Patent Grant
7850413
This invention relates in general to material handling systems, and more particularly, to a method and system for transporting inventory items within an inventory system.
Modern inventory systems, such as those in mail-order and e-commerce warehouses, airport luggage systems, and custom-order manufacturing facilities, face significant challenges in providing fast, accurate responses to requests for inventory items. Delays and backlogs in the process of responding to such inventory requests can result in reduced worker productivity, order cancellations, reduced throughput, or other losses. In recent years, automation has improved the speed and efficiency of storing and retrieving inventory items within such systems. Nonetheless, in high volume systems, the speed and efficiency of automated systems may still limit the overall effectiveness of automated systems.
In accordance with the present invention, the disadvantages and problems associated with inventory systems have been substantially reduced or eliminated. In particular, an inventory system is provided that utilizes improved techniques for transporting inventory holders.
In accordance with one embodiment of the present invention, an apparatus for transporting inventory items includes a housing, a drive module, a docking module, an elevating shaft, and a rotation module. The drive module is capable of propelling the apparatus in at least a first direction. The docking head is capable of coupling to or supporting an inventory holder. The rotation module is capable of inducing rotation in the housing relative to the elevating shaft. The elevating shaft connects to the docking head and is capable of raising the docking head when the housing is rotated relative to the elevating shaft.
In accordance with another embodiment of the present invention, a method for transporting inventory items includes positioning a mobile drive unit beneath an inventory holder at a first location. The mobile drive unit includes a housing, a docking head, and an elevating shaft. The docking head is connected to the elevating shaft, and the elevating shaft is capable of raising the docking head when the housing is rotated relative to the elevating shaft. The method also includes raising the docking head with the elevating shaft by rotating the housing relative to the elevating shaft and docking the mobile drive unit with the inventory holder so that the docking head couples to or supports the inventory holder. Additionally, the method includes moving the mobile drive unit and the inventory holder to a second location.
Technical advantages of certain embodiments of the present invention include an inventory-moving apparatus that increases system throughput, reduces power usage, and utilizes fewer mechanical parts. Additionally, particular embodiments of the present invention may support improved techniques for transporting and manipulating inventory storage components. Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, while specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages.
For a more complete understanding of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:
Mobile drive unit 20 is capable of moving within the workspace of inventory system 10 and may include any appropriate components for propelling itself and navigating to a particular destination within the workspace. Additionally, mobile drive unit 20 may dock with inventory holder 30 so that inventory holder 30 is coupled to and/or supported by mobile drive unit 20. When docked with inventory holder 30, mobile drive unit 20 is also capable of propelling and/or otherwise moving inventory holder 30. Mobile drive unit 20 may include any appropriate components for docking with inventory holder 30 and for maneuvering inventory holder 30 while inventory holder 30 is docked with mobile drive unit 20. The components of particular embodiments of mobile drive unit 20 are described in greater detail below with respect to
Inventory holder 30 stores inventory items 40 on or within inventory holder 30. In particular embodiments, inventory holder 30 includes multiple storage bins with each storage bin capable of holding inventory items 40. Additionally, in particular embodiments, inventory items 40 hang from hooks or bars within or on inventory holder 30. In general, inventory holder 30 may store inventory items 40 in any appropriate manner within inventory holder 30 and/or on the external surface of inventory holder 30. Inventory holder 30 is capable of being rolled, carried, or otherwise moved by mobile drive unit 20. Although
Inventory items 40 represent any objects suitable for storage, retrieval, and/or processing in an automated inventory system 10. As one example, inventory system 10 may represent a mail order warehouse facility, and inventory items 40 may represent merchandise stored in the warehouse facility. As another example, inventory system 10 may represent a merchandise-return facility, and inventory items 40 may represent merchandise returned by customers. As yet another example, inventory system 10 may represent a manufacturing facility, and inventory items 40 may represent individual components of a manufacturing kit to be assembled into a finished product, such as electronic components for a customized computer system. More generally, however, inventory items 40 may represent any appropriate objects that may be stored and retrieved in inventory system 10.
