Image forming apparatus

Information

  • Patent Grant
  • 6661984
  • Patent Number
    6,661,984
  • Date Filed
    Thursday, June 27, 2002
    21 years ago
  • Date Issued
    Tuesday, December 9, 2003
    20 years ago
Abstract
An image forming apparatus of the present invention is generally made up of a sheet storing unit and an image forming unit removably mounted on the top of the sheet storing unit when in use. The sheet storing unit accommodates a sheet tray loaded with sheets and selectively movable into the sheet storing unit to an operative position or out of the same to an inoperative position. A locking mechanism inhibits the sheet tray from being moved to the inoperative position. An unlocking device unlocks the locking mechanism when the image forming unit is mounted to the sheet storing unit. When the image forming unit is removed from the sheet storing unit, the sheet storing unit is prevented from falling down due to a moment ascribable to the pull-out of the sheet tray.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to an image forming apparatus of the type having a sheet storing unit accommodating a sheet tray, which is movable between an operative position and an inoperative position, and an image forming unit removably mounted on the top of the sheet storing unit when in use.




2. Description of the Background Art




An image forming apparatus of the type described is known in the art and made up of a sheet storing unit and an image forming unit removably mounted on the top of the sheet storing unit when in use. The sheet storing unit includes a sheet tray loaded with sheet rolls. A sheet selectively paid out from either one of the sheet rolls is fed to the image forming unit. The sheet tray is selectively slidable into the sheet storing unit to an operative position or out of the sheet storing unit to an inoperative position in substantially the horizontal direction.




The conventional image forming apparatus of the type described has the following problem unsolved. When the image forming apparatus is newly purchased and installed at the user's station or when it is moved to another place, the image forming unit is absent on the sheet storing unit. Assume that in such a condition a person pulls out the sheet tray loaded with the sheet rolls or loads the sheet rolls in the sheet tray pulled out. Then, a heavy moment of rotation ascribable to the sheet tray acts on the sheet storing unit and is apt to cause the sheet storing unit to falldown.




Technologies relating to the present invention are disclosed in, e.g., Japanese Patent Laid-Open Publication No. 6-242641.




SUMMARY OF THE INVENTION




It is an object of the present invention to provide an image forming apparatus capable of preventing a sheet storing unit thereof from falling down in the absence of an image forming unit due to a moment generated when a person pulls out a sheet tray loaded with sheets or replenishes sheets to the sheet tray pulled out.




An image forming apparatus of the present invention is generally made up of a sheet storing unit and an image forming unit removably mounted on the top of the sheet storing unit when in use. The sheet storing unit accommodates a sheet tray loaded with sheets and selectively movable into the sheet storing unit to an operative position or out of the same to an inoperative position. A locking mechanism inhibits the sheet tray from being moved to the inoperative position. An unlocking device unlocks the locking mechanism when the image forming unit is mounted to the sheet storing unit.











BRIEF DESCRIPTION OF THE DRAWINGS




The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which:





FIG. 1

is a front view showing a conventional image forming apparatus in a usable condition;





FIG. 2

is a front view showing a sheet storing unit included in the apparatus of

FIG. 1

in a condition wherein a sheet tray is pulled out of the sheet storing unit;





FIG. 3

is a front view showing an image forming apparatus embodying the present invention;





FIG. 4

is a front view showing a sheet storing unit included in the illustrative embodiment;





FIG. 5

is an isometric view showing a leaf spring forming part of a locking mechanism included in the illustrative embodiment;





FIG. 6

is a front view showing an alternative embodiment of the present invention; and





FIG. 7

is a front view showing another alternative embodiment of the present invention.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




To better understand the present invention, brief reference will be made to a conventional image forming apparatus, shown in FIG.


1


. As shown, the image forming apparatus is generally made up of a sheet storing unit


1


and an image forming unit


2


removably mounted on the top of the sheet storing unit


1


when in use. The sheet storing unit


1


includes a sheet tray


4


loaded with sheet rolls


3


. A sheet selectively paid out from the sheet rolls


3


is fed to the image forming unit


2


. The sheet tray


4


is selectively slidable into the sheet storing unit


1


to an operative position or out of the sheet storing unit


1


to an inoperative position in substantially the horizontal direction. The operative position and inoperative position are respectively indicated by a solid line and a dash-and-dots line in

FIG. 1

; the inoperative position is indicated by a solid line in FIG.


