Apparatus for detecting imperfections on a web

Claim 1

An apparatus for detecting imperfections on a longitudinally moving web which comprises: a. a plurality of photoconductive elements positioned below said web, b. means for reciprocating said photoconductive elements laterally to the longitudinal advancing direction of said moving web, c. a light source disposed on the side of said web opposite from that of said photoconductive elements, d. shielding means positioned between said web and said photoconductive elements and including a laterally extending slot aligned with and overlying said laterally moving photoconductive elements, e. individual lenses for each photoconductive element overlying said photoconductive elements and positioned between said photoconductive elements and said web for sharply focusing the imperfections of the web within the limited fields of view of each of said underlying photoconductive elements, and f. an electric circuit responsive to the output of said photoconductive elements for indicating the presence of an imperfection in said moving web.

Claim 2

An apparatus for detecting imperfections on a longitudinally moving web which comprises: a. a plurality of photoconductive elements positioned below said web, b. means for reciprocating said photoconductive elements laterally to the longitudinal advancing direction of said moving web, c. a light source disposed on the side of said web opposite from that of said photoconductive elements, d. shielding means positioned between said web and said photoconductive elements and including a laterally extending slot aligned with and overlying said laterally moving photoconductive elements, e. individual lenses for each photoconductive element overlying said photoconductive elements and positioned between said photoconductive elements and said web for sharply focusing the imperfections of the web within the limited fields of view of each of said underlying photoconductive elements, and f. an electric circuit responsive to the output of said photoconductive elements for indicating the presence of an imperfection in said moving web.

Claim 3

An apparatus for detecting imperfections on a longitudinally moving web which comprises: a. a plurality of said photoconductive positioned below said web, b. means for reciprocating said photoconductive elements laterally to the longitudinal advancing direction of said moving web. c. a light source disposed on the side of said web opposite that of said photoconductive elements, d. shielding means positioned between said web and said photoconductive elements including a laterally extending slot aligned with and overlying said laterally moving photoconductive element, e. additional photoconductive elements fixedly mounted to a support so as to be fixed relative to said moving web and to said reciprocating photoconductive elements and adjacent to said reciprocating photoconductive elements for detecting imperfections at the edges of said web during reciprocation of said moving photoconductive elements, and f. an electric circuit responsive to the output of said photoconductive elements for indicating the presence of an imperfection in said moving web.

Claim 4

An apparatus for detecting imperfections on a longitudinally moving web which comprises: a. a plurality of said photoconductive positioned below said web, b. means for reciprocating said photoconductive elements laterally to the longitudinal advancing direction of said moving web. c. a light source disposed on the side of said web opposite that of said photoconductive elements, d. shielding means positioned between said web and said photoconductive elements including a laterally extending slot aligned with and overlying said laterally moving photoconductive element, e. additional photoconductive elements fixedly mounted to a support so as to be fixed relative to said moving web and to said reciprocating photoconductive elements and adjacent to said reciprocating photoconductive elements for detecting imperfections at the edges of said web during reciprocation of said moving photoconductive elements, and f. an electric circuit responsive to the output of said photoconductive elements for indicating the presence of an imperfection in said moving web.

Claim 5

The apparatus for detecting imperfections on a web as defined in claim l, wherein said laterally reciprocating photoconductive elements constitute a first row, and said apparatus further includes additional photoconductive elements stationarily mounted parallel to said moving photoconductive elements at opposite ends of the path of movement of the same and constituting a second and fixed parallel row for detecting imperfections at the edges of said longitudinally moving web.