WO2001047787A1

WO2001047787A1 - Infusion bags

Info

Publication number: WO2001047787A1
Application number: PCT/AU2000/001581
Authority: WO
Inventors: Helmut Heinrich Roth
Original assignee: Rothtech Pty Ltd
Priority date: 1999-12-24
Filing date: 2000-12-22
Publication date: 2001-07-05
Also published as: AUPQ489199A0; WO2001047787A9

Abstract

An infusion bag, such as a tea bag, is formed from perforated material permitting infusion of a substrate contained in the bag when the bag is steeped in a fluid.

Description

Field of the Invention

The present invention relates to infusion bags, and, more particularly, to tea and coffee bags. Background to the Invention It is well known to produce tea and coffee beverages with the use of tea and coffee bags respectively. Tea bags and coffee bags are typically formed of high porosity paper which permits infusion of the tea or coffee when the bag is steeped in hot water. The high porosity paper is typically of a randomly woven type form. The porous nature of the paper is typically provided by areas of reduced density fibers which permit the infusion of the tea or coffee.

A significant problem with the above mentioned infusion bags is the cost of the high porosity paper.

Furthermore, due to the machinery required to produce high porosity paper, it is typically produced by paper mills. Because of the inherit characteristics of high porosity paper (such as low tensile strength and weight per square metre to paper machine speed ratio) , paper mills typically do not accept production orders of less than 25 tonne. Manu acturers of infusion bags are therefore typically required to have on hand large quantities of expensive high porosity paper, especially if they are to be able to meet any sudden increase in demand.

Another problem with high porosity paper infusion bags is that they are not able to be heat sealed. In recent times an additional layer of thermoplastic fibre has been added to the high porosity infusion bags for this purpose. Another problem with high porosity paper is its low tensile strength. Such a characteristic makes high porosity paper difficult to handle during packaging. Sophisticated and expensive packaging machines are therefore required for the production of high porosity paper infusion bags.

Other problems with the high porosity infusion bags arise due to the fact that they are formed of paper. The production of paper requires chemical bleaching of wood pulp. Because wood pulp fibers are typically bleached by either the oxygen or peroxide process, it is desirable, for environmental reasons, to decrease this source of paper usage .

During infusion of a tea or coffee bag, the paper from which the bag is formed releases an odor to the resulting brew. Such an odor is undesirable because it affects the quality of the brew. The paper from which the bags are formed can also absorb some of the desired properties of the brew. Summary of the Invention

In a first aspect, the present invention provides an infusion bag, the infusion bag being perforated to permit infusion of a substance contained within the bag when the bag is steeped in a fluid.

The infusion bag may have an unperforated region adjacent an edge of the infusion bag, the unperforated region being adapted for sealing of the infusion bag. The infusion bag may be sealed by a variety of techniques including embossing, cold or hot sealing techniques, or by folding and subsequently stapling.

During infusion of the substance which is contained within the infusion bag, the substance is typically not evenly distributed within the infusion bag For example, some infusion bags have a piece of string which is attached to an upper end of the infusion bag and is used for placing the infusion bag in hot water and for subsequently removing the infusion bag from a brew which has been created as a result of infusion of the substance.

Because the substance typically settles toward a lower region of the infusion bag it is desirable to have perforations provided in the lower region of the infusion bag. The perforations in the infusion bag may therefore have predetermined sizes and shapes and be positioned at predetermined positions which increase infusion of the substance which is contained within the infusion bag. To this end, perforations of the infusion bag may differ in size and shape and may be located in predetermined regions of the infusion bag. The perforations are preferably positioned at a lower region of an infusion bag where the substance which is contained within the infusion bag settles during infusion of the substance. Increased infusion of the substance may be achieved by providing an infusion bag having a greater concentration of perforation in one or more predetermined regions, larger sized and/or different shaped perforations in one or more predetermined regions, or by providing an infusion bag having a combination of increased concentration of perforations and increased size and varying shape of perforations in one or more predetermined regions. Increased infusion may be achieved by increasing the size of the perforations and/or increasing the concentration of the perforations . It is preferred that both the size and concentration of the perforations is maximized.

The infusion bag is preferably formed of paper, plastic film or foil and may be formed of aluminum foil. The perforations are preferably square or rectangularly shaped but other shapes may be satisfactorily employed. The infusion bag may be formed from a strip of material. The infusion bag may also be formed from a pocketed strip of material. The pocketed strip of material may include two separate strips of material having substantially equivalent widths which are joined together along their longitudinal edges. Alternatively, the pocketed strip of material may include a single strip of material which is folded along its longitudinal length to form a strip or web of material which is approximately half the width it was prior to folding, wherein adjacent free longitudinal edges of the folded strip of material are joined along the longitudinal_length of the folded strip of material. The longitudinal edges of the pocketed strip of material may be joined either before, during, or after perforations are formed in the pocketed strip of material. The surface area of an infusion bag over which perforations extend may gradually decrease in moving from an upper extremity of the lower region of an infusion bag toward the upper region. The lower region of an infusion bag may comprise greater than 50% of the total surface area of the infusion bag.

