Paper feed apparatus capable of feeding of common use papers and specifically processed papers

The paper feeding device of the present invention comprises a paper holder for holding a stack of large number of paper sheets; a first roller for sheetwise feeding out paper sheets from the stack in or on the holder; a regular rotation roller for further feeding each of paper sheets and rotatably mounted at a position downstream from the first roller when looking in the paper feeding direction; and a paging roller mounted in opposition to the regular rotation roller. The paging roller is driven always in such a rotational direction for drawback of sheet or sheets in the reverse direction relative to the regular and forward paper feed direction when one or more common class paper sheet or sheets or a plurality of special class paper sheet of a different quality then common class paper sheet is/are fed between the regular rotation roller and the paging roller. In addition the paging roller is rotated as a follower roller following the fed sheet under the action of the regular rotation roller when only one special class paper is introduced between the both rollers.

FIELD OF THE INVENTION 
This invention relates generally to paper feed apparatuses. It relates more 
specifically to paper feed apparatuses applicable to electronic 
photocopiers and fitted with a sheet stack or overlapped sheet loosening 
and individual paper feeding apparatus or briefly paging mechanism 
arranged at or in proximity of a downstream position from the paper 
feed-out or dispensing roller when seen generally in the paper feeding 
direction and comprising regularly rotating feed roller means and normally 
reversely rotating paging roller means cooperating therewith. 
BACKGROUND OF THE INVENTION 
As is well known to those skilled in the art, various kinds of paper are 
used nowadays for photocopiers. These papers or more broadly sheets are, 
however, classified mainly into two categories. One is the common class 
paper and the other is the special class paper. The common class papers 
herein referred to as such, are most commonly used in citizens' daily 
life. This kind of paper has a relatively rough surface on which, 
generally, additives thereto remain in powder-like state and as deposits 
thereon. During passage between and through a pair of feed rollers, it is 
believed that these additives will act as rolling medium to a certain 
degree, thus providing a lesser friction coefficient similar to rolling 
one, relative to the rotating feed rollers. The special class papers 
include overhead projector paper, briefly referred to herein as OHP-sheet; 
secondary original drawing sheet; offset printing master sheet and the 
like, having a relatively smooth surface and remaining on the surface 
substantially no powder-like additives. During use, this kind of paper is 
believed to provide a sliding friction coefficient through and between a 
pair of feed rollers. Therefore, the coefficient amounts to a relatively 
high value. 
It is demanded for the paper feed mechanism used in the photoelectric 
copier machine to use not only the comnon class papers, but also special 
class papers as specifically referred to above, and indeed, to provide a 
highly stabilized feedability. 
In the case of such a paper feed mechanism arranged at a downstream 
position when seeing in the paper feed direction and comprising a 
regularly revolving feed roller and a normally reversedly rotating paging 
roller as a mating member cooperating therewith, when the latter roller is 
driven in the reversed sense which means such rotational direction as 
returning the sheet(s) in the reversing direction, while the feed roller 
is kept always in regular rotation in paper feeding direction, for feeding 
a sheet of the special class paper, having thus a considerably high 
friction coefficient, failure in paper feed has occurred rather 
frequently, thereby constituting a grave drawback in the art. 
For dissolving such a conventional drawback in conventional art, a torque 
limiter was fitted to the paging roller, and indeed, for such purpose as 
to provide a stabilized paper feed performance, even in use of special 
class paper sheets having a high friction coefficient as was referred to 
hereinabove, while, on the other hand, always assuring the reliability in 
the paging roller performance. 
As an example thereof, Japanese Open Utility Model Publication No. 
(unexamined) Sho-60-47741 may be raised. In this specific prior art, a 
torque limiter is fitted to the paging roller and as the material for the 
both mutually mating rollers, polynorbonene rubber representing a superior 
antifrictional performance is utilized for molding purpose for these 
rollers. 
With provision of such torque limiter attached to in the aforementioned 
way, and if a paper sheet is fed at the nip of these mating rollers, the 
paging roller will rotate in the paper feed executing direction by virtue 
of the follower like motion of the paging roller under the influence of 
the sheet-carrying force provided by the regularly revolving feed roller. 
