US3635196A

US3635196A - Pneumatically controlled seal

Info

Publication number: US3635196A
Application number: US889271A
Authority: US
Inventors: George N Tsilibes
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1969-12-30
Filing date: 1969-12-30
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18

Abstract

Seal structure for xerographic developer apparatus. The development apparatus contemplated is of the type commonly referred to as a cascade development system wherein fine developer particles are moved in an upwardly direction and allowed to fall or be cascaded onto a xerographic surface and subsequently returned to the developer sump. The seal is characterized by being inflatable in order to block the space between the housing structure and the recording surface, after movement of the recording surface has commenced.

Description

[72] lnventor: George N. Tsilibes, Rochester/NY.

[73] Assignee: Xerox Corporation, Rochester, NY.

[22] Filed: Dec. 30, 1969 [21] Appl. No.: 889,271

[52] US. Cl ..118/637, 117/17.5, 49/477, 49/489, 96/1 SD [51] Int. Cl. ..G03g 13/00 [58] FieldofSearch ..1l8/637,636;117/17.5;

[56] References Cited UNITED STATES PATENTS 2,952,241 9/1960 Clark et a1. ..118/637 2,998,802 9/1961 Harris et a1. ..118/637 United States Patent [151 Tsilibes [451 Jan. 18,1972

54] PNEUMATICALLY CONTROLLED 3,339,785 9/1967 Nugent ..220/41 SEAL 3,424,131 1/1969 Aser et a1 ..118/637 Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Attorney.lames J. Ralabate, John E. Beck and Benjamin B. Sklar [57] ABSTRACT Seal structure for xerographic developer apparatus. The development apparatus contemplated is of the type commonly referred to as a cascade development system wherein fine developer particles are moved in an upwardly direction and allowed to fall or be cascaded onto a xerographic surface and subsequently returned to the developer sump. The seal is characterized by being inflatable in order to block the space between the housing structure and the recording surface, after movement of the recording surface has commenced.

4 Claims, 5 Drawing Figures PATENTEUJAN18 m2 SFEET 1 BF 3 F/ 1 INVENTOR.

GEORGE N. TSILI BES PATENTEU JAN 1 8 I972 SHEET 3 OF 3 BACKGROUND OF THE INVENTION This invention relates, in general, to xerographic developing apparatus and, more particularly, to a seal structure for the developer section thereof.

In the process of xerography, an electrostatic charge in image configuration of original copy is produced on the surface of a photoconductive drum or web. This electrostatic image on the photoconductive surface is developed with a powder material comprising electroscopic marking particles commonly known as toner. Toner normally consists of a finely divided pigmented resin attractable by the electrostatic forces to the photoconductive surface. The electrostatic charge on the photoconductive surface holds the toner on the photoconductive surface in image areas, thus, producing a developed powder image of the copy being reproduced.

One form of development system for developing the latent electrostatic image with toner or powder is commonly referred to as cascade developing. Cascade development is a two-component system wherein small glass beads are mixed with the toner to act as a carrier for the toner material. The glass beads provide mechanical control of the toner and, when agitated with the toner, provide a triboelectric charge which holds the toner on the surface of the glass bead. The combination of glass beads or carrier and toner is referred to as developer or developer material. When the developer material is cascaded over the surface of a xerographic plate containing an electrostatic latent image thereon, the toner, which is adhering to the carrier by triboelectric forces, is attracted away from the carrier by the strong electrostatic charges and is held on the surface of the xerographic plate. In conventional cascade development systems, the carrier continues to cascade over the surface of the xerographic plate back into a hopper or supply bin wherein it is again agitated with toner material and recascaded over the surface of the xerographic plate.

It is necessary in cascade and other types of development systems, for example, paddle wheel type of development system, to provide a quantity of material adjacent to the xerographic drum and to cause a developer material to flow over the drum surface. The container or housing structure which holds the developer material and which prevents the developer material from escaping from the housing to the rest of the machine must necessarily be open to a portion of the xerographic drum. In many instances the developer housing structure cannot contact the surface of the xerographic drum, and conventional sealing techniques employed in other arts cannot be used since the drum contains a latent electrostatic image and is also extremely susceptible to scratching or marring. The latent electrostaticimage cannot be disturbed prior to being developed, and, therefore, any seal which would conduct, drain off or disturb in any manner the electrostatic image is unsatisfactory for use as a sealing material or structure. Any material which is abrasive and would damage the surface of the xerographic drum likewise cannot be used in contact with the surface of the drum in those cases where the drum material is susceptible to marring.