In a second aspect, the present invention provides a perforated strip, perforated pocketed strip or perforated web of material arranged for the manufacture therefrom of a plurality of infusion bags according to the first aspect of the present invention. Manufacture of the plurality of bags may involve operations including cutting, folding and sealing.

A perforated infusion bag may be formed from the material according to the second aspect of the present invention by following a method which includes the steps of:

(a) cutting the perforated strip or perforated pocketed strip of material substantially transversely to the longitudinal axis of the strip of material to form sheets of material;

(b) partially sealing a sheet of material to form a partially formed infusion bag;

(c) loading the partially formed infusion bag with a substance which is to be infused through the perforated material to form a loaded partially formed infusion bag; and

(d) sealing unsealed portion (s) of the loaded partially formed infusion bag. In a third aspect, the present invention provides a method for producing an infusion bag, the method including the steps of:

(a) perforating a sheet of material;

(b) partially sealing the sheet of material to form a partially formed infusion bag;

(c) loading the partially formed infusion bag with a substance which is to be infused through the perforated material to form a loaded partially formed infusion bag; and (d) sealing unsealed portion(s) of the loaded partially formed infusion bag. The step of partially sealing the sheet of material may include embossing, cold or hot sealing techniques

The step of sealing the unsealed portion of the partially formed infusion bag may include folding the unsealed portion and stapling the folded unsealed portion so that it remains in the folded position.

The step of sealing the unsealed portion of the partially formed and sealed infusion bag may include embossing, cold or hot sealing techniques. The step of perforating the sheet of material may involve varying the position, concentration, size, and shape of perforations within the sheet of material or by varying any combination of these characteristics of the perforations, so that, upon folding and subsequently sealing the sheet of material to form an infusion bag, one or more predetermined regions of the infusion bag have perforations which are either more concentrated, a larger size or a different shape, or any combination thereof, than perforations of other regions of the infusion bag. However, some regions of the infusion bag may have no perforations and the concentration, size and shape of the perforations may be varied within the one or more predetermined regions or the other regions. The sheet of material may be perforated so that, upon folding and subsequently sealing the sheet of material to form an infusion bag one or more predetermined regions of the infusion bag have larger sized and more concentrated perforations than other regions of the infusion bag. To this end, the shape of the perforations formed in the sheet of material may be optimised to achieve both increased perforation size and concentration .

The one or more predetermined regions may be one region which corresponds to a lower region of an infusion bag .

The step of perforating the sheet of material may include perforating the sheet of material so that the sheet of material has an unperforated region adjacent edges of the sheet of material, the unperforated region being adapted for sealing of edges of the sheet of material .

The sheet of material may be formed of paper, plastic film or foil . The sheet of material may be formed of aluminum foil.

The step of perforating the sheet of material may include forming square or rectangularly shaped perforations in the sheet of material. However, other shapes may be formed in the sheet of material . The step of perforating a sheet of material may include the steps of:

(a) forming perforations within an strip of material; and

(b) cutting the strip of material into one or more sheets of material by cutting the strip of material substantially transversely to the longitudinal axis of the strip of material . The strip of material may include a pocketed strip of material or a web of material.

The step of perforating the strip, sheet or web of material may include the use of micro mechanical, electroerosion or laser perforation techniques . Micro mechanical methods of perforating the strip or sheet of the material may produce square or rectangular shaped perforations having dimensions of the order of 0.03mm x 0.03mm and upwards. Electroerosion methods of perforating the sheet or strip of material may include forming substantially round perforations ranging in size of the order of 0.01mm to 0.1mm in diameter. The laser method of perforating the sheet or strip of material may include forming substantially round perforations ranging in size of the order of 0.05mm to 0.3mm in diameter.

In a fourth aspect, the present invention provides an apparatus for forming a perforated strip or perforated pocketed strip of material according to the second aspect of the present invention, the apparatus including perforating means for forming perforations in a strip of material and feed means for feeding the strip of material through the perforating means so that strip of material passes lengthwise through the perforating means, the longitudinal axis of the strip of material being substantially aligned with the direction of movement of the strip of material.

The strip, pocketed strip or web of material may include a strip of paper, plastic film or foil. The foil may be aluminum foil .

