Patent Publication Number: US-2007104563-A1

Title: Materials handling system

Description:
The present invention concerns a system for transporting loads within a warehouse, particularly but not exclusively air cargo loads to be made up for transport on aircraft. Such loads are commonly made up in warehouses before being loaded onto a truck for transport to the aircraft where it is loaded into the hold. The system is equally applicable to the reverse operation of receiving loads from aircraft and breaking them down before they are forwarded to their next destination.  
      The loads in question are commonly of the order of 5-8 metric tonnes. Loads comprising a palette (or cargo platform) or air cargo container and cargo are made up in the warehouse at a static workstation on a palette or in a container. The workstation commonly communicates with a roller bed conveyor whereby the load can be transported from the workstation to a truck dock. The truck dock provides a lift whereby the load can be elevated to the height of the truck bed of a truck parked in a truck parking bay. The truck dock also provides a roller conveyor that allows the load to be displaced laterally in the truck dock to align it accurately with the truck bed before being discharged onto the truck bed. A truck dock is conventionally a large fixed structure requiring significant civil engineering works to install and is consequently expensive and permanently obstructs an access to the warehouse.  
      In some warehouses the roller conveyor may be replaced by an elevating travelling vehicle (ETV) such as the Combi Cargo Manager™ able to support and transport the load around warehouse passageways. These provide greater versatility than the fixed roller conveyors but the large loads require additional manpower to transfer from idle roller conveyors, a qualified operator is required and their size necessarily requires large passageways.  
      It is also often necessary to provide the fixed workstation with an elevator so that the load can be raised from floor height to that of the roller table which conventionally operates at a roller table plane of 508 mm. As with the truck dock this is usually achieved using a scissorlift, which requires civil works upon installation and permanently occupies floor space. The height at which conventional roller tables and workstations operate also imposes limitations on the use of warehouse space due to safety and other constraints on the maximum height of the loads which can be built up.  
      It is generally desirable to reduce the manpower required for materials handling systems of this type, to reduce the floor space required and to enhance the flexibility of such systems.  
      It is an object of the present invention to provide a system which alleviates at least some of the aforementioned disadvantages of the prior art.  
      Accordingly there is provided a materials handling system comprising, a mobile work station and a self propelled tug, said mobile workstation having a roller conveyor supported on a workstation chassis, said chassis having castors engageable with a floor and a tow bar extending from at least one of a side or end of said chassis,  
      said tug having a body mounted on at least three ground engageable wheels and a tow bar hitch adapted to couple with said extended tow bar such that the rotary axis of at least one of the tug wheels is at least as close to the workstation chassis as the tow bar.  
      According to a second aspect of the present invention there is provided a materials handling system comprising a mobile work station and a self propelled tug, said mobile workstation having a roller conveyor supported on a workstation chassis, said chassis having castors engageable with a floor,  
      said roller conveyor having a transmission whereby power may be transmitted from a drive coupling to at least one of the rollers of the conveyor, said drive coupling being disposed on an end or side of the mobile workstation to engage with a complementary drive coupling provided on the tug so that when coupled to the tug the roller conveyor can be powered to power a load on to or off of the workstation.  
      According to a third aspect of the present invention there is provided a materials handling system comprising a mobile work station and a self propelled tug, said mobile workstation having a roller conveyor supported on a workstation chassis, said chassis having castors engageable with a floor, said chassis comprising elongate side members connected at each end by laterally extending end members and a plurality of laterally extending strengthening beams extending between the side members at longitudinally spaced intervals which support an overlying roller conveyor,  
      a plurality of floor engaging castors disposed adjacent one end of the workstation and arranged to rotate about a common axis such that only a segment of the roller of each castor projects clear of the end and side members to engage the floor whereby the workstation can support loads of between 5 and 9 metric tonnes but presents a roller conveyor plane of between 180 mm and 230 mm.  
      According to a fourth aspect of the present invention there is provided a truck dock comprising a chassis supporting an elevator, said elevator being adapted to receive a mobile workstation and elevate the workstation between floor height and the height of a truck bed, said truck dock chassis being mounted on floor engaging wheels which in normal use, when situated in a warehouse door, allow the truck dock to be moved laterally to align a load with a truck bed and also allow the truck dock to be moved away from the warehouse door.  
