Sheet feeding device with adjustable feeding and inversely-rotating rollers

A sheet feeding device includes a feeding roller, which has a plurality of large-diameter portions and which rotates in a sheet-feeding direction, an inversely-rotating roller, which has a plurality of large-diameter portions alternately disposed with respect to the large-diameter portions of the feeding roller and which rotates in a direction reverse to the sheet-feeding direction, and an automatic adjustment unit for automatically adjusting the amount of overlap between the large-diameter portions of the feeding roller and the large-diameter portions of the inveresely-rotating roller in accordance with a sheet-feeding state.

BACKGROUND OF THE INVENTION 
FIELD OF THE INVENTION 
This invention relates to a sheet feeding device for supplying sheets of 
originals, transfer paper or the like to an electronic filing apparatus, a 
copier, a printer, a facsimile apparatus or the like. 
DESCRIPTION OF THE RELATED ART 
As shown in FIG. 9, in some sheet feeding devices for supplying sheets of 
mounted originals, transfer paper or the like to various kinds of 
apparatuses, there is a separation mechanism, which includes a feeding 
roller 101 comprising large-diameter portions 101a and a small-diameter 
portion 101b, and an inversely-rotating roller 102 comprising 
large-diameter portions 102a and a small-diameter portion 102b. The 
large-diameter portions of the feeding roller 101 and the large-diameter 
portions of the inversely-rotating roller 102 are alternately disposed, so 
that these portions of the respective rollers can overlap in the direction 
of their diameters. 
A driving system (not shown) for transmitting its driving force to 
inversely-rotating roller 102 includes a torque limiter for disconnecting 
the transmission of the driving force when a load having at least a 
predetermined value is applied to inversely-rotating member 102, and a 
one-way clutch for regulating the rotation of inversely-rotating roller 
102 in the forward direction. 
If multiple sheets are fed from among mounted sheets, sheets present at the 
side of inversely-rotating roller 102 are sequentially returned by 
inversely-rotating roller 102, and only one sheet present at the side of 
feeding roller 101 is separated and fed. While the one sheet is fed, 
inversely-rotating roller 102 is stopped by the one-way clutch to regulate 
the movement of sheets other than the fed sheet in the feeding direction. 
In the above-described separation mechanism in which the large-diameter 
portions of feeding roller 101 and the large-diameter portions of 
inversely-rotating roller 102 are alternately disposed, since respective 
adjacent large-diameter portions do not contact each other, and the amount 
of overlap in the direction of their diameter can be changed, the 
separation force of inversely-rotating roller 102 can be adjusted, for 
example, in accordance with the thickness and the surface state of sheets. 
Hence, such a mechanism is very suitable, for example, when separating and 
feeding sheets at high speed, or when durability is required. 
In the above-described configuration, however, malfeeding of a sheet or 
simultaneous feeding of multiple sheets may occur, if the adjustment of 
the separation force of inversely-rotating roller 102 by changing the 
amount of overlap between feeding roller 101 and inversely-rotating roller 
102 is inadequate. Conventionally, since the adjustment is manually 
performed, only a skilled operator can perform correct adjustment. 
The above-described configuration also has the problem that it is 
impossible to sequentially feed sheets from a bundle of sheets having 
different thicknesses. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a sheet feeding device 
which can securely separate and feed any sheets by automatically adjusting 
an optimum separation force. 
It is another object of the present invention to provide a sheet feeding 
device which can individually separate and feed sheets securely from even 
a bundle of sheets having different characteristics (for example, 
thicknesses, or coefficients of friction of surfaces). 
According to one aspect, the present invention which achieves these 
objectives relates to a sheet feeding device comprising a feeding rotating 
member having a plurality of large-diameter portions and rotating in a 
direction for moving a sheet in a sheet-feeding direction, an inversely 
rotating member having a plurality of large-diameter portions alternately 
disposed with respect to the large-diameter portions of the feeding 
rotating member and rotating in a direction tending to move a sheet in a 
direction inverse to the sheet-feeding direction, and automatic adjustment 
means for automatically adjusting an amount of overlap between the 
large-diameter portions of the feeding rotating member and the 
large-diameter portions of the inversely rotating member in accordance 
with a sheet-feeding state. 
The adjustment means adjusts the amount of overlap, for example, in 
accordance with the load of a sheet entering between the feeding rotating 
member and the inversely rotating member, or based on detection by 
thickness detection means for detecting the thickness of a sheet, or based 
on detection of sheet detection means, disposed at a side downstream from 
the feeding rotating member in the sheet-feeding direction, for detecting 
a sheet separated by the feeding rotating member and the inversely 
rotating member. 
As described above, in the present invention, since an optimum separation 
force corresponding to the state of a sheet (for example, the thickness of 
the sheet, or the coefficient of friction of the surface of the sheet) can 
be obtained by adjusting the amount of overlap between the feeding 
rotating member and the inversely rotating member based on the load of the 
sheet while being conveyed, the thickness of the sheet, or the detection 
of the sheet-feeding state, it is possible to securely separate and feed 
sheets, and automatically adjust the amount of overlap. Hence, even an 
unskilled operator can easily operate the device. 
