Device to produce polyurethane articles relative method and polyurethane articles thus obtained

2- Device as in claim 1, characterized in that said first position (22a) is outside the mold (30).

3- Device as in claim 1 or 2, characterized in that said second position (22b) is inside the mold (30).

4- Device as in any claim hereinbefore, characterized in that said annular ring-nut (22) has at least a perimeter edge (23) protruding forwards towards said molding cavity (18) and able to allow the formation of a perimeter undercut in correspondence with the perimeter edge of the polyurethane article (37).

5- Device as in any claim hereinbefore, characterized in that, at least on the perimeter, said annular ring-nut (22) has first vacuum means (26) able to be selectively activated and able to exert an action of at least temporary retention of said segment of film (19) during the insertion of said segment into said mold (30).

6- Device as in any claim hereinbefore, characterized in that, at least on the perimeter, said annular ring-nut (22) has second vacuum means (126) able to be selectively activated and able to locally create a vacuum to cooperate in the thermoforming of said segment of film (19) inside said mold (18).

7- Device as in claims 5 and 6, characterized in that said first (26) and said second (126) vacuum means include relative suction holes arranged in a position outside the figure of the polyurethane article (37) to be made.

8- Device as in any claim hereinbefore, characterized in that, at least on the perimeter, said annular ring-nut (22) has heating means (33) able to be selectively activated and able to heat said segment of film (19) at least locally during the thermoforming step inside said mold (30).

9- Device as in any claim hereinbefore, characterized in that it comprises pressure means (21) arranged at least on the perimeter in cooperation with at least part of the upper surface of said annular ring-nut (22) and able to mechanically retain said segment of film (19) at least during the thermoforming step.

10- Device as in claim 9, characterized in that, in cooperation with a relative part of the upper surface of said annular ring-nut (22), said pressure means (21) define at least a housing seating for perimeter sealing means (27).

11- Device as in claim 10, characterized in that said perimeter sealing means comprise at least an O-ring (27) housed partly in said annular ring-nut (22) and partly in said pressure means (21).

12- Device as in any claim from 9 to 11 inclusive, characterized in that, in cooperation with a relative part of the upper surface of said annular ring-nut (22), said pressure means (21) define tensioning means (25, 28) to prevent wrinkles in said film (19) during the forming step.

13- Device as in any claim hereinbefore, characterized in that it comprises means to deliver compressed air (34), able to be selectively activated and able to cooperate with said segment of film (19) at least during the thermoforming step.

14- Device as in any claim hereinbefore, characterized in that it comprises auxiliary heating means (38) able to heat, locally and in a desired fashion, pre-determined zones of said segment of film (19).

15- Device as in any claim hereinbefore, characterized in that, at the end of the operation to mold and form the polyurethane article (37) and to open the mold (30), said annular ring-nut (22) is able to return to a position (22a) outside the mold (30), taking with it said polyurethane article (37), to allow the extraction and discharge thereof.

16- Device as in claim 15, characterized in that it comprises expulsion means (35) able to cooperate with said annular ring-nut (22) in its position (22a) outside the mold (30) to allow said polyurethane article (37) to be discharged and to fall onto collection means (36).

17- Device as in claim 1, characterized in that it comprises extractor means (31) able to cooperate with said annular ring-nut (22) in its position (22a) outside the mold (30) to lay said segment of film (19) in cooperation with at least part of its perimeter.

18- Device as in any claim hereinbefore, characterized in that it comprises a mold used to form two figures simultaneously, cutting means (29) being provided in correspondence with an intermediate position between said two figures to cut said film (19).

19- Device as in claim 8, wherein said male part (12) and/or said female part (13) include heating means able to be selectively activated, characterized in that said heating means (33) of said annular ring-nut (22) are fed in independent and autonomous fashion with respect to said heating means of said male (12) and/or female (13) part.

20- Method to produce, inside a mold (30), polyurethane articles (37) covered with a film (19), wherein polyurethane (24) is injected inside a molding cavity (18) defined by the coupling of a female part (13) and a male part (12), at least one of the two parts, male (12) and female (13), being heated, wherein there are present, in association with the perimeter edge of said female part (13), means (22) able to perform a connection function in substantial cooperation with the zone of discontinuity between said female part (13) and said male part (12), said means (22) allowing to form a perimeter undercut in correspondence with an edge of said article (37), characterized in that, in order to insert a segment of said film (19) into the mold (30), the method provides that said means (22) are taken first to a position (22a) outside said mold (30) so that said segment of film (19) can be loaded and clamped onto at least part of the perimeter of said means (22), then that said means (22) are translated to a position (22b) inside the mold (30) and positioned at least partly overlapping the perimeter of said female part (13).

21- Method as in claim 20, characterized in that, during the displacement of said means (22) from the position (22a) outside the mold (30) to the position (22b) inside the mold, first vacuum means (26) present at least on the perimeter of said means (22) are activated to maintain said segment of film (19) clamped on the upper surface of said means (22).

22- Method as in claim 20, characterized in that, after said means (22) have been positioned partly overlapping the perimeter of said female part (13), the method provides a step of thermoforming of said segment of film (19) in order to make it adhere to the walls of said molding cavity (18).

23- Method as in claim 22, characterized in that, during the thermoforming step, second vacuum means (126) present at least on the perimeter of said means (22) and arranged outside the figure of the polyurethane article (37) to be made, are activated to attract said segment of film (19) against the walls of said molding cavity (18).

24- Method as in claim 22 or 23, characterized in that, during the thermoforming step, heating means (33), present at least on the perimeter of said means (22), are activated to heat said segment of film (19).

25- Method as in any claim from 22 to 24 inclusive, characterized in that, during the thermoforming step, means (34) to deliver compressed air are activated to cooperate in the adhesion of said segment of film (19) against the walls of said molding cavity (18).

26- Method as in any claim from 22 to 25 inclusive, characterized in that, during the thermoforming step, auxiliary heating means (38) are activated to locally heat specific zones of said segment of film (19).

27- Method as in any claim from 22 to 26 inclusive, characterized in that, after the thermoforming of said segment of film (19), the method comprises the following steps:

• polyurethane material (24) is injected by means of an injection head (117) with an injection channel (17);
• the polyurethane material is polymerized and molded, the thermoforming of said film (19) is consequently completed and said film (19) is stably constrained to the surface of the polyurethane material (24).

28- Method as in claim 27, characterized in that, when molding is complete, the method provides that said means (22) are removed from the mold (30) to proceed with the discharge of said polyurethane article (37), which remains with the segments of film (19) which are excess to the figure resting on the perimeter of said means (22).

29- Method as in claim 28, characterized in that it provides that said means (22) are taken to said position (22a) outside the mold (30) to cooperate with expulsion means (35) to expel said polyurethane article (37).

30- Method as in claim 20, characterized in that in said position (22a) outside the mold (30) extractor means (31) cooperate with means (20) to feed said film (19) in order to position a segment of said film (19) in co-operation with at least part of the perimeter of said means (22).

31- Polyurethane articles obtained through injection and molding, in a single step, inside a mold comprising at least a male part (12) and a female part (13), characterized in that at the end of the molding process they have their perimeter edge equipped with a perimeter undercut the formation of which is defined by auxiliary means (22, 23) able to perform a function of connection in substantial cooperation with the zone of discontinuity between the female part (13) and the male part (12) of the mold.

32- Polyurethane articles as in claim 31, characterized in that they have at least a film (19), thermoformed in the mold before the polyurethane (24) is injected, constrained at least partly onto a body made of expanded polyurethane.