U.S. patent application number 13/192679 was filed with the patent office on 2012-02-02 for networked motorized drive roller conveyor.
Invention is credited to Darin L. Danelski, Melvin W. Henry.
Application Number | 20120024669 13/192679 |
Document ID | / |
Family ID | 45525589 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120024669 |
Kind Code |
A1 |
Danelski; Darin L. ; et
al. |
February 2, 2012 |
Networked Motorized Drive Roller Conveyor
Abstract
A motorized drive roller conveyor includes an upstream zone and
a downstream zone, with each zone having a drive roller, an idler
roller that is driven by the drive roller, and a sensor. The
upstream zone and the downstream zone are controlled by a card,
which measures a gap between a first item on the conveyor and a
second item on the conveyor by beginning a counter when a trailing
edge of the first item passes the sensor of the upstream zone and
stopping the counter when a leading edge of the second item passes
the sensor of the upstream zone to generate a counter value. If the
first item is stopped in the downstream zone, the card of the
upstream zone causes the drive roller of the upstream zone to
advance the second item into the downstream zone for a distance
derived from the counter value before stopping the transportation
of the second item.
Inventors: |
Danelski; Darin L.;
(Oconomowoc, WI) ; Henry; Melvin W.; (Wales,
WI) |
Family ID: |
45525589 |
Appl. No.: |
13/192679 |
Filed: |
July 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61368902 |
Jul 29, 2010 |
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|
Current U.S.
Class: |
198/617 ;
198/780; 198/781.05 |
Current CPC
Class: |
B65G 43/08 20130101;
B65G 47/261 20130101; B65G 43/10 20130101; B65G 13/02 20130101;
B65G 2811/0673 20130101 |
Class at
Publication: |
198/617 ;
198/780; 198/781.05 |
International
Class: |
B65G 43/08 20060101
B65G043/08; B65G 13/02 20060101 B65G013/02 |
Claims
1. A networked motorized drive roller conveyor comprising: a
plurality of motorized drive roller assemblies, each assembly
comprising a zone; a plurality of networked cards, each card
controlling a pair of adjacent zones; a plurality of sensors for
detecting items on the conveyor, each sensor corresponding to a
zone; wherein for a pair of adjacent zones, the corresponding
networked card measures a gap between consecutive items on the
conveyor by beginning a counter when a trailing edge of a first
item passes the sensor of an upstream zone within the pair of
zones, and stopping the counter when a leading edge of the second
item passes the sensor of the upstream zone within the pair of
zones to generate a counter value.
2. The networked motorized drive roller conveyor of claim 1,
wherein for a pair of zones, if the first item is stopped in the
downstream zone, the networked card causes the motorized drive
roller assembly of the upstream zone to move the item into the
downstream zone a distance derived from the counter value before
stopping movement of the second item.
3. The networked motorized drive roller conveyor of claim 2,
wherein the gap is measured by counting the rotations of a drive
roller.
4. The networked motorized drive roller conveyor of claim 3,
wherein the rotations of the drive roller are counted by counting
pulses received from a Hall effect sensor within the drive
roller.
5. The networked motorized drive roller conveyor of claim 4,
wherein the networked cards are connected to a supervisory control
computer.
6. The networked motorized drive roller conveyor of claim 5,
wherein each of the networked cards includes a user interface.
7. A motorized drive roller conveyor comprising : an upstream zone
and a downstream zone, each zone including a drive roller, an idler
roller that is driven by the drive roller, and a sensor; and a card
that controls the upstream zone and the downstream zone; wherein
the card measures a gap between a first item on the conveyor and a
second item on the conveyor by beginning a counter when a trailing
edge of the first item passes the sensor of the upstream zone and
stopping the counter when a leading edge of the second item passes
the sensor of the upstream zone to generate a counter value; and
wherein if the first item is stopped in the downstream zone, the
card of the upstream zone causes the drive roller of the upstream
zone to advance the second item into the downstream zone for a
distance derived from the counter value before stopping movement of
the second item.
