Sheet feeder unit

A sheet feeder unit capable of separately supplying cut sheets of any thickness or characteristics without causing any residual deformation. The pile of cut sheets 11 are advanced one by one with a pair of feeding rollers 31 contacting thereto from one side thereof. A friction member 33 of various configurations is disposed at various positions for separating the outermost cut sheet 11 from the other sheets by the frictional force of contact generated therebetween when the friction member is backed away by the advancing cut sheet 11.

BACKGROUND OF THE INVENTION 
1. Technical Field of the Invention 
This application is based on applications Nos. 8-346010, 8-346013, 
8-346014, 8-346015, 8-346016, 8-346017, and 8-346019 filed in Japan, the 
contents of which are hereby incorporated by reference. 
The present invention relates to a sheet feeder unit which supplies cut 
sheets set in a pile thereon by a feeding roller which contacts to the cut 
sheets from one side thereof, and particularly to a sheet feeder unit 
which is capable of separating cut sheets to be supplied one after another 
by a frictional force generated when a leading end of the cut sheet is 
pushed forward to contact with a friction member which is supported at one 
end thereof and extended toward a conveying path of the cut sheet. The 
present invention may be employed for feeding a plurality of piled cut 
sheets one by one in various appliances such as a copying machine, 
printer, facsimile machine, or image reading apparatus. 
2. Description of Related Art 
Japanese published unexamined patent application No. 7-196186 discloses the 
like of such sheet feeder unit, which is shown in FIG. 1. The feeder unit 
according to this prior art has a friction member 933 rotatably supported 
at its lower end by a shaft 932 to be able to stand upright and tilt, and 
configured to be rectangular when viewed from the front. Each time a 
feeding roller 931 is rotated, an uppermost cut sheet 911 is pushed 
forward so that a whole width of a leading end of the cut sheet 911 comes 
into frictional contact with the friction member 933 and causes the same 
to back away against a rebounding force of a spring 934 as shown by 
phantom lines in FIG. 1. The cut sheet 911 is thereby separated from the 
other cut sheets, which are prevented from being supplied one upon 
another. 
In order to assure the separation of cut sheets from each other, the angle 
.alpha. made by a surface of the friction member 933 and an uppermost cut 
sheet 911 is set within the range of 55.degree. to 85.degree.. The above 
mentioned published application also teaches a friction member made of an 
elastic sheet and fixed at its lower end with the same angular condition 
as described above, instead of being rotatably supported by the shaft 932. 
The friction member of such configuration, however, requires a very fine 
adjustment to successfully separate the cut sheets. According to an 
experiment conducted by the inventors of the present invention, the 
rebounding force of the spring 934 toward its initial position should be 
set weak enough to prevent residual deformation of the cut sheet caused by 
the friction member 933. On the other hand, the rebounding force should be 
strong enough to increase the frictional force between the cut sheet 911 
and the friction member 933 so as to ensure the separation. It is 
difficult to satisfy both of these contradictory conditions. Moreover, 
physical properties of cut sheets such as resiliency or frictional 
coefficient vary depending on their quality and thickness, causing 
differences in frictional resistance even with the use of the same 
friction member. 
Also, the friction member 933 in this prior art arrangement is disposed 
downstream in a feeding direction and away from a nipping position where 
the feeding roller 931 presses and pushes the cut sheet 911 forward. The 
cut sheet is, when contacted against the friction member 933, warped and 
separated from the other cut sheets. Since the friction member 933 is 
distanced from the feeding roller 931 widely enough to allow the cut sheet 
911 to flexibly deform therebetween, the cut sheet 911 can easily escape 
from the friction member 933 which is being tilted backward. This 
configuration helps to prevent residual deformation of the cut sheets 911 
irrespective of their thickness. 
Still, the sheet feeder unit of this prior art is not fully capable of 
stably separating cut sheets 911 and sometimes supplies the cut sheets in 
plural one upon another for the following reason. Since the friction 
member 933 has an even surface against which the cut sheet 911 is 
contacted, the more the leading end of the cut sheet 911 pushes the 
friction member 933 and approaches a free end thereof, the more the 
contacting angle therebetween widens, to let the cut sheet 911 pass, 
causing the frictional force to become less than a desired degree. 
Multiple cut sheets 911 may thus slip through the friction member 933 from 
time to time without being fully separated from each other. Although the 
setting of the angle between the cut sheet 911 and the friction member 933 
helps prevent such slippage to some extent, it is not enough to fully 
prevent faulty feeding of cut sheets, especially those being less 
resilient or having a greater frictional coefficient due to their quality 
or thickness. 
The conditions required for successfully feeding sheets may be 
satisfactorily set, though it is only temporary as the sheet feeding 
performance is dependent on various ambient conditions. For example, a cut 
sheet made of paper which has high absorbency may be less smoothly 
conveyed. An unabsorbent cut sheet made of synthetic resin for an overhead 
projector may be also affected by humidity on its surface, which may cause 
the cut sheet to be fed one upon another. Even the fiber directions 
(whether parallel or right-angled with respect to the sheet feeding 
direction) of manufactured paper may slightly affect the resiliency of the 
cut sheet, causing instability in sheet feeding performance. 
Further, the friction member 933 of the prior art apparatus has an even 
friction surface with respect to a whole width of the leading edge of the 
cut sheet 911 contacted thereto. For this reason, when the conditions are 
set to provide enough frictional force in order to fully separate cut 
sheets of small size, cut sheets of greater size cannot be smoothly fed 
because of too much frictional force. On the other hand, when the 
conditions are set appropriately for feeding cut sheets of great size, cut 
sheets of small size may be fed one upon another due to insufficient 
frictional force. 
Further, when a cut sheet having its leading edge curled downwardly is fed, 
it is more likely that the cut sheet is curled even more when pushed 
against the friction member 933 because of its even frictional surface in 
the prior art arrangement, which can leads to a paper jam or cause the cut 
sheet to be crumpled or stuck to the following sheets. 
BRIEF SUMMARY OF THE INVENTION 
In view of the foregoing, it is a primary object of the present invention 
to provide a sheet feeder unit being capable of successfully separating 
and supplying cut sheets of any thickness or physical properties.

DETAILED DESCRIPTION OF THE INVENTION 
Preferred embodiments of the present invention will be hereinafter 
described in conjunction with the accompanying drawings. 
&lt;First Embodiment&gt; 
A first embodiment of the present invention is shown in FIGS. 2 to 4, and 
implemented as a sheet feeder unit 1 for supplying recording sheets in a 
digital copying machine 10 as shown in FIG. 4. An original document which 
is either manually placed on a platen glass or automatically fed by a 
document feeding apparatus (not shown) is scanned by a scanning optical 
system 2. A scanned image is formed in an image sensor 4 in an image 
reader unit 3, which is converted into electrical image signals to be 
transmitted to a print head 5. The print head 5 projects out a laser beam 
6 modulated by the image signals onto a photosensitive drum 7 to expose 
the image. 
The photosensitive drum 7 is positioned substantially at the center of the 
main body of the copying machine 10, and its surface is evenly charged by 
a charging brush 8 for the exposure of the image. An electrostatic latent 
image formed on the charged surface of the photosensitive drum 7 is 
developed with toners in a developing unit 9 to be a visible image, which 
is transferred onto a cut sheet 11 conveyed from the sheet feeder unit 1 
by a transfer roller 12 or the like. The cut sheet 11 is then carried to a 
fixing unit 13 to fix the transferred image thereon, after which the cut 
sheet 11 is discharged onto a discharge tray 15 directly or being by 
guided by a discharge roller 14. 
