GB2062049A

GB2062049A - Foam coating and levelling technique

Info

Publication number: GB2062049A
Application number: GB7937660A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-10-31
Filing date: 1979-10-31
Publication date: 1981-05-20
Also published as: GB2062049B

Abstract

A method is provided of foam coating a surface to present a generally flat finish, comprising securing a succession of parallel spaced apart battens (12) to said surface, foam coating the surface between said battens to a depth, which, when the foam sets, is at least equal to the depth of the battens, whilst leaving at least part of the front surface of each batten exposed; and levelling the rigid set foam coating by taking an elongate cutting member (15) which is long enough to span at least two successive battens, positioning opposite ends of said member on said front surfaces of said battens, and drawing said cutting member along said battens, so removing any part of said foam coating which projects beyond said front surfaces of said battens, leaving said foam coating substantially level with said front surfaces of said battens. <IMAGE>

Description

SPECIFICATION Foam coating and levelling technique The invention relates to foam coating techniques.

It is already well known to coat a wall, floor or ceiling of a building with a ployurethane foam which acts as a very effective heat-insulating medium and which, when set and properly treated can also form a substrate for a number of external final finishing coats. In one known example, two low viscosity liquids, namely an isocyanate and a resin blend, are introduced together, foamed, and sprayed onto the wall to a depth of approximately 25 mm. The foam emerges initially as a wet sticky liquid which clings to the wall and, within minutes, expands up to thirty times its original volume and sets to provide a rigid low density homogeneous mass over the entire area of the wall. Such foams have very high adhesive properties and form an excellent insulating coating.

Once set, the foam can be levelled to provide a suitable substrate or base layer for a final rendering and/or decorative textured finish. It is however difficult to leave the foam accurately over the entire coated area - skilled labour has to be used, since this is a highly skilled job somewhat akin to traditional hand-plastering, and the need for skilled labour inevitably adds considerably to the overall cost of coating and finishing the surface in question.

Conversely it is not, in general, possible to render and finish-texture the foam coating without levelling, because the rapid and violent expansion of the sprayed foam causes it to set with a generally uneven and randomly-contoured outer surface. Such a surface can be directly rendered and finish-textured only in circumstances where randomly-contoured final finish is deliberately sought. In general, this is not the case, and the final surface finish is most often desired to be as flat as possible.

The invention seeks to provide a method of foam-coating a surface (such as an internal or external wall or floor, or ceiling, of a building) and of levelling the foam coating, once it has set, relatively quickly and cheaply whilst still achieving an accurate levelling of the entire foamed area.

To that end, and in its broadest aspect, the invention provides a method of foam-coating a surface to present a generally flat finish, the method being characterised by the steps of securing a line of parallel spaced-apart battens along the surface; foam-coating the surface to a depth, which when the foam sets, is at least equal to the depth of the battens whilst leaving at least part of the front surface of each batten exposed; and levelling the rigid set foam coating by taking an elongate cutting blade which is long enough to span at least two successive battens, positioning opposite ends of the blade on said front surfaces of said battens, and drawing the blade down the battens.

The expression "cutting blade", whilst clearly including elongate sharpened knives, is also intended to include within its scope such implements as elongate reciprocable saws; and elongate hot-wire cutters.

In a presently preferred, but not essential, method of putting the invention into practice, the area between two battens is spray-coated with polyurethane foam, the area between the second of those battens and the next batten is left uncoated, and the area between said next batten and the batten after that is coated; so that, along the entire line of battens, in any one spraying operation, a succession of alternate foamed and unfoamed areas will be created. When the foam in the foam-coated areas has set, the set coating is levelled as outlined above; and the uncoated areas are then foamed and levelled in the same way.

An advantage of this preferred method is that it is easier to position the cutting blade, and draw it down the batten to level the foam coating, if the areas adjacent each end of the cutting blade are themselves uncoated. The ends of the blade are then not obstructed as they are drawn over the battens. By the same reasoning when the initiallyuncoated alternate areas come to be levelled, the ends of the cutting blade are once again unobstructed because they are being drawn over two already-levelled areas adjacent each respective end of the area which is being levelled by the blade.

