Image forming apparatus equipped with a bucket for accommodating a photosensitive sheet cartridge

Abstract: An image forming apparatus (1) which includes a bucket (55) for accommodating a cartridge (5) holding a roll of a photosensitive sheet (51) and a take-up (54) shaft for taking up the photosensitive sheet (51) after use, the bucket (55) having an exposure plate (60) disposed above the cartridge (5), a slidable means (55a) engageable with a slidable means (55b) provided on the image forming apparatus (1) so as to enable the bucket (55) to be slidably mounted in and dismounted from the image forming apparatus (1), and a positioning means for securing the exposure plate (60) in its optically proper position.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention: The present invention relates to an image forming apparatus equipped with a media bucket for accommodating a photosensitive sheet cartridge provided with a supply shaft for delivering a photosensitive sheet, and a take-up shaft for taking up the photosensitive sheet after use. The photosensitive sheet cartridge will hereinafter be called the "cartridge". 2. Description of the Prior Art: Japanese Laid-Open Patent Publication No.58-88739 discloses a method of forming an image by using a photosensitive sheet coated with microcapsules containing photosetting materials and image forming agent and an image receiving sheet coated with a developer that reacts with the image forming agent to develop colors. When the photosensitive sheet is exposed to light, the microcapsules are caused to harden on light-hit spots, thereby forming a latent image on the photosensitive sheet. When the image receiving sheet is superposed over the latent image and pressed together by a press roller unit, unhardened microcapsules rupture and enable the image forming agent contained therein to flow out and react with the developer to develop colors, thereby forming a colored image on the image receiving sheet. This conventional image forming method is provided with a cartridge for accommodating the photosensitive sheet in a roll form so as to protect the microcapsules from being subjected to accidental exposure to light or rupturing before the expected exposure. Where the cartridge is provided, a bucket is slidably mounted in the image forming apparatus so as to facilitate the mount and dismount of the cartridge. The bucket is drawn, and an exposure plate fixed thereto by means of fasteners such as screws, is removed so as to load a cartridge in the bucket. Then, the exposure plate is returned to the bucket and fixed thereto by means of screws, etc. A top portion of the photosensitive sheet is pulled from the cartridge over the exposure plate so as to make it ready for automatic delivery into a feed path. Finally, the bucket is inserted into the image forming apparatus. The conventional method is disadvantageous in that the dismount and mount of the bucket involves a complicated and labor-consuming task which consists of drawing the bucket, removing the exposure plate, loading the cartridge, returning the exposure plate, setting the photosensitive sheet, and mounting the bucket again. During the work small accidents often happen such as losing screws, accidentally breaking the cartridge, and entangling the photosensitive sheet. SUMMARY OF THE INVENTION The image forming apparatus of this invention, which overcomes the above-discussed problems and numerous other disadvantages and deficiencies of the prior art, comprises a main body; a bucket for accommodating a cartridge holding a roll of photosensitve sheet and a take-up shaft for taking up the photosensitive sheet after use, the bucket including an exposure plate which is disposed above the cartridge and on which the photosensitive sheet drawn from the cartridge is exposed to light; and a guide mechanism for allowing the bucket to be slidably mounted in and dismounted from the main body, the guide mechanism comprising first guide means provided for the main body and second guide means provided for the bucket, the first guide means and the second guide means engaging with each other in mounting and dismounting of the bucket; characterized by a swinging mechanism for swinging the exposure plate between a position where the exposure plate covers an opening of the bucket when the bucket is mounted in the main body and another position where the exposure plate uncovers the opening of the bucket when the bucket is dismounted from the main body. In a preferred embodiment, the swinging mechanism comprises connecting means for pivotally connecting the exposure plate to the bucket and positioning means for placing the exposure plate in its optically proper position when the bucket is mounted in the main body. In a further preferred embodiment, the connecting means comprises a support axis connected to the exposure plate and a pair of elongated holes in which two ends of the support axis are inserted, the two ends of the support axis being located at top ends of the holes when the bucket is mounted in the main body and being located at bottom ends of the holes when the bucket is dismounted from the main body. The positioning means lifts up the two ends of the support axis to the top ends of the holes when the bucket is mounted in the main body, thereby placing the exposure plate in its optically proper position. The elongated holes are provided for the bucket and the positioning means is provided for the main body. In another embodiment, the second guide means comprises a pair of guide members disposed on each side of the bucket, the first guide means comprises a pair of rails disposed on the main body. Thus, the invention described herein makes possible the objectives of (1) providing an image forming apparatus which facilitates the replacement of a used cartridge with a fresh cartridge, and (2) providing an image forming apparatus which constantly secures the exact focusing point for an image on