8. The motorized drive roller conveyor of claim 7, wherein the
distance is about the length of a gap between the first item and
the second item.
9. The motorized drive roller conveyor of claim 7, wherein the
distance is less than the length of a gap between the first item
and the second item.
10. The motorized drive roller conveyor of claim 7, wherein the
respective lengths of the first and second items are greater than
the length of the upstream zone.
11. The motorized drive roller conveyor of claim 7, wherein the
upstream zone and downstream zone comprise a first pair of a
plurality of pairs of zones, the conveyor further comprising a
plurality of cards that are in networked communication with one
another, each of the cards controlling a pair of zones.
12. The motorized driver roller conveyor of claim 11, wherein the
cards are connected to a supervisory control computer.
13. The motorized drive roller conveyor of claim 12, wherein the
sensors are photo-eye sensors.
14. A method for controlling a gap between items on a motorized
drive roller conveyor comprising the steps of: detecting a trailing
edge of a first item at a predetermined location in a first zone on
a conveyor system; beginning a counter once the trailing edge of
the first item passes the predetermined location; stopping the
counter upon the first occurrence of the following: (i) a leading
edge of a second item is detected at the predetermined location; or
(ii) the first item is stopped in a downstream zone adjacent the
first zone; and generating a counter value.
15. The method of claim 14, further comprising the steps of: moving
the second item into the downstream zone over a distance derived
from the counter value; and stopping the second item after the
distance has been traveled by the second item.
16. The method of claim 14, wherein the distance traveled by the
second item is about the same as a gap between the first and second
items.
17. The method of claim 15, wherein the distance traveled by the
second item is calculated by subtracting a predetermined value from
the counter value.
18. The method of claim 15, wherein the method is implemented using
a networked card.
19. The method of claim 18, further comprising the steps of:
receiving user input via the networked card; and computing the user
input with the counter value to derive the distance traveled by the
second item.
20. The method of claim 19, wherein the leading and trailing edges
of the items are detected using a photo-eye sensor.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates generally to a networked
motorized drive roller conveyor.
[0002] Conventional conveyor control systems utilize a central
Programmable Logic Controller ("PLC") mounted in a central control
panel. This type of system requires control devices, e.g.,
photo-eyes, solenoid valves, and motor starters, to be terminated
at the main control panel. A typical control system utilizing a PLC
requires several hundred to several thousand feet of control
wiring, which requires significant time, labor and money to route
and terminate the wiring. In addition, the PLC requires specialized
knowledge, e.g., knowledge of ladder logic, and familiarity with
the many different interface requirements unique to each
manufacturer's product. Moreover, since there is a central
controller, response time with respect to the control devices may
be increased because the single processor must account for all
operations occurring within the system.
[0003] A Motorized Drive Roller ("MDR") is a conveyor roller with
an integrated motor. An MDR is typically configured to drive a
plurality of idler rollers, usually by way of urethane belts or
chains. The MDR and idler rollers thus define a zone. There is
typically one MDR per zone.
[0004] For conveyor systems that utilize MDR technology, networked
motor controllers are frequently used to handle basic transport,
diversion, and accumulation tasks to move items through a conveyor
system. These motor controllers are mounted in close proximity to
the MDR rollers and directly interface with the product sensors
associated with each MDR. An MDR conveyor system has many
advantages over other conveyor technologies, such as lower power
consumption, noise reduction, and a decreased need for
maintenance.
[0005] Unlike conventional control systems, modular distributed
controls don't require hundreds to thousands of feet of wiring from
a centralized PLC to each device in the system. With controls
located near the control devices, wiring and wiring labor may be
reduced. This shortens the time to complete implementation and
provides a parallel control capability that minimizes response time
issues common to conventional PLC based systems. Because the system
is not limited by the speed of a central processor in a PLC, the
system can grow without worry of overtaxing a centralized
controller. Testing and start-up time is also reduced, as various
segments of the system can be installed and tested independent of
other segments.
