Method of making a video disc from a disc preform

Details Method of making a video disc from a disc preform Method of making a video disc from a disc preform

1980-10-29

1985-07-30

Czaja, Donald

Plastic and nonmetallic article shaping or treating: processes

Forming sound grooves in records

Die pressing disk type records

425810, B29D 1700

Patent

active

045320950

ABSTRACT:
A preform for use in making a video recorded disc in a body of plastic material having substantially flat top and bottom surfaces and a peripheral surface extending between the top and bottom surfaces. The peripheral surface includes a first portion intermediate the top and bottom surfaces and of a peripheral size greater than that of the top and bottom surfaces. Second and third portions extend from the first portion to the top and bottom surface, respectively. Each of the second and third portions has a peripheral dimension which decreases from that of the first portion to that of the top or bottom surface so that the surface of each of the second and third portions is angled away from the top and bottom surfaces, respectively. When the preform is engaged by the molds for making a disc the angled surfaces of the second and third portions serve to minimize if not eliminate the trapping of air and gasses along the surface of the record being formed which cause defects in the record surface.

REFERENCES:
patent: 2743478 (1956-05-01), Harlow
patent: 3412427 (1968-11-01), Flusfeder
patent: 3622427 (1971-11-01), Kelly
patent: 3635622 (1972-01-01), Wechsler
patent: 3932097 (1976-01-01), Press

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