It is also presently preferred, although again not essential, to make the battens of the same polyurethane foam with which the rest of the surface is to be coated inbetween the battens.

One advantage of this is that a homogeneous foam coating over the entire surface is eventually achieved. Another advantage is that the foam battens are light, and easily handled. They can be glued to the surface, or they could conceivably be sprayed onto the surface if the surface were first shuttered to define the area within which the foam is sprayed to create the battens. Yet another advantage is the fact that the subsequently sprayed foam coating itself not only grips the wall to which it is sprayed but also grips the sides of the adjacent battens: the batten is thus securely held to the wall.

Alternatively however the battens could be formed of wood, metal, an alternative synthetic plastics material to the foam itself, or any other suitable material.

The front surfaces of the battens (i.e. the surfaces which, when the battens are fixed to the surface to be foam-coated, face outwardly) may themselves be sufficiently flat and true to serve as guides down which the ends of the cutting blade are drawn. However, in certain circumstances -- for example where the battens are made from the very light low-density and easily-damaged foam itself -- elongate flat and relatively rigid guides may be inserted into the front surfaces of the battens, so that the ends of the cutting blade can be drawn down the guides without damaging the battens themselves and without wandering from a substantially linear path of travel.

Such guides can subsequently be removed, and any necessary infill can then be applied to the spaced left by the removed guides. Alternatively the guides may be used to effectively set the level of a subsequent rendering and/or finish-texturing coat. Alternatively again the guides may be removed, and replaced with further guides which then set the level of any further coat or coats.

One foam-coating and levelling method embodying the invention will now be described, by way of example only, and with reference to the accompanying drawings. In the drawings: Figure 1 shows a wall to which battens have been secured prior to foam-coating; Figures 2, 4 and 6 show the wall in perspective at various stages of coating and finishing; and Figures 3 and 5, both drawn to a larger scale than the rest of the Figures, show the wall when viewed in cross-section and from above, again at different stages of coating and finishing.

In Figure 1, the external wall surface (generally referenced 11) of a building is to be foam-coated with a polyurethane spray of known kind. The wall is elongate, and is substantially linear in both the horizontal and vertical directions. It is built of brick, and has been pointed.

A series of elongate and generally rectangular battens 12 is secured to the wall 11 along its length. The battens 12 are parallel with one another, and are spaced from one another by substantially the same amount in each case. Each batten is made of the same foamed polyurethane with which the wall as a whole is to be coated. It is rectangular in cross-section and is linearly elongate.

The battens 12 are glued to the wall 11 using suitable adhesives which are known in themselves. The known polyurethane foam is then spray-applied to the areas inbetween the battens 12, but missingout alternate ones of these areas.

as shown in Figure 2. The foam is applied to a depth of approximately 25 mm. which is also the depth of each batten. Deliberate over-foaming is practised, to ensure that each foamed area is coated to at least the depth of the battens.

The result, as shown in Figure 2, is a succession of alternate foamed and unfoamed areas referenced respectively A and B.

A metal guide 13 is then inserted into the front edge of each batten 12. The guides are knifeedged, and can simply be pressed into the relatively soft foam surface of each batten. In cross-section, as shown in Figure 3, each guide is T-shaped, the base 1 3a of the T is sharpened and is pressed into the front surface of the batten 12.

Each guide is pushed into the front surface of the foam batten until the underside of the bar of the T is hard against the front surface. All the guides are then substantially in line with one another in the vertical and horizontal directions, and are parallel to one another.

The front surface of each groove 13 incorporates an undercut groove 14. The groove 14 is trapezoidal, open-ended, and extends along the entire length of the front surface of each guide.

An elongate sharpened cutting blade 1 5 is provided, at each of its opposite ends, with a peg 1 5a which is shaped to engage in the trapezoidal undercut groove 14. As shown in Figure 4, the blade pegs can thus be positioned in two of the guides, at the top thereof, and can then be drawn slowly and carefully down the entire length of the guides to the bottom of the wall (as indicated by vertical arrows in Figure 4).

