DE2101904A1 - Device for applying an electrical charge to a sheet - Google Patents

Description

PATENT LAWYERS DR.-ING. WOLFF, H. BARTELS, DR. BRANDES, DR.-ING. HERO

STUTTGART ^ ... lL ·.> I. <m .... X9J.l

LANGE STRASSE 51 PHONE. (0711J 296310 and 297295

TELEXi 0722312

Our reference: 122.856-137333 kdk

Eastman Kodak Company, Rochester, New York State, United States of America

Device for applying an electrical charge to a sheet

109841/1078

The invention relates to a device for applying an electrical charge to a flexible material existing sheet fed forward, having a first roller having an electrically conductive surface with that is in contact with one broad side of the sheet. The sheet consists for example of a photographic film or Paper.

Such sheets are guided between and over rollers during manufacture, or by other processing devices passed through, which each cause an electrostatic charge of the transported sheet. Becomes a such an electrostatically charged sheet brought into the vicinity of a grounded object, so can for the sheet harmful sparks are generated. For example, if the sheet is already coated with a photosensitive emulsion, then so such sparks can cause local exposure of the layer. It can also occur in a darkroom Sparks can also expose other photographic material in addition to the sheet on which the spark is generated. Such sparks join Sheets made of primed photographic material that has not yet been primed with a If the light-sensitive emulsion is coated, the sparks can burn the base layer, so that the Emulsion is not properly distributed or applied correctly in a subsequent treatment stage. Beyond that electrostatic charges can also be present in the form of charge islands, which occur during the subsequent coating create cracks or empty areas with emulsion. Ultimately, electrostatic charges lead to a deterioration in quality detrimental dust particles are attracted and accumulate on the leaf.

10-9841 / 1 079

A device for the purpose described above is known (British patent specification 976 027), in which a belt is guided over a roller with an electrically conductive surface lying at ground potential, while electrically conductive bristles made of nylon, brass or od on the other broad side of the belt. like loops that are put under tension. This device has the disadvantage that the surface of the respective band section can be scratched by the bristles and that particles from the bristles can be deposited on the band. Another disadvantage g

is that when the tape breaks or runs out, there is direct contact between the bristles on the one hand and the grounded roller, on the other hand, may occur, creating sparks, which are particularly harmful to photographic Films or photographic paper are that are currently in the darkroom.

The object of the invention is to provide those listed above Eliminate disadvantages.

The object is achieved in a device of the type mentioned according to the invention in that a second roller is provided with a surface of an electrically preferably % weakly conductive material with which the other broad side of the sheet is in contact and that one of the two rollers is at a DC potential of a height and polarity causing a desired state of charge on the sheet, while the other roller is continuously at ground potential. The material treated by means of this device is expediently in an essentially dry initial state. The charge placed on it

109841/1079

is either positive or negative, so that a desired, E.g. a positive, negative or neutral state of charge is achieved on the sheet.

The surface of the roller lying at DC voltage potential can be conductive, semi-conductive or weakly conductive, whereby a weakly conductive surface is understood to mean a surface that has a surface resistance between

7 12 -

Has 1 χ 10 and 1 χ 10 ohms per square. The as Surface resistance, called resistance, is measured on the surface of a body by cutting two cutting electrodes of the same length into a good one Contact with the surface are brought in such a way that the cutting edges on the opposite sides of a Squares are placed on the surface, its side length corresponds to the length of each of the two cutting edges. The "surface resistance" measured between the two electrodes is measured in units of ohms / square or ohms / square for short. Within certain limits is that measured surface resistance of the surface of one and the same body regardless of the size of the square.

This arrangement and design of the second roller ensures that sparking occurs when the two rollers brought into contact v / earth is avoided. The risk of scratching the surfaces of the sheets when the charge is applied and that particles from the electrode at a higher potential are deposited on it is significantly reduced an advantageous embodiment of the device it is provided according to the invention that the second roller has a soft, flexible coating on its circumference, which consists of an electrically weakly conductive material. Through this coating the risk of a possible Loading

109841/1079

Damage to the surfaces of the leaves is further reduced.

