US3598487A

US3598487A - Electrostatic recording apparatus

Info

Publication number: US3598487A
Application number: US791084A
Authority: US
Inventors: Mamoru Mizuguchi; Teruo Kurihara; Masasumi Yana
Original assignee: Tokyo Shibaura Electric Co Ltd
Current assignee: Toshiba Corp
Priority date: 1968-01-18
Filing date: 1969-01-14
Publication date: 1971-08-10
Anticipated expiration: 1988-08-10

Abstract

An electrostatic recording apparatus is provided with means for removing a residual toner on a recording surface carried by a movable recording medium after image transfer. The means for removal includes a wiper, a nozzle, a vessel, a circulating device and a filter. The wiper sweeps the recording surface to wipe said residual toner, and is supplied with a liquid cleaner by the nozzle. The vessel stores therein the liquid cleaner discharged from the nozzle and dispersed with the toner removed from the wiper. The toner dispersed in the liquid cleaner is removed by the filter, and then the liquid cleaner is circulated by the circulator to be discharged again from the nozzle. When the wiper is made of a liquid-absorbing soft material, there is further provided a pressing means for squeezing said wiper material containing the residual toner removed from the recording surface.

Description

United States Patent [72] Inventors Mamoru Mizuguchi 3,l28,683 4/l964 Rubin 355/15 X Kawasaki-shi' Primary Examiner-Samuel S. Matthews i a g az Masasum' Assistant Examiner-R. A. Wintercorn an o ama-s I, a pan F [2U pp No' 791,084 Arlorne Flynn 8L rishauf [22] Filed Jan. 14. 1969 [45] Patented Aug. I0, 1971 [73] Assignee Tokyo Shibaura Electric Co., Ltd.

Kawasaki-ski, Japan 3g Pnomy i 1968 ABSTRACT: An electrostatic recording apparatus is provided 2 with means for removing a residual toner on a recording surl I face carried by a movable recording medium after image transfer. The means for removal includes a wiper, a nozzle, a [54] ELECTROSTATIC RECORDING APPARATUS vessel, a circulating device and a filter. The wiper sweeps the 9 Chins 4 Drawing Figs recording surface to wipe said residual toner, and IS supplied with a liquid cleaner by the nozzle The vessel stores therein [52] U.S.C| 355/15, h id cleaner discharged from the nozzle and dispersed 355/27 with the toner removed from the wiper. The toner dispersed in [Si] Int. Cl G031; 15/00 h? liquid cleaner i removed by the filt and the the liquid [50] Field Search; 355/l5, 27 Chaney is circuhned by the circulator to be discharged again from the nozzle. When the wiper is made of a liquid-absorbing Rd'num cued soft material, there is further provided a pressing means for UNITED STATES PATENTS squeezing said wiper material containing the residual toner 2.878.120 3/l959 Mayer et al 355/15 X removed from the recording surface.

PATENTEDAus 1 0197:

SHEET 1 OF 2 ELECTROSTATIC RECORDING AIPARATUS This invention relates to electrostatic recording apparatus,

surface of an electrostatic recording medium after image transfer.

It is well known'that a desired visible image is electrostatically recorded on an electrostatic recording surface or a recording sheet having a thin uniform dielectric surface layer, by impressing a potential across printor needlelike electrodes disposed in the vicinity of the recording sheet thereby to form an electrostatic latent image, and subjecting the electrostatic latent image to a pigment or dyes, a so-called toner. This method is generally called direct method and is widelyemployed in transmission of visible information, such as, figures, letters and characters. This prior art method is relatively expensive by reason of the fact that the electrostatic recording surface must be formed on therecording sheet itself.

An information transmission system is employed in recent years wherein a visible information representing various figures, letters and characters is transmitted as an electrical signal which is again converted into a visible image at a receiving station by means of electrostatic recording apparatus. In the recording apparatus of this'nature, the recording sheet is used mostly for temporarily securing visible information. Use of recording paper including an expensive electrostatic recording surface as above described is thus not economical. Further, visible information can not be reproduced on a desired recording sheet prepared by the information receiver side.

