U.S. patent number 3,774,016 [Application Number 05/186,234] was granted by the patent office on 1973-11-20 for control of process according to registration indicia on material being processed.
This patent grant is currently assigned to Sun Chemical Corporation. Invention is credited to Richard McGuire, Robert B. Sterns.
United States Patent |
3,774,016 |
Sterns , et al. |
November 20, 1973 |
CONTROL OF PROCESS ACCORDING TO REGISTRATION INDICIA ON MATERIAL
BEING PROCESSED
Abstract
A web cut off device is controlled to produce cuts in accordance
with registration marks on the web by measuring the deviation of
each cut from its associated registration mark, inserting a first
correction corresponding to this deviation and superimposing a
second correction based upon the statistical processing of a number
of preceeding deviation signals.
Inventors: |
Sterns; Robert B. (Great Neck,
NY), McGuire; Richard (Smithtown, NY) |
Assignee: |
Sun Chemical Corporation (New
York, NY)
|
Family
ID: |
22684155 |
Appl.
No.: |
05/186,234 |
Filed: |
October 4, 1971 |
Current U.S.
Class: |
700/51; 340/675;
700/125; 700/167; 700/193; 226/28 |
Current CPC
Class: |
B23D
36/005 (20130101) |
Current International
Class: |
B23D
36/00 (20060101); G06f 015/46 (); B65n
023/18 () |
Field of
Search: |
;235/151.1,151.13,151.32,92DN,92EV ;250/219LG ;340/259
;226/10,28-30,40 ;101/226 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Botz; Eugene G.
Assistant Examiner: Smith; Jerry
Claims
What is claimed is:
1. A method for controlling a device which operates on a medium in
a sequence of intervals so that the intervals of device operation
coincide with predetermined intervals on said medium, said method
comprising the steps of detecting each interval on said medium,
detecting each operation of said device, generating deviation
signals based upon each detection corresponding to the deviation
from coincidence of device operation and medium interval, adjusting
each interval of operation of the device based upon a first
combination of the deviation signal generated during the
immediately preceding interval and a first trend signal,
maintaining said first trend signal for a succession of intervals,
while comparing only the deviation signals generated during said
succession to produce a new trend signal, adjusting each of a
further succession of intervals of operation following the
production of the new trend signal, the last mentioned adjusting
being based upon a new combination of signals including the
deviation signal generated during the immediately preceding
interval and the new trend signal and maintaining the new trend
signal while comparing the deviation signals developed during said
further succession of intervals.
2. A method according to claim 1, wherein said adjusting comprises
the steps of generating first correction signals corresponding to
said deviation signals in each interval, generating second
correction signals corresponding to said trend signal being
maintained, algebraically combining said first and second
correction signals in each interval to produce a total correction
signal and adjusting the interval of operation of said machine
according to said total correction signal.
3. A method according to claim 2, wherein each said second
correction signal is stored and is combined with the first
correction signal produced in each of the intervals following
production of said second correction signal.
4. A method according to claim 1 wherein said new combination of
signals further includes said first trend signal algebraically
combined with said new trend signal.
5. Apparatus for regulating a system which operates on a medium in
a sequence of intervals so that the intervals of device operation
coincide with predetermined intervals on said medium, said
apparatus comprising means for generating deviation signals
corresponding to the deviation of each operation interval from an
associated predetermined medium interval, phase correction means
operative to produce a phase correction signal corresponding solely
to the immediately preceding deviation signal, average deviation
correction means operative to produce an average deviation
correction signal in response to the algebraic sum of successive
statistical combinations of separate groups of successive deviation
signals and means for adjusting each interval of operation of said
system by an amount corresponding to a combination of phase
correction signals and said average deviation correction
signals.
6. Apparatus according to claim 5, wherein said means for adjusting
each interval of operation of said system includes correction
signal combining means connected to receive said phase correction
signal and said average deviation correction signal and to combine
said correction signals to produce a total correction signal and
means responsive to said total correction signal for producing a
corresponding adjustment in the interval of operation of said
system.
7. Apparatus according to claim 6, wherein said means for
generating said correction signals includes means for generating
series of pulses corresponding in number to the magnitude of
deviation and means for indicating the direction of deviation and
wherein said correction signal combining means comprises pulse
counter means connected to receive said pulses and to combine said
pulses algebraically.
8. Apparatus according to claim 5, wherein said means operative to
produce a phase correction signal includes correction signal
storage means operative to retain an average deviation correction
signal following combination of such signal with a phase correction
signal.
9. Apparatus according to claim 5, wherein said means operative to
produce an average deviation correction signal comprises first and
second signal combining means, each operative to combine signals
applied thereto in an algebraic manner, in regard to magnitude and
sign, with signals previously applied to said signal combining
means, said first signal combining means being connected to receive
and combine algebraically the phase deviation signals of seperate
groups and to produce a corresponding first signal combining means
output, said second signal combining means being connected to
receive and combine algebraically each first signal combining means
output.
10. Apparatus according to claim 9, wherein said first signal
combining means includes signal accumulator means and means
operative to clear said signal accumulator means upon the
occurrence of each first signal combining means output.
11. A method of controlling a process which is carried out in
successive operations, said method comprising the steps of
producing, after each operation of the process, a deviation signal
representative of the magnitude and direction of the deviation of
the result of the operation from a desired result, cumulatively
combining each successive deviation signal in an algebraic manner
with previously produced deviation signals to produce a new
cumulative result following each operation, comparing each
cumulative result with a different norm corresponding to the number
of deviation signals which have been combined, and adjusting said
process whenever any cumulative result exceeds its associated
norm.
12. A method according to claim 11 further including the step of
beginning a new cumulative combining of successive deviation
signals whenever any cumulative result exceeds its associated
norm.
13. A method according to claim 11, wherein said process is
adjusted by an amount corresponding to the number of deviation
signals which have been combined to produce the adjustment.
14. Apparatus for use in regulating a system which performs a
series of similar operations in successive intervals, said
apparatus comprising means for producing deviation signals
corresponding to the deviation of the result of each operation from
a desired result, combining means for algebrically combining each
deviation signal as it occurs with the algebraic total of combined
preceding deviation signals to produce a new total upon the
occurrence of each deviation signal, system operation counting
means for producing different outputs corresponding to successive
operations of said system, plural gate circuits connected to be
opened by the different outputs of said counting means, said gate
circuits each being further connected to respond, when opened, to a
different count level in said combining means and means responsive
to the occurrence of a response from any of said gate circuits for
producing a correction in said system.
15. Apparatus according to claim 14, wherein the last-mentioned
means includes means for clearing said combining means and for
clearing said system operation counting means upon the occurrence
of a response from any of said gate circuits.
16. Apparatus according to claim 14, wherein the last-mentioned
means includes means for generating different correction signals
corresponding to the particular gate circuit which responds to the
count level in said combining means.
17. A method for controlling a web cut system wherein the location
of each web cut is adjustable by an amount corresponding to the
degree of rotation, which is applied between successive web cuts,
to the input of a differential mechanism connected along a drive
which synchronizes longitudinal web movement with operation of a
cutter through which the web is moved, said method comprising the
steps of producing deviation indications representative of the
deviation of the actual location of each web cut from a desired cut
location, deriving a first average deviation correction signal by
statistically processing a series of deviation indications and
preserving a phase correction signal corresponding to each
immediately preceding deviation indication, during each interval
between successive operations of said cutter following the
deviation of said average deviation correction signal, rotating the
input of said differential mechanism by an amount corresponding to
a composite of said average deviation correction signal and the
phase correction signal derived from the immediately preceding
deviation indication, statistically processing a series of
subsequent deviation signals which occur following the derivation
of said first average deviation correction signal and to produce a
subsequent average deviation correction signal and modifying said
first average deviation correction signal by an amount
corresponding to said subsequent average deviation correction
signal.
18. A method according to claim 17, wherein said composite of said
average deviation correction signal and said phase correction
signal is derived by storing said average deviation correction
signal and algebraically combining each phase correction signal
with a signal equal to the stored average deviation correction
signal during the interval immediately following the production of
said phase correction signal.
19. A method for controlling a system which operates at successive
intervals to produce a series of successive results, said method
comprising the steps of measuring each result so-produced and
comparing same with a predetermined desired result to obtain a
separate deviation indication for each operation, statistically
processing a group of said deviations to produce a first average
deviation indication, producing a first average deviation
correction in said system, corresponding to said first average
deviation indication, for subsequent successive operations of said
system, statistically processing a further group of said deviations
which occur under the influence of said first average deviation
correction to produce a second average deviation indication and
producing a second average deviation correction in said system
corresponding to said second average deviation indication for
successive operations of said system subsequent to the production
of said second average deviation indication.
20. A method according to claim 19, wherein said second average
deviation correction corresponds to the algebraic sum of said first
and second average deviation indications.