In certain areas of reproduction, for example, the reproduction of semimicroimages, such as for example, images which are reduced in size from 2% to 3 times original size prior to reproduction it is necessary to use a carrier bead which is considerably smaller than the carrier bead normally used in cascade developing. The carrier beads used in such systems are so small that they find their way out of the developer housing past conventional seals.

Prior attempts at solving the aforementioned problem have resulted in the intolerable situation of having to overcome the force of friction between the seal and the recording member. Motors powerful enough to overcome such friction forces usually utilize starting capacitors which generate undesirable radiofrequency interference, when switching out, of the starting capacitors is effected.

Accordingly, the primary object of this invention is to provide a new and improved xerographic apparatus.

A more particular object of this invention is to provide a new and improved seal structure for the developer section of a xerographic apparatus.

Another object of this invention is to provide a new and improved seal structure for the developing section of a xerographic apparatus which is actuable after the recording member associated therewith has started to move.

BRIEF SUMMARY OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of inflatable seals disposed intermediate the developer housing and the recording web along the sides of the developer housing such that the seals cooperate with a baffle structure to direct developer to the recording surface while preventing emission of developer from between the housing structure and the recording surface. The seal structures are inflated only after the recording medium has started to move thereby eliminating the need for conventionally high-powered motors for overcoming the starting friction forces attendant prior art constructions. Once the recording medium has begun to move, the inflated seal engages the side edges of the recording medium, preferably beyond that portion'of the photoconductor which is used in forming the image.

Further objects and advantages of the present invention will become apparent when considered in view of the description of the preferred embodiment of the invention and drawings forming a part hereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a xerographic apparatus utilizing the present invention; and

FIG. 2 is an enlarged fragmentary view of the developer housing and seal arrangement forming a part of the invention;

FIG. 3 is a cross-sectional view taken on the line 3-3 of FIG. 2 representing an inflatable seal in its noninflated position;

FIG. 4 is a view similar to FIG. 3, but with the seal member inflated; and

FIG. 5 is a schematic illustration of a seal arrangement representing the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, especially FIG. 1, reference character 9 designates generally a xerographic apparatus comprising a rotatable xerographic drum 10 mounted for rotation on a shaft 12. The drum rotates about the shaft 12 in the direction indicated by the arrow and passes a charging station generally indicated as 14 wherein a corotron 16, connected to a suitable power source, not shown, places a uniform electrostatic charge on the surface of the xerographic drum. Although any one of a number of types of corona-generating devices may be used, a corona-charging device of the type disclosed in Vyverberg US. Pat. No. 2,836,725 is preferably employed for the corotron 16. The drum rotates past an exposure station 18 wherein light images of copy to be reproduced discharge the electrostatic charge on the drum surface and produces a latent electrostatic image of the copy being reproduced on the drum surface. The drum then rotates past a developer station, generally indicated as 20, wherein a developer mechanism, described in detail below, develops the latent electrostatic image into a powder image. After the electrostatic image is developed, a pretransfer corotron 22 places an electrostatic charge on the drum surface to loosen the powder image for transfer purposes, The drum then rotates past a transfer station 24 wherein the powder image is transferred to a suitable support material surface by means of a transfer corotron 26 which places a suitable electrostatic charge on theback surface of the support material to attract the powder from the xerographic drum to the support material. The support material is then transported past a fusing station 28 wherein the support material and the powder image thereon are exposed to rays from a flash fuser 30 which heats the powder causing it to coalesce and to bond to the surface of the support material. The xerographic drum rotates past a cleaning station 32 wherein residual toner material remaining on the surface of the drum is cleaned therefrom by means ofa rotating brush 34.

