METHOD AND APPARATUS, IN CONTINUOUS PRODUCTION, FOR SUPPORTING DETAILS ON LARGE FORMING SURFACES AT HIGH SURFACE PRESSURE WITHOUT DEFORMING THE FORMING SURFACE

Abstract: Method and apparatus for supporting details, in the continuous production thereof, on large forming surfaces and at high surface pressures without obtaining any deformation of the forming surface. An air film is blown in between the forming surface, e.g. a table (52), and the detail (10, 18), this film decreasing friction when the detail moves over the table (52) as well as achieving the desired pressing pressure and giving a flat pressing surface. The air film has a thickness of up to 0.5 mm and the pressing pressure has a range of 10 to 1000 kPa.

Description: Method and Apparatus, in Continuous Production, for Supporting Details on large Forming Surfaces at high Surface Pressure without Deforming the Forming Surface The present invention relates to a method and apparatus, in continuous production, for supporting details on large forming surfaces and at high surface pressure. In the manufacturing process used today for such as webs or slabs of so-called sandwich construction, only pressure rolls or a combination of pressure rolls and belts are used. This is necessary to achieve the reguired laminating pressure of up to 1000 Pa. A disadvantage here is that pressure rol¬ lers and forming belts are very expensive, if the width of the web etc. is 3 to 4 meters, to which may be added that they are very sensitive to damage. Damage to the pressure rolls or forming belts always gives a visible result on the product. In order that the deflection for large widths shall be acceptable, there is the necessity of arranging different kinds of bolster rolls or other means counteracting deflection, which is expen¬ sive and technically complicated. When forming belts are used, it is known, e.g. from DE 2 224 977, to press slab£ between two moving press surfaces such as steel belts, which slide over a support surface, a pressurised medium being allowed to act between the belt and the support surface to decrease friction. However, this does not eliminate the above-mentioned problems of damage to the forming belts. The CH-PS 639 319 teaches a method and apparatus for ac- celerating curing of the adhesive in the production of la¬ minates with intermediate layers of carton and outer surfaces of plasterboard. Curing takes place by moving the laminate past a radiation source, and the laminate is kept together, while being conveyed past the radiation source, with the aid of air cushions pressing against it on either side of the horizontally conveyed laminate. To avoiding bucking in the intermediate layer of the laminate, the pressure in the air cushions is regulated to a relatively low value, and there - is achieved no pressing force of the same magnitude as with 2 pressure rolls or forming belts in this known method. The chief object of the present invention is to provide a method and apparatus of the kind mentioned in the introduc¬ tion, with which the problems described in connection with 5 known processes have been eliminated, and very large sliding forming surfaces are achieved with a minimum of friction and insignificant deflection of the forming surface. Another object is to achieve a method and apparatus par¬ ticularly suitable for use in continuous production of so- 10 called sandwich structural elements. These and other objects of the invention are attained by the method and apparatus having been given the distinguishing features disclosed in the accompanying claims. The invention together with further objects and advan- 15 tages thereof, will be understood from the following descrip¬ tion, which is made in connection with the accompanying draw¬ ings illustrating a preferred embodiment of an apparatus for carrying out the method, and where Fig. 1 is a perspective view of the upper part of a 20 plant for vertically manufacturing so-called sandwich struc¬ tural elements, Fig. 2 illustrates the continuation of the lower part of the plant in Fig. 1, more specifically showing the right hand part of the plant, which is symmetrical about the illustrated 25 centre line, this lower part being implemented in accordance with the invention, Fig. 3 illustrates to a larger scale a detail of the pressing plane in the plant of Fig. 2. The plant which is illustrated in Fig. 1, is intended for - 51 -' vertically manufacturing so-called sandwich structural elements. The method of manufacturing these elements and the illustrated plant for carrying out the method are described in detail in the Swedish patent application 86001441-2. Summarily described, the process proceeds such that a core material, e.g. cellular - > - > plastics, is supplied in pieces or panels 10 of the desired size to an input station. The panels 10 which can have a width of up to 3-4 meters are supplied to the input station by such as a mechanical direction-changing and collecting means 12. The input station comprises gripping belts 14, which are caused with the aid of platens 16 to excercise a pressure against the panels 10 sufficient for the belts to grip the panels and advance them to the forming station of the plant. A pressurised medium can be conventionally blown in between the belts 14 and platens 16 to facilitate movement of the belts over the platens. In the forming station the core material meets the cover- ing layers or skins 18, e.g. glass fibre reinforced plastics, sheet metal etc. The skins 18 are taken