The invention relates to a sheet sorter unit for sorting separate sheets into bins, the sheets having ⁽ mutually varying dimensions and being supplied con¬ secutively from a sheet processing machine, such as an 5 electrophotographic printer or a copying machine, the sorter unit comprising a number of sorting bins with an abutment plate to stop the movement of the sheet and a control unit controlling the sorting of the sheets.

In known sorter units of this type with vertic- 10 ally superposed sorting bins it is not possible to sort separate sheets of different size and/or thickness into a pile with straight edges, the kinetic energy of the sheet in relation to size and weight entailing varying rebounding from the abutment plate of the sorting bin. 15 DE patents Nos 24 56 046 and 26 00 951 deal with a sorter unit settable to sort separate sheets of vary¬ ing length, if only all the sheets discharged into a stack have the same length. The setting according to sheet size is effected in that an abutment extending 20 upwards through all the bins is manually moved forwards or backwards in the longitudinal direction of the bin. When the abutment is set to receive short sheets in the bin, the bin cannot receive longer sheets. It is there¬ fore not possible to make use of such an abutment in a 25 sorter unit in which sheets of varying size are to be sorted into the same pile of sheets in one bin.

E.g. in data or word processing systems where many users share a single centrally placed sheet printer, there may according to job be a need for

, 30 printing on different size and thickness of sheets that i are discharged into at least one bin.

It is the object of the invention to provide a sheet sorter unit capable of collecting separate sheets

having at least one varying dimension in the order they are delivered from a sheet processing machine, and of placing the sheets in a sorting bin in a pile having a straight front edge. With a view to this, the sorter unit according to the invention is characterized in that at least one bin is designed with at least two sheet feeding paths, one of which has feed meanr disposed in the bin for controlled delivery of sheets at a shorter distance from the abutment plate of the bin than the feed means of the second path, and that the sheet sorter unit from information about the size of the sheet is capable of guiding the sheet in the sheet feeding path suitable for the sheet size. The two sheet feeding paths in the bin allow a precise positioning of sheets therein, because smaller sheets may be fed into the bin along the path having the feed means positioned closest to the abutment plate, thereby forcibly guiding smaller sheets further into the bin where they are released at a shorter distance from the abutment plate than larger sheets. This avoids the mispositioning caused by the fact that the sheet after release is randomly influenced by electrostatic charging and air resistance, resp., which in connection with the circumstance that corners or edges of the sheets have a tendency to bend would otherwise result in discharging into a pile with uneven edges and possibly skewly disposed sheets.

Prior art sorter units only include one sheet feeding path for each bin and said feeding path is quite simply constituted by the internal volume of the bin, since an arriving sheet is simply delivered into the bin through the inlet opening by a sheet guide means located outside the inlet opening of the bin, following which the sheet without any further forced advancing slides into the bottom end of the bin. In a

particular simple embodiment according to the invention the first sheet feeding path consists of an ordinary inlet opening with posteriorly located bin spaces, while the second feeding path is positioned in the bin above the first path and comprises feed means in the form of at least two drive pulleys disposed consecut¬ ively in the sheet feeding direction. In view of the fact that said drive pulleys are positioned between the inlet opening and the abutment plate the sheet will in the second path be fed forward and unambiguously posi¬ tioned by the feed means far into the bin, thereby releasing the sheet at a distance from the abutment plate which is suitably short considering the small size of the sheet. In order to choose the feeding path which for a specific sheet gives the best placing of the sheet on a pile, it is necessary to know the length of the sheet. In a preferred embodiment advantageous in that the sorter unit is independent of the type or brand of the sheet processing machine, the unit has a sensor posi¬ tioned at the sheet feeding path between the inlet opening of the sorter unit and the bins, and which by the actual sheet passing transmits signals to the control unit for use in determining the length of the sheet, and on the basis of said signals the control unit selects the feeding means of the actual bin into which the sheet shall be fed.

The sorting of the sheets into a pile with straight front edge aimed at by the invention may be further improved if the unit appropriately has a signal means located at the sheet feeding path between the inlet opening of the sorter unit and the bins and which during a sheet passing by detects a value of the thick¬ ness thereof and emits a signal to the control unit in conformity therewith, following which the control unit from said signal determines the velocity with which the sheet has to be discharged into the bin.

