Abstract:
A vertical reciprocating conveyor includes a frame and a carrier movable up and down with respect to the frame to elevate and lower articles supported by the carrier. The conveyor also includes a prime mover and at least one sprocket rotating in response to operation of the prime mover. At least one flexible support member extends across the carrier from one side to an opposite side, and engages the at least one sprocket such that the at least one flexible support member is collected and let out in response to the direction of rotation of the sprocket to raise and lower the carrier with respect to the frame. The conveyor also includes brakes on the opposite sides of the carrier. The brakes are biased to engage the frame to prevent the carrier from free falling. The brakes are held out of engagement with the frame by the at least one flexible support member, and are permitted to substantially simultaneously engage the frame on opposite sides of the carrier in response to slack forming in the flexible support member. The conveyor further includes a sensor for sensing slack in one of the flexible support members.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to a vertical reciprocating conveyor.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0002]     The invention provides a vertical reciprocating conveyor that includes a frame and a carrier movable up and down with respect to the frame to elevate and lower articles supported by the carrier. The conveyor also includes a prime mover and at least one sprocket rotating in response to operation of the prime mover. At least one flexible support member extends across the carrier from one side to an opposite side, and engages the at least one sprocket such that the at least one flexible support member is collected and let out in response to the direction of rotation of the sprocket to raise and lower the carrier with respect to the frame. The conveyor also includes brakes on the opposite sides of the carrier. The brakes are biased to engage the frame to prevent the carrier from free falling. The brakes are held out of engagement with the frame by the at least one flexible support member, and are permitted to substantially simultaneously engage the frame on opposite sides of the carrier in response to slack forming in the flexible support member. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]      FIG. 1  is a perspective view of a vertical reciprocating conveyor embodying the present invention.  
         [0004]      FIG. 2  is a perspective view of the carriage and a portion of the frame of the conveyor.  
         [0005]      FIG. 3  is an enlarged perspective view of a prime mover portion of the conveyor.  
         [0006]      FIG. 4  is an enlarged perspective view of a side portion of the conveyor.  
         [0007]      FIG. 5  is a perspective view of a load yoke portion of the conveyor.  
         [0008]      FIG. 6  is a perspective view of a brake assembly of the conveyor.  
         [0009]      FIG. 7  is an exploded view of the brake assembly.  
         [0010]      FIG. 8  is a side view of a portion of the conveyor showing the brake assembly in a disengaged condition.  
         [0011]      FIG. 9  is a side view of a portion of the conveyor showing the brake assembly in an engaged condition. 
     
    
     DETAILED DESCRIPTION  
       [0012]     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 limited. 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. The terms “mounted,” “connected” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.  
         [0013]      FIGS. 1 and 2  illustrate a vertical reciprocating conveyor (“VRC”)  10  that includes a frame  15  supporting a carriage  20 . A prime mover assembly  25  is mounted to a side of the frame  15 , and will be discussed in greater detail below. Flexible support members  30  are interconnected between the carriage  20  and the prime mover assembly  25  to enable the prime mover assembly  25  to raise and lower the carriage  20 . As used herein, the term “flexible support members” means wire ropes, chains, roller chains, leaf chains, belts, or any other tension-bearing flexible member from which the carriage  20  may be suspended within the frame  15 . In the illustrated embodiment, the flexible support members  30  are connected to an upper portion of one side of the frame  15 , extend down along that side of the frame  15 , extend under the carriage  20 , and extend up the opposite side of the frame  15  to the prime mover assembly  25 . This arrangement will be discussed in more detail below.  
         [0014]     With particular reference to  FIG. 2 , the frame  15  includes a pair of vertical masts  35  upon which the carriage  20  rides. The masts  35  include a base portion  40  having side surfaces, and a flange  45  that is wider than the base portion  40  (see also  FIG. 4 ). The carriage  20  includes a support surface  50  for supporting objects to be raised and lowered on the carrier  20 , wheels  55  that roll along the side surfaces of the masts  35  to facilitate smooth movement of the carriage  20  relative to the masts  35 , and brake assemblies  60  which engage the flanges  45  of the masts  35  to resist free-fall of the carriage  20  in the event of slack developing in one or more of the flexible support members  30 . As used herein with respect to the flexible support members  30 , the term “slack” means a loss of tension in the flexible support members  30  sufficient to permit the brake assemblies  60  to engage the flanges  45  of the masts  35 . For example, and without limiting the foregoing, slack may arise due to a sudden jolt in the raising or lowering of the carriage  20  or due to the flexible support members  30  breaking or suddenly stretching.  