The copying machine 10 is provided with a sheet feeding apparatus 16 at its 
bottom for supplying cut sheets 11 of a standardized type or sheets 
commonly used, which comprises an extractable feeder cassette 17 and a 
feeding roller 18 mounted in the main body of the copying machine 10 for 
pushing the sheets forward. While the sheet feeding apparatus 16 is built 
in the copying machine 10, the sheet feeder unit 1 is a cassette type 
sheet feeder on which recording sheets are manually placed, and thus 
projected from a side of the copying machine 10. The sheet feeder unit 1 
is intended for use when it is desired to feed one or a plurality of cut 
sheets 11 of different quality or size which are not prepared in the main 
body of the copying machine 10. 
Referring to FIG. 3, the sheet feeder unit 1 has a pair of side guides 22 
provided at both sides of its feeder tray 21, the positions of which are 
adjustable according to a width of the cut sheets 11 corresponding to 
various different sizes thereof. Both side guides 22 are connectively 
moved with each other by a linking gear 23 within the feeder tray 21, so 
that the cut sheet 11 of any size is always centered on the feeder tray 
21. The sheet feeder unit 1 of such cassette type is suitable for various 
kinds of cut sheets 11 including postcards, plastic sheets for overhead 
projectors, very thin sheets, or various other types of sheets. 
The sheet feeder unit 1 is desired to have high sheet feeding performance 
capable of feeding any type of cut sheet 11, while its sheet feeding 
mechanism must be simple and compact, as the cassette type sheet feeder is 
one type of attachment which may not be very frequently used. While being 
highly capable of stably feeding any types of cut sheets 11, the sheet 
feeder unit 1 of the first embodiment is as simply constructed as the 
above mentioned prior art, in which the outermost cut sheet 11 pushed 
forward by the feeding roller 31 comes into contact with and causes the 
friction member 33 to back away, which prevents the other cut sheets from 
proceeding with the outermost cut sheet 11 by the frictional contact 
therebetween. It will be understood that the present invention may be 
applied to a sheet feeding apparatus commonly used and built in the 
copying machine, an automatic sheet feeder, or any other appliances. 
The feeding roller 31 of the sheet feeder unit 1 is disposed on a side face 
of the main body of the copying machine 10. The feeder tray 21 extends 
laterally and upwardly from a base 36 with an outer guide 35 which defines 
a sheet conveying path 34 for guiding a cut sheet 11 fed from the sheet 
feeding apparatus 16 toward the photosensitive drum 7. The base 36 is 
connected to the main body of the copying machine 10 by a hinge (not 
shown) at its one side, around which the base 36 is rotated together with 
the feeder tray 21 to open/close the sheet conveying path 34 for removing 
jammed paper. 
The feeder tray 21 has a plate 26 which is rotatably supported by a shaft 
24 at its one end and urged upward by a spring 25. The plate 26 presses 
the pile of cut sheets 11 on the feeder tray 21 toward the feeding roller 
31, which pushes the outermost or uppermost cut sheet 11 forward by its 
rotation. The surface of the feeding roller 31 is made of rubber such as 
ethylene propylene diene monomer (EPDM) or the like to provide an 
appropriate amount of frictional force. The material of the feeding roller 
31 is of course not limited to the one mentioned above. 
The feeding roller 31 is configured to be semicircular in cross section, 
the cutaway flat portion of which is usually opposed to the cut sheets 11, 
and the feeding roller 31 is rotated to cause its curved periphery to 
contact the cut sheet 11 to send it out. When the sheets are not to be 
fed, a cam 31b which is rotated in synchronism with the feeding roller 31 
is contacted with a cam follower 26a, which presses down the plate 26 
against the force of the spring 25, to bring the cut sheets 11 apart from 
the feeding roller 31, so that the pile of cut sheets 11 can be readily 
placed at a predetermined location on the feeder tray 21 by hand where the 
cut sheets 11 come into contact with the friction member 33, or the cut 
sheets 11 can be removed therefrom. 
At the time of feeding sheets, when the feeding roller 31 starts to rotate, 
the cam 31b comes apart from the cam follower 26a at the same time or 
slightly after the cutaway portion of the feeding roller 31 comes out of 
opposition to the cut sheets 11. The plate 26 being freed is thus pushed 
upward by the spring 25 to press the cut sheets 11 onto the periphery of 
the rotating feeding roller 31. 
The friction member 33 of this embodiment is made of an elastic sheet, so 
that the friction member 33 can be elastically deformed to warp when the 
cut sheet 11 is sent out by the feeding roller 31. The friction member 33 
stops the cut sheet except the uppermost one, thereby separating the 
uppermost cut sheets 11 from the other cut sheets 11 by the frictional 
contact therebetween and supplies the cut sheets one by one from the 
uppermost side thereof. For this reason, the friction member 33 is 
extended from the lowermost side of the pile of cut sheets 11 toward a 
conveying path 30 of the cut sheets, with its lower end fixedly connected 
to a support wall 37 standing upright under the conveying path 30 by any 
appropriate manner such as bonding or bolting. 
The mechanism of how the friction member 33 separates the cut sheets can be 
theoretically and quantitatively explained by the combination of the 
backing away movement of the friction member 33 and partial deformation of 
the cut sheets as follows. 
FIG. 5A shows a state where the force F of proceeding cut sheet 11 balances 
the frictional force on the surface 33a of the friction member 33, which 
is expressed by an equation 
EQU F cos .theta.=.mu.B.multidot.F sin .theta. (1), where 
.mu.B is a friction coefficient of the frictional surface 33a with respect 
to the cut sheet 11, and .theta. (fixed value) is the angle made between 
the cut sheet 11 and the frictional surface 33a. From above, the following 
relations are derived. 
EQU .mu.B.multidot.tan .theta.&lt;1 (cut sheet proceeds) (2) 
EQU .mu.B.multidot.tan .theta..gtoreq.1 (cut sheet stops) (3) 
FIG. 5B shows critical angles of contacting angle .theta. within the range 
of appropriate friction coefficient .mu.B where the cut sheet 11 slips to 
proceed. 
It can be seen from the above inequalities (2),(3) that, theoretically, 
whether the cut sheet 11 proceeds or not does not depend on the force F 
but on the values of the friction coefficient .mu.B and the angle .theta.. 
Thus, if the .mu.B is invariable, it is necessary to give a difference in 
the contacting angle .theta. between the outermost cut sheet 11 and the 
other cut sheets 11 with respect to the frictional surface 33a. In other 
words, the outermost cut sheet 11 can be separated by changing the 
contacting angle .theta. from the "STOP" area to the "PROCEED" area of the 
graph shown in FIG. 5B. 
However, the cut sheets 11 are normally placed in a pile in tight contact 
with each other and there is virtually no difference in the angle .theta. 
made by each cut sheet 11 and the frictional surface 33a. 
The friction member 33, while being pushed back by the advancing cut sheet 
11, causes the outermost cut sheet 11 to curve by the frictional force of 
contact more than the other following cut sheets 11, so that the angle 
.theta. made by the outermost cut sheet 11 and the frictional surface 33a 
becomes much more acute than that of the other cut sheets 11, thus 
separating the cut sheets 11 from each other and allowing only the 
outermost cut sheet to pass through while stopping the others. 
