[0001] The present invention rotates to a module for printing postage value, or other information,
on an envelope in a high speed mail processing and inserting system. Within the postage
printing module, a digital print mechanism is used at high speeds to create the postal
indicia for the envelopes. Also, the motion of the envelope is controlled to allow
continuous high speed envelope throughput, even if the postage printing device operates
at a lower velocity than other parts of the system.
[0002] inserter systems such as those applicable for use with the present invention, are
typically used by organizations such as banks, insurance companies and utility companies
for producing a large volume of specific mailings where the contents of each mail
item are directed to a particular addressee. Also, other organizations, such as direct
mailers, use inserts for producing a large volume of generic mailings where the contents
of each mail item are substantially identical for each addressee. Examples of such
inserter systems are the 8 series, 9 series, and APS™ inserter systems available from
Pitney Bowes Inc. of Stamford Connecticut, USA.
[0003] In many respects, the typical inserter system resembles a manufacturing assembly
line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter
the inserter system as inputs. Then, a plurality of different modules or workstations
in the inserter system work cooperatively to process the sheets until a finished mail
piece is produced. The exact configuration of each inserter system depends upon the
needs of each particular customer or installation.
[0004] Typically, inserter systems prepare mail pieces by gathering collations of documents
on a conveyor. The collations are then transported on the conveyor to an insertion
station where they are automatically stuffed into envelopes. After being stuffed with
the collations, the envelopes are removed from the insertion station for further processing.
Such further processing may include automated closing and sealing the envelope flap,
weighing the envelope, applying postage to the envelope, and finally sorting and stacking
the envelopes.
[0005] Current mail processing machines are often required to process up to 18,000 pieces
of mail an hour. Such a high processing speed may require envelopes in an output subsystem
to have a velocity in a range of 80-85 inches per second (ips) for processing. Consecutive
envelopes will nominally be separated by a 200 ms time interval for proper processing
while traveling through the inserter output subsystem. At such a high rate of speed,
system modules, such as those for sealing envelopes and putting postage on envelopes,
have very little time in which to perform their functions. If adequate control of
spacing between envelopes is not maintained, the modules may not have time to perform
their functions, envelopes may overlap, and jams and other errors may occur. In particular,
postage meters are time sensitive components of a mail processing system. Meters must
print a clear postal indicia on the appropriate part of the envelope to meet postal
regulations. The meter must also have the time necessary to perform the necessary
bookkeeping and calculations to ensure the appropriate funds are being stored and
printed.
[0006] A typical postage meter used with a conventional high speed mail processing system
has a mechanical print head that imprints postage indicia on envelopes being processed.
Such conventional postage metering technology is available on Pitney Bowes R150 and
R156 mailing machines using model 6500 meters. The mechanical print head is typically
comprised of a rotary drum that impresses an ink image on envelopes traveling underneath.
Using mechanical print head technology, throughput speed for meters is limited by
considerations such as the meter's ability to calculate postage and update postage
meter registers, and the speed at which ink can be applied to the envelopes. In most
cases, solutions using mechanical print head technology have been found adequate for
providing the desired throughput of approximately five envelopes per second.
[0007] However, use of existing mechanical print technology with high speed mail processing
machines presents some challenges. First, some older mailing machines were not designed
to operate at such high speeds for prolonged periods of time. Accordingly, solutions
that allow printing to occur at lower speeds may be desirable in terms of enhancing
long term mailing machine reliability.
[0008] Another problem is that many existing mechanical print head machines are configured
such that once an envelope is in the mailing machine, it is committed to be printed
and translated to a downstream module, regardless of downstream conditions. As a result,
if there is a paper jam downstream, the existing mailing machine component could cause
even more collateral damage to envelopes within the mailing machine. At such high
rates, jams and resultant damage may be more severe than at lower speeds. Accordingly,
improved control and lowered printing speed, while maintaining high throughput rate
in a mechanical print head mailing machine could provide additional advantages.
[0009] Controlling throughput through the metering portion of a mail producing system is
also a significant concern when using non-mechanical print heads. Many current mailing
machines use digital printing technology to print postal indicia on envelopes. One
form of digital printing that is commonly used for postage metering is thermal inkjet
technology. Thermal inkjet technology has been found to be an effective method for
generating images at 300 dpi on material translating up to 50 inches per second (ips)
and 200 dpi at 80 ips. Thus, while thermal inkjet technology is recognized as useful,
it is difficult to apply to high speed mail production systems that operate on mail
pieces that are typically traveling in the range of up to 100 ips in such systems.
[0010] As postage meters using digital print technology become more prevalent in the marketplace,
it is important to find suitable substitutes for the mechanical print technology meters
that have traditionally been used in high speed mail production systems. This need
for substitution is particularly important as it is expected that postal regulations
will require phasing out of older mechanical print technology meters, and replacement
with more sophisticated meters, Ink jet digital print technology is now capable of
printing a desired 200 dpi resolution on paper traveling at 80 ips., but has not yet
been incorporated in the metering portions of high speed mail production systems.
[0011] It is known that many standard ink jet print heads must be stopped occasionally in
order to perform maintenance routines. In particular, "drop-on-demand" style ink jet
print heads are known to require periodic maintenance. Maintenance may include a "print
head wipe" that occurs approximately every 500 prints, and has a duration of approximately
3 seconds. Maintenance also may include a "print head purge" that occurs after approximately
every 3000 prints, and has a duration of approximately 14 seconds. For an inserter
operating at 18,000 pieces per hour, the wipe and purge activities would occur every
100 seconds and ten minutes respectively. These maintenance activities result in reduced
throughput performance. For example, an inserter that would otherwise operate at 18,000
piece per hour, would be reduced to 17,000 pieces per hour as a result of purge and
wipe print head maintenance.
[0012] More expensive ink jet technology is available that does not require such frequent
maintenance. For example, Scitex™ ink jet printers can run continuously, with no significant
interruption. However, such continuous printers can be prohibitively expensive, and
it is preferred that less expensive drop-on-demand ink jet print head technology can
be used.
