Abstract:
A paddle urging system for use in a stacking bin having a constant force spring to provide an urging force to a paddle for supporting a stack of mailpieces. As mailpieces are accumulated into the stack, they push the stack against the paddle. A brake/clutch system is used to provide an additional drag to the paddle to resist against this movement of the paddle. The brake/clutch system is adjustable so that heavy mailpieces are supported more effectively, whereas lightweight mailpieces encounter less resistant force when they are accumulated into the stack.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a mail or document stacking machine and, more particularly, to a stack support for providing a resisting force to the stack as the mailpiece or document is accumulated into the stack. 
     BACKGROUND OF THE INVENTION 
     In a typical mail-handling machine, mailpieces are sorted and pushed into a plurality of stacking bins where the mailpieces are accumulated in substantially vertical stacks. In each stacking bin, a paddle, or an abutment member, is used to support the stack while allowing the stack thickness to increase. In order to providing sufficient support to the growing stack, a resisting force is usually provided to the paddle against the stack. As disclosed in U.S. Pat. No. 5,429,249 (Belec et al.), the paddle  40  is slidably mounted on a shaft or bar  32  by means of a cylindrical shaped member  34 . The cylindrical shaped member  34  is spring-loaded to provide a resisting force  150  to the paddle  40  as the stack  100  is pushed in a direction  102  when the mailpiece  110  is accumulated into the stack  100  by an input mechanism  90 , as shown in FIG.  1 . As disclosed in U.S. Pat. No. 4,524,965 (Kulpa), one end of a cord  54  is tied to the cylindrical shaped member  34  and the other end of the cord  54  is wrapped around a rotary displacement device  60 . As the cylindrical member  34 , along with the paddle  40  and the stack  100 , is pushed along the direction  102 , it causes the rotary displacement device  60  to rotate along a rotation direction  106 , as shown in FIG. 2. A pulley  70  is fixedly mounted on the rotary displacement device  60  for motion. One end of another cord  52  is wrapped around the pulley  70  and the other end of the cord  52  is tied to a spring  50 . When the rotary displacement device  60  is rotated along the rotation direction  106 , it causes the spring  50  is stretched along the direction  104 . As the spring  50  is stretched, it increases the tension  202  in the cord  52 , thereby increasing the resistance force  150  provided to the paddle  40 . 
     While the resisting force providing systems, as disclosed in Belec et al. and in Kulpa, are useful in supporting a stack of mailpieces as the thickness of the stack increases, the resisting force cannot be adjusted according to the load of the mailpieces. On the one hand, if the resistance force is too high, then lightweight mailpieces may be damaged when they are accumulated into the stack. On the other hand, if the resistance force is too low, the stack may overpower the paddle and cause the entire stack to topple over. 
     It is advantageous and desirable to provide a stack urging force system wherein the resistance force provided to the paddle is adjustable according to the load of the mailpieces. 
     SUMMARY OF THE INVENTION 
     According to first aspect of the present invention, a paddle urging system for use in a stacking bin having a first end and an opposing second end, wherein a paddle is provided in the stacking bin to support a stack of mailpieces in the stacking bin and wherein the mailpieces are accumulated into the stack at the first end of the stacking bin, thereby increasing the thickness of the stack and pushing the stack against the paddle in a first direction toward the second end of the stacking bin, said paddle system comprising: 
     an urging mechanism, operatively connected to the paddle, for providing an urging force to urge the paddle to move in a second direction opposite from the first direction while supporting the stack; and 
     an adjustable resisting force mechanism, operatively connected to the urging mechanism, for providing a resisting force to the paddle against the pushing of the stack toward the second end when the mailpieces are accumulated into the stack, in addition to the urging force provided by the urging mechanism. 
     According to the present invention, wherein the urging mechanism comprises a spring, connected to the paddle by a flexible member, for providing the urging force to the paddle. 
     According to the present invention, the adjustable resisting force mechanism comprises a clutch system for providing the resisting force, and the flexible member is mechanically engaged with the clutch system for conveying the resisting force provided by the clutch to the paddle. 
