WO2002026455A2

WO2002026455A2 - Method and apparatus for moulding synthetic wood and product used therein

Info

Publication number: WO2002026455A2
Application number: PCT/ZA2001/000127
Authority: WO
Inventors: Barry Lipman
Original assignee: Steinhoff Manufacturing (Pty) Ltd.
Priority date: 2000-09-29
Filing date: 2001-08-29
Publication date: 2002-04-04
Also published as: AU2001295096A1; WO2002026456A3; AU2001293317A1; WO2002026456A2; WO2002026455A8; WO2002026455A3; WO2002026456A8

Abstract

A method of and apparatus for moulding using a die (10) having a face (15) formed with at least one moulding cavity (12) therein including the steps of filling the mould cavity to excess with a desired moulding material (42), placing a backing sheet (20) over the face of the mould and pressing the backing sheet and mould against each other to compact and shape the mould material by moving the die and backing sheet at least once between two spaced, substantially parallel roller (26, 28). Excess mould material is removed by slicing across the face of the die prior to removing a moulding from the die.

Description

MOULDING SYSTEM

TECHNICAL FIELD:

This invention relates to moulding articles of a mouldable material by compressing the material and is concerned primarily, though not necessarily exclusively, with moulding synthetic wood articles from a synthetic wood paste.

BACKGROUND ART:

The carvings of so called "carved furniture" are very seldomly done by hand today. Instead, a craftsman carves a prototype of an article or trimming from which a reproduction mould is produced. The reproductions are made using a synthetic wood paste composed of a binder, a solvent and wood flour (usually obtained as residue from sanding) that can be stained, painted, sanded, polished, etc. when set to have the appearance of natural wood. The known moulding technique uses a flat die that is filled with the wood paste, inverted and placed on a backing board coated either with a release agent or a bonding agent if the board itself will be a furniture panel. The mould and board are then compressed using a hydraulic press, ranging in capacity from 20 to 800 tonnes depending on the size of the moulding or the number and size of mouldings in a multi-cavity die. In practice, only the larger or multi-cavity dies are commercially viable in even medium or small scale manufacturing operations, because of the cycle times required. On the otherhand large dies and presses are relatively expensive to purchase and operate.

Thus this invention seeks to provide a method of and apparatus for moulding wood paste that satisfactorily replaces the use of hydraulic presses at lower costs.

DISCLOSURE OF THE INVENTION:

The invention provides a method of moulding using a die having a face formed with at least one moulding cavity therein, including the steps of:

-- filling the mould cavity to excess with a desired moulding material; -- placing a backing sheet over the face of the die to cover the mould cavity;

~ moving the die and backing sheet at least once between two rollers, the rollers being spaced apart to apply a compressive force to the die and backing sheet and having their axes substantially parallel to each other; -- removing the backing sheet; and -- removing the moulded material from the moulding cavity.

The method may include one or more of the following features: -- moving the die and backing sheet several times in opposite directions between the two rollers;

-- driving at least one of the rollers, so that movement of the roller cause the die and backing sheet to move between the two rollers;

-- driving the roller alternatively in opposite directions to cause the die and backing sheet to move in opposite directions between the two rollers;

- interlocking the die and backing sheet in order to inhibit slipping of the backing sheet relatively to the die when they move between the rollers.

- trimming excess mould material, if any, from the face of the die in the region of the mould cavity; and

- trimming the excess mould material by slicing it along the plane of the face of the die immediately adjacent the face of the die.

Another aspect of the invention provides apparatus for moulding a settable material using a die having a face formed with at least one moulding cavity therein and a backing sheet for covering the face of the die and means for pressing the backing sheet against the die, wherein the pressing means comprises a pair of rollers having their axes of rotation substantially parallel to each other and being spaced apart sufficiently to allow the die and backing sheet to pass between them while compressing the backing sheet against the face of the die.

Preferably the apparatus includes support means providing a substantially planar support surface along which with the die and backing sheet can move, the plane of the support surface being parallel to the axis of at least one of the rollers and intersecting a nominal plane extending between the axes of the rollers. Preferably the support surface extends laterally on both sides of the rollers transverse to their axes, has an opening in the region of the rollers and the rollers are on opposite sides of the support surface. Preferably one of the rollers is spaced from the support surface and the other roller has a circumferential region that protrudes through the opening.

Preferably friction means, such as abrasive sheet material is provided on at least one of the rollers and on at least one of the exposed sides of the die and backing sheet in order to inhibit slipping of the backing sheet and die relatively to at least one of the rollers.