The feed means may include a reel from which the strip of material may be unrolled as it passes through the perforating means . The feed means may further include tension means for controlling the tension of the strip of material as it passes through the perforating means. The feed means may further comprise guide means for guiding the lateral alignment of the strip of material as it passes through the perforating means . The tension means may include one or more tension rollers which are adapted to rotate about a substantially central axis as the strip of material passes over an external surface of the tension roller, the tension roller being moveable in a direction toward and away from the strip of material to respectively increase and decrease the tension of the strip of material. The perforating means may include a perforating roller and corresponding impression roller, the perforating roller being adapted to rotate upon passage of the strip of material lengthwise between the perforating roller and impression roller and the impression roller being driven so as to assist the passage of the strip of material between the perforating and impression rollers. The perforating means may include compression means for applying pressure to an upper and lower surface of the strip of material as it passes through the perforating means. The compression means may include one or more compression members which are adapted to force the perforating roller and impression roller toward each other. The one or more compression members may be pneumatically operated.

The impression roller may be adapted to oscillate .

The perforating roller may include one or more perforation discs, each perforation disc having projections which extend outwardly from an outer annular surface, and each perforation disc having an inner annular surface which is adapted to slide over a corresponding outer annular surface of a compact guide cylinder head, the projections being adapted to perforate the strip of material upon passage of the strip of material lengthwise between the perforating roller and impression roller. An outer annular surface of the impression roller may be adapted to absorb the projections of the perforation disc to enable the perforating roller and impression roller to be forced together via the compression members and perforations to be formed in the strip of material by penetration of the strip of material by the projections of the perforation disc, as the strip of material passes lengthwise between the perforating roller and impression roller. The absorbing means may include a rubber/synthetic material which forms the outer annular surface of the impression roller. The rubber/synthetic material is preferably firm enough to effect perforation and resilient enough so that the outer annular surface of the impression roller is not permanently deformed after effecting perforations . Alternatively, the outer annular surface of the impression roller may be formed of embossed ceramic or may be laser engraved for receipt of corresponding projections of the perforation roller.

The perforating roller may have two or more perforation discs wherein the perforation discs are separated along the longitudinal length of the compact guide cylinder head by spacer rings, the spacer rings having an outside diameter corresponding to the diameter of the outer annular surface of the perforation discs . The diameter of the outer annular surface of the perforation discs may be of the order of 70mm. However, the diameter of the outer annular surface of the perforation discs and spacer rings may be varied to suit any given situation. Each perforation disc may have a thickness as small as 0.03mm. That is, a perforation disc, when appropriately mounted upon a compact guide cylinder head, may extend along the longitudinal length of the compact guide cylinder head a distance of 0.03mm. However, as previously explained, it may be desirable to form perforation discs having thicknesses of less than 0.03mm. The perforation disc projections may include teeth having a minimum tie of 0.4mm, a minimum cut of 0.03mm and a minimum depth of 0.2mm. With the use of laser perforation techniques, the minimum tie may be as small as 0.1mm. However, if the tie is too small, the resulting perforations may predispose the strip of material to tearing along a line of perforations.

The apparatus may further include one or more perforating disc shafts, the perforating disc shafts being adapted for preassembly of perforating discs over an outer annular surface of the perforating disc shaft prior to assembly of the perforation discs on the compact guide cylinder head to enable the projections of the perforation discs to be ground where necessary so that the outer diameter of the projections of adjacent assembled perforation discs is substantially equal.

