Image forming apparatus

An image forming apparatus includes: an image forming section, provided in an apparatus body, for forming an image on a sheet; a sheet transport path for transporting the sheet to the image forming section; a closing member, openably and closably mounted to the apparatus body, for exposing the sheet transport path in an opened state thereof; a first guide unit and a second guide unit, disposed along the sheet transport path, for guiding the sheet, the first and the second guide units being operable to shift between a proximate position where the first and the second guide units are close to each other, and an away position where the first and the second guide units are away from each other; and a position shifting mechanism for shifting the position of the second guide unit in association with a shifting operation of the first guide unit.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus that enables to easily remove a jammed sheet, in the case where a sheet to be fed to an image forming section along a transport path is jammed.

2. Description of the Related Art

Heretofore, there has been known a so-called vertical transport type image forming apparatus for transporting a sheet substantially in a vertical direction toward an image forming section, as recited in JP No. 2004-123393A (D1). Generally, the image forming apparatus has a closing member (a side part cover member in D1) which is opened and closed by swinging back and forth about an axis of a support shaft mounted at a lower part on a side wall of the apparatus body and extending in a sheet width direction orthogonal to the sheet transport direction. A sheet transport path is defined between an inner wall of the closing member in a closed state, and a portion of the image forming section opposing to the closing member. A photosensitive drum and a transfer roller are provided at respective appropriate positions on the transport path, as opposed to each other with respect to the transport path.

A sheet dispensed from a sheet storage provided at a lower part of the apparatus body, or manually fed by an operator is transported upwardly along the sheet transport path. Then, a toner image on a surface of the photosensitive drum is transferred to the sheet while the sheet passes a nip portion between the photosensitive drum and the transfer roller. After the transferring operation has been completed, the sheet has the toner image fixed by a heat in a fixing section provided immediately above the photosensitive drum, and then the sheet is discharged outside the apparatus body.

In the vertical transport type image forming apparatus, in the case where a sheet is jammed in the sheet transport path, the operator is allowed to remove the jammed sheet by swinging the closing member about the axis of the support shaft and exposing the jammed sheet.

It is often the case that an image forming apparatus has a manual tray for allowing the operator to feed sheets, in addition to a sheet cassette or cassettes. Generally, the manual tray is provided on a side wall of the apparatus body opposite to the side wall of the apparatus body where the closing member is mounted. A sheet placed on the manual tray is fed from a position above the sheet cassette toward the sheet transport path, and has a transport direction thereof changed from a horizontal direction to a vertical direction by about 90° upon reaching a transport direction changing position, whereby the sheet is transported in the vertical direction.

In the above arrangement, in the case where a sheet is jammed in the vicinity of the transport direction changing position, it is extremely difficult to remove the sheet bent with a substantially right angle from the sheet direction changing position, even if the closing member is opened.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention to an image forming apparatus that enables to easily remove a jammed sheet, in the case where a sheet to be fed to an image forming section along a sheet transport path is jammed.

An image forming apparatus according to an aspect of the invention includes: an image forming section, provided in an apparatus body, for forming an image on a sheet; a sheet transport path for transporting the sheet to the image forming section; a closing member, openably and closably mounted to the apparatus body, for exposing the sheet transport path in an opened state thereof; a first guide unit and a second guide unit, disposed along the sheet transport path, for guiding the sheet, the first guide unit and the second guide unit being operable to shift between a proximate position where the first guide unit and the second guide unit are close to each other, and an away position where the first guide unit and the second guide unit are away from each other; and a position shifting mechanism for shifting the position of the second guide unit in association with a shifting operation of the first guide unit.

According to the above arrangement, in the case where a sheet to be transported to the image forming position in the image forming section via the sheet transport path is jammed in the sheet transport path, the operator is allowed to easily remove the jammed sheet by opening the closing member and exposing the jammed sheet.

In the case where an upstream end of a jammed sheet is stuck in the space between the first guide unit and the second guide unit, in response to shifting the first guide unit from the proximate position to the away position, the position shifting mechanism is operable to shift the second guide unit to the away position where the second guide unit is away from the first guide unit in association with the shifting operation of the first guide unit. Thereby, the image forming apparatus is brought to a condition that the sheet jammed during the operation of shifting the first guide unit and the second guide unit to the away position is easily removable. This arrangement allows the operator to easily remove the jammed sheet by pulling the sheet from the space between the first guide unit and the second guide unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a perspective front view of an image forming apparatus embodying the invention, wherein the image forming apparatus is provided with a first guide unit and a second guide unit.FIG. 2is an elevational front view of an internal structure of the image forming apparatus shown inFIG. 1.FIG. 3is a partially enlarged view of the image forming apparatus shown inFIG. 2, specifically, showing a relay unit20in accordance with a first embodiment of the invention. InFIGS. 1 through 3, X-X directions indicate leftward and rightward directions, wherein −X direction indicates leftward direction, +X direction indicates rightward direction; and Y-Y directions indicate forward and backward directions, wherein −Y direction indicates forward direction, and +Y direction indicates backward direction.

First, the entire arrangement of an image forming apparatus10is described based onFIGS. 1 and 2, and referring toFIG. 3according to needs. The image forming apparatus10as illustrated in the embodiment is a copier of so-called internal discharge type, and includes, in an apparatus body11thereof, an image forming section12(seeFIG. 2), a fixing section13(seeFIG. 2), a sheet storing section14, a sheet discharging section15, an image reading section16, and an operating section17. The sheet discharging section15is formed by indenting a part of the apparatus body11below the image reading section16. In this context, the image forming apparatus10is called the internal discharge type.

The apparatus body11includes a lower part body111of a substantially rectangular parallelepiped shape in external view, an upper part body112of a substantially flat parallelepiped shape disposed above and opposite to the lower part body111, and a connecting part113extending between the upper part body112and the lower part body111. The connecting part113is a structural member for linking the lower part body111and the upper part body112, with the sheet discharging section15defined between the lower part body111and the upper part body112. The connecting part113extends upright from a left part of the lower part body111. A left part of the upper part body112is supported on an upper end of the connecting part113.

The image forming section12, the fixing section13, and the sheet storing section14are provided in the lower part body111, and the image reading section16is mounted on the upper part body112. In this embodiment, as show inFIG. 1, the operating section17projects in forward direction from a front end of the upper part body112.

The sheet storing section14includes sheet cassettes141detachably mounted in the apparatus body11. A sheet stack P1(seeFIG. 2) is stored in each of the sheet cassettes141. When an image forming operation is performed, a sheet P is dispensed from the sheet stack P1, and fed to the image forming section12where an image is formed or printed on the sheet P. In this embodiment, two sheet cassettes141are provided.

The sheet discharging section15is defined between the lower part body111and the upper part body112. The sheet discharging section15includes an internal discharge tray151formed of an upper wall of the lower part body111. After the toner image has been transferred in the image forming section12, the sheet P is discharged from a lower part of the connecting part113onto the internal discharge tray151.

The image reading section16includes a contact glass platen161, mounted in an opening in an upper wall of the upper part body112, for placing a document; an openable/closable document pressing cover162for firmly holding the document on the contact glass platen161; and a scan mechanism163(seeFIG. 2) for scanning an image of the document on the contact glass platen161.

Analog information of the document image read by the scan mechanism163is converted into a digital signal, and the digital signal is outputted to an exposure unit123to be described later for an image forming operation.

The operating section17allows the operator to input information relating to an image forming operation to operate the image forming apparatus10. The operating section17is provided with a ten key171(seeFIG. 1) for allowing the operator to input the number of sheets P for image formation and the like, various operation keys, and a LCD (Liquid Crystal Display)172(seeFIG. 1) for allowing the operator to perform a touch input.

A manual tray18is mounted on a right wall of the lower part body111at a position immediately above the sheet storing section14. The manual tray18is pivotally supported at a lower part thereof about an axis of a support shaft181to be shiftable between a close posture where the manual tray18stands upright to close an opening for manual feeding; and an open posture where the manual tray18projects in rightward direction. When the manual tray18is shifted to the open posture, the operator is allowed to manually feed sheets P.

