GB2145442A

GB2145442A - Apparatus and method for wood treatment

Info

Publication number: GB2145442A
Application number: GB08417169A
Authority: GB
Inventors: Derek William Whittle
Original assignee: UNIVERSAL WOOD PRODUCTS MACHIN
Current assignee: UNIVERSAL WOOD PRODUCTS MACHIN
Priority date: 1983-07-06
Filing date: 1984-07-05
Publication date: 1985-03-27
Also published as: GB8417169D0; GB2145442B

Abstract

Apparatus for treatment of wood by a treatment fluid such as a paint or impregnating material, comprising a chamber (68) through which the wood is passed via inlet and outlet ports (72, 74). The chamber (68) is subjected to a partial vacuum whereby to cause air to flow into the chamber via the clearances at the inlet and outlet ports (72, 74), the resulting air flow over the wood in these regions causing excess fluid to be pulled off the wood and led away to a reservoir (64). <IMAGE>

Description

SPECIFICATION Apparatus and method for wood treatment This invention relates to the treatment of wood by treatment fluids such as paints, stains and preservatives.

A known apparatus of this type includes what is termed a deluge-and-brush type priming machine which is used for painting wood components for the joinery industry. In such a priming machine, timber is saturated with a deluge of paint from nozzles supplied by a main paint holding tank via a self priming pump. A simple feed system, i.e. driven roller and an idle pressure roller, feeds the timber into the machine which then passes through the deluge area where it is saturated by paint on all faces. After passing through this deluge area, a number of fixed brushes which are generally adjustable for width and thickness, relative to the timber section being coated, remove the surplus paint thus evening out the paint over the surface.

A problem in practice with such machines is that, after a relatively short period of time, the brushes become loaded with paint and the timber which is being coated drips with excess paint on leaving the machine, thus resulting in a poor quality finish, excessive use of paint and long drying periods before the timber can be used or delivered to site. This also leaves a very untidy working area and the operators need protective clothing. The cost factors using this method are very high.

An object of the present invention is to provide a wood treatment apparatus which is cleaner in operation, uses less treatment fluid and results in quicker drying of the treated wood.

According to a first aspect of the present invention there is provided a method for the fluid treatment of wood wherein surplus fluid applied to the wood is removed by passing the wood progressively through a partialiy evacuated chamber whereby to establish an air flow over the wood within the chamber.

According to a second aspect of the invention there is provided an apparatus for the fluid treatment of wood, comprising a nonfluid-tight chamber through which the wood can be passed and evacuating means for subjecting the chamber to a continuous partial vacuum so as to remove surplus fluid from the wood by the flow of air pulled from the chamber.

According to a third aspect of the invention there is provided an apparatus for the treatment of wood by a treatment fluid, comprising a chamber having inlet and outlet ports via which treated wood or wood to be treated in the chamber can be passed through the chamber, and means for continuously subjecting the chamber to a partial vacuum so as to cause air to flow into the chamber via clearances at the inlet and outlet ports whereby the resulting air flow over the wood in these regions causes surplus treatment fluid to be pulled off the wood.

According to a fourth aspect of the invention there is provided a method for the fluid treatment of wood wherein surplus treatment fluid is removed from treated wood by passing the wood through a continuously evacuated chamber via inlet and outlet ports whereby to cause air entering the chamber at said inlet and outlet ports for the wood to flow over the wood at least in the regions of these ports.

The invention also provides an apparatus for treating wood, which comprises a means for spraying wood with treatment fluid, a means for brushing at least some surplus treatment fluid from the sprayed wood, and a means for applying a vacuum to the brushed wood to cause an airflow over the wood to thereby remove further treatment fluid from the wood.

The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic elevation of one embodiment of an apparatus in accordance with this invention for treating wood; Figure 2 is a perspective view showing in more detail the vacuum chamber of the embodiment of Fig. 1; and Figure 3 is a diagrammatic side view of a second embodiment of an apparatus in accordance with the present invention.

