Abstract: Provided are intermediate coupling unit that can maintain universal applicability of image forming apparatus so it can singly form images/be installed in small offices, but can also couple two apparatuses if necessary, and image forming apparatus adaptable to this unit. Intermediate coupling unit includes carry-in port at lower surface right side, plural conveying roller pairs sandwiching and conveying internally-carried-in recording medium, discharge ports formed near upper surface right/left ends for externally discharging recording medium, first/second flaps switching among conveying paths, A, B, C, paper discharge tray fixed at upper internal position, and internal paper feed cassette detachable downward. Two identical-shape printers are linked through conveying path A and enable double-speed-printing when coupled to top/bottom of intermediate coupling unit to face same direction, and linked through conveying path B and enable fast-double-side-printing when coupled to face opposite directions.

Abstract: A document feeding device includes an upstream guide member that forms an upstream side of a document conveying path along which a document is guided from a sheet feeding tray to a platen, and a downstream guide member located between the upstream guide member and the platen. The document feeding device has a guide moving mechanism that slidably moves the downstream guide member away from an opposite guide member located opposite the downstream guide member upon a pivoting operation of the upstream guide member. Consequently, even if the document conveyed toward the platen is, for example, inappropriately conveyed to cause jamming, the document can be easily removed without being damaged.

Abstract: An image forming device includes a body having a top, a bottom, a front and a back. In one embodiment, a plurality of horizontally-aligned imaging units, each comprising a photoconductive member, transfer toner images to an intermediate transfer mechanism located below the plurality of imaging units. A pick mechanism may pick media sheets from a media input tray and feeds the media towards the front of the body. For duplex printing, the media sheets may travel along a duplex path that extends along the front of the body. In one embodiment, an access door at the front of the body pivots between a closed position and an open position. In the open position, a user may gain access to both media paths.

Abstract: An image forming apparatus capable of easily performing exchange in a process cartridge with a new cartridge and performing removal of a jammed sheet without detachment of a drawer from a casing. The drawer detachably holds a plurality of process cartridges, and is movable in frontward/rearward direction to one of an operable position where each photosensitive drum is in direct confrontation with a conveyer belt, a cartridge exchangeable position where all of the cartridges are positioned out of the casing, and a jammed sheet processing position ahead of the cartridge exchangeable position for removing a jammed sheet. A regulation mechanism is provided for selectively regulating the movement of the drawer dependent on detachment of a rearmost process cartridge from the drawer.

Abstract: An image-forming device includes: a casing; an image-forming section including a plurality of image-forming units; a paper supply unit; and a discharge unit. The plurality of image-forming units are arranged substantially vertically within the casing when the casing is disposed in an orientation in which it is intended to be used, each image-forming unit forming an image in a corresponding color. The paper supply unit is disposed above the image-forming units when the casing is disposed in the orientation in which it is intended to be used. The paper supply unit is configured to accommodate a recording medium substantially in a vertical orientation and to supply the recording medium to the image-forming section. The discharge unit is disposed above the image-forming units when the casing is disposed in the orientation in which it is intended to be used. The discharge unit is configured to receive the recording medium discharged from the image-forming section substantially in a vertical orientation.

Abstract: A presser member which abuts on a sheet which passes through a sheet conveyance path, and rotates toward a sheet conveyance direction while being pressed by the sheet is provided rotatably in the sheet conveyance path where the sheet conveyed to a sheet stack portion passes, and a move portion to which this presser member is retracted from the sheet conveyance path is provided. When drawing out a jammed sheet from the sheet conveyance path in a direction reverse in a sheet conveyance direction, a jam recovery door is opened, the move portion is operated in connection with this opening motion, and the presser member is retracted from the sheet conveyance path.

Abstract: A document reader includes an exterior panel covering a region of a document feed path including a second image read position from outside. The document reader also includes a first open/close member forming a region of the exterior panel including a portion opposed to the image read position. The document reader further includes a second open/close member positioned inwardly of the first open/close member to define a region of the document feed path including the image read position. The first and second open/close members are supported at respective different fulcrums for opening/closing movement about respective shafts extending perpendicularly to the document feed direction, thereby shielding the second image read position from extraneous light.

Abstract: The automatic document transport device 2 comprises a device main body 4, an opening and closing body 20 pivotally supported by the device main body 4 about a support shaft 22 between a closed position and an open position, and a helical torsion coil spring 30 that urges the opening and closing body 20 positioned at the closed position in the open direction. The helical torsion coil spring 30 is provided and arranged at a position separate from the support shaft 22.