If, however, two or more paper sheets are introduced between these 
rollers, the paging roller will be caused to reverse its rotational 
direction for urging the second and further sheets, if any, to make a 
return movement towards the paper feed cassette. Therefore, it will be 
seen that even if a sheet of special class paper, having a high friction 
coefficient should be introduced into the nip portion between the both 
rollers, troubles in paper feed operation could not be encountered. 
On the other hand, we have experienced, however, such that the paging 
mechanism, even if fitted with torque-limiting means represents several 
drawbacks, as will be later more fully described with reference to the 
drawings. 
SUMMARY OF THE INVENTION 
A main object of the present invention is to provide an improved paper 
feeding device having a highly stabilized paper feed performance. 
Another object is to provide an improved paper feeding device of the above 
kind, irrespective of kind and nature of the feeding paper, either of 
common class or of special class, and without any feeding troubles as 
otherwise frequently met with. 
As a preferred advantageous aspect of the inventive paper feeding 
apparatus, the latter comprises means for holding a stack of large number 
of paper sheets; a first roller for sheetwise feeding out paper sheets 
from the stack in or on said holding means; a regular rotation roller for 
further feeding each of said paper sheets and rotatably mounted at a 
position downstream from said first roller when seeing in paper feeding 
direction; a paging roller mounted in opposition to said regular rotation 
roller; and drive means for driving said regular rotation roller and 
paging roller, said paging roller being operated at different modes 
depending upon the class of the paper sheet. 
The paging roller is driven always in such a rotational direction for 
draw-back of sheet or sheets in the reverse direction relative to the 
regular and forward paper feed direction when one or more common class 
paper sheet or sheets or a plurality of special class paper sheet is/are 
fed between said regular rotation roller and said paging roller. In 
addition, said paging roller is rotated as a follower roller following the 
fed sheet under the action of said regular rotation roller when only one 
special class paper sheet is introduced between the both rollers. 
The drive means comprises a drive source and a torque limiter adapted for 
transmitting the driving force from said drive means to said paging roller 
and within a predetermined range of torque. 
The above and other objects, features and advantages of the present 
invention will become more apparent from the following description when 
taken in conjunction with the accompanying drawings in which substantially 
a preferred embodiment of the present invention together with certain 
related prior art mechanisms, are shown by way of illustrative example.

DETAILED DESCRIPTION OF RELATED PRIOR ART 
In advance of commencement of detailed description of substantially a 
preferred embodiment of the invention, structure and related drawbacks of 
torque limiting means will be set forth hereinbelow and with reference to 
the accompanying drawings, so far as the related prior art is concerned. 
Although the torque limiter per se will be more fully described later 
herein, conventional drawbacks are further described with reference to 
substantially FIGS. 8 and 9, for better understanding of the invention. 
In FIG. 9 representing a graph for illustration of the rotating state of a 
paging roller, wherein the rotational speed, v, of the roller has been 
plotted against time, t. 
With ON-state of a paper feed signal, a paper feed clutch, not shown, is 
brought into ON. Then, a regularly rotatable roller 1 is driven in the 
paper feed direction "A", while a paging roller 2 is driven in the reverse 
direction through the intermediary of a torque limiter, not shown. With 
ON-state of the paper feed clutch, a torque limiter is operated by the 
friction force with the regularly rotating roller 1 and the paging roller 
2 will perform a regular rotation as a follower roller to the first roller 
1. In this respect, reference may be had to step (i) of FIG. 8. 
If more than two paper sheets S1;S2 are fed to the nip existing between the 
two rollers 1 and 2, a slip may occur between the sheets S1;S2 and thus 
the torque limiter will be brought into disabled and unoperational state 
and the paging roller 2 will turn to its reversedly rotating state. 
