Image forming apparatus having recording material carrying means

Abstract: An image forming apparatus includes a recording material carrying member (10) for carrying a recording material (P1), the recording material carrying member (10) having a seam (10a) and being movable along an endless path; an image forming means for forming an image on the recording material (P1) carried on the recording material carrying member (10); wherein a length of the recording material measured in a direction of movement of the carrying member, a distance A between a trailing edge of a the recording material and a leading edge of the next recording material when the recording materials are continuously supplied to the recording material carrying member, and a circumferential length L of the recording material carrying member (10) substantially satisfy: L = n( l + a) (n: integer).

Description: The present invention relates to an image forming apparatus for forming an image on a recording material carried on a recording material carrying means, more particularly to an image forming apparatus for forming a multi-color image on the recording material. A color copying machine or the like having plural image forming stations is known wherein different color images are formed by the respective image forming stations, and the images are superposedly transferred onto the recording material in the form of a transfer sheet. Referring first to Figure 5, an example of such an image forming apparatus will be described, wherein PA, PB, PC and PD are black, yellow, magenta and cyan image forming stations. Below the respective image forming stations PA, PB, PC and PD, a recording material carrying means in the form of a recording material conveying belt 200 is disposed which carries the recording material (transfer sheet) P and which is movable along an endless path. Each of the image forming stations PA, PB, PC or PD has an image bearing member in the form of a photosensitive drum 100a, 100b, 100c or 100d, around which there are disposed a latent image forming station 101a, 101b, 101c and 101d, a developing station 102a, 102b, 102c or 102d, an image transfer station 103a, 103b, 103c or 103d, a cleaning station 104a, 104b, 104c or 104d. The developing stations 102a, 102b, 102c and 102d contain different color developers. The transfer stations 103a, 103b, 103c and 103d comprise image transfer means disposed within the conveying belt path. The recording material P is fed out of a sheet cassette 110 and is attracted on the conveying belt 200. It is passed through the image forming stations PA, PB, PC and PD so that the color images formed on the photosensitive drums 100a, 100b, 100c and 100d are sequentially transferred onto the recording material P by the transfer stations 103a, 103b, 103c and 103d, by which a full (four) color image is formed on the recording material P. The recording material conveying belt 200 comprises a film sheet of polyethylene terephthalate resin, polyvinylidene fluoride resin or another dielectric resin material, having opposite ends which are overlaid and bonded into an endless film sheet. Therefore, it comprises a seam 200a. The seam portion 200a has a different nature from the other portion, and therefore, if an image is transferred onto the recording material P through the seam 200a, the transfer action is not satisfactory with the result of defective images. In view of this, when the recording material P is supported on the recording material conveying belt 200, the recording materials P is supplied to the conveying belt 200 so that it is not supported on the seam 200a. However, when the apparatus is operated in a continuous mode wherein images are continuously transferred onto plural recording materials P in response to one image formation signal, and therefore, the recording materials P are continuously supplied to the conveying belt 200, a problem arises depending on the circumferential length of the conveying belt 200. It is assumed for example that the total circumferential length of the conveying belt 200 is 800 mm, that the maximum selectable size is A3 (420x297 mm) and that the A3 recording material is supplied with 420 mm in the belt moving direction. As shown in Figure 6A, in order to avoid the seam 200a, the recording material P1 is supplied to the position 40 mm away from the seam 200a, for example. If the next recording material P2 is supplied to the position 70 mm away from the trailing edge of the first recording material P1, the recording material P2 is partly on the seam 200a. Therefore, it is required that the next recording material P2 is supplied to the conveying belt 200 at the position 40 mm away from the seam 200a. Thus, the efficiency of use K (the percentage of the transfer material carrying length in the entire circumferential length of the belt) of the transfer belt 200 is: K = 420/800x100 = 52.5 % This is small with the result of a significant reduction of the number of copies per unit time in the continuous image formation mode. The inconvenience is not significantly large in the sizes other than the maximum size sheet. For example, a recording material of A4 size (210 mm in the belt moving direction) is supplied to the transfer belt 200 having a circumferential length of 800 mm. As shown in Figure 6C, three recording materials P1, P2 and P3 are supplied to the belt 200. Even in this case, none of the recording materials is on the seam 200a of the belt 200, and sufficient distances between consecutive recording materials (approximately 56 mm in this case) can be assured. The efficiency of use K is: K = (210x3)/800x100 = 78.725 % Therefore, the above-described in inconveniences do not arise. The control means of the known image forming apparatus described above controls the supply timing of the supply means such that the recording materials