The number and location of perforation discs and spacer rings may be adjusted to produce different patterns of perforation disc projections which extend away from the outer annular surface of the compact guide cylinder head. Each perforation disc and spacer ring may have location means for location of the perforation disc and spacer ring respectively relative to the compact guide cylinder head. The location means may include a location hole which is adapted to receive a corresponding location pin, the location pin being adapted to engage a corresponding location hole which is formed in the compact guide cylinder head. However, the location means may also include a key and associated key-way. The location hole and corresponding location pin is typically easier to assemble than the key and key-way alternative. The perforation means is preferably adapted to perforate the strip of material at predetermined regions along the length of the strip of material . The perforation means is also preferably adapted to perforate the strip of material within a predetermined band, the band having a longitudinal axis which substantially overlays the longitudinal axis of the strip of material wherein the width of the band is less than the width of the strip of material . The perforation means is preferably adapted to cyclically perforate the strip of material to produce a perforated strip of material having unperforated regions along the longitudinal of the strip of material, which separate the perforated regions . The perforation means may be adapted to vary the concentration of perforations in predetermined regions of the strip of material . The perforation means may be adapted to perforate the strip of material in one or more predetermined regions so that the one or more predetermined regions have perforations which are either more concentrated, a larger size, or a different shape, or any combination thereof, than perforations of the other regions of the strip of material. However, some regions of the infusion bag may have no perforations and the concentration, size and shape of perforations may also vary within the one or more predetermined regions or the other regions . The perforating means may be adapted to vary the number of perforations which extend across the width of the strip of material, at any given location along the longitudinal length of the strip of material. The perforation means may be adapted to cyclically vary the number of perforations which extend across the width of the strip material at any given location along the longitudinal length of the strip of material so that the number of perforations at any given location along the longitudinal length of the strip of material vary in accordance with the following cycle: Maximum number, decreasing number, zero. The perforation means may be adapted to cyclically vary the number of perforations in accordance with the following cycle: minimum number, increasing number, maximum number, zero, maximum number, decreasing number. The perforation means may be adapted to vary the size of perforations which extend across the width of the strip of material, at any given location along the longitudinal length of the strip of material. The perforation means may be adapted to cyclically vary the size of perforations which extend across the width of the strip of material at any given location along the longitudinal length of the strip of material so that the size of perforations at any given location along the longitudinal length of the strip of material varies in accordance with the following cycle: maximum size, decreasing size, minimum size or no perforations . The perforation means may be adapted to cyclically vary the size of the perforations in accordance with the following cycle: minimum size, increasing size, maximum size, no perforations, maximum size, decreasing size .

The perforation means may include waste removal means, the waste removal means being adapted for removal of material which has been partially removed from the strip of material in the process of perforating the strip of material. The waste removal means may include one or more brush rollers, each brush roller having outer annular surfaces which are adapted to contact the impression roller, and each of the brush rollers being driven. If two or more brush cutter rollers are employed the brush rollers may be driven independently in either direction about the axis of rotation. However, they may be driven so that they counter rotate relative to each other. Alternatively, they may also be driven so that they rotate in the same direction to each other.. The impression roller may include an associated pulley which, in combination with the impression roller is arranged to drive a belt which extends around the pulley and impression roller, wherein the belt functions as the absorbing means and may be formed of a rubber/synthetic material. The pulley is adapted to be driven in the same direction as that which the impression roller is adapted to be driven. One or more brush roller may be adapted for rotation about axes which are substantially aligned with axes of the pulley and impression rollers and may be positioned so that outer annular surfaces of the one or more brush rollers rotate against an outer surface of the belt. In a case where two or more brush roller are used, one of the brush rollers may be positioned proximal the pulley and another of the brush rollers may be positioned proximal the impression roller. One of the brush rollers may be positioned so that a line extending between axes of rotation of the pulley and the brush roller is substantially horizontal. Another of the brush rollers may be positioned so that a line extending between axes of rotation of the impression roller and brush roller extends downwardly at an angle between approximately 20° and 60° to a line which extends substantially downwardly from the axis of rotation of the impression roller. In the case the absorbing means is provided in the form of the belt, an axis about which the perforation roller rotates may be positioned so that it is not substantially over head an axis about which the impression roller rotates but is at least partially between the axes about which the pulley and impression roller rotate. Offsetting of the axes of rotation of the perforation roller, relative to the impression roller in this manner may result in cleaner holes being formed in a strip of material which passes between the perforation roller and belt. The waste removal means may further include one or more diamond cutter rollers and an adjustment roller, each diamond cutter roller having outer annular surfaces which are adapted to contact a side of the strip of material, each diamond cutter roller also being adapted to be driven, and the adjustment roller having an outer annular surface which is adapted to contact the opposite side of the strip of material to that which the diamond cutter rollers contact. As with the brush rollers, the diamond cutter rollers may be independently driven in either direction about their axis of rotation. However, they may be driven so that they counter rotate relative to each. Alternatively, they may be driven so that_they rotate in the same direction as each other. The waste removal means may further include a vacuum chamber which is adapted to extract waste material which has been removed from the strip in the process of perforating the strip of material. The brush rollers, diamond cutter rollers and adjustment roller are adapted to rotate about axes which are substantially aligned with axes about which the perforating and impression rollers rotate.

The adjustment roller may have corresponding adjustment members which are adapted to move the adjustment roller toward and away from the strip of material to respectively increase and decrease the surface area of the strip of material which is in contact with the diamond cutter rollers. In this way the diamond cutter rollers may be used to increase the size of the perforations by up to approximately 10%. The feed means may include a second reel onto which the strip of material is adapted to be rolled after it passes through the perforating means. The feed means may include direct feed means which is adapted to feed the strip of material directly into a machine which is adapted to form infusion bags, after the strip of material has passed through the perforating means .

