Abstract:
A shuttle for transferring cargo between a storage area and a manufacturing area has a cargo platform for receiving the cargo along a horizontal transfer path. The shuttle has two telescoping tables, the first controlled by a single servomotor drive mechanism, while the second table is a slave to the first table. When the drive mechanism powered by the servomotor extends the first table, a second passive drive mechanism extends the second table from the first table an equal amount in the same direction. The tables are reversible, and can extend in either longitudinal direction of the shuttle in order to retrieve or replace cargo onto shelves located on either side of the shuttle. Sensors on the shuttle sense the presence of cargo on a shelf, the position of the cargo on the cargo platform, and the location of the tables relative to the shuttle base.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to an apparatus for automatically transferring a tote between shelving units, and more particularly to a tote shuttle portion of a crane for automatically transferring a tote between warehouse shelving and another transport medium such as a conveyor.  
         BACKGROUND  
         [0002]    The use of vertical storage devices such as shelving in a warehouse environment is only helpful when one can track what is stored on the shelving and retrieve the stored material in an efficient manner. Different types of shelving storage and retrieval mechanisms have been developed to place cargo onto shelves and to retrieve cargo from a predetermined shelf.  
           [0003]    One type of transfer apparatus is known as a running fork device. This device utilizes forks which lift the cargo container up from the shelf and moves the cargo away from its resting shelf location. Operation of this type of device is similar to a fork-lift device. The running fork device can include devices that grip opposing sides of the container and pull the container from the resting shelf location.  
           [0004]    In another type running fork device, a hook is integral with the transfer apparatus and is used to hook onto a loop on the container. In this manner, the hook is used to catch the container and pull the container from the resting shelf location.  
           [0005]    In fork-lift type devices, the containers must rest on shelving such that a space remains below the container for the forks to enter below the container and above the shelf. Leaving this additional space below the container reduces the amount of available vertical storage area. See for example U.S. Pat. No. 5,207,555.  
           [0006]    Side-grip type devices require clearance on the sides of the container, thereby reducing the amount of horizontal storage area on the shelving.  
           [0007]    Hook and loop type devices are limited to containers having compatible loops, limiting their use and increasing cost for custom containers.  
           [0008]    Another device for transferring containers from warehouse shelving involves the use of a cargo platform. Integrated with a crane-type device, the cargo platform extends from a base, slides below the container and frictionally engages the underside of the container. The cargo platform is driven by one motor in one direction, and a second motor in the opposite direction. Typically, the cargo platform employs rack and pinion gears to extend the platform from the neutral, or center position of the base. Additionally, the platform is supported and guided with cam following bearings riding in custom-machined slots. Control of the cargo platform is typically through the use of multiple roller switches that often require adjustment due to wear. See for example U.S. Pat. No. 5, 839,872.  
           [0009]    However, the prior art devices are heavy, use complicated combinations of parts, are costly to fabricate and maintain, and are unable to perform precision handling of the actual cargo.  
           [0010]    Consequently, there is a need for an apparatus and method for transferring containers from warehouse shelving having varying widths using a device that uses fewer parts, is lighter, lest costly to fabricate and maintain, and easier to adjust for precision handling.  
         SUMMARY OF THE INVENTION  
         [0011]    An object of the present invention is an improved apparatus for the transfer of cargo or totes containing cargo.  
           [0012]    Another object of the present invention is an improved apparatus for the transfer of cargo or totes containing cargo from a rack storage system.  
           [0013]    The present invention is directed to a cargo transfer apparatus, or shuttle. The shuttle is used in an automated process buffer for the storage and retrieval of totes or containers from a matrix of shelf locations. The shuttle has a rigid cargo platform that can extend towards one side or the opposing side. The ability to extend in either diametrically opposite direction allows for retrieval of totes stored on either side of the shuttle centerline. The shuttle is moved within the automated process buffer by a crane.  
           [0014]    The shuttle consists of a rigid frame and mount system that supports two tables that telescope out from the frame in either of the two opposing directions using a single motor and multiple chain drive system. The top table is fitted with a flat tooling plate that the payload sits directly upon.  
