HEAT AND MOISTURE EXCHANGE MEDIA

Abstract

This invention relates to heat and moisture exchange (HME) materials, particularly for use in heat and moisture exchange with respiratory gases, and methods for their manufacture. The invention provides an improved HME material (10a) comprising a plurality of discrete protrusions (510), as opposed to continuous ridges or corrugations, extending from at least part of one surface of the HME material (10a), and to an associated manufacturing method.

Claims

1. A heat and moisture exchange material comprising: a plurality of discrete protrusions extending from at least part of one surface of the heat and moisture exchange material wherein each protrusion is completely surrounded by substantially non-protruding HME material.

2. The heat and moisture exchange material according to claim 1, wherein the protrusions are formed from the heat and moisture exchange material.

3. The heat and moisture exchange material according to claim 1, wherein the regions of the heat and moisture exchange material from which each protrusion is formed has a maximum dimension of between 0.4 mm and 5.0 mm, between 0.6 mm and 3.0 mm or between 0.8 mm and 2.0 mm.

4. The heat and moisture exchange material according to claim 1, wherein the protrusions do not span the entire width of the heat and moisture exchange material.

5. The heat and moisture exchange material according to claim 1, wherein the protrusions are hemispherical, frustoconical, cylindrical, pyramidal, cuboid, hemicylindrical or any combination of these.

6. The heat and moisture exchange material according to claim 1, wherein the protrusions protrude from the surface of the heat and moisture exchange material by between 0.1 mm and 1.0 mm, between 0.3 mm and 0.8 mm or between 0.5 mm and 0.6 mm.

7. The heat and moisture exchange material according to claim 1, wherein the protrusions are distributed regularly on the surface of the heat and moisture exchange material.

8. The heat and moisture exchange material according to claim 1, wherein the density of the protrusions per cm.sup.2 is between 3 and 50, between 5 and 40, between 8 and 30 or between 10 and 20.

9. The heat and moisture exchange material according to claim 1, wherein each protrusion comprises a perforation in the heat and moisture exchange material.

10. The heat and moisture exchange material according to claim 9, wherein the perforations have a maximum dimension of between 0.4 mm and 5.0 mm, between 0.6 mm and 3.0 mm or between 0.8 mm and 2.0 mm.

11. The heat and moisture exchange material according to claim 9, wherein a portion of the heat and moisture exchange material around the edge of each perforation protrudes from the surface of the heat and moisture exchange material.

12. The heat and moisture exchange material according to claim 9, wherein the perforations are cuts in the heat and moisture exchange material that partially surround a region of heat and moisture exchange material, such that that region of heat and moisture exchange material forms a flap extending from the surface of the heat and moisture exchange material.

13. The heat and moisture exchange material according to claim 12, wherein the cut is generally C-shaped such that the flap is substantially circular.

14. The heat and moisture exchange material according to claim 1, wherein the heat and moisture exchange material comprises cellulose paper.

15. The heat and moisture exchange material according to claim 14, wherein the heat and moisture exchange material further comprises natural fibres such as cotton, or synthetic fibres such as polyamine, polyester, polyurethane, polyacrylonitrile and polyvinyl alcohol, or any combination thereof.

16. The heat and moisture exchange material according to claim 1, wherein the heat and moisture exchange material comprises a hygroscopic material.

17. The heat and moisture exchange material according to claim 16, wherein the hygroscopic material comprises polyols such as glycols and glycerine, hygroscopic polymers such as polyvinylpyrrolidone, polyacrylic acid and polyvinyl alcohol, and hygroscopic salts such as polyacrylate, calcium chloride, potassium chloride and lithium chloride, or any combination thereof.

18. The heat and moisture exchange material according to claim 1, wherein the heat and moisture exchange material has a thickness of between 0.01 mm and 1.0 mm, between 0.05 mm and 0.5 mm, between 0.1 mm and 0.3 mm, or about 0.2 mm.

19. The heat and moisture exchange material according to claim 1, wherein the heat and moisture exchange material is in the form of elongate strips.

