ES354696A1 - Improvements relating to the treatment of fabricated articles - Google Patents

Abstract

A manufactured article has burrs, flash or other objectional projections removed from its surface by placing the article in a gas-filled enclosure and generating a transient elevated temperature in the gas which serves to remove the projections and leave the rest of the article unaltered. The projections may be macroscopic, e.g. flash, or microscopic, e.g. surface irregularities. The article may be made of a plastics, metal, e.g. steel, copper, brass, aluminium, iron or alloys, glass, cermets or ceramics. The temperature rise may be produced by adiabatic compression, shock wave generation, or ignition of combustible gases. A heat mask may be provided in the form of a metal heat sink or a polythene coating over the parts not to be removed. In one embodiment for a steel article 10, the article is placed in a chamber 19, Fig. 4, and a hydrogen-oxygen mixture compressed therein by a piston 20 moved hydraulically, pneumatically or mechanically. A spark plug 27 is fired to ignite the mixture and the rise in temperature serves to remove flash 12a, 13a, 14a from bore holes 12, 13, 14. An oxide residue on the article is removed by hydrochloric acid. Alternatively the combustible gas is a mixture of Texas natural gas (90% methane) and oxygen. The same apparatus may be used for other materials using a lower temperature by using different gas mixtures and pressures. The chamber may have a fixed cover and a separate piston-cylinder assembly, Fig. 5 (not shown). The combustible mixtures are of oxidizable materials and oxidizer materials. The oxidizable materials are alkanes, alkenes or alkynes, ammonia, hydrazine, hydrogen sulphide, carbon monoxide, acetylene, ethylene oxide or cyanogen. Suitable oxidizer materials are oxygen, air, fluorine, chlorine, ozone, perchlorates or nitrogen oxides. The mixture may have an excess of oxidizing material particularly when used with ferrous articles. Alternatively the mixture may have an excess of reducing material when used with non-ferrous metals. The mixture may have glass, metal, ceramic or plastics beads which are violently disturbed by the combustion and serve to dislodge the flash. In a further embodiment the article 42, Fig. 7, forms part of the enclosure and a lower closure plate 45 has a gas inlet and a spark plug 46. The gas mixture may be ignited by the compression in the chamber or a shock wave produced by an explosive cartridge or electric arc may heat the gas. In a further embodiment the gas mixture is adiabatically compressed. Figs. 10-12 (not shown), by a piston 54 moved forward by hydraulic, pneumatic or mechanical means or by detonation of a gas mixture behind the piston The gas which is compressed is preferably inert. Alternatively the gas may be combustible and ignited by auto-ignition due to the compression.