Patent Application
20090175649
This application claims the benefit of Korean Patent Application No. 2008-0002167, filed on Jan. 8, 2008 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an image forming apparatus, and, more particularly, to a color image forming apparatus, which includes a plurality of photosensitive members, upon each of which is formed a visible image, whereby a visible color image can be formed by overlapping visible images of different colors formed on the respective photosensitive members.
2. Description of the Related Art
In general, an image forming apparatus is an apparatus to develop a black-and-white image or color image on a printing medium, such as paper, according to an image signal. Examples of the image forming apparatus include laser printers, inkjet printers, copiers, facsimiles, and devices performing various combination of functions thereof. Representative image forming methods of these various image forming apparatuses include an electro-photographic method, in which an electrostatic latent image is formed on a photosensitive member via irradiation of light beam, and in which the electrostatic latent image is developed with developer and transferred onto a printing medium, and an inkjet method, in which liquid-phase ink is ejected onto a printing medium surface according to an image signal.
In an electro-photographic image forming apparatus, after charging a photosensitive member surface with a predetermined electric potential, a light beam is irradiated onto the photosensitive member, to form an electrostatic latent image by potential difference between those portions that have been irradiated and those that have not. A developer is applied to the electrostatic latent image, to form a visible image. After the visible image, formed on the photosensitive member, is transferred to a printing medium, heat and pressure are applied to the printing medium, to fix the visible image, of, e.g., powder developer, on the surface of the printing medium. In such manner, an image is recorded on a printing medium.
Broadly speaking, an electro-photographic image forming apparatus could be a monochromatic image forming apparatus to print a black-and-white image and/or a color image forming apparatus capable of printing a color image.
A color image forming apparatus is classified into a so-called multi-path type color image forming apparatus having a single photosensitive member, and a so-called single-path type color image forming apparatus having a plurality of photosensitive members corresponding to the number of developing units of different colors.
In a multi-path type color image forming apparatus, only one developing unit is operated during one revolution of the single photosensitive member, forming a single color visible image on the photosensitive member. The visible image formed on the photosensitive member is transferred before another developing unit of different color is operated. Thus, a multi-path type color image forming apparatus may be equipped with a single photosensitive member and a single light scanning device.
In a single-path type color image forming apparatus, on the other hand, different colors of visible images are sequentially formed, sometimes with a slight time difference, on the respective ones of the photosensitive members corresponding to each of the developing units. A light scanning device in a single-path type color image forming apparatus may be formed with a plurality of light passage windows corresponding to the respective photosensitive members.
When the light passage window(s) becomes contaminated with debris, for example, toner or dust particles or dirt, etc., the image quality may be adversely affected. The likelihood of such contamination increases with the increased number of light passage windows, e.g., in the case of a single-path type color image forming apparatus.
An attempt to prevent toner or dirt from a developing unit from contaminating the optical parts of a light scanning device is disclosed by Japanese Patent Laid-Open Publication No. 2000-0263839 to Susumu (“Susumu”). Susumu discloses an image forming apparatus that includes a plurality of laser beam passage windows each facing a photosensitive member, a shutter to block the passage window, a shutter mover, and a laser beam passage formed on the shutter so as to be located on an optical path of a laser beam within a movement range of the shutter, the laser beam passage located so as to be not below a developing point of the photosensitive member. The shutter is divided into a shutter for black, and a shutter for chromatic colors, which are operated independently.
However, the image forming apparatus of Susumu requires a separate drive motor to drive the shutter, and suffers from increased manufacturing costs and/or size of the image forming apparatus in order to provide a space for the drive motor.
Moreover, in the image forming apparatus disclosed by Susumu the shutter moves along a single common plane, and if the plurality of light passage windows are not likewise arranged on a single plane, there may be gaps between some of the plurality of light passage windows and the shutter. These gaps may lessen the effectiveness of the shutters in preventing contaminations of the passage windows, and are wasted dead spaces contributing to a poor space utilization.
