WO1991013770A1

WO1991013770A1 - Method and means for removing layers of paint from a wood surface

Info

Publication number: WO1991013770A1
Application number: PCT/SE1991/000166
Authority: WO
Inventors: Birger Ericson
Original assignee: Fasadteknik International Efo Ab
Priority date: 1990-03-05
Filing date: 1991-03-04
Publication date: 1991-09-19
Also published as: NO178847C; SE9000763D0; SE465768B; CA2081376A1; FI93709C; FI923986A0; NO178847B; FI923986A; FI93709B; SE9000763L; NO923361D0; NO923361L

Abstract

A method and a means for removing layers of paint from a wood surface (10), the layers of paint comprising a base layer of oil paint. The paint is softened by radiation by means of at least one source (24) of infra-red radiation. Immediately thereafter, the paint is removed mechanically from the wood surface (10). The means comprises a carrier (23) for one or more sources (24) of infra-red radiation, means (14-16) for guided travel of the carrier in the horizontal plane along the facade (10), and means (19-21) for guided travel of the carrier in the vertical plane along the facade (10).

Description

TITLE

METHOD AND MEANS FOR REMOVING LAYERS OF PAINT FROM A WOOD

SURFACE

TECHNICAL FIELD The present invention relates to a method for removing layers of paint from a wood surface, said layers of paint comprising a base layer of oil paint. The invention also comprises a means for executing the method.

STATE OF THE ART When restoring wood surfaces on old houses, it is nor¬ mally obligatory to strip of a number of layers of ugly, cracked and flaking oil- and/or plastic-based paint. Nor¬ mally all layers of paint have to be completely stripped from the face of the wood, so that existing rot damages can be discovered.

There are several methods to remove old paint, but no existing method is free from problems. For example, paint can be stripped by scraping or sanding, either involving a large use of expensive labour or spreading of environ- mentally hazardous dust and disturbing noise. Previously, a blow torch was used to burn away paint, or rather to soften it by heating, so that it would be easier to scrape it away from the wood. This method has now been terminated because of the fire hazard from the open flame. Nowadays, a hot air gun is used as a substitute for the blow torch. However, it is very difficult to gain real efficiency with this tool, because transmittal of heat from the tool to the surface very much depends upon the outdoor climate with winds and air temperature. Thus, it is difficult to accomplish an equally distributed heating to the right temperature. If the surface is heated too much, the wood surface is unwontedly dried. If the surface is heated too little, the paint will be hard to remove and requires more work with the paint scraper. The work is demanding for arms and axles, because the hot air gun must be held continuously in one hand and the paint scraper in the other hand.

The presently most preferred professional methods for removing paint from wood facades use either caustic sol¬ ution or strong hydrocarbon based solutions. Washing with caustic solution causes many problems because caustic solution is strongly aggressive to the skin. Normally, a high pressure water spray is used for application of the caustic solution, for washing in several steps and for application of neutralizing agents. This method requires the spreading of several litres of liquid per square meter treated surface and affects the environment, for example plants surrounding the building. The neutralizing of the cleaned wood surface requires the use of acetic acid which, for example, attacks nails in a facade. Another significant drawback with this method is that the wood surface is dried out, i.e. the natural protective substances in the wood, e.g. resin, is removed and cracks appear in the wood, which in the long run can have very negative effects when restoring old historical buildings.

The use of hydrocarbon based solutions is associated with risks for occupational diseases because these substances are usually very toxic. These substances are also very expensive to buy, making this method expensive in com¬ parison with washing with caustic solution.

TECHNICAL PROBLEM

One aim of the present invention is therefore to solve the problem of removing paint from wood surfaces in an efficient, environmentally acceptable and economical way. SOLUTION

This aim is achieved according to the invention in that the paint is softened by radiation by means of at least one source of infrared radiation, and that the paint immediately thereafter is removed mechanically from the wood surface. Because the transmission of heat to the surface is made by radiation, an evenly distributed heat¬ ing of the surface is achieved, regardless of the weather conditions.

The mechanical work upon the surface can be done by scraping. It has been found to be surprisingly simple to remove the paint from the wood surface in this way, as soon as it has been softened.

