[0001] This invention relates generally to an electrophotographic printing machine and more
particularly concerns an apparatus for advancing suqcessive flexible sheets from a
stack thereof.
[0002] In the process of electrophotographic printing, a photoconductive member is charged
to a substantially uniform potential so as to sensitize the surface thereof. The charged
portion of the photoconductive member is exposed to a light image of an original document
being reproduced. Exposure of the charged photoconductive member selectively dissipates
the charge thereon in the irradiated areas. This records an electrostatic latent image
on the photoconductive member corresponding to the informational areas contained within
the original document. After the electrostatic latent image is recorded on the photoconductive
member, the latent image is developed by bringing a developer material into contact
therewith. Generally, the developer material comprises toner particles adhering triboelectrically
to carrier granules. The toner particles are attracted from the carrier granules to
the latent image forming a toner powder image on the photoconductive member. The toner
powder image is then transferred from the photoconductive member to a copy sheet.
The toner particles are heated to affix the powder image permanently to the copy sheet.
[0003] In a commerical printing machine of the foregoing type, the copy sheets are stacked
on a horizontal tray. The tray moves in a vertical direction. An elevator system is
employed to advance the tray automatically in an upward vertical direction so as to
position successive uppermost sheets in contact with the sheet feeder. When the supply
of copy sheets in the tray is below a pre-selected level, the printing machine is
automatically de-energized, and the elevator moves the tray downwardly to an inoperative
position for loading a new stack of copy sheets therein. A system of this type is
fairly complex and limits the printing machine configurations. It is desirable to
simplify the copy sheet stacking and feeding system and to eliminate the elevator
system associated therewith. Various approaches have been devised for sheet feeding.
The following disclosures appear to be relevant:
US-A-3 615 129 discloses a duplex tray for receiving copy sheets having a fused toner
image on one surface thereof. After the requisite number of copy sheets are received
in the duplex tray, a sheet feeder sequentially feeds these sheets through the printing
process for creating images on the opposite side thereof.
US-A-3 937 455 describes a sheet feeder having a vertically oriented hopper storing
a stack of sheets therein. Rollers are positioned at the bottom of the hopper to engage
successive sheets and advance them downwardly to a scanner of a facsimile scanner.
US-A-3 947 018 discloses a sheet feeder having a vacuum transport for advancing successive
bottom sheets from a stack of sheets. An air cushion is formed between the bottom
sheet and the plate adjacent thereto, and between the bottom edge of the sheets and
the bottom edge guide. A follow-up plate engages the top sheet of the stack and applies
a slight downward force on the stack.
US-A-4 348 019 describes a stack of vertically oriented sheets positioned in a magazine
with the bottom end of the magazine being open. A pair of feed rollers advances successive
sheets downwardly from the magazine through the open end thereof.
[0004] The present invention provides a sheet stacker which overcomes disadvantages of known
stackers, and which is as claimed in the appended claims.
[0005] Other aspects of the invention will become apparent from the following description
with reference to the accompanying drawings, in which;
Figure 1 is a schematic elevational view depicting an electrophotographic printing
machine incorporating the present invention therein;
Figure 2 is an elevational view showing the sheet feeder associated with the sheet
feeding and stacking apparatus of the Figure 1 printing machines;
Figure 3 is a schematic, perspective view showing the flow of air used to separate
the sheets of the stack of the sheet feeder and stacker used in the Figure 1 printing
machine;
Figure 4 is a schematic, perspective view showing one embodiment of the support for
the stack of sheets in the sheet feeder and stacker used in the Figure 1 printing
machine;
Figure 5 is a schematic, perspective view illustrating another embodiment of the support
for the stack of sheets in the sheet feeder and stacker used in the Figure 1 printing
machine;
Figure 6 is a schematic, perspective view depicting another embodiment of support
used in Figure 1 printing machine;
Figure 7 is a fragmentary, sectional elevational view showing a portion of the Figure
6 stack support.
