US2333213A

US2333213A - Static eliminator

Info

Publication number: US2333213A
Application number: US429216A
Authority: US
Inventors: Slayter Games
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-02-02
Filing date: 1942-02-02
Publication date: 1943-11-02
Anticipated expiration: 1960-11-02

Description

NOV. 2, 1943. a SLAYTER 2,333,213

STATIC ELIMINATOR Filed Feb. 2, 1942 III IIIIIII IIIIIIIII I INVENTOR.

GAMES SLAYTER 52 BY ATTORNEY Patented Nov. 2, 1943 UNITED STATES PATENT OFFICE STATIC ELIMINATOR Games Slayter, Newark, Ohio Application February 2,1942, Serial No. 429,216 8 Claims. (01'. 175-264) This invention relates generally to electric discharge apparatus and refers more particularly to improvements in equipment of the type employed to eliminate the interference caused by static electricity.

It has been proposed to eliminate interference resulting from static conditions by providing an electric discharge of alternating polarity between an emitting electrode and a collecting electrode so arranged in an alternating current circuit with respect to the electrically charged object that ions drift from the electrostatic field between the electrodes to neutralize'the charge on the object.

Although electric discharge equipment operating on the principle briefly outlined above has proved successful under widely varying conditions, nevertheless, the rate at which one electric discharge device is capable of operating to effect neutralization is not always sufficient to neutralize a relatively fast moving heavily charged material. This limitation is overcome to some extent by providing a series of electric discharge devices but this procedure complicates the installation and increases the cost of the equipment as well as the expense of operation.

It is, therefore, one of the principal objects of this invention to .overcome the above limitation without appreciably increasing the cost of the equipment or the expense of operating the latter by providing an electric discharge device having means for neutralizing a large quantity of charge of either polarity on a fast moving object before the object, registers with the electrostatic field produced by the emitting and collecting electrodes.

More particularly the present invention contemplates supporting one or more grounded pointed rods or electrodes in such relationship to the charged body that when the potential difference between the body and ground exceeds the onset? potential of the pointed electrodes, an electric discharge is created from the pointed ends of the electrodes and this discharge reduces the potential of the object to'the onset potential of the pointed electrodes. The onset potential of the pointed rods is usually small as compared to the total charge on the object and the electrical charge on the object represented by this onset potential is readily neutralized by the electric discharge device when the object has advanced. to a position in registration therewith.

made more apparent as this description proceeds,

and especially rapidly moving objects.

especially when considered in connection with the accompanying drawing wherein:

Figure 1 is a side elevational view partly in section of electric discharge equipment constructed in accordance with this invention;

Figure 2 is a cross sectional view taken on the line 2-2 of Figure 1 and showing the equipment in operative relation to a charged object; and

Figure 3 is a diagrammatic perspective view of the electric discharge equipment-and showing a part of the electrical circuit employed.

Although the electric discharge equipment forming the subject matter of this invention may be advantageously used in practically any case where it is desired to release or neutralize electrostatic charges, nevertheless, it finds particular utility when used for the purpose of removing or neutralizing static charges on moving objects For the purpose of illustrating this invention, therefore, I have diagrammatically shown in Figure 2 a travelling object l0 which may be a sheet of paper or any other materialadapted to acquire an electric charge of either polarity.

It is desired to neutralize static charges on travelling sheets of material because these charges often times seriously interfere with-processing the material and this invention insures expedient neutralization of charges of either polarity on the sheet of material ID as the latter is advanced along its path of travel. In general, the equipment for accomplishing the above results comprises an electric discharge device ll having a plurality of pointed emitting electrodes l2 arranged in spaced relation to each other ina single row and having collecting electrodes l3, respectively, supported at opposite sides of the emitting electrodes in lateral spaced relation to the latter. I

As shown in Figure 3, the electrodes are connected in an electric circuit 14 which includes an alternating current transformer l5 having a primary winding l6 connected to a source of alternating current and having a secondary winding l6. One end of the secondary winding I 8' is grounded as at I! and the other end of the secondary winding is electrically connected to each of the emitting electrodes I2. The collecting electrodes l3 are arranged in the circuit It in such a manner that they are also connected to the ground l1. As a result of the above circuit arrangement, a difference of alternating potential is connected to the emitting electrodes l2 and the collecting electrodes I3.

The difference of potential is predetermined in dependence upon the spacing between the emitting electrodes i2 and the collecting electrodes l3 so that an electric discharge of alternating polarity takes place between the pointed ends of the emitting electrodes l2 and the collecting electrodes. In other words, the arrangement is such that electrostatic fields of opposite polarity are produced between the electrodes on successive half cycles of operation so that both positive and negative charges are available in the gap between the electrodes. If desired, a suitable condenser l8 may be connected in the circuit to equalize the quantities of both positive and negative charges produced in the gap between the electrodes on successive half cycles of operation.