           [0015]    Totes are transferred from the shelf to the top table by first telescopically extending the top table and the middle table from the frame assembly towards the shelf. The top table, positioned parallel and beneath the tote, is extended into the shelf matrix and under the tote. The shuttle is moved slightly upward, thereby moving the top table upward and lifting the tote from the shelf upon which the tote was resting. The top table frictionally engages the tote. Retraction of the middle table and the top table withdraws the tote from the shelf matrix for transport to another location, friction between the bottom of the tote and the top table allows the tote to maintain contact with the top table as the tote is withdrawn from the shelf matrix. Lifting the tote eliminates the friction between the tote bottom and the shelf that would resist the tote from being withdrawn from the shelf matrix.  
           [0016]    When a tote is returned from the shuttle to the shelf matrix, the process is reversed, whereby the shuttle is positioned such that when the top table is telescopically extended, the bottom of the tote is above the resting position on the shelf. When the top table is lowered, the tote rests on the shelf matrix, contact with the top table is terminated, and the shuttle can be retracted and withdrawn without the tote.  
           [0017]    The shuttle uses one motor to extend the tables in either of the two opposing directions, using a single chain and sprocket drive system. “V” bearings and matching hardened rails are used to support and guide the top table.  
           [0018]    Control of the shuttle movements is performed with the use of a servomotor, allowing adjustments to be made with software. In this manner, precise adjustments can be made, and results in “set and forget” adjustments.  
           [0019]    Sensors are variously located throughout the shuttle. The middle table has a home sensor and a set of extend sensors. The home sensor defines where the neutral or home position is. The home position is when the top table, and by default the middle table, are approximately centered in the frame. The extend sensors are positioned such that when neither sensor is tripped, the top table is centered. As the top table moves in one direction or the other, the corresponding extend sensor will be tripped. This information, when input to the control system, determines which direction the tables must be driven to return them to the neutral position. These sensors can also be used as interlock to the other axes of motion. For example, if the shuttle is extending in either direction or becomes disabled in an extended position, all other axes of motion are disabled. That is, the shuttle and/or the crane will be prevented from moving in a manner that could damage the shuttle, the tote, the cargo or the shelving by moving up, down, towards or away from the shelving.  
           [0020]    The shuttle also uses sensors for tote detection. For example, a diffuse sensor located at each end of the shuttle verifies tote presence or absence in the shelf matrix being serviced. This sensor first scans the position where a tote is expected, and the information is sent to the control system.  
           [0021]    Movement of a tote can occur for various reasons, including, but not limited too, delivery of the tote and cargo to another manufacturing location, intermediate storage of the cargo between manufacturing or shipping processes, and consolidation of the cargo.  
           [0022]    It will be apparent that the shuttle of the present invention is adapted to be incorporated in a cargo transfer unit, also known as a transporter or crane, that is movable along racks of shelving.  
           [0023]    These and other features and advantages of this invention are described in or are apparent from the following detailed description of the preferred embodiments.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The preferred embodiments of this invention will be described in detail, with reference to the following figures, wherein:  
         [0025]    [0025]FIG. 1 is a perspective view of a tote shuttle of this invention in an extended position;  
         [0026]    [0026]FIG. 2 is an exploded perspective view of the shuttle detailing the tables, rails and bearings;  
         [0027]    [0027]FIG. 2A is a close-up perspective view of a bearing and rail;  
         [0028]    [0028]FIG. 3 is a partially exploded perspective view of the main drive;  
         [0029]    [0029]FIG. 4 is an exploded perspective view of the secondary drive;  
         [0030]    [0030]FIG. 5 is a perspective view depicting the stops and table sensors;  
         [0031]    [0031]FIG. 6 is a perspective view depicting the tote sensors;  
         [0032]    [0032]FIG. 7 is a perspective view of a tote shuttle integrated with a shuttle carrier in a shelf matrix;  
         [0033]    [0033]FIG. 8 is a perspective view of a tote alongside the shelf matrix;  
         [0034]    [0034]FIG. 9 is a perspective of a tote resting on a top table of a shuttle;  
         [0035]    [0035]FIG. 10 is a perspective view of a tote resting on a shuttle being transported;  
         [0036]    [0036]FIG. 11 is a perspective view of a tote extended into a shelf matrix by a shuttle; and  
         [0037]    [0037]FIG. 12 is a perspective view of a tote resting on a shelf in a shelf matrix.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0038]    FIGS.  1 - 6  depict various details of the shuttle  10  of this invention. The shuttle  10  has a top  12  attached to a first table  14 . The first table  14  is movably attached to a second table  16 . The second table  16  is removably attached to a frame assembly  18 . A primary drive mechanism  20  and a secondary drive mechanism  22  drive the first and second tables  14 ,  16  in a telescoping manner.  
