Patent EP-0373294-A3 (EP)
Title: Method for producing frp screw-like fastening elements
IPC: B29D1/00
Filed: 1989-08-11
Abstract: The present invention relates to a method for producing an 
FRP screw-like fastening element. The screw to be produced has a 
thread portion and a head the cross section of which is larger than 
that of the thread portion. The method includes the following 
steps of a primary molding process and secondary molding 
process. The primary molding process includes the following 
steps of: (a) preparing a rod material including an elongated 
matrix formed of a plastic material (6) and a plurality of elongated 
parallel fiber elements (2) embedded within the matrix along the 
length of the matrix, the fiber elements having melting points 
substantially higher than the softening point of the matrix; (b) 
placing the prepared rod material of the screw into a molding 
chamber, the molding chamber including an internal surface of a 
semi-circular cross section, the internal surface having a small 
diameter portion and a large cross section portion communicating 
concentrically to the small diameter portion, the material being 
placed in the molding chamber in such a manner that the 
longitudinal axis of the rod material is generally aligned with the 
axis of the internal surface of the molding chamber; (c) heating 
the placed rod material to a temperature not less than the 
softening point of the matrix; (d) pressing the heated material 
perpendicularly to the axis thereof by a ram which has a plane 
surface facing to the internal surface of the molding chamber, 
thereby forming a half round bar from the material, the half 
round bar being generally in the form of half a round bar cut at a 
 
 
plane including a center axis thereof, the half bar having an end 
portion and an other portion, the end portion being of a radius 
larger than the radius of the other portion; (e) cooling the half 
round bar to a temperature lower than the softening point of the 
matrix; and (f) taking the cooled rod material out of the molding 
chamber. The secondary molding process includes the following 
steps of: (g) joining the half round bar to another half round bar 
which is processed similarly to the half round bar to form a 
generally fully cylindrical material, the fully cylindrical material 
having a head portion of a larger cross section constituted by the 
end portion; (h) placing the fully cylindrical material within a 
cylindrical molding wall in such a manner that the longitudinal 
axis of the rod material is generally aligned with the axis of the 
molding wall, the molding wall including a large cross section 
portion for receiving the head portion, and a small diameter 
having an internal thread formed thereon to receive the 
portion except for the head portion of the fully cylindrical 
material; (i) heating the placed fully cylindrical material to a 
temperature not less than the softening point of the matrix; (j) 
inserting a stick member (48) into the heated fully cylindrical material 
along the longitudinal axis of the fully cylindrical material so as to 
laterally expand the full cylindrical material and to bring the 
peripheral face of the full cylindrical material into contact with 
the entire molding wall, thereby forming an external thread on 
the peripheral face of the fully cylindrical material; (k) cooling 
the thread-formed fully cylindrical material to a temperature 
 
 
lower than the softening point of the matrix; and (l) taking the 
cooled fully cylindrical material out of the molding wall.