| 摘要 |
A device for brewing hot beverages comprises a lower container for receiving water, an upper container for receiving brewed beverage, and a piston-cylinder assembly into which coffee grounds, tea leaves, and herbs are placed. The grounds, etc. are compressed and subjected to high temperature water and steam, to extract essences and produce a beverage, such as espresso coffee. The piston has a decompression chamber at its upper end, formed between the piston top and a perforated diffuser plate. Pressurized hot water from the lower container flows through a nozzle in the piston top, into the decompression chamber, through the holes of the diffuser plate, and then into the grounds. The piston moves upwardly to compress the grounds against an upper perforated plate, first with rising force, and then with constant force. Since the total flow path cross sectional area of the holes in the diffuser plate is several times greater than the flow area of the piston top nozzle, the pressure in the decompression chamber is substantially lower than the pressure in the lower container. This enables a lowered velocity of water and steam which pass through the diffuser plate and into the grounds.
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