U.S. patent application number 11/377945 was filed with the patent office on 2007-09-20 for method and apparatus for assuring proper media feeding.
Invention is credited to Avi Barazani, Aron Shmaiser, Gilad Tzori.
Application Number | 20070216088 11/377945 |
Document ID | / |
Family ID | 38516987 |
Filed Date | 2007-09-20 |
United States Patent
Application |
20070216088 |
Kind Code |
A1 |
Barazani; Avi ; et
al. |
September 20, 2007 |
Method and apparatus for assuring proper media feeding
Abstract
This invention relates to an apparatus for assuring media
feeding, comprising: an impression drum having a media gripper; an
input feed unit located substantially adjacent to the impression
drum for feeding a sheet of media; and a servo motor operatively
connected to the input feed unit such that a change in operating
characteristics of the servo motor is detected if the sheet of
media is properly retained by the gripper.
Inventors: |
Barazani; Avi; (Rehovot,
IL) ; Shmaiser; Aron; (Rehovot, IL) ; Tzori;
Gilad; (Rehovot, IL) |
Correspondence
Address: |
HEWLETT PACKARD COMPANY
P O BOX 272400, 3404 E. HARMONY ROAD
INTELLECTUAL PROPERTY ADMINISTRATION
FORT COLLINS
CO
80527-2400
US
|
Family ID: |
38516987 |
Appl. No.: |
11/377945 |
Filed: |
March 16, 2006 |
Current U.S.
Class: |
271/275 |
Current CPC
Class: |
B65H 2301/4474 20130101;
B65H 2301/4474 20130101; B65H 2301/4474 20130101; B65H 2513/10
20130101; B65H 5/12 20130101; B65H 2513/10 20130101; B65H 2220/02
20130101; B65H 2220/02 20130101; B65H 2220/01 20130101; B65H
2220/01 20130101; B65H 2220/11 20130101 |
Class at
Publication: |
271/275 |
International
Class: |
B65H 5/02 20060101
B65H005/02; B65H 5/04 20060101 B65H005/04 |
Claims
1. An apparatus for assuring media feeding, comprising: an
impression drum having a media gripper; an input feed unit located
substantially adjacent to the impression drum for feeding a sheet
of media; and a servo motor operatively connected to the input feed
unit such that a change in operating characteristics of the servo
motor is detected if the sheet of media is properly retained by the
gripper.
2. The apparatus, as in claim 1, wherein the input feed unit is
further comprised of: a plurality of rollers that create a nip.
3. The apparatus, as in claim 1, wherein the apparatus is further
comprised of: a servo motor controller operatively connected to the
servo motor to control operating characteristics of the servo
motor.
4. The apparatus, as in claim 1, wherein the apparatus is further
comprised of: a ITM drum located substantially adjacent to the
impression drum so as to create a nip between the impression drum
and the ITM drum.
5. A method for assuring media feeding, comprising: pushing a sheet
of media by an input feed unit to cause the media to move towards
an impression drum; determining a velocity of the input sheet unit;
detecting a change in the velocity of the input feed unit; and
determining if the media has been properly retained in media
grippers substantially located on the impression drum.
6. The method, as in claim 5, wherein the method is further
comprised of: allowing the media to enter into the media grippers;
pulling the media by the grippers such that the media will pull
against the input feed unit; creating a negative pulling force on
the input feed unit; detecting the change in a velocity level of
the input feed unit; and accelerating the velocity of the input
feed unit so that it becomes equal to a velocity of the
grippers.
7. The method, as in claim 6, wherein the pushing step is further
comprised of: operating a servo motor operatively connected to the
input feed unit to cause the media to move towards an impression
drum.
8. The method, as in claim 6, wherein the pulling step is further
comprised of: creating a pulling force that should be greater then
a driving force of the input feed unit but not great enough to
adversely affect the media or pull the media out of the
grippers.
9. The method, as in claim 7, wherein the detecting step is further
comprised of: operatively connecting the servo motor to the input
feed unit; detecting a change in velocity level of the servo motor;
and employing a servo motor controller to detect the change in the
velocity of the servo motor.
10. The method, as in claim 9, wherein the accelerating step is
further comprised of: operating the servo motor in order to change
the velocity of the input feed unit.
11. The method, as in claim 5, wherein the method is further
comprised of: the media does not properly engage with the grippers;
creating a decreased velocity of the input feed unit; and stopping
the media from moving towards the impression drum.
12. The method, as in claim 11, wherein the step of creating a
decreased velocity is further comprised of: eliminating any tension
force that is applied upon the input feed unit by the media.
13. A program storage medium readable by a computer, tangibly
embodying a program of instructions executable by the computer to
perform method steps for assuring media feeding, comprising:
pushing a sheet of media by an input feed unit to cause the media
to move towards an impression drum; determining a velocity of the
input sheet unit; detecting a change in the velocity of the input
feed unit; and determining if the media has been properly retained
in media grippers substantially located on the impression drum.
