WO1993017882A1

WO1993017882A1 - Method of removal of paint etcetera from a timber element and equipment for practising the method

Info

Publication number: WO1993017882A1
Application number: PCT/SE1993/000190
Authority: WO
Inventors: Göran HÅKANSSON; Holger SCHIØLER
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-03-06
Filing date: 1993-03-05
Publication date: 1993-09-16
Anticipated expiration: 1994-09-06
Also published as: DE69319228D1; EP0629157B1; HU9402561D0; HUT68842A; DK0629157T3; SE9200684D0; HU213518B; SE470255B; CA2131445A1; SE9200684L; AU3654793A; ES2120496T3; EP0629157A1; ATE167437T1; DE69319228T2

Abstract

Method of removal of paint etcetera from a timber element, e.g. a window frame or a door leaf, comprising a step during which the element is inserted into an oven, in which at least the paint and the outer layer of the timber is heated, and a step carried out soonest thereafter, in which step paint and/or similar material such as e.g. putty is mechanically removed utilizing as such known technique before the element has been cooled to room temperature. Equipment for carrying out the method is also disclosed. The method makes possible saving of labour and - in a specific embodiment - reuse of glass panes mounted in the element.

Description

METHOD OF REMOVAL OF PAINT ETCETERA FROM A TIMBER ELEMENT, AND EQUIPMENT FOR PRACTISING THE METHOD

The present invention relates to a method of removal of paint etcetera from window frames and other timber elements. The invention also relates to equipment for practising the .invention.

Practising restauration and renovation work on timber ele- 0 ments such as but not solely window frames and door leaves part of the work to be done is very often removal of old paint and other matters. This work is cumbersome and time consuming. Several methods of removal of paint are known.

5 Removal by sanding and by mechanical scraping off of tough paint and putty for the laying bare of the timber surfaces is time consuming and consequently costly, and imply consi¬ derable risk of damage especially of profiled capentry.

Θ The risk of damaging the carpentry work is reduced if the paint is softend by means of a solvent. Chlorinated solvents are technically efficient, but imply unacceptable health and environmental risks.

5 Softening of the paint by heating by means of a flame or a hot air jet lends considerable easing for mechanical remo¬ val, but the controlling of the flame or of the hot air jet is difficult, and damages caused by over heating are often seen, practising individuals do not unusually get burnt, and Θ excessive heating creates unpleasent and/or health influen¬ cing exhalations.

Mobile pieces of carpentry work or such pieces which can be dismantled can alternatively be treated by beeing soaked in 5 strong alkaline solution or acid. These mediums are water based and are often damaging the carpentry work treated, not least any glued joints. Timber is often distorted. Latest known, from window renovation in Denmark, is a remo¬ val method according to which the wooden element is soaked and heated in very hot linseed oil. The method is claimed to provide a good removal and at the same time an advantageous impregnation of the timber. A method which is using very hot oil must produce inconvenient vapour which has to be removed by ventilation. Drippings of hot linseed oil must cause a filthy place of work and cumbersome cleaning of the working area. Even though linseed oil as such imply no special risk, it is well known that absorbing paper or textile moistened with linseed oil may ignite spontaneously. A risk which is undesirabel in any carpentry shop. Old craftmans experience recognise risk of oil sweating through later applied paint cover in case soft wood such as pine has been inpregnated with linseed oil.

All the known methods of paint removal imply considerable risk of breakage of pane(s) of glass mounted in the carpen- try element. Even removal of panes of glass by removal of putty by milling with a special putty cutter imply conside¬ rable risk for breakage, and is a time consuming method re¬ quiring highly skilled labour.

There is thus a need for a new method of removal of paint etcetera which overcomes as many as possible of the above mentioned disadvantages associated with the known methods without introducing new ones. The new method should be at least as cost efficient as the known methods.

It is an object of this invention to provide a new method of removal of paint etcetera from pieces of carpentry, which meets the above mentioned needs. It is also an object to provide equipment for practising the new method.

The method according to the invention is characterized by a step in which the timber element is introduced into an oven in which at least the paint and the outer layer of the tim¬ ber is heated, and by a soonest after following step in which paint and/or similar material such as e.g. putty is removed mechanically by known technique(s) before the ele- ment is cooled to room temperature.

Advantages provided by this method are, that the mechanical removal is carried out by known technique(s) . No new disad¬ vantages are therefore introduced; but after the heating in the oven is it possible to remove paint etcetera from very large surfaces surprisingly fast. The even heating makes possible an even and easy mechanical removal of paint etce¬ tera. The relatively low temperature reached compared to heating accomplished by means of a flame or a hot air jet considerably reduces the release of unpleasant exhalations, and the timber is not damaged by local overheating. The re¬ moved paint and putty waste is a dry matter and can be delt with according to known practice without risk of spontaneous ignition. The inventors have tested the removal of paint and putty from vindow frames after heating in a convection oven and hereby experienced that the time required for the remo¬ val is considerably reduced, probably to half or less com¬ pared to the time required for similar xemoval after heating by means of a flame or a hot air jet. ----

If a piece of carpentry is large and/or it has a shape with a wealth of details is the work of more than one person re¬ quired if the removal should be accomplished before the the piece is cooled too much. For the removal of paint etcetera from such elements is it possible alternatively to proceed according to the method according to claim 2.