Nevertheless, it is still difficult to ensure that the cut sheets 11 are 
fed one by one without any residual deformation which may be caused by too 
much force from the friction member 33, because the resiliency of cut 
sheets varies depending on their type, quality, and thickness. 
In this embodiment, a pair of feeding rollers 31 is provided at symmetrical 
positions about the center of the sheet conveying path of the cut sheets 
11, so as to advance the cut sheets without skew. The pair of feeding 
rollers 31 allows the cut sheets 11, which may not be centered on the 
feeder tray 21 depending on their size, to also be fed without skew. 
The friction member 33 may be disposed in the middle between the pair of 
feeding rollers 31, in which case the force of advancing the cut sheets 11 
by the pair of feeding rollers 31 is exerted to the central area of the 
cut sheets 11, allowing the uppermost cut sheet 11 to naturally deform to 
be convex in a width-wise direction, without causing the cut sheet 11 to 
be skewed. The same is applied to a case in which multiple pairs of 
feeding rollers are provided. If there is only one feeding roller 
provided, friction pieces may be preferably provided at both sides of the 
feeding roller. In case that the feeding roller is eccentrically disposed 
or mounted in plurality at various positions, the friction pieces may be 
provided in a corresponding number at corresponding positions to balance 
the feeding rollers. 
The friction member 33 is positioned within the area defined by the outside 
dimension of the feeding rollers 31 as can be seen from FIG. 2, where the 
cut sheet 11 comes into frictional contact with a frictional surface 33a. 
The distance between the frictional surface 33a and a nipping position N, 
as indicated on FIG. 3 where the feeding rollers 31 contact the uppermost 
cut sheet 11 to advance the cut sheet 11, is much smaller than that of the 
prior art arrangement described above. The cut sheet 11 between the 
nipping position and the frictional surface 33a is restrained from being 
unfavorably deformed to ensure that the cut sheet 11 is received by the 
friction member 33 with an appropriate amount of frictional force, 
enhancing the performance of the friction member 33 and allowing it to be 
suitable for high-speed feeding. Favorable results were obtained by 
determining the angle of the friction member 33 in the manner described 
above. 
However, when the friction member 33 is disposed so near the feeding 
rollers 31 as in this arrangement, the leading end of the cut sheet 11 is 
prone to residual deformation: The leading edge is stopped by the friction 
surface 33a, while the other part of the cut sheet pressed by the feeding 
roller 31 is advanced, as a result of which the cut sheet 11 can become 
deformed as shown in FIG. 6. 
In order to prevent such residual deformation, the friction member 33 must 
be able to resiliently warp or to be backed away against an urging force 
of a rebounding spring. The friction member of the first embodiment is 
made of a resilient sheet, which is preferable in terms of production 
cost. More specifically, a polycarbonate film may be employed as the 
material for the resilient sheet, and a film of about 200 micrometers 
thickness which is available on the market will provide enough rebounding 
force. The friction member 33 allows the deforming cut, sheet 11 to 
proceed along the curved frictional surface 33a of the resilient friction 
member 33, thereby preventing residual deformation of the cut sheet 11. 
The frictional surface 33a may be formed to be substantially planar or 
slightly curved so as to smoothly allow the cut sheet 11 to pass through 
thereon. 
The friction member 33 may be extended to a position over an axis of a 
rotation shaft 31c for the feeding roller 31, so that the friction member 
33 can be initially warped by contacting the rotation shaft 31c. The angle 
made between the frictional surface 33a and an outermost cut sheet 11 may 
be preferably set within the range of about 90.degree. to 120.degree., 
whereby the cut sheet 11 is advanced to contact with the frictional 
surface 33a at an angle within this range, and can be smoothly conveyed 
along the curved frictional surface 33a. In contrast to the prior art 
arrangement in which the contacting angle of the cut sheet 11 is set 
smaller to enhance the sheet separating capacity, the cut sheet is 
advanced toward the frictional surface 33a at a wider angle of 90.degree. 
to 120.degree. in this embodiment, which was determined based on an 
experiment conducted by the inventors. The separation of cut sheets 11 is 
successfully made by disposing the friction member 33 close to the feeding 
roller 31 which allows the whole advancing force of the cut sheet to be 
used to prevent residual deformation, thereby increasing the sheet 
conveying speed. 
The frictional surface 33a is provided with a necessary friction 
coefficient by coating the surface of polycarbonate film with a material 
having a high friction coefficient such as urethane resin by a silk screen 
printing method or the like. The frictional surface 33a may preferably 
have about a 1.0 to 1.5 static friction coefficient with respect to 
standard fine paper. This makes the frictional force between the 
frictional surface 33a and the outermost cut sheet 11 to be greater than 
that between the frictional surface 33a and the following cut sheets 11, 
assuring the sheet separating performance. 
The feeding roller 31 is so positioned that when given one turn to send out 
one cut sheet 11 and the rear end of the cut sheet 11 is passed through 
the nipping position N, the friction member 33 becomes freed from the 
pressing force of the cut sheet 11 and returns to its initial position. 
Other cut sheets 11 following the previously fed cut sheet 11 are pushed 
back by the rebounding force of the friction member 33 to prevent them 
from becoming obstructions to the succeeding sheet feeding. The friction 
member 33 with the prescribed angle condition can successfully accomplish 
such object. 
When the base 36 of the sheet feeder unit 1 is opened to reveal the sheet 
conveying path 34, the friction member 33 is forwardly drawn out slipping 
under a rotating shaft 31c of the feeding rollers 31. The rotating shaft 
31c thus prevents the friction member from returning to its initial 
position as shown by a phantom line in FIG. 1, when the base 36 is closed. 
For that reason, a boss 31a is provided on the rotating shaft 31c which 
catches the tip of the friction member 33 to push it back to the position 
denoted by the solid line when the feeding rollers 31 are rotated to start 
feeding sheets, thus ensuring automatic restoration of the friction member 
33 to its proper position. 
&lt;Second Embodiment&gt; 
A second embodiment differs from the first embodiment in that the feeding 
roller 31 is provided with a projection 31d on its rotation shaft 31c 
which contacts the tip of the friction member 33 only for a given period 
of time before and after feeding sheets. 
Referring to FIG. 7A, the projection 31d contacts the friction member 33 
lower than its tip, thereby causing the friction member 33 to be warped 
when the feeding roller 31 is stationary. As the feeding roller 31 starts 
to rotate, the projection 31d causes the friction member 33 to warp 
further as shown in FIG. 7B, while the feeding roller 31 starts to feed 
the uppermost cut sheet 11 as shown in FIG. 7C. A broken line in FIGS. 7B 
and 7C denotes the friction member 33 in its initially curved state. As 
can be seen, the friction member 33 is further warped to cause the angle 
.theta. to become wider at the time when the sheet feeding is started. As 
shown in FIG. 7D, the uppermost cut sheet 11 is separated by the 
frictional contact between itself and the frictional surface 33a and fed 
out. The same effects as those of the first embodiment can be thereby 
achieved, while residual deformation of cut sheet 11 is further prevented 
by widening the angle between the cut sheet 11 and the frictional surface 
33a only when the cut sheet is advanced toward the frictional surface 33a. 
The projection 31d can also serve as the boss 31a described in the first 
embodiment. 
&lt;Third Embodiment&gt; 
FIGS. 8A and 8B show a third embodiment of the present invention in which a 
crank 31e is provided with the rotation shaft 31c of the feeding roller 
31, which, when the shaft is rotated, goes over the friction member 33. 
