GB2264930A

GB2264930A - Stacking apparatus

Info

Publication number: GB2264930A
Application number: GB9204950A
Authority: GB
Inventors: Edward John Ward; Leonard Alfred Whitehead
Original assignee: AUTOFEEDS LONDON Ltd
Current assignee: AUTOFEEDS LONDON Ltd
Priority date: 1992-03-06
Filing date: 1992-03-06
Publication date: 1993-09-15
Also published as: GB9204950D0

Abstract

A single stream 2 of sheets of material having local thickness variations (e.g. off-centre embossed areas) is divided at 4 into first and second streams A and B. First and second turning means 7, 8 turn the sheets such that the sheets of the first stream are orientated 180 DEG with respect to the sheets of the second stream. First and second stacking means 13, 14 form first and second stacks A", B" of sheets from the first and second streams. Third stacking means 17, 18 are each adapted to form a composite stack of the first and second stacks, the sheets of the first stacks A" being orientated 180 DEG with respect to the sheets of the second stacks B". Stability of the composite stacks is thus assured. <IMAGE>

Description

STACKING APPARATUS This invention relates to stacking separate sheets of material and is particularly, but not exclusively, suitable for stacking sheets of paper.

It is common practice within the paper supply industry to stack separate sheets of paper into stacks comprising a predetermined number of sheets, commonly a ream (500 sheets), and then to stack these 'sized' stacks into so-called 'deep pile' stacks, typically on a pallet. The deep pile stacks once formed may be secured to the pallet for delivery to a printing works or other such users.

A problem with stack stability is frequently encountered when stacking paper having a varying thickness. So-called security paper, for instance, often has a local embossed or raised watermark portion which has the effect of giving each sheet thereof a slight local variation in thickness. When stacked to form a ream, the cumulative effect of each thickness variation may be sufficient to produce a considerable variation in the thickness of the ream. Stability problems may be encountered when forming deep pile stacks of such variable thickness stacks, particularly when the local thickness variation is located off centre of the sheets.

An object of the invention is to overcome or at least reduce the above-mentioned stability problem when the local thickness variation is located off centre of the sheets.

Broadly this is achieved by providing an apparatus which forms a composite stack of first and second stacks, the sheets of the first stacks being orientated 1800 with respect to the sheets of the second stacks.

The invention includes an apparatus for stacking separate sheets of material comprising: supplying means for supplying a single stream of said separate sheets; dividing means for dividing said single stream into first and second streams; respective first and second conveying means for conveying said first and second streams; turning means associated with at least one of said conveying means for turning the sheets of at least one of said streams such that the sheets of said first stream are orientated 1800 with respect to the sheets of the second said stream; first stacking means for forming first stacks of sheets from the first stream, second stacking means for forming second stacks of sheets from the second stream; and respective conveying means for conveying said first and second stacks to third stacking means for forming a composite stack of said first and second stacks, the sheets of the first stacks being orientated 1800 with respect to the sheets of the second stacks.

Preferably the turning means of the apparatus comprises first turning means associated with said first conveying means and second turning means associated with said second conveying means, said first turning means arranged to turn the sheets of said first stream over diagonally in a first direction and said second turning means arranged to turn the sheets of said second stream over diagonally in a second direction opposite to said first direction.

It is preferred that each of said turning means comprises a guide disposed at an angle of 450 to the direction of the associated conveying means and each of said guides comprises an elongate member defining a curved surface for guidingly turning said separate sheets of material.

Preferably the first and second stacking means are each adapted to form stacks having a predetermined number of said separate sheets of material.

The third stacking means may comprise a plurality of stacking devices each adapted to form a composite stack and arranged to stack said first and second stacks alternately to form a said composite stack.

Preferably the third stacking means comprises at least one pick and place device.

The apparatus may comprise cover sheet feeding means for feeding cover sheets to at least one of said respective first and second stacking means, said cover sheet feeding means being adapted to feed a bottom cover sheet and a top cover sheet to each separate stack formed at said first and second stacking means.

