US20030219331A1

US20030219331A1 - Control system and unloading method

Info

Publication number: US20030219331A1
Application number: US10/417,201
Authority: US
Inventors: Thomas Brown; Patrick Carey; Dale Larson
Original assignee: Lockheed Martin Corp
Current assignee: Lockheed Martin Corp
Priority date: 2002-04-17
Filing date: 2003-04-17
Publication date: 2003-11-27

Abstract

A control and method of use implemented by an unloading mechanism for unloading products from an intermediate container onto a conveyor for downstream processing. The controls tilt the mechanism, in embodiments, to a relative angle from a horizontal or supporting surface and proximate the conveyor. A gate is controlled to slidably mount between an open position and a closed position in order to allow product slide from the structure.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Serial No. 60/372,787, filed on Apr. 17, 2002, the entire contents of which are herein incorporated by reference.[0001]

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a control system and method of unloading containerized cartons and mail trays and the like using an unloading mechanism and, more particularly, to a control system and method of use for automatically unloading mail trays, packages and the like from an intermediate container onto a conveyor for downstream processing.

2. Background Description

The sorting of mail is a very complex, time consuming task. In general, the sorting of mail is processed through many stages, including front, middle and back end processes. The front end process, for example, is used to orient and align mail trays; whereas, the middle and back end processes are used for the sorting and processing of the mail for future delivery. These processes can either be manual or automated, depending on the mail sorting facility, whether it is a postal facility or other delivery or transportation facility. A host of factors may also contribute to the automation of the mail sorting facility, from budgetary concerns to modernization initiatives to access to appropriate technologies to a host of other factors.

In general, however, most modern postal facilities have taken major steps toward mechanization (e.g., automation) by the implementation of a number of technologies. These technologies include, amongst others, singulators, letter sorters, facer-cancelers, automatic address readers, parcel sorters, advanced tray conveyors and flat sorters. As a result of these developments, postal facilities have become quite automated over the years I an effort to reduce costs.

In implementation, prior to the front end process, an operator must first remove containers, mail trays, packages and the like (referred to generally as mail trays) from intermediate containers or mail carts. Once removed from the intermediate containers, the mail trays are placed on a conveyor, at which time they are oriented and aligned into a single file for downstream processing. This orienting and aligning step is typically referred to as the front end process. However, this manual step of placing the mail trays onto the conveyor is time consuming, labor intensive and hence adds further expense to the sorting and delivery processes.

In order to provide automation for this stage of processing, some facilities have implemented a robotic arm and end effector used to remove the mail trays from the intermediate containers. The robotic arm and end effector mechanism typically removes one mail tray at a time or, alternatively, a single layer of mail trays at a time. The robotic arm and end effector is very expensive to manufacture, including the control systems and the mechanical features. It is also known that these robotic arm mechanisms are constrained by its gears and other mechanical features, making the robotic arm slow, cumbersome and costly from maintenance stand point. It has also been found that a robotic arm cannot effectively and efficiently unload mail trays which are irregularly stacked in the mail cart.

In another known removal system, a lifting mechanism hydraulically lifts the intermediate container and then dumps out of the top of the container, at one time, all of the mail trays onto the conveyor. This process, though, results in damage to the mail trays, mail trays falling off the conveyor, itself, as well as bar codes falling off the mail trays. This process is also susceptible to interference from shelves associated with the intermediate container.

As an alternative, a system can be employed which empties trays out of the front of the container instead. One such system is disclosed in U.S. patent application Publication US 2002/0150452A1. In this system, a cage of holding device is provided for holding containers. This holding device includes an open side which has a sliding wall or gate that is disposed over the open side. The holding device along with the container is tilted such that the open side of the container is generally directed downward. From this tilted orientation, the sliding wall or gate is withdrawn, exposing the open side of the container. This permits the egress of the packages, etc., from the container. However, while this system has utility on its own, the functionality of the system can be enhanced. First, when the holding device is tilted, the gate has a tendency to drive against the floor at certain angles, thus preventing the holding device from further tilting, jamming the gate or otherwise disrupting the operations of the apparatus. Second, during the titling mode the packages are typically thrown or tossed from the container in a disjointed manner thus making it difficult to provide a proper ordering of the packages for future bar code reading.

