GB829104A - Powder cloud generation - Google Patents

Abstract

829,104. Development of electrostatic images. BATTELLE DEVELOPMENT' CORPORATION. Feb. 13, 1956 [Feb. 18,. 1955(4)], No. 4400/56. Class 98(2) Apparatus for producing a powder cloud for developing an electrostatic latent image comprises a housing having an input tube for a supply of gas under pressure, an output tube to permit the gas to flow from the housing, a supply of powder particles deposited in the housing, a powder holding surface movably mounted in said housing and means for continuously moving the surface so as to transfer powder from the supply to the high pressure end of the output tube where it is caught -up by the gas and blown from the housing as a powder cloud. In Fig. 3, the housing 17 contains a powder holding surface in the form of a belt 21 which is driven by a roller 28 and moves over a lower roller (not shown) through a supply of powder 31 in the bottom of the housing. The belt is made of open material so that it picks up the powder and presents it to the high pressure end 25 of the outlet tube 20. The container is supplied with gas under pressure through tube 18. Another similar embodiment is described whereby the edges of the belt are provided wth chains which are driven by sprockets instead of rollers and the powder supply is contained wholly within the lower loop of the belt. In other embodiments the belt is horizontal and the powder is deposited in a small pile on top of the belt and held against bulk movement by a retaining arm which may press against an open type belt or be spaced from the belt to meter the required quantity of powder on to the belt. Scrapers (such as 33 in Fig. 3) or brushes may be provided to remove excess powder from the belt. In Fig. 5, the .powder holding surface is a porous membrane in the form of a rotating disc 47 on which a pile of powder 57 is deposited and held against movement by a retaining wall 56 which presses against the porous membrane. The powder loaded disc is presented to the orifice 61 of the output tube 62. The.housing is supplied with gas under pressure through a tube 58. A similar apparatus is described wherein the powder holding surface is cup-shaped rather than disc-shaped and the powder retaiing wall is spaced from the base of the cup member. Various constructions of output tube are described one of which is funnel-shaped with the large open end spaced somewhat from the powder laden surface, and another comprises a series of capilliary tubes. Specifications 672,767, 686,466 and 782,162 are referred to.