Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS3807854 A
Publication typeGrant
Publication dateApr 30, 1974
Filing dateJan 24, 1973
Priority dateFeb 7, 1972
Also published asDE2305684A1
Publication numberUS 3807854 A, US 3807854A, US-A-3807854, US3807854 A, US3807854A
InventorsY Enoguchi, T Fujiwara, S Tanaka
Original AssigneeMinolta Camera Kk
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Drive mechanism for photsensitive web in an image transfer type electrophotographic copier
US 3807854 A
Abstract
An apparatus comprising a photosensitive element made of a flexible sheet to be moved reciprocally for each image transfer cycle, a suction box fixedly supporting one end of the photosensitive element at its inlet portion and subjected to a reduced pressure in its interior by pressure reducing means to draw in the photosensitive element along its inner wall and to thereby tension the element to a planar form at an exposure station, and drive means for defining the path of advance of the photosensitive element and defining the direction of movement of the same.
Images(3)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent [191 Tanaka et al.

DRIVE MECHANISM FOR PHOTSENSITIVE WEB IN AN IMAGE TRANSFER TYPE ELECTROPHOTOGRAPHIC COPIER Inventors: Susumu Tanaka, Sakai; Yuji Enoguchi, Higashiosaka; Takao Fujiwara, Sakai, all of Japan Minolta Camera Kabushiki Kaisha, Osaka, Japan Filed: Jan. 24, 1973 Appl. No.: 326,360

Assignee:

Foreign Application Priority Data Feb. 7, 1972 Japan 47-13699 US. Cl 355/16, 355/8, 355/15 Int. Cl G03g 15/00 Field of Search 355/16, 11, 8, 3

References "Cited UNITED STATES PATENTS Morse 355/16 Apr. 30, 1974 3,697,160 10/1972 Clark 355/16 3,646,866 3/1972 Baltazzial 355/16 Primary ExaminerRichard L. Moses Attorney, Agent, or FirmWolder & Gross [57] ABSTRACT An apparatus comprising a photosensitive element made of a flexible sheet to be moved reciprocally for each image transfer cycle, a suction box fixedly supporting one end of the photosensitive element at its inlet portion and subjected to a reduced pressure in its interior by pressure reducing means to draw in the photosensitive element along its inner wall and to thereby tension the element to a planar form at an exposure station, and drive means for defining the path of advance of the photosensitive element and defining the direction of movement of the same.

14 Claims, 7 Drawing Figures PATENTEDAPR 30 m4 SHEET 1 (IF 3 Fig.7

BACKGROUND OF THE INVENTION The present invention relates to electrophotographic copiers of the image transfer type, more particularly to an apparatus for driving a photosensitive element to be used repeatedly in electrophotographic copiers of the image transfer type such as the electrostatic latent image transfer type, powder image transfer type and the like.

The photosensitive element used in electrophotographic copiers of the image transfer type has a photoconductive film which is electrostatically charged by a charger and then exposed to reflected light from the surface of document to form the image of the document as an electrostatic latent image. Suchphotoconductive film is generally adhered to a drum or belt for repeated use. When the photosensitive element gets deteriorated due to repeated use over a long period, the photosensitive element has to be replaced along with the drum or belt. The replacing procedure is therefore very cumbersome and expensive.

In recent years, it has been proposed to use a flexible photosensitive element in the form of a roll as disclosed in US. Pat. No. 3,588,242 by R. A. Berlier et al. and in Publication of Japanese Patent application No. 41356/1971 by K. Amemiya, the roll of photosensitive element being such that the deteriorated portion thereof will be wound up to pay out a fresh portion for use.

According to the US. Pat. No. 3,588,242, a drum of a large diameter for providing the photosensitive element on its surface has in its interior a supply roll and a takeup roll, and the photosensitive element wound on the.supply roll is paid out over the drum surface, with the leader end of the element wound on the takeup roll. When the photosensitive portion on the drum surface has been deteriorated, the deteriorated portion is wound up on the takeup roll to pull out a fresh photosensitive portion. The photosensitive element extending around the drum surface is subjected all the time to mechanical tension exerted by the takeup roll. The photosensitive elementof this apparatus is driven by the rotation of the drum to pass through a corona unit, exposure station, developing unit and transfer station which are disposed around the drum for the transfer copying operation already known.