The third embodiment differs from the first embodiment in this point but 
achieves the same effects. When the sheet feeding is completed, the 
friction member 33 can automatically return to its initial position 
without being obstructed by the rotation shaft 31c by the provision of the 
crank 31e as shown in FIG. 8A. The cut sheets 11 other than the uppermost 
one are pushed back by this rebounding force of the friction member 33 and 
the edges of the cut sheets 11 are aligned to facilitate the succeeding 
sheet separation. The amount of maximum eccentricity of the crank 31e may 
be set smaller than the radius of the feeding roller 31. Since the 
friction member 33 with pushed by the cut sheet 11 is deformed outside the 
outer dimension of the feeding roller 31, the friction member 33 and the 
crank 31e do not obstruct each other. 
&lt;Fourth Embodiment&gt; 
A fourth embodiment of the present invention shown in FIGS. 9 to 11 is also 
implemented as a sheet feeder unit incorporated in a copying machine 10 as 
shown in FIG. 4 for feeding recording sheets, which is given the reference 
numeral of 1a to be distinguished from the sheet feeder unit 1 of the 
foregoing embodiments. The arrangement of the entire sheet feeder unit 1a 
is substantially the same as that of the first embodiment, in which like 
parts are given the same reference numerals, and only the differences will 
be hereinafter described. 
The friction member 133 of the fourth embodiment is made of a rigid plate, 
and separates the outermost cut sheet 11 from the other cut sheets by the 
frictional force generated between itself and the cut sheet 11. Unlike the 
friction member 33 in the first embodiment, the rigid friction member 133 
of the fourth embodiment is not resiliently bent back when the cut sheet 
is advanced thereto. 
In this embodiment, the friction member 133 consists of a plate made of 
plastic or metal. The surface of the friction member 133 is coated with a 
material which generates a great frictional force such as urethane resin 
or the like by a silk screen printing method to provide a frictional 
surface 133a. Preferably, the frictional surface 133a has a static 
frictional coefficient of about 1.0 to 1.5 with respect to a standard 
sheet of fine paper, and the angle made between thefrictional surface 133a 
and the uppermost cut sheet 11 is set between 90.degree. to 120.degree.. 
The friction member 133 in this embodiment is formed to be continuously 
bending in such a way that its inclination becomes gradually moderate 
along the direction of frictional contact as can be seen from FIGS. 9 and 
10A. Specifically, friction member 133 may be provided with a given 
curvature by any appropriate means such as a thermal bending process which 
allows for prevention of springback of the plastic material. The friction 
member 133 made of plastic or metal may be thick enough to be rigid but 
not so thick as to cause the cut sheet to be unfavorably deformed. 
As described above, the friction member 133 is formed to be curved instead 
of being resiliently pushed back by an advancing cut sheet 11, and such 
arrangement allows the friction member 133 to separate cut sheets of any 
physical properties in a manner described below. The cut sheet 11 advanced 
toward the friction member 133 is first contacted against a steep slope at 
a lower part of the friction member 133, making an angle acutely enough to 
direct the cut sheet upwardly. As the cut sheet 11 proceeds toward the tip 
of the friction member 133, the portion of the curved frictional surface 
133a with a more moderate curvature allows the cut sheet 11 to readily 
pass through thereon. Cut sheets having any physical properties can be 
thus stably separated and fed one by one without any residual deformation. 
After the uppermost cut sheet 11 is fed out, the other cut sheets are 
stopped by the steep lower part of the friction member 133 and returned to 
their set position by gravity, thus preventing an obstruction for the next 
sheet feeding. Though rigid in this embodiment, the friction member 133 
may also be given a certain amount of resiliency to assist the above 
described function. 
Alternatively, when a pair of feeding rollers 31 is provided and the 
friction member 133 is disposed in the middle between the pair of feeding 
rollers 31, the friction member 133 may be so constructed to have its 
frictional surface 133a latitudinally warped with its central part 
extended toward the upstream side of the sheet feeding direction as shown 
in FIG. 10B. This helps the smooth separation of cut sheets 11, as the 
friction member 133 is capable of conveying a naturally deformed cut sheet 
11 along its own curved surface. 
The friction member 133 has such a length that its tip is positioned lower 
than the rotation shaft 31c of the feeding roller 31, so that it does not 
obstruct the open/close operation of the base 36 to open and close the 
sheet conveying path 34, as the tip of the friction member 133 can pass 
through under the rotation shaft 31c. 
&lt;Fifth Embodiment&gt; 
A fifth embodiment of the present invention is substantially the same as 
the fourth embodiment, and only differs in that the friction member 133 is 
configured in a wavy form as shown in FIG. 12. Like parts are denoted by 
the same reference numerals and the description thereof will be omitted. 
As can be seen from FIG. 12, the inclination of the slope becomes 
alternatively sharp and moderate along the direction of frictional contact 
at a given curvature to make at least two undulations. The friction member 
133 made of plastic or the like may be undulated, for example, by a 
thermal bending process or any other means which allows for the prevention 
of springback of the plastic plate. The friction member 133 made of 
plastic or metal may be thick enough to be rigid but not as thick as to 
cause the cut sheet to be unfavorably deformed. 
The same effects can be thereby achieved as those of the fourth embodiment, 
and the surface of the friction member 133 in this embodiment assures even 
more stable sheet feeding by effectively separating a cut sheet 11 with 
its plurality of undulations. 
&lt;Sixth Embodiment&gt; 
A sixth embodiment of the present invention shown in FIGS. 13 to 15 is also 
implemented as a sheet feeder unit incorporated in a copying machine 10 as 
shown in FIG. 4 for feeding recording sheets, which is given the reference 
numeral of 1b to be distinguished from the sheet feeder unit of the 
foregoing embodiments. The arrangement of the entire sheet feeder unit 1b 
is substantially the same as that of the fourth embodiment, in which like 
parts are given the same reference numerals, and only the differences will 
be hereinafter described. 
In this embodiment, a plurality of friction members 233 are disposed along 
a width direction of the cut sheet 11. For example, three friction members 
233A-233C are respectively supported at their base ends by the support 
metal 37 at different angles and distanced from each other as shown in 
FIGS. 13 and 14. Specifically, the friction member 233A is contacted with 
the tip of the cut sheet 11 at a different angle from that between the 
other friction members 233B and 233C and the cut sheet 11 as shown in FIG. 
14. 
By this arrangement, the uppermost cut sheet 11 is first stably conveyed by 
the first friction member 233A, while the second and third friction 
members 233B and 233C assist the smooth sheet feeding, dissipating 
deformation stress of the cut sheet 11. Cut sheets 11 of any thickness can 
be thereby separated without any residual deformation and stably supplied 
one by one. The friction members 233A-233C are disposed in symmetry around 
the center of the cut sheet 11, but the disposition of the friction 
members may be variously arranged other than the example shown in FIG. 14. 
In case that the feeding rollers 31 is provided, the first friction member 
233A may be disposed in the middle between the pair of friction rollers 
31, contacting the cut sheet 11 at a more acute angle than that between 
the other friction members 233B, 233C and the cut sheet 11. By this 
arrangement, the cut sheet 11 is basically treated by the central friction 
member 233A, by which the cut sheet 11 is smoothly separated along a 
natural curve of deformation without a twist or distortion. The first 
friction member 233A may be set to be shorter than the other friction 
members 233B, 233C so that, when supported at different angles, the 
heights of all the friction members 233A-233C are substantially aligned at 
the same level, which is desirable to prevent residual deformation of the 
cut sheet 11 when passing over the friction members 233A-233C. 
