Patent Publication Number: US-6702278-B1

Title: Paper hold mechanism for stacked paper handlers

Description:
FIELD OF THE INVENTION 
     This invention relates to paper handling devices, such as paper stackers, staplers, binders, and collators, which are used with printers and copiers and, more particularly, to holders for improving the quality of stacks of paper generated by such devices. 
     BACKGROUND OF THE INVENTION 
     Dedicated printers, copiers and facsimile machines commonly employ paper handling devices which perform tasks such as stacking, stapling, binding and collating. Dual-purpose machines which incorporate both printing and copying functions are becoming increasingly common in the office environment. For home offices, multi-function machines which incorporate not only printing and copying functions, but facsimile send and receive functions as well, have become very popular. 
     Designers of paper handling devices coupled to printers and copiers must take into consideration the quality of paper stacks generated during an output session. At the very least, high quality stacks output bins are aesthetically pleasing. If the paper handling device is engaged in stapling and binding operations, stack quality cannot be ignored. Unevenly stacked paper sheets will neither bind nor staple well. In addition, it is far simpler to provide additional handling operations for neatly stacked sheets than for those which are stacked unevenly. For paper handling devices which generate an intermediate stack that is fed to another paper handling device, good stack quality eliminates the need to subject the stack to an extra registration process. 
     Poor stack quality may be caused by several factors. Some of those factors are: 
     (a) motion of a sheet of paper when a new job arrives on top of an existing stack of already printed sheets; 
     (b) misalignment of sheets in an existing stack brought about by vertical movement of an output tray as it returns to its home position; 
     (c) non planarity of individual sheets; 
     (d) non-transnational movement of individual sheets as they are ejected into the output tray; 
     (e) improper vertical positioning of the output tray as it begins to receive a new job; 
     (f) non-uniform size of print media sheets; and 
     (g) strain induced in sheets overlying one or more stacks of stapled sheets. 
     In studies performed at the printer development labs of the Hewlett-Packard Co., it has been ascertained that factor (a) is one of the most common causes of poor stack quality. What is needed is a mechanism for holding an existing stack of printed pages while the output tray repositions itself to receive a new job and while the new job is being output to the tray. The holding mechanism will prevent relative motion from arriving sheets pertaining to the new job from being transferred to the sheets of an existing stack. 
     SUMMARY OF THE INVENTION 
     This invention includes a weighted apparatus for gently holding an existing stack of paper at opposite sides thereof so that a new job may be deposited over the existing stack without degrading the stacking quality of the existing stack. The apparatus may be readily incorporated into many existing paper handling devices which have a paper output tray which is upwardly and downwardly movable in a vertical direction. The apparatus includes a mirror-image pair of paper hold mechanisms, each of which secures a single edge of the existing stack. Each mechanism includes an arm having a longitudinally-oriented slot in a laminar upper end portion thereof and a guide pin anchored to the frame of the paper handling device which passes through the slot. The arm is retained on the pin between a pair of flanged collets. The pin limits movement, which together, limit movement of the arm in a plane and. The collars limit movement of the arm within a plane, while the pin constrains the arm to movement along the length of the slot. The arm also incorporates both a cam follower attached to a center portion thereof, and a foot having a stack contacting roller at its lower end. The mechanism further includes incorporates a cam which is rigidly affixed to the frame of the paper handling device. As the output tray having an existing stack thereon rises upwardly against the roller-equipped feet and is brought to a vertical machine reference level, the arm slides upwardly over the guide pin. As a new output job is deposited on top of the feet, the output tray is lowered in order to maintain the reference level even with the top of the accumulating stack. Near the bottom of the tray&#39;s travel, the arms swing outwardly, thereby disengaging the feet from both the existing stack and the newly deposited sheets. The arms are weighted so that each resets and holds both the existing stack and the newly deposited sheets as a single stack as the tray rises. 
