CA2273561C - Method and apparatus for packing stacks of flat articles - Google Patents

Abstract

Stacks (2) of flat articles supplied in a serial stack stream are wrapped with a foil (3) in a first packing step in such a way that said foil (3) covers the top, bottom and two vertical sides of each stack and projects over both sides of the covered stack sides. Then packing of the foil-wrapped stacks (2.3, 2.4) is finish in a second packing step in a strapping/welding position and depending on the stack height (d.1, d.2). Stacks (2.3) having a height (d.1) greater than a predetermined limit stack height are strapped and on stacks (2.4), whose height (d.2) is equal to or smaller than the limit stack height, the foil areas (3.1) projecting over the top and bottom of the stack are welded together, strapping being suppressed or performed simultaneously with the welding operation.

Description

Doc No. 35-35 CA Patent METHOD AND APPARATUS FOR PACKING STACKS OF FLAT ARTICLES
The present invention concerns the field of packing technology and relates to a method and an apparatus according to the preambles of the corresponding, independent claims. The method and apparatus are used for packing serially supplied, substantially parallelepipedic stacks each consisting of a plurality of superimposed, flat articles, such as e.g. newspapers or magazines. It is obviously possible also to pack other, substantially parallelepipedic articles with the aid of the method and apparatus according to the invention.
For dispatch purposes newspapers and magazines are usually stacked, the stacks being strapped at least once with a strap or band and they are optionally enveloped or wrapped with a film or foil prior to strapping. Stacks packed in this way are stable and easy to handle as a result of the strapping and due to the foil wrapping, at least the outermost products are protected against external influences such as moisture or dirt and also against mechanical damage. Depending on the stack stability and on the size of the stacked articles, single or multiple strapping is used, the multiple strapping consisting of at least two parallel straps or of at least two straps at right angles to one another.
For the wrapping and strapping of serially supplied stacks, as well as of other substantially parallelepipedic articles, the most varied methods and apparatuses are known and these are e.g. described in Swiss patent applications 01631/97, 01674/97 and 00504/98.
With the aid of most of these methods and apparatuses it is possible to produce with short cycle times adequately stable stack packs, provided that the height of all the supplied stacks falls within a predetermined range and in particular provided that none of the stacks has a height smaller than a predetermined minimum height.

Doc No. 35-35 CA Patent The downward stack height limitation may have various reasons. The stacked products can e.g. be so bendable or flexible, that in a small stack they are bent by the taut strap, so that the strap loosens and the pack becomes unstable. If the strap is welded together on a perpendicular lateral face of the stack, in a small stack, the weld point can be higher than the stack, so that a taut strapping cannot be obtained.
For dispatch purposes, predetermined numbers of newspapers and magazines are made ready by stacking and packing and a dispatch unit usually comprises a plurality of standard packs (stacks with a standard height) and e.g. one top pack (smaller than the standard pack). Such top packs can contain a very small number of magazines or newspapers or even a single magazine or newspaper. Due to the aforementioned limitation to the stack height in the known strapping machines, the top packs may have to be supplied to a separate apparatus, such that not only additional wrapping/strapping apparatuses but also additional conveying paths and switch points are required. As in most cases it is important that standard and top packs are discharged from the packaging process in the same order in which the corresponding stacks were supplied, the allocation of the stack flow to different packing machines and the bringing together of the packed flow after packing is complicated regarding automatic control or necessitates manual reorganization.
The object of the invention is to create a method allowing serially supplied stacks of flat articles such as newspapers or magazines to be processed into stable packs whereby the supplied stacks can have any heights between a standard height and a very small height. This means that with the inventive method, it is to be possible to pack without difficulties also stacks comprising e.g. a single newspaper or magazine. The method according to the invention is to be usable without modifying the stack sequence in a stack flow and with cycle times no longer than the cycle times expected in known stack packing methods.
A further object of the invention is to provide an apparatus for performing the method.

