| JP02180280 | RACKET FRAME AND MANUFACTURE THEREOF |
| JP02185494 | IC CARD |
| JP2002326221 | METHOD FOR MANUFACTURING TWO-LAYER PREFORM |
Zucchinali, Marcello (Via Carlo Botta 11, Bergamo BG, I-24122, IT)
Zucchinali, Marcello (Via Carlo Botta 11, Bergamo BG, I-24122, IT)
The present invention relates to a process for producing poles or the like, and in particular poles made of a plastic material molded with an inner rigid core. The present invention also relates to a mould which can carry out said process, as well as a pole produced with said process and/or mould. EP-A-945567 discloses a process for producing a pole by injecting melted plastic material around a metal rigid core. Said process requires a pair of supports arranged around the rigid core for keeping the pole in the middle of the mould or the molding of the plastic material in two separate portions which are provided with a seat in which the rigid core is inserted after the molding and before joining the two portions to each other. Said known processes thus require some operating steps which can be carried out only manually or by means of additional workings and/or members, anyway. It is therefore an object of the present invention to provide a process free from said disadvantages, i.e. a process which can be carried out in a completely automatic manner and/or without particular accessories. Said object is achieved with a process and a mould, the main features of which are disclosed in claims 1 and 9, respectively, while other features are disclosed in the remaining claims. Thanks to the retractable rods, the process and the mould according to the present invention allow to completely cover in a simple and quick manner with the plastic material the rigid core arranged in the middle of the mould. The production of plastic poles with a metal rigid core can thus be automated without additional members. According to a particular aspect of the invention, the retractable rods can be provided with holding means and/or shaped points, so as to improve their union with the rigid core. According to another particular aspect of the invention, the mould can be provided with nozzles for gas under pressure, so as to create one or more bubbles in the rigid core and to lighten the pole without reducing its mechanical resistance. Further advantages and features of the process and the mould according to the present invention will become clear to those skilled in the art from the following detailed and non-limiting description of two embodiments thereof with reference to the attached drawings, wherein: - figures 1, 2, 4, 5, 7, 9 to 13 and 15 show perspective views of the first embodiment of the mould during the different operating steps of the process; - figures 3, 6, 8 and 14 show partial cross-sectioned views of the mould of figures 2, 5, 7 and 13, respectively; and - figure 16 shows a partial cross-sectioned view of the second embodiment of the mould in the final step of the process. Referring to figures 1 to 3, it is seen that the mould according to the present invention comprises in a known way at least two complementary portions 1, 2 for molding plastic material, which can be mutually joined along a longitudinal plane and are provided with complementary cavities 3 for molding longitudinal portions of a pole or another similar elongated product, which can provided with external protrusions and/or grooves necessary for the desired use. According to the inventions, portions 1, 2 comprise one or more cross-holes in which rods 4 suitable for protruding into cavities 3 can slide for keeping therein a rigid core 5, so that the latter should not touch the walls of these cavities. In the present embodiment, the rigid core 5 comprises a tube with a quadrangular cross-section, for example made of iron or Nylon® with fiberglass, which is arranged in the middle between portions 1, 2 by a mobile support 6 provided with pliers and/or suction caps (not visible in the figures). Referring to figures 4 to 6, it is seen that the mobile support 6 arranges the rigid core 5 in contact with rods 4 protruding into cavity 3 of portion 1 and is retracted for setting the space between portions 1 and 2 of the mould free. One or more rods 4 can be provided with holding means for avoiding that the rigid core 5 leaves them. Said holding means can comprise magnets and/or suction ducts suitable for attracting and/or sucking the rigid core 5 toward rods 4. The point of rods 4 is shaped for obtaining a concave seat, so as to carry out a shape coupling between rods 4 and the rigid core 5. Referring to figures 7 and 8, it is seen that when the mobile support 6 has been removed, portions 1 and 2 of the mould are mutually joined, so that the rigid core 5 is arranged between rods 4 protruding into cavities 3 of these portions. Rods 4 of portion 1 are preferably aligned with rods 4 of portion 2, so that the rigid core 5 can be pressed between two opposing rods 4. Referring to figures 9 to 14, it is seen that melted plastic material 7 is injected into cavities 3 of portions 1 and 2, preferably through at least one inlet duct arranged at one end of portions 1 and/or 2 of the mould. When the melted plastic material 7 advances into cavities 3, rods 4 contacting this plastic material 7 do not press the rigid core 5 any longer but are progressively retracted, as shown by the arrows, so that the space set free by a retracted rod 4 is occupied by the melted plastic material 7. When the plastic material 7 has completely filled cavities 3, the rigid core 5 is kept in its central position no longer by rods 4, but by the same plastic material 7, as shown in figures 13 and 14. Referring to figure 15, it is seen that when the plastic material 7 has solidified, portions 1 and 2 of the mould are opened and the mobile support 6 extracts the complete pole comprising the rigid core 5 covered by the layer of plastic material 7. Referring to figure 16, it is seen that in a second embodiment of the invention portions 1 and/or 2 of the mould comprise at least one nozzle for gas under pressure, in particular, nitrogen with a pressure comprised between 3 and 30 MPa, so as to form at least one bubble 8 in the rigid core 5 when the plastic material 7 is still melted. Said nozzle is for example arranged at the ends of portions 1 and/or 2 comprising the inlet duct for the melted plastic material 7. In further embodiments of the invention, at least one nozzle can be inserted into an end of the rigid core 5 and/or be connected to a lateral hole made in the rigid core 5, so as to limit or prevent the penetration of the plastic material 7 in the rigid core 5. The nozzle can then be retracted in the mould as rods 4 when the plastic material 7 begins to solidify. Possible variations and/or additions may be made by those skilled in the art to the embodiments of the invention hereinabove described and illustrated while remaining within the scope of the same invention.
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