Sheet supply apparatus

The present invention provides a sheet supply apparatus comprising a lifter device for maintaining a height of an upper surface of a sheet stack supported by a sheet supporting device substantially constant by lifting or lowering the sheet supporting device, and a supply device for feeding out an uppermost sheet from the sheet stack maintained in a constant height position by the lifter device, and wherein the lifter device comprises a clutch member for transmitting a predetermined amount of rotation from a drive gear, a rock member for rocking a ratchet pawl by the rotation transmitted by the clutch member, a ratchet gear engageable by the ratchet pawl and rotated by a rocking movement of the ratchet pawl, a lifter member connected to the ratchet gear and adapted to lift the sheet supporting member by rotation of the ratchet gear, and an actuation device shifted in accordance with the height of the upper surface of the sheet stack rested on the sheet supporting device and adapted to actuate the clutch member when the height of the upper surface of the sheet stack is below a predetermined height.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sheet supply apparatus incorporated into 
an image forming apparatus such as a printer, a copying machine, a 
facsimile and the like, and more particularly, it relates to a sheet 
supply apparatus having a lifter means for maintaining a height of an 
uppermost sheet substantially constant. 
2. Related Background Art 
Among sheet supply apparatuses incorporated into an image forming 
apparatus, there is a sheet supply apparatus having a lifter means for 
maintaining a height of an uppermost sheet in a sheet stack substantially 
constant so that a sheet is fed out by a sheet supply means such as a 
sheet supply roller at a constant height position. In such a lifter means, 
in order to maintain the height of the uppermost sheet constant, for 
example, a lever is abutted against an upper surface of the sheet stack, 
displacement of the lever is detected by an electrical sensor such as a 
photo-sensor, and an electrical actuator such as a motor or a strong 
solenoid for lifting and lowering a sheet stacking plate on which sheets 
are stacked as the sheet stack is energized on the basis of a detection 
result of the electrical sensor. 
Further, in some conventional sheet supply apparatuses, a sheet supply 
roller can be shifted to be abutted against or separated from the 
uppermost sheet of the sheet stack the height of which is kept constant by 
the lifter means. In this arrangement, after the sheet is fed out by the 
sheet supply roller abutted against the sheet, by separating the sheet 
supply roller from the sheet, load (back tension) acting on the sheet is 
reduced. 
In the past, an exclusive electrical actuator such as a motor or a solenoid 
similar to that associated with the lifter means has been used as a 
mechanism for lifting and lowering the sheet supply roller with respect to 
the sheet. However, in the conventional sheet supply apparatus having the 
lifter means and the mechanism for shifting the sheet supply roller, the 
following problems arose: 
(1) Since the electrical sensor, the actuator for the lifter means and the 
exclusive actuator for lifting and lowering the sheet supply roller must 
be provided, the entire sheet supply apparatus becomes expensive, and 
large electrical capacity is required; 
(2) Since complex wiring is required for electrically connecting the 
electrical sensor and the exclusive actuators to associated elements, 
miss-wiring is apt to occur; and 
(3) Electrical control sequence for the sheet supply system becomes 
complex, and, thus malfunction is apt to occur. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a sheet supply apparatus 
which is inexpensive and which has good assembling feature and can reduce 
occurrence of malfunction. 
To achieve the above object, the present invention provides a sheet supply 
apparatus having a lifter means for maintaining a height of an upper 
surface of a sheet stack supported by a sheet supporting means 
substantially constant by lifting or lowering the sheet supporting means, 
and a sheet supply means for feeding out an uppermost sheet from the sheet 
stack maintained in a constant height position by the lifter means. 
Wherein the lifter means comprises a clutch means for transmitting a 
predetermined amount of rotation from a drive gear, a rock means for 
rocking a ratchet pawl by the rotation transmitted by the clutch means, a 
ratchet gear engageable by the ratchet pawl and rotated by a rocking 
movement of the ratchet pawl, a lifter member connected to the ratchet 
gear and adapted to lift the sheet supporting member by rotation of the 
ratchet gear, and an actuation means shifted in accordance with the height 
of the upper surface of the sheet stack and adapted to actuate the clutch 
means when the height of the upper surface of the sheet stack is below a 
predetermined height. 
The present invention also provides a sheet supply apparatus comprising a 
sheet supporting means adapted to support a sheet and removably mounted to 
the apparatus, a supply means movable in an up-and-down direction and 
adapted to be abutted against an upper surface of the sheet rested on the 
sheet supporting means to feed out the sheet at a supply position, a shift 
means for lowering the supply means to abut the supply means against the 
upper surface of the sheet when the sheet is to be supplied and for 
lifting the supply means to a waiting position spaced apart from the upper 
surface of the sheet when the sheet is not supplied, a rock means for 
rocking a ratchet pawl by rotation of a drive gear, a ratchet gear 
engageable by the ratchet pawl and rotated by a rocking movement of the 
ratchet pawl, a lifter member connected to the ratchet gear and adapted to 
lift the sheet supporting member by rotation of the ratchet gear, an 
actuation means for driving the rock means in accordance with an abutment 
position between the supply means at the supply position and the sheet 
supported by the sheet supporting means, a lock means for regulating 
movement of the shift means under a condition that the supply means is 
lowered in response to a mounting operation of the sheet supporting means 
to the apparatus, and a lock releasing means for releasing the regulation 
of the lock means when the upper surface of the sheet supported by the 
sheet supporting means is brought to a predetermined position by the 
lifter means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
First of all, a sheet supply apparatus according to a preferred embodiment 
of the present invention will be explained with reference to FIGS. 1 to 
14B. FIG. 1 shows a condition that a sheet cassette 4 is being inserted 
into the sheet supply apparatus from a direction shown by the arrow. 
The sheet supply apparatus comprises a feed roller 1, a retard roller 2 and 
a pick-up roller 3. Sheets S stacked in the sheet cassette 4 are separated 
and supplied one by one by these three rollers. A stepping motor (not 
shown) is attached to a frame 7 so that a driving force from the stepping 
motor is transmitted to a roller shaft 1a of the feed roller 1 and a 
roller shaft 2a of the retard roller 2. The pick-up roller 3 is rotated by 
transmitting a driving force of the feed roller 1 to the pick-up roller 2 
via a gear train (not shown ). 
As shown in FIGS. 2, 3A and 3B, the retard roller 2 is supported by a 
support member 50 rockably mounted on a bearing member 51 so that the 
retard roller can be abutted against and separated from the feed roller 1 
in a parallel condition. Further, the support member 50 is biased by a 
spring 52 connected between the support member and the bearing member 51 
so that the retard roller 2 is urged against the feed roller 1 with 
predetermined separation pressure. 
