U.S. patent application number 09/820944 was filed with the patent office on 2001-07-26 for flats bundle collator.
This patent application is currently assigned to Northrop Grumman Corporation. Invention is credited to Hendrickson, David Brian, McConnell, William P., Mileaf, Daryl, Tilles, David Jerome.
Application Number | 20010009233 09/820944 |
Document ID | / |
Family ID | 23201499 |
Filed Date | 2001-07-26 |
United States Patent
Application |
20010009233 |
Kind Code |
A1 |
Hendrickson, David Brian ;
et al. |
July 26, 2001 |
Flats bundle collator
Abstract
A method and an apparatus for collating a plurality of groups of
mail items, such as flats mail, each group being pre-sequenced
according to prioritized delivery addresses, into a final sequenced
set of the mail items from the groups, utilizing the prioritized
delivery addresses. Each bundle of mail items is formed into a
single input stream of the individual mail items. The mail items
are transported along a conveyor system from the input stream to a
staging station. The mail items are sorted at the staging station
into a plurality of subsets of mail items re-sequenced as an
intermediate step to achieving the final sequenced sets. The mail
items are then collated and merged into a single output stream from
the respective subsets of mail items in the final sequenced set.
Portions of the output stream from the staging station are
collected in batches having justified unbound edges which maintain
the sequence consistent with the prioritized delivery order
sequence of the mail for a given carrier route.
Inventors: |
Hendrickson, David Brian;
(Columbia, MD) ; Mileaf, Daryl; (Hanover, MD)
; McConnell, William P.; (Woodstock, MD) ; Tilles,
David Jerome; (Woodstock, MD) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Northrop Grumman
Corporation
|
Family ID: |
23201499 |
Appl. No.: |
09/820944 |
Filed: |
March 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09820944 |
Mar 30, 2001 |
|
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09310221 |
May 12, 1999 |
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6241099 |
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Current U.S.
Class: |
209/542 ;
414/1 |
Current CPC
Class: |
B07C 3/02 20130101; B65H
2301/4311 20130101; B07C 3/008 20130101; B07C 3/00 20130101; Y10S
209/918 20130101; Y10S 209/90 20130101 |
Class at
Publication: |
209/542 ;
414/1 |
International
Class: |
B25J 001/00 |
Claims
What is claimed:
1. A method of stacking flats mail having bound edges and opposed
unbound edges comprising the steps of: edge justifying the unbound
edges by aligning the unbound edges against a planar surface; and
placing the edge-justified flats mail into a vertical stack with
the unbound edges aligned on one side of the stack.
2. The method of claim 1 wherein the flats mail is from a group
consisting of magazines or newspapers.
3. The method of claim 2 further including the steps of:
transporting the flats mail along a conveyor with a major face
thereof supported on the conveyor and all unbound edges facing a
same side of the conveyor; and tilting the flats mail toward said
planar surface to thereby direct the unbound edges of the flats
mail against the planar surface.
4. The method of claim 3 wherein the step of tilting is performed
by skewing a top surface of a portion of the conveyor toward said
planar surface, said planar surface being disposed transversely of
a longitudinal axis of the conveyor.
5. The method of claim 4 wherein said planar surface is defined by
a back wall of a C-shaped channel.
6. The method of claim 1 further including the steps of:
transporting the flats mail along a conveyor with a major face
thereof supported on the conveyor and all unbound edges facing a
same side of the conveyor; and tilting the flats mail toward said
planar surface to thereby direct the unbound edges of the flats
mail against the planar surface.
7. The method of claim 1 wherein the step of tilting is performed
by skewing a top surface of a portion of the conveyor toward said
planar surface, said planar surface being disposed transversely of
a longitudinal axis of the conveyor.
8. The method of claim 1 wherein said planar surface is defined by
a back wall of a C-shaped channel.
9. A system for stacking flats mail having bound edges and opposed
unbound edges comprising: means for edge-justifying the unbound
edges by aligning the unbound edges against a planar surface; and
means for placing the edge-justified flats mail into a vertical
stack with the unbound edges aligned on one side of the stack.
10. The system of claim 9 wherein the flats mail is from a group
consisting of magazines or newspapers.
11. The system of claim 10 further including the steps of: means
for transporting the flats mail along a conveyor with a major face
thereof supported on the conveyor and all unbound edges facing a
same side of the conveyor; and means for tilting the flats mail
toward said planar surface to thereby direct the unbound edges of
the flats mail against the planar surface.
12. The system of claim 11 wherein the means for tilting includes a
top surface of a portion of the conveyor skewed toward said planar
surface, said planar surface being disposed transversely of a
longitudinal axis of the conveyor.
13. The system of claim 12 wherein said planar surface is defined
by a back wall of a C-shaped channel.
14. The system of claim 9 further including: means for transporting
the flats mail along a conveyor with a major face thereof supported
on the conveyor and all unbound edges facing a same side of the
conveyor; and means for tilting the flats mail toward said planar
surface to thereby direct the unbound edges of the flats mail
against the planar surface.
15. The system of claim 9 wherein the means for tilting includes a
top surface of a portion of the conveyor skewed toward said planar
surface, said planar surface being disposed transversely of a
longitudinal axis of the conveyor.
16. The system of claim 9 wherein said planar surface is defined by
a back wall of a C-shaped channel.
17. The system of claim 9 wherein the flats mail has various
dimensions in width between the bound and unbound edges
thereof.
18. The method of claim 1 wherein the flats mail has various
dimensions in width between the bound and unbound edges thereof.
Description
[0001] This application is a divisional application of application
Ser. No. 09/310,221, filed May 12, 1999, and is assigned to the
same assignee as the present invention.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a method and system for
collating a plurality of groups of mail items, each group being
pre-sequenced according to prioritized delivery addresses, into a
final sequenced set of the mail items from the groups, utilizing
the prioritized delivery addresses. More specifically, the present
invention relates to a process and system that merges several
sequenced bundles of flats mail into one sequenced set of mail for
delivery by a mail carrier according to a prioritized delivery
address sequence, commonly known as a delivery order sequence (DOS)
or walk sequence (WS).
