US2678895A

US2678895A - Compressed metal powder phonograph records and methods of making same

Info

Publication number: US2678895A
Application number: US140438A
Authority: US
Inventors: Belar Herbert; Preston John
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1950-01-25
Filing date: 1950-01-25
Publication date: 1954-05-18
Anticipated expiration: 1971-05-18

Description

May 18, 1954 BELAR ETAL 2,678,895

COMPRESSED METAL POWDER PHONOGRAPH RECORDS AND METHODS OF MAKING SAME Filed Jan. 25, 1950 Zmnentors HERBERT 312M114 cfawv B2- 2 0 attorney Patented May 18, 1954 UNITED STATES ATENT OFFICE COMPRESSED METAL POWDER PHONO- GRAPH RECORDS AND METHODS OF MAKING SAME Application January 25, 1950, Serial No. 140,438

17 Claims. 1

This invention relates to an improved phonograph record having sound grooves embossed in at least one surface thereof, and to methods of making the record.

Disc phonograph records have generally been made of thermoplastic materials such as shellac or various synthetic resins with or without mineral fillers. An important part of the cost of making these records is in the labor required to prepare the materials for the record molding step and in the actual moldin operation, itself. The various ingredients which go into the record must be thoroughly mixed for long periods of time. The molding operation then consumes a pressing cycle of between and 60 seconds. The press platens must be heated, usually with superheated steam, and then rapidly cooled to disengage the molded disc. The heating and cooling steps also add to the record cost.

Although the records made of synthetic resinous compositions are satisfactory for general home use, they, nevertheless, have limited durability. The number of plays which can be made without causing sufiicient groove wear to make the sound reproduction noisy and distorted varies, of course, with the type of record player used, the care of handling, and the materials out of which the record is made.

One object of the invention is to provide a phonograph record of satisfactory sound reproduction quality but which can be molded with an extremely short time cycle.

Another object of the invention is to provide a phonograph record which can be molded without the alternate application of high and low temperatures to the press platens.

Another object of the invention is to provide a phonograph record which can be molded at ordinary room temperature.

Another object of the invention is to provide a phonograph record adapted to be manufactured on an automatic press.

Still another object is to provide novel methods of manufacturing phonograph records.

These and other objects will be more apparent and the invention will be more readily understood from the following description including the illustrative drawings of which,

Figure l is a cross-section view of one embodiment of a phonograph record made according to the present invention,

Figure 2 is a cross-section view of a second embodiment of a phonograph record made according to the present invention, and

Figure 3 is a cross-section view of a modification of the record illustrated in Figure 2'.

In producing the phonograph records of the present invention, conventional stampers may be used such as are used in pressing records made of resinous compositions. The stampers are usually either of nickel faced with a hard layer of chromium or of copper faced with nickel. The sound track, being the negative of that which appears on the finished record, is a spiral ridge. When making a single sided record, a stamper is attached to the upper platen of a compression molding press. The press may be operated hydraulically or mechanically.

According to one embodiment of the invention, a quantity of powdered metal, preferably powdered tin of at least about mesh, or finer, is distributed over the face of the lower platen in an even layer and the platens are brought together with a pressure of about 13.5 to 18 tons per square inch. The molding is accomplished without raising the temperature of the powdered metal by any external means. The molding pressure may be released immediately after full contact. Pressing can be accomplished in one second, or less, with ease. Maintaining the pressure for longer periods of time, for example, 30 seconds, produced no different results. Themolded product, as illustrated in Figure 1, is a thin tablet 2 having a sound track 4 embossed in the top surface thereof. The surface is smooth and shiny. For this type of record, composed entirely of compressed powdered metal, sufficient powdered metal should be used to make a disc about 1% inch thick. This is sufficiently tough to withstand all ordinary handling.

In the above described process, the powder may be applied to the press platens, either in the dry state or mixed with a small quantity, for example, one or two percent, of a binder such as nitrocellulose lacquer. One or two percent of stearic acid or other fatty acid or other lubricant also may be added to the dry powder so that the molded record will have a surface offering less resistance to passage of th phonograph stylus.

