Abstract:
A gravity flow rail conveyor and picking system comprises a plurality of conveyor rail lanes having module or pallet support surfaces that rise at a suitable gravity flow angle from a selectively erected abutment chock. When erected, the chock abutment prevents gravity flow of modules along the support surface below the chock. When retracted, at least one module is allowed to flow by gravity onto a level support surface suitable for interfacing with an automatic picking machine. As the picking module flows onto a respective level surface, the chock rotates to an erect position for preventing additional modules from passing the abutment point.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to gravity conveyors. More particularly, the invention relates to order picking and assembly lines that are supplied and supported by gravity flow lanes. 
     Many trade articles are unitized into standardized modules for market transport and delivery. A module may constitute a compactly aligned and stacked assembly of numerous smaller units on a portable platform called a pallet. Furthermore, competitors within a single industry, such as for bottled beverages, will cooperate to standardize the size and shape of their product market packages to facilitate filling and handling by automatic machinery. 
     Warehouse storage of articles on pallets or modular containers is further facilitated by low friction pallet support platforms. These low friction platforms are often a multiplicity of parallel planar lanes set along a shallow slope such as 0.4 to about 0.5 in./ft. Each lane width is usually sufficient for only one line of modules or pallets. The low friction surface is usually provided by a multiplicity of small wheels or rollers supported on anti-friction on bearings for rotation about parallel axes. Conceivably, however, other forms of low friction surface may be used such as air-bearing tables. 
     The functional objective of these sloped, low-friction pallet lanes is to exploit gravity for movement of the warehouse stock. For an inventory management that desires the “first in first out” principle, newly arrived inventory is placed on a sloped pallet lane at the upper end and inventory to be removed is withdrawn from the low end of the lane. A queue of modules or pallets, terms hereafter used interchangeably and synonymously, advance by gravity alone from the high end to the low end of a lane without external power. 
     Such low friction surface lanes have come to be known and characterized in the art as “gravity conveyors”, “flow rails” and numerous similar terms and phrases. 
     Controls over such flow rails are usually limited and simple in principle. For example, velocity of a module along a flow rail is often restrained by conveyor surface support rollers having centrifugal drag braking. Manually or automatically engaged chocks may be used to prevent downward movement of modules past a predetermined point until desired. 
     In a separate but related practice, product distribution warehouses may draw from a multiplicity of individual product storage lanes to assemble a specified order. This order assembly process and practice is often characterized in the art by the term “picking”. A specified order is assembled by picking and choosing from among many available offerings. These offerings may be presented for picking convenience by gravity flow rails. For example, each of products A, B and C may be packaged in standardized units whereby four units may be aligned in a single tier plane above a pallet surface. Additionally, four tier planes of these units may be stacked vertically above the pallet surface for a full module comprising sixteen units of the product. 
     Representatively, an order may specify four units of product A, four units of product B and eight units of product C. Assembly of the order will therefore draw one pallet tier from the product A supply lane, one pallet tier from the product B supply lane and two pallet tiers from the product C supply lane. These four tiers are vertically assembled on a single order pallet for delivery to the buyer. 
     To expedite the picking process, powered grapples called “pickers” that are carried by overhead lifts or warehouse trucks have been devised to grasp, lift and transport one or all of the product tiers on a pallet, simultaneously. Implements such as the Tygard Claw® manufactured by the Tygard Machine and Manufacturing Co. of Washington, Pa. are representative. However, the reliable operation of such implements is predicated on a level planar alignment of the tiers. Since the alignment of several product units, within a tier includes no structural connection therebetween, only continuous surface friction between the units of a tier holds the tier together under the compressive grip of the grapple implement. A planar misalignment of a pallet tier with the picker grapples by the magnitude of a gravity flow slope exceeds the capacity of the implement. Hence, use of a picker to assemble specified orders from a gravity flow rail has required that the actively picked pallet in a product flow rail be removed from the flow rail lane and placed on a level surface that is accessible to the picker. 
     Traditionally, this removal and repositionment of a picked pallet to a level surface has required selectively applied power, such as a powered conveyor or a manually operated warehouse truck. 
     It is, therefore, an object of the present invention to provide gravity motivated transition of a flow rail module onto a level surface. 
     Another object of the invention is a picking system having a substantially self-regulating transfer of modules from a gravity flow rail to a level surface. 