[0003] Flats mail, routinely delivered by mail carriers, includes
magazines, newspapers, padded envelopes, single sheet fliers,
compact disks in boxes, poly-wrapped items, and miscellaneous other
types of mail items. These flats range in size from 4" to 15.75" in
length; 4" to 12" in width; 0.007" to 1.25" in thickness; and
{fraction (1/100)} lb. to 6 lb. in weight. Delivery of these flats
in delivery order sequence, or walk sequence, requires special
sorting in a post office facility such as a delivery unit (DU). In
general, DU operations are consistent from one office to another
within the U.S. postal system. However, different route types
(rural, city, park and loop) may process flats in slightly
different manners within the same facility. The flats to be
processed arrive from a variety of sources in a number of different
ways. Mailers may drop ship saturation mailings (mass mailings) two
to seven days prior to the delivery per an agreement with the local
Postmaster. Other mailings can arrive on pallets (periodicals,
national advertisements or catalogs) after passing through the
postal network of facilities as cross-dock material. Other material
may be broken down from pallets at an upstream facility if a pallet
was shipped as three-digit material. Other flats may have been
processed on flats sorting equipment known in the art, and are then
processed according to carrier route. Still more material can pass
through bulk mail centers as bundles before arriving at the
delivery unit (DU).
[0004] Currently, with the exception of saturation (mass) mailings,
the majority of this material is not in carrier walk sequence (WS)
or delivery order sequence (DOS). Bundles may be in enhanced
carrier line-of-travel (ECLOT) or in carrier route, but not walk
sequence. Less than 1% of the mailings in the field have an eleven
digit (ZIP+4+2) delivery point barcode representative of the
delivery point sequence (DPS). Many saturation mailings have no
barcode at all and are addressed to "Postal Customer" with no
address. Other mailings have 5 or 9 digit ZIP codes and "marriage"
mailings consisting of two materials; an address card or leaflet,
and a second mailing with no address label intended to be left at
the same address as the card. However, in order to provide for
flats bundle collating in an automated fashion, it is possible to
provide all of the flats mail with eleven digit coding inclusive of
delivery point sequence information.
[0005] In current operations, the source and configuration of the
flats being processed has little or no impact on how they are
processed in the DU in preparation for delivery. In general, the
following preparation of flats for delivery occurs (there are other
activities such as held mail or registered mail that are performed
that are not noted here to simplify the explanation):
[0006] 1. In preparation for casing operations, mail personnel sort
through flats, bundles and mailings from all sources and separate
them by carrier early in the morning (begining around 4:00 AM).
This is done in staging areas using tubs, hampers or large
cases.
[0007] 2. Flats are delivered to the carrier casing area and set in
a staging area.
[0008] 3. Carriers case the flats, along with other mail types
(this activity is performed in the morning usually from 6:00 AM or
7:00 AM to sometime between 9:00 AM and 11:00 AM, depending on
route size and the amount of mail). The current postal standard for
casing unsequenced flats is 8 per minute. On some routes or in some
DU's, carriers do not case saturation mailings and treat them as an
additional bundle during delivery. Other carriers may split
saturation mailings and deliver portions of them on consecutive
days to load level the amount of mail to be delivered.
[0009] 4. Cased mail is removed and placed in trays to be
delivered.
[0010] 5. The carrier leaves the facility and delivers the
mail.
[0011] 6. In some DU's, carriers case mail upon return to the
facility in the afternoon in preparation for the next day.
[0012] For some portion of the morning, activities 1 and 2 above,
can overlap with the casing operation and may extend until after
the carrier has left the facility leaving mail to be cased either
later that day or the next morning. All cased mail is removed in
carrier walk sequence, and carriers carefully case flats so that
all address labels are on the same edge of the mail (even if this
means that the label is upside down relative to other addresses in
the bundle) to ensure easy reading while doing deliveries.
Depending on the route type and/or the carrier's preference,
marriage mailings may case either the address card or both the
address card and the mailing cased (some prefer to case only the
card and pull the mailing at each house that has a card in the
delivery).
[0013] These activities can take up to 50% of a carrier's in-office
time, and therefore, limit the amount of deliveries can perform in
the remainder of the day. This is one of the limiting factors in
the number of stops that a carrier route can contain (obviously the
amount of mail, the distance between the stops, the demographics of
the route area, and other factors are involved as well). It stands
to reason, that by making the in-office activities more efficient,
i.e. providing delivery point sequence (DPS) flats, then carriers
can be expected to spend less time in the facility and more time on
the route. This added time can allow for additional stops on routes
and the possible consolidation of some routes into others. This
scenario is analogous to the introduction of DPS letter mail
through the use of automation to a great degree. However, the types
of mail (flats) and the different ways that the mail arrives at a
facility does make the task of creating a single bundle of DPS
flats a challenging proposition. The automation of sorting and
collating of flats by their physical nature is a very difficult
task due to the large variation in sizes and types of the flats
material.
SUMMARY OF THE INVENTION
[0014] Accordingly, it is a primary object of the present invention
to develop a system and process for collating flats mail using a
small, flexible, inexpensive machine that is easy to operate,
reliable, and requires easy and infrequent maintenance.
[0015] It is the further object of the present invention to develop
a process and system which utilizes standard sort schemes for
carrier walk sequences utilized for sorting conventional mail other
than flats.
[0016] It is another object of the present invention to provide an
apparatus for sorting flats having a small footprint in order to
take up a minimum amount of space in the sorting facility.
[0017] It is yet another object of the present invention to provide
an apparatus for sorting flats, which is modular in construction
for flexible sizing through the use of additional modular
components, including staging towers.
[0018] It is still another object of the present invention to
provide an apparatus for sorting flats wherein only a single
operator is required.
[0019] It is another object of the present invention to provide an
apparatus for sorting flats having low maintenance and operating
costs.
[0020] The objects of the present invention are fulfilled by
providing a method and apparatus for collating a plurality of
groups of mail items, such as flats, each group being pre-sequenced
according to prioritized delivery addresses (delivery order
sequence DOS), into a final sequenced set of the mail items from
the groups, utilizing the prioritized delivery addresses (DOS),
comprising the steps of:
[0021] separating each bundle of mail seriatim into a single input
stream of the individual mail items;
[0022] transporting the mail items from the input stream to a
staging station;
[0023] sorting the mail items at the staging station into a
plurality of subsets of mail items re-sequenced as an intermediate
step to achieving said final sequence sets;
[0024] merging the mail items into a single output stream from the
respective subsets of mail items in said final sequenced set;
and
[0025] collecting portions of the output stream of the mail items
consistent with the sequence of the final sequenced set to form
batches of mail for orderly delivery to the prioritized delivery
addresses (DOS) according to delivery criteria reflected in said
final sequenced set.