21. Apparatus for regulating the operation of a system which
operates at successive intervals to produce a series of successive
results, said apparatus comprising deviation signal producing means
operative to produce a deviation signal following each operation of
the system, said deviation signal corresponding to the deviation of
the actual results of the operation from a predetermined desired
result, signal combining means operative to combine several
successive ones of said deviation signals and to produce a
correction signal corresponding to a statistical average of said
deviation signals, correction signal storage means for maintaining
a correction signal produced by said signal combining means, means
for successively applying the correction signal from said
correction signal storage means to adjust each subsequent interval
of operation of said system, means for clearing said signal
combining means in response to the production of a correction
signal thereby and means for applying subsequently produced
deviation signals to the signal combining means after clearance
thereof and during each said subsequent interval of operation of
said system.
Description
This invention relates to process control and more particularly, it
concerns novel methods and apparatus for maintaining proper
registry between a machine which operates on a material in
intervals and the material itself.
While different aspects of the present invention are applicable to
many types of processing operations which occur at successive
intervals, either in time or in space, on various media, the
invention as a whole is particularly advantageous in web cut-off
operations wherein a length of webbing, such as corrugated
paperboard is cut into lengths corresponding to a preprinted
pattern which repeates itself along the length of the web.
The present invention makes feasiable the preprinting of paperboard
webbing prior to the use of that webbing as a facing for corrugated
board which is thereafter creased and cut into predetermined
lengths for later folding into containers and cartons of
predetermined size. By printing on the webbing before it is glued
to the corrugated board, a high quality image may be produced.
However, once the board is printed, the locations where the board
must be cut transversely into individual lengths become
established; and unless the board is cut very close to those
locations, the printed pattern will not be properly positioned on
the panels of the finished carton or container which is later
folded into shape from the cut lengths of board.
In general, a web of corrugated paperboard is severed into discrete
lengths by moving it continuously between a pair of knife rolls.
These rolls rotate in synchronism with each other; and knife blades
on the rolls come together once during each revolution thereof to
effect a transverse cut across the web. It will be appreciated that
the location of a cut may be moved downstream, i.e., further along
in the direction of board movement, either by speeding up the
cutter roll rotation or by slowing down the speed of longitudinal
web movement. Alternatively, the cut location may be moved upstream
of web movement by either slowing down the cutter roll rotation or
by speeding up the longitudinal web movement.
In order to maintain proper registry of the actual knife cut
locations with the preprinted patterns on the web, the ratio of web
speed to cutter roll speed must be controlled; and because of
variations in the operating conditions, e.g., stretch in the web,
slippage in web drive rolls, initial misadjustment, drift in the
machinery and backlash or deadzone conditions in the machinery,
adjustments must be made continuously to maintain proper
registry.
In order to make these adjustments, it is necessary to ascertain
the deviation of each actual knife cut location from a desired
knife cut location. The present invention, in one aspect, provides
novel techniques for obtaining representations of this deviation.
According to the present invention, register marks spaced along the
edge of the web in predetermined positional relationship with the
printed pattern are detected by an optical scanner which produces a
register mark signal whenever a web register mark passes the
scanner. A knife cut detector is provided to produce knife cut
signals whenever the cutter rolls produce a knife cut. In addition,
means such as a measuring wheel which rides on the web are provided
to produce a series of closely spaced pulses as the web moves along
so that each pulse corresponds to a given distance of web movement.
The distance between the scanner and the location where a register
mark should be when a proper knife cut is to be made is known; and
this distance, as represented by a corresponding number of
measuring wheel pulses, is preloaded into a counter. When a
registration mark passes the scanner, the resulting register mark
signal opens a gate which allows the measuring wheel pulses to be
applied to a count-down terminal of the counter. The occurrence of
a knife cut signal stops the count. If the knife cut signal occurs
before the counter has counted down fully, the remaining count in
the counter will correspond to the distance or deviation by which
the actual cut was short of its proper location, so that the web
element thus cut off would be short. On the other hand, if before
the knife cut signal occurs the counter counts down to zero, it
will produce an output signal which will switch the application of
subsequent measuring wheel pulses to a count-up input terminal of
the counter so that these subsequent pulse will count up from zero
until the next knife cut signal occurs. The count remaining in the
counter in this case corresponds to the distance or deviation by
which the actual cut is long with respect to its proper location.
In this case also, the output signal which switches the application
of input pulses to the count-up terminal is also used to produce an
indication that the deviation is long rather than short.
According to another feature of the present invention, error or
deviation information relating to each operation of an
intermittently operating process, for example cut location
deviation in a web cut-off system, is processed in a novel manner
to achieve an optimal correction situation. This feature of the
invention involves first, applying the deviation information for
one operation to the production of a corresponding adjustment for
the next successive operation and second, applying the deviation
information from the same operation to a statistical processing
unit which processes this information with corresponding
information from other operations to provide an average deviation
correction signal. The average deviation correction signal is used
to produce further correction which is applied to each of several
successive operations. Thus, in the case of a web cut-off control,
the measured deviation of each actual cut location from its
corresponding cut locations is used to generate a corresponding
correction to the system for changing cutter roll speed by a
corresponding amount for the next subsequent cut. At the same time,
this measured deviation is processed statistically with previously
obtained deviation measurements and an average deviation correction
signal is produced which is applied to change the cutter roll speed
by a corresponding further amount for each of several successive
cuts until further statistical processing produces a new or a
changed average deviation correction signal.
The combining of individual deviation correction adjustments and
average deviation correction adjustments serves to maintain close
and accurate control, especially where the effect of each operation
is dependent, to a certain extent, upon the deviation of a
preceding operation. In the case of web cutting by knife rolls, for
example, a cut made in the long direction of a registration mark
will be followed by another cut made in the long direction even
when the cutter roll speed is properly adjusted. In addition, the
combining of individual (or 37 phase") and average (or "trend")
deviation corrections serves to maintain close control without
danger of over-correction in the case of systems having backlash or
deadzone characteristics.
According to a further feature of the present invention, the
deviation signal for successive operations of a system are
statistically processed to provide an indication of an average
deviation for the system. In this manner, the effects of backlash
or deadzone characteristics are cancelled by allowing them to
distribute themselves substantially equally about a mean. In this
way, the system may be accurately set according to any changes
which may be present in the operating conditions.
The present invention provides improvements which, in certain
circumstances effectively isolate the effects of backlash or
deadzone characteristics from correctable deviations without
requiring such a large number of successive measurements as would
be necessary to have the effects of backlash or deadzone
characteristics distribute themselves about a mean. These
improvements involve combining the successive deviation indications
algebraically and comparing each result of each combining operation
with a different norm corresponding to the number of operations
undertaken since a previous average deviation correction was
initiated. In the case of a web cutting system, for example,
wherein it is known that the system is subject to backlash or
deadzone effects in the amount of about one-sixteenth inches, if
the first deviation exceeds this amount, it can be safely assumed
that more than backlash or deadzone effects are present in the
deviation indication. Accordingly, an average deviation correction
can be generated immediately without need for several successive
measurements. If two successive deviation signals, when combined
algebraically, provide a total nearly twice the amount of any
deadzone or backlash effects, then again an average deviation
correction signal may be generated. Similarly, as successive
deviations are combined, the resulting combination is compared with
a different norm, and if such combination exceeds the norm, a
correction signal will be generated.
There has thus been outlined rather broadly the more important
features of the invention in order that the detailed description
thereof that follows may be better understood, and in order that
the present contribution to the art may be better appreciated.
There are, of course, additional features of the invention that
will be described hereinafter and which will form the subject of
the claims appended hereto. Those skilled in the art will
appreciate that the conception upon which this disclosure is based
may readily be utilized as a basis for the designing of other
structures for carrying out the several purposes of the invention.
It is important, therefore, that the claims be regarded as
including such equivalent construction as do not depart from the
spirit and scope of the invention.
A specific embodiment of the invention has been chosen for purposes
of illustration and description and is shown in the accompanying
drawings, forming a part of the specification, wherein:
FIG. 1 is a schematic diagram of a web cut-off system in which the
present invention is embodied;
FIG. 2 is a plan view showing a length of preprinted web which may
be cut into lengths with the system of FIG. 1;
FIG. 3 is an enlarged view taken along line 3--3 of of FIG. 1
showing cutter rolls with knife blades in their relative positions
just prior to making a cut;
FIG. 4 is a view similar to FIG. 3 showing the knife blades in
their relative positions at the execution of a cut;
FIG. 5 is a graph illustrating relative rotational velocities and
positions of the cutter rolls of FIGS. 3 and 4; and
FIGS. 6A and 6B together form a block diagram of a correction unit
which is used in the system of FIG. 1.
The registration controlled web cutting system of FIG. 1 operates
to cut a preprinted paperboard web 10 into elements 12. The web 10
is printed with a recurring pattern; and it is important that each
element 12 contain the pattern properly centered or registered
thereon so that the element can later be folded into a carton or
other packaging arrangement with the printed pattern properly
displayed thereon. The present invention serves to ensure that the
cutting of the web 10 is such that the length of each element 12 is
properly related to the printed pattern so that each element will
contain the pattern accurately centered thereon.
As shown in FIG. 1, the web 10 passes through a pair of drive rolls
14 and is driven thereby in the direction of an arrow A. The web 10
then passes a set of slitter-scorer rolls 16 which form
longitudinal crease lines and slits for later folding of the web
into a carton configuration. After passing through the
slitter-scorer rolls 16, the web 10 passes between a set of cutter
rolls 18 which sever the web transversely into discrete elements
12.
