WO1989010849A1

WO1989010849A1 - A method of preparing a composite body of wood and plastic

Info

Publication number: WO1989010849A1
Application number: PCT/DK1989/000111
Authority: WO
Inventors: Bjarne Bo Andersen
Original assignee: Bo-Line A/S
Priority date: 1988-05-04
Filing date: 1989-05-05
Publication date: 1989-11-16
Also published as: DK242788A; DK242788D0; AU3747589A

Abstract

A composite body is made from wooden material and plastics material by forming in a wooden body (10) a pattern of surface depressions (14) and/or through-going passages (16) extending between opposite surface parts of the wooden body. The wooden body (10) is arranged in a closed mould cavity of an injection mould (12) having an injection opening (18). Heated plastics material is now injected into the mould cavity through the injection opening (18) so as to fill the depressions (14) and/or passages (16) in the wooden body (10). The composite body made may be machined and/or polished after hardening of the plastics material, which may serve decorative or strengthening purposes.

Description

A METHOD OF PREPARING A COMPOSITE BODY OF WOOD AND PLASTIC

The present invention relates to a method of making a composite body from a wooden material and a plastics material. Such composite bodies are known in the form of laminates, in which layers of wooden material and plastics material, respectively, are bonded together by glue or other bonding means. From Swedish Patent No. 216,092 it is known to cover the outer surface of a wooden body, such as a table top or window frame, with a layer of polymer material. The wooden body is arranged in a closed mould cavity, in which partly hardened drops of the polymer material are used as spacing means for . maintaining the wooden body in the position in which its outer surface parts are spaced from the opposite inner surface parts of the mould, whereafter polymer material is injected into the spaces provided.

Swedish published application No. 451,370 discloses a method of providing the outer edge portion of a wooden plate with a layer of polyurethane. This is obtained by arranging the edge portion of the wooden plate in a frame-like mould so that a mould cavity is defined between the outer edge portion of the wooden plate and the mould. The polyurethane may then be introduced into the mould cavity through a passage formed in the wooden plate.

The present invention provides a method by means of which it is possible to make composite bodies of the above type in which the various characteristics of the two materials may be combined and utilized to a much higher extent than hitherto possible.

Thus, the present invention provides a method of making a composite body from wooden material and a plastics material, which is preferably thermoplastic, said method comprising forming in a body of wooden material a pattern of surface depressions and/or through-going passages, which extend between opposite parts of the wooden body, arranging the wooden body in a closed mould cavity of an injection mould having an injection opening, injecting heated plastics material into the mould cavity through said injection opening so as to fill the depressions and/or passages, and cooling the injected plastics material so as to harden the same.

The said depressions may be of any type, including non-through- oing bores, and a great variety of composite bodies having desired decorative and/or strength characteristics, may be produced by forming a suitable pattern of the said depressions and/or passages. As an example, a composite body resembling a body made from a blond type of wood with a decorative pattern of an inlaid darker type of wood may be made by making a similar pattern of depressions in a surface part of the wooden body and by injecting a dark coloured plastics material into these depressions. If the wooden body used is made from a relatively soft type of wood, the plastics material, which is injected into the depressions formed in the surface of the wooden body, may alternatively or additionally serve to increase the wear-resistance of the composite body. It is also possible to arrange more than one wooden body provided with surface depressions and/or passages, in the mould cavity. In that case, the plastics material injected into the mould cavity may serve to bind these wooden bodies together so that they are included in the same composite body.

Channel- or groove-like depressions may be formed in a pair of opposite surface parts of the wooden body, and at least some of these depressions in the opposite side surfaces or surface parts may be interconnected by through-going passages. In that case the plastics material filling the depressions and passages will form a spacial structure. In addition to the decorative surface effect obtained it is also possible to obtain an advantageous increase of the strengthening or stabilizing effect. As an example, such spacial structure of plastics material injection-moulded into the wooden body may prevent a deformation or distortion of the wooden body. The depressions or channels formed in the surface or surfaces of the wooden body may, for example, form a pattern of mutually spaced, parallel, or co-extending channels, or they may form a rhomboid pattern or a check pattern, for example a square grid. Such pattern of channel-shaped depressions formed on opposite side surfaces of the wooden body may be interconnected by one or more through- oing bores extending through the wooden body. The decorative effect, which may be obtained by using the method according to the invention, may in some cases be increased by machining surface parts of the composite body subsequently to hardening of the injected plastics material. Such machining may comprise turning, milling, cutting, planing, grinding and/or polishing. The total surface of the composite body may be machined, but it is also possible to machine only the surface of the wooden material or the surface of the plastics material of the composite body.

