GB2359352A

GB2359352A - A balanced flue terminal

Info

Publication number: GB2359352A
Application number: GB0004064A
Authority: GB
Inventors: Arthur Hoare
Original assignee: DOCHERTY Ltd H
Current assignee: DOCHERTY Ltd H
Priority date: 2000-02-21
Filing date: 2000-02-21
Publication date: 2001-08-22
Also published as: GB0004064D0

Abstract

A balanced flue terminal comprises a first panel 2, having an exhaust outlet 21 attached to a second panel 3 having an air inlet 31, and having a shield 33 to inhibit flow of the exhaust gases into the air inlet. The first panel 3 is preferably disposed at the front with a plurality of the second panels 3 as side panels at least one having an air inlet 31 and shield 33.. Preferably each air inlet 31 is associated with a shield 33 with at least one side panel 3 having two air inlets 31 and shields 33. The air inlets 31 maybe a plurality of slit like apertures of different lengths and the shield may be a louvre 33 formed by stretching or bending the side panel 3. The terminal may be shaped like a truncated pyramid and is fixed to the wall by a detachable base plate 6. A rain shield 5 may also be provided and connected to the base plate 6 the terminal also having a drainage hole H. Preferably the air intake tube 32 has a flared end 323 and annular rib 322. The tube being secured to the base plate 6 by locating the plate between the rib 322 and flared end 323.

Description

2359352 - 1 FLUE TERMINAL The present invention relates to flue terminals

for mounting on walls, and in particular to balanced flue terminals, and to a method for attaching a tube to an apertured plate.

Balanced flue terminals are well known, and an example is shown in Figs. 1 and 2. The terminal comprises a square front panel 2, having an exhaust outlet 21, and four generally trapezoidal side panels 3, each comprising six rectangular air inlets 31. Heat shields 22.23,24 are arranged in front of the front panel 2, supported on spacer tubes which extend through the f ront panel to a base plate 4, to which they are attached by suitable means. The terminal includes a length of exhaust tube 26 which conveys exhaust gases from a flue to the outside world. The known terminal shown in Figs. 1 and 2 is typically of all-aluminium construction. One end of the soft aluminium exhaust tube 26 protrudes through a circular exhaust aperture in the front panel 2 and is crimpedor swaged 261 to attach the tube to the panel. The terminal includes a base plate 4 which is parallel to the front panel, and which is riveted to the side panels 3 and an air inlet tube 32 by means of rivets R. An end of the air inlet tube 32 is received in a circular aperture in the base plate 4, and an annular rib 322 formed around the circumference of the tube 32 prevents it from moving further in the forward direction. The end of the tube 32 is riveted to a flange 401 on the base plate 4. Attached to the base plate 4 is a weather shield 5 which extends underneath the four air inlets 31 of the top side panel 3 nearest the wall W. The lengths of the air intake and exhaust tubes are such that they extend partially into a hole provided in the wall W. In use, the terminal is typically connected to the end of a balanced flue by 2 - means of pliable metal straps 321, screwed to the outer flue tube 320.

The concentric tubes 320,260 of the balanced flue are typically arranged to form overlap joints i with the air intake and exhaust tubes of the shown terminal. The lightweight aluminium terminal is thus held in place against the wall by the straps 321 attached to the balanced flue.

Disadvantages with the above-described terminal are numerous and include the following:

1) The inventor has determined that a significant proportion of the exhaust gases from the exhaust outlet can be drawn back in through the air inlets, reducing the oxygen flow back down the balanced flue.

2) The air inlet apertures in the side panels weaken the side panels and decrease their rigidity. The larger the apertures (to provide increased air intake capacity) the greater this problem becomes. Rigidity considerations thus place a limit on the maximum air intake area that can be provided.

3) As the size of each air intake is made larger, or as the number of air intakes increased, the interior of the terminal becomes increasingly exposed to adverse weather conditions, in particular to rain and high winds. Adequate performance in high winds can thus place a low limit on the maximum air intake area wh ich can be provided for a given size terminal.

4) Flue joints inside the wall may leak, and exhaust gases may become trapped in wall cavities It is an object of the present invention to address the problems associated with the prior art.

