U.S. patent number 3,612,677 [Application Number 04/830,381] was granted by the patent office on 1971-10-12 for electrostatic transfer apparatus.
This patent grant is currently assigned to Xerox Corporation. Invention is credited to Michael J. Langdon, Alan F. McCarroll.
United States Patent |
3,612,677 |
Langdon , et al. |
October 12, 1971 |
ELECTROSTATIC TRANSFER APPARATUS
Abstract
An electrically biased transfer drum for use as a transfer
mechanism in an electrostatic reproduction machine and having
gripping devices for maintaining a sheet of paper on the drum
during one or multiple transfer operations and other means for
effecting stripout of the sheet.
Inventors: |
Langdon; Michael J. (Webster,
NY), McCarroll; Alan F. (Rochester, NY) |
Assignee: |
Xerox Corporation (Rochester,
NY)
|
Family
ID: |
25256878 |
Appl.
No.: |
04/830,381 |
Filed: |
June 4, 1969 |
Current U.S.
Class: |
399/304; 101/246;
399/310; 399/394; 101/177; 101/409 |
Current CPC
Class: |
G03G
15/167 (20130101); G03G 15/0131 (20130101) |
Current International
Class: |
G03G
15/16 (20060101); G03G 15/01 (20060101); G03g
015/16 () |
Field of
Search: |
;355/4
;101/409,177,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Matthews; Samuel S.
Assistant Examiner: Bero; E. M.
Claims
What is claimed is:
1. A transfer apparatus for use in a multicolor printing machine
having means for producing a series of one or a plurality of
transferable images of an original to be copied onto a printing
member,
support means for supporting a sheet of transfer material and
moving the same in a recirculating path into contact with the
member, said support means including means for holding the sheet
thereon and releasing the same to permit removal therefrom, and
means associated with the support means for controlling the
releasing in accordance with a predetermined number of images of
the original being produced.
2. A transfer apparatus for use in a multicolor printing machine
having means for producing a series of one or a plurality of
transferable images of an original to be copied onto a printing
member,
support means for supporting a sheet of transfer material and
moving the same in a recirculating path into contact with the
member, said support means including means for gripping the
transfer material for holding the same thereon and means for
releasing the sheet to permit removal therefrom, and
means associated with the support means for controlling activation
of the releasing means in accordance with a predetermined number of
images of the original being produced.
3. A transfer apparatus for use in a multicolor printing machine
having means for producing a series of one or a plurality of
transferable images of an original to be copied onto a printing
member,
support means for supporting a sheet of transfer material and
moving the same in a recirculating path into contact with the
member, said support means including means for registering and
gripping the transfer material for holding the same thereon in one
mode of operation and means for releasing the sheet to permit
removal therefrom in another mode of operation, and
means associated with the support means for placing said
registering and gripping means in said one mode of operation in
accordance with the time sequence of production of the first
transferable image of the original.
4. A transfer apparatus for use in a multicolor printing machine
having means for producing a series of one or a plurality of
transferable images of an original to be copied onto a printing
member,
support means for supporting a sheet of transfer material and
moving the same in a recirculating path into contact with the
member, said support means including means for registering and
gripping the transfer material for holding the same thereon in one
mode of operation and means for releasing the sheet to permit
removal therefrom in another mode of operation, and
means associated with the support means for placing said
registering and gripping means in said one mode of operation in
accordance with the time sequence of production of the first
transferable image of the original and to place said release means
in said other mode of operation in accordance with a predetermined
number of images of the original being produced.
5. A transfer apparatus operable in a multicolor printing machine
having means for producing a series of one of a plurality of
transferable images of an original to be copied onto a printing
member,
a rotatable drum for supporting a sheet of transfer material and
moving the same in a recirculating path into contact with the
member, said drum including means for registering and holding the
transfer material thereon,
means for normally maintaining said drum out of contact with the
printing means,
force-generating means associated with said last-named means for
overcoming its normal effect on the drum when said force means is
activated, and
means associated with the force-generating means for activating the
same when the latter is in condition for operation in the machine.