In the mould cavity, pressure forces may be applied to the wooden body so as to cause deformation of the same, and the plastics material may then be injected into such a pattern of depressions and bores or passages that, after hardening, the plastics material may substantially retain the wooden body in its deformed condition. The wooden body, which is arranged in the mould cavity, may, for example, be a plywood plate, which is pressed into a curved shape within the mould cavity. Alternatively, the wooden body may be a distorted wooden plate having an undesired curved shape. The distorted plate may then be pressed into its original, plane shape and may then be retained in this plane condition by the plastics material which has been injected into the depressions and passages.

The plastics material used in the method according to the invention may be a thermoplastic plastics material which is heated before it is injected into the mould cavity and hardens when cooled, or the plastics material may be any other known type of plastics which may be hardened in any other manner. When the hardened plastics material must have a certain tensile strength as in the example mentioned above, a fiber reinforced plastics material may be used. Because the plastics material may be given any desired colour, the versatility of the obtainable decorative effect is substantially improved.

The wooden body used in the method according to the invention may be any natural wooden body. However, it is also possible to use wooden bodies composed of several pieces of wood, such as plywood or chipboard. As explained below, the characteristics of such wooden bodies of plywood or chipboard may be improved when combined with plastics material by using the method according to the invention.

The wooden body or bodies arranged in the mould cavity of a mould, which may be of the type used in a conventional injection moulding apparatus, may - apart from the depressions and passages formed in the surface of the wooden body - completely fill the mould cavity. The inlet of the injection mould may then be positioned opposite to one or more of these depressions or passages so that they may all be filled with plastics material. Alternatively, a space may be defined between at least one surface part of the wooden body and an adjacent part of an inner wall surface defining the mould cavity. In that case not only the depressions and passages formed in the wooden body, but also the said space will be filled with plastics material, whereby the said surface part of the wooden body will be provided with an outer plastic layer.

The method according to the invention may be used for making items, which are normally made from plastics or wood, such as carving boards, platters, pepper querns, egg cups, table tops, chair seats, table and chair legs, and other furniture parts, sporting equipment, chess boards, window frames, window sills and other building parts, etc.

According to another aspect the present invention also relates to a composite body made by the method described above and comprising a wooden body having formed therein a pattern of depressions and/or through-going passages extending between opposite surface parts of the wooden body, and a hardened thermoplastic plastics material which has been injected into these depressions and/or passages in a heated condition so as to substantially fill the same.

The invention will now be further described with reference to the drawings, wherein

Fig. 1 diagra matically illustrates a wooden block arranged within a closed mould cavity, the walls of the mould being partly cut away, Fig. 2 is a first embodiment of a composite body made by the method according to the invention, Fig. 3 is a second embodiment of a composite body made by the method according to the invention, a fragment of said body having been cut away, and the injected plastics material having partly been removed, Fig. 4 is a fragment of a third embodiment of a composite body made according to the invention, the side surfaces of said body being covered by an outer layer of a plastics material, Fig. 5 is a wooden block, which may be used for making a fourth embodiment of a composite body by using the method according to the invention, and which is provided with axial, through-going bores, Fig. 6 shows said fourth embodiment of a composite body made by using the wooden block shown in Fig. 5,

Fig. 7 is a bended or curved fifth embodiment of a composite body made by the method according to the invention, and Figs. 8, 9 and 10 are sixth, seventh, and eighth embodiments, respectively, of composite bodies made by the method according to the invention.