According to a first aspect of the present invention there is provided a flue terminal (which may be a balanced flue terminal (BFT)), for wall mounting, comprising a front panel having an exhaust outlet and a side panel having an air inlet, wherein - 3 the side panel further comprises a shield arranged to inhibit flow of exhaust gases from the exhaust outlet into the air inlet.

By providing a shield to inhibit (i.e. disrupt) flow of exhaust gases into the air intake, the oxygen flow back down the balanced flue to which the terminal will be attached is increased. The proportion of exhaust gases being drawn back into the air intake is reduced. By disrupting the flow of exhaust gases into the air inlet, the shield improves the mixing of exhaust gases with 'clean"' air (i.e. increases the dilution of the exhaust gases) before they can be drawn into the air intake. In other words, the shield prevents combustion products from being drawn directing back into the terminal.

Preferably the flue terminal comprises four side panels and a generally rectangular front panel (which may be square).

More preferably, the side panels are generally trapezoidal and angled with respect to the front panel such that the front panel and side panels together form a boxlike structure which generally resembles a truncated, four-sided pyramid (with the exhaust outlet being arranged at the top of the box, and the air inlets being arranged on its sides).

This arrangement has been determined by the inventor to provide improved performance in high winds, especially when the side panels are louvred, compared with embodiments in which the side panels and front panel form a rectangular box.

Preferably, each side panel comprises a plurality of air inlets, each one shielded by a respective shield. Thus, a total desired air intake area can be divided between a number of small apertures, enabling the rigidity of the side panels to be maintained, whilst still retaining the advantage of inhibiting intake of exhaust gases.

- 4 On a single side panel, the plurality of air inlets may have the same or different areas, e.g. they may be generally rectangular with the same widths but different lengths.

Preferably, each shield is further arranged to inhibit entry of rain and/or wind into the respective air inlet. The shield may, for example, be a cover member attached to the side panel wall and extending outwards and rearwards, at least partially over an air inlet, towards a wall on which the flue terminal is mounted in use. The cover member and side panel wall may thus define an effective air inlet aperture which faces the wall, i.e. faces away from the front panel, out of which combustion products flow.

Preferably, each shield is a louvre, and preferably each louvre acts as a cover member for its respective air inlet.

Each louvre may be a separate slat, attached to the side panel wall, but preferably the side panel and louvre are integral. The louvres may be formed by slitting the side panels and stretching and/or bending the side panel material. This technique is convenient, and enables a plurality of shielded air inlets to be provided, which together provide a significant total air inlet area, without weakening the side panels unacceptably and without unacceptably increasing exposure of the inside of the terminal to wind and rain. Louvres formed in this way can increase the rigidity of the side panels providing the double advantage of increased air intake area and increased rigidity.

Preferably, the flue terminal comprises a detachable wall-mounting plate. This can be permanently fixed to an outside wall. The remainder of the flue terminal is then mounted/demounted on the wall by simple attachment/detachment to or from the wall plate. This arrangement provides the advantages - 5 that the full weight of the flue terminal is supported by the wall (and so no strain is placed on the balanced flue on the other side of the wall) and that mounting/demounting is facilitated.

Advantageously, the flue terminal further comprises a base plate arranged parallel to the front panel, and a weather shield attached the base plate and extending towards the front panel at least as far as a rear edge of the shield shielding an air inlet closest to the front panel. In a four-sided terminal, the weather shield is arranged under the air inlets on the top side panel, and intercepts all rain falling vertically through the top side air inlets. The weather shield thus inhibits the entry of rain into the air intake tube.

Preferably, the terminal comprises an air intake tube attached to the base plate by means of an annular rib and flared end portion formed on the tube, on either side of a circular aperture in the base plate.

The tube has a diameter substantially equal to that of the circular aperture, and the annular rib and flared end portions have larger diameters so that the base plate is trapped between them.

Advantageously, this jointing method can be performed in situ, i.e. the tube may be partially inserted through the aperture and the rib and flared end can then be formed by stretching (expanding) the tube radially. This provides a simple, strong mechanical joint between the tube and plate, and no riveting, welding or other jointing technique is required. Furthermore, the flared end portion of the air intake tube improves flow of air from the air inlets into the tube.

Similarly, the flue terminal may comprise an exhaust tube, partially protruding through an aperture in the front panel and jointed to it in the same way. The flared end portion of the exhaust tube provides - 6 improved exhaust gas flow out of the terminal.