    
    
      A materials handling system constructed in accordance with the present invention will now be described, by way of example only, with reference to the accompanying illustrative drawings, in which:  
       FIG. 1A  is a plan view of a first tug embodiment for use in the system,  
       FIG. 1B  is a perspective view from above and to one side of the tug in  FIG. 1A ,  
       FIG. 1C  is a perspective view from below and to one side of the tug in  FIG. 1A ,  
       FIG. 2A  is a plan view of a second embodiment of a tug for use in the system,  
       FIG. 2B  is a perspective view from above and to one side of the tug in  FIG. 2A ,  
       FIG. 2C  is a perspective view from below and to one side of the tug in  FIG. 2A ,  
       FIG. 3A  is a plan view of a first embodiment of a mobile workstation,  
       FIG. 3B  is a perspective view of the first embodiment of the workstation showing hidden detail,  
       FIG. 4A  is a plan view of a second embodiment of a mobile workstation,  
       FIG. 4B  is a perspective view of the second embodiment of the mobile workstation showing hidden detail,  
       FIG. 5A  is a plan view of a third embodiment of a mobile workstation,  
       FIG. 5B  is a perspective view of the third embodiment of the mobile workstation showing hidden detail,  
       FIG. 6A  is a plan view of a truck dock,  
       FIG. 6B  is a perspective view of the truck dock showing hidden detail,  
       FIG. 7A  is a plan view of a docking station and  
       FIG. 7B  is a perspective view of a docking station.  
    
    
      Referring to the drawings,  FIGS. 1A , B and C show views of a first embodiment of a self powered tug which is intended to be guided by a pedestrian operator.  FIGS. 2A , B and C show views of a self powered tug generally similar to that in  FIG. 1  but having a seat, saddle or deck (S) for the operator to ride on. The tug has a chassis  1  with a front section  1   a  which supports a pair of front wheels  2   a  and  2   b  and a rear section  1   b  which supports a motor for propulsion (not shown). The rear section also mounts a rear propulsion wheel  2   c  to be driven by the motor, which serves to steer the tug according to the position of a tiller  3 . The rear section also accommodates the power supply for the tug which will ordinarily be batteries to power an electric motor. The front section  1   a  has wings  4   a  and  4   b  extending laterally one each to either side of the rear section  1   b . The wings  4   a  and  4   b  also extend forwards of an intermediate part  4   c  of the front section so that the front wheels  2   a  and  2   b  can be spaced well away from the centre line of the tug for stability. The intermediate section  4   c  incorporates a tow hitch comprising a pair of laterally spaced hooks  5 . The front wheels  2   a  and  2   b  are each mounted to rotate about an axis further from the rear section  1   b  of the tug than the axis of engagement of the hooks  5 .  
       FIGS. 3, 4  and  5  each show variants of a mobile workstation. Each workstation comprises a rigid chassis formed primarily from a pair of longitudinally extending side members  6  and a pair of laterally extending end members  7  all of “U” section or box section and secured together to form a rigid rectangular structure. Additional strengthening beams  8  extend laterally between the side members at longitudinally spaced intervals.  
      The top of the work station is an arrangement of three roller conveyors  9  each extending longitudinally from the front of the workstation (to the left in  FIG. 3B ) to the rear (to the right in  FIG. 3B ). Each of the roller conveyors is separated by a longitudinally extending walkway  10 . Each roller conveyor  9  is powered by a pair of belt drive transmissions  11  which via a series of coupled belts, convey power to drive the rollers  12  of the roller conveyer to allow a load to be drawn onto or off of the workstation. Each of the transmissions is coupled one each to each of a pair of laterally spaced friction rollers  13  mounted in the front end member  7  so that the rim of each friction roller  13  projects from the side of the member to form a drive coupling. A similar pair of friction rollers (not shown) may be provided in the rear member  7 .  
      A laterally extending tow bar  14  is mounted on longitudinally extending guide rails  15  formed into the chassis. A recess is provided in the member  7  so that the tow bar can be set flush with the side of the chassis in one position and drawn out as illustrated in  FIGS. 4B and 5B  to an extended position. It will be appreciated that the mounting of the tow bar in the chassis is rigid to the extent required to prevent articulation or flexing in the vertical direction.  
