Valve arrangement for expandable support of seat has secondary expansion chambers to which excess pressure from main expansion chamber is supplied

摘要

When pressure in a main expansion chamber (1) exceeds a predetermined pressure, the pressure is supplied to secondary expansion chambers (2a,2b) and to an expandable support such that the support expands. When the pressure in the main expansion chamber falls below the predetermined pressure, the pressure in the secondary expansion chambers is reduced such that the support contracts.