Doc No. 35-35 CA Patent These objects are solved by the method and apparatus as defined in the independent claims.
According to the inventive method, in a first step a foil or film is placed around the serially supplied stacks and is closed to form a wrapping or envelope using a per se known method.
In a second step, enveloped or wrapped stacks having a greater stack height are pressed and strapped, whereas enveloped or wrapped stacks having a smaller stack height and therefore not being able to be packed to form a stable pack by strapping, are finished by side welding the foil wrapping instead of or in addition to strapping.
To permit the lateral or side welding of the foil wrapping for stacks with a smaller stack height the foil material used for wrapping is wider than the corresponding dimension of the stack and the foil is placed and closed around the stacks such that top, bottom and two vertical sides of the stack are covered by the foil and the foil projects from the stack on both sides. In the side welding step applied to small stacks, the foil parts projecting over the top and bottom of the stack are joined together.
With the inventive method, larger packs (particularly standard packs, but optionally also larger top packs) wrapped with a foil and strapped with at least one taut strap, advantageously perpendicular to the foil wrapping, as well as small packs (top packs) wrapped with a foil covering top, bottom and two vertical stack sides and being closed over the two other vertical stack sides by at least spot welds, are produced in a stack-height dependent sequence. In both larger and smaller packs, the stacked articles are not only protected, but are also held in the stack , held in one direction by the foil and in the other direction either by a strap or by the side welded foil.
The apparatus for performing the method is equipped in such a way that it permits in the same stack position (strapping/welding position) and without any specific setting, welding Doc No. 35-35 CA Patent laterally protruding portions of the foil wrapper (side-welding) and/or strapping. The apparatus according to the invention comprises means for wrapping serially supplied stacks with a foil, means for pressing wrapped stacks and means for strapping wrapped stacks, the pressing means being equipped as welding means for the side-welding operation, at least the strapping means and the welding means being controlled depending on the stack height of each supplied stack.
For controlling the stack height-dependent packing step the apparatus is to be equipped with sensor means for detecting the height of a stack to be packed, or with means for supplying corresponding data from a central computer to the apparatus.
The method and apparatus according to the invention are described in greater detail hereinafter in conjunction with the attached drawings, wherein:
Fig. 1 shows the successive steps for the packing a larger and a smaller stack of newspapers or magazines in accordance with the inventive method;
Figs. 2 & 3 show a diagrammatic representation of parts of an exemplified embodiment of the inventive apparatus as a plan view (Fig. 2) and in section (Fig. 3);
Figs. 4 & 5 show a diagrammatic representation of parts of a further, exemplified embodiment of the inventive apparatus as a plan view (Fig. 4) and in section (Fig. 5).
Fig. 1 shows the successive steps in which newspapers or magazines or other flat articles are supplied e.g. in a scale or flake stream 1, are stacked into stacks 2 with different heights d.l and d.2 and then are packed according to the inventive method. In Fig. 1 the steps (2.1, 2.3 and 2.5) for large stacks are shown at the top and the steps (2.2, 2.4 and 2.6) for small stacks are shown at the bottom. This may awaken the impression that stacks of different heights are Doc No. 35-35 CA Patent conveyed on different paths and are packed in different apparatuses. However, in the inventive method this is not the case and instead all the stacks are conveyed and packed on the same conveying path in a continuous sequence and the height-dependent packing step (strapping and/or side welding) is performed both for large and small stacks in the same apparatus part, i.e. in the same strapping/welding position and with substantially the same cycle time. As a result the speed of the stack or pack flow remains independent of the number of stacks having to undergo one or other height-dependent packing treatment.
This uninterrupted stack or pack sequence represents an important advantage of the method according to the invention.
Fig. 1 shows on the left a stream of flat articles, e.g. a scale stream 1 of newspapers or magazines. From this stream l, e.g. for dispatch or storage purposes, stacks 2.1 and 2.2 are produced, and said stacks having the most varied heights d.l and d.2, particularly a standard height and very small heights. The stacks 2 are wrapped or enveloped with a weldable foil or film 3 in a first packing step, such that the film covers the top, bottom and two vertical sides of the stack and projects on two sides over the stack (stacks 2.3 and 2.4).
In a fiurther packing step, the film-wrapped stacks 2.3 having a stack height greater than a predetermined limit stack height are e.g. strapped with a strap 4 and the film-wrapped stacks 2.4 having a height which is the same as or smaller than the limit stack height are side-welded, i.e. the foil areas 3.1 projecting over the top and bottom of the stack are welded together. In this second packing step strapped, foil-wrapped packs 2.5 or laterally welded, foil-wrapped packs 2.6 are obtained.
The welding of the projecting foil areas 3.1 can extend over the entire stack side or, as shown in Fig. 1, comprises a plurality of spot welds S.