In a further advantageous embodiment of the device The two rollers are adjacent to one another and are arranged as pinch rollers between which the sheet passes. In order to avoid sparking when the rollers come into contact, the two rollers can be advantageous be arranged to one another in such a way that the coating of the second roller touches the first roller when there is none Between the two rollers.

The arrangement can according to a further advantageous embodiment of the invention can also be made such that the sheet has an electrically conductive layer on one broad side, e.g. of carbon or metal, with which the first roller, which is at ground potential, is in contact, wherein advantageous the first roller is arranged at a distance from the second roller in the transport direction of the sheet. This arrangement tion, in which the two rollers are not arranged and act as pinch rollers, has the particular advantage that otherwise possible accompanying phenomena due to the clamping effect, such as possible marking of the sheets or undesired Pull, are completely turned off. Furthermore, this embodiment can be adapted to different spatial conditions, since the two rollers do not have to be arranged in a fixed predetermined position to one another. A device configured in this way requires very little space with a corresponding arrangement of the rollers.

By means of the device, the sheets or also continuous long strips, e.g. in a station of a Bring the processing chain to a given state of charge and then, i.e. after the intermediate treatment stages, by recharging while neutralizing those additionally absorbed or those not absorbed Bring charges to a neutral state of charge.

109841/1079 *

The invention is explained in detail below with reference to the exemplary embodiments shown in the drawing.

Show it:

1 shows a schematically drawn side view of an exemplary embodiment of a device for generating of a desired state of charge on a long belt, for example on belt-shaped photographic Film or paper;

FIG. 2 shows a side view corresponding to FIG. 1 of an exemplary embodiment for the use of individual, from a continuous band of cut portions of photographic material; and

3 shows a schematically drawn side view of an exemplary embodiment for the use of band-shaped Material that has an electrically conductive coating on one broad side.

From Fig. 1 it can be seen that a long uninterrupted Belt 11 of dry photographic film or paper continuous between a first metallic roller .13, which is grounded, and a second roller 15 made of steel or another metal, is carried out, it being the Roller ϊ3 touches. The roller 15 has a on its circumference soft, flexible coating 17 made of electrically / weakly conductive Material that is resiliently applied to the broad side of the belt 11 that is facing. Through the coating 17 a better touch is achieved than would be the case with the use of a metallic surface, where with light Surface irregularities would be expected and being others

109841/1079

Disadvantages would have to be taken into account / as mentioned below will be discussed in more detail.

The metallic surfaces of the rollers are spaced apart from one another which corresponds to the thickness of the belt 11 soft, resilient coating- 17, however, contacts roller 13 when there is no tape between the two rollers.

The roller 15 is mounted in electrically insulated bearings, which are not shown, so that the roller is against earth is isolated. A suitable variable voltage source 19 for direct voltage is connected to the roller 15 and ™

has adjusting devices 21, and 23 for setting the desired Polarity or the desired amount of voltage, so that the correct voltage on the roller 15 is created. Any voltage source can be used, for example batteries or a DC voltage generator or a rectifier connected to an alternating voltage network. The current flow is small, common the current strength is less than 1 milliampere,

The correct voltage to be applied to the roller 15 can be determined through experiments. Preferably, however, a electrostatic field strength meter 25 arranged in the vicinity of ^ the rollers 13 and 15 running belt 11, so that the electrostatic field generated by any electrical charge on the tape is continuously measured or monitored and anqezeiat on a measuring instrument 27

will. The operator monitors the value of the voltage and its polarity on the measuring instrument 27 and adjusts the voltage source accordingly, so that the desired state of charge of desired polarity is obtained. An electrostatic field strength meter suitable for the present purpose is, for example, in FIG

109841/1079

2 ϊ 01904

July edition, born in 1950 by "Journal of the Society of Motion Picture and Television Engineers" described in an article by HW Cleveland on pages 37 to 44. The . The title of this article is "A method of measuring electrification of motion picture film applied to cleaning operations".

The charge, which is on a belt 11 of photographic Material formed can be quite strong, causing electrostatic potentials between 100 volts and 50,000 volts may be present. The charge can be positive or negative, depending on the type of material of the belt and the type the rollers or other devices through which or over which the belt has been guided. To the cargo To neutralize, it is necessary to apply a voltage of opposite polarity to the roller 15 by corresponding Adjustment of the voltage source 19 to be supplied. The voltage to be applied is due to the special training the roller is much lower than the potential on the belt.

