Image reading device and image forming apparatus having same

An image forming apparatus for forming an image of an original using an optical image of the original has: a first assembly; a second assembly cooperable with the first assembly the second assembly being movable relative to the first assembly; between a closed position wherein the apparatus is operable and an open position wherein the apparatus is opened; a reciprocable original supporting member for supporting an original; an optical system, in the second assembly, for forming the image of the original supported on the original supporting member; a second guiding member, on the second assembly, for guiding and positioning the original supporting member adjacent one of the sides of the original support member, wherein the original supporting member is movable to be disengaged from the second guiding member, the second guiding member being contactable with the original supporting member to correctly position the original supporting member with respect to the second assembly when it is engaged with the original supporting member.

FIELD OF THE INVENTION AND RELATED ART 
The present invention relates to an image reading device and an image 
forming apparatus using the image reading device and is usable with an 
image reader and a copying apparatus of the like provided with an original 
supporting platen for supporting an original to be read or copied. More 
particularly, it relates to a device having means for guiding movement of 
the original supporting platen. 
Recently, image forming machines which can be separate into two or more 
assemblies to facilitate maintenance operation, servicing, replacement of 
consumable materials and jam disposal or the like, have come into wide 
use. For example, U.S. Pat. No. 4,462,677 discloses an assembly 
accommodating a process cartridge, separable from another assembly at the 
boundary of a transportation path for a recording medium, which is 
convenient from various aspects. 
In this apparatus, the upper assembly is rotatable about a hinge to be 
separated from the lower assembly. However, this structure involves 
disadvantages in that the upper assembly is rotated as a whole together 
with the original supporting platen so that the assembly to be rotated is 
bulky and heavy. An additional disadvantage is that when the upper 
assembly is opened, the original supporting platen and/or an original may 
fall, since the platen is inclined. 
In order to solve the above problems, it has been proposed that the 
original supporting platen should be the stationary assembly be rotating 
only a part of the upper part of the apparatus, as disclosed in Japanese 
Laid-Open Utility Model application 52-54633, U.S. patent application Ser. 
No. 36,812, filed on Apr. 10, 1987 by Morikazu Mizutani et al., claiming 
conventional priority from Japanese patent application No. 83932/1986 and 
U.S.application Ser. No. 38,200 filed on Apr. 14, 1987 by Tadyayuki Tsuda 
et al., claiming the convention priority from Japanese patent application 
No. 8608/1986. 
However, this structure involves another problem in that the original 
supporting plate has to be mounted accurately to the stationary assembly, 
with the result that the positional accuracy between the original 
supporting plate and the rotatable assembly can not be assured directly. 
Particularly, the accuracy deteriorates due to wear with use of the 
apparatus. This problem is more significant when the rotatable assembly 
contains an image reading optical system, since the positional inaccuracy 
results in defocusing of the image on the plane on which the image is to 
be formed. Further, and more particularly, when the reading optical system 
includes an array of short focus imaging elements, the resulting 
deterioration of the image is quite significant. 
SUMMARY OF THE INVENTION 
Accordingly, it is a principle object of the present invention to provide 
an image reading device and an image forming apparatus having the same 
wherein the image can be correctly read, even when an original supporting 
platen and an image reading optical system are mounted in different 
assemblies and those assemblies are separable. 
It is another object of the present invention to provide an image reading 
device and an image forming apparatus having the same wherein the accuracy 
of the image reading does not deteriorate with use of the device and the 
apparatus. 
It is a further object of the present invention to provide an image reading 
device and an image forming apparatus having the same wherein an image 
formed on an imaging surface such as a photo-sensitive member surface is 
not disturbed even when an original supporting member and the 
photosensitive member are mounted on different frames. 
These and other objects, features and advantages of the present invention 
will become more apparent upon a consideration of the following 
description of the preferred embodiments of the present invention taken in 
conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the present invention will be described in 
conjunction with the accompanying drawings, wherein like reference 
numerals have been used throughout to designate corresponding elements. 