     SUMMARY OF THE INVENTION 
     These and other objects of the invention are met with a gravity flow unit conveyor system for unitized package modules having a horizontal delivery or picking station. 
     In the usual application and preferred embodiment of the invention, a plurality of gravity flow lanes are constructed to rise along a slope plane at a preferred rate of about 0.4 to 0.5 inches per foot. These gravity flow means are low friction surfaces that are usually constructed with a multiplicity of wheels or rollers supported by anti-friction bearings. A warehouse may have hundreds of such gravity flow lanes in side-by-side and/or vertically aligned parallelism. 
     Articles stored in the warehouse may, for standardized handling and convenience, be containerized in hard-bottom modules or stacked on pallets. Such modules or pallets are queued serially along a gravity flow lane so as to slide in a line under the force of gravity toward the lower end of the lane. As a module is removed from the lower end of the lane the entire line advances. 
     At the lower end of each gravity flow lane is a level transition station where the lowermost module slides onto a level platform for subsequent handling or grappling by a picking machine. As the lowermost module moves onto the level surface, the module weight or presence thereon operates a retractable abutment that engages the module next in line on the gravity flow rail. This retractable abutment blocks further movement of the line until the module on the level station is removed. 
     A picking machine that requires a square and level article for proper grappling may act upon the level module without manual repositionment. Applied to customized order assembly, diverse products stored in respective flow lanes may be picked by need of a composite order with respective product contributions, assembled at an accumulation station until all elements are added. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is described in detail by reference to the accompanying drawings wherein like reference characters designate like or similar elements throughout the several figures of the drawings and wherein: 
     FIG. 1 is a schematic flow plan for a picking system according to the invention; 
     FIG. 2 is a schematic flow elevation for a picking system according to the invention; 
     FIG. 3 is a side elevation view of a preferred embodiment of the invention; 
     FIG. 4 is a side elevation of an alternative embodiment of the invention; 
     FIG. 5 is an isometric detail of a selective abutment mechanism; and, 
     FIG. 6 is a schematic elevation of a powered grapple. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With respect to the FIGS. 1 and 2, a representative gravity flow rail warehouse system is shown to include five gravity flow lanes  10 ,  20 ,  30 ,  40  and  50 . Flow lane  10  is structurally defined by a pair of roller rails  16  such as is illustrated more pictorially by the roller rails  56  of FIG.  5 . These roller rails  16  provide a low friction support surface sloped along a gravity flow plane  12  for a plurality of article modules  11  and  13 . Slope for a gravity flow plane  12  is variable depending on the nature of the low friction surface and the cooperative module bottom surface. Roller flow rails supporting load pallets with wood skids may use a slope of about 0.4 to about 0.5 in. per ft. Other flow plane surfaces and load containment modules may require more or less slope. 
     Flow lane  20  is defined by roller rails  26  disposed along gravity flow plane  22  for support of article modules  21  and  23 . Flow lane  30  is defined by roller rails  36  disposed along gravity flow plane  32  for support of article modules  31  and  33 . Flow lane  40  is defined by roller rails  46  disposed along gravity flow plane  42  for support of article modules  41  and  43 . Flow lane  50  is defined by roller rails  56  disposed along gravity flow plane  52  for support of article modules  51  and  53 . 
     Each of these flow lanes is terminated by a horizontal picking station  14 ,  24 ,  34 ,  44  and  54 . Roller rails  18 ,  28 ,  38 ,  48  and  58  provide a horizontal picking surface for the respective picking modules  15 ,  25 ,  35 ,  45  and  55 . Representatively, each picking module comprises three tiers, a, b and c. Respectively, each tier comprises nine loosely aligned article units. 
     A picking assembly station  60  provides a pallet  64  onto which three tiers of product units are assembled. For the present example, tiers  15   a ,  35   a  and  55   a  have been removed from picking modules  15 ,  35  and  55 , respectively, and stacked at the assembly station  60  on pallet  64  for development of a specified module  62 . 
     The picking movement for product unit tiers  15   a ,  35   a  and  55   a  onto assembly station pallet  64  is represented by the flow arrows  68 . This picking movement is carried out by a picking grapple  90  such as shown by FIG.  6 . The picker  90  may be supported by an overhead lift or a warehouse truck  99 . Operatively, the picker  90  grapple plates are manipulated over a picking station module  55 , for example. The grapple plates  92  are thereafter lowered over the picking module  55  to the desired tier level. The grapple plates  92  are then closed by hydraulic struts  94 , for example to compress the nine product units of a tier together. The tier or tiers selected are lifted and transferred to the assembly station  60 . 