A torque limiter 38 is arranged on the roller shaft 2a of the retard roller 
2 so that normal and reverse rotations of the retard roller 2 are 
controlled by the torque limiter 38. Incidentally, a universal joint 39 is 
also arranged on the roller shaft 2a so that the rotation can be 
transmitted even if the retard roller 2 is separated from the feed roller 
slightly due to the insertion of the sheet between the feed roller 1 and 
the retard roller 2. 
Returning to FIG. 1, the feed roller 1 and the pick-up roller 3 are 
supported by a roller holder 5 which is pivotally mounted on the roller 
shaft la of the feed roller 1, so that the pick-up roller 3 can be rocked 
around the roller shaft la of the feed roller 1. A shaft 6 (referred to as 
"pick-up roller shaft" hereinafter) of the pick-up roller extends to the 
right in FIG. 1 through a slot 8 formed in the frame 7. 
A mechanism for lifting and lowering the pick-up roller 3 in synchronous 
with a mounting movement of the sheet cassette 4 is arranged within the 
slot 8 of the frame 7. As shown in FIGS. 4A to 5, this mechanism comprises 
a lever member 40, and a spring 45 for biasing the lever member 40 in a 
clockwise direction. The lever member 40 is formed from a metal wire and 
is pivotally mounted in a bearing portion 7a integrally formed with the 
frame 7 and comprises an push-up portion 40a for pushing up the pick-up 
roller shaft 6 inserted in the slot 8, and an abutment portion 40b for 
rocking the lever member 40 in opposition to a biasing force of the spring 
45 when the sheet cassette 4 is mounted to the apparatus. 
In FIG. 1, a lift arm lever 10 is rotatably attached to a shaft 9 
integrally formed with the frame 7 and is biased in a clockwise direction 
(FIG. 1) by a spring 11 connected to the lift arm lever. Further, the 
pick-up roller shaft 6 is abutted against one end of the lift arm lever 
10. The other end of the lift arm lever 10 extends up to the proximity of 
a pick-up cam 12 so that, when the pick-up cam 12 is rotated, the lift arm 
lever 10 is rocked. Thus, when the pick-up cam 12 is rotated, the pick-up 
roller shaft 6 is shifted in an up-and-down direction via the lift arm 
lever 10, thereby lifting or lowering the pick-up roller 3. 
The pick-up cam 12 comprises a cam portion 12a with which the lift arm 
lever 10 is slidingly contacted, and a gear portion 12b engageable by a 
drive gear 13. The gear portion is a so-called notched gear having a 
partial notched portion (having no tooth). The pick-up gear 12 is biased 
in an anti-clockwise direction in FIG. 1 by a biasing means (not shown) 
such as a spring, and rotation of the pick-up gear 12 is regulated by a 
solenoid 14 of flapper type in opposition to a biasing force of the 
biasing means. Further, a driving force from a main motor 15 of the 
apparatus is transmitted to the drive gear 13 via a gear 16 so that the 
drive gear 13 is always rotated. 
Next, a lifter mechanism used in the illustrated embodiment will be 
explained. 
A gear 17 is rotatably supported by the frame 7 and a lift-up cam 18 is 
disposed on a rotary shaft of the gear 17. The gear 17 is engageable by 
the drive gear 13 and has a notched portion (having no tooth). Further, 
the gear 17 is biased in an anti-clockwise direction by a biasing means 
(not shown). 
A lift arm pawl 19 is pivotally mounted on a shaft 20 and is biased by a 
spring 19b so that a pawl portion 19a (FIGS. 11A to 14B) of the lift arm 
pawl is meshed with a toothed surface of a sector ratchet gear 22. The 
lift arm pawl 19 is rocked around the shaft 20 by rotation of the lift-up 
cam 18, thereby rotating the sector ratchet gear 22 in an anti-clockwise 
direction in FIG. 1 or FIGS. 11A and 11B step by step. 
A pawl portion 21a (FIGS. 8A, 8B and 11B) of a lift lock pawl 21 pivotally 
supported is urged against the toothed surface of the sector ratchet gear 
22 by a spring 21b, thereby preventing the sector ratchet gear 22 from 
rotating reversely (in a clockwise direction in FIG. 1). 
With this arrangement, in a condition that the reverse rotation of the 
sector ratchet gear 22 is prevented by the lift lock pawl 21, when the 
sector ratchet gear 22 is rotated by the lift arm pawl 19, a lift-up 
member 23 integrally formed with the sector ratchet gear 22 is lifted 
through an opening 4a formed in the sheet cassette 4, thereby lifting up 
the sheets S in the sheet cassette 4. Incidentally, the sheet cassette 4 
is provided with a rockable intermediate plate 4b on which the sheets S 
are stacked, so that, when a lift portion 23a of the lift-up member 23 is 
rocked upwardly, the sheets are lifted via the intermediate plate 4b. 
Now, the lift-up member 23 will be fully described with reference to FIGS. 
6A and 6B. 
FIG. 6A shows a one-piece lift-up member 23 comprising a lift portion 23a, 
a sector ratchet gear 22 and a connecting shaft portion 23b connecting the 
lift portion and the sector ratchet gear, which portions 23a, 2 and 23b 
are integrally formed with each other. The lift-up member 23 is made of 
glass-reinforced synthetic resin, for example, to provide high rigidity. 
FIG. 6B shows a two-piece lift-up member 23 comprising a sector ratchet 
gear 22 made of resin such as polyacetal providing the required sliding 
ability, and a lift portion 23a and a connecting shaft portion 23b which 
are made of glass-reinforced synthetic resin to provide high rigidity. The 
sector ratchet gear 22 is positioned with respect to the connecting shaft 
portion 23b by boss/hole fitting connection and is firmly secured to the 
connecting shaft portion 23b by a screw 27. Incidentally, the sector 
ratchet gear 22 may be removably connected to the connecting shaft portion 
23b via press-fit, for example. In this case, if the sector ratchet gear 
is damaged, the sector ratchet gear alone can be replaced by new one. 
Since the above-mentioned one-piece or two-piece lift member 23 can support 
a heavy weight, for example, such a lift member 23 can be used with a 
sheet cassette containing sheets of large size or a sheet cassette 
containing a large number of sheets. Further, in the one-piece lift 
member, the sector ratchet gear 22 is not displaced (i.e. not 
out-of-phase) with respect to the lift portion 23a, and, in the two-piece 
lift member, out-of-phase between the sector ratchet gear and the lift 
portion can be substantially prevented. Thus, it is possible to control a 
height of the sheet stack S with high accuracy. 