In addition, since the amount of overlap is automatically adjusted for each 
sheet so that the sheet can be appropriately separated and fed, even a 
bundle of sheets having different thicknesses and different coefficients 
of friction of the surfaces can be efficiently fed. 
According to another aspect of the present invention, a sheet feeding 
device includes a feeding rotating member, an inversely rotating member 
and adjustment means. The feeding rotating member has a plurality of 
large-diameter portions and rotates in a direction for moving a sheet in a 
sheet-feeding direction. The inversely rotating member has a plurality of 
large-diameter portions alternately disposed with respect to the 
large-diameter portions of the feeding rotating member and rotates in a 
direction tending to move a sheet in a direction reverse to the 
sheet-feeding direction. The adjustment means adjusts an amount of overlap 
between the large-diameter portions of the feeding rotating member and the 
large-diameter portions of the inversely rotating member in accordance 
with a load of a sheet entering between the feeding rotating member and 
the inversely rotating member. 
According to a further aspect of the present invention, a sheet feeding 
device includes a feeding rotating member, an inversely rotating member, 
sheet detection means and adjustment means. The feeding rotating member 
has a plurality of large-diameter portions and rotates in a direction for 
moving a sheet in a sheet-feeding direction. The inversely rotating member 
has a plurality of large-diameter portions alternately disposed with 
respect to the large-diameter portions of the feeding rotating member and 
rotates in a direction tending to move a sheet in a direction reverse to 
the sheet-feeding direction. The sheet detection means is disposed at a 
side downstream from the feeding rotating member in the sheet-feeding 
direction and detects a sheet separated by the feeding rotating member and 
the inversely rotating member. The adjustment means adjusts an amount of 
overlap between the large-diameter portions of the feeding rotating member 
and the large-diameter portions of the inversely rotating member based on 
detection of the sheet by the sheet detection means. 
According yet another aspect of the present invention, a sheet feeding 
device includes a feeding rotating member, an inversely rotating member, 
sheet-thickness detection means and adjustment means. The feeding rotating 
member has a plurality of large-diameter portions and rotates in a 
direction for moving a sheet in a sheet-feeding direction. The inversely 
rotating member has a plurality of large-diameter portions alternately 
disposed with respect to the large-diameter portions of the feeding 
rotating member and rotates in a direction tending to move a sheet in a 
direction reverse to the sheet-feeding direction. The sheet-thickness 
detection means detects the thickness of a sheet separated by the feeding 
rotating member and the inversely rotating member. The adjustment means 
adjusts an amount of overlap between the large-diameter portions of the 
feeding rotating member and the large-diameter portions of the inversely 
rotating member based on detection of the thickness of the sheet by the 
sheet-thickness detection means. 
According to still a further aspect of the present invention, a sheet 
feeding device includes a feeding rotating member, an inversely rotating 
member, adjustment means, mode setting means and separation-position 
storage means. The feeding rotating member has a plurality of 
large-diameter portions and rotates in a direction for moving a sheet in a 
sheet-feeding direction. The inversely rotating member has a plurality of 
large-diameter portions alternately disposed with respect to the 
large-diameter portions of the feeding rotating member and rotates in a 
direction tending to move a sheet in a direction reverse to the 
sheet-feeding direction. The adjustment means adjusts an amount of overlap 
between the large-diameter portions of the feeding rotating member and the 
large-diameter portions of the inversely rotating member. The mode setting 
means sets a separation adjusting mode in which separation adjustment 
between the feeding rotating member and the inversely rotating member is 
performed for each sheet, and a fixing mode in which separation adjustment 
is not performed for each sheet. The separation-position storage means 
stores the amount of overlap. When the separation adjusting mode has been 
set by the mode setting means, adjustment control of the amount of overlap 
is performed for each sheet, and when the fixing mode has been set by the 
mode setting means, adjustment is performed based on the amount of overlap 
stored in the separation-position storage means. 
Further aspects of the present invention include an image reading apparatus 
employing any of the sheet feeding devices described above as well as a 
reading device for reading an image formed on a sheet individually 
separated by the feeding rotating member and the inversely rotating 
member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A description will now be provided of a sheet feeding device according to a 
first embodiment of the present invention with reference to the drawings. 
FIG. 1 is a schematic cross-sectional view illustrating an image reading 
apparatus to which the sheet feeding device of the first embodiment is 
applied. 
In this apparatus, each sheet of mounted originals S is fed to the 
apparatus, images on the two surfaces of the fed sheet are read, the read 
images are displayed on a display device, and at the same time the images 
are recorded in a recording device. The apparatus also has the function of 
retrieving an image recorded in the recording device and displaying the 
retrieved image on the display device. 