      On the underside of the chassis adjacent the rear member  7  are disposed a plurality of ground engaging castors  16  each mounted to rotate on a common laterally extending axis. It is desirable that a large number of castors are mounted on the axis in order to disperse the load applied to the floor, and to this end sixteen castors have been used in the example of  FIG. 3B . The number of castors used will vary according to the duty required. Using a large number of castors also has the benefit of allowing the roller table plane height to be kept to a minimum.  
      A pair of ground engageable feet  17  are mounted one each at each front corner of the chassis to provide ground engageable elements. When at rest the ground engaging feet support and brake the workstation. Palette stops  18  are also provided at the front and rear of the workstation.  
      The variant of the workstation shown in  FIG. 4  has the tow bar extensible from the side member  8  with the castors  16  and feet appropriately repositioned. The combination of the variants of  FIGS. 3A  and  3 B is contemplated with a workstation having tow bars extensible from each of the front and the side and arrays of castors positioned on axis at the opposite end and side of the workstation. These variants present advantages in maneuvering the workstation in some confined warehouse environments.  
      The variant shown in  FIG. 5  is intended for smaller loads and so does not include a powered roller conveyor.  
      The tug is coupled to the workstation by extending the tow bar  14  and then driving the tug up to the front end of the workstation so that the tow bar is received into the recess formed between the sections  4  to overly the axis of the hooks  5 . The hooks  5  are then raised via a raising mechanism such as hydraulics or worm drives (not shown) provided in the tug to engage and lift the tow bar so that the feet  17  are raised clear of the ground. It is important that the location of the tow bar axis is closer to the rear section  1   b  of the tug then the front wheel axis, and hence when coupled to the workstation the tow bar axis and the weight of the workstation is further from the workstation than the front wheels of the tug so that the weight of the tug can be safely supported by the tug. Further the tow bar is laterally between the front wheels  2   a ,  2   b  so that the load is laterally stable. This permits the tug workstation combination to tow large loads of the order of 5 to 9 metric tonnes. The workstation can now be towed around the warehouse as required. It is also beneficial that the tug requires only three wheels.  
      The hooks  5  are shaped with an inclined surface so that when raised in engagement with the tow bar  14  the tow bar and hence the workstation are urged towards each other. As can readily be seen in  FIG. 1B  the tug has a pair of friction drive rollers  18  mounted one each in the front of each wing section  4   a  and  4   b  so that when the workstation is coupled to the tug the friction rollers  13  bear against the friction rollers  18 . Friction rollers  18  are coupled via a transmission (not shown) to the tug&#39;s motor drive, so that the tug can provide power to drive the roller conveyor of the workstation.  
      Because the workstation has a low profile it can be used as a floor standing workstation when disengaged from the tug. Alternatively it may be used in combination with an elevating station. Loads such as pallets or containers can conveniently be drawn onto the workstation from a roller table by use of the powered roller conveyor either at an elevating workstation or at a truck dock.  
      A truck dock in accordance with the invention is shown in  FIGS. 6A and 6B . A truck dock is conventionally mounted in a door of a warehouse facility and provides an interface between trucks with delivery loads to the warehouse and the conveyor workstation and other conveyor storage facilities in the warehouse. They are necessary because the elevation of any truck bed varies according to the nature of the truck and to a degree how it is loaded. Apart from vertical alignment (elevation) of the load it is also commonly necessary to adjust the lateral alignment of the load going onto or off of a truck, which facility is conventionally provided for by a roller conveyor on the truck dock. Conventional truck docks require substantial civil works which permanently obstruct the warehouse door. The truck dock shown in  FIG. 6  is used in combination with the previously described tug and workstation.  
