Abstract:
A mail handling system that imports data from a thickness measurement device regarding the thickness of a substantially flat mail article, counts the number of flat articles deposited on the top surface of the drop pocket, instructs the drop pocket to open to drop a unitary body of flat mail articles when the total stack thickness and/or number of articles exceeds threshold limits. A computer, operably connected to conventional conveyor system having, a drop pocket, a thickness measurement device, and a conveyor, implements the system.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to mail article handling, and, more particularly to drop pocket door control.  
           [0002]    Articles of mail currently are transported along a conveyor system with a plurality of drop pockets. Along the way the articles are sorted, identified, assigned, and oriented for a planned orderly placement in a specific drop pocket for distribution by the postal carrier. Sorting systems convey documents, such as mail, envelopes and the like, along a primary or main path from which the documents may be selectively diverted to a designated drop pocket or sorted according to predetermined criteria, such as a zip code as represented on a zip code label. An article will travel along the conveyor system until it reaches its designated drop pocket, at which time the drop pocket will open and the article is deposited within the drop pocket. The drop pocket will only open for those articles designated by a conveyor system controller for that specific drop pocket.  
           [0003]    The objective of the conveyor system is to minimize the postal carriers&#39; effort in resorting and reorienting the mail articles after distribution. However, this orderly process is disrupted in the final stage when the articles are dropped from the conveyor system into the drop pocket at a level that inherently causes some articles to float into the drop pocket, thereby becoming disoriented requiring the postal carrier to reorient and possibly resort the mail. This added step by the postal carrier delays the start of the delivery process and may cause misdelivery of the article.  
           [0004]    Buffering systems for stacking documents before being dropped into a receptacle or a bin are disclosed, for example, in U.S. Pat. Nos. 5,101,981; 5,503,388; and 5,538,140. These patents monitor the stack height or the quantity or the document thickness temporarily stored in a drop pocket at an elevation higher than the receptacle or the bin. U.S. Pat. Nos. 5,503,388, by Guenther et al, and 5,538,140, Guntherer et al, disclose mechanical and electronic devices that measure the current stack thickness. U.S. Pat. No. 5,101,981, by Carbone et al, monitors the quantity of documents fed to the buffer. U.S. Pat. No. 6,126,017, by Hours, measures the document thickness prior to entry on to the conveyor system, tracks stack height in the drop pocket, and opens the drop pocket bottom door and drops the contents of the drop pocket into a receptacle or bin disposed below when the stack in the drop pocket is nearly full.  
           [0005]    It is a significant drawback where a system cannot determine actually whether the next document to be fed to the drop pocket will exceed the drop pocket height limit. To avoid possible system jams, these systems must limit the fed documents to a substantially known, constant thickness or the activation height of the measuring device must be no higher than the thickness document except in the sort run or drop a stack before the optimal height is reached. Limiting fed documents to those that are substantially the same thickness or dropping the stack before optimal height is reached may impact throughput and efficiency  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a system that takes into consideration the individual thickness of substantially flat articles, preferably mail articles, stacked on top of other flat articles in order to determine the optimum thickness and number of flat articles that can be dropped together face down and still remain a unitary body during the drop. For the purposes of the present invention, a unitary body is defined as a stack of substantially flat articles oriented approximately on top of each other such that when the stack is dropped from a predetermined height the aerodynamic characteristics of the stack with a plurality of articles has substantially the same aerodynamic characteristics of a single article of the same height and weight. In other words, the present invention sortation and orientation system insures that the stack of flat articles do not separate when dropping into an output receptacle.  
           [0007]    A computer, a thickness measurement device, and a conveyor implement the present invention. The present invention imports data from the thickness measurement device in order to ascertain the thickness of the next flat article. In addition thereto, the system of this invention counts the number of flat articles deposited on the top surface of the drop pocket door. By analyzing this information, a computer generates a signal to open the drop pocket that permits the dropping of a unitary body of substantially flat articles, when the total stack thickness and/or number of articles reaches threshold limits.  
           [0008]    For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description and its scope will be pointed out in the appended claims.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a flow diagram illustrating the logic utilized within the system of the present invention;  
         [0010]    [0010]FIG. 2 is a schematic representation of a conveyor system configured to utilize the system of the present invention;  
         [0011]    [0011]FIG. 3 is a flow chart that describes the operation of the system of the present invention; and  
         [0012]    [0012]FIGS. 4 a  and  4   b  are schematic section views of IV-IV of FIG. 2 showing the drop pocket containing mail items during the stacking operating and dropping the mail items as a unitary body in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    The present invention is now described more fully hereinafter with reference to the accompanying drawings, in which the preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments&#39; set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The preferred embodiment is illustrated utilizing mail flats or substantially flat articles but the system or method of this invention is applicable to any system that utilizes objects that are stackable.  