supplied by the supply means do not overlap the seam of the recording material carrying means so that the quality of the super imposed images on the recording materials is not impaired by the seam of the recording material carrying means. The image forming apparatus described above is regarded as the closest prior art, and the pre-characterizing clause of claim 1 is based on this known image forming apparatus. Document JP-A-57063569 discloses an image forming apparatus which comprises a photosensitive belt having a seam. When the recording material is supplied to the photosensitive belt, this supply is effected such that the recording material abuts against the seam. However, this document does not refer to the supply of the recording materials during the continuous mode of operation. Document US-A-4 860 054 discloses a copying apparatus which forms single color images. This document does not refer to an apparatus by which plural images are superimposed on each of a plurality of recording materials. In this known copying apparatus, the image forming areas on a photoconductive belt are determined such that a seam of the photoconductive belt is avoided and that the distance between the first image forming area following the seam and the consecutive second image forming area is equal to the distance between the second image forming area and the third image forming area and so on. However, the distance between the image forming areas at the seam is larger than the distances between the image forming areas at the other positions of the photosensitive belt. Therefore, the distance at these other positions does not have a maximum value. Document JP-A-54 086 344 discloses an image forming apparatus in which a seam of a photosensitive drum and a seam of a transfer belt are detected. On the basis of this detection, the start timing of the recording materials is controlled. This results in that the seams of the photosensitive drum and of the transfer belt are avoided. In this document it is not referred to copying in a continuous mode of operation. It is an object of the present invention to improve the image forming apparatus according to the pre-characterizing clause of claim 1 such that during the continuous mode of operation of the apparatus, i.e. while recording materials which have the same selected size are continuously supplied to the recording material carrying means, an improved efficiency of use of the recording material carrying means as well as a good quality of the superimposed transferred images are achieved. This object is achieved by the image forming apparatus according to claim 1. The dependent claims define further developments of the image forming apparatus according to the invention. Figure 1 shows a supply of a recording material to a recording material conveying belt in an image forming apparatus according to a first embodiment of the present invention. Figure 2 shows the same in an image forming apparatus according to a modification of the first embodiment. Figure 3 is a sectional view of the image forming apparatus according to the first embodiment. Figure 4 is a sectional view of a major part of an image forming apparatus according to a second embodiment of the present invention. Figure 5 is a sectional view of a conventional image forming apparatus. Figure 6 shows the supply of the recording material to the recording material conveying belt in the image forming apparatus according to Fig. 5. Figure 7 is a top plan view illustrating the position of the recording materials attracted on the conveying belt. Figure 8 illustrates backside contamination of the recording material. Figure 9 shows sequential operations of the image forming apparatus. Figure 10 is a first block diagram for the image forming apparatus. Figure 11 illustrates a home position detecting system for the transfer belt. Figure 12 is a second block diagram for the image forming apparatus. Referring to Figures 1, 2 and 3, the description will be made as to a first embodiment. In Figure 3, there is shown an image forming apparatus according to this embodiment, wherein PA, PB, PC and PD designate black, yellow, magenta and cyan image forming means which in the following will be designated as "image forming stations", which are arranged on a horizontal line. Below the image forming stations PA, PB, PC and PD, there is disposed a recording material carrying means formed by a conveying belt 10 movable along an endless path. The image forming stations PA, PB, PC and PD have image bearing members formed by photosensitive drums 1a, 1b, 1c and 1d, respectively. Around each of the photosensitive drums 1a, 1b, 1c and 1d, there are disposed a charger 2a, 2b, 2c or 2d, a scanner unit 3a, 3b, 3c or 3d, a developing device 4a, 4b, 4c or 4d, a transfer means formed by an image transfer charger 5a, 5b, 5c or 5d, and a cleaning device 6a, 6b, 6c or 6d. The transfer charger 5a, 5b, 5c or 5d is disposed in the transfer material conveying belt 10 travel. The transfer charger 5a, 5b, 5c or 5d is effective to transfer the toner image from the photosensitive drum 1a, 1b, 1c or 1d onto the recording material (transfer sheet) P. The recording material conveying belt 10 is made of polyurethane resin, PVdF resin, PET resin, polycarbonate resin, polyether sulfone resin, polyurethane resin or another dielectric resin material. The conveying belt 10 is in the form of a film having opposite ends which are bonded by ultrasonic wave fusing means or the like into an endless film. It is rotated at a constant speed (100 mm/sec, for example) in the direction indicated by an arrow in Figure 3 by driving rollers 11 and 11. Designated by a reference numeral 12 is a tension roller. The conveying belt 10 electrostatically attracts the recording material P and carries it through the image forming stations PA, PB, PC and PD, so that