However, since there is a inertia force preventing such a sudden 
rotational change, the roller 2 will continue the regular rotation for the 
time being (refer to step (ii) in FIG. 8. Only after execution of regular 
revolution for a certain predetermined time period by virtur of the 
inertia force as referred to above, the roller 2 turns to rotate 
reversingly (refer to steps (iii) and (iv) in FIG. 8. When the paper feed 
clutch becomes OFF, the leading edge cf first sheet S1 is already squeezed 
by and between carrier rollers 30 and 40, FIG. 1, arranged at a downstream 
position, thereby the sheet being energized physically with a conveying 
force, while the regular rotation roller 1 is rotated in regular 
direction, but in the follower manner to the advancing movement of the 
first sheet S1 by virtue of OFF-state of the one way clutch (refer to step 
(v) in FIG. 8. On the other hand, second and occasionally accompanying 
further sheets, groupingly denoted with single symbol S2, will once 
protrude slightly downstream from the nip point and then pulled back to a 
point in close and rear proximity of the nip line, when seeing in the 
general paper conveying direction. 
In order to carry out the above pull-back operation for the second and 
occasionally appearing further sheets S2 rear of the nip line after 
execution of forward drive of the first sheet S1, the carrying momentum H2 
in the region including steps (iii) and (iv) must be larger than that H1 
in the region (ii) applied to the second and further sheets S2 by the 
paging roller 2, as is schematically illustrated in FIG. 9. 
It should be noted, however, that the torque limiter as used therein is 
designed and arranged to have a relatively small torque in such a way that 
when only a single sheet, irrespective of its material kind, either common 
class or special class, is squeezed at the nip line, the paging roller 
performs a normal rotational movement ny acting as a follower. Thus, at an 
occasional introduction of two or more paper sheets into the nip line, the 
time period necessary for transfer from regular to reverse rotation of 
page roller 2, from step (ii) to (iii) shown in FIG. 3, will become 
considerably longer than the optimal. In addition, it is to be noted that 
ON-period of the paper feed clutch should not be longer than a 
predetermined relatively short time interval, and indeed, in consideration 
of the sheet delivery force providing the timing destined at out-delivery 
roller pair as at 30;40, FIG. 1, which is mounted in downstream proximity 
of the paging mechanism. As a result, the time period allocated to steps 
(iii) and (iv) will become correspondingly short. If additional two or 
more sheets S2 should occasionally be introduced in position, the leading 
edges could frequently be squeezed at the nip, thus leaving thereat 
without being further conveyed. And, further occasionally, these 
overlapped sheets may be thence further conveyed to and caught by the 
delivery rollers as at 30;40. Such phenomenon is called "double feed" 
which means naturally a grave drawback in the art. Even if the leading 
edges of second and further sheets S2 should have been drawn back to such 
a point slightly rear of the nip line, the paging roller 2 will execute 
regular rotation as a kind of follower by receiving motion by contact with 
the forwardly moving first sheet S1, thereby the paging roller performing 
"accompanied rotation" (refer to a dotted small arrow shown at step "v" in 
FIG. 8 and resulting in an "accompanying double feed" of the second and 
further sheets. As is highly well known to those skilled in the art, this 
phenomenon constitutes another conventional drawback in the art. 
DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
Now, referring to FIG. 1, a static photocopier to which a preferred 
embodiment of the inventive paper feeding device has been applied will be 
described in detail. 
Numeral 10 represents a paper feed cassette, having a vertically movable 
mounting plate 11 mounting a number of sheets S formed into a stack. The 
mounting plate 11 is electrically urged upwards by a push-up roller 15 
kept in pressure contact therewith from below. The cassette-containing 
space of the machine, appearing in FIG. 1 is called "charging space". As 
seen, the upper surface of the paper stack S is kept in pressure contact 
with a paper feed-out roller 16. With regular rotation, shown by a small 
arrow a, paper sheets S is fed out, one by one, in the general feeding 
direction, shown by arrows "A", naturally beginning from the uppermost 
sheet. There is provided a paging mechanism arranged at a downstream 
position in the regular feed passage and in proximity of the paper 
feed-out roller 16. 
The paging mechanism comprises an upper, regular rotation roller 20 and a 
lower, paging roller 21 cooperating therewith. The paging roller 21 is 
mounted on a small movable frame member 22 through a short shaft 23, said 
frame member having an extension arm 22a which is pivotably mounted on a 
stationary pin 24 for allowing the frame member to execute a pivotal 
movement around the pin acting as a kind of pivot pin. 
