TREATMENT OF TIMBER

Abstract: Method and apparatus for applying treatment liquid to timber by dipping at atmospheric pressure. The timber is in a batch comprising pieces with flat faces engaged together face to face, and the timber batch is moved on a pivotally mounted support 1 into an open-topped container 2. The support receives the timber batch with the interengaged faces horizontal, and then moves through a 90° arc so that the batch is dipped with said faces vertical.

Description: "Treatment of timber" This invention relates to the treatment of timber with liquid, for example with preservative or fireretardant agents, or with decorative paints, or stains such as anti-sapstains, or base coats, or indeed any treatment which involves the application of a liquid to the timber surface. It is known to apply treatment liquid by dipping at atmospheric pressure, by lowering the timber into an unpressurised open container of treatment liquid and holding it there for an appropriate time. A disadvantage of this process as carried out at present is that if the timber comprises batches of flat pieces, e.g. boards or planks, piled on each other in face to face relationship, and often indeed pressed together in a pack by binding straps, substantial areas of the unexposed surfaces of the timber fail to receive any treatment liquid. Tests have indicated that only between about 50% and 60% of the boards in a close banded pack were wetted over their whole surface when the packs were dipped for 15 minutes in the conventional manner, i.e. with the interengaging faces of the boards substantially horizontal. Viewed from one aspect the present invention provides a method of applying treatment liquid to timber by dipping at atmospheric pressure, the timber being in batches comprising pieces with flat faces engaged together face to face, comprising dipping the timber in the treatment liquid with the said interengaged flat faces at a substantial angle to the horizontal, preferably in the region of 900 Tests have shown that when close-packed timber is dipped for 15 minutes with its interengaging surfaces substantially vertical, between 89% and and 92.5% of the boards were wetted over their whole surface. Furthermore the individual unwetted areas were substantially smaller than when the timber was dipped horizontally. Preferably the method of the invention involves turning the batch of timber from a horizontal orientation, in which it will normally be transported to and from the dipping station, to a (preferably substantially vertical) dipping orientation, and subsequently turning the treated batch back again to the horizontal. Preferably such changes in orientation are carried out whilst the timber is being lowered into the treatment liquid and lifted out again, respectively. Viewed from another aspect the invention provides apparatus for applying treatment liquid, by dipping at atmospheric pressure, to a batch of timber comprising pieces with flat faces engaged together face to face, comprising an unpressurised container for treatment liquid and a support for the said timber batch, the support being movable relative to the container between a timber receiving position, in which it is arranged to receive a said timber batch with said interengaging flat faces substantially horizontal, and a dipping position in which a timber batch on the support is located in the said container with said faces at a substantial angle to the horizontal, preferably in the region of 900. Preferably the said support comprises a cradle pivotally mounted above an open topped container for movement into and out of the latter through an arc of substantially 900. The cradle may be elongate and of substantially L-shaped transverse cross-section, one arm of the L being arranged to support a batch of timber when the cradle is in the receiving position and the other arm being arranged to support the batch when the cradle is rotated into the dipping position. Alternatively the cradle may comprise an elongate frame of substantially box-shaped transverse crosssection, one side of the frame being arranged to support a batch of timber when the cradle is in the receiving position and an adjacent side of the frame being arranged to support the batch when the cradle is rotated into the dipping position. Means for moving the cradle between its receiving and dipping positions may comprise, for example, one or more hydraulic cylinders pivotally connected to the cradle, or one or more vertical screw shafts mounting movable nuts pivotally connected to the cradle. An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of a timber dipping apparatus according to the invention, with the timber support cradle in its position for receiving a batch of timber to be treated; Figures 2 and 3 are diagrammatic end views of the apparatus of Figure 1, illustrating two stages in the dipping of a batch of timber; and Figure 4 is a diagrammatic end view of a second embodiment. The apparatus illustrated in Figures 1, 2 and 3 comprises a timber support cradle 1 on which a batch of timber can be loaded, and secured by straps or chains, in the orientation in which it is normally handled by for example a fork lift truck, i.e. with the interengaging surfaces of the timber in the batch extending horizontally. The timber is thus located above the treatment liquid in an open-topped container 2. Mechanism for moving the L-shaped cradle 1 between timber receiving and timber dipping positions comprises two hydraulic cylinders 3, 4 which act through their piston rods 5, 6 on riders 7, 8 running in guides 9, 10, the riders being connected one to each of two linking arms 11, 12 which transfer their movement to the cradle 1 through bearings 13, 14 in such a way as to cause the cradle to rotate about pivot bearings 15 to 20. Thus contraction of the cylinders 3, 4 causes the cradle and a batch of timber thereon to be lowered into the container 2 whilst at the same time the batch is re-orientated through 900 to a position in which the interengaging surfaces of the timber pieces are substantially vertical, for treatment. Extension of the cylinders after an appropriate dipping period returns the cradle and the batch to their starting position for the batch to be removed. Figure 4 illustrates a second embodiment in which the dipping position of the apparatus is shown by ghost lines. In this embodiment, the mechanism for moving the cradle comprises a pair of screw shafts 21 vertically mounted one at each end of the cradle 1. The screw shafts are rotatably driven by individual motors 22 which are mechanically linked by a shaft (not shown) to ensure synchronization of the motion of both ends of the cradle. Each screw shaft mounts a nut 23 fixed against rotation and connected to a linking arm 24 which transfers its vertical movement to the cradle to bring about movement thereof similar to the movement of the cradle in the first embodiment. Thus, rotation of the screw shafts in one direction lowers the cradle into the dipping position, while reversing the rotation returns it to the starting position. In this embodiment, as the ends of the cradle are unobstructed in the starting position, batches of timber may be delivered to and removed from the cradle in the direction of its length, for example on suitable conveyors. The method and apparatus of the invention are particularly useful for treating fresh sawn softwoods whose moisture content is so high as to make pressurised impregnation impracticable.

