Abstract:
A storage retrieval machine comprising an input area, an array of storage locations, an output area, a carriage assembly adapted to hold a product when being transferred to and from the storage locations, and a drive mechanism positioned to move the carriage assembly. The drive mechanism includes a flexible element (e.g., a chain) tensioned between two points and having a plurality of spaced recesses, and a toothed element mounted to the carriage assembly and engaging the flexible element. Preferably, the flexible element is pre-tensioned to a certain percentage of the rated load of the flexible element (e.g., 10%, 20%, 30%, or 40% of the rated load). It is also preferred that the pre-tensioned load on the flexible element is greater than the service load that is anticipated to be applied to the chain during normal operation.

Description:
BACKGROUND 
       [0001]    The present invention relates to storage retrieval machines (SRMs), and more specifically to drive mechanisms for such systems. 
         [0002]    SRMs are used to automatically store and retrieve items, such as in a warehouse. The storage area typically includes an array of storage locations that are each specifically identified. Each location is capable of storing a single unit, which can be stored or retrieved on command. Such systems commonly have a product input area, a product storage area, and a mechanism for moving products into and out of storage. 
         [0003]    Storage areas in SRMs are commonly arranged into rows and columns. As a result, mechanisms that move the products must be capable of both vertical and horizontal movement. Such mechanisms can include, for example, a robotic arm mounted on a platform with both vertical and horizontal actuators. Vertical movement is commonly provided by hydraulic lifts or rack and pinions (e.g., with a driven pinion). Horizontal motion is commonly provided by a driven wheel on a surface, such as a wheel on a rail, which is typically used with overhead cranes in manufacturing environments. 
         [0004]    Because precise placement into storage locations is important, the mechanisms that move the product must have a means to determine location. When using positive-position mechanisms, such as a rack and pinion, precise location can be determined by sensing the position of the drive wheel (e.g., counting rotations and detecting angular orientation of a drive pinion on a rack and pinion arrangement). When using other mechanisms where slippage can occur, such as a wheel on rail, the system must use other sensing systems, such as limit switches, to determine position. 
       SUMMARY 
       [0005]    The present invention provides an SRM drive system that can be used in conjunction with other systems in order to provide an economical means to move products, while at the same time providing positive positioning. In particular, the present invention provides a storage retrieval machine comprising an input area, an array of storage locations, an output area, a carriage assembly adapted to hold a product when being transferred to and from the storage locations, and a drive mechanism positioned to move the carriage assembly. The drive mechanism includes a flexible element (e.g., a chain) tensioned between two points and having a plurality of spaced recesses, and a toothed element mounted to the carriage assembly and engaging the flexible element. 
         [0006]    Preferably, the flexible element is pre-tensioned to a certain percentage of the rated load of the flexible element (e.g., 10%, 20%, 30%, or 40% of the rated load). It is also preferred that the pre-tensioned load on the flexible element is greater than the service load that is anticipated to be applied to the chain during normal operation. 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of an SRM embodying features of the invention. 
           [0009]      FIG. 2  is a perspective view of a first guide of the SRM of  FIG. 1 . 
           [0010]      FIG. 3  is a perspective view of a second guide of the SRM of  FIG. 1 . 
           [0011]      FIG. 4  is a perspective view of a third guide of the SRM of  FIG. 1 . 
           [0012]      FIG. 5  is a partial perspective view of the SRM of  FIG. 1 . 
           [0013]      FIG. 6  is a partial perspective view of the SRM of  FIG. 1 . 
           [0014]      FIG. 7  is a perspective view of an anchor of the SRM of  FIG. 1 . 
           [0015]      FIG. 8  is a perspective view of a horizontal drive system for another SRM embodying features of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0017]      FIG. 1  shows a storage facility  10  including a loading space  14 , an array of storage locations  22 , and a storage retrieval machine (SRM  26 ). The loading space  14  is positioned such that a product  30  may access the loading space  14  from a holding area  34 . In other embodiments, the storage facility  10  could be different, such as a warehouse, stocking area, car park, or another storage facility as desired. Correspondingly, the array of storage locations  22  could be arranged differently. For example, the array  22  could include any number of columns, any number of rows, or may include a three-dimensional matrix of storage locations. The storage locations could be sized and arranged to hold any product  30 , as desired. Additionally, the product  30  could be anything that is advantageously stored, such as cars, boats, produce, toys, or any other appropriate product  30 , as desired. 