[0013] Some systems that have been available from Pitney Bowes for a number of years address
some issues relating to using a slower speed meter with a higher speed mail production
system. These systems utilize mechanical print head R150 and R156 mailing machines
using 6500 model postage meters installed on an inserter system, The postage meters
operate at a slower velocity than that of upstream and downstream modules in the system.
When an envelope reaches the postage meter module, a routine is Initiated within the
postage meter. Once the envelope is committed within the postage meter unit, this
routine is carried out without regard to conditions outside the postage meter. The
routine decelerates the envelope to a printing velocity. Then, the mechanical print
head of the postage meters imprints an indicia on the envelope. After the indicia
is printed, the envelope is accelerated back to close to the system velocity, and
the envelope is transported out of the meter,
[0014] Using the R150 or R156 mailing machines in this manner postage can be printed on
envelopes at a lower print velocity. However, problems still occur for systems operating
at higher velocities, such as 80 ips. At this higher speed, the time interval between
consecutive envelopes is so short that the R150 and R156 machines cannot reset itself
in time to print an indicia on a second envelope. To solve this problem, Pitney Bowes
has offered a solution for number of years utilizing two mailing machines arranged
serially in the envelope transport path, A diagram of this prior art system is depicted
in Figure 1.
[0015] In this serial mailing machine solution, envelopes are transported along transport
path
100. When a first of a series envelopes reaches the first serial mechanical mailing machine
101, the first envelope is decelerated for a printing operation by postage meter
104. After printing is complete, the first envelope is carried away from the first serial
machine
101 via transport
102 to the second serial mechanical mailing machine
103.
[0016] At the second mailing machine
103, the first envelope is typically decelerated to the print velocity. However, since
an indicia has already been printed on the first envelope, no printing operation is
performed by the second postage meter
105. The first envelope is then accelerated back to the system velocity and carried out
of the serial postage printing arrangement,
[0017] The motion control of deceleration and acceleration at the second postage meter 105
without performing a print operation is done in order to maintain the displacements
of consecutive envelopes in the system. Failure to subject subsequent envelopes to
the same displacements may result in one envelope catching up to the other and causing
a jam.
[0018] Following the first envelope, a second envelope arrives at the first mailing machine
101. The second envelope is subjected to the deceleration and acceleration motion profile.
In a high speed system, however, the first postage meter 104 may not have had time
to reset to print another indicia. Accordingly, the second envelope passes through
the first mailing machine
101 without a printing operation. The second envelope is then passed via transport
102 to the second mailing machine
103 where it is again decelerated to the print velocity, This time, mailing machine
103 does perform a printing operation and an indicia is printed on the second envelope
by postage meter
105. Mailing machine
103 then accelerates the envelope back to the system velocity, and the second envelope
is carried away downstream.
[0019] In this manner, some of the shortcomings of conventional mailing machines are avoided
by allowing the serial mailing machines
101 and
103 to alternately take turns printing indicia on every-other envelope. One disadvantage
of this serial arrangement is that it remains very sensitive to gaps sizes between
consecutive envelopes. Gaps between subsequent envelopes are shortened every time
a lead envelope undergoes the printing motion profile. If an error occurs in the processing
to make the gap size smaller than expected, envelopes can catch-up to one another,
and a paper jam can result. Also, the R150 and R156 mailing machines are a bit too
long to have time to carry out printing motion profile before the arrival of the next
envelope, and to still have some margin for error in the arrival of a subsequent envelope.
As a result, envelopes can be passed off between sets of nips that are not going at
the same speed, creating potential for pulling or buckling. Accordingly, a solution
with better space utilization and that is less sensitive to gap size variation is
desirable.
[0020] Another problem with existing solution is that the conventional postage meters are
inflexible in adjusting to conditions present in upstream or downstream meters. For
example, if the downstream module is halted as a result of a jam, the postage meter
will continue to operate on whatever envelope is within its control. This often results
in an additional jam, and collateral damage, as the postage meter attempts to output
the envelope to a stopped downstream module.
[0021] The present application describes a printing apparatus and method to for use in a
continuous high velocity document processing system. In the preferred embodiment,
they printing system is used in connection with a postage meter for imprinting postal
indicia on mail pieces. The print apparatus is preferably located at the downstream
end of an inserter device for mass producing mail pieces.
[0022] Within the printing system, a transport path conveys a series of mail pieces at a
print velocity. In the preferred embodiment, there are at least two print heads to
perform printing operations. The print heads are preferably available ink jet print
heads capable of printing at high resolution on documents traveling at high speed.
During normal operation, only one print head is operating at a time. As mail pieces
pass the print head at the print velocity, postal indicia are printed on them.
[0023] However, continuous operation of the printing apparatus is potentially interrupted
when the print head that is in use must stop in order to undergo a maintenance operation.
Accordingly, in accordance with the present invention, the second print head goes
into operation without interruption of the document processing flow.
[0024] In the preferred embodiment, the print heads are in series. Thus, when one print
head is taken out of service, the other one continues to print on documents in the
same transport path. Because the second print head may be at a different location
along the transport path, appropriate adjustments to the triggering of the print cycle
are required.
[0025] In an alternate embodiment, a parallel print head arrangement may be used. Under
this alternate embodiment, a flipper switch redirects documents to a parallel transport
path and a parallel print head, when the first one is out of service. In either embodiment,
the activation of a second print head may also be triggered when the first print head
is subject to a failure that prevents it from being used, Thus, it may not be necessary
to halt operation of the mail production process.
[0026] In a further preferred embodiment, a motion control scheme is used in the printing
module to decelerate a mail piece for slower speed printing, and then returning the
mail piece back to the higher system transport speed after printing. In this embodiment,
different positions of the print heads may require that different portions of the
print module transport act to effectuate the necessary print transport motion profile.
Thus. when an upstream print head is in use, an upstream portion of the print module
transport may be required to undergo the motion profile to account for the lower print
speed. Likewise, when a downstream print head is in use, a downstream portion of the
print module transport may be required for the motion profile.