According to the Publication of Japanese Pat. application No. 41356/1971, a roll of flexible photosensitive element is paid out from a supply roll and the leader end is wound on a takeup roll, the photosensitive element extending between the two rolls in a taut planar fashion. If the extending portion gets deteriorated, the deteriorated portion is wound up on the takeup roll to pull out a fresh portion from the supply roll for use. The photosensitiveelement is always subjected to mechanical tension, with the two rolls kept spaced apart by a constant distance, and the rolls and the photosensitive elements in this state are moved reciprocally in a horizontal direction. Various means for transfer copying operation are disposed in series along the path of the reciprocation to conduct the copying operation already known.

The two examples described have the drawback that the photosensitive element is susceptible to fatigue due to stress, hence a short service life and marked wear of the element inasmuch as the flexible photosensitive element is subjected to mechanical tension all the time. Moreover, since the photosensitive element is driven on the support drum or is reciprocated over a distance several times the space between the rolls while being supported on the rolls, the construction requires a large space for driving the photosensitive element, making the copier greater in size to occupy an increased floor space.

SUMMARY OF THE INVENTION An object of this invention is to subject a flexible photosensitive element to a minimum of requisite tension when it is driven reciprocally for a transfer copying operation so as to keep the element planar at the exposure station and to thereby prevent the shortening'of its service life and cost increase due to its wear.

Another object of this invention is to simplify the construction of a mechanism for driving the photosensitive element to the greatest possible extent and to reduce the space volume required for driving the photosensitive element so as to provide a compact electrophotographic copier of the type described.

Still another object of this invention is to provide an apparatus of a very simple construction capable of returning the photosensitive element quickly for reciprocation.

To fulfil these objects, the apparatus of this invention is characterized by suction means for moving the photosensitive element along its inner wall by drawing the same in one direction so as to subject the element to tension and means for defining the direction of movement of the photosensitive element.

According to our experiment,the suction to be exerted on the photosensitive element to keep the same planar at the exposure station is given by suction means which produces a very low negative pressure of the order of 30 mm Aq'. and it has become possible to greatly reduce the tension on'the photosensitive element as compared with the known apparatus, this consequently making it possible to materially reduce the stress to be produced in the photosensitive sensitive element by the tension. Moreover, the invention simplifies the mechanism for driving the photosensitive element and reduces the space volume required for the reciprocation of the element.

Other objects and features of this invention will become more apparent from the following description of embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view partly in vertical section showing the principal part of an embodiment of this invention;

FIGS. 2(a) and (b) are views illustrating the operation of a photosensitive element in the embodiment of FIG. 1;

FIG. 3 is a view partly in vertical section showing the principal part of another embodiment of this invention;

FIG. 4 is a view partly in vertical section showing the principal part of another embodiment of this invention; and

FIGS. (a) and (b) are views illustrating the operation of a photosensitive element in the embodiments of FIGS. 3 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an electrophotographic copier of the electrostatic latent image transfer type. A document table 1 made of a transparent material such as a glass plate is fixedly positioned at the top of a frame A. A document B to be copied is placed face down on the table 1 and is illuminated by a lamp L of an illuminating system 2.

The illuminating system 2 has a first movable system comprising the lamp L and a reflecting mirror M 21 second movable system comprising reflecting mirrors M and M a stationary system comprising an imageforming lens 3 and a reflecting mirror M and an exposure slit 4 for projecting the reflected light from the surface of the document to an exposure station E. As described in detail in Japanese Pat. Publication No. 6647/ 1 964, the first movable system travels at a velocity of v while the second movable system travels at a velocity of v/2 so that the reflected light from the surface of the document illuminated by the lamp L is projected, by means of the first and second movable systems and the reflecting mirror and lens of the stationary system, onto a flexible photosensitive element P moving at the same velocity v in synchronism with the first movable system so as to form an electrostatic latent image on the photosensitive element P.

