Door apparatus of a fixing unit

Abstract: A door apparatus of a fixing unit includes a guide door (40) hinged to one side (31) of a frame (30) of the fixing unit, so that the guide door can be opened horizontally, securing an enough space for removing a jammed sheet. The frame comprises a plurality of bent plates (32) formed at the one side thereof, each of the bent plates having a hinge hole (32a), and the guide door comprises a plurality of extending plates (42) formed at one side (41) thereof, extending horizontally with respect to the bent plates, each of the extending plates having a hinge pin (42a). The hinge pins are inserted into the hinge holes. Further, the door apparatus includes a U-shaped locker (44) having a fixed end (44a) and a free end (44b), formed at another side (43) of the guide door such that an outer side of the free end elastically contacts an inner face of another side (33) of the frame. Further, the door apparatus includes a hook (44c) formed at a specified portion of the free end, slanting to an installation direction, and a hooking hole (34) formed at a corresponding portion of the another side of the frame, so that the hook is inserted into the hooking hole to lock the guide door to the fame.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a laser beam printer (LBP), a copier and a facsimile, and in particular, to a door apparatus of a fixing unit for fixing a toner on a recording sheet, which facilitates removal of a jammed sheet. 2. Description of the Related Art An electrophotographic image forming apparatus is composed of a sheet feeding unit for feeding recording sheets one by one, an image forming unit for forming an image on the fed sheet with a toner, a fixing unit for fixing the toner on the sheet, and a sheet discharging unit for discharging the sheet with the toner fixed thereon. Such an image recording apparatus having a releasable fixing device is known from US-A-5 253 013. Further, the fixing unit is composed of a heating roller for melting toner particles covering a latent image on the sheet and a pressure roller for pressuring the melted toner particles on the sheet, rotating in contact with the heating roller. FIG. 1 illustrates a cross-sectional view of a conventional fixing unit, and FIG. 2 illustrates a state where a guide door 120 is opened. Referring to FIGs. 1 and 2, the fixing unit includes a heating roller 111 and a pressure roller 115, mounted on a frame 110 such that they rotate in contact with each other. As illustrated, the heating roller 111 has a heat lamp 112 secured therein, for generating a heat of about 150-200°C to melt the toner particles attached onto a sheet 119. A temperature sensor 113 for sensing the surface temperature of the heating roller 111 is mounted on the frame 110, keeping in contact with the surface of the heating roller 111. Further, at the sheet discharging unit side of the fixing unit, a plurality of fingers 114 are mounted on the frame 110 in a lengthwise direction, keeping in contact with the heating roller 111, so as to separate the sheet 119 from the heating roller 111 and then guide the sheet 119 to the sheet discharging unit. Furthermore, the pressure roller 115 is installed below the heating roller 111, applying a constant pressure to and rotating in contact with the heating roller 111. Specifically, a busing 116 is fixed at an axle of the pressure roller 115, and a compression coiled spring 117 intervenes between the bushing 116 and the frame 110, so that the pressure roller 115 can rotate keeping in contact with the heating roller 111 by the pressure of the compression coiled spring 117. In addition, at the sheet discharging side of the fixing unit, the openable guide door 120 is hinged around a hinge axle 121, so as to allow a user to open the guide door 120 and then remove a jammed sheet in the case that the sheet 119 is jammed between the heating roller 111 and the pressure roller 115. However, since the guide door 120 is opened downward around the hinge axle 121, it cannot be fully opened, thus not providing an enough space for removing the jammed sheet. Therefore, it might be difficult for the user to completely remove the pieces of the jammed sheet. SUMMARY OF THE INVENTION It is therefore an object of the present invention defined in claim 1, advantageous embodiments thereof in the dependent claims, to provide a door apparatus of a fixing unit in which a jammed sheet can be easily and completely removed. To achieve the above object the guide door is hinged to one side of the frame so that the guide door can be opened horizontally, securing enough space for removing a jammed sheet. Preferably, the frame comprises a plurality of bent plates formed at the one side thereof, extending horizontally with respect to the frame, each of the bent plates having a hinge hole, and the guide door comprises a plurality of extending plates formed at one side thereof, extending horizontally with respect to the bent plates, each of the extending plates having a hinge pin. The hinge pins are inserted into the hinge holes. Further, the door apparatus comprises a U-shaped locker having a fixed end and a free end, formed at another side of the guide door such that an outer side of the free end elastically contacts an inner face of another side of the frame. Further, the door apparatus comprises a hook formed at a specified portion of the free end, slanting to an installation direction, and a hooking hole formed at a corresponding portion of the another side ofthe frame, so that the hook is inserted into the hooking hole to lock the guide door to the fame. BRIEF DESCRIPTION OF THE DRAWINGS The above objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: FIG. 1 is a cross-sectional view of a conventional fixing unit; FIG. 2 is a cross-sectional view illustrating a state where a guide door (120) is opened; FIG. 3 is a perspective assembly diagram of a fixing unit with a door apparatus according to an embodiment of the present invention; FIG. 4 is a perspective view of the fixing unit of FIG. 3, illustrating a state where a guide door (40) is closed; FIG. 5 is a perspective view of the fixing unit of FIG. 3, illustrating a state where the guide door (40) is opened; and FIG. 6 is a partial perspective view of a locking device for the guide door according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings, in which the like reference numerals denote the like or equivalent elements. In the specification, well-known functions or constructions which may obscure the invention in unnecessary detail are not described in detail. FIG. 3 is an assembly drawing of the fixing unit with a door apparatus according to an embodiment of the present invention. As illustrated, the fixing unit is composed of a frame 30 having a heating roller 10 and a pressure roller 20 installed therein, and a guide door 40 hinged to one side of the frame 30 so as to guide the sheet and secure an enough space for removing the jammed sheet, if any. Specifically, the heating roller 10 and the pressure roller 20 are mounted on the frame 30 such that they can rotate keeping in contact with each other. The heating roller 10 has a heat lamp (not shown) for heating the circumference of the heating roller 10 to melt the toner particles on the sheet passing through a gap between the heating roller 10 and the pressure roller 20, so as to fix the toner image on the sheet. The guide door 40 is hinged to the one side of the frame 30 so that it can be opened horizontally. Further, the frame 30 has a locking structure, at another side thereof, for locking the guide door 40 thereto when it is closed. The fixing unit of the invention employs a hinge coupling structure for allowing the guide door 40 to be opened horizontally with respect to the frame 30. Specifically, at the one side 31 of the frame 30, a plurality of rectangularly bent plates 32 having hinge holes 32a are formed, extending horizontally with respect to the heating roller 10 and the pressure roller 20. Further, at one side 41 of the guide door 40, a plurality of extending plates 42 having hinge pins 42a to be inserted into the hinge holes 32a are formed. The hinge pins 42a ofthe guide door 40 are inserted into the hinge holes 32a formed at the bent plates 32 of the frame 30, so that the guide door 40 can be rotated around the hinge coupler in the horizontal direction. FIG. 4 is a perspective view of the fixing unit, illustrating a state where the guide door 40 is closed. When the guide door 40 is closed to the frame 30, a guide member 45 formed at an upper portion of the guide door 40 is positioned to guide the sheet passing through a gap between the heating roller 10 and the pressure roller 20. FIG. 5 is a perspective view of the fixing unit, illustrating a state where the guide door 40 is opened, and FIG. 6 is a partial perspective view of a locking device for locking the guide door 40 to the frame 30 when the guide door 40 is closed. At another side 43 of the guide door 40, a U-shaped locker 44 having a fixed end 44a and a free end 44b is formed, such that an outer side of the free end 44b elastically contacts an inner face of a frame wall 33. Specifically, the fixed end 44a is formed, extending outward, on the another side 43 of the guide door 40, and the free end 44b having the same length as the fixed end 44a is formed to be elastically supported (or tensed) by the fixed end 44a. Further, a hook 44c slanting to an installation direction is formed on a specified outer portion of the free end 44b, and a hooking hole 34 is formed at a corresponding portion of the frame wall 33, so that the hook 44c may be inserted into the hooking hole 34. In assembling the guide door 40 into the frame 30, the hinge pins 42a of the guide door 40 are inserted into the hinge holes 32a of the frame 30. If the user pushes the another side of the guide door 40, the guide door 40 rotates around the hinge coupler, and the free end 44b of the locker 44 contacts the inner face of the fame wall 33. Here, if the user pushes the another side of the guide door 40 more strongly, the hook 44c formed on the free end 44b of the locker 44 is inserted into the hooking hole 34 formed at the fame wall 33, so that the guide door 40 is locked to the frame 30. Meanwhile, for opening the guide door 40 to remove the jammed sheet from the fixing unit, the user pushes the free end 44b toward the fixed end 44a. Then, the hook 44c formed on the free end 44b falls off from the hooking hole 34 of the frame 30. Thereafter, if the user pulls the locker 44 out, the guide door 40 is opened horizontally around the hinge coupler. Therefore, a portion of the fixing unit where the sheet is jammed can be completely exposed to the user. As described above, the door apparatus of the fixing unit according to the present invention allows the guide door to be opened horizontally with respect to the frame. Therefore, it is possible to secure a wider space for removing the jammed sheet so that the user may easily remove the jammed sheet. Although a preferred embodiment of the present invention has been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concepts herein taught which may appear to those skilled in the art will fall within the scope of the appended claims.

