This invention relates to a sheet feeding apparatus (sheet feeder)
used -for an image-forming apparatus such as a copier or a laser beam printer.
More particularly, the invention concerns a sheet feeder which can feed thick
sheets such as envelopes one by one.
US-A-1,919,238 discloses a sheet feeder, which feeds sheets with
the lowermost sheet in a sheet stack in contact with a feed roller.
US-A-3,963,339 discloses a sheet feeder, which feeds sheets with
the lowermost sheet of a sheet stack in contact with a conveyor belt, and in which
the sheet stack is urged against the conveyor belt by a lever.
Further, it is conceivable to put a weight on the sheet stack so
as to increase the sheet-feeding force in case where the lowermost sheet of sheet
stack is fed by the feed roller.
However, since such weight in such sheet feeder has a constant weight,
when a large number of sheets are stacked, the urging force is absorbed by an air
cushioning effect between adjacent sheets, the effect being pronounced particularly
between adjacent envelopes to be fed. In this case, the urging force is not sufficiently
transmitted to the lowermost sheet, and defective sheet-feeding is liable to result
from insufficient sheet-feeding force. Further, when sheets in the stack are reduced,
double feeding is liable due to excessive urging force.
According to the document US-A-4 458 890, there is disclosed a generic
sheet feeding apparatus, the construction of which shows an elongated arm with
a pressing roller being rotatably supported in the middle thereof, with one end
of said elongated arm being journaled by a shaft and the other end of said elongated
arm being provided with a spring biasing this end against a stopper. Thus, in
the case of this construction, the size of the urging means in the sheet feeding
direction is extended, and since the arm is disposed outside of the side plate,
the size of the urging means in the direction of the sheet width is also extended,
so that the known urging means becomes bulky, which causes various restrictions
as regards the arrangement of the urging means.
The present invention is intended in the light of the above, and
its object is to prevent the drawbacks inherent in the prior art.
This object is achieved by means of the features defined in the characterizing
portion of claim 1. According to these features, the first urging member includes
an outer weight and the second urging member includes an inner weight contained
in the outer weight.
In this sheet feeder, the urging means is constituted by a plurality
of urging members, these urging members being coupled to one another such that
they can be displaced vertically by a predetermined distance. The number of urging
members riding on the sheet stack is changed according to the number of sheets
stacked on supporting means, thus changing the urging force of the urging means
at least in two stages.
With the above construction, the sheets stacked on the supporting
means are urged against the feeding means by the urging means to be fed out by
the feeding means one by one from the lowermost one. The urging means changes
its urging force at least in two stages by changing the number of urging members
riding on the sheet stack according to the number of sheets stacked on the supporting
When the urging force applied to the sheet stack is reduced stepwise
as above, when the number of remaining sheets in the stack becomes very small,
the urging force may be excessive, possibly resulting in double or simultaneuous
feeding of sheets.
Accordingly, according to the invention there is also provided urging
means for a sheet feeder, which can provide continuously reducing urging force
to the sheet stack on stack support when the stacked sheets are reduced to a certain
According to the invention, there is further provided a sheet feeder,
which comprises feeding means for feeding out stacked sheets one by one from the
lowermost one, and urging means for urging the feeding means and urging the stacked
sheets thereagainst, the urging means including a plurality of urging elements
consisting of a second urging member comprising auxiliary urging elements which
cease to provide urging action according to reduction of stacked sheets and a
first urging member comprising main urging elements which provide continual urging
action, the number of operative urging elements being thereby reduced stepwise
according to the reduction of stacked sheets, a biasing member being provided
between an auxiliary urging element and a main urging element for continuously
reducing the urging force of the main urging elements.
With this construction, the stacked sheets are urged against the
feeding means by the urging means and are fed out one by one from the lowermost
one. When there are a large number of stacked sheets, the sheets are urged by both
the auxiliary and main urging elements of the urging means. When the stacked sheets
are reduced to a predetermined number of sheets, the auxiliary urging elements
cease to provide urging action, and only the main urging elements continually
provide urging action. The main urging elements are biased by biasing means such
as to continuously reducing urging force with reduction of stacked sheets, thus
preventing double feeding of sheets.