Referring first to Figs. 1 and 2 of the drawings, the wood or timber to be treated is fed between a feed roller 10 (driven by a gear drive 12) and an adjustable top feed roller 14 to a spray area 1 6 in which it is sprayed from all sides from nozzles 18 supplied with paint, stain or other treatment liquid from a reservoir 20 by a pump 22. The saturated timber is then passed between top, bottom and side rotating brushes 24, 26, 28, respectively, with a view to removing surplus paint from all surfaces of the wood, the brushes being driven by a common geared drive (not shown). The surplus paint removed by the brushes returns to the reservoir 20. These brushes, which preferably are of a cylindrical configuration, are adjustable for different widths and thickness of timber. Various qualities of brushes are used depending on the type of coating to be applied.After passing through the brushes 24, 26, 28, a further system using vacuum removes any remaining surplus coating and renders the timber evenly coated and relatively dry compared to current methods indicated above.

The vacuum system includes a vacuum chamber 30 (see Fig. 2) which has entrance and exit ports 32, 34, respectively, which are provided with shaped templates 36 to conform to the cross-sectional configuration of the timber being treated. Cylindrical wire brush pressure rollers 38 (Fig. 1) are disposed adjacent the inlet and outlet ports for guiding the timber on entering and leaving the vacuum chamber. The latter rollers, which are adjustable for width and thickness of timber to prevent any deviation of the timber on entering or leaving the vacuum chamber, rotate but are not necessarily driven, other than by the wood itself.

The chamber 30 is essentially in the shape of a rectangular box having a base wall 40, end walls 42, 44, side walls 46, 48 and a top wall 50 which can be in the form of a removable inspection lid. The entrance and exit ports are located in the end walls 42, 44 respectively. Extending upwardly into the chamber 30 adjacent the side walls 46, 48 are a pair of rectangular sectioned ducts 52, 54 whose upper, open ends lie below the level of the lid 50 but above the level of the ports 32, 34, i.e. above the top of the wood when the wood is passing through the chamber. The lower, open ends 52a, 54a of the ducts extend out of the chamber 30 and communicate with a main tank 56 (Fig. 1).

The main tank 56 also communicates, via baffles A, B and C, and via a filter 58 with one, two or more regenerative blowers 60 of a size determined by the maximum timber section to be handled.

By evacuating the tank 56 and hence the chamber 30 (by way of the ducts 52, 54) a high velocity air flow is established through the inevitable clearances between the wood and the surrounding templates 36 where the wood enters and leaves the chamber 30, this air flow running across the wood at these regions, and leaving the chamber 30 via the ducts 52, 54. Any surplus coating fluid remaining on the wood is pulled off by this air flow, and carried over the weirs defined by the edges 52b, 54b of the ducts and thence back to the main tank where such fluid is collected and returned to the spray area by way of a return pipe 62.

By means of the above described apparatus, coating material costs saving up to 30% or more can be obtained. Drying time can be more than halved leaving the work area in a clean and tidy condition.

The above described embodiment involves the three steps of spraying, brushing a vacuum application. Particularly when the treatment fluid to be applied is of a water-based nature, such as a water-based paint, it is possible to omit the spraying and brushing stages as illustrated in the embodiment of Fig.

3.

With reference to Fig. 3, the apparatus comprises a main tank 64 to which a coating fluid is supplied by means not shown. The tank 64 contains steel baffles C and D similar to the baffles A, B and C of the embodiment of Figs. 1 and 2, and a similar regenerative blower vacuum system (not shown) for pulling a high vacuum in the main tank 64. The coating material is pumped (by means not shown) from the base of tank 64 upwardly via a pipe 66 to an application chamber 68 through which a length of wood 70 to be treated is passed via inlet and outlet ports 72, 74, respectively. The application chamber 68 is of exactly the same construction as the vacuum chamber 30 of Fig. 2 except that the bottom wall 40' has an aperture through which the pipe 66 can introduce treatment fluid from the main tank 64.

The pipe 66 opens into the chamber 68 in the centre of the bottom wall 40', beneath the wood 70. As before, the lower ends of the two rectangular-sectioned ducts, whose upper ends form the weirs, communicate at their lower ends with the evacuated main tank 64 whereby air is drawn out of the chamber 68.

By pulling air at a high velocity back into the main tank 64 via the weirs and the clearance around the timber allowed for by the templates, the treatment fluid supplied via the pipe 66 is caused to lift upwards so that a vortex of such fluid is created which comes into contact with the lid of the chamber 68 and passes over the two weirs and back to the main tank 64 under gravity. Wooden pieces passing through the vacuum chamber have to penetrate the vortex of treatment fluid and leave the chamber duly coated. At the same time, there is established a strong inwardly directed air flow in the regions 72, 74 where the wood enters and leaves the chamber 68.