A transport unit184(seeFIG. 2), and a relay unit20(seeFIGS. 2 and 3) equipped with a first guide unit40and a second guide unit50of the embodiment are provided between the manual tray18and a vertical transport path101(seeFIG. 2) as a sheet transport path or a first transport path. A sheet P (seeFIG. 2) fed from the manual tray18is introduced to the vertical transport path101via the transport unit184and the relay unit20, guided upwardly along the vertical transport path101, and fed toward a nip portion between a photosensitive drum121and a transport roller125to be described later. A sheet transport path from the manual tray18to the vertical transport path101constitutes a second transport path.

An openable/closable maintenance door (closing member)19for use in maintenance service is mounted on a left wall of the lower part body111. An openable/closable external discharge tray152is mounted at a position immediately above the maintenance door19. After a printing operation has been completed in the image forming section12, the sheet P is selectively discharged on one of the external discharge tray152and the internal discharge tray151.

In the following, an internal structure of the image forming apparatus10is described in detail referring toFIG. 2. As shown inFIG. 2, the photosensitive drum121is provided substantially at a central part of the image forming section12. The photosensitive drum121has a surface thereof uniformly charged by a charging unit122provided immediately to the right of the photosensitive drum121, while being rotated clockwise about an axis of rotation of the drum.

An electrostatic latent image is formed on the surface of the photosensitive drum121by a laser beam from the exposure unit123, based on image information on the document image read by the image reading section16. A developing agent (hereinafter, called as “toner”) is supplied from a developing unit124provided below the photosensitive drum121toward the electrostatic latent image. Thereby, a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum121.

A sheet P dispensed from one of the sheet cassettes141in the sheet storing section14and guided upwardly along the vertical transport path101extending substantially in vertical direction is fed to the photosensitive drum121where a toner image is formed via a registration roller pair142in synchronism with the toner image formation. Thereby, the toner image on the surface of the photosensitive drum121is transferred to the sheet P by the transfer roller125disposed to the left of the photosensitive drum121and opposite thereto. The sheet P carrying the transferred toner image is separated from the photosensitive drum121, and fed to the fixing section13.

After the toner image has been transferred to the sheet P, the photosensitive drum121is continued to be rotated clockwise. Thereby, the surface of the photosensitive drum121is cleaned by a cleaning device126provided immediately above the photosensitive drum121. After the cleaning operation has been completed, the photosensitive drum121faces the charging unit122for a succeeding image forming operation.

The fixing section13is internally provided with a fixing roller131having an energization heater such as a halogen lamp, and a pressing roller132disposed to the left of the fixing roller131and opposite thereto. The sheet P fed from the image forming section12has the toner image fixed by a heat, while passing a nip portion between the fixing roller131and the pressing roller132.

In the case where single-sided printing is performed, a sheet P carrying a fixed toner image is selectively discharged to one of the internal discharge tray151and the external discharge tray152in the sheet discharging section15via a sheet discharge path102defined above the fixing section13.

On the other hand, in the case where double-sided printing is performed, after a front part of a sheet P carrying a fixed toner image on one surface thereof is temporarily discharged in a space153defined above the internal discharge tray151along a flip-flop transport path103above the sheet discharge path102, the sheet P is fed backward along an inverting transport path104extending substantially in vertical direction in the interior of the maintenance door19for inverting the transport direction, and then, the sheet P is fed to the image forming section12to print an image on the other surface of the sheet P. After the double-sided printing operation been completed, the sheet P is discharged onto the internal discharge tray151or the external discharge tray152. The maintenance door19has a cover member191at a position immediately to the right of the inverting transport path104and opposite to the left portion of the image forming section12. The cover member191is formed within the right wall of the maintenance door19. When the maintenance door19is set to a close posture, a part of the vertical transport path101for transporting a sheet P dispensed from the sheet cassette141or manually fed from the manual tray18is defined between the right wall of the cover member191and the left portion of the image forming section12.

Mounting the maintenance door19having the above arrangement is advantageous in allowing the operator to remove a jammed sheet P by shifting the maintenance door19to an open posture and exposing the jammed sheet P, in the case where a sheet is jammed in the vertical transport path101corresponding to the left portion of the image forming section12.

FIG. 4is an exploded perspective view of the relay unit20in accordance with the first embodiment.FIGS. 5 and 6are assembled perspective views of the relay unit20.FIG. 5shows a state that the first guide unit40and the second guide unit50are set to a proximity position S1, andFIG. 6shows a state the first guide unit40and the second guide unit50are set to an away position S2. The direction indications by the symbols “X” and “Y” inFIGS. 4 through 6are the same as shown inFIG. 1.

As shown inFIG. 4, the relay unit20includes a frame unit30fixed in the apparatus body11, the first guide unit40pivotally mounted in the frame unit30, the second guide unit50movable obliquely in vertical direction as opposed to the first guide unit40, and a position shifting mechanism60for shifting the first guide unit40and the second guide unit50between the proximity position S1and the away position S2.

The frame unit30includes a pair of side frames31opposed to each other in forward and backward directions, and a support frame32provided at a lower position and between the paired side frames31. Each of the side frames31has a trapezoidal shape, wherein a left end of the side frame31is formed into a slope extending obliquely downwardly in leftward direction. In this arrangement, the size of the side frame31in leftward and rightward directions is gradually increased, as the side frame31extends downwardly.

The support frame32has a substantially inverted V-shape in cross section, as viewed in forward direction, with a substantially middle part thereof in leftward and rightward directions formed into a ridge portion322. The support frame32has a right end thereof aligned with lower right corners of the side frames31. The support frame32has a manual-side guide slope321extending obliquely upwardly from the right end of the support frame32in leftward direction, with a recess formed in an upper surface thereof. A sheet P manually fed via the transport unit184is guided upwardly while being transported along the manual-side guide slope321.

The support frame32has a left-side portion323on the left side thereof with respect to the ridge portion322, with an arc-shaped recess indented obliquely downwardly in rightward direction in front view in an upper surface thereof.

Each of the side frames31has a guide groove311extending downwardly and slightly leftwardly from an upper end thereof. A first through-hole312is formed at a left position with respect to the ridge portion322in each of the support frames32, and a second through-hole313is formed at an obliquely upper right position with respect to the first through-hole312in each of the side frames31. The first through-holes312are adapted to mount a first shaft61, to be described later, for pivotally supporting the first guide unit40. The second through-holes313are adapted to mount a second shaft62, to be described later, for shifting the position of the second guide unit50.

A roller shaft insertion hole314is formed at a position substantially immediately below the corresponding first through-hole312in each of the side frames31. The roller shaft insertion holes314are adapted to support a roller shaft of a transport roller143aof a transport roller pair143on the side of the relay unit20.

The first guide unit40is adapted to guide a sheet P dispensed from the sheet cassette141via the transport roller pair143upwardly along the vertical transport path101, or guide a sheet P manually fed from the manual tray18to the vertical transport path101while changing the transport direction of the sheet P by about 90°. The first guide unit40includes a pair of operated side plates41opposed to each other in forward and backward directions, and a guide plate42extending between the paired operated side plates41.

The operated side plates41each is constituted of a rhombic-shaped operated portion411formed at a top part thereof, and a vertically extending guide plate support portion412extending downwardly from a lower part thereof. The operated portion411has such a shape that a corner portion (operated corner portion411a) of the operated portion411faces leftwardly in a state that the first guide unit40is set to the proximity position S1. Front and rear ends (indicated by the two-dotted chain lines inFIG. 5) of the cover member191press the operated corner portions411aor its vicinity rightwardly while the maintenance door19is closed (seeFIG. 2). Thereby, the first guide unit40is set to the proximity position S1where the first guide unit40stands substantially upright.