         [0039]    The top  12  shown in FIGS.  1 - 2  is a generally flat rectangular top that mounts to the first table  14 , and is preferably fabricated from stainless steel. Alternatively, the top  12  can be fabricated from any suitable material, such as steel, aluminum, or various metal-alloys such as brass, wood, and plastic. The choice of material for the table top can vary with cost, wear, ability to frictionally retain a tote or other container, and the ability of the material to withstand ambient environmental conditions such as humidity, temperature, corrosive gases and particulates. The bottom side of top  12  can be either permanently attached to the topside of the first table  14 , for example, by welding, riveting or adhesive, or removably attached, for example, by bolting or other mechanical attachment. When top  12  is a metal or other deformable material, side edges  24  of the top  12  can be folded over for stiffness. When the top  12  is a plastic or other moldable material, side edges  24  can be formed with integral stiffening members. Additional stiffening ribs can also be formed which can be integral with or otherwise attached to the top  12 .  
         [0040]    The first table  14  shown in FIGS.  1 - 2  is a generally rectangular table smaller than the top  12 , and is preferably fabricated from stainless steel or aluminum. Alternatively, first table  14  can be fabricated from any suitable material discussed above regarding the top  12 . A first track  26  is attached to the underside of the first table  14  along each longitudinal axis near the perimeter using methods known in the art. These two pieces of first track  26  allow the top  12  and first table  14  combination to glide along the second table  16 .  
         [0041]    The second table  16  shown in FIG. 2 is a generally rectangular table approximately the same size as the top  12 , and is preferably fabricated from stainless steel or aluminum. Alternatively, second table  16  can be fabricated from any suitable material discussed above regarding the top  12 . Three stiffener rails  28 ,  30 ,  32  are attached to the second table  16  in a generally longitudinal direction to reduce deflection of the table under load. Rail  32  is attached to the table  16  approximately longitudinally along the centerline, while the other two rails  28 ,  30  are attached near the second table longitudinal edges  34 ,  36 . Between the two rails  28 ,  30  and the second table  16  are second tracks  38 . Along each of the inside edges of the two rails  28 ,  30  is a first series of bearings  40  attached to the second table  16 .  
         [0042]    Each of the first tracks  26  interacts with a first series of bearings  40 . In the preferred embodiment, the first series of bearings, or guide wheels  40  are steel sealed guide wheels  42  arranged longitudinally along the top surface of the second table  16 . Shown in FIG. 2A, each of the wheels  42  has a fixed center, a concentric guide wheel  42 A and an adjustable, eccentric guide wheel  42 B. Each guide wheel  42  is adjustable. In the preferred embodiment, normal adjustment is obtained by rotating the eccentric guide wheel until the eccentric guide wheel can just be turned against the track  26 . If the eccentric guide wheel is overtightened it can exert a force greater than the load rating of the guide wheel. Thus, when adjusted properly, when the track  26  moves, the guide wheels turn, and the first table  14  glides along the top of the second table  16 .  
         [0043]    Frame assembly  18  shown in FIGS.  1 - 2  is fabricated from two longitudinal side walls  44 , two lateral side walls  46  and a base  48 . The primary drive mechanism  20  is mounted on the base  48 . A second series of bearings, or sealed guide wheels  68  are attached to the top edge  72  of the longitudinal side walls  44 . Each of the second tracks  38  interacts with the second series of guide wheels  68 . In the preferred embodiment, the second series of guide wheels  68  are steel sealed guide wheels  70  similar to the first series  40 . When adjusted properly, the second table glides along the frame assembly  18  in a manner similar to the first table  14  gliding along the second table  16 .  