Doc No. 35-35 CA Patent It is advantageous to use welding heads, which can be lowered against a surface supporting the stack for the welding step. In such a case, the projecting foil areas 3.1 are to be dimensioned such that they are wider than the limit stack height at least by the desired seam width.
The foil wrapping preceding the strapping/welding step can e.g. be carried out when conveying the stack into the strapping/welding position. This means that each stack on entering the strapping/welding position is conveyed against the wrapping foil extending in the form of a curtain and displaces the foil curtain such that the foil can be closed on the rear stack side, when the stack is positioned in the strapping/welding position. In such a case, the foil wrapping is parallel to the conveying direction and the strapping is advantageously a transverse strapping (perpendicular to the conveying direction). It is also conceivable for the stacks to be strapped prior to wrapping, e.g. perpendicular to the wrapping and to strap them parallel to the wrapping and at right angles to the first strapping in the strapping/welding position.
It is also possible for the foil wrapping to be produced in a wrapping position, which is spaced from the strapping/welding position. The wrapped stacks are then conveyed from the wrapping position into the strapping/welding position and can also be turned between the two positions by 90° relative to the conveying direction. For such a case also, it is conceivable for the strapping position being equipped as a welding position also, to be one of two strapping positions whereby in each of these strapping positions one part of a crosswise strapping is produced.
Figs. 2 and 3 show a first, exemplified embodiment of the inventive apparatus as a plan view (Fig. 2) and in section (Fig. 3 , section along section line III-III in Fig.
2). The apparatus is used for strapping a foil-wrapped stack and/or for side welding the wrapping foil along the stack sides oriented parallel to the conveying direction F. Figs. 2 and 3 show a foil-wrapped Doc No. 35-35 CA Patent stack 2 (foil wrapping parallel to the conveying direction F) in a wrapping/welding position, Fig. 3 showing with continuous lines a stack 2.4 having a small stack height and with interrupted lines a stack 2.3 having a larger stack height.
The apparatus further comprises conveying means (not shown) for conveying stacks 2 to the strapping/welding position and for conveying away packs in the conveying direction F and wrapping means for wrapping the stacks 2 with a foil 3. The stacks are wrapped with foil, parallel to the conveying direction, in a preceding or upstream apparatus part, or in the represented apparatus part (strapping/welding position), e.g. by passing through a foil curtain and carrying the latter along so that the foil curtain can be closed on the rear of the stack. All the apparatus parts relating to foil wrapping are known per se and are therefore not shown in Figs. 2 and 3.
As a strapping means 10 for transverse strapping (snapping at right angles to the conveying direction F),the apparatus e.g. comprises a strap channel, in which a loop of a strapping strap 4 is positioned. Furthermore, the apparatus comprises pressing means 11, e.g.
two pressing beams 11.1 and 11.2 being movable upwards and downwards and being positioned laterally of the strap position. These pressing beams are shown in Fig. 3 with continuous lines lowered onto the large stack 2.3 and in interrupted lines in a raised position. On the ends of the pressing beams 11.1 and 11.2, projecting laterally over a stack 2 to be packed, a welding head 12 is provided, in such a way that on lowering the pressing beams 11.1 and 11.2 the welding heads 12 are lowered on either side of the stack and on lowering onto a stack with a height which is smaller than the limit stack height, they reach the stack-supporting surface.
Preferably, the welding heads 12 are resiliently mounted on the pressing beams 11.1 and 11.2 (e.g. by means of springs 13),such that in a sufficiently lowered state they are pressed against the support 14 on which the stack 2 is conveyed or against a corresponding, stationary countermember.