[0026] The sorted items in the output stream are collected in tubs
in uniform stacks. This is achieved by a method of stacking flats
mail from a group consisting of magazines or newspapers of various
widths having bound edges and opposed unbound edges comprising the
steps of: edge-justifying the unbound edges by aligning the unbound
edges against a planar surface; and placing the edge-justified
flats mail into a vertical stack with the unbound edges aligned on
one side of the stack. The flats mail is transported along a
conveyor with a major face thereof supported on the conveyor and
all unbound edges facing a same side of the conveyor, and the flats
mail is tilted toward said planar surface to thereby direct the
unbound edges of the flats mail against the planar surface. The
tilting may be performed by skewing a top surface of a portion of
the conveyor toward said planar surface, said planar surface being
disposed transversely of a longitudinal axis of the conveyor.
[0027] Further scope of applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The present invention will become more fully understood from
the detailed description given hereinbelow and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention, and wherein:
[0029] FIG. 1 is a perspective view of a modular flats bundle
collator (FBC) system according to the preferred embodiment of the
present invention;
[0030] FIGS. 2A and 2B are perspective views illustrative of the
flats diverter module of the system of FIG. 1;
[0031] FIG. 2C is an exploded view of the embodiment of a combined
orienter and reader module for use in the system of FIG. 1;
[0032] FIG. 2D is a perspective view of the orienter/reader module
of FIG. 2 depicting the module assembled;
[0033] FIG. 3 is a perspective view of one of the staging tower
modules of FIG. 1 illustrating details of the elevator mechanism
thereof;
[0034] FIG. 4 is a perspective view of a portion of the transport
conveyor of the flats bundle collator system illustrating how the
flats are edge-justified as they traverse the surface of the
conveyor within the staging towers;
[0035] FIG. 5 is an alternative embodiment of conveyor roller
structures of a transport conveyor suitable for use in the system
of the present invention;
[0036] FIG. 6 is a top perspective view of the interleaved shelf
and conveyor structures of the present invention in the region of
the staging towers;
[0037] FIG. 7 is a perspective view illustrating a detail of the
shelves within the staging towers and their operative association
with the timing belts of the elevator mechanisms of the towers;
[0038] FIG. 8 is a side elevational view illustrating the shelf
transfer from one belt to another of the elevator mechanism;
[0039] FIG. 9 is a side elevational view showing the transfer of
shelves between the belts of the elevator mechanism in slightly
more detail than illustrated in FIG. 8;
[0040] FIGS. 10A and 10B are perspective views illustrating two
options of the present invention for storing mail in standard
United States Postal Service mail tubs;
[0041] FIG. 11 is a perspective view of a dual containerizer module
of the present invention and a reject tub;
[0042] FIG. 12 is a diagrammatic end view of a preferred method of
edge justifying flats mail in order to achieve a uniform stack
profile;
[0043] FIG. 13 is a block diagram of the hardware architecture for
controlling the flats bundle collator system of the present
invention;
[0044] FIG. 14 is a block diagram of the software architecture for
controlling the hardware of FIG. 13;
[0045] FIGS. 15A and 15B are illustrative of an operational block
diagram of the method performed by the flats bundle collator system
of the present invention;
[0046] FIG. 16 is a flowchart of the collation logic software of
the flats bundle collator system of the present invention; and
[0047] FIGS. 17, 18A, 18B and 19A to 19L are diagrammatic
illustrations of the flow of the pre-sequenced bundles of flats
through the flats bundle collator system of the present
invention;
[0048] FIGS. 20 through 23 are illustrative of flats position and
jam detection control parameters of the flats bundle collator
system of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0049] Referring now to the drawing figures, FIG. 1 depicts the
overall flats bundle collator system of the present invention. The
system includes the following components: a feeder assembly 10; a
combined orienter/reader assembly including a transport conveyor
TC, a flats orienter module 12, a barcode reader module 14; a
staging tower assembly 16 including multiple staging towers 16-1, .
. . , 16-n; and a containerizer module 18 including two
containerizer assemblies 18-1 and 18-2. Bundles of mail in the
United States Postal System mail tubs T are loaded onto the feeder
assembly 10 by an operator O. The mail is first oriented to have
the mailing label up by the orienter module 12. The address is then
read by the barcode reader module 14. All of the mailings F, except
for the last, are staged in the staging tower assembly 16. Mail is
removed from the multiple staging towers as the last mailing is fed
from the feeder 10 in such a way as to make the mail stream in a
desired final sequence. The mail is conveyed out of the staging
tower assembly 16 to the containerizer module 18, where it is
stacked in selected ones of United States Postal Service (USPS)
tubs, not shown. Multiple pre-sequenced mailings can be fed into
the machine. Each mailing can consist of several bundles of mail,
each bundle containing several pieces. Each mailing is in delivery
point sequence (DPS) or walk sequence (WS).
[0050] The operator 0 places all but the last mailing in the feeder
10 with the lower number stop in the first position. The feeder 10
then removes one piece of flats mail F at a time from the stack and
injects it into the flats orienter module 12. The feeder 10 will
feed all of the mail in this manner until it reaches the last
mailing. The last mailing is loaded with the lowest number stop in
the last position.
[0051] If there is not a saturation mailing (a mass mailing) to be
included in the sorting process, the operator notifies the system
that loading is complete by pressing a button on the system control
panel to be described hereinafter. However, if there is a
saturation mailing, the operator notifies the system and begins
loading the saturation mailing into the feeder 10. The system
compares the contents of the staging tower assembly 16 to the
carrier's walk sequence and calculates the output sequence to
collate the system contents into the sequence. If there is not a
saturation mailing, the system calculates the output sequence
directly from the tower contents. If a saturation mailing is
included, the system calculates the output sequence from the towers
16-1, . . . , 16-n and includes the feeder 10 saturation output in
the collation calculation.
[0052] The tower assembly 16 outputs the flats F, and the feeder 10
inputs saturation flats if they are present, such that they are
transported into the mail tubs in the containerizer module 18. The
operator 0 then removes the tubs and prepares to input the next
carrier route bundles into the system. A more complete description
of operation follows in the description of FIG. 15.
[0053] The flats bundle collator according to the preferred
embodiment of the subject invention occupies about 75 square feet
of floor space with a ten tower configuration. The system weighs
about 8000 pounds, and exerts floor loading not to exceed 42 psi.