In FIG. 1, sheet-feeding roller 4 feeds respective sheets of originals S on 
an original mount to the apparatus. Each of comb-like rollers 5 and 32 has 
large-diameter portions and a small-diameter portion. The large-diameter 
portions of one of the rollers 5 and 32 are arranged to face the 
small-diameter portion of the other roller, and vice versa. By driving 
comb-like rollers 5 and 32 in the forward direction and the reverse 
direction with respect to the original-feeding direction, respectively, 
sheets of originals S fed by sheet-feeding roller 4 are individually 
separated, and each of the separated sheets is fed to the apparatus. 
Each individually fed sheet of original S is conveyed by a pair of 
conveying rollers 46 and 52, and is further conveyed while being grasped 
by a pair of conveying rollers 70 and 71, and a pair of conveying rollers 
72 and 73 rotating at a constant speed. At that time, the two surfaces of 
the sheet of original S are illuminated by light sources 76 and 80 through 
transparent members 74a and 75a provided at guide plates 74 and 75, 
respectively. The images on the two surfaces of the sheet of original S 
are imaged onto image reading sensors 79 and 83, such as CCD's 
(charge-coupled devices) or the like, by plane mirrors 77 and 81, and 
imaging lenses 78 and 82, respectively. Thus, the images on the two 
surfaces of the sheet of original S are read. 
The read images are displayed on display device 93, and at the same time 
the images are recorded in recording device 95, such as a 
magnetooptical-disk device or the like. 
The image of original S recorded in recording device 95 can be retrieved, 
whenever needed, and displayed on display device 93. 
The read sheet of original S is grasped by conveying belts 87 and 90, and 
is discharged onto sheet-discharging unit 92. 
Reference numeral 94 represents an electric-component unit, which includes 
a power supply, a control substrate and the like, for controlling the 
apparatus to perform the above-described operations. 
The outline of the apparatus has now been described. 
FIG. 2 is a cross-sectional view illustrating the sheet feeding device of 
the present embodiment, and FIG. 3 is a plan view of the device. In FIG. 
2, there are shown tray 1 for mounting originals, original mount 2 which 
is rotatably mounted around shaft 2a, and original-mount raising lever 3 
which is rotatable around shaft 3a. 
Sheet-feeding roller 4 is rotatably mounted on U-shaped member 6 which is 
rotatably mounted around shaft 12. Solenoid 7 is mounted at one end 
portion 6a of U-shaped member 6 via plunger 7a. 
Comb-like roller 5 (hereinafter termed a "feeding roller"), which has 
large-diameter portions 5a and a small-diameter portion 5b, is mounted on 
shaft 12, which is rotatably supported at side plates 15 and 16, as one 
body. Gears 14 and 17 are mounted on shaft 12. Gear 14 is linked with gear 
11, which is mounted at one end of sheet-feeding roller 4, via gear 13. 
As shown in FIG. 4, planetary-gear device (differential mechanism) 20 
includes a sun gear 21, an internal gear 26, and planetary gears 22, each 
of which is rotatably mounted on one of shafts 23 secured on carrier 24 
and which meshes with sun gear 21 and internal gear 26. 
Sun gear 21 is mounted on shaft 19, which is rotatably supported by side 
plates 10 and 15, as one body. Internal gear 26 is rotatably mounted on 
shaft 19, and has gear teeth 26a at its outer circumference. Gear teeth 
26a are linked with gear 17 via gear 18. 
Gear 25 is mounted on carrier 24, which includes planetary gear 22, as one 
body so as to be rotatable around shaft 19. 
Gear 27 is mounted on shaft 19 via clutch 28. Gear 27 meshes with gear 29 
which is mounted on shaft 30. 
Original-detection sensor 9 detects the presence/absence of the sheet of 
original S using lever 8 which rotates around shaft 8a. The upper surface 
of original S is controlled so as to be always present at a predetermined 
position based on a signal from sensor 9. 
Fed-sheet sensor 51 and conveying roller 52 is rotatably driven via 
clutches (not shown). Reference numerals 67 and 67' represent guide plates 
for guiding the sheet of original S. 
As shown in FIG. 5, comb-like roller 32 (hereinafter termed an 
"inversely-rotating roller"), which has large-diameter portions 32a and a 
small-diameter portion 32b, is mounted on shaft 35 as one body. One end of 
shaft 35 is supported by bearing 36, and another end of shaft 35 is 
supported by bearing 33 via one-way clutch 34 for transmitting the driving 
force only in the direction of the arrow shown in FIG. 2. Shaft 35 is 
rotatably mounted on U-shaped member 31. 
Feeding roller 5 and inversely-rotating roller 32 are disposed so that the 
large-diameter portions of one of the rollers face the small-diameter 
portion of the other roller. 