As can be seen in FIG. 2, the web 10 is printed with a recurring
pattern P. Each pattern is accompanied by a registration mark 20
located along one edge of the web. These registration marks have a
preselected positional relationship with the pattern and with a
corresponding line of cut 22 (shown in dashed line) where the web
should be severed in order that each element will have its printed
pattern properly positioned hereon. The distance between the
successive registration marks 20 (which is also the distance
between successive pattern repeats and successive lines of cut 22),
is indicated as L in FIG. 2.
Reverting now to FIG. 1, it will be seen that there is provided a
common drive motor 24 which is connected to drive the drive rolls
14, the slitter-scorer rolls 16 and the cutter rolls 18 in
synchronism. The drive train between the motor 24 and the cutter
rolls 18 includes a differential transmission 26, a Reeves
mechanism 28 and a cycle cut mechanism 30. The differential
transmission 26 and the Reeves mechanism 28 both function to
control the ratio of cutter roll to drive motor rotation. The
cutter rolls each contain a knife blade 32 which come together once
during each revolution to sever the web 10. It will be appreciated
that by adjusing the ratio of cutter roll to drive motor rotation
(which controls web movement), the distance between successive
knife cuts, i.e., the length of cut, can be adjusted.
The Reeves mechanism 28 admits of a wide adjustment in length of
cut and is used as a presetting device for setting up the system to
a particular order. The Reeves mechanism, however, is not suitable
to short term adjustments since it requires a certain amount of
time following each adjustment to reach its normal operating
condition for the adjustment. Also, the Reeves mechanism is
generally unsuitable for fine adjustments. Because of these
limitations, the Reeves mechanism is used primarily for presetting
the system prior to operation thereof, while the differential
transmission 26 is used to make ratio changes i.e., length of cut
corrections, during operation of the system.
The manner in which the differential transmission is controlled
will be described more fully hereinafter.
The cycle cut mechanism 30 serves to modify the rotation of the
cutter rolls 18 so that their velocity in the vicinity of their
coming together for cutting is slightly greater than that of the
web. This serves to improve the sharpness of the cut and helps to
prevent torn or ragged edges on the various cut elements 12. This
is exemplified in FIGS. 3 and 4. In the example shown in FIG. 3,
the web 10 moves in the direction of the arrow A, while the knife
blades 32 are carried around through the arc .theta..sub.1 by their
respective rolls 18. Thereafter, as shown in FIG. 4, the knife
blades 32 traverse the arc .theta..sub.2 during which they sever
the web 10. During the first half of the arc .theta..sub.2, the
knife blades undergo an increase in velocity up to the point of
actual cut; and thereafter the knife blades undergo a decrease in
velocity to the end of the arc .theta..sub.2, whereupon they
continue to move at a lower velocity throughout the arc
.theta..sub.1.
This movement of the knife blades is illustrated diagramatically in
FIG. 5 wherein cutter roll rotational velocity is plotted against
cutter roll rotation. As can be seen, the cutter rolls 18, and
their associated knife blades 32, move at lower velocity throughout
the arc .theta..sub.1 and they undergo an increase followed by a
decrease in velocity while traversing the arc .theta..sub.2. This
occurs once during each 360 degrees of rotation of the cutter
rolls.
The length of cut i.e., the amount of web that moves between the
cutter rolls 18 between successive knife cuts is determined by the
average linear speed of the web 10 and the average rotational speed
of the cutter rolls 18. By decreasing the average cutter roll speed
for a given web speed, the length of cut can be increased, and by
increasing the average cutter roll speed, the length of cut can be
decreased. It will be appreciated from FIG. 5 that the average
cutter roll velocity for each complete rotation thereof will be
slightly greater than the constant velocity throughout the arc
.theta..sub.1. As indicated previously, this average velocity may
be preset with the Reeves mechanism 28 and it may be adjusted
during operation of the system by means of the differential
transmission 26.
Adjustment of the differential transmission 26 is made, as shown in
FIG. 1, by the rotational movement of a planetary carrier 34
between input and output gears 36 and 38. A plurality of planet
gears 40 are carried by the planetary carrier 34 and are meshed
with each of the input and output gears 36 and 38. For a given
rotational speed of the drive motor 24 and the input gear 36, the
speed of the output gear can be increased or decreased by an amount
corresponding to the direction and speed of rotation of the
planetary carrier 34. This, in turn, is controlled from a
correction unit 42.
The correction unit 42 receives registration pulses from a
registration scanner 44 located near the cutter rolls 18. A cut
detector 46 is also positioned adjacent the cutter rolls and is
connected to produce a knife pulse upon each severing operation of
the knife blades 32. These pulses also are applied to the
correction unit 42. Finally, a measuring wheel 48 is mounted to
ride on the web 10 and to turn as the web advances. The measuring
wheel is coupled to a pulse generator 50 which operates to produce
a web movement pulse for wheel rotation corresponding with each
hundredth of an inch of web movement in the direction of the arrow
A. These web movement pulses also are applied to the correction
unit 42.
OPERATION OF OVERALL SYSTEM
During operation of the system of FIG. 1, the drive rolls 14
advance the web 10 toward and between the cutter rolls 18. At the
same time, the cutter rolls are rotated and their knife blades 32
undergo a cyclic pattern of movement described above in connection
with FIGS. 3, 4 and 5, with the average rotational speed of the
cutter rolls 18 governing the length of each cut made.
As each cut is made, a measurement is made to ascertain the
deviation of the actual cut length from the desired cut length.
This measurement is used in the correction unit 42 to produce
adjustments of the differential transmission 26 to obtain control
of succeeding cuts.
Essentially, the measurement of deviation of each actual cut from
each desired cut are made by obtaining an indication of the amount
of web movement which takes place between the time that a
registration mark 20 is detected by the registration scanner 44 and
the time the next subsequent knife pulse is produced by the cut
detector 46. In the case illustrated, the registration mark 20 is
shown to be positioned along the lines of cut 22. Thus, for the
actual knife cuts to take place on the lines of cut 22, the web 10
should move a distance equal to the distance between the
registration scanner 44 and the point of cut of the knife blades 32
during the time between the occurrence of a pulse from the
registration scanner 44 and the occurrence of a knife pulse from
the cut detector 46. This movement, as pointed out above, is
indicated by the action of the measuring wheel 48 and the pulse
generator 50.
It is not necessary that the registration marks be in exactly the
same position as the desired lines of cut 22. In the event that
they are offset, the amount of this offset can be added to or
subtracted from the distance the web is to move between the
detection of a registration mark and the occurrence of a knife
pulse so that the knife pulse corresponding to a particular cut
will occur when the desired line of cut is positioned at the point
of cut of the knife blades.
Should the knife pulse for a particular cut occur at a time when
the signals from the measuring wheel 48 and the pulse generator 50
indicate that the desired line of cut 22 is not at the knife blades
32, the amount and direction of this deviation is noted in the
correction unit 42 which processes this information and makes
appropriate adjustments to the differential transmission 26 which
increases or decreases the average speed of the cutter roll
rotation so that subsequent cuts by the knife blades 32 will be
brought into closer registration with corresponding desired lines
of cut 22.
THE CORRECTION PROBLEM
Because of certain characteristics of the above-described
processing, i.e., web cut-off system, a simple feedback control
arrangement is not feasible for obtaining close and accurate
control of output.
The first characteristic lies in the cut-off machinery. Because of
several factors, including the peculiarities of the Reeves
mechanism 28 and the fact that the cycle cut mechanism 30 causes
the knife blades to undergo an acceleration and a deceleration
during each cutting operation, a certain region of randomness
exists due to backlash in gear systems and various "dead zones" in
the different mechanisms. It is, of course, impractical to attempt
to control any machine with any greater degree of precision than
the dead zones present in the machine will allow. For example, if
the backlash in the system herein will allow the knife blades 32 to
be moved by hand by a certain amount, e.g., .+-. 1/16 inch, without
any turning of the shaft of the drive motor 24, then it is
impractical, with any kind of control, to obtain a degree of
precision which will ensure that all pieces cut will deviate from a
desired length by less than one-sixteenth inch.
The second characteristic lies in the nature of the cut-off process
wherein the length of a subsequent cut is governed not merely by
the setting or operation of the cut-off machinery, but also by the
location of a previously made cut. Thus, if the distance between
successive registration marks 20 along the web 10 is, say, 3 feet,
and if the machinery deviates to a cut length of 2 feet, eleven
inches so that a preceding cut is made off register by one inch,
then, even if the machinery is corrected by one inch to make a cut
length of 3 feet, the next subsequent cut will also be 1 inch off
from its associated register mark, since the 3 feet is measured
from the previous cut which, itself, was 1 inch off register. Now
if the system is corrected to make a cut length of 3 feet 1 inch,
then the next subsequent cut will be on register; however,
following cuts will be off register in the opposite direction.
It will be appreciated that an over correction is necessary to
bring the system back to registry. However, as pointed out, an
overcorrection causes misregistration in the opposite direction of
following cuts. Such an arrangement has a tendency toward
instability since the corrections, in order to be effective, must
be such as to produce comparable misregistration in the opposite
direction.