20. The heat and moisture exchange material according to claim 19, wherein the width of the strip of heat and moisture exchange material is between 5 mm and 20 mm or between 8 mm and 18 mm.

21. The heat and moisture exchange material according to claim 1, wherein discrete protrusions extend from at least a part of two opposing surfaces of the heat and moisture exchange material.

22. A heat and moisture exchange medium comprising an heat and moisture exchange material according to claim 1.

23. The heat and moisture exchange medium of claim 22, wherein the heat and moisture exchange medium comprises a plurality of overlying layers of the heat and moisture exchange material.

24. The heat and moisture exchange medium of claim 23, wherein the heat and moisture exchange medium is in the form of a coil of the heat and moisture exchange material.

25. The heat and moisture exchange medium of claim 24, wherein the heat and moisture exchange medium is between 1.5 cm and 8.0 cm in diameter.

26. A heat and moisture exchange device comprising a heat and moisture exchange medium according to claim 22.

27. A method of embossing a heat and moisture exchange material comprising: urging an heat and moisture exchange material against an embossing surface comprising a plurality of discrete projections.

28. The method of claim 27, wherein the heat and moisture exchange material is urged against the projections on the embossing surface by a second embossing surface.

29. The method of claim 28, wherein the second embossing surface comprises recesses that correspond to the projections of the first embossing surface.

30. The method of claim 29, wherein the second embossing surface further comprises projections that correspond to recesses provided in the first embossing surface.

31. The method of claim 28, wherein the first and second embossing surfaces are circumferential surfaces of first and second embossing rollers.

32. The method of claim 31, wherein the first and second embossing rollers define a nip at which the circumferential surfaces of the rollers come into contact.

33. The method of claim 32, wherein the projections of the first embossing roller mesh with the recesses of the second embossing roller at the nip.

34. The method of claim 27, wherein the projections form perforations in the heat and moisture exchange material.

35. The method of claim 27, wherein the height of the projections is between 0.2 mm and 6.0 mm, between 0.4 mm and 4.0 mm or between 0.6 mm and 2.0 mm.

36. The method of claim 27, wherein the height of the projections may be between 1 and 30 times, between 2 and 20 times or between 3 and 10 times the thickness of the heat and moisture exchange material.

37. The method of claim 27, wherein the projections are in the form of a cylinder having a hemispherical end.

38. The method of claim 37, wherein the cylinder has a diameter that is greater than its height.

39. The method of claim 37, wherein the cylinder has a height that is greater than its diameter.

40. The method of claim 27, wherein the projections are in the form of a cylinder in which the surface of the distal end is inclined relative to its longitudinal axis.

41. The method of claim 27 further comprising winding the embossed heat and moisture exchange material into a coil.

Description

[0071] A currently preferred embodiment of the invention will now be described, by way of illustration only, with reference to the accompanying drawings, in which:

[0072] FIG. 1 is a schematic representation, not to scale, of an apparatus for manufacturing HME media;

[0073] FIG. 2A is a front view of a first embodiment of an upper embossing roller of the apparatus of FIG. 1;

[0074] FIG. 2B is a side view of the upper embossing roller of FIG. 2A with a partial cutaway depicting the internal structure of the roller;

[0075] FIG. 3A is a front view of a second embodiment an upper embossing roller of the apparatus of FIG. 1;

[0076] FIG. 3B is a side view of the upper embossing roller of FIG. 3A with a partial cutaway depicting the internal structure of the roller;

[0077] FIG. 4A is a front view of a first embodiment of a lower embossing roller of the apparatus of FIG. 1;

[0078] FIG. 4B is a side view of the lower embossing roller of FIG. 4A.

[0079] FIG. 5A is a front view of a second embodiment of a lower embossing roller of the apparatus of FIG. 1;

[0080] FIG. 5B is a side view of the lower embossing roller of FIG. 5A.

