US3906896A

US3906896A - Ink applicator

Info

Publication number: US3906896A
Application number: US422053A
Authority: US
Inventors: Stanley M Stansell
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1972-01-03
Filing date: 1973-12-05
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

A reproduction system includes an ink applicator body which is positioned adjacent to a surface to be inked for transferring ink from the body to the surface. The applicator body has an array of lands and depressions or grooves formed on a surface thereof. A means for supplying ink to the applicator is provided and an improved doctor means for regulating the ink on the applicator includes an elongated body of generally circular cross section which is formed of an elastomeric material and means for mounting the elastomeric body in contact with a surface of the applicator. Means provide relative motion between the applicator body and the doctor body.

Description

United States Patent [191 Stansell 1 INK APPLICATOR [75] Inventor: Stanley M. Stansell, Columbus, Ohio [73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Dec. 5, 1973 [21] Appl. No.: 422,053

Related US. Application Data 1 Sept. 23, 1975 2.676563 4/1954 Montgomery et a1. 118/249 X 3.626.833 12/1971 Koch 118/261 X 3,667,428 6/1972 Smith 118/D1G. 23

Primary Examiner.lohn P. Mclntosh [57] ABSTRACT A reproduction system includes an ink applicator body which is positioned adjacent to a surface to be inked for transferring ink from the body to the surface. The applicator body has an array of lands and depressions or grooves formed on a surface thereof. A means for supplying ink to the applicator is provided and an improved doctor means for regulating the ink on the applicator includes an elongated body of generally circular cross section which is formed of an elastomeric material and means for mounting the elastomeric body in contact with a surface of the applicator. Means provide relative motion between the applicator body and the doctor body.

7 Claims, 10 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of2 3,906,896

Sheet 2 of 2 3,906,896

. US Patent Sept. 23,1975

INK APPLICATOR This application is a division of Scr. No. 214,873, filed Jan. 3, I972, now abandoned.

This invention relates to ink applicator arrangements. The invention relates more particularly to an improved means for applying developer ink to an imaged area in a reproduction system.

In various reproduction and copying systems, it is desirable to apply a developer ink to an image or record medium. More particularly, in one form of electrostatic copying process, a latent image is established electrostatically on an image retention surface and is then de veloped by contacting the surface with a liquid developing material. The developing material adheres to the surface and conforms to the image. The image is transferred to a record medium for recording, or alternatively, the image retention surface may itself comprise a record medium.

In one image development process sometimes termed polar liquid development, a developer ink is delivered to the image retention surface by a dispensing body. The liquid ink transfers from the dispensing body to the retention surface by virtue of electrostatic forces established by charged areas on the image retention surface. The dispensing body generally comprises a roller having a surface which contacts the image retention surface and which includes an array of lands and grooves. The dispensing body is inked so as to provide a supply of ink which is contained in the grooves of the dispensing body. When the surface of the dispensing body is brought into contactwith the surface bearing the latent electrostatic image, the liquid development ink transfers from the grooves to the image retention surface by virtue of electrostatic forces exerted on the polar ink.

In order to reproduce an image with a clear background, it is preferable that the lands of the dispensing body be free of ink and that the grooves contain a level of ink which assures proper electrostatic transfer to the image retention surface. These requirements have therefore necessitated the use of ink applicator doctoring apparatus which provides for the removal of ink from the lands and for the reduction of the ink level within the grooves to a predetermined level. Such doctoring apparatus has generally comprised rigid, noncompressible doctor blades which are mounted in a stationary location and which are positioned in contact with a moving ink applicator body. The use of metallic or other essentially rigid, noncompressible doctor bleades is accompanied by various disadvantages which detract from the value of this method of ink control. For example, it has been found relatively difficult to initially adjust rigid blades in order to produce satisfactory clean wiping of the lands. Rigid blades generally require a break-in, or, alternatively a pre-grinding of the blade edges. In addition, because of their rigidity, these blades do not dip into the grooves appreciatively far beneath the level of the lands and the control of the ink level within the grooves with rigid metallic blades can only be obtained through the use of relatively higher viscosity inks or higher applicator speeds. The use of higher applicator speeds disadvantageously increases the wear on the blades.