[0006] It is common practice in existing conveyor systems that use
MDR roller conveyor along with associated motor controllers to
utilize smaller, localized PLC's distributed throughout the system
to handle conveyor operations such as diverting, bar code scanning,
RFID communication, label applications, etc. These peripherals
typically communicate serially (RS232 or RS485) or via a network
protocol such as Ethernet. Having multiple PLCs in this environment
creates other undesirable issues as single point diagnostics are
difficult to implement.
[0007] The networked, distributed control system of the present
invention provides localized controls for various operations, e.g.,
diverting, bar code scanning, RFID transactions, labeling, etc. The
inventive control system can also handle the basic MDR conveyor
drive and accumulation responsibilities, which greatly reduces the
wiring needed for the system, implementation time, and cost while
maintaining a centralized diagnostic capability. Additional
capability to allow localized programming as well as status and
diagnostics capability are additional benefits of the inventive
control system. Eliminating the need for PLCs and associated ladder
logic is a further benefit of the inventive design because it
reduces the complexity of installation, operation and modification
of the control system and corresponding conveyor system.
[0008] As noted above, MDR conveyor systems have many advantages
over other conveyor technologies, such as lower power consumption,
noise reduction, and less maintenance. However, prior to the
present invention, MDR systems lacked the ability to control the
size of gaps between items on the conveyor system. Prior art
systems are also limited to transporting "Items" that are shorter
in length than a single "Zone".
[0009] Existing technology is typically marketed as "Zero pressure
Accumulation" conveyor technology, as items on the conveyor are
allowed to accumulate with one item per zone. As such, with control
technology currently marketed, items accumulate with varying gaps
between items, based on the length of the items.
[0010] In accordance with one aspect of the inventive conveyor
control system, a gap control arrangement is used to control gaps
between items on the conveyor system. The elimination of gaps
between items on the conveyor system is desirable, in that gaps
reduce the number of items that can be accumulated on the conveyor,
providing lower accumulation efficiency. Thus, reducing or even
eliminating gaps between items helps to maximize the accumulation
efficiency of the conveyor system. The gap control system
incorporates the use of MDR technology and its desirable attributes
while at the same time providing the operator with the ability to
control the size of the gaps between items on the conveyor
system.
[0011] In one embodiment of the invention, a networked motorized
drive roller conveyor includes a plurality of motorized drive
roller assemblies, where each assembly comprises a zone. The
conveyor has a plurality of networked cards, with each card
controlling a pair of adjacent zones. The conveyor further has a
plurality of sensors for detecting items on the conveyor, with each
sensor corresponding to a zone. For a pair of adjacent zones, the
corresponding networked card measures a gap between consecutive
items on the conveyor by beginning a counter when a trailing edge
of a first item passes the sensor of an upstream zone within the
pair of zones, and stopping the counter when a leading edge of the
second item passes the sensor of the upstream zone within the pair
of zones, to generate a counter value. If the first item is stopped
in the downstream zone, the networked card causes the motorized
drive roller assembly of the upstream zone to move the item into
the downstream zone a distance derived from the counter value
before stopping the movement of the second item.
[0012] In another embodiment of the invention, a motorized drive
roller conveyor includes an upstream zone and a downstream zone.
Each zone has a drive roller, an idler roller that is driven by the
drive roller, and a sensor. A card controls the upstream zone and
the downstream zone. The card measures a gap between a first item
on the conveyor and a second item on the conveyor by beginning a
counter when a trailing edge of the first item passes the sensor of
the upstream zone and stopping the counter when a leading edge of
the second item passes the sensor of the upstream zone to generate
a counter value. If the first item is stopped in the downstream
zone, the card of the upstream zone causes the drive roller of the
upstream zone to advance the second item into the downstream zone
for a distance derived from the counter value before stopping the
movement of the second item.
[0013] In yet another embodiment of the invention, a method for
controlling a gap between items on a motorized drive roller
conveyor includes the steps of: (a) detecting a trailing edge of a
first item at a predetermined location in a first zone on a
conveyor system; (b) beginning a counter once the trailing edge of
the first item passes the predetermined location; (c) stopping the
counter upon the first occurrence of the following:(i) a leading
edge of a second item is detected at the predetermined location, or
(ii) the first item is stopped in a downstream zone adjacent the
first zone; and (d) generating a counter value.