the recording material P receives images in the respective image forming stations. After receiving the images, the recording material P is subjected to the discharging operation, and is separated from the conveying belt 10 by a separation charger 13 disposed at a sheet discharge side of the conveying belt 10. At the sheet supply side of the conveying belt 10, there are a cassette 14, a pick-up roller 15, and registration rollers 16. The pick-up roller 15 and the registration rollers form a supply means for supplying the recording materials P to the conveying belt 10. At the sheet discharge side of the conveying belt 10, there is an image fixing device 17 and others. The image forming operation of the image forming apparatus will be described, taking the black color image forming station PA as an example. The photosensitive drum la is uniformly charged by a charger 2a and is exposed to image light L for the black image through a scanner unit 3a, so that an electrostatic latent image is formed on the photosensitive drum 1a. The electrostatic latent image is moved to the developing device 4a having the black toner by the rotation of the photosensitive drum la. The developing device 4a visualizes the latent image into a black toner image. The toner image is transferred onto the recording material P on the conveying belt 10 by a transfer charger 5a at an image formation position, that is, the transfer position where the toner image on the photosensitive drum 1a and the transfer charger 5a are faced to each other through the belt 10. After the image transfer, the photosensitive drum 1a is cleaned by a cleaning device 5a so that the residual toner is removed therefrom, and the photosensitive drum 1a is prepared for the next image forming operation. In the yellow image forming station PA, the photosensitive member is uniformly charged and is exposed to yellow image light L in the similar manner but at a timed relation with the image forming operation in the former image forming station PA. The latent image is developed into a yellow toner image by the developing device 4b containing the yellow toner. The yellow toner image is superposedly transferred onto the recording material P already having the black toner and conveyed by the belt 10, at an image formation station, that is, an image transfer position where the photosensitive drum 1b and the transfer charger 5b are faced to each other. In the similar manner, the magenta and cyan images are formed in the image forming station PC and PD, so that magenta and cyan toner images are formed and transferred onto the recording material P. As a result, a full-color toner image is formed on the recording material P. The recording material P is singled out by the pick-up roller 15 from the sheet cassette 14, and is supplied to the registration rollers 16, which further feed the sheet to the recording material conveying belt 10 in synchronism with the drum. The recording material P is attracted on the conveying belt 10 by the attraction charger 18 and the attraction roller 19, and is carried through the four image forming stations PA, PB, PC and PD, so that four color toner images are superposedly transferred onto the recording material P. After receiving the images, the recording material P is subjected to the operation of the separation charger 13 adjacent a discharge side end of the belt 19, and therefore, is separated from the conveying belt 10. Then, it is conveyed to the fixing device 13 where the toner image thereon is fixed into a permanent image. As shown in Figure 1, the conveying belt 10 has a seam 10a. If the recording material P is on the seam 10a, the toner image is not properly transferred onto the recording material P at the position of the seam 10a. In view of this, when the recording material P is supplied to the conveying belt 10, it must be avoided that the recording material P is on the seam 10a. If the length of the circumference of the conveying belt 10 is arbitrarily determined, the recording material P is unable to be supplied to the conveying belt 10 with a constant distance (the distance from the trailing edge of a recording material to the leading edge of the next recording material on the belt 10) in a continuous copying or printing mode, when a maximum size recording material P is used. Therefore, the circumferential length L of the recording material conveying belt 10 and the constant distance a substantially satisfy: L = n( l +a) where l is the length of the maximum selectable size of the recording material P measured in the conveying belt movement direction, a is said distance between consecutive recording materials P, and n is an integer. By doing so, the above-described inconveniences can be avoided. In order to avoid the possibility of sheet jamming or the like, the distance a is preferably not less than 50 mm. If, for example, l = 420 mm, a = 70 mm, n = 2, and L = 980 mm (maximum selectable recording material P: A3), the recording material P1 is supplied to the recording material conveying belt 10 to the position 40 mm away from the seam 10a so as to avoid the seam 10a, as shown in Figure 1A. Then, as shown in Figure 1B, the next recording material P2 is supplied with an interval (at a distance) of 70 mm from the trailing edge of the first recording material P1. Then, the second recording material P2 is not on the seam 10a of the belt 10. Accordingly, the efficiency K of use of the conveying belt 10 is: Thus, the recording material conveying belt 10 is efficiently used. In addition, the number of image formations on the recording materials P per unit time is increased in the continuous operation mode. Because of the improvement of the use efficiency K of the conveying belt 10, the image formation speed in the image forming stations PA, PB, PC and PD can be reduced, including the rotational speed of