GB763065A - Improvements in or relating to plated ferrous metallic materials and articles and the plating thereof - Google Patents

Abstract

Prior to electrolytic or chemical plating an anodically degreased steel plate is pickled by immersion for 1 to 10 minutes in a 2 1/2 -20 per cent aqueous solution of sulphuric acid or 1 : 1 formic-nitric acids mixture. plurality of thin rings 82 slightly spaced from each other and clamped between end rings 78 and on each side of a central ring 80 which has radial slots for receiving vanes 81; in a modified form (Fig. 8, not shown), the vanes 81 are replaced by rods mounted on the ring 80. The longtitudinal passageways 59 between the radial members 53 are therefore in communication with the classifying means and open through the end closure 12 into curved passages 60 into the fan. The fan (see Group XXVI) is mounted on the rotor and its housing 11 is separated from the casing 10 either by a sleeve 25 having one or more air inlets 25A or braces providing for the free admission of air into the space 28 between the housing 11 and casing 10; sufficient air is allowed to enter the apparatus from the space 28 through annular openings 17, 22 to prevent the escape of the pulverised particles through these openings. Material is fed tangentially into the casing through a feed hopper 96, Fig. 4, extending the full length of the casing and having one or more gate-controlled opening 100 for the admission of air or other gas. An outlet 104 is provided along the bottom of the casing 10 for the discharge of unbreakable material under the control of a motor-driven roller 106. The casing 10 is provided with a lining which may be of smooth wear-resistant material or surfaced with cutting edges or as an abrasive. In the operation of the machine, material from the hopper 96, together with air or gas from the openings 100, is fed tangentially into the casing for grinding primarily by impact of particle against particle and particle against the gaseous stream. The particles first pass in a circular path 150a, Fig. 11, around the outer part of the grinding zone by the action of the rotating vanes and as they become smaller and therefore lighter move inwardly into inner high-speed vortices 152a set up between adjacent vanes. This operation is the same in both the grinding and classifying zones, but in the latter zones the inner vortices are distorted by the suction action of the fan to cause a further separation in the paths of particles of different sizes and the passage of the particles of desired size between the rings 82 into the longitudinal passages 59 for discharge by the fan. The shape and size of the inner vortices are dependent upon such factors as the speed of the rotor, the spacing of the vanes 81, and the suction effect of the fan; the size to which the particles are reduced is regulated by the diameter of the rings 82 (i.e. the extent to which they reach out in the inner vortices), the spacing of these rings, the spacing and depth of the vanes 81, and the speed of the rotor. The discs in each classifying zone may be formed alternately of large and small diameters or of diameters which increase or decrease gradually from the centre to the ends. If desired, the apparatus may comprise one grinding zone and two classifying zones or one classifying zone and two grinding zones. U.S.A. Specification 2,294,920 is referred to.