A tension spring 25 is tensioned between outer end of said frame extension 
and a certain fixed point, not shown, thereby the paging roller being 
always urged resiliently and upwardly towards pressure contact with the 
regular rotation roller 20 for cooperation therewith. 
As shown, the feed-out roller 16 and the regular rotational roller 20 are 
rotating in the regular direction as shown by respective small arrows a, 
adapted for feed-out of the sheet S, one by one and towards the conveying 
roller pair 30;40. The general paper feed direction is shown by arrows 
"A", as was referred to hereinbefore. 
On the contrary, the paging roller 23 is normally driven in the reverse 
direction, as shown at "b" of a double head arrow in FIG. 1, in comparison 
with the regular paper feeding direction "A". The necessary driving force 
for normal rotation of these rollers 16;20 and 21 derives from a main 
motor and proper and co-related transmission systems, not shown, for the 
reason of highly well-known nature. 
As seen, a conveyer roller pair 30;40 is provided at a downstream position 
when seeing in the paper feeding direction and at a small distance from 
the paging mechanism comprising several constituents 20-25, as was 
referred to hereinbefore. Although not shown, several further and similar 
conveyer roller pairs are provided within the machine. All these conveyer 
rollers including those which are denoted with 30;40, are driven from a 
main motor, not shown, and indeed, in the regular rotational direction as 
shown by small arrows "a" for execution of paper sheet conveying jobs. 
Paper feed roller 16 and regular rotation roller 20 are made of a 
conventionally employed material, while, on the other hand, paging roller 
21 comprises a core cylinder member 21a preferably made of foam resin 
material and wrapped with a cover cylinder 21b of rubber, thus showing a 
double layer structure. Kinds of material employed; hardness and surface 
treatment particulars will be set forth later more specifically. 
Paging roller 21 is fitted with a torque limiter which comprises, as a 
preferred embodiment shown in FIG. 2, a shaft member 26, a boss member 27 
coupled therewith and a coil spring 28 provided between hollow core member 
21a and boss member 27 and held under compression. When a reversely 
rotating torque is transmitted to paging roller shaft 23, thence further 
to boss member 27 and through the coil spring 28 held under pressure 
between the latter and foam resin-made hollow core 21a which is naturally 
part of the paging roller 21, thereby the latter being rotated in the 
reverse direction. This reversingly rotating state of paging roller 21 
will be referred to as "off service" position hereinafter. 
On the other hand, when an outside driving force in the regular rotational 
direction, larger than the spring pressure at 28, is applied to the paging 
roller, a slip may occur between the end of spring 28 and boss 27 or foam 
resin core 21a, thereby rotation of the paging roller being turned to 
regular one. This state will be referred to as "in service" or "operating" 
hereinafter. 
In the practice of the present invention, important are such factors as the 
torque value necessary for operation of the torque limiter from "off 
service" to "in service"; friction force acting between the roller 20/21 
and the sheet S, and among others, the following formulae must be 
satisfied: 
EQU .mu.i.Ns&gt;.mu.t.Ns&gt;Ts/R&gt;.mu.p.Ns&gt;.mu.o.Ns (1) 
EQU .mu.r.Ns&gt;Ts/R (2) 
where 
Ts: torque value at torque limiter; gr.cm. 
Ns: pressure force at paging roller; gr. 
R: radius of paging roller; cm. 
.mu.i: friction coefficient between regular rotation roller and sheet; 
.mu.t: friction coefficient between paging roller and sheet; 
.mu.p: friction coefficient between paging roller and common class sheet; 
.mu.o: friction coefficient between sheets; 
.mu.r: friction coefficient between regular rotation roller and paging 
roller. 
As shown by the formula (1), the acting force (Ts/R) at the torque limiter 
is set to be higher than the friction force (.mu.p.Ns) between common 
class sheet, having a relatively small friction coefficient, and the 
paging roller 21, and lesser than the friction force (.mu.t.Ns) between 
special class sheet, having a relatively high friction coefficient, and 
the paging roller. Further, the friction force (.mu.i.Ns) between regular 
rotation roll 20 and sheet S is set to be higher than any one of the 
foregoing values: (.mu.t.Ns), (Ts/R) and (.mu.p.Ns). And further, the 
intersheet friction force (.mu.o.Ns) is always smaller than any one of the 
foregoing specific values. 