Are metal fittings such as hinges and locks dismantled prior to the introduction of the element into the oven is the re- moval work faciliated considerably.

Is the element heated in a micro wave oven are several ad- vantages obtained. The heating is accomplished not only by thermal conduction from the surfaces of the element towards the inner parts but is instantly generated through a layer of material of may be one cm or more. The timber technologi- cal advantages are known. Regarding the paint and putty re¬ moval we have demonstrated, that after heating in a micro wave oven to a temperature at which the element may just be handled by a nacked hand and shows no sign of blistering, in most cases is easy and fast done. Just some types of paint requires heating to a temperature at which a gloved hand is necessary for the handling. No glass panes mounted in window frames, which we have treated in this way, have broken. We anticipate this technical effect is caused because the glass pane is not heated by micro wave energy, and only the edges of the pane is slightly heated from the putty and timber fixing the glass pane. By heating in a micro wave oven we also observed, that linseed oil putty is softened so that it can be removed by means of e.g. a putty knife without any trouble or risk for the glass pane. We therefore take the method according to claim 4 to be especially advantageous for renovation of windows and similar elements with glass panes of preservation value. It is obvious for a skilled person, that metal components such as hinges must be dis¬ mantled or screened off by an insolating material before heating in a micro wave oven.

The equipment according to the invention is characterized by an oven with an oven chamber that large, that the element will fit in it without direct mechanical contact with any oven surface, and by a work space for the removal of paint etcetera located in the vincity of the oven so that a heatet element can be tooled before any chilling of significance for the removal of the paint etcetera has occured. Such an oven can ensure the introduction and the extraction respec¬ tively of the element to be without risk of depositing soft¬ ened paint etcetera in the oven, and an even heat treatment of the element. The required speedy execution of the methods second step is made possible, and a rationel industrial re¬ moval of paint etcetera can thus be established.

The heating time especially in a hot air oven, for many ele¬ ments such as window frames and door leaves, is a- number of times the period typically required for the removal work. An optimised production flow is therefore achievable by means of equipment according to claim 6.

The inventors have, as stated, proved specific advantages in case the heating of the element is generated by micro waves. Particular advantages are realised in case the element com¬ prise a fixed glass pane. The equipment according to claim 7 is advantageous because they allow for the heating of the element by means of micro waves. It is also an advantage, that heating in a micro wave oven can be accomplished quick¬ ly. A single micro wave oven may thus produce heated ele¬ ments for a number of paint removal stations.

A particularly simpel and safe control of the heating of elements is based on the weight of the element. The moisture content of the timber is also of some importance. If the equipment comprises apparatuses for the controlling of weight and/or of moisture content is an expedient and simpel heating control made possible.

Larger jobs for removal of paint etcetera is to be found du¬ ring renovation works on old windows in existing buildings. The administrative registration and the transportation re¬ quired for this type of jobs can be simplified considerably by utilisation of equipment according to claim 9.

The technique according to the invention do not introduce any new type of waste in carpentry work shops, which are ta¬ king on removal of paint etcetera by mechanical methods. Un¬ controlled oil penetration into the timber implying risk of sweating through new paint cover, and risk of spontaneous ignition of waste impregnated with linseed oil are not existing. Over-heating damages of timber is eliminated, the heating and thus the removal work is industrially control1- able and therefore allows for an even quality compared to a manually controlled heating by means of a flame or a hot air jet. Exhalations or the formation of oil vapour is pro- nouncely reduced or eliminated compared to the known techni¬ ques. Solvents comprising fire-, health-, and/or environmen- ø tal risks are not to be found during the practising of the invention. The removal process is more cost efficient compa¬ red to the known techniques.

The invention is illustrated below by advantageous examples 5 of embodiements with reference to the drawing which shows

a diagram illustrating a workshop arrangement for removal of paint etcetera from window panes and door leaves accor¬ ding to the invention. ©

In figur 1 is 1 an A-shaped stand on the sides of which win¬ dow frames and door leaves to be treated are placed. 2 is a scale for the checking of each elements weight. In the vin- city of the scale 2 is also to be found an apparatus for the 5 checking of the moisture content of the timber of each ele¬ ment. 3 is a micro wave oven for the heating of the elements which are to have paint etcetera removed. The oven 3 has an efficient oven chamber 120 cm wide, 80 cm high and 240 cm long. A large oven is advantageous because it allows for the 0 heating of a large element. The oven material is not heated, so the loss of energy from the oven is not significantly in¬ creased by increased size of oven. The oven 3 is designed according to known technique regarding micro wave ovens for the drying of timber. 4 is a paint removal station of which 5 two are illustrated, both of which are designed according to known technique for mechanical removal of paint etcetera from a piece of carpentry. Each paint removal station is thus equipped wi h a rigid work bench comprising fixing tools for the fixing of elements during the removal of paint etcetera, and providing a convenient working hight. Alloca¬ ted to each paint removal station 4 is also known tools such as scrapers etcetera and work gloves for the handling of warm elements. 5 is a stand, which is of similar design to the design of stand 1. Stand 5 is used for storing treated elements.