Preferably means is provided for interlocking the die and backing sheet to each other in order to inhibit slipping of the backing sheet relatively to the die when they move between the rollers.

The apparatus preferably includes trimming means for trimming any excess mould material remaining on the face of the die after moulding. Preferably the trimming means slices across the face of the die to remove such excess mould material. Preferably the trimming means is a band saw, band knife and the like.

The invention also includes a moulding made using the method or the apparatus of the invention.

Further features, variants and/or advantages of the invention will emerge from the following non-limiting description of an example of the invention made with reference to the accompanying schematic drawings.

BRIEF DESCRIPTION OF THE DRAWINGS: Figure 1 shows a plan view of a multi-cavity die for use in the method of the invention;

Figure 2 shows a sectioned side view of the die of Figure 1 ;

Figure 3 shows a perspective view of die of Figure 1 , loaded with moulding material and a backing sheet; Figure 4shows a side view of a machine for pressing the die of Figure 1 ;

Figure 5 shows a perspective view of a roller of the machine of Figure 4;

Figure 6 shows a side view of the die after moulding, with the backing sheet removed and excess mould material being sliced away by a slicing machine; and Figure 7 shows an end view of the die and slicing machine in the direction of arrow VII of Figure 6.

BEST KNOWN MODE FOR CARRYING OUT THE INVENTION:

In the drawings the same or similar parts have the same reference numbers, certain parts having sub-numbers to identify them as part of a component or as substantially equivalent parts in different embodiments.

Figures 1 and 2 show a die 10 for moulding a plurality of synthetic wood carved ornamentations in mould cavities 12. The die comprises a wood base or body 14 having a face 15 formed with moulding recesses 16. The patterns to be moulded are formed in the recesses using a settable polyol that sets with minimal shrinkage, such as of the order of 1 to 2% maximum, and forms an accurate negative representation 18 of a master pattern. Holes 19 for registration pins 19.1 (shown in Figure 6) are formed in the die body.

Figure 3 shows the die 10 with the cavities filled to excess with a wood paste and the face substantially covered with a stiff backing sheet 20, for example 16 to 18 mm high density compressed wood particle board. The die is shown inverted, as this is how it will be further processed. The wood paste is composed of wood flour mixed with a suitable binder and a solvent as are known in the art. A filler, preferably of fine perlite, is included in the paste composition in order to decrease cost, improve or ensure homogenous mixing and decrease the cost of materials.

A strip of abrasive sheet material or sandpaper 22 is bonded to the reverse face of the die. A strip of similar abrasive sheet material is bonded to the outer face of backing sheet 20.

Registration pins 19.1 , as shown in Figure 6, are inserted through the holes 19 in the die body and registering holes in the backing sheet to hold the die and backing sheet relatively to each other.

Figures 4 and 5 show part of a machine 24 for compressing the die against the backing sheet. The machine comprises an upper, vertically movable, driven roller 26, a fixed lower roller 28, a support table 30 formed with a slot 31 through which the lower roller protrudes slightly upwardly. The roller 26 is driven by an electric drive motor through a gearbox, neither of which are shown. One of the drive motor and gearbox is reversible, so that the roller can be driven in opposite directions. The upper roller 26 is mounted so it can be moved vertically with respect to the lower roller 28 and then be locked in place to set the force by which the backing plate is compressed against the die 10. Each roller 26, 28 has a band of abrasive paper 22.1 bonded to it in a medial region.

Figures 6 and 7 shows a slicing machine 32 for removing excess wood paste from the face 15 of the die 10 after it has been compressed. The slicing machine 32 comprises two spaced rollers 34 and 36, of which roller 34 is driven by a motor, not shown, and a knife band 38 fitted over the two rollers. The roller 36 is biassed away from the roller 34 by a tension spring 40 in order to tension the band 38. The drawings also show moulded wood paste 42 in the mould cavities 12 and excess wood paste 42.1 on the face of the mould.

In practice, a wood moulding is made as follows. First a pattern is carved or formed in wood, clay, settable resin and the like. The pattern is then used to make the mould 10, using a settable polyol in the recesses 16 formed in a wood base. A wood paste mixture is then moulded by filling the cavities 18 to excess with the mixture, placing the backing sheet over the face 15 of the mould and feeding the mould and backing sheet between the rollers 26 and 28 first in one direction and then the other several times, e.g. two to four times. For this purpose the spacing between the rollers is set at the thickness of the mould plus the backing sheet, excluding the thickness of excess material on the face of the mould and the roller. The abrasive strips ensure a good grip between the mould, backing sheet and rollers. The abrasive strips also function to inhibit slip between the mould and backing sheet, though such slippage is mainly controlled by the registration pins 19.1 fitting into the holes 19. Moving the mould between the rollers successively presses the wood paste mixture, so that ultimately it is compacted and shaped to conform accurately to the mould cavity.

