Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
METHOD AND MEANS FOR REMOVING LAYERS OF PAINT FROM A WOOD
SURFACE
TECHNICAI, FIELD
The present invention relates to means for removing one
or more layers of paint from a wooden facade, said layers
of paint comprising a base layer of oil paint, and com-
prising a carrier for one or more sources of infra-red
radiation, means for guided travel o~ the carrier in th~
horizontal plane along the facade, and means for guided
travel of the carrier in the vertical plane along the
facade.
STATE OF THE ART
When restoring wood surfaces on old houses, it is nor-
mally obligatory to strip off a number of layers of ugly,cracked and flaking oil- and/or plastic-based paint. Nor-
mally all layers of paint have to be complekely 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,
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it is difficult to accomplish an equally distributed
heating to the right temperature. If the surface is
heatad too much, the wood surface i5 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 i5 demanding for arms and shoulders; because the
hot air gun must be held continuously in one hand and the
paint scraper in the other hand.
AU-A-545 584 describes a hand held device for removing
paint with which the user may direct a beam of infra-red
radiation to the surface. This known device is equally
demanding for arms and shoulders as the hot air gun.
The presently most preferred professional methods for
removing paint from wood facades use either caustic sol-
ution or strong hydrocarbon based solutions. Washing withcaustic 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
~0 application of neutralizing agents. This method requires
the spreading of several litres of liquid per s~uaxe
meter treated surface and affects thé 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 facadeO
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
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expensive to huy, making this method expensive in com-
parison with washing with caustic solution.
TECHNICAL PROBLEM
One aim of the present invention is therefore to solve
S 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 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, that the length of the
~uide rod is adjustable by screwing on or off rod seg-
ments, that the radiation source comprises one or more
infra-red heating tubes, which are longitudinally
oriented in parallel with the grain of the wood sur~ace,
that the carrier is rotatable at least about 90~ in rela-
tion to the guide rod, and that the infra-red heating
tubes are movably mounted in the carrier, so that their
relative distance is adjustable.
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.
According to a preferable embodiment of the invention,
the means for hori~ontal travel comprises a tubular pro-
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 boardO
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If the carrier also is provided with adjustable dis-
tance means, the distance between the carrier and the
facade can ~e adjusted for control of radiation inten-
sity.
DESCRIPTIO~ OF THE FIGVRES
An exemplary embodiment of the invention will now b~
described in greater detail with reference to the
attached drawings 7 in which
Fig. 1 is a perspective view of a facade with the means
according *o the invention SPt up for use, ancl
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-
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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 i5 adjustable because it is
formed by a number of segments l9a, which can be screwed
on to or off from the end, which is hinted at l9b . The
~0 rod 19 runs through a tubular holdsr 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 ~ox shap~d-~arrier 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 rotat~ the carrier from
a position where the infra-red heating tubes are verti-
cally oriented, to a position where they are horiæontally
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 beswitched 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.
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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 arr~n-
gement ma~es it possible to vary the radiation intensityover 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 covar boards lOa.
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 wh:ich is
delimited hy 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 ~rom the infra-red
heating tubes ~4 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 trans~ormed to the
liquid state, while other parts of the paint is gasified
and causes the paint to blister. Now it i5 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
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carrier 23 is moved for heat ~reatment 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 t~he 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 leachinq from outer wood facade du~in~ 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.