the photosensitive sheet. BRIEF DESCRIPTION OF THE DRAWINGS This invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings as follows: Figures 1(A) to 1(C) are perspective views showing the steps of exchanging a used cartridge with a fresh one in an image forming apparatus according to the present invention; Figures 2(A) and 2(B) are schematic views showing the state at which a guide pin guides an exposure plate; Figures 3(A) and 3(B) are schematic views showing the state at which the exposure plate moves with respect to the bucket; and Figure 4 is a cross-sectional view showing the internal structure of the image forming apparatus according to the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figure 4, the image forming apparatus of the invention uses a photosensitive sheet coated with microcapsules containing photosetting materials and an image forming agent and an image-bearing sheet coated with a thermoplastic resin and a developer that reacts with the image forming agent to develop colors. In the upper part of the image forming apparatus 1 , there is disposed an optical system 3 that includes a semiconductor laser 32 , a prismatic mirror 35 , a liquid crystal screen 36 , a lamp 37 , a filter 38 , and other related components. A photosensitive sheet 51 that is wound around a supply shaft 53 and housed in a cartridge 5 is delivered through a feed path before being wound around a take-up shaft 54 . The cartridge 5 and the take-up shaft 54 are detachably mounted in the bucket 55 which is inserted into the image forming apparatus along slidable guide members 55a provided on the outside of the bucket 55 . Disposed in the photosensitive sheet feed path are an exposure plate 60 , an automatic transport roller 62 , a buffer roller 61 , and a pair of press rollers 63 and 64 . The exposure plate 60 is swingably mounted on the bucket 55 . Disposed at an appropriate place in the image forming apparatus 1 (in the illustrated embodiment, at a bottom) is a cassette 40 holding receiving sheets 41 . A paper feed roller 47 and a timing roller 48 are disposed in the feed path of the image receiving sheet 41 from the cassette 40 to a pressure development section 6 . A gloss-imparting unit 7 is disposed to the left of the pressure development section 6 , to the left of which a paper discharging roller 81 is disposed. A paper discharging section 8 is provided in the upper part of the image forming apparatus 1 . The image forming apparatus is operated as follows: Light beams generated by the semiconductor laser 32 are directed by the optical system 3 that consists mainly of the prismatic mirror 35 and the liquid crystal screen 36 , so as to strike onto the photosensitive sheet 51 on the exposure plate 60 . At this stage the buffer roller 61 is moved in the direction (A). By exposure, the microcapsules in an area where the light strikes harden, thereby forming a latent image in that area. When the exposure is finished, the take-up shaft 54 is rotated, which causes the buffer roller 61 to return in the direction of arrow (B) to transport the latent image formed on the photosensitive sheet to the pressure development section 6 . Synchronized with the transport of the latent image, the image-receiving sheet 41 is fed from a paper feed section 4 toward the pressure development section, so that the photosensitive sheet 51 and the image-receiving sheet 41 are passed between the press rollers 63 and 64 for pressing together. As a result, unhardened microcapsules on the image-receiving sheet 41 rupture and cause the image forming agent contained therein to flow out and react with the developer on the image-receiving sheet 41 to develop colors. The image-receiving sheet 41 on which the pressure development is completed is wound around the take-up shaft 54 , while the image-receiving sheet 41 is thermally treated by the gloss-imparting unit 7 and transported by means of the paper discharging roller 81 to the paper discharging section 8 from which the image-receiving sheet 41 is discharged to the outside of the image forming apparatus 1 . Next, the procedure for exchanging a used cartridge with a fresh one will be described: Figure 1(A) shows the state at which a bucket 55 is drawn from the image forming apparatus 1 and the exposure plate 60 is opened. A pair of slidable guide members 55b are provided in the image forming apparatus 1 , extending crosswise thereof. A pair of guide pins 60a are provided for positioning the exposure plate 60 in an appropriate position. A pair of slidable guide members 55a are provided on the outside of the bucket 55 , and a pair of guide members 55b are provided on the image forming apparatus 1 . The guide members 55a are engaged with the guide members 55b , thereby securing the union of the bucket 55 and the image forming apparatus 1 . The bucket 55 accommodates the cartridge 5 in which the photosensitive sheet 51 is wound around the supply shaft 53 contained in the cartridge 5 . The photosensitive sheet 51 is taken out through a delivery opening 52 . The take-up shaft 54 is detachably mounted in the bucket 55 toward the image forming path. The exposure plate 60 is attached to the inside of the bucket 55 in such a manner that it can swing on a support 60d in the directions of arrows (D) and (E) as widely as possible. To replace the cartridge 5 with a fresh one, the bucket 55 is drawn out of the image forming apparatus 1 in the direction of arrow (C), and the exposure plate 60 is opened in the direction of arrow (E) as shown in Figure 1(A). Then, a fresh cartridge 5 is inserted in the bucket 55 in the direction of arrow (F) from above. Next, as shown in Figure 1(B), the exposure plate 60 is closed in the direction of arrow (D), and a top portion of the photosensitive sheet 51 is pulled out so as to be placed over the exposure plate 60 . After the cartridge 5 is set, the bucket 55 is inserted into the image forming apparatus 1 in the direction of arrow (G). The