GB1362232A - Method of suppressing constraining or diverting movement of gas-borne electrically charged particles or fibres - Google Patents

Abstract

1362232 Conveyers; hoppers S MASUDA 8 June 1971 [7 July 1970] 19313/71 Headings B8A and B8S [Also in Divisions B2 G2 and H2] The movement of gas-borne electricallycharged particles 8, Fig. 1, is suppressed, constrained or diverted by an alternating electric field set up between adjacent electrodes 1, 2. Under the influence of the field a particle 8 will tend to oscillate along the lines 6 of electric flux, but in doing so will experience centrifugal force 9 which has the effect of repelling it from the electrode pair. In practice a row of electrodes is provided, such as electrodes 1, 2, 1<SP>1</SP>, 2<SP>1</SP> ... in plane L-L<SP>1</SP> of Fig. 6. The electrodes are coated with, or embedded in, insulating material, e.g. P.T.F.E. or epoxy resin. General principles. 1. Single phase arrangements. - Alternate electrodes 1,2 ... (Fig. 6) are connected to opposite terminals of a single phase supply 3, setting up a standing-wave electric field pattern which prevents the particles passing through the plane L-L<SP>1</SP>. If, for one or more electrodes, a D.C. bias relative to earth is superimposed upon the alternating voltage, the particles will tend to collect near those electrode(s) (Fig. 4, not shown). If, as in Fig. 6, a D.C. bias is applied between every adjacent pair of electrodes, the particles will be driven laterally (33) above the row of electrodes. 2. Polyphase arrangements.-The electrodes 23, 24, 25 ... (Fig. 7) are connected to successive phases U, V, W of a polyphase supply, setting up a travelling-wave electric field pattern which not only prevents the particles passing through the plane L-L<SP>1</SP> but drives them laterally (33) in one direction or the other, depending on the phase sequence. If, as in Fig. 7, a D.C. bias relative to earth is applied to one electrode 23<SP>1</SP> lateral movement past this electrode will be prevented. If a D.C. bias is applied between every adjacent pair of electrodes the lateral movement can be either accelerated or suppressed, depending on the polarity of the bias. Applications. 1. Electrostatic hoppers/sprayers (Fig. 9).- A series of annular electrodes 56, 57 ...; 59, 60 ...; and 65-69 are energized by a single phase arrangement and define a closed volume 79 within which particles introduced from the top (77) are confined. At the bottom of the volume an outlet is provided by annular electrodes 71-74 energized by a three-phase arrangement of selectable phase sequence. Depending on the phase sequence, the outlet electrodes provide either an upward driving force, preventing release of the particles, or a downward force, ejecting the particles on to an object 80 to which (or to a conductive plate beneath which) is applied a D.C. bias 81. The arrangement may be used for painting by liquid paint particles, coating by powder particles, planting of short fibres, dyeing with liquid or powder dye particles, or developing an electrostatic latent image in electroprinting. A patternproducing gauze or plate may be interposed between the outlet 76 and the object 80. 2. Electrostatic conveyers/sprayers (Figs. 12, 13).-An insulating pipe 86, which may be flexible, either has longitudinal electrodes 103- 108 angularly spaced in its wall or has a set of elongated electrodes helically wound around its wall (Fig. 16, not shown), the electric field pattern set up within the pipe confining particles 92 to the central region of the pipe, away from its wall. In one embodiment (Fig. 12) the pipe is inclined so that the particles are driven along it under the influence of gravity. A D.C. bias 41 is applied in a vertical direction to help overcome the tendency of the particles to drop on to the lower surface of the pipe. In other embodiments, three-phase energization is used to drive the particles along the pipe. The arrangement may be used for spraying as in (1) above. 3. Preventing particle scatter (Fig. 18).- Scattering of particles being discharged (148) on to a conveyer 147 is prevented by an annular electrode array 150, the particles having automatically acquired a charge by friction. In another embodiment (Fig. 19, not shown) a scatter-preventing electrode array (159, 160 ...) completely surrounds an electrostatic spraying station where a succession of objects (155) suspended from a moving chain (153) is moved around and past a spray gun (158).