     Referring to the FIG. 3 elevational schematic, the flow lane  50  is shown in greater detail. The gravity flow plane  52  is structurally determined as a common plane of tangency to the conveyor rollers  66 . The roller  66  axes are supported by structural channels or beams  56  set at a strategic slope to the horizontal. A slope of about 0.4 to about 0.5 in. rise per ft. of horizontal length or run is typical for such applications. 
     At the lower end of the flow lane  50 , the flow plane  52  intersects with the horizontal picking plane  54  defined by the tangents of rollers  59 . The roller  59  axes are supported structurally by beams  58 . 
     At a convenient point about the intersection of planes  52  and  54 , retractable chock plates  82  are operatively secured to the channels  56  to oscillate about an axis  83 . These chock plates are selectively erected to bear against the pallet  64  of lower most module  53  in the serial continuity of modules along the flow plane  52  for preventing movement of module  53  and those above it past the chock  82 . To be noted from the side elevation of FIG. 3 is that due to the slopes, the upper loading edge  57  of the lowermost module  53  may be in a more advanced vertical plane than the edge of supporting pallet  64 . The chocks  82  hold this upper leading edge away from the operational space  61  necessary for penetration of the picker grapple plates  92 . The chock plate mechanism  80  of FIG. 5 includes a sensor plate  85  that is pivotally secured to the picking station level rails  58 . A spring biased crank rod  88  is pivotally connected by wrist pins to each of the sensor plate  85  and a crank shaft  86 . Toggle links  84  at opposite ends of the crank shaft  86  are pivotally connected to the chock plates  82 . 
     Operatively, the weight and presence of a pallet  64  on the horizontal picking plane  54  rotates the sensor plate  85  to the horizontal position against the bias of counter-rotating erecting springs. Such rotation of the sensor plate  85  strokes the crank rod  88  to rotate the crank shaft  86 . By the toggle links  84 , the chock plates  82  are rotated to a module abutment position. 
     It will be understood by those of ordinary skill that the chocks  82  may be raised and lowered by numerous other mechanisms and devices such as motors that are controlled by contact switches, proximity switches or photoelectric eyes. 
     When the picking module pallet  64  is emptied of product, the pallet is removed from the level picking plane  54  to release the sensor plate  85 . Bias of the preloaded springs rotationally raises the sensor plate and rotationally lowers the chock plates  82  thereby releasing the module  53  to gravity movement along the remaining increment of the gravity flow plane  52 . The inertia of such movement carries the module onto the level picking plane  54 . Strategic placement of the sensor plate  85  causes the oncoming module  53  to engage and depress the sensor plate  85  thereby erecting the chock plate  82  to prevent advancement of the next module  51  past the chock plate  82  position. 
     An alternative embodiment of the invention is shown by FIG.  4 . Gravity flow rails  75  support the flow plane  72  onto a picking station  70  section of flow rails  78  that pivots about an axis  77 . A fluid strut or motor  73  lifts the distal end of rails  78  about the axis  77  from a lower position  78   a  to an upper, horizontally level position during the presence of a pallet  64 . 
     When the picking station  70  is absent a picking module  71 , the support strut  73  lowers the rails  78  about the axis  77  to the  78   a  alignment position and retracts the chock plate  82 . When the chock plate  82  is retracted, the next pallet  64  rolls or slides by gravity onto the picking station  70  until stopped by a fixed abutment  79 . In transit between the retracted chock plate  82  and the fixed abutment  79 , a strategically positioned sensor plate or switch operates the chock plate  82  to the flow blocking position and energizes the strut  73  to raise the rails  78  to the level alignment position. 
     The foregoing descriptions of preferred embodiments of my invention have been presented for purposes of illustration and explanation. Disclosure of these embodiments is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obvious modifications or variations are possible in light of the above teachings. These embodiments were chosen and described to provide the best illustrations of the principles of the invention and its practical applications. Further, these preferred embodiments were selected to enable one of ordinary skill in the art to utilize the invention in various forms and with various modifications as is suited to a particular utility. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally and equitable entitled. 
     As my invention, therefore,