METHOD AND APPARATUS FOR MOULDING A LAYER OF FOAMED PLASTIC MATERIAL ON SHEET MATERIAL

Abstract: A method for moulding a layer of foamed plastic material on sheet material (18), in a mould comprising a lower mould part (10) having a moulding cavity (11), and an upper mould part (12), movable between an open position and a closed position. According to the invention, a preshaped sheet of material (18) having a front surface and a rear surface destined to adhere to the layer of foamed material, is placed and held firmly with its front face against an air suction surface (13) of the upper mould part (12), by means of continuous air suction; a mixture of foamable plastic material is fed into the cavity (11) of the mould, and the pneumatic support for the sheet material (18) is maintained for at least part of the time necessary for the complete foaming of the plastic mixture in the closed mould (10, 12).

Description: The present invention refers to a method for moulding a layer of foamed plastic material, in particular foamed polyurethane, on sheet material, for example cloth, plastic material and suchlike, as well as an apparatus comprising a suitable mould for the realization of the method. The invention is also directed to the product obtained with the use of the method claimed. In the production, for example, of carpets or other similar accessories for use in the motor car sector, in particular carpeting used to coat the inside floor areas of motor vehicles, a preshaped carpet corresponding to the bottom shape or other part of the motor vehicle to be coated, is provided with a layer of foamed polyurethane material on the rear surface, not seen in the end product, designed to be adapted to said bottom surface or other part of the above-mentioned vehicle, in order to obtain an adequate mating. In the production of carpets for the use mentioned, at present the preshaped sheet material is introduced upside down into the cavity of a mould, comprising a lower mould part and an upper mould part having complementary surfaces to define said mould cavity therebetween; then a metered quantity of a polyurethane mixture is fed into the mould cavity by injection and this is left to foam in the closed mould until it fills it and adheres completely to the sheet material underneath. Such a method of operating is rather laborious and complex, in particular when sheet materials of large dimensions have to be handled. As a consequence, the injection of polyurethane material in a closed mould is made possible only for a few simple models of carpet, also because of the difficulty in filling the cavity of the mould with a low density foam, which in its rising should expel the air, flowing along paths that are sometimes very long and intricate. In certain cases, therefore, one is obliged to use several mixing heads for the injection of the polyurethane mixture into one mould, with the negative consequence of obtaining polyurethane layers varying in density or with a density different from what is desired. Pouring of the polyurethane mixture on the carpet in an open mould would obviate the above-mentioned problems of filling and density; nevertheless, also pouring into an open mould according to traditional techniques proves practically unrealizable, insofar as the upside down position of the carpet on the lower part of the mould, with the rear surface of the carpet convex and turned upwards, would not allow the liquid polyurethane mixture to be contained in the mould. Therefore it should be desiderable to support the carpet from the front side by the upper part of the mould. From DE-A-1.147.029 it is know to use vacuum to preshape a plastic sheet maintaining the vacuum during the closure of the mould to held up the preshaped plastic sheet during foaming; nevertheless the vacuum may be destroied by seeping of air from the outside. Therefore, according to conventional technique it is impossible to support large and heavy carpets or sheet materials by vacuum which does not allow to create uniformely distributed pneumatic forces or support carpets or sheet material having apertures. The object of the present invention is to provide a method for the moulding a layer of foamed plastic material, on a carpet or preshaped sheet material, by means of which it is possible to support the sheet material adequately during the moulding operations, independently of the form and dimensions of the sheet itself, and also possible to pour the liquid mixture directly into the open mould or inject it into a closed mould in such a way as to ensure a homogeneous filling and an adequate density. A further object of the invention is to provide a method, as defined above, in particular for the formation of soundproof carpets or similar articles for coating the inside floor of motor vehicles, in which it is possible to reduce or eliminate the formation of air bubbles, or through which the air bubbles tend to form in the interface of adhesion between the layer of foamed material and the preshaped sheet, thus