SAFETY AND ARMING DEVICE USING CELLULOSE-BASED SENSOR/ACTUATOR

摘要

A safety and arming device has first and second portions of an explosive train fixably supported in a housing. A third portion of the explosive train is fixable in a first position such that the first and second portions remain operably separated from one another, and is further movable to a second position such that the first and second portions are operably coupled to one another via the third portion. An integrated water sensor/actuator is coupled to the third portion to provide the motive force that moves the third portion to its second position. The water sensor/actuator is based on a fibrous cellulosic material having anisotropic moisture-absorbing properties such that dried-in strain of the cellulosic material is greatest along one axis thereof. In the invention, a plug of the dry and compressed fibrous cellulosic material has a powder material coated thereon and mixed therewith. The plug is compressed along its axis of greatest dried-in strain and is fitted in a portion of a water-permeable housing adjacent one end thereof. The powder material initiates a chemical reaction when exposed to water to insure the plug's expansion and corresponding movement of the piston which, in turn, moves the third portion to the second position.