Various aspects and advantages of the embodiments of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which:
Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. While the embodiments are described with detailed construction and elements to assist in a comprehensive understanding of the various applications and advantages of the embodiments, it should be apparent however that the embodiments can be carried out without those specifically detailed particulars. Also, well-known functions or constructions will not be described in detail so as to avoid obscuring the description with unnecessary detail. It should be noted that in the drawings, the dimensions of the features are not intended to be to true scale, and may be exaggerated for the sake of allowing greater understanding.
The image forming apparatus in accordance with the embodiment is a so-called single path type color image forming apparatus, which includes a plurality of photosensitive members, on which different colors (for example, magenta, cyan, yellow, and black) of visible images are respectively formed, whereby the visible images formed on the respective photosensitive members are overlapped with one another, to form a color image.
The image forming apparatus in accordance with the first embodiment of the present invention, as shown in
The body 10 defines the external appearance of the image forming apparatus, and supports therein a variety of elements.
The paper supply device 20 serves to supply paper S as a printing medium to the transfer device 40. The paper supply device 20 may include a paper supply tray 21, on which the paper S is loaded, a pickup roller 22 to pick up the paper S loaded on the paper supply tray 21 sheet by sheet, and a delivery roller 23 to deliver the picked-up printing medium to the transfer device 40.
Accordingly, the paper S loaded in the paper supply tray 21 is picked up sheet by sheet by the pickup roller 22, and the picked-up paper is delivered to the transfer device 40 by the delivery roller 23.
The developing device 30 may be composed of four developing units 30Y, 30M, 30C, and 30K, which receive different colors of toners, for example, yellow toner Y, magenta toner M, cyan toner C, and black toner K, respectively. It should be understood that while by way of an example four developing units are included on this embodiment, any number of developing units may be provided as needed in a particular design or application.
Each of the developing units 30Y, 30M, 30C, and 30K may include a photosensitive member 31 (i.e., respective one of 31a, 31b, 31c and 31d), having a surface on which an electrostatic latent image is formed via operation of the light scanning device 100, a charge roller 32 to charge the photosensitive member 31, a developing roller 33 to develop the electrostatic latent image formed on the photosensitive member 31 into a toner image, and a supply roller 34 to supply the toner to the developing roller 33.
The light scanning device 100 serves to irradiate light, e.g., a laser beam, corresponding to image information of yellow, magenta, cyan and black, to the respective photosensitive member 31 of the developing unit according to the image to be printed, so as to form the electrostatic latent image. The light scanning device 100 may include a light source (not shown) producing the laser beam, polygonal mirrors 101 to deflect the laser beam within a predetermined angular range, F-theta lenses 102 to scan the laser beam toward the photosensitive member at a constant speed, and reflective mirrors 103.
The polygonal mirrors 101 serve to reflect the light irradiated from the light source in a scanning direction of a desired angle. The reflective mirrors 103 serve to reflect the light reflected from the polygonal mirrors 101 toward the F-theta lenses 102. The F-theta lenses 102 are installed on optical paths of the light reflected from the reflective mirrors 103 and serve to regulate the focus of the light. The scanning light, having passed through the F-theta lenses 102, is finally directed to the photosensitive members 31 through passage windows 104. The light scanning device 100 will be described in more detail later.
The transfer device 40 may include an intermediate transfer drum 41, and a transfer roller 42 to transfer a color image formed on the intermediate transfer drum 41 to a printing medium.
Different colors of visible images, which are formed on the respective photosensitive members 31, are sequentially transferred to the intermediate transfer drum 41, so as to overlap one another, forming a color image. The transfer roller 42 serves to transfer the color image formed on the intermediate transfer drum 41 to a surface of the printing medium. Specifically, when the printing medium passes through a gap between the intermediate transfer drum 41 and the transfer roller 42, the color image is transferred to the surface of the printing medium.
The fixing device 50 serves to fix the image transferred to the paper by applying heat and/or pressure to the image. The fixing device 50 may include a heating roller 51 having a heating source to apply heat to the paper on which the image was transferred, and a pressure roller 52 to be pressed against the heating roller 51 with a predetermined pressure.
The paper discharge device 60 serves to discharge the paper, on which the image is completely printed, to the outside of the body 10. The paper discharge device 60 includes a paper discharge roller 61, and a paper backup roller 62 installed opposite the paper discharge roller 61.