In the apparatus shown either images of original copy reduced to 2% to 3 times its size may be reproduced on data processing cards or previously reduced images on data processing cards may be reproduced onto other data processing cards. Documents which are to be reduced and copied on data processing cards are placed on a document tray 36. The tray is mounted on a pair of rollers 38 on a track 40. With the document to be reproduced on the tray 36, the tray is moved forward towards a scanning station 42. With the tray 36 and in the forward position, the document is picked up by a belt conveyor 44 and a feed roller 46 in a manner described in detail in application Ser. No. 436,168, filed Mar. 1, 1965, in the names of Thomas H. Galster, Alan M. Hitchcock and Gordon P. Taillie. The document is held on conveyor 44 by means ofa vacuum produced in a manifold 48 which produces suction through a series of openings in the manifold and corresponding perforations in the surface of the belt in conveyor 44. The conveyor 44 carries the documents past the scanning station 42 wherein a pair of lamps LMP-l illuminate incremental areas of the surface of the document. The illuminated areas of the document are reflected by a mirror 50 through a reducing lens 52 to the surface of the xerographic drum at exposure station 18. The movement of the conveyor 44 is synchronized with the movement of the drum so that the image is placed on the drum surface with the proper-sized reduction. The conveyor 44 then carries the document around a main drive roller 54 by means of a series of resilient rollers 56 rotatably mounted and in surface contact with the belt of the conveyor 44 as they extend around the roller 54. When the document emerges from the bands 56, it is again held on the belt of the conveyor 44 by means of a vacuum produced in manifold 48. The document is carried forward beyond the end of the manifold 48 where, with the suction released, it tends to drop away from the conveyor 44 and is deflected downward by a plate 60 into a receiving tray 62.

When it is desirable to reproduce images from data processing cards, a series of cards 64 containing xerographic images thereon are stacked in a conventional card-feeding hopper 67 and fed into a card conveyor system which is similar to the conveyor system 44. The card conveyor is not shown, but is a vacuum conveyor whiclcarries the cards past a scanning station similar to the scanning station 42 and deposits the cards into a card-receiving hopper. The illuminated portions of the card are deflected upwards into a mirror 66 which directs the images through: lens 68 to a mirror 70 which directs the image onto the surface of the xerographic drum at the exposure station 18.

Images reproduced on the surface of the xerographic drum are transferred to blank data processing cards 72 which are fed from a conventional card-feeding hopper 74 to a rollertype conveyor system 76. The conveyor 76 consists of a series of rollers 78 which feed the cards past a rotary card timing device into surface contact with the xerographic drum 10.

The cards 72 are forced into surface contact with the drum 10 by means of a series of bands 82 which are held in surface contact with the drum 10 by means of a pair of rollers 84 and are moved at the same speed as the periphery of the xerographic drum 10. The bands 82 force the card 72 into surface contact with the xerographic drum at the point at whiclthe corotron 26 places an electrostatic charge on the back of the card to transfer the powder image from the drum surface to the card surface. As the card emerges from the band 42, it is peeled off the surface of the drum by means of a blade structure, not shown, which extends into an undercut portion of the xerographic drum, also not shown.

When the card 72 containing a transfer powder image is deflected from xerographic drum 10 by the blade structure, it is held on a conveyor 9%] by the suction produced in a vacuum manifold 102. The conveyor 98 carries the card past the fuser station 28 wherein the powder image is heated to a point where is coalesces and bonds to the card surface. The card containing the fused image is then transferred to a second conveyor 104 whzh is also a vacuum conveyor having a vacuum manifold 106. A third vacuum conveyor 108, having a vacuum manifold 110, receives the card from the conveyor 104 and transports it to a card-receiving hopper 112 where it is deposited until such time as the machine operator removes it.

As seen in FIG. 2, there is provided a developer housing structure 114 which contains a supply of developer material 116 consisting of toner material and small carrier beads, the latter being on the order of 250- to 450-micron size. The developer material 116 is located in the bottom of the housing structure 114 and provides a supply of fresh developer material for continuous bucket conveyor 118. As the xerographic drum 10 rotates, the conveyor rotates its buckets through the developer material 116 in the bottom of the housing and conveys the material to the top of the housing structure 114 wlarein it discharges the developer material down on to a baffle structure 119 comprising a top baffle 120 and a flow baffle 121. The baffle structure 120 directs the developer material onto the surface of the xerographic drum where it is cascaded over the drum surface and directed back towards the bottom of the housing structure by a second baffle structure 122 which may form a part of the housing structure 114, as shown, or a separate structure apart from the housing structure. A toner feed mechanism 123 including a motor therefore provides for addition of toner as it is depleted from the developer material 116.

