BACKGROUND OF INVENTION
[0001] The present invention relates to a mechanism for feeding sheet from a sheet cassette
in an image recording apparatus such as a copying machine, and more particularly to
a mechanism for feeding a developer sheet from a sheet cassette in an image forming
machine which employs a photosensitive pressure-sensitive recording sheet for carrying
a latent image thereon and transferring a developed image to the developer sheet.
[0002] In general, image recording apparatuses such as the copying machines employ continuous
photosensitive recording mediums such as a microcapsule sheet and developer sheets
used in combination with the photosensitive recording mediums. Developer sheets are
stacked in a sheet cassette and usually fed one at a time from the sheet cassette
by a semicircular separator roller of rubber. The separator roller and the developer
sheets have coefficients of friction different from each other. The separator roller
frictionally separates the uppermost developer sheet from the lower stack of developer
sheets, and delivers the separated developer sheet to a certain position.
[0003] If the developer sheets are stacked such that their reverse sides face up, then the
separator roller contacts the reverse side of the uppermost developer sheet.Therefore,
when the uppermost developer sheet is fed out of the sheet cassette, the color developer
layer on the uppermost developer sheet rubs against the reverse side of the next
developer sheet, and the developer material tends to be partly peeled off from the
developer sheet. Thus, an image formed on the developer sheet may be damaged where
the developer layer has been removed, resulting in poor image quality.
[0004] If the developer sheet are stacked such that their developer layers face up, then
the separator roller contacts the developer layer on the uppermost developer sheet.
Therefore, when the uppermost developer sheet is fed out of the sheet cassette, the
separator roller tends to slip on the color layer, which may be partly peeled off.
Accordingly, an image on the developer sheet may also be impaired.
[0005] Japanese Patent Application Kokai No.55-93744, discloses a sheet feed mechanism
which does not employ a frictional separator roller but uses a suction cup for attracting
a sheet under a negative pressure and feeding the attracted sheet to a certain position.
According to the disclosed sheet feed mechanism, if the negative pressure is too intensive,
the uppermost sheet attracted by the suction cup also attracts the lower sheet or
sheets under suction, and hence more than one sheet may be fed out simultaneously.
The lower sheet or sheets may also be attracted to and fed with the uppermost sheet
due to static electricity developed between sheets. In order to separate sheet from
each other, air is ejected between them. If the negative pressure is too small, the
attracted sheet may drop off the suction cup due to the applied air. The sheet feed
mechanism includes a support base for placing a stack of sheets which is movable up
and down. Therefore, the sheet feed mechanism is relatively complex and requires a
large amount of energy to be consumed. Another problem is that some stacked sheets
are liable to be scattered by the applied air jet. When the support base is lowered
with the uppermost sheet being attracted by the suction cup, the suction cup is moved
laterally so that the leading end of the sheet can be nipped by a feed roller and
a pinch roller. While the suction cup is being moved laterally, however,the attracted
sheet may be dropped off from the suction cup. Therefore, the disclosed sheet feed
mechanism is not be operated with high reliability.
[0006] In order to solve above problems, one sheet feed mechanism is proposed as described
in a pending U.S. Patent Application Serial No.377,137 filed July 10, 1989. The proposed
sheet feed mechanism will be described below with reference to FIGS. 1 through 4(b)
wherein identical parts are denoted by identical reference numerals.
[0007] FIG.1 schematically shows a copying machine incorpo rating a sheet feed mechanism
according to an embodiment of that invention. The illustrated copying machine, generally
indicated at 1, comprises a photosensitive pressure-sensitive copying machine capable
of copying full-color images. The copying machine employs a continuous photosensitive
pressure-sensitive recording medium 11 such as a photosensitive microcapsule sheet
for recording a latent image thereon, and a developer sheet 16 for receiving a developed
color image from the microcapsule sheet. The photosensitive microcapsule sheet 11
and the developer sheet 16 are disclosed in U.S. Patent 4,399,209 and Japanese Patent
Application Kokai No.58-88739, for example, and therefore, further description can
be neglected.
[0008] The copying machine includes an upper panel assembly having an original support stand
glass 2 which is movable back and forth and an original support stand glass cover
3 that can be placed over the original support stand glass 2. An original 4 to be
copied is put on the original support stand glass 2 which is formed of light transmissive
material. The copying machine 1 also has a light source placed in an upper righthand
portion thereof below the original support stand glass 2 and comprising a halogen
lamp 5a extending in a direction normal to the direction in which the original support
stand glass 2 is movable back and forth, and a semicylindrical reflecting mirror 5b
disposed in surrounding relation to the halogen lamp 5a. The light source emits a
linear-line light toward the lower surface of the original support stand glass 2.