The guide plate42has a recess422(seeFIG. 3) indented obliquely downwardly in leftward direction in a right surface at a vertically middle part thereof. A sheet P fed to the relay unit20from the manual tray18via the transport unit184is transported upwardly while being guided along the recess422in the guide plate42.

Plural guide ribs421extending in the sheet transport direction are formed on the left surface of the guide plate42. A sheet P dispensed from the sheet cassette141via the transport roller pair143is transported toward the photosensitive drum121along the vertical transport path101while being guided by the guide ribs421.

The second guide unit50has an arc shape protruding obliquely downwardly in leftward direction, as viewed in forward direction. The second guide unit50has a horizontal portion51extending substantially horizontally and opposite to the manual-side guide slope321of the support frame32, and a vertical portion52extending substantially upwardly from a left end of the horizontal portion51. An outer corner of a joint portion between the horizontal portion51and the vertical portion52is formed into an arc-shape protruding obliquely downwardly in leftward direction, as viewed in forward direction.

As shown inFIG. 3, the second guide unit50has such dimensions that, in a state that the first guide unit40and the second guide unit50are respectively set to the proximity position S1, the horizontal portion51faces the manual-side guide slope321of the frame unit30with a slight clearance; and a lower part of the vertical portion52faces the guide plate42of the first guide unit40, and an upper part thereof faces the inner wall of the cover member191(seeFIG. 2) with a slight clearance.

A pair of vertically extending guided projections53is formed on front and rear end surfaces of the vertical portion52of the second guide unit50in directions opposite to each other, respectively. The paired guided projections53have such dimensions as to be slidably guided in the guide grooves311of the frame unit30. With this arrangement, guiding the guided projections53in the respective corresponding guide grooves311, as shown inFIG. 5, allows the second guide unit50to move to a lowermost position by the weight thereof, and set to the proximity position S1.

The position shifting mechanism60includes: the first shaft61which is integrally mounted between lower ends of the guide plate support portions412of the paired operated side plates41of the first guide unit40, with both ends thereof being slidably received in the first through-holes312in the side frames31of the frame unit30; the second shaft62having both ends thereof being slidably received in the second through-holes313in the side frames31; a first gear63integrally and rotatably mounted on a front end of the first shaft61; a second gear64in mesh with the first gear63, and integrally and rotatably mounted on a front end of the second shaft62; a torsion spring (biasing member)65for urging the first guide unit40toward the away position S2; and position shifting cams66, integrally and rotatably mounted on both ends of the second shaft61, respectively, for shifting the guided projections53between the proximity position S1and the away position S2by forward and backward pivotal movement of the second shaft62about the axis thereof.

A D-shaped cutaway portion611is formed in the front end of the first shaft61by cutting away a part of a surface of the front end. A D-shaped hole631corresponding to the D-shaped cut away portion611is formed in the middle of the first gear63. Fixedly mounting the D-shaped cutaway portion611in the first through-hole312via the D-shaped hole631allows the first shaft61to integrally rotate with the first gear63.

A D-shaped cutaway portion621is formed in the second shaft62by cutting away a part of a surface of the second shaft62. A D-shaped hole641corresponding to the front D-shaped cutaway portion621is formed in the middle of the second gear64. Fixedly mounting the D-shaped cutaway portion621in the D-shaped hole641allows the second shaft62to integrally rotate with the second gear64.

The torsion spring65includes an annular portion651to be wound around the first shaft61, and a first arm652and a second arm653each drawn from the annular portion651. The length of the first arm652is set slightly smaller than the diameter of the first gear63. The length of the second arm653is set longer than the diameter of the first gear63.

A gear mounting hole632is formed in a front surface of the first gear63to receive a lead end of the first arm652of the torsion spring65which is bent substantially at a right angle. A side-frame mounting hole315is formed in the side frame31to receive a lead end of the second arm653which is bent substantially at a right angle. Mounting the lead end of the first arm652in the gear mounting hole632in the first gear63in a state that the annular portion651is wound around the front end of the first shaft61, and mounting the lead end of the second arm653in the side-frame mounting hole315allows the torsion spring65to be mounted between the first gear63and the side frame31.

The angle between the first arm652and the second arm653is defined to such a value that the torsion spring65is operable to urge the first guide unit40toward the away position S2from the proximity position S1. In this arrangement, in response to closing the maintenance door19, as shown inFIG. 5, the cover member191presses the operated corner portions411aof the operated side plates41. Thereby, the first guide unit40is set to the proximity position S1against the biasing force of the torsion spring65. On the other hand, in response to opening the maintenance door19, the pressing force exerted to the operated side plates41by the cover member191is released. Thereby, the first guide unit40swings counterclockwise about the axis of the first shaft61by the biasing force of the torsion spring65, and is set to the away position S2, as shown inFIG. 6.

The position shifting cams66are adapted to shift the second guide unit50between the proximity position S1and the away position S2by forward and backward pivotal movement thereof about the axis of the second shaft62. The position shifting cams66are mounted on the second shaft62at inner walls of the side frames31, respectively. Each of the position shifting cams66has a substantially elliptical shape, and a D-shaped hole661is formed at one of the focus positions thereof for receiving the D-shaped cutaway portion621of the second shaft62.

Mounting the D-shaped cutaway portions621in the D-shaped holes661allows the position shifting cams66to be integrally and rotatably coupled to the second shaft62. The second gear64is mounted in a space corresponding to an outwardly projecting portion of the second shaft62in a state that the position shifting cams66are mounted on the second shaft62, and the lead end of the second shaft62projects outwardly through the second through-hole313in the side frame31.

The phase of the position shifting cam66is defined in such a manner that the second guide unit50faces leftwardly with respect to the second shaft62in a state that the second guide unit50is set to the proximity position S1. When the second guide unit50is set to the proximity position S1, the front ends of the position shifting cams66are aligned with the arc-shaped portion between the horizontal portion51and the vertical portion52of the second guide unit50. In this arrangement, in response to clockwise rotation of the second shaft62about the axis thereof in a state that the second guide unit50is set to the proximity position S1, a bottom portion of the second guide unit50is pressed upwardly by left ends of the position shifting cams66, as the position shifting cams66are integrally rotated about the axis of the second shaft62. Thereby, the second guide unit50is shifted to the away position S2as shown inFIG. 6, while the guided projections53are guided in the guide grooves31.

In the following, the operation of the relay unit20is described based onFIGS. 7A and 7B, and referring toFIGS. 1 through 6according to needs.FIGS. 7A and 7Bare sectional front views for describing an operation of the position shifting mechanism60in the relay unit20.FIG. 7Ashows a state that the first guide unit40and the second guide unit50are set to the proximity position S1, andFIG. 7Bshows a state that the first guide unit40and the second guide unit50are set to the away position S2. The direction indications by the symbol “X” inFIGS. 7A and 7Bare the same as those inFIG. 2. Specifically, −X indicates leftward direction, and +X indicates rightward direction.

As shown inFIG. 7A, in the case where the maintenance door19is closed, the cover member191presses the operated portions411of the operated side plates41rightwardly against the biasing force of the torsion spring65(seeFIG. 5). Thereby, the first guide unit40and the second guide unit50are respectively set to the proximity position S1. In this state, the recess422in the first guide unit40comes close to the left surface of the vertical portion52of the second guide unit50. Thereby, a sheet P fed from the transport unit184is smoothly guided toward the vertical transport path101while being held and guided by the first guide unit40and the second guide unit50.

In the case where the sheet P is jammed in the relay unit20or at a position posterior or anterior to the relay unit20, transport of the sheet P is automatically suspended. Then, the operator is allowed to open the maintenance door19to remove the jammed sheet. In response to opening the maintenance door19, the pressing force exerted to the operated portions411of the operated side plates41by the cover member191is released. Thereby, as shown inFIG. 7B, the first guide unit40swings counterclockwise about the axis of the first shaft61via the first gear63by the biasing force of the torsion spring65(seeFIG. 6), whereby the first guide unit40is shifted from the proximity position S1to the away position S2.