The collator requires 3-phase electric power for operation.
[0054] The feeder module 10, for use with the system of the present
invention, is a commercially available component manufactured by
Alcatel, known in the industry as the "Alcatel TOP Feeder". This
feeder is highly reliable and easy to maintain. The feeder has a
throughput of 3 flats per second; a jam rate of {fraction (1/2500)}
flats; a jam recovery in 5 seconds; accepts all USPS flats mail
sizes; feeds on demand with a 20 ms response time; and is well
accepted in the user community.
[0055] As noted above, the flats orienter module 12 receives the
output of the feeder module 10. Its operation is illustrated in
FIGS. 2A and 2B.
[0056] Referring now to FIGS. 2A and 2B, as flats F exit the feeder
module 10, the orienter module 12 places them label up on the
transport conveyor TC using one of two tiltable conveyor sections
12A and 12-B. Flats F to be staged are processed on one path as
illustrated in FIG. 2A and saturation mailings are processed on the
other path illustrated in FIG. 2B. The flats orienter module 12
indexes conveyor section 12A via a traversing carriage which moves
in the direction of the double arrow in FIGS. 2A and 2B to move the
section 12A between the respective left-hand and right-hand
positions illustrated in these figures. The carriage remains in a
"home" position for all mail to be staged in the towers, as
illustrated in FIG. 2A and indexes to the position shown in 2B only
if the operator notifies the system that a saturation mailing is
about to be fed. Where ten towers comprise the towers 16-1, . . . ,
16-n, saturation mailings (mass mailings) must be fed in reverse
order relative to mailings staged in the towers. Mail F enters the
towers from the first stop to last, and because the towers are Last
In First Out (LIFO), the mail F leaves the towers, last stop to
first, during the collation process. To process saturation mailings
directly from the feeder 10 the saturation mailing must be fed last
stop to first. This is accomplished by placing the bundles into the
feeder 10 facing the opposite direction of the staged mail. The
orienter module 12 then reorients the flats for reading by the
reader 14 as they exit the feeder 10. That is, all of the mail
flats F but the last mailing leave the feeder 10 with the bound
side of the flat (assuming there is a bound side) and the address
label facing right. The orienter 12 tips the mail over to the left,
so that mail leaves the orienter with the bound side to the right
and the label side up. The mail in the last mailing leaves the
feeder with the bound edge down, and the label facing the left
side. The orienter 12 tips this mail over to the right, so that the
mail leaves the orienter with the bound side to the left and the
label facing up. The mail leaves the flat orienter section 12 and
then enters the barcode reader module section 14. The barcode
reader module 14 is typically a reader, such as the AccuSort Model
No. AV1200. This type of barcode reader is a high quality
off-the-shelf reader, which has proven to be very reliable in
service to the USPS. In this reader section, a barcode including
the destination point sequence (DPS), carrier walk sequence printed
on the flats F is read by the reader 14 and the address is sent to
the main computer controller to be subsequently described. The
location that is assigned to the flat will be used later to
determine the output order of the flats F with the lowest number on
the top of the output stack. The flats mail then leaves the barcode
reader section 14 and enters the staging tower assembly 16. Each
piece of mail F is inducted into the staging tower 16 that has the
closest, lower number flat. If there is no tower that fits this
requirement, the flat is inducted into the first empty tower. When
all but the last mailing has been staged in one or more towers of
the tower assembly 16, the last mailing is loaded in the feeder 10
as described hereinbefore. The mail F is processed normally until
it reaches the staging tower assembly 16. When the first piece of
mail arrives at the staging towers 16-1, . . . , 16-n, a collation
algorithm stored in the control system operates the unloading of
the staging towers to form the final mail stream.
[0057] The mail is fed from the barcode reader module 14 and/or the
staging tower assembly 16 to achieve a final sequenced set of flats
with the highest number stop first. The mail is sequenced, and the
mail uniformly spaced. When the mail leaves the staging tower
assembly 16, it is fed into the containerizer assemblies 18-1 and
18-2 of containerizer module 18. The containerizers 18-1 and 18-2
stack mail in the sequence in which it was received, and maintains
that sequence. Two containerizers 18-1 and 18-2 are preferably
utilized so that when the operator is emptying one, the machine can
continue to fill the other.
[0058] Referring now to FIGS. 2C and 2D, the flats items are fed
between the feeder 10 and the staging tower assembly 16 through the
orienter module 12 and the reader module 14 via the transport
conveyor TC. The details of the combined orienter/reader assembly
is illustrated in the exploded view of FIG. 2C. The assembly
includes an open frame structure F having four juxtaposed sections
for receiving the orienter/diverter module 12, the barcode reader
module 14, a power distribution module 11 and system input/output
electronics assembly 13. These components are enclosed within a top
panel TP and two side panels SP in the upper two sections of the
frame structure. Side panels SP also include one or more
observation windows OW therein so that the flats items can be
observed as they pass through the modules 12 and 14 from the feeder
10 to the staging tower assembly 16. Observation windows, not
shown, can also be provided in the sections of the staging towers
16-1, . . . , 16-n.
[0059] FIG. 2D depicts the orienter/reader modules 12 and 14 in an
assembled condition. It can be seen that the path of flats items
fed from feeder 10 to the staging tower assembly 16 via the
orienter/reader modules 12 and 14 passes the items along a
horizontal path via the conveyor TC at the output side of the
module into the staging tower assembly 16.
[0060] Any number of staging towers 16-1, . . . , 16-n may be
utilized and any number of containerizers 18-1, . . . , 18-n
without departing from the spirit and scope of the present
invention. In fact, an advantage of the system of the present
invention is its modularity, which facilitates the addition or
deletion of staging towers and containerizers as needed to satisfy
the footprint requirement of the space in which it is to be
utilizd.
[0061] Details of one of the staging towers 16-1 is shown in FIG.
3. Staging tower 16-1 includes a section of a roller conveyor TC, a
shelving assembly S, a shelf drive system including a motor EM, a
chain and sprocket drive assembly 24, and drive shafts 26 coupled
to the elevator mechanism, timing belts 20A, 20B, 20C. Each tower
also includes a housing H formed from the frame and body
panels.
[0062] The conveyor drive systems are designed to be "daisy
chained" together allowing the system to function with a single
drive motor and providing easy expansion by simply adding more
towers 16-m to the drive line through the use of universal joint
couplings. The shelf drive system including motor EM, chain and
sprockets assembly 24, and drive shafts 26 is located in a bottom
section 16M of the tower for easy access. Each tower has an access
door, not shown, that fully exposes the interior of the tower when
open to provide easy access by an operator.