Abstract: A document feeder includes a substantially U-shaped document transporting pathway with an upper feeding tray and a lower discharging tray, a separating-transporting device including a first rotation driving member and a first contacting member, a reverse transporting device including a second rotation driving member and a second contacting member and a pathway cover, which includes at least the second contacting member among the first and second contacting members, and capable of rotating about a rotational shaft closer to the discharging tray than the feeding tray. When the pathway cover is opened, at least the second contacting member of the first and second contacting members is separated from the second rotation member and at least a part of the document transporting pathway is exposed.

Abstract: An image forming device includes: a main unit case; a process unit; a belt unit; a belt; a belt cleaning unit; a storing unit; and a duct unit. The process unit is configured to be attached to and detached from the main unit case. The belt unit is configured to displace between an opposed position and an opened position. The belt unit in the opposed position is opposed to the process unit. The belt unit in the opened position allows the process unit to be exposed in the direction of removing the process unit from the main unit case. The belt is provided on the belt unit and is rotatingly driven. The belt cleaning unit is fixedly attached to the belt unit and removes material adhered to the belt. The storing unit is fixedly attached to the main unit case and stores therein the material removed from the belt by the belt cleaning unit. The duct unit has a conveying path in fluid communication with the belt cleaning unit and the storing unit.

Abstract: A paper conveying apparatus, having a simple structure, in which variation in a load imposed on paper is reduced to suppress printing irregularities, and also a printer are provided. A pair of rollers of a second conveying apparatus, arranged at a predetermined interval away from a first conveying apparatus, are composed of a rotationally-driven driving roller and a driven roller which is trailingly rotated, with paper being gripped between the driving roller and the driven roller. The pairs of rollers of the second conveying apparatus are arranged in different positions along the paper conveying direction. The paper gripping pressure of the pair of driving rollers arranged on the upstream side along the paper conveying direction is set to be lower than that of the other pairs of driving rollers.

Abstract: An image forming apparatus, includes: a mainframe having an opening portion; an electrostatic latent image carrier being loadable in and unloadable from the mainframe through the opening portion; a transport path; a first opening and closing member provided openably and closably on the mainframe so as to open and close the opening portion; and a second opening and closing member disposed on a side opposite to the electrostatic latent image carrier with respect to the first opening and closing member and provided openably and closably on the mainframe so as to open and close the transport path. The first opening and closing member and the second opening and closing member are openable and closable integrally with each other. The second opening and closing member is openable and closable independently of the first opening and closing member.

Abstract: An image-forming device includes a body frame having a first contacting part and a second contacting part; and a belt unit detachably mounted in the body frame. The belt unit includes a belt unit main frame, a first roller, a second roller, a belt, a belt unit side frame, a handle part, a first contacted part, and a second contacted part. The belt unit side frame is attached to the belt unit main frame. The handle part is disposed at the belt unit main frame. The first contacted part is provided on the handle part to contact the first contacting part. The second contacted part is provided on one of the belt unit main frame and the belt unit side frame to contact the second contacting part. The second contacted part is closer to the second roller than the first roller.

Abstract: A pair of resist rollers, a transferring device, a fixing device, a recording medium discharging device, and a recording medium reversing device are integrated into a recording medium conveying unit. The recording medium conveying unit can be drawn out of a main unit of an image forming apparatus.

Abstract: A media path crossover for a printing system includes a first crossover pathway on which sheets of print media are conveyed across a crossover junction without interruption and a second crossover pathway on which sheets of print media are conveyed across the crossover junction without interruption. The second crossover pathway intersects the first crossover pathway at a crossover junction. The first crossover pathway comprises a first input path and a first output path and the second crossover pathway comprises a second input path and a second output path. At least the first input path includes a first access panel, whereby a sheet can be cleared therefrom while continuing conveyance of media along the second crossover pathway.

Abstract: A fixing device has a roller pair; a cover for defining a forward transport path, and a backward transport path for transporting a sheet discharged from the roller pair back to an image former for forming toner images on both sides of the sheet. A sheet detection arm has opposite ends extending respectively in the forward and backward transport paths. A first shaft in the cover is mounted to a center of pivotal movement of the sheet detection arm and extends orthogonal to the sheet transport direction. A secondary shaft transmits rotation of the first shaft when the cover is closed, but not when the cover is opened. A sensor detects whether the sheet is being transported forward or backward based on rotation of the second shaft. The sheet detection arm pivots out of the backward transport path in response to opening of the cover.

