Abstract:
A buffer device for buffering a flow of stacks of discrete objects between a stacking machine and a packaging machine is disclosed which buffer includes a plurality of individual trays mounted on carriers which carriers are mounted on a frame and driven about the periphery of the frame by a drive. A first number of stacks of objects is placed on a first number of carriers on a first side of the frame and a second number of stacks are removed from a second number of carriers on a second side of the frame where the first number can be greater than, less than or equal to the first number. The carriers clamp onto a continuously moving drive belt in a manner that allow the drive belt to slip through the carrier clamps when motion of the carriers is obstructed. A method of using the buffer device is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY  
       [0001]    The present application claims the benefit of U.S. provisional patent application serial No. 60/290,342, filed May 14, 2001, the disclosure of which is incorporated by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention is directed to a method and apparatus for buffering a flow of stacks of objects, and more specifically, toward a method and apparatus for receiving a first number of stacks of discrete planar objects, such as frozen hamburger patties, from a stacking machine and presenting a second number of those stacks to a packing machine, especially when the first and second numbers are unequal.  
         BACKGROUND OF THE INVENTION  
         [0003]    Frozen hamburgers, chicken patties, sausage patties, and other disk-like food products typically are prepared by a manufacturer on one piece of equipment and then fed into a freezer. After leaving the freezer, they are screened by a metal detector, which detects contaminated patties, and then conveyed to a stacker. The stacker forms the patties into one or more stacks, and the finished stacks are then placed in cases. Because the stacks formed by some stackers can vary in height, and because the number of stacks formed simultaneously by a stacker may be greater than the number of stacks that will fit in a row in a case, the finished stacks are often removed from the stacker and loaded into cases by hand. This manual loading step is labor-intensive, and, due to the presence of a human element, highly variable.  
           [0004]    The problem of forming uniform stacks of patties is addressed by the novel stacking machine disclosed in the co-pending application entitled “Method and Apparatus for Stacking Discrete Planar Objects” filed concurrently herewith and assigned to the assignee hereof. The disclosure of that application is hereby incorporated by reference. However, as with many prior art devices, the subject stacker simultaneously forms more stacks than will fit in one row of a typical case. For example, in a preferred embodiment, the subject stacker receives four rows of frozen patties from a conveyor belt and simultaneously forms four stacks of patties. Cases of patties, however, can often accommodate only three stacks of patties per row, or possibly five stacks or more.  
           [0005]    This problem could be addressed by adjusting the stacking machine to form only three stacks of patties at a time, but the reduction from four rows to three rows represents a twenty-five percent decrease in efficiency. Human packers can also address this problem by packing stacks one at a time and positioning each stack as required in a given case. However, as mentioned above, it would be desirable to fully automate the stacking and packing processes to provide greater consistency and to reduce costs.  
           [0006]    In addition, not all cases are packed in the same manner. Some cases may hold only two rows of patties, for example, and it would be useful to have a machine that could be rapidly adjusted to convert four incoming rows of stacks into two outgoing stacks, depending on the product being packaged, or even to accommodate cases that alternate between two stacks per row and three stacks per row. Ideally, the change would be software controlled or require no more than the push of button to make. And, while reducing the number of rows is the general problem faced by the industry, under some circumstances it may be desirable to present more stacks to a packing machine than are provided at one time by a stacker—for example, if the stacker forms four rows of stacks at a time and a certain case requires six stacks in a row. Finally, the machine should be able to function under conditions where the number of incoming rows is equal to the number of outgoing rows and to do so in an efficient manner.  
         SUMMARY OF THE INVENTION  
         [0007]    These and other difficulties are addressed by the present invention which comprises a novel buffering device that receives a first plurality of stacks of objects from a stacking machine and presents a second number of stacks to a packing machine for removal, where the second number may be greater than, less than, or equal to the first number. The invention includes a plurality of trays or similar receptacles sized and shaped to accommodate the stacked objects, which receptacles are mounted on carriers that can be moved between a first location where the stacks are received from a loading device and a second location where the stacks are removed by an unloading device.  