The information transmission systemv using an electrostatic recording device thus employs a so-called transfer-typerecording device capable of recording visible information on optionally selected ordinary sheets without requiring recording sheets of the type above described. The transfer-type device comprises an electrostatic recording medium or an endless belt which is advanced to successively effect formation, development and transfer of an electrostatic latent image during one cycle of operation, said electrostatic recording medium being formed of a conductive rubber belthaving a dielectric resinous film deposited thereon.

The formation of an electrostatic latent image is achieved, for example, by impressing an electrical potential representing an information signal across needle electrodes disposed in contact with the surface of the endless belt and depositing an electric charge on the surface of the endless belt by a corona discharge. The electrostatic latent image thus formed is developed by causing a fine iron powder carrying a toner, a particulate pigment or dyes coated with resinous material to be in contact with the surface of the endless belt by means of a magnetic brush, and permitting the toner only to be attracted onto the latent image.

The image thus developed is transferred onto an ordinary sheet by pressedly engaging the sheet under an electrical field. An excess toner, however, will remain on the surface of the endless belt after image transfer, so that such remanent toner must be completely removed'for succeeding cyclic operations of electrostatic recording.

A remanent or residual toner has heretofore been removed from the surface of an electrostatic recording medium or an endless belt by rotating a cylindrical brush at a high speed in contact with said surface to sweep the residual toner away from the said surface of the endless belt, said cylindrical brush being positioned rearwardly of a transfer station and having a surface formed of a soft hairy material, such as rabbit flix, and causing the toner to be collected into a filter by means of a vacuum device.

The brush, however, must be replaced as the function of the brush decreases by accumulation of toner on its hairy surface. In addition, a noise is produced when the vacuum device is operated to cope with the scattering of the toner.

In addition to the dry development method described above, a wet development method using a dielectric liquid in which a toner is dispersed is now widely used. since the toner can be treated easily. However, the method of sweeping or removing the toner as above-described is not applicable to the treatment of toner in the liquid developing method.

Accordingly, an object of this invention is to provide an improved electrostatic recording device including a wiper means capable of sweeping a residual toner present on an electrostatic recording medium after transfer of a powderor liquiddeveloped image, and which is repeatedly usable through a cleaning process.

Another object of this invention is to provide an improved electrostatic recording device wherein a liquid cleaner for cleaning a wiper which carries a residual toner transported from a recording medium after image transfer is purified for repeated use.

The present invention can be more fully understood from the following detailed description when taken in connection with the accompanying drawings, in which:

FIG. 1 is a front elevation, partly in section, embodying this invention;

FIG. 2 is an enlarged perspective view showing a modification of a filter shown in FIG. 1;

FIG. 3 is a front elevation, partly in section of a modification of a residual toner-cleaning means shown in FIG. 1; and

.FIG. 4 is a view similar to FIG. 3 illustrating a further modification of the cleaning means.

In FIG. 1, the reference numeral 10 designates an endless electrostatic recording medium extending over a pair of metallic rollers 11 and 12. The electrostatic recording medium 10 comprises a usual conductive endless rubber belt and a dielectric resinous film 10b adhered on the outer surface of the endless rubber belt 10a, said film 10b defining an electrostatic recording surface. The dielectric resinous film 10b may commonly be formed, for example, of polyethylene terephthalate, polycarbonate or polyvinyl chloride. The rollers 11 and 12 are synchronously driven by a motor (not shown) in the direction of arrows.

As is well known, a plurality of needle electrodes 14 each spaced from the other via insulators 13 are disposed adjacent to the recording surface of the electrostatic recording medium 10. The needle electrodes 14 are connected to a signal source (not shown) for a selective supply of electrical signals. The recording surface of the electrostatic recording medium 10 is charged by signal-fed needle electrode 14 to form a desired electrostatic latent image thereon.