In this manner account may be taken of the cir¬ cumstance that the sheets may also have different weight due to the varying length and/or thickness or quality of the sheet material, thereby allowing a heavier sheet to be discharged at a lower release velo¬ city from the sheet path than a lighter sheet, result¬ ing in that the sheets may be released with a kinetic energy mainly of the same size.

If the sheet processing machine is of the type capable of transmitting information about the length and/or weight of each sheet, the sheet sorter unit may alternatively have an interface connected with the control unit by signal transmission, and which from the sheet processing machine may transmit information to the control unit about the length of the arriving sheet and possibly also about the specific weight of the sheet so that the control unit on the basis of said information may determine the actual sheet feeding path and/or the discharge velocity of the sheet into the bin.

Even though the sheets may be controlled so that their kinetic energy is by and large the same immedi¬ ately before the sheet hits the abutment plate, there is always a tendency for the sheet to rebound a little after having hit and being stopped by the abutment plate of the bin. As a consequence, the sheet pile may get a front edge that is somewhat uneven, and thus the sorting of sheets into a pile with a straight front edge aimed at by the invention may be further promoted in that the paper holder arm under which the sheet slides prior to reaching the abutment plate of the bin, appropriately at its lower end carries a pulley jour- nalled so with a free-wheel block that the pulley is only allowed to rotate in the feed direction of the sheet and that the cylindrical peripheral face of the pulley appropriately has a frictional coating. When the

sheet passes under the paper holder arm and is moved towards the abutment plate, the sheet just makes the pulley rotate. When the sheet after having hit the abutment plate is influenced to move away therefrom, the free-wheel block prevents the roller from rotating in the blocking direction and the friction between the roller and the sheet therefore retains the sheet in engagement with the abutment plate. Consequently, the sheets may according to the invention be sorted into a pile having a completely straight front edge, not¬ withstanding the sheets have varying lenght, thickness or weight.

The invention also relates to a method of sorting separate sheets into the bins of a sorter unit, said sheets having mutually varying dimensions and being individually supplied consecutively from a sheet processing machine, such as an elektrophotographic printer or copying machine in which the sorting of the sheets into a number of consecutive bins is controlled by a control unit.

The method according to the invention is charac¬ terized in that the control unit receives information about at least the length dimension of the sheet to be sorted, and that on the basis of this information it is decided to feed the sheet into the bin through one of at least two feeding paths associated with the bin and which may release the sheet at mutually different distance from the abutment plate of the bin, the choice of feeding path being determined so that a com- paratively short sheet is released in the bin at a smaller distance from the abutment plate than a com¬ paratively long sheet.

It has thus been made possible to sort sheets of different length into one and the same pile of sheets while preserving a substantially straight front edge of the stack.

An embodiment of the invention will now be des¬ cribed in detail with reference to the very schematical drawings, in which

Fig. 1 illustrates a side elevation of a sheet sorter unit according to the invention, and

Fig. 2 on a larger scale illustrates some of the bins in the sorter unit.

A sheet processing machine, not shown, may deliver separate sheets to the sheet inlet 1 of the sorter unit, where the sheets are seized by a pair of driven pulleys 2 rotating at a rate of rotation adjusted to the discharge velocity of the sheet from the sheet processing machine, said adjustment being effected by manual pre-setting or by photoelectric recording of the discharge velocity of the sheet. The pulleys 2 may be provided with a slide coupling com¬ pensating for minor differences in velocity between the sheet and the pulleys 2.

A sensor 3 positioned immediately after the pulleys 2 may detect the presence of a sheet and emit a "sheet start" and a "sheet stop" signal to a control unit 4 which on the basis of this information and the rotational velocity of the pulleys 2 may calculate the length of the sheet which, as described in the following, forms the basis of determining the sheet

, path for sorting and possibly also the feed velocity of the sheet.

When the sheet has been released from the sheet processing machine, drive pulleys 5 may accelerate the sheet to the sorting velocity which may typically amount to ten times more than the infeed velocity of the sheet. The pulleys 5 deliver the sheet to a sheet feeding path, indicated by the arrow 6, in which the sheet is moved upwards past a number of consecutive sheet bins 9.

