Abstract:
A first embodiment of the present invention provides a method for transferring printed products and comprises the steps of pulling a printed product from a stack using a feed device running at a first preselected speed, accelerating the feed device after pulling the printed product from the stack and releasing the printed product from the feed device at a second preselected speed greater than the first speed.

Description:
This claims the benefit of U.S. Provisional Patent Application No. 60/582,565, filed Jun. 24, 2004, which is hereby incorporated herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to a method and device for feeding printed products, for example from a stack using a feeding device such as a gripper drum. 
     U.S. Pat. No. 6,082,724 describes a variable speed sheet material assembly apparatus with a feed mechanism driven by a feed motor, and is hereby incorporated by reference herein. Sheet material articles are delivered from the feed mechanism to moving pockets of a pocket conveyor driven by a conveyor drive motor. The feed motor operating speed is varied as a function of the conveyor drive motor to coordinate the relative speeds of the feed motor and the conveyor drive motor for proper delivery of the sheet materials from the feed mechanism to the pockets of the pocket conveyor. 
     Feeding devices comprising rotating drums for hoppers typically run at a constant speed over the entire 360 degrees of rotation. The feed drum is operated at a rotational speed that is sufficiently slow to avoid tearing of the printed product or other malfunctions. For example, it has been known to run the feed drum at half the speed of the conveyor, as a safer operational speed for the feed drum is often more limited than a speed feasible for a conveyor. However, twice as many feed drums are then required to collect a product of a certain size, and the set up time can become a longer and more complex operation due to a speed mismatch between the rotating feed drum and the conveyor. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and device for feeding printed products in a manner so as to reduce errors related to the transfer of printed products from a stack to a conveyor. 
     According to a first exemplary embodiment of the present invention, a method for transferring printed products comprises the steps of pulling a printed product from a stack using a feed device running at a first preselected speed, accelerating the feed device after pulling the printed product from the stack and releasing the printed product from the feed device at a second preselected speed greater than the first speed. 
     According to a second exemplary embodiment of the present invention, a method for transferring printed products comprises the steps of pulling a printed product from a stack using a feed device running at a first preselected speed, accelerating the feed device after pulling the printed product from the stack to a maximum speed, releasing the printed product from the feed device while the feed device is at a second preselected speed greater than the first speed, and decelerating the feed device to the first preselected speed for pulling a next printed product from the stack. 
     According to a third exemplary embodiment of the present invention, a device for feeding printed products from a stack to a conveyor comprises a feed device for pulling a printed product from a stack at a first location and releasing the printed product at a second location, and a variable-speed drive for driving the feed device so as to accelerate the feed device between the first and second locations. 
     According to a fourth exemplary embodiment of the present invention, a method for transferring printed products between a stack and a conveyor comprises the steps of pulling a printed product from the stack using a feed device running at a first preselected speed, accelerating the feed device after pulling the printed product from the stack to a maximum speed, releasing the printed product from the feed device to the conveyor, while the feed device is at a second preselected speed greater than the first speed, and decelerating the feed device to the first preselected speed for pulling a next printed product from the stack. Pursuant to a feature of the method of this exemplary embodiment of the present invention, the feed device is operated at an average speed over acceleration and deceleration, between pulling a printed product from the stack and pulling a next printed product from the stack, such that release of each printed product is in a preselected synchronization to operation of the conveyor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a hopper, gripper drum and pocket conveyor arrangement according to an exemplary embodiment of the present invention. 
         FIG. 2  shows a sucker of a hopper of the arrangement of  FIG. 1 , the sucker pulling down a printed product from a stack. 
         FIG. 3  shows a gripper of the gripper drum of  FIG. 1 , the gripper gripping the lead edge of a bottom printed product of a stack. 
         FIG. 4  shows the gripper of  FIG. 3 , the gripped printed product being pulled from the stack by rotation of the gripper drum, the gripper drum rotation being accelerated according to an exemplary embodiment of the present invention. 
         FIG. 5  shows the gripper of  FIG. 3 , with the gripped product on the gripper drum, and the gripper drum being accelerated according to an exemplary embodiment of the present invention. 
         FIG. 6  shows the gripper of  FIG. 3 , with the gripped product being released into a pocket of the pocket conveyor. 
         FIG. 7  is a schematic illustration of relatively slow and fast speed regions of a variable velocity profile for the gripper drum, according to an exemplary embodiment of the present invention. 
         FIG. 8  shows a graphical illustration of an exemplary velocity profile for a gripper drum using one gripper feeding every other pocket of a pocket conveyor, according to a preferred embodiment of the present invention. 
         FIG. 9  shows a graphical illustration of an exemplary velocity profile for a gripper drum using one gripper feeding every other pocket according to another preferred embodiment of the present invention. 