Abstract: A paper supply device includes: a paper supply cassette that is loaded into an image forming apparatus body, such that the paper supply cassette can be freely pulled out, and is disposed with a first sheet housing for supplying sheets to an image forming section of the image forming apparatus body; and a second sheet supply mechanism that is disposed in the paper supply cassette and is for supplying, to the image forming section of the image forming apparatus body, sheets housed in a second sheet housing different from the first sheet housing, wherein a recessed portion, through which paper supplying means that is disposed in the image forming apparatus body and supplies sheets to the image forming apparatus body from the second sheet housing passes when the paper supply cassette is loaded into and unloaded from the image forming apparatus body, is formed in the paper supply cassette.

Abstract: An electrophotographic printing apparatus includes a housing, a photoreceptor module located inside the housing that includes a photoreceptor, a raster output system located inside the housing for projecting an electrostatic image onto the photoreceptor, a charging station, a developer station, a transfer station, a pre-fuser transport, and a fusing station. The module may be removed from an operating position inside the housing. The transfer station is connected to the pre-fuser transport so that they are constrained to move as one unit when the photoreceptor module is in its operating position inside the housing but are disconnected when the photoreceptor module is removed from its operating position inside the housing. The transfer module may be mounted so as to be constrained by a pre-fuser transport.

Abstract: An image forming apparatus and a method of sensing a printing medium jam in the image forming apparatus. The image forming apparatus includes a developing unit, a transfer unit, a fixing unit, a feed-out unit, a lower cover to come in contact with a printing medium when the printing medium is jammed on a feed path and which opens upwards when a pressure of the printing medium caused by the printing medium jam is greater than a predetermined reference value, an upper cover to be opened by the contact of the lower cover when the lower cover opens, and a printing medium jam detection unit operated by the upper cover.

Abstract: An image forming apparatus is provided that easily allows for removal of paper jams, reduces space for disposing a locking means of a cover, and saves production costs relative to the locking means of a cover. The image forming apparatus forms an image on a printing medium and has a feeding unit, a developing unit, a transfer unit, and an out-feed unit. The image forming apparatus includes a scanning unit that optically reads an image on a paper sheet and creates an electrical image signal. A rear cover is disposed downwardly of the scanning unit and substantially perpendicular to a flat surface of the scanning unit in an opening and closing manner. A top cover is disposed downwardly of the scanning unit and substantially parallel to the scanning unit. The top cover is connected to the rear cover in an opening and closing manner.

Abstract: In an image-forming device, a belt unit is detachably mounted in the housing. The belt unit moves to an installation position along a linear insertion/removal path in an insertion direction when the belt unit is mounted in the housing. The belt unit includes: a plurality of rollers; and an endless belt that is supported by the plurality of rollers and is capable of moving circumferentially around the plurality of rollers. A surface of the endless belt contacts a surface of the at least one photosensitive member when the belt unit is located in the installation position. The endless belt moves in a belt-moving direction that is angularly shifted from the removal direction to allow the surface of the endless belt to separate from each photosensitive member when the belt unit starts moving in the removal direction from the installation position.

Abstract: An image forming apparatus includes: an image carrier on which an electrostatic latent image is formed; a toner cartridge detachably mountable to the image forming apparatus, including a toner casing accommodating a developing agent, an opening/closing member which opens/closes an opening formed in the toner casing to discharge the developing agent, and an operation member operating the opening/closing member; and a developing unit to develop the electrostatic latent image by the developing agent discharged from the opening. The operation member can move between an open position for operating the opening/closing member to open the opening, and a close position for operating the opening/closing member to close the opening, and the operation member forms a part of a transport path of a recording medium in the image forming apparatus at the open position in a state where the toner cartridge is mounted in the image forming apparatus.

Abstract: A fixing unit is disposed at a position closer to a rear side wall than to a front side wall of a casing. A top wall is formed with a depressed portion depressed toward inside the casing. The depressed portion serves as a sheet discharge tray for receiving a recording medium that has passed through the fixing unit. The sheet discharge tray includes a tray member detachably disposed at the top wall. The rear side wall is formed with an opening through which the fixing unit is removed. When the tray member is disposed at the top wall, the tray member is positioned above and adjacent to the fixing unit and overlaps the fixing unit when viewed through the opening, thereby preventing the fixing unit from being removed from the casing. The fixing unit is removable through the opening when the tray member is detached from the top wall.

