METHOD OF MECHANICAL REMOVAL OF PAINT AND PUTTY FROM A TIMBER ELEMENT AND EQUIPMENT FOR CARRYING OUT THE METHOD

Description

[0001] The present invention relates to a method of mechanical removal of an adhering agent such as paint and putty from window frames and other timber elements and comprising a step in which the adhering agent is heated. The invention also relates to equipment for carrying out the invention.

[0002] When carrying out restoration and renovation work on timber elements such as but not solely window frames and doorleaves part of the work to be done is very often removal of old adhering agents. This work is cumbersome and time consuming. Many methods of mechanical removal of adhering agents are known.

[0003] Removal of adhering agents by mechanical means only for the laying bare of the timber surfaces is time consuming and consequently costly. Such tooling also implies considerable risk of damage, especially of profiled carpentry.

[0004] The risk of damaging the carpentry work is reduced if the paint is softened.

[0005] Softening may be obtained by heating the adhering agent. Heating by means of a flame or a hot air jet lends considerable easing for the mechanical removal. The controlling of the flame or of the hot air jet, however, is difficult, and damages caused by over heating are often seen. Performing individuals get burns easily, and excessive heating creates unpleasant and health influencing exhalations.

[0006] Mobile pieces of carpentry work or such timber elements which can be dismantled can alternatively be treated by being soaked in a strong alkaline solution or an acid. These mediums are water based and are often damaging the carpentry work treated, not least any glued joints. Timber is often distorted.

[0007] Latest known, from window renovation in Denmark, is a removal 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 implies no special risk, it is well known that absorbing paper or textile moistened with linseed oil may ignite spontaneously. A risk which is undesirable in any carpentry shop. Old craftsman's experience recognises risk of oil sweating through later applied paint cover in case soft wood such as pine has been impregnated with linseed oil.

[0008] DE-A-3 518 725 discloses a method for pyrolytic removal of lacquer residuals on metal elements by thermal decomposition and oxidation of the organic matter of the lacquer. The high temperature chemical process (200 - 450 °C) transforms the lacquer into gaseous waste products. The pyrolysis takes place in an oven chamber in which the metal elements are heated by conventional means to above the ignition temperature of the lacquer residuals.

[0009] All the known methods of paint removal imply considerable risk of breakage of pane(s) of glass mounted in the carpentry element. Even removal of panes of glass by removal of putty by milling with a special putty cutter implies considerable risk for breakage, and is a time consuming method requiring highly skilled labour.

[0010] There is thus a need for a new method of mechanical removal of adhering agent from a timber element, 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.

[0011] It is an object of this invention to provide a new method of mechanical removal of paint and/or similar material such as e.g. putty from a timber element, which meets the above mentioned needs. It is also an object to provide equipment for carrying out the new method.

[0012] The method according to the invention is characterized by the steps specified in claim 1. The mechanical removal is carried out by known technique(s). No new disadvantages are therefore introduced by the removal as such. Heating of the adhering agent prior to the mechanical removal under the influence of microwave energy can be limited to temperatures well below those otherwise required in order to bring about a similar easing of the mechanical work. Such heating makes it possible to perform the removal step surprisingly fast covering very large surfaces. The even heating obtained makes possible an even and easy mechanical removal of adhering agents. The relatively low temperature reached compared to conventional heating by means of a flame or a hot air jet considerably reduces the release of unpleasant exhalations. The timber is not damaged by local overheating. The waste product is a dry matter and can be dealt with according to known practice without risk of spontaneous ignition.

[0013] If a timber element is large and/or it has a shape with a wealth of details, the work of more than one person is required if the removal should be accomplished before the element is cooled too much. For the removal of adhering agent from such an element it is possible alternatively to proceed according to claim 2.

[0014] The equipment according to the invention is characterized by a microwave oven and an adhering agent removal station as specified in claim 3. Such a micro wave oven can ensure an easy introduction and extraction respectively of the element and an even heat treatment of the timber element. The required speedy execution of the second step of the method is made possible, and a rational industrial mechanical removal of adhering agent can thus be established. It is also an advantage that the heating can be accomplished quickly in a microwave oven. A single microwave oven may thus produce heated elements for a number of paint removal stations.

[0015] Other advantages are obtained by microwave heating of the timber element. The heating is accomplished not simply by thermal conduction from the surfaces of the element towards the inner parts but is instantly generated through a layer of material of maybe one cm or more. The timber technological advantages are known.