A suction box 5 has at its one end an inlet portion 5a where a stock roller 6, serving to fix one end of the photosensitive element P, is removably mounted. The suction box 5 has at the'other end thereof an exhaust fan 7 or like suction means, with cloth 5b such as silicone cloth adhered to the inner surface of the box.

The flexible photosensitive element P has one end se cured to the stock roller 6 and the other end secured to a take-up roller 8 which is always urged by an unillustrated spiral coiled spring or the like toward a direction to wind up the photosensitive element P. A guide roller 9 positioned between the stock roller 6 and the take-up roller 8 defines the path of movement of the photosensitive'element. A drive roller 10 is out of contact with the'photosensitive face of the element P but is in elastic contact with the widthwise opposite edges of the element P or with the opposite ends of the guide roller 9 and rotates the roller 9 to drive the photosensitive element P at the same velocity as the first movable system in synchronism with the exposure making operation of the illuminating system 2.

The drive roller 10 rotates in the normal direction to advance the photosensitive element P in synchronism with the first movable system and rotates in the reverse direction upon completion of a transfer operation to move the element P backward. Alternatively, upon completion of the transfer operation, unillustrated electromagnetic means or suitable mechanical means may separate the drive roller 10 from the photosensitive element P or from the guide roller 9 as shown in FIG. 2(b) to permit the photosensitive element P to be returned by the suction of the suction box 5.

In the case where a photosensitive element in the form of a roll is used, the stock roller 6 is formed with a cavity for accommodating the unused portion (with fresh photosensitive face) of the element and the takeup roller 8 is formed with a cavity for housing the used portion (with deteriorated photosensitive face) of the photosensitive element. The rollers are provided with slits for paying out and for drawing in the photosensitive element respectively, the slits having means for securing the opposite ends of the operative portion of the photosensitive element respectively. When the operative portion (i.e. the portion in use) gets fatigued or deteriorated, the deteriorated portion is wound up into the take-up roller 8, with a fresh photosensitive portion paid out from the stock roller 6. Such winding and unwinding operations can be conducted by any desired means automatically or manually.

Disposed along the path of advance of the photosensitive element P are a charger 11 for charging the photosensitive element P electrostatically, the aforementioned exposure station E, a transfer belt 12 for moving copy paper at the same speed as the photosensitive element in snug-fit pressing contact with the element so that an electrostatic latent image formed on the surface of the photosesitive element by exposure may be transferred onto the copy paper, and transfer rollers 13 and 14 supporting the belt 12. A roll of copy paper 15 is cut to a predetermined copy size by a cutter 16 and pressed by the belt 12 against the surface of the photosensitive element P for the transfer of the electrostatic latent image.

The copy paper bearing the electrostatic latent image thereon is separated from the photosensitive element P by a separator 17, led to developing means 18 for development, passed under a heater 19 by a fixing belt 19a and sent out from the frame through a copy outlet 20.

The photosensitive element is driven in the following manner. When an unillustrated main switch is closed, the exhaust fan 7 is driven to exhaust the air from the suction box 5, with the result that the photosensitive element P is drawn into the box along its inner wall as shown in FIG. 1 (by solid line) and FIG. 2(a) and thereby subjected to predetermined tension.

The document B is placed on the table 1 and an unillustrated start switch is depressed, whereupon the lamp L is lighted and the first and second movable systems of the illuminating system 2 are initiated into travel from the solid line position in FIG. 1 toward the broken line position while maintaining the aforesaid relationship therebetween. At the same time, the photosensitive element P is driven in synchronism with the first movable system against the suction of the box 5. Thus the charging, exposure and transfer of the image are conducted and the element P is wound up on the takeup roller 8.