over pressure rolls 27, which lead the skins 18 downwards while pressing them against the core material. Before meeting the core material, i.e. the panels 10, the skins 18 are coated with adhesive on their sides coming into contact with the panels, and this ad¬ hesive forms a pool 24 immediately before the nip between panels 10 and skins 18, as is described in more detail in the mentioned patent application. The skins 18 are pressed against the panels 10 while the adhesive cures, the latter forming, as mentioned, an adhesive pool 24 (see Fig. 2) in front of the nip between panel 10 and skin 18 on either side of the panel. To provide the necessary pressure for the joints between panel 10 and skins 18 and for urging back excess adhesive to the pool 24 there is reguired a pressing force of between 10 and 1000 kPa. In accordance with the invention, this is arranged for by the sandwich ele¬ ment formed from the panel 10 and skins 18 being caused to pass over a forming table 52, which has holes or perforations 54 (see Fig. 3) for the passage of air, thus permitting air pressure to act on the skins 18. The air pressure is regulated such as to provide a desired pressing force, e.g. a pressing force of 10 kPa at 0,1 effective atmosphere. The air film be¬ tween the skins 18 and the surface of the forming table 52 has a thickness of up to 0,5 mm and allows the sandwich element which is produced to' pass frictionless over the surface of the forming table 52. The air access perforations 54 in the surface of the table are adapted in size and number so that lateral ' air leakage from the gap between the produced sandwich element and table 52 corresponds to the air passing through the table, without there being any pressure drop therein. The air pressure is created in an air pressure chamber 56 situa- ted against the table 52, and in accordance with the inven¬ tion this overpressure is taken up by a bolster slab 58, which can be allowed an optional bending deflection without the production of sandwich elements being affected, the press¬ ing surface remaining quite fait. The air which is supplied to the gap between the sandwich element and forming table 52 may be given a temperature adaplted for curing the adhesive joining the core material 10 and skins 18, and for this pur¬ pose the pressure chamber 56 may be subdivided into a plural¬ ity of separately regulatable heat zones. In a further development of the invention, illustrated in Fig. 2, the skins 18 can alternately be made up from webs 28 of glass fibre fabric which are reeled off from two storage rolls 26, the webs 28 coming into mutual contact as they pass round an idler roll 30. At this roll they also meet up with a thin sheet, e.g. a foil or film 32, which is reeled off from a storage roll 34. The sheet 32 is caused, with the aid of a cambered idler roll 36, to pass over the upper side of a hori¬ zontal table 20 and before meeting with the web 28 the foil 32 is on its upper side given a coating of gel sprayed on to the sheet by unillustrated nozzles to form a gel pool 40 in front of a doctor blade 42. After that the gel coating is coated with adhesive from a sprayed-on adhesive pool in front of a doctor blade 46 and then the sheet 32 comes together with the glass fibre fabric web 28, as described above. The table 20 is heated and can be subdivided into separately regulatable heat zones for regulating heat supply to the coatings of gel and adhesive. The table 20 is suitably similarly provided with means for the passage of air to facilitate the movement of the sheet 32 and the web 28 over its surface. The glass fibre coated skin 18 is carried over a pressure roll 22 arranged at the left side of the table to the vertical path and at the same time the skin is brought into contact with the core panel 10 by the pressure roll 22. After the panel 10 has come into contact with the skin 18 the sandwich element thus formed passes over the forming table 52 as described, whereby the element is formed by the sheet 32 the air pres- sure now acting against the sheet 32, as described earlier. The sheet 32 can either be smooth or patterned depending on what surface is desired on the final product. After passage over the forming table 52 the sheet 32, which has now fulfilled its purpose, is pulled off with the aid of a support roll 60 and a cambered roll 62, and reeled onto a receiving roll 64, while the sandwich element compris¬ ing panel 10 and skin or skins 18 continues vertically down¬ wards for further processing. It will be understood from the description given above that, in accordance with the invention, there has been provi¬ ded a method of achieving freely suspended, very large sliding form surfaces which can operate at large surface pressures, and where friction has been reduced to a minimum. At the same time there is afforded a flat pressing surface with, insignifi- cant deflection of the forming surface itself, since the air film acts directly on the workpiece itself, and the reaction pressure is taken up via the pressure chamber 56 by a bolster slab 58 which can be permitted bending deflection without this affecting the form of the structural element being produced. Although the invention has been illustrated and described in connection with the production of so-called sandwich struc¬ tural elements with vertical manufacture, it will be under¬ stood that this is only one example of how the invention may be realized, and variations are possible within the scope of the accompanying claims.

