Abstract:
A process for manufacturing products made of composite materials, is disclosed which includes the steps:
       screwing at least one insert provided with a threaded hole on the outer thread of at least one pin partially inserted in a removable manner in a mold;   arranging on the mold one or more fiber layers provided with at least one opening in which the insert is arranged;   curing resin with the layers arranged on the mold, so as to obtain a product made of a composite material which incorporates the insert and the layers; and   rotating the pin in the insert for removing it from the mold.       
 
     The present invention also relates to a mold, devices and a kit which can be employed for carrying out said process, as well as to products manufactured with this process and/or these means.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is a Division of U.S. patent application Ser. No. 13/807,648, filed Feb. 14, 2014, which is a 371 of PCT/IB2011/052906, filed Jul. 1, 2011, which claims the benefit of Italian Patent Application No. MI2010A001220, filed Jul. 2, 2010, the contents of each of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a process for manufacturing products made of composite materials. The present invention also relates to a mold, some devices and a kit which can be employed for carrying out said process, as well as to the products manufactured with this process and/or these means. 
     BACKGROUND OF THE INVENTION 
     Known products made of composite materials incorporate threaded inserts for the fastening of components and/or structures. These inserts can be inserted in the unprocessed state between the fiber layers and worked after the cure of the resin with digital control machines, which make the holes and the threads. The precision needed by this working is extremely important since the exact position of the threaded holes must be ensured in the final product. However, this working is expensive, long and difficult to be carried out. 
     For overcoming this problem, WO 2006/063185 discloses inserts which are already threaded and are slipped onto smooth pins firmly fixed to the mold, after which pieces or powder of fibers are arranged and cured on the mold, so as to incorporate the threaded inserts. However, this known process does not ensure the exact arrangement in the final product and furthermore only inserts having holes which are arranged on axes perfectly parallel to the extraction axis of the product from the mold can be incorporated, otherwise this extraction would be impossible. 
     An and of the insert of WO 2006/063185 comprises a non-threaded cylindrical cavity coaxial to the threaded hole, while the opposite end comprises a perimetric outer ridge for preventing the insert from penetrating into the final product when a screw is screwed into the threaded hole of the insert through the end provided with the cylindrical cavity. However, only the contact between the outer surfaces of the insert and the final product prevents the insert from coming off in the opposite direction, for example if an excessive pressure is exerted during the screwing of the screw. 
     FR 2664529 discloses another threaded insert with a perimetric ridge, which insert is slipped onto a smooth pin which is provided with a threaded end screwed into a threaded hole of a mold, while the opposite end of the pin is provided with a washer for keeping the insert on the pin. This known pin can be unscrewed from the mold at the end of the process, however it has the above inconveniences of WO 2006/063185, in particular the imprecise axial and/or radial arrangement of the insert with respect to the mold. 
     Said technical problems would be particularly critical if said known inserts were employed in a process in which the fibers are grouped and arranged in overlapping layers on the mold, thus not in pieces or powder as in WO 2006/063185 or in bobbins as in FR 2664529. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a process free from said disadvantages. Said object is achieved with a process, a mold, some devices and a kit, whose main features are disclosed in the claims. 
     Thanks to the particular partially threaded pins which are inserted in a removable manner in the mold, the process according to the present invention allows not only to arrange in extremely precise positions on the mold inserts which are already threaded, since the pins are inserted in holes which can be easily made on the mold with digital control machines, but also to orientate these inserts along axes which are not parallel to the extraction axis, since the pins can be easily removed before extracting the product from the mold. The pins can further be easily reinserted into the mold for manufacturing a new product. 
     The process according to the present invention also allows to arrange some fiber layers between the insert and the mold, without losing the exact position of the insert, so as to obtain a better union between insert and final product. 
     The inserts are provided with particular perimetric ridges which allow a precise coupling with the fiber layers and/or provided with a cylindrical cavity for hermetically closing the threaded hole with a particular complementary plug, so that the final product can in turn be used as a mold for other products, in which case the mold with the pins is called master. 
     The inserts can further be provided with particular bushings to be inserted into the threaded hole and to be replaced once they are worn out by use, so as to protect the thread of the inserts and prolong the life of the products provided with these inserts. For this purpose, the bushings are preferably kept in the inserts by particular removable stop means. 
     A particular extractor provided with an inverse thread allows the mechanical coupling and the subsequent removal of the pin in an easy and fast manner, since only a rotation of the extractor in the same hand is needed. 