Description
This invention relates to an electrostatic printing machine and in
particular to a transfer mechanism for use in supporting a sheet of
transfer material during the transfer of developed images in
multiple-image-recirculating programming.
With the advent of electrostatic color reproduction involving the
use of processing components which will produce a series of
electrostatic images of an original wherein each image is
representative of a particular color in the original and there is
the need to superimpose corresponding series of developed images
upon a sheet of transfer material, it is necessary that the images
being superimposed be accomplished with extreme accuracy of
registration. In addition, for high-speed automatic machine
operation, and for flexibility in the event that one or more images
of a series is possible, it is necessary that the transfer
mechanism be adapted for programming for single transfer as well as
multiple superimposed transfers.
Therefore, it is a principal object of the present invention to
incorporate a transfer mechanism in an electrostatic printing
machine which will render the machine capable of effecting one or
more transfers of developed images upon a sheet of transfer
material.
Another object of the invention is to utilize registration devices
and sheet-edge-gripping devices in a transfer mechanism for
accurately positioning the sheet to insure that successive images
being transferred will be registered with a previously transferred
image.
Another object of the invention is to control and effect the
registration, supporting and stripout of a sheet of transfer
material in accordance with desired requirements.
The foregoing objects are acquired by a transfer drum serving as a
biased electrode which is arranged to support a sheet of paper, and
to move the same in recirculating fashion into contact with a
photoconductive surface bearing a developed image. Registration
devices are mounted with the drum along with control mechanisms for
controlling the actuation of the device in timed sequence relative
to developed images moving into contact with the drum.
For a better understanding of the invention as well as other
objects and further features thereof, reference is had to the
following detailed description of the invention to be read in
conjunction with the accompanying drawings wherein:
FIG. 1 is a schematic view of a reproduction machine showing
various electrostatic processing components;
FIG. 2 is an enlarged view with parts broken away of the transfer
drum utilized in the present invention in one condition of
operation;
FIG. 3 is a longitudinal cross-sectional view of the transfer drum
and supporting structure;
FIG. 4 is a cross-sectional view of the drum showing some parts in
another condition of operation;
FIG. 5 is a cross-sectional view of the drum showing registration
of a sheet of transfer material;
FIG. 6 is a cross-sectional view of the drum showing the
sheet-gripping mechanism in a gripping condition; and
FIG. 7 is a cross section of a detail of the drum just prior to
stripout of the sheet.
For a general understanding of the illustrated copier/reproduction
machine, in which the invention may be incorporated, reference is
had to FIG. 1 in which the various components for the machine are
schematically illustrated. As in all electrostatic systems as well
as a xerographic machine of the type illustrated, a light image of
a document to be reproduced is projected onto the sensitized
surface of a xerographic plate to form an electrostatic latent
image thereon. Thereafter, the latent image is developed to form a
xerographic powder image, corresponding to the latent image on the
plate surface. The powder image is then electrostatically
transferred to a support surface to which it may be fixed by a
fusing device whereby the powder image is caused permanently to
adhere to the support surface.
In the illustrated machine, an original D to be copied is placed
upon a transparent support platen fixedly arranged relative to an
illumination lamp assembly 10 positioned at the upper end of the
machine as viewed in FIG. 1. While upon the platen, a programming
system for the machine introduces a lamp control circuit to cause
successive energization of the lamps in the lamp assembly 10 for
impinging light rays upon the original thereby producing image rays
which when acted upon by separation filters correspond to the color
informational areas on the original. The image rays are projected
by means of an optical lens system 11 for exposing the
photosensitive surface of a xerographic plate at the exposure
section A, the plate being in the form of a flexible
photoconductive belt 12 arranged on a belt assembly generally
indicated by the reverence numeral 13.
The photoconductive belt assembly 13 may be mounted upon the frame
of the machine and is adapted to drive the selenium belt 12 at a
constant rate in the direction of the arrow as shown in FIG. 1.