Figure 8 is a schematic, perspective view illustrating the housing for holding the
stack of sheets in the feeder and stacker used in the Figure 1 printing machine; and
Figure 9 depicts the Figure 8 housing in an operative position wherein successive
outermost sheets are in a feeding relationship with Figure 2 sheet feeder, and in
an inoperative relationship wherein a new stack of sheets may be loaded in the Figure
8 housing.
[0006] For a general understanding of the features of the present invention, reference is
made to the drawings. In the drawings, like reference numerals have been used throughout
to identify identical an illustrative electrophotographic printing machine incorporating
the sheet feeding and stacking apparatus of the present invention therein. The sheet
feeding and stacking apparatus of the present invention may be employed for stacking
and advancing original documents as well as copy sheets. It will become evident from
the following discussion that this apparatus is equally well suited for use in a wide
variety of printing machines and is not necessarily limited in its application to
the particular printing machine shown herein.
[0007] Inasmuch as the art of electrophotographic printing is well known, the various processing
stations employed in the Figure 1 printing machine will be shown hereinafter schematically
and their operation described briefly with reference thereto.
[0008] As shown in Figure 1 the electrophotographic printing machine employs a belt 10 having
a photoconductive surface 12 deposited on a conductive substrate 14. Preferably, photoconductive
surface 12 is made from a selenium alloy with photoconductive substrate 14 being made
from an aluminum alloy. Other suitable conductive materials and conductive substrates
may also be employed. Belt 10 moves in the direction of arrow 16 to advance successive
portions of photoconductive surface 12 sequentially through the various processing
stations disposed about the path of movement thereof. Belt 10 is entrained about a
stripping roller 18, tensioning roller 20 and drive roller 22. Stripping roller 18
is mounted rotatably so as to rotate with the movement of belt 10. Tensioning roller
20 is resiliently urged against belt 10 to maintain belt 10 under the desired tension.
Drive roller 22 is rotated by motor 24 coupled thereto by suitable means such as a
drive belt. As roller 22 rotates, it advances belt 10 in the direction of arrow 16.
[0009] Initially, a portion of the photoconductive surface passes through charging station
A. At charging station A, a corona generating device, indicated generally by the reference
numeral 26 charges photoconductive surface 12 to a relatively high, substantially
uniform potential.
[0010] Next, the charged portion of photoconductive surface 12 is advanced through imaging
station B. At imaging station B, an original document 28 is positioned face down on
platen 30. Lamps 32 illuminate original document 28 disposed upon platen 30. Light
rays reflected from the original document are transmitted through lens 34. Lens 34
focuses the light image of the original document onto the charged portion of the photoconductive
surface of belt 10 to dissipate the charge thereon selectively. This records an electrostatic
latent image on the photoconductive surface which corresponds to the informational
areas contained within the original document. Thereafter, belt 10 advances the electrostatic
latent image recorded on the photoconductive surface to development station C.
[0011] At development station C a pair of magnetic brush rollers, indicated generally by
the reference numerals 36 and 38, advance developer material into contact with the
electrostatic latent image. The latent image attracts toner particles from the carrier
granules of the developer material to form a toner powder image on the photoconductive
surface of belt 10.
[0012] Belt 10 then advances the toner powder image to transfer station D. At transfer station
D, a copy sheet is advanced into contact with the powder image. Transfer station D
includes corona-generating device 40 which sprays ions onto the backside of the copy
sheet. This attracts the toner powder image from photoconductive surface 12 of belt
10 to the sheet.
[0013] The sheet feeding and stacking apparatus, indicated generally by the reference numeral
44, advances successive copy sheets to transfer station D. Sheet feeding and stacking
apparatus 44 includes a housing 46 supporting stack of sheets 48 in a substantially
vertical orientation. Upright 50 engages one side of the stack of sheets 48 and moves
the stack of sheets toward sheet feeder 52. In this way, successive outermost sheets
from one side of stack 48 are continuously in a feeding relationship with sheet feeder
52 so as to be advanced thereby to transfer station D. After transfer of the toner
powder image to the copy sheet, the copy sheet is advanced by conveyor 42 to fusing
station E. The detailed structure of sheet feeding and stacking apparatus 44 will
be described hereinafter with reference to Figures 2 through 7, inclusive.
