Patent Publication Number: US-6340804-B1

Title: Paper sheet sorting apparatus and sorting method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a paper sheet sorting apparatus such as a letter sorter for sorting letters or the like mails in accordance with addresses thereof, or more in particular to a paper sheet sorting apparatus for controlling the interval of supplied letters in accordance with the information amount of the letters to be processed. 
     2. Description of the Related Art 
     A letter sorter will be explained as an example of the paper sheet sorting apparatus. In the letter sorter, letters supplied one by one from a supply means are transported to a deposit means by a transport means. In the process, the information on the hardness and shape of the letters and the sorting information such as the address are fetched, and the letters are introduced to a predetermined deposit means accordance with the result of processing the information. 
     The information processing speed is one of stumbling blocks to increasing the number of letters capable of being processed in a unit time by the letter sorter (hereinafter referred to as “the processing speed”). Especially, the character recognition for reading an address is a time-consuming process. Letters have addresses, some printed in characters and others handwritten. Since different users have different characteristics, characters of handwritten addresses are more difficult and require longer time to recognize than those of printed addresses. 
     As disclosed in JP-A-63-143132, for example, some conventional letter sorters can change the interval of letters supplied according to the size of the letters involved. According to the prior art, the interval of letters supplied can be changed according to the size of the letters, but cannot be changed according to the load of information to be processed. In the case where an address is printed in characters, the recognition is accomplished with a margin. In other words, the performance of the character recognition means is not fully utilized. In the case where an address of a letter is handwritten, on the other hand, the performance of the character recognition means may be exceeded since the address may not be recognized. As described above, with the conventional letter sorters, the interval at which letters are supplied cannot be changed according to the information load to be processed. The problem is posed that the performance of the character recognition means cannot be effectively utilized or the address cannot be read and sorted successfully. 
     SUMMARY OF THE INVENTION 
     Accordingly, the object of the present invention is to improve the processing speed of a paper sheet sorting apparatus by making the most of the information processing means such as a character recognition means. 
     According to the present invention, in order to solve the above-mentioned problems, there is provided a paper sheet sorting apparatus comprising at least a supply means for supplying paper sheets one by one, a supply control means for controlling the supply means, an information acquisition means for acquiring information on the paper sheets, an information processing means for processing the information acquired by the information acquisition means, a deposit means for depositing the paper sheets processed by the information processing means, a distribution means for distributing the paper sheets processed by the information processing means among predetermined ones of the deposit means, a transport means for transporting the paper sheets from the supply means to the deposit means, a load measuring means for measuring the amount of the load to be processed by the information processing means and a transfer means for transferring the load measured by the load measuring means to the supply control means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram showing a configuration of a letter sorter according to an embodiment of the present invention. 
     FIG. 2 is a model diagram showing the manner in which letters are distributed in the distribution means. 
     FIG. 3 is a model diagram showing the processing in the character recognition means. 
     FIG. 4 is a schematic diagram of a letter sorter having a configuration partly changed. 
     FIG. 5 is a diagram for explaining the operation when the load condition undergoes a change. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a schematic diagram showing a letter sorter constituting a paper sheet sorting apparatus according to an embodiment of the present invention. Paper sheets handled in the apparatus according to this embodiment mainly include mails of predetermined size such as post cards and envelopes. 
     A letter sorter  50  shown in FIG. 1 reads the sorting information such as an address or a bar code written on letters  1  and processes the letter in accordance with the sorting information. 
     First, each component element of the letter sorter  50  will be explained. 
     A supply means  2  is for supplying letters  1  one by one sequentially. For example, the letters  1  are attracted to a belt under a negative pressure, moved onto the belt, and sequentially supplied one by one into the letter sorter. 
     A transport means  3  transports the letters  1 . This transport means  3  includes, for example, a pair of belts moving in opposed relationship to each other for holding and transporting the letters  1 . 