The electric discharge device I l is shown in Figure 2 as positioned in relatively close proximity to the underside of the sheet of material Ill so as to-influenceany electric charge on this sheet of material. The relationship between the electrostatic field produced by the device II and the sheet of material in is such that when the latter is charged with a negative polarity, positive charges drift from the electrostatic field to the sheet of material 10 during the positive half cycle of operation of the device ll. Thus, during each positive halt cycle of operation of the electric discharge device ll, positive charges are supplied to the negatively charged sheet of material l0 and the latter eventually becomes neutralized. On the other hand, if the sheet of material Ill carries a positive charge, negative charges are released from the electrostatic field during the negative half cycle of operation of the device II and are supplied to the sheet of material "I to neutralize the latter. It follows, therefore, that the electric discharge device ll acts to neutralize the sheet of material Ill regardless of the polarity of the charge on the latter.

In some instances the quantity of electrical charge on the sheet of material II and the rate of travel of this sheet is such that the electric discharge device ll does not operate with suflicient rapidity to completely neutralize the electric charge on the sheet of material III. In order to overcome this objection, the action of the electric discharge device I I is supplemented byone or more rows of pointed discharge electrodes l9. Although the number of rows of discharge electrodes I! are not critical and may be varied to suit diiferent conditions, nevertheless, I have shown two distinct rows of discharge electrodes I! herein for the purpose of illustration.

In general, the two rows of discharge electrodes I! are spaced laterally from each other a sumcient distance so that the electrodes in one row do not interfere with the electrodes in the other row and the electrodes in each row are spaced from each other a suflicient distance so that they do not interfere with one another. In addition, the electrodes in each row are electrically connected in series and are also electrically connectedtothe ground ll. Inthepresentinstance the discharge electrodes I! are carried by the right hand collecting electrode l3 shown in Figure 2 and are pointed toward the underside of the sheet of material II. this time that both rows of the discharge electrods I! are spaced in advance of the adjacent collecting electrode I! a suflicient distance that they do not interfere with the electrostatic field produced between the emitting electrodes I2 and the collecting electrodes l3.

Owing to the above construction, the discharge electrodes I! operate to neutralize a substantial quantity of the electric charge on the sheet 01 material It before the latter comes under the It may be pointed out at influence of the electrostatic field produced by the electric discharge device II. It will, of course, be understood, however, that the pointed discharge electrodes 18 will not entirely neutralize the charge on the sheet ofmaterlal l0 because these electrodes have a certain resistance which is commonly referred to as the onset. potential characteristic. This potential characteristic varies in dependence on the sharpness of the emitting tips of the discharge electrodes and, in the present instance, the emitting tips are very sharp. As a result, the electrodes l9 are very sensitive and function to initiate the desired electric discharge upon a relatively small potential difference between the sheet and discharge electrodes. This action is desirable because it renders it possible to more nearly neutralize the charge on the sheet before the latter registers -with or comes under the influence of the ionic field produced by the electric discharge device ll.

It follows from the above that if the electric charge on the sheet of material I0 is suflicient to cause the sheet to have a potential with respect to ground greater than the onset" potential for electrical discharge from the pointed electrodes l9, then an electric discharge takes place at the pointed ends and the potential of the paper with respect to ground is thereby reduced to the onset" potential of the pointed discharge electrodes IS. The electric charge remaining on the sheet of material I0 is neutralized by the electrostatic field produced by the electric discharge device I I and, as a result, the charge on the'sheet of material II is completely neutralized.

Assuming, for example, that the electric charge on the sheet of material III is of negative polarity, it will be noted that the discharge electrodes l9 are of a positive polarity with respect to the sheet l0 because they are connected to ground. As a result, an lectric discharge is produced between the pointed ends of the discharge electrodes l9 and the sheet II and electrons are drawn from the sheet ll tending to reduce the potential of the sheet to the onset" potential of the pointed discharge electrodes l9. It may be pointed out that the electrons approaching the points of the electrodes l9 are accelerated by the more intense field in the regions of the points and this produces ionization. The positive ions thus produced are forced back toward the sheet of material ll because the latter is of negative polarity and, accordingly, these positive ions assist in effecting neutralization of the charge on the sheet of material ll.

Asuming now that the charge on the sheet II is of a positive polarity, it will be noted that the electrodes I! will be of a negative polarity with respect to the sheet II. This results in an electric discharge from the pointed ends of the electrodes is to the sheet II and causes electrons to accumulate on the sheet ll tending to neutralize the latter. Thus, it will be apparent that the combination of the electrodes I! and the electric discharge device ll renders it possible to completely neutralize the charge on the sheet ll even though this charge is relafively heavy and even though the rate of travel of the sheet is relatively fast.