The instability problem is further complicated by the precision
limitations of the system described previously. This is because it
is not possible to know, on an individual measurement which shows a
cut misregistration of say plus three thirty-seconds inch, how must
of this misrepresentation is attributable to dead zone or backlash
variation in the machine and how much is due to improper adjustment
of the system. If the 3/32 inch error is made up of 1/16 inch
backlach or dead zone error and only 1/32 inch system
misadjustment, then any correction which is made with the
assumption that the entire error is system misadjustment will upon
correction, introduce an oppositely directed adjustment error of
more than 1/16 inch, thereby causing instability. On the other
hand, if any correction is made with the assumption that the entire
error is dead zone error then the system will never be brought back
to full registration.
The present invention handles the above problem by using each
measurement made in two ways: first, the measurement of
misregistration is used to make a "phase correction," that is a
correction in the opposite direction from the misregistration, for
the next subsequent cut only, and second, the measurement of
misregistration is statistically processed to eliminate its
deadzone or backlash components and thereafter continued correction
or system adjustments are made based upon the results of the
statistical processing. The application of a phase correction
eradicates the effects of a preceeding misregistered cut while the
statistical processing of the error or misregistration measurement
permits a proper adjustment of the system which is sufficient to
correct any errors without however overcorrecting to the point of
instability.
The statistical processing of detected misregistrations to
eliminate their deadzone or backlash components is based upon the
realization that these components are purely randomly distributed
and therefore over a large number of successive measurements they
will cancel themselves out. In the present case, the
misregistration errors for at least five successive cuts are
combined algebraically. Should the cumulative algebraic sum of five
or more successive misregistration errors exceed a given minimum
number then that sum is taken as the adjustment error of the system
and a corresponding correction, amounting to a system adjustment,
is made. In the present case, this system adjustment is made by
superimposing on the phase correction for each cut, a system or
average deviation correction. While the phase correction is made
only once however, the system or average deviation correction is
repeated for each cut until further statistical processing causes
it to change.
The present invention additional provides refinements to the
statistical processing whereby, under certain circumstances, it
serves to separate the deadzone or backlash components from system
adjustment errors in less than five measurements. This is achieved
by comparing the magnitude of these initial misregistration errors
with certain criteria set up in accordance with the known system
dead zone characteristics. Thus, if the first measurement made
indicates a misregistration of say + 3/32 inch while the system
dead zone is = 1/16 inch, then it may be assumed from this one
measurement that a system error exists which is at least + 1/32
inch. Further, if upon two successive measurements, the cumulative
algebraically combined misregistration error amounts to + 1/8 inch,
it may be assumed that a system error exists.
The present invention thus statistically processes successive
misregistration measurements and separates their system
misadjustment components from the dead zone components by combining
several successive measurements algebraically.
THE CORRECTION UNIT
As shown in FIG. 1, the correction unit 42 includes a measurement
section 52, a program control section 54, an average length
correction section 56, an average length accumulation section 58
and a correction section 60.
Signals from the registration scanner 44, the measuring wheel pulse
generator 50, and the cut detector 46 are supplied via a
registration pulse line 62, a digital wheel pulse line 64 and a
knife pulse line 66 to the measurement section 52. Knife pulse
signals are also supplied to a delay circuit 68 and delayed knife
pulses are applied to the program control section 54.
The various signals supplied to the correction unit 42 are
processed therein to provide measurements of cut misregistration.
These measurements are processed, as described above, individually
to provide phase corrections, and statistically to provide system
or average length corrections. These two types of correction are
combined in the correction section 60 and are converted therein to
a corresponding mechanical shaft rotation. This rotation is
transmitted (as indicated by a heavy dashed line 70) to the
planetary carrier 34 of the differential transmission 26 for
adjusting the average speed of rotation of the cutter rolls 18
which, in turn, controls the length of web cut between successive
operations of the knife blades 32.
The various sections of the correction unit 42 will now be
described in detail.
THE MEASUREMENT SECTION
The purpose of the measurement section is to obtain a count
indicative of the distance along the web 10 by which each actual
knife cut deviates from its desired location. In general, this is
achieved by first storing in an up-down counter, a count
corresponding to the distance a registration mark 20 should have
travelled from the registration scanner 44 at the time a knife cut
is made. When a registration mark is detected, the count is loaded
into the up-down counter 72, and then as the web 10 moves along the
pulses from the measuring wheel pulse generator 50 (which
correspond each to 0.01 inches) are applied to reduce the stored
count. Ideally, the count should be zero at the time a knife pulse,
which stops the count, occurs. Should the knife pulse occur before
down is complete, the remaining count will indicate the amount by
which the cut length is too short; and should the knife pulse not
occur until after count down is complete, the counter will count up
again and produce a "long" indication of the amount by which the
actual cut length is too long.
The measurement section transfers these long and short indications
directly to the correction section 60 for phase (i.e., cut to cut)
correction, and to the average length correction section for
statistical processing.
Referring now to FIG. 6A, the measurement section 52 of the
correction unit 42 is shown to include a series of decade counters
72. These decade counters are constructed to count applied pulses
according to a binary decimal code. The counters 72 are also
adapted to be preset manually to any desired count, as indicated by
double arrows 74 extending up to each counter. The counters
represent, respectively, hundredths of an inch, tenths of an inch,
inches and tens of inches. Each applied pulse represents one one
hundredth of an inch. The counters will count up or down and
thereby increase or decrease their count in response to pulses
applied to count up and count down terminals 76 and 78
respectively.
A count storage register 80 is arranged in association with the
decade counters 72 to receive and retain the information present at
certain times in the decade counters 72. A digital display
arrangement 82 is also provided and, as shown by the double arrows
leading thereto from the count storage register 80, is adapted to
receive, for display purposes, the count present in the storage
register 80. There are also provided preset AND gates 84 which
receive information from the storage register 80 and compare it to
preselected criteria for producing signals on an "accept cut" line
86, and "unaccept cut" line 88 and "over four inch" line 90. These
lines are connected to various display and control circuits (not
shown) for providing a continuous indication of the operating
conditions of the system.
The count-up terminal 76 of the decade counters 72 is connected to
receive signals from an AND-NOT gate circuit 92. This circuit has
an inhibit terminal 94 connected to receive input signals from a
"short" output terminal 96 of a direction flip-flop circuit 98. The
remaining input terminal of the AND gate circuit 92 is connected to
the output terminal of a digital wheel pulse AND gate circuit 100.
One input of the digial wheel pulse AND gate circuit 100 is
connected to the digital wheel pulse line 64 for receiving input
pulses representative of web movement. The other input terminal of
the digital wheel pulse AND gate circuit 100 is connected to a
start count output terminal 102 of a start measurement flip-flop
circuit 104. The corresponding input terminal of the start
measurement flip-flop circuit 104 is connected to the registration
pulse line 62 to receive registration pulses from the registration
scanner 44. The other input terminal of the start measurement
flip-flop circuit 104 is connected to the knife pulse line 66 to
receive knife pulses from the cut detector 46.
One of the inputs to the short measure AND gate circuit 108 is
applied from the digital wheel pulse AND gate circuit 100, while
the other input terminal of the short measure AND gate circuit is
connected to receive inputs from the "short" output terminal 96 of
the direction flip-flop circuit 98. The direction flip-flop circuit
98 is also provided with a "long" output terminal 110 which is
energized upon the reception of signals at a "long" input terminal
112. The "long" input terminal 112 is connected to receive signals
from a borrow output terminal 114 of the decade counters 72.
Signals appear at this borrow output terminal 114 whenever the
decade counter passes through a zero count in the down
direction.
The "short" output terminal 96 of the direction flip-flop circuit
98 is connected to the count storage register 80 to indicate the
direction, i.e., short or long or error represented by the numbers
which are transferred to the storage counter. These signals are
supplied from the storage counter via a plus-minus line 116 to the
digital display 82. The count storage register 80 has a storage
input terminal 118 connected to the knife-pulse line 66 so that it
will accept and store information present in the decade counters 72
upon the reception at the terminal 118 of a knife pulse signal.
The presetting of the decade counters 72, as indicated previously,
is undertaken manually prior to operation of the system. The actual
preset count, however, is not transferred to the decade counters
until the reception of a load signal via a decade counter load line
120. This line, as shown in FIG. 6A, is connected to the
registration pulse line 62.
THE PROGRAM CONTROL SECTION
The program control section 54 serves to control the sequence of
operation of the various sections of the correction unit 42. As
shown in FIG. 6A, the program control section 54 includes a
demultiplex unit 122 and a multiplex unit 124, interconnected by a
switch line 126. The demultiplex unit receives "call-back commands"
via a plurality of input lines indicated by arrowed boxes numbered
1 through 7. These call-back commands are processed within the
demultiplex unit and are applied to the multiplex unit 124. The
multiplex unit 124 produces output signal commands on various
circled command lines indicated by the numbers 1 through 7.