Preferable embodiments of the invention are defined in the claims
2 to 6.
In the following the invention is further illustrated by an embodiment
of a sheet feeding apparatus with reference to the enclosed figures.
- Fig. 1 is a sectional view showing an embodiment of the invention;
- Fig. 2 is a plan view showing the same embodiment;
- Fig. 3 is a sectional view showing a driving system of the same embodiment;
- Fig. 4 is a sectional view showing an image forming apparatus;
- Figs. 5 and 6 are views for explaining a sheet-feeding operation;
- Figs. 7 to 10 are views for explaining the function of weight;
- Fig. 11 is an exploded perspective view showing a weight construction;
- Fig. 12 is a graph showing a weight characteristic;
- Figs. 13 to 19 are views for explaining different examples of weight;
- Figs. 20 to 24 are views for explaining a friction member provided on weight;
- Fig. 25 is a sectional view illustrating the relation between weight and detecting
Now, an embodiment of the sheet feeding apparatus will be described
with reference to the accompanying drawings.
Fig. 1 is a sectional view best illustrating the features of the
embodiment, Fig. 2 is a plan view showing the embodiment, and Fig. 3 is a side
view showing a driving system of the embodiment.
Referring to these Figures, there is shown a sheet feeding apparatus
or sheet feeder which is generally designated by reference numeral 1. Sheet feeder
1 has a pair of positioning members 10 provided at its front end (i.e., left end
in Fig. 1). It can be mounted in or dismounted from laser beam printer 2 serving
as image forming means by inserting or removing the positioning members 10 into
or out of holes 10b provided in an upper portion of housing 3 of the printer 2.
Beneath the sheet feeder 1, the cassette 11 can be mounted in and dismounted from
the laser beam printer 2. Ordinary sheets are stacked in the cassette 11. A wall
of the laser beam printer 2 above the cassette 11 has a manual feed opening 3a,
through which a sheet can be fed manually.
A housing 13 of the sheet feeder 1 has stack support 15 serving as
supporting means for stacking sheets S thereon. The stack support 15 has restricting
members 16a and 16b for restricting the stacked sheets S against movement in the
width directions. The restricting members 16a and 16b, have respective slidable
racks 17 and 19 extending in the width direction of the stack support 15. The
racks 17 and 19 are in mesh with pinion 20 rotatably mounted on the back surface
of the stack support 15. Thus, the racks 17 and 19 with the respective integral
restricting members 16a and 16b are movable in the width directions in an interlocked
relation to each other.
A detecting lever 21 is pivotally mounted by pin 22 on the stack
support 15 for detecting the presence or absence of sheets S. A lower end portion
of the lever 21 can be advanced into and retreated from an on-off operated photointerpreter
23 provided on the back surface of the stack support 15. When the stack support
15 gets out of sheet S, an upper end portion of the detecting lever 21 is turned
upwardly with respect to the stack support 15, thus indicating the absence of sheet
After the photointerpreter 23 in the sheet-feeding direction, feed
roller 25 serving as feeding means is rotatably mounted for feeding sheets stacked
on the stack support 15 one by one from the lowermost one. Above the feed roller
25, a weight 26 serving as urging means is provided for vertical displacement with
its opposite end ears 79b (see Fig. 2) loosely received in pair guide grooves
27 (see Fig. 2) provided in the housing 13. The weight 26 serves to urge sheets
S against the feed roller 25 in a manner as described later. Sheets S are envelopes
or like thick sheets.