     Two embodiments of cam and cam follower are disclosed. The first embodiment utilizes a cam having opposing faces first and second faces, each of which incorporates a path. The free end of the cam follower arm is positioned between both faces. A collar, which is rigidly affixed to the free end, encloses a follower pin that is laterally slidable between the two faces, so that the pin can engage a path on either face. The path on each face has a raised portion so that the follower pin can be transferred between the paths on the opposing faces. The second embodiment utilizes a cam having a single face and a topographic path. The lower portion of the upward vertical path is raised above the downward and outward curving path. A follower pin retainer is rigidly affixed to the free end of the cam follower arm. The retainer holds a spring-loaded laterally-slidable follower pin. Spring loading of the follower pin allows the pin to follow the topographic path. On the downward and outward curving path taken by the holder arm, the follower pin engages a low-level groove. However, on the lower portion of the upward vertical path, the path rises to a higher level. Thus, at the intersection of the rising vertical path and the downward and outward curing path, the follower pin abruptly drops off a high level ledge to the lower level. The follower pin continues to engage the lower level groove during the remainder of the upward travel. Other cam/cam follower systems that use separate downward and upward paths are also possible. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of a representative printing device coupled to a paper handling device incorporating the invention, the paper handling device being shown in a left-side elevational view; 
     FIG. 2 is a see-through side elevational view of a portion of the paper handling device, showing the paper eject rollers and an empty output tray positioned at the reference level for the receipt of a new output job; 
     FIG. 3 is a see-through side elevational view of a portion of the paper handling device, showing the paper eject rollers and a partially-full output tray with the top of the stack positioned at the reference level for the receipt of additional output; 
     FIG. 4 is a front elevational of the paper handling device shown in FIG. 1; 
     FIG. 5 is a front elevational view of the left-side paper hold mechanism, with the arm positioned at the point of maximum upward travel, the right-side mechanism being a mirror image thereof; 
     FIG. 6 is a front elevational view of the left-side paper hold mechanism of FIG. 5, showing the arm at a first point of downward travel; 
     FIG. 7 is a front elevational view of the left-side paper hold mechanism of FIG. 5, showing the arm at a second point of downward travel; 
     FIG. 8 is a front elevational view of the left-side paper hold mechanism of FIG. 5, showing the arm at a third point of downward travel; 
     FIG. 9 is a front elevational view of the left-side paper hold mechanism of FIG. 5, shown with the foot at the point of maximum lateral displacement; 
     FIG. 10 is front elevational view of the left-side paper hold mechanism of FIG. 5, with the arm positioned at the point of maximum downward travel, and ready to be lifted vertically upward by the output tray; 
     FIG. 11 is a front elevational view of the left-side paper hold mechanism of FIG. 5, showing the arm at a first point of upward vertical travel; 
     FIG. 12 is a front elevational view of the left-side paper hold mechanism of FIG. 5, showing the arm at a second point of upward vertical travel; 
     FIG. 13 showing the arm at a third point of upward vertical travel; 
     FIG. 14 is a top planar view of a first embodiment cam follower having a follower pin slidable between first and second detent positions; 
     FIG. 15 is a front elevational view of the first face of a first embodiment cam; 
     FIG. 16 is a front elevational view of the second face of a first embodiment cam; 
     FIG. 17 is diagram which shows the entire path of the cam follower, together with transition regions where the cam follower shifts from one face of the cam to the other face; 
     FIG. 18 is a side elevational view of the first embodiment cam, showing both faces in profile view, each of which provides a portion of the cam follower path; 
     FIG. 19 is a top planar view of a second embodiment cam follower having a spring-loaded slidable follower pin trapped within a pin housing; 
     FIG. 20 is a front elevational view of the single face of the second embodiment cam which has the entire follower path thereon; and 
     FIG. 21 shows an alternative embodiment for a roller-equipped foot, the roller having a shielded upper portion. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention includes a weighted apparatus for gently holding an existing stack of paper at opposite sides thereof so that a new job may be deposited over the existing stack without degrading the stacking quality of the existing stack. The apparatus may be readily incorporated into many existing paper handling devices which have a paper output tray which is upwardly and downwardly movable in a vertical direction. 