         [0044]    The primary drive mechanism  20  shown in FIG. 3 consists of a servomotor  50  connected to a gearhead  52 . The gearhead  52  is connected to a sprocket  54  which moves the first drive chain  56 . One end of the first drive chain  56  is mounted to the underside of the second table  16  at a fixed chain mount  58 . The first drive chain  56  is routed around an idler  60 , and the other end of the first drive chain is attached to an adjustable chain mount  62 . The adjustable chain mount  62  is attached to the underside of the second table  16 .  
         [0045]    As the motor  50  runs, the second table  16  moves in the appropriate direction. When the motor  50  is reversed, the second table  16  moves in the opposite direction. Under normal conditions, the second table  16  will be centered in the frame assembly  18 . When the motor  50  is operating, it will drive the second table  16  a desired distance from its neutral position in the desired direction. The motor  50  then stops, reverses direction, and the second table  16  is driven back to its neutral position.  
         [0046]    The secondary drive mechanism  22  shown in FIGS. 1 and 4 uses a second drive chain  64  and a third drive chain  66  to move the first table  14  relative to the second table  16 . One end of each of the second and third drive chains  64 ,  66  is fixedly attached to the frame assembly  18  using mount  65 . The other end of each of the second and third drive chains is attached to the underside of the first table  14  using mount  67 . In this manner, as the second table  16  begins to move, it pulls against both the second drive chain  64  and the third drive chain  66  which moves the first table  14  an equal distance relative to the second table  16  and in the same direction. For example, as the second table  16  moves one inch from the frame  18 , the first table  14  will move out one inch, resulting in a two-inch change in overall distance moved from the frame  18 . This telescoping action allows the shuttle  10  to reach farther than the length of the shuttle. Additionally, it also allows the load placed on the top  12  to be distributed over several first series bearings  40  and second series bearings  68 .  
         [0047]    Mounted at both ends and to the underside of the second table  16  are hard stops  74 , as shown in FIG. 5. These stops  74  are mounted so that a predetermined stroke, or distance traveled, can be reached. Stop block  76  is mounted to the frame assembly  18  to catch the hard stops  74  and prevent the table  16  from exceeding the preset stroke distance. The hard stops  74  and the stop block  76  are positioned such that the table  16  can move in either longitudinal direction without interference. It will be understood that the hard stops  74  are positioned to a predetermined stroke, or distance.  
         [0048]    As shown in FIG. 5, a pair of overrun sensors  78  are mounted to the frame assembly  18 , and are tripped by the hard stops  74  prior to the hard stops  74  reaching the stop block  76 . In this manner, as the table  16  is extended, the trailing hard stop  74  reaches an overrun sensor  78  prior to the trailing hard stop  74  reaching the stop block  76 . When the overrun sensor  78  detects a hard stop  74 , a signal is sent to the controller to stop movement of the table  16 . In the preferred embodiment, the overrun sensors  78  are roller switches.  
         [0049]    A sensor rail  84  is mounted to the underside of the second table  16  for detection by the home sensor  80  and the extend sensors  82 . The sensor rail  84  is positioned such that each end of the rail is approximately equidistant from the ends of the table  16 , and a gap  86  is positioned near the center line of the table  16 . A home sensor  80  and a pair of extend sensors  82  are also mounted on the frame assembly  18 . The home sensor  80  is used to indicate where the home, neutral, or centered position is. The extend sensors  82  are positioned so that if neither sensor is tripped, then the table  16  is centered. In this manner, when the table  16  is in the home position, the gap  86  is located at the home sensor  80 , and the ends of the sensor rail are inside the extend sensors  82 . Movement of the table  16  in either direction will trip a corresponding extend sensor  82 . The signal from the extend sensor  82  is sent to the controller, and is used to indicate which direction to drive the tables  14 ,  16  to return to a neutral, or home position. In the preferred embodiment, the home sensor  80  and the extend sensors  82  are photo microswitches.  
