GB2189438A - Electrophotographic printer - Google Patents

Description

GB 2 189 438 A

SPECIFICATION printer embodying the invention;

Figure 10 is a plan view in cross-section of the Electrophotographic printers printer shown in Figure 9; and Figure 11 is a schernaticfront elevation of a The present invention relates to electrophotographic 70 previously proposed printer.

printers. A previously proposed printer is shown in Figure In recentyears, page printers typified by laser 1 twhere an electrifier 2, an optical write head 3, a printers are gaining greater popularity in the market developer4, a transfer device 5, a fixing device 6, a of printers because of their quietness in operation, charge remover7 and a cleaner 8 are disposed high speed, and high print quality. Most of the page 75 around a photosensitive drum 1 Whose width printers rely on electrophotography. corresponds to the width of paper on which Page printers are expected to gain higher characters are printed. The printerfurther includes a acceptance in the market of printers because of their paperfeed cassette 9 and a paperwithdrawal tray 10.

quietness in operation, high speed, and high print When characters areto be printed,the drum 1 which quality. Printers of this kind are large in size and 80 is being rotated in the direction indicated bythe expensive. Therefore,these problems are arrowA is uniformly electrically charged bythe considered as obstaciesto wider acceptance of the electrifier 2. Then, thewrite head 3forms an printer in the market. Especially, it seems doubtful electrostatic latent image on the drum 1 atthe whethercheap personal page printers enjoywider position of the head 3, the image corresponding to acceptance. 85 the pattern to be printed. The developer4 applies It is an object of the present invention to provide an tonerto those portions of the surface of the drum 1 improved electrophotographic printer. which are electrostatically charged, in orderto The printer embodying the invention to be develop the image. When the drum 1 reaches the described comprises a photosensitive belt having a position of the transfer device 5, the electrostatic width narrowerthan paper on which characters are 90 attracting force of the transferdevice 5 transfers the printed, a meansfor carrying the belt, and another toner image on the drum 1 to paper 11. The image on means for carrying the paper in a direction in which the paper is then fixed to the paper by heat or the belt is carried. pressure using the fixing device 6. Afterthe drum 1 In the operation of this printer, a latent image is passes across the transfer device 5,the electric formed on the photosensitive belt by 95 charge remaining on the drum 1 is removed bythe electrophotography such that the width of the image charge remover 7. Subsequently, the toner still is equal to the width of the paper. The latent image is adhering to the drum 1 is removed by the cleaner 8.

moved to a position where itfaces the paper. Then, Thus, one page of print process is completed.

the whole image is transferred to the paper at a time. In the electrophotographic page printertypified by Another latent image is transferred while the paper is 100 a laser printer, however, the width of the caused to move a distance equal to the width of the photosensitive drum 1 corresponds to the width of belt. When the paper and the latent image arefully the paper and so the sizes of all other components moved, the whole image is transferred to the paper which are used for electrophotography and disposed at a time. Subsequently, this series of operations is around the drum are also required to correspond to repeated to print characters. 105 the width of the paper. This has made the printer Electrophotographic printers embodying the bulky and has rendered the drum 1,the head 3,the present invention will now be described, byway of developer 4, the fixing device 6, and the cleaner8 example, with referenceto the accompanying large; hencethey have been expensive.

diagrammatic drawings, in which: In the electrophotographic printer shown in Figure 1 is a fragmentary vertical cross-section of 110 Figures 1 to 4 all of the components of the printer an electrophotographic printer embodying the which are used in electrophotography are housed in invention; a cartridge 20 made from synthetic resin, exceptfor a Figure2 is a fragmentaryfront elevation partially fixing device.

in cross-section of the printer shown in Figure 1; Referring particularlyto Figures 1-3, a Figure 3 is a fragmentary side elevation in 115 photosensitive endless belt 21 has two lateral end cross-section of the printer shown in Figures 1 and 2; portions on to which no information is to be written.

Figure 4 is a schematic side elevation of the printer These end portions are supported by guide rollers shown in Figures 1-3, for showing the whole 22, and are driven in the direction indicated bythe arrangement; arrowAwithin the cartridge by means of a driving Figure 5is a view similarto Figure 1, butshowing 120 roller23. An electrifier 24 in theform of a corona another electrophotographic printer embodying the discharge device uniformly electrically chargesthe invention; belt 21. An electrostatic latent image isformed onthe Figure 6is a fragmentary front elevation in electrically charged belt 21 by a head 25 carrying an cross-section of the printershown in Figure 5; array of LEDs, in accordancewith a print pattern Figure 7is a fragmentary side elevation in 125 supplied from a controller (not shown). A plurality of cross-section of the printer shown in Figures 5 and 6; light-emitting sections are arranged on the head 25 Figure 8 is a vertical cross-section of a further in a direction perpenclicularto the direction in which electrophotographic printer shown in Figures 5-7; the belt 21 moves. A developing device 26 develops a Figure 9 is a front elevation partially in latent image on the belt 21. Toner 27 adheres to the cross-section of a still other electrophotographic 130 latent image on the belt, and the image is developed.