[0014] Fusing station E includes a fuser assembly, indicated generally by the reference
numeral 54, which permanently affixes the tranferred powder image to the copy sheet.
Preferably, fuser assembly 54 includes a heated fuser roller 56 and a back-up roller
58. The sheet passes between fuser roller 56 and back-up roller 58 with the powder
image contacting fuser roller 56. In this manner, the powder image is permanently
affixed to the copy sheet.
[0015] After fusing the toner powder image to the copy sheet, the copy sheets are advanced
by conveyor 60 to catch tray 62 for subsequent removal from the printing machine by
the operator.
[0016] Invariably, after the copy sheet is separated from photoconductive surface 12 of
belt 10, some residual particles remain adhering thereto. These residual particles
are removed from photoconductive surface 12 at cleaning station F. Cleaning station
F includes a rotatably mounted fibrous brush 64 in contact with photoconductive surface
12 of belt 10. The particles are cleaned from photoconductive surface 12 and belt
10 by the rotation of brush 64 in contact therewith. Subsequent to cleaning, a discharge
lamp (not shown) floods photoconductive surface 12 with light to dissipate any residual
electrostatic charge remaining thereon prior to the charging thereof for the next
successive imaging cycle.
[0017] It is believed that the foregoing description is sufficient for purposes of the present
application to illustrate the general operation of an electrophotographic printing
machine incorporating the features of the present invention therein.
[0018] Referring now to the specific subject matter of the present invention, the general
operation of the sheet feeding and stacking apparatus will be described hereinafter
with reference to Figure 2 through 7, inclusive.
[0019] As shown in Figure 2, sheet feeder 52 of sheet feeding and stacking apparatus 44
includes a pair of belts 66 having a multiplicity of substantially equally spaced
apertures or holes 68 therein. Belts 66 are entrained over spaced support rollers
70 and 72. Roller 70 is coupled to clutch drive 74 which rotates roller 70 so as to
advance belts 66. Vacuum plenum 76 is disposed adjacent the underside of belts 66.
Blower 78 is coupled to plenum 76 via duct 80. A solenoid-actuated valve 82 is positioned
in duct 80. When valve 82 is open, air is exhausted by blower 78 from plenum 76. In
this way, a copy sheet on one side of stack 48 closely adjacent to belt 66 is attracted
thereto. When the clutch is energized, the belts move the copy sheet to transfer station
D (Figure 1). When valve 82 is closed, air is not exhausted from plenum 76 and the
copy sheets are not attracted to belt 66. The air exhausted by blower 78 is fed to
an air knife which directs a supply of air to the side edges of the stack of sheet,
as shown more clearly in Figure 3.
[0020] Referring now to Figure 3, there is shown stack 48 having air flow directed toward
the side edges thereof as indicated by arrows 84. An air knife (not shown) receives
the air being exhausted from blower 78 and directs this flow of air toward the side
edges of stack 48, as indicated by arrows 84. This facilitates the separation of the
outermost copy sheet adjacent sheet feeder 52. In this way, the outermost copy sheet
is attracted to belts 66 more readily and does not remain adhering to the remainder
of the sheets of stack 48. Stack 48 is moved continuously toward sheet feeder 52.
The foregoing is shown more clearly in Figure 4.
[0021] Turning now to Figure 4, there is shown one embodiment of stack supports 86. Stack
supports 86 are substantially L-shaped with one leg 86(a) thereof engaging the bottom
edge of stack 48 and the other leg 86(b) engaging the outermost sheets of stack 48
remote from sheet feeder 52. Stack supports 86 move toward sheet feeder 52 as indicated
by arrow 88 so as to position an outermost sheet of stack 48 continuously adjacent
sheet feeder 52. Stack supports 86 are mounted on a plate 87, which in turn, is mounted
on slides 89. The slide mechanism minimizes friction and enables the stack supports
to move, under the influence of gravity, toward the sheet feeder. One skilled in the
art will appreciate that a drive mechanism, e.g. a belt drive or a rack and pinion
system, may be utilized in lieu of gravity to move the stack supports toward the sheet
feeder.
