MACHINE A COPIER

COPYING MACHINE

Abrégé français

Cette invention concerne une machine à copier alimentée feuille à feuille à partir d'un magasin d'alimentation. Entre la partie alimentation et la partie copiage de la machine se trouve un séparateur servant à empêcher plusieurs feuilles d'arriver simultanément à la partie copiage. De plus, entre le séparateur et la partie copiage se trouve un détecteur de position des feuilles. Les feuilles sortant simultanément du magasin sont séparées par le séparateur qui, après s'être mis en synchronisme avec la partie copiage grâce au détecteur de position précité, alimente celle-ci feuille à feuille pour éviter les copies mal centrées.

Abrégé anglais

A copying machine wherein sheets stacked in a
sheet cassette are conveyed one by one to a sheet
copying portion to take copies. Between a sheet
supply portion and the copying portion there is
disposed a sheet separating mechanism for separating
plural sheets when taken out at a time from the sheet
supply portion. Further, between the said sheet
separating mechanism and the sheet copying portion
there is disposed a sheet position detecting measure.
Plural sheets delivered from the sheet supply portion
are separated one by one by the sheet separating
mechanism, then after taking synchronism with the
copying portion through the sheet position detecting
measure, each sheet is conveyed, so copying can be
done accurately.

Revendications

Claims:
1. A copying machine comprising:
a sheet separating mechanism including a roller
adapted to rotate to feed a sheet in a forward
direction, a separating piece having a predetermined
frictional force and adapted to hold the sheet between
said separating piece and said roller, a pressing piece
for pressing said separating piece toward said roller;
a sheet guide means comprising a low friction
member, disposed on an upstream side in a sheet
conveyance direction from a sheet supply portion to a
sheet copying portion with respect to a contact portion
of said roller on the surface of said separating piece;
and
a sheet position detecting means disposed between
said sheet separating mechanism and said sheet copying
portion, said sheet supply portion taking out stacked
sheets, said sheet copying portion copying to such
sheets,
wherein said sheet separating mechanism separates
only a sheet which is in close contact with said roller
from other sheets when a plurality of sheets are taken
out between said sheet supply portion and said sheet
copying portion from said sheet supply portion.
2. A copying machine according to claim 1, wherein
said sheet separating mechanism is constructed so that
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if said predetermined frictional force between the
surface of said separating piece and the sheet which is
in close contact therewith among the plurality of sheets
is N3, a second frictional force between said roller and
the sheet which is in close contact therewith among the
plurality of sheets is N1, and a third frictional force
between the plurality of sheets is N2, said frictional
forces satisfy the following relationship: N1>N3>N2.
3. A copying machine according to claim 1, wherein
said sheet position detecting means further comprises a
second guide means having a register roller, thereby
detecting a front end position of the sheet which has
been conveyed from said sheet separating mechanism, and
wherein said second guide means stops said sheet for a
time period to allow synchronism with said sheet copying
portion and thereafter conveying said sheet.
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Description

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COPYING MACHINE
The present invention relates to a copying machine
wherein sheets stacked in a sheet cassette are conveyed
one by one to a sheet copying portion and copies therein.
The prior art will be discussed in detail
hereinbelow with respect to the drawings.
The present invention has been accomplished for
solving the problems of the prior art and it is an object
thereof to provide a copying machine capable of
separating and delivering only the sheet to be fed and
copying sheets accurately one by one even in the event of
feed of plural sheets at a time.
It is another object of the present invention to
provide a copying machine capable of separating and
delivering only the sheet to be fed and copying sheets
accurately one by one even in the event of feed of plural
sheets at a time, by a simple and inexpensive means
without using a complicated and expensive apparatus.

It is a further object of the present invention to
provide a copying machine which is far superior to the
conventional copying machines in point of sheet
separating accuracy and performance in feeding paper and
can be'realized at a relatively low cost.
In the copying machine of the present invention, in
order to achieve the above-mentioned objects, a sheet
separating mechanism for separating plural sheets when
taken out from a sheet supply portion is provided
between the sheet supply portion and a copying portion,
and a sheet position detecting means is provided between
the sheet separating mechanism and the sheet copying
portion.
Thus, in the copying machine of the present
invention, in the event of feed of plural sheets at a
time in the sheet supply portion, the sheets are
separated one by one in the sheet separating mechanism
and the position of each sheet thus separated is
detected to take synchronism with the sheet copying
stage.
In accordance with one aspect of the present
invention there is provided a copying machine
comprising: a sheet separating mechanism including a
roller adapted to rotate to feed a sheet in a forward
direction, a separating piece having a predetermined
frictional force and adapted to hold the sheet between
said separating piece and said roller, a pressing piece
for pressing said separating piece toward said roller; a
sheet guide means comprising a low friction member,