     A kit comprising one or more pins, inserts and/or plugs, as well as preferably also an extractor, is particularly useful for manufacturing products made of composite materials by adapting molds or masters previously employed with other processes, also of the know kind. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages and features of the process, the mold, the devices and the kit according to the present invention will become clear to those skilled in the art from the following detailed and non-limiting description of an embodiment thereof with reference to the attached drawings, wherein: 
         FIG. 1  shows a longitudinal section of the insert; 
         FIG. 2  shows a perspective view of the insert of  FIG. 1 ; 
         FIG. 3  shows a longitudinal section of the pin; 
         FIG. 4  shows a perspective view of the pin of  FIG. 3 ; 
         FIG. 5  shows a longitudinal section of the extractor; 
         FIG. 6  shows a perspective view of the extractor of  FIG. 5 ; 
         FIG. 7  shows a longitudinal section of the plug; 
         FIG. 8  shows a perspective view of the plug of  FIG. 7 ; and 
         FIGS. 9 to 15  show longitudinal sections of the kit, the mold and the product during the operating steps of the process. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , it is seen that an insert  1  for composite materials comprises in a known way a through hole  2  provided with an inner thread  3 , wherein the diameter of through hole  2  is greater than or at least equal, in particular equal, to the first diameter d 1  of inner thread  3 . Insert  1  has a substantially cylindrical shape wherein its outer wall has a second diameter d 2  and at least one perimetric ridge  4 ,  5 ,  6 . The outer wall of insert  1  is preferably treated, in particular with a sandblast process, for removing contaminant agents, if any, and then cleaned. A first perimetric ridge  4  has a polygonal, in particular hexagonal, outer profile and is arranged around a first end  1   a  of insert  1 , in particular the end which is accessible from the outside when insert  1  is inserted in a product made of composite materials. A second perimetric ridge  5  is arranged around second end  1   b  of insert  1  opposite to first end  1   a  and has an outer cylindrical profile having a diameter shorter than first perimetric ridge  4 , namely the outer profile of second perimetric ridge  5  is contained in the outer profile of first perimetric ridge  4 , as it is clearly shown in  FIGS. 1 and 2 . A third perimetric ridge  6  is substantially the same as second perimetric ridge  5  and is arranged between the two ends  1   a ,  1   b  of insert  1 , namely between first perimetric ridge  4  and second perimetric ridge  5 . An end of through hole  2  leads to a cylindrical non-threaded cavity  7  which is coaxial to through hole  2  and has a third diameter d 3  greater than or equal to first diameter d 1  of inner thread  3  of through hole  2  and shorter than second diameter d 2  of insert  1 . Cylindrical cavity  7  leads in turn to second end  1   b  of insert  1 , namely to the end opposite to first perimetric ridge  4 . 
     Referring to  FIGS. 3 and 4 , it is seen that pin  8  according to the present invention comprises a blunted, in particular rounded, point  9  and an outer thread  10  having substantially the same diameter d 1  of inner thread  3  of insert  1 . Outer thread  10  covers only a portion of pin  8 , while the remaining portion  8   a  is not threaded and has a fourth diameter d 4  shorter than diameter d 1  of inner thread  10 . The end of pin  8  opposite to non-threaded portion  8   a  is provided with a first connection member  11  for rotating pin  8  around its longitudinal axis. In the present embodiment, first connection member  11  is preferably a coaxial hole provided with an inner thread  12  having a fifth diameter d 5  and made in the opposite hand of outer thread  10 , but in other embodiments first connection member  11  may comprise for example a prismatic coaxial seat or head, having a square-, octagonal- or cross-shaped section. 
     Referring to  FIGS. 5 and 6 , it is seen that extractor  13  according the present invention comprises a stem with an end provided with a second connection member  14  complementary to first connection member  11  of pin  8 , in particular an outer thread having the same hand and a diameter substantially equal to fifth diameter d 5  of inner thread  12  of pin  8 . The other end of extractor  13  comprises rotation means  15 , for example a knurled cylindrical head for allowing the manual rotation of extractor  13  around its longitudinal axis. Rotation means  15  may also be mechanical and/or electrical, for example comprising a shaped head for being coupled with a complementary point of a drill or an electric screwdriver. 