     A foreign matter detection means  4  is for measuring the geometric information of the letters  1 , and a foreign matter discrimination means  5  receives the information from the foreign matter detection means  4  and discriminates the letters that cannot be handled in the letter sorter  50 . An improper size or hardness of the letters  1 , or a situation in which two or more letters supplied at a time, is discriminated as an abnormal condition. 
     A first positioning means  6  is for correcting the position of the letters  1  and a character reading means is for reading the addresses written on the letters  1  as image information. A bar code reading means  8  is for reading any address bar code printed on the letters  1  as image information. The first positioning means  6  is located upstream of the character reading means  7  and the bar code reading means  9  for setting the letters in position thereby to improve the reading accuracy. 
     The character recognition means  9 , on the other hand, receives the image information obtained by the character reading means  7  and retrieves the sorting information by recognizing the characters from the particular image information. In the process, in order to process a plurality of the letters  1  concurrently, the character recognition means  9  includes a plurality of recognition units  9   a ,  9   b , and so forth. 
     A sorting information input means  10  processes the letters that cannot be recognized by the character recognition means  9 . In this sorting information on input means  10 , for example, the operator viewing the image inputs the sorting information by key entry or the like. A plurality of the sorting information input units  10   a ,  10   b , and so forth can be provided to process the letters concurrently. 
     A bar code recognition means  11  receives the image information obtained by the bar code reading means  8 , and recognizes the bar code from the image information thereby to retrieve the sorting information. In order to process a plurality of letters  1  concurrently, the bar code recognition means  11  includes a plurality of recognition units  11   a ,  11   b , and so forth. 
     A hopper  12  is for transporting the letters  1  stacked along the thickness thereof to the supply means  2 . 
     A first distribution means  13  is for distributing the letters and a reject-deposit means  14  is for depositing the letters rejected. The letters  1  that have been judged as abnormal by the foreign matter discrimination means  5  based on the information from the foreign matter detection means  4  are not sorted but changed in the direction of transportation by the first distribution means  13  and led to the reject-deposit means  14 . 
     A second positioning means  15  is for positioning the letters. A bar code printing means  16  is for printing a bar code on the letters  1  not printed with any bar code. A second positioning means  15 , which is located upstream of the bar code printing means  16 , sets the letters  1  in position, and a bar code is printed on them in the bar code printing means  16 . 
     A bar code checking means  17  is for checking that a bar code has been normally printed. 
     A letter deposit means  18  is for depositing the letters  1 , a second distribution means  19  is for distributing the letters  1  into stages, and a third distribution means  20  is for distributing the letters  1  among a plurality of predetermined slots of the deposit means  18 . The letters  1  are sorted into a predetermined slot of the deposit means  18  by switching between the second distribution means  19  and the third distribution means  20  in accordance with the sorting information obtained by the information processing means including the character recognition means  9 , the sorting information input means  10  and the bar code recognition means  11 . 
     An overlap means  21  is configured of two transport paths  21 A,  21 B having different lengths and an overlap distribution means  21 C. Letters entering the latter deposit means  18  at short intervals may bump each other and cause a jam. In view of this, each pair of letters are laid one on the other in advance so as to prevent them from bumping each other in the letter deposit means  18 . In the case where the transport path  21 A is shorter than the transport path  21 B, for example, two letters can be laid one on the other by leading the first letter to the transport path  21 B and the second letter to the transport path  21 A. 
     A supply control means  22  is for controlling the supply means  2 . The supply control means  22  controls the operation of the supply means  2  and thereby adjusts the interval of the letters  1  supplied. 
     A transport control means  23  is for controlling the first distribution means  13 , the second distribution means  19 , the third distribution means  20  and the overlap distribution means  21 C and for transporting the letters  1  to a predetermined slot deposit means  18  or the reject-deposit means  14  in accordance with the sorting information obtained by the character recognition means  9  or the bar code recognition means  11  and the judgment at the foreign matter discrimination means  5 . 