Testing of the method has proven that it compares more than the favourably with the known use of large hydraulic presses. Even a relatively small, table top machine provides a compression that is comparable to a 800 tonne hydraulic press, yet it is significantly less expensive to buy, make and operate than the hydraulic press and is quicker to use, reducing the cycle time for each multi-cavity mould by about 50%.

The invention is not limited to the precise details described above and shown in the drawings. Modifications may be made and other embodiments developed without departing from the scope of the invention as set out in the appended claims. The numbers in the claims are for illustration to facilitate understanding the claims only and are not intended to restrict the scope of the claims in any way.

Claims

CLAIMS:

1. A method of moulding using a die (10) having a face (15) formed with at least one moulding cavity (12) therein, including the steps of: filling the mould cavity to excess with a desired moulding material (42), placing a backing sheet (20) over the face of the mould to cover the mould cavity, pressing the backing sheet and mould against each other to compact and shape the mould material, removing the backing sheet and removing the moulded material from the moulding cavity, characterised by pressing the backing sheet against the die by moving the mould and backing sheet at least once between two rollers (26, 28), the rollers having their axes substantially parallel to each other and being spaced apart to apply a desired compressive force to the mould and backing sheet.

2. The method of claim 1 , characterised by moving the mould and backing sheet several times in opposite directions between the two rollers.

3. The method of claim 1 , characterised by driving at least one of the rollers (26), so that movement of the roller cause the mould and backing sheet to move between the two rollers.

4. The method of claim 1 , characterised by driving the roller alternatively in opposite directions to cause the mould and backing sheet to move in opposite directions between the two rollers.

5. The method of claim 1 , characterised by interlocking the mould and backing sheet (19, 19.1 ) in order to inhibit slipping of the backing sheet relatively to the mould when they move between the rollers.

6. The method of claim 1 , characterised by trimming (38) any excess mould material from each moulded article by removing such excess moulding material from the face of the die in the region of the mould cavity.

7. The method of claim 6, characterised by trimming the excess mould material by slicing it along the plane of the face of the die immediately adjacent the face.

8. Apparatus for moulding a settable material using a die (10) having a face (15) formed with at least one moulding cavity (12) therein, a backing sheet (20) for covering the face of the die and means for pressing the backing sheet against the die, characterised in that the pressing means 5 (24) comprises a pair of rollers (26, 28) having their axes of rotation substantially parallel to each other and being spaced apart sufficiently to allow the die and backing sheet to pass between them while compressing the backing sheet against the face of the die.

10 9. The apparatus of claim 8, characterised in that it includes support means (30) providing a substantially planar support surface along which with the die and backing sheet can move, the plane of the support surface being parallel to the axis of at least one of the rollers and intersecting a nominal plane extending between the axes of the rollers.

15

10. The apparatus of claim 9, characterised in that the support surface (30) extends laterally on both sides of the rollers transverse to their axes, has an opening (31 ) in the region of the rollers and the rollers are positioned on opposite sides of the support surface.

20

1 1 . The apparatus of claim 10, characterised in that one of the rollers (26) is spaced from the support surface and the other roller (28) has a circumferential region that protrudes through the opening (31 ).

25 12. The apparatus of claim 8, characterised in that friction means (22), such as abrasive sheet material, is provided on at least one of the rollers (26) and on at least one of the exposed sides of the mould (10) and backing sheet (20) in order to inhibit slipping of the backing sheet and die relatively to at least one of the rollers.

30

13. The apparatus of claim 8, characterised in that means (19, 19.1 ) is provided for interlocking the mould and backing sheet to each other in order to inhibit slipping of the backing sheet relatively to the mould when they move between the rollers.

35

14. The apparatus of claim 8, characterised in that the apparatus includes trimming means (32) for trimming any excess mould material (42.1 ) remaining on the face of the die after moulding.

15. The apparatus of claim 14, characterised in that the trimming means (32) slices across the face of the mould to remove such excess mould material.

16. The apparatus of claim 15, characterised in that the trimming means (32) is a band saw, band knife and the like.

17. The apparatus of claim 8, characterised in that the spacing between the rollers is adjustable.