In FIG. 1, a lifter trigger lever 24 is pivotally mounted on the shaft 9 
integrally formed with the frame 7 and is biased in a clockwise direction 
in FIG. 1 by a spring 25. One end of the lifter trigger lever 24 acts as a 
regulating member for regulating the rotation of the notched gear 17 
integral with the lift-up cam 18 in a condition that the notched portion 
of the notched gear 17 is opposed to the drive gear 13. The other end of 
the lifter trigger lever 24 is abutted against the pick-up roller shaft 6 
when the pick-up roller 3 is lowered to a predetermined position. 
When the pick-up roller shaft 6 is lowered to a predetermined position, the 
lifter trigger lever 24 is rocked to release the regulation of rotation of 
the lift-up cam 18 (regulated by one end of the lever 24), thereby 
slightly rotating the lift-up cam 18 by the biasing means (not shown). As 
a result, the notched gear 17 is engaged by the drive gear 13 to rotate 
the lift-up gear 18, thereby rocking the lift arm pawl 19 to rotate the 
sector ratchet gear 22, with the result that the lift-up member 23 is 
lifted. Further, when the lift-up member 23 is lifted to lift the pick-up 
roller 3 via the sheets S, the lifter trigger lever 24 is returned to 
rotate in the clockwise direction, thereby regulating the rotation of the 
lift-up cam 18 again. 
A pick-up lock lever 30 is biased in a clockwise direction in FIG. 1 by the 
spring 25 and comprises a pawl portion a and a hood portion b overhanging 
above the pick-up roller shaft 6. The pawl portion a serves to catch and 
lock the lift-up lever 10 when the lever 10 is lowered to a lowermost 
position, and the hood portion b serves to rotate the pick-up lock lever 
30 in an anti-clockwise direction in FIG. 1 in opposition to a biasing 
force of the spring 25 when the pick-up roller shaft 6 is lifted, thereby 
releasing the end of the lift-up lever 10 from the pawl portion a to 
permit the lifting movement of the lift-up lever 10. 
A photo-sensor 31 serves to detect the mounting of the sheet cassette 4, 
and a connecting lever 32 is pivotally mounted on a shaft 33. 
As shown in FIGS. 7A and 7B, a ratch pawl 41 is rotatably attached to the 
sheet cassette 4, when ratch pawl is connected to a grip 48 formed on a 
front side of the sheet cassette 4 via a rod 47. The ratch pawl 41 is 
normally biased in an anti-clockwise direction by a spring 46. However, 
when the grip 48 is pulled, the ratch pawl 41 can be rotated in a 
clockwise direction. 
When the ratch pawl 41 is fitted into the connecting lever 32, the latter 
is rocked. As shown in FIG. 7A, when the sheet cassette 4 is not mounted, 
the connecting lever 32 is in a lowered position where the connecting 
lever 32 is fixed or stopped by a lock member 34. When the sheet cassette 
4 is mounted, as shown in FIG. 7B, a projection 36 formed on the sheet 
cassette 4 enters into a hole 53 formed in the frame 7 to rock the lock 
member 34 in opposition to an elastic force of a leaf spring 35, thereby 
releasing a locking condition. As a result, the ratch pawl 41 is fitted 
into the connecting lever 32 to rock the latter upwardly. When the ratch 
pawl 41 is fitted into the connecting lever 32, a pawl portion 41a of the 
ratch pawl 41 is engaged by an engagement portion 7a formed on the frame 
7, thereby fixing the sheet cassette 4. 
Incidentally, a flat 32a for blocking the photo-sensor 31 is formed on the 
connecting lever 32 so that, when the sheet cassette 4 is mounted in 
place, the photo-sensor 31 is blocked by the flag 32a, thereby detecting 
the mounting of the sheet cassette 4. 
Although not shown, a portion of the connecting lever 32 protrudes up to 
the proximity of the lift-up cam 18 to regulate the rotation of the 
lift-up cam 18 when the connecting lever 32 is in the lowered position 
(i.e. when the sheet cassette 4 is not mounted). In this condition, the 
lift-up cam 18 cannot be rotated regardless of the position of the lifter 
trigger lever 24. When the sheet cassette 4 is mounted and the connecting 
lever 32 is lifted, the regulation of rotation of the lift-up cam 18 is 
governed by the lifter trigger lever 24. 
Further, as shown in FIGS. 2, 3A, 3B, 8A and 8B, one end of a release rod 
37 is rotatably supported by the connecting lever 32 to separate the 
retard roller 2 from the feed roller 1. The other end of the release lever 
37 is fitted into a groove 7c formed in the frame 7. An intermediate 
portion of the release lever 37 can be engaged by a protruded portion 50a 
formed on the support member 50 for supporting the retard roller 2. In a 
condition that the connecting lever 32 is lifted, the release lever 37 is 
not engaged by the protruded portion 50a. However, when the connecting 
lever 32 is lowered, the release lever 37 is engaged by the protruded 
portion 50a, thereby pushing the support member 50 downwardly. As a 
result, the retard roller 2 is separated from the feed roller 1, thereby 
releasing the separation pressure. 
Next, the notched gears 12b, 17 associated with the pick-up cam 12 and the 
lift-up cam 18 will be explained with reference to FIGS. 6A to 7B. 
Incidentally, FIGS. 9A and 9B show an example of a conventional notched 
gear. 
In the illustrated embodiment, as shown in FIGS. 10A and 10B, the notched 
gears 12b, 17 have mesh start portions 12c, 17a which are firstly engaged 
by the drive gear 13. Each of the mesh start portions 12c, 17a has a width 
gradually decreasing toward a tip end of the mesh start portion. 
Further, recesses 12d, 17b are formed under the mesh start portions 12c, 
17a of the notched gears 12b, 17, thereby damping any shock generated when 
the gears are meshed with each other. 
With this arrangement, as shown in FIG. 10B (which is a view looked at from 
a radial direction of FIG. 10A), even if the parallelism between the gear 
shafts of the gears to be meshed with each other is slightly wrong, it is 
possible to prevent the collision between tip ends of teeth of the gears. 
As apparent from the comparison between the notched gear shown in FIGS. 
10A and 10B and the conventional notched gear shown in FIGS. 9A and 9B, 
this can be understood from the fact that an intersect amount C between 
the notched gear 17 (12b) and the drive gear 13 when these gears are just 
meshed with each other is considerably smaller than a conventional 
intersect amount Cp (FIG. 9B). 
Incidentally, in the illustrated embodiment, while the width of the mesh 
start portion of each notched gear was smaller than that of the other 
portion to prevent the reduction of rigidity of the other portion, for 
example, even when the notched gear is made of material having high 
rigidity, the width of the entire notched gear may be smaller than that of 
the associated gear (drive gear) to be meshed with the notched gear. 