[0009] When the original support stand glass 2 moves, the light emitted from the halogen
lamp 5a continuously irradiates the entire surface of the original support stand
glass 2 from the lefthand to the righthand end thereof (as viewed in FIG.1). The light
from the light source passes through the transparent original support stand glass
2, and is then reflected by the original 4 placed on the original support stand glass
2. The original support stand glass cover 3 covers the entire upper surface of the
original support stand glass 2 so that the light applied to the original support stand
2 will not leak out from those areas of the original support stand glass 2 which are
not covered by the original.
[0010] A reflector 5c is positioned on the lefthanded on the side of the light source for
applying lights emitted from the halogen lamp 5a to the original highly efficiently.
The reflector 5b reflects those emitted lights which are not directed toward the original
support glass 2.
[0011] The light reflected from the original on the original support stand glass 2 is directed
downwardly and the passes through a filter 6 and a lens 7. The filter 6 serves to
pass desired wavelengths of light dependent on the sensitivity of a microcapsule sheet
11 for adjusting the colors of a copied image. The lens 7 is mounted on a lens attachment
7a which is slightly adjustable with respect to the path of the light through the
filter 6 and the lens 7.
[0012] The light converged by the lens 7 is directed 180 degrees back by two reflecting
mirrors 8,9 and then focused on the microcapsule sheet 11 held closely against the
lower surface of an exposure table 10. The reflecting mirrors 8,9 are mounted on a
mirror attachment 8a which is slightly positionally adjustable to vary the length
of the light path and the focused condition.
[0013] The microcapsule sheet 11 is of a continuously elongated length and is wound around
a cartridge reel 12. The sheet 11 is placed in a removable cartridge 12a positioned
below the original support stand glass 2. A leading end portion of the microcapsule
sheet 11 extends through many rollers and a pressure developing unit 13 toward a takeup
reel 15.
[0014] More specifically, the microcapsule sheet 11 drawn out of the cartridge 12a from
its lower end is fed and guided by a feed roller 14a and a guide roller 14b, and extends
beneath the exposure table 10 into the pressure developing unit 13. The microcapsule
sheet 11 which has passed through the pressure developing unit 13 is fed by a pair
of feed roller 14c, travel past a separator roller 14d and an ad justment roller
14e, and is then wound around the takeup reel 15. The microcapsule sheet 11 discharged
from the cartridge 12a remains unexposed by a light-shielding cover 12b before the
microcapsule sheet 11 reach the exposure table 10.
[0015] The speed at which the microcapsule sheet 11 is fed is controlled so as to be held
at a constant level, and remains the same speed at which the original support stand
glass 2 is moved. Therefore, a latent image can be formed successively line by line
on the microcapsule sheet 11 when it moves past the exposure table 10.
[0016] A developer sheet cassette 17 storing a stack of developer sheet 16 is disposed below
the pressure developing unit 13. One, at a time, of the developer sheet 16 is taken
out of the cassette 17 by a sheet feed mechanism 18 which attracts the developer sheet
16 under suction. The developer sheet 16 which is taken from the cassette 17 is delivered
by a feed roller 19a and a pinch roller 19b. After the leading end of the developer
sheet 16 is aligned by rollers 19c,19d and a resist gate 19e, the developer sheet
16 is fed into an inlet slot of the pressure developing unit 13.
[0017] The microcapsule sheet 11 and the developer sheet 16 are closely held against each
other when they are introduced into the pressure developing unit 13. The pressure
developing unit 13 includes a small diameter roller 13a and a backup roller 13b.
The microcapsule sheet 11 and the developer sheet 16 are sandwiched and pressed together
between the small diameter roller 13a and the backup roller 13b. At this time, a microcapsule
layer on the microcapsule sheet 11 with the latent image formed thereon and a color
developer layer on the developer sheet 16 are held against each other. Those microcapsule
in the microcapsule layer which are not exposed are ruptured under pressure, and a
developed image is transferred onto the developer sheet 16.
