US2483542A - Static eliminator for printing presses - Google Patents

Description

Oct. 4, 1949. w, J, HOQPER 2,483,542

STATIC ELIMINATOR FOR PRINTING PRESSES Filed Oct. 24, 1945 4 Shee'ts-Sheet 1 (fau ro@ J 7 if :2li l? jj@ E14 E @Jg Oct. 4, 1949. w. J. HooPER STATIC ELIMINATOR FOR PRINTING 'PRESSES Filed oct. 24, 1945 4 sheets-sheet 2 oct. 4, 1949. Wfl HOOPER 2,483,542

STATIC ELIMINATOR FOR PRINTING PRESSES Oct. 4, 1949. w J, HOOPER 2,483,542

STATIC ELIMINATOR FOR PRINTING PRESSES Filed OC. 24, 1945 4 Sheets-Shea?I 4 Patented Oct. 4, 1949 STATIC ELIMINATOR FOR PRINTING PRESSES william J. Hooper, man, m., mmm to, Goss Printing Press Company, a corporation of 111i-r nois Application October 24, 1945, Serial No. 624,191

a claims. (c1. irs-264) This invention relates to a static eliminator for printing presses, and more particularly to means for varying the electrical charge on the surface of a web of moving sheet material, as paper, by

, means not making mechanical contact with such web.

In forms of printing operations where the sheet material moves in frictional engagement with` guide rolls, guide bars, and the like, undesirable static electric charges develop. This phenomenon gagement between the web and a different material causes the creation of static electric charges on the surface of the web. generally positive, which may run up into thousands of volts. This situation is a direct danger to workers who can be startled into an incautious and disastrous move around the running presses by shocks from this static electricity; and presents a fire hazard in connection with the inflammable volatile constituents of the conventional oil base ink, for ex ample.

In order to obviate this dimculty and keep the web at some desired electrical condition, as at ground potential, various forms of static eliminators have been developed. The majority of these operate by virtue of actual mechanical contact with the paper, creating still further sets of conditions conducive to static electric charges, or by and causing these to move against Vthe surface of the web and give up their charge to the web to bring its electrical condition to the desired state. While .the problem of static electricity may be encountered in connection with any type of press work, as mentioned above, it constitutes aparticularly diiilcult problem in presses using rubber impression blankets or offset rolls and operating at high speed, as for example in newspaper presses of the rotogravure type. The general construction and arrangement of `a newspaper press where the problem of static electricity becomes particularly diilicult are well known, and accordingly I will not go into a descriptionof such a press here. If desired, Crafts Patent 2,085,185, issued June 29, 1937, may be referred rto to supplement this disclosure as to one commercial form of such a press.

Another place where the electrical condition of the web is of considerable importance is inconnection with electric printing, where electric yforces are used to eil'ect or assist the transfer of ink from the ink'source, as a type roll, to the moving web. Methods and apparatus for electric printing form the subject matter of Huebner Patent 1,820,194 and of certain copending applications of mine. In such printing theelectrical condition of the web is of considerable importance, as it must not have electrical charges opposing the elds of force associated with the transfer of ink, and preferably should have A charges assisting such -field.

endeavoring to render the air adjacent the sury face of the sheet material suiiiciently conductive to cause any substantial charge to leak ofi, as by use of gas flames. Previous attempts in thisy re- `gard have also involved considerable disadvanl claiming a static eliminator or charge varying arrangement which makes no mechanical contact with the moving sheet material, which has no tendency to ignite the web, and which is very eiective in bringing the electrical condition of the yweb to a desired value. whether that be ground potential or a potential somewhat positive or negative with respect to ground. In general, I` accomplish this by generating charged gas particles, normally negatively charged air particles,

In any event, the accompanying drawings and the following description are limited to means for varying the electrical condition of moving sheet material, as the web used in newspaper printing, and for the purpose of this application vit will be assumed that the web, and particularly the sur- 40 vfaces thereof, is at some electrical condition which it is desired'to vary. Normally, of course, the web will have positive electrical charges which it is desiredto eliminate; but it will be understood that my invention is broader than merely eliminatingypositive charges. l