The soft, flexible, weakly conductive coating 17 of the metallic roller 15 may be in the form of a sleeve-like coating or a sheet-like coating and in the case of the sleeve-like cover it can be shrunk on or, in the case of a sheet-like design, by gluing on the roller 15 be attached. Preferably, the coating 17 is formed by a cotton velor plush with a surfactant is treated to make the plush fabric weakly electrically conductive, and the the roller 15 is fixed by an adhesive layer.

1098 ^ 1/1079

A suitable surfactant is, for example, a sodium salt an alkylaryl polyether sulfonate sold by Atlas Chemical Company under the name "Triton X 200 E "is sold. Plush fabric is particularly suitable because the fibers are in a uniform Make total contact with the surface of the belt without leaving small areas untouched, and because of this an electrification through friction and a stronger transfer of the electric charge than with certain others Coating is given. Other suitable materials For the low-conductivity coating are rubber that contains carbon black, carbon black-soaked fabric and polyurethane materials that have been soaked or filled with a conductive, surface-active substance.

The rollers are arranged so that the flexible coating 17 is in contact with the surface of the roller 13 when there is no belt 11 or between the two rollers Sheet is located. This state of contact can occur, for example, if the tape 11 should tear or run out. An undesirable spark formation is avoided by the weakly conductive coating 17, whereas otherwise the two metallic ones Surfaces on the rollers prevent sparking (| causes.

The types of material of the tape that can be treated by means of the device according to the invention, and various, such as cellulose triacetate film base or polyethylene terephthalate film base, those not coated or with photosensitive emulsions, basecoats or with antihalation layers can be coated on the back. Other types of ribbons can be made from photographic paper be formed, which has coatings of photosensitive emulsions, polyethylene or the like, or the has no coatings. The described

109841/1079

λ ίO1904

Device works effectively when the material of the tape is electrically non-conductive, is in a dry state and has a constant thickness or thickness and after passing through the rollers with no liquid or semi-liquid layer thereon.

The rollers 13 and 15 can consist of loosely rotating rollers, the belt 11 being transported by means of rollers, which are driven by a motor and are arranged at any point. If desired, you can one or both rollers 13 and 15 are also driven by a motor.

The device described is effective whether the band is bent around the roller 13 or 15 or straight between runs through it. The arrangement in Fig. 1 in which the tape is bent around roller 13 is particular advantageous because in this case there is essentially a line contact of the coating 17 with the tape, which leads to a more effective transfer of the charge and enables it to neutralize a large static potential by having the roller 13 is applied a lower voltage.

In the embodiment shown in Fig. 2, the rollers 13 'and 15', the variable voltage source 19 ', the The field strength meter 25 'and the measuring instrument 27' for voltage display are each the same as in the case of the one based on FIG. 1 described embodiment.

In the embodiment in Fig. 2, a tape ^11f of photographic paper or film is passed through two driven rollers 31 and 33 and into a cutter 35 to cut the tape into individual sheets 37 of relatively small dimensions, which successively from the cutter led out and between the rollers 13 'and 15 *

109841/1079

01904

carried out v / ground, where their static charges are neutralized. The leaves then fall into a container 39 into it, each in a stacked arrangement, with one sheet on top of the other on top, stacked until the container is full. Without the device to neutralize the charge the static electrical charges would tend to generate sparks if some single sheets were on top of the previous sheets of paper. Such sparks have caused the quality to deteriorate | and exposure of other photographic products in the same room is effected. The surfaces of the rollers 13 'and 15 "touch briefly between successive ones Scroll. However, spark formation on contact is caused by the coating 17 'made of a weakly conductive material avoided.

It has been shown that when a voltage of about -IO volts is applied to the roller 15 ', the charge on the sheets 37 with it Success is neutralized, which was displayed before neutralization with 1000 volts on the field strength meter 25 '.