remaining out of sight. A further object of the invention is to provide an apparatus for carrying out the method mentioned above, which allows an easy positioning of a preshaped sheet material on an open part of the mould, an easy accessibility for cleaning operations on the mould itself, and the retention of said preshaped sheet without being negatively influenced by seeping of air from the outside. These and other objects are obtained according to the invention, by means of the method of claim 1 and the apparatus according to claim 6. The method and some examples of embodiments of an apparatus according to the invention, are illustrated here below with reference to the attached drawings, in which: Fig.1 shows a first embodiment of an apparatus, in which the mould is shown open with the parts tilted and ready for the cleaning operations and the positioning of the preshaped sheet material. Fig.2 shows the apparatus illustrated in the preceding figure, with the mould open in position for pouring or feeding the foamable material mixture into the cavity of the mould. Fig.3 is a view of the same apparatus, in the closed condition. Fig.4 shows a first possible variation of the apparatus shown in Fig.1. Fig.5 shows the scheme of a second possible variation, of the apparatus and method according to the invention. Fig.1 shows an apparatus according to the present invention, comprising a generic mould for the moulding of a layer of polyurethane material on the rear surface of a piece of sheet material, for example a preshaped carpet, designed to cover part of the inside of a motor vehicle, the front surface of which, that is the part that remains seen, may be "hairy" or permeable to air. As shown, the mould comprises a first mould part 10, or lower mould part, containing a cavity 11, and a second mould part 12, or upper mould part, having a surface 13 substantially complementary to the preceding cavity 11 of the mould. Both the mould parts 10 and 12 are rotatably or ti Itably supported around horizontal axes 14 and 15. The apparatus according to this first example, comprises a base support structure 16 for the closure press of the mould. The press in its turn comprises a structure 17 designed to rest on the base structure 16 and connected to the latter in such a way that it is rotatable round the axis 15; the lower mould part 10 is carried by the press structure 17 in a sliding way along guides 20a and its movement is controlled by means of hydraulic cylinders 20 or other suitable control means, the movement being between a retracted position against a support plane of the structure 17 and an advanced position in the operative condition of Fig.1, which allows easy access to an operator for cleaning the cavity 11 of the mould. The press also comprises a closure element 17a to which the upper mould part 12 is attached; the closure element 17a in its turn is rotatable, in relation to the press structure 17, around axis 14, in such a way as to allow the two parts 17 and 17a of the press to rotate independently. Therefore the apparatus can assume either the operative position of Fig.1 , with the two mould parts open, which allows the usual cleaning operations and the positioning of the sheet material 18, as is clarified further on, or the operative position of Fig.2, with the mould parts 10 and 12 open in condition for the pouring or feeding of a polyurethane foam into the cavity 11, by means of a movable mixing head 19, carried for example by a supporting arm (not shown), as well as the closure position of the mould, as shown in Fig.3. The two parts 17 and 17a of the press with the mould, can be tilted or moved between the operative positions shown, or other work positions if desired, by any system of control devices, for example by means of hydraulic or pneumatic cylinders, mechanical control devices or by control means of some other type. In particular, in the example shown, the lower part 17 of the press is actuated to rotate by a cylinder 25, while the upper or closure part 17a is actuated to rotate by means of a second cylinder 26 and a system of articulated levers 27. In the operative condition of Figure 1, the support structure 17 of the press is tilted upwards and backwards from the base structure 16; on the contrary, the closure part 17a of the press is rotated by about 90° in such a way that the upper mould part 12 in the operative position shown, is low down with its surface 13 or part of it, substantially turned upwards or towards the operator. This operative condition facilitates the operation of placing or positioning the preshaped sheet material or carpet 18 on the surface 13. The positioning of the carpet 18 is carried out in such a way that the hairy part of its front surface, designed to remain seen, is turned towards the surface 13 of the mould and therefore remains in contact with it. Since the carpet 18, both in the position of Fig.1 and in the positions shown in the other figures, would tend to fall and detach itself from the surface 13 of