         [0018]    The illustrated storage facility  10  includes four rows and four columns of storage locations  22 . The four rows extend along an X-axis and are referred to throughout this application as the first level  38  (i.e., closest to the base), the second level  42 , the third level  46 , and the fourth level  50  (i.e., farthest from the base). The four columns extend along a Y-axis and are referred to as the first position  54  (i.e., farthest to the right), the second position  58 , the third position  62 , and the fourth position  66  (i.e., the farthest to the left). A Z-axis is defined perpendicular to the X-axis and the Y-axis (i.e., extending out of the page of  FIG. 1  and indicated in the lower left). 
         [0019]    A support structure is built into the storage facility  10  and includes rails  70  that support the SRM  26  for movement from the first through fourth positions  54 ,  58 ,  62 ,  66  and from the first through fourth levels  38 ,  42 ,  46 ,  50 . In the illustrated embodiment, the support structure is a part of the storage facility  10 , and the rails  70  project from the walls of the storage facility  10  to support the SRM  26 . In other embodiments, the support structure may be free standing within the storage facility  10  or arranged differently, as desired. 
         [0020]    The SRM  26  further includes a SRM frame  74 , a carriage assembly  86 , an upper drive assembly  78 , and a lower drive assembly  82 . The SRM frame  74  includes vertical columns  87  that extend from the first level  38  to the fourth level  50 , an upper cage  88 , and a lower cage  89 . The vertical columns  87  connect the upper cage  88  and the lower cage  89  and are further reinforced by struts  90 . The upper cage  88  connects the SRM frame  74  to the upper drive assembly  78  such that the upper drive assembly  78  supports the SRM frame  74  for movement on the rails  70 , and the lower cage  89  provides a frame work that supports the lower drive assembly  82 . The upper and lower cages  88 ,  89  include additional frame work such that the SRM frame  74  is a rigid structure. 
         [0021]    Three of the four vertical columns  87  include guide rails. A first guide rail  91  is attached to one of the vertical columns  87  (lower right in  FIG. 1 ), a second guide rail  92  is attached to another vertical column  87  (lower left in  FIG. 1 ), and a third guide rail  93  is attached to another vertical column  87 . The first, second, and third guide rails  91 ,  92 ,  93  are formed separately from and are attached to the vertical columns  87 . In other embodiments, the first, second, and third guide rails  91 ,  92 ,  93  could be formed integrally with the vertical columns  87 . 
         [0022]    The SRM frame  74  also includes four bumpers in the form of shock absorbers or barriers  98  that cushion and stop the SRM  26  if it moves past the desired location. For example, if the SRM  26  is moving to the fourth position  66  but overshoots the location slightly, the barriers  98  will slow the SRM  26  movement and inhibit damage to the SRM  26  and/or the storage facility  10 . In other embodiments, the bumpers may be air bladders, hydraulic cylinders, compressible bumpers, or another type, as desired. 
         [0023]    The carriage assembly  86  includes a carriage frame  102  that is supported by the SRM frame  74  and is positioned between the vertical columns  87 . The carriage frame  102  includes a first guide member  110  that engages the first guide rail  91 , a second guide member  114  that engages the second guide rail  92 , and a third guide member  118  that engages the third guide rail  93 . The first, second, and third guide members  110 ,  114 ,  118  are positioned at three corners of the carriage frame  102  corresponding with the first, second, and third guide rails  91 ,  92 ,  93  of the SRM frame  74 , and engage the guide rails  91 ,  92 ,  93  to guide the carriage assembly  86  during vertical movement of the carriage assembly  86  (i.e., along the Y-axis).  FIGS. 3-5  include more details about the interaction between the guide rails  91 ,  92 ,  93  and guide members  110 ,  114 ,  118  and will be discussed in detail below. The fourth corner of the illustrated carriage frame  102  (upper left in  FIG. 2 ) does not include a guide member such that alignment of the carriage assembly  86  is maintained by the first, second, and third guide members  110 ,  114 ,  118 . This arrangement allows the carriage assembly  86  to move freely along the Y-axis while inhibiting binding. 
