US3865609A

US3865609A - Method for toning a latent image

Info

Publication number: US3865609A
Application number: US437949A
Authority: US
Inventors: Curt Robert Raschke
Original assignee: Multigraphics Inc
Current assignee: AB Dick Co
Priority date: 1974-01-30
Filing date: 1974-01-30
Publication date: 1975-02-11
Anticipated expiration: 1992-02-11

Abstract

This specification shows and describes the general arrangement of an electrostatic copy machine, and illustrates the principle of cloud formation toning which is the novel element of the machine. The toner is semi-conducting and is positioned between oppositely charged electrodes. The surface of the toner pile will take on the charge of the electrode upon which it rests, and the top surface toner particles will be attracted to the top electrode. The top electrode is a screen. Some of the particles will attain enough speed and alignment to be able to continue through the mesh of the screen. The like-charged particles which do pass the screen will then repel one another and move about in an agitated cloud. These particles may be attracted to a charged image on a sheet carrier if the charged area is of opposite polarity. If of the same charge polarity, and an opposite bias on a field plain behind the charged image, then the background will attract the toner, and the image will repel the toner.

Description

United States Patent [191 Raschke [111 3,865,609 [451 Feb. 11, 1975 METHOD FOR TONING A LATENT IMAGE [75] Inventor: Curt Robert Raschke, Warrensville Heights, Ohio [73] Assignee: Addressograph-Multigraph Corporation, Cleveland, Ohio [22] Filed: Jan. 30, 1974 211 App]. No.: 437,949

[52] US. Cl ll7/l7.5, 118/637 [51] Int. Cl. 603g 13/08, 603g l5/08 [58] Field of Search 117/175; 118/637; 96/1 R,

96/1 SD; 355/3 D, 3 P; IOl/DIG. l3

[56] References Cited UNITED STATES PATENTS 2,758,525 8/1956 Moncrieff-Yeates ll7/l7.5 3,011,473 l2/l96l Gundlach ll7/l7.5 3,057,997 lO/l962 Kaprelian ll7/l7.5 3,178,281 4/1965 Jarvis 96/l.2 3,232,190 2/1966 Willmott ll7/l7.5 3,420,168 l/l969 Johnson.... 3,470,009 9/l969 Gundlach.. 3,518,969 7/1970 Snelling 3,789,753 2/1974 Rutherford lOl/l Primary Examiner-Michael Sofocleous Attorney, Agent, or Firm-Ray S. Pyle [57] ABSTRACT This specification shows and describes the general arrangement of an electrostatic copy machine, and illustrates the principle of cloud formation toning which is the novel element of the machine.

The toner is semi-conducting and is positioned between oppositely charged electrodes. The surface of the toner pile will take on the charge of the electrode upon which it rests, and the top surface toner particles will be attracted to the top electrode.

The top electrode is a screen. Some of the particles will attain enough speed and alignment to be able to continue through the mesh of the screen. The like-charged particles which do pass the screen will then repel one another and move about in an agitated cloud. These particles may be attracted to acharged image on a sheet carrier if the charged area is of opposite polarity. If of the same charge polarity, and an opposite bias on a field plain behind the charged image, then the background will attract the toner, and the image will repel the toner.

3 Claims, 2 Drawing Figures 1 METHOD FOR TONING A LATENT IMAGE SUMMARY OF THE INVENTION The purpose of the invention is to produce a cloud of charged toner particles, which are then available for any purpose.

It is one object of this invention to use such toner cloud to tone an electrostatic image.

The cloud may be produced in any polarity.

Therefore, it is a further purpose, and object of this invention, to provide a reversible charge formation device, in order that a background bias behind a carrier with an image charge will cause the image to repel the toner and the background to attract the toner.

BACKGROUND OF THE INVENTION An electrostatically produced latent image on a sheet, whether a single copy ofa page, or one in a series of duplicated reproductions, is made visible by first attracting visible particles, known as toner, to the electrostatic charge for a temporary development of the image. Thereafter the toner is fixed to the sheet upon which the charge is carried, or transferred to a final sheet and then fixed. The latter option is used for making plain paper prints without the need for special coatings on the paper.