the mould, if not suitably held in position, according to the present invention pneumatic means for holding and supporting the carpet 18 have been provided; these make use of a strong peripheral air suction current, which is maintained continuously between the surface 13 of the mould and the front surface of the carpet 18. Apropos of this, the mould part 12 has been provided with internal channels 21, which communicate, at one end, with air fans 22 or air suction devices. The air suction devices 22 can be positioned in the mould or on the support structure 17a of the mould part 12 or placed elsewhere and connected by means of flexible tubes to the internal channels 21 of the mould in such a way as to allow a rotation or tilting of the mould itself. At the other end, the channels 21 open on the shaped surface 13 of the mould 12 by means of one or more air suction apertures, provided in a suitable position on the surface 13 in order to support the sheet material 18 or make it adhere, in several points, suitably spaced out on the above mentioned surface 13, according to the dimensions and the shape of the carpet to be manufactured. The continuous air suction by means of the air fan 22 will naturally have to be such as to create a sufficient support force for the sheet 18, by calculating an air delivery which takes into account both the tranversal flow of air that may tend to pass across the material 18, and the longitudinal flow of air created between the sheet 18 and the surface 13 starting from the peripheral edge. The action of the longitudinal air flow, perhaps combined with the action of the transversal air flow, creates a pneumatic action on the face of the material 18 turned towards the surface 13 of the mould, which maintains the sheet material 18 firmly adherent or against the surface 13 with a force sufficient to overcome the weight of the material itself and concentrated mainly in correspondence with the suction holes. The dimensions of the channels 21 inside the mould and those of the openings through the said channels emerge on the surface 13 of the mould, will have to be calculated from time to time according to the shape, dimensions and weight of the sheet material 18, in order to obtain the necessary air delivery sufficient to provide the support force required; as a guide, the apertures through which the channels 21 open out onto the surface 13 of the mould, in any case must not be so large as to cause a partial penetration of the sheet into the apertures themselves, since this would cause an undesiderable defect in the product manufactured; therefore, in the case of suction apertures of a considerable width, it would be advisable to provide for the use of pads of porous material or perforated plates, provided with a considerable number of small passage holes for the air necessary to create the required pneumatic support force for the sheet, and capable also of contrasting the pressure of the polyurethane foam during foaming. The use of the apparatus described with reference to the figures from 1 to 3, according to the method of this invention is as follows: starting from the operative conditions illustrated in Fig.1, the mould is completely open and tilted backwards so that the second mould part 12, which has to support the preshaped sheet, or carpet 18 pneumatically, presents the surface 13, or part of it, oriented upwards and towards the operator; in the meantime, the mould part 10 has been advanced and lowered towards the operator, who carries out all the necessary operations for cleaning the cavity 11 of the mould, which in this way is easily accessible because of the particular arrangement of the two parts. Once the preliminary mould-cleaning operations have been completed, the operator takes a sheet or carpet 18, already preshaped so as to be substantially identical to the surface 13 of the mould, and he places it with its front surface, that is the side destined to remain seen, on the surface 13 of the mould part 12 in such a way that the rear convex face of the carpet is turned upwards. The air fans 22 for the air suction system are started up, creating a strong suction and a pneumatic anchoring action on the carpet 18, concentrated particularly in correspondence with the suction points of the channels 21. The carpet 18 is thus held firmly against the surface 13 of the mould and therefore can be easily manipulated or moved with the corresponding part 12 of the mould. Once the carpet 18 has been positioned and the suction system put into operation, the mould part 10 is retracted and the entire structure of the press 17, 17a with the mould open, is tilted into the operative condition of Fig.2, in which the first mould part 10 now has the cavity 11 turned upwards, while the mould part 12 is in an erect or vertical position, with the sheet material or carpet 18 always held firmly against the surface 13 by the continuous air suction action created by the fans 22. With the mould open and in this condition, it is now possible to pour or feed