3 ~
disposed on an upstream side in a sheet conveyance
direction from a sheet supply portion to a sheet copying
portion with respect to a contact portion of said roller
on the surface of said separating piece; and a sheet
position detecting means disposed between said sheet
separating mechanism and said sheet copying portion,
said sheet supply portion taking out stacked sheets,
said sheet copying portion copying to such sheets,
wherein said sheet separating mechanism separates only a
sheet which is in close contact with said roller from
other sheets when a plurality of sheets are taken out
between said sheet supply portion and said sheet copying
portion from said sheet supply portion.
The above and further objects and novel features of
the present invention will more fully appear from the
following detailed description when read in connection
with the accompanying drawings, in which:
Fig. 1 is a schematic sectional view of a body of a
conventional copying machine;
Fig. 2 is a schematic sectional view of a copying
machine according to an embodiment of the present
nvent lon;
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2 ~ 4
Fig. 3 is a partial enlarged view of a separating
mechanism disposed in the copying machine body shown in
Fig. 2; and
Fig. 4 is a schematic sectional view of a body of a
copying machine according to another embodiment of the
present invention.
Fig. 1 is a sectional view showing a conventional
paper feeder disclosed, for example, in Japanese Patent
Publication No. 52378/88~ In the same figure, the
reference numeral 1 denotes a photosensitive drum for
copying; the numeral 2 denotes a sheet; numeral 3 denotes
a sheet cassette; numeral 4 denotes an inner plate on
which are stacked sheets 2 in the sheet cassette 3;
numeral 5 denotes a spring for pushing the inner plate 4
upwards; numeral 6 denotes a sheet separating pawl for
separating the sheets 2; numeral 7 denotes a pickup
roller for conveying the sheets 2; numerals 8a and 8b
denote register rollers; numerals 9a and 9b denote fixed
guide plates for guiding each sheet 2 to the register
rollers 8a and 8b; numeral 10 denotes a movable guide
plate for guiding each sheet 2 to the register rollers 8a
and 8b; numerals lla and llb denote guide plates for
guiding each sheet 2 to the photosensitive drum 1;
numeral 12 denotes a corona discharger; numeral 13
:

denotes a separating belt provided at an end portion of
the photosensitive drum l; numeral 14 denotes a
separating roller; numeral 15 denotes a separating roller
which is in pressure contact with the separating roller
14; numeral 16 denotes a fixing device; and numeral 17
denotes a conveyor belt for conveying each sheet 2 to the
fixing device 16.
The operation will now be described. The sheets 2
which are each conveyed in synchronism with an image on
the photosensitive drum 1 are stacked on the inner plate
4 in the sheet cassette 3. The inner plate 4 is pushed
upwards by the spring 5 and the height of the stacked
sheets 2 is kept constant by the sheet separating pawl 6.
In this position the sheets 2 are delivered one by one
from the sheet cassette 3 and conveyed by a predetermined
length with rotation of the pickup roller 7 having a
sectional shape corresponding to a partially cut-out
circumference. Each sheet 2 thus delivered is guided by
the fixed guide plates 9a, 9b and the movable guide plate
10 and reaches the register rollers 8a, 8b, then is
further guided by the guide plates lla, llb and reaches
the photosensitive drum 1.
At an end portion of the photosensitive drum 1 there
is provided the separating belt 13, and one end of the
sheet 2, in a separated state from the photosensitive
h