[0081] FIG. 6A is a front view of a third embodiment of a lower embossing roller of the apparatus of FIG. 1;

[0082] FIG. 6B is a side view of the lower embossing roller of FIG. 6A.

[0083] FIG. 7A is a front view of a fourth embodiment of a lower embossing roller of the apparatus of FIG. 1;

[0084] FIG. 7B is a side view of the lower embossing roller of FIG. 7A.

[0085] FIG. 8 is a perspective view of an embossing assembly;

[0086] FIG. 9 is a cross-sectional view, schematic and not to scale, of the embossing assembly of FIG. 8 immediately before the HME material passes between the upper and lower embossing rollers;

[0087] FIG. 10A is a plan view, schematic and not to scale, of an embossed HME material;

[0088] FIG. 10B is a cross-sectional view taken along line A-A of a first embodiment of the embossed HME material of FIG. 10A;

[0089] FIG. 10C is a cross-sectional view taken along line A-A of a second embodiment of the embossed HME material of FIG. 10A;

[0090] FIG. 10D is a cross-sectional view taken along line A-A of a third embodiment of the embossed HME material of FIG. 10A;

[0091] FIGS. 11A-C are plan views, schematic and not to scale, of further embodiments of embossed HME material;

[0092] FIG. 12A is a side view of an HME medium in the form of a coil of embossed HME material;

[0093] FIG. 12B is a perspective view of the HME medium of FIG. 12A in a partially unwound configuration;

[0094] FIG. 13A is a plan view, schematic and not to scale, of an embodiment of an embossed HME material;

[0095] FIG. 13B is a cross-sectional view of the embossed HME material of FIG. 13A;

[0096] FIG. 13C is a plan view, schematic and not to scale, of a further embodiment of an embossed HME material;

[0097] FIG. 13D is a cross-sectional view of the embossed HME material of FIG. 13C;

[0098] FIG. 14 is a side view of a cutaway section of a further embossing roller, schematically depicting the internal structure of the roller; and,

[0099] FIG. 15 is a cross-sectional view of a further example of embossed HME material.

[0100] FIG. 1 depicts an apparatus for manufacturing HME media 100. The apparatus 100 comprises a source reel 10 carrying HME material 10a, an embossing or cutting assembly 20, a tension control assembly 30, and a winding assembly 40.

[0101] The HME material 10a is in the form of a strip that is unwound by the rotation of the source reel 10 in the direction of arrow A and transferred along the apparatus 100 in the direction of arrow B towards the embossing assembly 20.

[0102] The embossing assembly 20 comprises an upper embossing roller 200 and a lower embossing roller 300 that together define a nip 400. A motor (not shown) drives the rotation of the embossing rollers 200,300 in the direction or arrows C. The circumferential surface 210 of the upper embossing roller 200 comprises a pattern of recesses (see, for example, FIGS. 2A and 2B) while the circumferential surface 310 of the lower embossing roller 300 comprises a corresponding pattern of projections (see, for example, FIGS. 4A and 4B). The recesses of the upper embossing roller 200 mesh with the projections of the lower embossing roller 300 at the nip 400.

[0103] The HME material 10a is drawn into the nip 400 by the rotation of the embossing rollers 200,300 in the direction of arrows C. As the HME material 10a passes through the nip 400 it is compressed between the meshing recesses and projections on the circumferential surfaces 210,310 of the embossing rollers 200,300, thereby producing an embossed pattern on the HME material 10b. The embossed pattern comprises a plurality of protrusions corresponding to the pattern of recesses and projections on the circumferential surfaces 210,310 of the embossing rollers 200,300.

[0104] The embossed HME material 10b passes out of the nip 400 and enters the tension control assembly 30, which comprises a number of rollers 32 that control the tension of the HME material 10a,10b as it passes through the nip 400.