Gear 37 is rotatably mounted on shaft 35, and member 39 is mounted on shaft 
35 as one body so as to be movable only in the thrust direction. Member 39 
is pressed against gear 37 by spring 40 via frictional member 38. Stopper 
41 for blocking spring 40 is provided as one body with shaft 35. According 
to the above-described configuration, if a load having at least a 
predetermined value is applied to inversely-rotating roller 32, a slip is 
produced between frictional member 38 and gear 37 to disconnect the 
transmission of the driving force to inversely-rotating roller 32. Gear 37 
is linked with gear 45, which is mounted on shaft 30, via gears 44, 43 and 
42, which are provided on U-shaped member 31. 
Conveying roller 46 is rotatably mounted on U-shaped member 47. U-shaped 
member 47 is rotatably mounted on shaft 30. One end of U-shaped member 47 
is driven in a clockwise direction by spring 48 which is mounted on raised 
member 31b of U-shaped member 31. That is, conveying roller 46 is pressed 
against conveying roller 52 with a predetermined force. 
U-shaped member 31 is rotatably mounted on shaft 30, and is driven in a 
clockwise direction by spring 49. Semicircular member 50 is provided on 
raised member 31a of U-shaped member 31. Semicircular member 50 contacts 
inclined portion 53a (see FIG. 6) of member 53 so as to regulate the 
position of inversely-rotating roller 32. 
FIG. 6 is a plan view illustrating a mechanism for regulating the position 
of inversely-rotating roller 32. 
FIG. 7 is a cross-sectional view of the mechanism taken along line 7--7' 
shown in FIG. 6. FIG. 8 is a cross-sectional view of the mechanism taken 
along line 8--8' shown in FIG. 6. 
Shaft 54, which has screwed portion 54a at a part thereof, is rotatably 
mounted at side plates 57a and 57b of base 57. Gear 56 is mounted at one 
end of shaft 54. A load having a predetermined value is applied to carrier 
24 by torque limiter 55 via gear 56. 
Inclined member 53 having inclined portion 53a is slidably mounted on 
cylindrical portions of shafts 58 and 54, which are mounted at side plates 
57a and 57b of base 57. 
Laterally-moving member 65, which includes semicircular screwed portion 65b 
fitted to screwed portion 54a of shaft 54, is rotatably mounted on shaft 
58. 
Release lever 62 is rotatably mounted on shaft 58. Solenoid 66 is mounted 
on release lever 62 via plunger Shaft 63, which is fitted in slot 65a of 
laterally-moving member 65, is also mounted on release lever 62. Release 
lever 62 is driven in a counterclockwise direction (see FIG. 7) by spring 
64, one end of which is mounted on base 57. Accordingly, semcircular 
screwed portion 65b of laterally-moving member 65 is pressed against 
screwed portion 54a of shaft 54 by shaft 63. 
Shaft 58 has screwed portion 58a, and screwed portion 60a of stopper 60, 
which is fitted to shaft 58, is screwed to screwed portion 58a. 
Stopper 60 has projection 60b which is fitted in a hole (not shown) 
provided at side 57a of base 57. By turning slot 58b provided at an end 
portion of shaft 58 with a driver, stopper 60 can be moved in the axial 
direction. Stopper 60 is fixed to the shaft by setscrew 61. 
Spring 59 is provided around the outer circumference of shaft 58, and 
drives member 53 so that it is pushed toward stopper 60 (direction D). 
Next, the operation of the present embodiment will be desribed. 
When a switch (not shown) has been depressed to start a recording 
operation, original-mount raising lever 3 rotates around shaft 3a to 
rotate original mount 2 in a counterclockwise direction. 
When the surface of the uppermost sheet of originals S on original mount 2 
has contacted original-detection sensor lever 8 and original detection 
sensor 9 has then detected another end of original-detection sensor lever 
8, original-mount raising lever 3 stops to rotate. At the same time, power 
supply for solenoid 7 is interrupted, and U-shaped member 6 rotates in a 
counterclockwise direction by its own weight, so that sheet-feeding roller 
4 contacts the surface of the uppermost sheet of originals S. 
Then, clutch 28 operates to link gear 27 with shaft 19. The driving force 
is thereby transmitted from gear 29 to gear 27 and to sun gear 21 of the 
sun-gear device. Since carrier 24 is stopped due to the load of torque 
limiter 55, the driving force is further transmitted to planetary gear 22, 
to internal gear 26, and to gear 17 by gear teeth 26a of internal gear 26 
via gear 18. Feeding roller 5 and sheet-feeding roller 4 thereby rotate to 
feed sheets of originals S into the apparatus. At that time, sheets after 
the second sheet of originals S are blocked by inversely-rotating roller 
32, and the uppermost sheet of original S mounted on original mount 2 is 
separated and fed. 
The sheet of original S separated by feeding roller 5 and 
inversely-rotating roller 32 is fed to a nip portion between the pair of 
conveying rollers 52 and 46. 
When the leading end of the sheet of original S has been detected by 
fed-sheet sensor 51, power is supplied to solenoid 7 to rotate U-shaped 
member 6 in a clockwise direction, whereby sheet-feeding roller 4 is 
separated from the surface of the sheet. When the leading end of the sheet 
of original S has reached the nip portion between the pair of conveying 
rollers 52 and 46, clutch 28 is disconnected, whereby feeding roller S 
stops to rotate. 