[0018] The microcapsule sheet 11 and the developer sheet 16 which have left the pressure
developing unit 13 are fed by the roller 14c. Then, the microcapsule sheet 11 is separated
from the developer sheet 16 by the separator roller 14d. The microcapsule sheet 11
is directed upwardly, whereas the developer sheet 16 travels straight ahead into a
thermal fixing unit 20. The thermal fixing unit is composed a heater roller 20a and
feed roller 20b. After color development on the developer sheet 16 is promoted and
the color image is fixed by the heat fixing unit 20, the developer sheet 16 is discharged
into a tray 21 with the developed image facing up.
[0019] The separated microcapsule sheet 11 travels past the adjustment roller 14e and is
wound around the takeup reel 15.
[0020] The sheet feed mechanism 18 disclosed in the co-pend ing U.S. Patent Application
will be described in greater detail with reference to FIGS. 2 and 3.
[0021] The sheet feed mechanism 18 includes a pair of suction cups 31 mounted on an angularly
movable elevator arm 32 by means of an attachment plate 32a. The elevator arm 32 has
two pivot shafts 34 ( one shown in FIG.2 ) rotatably supported on elevator frames
36 vertically movably mounted on machine side plates 35 (one of which is shown in
FIG .2). The pivot shafts 34 about which the suction cups 31 are angularly movable
have their central axes lying on a plane which contains the suction surfaces of the
suction cups 31. The pivot shafts 34 are positioned behind, or upstream of, the position
where the suction cups 31 attract the developer sheet 16, with respect to the direction
in which the color developer sheet 16 is fed from the cassette 17.
[0022] The suction cups 31 are positioned such that they attract the developer sheet 16
at its relatively forward portion in the direction of feed of the developer sheet
16. An uppermost sheet sensor 33 which may comprise a microswitch, for example, is
mounted on the elevator arm 32 by means of an attachment plate 32b extending from
and inclined at an angle to the attachment plate 32a. When the attachment plate 32b
extends vertically, the sensor 33 and the pivot shafts 34 are disposed in a common
horizontal plane.
[0023] A motor 37 is mounted on one of the frames 36, and a gear 38 rotatable by the motor
37 is also supported on the frame 36. The gear 36 is held in mesh with a swing gear
39 fixed on the pivot shaft 34. Therefore, when the motor 37 is energized, the elevator
arm 32 is angularly moved about the pivot shafts 34 in the directions indicated by
the arrows A,B (FIG.3).
[0024] Each of the frames 36 is supported by a vertical guide mechanism (not shown), and
can be moved vertically in the direction indicated by the arrow C,D, by a stepper
motor 40. Shafts 41,42 mounted on the machine side plate 35 extend through respective
vertical slots 43,44 defined in the frame 36. Gears 45, 46 fixed to the sifts 41,42,
respectively, are held in mesh with racks 47,48 defined on edges of the slots 43,44.
A timing belt 51 is trained around pulleys 49, 50 fixed respectively to the shafts
41, 42. A helical gear 52 fixed to the end of the shaft 41 is held in mesh with a
worm gear 53 fixed to the output shaft of the stepper motor 40.
[0025] Each of the suction cups 31 has an inner hole defined in its bottom and connected
through a flexible tube 54 to an evacuating means 55 mounted on the other machine
side plate. The evacuating means 55 includes a cylinder 56, a piston 58 having an
O-ring 57 and slidably fitted in the cylinder 56, intermeshing gears 59, 60, and a
stepper motor 61. When the stepper motor 61 is energized, the gear 60 mounted on the
output shaft of the stepper motor 61 causes the gear 59 to rotate about a shaft 62.
A pin 63 is disposed on the gear 60 near an outer peripheral surface thereof and fitted
in a slot defined in one end of a piston rod 64 joined to move linearly in the cylinder
56 in the direction indicated by the arrow E, thereby developing a negative pressure
in the cylinder 56 which is connected to the tube 54.
[0026] The cylinder 56 has an open end through which the piston rod 64 extends. The open
end of the cylinder 56 is preferably directed downwardly so that dust will not be
deposited in the cylinder 56 and grease for lubricating the inner surface of the cylinder
56 will not flow through the tube 54 toward the sheets 16. If the open end of the
cylinder 56 is directed upwardly, then it should be closed by a cover to prevent
foreign matter such as dust and dirt from entering the cylinder 56.