While some of these problems can be corrected by the use of relatively soft metallic materials such as copper and brass, it has been found to be relatively difficult to achieve a desired uniformly sharp edge while the attending requirement for the application of greater pressures to the doctor blades for wiping the lands clean results in an undesirable and relatively large depression of the ink in the grooves.

In various electrostatographic reproduction apparatus, it is desirable to use polar developing inks or relatively low viscosity It is found that the ink level in the applicator grooves shears relatively close to the level of the lands when a rigid doctor blade is employed. It is desirable that a relatively low viscosity ink shear below the level of the lands in order to prevent direct contact between the ink in the grooves and the photoreceptive surface.

There is disclosed in my co-pending US. patent application which is filed concurrently herewith and which is assigned to the assignee of this invention, an improved ink doctoring arrangement which utilizes an elastomeric material. The present invention is elastomeric doctoring arrangement.

Accordingly, it is an object of this invention to provide an improved ink applicator arrangement for a re production system.

Another object of the invention is to provide an improved ink applicator arrangement for a liquid development electrostatographic reproduction apparatus.

Another object of the invention is to provide an improved arrangement for doctoring the level ofink on an ink applicator in a reproduction system.

A further object of the invention is to provide an improved ink applicator doctoring arrangement which is adapted for cleaning the land areas on the applicator and for shearing relatively low viscosity inks at a level below the land areas.

Another object of the invention is to provide a doctoring apparatus which corrects one or more of the above enumerated disadvantages.

In accordance with features of this invention, a reproduction system includes an ink applicator body which is positioned adjacent to a surface to be inked for transferring ink from said body to said surface. The applicator body has an array of lands and depressions formed on a surface thereof. A means for supplying ink to the applicator is provided and an improved doctor means for regulating the ink on the applicator includes an elongated body of generally circular cross section which is formed of an elastomeric material and means for mounting the elastomeric body in contact with a surface of the applicator. Means provides relative motion between the applicator body and the doctor body.

In accordance with more particular features of the invention, the elastomeric body is supported in contact with the applicator surface by a resilient body which effects a loading of the elastomeric material against the moving applicator body. In accordance with other features of the invention, the elongated body of circular cross section comprises a cylinder of elastomeric material. In accordance with another feature of the invention, the elongated body of circular cross section comprises a tubular shaped body of elastomeric material.

These and other objects and features of the invention will become apparent with reference to the following specification and to the drawing wherein:

FIG. 1 is a schematic view of a liquid development electrostatographic reproduction apparatus constructed in accordance with features of this invention;

FIG. 2 is a plan view of an ink applicator and ink doctoring arrangement in accordance with one embodiment of this invention;

FIG. 3 is a view taken along line 33 of FIG. 2'.

FIG. 4 is an enlarged view of a portion of a doctoring arrangement constructed in accordance with features of this invention and illustrating an arrangement for loading an elastomeric doctoring bo y against an ink applicator;

FIG. 5 is an elevation view of a support body for an elastomeric doctoring body in accordance with this invention',

FIG. 6 is a perspective view of an elastomeric doctoring body constructed in accordance with features of this invention;

FIG. 7 is a perspective view of an alternative embodiment of an elastomeric doctoring body constructed in accordance with features of this invention;

FIG. 8 is a side view of an alternative arrangement for supporting and loading an elastomeric doctoring body against the surface of a rotating ink applicator;

FIG. 9 is an enlarged view of a portion of the doctoring body support means of FIG. 8; and,

FIG. 10 is a sbction view of the surface of an ink applicator utilized in the apparatus of FIG. 1.