         [0015]     Turning now to  FIG. 3 , the illustrated prime mover assembly  25  includes a prime mover  65  and a gear box  70 . The prime mover  65  may be, for example and without limitation, a motor or an engine. The prime mover  65  may be powered by substantially any source, such as electricity, gasoline, diesel, natural gas or other fuel, or hydraulic or pneumatic fluid, and the invention is not limited to any particular type of prime mover. The prime mover  65  is mounted to the side of the frame  15  (as opposed to mounting it on top of the frame), so that the frame  15  may extend substantially all the way to the ceiling of the building in which it is positioned. This arrangement permits objects to be raised substantially to the ceiling of the building to maximize the storage capacity from floor to ceiling of the building. The prime mover  65  includes an output shaft that engages and drives the gear box  70 . The gear box  70  reduces the output speed of the output shaft with a relatively large gear that creates a mechanical advantage and increases the torque capacity of the prime mover  65 . The increased torque capacity permits the prime mover  65  to lift heavier loads than would be possible with a direct coupling to the prime mover  65  itself.  
         [0016]     A spindle  75  is supported by a pair of bearings  80 , and is coupled to the gear box  70  for rotation in response to operation of the prime mover assembly  25 . The spindle  75  has mounted thereto a pair of sprockets  85  that are fixed for rotation with the spindle  75  with splines, keys, fasteners, or another suitable method. As used herein, the term “sprockets” includes the illustrated sprockets commonly used with chains, sheaves commonly used to drive belts, drums, pulleys, and any other apparatus that can be rotated to take up or let out a flexible support member. The flexible support members  30  extend across the sprockets such that, depending on the direction of rotation of the spindle  75 , the sprockets  85  take up or let out the flexible support member  30  to raise or lower, respectively, the carriage  20 .  
         [0017]     In the illustrated embodiment of the invention, each flexible support member  30  forms a loop  87  that hangs down from the sprockets  85 . The loop  87  increases in size when the carriage  20  is raised and decreases in size when the carriage is lowered. In alternative embodiments the flexible support member  30  may be wrapped around a drum or other device, in which case there would be no loop  87  hanging down.  
         [0018]     With reference to  FIG. 4 , each side of the carriage  20  has mounted thereto a pair of sprockets  90  for the respective flexible support members  30 . The embodiment illustrated has the sprockets  90  at the bottom of the carriage  20  such that the flexible support members  30  extend underneath the carriage  20  and cradle the carriage  20 . In other embodiments, the flexible support members  30  extend across the top of the carriage  20  or across other parts of the carriage  20  to cradle it. The cradling action of the flexible support members  30  self-corrects the orientation of the carriage  20  to reduce the likelihood of one side of the carriage  20  rising above the other.  
         [0019]     The prime mover assembly  25  and the spindle  75  should be positioned so that the top of the carriage  20  is about even with the top of the frame  15  when the sprockets  90  are even with or slightly below the sprockets  85 . Thus, in the illustrated embodiment, the prime mover assembly  25  and spindle  75  are lower than the top of the frame  15  by a distance that is slightly less than the height of the carriage  20 . In alternative embodiments, the frame  15  may be constructed with an open top such that the top of the carriage  20  may actually extend above the top of the frame  15 . In such constructions, the prime mover assembly  25  and spindle  75  may be positioned even higher when an underslung flexible support member  30  arrangement (as in the illustrated embodiment) is used. If the flexible support members  30  extend across the top of the carriage  20 , as may be the case in other embodiments, the prime mover assembly  25  and spindle  75  should be positioned very near the top of the frame  15  to maximize the vertical travel of the carriage  20  in the frame  15 .  
         [0020]     Because there are two flexible support members  30  in the illustrated embodiment, each flexible support member  30  carries half of the weight of the carriage  20  and its cargo. Because each flexible support member  30  extends vertically along both sides of the carriage  20 , each vertical portion of each flexible support member  30  carries half of the weight born by that flexible support member  30 . In other words, each vertical portion of the flexible support members  30  carries a quarter of the weight of the carriage and its cargo. This load-sharing arrangement permits the use of lower rated flexible support members  30  and smaller sprockets  85 ,  90 . The arrangement also creates a mechanical advantage for the prime mover assembly  25  because the ratio of flexible support member  30  gathered or let out by the sprockets  85  to carriage  20  vertical displacement is 2:1. The overall result of the arrangement permits the use of a smaller prime mover  65  (compared to an arrangement in which one or two flexible support members  30  raised and lowered the carriage in a 1:1 ratio), and permits smaller gears to be employed in the gearbox  70 . The reduction in size of the flexible support members  30 , sprockets  85 ,  90 , prime mover  65 , and gear box  70  may reduce the cost of the VRC.  