The clockwise rotation of the first gear63about the axis of the first shaft61by the biasing force of the torsion spring65is transmitted to the second gear64in mesh with the first gear63. Thereby, the second gear64is integrally rotated clockwise about the axis of the second shaft62. Then, the clockwise rotation of the second gear64about the axis of the second shaft62is transmitted to the position shifting cams66, and the position shifting cams66are pivotally rotated clockwise about the axis of the second shaft62.

By the pivotal rotation of the position shifting cams66, the left ends of the position shifting cams66press the bottom portion of the second guide unit50upwardly. As a result, as shown inFIG. 7B, the second guide unit50is shifted from the proximity position S1to the away position S2, as the guided projections53are guided in the guide grooves311.

Specifically, in response to opening the maintenance door19to remove a jammed sheet, the force to open the maintenance door19is transmitted to the first guide unit40via the operated side plates41, and to the second guide unit50via the first gear63, the second gear64, and the position shifting cams66. Thereby, both of the first guide unit40and the second guide unit50are shifted from the proximity position S1to the away position S2. Then, in the case where the first guide unit40and the second guide unit50are set to the away position S2, as shown inFIG. 7B, a significantly large clearance is defined between the first guide unit40and the second guide unit50. Thereby, the operator is allowed to easily remove the jammed sheet P. The above arrangement contributes to remarkably improving the operability in removing a jammed sheet.

After the jammed sheet has been removed, the maintenance door19is closed. In response to closing the maintenance door19, the right ends of the cover member191press the operated side plates41of the first guide unit40rightwardly. Thereby, the first guide unit40swings clockwise about the axis of the first shaft61, and the second guide unit50swings counterclockwise about the axis of the second shaft62via the first gear63, the second gear64, and the position shifting cams66. Thereby, the first guide unit40and the second guide unit50are returned to the proximity position S1shown inFIG. 7A.

FIG. 8is a sectional front view (taken along the line IIX-IIX inFIG. 10) of a relay unit20′ in accordance with a second embodiment of the invention.FIGS. 9 and 10are perspective views of the relay unit20′ shown inFIG. 8, whereinFIG. 9is an exploded perspective view, andFIG. 10is an assembled perspective view. The direction indications by the symbols “X” and “Y” inFIGS. 8 through 10are the same as shown inFIG. 1. Specifically X-X directions indicate leftward and rightward directions, wherein −X direction indicates leftward direction, +X direction indicates rightward direction; and Y-Y directions indicate forward and backward directions, wherein −Y direction indicates forward direction, and +Y direction indicates backward direction.

As shown inFIG. 8, the relay unit20′ in the second embodiment is basically the same as the relay unit20in the first embodiment in that the relay unit20′ includes a frame unit30′ fixed in an apparatus body11, a first guide unit40′ pivotally mounted in the frame unit30′, and a second guide unit50′ mounted to the right of the first guide unit40′ in the frame unit30′, as opposed to the first guide unit40′, except for the detailed arrangement of the first guide unit40′ and the second guide unit50′.

In the relay unit20′ in the second embodiment, a posture shifting mechanism70for shifting the posture of the first guide unit40′ and the second guide unit50′ is employed to allow the first guide unit40′ and the second guide unit50′ to perform a predetermined operation, in place of the position shifting mechanism60in the first embodiment. In the following, the first guide unit40′ and the second guide unit50′ are described, and then, the posture shifting mechanism70is described.

The frame unit30′ includes a pair of side frames33opposed to each other in forward and backward directions, a lower support frame34extending between the paired side frames33at a right part of the paired side frames33, and an upper support frame35formed above the lower support frame34and opposite to the lower support frame34. The lower support frame34has a manual-side guide slope341extending obliquely upwardly in leftward direction, with an arc-shaped recess indented obliquely downwardly in leftward direction in an upper surface thereof. A downstream end of the manual-side guide slope341faces a lower part of the right wall of the second guide unit50′.

The upper support frame35has a length substantially twice as long as the length of the lower support frame34in leftward and rightward directions. The upper support frame35has an arc shape protruding toward lower left corners of the side frames33in its entirety, with a right half portion thereof opposing to the manual-side guide slope341of the lower support frame34, and a left half portion thereof opposing to an upper part of the right wall of the second guide unit50′. In this arrangement, a sheet P fed from a transport unit184is guided to the clearance between the upper support frame35and the lower support frame34, and is transported to a vertical transport path101from a downstream end of the clearance via a clearance between the left surface of the upper support frame35and the second guide unit50′, while being guided along the manual-side guide slope341.

The rear side frame33has a cutaway groove332extending from a slope surface331on an upper left corner thereof toward a lower right corner thereof. As shown inFIG. 8, the cutaway groove332is adapted to receive a rear end of a first elliptical shaft442to be descried later, in a state that the first guide unit40′ is set to a transport posture.

Left support holes333(seeFIG. 9) are formed in lower left corners of the front and rear side frames33, respectively, at positions opposite to each other. Middle support holes334are formed substantially in the middle of the front and rear side frames33in leftward and rightward directions at positions slightly above the left support holes333, respectively. The left support holes333are adapted to support a first link shaft71to be described later. The middle support holes334are adapted to support a second link shaft72to be described later.

The first guide unit40′ includes: a first guide body43, disposed opposite to the vertical transport path101, for guiding a sheet P dispensed from a sheet cassette141toward the photosensitive drum121(seeFIG. 2); a first transport roller44mounted at an upper left position of the first guide body43; a first transport roller gear45coaxially mounted on the first transport roller44to be integrally rotated with the first transport roller44; a second transport roller46mounted at a lower right corner of the first guide body43; and a second transport roller gear47coaxially mounted on the second transport roller46to be integrally rotated with the second transport roller46, and in mesh with the first transport roller gear45.

The first transport roller44is adapted to transport a sheet P from the sheet cassette141. The second transport roller46is adapted to transport a sheet P fed from a manual tray18to the relay unit20′ via the transport unit184.

The first guide body43includes a frame member431of a plate-like shape with one step portion in front view, and plural guide fins435mounted on the frame member431. The mounting manner of the guide fins435is not limited to the above. Alternatively, in the case where the first guide body43is made of a synthetic resin, the frame member431and the guide fins435may be integrally formed by e.g. injection molding.

The frame member431includes an intermediate portion432extending in forward and backward directions, with a middle part thereof being indented upwardly; a suspending portion433extending downwardly from a left end of the intermediate portion432; and an upward extension434upwardly extending from a right end of the intermediate portion432.

The guide fins435each has such dimensions as to be mounted on the frame member431. Each of the guide fins435has an upper fin portion436of a substantially triangular shape at an upper side of the intermediate portion432, and a lower fin portion437of a shape other than the triangular shape at a lower side of the intermediate portion432.

The upper fin portion436has a slope surface436aextending obliquely downwardly in leftward direction. A sheet P from the sheet cassette141is guided upwardly along the slope surface436a, while being guided by driving rotation of the first transport roller44. A first circular hole436bis formed in each of the upper fin portions436to receive the first elliptical shaft442to be described later.

The foremost upper fin portion436and the rearmost upper fin portion436have arc-shaped stoppers436cbulging from upper ends thereof in rightward direction, respectively. As shown inFIG. 8, the arc-shaped stoppers436care abutted against lower ends of a guide wall101aof the vertical transport path101on the side of an image forming section12in a state that the first guide unit40′ is set to a transport posture. Thereby, a further clockwise swing of the first guide unit40′ is restrained.

Each of the lower fin portions437has a leg portion437aextending downwardly along the suspending portion433. A pivot center hole437cis formed in a lower end of each of the leg portions437aon the right of the suspending portion433. The pivot center holes437care aligned with the left support holes333, and adapted to receive and support the first link shaft71to be described later. Each of the lower fin portions437also has a second circular hole437bat a lower right of the intermediate portion432for receiving a second elliptical shaft462to be described later.

