Abstract A sheet of flexible material such as photographic film or paper is passed between a pair of rollers of electrically conducting material. One roller is connected to ground, and there is applied to the other roller a direct current voltage of magnitude and sign such as to develop a desired electrical charge condition on the sheet. Advantageously, the other roller has a soft yielding coat thereon of an electrically partially conducting material such as surfactant-treated plush cloth which improves contact with the sheet and prevents sparking if the two rollers should come into contact with one another. The sheet can be in the form of a continuous web or an individual sheet of small dimensions which has been chopped from a web. The electrical charge on a sheet can be monitored by an electrostatic field meter or volt meter, and the sign and magnitude of the applied voltage can be regulated to maintain the desired charge condition. When the sheet of flexible material has a coating of electrically conductive material such as carbon, aluminum, silver or gold on one side it is not necessary to employ the grounded roller adjacent to the charged roller. Instead, the charged roller engages a first side of the sheet opposite the second side carrying the electrically conductive coating, and the second side subsequently passes over a grounded roller such as an idler roller.
In an apparatus for neutralizing the static electrical charge on a photographic material to prevent sparking, the combination comprising: a first roller having an electrically conducting surface; a second roller having a soft yielding surface of semiconducting material in engagement with said first roller; means for applying to one of said rollers a direct current voltage of an adjustable magnitude and sign; means for electrically connecting the other of said rollers to ground; means for transporting a photographic material through the nip formed by said first and second rollers; means adjacent said photographic material when it exits from said nip for measuring the electrical charge on said material; and means responsive to said measuring means for adjusting the magnitude and sign of said direct current voltage applied to said one roller whereby the static electrical charge on said material at said nip is neutralized.
Claim 2
Dependent Claim
27 words
The invention according to claim 2 wherein said soft yielding surface of semi-conducting material comprises a cotton velour plush cloth which has been treated with a surfactant.
Claim 3
Dependent Claim
19 words
The invention according to claim 2 wherein said direct current voltage is adjusted substantially between -400 and +600 volts.