High speed thermochemical actuator

Abstract

A heat sink (14) provides thermal communication between an actuator (18) and fluid controlled by a valve (12) which is flowing through a conduit (10). The actuator includes a vessel which is defined on its largest surfaces by plates (22, 50) of beryllium oxide thermally conductive ceramic covered with thermally conductive, relatively electrically non-conductive nichrome foil (24, 26). Longitudinal sides (30, 32) of the vessel are also relatively non-conductive. A thermally and electrically conductive core, such as accordion pleated beryllium copper foil (44) or a carbon fiber mat (82, 116) is disposed in the chamber. Electrical current flows through the core itself (FIG. 4) or through electrically insulated heating wires (80) (FIG. 5) or through an electrically insulated heating surface layer (FIG. 6) causing resistance heating and melting of a non-gaseous polymeric phase change compound (46). The resistance heating current is inductively induced in the embodiment of FIG. 8. The polymeric core material expands transferring force through a rubber core (66, 108) to a push pin ( 68, 130). Fluid flowing through the conduit (10) draws heat from the phase change material through the core, the vessel, and the heat sink to solidify the phase change compound, causing the push pin to be retracted. The phase change compound is selected and the actuator is sized to achieve an actuation time of less than 500 milliseconds.