[0027] Accordingly, a system using the present invention transports a first envelope at
a nominal transport velocity to the postage printing module. The postage printing
module receives the envelope at the nominal transport velocity. Based on predetermined
criteria, one or the other of the at least two print heads is selected for printing
the indicia on the envelope. If one print head is unavailable because of a failure,
or because of a periodic maintenance sequence, then the other one is used. When the
envelope has passed completely into the control of the postage printing module it
is decelerated to a predetermined lower print velocity for printing an image of a
predetermined length. After the printing is complete the envelope is accelerated back
to the transport speed and transported to a downstream module. None of the intervals
of deceleration, low print velocity, or acceleration may occur white an envelope in
the postage printing module is also in the control of another module.
[0028] This motion control is carried out by different transport elements in the print module
depending on which print head is being used. Transport elements, such as rollers,
are grouped together to act in unison in order to effectuate the motion control at
the appropriate location in relation to the print head. Depending on which print head
is used, a particular transport element may or may not be in the group performing
the motion control. Some transport elements may be in more than one grouping.
[0029] Deceleration in the motion control profile is activated by a sensor sensing the presence
of the envelope at a trigger point. Further sensors at the upstream and downstream
modules can be used to verify that no envelopes are under the shared control of the
postage printing module and another module.
[0030] In another preferred embodiment, the print head is geared to operate in synchronism
with the print transport, such that an image will not be distorted if there is a variation
in print velocity.
[0031] The preferred system and method also provide a way to ensure that correct displacement
is maintained between subsequent envelopes under the control of the invention in the
event of a stop and/or restart of the system resulting from an exception condition,
such as an envelope jam. When an envelope is within the print transport during an
exception condition, the envelope must be decelerated to a stop, so as not to create
further jams or collateral damage. In most modules in the system, a linear uniform
deceleration is preferred to minimize disruption of the desired spacing between mail
pieces being processed.
[0032] For the postage printing module, however, optimal performance using the present invention
may require that deceleration not occur in the same uniform linear fashion as the
rest of the system. Rather, deceleration is preferably controlled to maintain the
relative displacement of envelopes in the postage printing module with respect to
upstream and downstream modules, Because displacement varies in that module during
normal operation, a uniform stopping and starting of the print module to mirror other
modules will result in envelope spacing different than originally intended. Such changing
in envelope gaps may result in further jams or misprocessing.
[0033] For this reason, the deceleration and acceleration resulting from the exception condition
is controlled to maintain relative displacements as those displacements would have
been if the exception condition had not occurred. To achieve this result, a controller
in the print module controls the displacement of the print module according to a predetermined
algorithm. This algorithm relates displacements of the print module with other modules
for segments of the motion profile as they would have been executed during normal
operation. During the exception condition, deceleration and acceleration of the print
module is thus controlled as a predetermined function, or set of functions, of the
displacements in other transport modules. The appropriate function is determined as
a result of the position of the envelope in the print module during the course of
the exception condition.
[0034] This displacement mapping functionality of the preferred embodiment operates cooperatively
with the gearing of the print head mechanism to the print transport. In that preferred
embodiment, stopping and restarting of the print module may not affect printing of
an image on the envelope, even if a printing operation had already begun at the time
of the stoppage.
[0035] The principles discussed herein are also applicable to a system condition in which
the system is stopped without the occurrence of any problems. For example, this embodiment
may be applied in a situation where an operator simply wishes to turn off the system
in order to take a lunch break, without waiting for the job to finish. Using this
embodiment, the process of routine stopping and starting of the system is simplified,
and the risk of errors occurring from such stopping and starting is reduced. It will
be understood that these features. Stoppage conditions include errors and exception
conditions, as well as routine starting and stopping.
[0036] Further details of the present invention are provided in the accompanying drawings,
detailed description and claims.
[0037] Figure 1 depicts a prior art inserter metering system using two mechanical meters
in series.
[0038] Figure 2 is a diagrammatic view of a postage printing module in relation to upstream
and downstream modules.
[0039] Figure 3 is a graphical representation of a print motion control profile for controlling
the speed of envelopes in the postage printing module.
[0040] For the preferred embodiment of the present invention, it is desired that envelope
printing throughput of 18,000 to 22,000 mail pieces per hour be achieved. To accomplish
this goal, the transport velocity of the inserter system is typically 100 ips or greater.
However, the preferred ink jet printing device to be used for printing a postage indicia
is only capable of achieving a desired resolution of 200 dpi at a speed of 80 ips.
Such print heads are known to be available from printer manufacturers Canon, Brother
and Hewlett-Packard. Accordingly, the present invention will be described primarily
in regard to a system whereby the print module 1 is used to decelerate envelopes from
100 ips, to 80 ips for printing, and back to 100 ips for further processing.
[0041] As seen in FIG. 2, the present invention includes a postage printing module
1 positioned between an upstream module
2 and a downstream module
3. Upstream and downstream modules
2 and
3 can be any kinds of modules in an inserter output subsystem. Typically the upstream
module
2 could include a device for wetting and sealing an envelope flap. Downstream module
3 could be a module for sorting envelopes into appropriate output bins.
[0042] Postage printing module
1, upstream module
2, and downstream module
3, all include transport mechanisms for moving envelopes along the processing flow path.
In the depicted embodiment, the modules use sets of upper and lower rollers
10, 20, 30, 40, 70, and
80 called nips, between which envelopes are driven in the flow direction. In the preferred
embodiment rollers
10, 20, 30, 40, 70, and
80 are hard-nip rollers to minimize dither. The transport for module 1 may also be belts,
or other known transport mechanisms.
[0043] Print heads
50 and
60 are preferably located at or near the output end of the print transport portion of
the postage printing module 1 (see locations D and E). To satisfy desired readability
the print heads
50 and
60 should be capable of printing an indicia at a resolution of 200 dots per inch (dpi).
In the preferred embodiment, the print heads 50 and 60 are drop-on-demand ink jet
print heads capable of printing 200 dpi on media traveling at 80 ips. Alternatively,
the print heads
50 and
60 can be any type of print heads, including those using other digital or mechanical
technology, which may benefit from printing at a rate less than the system velocity.