           [0008]    In a preferred embodiment, the invention comprises a carousel around which a belt rotates continuously in a path having two generally parallel linear sections connected by curved portions. Each carrier is attached to the belt by a clamp which engages the belt in a jaw-like manner on opposites sides thereof. The clamp is attached tightly enough to cause the receptacle to move with the belt when the path of the carrier is unobstructed, but loosely enough that the belt will slide through the clamp when the path of the carrier is blocked. In this manner, the position of the carriers can be controlled somewhat independently of the positions of the other carriers without the need to provide separate controllers for the clamps on each carrier.  
           [0009]    The movement of the receptacles is controlled so that a first number of receptacles is always available when needed to receive a first number of incoming stacks at a first location. The receptacles are then released to a second location from which the stacks are removed in groups of a second number. When the second number is less than the first number, the stacks must be removed at a rate greater than the rate at which the stacks of patties arrive at the carousel, and full carriers are buffered at a location between the first and second locations. When the second number of carriers is greater than the first number, the full carriers are accumulated at the second location until a second number of carriers is present. When the first and second numbers are the same, the carries merely move around the carousel in equally sized groups. While such a buffer can be incorporated into a stacking or packing machine, in the preferred embodiment, it comprises a stand-alone device that is connected between a stacker and a packer, thus allowing greater flexibility for use with different types stacking and packing machines.  
           [0010]    In a preferred embodiment, the device further includes sensors for detecting the presence of carriers at different points around the carousel. A proximity sensor mounted near the path of the carriers detects the carriers as they pass. The sensors are operably connected to stops that block the passage of carriers when the stops are in an extended or in a blocking position. Because the carriers are somewhat loosely connected to the drive belt, the drive belt continues to move through the clamp when a carrier is blocked. Other carriers being moved by the belt engage the stopped carrier, and are likewise stopped. When the stop is moved to a releasing position, the carriers that were blocked begin again to move with the belt. A controller connected to the stops controls them so that so that carriers are released from the first stop in groups of a first number and released from the second stop in groups of a second number, where the first number can be greater than, less than or equal to the second number. Alternately, additional sensors can be used to determine whether the carriers are full or empty. When additional sensors are used, the controller releases only full carriers from the first location, and releases only empty carriers from the second location. Thus, with either embodiment, empty carriers are stopped at the first location and filled with stacks of frozen hamburger patties. When the carriers are full, the controller releases the stop to allow the filled group of carriers to pass and the next empty carrier is stopped. The full carriers travel around the carousel until they reach the second stop, which moves into the blocking position to keep the full carriers from passing. The full carriers remain at this location until stacks are removed by a stack transfer mechanism, and empty carriers are then released to travel back to the first location.  
           [0011]    In the preferred embodiment, the number of carriers is related to the maximum number of incoming or outgoing rows of patties in a certain way to minimize the number of carriers needed, and this reduces the amount of space occupied by the machine. Applicant has found, for example, that a buffer for use between a stacking machine that produces four rows of patties and a packaging machine that requires three rows of patties as input, needs eleven carriers. By limiting the number of carriers, the width of the buffer can be kept small and the resulting buffer need not be much greater than the width of the stacking machine.  
           [0012]    It is therefore a principal object of the invention to provide an apparatus for receiving a first number of stacks of objects at an input location and presenting a second number of stacks of objects at an output location.  
           [0013]    It is another object of the invention to provide a method of buffering the flow of stacks of objects between a stacking machine and a packing machine.  
           [0014]    It is a further object of the invention to provide an apparatus for matching the output rate of a first machine to the input rate of a second machine.  
           [0015]    It is still another object of the invention to provide a carousel having a plurality of selectively positionable receptacles for receiving a plurality of stacks from a first machine and presenting a plurality of stacks to a second machine.  