This acts to draw off surplus coating from the wood. Adjustment or control of the air at the point of exit from the chamber can be achieved by means of a vacuum regulator valve (not shown).

Pieces of timber inside the chamber 68 are held in position by two adjustable plastics side guides and/or two adjustable plastics roller guides 80 positioned above the timber or moulding at the entry and exit ports 72, 74.

It is found that this latter system probably only works with water-based coatings due, inter alia, to the amount of turbulence created by the vacuum. A defoaming agent added to the coating material prevents excessive foaming under vacuum.

Claims

1. A method for the fluid treatment of wood wherein surplus fluid applied to the wood is removed by passing the wood progressively through a partially evacuated chamber whereby to establish an air flow over the wood within the chamber.

2. An apparatus for the fluid treatment of wood, comprising a non-fluid-tight chamber through which the wood can be passed and evacuating means for subjecting the chamber to a continuous partial vacuum so as to remove surprc,-.fluid from the wood by the flow of air pulled from the chamber.

3. An apparatus for the treatment of wood by a treatment fluid, comprising a chamber having inlet and outlet ports via which treated wood or wood to be treated in the chamber can be passed through the chamber, and means for continuously subjecting the chamber to a partial vacuum so as to cause air to flow into the chamber via clearances at the inlet and outlet ports whereby the resulting air flow over the wood in these regions causes surplus treatment fluid to be pulled off the wood.

4. Apparatus as claimed in claim 3, wherein air is evacuated from the chamber by way of one or more ports disposed above the horizontal level of said inlet and outlet ports through which the wood enters and leaves the chamber.

5. Apparatus as claimed in claim 4, wherein the, or each, said outlet port is defined by the upper end of a generally downwardly extending duct disposed in said chamber, said upper end of the duct defining a weir over which fluid is drawn from the chamber by the evacuating means, fluid entrained in the air flow and passing over the weir being collected at the lower end of, or beneath, the duct for re-use.

6. Apparatus as claimed in any of claims 3 to 5, wherein the fluid is applied to the wood for the purposes of said treatment by supplying same to the bottom of said chamber, the evacuation of said chamber causing a vortex of treatment fluid therewithin through which the wood passes.

7. Apparatus as claimed in claim 6, when appendent to claim 5, wherein said lower end of the duct communicates with a reservoir tank for containing the treatment fluid, and wherein a pump pumps fluid from the tank to said chamber, the evacuating means being connected to the tank for subjecting the chamber to said partial vacuum via the duct.

8. Apparatus as claimed in any of claims 3 to 7, including one or more guides disposed within the chamber and spaced inwardly of said inlet and outlet ports for engaging the wood when passing through the chamber such as to prevent the wood from being drawn against the walls of the inlet and outlet ports under the effect of the partial vacuum.

9. Apparatus as claimed in any of claims 3 to 5, including means for spraying the wood with treatment fluid and means for brushing at least some surplus fluid from the sprayed wood prior to its passage through said chamber,

10. Apparatus as claimed in claim 9, wherein the brush means comprises a plurality of rotary brushes, some of which are disposed for rotation about axes parallel to the direction of feed of the wood therepast and others of which rotate about axes perpendicular to the feed direction of tie wood.

11. An apparatus for treating wood, which comprises a means for spraying wood with treatment fluid, a means for brushing at least some surplus treatment fluid from the sprayed wood, and a means for applying a vacuum to the brushed wood to cause an airflow over the wood to thereby remove further treatment fluid from the wood.

1 2. Apparatus for the fluid treatment of wood, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

1 3. A method for the fluid treatment of wood wherein surplus treatment fluid is removed from treated wood by passing the wood through a continuously evacuated chamber via inlet and outlet ports whereby to cause air entering the chamber at said inlet and outlet ports for the wood to flow over the wood at least in the regions of these ports.

14. A method as claimed in claim 13, wherein treatment fluid is applied to the wood within said chamber.

1 5. A method as claimed in claim 13, wherein treatment fluid is applied to the wood prior to its passage through the chamber.

16. A method for the fluid treatment of wood, substantially as hereinbefore described with reference to the accompanying drawings.