[0014] These and other aspects and advantages of the present
invention will be made apparent from the following description
taken together with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] An exemplary embodiment of the invention is illustrated in
the accompanying drawings in which like reference numerals
represent like parts throughout.
[0016] In the drawings:
[0017] FIG. 1 is an isometric view of a networked MDR conveyor in
accordance with the present invention;
[0018] FIG. 2 is schematic of a card used in connection with the
networked MDR conveyor of the present invention;
[0019] FIG. 3 is a representation of a physical embodiment of a
card used in connection with the networked MDR conveyor of the
present invention;
[0020] FIG. 4 is another isometric view of the networked MDR
conveyor of FIG. 1;
[0021] FIG. 5 is a schematic side elevation view of a networked MDR
conveyor of the present invention;
[0022] FIG. 6 is an enlarged partial isometric view of the
networked MDR conveyor of FIG. 1;
[0023] FIG. 7 is a side view of the networked MDR conveyor of FIG.
1 illustrating gaps between items on the conveyor;
[0024] FIG. 8 is a top view of the networked MDR conveyor of FIG.
1;
[0025] FIG. 9 is a side isometric view of a second embodiment of a
networked MDR conveyor in accordance with the present
invention;
[0026] FIG. 10 is an enlarged partial side isometric view of the
networked MDR conveyor of FIG. 9;
[0027] FIGS. 11A-11G are schematic views of various conveyor
configurations that may be integrated into a networked MDR conveyor
in accordance with the present invention; and
[0028] FIG. 12 is a flow chart illustrating a method of determining
the size of a gap between items in the networked MDR conveyor in
accordance with the present invention.
DETAILED DESCRIPTION
[0029] FIG. 1 shows a portion of the conveyor system 10 of the
present invention that incorporates control cards 20 in accordance
with the present invention. Generally speaking, a number of items
11 are supported on the conveyor 10, which includes a plurality of
rollers 13, including MDRs and corresponding idler rollers. The
conveyor system 10 further includes a plurality of sensors 14 that
detect items 11 as the items 11 move along the conveyor system 10.
The conveyor system 10 is divided into zones 15. Each zone 15 is
defined between adjacent sensors 14. Additionally, each zone 15
corresponds with an MDR/idler roller assembly. In the inventive
system, each zone 15 is shorter than the length of the respective
items 11 being conveyed by the conveyor system 10.
[0030] FIGS. 2 and 3 illustrate a networked, distributed MDR
control card 20 with local control capabilities. Accordingly, the
inventive card 20 eliminates the need for a central PLC and reduces
and/or eliminates the need for wiring associated with a system
using a PLC. As a result, implementation and installation costs of
a conveyor control system 10 incorporating the MDR control cards 20
of the present invention may also be reduced while, at the same
time, providing a more efficient installation and implementation
process. Still further, the card 20 of the present information is
programmable, and therefore is able to be reprogrammed depending on
its desired utilization.
[0031] In the illustrated embodiment, the card 20 contains drivers
22, e.g., on a microprocessor, for one or more MDR rollers, which
preferably feature a dual brushless motor. More specifically, for
zero-pressure accumulation mode of operation, e.g., one in which
the items on the conveyor are not intended to contact one another,
each card 20 will service two zones 15. In other words, the card 20
will contain drivers for respective MDR rollers in adjacent zones
15. The drivers are adapted to support any variation of MDR roller,
e.g. commonly available MDR rollers, e.g., those ranging from 22
watts to 50 watts, may be used.
[0032] The card 20 of the present invention includes a plurality of
Inputs and Outputs ("I/O") 23 for interfacing with various
components that are typically utilized in conveyor assemblies,
e.g., limit switches, solenoid valves, motor contactors,
alarms/buzzers, and status beacons.
[0033] The card 20 further includes a plurality of photo sensor
input jacks 24 that connect with sensors 14, which, as discussed
above, detect items 11 that move along the conveyor system 10. For
example, four such jacks 24 are shown on the block diagram in FIG.
