PURPOSE: To provide an apparatus for producing a controllable uniform conveying pressure for processing highly viscous, temperature sensitive rubber or thermoplastics in which conveying function of return channel and sealing capacity are substantially improved.

CONSTITUTION: An apparatus that produces a controllable uniform conveying pressure has two rotating conveying elements. These rotating elements form a tooth-like sealing profile, and are bore on a shaft in a casing. The root diameter D of the conveying elements 1, 2 forming the tooth-like sealing profile is almost equal to the diameter d of the shaft sections 12a, 13a that are axially adjacent to the conveying elements on either side and guide them. The return channels 20, 21, 22, 23 are so formed that decrease in the conveying direction the channel volumes in shaft section guiding the conveying elements.