Cassette

A cassette is attachable to an image forming apparatus including a feed roller. The cassette is provided with a push-up member for pushing up leading edges of sheets placed in the cassette so as to bring the uppermost one of the contained sheets into contact with the feed roller, and a restricting member for restricting displacement of the contained sheets from a specified position. By attaching thus constructed cassette to the image forming apparatus, sheets can be fed properly by the feed roller.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
This invention relates to a cassette attachable to feeder of a printer, 
copying machine, or like image forming apparatus. 
A cassette for use in an image forming apparatus such as a printer and a 
copying machine is provided with a pair of upright side plates which are 
provided at opposite lateral ends of a sheet holding plate and are 
slidable in a direction perpendicular to a sheet feeding direction 
(hereinafter referred to as a lateral direction). By moving these side 
plates up to positions where these plates are in contact with left and 
right lateral edges of sheets contained in the cassette, cut sheets of A4 
size, B5 size, or the like, and various envelopes of specified sizes and 
unspecified sizes are allowed to be aligned and contained on the sheet 
holding plate. When this cassette is attached to the feeder of the image 
forming apparatus, the sheets contained in the cassette are lifted by an 
upward biasing force given from the sheet holding plate, thereby being 
brought into pressing contact with a feed roller. The sheets are fed by 
rotation of the feed roller. 
Sheet pressing members are provided at opposite front ends of the cassette 
so as to hold a leading edge of an uppermost sheet. The sheet pressing 
members are slidable in the lateral direction integrally with the side 
plates. Thereby, the sheets are prevented from floating. The pair of side 
plates restrict the transport of sheets in the lateral direction, thereby 
preventing an oblique feeding of sheet. 
Since the side plates are required to be in contact with the corresponding 
lateral edges of the uppermost sheet reliably, an upper end of each side 
plate is located above a lower end of a circumferential surface of the 
feed roller when the cassette is attached to the feeder of the image 
forming apparatus. Further, since the sheet pressing members press the 
uppermost sheet, an upper end of each sheet pressing member is also 
located above the lower end of the circumferential surface of the feed 
roller. 
Thus, particularly in the case where the side plates and the sheet pressing 
members are moved laterally inward of the cassette so as to contain sheets 
of narrow width such as envelopes in the cassette, the side plates and the 
sheet pressing members strike against the feed roller when the cassette is 
attached or detached to or from the image forming apparatus. This causes 
the inconvenience that the feed roller, the side plates, and the sheet 
pressing members are deformed or damaged. In view of the above 
inconvenience, it can be considered to arrange the feed roller within the 
width of the smallest possible sheet contained in the cassette. However, 
if the feed roller is arranged near the lateral center of the cassette, it 
becomes difficult to feed the large size sheets properly. 
On the other hand, in the case where envelopes formed into a flat container 
by folding the sheet are contained in the cassette, corners of some of the 
envelopes project outward from the lateral sides thereof. Accordingly, 
there outward projecting corners are brought into pressing contact with 
the side plates, which becomes a load against the upward biasing force 
given from the sheet holding plate and the envelopes cannot be lifted 
properly. As a result, the envelopes cannot be brought into pressing 
contact with the feed roller properly, and the envelopes cannot be 
transported. 
SUMMARY OF THE INVENTION 
In view of the problems residing in the prior art, it is an object of the 
invention to provide a cassette which prevents deformation and damage 
caused by a sheet pressing member thereof striking against a feed roller 
when the cassette is attached or detached to or from an image forming 
apparatus, and is capable of feeding even narrow envelopes properly and 
reliably. 
Accordingly, the invention is directed to a cassette attachable to an image 
forming apparatus including a feed roller. This cassette comprises push-up 
means for pushing up leading edges of sheets contained in the cassette so 
as to bring the uppermost one of the contained sheets into contact with 
the feed roller; and restricting means for restricting displacement of the 
contained sheets from a specified position. 
With thus constructed cassette, the contained sheets can be fed from the 
uppermost one by the feed roller while restricting displacement thereof 
from the specified position. 
The restricting means may preferably include a sheet pressing member 
provided movably vertically in the vicinity of the leading edges of the 
contained sheets and adapted for restricting vertical displacement of the 
contained sheets. 
With this arrangement, since the sheet pressing member lowers upon coming 
to contact with the feed roller, an impact generated when the feed roller 
comes to contact with the sheet pressing member can be cushioned. 
The sheet pressing member may be advantageously movable in the widthwise 
direction of the cassette. In thus construction cassette, the displacement 
of the contained sheets can be restricted properly regardless of the size 
thereof. 