Various features and advantages of my invention will be apparent from the following specification and the drawings, in which:

Figure 1 is a schematic diagram of one embodiment of my invention; Figure 2 is a planvview of one of the charge lvarying units adapted, to be associated with the moving web, with theupper part of the air chamber removed; Figure 3;is a

' fragmentary ,transverse sectional view of the devie shown in Figure 2; Figure4 is a diagram` illustrating a. modiied electrical circuit arrangement'for the apparatus shown in Figures 1-3; Figure 5 is a schematic diagram of another form of my' invention; Figure 6 is a vertical sectional View of one 0f the charge varying units shown in 3 Figure 5: Figure 7 is a transverse sectional view filonw thc line l-'I of Figure 6; Figure 8 is a schrmti. diagram of still another embodiment of my invention; and Figure 9 is an enlarged vertical sectional view of one of the charge varying units shown in Figure 8.

In the particular embodiment of my invention illustrated in Figures 1-3, a moving web of paper I is illustrated as passing over guide rolls II and l2 and as moving to the right as illustrated in Figure 1. This web may, for example, be a web of the type used in newspaper printing and comprises a portion of the web passing at high speed through a press of the type known in Crafts Patent 2,085,185, merely as one representative example, The web is illustrated as passing between portions of charge varying units here identified in general as A and B, the first being designed particularly to vary the charges on the upper surface of the web I0 (speaking with respect to the position as shown in Figure 1) and the second being designed primarily to operate on the lower surface of the web. Since static electric charges on a web are generally cumulative, the fact that the web passes over the guide roll I2 after being brought to ground potential or having its electrical condition brought to some other predetermined value is not too critical; although, if desired, the second guide roll I2 may be eliminated and the web may enter directly into a printing zone or the like after it leaves the second conditioning unit B.

Inasmuch as the two conditioning or charge varying units A and B are identical, merely being reversed in their relationship to the web, only the unit A will be describedin detail. This comprises an upper section or portion identined in general as I3 and including first electrode means and means for causing a stream of air to move thereby and toward and against the upper surface of the web; and another portion Il, this comprising the second electrode member and being, in this particular embodiment, a plate of metal extending across the entire width of the web, as may be best seen in Figure 2, and electrically grounded. A relatively high direct current potential, preferably of the order of 5,000 or 10,000 volts, is developed between the two electrode members by a high potential D. C. source I5 having its positive terminal grounded and its negative terminal connected to the electrode in the upper surface I3 of the conditioning units, where the web is to have its electrical condition rendered more negative, as to remove or neutralize positive static electric charges.

The source I5 is preferably of a type permitting variation of its output voltage by manual means, as changing of the rheostat setting. It will not be described or illustrated in detail as it may be of a conventional type which may be secured on the commercial market, as for example those built for high-voltage X-ray tube supply purposes. Such equipment takes power from an ordinary commercial current source, steps its voltage up to the desired value, and recties and filters it to provide a high D. C. voltage. The equipment preferably includes manually variable means enabling variation of the output voltage as mentioned above, meters by* means of which the output voltage and current may be determined and the like. While the current requirements for this purpose are not heavy in the ordinary sense of the word, a certain current flow is necessary to keep charging the air molecules 4 negatively. and accordingly the high potential source should preferably be capable of operating at the desired voltages with current drains in the neighborhood of milliamperes, weil within the range of commercial X-ray equipment.

Referring now more particularly to Figures 2 and 3, it will be seen that the first electrode means or source of electrons comprises a plurality oi' electrically interconnected sharp pointed needle members lla, IIb. etc., these members having their sharp points adjacent and pointing toward the web but spaced therefrom, as for example one-half inch; and being spaced at suitable intervals across the entire width oi' the web, a preferred arrangement in the form of staggered rows being shown in Figure 2. The needle members are suitably mounted, as by mounting plugs Ila, Ilb, etc. in openings in a block Il of insulating material,`these openings terminating in nozzles or small orifices Isa, ISb, etc. surrounding the points of the needle members Ila, lib, etc. Inasmuch as all of these individual arrangements are identical, only one will be described in detail. reference now being had more particularly to Figure 3.