Next, the operation of the sheet supply apparatus will be explained. 
First of all, before the sheet cassette 4 containing the sheets S is 
mounted to the sheet supply apparatus, as shown in FIGS. 1 and 14A, while 
the drive gear 13 is being continuously rotated by the driving force of 
the main motor 15 of the apparatus, since both of the notched portions of 
the notched gears (12b, 17) associated with the pick-up cam 12 and the 
lift-up cam 18 are opposed to the drive gear 13, the driving force of the 
drive gear is not transmitted to the cams 12, 18, with the result that 
these cams are not rotated. 
In this condition, the connecting lever 32 is fixed in the lowered position 
by the lock member 34. Consequently, as shown in FIG. 11A, both of the 
lift arm pawl 19 and the lift lock pawl 21 are spaced apart from the 
sector ratchet gear 22 of the lift-up member 23. Accordingly, the lift-up 
member 23 is in the lowermost position. 
If the engagement between these pawls is not released, when any force acts 
on the sheet supply apparatus or on the lift-up member 23 in the condition 
that the sheet cassette 4 is dismounted from the apparatus, as shown in 
FIG. 7B, the lift-up member 23 is sometimes maintained in the lifted 
condition. In such a condition, a serious problem that the sheet cassette 
4 cannot be mounted to the sheet supply apparatus will arise. However, by 
adopting the above-mentioned arrangement, such a problem can be avoided. 
Further, as shown in FIGS. 3A and 8A, since the release rod 37 extending 
between the connecting lever 32 and the groove 7c is locked in the 
condition that the connecting lever 32 is lowered, the release rod is 
engaged by the protruded portion 50a to push the support member 50 
downwardly. As a result, the retard roller 2 is separated from the feed 
roller 1, thereby releasing the separation pressure. 
In this way, when the sheet cassette 4 is dismounted from the apparatus, 
since the connecting lever 32 is shifted to lower the lift-up member 23 
and to release the separation pressure between the retard roller 2 and the 
feed roller 1, the sheet supply apparatus can be simplified, thereby 
making the apparatus compact and reducing the cost. Further, since the two 
operations can be effected by the single manipulation, the operability can 
be improved. 
Further, by pushing the pick-up roller shaft 6 upwardly by the lift-up 
lever 10, the pick-up roller 3 is maintained in the uppermost position. 
Incidentally, as shown in FIG. 4A, the lever member 40 is also maintained 
in a position where the pick-up roller shaft 6 is lifted by the lever 
member. In this case, as shown in FIG. 7A, the connecting lever 32 is in 
the lowered position. Thus, since the photo-sensor 31 is not blocked by 
the flag 32a, the mounting of the sheet cassette 4 is not detected. 
Next, a condition after the sheet cassette 4 is mounted will be explained. 
After the sheet cassette 4 is mounted to the sheet supply apparatus, as 
shown in FIG. 7B, the lock member 34 is released by the projection 36, 
with the result that the connecting lever 32 is rocked upwardly by the 
ratch pawl 41 of the sheet cassette 4. Thus, the photo-sensor 31 is 
blocked by the flag 32a, thereby detecting the mounting of the sheet 
cassette 4. 
In this case, since the connecting lever 32 is lifted, as shown in FIGS. 3B 
and 8B, the release rod 37 is lifted to be disengaged from the protruded 
portion 50a. As a result, the support member 50 is shifted by the spring 
52 to urge the retard roller 2 against the feed roller 1 with the 
predetermined separation pressure. 
As shown in FIGS. 13 and 14B, when the mounting of the sheet cassette 4 is 
detected, the solenoid 14 is activated to release the regulation of 
rotation of the pick-up cam 12. As a result, the pick-up cam 12 is 
slightly rotated by the biasing means (not shown) to engage the gear 
portion 12a of the pick-up cam 12 by the drive gear 13, thereby 
transmitting the driving force (from the drive gear to the cam 12) to 
rotate the pick-up cam 12 in the direction shown by the arrow by one 
revolution. When the pick-up cam 12 is rotated by one revolution, the 
notched portion of the gear portion 12a is opposed to the drive gear 13, 
thereby interrupting the transmission of the driving force. 
Then, when the pick-up cam 12 is rotated by one revolution, the lift-up 
lever 10 is lowered so that one end of the lift-up lever is caught by the 
pawl portion a of the pick-up lock lever 30, thereby locking the lift-up 
lever 10. In this case, the pick-up roller 3 is lowered by its own weight 
or by a biasing means (not shown) such as a spring. As a result, the 
pick-up roller shaft 6 is lowered to rotate the lifter trigger lever 24, 
with the result that the other end of the lifter trigger lever 24 is 
shifted to release the regulation of rotation of the lift-up cam 18. 
Incidentally, as shown in FIG. 4B, when the sheet cassette 4 is mounted, 
since the lock member 40 is lowered from the position for lifting the 
pick-up roller shaft 6, the lowering of the pick-up roller shaft 6 is not 
obstructed. 
The released lift-up cam 18 engaged by the drive gear 13 to be rotated, 
thereby rocking the lift arm pawl 19. As a result, the sector ratchet gear 
22 is rotated in the anti-clockwise direction to rotate the lift portion 
23a of the lift-up member 23 in the same direction, thereby lifting the 
sheets in the sheet cassette 4 (condition shown in FIGS. 15 and 16A). 
As the sheets are lifted, the pick-up roller 3 is also lifted. When the 
pick-up roller 3 is lifted to a predetermined height position, the hood 
portion b of the pick-up lock lever 30 is lifted to rotate the pick-up 
lock lever 30 in the anti-clockwise direction, thereby unlocking the 
lift-up lever 10. As soon as the lift-up lever 10 is unlocked, the lift-up 
lever 10 causes the pick-up roller 3 to lift to the uppermost position 
under the action of the spring 11, thereby providing a stand-by condition 
for permitting the supply of the sheet (condition shown in FIG. 16B). 
In this way, in the sheet supply apparatus of the type wherein the pick-up 
roller 3 is lowered and lifted by the locking and unlocking operations for 
the pick-up roller 3 and the sheets are lifted in accordance with the 
position of the pick-up roller 3, the sheets can be lifted up positively 
and swiftly when the sheet cassette 4 is mounted to the apparatus. 
