Abstract: A system for producing a control signal upon intrusion of a human part into a protected area, for example the area about the needle of a sewing machine, whereby radio frequency signals at a predetermined frequency are coupled to the human machine operator from a plate on which he sits or stands. As the operator's fingers or other body part approaches the protected area, an antenna receives the rf signal and applies it to an rf phase lock loop receiver which produces an output pulse when the received signal is at the predetermined frequency and is above a predetermined amplitude to operate solenoids which prevent or terminate machine operation. Preferably, withdrawal of the body part triggers a timer which produces a signal permitting the machine to operate for a given time which is greater than the normal time between intrusions, thus continuously checking that the system is working properly.

Abstract: A process is described for making shaped refractories by impregnating cold pitch-bonded shaped refractories with a liquid composition comprising hot pitch.

Abstract: A binder composition comprising pitch, an aqueous solution of a water soluble resin, and an organic solvent solution of a thermosetting polymer. The binding composition in combination with particulate refractory aggregate forms a molding composition suitable for use in making shaped refractory articles. Shaped refractory articles prepared from such a molding composition are particularly suitable for use as linings in basic oxygen process steel refining vessels. Shaped refractory articles may be prepared by coating coarse refractory aggregate with the organic solvent solution of a thermosetting polymer, admixing powdered pitch with the coated coarse refractory aggregate, blending fine refractory aggregate and the aqueous solution of the water soluble resin with the coated refractory aggregate-pitch mixture, and forming the resultant composition into shaped refractory articles.