           [0016]    It is still a further object of the present invention to provide a free-standing stack transfer device that receives a first number of stacks of objects at a first location and presents a second, smaller number of stacks of objects at a second location.  
           [0017]    It is yet another object of the present invention to provide a free-standing stack transfer device that receives a first number of stacks of objects at a first location and presents a second, larger number of stacks of objects at a second location.  
           [0018]    It is yet a further object of the present invention to provide a buffer device that can be configured to accommodate different numbers of incoming stacks and differing numbers of outgoing stacks.  
           [0019]    In furtherance of these objects, a method for buffering a flow of stacks of objects from a first location presenting a first number of stacks to a second location adapted to receive a second number of stacks is provided that includes the steps of providing a frame between the first location and the second location which frame has a first position and a second position. A plurality of carriers each adapted to hold a single stack is associated with the frame and a first number of carriers are moved to the first position. The first number of stacks are transferred from the first location to the first number of carriers at the first position, and then the first number of filled carriers at the first position are moved toward the second position. Whenever at least a second number of filled carriers are present at the second location, the stacks from the second number of filled carriers at the second position are removed to the second location. Lastly, empty carriers are returned from the second position toward the first position.  
           [0020]    Another aspect of the invention comprises a system for buffering a flow of stacks between a first location and a second location that includes a frame having a first position with an exit end proximate the first location and a second position with an exit end proximate the second location and a drive. A plurality of carriers is supported by the frame and connected to the drive. The device further includes a first stop at the first position exit end, a second stop at the second position exit end, and a controller for actuating the first stop to allow carriers to pass the first location exit end in groups of a first number and for actuating the second stop to allow carriers to pass the second location exit end in groups of a second number.  
           [0021]    A further aspect of the invention involves a method for receiving a first number of stacks of discrete objects from a stacking machine and presenting a second number of the received stacks for removal by a stack transfer machine. The method requires a frame having a periphery, a first location on the periphery, and a second location on the periphery, and a drive on the frame. A plurality of carriers adapted to hold a single stack are mounted on the frame and connected to the drive. A first sensor is provided for counting the number of carriers passing a first point and a second sensor is provided for counting the number of carriers passing a second point. A first stop is provided near the first point for preventing empty carriers from passing the first stop, and one stack is received in each of the first number of carriers at the first location. The first number of carriers are released from the first stop, but stopped at a second location by a second stop near the second point that prevents carriers from passing the second location. A second number of stacks is removed from the first number of carriers at the second location, and the second number of carriers are released by the second stop and moved toward the first location.  
           [0022]    Yet another aspect of the invention comprises a buffer including a support frame, a platform having a periphery mounted on the support frame, and a guide extending around the periphery. A drive belt is mounted adjacent the platform along the periphery, and a drive is operatively coupled to the drive belt. A plurality of carriers is supported by the platform, each including a first member engaging the guide and a second member engaging the drive belt such that movement of the drive belt moves the carriers about the periphery of the platform. A first sensor is mounted at a first location for counting the number of carriers passing the first location, and at least one stop is provided that can be shifted between a first position in a path of travel of the carriers around the platform and a second position outside the path of travel of the carriers around the platform. A controller operatively coupled to the first sensor controls the position of the at least one stop.  
           [0023]    A further aspect of the invention comprises a carrier having a trolley adapted to support a tray for holding stacks of objects. The trolley has a body with a first side and a second side and includes a first wall portion having an end and a second wall portion extending from the end of the first wall portion at an obtuse angle. An axle extends from the first side of the second wall portion and a wheel is rotatably supported by the second wall portion axle. A clamp is mounted on the first side of the first wall portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    These and other objects of the invention will become apparent from a reading and understanding of the following detailed description of the invention together with the following drawings of which:  
         [0025]    [0025]FIG. 1 is a perspective view of a carousel buffer device having a plurality of trays supported on carriers according to the present invention.  
         [0026]    [0026]FIG. 2 is an assembly drawing of a portion of the buffer device of FIG. 1 with the carriers and trays removed.  
