US1782712A - Method of controlling electrostatic charges on moving surfaces - Google Patents

Description

Nov. 25,1930. w. H. CHAPMAN 1,782,712-

METHOD OF CONTROLLING ELECTROSTATIC CHARGES ON MOVING SURFACES Filed Jan. ll 1930 6 I Q 0 F 4 mlfi g9 Inventor mIlzam/Empuzan Patented Nov. 25, 1930 UNITED STATES PATENT OFFICE WILLIAM HENRY CHAPMAN, OF PORTLAND, MAINE, ASSIGNOR T C HAPIEAN ELEC- TRIC NEUTRALIZER COMPANY, OF PORTLAND, MAINE, A CORPORATION OF MAINE METHOD OF CONTROLLING ELECTROSTATIC CHARGES ON MOVING SURFACES Application filed January 11, 1930. Serial No. 420,058.

My present invention relates to the control of electro-static. charges on a moving web of paper or fabric in the course of its manufacture or printing and to a method of controlling the degree and character of dischalrges such as are required forsuch contro In this art and under the widely varying conditions and constructions of the apparatus used', it is' frequently difiicult, if not impossible, to locate the discharge bar at the point where the neutralization is desired. It sometimes happens that after passing ;the neutralizer the sheet by reason of some inanipulation' takes on another charge and becomes diificult to handle. A characteristic instance of this is in printing presses with a fly stick delivery. Here the paper having been neutralized picks up another charge in passing over the fly sticks and becomes difficult to handle. It is, of course, impossible to locate a bar close enough to the widely moving fly sticks to neutralize the charge.

My present invention conceives of anticipating this difliculty by providing for neutralizing the static charge before it is actually.

formed on the paper. In other words, it contemplates the application of a high tension alternating charge of electricity in a manner to cause the reversal of the polarity of the initial charge on the paper so as to counteract subsequent charges that may be generated on the paper after it has reached any location that would be inaccessible for its direct treatment.

It also has for its object the application of the high tension alternating charge of electricity in a manner to counteract the neg-- ative charge normally produced on paper by an alternating charge when the paper is backed by a solid conducting substance at the pointof treatment.

In my Patent No. 1,228,405,,1 announced the discovery of the negative charging action of pointed conductors having alternating charges in them and showed how that action can be utilized for generating a very high voltage charge of negative electricity on a moving web of paper. That action has al- Fig. 3 shows the factors adjusted to neu-- tralize, and

Fig. 4 shows a further adjustment for counteracting the negative charge that would otherwise be generated where the paper has a solid substance on the side of it opposite to the discharge points.

My present invention or discovery aifords a new basis of practice. It 'aifords a definite control by which factors may be given new uses. 7

The use of an alternating current as a source of neutralizing discharge as disclosed by me in 1904 and subsequently is of great efliciency in neutralization. 4

As heretofore disclosed, this has been effected by discharge points either connected directly to the source of alternating current or else capacitively coupled to it. My present method also may be practiced with discharge points either connected directly or capacitively coupled with the source of alternating current.

The factors involved in my method are only those heretofore usually employed. The novel effects are attained by new methodical relations by which not only improved but new and definite results are made possible.

Considered broadly these are the electrical discharge upon the surface at a predetermined angle which is one factor of control and in relation to a ground factor which may be positioned relative to the axis of discharge and to the surface or body to be controlled.

There are, therefore, involved angles, po-

sitions, distances of separation, and as will be explained, correlated and c'ombinative factors by which methodical procedure may be attained.

Where the sheets come from some operation, as that of a printing press, over a conveyor to fly sticks which deposit them in a stack on a table, there is an electrical charge developed by the printing press or other agency and such charge may be either positive or negative according to circumstances.

By way of illustration I have shown in Fig. 1 a somewhat diagrammatic view in which a distributor bar A is directly connected to a source of high tension alternating current and the discharge points D capacitively. coupled with the bar. This. is preferable because it limits the amountof shock that an operative can get by touching the points. The discharge points D, however, may be directly connected to the bar although not so shown.

P indicates the plane of travel of the surface to be controlled.

G indicates a ground which may be and usually is in practice a definite conductor such as abar usually of substantial diameter such as three-eights or one-half inch.

These physical factors are to be understood as merel physical elements but their relationship w1ll be better understood by a diagrammatic consideration 'of their functions.

To this end I have illustrated several characteristic situations.

For example, we may take a situation such as is indicated in Fig. 2. In this the paper or like material is previously charged with a minus charge and is destined to arrive under the influence of a mechanical factor which will impart a new minus charge. My concept is to anticipate by reversal.

In accordance with my method I dispose the ground G toward the new char e producer or on that side of the discharg from the point D towards which the surface is moving.

The result of this is to neutralize the minus charge of the surface and at the same time to reverse it so that upon arrival under the influence of X with its minus tendency the effect is neutralization.

If the influence X is not present reversal is not necessary. In Fig. 3, I illustrate the case of a minus charge neutralized butnot reversed. In Fig. 4 I illustrate the case where there is a surface of solid conducting material immediately underneath the paper to be treated. In this case I place the ground G closely adjacent to the upper surface of the paper, preferably just in contact with it, and the discharge points D are directed so that the axial line of the point is approximately tangent to that side of G toward ing. Under these conditions any charge on the paper whether positive or negative be-'' comes neutralized and the ordinary detrimental influence of the solid conducting sur- I face under the paper is counteracted.

My invention as herein disclosed may be variously practiced and is of general applicability as will be obviously to those skilled in this art.

What I therefore claim and desire to secure by Letters Patent is:

1. That method of attaining predetermined degrees and polarities in the neutralization of electric charges on moving surfaces which consists in directing neutralizing discharges at a predetermined angle to the surface in the direction of its movement and in maintaining a ground laid transversely on one side or the other of the line of discharge to effect the desired polarity and at a predetermined distance from the surface to control the degree.

2. That method of attaining predetermined degrees and polarities in'the neutralization of electric charges on moving surfaces which consists in directing neutralizing discharges coming from a capacitively coupled conductor at a predetermined angle to the surface in the direction of its movement and in maintaining a ground laid transversely on one side or the other of the line of discharge to effect the desired polarity and at a predetermined distance from the surface to control the degree.

3. That method of attaining predetermined clegrees and polarities in the neutralization of electric charges on moving surfaces which consists in directing neutralizing discharges at a predetermined angle to the surface in the direction of its movement and relative to a ground laid transversely of the surface and positioned at that side of the line of discharge controlling the desired polarity and at a predetermined distance from the surface to control the degree.

4. That method of attaining predeter-- mined degrees and polarities in the-neutralization of electric charges on moving surfaces which consists in directing neutralizing discharges coming from a capacitively coupled conductor at a predetermined angle to the surface in the direction of its movement ar '1 relative to a ground laid transversely of the surface and positioned at that side of the line of discharge controlling the desired polarity and at a predetermined distance from the surface to control the degree.

5. That method of effecting the neutralization of electric charges on moving sheets which consists in producing a reversal of the polarity of the preceding charge upon the paper to a degree which will neutralize a succeeding charge formed on the sheet after it has passed the neutra-lizer.

6. That method of efiecting the neutralization of electric charges on moving sheets which consists in producing a reversal of the polarity of the preceding charge bydischarging upon the sheet in the direction of its motion to a degree which will neutralize a succeeding charge formed on the sheet after it has passed the neutralizer. I

In testimony whereof I aflix my signature.

WILLIAM HENRY CHAPMAN.

Images