In the case where the copy is of a maximum size set for the copier of FIG. 1, the image transfer operation will be completed upon the first and second movable system and the photosensitive element P reaching the broken line position of FIG. 1. At this time the photosensitive element P has reached the broken line position of FIG. 1 (i.e. the position shown in FIG. 2(b) Upon completion of the copying operation, the drive roller 10 is driven in the reverse direction to return the photosensitive element P or, as shown in FIG. 2(b), the

2(a) by the suction of the box 5 against the biasing force acting on the take-up roller 8. The biasing force of the spiral coiled spring acting on the take-up roller 8 is of course set at a lower level than the suction of the I box 5. Further during the return movement of the photosensitive element P, the transfer belt 12 is of course released from the photosensitive surface.

The first and second movable systems of the illuminating system 2 are returned to the solid line position of FIG. 1 simultaneously with the completion of the image transfer operation or upon completion of exposure.

If the copy size is smaller than the maximum size designed for the copier, the movable systems and the photosensitive element are stopped when they have travelled a distance corresponding to the smaller copy size before reaching the broken line position of FIG. 1 and are then returned to the respective solid line positions.

' The silicone cloth5b provided on the inner wall of the suction box 5 serves to automatically clean the photosensitive surface of the element P by sliding contact therewith during the movement of the element P, eliminating the need to incorporate a special cleaner in the copier to simplify the construction. The cloth further serves to protect the photosensitive surface from scratching.

If the photosensitive element P is adapted to be returned by the suction of the box 5, it becomes possible to greatly simplify the mechanical construction required for the quick return of the element P. The suction box prevents the lateral deflection of the photosensitive element with its side wall during the reciprocal movement of the element so as to enable the element to advance straight. The suction box 5 further serves to guide the photosensitive element with its upper wall and eliminates the vertical shake or the photosensitive element along with the guide roller 9.

If the stock roller 6 and the take-up roller 8 are designed to be removably mounted in place, the assembly .of the rollers including the roll of photosensitive element P accommodated in the stock roller 6 may be constructed in the form of a cassette, this making it possible to replace the photosensitive element P very easily and quickly. Since the tension acting on the photosensitive element during the copying operation is very small, the element is almost free of fatique and deterioration due to the tension. Thus one photosensitive surface is able to conduct several tens of thousands of copying cycles. If the roll of photosensitive element loaded in the stock roller is so adapted that a fresh photosensitive portion can be paid out when the preceeding portion gets fatigued, one roll of photosensitive element will be able to perform hundreds of thousands of copying cycles, with troubles reduced for the replacement of the photosensitive element.

FIG. 3 shows an electrophotographic copier of the electrostatic image transfer type as described in which a suction box 30 has two reduced pressure chambers 31 and 32. A stock roller 6 is positioned at an inlet portion 31a of the first reduced pressure chamber 31 and a take-up roller 8a is disposed at an inlet portion 32a of the second reduced pressure chamber 32. The rollers are removably but fixedly mounted in place. In this embodiment, the take-up'roller 8a need not be provided with a spiral coiled spring or the like for winding up the operative photosensitive portion during the advance of the element as in the embodiment of FIG. 1. During the reciprocal movement of the photosensitive element, the take-up roller 8a remains stationary against rotation. The same parts as those shown in FIG. 1 are referred to by the same reference numerals.

The suction box 30 is divided by a partition wall 30a into upper and lower sections, i.e. into the first reduced pressure chamber 31 and second reduced pressure chamber 32, and both chambers 31 and 32 are given suction by a common exhaust fan 7 through passages 31b and 32b. Cleaning cloth 320 such as silicone cloth is adhered to a portion to be in sliding contact with the photosensitive surface of the element P. The stock roller 6 and the take-up roller 8a are disposed at the inlet portions 31a and 32a of the first and second reduced pressure chambers 31 and 32 respectively. The photosensitive element P held at its opposite ends to the rollers 6 and 8a has a portion thereof to be exposed passed around guide rollers 9 and 21 and is driven forward by a drive roller 10. Between the guide rollers 9 and 21, the photosensitive element P is in contact with a transfer belt 12.

