PURPOSE: To secure the high dimensional accuracy of a scroll and to reduce frictional resistance during its machining by providing the spiral engraved mold section of a metallic mold for forming a scroll lap with a land part and a relief part for forming the scroll whose lap has no draft angle.
CONSTITUTION: A forging device is provided with a lower mold 2 which supports a workpiece 1 and shares the reaction force of a forging load and a upper mold 3 provided with a spiral engraved mold section 4 to form a scroll lap 10, and moreover provided with an upper mold restraining member 5 provided with an air vent hole 6 communicating with the engraved mold, a holder 7 to hold the upper mold 3, a restraining mold 8 to restrain the radial deformation of the workpiece 1, and a boss 9. In this case, the engraved mold section 4 formed into the spiral shape of the upper mold 3 is formed of the and 4a of a parallel part to form the scroll lap 10 and a relief part 4b provided with a clearance angle α. Thus the scroll whose lap 10 has no draft angle can be formed with highly secured dimensional accuracy.
KONO AKIOMI
ABE NOBUO
