GB2074990A

GB2074990A - Sheet delivery and stacking method and apparatus

Info

Publication number: GB2074990A
Application number: GB8110852A
Authority: GB
Original assignee: DRG UK Ltd
Current assignee: DRG UK Ltd
Priority date: 1980-04-09
Filing date: 1981-04-07
Publication date: 1981-11-11
Also published as: GB2074990B

Abstract

Sheets are delivered to a stack (32) e.g. in a shingled series, by first and second conveyors (10, 12), and to allow time for the removal of a completed stack (32) when formed, without stopping the sheets, the conveyor (12) is accelerated to form a break (27) in the series. At the same time, a transition region (18) between the conveyors is translated in the direction of sheet movement by a reciprocable carriage (42), so that sheets (24A) on the conveyor (10) do not pass onto the conveyor (12). <IMAGE>

Description

SPECIFICATION Sheet delivery method and apparatus This invention relates to handling sheets of paper, board or like material, and more particularly to delivering a series of sheets to a stack. It is also applicable to handling for example carton blanks, partially erected, flattened cartons and folded bundles of sheets, e.g. the sections of books before they have been collated and bound together. The term "sheet" is to be interpreted as including such articles.

Existing machines for this purpose incorporate means at the stacking region for enabling a completed stack of sheets to be removed without interrupting the flow of sheets being delivered.

One way of doing this is to arrange for the sheets to be stacked in an upper tray until the required number of sheets has been stacked, and then delivering the following sheets to a lower tray while the upper stack is removed, when a complete stack is formed on the lower tray the sheets are again diverted to the upper tray whilst the stack is removed from the lower tray. This arrangement suffers from numerous disadvantages in construction and operation of the apparatus.

Another method is to insert a finger or other stop means in the path of the oncoming sheets while a stack is being removed. The sheets then pile up behind the stop means, and this can cause the next stack to be untidy and unsuitable for subsequent automatic handling, or can cause the sheets to jam up. An example of this is seen in U.S. Patent Specification 1547342, which attempts to solve this problem by slowing down the discharge conveyor leading to the stacking region when the stop means is inserted in the path of the sheets. Unless the discharge conveyor is stopped entirely, however, this still has the sheets piling up against the stop means, so that problems would still be caused if the machine were run at high speed.Moreover, to cope with the slowing or stopping of the discharge conveyor, another conveyor upstream has a telescopic end over the discharge conveyor, which is retracted simultaneously to deposit sheets at successively earlier positions on the discharge conveyor.

Because the sheets have to be dropped from one conveyor to the other, this method is not of general applicability but would only be suitable for relatively stiff sheets of board. Thinner materials such as paper would not drop neatly onto the discharge conveyor.

The present invention provides a method of delivering sheets to a stack, which comprises conveying a series of the sheets towards a stacking region, and periodically forming a break in the series, characterised in that the break is formed by accelerating a leading portion of the series away from the remaining portion without stopping the remaining portion. After stacking of the sheets forwardly of the break the stack thus formed can be removed before further sheets are delivered to the stacking region.

In one form of the present invention the method comprises: (i) transporting the series of sheets on a first conveyor, and in a transition region discharging them from the end of the first conveyor and receiving them onto a second conveyor which transports them towards the stacking region; (ii) forming said break by moving the end of at least the first conveyor to translate the transition region in the direction of travel of the sheets, while at the same time increasing the conveying speed of the second conveyor so that sheets on the first conveyor are temporarily prevented from passing to the second conveyor and the sheets on the second conveyor are moved away from the transition region;; (iii) then moving the end of at least the first conveyor to return the transition region to its original position, with the second conveyor travelling at its original conveying speed until the time comes to form another break.

