Method and apparatus for detecting pinholes in sheet material

Claim 2

Apparatus for detecting holes in electrically non-conductive sheet material, comprising a pair of electrodes situated one on each side of the sheet material, a power source, the power source being connected to the electrodes and adapted to create a voltage across them, current detection means associated with the electrodes, said current detection means being adapted to monitor the flow of current between said electrodes to indicate the presence of a hole on the sheet material wherein one of the said electrodes is comprised by a conductive liquid adapted to flow through any holes in the sheet material to contact said other electrode and roller means for applying the conductive liquid under pressure to the sheet material.

Claim 3

Apparatus for detecting holes in electrically nonconductive sheet mAterial, comprising a pair of electrodes situated one on each side of the sheet material, a power source, the power source being connected to the electrodes and adapted to create a voltage across them, current detection means associated with the electrodes, said current detection means being adapted to monitor the flow of current between said electrodes to indicate the presence of a hole on the sheet material wherein one of the said electrodes is comprised by a conductive liquid adapted to flow through any holes in the sheet material to contact said other electrode, a first roller over which the sheet material passes, biasing means for engaging the sheet material with the first roller, an absorbent coating material on the surface of the first roller and means for impregnating said absorbent coating material with said conductive liquid.

Claim 4

Apparatus for detecting holes in electrically nonconductive sheet mAterial, comprising a pair of electrodes situated one on each side of the sheet material, a power source, the power source being connected to the electrodes and adapted to create a voltage across them, current detection means associated with the electrodes, said current detection means being adapted to monitor the flow of current between said electrodes to indicate the presence of a hole on the sheet material wherein one of the said electrodes is comprised by a conductive liquid adapted to flow through any holes in the sheet material to contact said other electrode, a first roller over which the sheet material passes, biasing means for engaging the sheet material with the first roller, an absorbent coating material on the surface of the first roller and means for impregnating said absorbent coating material with said conductive liquid.

Claim 5

Apparatus according to claim 2 in which the means for impregnating the absorbent coating material comprises a bath containing the electrically conductive liquid, the first roller being arranged to run with a part of its surface in the liquid.

Claim 6

Apparatus according to claim 3 in which a second roller is located for free rotation in the bath, the second roller abutting the first roller and in operation removing air from the absorbent coating material.

Claim 7

Apparatus according to claim 2 in which the biasing means comprises a roller situated on each side of the non-liquid electrode.

Claim 8

Apparatus according to claim 2 and including a roller adapted in use to bear on the sheet material and force it against the absorbent coating whereby a back pressure of conductive liquid is created in the area of the non-liquid electrode.

Claim 9

Aparatus for detecting holes in electrically insulating sheet material comprising a driven first roller having an absorbent surface coating, a bath of electrically conductive liquid through which the surface passes, an electrode positioned over the first roller, the electrode extending across the width of the first roller and adapted in use to contact one side of sheet material passing over and in contact on its other side with the first roller, a pair of biassing rollers, one roller of the pair being situated on each side of the said electrode and adapted to bias the sheet material in contact with a substantial area of the first roller; a roller extending across the width of the sheet material and being positioned between the leading one of the biasing rollers and the electrode and being adapted in use to create a pressure in the absorbent coating to force conductive liquid into the area of the said electrode, a power source and current detection means, the power source being connected in a circuit to the said electrode and the electrically conductive liquid and the current detection means being also connected in said circuit.

Claim 10

Aparatus for detecting holes in electrically insulating sheet material comprising a driven first roller having an absorbent surface coating, a bath of electrically conductive liquid through which the surface passes, an electrode positioned over the first roller, the electrode extending across the width of the first roller and adapted in use to contact one side of sheet material passing over and in contact on its other side with the first roller, a pair of biassing rollers, one roller of the pair being situated on each side of the said electrode and adapted to bias the sheet material in contact with a substantial area of the first roller; a roller extending across the width of the sheet material and being positioned between the leading one of the biasing rollers and the electrode and being adapted in use to create a pressure in the absorbent coating to force conductive liquid into the area of the said electrode, a power source and current detection means, the power source being connected in a circuit to the said electrode and the electrically conductive liquid and the current detection means being also connected in said circuit.

Claim 11

Apparatus according to claim 7 and including end sealing means clamped to the edge of the first roller over the absorbent coating.