The one or more compression members may include shock absorbing means for reducing the initial force of impact between the perforating roller and impression roller when the perforating roller and impression roller are forced together via the one or more compression members. Brief Description of the Drawings

Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure la is a schematic side elevation of an apparatus for producing perforated infusion bags;

Figure lb is a schematic side elevation of an alternative impression roller and brush roller arrangement to that of figure 1A;

Figure 2 is a plan view of segment of a strip of material after it has passed through the apparatus of figure 1A;

Figure 3 is a magnified view of a region of the strip of material of figure 2;

Figure 4 is a plan view of a segment of strip of material after it has passed through the apparatus of figure 1A with the apparatus of figure 1A configured to leave unperforated margins adjacent edges of the strip of material;

Figure 5 is a plan view of a segment of a strip of material similar to figure 4, except that the strip of material includes lateral unperforated bands which extend periodically across the strip of material; and

Figures 6 and 7 are plan views similar to figure 5 showing alternative patterns of perforated and unperforated regions of the strip of material. Best Mode of Carrying out the Invention

Referring to figure 1A the apparatus 10 for producing perforated infusion bags generally comprises perforating means in the form of a perforating roller 12 and a corresponding impression roller 14, and feed means in the form of an infeed reel 16, tension rollers 18 and 20 and lateral guide rollers 22 and 24. Each of the aforementioned rollers 12-24 are mounted for rotation about axes which are substantially aligned with each other. The aforementioned rollers 12-24 are positioned relative to each other to enable a strip of material in the form of a web of material 26 to be unwound from the reel 16, pass over the tension roller 18, over the lateral guide roller 22, between the perforating roller 12 and impression roller 14, over the other lateral guide roller 24 and subsequently over the other tension roller 20. The tension rollers 18 and 20 are movable toward and away from the web 26 to enable the tension in the web 26 to be respectively increased and decreased. The guide roll 22 is designed to control the lateral position of the web 26 prior to it passing between the perforating roller 12 and impression roller 14 and the lateral guide roll 24 is similarly designed to control the lateral position of the web 26 after it has passed between the perforating roller and impression roller 12 and 14 respectively.

The impression roller 14 is driven in a clockwise direction, as viewed in viewing the impression roller 14 of figure la. The direction of rotation of the impression roller 14 therefore assists passage of the web 26 between the perforating roller 12 and impression roller 14. The other rollers 12 and 16-24 are not driven and the input reel 16 provides some back pressure to able tension to be applied, via the tension roller 18, to the web 26, between the input reel 16 and perforating and impression rollers 12 and 14 respectively.

The apparatus 10 may further include a rewind reel 28 which is designed for rewinding the web 26 after it has passed between the perforating and impression rollers 12 and 14 respectively. Alternatively, the apparatus 10 may be directly linked to an infusion bag manufacturing apparatus (not shown) in which case the web 26 passes directly into such an apparatus after it passes over the tension roller 20.

The apparatus 10 also has brush rollers 30 and 32, diamond cutter rollers 34 and 36 and an associated adjustment roller 38, and air jets 40 and 42. The brush rollers 30 and 32 are mounted for rotating about axes which are substantially aligned with axis of the other rollers 18-24. The brush rollers are driven so that they counter rotate relative to each other and are positioned for rotation against the impression roller 14. Referring to figure 1A, the brush roller 30 is positioned to the left hand side of the brush roller 32. The brush roller 30 is driven so that it rotates in a counter clockwise direction and the brush roller 32 is driven so that it rotates in a clockwise direction. The brush rollers 30 and 32 are positioned against a lower outer annular surface of the impression roller 14. However, a third brush roller (not shown) or a series of brush rollers (not shown) may be used and each of the brush rollers forming the series of brush rollers may be rotated in either a clock wise or counter clock wise direction, as viewed in figure 1A. The speed of each of the brush rollers may be variable. The diamond cutter rollers 34 and 36 are positioned beneath the web 26 and are also mounted for rotation about axes which are substantially aligned with axes of the other rollers 18-24 and 30-32. The diamond cutter rollers 34 and 36 are driven so that they counter rotate relative to each other and are positioned so that outer annular surfaces of these rollers which contact an underneath surface of the web 26 rotate away from each other. The adjustment roller 38 is substantially centrally positioned between the diamond cutter rollers 34 and 36, the adjustment roller 38 being a freewheeling roller which is capable of moving toward and away from the web 26 to increase and decrease respectively the surface area of the web 26 which contacts the diamond cutter rollers 34 and 36. The airjets 40 and 42 are positioned above the web 26, the airjet 40 being positioned so that it projects air downwardly from the airjet 40 onto an upper surface of the web 26, across the width of the web 26, prior to the web 26 contacting the diamond cutter roller 34 and the airjet 42 is similarly positioned relative to the diamond cutter roller 36. As described above in relation to the brush rollers, a third diamond cutter roller (not shown) may be employed. Alternatively, a series of diamond cutter rollers (not shown) may be employed. Each of the diamond cutter rollers may be rotated in either a clock wise or counter clock wise direction as viewed in figure 1A.