The means according to the invention is characterized in a carrier for one or more sources of infra-red radiation, means for guided travel of the carrier in the horizontal plane along the facade, and means for guided travel of the carrier in the vertical plane along the facade. With the help of this carrier the work can be done rapidly and efficiently, because an entire surface section can be treated at the same time, and the operator is relieved from the burden of the carrier weight.

According to a preferable embodiment of the invention, the means for horizontal travel comprises a tubular prό- file rail which has a slit in the bottom and at least one trolley which can move within the tubular profile rail and is vertically connected to the carrier. This rail can easily be attached to the bottom of the eave board.

Preferably, the means for vertical movement comprises at least one vertical guide rod running through lock means at the carrier, enabling movement of the carrier along the rod and locking at optional height. The length of the guide rod/rods can be made adjustable by screwing on or off rod segments.

Preferably, the radiation source comprises one or more infra-red heating tubes, which are longitudinally oriented in parallel with the fibres of the wood surface. This makes it possible to shift the vertical veining of a cover boarding to the horizontal veining of a weather boarding in an easy way, because the carrier is rotatable at least about 90° in relation to the guide rod.

When the infra-red heating tubes are movably mounted in the carrier, so that their relative distance is adjust¬ able, for example so that the radiation intensity can be adjusted to the surface of a cover boarding. If the car¬ rier also is provided with adjustable distance means, the distance between the carrier and the facade can be adjusted for control of radiation intensity.

DESCRIPTION OF THE FIGURES

An exemplary embodiment of the invention will now be described in greater detail with reference to the attached drawings, in which

Fig. 1 is a perspective view of a facade with the means according to the invention set up for use, and Fig. 2 is an explosion view in perspective showing the arrangement of the infra-red heating tubes in the carrier.

PREFERRED EMBODIMENTS

Fig. 1 shows a wood facade 10 which is made as a cover boarding, and ending at the top with a angled eave board 11 with a roof gutter 12 and roofing tiles 13.

A tubular profile rail 14 which is slit at the bottom is attached to the bottom of the eave, at a suitable dis- tance from the facade 10. A trolley 16 with wheels 15 runs inside the tubular rail. The trolley is provided with an attachment ear 17 protruding downwards through the slit and to which is mounted a vertical toggle link 18, which in its turn forms an attachment for a vertical rod 19.

The length of the rod 19 is adjustable because it is formed by a number of segments 19a, which can be screwed on to or off from the end, which is hinted at 19b. The rod 19 runs through a tubular holder 20, which can be locked relative the rod by means of a handle 21. The holder 20 is rotatable connected via a bearing 22 to the middle of a rectangular box shaped carrier 23 with four internally mounted infra-red heating tubes 24 (see Fig. 2) . The holder 20 can be arrested relative the carrier 23 by means of a spring loaded pin 25 in one of two with an angle of about 90° from each other distanced angle posi¬ tions. This makes it possible to rotate the carrier from a position where the infra-red heating tubes are verti- cally oriented, to a position where they are horizontally oriented.

The infra-red heating tubes are connected via a mutual cable 26 and a jack plug to a plug socket for two- or three phase current. The carrier is provided with a con- tact breaker 27 for each tube, so that the tubes can be switched on and off individually for adjustment of the radiation intensity.

Each of the four corners of the carrier 23 is provided with a distance means 28, in the form of a pointed stick with its point towards the facade and a ball shaped handle at the opposite end. Each stick can be moved axially through the carrier 23 and locked relative to it by means of a screw 29. Fig. 2 shows that the tubes 24 are mounted between two rails 30 at the inside of the rear wall of the carrier 31. This makes it possible to move the tubes 24 sideways, so that their respective interval is altered. This arran- gement makes it possible to vary the radiation intensity over the surface which is delimited by the side walls 32 of the carrier, for example, so that a main proportion of the radiation can be concentrated to the space between two cover boards 10a.

It is possible to move the carrier 23 with the infra-red heating tubes 24 advantageously both horizontally and vertically along the entire facade 10, for systematic treatment of one part of the facade at time which is delimited by the side walls of the carrier, until the entire facade surface has been stripped from paint.

