GB2384459A

GB2384459A - Manufacture of air cushions from tubing with a gas injector continuously within the tubing

Info

Publication number: GB2384459A
Application number: GB0201693A
Authority: GB
Inventors: John Stuart Greenwood; Neil Glynn Price
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-01-25
Filing date: 2002-01-25
Publication date: 2003-07-30
Also published as: GB0201693D0

Abstract

An apparatus 10 comprises a continuous drive means 14,16 to move plastic tubing 32 through the apparatus 10, and a gas / air injector member (12, fig.1), such as with outlet 22, located continuously within, or within a portion of, the tubing 32. This arrangement may permit the formation of air filled cushions in a continuous stream. Also disclosed is a roll of plastic tubing 32 (from the last reference onwards, 32 refers to that numeral in fig.5 only) being sealed transversely 34, 35 at a succession of intervals, with each pair of seals stopping just short of a longitudinal centre line of the tubing 32. Such tubing 32 might be used in conjunction with the apparatus 10, the central gap between seals 34,35 allowing passage of the injector member (12, fig.1). Further disclosed is a method of producing air filled cushions comprising providing a tubing as previously described, with reference to fig.5, continuously inflating the tubing 32 between successive seals 34,35 and sealing the tube 32 along a pair of longitudinal lines, each extending across two transverse seals 34, 35. Such longitudinal sealing might be provided such as by the apparatus 10 by means of sealing blocks 50, 52, 54, 56. The apparatus 10 may further comprise an air barrier arrangement 11 upstream of the air injector (12, fig.1) and may produce two parallel lines of air cushions joined in two rows on the same piece of tubing 32 with a sealed longitudinal line therebetween which may be perforated for separation into two halves by a perforator 18.

Description

Title: Machine and Methods for the Manufacture of Air Filled Cushions Description of Invention This invention relates to improvements in the manufacture of air filled cushions. In particular, although not exclusively, this invention relates to air cushions of thin-walled plastic sheet, which may be used as infill or cushioning in the packaging and transportation of fragile articles.

Conventionally, air filled cushions are manufactured from a roll of plastic tubing. A typical example of a method of manufacturing these cushions is described in International Patent Application WO 01/21391. In this method the plastic tubing is drawn through the machine from a supply roll. The walls of the plastic tubing are separated by drawing the tubing over a separator member. Air is then injected into the space between the wall through a needle, which pierces one of the walls of the tube, the hole left by the needle later being isolated by a heat seal. This process requires careful co-ordination of the position of the separator member and the air injecting needle, and good control of the air injecting needle so that only one wall of the tubing is pierced.

A different way of manufacturing air filled cushions is to pre-perforate the plastic tubing and blow air into the tube through the perforations. Again, this requires careful co-ordination of the position of the injection head and the plastic tubing.

Both of these processes are stop-start processes, in that the movement of the plastic tubing through the machine must be halted whilst the cushion is filled. The throughput rate of the machines is therefore limited. Furthermore, since both processes inject air into the cushions through relatively small holes, a high pressure air injection system, including an air compressor, may be required.

Various attempts have been made to develop a continuous process for filling air cushions, but have been only partially successful, problems being encountered in a number of areas. The difficulty of injecting air into a moving cushion leads to problems with under and over inflation of the cushions. One solution to this has been to inject air into the cushion using high pressure bursts of air, but this requires a high pressure air injection system and a complex control system.

An additional problem relates to the heat sealing mechanism. When the machine must be stopped the heat sealer cools down, and when it is restarted the heat sealer takes a small amount of time to reach operating heat, so that one or more air cushions may be lost.

Difficulties are further encountered in conventional machines, in the convenient setting up of the machine to commence operation, particularly in drawing the tubing into and through the machine.

According to this invention there is provided a machine for the production of air filled cushions comprising : a) drive means which is operative continuously to move plastic tubing through the machine along a redefined path; and b) an injector member located in the path and which, in use, is located within the plastic tubing as the tubing is moved through the machine; characterised in that the injector member has an air inlet and an air outlet and the drive means is operative to move the plastic tubing over the air outlet of the injector member, whereby air may be injected through the injector member into the plastic tubing.

In this way relatively low pressure air may be used, allowing for the use of a simpler air delivery and/or control system. Preferably the pressure is less than 5 psi, and most conveniently a pressure of 1-2 psi is used.

The injector member may be provided with a single air outlet, but preferably has two or more air outlets, arranged around its periphery, each outlet being operative to inflate a portion of the plastic tubing.