&lt;Seventh Embodiment&gt; 
A seventh embodiment of the present invention shown in FIGS. 16 to 18 is 
also implemented as a sheet feeder unit incorporated in a copying machine 
10 as shown in FIG. 4 for feeding recording sheets, which is given the 
reference numeral of 1c to be distinguished from the sheet feeder unit of 
the foregoing embodiments. The arrangement of the entire sheet feeder unit 
1c is substantially the same as that of the first embodiment, in which 
like parts are given the same reference numerals, and only the differences 
will be hereinafter described. 
The friction member 333 in the seventh embodiment is, similarly with the 
first embodiment, made of a resilient sheet such as a polycarbonate film, 
which can be available on the market, having about 200 micrometers 
thickness to provide a proper amount of rebounding force. The surface of 
the polycarbonate film is coated with a material having a great frictional 
coefficient such as urethane resin applied by a screen printing method, 
preferably with a screen of about 200 meshes and finishing with 
thermosetting treatment for 30 minutes at 80.degree. C. Preferably, the 
frictional surface 333a has a static frictional coefficient of about 1.0 
to 1.5 with respect to a standard sheet of fine paper, and the angle made 
between the frictional surface 333a and the uppermost cut sheet 11 is set 
between 90.degree. to 120.degree.. 
Further, the friction member 333 is so configured that the width of the 
frictional surface 333a greatly increases from a base side (B1) toward a 
distal end (B2) along the direction of frictional contact denoted by an 
arrow X in FIG. 17A. 
When the cut sheet 11 is advanced by the feeding roller 31 to cause the 
friction member 333 to bend back and proceeds toward the tip of the 
friction member 333, the angle .theta. made between the friction member 
333 and the cut sheet 11 as shown in FIG. 5A becomes acute. However, the 
friction member 333, formed to have a frictional surface 333a of which 
width becomes sharply greater toward the distal end thereof, can provide a 
sufficient amount of frictional force and keep the cut sheet 11 favorably 
warped, thereby assuring the stable sheet separation. 
The above described configuration of the frictional surface 333a can be 
readily formed by providing notches 333b at side edges of the friction 
member 333 as shown in FIG. 17A. Alternatively, the frictional surface 
333a of such configuration may be provided on a rectangular friction 
member 333 by coating urethane resin in a proper form as described above 
or by any other coarsening treatments to increase the frictional 
coefficient. 
Also, instead of using a resilient sheet for the friction member 333, the 
friction member 333 may be made of a rigid material and given a rebounding 
force with a spring, without changing any of the above described effects 
and advantages. 
Specifically in this embodiment, side edges 333c, configured in accordance 
with the figure of the frictional surface 333a of which width is sharply 
increased from B1 to B2, are formed to rise slightly toward the upstream 
side of the sheet feeding direction from narrower parts 333d to wider 
parts 333e. According to this arrangement, when the leading edge of the 
cut sheet 11 reaches the side edges 333c while causing the friction member 
333 to resiliently bend back, the upturned side edges 333c catch the cut 
sheet 11 and push it back by the amount H, causing a twist in a direction 
denoted by an arrow Y while making the whole width of the frictional 
surface 333a at every position thereof contact with the cut sheet 11. Such 
frictional resistance is exerted on the advancing cut sheet 11, causing 
the cut sheet 11 to warp, thereby facilitating the separation from the 
following cut sheets 11. This, with the help of a sharp increase in width 
of the frictional surface 333a, enhances the sheet separating capacity, as 
well as decreases a necessary maximum width of the friction member 333. 
Further, the friction member 333 of this embodiment is provided in a 
symmetrical pair as can be seen from FIGS. 17A and 17C, which further 
helps the friction member 333 to convey the cut sheet 11 smoothly along a 
lateral curve thereof without unfavorable residual deformation. The 
friction member 333 may also be provided in plurality and dispersedly 
disposed. 
&lt;Eighth Embodiment&gt; 
An eighth embodiment of the present invention is substantially the same as 
the seventh embodiment, and only differs in that the friction member 333 
is provided with the notches 333b at inner edges thereof so that the whole 
width of the frictional surface 333 becomes sharply increased from B1 to 
B2 as shown in FIG. 19. The same effects as those of the seventh 
embodiment can be thereby achieved. Further, it is advantageous to have an 
aperture 41 made by the notches 333b of the pair of the friction members 
33, as this can be utilized in case a nozzle 42 is provided to blow air 
toward the leading edges of the cut sheets 11 to assist the sheet 
separation. Such an arrangement may be applied to a high speed machine. In 
any case, the aperture 41 may not be necessarily provided. 
&lt;Ninth Embodiment&gt; 
A ninth embodiment of the present invention shown in FIGS. 20 to 23 is also 
implemented as a sheet feeder unit incorporated in a copying machine 10 as 
shown in FIG. 4 for feeding recording sheets, which is given the reference 
numeral of 1d to be distinguished from the sheet feeder unit of the 
foregoing embodiments. The arrangement of the entire sheet feeder unit 1d 
is substantially the same as that of the first embodiment, in which like 
parts are given the same reference numerals, and only the differences will 
be hereinafter described. 
In this embodiment, similarly with the seventh embodiment, the friction 
member 433 is made of a resilient sheet such as a polycarbonate film, 
having about 200 micrometers thickness to provide a proper amount of 
rebounding force. The surface of the polycarbonate film is coated with a 
material having a great frictional coefficient such as urethane resin 
applied by a screen printing method, preferably with a screen of about 200 
meshes and finishing with thermosetting treatment for 30 minutes at 
80.degree. C. Preferably, the frictional surface 433a has a static 
frictional coefficient of about 1.0 to 1.5 with respect to a standard 
sheet of fine paper, and the angle made between the frictional surface 
433a and the uppermost cut sheet 11 is set between 90.degree. to 
120.degree.. Under favorable ambient conditions with low humidity, the 
friction member 433 being fabricated as described above can have a stable 
sheet feeding performance for soft or thin cut sheets as well as thick 
sheets such as postcards. 
Further, in this embodiment, an adjusting means 51 is provided for 
adjusting a rebounding force of the friction member 433 when pushed 
backward by the advancing cut sheets 11 as shown in FIGS. 20 to 22. When 
the sheet feeding performance is unstable due to various reasons including 
types of cut sheets 11 and the humidity which varies depending on weather, 
season, or region, the most appropriate sheet separating characteristics 
corresponding to differences in types of cut sheets or ambient conditions 
can be obtained by adjusting the rebounding force of the friction member 
433 with the adjusting means 51. 
The adjusting means 51 in this embodiment comprises a resilient sheet 52 
which is attached to the back of the friction member 433 to assist the 
friction member 433 by giving a part of the rebounding force. The 
rebounding force can be increased or decreased by attaching and detaching 
the resilient sheet 52, or can be finely adjusted by using a resilient 
sheet 52 with different resiliency depending on its material or thickness. 
Even with the use of the same resilient sheet 52, the resiling force of 
the friction member 433 can be adjusted by changing the position or range 
of attachment of the resilient sheet 52. 