[0063] The tower roller conveyors TC transport flats mail F through
the tower assembly 16. The shelves S include outwardly projecting
fingers 17 which are designed to interleave with and pass through a
plurality of cantilever mounted rollers 28 of the conveyor TC as
illustrated in FIG. 6, allowing the shelves S to lift flats off the
rollers 28 of the conveyor TC. This will place the flats F onto or
off of the rollers as the shelves S are indexed down or up,
respectively. The rollers 28 of the conveyor TC-16 are skewed to
the direction of travel by 2 degrees, as illustrated in FIG. 4 to
facilitate edge justification of the flats F against a C-shaped
channel 30 for reliable mail orientation. An alternative
configuration for the interleaved numbers 17 and 28 is shown in
FIG. 5 where the finger members 17A and roller members 28A include
transversely oriented projections P.
[0064] Tower shelves S are supported by a set of guides 31 as
shown, for example, in FIG. 7 which engage slotted arms 29. Guides
31 maintain orientation and the belts determine the vertical
position of the shelves S. Further as shown in FIG. 3, each staging
tower, such as tower 16-1, has three zones 16A, 16B, 16C through
which the shelves S move. 16A designates the shelfs storage zone,
16B the mail stream or transfer zone, and 16C the mail staging
zone. Shelf position is determined by the operation of the
respective endless timing belts 20A, 20B, 20B in the respective
zones. Each shelf S is driven by a tooth or lug protruding from the
endless timing belts in a manner illustrated in more detail in
connection with FIGS. 7 to 9.
[0065] The timing belts 20A, 20B, 20C collectively constitute an
elevator mechanism for raising and lowering the shelves S and flats
F thereon within each tower of the tower assembly 16. Each timing
belt comprises an endless belt with protruding lugs L thereon
spaced in predetermined pitches which differ between the respective
vertical zones between the tower. These endless belts are wound
around pulleys 22. Pulleys 22 are driven by the drive mechanism in
zone 16. As depicted in FIG. 3A, the drive mechanism includes an
electric motor EM coupled to drive shafts 26 via a chain and
sprocket drive assembly 24. The respective endless belts of the
timing belts are wound around the drive shafts 26 and are
selectively driven in response to rotation of those shafts, which
are under control of the central computer of the system to be
described further hereinafter.
[0066] In the transition zones between the respective timing belts,
the shelves S are moved up and down the support guides 31 and are
transferred from one belt to another. The shelves S are engaged by
the lugs L on the respective timing belts to effect movement and
transfer of the shelves from one belt to another. When a shelf S
comes to the top of a zone, its supporting belt curves around a
pulley 22. As the shelf S rises, its support tooth or lug L begins
to disengage from the shelf S. There is a large window of time when
the support tooth or lug is still supporting the shelf, but the
tooth or lug above the shelf no longer restricts the shelf from
traveling up. In this window, a tooth from the belt in the next
zone rises to lift the shelf S from the first zone to the next
within the tower 16. This transition from one zone to another is
depicted in FIGS. 8 and 9.
[0067] Referring to FIG. 9, timing belt 20A in the shelf storage
zone, is a low-speed timing belt with a narrow pitch to accommodate
a plurality of shelves S in close, juxtaposed, stacked positions.
The timing belt 20B, in the transfer zone in the mail stream region
of the towers 16, is a high-speed timing belt with a coarse or wide
pitch between the lugs L. The pitch of the timing belt 20B is
chosen to be wide enough to accommodate the maximum thickness of a
piece of flat mail moving along the conveyor.
[0068] The upper timing belt 20C is not shown in FIG. 9 for
clarity, but it preferably includes a low-speed timing belt with a
pitch wide enough to accommodate both the shelves S and flats mail
F disposed thereon.
[0069] As the staging towers are unloaded by the lowering of the
shelves in the staging or storage zone 16C by selective operation
of the timing belts under control of the central computer, a stream
of flats mail arranged in delivery point sequence emerges from the
staging towers and approaches the containerizers 18, which maintain
the sequence of the stack.
[0070] The flats may be stacked in mail tubs 40, either as
illustrated in FIG. 10A with the edges facing up, or in FIG. 10B
with the edges extending horizontally and vertically stacked. FIG.
10A depicts the flats mail being stacked on edge in a USPS mail tub
40. This method is desirable because it is a preferred arrangement
for letter carriers, since the mail standing on edge in the tub is
similar to the arrangement of file folders in a filing cabinet and
lets the carrier flip through the mail easily. Optionally, the
containerizer stacking arrangement illustrated in 10B can be used.
This type of output gives a tub of mail that looks similar to the
tubs produced by popular flats sortation machines for other types
of mail.
[0071] As the flats mail F leaves the staging tower section 16 of
the flats bundle collator, it enters the containerizer section 18
as shown in FIG. 11. Flats F are diverted into either of two output
tubs 40-1 or 40-2. This diversion is achieved by movement of the
pop-up conveyor sections 42-1 and 42-2 up or down in response to
activation of fluid motors 44-1 or 44-2. This up or down movement
of the conveyor section 42-1 or 42-2 permits the flats F to slide
down one of the respective angular shoots 46-1 or 46-2, which
communicate with the open sides of the mail tubs 40-1, 40-2. Each
mail tub 40-1 and 40-2 includes an angular guide flap 40A-1 and
40A-2 in order to capture and guide the flats entering the tub for
assembly into a stack. The shoots 46-1 and 46-2 constitute
acceleration ramps, which are shaped to justify the flat to one
side of the ramp. There flats F are accelerated to the end of the
ramp where they enter either the tub 40-1 or tub 40-2, and slip
onto the mail stack being formed therein as they are guided by the
flaps 40A-1 and 40A-2. The relative height of the stack at the end
of the acceleration ramp 46-1, 46-2 is controlled by sensing the
stack height and indexing the tubs 40-1, 40-2 downward as the stack
height grows. This indexing of the tubs 40-1 and 40-2 is affected
by an elevator mechanism including motors M1, M2 and a plurality of
belts 48-1, 50-1 driven by the motors M1, M2. The tubs 40-1, 40-2
are supported on the belts 48-1, 48-2, 50-1 and 50-2 at 52 by
appropriate teeth or lugs protruding from the belt. A third tub
40-3 is provided at the end of conveyor section 42-2 for system
rejects, which is selectively loaded by operation of the pop-up
conveyor sections 42-1 and 42-2 described herein before.