Although the description below focuses, for purposes of simplicity, on embodiments of inventory system 10 in which a single mobile drive unit 20 docks with and transports a single inventory holder 30, mobile drive unit 20 may, in particular embodiments, be capable of docking with multiple inventory holders 30 simultaneously and/or docking with additional inventory holders 30 after docking with a first inventory holder 30. Furthermore, in particular embodiments, mobile drive units 20 and inventory holders 30 may be configured to allow multiple different mobile drive units 20 to dock with a single inventory holder 30 or group of inventory holders 30.
Furthermore, although the description below also focuses on embodiments of mobile drive unit 20 that are utilized to transport one or more inventory holders 30 storing inventory items 40 in an inventory system 10, mobile drive unit 20 may be used to transport other types of objects and equipment in other types of systems. For example, instead of inventory items 40, inventory holders 30 may, in particular embodiments, hold other appropriate objects suitable for storage in inventory holder 30. Moreover, in alternative embodiments inventory holder 30 may also be replaced by vacuum cleaners, floor sweepers, inventory checking units, or other suitable equipment, which mobile drive unit 20 may transport within inventory system 10 or other types of systems.
In operation, mobile drive unit 20 is capable of moving between points within a workspace associated with inventory system 10 and, when coupled to inventory holder 30, of transporting inventory holder 30 between locations within the workspace. Mobile drive unit 20 may determine the movement of mobile drive unit 20 autonomously and/or based on commands received by mobile drive unit 20. For example, in particular embodiments, mobile drive unit 20 may receive information that identifies destinations for mobile drive unit 20 from a management device of inventory system 10, from an operator of inventory system 10, or any other suitable party or device. Mobile drive unit 20 may receive the information through a wireless interface, over a wired connection, or using any other suitable components to communicate with an operator or management device of inventory system 10. Additionally, in particular embodiments, mobile drive unit 20 may use fixed objects, such as fiducial marks, located in the workspace as reference points to assist in navigation. In such embodiments, mobile drive unit 20 may be configured to detect fiducial marks and to determine the location of mobile drive unit 20 and/or measure its movement based on the detection of fiducial marks. In general, however, movement of mobile drive unit 20 may, depending on the configuration of mobile drive unit 20 and inventory system 10, be controlled, in whole or in part, by mobile drive unit 20, or any appropriate external devices or parties.
For the sake of simplicity, however, the remainder of this description assumes that mobile drive unit 20 wirelessly receives orders, data, instructions, commands, or information structured in any other appropriate form, referred to here as a “command” or “commands,” from a remote component of inventory system 10. These commands identify a particular inventory holder 30 to be moved by mobile drive unit 20 and/or a current location for that inventory holder 30, and a destination for that inventory holder 30. Mobile drive unit 20 then controls operation of motors, wheels, and/or other components of mobile drive unit 20 to move mobile drive unit 20 and/or inventory holder 30.
In response to receiving such a command, mobile drive unit 20 moves to a storage location identified by the command. Mobile drive unit 20 may then initiate a docking process with the identified inventory holder 30. Mobile drive unit 20 may dock with inventory holder 30 in any appropriate manner so that inventory holder 30 is coupled to and/or supported by mobile drive unit 20 when mobile drive unit 20 is docked with inventory holder 30. In particular embodiments, mobile drive unit 20 docks with inventory holder 30 by positioning itself beneath inventory holder 30 and raising a docking head of mobile drive unit 20 until the docking head lifts inventory holder 30 off the ground.
As discussed in greater detail with respect to
As a result of the docking process, mobile drive unit 20 may support none, some, or all of the weight of inventory holder 30. Additionally, in particular embodiments, one or more components of mobile drive unit 20 may grasp, connect to, interlock with, or otherwise interact with one or more components of inventory holder 30 to form a coupling between mobile drive unit 20 and inventory holder 30. As one example, in particular embodiments, docking head 202 may include one or more spines that fit within apertures of inventory holder 30 when mobile drive unit 20 docks with inventory holder 30, allowing mobile drive unit 20 to maneuver inventory holder 30 by applying force to inventory holder 30. As another example, in particular embodiments, docking head 202 may include a high-friction surface that abuts a high-friction surface of inventory holder 30 when mobile drive unit 20 is docked with inventory holder 30. In such embodiments, mobile drive unit 20 may utilize friction forces induced between the abutting surfaces to move and rotate inventory holder 30.
