WO1991004849A1

WO1991004849A1 - Improved packaging material and machine for manufacturing same

Info

Publication number: WO1991004849A1
Application number: PCT/AU1990/000462
Authority: WO
Inventors: George B. Saray; Clive Harry Maxwell Townsend
Original assignee: Corex Plastics (Australia) Pty. Ltd.
Priority date: 1989-09-26
Filing date: 1990-09-26
Publication date: 1991-04-18

Abstract

A twin-walled sheet (10) formed of plastics material has spaced planar walls (11) joined by parallel webs (12) extending between opposite parallel edges of the sheet to form tubular cavities. The walls are turned inwardly towards each other around the perimeter of the sheet and are welded together to form a generally round edge (in section) which thereby seals the cavities against contamination from externally. The sheet has rounded corners. A machine for forming the rounded edges has parallel belt conveyors (22) for transporting the sheet through the machine and heaters (31) adjacent said opposite edges. The heaters heat the edge of the sheet and a pair of pinch rollers (32) at each said edge squeeze the walls together at their edge and cause them to be welded together. A further heater (33) on each side and grooved rollers (34) form the welded edge around said corners.

Description

INVENTION: IMPROVED PACKAGING MATERIAL AND MACHINE FOR MANUFACTURING SAME

The present invention relates to an improved packaging material and a machine for manufacturing same. More particularly the invention relates to improvements in twin-walled corrugated plastic sheet material known under one trade mark as Fluteboard, and a machine for making the improvements.

The material known as Fluteboard comprises two thin walls of polypropelene material spaced apart by parallel closely spaced webs which are moulded integrally with the walls. The webs thus provide parallel tubular cavities which extend across the sheet between two opposite sides and the cavities are open at their ends.

The twin-walled packaging material has many and varied uses, mainly in the packaging industry, as a partition to separate goods as well as for forming containers for goods, to quote merely two examples. One of the many advantages of the material over corrugated cardboard for example, is its durability which renders it reusable. One popular use is to provide a platform between layers of stacked glass bottles, the completed stack being shrink-wrapped for transportation and storage purposes. For such a use the corners of each sheet of Fluteboard are rounded to prevent the sharp corners penetrating the plastic shrink wrapping material, although a problem can still arise if a relatively sharp edge exists along the normal edge of the material which can occur particularly where a sheet is cut or finishes along an edge parallel to said webs and between two webs. In this case the edges of the walls of polypropelene can be somewhat sharp.

A further and more significant problem arises due to the open ended cavities which extend through the Fluteboard, because in many situations, particularly in the food and beverage industry, the sheets must be thoroughly cleaned between uses. It is extremely difficult to thoroughly clean all the cavities or more precisely it is impossible, in practice, to ensure that there are no contaminants remaining in the cavities. In the brewing industry for example, the use of Fluteboard for packaging has not been extensive because of yeast becoming lodged in the cavities and being impractical to dislodge.

Accordingly, it is an object of this invention to provide an improved twin-walled sheet which obviates the aforementioned problem.

It is a further object to provide a machine for manufacturing improvements to twin-walled sheets and like materials.

Thus, one form of the invention provides a twin-walled sheet formed of plastics material and comprising spaced planar walls joined by webs extending therebetween, characterised in that, said walls are joined together by welding along edges of the sheet to provide a generally rounded edge, in section, thereby sealing the space between the walls against contamination from externally.

A further form of the invention provides a machine for manufacturing improvements to a twin walled sheet formed of plastics material and having spaced planar walls joined by integrally moulded webs extending therebetween, characterised in that, said machine included transport means for conveying said sheet through said machine, heater means for applying heat along an edge of said sheet as it is transported past said heater means and squeeze rollers located past said heater means in the direction of conveying of said sheet and adjacent said heater means, said squeeze rollers applying pressure to said edge to squeeze said spaced walls together along said edge whereby the walls are welded together to form a sealed edge which is substantially rounded in section.