Referring to FIGS. 1 and 2, there is shown an image forming apparatus, more 
particularly, a copying machine, according to an embodiment of the present 
invention. In FIG. 1, the apparatus is closed, while it is opened in FIG. 
2. 
FIG. 3 is a perspective view of the apparatus shown in FIGS. 1 and 2. 
The apparatus comprises a process cartridge K. The process cartridge K 
contains a rotatable photosensitive drum 1 as an image bearing member 
having a surface photosensitive layer, a discharger 2 for uniformly 
charging the photosensitive drum 1 to a predetermined potential of 
positive or negative polarity, a developing device 3 for developing a 
latent image formed on the photosensitive drum 1 with a predetermined 
color developer, such as black and red, and a cleaning device 4 for 
cleaning the photosensitive drum 1 to remove the developer remaining on 
the surface of the photosensitive drum 1. 
The apparatus comprises a rotatable or pivotable assembly 104 which 
contains the process cartridge K. The process cartridge K is detachably 
mounted into the rotatable assembly 104. The rotatable assembly 104 
further comprises a light source 9 for illuminating an original to be 
copied, a condenser mirror 91, an array 10 of short focus imaging elements 
and other elements, which constitute an image exposure optical system. A 
stationary assembly comprises a transfer discharger 11, a transfer 
material feeding mechanism 12, an image fixing device 14 and other 
necessary elements. The stationary assembly has an upper surface on which 
a guiding rail 102 is fixed extending along the rear side of the 
apparatus. An original supporting platen or carriage 5 for supporting and 
reciprocating an original to be copied is reciprocably positioned and 
guided by the guiding rail 102 at the rear side. The original supporting 
carriage 5 includes a transparent plate 51 made of glass or plastic 
material and an original pressing plate hinged to cover and uncover the 
originally by pivoting movement in the direction of the arrow. 
Thus, the original carriage 5 is correctly positioned and guided by the 
guiding rail 102 fixedly mounted on the top surface at the rear side of 
the apparatus. Preferably, the guiding rail 102 extends over substantially 
the entire length of the stationary assembly so as to insure the accuracy 
of movement of the original carriage 5. At the front side, the original 
carriage 5 is guided by a guiding rail 103A fixedly mounted to the 
rotatable assembly 104 and extending parallel to the guiding rail 102, so 
that the original carriage 5 can be moved while it is maintained at a 
correct position with respect to the rotatable assembly 104, whereby the 
distance from the original carrying surface of the original carriage 5 of 
the stationary assembly 100 and the imaging array 10 can be maintained 
constant while the original carriage 5 is being moved along the guide rail 
102. The guiding rail 103A will be described in detail hereinafter. 
At the rear side of the original carriage 5, a rack is fixedly mounted 
extending along the guide rail 102. The rack is meshed with a driving 
pinion rotatably mounted in the stationary assembly 100. The pinion is 
rotatably in forward and backward directions to reciprocably drive the 
original carriage 5. 
In operation, the apparatus is maintained in the closed state shown in FIG. 
1, and an original 6 to be copied is placed face down on the transparent 
plate 51 at a predetermined position, while the original pressing plate 52 
is open, and then the original is covered and pressed by the pressing 
plate 52. When a copy button is depressed, the original carriage 5 starts 
to move, and the bottom surface of the original 6 is slit-scanned by 
passing by an original illuminating slit 8 during a forward or backward 
stroke of the original carriage 5 movement. Since the slit is illuminated 
by an illuminating lamp, an image of the bottom surface of the original 
formed by the short focus imaging element array 10 onto the surface of the 
photosensitive drum 1 which is rotating, so that the surface of the drum 1 
is sequentially exposed to the moving image of the original. The 
subsequent process of forming a fixed image on a recording sheet may be of 
any well known type, and therefore detailed description is omitted for 
simplicity. The original carriage 5 is shown in FIG. 1 as being placed at 
its home position, where the stationary assembly 100 is completely covered 
by the original carriage 5. After the original scanning operation, the 
original carriage 5 returns to the home position. 
