Conveyor systems

• US 7,909,155 B2
• Filed: 09/08/2008
• Issued: 03/22/2011
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Dematic Corporation
• Original Assignee: Dematic Corporation
• Inventors: Kane, Kenneth D., Butler, Phillip C., Lupton, Clinton R., DeWildt, Charles J.
• Primary Examiner(s): Bidwell; James R
• Application Number:
  US12/206,011
• Publication Number:
  US 20090065330A1
• Time in Patent Office: 925 Days
• Field of Search: 198/357, 198/358, 198/444, 198/448
• US Class Current: 198/357
• CPC Class Codes: B65G 43/08 Control devices operated by article or material being fed, conveyed or discharged and controlling the discharging devices B65G47/42
• CPC Class Codes: B65G 43/10 Sequence control of conveyors operating in combination
• CPC Class Codes: B65G 47/684 with recirculation of articles forming a buffer

Abstract

Systems and methods for accumulating articles on transport conveyors, for efficiently merging articles, and for automatically controlling sortation speed are disclosed. Transport conveyor beds upstream of an accumulation conveyor bed may be controlled to more densely pack articles, as well as to more timely deliver articles to the downstream subsystem when accumulation terminates. Slugs of articles in a merge subsystem may be released based on a prioritization scheme that heavily weighs the ability of the slug to attach to the next-most downstream slug. A combination of closed and open-looped control of the slug'"'"'s movement may be used to accurately position slugs on the merge bed. A downstream sortation speed may be automatically adjusted based on the amount of merge traffic.

Claims

1. A conveyor system comprising:

a merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor;

a sortation conveyor downstream of said merge subsystem, said sortation conveyor adapted to transport articles that have passed through said merge subsystem to selected ones of a plurality of takeaway conveyors;

a sensor adapted to detect a usage level of said merge subsystem; and

a controller adapted to adjust a speed of said sortation conveyor based upon a value of the usage level of said merge subsystem, wherein said controller repetitively determines the value of the usage level of said merge subsystem and calculates an average of said value over a time period, said controller adapted to adjust the speed of said sortation conveyor based upon said average.

2. The system of claim 1 wherein said controller adjusts said speed of said sortation conveyor between a minimum speed and a maximum speed, said minimum and maximum speeds both being adjustable by a user of said conveyor system.

3. The system of claim 1 wherein the value of the usage level is based at least partially upon a degree to which articles have accumulated in an area upstream of the feed conveyors.

4. The system of claim 1 wherein said controller increases the speed of said merge subsystem when the speed of the sortation conveyor is increased, and said controller decreases the speed of said merge subsystem when the speed of the sortation conveyor is decreased.

5. A conveyor system comprising:

a merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor;

a sortation conveyor downstream of said merge subsystem, said sortation conveyor adapted to transport articles that have passed through said merge subsystem to selected ones of a plurality of takeaway conveyors;

a sensor adapted to detect a usage level of said merge subsystem; and

a controller adapted to adjust a speed of said sortation conveyor based upon a value of the usage level of said merge subsystem, wherein said controller repetitively determines the value of the usage level of said merge subsystem and calculates a first average of said value over a first time period and a second average of said value over a second time period, said first and second time periods partially overlapping each other, and said controller adjusts the speed of said sortation conveyor based upon whichever one of said first and second averages is greater.

6. A conveyor system comprising:

a merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor;

a sortation conveyor downstream of said merge subsystem, said sortation conveyor adapted to transport articles that have passed through said merge subsystem to selected ones of a plurality of takeaway conveyors;

a sensor adapted to detect a usage level of said merge subsystem; and

a controller adapted to adjust a speed of said sortation conveyor based upon a value of the usage level of said merge subsystem, wherein the value of the usage level is based at least partially on calculations of whether slugs of articles on said feed conveyors can be transported onto said merge conveyor such that leading articles of said slugs can be positioned on said merge conveyor within a desired distance from an adjacent downstream article on said merge conveyor.

7. In a conveyor system having merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor, and a sortation conveyor downstream of the merge subsystem wherein the sortation conveyor is adapted to transport articles that have passed through the merge subsystem to selected ones of a plurality of takeaway conveyors, a method of controlling the sortation conveyor comprising:

repetitively determining a value of a usage level of the merge subsystem using a plurality of sensors;

calculating an average of said repetitive determinations of said value; and

adjusting a speed of the sortation conveyor based upon said average.

8. The method of claim 7 wherein determining the value of the usage level includes determining a degree of accumulation of articles in an area upstream of each of said feed conveyors.

9. The method of claim 7 further including reducing a speed of the merge subsystem when the speed of the sortation conveyor is decreased and increasing the speed of the merge subsystem when the speed of the sortation conveyor is increased.