[0044] In the preferred embodiment only one of print heads
50 or
60 is in use at a given time. Typically. one of the print heads, for example
50, will be used to print indicia on the stream of envelopes. Using the present invention,
when it is time for print head 50 to undergo a maintenance cycle, rather than stop
printing of indicia, print head 60 is brought into service to do the same job. Thus,
only one print head operates at a time, with one print head operating as a back-up,
and going into service when the primary undergoes a maintenance routine, or otherwise
becomes unavailable. The reserve may then continue operation as the primary print
head, and the former primary may become the reserve when the maintenance operation
is complete. Alternately, the primary may be brought back into service when maintenance
is complete, and the reserve returned to inactive status. Adjustments to the transport
system of print module
1 in support using the two print heads
50 and 60 in this manner are discussed below.
[0045] The rollers
10, 20, 30, and
40 for postage printing module
1 are driven by motors
11,
21, 31, and
41. For modules
2 and
3, rollers
70 and
80 are driven by electric motors
12 and
13 respectively. Motors
11, 21, 31, 41, 12, and
13 are preferably independently controllable servo motors. Motors
12 and
13 in upstream and downstream modules
2 and
3 drive rollers
70 and
80 at a constant velocity, preferably at the desired nominal velocity for envelopes
traveling in the system. Thus in the preferred embodiment, upstream and downstream
modules
2 and
3 will transport envelopes at 100 ips in the flow direction.
[0046] Instead of independently controllable motors, the transports for module 1 may be
driven in any known manner. For example, the rollers
10, 20, 30, and
40 could be all geared to a single driving mechanism. However, the arrangement of separate
control is preferred because it allows for more flexibility in controlling motion
within the print module 1.
[0047] Motors
11, 21, 31, and
41 drive rollers
10, 20, 30, and
40 in the postage printing module
1 at varying speeds in order to provide lower velocity printing capabilities. Postage
printing module motors
11, 21, 31, and
41 are controlled by controller
14 which in turn receives sensor signals. Signals may be provided to the controller
14 from upstream sensor
15, downstream sensor
18, and trigger sensors
16 and
17. Sensors
15 and
18 are preferably used to detect the trailing edges of consecutive envelopes passing
through the postage printing module
1, and to verify that the printing motion control adjustment only occurs while a single
envelope under the control of the set of rollers performing the velocity change. Trigger
sensor 16 determines that an envelope to be printed with an indicia is in the appropriate
position to trigger the beginning of the print motion control scheme for print head
50, as described further below. Similarly trigger sensor
17 may be used for triggering the motion control scheme for print head
60.
[0048] Sensors
15, 16, 17 and
18 are preferably photo sensors that are capable of detecting leading and trailing edges
of envelopes. While four photo sensors are depicted in the embodiment of Fig. 2, the
system can be operated with as few as one photo sensor at an upstream location. The
upstream single photo sensor would generate a signal upon deteting the presence of
a lead or trail edge of an envelope. Subsequent to sensing the envelope, encoder pulses
from the servo motors
(11, 21, 31, 41) transporting the envelope could be counted, and the corresponding displacement can
be accurately determined. Thus the controller
14 could trigger an action based on the sensing of an envelope edge, and then counting
a predetermined quantity of pulses from the motor encoders. The preferred positioning
of the sensors, and the utilization of signals received from the sensors are discussed
in more detail below.
[0049] Referring to FIG.2, the location of the output of the transport for upstream module
2 is location A. The location for the input to the print transport of postage printing
module
1 is location B. An intermediary transport roller
20 is located at point C. Transports
30 and
40 for print heads
50 and
60 are located at points D and E. Point E is also the output of the print transport
mechanism for postage printing module
1. The input for the transport of downstream module
3 is location F.
[0050] The modules may also include other rollers, or other types of transports, at other
locations. To maintain control over envelopes traveling through the system, consecutive
distances between rollers
10, 20, 30, and
40 must be less than the shortest length envelope expected to be conveyed. In the preferred
embodiment, it is expected that envelopes with a minimum length of 6.5" will be conveyed.
Accordingly and the rollers
10, 20,
30, and
40 will preferably be spaced not more than 6.25" apart, so that an envelope can be handed
off between sets of rollers without giving up control transporting the envelope at
any time. The preferred embodiment is also designed to handle an envelope 10.375 inches
long.
[0051] Upstream sensor
15 is preferably located at or near location B, while downstream sensor
16 is preferably located at or near location E. Trigger sensors
17 and
18 are preferably located upstream from print heads
50 and
60 by a sufficient distance to permit deceleration of the print transport from the nominal
transport velocity to the print velocity upon the detection of a lead envelope edge.
The trigger sensors
17 and
18 may be located any distance upstream from the minimum deceleration point, even as
far upstream as upstream sensor
15, so long as the motion control profile determined by controller
14 is adjusted accordingly.
[0052] Controller
14 controls the motors
11, 21, 31, and
41 in accordance with a print motion control profile in order to achieve the goals of
(1) reducing the speed of an envelope so that the lower velocity print heads
50 and
60 can print an indicia, (2) controlling the motion of the envelopes so that consecutive
envelopes do not interfere with each other, and (3) allowing the printing duties to
be shared between print heads
50 and
60 located at different positions along the transport path. The preferred motion control
profile further allows that multiple envelopes may be handled within the print module
1 at a given time, and not interfere with one another, even when they are at different
velocities, and without creating mismatches between print module
1 and the upstream and downstream modules
2 and
3.
[0053] Depending on which of the print heads
50 or
60 is in use, different groupings of transport rollers
(10, 20, 30, 40) in print module
1 will be used to perform the print motion control profile to decelerate envelopes
to the print velocity and to return them to the transport velocity. A preferred embodiment
of a print motion control profile for use with the present invention is depicted in
FIG. 3, and described further below.
[0054] Because print heads
50 and
60 are located at different locations along the transport path, the present invention
enables the speed adjustment motion profile to begin and end at different locations
in the print module 1. Thus, when print head 50 is in use, transport rollers
10, 20, and
30 will be used to perform the speed adjustment, while roller
40 will remain at the constant transport velocity.
[0055] When print head
60 is in use, roller
10 operates at constant velocity, as if it were part of the upstream module
2. Meanwhile, rollers
20,
30, and
40 are grouped together to perform the motion profile.
