Flow-controlled conveyor system

Abstract

A flow-controlled conveyor system has images captured by depth-perceptive parcel sensors to estimate a count of parcels atop a conveyor belt in fixed-length or dynamically adjusted-length measurement frames. The estimated parcel count is used to adjust the speed of the conveyor belt to control the flow of parcels to downstream processing operations. The greater the count of parcels in a frame, the slower the conveyor belt is advanced, and vice versa.

Description

[0001] FLOW-CONTROLLED CONVEYOR SYSTEM

[0002] TECHNICAL FIELD

[0003] The invention relates to power-driven conveyors and in particular to bulk-loaded conveyors whose conveying speed is adjusted to match the supply of parcels exiting the conveyor to downstream demand.

[0004] BACKGROUND

[0005] Today's flow-controlled sorting systems rely on overhead scanning technology to estimate the bulk flow of parcels entering the sorting system. The bulk flow is adjusted based on the density of the parcels by adjusting the speed of a flow-control conveyor upstream of the sorting or other downstream material-handling operations. The flow-control conveyor is sped up when the parcel density is low and slowed when the parcel density is high so as to match the downstream demand for parcels. Because parcels supplied in bulk are often stacked atop one another, packages below the top of a stack are partially or completely occluded from overhead scanners. A parcel undercount results in an oversupply of parcels downstream. The overhead scanners can also produce an inaccurate overcount. When parcels are overcounted, the belt is slowed and undersupplies parcels downstream. Instead of an optimal steady flow of parcels to downstream material-handling operations, the overfed and underfed conditions result in peaks and valleys in the flow as the flowcontrol logic hunts for the optimal flow rate. The resulting variations in parcel flow not matched to downstream demand fail to achieve optimal flow and, thus, operation is not as efficient as it could be.

[0006] SUMMARY

[0007] One version of a flow-controlled conveyor system comprises a conveyor belt extending in width from a left side to a right side and having an upstream end and a downstream end and adapted to receive a bulk flow of parcels at the upstream end and convey the parcels in a conveying direction off the downstream end and an imaging system. The imaging system includes an overhead parcel sensor that is arranged to capture overhead images of the parcels on the conveyor belt from above the conveyor belt, a left-side parcel sensor arranged to capture left-side images of the parcels on the conveyor belt over the left side of the conveyor belt, and a right-side parcel sensor arranged to capture right-side images of the parcels on the conveyor belt over the right side of the conveyor belt. A processor receives the overhead images, the left-side images, and the right-side images and executes program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame covering a length of the conveyor belt from the overhead, left-side, and right-side images. The processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

[0008] Another version of a flow-controlled conveyor system comprises a conveyor belt having an upstream end and a downstream end and adapted to receive a bulk flow of parcels at the entrance end on a conveying surface and convey the parcels downstream in a conveying direction off the downstream end and an imaging system. The imaging system includes a first overhead parcel sensor that is arranged to capture first overhead images of the parcels on the conveyor belt from above the conveyor belt along a first line perpendicular to the conveying surface and a second overhead parcel sensor arranged to capture second overhead images of the parcels on the conveyor belt from above the conveyor belt along a second line oblique to the conveying surface. A processor receives the first and second overhead images and executes program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame from the first and second overhead images. The processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

[0009] Yet another version of a flow-controlled conveyor system comprises an infeed conveyor conveying a bulk flow of parcels to an exit end of the infeed conveyor and a conveyor belt that has a conveying surface that extends from an upstream end to a downstream end and is adapted to receive the bulk flow of parcels at the upstream end from the infeed conveyor and convey the parcels downstream in a conveying direction off the downstream end. The exit end of the infeed conveyor is disposed at a level above a level of the upstream end of the conveyor belt so that a space is formed between the exit end of the infeed conveyor and the upstream end of the conveyor belt and parcels drop from the infeed conveyor onto the conveyor belt. An imaging system includes a first parcel sensor arranged to capture first images of the parcels dropping from the infeed conveyor onto the conveyor belt along a line oblique to the conveyor belt and a second parcel sensor arranged below the infeed conveyor to capture second images of the parcels on the conveyor belt through the space between the exit end of the infeed conveyor and the upstream end of the conveyor belt. A processor receives the first and second images and executes program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame from the first and second images. The processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a top plan view of one version of a flow-control conveyor system using overhead, left-side, and right-side parcel sensors.

[0012] FIG. 2 is an isometric view of the flow-control conveyor of FIG. 1.

[0013] FIG. 3 is an isometric view of a second version of a flow-control conveyor using a vertically oriented parcel sensor.

[0014] FIG. 4 is an isometric view of a third version of a flow-control conveyor using a sensor technology capable of seeing through opaque surfaces.

[0015] FIG. 5 is an isometric view of a fourth version of a flow-control conveyor feeding parcels to a cascade destacker.