[0072] Edge justification of the flats within the tubs is
preferably performed by justifying the unbound edges of flats,
rather than the bound edges. As the mail stack grows in height in a
tub 40-1, 40-2, the uniformity of the stack is maintained by the
tilt of the tub, and the type of edge justification. It is a
discovery of the present invention that a stack of mail quickly
becomes lop-sided if it is edge justified with the bound edge of
the mail, which tends to be thicker than any other part of the
flats mail. This phenomenon is illustrated in the diagrammatic
illustration of FIG. 12, wherein the left-hand portion of the
figure shows "bound edge justification" and the right-hand portion
of the figure depicts "unbound edge justification". With the
unbound edge justification the mail stack grows uniformly, as
illustrated in FIG. 12, during testing stacks of mail which were
12" tall with bound edge justification and had an average height of
103/4" when justified by the unbound edge. Therefore, a stack of
flats mail justified by the unbound edge is more compact and less
lop-sided than one stacked by bound edge justification.
[0073] The operation of the flats bundle collator of the present
invention is controlled by a combination of hardware and software
described in connection with FIGS. 13 to 19. Referring first to
FIG. 13, which depicts the hardware architecture of the system of
the present invention; a system controller 50 is the heart of the
hardware and in a preferred embodiment is a commercially available
IBM compatible, Pentium class computer, with monitor and keyboard.
The various control devices are coupled to the system computer 50
and include an operator interface 54, and a power controller 52.
The other operative components of the system including the feeder
10, barcode reader 14, staging towers 16, conveyor TC,
containerizer 18, reject tub 56, and diverter module 12 are also
operatively connected to system computer 50.
[0074] The system controller 50 is a computer containing the
application programs and databases. It also contains a controller
card for a commercially available high-speed daisy chain controlled
bus. This bus is used throughout the system to activate and sense
the other control components. For position tracking, the computer
50 also contains a counter card to interface with conveyor encoders
to be described hereinafter.
[0075] The operator interface 54 allows the computer 50 to display
information on its monitor to the operator and to receive inputs.
The computer also includes a standard keyboard. Also included are
emergency stop controls. These controls consist of buttons and
indicators.
[0076] The power controller 52 provides the 3-phase electrical
connection to the building power source. It includes power on/off
indicators, circuit breaker protection, phase load balancing, and
motor power emergency stop capability. The computer senses when an
emergency stop has occurred. The components of the subsystem are
located throughout the flats bundle collator modules, and will be
described hereinafter with reference to FIGS. 20 to 23.
[0077] The feeder 10, described hereinbefore, interfaces with the
computer 50 through a control bus in order to synchronize the
feeder operation with the other components of the system.
[0078] The barcode reader 14 is a commercially available item as
described hereinbefore. The computer 50 interfaces to the barcode
reader 14 through the control bus.
[0079] The computer controls the operation of the mail transport
conveyors TC. There are two independently powered sections. The
first section TC-1 is located between the feeder 10 and the first
staging tower 16. The second section TC-2 runs from the first tower
16 to the end of the system. To track mail position, the computer
reads an encoder from each section. These encoders will be
described further hereinafter with reference to FIGS. 20 to 23.
[0080] The staging towers 16 handle the insertion and extraction of
mail pieces to the staging towers 16-1 to 16-n, wherein n
represents the total number of modular staging towers assembled for
a given configuration. Mail F is inserted or extracted by indexing
the towers 16 up or down. Because this is a modular system, where
additional towers can be added, the controls interface to the
computer 50 is a commercially available control bus described
hereinbefore. The computer 50 controls the indexing of the shelves
S within the towers 16. It reads a sensor position on a conveyor
and keeps track of the locations of mail pieces travelling on that
section. The components of the staging tower 16 have been described
hereinbefore and include a shelf lift motor, position sensors,
limit switches, and override switches.
[0081] The containerizer module 18 is also coupled through the
control bus to the system computer 50. This provides the controls
for the loading of the mail pieces into the output tubs 40-1, 40-2.
The computer 50 diverts the conveyor section to pass the mail into
a tub 40 or allows it to continue along the conveyor through the
use of the pop-up conveyor sections in containerizer 18. The
elevation of the mail tub is controlled locally and the operator
has manual override controls. The computer 50 senses when an output
tub is present and when it is full.
[0082] The reject tub 56, receives nonconforming mail pieces. It is
similar to the mail tubs 40 and is illustrated at the output of the
containerizer module 18 in FIG. 11. The elevation of the reject
mail tub 56 is controlled locally and the operator has manual
override controls. The computer 50 can sense when a reject tub is
present and when it is full. The components include a tub elevation
motor, position sensors and indicators, limit switches and override
switches.
[0083] All of the control hardware of the system, illustrated FIG.
13, is run by appropriate software architecture. The computer 50
runs under the standard Microsoft NT operating system, with a
commercially available real-time kernel. Parts of the application
software are interrupt driven, from the conveyor encoders, and need
to be executed soon after they interrupt the curves. Because NT is
not a true real-time operating system, it does not have a
consistent or fast capability in this area. The purpose of the
real-time kernel is to provide this capability. Application
software is programmed using high-level Microsoft C/C++ language
using standard coding practices.
[0084] The operator 0 interacts with the system using the computer
50, its associated keyboard and monitor, and the feeder control
panel. There are also emergency stop buttons within easy reach.
Operator displace grains conform to standard usage guidelines and
lead the user with appropriate prompts through the task to
perform.
[0085] The application software is grouped into modules illustrated
in FIG. 14. These modules include a main control sequencer
(software of computer 50) 57 initialized by appropriate
initialization procedures 58, a data manipulation module 62,
operational process module 64, and machine control interface
modules 66.
[0086] After power on and computer initialation is effected by
procedures 58, the application program is automatically started.
Initialization includes the tasks such as reading hardware sensors,
and setting actuators, setting software data tables and
configurations. The main control sequencer software 57 is then
started.
[0087] The main control sequencer software 57 has primary control
over all the tasks to be performed. It starts tasks, controls the
sequence of events, and stops tasks. The type of tasks performed
include; user logon/logoff, accessing carrier route data for
display or update, initiating carrier route sortations, generating
reports, accessing machine performance statistics, and initiating
maintenance tasks.