         [0027]    [0027]FIG. 3 is a side elevational view of one of the carriers shown in FIG. 1.  
         [0028]    [0028]FIG. 4 is a rear elevational view of the carrier of FIG. 3.  
         [0029]    [0029]FIG. 5 is a side elevational view of the buffer of FIG. 1.  
         [0030]    [0030]FIG. 6 is a side elevational view of the buffer of FIG. 1 showing a stop for preventing the movement of the carriers in a non-engaged position.  
         [0031]    [0031]FIG. 7 is a side elevational view of the buffer and stop of FIG. 6 showing the stop in an engaged position.  
         [0032]    [0032]FIGS. 8 a - h  are top plan views of the buffer of FIG. 1 showing the locations of full and empty trays around the periphery of the buffer as the buffer is used according to the method of the present invention.  
         [0033]    [0033]FIG. 9 is a top plan view of the buffer device with the trays removed to show the positions of several sensors. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0034]    Referring now to the drawings, wherein the showings are for purposes of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, FIGS. 1 and 2 illustrate a buffer device designated generally by the numeral  10  which includes a frame  12 , a drive  14  and a plurality of carriers  16  supported by the frame  12 . Frame  12  includes vertical support portions  18  adapted to support the frame on a horizontal support surface, a generally planar upper support portion  20  that includes first and second openings  22 , and a motor support  24  mounted beneath upper planar portion  20 .  
         [0035]    Drive  14  includes a motor  26  mounted on motor support  24  and operably connected to a drive gear  28  which turns a continuous drive belt  30  about a plurality of flanged wheels, including a first wheel  32  and a second wheel  34 . First and second wheels  32  and  34  each include a center opening  36  having a notch  38  for receiving a splined shaft. Two splined shafts  40  extend from center openings  36  upwardly through first and second openings  22  in the frame upper support  20 .  
         [0036]    A bottom plate  42  having first and second openings  44 , as best shown in FIG. 5, a peripheral edge  46  and a raised rail  48  running around the peripheral edge is mounted on frame upper support  20  with first and second openings  44  aligned with openings  22  in the frame upper support  20  so that splined shafts  40  extend though these openings. Wheels  50 , as best shown in FIG. 2, are mounted on each of the splined shafts which wheels include center openings  52  shaped to receive shafts  40  and peripheral grooves  54  for receiving and holding a drive belt  56 . The drive belt  56  preferably has a circular cross section and is formed from a flexible, wear-resistant material, such as urethane.  
         [0037]    A top plate  58  having first and second openings  60 , a peripheral edge  62  and a raised rail  64  running around the peripheral edge is mounted over bottom plate  42  and spaced apart therefrom by spacers  66 , with openings  58  positioned to receive splined shafts  40 . Bearings  68  are mounted on top plate  56  to rotatably secure the ends of shafts  40 . Thus, motor  26  turns drive gear  28  and causes drive belt  30  to move about first wheel  32  and second wheel  34 , which in turn causes splined shafts  40  and wheels  50  mounted thereon to rotate and drive drive belt  56  about a continuous path between bottom plate  42  and top plate  58 . Drive belt  56  preferably has a diameter greater than the width of peripheral grooves  54 , so that the belt only contacts the wheels about a small portion, less than 180 degrees, of the belt&#39;s circumference.  
