Molded-in pneumatic circuit

摘要

The circuit, e.g. for testing pressure instruments in an aircraft, consists of at least one pneumatic chamber, one or more valve (40) and flexible connecting tubes (31). The circuit is encased in an over-moulded resin block (30) which both seals its components and acts as a mechanical support for them. The pneumatic chamber consists of a section of PVC tube which is closed at both ends and has at least one orifice for inserting the end of a supple tube. The resin block is equipped with metal inserts with threaded holes and is made from a bi-component polyurethane resin with a relatively low expansion coefficient and a vitreous transition point above that of the temperature range to which the pneumatic circuit is subjected.