The restricting means may further include a pair of intermediate 
restricting members for restricting widthwise displacement of the 
contained sheets. The intermediate restricting members are arranged at 
opposite lateral sides behind the sheet pressing members movably in the 
widthwise direction of the cassette. 
With this arrangement. the contained sheets can be fed from the uppermost 
one by the feed roller while restricting the widthwise displacement 
thereof from the specified position. 
The restricting means may include advantageously an intermediate 
restricting member for restricting widthwise displacement of the contained 
sheets and a front restricting member for restricting forward displacement 
of the contained sheets. The intermediate restricting member includes a 
side wall provided upright at an intermediate portion of each lateral side 
of the contained sheets. The front restricting member includes a side wall 
provided upright at a front end of each lateral side of the contained 
sheets. The side walls of the front restricting member are positioned 
outward of the corresponding side walls of the intermediate restricting 
member by a specified length in the widthwise direction. 
With this arrangement, when the spacing between the side walls of the 
intermediate restricting member is set in correspondence with the width of 
envelopes which are one type of sheets to be contained in the cassette, 
the side walls of the front restricting member are spaced apart wider than 
that spacing. Accordingly, even if an envelope has outward projecting 
corners at a leading edge portion thereof, the envelope is not pressed 
between the side walls of the front restricting member and is pressed 
against the feed roller so as to be fed properly. 
These and other objects, features and advantages of the present invention 
will become more apparent upon a reading of the following detailed 
description and accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
There will be first described a schematic construction of an image forming 
apparatus to which a cassette embodying the invention is attached with 
reference to FIG. 1. 
The image forming apparatus is provided with a plurality of cassettes 1, 
1', feed rollers 10, 10', a first pair of separating rollers 11, a second 
pair of separating rollers 12, a pair of registration rollers 13, a 
photosensitive member 14 in the form of a drum, a charger 15 and other 
unillustrated imaging devices arranged around the member 14, a light 
emitting device 16, a polygonal mirror 17, a transfer device 18, a fixing 
device 19, pairs of discharge rollers 20, 21, a discharge guide 22, a 
discharge tray 23, etc. The first separating roller pair includes a 
forward roller 11a and a retard roller 11b, and a second separating roller 
pair includes a forward roller 12a and a retard roller 12b. The light 
emitting device 16 includes a laser beam emitter for emitting a laser beam 
to print an image. 
The image forming apparatus is further provided with sheet sensors 24, 25, 
multifeed sensors 26, 27, a registration sensor 28, a timing sensor 29, a 
discharge sensor 30, and the like. The sheet sensors 24, 25 detect the 
presence or absence of sheets in the cassettes 1, 1' respectively. The 
multifeed sensors 26, 27 detect the multiple feeding of sheets. The 
registration sensor 29 is adapted for measuring a timing at which the 
registration rollers 13 are driven. The timing sensor 29 is adapted for 
measuring a timing at which the light emitting device 17 starts emitting 
the light. The discharge sensor 30 detects discharge of the sheet. 
In the image forming apparatus thus constructed, sheets are dispensed, for 
example, from the lower located cassette 1, are separated and transported 
one by one by the second separating rollers 12. The separated sheet is 
nipped by the registration rollers 13 after passing between the first 
separating rollers 11. When the sheets are fed from the cassette 1, the 
retard roller 11b is rotated idly. Accordingly, the sheet having passed 
between the second separating rollers 12 is permitted to pass between the 
first separating rollers 11 smoothly. It is controllably discriminated 
based on a data from a cassette information unit (not shown) provided at a 
front portion of the cassette 1 whether the retard roller 11b should be 
driven or not. The cassette information unit consists of four bits, and a 
magnet is mounted to each of desired bits thereof. Alternatively, the 
driving of the retard roller 11b is controlled based on which of the upper 
and lower cassettes 1 is selected through manual designation. The 
registration rollers 13 are driven controllably in accordance with a 
signal from the registration sensor 28. 