Fig. 1 shows a wooden block 10, which is arranged in and surrounded by a substantially closed mould 12, such as an injection mould. A pattern of channel-shaped depressions 14 is formed in opposite side surfaces of the wooden block 10, and each pattern comprises a plurality of mutually spaced, parallel depressions, which are interconnected by one or more transversely extending depressions, and the patterns of channel-shaped depressions in the opposite side surfaces of the wooden block may be interconnected by through- oing passages or bores 16, vide Figs. 2 and 3. The mould 18 comprises an injection inlet 18, through which plastics material in a plastic or liquid condition may be injected. The plastics material injected into the mould cavity will completely fill the free spaces in the mould, including the channel-shaped depressions 14 and the through-going bores 16. The plastics material is now allowed to harden or solidify at least partly, so that the composite body produced may be removed from the mould cavity. If the plastics material has not been completely hardened before the body is removed from the mould, the final hardening may take place after removal.

Fig. 2 shows a first embodiment of a finished composite body 20, which may, for example, be used as a carving board, and which may be made by the method described above with reference to Fig. 1. The plastics material not only forms a decorative pattern 22 in the opposite side surfaces of the wooden block, but may also serve to improve the wear-resistance of the composite body. As shown in the drawings, the colour of the pattern 22 may be in contrast to the colour of the wooden body, and, if desired, the plastics material forming the pattern 22 may extend slightly beyond the adj cent surface of the wooden body 10.

Fig. 3 shows a second embodiment 24 of a composite body made by the method according to the invention. This composite body comprises a wooden block 18 having a pattern of endless, annular, channel-shaped or groove-shaped depressions, which extend along all of the outer surfaces of the wooden block 18. In order to facilitate distribution of the injected plastics material into the depressions 14, the depressions formed in the upper and lower side surfaces of the block 18 may be interconnected by through-going bores 16. Thus, when the depressions 14 and the bores 16 have been filled with plastics material 26, the hardened plastics material forms a spacial structure, which has not only a decorative effect, but also improves the strength of the composite body 24 and tends to counteract distortion of the wooden block 18.

The third embodiment 24 shown in Fig. 4 comprises a wooden block 18 having a pattern of depressions and bores substantially like the wooden block shown in Fig. 3. The wooden block shown in Fig. 4 has been provided with an outer layer 28 of plastics material which may be impermeable to water and moisture so as to prevent delamination of the wooden block 18, when it is made of plywood or a similar laminated material.

Figs. 5 and 6 show a wooden block 30 for making a fourth embodiment of the composite body according to the invention, and such composite body 32, respectively. The wooden block 30 defines therein a large, central, through-going bore 34 and a plurality of smaller through- going bores 36 arranged along a circle concentric with the larger bore 34. When the block 30 has been arranged in a mould cavity defined by inner walls which may engage tightly with the outer side surfaces of the block 30, plastics material may be injected into the smaller bores 36, for example through an annular injection inlet opening registering with one end on the bores 36. When the plastics material injected into the bores 36 has hardened, the block 30 may fee turned in a turning lathe or exposed to machining of any other kind so as to obtain a cylindrical, tubular composite body 32 as that shown in Fig. 6 where the plastics material injected into the bores 36 is exposed. The composite body 32 shown in Fig. 6 may, for example, be used for making a pepper quern or a similar device.

Fig. 7 shows a fifth embodiment 40 of the composite body according to the invention. This composite body may be made of a substantially plane wooden block 41. In the injection mould the wooden block may foe exposed to a pressure so as to bend the same into a desired curved shape. Plastics material 42 may now be injected into a pattern of depressions formed in the wooden block, and provided that the composite body made is not removed from the mould until the plastics material 42 has hardened, the plastics material may retain the wooden body in its bended shape. The plastics material 42 used by making tke composite body 40 shown in Fig. 7 is preferably a fiber reinforced plastics material. The principle of bending a wooden body in the mould as described with reference to Fig. 7 may advantageously be used for making furniture parts, such as backs and arm rests for chairs.

Fig. 8 shows a sixth embodiment 44 of the composite body according to the invention. In this embodiment plastics material 45 has been injected into surface depressions of a wooden block 46 so that the outer surface of the plastics material 45 substantially flushes with, the outer surface of the wooden block 46 after hardening of the plastics material. Such flushing may also have been obtained by machining and/or grinding or polishing the outer surfaces of the composite body subsequently to the moulding process.