         [0038]    [0038]FIG. 1 illustrates a plurality of carriers  16  mounted on the top and bottom plates which carriers comprise trays  70  supported by trolleys  72  as best shown in FIGS.  2 - 4 . Each tray  70  includes a bottom wall  74  having a centrally located slot  76  with a slot edge  78 , a rear wall  80  and sidewalls  82 . The trays  70  are preferably mounted on the trolleys  72  in a manner that allows for easy removal thereof, so that appropriately sized trays  70  can be used for the objects being processed. Each trolley  72 , shown in more detail in FIGS. 3 and 4, includes a body portion  86  having a lower portion  88  with a lower end  90  and an upper portion  92  angled with respect to the lower portion  88 . A wall  94  projects from body lower portion  88  in the same direction as the angle of the upper portion, and includes a small wall  96  projecting from its end in the direction of angled upper portion  92 . A boss  98  is mounted on upper portion  92  and supports a shaft  100  on which a wheel  102  having a V-shaped peripheral notch  104  is rotatably mounted and held in place by a retainer  106 . A wheel support  107  is connected to wall  94 , and small wall  96  supports two shafts  108  on which first and second guide wheels  110  are mounted for rotation about axes parallel to lower portion  88  of body portion  86 . Projections  112  extending from the lower side of wall  94  support two additional guide wheels  114 , which guide wheels are mounted for rotation about axes normal to body lower portion  88 . Guide wheels  115  are also mounted on the bottom side of wall  94 , with axes parallel to body portion  88  and between guide wheels  114  and body portion  88 .  
         [0039]    A clamp  116  is mounted on body lower portion  88  between guide wheels  110  and  110  notched wheel  102 , and includes an upper clamp member  118  pivotably supported on lower body portion  88  by a shaft  120 , and a lower clamp member  122  pivotably supported on a shaft  124  extending between lower body portion  88  and small wall  96 . Both the upper and lower clamp members are coated with, or preferably formed from, a low-friction, wear resistant material, such as UHMW polyurethane. The angular relationship between the upper and lower clamp members, and hence the distance separating the ends of the clamp members, can be adjusted by pivoting the upper clamp member and fixing it in place with fastener  126 .  
         [0040]    The mounting of carriers  16  on the upper and lower plates is best shown in FIG. 5, wherein trays  70  are detachably connected to trolleys  72 , and the trolleys are arranged such that notch  104  of wheel  102  on the angled upper portion  92  of the trolley fits over an edge of raised rail  64  on the periphery of top plate  58 , guide wheels  110  engage the inner edge of raised rail  48  on bottom plate  42 , guide wheels  115  engage the outer edge of raised rail  48 , and guide wheels  114  engage the underside of bottom plate  42 .  
         [0041]    The upper and lower members  118  and  122 , respectively, of clamp  116  are attached to drive belt  56  by placing the belt between the members and clamping the upper member in place so that a small force is exerted against the belt by the clamp members. The force must be great enough that friction between the clamp  116  and the belt  56  will keep the trolleys  72  fixed with respect to the belt when the path of the trolleys  72  is clear. The force also must be small enough that the frictional force between the belt  56  and the clamp  116  can be overcome by the drive motor to cause the belt to slip through the clamp when movement of one or more of the trolleys  72  is blocked by a stop.  
         [0042]    A first solenoid-actuated stop  128  is mounted on frame  12  with a trolley-engaging portion  130  shiftable between a first, release position, shown in FIG. 6, below the lower ends  90  of the trolley bottom portions  88  and a second, stop, position, shown in FIG. 7, where the trolley engaging portion  130  blocks a path of the trolley  72  by forming a stop against which the lower ends  90  of the trolleys impact when the stop  128  is in its stopping position. A second, separately controllable, solenoid-actuated stop  134  is provided on the other side of the buffer device.  
         [0043]    The shifting of the stops between stopping and releasing positions is controlled by a controller  136 , operably coupled to sensors  132  and  133  mounted on frame  12  below the tray bottom walls  94 , as best shown in FIGS. 5 and 9. These sensors are used to count the number of trays passing thereby. The controller  136  monitors the number of trays  70  passing over each of the sensors  132  or  133 , and causes the first stop  128  to shift to its stop position when a predetermined number of trays has passed. For example, when the buffer receives four stacks of patties at a time from a stacker, the trays  70  will be released in groups of four. Similarly, when stacks are removed in groups of three, the controller  136  shifts the second stop  134  into the blocking position and only allows the trays  70  to pass in groups of three. The operation of the stops  128  and  134  is coordinated with the operation of the stacker and stack transfer mechanism so that, in the embodiment described herein, at least four empty trays are always available to receive incoming stacks of patties and that at least three stacks of patties are present at the second stop  134  to be removed by a stack transfer device. An optical sensor  135  is also provided for detecting patties on the trays as they approach the loading position. Since these trays  70  should all be empty, an alarm occurs or the system shuts down when full trays are seen approaching the loading position.  
