US 4,027,201 A · Apparatus and method for neutralizing static charges in sheet/web feeding devices

Abstract

A corona and associated electrical drive as shown herein, neutralize the static charges on non-conductive sheets or webs. The neutralization of static charge is accomplished by passing the material to be neutralized under a double wire corona. Both wires in the corona are connected to an AC signal. The AC signal drives both wires with a signal that alternates in polarity at frequency f. The wires are spaced apart a predetermined distance calculated from a function dependent upon the frequency of the AC signal and the speed of the paper moving under the corona wires. The predetermined distance is such that a given area of the paper will pass under one wire at a first polarity and under the second wire at the opposite polarity. Further enhancement of neutralization can be accomplished by using a second double wire corona out of phase with the first double wire corona. In addition the sheet or web as it passes under the corona wires is supported to prevent static charge on the support from balancing a static charge on the sheet or web. Accordingly, the only static charge present as the sheet or web moves under the corona is that charge carried by the sheet or web. The corona wires will neutralize that charge either by discharging it with oppositely charged ions or depositing oppositely charged ions to balance the charge already on the sheet or web. Thus as the sheet or web moves away from the neutralizing station the sheet or web has a net charge which is substantially zero.

Claims19

Dependent claims

Apparatus for neutralizing static electric charge on a sheet or web moving at a velocity Vs relative to said neutralizing apparatus, said neutralizing apparatus comprising:

first means for ionizing gas adjacent said sheet or web;
second means for ionizing gas adjacent said sheet or web;
means electrically connected to said first and second ionizing means for supplying a periodic alternate polarity signal of a frequency f to said first and second ionizing means so that periodically each ionizing means produces positive and negative ions;
means for supporting the sheet or web with a substantially charge-free support adjacent said first and second ionizing means whereby charges on said sheet or web alone will attract ions to neutralize the sheet or web as the sheet or web moves relative to said first and second ionizing means;
said first and second ionizing means points of said gas ionization adjacent said sheet or web separated a predetermined distance along the direction of relative motion, said predetermined distance being a multiple of 1/2 Vs/f such that a given point on the sheet or web attracts ions of a first polarity as the point moves past the first ionizing means and attracts ions of a second polarity as the point moves past the second ionizing means.

2 more elements

In an electrophotographic copy machine using electrostatic charge to develop and transfer the copy image to a copy sheet, apparatus for neutralizing the electrostatic charges on the copy sheet after the copy image transfer and while the copy sheet moves at a relative velocity Vs to the neutralizing apparatus, said neutralizing apparatus comprising:

a source of alternating current having a frequency f;
a first plurality of wires mounted across and adjacent to the path of the copy sheet and electrically connected in common to said source for producing alternate positive and negative coronas, said wires separated approximately from each other by an odd multiple of one-half the neutralization wavelength where the neutralization wavelength equals V.sub.S .div.f;
said copy sheet receiving charge from said coronas on demand depending upon the quantity of electrostatic charge on said copy sheet and differences between the polarity of each corona and the polarity of charge on the copy sheet as the copy sheet moves past each wire.

Method for neutralizing electrostatically charged sheet or web as the sheet or web moves past a neutralizing corona comprising the steps of:

supplying charge of one polarity as a given point on the sheet or web moves past one neutralizing corona wire, said charge being supplied on demand dependent upon quantity and polarity of the electrostatic charge on said given portion and depending upon the polarity of the charge being supplied by the corona wire;
supplying charge on the opposite polarity as said given portion of the sheet or web moves past a second neutralizing corona wire;
supporting said sheet or web in a substantially non-conductive environment as it moves past said corona wires whereby only the charge on the sheet or web is effective in demanding charge from said corona wires;
and
alternating the polarity of charge in said supplying steps at a frequency directly related to the relative velocity of the sheet or web to the neutralizing corona and indirectly related to the separation between said corona wires, the frequency of alternation being such as to insure that a given portion of the sheet or web will see both said polarities of charge as it moves past the neutralizing corona.

2 more elements

Dependencies are inferred from the claim text.

Apparatus and method for neutralizing static charges in sheet/web feeding devices

Life of this patent

Apparatus and method for neutralizing static charges in sheet/web feeding devices

Life of this patent

Abstract

Claims19