in association with a thermo.

plastic binder. l The details of this process per se form no part of the present invention and the process will here be described briefly as follows.

The thermoplastic binder, preferably shellac alone or in combination with other thermoplastic material is kneaded under heat with wet fibrous material until a substantially uniform mass is obtained, the resultant mass is broken down to a pulp by the addition of water followed by a final fibration in a paper mill beater andthe pulp is then felted into continuous sheets on paper mill equipment.

As a result of this process the binder and fibrous material are intimately associated throughout the mass, the binder being uniformly dispersed in the form of discrete particles in an amount in excess of that which can be absorbed by the fibrous material.

The base 20 of the record sheet may be prepared according to the foregoing method using the following proportion of materials.

Formula #1 Per cent Shellac 48 Graphite 25 Carbon black 2.5

Rosin 2.5

kraft 25% Paper pulp {news 75% 22 It will be understood that the above formula can be modified in several respects both as to the materials and the proportions used. Thus in place of shellac and rosin, shellac alone may be used or other resins or thermoplastic material may be used, either alone or in combination, suitable for a playing surface, the graphite and carbon black may be replaced by other fillers and pigments and other fibrous materials may be used.

The combining sheets 15 may be made by the same formula, or, if greater economy in materials is desired, the following composition has been found suitable:

Formula #2 lPer cent shellac 25% 'I'hermoplast1cb1nder {rosn ,.15 66 l kraft pulp 60% Fibrous mater1al{news pulp 40%} 34 This composition is here given merely as an example of the many that might be used, and obviously the invention is not limited thereto.

The coating 21 may be prepared with varying formulae and in many ways, but I have found the' following to give very satisfactory results. The ingredients and proportions are as follows: (the proportions being by weight).

Formula #3 Per cent Binder; shellac or other thermoplastic material that will produce a satisfactory playing surface 30 Abrasive filler; rotten stone or similar material 34 Filler to give body; china clay or the like 34 Pigment; such as carbon black 2 The ingedients are mixed together on rolls and sheeted in the well known and customary manner.

The record sheet 12 is made by applying to the base 20 the coating 21 which step may be performed in either of the following methods which may be differentiated roughly as dry and wet. In the first of these methods the coating composition is ground dry to a powder which is dusted upon the base sheet 20 and caused to adhere by passing the sheet through an oven so that the powder is incipiently fused. In the other method, the Acoating composition is ground in water, and to it is added, if necessary, more shellac to enhance its molding properties. The result is a paint having adhesive, binding and molding properties particularly suitable for coating the base sheet 20. The paint may be applied as a. liquid to the base by means of a brush or in any desired manner, and sets upon drying.

The backing or core 11, when made of lamina, as shown in Fig. 1, consists of alternately arranged disks of combining and filling sheets. The filling sheets are preferably formed of fairly dense or hard paper, e. g. kraft paper, to avoid the tend-` ency of the finished core to spring back after the final pressure used for `making the core is relieved. The filling sheets may be of paper impervious to moisture, such` as paper having a waterproofing filler of asphalt or similar material. One satisfactory arrangement is to provide ve filling disks and four combining disks. These may be assembled as disks when the sound record is tobe made or may be assembled and formed, previous to the making of the record, into a unit, by the use of heat and pressure either as disks or as sheets, the backing being cut as a unit disk from the sheet if the second p-rocedure is followed.

From the record sheet are cut disks which, when manufacturingv a sound record having two playing surfaces, are placed upon each side of the backing, whether preformed or not, with the coated surfaces exposed. The assembled article is then placed between two dies each supporting a stamper which constitutes a matrix of the record grooves which are to be impressed into the sheet.` The dies are steam heated and compress the article with a pressure of from 2000 to 4000 pounds per square inch, being so held for a period of predetermined length. The dies are then chilled by cold water and after the completed record has been suiciently cooled the pressure is released and the record removed.

The grooves 25 thus formed in the recording surfaces are impressed into thebase 20 and completely lined by the coating 21 so that the walls 26 of the grooves are very strongly reenforced at their roots as shown in Fig. 3. In this feature resides one of the differences between my record and those previously made wherein the coating upon the paper base was necessarily made of sufficient thickness to receive the grooves and the f grooves were formed wholly in the coating and their walls were formed by the coating alone.

It has therefore been previously thought thatv since the walls of the grooves must be formedby the coating alone, the coating should contain flock or other fibrous material which would give the necessary strength to the walls to prevent the needle from breaking through after the record has been in use. While this procedure didtend to strengthen the walls, it was objectionable in that it was found practically impossible to prevent the flock or other fibrous material from being exposed or so thinly covered in spots that it was picked up by the needle when the record was used.

