Abstract:
An arrangement for adaptively driving the flag element of a document handling device, such as a document sorter. The invention uses a force generating mechanism to produce torque at the periphery of a cam. A flexible connector that is wrapped around the cam is used to pull the flag element. The cam is shaped such that the force exerted on the flag element produced by constant torque varies in accordance with the size of the document stack in the hopper of the document handling device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The subject matter of this application is related to the subject matter set forth in co-pending U.S. patent application No. 09/740,681, entitled “Adaptive Flag Weight For Document Handling Apparatus,” filed Dec. 19, 2000, which is assigned to the assignee of the application hereof. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to document handling devices, and more particularly, to an arrangement for adaptively driving a flag element of a document handling device. 
     2. Discussion 
     Document handling devices are commonly used today to quickly move and sort a variety of documents. Documents are often stacked and automatically fed from the document stack. A feeding mechanism is used to introduce each document to its document transport for processing and sorting. It is important to introduce each document singly, with consistent spacing, to permit the fastest feed rate possible while still maintaining proper document processing. 
     In high speed sorters, a hopper is often used to supply documents to the feeding mechanism. A device, commonly known as a flag, is used to move documents across the hopper during feeding. To create this movement, the flag applies a force to the last document in the stack. 
     A number of systems are commonly known for applying the flag force. One such flag driving system is a non-controllable dead weight system. This system uses potential energy derived from a constant weight that is attached to the flag by a cord or some other flexible connector to create a tension on the cord, and therefore, a force on the flag. The net result is a force transmitting from the flag onto the document stack. 
     A drawback of this non-controllable dead weight system is that it is not able to maximize the performance of the document handling device. Specifically, it is deficient in maintaining proper document spacing. The source of this deficiency relates to the force exerted by the flag on the document stack. For example, pushing a stack of several thousand documents requires far more force than pushing the last few documents. In this system, however, the force exerted by the flag on the document stack does not vary according to the number of documents in the stack. This inability to adequately control the force exerted on the document stack results in inconsistent spacing, thereby causing the performance of the document handling device to suffer. 
     A variation of the dead weight system, herein referred to as the variable dead weight system, attempts to improve the non-controllable dead weight system to maximize the performance of the document handling device. The variable dead weight system attempts to adjust the flag force by using a variable dead weight, such as a chain that falls onto a supporting surface during flag travel, attached to the flag. As the document stack is reduced and the flag moves accordingly, the chain falls onto the supporting surface, thereby reducing the flag force. Although this system can better match the flag force to the force required to move the document stack, it is still not responsive to the actual force requirements that may vary due to conditions in the document stack. 
     Another method of producing flag force against a document stack is to use some sort of motor arrangement. To best adapt to flag force requirements, many motor driven flag systems often use sensors to measure and adjust the flag motion and force. However, because the mechanical environment created by a feed sorter can be violent, the sensors must undergo filtering to ensure that the sensed values are accurate. Although these systems are more responsive to flag force requirements, they are complex, costly and are subject to maintenance issues. It is desirable to provide an improved mechanism that produces a flag force that is responsive to the force needed to move the document stack. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide an apparatus for driving a flag element capable of presenting an adjustable force for moving a document stack. 
     A further object of the present invention is to provide an arrangement for adaptively driving the flag element of a document handling device that is durable, reliable, and economical to produce. 
     Accordingly, the present invention is directed to an arrangement for adaptively driving the flag element of a document handling device, such as a document sorter. The invention uses a force generating mechanism to produce a torque on the periphery of a cam. A flexible connector that wraps around the cam is used to pull the flag element. The cam is shaped such that the force exerted on the flag element produced by constant torque varies in accordance with the size of the document stack in the hopper of the document handling device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional objects, features, and advantages of the present invention will become apparent from studying the following detailed description and claims when taken in conjunction with the accompanying drawing, in which: 
     FIG. 1 is a perspective view of an arrangement for adaptively driving the flag element of a document handling device according to the principles of the present invention; and 
     FIG. 2 is a perspective view of an alternative driving means for rotatably driving a cam of the arrangement of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     The drawing shows merely exemplary embodiments of the present invention for purposes of illustration only, one skilled in the art will readily recognize that the principles of the invention are well adapted for application to devices other than document handling devices as well as to document handling devices other than the one shown in the drawing. Furthermore, one skilled in the art will readily appreciate that various adaptations of the preferred embodiment may be combined or otherwise modified without departing from the scope of the invention. 
