Abstract: In some embodiments, a head-mounted, near-eye display system comprises a stack of waveguides having integral spacers separating the waveguides. The waveguides may each include diffractive optical elements that are formed simultaneously with the spacers by imprinting. The spacers are disposed on one major surface of each of the waveguides and indentations are provided on an opposite major surface of each of the waveguides. The indentations are sized and positioned to align with the spacers, thereby forming a self-aligned stack of waveguides. Tops of the spacers may be provided with light scattering features, anti-reflective coatings, and/or light absorbing adhesive to prevent light leakage between the waveguides. As seen in a top-down view, the spacers may be elongated along the same axis as the diffractive optical elements. The waveguides may include structures (e.g.

Abstract: An apparatus for providing indication of valve position of a manual valve is disclosed for a valve having a rotary, operating assembly journaled in a housing, the operating assembly comprising a handwheel, a bushing fastened to the handwheel, and a spindle threadedly engaged to the bushing to cause translation of the spindle in response to rotation of the handwheel and the bushing, the apparatus for enclosure in the housing comprising a hub coupled to the bushing for transmitting rotary motion in response to rotation of the bushing; translation means for translating the rotary motion into an electrical signal; and circuitry means responsive to the electrical signal for indicating position of the valve.

Abstract: A circular body, having a throughgoing orifice, an externally threaded periphery, and a pair of stepped recesses, defines a valve seat for a reciprocating piston. A retaining ring is made fast in one of the recesses, and a seal which contracts upon cooling to the ambient, after having been exposed to elevated temperatures, is set in the other recess. The seal is formed of a composite of plastic in which are dispersed carbon fibers to render the seal resistant to creep. A housing having a pair of chambers formed therein has the orificed body and piston interposed between the chambers for valvingly controlling inter-chamber communication.