[0016] FIG. 6 is a side elevation view of a fifth version of a flow-control conveyor with parcel sensors viewing parcels falling off the outfeed of a conveyor feeding parcels to a cascade destacker.

[0017] FIG. 7 is a side elevation view of a sixth version of a flow-control conveyor with a second parcel sensor at an oblique angle feeding parcels to a cascade destacker.

[0018] FIG. 8 is a block diagram of a control system for a flow-control conveyor.

[0019] FIG. 9 is a screen shot of parcel images captured by a Lidar parcel sensor.

[0020] DETAILED DESCRIPTION

[0021] One version of a flow-controlled conveyor system 20 is shown in FIG. 1. A bulk flow of parcels on an infeed conveyor 22 is fed off an exit end 23 onto a flow-control conveyor 24, such as a conveyor belt. The conveyor belt 24 has an upper conveying surface 25 that extends in width from a left side 26 to an opposite right side 27 and that has an upstream end 28 and a downstream end 29. The belt 24 is driven by a motor 30 in a conveying direction 32 from the upstream end 28 to the downstream end 29. Parcels are fed off the downstream end 29 of the conveyor belt 24 onto a downstream conveyor 34.

[0022] An overhead parcel sensor 36 is arranged to capture overhead images of the parcels from above the conveyor belt 24. A left-side parcel sensor 38 is arranged to capture left-side images of the parcels over the left side 26 of the conveyor belt 24. A right-side parcel sensor 40 is arranged to capture right-side images of the parcels over the right side of the conveyor belt 24. A belt-motion sensor 42, such as an encoder, rotationally coupled to the conveyor belt 24, produces belt-motion signals that indicate the speed of the conveyor belt 24 in the conveying direction 32. Each of the parcel sensors 36, 38, 40 can be realized as a single sensor or as multiple sensors of the same type.

[0023] As shown in FIG. 8, the overhead parcel sensor 36, the left-side parcel sensor 38, and the right-side parcel sensor 40 send the overhead, left-side, and right-side images to a processor 44, such as a programmable logic controller, or one or more distributed processors executing program steps stored in a memory. The processor also receives the belt-motion signals from the belt-motion sensor 42. The processor 44 executes program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame 46 that covers a length of the conveyor belt 24 from the overhead, left-side, and right-side images. The processor 44 adjusts the speed of the conveyor belt as a function of the estimated number of parcels in the measurement frame 46 to control the flow of parcels to downstream processing operations. The length of conveyor belt in the measurement frame 46 can be a predetermined set length or can be dynamically adjusted.

[0024] Dynamically adjusted frame lengths can be used to improve product flow. The length of the conveyor belt in each frame can be adjusted from frame to frame based on size characteristics of parcels in the flow. For example, if a large parcel occupies over, say, 75% of the width of the conveyor belt 24, the end of the current frame can be rolled back to the leading end of the large parcel and the next frame started from there. As another example, if there is a noticeable change in the size characteristics of the parcel flow in the middle of a frame, such as a change from small parcels to larger parcels, the end of the current frame can be rolled back to the end of the group of small parcels and the next frame started from there. One arrangement of the overhead, left-side, and right-side parcel sensors 36, 38, 40 relative to the conveyor belt 24 is shown in FIG. 2. Left and right side rails 48, 49 mounted on a conveyor frame 50 flank the conveyor belt 24 along its left and right sides 26, 27. The side rails 48, 49 prevent parcels from falling off the sides 26, 27 of the conveyor belt 24. A transparent panel 51 in each of the side rails 48, 49 allows the left- and right-side parcel sensors 38, 40 to be mounted outside the side rails and still capture images through the transparent panels 51 in the side rails. Examples of parcel sensors usable with the transparent panels 51 include Lidar devices, conventional video cameras, laser range finders, line-scanning cameras, and stereoscopic cameras.

[0025] FIG. 3 shows a flow-control conveyor that differs from that of FIG. 2 in that left-side and right-side parcel sensors 52, 53 capture left-side and right-side images through gaps 54 in left and right side rails 56, 57.

[0026] In FIG. 4, left-side and right-side parcel sensors 58, 59 mounted outside continuous, opaque left and right side rails 60, 61 capture left- and right-side images through the side rails, which are opaque to visible light. Although Lidar and laser sensors and video cameras can't "see" through the opaque side rails 60, 61, other sensors, such as sonar, x-ray, magnetic-resonance, ultrasonic, and computed tomography sensors can.