During this movement of the belt, the light-imaging rays of an
original are successively flashed full frame upon the surface of
the belt. The belt structure utilized comprises a layer of
photoconductive insulating material such as selenium on a
conductive backing that is sensitized prior to exposure by means of
a suitable charging corona generator device 14.
The flash exposure of the belt surface to the light image
discharges the photoconductive layer in the areas struck by light,
whereby there remains on the belt an electrostatic latent image for
each exposure, each being in image configuration corresponding to
the light image projected from the original D on the supporting
platen through the corresponding separation filters. As the belt
surface continues its movement, the latent electrostatic images
pass through a developing station B at which there is positioned a
developer assembly generally indicated by the reference numeral 15
and where the belt is maintained in a flat condition. The developer
assembly 15 comprises a plurality of developing devices 16, 17, 18
and 19 each of which contains a different color-developing material
to provide individual development of the electrostatic images.
The successively developed electrostatic images are transported by
the belt to a transfer station C whereat a sheet of copy paper is
moved at a speed in synchronism with the moving belt in order to
accomplish transfer of the developed images. There is provided at
this station a sheet transport mechanism in the form of a transfer
drum 20 adapted to support a sheet of paper and to carry the same
into image transfer relationship with the belt 12 once for each
image transfer operation. A sheet of paper S from a paper-handling
mechanism, generally indicated by the reference numeral 21 is
transported into position upon the drum 20 where it is supported
during the image transfer function. The transfer of the developed
image from the selenium belt surface to sheet material is effected
by means of an electrical bias of the opposite polarity as the
triboelectric charge on the developing particles utilized in image
development being applied to the transfer drum 20 at the point of
contact between the sheet and selenium belt as the sheet passes the
transfer station C.
After the sheet is stripped from the transfer drum 20, it is
conveyed by conveyor 22 into a fuser assembly generally indicated
by the reference numeral 23 wherein the developed and transferred
powder image on the sheet material is permanently affixed thereto.
After fusing, the finished copy is discharged from the apparatus at
a suitable point for collection externally of the apparatus.
It is believed that the foregoing description is sufficient for the
purposes of this application to show the general operation of an
electrostatic copier constructed in accordance with the present
invention.
After development, each image of the series of color-responsive
images formed and developed on the selenium belt 12 or in the case
of black and white reproduction, each of the white-light-exposed
images is moved out of the development station B and carried to the
transfer station C. In this station, the belt 12 is carried around
a roller 70 which forms one of the three rollers of the belt
assembly 13. Transfer occurs at the line on the belt 12 resulting
when the transfer drum 20, which serves as a biased electrode, is
in contact with the adjacent surface thereof as it is moved about
the roller 70.
The transfer drum 20 is normally held away from the selenium belt
12 by means of a spring retaining force and upon a control signal
from the programming system for the machine, will energize a
solenoid for overcoming the spring force and to force the drum
against the belt. In this manner, the operation of the transfer
drum is fail-safe; that is, in the event of power failure or
machine malfunctions, the drum will be normally moved into position
of safety relative to the more delicate structure of the selenium
belt.
The drum 20 comprises a metallic cylinder mounted on two
independently swinging arms and having an electrically conductive
rubber blanket fixed therearound and connected to a suitable source
of electrical current for image transfer purposes. As shown in
FIGS. 2 and 3, a rubber-coating blanket 71 is applied to a metallic
cylinder 72 and is preferably made of rubber having a resiliency
such that with light pressure being applied thereto while in
contact with the belt 12, there will be a very slight flattening of
or indentation into the rubber for enhancing image transfer.
One end of the metal cylinder 72 is closed by an end cap 73 having
a drive shaft 74 mounted centrally thereof. The other end of the
cylinder 72 is also closed by a cap 75 which includes a centrally
positioned hollow shaft 76. Means are provided for supporting the
drum 20 by way of its supporting shafts 74, 76, which will permit
movement of the drum into its two controlling positions. For this
goal, the shaft 74 is suitably journaled on one end of an arm 77
which is rotatably supported at its other end on a shaft 78 secured
to the frame 80 of the machine with its axis parallel to the axis
of the drum. Similarly, the shaft 76 extends through and is
journaled on one end of an arm 81 which is similar to the arm 77
and which is also journaled upon the shaft 78. The machine frame 80
is provided with vertically extending plates 82 for supporting a
shaft 83 in a position parallel to the axis of the drum and the
shaft 78 and to one side of one edge of each of the arms 77,
81.
