| 摘要 |
PROBLEM TO BE SOLVED: To prevent a form made of a plastic from being bent by bending stress by arranging a movable core for pressing which faces to a hollow rib placed between recessed parts of a form for concrete and welds integrally the rib from hollow condition to filled condition to a projected part which is located on the male mold side of a male-female molds for blow molding and forms a recessed part. SOLUTION: When a molten resin is fed into a die head 12 through a resin feeding hole 12a, the molten resin is extruded from an annular space path 17 to form a parison P. The hollow parison P being cylindrically injected or extruded from the die head 12 is made into a bag shape by means of a parison pinch and is a little expanded by performing preblowing and is hung between a pair of a male mold 18R and a female mold 18L being opened and located left and right. The male mold 18R and the female mold 18L are brought close to the parison P by means of a mold clamping cylinder wherein the parison P is hung from the die head 12 and when the parison P is pinched in some extent between both male and female molds 18, a movable core 24 is advanced by feeding oil under pressure into the cylinder. |