[0056] As a further enhancement to the performance of the present invention, the groupings
of the rollers will only remain in place so long as the rollers are needed as part
of the group. Upstream members of the groups will return immediately to the transport
velocity as soon as an envelope being printed passes from its control. For example,
if print head
50 is in use, rollers
10, 20, and
30 will operate in unison as the envelope comes under the control of the group, However,
the envelope may pass out of the control of roller
10, even while the printing operation, and corresponding transport motion control, are
being carried out. When this happens, roller
10 leaves the uniformly controlled group and immediate accelerates back to transport
velocity. Similarly, roller
20 would return immediately to the transport velocity when the envelope leaves its control.
In this manner, the upstream rollers are more quickly ready to receive envelopes from
upstream sources, even as print speed adjustments are still underway.
[0057] In a preferred method of controlling the velocity adjustment groups is to designate
master and slave roller nips. When print head
50 is in use, roller
30 (and motor
31) become a master for slave rollers
10 and
20 when an envelope comes under the complete control of the group. When the envelopes
leave rollers
10 and
20, they cease to be slaved to roller
30 and may be slaved to the roller
70 for upstream module
2. For this example, roller
40 was never part of the velocity adjustment grouping, and may be slaved to roller
80 of downstream module
3.
[0058] When print head
60 is in use, the master roller for the velocity adjustment control group is roller
40. When an envelope enters the control of the control group, rollers
20 and
30 will be slaved to the master
40. In this situation, roller
10 may be continuously slaved to roller
70 of upstream module
2. As the envelope passes through the control group, and out of the control of rollers
20 and
30, they are preferably released from the master
40 and return to the transport velocity. In returning to the transport velocity, they
may in turn be slaved to upstream roller
70.
[0059] Accordingly, controller
14 is programmed to designate the appropriate individually controllable rollers and
motors as masters and slaves based on positions of envelopes sensed by the sensors.
Concurrently, the controller
14 is also providing the appropriate motion profile for the control group to allow reduced
velocity printing.
[0060] Initiation of the slaving of rollers and the print motion adjustment may be triggered
by the controller when an envelope reaches a predetermined displacement downstream
from sensor
15. The predetermined displacement is based on the distance between the trip photocell
15 and the print head
50, the deceleration rate, the indicia offset, upstream module velocity, print velocity,
and settle time (before printing begins). For control purposes, the locations of the
edges of envelopes may be detected based on the positioning of photocells at the exact
locations. Alternatively, positions may be calculated by measuring encoder pulses
from the servo motors, and adding the envelopes positional displacement from a known
location of a previously tripped upstream sensor.
[0061] In the preferred embodiment depicted in Fig. 2, the following distances between components
has been found to most effectively handle the expected range of envelope sizes:
A to B, 3.7 inches;
B to C, 3.9 inches;
C to D, 3.9 inches;
D to E, 6.25 inches; and
E to F, 6.1 inches.
[0062] Fig. 3 is an exemplary motion profile of master rollers
30 or
40 at locations D and E, depending on which of the print heads
50 or
60 is in use. Based on the criteria discussed above, rollers slaved to the master rollers
will also perform portions of motion profile. Notations provide the translation distances
of envelopes within the velocity adjustment control group of rollers for different
intervals. The depicted profile is based on a system that is printing on envelopes
10.375" inches in length, that requires a maximum length printed indicia of 5". The
nominal transport velocity is 100 ips, and the print velocity is 80 ips. The accelerations
for adjusting speeds are 8.0 G's, or 3091 in/s
2. For this embodiment, the throughput rate is 22,000 mailpieces per hour. At the nominal
transport speed the period between envelopes is 164 ms.
[0063] The print heads 50 and 60 are preferably located just downstream of nip roller sets
30 and 40. This location allows greater control at the print head location, and also
minimizes the opportunity for errors relating to an envelope tail kick. Tail kick
occurs when the trail edge of an envelope is not adequately constrained and comes
into contact with a print head, thereby causing print head damage and failure.
[0064] At point
201 on the profile, a lead edge of a first envelope reaches the output of the upstream
module
2, at location A. In this exemplary profile, there is no envelope to be printed in the
cycle before the first envelope. After crossing between the gap between the module
transports, at point
202 the lead edge of the first envelope is at the most upstream roller of the velocity
adjustment control group (location B or C). At point
202 there can be no unilateral change in velocity of the print module transport by the
control group. Sensors
15 and
16 can provide signals to controller
14 to prevent initiation of a change in velocity white an envelope is under the control
of more than one module, or more than one control group.
[0065] At point
203 on the motion profile, the first envelope is under the sole control of the control
group of roller for print module
1, and the control group may slow down to allow the slower velocity printing. Controller
14 can begin the necessary deceleration by sensing the lead edge of the first envelope
with the trigger sensor
16, 17. Alternatively, the deceleration can begin as a result of upstream sensor
15 detecting the position of the tail end of the first envelope. Preferably, before
printing begins, 10 ms of settle time is allowed (or 80 ips* .010s = 0.8 inches) after
the mail piece reaches the print velocity.
[0066] After point
203, the three nips of the control group of the print module
1 initiate a predetermined deceleration to reach the desired print velocity, in this
case 80 ips. The control group master roller then operates at 80 ips to transport
the envelope a predetermined distance while an indicia is printed on it. In this exemplary
embodiment the print distance is five inches. After the predetermined print distance
has been completed, the envelope is accelerated back to the transport speed. Slaved
control group rollers upstream of the master roller, preferably return to the transport
velocity of 100 ips prior to completion of the motion control profile of Fig. 3, once
the envelope has passed out of their control.
[0067] After the motion control profile has been complete, such as at point
205, the lead edge of the first envelope reaches the first nip downstream of the master
nip. At this point in time, the first envelope is no longer under the exclusive control
of the control group and variations in the print transport speed are not permissible.
[0068] Using the motion profile depicted in Fig. 3, and the control scheme discussed previously,
envelopes can be slowed for lower speed printing, but without having subsequent envelopes
collide. The nominal distance between envelopes for the example described would be
about 6.025 inches before entering the print module
1. After performing the print motion profile, the minimum distance between envelopes
is reduced to 4.49 inches. However, the nominal distance is restored as the subsequent
envelope has the same motion profile performed on it, and the prior envelope travels
away at the nominal travel velocity of 100 ips. Accordingly, the throughput of the
system remains intact.