insertion of the bucket 55 into the image forming apparatus 1 is facilitated by the engaged slidable guide members 55a and rail members 55b . As shown in Figures 2(A) and 2(B), the exposure plate 60 is caused to ride on the guide pins 60a along their tapered ends, and locate itself at a proper exposure position. This arrangement of the invention eliminates the necessity of any subsequent adjustment, thereby contributing to labor-saving. Furthermore, since the exposure plate 60 can be precisely positioned, the focusing point is determined for production of a clear image. More specifically, referring to Figure 2, the exposure plate 60 is guided by the guide pins 60a fixed on the inside wall of the image forming apparatus 1 . When the bucket 55 is pushed in the direction of arrow (G), the exposure plate 60 slides along the tapered surfaces of the end portions of the guide pins 60a as shown in Figure 2(A) and caused to ride on the guide pins 60a and is fixed in position as shown in Figure 2(B). The reference numeral 60d indicates a support about which the exposure plate 60 turns and which moves up and down in elongated holes provided in the side wall of the bucket 55 , thereby adjusting the position of the exposure plate 60 vertically. Figure 3 shows the functions of the elongated hole in the side wall of the bucket 55 and the support 60d for the exposure plate 60 in the image forming apparatus 1 . Figure 3(A) shows a state in which the exposure plate 60 is closed. The exposure plate 60 is held in position, one side thereof resting on a stopper 55c provided on a front frame 55f of the bucket 55 and the opposite side thereof being positioned on the guide pins 60a as described above. The support 60d for the exposure plate 60 is fitted in the elongated holes 55d provided in the side wall of the bucket 55 , and is moved up and down in and along the elongated holes 55d , thereby positioning the exposure plate 60 precisely. Figure 3(B) shows a state in which the exposure plate 60 is opened. The support 60d moves in and along the elongated holes 55d so that the exposure plate 60 is opened as widely as possible. In this embodiment, the exposure plate 60 is rotatably connected to the side wall of the bucket 55 by means of the support 60d , but it can be mounted in any convenient manner if it allows the cartridge 5 to be mounted in the bucket 55 easily, and if it allows the exposure plate 60 to be located precisely. The positioning of the exposure plate 60 can be achieved precisely by other means than the guide pins proposed in this embodiment. According to the present invention, the exposure plate 60 can be easily opened and closed, thereby facilitating the replacement of cartridges. The bucket can be easily returned to the image forming apparatus so that the exposure plate takes its proper position under the guidance of the guide members and rails, thereby avoiding the misalignment of the focussing point of an image with respect to the photosensitive sheet.

Claims: An image forming apparatus comprising: a main body (1); a bucket (55) for accommodating a cartridge (5) holding a roll of photosensitive sheet (51) and a take-up shaft (54) for taking up the photosensitive sheet (51) after use, the bucket (55) including an exposure plate (60) which is disposed above the cartridge (5) and on which the photosensitive sheet (51) drawn from the cartridge (5) is exposed to light; and a guide mechanism (55a, 55b) for allowing the bucket (55) to be slidably mounted in and dismounted from the main body (1), the guide mechanism comprising first guide means (55b) provided on the main body (1) and second guide means (55a) provided on the bucket (55), the first guide means (55b) and the second guide means (55a) engaging with each other in mounting and dismounting of the bucket (55); characterized by a swinging mechanism (55d, 60a, 60d) for swinging the exposure plate (60) between a position where the exposure plate (60) covers an opening of the bucket (55) when the bucket (55) is mounted in the main body (1) and another position where the exposure plate (60) uncovers the opening of the bucket (55) when the bucket (55) is dismounted from the main body (1). An image forming apparatus according to claim 1, wherein the swinging mechanism comprises connecting means (55d, 60d) for pivotally connecting the exposure plate (60) to the bucket (55) and positioning means (60a) for placing the exposure plate (60) in its optically proper position when the bucket (55) is mounted in the main body (1). An image forming apparatus according to claim 2, wherein the connecting means comprises a support axis (60d) connected to the exposure plate (60) and a pair of elongated holes (55d) in which two ends of the support axis (60d) are inserted, the two ends of the support axis (60d) being located at top ends of the holes (55d) when the bucket (55) is mounted in the main body (1) and being located at bottom ends of the holes (55d) when the bucket (55) is dismounted from the main body (1). An image forming apparatus according to claim 3, wherein the positioning means (60a) lifts up the two ends of the support axis (60d) to the top ends of the holes (55d) when the bucket (55) is mounted in the main body (1), thereby placing the exposure plate (60) in its optically proper position. An image forming apparatus according to claim 4, wherein the elongated holes (55d) are provided on the bucket (55) and the positioning means (60a) is provided on the main body (1). An image forming apparatus according to claim 1, wherein the second guide means comprises a pair of guide members (55a) disposed on each side of the bucket (55), the first guide means comprises a pair of rails (55b) disposed on the main body (1).

Inventors: NARUMIYA MASAO, SHIMAZU FUMIO, TAKENO TSUYOSHI, NARUMIYA, MASAO, SHIMAZU, FUMIO, TAKENO, TSUYOSHI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1990
Main classification: G03F7
IPC codes: G03D13, G03F7, G03B27, B65H19