Once the mail trays are placed on the conveyor, the front end process then orients and aligns the mail trays so as to allow the mail trays to be conveyed to other stations for scanning, preparation for mail processing and future delivery. To accomplish this, a “singulator” is employed which is capable of manipulating the mail trays into a single file. Known singulators include, for example, cascading metal chutes incorporated at right angles, metering belts, skewed rollers and other mechanisms. However, in these systems, the footprint or layout is quite large (e.g., exceeding 100 sq./ft), and cannot easily be fitted within a confined floor space.

The present invention solves one or more of the above problems.

SUMMARY OF THE INVENTION

In a first aspect of the present invention, a method of unloading product from an intermediate container onto a conveyor for downstream processing/is provided. The method includes loading a mail cart having the product into the holding structure. The holding structure is then tilted at a relative angle, in embodiments to approximately 30° with respect to a horizontal surface. The gate is incrementally opened to allow one layer at a time of product to slide from the mail cart and exit from the holding structure. A determination is made as to whether the one layer of product has exited from the holding structure and onto the conveyor. If so, then the opening of the gate and the determination step are repeated until the gate has realized its full open position.

In another aspect of the present invention, a control system for controlling the unloading of product from an intermediate container onto a conveyor for downstream processing is provided. The control system comprises:

(a) a module that controls tilting the unloading mechanism to a relative angle with respect to a supporting surface;

(b) a module that incrementally opens a gate of the unloading mechanism to allow a single layer of product at a time to slide from a mail cart within the unloading mechanism and exit therefrom onto the conveyor; and

(c) a module that controls determining whether the single layer of product has exited from the unloading mechanism and onto the conveyor and if the step (c) is affirmative, repeating the steps of (b) and (c) until all the gate has realized it full open position.

In embodiments, the module that controls tilting further controls determining whether the relative angle of the unloading mechanism is at approximately 30° with respect to the supporting surface. The control that controls incrementally opening of the gate further controls raising the gate to the closed position. In further embodiments, a module is provided for controlling a relative angle of the unloading mechanism at approximately 30° with respect to the supporting surface. A module is also provided that controls raising the gate to the closed position, raising the unloading mechanism to an original position after the gate has been fully opened as determined by a sensor, and returning the unloading mechanism to an original position after the gate has been fully opened. A machine readable medium containing code is also provided for performing unloading of product.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: [0019]
FIG. 1 shows a general schematic diagram of the unloading system implementing the control and method of the present invention; [0020]
FIG. 2 shows a top view of the unloading system implementing the control and method of the present invention; [0021]
FIG. 3 shows a side view of the unloading system implementing the control and method of the present invention; [0022]
FIGS. [0023] 4 though 7 show the various stages of operation of the unloading system under the control of the control and method of the present invention; and
FIG. 8 is a flow diagram showing the steps of implementing the method of the present invention. [0024]