Still further, as shown by the formula (2), the acting force (Ts/R) at the 
torque limiter is set to be lesser than the friction force (.mu.r.Ns) 
between regular rotation roller 20 and paging roller 21. 
As a reference, in the case of conventional automatic paper feeders, the 
torque value, Ts, at the torque limiter for paging roller has been set to 
satisfy the following formula: 
EQU .mu.o.Ns&lt;Ts/R&lt;.mu.p.Ns 
where, .mu.o: friction coefficient between common class sheets. 
In the present embodiment, more specifically, the pressure force, Ns, of 
paging roller is 300-400 gr. 
______________________________________ 
the torque value, Ts, 500-600 gr.cm; 
radius of paging roller, R 
1.5 cm; 
friction coefficient, .mu.r, 
2.0-3.0, preferably 
between regular rotation roller 
about 2.5; 
20 and paging roller 21 
friction coefficient, .mu.p, between 
0.7-1.2, 
common class sheet and paging roller 21 
preferably 
1.0-1.2; 
friction coefficient, .mu.t, between paging roller 
1.5-3.0, 
21 and special class sheet 
preferably 1.6-2.5; 
intersheet friction coefficient, .mu.o,: 
for common class sheets about 0.3-0.7; 
for special class sheets 
about 0.3-1.0. 
______________________________________ 
The regular rotation roller 20, made of polynorbonene, hardness: 25 degree 
(JIS - A), while, in the case of paging roller 21, foam material 21a is 
urethane resin, and rubber material 21b is polyolefine rubber, hardness 40 
degrees (ASKER-C), thickness: 0.8 mm. The surface of polyolefine rubber 
has been roughened by means of sand paper or by sand blasting, to 
100.+-.50 .mu.m or so. Adoption of covering with polyolefine rubber 
material and surface-treated as was referred to above concerning the 
paging roller 21, was made for the purpose of proper adjustment of 
friction coefficient and additionally for absorbing occasionally 
generating vibrations during cooperation with the mating roller 20. In 
this way, necessarily invited time-functional variation of the friction 
coefficient can be suppressed to a possible minimum. 
Next, the operation mode of paging roller will be described more in detail 
with reference to FIGS. 3 and 4 in combination. In these drawings, steps 
(i)-(v) correspond to those denoted (i)-(v) in FIGS. 8 and 9. 
FIG. 3 illustrates the feeding mode with use of common class sheets, while 
FIG. 4 illustrates the corresponding steps using, however, special class 
sheets. 
With the paper feed clutch ON, the roller 20 is driven to rotate in the 
regular rotational direction. As for the paging roller 21, its shaft 
portion 23 is driven in the reverse direction at this stage. Since, 
however, the friction force .mu.r.Ns, has been preset to be stronger than 
the operational force, Ts/R, of the torque limiter, the latter can 
operate, thereby paging roller 21 operating as a kind of a follower to the 
regular rotation roller 20. In this respect, reference shall be had to 
step (i) at FIGS. 3 and 4. 
When more than two sheets, S1; S2, are introduced to the nip line, the 
torque limiter will become off-service, by virtue of the intersheet 
friction force, .mu.o.Ns, being lesser than the operational force, Ts/R, 
resulting into rotational conversion at paging roller 21 from regular to 
reverse. However, on account of the very existence of rotational inertia 
thereat, the conversion, refer to FIGS. 3 and 4 at (iii), is brought 
about, only after a lapse of a certain short time period of regular 
revolutions, refer to steps (ii) in FIGS. 3 and 4. Since the torque force 
value, Ts, at the torque limiter, has been preset at a certain higher 
level than that adopted in the conventional technique, the time lapse 
before execution of rotation reversal will be highly short. And, by such 
rotation reversal, the second and occasionally existing further sheets, 
S2, will be drawn back to such a position where the otherwise leading edge 
or edges of this or these sheets arrive(s) at slightly rear of the nip 
line. 
