additional core being required for molding the section of the hollow body of the housing 5 the corresponding mold discharge directions have been indicated by arrows 13 14 and 15 in the embodiment of fig1 two cores are required for molding the housing 5 the first core being indicated by mold discharge direction 13 and the second core being indicated by mold discharge direction 15 the mold discharge direction 14 of the molding tool is away from the cap 3 the embodiment according to fig2 requires but one core for molding the air trap housing 5 it is moved out of the lower section of the bore 8 in the direction of arrow 13 by looking at both fig1 and 2 it will become apparent that the housing 5 with its opening nipple 6 constitutes a part of the surface 7 of the outer wall of the washing fluid container cap 3 the opening nipple 6 being preferably molded to extend in an upward direction and at an acute angle relative to the surface 7 of the outer wall this area is formed by the single core the arrow 15 representing it having been indicated to point in an upward direction the other core serves to form the housing 5 with its downwardly opening section 8 which constitutes part of the inner wall surface 9 of the washing fluid container cap 3.