         [0021]     Turning now to  FIG. 5 , a load yoke  95  is mounted to the mast  35  on the opposite side from the prime mover assembly  25 . The load yoke  95  is pivotally mounted with respect to the mast  35  by way of a pin  100 . The pin  100  is off-center with respect to the span of the load yoke  95  so that the load yoke  95  will tip to one side when under the influence of gravity alone. Alternatively or in addition to the offset pin arrangement, a weight may be affixed to one end of the load yoke  95  to ensure that the load yoke  95  will tip when under the influence of gravity alone. Two links  105  are mounted to the load yoke  95  at equidistant points on either side of the pin  100 . The flexible support members  30  are connected to the links  105 .  
         [0022]     The tension in the flexible support members  30  applies equal and offsetting moment forces to the load yoke  95  and keeps the load yoke  95  substantially level. If there is slack in one of the flexible support members  30  the moment force applied through the other flexible support member  30  causes the load yoke  95  to tip. If slack develops in both flexible support members  30 , the yoke  95  will tip of its own accord under the influence of gravity alone. A tip sensor  110  is mounted to the frame  15  adjacent the load yoke  95 , senses when the load yoke  95  tips, and sounds an alarm that indicates slack in one or both of the flexible support members  30 .  
         [0023]      FIGS. 6-9  illustrate one of the brake assemblies  60 . Each brake assembly  60  include a base  115  having a pair of upright portions having aligned holes  120 . The base  115  is affixed to the carriage  20 . A cam  125  also has a hole  130  that is placed into alignment with the holes  120  in the upright portions of the base  115 . The cam  125  has a toothed end  135  for engaging the flange  45  of the mast. A shaft  140  extends through the holes  120 ,  130  such that the cam  125  is supported by the shaft  140  for pivotal movement with respect to the base  115 . A supporting bar  145  extends from the cam  125  and supports a brake plate  150 . The brake plate  150  includes an engaging surface, which in the illustrated embodiment is a wear surface  153  attached to the brake plate. The wear surface  153  is preferably constructed of a low-friction material. In alternative constructions, the engaging surface may include rollers or other friction-reducing components to facilitate low friction sliding of the flexible support members across the face of the brake plate  150 .  
         [0024]     A support link  155  is pivotally mounted to the shaft  140  and is affixed to the supporting bar  145  to provide additional support to the brake plate  150 . A torsion spring  160  is wrapped around the shaft  140  and is anchored at one end to the base  115  and at the other end to the supporting bar  145 . A spacer  165  may be employed between the upright portions of the base  115  to reduce or prevent sliding of the cam  125  and torsion spring  160  on the shaft  140 .  
         [0025]     The brake assemblies  60  are mounted to the carriage  20  to position the brake plates  150  over the carriage sprockets  90  with the flexible support members  30  extending across the face of the brake plates  150 . During ordinary operation of the VRC  10  (as illustrated in  FIG. 8 ), the torsion springs  160  bias the brake plates  150  into engagement with the flexible support members  30  and the cams  125  of the brake assemblies  60  are held out of engagement with the flanges  45  by the flexible support members  30 . In the event slack develops in one of the flexible support members  30  (as illustrated in  FIG. 9 ), the cams  125  of the two brake assemblies  60  engaging that flexible support member  30  (i.e., the brake assemblies on opposite sides of the carriage  20 ) will both be released substantially simultaneously and the torsion springs  160  will cause the toothed ends  135  of the cams  125  to substantially simultaneously engage the flanges  45  of the respective flanges  45  to brake the carriage  20 .  
         [0026]     The substantially simultaneous engagement of the brakes  60  on opposite sides of the carriage  20  helps to keep the carriage  20  level, even when one or both of the flexible support members  30  breaks. Since the brakes  60  on opposite sides engage substantially simultaneously, they share the load of the carriage  20  and its cargo. It is therefore believed that the illustrated arrangement of brake assemblies  60  reduces damage to the frame  15  and carriage  20  when slack develops in one or both of the flexible support members  30 . Also, because two brake assemblies  60  engage substantially simultaneously and share the load, smaller brake assemblies  60  may be used when compared to a constructions relying on a single, larger brake assembly.  
         [0027]     It should be noted that, although the illustrated embodiment discloses cam style brake assemblies  60 , other types of brake assemblies may be used in the present invention as well. For example, the carriage  20  may include an angled surface, together with the flange  45 , defines a wedge-shaped space opening downwardly. A roller or gear may be positioned in a relatively wide portion of the wedge-shaped space during normal operation of the VRC  10  such that the roller does not engage the flange  45  and carriage  20  simultaneously. The brake assembly may further include a mechanism for moving the roller into a relatively narrow portion of the wedge-shaped space where it is pinched between the flange  45  and a portion of the carriage  20  so that the carriage  20  cannot move downwardly with respect to the frame  15 . The mechanism for moving the roller into the narrow portion of the wedge-shaped space may include, for example, a spring biasing the roller toward the narrow portion and a wheel or other low-friction member engaging the flexible support member  30  and resisting the biasing force of the spring while there is tension in the flexible support member  30 .