Preferably, the air intake and exhaust tubes are concentric and are each long enough to extend through a wall on which the terminal is to be mounted. Thus, no joints are necessary inside the wall.

Preferably, the flue terminal further comprises a closure plate adapted for mounting on an inside surface of the wall and including an aperture for receiving a protruding end portion of the air intake tube. The closure plate may thus seal an aperture cut or core-drilled in a wall to receive the terminal, and may contribute to the mechanical support of the terminal on the wall.

Preferably, the terminal further comprises a plurality of heat shields, arranged in front of the front panel and being supported by a plurality of spacer tubes or lengths of studding (or any other suitable means), the spacer tubes (studding, support means) terminating at, or substantially at, the front panel. Thus the heat shields may be supported only by the front panel, as the support means (tubes, studding) does not extend to the base plate (unlike the prior art arrangement). Louvred side panels contribute to the rigidity of the terminal structure and can enable the simplified heat shield support structure to be employed.

A second aspect of the present invention provides a flue terminal, for wall mounting, comprising a front panel having an exhaust outlet and a plurality of louvred side panels, the louvred side panels each comprising louvres arranged to permit air intake through the side panels and to inhibit intake of exhaust gases from the exhaust outlet.

Preferably, the louvres are arranged to define a plurality of air intake apertures, each air intake aperture, in use, facing a wall on which the terminal is mounted.

7 - is According to a third aspect of the present invention there is provided an attachment method for attaching a cylindrical tube to a plate having a circular aperture, the method comprising the steps of inserting an end of the tube through the aperture, flaring out said end in front of the plate to a diameter greater than that of said aperture and stretching said tube to form an annular rib behind said plate, said annular rib having a diameter greater than that of said aperture, whereby said plate is held between said annular rib and the flare end.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Fig.1 is a perspective view of a balanced flue terminal according to the prior art;

Fig.2 is a schematic cross-section of the terminal of Fig.1 in use; Fig.3 is a schematic expanded perspective view of a balanced flue terminal embodying the present invention; Fig.4 is a cross-section of the embodiment of Fig.3 in use; Fig.5 is a plan view of a side panel of the first embodiment; Fig.6 is a cross-section of the side panel of Fig.5; Fig. 7 is a plan view of the weather shield of the first embodiment; Fig. 8 is a crosssection of the weather shield of Fig. 7; Fig. 9 is a plan view of a sheet from which the wall plate of the first embodiment is fabricated; Fig.10 is a cross-section of the wall plate of the first embodiment; Fig. 11 shows detail of the wall plate of Fig. 10; Fig. 12 shows corner detail of the wall plate 8 - sheet of Fig.9; Fig.13 shows a plate from which the front plate of the first embodiment is fabricated; Fig.14 is a cross-section of the front plate of the first embodiment; Fig.15 is a plan view of a sheet from which the discharge plate (heat shield) of the first embodiment is fabricated; Fig.16 is a cross-section of the discharge plate of the first embodiment; Fig.17 is a plan view of a metal sheet from which the front heat shield of the first embodiment is fabricated; and Figs.18 and 19 are schematic diagrams of the first embodiment in use.

Referring now to Fig.3, a first embodiment of the present invention comprises a front plate 2 and four louvred side panels 3 arranged to form a box-like structure resembling a truncated four-sided pyramid.

The louvres 33 form shields over air intakes and inhibit intake of exhaust gases expelled from an aperture in the front plate. Three heat shields 22,23,24 are arranged in front of the front plate 2, and are supported on spacer tubes 25. The first and second heat shields 22,23 form a barrier to the exhaust gases, forcing the gases to escape to the sides of the terminal. The third heat shield 24 is a discharge plate, and contains a large central aperture through which the exhaust gases can pass. The terminal includes an air intake tube 32 which protrudes to the rear of the box-like structure. The terminal includes a wall plate 6. The wall plate 6 has a flat plate portion 65 which includes a circular aperture 64 through which the air intake tube can pass. The flat plate section 65 includes a plurality of fixing holes 63 by means of which it may be screwed to a wall. The wall plate also includes side walls 9 61, each including fixing holes 62. In use, the wall plate is first secured to a wall, around a suitable aperture. The air intake tube 32 is then inserted through the circular aperture 64 until holes 36 on each side panel 3 of the terminal are brought into alignment with the fixing holes 62. Nuts 621 (or other suitable means) are attached to the inside surfaces of the side walls 61, aligned with the fixing holes 62. Thus, when the side panel fixing holes 36 are aligned with those on the wall plate, the box structure is secured to the wall plate by means of bolts or screws passing through the aligned holes, and engaging the nuts 621. The wall plate may thus remain secured to a wall, whilst enabling the remainder of the terminal to be easily attached/detached as necessary.