FIG. 4 shows the suction box 30 of FIG. 3 as it is incorporated in a frame A of an electrophotographic copier of the powder image transfer type to apply this invention to the copier. The parts similar I to those shown in FIG. 3 are referred to by the same reference numerals.

Disposed along the path of movement of the photosensitive element P are a transfer charger 22 in place of the transfer belt of FIG. 3 and a developing and cleaning box 23 in place of the developing means. The developing and cleaning box 3 is supported on the frame A in upwardly and downwardly movable manner. During the advance of the photosensitive element P, developing means 24 is rotated at the illustrated position near the path of movement of the photosensitive element P to supply toner from a toner feeder 25 to the photosensitive element P to form an electrostatic latent image on the photosensitive surface into a visual powder image. The visual image is then transferred by the transfer charger 22 to copy paper. The copy paper with the transferred image thereon is carried by a belt 26a to fixing means 26 for fixing and then sent out from the frame through the copy outlet 20.

During the backward movement of the photosensitive element P, the developing and cleaning box 23 is moved upward as indicated by the arrow to bring a cleaner 27 to the path of movement of the photosensitive element P, and the cleaner 27 is driven to clean the photosensitive surface. The dust is drawn into a dust box 29 by a dust fan 28.

The photosensitive element P in the embodiments of FIGS. 3 and 4 is driven as illustrated in FIGS. 5(a) and (b).

As already described, the first chamber 31 and the second chamber 32 are given interior reduced pressure by the common exhaust fan 7 to draw in the photosensitive element P along their inner walls. In the illustrated embodiments, the passage 31b between the first chamber 31 and the exhaust fan 7 is larger than the passage 32b between the second chamber 32 and the exhaust fan 7 to give a greater suction to the first chamber 31 than to the second chamber 32.

When the exhaust fan 7 is initiated into operation by depressing the main switch, the photosensitive element P is drawn into the first reduced pressure chamber 31 as illustrated in FIG. (a) and is subjected to tension in contact with the inner wall face thereof under the suction of the first and second chambers 31 and 32.

The depression of the start switch causes the drive roller to rotate the guide roller 9, forcing the photosensitive element P to start from the position of FIG. 5(a) against the suction of the first chamber 31, followed by exposure and image transfer as previously described. Upon completion of the transfer operation, the element P reaches the position of FIG. 5(b) (if the copy size is maximum). More specifically, the photosensitive element P is drawn into the second chamber 32 along its inner wall. At this time, the photosensitive surface is cleaned by the cleaning cloth 32c.

Upon completion of the transfer operation, the drive roller 10 is driven reversely or is released from the guide roller 9 as shown in the drawing, whereupon the photosensitive element P is returned quickly from the position of FIG. 5(b) to the position of FIG. 5(c) inasmuch as the first chamber 31 has greater suction than the second chamber 32.

Although the foregoing construction is such that the passages 31b and 32b are different in size so as to give different suctions to the first and second reduced pressure chambers 31 and 32, the passages 31b and 32b may alternatively be provided with a changeover valve or throttle valve to give greater suction to the second chamber 32 than to the first chamber 31 during the advance of the photosensitive element P and further to give greater suction to the first chamber 31 than to the second chamber 32 during the backward movement of the element P. The drive roller 10 may then act simply to control the velocity of movement of the photosensi tive element P.

Although the foregoing embodiments have been described with respect to electrophotographic copiers of the image transfer type in which the document is held stationary and the illuminating system is movable, the present invention can likewise be embodied in the type in which the document is movable. Such modification will be included within the scope of this invention.