Instead of using tin as the metal out of which the records are molded, other soft metals which aggregate when cold-pressed may be used. Zinc, for example, is nearly as good as tin for this purpose although the surface which results is somewhat rougher and noisier than when tin is used. To improve the sound qualities of a zinc surfaced record, a very thin film of lacquer. such as a nitrocellulose lacquer or a lacquer composed of a copolymer of polyvinyl chloride and *6 has been applied over the surface of the sound track 4. The thickness of the film is just sufficient to be continuous with no breaks. only .0003 inch in thickness has been found satisfactory.

An alternate way of molding the typeof record which has been described above is to place a cushion of resilient material, such as naturalor synthetic rubber, first on the lower platen of the molding press, cover this cushion with a layer of the metal powder and then close the press platens with application of molding pressure. When the molding pressure is released and the press platens are opened, the compressed metal tablet may be readily separated from the molding cushion. Use of a molding cushion facilitates the molding operation since it prevents small irregularities on the face of the platen, or behind the stamper carrying the sound track, fromcaus ing imperfections in the product when the thinnest layers of metal power are used. Ofcou-rse, even when a. resilient molding cushion is used, the product must not be so thin that it is broken during ordinary handling "operations. Records having a thickness of only be made using this process.

In order to provide a record having great breaking strength and also to economize on the more expensive surface metal, the core of the record may be made of'a disc of relatively dense,

rigid material such as Castor rolled metal of any desired type and the playing surface, only, may be made of a thin layer of' compressed metal powder. Referring toFigure 2,the record may be composed of a central core 8 which may beof aluminum, brass, steel 'or any other of the stronger metals, and a thin surface layer H] of compressed powdered tin or zinc. The label area [2 if the record, upon which no sound groove is embossed, need' have no surface layer or com "ressed powdered metal. Only the actual "area covered by the sound track need carry the metal powder. Inmaking this type or record, the core disc e is placed on the lower platen of the molding press, a small quantity of powdered metal is distributed evenly over that part'of the top surface of the core which is to correspond to the playing area of the finished record, the press platens are closed "on the assembly, inolding pres sure is applied, and a sot-ind track is is embossed during the molding operation. powdered metal may be thin enough to preduce a compressed layer of only about OLOl inch but may also be made thicker, for example, to

0.10inch, if desired.

Between the solid metal core and the surface layer of powdered metal, a cushioning layer may be provided to facilitate molding, although this may be Omitted, if desired. This is illustrated in Figure 3 wherein a metal core disc 8 has one of its surfaces 16 provided. with a thin film or waxi'dbeforethe layer of metal powder H3 is spread over it. The waxshould be one of the harder waxes such as beeswax, parafiin, or carriauba. The particular wax used has not been found to be critical except that it should present a firm surface at ordinary room temperatures. Instead of wax, a bituminous material, such as asphalt, may be used ora sheet of fibers impregnated with a plastic, adhesive material such as asphalt or tar. In general, the cushioning layer should be of a material which is plastic at the high pres- 3 2' inch can readily The layer of furth'er improvement will be noted and material will "be wasted.

Although the compressed metal powder sound records of the present invention have been described as being suitable for playing on ordinary home phonographs or other instruments with which sound is reproduced by means of a vibrat- 'ing stylus riding in a grooved sound track, it will also be evident that the product has other uses. For example, in the manufacture of disc phonograph records made of synthetic resinous materials, the records are molded by embossing the soundtrack in the surface of a resinous body by pressing with a metal Stamper carrying a negative of the sound groove. The Stampers are, in turn, made by electroplating metal against the face of a metal positive called a master mold. The master mold is made by electroplating a, deposit of metal onan original metal master derived from a wax or lacquer recording. Each one of the electroplating processes is lengthy and if one or more is eliminated, the time required to obtain record Stampers after making the recording is correspondingly reduced. With the present process, the molds from which the Stampers are derived can be formed by molding metal powder instead of by electroplating against the master mold. This reduces the time consumed in one of the operations of record making from hours to minutes. There has thus been described an improved sound record which can be quickly and easily made on ordinary presses designed for cold molding operations at high pressures, Although theprocess has been described, for the sake of simplicity, as applied to records having a sound groove on only one side, it will be apparent that it may also be applied to two-sided records.