Whenever the demultiplex unit receives a signal on one of its
arrowed boxes of a given number, it causes a signal to be supplied
via the switch line 126 so as to produce output commands on the
circled command line of the next higher number. The switching
sequence is initiated by a program counter 128 which maintains
sequence of switching and which supplies clock pulses at the
various command output terminals. The program counter 128 receives
input signals from a command AND gate 130 and this, in turn,
receives input signals from a source of clock pulses (not shown)
via a main clock pulse line 132, demultiplex signals from the
switch line 126 and program start signals via a program start line
134 from a program start flip-flop 136. The program start line 134
is energized by application of a delayed knife-pulse signal to a
start terminal 138 of the program start flip-flop 136. The other
input terminal of the program start flip-flop circuit 136 is
connected to a program stop OR gate 140 which receives program stop
input signals via a register mark line 142, a preprint automatic
line 144 and the "over four inch line" 90 from the measurement
section 52.
It will be noted that in the various sections of the correction
unit 42, there are shown arrowed boxes numbered 1, 3 and 7.
Whenever signals appear on these boxes, they are applied
simultaneously to correspondingly numbered boxes indicating input
to the demultiplex unit 122. Similarly, signals which are generated
at the command lines of the multiplex unit 124 are applied to
corresponding circled lines similarly numbered in the various
sections of the correction unit. In addition, the demultiplex unit
122, the multiplex unit 124 and the program counter 128 are set to
advance automatically, without inputs to the arrowed boxes numbered
2, 4 and 6, respectively, to advance the outputs of the multiplex
unit 124 so that command appear on the circled command lines 3, 5
and 7.
In operation of the program control section 54, the occurrence of a
delayed knife pulse signal from the knife pulse line 66 is applied
to the program start flip-flop circuit 136 causing it to produce a
signal on the program start input line 134. This signal opens the
command AND gate 130 causing it to apply clock signals to the
program counter 128. The program counter 128 first causes clock
pulse signals to occur at the No. 1 circled command line of the
multiplex unit 124. Corresponding circled command lines No. 1 are
found in the measurement section 52 and in the correction section
60, and the clock pulses are applied to both these lines
simultaneously. These clock pulses continue until a signal appears
at the borrow output terminal 114 of the decade counters 72 in the
measurement section, indicating that these counters have been
reduced to a zero count. Since the terminal 114 is shown connected
to an arrowed box No. 1 a call-back signal is applied at this time
to the correspondingly numbered arrowed box in the demultiplex unit
122. This signal is processed in the demultiplex and multiplex
units so that the pulses on the circled command line No. 1 stop and
a signal instead appears at the circled command line No. 2. As can
be seen in the drawing, and as will be explained more fully
hereinafter, this signal is applied to the average length
accumulator section. The signal on the No. 2 command line is
automatically terminated by the program counter 128 and the
multiplex unit 124 after a predetermined duration, and the
multiplex unit is advanced to produce a series of clock pulse
signals on its circled command line No. 3. As shown in the drawings
and as will be described more fully hereinafter, these clock pulse
signals are applied simultaneously to correspondingly numbered
circled command lines in the average length correction section 56
and in the average length accumulator section 58. The clock pulses
continue on the No. 3 circled command lines until a call-back
signal appears at a call-back line indicated by the arrowed box No.
3 in the average length correction section 56. This call-back
signal also appears at the call-back line indicated by the arrowed
box No. 3 at the demultiplex unit 122 in the program control
section 54. This signal is processed in the control section and
causes the multiplex unit 124 to terminate the clock pulses on the
circled command line No. 3 and instead to produce a command signal
on the circled command line No. 4. This command signal is applied
to a corresponding circled command line No. 4 in the average length
accumulator section 58.
The program counter 128 automatically terminates the signal on the
No. 4 circled command line after a preselected time and then causes
the multiplex unit 124 to produce a series of clock pulses on a
circled command line No. 5. As shown in the drawings, these clock
pulses are applied simultaneously to corresponding circled command
lines No. 5 in the average length accumulator section 58 and in the
correction section 60.
The clock pulses on the No. 5 circled command lines continue until
a call-back signal appears at the call-back line indicated by the
arrowed box No. 5 in the average length accumulator section 58.
This signal is applied to the demultiplex unit 122 in the program
control section 54 causing it to advance the multiplex unit 124 so
that the clock pulse signals are terminated and a signal appears
for a preselected duration on the No. 6 circled command line of the
multiplex unit. This signal is applied to a corresponding line in
the average length accumulator section 58.
After the preselected duration, the signal on the No. 6 circled
command line is terminated and the program control section
automatically advances to cause a series of pulse signals to occur
at the No. 7 circled command line. These signals are applied to the
correction section 60 until a call-back signal appears at a
call-back line indicated by the arrowed box No. 7 in the correction
section. The call-back signal is applied to the demultiplex unit
122 and terminates its operation and resets it to undergo a similar
sequence of events following a subsequent knife cut.
THE AVERAGE LENGTH CORRECTION SECTION
The average length correction section serves statistically to
process information concerning deviations of actual from desired
locations for a plurality of knife cuts along the web 30 and then
to provide a length setting correction to the system. The length
setting correction differs from the phase correction in that it is
repeated for all subsequent cuts and is changed only by the amount
of a subsequently generated length setting correction. The phase
correction, on the other hand occurs only for the knife cut which
immediately follows the generation of each phase correction
signal.
The statistical processing of the deviations of several successive
cuts consists essentially in algebraically combining the successive
deviations and then producing a correction signal when the mean of
a large number of thsee individual deviations exceeds a
predetermined limit. This serves to nullify the random effects of
backlash and dead-zone conditions in the system since the average
or mean of a large number of successive random deviations within
the dead-zone should occur in the center of the zone.
The "large" number of these successive measurements has, in the
illustrated case, been chosen empirically as five; and the mean
deviation beyond which an average length setting correction is made
is also empirically taken at plus or minus 0.32 inches for a system
wherein a total deadzone of 0.12 inches exists.
The statistical processing of several successive deviation
indications is further modified, according to the present
invention, by monitoring the extent of the algebraically combined
deviations for less than five and by producing correction signals
whenever the combined deviations exceeds predetermined limits
corresponding to the number of cuts which have been combined since
a previous correction. This provides rapid length correction for
situations where substantial adjustments must be made to the
system. For example, where it is known that the deadzone region
within which the system may vary its cut deviation for a given
setting is a total of 0.12 inches, and the initial cut has deviated
off register by 0.13 inches then it can be said that there is a
substantial error in the system setting and an adjustment should be
made. In such case to wait until five successive cuts have been
made is not necessary.
In the illustrated embodiment the following criteria for system
correction are established in the average length correction
section:
Accumulated Algebraic Deviation Which, if Knife Cut Since Exceeded,
will result Amount of Previous Average In an Average Length Average
Length Length Correction Correction Correction 1 0.13 0.05 2 0.24
0.04 3 0.24 0.04 4 0.32 0.03 5 or more 0.30 0.01
The average length correction section 56 includes a two decade
counter 150 having an up-count input terminal 152 and a down-count
input terminal 154. The two decade counter 150 also includes a
borrow terminal 156 which produces a signal each time the counter
reaches a zero count. A decoder circuit 158 is provided to receive
count information from the two decade counter 150 and to transfer
this information to various AND gate circuits 159. The decoder
circuit 158 presents signals upon various output terminals 160
corresponding to the count in the counter circuit 156. As shown in
the drawing, the output terminals used in the present case are
those which represent counts corresponding to 13, 24, 30 and 32 one
hundreths of an inch, respectively. It is these terminals which are
connected to corresponding ones of the AND gate circuits 159. Each
of the AND gate circuits 159 is also connected to receive signals
from associated ones of output terminals 162 of a knife pulse
counter 164. The knife pulse counter 164, as indicated, has a five
count capacity. Knife cut signals from the knife pulse line 66 are
applied to the knife pulse counter 164, and upon the reception of
successive knife pulse signals, successive ones of the output
terminals 162 become energized. The last of the terminals, i.e.,
that indicated by the numeral 5, remains energized for every pulse
following the fifth pulse unitl a reset signal is applied to a
reset terminal 166 thereon. The outputs of the various AND gate
circuits 159 are connected to corresponding loading input terminals
168 of a correction counter 170. As indicated, the output of the
AND gate circuit 159, which is connected to the first output
terminal 162 of the knife pulse counter, is connected to the
loading input terminal 168 of the correction counter corresponding
to a count of five and thereby a signal from this AND gate circuit
loads a five count into the correction counter 170.
The next two AND gate circuits 159, which are connected,
respectively, to receive input signals from a second and third
output terminals 162 of the knife pulse counter 164 and from the 24
count output terminal 160 of the decoder circuit 158, are applied
via a first OR gate circuit 171 to the correction counter input
terminal 168 corresponding to a four count to be loaded into the
correction counter. The remaining AND gate circuits 159 are
connected to the correction counter input terminals 168
corresponding to a three count and a one count respectively. The
correction counter 170 additionally is provided with a load
terminal 172, which, upon the reception of a proper command signal,
causes the correction counter to be loaded with a count
corresponding to the particular one of its load input terminals
168, which happens to be energized. Thereafter, countdown signals
are applied via one of the command lines to an input terminal 174
which cause the count which has been loaded into the correction
counter 170 to diminish. Upon complete removal of the count from
the correction counter 170 in this manner, the correction counter
will produce a signal on a borrow output terminal 176 and, at the
same time, will send a callback signal back to the demultiplex unit
122 of the program control section 54.