The resilient sheet 52 is arranged to be adjustable in its position on the 
backside of the friction member 433 in a manner described below. The 
friction member 433 may be, for example, bonded at its lower end to the 
front inner side of a slit 37a which vertically penetrates the support 
wall 37, while the resilient sheet 52 is arranged to be vertically movable 
within the slit 37a behind the friction member 433 and is fixed with a 
screw 53 extending from the backside of the support wall 37 into the slit 
37a at a given height. Since the screw 53 can also secure the friction 
member 433 together with the resilient sheet 52, the friction member 433 
may not be separately bonded to the support wall 37. Though not essential, 
a step 37b may be provided within the slit 37 to receive the lower end of 
the friction member 433 as shown in FIG. 20. By providing such step 37b, 
the friction member 433 can be readily set at a given regular height 
before being secured by the screw 53 when it is unnecessary to adjust the 
height of the friction member 433. 
When the area of the resilient sheet 52 contacting the backside of the 
friction member 433 is changed by adjusting its height, the rebounding 
force of the friction member 433 when pushed backward by the advancing cut 
sheet 11 as shown in FIG. 23 is changed even with the same resilient sheet 
52. By increasing the area of the resilient sheet 52 in contact with the 
friction member 433, the more the rebounding force of the friction member 
433 increases, thus enhancing the sheet separating performance, and by 
decreasing the area of the resilient sheet 52 contacting the friction 
member 433, the more the rebounding force of the friction member 433 
decreases. The friction member 433 can thus be set to have desired sheet 
separating characteristics corresponding to types of the cut sheets or the 
ambient conditions depending on weather, season, or region. 
It is also possible to mount the resilient sheet 52 fixedly instead of the 
friction member 433, in which case the rebounding force may be changed by 
adjusting the height of the friction member 433. Although the rebounding 
force generated by the resilient sheet 52 may be fixed, the whole 
rebounding force can be adjusted by varying the length of the friction 
member 433, allowing for delicate control of the sheet separating 
characteristics. Theoretically, the rebounding force is adjustable by the 
relative movements between the friction member 433 and the resilient sheet 
52 in the direction of frictional contact between the friction member 433 
and the cut sheet 11. 
When the base 36 is opened, the guide 35 is exposed and provides an opening 
50, through which the screw 53 is manually operated to adjust the height 
of the resilient sheet 52. Such operation may be, however, variously 
modified. 
&lt;Tenth Embodiment&gt; 
A tenth embodiment of the present invention shown in FIG. 24 is 
substantially the same as the ninth embodiment except that the adjusting 
means 51 is arranged to have the resilient sheet 52 with its tip 52a 
obliquely contacting the backside of the friction member 433 from behind. 
The same parts are given the same reference numerals of which illustration 
and description will be omitted. 
Since the resilient sheet 52 provides a part of the rebounding force of the 
resilient sheet 52 at the tip thereof where it increases the frictional 
force between the friction member 433 and the cut sheet 11, the desired 
amount of rebounding force, which is defined corresponding to the material 
or thickness of the resilient sheet 52, can be finely adjusted to have 
appropriate sheet separating characteristics for cut sheets of various 
kinds or conditions. 
As the friction member 433 warps by being pushed back by the cut sheet 11, 
the resilient sheet 52 is also bent backward, contacting a greater area of 
the friction member 433 thus increasing the rebounding force. The 
resilient sheet 52, attached near the tip of the friction member 433, 
greatly helps the friction member 433 to generate enough frictional force 
between the frictional surface 433a and the leading edge of the cut sheet 
11 to separate one cut sheet 11 from another. The resilient sheet 52 may 
be positioned lower to come apart from the friction member 433, allowing 
for the control of the point of time when the resilient sheet 52 starts 
contacting and assisting the friction member 433. In such a case, the 
resilient sheet 52 contacts the friction member 433 nearer to the base end 
thereof thus generating less rebounding force. The separating 
characteristics can be thereby finely adjusted. 
&lt;Eleventh Embodiment&gt; 
An eleventh embodiment shown in FIG. 25 is substantially the same as the 
ninth and the tenth embodiments except that the adjusting means 51 
comprises the resilient sheet 52 being configured in the form of the 
letter T, consisting of a narrow tape-like leg portion 52b and a pressing 
portion 52c extending to both sides at the tip of the leg portion 52b. The 
height of the resilient sheet 52 is varied to change the position of the 
pressing portion 52c and its contact with the friction member 433 in order 
to adjust the rebounding force, similarly with the tenth embodiment. 
&lt;Twelfth Embodiment&gt; 
In a twelfth embodiment shown in FIG. 26, another slit 37c is provided in 
the support wall 37 behind and at a certain distance from the slit 37a for 
the friction member 433. The resilient sheet 52 is inserted in this slit 
37c parallel to and separated from the friction member 433 at a certain 
distance. In addition, a support portion 52c is provided to the distal end 
of the resilient sheet 52 which is contacted with the friction member 433. 
Similarly with the tenth embodiment, the height of the resilient sheet 52 
is adjusted to change the contacting position, thus having the same 
effects and advantages as those of the previously described embodiments. 
&lt;Thirteenth Embodiment&gt; 
In a thirteenth embodiment shown in FIG. 27A, the adjusting means 51 is 
capable of adjusting the height of the resilient sheet 52 disposed 
parallel to and at a certain distance from the back of the friction member 
433 as well as adjusting the distance between the resilient sheet 52 and 
the friction member 433. For such adjustment, the resilient sheet 52 is 
mounted to a metal base 52d which is urged by a leaf spring 54 within the 
slit 37b toward a direction away from the friction member 433 as shown in 
FIG. 27A. The base 52d is pressed against the force of the spring 54 by 
the screw 53 bolted from behind the slit 37b so that the position of the 
resilient sheet 52 with respect to the friction member 433 can be 
adjusted. The height adjustment of the resilient sheet 52 is made by 
moving the base 52d against the frictional force between itself and the 
leaf spring 54. In order to stably support the base 52d with the spring 54 
and the screw 53, the spring 54 is configured to be wavy having a 
multiplicity of undulations in the widthwise direction as shown in FIG. 
27B, so as to have an enough pressing force for retaining the base 52d in 
position when vibrated or pressed by external force. 
The adjustment of the height of the resilient sheet 52 and the distance 
between the resilient sheet 52 and the friction member 433 may be also 
accurately made by other mechanisms using various other means including 
cams or screws. 
Since the resilient sheet 52 is disposed parallel to and distanced from the 
friction member 433 in this embodiment, it comes into contact with the 
friction member 433 from the tip thereof only when the friction member 433 
is bent to a certain extent, and starts to resiliently warp with the 
friction member 433 which is further being bent, thus having the same 
effects as those of the tenth embodiment. The timing when the friction 
member 433 comes into contact with the tip of the resilient sheet 52 can 
be determined by adjusting the distance between the resilient sheet 52 and 
the friction member 433, and the area of contact between the base side of 
the resilient sheet 52 and the friction member 433 can be adjusted by 
varying the height of the resilient sheet 52. 
The resilient sheet 52 in the ninth to thirteenth embodiments described 
above may be applied to a friction member made of a rigid material 
supported around a shaft at its lower end and given a resiling force with 
a spring, without failing to have the same effects and advantages. 