a certain quantity of a polyurethane mixture or other foamable plastic material into the cavity 11 of the mould part 10, for example by means of a mixing head 19 carried by a robotized arm (not shown) which distributes the mixture over the bottom of the cavity in the way desired. Once the polyurethane mixture has been poured into the cavity of the mould, the mould is closed as shown in Fig.3, by lowering or rotating the upper mould part 12 forwards, always maintaining the air suction to hold the carpet 18 firmly against the surface 13 of the above-mentioned mould part. The polyurethane mixture can then foam freely and completely fill the cavity of the mould, thus adhering to the rear surface of the carpet or sheet material 18, which always remains firmly held pneumatically against the surface 13. The fact that the preshaped sheet 18 is kept in contact with the upper part of the mould during the foaming of the polyurethane foam facilitates the filling of the cavity of the mould and the formation of a layer 23 of foamed material without defects or air bubbles. Although it is preferable to maintain the air suction for the whole of the hardening or polymerization phase of the resin, nevertheless, if desired, the air suction could even be stopped before, when the foam has partially or completely filled the cavity of the mould, since the sheet or carpet 18 would be supported in any case by the pressure exerted by the foam. Once the foam has completely hardened, the mould is opened again and brought back into the operative condition shown in Fig.1, and the air suction is now stopped, if it was not stopped previously; in this way, it is possible to remove the moulded article and proceed to a new cleaning and moulding operation, as described above. It is evident that the method can be realized with any type of mould and with the mould parts tiltable in any position, provided that the position is suitable to allow the loading of the sheet material 18 and the unloading of the finished article, without departing from the principle of supporting the sheet 18 pneumatically by means of air suction through the surface 13 of the mould part 12 destined to come into contact with the external face of the sheet 18, the other side being the one with the formation of the foamed layer 23. For example, as illustrated in Fig.3, the polyurethane foam or other suitable foamable material, could be fed into the mould by injection also with the mould closed, by means of a head 19', always supporting the sheet material 18 pneumatically so that it does not form bulges or hang into the inside of the cavity of the mould during the foaming phase. Fig.4 shows another possible solution for the apparatus described previously. In the case of Fig.4, unlike the previous case, now the mould part 10 can remain fixed in a horizontal position and the mould part 12, destined to support the sheet material 18, can rotate to an angle of 180° round a single axis 14a in order to present the surface 13 oriented upwards, or in a position such as to allow the placing of the sheet material 18 on it. Nevertheless, the mould shown in Fig.4 presents the same characteristics and functions in the same way as the mould described previously. Alternatively, both the mould parts 10 and 12 carried by the respective structures 17 and 17a of the press, could rotate round the common rotation axis 14a, thus assuming corresponding operative positions. The scheme illustrated in Fig.5 shows a further possible solution, without departing from the innovative principles of the invention. In the case of Fig.5, the mould part 10 remains fixed in a lower position, while the mould part 12 is supported by means of an usual control system (not shown), which makes it possible to move the mould horizontally and vertically into four different operative positions, as shown in the drawing itself. In this case, the mould part 12, which has to support the preshaped sheet 18, presents its surface 13 oriented downwards. Therefore an auxiliary jig 24 on one side of the mould part 10, has been used ; this presents a cavity that is complementary to the one in mould part 12 and on this the sheet 18 is initially positioned, this time with the part destined to remain seen and to come into contact with the surface 13, turned upwards. Therefore, in the operational sequence shown, the upper mould part 12 is moved to a position above the jig 24, on which a preshaped sheet 18 has already been placed, then it is lowered against the jig 24 with the air fans 22 in action so as to pick up the sheet 18 pneumatically, then it is moved upwards again and towards the right, stopping in a position above and in line with the mould 10. In the meantime, a metered quantity of a foamable mixture has been poured or fed into the cavity of the mould 10, then the upper mould part 12 is lowered and closed against the lower mould part 10, while the air suction is maintained until the foam has completely filled the cavity of the mould, as in the cases explained previously.