         [0014]    The preferred embodiment of this invention, being a system generally indicated by numerical designation  10 , is illustrated in FIG. 1. The present invention takes into consideration the individual thickness of objects, such as flat mail articles, to be stacked on top of other objects or like articles in order to determine the optimum thickness and number of flat mail piece that can be dropped together face down and still remain as a unitary body during the drop without the stack separating.  
         [0015]    The system  10  is implemented by a computer  12  operably connected to conventional conveyor system having a drop pocket  16 , a thickness measurement device  18 , and a conveyor  20 , as illustrated in FIG. 2. A conveyor  20  automatically directs object  22 , such as a mail article, to be stacked in drop pockets  16 . Single objects  22  travel along a conveyor  20  to a commercially available thickness-measuring device  18 , such as a shaft encoder or optical scanner. The object  22  then advances to a conventional drop pocket  16  to be stacked and await an instruction from the computer  12  that opens the drop pocket  16 . The objects  22  are stacked on top of each other in the same orientation as received. Returning to FIG. 1, the system  10  sums the object thickness&#39; to determine a stack thickness (or height) and sums the number of objects on the stack. When the stack thickness or object count reach threshold limits or minimum conditions explained in greater detail below, then drop pocket  16  opens, the stack of objects drop as a unitary body, and the counters are reset for the next batch of objects.  
         [0016]    The process steps of the system  10  are indicated in FIG. 3. In the preferred embodiment of the present invention, there are three conditions monitored by the computer  12  on a constant basis to determine whether an instruction would be sent to the drop pocket  16  to open. For illustration purposes, the stack thickness ranges from 1-inch (minimum) to 1.5 inches (maximum) and the article count ranges from 1 (minimum) to 10 (maximum) articles. The first condition checked is whether the stack thickness reaches the maximum value (1.5 inches). If so, then the computer  12  generates an instruction to the drop pocket  16  to open. If not, then a second check is performed to determine whether the number of articles equals the maximum value (10 articles). If so, then an instruction is sent to the drop pocket  16  to open. If not, a third check is performed whether the minimums of both conditions are exceeded (for example, a 1-inch stack thickness and 1 article). If so, then an instruction is sent to the drop pocket  16  to open. The objective of the limits is to optimize the process where the throughput is maximized and the resorting is minimized, if not eliminated all together. Therefore, these limits are for illustration purposes only and will increase or decrease based on the throughput requirements of each conveyor system, the size of the articles and capability of the drop pockets.  
         [0017]    [0017]FIGS. 4 a  and  4   b  are section views of IV-IV of FIG. 2 showing the conveyor  20  with a drop pocket  16  and output receptacle  24  for transporting objects, for example mail articles  22 . The system  10  provides a drop pocket  16  at each output receptacle  24 . These drop pockets  16  are mounted on a structure (not shown) supporting the conveyor  20 . Each drop pocket  16  is preferably vertically aligned with the corresponding output receptacle  24  so that mail articles  22  are transferred from the drop pocket  16  to the corresponding output receptacle  24  by gravity, which helps to simplify the layout of the conveyor. Each drop pocket  16  is adapted to store at least temporarily a certain quantity of mail articles  22 . The drop pocket  16  has a generally retractable bottom, for example a horizontally sliding door  26  adapted to be closed for storage, as shown in FIG. 4 a , or opened to release the mail articles  22  into the corresponding output receptacle  24 , as shown in FIG. 4 b . Other types of closure/opener devices can also be utilized with the present invention, for example a sweeper that will push the unitary body to an output receptacle waiting along side the drop pocket.  
         [0018]    As mentioned above, to stack objects, such as mail articles  22 , with a device of this kind, the computer  12  is programmed to monitor the stack height (or thickness) and the quantity of objects stacked in each drop pocket  16  on the basis of information supplied by the measuring device  18 . The computer  12  retains the drop pocket  16  in a normally closed position as shown in FIG. 4 a . The mail articles  22  are stacked temporarily in the drop pocket  16 . On detecting that the drop pocket  16  exceeds the stack height and/or object count limits, the computer  12  commands the opening of the drop pocket door  26  to open with sufficient speed to overcome fictional effects and drop the temporarily stacked mail articles  22  into the corresponding output receptacle  24 , as shown in FIG. 4 b , as a unitary body. A unitary body will not bend significantly due to the cumulative stiffness of the individual mail articles  22 , thereby maintaining the object sequence and orientation. As the mail articles  22  are stored flat, both in the drop pocket  16  and in the output receptacle  24 , the mail articles  22  are stored more efficiently in the receptacle  24  by transferring them as a unitary body rather than by transferring them individually.  
         [0019]    It will now be apparent to those skilled in the art that other embodiments, improvements, details, and uses can be made consistent with the letter and spirit of the foregoing disclosure and within the scope of this patent, which is limited only by the following claims, construed in accordance with the patent law, including the doctrine of equivalents.