The first transport roller44is provided in plural number and has such dimensions that the first transport rollers44are respectively mounted in upper roller mounting chambers4apartitioned by the adjacent upper fin portions436of the first guide body43. In this embodiment, the first guide body43has ten fins. Accordingly, nine upper roller mounting chambers4aare provided. The number of fins of the first guide body43is not limited to ten, but may be less than ten or more than ten. The number of the first transport rollers44may be less than nine or more than nine in correspondence to the number of fins.

A first elliptical hole441with an elliptical shape is formed in the middle of each of the first transport rollers44. The first elliptical shaft442whose cross sectional shape coincides with the shape of the first elliptical hole441is passed through the first elliptical holes441. The first elliptical shaft442has a curvature diameter thereof slightly smaller than the diameter of the first circular hole436b, and a length thereof slightly larger than the outer distance between the paired side frames33of the frame unit30′.

In this arrangement, passing the first elliptical shaft442through the first elliptical holes441via the first circular holes436bin a state that the first transport rollers44are mounted in the respective corresponding upper roller mounting chambers4aallows the first transport rollers44to integrally rotate about the axis of the first elliptical shaft442, in a state that the first transport rollers44are mounted in the upper roller mounting chambers4a, as shown inFIG. 10.

In the above state, the first transport roller gear45is mounted on the first elliptical shaft442at a rear surface of the rearmost upper fin portion436to be integrally rotated with the first elliptical shaft442. Specifically, an elliptical center hole451with a shape coincident with the cross sectional shape of the first elliptical shaft442is formed in the middle of the first transport roller gear45. The first elliptical shaft442is received in the center hole451.

C-rings or a like member are mounted on both ends of the first elliptical shaft442in a state that the first elliptical shaft442is passed through the first transport rollers44in the upper roller mounting chambers4a, and through the first transport roller gear45to prevent disengagement of the first elliptical shaft442. A rear end of the first elliptical shaft442projects rearwardly through the cutaway groove332in the rear side frame33in a state that the first guide unit40′ is set to a transport posture, as shown inFIG. 10. The rearwardly projecting rear end of the first elliptical shaft442is connected to an unillustrated driving motor via a predetermined coupling member in a state that the first guide body43is set to the transport posture. Thereby, a driving force of the driving motor is transmitted to the first transport rollers44and the first transport roller gear45via the first elliptical shaft442.

The second transport roller46is provided in plural number and has such dimensions that the second transport rollers46are respectively mounted in lower roller mounting chambers4b(seeFIG. 8) partitioned by the adjacent lower fin portions437of the first guide body43. In this embodiment, the second transport roller46is not provided in a space between the lower fin portions437at a middle part of the first guide body43in forward and backward directions, in view of the construction of the second guide unit50′. Accordingly, eight lower roller mounting chambers4bare defined between the adjacent lower fin portions437, wherein four lower roller mounting chambers4bare defined in a front part of the first guide body43, and four lower roller mounting chambers4bare defined in a rear part of the first guide body43, except for the middle part thereof.

A second elliptical hole461with an elliptical shape is formed in the middle of each of the second transport rollers46. The second elliptical shaft462whose cross sectional shape coincides with the shape of the second elliptical hole461is passed through the second elliptical holes461. The second elliptical shaft462has a curvature diameter thereof slightly smaller than the diameter of the second circular hole437b, and a length thereof slightly larger than the outer distance between the paired side frames33of the frame unit30′.

In this arrangement, passing the second elliptical shaft462through the second elliptical holes461via the second circular holes437bin a state that the second transport rollers46are mounted in the respective corresponding lower roller mounting chambers4ballows the second transport rollers46to integrally rotate about the axis of the second elliptical shaft462, in a state that the second transport rollers46are mounted in the lower roller mounting chambers4b.

In the above state, the second transport roller gear47is mounted on the second elliptical shaft462at a rear surface of the rearmost lower fin portion437to be integrally rotated with the second elliptical shaft462. Specifically, an elliptical center hole471with a shape coincident with the cross sectional shape of the second elliptical shaft462is formed in the middle of the second transport roller gear47. The second elliptical shaft462is received in the center hole471.

C-rings or a like member are mounted on both ends of the second elliptical shaft462in a state that the second elliptical shaft462is passed through the second transport rollers46in the lower roller mounting chambers4b, and through the second transport roller gear47to prevent disengagement of the second elliptical shaft462. The length of the second elliptical shaft462is set slightly smaller than the inner distance between the paired side frames33of the frame unit30′. Accordingly, the second elliptical shaft462is mounted between the paired side frames33in a state that the first guide unit40′ is set to a transport posture, as shown inFIG. 10.

The second transport roller gear47is engaged with the rearmost first transport roller44. Accordingly, in response to driving the unillustrated driving motor, rotation of the first transport roller gear45is transmitted to the second transport roller gear47. Thereby, the first transport rollers44and the second transport rollers46are rotated in directions opposite to each other. Specifically, the first transport rollers44are rotated clockwise, and the second transport rollers46are rotated counterclockwise inFIG. 8.

The second guide unit50′ is pivotally supported about the axis of the second link shaft72to be described later. The second guide unit50′ includes an elongated and planar-shaped second guide body54extending in forward and backward directions, with a substantially E-shape in plan view; and a pair of brackets55fixed at front and rear ends of the second guide body54, respectively.

The second guide body54includes a bent portion541formed by bending a base end thereof at a substantially right angle and extending in leftward direction. Forming the bent portion541is advantageous in increasing the mechanical strength of the second guide unit50′. The second guide body54further has upwardly projecting extension arms542at a front end, a rear end, and a middle part thereof in forward and backward directions, respectively. As shown inFIG. 8, eight second transport rollers46are mounted in the clearances between the front extension arm542, the middle extension arm542, and the rear extension arm542in a state that the second guide unit50′ is set to a transport posture. Specifically, four second transport rollers46are mounted in the front clearance between the front extension arm542and the middle extension arm542; and four second transport rollers46are mounted in the rear clearance between the middle extension arm542and the rear extension arm542.

The brackets55each has a substantially right triangular shape. The brackets55are fixedly mounted between the bent portion541and the second guide body54at front and rear ends of the second guide body54, respectively. An insertion hole551is formed in each of the brackets55to receive the second link shaft72to be described later.

The posture shifting mechanism70is adapted to move the second guide unit50in association with a movement of the first guide unit40′. The posture shifting mechanism70includes the first link shaft (first shaft)71for pivotally supporting the first guide unit40′ about the axis thereof, the second link shaft (third shaft)72for pivotally supporting the second guide unit50′ about the axis thereof, and a linking arm73extending between the first guide unit40′ and the second guide unit50′ at a position above a straight line connecting the axes of the first link shaft71and the second link shaft72to swing the first guide unit40′ and the second guide unit50′ relative to each other.

Front and rear ends of the first link shaft71are received in the left support holes333in the paired side frames33of the frame unit30′ respectively in a state that the first link shaft71is passed through the pivot center holes437cin the leg portions437aof the first guide body43to prevent disengagement of the first link shaft71. In this arrangement, the first guide unit40′ is allowed to be shifted between the transport posture shown inFIG. 11Aand the open posture shown inFIG. 11Bby swinging back and forth about the axis of the first link shaft71.

Front and rear ends of the second link shaft72are received in the middle support holes334in the paired side frames33of the frame unit30′ respectively in a state that the second link shaft72is passed through the insertion holes551in the paired brackets55attached to the front and rear ends of the second guide body54to prevent disengagement of the second link shaft72. In this arrangement, the second guide unit50′ is allowed to be shifted between the transport posture shown inFIG. 11Aand the open posture shown inFIG. 11Bby swinging back and forth about the axis of the second link shaft72.

As shown inFIG. 9, a first bracket438of the first guide unit40′ is attached to the suspending portion433substantially in the middle of the first guide body43in forward and backward directions; and a second bracket543of the second guide unit50′ is attached to the middle extension arm542of the second guide body54, as opposed to the first bracket438. The linking arm73extends between the first bracket438and the second bracket543.