[0027] All the parcel sensors described thus far are of the type that can perceive depth, and not just occlusion, so as to provide more details of the parcels beyond their mere presence. An example of a parcel image in a measurement frame produced by one of the parcel sensors is shown in FIG. 9. The image shows the height, width, and depth of parcels in the measurement frame. With measurement-frame data from all three sensors as in FIGS. 2-4, the processor 44 estimates the volume V of the mass of parcels in a measurement frame. The processor also estimates the average volume VP of the parcels detected in the frame. Instead of a dynamically measured average parcel volume VP, a predetermined constant value VP could be used. The ratio V / VP is proportional to the number of parcels in the frame. A constant of proportionality, such as an empirically determined value, is multiplied by the V / VP ratio to provide a more accurate count C of articles in the mass on the conveyor belt 24.

[0028] Each measurement frame 46 covers a predetermined fixed length or a dynamically computed length of the conveyor belt 24. The processor 44 uses the belt-motion signals from the belt-motion detector 42 to determine the start and end of each frame 46, as well as to sample the parcel sensors 36, 38, 40 at equi-spaced intervals. When the belt 24 is moving fast, the sample interval is short in time; when the belt 24 is moving slowly, the sample interval is long in time. And, when a predetermined fixed belt length is used, each measurement frame 46 is composed of the same number of samples covering the predetermined fixed frame length LF.

[0029] After computing a parcel count for each frame 46, the processor 44 compares a desired throughput value Q to the ratio of the parcel count to the measurement frame length (C / LF), i.e., the parcel density in the frame. The processor 44 then sets the speed of the conveyor belt to Q / (C / LF). Thus, the speed is increased when the parcel density is lower than the desired throughput and decreased when the parcel density exceeds the desired throughput. In that way, downstream processing is provided with a steady flow of parcels and not alternately starved of and glutted with parcels.

[0030] Another version of a flow-controlled conveyor system 62 is shown in FIG. 5 with a flow-control conveyor belt 24 as in FIG. 1 feeding a downstream destacking conveyor 64 with a staggered cascade of inclined belts 66. The destacking conveyor 64 helps unstack parcels as do the drops from one inclined belt 66 to the next. In this version only two parcel sensors are used: (a) a first overhead parcel sensor 68 directed vertically downward perpendicular to the belt's conveying surface 25; and (b) a second overhead parcel sensor 69 directed obliquely to the conveying surface. The two overhead parcel sensors 68, 69 capture first and second overhead images of the parcels from which the processor estimates the parcel count in each measurement frame and, from that count, speeds up or slows down the conveyor belt 24. In this example the oblique parcel sensor 69 is positioned downstream of the first overhead sensor 68, but the oblique parcel sensor could be disposed upstream instead.

[0031] In the flow-controlled conveyor system 70 of FIG. 6, an infeed conveyor 72 has an exit end 74 at a level 76 above the level 77 of the upstream end 78 of the flow-control conveyor belt 24. The imaging system for this version includes a first parcel sensor 80 arranged to capture first images of parcels dropping from the infeed conveyor 72 onto the conveyor belt 24 and a second parcel sensor 82 disposed below the infeed conveyor to capture second images of the parcels on the conveyor belt through a space 84 between the exit end 74 of the infeed conveyor and the upstream end 78 of the conveyor belt. The second parcel conveyor is preferably aimed parallel to the conveying surface of the conveyor belt 24.

[0032] The flow-controlled conveyor system 86 of FIG. 7 is similar to the conveyor system 62 of FIG. 5, except that a second overhead parcel sensor 88 is obliquely arranged upstream of the perpendicularly disposed first overhead sensor 68. But the oblique second overhead parcel sensor 88 could alternatively be located downstream and aimed obliquely upstream. A flow-control conveyor 90 includes means for jostling the conveyor up and down, such as a crank 92 and link 94 system to help unstack and separate parcels for better viewing. Other vibratory devices, such as motorized cams, could be used instead. The flow-control conveyor's speed is adjusted as a function of the count of parcels in each frame.

[0033] The term parcel is used to provide consistent terminology throughout the description and claims; it is not used in a limiting sense. The term parcel stands for any conveyable object, including packages, boxes, polybags, envelopes, and containers, as just a few examples.

Claims

What is claimed is:

1. A flow-controlled conveyor system comprising: a conveyor belt extending in width from a left side to a right side and having an upstream end and a downstream end and adapted to receive a bulk flow of parcels at the upstream end and convey the parcels in a conveying direction off the downstream end; an imaging system including: an overhead parcel sensor arranged to capture overhead images of the parcels on the conveyor belt from above the conveyor belt; a left-side parcel sensor arranged to capture left-side images of the parcels on the conveyor belt over the left side of the conveyor belt; a right-side parcel sensor arranged to capture right-side images of the parcels on the conveyor belt over the right side of the conveyor belt; a processor receiving the overhead images, the left-side images, and the right-side images and executing program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame covering a length of the conveyor belt from the overhead, left-side, and right-side images; wherein the processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

2. The conveyor system as claimed in claim 1 comprising a belt-motion sensor producing belt-motion signals indicative of the motion of the conveyor belt in the conveying direction, wherein the processor receives the belt-motion signals and executes program instructions to define the beginning and end of the measurement frames.