         [0044]    As best shown in FIG. 9, two additional sensors  144  and  146  are also provided to help ensure that enough trays  70  are present upstream of stop  128  to receive incoming stacks of patties and that the correct number of stacks of patties are available for removal by a stack transfer device. Thus, for example, as sensor  128  is counting the passage of four trays  70 , sensor  144  upstream of sensor  128  is counting the passage of empty trays toward sensor  132  and stop  128 . Controller  136  is preferable coupled to the controller for a transfer device that brings stacks of patties to the buffer device  10  and configured so that stacks of patties will not be transferred to buffer device  10  until sensor  144  has detected the passage of four trays  70 . Thus, in the event that a problem arises that prevents four empty trays from lining up behind stop  128 , the transfer device will not attempt to transfer stacks of patties to the buffer device  10 . This reduces the likelihood that patties will be dropped or otherwise mishandled during processing. In a similar manner, sensor  146  counts trays  70  approaching sensor  133 , and as sensor  133  is counting the release of three empty trays  70 , for example, sensor  146  is counting approaching trays to ensure that at least three full trays are present at stop  134  and that at least three stacks are available for removal. Controller  136  is preferably connected to the controller for the downstream stack transfer device and prevents stacks from being removed from the trays stopped at stop  134  until three stacks are present for removal. The number of stacks arriving at and leaving the buffer device  10  can be varied, and the position of sensors  144 ,  146  is adjustable so that these sensors can be placed near the location where the last of a given group of trays  70  will be found when the system is operating properly.  
         [0045]    In a second embodiment, sensors  132  and  133  are used both to count the number of trays passing thereby and to detect whether the tray adjacent the sensor is full or empty, based upon whether slot  76  is blocked. The controller  136  monitors the status of the trays  70  passing over each of the sensors, and causes the first stop to shift to its stop position whenever an empty tray is detected and to shift to its release position when a full tray is detected. Similarly, controller shifts the second stop into the blocking position when a full tray is detected by sensor  133  and into the releasing position when actuated in an opposite manner, that is, set to prevent the passage of full trays while allowing empty trays to pass.  
         [0046]    In operation, motor  26  drives drive belt  30 , turning first and second wheels  32 ,  34  and rotating shafts  40  and wheels  52  mounted thereon. This in turn causes drive belt  56  to move continuously about the periphery of the buffer between plates  42  and  58 . The carrier trolleys  72  are clamped to belt  56  tightly enough that they are pulled about the peripheries of the upper and lower plates by the movement of the belt. The trolleys are guided by the engagement of trolley wheels  102  with upper plate raised rail  64  and the engagement of guide wheels  110 ,  112  and  114  with the peripheral portion  46  of lower plate  42 . Stops  128  and  134  are selectively moved into and out of the path of travel of the trolleys and, when positioned in a stopping position, prevent trolleys from moving past the stops. The motor  26  continues to operate at a continuous speed, however, sliding belt  56  through clamps  116  even when all trolleys are prevented from moving by the positions of the stops. The urethane from which belt  56  is formed is sufficiently wear resistant that it provides reliable operation even after many hours of continuous use. And, as the relative positions of clamp upper member  118  and lower member  122  are adjustable, the clamps can be repositioned in the event that the diameter of belt  56  decreases slightly after a long period of use to maintain the proper pressure on the belt.  
         [0047]    The operation of the subject system will now be described with particular reference to FIGS. 8 a - 8   h  which shows the system set up for use with a patty stacker that forms four stacks of patties simultaneously which patties must be packed in boxes that are three patties wide. Thus the buffer will receive stacks of patties four at a time from a first direction, shown by arrows  138  in FIG. 8A, on a first side of the buffer and present them for removal three stacks at a time on a second side of the buffer where they are removed in a the direction of arrows  140  in FIG. 8C.  