     A load measuring means  24  is for measuring the amount of the load on the information processing means for processing the information of the letters  1 . In the letter sorter  50 , the information processing means for processing the information of the letters  1  includes the foreign matter discrimination means  5 , the character recognition means  9 , the sorting information input means  10 , the bar code recognition means  11  and the transport control means  23 . 
     A transfer means  25  is for transmitting the load measured by the load measuring means  24  to the supply control means  22 . 
     A select means  26 , on the other hand, is for selecting an object of which the load is measured at the load measuring means  24 . 
     Now, explanation will be made about an example process of sorting the letters  1  by the letter sorter  50 . Assume that the select means  26  selects the character recognition means  9  alone as an object of load measurement. Also, assume that an address is written in characters but no bar code is printed on the letters  1 . 
     First, the letters  1  placed in the hopper  12  are supplied one by one from the supply means  2  and transported by the transport means  3 . In order to remove the letters  1  beforehand that cannot be processed by the letter sorter  50 , the foreign matter detection means  4  detects the information of the geometry of the letters  1 . The normality of the letters  1  is checked from this information using the foreign matter discrimination means  5 . 
     In the case of a given letter  1  is abnormal, the abnormality thereof is reported from the foreign matter discrimination means  5  to the transport control means  23 . The transport control means  23 , upon receipt of the report, activates the first distribution means  13  when the letter  1  reaches the neighborhood of the first distribution means  13 , and transports the particular letter  1  to the reject-deposit means  14 . As a result, the abnormal letter  1  is completely processed and not subjected to the sorting. 
     In the case where a given letter  1  is normal, the address thereof is read by the character reading means  7 . The character reading means  7  fetches the address of the letter  1  as an image, and transmits the image to the character recognition means  9 . The character recognition means  9  delivers an image to a character recognition unit (say,  9   a ) and thus recognizes the address. Once the address could be recognized, the sorting information obtained from the address could be transmitted to the transport control means  23 . 
     In the case where the address cannot be recognized, the image is transmitted to the sorting information input means  10 . At the sorting information input means  10 , the operator viewing the address displayed on the screen enters a corresponding sorting information by way of a keyboard or the like. Then the sorting information is transmitted to the transport control means  23 . 
     Next, the letters  1  pass the bar code reading means  8 . In the case under consideration, the letters  1  not printed with a bar code are assumed and therefore are not processed in the bar code reading means  8 . 
     In the case where a bar code is printed, in contrast, as in the case of reading an address, the bar code is fetched as an image by the bar code reading means  8  and transmitted to the bar code recognition means  11 . The sorting information is recognized in a bar code recognition unit (say,  11   a ) from the bar code, and transmitted to the transport control means  23 . 
     In the process mentioned above, any letter  1  not printed with a bar code for which the sorting information obtained by the address read operation has been read is printed with an appropriate bar code. The second positioning means  15  sets the letter  1  in position. The bar code printing means  16  converts the sorting information into a bar code and prints the bar code. This letter  1 , when sorted subsequently by the letter sorter  50 , is done so by reading the bar code. The sorting information can be read more quickly and more accurately by recognizing a bar code than by recognizing a character, and thus the processing performance can be improved. 
     Then, the letters  1  pass through the overlap means  21 . The letters, if loaded continuously in the same deposit means  18 , are apt to bump each other and cause a jam in the deposit means  18 . The transport control means  23 , when judged that two letters are distributed continuously to the same deposit means  18 , switches the-overlap distribution means  21 C to lay the two letters one on the other in advance. 
     After that, the transport control means  23  switches the direction of transportation by the second distribution means  19  and the third distribution means  20 , and thus leads the letters  1  to any one of the deposit means  18  corresponding to the sorting information. 
     The sorting process on the letters  1  is thus completed. 
     The foregoing description concerns the case in which the letters  1  are sorted one by one sequentially. Actually, however, a multiplicity of letters are processed concurrently in order to improve the performance of the letter sorter  50 . By doing so, the number of letters processed per unit time (hereinafter referred to as the processing speed) can be improved. 