At each end of the shaft 83 there is formed a cam 85, only one of
which is shown in the drawings, and at one end of the shaft
adjacent the cam there is also provided an integral lever 86. Both
cams 85 are adapted to engage the adjacent edges 87 of the arms 77,
81 for forcing these arms to rotate about their common shaft 78
during slight rotation of the shaft 83. With the cams 85 having
slight camming surfaces, this rocking movement of the arms is
slight, being sufficient to disengage contact between he roller 20
and the belt 12. A coil spring 88 is held in tension between one
end of the lever 86 and the machine frame 80 for normally tending
to rotate the cams 85 against the arms in a direction to force the
drum 20 away from the belt 12 (clockwise rotation of the arm 77, 81
in FIG. 2).
In order to overcome the spring force of spring 88, and to enable
the drum 20 to contact the belt 12 for the image transfer function,
there is provided a solenoid SOL-2 for rotating the shaft 83 in a
direction opposite that produced by the spring 88. The solenoid
SOL-2 is secured to the machine frame 80 and includes a plunger 90
pivotally connected to a link arm 91 secured to the shaft 83. As
shown in FIG. 4, the link arm 91 is on the other side of the shaft
83 from the lever 86 so that upon energization of solenoid SOL-2,
which results in the pull-in drive motion of the plunger 90, will
overcome the spring force and cause rotation of the shaft 83 in a
direction opposed to the spring action. This energization in effect
will cause the arms 81, 77 to rotate in a counterclockwise
direction and allow the drum 20 to engage the belt 12.
The transfer drum 20, in serving as an image transfer arrangement,
is capable of registering and supporting a sheet of transfer
material for either one transfer cycle or for recirculating the
sheet through a plurality of transfer cycles. As previously
described, the original D is exposed three times in order to
produce a series of three latent electrostatic images each of which
is developed in sequence and made ready for transfer. In order to
make a single color reproduction of the original, the three
developed images are transferred individually and to the same sheet
of transfer material.
In order to effect precise registration and positioning of sheets
of transfer material upon the drum 20, there is provided a
plurality of registration elements 95 mounted within and for
movement radially of the drum. To permit registration, the elements
extend through openings 96 formed in the periphery of the drum
surface, the openings being in a line parallel to the axis of the
drum. Each of the elements 95 has a flat rectangular configuration
and is formed with a outward-extending projection 97 which is
movable radially with the elements from a position within the
periphery surface of the drum to two positions slightly outwardly
of the periphery of the drum. When in use, the leading edge of a
sheet S engages the elements 95 immediately outwardly of the
projections 97 upon which the edge will be held during
recirculation of the sheet (see FIG. 5).
Radial movement of the elements 95 is provided by means of a shaft
98 mounted for rotation within the drum working in conjunction with
drive rods 100 secured to the shaft and which are adapted to be
slidably held within apertures 101 formed at the innermost ends of
the element. The shaft 98 is supported and journaled upon the inner
surface of the cylinder 72 by means of bearing blocks 102, and upon
rotation of the shaft 98 the rods 100 will be swung therewith for
causing the elements 95 to move outwardly or inwardly as the case
may be, relative to the axis of the drum 20. In operation, the
elements 95 are adapted to assume three positions: the first, when
no sheet is being transported, the elements occupy their innermost
position, the second in a slightly outward position so that the
projections 97 are positioned slightly away from the peripheral
surface of the drum when a sheet has been registered as shown in
FIG. 5 and third, with the projections 97 at a slightly greater
distance from the periphery so as to move the leading edge of the
sheet away from the drum periphery just prior to stripout of the
sheet as shown in FIG. 6.