         [0048]    [0048]FIG. 8A shows four trays  70   a ,  70   b ,  70   c  and  70   d  on a first side of buffer  10  which trays have just received four stacks  142  of hamburger patties from a transfer mechanism (not shown). Controller  136  causes stop  128  to move between blocking and releasing positions in order to release carriers in groups of four at predetermined intervals. After four stacks of patties are received in trays  70   a - 70   d , stop  128  shifts to its release position and allows these carriers to pass. The fifth carrier,  70   e , which is empty, and the carriers behind it, are stopped by stop  128  for a predetermined period of time, a period long enough for theses carriers to receive four more stacks of patties from the stacking machine.  
         [0049]    As shown in FIG. 8B, additional carriers  70   f  and  70   g  impact against stopped carrier  70   e  and are held in this position as belt  56  slips through clamps  116  on each trolley. Carriers  70   e - g  will remain in this position for a predetermined amount of time. Meanwhile, carriers  70   a - d  have been carried around buffer  10  by belt  56  toward a second stop  134  that blocks the path of the trays, and tray  70   a  impacts against the second stop. Trays  70   b - d  impact against stopped tray  70   a  and are also brought to a stop with drive belt  56  sliding freely through clamps  116  on each of the stopped trays.  
         [0050]    As shown in FIG. 8C, a second transfer device, not shown, removes three stacks of patties from carriers  70   a ,  70   b  and  70   c  in the direction of arrows  140 , and the first transfer device places four additional stacks of patties on carriers  70   e ,  70   f ,  70   g  and  70   h  on the first side of the buffer. After a predetermined time, carriers  70   a - c  will be empty, and therefore the controller cause these three trays to be released, while the next tray (the last full tray) is stopped. Full carriers  70   e ,  70   f ,  70   g  and  70   h  are released by first stop  132  in FIG. 8C and moved around the buffer until they impact full carrier  70   d  held up at second stop  134  resulting in the positioning of trays shown in FIG. 8D.  
         [0051]    [0051]FIG. 8E shows that three stacks of patties have been removed from carriers  70   d ,  70   e  and  70   f  and that additional stacks of patties have been placed on carriers  70   i ,  70   j ,  70   k  and  70   a . Four full carriers are released by stop  128  and three empty carriers are released by stop  132  as described above resulting in the arrangement of carriers shown in FIG. 8 f . As shown in FIG. 8G, three additional stacks of patties are removed from trays  70   g ,  70   h  and  70   i  and these now-empty carriers are also released. Full carriers  70   j ,  70   k  and  70   a  remain stopped at stop  132 . Three additional stacks of patties will be removed from carriers  70   a ,  70   k  and  70   j  as shown in FIG. 8H while an additional four stacks are added to trays  70   c ,  70   d ,  70   e  and  70   f  at the first side of the buffer, and from there the process continues repeatedly as described above.  
         [0052]    The above invention has been described above in terms of a preferred embodiment. However, obvious changes and additions to the invention will become apparent to those skilled in the relevant arts upon a reading of the foregoing disclosure. For example, while the trolleys are described as being connected to a urethane belt in a manner that allows the belt to slide through the trolleys when the motion of a trolley is blocked, a plurality of separately controllable clamps could be used on each carrier to independently control whether a given carrier is connected to a drive belt. Additional sensors could also be added to provide additional information on the position and status of carriers as they travel around the buffer. And, while the buffer has been described in terms of reducing a flow of four incoming stacks of patties to three outgoing stacks of patties, the number of incoming patties could be changed, the number of outgoing patty stacks could be greater than the number of incoming stacks or the incoming and outgoing stacks could be equal in number without departing from the scope of this invention. It is intended that all such obvious changes and additions be included within the scope of this invention to the extent that they are defined by the several claims appended hereto.