As the blade 1 5 descends, it automatically slices off the top layer of the foam coating 13, and leaves behind a flat and substantially undamaged surface indicated in Figures 3 and 4 as A'. Each foamed area A is levelled in this way.

The blades 1 5, at the end of their travel, are then removed from the guides 13. The remaining areas 13 of the wall 11 are foam-sprayed. The foam is allowed to set. The blades 1 5 are replaced within the guides, at the top ends of the guides, this time spanning the newly-foamed areas, and are drawn down the guides as before so that the newly-foamed areas B are again levelled with the battens 12 and with the previous areas A'.

The knife-edge guides 13 are then withdrawn from the foam battens 12. Because of the inherent resilience of the foam, the slits which accommodated the knife edges tend immediately to close. The foamed levelled areas, and the battens, between them then present a substantially uninterrupted and homgeneous rigid low-density foam coating, with a flat surface over its entire area, indicated as A" in Figure 5.

Another, and different, set of guides, referenced 16, is then inserted into the slits created by the original guides 1 3. The new guides, shown in Figure 5, are again substantially of T cross-section.

However the base 1 6a of the T is rounded, not sharpened. In addition, the head of the Y is plain, unlike that of the first set of guides 13. In use, therefore, the second set of guides 16, when inserted into the slits created by the first set of guides 13, will travel as far as the base of each slit; and the head of the guide 1 6 in each case will protrude from the front surface of the foam batten 12 as shown.

The protruding front surface 1 6b of each of these second guides 1 6 then effectively sets the level for a rendered coating C (Figure 5) which is applied to the previously levelled foam surface A".

Once the rendering has been initially applied, to at least the level of the protruding front surfaces 1 6b of the guides 16, a flat bar (not shown) can be drawn down the guides 1 6 from top to bottom thereof to skim-level the surface of the still-wet rendered coating, in the same as the set foams At were sliced level.

Again, therefore, highly skilled labour is not needed in order to achieve an acceptably flat final surface finish on the rendered coating.

The protruding second set of guides 1 6 are then removed from the battens 12, the gaps left by these guides (in the rendering C) and the foam battens 12) are filled in, and the entire rendered surface is oversprayed or otherwise coated with the desired final texture finish.

This final finish, and the rendering itself can be selected from a wide range of proprietary known coatings. It will of course be borne in mind that the final coatings must not be of an unduly high density, because they have to be supported by the foam coating beneath them. The properties of known foam coatings, however, are such that a very wide range of proprietary renderings and/or final texture finishings can safely be applied to them.

Figure 6 shows the resultant series of coatings on the wall 11, from the homogeneous foam coating A" through the rendering C to the final texture-finish D.

Such features as fall pipes, window frames and windowsill present no undue problems. These items can be battened around each side, enabling the foam coating A" and the rendering C to be applied; the guides (if any) and the battens (if necessary) can be removed; and any necessary filling-in to the very edge of the fall pipe or window can then be carried out by hand. The final texture-finish D can then be applied, either by hand or tif the fallpipes and windows are suitably masked) by spray.

Modifications may be made to the method described and illustrated. For example, the guides 13, instead of incorporating any form of grooved head, could simply be plain T-guides similar to the later set of guides 1 6. In such a case, the heads of the plain T-guides 13 would be, say, not more than 2 mm. deep. A plain (but sharp-edged) elongate flat blade could then be drawn down the flat front faces of the plain T-guides 1 3 to level the set foam coating between adjacent guides, the blade simply being pressed constantly against the front faces of the guides (like the flat bar against the guides 16) without being positively retained by the guides 1 3 during its travel. Such a blade would not then need to be offset, as the Figure 3 blade is offset; but the subsequent render-coating guides 1 6 would have heads whose depth would equal the desired depth of render plus the thickness of the heads of the plain guides 13.