A developing means is provided ahead of the needle electrodes 14, and comprises a developing tank 15 for storing a liquid developer in which a toner containing, as is well known, a pigment or dyes is dispersed, anda developing roller 16 having its lower portion immersed in the body of the liquid developer A. The developing roller 16 has a core 17 supported so as to be continuously rotatable and has its circumferential surface covered with spongy, foamed plastics material 18 capable of adsorbing liquid. The foamed plastics material 18, when immersed in the liquid developer, carries the toner dispersed therein to supply it to the recording surface of the electrostatic recording medium 10 by successively engaging the recording surface, and thus permits an electrostatic latent image on the recording medium to be developed.

A transfer means is provided forwardly of said developing roller 16. As is well known, a transfer roller 19 is provided in such a manner that it is constantly urged against the surface of the roller 11 carrying the recording medium 10 therebetween, by means of spring, not shown. Between said transfer roller 19 and the recording medium 10 is inserted a rolled sheet or a transfer sheet 21 wound on a supply reel 20. The transfer sheet 21 is fed toward the roller 11 by the transfer roller 21 which rotates in synchronism with the roller 11 and taken out by a pair of sheet rollers 22 after transfer of the image formed on the electrostatic recording medium takes place. Between the transfer roller 19 and the roller 11 may be produced an electrical field by a power source-not shown, appropriate to the polarity of the charged toner, to assist the transport of the toner to the transfer sheet, as is well known.

A residual toner present on the electrostatic recording medium after image transfer must be completely removed therefrom for succeeding cyclic electrostatic recording. Forwardly of the transfer roller 19 is thus provided means for removing the residual toner, which constitutes the main feature of this invention.

Stated in detail, a rotary brush 25 is disposed in contact wit the recording surface at a position ahead of the needle electrodes l4 and following the image transfer station. Said rotary brush comprises a metallic roller 24 and a wiper means or a brush member 25 adhered on the circumferential surface of said metallic roller 24, said brush member 23 having a surface provided with a number of short hairy elements, such as velvet. The brush member 23 is located within a vessel 26 containing a liquid cleaner B- and so rotated that it moves in the direction opposite to that of travel of the recording medium. The vessel 26 consists of a first chamber 27 within which said rotary brush 25 is mounted, and a second chamber 28 which communicates with said first chamber at its bottom portion. Within said second chamber is mounted a pump 30 having a suction pipe 29 whose inlet port is located in the body of the liquid'cleaner B and a discharge pipe 31 extending upwardly therefrom and connected to a nozzle 33. The nozzle 33 penetrates through the wall of the first chamber 27 with its forward open end positioned adjacent the brush member 23.

In the lower portion of the first chamber 27 is disposed a replaceable filter 34 which comprises a pair of

electrodes

35 and 36 each formed, for example, of wirenetting of several to 200 mesh, and a spongy porous dielectric material 37 having a thickness of from 1 to 300 mm. accumulatedly inserted between said

electrodes

35 and 36, said electrodes being impressed by a potential of from 200 to 2,000 volts fed from a source of DC power (not shown). As will be described later in detail. the liquid cleaner carrying a toner dispersed therein in the first chamber 27 is purified by the filter 34 to cause the toner to be caught by the filter 34, and the purified liquid cleaner is then supplied to the second chamber 28. The liquid cleaner is formed of a liquid incapable of dissolving the toner, but capable of readily dispersing the toner. Examples of the liquid used are hydrocarbons of paraffin series, carbon tetrachloride and freon.