Support member 29 (see Fig. 1) secured in position after the weight
26 in the sheet-feeding direction supports an end-restricting member 30 for restricting
and aligning the front ends of sheets S stacked on the stack support 15. The lower
end of the end-restricting member 30 is spaced apart from the front end of the
stack support 15 by a predetermined distance to permit feeding of sheets S through
this space. Separating pad support 31 secured to a lower portion of the support
member 29 is provided with separating plate (separating pad) 32 serving as separating
means made of rubber or like highly frictional material. The separating pad 15
has a suitable inclination angle with respect to the sheet-feeding direction,
in which each sheet S is fed out from the stack support 15. An elastic member 33
having flexibility is secured in position such that it faces the separating pad
32 for urging sheets S fed out from the feed roller 25 against the separating pad
32 and thus preventing double feeding of sheets S.
Pair transport guides 35 and 36 for guiding sheet S and transport
roller 37 are disposed after the separating pad 32 in the sheet-feeding direction.
A pinch roller 39 biased by a spring (not shown) is urged against the transport
roller 37. A bracket 40 secured in position above the transport guides 35 and 36
has microswitch 41 secured to it.
To bracket 40 is also pivoted by set screw 43 detecting lever 42
for detecting the set state of sheet feeder 1 with respect to laser beam printer
2. Detecting lever 42 is biased in the counterclockwise direction in Fig. 1 by
torsion spring 45 having the opposite ends secured to bracket 40 and detecting
lever 42, respectively. When setting sheet feeder 1 in position, detecting lever
42 is urged by housing 3 and rotated in the clockwise direction in Fig. 1. As
a result, projection 42a of detecting lever 42 urges an operating lever of microswitch
41 and turns on the same, thus detecting the setting of sheet feeder 1.
Now, a driving system of the sheet feeder having the above construction
will be described with reference to Figs. 2 and 3.
Referring to the Figures, sheet feeder 1 has a pair of side plates
46 and 47, which are formed with guide grooves 27 noted above for guiding weight
26. Board 49 is secured by a plurality of supports to the outer surface of side
plate 46. It undertakes control of drive motor 50 secured to its inner surface
and also transfer of signals between laser beam printer 20 and sheet feeder 1.
To other side plate 47 is connected one end of cable 51, which connects sheet feeder
1 and laser beam printer 2 to each other.
Solenoid 53 for spring clutch control to be described later is secured
to bracket 52 which is in turn secured to side plate 46. Bracket 52 also serves
as a grounding member to ground metal bearing 56 supporting transport roller 37
As shown in Fig. 3, relay gear 59 integral with relay gear 49a is
rotatably supported by shaft 60 in support 57, which is secured in position at
a suitable spacing from side plate 46. Relay gear 59 is in mesh with gear 61 secured
to output shaft 50a of drive motor 50. Relay gears 62 and 63 meshing with relay
gear 59 are supported by shaft 64 in support 57, and also relay gear 65 meshing
with relay gear 59a is supported by shaft 66 in support 57. Support 57 is electrically
connected via shaft 64 to bracket 52. Thus by grounding bracket 52 shaft 25a of
feed roller 25 and shaft 37a of transport roller 37 are also grounded.
Relay gear 62 meshing with relay gear 59 is coupled to gear 63 via
clutch unit 55 having a well-known spring clutch. Clutch unit 55 is on-off operated
to on-off control drive power transmission of gears 62 and 63 under on-off control
of solenoid 53.
Lever 53a for locking clutch unit 55 is pivoted to bracket 52. It
is coupled at one end to spring 53b, which is provided on bracket 52, and thus
it is spring-biased in the clockwise direction. Solenoid 53 serves to attract
and release lever 53a. Gear 63 is in mesh with gear 67 secured to shaft 25a of
feed roller 25 (see Fig. 1). Relay gear 65 is in mesh with gear 69 mounted on
shaft 37a of feed roller 37. A one-way clutch (not shown) is provided between shaft
37a and gear 69. When gear 69 is rotated in the counterclockwise direction in
Fig. 3, shaft 37a is rotated in the same direction, while it idles when gear 69
is rotated in the clockwise direction.