Referring now to FIG. I, an electrostatic copying apparatus employing liquid development includes a rota bly mounted drum 3 having an image retention surface comprising, for example, a layer 10 of vitreous or amorphous selenium positioned on an outer surface 11 of the drum. The drum is continuously rotated in a counterclockwise direction past a charging station 12 which establishes a uniform electrostatic charge on the image retention surface. The charging electrode 12 comprises, for example, a high voltage corona discharge electrode adapted to supply ions or electric charge to the image retention surface. The uniformly charged image retention surface is rotated to an imaging station 1L3. There is positioned at the imaging station a means for projecting an image on the charged surface for forming a latent electrostatic image conforming to the original image. This means includes a projection system including a lamp 14, a photographic transparency 15 bearing an image which is to be reproduced, and a lens 16 for focussing the image on the uniformly charged surface 10. The latent electrostatic image which is thus formed is rotated by the drum to a development station referenced generally as At the development station, which is described in greater detail hereinafter, the latent electrostatic image is developed and is then transferred by the drum to an image transfer station lfl at which location the image is transferred from the drum to a suitable transfer web 20. The web 20 comprises for example a web of liquid developer receptive paper or the like which is fed from a supply roller 22 to a takeup roller 24, and passes between the drum 8 and a transfer roller 26. After image transfer, the image retention surface is rotated past a cleaning station designated generally as 25 where residual developer material, if any, is removed by a rotating brush from the drum surface in order to prepare the drum for recycling through the above-described operational stations. Although a photoreceptive surface is shown in FIG. l to be formed on the surface II of the drum. other forms of photoreceptor surfaces known in the art can be employed. For example, a web or sheet of zinc oxide recording medium can be transported by the drum 11 through various stations and can be used in place of the transfer web 20. Alternatively, the web 20 can be replaced by sheet collection station.

A development means is positioned at the development station 1 for providing liquid development of the latent electrostatic image on the image retention sur face 10. The development means includes a liquid developer applicator comprising a rotating drum 30. and inking roller 32 and a reservoir 34- containing developer ink 36. The drum 30 which is described in greater detail hereinafter has deposited on its surface a film of ink for transport to the rotating drum 8 and for application to the image retention surface 10. The development ink 36 is withdrawn from the reservoir 34 by the inking roller 32, which is partially submerged in the ink, and is conveyed and applied to the ink applicator drum 30. An ink applicator doctoring arrangement 38 which is constructed in accordance with features of this invention and which is described in greater detail hereinafter is positioned for contacting a surface of the rotating developer dispensing drum 30. The doctoring means is provided for removing excess ink from the dispensing drum 30 after ink loading of the applicator and prior to transfer of ink to the image retention surface.

The surface of the applicator dispensing member 30 of FIG. 1 is shown in greater detail in FIGS. 2 and 10. The drum 30 is shown to comprise a metal base 50 having a pattern formed on a surface thereof by, for example, a plurality of fine raised lines. dots or other geometrical configurations which result in a configuration of lands 52 and valleys or depressions 54 located between the lands A triangular-helix-patterned gravure applicator drum has been found particularly advantzv geous in that a two-walled structure of a gravure cell of this configuration will yield less overall image background with respect to other \vall-to-wall gravure ccll configurations and any tendency for air entrapment in the individual gravurc cells is substantially diminished during the inking operation. The surface of the drum 30 is characteristically wcttable by the liquid developer in the depressions or valleys formed between the raised peak of the raised patterns but is substantially nonwettable along the upper surface of the raised lines or peaks. This is accomplished. for example. by the use of a support base 50 having a relatively uniform surface and comprising a material that is usually wettablc by a liquid development material employed.

The ink which is deposited on the surface of the applicator drum 30 comprises a polar ink which is con tained in the valleys 54, on the surface. The ink will transfer from these valleys to the image retention surface llt) by creeping up the sides of the pattern material and by migrating to the facing image on the receiving surface 10. It is believed that the mechanism of developer migration employs the cooperation of an electrostatic attractive force and a surface tension force. The force of surface tension retains the developer in cohesive configuration on the surface of the applicator while electrostatic attraction applies forces which cause the developer to creep up the sides of the pat terned material and to transfer only in accordance with the pattern of electric charge on the surface ID. Thus, the developer ink remains in the valleys of the applicator except when it comes under the influence of an attractive electrostatic force on the surface It).