[0016] The mechanical removal in most cases is easily and fast done after heating the timber element in a microwave oven to a temperature at which the element may just be handled by a naked hand and shows no sign of blistering. Some types of adhering agent, however, requires heating to a temperature at which a gloved hand is necessary for the handling.

[0017] No glass panes mounted in window frames, which we have treated in this way, have broken due to thermal stress. We anticipate this technical effect is caused because the glass pane is not heated by the microwave energy. Only the edges of the pane are slightly heated by the putty and timber fixing the glass pane. By heating the timber element in a microwave 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 of breaking the glass pane. The method and equipment according to the invention is therefore especially advantageous for renovation of windows and similar timber elements with glass panes of preservation value.

[0018] Solvents comprising fire-, health-, and/or environmental risks are not to be found during the carrying out of the invention. The removal process is more cost efficient compared to the known techniques.

[0019] If metal fittings such as hinges and locks are dismantled prior to the introduction of the element into the oven the removal work is facilitated considerably.

[0020] A particularly simple 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 an expedient and simple heating control is made possible.

[0021] Larger jobs for mechanical removal of adhering agent from timber elements are to be found during renovation works on old windows in large existing buildings. The administrative registration and the transportation required for this type of jobs can be simplified considerably by utilization of equipment according to claim 4.

[0022] The invention is illustrated below by advantageous examples of embodiments with reference to the drawing which shows
   a diagram illustrating a workshop arrangement for removal of adhering agent from window panes and door leaves according to the invention.

[0023] In the drawing 1 is an A-shaped stand on the sides of which window frames and door leaves to be treated are placed. 2 is a scale for checking the weight of each element. In the vicinity of the scale 2 is also to be found an apparatus for checking the moisture content of the timber of each element. 3 is a microwave 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 heating of a large element. The oven material is not heated so the loss of energy from the oven is not significantly increased by increased size of oven. The oven 3 is designed according to known technique regarding microwave ovens for the drying of timber. 4 is a paint removal station of which two are illustrated, both of which are designed according to known technique for mechanical removal of adhering agent from a timber element. Each removal station is thus equipped with a rigid work bench comprising fixing tools for the fixing of elements during the removal of adhering agents, and providing a convenient working height. Allocated to each removal station 4 are also known tools such as scrapers etcetera and work gloves for the handling of warm elements. 5 is a stand, which is similar to stand 1. Stand 5 is used for storing treated elements.

[0024] The removal of adhering agent from a window frame is carried out according to the invention in the following way:

[0025] 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 content of its timber. A typical window frame the size of 50 x 90 cm designed with one horizontal glazing bar and two glass panes each the thickness of 2 mm weighs about 5 kilogrammes. The moisture content may be approximately 20%. The window frame is placed horizontally in the oven 3 in order to be heated. Based on experience and the weight and moisture content such an oven setting is chosen that the timber in the window frame within 4 minutes will reach a temperature, at which the frame may just be handled by an ungloved hand.

[0026] The heated window frame is carried to a paint removal station 4 and is clamped to the work bench the glass rebate facing 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 unclamped and turned upside down. Using a knife with a blade bend in an angle each glass pane in turn is loosened from the window frame. When a glass pane is loosing its adherence to the window frame it falls to the work bench from where it is removed, marked with window frame identification markings, and taken to a storage place to await refitting. The window frame - now without glass panes - is ridded of remaining paint and left over putty. The window frame is placed on stand 5, when the renovation works have been carried out that far, that it is ready for refitting of the panes.

[0027] The inventors have tested the method according to the invention using window frames and door leaves of various origins. Different types of paints vary in ease of removal. We have compared the labour required for processing identically painted identical elements and demonstrated that the mechanical removal of adhering agents according to the invention typically requires half the labour or less compared to the combined requirement for the ridding of profiled surfaces using a hot air jet, and sanding of larger plane surfaces using band sanding. All glass panes fitted in the test elements were removed unbroken and could be refitted in all tests. Tests demonstrate that the paint normally is easily scraped off during a period of 10 - 12 minutes after termination of the microwave heating. This span of time was sufficient for the finishing of the work on window frames designed with one or two window panes.

[0028] It is obvious for a person skilled within the art to test various microwave combinations combined with various moisture contents in the timber, and to study to which depth the heat generated by the microwaves should be generated most advantageously, and to which temperature each element should be heated in order to obtain optimal results.

[0029] Also, it is obvious that the invention can be modified in several ways. It can be used not only for mechanical removal of adhering agents from window frames and door leaves, but it can facilitate such work on all pieces of carpentry. The method according to the invention may also be combined with other methods.

