CA1151224A - Magnetic transport system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A magnetic transport system includes a ferromagnetic belt which is used in conjunction with a magnetic ski to transport substrates. The belt and ski cooperate to form a path of travel for the substrate. Magnetic attraction between the belt and ski provides the normal force necessary for the high friction surfaced belt to drive the substrate along the path of travel.

Description

MAGNETIC TRANSPORT SYSTEM

This invention relates to an electrophotographic printing machine, and more particularly concerns an apparatus for advancing sheets employed therein along a predetermined path.
A typical electrophotographic printing machine utilized in the business office environment contains stacks of cut sheets of paper on which copies of original documents are reproduced. Generally, these cut sheets of paper are advanced through the printing machine, one sheet at a time, for suitable processing therein. Frequently, papers are advanced through the printing machine by transport subsystems. These subsystems are those sections of the paper handling module which drive copy paper from one printing processing station to another. Copy paper is directed to and from various subsystems by baffles and/or selection gates. All transports are directly driven from the main power drive and become operational upon "print command." The gates are usually solenoid operated and direct the copy paper as required to meet user selected output requirements~ Attempts are made to design each transport where possible to allow ready accessibility to the copy paper by untrained machine operators. Coin switches are located throughout the various transports to provide jam protection.
One of the existing methods of transporting copy paper within a xerographic process i8 to use "skls"
which bias the paper against a rubberized belt. Selection of the skl shape and flexibility so as to insure a relatively uniform contact is difficult to achieve. Additionally, it is relatively easy to cause the ski to bounce out of contact with the paper due to the valid combinations of ski mass and maximum loading force. This causes indeter-minancy in the copy paper transport speed and in copy paper skew control. Yet another limitation on conventional ski transports is the cost constraints of providing for d~

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-;224 application of the normal load, restraining lateral motion of the ski and fabrication of a smooth-bottomed ski.
Various other methods have been used to transport items in the past with the following prior art appearing relevant toward that showing:
APplicant(s) ~,S Patent No. Issue Date Pittwood 2,995,363 Aug. 8, 1961 Fowler 3,228,680 Jan. 11, 1966 Bernard 3,428,308 Feb. 18, 1969 Street 3,630,518 Dec. 28, 1971 Wickers 3,663,613 May 16, 1972 Kercher 3,926,352 Dec. 16, 1975 Ono 4,081,069 Mar. 28, 1978 Xerox 9200 and 9400 Copiers Xerox Disclosure Journal, Vol. 3, No. 2, March/April, 1979, page 107.
The pertinent portions of the foregoing prior art may be briefly summarized as follows:
Pittwood, Fowler, and Bernard show magnetically attractable rollers that transport substrates when in the attracted state.
Street discloses a sheet feeding device that includes a feed path between a pair of superimposed plates and an intervening aligned surface wherein the sheets are transported along the feed path and toward the aligning surface by at least one row of balls with the balls being rotated by a common drive belt.
Wicker~ discloses a bottom feeding mechanism comprised of a plurality of caged balls and an endless belt in frictional driving contact with the balls.
Kercher discloses a clamp suitably supported on a labeling head and includes spaced hold down fingers that ride lightly and slightly above labels being fed pass the labeling head.
Ono shows a feeding apparatus for caps which are made of a magnetic substance, in which the caps can be fed one by one continuously and constantly by the employment of a conveyor belt having magnetism.
In accordance with an aspect of the present invention, there is provided an apparatus for advancing a sheet along a predetermined path. It includes an improvement over the above-mentioned ski and rubberized belt transport concept and involves the use of magnets in combination with the skis and ferromagnetic or magnetic belts. Flexible magnets are used to provide the normal force against the moving high friction belts. Low friction plastic, flexible skis are in direct contact with the high friction belt. As paper enters the transport nip between the ski and belt, the ski separates from the moving belt just enough to allow paper to enter therebetween thereby trapping and driving the paper as required.
In accordance with another aspect of this invention there is provided in a copier having a processor, said processor having means for applying an image of a document to a substrate, and means for transporting the substrate along a path to said processor, said transport means includes a ski arranged for applying a normal force to the substrate supported and driven toward said processor by a flexible belt, comprising the improvement in said transport means, wherein:
said ski comprises a low friction magnetic strip, ~ 25 and said flexible belt comprises a high friction magnetic ; belt which attracts said ski, whereby a normal force is applied to the substrate trapped between said ski and belt sufficient for said belt to drive the substrate toward said processor.
Other features of the present invention will become apparent as the following description proceeds and upon reference to the drawings in which:
Figure 1 is a schematic elevational view of an electrophotographic printing machine incorporating the features of the present invention therein.
While the present invention will be described hereinafter in connection with a preferred embodiment thereof, it will be understood that it is not intended .

