Abstract: An air filter is substantially made up of a filter element having a pleated filtering portion and a collar portion that extends on an outer periphery of the filtering portion and that has a sealing function, the filtering portion and the collar portion being integrally formed from the same material, and a cap and a case each of which has a flange for clamping the collar portion of the filter element. One of the flange of the cap and the flange of the case has a protruded portion that has an inclined portion. The collar portion of the filter element has a recess portion that contacts the inclined portion of the protruded portion and is guided by the inclined portion and fits to the protruded portion at a predetermined position so as to become set in position.

Abstract: At least one of grid electrodes which serves as a main lens of an electron gun for use in a color cathode ray tube is divided into a plurality of cylindrical electrodes coaxially connected. An inner electrode is provided at the connection part between the cylindrical electrodes so that the center of an elliptical aperture of the inner electrode coincides with the center of an inner wall of the grid electrode. Thus, astigmatism in the main lens is removed, thereby improving the resolution of the color cathode ray tube.

Abstract: In a composite material of metal and ceramic, the excellent properties of metal and ceramic are combined, so that, when the composite material is flame sprayed, a flame sprayed coating having good mechanical strength and heat- corrosion- and wear-resistance can be obtained. Conventional composite material, in which metal and ceramic are merely mixed or mechanically bonded with one another, cannot provide a plasma sprayed coating having a high bonding strength to the substrate. The present invention improves the plasma spraying composite material by means of a chemical bond between the metal and ceramic parts. The chemical bond may be a compound-or solid solution formation between these parts. The core of the composite material is ZrO.sub.2 and the coating is a metal, metallic compound or combination thereof.