As shown in FIG. 2, a mark 22 is formed on the original pressing plate 52 
of the original carriage 5. Correspondingly, a mark 21 is formed on the 
top surface of the stationary assembly 100. When the original carriage 5 
is moved leftward in those FIGS. and is positioned so that the mark 22 and 
the mark 21 are aligned, a releasing lever 105 and the top surface of the 
rotatable assembly 104 are exposed, although they have been covered by the 
original carriage 5 while the latter has been located at the home 
position. The releasing lever 105 is engaged with a locking member 106, 
which is engageable with a latch 107. The locking member 106 and the latch 
107 are engaged when the apparatus is closed. When the releasing lever 105 
is pulled upwardly, the locking member 106 is disengaged from the latch 
107, and the spring biased rotatable assembly 104 rotates about the hinge 
108 by an urging spring in the counter clockwise direction so that the 
rotatable assembly 104 is raised from the top surface 101 of the 
apparatus, as shown in FIG. 2. And, the rotatable assembly 104 is 
maintained at a predetermined open angle. When the rotatable assembly 104 
is pushed down against the spring force sufficiently, the locking member 
106 is engaged with the latch 107 so that the closed position is 
maintained. 
The process carriage K can be mounted into or demounted from the rotatable 
assembly 104 when it is at the open position described above and shown in 
FIG. 2. More particularly, the process carriage K is guided toward the 
rear side along guiding rails 109 and 110 extending parallel with the 
hinge shaft 108 until it is positioned to a predetermined plates. 
Thus, the rotatable assembly 104 can be opened with the original carriage 5 
left in the stationary assembly 100. Therefore, the weight of the 
rotatable assembly 104 can be reduced, with the possibility of the 
original carriage 5 falling also thus being reduced. 
Now, the guiding rail 103A extending parallel to the guide rail 102 and 
fixed on the top surface of the rotatable assembly 104, will be described 
referring to FIG. 5. The guiding rail 103A is fixedly mounted to the 
rotatable assembly 104 and extends at least beside the slit 8, as best 
seen in FIG. 3, and therefore, it is shorter than the guide rail 102. The 
guiding rail 103A also extends parallel to the direction of reciprocable 
movement of the original carriage 5. 
As best seen in FIG. 5, which is a rear view with the guide rail 102 and 
the mechanism therearound omitted, the guiding rail 103A has a slot having 
a projection 103D so that the transparent plate 51 contacts at its upper 
surface and lower surface with the projection 103D and the lower surface 
of the slot, whereby the top surface of the transparent plate 51 is 
correctly positioned in the vertical direction. It should be noted that 
the projection 103D is located substantially in alignment with the slit 8, 
and therefore the vertical position of the transparent glass 51 is 
maintained at a predetermined level at the slit position, which is the 
very position where the distance from the original to the short focus 
imaging element array 10 needs to be corrected, since the image reading is 
effected there. Also, it should be understood that the guiding rail 103A 
having the projection 103D is fixed to the rotatable assembly 104, which 
is the very assembly that contains the imaging element, since the top 
surface of the transparent glass 51 is directly positioned with respect to 
the imaging element, more particularly since the guide rail 103A is 
fixedly mounted on the assembly that contains the imaging element. It is 
now not necessary to expect that the top surface of the supporting glass 
is correctly positioned with respect to the imaging element on the ground 
that the assembly containing the imaging element is positioned with 
respect to the stationary assembly and that the original supporting 
surface is positioned with respect to the fixed assembly. In other words, 
the relative positioning between the imaging element and the original 
supporting surface is not effected by way of the stationary assembly, but 
is effected directly, according to this embodiment. 