     FIG. 1 depicts a representative printing device  101  which is connected to a paper handling device  102  which incorporates the invention  103 , which is the stack holding apparatus. The paper handling device includes a frame  104  and a base  105  having casters  106 , which permit the paper handling device  102  to be rolled away from the printing device  101  to facilitate servicing of both devices. The paper handling device  102  also includes a paper receiving module  107 , a paper eject module  108 , an output tray position sensing module  109 , and a tray positioning module  110  which raises and lowers an output tray  111 , in response to stack position sensing signals received from the sensing module  107 , as sheets are ejected by the paper eject module  108  into the tray  111  to form an output stack  112 . The invention, or stack holding apparatus,  103  is affixed to the paper handling device  102  via a pair of stand-off structures  113 L and  113 R (generally  113 ), one of which ( 113 L) is seen in a side profile in this view. Each stand-off structure  113  is rigidly affixed to an upper sheet metal wall (not shown in this view) of the paper handling device  102 . 
     Referring now to FIG. 2, this view of a portion of the paper handling device shows the upper and lower paper eject rollers ( 201 U and  201 L, respectively) and an empty output tray  111  awaiting the receipt of a new print/copy job, being positioned at a reference level  202  on the frame  104  of the paper handling device  102 . The left frame rail  204 L of the paper handling device  102  is visible in this view, as is the sheet metal upper wall  205 , which provides a mounting surface for the stand-off structures  113 L and  113 R. FIG. 3 shows the same portion of the paper handling device, but with the output tray  111  partially-full. It will be noted that as additional sheets are ejected onto the tray  111  by eject rollers  201 U/ 201 L, the tray  111  is lowered so as to maintain the upper rear edge  301  of the output stack  112  positioned at the reference level  202 . By maintaining the upper rear edge  301  of the stack  112  at the reference level  202 , optimum stacking of sheets is enabled. As additional sheets are fed from the eject rollers  201 U/ 201 L to the output tray  111 , the tray is lowered still farther in order to maintain the upper rear edge  301  of the stack  112  at the reference level  202 . 
     Referring now to FIG. 4, more details of the invention  103  and of the paper handling device  102  are visible. The frame of the device  102  includes the base  105 , the left frame rail  204 L, a right frame rail  204 R, and a top cross member  204 T. The output tray  111  is raised and lowered by a jack  401  that is controlled by the tray positioning module  110  (see FIG.  1 ). An output  112  stack is shown resting on the tray  111 . The invention  103  is an apparatus which comprises a mirror-image pair of paper hold mechanisms  402 L and  402 R (generally  402 ), each of which secures a single edge of an existing output stack  112 . 
     Referring now to FIG. 5, an upper edge of an existing output stack  112  is secured by one of the paper hold mechanisms (in this case the left mechanism  402 L). As the description and function of the left mechanism is identical to that of the right mechanism  402 R, except that its operation and appearance is a mirror of that of the left mechanism, the left and right designators will be dropped for the description of the mechanism. Furthermore, when one mechanism  402  is referred to and described, the description is applicable to both mechanisms. The mechanism  402  includes a foot  501 . The free end of foot  501  is equipped with a roller  502  which rests on the stack  112 , thereby securing it. The foot  501  is an extension of the lower end of an arm  503 . The arm  503  has a longitudinally-oriented slot  504  near the upper end thereof which slides over a guide pin  505  that is anchored via a stand-off structure  113  to the sheet metal upper wall  205  of the paper handling device  102 . Flanged collets  506 A and  506 B (only  506 A is shown in this view) mounted on the pin  505  secure the arm  503  so that its movement substantially constrained within a plane. The arm  503  also incorporates a cam follower  507  that is affixed to a stalk  508  that, in turn, is rigidly affixed to the arm  503 . The cam follower  507  follows the grooved path  509  of a cam  510  that is also rigidly affixed to the stand-off structure  113 . It will be noted that the arm further incorporates a counterbalance weight  511 , which more than counterbalances the foot  501  and roller  502 . The counterbalance weight  511  is important for the successful functioning of the retract movement shown in FIG.  10 . 