The specific construction of the electric dischargedevice ll selected herein forthepurpose of illustration is similar to the electrlc discharge device shown and described in the John Thomay application, Serial No. 413,965, filed October '1,

- ing material and this material is supported on a cylinder 23 of dielectrical material. The sleeve 22 may be either a semi-conducting inli or a semiconducting paper and in either case possesses sumcient. resistive characteristics to not only assist in controlling theelectric discharge but also functions as a resistance between adjacent emitting electrodes I2. As a result, the current drawn by any one emitting electrode is limited and this is advantageous because it minimizes the tendency for the emitters to become overloaded to the point of arcing.

The electrical conductor 2| projects through one end of the dielectric tube 20 and is electrically connected to the secondary coil l6 of the alternating current transformer I! in the manner shown in the diagram in Figure 3. After the electrical conductor 2| and the cylinder 23, with the semi-conducting material 22 thereon, are assembled in the tube 20, the opposite ends of the latter are sealed with suitable plugs 24. These plugs are formed of a dielectric material and extend beyond the opposite ends of the tube 20 a sufficient distance to enable the device to be readily mounted The collecting electrodes I3 are supported at opposite ends in end plates 25 which are also formed of dielectric material. The end plates 25 are apertured to respectively receive the projecting plugs 2i and are preferably rigidly secured to the tube 20. This construction is advantageous because it provides for sealing the electrical conductor and its electrical connection to the emitting electrodes from the atmosphere so that the discharge device will operate satisfactorily in moisture laden atmospheres without the danger of short circuiting.

It is also important to control the electric. discharge in the gap between the emitting electrodes l2 and the collecting electrodes ii in order to prevent this discharge from becoming disruptive in nature. In other words, it is desired to provide a diffuse discharge in the gap and this discharge is one which is free from sparking, arcing and streamering.

The diffuse discharge is obtained by controlling the maximum current tendency which can occur in the gap between the emitting electrodes and the collecting electrodes. This control is dependent on a number of variables which vary in dependence upon different uses of the electric dis-.

charge device and to some extent on the power supplied to the circuit H. Therefore, it is not practical to define specific values for these variables which will afl'ord the maximum efficiency of operation under all conditions. However, an electric discharge device constructed in accordance with the following specifications has been found to produce the desired diffuse discharge in the gap between the electrodes. It is to be understood, however, that the specific values noted below are merely for the purpose of illustrating one particular use of the electric discharge device and should not be considered as limiting this invention.

Assuming for the purpose of this description a 10,000 volt tranformer is used in the circuit and that this transformer has an operating out- .put of approximately 200 microamperes when the primary is connected to a 110 volt alternating current source, it has been found that the tips of the emitting electrodes i2 should be approximately three-fourths of an inch from the collecting electrodes i3. It has also been found that the tip diameter of the emitting electrodes should be relatively small and particular satisfactory results have been obtained by forming the tips of the emitting electrodes l2 of approximately two thousandths of an inch in diameter. Also adjacent emitting electrodes l2 should be spaced from each other a sumcient distance-that thedischarge from the tip of one emitting electrode does not interfere with the discharge from the tip of adjacent electrodes.

The blocking condenser l8 employed in the circuit M to equalize the discharges of opposite polarities may be of a relatively small capacity, and I have found that a 2,000 volt condenser having approximately .01 microfarad capacity is zrtisfactory under average conditions of opera- The resistivity of the electrical connection 23 between the emitting electrodes l2 and the electrical conductor 2| is not particularly critical. However, it is desired to embody some resistance in the circuit because it has been found that such practice stabilizes the operation of the device and assists in obtaining a diffuse discharge over a long period of use with the minimum attention. For the purpose of illustration a resistance of approximately 200 megohms is satisfactory to perform the desired results.

The pointed discharge electrodes is are carried by one of the collecting electrodes l3 and are electrically connected to the latter collecting electrode in order to have the same potential as this electrode. As shown in Figure 3, the discharge electrodes in each row are anchored to a conducting rod 26 in such a manner that the discharge electrodes in each row are electrically connected together in series. The two conductor rods 26 are connected together at longitudinally spaced points by means of a conductor rod 21 and the rod 26 adjacent the collecting electrode I3 is similarly connected to the electrode l3 by means of conductor rods 28. Thus, it will be seen that the discharge electrodes [9 form a unit with th; Ielectric discharge device ll.

e spacing between adjacent rows of i electrodes is and the spacing betweenili e l ei trodes in each row is such that the electrostatic field at the tip of any one of the electrodes is not disrupted or affected by the discharge from the tip of adJacent electrodes. This spacing will depend to some extent on the distance between the tips of discharge electrodes 9 and the travelling sheet of material [0. However, in most applications the distance between adjacent electrodes i9 shouldbe within the range of onequarter inch to one-half inch. Also the distance between the electric discharge electrodes l9 and the device H is predetermined so that the discharge electrodes l9 have no effect on the electrostatic field in the gap between the emitting electrodes l2 and the collecting electrodes l3. In

addition, the number of discharge electrodes l9 is determined for each application so that the current is equally divided between a sufiicient number of electrodes to avoid overloading any one electrode to the point where the discharge becomes disruptive and produces streamering,

arcing and sparking conditions. This is important because it enables the equirment to be safely used under practically any existing conditions.