Torsion spring 71 is mounted on dowel 70 secured to side plate 46
and has its opposite ends attached to shaft 39a of pinch roller 39 and shaft 66,
respectively. Pinch roller 39 is urged against transport roller 37 by the spring
force of torsion spring 71. In Fig. 2, reference numeral 72 designates a connection
member for electrically connecting transport roller 37 via metal bearing 73 supporting
roller 37. Connecting member 72 has a stem portion secured to side plate 46 and
its free end bolted to shaft 66, and it also serves as cover of gear 69.
In the above construction, when drive motor 50 is operated by a sheet-feeding
signal from housing 3 of printer 2, transport roller 37 starts rotation via the
gear train noted above. When predetermined period T1 of time has been passed from
the instant of generation of the sheet-feeding signal, solenoid 53 is turned on
to cause rotation of feed roller 25, thus causing start of feeding of sheets S
such as envelopes.
After the lapse of predetermined period T2 of time, solenoid 53 is
turned off to cut drive power transmission to feed roller 25. At this time, the
leading end of sheet S being fed has reached guide while the trailing end of the
sheet is on feed roller 25. Thus, the sheet is fed by the guide while feed roller
25 is rotated by the action of the one-way clutch. Sheet S fed out from Sheet
feeder 1 is fed by feed roller 75 in laser beam printer 2 as shown in Fig. 4 into
housing 3. Sheet S fed manually through manual feed opening 3a of laser beam printer
2 is detected by paper sensor 76 shown in Fig. 4 to be fed by feed roller 75 into
housing 3 of laser beam printer 2 for printing and then discharging.
Laser beam printer 2, as shown in Fig. 4 has feed roller 75 for feeding
out sheets S accommodated in cassette 11 and separating pad 180, which is urged
by a spring (not shown) against feed roller 75 for blocking second and subsequent
sheets S to separate the first fed sheet. Reference numerals 181 and 182 designate
transport guides. The leading end of a sheet fed out from the stationary state
is brought into contact with a nip of pair registration rollers 183 for skew feeding
before being fed with a timing synchronized to an image formed on photosensitive
drum 185 to be described later.
Reference numeral 110 designates an image-forming unit, 185 a photosensitive
drum, 186 a scanner for scanning photosensitive drum 185 with a laser beam for
forming a latent image, 187 a developing unit for developing the latent image
on the photosensitive drum to a tonor image, and 188 a transfer roller for transferring
the tonor image formed on photosensitive drum 185 onto sheet. Reference numeral
190 designates a fixing unit for fixing the transferred tonor image on the sheet,
and 191 a tray for stacking sheets discharged after the fixing operation. Reference
numeral 184 designates a guide for guiding sheet from registration roller pair
183 to photosensitive drum 185, and 189 a torque conveyor for transporting the
sheet from photo-sensitive drum 185 to fixing roller 190.
The operation of separating and feeding out each sheet will now be
described with reference to Figs. 5 and 6.
Sheets S stacked on stack support 15 with their leading ends aligned
in contact with end-restricting member 30 are fed out one by one from the lowermost
one Sa with an urging force provided by weight 26 and rotation of feed roller
25 in the direction of arrow. At this time, subsequent sheets Sb, Sc, ... come
out with sheet Sa due to frictional force between adjacent sheets. However, since
their leading ends are urgedly retained by separating pad 32, which has a high
coefficient of friction. Consequently, only sheet Sa which directly receives the
feeding force of feed roller 25 is advanced by surpassing the frictional resistance
offered by separating pad 32, and it thus fed out by clearing end 32a of separating
Elastic member 33 is a thin sheet having flexibility, with its stem
portion secured to support 77. When sheet Sa is fed to elastic member 33, the
free end thereof is flexed toward the sheet-feeding direction, and the reaction
force at this time has an effect of raising sheets Sa, Sb, Sc, ... toward upper
separating pad 32, thus helping the separation of the sheet. After the clearing
free end 32a of the separating pad 32, serving as separating means, sheet Sa is
transported by being guided by transport guides 35 and 36 to enter between transport
roller 37 and pinch roller 39. The sequence of operations described above takes
place for succeeding sheets Sb, Sc, ... for separation thereof.
Weight 26 will now be described in detail with reference to Figs.
7 to 11.