[0027] The feed roller 19a, which is shown as a plurality of feed rollers 19a in FIG.2,
is disposed upwardly of the leading ends of the developer sheets 16 stacked in the
cassette 17. The pinch roller 19b is movable toward and away from the feed roller
19a and rotatably supported on the distal ends of swing arm 72 (one shown in FIG .3)
which are angularly movable about a shaft 71 in the directions indicated by the arrow
G,H. The swing arm 72 are angularly moved by a drive source (not shown) each time
a developer sheet 16 is to be fed out of the cassette 17, for thereby moving the pinch
roller 19b toward and away from the feed roller 19a. A guide member 73 is disposed
downstream of the roller 19a, 19b with respect to the direction of feed of the developer
sheets 16, the guide member 73 defining a sheet feed path. The roller 19c, 19d and
the resist gate 19e are also disposed downstream of the rollers 19a, 19b. The resist
gate 19e includes one end of a lever 74 rotatable about a shaft 73. The roller 19d
is supported on another end of the lever 74. The roller 19d and the resist gate 19e
are angularly movable alternatively between the solid-line position and the two-dot-and-dash-line
position in FIG.3.
[0028] Operation of the sheet feed mechanism 18 thus constructed will be described below
with reference to FIGS.2,3,and 4(a) through 4(d).
[0029] It is assumed that the frames 36 are first disposed in a home position. In response
to a sheet feed signal from the controller of the copying machine 1, the stepper motor
40 is energized, and its rotation is transmitted through the worm gear 53 and the
helical gear 52 to the shaft 41 to rotate the gear 45 in the clockwise direction in
FIG.2. At the same time, the gear 46 on the shaft 42 is rotated in the clockwise
direction through the pulley 49, the timing belt 51, and the pulley 50. As the gear
45,46 are in mesh with the respective racks 47,48, the frame 36 is moved downwardly
in the direction indicated by the arrow D. Upon the downwardly movement of the frame
36, the attachment platen 32b is its vertical position as shown in FIGS.3 and 4(a),
and the sensor 33 can first detect the uppermost sheet surface in the cassette 17.
[0030] When the sensor 33 detects the uppermost sheet surface, the stepper motor 40 is
deenergized to stop the downward movement of the frame 36. Then, the stepper motor
37 is energized, and its rotation is transmitted to the gear 38, 39 to rotate the
shafts 34 about their own axes. The suction cups 31 are then moved downwardly along
an arcuate path until they are held against the uppermost color developer sheet 16
as shown in FIG.4 (b).
[0031] Then, the motor 61 is energized to move the piston 58 in the direction indicated
by the arrow E. A negative pressure is developed in each of the suction cups 31 to
enable the suction cups 31 to attract the uppermost developer sheet 16.
[0032] With the suction cups 31 attracting the uppermost developer sheet 16, the stepper
motor 37 is reversed to turn the arm 32 through a predetermined angle about the shaft
34 in the direction indicated by the arrow A until the arm 32 assumes the position
shown in FIG. 4(c). At this time, the arm 32 is not turned about the suction cups
31, but is turned about the shafts 34 positioned behind the suction cups 31. Therefore,
the suction cups 31 also turned about the shafts 34. The suction cups 31 attracts
the uppermost developer sheet 16 under suction and lifts the leading end position
of the developer sheet 16 off the next developer sheet 16. At this time, the uppermost
developer sheet 16 is separated from the lower sheet 16 because of the stiffness of
the upper developer sheet 16. Even if the negative pressure developed in the suction
cups 31 is relatively small in pressure, the suction cups 31 can separate the upper
most sheet 16 since it is simply lifted off the lower developer sheet 16 without frictional
engagement therewith. If the suction cups 31 were not turned but were operated only
to attract the developer sheet 16, two or more developer sheets would be fed out at
the same time when an electrostatic force acting on these sheets is greater than the
weight of the developer sheet 16. Since the suction cups 31 are actually turned about
the shafts 34, however, two or more developer sheets are prevented from being fed
out together. An experiment conducted on the sheet feed mechanism 18 indicated that
the uppermost sheet 16 could sufficiently be separated from the lower developer sheet
16 by the suction cups 31 when the arm 32 was turned through about 30 degrees. After
the uppermost developer sheet 16 has been separated, the stepper motor 40 is reversed
to elevate the frames 36 and hence the elevator arm 32 in the direction indicated
by the arrow C up to the position shown in FIG.4(a) in which the leading end of the
developer sheet 16 is positioned directly below the feed roller 19a.
