AN ELECTROPHOTOGRAPHIC COPYING APPARATUS

Abstract: The electrophotographic copying apparatus comprising an optical means (4) that is installed into and removed from the body (1) of said electrophotographic copying apparatus and an image-forming unit (15) that is installed into and removed from the body (1) of said electrophotographic copying apparatus, said optical means (4) being engaged with said image-forming unit (15) by positioning means (1c,4a,4c,15a) of both said optical means (4) and said image-forming unit (15), so that the position of said image-forming unit (15) with respect to said optical means (4) can be decided when said optical means (4) and said image-forming unit (15) are installed into the body (1) of said electrophotographic copying apparatus.

Description: 1. Field of the invention: This invention relates to electrophotographic copying apparatuses such as copying machines, laser printers, and the like. 2. Description of the prior art: When electrophotographic copying apparatuses such as copying machines are used for a long period of time, the photosensitive drum must be replaced, the developer must be added or replaced, the charging wires must be cleaned or replaced, the used toner must be replaced, and other such maintenance tasks must be done. Generally, these kinds of maintenance tasks take place during servicing or the like, but with the recent spread of the use of miniature copying machines, etc., some copying machines are being made in which a plurality of parts that are essential to form an image are incorporated into the body of the copying machines as a unit, and this unit can be removed from and replaced into the body of the copying machines, making it easy for the user to replace these parts. In miniaturized copying machines mentioned above, as the optical means that conveys the image of light from the document to the photosensitive drum, there is used a light-transmitting device through which light is converged (trade name, Selfoc lens), etc. This light-transmitting device is constructed so that it usually has a fixed magnification, so when the magnification of images to be obtained is to be changed, the light-transmitting device is replaced with another one with a different magnification (US-A-4632536). However, as described above, when electrophotographic copying apparatuses such as copying machines and the like are constructed so as to have an image-forming unit and an optical means that can be installed into and removed from the body of the electrophotographic copying apparatus, the relative positions of the three parts, the body of the electrophotographic copying apparatus, the image-forming unit, and the optical means, can readily shift, and when this occurs, the image that is formed is affected for the worse in terms of changes in the magnification, distortion of the image, and the like. JP-A-58139162 and FR-A-2521739 disclose a copying machine which comprises an optical means fixed to the body of the copying machine and a process kit. The position of the process kit is accurately decided with respect to the optical means by a positioning mechanism. In this way, because the said optical means is fixed to the body of the copying machine and cannot be replaced by another one with a different magnification, it is impossible for this copying machine to form images with a different magnification. Even if the said optical means were to be constructed to be removably disposed in the body of the copying machine, because the process kit partially overlies the said optical means, the said optical means could not be replaced by another one without the removal of the process kit from the said optical means at the time when changes in the magnification of images are required. According to the present invention, an electrophotographic copying apparatus having a body, an optical means in the body and an image-forming unit detachably mounted in the body, is characterised in that the optical means is also detachably mounted in the body and is provided at its opposite ends with first positioning means co-operable with second positioning means on the body and also at its opposite ends with third positioning means co-operable with fourth positioning means on the image-forming unit, whereby, upon insertion of the optical means in the body with the image-forming unit already installed in the body, the first and third positioning means are engaged respectively with the second and fourth positioning means to determine the position of said image-forming unit with respect to the optical means as well as to determine the position of the optical means with respect to the body. In a preferred embodiment, the positioning means of said optical means are projections or holes which are engageable with said positioning means of said body, which are holes or projections, respectively. The positioning means of said optical means are projections or holes which are engageable with said positioning means of said image-forming unit that are holes or projections, respectively. In a preferred embodiment, the image-forming unit comprises a housing and a photosensitive drum which is disposed in the housing