         [0050]    Additionally, the sensors  80 ,  82  are used as interlocks to the other axis of motion. In this manner, when the sensors  80 ,  82  indicate that the table  16  is in an extended position, all other axis of motion of the crane  100  are disabled. For example, when the tables  14 ,  16  are extended, the crane  100  will be prevented from moving either side to side or up and down.  
         [0051]    [0051]FIG. 6 depicts sensors used for tote detection. A first tote sensor  88  is mounted to both ends of the frame assembly  18 . The first tote sensor  88  is used to verify the presence or absence of a tote in the location being serviced. For example, if the shuttle  10  is supposed to extract a tote from a shelf location, the tote detect sensor  88  will scan the position to verify the presence of the tote prior to the shuttle  10  extending the tables  14 ,  16  to retrieve the tote. Conversely, if the shuttle  10  carrying a tote and is to place the tote, for example, on a conveyor, the first tote sensor  88  will be used to verify that there is no tote presently on the conveyor before the shuttle  10  extends the tables  14 ,  16  to deliver the tote. In the preferred embodiment, the first tote sensors  88  are diffuse reflective photoelectric sensors.  
         [0052]    Two second tote sensors  90  are mounted to the frame assembly  18  positioned to look across the shuttle  10 . These second tote sensors  90  are used to verify the presence of a tote on the top  12  and that the tote is centered. For the tote to be considered centered, the shuttle  10  must be in the neutral position and both sensors  90  detecting the tote. In the preferred embodiment, the second tote sensors  90  are retroreflective photoelectric sensors.  
         [0053]    Four tactile sensors  92 ,  94 ,  96 ,  98  are mounted near the four corners of the frame assembly  18 , and are adjusted to detect the presence of a tote just outside the nominal path of a tote on the top  12 . In this manner, if a tote is picked crooked, as the tote is moved onto the shuttle  10 , it will trip one of the tactile sensors  92 ,  94 ,  96 ,  98 , and a signal will be sent to the controller indicating a non-nominal tote position. In the preferred embodiment, the tactile sensors are short spring wobble stick tactile switches.  
         [0054]    By way of example, FIGS.  7 - 12  depict perspective views of the tote shuttle  10  moved by a crane assembly  100 . The crane assembly  100  moves the shuttle  10  along a rail system  102  among a shelving matrix  104 . A tote  106  is on a conveyor  108  awaiting transport to a location in the shelving matrix  104 .  
         [0055]    In FIG. 8 tote  106  is placed alongside the shelf matrix  104  for pickup. FIG. 9 depicts the shuttle  10  in an extended position with the tote  106  resting on the top  12 . After retraction of the tables  14 ,  16  to the home position, the tote  106  is centered on the shuttle  10 , and the crane  100  moves the shuttle  10  and the tote  106  to a new location.  
         [0056]    In FIG. 11, the tables  14 ,  16  are extended and the tote  106  is extended into a shelf in the shelf matrix  104  by the shuttle  10 . FIG. 12 depicts the tote  106  resting on a shelf in the shelf matrix  104 , the shuttle  10  having retracted the tables  14 ,  16  to their home position and the crane  100  having moved the along the rail system  102  to another location.  
         [0057]    While advantageous embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention, as defined in the appended claims. For example, an anti-slip coating or a separate anti-slip surface or tape can be applied to the top  12 . Various clips, tie-downs, and holders can be attached to the top  12  to aid in retaining a tote in a preferred location, or limiting movement of a tote once it is place in the top  12 . Nets or fences can be attached to the top  12  to prevent a tote from falling, or to help direct placement of a tote on the top. Different materials can be used to fabricate the top or the tables as may be appropriate to the work environment, for example, an anti-static top might be beneficial when the tote or unit to be transported can react with an improperly grounded metal surface. Various control systems can be used as is known in the art, and may be operated by various known computers systems. The shuttle  10  can also incorporate a minicomputer for overall control, and a graphical user interface can be incorporated for ease of programming the shuttle.