The sheet feeding may for instance be effected by means of a suction table 7 with driving belts 8

pulling up the sheet past the inlet openings of the bins. Opposite the inlet openings of the bins there are provided sheet guide means 10 which by means of control signals from the unit 4 may be set to guide the sheet into the desired bin either through a first feeding path 11 where the sheet is simply sent through the inlet or end opening 12 of the bin in order to subsequently move freely into the bin under the influence of its own kinetic energy, or through another feeding path 13 in which the sheet is advanced through a sheet slit 14 extending into the bin in its longitudinal direction and being delimited by guide plates 15 or by pull belts, not shown. The sheet is forced through the sheet slit by means of feed means in the form of two drive pulleys 16, 17 located at the beginning and end, respectively, of the slit together with associated opposite abutment pulleys 18, 19. The pulleys 16 to 19 are appropriately located on shafts, not shown, joumalled in the lateral plates of the frame of the sheet bins. The driven shafts may each individually at their end have a belt pulley engaging a driving belt common to the pulleys 16 and which runs over the belt pulleys and is driven by a drive motor the velocity of which is controlled by unit 4.

The control unit 4 selects that of the feeding paths 11, 13 which offers the longest possible con¬ trolled feeding before release, meaning that short sheets are advanced through the feeding path 13 where the sheet is not released until well into the bin at pulleys 17, 19. If the sheet is longer than the dist¬ ance between pulleys 17, 19 and the abutment plate of the bin the first feeding path 11 is chosen in which the sheet is released already at the end opening 12. The bottom 20 of each bin is preferably designed with a descending shoulder 21 in the proxi-

mity of the end opening 12 and an inclined shoulder 22 in the proximity of the superposed pulleys 17, 19 in the second feeding path. The shoulders ensure that an arriving sheet does not meet the end face of a pile of already discharged sheets. If the bin for example is designed to receive A4 and A3 sheets, the A4 sheets will be passed through the second feeding path 13 for delivery at the far end of the bin, whereas A3 sheets will be passed into the first feeding path. The outer end of the A4 sheets will be positioned after the shoulder 22 so that arriving sheets A3 are pushed in over the A4 sheets and the outer end of the A3 sheets will be hidden behind the shoulder 21, as illustrated in Fig. 2. The control unit 4 adjusts the feed velocity of the sheet so that the sheet is released having a kinetic energy entailing the minimum rebounding from the abutment plate 23 in the bin. Besides varying according to length of sheet, the weight also varies according to the sheet thickness which may be detected by a signal means 3 ¹ . Alternatively, the weight of the sheet may be determined on the basis of the sheet length and signals originating from manually keying in the basis weight of the sheet on a keyboard, e.g. asso- ciated with the sheet sorter unit, the sheet sorter machine or a data processor. It is further possible to provide the sorter unit with an interface, not shown, to be connected with the sheet processing machine so that the necessary information may be transmitted from said machine from manually keyed information or infor¬ mation associated with the sheet supply bin from which the sheet has been taken.

A paper holder arm 24 is at its upper end sus¬ pended at the top of the bin 9. At its lower end, the arm carries a pulley 25 provided with a free-wheel block and whose periphery consists of a friction

material 26, such as rubber or a plastics material capable of effectively seizing the sheet surface. The free-wheel block ensures that the pulley 25 may rotate only in the direction of the arrow 27, meaning that the pulley allows a sheet inserted under this pulley to move in the direction towards the abutment plate 23 but not in the opposite direction. The arm 24 may carry a shaft, not shown, extending transverse¬ ly of the longitudinal direction of the arm and carry- ing a pulley 25 at each of its two ends. The use of two pulleys ensures that the sheet at two points separated as to the direction of width is not subjected to rebounding away from the abutment plate 23, thereby counteracting skew sheet piling. It is of course possible to design both of the sheet feeding paths in the bin with feed means, e.g. by placing a drive pulley with associated abutment pulley in path 11 immediately beneath the pair of pulleys 16, 18 in path 13. This may be desirable if the dis- charge velocity of the sheet into the bin is precisely adjusted by said pulleys and not by the driving belts 8 in suction table 7. If sheets of many different lengths are to be sorted into a pile there may obvious¬ ly be more than two sheet feeding paths of varying length in the bin 9.