Figs. 7 and 9 show, in a section taken along line B-B in Fig. 1,
a state when there is no sheet on stack support 15 and a state when there are at
least a certain number of sheets on the support, respectively. Figs. 8 and 10
are sectional views corresponding to Figs. 7 and 9, respectively.
Referring to these Figures, weight 26 includes outer weight 79 and
inner weight 81. Outer weight 79 has a channel-like sectional profile open upwardly.
Inner weight 81 is accommodated in outer weight 79 and has a channel-like sectional
profile open downwardly. A plurality of (i.e., two in Fig. 8) auxiliary weights
82 are accommodated in and secured by bolts 82a to inner weight 81. These auxiliary
weights 82 are provided for controlling the weight of inner weight 81. Weight cover
83 is fitted on outer weight 79 to permit weight 26 to be held with a hand of
The outer surface of weight cover 83 is formed with grooves 83a.
Pair pins 85, which penetrate weight cover 83 and outer weight 79 and are retained
against detachment by E-rings 85a, also penetrate vertically elongate slots 80a
and 80b formed in inner weight 81 and auxiliary weights 82. With this arrangement,
inner weight 81 is capable of being displaced vertically with respect to outer
weight 79 by the distance, by which pins 85 can be displaced along slots 80a and
80b. Inner weight 81 has opposite end projections 81a and 81b, and stopper means
or stoppers 46a and 47a formed as shoulders in side plates 46 and 47 of housing
13 are found below and face respective projections 81a and 81b. Grounding spring
86 has one end connected to outer weight 79 for grounding the same. Its other
end is secured to a grounding plate (not shown). Outer weight 79 has projections
79b received in guide grooves 27 on the printer side. Friction member 79c is applied
to the outer surface of a bottom portion to vertical front side portion in the
sheet-feeding direction of outer weight 79. It is made of a material having substantially
the same coefficient of friction as that of sheet. Further, buffering members
79d are applied to opposite end portions of the inner surface of the bottom portion
of outer weight 79.
When a certain number of sheets S are stacked on stack support 15,
as shown in Figs. 9 and 10, projections 81a and 81b are found above stoppers 46a
and 47a. In this state, inner weight 81 is supported by bottom portion 79a of
outer weight 79. Thus, the total weight of weight 26 mainly comprising outer weight
79, inner weight 81 and weight cover 83 is acting as urging force on sheets S.
As the number of sheets S on stack support 15 is reduced due to one-by-one feeding,
weight 26 is progressively lowered, and eventually projections 81a and 81b of inner
weight 81 come to engage with stoppers 46a and 46b.
As the number of stacked sheets S is further reduced, inner weight
81 is separated from bottom 79a of outer weight 26, and only the weight the other
part of weight 26 than inner weight 81 and auxiliary weights 82 is applied to
sheets S. This operation is graphically shown as in Fig. 12. As is shown, the urging
force is constant from the instant when there is a full stack of sheets S until
projections 81a and 81b engage with stoppers 46a and 47a. This operation is represented
by a plot segment from point a to point b. When projections 81a and 81b
come to engagement with stoppers 46a and 47a, the urging force is reduced from
point b to point c. Subsequently, the urging force is fixed until the number of
stacked sheets becomes zero as represented by a plot segment from point c to point
The urging force is varied step-wise as shown above because the optimum
urging force applied to sheets S is high when there are many stacked sheets S and
low when there are a small number of sheets S. Thus, when there are many sheets
stacked on the sheet-stacking means, a sufficient urging force can be ensured to
provide a stable sheet-feeding force. Also, when the number of stacked sheets
is reduced, excessive urging force is prevented to prevent double feeding. If the
urging force applied to the stack of sheets S is inadequate, defective feeding
or double feeding is liable.
In the above embodiment the urging force applied to the stack of
sheets S is varied stepwise. However, the urging force is still too high when remaining
stacked sheets S are reduced to a very small number, and therefore double feeding
of sheets S is liable.