The perforating roller 12 is forced against the impression roller 14 to compress the web 26 therebetween as the web 26 passes between the perforating roller 12 and impression roller 14. The surface of the perforating roller 12 which is pressed toward a corresponding surface of the impression roller 14, and which contacts an upper surface of the web 26, has projections (not shown) which are designed to punch holes through the web 26 where they contact the web 26. An outer surface of the impression roller 14 which contacts an underneath surface of the web

26 is covered with a rubber/ synthetic material which enables the projections of the perforating roller 12 to penetrate the outside surface of the impression roller 14. The rubber/synthetic material must be firm enough to effect perforation but resilient enough so that the rubber/synthetic material is not permanently deformed after effecting perforation. Alternatively, the impression roller 14 could include a ceramic embossed or laser engraved cylinder. As the projections of the perforating roller 12 press into the outer compressible surface of the impression roller 14, the projections cut through the web 26 to perforate the web 26. As a result of this process the punched out material which has been punch out of the web 26 by the projections of the perforating roller 12 can be depressed into the impression roller 14. The brush rollers

30 and 32 are designed to remove the punched out material from the outer surface of the impression roller 14.

Referring to figure IB, the impression roller 14 and brush rollers 30 and 32 may be alternatively arranged so that the outer rubber/ synthetic surface of the impression roller 14 is provided by a rubber/synthetic timing belt 80. The timing belt 80 extends about the impression roller 14 and a pulley 82 which is driven in the same direction as the impression roller 14 about axis which is substantially aligned with the axis about which the impression roller 14 rotates. The pulley 82 is positioned to the left of the impression roller 14, as viewed in figure IB. One of the brush rollers 30 is positioned adjacent the pulley 82 and arranged to be driven in the same direction as the pulley 82 and impression 35 roller 14. The other brush roller 32 is positioned so that its axis of rotation is slightly below an outside lowermost surface of the timing belt 80, and slightly to the left of an outer right hand surface of the timing belt

80, as viewed in figure IB. The impression roller and brush roller arrangement of figure IB provides an impression roller that is less prone to wear and hence capable of lasting longer than the covered impression roller of figure 1A. The rubber/synthetic timing belt can also be replaced more efficiently. Furthermore, by moving the axis of rotation of the perforating roller 12 toward the left hand side of figure IB, so that it is slightly to the left of the axis of rotation of the impression roller 14, a greater number of teeth of the perforating roller 12 come into contact with an outer surface of the timing belt 80. This is expected to result in cleaner holes being formed in the web 26.

The region of the apparatus 10 which includes the perforating roller 12, impression 14, brush rollers 30 and 32, diamond cutter rollers 34 and 36 and associated adjustment roller 38, and airjets 40 and 42 is enclosed within a vacuum chamber 44. The vacuum chamber 44 operates to extract the punched out material . Any punched out material which is still either partly attached to the web 26 or in contact with the web 26, after the web 26 has passed between the perforating roller 12 and impression roller 14, is removed from the web 26 and subsequently extracted via the vacuum chamber 44 upon passage of the web 26 under the airjets 40 and 42 and subsequently over the diamond cutter rollers 34 and 36 respectively. The diamond cutter rollers 34 and 36 can also operate to increase the size of the perforations . This can be achieved by forcing the adjustment roller 38 toward the diamond cutter rollers 34 and 36. In this way the size of the perforations can be increased by up to approximately 10%. The perforating roller 12 is formed of an actuator compact guide cylinder head and corresponding perforation discs and spacer rings, all of which are not shown in figure 1A. An outer annular surface of the perforation discs has a diameter of greater than or equal to 70mm. The perforation discs are designed so that their inner annular surfaces slides over an outer annular surface of the actuator compact guide cylinder head. Projections in the form of teeth extend outwardly of the outer annular surface of the perforation discs. Perforation discs can be designed to have different patterns and types of teeth extending from their outer annular surface. Perforation discs can also be combined with other perforation disc and spaced relative to such other perforation discs by spacer rings so that different perforation patterns are produced within the web 26 as it passes between the perforating roller 12 and impression roller 14. In order to produce infusion bags having regions where the concentration of perforations is maximised, it is desirable that the thickness of the perforations discs is as small as possible. The thinnest perforation disc currently available is 0.03mm. When a perforation disc having a thickness of 0.03mm is assembled onto the actuator compact guide cylinder head, it extends along the longitudinal length of the actuator compact guide cylinder head a distance of 0.03mm. Figures 2 and 4-7 show different patterns of perforations which can be produced in the web 26. Figure 3 shows one example of how the holes which form the perforated pattern may be positioned relative to each other .