the conveying belt 10, and therefore, the size and cost of the apparatus can be reduced. The conveying belt 10 is usable not only with the A3 size sheets but also with ledger size (17x11 inch) relatively frequently used in U.S.A., if the distance a is 58.2 mm in the continuous mode with sufficiently high use efficiency K of the conveying belt. When an image is formed on the recording material P having an A4 size ( l = 210 mm), using the above-described conveying belt 10, with a distance a of 116 mm and n equal to 3, use efficiency K of the belt 10 is: therefore, the efficiency slightly lowers. If the circumferential length of the conveying belt 10 is 1080 mm; l = 420 mm; a = 120 mm; and n = 2, as shown in Figure 2A, then the use efficiency K for A4 size is: K = 420x2/1080x100 = 77.8 % This is still slightly lower, but when the images are continuously formed on the recording material P having the size of A4 ( l = 210 mm) using this conveying belt 10, the distance is one half the distance in the case of A3 size as shown in Figure 2A, a = 60 mm, then n = 4, and the use efficiency K is: Thus, the efficiency is improved. Thus, when the images are formed in the continuous mode using a recording material conveying belt 10, on a recording material P having a size which is one half the maximum selectable size, the distance a is set to approximately 50 mm (minimum limit), and the distance is approximately one half the distance for the maximum size of the recording material. By doing so, even in the case of the continuous mode for the maximum selectable size recording material P, the efficiency K of use of the recording material conveying belt 10 can be maintained at a substantially high level. Referring to Figure 4, the description will be made as to the second embodiment. The same reference numerals as in the first embodiment are assigned to the elements having the corresponding functions. In this embodiment, a transfer drum 30 replaces the recording material conveying belt in the first embodiment and forms the recording material carrying means of the second embodiment. In Figure 4, outside the transfer drum 30, there are disposed black, yellow, magenta and cyan image forming stations PA, PB, PC and PD to constitute a multi-color image forming apparatus. At the sheet feeding side of the transfer drum 30, there are disposed a sheet supply cassette 14, a sheet pick-up roller 15, registration rollers 16, an attraction charger 18 and an attraction assisting roller 19. At the sheet discharge side of the transfer drum 30, there are disposed a separation charger 20, a separating pawl 21 and an image fixing device 17. The recording material P is supplied to the transfer drum 30 by the sheet cassette 14, the pick-up roller 15 and the registration roller 16 and is charged by an attraction charger 18 and is attracted and supported on the outer surface of the transfer drum 30 by the grounded attraction assisting roller 19. Through the rotation of the transfer drum 30, the black, yellow, magenta and cyan toner images are superposedly transferred onto the recording material P by image forming stations PA, PB, PC and PD. After the image transfer, the recording material P is discharged by the separation charger 20, and is separated from the transfer drum 30 by a separation pawl 21. It is then fed to the fixing device 17 where the superposed toner images are heated and fixed on the recording material P so that they are fused and mixed into a full-color image. The outer surface of the transfer drum 30 is provided by a film sheet 31 made of the same material as the conveying belt 10 of the first embodiment. The sheet 31 is in the form of an endless sheet with a seam 31a and mounted on opposing rings made of metal or the like. The recording material P is attracted and supported on the film sheet 31. It is therefore desirable that the recording material P is supplied to the transfer drum 30 in the manner that the recording material P is not on the seam 31a. Also in this embodiment, the following is satisfied; L = n( l + a) where l is a length of the maximum selectable size of the recording material P measured in the direction of the transfer drum 30 rotation, a is the distance between consecutive recording materials, and n is an integer. By determining the circumferential length (L) of the transfer drum 30 and the distance a in the above manner, the film sheet 31 can be efficiently used, and in the continuous mode, the number of image formations on the recording material P per unit time is increased. In the image forming apparatus of Figures 3 and 4, it is desirable to determine the distance a in accordance with the sizes of the recording materials so as to satisfy the above condition for all of the sizes of the recording materials selectable with the apparatus. Given distances a for various selectable sizes in the case of the circumferential length L of 1600 mm. Figure 7 shows the positions of the recording material P on the conveying belt 10 in the first embodiment. In this Figure, the conveying belt 10 is expanded. The distance a is 110 mm which is slightly long. However, in the continuous mode, the position of the recording material attracted on the conveying belt 10 is the same, and therefore, the backside of the recording material is not contaminated. The contamination at the back of the recording material will be described. A second recording material is not always supported on the conveying belt exactly at the same position as the first recording material. It is possible that the second recording material is supported with deviation from the first recording material supported position with some overlapping. Because of the toner attraction in the recording material interval region, which will be described hereinafter, the second and subsequent recording materials are contaminated at the