We claim as our invention:

v l. A sound record comprising a tablet of compressed powder of a single metal from theclass consisting of zinc and tin and having a sound track embossed on at least one surface thereof.

2 A sound record according to claim 1 in which said metal is tin. A I v 3. A sound record according to claim 1 in which said metal -is zinc. 4. Aphonograph record comprising a tablet of compressed zinc metal powder, a sound track embossed on a surface of said tablet, and a thin film of lacquer on said sound track.

5. A phonograph record comprising a central core of a relatively rigid non-plastic material, a layer consisting of compressed powder of a soft metal which aggregates when cold pressed, 0 to 2% by weight of a binder "and 0 to 2% by weight of a lubricant, said layer being integrally united molded by compression into said layer and extending partially therethrough.

'6. A phonograph record according to claim 5 in which said core is a me'tal plate.

'7. A sound record comprising a central core of a relatively rigid non-plastic material, an intermediate cushioninglayer of a material from the class consisting of waxes and asphalts, a

surface layer of compressed powder of a soft metal which aggregates when cold pressed integrally united to a surface of said cushioning layer, and a sound track compressed into said surface layer and extending partially there through.

8. A sound record according to claim 7 in which said core is a plate of rolled metal, said cushioning layer is wax, and said metal powder is tin.

9. A sound record according to claim 7 in which said core is a plate of cast metal, said cushioning layer is wax, and said metal powder is tin.

10. A sound record according to claim '7 in which said core is a plate of rolled metal, said cushioning layer is asphalt impregnated fibrous material, and said metal powder is tin.

11. A sound record according to claim '7 in which said core is a plate of cast metal, said cushioning layer is asphalt impregnated fibrous material, and said metal powder is tin.

12. A method of making a sound record comprising compressing a quantity of soft powdered metal of the class consisting of zinc and tin with suflicient pressure to make a strong, coherent tablet and, simultaneously, embossing a sound track in a surface thereof.

13. A method according to claim 12 in which said metal is tin.

14. A method according to claim 12 in which said metal is zinc.

15. A method of making a sound record comprising distributing a uniform layer of a soft powdered metal which aggregates when cold pressed over a surface of a metal disc, pressing said powder upon said disc with a sound track embossing member having a sound track upon the surface thereof, simultaneously to form a coherent layer of compressed metal powder in- 6 tegrally united to said disc and to emboss a sound track in said coherent layer extending partially therethrough.

16. A method of making a phonograph record comprising applying a cushioning layer of soft, resilient material to a surface of a metal disc, covering said cushioning layer with a uniform layer of a soft metal powder which aggregates when cold pressed, pressing said powder upon said cushioning layer and said disc with a sound track embossing member having a sound track upon the surface thereof, simultaneously to compress said pcwder layer to a hard, coherent layer, integrally to unite said powder layer, said cushioning layer and said disc, and to emboss a sound track in said coherent layer extending partially therethrough,

1'7. A method of making a sound record by compression molding in a press having upper and lower platens, comprising placing a molding cushion of resilient material on the lower one of said platens, distributing a layer of metal powder over the surface of said cushion, closing said platens and compressing said powder with sufficient pressure to make a strong, coherent tablet while simultaneously embossing a sound track in a surface of said tablet, removing the molding pressure, and separating said tablet from said cushion.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 336,824 Riker Feb. 23, 1886 1,548,737 Owen et al. Aug. 4, 1925 2,094,280 Proctor Sept. 28, 1937 2,352,285 Proctor June 27, 1944

Claims

1. A SOUND RECORD COMPRISING A TABLET OF COMPRESSED POWDER OF A SINGLE METAL FROM THE CLASS CONSISTING OF ZINC AND TIN AND HAVING A SOUND TRACK EMBOSSED ON AT LEAST ONE SURFACE THEREOF.