the first front core 102 a to entirely penetrate the first blind hole 23 a accordingly the first area 31 a is spaced from the core 102 a and thus not supported the second area 32 a is located partially within the mold space 101 and partially covered by a front face of a first rear core 103 a the covered area of the second area 32 a is therefore also located outside the mold space because material provided in the mold space is prevented from getting into contact with the covered area within the second area 32 a the valve member 16 in this example further has at least a second portion 30 b formed between a third area 31 b and a fourth area 32 b part of the fourth area 32 b is covered by a second rear core 103 b and a second front core 102 b is placed within a second blind hole 23 b the second portion 30 b the third and the fourth area 31 b 32 b are preferably configured substantially identical to the first portion 30 a with the first and second areas 31 a 32 a respectively further the second front and rear cores 102 b 103 b are configured and arranged generally identical to the configuration and arrangement of the first front and rear cores 102 a 103 a respectively the second blind hole 23 b further generally corresponds in configuration to the first blind hole 23 a fig8 shows the first and second rear cores 103 a 103 b placed further toward the valve member 16 as a result the first portion 30 a and the second portion 30 b of the valve member 16 are displaced relative to the remainder of the valve member 16 preferably the.