- 3a --to limit the invention to that embodiment. On the con-trary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
For a general understanding of the features of the present invention, reference is had to the drawings.
In the drawings, like reference numerals have been used throughout to designate identical elements. Figure 1 schematically depicts the various components of an illustra-tive electrophotographic printing machine incorporating ~, ~ a~224 -- 4 ~

the magnetic transport apparatus of the present invention therein. It will become evident from the following dis-cussion that the magnetic transport system is equally well suited for use in a wide variety of devices and is not necessarily limited to its application to the particular embodiment shown herein. For example, the apparatus of the present invention may be adapted for use in document handlers or readily employed in non-xerographic environments and substrate transportation in general.
Inasmuch as the art of electrophotographic printing is well known, the various processing stations employed in the Figure 1 printing machine will be shown hereinafter schematically and the operation described briefly with reference thereto.
As shown in Figure 1, the electrophotographic printing machine employs a belt 10 having a photocon-ductive surface 12 deposited on a conductive substrate 14. Preferably, photoconductive surface 12 is made from a selenium alloy with conductive substrate 14 being made from nickel. Belt 10 moves in the direction of arrow 16 to advance successive portions of photoconductive surface 12 sequentially through the various processing stations disposed about the path of movement thereof.
Belt 10 is entrained around stripper roller 18, tension roller 20, and drive roller 22.
Drive roller 22 is mounted rotatably in engage-ment with belt 10. Motor 24 rotates roller 22 to advance belt 10 in the direction of arrow 16. Roller 22 i5 coupled to motor 24 with a suitable means such as a belt drive.
Drive roller 22 includes a pair of opposed spaced flanges or edge guides 26. Edge guides 26 are mounted on opposite ends of drive roller 22 defining its space therebetween which determines the desired predetermined path of move-ment for belt 10. Edge guide 26 extends in an upwardly direction from the surface of roller 22. Peeferably,edge guides 26 are circular members or flanges.
Belt 10 is maintained in tension by a pair of springs (not shown), resiliently urging tension roller 20 against belt 10 with the desired spring force. Both stripping roller 18 and tension roller 20 are mounted rotatably. These rollers are idlers which rotate freely as belt 10 moves in the direction of arrow 16.
With continued reference to Figure 1, initially a portion of belt 10 passes through charging station A. At charging station A, a corona generating device, indicated generally by the reference numeral 28, charges photoconductor surface 12 of the belt 10 to a relatively high, substantially uniform potential. A suitable corona generatiny device is described in U.S. Patent No. 2,836,725 issued to Vyverberg in 1958.
Next, the charged portion of photoconductive surface 12 is advanced through exposure station B. At exposure station B, an original document 30 is positioned face down upon transparent platen 32. Lamps 34 flash light rays onto original document 30. The light rays reflected from the original documen~ 30 are transmitted through lens 36 from a light image thereof. The light image is projected onto the charged portion of the photo-conductive surface 12 to selectively dissipate the charge thereon. This records an electrostatic latent image on photoconductive surface 12 which corresponds to the informational areas contained within original document 30.
Thereafter, belt 10 advances the electrostatic latent image recorded on photoconductive surface 12 todevelopment station C. At development station C, a magnetic brush developer roller 38 advances a developer mix into contact with the electrostatic latent image. The latent image attracts the toner particles from the carrier granules ~ 2 ~