The operation of the device of this invention is as follows. First, the rollers 11 and 12 are rotated in the direction of arrows to cause the recording medium 10 to continuously travel in the same direction. An electrical signal, usually a negative DC voltage, is selectively supplied to the needle electrodes 14, which produce a corona discharge at the tip ends thereof to cause the dielectric resinous film 10b or the electrostatic recording surface of the recording medium 10 to be charged to a negative potential, thereby to form an electrostatic latent image. The recording medium 10 bearing said electrostatic latent image moves and arrives at the developing roller 16. The developing roller 16 rotates in the direction of arrow so that the foamed plastics material contacts with the electrostatic recording surface to feed the liquid developer A thereto. A positively charged toner carried by the liquid developer is attracted toward the negative charge of the electrostatic latent image to form a visible image.

i The electrostatic recording medium 10 carrying the visible image continuously moves to the transfer roller 19, where the transfer sheet 21 from the supply reel is pressedly held against the electrostatic recording medium positioned on the circumferential surface of the roller 11, thus causing the visible image on the recording surface to be transferred onto the transfer sheet with the assistance of the negative electrical field formed thereabout. The transfer sheet 21 bearing the image thus transferred is taken out through the sheet rollers 22 and cut in a predetermined size, if required.

After image transfer, the recording surface on which a residual toner is present is advanced to the rotary brush as the rollers 11 and 12 rotate. The rotary brush 25 rotates in the direction opposite to that of travel of the electrostatic recording medium 10, as shown by an arrow and the brush member 23 contacts with the recording surface and sweeps the residual toner therefrom. The short hairy elements of the brush member 23 should preferably so soft as not to damage the recording surface, but so rigid as not to lie down when they are subjected to the liquid cleaner B. The height of the hairy elements should be from 0.5 to l0 mm., preferably from 1 to 2 mm. if desired, such hairy elements may be planted directly in the surface of the metallic roller 24. r

The pump 30 is driven to cause the cleaner B to flow through the discharge pipe 31 and ejected from the nozzle 33, whereby the toner deposited on the brush member 23 is rinsed and dispersed in the cleaner B. Since the cleaner liquid B is circulated by the action of the pump 30 through the second chamber 28, pump 30, nozzle 33 and the first chamber 27, it is filtered and purified by the filter 34 before it fiows into the second chamber 28. Namely, the positively charged toner is wholly caught by the porous dielectric material 37 while being attracted to either one of the

electrodes

35 and 36 which is negative, so that the liquid cleaner to be sent to the second chamber 28 is purified for reuse.

The recording medium 10 from which the residual toner has been removed by the rotary brush 25 is again applied to another cycle of electrostatic recording. Most of the amount of the cleaner liquid poured onto the brush member 23 is dropped into the vessel 26 because the short hairy elements swish liquid off well. Since the brush member 23 arriving at the recording surface is kept wet by the cleaner liquid and is effective to the removal of the residual toner during the next cycle. This method is thusapplicable also to'the dry development method in which a dry toner is used. In practice, discharge electrodes (not shown) may preferably be provided to remove the charge remaining in the electrostatic recording surface after removal of the residual toner and before the next succeeding cyclic operation. An auxiliary roller (not shown) may be provided in contact with the rotary brush 25 through the recording medium 10 so as to control the contact pressure between the rotary brush 25 and the recording medium 10. Further, a negative potential may be applied to the brush 25 to accelerate the removal of residual toner.

A filter 38 of the construction as shown in FIG. 2 may be used in lieu of the filter 34. The filter 38 comprises a plurality of parallel spaced electrode plates 39 and pieces 40 of porous dielectric material each inserted between two adjacent electrode plates. Alternate electrode plates 39 form a group, across which a potential is impressed. The filter 38 of this arrangement has the advantage that it does not form a bar against a flow of the liquid cleaner when compared with the

electrodes

35 and 36 in the previous embodiment.

FIG. 3 shows a modification of the means for removing a residual toner, which forms the essential feature of this invention.