Claims: CLAIMS 1. A method of applying treatment liquid to timber by dipping at atmospheric pressure, the timber being in a batch comprising pieces with flat faces engaged together face to face, comprising dipping the timber in the treatment liquid with the said interengaged flat faces at a substantial angle to the horizontal. 2. A method as claimed in claim 1, wherein said angle is in the region of 900, so that said interengaged flat faces are substantially vertical. 3. A method as claimed in claim I or 2, including the steps of turning the batch of timber from a horizontal orientation through said substantial angle to a dipping orientation, and subsequently turning the treated batch back again to the horizontal. 4. A method as claimed in claim 3, wherein the changes in orientation are carried out whilst the timber is being lowered into the treatment liquid and lifted out again, respectively. 5. Apparatus for applying treatment liquid, by dipping at atmospheric pressure, to a batch of timber comprising pieces with flat faces engaged together face to face, comprising an unpressurized container for treatment liquid and a support for said timber batch, the support being movable relative to the container between a timber receiving position, in which it is arranged to receive a said timber batch with said interengaged faces substantially horizontal, and a dipping position in which the timber batch on the support is located in the said container with said faces at a substantial angle to the horizontal. 6. Apparatus as claimed in claim 5r wherein said angle is in the region of 900, so that said interengaged flat faces are substantially vertical. 7. Apparatus as claimed in claim 5 or 6, wherein the said support comprises a cradle pivotally mounted above said container, which is open topped, for movement into and out of the latter through an arc. 8. Apparatus as claimed in claim 7, wherein the said cradle is elongate and of substantially L-shaped transverse cross-section, one arm of the L being arranged to support a batch of timber when the cradle is in the receiving position and the other arm being arranged to support the batch when the cradle is rotated into the dipping position. 9. Apparatus as claimed in claim 7, wherein the said cradle is elongate and comprises a frame of substantially box-shaped transverse cross-sction, one side of the frame being arranged to support a batch of timber when the cradle is in the receiving position and an adjacent side of the frame being arranged to support the batch when the cradle is rotated into the dipping position. 10. Apparatus as claimed in claim 8 or 9, wherein means for moving the cradle between its receiving and dipping positions comprises one or more hydraulic cylinders pivotally connected to the cradle. 11. Apparatus as claimed in claim 8 or 9, wherein means for moving the cradle between its receiving and dipping positions comprises one or more vertical screw shafts mounting movable nuts pivotally connected to the cradle.

Inventors: HANSON, ARTHUR NEVILLE
Applicants: HICKSON'S TIMBER PRODUCTS LIMITED
Application year: 1983
Main classification: B27K3
IPC codes: B27K3