of said image-forming unit. In a preferred embodiment, a processing unit is disposed around said photosensitive drum. The processing unit comprises a charging device. The processing unit further comprises a cleaning device. In a preferred embodiment, the optical means can be installed into and removed from the body of said electrophotographic copying apparatus through a hole which extends, in the longitudinal direction of said photosensitive drum, above said photosensitive drum. Thus, the invention described herein makes possible the objective of providing an electrophotographic copying apparatus in which the optical means has a positioning means by which the position of an image-forming unit with respect to the body of the electrophotographic copying apparatus is determined accurately and the positions of the optical means and the image-forming unit with respect to each other are also fixed accurately, so that the desired images can be obtained reliably. BRIEF DESCRIPTION OF THE DRAWINGS This invention is further described with reference to the accompanying drawings; Figure 1 is a sectional front view showing an electrophotographic copying apparatus of this invention, Figure 2 is an enlarged side view showing a portion of the electrophotographic copying apparatus of Figure 1, Figure 3 is a perspective view showing the installation of a light-transmitting device in the body of the electrophotographic copying apparatus of Figure 1, Figure 4 is a perspective view showing a first image-forming unit to be used in the electrophotographic copying apparatus of Figure 1, and Figure 5 is a perspective view showing a second image-forming unit to be used in the electrophotographic copying apparatus of Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows an electrophotographic copying apparatus of this invention which is an image-formation apparatus, which comprises a photosensitive drum 2 that is clockwise rotatable, a charging device 3, an optical means 4 which is a light-transmitting device by which light from a light source is converged on the photosensitive drum 2, a developing device 5, a transcription device 6, and a cleaning device 7. The above-mentioned devices 3 to 7 are disposed around the photosensitive drum 2 in this order. The charging device 3 and/or the cleaning device 7 are incorporated in a processing unit which is disposed around the photosensitive drum 2. On the body 1 of the electrophotographic copying apparatus, a document plate 8 on which a document is placed is disposed so that the document plate 8 is movable from one side to the other of Figure 1 by means of a driving mechanism (not shown). A light source 10 that radiates light onto the document is disposed below the document plate 8. On the lower portion of the body 1 of the electrophotographic copying apparatus, a paper supply cassette 11 is disposed. Copier paper (not shown) from the paper supply cassette 11 is supplied to the photosensitive drum 2 via a route of conveyance 12 for copier paper. In the downstream direction of the photosensitive drum 2, a fixing device 13 and an ejection plate 14 are further disposed. The formation of images is carried out by the use of the above-mentioned electrophotographic copying apparatus as follows: First of all, the photosensitive drum 2 is charged with static electricity at a fixed potential by the charging device 3. Then, the document that has been placed on the document plate 8 is irradiated with light from the light source 10. The light reflected from the document radiates the photosensitive drum 2 via the light-transmitting device 4, resulting in an electrostatic latent image on the photosensitive drum 2 that corresponds to the pictures and/or letters of the document. The electrostatic latent image is then developed by toner that is fed from the developing device 5, resulting in a toner image on the photosensitive drum 2. The toner image is transcribed onto a copier paper from the paper supply cassette 11 by the transcription device 6, and then fixed on the copier paper by the fixing device 13. The copier paper on which the toner image has been fixed is ejected onto the plate 14. After the toner image has been transcribed onto copier paper, any toner remaining on the photosensitive drum 2 is removed and recovered by the cleaning device 7. As shown in Figure 3, the front panel of the body 1 of the electrophotographic copying apparatus that corresponds to the inside of the front cabinet 1a has a positioning means of the light-transmitting device 4, e.g., a hole 1b, above the photosensitive drum 2, which hole is extended in the longitudinal direction of the photosensitive drum 2. When the front cabinet 1a of the body 1 of the electrophotographic copying apparatus is opened, the light-transmitting device 4 can be installed into and removed from the body 1 of the electrophotographic copying apparatus 1 through the hole 1b. In general, the light-transmitting device 4 has a fixed magnification. Thus, when changes of the magnification of images to be obtained are required, the light-transmitting device 4 with a certain magnification can be readily replaced by another light-transmitting device