Thereafter, as shown in FIG. 17, in response to a sheet supply start 
signal, the solenoid 14 is activated to rotate the pick-up cam 12, with 
the result that the lift-up lever 10 is rocked to lower the pick-up roller 
shaft 6. In this case, since the pick-up roller 3 is not lowered below a 
height of an uppermost surface of the sheet stack S, the movement of the 
pick-up lock lever 30 is regulated by the pick-up roller shaft 6, so that 
the pick-up lock lever 30 is not further rotated in the clockwise 
direction from the position shown in FIG. 17. Accordingly, when the 
lift-up lever 10 is in the lowered position, it is not locked by the 
pick-up lock lever 30, and, thus, the pick-up roller shaft 6 positioned at 
the lowered position is not fixed. 
That is to say, the pick-up roller 3 is abutted against the uppermost 
surface of the sheet stack S for a time duration determined by the 
configuration and angular velocity of the pick-up cam 12, and, thereafter, 
the pick-up roller 3 is separated from the sheet stack and is lifted. 
Meanwhile, the feed roller 1, retard roller 2 and pick-up roller 3 are 
rotated by the stepping motor (not shown), thereby separating and 
supplying the sheets S one by one from the sheet cassette 4. 
As the uppermost surface of the sheet stack is lowered due to the 
continuous supply of sheets, one end of the lifter trigger lever 24 is 
pushed upwardly by the pick-up roller shaft 6 to release the regulation of 
rotation of the lift-up cam 18. As a result, whenever the lift-up cam 18 
is rotated by one revolution, the sector ratchet gear 22 is rotated by an 
amount corresponding to one tooth, so that the sheet stack S is lifted by 
the lift portion 23a of the lift-up member 23. By repeating such 
movements, the height of the upper surface of the sheet stack is kept 
substantially constant. In this way, since the lift-up cam 18 is rotated 
only when the lifting of the sheet stack S is required, the lift-up cam 18 
and the lift arm pawl 19 are not slidingly contacted with each other 
excessively, thereby preventing the wear and noise. That is to say, if the 
lift-up cam 18 is always rotated and the lift-up pawl 19 is separated from 
the sector ratchet gear 22 in response to the lifting of the sheet stack 
S, the lift-up cam 18 is not frequently separated from the lift-up pawl 19 
adequately to maintain the contact between these elements, thereby wearing 
such elements or generating the undue noise. However, as is in the present 
invention, by rotating the lift-up cam 18 only when the lifting of the 
sheet stack is required, such a problem can be solved. 
Due to the above-mentioned series of operations, the pick-up roller 3 is 
abutted against the sheet stack S only when the sheet S is supplied from 
the sheet cassette 4. When the sheet is not supplied, the pick-up roller 3 
is separated from the sheet stack S, with the result that the double-feed 
of the sheets can be prevented effectively and positively by the feed 
roller 1 and the retard roller 2. 
Now, the stand-by condition (i.e. the setting of the height of the upper 
surface of the sheet stack before a first sheet is supplied and after the 
sheet cassette 4 is mounted to the sheet supply apparatus) will be 
explained. 
When the sheet cassette 4 is mounted, the sheet stack is firstly lifted by 
the lifter mechanism and the lift-up lever 10 is released by the pick-up 
lock lever 30, with the result that the pick-up roller 3 is shifted 
upwardly by the lift-up lever 10 via the pick-up roller shaft 6. During 
the upward shifting movement of the pick-up roller, the lifter trigger 
lever 24 is shifted to the position for regulating the rotation of the 
lift-up cam 18, thereby stopping the lifting movement of the sheet stack S 
effected by the lifter mechanism. That is to say, the position of the 
upper surface of the sheet stack is determined by the timing for releasing 
the lift-up lever 10 by means of the pick-up lock lever 30. As shown in 
FIG. 19, this releasing timing can be appropriately set by the 
configuration of the pick-up lock lever 30. In the stand-by condition, the 
height of the uppermost surface of the sheet stack is designated by 
P.sub.1. 
Then, as mentioned above, during the continuous supply of the sheets, when 
the height position of the uppermost surface of the sheet stack S reaches 
P.sub.2 as an amount of the sheets in the cassette is decreased, the 
lifter trigger lever 24 is shifted from the position for regulating the 
rotation of the lift-up cam 18, thereby releasing the regulation of 
rotation of the lift-up cam. As a result, the lift-up cam 18 is rotated to 
rock the lift arm pawl 19, thereby rotating the sector ratchet gear 22 in 
the anti-clockwise direction by the amount corresponding to one tooth of 
the ratchet to cause the lift-up member 23 to lift the sheet stack S. When 
a shifting amount of the sheet stack S corresponding to one tooth of the 
ratchet is .DELTA.p and the height of the uppermost surface of the shifted 
sheet stack is P.sub.3 (FIG. 20), it is ideal that the setting of the 
position of the uppermost surface of the sheet stack satisfies the 
following relation: 
EQU P.sub.2 &lt;P.sub.1 &lt;P.sub.3 (=P.sub.2 +.DELTA.P) 
Incidentally, practically, since the adequate advantage can be obtained 
even when P.sub.1 is substantially the same as P.sub.2 it was found, from 
the test, that the following relation may be satisfied: 
EQU (P.sub.2- 5 mm)&lt;P.sub.1 &lt;P.sub.3 +5 mm (=P.sub.2 +.DELTA.P+5 mm) 
By setting the height P.sub.1 of the uppermost surface of the sheet stack 
in the stand-by condition in this way, the optimum sheet supply can be 
achieved. 
Now, the case where such setting is not performed will be explained. For 
example, if (P.sub.2 -5 mm)&gt;P.sub.1, as shown in FIG. 21A, in the stand-by 
condition after the sheet cassette 4 is mounted, the position of the 
uppermost surface of the sheet stack becomes too low, with the result that 
the sheet fed out by the pick-up roller 3 is struck against the retard 
roller (separation means) 2, thereby causing the poor supply such as sheet 
jam. 
Further, if P.sub.1 &gt;(P.sub.3 +5 mm), as shown in FIG. 21B, the position of 
the uppermost surface of the sheet stack in the stand-by condition becomes 
too high, with the result that the sheet fed out by the pick-up roller is 
struck against the feed roller (separation means) 1, thereby causing the 
poor supply such as sheet jam. Accordingly, in order to avoid such 
problems, the optimum setting of the height of the uppermost surface of 
the sheet stack is required. 
When the sheet supplying operation is effected in the optimum condition set 
in this way, the double-feed of the sheets S can be prevented by the 
retard roller 2 to which a driving torque in a reverse direction is 
applied. However, the sheet which is not supplied due to the prevention of 
the double-feed is sometimes pinched between the feed roller 1 and the 
retard roller 2. In this condition, if the sheet cassette 4 is retracted 
from the sheet supply apparatus, the pinched sheet S will be broken. 
