Capacitance detection type stylus for grooveless disc records and method for making same

Claim 1

A reproducing stylus for grooveless capacitance disc records in which signals are stored in the form of minute pits along a plurality of tracks having particular widths, comprising: a body of hard, insulative material having a truncated, generally conical end portion, said conical end portion having a pair of angled, substantially identical surfaces extending from the truncated end of said conical end portion toward the opposite end of said body in a symmetrical relationship with respect to a plane which includes the center axis of said body and bisects the angle formed between said surfaces, so that said truncated end has an area defined by a front curved edge spanning a plurality of the widths of said tracks and a rear curved edge spanning the width of one of said tracks, and by a pair of angled straight edges each extending between opposite ends of said front and rear curved edges, and an electrode extending from said rear curved edge to the opposite end of said body.

Claim 10

A method for manufacturing a capacitance detection type reproducing stylus for use with a grooveless disc record having a plurality of tracks in which signals are recorded in the form of microscopic pits, comprising the steps of: (1) providing a body of a hard, insulative material; (2) forming one end portion of said body into a conical shape; (3) coating a conductive layer on the surface of said body to cover an area extending from one end of the conical portion to the opposite end of the body, said area having a circumferential extent smaller than the full circumference of said body; (4) truncating the coated conical portion of said body to form a record contacting face; and (5) removing a pair of substantially identical, spaced apart portions from said coated conical portion of said body to form a pair of angled surfaces of equal area which extend from said record contacting face toward the opposite end in a symmetrical relationship with respect to a plane which bisects the angle of said surfaces and includes the center axis of the body, the portion of said conductive layer which lies between said flat surfaces substantially spanning the width of one of said tracks and forming an electrode and the portion of said truncated end which lies between said flat surfaces opposite to said electrode spanning a plurality of the widths of said tracks.

Claim 11

A method for manufacturing a capacitance detection type reproducing stylus for use with a grooveless disc record having a plurality of tracks in which signals are recorded in the form of microscopic pits, comprising the steps of: (1) providing a body of a hard, insulative material; (2) forming one end portion of said body into a conical shape; (3) coating a conductive layer on the surface of said body to cover an area extending from one end of the conical portion to the opposite end of the body, said area having a circumferential extent smaller than the full circumference of said body; (4) truncating the coated conical portion of said body to form a record contacting face; and (5) removing a pair of substantially identical, spaced apart portions from said coated conical portion of said body to form a pair of angled surfaces of equal area which extend from said record contacting face toward the opposite end in a symmetrical relationship with respect to a plane which bisects the angle of said surfaces and includes the center axis of the body, the portion of said conductive layer which lies between said flat surfaces substantially spanning the width of one of said tracks and forming an electrode and the portion of said truncated end which lies between said flat surfaces opposite to said electrode spanning a plurality of the widths of said tracks.