[0105] The winding assembly comprises a spindle 42 to which the embossed HME material 10b is attached. The spindle 42 is rotated to wind the embossed HME material 10b into a coil as it passes out of the tension control assembly 30. When sufficient embossed HME material 10b has been wound into the coil to form an HME medium, the embossed HME material 10b is cut and the HME medium is removed from the spindle 42. The free end of the embossed HME material 10b is then attached to the spindle 42 and the process repeated. However, in alternative embodiments, the embossed HME material 10b may be wound directly onto a roller after passage through the tension control assembly 30 and processed into HME media in a separate process.

[0106] The embossed pattern maintains separation between the adjacent layers of the HME material 10b in HME media, thereby improving the heat and moisture exchange performance of the HME media and reducing the resistance of the HME media to gas flow. The HME media may be introduced into a housing in order to produce an HME device.

[0107] The integrity of the embossed pattern and hence its ability to maintain separation between the adjacent layers of the HME material 10b in HME media is less susceptible to relative humidity during manufacture and hence this method is capable of producing HME media with more consistent performance without the need to control humidity during manufacture.

[0108] FIGS. 2A and 2B depict a first embodiment of upper embossing roller 200a and FIGS. 3A and 3B depict a second embodiment of an upper embossing roller 200b. The upper embossing rollers 200a,200b are generally disk-shaped and each comprise a circumferential surface 210a,210b, two generally circular faces 220a,220b, a channel 230a,230b passing between the centres of the circular faces 220a,220b, and ridges 240a,240b extending radially from both edges of the circumferential surfaces 210a,210b.

[0109] The circumferential surface 210a of the first embodiment of the upper embossing roller 200a (FIGS. 2A and 2B) comprises a pattern of generally cylindrical recesses 250a. The recesses 250a are arranged in four staggered rows extending around the circumference of the roller 200a.

[0110] The circumferential surface 210b of the second embodiment of the upper embossing roller 200b (FIGS. 3A and 3B) has a greater width than that of the first embodiment of the upper embossing roller 200a. The circumferential surface 210b also comprises a pattern of generally cylindrical recesses 250b, which in this embodiment are arranged in seven rather than four staggered rows extending around the circumference of the roller 200b.

[0111] FIGS. 4A and 4B depict a first embodiment of a lower embossing roller 300a, FIGS. 5A and 5B depict a second embodiment of a lower embossing roller 300b, FIGS. 6A and 6B depict a third embodiment of a lower embossing roller 300c, and FIGS. 7A and 7B depict a fourth embodiment of a lower embossing roller 300d. The lower embossing rollers 300a,300b,300c,300d are also generally disk-shaped and each comprises a circumferential surface 310a,310b,310c,310d, two generally circular faces 320a,320b,320c,320d, a channel 330a,330b,330c,330d passing between the centres of the circular faces 320a,320b,320c,320d, and annular collars 340a,340b,340c,340d that surround each end of the channel 330a,330b, 330c,330d on each circular face 320a,320b,320c,320d.

[0112] The circumferential surfaces 310a,310b,310c,310d of the lower embossing rollers 300a,300b,300c,300d comprises patterns of projections 350a,350b,350c,350d. The projections 350a of the first embodiment of a lower embossing roller 300a (FIGS. 4A and 4B) are in the form of a relatively short cylinder (ie the diameter of the cylinder is significantly greater than its height) having a hemispherical end. The projections 350a are arranged in four staggered rows extending around the circumference of the roller.

[0113] The projections 350b of the second embodiment of a lower embossing roller 300b (FIGS. 5A and 5B) are in the form of a relatively long cylinder (ie the height of the cylinder is significantly greater than its diameter) having a hemispherical end. The projections 350b are arranged in four staggered rows extending around the circumference of the roller 300b.

[0114] The projections 350c of the third embodiment of a lower embossing roller 300c (FIGS. 6A and 6B) are in the form of a cylinder having a top surface inclined at 45 degrees to its longitudinal axis. The projections 350b are arranged in four staggered rows extending around the circumference of the roller 300c.