One form of apparatus for delivering sheet material to a stack comprises a first conveyor and a second conveyor, the second conveyor being arranged to receive a series of sheets from the first conveyor at a transition region and transport them to a stacking region, characterised in that the second conveyor has drive means arranged to periodically increase its speed to form a break between a leading portion of the series of sheets and the remaining portion thereof, and in that means is provided to move the end of at least the first conveyor in the direction of movement of the sheets when the speed of the second conveyor is increased, in order to translate the transition region in said direction of movement.

In a machine suitable for handling some materials, the movable end of the first conveyor may extend over the second conveyor so that the sheets are dropped onto the second conveyor.

However, to produce a machine of more general applicability, it is preferred that the end of the first conveyor and the beginning of the second are substantially aligned, and are moved together in the same relative positions when the transition region is translated.

Preferably the counting means is located at the end of the first conveyor.

Preferably the lower conveying speed of the second conveyor is the same as or lower than the conveying speed of the first conveyor. The sheets are preferably conveyed in shingled formation, and means are preferably provided for gripping the shingled layer of sheets at the end of the first conveyor during the period when the transition region between the two conveyors is moving forward, so as to ensure a clean break in the shingled layer of sheets at the transition. The grip can conveniently be provided by an upper roller which forms a nip with the end of the first conveyor, through which nip the shingled layer of sheets passes.

In order that the invention may be more clearly understood, one embodiment will now be described with reference to the accompanying drawings, wherein: Figs. 1 to 4 show diagrammatically successive stages in the operation of the method and apparatus, and Fig. 5 shows diagrammatically a carriage movement mechanism for the apparatus.

Referring to the drawings, the apparatus comprises a first endless conveyor 10 and a second endless conveyor 12 aligned therewith so that sheets carried on the top of the first conveyor are discharged from the end 14 thereof onto the beginning 1 6 of the second conveyor at a transition point indicated by support plate 18.A primary tape conveyor unit 20 feeds sheets from a rotary cutting unit (not shown) which has severed the web transversely into separate sheets 24, and thence delivers the separate sheets onto the first conveyor 10 which is travelling at a slower speed so that the sheets 24 form a shingled layer 26 on the conveyors 10, 12. In Figs. 1 to 4, the web, the individual sheets and the shingled layer of sheets have, for clarity, been shown above the apparatus, but in the correct longitudinal position appropriate to the indicated stage of operation of the method.

Also, the thickness of the layer has been greatly exaggerated for the purpose of illustration. At the end of the second conveyor 1 2 the layer of sheets is discharged through a pair of nip rollers 28 and into a collection tray 30 where they form a stack 32. The roller 34 at the end of the first conveyor and the roller 36 at the beginning of the second conveyor, together with associated rollers 38, 40 are mounted on a carriage 42 which is arranged for reciprocating movement, as indicated by the arrows A, longitudinaily of the conveyors. Also mounted on the carriage 42 is an upper roller 44 which forms a nip with the end roller 34 of the first conveyor, and a sheet counter 46 adjacent the nip roller 44.The various conveyors and the carriage are driven by suitable drive means, typically an electric motor with drive transmission, speed changers, direction changers, clutches and the like where appropriate, in conjunction with the cutting unit.

The operation of the apparatus can be seen more clearly from the successive stages illustrated in Figs. 1 to 4. In Fig. 1 the carriage 42 is stationary at its normal position nearer the primary tape conveyor unit 20. Both conveyors 10, 12 are travelling at the same speed, and an unbroken shingled layer 26 is travelling along the conveyors 1 0, 1 2, with the sheets at the leading end of the layer discharging into the collection tray 30. While this is happening, the counter 46 is counting the sheets passing through the nip between the rollers 34, 44; in other words the sheets passing from the first to the second conveyor.