     Nevertheless, the performance of the letter sorter  50  imposes a certain upper limit on the processing speed. The upper limit is determined by the three factors described below. 
     First, in order not to damage the letters  1 , the transport speed of the transport means  3  is desirably as low as possible. A high transport speed may sometimes damage the letters  1  suddenly coming to stop when led into the deposit means  18 . Also, a high transport speed may undesirably shorten the service life of the parts (such as bearings) of the letter sorter  50 . A low transport speed, on the other hand, cannot meet the requirement of a specified processing speed. This letter sorter  50  is set to a proper transport speed taking the trade-off between these factors into account. 
     Secondly, in order to sort the letters  1 , the direction of transportation is switched by the distribution means such as the first distribution means  13 . As shown in the example of FIG. 2, the first distribution means  13  begins to operate after the leading letter  1   a  has passed therethrough and finishes the switching operation before the arrival of the succeeding letter  1   b . The letters, therefore, are required to have not less than a predetermined interval G. In view of this, the letter sorter  50  is adjusted to secure at least the interval G between the letters  1  supplied from the supply means  2  by use of the supply control means  22 . 
     Thirdly, the images of the addresses on the letters  1 , as shown in FIG. 3, are distributed by the character recognition units of the character recognition means  9 . However, the characters of some addresses may take a long time to recognize while the characters of other addresses may be easily recognized and processed in a short time. For example, handwritten characters are varied from one person to another in style and generally are difficult and require a long time to recognize. The characters printed in characters, on the other hand, have predetermined patterns and more definite than handwritten characters. Therefore, the recognition of printed characters is easier and requires less time. 
     As an example, FIG. 3 shows the case in which letters having addresses of handwritten characters and printed characters are processed by four character recognition units. In the order of supply, the image of the address of the letter  1   a  is transmitted to the character recognition unit  9   a , and the image of the address of the letter  1   b  to the character recognition unit  9   b . Similarly, the letter  1   c  is transmitted to the character recognition unit  9   c , the letter  1   d  to the character recognition unit  9   d , and so on. 
     The handwritten characters require about twice as much time as the printed characters to recognize (two seconds for a handwritten character, and one second for a printed character, for example). Therefore, recognition of the images of the letters  1   a  to  1   c  indicated by dashed lines is not yet complete. Thus, when the image of the address of the letter  1   e  is read, all the character recognition units are still in the process of image recognition. Thus the image of the letter  1   e  cannot be recognized and the sorting information thereof cannot be obtained, thereby making the sorting thereof impossible. Generally, the printed letters represent about 70% and the handwritten letters represent about 30% of all the letters handled. This ratio, however, is varied according to the time zone of the day and the day of the week. 
     The printed characters, in contrast, consume less time to-recognize than the handwritten characters. When the image of the address of the letter  1   e  has been read, the recognition of the images of the letters  1   a  to  1   c  indicated by dashed lines is already complete and the sorting information has been sent out. Consequently, the image of the letter  1   e  can be processed, and can reach the character reading means  7  at an earlier timing. Conversely, a delayed processing of the letter  1   e  may reduce the load of the character recognition unit for a lower processing speed of the letter sorter  50 . 
     For this reason, the letter sorter  50  includes a load measuring means  24  to measure the load for recognition by the character recognition means  9 . The measurement is taken, for example, of the availability of the character recognition units. As an alternative method, information on whether the image being processed represent printed characters or handwritten characters and the approximate number of characters are acquired from each character recognition unit, and the recognition load is calculated from these information. The load thus measured is transferred through the transfer means  25  to the supply control means  22 . When the load is heavy, the supply control means  22  lengthens the interval between the letters  1  supplied. In the case where the load is small, on the other hand, the interval between the letters  1  supplied is shortened. In this way, a proper load is maintained and the processing speed of the letter sorter  50  can-be improved. 