2


.




As for weight, the image forming unit


2


is heavy because it accommodates an image forming mechanism including a photoconductive element and a heat roller. By contrast, the sheet storing unit


1


is a simple casing having a space in which the sheet tray


4


is disposed, and is therefore light. The sheet tray


4


is also light, but becomes heavy when loaded with the sheet rolls


3


. As shown in

FIG. 1

, when the image forming unit


2


is mounted on the sheet storing unit


1


when in use, the weight of the heavy image forming unit


2


acts on the sheet storing unit


1


vertically downward. Therefore, when the sheet tray


4


loaded with the sheet rolls


3


is pulled out to the inoperative position or when the sheet rolls


3


are replenished to the sheet tray


4


pulled out, the image forming unit


2


does not fall down despite a heavy moment of rotation acting thereon due to the sheet tray


4


and remains stable on the sheet feeding unit


1


.




On the other hand, when the image forming apparatus is newly purchased and installed at the user's station or when it is moved to another place, the image forming unit


2


is absent on the sheet storing unit


1


. Assume that in such a condition a person pulls out the sheet tray


4


loaded with the sheet rolls


3


or loads the sheet rolls


3


in the sheet tray


4


pulled out. Then, a heavy moment of rotation ascribable to the sheet tray


4


acts on the sheet storing unit


1


and is apt to cause the sheet storing unit


1


to fall down in a direction indicated by an arrow a in FIG.


2


. To solve this problem, the leg portion of the sheet storing unit


1


may be extended outward in the direction in which the sheet tray


4


is slidable, as indicated by a dash-and-dots line in FIG.


2


. However, the extended leg portion increases the floor area to be occupied by the image forming apparatus and is likely to trip up the operator's foot.




Referring to

FIGS. 3 through 5

, an image forming apparatus embodying the present invention is shown and generally made up of a sheet storing unit


11


and an image forming unit


12


removably mounted on the top of the sheet storing unit


11


when in use. The image forming unit


12


is so sized as to be capable of forming images on sheets of relatively large sizes including sizes A


0


and A


1


.




Again, the image forming unit


12


accommodates an image forming mechanism including a photoconductive element and a heat roller and is therefore heavy. The sheet storing unit


11


includes a sheet tray


14


loaded with sheet rolls


13


. A sheet selectively paid out from the sheet rolls


13


is fed to the image forming unit


12


. The sheet tray


14


is selectively slidable into the sheet storing unit


11


to an operative position or out of the sheet storing unit


11


to an inoperative position in substantially the horizontal direction. The operative position and inoperative position are respectively indicated by solid lines in

FIGS. 3 and 4

and a dash-and-dots line in FIG.


3


. The sheet storing unit


11


is a simple casing having a space in which the sheet tray


14


is disposed, and is therefore light. The sheet tray


14


is also light, but becomes heavy when loaded with the sheet rolls


13


.




A locking mechanism


15


is arranged in the upper portion of the sheet storing unit


11


for locking the sheet tray


14


at the operative position to thereby prevent it from being slid to the inoperative position. The locking mechanism


15


is implemented by a projection or first engaging portion


16


and a leaf spring or locking member


17


. The projection


16


is affixed to the top wall of the sheet storing unit


11


and extends downward. The leaf spring


17


is affixed to the sheet tray


4


and formed with a hole or second engaging portion


18


configured to mate with the projection


16


. The leaf spring


17


is resiliently deformable between a locking position where it mates with the projection


16


and an unlocking position where it is released from the projection


16


. The leaf spring


17


is constantly biased toward the locking position.




A plurality of legs protrude downward from the bottom of the image forming unit


12


. One of the legs, labeled


19


, plays the role of a pressing member or unlocking member for unlocking the locking mechanism


15


. More specifically, when the image forming unit


12


is mounted to the sheet storing unit


11


, the leg


19


presses the leaf spring


17


downward to the unlocking position.