[0115] The circumferential surface 310d of the fourth embodiment of the lower embossing roller 300d (FIGS. 7A and 7B) has a greater width than the circumferential surfaces 310a, 310b,310c of the other embodiments of the upper embossing roller 300a,300b, 300c. The projections 350d are in the form of relatively short cylinders (ie the diameter of each cylinder is significantly greater than its height) having a hemispherical end, and are similar in form to the projections 350a of the first embodiment of a lower embossing roller 300a. The projections 350d are arranged in seven rather than four staggered rows extending around the circumference of the roller 300d.

[0116] Referring now to FIGS. 8 and 9, the embossing rollers 200,300 engage the apparatus for manufacturing HME media 100 via axles 260,360 that pass through the channels 230,330. The rotation of the embossing rollers 200,300 may be driven by a motor (not shown) acting upon one or both axles 260,360. The recesses 250 of the upper embossing roller 200 have the same distribution as, and are of sufficient size to accommodate, the projections 350 of the lower embossing roller 300, and hence are able to mesh at the nip 400 as the embossing rollers 200,300 are rotated.

[0117] A precise fit between the recesses 250 and projections 350 is not necessarily required and hence it is possible for the same upper embossing roller 200 to be used in conjunction with different lower embossing rollers 300. In particular, the distribution of the recesses 250a in the first embodiment of the upper embossing roller 200a is the same as the distribution of the projections 350a,350b,350c in the first, second and third embodiments of the lower embossing rollers 300a,300b, 300c, and hence any of these lower embossing rollers may be used in conjunction with this upper embossing roller. This arrangement may be used to emboss a narrower HME material.

[0118] In addition, the distribution of the recesses 250b in the second embodiment of the upper embossing roller 200b is the same as the distribution of the projections 350d on the fourth embodiment of the lower embossing rollers 300d and hence these lower and upper embossing rollers may be used in conjunction. This arrangement may be used to emboss a broader HME material.

[0119] The HME material 10a is drawn into the nip 400 by the rotation of the embossing rollers 200,300 in the direction of arrows C and is guided onto the circumferential surfaces 210,310 and into contact with the projections 350 by the ridges 240. As the HME material 10a is drawn into the nip 400, the projections 350 apply increasing pressure to the HME material 10a, thus creating indentations in the lower surface of the HME material 10a and corresponding protrusions on the upper surface of the HME material 10a. The presence of the recesses 250 on the upper embossing roller permits the projections 350 to extend through the plane of the HME material 10a at the point at which maximum pressure is applied to the HME material at the nip 400. This permits greater deformation of the HME material 10a by the projections 350 and hence the formation of more prominent protrusions, and potentially also perforations, in the HME material 10a by the projections 350.

[0120] The pressure applied to the HME material 10a at the nip 400 should be sufficient to form a protrusion or perforation in the paper. It will be appreciated that the specific pressure required may vary, depending on the thickness and composition of a particular HME material, but can be readily determined by a skilled person. It is envisaged that the operating pressure provided at the nip 400 will be similar regardless of whether protrusions or perforations are required. Different pin sizes and geometries will nonetheless result in different pressures ultimately being applied to the material.

[0121] The height or length of projections, for example, can have a relatively significant influence on the ultimate pressure applied to the HME material. More tension will be created in HME material drawn through a nip including longer protections, and so the pressure applied to the material will effectively increase. Similarly, a larger number or denser pattern of projections will similarly increase the tension in the material and, thus, the ultimate pressure applied. By controlling these factors, the invention allows some control of applied pressure without the need to adjust the pressure at the nip 400.

[0122] The HME material 10b that is ejected from the nip 400 by the rotation of the embossing rollers 200,300 in the direction of arrows C thus carries an embossed pattern comprising a plurality of protrusions. The form and distribution of the protrusions is determined by the form and distribution of the projections 350 on the lower embossing roller 30 as well as the level of pressure that is applied to the HME material at the nip 400. Accordingly, a wide variety of embossed patterns can be formed by this method with the use different embossing rollers 200,300 and the application of different pressures at the nip 400.