Abstract: An image forming apparatus includes an image forming unit, a first sheet stack portion, a sheet output section, and a post processing unit. The image forming unit forms an image on a sheet. The first sheet stack portion is provided at an upper face of the image forming unit. The sheet output section outputs the sheet on which the image is formed by the image forming unit from one side of the image forming apparatus to the first sheet stack portion. The post processing unit is provided adjacent to a lateral side of the image forming unit at an upstream side of the sheet output section to execute post processing on the sheet. A sheet subjected to post-processing by the post-processing unit is output to the first sheet stack portion from the same direction as a sheet not subjected to post-processing by the post-processing unit.

Abstract: An image forming apparatus includes an image bearing member which bears a toner image; an intermediate transfer member on which the toner image on the image bearing member is primary transferred; an intermediate transfer unit which supports the intermediate transfer member to allow rotation of the intermediate transfer member; a secondary transfer member which secondly transfers the toner image on the intermediate transfer member to a recording medium; a main body frame including at least the secondary transfer member; an opening unit which supports the intermediate transfer unit and which allows the intermediate transfer member to swing relative to the main body frame by pivoting on a rotation axis on the main body frame, thereby exposing the intermediate transfer unit when the intermediate transfer unit swings away from the main body frame; and a fitting portion which fits with the intermediate transfer unit, the fitting portion being disposed on the main body frame at a nearer portion to the intermediate t

Abstract: A sheet conveying apparatus including: a plurality of doors for opening a sheet conveying path are provided vertically adjacent to one another in an apparatus main body, and openably and closably about an axis provided in a vertical direction; and a restricting mechanism, which restricts, before an upper door of the plurality of doors is closed, the closing of a door just below the upper door.

Abstract: A paper feed apparatus includes a paper cassette, a registration roller pair, a first feed roller, and a second feed roller. In the paper feed apparatus, a pick-up unit is provided which is mounted to an image formation apparatus main body, and which has the registration roller pair, the first feed roller; a first guide part constituting a paper feeding path ranging from the first feed roller to the registration roller pair; a second guide part constituting a paper feeding path ranging from the second feed roller to the registration roller pair; and a paper feed base part that holds the registration roller pair, the first feed roller, the first guide part, the second feed roller, and the second guide part on the roller both end sides, respectively, for unitization.

Abstract: A paper delivering device to deliver printing paper, including: a lower frame; an upper frame rotatably coupling with the lower frame by a hinge part and rotating between a driving position in which the upper frame is disposed to parallel with respect to the lower frame with putting a delivery pathway of the printing paper between there and an opened position where the upper frame is spaced from the driving position; an upper delivery roller disposed on a lateral surface facing to the lower frame in the upper frame; a plate, interposed between the lower frame and the upper frame, to be detachable from the lower frame in a surface direction of the printing paper; and a lower delivery roller disposed on a lateral surface facing the upper frame of the plate and delivering the printing paper by oppositely rotating with the upper delivery roller when the plate is disposed at the lower frame.

Abstract: A sheet feeding apparatus includes: a body; a tray unit on which a plurality of sheets are mounted, the tray unit being provided in the body; a separating unit that separates the plurality of sheets by blowing air toward the plurality of sheets mounted on the tray unit; and a cover that is attached to the body at a position near the tray unit so as to be capable of opening and closing, the cover being provided with at least a part of the separating unit.

Abstract: An image forming apparatus is provided with an apparatus main body, a cover member openably and closably mounted on the apparatus main body, and an engaging portion. The cover member includes an outer cover and an inner cover which are independently opened and closed, and the inner cover is positioned by being pushed by the outer cover when the cover member is closed. The engaging portion is provided in the apparatus main body for temporarily holding the inner cover in the apparatus main body.

Abstract: An image forming apparatus includes a coupling arm that moves, when a releasing handle is pulled up, in association with the movement of the release handle and separates a secondary transfer roller from a secondary-transfer-roller positioning member. The image forming apparatus includes a pivoting arm having a push-down spatula that moves, when the release handle is pulled up, in association with the movement of the release handle and separates the secondary transfer roller from the secondary-transfer-roller positioning member. The coupling arm or the pivoting arm transmits force applied to the release handle to the secondary transfer roller using leverage to thereby separate the secondary transfer roller from the secondary-transfer-roller positioning member and release the secondary transfer roller.