3. The conveyor system as claimed in claim 2 wherein the belt-motion sensor is an encoder rotationally coupled to the conveyor belt.

4. The conveyor system as claimed in claim 1 wherein the processor computes a volume V of the mass of parcels in each frame and an average individual parcel volume VP in the frame from the overhead, left-side, and right-side images and computes the estimated number of parcels in each frame as proportional to V / VP.

5. The conveyor system as claimed in claim 1 wherein the speed of the conveyor belt is adjusted to achieve a flow rate that supplies parcels matching the demand of downstream processing operations for the parcels.

6. The conveyor system as claimed in claim 1 wherein the processor samples the overhead, left-side, and right-side images at equi-spaced intervals along the conveyor belt as it advances in the conveying direction past the overhead, left-side, and right-side parcel sensors.

7. The conveyor system as claimed in claim 1 comprising a conveyor frame having left and right side rails flanking the conveyor belt along the left and right sides of the conveyor belt and wherein the left-side parcel sensor is mounted on the conveyor frame outside the left side of the conveyor belt and wherein the right-side parcel sensor is mounted on the conveyor frame outside the right side of the conveyor belt.

8. The conveyor system as claimed in claim 7 wherein the left and right side rails have transparent panels through which the left-side and right-side parcel sensors capture the left-side and right-side images.

9. The conveyor system as claimed in claim 7 wherein the left and right side rails have a gap through which the left-side and right-side parcel sensors capture the left-side and right-side images.

10. The conveyor system as claimed in claim 7 wherein the left and right side rails are opaque and wherein the left-side and right-side parcel sensors are selected from the group consisting of sonar, x-ray, magnetic-resonance, ultrasonic, and computed tomography sensors and capture the left-side and right-side images through the opaque left and right side rails.

11. The conveyor system as claimed in claim 1 wherein the overhead, left-side, and rightside parcel sensors are selected from the group consisting of conventional video cameras, Lidar devices, laser rangefinders, line-scanning cameras, and stereoscopic cameras.

12. The conveyor system as claimed in claim 1 wherein the overhead, left-side, and rightside images include depth perception.

13. The conveyor system as claimed in claim 1 wherein the length of the conveyor belt in each measurement frame is a predetermined fixed length.

14. The conveyor system as claimed in claim 1 wherein the length of the conveyor belt in each measurement frame is dynamically adjusted based on size characteristics of the parcels.

15. A flow-controlled conveyor system comprising: a conveyor belt having an upstream end and a downstream end and adapted to receive a bulk flow of parcels at the entrance end on a conveying surface and convey the parcels downstream in a conveying direction off the downstream end; an imaging system including: a first overhead parcel sensor arranged to capture first overhead images of the parcels on the conveyor belt from above the conveyor belt along a first line perpendicular to the conveying surface; a second overhead parcel sensor arranged to capture second overhead images of the parcels on the conveyor belt from above the conveyor belt along a second line oblique to the conveying surface; a processor receiving the first and second overhead images and executing program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame from the first and second overhead images; wherein the processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

16. The conveyor system as claimed in claim 15 wherein the second overhead parcel sensor is downstream of the first overhead parcel sensor.

17. The conveyor system as claimed in claim 15 comprising means for jostling the conveyor belt to help unstack parcels and make more of the parcels visible to the imaging system.

18. A flow-controlled conveyor system comprising: an infeed conveyor conveying a bulk flow of parcels to an exit end of the infeed conveyor; a conveyor belt having a conveying surface that extends from an upstream end to a downstream end and adapted to receive the bulk flow of parcels at the upstream end from the infeed conveyor and convey the parcels downstream in a conveying direction off the downstream end;wherein the exit end of the infeed conveyor is disposed at a level above a level of the upstream end of the conveyor belt so that a space is formed between the exit end of the infeed conveyor and the upstream end of the conveyor belt and parcels drop from the infeed conveyor onto the conveyor belt; an imaging system including: a first parcel sensor arranged to capture first images of the parcels dropping from the infeed conveyor onto the conveyor belt along a line oblique to the conveyor belt; a second parcel sensor arranged below the infeed conveyor to capture second images of the parcels on the conveyor belt through the space between the exit end of the infeed conveyor and the upstream end of the conveyor belt; a processor receiving the first and second images and executing program instructions to compute an estimated number of parcels in a mass of parcels in a measurement frame from the first and second images; wherein the processor further executes program instructions to adjust the speed of the conveyor belt in the conveying direction as a function of the estimated number of parcels.

19. The conveyor system as claimed in claim 18 wherein the second parcel sensor captures the second images along a line parallel to the conveying surface of the conveyor belt.

Images