US Patent 6971193 Bladder with high pressure replenishment reservoir

A shock absorbing bladder for use in the sole of an article of footwear is disclosed. The bladder includes a plurality of inflated chambers at different pressure levels. The bladder includes a first sealed chamber formed of a barrier material. The first chamber contains a fluid at a first fluid pressure. A second sealed chamber also forms part of the bladder. The second chamber is formed of a second barrier material and contains an inflation fluid at a second fluid pressure that is greater than said first fluid pressure. The second chamber is operatively coupled to the first chamber so that the inflation fluid from the second chamber moves into the first chamber to replenish fluid leaving the first chamber.