Abstract: An image forming apparatus to perform duplex printing, including a duplex printing unit selectively detached and mounted with respect to a main body thereof, a pivotable duplex printing unit cover to form a document circulation path for a recording medium, a pivotable guide, and a door openably mounted to the main body to correspond to the guide.

Abstract: An image forming apparatus includes: an apparatus main body that is provided with an image forming section that forms image on a sheet; a first guide member that guides the sheet along a sheet conveying path and is configured to be displaceable relative to the apparatus main body; a second guide member that guides the sheet along the sheet conveying path and is configured to be displaceable relative to the apparatus main body; and a single detecting unit that detects that both of the first guide member and the second guide member are respectively disposed at normal guide positions for guiding the sheet.

Abstract: An image forming apparatus includes a main casing; a photosensitive member; a process cartridge that can be installed or removed with respect to the main casing along a removal path; a pick-up roller located above a sheet accommodating portion; and a feed path along which a sheet can be conveyed from the sheet accommodating portion to a discharge port. At least a part of the feed path is substantially parallel to the removal path and located between the sheet accommodating portion and the process cartridge when the process cartridge is installed in the main casing; and an image forming position where an image is transferred from the photosensitive member to the sheet is located along the feed path at a position lower than an upper surface of the pick-up roller in a verticle direction.

Abstract: A paper jam removing structure for an image forming apparatus is provided. The image forming apparatus includes at least one roller located in the image forming apparatus on a paper feeding path that feeds paper. A reflection mirror is located such that the roller and the portion around the roller may be seen from the front of the image forming apparatus.

Abstract: A pressure lever includes an oscillating edge that is capable of contacting a supporting shaft of a pressure roller. An oscillating lever includes a plurality of oscillating edges around a fixed edge. An elastic unit is latched between the fixed edge of the oscillating lever and an immovable portion, and biases the oscillating lever towards one of the rollers. A position of the fixed edge of the oscillating lever is capable of being changed in a state of being deviated from a position before oscillating based on an oscillating position of the oscillating lever separately from an oscillation of the fixed edge.

Abstract: In an image forming apparatus (10), one (wall surface (201)) of facing wall surfaces of an inverting conveyance path (R3) for turning a sheet (P), which had a toner image formed after an image forming operation in an image forming unit (13) fixed thereto, front side back is formed on a swing door (20) openably and closably provided on an apparatus main body (11). A swing-door supporting structure (30) is provided to rotatably support the swing door (20) at positions of supporting points of rotation of the swing door (20) (center axis positions of shaft main bodies (41)). The swing-door supporting structure (30) is so constructed as to ensure a specified width of the inverting conveyance path (R3) with the swing door (20) closed while moving the swing door (20) in a direction away from the inverting conveyance path R3 by opening the swing door (20).

Abstract: An image forming apparatus includes a removable body that is removably set in a main body of the image forming apparatus, and an engaging mechanism that causes the removable body and the main body to engage with each other when the removable body is lifted by a user.

Abstract: In an image forming device comprising an image forming part forming an image on a recording sheet, a sheet ejection part provided above the image forming part and stacking the recording sheet on which the image is formed by the image forming part, and an image reading part provided above the sheet ejection part and reading an image of an original document, the sheet ejection part is provided with a cover which is capable of being opened or closed to the sheet ejection part.

Abstract: An image forming apparatus is provided which includes a housing, a series of photoconductors on which an electrostatic latent image is formed, and developing devices, which each include a developing agent carrier for holding a developing agent. Also, the apparatus may include a holder, which is removable from the housing, for supporting the photoconductors and the developing devices, and an image reader provided at a top portion of the housing, which is configured to read an image on a document.

Abstract: A feeding unit is disposed near the lower edge of an access opening formed in a front cover of a main casing. The feeding unit includes a pair of registration rollers and a pair of guide parts. One of the registration rollers and one of the guide parts are retained on the front cover. Thus, when the front cover is pulled to an open position, the registration roller and the guide part retained on the front cover displace together with the front cover, exposing a paper conveying path.