Turning now to Fig.4, the terminal is shown fixed to a cavity wall W. The wall plate 6 is secured to the wall by means of screws S. The second.heat shield 23 and the third heat shield (discharge plate) 24 are supported by spacer tubes 25 which terminate at the front plate 2. Lengths of studding 251 pass through the spacer tubes and nuts N on each end of the lengths of studding 251 hold the heat shield assembly in place.

The front plate 2 includes a circular aperture through which an end 263 of the exhaust tube 26 protrudes towards the heat shield. The exhaust tube 26 has an outer diameter substantially the same as the diameter of the circular aperture in the front plate 2. The exhaust tube 26 is formed from stainless steel and has been radially stretched in situ to form an annular rib 262 behind the front plate and a flared end section 263 in front of the front plate, which together form a rigid joint between the front plate and exhaust tube 26. This joint is mechanical, and no soldering or welding is required, thereby simplifying fabrication. The annular rib 262 and flared end portion 263 are formed at the same time by a tool with suitably shaped, radially expanding jaws. The flared out end section 263 of the exhaust tube 26 provides improved flow of exhaust gases out of the terminal.

The side panels 3 are spot welded to the front panel 2, and each include two air inlets 31. Each air inlet is shielded by a louvre 33, which extends from the front edge of each air inlet outwards and towards the rear of the terminal. Thus, the louvres 33 define air inlet apertures 311 which face towards the wall on which the terminal is mounted, i.e. which face away from the front panel from which combustion products are ejected.

The side panel 3 at the bottom of the box structure is provided with drainage holes H adjacent its lower edge. This prevents water from being collected in the corner of the box structure, between the base plate 4 and the bottom side panel 3.

The base plate 4 includes a circular aperture through which an end 323 of the air inlet tube 32 protrudes. The air inlet tube 32' is attached to the base plate 4 in the same way as the exhaust tube attached to the front plate, the annular rib 322 flared end portion 323 being formed by a tool of increased diameter.

The air intake tube 32 and exhaust tube 26 are concentric, and air is drawn into the terminal and passes down the annular space between the two tubes.

A weather shield 5 is attached to the base plate 4 and extends towards the front plate. In this example the weather shield extends as far as the rear edge of the front louvre 33, but in other embodiments may extend even further. This weather shield arrangement further inhibits entry of rain into the air intake tube, and improves performance in high winds.

is and The side panels 3 are spot welded to the base plate 4, and the side panels and base plate are then attached to the side walls 61 of the wall plate 6 by means of screws/bolts engaging with the captive nuts on the inner surfaces of the side wall 61. Any other suitable attachment means may be used, and if easy demountability is not required, rivets may be employed for example.

The air intake tube 32 and exhaust tube 26 each have lengths significantly greater than the thickness t of the wall W on which the terminal is mounted, and protrude beyond its inner surface, thereby avoiding the need to make any joints inside the wall.

Turning now to Fig.5, the side panels of the first embodiment include two louvres 33 of substantially the same dimensions, although in other embodiments the number and sizes of the louvres may be different. The side panel 3 is formed from a single stainless steel sheet and includes two parallel sections 301,302 connected by the portion which includes the louvres 33. The louvres 33 are formed by slitting and stretching and bending the stainless steel sheet. This is a convenient fabrication procedure, and provides a side panel with improved rigidity. In this example the louvres are thus integral with the remainder of the side panel, but in other arrangements the shields may be formed from separate members.

Fig.6 shows a cross-section of the side panel, and provides further detail of the shape and dimensions of the features. Preferred dimensions are indicated on Figures 5 to 17 in millimetres.

Fig.7 shows the weather shield of the first embodiment. The weather shield 5 is formed from a generally trapezoidal sheet with a single bend to form a vertical section 51 and forward projecting portion. Any rain entering the air inlets 31 in the f irst embodiment hits the weather shield and runs off in the forward direction, then dropping on to the exhaust tube 26 or past each side of it. The annular ribs and flared end sections of the exhaust and air intake tubes inhibit ingress of water, guiding water around the circumferences of the tubes to their lower points, from which the water runs off and then escapes.