In this instance, only first sheet S1, exists with its originally leading 
edge covering the nip. In the case of the first sheet S1 being of the 
common class, the foregoing formula (1): Ts/R&gt;.mu.p.Ns will be satisfied, 
the torque limiter being off service and kept in unoperational position 
and the paging roller 21 continuing its reverse revolution, refer to step 
(iv) in FIG. 3. On the other hand, as for the regular revolution roller 
20, the friction force (.mu.i.Ns) between roller and sheet is higher than 
the friction force (.mu.p.Ns) between paging roller (21) and common class 
sheet, the first common sheet S1 will be fed forward, even though the 
torque limiter is kept in off-service position. Further, in the case of 
the first sheet S1 belonging to the special class and kept by its 
originally leading edge in contact with the nip, the condition: 
.mu.t.Ns&gt;Ts/R shown in the foregoing formula is satisfied, and then the 
torque limiter is brought into operation, thereby the rotation of paging 
roller 21 being converted to regular one (refer to FIG. 4 at (iv) by 
acting as a follower to the special class first sheet S1 which is now 
being fed forward. 
Even when second and occasionally further sheets S2 are urged to invade 
into and through the nip line, the torque limiter is instantly brought 
into off-service position by virtue of the intersheet friction force 
(.mu.o.Ns) acting between S1 and S2 preselected lesser than that 
(.mu.t.Ns) acting between special class sheet and paging roller 21 and 
further, since the aforementioned relationship: .mu.t.Ns&gt;Ts/R is 
satisfied, resulting in invitation of the reversed rotation thereof and 
second and further sheets being drawn back to slightly rear of the nip 
line. 
When the fed first sheet S1 has passed through the paging mechanism, thence 
instantly conveyed forward to the carrier roller pair 30;40 and caught 
therebetween and still further conveyed on exclusively by subjecting to 
the conveying force provided by this roller pair, until the sheet reaches 
a resist roller, not shown, which is positioned in rear of the transfer 
section, not shown, of the machine. 
Simultaneously with reception of carrier force by the leading end of first 
sheet from the carrier roller pair 30;40, paper feed clutch becomes off, 
and the paging roller 21 will hold its off-service position, refer to 
steps (v) in FIGS. 3 and 4, since the torque limiter is kept in 
off-service position. It should be noted at this stage of description that 
the torque limiter acts as a kind of brake means for the paging roller 21. 
In the following, various and different characteristics caused by material 
difference and the like of said both rollers 20; 21 will be described 
based upon our practical experiments. 
In the chart shown in FIG. 5, stress-strain characteristics of the roller 
as per se will be described with use of various materials. In this case, 
the stress (N) is found from the formula: N=A.multidot.X.sup.R and values 
A and R for several selected materials are shown in the following Table 1. 
TABLE 1 
______________________________________ 
material A B 
______________________________________ 
Silicone EPDM Polymer 
165 1.14 
Polyolefine 440 1.14 
Polynorbonene 1450 1.46 
Foam-Urethane 1030 1.25 
______________________________________ 
In the following Table 2, 
TABLE 2 
______________________________________ 
Temp. 
26 deg. C., 43% RH 
5 deg. C., 35% RH 
Sheet 
OHP- Common OHP- 
Common Class 
Sheet Class Sheet 
Sheet, Unit non- Sheet, Unit 
non- 
material weight, 64 g/m.sup.2 
treated Wt., 64 g/m.sup.2 
treated 
______________________________________ 
Silicone-EPDM 
0.82 2.19 0.83 2.60 
Polymer 
Polyolefine 
0.90 1.85 0.70 1.70 
Polynorbonene 
1.90 2.37 1.95 2.40 
Foam-Urethane 
0.90 1.45 0.57 1.66 
______________________________________ 
As may be well understood, silicone EPDM polymer and polyolefine are highly 
suitable for the manufacture of paging roller 21 as used in the present 
invention. 
As for the friction coefficient thereof, it amounts to about 1.0 or so for 
common class sheets, and to about 2 or so for special class sheets, as is 
clearly seen from Tale 2. The material polynorbonene represents solid 
rubber, generally being used, and shows a high friction coefficient about 
2 or so, relative to common class and special class sheets. Thus, this 
material is highly suitable for the manufacture of regular rotation roller 
20. 