When any predetermined number of sheets have passed (for example five hundred sheets, making up one ream) the counter triggers the drive mechanism for the apparatus so that the carriage 42 starts to move forward from its normal position, and at the same time the second conveyor 12 starts to run at a higher speed than the first conveyor 1 0. This condition is shown in Fig. 2. The carriage moves forward at the same speed as the conveying speed of the first conveyor 10.Thus, the transition point 1 8 between the two conveyors, and the nip between the rollers 34, 44 moves forward at the same speed as the layer 26A carried by the first conveyor 1 O. Thus, the leading sheet 24A in the layer 26A, together with those sheets which overlap it, remain trapped in the nip between the rollers 34, 44. Meanwhile, the layer 26B carried by the second conveyor 12 moves away from the layer 26A because the second conveyor is now moving at a higher conveying speed than that of the first layer. The sheets are of course then delivered more quickly into the tray 30, but more importantly a clean break 27 is produced in the layer 26.

The forward movement of the carriage 42 continues until it reaches the forward end of its travel, as indicated in Fig. 3. At about this time the last sheet 24B of the layer 26B has been discharged from the second conveyor 12 to complete the stack 32 in the tray 30, which should now contain one ream (or whatever other predetermined number of sheets has been determined by the counter 46).

The carriage 26 then returns to its original position, as shown in Fig. 4 (the same position as shown in Fig. 1). As it returns the layer 26 which has temporarily remained on the first conveyor 10 (and has been denoted by the reference 26A) passes through the nip formed between the rollers 24, 44 across the transition point 1 8 and onto the second conveyor 12, which has now been switched back to its original conveying speed which is the same as that of the conveyor 10.

Thus, by the time the carriage has reached its normal, starting position once more, as shown in Fig. 4, the layer 26 is approaching or has reached the end of the second conveyor 12, and thereafter the sheets from the layer discharge, in the manner indicated in Fig. 1, into the empty tray 30 from which the previously counted stack has been removed during the time it has taken for the leading end of the layer 26 to reach the end of the conveyor 12. By suitable choice of length of conveyor 12 and difference of conveying speed between the two conveyors during the forward movement of the carriage, this break in the discharge of sheets from the second conveyor can be made long enough to allow ample time for removal of the counted stack.

During the return movement of the carriage, when the layer 26 is once more passing across the transition point from the first to the second conveyor, the counter 46, which has been reset during the forward movement of the carriage, starts to count the passing sheets once more, and continues to do so until the predetermined number of sheets has again been reached, at which time the sequence previously described is again triggered.

The counter may if desired be mounted over the primary tapes 20. This is before the sheets are shingled, and may give more reliable operation of counters of the opto-electronic type.

Fig. 5 shows one way in which the carriage 42 may be driven. Drive is received from the drive source of the conveyor 10 via a clutch (not shown) operated from the counter and via a belt or chain 50. This drives an endless chain 52 entrained around sprocket wheels 54, 56. The chain 52 carries a pin 58 on which one end of a crank arm 60 is journalled. The other end of the crank arm 60 is pivoted at 62 to an arm 64 which is fixed to the carriage 42. When the carriage is in its Fig. 1 position, the part of the chain carrying the pin 58 is wrapped around the wheel 54. When the clutch is engaged, the pin 58 will travel to the wheel 56, giving the carriage a constant speed the same as the conveying speed of the conveyor 10. The carriage decelerates as the pin 58 passes around the wheel 56, and returns to its normal position as the pin returns to the wheel 54.

Although it is desirable for the carriage to move at the same speed as the conveyor 10 (since this keeps the sheet 24A in the nip formed by rolls 34, 44) it can be given a greater speed. The transition region will then move faster than the series of sheets 26A. This has the advantage that the drive mechanism for the carriage can be made simpler. For example, it could be actuated by a double acting hydraulic ram or a wheel 54 driven by a separate electric motor. In either case, the speed could be sypchronised with the speed of the conveyor 10. Alternatively, the wheels 54, 56 and chain 52 in Fig. 5 could be replaced by a single rotatable wheel on which the crank pin 58 is fixed.

The single rotatable wheel could be driven by the belt or chain 50, or by a separate electric motor, and could operate at either constant or varying angular velocity to give the carriage any desired velocity characteristic.