[0022] Turning now to Figure 5, there is shown another embodiment of the stack support.
As shown thereat, legs 86(b) are mounted on conveyor 90 and extend in a substantially
perpendicular direction thereto, i.e. substantially perpendicular to the planar surface
of conveyor 90. Legs 86 (b) engage the outermost sheet of stack 48 opposed to sheet
feeder 52. As conveyor 90 moves in the direction of arrow 88, legs 86(b) move in conjunction
therewith. In this way legs 86(b) move stack 48 toward sheet feeder 52.
[0023] Figure 6 depicts another embodiment of the stack support. As shown thereat, stack
support member 100 includes a generally planar member having two endless, curvilinear
grooves 104 and 106 therein. Grooves 104 and 106 are race tracks. A plurality of balls
108 is positioned in grooves 104 and 106, balls 108 providing a rolling support for
the stack. When the stack 110 is moving toward the sheet feeder, balls 108 move in
the direction of arrow 110 in portions 104(a) and 106(a) of grooves 104 and 106. The
balls return to their initial position in portion 104(a) and 106(a) by travelling
in the direction of arrow 112, through portions 104(b) and 106(b) of grooves 104 and
106, respectively. In this way, the balls in grooves 104 and 106 move in a continuously
recirculating path.
[0024] Turning now to Figure 7, there is shown a fragmentary, sectional elevational view
depicting the detailed structure of groove 104. Groove 104 is identical to groove
106. As shown thereat, portion 104(a) of groove 104 is of a depth less than portion
104(b) thereof. Thus, as balls 108 move in portion 104(a) the exterior circumferential
surface thereof extends above surface 114(a) of planar member 114. Strip 116 is positioned
on balls 108. In this way, strip 116 supports the side edge of the stack as balls
108 move in portion 104(a) of groove 104. During the return path, i.e. after balls
108 move from portion 104(a) to portion 104(b), balls 108 have the exterior circumferential
surface thereof below surface 114(a) of planar member 114. Cover 118 covers portion
104(b). Thus, when balls 108 are in the portion 104(b), they are merely returning
to their initial position in portion 104(a). Inasmuch as there is a multiplicity of
balls in portions 104(a) and 104(b) of groove 104, the balls are continually moving
in a recirculating path. When balls 108 are in portion 104(a) they support strip 116
above surface 114(a) of planar member 114 and support the side edge of the stack rollably
relative thereto. However, when balls 108 are in the return portion, i.e. portion
104(b) of groove 104, they are beneath surface 114(a) and no longer provide support
for the side edge of the stack. In this way, flexible strips 116 move with the stack
with only rolling friction impeding motion.
[0025] Stack 48 is placed in housing 46. Housing 46, as shown in Figure 8, includes slots
92 for receiving stack supports 86. Opening 94 is positioned to receive belts 66 of
sheet feeder 52. Thus, the bottom edge of stack 48 rests on surface 96 of housing
46 with stack supports 86 moving therealong through slots 92. Housing 46 is substantially
an open-ended box to enable successive stacks of copy sheets to be loaded therein.
In loading and unloading copy sheets from housing 46, housing 46 pivots about rods
98. Thus, housing 46 is mounted pivotably about rods 98 in the frame of sheet feeding
and stacking apparatus 44.
[0026] With reference to Figure 9, there is shown housing 46 in the operative position,
and in the inoperative position for receiving a new stack of copy sheets. As shown
in Figure 9, when stack support 86 reaches a predetermined position, a signal is generated
indicating that the copy sheets in copy housing 46 are depleted. Housing 46 is then
pivoted about rods 98 so that a new stacks of sheets 48 may be loaded in the open
end thereof. In the loading or inoperative position, housing 46 pivots about rods
98 away from stack support 86. In this manner, an additional supply of copy sheets
may be readily placed within housing 46. After stacks 48 have been loaded in housing
46, housing 46 pivots about rods 98 in a counterclockwise direction so as to position
stacks 48 in a substantially vertical direction. Thus, housing 46 returns to the operative
position wherein stack support 86 is in engagement with the side of stack 48 remote
from sheet feeder 52.