In this embodiment, the slit of the guiding rail 103A is larger outside the 
region of the slit 8 as shown in FIG. 5, and is larger than the thickness 
of the transparent plate 51 so as to insure the correct positioning at the 
slit region. The width of the slot is indicated by 11. 
Additionally, in this embodiment the stationary assembly 100 is provided 
with a guiding rail 103B on top of the surface thereof. The guiding rail 
103B is in alignment with the guiding rail 103A when the apparatus is 
closed. The guiding rail 103B has a slot for receiving the transparent 
plate 51. The slot is in alignment with the slot of guiding rail 103A, 
when the apparatus is closed, that is, the rotatable assembly 104 is in 
the closed position. The width 1.sub.2 is slightly larger than the width 
1.sub.1 since the vertical position of the original supporting surface 
thereat hardly influence the imaging at the slit region. Thus, the 
original supporting surface of the transparent plate 51 is correctly 
positioned at the slit region by the projection 103D, and therefore load 
required for moving the original carriage 5 is minimized without 
deteriorating the positioning accuracy at the slit position. 
The guiding rail 103B is constructed and placed to cantilever the original 
carriage 5 when it is located to the left for allowing opening of the 
rotatable assembly 104 as shown in FIGS. 2 and 3. However, the original 
carriage 5 may be supported only by the rear side guiding rail 102 which 
is suitably configured so as to cantilever the original carriage 5, 
although the provision of the guiding rail 103B is preferable to ensure 
the supporting and to guide the original carriage 5 into the guiding rail 
103A of the rotatable assembly 104. 
An upper surface 103F of the guiding rail 103B is slightly lower than the 
level of the upper surface 103E of the guiding rail 103. By means of this, 
even if the original carriage 5 is inclined when it is cantilevered as 
shown in FIGS. 2 and 3, the original carriage 5 is easily reengaged into 
the guiding rail 103A when it is returned toward the home position. 
Further, the ends of the slots of the guiding rails 103A and 103B are 
enlarged as best seen in FIG. 5 to facilitate the reengagement. The 
guiding rail 103A provides an additional advantage, which will be 
described. 
An original to be copied may sometimes be so large that a part thereof 
extends beyond the front edge of the apparatus toward the operator. In 
this case, the portion of the original extending beyond the front edge 
inclines downward, with the result that a part of the original is raised 
or spaced from the original supporting surface of the transparent plate, 
as shown in FIG. 4A. This spacing results in deterioration of the reading 
of the original. 
As shown in FIG. 4B, according to the present invention, the guiding rails 
103A and 103B, particularly the guiding rail 103A are effective to solve 
this problem. More particularly, the top surface of the guiding rail 103A, 
and possibly the top surface of the guiding rail 103B, are effective to 
function as an extension of the transparent plate 51 to provide additional 
support to the original O, thus minimizing the original rise. 
The top surface of each of the guiding rails 103A and 103B are inclined 
downwardly toward the ends as shown in FIG. 5 so as to allow the portion 
of the original extending beyond the front edge of the apparatus to be 
smoothly guided to the top surface of the guiding rails. The inclined 
portions are preferably formed at the upstream side thereof with respect 
to original scanning movement of the original carriage 5, although it is 
more preferably that the inclined portions are formed at both ends. 
A projection 103C is formed on the top surface 101 of the stationary 
assembly 101. The projection 103C may be integrally formed with the top 
plate 101 of the stationary assembly 100. It is aligned with the guiding 
rails 103A and 103B. 
Similarly to the guiding rails 103A and 103B, the top surface of the 
projection 103C is slightly higher than the top surface of the original 
supporting platen 51, whereby the original 0 is prevented from spacing 
from the original supporting surface of the platen 51 at the slit position 
and also at the downstream and upstream sides of the slit portion with 
respect to the scanning movement of the original carriage, whereby the 
reading accuracy of the original is further increased. In this embodiment, 
the projection 103C is not engageable with the original supporting 
carriage 5, and therefore it does not influence the accuracy of movement 
of the original carriage 5. 