Similarly as in the foregoing embodiment, the liquid cleaner 8 is contained in a vessel 26 having a first chamber 27 and a second chamber 28 each communicating with each other at the bottom portions, and a pump 30 disposed in said second chamber 28 with its suction pipe 29 immersed in the liquid cleaner. Above the first chamber 27 is positioned a roller 42 which rotates in the direction of arrow or a direction opposite to that of movement of the electrostatic recording surface 10, said roller 42 having a wiper or a spongy or feltlike liquid-absorbing soft material 41 adhered on the circumferential surface of the roller 42 in face to face contact with the recording surface of the electrostatic recording medium 10. Adjacent said soft material 41 is disposed an open end of a nozzle 33 connected to a discharge pipe 31 of the pump 30. At the lower portion of the roller 42 is a roller 43 which is rotatably mounted in such a manner that the roller 43 partly thrusts into said soft material 41 thereby constituting a pressing means, and which engages a palletlike member 44 at the circumferential surface thereof.

A toner remaining on the recording surface after image transfer is wiped by said soft material 41 and thereafter rinsed by the cleaner supplied from the nozzle 33. However, part of the remanent toner still remains on the soft material together with the liquid cleaner. As the roller 42 rotates, the soft material 41 containing the cleaner is pressed between the

rollers

43 and 42, so that the cleaner containing the still remaining toner will be squeezed from the soft material to completely remove the toner from the soft material. The liquid cleaner remaining on the surface of the roller 43 with the toner is scraped therefrom by the palletlike member 44 and thus prevented from travelling along one entire rotation of the roller 43. The soft material 41 is more or less wet after squeezing and is effective in the succeeding toner removing operation.

A further modification of the means for removing a residual toner is shown in FIG. 4, in which corresponding parts are designated by the same reference numerals as in FlG. 3, and description thereof is omitted.

in the modification shown, the wiper means comprises a plurality of rollers 45 and a belt 46 formed of soft water-absorbing material, such as, sponge or felt, and which extends over said rollers 45, said belt being in contact with the record ing surface of the electrostatic recording medium and advanced in the direction of arrow by said rollers 45. Between two adjacent rollers 45, namely one in the left and one positioned at a lower portion respectively in the figure, are mounted a pair of pressing rollers 47 through which the belt pressedly travels.

A residual toner swept by the soft belt 46 is rinsed by the cleaner liquid from the nozzle 33 and further removed together with the cleaner liquid from the soft belt 46 when the belt is squeezed by said rollers 47.

We claim:

L'An electrostatic recording apparatus comprising a movable electrostatic recording medium having an electrostatic recording surface, means for supplying an electrostatic latent imageon said electrostatic recording surface, a developing means for supplying a toner to said electrostatic latent image, means for transferring the image developed on said electrostatic recording surface onto another material, and means for removing a residual toner present on said recording surface after image transfer, characterized in that said means for removing a residual toner comprises a wiper including a soft rotary brush sweeping said recording surface to wipe said residual toner therefrom, a nozzle for pouring a liquid cleaner on said wiper, a vessel for storing the liquid cleaner discharged from said nozzle and in which an amount of the toner deposited on said wiper is dispersed, means for circulating the liquid cleaner to supply it to said nozzle, and a filter for removing the toner dispersed in the liquid cleaner.

2. An electrostatic recording apparatus as claimed in claim 1 wherein said brush includes a number of short hairy elements having unidirectional orientations on the surface thereof which sweeps said recording surface.

3. An electrostatic recording apparatus as claimed in claim 1 in which said wiper sweeps said electrostatic recording surface in a direction opposite to that of movement of said recording surface.

4. An electrostatic recording apparatus comprising a movable electrostatic recording medium having an electrostatic recording surface, means for supplying an electrostatic latent image on said electrostatic recording surface, a developing means for supplying a toner to said electrostatic latent image, means for transferring the image developed on said electrostatic recording surface onto another material, and means for removing a residual toner present on said recording surface after image transfer, characterized in that said means for removing a residual toner comprises a wiper including a liquid-absorbing soft body for sweeping said recording surface in a direction opposite to that of movement of said recording surface to wipe said residual toner therefrom, a nozzle for pouring a liquid cleaner on said wiper, a vessel for storin the iquid cleaner discharged from said nozzle and in whic an amount of the toner deposited on said wiper is dispersed, means for circulating the liquid cleaner to supply it to said nozzle, and a filter for removing the toner dispersed in the liquid cleaner.