     Still referring to FIG. 5, the cam follower  507  is designed and the path  509  of the cam  510  is shaped such that as the output tray  111  pushes upwardly against the foot  501 , the arm  503 -maintaining an approximately vertical orientation—slides upwardly over the guide pin  505 . When the arm  503  has reached the highest point of upward travel as depicted in this view, the top of the existing stack  112  is positioned near the reference level  202 , and is ready to receive a new output job. It should be mentioned that with the invention  103  installed on the paper handling device  102 , the height of the foot  501  should be taken into account in order to calibrate the reference level  202 . Thus, with the invention  103  installed, the tray will be portioned slightly lower when at the reference level  202  than it would be if the invention  103  is not installed thereon. 
     Referring now to FIG. 6, gravitational force has caused the arm  503  to fall as the output tray  202  is lowered by jack  401  in response to the output of a certain quantity of newly printed sheets  601  on top of the existing stack  112 . The lowering of the tray  111  has maintained the top of the new stack  602  at the reference level  202 . Working together, the guide pin  505 , the cam follower  507 , and the cam  510  direct the downward movement of the arm  503 . 
     Referring now to FIG. 7, the arm  503  has fallen further in response to a lowering of the output tray  111  as additional sheets  701  have been deposited thereon. It will be noted that the arm  503  is beginning to move to the left in response to the arcuate portion  702  of path  509  on cam  510 . 
     Referring now to FIG. 8, it will be noted that the arm  503  fallen still further downward, and the roller  502  has just disengaged the stack as the path  509  of cam  510  displaces the arm  503  laterally to the left. The arm  503 R of the right paper hold mechanism  401 R (not shown) is, of course, mirroring the action of the right mechanism  401 L, with disengagement of the roller  502 R from the stack  112  being to the right rather than the left. 
     Referring now to FIG. 9, the arm  503  has reached it point of maximum displacement from the vertical, thereby completely disengaging the roller  502  from its position between the old stack  112  and the new stack  602 . 
     Referring now to FIG. 10, the arm  503  fallen to its lowest point of downward travel, thereby allowing the cam follower  507  to engage a retract portion  1001  of path  509  on cam  510 . The output tray  111  is now ready to be lifted vertically, thereby raising the arm  503  with it as the roller  502  makes contact with the composite stack  1002 , which includes sheets from both the old and new stacks ( 112  and  602 , respectively). 
     FIGS. 11,  12  and  13  show various positions of the arm  503  on its upward path, which will end when the top of the composite stack  1002  reaches the reference level  202 . The cycle then begins anew. 
     Referring now to FIG. 14, a first embodiment cam follower  507 A includes a collar  1401  that is rigidly affixed to the stalk  508  which, in turn, is rigidly affixed to the arm  503 . A follower pin  1402  having two circumferential detent grooves  1403 A and  1403 B (generally  1403 ) is slidably mounted within the collar  1401 . A detent spring  1404  and detent ball  1405  are mounted within a cylindrical cavity  1406  that is perpendicular to and centrally located along the axis of the collar  1401 . The two grooves  1403 A and  1403 B represent the outer limits of travel of follower pin  1402  during the operation of the paper holding apparatus  102 . When the detent ball  1405  engages one of the detent grooves  1403 A or  1403 B, vibration, alone, is unable to move the follower pin  1402 . However, ramps (hereinafter described) incorporated within the grooved path  509  on the first embodiment cam  510 A are able to shift the follower pin  1402  from one detent position to the other. 
     Referring now to FIGS. 15 and 16, a first embodiment cam  510 A has been disassembled to show a first cam face  1501 A, which is spaced apart from, parallel to and opposed to a second cam face  1501 B. For the first embodiment cam  510 , a first path portion  1502 A of the grooved path  509  is contained on the first cam face  1501 A, while a second remaining portion  1502 B is contained on the second cam face  1501 B. The first path portion  1502 A guides the first embodiment cam follower  507 A from the beginning of the downward stroke, through the point of maximum displacement (shown in FIG.  8 ), and to the retract position (shown in FIG.  9 ). After retraction of the arm  503  is accomplished, the first path portion  1502 A incorporates a first ramp  1503  which shifts the slidable follower pin  1402  of cam follower  507 A to the second path portion  1502 B contained in the second cam face  1501 B. The second groove  1502 B directs the first embodiment cam follower  507 A from the beginning of the upward stroke to the top of the upward stroke. At the top of the upward stroke, the second path portion  1502 B incorporates a second ramp  1504 , which shifts the follower pin  1402  back to the first path portion  1502 A in the first cam face  1501 A. 