A clutch (not shown) is then operated with an appropriate timing, the 
driving force is transmitted to conveying roller 52, and the sheet of 
original S is fed to the following step while being grasped by the pair of 
conveying rollers 52 and 46. Thereafter, the above-described image 
processing operation is performed. 
When the trailing end of the sheet of original S has been detected by 
fed-sheet sensor 51, power supply for solenoid 7 is interrupted with an 
appropriate timing, whereby U-shaped member 6 rotates in a 
counterclockwise direction by its own weight, so that sheet-feeding roller 
4 contacts the surface of the uppermost sheet of originals S. Then, clutch 
28 operates, so that sheet-feeding roller 4 and feeding roller 8 again 
rotate to feed the sheet of the next original S into the apparatus. 
When sheets of originals S have been sequentially fed by the 
above-described operation, the position of the surface of originals S has 
descended, and original-detection sensor lever 8 in contact with the 
surface of the uppermost sheet of originals S has rotated in a 
counterclockwise direction and left original detection sensor 9, 
original-mount raising lever 3 rotates to raise original mount 2. When 
original detection sensor 9 has detected original-detection sensor lever 
8, original-mount raising lever 3 stops. By detecting the position of the 
surface of originals S by original detection sensor 9 in the 
above-described manner, the position of the surface of originals S is 
always maintained at a constant position. 
If the thickness of originals S is greater than the amount of overlap 
between feeding roller 5 and inversely-rotating roller 32 required for 
obtaining an appropriate separation force, a large load is applied to 
feeding roller 5. If the value of this load is greater than the value of 
the load set by torque limiter 55, feeding roller 5 and sheet-feeding 
roller 4 linked therewith stop, and internal gear 26 of planetary-gear 
device 20 also stops. On the other hand, carrier 24 which has been kept 
stopped starts to rotate, therefore gear 25 starts to rotate in a 
clockwise direction, and shaft 54 starts to rotate in a counterclockwise 
direction by gear 56 which meshes with gear 25 (see FIG. 4). 
Laterally-moving member 65 screwed to screwed portion 54a of shaft 54 is 
thereby moved in the direction of arrow C shown in FIG. 6 together with 
member 53. Semicircular member 50 contacting the inclined portion of 
member 53 is thereby pushed, to rotate U-shaped member 31 in a 
counterclockwise direction in FIG. 2. Accordingly, the distance between 
the shafts of inversely-rotating roller 32 and feeding roller 5 increases, 
and the amount of overlap of the rollers is reduced. 
The load of originals S applied to feeding roller 5 is thereby reduced. If 
the value of this load becomes smaller than the value of the load set by 
torque limiter 55, carrier 24 of planetary-gear device 20 stops to rotate, 
and internal gear 26 starts to rotate by planetary gear 22 provided in 
carrier 24. Feeding roller 5 and sheet-feeding roller 3 thereby start to 
rotate again to feed sheets of originals S. 
By arranging so that the drive of sheet-feeding roller 4 is linked with 
feeding roller 5, sheet-feeding roller 4 also stops when feeding roller 5 
stops. Hence, it is possible to overcome the problem that the 
sheet-feeding roller feeds originals while the feeding roller stops, 
causing a jam of an original. 
In an initial state, the distance between the shafts of feeding roller 5 
and inversely-rotating roller 32 is set to a minimum value so that an 
appropriate separation force can be obtained for the thinnest set 
originals. 
In this state, inclined member 53 contacts stopper 60. 
The position of initial setting is provided by rotating shaft 58 to move 
stopper 60 in the axial direction (see FIGS. 6, 7 and 8). 
When the trailing end of the sheet of original S has been detected by 
fed-sheet sensor 51, power is supplied to solenoid 66 to rotate release 
lever 62 in a clockwise direction in FIG. 7 against spring 64. 
Laterally-moving member 65 thereby rotates in a clockwise direction in 
FIG. 8 by shaft 63 provided at release lever 62, and leaves screwed 
portion 54a. Laterally-moving member 65 which moved to an arbitrary 
position in direction C in accordance with the thickness of originals S is 
returned in direction D by spring 59 together with inclined member 53 
until it contacts stopper 60. The distance between the shafts of feeding 
roller 5 and inversely-rotating roller 32 returns to the initial state. 
Even if the thickness of originals S mounted on original mount 2 differs, 
the distance between the shafts of feeding roller 5 and inversely-rotating 
roller 32 is adjusted so that a separation force corresponding to the 
thickness is obtained, and sheets of originals S are individually 
separated and fed. 
Although in the above-described embodiment a releasing operation of 
returning the distance between the shafts of feeding roller 5 and 
inversely-rotating roller 32 to the original state is performed for each 
original, the releasing operation may be performed after the completion of 
feeding of mounted originals at least when the mounted originals have the 
same thickness. 