Claims

1. Method of mechanical removal of adhering agent in the form of paint or putty from a timber element such as a window frame or a door leaf and comprising a step in which the adhering agent is heated, characterized by a step in which the adhering agent to be removed and at least the outer layer of the timber to which the adhering agent adheres are heated influenced by microwave radiation, and by a step in which mechanical removal of heated adhering agent is carried out by per se known mechanical removal technique, before the element is cooled to ambient temperature.

2. Method according to claim 1, characterized by removal of only part of the agent, and by the repeating of both of the steps or by removal of remaining agent utilizing any other method.

3. Equipment for carrying out the method of mechanical removal of an adhering agent in the form of paint or putty from a timber element and comprising a step in which the adhering agent is heated, according to at least one of the claims 1 or 2, characterized by a microwave oven with an oven chamber able to hold the timber element without direct mechanical contact to the inner surfaces of the oven chamber, and by an adhering agent removal station comprising mechanical removal equipment.

4. Equipment according to claim 3, characterized by being designed to be mobile.

Ansprüche

1. Verfahren des mechanischen Entfernens von Haftstoff in Form von Farbe oder Kitt von einem Holzelement, wie beispielsweise einem Fensterrahmen oder einem Türblatt, das einen Schritt umfaßt, bei dem der Haftstoff erwärmt wird, gekennzeichnet durch einen Schritt, bei dem der zu entfernende Haftstoff und wenigstens die äußere Schicht des Holzes, an der der Haftstoff haftet, durch den Einfluß von Mikrowellenstrahlung erwärmt werden, und durch einen Schritt, bei dem mechanisches Entfernen von erwärmtem Haftstoff mittels eines an sich bekannten mechanischen Entfernungsverfahrens ausgeführt wird, bevor das Element auf auf Umgebungstemperatur abgekühlt wird.

2. Verfahren nach Anspruch 1, gekennzeichnet durch das Entfernen lediglich eines Teils des Stoffes und durch das Wiederholen beider Schritte oder durch das Entfernen von verbliebenem Stoff unter Einsatz eines beliebigen anderen Verfahrens.

3. Einrichtung zum Ausführen des Verfahrens des mechanischen Entfernens eines Haftstoffs in Form von Farbe oder Kitt von einem Holzelement, das einen Schritt umfaßt, bei dem der Haftstoff erwärmt wird, nach wenigstens einem der Ansprüche 1 oder 2, gekennzeichnet durch einen Mikrowellenherd mit einer Herdkammer, die das Holzelement ohne direkten mechanischen Kontakt mit den Innenflächen der Herdkammer aufnehmen kann, und durch eine Haftstoff-Entfernungsstation, die eine mechanische Entfernungseinrichtung umfaßt.

4. Einrichtung nach Anspruch 3, dadurch gekennzeichnet, daß sie für den mobilen Einsatz bestimmt ist.

Revendications

1. Procédé de décapage mécanique d'un corps adhérent, se présentant sous la forme de peinture ou mastic, d'une pièce en bois de construction telle qu'un cadre de fenêtre ou un battant de porte, et comprenant une étape dans laquelle le corps adhérent est chauffé, caractérisé par une étape dans laquelle le corps adhérent à enlever et au moins la couche extérieure du bois de construction auquel le corps adhérent adhère, sont chauffés au moyen de radiation micro-ondes, et par une étape dans laquelle le décapage mécanique du corps adhérent chauffé est réalisé au moyen d'une technique de décapage mécanique connue en elle-même, avant que la pièce soit refroidie à la température ambiante.

2. Procédé selon la revendication 1, caractérisé par le décapage d'une partie seulement du corps, et par la répétition des deux étapes ou par le décapage du corps restant en utilisant toute autre méthode.

3. Equipement pour la mise en oeuvre du procédé de décapage mécanique d'un corps adhérent se présentant sous la forme de peinture ou mastic d'une pièce en bois de construction et comprenant une étape dans laquelle le corps adhérent est chauffé, selon au moins une des revendications 1 ou 2, caractérisé par un four micro-ondes muni d'une chambre de chauffe apte à contenir la pièce en bois de construction sans contact mécanique direct avec les surfaces intérieures de la chambre de chauffe, et par un poste de décapage de corps adhérent comportant des moyens de décapage mécanique.

4. Equipement selon la revendication 3, caractérisé en ce qu'il est conçu pour être mobile.

Drawing