[0123] FIG. 10A depicts an HME material 500 having an embossed pattern formed of a plurality of protrusions 510. The protrusions 510 are generally circular in plan view and are arranged regularly in seven offset rows extending longitudinally along the HME material 500.

[0124] FIG. 10B is a cross-sectional view of a first embodiment of the HME material 500a depicted in FIG. 10A taken along line A-A in which the protrusions 510a are generally hemispherical in shape and the HME material 500a is not perforated. The protrusions 510a may be formed by projections in the form of a relatively short cylinder having a hemispherical end, such as those of the first embodiment of the lower embossing roller (FIGS. 4A and 4B).

[0125] FIG. 10C is a cross-sectional view of a second embodiment of the HME material 500b depicted in FIG. 10A taken along line A-A in which the protrusions 510b are generally frustoconical in shape and comprise perforations 520b in the HME material 500b at their apex. The protrusions 510b may be formed by generally bullet-shaped projections, for example in the form of a relatively long spiked cylinder. Such projections are able to punch through the HME material 500b when sufficient pressure is applied at the nip 400. This has been found to produce a significant amount of swarf in the form of particles of HME material.

[0126] FIG. 10D is a cross-sectional view of a third embodiment of the HME material 500c depicted in FIG. 10A taken along line A-A in which the protrusions 510c are in the form of a flap 530c extending from one side of a perforation 520c. The protrusions 510c may be formed by projections in the form of a cylinder having a hemispherical end, such as those of the second embodiment of the lower embossing roller (FIGS. 5A and 5B). Alternatively, cylinders having a top surface inclined at 45 degrees to its longitudinal axis, such as those of the third embodiment of the lower embossing roller 300c (FIGS. 6A and 6B), could be used. Such projections are able to cut into the HME material 500c as pressure is applied at the nip 400 in order to produce the perforations 520c and flaps 530c. This has been found to produce a cleaner cut with less swarf than perforation with longer hemispherical projections of the type found on the second embodiment of the lower embossing roller (FIGS. 5A and 5B), where the perforations are typically formed by a tearing action.

[0127] FIGS. 11A-C depict further embodiments of an embossed HME material 600a, 600b, 600c with an embossed pattern comprising a plurality of protrusions 610a, 610b, 610c. The embodiment depicted in FIG. 11A comprises generally circular protrusions arranged regularly in four non-offset rows. The embodiment depicted in FIG. 11B comprises generally circular protrusions arranged irregularly. The embodiment depicted in FIG. 11C comprises generally rectangular protrusions arranged regularly in five offset rows.

[0128] FIGS. 12A and 12B depict an HME medium 700 in the form of a coil of embossed HME material. FIG. 12B indicates that the HME material from which the HME medium 700 is formed comprises an embossed pattern in the form of generally circular indentations 710 arranged regularly in three non-offset rows. The protrusions 710 maintain the separation between the adjacent layers of the HME material in the HME medium 700, which improves the heat and moisture exchange performance of the HME medium 700 and reduces the resistance of the HME medium 700 to gas flow.

[0129] Protrusions produced by the method described above maintain the separation between the adjacent layers of the HME material even when the HME material is placed under a relatively high level of tension, such as when the HME material is wound into a relatively tight coil. This is particularly significant for relatively small HME media in which the HME material must be wound more tightly in order to prevent the formation of an opening at the centre of the HME media, which would create a passage through which gas would be able to flow without being adequately exposed to the HME material.

Example 1Embossing a 9.5 mm Wide Strip of HME Material Using the Lower Embossing Roller Depicted in FIGS. 4A and 4B

[0130] An HME material was embossed using an embossing assembly substantially as discussed above with reference to FIG. 8, using an upper embossing roller substantially as discussed above with reference to FIGS. 2A, 2B and a lower embossing roller substantially as discussed above with reference to FIGS. 4A and 4B. The embossing rollers had a diameter of 69.95 mm and circumferential surfaces with a width of 9.5 mm.