[0088] The machine control interface software modules 66 are the
interface and low level drivers for the system. These are used by
the software to sense and control the operation of the hardware
components of FIG. 13. Examples of these operations include: feed a
single mail piece; start conveyor section one; and check to see if
the mail output tub is full.
[0089] The data manipulation software 62 handles the storage and
retrieval of various types of data. Examples of this data include:
number of stops on a route; the DPS code for each stop on a route,
in order of delivery; the number of pieces misread by the barcode
reader; and total number of mail pieces fed by the feeder. The
operational processing software modules 64 handle the operations
associated with several larger tasks. These are identified in each
of the blocks within block 64 in FIG. 14, and include: flats
insertion sort algorithms; flats extraction sort algorithm;
error/jam handler; maintenance trouble-shooting routines; and
report generation.
[0090] As the main control sequencer software 57 executes, it calls
functions in the various modules. The hardware 50 and software 57
work together to lead the operator through the completion of
desired tasks.
[0091] The overall operation of the flats bundle collator system of
the present invention is illustrated in the block diagram of FIGS.
15A and 15B . A typical carrier route sortation includes the
following sequence of steps. At the start, in step 68, the operator
enters the route ID and sets up an output tub 40-1 or 40-2 to be
filled. This data is stored in database 86 and fed to the computer
50 for processing at step 94 to be described hereinafter. In step
70, the operator loads the bundles of flats into the feeder 10. The
bundles are separated according to mailings. In step 72, the
operator tells the computer 50 to start the sortation. In step 74,
the feeder 10 singulates and feeds the flats F to the diverter
module 12. In step 76, the barcode reader 14 reads the barcode on
the flats F, including the delivery point sequence (DPS), namely,
the walk sequence of the route carrier (WS). In step 78, the system
computer 50 checks the barcode for validity and identifies the
tower for staging. This information is stored in the database 88
for comparison with the database 86 at step 94 by the computer 50.
In step 80, the flats F travel on the conveyor to the target tower
16 and are inducted therein. In step 82, the system computer 15
waits for the last flat to be inducted into the towers 16. In step
84, the operator removes tub 56 of rejected flats, which have been
processed in step 86 to include misreads on the conveyor placed in
the reject tub. The process continues onto Routine A in FIGS. 15A
and 15B.
[0092] In step 90 of routine A, the operator loads saturation (mass
mailing) bundles into the feeder 10. In step 92, the operator
notifies the computer 50 to begin collation. In step 94, as
described hereinbefore, the computer 50 checks the inventory in the
towers against the carrier sequence and determines the proper
output sequence. In step 96, the flats F are moved onto the
conveyor TC in carrier walk sequence (WS). In step 98, the flats F
travel to a selected one of the output tubs 40-1, 40-2 in
containerizer module 18. In step 100, the system notifies the
operator that the collation process for unloading tower 16 is
complete. The operator in step 102 removes the tub of collated
flats and substitutes the next tub to be filled. In step 104, any
rejected flats in the reject tub 56 are manually placed in proper
sequence for the mailings. This completes a typical operational
scenario for the collation of a carrier's route of flats mail.
[0093] There is a simple order in which the mailings are fed
through the FBC of the present invention. If there is a mailing
with pieces thicker than 0.375", the operator feeds those first.
The normal thickness mailings are fed next. If there is a
saturation mailing, it is fed last. This provides better
utilization of the tower capacity. The saturations are fed last,
because they can be collated directly from the feeder 10 and do not
have to be stored in the tower 16. This increases the actual
capacity of the system, as well as increasing the system
throughput.
[0094] The FBC system operation consists of two phases. During the
induction phase, mail pieces are fed into the system and stored in
tower locations 16. During the collation phase, an algorithm
determines the extraction sequence; mail pieces are extracted from
their storage locations in towers 16 and placed in a selected one
of output mail tubs 40-1, 40-2, 56. If a saturation mailing is to
be sorted, it is fed into the system during the collation phase. As
the regular pieces are extracted, the system intermingles the
saturation pieces at the proper times to achieve the desired output
sequence. This allows the system to handle a larger volume of mail
and have higher throughput. A flowchart of the coordination of the
induction and collation phases of the system of the present
invention is illustrated in the flowchart of FIG. 16. At the start,
in step 106, mail induction is performed. At this point, the
operator has selected the carrier's route. The computer 50 has
retrieved this route information from the internal databases and
performed necessary utilzations.
[0095] In step 106, the operator places the mailings into the
feeder. If there is a saturation or other large mailing, the
operator will feed that during the performed mail extractions, step
114, to be described hereinafter. As each piece of mail F is fed,
it is read by the barcode reader 14 and its carrier stop is
determined from the database. Starting at the first upstream tower
16-1, the computer 50 examines the carrier stops of the last piece
in each tower. It determines the tower whose last piece is closest,
but still earlier, to the fed piece and sends the pieces down the
conveyor to be conducted into that tower. All barcode misreads and
pieces that the system is unable to stage are sent to the reject
tub 56, as illustrated in FIG. 15. This operation continues for all
non-saturation pieces.
[0096] As pieces are fed, the computer 50 tracks where each piece
goes and all other relevant information about it. When all of the
non-saturation pieces have been fed, the operator informs the
computer and loads the saturation, or large mailings, as
illustrated in Routine A of FIGS. 15A and 15B. This is done at the
beginning of the collation phase.
[0097] Returning to the description of the flowchart of FIG. 16,
step 108 is a decision block as to whether or not a saturation
mailing is being processed. If "NO", the process proceeds to step
112 to determine the extraction sequence. If "YES", the process
proceeds to perform mail feed at step 110. In step 110, this
function is only performed if there is a saturation or large
mailing. If a piece needs to be fed, the feeder will feed pieces
until the barcode reader 14 has read a valid piece for the
carrier's route. This piece travels down the first conveyor
connected to the output of the feeder 10 and stops just before the
first upstream tower 16. At this time, the feeder 10 will stop
feeding the pieces. This piece remains stored at the end of the
first conveyor TC-1, until the computer determines that it needs to
be extracted, and placed on the second conveyor TC-2, to be sent
directly to a selected one of the output tubs in containerizer
module 18. In step 112, the determination of the extraction
sequence consists of several steps. The end result is an ordered
list describing the extraction and move events. This list begins
with the current events and continues until the last piece is
placed in the tub selected.