The up-count input terminal 152 of the two-decade counter 150 is
connected to receive input pulses from an AND circuit 178, while
the down-count input terminal 154 is connected to receive input
signals from a AND-NOT gate circuit 180. One input terminal of each
of the AND and AND-NOT gate circuits 178 and 180 is connected to
the No. 1 circled command signal line from the multiplex unit 124
in the program control section 54. The inhibit terminal 182 of the
AND-NOT gate circuit 80 and the remaining input terminal of the AND
gate circuit 178 are both connected to receive input signals from
an EXCLUSIVE OR gate circuit 184. This EXCLUSIVE OR gate circuit
184 receives "long" signals from the "long" output terminal 110 of
the direction flip-flop circuit 98 in the measurement section 52.
The remaining input terminal of the EXCLUSIVE OR gate circuit 184
is connected to receive outputs from one side of a second direction
flip-flop circuit 186. The direction flip-flop circuit 186 has a
common input terminal 188 which is connected to receive borrow
signals from the borrow input terminal 156 of the two-decade
counter 150 so that each time the two-decade counter 150 has its
count reduced to zero, a signal is applied to the common input
terminal 188 of the direction flip-flop circuit 186, causing the
output terminal thereof connected to the EXCLUSIVE OR gate circuit
184 to change state.
As indicated previously, the average length correction sections 56
serves statistically to process information concerning deviations
of actual from desired locations for a plurality of knife cuts
along the web 30 and to provide a length setting correction to the
system corresponding thereto. Thus, for each deviation measurement
which appears in the decade counters 72 of the measurement section
52, this deviation amount is transferred to the two-decade counter
150 and is algebraically combined with counts applied to the
two-decade counter 150 from previous measurements. The algebraic
combining of successive deviation indications from successive
measurements is made by application of clock pulses via the No. 1
circled command line to the AND and AND-NOT gate circuits 178 and
170. If no input signal is being applied to the inhibit terminal
182 of the AND-NOT gate circuit 180, the clock pulses from the No.
1 circled command line are applied through the AND-NOT gate circuit
180 to the down-count input terminal 154, thereby counting down
toward zero in the counter. If, during this countdown, the number
in the two-decade counter 150 becomes reduced to zero, a signal
will appear on its borrow terminal 156 and this signal will be
applied to the input terminal 188 of the direction flip-flop
circuit 186. As a result, a signal is produced at the output of the
EXCLUSIVE OR gate circuit 184 and is applied to the inhibit
terminal 182 of the AND-NOT gate circuit 180. This signal is also
applied to the second input terminal of the AND gate circuit 178.
As a result, the following clock pulse signals from the No. 1
circled command line are applied through the AND gate circuit 178
to the up-count input terminal 152 of the two-decade counter 150,
thereby causing its count to increase. Thus, for example, if the
two-decade counter 150 has a count in it of five, and then ten
successive clock pulses are to be transferred from the decade
counters 72 of the measurement section 52, these clock pulses will
first be applied via the AND-NOT gate circuit 180 so that the count
in the two-decade counter 150 becomes reduced to zero after the
occurrence of five of these clock pulses. The remaining five clock
pulses, however, will be applied to the up-count input terminal 152
for a net count of five, which is equal in magnitude to the
algebraic sum of the newly added count and the previous count in
the counter. It will be appreciated that the two-decade counter 150
in the described system always counts in an upward direction from
zero and, at the same time, serves to provide a count whose
magnitude corresponds to the algebraic sum of the previously
supplied signals.
As each measurement is made and transferred to the two-decade
counter 150 as above-described, another knife pulse signal is
applied via the knife pulse line 66 to the knife pulse counter 164.
If, after a first knife pulse and the measurement associated
therewith, the decoder 158 produces a signal at its output terminal
160 corresponding with a deviation of 0.13 inches, then both inputs
of the AND gate circuit 159 associated with the five count input
terminal 168 of the correction counter 170, will be energized and a
five count will be loaded into the correction counter. However, if
the first measurement shows a deviation of less than 0.13 inches no
count will be loaded into the correction counter. If, however, on
the second measurement the magnitude of the algebraically combined
first and second measurements should produce an indication
corresponding to 0.24 inches, then the AND gate circuit 159, whose
input terminals are connected with the 24 count output terminal 160
of the decoder 158 and with the two-count output terminal 162 of
the knife pulse counter 164, will be energized and will produce an
output signal which will be applied via the OR gate circuit 171 to
the four count input terminal 168 of the correction counter 170,
thereby loading a count of four into the correction counter 170. In
a similar manner, other counts may be loaded into the correction
counter 170, corresponding to measured deviations.
After each measurement is made, a signal is applied via the No. 2
circled command input line to the load terminal 172 of the
correction counter 170, allowing the correction counter to become
loaded to the count corresponding to the particular one of its
input terminals 168 which is energized. Following this loading, a
series of clock pulses appears upon the No. 3 circled command line
and these are applied to a count-down input terminal 174 on the
correction counter. If no count has been placed into the correction
counter 170, then immediately upon the application of the first
countdown pulse, a signal will appear on the borrow line and will
produce a callback signal on the No. 3 call-back signal line of the
demultiplex unit 122 to advance the program. On the other hand, if
a finite count is present in the correction counter 170, the
application of clock pulses to the correction counter 170 will
continue until the correction counter reaches zero, whereupon a
signal will appear on its borrow line, and on the No. 3 callback
signal line.
It will be appreciated from the foregoing that as each measurement
is made, the measurement count is transferred from the decade
counters 72 in the measurement section 52 to the two-decade counter
150 in the average length correction section 56 and is there
combined algebraically with those counts which have previously been
entered and previously been combined algebraically with each other
in the two-decade counter. Whenever this algebraic total exceeds an
amount corresponding to the count in the knife pulse counter that
total is loaded into the correction counter. If no such loading
takes place prior to the knife pulse counter reaching a count of
five, then the knife pulse counter will remain at a five count for
subsequent measurements and these measurements will continue to be
combined algebraically in the two-decade counter 150 until its
count exceeds thirty i.e., (0.30 inches). When this occurs, a one
count is loaded into the correction counter 170.
The count in the correction counter is transferred, following
loading thereof, into the average length accumulator section 58
where it is combined algebraically with previous similarly
developed average length correction signals. The resulting average
length correction is thereafter transferred to the correction
section where it is combined with a phase correction count and
converted to a shaft rotation for adjustment of the differential
transmission 26.
Whenever a count is loaded into and transferred from the correction
counter 170 the knife pulse counter 164 and the two-decade counter
150 are both reset to zero so that deviation measurements for knife
cuts subsequent to resulting average length correction may be
statistically processed and, if necessary a subsequent average
length correction may be similarly derived.
THE AVERAGE LENGTH ACCUMULATOR SECTION
The purpose of the average length accumulator section is to receive
and store the count which was generated in the last previous
operation of the correction counter 170 in the average length
correction section 56. The signal from the correction counter 170
is removed from the correction counter following operation of the
average length correction section 56 so that it can begin a new
statistical processing of subsequent measurements. The average
length accumulator section 58 serves to combine algebraically the
average length correction signal from the correction counter 170
with an average length correction signal previously generated and
presently being applied to each knife cut operation, thereby
updating the average length correction. The average length
correction which is thus derived is transferred, for knife cut
made, to the correction section for combination with a phase
correction and from there to the differential transmission 28 for
adjustment of the average rotational speed of the cutter rolls
18.
As shown in FIG. 6B, the average length accumulator section 58
includes a two-decade counter 200 and a storage register 202. As
indicated by a first set of double arrows 203, signals from the
two-decade counter may be transferred and stored in the storage
register 202. This will occur upon the application of an input
signal to a load input terminal 204 whenever the No. 4 circled
input command line is energized. Similarly, the count in the
storage register 202 may be transferred back, as indicated by a
second set of double arrows 205, upon the application of a reload
signal to a reload input terminal 206 upon energization of the No.
6 circled input command line.
The two-decade counter 200 is provided with an up-count input
terminal 208 and a down-count input terminal 210. The up-count
input terminal 208 is connected to receive input signals from an
AND gate circuit 212. One terminal of the AND gate input circuit
212 is connected to receive clock pulses from the No. 3 circled
input command line and, at the same time, to receive input signals
from an EXCLUSIVE OR gate circuit 214. The down-count input
terminal 210 is connected to receive signals via an OR gate circuit
216 from either and AND-NOT gate circuit 218 or from the No. 5
circled command line. The AND-NOT gate circuit 218 has an inhibit
terminal 220 connected to receive outputs from the EXCLUSIVE OR
gate circuit 214. The remaining input terminal of the AND-NOT gate
circuit 218 is connected to receive clock pulses from the No. 3
circled command line. One input terminal of the EXCLUSIVE OR gate
circuit 214 is connected to receive "long" input signals from the
"long" output terminal 110 of the direction flip-flop circuit 98 in
the measurement section. The other input terminal of the EXCLUSIVE
OR gate circuit 214 is connected to receive input signals from one
side of a direction flip-flop circuit 222. The direction flip-flop
circuit 222 contains a common input terminal 224 which is connected
to receive signals from a borrow output terminal 226 of the
two-decade counter 200. The borrow input terminal 226 is also
connected to supply signals via the No. 5 callback line to the No.