In an image forming apparatus of the above-described embodiment, at the beginning of a printing operation, the pickup roller 22 is operated to pick up printing media, loaded in the paper supply tray 21, sheet by sheet. Although the pickup roller 22 is rotatably installed at a fixed position, it can successively pick up a plurality of printing media loaded in the paper supply tray 21 because the paper supply tray 21 moves the printing media upward to the pickup roller 22. After picking up, the pickup roller 22 delivers the picked-up printing medium to the delivery roller 23, the delivery roller 23 delivers the printing medium toward the transfer device 40 after aligning the leading end of the printing medium.
The charge rollers 32, located close to the respective photosensitive members 31 charge the surfaces of the photosensitive members 31 with a predetermined electric potential. The light scanning device 100 irradiates beams to the respective photosensitive members 31 according to an image signal, forming electrostatic latent images on the surfaces of the photosensitive members 31.
After the electrostatic latent images are formed on the respective photosensitive members 31, different colors (for example, magenta, cyan, yellow, black) of toners (i.e. developers) of the respective developing units 30Y, 30M, 30C, and 30K are attached to the respective photosensitive members 31, forming visible images of different colors. The visible images are sequentially transferred to the intermediate transfer drum 41 in a manner overlapping one another to form a color image on the intermediate transfer drum 41.
The color image is transferred from the intermediate transfer drum 41 to the surface of the printing medium when the printing medium passes through the gap between the intermediate transfer drum 41 and the transfer roller 42. Then, the printing medium, to which the color image was transferred, is delivered to the fixing device 50, which applies heat and pressure to the printing medium, allowing the color image composed of toner to be melted and fixed to the surface of the printing medium.
The printing medium, having passed through the fixing device 50, is discharged out of the body 10 via operation of the paper discharge device 60.
The image forming apparatus in accordance with the first embodiment of the present invention, as shown in
The cover 11 is provided to be selectively open so as to allow an access into the body 10 when, e.g., it is desired to change consumables in the body 10 such as the developing units, etc., or to remove a jammed printing medium.
Hinges 12 are formed at the lower end of the cover 11, to allow the cover 11 to be pivotally rotated up and down about the hinges 12, so as to open and close the front side of the body 10.
A hook 13 may be formed at the center of an upper end of a rear surface of the cover 11 to engage with a portion of the body 10 to retain the cover 11 in a closed position. A pusher (not shown) or the like may be formed at an upper end of a front surface of the cover 11 to allow a user to operate the hook 13. Any known structures and operations for the hook 13 and the pusher for opening or closing of the cover 11 may be used, the detailed descriptions thereof thus are not necessary.
A fixing member 14 is provided on the rear surface of the cover 11, to support the light scanning device 100 in place. The light scanning device 100 may be disposed inside the fixing member 14 in such a manner to allow a slight movement of the light scanning device 100 toward or away from the cover 11. The fixing member 14 has an opening 15 formed at the front surface thereof to expose the passage windows 104 of the light scanning device 100.
The light scanning device 100 includes a case 110, and the polygonal mirrors 101, F-theta lenses 102 and reflective mirrors 103 installed within the case 110.
Elastic members 16 are provided between the cover 11 and the light scanning device 100, to allow the light scanning device 100 to slightly move toward or away from the cover 11 in accordance with opening/closing operations of the cover 11.
The elastic members 16 are installed to exert an elastic force in a direction of moving the cover 11 and the light scanning device 100 away from each other. When the cover 11 closes the body 10, the elastic members 16 become contracted, reducing the distance between the cover 11 and the light scanning device 100. When the cover 11 opens the body 10, as long as no external force acts thereon, the elastic members 16 become restored to increase the distance between the cover 11 and the light scanning device 100.
With the above arrangement, in which the light scanning device 100 and the cover 11 support each other via the elastic members 16, a movement of the light scanning device 100 and the cover 11 in relation to each other may occur, fQr example, the light scanning device 100 being dropped down relative to the cover 11, which may cause the photosensitive members 31 and the passage windows 104 to become misaligned when the cover 11 closes the body 10.