FIG. 10 illustrates a second embodiment of the present invention. 
When sheets of originals 121 have been mounted on original mount 122 and a 
start key (not shown) has been depressed, sensor 136 confirms the 
presence/absence of originals. When the presence of originals has been 
confirmed, respective rollers are driven. The originals pressed against 
sheet-feeding roller 124 by spring 123 are fed toward feeding roller 125 
and separation roller 126 in the following stage by friction between the 
originals and sheet-feeding roller 124. 
Feeding roller 125 and separation roller 126 rotate in respective 
directions indicated by the corresponding arrows. Feeding roller 125 tends 
to feed the uppermost sheet of originals 121 to the subsequent roller, and 
separation roller 126 tends to return sheets under the second sheet of 
originals 121 (other than the uppermost sheet). 
Separation roller 126 is supported by separation-roller support (moving 
means) 127, which is rotatable around fulcrum 128, is driven downwardly by 
spring 129, and is supported upwardly by eccentric cam 130. Eccentric cam 
130 is rotated by driving motor 131 via a belt. 
In the above-described configuration, when starting to feed the sheet of 
original 121, eccentric cam 130 is arranged so that its separation unit is 
at an upper position (a first position which is close to feeding roller 
125). Even if the sheet of original 121 is fed in this state, the sheet 
cannot pass between feeding roller 125 and separation roller 126 since the 
space between these rollers is narrow. Therefore, the sheet of original 
121 is not detected by sensor 132. 
Then, motor 131 is rotated to rotate eccentric cam 130, whereby separation 
roller 126 is lowered by a predetermined amount. This operation is 
continued until sensor (detection means) 132 detects the sheet of original 
121. When the sheet of original 121 has been detected, motor 131 is 
stopped to fix the position of separation roller 126, and the sheet of 
original 121 continues to be fed. 
FIG. 11 is a flowchart of the present embodiment. 
When sheets of originals 121 have been mounted on original mount 122 and 
the start key has been depressed, sensor 136 confirms the presence/absence 
of originals. When the presence of originals has been confirmed, the 
respective rollers are rotated, and separation roller 126 is lowered until 
the uppermost sheet of originals starts to be conveyed (step 1). When the 
original starts to be conveyed, eccentric cam 130 is fixed at the current 
position (step 2), and the originals are conveyed until no originals 
remain on original mount 122 while maintaining separation roller 126 at 
the current position (step 3). 
As described above, by automatically adjusting the position of separation 
roller 126 when starting feeding of sheets of originals 121, each sheet of 
original 121 can be securely converted (a separation adjusting mode). 
Although in the above-described second embodiment a description has been 
provided of only a case in which sheet feeding is started, the second 
embodiment can also be applied to other cases. For example, in a 
conventional apparatus, if the thickness of originals 121 is reduced from 
a certain sheet in one file, multiple sheets of thin originals are always 
fed. However, the occurrence of feeding of multiple sheets is minimized by 
linking separation roller 126 with multiple-sheet-feeding detection means, 
and by moving separation roller 126 upwardly upon detection of feeding of 
multiple sheets, thereby reducing the space between separation roller 126 
and feeding roller 125. 
When feeding sheets of originals 121 having the same thickness a plurality 
of times, separation-means-position storage means stores the position of 
separation roller 126 at the preceding time, or the position of separation 
roller 126 determined at the feeding of the first sheet in the present 
time, and a separation/feeding operation is performed by positioning 
separation roller 126 at the stored position without performing adjustment 
every time (separation fixing mode). According to such an approach, the 
time required for adjustment can be omitted, and therefore sheets of 
originals 121 can be efficiently fed. A mode is set by mode setting means 
(not shown). 
In the above-described separation adjusting method, the space between 
separation roller 126 and feeding roller 125, which has been first 
adjusted to be narrow, is gradually increased, and sheets are fed with 
such a space that the first sheet can pass, However, the best space may, 
of course, be determined according to various factors. For example, a 
space which is more or less greater than the minimum space for passing a 
sheet may be preferred for originals 121, for example, depending on the 
material of the original, or the separation method. 
FIGS. 12 and 13 are diagrams illustrating characteristics of a third 
embodiment of the present invention. FIG. 14 is a cross-sectional view 
taken along line 14--14' shown in FIG. 13. 
In FIGS. 12 and 13, there are shown sheets of originals S, sheet feeding 
device 201, original-mounting plate 202 for mounting originals before 
recording, sheet- feeding roller 203 for feeding sheets of originals S on 
original mounting plate 202 toward the downstream side, feeding roller 204 
for feeding the sheets of originals S fed by sheet-feeding roller 203 
further to the downstream side, separation roller 205 which rotates in a 
direction A such that it contacts originals S while moving in a direction 
reverse to the original-feeding direction in order to prevent feeding of 
multiple sheets of originals S, separation-roller supporting member 206, 
and sheet-conveying roller 207. These rollers are driven by a driving 
system (not shown). 