[0098] A general indication of the flow of mail is illustrated in
FIG. 17. This figure depicts only three towers for simplicity to
provide a coherent overview of the collation of pieces of mail
through the system. In the left-hand portion of FIG. 17, the three
towers are indicated as Tower 1, Tower 2, and Tower 3. In each
tower, the pieces of mail are inserted as designated mailings M,
bundles B, and pieces, represented by a numeral, 1, 2, 3, etc. As
indicated, Tower 1 includes mailings M3, bundles B1, and pieces 1,
2 and 3 of those mailings and bundles. Tower 2 stores mailings M2,
bundles B1, and pieces 1 and 2. Tower 3, stores mailings M1,
bundles B1, and B2, and pieces 1 and 2 from the respective
bundles.
[0099] In the middle section of FIG. 17, the mailings, bundles, and
pieces of the left-hand section are designated by the delivery
point sequence numbers (carrier walk sequence) obtained from the
ZIP code on the pieces of mailing as read by reader 14. It can be
seen that the pieces are stored in descending order from bottom to
top in the respective towers in the walk or delivery point
sequence.
[0100] FIG. 17 depicts the collation output sequence of the pieces
of mail, which is in reverse of the delivery point or walk sequence
in the center portion of the figure.
[0101] Returning to the flowchart of FIG. 16, in step 112, the
determination of the extraction sequence consists of several steps.
The end result is an ordered list describing the extraction and
move events. The list begins with the current events and continues
until the last piece is placed in the output tub.
[0102] In step 1, the carrier's walk sequence is stored in the
system database. Using this sequence and the known piece
information, the algorithm calculates through all available pieces
and creates an output sequence table illustrated in FIG. 18A. This
table shows the sequence each piece will be in, in the final output
stack and the pieces' current location. The collation rules are
illustrated in the left-hand column of FIG. 18, the sequence number
in the next column, the current time in the next column, the
calculation in the next column, and the resulting feed time in the
final column. The last piece to be delivered by the carrier will be
the first piece into the selected mail tub.
[0103] Exactly what time to extract a mail piece from its storage
location is dependent on several factors. If the current piece
tower 16 is downstream from the previous piece tower, then the
current tower has to postpone extraction until the previous piece
has passed by. If the current piece tower is upstream from the
previous piece tower, then the current tower may possibly extract
before the previous piece is extracted, because current piece will
be on the conveyor for some time before it reaches the previous
piece's tower. The algorithm steps through each piece in the output
sequence table of FIG. 18A and calculates an extraction time for
each piece. The extraction time computed is listed in the output
sequence table of FIG. 18B.
[0104] Referring again to the flowchart of FIG. 16, the program
proceeds to step 114; perform mail extraction. In this step, which
is completely illustrated in the diagrammatic sequence of
extraction steps of FIGS. 19A to 19L, the extraction events in the
extraction time list of FIG. 18B are performed. This places one or
more pieces of flats from the tower 16 on the second conveyor
section TC-2, as illustrated in the steps of FIG. 19. The mail
pieces are numbered in FIG. 19 in correspondence to the numbers
assigned in FIGS. 17, 18A, and 18B described hereinbefore.
[0105] In the final step of the flowchart of FIG. 16, the computer
50 at step 116 checks to see if there is more mail in the system to
be processed. If there is, the computer needs to get ready to
perform another extraction of mail. At this point, the routine is
done and the collation of this particular carrier's mailings is
complete. The operator can then start another carrier's route and
the input associated bundles of mail therefor.
[0106] Referring to FIG. 20, there is illustrated in diagrammatic
form, tracking information for the pieces of flats mail passing
through the system; and FIGS. 21 and 22 illustrate tracking data
obtained from the system of FIG. 20. FIG. 23, in conjunction with
FIGS. 20 to 22 illustrate how a jammed condition of flats mail can
be detected in the system of the present invention.
[0107] As pieces of mail travel along the conveyors TC-1 and TC-2,
the computer 50 needs to track where they are. It needs to know
when a piece is at a tower 16 and can be inserted into that tower,
when a piece is not at a tower and one can be extracted, and when a
piece did not arrive when it was supposed to and may be jammed.
There are two types of hardware in system of the present invention
used for tracking mail, namely, pulse encoders PE and photo sensors
PS. Each conveyor section TC-1, TC-2 has an encoder PE that
generates a pulse as the conveyor system moves. There are a fixed
number of pulses during an inch of conveyor travel. Therefore, by
counting pulses, the computer 50 can determine how far along the
conveyor TC-1, TC-2 a piece should have traveled. Since the
position is derived directly from the conveyor, instead of by
timing the pieces based on a speed calculation, the system
automatically accounts for start and stop accelerations, as well as
running speed variations.
[0108] Several photo sensors PS are placed along the conveyor to
detect when a piece F actually passes by. They are spaced such that
only one mail piece F would be between them. The distance from the
feeder 10, for each sensor, can be determined and expressed as a
number of encoder pulses from pulse encoder PE. This hardware
provides information on where the piece should be and where it
actually is or is not to the computer 50. This tracking information
is illustrated in the tables of FIGS. 21 and 22.
[0109] When a piece of mail is fed, the software adds information
about the piece to a temporary tracking table. As the piece travels
along the conveyor, the table in FIG. 21 is updated. This is used
to track the piece and detect abnormal conditions. The table in
FIG. 22 includes information such as the last known position of the
piece, the next expected sensor position, the gap between adjacent
pieces, and the destination tower for that piece.
[0110] Because the mail pieces are not physically constrained on
the conveyors TC-1, TC-2, they may slip and move slightly slower
than the conveyor itself. At a given sensor PS, this effect appears
as a larger actual pulse.
[0111] The system is very tolerant of slippage because it initiates
tower motion based on the actual location of the piece. If the
difference in pulse counts from the encoders is too large or the
gap too small, then something significant must have happened to the
piece, which is interpreted as a jam condition. The test threshold
conditions for determining a jam are illustrated in FIG. 23. When a
jam condition is detected, the computer 50 stops the system and
describes the problem to the operator. In addition, there are a
series of indicator lights along the length of the machine. These
will light at the location of the jam. When the operator has
cleared the jam condition, he/she notifies the computer to continue
with the sortation.
[0112] The present invention has been described for sorting flats
mail, which are the preferred items to be collated. However, other
items of manufacture requiring orderly sequencing could be sorted
in accordance with the present invention, such as circuit boards,
and other electrical components.
* * * * *