5 input terminal of the demultiplex unit 122 in the program control
section 54.
A reset terminal 228 is provided in the two-decade counter 200 for
resetting the counter to zero at the start of operation. This
signal may be applied manually to clear the two-decade counter
200.
In operation of the average length accumulator section 58, signals
are applied from the No. 3 circled command line to one of the input
terminals 208 or 210 of the two-decade counter 200. This occurs
simultaneously with the counting down of the count in the
correction counter 170 so that the count in that counter is
effectively transferred to the two-decade counter 200 in the
average length accumulator section 58. When this transfer is
completed and a signal appears at the borrow terminal 176 of the
correction counter 170, that signal is also applied to the No. 3
callback line. This causes the program control section 54 to
advance its operation and terminate the pulses on the No. 3 circled
command line and at the same time, to produce a signal for a
predetermined duration on the No. 4 circled command line. This
last-mentioned signal, as indicated in the drawing, is applied to
the load input terminal 204 of the storage register 202, thereby
causing the count in the two-decade counter 200 to produce an
identical count in the storage register 204. When this transfer has
been completed, the program control section 54 automatically
terminates the load signal on the No. 4 circled command line and
causes a series of clock pulses to appear on the No. 5 circled
command line. These clock pulses are applied through the OR gate
circuit 216 to the down-count terminal 210 of the two-decade
counter 200. This down-count continues until the two-decade counter
200 reaches a zero count at which time a signal appears on its
borrow output terminal 226 and on the No. 5 callback line. The
signal on the No. 5 callback line is applied to the program control
section 54 and causes it to advance its program to terminate clock
pulses on the No. 5 circled command line and instead, to produce a
reload pulse for a short duration on the No. 6 circled command
line. The counting down of the two-decade counter occurs
simultaneously with the application of clock pulses to the
correction section 60. This serves to transfer the count present in
the two-decade counter 200 to a counter in the correction section
60. When this transfer is complete and a signal appears via the No.
6 circled command line to the reload input terminal 206, the
two-decade counter 200 is reloaded with its original count which
had been stored in the storage register 202.
The count in the two-decade counter is thus preserved in a manner
which allows it to be combined with a subsequent average length
correction signal which may subsequently be derived in the average
length accumulator section 58.
Signals representative of successive outputs from the correction
counter 170 in the average length correction section 56, are
combined algebraically in the two-decade counter 200 of the average
length accumulator section 58 in substantially the same manner that
successive deviation signals are algebraically combined in the
two-decade counter 150 in the average length correction section 56.
Thus, where a previous average length correction signal is present
in the two-decade counter 200, a subsequent correction signal is
transferred from the average length correction section 56 to the
two-decade counter 200 to change the count in that counter. This
correction signal is applied in the form of clock pulses via the
No. 3 circled command line. These signals, if representative of an
average deviation, whose algebraic sign is different then that of
the algebraic sum of the accumulated average deviation count in the
counter, are applied via the AND-NOT gate circuit 218 and the OR
gate circuit 216 to the down-count terminal 210 to count down
toward zero the count in the two-decade counter 200. Should the
correction signal being applied in this manner have a magnitude
which exceeds the previous count in the two-decade counter 200, a
borrow signal will appear at the borrow output terminal 226 when
the two-decade counter 200 reaches a zero count. This signal is
applied to the common input terminal 224 of the direction flip-flop
circuit 222 which, in turn, causes a signal to be applied to the
EXCLUSIVE OR gate circuit 214 and from there to the inhibit
terminal of 220 of the AND-NOT gate circuit 218 and to the second
input terminal of the AND gate circuit 212. As a result, the
remaining clock pulses to be transferred to the two-decade counter
200 from the No. 3 circled command line are applied via the AND
gate circuit 212 and the up-count input terminal 208, thereby
causing the counter 200 to count upwardly again.
The presence of a signal at the borrow output terminal 226 of the
two-decade counter 200 during the transfer of information from the
average length correction section 56 will not advance the program,
even though such signals appear on the No. 5 callback line. This is
because the program control section 54 is arranged to advance the
program only when a callback signal appears on a callback line
which has the same number as the circled command line from which
signals are presently being generated.
In the event that the average length correction signal is of the
same algebraic sign as that of the accumulated count in the counter
200, then a count up signal is generated in the EXCLUSIVE OR gate
circuit 214 and is applied to the inhibit terminal 220 of the AND
NOT gate 218 and to the remaining input of the AND gate 212. This
closes the AND NOT gate and opens the AND gate so that the clock
pulse signals on the No. 3 circled command line are directed to the
up-count input terminal 208 of the two-decade counter 200. The
count-up signals from the EXCLUSIVE OR gate circuit 214 occur
whenever the algebraic sign of the count in the counter is the same
as that of the correction count applied via the No. 3 circled
command line. Each time the count in the two-decade counter 200
passes through zero, the resultant signal on its borrow terminal
226, which is applied to the input 224 of the direction flip-flop
circuit 222, causes the flip-flop circuit to change state; so that
the output from the flip-flop circuit which is applied to the
EXCLUSIVE OR gate circuit 214 occurs only when the algebraic sign
of the count in the counter is negative or "short." If, during this
time, the sign of the correction signal from the No. 3 circled
command line is also short, no "long" signal will appear at the
other input of the EXCLUSIVE OR gate circuit so that it will
generate an output to open a path from the No. 3 circled command
line to the up count terminal 208 of the counter. If, on the other
hand, the sign of the correction signal from the No. 3 circled
command line is long, a "long" signal will appear at the remaining
input terminal of the EXCLUSIVE OR gate circuit and it will not
then produce an output. In this case the pulse on the No. 3 circled
command line will be directed to the down count input terminal
210.
When the direction flip-flop circuit 222 is in its opposite state,
that is, when the signal of the accumulated count in the counter
200 is positive or "long," then no signal is applied to the
EXCLUSIVE OR gate circuit 214 from the direction flip-flop circuit
222 and the reverse of the above described AND and AND NOT gate
control occurs for clock pulses on the No. 3 circled command line.
It will be appreciated from the foregoing that the count in the
counter 200 is equal in magnitude to the algebraic sum of the
various signals supplied to it.
As indicated previously, both phase corrections (i.e., corrections
made only once based on each preceding measured deviation) and
average length corrections (i.e., corrections made continuously
based on a statistical processing or several preceding deviations)
are made by adjustment to the differential transmission 26. In the
event that the adjustment called for exceeds a certain
predetermined limit, the system will automatically generate a
signal indicating that an override adjustment should be made to the
Reeves mechanism 28 so as to relieve the amount of adjustment that
must be made to the differential transmission 26 between each
successive operation of the knife blades 32. As shown in FIG. 6B,
the signals in the two-decade counter 200 are applied, as indicated
by arrows 203A, to an average length correction AND gate 230. This
AND gate is set to produce an output when the signals applied via
the line 203 A indicate a predetermined magnitude. When this
occurs, the signals are transferred from the AND gate 230 to an
excessive correction input terminal 232 of an excessive correction
flip-flop circuit 234. Signals applied to this terminal cause the
flip-flop circuit 234 to produce a signal on an output terminal 236
which may be used in any manner to indicate that the system should
be adjusted by the insertion of a correction to the Reeves
mechanism 28. The excessive correction flip-flop circuit 234 is
also provided with a second input terminal 238 which receives
signals via a delay circuit 240 from the borrow output terminal 176
of the correction counter 170 in the average length correction
section 56. Whenever the count present in the correction counter
170 is transferred to the two-decade counter 200 in the average
length accumulator section 58, the resulting count in the
two-decade counter is applied to the AND gate 230 and upon the
occurrence in that counter of a correction signal beyond a certain
magnitude, the excessive correction flip-flop circuit will be
switched to produce an output signal indicating a correction should
be made to the Reeves mechanism 28. Shortly thereafter, a signal
will be applied to the second input terminal 238 of the excessive
correction flip-flop circuit 234 to remove any previously generated
output signal.
THE CORRECTION SECTION
The purpose for the correction section 60 is to generate a total
correction signal corresponding to the algebraic sum of the phase
correction signal produced in the measurement section for the
deviation of the immediately preceding cut and the average length
correction signal stored in the average length accumulator section;
and to convert the total correction signal into a corresponding
rotation of the shaft 70 for adjustment of the differential
transmission 26. This is done during the interval between each
successive operation of the knife blades 32. As indicated
previously, the total correction signal is a composite of a phase
deviation signal and an average length deviation signal. The phase
deviation signal is generated in the measurement section 52
following the occurrence of each operation of the knife blades 32.
The amount of this deviation is transferred from the decade
counters 72 in the measurement section to further decade counters
250 in the correction section. The average length correction
signal, as indicated previously, is maintained in the average
length accumulator section 58 and is updated periodically by
operation of the average length correction section 56. Thus, after
the occurrence of each operation of the knife blades 32 and the
obtaining of a count in the measurement section 52 corresponding to
the deviation of the actual knife cut location from the location of
its corresponding desired line of cut, this deviation, as
represented in the decade counters 72 of the measurement section,
is transferred to the decade counters 250 of the correction section
60. Following this, the count which has been maintained in the
average length accumulator section 58 is combined algebraically
with the phase deviation signal in the decade counters 250. The
resulting count is then used to produce a corresponding rotation of
the shaft 70 for adjustment of the differential tranmission 26.