Such a machine may be adapted for use with plastic tubing having two rows of transverse, parallel, welds, the welds of each row extending toward a longitudinal centreline of the tubing from a respective one of the side edges, a weld of one row being generally co-linear with a weld of the other row, with an unwelded section between them, and, in use, the injector member is located generally within the unwelded section, whereby at least one air outlet of the separator member is operative to inflate portions of the plastic tubing defined by adjacent welds in each row.

Preferably the machine further comprises sealing means, located downstream of the air outlet to seal the plastic tubing longitudinally. Preferably the sealing means is a heat sealer, which has an operating position in which it abuts the plastic tubing and a standby position in which it is removed from the plastic tubing and the heat sealer may be moved from the operating position to the standby position when the machine is stopped.

In a preferred embodiment the heat sealer comprises at least two spaced elongate bars, which are preferably generally equal in length to the air filled cushions produced by the machine. This ensures a good seal can be achieved.

The machine may further comprise a perforator, located downstream of the sealing means, operative to perforate the plastic tubing longitudinally.

Preferably the injector member is provided with a cutter, upstream of the air inlet, to cut a surface of the plastic tubing, allowing the plastic tubing to pass around the air inlet.

Preferably the machine further comprises a barrier, upstream of the injector member, which is operative to maintain portions of the tubing deflated.

Preferably the machine further comprises a pressure sensor which is operative to open an outlet in the air inlet if the pressure in the injector member

becomes too high. The machine may be provided with further sensors and control mechanisms, such as a speed sensor and control and an inflation sensor and control.

According to this invention there is further provided a roll of plastic tubing being sealed transversely at a succession of spaced intervals along its length, by pairs of seals, each seal extending in a line from a respective opposite edge of the plastic tubing to a short distance from the centre thereof.

Preferably the sealing lines have no or no significant longitudinal components.

Such a machine and such a roll of plastic tubing may usefully be used in combination.

According to this invention there is also provided a method of producing air filled cushions comprising: providing a roll of plastic tubing being sealed transversely at a succession of spaced intervals along its length, by pairs of seals, each seal extending in a line from a respective edge of the plastic tubing to a short distance from the centre thereof; continuously inflating the tubing between successive seals to form cushions; and sealing the tube along a pair of longitudinal lines each extending across two transverse seals.

Preferred embodiments of the invention, selected by way of example, will now be described, with reference to the following drawings, in which :- FIGURE 1 shows schematically a perspective view of internal components of a machine suitable for the manufacture of air-filed cushions ; FIGURE 2 shows schematically a section view of the internal components of the machine during the manufacturing process; FIGURE 3 shows schematically a section view of the internal components of the machine when opened to load or unload plastic tubing; FIGURE 4 shows schematically a top view of the internal components of the machine during the manufacturing process; FIGURE 5 shows schematically a portion of plastic tubing suitable for use in the machine;

FIGURE 6 shows schematically a rear view of the machine ; and FIGURE 7 shows schematically a second embodiment of the invention, having a more compact structure.

The internal components of a machine for the manufacture of air-filled cushions is illustrated in Figure 1. The machine 10 comprises an air barrier 11, an injector member 12, heat sealers 14, and pull rollers 16, which incorporate a perforator 18. These components of the machine 10 define a path along which plastic, conveniently polythene, tubing passes through the machine 10.

The air barrier 11 is disposed upstream of the injector member 12 and comprises two tracked belts made from spongy, rubberised tracking.

The injector member 12 comprises an elongate hollow tube having an air inlet 20 and a plurality of air outlets 22. At its upstream end it has a smooth rounded tip 24. The air outlets 22 are disposed close to the tip 24 and comprise a pair of elongate slits which are disposed diametrically opposite each other on the circumference of the injector member 12.

The heat sealers 14 are disposed downstream of the injector member, adjacent to the air outlets. Since the heat sealers are identical only one heat sealer will be described, which comprises a two belts 40 each arranged around four wheels, a drive wheel 42, a tensioner wheel 44 and two idler wheels 46, 48. The two belts 40 run parallel and adjacent to each other between the idler wheels 46, and between them define a path through which the plastic tubing is drawn. Four heat sealing blocks 50,52, 54,56 are disposed along this portion of the belts arranged in pairs of blocks of which one is positioned above and one is positioned below the belts. The upper upstream one of these blocks 50 is heated sufficiently to weld the plastic tubing together and all four blocks 50,52, 54,56 are spring loaded to press together and close the belts onto the plastic tubing, providing sufficient pressure to complete the seal.

The air inlet 20 is a hollow tube, which is disposed downstream of the sealing rollers. It projects downwardly from the injector member 12. A cutter,

preferably a knife 30, although a hot wire cutter could be used instead, is disposed at the upstream end of the air inlet 20, and projects diagonally between the air inlet 20 and the injector member 12. The air inlet 20 also supports the machine 10, being attached to a superstructure (not shown) which holds the injector member 12 in a fixed position in use.