[0033] Then, the pinch roller 19b is swung about its own axis in the direction indicated
by the arrow G to pinch or nip the leading end of the developer sheet 16 between the
pinch roller 19b (indicated by the two-dot-and-dash line) and feed roller 19a. Thereafter,
the motor 61 of the evacuating means 55 is reversed to move the piston 58 in the direction
of the arrow F. The negative pressure in the suction cups 31 is eliminated, and the
developer sheet 16 is released from the suction cups 31.
[0034] The stepper motor 40 is further energized to lift the frames 36 and the arm 32 by
a certain distance to avoid engagement or interference between the suction cups 31
and the developer sheet 16 as is fed along.
[0035] Through the above operation, the uppermost one of the stacked developer sheets 16
is separated and delivered into the sheet feed path. In an initial stage of the sheet
feeding operation, the roller 19d and the resist gate 19e are in the two-dot-and-dash
position shown in FIG. 3, and hence the roller 19c, 19d are spaced from each other.
The developer sheet 16 is fed by the feed roller 19a and the pinch roller 19b until
its leading end is engaged by the resist gate 19e, whereupon the leading end of the
developer sheet 16 is properly aligned and corrected out of the any skewed condi
tion. Then, the lever 74 is turned to displace the roller 19d against the roller 19c
and pull the resist gate 19e out of the sheet feed path. The developer sheet 16 is
now fed along the sheet feed toward the pressure developing unit.
[0036] The sheet feeding mechanism 18 described in the U.S. Application has a simple construction,
and the sheet is surely delivered from the sheet cassette without any damage to the
sheet. The sheet feeding mechanism 18 is incorporated into an image recording apparatus
or a copying machine which employs voluminous papers as recording mediums. In such
circumstances, dusts or a fibrous particles are released from the paper sheets. Further,
in the image recording apparatus or the copying machine, heat is released in its interior.
Therefore, external air is normally introduced into its interior by means of a fan
etc. in order to cool internal components.
[0037] In this case, ambient dusts may also be introduced into the interior together with
the external air. Accordingly, such dusts are also introduced into the sheet feeding
mechanism 18. If the latter is the case, dusts may be entered into the flexible tube
54 of the sheet feeding mechanism due to aspiration of the evacuating means 55. Therefore,
the tube 54 may be choked up with the dusts. Further, dusts may be adhered to the
suction cup 31, so that intimate contact between the suction cup 31 and the sheet
16 may be degraded, to thus degrade separation and absorption efficiency of the evacuating
means 55.
[0038] If the dusts are entered into the cylinder 56 of the evacuating means 55, the 0-ring
57 of the piston 58 may be impaired, which may reduce service life of the evacuating
means.
[0039] It is, therefore, an object of the present invention to provide a sheet feed mechanism
capable of preventing dusts from being entered into evacuating means.
[0040] Another object of the invention is to provide a method for positively discharging
dusts accumulated within the flexible tube or the suction cups toward outside of the
sheet feed mechanism.
[0041] These and other objects of the present invention will be attained by providing a
sheet feeding mechanism for feeding an uppermost sheet of a sheet stack stacked in
a sheet cassette, the sheet having a leading end with respect to a sheet feed path,
the sheet feeding mechanism comprising suction cup means movable into and out of contact
with the uppermost sheet in the sheet cassette, evacuating means for developing a
negative pressure in the suction cup means to enable the suction cup means to attract
the uppermost sheet, tube means connecting the suction cup means and one end of the
evacuating means, lifting means for lifting the suction cup means with the uppermost
sheet being attracted thereto, nipping means for nipping the leading end of the attracted
and lifted uppermost sheet and delivering the uppermost sheet into the sheet feed
path, and dust preventing means positioned near or in the evacuating means for preventing
dust from being entered into the evacuating means.
[0042] In another aspect of the invention there is provided a method for cleaning a sheet
feeding mechanism which feeds an uppermost sheet of a sheet stack stacked in a sheet
cassette, the sheet having a leading end with respect to a sheet feed path, the sheet
feeding mechanism including suction cup means movable into and out of contact with
the uppermost sheet in the sheet cassette, evacuating means for developing a negative
pressure in the suction cup means to enable the suction cup means to attract the uppermost
sheet, tube means connecting the suction cup means and one end of the evacuating means,
the evacuating means including a cylinder, a piston provided movable within the cylinder
and a drive means connected to the piston for reciprocally moving the piston, the
method comprising the steps of: energizing the drive means when the suction cup means
is out of contact with the uppermost sheet for reciprocating the piston, thereby generating
an air stream, and discharging dusts accumulated within at least one of the tube means
and the suction means by the air stream.