The lgrooves 25 are about 1/300th of an inch in depth in accordance with the usual practice, and since the coating 21 is usually less o-r not substantially greater than the depth of the grooves it is obvious that satisfactory grooves could not be sof formed in the coatings alone. lThe'walls 26 of the groovesr are in places very thin as whenthe sinuosities of the adjacent groovesare such that a'particular portion of one groove is brought into very close relation to a particular portion of the adjacent groove. The needle bears` against the roots of the groove walls and hence the 4reenforcement of the coating which forms the wall by the fibrous stratum of the base as shown in Fig. 3, strengthens the wall and prevents the needle from breaking it down. The strength of the walls so made is such that it is possible to increase the number of grooves per inch and thus provide a record having a greater playing surface without increasing the diameter of the record disk.

The thermoplastic binder extends through the entire mass of the 'record sheets and backing and when cooled securely unites them. Nevertheless, due to the variance in the amount of thermoplastic binder in the various strata of the sheets the record is flexible and may be bent without danger of cracking or developing .hair lines in the playing surface.

The heat and pressure in the die acts upon ,the thermoplastic binder in the base of the record sheet and in combining sheets, aswell as forming the record grooves inthe coating. The binder While intimately associated with the fibers throughout the mass of each sheet is present in an amount greatly in excess of that which can be absorbed bythe bers and flows outwardly from thebers to the surfaces. Thus each record sheet 12v novv comprises (see Fig. 3) a base or substratum a of thermoplastic material having felted bers uniformly distributed throughout its mass, a subsurface stratum b of fiber-free thermoplastic material intimately united to one side ofthe first stratum and wholly encasing the bers thereof, anda'superstratumc comprising a superficial coating of thermoplastic material containing fillers and integrally united to the subsurface stratum. The thermoplastic material flowing from the fibers of the base toward the backing serves to bondthe backing to the record sheet. In the same Way the thermoplastic mafree stratum b is, as pointed out above, suitable for a playing surface and being fused to the coating prevents the entry of fibres into the surfaces of the grooves, and in case the coating should Wear in theY groove will form a playing surface. Moreover, this stratum prevents the escape of any of the binder` in the coating 21 into the base.

` When it is desired to make a sound record having only one playing surface, av suitable sheetis substituted for arecord sheet on one side of the backing. -Inother respects the procedure described above and the product obtained thereby are the same.

In place of the laminated core, there might be employed a solid non-resilient core 30, (Fig- 5) which, when assembled with the record sheet 12a, would give a very satisfactory record so` far as playing is concerned but which would not have the bending and exible qualities of a record made in accordance with the above invention.

It will be understood that, While the Word shellac is used throughout the specification and claims, I intend to include thereby all gums, natural resins and phenolic condensation products which are shellac-like in function.

One ofthe procedures for making a record ac- `preferably a hydraulic press. 'is subjected to a pressure of from 2000 to '4000 ist here set' forth as illustrative not as limitative;r

v .The record is composed of two surface or record sheets and a core of nine laminas made up of five sheets of filling paper of ten point thickness, sep-r arated by four combining sheets of ten' point thickness. and made according toFormula ,Noi 2. The record sheets comprise bases made according to Formula No. 1 to ywhich is lapplied coating made according'to Formula No. 3 by either of the before described methods. I have found a very thin, flexible, non-cracking coating of five grams to a ten-inch disk of vmolclable compound to give a satisfactory result. For the filling paper ahard finished kraft paper of ten point thickness is used.- Each of the various sheets is substantially as dry as is feasible under working conditions.

The rst step in stamping the record from kthis lmaterial is tor cut from these sheets disks of the desired diameter, properly centered by a hole punched in the middle and then assemblethem as in Fig. l. The record blank so formed is placed between stampers mounted on the dies of a press,

pounds per square inch, during which time the blank is heated by steam circulated through the dies under a pressure of from 80 to 100 pounds.`

The temperature of the stampers is about .300 F. less whatever loss of heat may occur through radiation. The time of heating and of bringing the press to maximum pressure should be from 15 to i seconds. The steam is turned on when the press is started, and as soon as the maximum pressure has been applied the steam' is turned oif and cold water run through the dies to cool .the stamps. The time" of cooling usually requires about 20 seconds. As soon as the dies have been cooled, as above described, the pressure may be released and the record removed. All that remains to be done to finish this record is the trimming Vand finishing of the edges.

Unless the foregoing procedure is closely Vadhered to, difficulty may be experienced in having the recordsstick to the stampers, due in part to the tendency of the shellac to undergo decomposition if heated for a time appreciably longer than with the foregoing temperatures.

Moreover due to the large amount of thermoplastic material throughout the record there will be a tendency for the record to contract as it cools. This tendency isV exerted in all three dimensions, length, breadth, and thickness, and

since the recordis held firmly in the dies a strain or tension is set up. This strain or tension is of coursereleased when the press is open and the record springs free from the-matrices. The presence of water or moisture in the press will cause therecords to stick, and unless the moisture is removed as soon as discovered the records will be spoiled.