14. The method, as in claim 13, wherein the method is further
comprised of: allowing the media to enter into the media grippers;
pulling the media by the grippers such that the media will pull
against the input feed unit; creating a negative pulling force on
the input feed unit; detecting the change in a velocity level of
the input feed unit; and accelerating the velocity of the input
feed unit so that it becomes equal to a velocity of the
grippers.
15. The method, as in claim 14, wherein the pushing step is further
comprised of: operating a servo motor operatively connected to the
input feed unit to cause the media to move towards an impression
drum.
16. The method, as in claim 14, wherein the pulling step is further
comprised of: creating a pulling force that should be greater then
a driving force of the input feed unit but not great enough to
adversely affect the media or pull the media out of the
grippers.
17. The method, as in claim 15, wherein the detecting step is
further comprised of: operatively connecting the servo motor to the
input feed unit; detecting a change in velocity level of the servo
motor; and employing a servo motor controller to detect the change
in the velocity of the servo motor.
18. The method, as in claim 17, wherein the accelerating step is
further comprised of: operating the servo motor in order to change
the velocity of the input feed unit.
19. The method, as in claim 13, wherein the method is further
comprised of: the media does not properly engage with the grippers;
creating a decreased velocity of the input feed unit; and stopping
the media from moving towards the impression drum.
20. The method, as in claim 19, wherein the step of creating a
decreased velocity is further comprised of: eliminating any tension
force that is applied upon the input feed unit by the media.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an apparatus for assuring media
feeding, comprising: an impression drum having a media gripper; an
input feed unit located substantially adjacent to the impression
drum for feeding a sheet of media; and a servo motor operatively
connected to the input feed unit such that a change in operating
characteristics of the servo motor is detected if the sheet of
media is properly retained by the gripper.
[0003] 2. Description of the Related Art
[0004] Prior to the present invention, as set forth in general
terms above and more specifically below, it is known, in the
printing art to employ sensors at the entrance between the
impression drum and the intermediate transfer drum in order to
detect the media leading-edge position and timing. While this
system is capable of detecting the leading edge and timing of the
media, this solution requires additional sensors inside of the
printing device. Also, the leading edge position and timing of the
media are detected outside of the media grippers that can result in
an inadequate detection of paper stick to blanket (PSTB). Finally,
the sensors of this system may send faulty alarms due to dirt and
paper dust adversely affecting the sensors. Consequently, a more
advantageous system, then, would be provided if such sensors can be
avoided.
[0005] It is also known, in the printing art to employ a
pressurized system to determine if the media is located against the
impression drum. In this manner, a vacuum is applied to the
impression drum. If a sheet of media is located on the impression
drum, a change in the vacuum properties is detected. While this
system is capable of detecting the presence the media, this
solution requires additional sensors inside of the printing device.
Also, the system is not capable of detecting if the media is
properly located within grippers. Finally, the vacuum sensors of
this system may send faulty alarms due to vacuum ports becoming
inadvertently clogged. Therefore, a further advantageous system,
then, would be provided if such a vacuum system could be
avoided.
[0006] It is apparent from the above that there exists a need in
the art for a method and apparatus for assuring proper media
feeding such that the proper retention of the media within the
grippers can be detected without the use of sensors or other
complicated systems so as to avoid paper stick to blanket (PSTB).
It is a purpose of this invention to fulfill this and other needs
in the art in a manner more apparent to the skilled artisan once
given the following disclosure.
SUMMARY OF THE INVENTION
[0007] Generally speaking, an embodiment of this invention fulfills
these needs by providing an apparatus for assuring media feeding,
comprising: an impression drum having a media gripper; an input
feed unit located substantially adjacent to the impression drum for
feeding a sheet of media; and a servo motor operatively connected
to the input feed unit such that a change in operating
characteristics of the servo motor is detected if the sheet of
media is properly retained by the gripper.
[0008] In certain preferred embodiments, the input feed unit is a
plurality of rollers that create a nip to feed the sheet of media
towards the impression drum. Also, if a change in the torque on
servo motor is detected then it can be assumed that the sheet of
media is properly retained by the gripper. Finally, if a change in
the velocity of the servo motor is detected, then it can be assumed
that the media has not been properly retained by the grippers.
[0009] In another further preferred embodiment, a method and
apparatus is presented for assuring proper media feeding such that
the proper retention of the media within the grippers can be
detected without the use of sensors or other complicated systems so
as to avoid paper stick to blanket (PSTB).