The mounting block IIa is drilled with openings I la communicating with the opening in the block I8 terminating in the orifice Ila; and the block I 0 has its cover portion I l spaced from the main body portion thereof to provide a chamber 20 adapted to be supplied with compressed air from any conventional source through a feed line or hose 2| shown in Figure 2. Compressed air in the chamber 20 passes through the openings I'Ia and eventually issues in a stream from the orifice Isa', passing immediately around the sharp needle point of the member I6a as it issues from the orifice. Since the needle member ISa is several thousand volts negative with respect to the other electrode member I4, movement of air past its sharp point effects transfer of negative electrons or negative units of charge from the metal of the needle member to the molecules of the air passing immediately adjacent it, generating negatively electrically charged gas or air particles or molecules. Since the stream of air is directed toward the upper surface of the web i0, the charged air molecules pass across the space and contact such surface where they give up their excess negative charge to the web, in the particular embodiment here being illustrated, and continually render the surface of the web more negative; i. e., if the web was charged positively, they tend to neutralize such charge and bring the web to ground potential or any other desired less positive electrical condition. In order to maintain the eiiiciency of the conditioning unit it is preferable that the sharp points of the needle members IGa, lib, etc. be gold plated or otherwise made in such manner as to prevent loss of sharpness of the needle point due to corrosion.

The use of a sharp pointed needle-like member as one electrode member, in combination with a stream of air thereby, appears to have inherent rectifying characteristics, and accordingly the conditioning unit can be actuated directly from an alternating current source, as illustrated in Figure 4, if desired. In this modiication the needle member I 6a, illustrated as representative of all of the needle members forming the rst electrode means is shown as connected to one end of the secondary 22a of a step-up transformer 22, the primary 22h of' this transformer being connected to a conventional sections.

, s 4 commercial source of alternating current. The other end of the secondary winding 22a is connected to the electrode member I4, so that the member |611 is alternately positive and negative with .respect to the member I4. With cold needle members and voltages of the order of 5,000 or 10,000 volts, substantially no charge is given to the moving air molecules passing the point of the member 16a while this member is positive with respect to the other electrode member I4; but substantial negative charge is given to` the moving air molecules when the needle member is negative with respect to the other electrode member. While this form of energization is somewhat simpler and less expensive than that illustrated'in Figure l, it is apparent that it is operative over only half, or less than half, of each cycle, so that I prefer the energizing arrangement illustrated in Figure 1.

Referring now more particularly to Figures 5,

6 and?, another .embodiment of my invention will be described. In order to keep the description brief and enable reference back to earlier portions ofthis specification if desired, parts,

shown in these figures, where analogous to parts already described, will be given reference numerals 20 higher than those heretofore used.

erably accelerated by field gradients developed which such a tube can be associated with another electrode member (as the plate 84) in such manner as to vary the electrical condition of a moving web of sheet material without physical contact therewith. f

In this particular form of my invention the charged particle leaving the filament 46 is prefboth by the foil 48 and the plate 34, so that these latter act as first and second portions, respectively, of the second electrode means, the filament constituting the lrst electrode means. That is, as may be best seen in Figure 5, the high potential D. C. output of the source 35, while it again has its positive terminal grounded and its negative terminal connected to the first electrode member (the filament 46 in this case), has its voltage developed across a bleeder resistor 49. The plate 64, being grounded, is therefore positive with respect to the filament 46 in an amount corresponding to the full potential drop developed by the source 35; but the foil 461s connected to some intermediate point on the voltage divider 46, so that while it is positive with respect to the filament 46 it is not-as highly so as the plate 34.

l This results in electrons attracted from the fila- Referring first to Figure 5, the moving web is shown as passing over guide rolls 3l and 32 and as passing between oppositely arranged conditioning or charge varying units A' and B'. Each of these units, as before, comprises a source of charged particles on one side of the web, as the means identified as 33, and a grounded electrode member or plate on the other side of the web. Inasmuch as the units are identical, only the unit A' will be described in more detail.