[0069] The exemplary motion profile described above complies with requirements necessary
for a successful reduced velocity print operation. As mentioned above, when print
speed adjustment is performed on an envelope, the velocity adjustment control group
of nip in print module
1 must have total control of the envelope. For example, the envelope cannot reside
between nip rollers at location A or F during execution of the print motion control
profile.
[0070] In a further preferred embodiment of the present invention, to ensure accurate printing,
the rate at which the print heads
50 and
60 print the indicia can be electronically or mechanically geared to the speed of the
print transport in the print module
1. In such case, under circumstances where the print transport is operating outside
of nominal conditions, a correct size and resolution print image can be generated.
In the electronic version of this preferred embodiment, controller
14, print head
50 or
60, and the master roller servomotor
31 or
41 are geared to the same velocity and timing signals to provide that the transport
and printing are always in synchronism.
[0071] Another preferred embodiment of the present invention addresses a problem that occurs
when the print module
1 is forced to deviate from the motion control profile depicted in Fig. 3. For example,
in a conventional inserter system, when an envelope jam occurs downstream from the
postage printing module, upstream and downstream modules typically come to a halt
in accordance with a uniform rapid linear deceleration profile. Unfortunately, in
conventional inserter systems, the postage printing modules have no mechanism for
halting envelopes that are committed within the postage meter. As a result, additional
paper jams and damaged envelopes commonly occur as the postage printing module forces
envelopes against a halted downstream module.
[0072] To address this problem, in the preferred embodiment of the present invention the
print module
1 will also decelerate to a stop upon the occurrence of an exception event. Such exception
events may include detection of jams, detection that mail pieces are out of order,
or detection of equipment malfunctions. If the print head 50 or
60 is geared to the master motor
31 or
41, then an envelope can be stopped anywhere in the print module
1 upon the occurrence of an exception event without damaging the envelopes, and without
compromising the image to be printed on the envelope. After the error condition has
passed, print module
1 can be accelerated back to the velocities in accordance with the motion profile depicted
in Fig. 3.
[0073] A uniform linear deceleration and acceleration during an exception condition is preferred
for the upstream and downstream modules
2 and
3. However, a deceleration and acceleration having that same uniform linear profile
may cause problems in print module
1. For example, if the print transport was about to reach point
203 in the motion profile of Fig. 3 when the exception condition occurred, the control
group of the print transport could decelerate down to zero velocity in a linear fashion
the same as modules
2 and
3. However, after the exception condition has been cleared, the envelope in the print
module
1 will be closer to the downstream module than it would have been if the normal motion
profile had been executed. This is because during the uniform deceleration, the print
module
1 has essentially skipped a portion of the motion profile. During this "skipped" portion,
it was intended that the envelope decelerate to the print velocity. A result of that
deceleration would have been an increase in the gap with a downstream envelope and
a decrease in a gap with an upstream envelope. A uniform shutdown profile for all
modules interferes with this planned variation in gap sizes.
[0074] Accordingly, the present invention maintains the expected displacements between consecutive
documents by controlling the transport of envelopes in print module
1 as a function of the displacement positions of upstream and/or downstream modules
2 and
3. Thus, the variations in velocity that result from the stoppage and starting in an
exception condition should not affect the relative spacing of the envelopes. In the
equations provided below for determining the appropriate displacement relationship,
the velocity variables will be eliminated, and positions of the transports expressed
in terms of variable displacements and known constants.
[0075] To achieve this desired result, the desired displacements of the print module
1, as they would have resulted from performance of the motion profile under nominal
conditions, must be describable in terms of the position of upstream or downstream
modules. Also, the descriptions must be expressed in terms of the displacement relationships
that would have resulted from the distinct segments in the motion profile.
[0076] For example, for the portion of the motion profile where the print module
1 should transport the envelope at the transport velocity, there should be a one-to-one
correspondence in the displacements produced by an upstream module
2 and print module
1. Thus, if an exception condition occurs while an envelope is at a location within
the print module
1 where it would normally be traveling at the transport velocity, then the deceleration
of the print module
1 during an exception condition will mirror that of the upstream module
2. For this exemplary situation, the equation relating the displacement position of
the print module
1, "P
1," to the displacement position of the upstream module
2, "P
2," will be:

[0077] If the envelope is located at a position where it would normally be subject to deceleration
in preparation for a printing operation, then, during an exception condition, print
module
1 must decelerate more quickly than upstream module
2 in order that the shortening of the gap between envelopes in those modules be preserved.
To derive the appropriate displacement relationship for this segment of the print
module
1 motion, the following symbols are defined:
V = velocity of the print module 1 transport;
Vtransport = the transport velocity for the system, (nominally 100 ips);
vprint = the print velocity for print module 1 during the printing segment of the motion profile (nominally 80ips);
a1 = acceleration that print module 1 would normally undergo in the deceleration segment of the motion profile (deceleration
being a negative value acceleration) (nominally -1500 in/sec);
a2 = acceleration that print module 1 would normally undergo in the acceleration segment of the motion profile (nominally
1500 in/sec);
Pdecel = the displacement that print module 1 normally undergoes during the deceleration portion of the motion profile (nominally
0.58 inches); and
Paccel = the displacement that print module 1 normally undergoes during the acceleration portion of the motion profile (nominally
0.58 inches).
[0078] During normal operation in accordance with the motion profile, the displacement position,
P
1, of the print module
1, starting at the beginning of the deceleration segment, is described according to
the equation:

[0079] An expression can also be derived relating the velocity, v, of print module 1 as
a function of the displacement position, P
2, of upstream module
2, during normal operation of the deceleration portion of the motion profile:

[0080] Thus, an equation relating P
1 and P
2, independent of instantaneous velocities, is derived by substituting the value of
"v" derived in equation [3] into equation [2]. Performing this substitution, displacement
relationship between print module
1 with upstream module
2, for the deceleration segment of the motion profile is:

[0081] Using this relationship in equation [4], controller
14 of print module 1 can adjust the displacement of print module
1 when an envelope is present at a location where it normally would undergo the deceleration
portion of the motion profile.