         [0024]      FIG. 2  shows the first guide member  110  engaged with the first guide rail  91 . The first guide member  110  is fixed to the carriage frame  102  with a rod  122  with bearings (not shown) such that the first guide member  110  can rotate with respect to the carriage frame  102 . The first guide member  110  engages the first guide rail  91  that has a T section and constrains the movement of the carriage assembly  86  with respect to the SRM frame  74  in the X-axis and the Z-axis such that the carriage assembly  86  can move in the Y-axis along the guide rail  90 . 
         [0025]      FIG. 3  shows the second guide member  114  engaged with the second guide rail  92 . The second guide member  114  includes a first portion  126  and a second portion  130 . The first portion  126  is fixed to the carriage frame  102  with a rod  122  with bearings (not shown), similar to the first guide member  110 , such that the second guide member  114  can rotate with respect to the carriage frame  102 . The first portion  126  also includes a T-shaped slot  135 . The second portion  130  engages the second guide rail  92  that has a T section such that the second portion  130  is constrained in the X-axis and the Z-axis and moves freely along the Y-axis. The second portion  130  also includes a T-shaped protrusion  136  that engages the corresponding T-shaped slot  135  formed in the first portion  126 . The first portion  126  can slide along the X-axis relative to the second portion  130  via the T-shaped slot and protrusion  135 ,  136  such that the second guide member  114  constrains the movement of the carriage assembly  86  with respect to the SRM frame  74  in the Z-axis but allows movement along the X-axis. 
         [0026]      FIG. 4  shows the third guide member  118  engaged with the third guide rail  93 . The third guide member  118  is fixed to the carriage frame  102  with a rod  122  with bearings (not shown) such that the third guide member  118  can rotate with respect to the carriage frame  102 . The third guide member  118  engages the third guide rail  93  and constrains the movement of the carriage assembly  86  with respect to the SRM frame  74  in the X-axis such that the carriage assembly  86  can move in the Y-axis along the third guide rail  93 . The third guide member  118  allows the carriage assembly  86  to translate slightly relative the third guide rail  93  along the Z-axis. 
         [0027]    Referring to  FIG. 1 , the upper drive assembly  78  includes a vertical drive system  138  that moves the carriage assembly  86  relative to the SRM frame  74  along the Y-axis between the first level  38  and the fourth level  50 , and a horizontal drive system  142  that moves the SRM  26  along the X-axis between the first position  54  and the fourth position  66 . 
         [0028]    With reference to  FIG. 5 , the illustrated vertical drive system  138  includes a motor  146 , a gear box  150 , a drive shaft  154 , and counterweights  158 .  FIG. 5  shows one side of the vertical drive system  138 , and the opposite side of the upper drive assembly  78  includes an identical arrangement and the two motors  146  are coupled together with a synchronizer shaft  162 . The synchronizer shaft  162  provides for the motors  146  to run synchronously and to move the carriage assembly  86  along the Y-axis smoothly. The illustrated motor  146  is an electric motor that drives the drive shaft  154  via the gear box  150 . In other embodiments, the motor  146  may be a servo-motor and the synchronizer shaft  162  may be removed. The motor  146  may be any drive unit that moves the carriage assembly  86  along the Y-axis. For example, hydraulic cylinders are contemplated. 
         [0029]    The drive shaft  154  is rotated by the motor  146  via the gear box  150  and includes four sprockets  166 , two positioned on each end of the SRM frame  74 , respectively. The drive shaft  154  is mounted to the SRM frame  74  with mounts  170  that allow the drive shaft  154  to rotate freely. 
