Abstract: A miniature non-return valve comprises a circular recess with an inlet at its center, an annular groove coaxial with the recess and communicating with the recess at a number of points within the groove, and an outlet duct communicating with the groove. Fluid entering the inlet passes through the recess, the annular groove and the outlet duct substantially unimpeded, whereas fluid entering the outlet duct forms a vortex in the recess so that flow of that fluid to the inlet is inhibited. Control fluid may be fed into the recess to initiate or enhance formation of the vortex. The inlet and the circular recess may be provided in first and second substrates, respectively, and the annular groove and the outlet duct may be provided in a third substrate, all by a micromachining process, the substrates being bonded together in a stack. The substrates may be formed of silicon.

Abstract: A fluid dispenser for use, for example, in an ink jet printing head, comprises a switching device, preferably a bistable fluidic device, which switches fluid under pressure between a path in which the fluid circulates back to the fluid source and a second path in which it issues from a jet. The fluidic device is preferably formed by micro-machining cavities in a silicon substrate, or in two substrates which are then bonded together face to face. A printing head may be formed by locating a number of the dispensers in side-by-side relation with spacers therebetween, the spacers being used to provide feed paths for the ink.