In order that the invention may be more readily understood a particular embodiment will now be described with reference to the accompanying drawings wherein.

Figure 1 is a perspective view of an improved twin-walled sheet according to the invention,

Figure 2 is a section on the line 2-2 of Figure 1,

Figure 3 is a side elevation of a machine for manufacturing the improvement to the sheet shown in Figures 1 and 2,

Figure 4 is an end view of the machine shown in Figure 3 showing only the end portion of the machine,

Figure 5 is a plan view of the machine shown in Figures 3 and 4, but with only one half of the machine shown in detail since the other half is essentially a mirror image, and

Figure 6 is a sectional view on the line 6-6 of Figure 5 -

Firstly, referring to Figures 1 and 2, the twin-walled sheet is shown to comprise a generally rectangular sheet 10, which comprises two spaced planar walls 11 separated by parallel webs 12 which are moulded integrally with the walls 11. The sheet shown in Figures 1 and 2 is formed from known twin-walled sheet and involves turning the walls 11 towards each other around the edges of the sheet and welding them together to form a rounded edge 13 which extends entirely around the perimeter of the sheet 10. Prior to forming the rounded edge 13 the corners of the sheet are rounded as shown in Figure 1 so that there are no sharp points or sharp edges which may be likely to cause problems when the sheet is used in the packaging industry, particularly if it is used inside a shrink wrapped package.

As the existing twin-walled sheet is made of polypropelene, heat and pressure are used to weld the planar walls 11 together around the edges of the sheet. According to the finished sheet the tubular cavities 14 between the webs 12 are not externally accessible. In other words the cavities are sealed against the ingress of contaminants and thus, the sheet is easily cleaned for reuse.

Referring now to Figures 3» 4 and 5_> the machine for manufacturing the sheet is shown to comprise essentially a mainframe 15 supporting a pair of transverse linear bearings 16, the linear bearings 16 supporting a pair of tables 17 which extend along the length of the machine and are separated from each other along the longitudinal centre line. Further linear bearings 18 mount the respective tables on the linear bearings 16.

A handle and pulley assembly 19 on each side of the machine drives chains 20 to rotate screw 21 (Figure 6) which, when rotated, causes the respective tables to move in a transverse direction whereby the tables may be drawn close together or further apart. Only one handle and pulley assembly is shown in the drawings (Figures 3 and 6). An endless belt 22 is mounted on each of the tables 17 and extends substantially along the length of the machine over pulleys 23, one of which in each case is driven by an electric motor 24 through gearbox 24a. The electric motor drives the pulley 23 by means of chain 25 which extends between a sprocket on the output shaft of motor 24 and a further sprocket 26 which is fixed to spline 27- The spline 27 engages sprockets 28, 28a which depend, respectively, from a mounting assembly on the underside of the tables 17- Thus, transverse movement of the tables allows the sprockets 28, 28a to slide along the spline 27. Parallel drive chains 38, 39 from the sprockets 28, 28a, respectively ensure that the motor 24 serves to drive the pulleys 23 of each table as well as a roller 40 on each table.

The top of each endless belt 22 is coplanar with the top surface of the respective table 17 whereby a generally planar surface is formed for transportation of a twin-walled sheet along the length of the machine during which time conventional sheet is formed into the improved sheet of the invention. The sheet is in a horizontal plane when being transported. A series of pairs of rollers 29 bear on the upper surface of the endless belt 22 and are each spring loaded by spring 41 so as to be raised slightly when the sheet passes along the belts such that the rollers force the sheet against the respective belts 22.