         FIG. 10  shows a position profile for the velocity profile of  FIG. 9 . 
         FIG. 11  shows a graphical illustration of an exemplary velocity profile for a gripper drum using one gripper feeding every other pocket according to a still further preferred embodiment of the present invention. 
         FIG. 12  shows a position profile for the velocity profile of  FIG. 11 . 
         FIG. 13  shows a graphical illustration of an exemplary velocity profile for a gripper drum using one gripper feeding every other pocket at a higher speed. 
         FIG. 14  shows a position profile for the velocity profile of  FIG. 13 . 
         FIG. 15  shows another exemplary velocity profile for a gripper drum using one gripper feeding every other pocket at a higher speed. 
         FIG. 16  shows a position profile for the velocity profile of  FIG. 15 . 
         FIGS. 17 &amp; 18  show exemplary velocity profiles for two grippers feeding every pocket. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and initially to  FIG. 1 , there is illustrated a hopper, a feed device comprising a gripper drum and a pocket conveyor arrangement according to an exemplary embodiment of the present invention. The arrangement comprises a first hopper  10  and a second hopper  100 . The first hopper  10  has a printed product stack  12  supported by a front wall  14  and a bottom wall  16 . A sucker  18  is rotatable to grip a bottom printed product  13  of the stack  12  and move it toward a printed product feed device such as a gripper drum  20 . The printed product feed device can also comprise a feed chain or belt. The gripper drum  20  includes a first gripper  22  and a second gripper  24  and rotates in a direction D. The arrangement of the hopper  10 , gripper drum  20  and sucker  18  is generally known in the related art. 
     Pursuant to a feature of the present invention, a variable speed motor M, for example, a servomotor  26 , is arranged to control the rotational speed of the gripper drum  20  within a 360 degree rotation. However the drive for the drum  20  could be any type of electrical, mechanical, hydraulic or pneumatic system, for example, which permits a controllable varying speed profile for the drum  20 . Motor M may be controlled for example by a controller  28 . The controller  28  can also control the speed of a conveyor  30 , in this embodiment a pocket conveyor having a plurality of pockets  32 , as is also generally known in the related art. The printed products from a plurality of hoppers, such as hoppers  10 ,  100 , may be collected into the pockets  32  of the pocket conveyor  30 , to form, for example, newspapers or books. The arrangement of the second hopper  100  may be similar to the first hopper  10 . 
       FIG. 2  shows the sucker  18  of the hopper  10  operating to contact the bottom printed product  13  from the stack  12 . 
       FIG. 3  shows the gripper  22  gripping the lead edge of the bottom printed product  13  as it is moved from the stack  12  due to the rotation of the sucker  18 . According to a feature of the present invention, once the product  13  is gripped by the gripper  22 , the motor M can be controlled by the controller  28  to drive and accelerate the speed of the drum  20 . 
     Referring to  FIG. 4 , the gripped printed product  13  is pulled from the stack  12  by the gripper  22 , while, according to a feature of the present invention, the gripper drum  20  continues to be accelerated by the motor M. 
     Continuing to the illustration of  FIG. 5 , the gripped product  13  is pulled onto the gripper drum  20 , due to the continued rotation of the gripper drum  20 , with the gripper drum  20  being accelerated by motor M.  FIG. 6  shows the printed product  13  being released by the gripper  22  into a pocket  32  of the pocket conveyor  30 . 
       FIG. 7  is a schematic illustration of relatively slow and fast speed regions of a variable velocity profile for the gripper drum  20 , according to an exemplary embodiment of the present invention. Positions  22   a  and  24   a  indicate where the grippers  22 ,  24  enter a slow region of rotation of the gripper drum  20 . A slow region is a region of the rotation of the gripper drum  20  where the speed of the gripper drum  20  is slower than the average speed during an entire rotation of the gripper drum  20 . A fast region is a region of the rotation of the gripper drum  20  where the speed of the gripper drum  20  is faster than the average speed during an entire rotation of the gripper drum  20 . 
     By permitting the printed products, such as the printed product  13 , to be pulled from the stack  12  at a lower speed (a slow region of rotation) than the speed at which the printed product is released into a pocket  32  (a fast region of rotation), deficiencies such as printed product tears, insufficient separation and pulling time, a misfeed, multiple feeds and rollover of subsequent products in the stack, can be reduced. 