[0043] In still another aspect of this invention, there is provided a sheet feeding method
for feeding an uppermost sheet of a sheet stack stacked in a sheet cassette, the sheet
having a leading end with respect to a sheet feed path, the sheet feeding mechanism
including suction cup means movable into and out of contact with the uppermost sheet
in the sheet cassette, evacuating means for developing a negative pressure in the
suction cup means to enable the suction cup means to attract the uppermost sheet,
tube means connecting the suction cup means and one end of the evacuating means, the
evacuating means including a cylinder, a piston provided movable within the cylinder
and a drive means connected to the piston for reciprocally moving the piston, the
sheet feeding method comprising the steps of energizing the drive means for moving
the piston when the suction cup means is out of contact with the uppermost sheet,
thereby generating an air stream, discharging dusts accumulated within at least one
of the tube means and the suction means by the air stream moving the suction cup means
to allow the suction cup means to be brought into contact with the uppermost sheet,
again energizing the drive means for moving the piston, to thereby generate negative
pressure, to thus attract the uppermost sheet to the suction cup, lifting the suction
cup means which attracts the uppermost sheet, and moving the suction cup means toward
the sheet feed path for introducing the uppermost sheet thereinto.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] In the drawings:
FIG.1 is a schematic vertical cross-sectional view showing a copying machine incorporating
a sheet feed mechanism, according to an embodiment of an invention disclosed in a
pending U.S.Patent Application;
FIG.2 is a enlarged fragmentary perspective view showing the sheet feed mechanism
described in the pending application;
FIG.3 is a side elevational view, partly cut away, showing the sheet feed mechanism
described in the pending application;
FIG.4(a) through 4(d) are sectional side elevational view showing a sequence of operation
in the sheet feed mechanism described in the pending application;
FIG.5 is a side elevational view, partly cut away, showing a sheet feed device having
dust preventing means according to a first embodiment of the present invention; and
FIG.6 is a side elevational view, partly cut away, showing a sheet feed device having
dust preventing means according to a second embodiment of the present invention.
[0045] Embodiments of the present invention will be described below with reference to FIGS.
5 and 6, wherein like parts and components are designated by the same reference numerals
and characters as those shown in FIGS. 1 thru 4(d) for eliminating a duplicating description.
[0046] FIG.5 shows a sheet feed mechanism according to a first embodiment of the present
invention. Apparently, the sheet feed mechanism according to the first embodiment
is applied to an image recording apparatus or a copying machine as described above.
[0047] A suction cup 31 has an inner hole defined in its bottom and connected through a
flexible tube 54 to an evacuating means 55 mounted on another side frame (not shown).
The evacuating means 55 includes a cylinder 56, a piston 58 having an 0-ring 57 and
slidably fitted in the cylinder 56, intermeshing gears 59, 60, and a stepper motor
61 having an output shaft. The intermeshing gear 59 has one end pivotally supported
by a pivot shaft 62, and has another end adjacent its gear portion provided with a
pin 63. The piston 58 is connected to a piston rod 64 whose distal end is formed with
a slot. The pin 63 is provided engageable with the slot. When the stepper motor 61
is energized, the gear 60 mounted on the output shaft of the stepper motor 61 permits
the gear 59 to rotate about the shaft 62. Therefore, the gear 59 causes the piston
58 to move linearly in the cylinder 56 by way of the pin 63 and the slot in the direction
indicated by an arrow E, thereby developing a negative pressure in the cylinder 56
which is connected to the tube 54.
[0048] In the first embodiment, a filter 73 is provided in the tube 54 for purifying the
air intaken into an interior of the suction cup 31 and the tube 54 by the evacuating
means 55, so that dust such as paper powders in the intaken air is trapped by the
filter 73. Therefore, the filter 73 prevents the dusts from reaching an interior of
the evacuating means, and accordingly, dusts are not involved at a sliding portion
of the piston 58. As a result, prolonged service life of the evacuating means 55 would
be obtainable. If great amount of dusts are accumulated at the filter 73, the filter
73 together with the tube 54 are replaced by a new filter and the tube. Consequently,
inherent filtering function can be obtained.