[0131] The HME material was a continuous strip having a width of 9.5 mm and a thickness of 0.2 mm, and was formed of cellulose based paper containing cotton fibres. However, this embossing method is equally applicable to other forms of HME material, including HME materials containing any form of natural or synthetic fibres and hygroscopic additives such as CaCl.

[0132] The projections of the lower embossing roller were in the form of a relatively short cylinder (ie the diameter of the cylinder is significantly greater than its height) having a hemispherical end (see FIGS. 4A and 4B). The apex of each projection extended 0.7 mm from the circumferential surface of the lower embossing roller.

[0133] The HME material was passed through the nip between the embossing rollers in order to produce an embossed pattern made up of a plurality of substantially hemispherical protrusions (see FIG. 10B) on one surface of the HME material. The protrusions were arranged in four offset rows extending along the length of the strip of HME material.

[0134] FIGS. 13A and 13B are schematic representations of an embodiment of an embossed HME material having four offset rows of protrusions, on which measurements relating to the separation between the protrusions (L1-L6), and the diameter (D) and height (h) of the protrusions are marked. With reference to FIGS. 13A and 13B, the average dimensions and separation between the protrusions was:

TABLE-US-00001 L.sub.1 0.79 mm L.sub.2 2.25 mm L.sub.3 2.92 mm L.sub.4 2.92 mm L.sub.5 2.28 mm L.sub.6 0.97 mm D 1.85 mm h 0.45 mm

[0135] It will be understood that various known methods, such as shadowgraphy, can be used to measure these dimensions.

[0136] All protrusions were formed under substantially identical conditions although their height (h) ranged from 0.41 mm to 0.51 mm. This variation is believed to be indicative of the tolerance of the HME material when forming protrusions and possibly arises due to small changes in pressure depending on the unique conditions at the nip.

[0137] A strip of the embossed HME medium of 73 cm (+/10 mm) in length was then wound into a coil in order to form an HME medium for inclusion into an HME device.

Example 2Embossing a 9.5 mm Wide Strip of HME Material Using the Lower Embossing Roller Depicted in FIGS. 5A and 5B

[0138] The HME material was also embossed using the protocol of Example 1 in which the lower embossing roller was substantially as depicted in FIGS. 5A and 5B. This lower embossing roller also had a diameter of 69.95 mm and circumferential surfaces with a width of 9.5 mm. The projections were in the form of a relatively long cylinder (ie the height of the cylinder is significantly greater than its diameter) having a hemispherical end (see FIGS. 5A and 5B). The apex of each projection extended 1.5 mm from the circumferential surface of the lower embossing roller.

[0139] The HME material was passed through the nip between the embossing rollers in order to produce an embossed pattern made up of a plurality of protrusions on one surface of the HME material that were generally frustoconical in shape, similar to those shown in FIG. 10B or 10C, but with flaps of material remaining at their apex as in FIG. 10D). The protrusions were arranged in four offset rows extending along the length of the strip of HME material.

[0140] The dimensions and distribution of the protrusions was measured at five locations along the embossed strip of HME material using the method used in Example 1. With reference to FIGS. 13A and 13B, the average dimensions and separation between the protrusions was:

TABLE-US-00002 L.sub.1 1.64 mm L.sub.2 3.09 mm L.sub.3 2.96 mm L.sub.4 3.65 mm L.sub.5 3.10 mm L.sub.6 0.94 mm D 1.03 mm h 0.62 mm

Example 3Embossing a 9.5 mm Wide Strip of HME Material Using the Lower Embossing Roller Depicted in FIGS. 6A and 6B

[0141] The HME material was also embossed using the protocol of Example 1 in which the lower embossing roller was substantially as depicted in FIGS. 6A and 6B. This lower embossing roller also had a diameter of 69.95 mm and circumferential surfaces with a width of 9.5 mm. The projections of the lower embossing roller were in the form of a cylinder having a top surface inclined at 45 degrees to its longitudinal axis (see FIGS. 6A and 6B). The apex of each projection extended 1.3 mm from the circumferential surface of the lower embossing roller.

