A back mold core for double -wall pipe expansion mould

The utility model discloses a back mold core for double -wall pipe expansion mould, including back mold core body, the tip is provided with a portion of inserting before the mold core body of this back, wherein, set up a perforation that runs through back mold core body and just supply the double -wall pipe to pass on the mold core body central axis direction of this back, just it has seted up anevacuation cavity to be located the perforation periphery on the mold core body of this back, this evacuation cavity runs through to inserting a front end, and a plurality of through -holes of setingup on this evacuation cavity inner wall and perforating and be linked together, set up an evacuation hole that is linked together with the evacuation cavity on the mold core body of this back. The utility model discloses structural design is special, novel, reasonable, can be used to double -wall pipe expansion mould, realize expanding the size of a dimension that becomes to need with the double -wall pipe, satisfy the dem