US3470850A

US3470850A - Apparatus for developing electrostatic charge images

Info

Publication number: US3470850A
Application number: US688434A
Authority: US
Inventors: Walter Simm
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert AG
Priority date: 1967-12-06
Filing date: 1967-12-06
Publication date: 1969-10-07
Anticipated expiration: 1986-10-07

Description

Oct. 7, 1969 w. SIMM 3,470,850

APPARATUS FOR DEVELOPING ELECTROSTATIC CHARGE IMAGES Filed Dec. 6. 1967 INVENTOR.

WALTER S/MM United States Patent 3,470,850 APPARATUS FOR DEVELOPING ELECTROSTATIC CHARGE IMAGES Walter Simm, Leverkusen, Germany, assignor to Agfa- Gevaert Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Dec. 6, 1967, Ser. No. 688,434 Int. Cl. Bb 5/02; B05c 5/02; G03g 13/10 US. Cl. 118637 5 Claims ABSTRACT OF THE DISCLOSURE A set of charged rapidly rotating rollers providing spaces about 0.5 to 5 mm. wide restrict flow of aerosol dye particles used to develop electrostatic image, but constitute effective maintenance-free auxiliary developing electrode. Rollers are rotated in direction that helps particles move through the spaces.

This invention relates to an apparatus to be used for developing electrostatic images with electrostatically charged dye aerosols. The apparatus consists of a conductive support for the recording material containing the electrostatic image, an electrostatic atomization electrode, and a development electrode arranged between the recording material and atomization electrode and close to the recording surface of the recording material.

It is already known that one may use grid-shaped development electrodes in the above-described arrangement and that the charged dye aerosol which is produced from an atomization electrode may be sprayed through this grid onto the surface on which development is to take place. The grid electrode can be used to control the deposition of the aerosol on the recording material by trapping excess developer dye. An apparatus of this type is described in German Patent No. 1,172,955.

One disadvantage which arises out of the use of a grid electrode is that the meshes of the grid soon become partly or completely blocked by developer dye unless they are frequently cleaned. If the grid were not cleaned, it would very soon become useless. However, cleaning entails considerable expense in taking time and requiring equipment, and cleaning agents, especially in the case of automatic developing equipment.

The object of the present invention is to replace the grid electrode by a different type of development electrode which is easier to clean. Any changes which are made to the external form of the grid electrode should not affect the desired electrical properties and the particular advantages of the grid. These include, for example, the function of the grid whereby it serves as counterelectrode for the charge image, an auxiliary field being produced which controls the deposition of the aerosol in imagewise fashion. Another advantage of the grid is its simultaneous use as a counterelectrode for the atomization electrode, the powerful electrical atomization field produced on one side of the grid being separated from the relatively Weak image field on the other side of the grid.

According to the present invention, this problem is solved by using, in the development of charge images with electrically charged dye aerosols, an apparatus which comprises a conductive support for the recording material having the electrostatic image, an electrostatic atomization electrode, and a development electrode arranged between the recording material and atomization electrode, close to the recording surface of the material, and which is characterised in that the development electrode comprises a plurality of electrically conductive rotating rollers which are arranged with their axes parallel and in one plane which is parallel to the surface of the recording material.

This development electrode which takes a completely different form from the grid electrode previously in use surprisingly fulfils all requirements. It is eminently suitable both for developing line images and for developing half-tone images, and has moreover the advantage that it can be cleaned in a simple manner while it is in continuous operation.

The rollers are rotatably mounted and when in operation they rotate at high speed about their longitudinal axes. The rollers can be in pairs, those of a pair preferably rotating in an opposite sense to each other. The disstance between the rollers is so small that the electrical field of the atomization electrode on one side of the roller arrangement is sufficiently separated from the image area on the other side of the arrangement. The rotation of the roller causes part of the dye aerosol which is sprayed from one side through the atomization electrode to be carried by the layers of air rotating with the rollers, and thus enter the region of the electrostatic image field over the surface of the recording material, where deposition takes place and hence the image is developed. The remainder of the dye is deposited on the surface of the rollers and can be removed by a suitable stripper, either continuously or intermittently. The imagewise deposition of aerosol is controlled by the fact that the rollers and the surface on which the image is to be formed are connected to each other through a source of direct voltage which yields an adjustable voltage up to the maximum voltage of the image charge.