In the art, toning has been done by dusting, cascading, magnetic brush application, and liquid suspension. Dusting by a cloud of charged particles has been proposed and attempted often. Carlson, US. Pat. No. 2,815,734, shows an early attempt to tone from a cloud and Xerox, US. Pat. No. 3,646,910, shows that the search continues, but with the air blower concept now quite commonly shown in literature, but seldom used in commerce.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration of the essential elements of an electrostatic copy machine, embodying acloud tone of this invention.

FIG. 2 is a schematic illustration of a cloud toner for a machine as in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT .The drawings illustrate an apparatus of novel construction which is suitable for carrying out the new and novel method disclosed herein.

An intake into the electrostatic copier machine will accept original documents to be copied. The term original document may -be applied to a document which was prepared for some primary purpose other than to be a master for duplication. A business letter is an example. Or, the original document may be a specially prepared original intended for the purpose of being a master. A news bulletin, for example. In the instance where the machine is to be used as a duplicator, such a master simply provides the source material from which a long series of identical originals is produced. The difference between a copy machine and a duplicator is primarily one of speed and repetition.

In the FIG. I, which is intended to illustrate a copy machine more than a duplicator, a belt 11 is shown as a transport device to take an original document from the intake 10 into the field of the optical system. Pinch rolls 12 are used as intake feed rolls and pinch rolls 13 are used as exit feed rolls. The original document is either brought to a halt in the field of the optical system, .or a proper optical system will be enabled to make a fully acceptable exposure as the document continues in motion.

A corner 14 beyond the pinch rolls 13 will cause the document to turn and drop into a receptacle tray 15 where it may be recovered.

The optical system is illustrated by means of mirror 18, lens 19 and mirror 20 for projecting an image of the original document on the'belt 11 into an exposure station within the machine.

Photoconductive paper 22 is shown in a roll stored within the machine, and fed over a series of roller 24 in a feed system to the output of the machine.

A corona 26 is placed to flood the surface of the paper 22 with charged ion particles to produce a uniform charge on the surface of the paper as it is fed from the roll storage to the exposure station indicated by reference character 27. At station 27 the light and dark image will discharge the surface where light strikes.

The rollers 24 direct the charged and exposed paper 22 to a toner station 28 where a cloud of toner bearing a charge opposite that placed on the surface of the paper 22 by the corona 26 is caused to be attracted to the charge remaining on the paper and produce a visibleimage.

The toner material is conveyed by a supply system 29 to the surface of a conveyor belt 30 where it is trans ported through the toner station 28 and then returned to a sump 31 for recirculation.

A layer of toner 32 is transported on the surface of the belt 30 into a position below a screen 34, see FIG. 2. The belt 30 is composed of conductive material, preferably metal, and the screen 34 is of open mesh construction and is also conductive and preferably of metal.

A field plate 36 provides a backing for the paper 22 in the toner station 28.

In FIG. 2, the reference character 38 indicates a group of marks suggesting a positive charge in image configuration Production of such a charge on the surface of paper 22 is old and well-known and does not constitute part of this invention. The FIG. 1 apparatus is merely a suggestion of one possible means for obtaining a charge in image configuration upon the surface of some carrier. In this instance, a coated paper 22 is used and the coated paper 22 is toned and fixed and then serves as the final product.

Power supply 40 illustrates an application of high voltage potential between the screen 34 and the belt 30.

This invention is embodied principally in the construction and operation of the

elements

30 and 34 in harmony with the layer of semiconducting toner particles 32. However, the cloud of toner that can be produced by these elements is useless unless utilized by an output which consumes the cloud. The paper 22 is one example of that output and the field plate 36 assists the paper 22 in making use of the output.

The method of producing a cloud of charged toner particles, and developing an electrostatic image from the cloud, comprises the steps of establishing a base electrode, which in this case is the conducting metal belt 30. The base electrode of necessity is oriented in a configuration to support a quantity of pulverized toner particles 32. In this embodiment the particles are transported through the toner station but an occasional replenishing and vibrating system may also be employed.

In the process, the screen 34 functions as a screen electrode which is superposed with the base electrode, and a high voltage is imposed having opposite polarity between the base and the screen electrodes.

Then, by supplying a semiconductor layer of toner particles 32 upon the base electrode 30, the surface particles of the layer of toner will take on the polarity of the base 30 and thereby be attracted to the screen 34 of opposite polarity.