What I claim as my invention is:

11. Electric discharge equipment comprising an emitting electrode and a collecting electrode connected in a circuit with-a source of alternating potential in a manner to provide an electric discharge oi alternating polarity from the emitting electrode to the collecting electrode, and a discharge electrode connected in the circuit and having the same potential as the collecting electrode. 4

2. Electric discharge equipment comprising a row of pointed emitting electrodes spaced from each other and serially electrically connected together, a collecting electrode supported on each side of the row of emitting electrodes in such relation to the pointed ends of the emitting electrodes to enable a discharge of electriciiw from the pointed ends of said emitting electrodes to the collecting electrodes, and a second row of pointed discharge electrodes spaced laterally from the row of emitting electrodes and electrically connected to said collecting electrodes.

3. Electric discharge equipment comprising an emitting electrode and a collecting electrode connected in a circuit with a source of alternating potential and spaced from each other to provide an electric discharge of alternating polarity in the gap between the electrodes, means in the circuit providing an electric discharge in the gap of only one polarity at one time, and an additional discharge electrode having the same potential as the collecting electrode and spaced sufliciently from the emitting electrode to be substantially free from the electrostatic field in the gap between the emitting and collecting electrodes.

4. Electric discharge equipment comprising a row of pointed emitting electrodes spaced from each other and serially electrically connected together, an electric circuit including the emitting electrodes and a source of alternating .potential, a common collecting electrode for said emitting electrodes and connected in the circuit in such spaced relation to the pointed ends of the emitting electrodes to provide an electric discharge of alternating po'larityin the gap between said electrodes, and a row of discharge electrodes extending in the same general direction as the emitting electrodes and having the same polarity as the collecting electrode, said discharge electrodes being spaced laterally from the emitting electrodes a sumcientdistance to be substantially free from the influence of the electrostatic held in the gap between the emitting and col- .lecting electrodes.

5. 'Eflectric discharge equipment for neutraliza charge of electricity on a travelling object, comprising a discharge electrode having a end directed toward the object and so positioned with respect to the object that an ionic field is produced between the point and charged object which reduces the potential of the object to the onset'potentia1 of the pointed electrode, and

means spaced from the pointed electrode in the direction of travel or the object for producing an electric discharge of alternating polarity in such relationship to the object to neutralize the charge remaining on the object regardless of the polarity of this charge.

6. Electric discharge equipment for neutralizing a charge oi. electricity on a travelling object, comprising a row 0! pointed discharge electrodes spaced from each other and positioned to one side of the path of travel of the object with the pointed ends directed toward the object, the spacing between the pointed ends and object being predetermined to produce an electric discharge between the pointed ends of the electrodes and object and thereby reduce the charge on the object to the "onset potential 01 the pointed electrodes, and means spaced from the row of discharge electrodes in the direction of the travel of the object for producing an electric field of alternating polarity in proximity to the object to thereby neutralize the charge remaining on the object.

'1. Electric discharge equipment for neutralizing a charge of electricity on a travelling object, comprising a discharge electrode having a pointed end directed toward the object and so positioned with respect to the object that an ionic field is produced between the point and charged object which reduces the potential of the object to the onset potential of the pointed electrode, a collecting electrode spaced from the discharge electrode in the direction of travel of the object and having the same potential as the discharge electrode, an emitting electrode spaced from the collecting electrode and connected to a source of alternating potential suflicient to produce an electric discharge of alternating polarity between the emitting electrode and collecting electrode. said emitting and collecting electrodes being so positioned with respect to the object that the electrostatic field in the gap between the emitting and collecting electrodes neutralizes the charge remaining on the object.

8. Electric discharge equipment for neutralizing a charge of electricity on a travelling object, comprising a row of pointed discharge electrodes spaced from each other and positioned to one side of the path of travel of the object with the pointed ends directed toward the object, the spacing between the pointed ends and object being predetermined to produce an electric discharge hetween the pointed ends of the electrodes and object and thereby reduce the charge on the object to the "onset" potential of the pointed electrodes, 2. row of emitting electrodes spaced from the row of discharge electrodes in the direction of travel of the object and connected to a. source of alternating a collecting electrode electrically connected to the row oi. discharge electrodes and operatively positioned with respect to the emitting electrodes and object to produce an electric discharge of alternating polarity between the emitting electrodes and collecting electrode .suflicient to neutralize the charge remaining on the object.

GAMES SLAYTER.