     According to the present invention, the clutch system comprises a pulley engaged with a one-way clutch such that the pulley is allowed to turn in a first rotation direction with respect to a rotation axis and the pulley is prevented from turning in a second rotation direction opposite from the first rotation direction, and wherein the one-way clutch is further engaged with a rotating member with an adjustable friction force and the rotating member is disposed axially with the rotation axis, such that when the pulley is caused to turn in the second rotation direction by the pushing of the stack toward the second end of the stacking bin, the one-way clutch causes the rotating member to rotate against the friction force for providing the resisting force to the flexible member, and when the pulley is caused to turn in the first rotation direction, the one-way clutch and the rotating member are effectively disengaged from the pulley. 
     According to the second aspect of the present invention, a stacking bin for use in a mail processing machine for accumulating mailpieces into a stack from a first end of the stack, wherein the stack is pushed toward a first direction when the mailpieces are accumulated into the stack, thereby increase the thickness of the stack and pushing the stack along a first direction, said stacking bin comprising: 
     a paddle, provided at the second end of the stack opposite from the first end, for supporting the stack, 
     an urging mechanism, operatively connected to the paddle, for providing an urging force to urge the paddle to move against the stack toward a second direction opposite from the first direction; and 
     an adjustable resisting force mechanism, operatively connected to the urging mechanism, for providing a resisting force to the paddle against the pushing of the stack when the mailpieces are accumulated into the stack, in addition to the urging force provided by the urging mechanism. 
     The present invention will become apparent upon reading the description taken in conjunction with FIGS. 1 to  4 . 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic representation showing the top view of a prior art stacking bin. 
     FIG. 2 is a diagrammatic representation showing the top view of another prior art stacking bin. 
     FIG. 3 is a diagrammatic representation showing a side view of the stacking bin, according to the present invention. 
     FIG. 4 is an exploded view of the adjustable resisting force mechanism, according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIG. 3, a stacking bin  10 , according to the present invention, has a platform  20  to support a stack  100  of mailpieces  110 . The stacking bin  10  has a first end  12  and an opposing second end  14 , and the stack  100  has a first end  122  and an opposing second end  124 . A paddle  40  is provided at the second end  124  of the stack  10 O for supporting the stack  100 . As the mailpieces  110  are accumulated into the stack  100  at the first end  12  of the stacking bin, the thickness of the stack  100  increases and the stack  100  is pushed toward the second end  14  along a direction  102 . As shown, a shaft  32  is mounted on the platform  20  by means of shaft mounts  30 . A sleeve or cylindrical shaped member  34  is slidably mounted on the shaft  32  and a paddle  40  is mechanically connected to the cylindrical shaped member  34  so that the paddle  40  is moved when the cylindrical shaped member  34  is moved along the shaft  32 . A spring  210 , preferably a constant force spring, mounted on the platform  20 , is used to provide an urging force  150  to the paddle  40  via a cord  220  (or a steel cable) and the like. An adjustable resisting force mechanism  230  is operatively connected to the spring  210  to provide an additional force to the paddle when the paddle is pushed toward the second end  14  of the stacking bin  10  as the mailpieces  110  are accumulated into the stack  100 . As shown in FIG. 3, the adjustable resisting force mechanism  230  has a one-way clutch, which produces a friction force only when the resisting force mechanism  230  is caused to rotate along a rotation direction  232 . There is no significant friction force when the resisting force mechanism  230  is caused to rotate in a direction opposite from the direction  232 . Thus, when there is no accumulation, the resistance force  150  provided to the paddle  40  is substantially equal to the tension force of the spring  210 , reduced by the friction force between the cylindrical shaped member  34  and the shaft  32 , and some small friction force in the resisting force mechanism  230 . Moreover, when the stack  100  is taken out to empty the stacking bin  10 , the paddle  40  is automatically retracted to the first end  12 . 
