PURPOSE: To make it possible to obtain an extract in a high concentration, by stopping the operation of a piston in the course of a section from the starting position to the top dead point for a given time at least once, and steaming the raw material during the time.
CONSTITUTION: A filter 3 is placed between the upper and lower cylinders 2 and 1, and a raw material and hot water are fed into the upper cylinder 2. A piston 5 in the lower cylinder 1 is then lifted to extrude air in the lower cylinder 1 through the filter 3, and the raw material and hot water are agitated and mixed with the air. The piston 5 is then lowered to separate the extract in the raw material into the lower cylinder 1 by the corresponding suction force under negative pressure in the lower cylinder 1. The operation of the piston 5 is stopped at least once in the course of a section from the starting position to the top dead point for a given time. As a result, the raw material is steamed, and the aimed extract in a high concentration can be obtained without increasing the amount of the raw material or taking much steaming time.
AKIYAMA YOSHIO
MACHIDA YOSHIAKI
