Bladder rings for tire vulcanization mold

A tire vulcanization mold comprising:

• a plurality of mold surfaces defining a tire cavity;
• a center post disposed in the tire cavity;
• a first ring disposed about the center post, the first ring having a first rigid outer surface defining a first diameter and having a first axial length;
• a second ring disposed about the center post, the second ring having a second rigid outer surface defining a second diameter equal to the first diameter, and having a second axial length;
• a bladder having a first end connected to the first ring and a second end connected to the second ring,
• wherein at least one of the first and second rings is configured to move axially along the center post between a first, extended position in which the first ring is distal from the second ring and a second, compressed position in which the first ring is proximate to the second ring, and
• wherein, when the first and second rings are in the first, extended position the sum of the first axial length and second axial length is greater than a space between the first ring and the second ring;
• a vacuum configured to apply vacuum pressure to an inside of the bladder such that the bladder contacts an axially inner portion and an axially outer portion of the first ring and an axially inner portion and an axially outer portion of the second ring when the first and second rings are in the first, extended position;
• and
• a hot pressure medium supply configured to provide a hot pressure medium to the inside of the bladder such that the bladder contacts the axially outer portion of the first ring and the axially outer portion of the second ring when the first and second rings are in the second, compressed position, and such that the bladder does not contact the axially inner portion of the first ring and the axially inner portion of the second ring when the first and second rings are in the second, compressed position.