     An example of sorting operation in this letter sorter  50  will be explained with reference to FIG.  5 . 
     FIG. 5 shows the manner in which the letter interval G automatically changes in order for the recognition load to approach a reference load. The upper curve represents the manner in which the recognition load changes as measured by the load measuring means  24 , and the lower curve shows the change of the indication of the letter interval G by the supply control means  22  characters a to f designate time points. 
     In terms of the load per letter, the range before a and from d to f represents letters of small recognition load (such as letters having a printed address, hereinafter referred to as the printed letters), while the range from a to d and after f represents letters of large recognition load (such as letters having a handwritten address, hereinafter referred to as the handwritten letters). 
     Before time point a, letters having a printed address are read, and therefore the character recognition means  9  can complete the recognition process within a comparatively short time. The recognition load measured by the load measuring means  24 , therefore, is smaller than the reference load. The supply control means  22  thus controls the supply means  2  in such a manner as to shorten the letter interval G as compared with the reference interval. As a result, the processing speed of the letter sorter  50  is improved. 
     In the range from time point a to d, the letters having a handwritten address are read, and therefore a longer time is required for the character recognition means  9  to perform the recognition process. After time point a, therefore, the recognition load begins to increase. As soon as the recognition load exceeds a maximum load, the address cannot be recognized and the letters involved are rejected. Thus, the number of letters supplied is reduced to prevent rejection. For this purpose, the supply control means  22  controls the supply means  2  in such a manner as to increase the letter interval G from time point b. 
     In view of the time lag that exists between the operation of the supply means  2  and the operation of the character reading means  7 , the effect of lengthening the letter interval G at time point b is not exhibited until time point c. At time point c, the recognition load begins to steadily decrease toward the reference load. 
     Further, the letters having a printed address are read in the range of time point d to time point f, during which the recognition load is reduced. The supply control means  22  thus shortens the letter interval G as compared with the reference interval at time point e. 
     As described with reference to examples above, the processing performance of the letter sorter  50  can be improved by shortening the supply interval in the case of reading letters having a small recognition load such as those having a printed address. When reading letters of large recognition load such as those having a handwritten address, in contrast, the supply interval is lengthened to reduce the number of letters rejected. 
     In the above-mentioned case, the object of which the load is measured is limited to the character recognition means  9  by the select means  26 . The object, however, can be any or all of the means for processing the letter information including the foreign matter discrimination means  5 , the sorting information input means  10 , the bar code recognition means  11  and the transport control means  23 . 
     As described above, the processing speed can be improved by adjusting the interval at which letters are supplied based on the interval required for switching the distribution means and the load of the means for processing the letter information. 
     Of all the objects of load measurement described above, the load on the character recognition means  9  is technically most difficult to recognize in the state of art. A configuration is desired, therefore, that reflects the load of the character recognition means  9  most significantly. 
     FIG. 4 shows an example number of letters on the transport path  3  between the supply means  2  and the character reading means  7 . The character reading means  7   a  is associated with the position in the case where the transport means  3  is long between the supply means  2  and the character-reading means  7 , and the character reading means  7   b  represents the position in the case where the transport means  3  is short between the supply means  2  and the character reading means  7 . 
     Assume the position of the character reading means  7   a . FIG. 4 shows that five letters are located on the transport means  3 . Also assume that the load of the character recognition means  9  is measured by the load measuring means  24  when the letter  1   a  arrives at the character reading means  7   a . This load is reflected in the interval at which letter  1   f  is supplied but not reflected in the interval of supplying the letters  1   b  to  1   e  already placed on the transport means  3 . 
     Assume, for example, that the letters before the letter  1   a  have an address of printed characters, and the letters including and after the letter  1   a  have a handwritten address. When the letter  1   a  having an address of handwritten characters is read, therefore, the load increases, so that the interval at which the letter  1   f  and subsequent letters are supplied is lengthened. The letters  1   b  to  1   e , however, continue to be supplied at the original short interval, thereby further increasing the load. The result may be that the performance of the character recognition means  9  is exceeded and an address cannot be read. 