forming a toner powder image on photoconductive surface 12 of belt 10.
Belt 10 then advances the toner powder image to transfer station D. At transfer station D, a sheet of support material S is moved into contact with the toner powder image. The sheet of support material is advanced to transfer station D by a sheet feeding apparatus 42. Preferably, sheet feeding apparatus 42 includes a feed roll 44 contacting the upper sheet of stack 46.
Feed roll 44 rotates so as to advance the uppermost sheet from stack 46 into one or more ferromagnetic transport belts 80. The transport belts direct the advancing sheet of support material into contact with the photoconductive surface 12 of belt 10 in a timed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D.
Transfer station D includes a corona generating device 50 which emits ions onto the backside of sheet S. This attracts the toner powder image from the photo-20 conductive surface 12 to sheet S. After transfer, thesheet continues to move in the direction of arrow 52 onto a conveyor (not shown) which advances the sheet to fusing station E.
Fusing station E includes a fuser assembly, ` 25 indicated generally by the reference number 54, which permanently affixes the transferred toner powder image to sheet S. Preferably, fuser assembly 54 includes a heated fuser roller 56 and a backup roller 58. Sheet S passes between fuser roller 56 and backup roller 58 30 with the toner powder image contacting Puser roller 56.
In this manner, the toner powder image is permanently affixed to sheet S. After fusing, shoot 60 guides the advancing sheet S to catch tray 62 for removal from the printing machine by the operator.
Invariably, after the sheet support material is separated from the photoconductive surface 12 of belt 10, some residual particles remain adhering thereto.
These residual particles are removed from photoconductive surface 12 at cleaning station F. Cleaning station F
includes a rotatably mounted fiberous brush 64 in contact with the photoconductive surface 12. The particles are cleaned from photoconductive surface 12 by the rotation of brush 64 in contact therewith. Subsequent to cleaning, a discharge lamp (not shown) floods photoconductive surface 12 with light to dissipate any residual electrostatic charge remaining thereon prior to the charging thereof for the next successive image cycle.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrostatographic printing machine.
Referring now to the specific subject matter of the present invention, Figure 1 shows a sheet or sub-strate S being forwarded by drive roller 44 from stack 46 into a nip formed between ferromagnetic belt or belts 80 entrained over roller 70 adjacent the sheet stack and idler roller 72 remote from the stack. Roller 70 is driven by motor 24 through appropriate gearing and linkage. Curvature is supplied to the belts by guide member 45 located on the interior of belt 80. The guide is made from any suitable material such as plastic.
As the sheets enter the transport path formed between belt 80 and ski 91, the normal force required to force the sheet against belt 90 for frictional transport is provided by the attracting magnetic field existing between the belt and magnet 92 which is fixedly secured to ski '~ 91.
As one example, a ferromagnetic belt made of nearly pure nickel similar to the Xerox 9200 photoreceptor substrate could be employed. Nickel being an excellent ferromagnetic material that represents the state of the art.

1~5~2Z4 Referring now to the embodiment of the present invention shown in Figure 1, ferromagnetic belt 80 is shown used in conjunction with flexible ski 91 and flexi-ble magnet g2. A backup plate 45 gives the required curvature to ferromagnetic belt 80. This paper transport configuration eliminates the need for sheet metal super-structure for attracting magnets and thereby cost reduces the transport system while increasing jam accessibility.
Increased normal force is also obtained with this system since ferromagnetic belt 80 is 0.101 cm. closer to magnet 92 than a system employing a metal superstructure as the attracting member. If the increased normal force is not necessary, the strength of the magnet 92 can be reduced making it more flexible and less expensive.
After sheets S are fed from paper feeder 42, they enter into a nip formed between ferromagnetic belt 80 which is entrained over rollers 70 and 72 and flexible ski 91. An advantage of using ferromagnetic belt 80 as the transport member is the extension of the nip to the tangent point of the belt and pulley on both the lead and trail edges of the paper allowing better inter-face with other machine subsystems. Also, since the belt is the attracting member, both sides of the belt can be used to transport paper, i.e. with the present ; 25 invention being employed as a vertical transport, paper can be driven up one side of the transport and down the other.
The magnetic attraction between belt 80 and magnet 92 provides the necessary normal force to ski member 91 such that paper that has entered the nip formed by the belt and ski is forwarded toward roller 26 which has photoconductive member 12 entrained thereover. If one desired, ski 91 could be ferromagnetic and belt 80 magnetic.
Belt 80 is preferably an endless nickel belt coated with a high coefficient of friction elastomer.

-h~ Z~4 g However, the belt could be made from iron, cobalt, gadolinium or alloys, mixtures and combinations of these and other materials. The belt could also be elastomeric and filled with magnetic material such as barium ferrite possibly reinforced to give the belt better physical properties or an elastomeric material in belt configuration filled with a combination of a ferromagnetic material and a magnetic material, reinforced if desired.
In conclusion, an improved substrate transport system is disclosed for advancing a substrate along a predetermined path. The transport system includes the use of skis forced against a transport belt by magnetic attrac-tion between two adjacent members. This apparatus fully satisfies the aims and advantages hereinbefore set forth.
While this invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
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Claims (4)

CLAIMS:

1. In a copier having a processor, said processor having means for applying an image of a document to a substrate, and means for transporting the substrate along a path to said processor, said transport means includes a ski arranged for applying a normal force to the substrate supported and driven toward said processor by a flexible belt, comprising the improvement in said transport means, wherein:
said ski comprises a low friction magnetic strip, and said flexible belt comprises a high friction magnetic belt which attracts said ski, whereby a normal force is applied to the substrate trapped between said ski and belt sufficient for said belt to drive the substrate toward said processor.

2. The copier of Claim 1 wherein said ski is ferro-magnetic.

3. The copier of Claim 1 wherein said belt is ferromagnetic.

4. The copier of Claim 1 wherein said path along which said substrate is transported is curved.