Thereafter, when the registration rollers 13 start transporting the sheet 
and a sensor signal is output from the timing sensor 29, the 
photosensitive member 14 is driven in accordance with this sensor signal 
and image signals input from an unillustrated data storage of a storage 
medium externally connected to the image forming apparatus or arranged at 
a specified position thereof are optically modulated into modulated beams 
(laser beams) in the light emitting device 16, and emitted therefrom. The 
photosensitive member 14 is exposed to this laser beam introduced by way 
of the polygonal mirror 17. It may be appropriate to drive the 
photosensitive member 14 at a timing when the driving of the feed roller 
10 is started. The surface of the photosensitive member 14 is charged by 
the charger 15, and an electrostatic latent image is formed on a charged 
region of the member 14 by an exposing operation. Thus formed 
electrostatic latent image is developed into a toner image by an 
unillustrated developing device. This toner image is transferred to a 
sheet by the transfer device 18, and then fixed onto the sheet by the 
fixing device 19. Consequently, the sheet bearing the image is discharged 
onto the discharge tray 23 through the pairs of discharge rollers 20, 21 
and the discharge guide 22. 
There will be described a first cassette embodying the invention next with 
reference to FIGS. 2 and 3. 
A first cassette 1 is adapted for containing cut sheets and sheet materials 
such as envelopes therein. The cassette 1 includes a cassette main body 2 
formed into a box-like figure, a trailing edge regulating member 3, a 
sheet holding plate 4 for holding sheets thereon, helical springs 5, a 
pair of side plates 6 arranged at left and right sides (sides parallel 
with a sheet feeding direction) of the cassette main body 2, etc. By 
attaching the cassette 1 to the image forming apparatus, sheets in the 
cassette 1 are allowed to be fed by the feed roller 10. 
The trailing edge regulating member 3 has at a bottom end thereof an 
engaging portion engageable with a guide groove 2b which is defined in a 
bottom plate 2a of the cassette main body 2 and extends in the sheet 
feeding direction. The member 3 slides forward and backward along the 
guide groove 2b to thereby align the trailing edges of the sheets. The 
sheet holding plate 4 is supported rotatably by shafts disposed at 
specified positions of the side walls of the cassette main body 2, and a 
leading end thereof is pivotable vertically. At opposite lateral side 
portions of the sheet holding plate 4 are formed cut-away portions 4a, 4b, 
such that the sheet holding plate 4 does not prevent front and rear side 
plates 6a and 6b to be described later from moving inward with respect to 
a widthwise direction of the cassette 1. A desired number of helical 
springs 5 are provided between the sheet holding plate 4 and the bottom 
plate 2a so as to bias and lift the leading end of the sheet holding plate 
4. By the biasing force of these helical springs 5, the uppermost sheet of 
the sheets placed on the sheet holding plate 4 is brought into contact 
with pressing member 60a of the front side plates 6a, and thereby a 
desired pressing force is attained between the cassette 1 and the feed 
roller 10 in a state where the cassette I is attached to the image forming 
apparatus. 
Each side plate 6 consists essentially of the front side plate 6a, the rear 
side plate 6b, a base portion 6c, and a rack portion 6d. The front side 
plate 6a is mounted to the side plate 6 through a guide plate 60c to be 
described later. The base portion 6c is held between the bottom plate 2a 
of the cassette main body 2 and the sheet holding plate 4. At a front end 
of each base portions 6c is provided the guide plate 60c which supports 
the front side plate 6a movably upward and downward. Accordingly, the 
front side plates 6a are movable upward and downward independently of the 
rear side plates 6b. The front and rear side plates 6a and 6b are adapted 
for restricting a lateral movement of sheets and feeding the sheets toward 
the feed roller 10 accurately. 
The front side plate 6a is formed of synthetic resin or the like, and 
includes the pressing member 60a, a slidable member 61a, and a spring 62a. 
Front end portions of the front side plates 6a are bent laterally inward 
of the cassette 1 at a right angle so as to align leading edges of the 
sheets. A guide portion 66a extends obliquely upward from the top of the 
front end of the front side plate 6a. The guide portion 66a guides the 
sheets to be fed from the cassette main body 2 by the feed roller 10 to 
the pairs of separating rollers 11, 12 located above the cassette 1. 
Further, a notch 68a is defined in the front side plate 6a, such that the 
feed roller 10 is not contact with the front side plate 6a when the 
cassette 1 is attached to the image forming apparatus. 
On the guide portion 66a is adhered a friction pad 67a. Further, between 
the friction pad 67a and the lower end of the feed roller 10 is defined a 
clearance which is twice the thickness of two sheets (two envelopes). When 
two sheets are dispensed out of sheets placed on the sheet holding plate 4 
through this clearance to the guide portion 66a, a lower sheet comes to 
contact with the friction pad 67a and transport thereof is deterred due to 
a frictional force generated between this sheet and the friction pad 67a. 
Accordingly, only an upper sheet of the two (i.e., the uppermost sheet) is 
fed. 