As indicated hereinbefore, it is desirable to establish a relatively free or clean background upon the transfer of the development ink to the photoreceptive surface It). This result is accomplished when the lands 5'2 remain substantially free of ink after the applicator is inked by a supply roll-32 and when the level ofthe liq- I vention, an elongated body of elastorner material 56 of.

generally circular cross section, is positioned and,sup-

ported with respectto ,the body for providing.

contact between the elastomer material: 56 and the body 30. The elastomer rnaterialsods positioned in a groove 58 of an elongated bar GOJ a nd extendsacross the width of the applicator drum 30. The grooved bar 60 is supported on a platform 62 which is mounted between upright spaced apart

support members

64 and 66. The bar of which can be positioned at various locations along the platform 62 is forced toward theright as viewed in FIGS. 3 and 4 andapplis a' loading force between the elastorneric doc to'ring bod'yf56 and'the ies which are described in greaterdetail hereinafter, is

forced to the right as viewed in FIGS. 3and 4 by a spring loading means. The spring loading means comprises coil spring which is connected to a stationary post 72 on the upright body 64 and tea rod 74-which' is secured to the backing plate 68 and which extends through a groove 76 in the upright body 64-, and, a coil spring '77 [FIG. No. 2] is similarly connected between a post 81 on the plate 68 and a stationary post 83 on the upright 66. A resilient loading force is thereby established on the elastomeric material 56 and urges it into contact with the surface of the drum 30. While the elastomer material 56 is maintained in contact with the drum 30 by virtue of the spring loading force exerted thereon through the backing plate 68 and the bar 60, the material can be secured in a fixed position when desired by locking the bar 66) at a fixed location. This is accomplished as illustrated in FIGS. 3 and 4 by a locking screw 78 which extends through a threaded aperture in a plate 80. The plate 80 is mounted to and extends between the

uprights

60 and 66. Rotation of the locking screw 78 forces the bar 60 against the platform 62 and locks it in fixed position.

The doctoring body 56 comprises an elongated body of generally circular cross section which extends across the width of the applicator body 30. In accordance with one embodiment, the elongated doctoring body comprises a cylindrically shaped body as illustrated in FIG. 6. In an alternative arrangement, the elastomeric doctoring body 56 comprises a tubular shaped elongated body. While various elastomeric materials may be employed, a preferred material from which the body 56 is fabricated comprises neoprene rubber. The elastomeric body may be molded or extruded within a range of diameters. A range of one-sixteenth to one-eighth of an inch has been found to provide satisfactory operation.

The doctor body support bar 60 includes a plurality of grooves formed along its length for supporting conventionally replaceable doctor bodies when wear occurs in the material. In FIG. 5, the elastomeric body 56 is shown fitted in the groove 58. When this material exhibits signs of wear, the bar 60 can be reversed on the platform 62 for positioning a replacement doctor body 82 against the surface of the applicator drum 30. Additionally another groove 84- is formed in the bar 60 and an additional replacement doctor body 86 is located in this groove. The bar 60 is then reversed and inverted for:v positioning the replacement doctor body 86 ,in contact .withthe surface of the drum 30. The

grooves

58, 83 and 84 are located on the bar for providing that adoctor body positioned -therein is brought into contact with the surface of the drum when the bar 60 is forced toward the drum by the spring loading means discussed hercinbefore. Alternatively, the

grooves

58,

, 83..and 84 are. dimensioned as illustrated in FIG. 5 for receiving doctor bodies of different diameters for satisfying differing operational requirements.

In an'alternative arrangement in accordance with this invention for positioning and loading an elastomeric doctoring body against the surface of an ink applicator drum,the elastomeric material is supported by a strip of relativelystiff and resilient material. In FIGS. 8 and 9; an elastomeric doctoring body 56 of circular cross section is supported against a surface of the applicator 30 by an arcuate shaped segment 88 of an elongated spring metal strip 90. The strip 90 is positioned between

spacer members

93 and 94 andis locked in place therein within the jaw of the doctor blade assembly by hold down screw 96. The doctor blade assembly 92 includes rod segments 98 which are rigidly secured thereto and which extend through apertures 100 in spaced apart upstanding support bodies, 64' and 66. The doctor blade assembly which is thus pivotally supported is biased against the surface of the applicator drum 30 by a spring 104 which is connected between a stationary post 106 and a lever arm 110 which is coupled to the pivot rod 98. In addition to the resilient biasing action provided by this spring loading, the strip 90 is formed of a resilient material which flexes during operation and aids in establishing a desired loading between the elastomeric material 56 and the surface of the drum 30. The strip 90 is formed for example of brass shim stock and in a preferred embodiment, the elastomeric material comprises a /:3 inch diameter extruded neoprene rubber which is cylindrical shaped as illustrated in FIG. 6 while the strip 90 comprises a 12 mil thickness of brass shim stock.