In the following, an embodiment which can solve the above problem
will be described. Parts like those in the preceding embodiment are designated
by like reference numerals and symbols while omitting their description.
Figs. 13 and 14 show weight (or urging means) 5 when there is no
sheet S on stack support 15, while Figs. 15 and 16 show the weight when there is
a stack of sheets S.
Referring to Figs. 13 to 17, biasing member 7 consisting of a leaf
spring having channel-shaped stem 7a is provided between weight cover 83 and inner
weight 6, with a folded upper portion of stem 7a urged against the back or inner
surface of weight cover 83. Biasing member 7 has a pair of opposite side projections
7b and 7c projecting from its portion facing the folded portion. Stem 7a of biasing
member 7 is supported with projections 7b and 7c urgedly held in notches 9b formed
in upper portions of the inner surface of the side portions of outer weight 9.
Biasing member 7 has arcuately curved feed end 7d, which urges a central portion
of the inner surface of the top of inner weight 6.
When more than a certain number of sheets S are stacked on stack
support 15 as shown in Fig. 15, projections 6a and 6b at the opposite ends of inner
weight 6 are found above stoppers 46a and 47a. In this state, inner weight 6 is
supported by bottom portion 9a of outer weight 9. In this state, any urging force
applied to inner weight 6 by biasing member 7 does not become a force urging sheets
Thus, in this state, like weight 26 shown in Figs. 9 and 10, the
weight of the total components of weight 5 including outer weight 9, inner weight
6 and weight cover 83 is being applied as urging force to sheets S. When the number
of sheets S on stack support 15 is reduced after the engagement of projections
6a and 6b of inner weight 6 with stoppers 46a and 47a, inner weight 6 is separated
from bottom portion 9a of outer weight 9. This time, the distance h between the
top of inner weight 6 and top of weight cover 83 is reduced progressively to cause
progressive increase of the flexing of biasing member 7.
As a result, a weight is applied to sheets S, which is the weight
of weight 5 minus the sum of the weights of inner weight 6 and auxiliary weights
82 and an acting force provided by the elasticity of biasing member 7. Since distance
h is reduced with reducing number of stacked sheets S, the urging force of weight
5 applied to sheets S is reduced progressively as shown in Fig. 12. More specifically,
the urging force of weight 5 is changed in the order of points a, b, c and
d in Fig. 12, and the urging force when there is no stacked sheet is less than
that in the prior art case.
In the above embodiment, the point of action of biasing member 7
on inner weight 6 is set to be substantially the center of the top of inner weight
6 in order to permit automatic adjustment of urging forces on the opposite sides
of the point of action lest the opposite side urging forces should be different
in case of envelopes having different opposite side swelling portions as sheets
Inner weight 5, outer weight 9 and biasing member 7 are made of an
electrically conductive material and are held in contact with one another. By so
doing, weight 5 can be perfectly grounded.
Figs. 18 and 19 show a different example of urging means according
to the invention.
Referring to the Figures, biasing member 7 provided between weight
cover 83 and inner weight 6 of weight 5 is a compression coil spring, and the other
structure is the same as that of weight 5 shown in Figs. 13 and 14. With this
example of weight 5, the same function and results as with weight 5 shown in Fig.
13 can be obtained when urging sheets S. While urging member 7 in this example
and also that in the previous example of Fig. 13 are provided between weight cover
83 and inner weight 6, since weight cover 83 is made integral with outer weight
9 via pins 85, biasing member 7 equivalently intervenes between outer weight 9
and inner weight 6.
While in each of the above examples the action of weight 5 is changes
stepwise in two stages, it is also possible to permit reduction of the urging force
of weight 5 in three stages.
Further, while in the above cases the initial biasing force of biasing
member 7 is zero as shown by points a, b, c and d in Fig. 12, it is of course
possible to permit variation of the urging force as shown at points
a, b, f and g by providing biasing member 7 with a suitable initial biasing
Further, it is possible to vary the weight applied to sheets S by
varying the position of contact between projections 81a and stoppers 46a and 47a
with variation of the thickness of buffering members 79d.
