PUNCHING DIE SET Russian patent published in 1999 - IPC

FIELD: plastic metal working, namely die sets for punching one small size hole or group of such holes in parts of sheet materials. SUBSTANCE: die set includes upper plate, punch holder, stripper, one punch or group of punches in the form of rod beaded in its upper portion and lower plate with die. Working part of punch is in the form of truncated cone whose angle is equal to conicity angle of die opening. Small bases of cones of punch and die are turned one to another. Gap between die and punch corresponds to maximum gap for worked material and its thickness and it keeps its value at further regrinding. Dimension of small base of truncated cone of punch corresponds to less size of hole of worked part. Length of free portion of punch is no more than two diameters of holes of worked part. Working end of punch with conicity angle of working portion more than 2 degrees is arranged higher than working end of die at time moment of punching termination. Hollow cylinder is arranged in addition between stripper and punch holder. Inner surface of hollow cylinder engages with punch. Hollow cylinder has helical groove whose depth is equal to the whole thickness of cylinder wall. Stripper may be builtup in the form of two strips between which guiding sleeve is arranged with gap. Inner surface of guiding sleeve engages with punch. Guiding sleeve has flange with spherical surface around which stripper may be rotated. Punch contacting with inner surface of stripper opening may be mounted with clearance in opening of spring-loaded punch holder that may rotate relative to spherical surface of punch flange. Sleeve may be mounted between punch holder and punch. Said sleeve has bead in its upper portion, its outer surface contacts with opening of punch holder or stripper, it is spring loaded and mounted with gap in stripper or in punch holder with possibility of axial motion relative to it. Punch is arranged in stepped opening of sleeve and it may move axially relative to sleeve. EFFECT: improved design providing enhanced strength of die set. 6 cl, 7 dwg