Claims

1. A method of foam coating a surface to present a generally flat finish, comprising securing a plurality of substantially parallel, spaced-apart battens along the surface; foam coating the surface to a depth, which, when the foam sets is at least equal to the depth of the battens, whilst leaving at least part of the front surface of each batten exposed; and levelling the rigidly set foam coating by taking an elongate cutting member which is long enough to span at least two successive battens, positioning opposite ends of the member on said front surface of said battens, and drawing said member along the front surfaces of said battens, so removing any part of said foam that, when set, projects beyond the front surfaces of said battens.

2. A method according to claim 1 wherein said elongate cutting member is in the form of a sharpened knife.

3. A method according to claim 1 wherein said elongate cutting member is in the form of a reciprocable saw.

4. A method according to claim 1 wherein said elongate cutting member is in the form of a hotwire cutter.

5. A method according to any of the preceding claims wherein the surface is first foam coated to the extent that successive areas between battens are alternately coated and uncoated and then, after levelling the coated areas, remaining areas are coated and levelled.

6. A method according to any of the preceding claims wherein said battens are wood, metal, or a synthetic plastics material.

7. A method according to any of the preceding claims wherein said battens are of the same material as the material with which said surface is being coated.

8. A method according to any preceding claim wherein coating is a polyurethane foam.

9. A method according to any preceding claim wherein said coating is applied to said surface by spraying.

10. A method according to any of the preceding claims wherein each of said battens has a front surface which is capable of acting as a guide down which an end of the cutting member may be drawn.

11. A method according to any of the preceding claims up to claim 10 wherein elongate flat and relatively rigid guides are attached to said front surfaces of said battens, for guiding the path of the cutting member.

12. A method according to claim 11 wherein said guides are detachabiy attached to said front surfaces of said battens.

13. A method according to claim 1 and substantially as herein described.

14. Apparatus according to claim 1 3 and substantially as herein described.

1 5. Apparatus for use in foam coating a surface to present a generally flat finish, substantially as described with reference to the accompanying drawings.

14. A method of foam coating a surface substantially as described with reference to the accompanying drawings.

1 5. Apparatus for the foam coating of a surface to present a generally flat finish, the apparatus comprising a plurality of battens, each batten carrying guide means for cooperating with one end of an elongate cutting member to be drawn along the front surfaces of two of said battens when they are secured to a surface substantially parallel and a spaced-apart positions.

1 6. Apparatus according to claim 1 5 and substantially as herein described.

1 7. Apparatus for use in foam coating a surface to present a generally flat finish, substantially as described with reference to the accompanying drawings.

New claims or amendments to claims filed on 8th Jan 1981.

Superseded claims 1-17.

New or amended claims:- 1-15.

1. A method of foam coating a surface to present a generally flat finish, comprising securing a plurality of substantially parallel, spaced-apart battens along the surface, said battens being formed of a foam material; foam coating the surface to a depth which, when the foam sets, is at least equal to the depth of the battens, whilst leaving at least part of the front surface of each batten exposed; and levelling the rigidly set foam coating by taking an elongate cutting member which is long enough to span at least two successive battens, positioning opposite ends of the member on said front surfaces of said battens, and drawing said member along the front surfaces of said battens, so removing any part of said foam that, when set, projects beyond the front surfaces of said battens.

6. A method according to any of the preceding claims wherein said battens are of the same material as the material with which said surface is being coated.

7. A method according to any preceding claim wherein the coating is a polyurethane foam.

8. A method according to any preceding claim wherein said coating is applied to said surface by spraying.

9. A method according to any of the preceding claims wherein elongate flat and relatively rigid guides are attached to said front surfaces of said battens, for guiding the path of the cutter member.

10. A method according to claim 9 wherein said guides are detachably attached to said front surfaces of said battens.

11. A method according to claim 1 and substantially as herein described.

12. A method of foam coating a surface substantially as described with reference to the accompanying drawings.

13. Apparatus for the foam coating of a surface to present a generally flat finish, the apparatus comprising a plurality of battens, said battens being of a foam material, each batten removably carrying guide means for co-operating with one end of an elongate cutting member to enable the cutting member to be drawn along the front surfaces of two of said battens when they are secured to a surface substantially parallel and at spaced-apart positions.