     At the position of the character reading means  7   b , on the other hand, the load generated by reading the letter  1   e  is reflected in the letter  1   f . As a result, the load increase is reduced and the performance of the character recognition means  9  is not exceeded. 
     The character reading means  7  thus is desirably located in the neighborhood of the supply means  2 . From the viewpoint of the system configuration, however, the character reading means  7  cannot sometimes be installed in the neighborhood of the supply means  2 . In such a case, as shown by dashed line in FIG. 1, a load prediction means  27  is added. By doing so, the load is predicted when the letter  1   f  located in the supply means  2  reaches the character reading means  7  thereby making it possible to determine the interval at which letters are supplied. As an example method, an average recognition time is determined for several letters recognized before the letter  1   a  by the character recognition means  9 . This average recognition time is used to determine the number of letters of which the images are completely recognized in the character recognition means  9  before the letter  1   f  reaches the character reading means  7 . Also, the number of letters existing between the supply means  2  and the character reading means  7  is determined. This number of letters can be easily determined since the letter position is controlled by the transport control means  23 . The change in image amount is multiplied by the average recognition time to predict the load. 
     An example of the load prediction means  24  is realized by a method of predicting the recognition load from the size difference of the address space of letters. The larger the address space, the greater the amount of image information and a longer time is required for detecting a character from the particular image. The envelope having the largest specified size, for example, has an address space of 120 mm×235 mm, which is about 1.9 times as large as the size 100 mm×148 mm of the address space of the post card. The time required to detect characters indicating an address on a letter, therefore, is about twice as long as that for the postcard. Consequently, the load can be predicted also at a time point when the size of the address space of the letter is detected by the foreign matter detection means  4 , for example. 
     Another method for attaining a similar purpose consists in adjusting the timing of the letter  1  reaching the character reading means  7  by changing the transport speed of the letter  1  and thus maintaining a proper load value. For this purpose, a variable speed transport means  3   b  having a variable speed and a speed control means  28  for controlling the transport speed of the variable speed transport means  3   b  are interposed between the supply means  2  and the character reading means  7 . 
     The speed control means  28  reduces the speed of the variable speed transport means  3   b  when the load is heavy and thereby retards the timing of the letters reaching the character reading means  7 . The character recognition means  9  can thus take time to proceed with the recognition of characters before receiving the next image. When the load is small, the speed of the variable speed transport means  3   b  is increased thereby to advance the timing at which the letters arrive at the character reading means  7 . As a consequence, the image can be transmitted to an idle character recognition unit in the character recognition means  9  for an improved processing performance. 
     An example is shown in FIG.  4 . In FIG. 4, the load of the character recognition means  9  undergoes a change as the result of the character reading means  7  having read the letter  1   a . The load thus changed is measured by the load measuring means  24 , and transmitted through the transfer means  25  to the supply control means  22  and the speed control means  28 . The supply control means  22 , as described above, changes the interval of the letter  1   f  supplied by the supply means  2 . 
     In this example, the load of the letter  1   a  can be reflected also in the letter  1   b  by changing the transport speed of the variable speed transport means  3   b  by the speed control means  28 . 
     Also, the variable speed transport means  3   b , which has been interposed between the supply means  2  and the character reading means  7  in the above-mentioned example, can alternatively be located downstream of the character reading means  7  as far as the character reading means  7  is capable of following the changing transport speed. 
     The description is made above with reference to a letter sorter for handling letters as an object to be sorted. The present invention, however, is also applicable to any sorting apparatus in which processed the information of paper sheets and changes the sorting mode on the basis of the result of processing the information. 
     According to the present invention, the interval at which paper sheets are supplied can be changed according to the load of processing the information on the paper sheets. Therefore, the amount of paper sheets incapable of sorting can be reduced while at the same time improving the processing speed.