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The present invention is directed to a control system and method of unloading containers. In general, the control system and method is capable of unloading items such as cartons, packages and mail trays (referred to generally as mail trays) from intermediate transport containers or carts and onto the conveyor in a gentle, organized, smooth manner. In one embodiment, the unloading system is used in conjunction with a take away conveyor which is inclined to (i) unstack mail trays which are “piggy-backed” (i.e., stacked on top of one another) after the unloading process and (ii) further enhance the “gentleness” of the unloading process. [0025]
Unloading System [0026]
Referring now to FIG. 1, a general schematic diagram of one type of unloading system implementing the control and method of the present invention of the present invention is shown. It should be understood that the control and method of the present invention may be implemented with other unloading mechanisms having a gate and tilting mechanism. The unloading system is depicted generally as reference numeral [0027] 100 and includes a frame 102 and a bottom supporting surface 104. In embodiments, a closed top portion 105 is also provided in order to ensure that mail trays and other types of packages will not be ejected from the top thereof during the tilting operation. The frame 102 and the bottom supporting surface 104 (and, in embodiments, the closed top portion 105) form a general caged or holding structure which is capable of accommodating an intermediate transport container or cart 106. Although the cart 106 makes no part of the present invention, it is noted that the cart accommodates items such as mail packages, mail trays and the like which need to be transferred to the conveyor for downstream processing.
Still referring to FIG. 1, a [0028] gate 108 is slidably mounted to a front portion 109 of the holding structure, and more specifically to the front portion of the frame 102. The gate 108 includes a ramp portion 110 and a reverse hinge portion 112 at an opposing end. The reverse hinge portion 112 is adapted to move away from the bottom supporting surface 104 as the gate 108, itself, is retracted or opened.. That is, the reverse hinge portion 112 will be capable of sliding along the horizontal surface (e.g., a floor or other surface) upon contacting such surface. This ensures that the gate 108 will not be hindered, jammed or otherwise lock up during the unloading operation. At least one open side 114 is provided on the holding structure in order to allow entry of the cart 106 into the unloading system 100 of the present invention. In embodiments, a hinged ramp 116 may extend from the bottom supporting surface 104, at the open side 114, so that a fully loaded cart 106 can be easily rolled into unloading system 100 (i.e., into the holding structure).
FIG. 1 further shows a door [0029] 118 hingedly mounted to the frame 102 via a hinge mechanism 120. In more specific embodiments, the door 102 is hingedly mounted to the frame 102 on the open side 114, and is designed to move back and forth between an open position (FIG. 1) and a closed position (FIG. 3). In the closed position, a locking mechanism 122 such as, for example, a latch mechanism, may be used for locking the door 118 to the frame 102. This ensures that the cart 106 (and mail trays) remains within the holding structure of the present invention during the lifting and tilting operations.
In further embodiments, the [0030] frame 102 may be hinge mounted to a supporting structure (FIG. 4). This configuration allows the frame structure 102 to be moved into an open position so that the cart 106 can be rolled onto the bottom supporting surface 104 allowing access to the front of the cart. In this configuration, the holding structure may be slightly lifted from the floor in order to allow the operator to easily open and close the holding structure of the present invention. The ramp 116 is still used to assist the user in carting the cart 106 onto the bottom supporting surface 104.
FIG. 2 shows a top view of the unloading system [0031] 100 of the present invention. In this view, a tilting mechanism 124 and a lifting mechanism 126 are shown mounted between the frame 102 and a supporting structure 128. Both the tilting mechanism 124 and the lifting mechanism 126 are preferably hydraulically powered mechanisms; however, it should be understood by those of ordinary skill in the art that other mechanisms such as stepper motors, screw drives and the like may also be used as the tilting mechanism 124 and the lifting mechanism 126. The tilting mechanism 124 is adapted to tilt the holding structure in the direction of the gate 108 to approximately 30° from a horizontal surface (i.e., a supporting surface of the holding structure). This tilt angle ensures that the mail trays will gently slide, not drop or tumble, in a controlled manner from the cart 106 onto the conveyor. This tilt angle, in conjunction with the inclined take away conveyor, will also ensure that the majority, if not all, of the mail trays will be oriented right side up when unloaded onto the conveyor. It should be understood that other tilt angles such as, for example, a tilt angle of approximately 100 or otherwise may also be contemplated by the present invention. In these other tilt angles, there may be no need then to incline the take away conveyor, itself. In embodiment, it is thus accordingly understood that many different combinations of tilt angles and inclines of the conveyor are possible to ensure that the container contents gently slide, not drop or tumble, from the unloading system of the present invention. In embodiments, the supporting structure 128 provides stability to the holding structure 100 during the lifting and tilting operations.
A motor and [0032] drive system 130 may also be mounted to the frame 102 in order to drive the gate 108 between an open position and a closed position. The drive system 130 may be a screw type system, a rack and pinion type system or other drive mechanism. In the open position, a chute or opening 129 is formed between the ramp 110 and an upper, horizontal bar 102 a of the frame 102. The chute 129, in embodiments, is approximately 20 inches in length, but may equally be other lengths to accommodate different sized mail trays, packages and the like. In an embodiment, the chute 129 is formed only after the holding structure is tilted to 30° from the horizontal surface. The tilt angle in combination with the ramp 110 and the opening of the chute 129 is designed to allow a single layer of mail trays, at a time, to gently slide from the cart 106 onto the conveyor in a controlled manner.
