METHOD AND APPARATUS FOR THE SPREADING OF THERMOPLASTIC MATERIALS, COATING OF OBJECTS AND MANUFACTURING OF PROFILED OBJECTS

Abstract: A fast spreading and pressing procedure is achieved in that thermoplastic material is applied onto an object (1) or a fibrous reinforcement, fabric or gauze by means of a spreading device in which the volume of the plastic outflow is adjustable, and that the plastic material is pressed onto the surface of the objects using at least one hydraulically controlled pressing membrane.

Description: METHOD AND APPARATUS FOR THE SPREADING OF THERMOPLASTIC MATERIALS, COATING OF OBJECTS AND MANUFACTURING OF PROFILED OBJECTS The present invention relates to a method and apparatus for spreading thermoplastic materials, coating objects and manufacturing profiled objects. Veneer sheets are currently coated with various plastic materials using methods involving several stages of operation. Current coating procedures are also slow in operation. The object of the present invention is to eliminate these drawbacks. The method of the invention is characterized in that a thermoplastic material is applied onto an object or a fibrous reinforcement, fabric or tissue b means of a spreading device in which the volume of the plastic outflow is adjustable, and that the plastic material is pressed onto the surface of the object to be coated .using at least one hydraulically controlled pressing membrane. A preferred embodiment of the method of the invention is characterized in that the plastic material is applied onto the objects through an aperture in at least one distribution tube incorporated in the spreading device, the plastic material being supplied to the distribution tube via a perforated supply tube. Another preferred embodiment of the method of the invention is characterized in that the plastic material is applied onto the objects by first spreading it on a raster surface, from which the plastic is then transferred to the areas on the object surface determined by the raster pattern.. A further preferred embodiment of the method of the invention is characterized in that the pressing membrane is attached at its edges onto the sides of a box, the membrane and the box constituting a container for oil in which the amount of oil can be hydraulically controlled and the oil temperature changed .from cold to hot and vice versa. Yet another preferred embodiment of the method of the invention is characterized in that a perforated tissue is used and that a coat of material such as polyester is pressed onto one side of the object in such manner that the melting point of the coat is higher than that of the melt glue used for gluing the object. The apparatus designed for applying the method of the invention is characterized in that the apparatus comprises a plastic spreader for spreading the plastic material, the spreader being provided with means for adjusting the amount σf material flowing out, and a press for pressing the plastic coat onto the object with the aid of at least one hydraulically controlled pressing membrane incorporated in the press. A preferred embodiment of the apparatus designed for applying the method of the invention is characterized in that the apparatus is provided with a suction bench on which the objects to be coated can be conveyed to the spreader or the press, the objects being held in place on the suction bench by the force of a suction generated in the bench. Another preferred embodiment of the apparatus designed for applying the method of the invention is characterized in that the plastic spreader is provided with a perforated supply tube for supplying the plastic material from a container, and at least one distribution tube provided with an aperture for spreading the plastic material onto the object. A further preferred embodiment of the apparatus designed for applying the method of the invention is characterized in that the press is provided with eccentrics for raising the lower part of the press. The invention is described in the following in greater detail by the aid of an example, referring to the drawings attached, wherein: Fig. 1 represents the apparatus for coating veneer. Fig. 2 represents a roller spreader. Fig. 3a represents the equipment for the supply of plastic material. Fig. 3b represents a plastic spreader. Fig. 4a represents a second plastic spreader. Fig. 4a represents the second plastic spreader in section. Fig. 5 represents a raster surface. Fig. 6a represents the press. Fig. 6b represents the press in section. Fig. 7 represents the suction bench with an object on it. Fig. 8 represents the suction bench. Fig. 9 represents the suction bench in section. Fig. 10 represents the manufacturing process employed in the production of glued tissue. Fig. 1 shows an apparatus for the coating and jointing of veneer. Before the veneer is coated, it has to be prepared in a suitable manner. This is done by cutting the logs with a veneer plane and sorting the veneer leaves thus obtained either manually or using e.g. a computer-controlled system to select the leaves with the desired surface patterns. The wood material is planed using e.g. a bevel cutter, producing veneer leaves of a thickness varying from 0.15 mm to a few mm. The thinner the veneer leaf, the better the veneer surface. The width of the veneer sheets obtained depends on the diameter of the logs from which they are planed. The veneer sheets can also be produced by cutting the logs with a veneer-cutting machine along the annual rings. Veneer sheets produced in this manner have a rougher surface than those obtained by planing. If necessary, sheets with repeated surface patterns can be produced from one log. The veneer leave ' s 1 are moved to the roller spreader 3 by means of a suction bench 2, on which the suction keeps them tightly in place. In the spreader., the veneer leaves are coated with a layer of thermoplastic material, which may contain a fibrous reinforcement, e.g. non-woven polyamid fibres of 30 - lOOg/ . From the roller spreader, the veneer leaves are passed to the press 4. The press 4 consists of an upper 5 and a lower metal box 6 and is provided with a pressing membrane