The removal of paint etcetera from a window frame is carried out according to the invention the following way:

A window frame, which after dismounting of all metallic fittings, has been placed on the stand 1, is carried to the scale 2 for checking of its weight and of the moisture con¬ tent of its timber. A typical window frame the size of 50 x 9© cm designed with one horisontal glazing bar and two glass panes each the thickness of 2 mm weighs about 5 kilo¬ grammes. The moisture content may be aproximately 2©%. The window frame is placed horisontally in the oven 3 in order to be heated. Based on the weight and moisture content, and on successively collected experience is such an oven setting chosen, which within 4 minutes will produce the heating of the timber in the window frame to a temperature, at which the frame may just be handled by an ungloved hand.

The heated window frame is carried to a paint removal sta¬ tion 4 and is clamped to the work bench the glass grove fa¬ cing upwards. Paint covering the upwards facing surfaces is scraped off, and putty is removed e.g. by means of a putty knife. The glass pins now freely accessible are removed. The window frame is undamped and turned upside down. Using a knife with a blade bend in an angel is each glass pane in turn loosened from the window frame. When a glass pane is loosing its adherence to to the window frame it is falling to the work bench from where it is removed, marked with win¬ dow frame indentification markings, and taken to a storrage δ

place for refitting, when the renovation works on the window frame has been carried out that far, that the frame is ready for refitting of the panes. The window frame - now without glass panes - is now ridded of paint and left over putty, and is thereafter placed on stand 5.

The inventors have tested the method according to the inven¬ tion using window frames and door leaves of various origin. Different types of paints varies in ease of removal. By testing we have compared the labour required for processing identically painted identical elements and demonstrated, that the removal of paint etcetera according to the inven¬ tion typically requires half the labour or less compared to the combined requirement for the ridding of profiled surfa- ces using a hot air jet, and sanding of larger plane surfa¬ ces using band sanding. All glass panes fitted in the test elements were removed unbroken and could be refitted in all tests. Tests demonstrates, that the paint normally is easily scraped off during a period of 10 - 12 minutes after ter i- nation of the heating. This span of time was sufficient for the finishing of the work on window frames designed with one or two window panes.

Tests of heating in a convection oven shows requirement of relatively long heating periods, but the work required for the removal of paint etcetera was even easy compared to the required work after heating in a micro wave oven. Even by slow heating in a convection oven have we experienced consi¬ derable risk of thermal breakage of glass panes.

It is obvious for a person skilled within the art to test various micro wave combinations combined with various moist¬ ure contents in the timber, and to study to which depth the heat generated by the micro waves most advantageously should be generated, and to which temperature each element should be heated in order to obtain optimal results. Also, it is obvious that the invention can be modified in several ways. It can be used not only for the removal of paint etcetera from window frames and door leaves, but it can be used for all pieces of carpentry, which can be placed in the oven. The method according to the invention can also be combined with known method(s).

Claims

C A I M S

1. Method of removal of paint etcetera from a timber element e.g. a window frame or a door leaf, c h a r a c t e ¬ r i z e d by a step in which the element is inserted into an oven, where at least the paint and the outer layer of the timber is heated, and by a step carried out shortly there¬ after, in which step paint and/or similar materials such as e.g. putty, is removed mechanically by using as such known technique, before the element is cooled to room temperature.

2. Method according to claim 1, c h a r a c t e r i z e d by the removal of only part of the paint etcetera, and by the repeating of both of the defined steps and/or by removal of remaining paint etcetera utilizing other method(s).

3. Method according to claim 1 or 2, c h a r a c t e ¬ r i z e by a step carried out before the element is in- serted into the oven, in which step existing mounting ele¬ ments of metallic material i.e. hinges and locks are dis¬ mantled.

4. Method according to claim l, 2 or 3, c h a r a c t e - r i z e d by, that a micro wave oven is chosen, and that the element is heated influenced by micro waves.

5. Equipment (apparatus) for practising the method according to at least one of the claims 1 - 4, c h a r a c t e - r i z e d by, an oven having an oven chamber that large, that the element can be inserted in the chamber without di¬ rect mechanical contact to the inner surfaces of the oven, and by a paint removal station for the removal of paint et¬ cetera placed in the vincity of the oven so that a heated element can be tooled before the element has been cooled to a degree at which the removal work is influenced to a consi¬ derable extend.

6. Equipment according to claim 5, c h a r a c t e ¬ r i z e d by a number of oven chambers, each of which are individually controllable.

7. Equipment according to claim 5 or 6, c h a r a c t e ¬ r i z e d by, that the oven is a micro wave oven, and that the oven control organ or organs preferrably is/are time control organ(s).

8. Equipment according to claim 7, c h a r a c t e ¬ r i z e d by a scale for checking the weight of the element and possibly by a measuring instrument for measuring the moisture content of timber component(ε) of the element.

9. Equipment according to any of the claims 5 - 8, c h a ¬ r a c t e r i z e d by beeing designed to be mobile or se- mimobile.