Method and apparatus for detecting pinholes on sheet articles

Claim 1

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the other side surface on the other side of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity passing the edge of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 2

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the other side surface on the other side of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity passing the edge of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 3

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the other side surface on the other side of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity passing the edge of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 4

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the other side surface on the other side of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity passing the edge of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 5

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the said one surface of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity reflected from said sheet article as compared to light which passes the edges of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 6

A method for detecting defects in sheet articles which comprises: projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; scanning optically the said one surface of said article on a scanning line across the sheet article and outwardly beyond the edges of said sheet article in a direction perpendicular to the direction of movement of said sheet article for detecting light of a predetermined intensity reflected from said sheet article as compared to light which passes the edges of said article; generating a signal each time during scanning light of a predetermined intensity is detected; delaying the thus generated detection signal for a time which is an integral number of times of the scanning period; combining a signal generated in a successive scanning with the delayed signal for producing a signal representing such defects as edge cracks and projections which are present at the edges of the sheet article; delaying said signal representing such defects for a required length of time; combining said signal representing such defects with said lastmentioned delayed signal for eliminating signals generated by negligible defects and generated by the snaking of the sheet article and leaving only signals representing defects of a magnitude which it is desired to detect; and causing an indication means to operate in response to signals representing defects of a magnitude which it is desired to detect, thereby indicating the presence of such defects.

Claim 7

An apparatus for detecting defects in sheet articles which comprises: a light source for projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; a scanning means for scanning the surface on the other side of said sheet article on a scanning line perpendicular to the direction of movement of said sheet article from beyond the outside of said sheet article toward the center of said sheet article and for converting to electric signals light of a predetermined intensity from said source which passes the edges of said sheet article; a wave shaping means coupled to said scanning means for shaping of output signals from said scanning means into a wave-like signal substantially consisting of rectangular pulse signals; a pulse generating means coupled to said scanning means for generating a pulse at the starting point of said scanning; a flip-flop means to which said wave shaping means and said pulse generating means are coupled for receiving output signals from said wave shaping means and said pulse generating means and for being set at the finish of the first rectangular output signal from said wave shaping means and for being reset by an output signal from said pulse generating means; a primary time delay means coupled to said flip-flop means for receiving output signals from said flip-flop means as input signals and for delaying said input signals for a time which is an integral number of times of the scanning period of said scanning means; wave form reversing means coupled to said primary time delay means of the output signals from said primary time delay means; a primary AND gate means coupled to said flip-flop means and said wave form reversing means for receiving output signals from said flip-flop means and from said wave form reversing means as input signals, and for being opened when output signals issued from said flip-flop means and from said wave form reversing means are on-signals, and for producing output signals representing defects such as edge cracks and projections on said sheet article; a secondary time delay means coupled to said primary AND gate means for receiving output signals from said primary AND gate means and for delaying said output signals from said primary AND gate means for a time depending on the size of defects to be detected and for offsetting the effect of the snaking of said sheet article; a secondary AND gate means coupled to said secondary time delay means and to said primary AND gate means for receiving output signals from said primary AND gate means and from said secondary time delay means for being opened when output signal issued from said primary AND gate means and from said secondary time delay means are on-signals, and for eliminating from the output signals of said primary AND gate means those signals representing defects of a size less than those desired to be detected and those signals caused by snaking of the sheet article; and an indication means coupled to said secondary AND gate means and operated by output signals from said secondary AND gate means for indicating the presence of defects of the size to be detected.

Claim 8

An apparatus for detecting defects in sheet articles which comprises: a light source for projecting light on the surface of one side of a sheet article moving in a certain direction over a range greater than the width of said article; a scanning means for scanning the surface on the other side of said sheet article on a scanning line perpendicular to the direction of movement of said sheet article from beyond the outside of said sheet article toward the center of said sheet article and for converting to electric signals light of a predetermined intensity from said source which passes the edges of said sheet article; a wave shaping means coupled to said scanning means for shaping of output signals from said scanning means into a wave-like signal substantially consisting of rectangular pulse signals; a pulse generating means coupled to said scanning means for generating a pulse at the starting point of said scanning; a flip-flop means to which said wave shaping means and said pulse generating means are coupled for receiving output signals from said wave shaping means and said pulse generating means and for being set at the finish of the first rectangular output signal from said wave shaping means and for being reset by an output signal from said pulse generating means; a primary time delay means coupled to said flip-flop means for receiving output signals from said flip-flop means as input signals and for delaying said input signals for a time which is an integral number of times of the scanning period of said scanning means; wave form reversing means coupled to said primary time delay means of the output signals from said primary time delay means; a primary AND gate means coupled to said flip-flop means and said wave form reversing means for receiving output signals from said flip-flop means and from said wave form reversing means as input signals, and for being opened when output signals issued from said flip-flop means and from said wave form reversing means are on-signals, and for producing output signals representing defects such as edge cracks and projections on said sheet article; a secondary time delay means coupled to said primary AND gate means for receiving output signals from said primary AND gate means and for delaying said output signals from said primary AND gate means for a time depending on the size of defects to be detected and for offsetting the effect of the snaking of said sheet article; a secondary AND gate means coupled to said secondary time delay means and to said primary AND gate means for receiving output signals from said primary AND gate means and from said secondary time delay means for being opened when output signal issued from said primary AND gate means and from said secondary time delay means are on-signals, and for eliminating from the output signals of said primary AND gate means those signals representing defects of a size less than those desired to be detected and those signals caused by snaking of the sheet article; and an indication means coupled to said secondary AND gate means and operated by output signals from said secondary AND gate means for indicating the presence of defects of the size to be detected.