The invention further provides a method of stacking separate sheets of material comprising the steps of: supplying a single stream of said separate sheets; dividing said single stream of said separate sheets into first and second streams; turning the sheets of at least one of said first and second streams such that the sheets of the first stream are orientated 1800 with respect to the sheets of the second stream; stacking the separate sheets of material of said first and second streams to form first stacks of sheets from the first stream and second stacks of sheets from the sheets of the second stream; and stacking said first and second stacks to form a composite stack of first and second stacks at a predetermined location, the sheets of the first stacks being orientated 1800 with respect to the sheets of the second stacks.

Preferably the turning step comprises turning the sheets of the first stream over diagonally in a first direction and turning the sheets of the second stream over diagonally in a second direction opposite to said first direction.

Preferably said first and second stacks are arranged alternately in said composite stack.

The method may include the step of forming a second said composite stack at a location spaced from said predetermined location.

The method may include providing at least each first stack with a cover sheet.

Preferably the method comprises providing each first stack and each second stack with respective top and bottom cover sheets.

In order that the invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Fig. 1 is a schematic representation layout of a stacking apparatus; Fig. 2 is a perspective view of a stacking apparatus; and Fig. 3 shows a section of the stacking apparatus of Fig. 1 with cutting means added thereto.

As shown in Figure 1, separate sheets of paper are fed from a sheeter 1 into a supplying means of the stacking apparatus to form a single stream 2 of such sheets. A sheeter is a device well known to those skilled in the art and need not be described in detail in order to understand the stacking apparatus. The supplying means is preferably a plurality of parallel conveyor tapes 3 arranged to convey the single stream 2 into the apparatus. The spacing of the tapes is adjustable for varying sheet size. Typically, the sheeter delivery speed may be 200 metres/min.

The single stream 2 is conveyed by the conveyor tapes 3 to a dividing means comprising a stream divider 4 where the single stream 2 is divided into two separate streams. Preferably the stream divider 4 directs alternate sheets (A and B respectively) from the single stream 2 to respective first and second conveying means to form a first stream of sheets A and a second stream of sheets B. The first and second streams may typically flow at speeds of 150 metres/min which permits stacking on a sheet by sheet basis with high reliability for accurate sheet counting and control. The first and second conveying means are preferably conventional belt conveyors 5, 6.

It is to be understood that while the first and second conveying means 5, 6 may be spaced apart on the same horizontal plane as shown in Fig. 1, this is not a necessary feature of the apparatus. Indeed, it is preferred that one of the conveyor means be disposed vertically above the other.

The separate sheets A, B of the respective first and second streams are conveyed by the first and second conveyor belts 5, 6 to associated first and second turning means which each comprise a guide 7, 8 disposed at an angle of 450 to the direction of the respective conveyor belts 5, 6 and therefore the direction of first and second streams. The guides 7, 8 which are known as ploughs or formers, each comprise an elongate member defining a concave surface 9, 10 for guidingly turning said separate sheets. The guides 7,8 each disposed at 450 to the associated conveyor belts 5, 6 and thus mutually orthogonal, are orientated such that the respective concave surfaces 9, 10 may receive the separate sheets of material A, B of the respective streams (as shown in Fig. 2) wherein the sheets are guided so as to turn.

The turning action of the guide 7 of the first turning means is such that the sheets A of the first stream are turned over diagonally in a first direction while the turning action of the guide 8 of the second turning means is such that the sheets B of the second stream are turned over diagonally in a second direction which is opposite to the first direction.

Effectively the sheets A, B of the first and second streams are each turned through an angle of 90" and inverted simultaneously but in opposite directions, such that the turned sheets A' of the first stream are orientated 1800 with respect to the turned sheets B' of the second stream. It is an important feature of the stacking apparatus that the sheets A, B of the first and second streams are each turned so that the same face orientation is maintained.