back sides thereof. The causes of the backside contamination are as follows: (1) Deposition of suspending toner In addition to the toner deposited to the photosensitive drum 1 (1a to 1d) during the developing operation or the like from the developing device 4 (4a to 4d), there is toner scattered from the developing device by the centrifugal force due to the developing sleeve rotation or the like. The cleaning device 6 (6a to 6d) has the function of removing the residual toner from the photosensitive drum 1 and collect it. However, the toner removed from the photosensitive drum is not completely collected in the container of the cleaning device, but a slight amount of the toner scatters. These toner particles fall on the conveying belt 10 and cause the backside contamination. (2) Deposition of fog toner (i) In the case wherein the developing operation is carried out for the interval region (non-image formation area) between consecutive recording materials, the developing action occurs in the non-image formation area because of the existence, in the developer, of the toner having smaller charge or having the opposite polarity charge. (ii) In the case wherein the developing operation is not carried out for the interval region, the sleeve rotation is stopped and resumed at the edge of the non-image formation area. The movement of the developing sleeve is as shown in Figure 8(a). The toner remaining on the photosensitive drum 1 at this time is as shown in Figure 8(b). Generally, the toner contamination due to the stoppage and resumption of the developing sleeve rotation is more significant than in the case of (i). However, according to the present invention, the control is effected during the continuous image forming operation so that the recording materials are always supported on the conveying belt at the constant position, by properly setting the belt circumferential length and the recording material distance. Therefore, the backside of the recording material is not contaminated. The distance a is dependent on the size of the recording material. However, in the continuous mode, the distance a is always constant (110 mm for A4 size as shown in Table 1). The time intervals between adjacent recording materials are constant, and therefore, the operator is not threatened by the recording material discharge at different time intervals. In addition, the sequential control for the apparatus may be simplified. Figure 9 shows the sequential operations of the apparatus in the continuous mode when the size of the recording material is A4. Figure 10 is a block diagram of the control system for the image forming apparatus of this embodiment. The sequential operations are controlled by CPU 501, and the sequential operations are instructed by ROM 502. Various elements in the main assembly, such as the sheet pick-up roller, registration rollers, photosensitive drum motor, a high voltage source for supplying electric power to the chargers, are controlled by the CPU 501 through a DC controller 506, D/A converter, I/O port. The operational timing is determined by counting pulse clocks produced by the conveying belt driving motor (pulse motor) 505 by a counter 503, and by referring the counts to ROM 502 through the CPU 501. The recording material distance corresponding to the size of the recording material as defined in Table 1 is stored in a part of the ROM 502. In accordance with the size of the recording material and the number of copies to be produced which are inputted by operation keys 504 by the operator, the control is effected in the continuous mode such that the positions of the recording materials attracted on the conveying belt are at all times constant on the conveying belt. However, if the sequential operations are performed on the basis only of the pulse clock signals produced by the belt driving motor 505, there is a possibility of a problem particularly when the strict control accuracy is required or when a number of copies or prints which can be set by the operator by one input is large, because the number of the produced clockpulses involves approximately ±0.5 % at the maximum. Therefore, a light blocking plate 30 can be provided to detect the home position of the conveying belt 10 by a photosensor 508 at every rotation. On the basis of the detection, the pulse clock from the belt driving motor 505 is reset for every one rotation of the transfer belt. Figures 11A and 11B show the detecting method. Figure 11(a) is a top plan view of the transfer belt 10, and Figure 11(b) is a partial sectional view thereof. In this embodiment, the detecting means is an optical type using a photosensor, but it is not limiting, and the electric, magnetic or the like type is usable. Figure 12 is a block diagram of this embodiment. The pulse clock supplied from the belt driving motor 505 is counted by the counter 503, and the count is supplied to the CPU 501. When a predetermined number of clockpulses X is counted, the one full-rotation of the conveying belt 10 is discriminated. In the case of the block diagram of Figure 10, the start of the second period is discriminated. In the case of the embodiment shown in Figure 12, the counter 503 is reset upon detection of the home position by the photosensor 508 irrespective of whether the count reaches the predetermined value X or not. Then, the count becomes "zero", and the start of the second period is discriminated. Using the block diagram of Figure 12, the further accurate operational sequence can be used as compared with Figure 10 case. The present invention is applicable to an ink jet type apparatus using image forming stations PA, PB, PC and PD having ink jet recording heads. The images are directly formed on the recording material carried on the belt 10. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the scope of the following claims.

