'~0()~(~99 PATENT APPI.ICATION OF
HOWARD W. SELBY, I~
FOR
IMPROVED PROCESS FOR EXTRACTING ESPRESSO COFFEE
Backqround of the Invention Field of Invention This invention relates generally to extracting espresso coffee and specifically to an improved process of extracting espresso coffee in whlch the extraction pre~sure is prQcisely reyulated.
Description of Prior Art Espresso coffee is brewed by forcing hot water through finely ground coffee beans under high pressure which extracts the coffee from the coffee beans. Both the amount of ground coffee beans and water are volumetrically measured. For the coffee to be properly extracted there must be a pressure differential across the ground coffee beans.
In conventional esprssso machines, the coffee beans are finely ground then volumetrically measured and packed in a filter device. The filter is then attached to the espresso machine. A measured volume of hot water is forced through the filter by means of a volumetric piston displacement pump which is hand operated or by means of an electric pump device. The hot water is forced into the ground coffee beans in the filter. The fineness of the coffee grind and the degree of compaction creates a pressure differential across the ground coffee beans. The pressure differential varies across the ground coffee beans being highest on the upstream side of the ground coffee beans and lowest on the downqtream side. Because X~3()5~9 of the pressure gradient, not all of the ground coffee beans are subjected to the optimum ex~ractio~ pressure resulting in extraction inefficiencies which require larger volumes of ground coffee beans to be used.
The water, under pressure, is forced through the ground coffee beans and extracts the coffee from the beans. Extraction time is very short compared to other coffee brewing methods. The extracted coffee drains through an opening in the bottom of the filter and 1s collected in a cup for consumption. The pressure differential in the filter is directly related to the grind of the coffee beans and the degree of their compaction.
The quality of the extracted coffee is a function of the following: the freshness of tha coffee beans; the finenPss of the grind; the volume of ground coffee beans;
the compaction of thc ground coffee beans; the volume of water; the temperature of the water; and the extraction pressura. Tha degree of compaction of the ground coffee beans and thus the resulting extraction pressure are controlled by the espresso machine operator so operator skill plays an important part in the quality of the coffee produced.
In ~rance and Italy, where espresso coffee has been popular for many years, there are many skilled espresso machine operators. The chances of obtaining a high quality of espresso coffee from such operators is high. In other countries where espresso coffee is growing in popularity, there are not many skilled operators and the resultant quality of espresso coffee suffers.
It would be desirable to have an espresso coffee extraction process that did not rely on operator skill to produce high guality espresso coffee.
In view of the foregoing, it is an objeck of this invention to provide an improved espresso coffee extraction process in which the extractivn pressure is precisely regulated by the espresso machine and is not a function of operator skill.
0~3 It is a further o~jeck of this invention to provide an improved espresso coffee extraction process in which the pressure ~or coffee extraction is kept constant throughout the ground coffee beans resulting in optimum extraction from all the ground coffee bean~.
It is a ~urther object of thi~ invention to provide an improved espresso coffee extraction process in which a range of roffee ~ean ~rinds sizes can be accommodated.
SummarY of the Invention These~and other ob;ects of the invention are accomplished in accordance with the principles of the invention by use of an espresso coffee extraction process in which the extraction pressure necessary to produce high quality espresso coffee is not dependent on the compaction of the ground coffee beans by the operator. The pressure is controlled by a pressure valve on the outflow of the filter which holds the ground coffee beans.
As in the conventional espresso coffee extraction process, the volume of ground coffee and the volume of water forced through the ground coffee are volumetrically measured. Unlike the conventional pxocess, however, the fineness of the coffee grind used in the improved process can range from a fine aspresso grind to a coarser or ~iner coffee grind. In addition, in the improved process, the ground coffee beans need not be compacted.
A measured volume of water, either hot or cold, is forced through the ground coffee beans as in a conventivnal pro~ess. In the conventional process the pressure re~uired to sxtract the ooffee from the ground beans is created by the compacted co~ee grinds which restricts the flow of water through the coffee grinds until the water pressure is hi~h enough to penetrate the barrier creatPd by the compacted ground coffee. The pressure varies throughout the ground coffee beans being '~ 0'~'3~'3 highest on the side o~ the ground coffee o~ water inflow decreasing to zero pressure at the water outflow point.
In the imprsved process, however, the re~uisite pressure results from a mechanical valve on the outflow o~
the filter. A measured volume of water is introduced into the filter which holds the ground coffee beans. When the pressure reaches the optimum pressure for extraction, the valve regulator opens allowing the water to pass through the ground coffee beans. The pressure throughout all the lo ground coffee beans is the same - there is no pressure gradient. Because the optimum ex~raction pressure extends to all of the ground coffee beans, less ground coffee beans are required to make espresso coffee than conventional methods.
Further features of the invention, its nature and various advantages will be more apparent from the accompanyin~ drawings and the following detailed description of the invention.
Brief Description of the Drawinqs FIG. 1 is a illustration of part o~ an espresso machine showing the filter and coffee collection cup.
FIG. 2 is a flow chart of the improved espresso coffee extraction process.
X~0~ 9 Detailed Description o~ the Invention Referring now to the drawings, there is shown in FIG. 1 a partial view of an espreæso coffea machine }o showing the handle assembly 12, the pressure regulation valve mechanism 16, the ground coffee bean filter 14 of the handle assembly 12, the outflow spout 18 from the filter and the cups 20 in which the espresso cofee is collected upon extraction.
FIG. 2 is a flow chart of the steps in the process of extracting espresso coffee which includes the improved process. In the following discussion reference will be m~de to both figures.
At step 100 coffee beans are ground. The grind that can be accommodated in the improved process includes a ranges from grind sizes finer than conventional e~presso coffee grinds to the grind sizes coarser than conventional espresso coffee grinds.
At step 101 a measured volume of the ground coffee beans is placed in the filter 14 of the filter 12.
Unlike conventional espresso extraction processes, the ground coffee does not need to be compacted in the filter 14.
At step 102 a measured quantity o~ water is moved through the ground coffee beans in the filter 14. Water pressure builds within the filter until a particular pressure level is reached. The particular pressure level is based on the optimum extraction pressure for a glven volume and temperature of water.
When the optimum pressure is reached a valve mechanism 16 on the out~low spout 18 o~ the filter opens (step 103) allowing the extracted espresso coffee to exit the filter. Any commarcially a~ailable pressure regulating valve can be used/ such as a Speedaire Model No. 2X347A, Dayton Electric Manufacturing Co., Chicago, IL
66648. The outflow spout 18 is downstream of the ground coffee beans. At step 104 the extracted espresso coffee is collected in a cup 20.
iO99 In the improved process of extraction, extraction pressure i8 controlled by the valve mechanism 16 and not by a variable such as the dagree o~ compaction of the ground coffee bean~ as in a conventional process.