Abstract: A sheet conveying device for an image forming apparatus of the present invention includes a cover hinged to the casing of the apparatus and supporting a roller shaft on which a drive roller is mounted. A driven roller and a positioning section for positioning the drive roller are mounted on the casing. The cover is movable between a closed position where the drive roller is pressed against the driven roller and an open position where the former is released from the latter. A first drive gear is affixed to the end of the roller shaft while a second drive gear, meshing with the first drive gear, is mounted on the cover and receives the output torque of a drive source. The roller shaft is mounted on the cover such that the pitch circle of the first drive gear moves on the pitch circle of the second drive gear while touching it externally.

Abstract: An image forming apparatus, includes: a mainframe; a photoreceptor; an exposing unit that exposes a surface of the photoreceptor to form an electrostatic latent image; and a developing unit that develops the electrostatic latent image by supplying a charged developer on the surface of the photoreceptor having the electrostatic latent image formed thereon. The photoreceptor is loadable in and unloadable from the mainframe separately from the developing unit.

Abstract: An image forming apparatus includes: a moisture feeding unit which supplies moisture to a sheet when the sheet passes through a nip portion of a pair of porous rollers, which has a lower roller absorbing water and an upper roller absorbing water in contact with the lower roller, and comprises a water supplying unit which supplies water to the pair of porous rollers, after the sheet onto which a toner image has been formed by and image forming unit passes through a fixing unit. A contact of a contact member in contact with each of a circumference surface of the upper roller and the lower roller is released when a sheet jam occurs.

Abstract: An apparatus is provided for clearing paper jams in a module along a print path of a printer, the module having nip baffles and a rotatable and removable core element defining a print path therethrough. The apparatus comprises at least one cam, a rotatable handle mechanism and a ramp drive mechanism to facilitate the paper jam clearing and removal of the core element from the module.

Abstract: A plurality of process cartridges, each including an electrophotographic photosensitive drum, and a process device actable on the photosensitive drum, are detachably mountable to an electrophotographic image forming apparatus for forming an image of a recording medium. The image forming apparatus includes an opening and closing member; an intermediate transfer member or a recording medium bearing member provided in the opening and closing member such that the intermediate transfer member can face the process cartridges under a condition in which the opening and closing member is closed, and the intermediate transfer member can be separated from the process cartridges under a condition in which the opening and closing member is open; and a moving guide for holding the process cartridges.

Abstract: An image forming apparatus including an image forming unit which forms an image on a recording sheet, a casing which houses the image forming unit and holds the image forming unit, a conveying roller which contacts the recording sheet to be conveyed in the casing, conveys the recording sheet, and is supported to rotate by the casing, a cover which opens and closes an opening formed in a portion of the casing which corresponds to the conveying roller, and a pushing unit. If the cover is closed, the pushing unit exerts a pushing force to push the conveying roller toward the recording sheet to act on a spindle of the conveying roller. If the cover is opened, the pushing unit releases the pushing force by moving in association with the cover.

Abstract: To handle a paper jam, an opening/closing cover 21 is swiveled a predetermined angle around a pivoting shaft 16a, with the opening/closing cover 21 and a paper transport guide member 22a in an unlocked state, to open the opening/closing cover 21. The paper transport guide member 22a opens thereupon by swiveling around a pivoting shaft 16b in response to the opening movement of the opening/closing cover 21, thereby opening simultaneously a paper transport path 10 and a reverse transport path 15.

Abstract: A mounting relief portion for mounting a duplex unit on an image forming apparatus main body is provided in an exterior cover pivotally movably provided on the image forming apparatus main body, and capable of opening and closing a sheet conveying path for conveying a sheet fixed by a fixing device, and this mounting relief portion is shaped so as not to contact with a protrusion of the duplex unit mounted on the image forming apparatus main body when the exterior cover is opened.

Abstract: A paper-releasing mechanism includes a paper-feeding device for feeding papers, a supporting shelf arranged under the paper-feeding device, a driving roller and an idle roller arranged in the front of the paper-feeding device and an elastic unit engaged with the idle roller and the supporting shelf. The elastic unit includes a connecting arm, act arms bending from the ends of the connecting arm respectively, two helixes each of which extends from the act arm and forms an aperture and two follow act arm each of which extends from the helix and forms a ring at the end thereof, the ring being sleeved on the rolling pivot of the idle roller, the apertures being sleeved on a pivot formed on the supporting shelf.