What is claimed is:

1. An electrophotographic copier of the image transfer type comprising:

a photosensitive element made of a flexible sheet to be used repeatedly by being driven reciprocally for each image transfer cycle,

a suction box having means for securing one end of the photosensitive element to its inlet portion and subjected to a reduced pressure in its interior by pressure reducing means, the suction box being operable to exert suction on the photosensitive element to draw in the element along the inner wall of the box upon actuation of the pressure reducing means and to thereby tension the element to a planar form at an exposure station,

means for fixedly supporting the other end of the photosensitive element,

drive means for advancing the photosensitive element along a predetermined path extending through the exposure station,

means for electrostatically charging a face of the photosensitive element,

exposure means for forming an image of an original on the charged face of the photosensitive element in the exposure station forward of the charging means to form a latent electrostatic image of the original on the photosensitive element face, and

means for transferring said latent electrostatic image from said photosensitive element to a substrate exposed to said latent electrostatic image on said photosensitive element face, said charging means, exposure means and transfer means being actuated during the advance of the photosensitive element.

2. The electrophotographic copier as set forth in claim 1 wherein the means for fixedly supporting the other end of the photosensitive element comprises a take-up roller so biased all the time as to wind up the photosensitive element in a direction opposite to the direction of suction of the suction box.

3. The electrophotographic copier as set forth in claim 1 wherein the means for fixedly supporting the other end of the photosensitive element comprises a second suction box having means for securing the other end of the photosensitive element to its inlet portion and subjected to a reduced pressure in its interior by pressure reducing means for exerting suction on the photosensitive element in a direction opposite to the direction of suction of the first-mentioned suction box, the second suction box being operable to draw in the photosensitive element along the inner wall of the box during the advance of the element.

4. The electrophotographic copier as set forth in claim 1 wherein the drive means for the photosensitive element comprises a guide roller for passing the photosensitive element thereon to define the path of advance of the same and a drive roller for defining the movement of the photosensitive element in cooperation with the roller.

5. The electrophotographic copier as set forth in claim 1 wherein the photosensitive element is a roll of flexible sheet having an unused roll portion accommodated in a stock roller mounted at the inlet portion of the suction box, another portion in use one end of which is fixedly supported on the stock roller and a used roll portion wound up on a take-up roller, the other end of the portion in use being fixedly supported on the take-up roller.

6. The electrophotographic copier as set forth in claim 5 wherein the take-up roller is rotatably supported on the frame of the copier and is so biased all the time as to wind up the photosensitive element in a direction opposite to the direction of suction of the suction box.

7. The electrophotographic copier as set forth in claim 5 wherein the take-up roller is mounted at an inlet portion of a second suction box exerting suction on the photosensitive element in a direction opposite to the direction of suction of the first-mentioned suction box.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3646866 *Jul 18, 1970Mar 7, 1972Addressograph MultigraphPhotoelectrostatic copier having a single station for simultaneously applying toner particles and cleaning the photoconductive medium
US3650622 *Mar 9, 1970Mar 21, 1972Eastman Kodak CoApparatus for control of bias potential in an electrophotographic copier
US3697160 *Apr 30, 1969Oct 10, 1972Xerox CorpContinuous imaging apparatus
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4218026 *Jun 23, 1978Aug 19, 1980Xerox CorporationPaper web buffer system
US4355882 *Feb 26, 1981Oct 26, 1982Xerox CorporationMultiple function reproduction apparatus
US4367942 *Mar 25, 1981Jan 11, 1983Fuji Photo Film Co., Ltd.Xerographic copying machine
US4396274 *Jan 29, 1982Aug 2, 1983International Business Machines CorporationElectrophotographic copier configuration
US4490033 *Apr 28, 1983Dec 25, 1984Xerox CorporationReproducing apparatus with scrolled imaging web
US4970551 *Sep 16, 1988Nov 13, 1990International Business Machines CorporationCartridge containing a reciprocating photoconductor ribbon for serial electrophotographic printing
EP0124375A2 *Apr 27, 1984Nov 7, 1984Xerox CorporationElectrostatographic apparatus
EP0124375A3 *Apr 27, 1984Nov 21, 1985Xerox CorporationElectrostatographic apparatus
Classifications
U.S. Classification399/155, 399/165
International ClassificationG03G15/18, G03G21/00, G03G15/28, G03G15/00
Cooperative ClassificationG03G15/283, G03G15/754
European ClassificationG03G15/75D, G03G15/28B