The decade counters 250 in the correction section 60 are provided
with an up-count input terminal 252 and a down-count input terminal
254. The up-count input terminal is connected to receive clock
pulses via a first OR gate circuit 256 from the No. 1 circled
command line. Signals are also applied via the first OR gate
circuit 256 from an AND gate circuit 258. One input terminal of the
AND gate circuit 258 is connected to receive signals from an
EXCLUSIVE OR gate circuit 260. One input terminal of this EXCLUSIVE
OR gate circuit 260 is connected to receive signals from the
direction flip-flop circuit 222 in the average length accumulator
section 58 whenever that direction flip-flop circuit applies
signals to its own EXCLUSIVE OR gate circuit 214. The other input
terminal of the EXCLUSIVE OR gate circuit 260 is connected to
receive signals from a "long" correction output terminal 262 of a
direction flip-flop circuit 264.
The down-count input terminal 254 of the decade counters 250 is
connected to receive signals via a second OR gate circuit 266 from
either an AND-NOT gate circuit 268 or from a variable divider
circuit 270. The AND-NOT gate circuit 268 has an inhibit terminal
272 which is connected to receive outputs from the EXCLUSIVE OR
gate circuit 260. The other input terminal of the AND-NOT gate
circuit 268 and the remaining input terminal of the AND gate
circuit 258 are each connected to receive clock pulse signals from
the No. 5 circled command line. The direction flip-flop circuit 264
is provided with a "long" measurement input terminal 274 which is
connected in a manner not shown to receive signals corresponding to
the occurrence of "long" measurements from the "long" output
terminal 110 of the direction flip-flop circuit 98 in the
measurement section 52. The direction flip-flop circuit 264 is also
provided with a common input terminal 276 which is connected to a
borrow terminal 278 on the decade counters 250. The direction
flip-flop circuit 264 changes state upon each reception of a signal
at its common input terminal 276; and this occurs whenever the
decade counters 278 pass through a zero count condition and thereby
produce a signal at their borrow terminal 278. The borrow terminal
278 of the decade counters 250 is also connected, as indicatd, to
the No. 7 callback line.
The variable divider 270 operates to produce a series of pulses at
an output terminal 280 at a rate corresponding to some
predetermined sub-multiple of pulses applied to an input terminal
282 thereon. The pulses which are applied to the input terminal 282
are generated by an oscillator 284 and these signals pass through
an AND gate 286 to the variable divider 270. The AND gate circuit
286 is also connected to receive signals from the No. 7 circled
command line.
The output of the oscillator 284 which passes through the AND gate
286 and is applied to the variable divider 270 is also applied to a
divider circuit 288 which produces a series of pulses at a
predetermined sub-multiple of the applied oscillator frequency.
These pulses are applied to one input terminal each of an AND gate
circuit 290 and an AND-NOT gate circuit 292. The AND-NOT gate
circuit 292 has an inhibit terminal 294 which, together with the
remaining input terminal of the AND gate circuit 290, is connected
(in a manner not shown) to receive long correction signals from the
"long" output terminal 110 of the direction flip-flop circuit 98 in
the measurement section 52. The output of the AND gate circuit is
applied to a CW (clockwise) input terminal 296 of an
electrohydraulic stepper motor system 298. The output signals from
the AND-NOT gate circuit 292 are applied to a CCW
(counter-clockwise) input terminal 300 of the stepper motor system
298. The stepper motor system operates to produce rotation of the
shaft 70 in a direction corresponding to the particular one of its
input terminals 296 and 300 upon which signals appear and in an
amount corresponding to the number of pulses received at that
terminal.
The correction section 60 operates in the following manner. When a
cut has been made on the web 10, the deviation of the location of
that cut from a desired cut location is made in a manner previously
described by the measurement section 52. This deviation is
represented as a count in the decade counters 72 of the measurement
section. This count is then transferred from the counters 72 of the
measurement section to the decade counters 250 of the correction
section 60. This transfer occurs during that portion of the program
when clock pulse signals appear on the No. 1 circled command line
and this transfer becomes completed when the count on the decade
counter is reduced to zero and it produces a borrow signal at its
borrow terminal.
The transfer of the deviation count in the measurement section 52
to the decade counters 250 of the correction section 60 constitutes
the generation of a phase correction signal. This phase correction
signal is then combined algebraically with the average deviation or
trend correction signal which is present in the average length
accumulator section 58. This algebraic combination takes place
simultaneously with the transfer of a count from the decade
counters 200 of the average length accumulator section 58 to the
correction section 60.
The transfer from the average length accumulator section takes
place during that portion of the program when clock pulses are
being generated on the No. 5 circled command line. These pulses are
applied simultaneously to the down count terminal 210 of the
counters 200 in the average length accumulator section 58 and to
one terminal of the AND gate circuit 258 and of the AND NOT gate
cirucit of the correction section 60. These clock pulses continue
until the count in the average length accumulator section has been
reduced to zero. This produces a corresponding count in the
correction section 60. The pulses applied to the correction section
60 are directed to either the up count terminal 252 or to the down
count terminal 254 of the counter 250 depending upon which of the
gates 258 or 268 is opened. This is controlled by the output of the
direction flip-flop circuit 222 in the average length accumulator
section. As shown in FIG. 6B, this circuit is connected to supply a
signal to the EXCLUSIVE OR circuit 260 in the correction section
60. This circuit will receive a "short" signal from the average
length accumulator section whenever the count stored in that
section indicates a long average deviation correction. Now if the
phase deviation happens to be "long," the direction flip-flop 264
in the correction signal will be energized at its terminal 274 so
that it will produce a long signal at its output terminal 262 and
at the EXCLUSIVE OR gate 260. In such a case the gates 258 and 260
will be switched so that the transfer of the average length
correction signal to the counter 250, which is applied via the No.
5 circled command line will be directed to the down count terminal
254. It will be seen therefore that the "long" phase correction
signal count and the "short" average length correction signal count
are differenced in this case. Whenever the phase and average
deviation correction signals are both "long" or both "short" the
gates 258 and 268 are switched to direct the average length
correction signals applied via the No. 5 circled command line to
the up count input terminal 252 of the counters 250. When the phase
and average length correction signals are different, i.e., when one
is "short" while the other is "long" the average length correction
signals applied via the No. 5 circled command line will be directed
to the down count terminal 254 of the decade counters 250. In this
latter case, the count in the counters 250 may be reduced by zero.
At the zero count a signal will appear on the borrow output
terminal 278 and will be applied to switch the correction direction
flip-flop circuit 264 to switch the gates 258 and 268 so that the
remaining signals will be applied to the up count terminal of the
counters 250.
When the phase and average deviation correction signals have been
thus combined a signal appears on the No. 7 circled command line to
the AND gate 286. This opens the gate and allows the pulses from
the oscillator 284 to be applied, via the divider circuit and the
AND and AND-NOT gate circuits 290 and 292 to either the CW or CCW
terminals 296 or 300 of the electro-hydraulic stepper motor system
298 to turn the shaft 70 by an amount corresponding to the number
of pulses applied to the system 298 while the gate 286 is opened
and in a direction corresponding to which of the gates 290 or 292
is opened. This direction is controlled by the appearance or
absence of a signal on a long correction line 304 which signal is
applied to one terminal of the AND gate circuit 298 and to the
inhibit terminal 294 of the AND-NOT gate circuit 292. The long
correction line 304 is connected (in a manner not shown) to the
long correction terminal 262 of the correction direction flip-flop
264.
As pulses from the oscillator 284 are applied via the AND gate 286
to the electro-hydraulic stepper motor system 298, they are also
applied via the variable divider 270 to the down count terminal 254
of the counters 250. These pulse signals continue to be applied to
this counter until its count is reduced to zero whereupon a signal
appears at its borrow terminal 278 and on the No. 7 call back line.
This advances the program and removes the signal from the No. 7
circled command line to close the gate 286 and stop further
application of oscillator pulses to the electrohydraulic stepper
motor system 298 and to the counters 250.
It will be appreciated that the shaft 70 of the differential
transmission mechanism is adjusted by an amount and in a direction
corresponding to the combination of phase and average deviation
correction signals supplied to the counters 250 in the correction
60 following each knife cut.
It may be desired to control the electro-hydraulic stepper motor
system 298 so that instead of abruptly stopping operation when the
gate 286 is closed, it will begin to slow down and come to a more
gradual stop at this point. For this purpose there is provided a
comparator 306 which receives a continuous sampling of the count
present in the counters 250. The comparator 306 is "hard wired" to
establish a predetermined slowdown count. The count in the counters
250 is compared with this slowdown count and when the count in the
counters 250 falls below this number, the comparator 306 sends a
"near zero" signal to the oscillator 284 to reduce its output
frequency.
Having described the invention with particularity with reference to
the preferred embodiment of the same, it will be obvious to those
skilled in the art, after understanding the invention, that various
changes and modifications may be made therein without departing
from the spirit and scope of the invention; and the appended claims
are intended to cover such changes and modifications as are within
the scope of the invention.
* * * * *