FIG. 3 shows a side view of the unloading system [0033] 100 of the present invention. As seen in this view, at least one or more photoeye or other sensor 131 may be mounted to the frame 102 or other placement such as a conveyor rail to monitor the movement of the sliding gate and hence the removal of the mail trays from the unloading system 100 of the present invention. Additionally, the tilt angle may be governed by one or more limit switches 138 mounted to the supporting structure 128 or the frame 102. This ensures that the unloading system 100 of the present invention will tilt to a predetermined angle.
A hinged pivot [0034] 132 is provided between the frame 102 and the supporting structure 128. By use of the combination of the tilting mechanism 124 and the hinged pivot 132, it is possible to tilt the unloading system 100 of the present invention between various angles. Upright walls 134 may also be mounted to the frame 102, which further encloses the holding structure of the present invention.
A [0035] controller 136 is also shown in FIG. 3. The controller 136 may be mounted remote from the frame or other placement, depending on the specific applications. The controller 136 is designed to control the tilting mechanism 124, lifting mechanism 126 and the gate 108 in conjunction with the limit switches 138, proximity switches 140 (placed, for example, on the on the supporting structure 128) and photoeyes for the conveyor. In embodiments, the controller 136 controls the incremental movement of the gate 108 through a predetermined distance and at a predetermined velocity. For example, the controller 136 may incrementally control the movement of the gate 108 between a closed position and a completely retracted, open position. The gate 108 retracts in predetermined increments to allow only one layer of mail trays at a time to gently slide from the chute 129 onto the conveyor, without damaging the mail trays and other types of packages.
Method of Unloading Mail Trays from the Unloading System of the Present Invention [0036]
FIGS. [0037] 4 though 7 show the various stages of operation of the present invention. In FIG. 4, the holding structure 100 is opened, via a hinge 140, in order to accommodate the cart 106 on the bottom supporting surface 104. In FIG. 5, the holding structure 100 is closed such that the cart 106 is now enclosed therein. In FIG. 6, the system of the present invention is lifted and then tilted toward the conveyor. In this figure, it is shown that the reverse hinge portion 112, upon contacting the floor, continues to move away the bottom supporting surface 104. This ensures that the gate 108 will not be hindered during the opening operation. In FIG. 7, the gate 108 begins to slide downward to thus form the chute 129. The chute 129, in combination with the ramp 110 and tilt angle, ensures that the mail trays or other mail packages will gently slide from the cart 106 and onto the conveyor. Additionally, during this operational stage, the controller controls the tilting mechanism 124, lifting mechanism 126 and the gate 108. Also, the limit switches 138 and the photoeyes 131, controlled by the controller 136, ensure that the mail trays and other mail packages are metered, in a controlled manner, from the unloading system 100 to the conveyor.
The cycle time for unloading the mail trays onto the conveyor may be set to a maximum of approximately 90 seconds, although other cycle times are also contemplated by the present invention. The holding structure is also designed to accommodate mail trays of varying sizes and shapes, and it should thus be understood that the present invention should not be limited to any particular size. [0038]
FIG. 8 is a flow diagram showing the steps of implementing the method of the present invention. The steps may be implemented on computer program code in combination with the appropriate hardware. This computer program code may be stored on storage media such as a diskette, hard disk, CD-ROM, DVD-ROM or tape, as well as a memory storage device or collection of memory storage devices such as read-only memory (ROM) or random access memory (RAM). FIG. 8 may equally represent a high level block diagram or a control system of the present invention, implementing the steps thereof. [0039]
In particular, in [0040] step 802, the operator loads the system of the present invention. In one embodiment, this may include opening the door, placing the mail cart on the bottom supporting surface and thereafter closing and locking the door. In another embodiment, this may include opening the entire holding structure, as shown in FIG. 4, and placing the mail cart on the bottom supporting surface and thereafter closing and locking the holding structure. In step 804, the system begins to tilt to approximately 30° from the horizontal. In step 806, the limit switch is used to determine when there is a proper tilt angle. If there is not a proper tilt angle, then steps 804 and 806 repeat. If there is a proper tilt angle, in step 808, the gate is incrementally moved or retracted downward in order to allow one layer of mail trays to gently exit the chute and onto the conveyor.
In [0041] step 810, the photoeyes determine whether the entire layer of mail trays is on the conveyor. If the photoeyes are blocked (mail trays on the conveyor adjacent to the unloading area), then the gate is stopped and until the photoeye is unblocked (step 812). This allows the mail trays to be conveyed away from the unloading system of the present invention thereby preventing a pile up of mail trays. When the photoeyes are not blocked, then, in step 810, the gate continues to open allowing another layer of items to slide down onto the conveyor. In this manner, the unloading of the items is metered so that the cart contents are not unloaded into a pile (i.e., piggy backed) on the conveyor. Now, in step 814, a determination is made as to whether the gate has been fully opened. This is accomplished when the photoeye becomes tripped by the ramp at the front of the gate. If the gate is not fully retracted, then the control of the present invention may revert back to step 808. Then steps 808 through 812 repeat until the gate is fully retracted. If the gate is filly retracted, then the gate will stop and be raised to its closed, original position (step 816). In step 818, the holding structure of the present invention will then tilt back to its original position.
While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. [0042]