made of.silicone rubber or teflon. Using an oil pump, a pressure is generated in the oil container constituted by the membrane and the box to press the veneer and plastic surfaces against each other. The pressure in the container is thus about equal to that in the hydraulic pump. The oil can be heated and cooled by means of a heating unit. Fig. 2 shows the roller spreader used for spreading the thermoplastic material, e.g. polyethylene, onto the veneer. The spreader comprises a spreading device 7 and a pressing device consisting of two rollers, of which the upper one 8 is provided with a raster surface like that shown in fig. 5. The glue is spread on the veneer leaves as determined by the pattern in the raster surface. The glue spreader comprises a scraper 10 and a counterpart 11, whose position is controlled by means of a hydraulic hose 12 by varying the pressure in the hose. In this way, the distance between the counterpart 11 and the stop 13 can be varied and the glue spreader turned on its shaft to the correct position. The raster pattern on the surface of the roller 8 is produced e.g. by arc machining or etching. The veneer leaves are passed between the two pressing rollers, whereupon they can be brought back to the suction bench. The plastic material is spread using the spreading equipment shown in figures 3a, 3b, 4a and 4b. Fig. 3a shows how the plastic material is supplied to the plastic spreader. Fig. 3b shows the spreader as sectioned along the line A-A. The plastic material is supplied by a pump 17 from a container 15 consisting of a cylinder 16 via a hose 18 into the spreading device 19, the container and the hose being provided with heating means. In the spreading device 19, the plastic material is first fed via a proportionally perforated supply tube 20 into an expansion chamber formed inside the two distribution tubes 21 and 22, which are mounted one inside the other, the expansion chamber being provided with heating channels 23 to keep the plastic material warm. The distribution tubes are provided with apertures 24 and 25, whose position relative to each other determines the volume of plastic material flowing out of the spreading device, as the relative position of the tubes can be changed by rotating the inner tube 22 by means of a rotating mechanism, which is not shown in the figure. The outer tube 21 has to be provided with isthmuses 26 to render the tube sufficiently rigid in the region of the apertures. The tube may also be provided with a comb-shaped outlet port." Figs 4a and 4b show another device for spreading the plastic material. The device is provided with a perforated supply tube 27 through which the plastic is supplied from the container, not shown in the figure. Through the holes in the supply tube, the plastic mass flows into the space inside the distribution tube 28, from where it spreads through the aperture 29 onto the veneer surface. The plastic material is heated by means of heating pipes 30 mounted inside the distribution tube, and the volume of plastic flow out of the ube is determined by the position of the aperture 29 in the distribution tube 28 relative to the aperture 32 in the distributor section 31. The distributor piece 31 is attached to the distribution tube 28 by means of securing screws 33, with which the distributor piece is fixed in the desired position to provide a suitable size of aperture. The device is also provided with securing flanges 34 and 36 and a tightening flange 35 with which the device is secured and tightened. The outlet port serves to spread the molten plastic e.g. on a fibrous reinforcement produced as illustrated by fig. 10, from the raster pattern of a r sterized roller or band, from where the plastic is transferred to the colder surface when subjected to a pressure by a pressing roller provided with cooling means. The raster surface shown in fig. 5 consists of grooves 37 and elevations 38. The glue is scraped off from'the elevated surfaces 38, so that glue is only applied to those areas of the veneer leaves which are covered by the grooves. A press like the one in fig. 6a is provided with two pressing membranes 39 and 40 made of -an elastic material such as strong silicone rubber having a good resistance to heat. The pressing membranes are fixed at their edges on metal boxes 41 and 42 whose edges in the areas holding the membranes are bent in a manner explained below so that when the pressure in the container formed by the membrane and the box increases, the edges of the pressing membrane are squeezed against the box edges so as to maintain the desired level of pressure in the container. The hydraulic pressure in said containers is controlled by adjusting the volume of oil flowing into the container. At the beginning of a pressing operation, the lower box frame 42 is raised to a desired level by means of eccentrics 45 controlled by a cylinder 43 and a piston 44, said eccentrics' being provided with rods 46 serving to adjust the vertical position of the frame 42. Next, oil is pumped into the containers to increase the pressure in them to an appropriate value. By the force of the pressure and a suction created by a vacuum device, the pressing membranes 39 and 40 are pressed against the objects to be coated, thus forcing the plastic onto the objects, so that a plastic coat is fixed on the surface of the objects. Fig. 6c is a magnified view of the detail A in fig. 6a, showing how the membranes 39 and 40 are attached to the boxes 41 and 42. In both containers, the edge of the membrane is bent inward against the inside of the protruding extremity 47,48 of the box, so that the pressure in the container forces the edges of the membranes againgst the protrusions, thus preventing fluid leakages and consequent pressure drops. In addition, the containers are provided with protective membranes attached on the outside of the pressing membranes. Fig. 8 shows the suction bench 52 with veneer leaves 53 on it. The suction bench moves horizontally, and the veneer leaves on the bench are coated and jointed with a plastic material. The veneer leaves are prepared appropriately before the plastic material is spread on them. The