With high humidity, the positive charge on the developer beads decreases so much that the negatively charged toner is held very loosely to the beads. As a result, loose toner powder is mixed with the beads as they come out of the top and flow baffles and cascade across the drum. Since the toner in this powder cloud is not held by the carrier heads, the powder is attracted strongly by the charge on the drum. As a result of this powder development, the toner deposited across the drum results in a dirty background on the copy under high-humidity conditions.

To prevent development of this powder cloud, the top and flow baffles are charged with approximately 800 volts, the drum being initially chrged with 1,000 volts on its surface, After exposure, the charge on the image areas has decreased to about 900 volts, but the background charge has dropped to about 350 volts. Although the static charge on the baffles is the same polarity as the drum charge, the baffle charge is weaker than the drum image charge and stronger than the drum background charge. The static charge of the baffles extends around the baffles so that the powder cloud is attracted away from the drum background and towards the baffles. Any toner that tends to collect on the baffles is wiped away by the cascading beads. Since a great deal of the image development occurs in the area near the top and flow baffles, elimination of powder cloud development around this area is very effective in reducing background.

To further reduce copy background, a developer electrode 127 charged with a plus 2,000 volts is used. This electrode is located approximately 2 inches away from the bias baffles at a point where most of the development has been completed. At this point, most of the image has been coated with toner and an electrical equilibrium has been established between the drum charge and the developer bead charge. Because of this equilibrium, additional toner is not strongly attracted to the image. Any toner removed by empty" beads is immediately replaced by succeeding beads. The effect of the charged developer electrode at this point is to shift the electroequilibrium away from the drum and toward the beads. The static charge on the electrode extends around it so that effectively a greater positive charge exists in the area of the beads. This results in a greater ability of the beads to pull toner off the drum in the background areas, where the toner is not held strongly. This action is called scavenging," and has no effect on the toner held to the drum by the strong fringe field at the edge of the image.

While the foregoing method of presenting developer material to the xerographic drum creates the type of problem to be overcome by the present invention, other systems inherently possess like deficiencies. For example, a system comprising a paddle wheel having a rotatable shaft, and a plurality of paddles extending outwardly from the periphery of the shaft would possess this deficiency. The paddle wheel would be coextensive with the longitudinal axis of the drum and would be supported within the housing structure 114. Rotation of the paddle wheel in a direction and at a rate of speed so as to throw developer upwardly from the bottom of the developer housing structure would have the effect of presenting the developer material to the xerographic drum 10.

As seen in FIG. 5, an inflatable seal structure 124 is provided in a groove 126 of the developer housing structure 114. There are two such structures 124, one each, adjacent opposite sides of the xerographic drum. The seals 124 serve to close the gaps 128 between the xerographic drum and the developer housing structure after the drum structure has started to rotate.

A compressor 130 supplies positive air pressure to the seals 124 through conduits 132. The seals which are made from any suitable material, for example, neoprene, are suitably inflated at a pressure of approximately 1 to 2 p.s.i.g. through a solenoid-actuated valve 134 which is adapted to be actuated subsequent to start of rotation of the xerographic drum through the machine program control, not shown. The compressor is of a conventional type used in xerographic recording apparatus and constitutes therefore existing hardware of the machine which is modified by means of the solenoid valve and conduits to supply air to the inflatable seals.