      The truck dock in  FIG. 6  consists of a “U” shaped chassis having two similar substantially parallel side members  20   a  and  20   b  connected together by an end member  21 . The two side members  20  are each mounted on pairs of floor engaging wheels  22   a  and  22   b  respectively. The end member  21  is disposed towards the truck end of the truck dock and ensures that the structure is sufficiently rigid to keep four elevator towers  23  upright. The elevator towers  23  support an elevator assembly comprising a pair of longitudinally extending elevator parts  24  extending in opposition to each other adjacent the side members  20  to leave a clear floor space large enough to accommodate a workstation such as that described above between them (the elevator bay). Each of the elevator parts  24  includes a projecting part provided by a flange  25  which projects parallel to and adjacent the floor and may be capable of resting on the floor so that the side members  6  of a workstation received into the elevator bay overlie the flanges.  
      The truck end of each elevator part  24  is connected by a narrow roller conveyor  26  with a motor (not shown) provided to power the roller conveyor  26 . A pair of friction rollers  27  project from the workstation bay side of the roller conveyor  26  and are disposed to couple with the friction rollers  13  provided on the rear end of the workstation. Means is provided to urge the friction rollers of the workstation and truck dock together and may comprise powered clamps (not shown) mounted on the end of the parts  24  to engage the front corners of a workstation.  
      A track  28  is mounted onto or into the floor and is engaged by a guide runner  29  mounted onto the chassis  20 .  
      In use with a workstation and tug as described above the tug may tow and/or push the workstation into the workstation bay with the elevator assembly lowered. The urging means are actuated on the truck dock to engage the front corners of the workstation chassis and urge the friction rollers to couple. The tug will disengage the hooks  5  and can be driven away for other tasks. The elevator assembly is then raised via the action of hydraulic or electric motors during which operation a self levelling assembly ensures that the elevator assembly remains horizontal. The operator controls this aspect of the operation from one of two control consoles  30  mounted one each towards each end of an operator platform  31  cantilever supported off the chassis  20  to one side of the chassis. When the workstation is elevated to the height of the truck bed of a truck parked on the truck side of the truck dock, the operator checks and adjusts the lateral alignment of the load with the truck bed. If adjustment is required, the wheels  22  are powered and guided to move the entire truck dock laterally to the left or right as required until alignment is achieved.  
      When alignment is achieved the operator actuates a roller conveyor drive in the lift assembly which simultaneously drives the roller conveyor  26  and via the friction roller coupling  27  with friction rollers  13  the roller conveyor of the workstation so that the load on the workstation is urged towards the truck bed. It will be apparent that this operation can be reversed when taking loads into the warehouse.  
      In the event that the door in which the truck bed is located is required to provide access to the warehouse by large machinery, the truck dock can readily be displaced out of the way by virtue of the wheels  22  which are preferably powered by an onboard motor.  
       FIG. 7  show a docking station for use in combination with the workstation and tug described above to provide an interface with conventional roller conveyors from the 200 mm workstation roller lane height to the 508 mm roller plane height which is conventional. The docking station comprises a “U” shaped floor mounted chassis, which will commonly be bolted to the floor. The chassis has a pair of longitudinally extending “U” section parallel arms  32 . Each of the arms  32  accommodates a parallelogram lifting mechanism  33  which engages an overlying “U” section elevating member  34 . The elevating member  34  envelopes the associated arm  32  so that a shelf part  35  projects from the lower edge of the elevating member  34  adjacent the floor. The rear ends of the parallel arms  32  are connected via a lateral chassis member  36  which is hollow to accommodate the motors to drive the parallelogram lift. The lateral member  36  also supports a powered roller conveyor  37  at a height of 508 mm which is intended to communicate with conventional 508 mm roller conveyors. In use a low profile 200 mm workstation such as that described above can be driven into the workstation bay formed between the opposing elevating members  34  so that the side members  7  of the workstation overly the shelves  35 . The front end member of the workstation will abut stops  38  formed on the shelves  35  before the tug will release the workstation. The parallelogram elevator is then actuated to raise the workstation. An advantage of the parallelogram elevator is that it not only raises the workstation but also urges the drive couplings  13  on the front of the workstation into engagement with corresponding drive couplings (not shown) formed on the opposing edge of the roller conveyor  37 . Thus at the elevated height the roller conveyors  37  and  9  can be powered to drive a load on or off of the workstation.  
       FIG. 7C  shows a variant of the docking station for use with the workstation of  FIG. 4A . The variant docking station has roller tables  37   a  mounted on the elevating members  34  so that the docking station could be installed between two lengths of conventional roller conveyor.