     FIG. 4 shows the preferred embodiment of the resisting force mechanism  230 . As shown in FIG. 4, the resisting force mechanism  230  comprises a brake shaft  231  for axially mounting a brake disk  236 , a brake hub  238 , a pulley/clutch assembly  240 , a thrust washer  252 , a washer  254 , a spring  256 , washers  258  and  260 , an adjustment knob  262  and a retaining ring  264 . The pulley/clutch assembly  240  consists of a pulley  242  and a one-way clutch  250 . The pulley  242  has an outer periphery  243 , around which the cord  220  is wrapped about 1.5 turns for engaging the resisting force mechanism  230  with the paddle  40 . This wrap prevents the cord from slipping. The brake shaft  232  has a threaded front section  233  to allow the adjustment knob  262  to screw thereon. The lock washer  264  is pushed onto the tip  234  of the threaded section  233  to prevent the adjustment knob  262  from being mechanically disengaged from the brake shaft  232 . A one-way bearing  250  is mounted on the inner periphery  244  of the pulley  242  for engaging with the brake hub  238 . The one-way clutch  250  allows the brake hub  238  to rotate against the pulley  240  in a direction, with respect to a rotation axis defined by the longitudinal axis of the brake shaft  232 , but prevents the brake hub  238  from doing so in the opposite direction. When these components are assembled, the thrust washer  252  is in direct contact with the front end  239  of the brake hub  238 , the brake disk  236  is in direct contact with the rear end  237  of the brake hub  238 , and the adjustment knob  262  compresses the spring  256 . As such, the spring  256  creates a clamping force between the thrust washer  252 , the brake hub  238  and the brake disk  236 . The clamping force is adjustable by adjusting the adjustment knob  262  against the spring  256  As mailpieces  110  are accumulated into the stack  100 , the movement of the paddle  40  causes the pulley  242  to rotate. The rotation of the pulley  242  causes the one-way clutch  250  to engage the brake hub  238 , causing it to turn along with the pulley  242 . As the brake hub  238  turns, its motion is resisted by the clamping force, resulting in an addition drag on the entire paddle urging system. The additional drag increases the force required to move the paddle  40  towards the second end  14  The end effect is that heavy mailpieces are supported more effectively. Upon retraction, the one-way clutch  250  overruns, allowing the paddle  40  to return to its home position near the first end  12  without having to overcome the drag provided by the resisting force mechanism  230 . 
     With the adjustment knob  262  turned all the way out, the spring  256  is not compressed and the clamping force between the thrust washer  252 , the brake hub  238  and the brake disk  236  does not produce any significant additional drag. At such, the force seen at the paddle  40  is mainly the tension force provided by the constant force spring  210 . This setting can be used for mailpieces that are on the lower end of the weight spectrum. 
     The advantage of the paddle urging system, which comprises the constant force spring  210  and the resisting force mechanism  230 , is that it allows the operator to easily adjust the resistance force  150  to an optimal level according to a particular type of mailpiece weight. Once the adjustment knob  262  is turned to a particular setting, the force provided to the paddle  40  remains relatively constant over the full travel of the paddle between the first end  12  and the second end  14  of the stacking bin  10 . In contrast, a simple torsion or extension spring normally exhibits a relatively high spring rate, which would cause the paddle force to increase as the stack fills. 
     The present invention allows a mail sorter operator to adjust the paddle&#39;s normal force according to the weight of the mailpieces being handled. The present invention uses a constant force spring  210  as an urging mechanism for providing an initial paddle force and to provide the force required to retract the paddle after the stack has been emptied. In addition, a brake/clutch assembly and a compression spring are used as an adjustable resisting force mechanism for providing a drag when the mailpieces are accumulated into a mail stack. As disclosed, the cord  220  is wrapped around the pulley  242  to engage the adjustable resisting force mechanism  230  with the constant force spring  210 . However, it is possible that the adjustable resisting force mechanism  230  is operatively connected to the paddle  40 , separately from the constant force spring  210 . 
     Thus, although the invention has been described with respect to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the spirit and scope of this invention.