A left end of the linking arm73is pivotally supported about the axis of a third link shaft74passing through the first bracket438. A right end of the linking arm73is pivotally supported about the axis of a fourth link shaft75passing through the second bracket543. Thus, the posture shifting mechanism70is configured into a four-sided link structure constituted of a portion of the side frames33between the first link shaft71and the second link shaft72, a portion of the leg portions437aof the first guide body43between the first link shaft71and the third link shaft74, and a portion of the second guide body54between the second link shaft72and the fourth link shaft75.

FIGS. 11A and 11Bare diagrams for describing an operation of the posture shifting mechanism70in the relay unit20′ of the second embodiment.FIG. 11Ashows a state that the first guide unit40′ and the second guide unit50′ are respectively set to the transport posture, andFIG. 11Bshows a state that the first guide unit40′ and the second guide unit50′ are respectively set to the open posture. The direction indications by the symbol “X” inFIGS. 11A and 11Bare the same as shown inFIG. 1, wherein −X indicates leftward direction, and +X indicates rightward direction.

As shown inFIG. 11A, in the case where the first guide unit40′ and the second guide unit50′ are respectively set to the transport posture, the left ends of the guide fins435and the outer surfaces of the first transport rollers44in the first guide unit40′ face the right wall of a maintenance door19in a closed state; and the right surface of the second guide body54and the outer surfaces of the second transport rollers46face the arc-shaped portion on the left surface of the upper support frame35in the frame unit30′.

In the above state, a sheet P fed from the sheet cassette141is passed through the clearance between the guide fins435and the left wall of the maintenance door19, and is transported toward the photosensitive drum121along the vertical transport path101, while being guided by rotation of the first transport rollers44.

On the other hand, a sheet P fed from the manual tray18to the clearance between the upper support frame35and the lower support frame34of the relay unit20′ via the transport unit184is passed through the clearance between the right surface of the second guide body54and the left surface of the upper support frame35while being guided along the right surface of the second guide body54, and is transported toward the photosensitive drum121along the vertical transport path101, while being guided by integral rotation of the second transport rollers46about the axis of the second elliptical shaft462.

In the case where the sheet P fed from the manual tray18is jammed in the relay unit20′, the operator opens the maintenance door19. Then, the first guide unit40′ swings counterclockwise about the axis of the first link shaft71shown inFIG. 11A. Then, the linking arm73pivotally supported on the third link shaft74of the first guide body43is moved leftward. Thereby, the second guide unit50′ coupled to the right end of the linking arm73via the fourth link shaft75swings counterclockwise about the axis of the second link shaft72inFIG. 11A. Thereby, the second guide unit50′ is shifted to the open posture, as shown inFIG. 11B.

Then, in the case where the second guide unit50′ is set to the open posture, the clearance between the second guide body54and the upper support frame35is increased, as shown inFIG. 11B. Thereby, the operator is allowed to easily remove the sheet P jammed in the relay unit20′. The above arrangement contributes to improving the operability in removing a jammed sheet.

As described above in detail, the image forming apparatus10of the embodiment includes the image forming section12, provided in the apparatus body11, for forming an image on a sheet P; the maintenance door19, openably and closably mounted to the apparatus body11, for exposing the image forming section12in an opened state thereof; and the vertical transport path101defined by the inner wall of the maintenance door19and a portion of the image forming section12opposite to the maintenance door19to transport the sheet P toward the image forming section12.

The relay unit20in the first embodiment includes: the first guide unit40and the second guide unit50operable to shift between the proximity position S1where the first guide unit40and the second guide unit50are close to each other to guide the sheet P to the vertical transport path101while holding the sheet P therebetween, and the away position S2, where the first guide unit40and the second guide unit50are away from each other to release the sheet P; and the position shifting mechanism60for shifting the position of the second guide unit50in association with a shifting operation of the first guide unit40.

According to the above arrangement, in the case where the sheet P to be transported to the image forming position in the image forming section12via the vertical transport path101is jammed in the vertical transport path101, the operator is allowed to easily remove the jammed sheet P by opening the maintenance door19, and exposing the jammed sheet.

In the case where an upstream end of a jammed sheet P is stuck in the space between the first guide unit40and the second guide unit50, in response to shifting the first guide unit40from the proximate position S1to the away position S2, the second guide unit50is shifted to the away position S2where the second guide unit50is away from the first guide unit40in association with the shifting operation of the first guide unit40. Thereby, the image forming apparatus is brought to a condition that the sheet P jammed during the operation of shifting the first guide unit40and the second guide unit50to the away position S2is easily removable. This arrangement enables the operator to easily remove the jammed sheet P by pulling the sheet P from the space between the first guide unit40and the second guide unit50. The above arrangement is advantageous in allowing the operator to easily remove the jammed sheet P, and remarkably improving the operability in removing the jammed sheet P.

In the first embodiment, the opening/closing operation of the maintenance door19is associated with the shifting operation of the first guide unit40by a biasing force of the torsion spring65. Accordingly, in the case where a sheet jam has occurred, the operator can easily remove the jammed sheet by opening the maintenance door19, without operating the first guide unit40, since the first guide unit40and the second guide unit50are automatically shifted from the proximate position S1to the away position S2in association with the opening operation of the maintenance door19. The above arrangement enables the operator to efficiently remove the jammed sheet.

In the first embodiment, the position shifting mechanism60includes: the first shaft61for pivotally supporting the first guide unit40about the axis thereof; the guide grooves311for guiding the second guide unit50in directions toward and away from the first guide unit40; the torsion spring65for urging the first guide unit40toward the away position S2; the first gear63coaxially mounted on the first shaft61to be integrally rotated with the first shaft61; the second gear64in mesh with the first gear63and rotated about the axis of the second shaft62; and the position shifting cams66for shifting the second guide unit50between the proximate position S1and the away position S2along the guide grooves311by rotation of the second gear64, and the first guide unit40has such a shape that the first guide unit40is set to the proximate position S1by interference with the maintenance door19in a state that the maintenance door19is closed.

In the above arrangement, in a state that the maintenance door19is closed, the maintenance door19interferes with the first guide unit40. Thereby, the first guide unit40is set to the proximate position S1against the biasing force of the torsion spring65, and the second guide unit50is also set to the proximate position S1along with the first guide unit40.

In the above condition, in the case where a sheet P being transported along the transport path is jammed, the operator opens the maintenance door19to remove the jammed sheet P. In response to the operation of opening the maintenance door19, the first guide unit40is released from the interference by the maintenance door19. Thereby, the first guide unit40swings about the axis of the first shaft61by the biasing force of the torsion spring65, and is shifted from the proximate position S1to the away position S2. Then, the rotation of the first shaft61is transmitted to the second gear64via the first gear63for integral rotation of the second gear64about the axis of the second shaft62. The rotation of the second shaft62is transmitted to the second guide unit50by the position shifting cams66. Thereby, the second guide unit50is moved in a direction away from the first guide unit50while being guided in the guide grooves311.

As described above, the position shifting mechanism60for swinging the first guide unit40about the axis of the first shaft61, and shifting the second guide unit50in the direction away from the first guide unit40is constituted of the first gear63, and the second gear64in mesh with the first gear63. This arrangement enables to simplify the construction of the position shifting mechanism60, and shift the first guide unit40and the second guide unit50between the proximate position S1and the away position S2.

The image forming apparatus10further includes the registration roller pair142, provided at a position immediately in front of the image forming section12in the transport path, for adjusting a timing of feeding the sheet P to the image forming section12. This arrangement enables to feed the sheet P being transported along the vertical transport path101to the image forming section12at an appropriate timing after a lead end of the sheet P has reached the registration roller pair142by driving the registration roller pair142. This arrangement is advantageous in performing a proper image forming operation on the sheet P.

A sheet jam is likely to occur in the vicinity of the registration roller pair142. A sheet jammed in the vicinity of the registration roller pair142can be easily removed by shifting the first guide unit40and the second guide unit50from the proximate position S1to the away position S2.