         [0030]    The illustrated counterweights  158  slide along the corresponding vertical columns  87  (along the Y-axis) of the SRM frame  74 . Two chains  174  connect each weight  158  to the SRM frame  74 . One end of each chain  174  attaches to a connecting portion  178  of the weight  158 , loops over the sprocket  166 , and attaches at the opposite end of the chain  174  to the carriage assembly  86  at connecting portions  182  (see  FIGS. 2-4 ). Each corner of the carriage assembly  86  is lifted by two chains  174  (i.e., two chains  174  are attached to each weight  158  and each corner of the carriage assembly  86 ). 
         [0031]    With reference to  FIGS. 5 and 6 , the illustrated horizontal drive system  142  includes a motor  186 , a gear box  190  (see  FIG. 5 ), a toothed element in the form of a drive sprocket  194 , two idler sprockets  198 , a flexible element in the form of a chain  202 , two anchor points  206  (see  FIGS. 1 and 7 ), and two wheels  210  that ride on the rails  70  of the support structure to support the SRM  26 .  FIG. 6  shows one side of the horizontal drive system  142 , and the opposite side of the upper drive assembly  78  includes an identical arrangement. The illustrated motor  186  is an electric motor that drives the drive sprocket  194  via the gear box  190 . The motor  186  may be any drive unit that moves the carriage assembly  86  along the X-axis. For example, hydraulic cylinders are contemplated. 
         [0032]    The chain  202  includes a number of spaced recesses that the teeth of the sprockets  194 ,  198  engage. The chain  202  is stretched along the X-axis and mounted at the anchor points  206  (see  FIG. 7 ) on opposite ends of the storage facility  10 . The SRM  26  exerts a service load on the chain  202  while in operation and, in the illustrated embodiment, the chain  202  is pre-tensioned to a force greater than the service load to reduce the effects of the chain&#39;s  202  elasticity. For example, when the illustrated SRM  26  is accelerating along the X-axis, a force of about three thousand pounds is exerted on the chain  202 . The illustrated chain  202  is pre-tensioned to about five thousand pounds. This pre-tension inhibits slack in the chain  202  during acceleration and stopping of the SRM  26  and reduces elastic elongation by at least about fifty percent. 
         [0033]    The chain  202  also has a rated load that is a physical characteristic of the chain  202  and is set by the chain manufacturer. In the preferred embodiment, the chain  202  is pre-tensioned to at least forty percent of the rated load. In other embodiments, the chain  202  may be pre-tensioned differently, as desired. This pre-tension provides accurate positioning of the SRM  26  and at least partially avoids exaggerated chain  202  flexing. 
         [0034]    The drive sprocket  194  and two idler sprockets  198  are arranged such that the chain  202  serpentines through the sprockets  194 ,  198  and maintains a desired angle of engagement with the sprockets  194 ,  198  during movement of the SRM  26 . The drive sprocket  194  is driven by the motor  186  via the gear box  190  such that the SRM  26  is translated along the X-axis between the first position  54  and the fourth position  66 . The idler sprockets  198  are mounted to the SRM frame  74  with bearings (not shown) such that they rotate freely and maintain the chain  202  in engagement with the drive sprocket  194 . 
         [0035]    With reference to  FIG. 7 , the anchor points  206  are fixed relative to the rail  70  and include a tensioning system to pre-tension the chain  202 . The tensioning system includes a threaded rod  214 , washers  218 , and fasteners  222 . The fasteners  222  are rotated on the threaded rod  214  to move the threaded rod  214  relative to the anchor point  206  such that the chain  202  is tensioned along the X-axis. 
         [0036]    Referring to  FIG. 1 , the lower drive assembly  82  is mounted to the lower cage  89  and is similar to the horizontal drive system  142  of the upper drive assembly  78 . The horizontal drive system of the lower drive assembly includes a motor, a gear box, a toothed element in the form of a drive sprocket, two idler sprockets, a flexible element in the form of a chain, and two anchor points. The lower drive assembly  82  operates in a manner similar to the horizontal drive system  142  of the upper drive assembly  78  to move the SRM  26  along the chain in the X-axis. 
         [0037]    A control system  94  is coupled to the SRM  26  adjacent the upper drive assembly  78  and controls the movement of the SRM  26  in response to user input. The control system  94  may control the synchronization of the system to provide smooth operation. In other embodiments, the control system  94  may be located remotely or on another part of the SRM  26 , as desired. 