Claims: The fixing unit of an image forming apparatus, comprising: a frame (30) a heating roller (10) rotatably mounted in said frame about a longitudinal axis of said heating roller: a pressure roller (20) rotatably mounted in said frame (30) and in contact with said heating roller (10) and a guide door (40) pivotally attached to said frame (30), characterized in that for pivotal attachment, said guide door (40) is hinged to one side of said frame (30) with a hinge axis oriented perpendicular to said longitudinal axis, such that the guide door (40) opens horizontally, securing enough space for removing a jammed sheet. The door apparatus according to claim 1, characterised in that the frame (30) comprises a plurality of bent plates (32) formed at the one side (31) thereof, extending horizontally with respect to the frame (30), each of the bent plates (32) having a hinge hole (32a) wherein the guide door (40) comprises a plurality of extending plates (42) formed at one side (41) thereof, extending horizontally with respect to the bent plates (32), each of the extending plates having a hinge pin (42a) that can be inserted into the corresponding hinge hole (32a). The door apparatus according to claims 1 or 2, characterised in that a U-shaped locker (44) having a fixed end (44a) and a free end (44b) is formed at another side (43) of the guide door (40) such that an outer side of the free end (44b) elastically contacts an inner face of another side (33) of the frame. The door apparatus according to claim 3, characterised in that a hook (44c) is formed at a specified portion of the free end (44b), slanting to an installation direction, and a hooking hole (34) is formed at a corresponding portion of another side (33) of the frame (30) into which hooking hole the hook is inserted for locking the guide door to the frame.

Inventors: CHO WON-MO, CHO, WON-MO
Applicants: SAMSUNG ELECTRONICS CO LTD, SAMSUNG ELECTRONICS CO., LTD.
Application year: 1998
Main classification: G03G15
IPC codes: G03G15