In the relay unit20′ of the second embodiment, each of the first guide unit40′ and the second guide unit50′ is allowed to swing individually. The posture shifting mechanism70is employed in the second embodiment, in place of the position shifting mechanism60in the first embodiment. The posture shifting mechanism70is operable to swing the second guide unit50′ in association with a swinging operation of the first guide unit40′ to shift the second guide unit50′ between the transport posture and the open posture. In this arrangement, in the case where a sheet P is jammed on the side of the second guide unit50′, the second guide unit50′ is shifted from the transport posture to the open posture in association with the swinging operation of the first guide unit40′ about the axis of the first link shaft71. Thereby, the image forming apparatus is brought to a condition that the sheet P jammed on the side of the second guide unit50′ is easily removable. This arrangement enables the operator to remove the jammed sheet P by pulling the sheet P from the side of the second guide unit50′.

The posture shifting mechanism70includes: the first link shaft71for pivotally supporting the first guide unit40′ about the axis thereof; the third shaft for pivotally supporting the second guide unit50′ about the axis thereof; and the linking arm73extending between the first guide unit40′ and the second guide unit50′ to swing the first guide unit40′ and the second guide unit50′ relative to each other, wherein the linking arm73, the first guide unit40′, and the second guide unit50′ constitute a four-sided link structure. Providing the four-sided link structure enables to simplify the construction of the posture shifting mechanism70, and securely and properly move the first guide unit40′ and the second guide unit50′ in association with each other.

The invention is not limited to the foregoing embodiments, but may embrace the following contents.

In the embodiment, the image forming apparatus is a copier. The image forming apparatus is not limited to a copier, but may be a printer for printing an image based on image information from a computer, or a facsimile machine for forming an image based on image information transmitted from a remote device.

In the first embodiment, the first guide unit40and the second guide unit50are shifted between the proximate position S1and the away position S2in association with an opening/closing operation of the maintenance door19. Alternatively, the first guide unit40may be manually shifted from the proximate position S1to the away position S2, after the maintenance door19is opened.

In the first embodiment, the second guide unit50is linearly shifted between the proximate position S1and the away position S2. Alternatively, the second guide unit50may swing back and forth about a right end of the horizontal portion51as a pivot axis.

In the first embodiment, the guide grooves311serve as a guide rail for linearly moving the second guide unit50. Alternatively, the guide rail may be ribs vertically extending from the side frames31. In the modification, it is required to form grooves in the second guide unit50with which the ribs are slidably contacted.

In the embodiment, the second guide unit50is set to the proximate position S1by a weight thereof. Alternatively, the second guide unit50may be set to the proximate position S1by a biasing force of a biasing member.

In the first embodiment, both of the first shaft61and the second shaft62are arranged at side portions of the sheet transport path in view of the positional relations of the parts.

In the above arrangement, however, the number of gears may be increased, and the number of parts may be increased accordingly. Also, the phases of the left-side and right-side position changing cams66may be required to be adjusted individually, which may increase the number of steps in assembling.

FIGS. 12A through 12Cshow an approach for eliminating the above drawback. Specifically,FIGS. 12A and 12Bare cross-sectional views showing a modification of the position shifting mechanism60in the first embodiment.FIG. 12Ashows a state that a first guide unit40and a second guide unit50are set to a proximate position, andFIG. 12Bshows a state that the first guide unit40and the second guide unit50are set to an away position.FIG. 12Cis an exploded perspective view showing the modification of the position shifting mechanism60and a relay unit. The direction indications by the symbol “X” inFIGS. 12A and 12Bare the same as those inFIGS. 7A and 7B. Specifically, −X indicates leftward direction, and +X indicates rightward direction.

First, as shown inFIG. 12A, a first shaft61is arranged at a position displaced from a vertical transport path101in rightward direction, and a second shaft62is arranged above the second guide unit50. The first shaft61and the second shaft62extend through front and rear side frames31. A D-shaped cutaway portion611is formed in a front end of the first shaft61. Similarly to the first embodiment, a first gear63is fixed to the first shaft61at a position projecting from the front side frame31, and a torsion spring65is mounted on the first gear63. A D-shaped cutaway portion621is formed at both ends of the second shaft62. Position changing cams66are fixed to the D-shaped cut away portions621, respectively. The second gear64is fixed to the second shaft62at a position projecting from the front side frame31. The second gear64is meshed with the first gear63. A rightwardly extending projecting piece521is attached to a vertical portion52of the second guide unit50to move the second guide unit50up an down by rotation of position shifting cams66. Lead ends of the position shifting cams66extending obliquely upwardly in leftward direction from the second shaft62are contacted with the backside surface of the projecting piece521.

The above arrangement enables to prevent a lead end of a sheet P being transported from the sheet cassette141(seeFIG. 2) along the vertical transport path101via a transport roller pair143from interfering with the first shaft61, and prevent a lead end of a sheet P fed from the manual tray18(seeFIG. 2) to the clearance between a support frame32and the second guide unit50via a transport unit184from interfering with the second shaft62.

In the modification, similarly to the embodiment, in the case where a sheet jam has occurred, in response to opening the maintenance door19, a first gear63is rotated counterclockwise about the axis of the first shaft61by a biasing force of the torsion spring65(seeFIG. 5). Thereby, the first guide unit50swings counterclockwise about the axis of the first shaft61, and is set to the away position.

Likewise, similarly to the embodiment, in response to rotation of the first gear63about the axis of the first shaft61, the second gear64in mesh with the first gear63is integrally rotated clockwise about the axis of the second shaft62. Thereby, the position shifting cams66integrally mounted on the second shaft62are rotated clockwise. As the position shifting cams66are rotated, the lead ends of the position shifting cams66lift the projecting piece521upwardly. Thereby, the second guide unit50is moved upwardly, and is set to the away position, as shown inFIG. 12B.

As described above, an image forming apparatus according to an aspect of the invention includes: an image forming section, provided in an apparatus body, for forming an image on a sheet; a sheet transport path for transporting the sheet to the image forming section; a closing member, openably and closably mounted to the apparatus body, for exposing the sheet transport path in an opened state thereof; a first guide unit and a second guide unit, disposed along the sheet transport path, for guiding the sheet, the first guide unit and the second guide unit being operable to shift between a proximate position where the first guide unit and the second guide unit are close to each other, and an away position where the first guide unit and the second guide unit are away from each other; and a position shifting mechanism for shifting the position of the second guide unit in association with a shifting operation of the first guide unit.

According to the above arrangement, in the case where the sheet to be transported to the image forming position in the image forming section via the sheet transport path is jammed in the sheet transport path, the operator is allowed to easily remove the jammed sheet by opening the closing member and exposing the jammed sheet.

In the case where an upstream end of a jammed sheet is stuck in the space between the first guide unit and the second guide unit, in response to shifting the first guide unit from the proximate position to the away position, the position shifting mechanism is operable to shift the second guide unit to the away position where the second guide unit is away from the first guide unit in association with the shifting operation of the first guide unit. Thereby, the image forming apparatus is brought to a condition that the sheet jammed during the operation of shifting the first guide unit and the second guide unit to the away position is easily removable. This arrangement allows the operator to easily remove the jammed sheet.

In the above arrangement, preferably, the sheet transport path may be constituted of a closing member transport path defining portion defined by an inner wall of the closing member, and a body transport path defining portion defined by a portion of the image forming section opposite to the closing member.

According to the above arrangement, in response to opening the closing member, the sheet transport path is split into the closing member transport path defining portion and the body transport path defining portion. This allows the operator to easily remove the jammed sheet from the sheet transport path.

In the above arrangement, preferably, the closing member may be operable to expose the image forming section along with the sheet transport path in the opened state thereof.

According to the above arrangement, in response to opening the closing member, the operator is allowed to easily remove a sheet jammed in the image forming section, or a sheet jammed in the sheet transport path and the image forming section.