The carrier 23, which is open towards the wall, is anchored in the correct position on the wall by means of the points of the sticks 28. To this end, the toggle link 18 provides for a certain room for sideways adjustment of the carrier 23. Then the radiation from the infra-red heating tubes 24 are put to work until the paint warmed through and made soft. The radiation heat results in that certain elements of the oil paint are transformed to the liquid state, while other parts of the paint is gasified and causes the paint to blister. Now it is very easy to remove the paint with a scraper. Most old wood buildings are painted in a large number of layers with oil based paint, and even if these layers have been painted over with plastic based paint, it will be just as easy to remove said paint, because the bottom layers on the wood are loosened up in the manner described above.

The above described heating of a section of the facade takes between a half minute and one minute. Then the carrier 23 is moved for heat treatment of the next untreated section. During heating of the next following facade section, the soft paint is removed from the already heated section. In this way the paint is removed rapidly and efficiently. It has been showed that radi¬ ation treatment of a wood facade has a deep effect in the wood, which is advantageous because there will be plenty of time for removing paint before it again gets hard by cooling. At the same time, moisture in the facade is removed.

A surprising technical effect from this treatment is also provided because resin gum in the wood board which has been leaching from outer wood facade during all the years, and therefore is more current at the inside of the board, tend to be evenly distributed in the board by the heating, i.e. will be drawn to the outside. This partly rejuvenates the natural defence of the outer wood surface against attacks moisture and mould. It has also been shown that the facade only needs a very short period of drying before it can be coated with new paint, if it has been wet by rain in the interval.

The invention is not limited to the exemplary embodiment described above, but various alternatives are conceivable within the scope of the subsequent claims. For example, the carrier can have a different design, as well as dif¬ ferent means for travelling along a facade.

Claims

1. Method for removing layers of paint from a wood surface (10) , said layers of paint comprising a base lay¬ er of oil paint, c h a r a c t e r i z e d in that the paint is softened by radiation by means of at least one source (24) of infra-red radiation, and that the paint immediately thereafter is removed mechanically from the wood surface (10) .

2. Method according to claim 1, c h a r a c t e - r i z e d in that the mechanical removal is done by scraping.

3. Means for removing one or more layers of paint from a wooden facade (10) , said layers of paint compri¬ sing a base layer of oil paint, c h a r a c t e r i - z e d in a carrier (23) for one or more sources (24) of infra-red radiation, means (14-16) for guided travel of the carrier in the horizontal plane along the facade (10) , and means (19-21) for guided travel of the carrier in the vertical plane along the facade (10) .

4. Means according to claim 3, c h a r a c t e ¬ r i z e d in that the means for horizontal travel comp¬ rises a tubular profile rail (14) which has a slit in the bottom and at least one trolley (16) which can move wit¬ hin the tubular profile rail and is vertically connected to the carrier (23) .

5. Means according to claim 3 or 4, c h a r a c ¬ t e r i z e d in that the means for vertical movement comprises at least one vertical guide rod (19) , running through lock means (20, 21) at the carrier, enabling movement of the carrier along the rod and locking at optional height.

6. Means according to claim 5, c h a r a c t e ¬ r i z e d in that the length of the guide rod (19) is adjustable by screwing on or off rod segments (19a) .

7. Means according to any of claims 3 to 5, c h a r a c t e r i z e d in that the radiation source comprises one or more infra-red heating tubes (24) , which are longitudinally oriented in parallel with the fibres of the wood surface (10) .

8. Means according to any one of claims 5 to 7, c h a r a c t e r i z e d in that the carrier (23) is rotatable at least about 90° in relation to the guide rod (19).

9. Means according to any one of claims 7 or 8, c h a r a c t e r i z e d in that the infra-red heating tubes (24) are movably mounted in the carrier (23) , so that their relative distance is adjustable.

10. Means according to any one of claims 3 to 9, c h a r a c t e r i z e d in that the carrier (23) is provided with adjustable distance means (28) , enabling adjustment of the distance between the carrier and the facade (10) .