In this particular form of my invention an evacuated tube 45 extends substantially entirely across the width of the web and has its closest portion suitably spaced therefrom, as a half inch. The tube contains a filament 46 adapted to be heated to incandescence by electric 'current in conventional manner, this filament being of platinum or other suitable material. While this filament is shown as a single wire mounted on suitable spacers 41a-c, it will be understood that the important thing is a hot filament, as a source of electrons, extending transversely across the width of the web, whether this be in the form of a single wire or a plurality of aligned Opposite the filament 46 and facing toward the web 30, as may be best seen in Figure 7, the envelope is provided with what is being here termed a window, this comprising slots in the material of the tube envelope, as glass, covered by a thin metal foil 46, as aluminum. Applieation of a positive potential to this aluminum foil 48. if there is suitable potential drop between it and the filament 46, causes the electrons to reach the aluminum foil with such velocity that the majority of them pass straight through the foil and travel on to the web 30, where they operate as free electrons or as charges on air molecules withA which they have collided. The terms charged gas particle" and ion are being used herein in a sense intended to cover a molecule of air or other gas which has picked up a charge,

' as by acquisition of anvelectron; or a free electron itself, as these particles have electric charges and move in a manner analogous to those of gas particles as distinguished from liquid or solid material. While such a tubing as that illustrated here is not new per se, I believe that I am the rst to appreciate and disclose a manner in ment 46 and caused to pass through the foil primarily by the voltage diierential between the voltage 48 and the filament 46 to continue on toward the web 30 by virtue of the attraction of the even more positive second portion of the'positive electrode means, the plate 34. Again it will be apparent that this particular embodiment of my inventions is adapted to render the web less positive; i. e., partially or entirely to neutralize positive static electric charges thereon.

Referring now more particularly to Figures 8 and 9, still another embodiment of my invention will be illustrated. In order to keep the description brief, reference numerals applied to parts analogous to those heretofore described will be employed which are 50 higher than those used in connection with the first-described embodiment of my invention, and 30 higher than those used in connection with the embodiment illustrated in Figures 5 7.

A web 60 of sheet material, as paper, is again illustrated as passing o ver guide rolls 6| and 62 and as passing between sections of oppositely arranged identical conditioning units here identified in general as A and B", only the first of which will be described in detail. Each unit again comprises two principal sections, the unit A being shown as comprising the section' 63, which provides the source of charged gas particles above the web, and the section 64, comprising a grounded plate electrode member, below the web.

Referring now more particularly to Figure 9, the upper section 63 will be seen as comprising a central filament 16 adapted to be electrically heated to incandescence in conventional manner, this being here shown as a twisted strip of suitable material, as platinum. Instead of being housed in an air-tight envelope, the filament 16 in this form of my invention lies substantially at the axis of a pair of spaced and electrically insulated cylindrical screen members 80 and 6l, of copper mesh screening analogous to that used in a miners safety lamp. Since the hot filament 16 is in this case exposed to air movements, with different heat losses, a thermostat 62 is provided and associated with the heating circuit for the filament 16 (as by control of a thyratron tube) in such manner as to maintain the temperature of the lament 16 substantially uniform despite variations in heat loss therefrom. All of the related parts are held in their desired association by end blocks of suitable insulating material, these being here identified as 83 and 84.