Thus there has been described an improved ink applicator arrangement for use with reproduction systems. The ink applicator arrangement is particularly advantageous for use with relatively low viscosity inks wherein the lands of an applicator body can be wiped relatively clean while the level of ink within the valleys of the applicator can be reduced to desired low levels. The background of the reproduced image is thereby enhanced. A relatively uniform loading of the doctoring body against the applicator drum is also provided.

While I have described and illustrated particular embodiments of my invention, various modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In an electrostatographic reproduction system having a means for establishing a latent electrostatic image on a photoreceptive surface. a means for developing said latent electrostatic image by applying a polar ink to the image areas of the surface, said developing means having an ink applicator body which is positioned adjacent said photoreceptor surface for transferring ink from said applicator body to said photoreceptive surface, said applicator body having an array of lands and depressions formed on a surface thereof, a

means for supplying ink to said applicator, the im provement for removing ink from said lands and regulating the level of ink in said depressions comprising; an elongated body of elastomeric material of generally circular cross section; means for supporting the elastomeric material in contact with the surface of said applicator. said means including a pair of spaced apart support members, a platform supported by the support members, a bar having a longitudinally extending groove in which the elongated body is supported, the bar being slidably seated on the platform, bias means coupled to the bar for pressing the elasto meric material into contact with the applicator, said bias means include a backing bar and a pair of springs, one of the springs coupling the backing bar to one of the support members and the other of the springs coupling the backing bar to the other of the support members, and means for rigidly securing the bar after the elastomeric material has been pressed against the applicator; and means for providing relative motion between said elastomeric material and said applicator surface. 2. Apparatus as defined in claim 1 wherein each of the support members includes a slot extending in a direction parallel to the platform; wherein the backing bar includes a pair of rods, each of the rods projecting transversely through a different one of the slots; and wherein said one of the springs is connected to an end of one of the rods and the other of the springs is connected to an end of the other of the rods.

3. Apparatus as defined in claim 2 wherein said means for rigidly securing the bar include a screw and means for supporting the screw, said means for supporting the screw being located so as to permit rotation of the screw into abutment with the bar.

4. Apparatus as defined in claim 3 further including at least one other elongated body; and wherein said bar includes at least one other longitudinally extending groove, each of said one other groove accommodating a different one of said at least one other elongated body.

5. Apparatus as defined in claim 3 wherein said means for supporting the screw includes a plate connected to each of the support members.

6. Apparatus as defined in claim 1 wherein said means for rigidly securing the bar include a screw and means for supporting the screw, said means being located so as to permit rotation of the screw into abutment with the bar.

7. Apparatus as defined in claim 1 further including at least one other elongated body; and wherein said bar includes at least one other longitudinally extending groove, each of said one other groove accommodating a different one of said at least one other elongated body.

Claims

1. In an electrostatographic reproduction system having a means for establishing a latent electrostatic image on a photoreceptive surface, a means for developing said latent electrostatic image by applying a polar ink to the image areas of the surface, said developing means having an ink applicator body which is positioned adjacent said photoreceptor surface for transferring ink from said applicator body to said photoreceptive surface, said applicator body having an array of lands and depressions formed on a surface thereof, a means for supplying ink to said applicator, the improvement for removing ink from said lands and regulating the level of ink in said depressions comprising; an elongated body of elastomeric material of generally circular cross section; means for supporting the elastomeric material in contact with the surface of said applicator, said means including a pair of spaced apart support members, a platform supported by the support members, a bar having a longitudinally extending groove in which the elongated body is supported, the bar being slidably seated on the platform, bias means coupled to the bar for pressing the elastomeric material into contact with the applicator, said bias means include a backing bar and a pair of springs, one of the springs coupling the backing bar to one of the support members and the other of the springs coupling the backing bar to the other of the support members, and means for rigidly securing the bar after the elastomeric material has been pressed against the applicator; and means for providing relative motion between said elastomeric material and said applicator surface.

2. Apparatus as defined in claim 1 wherein each of the support members includes a slot extending in a direction parallel to the platform; wherein the backing bar includes a pair of rods, each of the rods projecting transversely through a different one of the slots; and wherein said one of the springs is connected to an end of one of the rods and the other of the springs is connected to an end of the other of the rods.