Before the perforation discs are assembled onto the actuator compact guide cylinder head they are assembled onto a separate shaft which has an outer annular surface that is the same diameter as the outer annular surface of the actuator compact guide cylinder head. After assembling the perforation discs on the separate shaft they are locked relative to the shaft to prevent both axial and rotational movement of the perforation discs relative to the shaft. With the perforation discs locked in this manner relative to the shaft, the teeth which extend from the outer annular surface of the perforation discs can be ground to ensure all teeth will have the same outer side diameter, when assembled on the actuator compact guide cylinder head. Referring to figure 2, the projections of the perforating roller 12 can be such that the full width of the web 26 is perforated. The projections of the perforating roller 12 are aligned laterally across the width of the perforating roller 12 to perforate the web 26 with perforations that extend laterally across the web 26 to form linear arrays of perforations, each linear array of perforations being aligned substantially transversely relative to the longitudinal axis of the web 26. The smallest perforation which can currently be produced using a perforating roller 12, is one having a size of approximately 0.03mm x 0.03mm

Referring to figure 3 the projections of the perforating roller 12 can be configured to form a pattern of square perforations having dimensions of 0.03mm x 0.03mm in the web 26, the pattern comprising the following repeating unit: five 0.03mm x 0.03mm perforations, four of these perforations being located at four corners of a 0.13mm x 0.54mm rectangle, the rectangle having a longitudinal axis which is substantially aligned with a longitudinal axis of the web 26, and the fifth perforation being substantially centrally positioned relative to the other four perforations .

Referring to figure 4, the projections of the perforating roller 12 can be arranged such that the perforated web 26 has unperforated margins 50 and 52 which extend down the left and right hand edges respectively of the web 26 as shown in figure 4. The unperforated margins are desirable for enabling the left and right hand edges of the web 26 to be heat sealed together. With the perforating pattern of figure 4, the web 26 can be cut into sheets (not shown) by cutting the web 26 substantially laterally to the longitudinal axis of the web 26. The sheets can then be folded and heat sealed in regions which correspond to the margins 50 and 52 to form infusion bags.

Referring to figure 5, the perforating roller 12 is designed to leave unperforated margins 50 and 52 down the left and right hand sides respectively of the web 26, as described above in relation to figure 4. The perforating roller 12 which produces the perforated pattern of figure 5 is also designed to leave lateral bands 58 of the web 26 unper orated. The lateral bands 58 are a similar width to that of the margins 50 and 52. The lateral band 58 extends substantially transversely to a longitudinal axis of the web 26 and occurs periodically along the longitudinal length of web 26. The unperforated lateral bands 58 are spaced so that the distance between adjacent center lines of adjacent unperforated lateral bands 58 corresponds to the length of the web 26 which is required to form a perforated infusion bag. To form perforated infusion bags, the web 26 is cut laterally at positions along the longitudinal length of the web 26 which substantially align with center lines of the unperforated bands 58.

Referring to figure 6, the perforating roller 12 can be configured to produce a more complex perforated pattern on the web 26. The perforated pattern of figure 6 has unperforated margins 50 and 52 which correspond to the unperforated margins of figures 4 and 5, and also has unperforated lateral bands 58 which corresponds to the unperforated lateral bands 58 of figure 5. The unperforated lateral bands 58 are spaced the same distance apart as the bands 58 of figure 5. The perforated pattern of figure 6 also has unperforated triangular regions 60 and 62 which are positioned periodically on the left and right hand sides respectively of the longitudinal axis of the web 26. The unperforated triangular regions 60 and 62 are positioned so that the longitudinal axes of the unperforated triangular regions 60 and 62 are substantially aligned. Bases of the unperforated triangular regions 60 and 62 extend from the unperforated margins 50 and 52. In this way, the unperforated margins 50 and 52 extend inwardly toward the longitudinal axis of the web 26 to form the triangular unperforated regions 60 and 62. A small perforated region 64 separates apexes 66 and 68 of the unperforated triangular regions 60 and 62 respectively. In order to form perforated infusion bags from the web 26 having the perforated pattern of figure 6, the web 26 is cut laterally along lines which substantially correspond to center lines of the laterally extending unperforated bands