Various of the rollers and drive band wheels are also supported, being attached to the side of the machine by axles 60,62, as shown in Figure 4.

The pull rollers 16 are arranged just downstream of the air inlet 20 and the injector member 12. The perforator 18 is arranged along the centreline of the machine 10, to perforate between the seals produced by the heat sealers 14.

Figure 2 illustrates the machine 10 in use, with polythene tubing being drawn through it. Figure 4 provides a top view of the air cushion production process. A tube 32 of polythene film, typically 400 mm wide, is provided. The tubing, shown in Figure 5, has two rows of transverse, parallel welds, 34,35.

The tube 32 may also be pre-perforated across its width, along the line of the transverse seals 34,35. The rows of seals 34,35 extend toward a longitudinal centreline of the tubing 32 from a respective one of the side edges, a weld of one row 34 being generally co-linear with a weld of the other row 35, and the rows of welds having an unwelded portion between them.

To load the polythene tubing 32 onto the machine, the air barrier 11 is lifted apart, as shown in Figure 3, and the injector member 12 is inserted into the tubing at the unwelded portion between the rows of the transverse seals 34, 35. The upper halves of the heat sealers 14 may be pivoted into a standby position, as shown in Figure 3 so that the plastic tubing 32 can be drawn over the injector member 12 and positioned between the pull rollers 16.

The polythene tubing 32 is drawn through the machine 10 by the tracks which make up the air barrier 11, by the belts 40 of the heat sealers 14 and by the pull rollers 16. The pull rollers 16 operate marginally more quickly than the

rest of the machine which places the tubing 32 under tension, even to the extent where some slippage through the rest of the machine may occur.

In normal operation the tubing 32 is continually drawn from a roll through the air barrier 11 by its tracks. The two layers of the tubing 32 are separated in its central, unwelded portion on reaching the smooth, rounded tip 24 of the injector member 12. Air, at atmospheric pressure, enters the injector member 12 at the air inlet 20 and is continually blown through the injector member to the air outlets 22. The presence of the air barrier 11 prevents excess upstream inflation.

As the tubing 32 is drawn past the air outlets 22 the portions of the tubing defined by adjacent welds 34,35 in each row become inflated, as shown in Figure 2. Since the injector member 12 is disposed centrally in the tubing, with air outlets 22 directed to either side, two portions, one at either side of the injector member 12 are inflated as the tubing 32 is drawn over the air outlets 22.

To encapsulate the air in each portion the open side of each portion is sealed by heat sealers 14. These produce two longitudinal welds 36 which each join a pair of transverse welds 34,35, sealing off the inflated air cushions. The downstream sealing blocks 54,56 compress the tubing over the longitudinal weld 36, making it more secure.

Once sealed the tubing 32 must pass the air inlet 20 of the injector member. To allow the tubing to pass around this inlet 20 the lower face of the tubing 32 is slit as it passes the knife 30 disposed just upstream of the air inlet.

The pull rollers 16 draw the tubing toward the perforator 18. The perforator 18 produces a row of perforations 38 in the centre of the bottom face of the tubing, between the longitudinal welds. These allow the tubing to be separated longitudinally if desired.

Finished cushions 64, supported by a cushion bed plate 66 are shown in Figure 6, just before they leave the machine.

This machine 10 has a much higher output rate than previous machines, both because it is able to run continually, and because it can produce two streams of air cushions at once. Since the air may be injected through relatively large air outlets 22 there is no need for compressed air to be used. The machine, 10 is, therefore, simple to use, having just an on-off and a temperature control. Further controls, such as a speed control and an inflation control could be added to the system if desired.

The machine 10 is able to produce air cushions which are joined together to form a matrix of cells. Since these cells are more difficult to force apart they are more effective at protecting packages with irregular shapes. Furthermore, since the machine 10 can inflate multiple cushions through one central tube it uses the plastic tubing more efficiently than previous machines and generates less waste.

Although the machine 10 is designed to run continually it is sometimes necessary to stop it during a production run to maintain or repair the equipment.

This can cause problems with the heat sealers 14, since conventionally the heated block 52 has to be cooled, to prevent the tubing being melted, and thus, when production is restarted, there is a warm-up time before it becomes operationally effective, during which cushions are unsealed and lost.

This machine provides a facility for such eventualities. A top half of the heat sealer 14 is defined by the upper belt 40, its four wheels 42,44, 46 and includes the upper heated sealing block 50 and the other upper sealing block 54.