In the above arrangement, preferably, the sheet transport path may include a first transport path for transporting the sheet dispensed from a sheet storing section to the image forming section, and a second transport path for transporting the sheet toward the first transport path in a direction different from the first transport path to change a transport direction, the second transport path joining the first transport path, and the first guide unit and the second guide unit may be provided at a joint portion between the first transport path and the second transport path.

According to the above arrangement, the first guide unit and the second guide unit are provided at the joint portion between the first transport path and the second transport path. The joint portion corresponds to a position where the transport direction of the second transport path is changed. In the case where a sheet is jammed at the joint portion, it is difficult to remove the jammed sheet in a conventional arrangement. In the inventive image forming apparatus, in response to shifting the first guide unit provided at the joint portion from the proximate position to the away position, the position shifting mechanism is operable to shift the second guide unit to the away position where the second guide unit is away from the first guide unit in association with the shifting operation of the first guide unit. Thereby, the image forming apparatus is brought to a condition that the sheet jammed at the joint portion is easily removable. This arrangement enables the operator to easily remove the jammed sheet.

In the above arrangement, preferably, the second transport path may be adapted to transport the sheet from a manual tray mounted on the apparatus body toward the first transport path.

In the above arrangement, preferably, the first guide unit may constitute a part of the first transport path and a part of the second transport path, and the second guide unit may constitute a part of the second transport path.

It is more difficult to remove a sheet jammed at the joint portion from the second transport path, where the transport direction is changed, than from the first transport path. In the above arrangement, the part of the second transport path is defined by the first guide unit and the second guide unit. Accordingly, in the case where a sheet is jammed in the second transport path, in response to shifting the first guide unit from the proximate position to the away position, the position shifting mechanism is operable to shift the second guide unit to the away position where the second guide unit is away from the first guide unit in association with the shifting operation of the first guide unit. Thereby, the image forming apparatus is brought to a condition that the sheet jammed in the second transport path at the joint portion is easily removable. This arrangement enables the operator to easily remove the jammed sheet.

In the above arrangement, preferably, an opening/closing operation of the closing member may be associated with the shifting operation of the first guide unit.

According to the above arrangement, in the case where a sheet jam has occurred, the operator can remove the jammed sheet by opening the closing member, without operating the first guide unit, since the first guide unit and the second guide unit are automatically shifted from the proximate position to the away position in association with the opening operation of the closing member. The above arrangement enables the operator to efficiently remove the jammed sheet.

In the above arrangement, preferably, the position shifting mechanism may include: a first shaft for pivotally supporting the first guide unit about an axis thereof; a guide rail for guiding the second guide unit in directions toward and away from the first guide unit; a biasing member for urging the first guide unit toward the away position; a first gear coaxially mounted on the first shaft to be integrally rotated with the first shaft; a second gear in mesh with the first gear and rotated about an axis of a second shaft; and a position shifting member for shifting the second guide unit between the proximate position and the away position along the guide rail by a rotation of the second gear, and the first guide unit may include an operated portion operable to be set to the proximate position by interference with the closing member in a state that the closing member is closed.

According to the above arrangement, in a state that the closing member is closed, the closing member interferes with the first guide unit. Thereby, the first guide unit is set to the proximate position against the biasing force of the biasing member, and the second guide unit is also set to the proximate position along with the first guide unit.

In the above condition, in the case where a sheet being transported along the sheet transport path is jammed, the operator opens the closing member to remove the jammed sheet. In response to the operation of opening the closing member, the operated portion of the first guide unit is released from the interference by the closing member. Thereby, the first guide unit swings about the axis of the first shaft by the biasing force of the biasing member, and is shifted from the proximate position to the away position. Then, the rotation of the first shaft is transmitted to the second gear via the first gear for integral rotation of the second gear about the axis of the second shaft. The rotation of the second shaft is transmitted to the second guide unit by the position shifting member. Thereby, the second guide unit is moved in a direction away from the first guide unit while being guided in the guide rail.

As described above, the position shifting mechanism for swinging the first guide unit about the axis of the first shaft, and shifting the second guide unit in the direction away from the first guide unit is constituted of the first gear, and the second gear in mesh with the first gear. This arrangement enables to simplify the construction of the position shifting mechanism, and easily and securely shift the first guide unit and the second guide unit between the proximate position and the away position.

In the above arrangement, preferably, the position shifting member may be an eccentric cam to be rotated by the rotation of the second gear to displace the second guide unit in contact therewith. This arrangement enables to simplify the construction of the position shifting mechanism.

In the above arrangement, preferably, the guide rail may have such a shape that the proximate position of the second guide unit is set below the away position of the second guide unit so that the second guide unit is set to the proximate position by a weight thereof.

According to the above arrangement, since the second guide unit is set to the proximate position by the weight thereof, there is no need of providing an additional member (a biasing member or the like) for setting the second guide unit to the proximate position. This is advantageous in simplifying the construction of the image forming apparatus.

In the above arrangement, preferably, the first shaft and the second shaft may be provided outside the sheet transport path.

According to the above arrangement, since the first shaft and the second shaft are provided outside the sheet transport path, there is no likelihood that a sheet may be jammed resulting from collision of the sheet against the first shaft or the second shaft.

An image forming apparatus according to another aspect of the invention includes: an image forming section, provided in an apparatus body, for forming an image on a sheet; a sheet transport path for transporting the sheet to the image forming section; a closing member, openably and closably mounted to the apparatus body, for exposing the sheet transport path in an opened state thereof; a first guide unit, disposed along the sheet transport path and opposite to the closing member, for guiding the sheet, the first guide unit being operable to shift between a transport posture where the sheet is transportable, and an open posture where the sheet is removable; a second guide unit disposed opposite to the closing member with respect to the first guide unit; a posture shifting mechanism for shifting the posture of the second guide unit in association with a shifting operation of the first guide unit.

According to the above arrangement, in the case where a sheet to be transported to the image forming position in the image forming section via the sheet transport path is jammed on the side of the first guide unit in the sheet transport path, the operator is allowed to easily remove the jammed sheet by opening the closing member and exposing the jammed sheet.

In the case where a sheet is jammed on the side of the second guide unit, swinging the first guide unit about the axis of the first shaft allows the second guide unit to shift from the transport posture to the open posture in association with the swinging operation of the first guide unit. Thereby, the image forming apparatus is brought to a condition that the sheet jammed on the side of the second guide unit is easily removable. This arrangement allows the operator to easily remove the jammed sheet by pulling the sheet from the side of the second guide unit.

In the above arrangement, preferably, the posture shifting mechanism may include: a first shaft for pivotally supporting the first guide unit about an axis thereof; a third shaft for pivotally supporting the second guide unit about an axis thereof; and a linking arm extending between the first guide unit and the second guide unit to swing the first guide unit and the second guide unit relative to each other, wherein the linking arm, the first guide unit, and the second guide unit constitute a four-sided link structure.

According to the above arrangement, the posture shifting mechanism has the four-sided link structure constituted of the linking arm, the first guide unit, and the second guide unit. This arrangement enables to simplify the construction of the posture shifting mechanism, and securely and properly move the first guide unit and the second guide unit in association with each other.

In the above arrangement, preferably, the image forming apparatus may further include a registration roller pair, provided at a position immediately in front of the image forming section in the sheet transport path, for adjusting a timing of feeding the sheet to the image forming section.

According to the above arrangement, the sheet being transported along the sheet transport path is fed to the image forming section at an appropriate timing after the lead end of the sheet has reached the registration roller pair by driving the registration roller pair. This arrangement is advantageous in performing a proper image forming operation on the sheet.

A sheet jam is likely to occur in the vicinity of the registration roller pair. A sheet jammed in the vicinity of the registration roller pair can be easily removed by shifting the first guide unit and the second guide unit from the proximate position to the away position.

This application is based on Japanese Patent Applications No. 2007-293376 and No. 2008-26975 filed on Nov. 12, 2007 and Feb. 6, 2008, respectively, the contents of which are hereby incorporated by reference.