[0010] The preferred method and apparatus for assuring media
feeding, according to various embodiments of the present invention,
offers the following advantages: ease-of-use; elimination of
extraneous sensors; improved detection times; reduced printer
downtime; decreased paper stick to blanket occurrences; and reduced
blanket damage. In fact, in many of the preferred embodiments,
these factors of elimination of sensors, improved detection times,
reduced printer downtime, decreased paper stick to blanket
occurrences, and reduced blanket damage are optimized to an extent
that is considerably higher than heretofore achieved in prior,
known method and apparatus for assuring media feeding.
[0011] The above and other features of the present invention, which
will become more apparent as the description proceeds, are best
understood by considering the following detailed description in
conjunction with the accompanying drawings, wherein like characters
represent like parts throughout the several views and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic illustration of a method and apparatus
for assuring proper media feeding wherein the media has reached the
grippers on time, according to another embodiment of the present
invention;
[0013] FIG. 2 is a schematic illustration of a method and apparatus
for assuring proper media feeding wherein the media has missed the
grippers, according to another embodiment of the present
invention;
[0014] FIG. 3 is a graphical illustration of paper velocity at
various feed stages (time (ms) versus paper velocity (mm/s)),
according to the prior art;
[0015] FIG. 4 is a graphical illustration of paper velocity with
servo detection at various feed stages (time (ms) versus paper
velocity (mm/s)) as the media enters into the grippers properly,
according to another embodiment of the present invention; and
[0016] FIG. 5 is a graphical illustration of paper velocity with
servo detection at various feed stages (time (ms) versus paper
velocity (mm/s)) as the sheet of media misses the grippers,
according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The paper stick to blanket (PSTB) phenomenon is one of the
main reasons for blanket (the soft material that is wrapped around
the ITM drum) damage due to its interaction with jammed media. When
PSTB occurs, the printer stops printing and the operator must then
get to the blanket. The jammed media and any residual ink must be
cleaned from the blanket. During this operation, the image may be
fused to the blanket and then the operator is forced to replace the
blanket. Also, in some cases, the jammed media may become bent and
this bend may cause a mechanical defect in the blanket, which may
also force the operator to place to blanket. It is to be kept in
mind that under normal operating conditions, it takes about 30
milliseconds between the time the grippers are closed and the
grippers reach the next drum. Clearly, media jamming is an issue
and, even greater, is the concern of how to quickly determine that
a media jammed has occurred in order to avoid undue amounts of lost
downtime.
[0018] With this background in mind, apparatus 2 for assuring
proper media feeding is illustrated in FIGS. 1 and 2. Apparatus 2
includes, in part, conventional ITM drum 4, conventional impression
drum 6, conventional grippers 8, input feed unit 10, a sheet of the
media 12, servo motor 14, and servo motor controller 16.
Preferably, input feed unit 10 includes a plurality of rollers that
create a nip. This nip interacts with media 12 in order to feed
media 12 towards impression drum 6 and grippers 8. Servo motor 14,
preferably, is operatively connected to input feed unit 10 and is
any suitable electromechanical mechanism that supplements a primary
control operated by comparatively feeble force through servo motor
controller 16. It is to be understood that controller 16 can be
part of servo motor 14 or located outside of servo motor 14.
[0019] FIGS. 1 and 2 illustrate two scenarios that can occur with
respect to apparatus 2. In the first scenario, media 12 properly
enters into grippers 8, as illustrated in FIG. 1. In FIG. 1, input
feed unit 10 pushes the media 12 to cause the media 12 to move
towards the nip between ITM drum 4 and impression drum 6 and at the
right time, apply a tension force. Media 12 properly enters into
grippers 8. Grippers 8 will pull media 12 against input feed unit
10 and servo motor 14. This pulling creates a negative pulling
force (tension mode) on servo motor 14. It is to be understood that
the pulling force of grippers 8 should be greater than the driving
force of servo motor 14 on input feed unit 10 so that grippers 8
are capable of pulling media 12 through input feed unit 10 but not
great enough to rip or otherwise adversely affect media 12 or pull
media 12 out of grippers 8. At this point, servo motor controller
16 will detect a change at the velocity levels (or current levels)
of servo motor 14 and will cause input feed unit 10 to accelerate
the velocity of media 12 so that it is equal to the process
velocity (the velocity of media 12 at grippers 8) in order to avoid
unnecessary tension upon media 12. In this manner, the proper
gripping of media 12 by grippers 8 can be quickly and easily
detected.
[0020] With respect to FIG. 2, input feed unit 10 pushes the media
12 to cause the media 12 to move towards the nip between ITM drum 4
and impression drum 6 and at the right time, apply a tension force.
In this Figure, media 12 misses grippers 8. It is to be understood
that media 12 may miss the grippers 8 for a variety of reasons. For
example, there may be a delay in the conveyor (not shown) that
feeds media 12 into input feed unit 10. Also, media 12 may be
skewed when it reaches grippers 8. Also, there may be a malfunction
in the mechanical system which controls the gripper's actuation.