1. A record sheet yadapted to receive and retain record-grooves, said sheet being made of an uncoated sheet of felted fibers containing in its interior and Within the confines of its surface enough shellac to flow outwardly upon fusion under heat and pressure so as to form a continuous outer surface Wholly encasing the fibers, and a superficial coatingy containing shellac and filler on said sheet.

2. A record sheet adapted to receive and retain record-grooves, said sheet being made of an uncoated sheet of felted fibers containing in its in- The record blank terior and within the confines of its surface enough shellac-like material adapted to` producea playing surface to'iow outwardly upon fusion under heat and pressure so as to form a continuous outer surface Wholly encasing the fibers, and a supericial coating containing shellac and filler on said sheet.

3. A record sheet adapted to receive and retain record-grooves, said sheet being made of an uncoated sheet offelted iibers containing in its interior and within the connes of its surface enough thermoplastic binder to ow outwardly upon fusion under heat and pressure so as to form a continuous outer surface Wholly encasing the fibers, and aV superiicial coating containing shellac'and filler on said sheet.

4. A' record sheet adapted to receive and retain record-grooves, said sheet comprising an uncoated base of molding compound in sheet form including a thermoplastic binder and felted fibrous material intimately associated with the binder throughout the mass of f the compound, the amount of binderr being approximately double the amount oi fibrous material and a superiicial coating containing thermoplastic binder and an abrasive -upon the base.

5. The method of making a sound record from arecord sheet containing a base of felted bers and thermoplastic material, the latter Vin an amount in excess of that which can be absorbed bythe fibers, and a supercial coating of thermoplastic material suitable for a playing surface, which comprises assembling said record sheet and a backing sheet, and subjecting the assembled sheets to heat and pressure to cause thermoplastic material to flow outwardly from the felted liber of the base and forma ber-free subsurface layer between the bers and the coating and a bond between said base and backing sheet.

`6. The method of making a sound record from a backing and a record sheet comprising a base of felted iibers and thermoplastic material, the latter in an amount in excess of that which can be absorbed by the bers, and a superiicial coating of thermoplastic materialsuitable for a playingsurface, which includes as steps applying said record sheet to the backing with the coated side outward and subjecting the backing and record sheet to heat and pressure to cause thermoplastic material to flow outwardly from the felted bers of the base,-thereby forming a fiber-free subsurface layer between the fibers and the coating, and simultaneously bonding the base to the backing.

7. The method of making a sound record from a backing consisting of lamin of combining sheets of felted bers and thermoplastic material, the latter in an amount in excess of that which can be absorbed by the fibers, and lling sheets, and a record `sheet comprising a base oi felted fibers and thermoplastic material suitable fora playing surface, the latter in an'amount in excess of that which can be Aabsorbed by the fibers, and a supercial coating of :thermoplastic material suitable for a playing surface, which includes as steps assemblingsaidlaminae ofl the backing and said record sheet and subjecting the same to heat and pressure to cause thermoplastic material to flow outwardly in both directions from the felted fiber in each combining'sheet in the base of the record sheet, thereby bonding all the sheets together and simultaneously forming a ber-free subsurface layer of said thermoplastic material between the bers-of the base and the coating.` 1

8. A record sheet adapted to receive and retain record grooves, said record sheet comprising a substratum ofy uncoated felted fibers containing in its interior and within its connes enough thermoplastic binder to flow outwardly upon fusion underheat and pressure so as to form a continuous subsurface stratum wholly encasing the fibers of the substratum, and a surface stratum of thermoplastic material containing a filler.

9. A sound recordblank having at one side a record sheet comprising a substratum of uncoated felted berscontaining in its interior and within its confines enoughy thermoplastic binder to flow outwardly uponfusion under heatgand pressure so as to form a continuous subsurface stratum wholly encasing said substratum, said substratum being capable `of providing record grooves having walls which are internally reinforced by its fibrous structure, and a superiicial coating of material on the outer surface of said record sheet suitable for a playing-surface.

10. A sound `record blank comprising a laminated backingbuilt up of combiningsheets and iilling sheets interposed between said combining sheets, said combining sheets comprising uncoated felted fibrous material containing in its interior and Within its contines enough thermoplastic binderto flow outwardly upon fusion under heat and pressure-so as to form a continuous stratum wholly encasing the yfibers of the combining sheets and operative to bond the lling andA combining sheets together `to provide 'a laminated structure. 11. Asound record blank comprising arecord sheet adapted to receive and retain record grooves, said record sheet comprising a substratum of uncoated felted bers containing in its interior and withinitsconnes enough thermoplastic binder to ilow outwardly upon fusion under heat and pressure so as to form a continuous subsurface stratum wholly encasing the bers of the substratum, and a laminated backing adjoining said record sheet, saidbacking comprising a plurality of combining sheets and filling sheets interposed between said combining sheets.-

HOWARD 4J. iiLLiNGs.

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