[0027] It is clear that sheet feeder 52 advances seriatim successive outermost sheets from
stack 48 in a direction substantially opposed to the gravitational force exerted on
the advancing sheet. Thus, each successive sheet advances in a substantially-vertical
upward direction opposed to the direction of the gravitational force. The foregoing
arrangement has total mechanical movement as opposed to electrical impulses. Moreover,
this system reduces the size and complexity of the sheet feeding and stacking system
by eliminating any elevator systems while providing a simpler sheet path.
[0028] In recapitulation, it is evident that the sheet feeding and stacking apparatus of
the present invention supports a stack of sheets in a substantially vertical orientation.
Successive outermost sheets are advanced in an upward direction against gravity. When
additional sheets have to be added to the housing storing the sheets in the sheet
feeder, the housing is pivoted to an inoperative position to facilitate the loading
of a new stack of sheets therein. Thereafter, the housing is pivoted to its operative
position wherein the stack of sheets is positioned vertically. Thus, the sheet feeding
and stacking apparatus of the present invention significantly reduces the complexity
and cost associated with devices hereinbefore employed.
1. Apparatus (44) for advancing successive flexible sheets from a stack (46) thereof,
including:
means (50) for holding the stack of sheets so that each sheet is substantially-vertical;
means (52) for feeding successive, outermost sheets from one end of the stack in a
substantially-vertical direction against gravity and
means, engaging the outermost sheet of the other end of the stack, for moving the
stack toward the feeding means so as to position successive, outermost sheets of the
said one end of the stack in feeding relationship therewith, the holding means being
arranged to move from an operative position, in which the moving means positions the
outermost sheet of the said one end of the stack in feeding relationship with said
feeding means to an inoperative position spaced from the moving means, to permit a
new stack of flexible sheets to be loaded into the holding means.
2. Apparatus according to claim 1, wherein said moving means includes:
at least one upright member (86) engaging the outermost sheet of the said other end
of the stack and
means for advancing the upright member toward said feeding means.
3. Apparatus according to claim 2, wherein said holding means includes a housing having
a slot in which the upright member is movably seated, enabling the upright member
to move therealong the length of the slot.
4. Apparatus according to any preceding claim, including a housing (46) for the stack
of sheets, the housing having an opening (94) therein adjacent the feeding means to
enable the outermost sheet of the one end to be placed in feeding relationship with
the feeding means.
5. Apparatus according to claim 1, wherein the holding means includes:
a substantially-planar member (100) having at least one groove (104) therein extending
in an endless curvilinear path; and
balls (108) positioned in one portion of the groove for engaging one side face of
the stack, and those in another portion of the groove being spaced from the same side
face.
6. Apparatus according to claim 5, wherein the plurality of balls disposed in the
groove support
a strip (116) positioned between the respective balls and the side face of the stack
for low-friction movement therewith.
7. Apparatus according to claim 6, wherein the balls in the said one portion of the
groove have a portion of their exterior surface protruding above the surface of the
planar member, while the balls in the said another portion of the groove are spaced
below the surface of the planar member.
8. Apparatus according to claim 7, wherein the plurality of balls rolls in a recirculating
path containing both portions of the groove.
9. Apparatus according to any preceding claim, wherein the feeding means includes:
an endless belt (66) having at least one generally-planar surface moving in a substantially-vertical
direction; and
means (78) for reducing the air pressure between the outermost sheet of the one end
of the stack and the belt so as to suck the sheet into contact with the adjacent planar
surface of the belt for movement therewith in a vertical direction.
10. Apparatus according to any preceding claim, including means for directing a flow
of air (84) toward the side faces of the stack to facilitate separation of successive
outermost sheets of the one end of the stack from the remainder of the stack.