The pressing member 60a extends laterally inward of the cassette main body 
2 from an upper end of a lateral face of the front side plate 6a, and is 
adapted for pressing the leading end of the uppermost one of sheets placed 
on the sheet holding plate 4. 
The slidable member 61a extends laterally outward of the cassette main body 
2 from the front side plate 6a, and holds the front side plate 6a tightly 
slidably upward and downward with the use of a required number of hooks 
formed at opposite lateral ends thereof. On the slidable member 61a is 
defined an oblong groove 65a extending vertically. On the guide plate 60c 
is formed a pin 64a including a small screw or the like projecting 
backward. By loosely fitting this pin 64a in the oblong groove 65, a 
movable range of the front side plate 6a is restricted (between a position 
shown in FIG. 4 and a position shown in FIG. 5). The spring 62a is 
provided between the front side plate 6a and the base portion 6c so as to 
bias the front side plate 6a upward. 
The rack portion 6d extends laterally inward of the cassette main body 2 
from a specified inner lateral position of each base portion 6c. The rack 
portions 6d of the opposite site side plates 6 are spaced apart by a given 
distance in parallel with each other, and are meshable with a pinion 7 
mounted at a widthwise center of the bottom plate 2a therebetween. With 
this arrangement, the opposite side plates 6 are movable toward or away 
from each other simultaneously along the widthwise direction of the 
cassette 1. Since the front and rear side plates 6a, 6b are movable within 
the width of the sheet holding plate 4 in this way, the cassette 1 is 
capable of containing therein not only cut sheets of large size but also 
envelopes of small size. 
Further, the front side plates 6a formed of synthetic resin or the like 
serve to cushion an impact generated when the front side plates 6a come to 
contact with the feed roller 10 in attaching or detaching the cassette 1. 
There will be described an operation when thus constructed cassette 1 is 
attached or detached to or from the image forming apparatus next with 
reference to FIGS. 4 and 5. Here, it is assumed that narrow sheets such as 
envelopes are contained in the cassette main body 2 and the side plates 6 
are moved to the position of the feed roller 10. 
The cassette 1 is inserted to a cassette inserting portion of the image 
forming apparatus to be attached thereto. At this time, the upper ends of 
the front side plates 6a and the pressing members 60a are located above 
the lower end of the circumferential surface of the feed roller 10. As the 
cassette l is inserted more, the feed roller 10 comes to contact with the 
front side plates 6a and the pressing members 60a. Thereby, the front side 
plates 6a are pressed downward to be thereby lowered against the biasing 
force of the springs 62a as shown in FIG. 4. 
When the cassette 1 is inserted further into the cassette inserting 
portion, the feed roller 10 moves over the front side plates 6a and is 
positioned between the front side plates 6a and the rear side plates 6b. 
At this time, the feed roller 10 gets out of contact with the upper ends 
of the front side plates 6a and the pressing members 60a, thus the front 
side plates 6a are elevated due to the biasing force of the springs 62a 
and return to the position shown in FIG. 5. In this state, the sheets 
contained in the cassette 1 are allowed to be fed by the feed roller 10. 
On the other hand, when the cassette 1 is moved backward to be detached 
from the image forming apparatus, the feed roller 10 comes to contact with 
the upper ends of the front side plates 6a and the pressing members 60a to 
thereby lower the front side plates 6a similar to the aforementioned case 
(see FIG. 4). When the cassette 1 is moved further backward, the upper 
ends of the front side plates 6a and the pressing members 60a get out of 
contact with the feed roller 10, and the front side plates 6a return to 
the position shown in FIG. 5 by the biasing force of the springs 62. 
In this way, even when the feed roller 10 comes to contact with the upper 
ends of the front side plates 6a and the pressing members 60a in attaching 
or detaching the cassette 1 to or from the image forming apparatus, the 
front side plates 6a are lowered and therefore the feed roller 10, the 
front side plates 6a, and the pressing members 60a are prevented from 
being deformed or damaged due to the collision with one another in 
attaching or detaching the cassette 1. 
While each pressing member 60a is formed integrally with the front side 
plate 6a in this embodiment, these members may be formed separately. In 
this case, the slidable members 61a and the springs 62a are provided for 
each of the pressing members 60a and the front side plates 6a so as to 
make the pressing members 60a and the front side plates 6a movable upward 
and downward independently of each other. 
There will be described a second cassette embodying the invention next with 
reference to FIG. 6. This cassette 1 contains envelopes therein in this 
embodiment, and includes a cassette main body 2 formed into a box-like 
figure, a trailing edge regulating member 3, a sheet holding plate 4 for 
holding envelopes thereon, helical springs 5, a pair of side plates 106 
arranged at left and right sides of the cassette main body 2, etc. 