2; see also, FIG. 3. The card 20 also includes one or more network
jacks 25 to provide network communications capabilities for
connection to a supervisory control computer (e.g., a personal
computer or industrial computing device). The illustrated
embodiment incorporates a CAN network using Can-Open or Device-Net
protocols, although Ethernet or serial communications could also be
utilized. In this arrangement, any card 20 in the conveyor system
10 can communicate over the network to any other card 20 attached
to the network or to a supervisory control element, such as a PC or
industrial controller. Accordingly, system-wide changes, e.g.,
relating to product volume, conveyor speed, etc., can be
implemented using any card 20 on the network.
[0034] The card 20 further includes a serial I/O port 26 to
facilitate communications with external peripheral devices such as
bar code scanners, RFID reader/writer devices, label applicators,
in motion weigh scales, or other serial devices.
[0035] The card 20 may also feature an operator interface display
27. For example, the display may include button switches for
interfacing with the module, a high intensity beacon for fault and
error notification, and a display element that provides textual
and/or graphical information to the operator. An operator interface
display allows parameters such as roller speed, acceleration and
deceleration rates, delays, etc. to be set locally from any card
20, rather than from a central point such as a PLC.
[0036] In this description, the term "card" is used to describe
item 20, which controls operation of adjacent zones in conveyor
system 10. It is understood that the term "card" is used for
convenience, and that item 20 may be any satisfactory control
device that includes the features and functionality to connect to
the sensors and drive rollers of the adjacent zones of conveyor
system 10 and to control their operation. The term "card" is not
intended to denote any particular structural or physical
characteristics of the control device.
[0037] The inventive conveyor system 10 improves upon existing
designs by entirely eliminating the need for a PLC controller for
normal conveyor operations. The conveyor system 10 allows
additional functions to be implemented seamlessly without the need
for PLCs or any knowledge of ladder logic on the part of the
operator or system installer.
[0038] FIG. 11 shows typical configurations that are included in
conveyor systems. While typically controlled by a PLC, in the
inventive conveyor system 10 these operations are controlled
locally by any one or group of cards 20 in the conveyor system 10.
Such typical configurations include but are not limited to the
following examples. For example, FIG. 11A shows a zone accumulator
and FIG. 11B shows a back-to-back accumulator.
[0039] One configuration is an interface with an in-motion weigh
scale as shown in FIG. 11C, which allows items 11 to be singulated
and transported singly over an in-motion weigh scale. An
identification device, such as a bar code scanner or RFID device,
is connected directly to a card 20 and provides the method of
identification of the item 11. The weight of the item 11 is
compared locally, i.e., at a card 20, with an expected result and a
decision is made locally, i.e., at a card 20, to allow the item 11
to continue along the conveyor system 10 or to be diverted off to a
second conveyor in the event the weight of the item 11 is not
within a defined tolerance. The I/O 23 on the card 20 will be
utilized to communicate with the in-motion weigh scale.
[0040] Another type of configuration is an interface with a label
applicator or "print and apply" label applicator as shown in FIG.
11D. This configuration allows items 11 to be singulated and
transported singly past a labeler, such as an in-motion labeler,
static label only, or "print and apply" labeler. An identification
device, e.g., a bar code scanner or RFID device, is connected
directly to the card 20 and provides the method of identification
of the item 11. The information required on the label is determined
locally on the card 20. The label is printed (if necessary) and
applied and then the item 11 is passed on to the next conveyor zone
15. The I/O 23 on the card 20 will be utilized to communicate with
the printer/applicator.
[0041] Another type of configuration is a 90 degree transfer as
shown in FIG. 11E. This pre-programmed operation will facilitate an
item 11 transfer from one conveyor zone 15 to another completing a
90 degree right angle transfer. A corresponding card 20 processes
the timing required to ensure that the item 11 is completely
transferred prior to initiating the next transfer of an item. The
card 20 further processes any additional input/output required to
signal the transfer device.