The turned sheets A', B' of the first and second streams are conveyed from the respective guides 7, 8 by the associated first and second belt conveyors 5, 6 to respective first and second stacking means as indicated in Fig. 1. The first and second stacking means comprise respective vertical pile stackers 13, 14 wherein first stacks A" of sheets A' and second stacks B'' of sheets B' each comprising a predetermined number of sheets may be assembled. As previously mentioned, stacks of 500 sheets (a ream) are a typical size used in the industry. Vertical pile stackers and the associated counting means used to form the 'sized' stacks are well known to those skilled in the art and a detailed description thereof is not required for understanding the stacking apparatus.

It is further envisaged that the stacks formed at the vertical pile stackers 13, 14 be protected by cover sheets placed at the top and bottom of each 'sized' stack. These cover sheets may be of paper for example, but are preferably boards having width and length dimensions substantially as those of the sheets of material of the stacks, but having a substantially greater stiffness. The cover sheets are provided from respective cover sheet feeders (devices well known to those skilled in the art) 11, 12 positioned adjacent the vertical stackers 13, 14 and arranged for cooperation with the stackers such that, a cover sheet is fed into the stacker from the associated cover sheet feeder before assembly of each stack is commenced and another cover sheet is fed on to the top of each completed stack.Further, alternate sheets in the cover board feeders may be pre-printed with a customer's required production control information.

It is to be understood that the provision of cover sheets is not essential to the operation of the stacking apparatus, but is desirable both for protecting the stacks and where the sheets are such that the stiffness of the stack is increased, improving the handleability thereof.

The respective stacks A", B" of sheets A', B' are discharged from the respective vertical pile stackers 13, 14 to respective conveying means for conveying to third stacking means. The respective conveying means are preferably belt conveyors 15, 16.

The first stream of first stacks A" and second stream of second stacks B" are discharged from the respective vertical pile stackers 13, 14 without interruption to the stacking process.

The third stacking means 17, 18 are disposed at spaced locations and are preferably pick and place devices arranged such that each may pick up a first stack A" from conveyor belt 15 or a second stack B" from conveyor belt 16 and place it on a suitable stacking surface such as a pallet. Each pick and place device 17, 18 forms a deep pile stack by taking a first stack A" from the first stream conveyor belt 15 and a second stack B' from the second stream conveyor belt 16 alternately.In this manner a stable composite deep pile stack of stacks A'' and B" is formed on the pallet, comprising first and second stacks arranged alternately, with the sheets of the first stacks A" orientated 1800 with respect to the sheets of the second stacks B". The deep pile stacks thus formed may typically be 1.5 metres deep.

The pick and place devices 17, 18 are arranged to operate alternately, such that a deep pile stack is being unloaded from one of the devices while the other is stacking another deep pile stack so that a continuous stacking operation is maintained.

Typically the vertical pile stackers 13, 14 each discharge a stack at a rate of one stack per minute.

Therefore, the stacking devices of the third stacking means must be capable of taking a stack A'' from the first stream and a stack B" from the second stream and stacking one upon the other in less than a minute.

It will be appreciated that the embodiment of the stacking apparatus described herein is for the purpose of illustration only. It will be apparent to those skilled in the art that additional devices may be incorporated in the stacking apparatus for processing the sheets of material during the stacking operation.

For example, as shown in Figure 3, cutting means 20 may be disposed so as to be substantially in alignment with the edges of the first and second conveyor belts 15, 16 for trimming the edges 21 of said separate turned sheets A', B' of the first and second streams respectively to bring the separate sheets of material to a required size, before the sheets are stacked at the respective first and second stacking means 13, 14.

It is to be understood that a guide for turning the sheets as described hereinbefore is not limited to a member having a concave surface. The turning action described in respect of the guides 7, 8 is also obtainable by taking a sheet of material around an elongate member defining at least a convex surface portion. In particular, the sheet may be taken around the outside diameter of a cylindrical shaft known as a turner bar. The turner bar may be fixed or alternatively, may be revolved about its axis or have air supplied to a bleed hole at the surface thereof by means of a bore therein for obtaining the turning action.