         [0038]    The invention provides several advantages over prior art SRMs. The chains  202  provide a built in shock absorber due to the chain  202  elasticity while minimizing the negative effects associated with chain elasticity by pre-tensioning the chain  202  above the maximum operational force. In other words, during normal operation, the chain  202  will not stretch an unreasonable amount because the pre-tension is above the normal service load. However, if the SRM  26  stops suddenly or experiences another abnormality, the chain  202  can absorb some of the shock by stretching beyond the pre-tension. 
         [0039]    The chains  202  also avoid the alignment problems of many prior art designs. The chain  202  and sprocket  194 ,  198  arrangement does not require the tight tolerances required when using other systems (e.g., a rigid rack and pinion). As such, minor skewing of the SRM  26  will not cause substantial service damage. Additionally, previous systems required installation across the entire length of the SRM&#39;s  26  movement, whereas the chain  202  need only be fixed at two points at the ends of the rails  70 . The anchor points  206  fix the chain  202  to the support structure (not shown) and pre-tension the chain  202 . The chain  202  may be designed with self lubricating materials and/or materials that are highly resistant to corrosion such that prior art lubrication and corrosion problems may be avoided. 
         [0040]    The operation of the illustrated embodiment will be described with respect to  FIGS. 1 . To initiate a storing operation, the product  30  is placed in the loading space  14 . The control system  94  determines which storage location  22  the product  30  will be stored in and actuates the SRM  26 . The product  30  is placed on the carriage assembly  86  and the SRM  26  is then ready to move to the appropriate level and position. 
         [0041]    The horizontal drive systems  142  of the upper and lower drive assemblies  78 ,  82  then move the SRM  26  to the appropriate position (e.g., the third position  62 ). The motors  186  turn the drive sprockets  194  such that the SRM  26  is pulled along the chains  202  and rolled on the wheels  210  along the rails  70 . 
         [0042]    Once in the desired position (e.g., the third position  62 ), the SRM  26  moves the carriage assembly  86  to the desired level (e.g., the second level  42 ). The motors  146  turn the drive shaft  154  such that the sprockets  166  are turned and pull the carriage assembly  86  between the first level  38  and the fourth level  50  on the chains  174 . As the carriage assembly  86  is raised the counterweights  158  are lowered to maintain contact between the chains  174  and the sprockets  166 . The motors  146  continue to raise the carriage assembly  86  until the carriage assembly  86  is at the desired level (e.g., the second level  42 ). 
         [0043]    Once located at the desired storage location  22 , the product  30  is unloaded into the storage location  22 , and the SRM  26  returns the carriage assembly  86  to the first level  38  and translates back to the loading space  14 . 
         [0044]    When it is desired to remove the product  30  from the storage facility  10 , the control system  94  initiates a retrieval operation. The control system  94  will take an input from a user to determine which product  30  must be retrieved and where in the array that product  30  is located. Once the correct storage location  22  is determined, the SRM  26  translates along the X-axis to the appropriate position (e.g., the third position  62 ). The vertical drive system  138  then lifts the carriage assembly  86  to the appropriate level (e.g., the second level  42 ). Then the product  30  is loaded onto the carriage assembly  86 , the vertical drive system  138  lowers the carriage assembly  86  to the first level  38 , and the horizontal drive system  142  translates the SRM  26  to the loading space  14 . Once the product  30  is placed in the loading space  14 , the product  30  is removed to the holding area  34 . 
         [0045]      FIG. 8  shows an alternate horizontal drive system  230  that includes a motor  234 , a gear box  238 , a toothed element in the form of a drive sprocket  242 , an idler shoe  246 , a flexible element in the form of a chain  202 , two anchor points  206  (same as shown in  FIGS. 1 and 7 ), and two wheels  250  that ride on the rails  70  of the support structure to support the SRM  26 . In operation, the idler shoe  246  moves with the horizontal drive system  230  to maintain the chain  202  in contact with the drive sprocket  242 . The operation of the horizontal drive system  230  is similar to the operation of the horizontal drive system  142  described above. 
         [0046]    Various features and advantages of the invention are set forth in the following claims.