drum 1, is supplied with potential by the discharge from
the corona discharger 12. A toner image on the drum 1 is
here transferred onto the sheet 2. After completion of
the transfer, the ~ront end of the sheet 2 is separated
from the drum 1 by the separating belt 13 and is held
between the separating roller 14 and the separating
roller 15 which is in pressure contact with the roller
14. In this way the front end of the sheet 2 is
completely separated from the photosensitive drum 1.
Subsequently, the sheet is conveyed to the fixing device
16 by the conveyor belt 17.
The conventional copying machine is constructed as
above, so in the event of feed of plural sheets at a
time, the plural sheets are conveyed in a stacked state.
Consequently, the conveyance of sheet and the copying
operation may not be synchronized with each other, or
there may arise deterioration of the image ~uality due to
paper jam or defective transfer.
Preferred embodiments of the present invention will
be described in detail hereinunder with reference to the
accompanying drawings. The portions indicated by the
same reference numerals as those referred to above in
connection with Fig. l represent the same portions, so
explanation will be omitted with respect to some of them.
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20~3665
In Fig. 2, the reference numeral 18 denotes a
roller provided between a pickup roller 7 and register
rollers 8a, 8b and adapted to rotate in the direction
of arrow A; numeral 19 denotes a separating piece made
of rubber for example, numeral 20 denotes a pressing
piece made of a spring material for example to press
the separating piece 19 to the roller 18; numeral 21
denotes a separating mechanism constituted by the
roller 18, separating piece 19 and pressing piece 20;
numerals 22a and 22b denote guide plates for guiding
sheets 2 to the separating mechanism 21; numerals 23
denotes guide plate for guiding each sheet 2 to the
register rollers 8a and 8b; and numeral 24 denotes a
sensor for detecting a front end position of each sheet 2.
Referring to Fig. 3, which is a partial enlarged
view of the separating mechanism shown in Fig. 2, the
same members as in Fig. 2 are indicated by the same
reference numerals. In Fig. 3, numeral 25 denotes a
top sheet to be fed; numeral 26 represent the second
and following sheets fed plurally; arrow B represents
an urging force created by the pressing piece 20; Nl
represents a frictional force created between the
roller 18 and the sheet 25; N2 represents a frictional
force created between the sheets 25 and 26; N3
represents a frictional force created between the
sheets 26 and the separating piece 19.
Next, operation of the paper feeder constructed
as above will now be described. The sheets 2 are

stacked in a sheet cassette, and with rotation of the
pickup roller 7, the sheets are delivered one by one
from the sheet cassette 3 and conveyed a predetermined
length. Each sheet 2 thus delivered is guided by the
guide plates 22a and 22b and reaches the separating
mechanism 21. In the event of feed of plural sheets at
a time, the top sheet 25 is conveyed by the roller 18
which is rotating in the direction of arrow A, under the
frictional force N1, rotatively together with the roller
18, while the conveyance of the second and following
sheets 26 is prevented by the frictional force N3 which
is larger than the frictional force N2, but smaller than
N1, whereby the sheets which have been fed plurally are
separated one by one and then conveyed. The sheet 25
thus delivered is detected its front end position by the
sensor 24 to take synchronism with an image on the
photosensitive drum 1. The sheet 2 which has passed the
sensor 24 is guided by the guide plate 23 and the
movable guide plate 10 and reaches the register rollers
8a and 8b, then is further guided by guide plates lla
and llb and reaches the photosensitive drum 1. The
operations which follow are the same as in the prior
art.
In the above embodiment, at a certain mounting
angle of the separating piece 19, the sheet 2 when
entering the separating mechanism 21 buckles due to the
frictional force of the separating piece and causes

20436~
paper jam, so it is difficult to adjust the mounting
angle of the separating piece 19. For solving this
problem, in the embodiment illustrated in Fig. 4, the
separating piece 19 is covered with a sheet 27 of a low
friction material up to a position near the separating
portion. Consequently, even without adjusting the
mounting angle of the separating piece 19, or even when
the sheet 2 is of weak stiffness, the sheet does not
buckle when entering the separating mechanism 21, the
assembling work efficiency is high, and there can be
attained the same effects as in the previous embodiment.
Although in the above embodiments the sensor 24 is
provided between the separating mechanism 21 and the
register rollers 8a, 8b, even the provision thereof
between the register rollers 8a, 8b and the photo-
sensitive drum 1 can afford the same effects as in the
above embodiments.
According to the present invention, as set forth
above, since the sheet separating mechanism is provided
between the sheet supply portion and the sheet copying
portion, only the sheet to be fed can be separated and
delivered even in the event of feed of plural sheets of
paper at time. Besides, since the sheet position
detecting means is provided between the sheet
separating mechanism and the sheet copying portion, it
is possible to make copying accurately.

Dessin représentatif