Fig.8 shows a cross-section of the weather shield 5. The vertical portion 51 is spot welded to the base plate 4.

Fig.9 shows the metal sheet from which the wall plate 6 is fabricated. The sheet is cut at the corners, as shown in Fig.12, to provide wall sections 61 which are bent to form the structure whose cross-section is shown in Fig.10. Detail of the fixing holes 62 in each side wall section 61 is shown in Fig.11. The front plate 2 has similar construction, and features of the sheet from which it is fabricated are provided on Fig.13, with the cross-section shown in Fig.14.

Fig.15 shows the stainless steel sheet from which the discharge plate 24 is fabricated. The plate 24 includes a circular aperture 242 and a plurality of side flaps 241 which are folded over, through approximately 180', to form the structure whose cross-section is shown in Fig.16. This fabrication technique provides rounded, safe edges to the plate.

Fig.17 similarly shows the metal sheet from which the front heat shield 22 is fabricated. Flaps 221 are again provided, and are folded to form rounded, safe edges.

Fig.18 shows the terminal guard mounted on a wall W constructed from brick with a cavity C. Also shown is a closure member 7 which comprises a radial flange 71 which screws to the wall W, and an annular portion 72 which receives the air inlet tube 32 protruding through the aperture B in the wall. The closure member 7 thus tidies the aperture B and further supports the terminal on the wall so that strain is not transmitted to the balanced flue 8 to which it is attached. Fig.18 also shows a gas fire attached to the balanced flue 8.

Fig.19 similarly shows the terminal mounted on a wall which has wooden skins with insulating material in between. The aperture B in the wall W through which the terminal protrudes is lined with a liner element L.

It will be apparent that in certain embodiments of the present invention, the ends of the air intake and exhaust tubes are belled (i.e. flared outwards) to retain the base and front plates, and form mechanical joints which require no soldering or welding. The belled end portions help guide air in and exhaust gases out. Thus, the flared arrangement provides better gas flow through the terminal. Furthermore, helps prevent water run-in.

The side panels may be formed by pressing of metal sheet. Preferably, the terminal is fabricated from stainless steel sheet and incorporates spot welds. A preferred embodiment provides a balanced flue terminal for a gas fired stove. The terminal may include a wall plate which is screwed to the outside of a wall, and the terminal may be attached by passing the flue pipe through the hole in the plate and securing with fixing screws.

The wall plate may include threaded bushes for receiving fixing screws, and the remainder of the terminal may be a push fit over the wall plate. The wall mounting plate also provides a cover for the hole drilled in the wall to receive the terminal.

For a particular application, there will be a particular requirement for total air intake area. The number and sizes of air inlets can be adjusted accordingly, and preferably this can be achieved by 14 adjusting the size and number of the louvres on the side panel. The louvres allow bigger air takes to be provided, whilst also providing weatherproofing advantages. With previous arrangements, there were significant limits on how large the air intake slots could be made.

It will be apparent that each feature of the invention described may be incorporated in embodiments of the invention independently of, or together with other described features.

Furthermore, it will be apparent that the front (first)panel may be directly or indirectly attached to the or each side (second) panel, for example by means of spot welds, or by means of an intermediate member or members (e.g. further panels).

Claims

CLAIMS:

1 A flue terminal, for wall mounting, comprising: a f irst panel having an exhaust outlet; and a second panel attached to the first panel and having an air inlet, wherein the second panel further comprises a shield arranged to inhibit flow of exhaust gases from the exhaust outlet into the air inlet.

2. A flue terminal in accordance with claim 1, wherein the first panel is a front panel, and the second panel is a side panel.

3. A flue terminal in accordance with Claim 2, comprising a plurality of side panels attached to the front panel, at least one of the side panels having an air inlet and a shield.

4. A flue terminal in accordance with Claim 3, wherein the side panels are inclined with respect to the front panel such that the front and side panels together form a box-like structure which generally resembles a truncated pyramid.

5. A flue terminal in accordance with claim 3 or claim 4, comprising four side panels and a generally rectangular front panel.