with a different magnification. As shown in Figure 2, the light-transmitting device 4 has positioning means, e.g., positioning pins 4a and 4b that can be engaged with positioning means, e.g., positioning holes 1c and 1d, respectively, of the body 1 of the electrophotographic copying apparatus, and positioning means, e.g., positioning pins 4c and 4d that can be engaged with positioning means, e.g., positioning holes 15a and 15b, respectively, of the first image-forming unit 15 to be mentioned below. Figure 4 shows the above-mentioned first image-forming unit 15 that comprises the photosensitive drum 2, the charging device 3, and the cleaning device 7 in the housing of the image-forming unit 15. The cleaning device 7 is provided with a used toner-ejection opening 7b that has a lid 7c. The used toner, which has been recovered by the cleaning device 7 from the surface of the photosensitive drum 2, is conveyed from the cleaning device 7 to the ejection opening 7b of a conveyance portion of the first image-forming unit 15 by means of a conveyance means 7a (Figure 1) such as a conveyance screw, and then ejected from the ejection opening 7b. The used toner is carried from the ejection opening 7b to the opening of a used toner-collecting tank 17 (Figure 5) that is a part of the second image-forming unit 18 to be mentioned below. The housing of the first image-forming unit 15 is provided with a guiding portion 15c, in the longitudinal direction of the photosensitive drum 2, below the portion of the photosensitive drum 2 that is exposed to the outside of the housing of the first image-forming unit 15. The guiding portion 15c supports the second image-forming unit 18 in a manner to guide the second image-forming unit 18 to a given position of the body 1 of the electrophotographic copying apparatus when the second image-forming unit 18 is installed into the body 1 of the electrophotographic copying apparatus. The first image-forming unit 15 is provided with a positioning hole 15d that is engaged with a positioning boss 24 of the second image-forming unit 18. The first image-forming unit 15 is fixed to the body 1 of electrophotographic copying apparatus by means of a guide-supporting means (not shown) of the body 1 of the electrophotographic copying apparatus so that the first image-forming unit 15 can be freely installed into and removed from the body 1 of the electrophotographic copying apparatus, making it easy for the user to replace the said unit by another. In order to remove the first image-forming unit 15 from the body 1 of the electrophotographic copying apparatus, the front cabinet 1a of the body 1 is opened and the light-transmitting device 4 is removed from the body 1, and thereafter the first image-forming unit 15 is removed from the body 1 of the electrophotographic copying apparatus. On the other hand, in order to install the first image-forming unit 15 into the body 1, the first image-forming unit 15 is inserted into the body 1 of the electrophotographic copying apparatus along the above-mentioned guide-supporting means of the body 1 and the light-transmitting device 4 is then inserted into the body 1 along the hole 1b of the body 1 so as to engage the positioning pins 4a and 4b of the light-transmitting device 4 into the positioning holes 1c and 1d of the body 1, so that the position of the light-transmitting device 4 with respect to the body 1 can be determined. Moreover, the positioning pins 4c and 4d of the light-transmitting device 4 are engaged with the positioning holes 15a and 15b of the first image-forming unit 15, so that the position of the first image-forming unit 15 with respect to the light-transmitting device 4, (namely, the position of the first image-forming unit 15 with respect to the body 1 of the electrophotographic copying apparatus) can be determined. Figure 5 shows the above-mentioned second image-forming unit 18, which has a developing device 5 and a used toner-collecting tank 17. The developing device 5 has a cover 21 for covering a developing sleeve 20 (Figure 1). The developing device 5 is provided with a label 22 that indicates the color of toner that is used for the formation of images. The indication of the label 22 can be seen through the window that is formed on the front cabinet 1a of the body 1 of the electrophotographic copying apparatus. On the used toner-collecting tank 17, a slidable shutter 23 is disposed. The shutter 23 is closed while the second image-forming unit 18 is being removed from the body 1 of the electrophotographic copying apparatus, so that leakages of the used toner from the tank 17 can be prevented. The shutter 23 is slid in the arrow direction to open while the second image-forming unit 18 is being installed into the body 1, so that the opening of the tank 17 faces the opening 7b (Figure 4) of the cleaning device 7 of the first image-forming unit 15. The second image-forming unit 18 (Figure 5) has a positioning boss 24 by which the position of the said second image-forming unit 18 with respect to the first image-forming unit 15 is fixed, a lock projection 25 by which the second image-forming unit 18 is fixed to the body 1 of the electrophotographic