[0082] The next segment of the motion profile for discussion is the printing portion. During
that segment the envelope is transported at a constant velocity. v
print. Accordingly, for that segment, the relative displacements that would be seen in
upstream module
2 and print module
1 would be described as a fixed ratio. This relationship is described by the following
equation:

[0083] it should be noted that the appropriate displacement relationship may change white
the print module
1 is decelerating to a stop. For example, an envelope that is slightly upstream of
trigger sensor
16 or
17, and traveling at the transport velocity, may begin to stop in accordance with the
displacement relationship described in equation [1], above. However, during the deceleration,
but before stopping, the envelope may reach the trigger position marked sensor
16 or
17. After the trigger sensor
16 or
17 has been reached controller
14 will switch the displacement relationship to that described in equation [4] above.
Thus, as many different displacement relationships may be utilized as may be necessitated
by the positions reached by the envelope during the deceleration process. Thus, if
the deceleration were protracted to reach a location where a printing segment was
intended, then displacement may be controlled in accordance equation [5] above. Also,
based on the gearing of the print head
50 or
60 with the motor
31 or
41, the print head may begin printing a portion of the image on the envelope before it
stops. When the print module 1 restarts, the geared print head will also resume printing
at the appropriate geared speed.
[0084] A final segment of the motion profile is the acceleration of the envelope from the
print velocity, back to the transport velocity. The displacement mapping relationship
for this segment can be derived in the same way as for equation [4] above. A difference
in the result being that this acceleration segment is causing an envelope in the print
module
1 to increase its distance from a subsequent envelope in upstream module
2. Accordingly, the displacement relationship when an envelope is at the acceleration
motion profile segment during a stopping or restarting condition is as follows:

[0085] Displacement information for respective print, upstream, and downstream modules
1, 2, and
3 may typically be monitored via encoders in motors
11, 21, 31, and
41. The encoders register the mechanical movement of the module transports and report
the displacements to controller
14 for appropriate use by controller
14 to maintain correct displacement mapping between the modules.
[0086] The preferred embodiment depicted in Fig. 2, depicts an exemplary serial arrangement
of two print heads, whereby one may be taken out of service while the other undergoes
a maintenance cycle, An alternative embodiment could utilize a parallel arrangement.
Under this parallel arrangement, a flipper gate would be activated when the active
print head is taken out of service. The flipper gate would redirect envelopes to a
second parallel transport where the back-up print head prints indicia on envelopes.
An exemplary parallel path system that would be suitable for use in this manner is
depicted in co-pending European Patent Publication number 1391849, published February
25, 2004 and entitled PARALLEL PROCESSING HIGH SPEED PRINTING SYSTEM FOR AN INSERTING
SYSTEM.
[0087] In this application, a preferred embodiment of the system has been described in which
documents being processed are envelopes. It should be understood that the present
invention may be applicable for any kind of document on which printing is desired.
Also a package or a parcel to which a printed image is applied as part of a processing
system should also be considered to fall within the scope of the term "document" as
used in this application,
[0088] The preferred embodiment was also described herein as including two print heads.
It will be understood by one of ordinary skill in the art that the invention may utilize
more than two print heads, and that nothing in this description is intended to limit
the invention from using more than two.
[0089] Although the invention has been described with respect to a preferred embodiment
thereof, it will be understood by those skilled in the art that the foregoing and
various other changes, omissions and deviations in the form and detail thereof may
be made without departing from the spirit and scope of this invention.
1. A printing apparatus for use in a high velocity document processing system, the printing
apparatus comprising:
a transport path conveying a series of documents;
an upstream print head contiguous with the transport to print on documents transported
thereon;
a downstream print head, downstream of the upstream print head, and contiguous with
the transport to print on documents transported thereon;
a controller controlling a first one of the upstream or downstream print heads to
print on transported documents, the controller further switching to a second of the
upstream or downstream print heads when the first one is out of service.
2. The printing apparatus of claim 1 wherein the documents are mail pieces and further
comprising a postage meter coupled to the print heads, whereby postal indicia are
printed on the mail pieces.
3. The printing apparatus of any of claims 1 or 2 wherein the print heads are ink jet
print heads.
4. The printing apparatus of any of claims 1-3 wherein the controller periodically takes
the print head that is in use out of service to perform maintenance operations.
5. The printing apparatus of any of claims 1-3 wherein the controller switches from using
the first print head to the second print head when a failure is detected in the first
print head.
6. The printing apparatus of any of claims 1-5 wherein:
the transport path further comprises an upstream transport conveying documents at
a transport velocity, a downstream transport conveying documents at the transport
velocity, a print transport located between the upstream transport and the downstream
transport, the print transport driven independently of the upstream transport and
the downstream transports and comprising a plurality of individually controllable
rollers;
the controller further controlling a roller group of less than all of the plurality
of individually controllable rollers according to a predetermined motion profile,
whereby under nominal conditions the roller group decelerates the print transport
to a nominal print velocity prior to a printing operation in a first segment, maintains
the nominal print velocity during the printing operation in a second segment, and
accelerates the print transport back to the transport velocity after completion of
the printing operation in a third segment; and
the controller controls the roller group to comprise of an upstream portion of the
plurality of individually controllable rollers if the upstream print head is in use,
and to comprise a downstream portion of the plurality of individually controllable
rollers if the downstream print head is in use.
7. The printing apparatus of claim 6 wherein one or more of the individually controlled
rollers that are not part of the roller group when a given print head is in use are
operated at the transport velocity.
8. The printing apparatus of claim 6 wherein the roller group controlled by the controller
decelerates to a stop upon the occurrence of a stoppage condition in the document
processing system, the deceleration controlled by the controller in accordance with
a predetermined algorithm to maintain a relative displacement of the roller group
with respect to upstream or downstream transports to maintain the relative displacements
that would have occurred under the predetermined motion profile under nominal conditions,
the predetermined algorithm determining the displacement of the roller group as a
function of displacement of upstream or downstream transports.