10. In a conveyor system having a merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor, and a sortation conveyor downstream of the merge subsystem wherein the sortation conveyor is adapted to transport articles that have passed through the merge subsystem to selected ones of a plurality of takeaway conveyors, a method of controlling the sortation conveyor comprising:

repetitively determining a value of a usage level of the merge subsystem using a plurality of sensors;

calculating a first average of said repetitive determination of said value over a first time period;

calculating a second average of said repetitive determinations of said value over a second time period wherein said first and second time periods partially overlap each other; and

adjusting a speed of the sortation conveyor based upon the greater of the first and second averages.

11. In a conveyor system having a merge subsystem adapted to merge articles from a plurality of feed conveyors onto a merge conveyor, and a sortation conveyor downstream of the merge subsystem wherein the sortation conveyor is adapted to transport articles that have passed through the merge subsystem to selected ones of a plurality of takeaway conveyors, a method of controlling the sortation conveyor comprising:

determining a value of a usage level of the merge subsystem using a plurality of sensors, said determining of the value of the usage level including determining whether a slug of articles on a particular feed conveyor can be transported onto the merge conveyor such that a leading article of said slug can be positioned on the merge conveyor within a desired distance from an adjacent downstream article on the merge conveyor; and

adjusting a speed of the sortation conveyor based upon a value of the usage level of the merge subsystem.

12. A method of merging articles from a plurality of feed conveyors onto a merge conveyor comprising:

accumulating articles on said plurality of said feed conveyors;

releasing a first slug of articles from a selected one of said feed conveyors onto said merge conveyor, said first slug of articles including a leading article and a trailing article;

determining a set of feed conveyors, that include another slug of articles able to be delivered to said merge conveyor such that a leading article in said another slug is able to be positioned on said merge conveyor at a specified distance behind the trailing article of said first slug;

releasing, from one of said feed conveyors in said set, said another slug of articles onto said merge conveyor such that a leading article in said another slug of articles is positioned on said merge conveyor at a specified distance behind the trailing article of said first slug; and

transporting said first slug and said another slug to a sortation conveyor adapted to sort the articles.

13. The method of claim 12 further including adjusting a speed of the feed conveyors such that gaps between articles within the slugs are adjusted toward a non-zero target length while the slugs are on the feed conveyors wherein the non-zero target length is based on a length of an article adjacent to a particular gap.

14. The method of claim 12 wherein releasing the another slug of articles onto the merge conveyor includes accelerating the one of said feed conveyors in said set toward a threshold speed while controlling the one of said feed conveyors in said set in an open loop manner, and, after reaching the threshold speed, controlling the one of said feed conveyors in said set in a closed loop manner with respect to a target position on the merge conveyor for a particular article in the another slug whereby an estimated position for said particular article is adjusted toward said target position.

15. The method of claim 12 further including determining an actual location on the merge conveyor of a particular article within the another slug, comparing said actual location to a target location and using said comparison to adjust the speed of the one of said feed conveyors in said set during at least one subsequent release of slugs onto the merge conveyor by said one of said fee conveyors in said set.

16. A conveyor system comprising:

a plurality of feed conveyors, each said feed conveyor having an upstream end and a downstream end, and each said feed conveyor adapted to transport articles from said upstream end to said downstream end;

a merge conveyor positioned within a vicinity of said downstream ends of said plurality of feed conveyors such that articles exiting said feed conveyors are delivered to said merge conveyor;

a plurality of sensors adapted to determine locations of articles on said feed conveyors and on said merge conveyor;

a sortation conveyor downstream of the merge conveyor, said sortation conveyor adapted to sort the articles; and

a controller adapted to control said feed conveyors such that slugs of articles tend to accumulate on said feed conveyors, said controller also adapted to use said plurality of sensors to determine a set of feed conveyors having a slug that is able to be positioned on said merge conveyor at a specified distance behind a particular article on said merge conveyor, and said controller further adapted to select from said set of feed conveyors a particular conveyor to release its slug based upon a priority level assigned to each of said feed conveyors in said set.

17. The system of claim 16 wherein said priority level is based upon at least two of the following criteria:

(1) a degree of article accumulation upstream of each feed conveyor in said set;

(2) a number of articles in a wave of articles remaining to be delivered by each feed conveyor in said set to said merge conveyor;

(3) a size of the slug in each feed conveyor in said set; and

(4) an amount of time a slug has remained on each feed conveyor in said set.

18. The subsystem of claim 17 wherein said controller is further adapted to release the slugs from said feed conveyors by accelerating the feed conveyors toward a threshold speed in an open loop manner, and, after reaching said threshold speed, controlling said feed conveyors in a closed loop manner with respect to a target position on the merge conveyor for a particular article in the slug whereby said controller adjusts an estimated position for said particular article toward said target position.