     Referring now to FIG. 17, the entire path of the first embodiment cam, comprising opposing cam faces  1501 A and  1501 B, is shown as a single diagram  1701 , together with the ramped transition regions  1503  and  1504  where the follower pin  1402  shifts from one face of the cam to the other face. The second path portion  1502 B is vertically upward, while the first path portion  1502 A includes a upper downward vertical portion  1505 , a lower downward portion  1506  that arcs away from the center of the stack  112 , and a horizontal return portion  1507  which connects the lowermost points of the downward and upward portions. The first path portion  1502 A and the second path portion  1502 B are connected by dotted lines at points A and C so that they may be shown in a non-overlapping format. From point A to point B, the cam follower follows the first path  1502 A on first cam face  1501 A. Between point B and point C, the first ramp  1503  shifts the follower pin  1402  from the first detent position (defined by circumferential groove  1403 A) to the second detent position (defined by circumferential groove  1403 B), thereby transferring control of the follower pin  1402  to the second path  1502 B on the second cam face  1501 B. From point C to point D, the cam follower follows the second path  1502 B on the second cam face  1501 B. Between point D and point A, the second ramp  1504  shifts the follower pin  1402  from the second detent position back to the first detent position, thereby transferring control of the follower pin  1402  to the first path  1502 A on the first cam face  1501 A. 
     Referring now to FIG. 18, both faces are shown coupled together in a side view. The first ramp  1503  is visible on the first cam face  1501 A, while the second ramp  1504  is visible on the second cam face  1501 B. When the two halves of the cam  412 B are assembled, a follower guide slot  1801  is formed which guides the stalk  410  to which the cam follower  409 A is attached. 
     Referring now to FIG. 19, a second embodiment cam follower  507 B includes a pin carrier  1901  that is rigidly affixed to the stalk  508  which, in turn, is rigidly affixed to the arm  503 . The pin carrier  1901  has a cylindrical cavity  1902  in which a collet-head follower pin  1903  and a spring  1904  biased against the collet head  1905  of follower pin  1903  are slidably trapped by an end cap  1906 . A cylindrical end  1907  of the pin  1903  extends outside the pin carrier  1901  and rides on the single face of the second embodiment cam  510 B, which will be described hereinafter. The resiliently biased collet-head follower pin  1903  allows the second embodiment cam follower  507 B to follow a path or groove on the second embodiment cam  510 B that is of non-uniform depth. 
     Referring now to FIG. 20, a second embodiment cam  510 B is shown. The upward and downward grooved paths are identical in shape to those provided by the first embodiment cam  510 A. Rather than using two opposed faces as does the first embodiment cam  510 A, the second embodiment cam  510 B employs a single ramp  2001  within the grooved path  2002 , which acts as a one-way switch or deflector on the downward arcuate stroke of cam follower  507 B. Because the cam follower  507 B is gravitationally biased against the outside wall of grooved path  2002 , the precipitous transition from the high point of the ramp  2001  to the lower portion  2003  of grooved path  2002  is smooth. The second embodiment cam  510 B may also incorporate a follower guide slot such as the guide slot  1801  of the first embodiment cam  510 A. 
     Referring now to FIG. 21, an alternative embodiment for a roller equipped foot  2101  is shown. As the arm retracts away from the stack, the roller is turning against any sheets that are resting thereupon. To prevent the rotating roller from disturbing the sheets of the newly accumulated stack  602 , the upper portion  2102  of the roller  502  is shielded. This is accomplished most simply by designing the foot body  2103  so that it has greater height than the uppermost portion of the roller  502 . 
     Although only a single embodiment of the invention has been heretofore described, it will be obvious to those having ordinary skill in the art that changes and modifications may be made thereto without departing from the scope and the spirit of the invention as hereinafter claimed.