9. The printing apparatus in accordance with claim 8 wherein the controller further controls
the roller group to accelerate from a stop back to nominal condition upon the occurrence
of a restart after the stoppage condition, the acceleration controlled by the controller
in accordance with the predetermined algorithm to maintain the relative displacement
of the roller group with respect to upstream or downstream transports to maintain
the relative displacements that would have occurred under the predetermined motion
profile under nominal conditions, the predetermined algorithm determining the displacement
of the roller group as a function of displacement of upstream or downstream transports.
10. The printing apparatus any of claims 1-9 wherein the print heads are electronically
or mechanically geared to the corresponding roller group so that variations in print
transport velocity during a printing operation will not affect an image being printed.
11. The printing apparatus of any of claims 9 or 10 wherein the predetermined algorithm
for determining relative displacements includes a first function for accounting for
changes in relative displacements that would have occurred during deceleration of
the roller group in the first segment of the motion profile, a second function for
accounting for changes in relative displacements that would have occurred during the
reduced nominal print velocity of the second segment of the motion profile, and a
third function for accounting for changes in relative displacements that would have
occurred during acceleration of the print transport in the third segment of the motion
profile, the appropriate of the first, second, and third functions being invoked by
the controller based on the position of a document in the roller group during the
occurrence of the stoppage condition.
12. The printing apparatus of any of claims 6-11 wherein the upstream portion and the
downstream portion of the plurality of individually controllable rollers include at
least one same roller and at least one different roller.
13. The printing apparatus of claim 6 wherein the controller further controls an arrangement
of the roller group whereby a member of the roller group leaves the roller group after
an envelope passes downstream from the members control.
14. The printing apparatus of claim 13 wherein the controller controls a velocity of the
member that leaves the roller group after the envelope passes downstream from the
member's control to be the transport velocity.
15. A printing method for high velocity document processing, the printing method comprising:
transporting a series of documents on a transport;
positioning an upstream print head contiguous with the transport to print on documents
transported thereon;
positioning a downstream print head, downstream of the upstream print head, and contiguous
with the transport to print on documents transported thereon;
controlling a first one of the upstream or downstream print heads to print on transported
documents; and
switching to a second of the upstream or downstream print heads for printing when
the first one is out of service.
16. The printing method of claim 15 further comprising printing postal indicia on mail
pieces by coupling a postage meter to the print heads.
17. The printing method of any of claims 15 or 16 wherein the step of printing comprises
ink jet printing.
18. The printing method of any of claims 15-17 further comprising periodically removing
the print head that is in use out of service and performing maintenance operations
on the print head.
19. The printing method of claim 15 wherein further including switching from using the
first print head to the second print head when a failure is detected in the first
print head.
20. The printing method of any of claims 15-19 further comprising detecting a document
approaching the upstream or downstream print head, triggering the upstream or downstream
print head based on a predetermined interval subsequent to detecting the document,
and adjusting the predetermined interval depending on which of the upstream or downstream
print head is in use to account for the different locations of the upstream and downstream
print heads,
21. The method for printing of claim 15-20 wherein:
the step of transporting further comprises
transporting a document at a transport velocity in an upstream transport to a print
transport;
transporting the document on the print transport; and
transporting the document at the transport velocity in a downstream transport from
the print transport;
and including a further step, while the document is within the print transport during
nominal system conditions, of controlling the velocity of the print transport in accordance
with a motion profile, whereby the motion profile includes the steps of decelerating
the document to a print velocity, maintaining the print velocity during the step of
printing, and accelerating the document to the transport velocity after the step of
printing is complete, the motion profile resulting in a relative displacement of the
document with respect to upstream and downstream documents to vary during the motion
profile; and
performing the print transport motion profile with an upstream portion of the print
transport when the upstream print head is in use, and with a downstream portion of
the print transport when the downstream print head is in use, the upstream and downstream
portions each comprising at least one different transport mechanism from the other.
22. The method of claim 21, wherein upon the occurrence of a stoppage condition while
the document is within the print transport, further including the steps of:
modifying the motion profile by stopping the document within the print transport during
a stoppage condition,
decelerating the document to a stop, the step of decelerating to the stop including
the step of maintaining the relative displacement of the document on the print transport
with respect to upstream and downstream documents, the step of maintaining the relative
displacement including controlling the deceleration according to a predetermined algorithm
describing relative displacement between documents as such displacement would have
occurred under the motion profile under nominal conditions, the predetermined algorithm
determining the displacement of the print transport as a function of displacement
of upstream or downstream transports.
23. The printing method in accordance with claim 22 further comprising the steps of:
restarting the print transport while the document is within the print transport during
the stoppage condition, the step of restarting including the step of accelerating
the document from the stop to a velocity of the motion profile, the step of accelerating
including the step of maintaining the relative displacement of the document on the
print transport with respect to upstream and downstream documents, the step of maintaining
the relative displacement including controlling the acceleration according to the
predetermined algorithm.
24. The printing method of any of claims 15-23 including the step of electronically or
mechanically gearing the printing step to the print transport motion so that variations
in print transport velocity during the printing step will not affect the image being
printed.
25. The printing method claim 23 wherein the predetermined algorithm for determining relative
displacements including a first function accounting for changes in relative displacements
that would have occurred during deceleration of the print transport in the first segment
of the motion profile. a second function accounting for changes in relative displacements
that would have occurred during the reduced nominal print velocity of the second segment
of the motion profile, and a third function accounting for changes in relative displacements
that would have occurred during acceleration of the print transport in the third segment
of the motion profile, and
the method further including the step of invoking the appropriate of the first,
second, and third functions based on the position of the document in the print transport
during the occurrence of the stoppage condition.
26. The printing method of claim 21 wherein upstream and downstream portions of the print
transport are comprised of a grouping of individually controllable rollers, the method
further comprising:
controlling the grouping of rollers whereby a member of the grouping leaves the grouping
after an envelope passes downstream from the member's control, regardless of the motion
profile.
27. The printing method of claim 26 further comprising controlling a velocity of the member
that leaves the grouping to be the transport velocity.