copying apparatus, and a grip 26 that the user grasps while the second image-forming unit 18 is being installed into the body 1 of the electrophotographic copying apparatus. The second image-forming unit 18 is installed into the body 1 of the electrophotographic copying apparatus as follows: First of all, the first image-forming unit 15 is installed in the body 1 of the electrophotographic copying apparatus. Then, the cover 21 of the second image-forming unit 18 is opened to expose a magnet brush that has been formed on the surface of the developing sleeve 20, and the second image-forming unit 18 is inserted into the body 1 of the electrophotographic copying apparatus along the guiding portion 15c of the first image-forming unit 15. Then, the positioning boss 24 of the second image-forming unit 18 is engaged with the positioning hole 15d of the first image-forming unit 15 so that the position of the second image-forming unit 18 with respect to the first image-forming unit 15 is precisely fixed. Moreover, the second image-forming unit 18 is fixed to the body 1 of the electrophotographic copying apparatus by means of the locking projection 25 of the second image-forming unit 18. When the second image-forming unit 18 is removed from the body 1 of the electrophotographic copying apparatus, the same operation as mentioned above is performed in the reverse order. The guiding portion 15c and the positioning hole 15d of the first image-forming unit 15 function to fix the position of the second image-forming unit 18 with respect to the first image-forming unit 15, so that the position of the magnet brush, which has been formed on the surface of the developing sleeve 20, with respect to the surface of the photosensitive drum 2 can be fixed accurately. When a copying operation is to be carried out with a colored toner different from the colored toner that has been used previously for the formation of images, the second image-forming unit 18 with the developing device 5 is only replaced by another one. In this way, because the replacement of both the first image-forming unit 15 and the light-transmitting device 4 is unnecessary even when a copying operation with a colored toner different from that of the previous copying operation is needed, such a copying operation can be readily performed. Although the above-mentioned example only discloses the application of this invention to a copying machine, this invention is applicable to electrophotographic copying apparatuses such as laser printers and other types of electrophotographic copying and printing machine.

Claims: An electrophotographic copying apparatus having a body (1), an optical means (4) in the body (1) and an image-forming unit (15) detachably mounted in the body (1), characterised in that the optical means (4) is also detachably mounted in the body (1) and is provided at its opposite ends with first positioning means (4a, 4b) co-operable with second positioning means (1c, 1d) on the body (1) and also at its opposite ends with third positioning means (4c,4d) co-operable with fourth positioning means (15a, 15b) on the image-forming unit (15), whereby, upon insertion of the optical means (4) in the body (1) with the image-forming unit (15) already installed in the body (1), the first and third positioning means (4a,4b; 4c,4d) are engaged respectively with the second and fourth positioning means (1c,1d; 15a,15b) to determine the position of said image-forming unit (15) with respect to the optical means (4) as well as to determine the position of the optical means (4) with respect to the body (1). An electrophotographic copying apparatus according to claim 1, wherein said first positioning means (4a, 4b) of said optical means are projections or holes which are engageable with said second positioning means (1c, 1d) of said body which are holes or projections, as the case may be. An electrophotographic copying apparatus according to claim 1 or 2, wherein said third positioning means (4c, 4d) of said optical means (4) are projections or holes which are engageable with said fourth positioning means (15a, 15b) of said image-forming unit (15), which are holes or projections, as the case may be. An electrophotographic copying apparatus according to claim 1, 2 or 3, wherein said image-forming unit (15) comprises a housing and a photosensitive drum (2) therein. An electrophotographic copying apparatus according to claim 4, wherein a processing unit is disposed around said photosensitive drum (2). An electrophotographic copying apparatus according to claim 5, wherein said processing unit comprises a charging device (3). An electrophotographic copying apparatus according to claim 5 or 6, wherein said processing unit comprises a cleaning device (7). An electrophotographic copying apparatus according to claim 4, 5 or 6, wherein said optical means (4) is installed into and removed from the body (1) through a hole (1b) which extends, in the longitudinal direction of said photosensitive drum (2) above said photosensitive drum.

Inventors: YOSHIURA, SYOICHIRO
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1988
Main classification: G03G15
IPC codes: G03G15, G03G21