A further embodiment will now be described, in which the weight is
provided with a friction member. As shown in Figs. 20 and 21, the lower or outer
surface of the bottom portion of weight 5 has a pair of urging surfaces 5a for
urging sheets S. Urging surfaces 5a are provided with friction members 106 for
preventing double feeding of sheets S. The materials of friction members 106 and
feed roller 25 are selected such as to satisfy a relation
µ&sub3; < µ&sub1; < µ&sub2;
where µ&sub1; is the coefficient of friction of between friction members 106 and
sheet S, µ&sub2; is the coefficient of friction between feed roller 55 and sheet
S, and µ&sub3; is the coefficient of friction between adjacent sheets S.
Since the coefficient µ&sub1; of friction between friction members
106 provided on urging surfaces 5a of weight 5 and sheet S is greater than the
coefficient µ&sub3; of friction between adjacent sheets S and less than the coefficient
µ&sub2; of friction between feed roller 25 and sheet S as noted above, when it
becomes that two sheets S remain on stack support 15, the feeding-out of the last
sheet S from stack support 15 is prevented by the frictional force provided by
friction members 106 of weight 5, and only the last but one sheet S (i.e., the
lowermost sheet) is thus fed out by feed roller 55. It is thus possible to prevent
double feeding of the last sheet along with the last but one sheet. In addition,
since the frictional force provided by feed roller is greater than the frictional
force provided by friction members 106, the last sheet can be fed out smoothly
after completion of the feeding-out of the last but one sheet.
A further embodiment will be described with reference to Fig. 22.
Referring to the Figure 22, a pair of friction members 106 are applied to the bottom
surface to a front upright surface in the sheet-feeding direction. Friction members
106 are made of a material having substantially the same coefficient of friction
as that of sheets. They are covered by or located inwardly of weight cover 83.
In this construction, the operator inserts sheet stack S in the direction of arrow
A. At this time, even if the leading ends of sheets S strike weight 5, they will
never touch end portions of friction members 106 covered by or located inwardly
of weight cover 83. The operator aligns the leading ends of sheets S by bringing
them into contact with end-restricting member 30. Also, the operator restricts
movement of sheets S in the width direction thereof by displacing restricting members
16a and 16b. Further, the operator lowers weight 5 to urge sheets S against feed
Further, as shown in Figs. 23 and 24, on the front side of outer
weight 9 low frictional coefficient projections 9a projecting from friction members
106 by slight distance D are provided on the opposite sides of friction members
106 or on outer weight 9. With this structure, when ends of sheets touch weight
5 while weight 5 is held raised for replenishment with sheets, they strike projections
9a and are smoothly guided downwardly of weight 5. It is thus possible to prevent
sheet end portions from being bent or curled in contact with friction members
106 being raised.
A further embodiment will be described with reference to Fig. 25.
Referring to the Figure, detecting lever 21 for detecting sheet S is pivoted by
pin 22 to stack support 15, and its lower portion can be advanced into and retreated
from and thus on-off operate photointerpreter 23 provided on the back surface of
stack support 15. When there is no sheet S on stack support 15, an upper end portion
of detecting lever 21 is turned upwardly with respect to stack support 15, thus
indicating the absence of sheet S. Stack support 15 is provided with escapement
15b for avoiding interference of sheet-detecting means (21, 23) with detecting
If detecting lever 21 is exposed without any sheet S on stack support
15, sheet-detecting means (21, 23) are liable to execute an erroneous operation
With detecting lever 21 disposed beneath weight 26 as shown in Fig.
25, the user can difficultly touch detecting lever even when there is no sheet
S on stack support 15. Even if detecting lever 21 is touched, only its portion
near the center of its rotation is touched.
As one goes toward the free end of detecting lever 21, the contact
action is more delicate. That is, slightly touching a portion of detecting lever
21 near the rotational center thereof has no substantial adverse effects compared
to the case of touching the free end of the lever. It is thus possible to realize
prevention of erroneous operation or damage to detecting lever 21 due to touching.