It will be seen that the method and apparatus of the present invention enables a stack of sheets to be removed in conjunction with any stack removing system without any interruption or change of rate of supply of sheets to the apparatus, and without any complex or duplicate machinery for alternative discharge paths and diverting sheets from one path to another, as with conventional practice. The advantage of the present invention is essentially achieved by speeding up the discharge of the sheets over the latter part of the formation of the stack, this speed-up being of sufficient magnitude and for a sufficient duration to create a break in the discharge of sheets long enough, once the stack has been completed, to allow the stack to be removed.

If desired, the normal, lower speed of the second conveyor can be less than that of the first conveyor. This gives a second stage of shingling in the transition region.

Claims

1. A method of delivering sheets to a stack, which comprises conveying a series (26) of the sheets (24) towards a stacking region (26) of the periodically forming a break in the series (26), characterised in that the break (27) is formed by accelerating a leading portion (26B) of the series away from the remaining portion (26A) without stopping the remaining portion.

2. A method according to claim 1 wherein the series of sheets (24) are conveyed in a shingled formation (26).

3. A method according to claim 1 or claim 2 comprising: (i) transporting the series (26) of sheets (24) on a first conveyor (10), and in a transition region (18) discharging them from the end (14) of the first conveyor and receiving them onto a second conveyor (12) which transports them towards the stacking region (30); (ii) forming said break (27) by moving the end (14) of at least the first conveyor (10) to translate the transition region (1 8) in the direction of travel of the sheets, while at the same time increasing the conveying speed of the second conveyor (12), so that sheets (26A) on the first conveyor are temporarily prevented from passing to the second conveyor and the sheets (26B) on the second conveyor are moved away from the transition region (18);; (iii) then moving the end (14) of at least the first conveyor (10) to return the transition region (18) to its original position, with the second conveyor (12) travelling at its original conveying speed until the time comes to form another break (27).

4. Apparatus for delivering sheets to a stack, which comprises a first conveyor (10) and a second conveyor (12), the second conveyor being arranged to receive a series (26) of sheets (24) from the first conveyor at a transition region (18) and transport them to a stacking region (30), characterised in that the second conveyor (12) has drive means arranged to periodically increase its speed to form a break (27) between a leading portion (26B) of the series of sheets and the remaining portion (26A) thereof, and in that means (42) is provided to move the end (14) of at least the first conveyor (10) in the direction of movement of the sheets (24) when the speed of the second conveyor is increased, in order to translate the transition region (18) in said direction of movement.

5. Apparatus according to claim 4 wherein the transition region (18) is between adjacent ends (14, 16) of the conveyors (10, 12), and the means (42) for moving the end (14) of the first conveyor (10) is also arranged to similarly move the end (16) of the second conveyor (12).

6. Apparatus according to claim 4 or claim 5, including counting means (46) arranged to count the passing sheets (24), and when a predetermined count is reached to operate the means (24) for translating the transition region (18) and increase the speed of the second conveyor (12).

7. Apparatus according to claim 4, 5 or 6, wherein the second conveyor (12) runs at a speed the same as or lower than the first conveyor (10) when its speed is not increased to form the break (27).

8. Apparatus according to any one of claims 4 to 7, having means (44) for gripping the series (26) of sheets (24) at the end (14) of the first conveyor (10) during the period when the transition region (18) is being translated.

9. Apparatus according to claim 8 wherein the gripping means comprises an upper roller (44) which forms a nip with the end (14) of the first conveyor, through which nip the series (26) of sheets passes.

10. Apparatus according to any one of claims 4 to 9 wherein the means for translating the transition region (18) comprises a reciprocable carriage (42) on which at least an end roller (34) of the first conveyor (10) is mounted.

11. A method of delivering sheets to a stack, substantially as described herein with reference to the accompanying drawings.

12. Apparatus for delivering sheets to a stack, substantially as described herein with reference to the accompanying drawings.