To avoid this, in the illustrated embodiment, by manipulating the grip 48 
of the sheet cassette 4, the ratch pawl 41 of the sheet cassette 4 is 
lowered, thereby lowering the connecting lever 32, with the result that, 
as shown in FIG. 3A, the retard roller 2 is separated from the feed roller 
1 via the release rod 37, thereby releasing the separation pressure. At 
the same time, as shown in FIG. 11A, the lift arm pawl 19 and the lift 
lock pawl 21 are separated from the sector ratchet gear 22, so that the 
lift-up member 23 is lowered to lower the upper surface of the sheet 
stack. As a result, the sheet cassette 4 can be retracted from the sheet 
supply apparatus. In this case, since the retard roller 2 is separated 
from the feed roller 1 to release the separation pressure, the pinched 
sheet is dropped into the sheet cassette 4 so that the sheet does not 
obstruct the retraction of the sheet cassette. 
Further, in the condition that the sheet cassette 4 is dismounted from the 
sheet supply apparatus, as shown in FIG. 3A, since the separation between 
the retard roller 2 and the feed roller 1 is maintained, even when the 
dismounted sheet cassette is left as it is for a long time, permanent 
deformation of the feed roller 1 and the retard roller 2 can be prevented. 
Next, the retraction of the sheet cassette 4 from the sheet supply 
apparatus which is effected, for example, when new sheets are to be 
replenished into the sheet cassette will be explained. When the sheet 
cassette 4 is retracted from the sheet supply apparatus, by manipulating 
the grip 48 of the sheet cassette 4, the ratch pawl 41 of the sheet 
cassette 4 is lowered, thereby lowering the connecting lever 32 to 
regulate the rotation of the lift-up cam 18. At the same time, the lift 
arm pawl 19 and the lift lock pawl 21 are separated from the sector 
ratchet gear 22, so that the lift-upper member 23 is lowered to lower the 
upper surface of the sheet stack. As a result, the sheet cassette 4 can be 
retracted from the sheet supply apparatus. 
During the sheet supplying operation, for example, if the power source of 
the sheet supply apparatus is erroneously turned OFF to stop the main 
motor 15, the pick-up cam 12 will be stopped while engaging by the drive 
gear 13. In such a case, the lift-up lever 10 may be stopped at the 
lowermost position in accordance with the phase of the pick-up cam 12. In 
this case, since the pick-up roller 2 is positioned at the lowermost 
position within the sheet cassette 4, it is very difficult to retract the 
sheet cassette 4 from the sheet supply apparatus. 
However, also in this case, as mentioned above, under the action of the 
lever member 40 for lifting and lowering the pick-up roller 2 in 
synchronous with the mounting and dismounting movements of the sheet 
cassette 4, when the sheet cassette 4 is slightly retracted, the pick-up 
roller 2 is lifted, thereby facilitating the retraction of the sheet 
cassette 4. 
In the illustrated embodiment, while the mounting of the sheet cassette 4 
was detected by the photo-sensor 31 and the solenoid was activated on the 
basis of the detection result to achieve the stand-by condition, the 
stand-by condition may be achieved by an arrangement shown in FIGS. 22A to 
22C. 
In such an arrangement, as shown in FIG. 22B, when the ratch pawl 41 of the 
sheet cassette 4 is engaged by the frame 7, the ratch pawl 41 is rotated 
to push the connecting lever 32 downwardly in FIG. 22B. In this case, by 
pulling the lift-up lever 10 downwardly in FIG. 22B by the engagement 
portion 32b of the connecting lever 32, the pick-up lever 10 is fixed by 
the pick-up lock lever 30. In this fixed condition, the lift arm pawl 19 
is rocked and the sector ratchet gear 22 is rotated in the anti-clockwise 
direction, with the result that the sheet stack in the sheet cassette is 
lifted by the lift-up member 23. The further operations are the same as 
those of the aforementioned embodiment. Incidentally, after the ratch pawl 
41 is fitted into the connecting lever 32, since the connecting lever 32 
is lifted, the upward and downward movements of the lift-up lever 10 are 
not obstructed by the engagement portion 32b (condition shown in FIG. 
22C). 
In this way, in the arrangement wherein the lift-up lever 10 is fixed by 
the lift-up lock lever 30 in synchronous with the mounting movement of the 
sheet cassette 4 without activating the solenoid 14, it is possible to 
achieve the stand-by condition without using the photo-sensor 31 for 
detecting the mounting of the sheet cassette 4 as shown in FIGS. 22A to 
22C. 
Next, an image forming apparatus having the above-mentioned sheet supply 
apparatus will be explained with reference to FIG. 23. Incidentally, in 
this embodiment, as an image forming apparatus, a laser beam printer will 
be described. 
A sheet cassette 4 is of front loading type which can be mounted to the 
laser beam printer 100 from a front side thereof, and sheets S stacked in 
the sheet cassette 4 are supplied along a direction perpendicular to a 
mounting direction of the sheet cassette 4. 
The sheet supplied from the sheet cassette 4 passes through an image 
forming portion 101 and a fixing portion 109 (described later) and then is 
discharged out of the printer. The image forming portion 101 includes a 
process cartridge 102 which is removable with respect to the printer 100, 
which process cartridge comprises an electrophotographic photosensitive 
drum (image bearing member) 103, a charge means 104 for charging a surface 
of the photosensitive drum 103, a developing means 105 for forming a toner 
image on the photosensitive drum 103, and a cleaning means 106 for 
removing the residual toner remaining on the surface of the photosensitive 
drum 103. The photosensitive drum 103 is exposed by image light emitted 
from a scanner portion 107 in response to an image signal. 
Further, the image forming portion also includes a transfer roller 108 for 
transferring the toner image formed on the surface of the photosensitive 
drum 103 onto the sheet. The transfer roller 108 serves to urge the sheet 
supplied from the sheet cassette 4 against the photosensitive drum 103. By 
applying voltage having polarity opposite to that of the toner image to 
the transfer roller 108, the toner image formed on the surface of the 
photosensitive drum 103 onto the sheet. 
The sheet to which the toner image was transferred by the transfer roller 
108 is sent to the fixing portion 109 which includes a fixing roller 110 
for applying heat and pressure to the sheet to fix the toner image onto 
the sheet. In this way, the toner image is transferred onto the sheet 
supplied from the sheet cassette 4 by means of the process cartridge 102 
and the transfer roller 108, and the toner image is then fixed to the 
sheet by the fixing portion 109, and then the sheet is discharged out of 
the printer. 