A simple embodiment of the development apparatus is illustrated in FIGURES l and 2 of the accompanying drawings which are vertical sectional views taken transversely and longitudinally of such an apparatus. A recording material 1 which carries an electrostatic charge image which is to be developed, e.g. an electrophotographic layer, is situated on a conductive, grounded support 2. Two metal rollers 3 and 4 which are rotatably mounted on a shaft in bearings 5 and 6 and which can each be rotated by drive motors 7 are arranged 0.5 to 3 mm. from the recording material 1. The motors are designed for very high speeds of rotation, e.g. 15,000 revs./ min. The length of the rollers depends on the size of the image, their diameter preferably being in the region of 10 to 50 mm. The distance between the rollers is adjusted to 0.5 to 5 mm.

The support 2 with recording material 1 is slidably arranged on glide rails 8 and 9 to he slid in the directions of the arrows. It is necessary that one be able to displace this assembly during development, since otherwise the image would be developed only in an area corresponding to the space between the upper portions of the rollers.

An atomization electrode 10 which is in the form of a rotating disc the edge of which is wetted with dye solution by immersion in a dye container 11 is situated below the pair of rollers. Electrode 10 is related by means of a motor 12 and a shaft 13 part of the length of which, at least, is of insulating material. The high voltage required for atomization of the dye liquid, which voltage is taken from a high voltage source 14, is applied to the disc 10.

Instead of the disc electrode 10, a ring electrode according to German patent application A 51,884 may be used (certified copy in file of Ser. No. 619,415 filed Feb. 28, 1967). Other suitable types of electrodes are described in German patent specifications Nos. 1,187,134 and 1,202,- 639. The electrode 10 is surrounded by a housing 15 made of electrically insulating material, which is open at the top and is largely covered by the pair of rollers 3 and 4. In this housing, a gas of high electrical potential, e.g. the compound CF Cl can be supplied to the atomization electrode from a pipe connection 19, the atomization efficiency of the electrode being thereby improved in known manner.

The rollers 3 and 4 are connected via the bearings to a rotating structure is connected to rotate the rollers in the voltage source 16 which supplies an adjustable voltage of to 5000

v. Strippers

17 and 18 contact the outsides of the rollers to remove the dye that is deposited on the surface of the rollers and hence prevent the building up of such deposits.

In principle, the pair of rollers could-be replaced by a single roller, but this significantly reduces the efliciency of transfer of dye to the image support.

To shorten the development time and to make possible the development of'large image surfaces, apparatuses may be used which comprise several electrode arrangements according to FIGURES 1 and 2.

By using the apparatus according to the invention, development of charge images with particles of dry dye, which have been produced e.g. as described in German patent application A 49,273 (certified copy on file in US. application Ser. No. 549,808 filed May 13, 1966) can be carried out continuously. Additional measures for cleaning the development electrodes are then no longer necessary.

I claim:

1. In an apparatus for developing electrostatic images with electrically charged aerosol dye particles and having guide structure for guiding into developing position a member carrying the electrostatic image to be developed, an electrically charged development electrode opposing the image, and atomizing elements to atomize particles of dye solution into the space beyond the auxiliary electrode for migration through that electrode to the image, the improvement according to which the development electrode is in the form of a set of spaced generally parallel rollers confining the movement of the atomized developer particles to spaces about 0.5 to millimeters wide, and

- direction thathelps carry the particles through the spaces.

2. The combination of claim 1 in which the rollers are arranged in pairs with the spaces between the two rollers of each pair, and the rotating structure is connected to rotate the two rollers of each pair' in opposite directions at very high speeds. j' m 3. The cornbiria'tion'ofclaim 1 in which each roller has a stripper that scrapes deposits from its surface as it rotates. i r p 4. The combination of claim 1 in which a housing confines the atomizing elements as well as the'space below each roller.

5. Theicornbination of claim 4 in which the housing is provided with an inlet for receiving a blanketing gas.

lieferences Cited STATES PATENTS UNITED 2,777,784 7 1/1957 Miller 117-93 2,928,575 3/1960 Carlson 222-193 3,140,199 7/ 1964 York 1 18-637 3,169,887 2/1965 York 118-637 3,171,600 3/1965 Eckey 239-220 3,256,855 6/1966 Oliphant 118-637 3,323,933 6/1967 Barford et a1. 117-17 3,355,288 11/1967 Matkan 117-175 XR 3,367,791 2/1968 Lein 118-637 XR PETER FELDMAN, Primary Examiner v US. 01. X.R. 117-37, 93.4; 11s 300, 626; 239-420