Claims

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is as follows:

1. A method of unloading product from an intermediate container mechanism onto a conveyor for downstream processing, the unloading mechanism including a holding structure having a gate slidable between an open position and a closed position, the method including the steps of:

(a) loading a mail cart having product into the holding structure;

(b) tilting the holding structure to a relative angle with respect to a supporting surface;

(c) incrementally opening the gate to allow a single layer of product to slide from the mail cart and exit from the holding structure onto the conveyor;

(d) determining whether the single layer of product has exited from the holding structure and onto the conveyor;

(e) if the step (d) is affirmative, repeating the steps of (c) and (d) until the gate has reached it full open position.

2. The method of claim 1, further comprising the step of determining whether the relative angle of the holding structure is at approximately 30° with respect to the supporting surface.

3. The method of claim 1, further comprising the step of raising the gate to the closed position and returning the holding structure to an original position after the gate has been fully opened as determined by a sensor.

4. A control system for controlling the unloading of product from an unloading mechanism onto a conveyor for downstream processing, the control system comprising:

(a) a module that controls tilting of the unloading mechanism to a relative angle with respect to a supporting surface;

(b) a module that incrementally opens a gate of the unloading mechanism to allow a single layer of product to slide from a mail cart within the unloading mechanism and exit therefrom onto the conveyor; and

(c) a module that controls determining whether the single layer of product has exited from the unloading mechanism and onto the conveyor and if the step (c) is affirmative, repeating the steps of (b) and (c) until the gate has reached it full open position.

5. The control of claim 4, wherein the module that controls tilting further controls determining whether the relative angle of the unloading mechanism is at approximately 30° with respect to the supporting surface.

6. The control of claim 4, wherein the control that controls incrementally opening of the gate further controls raising the gate to the closed position.

7. The control of claim 4, further comprising a module that controls a relative angle of the unloading mechanism is at approximately 30° with respect to the supporting surface.

8. The control of claim 4, further comprising a module that controls raising the gate to the closed position and returning the unloading mechanism to an original position after the gate has been fully opened as determined by a sensor.

9. A machine readable medium containing code for performing unloading of product from an unloading mechanism onto a conveyor for downstream processing, the code implementing the steps of:

(a) tilting the unloading mechanism to a relative angle with respect to a supporting surface;

(b) incrementally opening a gate of the unloading mechanism to allow a single layer of product to slide from a mail cart within the unloading mechanism and exit from therefrom onto the conveyor; and

(c) determining whether the single layer of product has exited from the unloading mechanism and onto the conveyor and if the step (c) is affirmative, repeating the steps of (b) and (c) until the gate has reached it full open position.