[0142] The HME material was passed through the nip between the embossing rollers in order to produce an embossed pattern made up of a plurality of protrusions in the form of a flap extending from one side of a perforation (see FIG. 10D). The protrusions were arranged in four offset rows extending along the length of the strip of HME material.

[0143] The dimensions and distribution of the protrusions was measured at five locations along the embossed strip of HME material using the method used in Example 1. With reference to FIGS. 13A and 13B, the average dimensions and separation between the protrusions was:

TABLE-US-00003 L.sub.1 1.30 mm L.sub.2 3.10 mm L.sub.3 3.29 mm L.sub.4 3.30 mm L.sub.5 3.05 mm L.sub.6 1.27 mm D 0.97 mm h 0.58 mm

Example 4Embossing a 16 mm Wide Strip of HME Material Using the Lower Embossing Roller Depicted in FIGS. 7A and 7B

[0144] A strip of the HME material 16 mm rather than 9.5 mm wide was also embossed using the protocol of Example 1 in which the lower embossing roller was substantially as depicted in FIGS. 7A and 7B. The lower embossing roller had a diameter of 69.95 mm and a circumferential surface having a width of 16 mm and carrying projections arranged in seven offset rows extending around the circumference of the roller. The projections were in the form of relatively short cylinders (ie the diameter of the cylinder is significantly greater than its height) having hemispherical ends (see FIGS. 7A and 7B). The apex of each projection extended 0.7 mm from the circumferential surface of the roller.

[0145] An upper embossing roller substantially as depicted in FIGS. 3A and 3B having a 16 mm wide circumferential surface and recesses arranged in seven offset rows extending around the circumference of the roller was used in combination with this upper embossing roller.

[0146] The HME material was passed through the nip between the embossing rollers in order to produce an embossed pattern made up of a plurality of substantially hemispherical protrusions on one surface of the HME material. The protrusions were arranged in seven offset rows extending along the length of the strip of HME material.

[0147] The dimensions and distribution of the protrusions was measured at five locations along the HME material using the method used in Example 1. FIGS. 13C and 13D are schematic representations of an embodiment of an embossed HME material having seven offset rows of protrusions, on which measurements relating to the separation between the protrusions (L1-L9), and the diameter (D) and height (h) of the protrusions are marked. With reference to FIGS. 13C and 13D, the average dimensions and distribution of the protrusions was:

TABLE-US-00004 L.sub.1 1.41 mm L.sub.2 3.33 mm L.sub.3 3.31 mm L.sub.4 3.28 mm L.sub.5 1.84 mm L.sub.6 3.37 mm L.sub.7 3.29 mm L.sub.8 3.25 mm L.sub.9 3.87 mm D 0.76 mm h 0.44 mm

[0148] A small difference in average protrusion height can be seen in comparison to example 1 above (example 1-0.45 mm, example 4-0.43 mm), which would indicate a difference in pressure despite the similar conditions and projections used in both examples. This could be a result of different projection distribution/patterns, and/or the wider paper may result in a slightly lower material tension at the nip, even if the tension control assembly was the same in both examples, leading to a lower applied pressure in example 4.

[0149] It will be understood that the invention is not limited to the specific examples described above. For example, an embodiment is considered where both upper and lower rollers contain both projections and depressions, so that protrusions are formed on both sides of the paper. An example of this type of roller is illustrated in FIG. 14, which shows a cutaway section 720 of a roller similar to that illustrated in FIG. 3B, but with raised protrusions 750a provided alternately with the recesses 750b. It will be understood that providing a pair of such rollers allows the creation of protrusions from opposite sides of a paper or other material simultaneously. FIG. 15 shows an example of a section of HME material 800 with protrusions 810a,810b projecting, respectively, from the upper and lower surfaces as shown. The dimensions D and h may be of similar magnitude to the examples already described herein.

[0150] Although introducing some additional complexity, for example in gear timing and design, providing protrusions from both sides of HME material may allow even greater control of the properties of filters formed using such material.