In this particular form of my invention electrons boil off as it were from the hot filament 16 and are caused to travel toward and pass through the screens 80 and 8| by virtue of positive potentials applied to these screens; and those electrons which travel in the general direction of the web 60 are caused to continue movement toward said web and to strike a surface thereby by virtue of a higher positive potential of the member 64 relative to the filament 16. The high potential D. C. source 65 again has its positive potential grounded and its negative potential connected to the filament 16 as the first electrode member, the potential differential developed by this source being applied across a bleeder resistor 19. In this particular case the screens 80 and 8|, and the plate 64 all constitute portions of the second electrode means, and in order to facilitate continued movement of the electrons in the desired direction I prefer to apply the full potential differential between the plate 64 and the filament 16, a somewhat lesser potential differential between the screen 8i and the filament, and a still lesser potential differential between the screen 80 and the filament 16, the reduced but still positive potentials for the screens 80 and 8| preferably being effected by intermediate connections to the bleeder resistor 19, as illustrated in Figure 8. As will be readily apparent this provides another form wherein electrically charged particles originate at a source (here the filament 16) and are caused to move toward and impinge upon a surface of the web 60 to give up their charge thereto and thereby vary the electrical condition of the web. In this particular embodiment of the invention the charged particles are again electrons, and any positive static electric charges on the upper surface of the web 60 would be eliminated or reduced in an amount determined by the number of electrons striking the web, this in turn being a function of the filamenttemperature and the positive electrode voltages used, and being readily controllable.

While I have shown and described certain embodiments of my invention, it will be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In a press of the character effecting printing on a moving web of sheet material, as paper, means for neutralizing static electric charges on the web, comprising: first electrode means adjacent the path of movement of the sheet material on one side thereof, this means comprising a hot filament extending across the width of said web; second electrode means having a rst portion on the same side of said web as the filament and a second portion on the opposite side of the web; and means for creating a substantial potential differential between said electrode means, both portions of the second electrode means having the same polarity with respect to the filament but the second portion being at a higher potential differential than the first, said potential differential being such as to cause electrically charged gas particles to move toward said second portion wilg.

of said second electrode and contact a surface of said sheet material during such movement to vary the charge therein.

2. In a press of the character effecting printing on a moving web of sheet material, as paper, means for neutralizing static electric charges on the web, comprising: first electrode means adjacent the path of movement of the sheet material on one side thereof, this means comprising a hot filament extending across the width of said web; second electrode means having a. portion of screen material between the filament and the web and a second portion on the opposite side of the web; and means for creating a substantial potential differential between said electrode means, both portions of the second electrode means having the same polarity with respect to the filament but the second portion being at a higher potential differential than the first, the construction and arrangement being such as to attract electrically charged gas particles to said second portion of said second electrode and cause said particles to move toward said second portion of said second electrode and contact a surface of said web during such movement to vary the charge therein.

3. In a press of the character effecting printing on a moving web of sheet material of substantial width, as paper, means for neutralizing static electric charges on the web, comprising: first electrode means adjacent the path of movement of the sheet material on one side thereof, this means comprising a hot filament extending across the width of said web; second electrode means having first and second portions of screen material between the filament and the web and a third portion on the opposite side of said web; and means for creating a substantial potential differential between said electrode means, all portions of the second electrode means having the same polarity with respect to the filament but the second portion being at a higher potential differential than the first, and the third portion being at a higher potential difference than the second, the construction and arrangement being such as to cause electrically charged gas particles to move toward said third portion of said second electrode and contact a surface of said sheet material during such movement to vary the charge therein.

WILLIAM J. HOOPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 844,300 Chapman Feb. 12, 1907 878,273 Chapman Feb. 4, 1908 900,830 Chapman Oct. 13, 1908 940,429 Chapman Nov. 16, 1909 1,169,428 Rogers Jan. 25, 1916 1,678,869 Morrison July 3l, 1928 2,164,595 Siebertz July 4, 1939 2,174,328 Meston Sept. 26, 1939 2,233,786 Law Mar. 4, 1941 FOREIGN PATENTS Number Country Date 466,768 Great Britain June 3, 1937 556,067 Germany July 14, 1932 767,652 France July 23, 1934

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