For this reason, guides 17 are provided at both side surfaces of the case 110 of the light scanning device 100. The guides 17 serve to appropriately position the respective passage windows 104 corresponding to the respective photosensitive members 31 arranged in the body 10 when the cover 11 closes the body 10, thereby allowing laser beams having passed through the passage windows 104 to be accurately scanned to the photosensitive members 31.
Each of the guides 17 is formed at a tip end thereof with a guide hole 18, and the body 10 incorporates a guide rod 10a to be engaged with the guide hole 18.
The case 110 of the light scanning device 100 encases a variety of optical parts of the light scanning device 100, to prevent the optical parts from being contaminated by impurities and/or to protect them from shock, etc. The case 110, as shown in
The photosensitive members 31, as shown in
Specifically, of the four developing units 30Y, 30M, 30C, and 30K, the right ends of two inner developing units 30M and 30C protrude laterally beyond the right ends of two outer developing units 30Y and 30K.
Accordingly, for compact arrangement of the developing device 30 and the light scanning device 100, the light scanning device 100 is formed with a receiving portion 105 recessed from the outer surface of the light scanning device 100, to receive the ends of the two inner developing units 30M and 30C. Correspondingly, portions above and below the receiving portion 105 define protruding portions 106.
The protruding portions 106 are provided with first and fourth passage windows 104a and 104d corresponding to the photosensitive members 31a and 31d of the two outer developing units 30Y and 30K. The receiving portion 105 is provided with second and third passage windows 104b and 104c corresponding to the photosensitive members 31b and 31c of the two inner developing units 30M and 30C.
Specifically, for compact arrangement of the developing device 30 and the light scanning device 100, the first and fourth passage windows 104a and 104d and the second and third passage windows 104b and 10c are located on different planes from each other.
As the light scanning device 100 is supported on the cover 11, the passage windows 104 may become contaminated with debris, etc. attaching to the passage windows 104 or a user may be exposed to the laser beam of the light scanning device 100 when the cover 11 is open.
To address the above, the shutter device 120 operating to close the passage windows 104 of the light scanning device 100 in accordance with opening of the cover 11 is provided.
The shutter device 120, as shown in
The pair of shutters 130 and 140 are slidable relative to the case 110. Specifically, the first and second shutters 130 and 140 rectilinearly move in different directions in accordance with rotation of the first gears 150.
The first shutter 130 includes first and third shutter plates 131 and 132 to open and to close the first passage window 104a provided at the upper protruding portion 106 and the third passage window 104c provided at the receiving portion 105, first connectors 133 provided at both sides of the first shutter 130 to connect the first and third shutter plates 131 and 132 to each other, and first racks 134 formed at the first connectors 133 to convert rotating motion of the first gears 150 into rectilinear motion.
To keep the distance between the first passage window 104a and the first shutter plate 131 approximately equal to the distance between the third passage window 104c and the third shutter plate 132, the first shutter plate 131 protrudes beyond the third shutter plate 132.
The second shutter 140 includes second and fourth shutter plates 141 and 142 to open and to close the second passage window 104b provided at the receiving portion 105 and the fourth passage window 104d provided at the lower protruding portion 106, second connectors 143 provided at both sides of the second shutter 140 to connect the second and fourth shutter plates 141 and 142 to each other, and second racks 144 formed at the second connectors 143 to convert rotating motion of the first gear 150 into rectilinear motion.
To keep the distance between the second passage window 104b and the second shutter plate 141 approximately equal to the distance between the fourth passage window 104d and the fourth shutter plate 142, the fourth shutter plate 142 protrudes beyond the second shutter plate 141.
The plurality of shutter plates 131, 132, 141, and 142 are arranged adjacent to the plurality of passage windows 104, respectively, to maintain a predetermined distance therebetween that allows the shutter plates 131, 132, 141, and 142 to slide relative to the case 110 while being arranged adjacent to the passage windows 104.
With the above-described configuration, the ends of the inner developing units 30M and 30C can be received in the space 107 defined in the receiving portion 105 of the case 110. This enables compact arrangement of the developing device 30 and the light scanning device 100, improving space utilization within the body 10.