[0049] FIG. 6 shows a sheet feed mechanism according to another embodiment of the present
invention. In the first embodiment shown in Fig. 5, the cylinder 56 of the evacuating
means 55 extends in vertical direction similar to the cylinder 56 of the above described
copending U.S.Patent Application. Further, a lower end of the cylinder 56 is fully
opened to an atmosphere. On the other hand, in the second embodiment, the cylinder
56′ extends in horizontal direction, and relevant end portion of the cylinder 56′
is closed by an end plate 56′A.
[0050] More specifically, the cylinder 56′ has one end connected to a tube 54 and has another
end covered with the end plate 56′A. The cylinder 56′ is supported by a side frame
(not shown) with maintaining its horizontal orientation. Further, a hole 65 is bored
at a lower portion of a cylindrical wall of the cylinder 56′ and at a position adjacent
the end plate 56′A for discharging air when a piston 58 is moved in a direction E.
[0051] Similar to the first embodiment, when the stepper motor 61 is energized, the gear
59 causes the piston 58 to move linearly in the cylinder 56 in the direction indicated
by the arrow E, thereby developing a negative pressure in the cylinder 56 which is
connected to the tube 54.
[0052] Since the hole 65 is bored downwardly and the cylinder 56′ is substantially hermetically
sealed by the end plate 56′A except the hole 65, dust is hardly entered into the interior
of the cylinder 56′. Therefore, prolonged service life of the evacuating means 55
is obtained. Further, since the cylinder 56′ extends in horizontal direction and the
tube 54 is connected to the one end of the cylinder 56′ at a radially center portion
thereof, grease for lubrication purpose would not flow out of the cylinder toward
the tube 54. Accordingly, sheet contamination with the grease can be obviated.
[0053] In the second embodiment various modifications may be conceivable. For example, a
filter member 73 shown in the first embodiment can be assembled into the flexible
tube 54 for further avoiding dust sucking into the interior of the cylinder through
the suction means 31. Furthermore, a filter may be attached to an open end of the
hole 65 of the cylinder 56′ for completely avoiding dust sucking into the interior
of the cylinder 56′.
[0054] Next, in the present invention, positive discharge of the dusts out of the sheet
feed mechanism 18 is attainable prior to the sheet feeding operation or at an instance
in which dusts are considered to be attached to the interior of the tube 54 or the
suction cups 31. In the latter case, such dust discharge may be conducted after predetermined
numbers of copying are carried out. That is, in an idling state of the sheet feed
mechanism, i.e., in a state where the suction cups 31 are separated from the sheet,
a motor 61 (Fig. 3) is energized for reciprocatingly moving the piston 58 in directions
E and F in order to produce an air stream within the flexible tube 54 and the suction
cups 31, to thereby positively discharge paper fibrous chips or dusts out of the
tube or the suction cups.
[0055] According to this idling operation, i.e., positive dust discharging operation, dusts
attached to the tube etc. can be removed therefrom. Therefore, probability in dust
entry into the evacuation means can be reduced. Further, since the dust attached to
the suction cups can also be removed by the positive discharge, intimate contact between
the suction cups and the sheet can be provided, to thereby ensure sheet feeding operation.
[0056] Further, this idling operation can be applied to the above described first and second
embodiments of this invention. That is, upon energization of the motor 61 (Fig. 5),
the piston 58 is reciprocally moved within the cylinder 56′ to generate an air stream
within the tube 54 and within the cylinder 56′. Therefore, dusts accumulated to the
filter 73 as well as to the flexible tube 54 can be blown by the air stream and is
discharged to the atmosphere. Therefore, service life of the filter can also be prolonged.
[0057] Furthermore, in order to positively discharge the dusts accumulated within the flexible
tube 54 or the filter 73, moving speed of the piston 58 may be changed. That is, moving
speed of the piston in the direction F is arranged to be higher than that in the direction
E so as to produce positive air stream having high velocity directing to F direction.
[0058] The above described cleaning method or idling operation is not limited to the copying
machine described above, but is available to other types of image recording apparatus
using photosensitive pressure sensitive recording medium. Further, various modifications
may be effected to the sheet feed mechanism per se. For example, crank-mechanism may
be available in the evacuating means 55. Furthermore, numbers of the suction cups
31 can be changed in accordance with the size and weight of the sheets to be fed.