A third seal member 136, see P16. 5, is disposed in a groove 138 in the developer housing. This groove is coextensive with the longitudinal axis of the drum adjacent the top portion thereof where it extends into the developer housing structure. A conduit 140 operatively connecting the compressor 130 and the top seal 136 supplies air under pressure to the seal 136 for inflation thereof at the prescribed time. it will be appreciated that since the drum 10 rotates in the counterclockwise direction, the seal 136 which engages the surface of the drum will not interfere with a developed image since the developed image is formed after the drum passes the area of the seal 136. While it is not possible for the top seal 136 to disturb a developed image, it is quite possible that the latent electrostatic image can be affected by the seal, for example, if the seal were to deposit impurities on the drum surface. Furthermore, the seal can affect the surface finish of the more delicate types of xerographic drum materials, consequently, the seal material should be nonabrasive in those situations where the seal contacts that portion of the drum which is used in forming the image.

A lower or bottom seal 142 is provided in a groove 144 which extends along the longitudinal axis of the xerographic drum adjacent the bottom portion of the drum where it extends into the developer housing structure 114. The bottom seal is adapted to be supplied with air under pressure from the compressor 130 through a solenoid-actuated valve 146 a conduit 148 and a selector valve structure 150, the latter of which is adapted to provide communication between the compressor and the

valves

134 and 146 either separately or simultaneously. The bottom seal 142, it will be appreciated, is adapted for sealing the lower edge of the developer housing structure in a machine where the developer housing structure 114, the charging device, the xerographic drum and cleaning device are arranged such that rotation of the drum relative to developer housing structure would be in the opposite direction to that shown.

Additionally, with the provision of both the upper and lower seals 136 and 142 a seal system is available for sealing between the housing structure 114 and the xerographic drum 10 when the xerographic drum is not in use, for example, when the machine is being shipped. It will be appreciated that all of the

seal structures

124, 136, and 142 could at this time be inflated for such purposes. Each of the seals would be provided with a bleed valve which would be actuated at the same time the machine is put into operation. Consequently, only the appropriate seals would be inflated subsequent to start of rotation of the xerographic drum while one or the other of the top or bottom seals would be deflated depending on the arrangement of the components. The top seal is optional during normal operating conditions and the bottom seal is optional if the developer trough extends well beyond the point where the developer falls off the drum.

It will be understood that various changes in the details, materials, steps and arrangement of parts which have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. However, while the invention has been described with reference to the structure disclosed herein, it is not intended that the invention be confined to the details as set forth, this application is intended to cover such modifications or changes as may come within the scope of the following claims. For example, the inflatable seals may be replaced by conventional seal material for xerographic apparatus such as sponge rubber which is affixed to the free edge of the displaceable member that is moved in and out of contact with the drum as by means of an air-actuated piston arrangement. Furthermore, the seals could be constructed in the fonn of a bellows or diaphragm in lieu of the tubular seal structures disclosed.

What is claimed is:

1. In a xerographic machine of the type utilizing a development system wherein a powder image is developed on a xerographic surface by presenting carrier particles and toner material to the surface and structure for effecting return of unused particles to a developer sump the improvement comprising, in combination:

housing structure enclosing at least a portion of the xerographic surface, said housing structure being spaced from said surface;

seal means disposed intermediate said surface and said housing structure; and

means for moving said seal means into engagement with said xerographic surface for impeding emission of particles and material from said housing structure and moving said seal means out of engagement with said surface to permit initial movement of said surface without the retarding friction due to the seal means.

2. Structure as specified in claim 1 wherein said seal means comprises an extensible means.

3. Structure according to claim 2 wherein said extensible means comprises inflatable seals extending at least along the sides of said housing structure and including means for selectively supplying air to said seals under pressure for effecting said engagement.

4. Structure according to claim 2 wherein said extensible means comprises a first pair of inflatable seals extending along the sides of said housing structure and a second pair of inflatable seals intermediate said first pair of inflatable seals at the ends thereof and including means for selectively supplying air to said seals.

Claims

1. In a xerographic machine of the type utilizing a development system wherein a powder image is developed on a xerographic surface by presenting carrier particles and toner mateRial to the surface and structure for effecting return of unused particles to a developer sump the improvement comprising, in combination: housing structure enclosing at least a portion of the xerographic surface, said housing structure being spaced from said surface; seal means disposed intermediate said surface and said housing structure; and means for moving said seal means into engagement with said xerographic surface for impeding emission of particles and material from said housing structure and moving said seal means out of engagement with said surface to permit initial movement of said surface without the retarding friction due to the seal means.