Method and device for stacking flat mail items

Abstract

In a stacker, a mail item to be stacked is propelled against a stop wall at a stacking point by a stacking roll. A controlled driven underfloor belt and a stack support are displaced from the stack as the stack grows. The mail item to be stacked meets the preceding, already stacked item at an acute angle. Before it is stacked the mass of each item is determined. Stacking forces are measured with a measurement device in a preceding test phase the target values for the stacking pressures and the braking curve of the stacking roll up until the mail items have reached the stop are defined and stored based on statistical analyses in accordance with the mass of the mail items to be stacked. The speed of the respective mail item is reduced according to the braking curve assigned to the determined mass of the mail item.

1 . A method for stacking flat mail items, whereby 
 the mail items are transported with a transport means in turn into stackers and are stacked in a vertical position in these,    in each stacker at a stacking point a mail item to be stacked is transported by means of a stacking roll which can be displaced from a stack against a spring pressure, which is controlled to be driven in a start-braking mode, against a stop wall, and a controlled driven underfloor belt and a stacking support coupled so that it can be released from this or driven separately is moved away from the stacking point as the stack grows,    the mail item to be added to the stack in each case arrives at an acute angle to the previous, already stacked mail item,    before the stacking the mass of each mail item to be stacked is determined,    stacking pressures are measured with a measuring device arranged in an area of the stacking roll in a mail item transport plane or on the stacking roll itself, if the stacking roll has engaged with the mail item to be stacked,    in a preceding test phase based on statistical investigations the target values for the stacking pressures and braking curves of the stacking roll until the mail items have reached the stop wall are defined as a function of the mass of the respective mail items to be stacked and stored,    the respective mail item is braked in accordance with the braking curve of the stacking roll assigned to the mail item mass.    
   
   
       2 . The method of  claim 1 , whereby a thickness of the mail item to be stacked is determined and for the stacking of a mail item the underfloor belt and/or the stacking support is moved away from the stacking point by the measured thickness of this mail item plus or minus a correction value for setting the target stacking pressure assigned to the determined mass of the mail item as a function of mass and the thickness of the mail item to be stacked and of a spectrum and characteristics of the previously stacked mail item and then, for an actual stacking pressure measured at the stacking roll deviating from the target stacking pressure for this mail item, is moved to maintain the target stacking pressure.  
   
   
       3 . The method of  claim 1 , whereby for determination of the mass of the mail items, their dimensions are measured, a volume is calculated from this and multiplied by a defined mass factor per volume.  
   
   
       4 . The method of  claim 1 , whereby the braking curve of the stacking roll runs so that a circumferential speed of the stacking roll at the point when the mail item has reached the stop wall is inverse to the mass of the mail item and whereby the stacking roll is subsequently stopped if the following mail item is far enough away for there to be sufficient time to accelerate the stacking roll to its rated speed, before the mail item has reached it.  
   
   
       5 . The method of  claim 1 , whereby a circumferential speed of the stacking roll after the stacking of the respective mail item is accelerated immediately to a rated speed of the means of transport if the subsequent mail item is further than a defined distance from the stacker.  
   
   
       6 . A device for stacking flat mail items with 
 a means of transport to transport the mail items in turn into stackers, in which they are stacked vertically,    a stacking roll located in each stacker at a stacking point, displaceable away from a stack against a spring pressure, which are driven controlled in starting-braking mode and which transport the mail items up to a stop wall, and with a controlled driven underfloor belt and a stacking support coupled to this so that it can be released or driven separately which is moved away from the stacking point as the stack grows,    a measuring device determining the mass of each mail item to be stacked,    a measuring device arranged in the area of the stacking roll on the mail item transport plane or on the stacking roll itself for measurement of stacking forces, whereby in a previous test phase, on the basis of statistical investigations, the target values for the stacking pressures and the braking curves of the stacking roll until the mail items have reached the stop wall, depending on the mass of the respective postal item to be stacked are defined and stored, and whereby the respective mail item can be braked by the stacking roll in accordance with the braking curve assigned to the mass of the mail item.