In

FIG. 3

, the image forming apparatus is shown in a condition for use, as indicated by solid lines. In this condition, the image forming unit


12


is mounted on the top of the sheet storing unit


11


and ready to receive the sheet


13


from the sheet feeding unit


11


for forming an image. The leaf spring


17


is pressed downward by the leg


19


out of engagement with the projection


16


. The sheet tray


14


can therefore freely slide from the operative position to the inoperative position without being restricted by the locking mechanism


15


. The sheet tray


14


will be pulled out to the inoperative position when the roll sheets


13


should be replaced with roll sheets of different sizes, when the sheet rolls


13


should be replenished or when the sheet tray


14


should be maintained in the event of, e.g., a sheet jam.




So long as the image forming unit


12


is mounted on the sheet storing unit


11


for use, the weight of the heavy image forming unit


12


acts on the sheet storing unit


11


vertically downward. Therefore, when the sheet tray


14


loaded with the sheet rolls


13


is pulled out to the inoperative position or when the sheet rolls


13


are replenished to the sheet tray


14


so pulled out, the image forming unit


12


does not fall down despite a heavy moment of rotation acting thereon due to the sheet tray


14


and remains stable on the sheet feeding unit


11


.




Assume that the image forming unit


12


is removed from the top of the sheet storing unit


11


when the image forming apparatus is newly purchased and installed at the user's station or when it is moved to another place. Then, as shown in

FIG. 4

, the leaf spring


17


resiliently deforms upward to the locking position where the hole


18


mates with the projection


16


due to the absence of the leg


19


, thereby locking the locking mechanism


15


. In this condition, the sheet tray


14


is inhibited from sliding out of the sheet feeding unit


11


and maintained in the operative position. More specifically, when the image forming unit


12


is absent on the sheet storing unit


11


, the locking mechanism


15


inhibits a person from pulling the sheet tray


14


out of the sheet storing unit


11


. This successfully obviates a moment that would cause the sheet storing unit


11


to fall down due to the displacement of the center of gravity.




Further, the illustrative embodiment does not need the extension of the leg portion described in relation to the conventional image forming apparatus and therefore saves space and obviates the previously stated accident.




The hole


18


of the leaf spring


17


and the projection


16


may be replaced with each other, if desired. Further, the projection


16


and leaf spring


17


may alternatively be affixed to the sheet tray


14


and sheet storing unit


11


, respectively. Moreover, the leaf spring


17


may be removably mounted to the sheet tray


14


, i.e., it may be detached after the image forming unit


12


has been mounted to the sheet storing unit


11


and attached before the former is dismounted from the latter. In addition, the sheet rolls


13


loaded on the sheet tray


14


may, of course, be replaced with cut sheets of a preselected size.




An alternative embodiment of the present invention will be described with reference to FIG.


6


. In

FIG. 6

, structural elements identical with those shown in

FIGS. 2 through 5

are designated by identical reference numerals and will not be described specifically in order to avoid redundancy. As shown, the image forming apparatus is generally made up of a sheet storing unit


11




a


and the image forming unit


12


removably mounted on the sheet storing unit


11




a


when in use. Again, the image forming unit


12


is so sized as to be capable of forming images on sheets of relatively large sizes including sizes A


0


and A


1


.




The sheet storing unit


11




a


includes a sheet tray


14




a


loaded with a sheet roll


13


. In the illustrative embodiment, the sheet tray


14




a


is angularly movable about a shaft


20




a


extending in the horizontal direction. The sheet tray


14




a


is selectively movable about the shaft


20




a


into the sheet storing unit


11




a


to an operative position or out of the sheet storing unit


11




a


to an inoperative position. The operative position and inoperative position are respectively indicated by a solid line and a dash-and-dots line in FIG.


6


. The shaft


20




a


is positioned above the sheet tray


14




a.






The sheet storing unit


11




a


is a simple casing having a space in which the sheet tray


14




a


is disposed, and is therefore light. The sheet tray


14




a


is also light, but becomes heavy when loaded with the sheet rolls


13


.