Doc No. 35-35 CA Patent The apparatus may also comprise means for adding a cover sheet 16 to a stack 2 to be packed, particularly to a stack 2 to be strapped. These cover sheet addition means e.g.
comprise a two-part, channel-like cover sheet holder 15, to which a cover sheet 16 is supplied in the direction of the arrow A and from which the cover sheet 16 is carned along and positioned on the stack and pressed against the stack 2.3 by the pressing beams 11.1 and 11.2 being lowered. In Fig. 3, the cover sheet being pressed against the large stack 2.3 is shown with continuous lines and is designated 16, and in the cover sheet holder 15 it is shown in interrupted lines and designated 16'.
The cover sheet holder 15 may also be located on the pressing means 11 and be lowered against the stack together with the latter. A cover sheet ready in the cover sheet holder is then pressed against the stack by the strapping strap and is freed from said holder on raising the pressing means and cover sheet holder after strapping.
Figs. 4 and 5 show another exemplified embodiment of the inventive apparatus in plan view (Fig. 4) and in section (Fig. 5, section along section line V-V in Fig. 4).
The apparatus is used for strapping foil-wrapped stacks 2 transversely to the conveying direction F
or for side welding along the leading and trailing stack sides (foil wrapping perpendicular to the conveying direction F). The apparatus according to Figs. 4 and 5 differs from the apparatus according to Figs. 2 and Sin particular in that the welding means 12 are located in the vicinity of the leading and trailing sides of the stack 2. The apparatus also has no means for applying a cover sheet to stacks to be packed. The same parts are given the same reference numerals in all four drawings.
In Fig. 5 it is clearly visible how the foil areas 3.1 projecting over the top and bottom of the stack are pressed against the supporting surface 14 and welded together by the welding heads.

Claims (12)

1. Method for packing substantially parallelepipedic stacks consisting of flat articles, particularly of newspapers or magazines, the stacks being supplied in succession to the packing operation, wherein in a first packing step, the stacks are wrapped with a weldable foil in such a way that said foil covers the top, bottom and two vertical sides of the stack, and in a second packing step the stacks are pressed and strapped, characterized in that the foil wrapping produced in the first packing step projects over both sides of the covered stack sides and that in the second packing step, stacks with a height greater than a predetermined limit stack height are strapped and stacks with a height smaller than the predetermined limit stack height are packed by welding the foil areas projecting over the top and bottom of the stack together, strapping being simultaneously performed or suppressed.

2. Method according to claim 1, characterized in that the height of the supplied stacks is detected by sensor means.

3. Method according to claim 1 or 2, characterized in that the projecting foil areas are welded together in a plurality of weld points.

4. Method according to one of claims 1 to 3, characterized in that the stacks are supplied to the second packing step in a conveying direction parallel to foil wrapping and in the second packing step are packed by strapping at right angles to the foil wrapping and/or by welding on their sides extending parallel to the conveying direction.

5. Method according to one of claims 1 to 3, characterized in that the stacks are supplied to the second packing step in a conveying direction at right angles to the foil wrapping and in the second packing step are packed by strapping at right angles or parallel to the foil wrapping and/or by welding along their leading and trailing sides.

6. Method according to one of claims 1 to 5, characterized in that the stacks, which are to be strapped in the second packing step, are supplied with a cover sheet before or together with the strapping.

7. Apparatus for performing the method according to one of claims 1 to 6, said apparatus comprising conveying means for supplying a serial stack stream and for conveying away a serial pack stream, wrapping means for wrapping the supplied stacks with a foil, pressing means for pressing wrapped stacks and strapping means for strapping pressed stacks, characterized in that the apparatus in addition comprises welding means for welding together foil areas projecting over the top and bottom of the stack and that control means are provided for controlling at least the welding means in dependence of the height of the stack to be packed.

8. Apparatus according to claim 7, characterized in that the welding means are mounted to the pressing means.

9. Apparatus according to claim 8, characterized in that the pressing means are constituted by pressing beams being movable upwards and downwards and being positioned on either side of the strapping means and that the welding means are mounted to the pressing beams in such a way that they can be lowered against a stack-supporting surface on either side of a stack to be packed or upstream and downstream of a stack to be packed.

10. Apparatus according to claim 9, characterized in that the welding means comprise a plurality of welding heads.

11. Apparatus according to one of claims 7 to 10, characterized in that it additionally comprises a channel-like cover sheet holder being positioned such that a cover sheet located in the cover sheet holder is drawn out of the latter by the pressing means or by the strapping strap.

12. Apparatus according to claim 11, characterized in that the cover sheet holder is firmly connected to and movable with the pressing means.