Finally, there may be a malfunction in input feed unit 10 which
feeds media 12 into grippers 8. Due to the fact that media 12
misses or otherwise does not properly engage with grippers 8, there
will be no tension force on servo motor 14 on that will resist
against grippers 8 and pull media 12 away from grippers 8. In this
manner, servo motor controller 16 will detect a decreased change in
velocity level (or current level) of servo motor 14 and stop media
12 from entering into the nip between ITM drum 4 and impression
drum 6. Consequently, PSTB will be efficiently detected and
prevented.
[0021] To demonstrate further proof of the concepts of the present
attention, FIGS. 3-5 are presented. With respect to FIG. 3, a
conventional current input feed unit operation is driven by a
stepper motor, according to the prior art. As shown in the graph,
media reaches the input feed unit, stops, and, at the right moment,
the media is fed into the impression drum grippers. During the
movement of the media, the input feed unit accelerates and
decelerates the media until the media reaches the grippers. When
the grippers close, the media velocity is equal to the process
velocity (the velocity of the grippers). The input feed unit drives
the media at this velocity until the trailing edge of the sheet of
media exits the input feed unit.
[0022] FIG. 4 is a graphical illustration showing how the media
enters into the grippers properly, according to the present
invention. As shown in FIG. 4, grippers 8 (FIGS. 1 and 2) will pull
media 12 against servo motor 14 to create a negative pulling force
(tension mode) on servo motor 14. The pulling force of grippers 8
should be greater than the force applied by input feed unit 10 and
servo motor 14 so that grippers 8 will pull media 12 through input
feed unit 10. Servo motor controller 16 will detect a change in
velocity levels (or current levels) of servo motor 14 and will
accelerate the velocity of media 12 through input feed unit 10 so
that it is equal to the process velocity (the velocity of grippers
8) in order to avoid unnecessary tension on media 12. In this
manner, the proper retention of media 12 within grippers 8 can be
efficiently detected.
[0023] FIG. 5 is a graphical illustration showing how the media
missed the grippers, according to present invention. As shown in
FIG. 5, input feed unit 10 will apply a tension force to media 12.
Due to the fact that media 12 misses grippers 8, there will be no
tension force on media 12 by grippers 8 that will pull media 12.
Due to this loss of tension force, the velocity of media 12 will be
reduced. Servo motor controller 16 will detect this change in
velocity of media 12 through input feed unit 10 and stop media 12
from entering into the nip between ITM drum 4 and impression drum
6. In this manner, PSTB will be efficiently detected and
prevented.
[0024] The present invention can be embodied in any
computer-readable medium for use by or in connection with an
instruction-execution system, apparatus or device such as a
computer/processor based system, processor-containing system or
other system that can fetch the instructions from the
instruction-execution system, apparatus or device, and execute the
instructions contained therein. In the context of this disclosure,
a "computer-readable medium" can be any means that can store,
communicate, propagate or transport a program for use by or in
connection with the instruction-execution system, apparatus or
device. The computer-readable medium can comprise any one of many
physical media such as, for example, electronic, magnetic, optical,
electromagnetic, infrared, or semiconductor media. More specific
examples of a suitable computer-readable medium would include, but
are not limited to, a portable magnetic computer diskette such as
floppy diskettes or hard drives, a random access memory (RAM), a
read-only memory (ROM), an erasable programmable read-only memory,
or a portable compact disc. It is to be understood that the
computer-readable medium could even be paper or another suitable
medium upon which the program is printed, as the program can be
electronically captured, via, for instance, optical scanning of the
paper or other medium, then compiled, interpreted or otherwise
processed in a single manner, if necessary, and then stored in a
computer memory.
[0025] Those skilled in the art will understand that various
embodiment of the present invention can be implemented in hardware,
software, firmware or combinations thereof. Separate embodiments of
the present invention can be implemented using a combination of
hardware and software or firmware that is stored in memory and
executed by a suitable instruction-execution system. If implemented
solely in hardware, as in an alternative embodiment, the present
invention can be separately implemented with any or a combination
of technologies which are well known in the art (for example,
discrete-logic circuits, application-specific integrated circuits
(ASICs), programmable-gate arrays (PGAs), field-programmable gate
arrays (FPGAs), and/or other later developed technologies. In
preferred embodiments, the present invention can be implemented in
a combination of software and data executed and stored under the
control of a computing device.
[0026] It will be well understood by one having ordinary skill in
the art, after having become familiar with the teachings of the
present invention, that software applications may be written in a
number of programming languages now known or later developed.
[0027] Once given the above disclosure, many other features,
modifications or improvements will become apparent to the skilled
artisan. Such features, modifications or improvements are,
therefore, considered to be a part of this invention, the scope of
which is to be determined by the following claims.
* * * * *