After docking with inventory holder 30, mobile drive unit 20 may move inventory holder 30 to a second location, such as an inventory station, where inventory items 40 may be removed from inventory holder 30 (e.g., to be packed for shipping), added to inventory holder 30 (e.g., to replenish the supply of inventory items 40 available in inventory system 10), counted, or otherwise processed. Mobile drive unit 20 may navigate between the first and second location using any appropriate techniques.
In particular embodiments, mobile drive unit 20 is capable of moving inventory holder 30 along a two-dimensional grid, combining forward and backward movement along straight-line segments with ninety-degree rotations and arcing paths to transport inventory holder 30 from the first location to the second location. Additionally, while moving forward or backwards, mobile drive unit 20 may also be capable of performing smaller rotational movements to make navigational corrections or otherwise adjust its heading. When mobile drive unit 20 rotates, mobile drive unit 20 may maintain the orientation of docking head 204. Techniques for achieving this are described in greater detail below with respect to
After mobile drive unit 20 arrives at the second location, mobile drive unit 20 may undock from inventory holder 30. Mobile drive unit 20 may undock from inventory holder 30 in any appropriate manner based on the configuration and characteristics of mobile drive unit 20. In particular embodiments, docking head 204 is attached to an elevating shaft 202 that is raised and lowered in response to the rotation of some or all of the remainder of mobile drive unit 20. In such embodiments, mobile drive unit 20 may lower docking head 204 by rotating elevating shaft 202 relative to the remainder of mobile drive unit 20. Moreover, in particular embodiments, mobile drive unit 20 may raise docking head 204 by rotating the relevant portion of mobile drive unit 20 in a first direction relative to elevating shaft 202 and lower docking head 204 by rotating the relevant portion of mobile drive unit 20 in a second direction relative to elevating shaft 202.
Once mobile drive unit 20 has undocked from inventory holder 30, mobile drive unit 20 may move away from inventory holder 30. Mobile drive unit 20 may then begin performing other tasks within inventory system 10. As a result, in particular embodiments, mobile drive unit 20 is capable of transporting any of a plurality of inventory holders 30 between locations within inventory system 10 for purposes of fulfilling orders or completing other tasks involving inventory items 40.
Because mobile drive unit 20, in particular embodiments, is able to dock and undock from inventory holder 30 by rotating elevating shaft 202 relative to mobile drive unit 20, particular embodiments of mobile drive unit 20 may be able to dock and undock from inventory holders 30 in less time and using less power. Furthermore, configuring mobile drive unit 20 to utilize the described rotation movement for docking and undocking with inventory holder 30 may make it possible to reduce the number of mechanical parts included in mobile drive unit 20, as discussed further below. In addition, by maintaining the orientation of inventory holder 30 while rotating, mobile drive unit 20 may maneuver inventory holder 30 without inventory holder 30 colliding with other nearby inventory holders. As a result, particular embodiments of mobile drive unit 20 may provide multiple benefits. Alternative embodiments, however, may provide some, none, or all of these benefits.
Housing 200 encloses and/or connects to one or more of drive module 206, rotation module 208, load control module 210, and processing module 212. Alternatively, housing 200 may represent all or a portion of the physical components of any one or more of drive module 206, rotation module 208, load control module 210, and processing module 212. Housing 200 may comprise any appropriate material. In particular embodiments, housing represents a metal or plastic casing that encloses components of drive module 206, rotation module 208, load control module 210, and processing module 212, and includes a cavity that holds elevating shaft 202.
Docking head 204 couples mobile drive unit 20 to inventory holder 30 and/or supports inventory holder 30 when mobile drive unit 20 is docked to inventory holder 30. Docking head 204 may additionally allow mobile drive unit 20a to maneuver inventory holder 30, such as by lifting inventory holder 30, propelling inventory holder 30, rotating inventory holder 30, and/or moving inventory holder 30 in any other appropriate manner. Docking head 204 may also include any appropriate combination of components, such as ribs, spikes, and/or corrugations, to facilitate such manipulation of inventory holder 30. For example, in particular embodiments, docking head 204 may include a high-friction portion that abuts a portion of inventory holder 30 while mobile drive unit 20a is docked to inventory holder 30. In such embodiments, frictional forces created between the high-friction portion of docking head 204 and a surface of inventory holder 30 may induce translational and rotational movement in inventory holder 30 when docking head 204 moves and rotates, respectively. As a result, mobile drive unit 20a may be able to manipulate inventory holder 30 by moving or rotating docking head 204, either independently or as a part of the movement of mobile drive unit 20a as a whole.