Operating in close conjunction with the registration elements 95
are a plurality of gripper fingers 105 which are secured to the
shaft 98 by means of clamps 106 and which extend through openings
107 formed in the periphery of the drum 20 in alignment with the
openings 96 for the elements 95. As shown in FIG. 6, when viewing
the drum 20 axially, the fingers 105 and the elements 95 are in
alignment parallel to the axis of the drum. A spring 108 is held in
tension between an anchor fixed to the interior of the cylinder 72
and a link 109 secured to the shaft 98 for normally biasing the
elements 95 in their retracted or innermost position and the
fingers 105 in their paper-clamping position.
One end of the shaft 98 has a crank arm 110 secured thereto
adjacent to and inwardly of the end cap 75. A connecting rod 111
secured to one end of the arm 110 projects through an opening 112
in the end cap 75, and is connected externally of the drum to a
linkage system which will control the operation of the registration
elements 95 and the gripper fingers 105.
The linkage system comprises a link member 113 pivotally mounted at
one end by a pivot pin 114 to the upper end of the arm 81; a second
link member 115 pivotally connected at one end to the free end of
the link member 113; and a third link member 116 pivotally
connected at one end to the free end of the link member 115. The
link member 116 is secured intermediate its ends to a shaft 117 of
a rotary solenoid SOL-3 mounted on the arm 81. When the solenoid
SOL-3 is not energized, a spring (not shown) built into the
solenoid will normally maintain the linkage in the position shown
in FIG. 3. When the solenoid is energized, clockwise rotation is
imparted to the link 116 thereby forcing the link member 115
downwardly and to the left causing clockwise rotation of the link
113 about the pivot pin 114. This position of the linkage system is
shown at FIG. 2, with the solenoid energized. In effect, the pivot
pin 114 and the solenoid shaft 117 supports the linkage system.
A cam lobe in the form of a detent 120 is formed on the inner edge
of the link 113, and similarly the inner edge of the link 116 is
formed with a cam lobe in the form of a detent 121. Actually, the
inner edges of the links 113, 116 are camming surfaces as will be
presently described, and the detent curves mainly control the
camming effect of these edges. Each of the detents 120, 121 is
adapted to cooperate for specific operation with a cam follower 122
in the form of a bearing race secured to the exterior end of the
rod 111. During rotation of the transfer drum 20, the connecting
rod 111 revolves about the axis of the drum since the shaft 98 and
the opening 112 for the rod 111 move in a revolving motion about
the axis. As the rod 111 revolves, it carries the cam follower 122
therewith in a circulating path having a predetermined radius with
its center coincident with the axis of the drum 20 as illustrated
by the letter P in FIGS. 2 and 4.
In the condition of operation for effecting either single or
multiple image transfer with the solenoid SOL-3 energized to move
the linkage to its position shown in FIG. 2, the cam follower 122
(see dotted position) in its revolution along the path P will
engage the inner edge of the link 116 at a point to the left of the
shaft 117 which is in the path of movement of the follower for
forcing the rod 111 inwardly. The follower makes contact with the
adjacent end of the detent 121 which slows down radial movement of
the rod 111 as it slides along the curve of the detent. Without
this detent upon striking the edge of the link 116, the rod 111
would be propelled inwardly at too great a speed for the structural
parts of the drum. The resultant movement of the rod 111 toward the
axis of the drum is in opposition to the force provided by the
spring 108 upon the shaft 98. The opening 112 is of a size
sufficient to permit this limited movement of the rod 111 relative
thereto. This slight inward movement of the rod 111 will produce
slight rotation of the shaft 98 and consequently will produce
slight onward radial movement of the registration elements 95 at
the same time that the leading edge of a sheet of paper reaches
these elements for registration thereby (see FIG. 5). At the same
time, the gripper fingers 105 are rotated slightly out of the way
to permit sheet registration. Immediately after registration, the
solenoid SOL-3 is deenergized for multiple image transfer to allow
the linkage to assume the position shown in FIG. 4 by virtue of the
solenoid spring, and to allow the spring 108 to rotate the shaft 98
back to its original position. This movement produces outward
movement of the rod 111 as it continues its revolving motion and
out of the inner edge of the link 116. With the shaft 98 moved to