     A document handling apparatus  100  is illustrated in FIG.  1 . As shown, the document handling apparatus  100  includes a hopper  104  which contains a document stack  106 . The hopper  104  has a floor  104   a  and a leading edge guide wall  104   b  that serve to support the documents in the document stack  106 . Leading edge guide wall  104   b  also provides support for a flag element  102 . Flag element  102  abuts the document stack  106  and, during feeding, is used to move the document stack  106  across the hopper floor  104   a  toward feeding elements  108 . Feeding elements  108  include mechanisms commonly known in the art, such as a nip, nudger, and feed wheel. Documents are then individually removed from the hopper  104  by feeding elements  108  and are introduced into a document transport (not shown) for processing and sorting. 
     The flag element  102  is associated with a cam  114  by a flag drive string  110 , as seen in the preferred embodiment of FIG. 1, or by some other suitable flexible connector, such as a cable or chain. The flag drive string attaches to the flag element  102  and is guided by pulley  118   a  and pulley  118   b , which are attached along the leading edge guide wall  104   b . An additional pulley  118   c  guides the flag drive string  110  to its attachment at cam  116 . FIG. 1 shows a preferred embodiment in which the flag drive string  110  attaches to a constant weight  112 . Alternatively, the constant weight  112  may be excluded from the system. 
     The cam  114  is shaped such that its radius varies. As depicted in FIG. 1, cam  114  has a minimum radial distance  114   b  and gradually increases to a maximum radial distance  114   a . The cam  114  is rotatively supported by shaft  116 . In the preferred embodiment of FIG. 1, the shaft  116  connected to an electric motor  120  is shown as a method of producing a torque on the cam. Alternatively, other known force generating mechanisms may be used to create a torque on the cam  114 , such as a dead weight  115  suspended from a cable. 
     During operation, electric motor  120  produces a constant torque. Shaft  116  acts to transfer the torque developed by the electric motor  120  to the cam  114 , causing it to rotate. The rotation of the cam  114  exerts a tension on the flag drive string  110  and subsequently on the flag element  102 . Accordingly, the flag element  102  then exerts a force at the back end of the document stack  106 . The flag drive string  110  prevents free motor rotation. 
     The cam  114  takes advantage of the known relationship between the flag element  102  position and the flag drive string  110  position. The cam  114  is shaped such that the force of the flag element  102  produced by a constant motor torque varies to suit the size of the document stack  106  in the hopper  104 . For example, if the document stack is large, a large flag force is required; since the motor torque is constant, the radial length of the cam is small. As the size of the document stack decreases, the force required to move the document stack decreases; since the motor torque is constant, the radial length of the cam must increase. 
     As stated above, in the preferred embodiment of FIG. 1, a constant weight  112  is interconnected between the flag element  102  and the cam  114 . The constant weight  112  is supplemental to the motor  120  to reduce the requirement on the motor  120 , thereby reducing wear and increasing its service life. In addition, should the motor  120  fail, the constant weight  112  could allow the document handling device  100  to continue to function at a reduced performance level. 
     The arrangement of the present invention allows the cam to take advantage of the known relationship between the flag element position and the flag drive string position in order to match the flag element force needed to move the document stack. Because the arrangement is capable of adjusting flag force requirements without the use of sensors, it is economical to produce and minimizes system complexity issues. 
     In addition, if an electric motor is used with the cam, additional adjustments can be made to increase the performance of the document handling device. For example, the current supplied to the motor could be altered to accommodate document handling devices of different speeds. Since document handling devices use a variety of speed selections to perform simple, high volume document processing or complex, low volume document processing, the electric current could be adjusted to match the speed requirement of the particular document processing operation. In addition, since the feeding elements of document handling devices are subject to wear, the motor could be adjusted to work in harmony with the performance of the worn feeding elements. 
     A variation of the present invention would be to include sensors with the present invention to further optimize the performance of the document handling device. 
     The foregoing discussion and drawing discloses and describes merely an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion that various changes, modifications and variations may be made therein without departing from the scope of the invention as defined in the following claims.