6. A flue terminal in accordance with any one of Claims 2 to 5, wherein at least one of said side panels comprises at least one water drainage hole in addition to an air inlet or air inlets.

7. A flue terminal in accordance with any one of Claims 3 to 6, wherein at least one side panel comprises a plurality of air inlets and a plurality of 16 - shields, each shield being associated with a respective air inlet.

8. A flue terminal in accordance with Claim 7, wherein at least one side panel comprises two air inlets and two shields.

9. A flue terminal in accordance with Claim 7 or Claim 8, wherein said plurality of air inlets comprises a plurality of slit-like apertures having different lengths.

10. A flue terminal in accordance with any preceding claim, wherein the or each shield is further arranged to inhibit entry of rain into the air inlet.

11. A flue terminal in accordance with any preceding claim wherein the or each shield is a louvre.

12. A flue terminal in accordance with Claim 11, wherein the louvre is formed by stretching and/or bending the side panel or second panel material.

13. A flue terminal in accordance with any preceding claim, further comprising a detachable wall-mounting plate, the wall-mounting plate being adapted for fixture to a wall.

14. A flue terminal in accordance with any preceding claim, further comprising a base plate arranged parallel to the front or first panel, and a weather shield attached to the base plate, the weather shield extending towards the front or first panel, beneath the air inlet or air inlets on a side panel, to or beyond the rear edge of the shield shielding the air inlet closest to the front or first panel.

15. A flue terminal in accordance with any preceding claim, further comprising: a base plate arranged parallel to the front or first panel and having a circular aperture; and an air intake tube having an outer diameter substantially equal to the diameter of the circular aperture, the air intake tube being attached to the base plate by means of a flared end portion of the tube, protruding through the circular aperture towards the front or first panel and constraining movement in a first direction, and by means of an annular rib, f ormed on the tube behind the base plate and constraining movement in a second direction.

16. A flue terminal in accordance with any preceding claim wherein the front or first panel comprises a circular exhaust aperture, and further comprising an exhaust tube having an external diameter substantially equal to the diameter of the exhaust aperture, the exhaust tube being attached to the front or first panel by means of a f lared end portion and annular rib formed on the exhaust tube on either side of the front or first panel.

17. A flue terminal in accordance with any preceding claim, comprising an air intake tube and an exhaust tube, wherein said air intake and exhaust tubes are arranged concentrically, with the exhaust tube inside the air intake tube.

18. A flue terminal in accordance with Claim 17, wherein the air intake tube and exhaust tube each have a length greater than a nominal thickness of a wall on which the terminal is to be mounted.

18 -

19. A flue terminal in accordance with Claim 18, further comprising a closure plate adapted for mounting on an inside surface of said wall and adapted to receive the air intake tube.

20. A f lue terminal in accordance with any preceding claim, further comprising a plurality of heat shields, arranged in front of the front or first panel and being supported by spacer tubes, the spacer tubes terminating at the front or first panel.

21. A flue terminal, for wall mounting, comprising: a front panel having an exhaust outlet; and a plurality of louvred side panels, the louvred side panels each comprising louvres arranged to permit air intake through the side panels and to inhibit intake of exhaust gases from the exhaust outlet.

22. A flue terminal in accordance with Claim 21, comprising a generally rectangular front panel and four louvred, generally trapezoidal side panels, the front and side panels being arranged as a boxlike structure resembling a truncated four-sided pyramid.

23. A flue terminal in accordance with Claim 21 or Claim 2.2, wherein said louvres are arranged to define a plurality of air intake apertures, each said air intake aperture, in use, facing a wall on which the BFT is mounted.

24. A flue terminal in accordance with any one of Claims 21 to 23, wherein each side panel comprises two louvres.

25. A flue terminal in accordance with any preceding claim, wherein the flue terminal is a balanced flue 19 - terminal.

26. An attachment method for attaching a cylindrical tube to a plate having a circular aperture, the method comprising the steps of: inserting an end of the tube through the aperture; flaring out said end in front of the plate to a diameter greater than that of said aperture; and stretching said tube to form an annular rib behind said plate, said annular rib having a diameter greater than that of said aperture, whereby said plate is held between said annular rib and the flared end.

27. A flue terminal substantially as hereinbefore described with reference to the accompanying drawings.

28. An attachment method substantially as hereinbefore described with reference to the accompanying drawings.