2 GB 2 189 438 A 2 Thereafter, the belt 21 is shifted via a large roller 28 to determined, depending on the width of the belt 21.

a position 29 at which the toner image is transferred Therefore, they are smaller in size than conventional to a sheet of paper 32. Specifically, when the front devices. Hence, the novel electrophotographic end of one line of characters arrives atthetransfer printer can be made cheaper and smaller in sizethan position 29, a transfer device30 isturned OFFto 70 the conventional printer. The amount of toner transfer the toner 27 on the belt21 to the paper32 transferred at a time can be increased by increasing that is inserted through a slit 31. When the transferof the width of the belt 21. This results in a higher print one line of characters is completed, the paper is speed. Consequently, it is possible to strikethe caused to move a distance corresponding to the optimum compromise between the print speed, the distance between neighbouring lines of characters. 75 cost, and the size. Also in the present example,the Atthe same time, the belt 21 having the developed LED head 25 is employed. Obviously, a head using a latent image is moved across thetransfer position 29 laser or LCD may be applied with similar utilityto the over a distance corresponding to one line of invention.

characters, followed bythe nexttransfer. A partition Referring nextto Figures 5-7, there is shown wall 33 is provided to preventthe transfer device 30 80 another electrophotographic printer embodying the from attracting the toner 27 that is on the opposite invention. This printer has a cartridge 60 that is side of the device 30 when a transfer operation is similarto the cartridge 20 described already. In the performed. printer shown in Figures 1-4, the toner 27 is stuckto Afterthe belt 21 undergoes the transfer operation, the inner su rf ace of the belt 21 duri ng a developing the electric charge remaining on the belt 21 is 85 operation. In the printer shown in Figu re 5, toner 27 removed bya charge remover34. Subsequently, the is stuckto the outer surface of the belt21.The toner27 adhering tothe belt21 is removed bya photosensitive belt21,the guide roller22, andthe cleaner 35 consisting of a roll 35a of sponge,a large roller28 are combined into a unit.This unitcan magnet roll 35b and a blade 35c. The toner 27a be readilyand detachably mounted to the cartridge removed bythe cleaner35 is addedto unusedtoner 90 60.As clearlyshown in Figures 6 and 7,thetoner27 27bwithin a toner cartridge 36 by a stirrer37 sothat is supplied obliquelyfrom abovethe belt21.The the toner 27a may be reused. The belt 21 from which paper 32 is moved in the same manner as in the first the remaining toner 27 has been removed is embodiment described in connection with Figures uniformly charged bythe electrifier 24. Then, the 1-4.

printer starts the second electrophotographic 95 Afurther printer embodying the invention is process. shown in Figure 8. A cartridge for use in A paperfeed operation and a fixing operation are electrophotography is indicated by reference now described by referringto Figure 4, where said numeral 70. In the present example, fourtoners, i.e.

cartridge for electrophotography is also indicated by cyan (C), magenta (M), yellow (Y), and black (B), are reference numeral 20. Paper 32 is transported by 100 used. Developing devices 71 C, 71 M, 71 Y, 71 B, toner paperfeed rollers 38 and 39 into a location where a cartridges 72C, 72M, 72Y, 72B and heads 73C, 73M, transfer operation is performed. The paper is placed 73Y, 73B are provided, corresponding to the four in that location by a paper locating plate 40. Toner 27 toners, respectively. Each of the heads comprises an istransferred to the paper32which has been placed LED, and these heads are operated in a serial in that location. After the transfer of one line of 105 manner. An electrifier74 servesto uniformly characters is completed,the paper32 and the belt 21 electrically charge a photosensitive belt75 which is are caused to move a minute distance in the direction driven in the direction indicated bythe arrow A by a indicated bythe arrow B, by a solenoid 41, cam, or driving roll 76. Afterthe belt 75 is electrically other means to peel the paper 32 off the belt 21. After charged, a pattern of latent image isformed on the the first line of characters is transferred to the paper 110 belt 75 bythe head 73c. Then, the pattern is 32 and the peeling operation is completed, the developed bythe developing device 71 cto form a solenoid 41 is de-energized to allowthe locating tonerimage.

