| 摘要 |
PROBLEM TO BE SOLVED: To obtain a hollow core having good precision, to shorten the time for molding and to reduce a manufacturing cost. SOLUTION: In a blowing machine 25, a basis hole 42 having a little larger diameter than the outer diameter of a pin 23 and a conical hole 43 expanding the diameter from this basis hole 42, are arranged along the flowing of molding sand 21, and spline groove state vertical grooves 44 are arranged in this basis hole 42. The upper end 23a of the pin 23 during ascending movement, is introduced into the basis hole 42 with a tapering action of the conical hole 43 so that the molding sand 21 can be filled up into a cavity 33 through the vertical grooves 44 under the state of inserting the pin 23 into this basis hole 42.
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