A guide roller 30 is arranged on each of the tables 17 at the input end of a sheet. The transverse position of the tables in adjusted such that each guide roller 30 bears on an opposite edge of the sheet as it is fed into the machine. A sheet fed into the machine is a conventional twin-walled sheet except the corners are rounded prior to feeding into the machine in the manner shown in Figure 1. The guide rollers 30 are free running rollers, that is they are not driven to rotate. Once the sheet is fed past the guide rollers 30 it comes between the first set of rollers 29 and the belt 22 on each table 17 and is conveyed through the machine in a direction left to right in Figures 3 and 5-

On each table 17 a first heater 31 is arranged to apply heat to the edge of the sheet, that is, the edge parallel to the direction of travel in each case. The heaters 31 have a bight 42 (Figure 6) which surrounds the edge of the sheet to ensure that heat is concentrated at the edge. The heaters 31 are conventional electric heaters which can be purchased "off the shelf". As the sheet progresses past the first heaters 31 the heated edge comes between squeeze rollers 32 whereby the walls 11 of the sheet are forced together at the edges and because of the pressure and heat which is applied, they are welded together to form the rounded edge 13- The rollers 32 are configured so as to form the rounded edge 13_* Cooling means (not shown) adjacent the squeeze rollers 32 and downstream thereof in the direction of travel of the sheet 10 ensures that the edge of the sheet is cooled after it passes the squeeze rollers 32. Such cooling may be by means of air or water.

Once the sheet passes the squeeze rollers 32 and the cooling means, it encounters a second heater 33 on each of the tables 17. The second heaters 33 are again arranged adjacent the opposite edges of the sheet and again have a bight portion which concentrates the heat towards the opposite sides of the sheet, but in the case of the second heaters 33 they are arranged further inwardly as evident in Figure 5_» that is, towards each other slightly more than the first heaters. This ensures that heat applied to the sheet 10 is applied slightly inwardly of the edges. In this way it is ensured that heat is applied around the corners of the sheet in a direction along the leading and trailing edge of the sheet. The leading and trailing edges are the edges which extend transverse to the direction of travel. Still further downstream in the direction of travel are a pair of grooved rollers 34 on each table 17• The grooved rollers 34 are each mounted for rotation about an axle, which axle may also be pivoted so as to move towards and away from the sheet 10. The grooved rollers are in fact mounted on pivotal arms 35 which are actuated by pneumatic cylinders 3 causing the rollers to move towards the longitudinal centre line of the machine or outwardly in the opposite direction.

Initially the second of the two rollers 34, that is, the roller which is further downstream, is in a position inwardly towards the centre line of the machine such that it is encountered by the leading edge of the sheet 10 as it progresses through the machine. A light sensor (not shown) detects the position of the leading edge when it contacts the second of the rollers 3 and actuates the relevant pneumatic cylinder 3 to cause the roller 34 to move outwardly around the rounded edge of the sheet 10 to a position where it is in contact with the edge of the sheet 10 parallel to the direction of travel. In a similar manner, as the trailing edge of the sheet moves over the light sensor 37 the first of the rollers 34 is actuated by means of its pneumatic cylinder to move inwardly and follow the edge of the sheet 10 around the corner to the trailing edge of the sheet. The grooved rollers have grooves which form the rounded edge on the sheet 10 particularly around the corners thereof. Ultimately, the sheet passes out of the machine on the right hand side in Figures 3 and 5 and this final movement is ensured by the rollers 40. A single pass through the machine ensures that two opposite edges are sealed in the manner described above. In order to seal the other two edges the sheet is rotated through 90° in the plane of the sheet and in fed back through the machine for one more pass. This ensures that the other two edges are sealed.

Whilst some features of the machine have not been described in detail above, the overall construction and operation of the machine should be readily evident to persons skilled in the art, particularly when referring to the enclosed drawings.

Of course if it is intended to manufacture a sheet without the rounded corners, the second heater 33 and the grooved rollers 34 are not required. Also, if the rounded edges are not critical to the final usage of the sheet, it is only necessary to seal those edges which are transverse to the direction of the tubular cavities 14 in which case it is only necessary to pass the sheet once through the machine.