Claims: A method for moulding a layer of foamed plastic material on one side of a preshaped sheet of material (18) while maintaining the other side free of foamed plastic material (23) in a mould having upper (12) and lower (10) mould parts, movable relative to one another so as to form a mould cavity (11) therebetween, comprising the steps of placing the preshaped sheet of material with the other side against the upper mould in (12), in the open condition, holding the same sheet (18) pneumatically against the upper mould (12), feeding a metered quantity of foamable plastic material (23) into the lower mould (10), characterized by directly connecting at least one air suction source (22) to apertures in concentrated areas on a surface of the upper mould part (12) through a set of conduits (21) defined through said upper mould part; and supporting the preshaped sheet material (18) during closure of the mould (10, 12) and for at least part of the time necessary for the plastic material (18) to foam by maintaining a continuous air suction within the mould cavity through said apertures and between said sheet of the material and said upper mould surface. A method as claimed in claim 1, characterized by maintaining the air suction until the cavity (11) of the mould is completely filled up with the foamed plastic material. A method as claimed in claim 1, characterized by maintaining the air suction for at least part of the time necessary for the filling of the cavity (11) of the mould and the polymerization of the foamed plastic material in the mould. A method as claimed in claim 1, in which the mould comprises a lower mould part (10) and an upper mould part (12) which is tiltable in an open condition of the mould, in such a way that the upper mould part (12) presents at least part of an air suction surface (13) upwardly oriented characterized by laying of a preshaped sheet material (18) on the above-mentioned air suction surface (13), and turning the open mould (10, 12) until the lower mould part (10) is positioned with the cavity turned upwards, holding the sheet material (18) against the air suction surface (13) of the upper mould part (12), and by the fact that a metered quantity of foamable plastic material is fed into the cavity (11) of the mould, after which the mould (10, 12) is closed in order to allow the foaming of the plastic material. A method as claimed in claim 1, in particular for the moulding of carpeting for coating the inside of motor vehicles, in which said sheet material (18) comprises a carpet, having a front face permeable to air, characterized by the fact of making the said carpet (18) adhere to said air suction surface (13) of the upper mould part (12), with said front face of the carpet (18) oriented towards said suction surface (13) of the mould. An apparatus for moulding a foamed plastic material (23) on one side of a preshaped sheet of material (18), the apparatus comprising a support structure (16) for a mould having a lower mould part (10) and an upper mould part (12) movable relative to one another and defining a mould cavity (11) therebetween, said upper mould part (12) having a surface (13) complementary to the moulding cavity (11) of the lower mould part (10), said upper mould part (12) comprising support means for supporting the sheet material (18) against corresponding complementary surface (13) characterized in that said support means comprising air suction channels (21) defined in the upper mould part (12), said air suction channels being connected to air suction devices (22) and to apertures to continuously suck air within the mould cavity through openings in selected areas of said complementary surface of the upper mould part (12). An apparatus as claimed in claim 6, characterized by the fact that the said upper mould part (12) comprising the air suction means (21, 22), is supported rotatably in relation to the lower mould part (10). An apparatus as claimed in claim 6, characterized by the fact that the said upper mould part (12) comprising the air suction means (21, 22), is rotatably supported in relation to the lower mould part (10), moving between a closed condition and an open condition of the mould, and by the fact that both the parts (10, 12) of the mould, in the open position, can rotate to a third operative position in which at least part of the air suction surface (13) of said upper mould part (12) is upwardly oriented. An apparatus as claimed in claim 6, characterized by the fact of comprising a fixed support structure (16) for a press, comprising a first support frame (17) for the lower mould part (10) and a second support frame (17a) for the upper mould part (12), rotatable in relation to the preceding one, the said first and second frames (17, 17a) of the press being further rotatable on the fixed support structure (16), and comprising control means (26) operable for making the said second frame (17a) of the press rotate between a closed condition and an open condition of the mould, as well as control means (25) for making the said first and second frames (17, 17a) of the press rotate contemporaneously, in the open condition of the mould, between a first position in which the lower mould part (10) is horizontal with its open cavity oriented upwards, and a second position in which the air suction surface (13) of the upper mould part (12) is partially oriented upwards. An apparatus as claimed in claim 9, characterized by the fact that the said second support frame (17a) for the upper mould part (12), is hinged rotatably to the said first support frame (17) for the lower mould part (10). An apparatus as claimed in claim 9, characterized by the fact that the said lower mould part (10) is movable between a retracted position towards the first frame (17) of the press, and an advanced position, and by the fact that guide means (20a) and control means (20) are provided for moving the said lower mould part (10) between the above-mentioned retracted and advanced positions. An apparatus as claimed in claim 6, in which the mould comprises a lower mould part (10) having an upward-oriented cavity (11), and an upper mould part (12) having a downward-oriented air suction surface (13), characterized by the fact that the said upper mould part (12) is movable horizontally between a position directly above the lower mould part (10) and a lateral position directly above a support jig (24) for the preshaped sheet material (18), the said upper mould part (12) being movable also between a raised position and a lowered position, in which it picks up the preshaped sheet material (18) pneumatically from the support jig (24), and respectively between a raised position and a second lowered position in which it closes on to the lower mould part (10), control means being provided for moving the said upper mould part (12) between the above-mentioned operative positions.

Inventors: DRAGONI, LORENZO
Applicants: TECNOS S.P.A.
Application year: 1988
Main classification: B29C67
IPC codes: B29C33, B29C44