Each side plate 106 is made of a metal member, and consists essentially of 
integrally formed front side plate 106a, rear side plate 106b, base 
portion 106c, and rack portion 106d. The base portion 6c is held between a 
bottom plate 2a of the cassette main body 2 and the sheet holding plate 4. 
The front and rear side plates 106a, 106b are provided upright at front 
and rear ends of the base portion 106c, and are adapted for restricting a 
lateral movement of the envelopes so that the envelopes can be fed toward 
the feed roller 10 accurately. By forming the front and rear side plates 
106a, 106b separately, the feed roller 10 is permitted to be positioned 
therebetween when the cassette 1 is attached to the image forming 
apparatus. Further. the front and rear side plates 106a, 106b are made 
movable within the width of the sheet holding plate 4 along a widthwise 
direction of the cassette 1, such that the cassette 1 is capable of 
containing therein not only cut sheets of large size but also envelopes of 
small size. 
The rack portion 106d extends laterally inward of the cassette main body 2 
from a specified inner lateral position of each base portion 106c. The 
rack portions 106d of the opposite side plates 106 are spaced apart by a 
given distance in parallel with each other, and are meshable with a pinion 
7 mounted at a widthwise center of the bottom plate 2a therebetween. With 
this arrangement. the opposite side plates 106 are movable toward or away 
from each other simultaneously along the widthwise direction of the 
cassette 1. At the top of the front end of each front side plate 106a is 
formed a pressing member 160a extending laterally inward of the cassette 
main body 2. The pressing members 160 press downward a leading edge of the 
uppermost one of the envelopes placed on the sheet holding plate 4. 
FIG. 7 is a fragmentary plan view showing the front side plates 106a. The 
front side plates 106a are formed such that the width thereof is greater 
than the rear side plates 106b by L0. Accordingly, the distance between 
the front side plates 106a is L2 (=L1+2L0) when the side plates 106 are 
moved and the rear side plates 106b come to contact with lateral edges of 
the envelopes of the width L1. 
The leading and trailing edges of the envelopes P are both aligned and 
positioned properly as shown in FIG. 8 by moving the trailing edge 
regulating member 3 to contact the same with the trailing edges of the 
envelopes P. Thereafter, the cassette 1 is attached to a printer, copying 
machine, or like image forming apparatus, and the envelopes P are fed one 
by one from the uppermost one by the feed roller 10. 
Now, description will be given on the meaning of the distance L0. 
Since the envelopes P are formed by folding a sheet into a flat container 
as shown in FIG. 9, some of them have four corners P1 projecting outward 
from sides P2 by about 0.3 mm. In the case where these envelopes P are 
contained in the cassette 1, these corners P1 generate an unnecessary 
pressing force between the front side plates 106a. This pressing force 
undesirably becomes a resistance against such a biasing force of the 
helical spring 5 as to elevate the envelopes P placed on the sheet holding 
plate 4, with the result that the envelopes P cannot be fed properly. 
In consideration of a projected amount of the corners P1, the distance L0 
is set so as to accommodate these corners P1 appropriately. For example, 
the distance L0 is set at about 1 mm. When the distance L0 is set at an 
exceedingly large value, the leading edges of the envelopes cannot be 
aligned reliably by the front side plates 106a, for example, in feeding 
the short envelopes, and thereby the likelihood of oblique feeding arises. 
However, if the distance L0 is set at about 0.6 mm to 1.5 mm, it does not 
affect a feeding direction of the envelopes. 
With the above consideration, even when the envelopes P are used as sheets, 
the envelopes P are allowed to come to contact with the feed roller 10 
without affecting the feeding direction of the envelopes P, and to be fed 
properly and reliably by the feed roller 10. In this embodiment, the rear 
side plates 106b are not in contact with the trailing edge portions of the 
envelopes P. This considers the existence of the outward projecting 
corners at the trailing edge portions of the envelopes P. 
Although each side plate 106 includes the separately formed front and rear 
side plates 106a, 106b in this embodiment, the front and rear side plates 
may be formed integrally according to the invention. In this case, the 
side plates 106 are formed such that the distance between the front end 
portions thereof is greater than the distance between other portions 
thereof. Further, the distance L0 is preferably set in the aforementioned 
range of about 0.6 mm to 1.5 mm, but may be set outside this range. 
Although the present invention has been fully described by way of example 
with reference to the accompanying drawings, it is to be understood that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be construed as being 
included therein.