It is understood that many of the particles will lift away from the body of the toner supply and migrate rapidly toward the screen 34. Some of those particles will strike the screen and be neutralized and then return to the body of the supply 32 but others will manage to pass through the mesh of the screen to circulate as a cloud above the screen.

Therefore, when the carrier in the form of paper 22, which has an electrostatic image of a polarity the same as the screen, is moved into superposed registration over the screen, the image is immersed in the cloud that is formed by the particles which pass through the screen.

Then, the particles which do pass through the screen, being all of like charge, will be an agitated cloud and will seek an opposite charge such as the charge 38.

ln the FIG. 2 illustration, the belt 30 will have a negative charge and the screen a positive charge. The toner particles which move towards and through the screen will then have a negative charge and will be attracted to the positive charge in the image configuration 38 on the paper 22.

This invention is essentially a toner process and construction of toner equipment. It will tone any charged surface. Therefore, if a dielectric surface is charged in an image of a document to be reproduced, and moved into the toner cloud, it will be toned. That toned image can thereafter be transferred to plain paper by contact under pressure, or if the toner is magnetic as well as semi-conducting, a magnetic roller may be used to assist in the transfer. These are known techniques and do not enter into the toner invention.

For illustration purposes, FIG. 1 provides coated photoconducting paper 22, which after toning is passed by roller 42 to a fusing and cut-off device indicated by reference 44 before being transported through exit conveyor 45 to a tray 46.

What is claimed is:

l. The method of producing a cloud of charged toner particles, and developing an electrostatic image from the cloud, comprising the steps of:

a. establishing a base electrode in a configuration to support a quantity of pulverized particles b. establishing a screen electrode superposed with said base electrode c. imposing a high voltage of opposite polarity between said base and screen electrode d. providing a supply of pulverized semi-conducting toner particles upon said base electrode, whereby the surface particles of said supply take on the polarity of said base and are thereby attracted to said screen of op posite polarity, some being neutralized by said screen to return to said supply, and others passing through said screen to circulate as a cloud above the screen; and

e. moving a carrier having an electrostatic image into superposed registration over said screen with said image immersed in said cloud to thereby attract toner to the carrier in a pattern according to the image.

2. The method as defined in claim 1, wherein step (e) is further characterized in that the polarity of the image is the same as the screen; the cloud thereby being of opposite polarity and attracted to the image.

3. The method of producing a toner cloud according to claim 1, further characterized by providing a bias field on the back side of said carrier, and establishing said screen and bias oflike polarity, whereby said cloud will be of a polarity the same as the image and will be attracted to the background.

' l l= l

Claims

1. THE METHOD OF PRODUCING A CLOUD OF CHARGED TONER PARTICLES, AND DEVELOPING AN ELECTROSTATIC IMAGE FROM THE CLOUD, COMPRISING THE STEPS OF: A. ESTABLISHING A BASE ELECTRODE IN A CONFIGURATION TO SUPPORT A QUANTITY OF PULVERIZED PARTICLES B. ESTABLISHING A SCREEN ELECTRODE SUPERPOSED WITH SAID BASE ELECTRODE C. IMPOSING A HIGH VOLTAGE OOF OPPOSITE POLARITY BETWEEN SAID BASE AND SCREEN ELECTRODE D. PROVIDING A SUPPLY OF PULVERIZED SEMI-CONDUCTING TONER PARTICLES UPON SAID BASE ELECTRODE, WHEREBY THE SURFACE PARTICLES OF SAID SUPPLY TAKE ON THE POLARITY OF SAID BASE AND ARE THEREBY ATTRACTED TO SAID SCREEN OF OPPOSITE POLARITY,SOME BEING NEUTRALIZED BY SAID SCREEN TO RETURN TO SAID SUPPLY, AND OTHERS PASSING THROUGH SAID SCREEN TO CIRCULATE AS A COLD ABOVE THE SCREEN, AND E. MOVING A CARRIER HAVING AN ELECTROSTATIC IMAGE INTO SUPERPOSED REGISTRATION OVER SAID SCREEN WITH SAID IMAGE IMMERSED IN SAID CLOUD TO THEREBY ATTRACT TONER TO THE CARRIER IN A PATTERN ACCORDING TO THE IMAGE.

3. The method of producing a toner cloud according to claim 1, further characterized by providing a bias field on the back side of said carrier, and establishing said screen and bias of like polarity, whereby said cloud will be oF a polarity the same as the image and will be attracted to the background.