Elevating shaft 202 attaches docking head 204 to the remainder of mobile drive unit 20a and is capable of raising and/or lowering docking head 204. Elevating shaft 202 may include or represent any element capable of being raised or lowered as a result of rotation induced in elevating shaft 202 or portions of mobile drive unit 20a in contact with elevating shaft 202. In particular embodiments, elevating shaft 202 may represent a shaft or other element that, when rotated, rises as a result of threading on its surface and/or as the result of bearings or other rolling elements following a sloped track within the cavity that holds elevating shaft 202. As one example, elevating shaft 202 may represent a threaded shaft that rests in a threaded cavity within housing 200. As a result, the threading of the shaft and cavity causes elevating shaft 202 to move upwards or downwards when housing 200 is rotated relative to the elevating shaft 202. In general, however, elevating shaft 202 may represent any appropriate component or components configured to raise or lower as a result of the rotation of housing 200 and/or elevating shaft 202.
Drive module 206 (shown in
Rotation module 208 (shown in
Additionally, in particular embodiments, rotation module 208 may include or represent some or all of the components of drive module 206. This may reduce the number of components in mobile drive unit 20a, making mobile drive unit 20a less expensive to manufacture. For example, as shown in
Load control module 210 controls the orientation of an inventory holder 30 to which mobile drive unit 20a is docked. In particular embodiments, load control module 210 may control the orientation of the relevant inventory holder 30 by adjusting or maintaining the orientation of elevating shaft 202 and/or docking head 204. Load control module 210 may include any appropriate components, based on the configuration of mobile drive unit 20a and inventory holder 30, for adjusting the orientation of elevating shaft 202, docking head 204, and/or other appropriate components of mobile drive unit 20a. Load control module 210 may adjust the orientation of docking head 204 to rotate a docked inventory holder 30, for example, to present a particular face of the inventory holder 30 to a user. Additionally, as described in greater detail below, load control module 210 may maintain the orientation of docking head 204 while the remainder of mobile drive unit 20 is rotating to prevent any rotation in the docked inventory holder 30.
For example, in the illustrated embodiment, load control module 210 includes an actuator 222c capable of applying a torque to elevating shaft 202. As a result, in particular embodiments, actuator 222c may be capable of inducing a rotation in elevating shaft 202 to change the orientation of inventory holder 30. Additionally, actuator 222c may also be capable of applying a torque to elevating shaft 202 that counteracts a torque induced by the rotation of the remainder of mobile drive unit 20a. Thus, in particular embodiments, load control module 210 may be capable of maintaining an orientation of inventory holder 30 while mobile drive unit 20a is rotating. This may allow mobile drive unit 20a to rotate (e.g., to dock with inventory holder 30 or to change its direction of travel) without rotating the inventory holder 30 to which it is docked. Additionally, in alternative embodiments, load control module 210 may represent, in part, a portion of rotation module 208, such as an actuator that is responsible for driving motorized wheels 224 and that is coupled to load control module 210 through a clutch mechanism. When the clutch is engaged, the actuator can provide a counter-rotational torque to elevating shaft 202 that maintains the orientation of elevating shaft 202 and/or docking head 204 despite any rotation in the remainder of mobile drive unit 20.
Processing module 212 monitors and/or controls operation of drive module 206, rotation module 208, and load control module 210. Processing module 212 may also receive information from sensors and adjust the operation of drive module 206, rotation module 208, load control module 210, and/or other components of mobile drive unit 20a based on this information. More specifically, processing module 212 may generate control signals and transmit these control signals to the various components of mobile drive unit 20a to initiate any or all of their described functionality. Additionally, in particular embodiments, mobile drive unit 20a may be configured to communicate with a management device of inventory system 10, and processing module 212 may receive commands transmitted to mobile drive unit 20a and communicate information back to the management device utilizing appropriate communication components of mobile drive unit 20a.