5. An electrostatic recording apparatus comprising a movable electrostatic recording medium having an electrostatic recording surface, means for supplying an electrostatic latent image on said electrostatic recording surface, a developing means for supplying a toner to said electrostatic latent image, means for transferring the image developed on said electrostatic recording surface onto another material, and means for removing a residual toner present on said recording surface after image transfer characterized in that said means for removing a residual toner comprises a wiper including a liquid-absorbing soft material for sweeping said recording surface to remove the residual toner therefrom, a nozzle for pouring a liquid cleaner on said wiper, a pressing means for squeezing said liquid-absorbing soft material containing the liquid cleaner discharged from said nozzle, a vessel for storing the liquid cleaner in which the toner squeezed by said pressing means is dispersed, means for circulating the liquid cleaner within said vessel to supply it to said nozzle, and a filter for removing the toner dispersed in the liquid cleaner.

6. An electrostatic recording apparatus as claimed in claim 5 in which said wiper includes a rotatable shaft and said liquidabsorbing soft material is disposed on the circumference of said rotatable shaft, and said pressing means includes a roller for inserting said soft material between said rotatable shaft and said roller in cooperation with the rotatable shaft.

7. An electrostatic recording apparatus as claimed in claim 5 in which said wiper includes a plurality of rollers and a liquid-absorbing beltlike soft material extending over said plurality of rollers, and said pressing means includes a pair of rollers to hold said beltlike soft material therebetween.

8. An electrostatic recording apparatus as claimed in claim 1 in which said filter includes a plurality of electrodes and porous dielectric materials each inserted between two adjacent electrodes, said electrodes being impressed by a DC voltage.

9. An electrostatic recording apparatus as claimed in claim 5 in which said filter includes a plurality of electrodes and porous dielectric materials each inserted between two adjacent electrodes, said electrodes being impressed by a DC voltage.

Claims

1. An electrostatic recording apparatus comprising a movable electrostatic recording medium having an electrostatic recording surface, means for supplying an electrostatic latent image on said electrostatic recording surface, a developing means for supplying a toner to said electrostatic latent image, means for transferring the image developed on said electrostatic recording surface onto another material, and means for removing a residual toner present on said recording surface after image transfer, characterized in that said means for removing a residual toner comprises a wiper including a soft rotary brush sweeping said recording surface to wipe said residual toner therefrom, a nozzle for pouring a liquid cleaner on said wiper, a vessel for storing the liquid cleaner discharged from said nozzle and in which an amount of the toner deposited on said wiper is dispersed, means for circulating the liquid cleaner to supply it to said nozzle, and a filter for removing the toner dispersed in the liquid cleaner.

4. An electrostatic recording apparatus comprising a movable electrostatic recording medium having an electrostatic recording surface, means for supplying an electrostatic latent image on said electrostatic recording surface, a developing means for supplying a toner to said electrostatic latent image, means for transferring the image developed on said electrostatic recording surface onto another material, and means for removing a residual toner present on said recording surface after image transfer, characterized in that said means for removing a residual toner comprises a wiper including a liquid-absorbing soft body for sweeping said recording surface in a direction opposite to that of movement of said recording surface to wipe said residual toner therefrom, a nozzle for pouring a liquid cleaner on said wiper, a vessel for storing the liquid cleaner discharged from said nozzle and in which an amount of the toner deposited on said wiper is dispersed, means for circulating the liquid cleaner to supply it to said nozzle, and a filter for removing the toner dispersed in the liquid cleaner.

6. An electrostatic recording apparatus as claimed in claim 5 in which said wiper includes a rotatable shaft and said liquiD-absorbing soft material is disposed on the circumference of said rotatable shaft, and said pressing means includes a roller for inserting said soft material between said rotatable shaft and said roller in cooperation with the rotatable shaft.