[0059] While the invention has been described in detail and with reference to specific embodiments
thereof, it would be apparent to those skilled in the art that various changes and
modifications can be made therein without departing from the spirit and scope of the
invention.
1. A sheet feeding mechanism for feeding an uppermost sheet of a sheet stack stacked
in a sheet cassette, the sheet having a leading end with respect to a sheet feed path,
the sheet feeding mechanism comprising;
suction cup means movable into and out of contact with the uppermost sheet in the
sheet cassette;
evacuating means for developing a negative pressure in the suction cup means to enable
the suction cup means to attract the uppermost sheet;
tube means connecting the suction cup means and one end of the evacuating means;
lifting means for lifting the suction cup means with the uppermost sheet being attracted
thereto;
nipping means for nipping the leading end of the attracted and lifted uppermost sheet
and delivering the uppermost sheet into the sheet feed path; and
dust preventing means positioned near the evacuating means for preventing dust from
entering into the evacuating means.
2. The sheet feeding mechanism according to claim 1, wherein the evacuating means
comprises a cylinder, a piston movably provided within the cylinder, and piston driving
means connected to the piston for reciprocally moving the piston, the cylinder having
one end connected to the tube means.
3. The sheet feeding mechanism according to claim 1 or 2, wherein the dust preventing
means is positioned in the tube means.
4. The sheet feeding mechanism according to claim 3, wherein the dust preventing means
comprises filter means.
5. The sheet feeding mechanism according to claim 2, wherein the cylinder extends
in horizontal direction.
6. The sheet feeding mechanism according to claim 5, wherein the dust preventing means
comprises an end plate covering another end of the cylinder, the cylinder having a
cylindrical wall formed with a hole positioned near the end plate and at a lower portion
of the cylindrical wall.
7. The sheet feeding mechanism according to claim 6, wherein the dust preventing means
further comprises a first filter means positioned within the tube means.
8. The sheet feeding mechanism according to claim 7, wherein the dust preventing means
further comprises a second filter means positioned at the hole.
9. A method for cleaning a sheet feeding mechanism which feeds an uppermost sheet
of a sheet stack stacked in a sheet cassette, the sheet having a leading end with
respect to a sheet feed path, the sheet feeding mechanism including suction cup means
movable into and out of contact with the uppermost sheet in the sheet cassette, evacuating
means for developing a negative pressure in the suction cup means to enable the suction
cup means to attract the uppermost sheet, tube means connecting the suction cup means
and one end of the evacuating means, the evacuating means including a cylinder, a
piston provided movable within the cylinder and a drive means connected to the piston
for reciprocally moving the piston, the method comprising the steps of:
energizing the drive means when the suction cup means is out of contact with the uppermost
sheet for reciprocating the piston, thereby generating an air stream, and
discharging dust accumulated within at least one of the tube means and the suction
means by the air stream.
10. The method according to claim 9 wherein the energizing step is conducted prior
to the sheet feeding operation.
11. The method according to claim 9 or 10 wherein the enegizing step is conducted
after a predetermined number of copying operations are carried out.
12. The method according to claim 9 10 or 11 wherein the piston is movable in one
direction for generating the negative pressure in the suction cup and is movable in
opposite direction, the moving speed of the piston in the opposite direction being
faster than that in the one direction.
13. A sheet feeding method for feeding an uppermost sheet of a sheet stack stacked
in a sheet cassette, the sheet having a leading end with respect to a sheet feed path,
the method using suction cup means movable into and out of contact with the uppermost
sheet in the sheet cassette, evacuating means for developing a negative pressure
in the suction cup means to enable the suction cup means to attract the uppermost
sheet, tube means connecting the suction cup means and one end of the evacuating means,
the evacuating means including a cylinder, a piston provided movable within the cylinder
and a drive means connected to the piston for reciprocally moving the piston, the
sheet feeding method comprising the steps of:
energizing the drive means for moving the piston when the suction cup means is out
of contact with the uppermost sheet, thereby generating an air stream;
discharging dust accumulated within at least one of the tube means and the suction
means by the air stream;
moving the suction cup means to allow the suction cup means to be brought into contact
with the uppermost sheet;
again energizing the drive means for moving the piston, to thereby generate negative
pressure, to thus attract the uppermost sheet to the suction cup;
lifting the suction cup means which attracts the uppermost sheet; and
moving the suction cup means toward the sheet feed path for introducing the uppermost
sheet thereinto.