Incidentally, the present invention is not limited to the aforementioned 
embodiment. For example, in the illustrated embodiment, while the other 
end of the release rod 37 was supported by the frame 7, it may be directly 
supported by the support member 50. Further, when the lock member 34 is 
released by the sheet cassette 4, the support member 50 may be directly 
pushed donwardly by the connecting lever 32 without through the release 
rod 37, thereby releasing the separation pressure. In this case, the 
number of parts can be reduced to make the apparatus inexpensive. Further, 
while the release rod 37 was formed from the metal wire, the release rod 
may be made of other material. 
Further, in the illustrated embodiment, while an example that the retard 
roller is used as the separation means was explained, any friction 
separation means (for example, a friction pad) abutted against the feed 
roller to separate the sheets between the feed roller and the separation 
means may be used. 
As fully described above, since the urging contact between the friction 
separation means and the sheet supply means is released in synchronous 
with the mounting and dismounting movements of the sheet supporting means 
and the released condition is maintained by the lock means, any adjustment 
by means of two springs as in the conventional case is not required, 
thereby simplifying the construction of the apparatus, improving the 
assembling feature and making the apparatus inexpensive. Further, since 
the sheet cassette may be mounted in opposition to the urging force 
between the friction separation means and the sheet supply means, the 
excessive operating force is not required, thereby improving the 
operability. 
Further, by combining the above arrangement with the lifter mechanism for 
lifting the sheet supporting means to the predetermined position, the 
urging contact between the friction separation means and the sheet supply 
means, and the lifting movement of the lifter mechanism can be effected 
simultaneously in synchronous with the mounting and dismounting operations 
of the sheet supporting means, thereby simplifying the apparatus to make 
the apparatus compact and to reduce the cost, and improving the 
operability. 
FIGS. 24 and 25 shows a laser beam printer according to another embodiment 
of the present invention having the sheet supply apparatus of the present 
invention. Now, this laser beam printer will be explained. 
As shown in FIG. 24, cassettes 201a, 201b containing the sheets S1 and S2, 
respectively, are arranged in an overlapped relation along a vertical 
direction at a lower portion of the printer, and sheet supply portions 
203a, 203b are provided in association with the cassettes 201a, 201b. 
The sheet supply portions 203a, 203b are the same as that described above 
and comprise pick-up rollers 203a, 203b abutted against the upper surface 
s of the sheet stacks S1, S2 contained in the cassettes 201a, 201b to feed 
out the sheets, and feed rollers 204a, 204b and retard rollers 205a, 205b 
(pairs of separation rollers) for separating the sheets S1, S2 fed out by 
the pick-up rollers 203a, 203b one by one. 
The sheet S1 supplied from the cassette 201a by the sheet supply portion 
203a is conveyed along a convey path 210, and the sheet S2 supplied from 
the cassette 201b by the sheet supply portion 203b is conveyed along a 
convey path 211. The convey paths 210, 211 are joined to each other on the 
way so that the sheets S1, S2 conveyed through the convey paths 210, 211 
are fed through a common convey path 212 after the sheets pass through the 
junction. A pair of convey rollers 208a, 208b for sending the sheets S1, 
S2 supplied from the cassettes 201a, 201b to the image forming portion 101 
are arranged in the common convey path 212. 
The lower cassette 201b and the sheet supply portion 203b are offset toward 
a downstream side (right in FIG. 24) of the upper cassette 201a and the 
sheet supply portion 203a in a sheet conveying direction by a 
predetermined amount so that a distance D1 from the upper sheet supply 
portion 203a to the junction between the convey paths 210, 211 is 
substantially equal to a distance D2 from the lower sheet supply portion 
203b to the junction. 
As shown in FIG. 25, the cassettes 201a, 201b are arranged in such a manner 
that they can be mounted to and dismounted from the printer along a 
direction perpendicular to the sheet conveying direction, so that an 
operator can replenish new sheets at a front side (operating side) of the 
printer (front loading type). 
Outer profiles of the cassettes 201a, 201b (configurations shown by the 
broken lines P in FIG. 24) looked at from the front side of the printer 
are the same as each other, and these cassettes are aligned with each 
other in a vertical direction. Further, since size indication portions 
216a, 216b for indicating the sizes of the sheets S1, S2 contained in the 
cassettes 201a, 201b, remaining amount indication portions 217a, 217b for 
indicating remaining amounts of the sheets S1, S2, and grip portions 48a, 
48b gripped by the operator when the cassettes 201a, 201b are to be 
retracted are aligned with each other, respectively, in the vertical 
direction, when the cassettes 201a, 201b are mounted to the printer, the 
outer configurations of the cassettes 201a, 201b are not offset from each 
other in a left-and-right direction, thereby providing good appearance. 
In the illustrated embodiment, since the lower cassettes 201b and the lower 
sheet supply portion 203b are offset toward the downstream side of the 
upper cassettes 201a and the upper sheet supply portion 203a in the sheet 
conveying direction so that the distance between the upper sheet supply 
portion and the junction becomes equal to the distance between the lower 
sheet supply portion and the junction, a convey distance from the upper 
sheet supply portion to the image forming portion 101 becomes 
substantially the same as a convey distance from the lower sheet supply 
portion to the image forming portion, thereby eliminating or minimizing 
the difference in convey speed. 
Thus, the optimum supply and separation condition regarding the upper sheet 
supply portion 203a can be substantially equal to that regarding the lower 
sheet supply portion 203b, thereby permitting the use of common parts. 
That is to say, the most important supply and separation conditions for 
the automatic sheet supply apparatus including biasing pressures and 
reverse torque values of the retard rollers 205a, 205b, materials forming 
the rollers and the like can be equalized regarding the upper and lower 
sheet supply portions, and important parts satisfying the supply and 
separation condition, for example, parts such as pick-up rollers 203a, 
203b, feed rollers 204a, 204b and retard rollers 205a, 205b used for 
supply and separation of the sheets can be identical. 
Further, by do so, since the endurances of the parts are equalized 
regarding the upper and lower sheet supply portions, service lives of the 
parts are also equalized regarding the upper and lower sheet supply 
portions. In the past, in order to avoid the confusion or trouble in the 
market, the exchange of parts was effected on the basis of the part having 
shorter service life. In the illustrated embodiment, however, such waste 
can be avoided. 
Incidentally, so long as the supply and separation conditions are equalized 
regarding the upper and lower sheet supply portions 203a, 203b by 
constituting these portions by the identical parts, the convey distance 
between the upper sheet supply portion and the image forming portion may 
be differentiated from the convey distance between the lower sheet supply 
portion and the image forming portion. Further, since the optimum supply 
and separation conditions for the upper and lower sheet supply portions 
203a, 203b have any plays to some extent, even if the convey distances are 
differentiated from each other more or less, the conveying speed of the 
sheet supply portions may be changed accordingly to equalize the sheet 
conveying times from the upper and lower cassettes 201a, 201b. 