The cutter 35 can be of any desired arrangement suitable for repeatedly cutting the tape transversely along suitable lines so that finished sheets of the desired small size can be made. A suitable cutting device is shown, for example, in U.S. Patent 3 000 250 described in more detail. The cutting device 35 can be designed so that they either by hand operated or driven by a motor.

Shown in Fig. 3 is a device for treating a strip 11 '",

the lower broad side of which has a coating on the surface

1 Q 9 8 k 1/1 0 7 9

made of an electrically conductive material, e.g. made of copper or

ytragt

a metal such as aluminum, silver or gold. For example, photographic film material often carries one electrically conductive, carbon-containing, loan-free Layer applied to a surface.

When treating such a material it is not necessary to to pass the tape through two pinch rollers as in Fig. 1 and, whereby the difficulties are avoided caused by the pressure effect, e.g. the possible marking of the tape, and by the undesired pulling and thereby further enabling the device to be in a more limited space than the devices in Figs can work.

In this embodiment, the tape II ¹¹ is bent around a coated roller 15 ^{lf of} the type described above, the electrically conductive coating of the tape on its first side or back not coming into contact with the roller and the appropriate charge on the non-conductive second side or top is applied. The belt II ^{11 then runs} over an electrically grounded metallic roller 43, the conductive rear side of the belt coming into contact with the roller 43 on the surface.

The charge applied to the second side by means of the roller 15 ″ induces a charge of the same size and opposite Polarity in the conductive layer on the first side. Therefore the charge is double or as a dipole layer available and cannot be measured with a field strength meter. For this reason, a voltmeter 41 is about 1 mm from the grounded loosely rotating roller 43 adjacent to the belt as a basis for determining the size of the arranged by means of the roller 15 ″ charge to be applied,

10984 1/1079

2 KiI904

to achieve a desired state of charge on the belt.

Successful tests have been carried out with the embodiment of a device shown in FIG. 3, in which rollers 15 ^{11 were} used, which were covered with ordinary cotton fabric and with plush fabric, both fabrics having been treated with known surfactants in order to render the fabrics weakly conductive do. These surface-active substances include sodium salts of sulfonated naphthalenes (Tamole, manufacturer: Röhm & Haas) and long-chain quaternary ammonium salts (Catanac products, manufacturer: American Cyanamid Co.). Another suitable roller material is formed from phenol-formaldehyde resins (Synthane, manufacturer: Synthane Corporation USA) which are filled with fabric and ground with a "surface-active substance made from Tamol.

Band II ¹¹ , which showed a charge of +75 volts on voltmeter 41, was brought back to zero by applying a negative charge of -400 volts to a roller 15 "which was covered with a tamol-treated cotton fabric ; it was brought to +200 volts by applying a positive charge of 600 volts.

A plush-covered low-conductivity roller 15 ¹¹ was somewhat more effective and a low-conductivity Synthane roller was somewhat less effective.

There are various modifications which will be apparent to those skilled in the art of the invention, which include the following cases:

A. Arrangement of the rollers as shown in Figures 1 and 2, with the tension applied to the resiliently coated Roller 15 or 15 · is applied and

"10 9841/1079 ......

/ Λ 01904

the metallic roller 13 or 13 'is grounded. Around To neutralize or reduce the charge on a sheet, a voltage is applied whose Polarity is opposite to that of the incoming sheet.

B. Arrangement of the rollers as shown in Figures 1 and 2, with the tension applied to the metallic roller 13 or 13 'is applied and the resiliently coated Roller 15 or 15 'is grounded. To neutralize or increase the charge on a sheet reduce, a voltage is applied whose polarity corresponds to that of the incoming sheet.

C. As in case A, with the positions of the rollers

13 and 15 or the rollers 13 'and 15' are interchanged, but the electrical connections and the operation is the same as in case A.

D. As in case B _f where the positions of the rollers

13 and 15 or the rollers 13 'and 15' one below the other are reversed, but the electrical connections and operation are the same as in the case B.