     According to the exemplary embodiment of the present invention illustrated in  FIGS. 1-6 , the gripper drum  20  can be rotated at various velocity profiles. For example, for a collecting apparatus running at, for example, a top speed of 30,000 products per hour (pph), the drum would run at 250 rpm if each of the two grippers  22 ,  24  is delivering a product to each successive pocket  32 . In other words, 500 products are delivered each minute. Thus, the time for the drum  20  to make a complete revolution is 240 ms, and the time for one product is 120 ms. It is also possible for the drum  20  to only use one of the grippers  22 ,  24  to deliver a product to every other pocket  32 . In this case, the conveyor  30  may run at the same speed and two hoppers  10 ,  100  are used for alternating pockets  32 . It is also possible for the drum  20  to use two grippers  22 ,  24  and still deliver a product to only every other pocket  32 , in which case the speed requirements for the hoppers are halved. 
       FIG. 8  shows an exemplary velocity profile  60  for a gripper drum  20  using one gripper  22  feeding every other pocket  32 , of a pocket conveyor  30  at a collecting apparatus speed of 15,000 pph. The profile illustrates the velocity as a percentage of the top speed of the drum  20 . The nominal speed  62  is the average speed of the drum  20 , in this case 125 rpm, or 50% of the top speed, needed for the collecting apparatus speed. The time for a complete revolution is 480 ms. In this profile, shown by the double lines  60 , the drum  20  is at a slow speed during suction, for 144 degrees and 192 ms, accelerates for 96 degrees or 128 ms to a fast speed (100%), is at the fast speed (here 250 rpm) for 24 degrees and 32 ms, and then decelerates for 128 ms back to the slow speed. The acceleration point AP can coincide with the gripping of the printed product  13 , and the product may be released during a fast region of rotation to coordinate between the speeds of the pocket conveyor  30  and the drums  20  for accurate delivery of the printed product  13  by the rotating gripper drum  20  to a pocket  32  of the conveyor  30 . This minimizes set up difficulties attributed to a speed mismatch between the drum  20  and conveyor  30 , as encountered in previously known designs, as discussed above. 
     Pursuant to a feature of the present invention, the speed at which the printed product  13  is gripped by the gripper  22  is slower than average speed of the gripper drum  20 , and thus, tearing and other transfer-related errors can be reduced. 
       FIG. 9  shows another exemplary velocity profile  70  for a gripper drum  20  using one gripper feeding every other pocket as in  FIG. 8 . The velocity is expressed in degrees/ms, but again the average single line speed  72  is at 50% or 125 rpm (0.75 degrees/ms*60000 ms/min divided by 360 degrees/revolution). Here the drum  20  is again at a slow speed for 192 ms, but accelerates for 144 ms (108 degrees) and then decelerates again for 144 ms (108 degrees).  FIG. 10  shows a graph plotting the related positional movement for the drum  20  during the velocity profile of  FIG. 9 . In the graph of  FIG. 10 , the position of the drum  20 , in degrees of the 360 degree rotation, is illustrated by a double line, and is plotted against elapsed time of the rotation in ms. The single line indicates the position the drum  20  would have if driven at the average single line speed  72  shown in  FIG. 9 . 
       FIG. 11  shows a further exemplary velocity profile for a gripper drum  20  using one gripper  22  to feed every other pocket  32  of the conveyor  30 .  FIG. 11  illustrates half a revolution of the drum  20 , occurring in 240 ms. The drum  20  is run from zero to a speed Vm (250 rpm) and back again in 240 ms. The average speed of the conveyor is thus again 15,000 pph. This velocity profile produces high torque fluctuations, and thus may be less advantageous than the velocity profiles illustrated in  FIGS. 9 and 10 .  FIG. 12  shows the positional angle of the drum  20  using the velocity profile of  FIG. 11  as opposed to when the drum is run at 250 rpm, i.e. Vm. 
     In  FIG. 13  there is illustrated yet another exemplary velocity profile for a gripper drum  20  using one gripper  22  to feed every other pocket  32 . In this embodiment of the present invention, the drum  20  is operated to run at an average speed of 250 rpm. As shown in  FIG. 13 , the drum  20  is accelerated for 180 degrees and decelerated for 180 degrees.  FIG. 14  shows a related positional angle over the 240 ms needed for one rotation of the drum  20 . 
       FIGS. 15 and 16  show velocity and position profiles that are similar to those of  FIGS. 13 and 14  respectively, but with a speed reduction for the drum  20  of 25%, rather than 50%. 
       FIG. 17  shows a velocity profile for two grippers  22 , 24  feeding each pocket  32  of the conveyor  30 , at 15,000 pph. Each alternating 90 degrees of rotation of the drum  20  produces either an acceleration phase or a deceleration phase. This profile can correspond to the schematic shown in  FIG. 7 . The starting point for the acceleration or deceleration can also be shifted to correspond to the gripping of a printing product. 
     In  FIG. 18  there is illustrated a profile similar to the profile of  FIG. 17 , however, the speed of product delivery is increased to a speed of 30,000 pph so that the acceleration and deceleration phases alternate every 60 ms. 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.