[0042] Yet another configuration is a "+" transfer as shown in FIG.
11F. This pre-programmed operation will facilitate an item transfer
from one conveyor zone to one of three possible divert points. An
identification device, e.g., a bar code scanner or RFID, is
connected directly to a corresponding card 20 and provides the
method of identification of the item 11. The desired divert
location is determined locally on the card 20 and the item 11 is
either allowed to continue on or is diverted to one of two other
conveyors completing a 90 degree right angle transfer. The card 20
processes the timing required to ensure that the item 11 is
completely transferred prior to initiating the next decision
relating to a subsequent item transfer. The card 20 further
processes any additional input/output required to signal the
transfer device.
[0043] Another configuration is a "T" transfer as shown in FIG.
11G. This pre-programmed operation facilitates an item transfer
from one conveyor zone to one of two possible divert points. An
identification device, e.g., a bar code scanner or RFID, is
connected directly to a corresponding card 20 and provides the
method of identification of the item 11. The desired divert
location is determined locally on the card 20 and the item 11 is
either allowed to continue on or is diverted to another conveyor
completing a 90 degree right angle transfer. The card 20 processes
the timing required to ensure that the item 11 is completely
transferred prior to initiating the next decision relating to a
subsequent item transfer. The card 20 further processes any
additional input/output required to signal the transfer device.
[0044] The illustrated embodiment includes either a display on the
card 20 or a touch screen type interface on a personal computer or
industrial computing device. The touch screen allows a setup
operator to easily drag and drop the aforementioned pre-programmed
operations to each card 20, with no knowledge of programming ladder
logic or other programming required. The interface also allows
parameters such as speed, timing, direction, etc. to be easily
communicated to the individual cards 20 via the network.
[0045] The illustrated embodiment of the conveyor system 10 also
has the ability to retain a backup of each card 20 in the system,
should a replacement be required because of a card failure. The
parameters and standard code blocks can simply be downloaded to the
card 20, greatly minimizing downtime in the event of a card
failure.
[0046] As discussed above, it is not desirable to have gaps 30
between items 11 on a conveyor system 10. The gap control system of
the present invention uses MDR rollers in conjunction with cards 20
and sensors 14 to control the gaps 30 between items 11. As shown in
FIG. 5, for example, in the illustrated embodiment, any item 11
being conveyed is greater in length "L" (measured longitudinally
along the direction of flow of the conveyor) than the distance "d"
between the zone sensors 14. The sensors 14 are preferably
photo-eye type sensors, but any type of sensor capable of
determining the presence of an item 11 could be used, including,
but not limited to, proximity sensors, limit switches, strain
gauges, weight measurement devices, imagers, or ultrasonic
sensors.
[0047] Depending on the nature of the items 11 being conveyed, the
size of the zones 15 may be smaller than the arrangement shown in
FIG. 1. Accordingly, the spacing of sensors 14 may be varied to
accommodate items 11 of various sizes. Referring to FIG. 6, items
11 of length "L" must be greater than distance "d," the distance
between sensors (and also the length of the zone), in other words,
the length of zone 15, in order to effectively eliminate gaps
between items. Alternatively, where the item length "L" is less
than distance "d," in some circumstances it may not be possible to
effectively eliminate the gap between an upstream item and a
stopped downstream item depending upon the location at which the
downstream item is stopped within the downstream zone. The zone
length can be varied as desired depending on the size of the items
to be conveyed. Thus, the zone length may be greater than the item
length or less than the item length as desired.
[0048] FIGS. 4-8 show one embodiment of the conveyor system 10
featuring the gap control system of the present invention. FIGS.
9-10 show a second embodiment of a conveyor system 10 featuring the
inventive gap control system.
[0049] The illustrated embodiment uses brushless DC motors
integrated within the MDRs. These motors provide feedback as to the
position of the roller, e.g., via Hall effect sensors that are
integral with the motor itself. The inventive gap control system
utilizes the feedback from the Hall effect sensors to dynamically
determine the length of the gap 30 between items 11 that are
transported on the conveyor system 10.