E. Arrangement of the rollers and mode of operation as shown and described with reference to FIG.

Some of the advantages achieved by the invention are listed below:

Spark discharges when a sheet of photographic material is grounded / causing damage

are avoided

109841/1079

of the sheet itself. by sparks and the addition of other photographic materials in the same darkroom is avoided. Furthermore, the formation of harmful islands of high charge density on a sheet of a photographic film or paper support is avoided, whereby the subsequent coating processes are improved. The accumulation of dust particles on a sheet of photographic material can be prevented by lowering the static potential which attracts and holds the dust particles in place. Spark discharges when two rollers are brought into contact _r eg when a belt breaks or j | leaks, or between following leaves with a gap, which pass between the rollers, are avoided.

109841/1079

Claims (15)

Claims .JL_J Device for applying an electrical charge to a sheet made of flexible material and transported forward, with a first roller, which has an electrically conductive surface, is in contact with the broad side of the sheet, characterized in that a second roller (15 15 ';15'') is provided with a surface made of an electrically / scnwacn ^e lextenden material (17; 17'; 17 '') with which the other broad side of the sheet (11-37; II ¹¹ ) is in contact , and that one of the two rollers is at a DC potential of a level and polarity which will produce a desired state of charge on the sheet, while the other roller is continuously at ground potential. 2. Apparatus according to claim 1, characterized in that the second roller (15; 15 ', 15 ¹¹ ) has on its periphery a soft, resilient coating (17; 17', * 17 ''), which consists of an electrically weakly conductive Material. 3. Apparatus according to claim 1 and 2, characterized in that the two rollers (13, 15; 13 ', 15 ¹ ) are arranged adjacent to one another and as pinch rollers, between which the sheet passes. 4. Apparatus according to claim 3, characterized in that the two rollers (13, 15; 13 ¹ , 15 ') are arranged to each other in such a way that the coating (17; 17') of the second roller (15; 15 ') the first Roller (13; 13 ') touches when there is no sheet (11; 37) between the two rollers. 10984 1/1079 5. Device according to one of claims i to 4, characterized in that the second roller (15; 15 '; 15 * ^f ) is at the DC voltage potential. 6. Device according to one of claims 1 to 4, characterized in that that the first roller (13; 13 '; 43) is at the direct voltage potential. 7. Apparatus according to claim 1 and 2, characterized in that the sheet (II ¹¹ ) on a broad side has an electrically conductive layer with which the λ first roller (43) at ground potential is in contact. 8. Apparatus according to claim 7, characterized in that the first roller (43) is arranged in the transport direction of the sheet (II ¹¹ ) at a distance from the second roller (15 ¹¹ ). 9. Device according to one of claims 1 to 8, characterized in that the sheet of a long belt (11; II ¹¹ ) is formed, which is continuously with the transport both rollers (13, 15; 43, 15 '') is in contact. - 10. Device according to one of claims 1 to 6, characterized in that the sheet (37) has relatively small dimensions and carries an electrostatic charge that several of these sheets (37) between the two / l'en rollers (13 ¹ , 15 ') and that the direct voltage potential of the second roller (15 ¹ ) is selected in terms of height and polarity so that the electrostatic charge of the sheets is neutralized. 11. The device according to claim 10, characterized in that the sheets (37) consist of photographic material 109841/1079 2 0190Α .and after neutralizing the electrostatic charge stacked in a stack. 12. The device according to claim 11, characterized in that a cutting device (35) for cutting up a continuous - A running belt (II ¹ ) of photographic material is provided in individual sheets (37), and that the cutting device (35) is arranged in front of the two rollers (13 ¹ , 15 ·) in the direction of transport of the belt. 13. The apparatus according to claim 12, characterized in that a transport device (31, 32) which feeds the tape (II ¹ ) of the cutting device (35), and a further transport device which after cutting the individual sheets (37) between one after the other the rollers (13 ·, 15 ') guides are provided. 14. Device according to one of claims 1 to 13, characterized characterized in that a control device is provided which comprises a measuring element arranged adjacent to the blade (25; 25 '; 41) for measuring the electrostatic charge of the sheet and an adjusting device (21, 23; 21', 23 ') to adjust the level and polarity of the direct voltage potential depending on the state of charge of the Has sheet. 15. Device according to one of claims 1 to 14, characterized in that that a variable voltage source (19; 19 ') is provided for generating the direct voltage potential is. 1 0 9 8 Λ 1/1079