&lt;Fourteenth Embodiment&gt; 
In a fourteenth embodiment shown in FIG. 28, the adjusting means 51 is 
capable of adjusting the angle of friction member 433 made of a resilient 
sheet. As shown in FIG. 28, the friction member 433 is mounted to the base 
52d, which is rotatably supported at its lower end around a shaft 55 
within the slit 37b. The base 52d is urged by a spring 56 toward the 
downstream side of the sheet feeding direction. The angle of inclination 
of the friction member 433 around the axis 55 can be adjusted by fixing 
the base 52d at a given position with the screw 53 bolted from behind the 
slit 37b. 
When the friction member 433 is greatly inclined, the cut sheet 11 can 
readily pass over the friction member 433 with little force, whereas the 
cut sheet 11 receives a greater force from the friction member 433 by 
setting the angle of inclination closer to vertical. Desired sheet 
separating characteristics can be thereby obtained. 
&lt;Fifteenth Embodiment&gt; 
A fifteenth embodiment is shown in FIG. 29, in which the friction member 
433 made of a rigid material is lever-like rotatably supported around a 
shaft 55 at its lower end and given a rebounding force by a spring 57 
toward its initial position contacting a stopper 38. One end of the spring 
57 is received by a spring holder 53a rotatably mounted to the end of the 
screw 53. The adjusting means 51 adjusts the rebounding force of the 
friction member 433 provided by the spring 57 by adjusting the screw 53 
bolted from the backside of the support wall 37. By this adjustment, 
various sheet separating characteristics can be defined corresponding to 
types of cut sheet 11 or ambient conditions. 
The adjustment of the resiling force of the friction member in the ninth to 
fifteenth embodiments described above can be automatically made based on 
the information on types of paper which is either inputted or 
automatically detected, or the information on ambient conditions such as 
humidity which is automatically detected. Such automatic adjustment of the 
resiling force of the friction member can be readily conducted with an 
electric actuator. 
&lt;Sixteenth Embodiment&gt; 
A sixteenth embodiment of the present invention shown in FIGS. 30 to 34 is 
also implemented as a sheet feeder unit incorporated in a copying machine 
10 as shown in FIG. 4 for feeding recording sheets, which is given the 
reference numeral of 1e to be distinguished from the sheet feeder unit of 
the foregoing embodiments. 
The feeding roller 31 of the sheet feeder unit 1e disposed in the copying 
machine 10 comprises a first feeding roller 31A positioned in the middle 
of the sheet conveying path 30 through which the cut sheets 11 sent out 
from the feeder cassette 21 pass, and a pair of second feeding rollers 31B 
arranged symmetrically about the first feeding roller 31A for conveying 
cut sheets 11 of the size greater than a given regular size. The first 
feeding roller 31A always comes to a central position of all sizes of cut 
sheets 11. 
The friction member 533 comprises a first friction member 533A disposed at 
the same position of the first feeding roller 31A or close to the same, 
and second friction members 533B arranged at the same position of the 
second feeding rollers 31B or close to the same. The first friction member 
533A is supported at its lower end being secured to the support wall 37 
standing upright under the sheet conveying path 30 by any appropriate 
means such as bonding or bolting. The second friction members 533B are 
positioned closer to the center than the second feeding rollers 31B as 
shown in FIG. 31, and supported in the feeder cassette 21 in such a way 
that the second friction members 533B can advance to the separating 
position denoted by a solid line in FIG. 31 and retract therefrom to the 
retracted position denoted by a broken line by the function of a slide 
guide 61 shown in FIGS. 30 and 32 to 34. The slide guide 61 is secured to 
a predetermined position by being bolted to the feeder cassette 21 with a 
screw 63. 
The slide guide 61 is provided with a cam follower 62 which engages with a 
cam groove 22a disposed in the side guide 22 at both sides. When the side 
guide 22 is moved to a position where it determines the position of the 
side of the cut sheet of greater size, for example, the position denoted 
by the solid line in FIG. 31, the second friction members 533B are 
advanced to the separating position by the function of the cam groove 22a. 
When the side guide 22 is moved to a position where it defines the side of 
the cut sheet 11 of smaller size as shown by the broken line in FIG. 31, 
the second friction members 533B are withdrawn to the retracted position. 
Accordingly, the second friction members 533B come to their separating 
position to separate the cut sheets 11 only when the cut sheets 11 of the 
size greater than a given regular size are to be fed. 
In this embodiment, the friction member 533 made of a polycarbonate film of 
about 200 micrometers in thickness is fabricated similarly with the 
previously described embodiments. Preferably, the angle made between the 
frictional surface 533a and the uppermost cut sheet 1 is set between 
90.degree. to 120.degree.. The first and second friction members 533A and 
533B fabricated as described above are disposed together with the first 
and the second feeding rollers 31A and 31B in such an arrangement as 
described above. 
The first feeding roller 31A and the first friction member 533A disposed in 
the middle between the pair of second feeding rollers 31B and the second 
friction members 533B is capable of feeding cut sheets of the size smaller 
than a given normal size one by one, because the sheet conveying force can 
be evenly applied to the central part of the cut sheets 11. Such settings 
of the sheet conveying force and the sheet separating characteristics are 
also applied to cut sheets 11 of larger size. Further, when feeding cut 
sheets of the size larger than the normal size, the second feeding roller 
31B and the second friction members 533B disposed symmetrically on both 
sides of the first feeding roller 31A provide the necessary sheet 
conveying force and sheet separating characteristics, which may not be 
sufficiently provided by the first feeding roller 31A and the friction 
member 533A. It is thus prevented that sheet conveying force is 
exceedingly exerted or unequally applied, causing the cut sheet 11 to be 
fed obliquely. Accordingly, such arrangement of the feeding rollers and 
friction members allows the sheet feeder unit to have a stable sheet 
feeding performance irrespective of sizes of the cut sheet. 
If the second friction members 533B were positioned far from the center of 
the cut sheet 11, they would tend to obstruct the advancing action of the 
cut sheet 11. For that reason, each second friction member 533B is 
disposed at the inner side of each second feeding roller 31B. In other 
words, the second friction members 533B are symmetrically positioned 
within the range where the cut sheet is forcibly sent out by the pair of 
second feeding rollers 31B and the first feeding roller 31A in the middle, 
allowing the cut sheet 11 to positively advance, pushing back the second 
friction members 533B. The sheet feeding performance is thereby further 
enhanced, as it is prevented that the cut sheets are stopped or fed 
obliquely in case the friction members are positioned far away from the 
center. Since the second friction members 533B are not disposed directly 
under each second feeding roller 31B but inwardly shifted therefrom, the 
second friction members 533B provide less sheet feeding capacity as 
compared to the first friction member 31A. In addition to this, the width 
of each second friction member 533B is set to be smaller while the 
material, thickness, length, and disposing conditions are set identical to 
those of the first friction member 533A in this embodiment, so as to 
prevent the sheet separating characteristics from exceeding the desired 
level. Such adjustment can be variously made by setting various parameters 
including conditions of the frictional surface 533a. 
When the cut sheet 11 pushed out by the feeding rollers 31 is smaller than 
a given size passing through inside the second feeding rollers 31B, the 
second friction members 533B positioned at the inner side of the second 
feeding rollers 31B are automatically withdrawn from the sheet conveying 
path 30 by the function of the cam groove 22a and the cam follower 62, as 
the side guide 22 is moved to determine the position of the side of the 
cut sheet 11. It is thus prevented that the sheet feeding characteristics 
exceed the desired level when smaller cut sheets are fed. 