[0050] More specifically, as an item 11 passes a sensor 14, the
sensor 14 transitions from blocked (i.e., when the item 11 is
triggering the sensor 14) to unblocked (i.e., when the item 11 is
not triggering the sensor 14). Accordingly, as an item 11 passes a
sensor 14, a counter is initiated within a microprocessor 28 on the
card 20. The counter counts the number of pulses received by the
Hall effect sensor within an MDR until a subsequent item 11 blocks
the sensor 14. In other words, the counter records the number of
pulses received from the MDR while no item 11 was being transported
by the MDR, which is a measure of the gap 30 between consecutive
items 11. A counter value is calculated and maintained for every
sensor 14 in the conveyor system by corresponding cards 20. Thus,
as a downstream item 11 approaches a blocked zone 15, the
corresponding counter value is used to continue to transport an
item 11 the requisite number of pulses, i.e., the number of pulses
stored in the counter value, in order to close the gap 30. This
effectively transports the item 11 right up to the stopped item 11,
barely touching it, providing zero pressure accumulation as
desired.
[0051] In addition to the scenario discussed above, i.e., wherein a
sensor 14 detects a second item 11 after a first item 11 has passed
the sensor 14, there is another scenario in which the counter may
be stopped. Specifically, the second scenario occurs when an item
11 that has passed a particular sensor 14 is stopped on the
conveyor system 10 before a second item 11 is detected by the
particular sensor 14. In other words, the item 11 is stopped before
the second item 11 reaches the particular sensor 14. Thus, when the
item 11 has been stopped, the card 20 corresponding to the
downstream zone 15 in which the item 11 is stopped communicates
with the card 20 corresponding to the adjacent upstream zone 15,
which then stops the counter. Accordingly, the counter value
represents the distance between the end of the stopped, downstream
item 11 and the sensor 14 in the adjacent, upstream zone 15. Thus,
the cards 20 communicate with one another such that a subsequent
item 11 is moved up to the stopped item 11, thus closing the gap 30
between the two items.
[0052] The illustrated embodiment also allows the counter value to
be converted to a known distance, such that the counter value could
be modified to allow the user to select a desired gap distance
between items 11 so that items 11 do not touch, but have a minimal
gap 30.
[0053] The present invention further includes a method for
determining a gap 30 between items 11 on a conveyor system 10.
Generally speaking, as shown in FIG. 12, the method includes the
steps of (a) detecting a first edge of a first item at a
predetermined location on a conveyor system; (b) detecting a second
edge of the first item at the predetermined location on the
conveyor system; (c) beginning a counter once the second edge of
the first item passes the predetermined location on the conveyor
system; (d) stopping the counter once a first edge of a second item
is detected at the predetermined location; and (e) generating a
counter value based upon the counter data. Accordingly, the counter
value represents a gap 30 between adjacent items 11 on a conveyor
system 10.
[0054] Additional steps of the method may include using the counter
value to eliminate the gap 30 between the items 11. For example,
the counter value may be used to rotate an MDR a corresponding
number of rotations in order to close the gap 30 between the
adjacent items 11 in the event that the downstream item 11 has been
stopped on the conveyor system. Moreover, the counter value may be
adjusted or converted to a predetermined value so that the size of
the gap remains fixed if a gap (preferably minimal) between items
11 is desired.
[0055] The method may also include steps to stop the counter when
an item has been stopped in a downstream zone. For example, the
method may include the steps of (a) detecting a first edge of a
first item at a predetermined location on a conveyor system; (b)
detecting a second edge of the first item at the predetermined
location on the conveyor system; (c) beginning a counter once the
second edge of the first item passes the predetermined location on
the conveyor system; (d) stopping the counter when the item has
been stopped on the conveyor system; and (e) generating a counter
value based upon the counter data. Further steps may include using
the counter data to rotate an MDR a corresponding amount of
rotations in order to close the gap 30 between the adjacent items
11.
[0056] Various alternatives and modifications are contemplated as
being within the scope of the following claims particularly
pointing out and distinctly claiming the subject matter regarded as
the invention.
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