Fig. 9 shows a seventh embodiment 48 of the composite body according to the invention corresponding to the embodiment shown in Fig. 8. However, in Fig. 9 the injected plastics material 49 has been raised in relation to the adjacent outer surface of the wooden block 50. The embodiment shown in Fig. 9 may be made by arranging the wooden block 50 in a mould having channel- or groove-shaped depressions formed in the inner walls defining the mould cavity opposite to the depressions formed in the wooden block. Alternatively, the plastics material 49 may be expanded, for example by foaming, after removal of the composite body from the mould. It is also possible to obtain the raised patterns of plastics by machining or grinding the surface of the wooden block in which the depressions receiving the plastics material are formed, without machining the plastics material.

Fig. 10 shows an eighth embodiment 52 of the composite body according to the invention, where the outer surface of the plastics material 53 injected into a pattern of depressions formed in a wooden block 54 is somewhat retracted in relation to the adjacent surface of the wooden block. Such an embodiment may be made by arranging the wooden block 54 in a mould cavity having fins or ridges which may partly extend into the depressions formed in the wooden block. Alternatively, a type of plastics material which shrinks during hardening may be used. It is also possible to remove a part of the plastics material by grinding or machining the same after hardening.

Composite bodies of the types shown in Figs. 9 and 10 where a groove¬ like depression or a small ridge of plastics material extends along the edge portion of a plate-like wooden body, may, for example, be used as a table top, a carving board or the like. The raised or retracted plastics material may then prevent liquid from passing the edge portion of the table top or the carving board.

It should be understood that a large variety of other composite bodies than those shown in the drawings could be made by using the method according to the invention. As an example, the mould cavity in which the wooden body is arranged, may have such a shape that plastic parts, which are securely anchored in the wooden block, but extends from the outer surface thereof, may be made. Such extending plastic parts may comprise hinge parts, handles or hand grips and other parts which are normally fastened to the wooden body by means of glue, screws, nails, staples or similar fastening means.

Claims

1. A method of making a composite body from wooden material and plastics material, said method comprising forming in a body of wooden material a pattern of depressions and/or through-going passages, which extend between opposite surface parts of the wooden body, arranging the wooden body in a closed mould cavity of an injection mould having an injection opening, injecting heated plastics material into the mould cavity through the injection opening so as to fill the depressions and/or passages, and cooling the injected plastics material so as to harden the same.

2. A method according to claim 1, wherein a pattern of channel- or groove-like depressions are formed in each of a pair of opposite surface parts of the wooden body, and at least some of the depressions in the opposite surface parts being interconnected by through-going passages.

3. A method according to claim 2, wherein the wooden body is a plate-shaped body having a pair of opposite side surfaces in which said depressions are formed, the depressions in each side surface comprising a plurality of substantially rectilinear, mutually spaced, parallel depressions.

4. A method according to claim 3, wherein said plurality of parallel depressions are interconnected by at least one transversely extending channel- or groove-like depression.

5. A method according to any of the claims 1-4, further comprising machining surface parts of the composite body subsequently to hardening of the injected plastics material.

6. A method according to any of the claims 1-5, further comprising applying pressure forces to the wooden body in the mould cavity so as to cause deformation of the wooden body prior to hardening the plastics material, the plastics material being injected into such a pattern of depressions and passages that after hardening the plastics material may retain the wooden body in its deformed position.

7. A method according to any of the claims 1-6, wherein the plastics material injected is a fiber reinforced plastics material.

8. A method according to any of the claims 1-7, wherein the wooden body is a composite wooden body, which is for example made from plywood or chipboard.

9. A method according to any of the claims 1-8, wherein a space is defined between at least one surface part of the wooden body and an adjacent part of an inner wall surface defining the mould cavity.

10. A composite body made by the method according to any of the claims 1-9, and comprising a wooden body having formed therein a pattern of depressions and/or through-going passages extending between opposite surface parts of the wooden body, and a hardened thermoplastic plastics material, which has been injected into these depressions and/or passages in a heated condition so as to substantially fill the same.