58, as explained in relation to the web 26 of figure 5. Perforated sheets which are cut in this way from the web 26 of figure 6 are folded so that the perforated bands 58 which extend from opposite ends of the sheet overlay to enable these regions to be heat sealed together. In so folding these sheets opposite halves of the unperforated margin 50 of the sheet overlay, enabling them to be heat sealed together and opposite halves of the unperforated margin 52 similarly overlay, enabling them to also to be heat sealed together. After folding and heat sealing a sheet which has been cut from the web 26 having the perforated pattern of figure 6, the unperforated bands 58 extend from a region of an infusion bag which, in use, is the lower region of an infusion bag and the apexes 66 and 68 of the unperforated triangular region 60 and 62 are positioned at the upper region of a perforated infusion bag . Referring to figure 7, an alternative perforated pattern similarly has unperforated margins 50 and 52 which correspond to the unperforated margins 50 and 52 of figures 4-6. The perforated pattern of figure 7 also has unperforated triangular regions 72 and 74 similar to the unperforated triangular regions 60 and 62 of the perforated pattern of figure 6. That is, the unperforated triangular regions 72 and 74 extend laterally inwardly from the unperforated margins 50 and 52 respectively. However, bases of the unperforated triangular regions 72 and 74 are longer than bases of corresponding unperforated triangular regions 60 and 62 respectively and the apexes of the unperforated triangular regions 72 and 74 partially overlay opposite unperforated triangular regions 74 and 72 respectively, so that the unperforated regions formed by the unperforated triangular regions 72 and 74 extends completely from one side of the web 26 to the other side of the web 26. The unperforated triangular regions 72 and 74 result in triangular perforated regions 75 and 77 which are positioned on either side of a longitudinal axis 79 of the unperforated triangular region 72 and 74 which extends laterally across the web 26. The perforated triangular regions 75 and 77 have apexes 76 and 78 respectively which are substantially aligned with the longitudinal axis of the web 26 and are positioned opposite each other. The apexes 76 and 78 are separated by a greater distance then the width of the laterally extending unperforated bands 58 of figures 5 and 6. The unperforated triangular regions 72 and 74 are positioned periodically along the longitudinal length of the web 26 so that longitudinal axes 79 of adjacent unperforated triangular regions 72 and 74 of the web 26 are spaced far enough apart so that the length of web 26 therebetween is sufficient for forming one perforated infusion bag. To form a perforated infusion bag the web 26 of figure 7 is cut laterally across the width of web 26 at positions which substantially correspond to the longitudinal axes 79 of the unperforated triangular regions 72 and 74. By folding a sheet which is cut in this way from the web 26, symmetrically about an axis which extends laterally across the width of the sheet, apexes 76, which are positioned at opposite ends of the sheet, can be folded toward each other to enable the perforated infusion bag to be heat sealed laterally across the width of the sheet at a position proximal the apexes 76. Opposite halves of the unperforated margin 50 can also be heat sealed together as describe in relation to the margin 50 of figures 4-6. Opposite halves of the margin 52 can similarly be heat sealed together.

Claims

CLAIMS :

1. An infusion bag perforated to permit infusion of a substance contained within the bag when the bag is steeped in a fluid.

2. An infusion bag as claimed in claim 1 having an unperforated region adjacent an edge of the bag adapted for sealing of the bag.

3. An infusion bag as claimed in claim 1 or claim 2 wherein the bag is formed from heat sealable material .

4. An infusion bag as claimed in claim 1 or claim 2 formed of paper, plastic film or foil.

5. An infusion bag as claimed in any one of the preceding claims wherein the bag has a greater concentration of perforations in one or more predetermined regions .

6. A perforated strip, perforated pocketed strip, or perforated web of material arranged for the manufacture therefrom of a plurality of infusion bags as claimed in any one of the preceding claims.

7. An apparatus for forming perforated material as claimed in claim 6, the apparatus including perforation means for forming perforations in a length of the material and feed means for feeding the material lengthwise through the perforating means with the longitudinal axis of the length of material being substantially aligned with the direction of movement of the material.

8. An apparatus as claimed in claim 7 wherein the perforation means is selected from micro-mechanical perforation means, electroerosion perforation means and laser perforation means .

9. An apparatus as claimed in claim 7 wherein the perforation means includes a perforating roller and an impression roller arranged for the passage therebetween of the material.

10. An apparatus as claimed in any one of claims 7 - 9, further including separating means for separating the length of perforated material into a plurality of discrete elements, each element being arranged to be formed into an infusion bag.

11. An apparatus as claimed in claim 10 further including sealing means arranged to seal each discrete element during formation of said infusion bag.