On the other hand, the material foam-urethane represents friction 
coefficient about 0.6 or so for common class sheets and about 1.5 or so 
for special class sheets. This material has been used for conventional 
reverse drive type paging rollers without fitting with torque limiting 
means. In the case of special class sheets, however, this material shows 
too much higher friction coefficient, resulting in an excess degree of 
sheet-drawback force and giving rise frequently to failures in paper sheet 
feeding operation. 
Further, in the case of conventional torque limiter systems, both regular 
rotation roller end and paging roller have been prepared from general 
purpose solid rubber. In case of a single sheet kept in contact by its 
leading edge with the nip line between these two rollers, the torque Ts 
exerted by torque limiter must be properly preset, so as to satisfy the 
necessary mathematical requirement of Ts/R&lt;.mu.p.Ns, in order to let the 
paging roller rotate always definitely and reliably in the regular 
sheet-feeding direction by revolving in regular sense for execution of 
"accompanied" rotation. 
However, as in the present embodiment, use is made of silicone-EPDM-polymer 
or polyolefine rubber for the preparation of outside peripheral layer of 
the paging roller 21, the feeding job of common class sheet can not be 
disturbed, even if tee roller should be kept in reversed rotation, refer 
to FIG. 3 at step (iv), since these specifically selected materials 
demonstrate highly favorable friction coefficient less than unity relative 
to common class sheets. 
FIG. 6 is a combined chart showing various sheet-feeding characteristics at 
different torque values Ts relative to common class sheet, unit weight: 64 
gr/m.sup.2. In this case, in the positive value field, the sheet-feeding 
force, (F), while a single sheet is kept in contact with the nip line, and 
in the negative value field, the paging and rearwardly drawback force (Fr) 
relative to the second sheet while two overlapped sheets are kept in 
contact with the nip, are plotted against the pressure force (Ns) 
appearing at the paging roller 21. 
As may be well understood from this chart, paper- or sheet feeding force 
(F) will become larger with increase of pressure force (Ns) and smaller 
with increase of torque value (Ts). The paging force (Fr) will become 
larger with increase of the torque value (Ts). At smaller values of torque 
(Ts), the paging force (Fr) will become reduced with increase of pressure 
force (Ns). 
FIG. 7 is a chart showing the generating percentage of overlapped sheets 
feeding troubles plotted against the pressure force (Ns) and with various 
values of torque (Ts), say 420 gr.cm, favorable low generating percentage 
could be realized only with a highly limited range of pressure force (Ns), 
say 180 gr or so. However, with stepwise increase of torque value (Ts) to 
540; 590 and 770 gr, the range of pressure force (Ns) capable of providing 
favorable low percentage of overlapped sheets can be considerably 
broadened, resulting in considerable improvement to avoid such failured 
feeds. 
It will be clearly understood that with use of specifically selected-out 
materials for the preparation of regular rotation roller and paging 
roller, even if the paging roller 21 is kept in reverse rotational state, 
successful forward paper feed operation can be realized for a single 
common class paper sheet existing at the nip, only by keeping the 
condition of Ts/R&gt;.mu.p.Ns existing. Further, even when a single sheet of 
special class exists at the nip, successful and reliable paper sheet 
feeding can be realized, by keeping the condition of .mu.t.Ns&gt;Ts/R 
existing, and by keeping the paging roller 21 in regular rotating 
condition acting as a follower. 
It may be further possible, by use of a considerably higher values of the 
torque (Ts) than those conventionally adoped and preset by those skilled 
in the art, to provide an automatic high speed paper sheet feeding 
apparatus satisfying conventional sincere demands and capable of 
substantially suppressing otherwise liably invited accompanying or 
accompanied feedings as conventionally and frequently met with. 
It will be clear that the automatic paper feeding apparatus embodying the 
inventive principles foregoingly set forth generally as well as 
specifically illustrated, must not be limited only to the emodiment(s) per 
se. As an example, the torque limited may be embodied in other styles and 
arrangements, such as powder limitter type, a magnetically combined type 
wherein a permanent magnet is combined with magnetic sheet or sheets. 
Although the present invention has been fully described by way of example 
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.