This half of the heat sealer is pivotally mounted along the axis of drive wheel 42 so that it may be swung away from its operative position, in which the portion of the belt between the idler wheels abuts the plastic tubing, to a standby position in which the belt lies away from the plastic tubing. This means that, should the machine need to stop during a production run the upper upstream sealing block may remain hot, ideally being maintained at a somewhat lower, standby, temperature by a simmerstat. When the machine 10 is restarted

the top section of the heat sealer 14 is pivoted back into its operating position and, since the heated sealing block 52 is still hot the sealing process can be immediately continued without losing any cushions.

A second embodiment will now be described only in as much as it differs from the first embodiment, the same reference numerals being used for the same parts.

If desired the machine lOa can be made more compact, as shown in Figure 7. The injector member 12a has been shortened in this embodiment so that the air inlet 20a projects downwards just downstream of the heat sealing blocks 50a, 52a, 54a, 56a. Furthermore the pull rollers 16a form the driving

element for the heat sealer belts 40a, the other wheels 42a, 44a, 46a being idler wheels. The perforator 18a is thus arranged just downstream of the air inlet 20a. Since the upper heat sealer 14a is still capable of pivoting to a standby position the perforator 18a is arranged on the lower pull roller 16a.

Since the injector member 12a is significantly shorter in this arrangement even less pressure is required to cause air to flow to the air outlets 22a, making the machine lOa even more efficient to run.

In the present specification"comprises"means"includes or consists of' and"comprising"means"including or consisting of.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS 1. A machine for the production of air filled cushions comprising: a) drive means which is operative continuously to move plastic tubing through the machine along a predefined path; and b) an injector member located in the path and which, in use, is located within the plastic tubing as the tubing is moved through the machine; characterised in that the injector member has an air inlet and an air outlet and the drive means is operative to move the plastic tubing over the air outlet of the injector member, whereby air may be injected through the injector member into the plastic tubing.
2. A machine according to Claim 1 characterised in that the injector member has two or more air outlets, arranged around its periphery, each outlet being operative to inflate a portion of the plastic tubing.
3. A machine according to Claim 1 or Claim 2 adapted for use with plastic tubing having two rows of transverse, parallel welds, the welds of each row extending toward a longitudinal centreline of the tubing from a respective one of the side edges, a weld of one row being generally co-linear with a weld of the other row, with an unwelded section between them, and, in use, the injector member is located generally within the unwelded section, whereby at least one air outlet of the separator member is operative to inflate portions of the plastic tubing defined by adjacent welds in each row.
4. A machine according to any preceding claim characterised in that it further comprises sealing means, located downstream of the air outlet to weld the plastic tubing longitudinally.

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5. A machine according to Claim 4 characterised in that the sealing means is a heat sealer, which has an operating position in which it abuts the plastic tubing and a standby position in which it is removed from the plastic tubing and the heat sealer may be moved from the operating position to the standby position when the machine is stopped.
6. A machine according to Claim 4 or Claim 5 characterised in that the heat sealer comprises at least two spaced elongate bars, which are generally equal in length to the air filled cushions produced by the machine.
7. A machine according to any of claims 4 to 6 characterised in that it further comprises a perforator, located downstream of the sealing means, operative to perforate the plastic tubing longitudinally.
8. A machine according to Claim 7 in which the heat sealer includes a driven belt, and the perforator is arranged on one of the rollers which support the belt.
9. A machine according to any preceding claim in which the injector member is provided with a cutter, upstream of the air inlet, to cut a surface of the plastic tubing, allowing the plastic tubing to pass around the air inlet.
10. A machine according to any preceding claim characterised in that it further comprises a barrier, upstream of the injector member, which is operative to maintain portions of the tubing deflated.

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11. A machine according to any preceding claim further comprising a pressure sensor which is operative to open an outlet in the air inlet if the pressure in the injector member becomes too high.
12. A roll of plastic tubing being sealed transversely at a succession of spaced intervals along its length, by pairs of seals, each seal extending in a line transversely from a respective opposite edge of the plastic tubing to a short distance from the centre thereof, and having no significant longitudinal component.
13. In combination, a machine according to any of Claims 1 to 6 and a roll of plastic tubing according to Claim 7.
14. A method of producing air filled cushions comprising: providing a roll of plastic tubing being sealed transversely at a succession of spaced intervals along its length, by pairs of seals, each seal extending in a line from a respective opposite edge of the plastic tubing to a short distance from the centre thereof; continuously inflating the tubing between successive seals to form cushions; and sealing the tube along a pair of longitudinal lines each extending across two transverse seals.
15. A machine for the production of air filled cushions substantially as described herein with reference to the accompanying drawings.
16. A roll of plastic tubing substantially as described herein with reference to the accompanying drawings.

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17. A method for the production of air filled cushions substantially as described herein.
18. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.