its original position, it allows the registration elements 95 to
assume their initial inactive condition and the fingers 105 to grip
the leading edge of the sheet material thereby permitting transport
and support of the sheet around the drum 20 (see FIG. 6 for this
completed action). As the drum 20 rotates, it carries the leading
edge of the sheet and the remaining portion thereof into the
transfer station C to effect developed image transfer thereon. As
the cam follower 122 continues its revolving movement and with the
solenoid SOL-3 energized for single transfer, the follower engages
the inner edge of the link 113 at the leading end of the detent 120
and the rod 111 is driven inwardly again in a softened action as
provided by the detent. The position of the link 113 is such that
this inward movement of the rod 111 is greater than its inward
movement provided by the detent 121. This action again rotates the
shaft 98 against the spring force of the spring 108 except that the
rotation is slightly larger than the initial rotation when the
leading edge of a sheet was being registered. This additional
rotation causes movement of the gripper fingers 105 out of contact
with the leading edge of the sheet and additional clearance
therefrom, and permits the projections 97 of the registration
elements 95 to move the leading edge away from the periphery of the
drum. A slight additional rotation of the drum will transport the
leading edge of a sheet over the leading points of fixed stripout
fingers 130 (see FIG. 7) and thereby remove the sheet from the drum
as continued rotation thereof is made. As shown in FIG. 7, when the
projections 97 have been moved to their outermost position for the
stripout mode of operation to separate the leading edge of the
sheet S from the drum, the leading points of the stripout fingers
130 are adapted to enter slightly below the surface of tee
projections upon which the leading edge of the sheet S is
placed.
In operation just prior to a sheet being fed to the drum 20, the
linkage system comprising the links 113, 115 and 116 are arranged
as shown in FIG. 4 wherein the detents 120 and 121 are positioned
so that the cam follower 122 will not coact with either during a
complete revolution. In the event that only one transfer is to be
made per copy, say when black and white copies are being made, upon
a sheet S being fed by the feeder 21, the solenoid SOL-3 is
energized to bring the inner edge of the link 116 into the path of
the follower 122. After the leading edge of the sheet is registered
and gripped, the solenoid remains energized so that the follower
may engage the detent 120 in order to produce sheet stripout. In
the event a three-color series of images have been produced and
three transfers on the same sheet are to be accomplished, after the
solenoid is energized to register and grip a sheet of support
material, it is quickly deenergized, before the follower 122 can
reach the link 113. In this event, the sheet cannot be stripped off
the drum 20 as the camming surface of the detent 120 is held away
from the path of movement of the follower and the sheet will remain
on the drum until three image transfers have been completed. After
the last transfer and when the follower 122 has passed the detent
121, the solenoid SOL-3 is again energized to position the linkage
as shown in FIG. 2 in order to permit the follower to engage the
inner edge of the link 113. As previously described, upon this
occurrence, the sheet S will be stripped off the transfer drum as
it continues its rotation. In summary, when the solenoid SOL-3 is
energized, both camming detents 120, 121 are actuated into the path
of movement P of the follower 122. When deenergized both detents
are actuated out of the path of the follower. For single image
transfer copies, after registration, the solenoid remains
energized. For multiple image transfer copies, after registration,
the solenoid is deenergized and remains so until stripout.
For automatic operation, another sheet S of paper fed toward the
drum by the paper sheet feed mechanism 21 will be registered and
gripped by the elements 95 and 105 as these elements continue
around to the paper register position of the drum 20. The paper
feed mechanism working in automatic conjunction with the transfer
drum registration and gripping mechanisms feed individual sheets of
paper into pinch rollers 135 (see FIG. 1) which are arranged to
feed the leading edge of the sheet at a greater speed than the
circumferential speed of the drum 20 in order to permit the leading
edge to contact the registration elements 95.
While the invention has been described with reference to the
structure disclosed herein, it is not confined to the details set
forth; but is intended to cover such modifications, or changes as
may come within the scope of the following claims.
* * * * *