Gear 208 is fixed to shaft 207a of sheet-conveying roller 207. Intermediate 
gears 209 and 210 are provided next to gear 208. Gear 211 is rotatably 
provided on shaft 208a of separation roller 205, and is linked with 
intermediate gear 210. The rotation of sheet-conveying roller 207 is 
transmitted to gear 211 via gear 208, and intermediate gears 209 and 210. 
Driven roller 212 is in pressure contact with sheet-conveying roller 207. 
One-way clutch 228 is fitted to separation-roller shaft 205a so as to 
prevent separation roller 205 from rotating in a direction opposite to the 
direction of arrow A shown in FIG. 12. 
Reference numeral 229 represents a housing for mounting one-way clutch 228 
on separation-roller supporting member 206. Reference numeral 230 
represents a torsion coil spring for applying a rotational force in the 
direction of arrow A shown in FIG. 12 to housing 229. One end 230a of 
torsion coil spring 230 is inserted in hole 206b provided in 
separation-roller supporting member 206, and another end of torsion coil 
spring 230 is anchored in groove 229a provided at the inner side of 
housing 229 (see FIG. 14). There are also shown bearing members 231 and 
232, longitudinal-direction restricting members 233 and 234, frictional 
member 235, resin disk 236, and compression spring 237. These components 
constitute a torque limiter for disconnecting the transmission of the 
driving force when a predetermined amount of load is applied. 
Hole 206a provided in separation-roller supporting member 206 has the shape 
shown in FIG. 15. By the function of torsion coil spring 230, housing 229 
rotates by .theta..degree. in a counterclockwise direction from the state 
shown in FIG. 12 to assume the state shown in FIG. 16. 
While sheet-conveying roller 207 rotates, separation roller 205 also 
rotates. Separation roller 205 stops only when a predetermined amount of 
load is applied to separation roller 205. 
When a reading start switch (not shown) has been switched on, sheets of 
originals S on original-mounting plate 202 are fed by sheet-feeding roller 
203. The fed sheets of originals S are individually separated by the pair 
of feeding roller 204 and separation roller 205, and each of the separated 
sheets is fed to the downstream side. Since no load is applied to 
separation roller 205 until sheets of originals S reach a nip portion 
between the pair of feeding roller 204 and separation roller 205, 
separation roller 205 rotates in the direction of arrow A shown in FIG. 
12. 
When originals S have reached the nip portion between the pair of feeding 
roller 204 and separation roller 205, separation roll 205 stops to rotate 
due to a load received from originals S. Originals S are further pushed 
toward the downstream side by sheet-feeding roller 203 and feeding roller 
204, so that separation roller 205 intends to rotate in a direction 
reverse to the direction of arrow A. 
When separation roller 205 rotates in the direction of arrow A, one-way 
clutch 228 is free, and therefore does not receive a rotational force from 
separation roller 205. However, when separation roller 205 intends to 
rotate in a direction reverse to the direction of arrow A, one-way clutch 
228 is locked, and therefore intends to rotate in the same direction as 
separation roller 205. 
Accordingly, a rotational force is applied to housing 229, to which one-way 
clutch 228 is fitted, to rotate housing 229 by .theta..degree. from the 
state shown in FIG. 16 to the state shown in FIG. 12 against the action of 
torsion coil spring 230. 
At that time, since separation roller 205 and one-way clutch 228 also 
rotate as one body with housing 229, separation roller 205 rotates in the 
original-feeding direction until the leading end of the sheet of original 
S reaches and then passes through the nip portion between the pair of 
feeding roller 204 and separation roller 205. 
While the sheet of original S passes through the nip portion after housing 
229 has assumed the state shown in FIG. 12, the sheet of original S 
intends to rotate separation roller 205 in a direction opposite to the 
direction of arrow A. Hence, housing 229 maintains the state shown in FIG. 
12. Since separation roller 205 does not rotate in the original-feeding 
direction, feeding of multiple sheets of originals S do not occur. 
When the trailing end of the sheet of original S has passed through the nip 
portion between feeding roller 204 and separation roller 205, the force 
applied from the sheet of original S to separation roller 205 disappears. 
Hence, housing 229 is returned to the state shown in FIG. 16 by the action 
of torsion coil spring 230. 
Thereafter, the same operation is repeated every time the sheet of original 
S is fed. As in the conventional approach, images of the two surfaces of 
the sheet of original S passing through the pair of feeding roller 204 and 
separation roller 205 are read by an original-reading unit (not shown), 
and the sheet of original S is then discharged onto a sheet-discharging 
tray (not shown). 
As described above, when each sheet of original S is separated and fed, 
separation roller 205 rotates in the original-feeding direction until the 
leading end of the sheet of original S reaches and passes through the nip 
portion between the pair of feeding roller 204 and separation roller 205. 
Hence, the leading end of the sheet of original S is prevented, for 
example, from being folded or raised even if the sheet is thin and has low 
stiffness, or the surface of the sheet is apt to be raised. 