Processing module 212 may include any appropriate hardware and/or software suitable to provide the described functionality. In particular embodiments, processing module 212 includes a general-purpose microprocessor programmed to provide the described functionality. Additionally, processing module 212 may include all or portions of drive module 206, rotation module 208, and/or load control module 210, and/or share components with any of these elements of mobile drive unit 20a.
Thus, overall, particular embodiments of mobile drive unit 20a may provide a number of operational benefits. For example, the rotation movement used by particular embodiments of mobile drive unit 20a to dock with inventory holder 30 may reduce the time and energy utilized in docking. Additionally, in particular embodiments, load control module 210 may allow portions of mobile drive unit 20a to rotate (e.g., for purposes of docking or turning) without changing the orientation of an inventory holder 30 with which mobile drive unit 20a is docked. As a result, particular embodiments of mobile drive unit 20a may reduce or eliminate collisions between the docked inventory holder 30 and other nearby inventory holders while mobile drive unit 20a is rotating. Nonetheless, while mobile drive unit 20a may provide such benefits, particular embodiments may provide some, none, or all such benefits.
More specifically, actuator 222a applies a torque (shown in
In particular embodiments, processing module 212 may be responsible for monitoring and controlling the operation of the various actuators 222 to insure that the torque applied by actuator 222c substantially counteracts the torque applied by actuators 222a and 222b so that docking head 204 experiences no substantial net rotational velocity. As a result, the torque applied by each of the various actuators 222a-c may be dynamically determined during operation. In alternative embodiments, actuators 222a-c may each be configured to provide a torque of a predetermined magnitude chosen so that, overall, the various torques applied by actuators 222a-c produce no rotation in docking head 204.
Load control module 310, like load control module 210 illustrated in
As shown in
As shown in
More specifically, actuator 222a applies a torque (shown in
Meanwhile, at an appropriate time before or after this process is initiated, processing module 212 or another element of mobile drive unit 20b activates braking element 312. Mobile drive unit 20b is illustrated in
As noted above, elevating shaft 202 may represent or incorporate any components suitable to lift docking head 204 in response to rotation of all or a portion of housing 200 relative to elevating shaft 202.
Races 402 comprise pathways in which bearings, rollers, or other rolling or sliding contact elements can move. In particular embodiments, mobile drive unit 20 includes both an inner race 402a and an outer race 402b. As shown in
Bearings 404 may represent any form of bearings, rollers, or other components capable of rolling along or within races 402 and, in particular embodiments, may abut or contact either or both of races 402 while rolling. In particular embodiments, bearings 404 may be lubricated or made of a low-friction material to facilitate movement along races 402. In general, however, bearings 404 may be comprised of any appropriate material.
Although
Recirculating path 406 comprises a pathway through mobile drive unit 20 that connects one endpoint of outer race 402b with the other endpoint of outer race 402b. Recirculating path 406 is sized and shaped to allow bearings 404 to pass between the two endpoints. Although the embodiment of mobile drive unit 20 shown in
In operation, inner race 402a and outer race 402b rotate relative to one another when mobile drive unit 20 rotates housing 200. As a result of the slope of one or both races 402, this rotation also raises or lowers elevating shaft 202. Bearings 404 situated between inner race 402a and outer race 402b may reduce friction forces that inhibit the relative rotation of elevating shaft 202 and housing 200. Consequently, the inclusion of bearings 404 may reduce the amount of torque required for mobile drive unit 20 to raise docking head 204 and may reduce the amount of energy and/or time expended in raising or lowering loads supported by docking head 204.
Additionally, in particular embodiments, mobile drive unit 20 may also include recirculating path 206 connecting one endpoint of outer race 402b with the other endpoint of outer race 402b. The relative rotation of inner race 402a and outer race 402b may cause bearings 404 to move along races 402. When the rotation of races 402 carries a particular bearing 404 beyond one of the endpoints of outer race 402b, the movement of other bearings along races 402 may force the relevant bearing 404 into and through recirculating path 406. As races 402 continue to rotate relative to one another, the relevant bearing 404 is eventually circulated back to the other endpoint of outer race 402b where that bearing 404 re-enters outer race 402b.