Next, other embodiments regarding an image forming apparatus will be 
explained with reference to the accompanying drawings. 
In the case where each sheet supply portion is arranged in the proximity of 
the front end of the associated cassette and the cassettes are overlapped 
in the vertical direction, since the lower sheet supply portion must be 
arranged below the upper cassettes in a spaced relation, the entire height 
of the automatic sheet supply apparatus is increased. 
To avoid this, in an embodiment shown in FIG. 26, the lower cassette 201b 
is offset toward the downstream side of the upper cassette 201a in the 
sheet conveying direction so that the upper cassette 201a and the lower 
sheet supply portion 203b are arranged side by side in a horizontal 
direction. With this arrangement, the upper cassette 201a can be disposed 
adjacent to the lower cassette 201b in the vertical direction. 
Incidentally, as is in the aforementioned embodiment, also in this 
embodiment, the outer profiles of the cassettes 201a, 201b looked at from 
the front side of the printer are the same as each other. 
With this arrangement, not only the entire height of the automatic sheet 
supply apparatus can be greatly reduced, but also the useless space can be 
eliminated, thereby making the printer compact. In this way, since the 
cassettes 201a, 201b can be overlapped regardless of the height of the 
sheet supply portion 203b, it is possible to provide an automatic sheet 
supply apparatus wherein various kinds of sheets can be contained without 
increasing the total height of the printer and while making the apparatus 
compact. 
In an embodiment shown in FIG. 27, a sheet stacking or containing amount is 
increased without increasing the height of the automatic sheet supply 
apparatus. That is to say, as is in the embodiment shown in FIG. 24, when 
the lower cassette 201b and the lower sheet supply portion 203b are offset 
toward the downstream side of the upper cassette 201a and the upper sheet 
supply portion 203a in the sheet conveying direction, a space between the 
upper and lower cassettes 201a, 201b is increased. In this embodiment, an 
upper cassette 201a is enlarged to fill such a space, thereby increasing 
the sheet containing ability of the upper cassette 201a'. 
In this way, by utilizing the space created by offsetting the lower 
cassette 201b and the lower sheet supply portion 203b toward the 
downstream side of the sheet conveying direction, the sheet containing 
ability can be increased without increasing the height of the automatic 
sheet supply apparatus. 
Also in this embodiment, the outer profiles of the cassettes 201a', 201b 
are aligned with each other in the vertical direction. In the 
above-mentioned embodiments, while examples that the sheet supply 
apparatus has two cassettes 201a, 201b were explained, the present 
invention is not limited to these examples. For example, as shown in FIG. 
28, three cassettes 201a, 201b, 201c overlapped with each other in a 
vertical direction may be used. As shown in FIG. 28, an upper cassette 
201a is arranged at a most upstream side of a sheet conveying direction, 
and a lower cassette 201b is arranged at a most downstream side of the 
sheet conveying direction with the interposition of an intermediate 
cassette 201c between the upper and lower cassettes. 
When three cassettes 201a, 201b, 201c are used in this way, convey 
distances from the sheet supply portions 203a, 203b, 203c to the image 
forming portion 101 can also be equalized to each other, and the optimum 
supply and separation conditions for the sheet supply portions 203a, 203b, 
203c can also be equalized to each other so that common parts can be used 
in the sheet supply portions. Further, the cassettes 201a, 201b, 201c and 
the sheet supply portions 203a, 203b, 203c can be offset in the 
left-and-right direction to reduce the height of the sheet supply 
apparatus, thereby making the apparatus compact. 
Next, in an embodiment shown in FIG. 29, a plurality of modules each having 
an upper cassette 201a and a lower cassette 201b are adopted to an 
automatic sheet supply apparatus. 
In this embodiment, each module includes two upper and lower cassettes 
201a, 201b in which the lower cassette 201b and associated lower sheet 
supply portion 203b are offset toward a downstream side of a sheet 
conveying direction, and a plurality (two in the illustrated embodiment) 
of such modules A, B are overlapped in a vertical direction. The upper and 
lower sheet supply portions 203a, 203b in each module have the same convey 
and separation conditions, as is in the aforementioned embodiment, and the 
supply and separation conditions of the modules A, B are same as each 
other. 
The sheet supplied from the module B is conveyed toward the image forming 
portion 101 by a pair of convey rollers 209a, 209b which are disposed in 
the convey path and which can adjust a sheet conveying speed. The sheet 
conveying speed provided by the pair of convey rollers 209a, 209b is 
selected to be greater than sheet feeding speeds provided by the sheet 
supply portions 203a, 203b so that the sheet supplied from the module B is 
pulled toward the downstream side at a high speed. Now, even when the 
sheet feeding speeds provided by the sheet supply portions 203a, 203b are 
differentiated from the sheet conveying speed provided by the pair of 
convey rollers 209a, 209b, since such difference in speed occurs after the 
sheet is separated and supplied at the sheet supply portion 203a or 203b, 
such difference does not affect a bad influence upon the supply and 
separation of the sheet. 
In this way, by increasing the sheet conveying speed provided by the pair 
of convey rollers 209a, 209b, a time duration during which the sheet from 
the module A reaches the image forming portion 101 can be equalized to a 
time duration during which the sheet from the module B reaches the image 
forming portion 101. Further, since the sheet conveying speed provided by 
the pair of convey rollers 209a, 209b can be adjusted, by switching the 
sheet conveying speed in such a manner that the sheet conveying speed 
becomes the same as the sheet feeding speed provided by the sheet supply 
portion 203a or 203b when the sheet reaches the image forming portion 101, 
the sheet feeding speeds from the modules A, B can be equalized to each 
other at the image forming portion 101. 
With this arrangement, the supply and separation conditions of the sheet 
supply portions 203a, 203b can be equalized and optimized, and, since the 
sheet conveying times (to the image forming portion 101) can be equalized 
by changing the sheet conveying speed even if the conveying distances are 
differentiated, the stable supply and separation can be achieved. Further, 
even when the plurality of cassettes are overlapped in the vertical 
direction, the height of the apparatus can be reduced. 
In the embodiment shown in FIG. 29, while an example that two modules A, B 
are used were explained, it should be noted that three or more modules can 
be used. 
Incidentally, in the above-mentioned embodiments, outer profiles of the 
upper and lower cassettes 201a, 201b looked at from the front side of the 
image forming apparatus are identical, and sheet size indication portions 
for indicating sizes of sheets contained in the cassettes, sheet remaining 
amount indication portions for indicating remaining amounts of sheets 
contained in the cassettes and grip portions for retracting the cassettes 
are provided on the respective cassettes in such a manner that such 
portions are aligned with each other in a vertical direction.