The first and second racks 134 and 144 are arranged in parallel at positions opposite each other. With the first and second racks 134 and 144, the first and second shutters 130 and 140 slide away from each other while the first gears 150 rotate in one direction, but slide toward each other while the first gears 150 rotate in the other direction.
Each first gear 150 is rotatably fixed to either side surface of the case 110 and is used to transmit a drive force of the lever 160 to the first and second racks 134 and 144.
The lever 160 is pressed upon closing of the cover 11 so as to rotate the first gear 150 in a direction designated by the arrow A as shown in
With the above-described configuration of the shutter device 120, as shown in
Thereby, the first shutter 130, engaged with the first gears 150, slidably move in a direction designated by the arrow B, causing the first and third shutter plates 131 and 132 to open the first and third passage windows 140a and 140c. Simultaneously, the second shutter 140, engaged with the first gears 150, slidably move in a direction designated by the arrow C, causing the second and third shutter plates 141 and 142 to open the second and fourth passage windows 140b and 104d.
On the other hand, when the cover 11 is pivotally rotated to open the body 10, as shown in
Thereby, the first shutter 130 engaged with the first gears 150 slidably move in a direction designated by the arrow B′, causing the first and third shutter plates 131 and 132 to close the first and third passage windows 104a and 104c. Simultaneously, the second shutter 150 engaged with the first gears 150 slidably moves in a direction designated by the arrow C′, causing the second and fourth shutter plates 141 and 142 to close the second and fourth passage windows 104b and 104d.
Next, the shutter device to open or close the passage windows of the light scanning device of the image forming apparatus in accordance with a second embodiment of the present invention will be described.
The present embodiment is substantially similar to the previously described embodiments, except for the features and configuration of the shutter device to open or close the passage windows of the light scanning device. Thus, the features and configurations that are commonly shared with the previously described embodiments will be designated by the same reference numerals, and the descriptions thereof will not be repeated.
As shown in
The shutter 230 has an integral configuration and is slidably coupled to the case 110.
The integral shutter 230 includes first and fourth shutter plates 231 and 234 to open or close the first and fourth passage windows 104a and 104d provided at the protruding portions 106, second and third shutter plates 232 and 233 to open or close the second and third passage windows 104b and 104c provided at the receiving portion 105, connectors 235 to connect the respective shutter plates 231, 232, 233, and 234 to one another, and racks 236 formed at the connectors 235 to convert rotating motion of the first gears 150 into rectilinear motion.
To keep the distances between the first and fourth passage windows 104a and 104d and the first and fourth shutter plates 231 and 234 approximately equal to the distances between the second and third passage windows 104b and 104c and the second and third shutter plate 232 and 233, the first and fourth shutter plates 231 and 234 protrude beyond the second and third shutter plates 232 and 233.
Accordingly, the shutter plates 231, 232, 233, and 234 are spaced apart from the passage windows 104 by a predetermined distance, and are arranged on two different planes.
With the above-described configuration of the shutter device 220, upon closing of the cover 11, the protrusions 11a formed at the rear surface of the cover 11 press the cams 161 of the levers 160 while the elastic members 16 becomes contracted. As the levers 160 rotate, the second gears 162 rotate, causing the first gears 150 to rotate in the direction designated by the arrow D.
Thereby, the shutter 230, engaged with the first gears 150, slidably moves in a direction designated by the arrow E, causing the plurality of shutter plates 231, 232, 233, and 234 to open the plurality of passage windows 140 simultaneously.
On the other hand, when the cover 11 is pivotally rotated to open the body 10, the elastic members 16 between the cover 11 and the light scanning device 100 are restored, and the cams 161 of the levers 160 are returned to rotate the levers 160. As the levers 160 rotate, the second gears 162 rotate in an opposite direction, causing the first gears 150 to rotate in a direction designated by the arrow D′.
Thereby, the shutter 230 engaged with the first gears 150 slidably moves in a direction designated by the arrow E′, causing the plurality of shutter plates 231, 232, 233, and 234 to close the plurality of passage windows 104 simultaneously.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2008-0002167 | Jan 2008 | KR | national |