When the side guide 22 is moved to a position which defines the position of 
the side of the cut sheet 11 as being larger than a given size, the second 
friction members 533B are advanced to the separating position via the cam 
groove 22a and the cam follower 62, so as to effect the separation of cut 
sheets one by one. 
The means for causing the second friction members 533B to retract is 
preferably constructed to link with the movement of the side guide 22, as 
such structure is simple while acting reliably. The construction of the 
retraction means is of course not limited to such mechanism, and the 
second friction member 533B may be electrically actuated to advance and 
retract based on the detection signals obtained by electrically detecting 
the position of the side guide 22. 
Although the embodiment has been described as a centering type sheet 
feeder, the entire structure of the embodiment may be applied to the sheet 
feeder which aligns the cut sheets thereon at one side, because a 
plurality of feeding rollers 31 prevents the cut sheet 11 from being fed 
obliquely. In either case, at least one of the first feeding roller 31A 
and the first friction member 533A may be also provided in plurality. 
If the cut sheets 11 are aligned on one side of the feeder tray, the first 
feeding roller 31A and the first friction member 533A may be disposed at a 
common position where cut sheets 11 of all sizes pass and only one of the 
second feeding roller 31B and the second friction member 533B may be 
provided at a position where cut sheets 11 of larger size pass, in order 
to perform stable sheet feeding for all sizes of cut sheets 11. Also, the 
friction member 533 may not necessarily be made of a resilient sheet, and 
may be made of a rigid material and axially supported at its end with a 
spring providing a resiling force. 
&lt;Seventeenth Embodiment&gt; 
In a seventeenth embodiment shown in FIG. 35, the second friction member 
533B are arranged to tilt laterally between the separating position 
denoted by a solid line and the retracting position withdrawn from the 
sheet conveying path 30 as denoted by a broken line. The movement of the 
second friction members 533B is linked with the movement of the side guide 
22 between the position which defines the side of the cut sheets being 
greater than a normal size (solid line) and the position which defines the 
side of the cut sheets being smaller than the normal size (broken line). 
This embodiment differs from the sixteenth embodiment only in the 
direction of retracting movement of the friction members 533B, and has the 
same effects and advantages as those of the sixteenth embodiment. 
Description of a specific linking means in this embodiment will be thus 
omitted. The second friction members 533B may also be retracted from the 
conveying path 30 by tilting the same along the sheet feeding direction. 
Method and means for causing the friction member to retract from the 
conveying path 30 are not limited to specific ones described herein. 
&lt;Eighteenth Embodiment&gt; 
An eighteenth embodiment of the present invention shown in FIGS. 36 to 38 
is also implemented as a sheet feeder unit incorporated in a copying 
machine 10 as shown in FIG. 4 for feeding recording sheets, which is given 
the reference numeral of if to be distinguished from the sheet feeder unit 
of the foregoing embodiments. 
In this embodiment, the friction member 633 made of a polycarbonate film of 
about 200 micrometers in thickness is fabricated similarly with the 
previously described embodiments. Preferably, the angle made between the 
frictional surface 633a and the uppermost cut sheet 11 is set between 
90.degree. to 120.degree.. The friction member 633 is disposed at a 
certain distance from the feeding roller 31, and a restriction member 65 
is mounted at the upstream side of the sheet feeding direction above the 
cut sheet 11 for limiting the upward deformation of the cut sheet 11. 
Even if the leading edge of the cut sheet 11 is downwardly curled as shown 
by a phantom line in FIG. 36, the restriction member 65 presses the sheet 
to rectify its curve as denoted by a broken line, thereby causing the cut 
sheet 11 to advance straight toward the friction member 633. Similarly, 
even when the leading edge of the cut sheet 11 may be partly bulged as 
denoted by a phantom line in FIG. 37B caused by the resistance generated 
when the cut sheet proceeds toward the frictional surface 633a, the 
restriction member 65 opposed to the leading edge of the cut sheet 11 from 
above in the vicinity of the upstream side of the sheet feeding direction 
presses down the cut sheet effectively as shown by the broken line in FIG. 
36 to allow the cut sheet 11 to advance toward the friction member 633 
smoothly at a predetermined angle. Cut sheets of many types can thereby be 
separated from each other without any residual deformation and fed stably. 
Specifically in the eighteenth embodiment, the friction member 633 is 
disposed substantially in the middle between a pair of feeding rollers 
distanced from each other. The uppermost cut sheet 11 can be pushed 
straight out by the two feeding rollers 31 proportionally and evenly 
exerting the sheet conveying force, while the friction member 633 
positioned in the middle provides a desired amount of frictional force. 
The arrangement of this embodiment may also be applied to a sheet feeder 
which aligns cut sheets at one side thereof, as the cut sheets can be 
straightly conveyed due to the provision of a pair of feeding rollers 31. 
Further, an additional feeding roller may be provided or a pair of 
friction members may be mounted on both sides of one feeding roller. It is 
anyway advantageous to provide such a restriction member as described 
above. In case the friction member 633 is configured to contact the whole 
width of the cut sheet 11, the restriction member 65 is preferably 
provided across the entire width of the friction member 633 except where 
there are the feeding rollers 31, or is disposed in plurality. 
The restriction member 65 comprises a pad 71 made of a plate having a 
smooth surface 71a facing the cut sheet 11. Such pad 71 is compact and can 
be flexibly mounted as shown in FIG. 36 corresponding to needs, thus being 
able to be placed even between the rotation shaft 31c of the feeding 
roller 31 and the cut sheet 11 which are close to each other. The smooth 
surface 71a is positioned higher than the nipping position N where the 
feeding roller 31 contacts the cut sheet 11, thus limiting or rectifying 
the deformation of the cut sheet only when the cut sheet 11 is curled up 
or bulged. Otherwise, the pad 71 does not apply any external force to the 
cut sheet 11. 
&lt;Nineteenth Embodiment&gt; 
In a nineteenth embodiment shown in FIG. 39, the restriction member 65 is 
comprised of a roller 72 having a smaller outside dimension than the 
feeding roller 31. The roller 72 is rotatably supported by a shaft 73 at 
the distal end of a lever 74, which is pivotally supported at its base end 
by a shaft 75 within the copying machine 10. 
Since the roller 72 is small and compact, it can be mounted very close to 
the friction member 633 without adversely affecting the movement of the 
rotating shaft 31c of the feeding roller 31. The roller 72 is supported to 
be freely rotatable and to run idly when contacting to the cut sheet 11, 
thus causing no adverse effects or damage to the cut sheet 11. As it 
presents no problems if the roller 72 is lightly pressed against the cut 
sheet 11 from above, the roller may be supported by the lever in such a 
way that the roller 72 is brought to contact with the cut sheet 11 by its 
own weight, whereby the functions of rectifying the deformation or bulge 
of the cut sheet 11 can be further enhanced. It is also possible to 
lightly urge the lever 74 to cause the roller 72 to be pressed against the 
cut sheet 11. 
Other parts and effects are identical to those of the eighteenth 
embodiment, and like parts are given the same reference numerals, of which 
illustration and description will be omitted. 
The present invention has been described with respect to a sheet feeder 
unit which feeds sheets from the top side, but it is of course possible to 
apply the present invention to a sheet feeder unit sending out sheets from 
the bottom side. 
It is also possible to variously combine any of these embodiments from 1 to 
19, or to apply one arrangement to another. 
Although the present invention has been fully described by way of examples 
with reference to the accompanying drawings, it is to be noted that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be construed as being 
included therein.