plate 40 to be rotated about a centre of rotation 42 in Subsequently, patterns of latent image are formed the direction indicated by the arrow C by a spring 43. and developed, using magenta, yel low and black in Then, the paper is released from the locating plate 115 this order in the same man ner as the process using 40. cyan. The toner image corresponding to one line of Subsequently, the paper 32 is moved to a fixing characters is developed in this way and then moved device 44 by paperfeed rollers 38 and 39. Then,the into a position where the image is opposite to paper toner is fixed to the paper by a heating roll 45 and a 77. The image is transferred to the paper by a transfer pressure roll 46. After a sensor (not shown) senses 120 device 78. Thereafter,the belt 75 is shifted, and the thatthe front end of the paper 32 enters thefixing electric charge remaining on the belt 75 is removed device 44,the paperfeed rollers 38 and 39 cease to by a charge remover 79. Subsequently, thetoner drive the paper. Then, the paper is carried bythe remaining on the belt 75 is removed by a cleaner80 fixing device 44 and paperwithdrawal rolls 48 and comprising a roll 80a of sponge, a roll 80b of magnet, 49. These rolls 48 and 49 are disposed atthe rear of 125 and a blade 80c. The portion of the belt on which the the fixing device 44. A peeling claw 47 actsto peel the tonerwas put arrives atthe position of the electrifier paper32 off the heating roll 45. 74, and enters into the developing operation forthe In the present example, the sizes of the electrifier next line. In this way, four kinds of toners are 24, the LED head 25, the developing device 26, the successively transferred to the paperfor each line of charge remover 34, the cleaner 35, etc. are 130 characters. One line feed is effected over the paper 3 GB 2 189 438 A 3

Claims (2)

1. 77 in the same manner as in the first embodiment. Claim 1, wherein the

   belt is an endless belt and

   The cartridge 70 is connected with the body of the moved within a cassette in which the various printervia connector portions 81 and 82, and can be components excluding a fixing device are housed.

   quickly detached from it. In the printer shown in 3. An electrophotographic printer according to Figure 8, a toner image is formed on the outer 70 Claim 1 orto Claim 2, wherein the widths of various surface of the belt 75. Of course, a toner image may components including an electrifier, a write head, a be formed on the inner surface of the belt. developing device, a charge remover, and a cleaner Referring to Figures 9 and 10, there is shown a yet correspond to the width of the belt.

   other printer embodying the invention. This printer 4. An electrophotographic printer according to is equipped with a plurality of cartridges 90 which 75 Claim 2, wherein said cassette includes a plurality of are similar in function to the cartridge 60 shown in developing devices, an equal number of toner Figures 5-7. These cartridges 90 are arranged in the cartridges charged with different kinds of toners, and direction in which the paper 32 is moved. The an equal number of write heads.

   cartridges 90 are charged with different toners, i.e. 5. An electrophotographic printer according to cyan (C), magenta (M), yellow (Y) and black (B), 80 anyone of Claims 1 to 3, including a plurality of respectively. A transfer operation is performed for cartridges charged with toner of different colours are each cartridge 90 while the paper 32 is being shifted arranged in the direction in which the paper is bythe paperfeed roller 38. Fourtransfer operations moved.

   are performed for each line. Then, the toner image is 6. An electrophotographic printer substantially fixed to the paper by a fixing device 44. In this way, 85 as hereinbefore described, with reference to Figures characters are printed in several colours. Each 1 to 4,5 to 8 or9 and 10 of the accompanying cartridge 90 has a connector portion 91. A gear92for drawings.

   driving the belt 21 is mounted above a motor gear93 so as to be capable of engaging the gear93.

   Therefore, the cassettes can be easily and quickly Printed for Her Majesty's Stationery Office by Croydon Printing Company (UK) Ltd,9187, D8991685.

   mounted and detached. Hence, the user can buythe Published byThe PatentOffice,25 Southampton Buildings, LondonffiC2A lAY, printer, togetherwith only one cartridge to curtail the from which copies maybe obtained.

   expenditure first. In this case, the printer is used as a monochromatic printer. Later, he or she can buy additional cartridges which permitthe printerto be employed as a multicolour printer.

   In the printershown in Figures 9 and 1 0,the cartridges 90 are separable. Obviously, it is also possibleto mould the four cartridges 90 as a unitand to combine theshafts of the rollers for driving the r belt into a unit. In this case, characters can be printed in several colours. Also,the cartridge 20 shown in Figures 1-4 may also be employed as each of the cartridges 90.

   As can be understood from the description thusfar made, the novel printer comprises a photosensitive belt having a width narrowerthan paper on which characters are printed, a means for carrying the belt, and another means for carrying the paper in a direction perpendicularto the direction in which the belt is carried. The devices used for electrophotography are fabricated so thattheirwidth corresponds to the width of the photosensitive belt. Consequently, these devices can be made in small sizes. Thus, the electrophotographic printer can be manufactured economically and in small size. Also, since these devices for electrophotography are small in size and inexpensive, multicolour printing can be readily achieved.

   CLAIMS 1. An electrophotographic printer comprising: a photosensitive belt having a width substantially narrowerthan the width of a sheet on to which characters are to printed; a means for displacing the belt; and another means for displacing the sheet in a direction perpenclicularto that in which the belt is carried.
2. 2. An electrophotographic printer according to