Furthermore, even if the space between the pair of feeding roller 204 and 
separation roller 205 is adjusted to be narrower than the thickness of the 
sheet of original S to be fed, the leading end of the sheet of original S 
does not stay at the entrance of the nip portion between the pair of 
feeding roller 204 and separation roller 205, as in the conventional 
approach, but enters the nip portion in accordance with the rotation of 
separation roller 205 in the sheet-feeding direction Hence, the sheet of 
original S can be fed. 
Accordingly, the range of adjustment of the space between the pair of 
feeding roller 204 and separation roller 205 is much widened, and 
therefore it becomes easier to adjust the space between the pair of 
feeding roller 204 and separation roller 205 than in the conventional 
approach. 
Next, a description will be provided of a fourth embodiment of the present 
invention. 
In the above-described first and second embodiments, the amount of overlap 
between the feeding roller and the inversely-rotating roller is adjusted 
based on the load of the sheet, or the feeding state of the sheet. In the 
present embodiment, however, the thickness of the fed sheet is detected, 
and the amount of overlap is adjusted based on the result of the 
detection. 
The present embodiment is effective when the thickness of each of sheets 
which have been mounted in order to be fed is substantially constant. That 
is, sheet-thickness detection means is disposed at a side downstream from 
separation means in order to detect the thickness of each separated sheet. 
The amount of overlap between the feeding roller and the 
inversely-rotating roller is first set to an average value. After 
separating the first sheet, the amount of overlap is adjusted to an 
optimum value based on the result of detection of the thickness of the 
separated sheet. Thus, each sheet after the next sheet is separated in an 
excellent manner. 
Referring again to FIG. 10, in one embodiment the thickness of the sheet is 
detected, for example, by providing a pair of rollers 133a, 133b so as to 
be contactable and separable at a side downstream from the feeding roller 
125, and means 330 for measuring the displacement of the rollers 133a, 
133b, and by measuring the amount of displacement between the pair of 
rollers 133a, 133b when the sheet is inserted using measuring means. 
Alternatively, as shown in phantom therein, 340 a light-emitting unit for 
projecting light onto the sheet, and light-receiving unit 350 for 
receiving light passing through the sheet may be provided, and the 
thickness of the sheet may be detected based on the transmittance of the 
sheet. 
A detection signal representing the thickness of the sheet detected by such 
sheet-thickness detection means is transmitted to a control unit 135. As 
in the above-described second embodiment, control means 135 adjusts the 
amount of overlap between the feeding roller and the inversely-rotating 
roller based on the detection signal. 
Usually, the thickness of the sheet is proportional to the stiffness of the 
sheet, i.e., the stiffness increases as the thickness increases. Hence, it 
is necessary to set the amount of overlap between the feeding roller and 
the inversely-rotating roller to a small value for a thick sheet. That is, 
the amount of overlap is adjusted to a smaller value as the thickness of 
the sheet increases. 
As a modification of the fourth embodiment, the amount of overlap between 
the feeding roller and the inversely-rotating roller may be adjusted 
directly based on the result of detection of the thickness of the sheet. 
For example, a pair of rollers, which is linked with the inversely-rotating 
roller or the feeding roller, may be provided at a side downstream from 
the feeding roller, and the inversely-rotating roller or the feeding 
roller may be displaced by a linking mechanism or the like in accordance 
with the displacement of the pair of rollers corresponding to the 
thickness of the sheet. In this case, since the thickness of the sheet 
(the amount of displacement of the pair of rollers) is inversely 
proportional to the amount of overlap, the inversely-rotating roller or 
the feeding roller is moved so that the amount of overlap is reduced as 
the amount of displacement of the pair of rollers increases. 
The present invention is not limited to the above-described embodiments. 
For example, the present invention is not limited to the method of 
separating sheets by the feeding roller and the inversely-rotating roller 
as in the above-described embodiments, but may also be applied to a method 
of separating sheets using a conveying belt. While in the above-described 
embodiments a description has been provided of the sheet feeding device 
for supplying originals to an electronic filing apparatus (an image 
reading apparatus), the present invention is not limited to such 
apparatuses, but may be applied to a sheet feeding device for feeding 
sheets to an image forming apparatus, such as a printer, a facsimile 
apparatus or the like, an original automatic feeding apparatus provided in 
a copier or an image reader, or the like. 
The individual components shown in outline or designated by blocks in the 
drawings are well-known in the image conveying, recording and reading arts 
and their specific construction and operation are not critical to the 
operation or best mode for carrying out the invention. 
While the present invention has been described with respect to what is 
currently considered to be the preferred embodiments, it is to be 
understood that the invention is not limited to the disclosed embodiments. 
To the contrary, the invention is intended to cover various modifications 
and equivalent arrangements included within the spirit and scope of the 
appended claims. The scope of the following claims is to be accorded the 
broadest interpretation so as to encompass all such modifications and 
equivalent structures and function.