A locking mechanism


15




a


is arranged in the upper portion of the sheet storing unit


11




a


for locking the sheet tray


14




a


at the operative position to thereby prevent it from being slid to the inoperative position. The locking mechanism


15




a


is implemented by a projection or first engaging portion


16




a


and a leaf spring or locking member


17




a


. The projection


16




a


protrudes obliquely downward from the sheet tray


14




a


. The leaf spring or locking member


17




a


is affixed to the sheet storing unit


11




a


and formed with a hole or second engaging portion


18




a


configured to mate with the projection


16




a


. The leaf spring


17




a


is resiliently deformable between a locking position where it mates with the projection


16




a


and an unlocking position where it is released from the projection


16




a


. The leaf spring


17




a


is constantly biased toward the locking position.




In

FIG. 6

, the image forming apparatus is shown in a condition for use, as indicated by solid lines. In this condition, the image forming unit


12


is mounted on the top of the sheet storing unit


11




a


and ready to receive the sheet


13


from the sheet feeding unit


11




a


for forming an image. The leaf spring


17




a


is pressed downward by the leg


19


of the image forming unit


12


out of engagement with the projection


16




a


. The sheet tray


14




a


can therefore freely move about the shaft


20




a


out of the sheet feeding unit


11




a


without being restricted by the locking mechanism


15




a.






So long as the image forming unit


12


is mounted on the sheet storing unit


11




a


for use, the weight of the heavy image forming unit


12


acts on the sheet storing unit


11




a


vertically downward. Therefore, when the sheet tray


14




a


loaded with the sheet roll


13


is pulled out to the inoperative position or when the sheet roll


13


is replenished to the sheet tray


14




a


pulled out, the image forming unit


12


does not fall down despite a heavy moment of rotation acting thereon due to the sheet tray


14




a


and remains stable on the sheet feeding unit


11




a.






Assume that the image forming unit


12


is removed from the top of the sheet storing unit


11




a


when the image forming apparatus is newly purchased and installed at the user's station or when it is moved to another place. Then, the leaf spring


17




a


resiliently deforms upward to the locking position where the hole


18




a


mates with the projection


16




a


due to the absence of the leg


19


, thereby locking the locking mechanism


15




a


. In this condition, the sheet tray


14




a


is inhibited from sliding out of the sheet feeding unit


11




a


and maintained in the operative position. More specifically, when the image forming unit


12


is absent on the sheet storing unit


11




a


, the locking mechanism


15




a


inhibits a person from pulling the sheet tray


14




a


out of the sheet storing unit


11




a


. This successfully obviates a moment that would cause the sheet storing unit


11




a


to fall down due to the displacement of the center of gravity.




Further, the illustrative embodiment, like the previous embodiment, does not need the extension of the leg portion described in relation to the conventional image forming apparatus and therefore saves space and obviates the previously stated accident.





FIG. 7

shows another alternative embodiment of the present invention. As shown, the image forming apparatus is generally made up of a sheet storing unit


11




b


and the image forming unit


12


removably mounted on the sheet storing unit


11




b


when in use. Again, the image forming unit


12


is so sized as to be capable of forming images on sheets of relatively large sizes including sizes A


0


and A


1


.




The sheet storing unit


11




b


includes a sheet tray


14




b


loaded with the sheet roll


13


. In the illustrative embodiment, the sheet tray


14




b


is angularly movable about a shaft


20




b


extending in the horizontal direction. The sheet tray


14




b


is selectively movable about the shaft


20




b


into the sheet storing unit


11




b


to an operative position or out of the sheet storing unit


11




b


to an inoperative position. The operative position and inoperative position are respectively indicated by a solid line and a dash-and-dots line in FIG.


7


. The shaft


20




b


is positioned above the sheet tray


14




b.






The sheet storing unit


11




b


is a simple casing having a space in which the sheet tray


14




b


is disposed, and is therefore light. The sheet tray


14




b


is also light, but becomes heavy when loaded with the sheet rolls


13


.




The illustrative embodiment also includes the locking mechanism


15


arranged in the upper portion of the sheet storing unit


11




b


. The locking mechanism


15


is identical in configuration and operation with the locking mechanism


15


described with reference to

FIGS. 3 through 5

and will not be described specifically in order to avoid redundancy.




In summary, in accordance with the present invention, an image forming apparatus is made up of a sheet storing unit and an image forming unit removably mounted on the sheet storing unit when in use. When the image forming unit is removed from the sheet storing unit, the sheet storing unit is prevented from falling down due to a moment ascribable to the pull-out of a sheet tray. This can be done with a simple locking mechanism, a first and a second engaging portion simple in configuration, simple unlocking means without resorting to an exclusive pressing member, which would increase the cost of the apparatus.




Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.



Claims
  • 1. An image forming apparatus comprising:a sheet storing unit comprising a sheet tray loaded with a sheet and selectively movable into said sheet storing unit to an operative position or out of said sheet storing unit to an inoperative position; an image forming unit removably mounted on a top of said sheet storing unit when in use; a locking mechanism configured to inhibit said sheet tray from being moved to the inoperative position; and unlocking means configured to unlock said locking mechanism when said image forming unit is mounted on said sheet storing unit.
  • 2. The apparatus as claimed in claim 1, wherein said sheet storing unit is slidable in a horizontal direction.
  • 3. The apparatus as claimed in claim 2, wherein said locking mechanism comprises:a first engaging portion included in one of said sheet storing unit and said sheet tray; a second engaging portion included in the other of said sheet storing unit and said sheet tray; and a locking member elastically deformable between a locking position in which said second engaging portion mates with said first engaging portion and an unlocking position in which said second engaging portion leaves said first engaging portion, said locking member being constantly biased toward said locking position.
  • 4. The apparatus as claimed in claim 3, wherein one of said first engaging portion and said second engaging portion comprises a projection while the other of said first engaging portion and said second engaging portion comprises a hole.
  • 5. The apparatus as claimed in claim 4, wherein said unlocking means comprises a pressing member included in said image forming unit for pressing said locking member toward the unlocking position.
  • 6. The apparatus as claimed in claim 5, wherein said pressing member comprises a leg protruding downward from a bottom of said image forming unit.
  • 7. The apparatus as claimed in claim 1, wherein said sheet storing unit is angularly movable about a horizontal shaft.
  • 8. The apparatus as claimed in claim 7, wherein said locking mechanism comprises:a first engaging portion included in either one of said sheet storing unit and said sheet tray; a second engaging portion included in the other of said sheet storing unit and said sheet tray; and a locking member elastically deformable between a locking position in which said second engaging portion mates with said first engaging portion and an unlocking position in which said second engaging portion leaves said first engaging portion, said locking member being constantly biased toward said locking position.
  • 9. The apparatus as claimed in claim 8, wherein one of said first engaging portion and said second engaging portion comprises a projection while the other of said first engaging portion and said second engaging portion comprises a hole.
  • 10. The apparatus as claimed in claim 9, wherein said unlocking means comprises a pressing member included in said image forming unit for pressing said locking member toward the unlocking position.
  • 11. The apparatus as claimed in claim 10, wherein said pressing member comprises a leg protruding downward from a bottom of said image forming unit.
  • 12. The apparatus as claimed in claim 1, wherein said locking mechanism comprises:a first engaging portion included in either one of said sheet storing unit and said sheet tray; a second engaging portion included in the other of said sheet storing unit and said sheet tray; and a locking member elastically deformable between a locking position in which said second engaging portion mates with said first engaging portion and an unlocking position in which said second engaging portion leaves said first engaging portion, said locking member being constantly biased toward said locking position.
  • 13. The apparatus as claimed in claim 12, wherein one of said first engaging portion and said second engaging portion comprises a projection while the other of said first engaging portion and said second engaging portion comprises a hole.
  • 14. The apparatus as claimed in claim 13, wherein said unlocking means comprises a pressing member included in said image forming unit for pressing said locking member toward the unlocking position.
  • 15. The apparatus as claimed in claim 14, wherein said pressing member comprises a leg protruding downward from a bottom of said image forming unit.
Priority Claims (2)
Number Date Country Kind
2001-196906 Jun 2001 JP
2002-149168 May 2002 JP
US Referenced Citations (7)
Number Name Date Kind
5157448 Lang Oct 1992 A
5191382 Okamura et al. Mar 1993 A
5270772 Akiyama Dec 1993 A
5666595 Sameshima et al. Sep 1997 A
5701573 Yoshiuchi et al. Dec 1997 A
5926671 Leibman Jul 1999 A
6481081 Kilian Nov 2002 B1
Foreign Referenced Citations (1)
Number Date Country
6-242641 Sep 1994 JP