In this embodiment, the top surface of the guiding rail 103A is slightly 
higher than the levels of the top surfaces of the guiding rails 103B and 
the projection 103C. By means of this, the above-described function of the 
top surface of the guiding rail 103A is assured. 
As will be understood, the guiding rail 103A is effective to maintain the 
correct distance between the original supporting surface of the original 
carriage 5 and the openable assembly 104, even if the apparatus is 
operated many times which may wear, the locking member 106 and the latch 
107 may be worn. It should be noted that the guiding rail 103A is 
effective to correctly position the original supporting glass 51, since it 
confines the original supporting glass 51 at its front side which is the 
free side of the original supporting platen 51 and which is the side where 
is the guiding rail 103A is not provided, while the rear side is already 
securedly supported by the guiding rail 102. Therefore, the guiding rail 
103A provides proper positioning where it is desirable. 
The guiding rail 103A is not engaged with the original carriage 5, when the 
original carriage is in its retracted position as shown in FIGS. 2 and 3. 
As described hereinbefore, when it is at the retracted position, the 
original carriage 5 is supported by the guiding rail 102 and additionally 
by the guiding rail 103B in this embodiment. 
Now, operations of the embodiment will be described with respect to opening 
and closing of the openable assembly 104. When the inside of the apparatus 
is to be inspected, when a jammed sheet is to be disposed of, when the 
process cartridge K is to be replaced or interchanged, or the like, the 
original carriage 5 is moved leftward above the top plate 101 of the 
stationary assembly 100 along the guiding rails 102, 103A and 103B as far 
as the top plate of the rotatable assembly 104 in the top plate 101 of the 
stationary assembly 100 is sufficiently exposed as shown in FIG. 3, and 
more particularly is moved far enough for the marks 22 and 21 to come into 
alignment with each other. Then, the original supporting plate 5 is 
disengaged from the guiding rail 103A of the rotatable assembly 104; 
however, the original carriage 5 is still engaged with the guiding rail 
102, and additionally with the guiding rail 103B in the embodiment. 
Subsequentially, the lever 105 is pulled up so as to disengage the locking 
member 106 from the latch 107, and the rotatable assembly 104 is opened as 
shown in FIG. 2. 
After completion of the required operations or servicing, the assembly 104 
is pushed down against the urging spring force until the locking member 
106 is engaged with the latch 107. Then, the closed position is 
maintained. Then, the original carriage 5 is moved rightwardly. During 
this movement, the original carriage 5 is maintained engaged with the 
guiding rail 103B. Since the guiding rail 103B fixed on the stationary 
assembly is substantially in alignment with the guiding rail 103A fixed on 
the openable assembly 104 when it is closed, the original carriage 5 is 
smoothly engaged into the guiding rail 103A so as to allow the original 
carriage 5 to be returned to its home position. 
Thus, the original supporting surface of the original carriage 5 is 
correctly positioned with respect to the movable assembly 104 containing 
an imaging element. Further, the provision of the additional guiding rail 
103B on the stationary assembly 100 on a top surface thereof at its side 
where the original carriage 5 is present when the original carriage 5 is 
retracted, is effective to ensure the supporting of the original carriage 
5 when it is at the retracted position and is also effective to ensure the 
guiding of the original carriage 5 into the guiding rail 103A. 
In the foregoing description of the embodiment, the member on which an 
image of the original is formed through the imaging element is a 
photosensitive member on which an electrostatic latent image is formed in 
a known process. However, this detail is not necessary and the 
photosensitive member may be replaced by another image reading device, 
such as a charge coupled device (CCD). 
While the invention has been described with reference to the structures 
disclosed herein, it is not confined to the details set forth and this 
application is intended to cover such modifications or changes as may come 
within the purposes of the improvements or the scope of the following 
claims.