19. A method of merging articles from a plurality of feed conveyors onto a merge conveyor comprising:

accumulating slugs of articles on said plurality of said feed conveyors;

releasing a slug of articles from a selected one of said feed conveyors onto said merge conveyor, said slug of articles including a leading article and a trailing article;

controlling a speed of the selected one of said feed conveyors during the release of the slug of articles in order to position said leading article on said merge conveyor at a target location on said merge conveyor;

determining an actual location of the leading article on the merge conveyor;

comparing said actual location to said target location and using the comparison to adjust an aspect of a subsequent release of the selected one of said feed conveyors; and

transporting said slug of articles to a sortation conveyor positioned downstream of said merge conveyor, said sortation conveyor adapted to sort the articles.

20. The method of claim 19 further including, after said leading article in said slug has reached said merge conveyor, adjusting a speed of the selected one of said feed conveyors such that the trailing article in the slug tends to be positioned on said merge conveyor at a trailing target location on the merge conveyor.

21. The method of claim 19 wherein said aspect of a subsequent release is one of a speed of the selected one of said feed conveyors and a time at which said selected one of said feed conveyors is accelerated.

22. The method of claim 19 wherein releasing the slug of articles from the selected one of said feed conveyors includes accelerating the selected one of said feed conveyors toward a threshold speed while controlling said selected one of said feed conveyors in an open loop manner, and, after reaching said threshold speed, controlling said selected one of said feed conveyors in a closed loop manner with respect to a leading target position on said merge conveyor for a particular article in the slug whereby an estimated position for said particular article is adjusted toward said leading target position.

23. The method of claim 22 wherein controlling said selected one of said feed conveyors in a closed loop manner further includes, after a leading article in said slug has moved onto said merge conveyor, controlling said selected one of said feed conveyors in a closed loop manner with respect to a trailing target position on said merge conveyor whereby an estimated position for a trailing article within said slug is adjusted toward said trailing target position.

24. A method of merging a slug of articles from a feed conveyor onto a merge conveyor wherein said slug includes a leading article and a trailing article, said method comprising:

determining a leading target position for said leading article on said merge conveyor;

controlling said feed conveyor such that said leading article moves toward said merge conveyor;

determining an estimated position for said leading article on said merge conveyor;

comparing said leading target position to said estimated position;

adjusting the speed of said feed conveyor in a manner in which any differences between said estimated position and said leading target position are reduced; and

transporting the slug of articles to a sortation conveyor downstream of said merge conveyor, said sortation conveyor adapted to sort the articles.

25. The method of claim 24 further including determining a trailing target position for the trailing article in said slug;

determining when said leading article has exited said feed conveyor and, after said leading article has exited said feed conveyor, determining an estimated position for said trailing article on said merge conveyor, comparing said estimated position for said trailing article to said trailing target position, and adjusting the speed of said feed conveyor in a manner in which any differences between said estimated position for said trailing article and said trailing target position are reduced.

26. A conveyor system comprising:

an accumulation conveyor;

a transport conveyor upstream of said accumulation conveyor;

a second transport conveyor upstream of said transport conveyor;

a merge subsystem downstream of said accumulation and transport conveyors, said merge subsystem merging a plurality of feed conveyors into a merge conveyor;

a sortation conveyor downstream of said merge subsystem; and

a controller adapted to accumulate articles on said accumulation conveyor until articles have accumulated to a first threshold level on said accumulation conveyor, said first threshold level being less than an entirety of said accumulation conveyor, said controller further adapted to commence accumulating articles on said transport conveyor after articles have accumulated to said first threshold level on said accumulation conveyor;

wherein said controller is further adapted to commence accumulation of articles on said second transport conveyor when articles have accumulated to a second threshold level on said transport conveyor, said second threshold level being less than an entirety of said transport conveyor; and

wherein said controller is further adapted to transport a downstream article at a downstream end of said transport conveyor to said accumulation conveyor if the accumulation conveyor has not yet accumulated articles to a higher threshold level, said higher threshold level being higher than said first threshold level.

27. The system of claim 26 wherein said controller stops accumulating articles on said transport conveyor when both:

(1) articles have accumulated to said higher threshold level on said transport conveyor, and (2) an article is detected at the downstream end of said transport conveyor.

28. The system of claim 26 wherein said second transport conveyor has a conveying surface defined by an endless belt, and each of said transport and second transport conveyors have a length of at least fifty feet.

29. The system of claim 26 wherein said accumulation conveyor is a rollered accumulation conveyor having a plurality of rollers that define a conveying surface wherein said rollered accumulation conveyor includes a plurality of conveying zones that may be operated at different speeds from each other.