Claims: An image forming apparatus, comprising: a recording material carrying means (10, 30) for carrying recording materials (P), said recording material carrying means (10, 30) having a seam (10a, 31a) and a predetermined circumferential length "L" and being movable along an endless path; image forming means (PA, PB, PC, PD), having a plurality of image forming positions, for sequentially forming a plurality of superimposed images on each of the recording materials carried on said recording material carrying means; supply means (15, 16) for supplying the recording materials (P) to said recording material carrying means (10, 30); a control means (501, 502) which controls a supply timing of said supply means (15, 16) such that the recording materials supplied by said supply means do not overlap the seam (10a, 31a); wherein recording materials (P) of different predetermined sizes (A4, B4, A3) can be selected; CHARACTERIZED IN THAT said control means (501, 502) controls said supply means (15, 16) such that when a plurality of recording materials (P) which have the same selected size are continuously supplied to said recording material carrying means (10, 30) to form said superimposed images by said image forming means (PA, PB, PC, PD) on the plurality of the recording materials, the recording materials (P) are supplied at substantially regular time intervals so as to satisfy a=(L/n)- 1 , irrespective of the number of said plurality of recording materials, where "a" is a distance between a trailing edge of one of said recording materials (P) and a leading edge of the next recording material, 1 is a length of the selected size of said recording material (P) measured in a direction of movement of said recording material carrying means (10, 30) and n is a maximum number of at least 2 of the recording materials (P) capable of being carried on said recording material carrying means (10, 30) during one full rotation of said recording material carrying means, wherein the number n is different depending on the length 1 . An apparatus according to Claim 1, wherein said constant distance "a" corresponding to a length "l" of a selectable size of the recording materials (P) is twice the constant distance "a" corresponding to a length "l" of recording materials (P) having half the size of the selectable size. An apparatus according to Claim 1 or 2, wherein said recording material carrying means is in the form of an endless belt (10). An apparatus according to Claim 1, wherein said image forming means (PA, PB, PC, PD) includes an image bearing member (1a to 1d) and transfer means (5a to 5d) for transferring the image from said image bearing member (1a to 1d) to the recording materials (P). An apparatus according to Claim 4, wherein said image forming means (PA, PB, PC, PD) includes plural image bearing members (1a to 1d) and transfer means (5a to 5d), and wherein plural images are formed on the same recording material (P). An apparatus according to Claim 1 or 5, wherein said apparatus is capable of forming a full-color image. An apparatus according to Claim 1, wherein said control means controls said supply means to supply a first recording material to a position away from the seam by a distance smaller than a.

Inventors: HASEGAWA TAKASHI, INOUE MASAHIRO, TAKEKOSHI NOBUHIKO, HASEGAWA, TAKASHI, INOUE, MASAHIRO, TAKEKOSHI, NOBUHIKO, HASEGAWA, TAKASHI, C/O CANON KABUSHIKI KAISHA, INOUE, MASAHIRO, C/O CANON KABUSHIKI KAISHA, TAKEKOSHI, NOBUHIKO, C/O CANON KABUSHIKI KAISHA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1991
Main classification: G03G15
IPC codes: G03G15