     Referring to  FIGS. 7 and 8 , it is seen that plug  17  according to the present invention comprises a cylindrical body having a diameter substantially equal to third diameter d 3  of cylindrical cavity  7  of insert  1 . At least one annular gasket  18  is arranged in a perimetric groove made in the outer wall of the cylindrical body, which is joined to a coaxial threaded stem  19  having a diameter substantially equal to first diameter d 1  of inner thread  3  of insert  1 , namely a diameter shorter than or equal to diameter d 3  of the cylindrical body, so that plug  17  can be screwed into insert  1  with the cylindrical body arranged in cylindrical cavity  7  of insert  1 . Plug  17  also comprises a head  20  at the end opposite to threaded stem  19 , which head  20  has a shaped portion  21 , for example a prismatic seat with a polygonal, in particular hexagonal, profile, so that threaded stem  19  can be rotated by operating shaped portion  21 , for example with a tool, until head  20  abuts against second end  1   b  of insert  1 . Shaped portion  21  may also consist of a knurled cylindrical head as rotation means  15  of extractor  13 . 
     Referring to  FIG. 9 , it is seen that in a first operating step of the process according to the present invention pin  8  is covered with a detaching substance and inserted into a hole  22  made on a mold  23 . Hole  22  has substantially the same diameter d 4  of non-threaded portion  8   a  of pin  8 , so that outer thread  10  of pin  8  projects from mold  23 . 
     Referring to  FIG. 10 , it is seen that in a second operating step one or more first layers  24  of fibers, in particular carbon fibers, are arranged onto mold  23 . First layers  24  are provided with at least one hole having a diameter substantially equal to diameter d 1  of outer thread  10  of pin  8 , so that the latter can be arranged in this hole. 
     Referring to  FIG. 11 , it is seen that in a third operating step insert  1  is screwed onto outer thread  10  of pin  8 , until first perimetric ridge  4  does not contact a first layer  24 . In an alternative embodiment, insert  1  is screwed onto pin  8  without arranging first layers  24  on mold  23 , so that insert  1  contacts mold  23 . Insert  1  can be rotated by means of a tool coupled with the polygonal surface of first perimetric ridge  4 . 
     Referring to  FIG. 12 , it is seen that in a fourth operating step one or more second layers  25  of fibers, in particular carbon fibers, are arranged one on the other onto first layers  24  or, if the latter are absent, directly onto mold  23 . Second layers  25  are provided with at least one opening having a diameter substantially equal to second diameter d 2  of insert  1 , so that the latter is arranged in this opening. Some second layers  25  can be provided with a larger opening for adapting to the outer profile of first perimetric ridge  4 . Second layers  25  are arranged one on the other until they reach third perimetric ridge  6 . During their deposition, layers  24 ,  25  are slightly forced on insert  1  for overcoming perimetric ridges  4 ,  5  and/or  6 . 
     Referring to  FIG. 13 , it is seen that in a fifth operating step mold  23  is closed and layers  24  and  25  are impregnated with a resin, which is then cured so as to form a product  26  made of a composite material which incorporates insert  1  and layers  24 ,  25 , after which mold  23  is opened. Pin  8  is then unscrewed from insert  1  and removed from hole  22  of mold  23  by rotating extractor  13 . During this removal, second connection member  14  of extractor  13  is mechanically coupled with first connection member  11  of pin  8 . Pin  8  is preferably removed also from insert  1 . Layers  24 ,  25  can be dry, namely with a content of resin lower than 10%, or be pre-impregnated with resin, in which case no resin is injected into mold  23  for manufacturing product  26 . 
     Referring to  FIG. 14 , it is seen that before extracting product  26  from mold  23 , insert  1  can be hermetically closed by plug  17  screwed by means of a tool  28  into second end  1   b  opposite to hole  27  made in piece  26  in correspondence with through hole  2  of insert  1 . 
     Referring to  FIG. 15 , it is seen that a bushing  29  is screwed into through hole  2  of insert  1 . For this purpose, bushing  29  is provided with an outer thread having a diameter substantially equal to first diameter d 1  of inner thread  3  of insert  1 . Bushing  29  comprises a through hole  30  provided with an inner thread having a sixth diameter d 6  shorter than first diameter d 1 . An end of through hole  30  is provided with a polygonal, in particular hexagonal, seat  31 , for facilitating the screwing of bushing  29  into insert  1 . Removable stop means are arranged in through hole  2  for keeping bushing  29  in insert  1 . In particular, said removable stop means comprise plug  17  which prevent bushing  29  from going out through second end  1   b  of insert  1 , as well as a retaining ring  32  snap-fitted in a removable manner into a circular seat which can be made in through hole  2  for preventing bushing  29  from coming out through first end  1   a  of insert  1 . Bushing  29  can also be screwed into through hole  2  of insert  1  before screwing plug  17 , in which case bushing  29  can be also inserted through second end  1   b  of insert  1 . 
     Possible modifications and/or additions may be made by those skilled in the art to the hereinabove disclosed and illustrated embodiment while remaining within the scope of the following claims.