Similar to races 402 in
Rollers 504 may represent any appropriate components of any suitable shape attached to either elevating shaft 202 or housing 200 and capable of rolling along race 502. Rollers 504 may be attached to elevating shaft 202 or to housing 200 in any suitable manner.
In operation, elevating shaft 202 rotates relative to race 502 when mobile drive unit 20 rotates housing 200. As a result of this rotation, rollers 504 roll along race 502. Because race 502 is sloped, rollers 504 rise or fall as they traverse race 502. Furthermore, because rollers 504 are pinned to elevating shaft 202 this also causes elevating shaft 202 to rise or fall. In particular embodiments, use of this rolling action to raise and lower elevating shaft 202 may result in lower friction forces than in embodiments of mobile drive unit 20 that utilize a conventional screw. Consequently, the inclusion of rollers 504 may also reduce the amount of torque required for mobile drive unit 20 to raise docking head 204 and may reduce the amount of energy and/or time expended in raising or lowering loads supported by docking head 204.
In this example, operation begins with mobile drive unit 20 positioning itself beneath a selected inventory holder at a first location at step 600. Once mobile drive unit 20 positions itself beneath the selected inventory holder 30, mobile drive unit 20 may begin a docking process. As part of this process, mobile drive unit 20 may raise docking head 204 at step 610. In particular embodiments, mobile drive unit 20 raises docking head 204 by rotating housing 200 in a first direction relative to elevating shaft 202. Mobile drive unit 20 may then execute any other appropriate steps to complete the docking process based on the configuration of mobile drive unit 20 and the selected inventory holder 30. As a result of the docking process, mobile drive unit 20 is coupled to and/or supports the inventory holder 30.
Mobile drive unit 20 may then move the selected inventory holder 30 to a destination where inventory items 40 may be picked from inventory holder 30, replenished, counted, or otherwise processed and/or where inventory holder 30 may be stored until used by inventory system. In the described example, mobile drive unit 20 is capable of moving in a forward and backward direction and rotating. Thus, mobile drive unit 20 moves to the destination by performing an appropriate combination of straight-line movements and rotations. Furthermore, while rotating to change its direction of travel, mobile drive unit 20 may maintain the orientation of the selected inventory holder 30 to prevent the selected inventory holder 30 from colliding with other objects or components in inventory system 10.
An example of this movement is shown in
When mobile drive unit 20 arrives at the destination, mobile drive unit 20 may rotate inventory holder 30 to present a particular face of inventory holder 30 to an operator of inventory system 10, for example, to allow the operator to select an inventory holder 30 from a bin accessible through the presented face. As a result, mobile drive unit 20 may rotate both mobile drive unit 20 and inventory holder 30. This is illustrated in
More specifically, mobile drive unit 20 applies a torque to housing 200 at step 660 using the first actuator 222. While applying this torque, mobile drive unit 20 does not apply any torque to elevating shaft 202 to counteract the torque applied to housing 200. As a result, the applied torque rotates both mobile drive unit 20 and inventory holder 30 at step 670.
After any appropriate actions are taken by the operator with respect to the selected inventory holder 30, mobile drive unit 20 may move the selected inventory holder 30 to a storage location or another final destination at step 680. In particular embodiments, mobile drive unit 20 then lowers docking head 204 by rotating housing 200 in a second direction relative to elevating shaft 202 at step 690. Mobile drive unit 20 may then execute any other appropriate steps to complete the undocking process based on the configuration of mobile drive unit 20 and the selected inventory holder 30. As a result of this undocking process, mobile drive unit 20 is no longer coupled to or supports the inventory holder 30. Mobile drive unit 20 may then move away from the selected inventory holder 30, at step 700, and begin completing other tasks within inventory system 10 or elsewhere. Operation of mobile drive unit 20 with respect to transporting the selected inventory holder 30 may then end as shown in
Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformations, and modifications as fall within the scope of the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5075853 | Luke, Jr. | Dec 1991 | A |
| 6705815 | Bennett et al. | Mar 2004 | B1 |
| Number | Date | Country |
|---|---|---|
| 0 102 706 | Mar 1984 | EP |
| 0 192 402 | Aug 1986 | EP |
| 2005187120 | Jul 2005 | JP |
| WO 2006044108 | Apr 2006 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20080166217 A1 | Jul 2008 | US |