It will be appreciated by those skilled in the art that the supplying means 3 and conveying means 5, 6, 15, 16 may be any form of handling equipment suitable for conveying the separate sheets of material or stacks and are not limited to tape conveyors and conventional conveyor belts as described herein. For example, the respective stacks A", B" of the first and second streams might be conveyed from the respective first and second stacking means to the third stacking means suspended from overhead lines by vacuum cup devices.

It is to be understood that the stacking apparatus, while particularly suitable for stacking paper, is equally suitable for stacking other sheet materials particularly where those sheets have a local variation in thickness.

Claims

CLAIMS:

1. An apparatus for stacking separate sheets of material comprising: supplying means for supplying a single stream of said separate sheets; dividing means for dividing said single stream into first and second streams; respective first and second conveying means for conveying said first and second streams; turning means associated with at least one of said conveying means for turning the sheets of at least one of said streams such that the sheets of said first stream are orientated 1800 with respect to the sheets of the second said stream; first stacking means for forming first stacks of sheets from the first stream, second stacking means for forming second stacks of sheets from the second stream; and respective conveying means for conveying said first and second stacks to third stacking means for forming a composite stack of said first and second stacks, the sheets of the first stacks being orientated 1800 with respect to the sheets of the second stacks.

2. An apparatus as claimed in claim 1, wherein said turning means comprises first turning means associated with said first conveying means and second turning means associated with said second conveying means, said first turning means arranged to turn the sheets of said first stream over diagonally in a first direction and said second turning means arranged to turn the sheets of said second stream over diagonally in a second direction opposite to said first direction.

3. An apparatus as claimed in claim 2, wherein each of said turning means comprises a guide disposed at an angle of 450 to the direction of the associated conveying means.

4. An apparatus as claimed in claim 3, wherein each of said guides comprises an elongate member defining a curved surface for guidingly turning said separate sheets of material.

5. An apparatus as claimed in any one of the preceding claims, wherein said first and second stacking means are each adapted to form stacks having a predetermined number of said separate sheets of material.

6. An apparatus as claimed in any one of the preceding claims, wherein said third stacking means comprises a plurality of stacking devices each adapted to form a composite stack.

7. An apparatus as claimed in claim 6 wherein each of the stacking devices is arranged to stack said first and second stacks alternately to form a said composite stack.

8. An apparatus as claimed in claim 7, wherein said stacking devices are operable in a predetermined sequence.

9. An apparatus as claimed in any one of the preceding claims, wherein said third stacking means comprises at least one pick and place device.

10. An apparatus as claimed in any one of the preceding claims, further comprising cover sheet feeding means for feeding cover sheets to at least one of said respective first and second stacking means.

11. An apparatus as claimed in claim 10, wherein said cover sheet feeding means is adapted to feed a bottom cover sheet and a top cover sheet to each separate stack formed at said first and second stacking means.

12. A method of stacking separate sheets of material comprising the steps of: supplying a single stream of said separate sheets; dividing said single stream of said separate sheets into first and second streams; turning the sheets of at least one of said first and second streams such that the sheets of the first stream are orientated 180 with respect to the sheets of the second stream; stacking the separate sheets of material of said first and second streams to form first stacks of sheets from the first stream and second stacks of sheets from the sheets of the second stream; and stacking said first and second stacks to form a composite stack of first and second stacks at a predetermined location, the sheets of the first stacks being orientated l80O with respect to the sheets of the second stacks.

13. A method as claimed in claim 12, wherein said turning step comprises turning the sheets of the first stream over diagonally in a first direction and turning the sheets of the second stream over diagonally in a second direction opposite to said first direction.

14. A method as claimed in claim 12 or 13, wherein said first and second stacks are arranged alternately in said composite stack.

15. A method as claimed in claim 12, 13 or 14, comprising forming a second said composite stack at a location spaced from said predetermined location.

16. A method as claimed in any one of claims 12 to 15, including providing at least each first stack with a cover sheet.

17. A method as claimed in claim 16, comprising providing each first stack and each second stack with respective top and bottom cover sheets.

18. An apparatus or method substantially as hereinbefore described with reference to the accompanying drawings.