Claims: Claims 1. Method, in continuous production of details which are to be pressed or formed, of supporting said details on large forming surfaces and at high surface pressures, c h a r a c t e r i z e d in that an air film is blown in- to a gap between the forming surface and the detail, this gap having a distance between its surfaces such that the de¬ sired pressing pressure is built up against the detail, the air film being blown in through a table constituting the forming surface, from an air pressure chamber situtated ad- jacent to the table, a pressure being created in the chamber corresponding to the desired pressing pressure, said chamber being defined on its side facing away from the table by a surface of a bolster platter, which takes up any deflection due to the overpressure. 2. Method as claimed in claim 1, c h a r a c t e r ¬ i z e d in that the gap between the forming surface and the detail has a width of up to 0,5 mm. 3. Method as claimed in claim 1 or 2, c h a r a c ¬ t e r i z e d in that a pressure of between 10 and 1000 kPa is created in the pressure chamber. 4. Method as claimed in any one of claims 1 to 3, c h a r a c t e r i z e d in that the detail is advanced vertically from above and downwards. 5. Method as claimed in any one of claim 1 to 4, c h a r a c t e r i z e d in that the detail comprises a cellular core material, which is provided on at least one side with a covering skin or facing, in that the skin is brought together with, and pressed against, the core material such as to form a nip where the skin comes against the core material, and in that an excess of adhesive is supplied to the nip, there to form a pool of adhesive against the core mate¬ rial, for filling out the open cells or pores at its surface and urging away air or other gas, which departs upwardly. 6. Method as claimed in any one of claims 1 to 5, - c h a r a c t e r i z e d in that a thin sheet (32), e.g. a foil or film is inserted between the detail and forming surface, and in that the air film is blown in between said sheet and forming surface. 7. Method as claimed in claim 6, c h a r a c t e r ¬ i z e d in that the sheet is pulled off from the detail 5 after its passage over the forming surface. 8. Method as claimed in claim 6 or 7, wherein the detail comprises a sandwich structural element built up from a core material with a covering skin on either side, c h a r a c ¬ t e r i z e d in that the sheet (32) is used as a sub- 10 structure for building up the covering skin (18). 9. Method as claimed in any one of claims 1 to 8, c h a r a c t * e r i z e d in that the air in the air film is given a temperature such as to heat the detail, e.g. for curing adhesive joints in it. 15 10. Method as claimed in any one of claims 6 to 9, c h a r a c t e r i z e d in that the sheet (32) is pattern¬ ed for embossing the pressing surface. 11. Apparatus for carrying out the method according to any one of claims 1-10, for supporting details, in the con- 20 tinuous production thereof, on large forming surfaces and at high surface pressures, c h a r a c t e r i z e d in that the detail is pressed with the aid of at least one form¬ ing table (52), which is provided with perforations (54) for creating an air film of up to a thickness of 0,5 mm be- 25 tween the detail (10, 18) and the forming table (52), said air film being supplied from a pressure chamber (56) defined by the forming table and a bolster slab (58), which is situat¬ ed opposite to the forming table and which takes up any de¬ flection stemming from the excess pressure. 30 12. Apparatus as claimed in claim 11, c h a r a c ¬ t e r i z e d in that means (34, 36) are arranged for the supply of a sheet (32) between the forming table (52) and the detail (10, 18), and in that means (60, 62, 64) are arranged for pulling off the sheet after it has passed over the forming - 35 table (52). 13. Apparatus as claimed in claim 11 or 12, c h a r - a c t e r i z e.d in that means are arranged for adjusting the temperature of the air in the pressure chamber (56). 14. Apparatus as claimed in any one of claims 11 to 13, c h a r a c t e r i z e d in that the pressure chamber (56) is divided into a plurality of separately regulatable heat zones.

Inventors: BAECKLUND JAN, ERICSSON KARL-GUSTAV, JILKEN LEIF, KIHLBERG HARRY, NILSSON CHRISTER, SVENSSON PAUL, BAECKLUND, JAN, ERICSSON, KARL-GUSTAV, JILKEN, LEIF, KIHLBERG, HARRY, NILSSON, CHRISTER, SVENSSON, PAUL
Applicants: BAECKLUND JAN, ERICSSON KARL GUSTAV, JILKEN LEIF, KIHLBERG HARRY, NILSSON CHRISTER, SVENSSON PAUL, BAECKLUND, JAN, ERICSSON, KARL-GUSTAV, JILKEN, LEIF, KIHLBERG, HARRY, NILSSON, CHRISTER, SVENSSON, PAUL
Application year: 1987
Main classification: B29C51
IPC codes: B21B1, B29C43, B29C51, B32B37