Apparatus for developing latent electrostatic images

Abstract

Apparatus for developing latent electrostatic images on dielectric carrier sheets has a rotary cylinder whose periphery supports a carrier sheet with a latent image thereon, and a metallic block having a concave surface which constitutes a grounded electrode and defines with the exposed side of the carrier sheet on the cylinder a narrow gap of constant or gradually decreasing width, as considered in the direction of rotation of the cylinder. The block has alternating fluid-admitting and fluid-evacuating orifices which communicate with the gap and extend transversely of the path of movement of the carrier sheet. Each fluid-admitting orifice is nearer to the preceding than to the next-following fluid-evacuating orifice, and the width of the fluid-evacuating orifices exceeds the width of the fluid-admitting orifices. The block is located below the cylinder and the fluid-evacuating orifices communicate with a collecting tank into which spent developing fluid flows by gravity. The fluid-admitting orifices receive pressurized fresh developing fluid from a pump. Each unit volume of freshly admitted fluid dwells in the gap for the same interval of time because some of the fluid issuing from a fluid-admitting orifice flows forwardly toward the next-following fluid-evacuating orifice at a speed higher than the speed of the remainder of the fluid issuing from the same fluid-admitting orifice and flowing backwards toward the preceding fluid-evacuating orifice.