veneer leaves are pressed againgst the suction bench with pressing members 54, the number of which depends e.g. on the length of the bench. The direction of movement of the bench in fig. 8 is indicated by arrows. The mechanism used for moving the bench will be described in greater detail in a later paragraph. Once the veneer leaves have been placed on the bench as required, the bench is moved to the roller spreader 55, which spreads the plastic material onto the veneer leaves. It is also possible to use a glued tissue made as shown in fig. 10. Next, the suction bench is brought to a compacting station, where the veneer leaves are pushed sideways together by a suitable actuator 56. Thereupon the suction bench is brought to a pressing station, where the plastic and the reinforcement are finally fixed on the veneer surface using a thermopress 57 as described above. The coated veneer is then removed from the suction bench, and the latter is taken to an intermediate station 58 to await the next batch of veneer leaves. Fig. 9 represents the suction bench 52, the pusher 56, the pressing member 54, the bench motion mechanism and the veneer leaves 53 as sectioned along the line A-A in fig. 8. As indicated by the arrows, the pressing member 54 moves in the vertical direction and the pusher 56 in the sideways direction. The suction bench consists of individual suction blocks 59, permitting adjustment of the suction in each block independently of the other blocks. This makes it possible e.g. to keep one leaf in place while moving another to bring it closer to the first one. In this case no suction or only a slight suction is applied to the second leaf. The bench motion mechanism consists of a rail/bearing combination 60, which is controlled by a controller 61, and rollers 62 mounted under the suction bench by means of adjustable suspension springs allowing the rollers to be raised and lowered. The apparatus in fig. 10 serves for producing the glued tissue which is used for jointing the veneer leaves and which gives the resulting veneer sheet an elastic property and a finished surface. The glued tissue is made e.g. from a polyester gauze 63 and melt glue, which is spread on the gauze with a glue spreader 63, thus producing a finished surface to be fixed on the veneer. The figure also shows an auxiliary band 65 which can be used as a support in producing the glued gauze and which is reeled back on another roll 66. The figure also shows rollers 67 over which the glued gauze produced can be passed to let it cool down before being reeled up on a roll 68. A perforated tissue may also be used. In this case, a coat of material such as polyester is pressed onto one side of the object in such manner that the melting point of the surface coat is higher than that of the melt glue used for gluing the object. It is obvious to a person skilled in the art that the different embodiments of the invention are not restricted to the examples discussed above, and that they may instead be varied in the scope of the following claims.

Claims: CLAIMS 1. Method for the spreading of thermoplastic materials, coating of objects and manufacturing of profiled objects, characterized in that a thermoplastic material is applied onto an object (1?14;53) or a fibrous reinforcement (63), fabric or gauze by means of a spreading device (3r7;19) in which the volume of the plastic outflow is adjustable, and that the plastic material is pressed onto the surface of the objects (1;14;53) using at least one hydraulically controlled pressing membrane (39,40). 2. Method according to claim 1, characterized in that the plastic material is applied onto the objects through an aperture in at least one distribution tube (21,22;28) incorporated in the spreading device, the plastic material being supplied to the distribution tube via a perforated • supply tube (20;27). 3. Method according to claim 1 or 2, characterized in that the plastic material is applied onto the objects (1;14;53) by first spreading it on a raster surface (8), from which the plastic is then transferred to the areas on the object surface determined by the raster pattern. 4. Method according to claim 1, 2 or 3, characterized in that the pressing membrane is attached at its edges to the edges of a box (41,42), the membrane and the box constituting a container for oil in which the amount of oil can be hydraulically controlled and the oil temperature • changed from cold to hot and vice versa. 5. Method according to any one of the above claims, characterized in that the tissue used is a perforated gauze and that a coat of material such as polyester is pressed onto one side of the object in such manner that the melting point of the surface coat is higher than that of the melt glue 1 used for gluing the object. 6. Apparatus for implementing the method of claim 1, ' characterized in that the apparatus comprises a plastic spreader (3;7;19) for spreading the plastic material, the spreader being provided with means for adjusting the volume of material flowing out, and a press (4) for pressing the plastic onto the objects using at least one hydraulically controlled pressing membrane (39,40) incorporated in the press. 7. Apparatus according to claim 6, characterized in that the apparatus is provided with a suction bench (2;49;52) on which the objects (1;14;53) to be coated can be moved to the spreader (3;7;19) or the press (4), the objects being held in place on the suction bench by the force of a suction generated in the bench. 8. Apparatus according to claim 6 or 7, characterized in that the plastic spreader is provided with a perforated supply tube (20;27) for supplying the plastic material from a container (15), and at least one distribution tube (21;22;28) provided with an aperture for spreading the plastic material onto the object. 9. Apparatus according to any one of the claims 6 - 8, characterized in that the press (4) is provided with eccentrics (45) for raising the lower part (42) of the press.

Inventors: RINNE ERKKI, RINNE, ERKKI
Applicants: RINNE ERKKI, RINNE, ERKKI
Application year: 1987
Main classification: B29C41
IPC codes: B27D1, B27G11, B29C31, B29C41, B29C43, B29C63