Claims

CLAIMS :

1. A twin-walled sheet (10) formed of plastics materia and comprising spaced planar walls (11) joined by webs (12 extending therebetween, characterised in that, said walls ar joined together by welding along edges of the sheet to provide generally rounded edge (13), in section, thereby sealing the spac between the walls against contamination from externally.

2. A twin-walled sheet as defined in claim 1 wherei said webs are moulded integrally with said walls and are paralle webs which extend between a pair of opposite edges of said shee so as to provide parallel tubular cavities (14) extending betwee said opposite edges, characterised in that, said welding occur at least along said opposite edges.

3. A twin-walled sheet as defined in claim 2, characterised in that, said sheet is generally rectangular and sai welding occurs around the entire perimeter of said sheet.

4. A twin-walled sheet as defined in claim 3, characterised in that, said plastics material is polypropylene o the like.

5- A twin-walled sheet as defined in claim 4, characterised in that, said sheet has rounded corners.

6. A machine for manufacturing improvements to a twi walled sheet (10) formed of plastics material and having space planar walls (11) joined by integrally moulded webs (12) extendin therebetween, characterised in that, said machine includes transport means (22) for conveying said sheet through said machine, heater means (31) for applying heat along an edge of said sheet as it is transported past said heater means and squeeze rollers (32) located past said heater means in the direction of conveying of said sheet and adjacent said heater means, said squeeze rollers applying pressure to said edge to squeeze said spaced walls together along said edge whereby the walls are welded together to form a sealed edge (13) which is substantially rounded in section.

7. A machine as defined in claim 6, characterised in that, said transport means comprises spaced parallel continuous belts (22) which may be moved towards or away from each other to vary the spacing such that the belts are arranged adjacent and along opposite first parallel edges of said sheet and parallel to said conveying direction, rollers (29) associated with each said belt for maintaining said sheet in contact with said respective belts, and said heater means comprises separate first heaters on opposite sides of said sheet for heating said respective first edges, and said squeeze rollers comprise separate sets of said squeeze rollers adjacent said respective first edges, whereby said machine is able to form said sealed edge along said respective first edges simultaneously during conveying of said sheet through said machine.

8. A machine as defined in claim 7, wherein said sheet has rounded corners prior to insertion into said machine, characterised in that, said machine includes further heater means (33) comprising separate further heaters adjacent said respective first edges and located past said squeeze rollers in the conveying direction, said further heaters are arranged for applying heat to said first edges of the sheet inwardly a short distance from said first edges whereby said rounded corners are heated a short distance along the edges normal to said conveying direction (leading and trailing edges) as said leading and trailing edges pass thereby, and further roller means (34) are provided respectively on each side of said machine adjacent each said first edge and past said further heaters in said conveying direction, said further rollers means being adapted for movement along said leading and trailing edge a short distance as said leading and trailing edges pass thereby and be drawn back around said rounded corner to said respective first edges to form said sealed edge around said corners.

9. A machine as defined in claim 8, characterised in that, said further roller means each comprise a pair of spaced grooved rollers (34) mounted for rotation on an axis normal to the plane of said sheet, each grooved roller being mounted on a pivotal arm (35) and each arm being actuated by a pneumatic cylinder (36) to effect said movement whereby the rollers are cammed around the leading and trailing edge corners, respectively as the sheet passes thereby.

10. A machine as defined in claim 9, characterised in that, a light sensor is provided to detect when said leading an trailing edges reach specific points to actuate said pneumati cylinders in synchronism with movement of said sheet through sai machine.

11. A machine as defined in claim 10, characterised i that, cooling means is arranged adjacent each said first edge t cool said edge after passing said squeeze rollers.

12. A machine as defined in claim 11, characterised i that, an electric motor (24) is provided to drive said belts an respective further rollers (40) arranged past the end of belts i the direction of travel, said motor being connected to said belt and further rollers by respective chain drives (25, 38).