Generally, oil for eating is extracted from grains or seeds for oil extraction like sesame seeds, perilla seeds, and sunflower seeds, and in this case, such grains are roasted and then compressed, so that they are extracted to the form of oil.  In conventional practices, press means is used to compress the grains with a large pressure so as to extract oil from the grains, but such press means is installed only on a place where large-scale equipment is provided like a mill.  Recently, a screw type oil extractor for household purposes has been introduced to compress a small quantity of grain successively fed thereto. 
The conventional screw type oil extractor generally includes a cylindrical shell located in a main body casing, feed means for supplying grains for oil extraction to the interior of the shell, a screw disposed in the shell to which the feed means is connected to compressingly move the grains therealong, and a heater for heating the shell to a given temperature. 
According to the conventional screw type oil extractor having the above-mentioned configuration, by the way, the screw inserted into the shell is mounted integrally with a motor shaft, so that so as to clean the interior of the shell, the main body casing having the screw is disassembled and next, the shell mounted on the outside of the screw is separated, thereby making it difficult to often clean the interior of the shell. 
To solve the above-mentioned problems, accordingly, there are proposed Korean Patent Registration No.  10-0752957 (entitled ‘oil expeller’) and Korean Patent Application Laid-open No.  2002-0057736 (entitled ‘oil expeller machine’) wherein the oil expeller is provided separately from a food processor (juice extractor body) onto which a motor is mounted, and the oil expeller includes a shell assembly having a heater mounted thereon, a screw, and a casing in which the shell assembly and the screw are located, so that if the casing is coupled to the juice extractor body, one end (a shank portion) of the screw is detachably connected to the motor shaft. 
In case of the conventional oil expeller, however, the casing has to be inconveniently disassembled so as to clean the interior of the shell.  On the other hand, coupling means for coupling the casing to the food processor (juice extractor body) is complicated in configuration and it is inconvenient to perform the coupling work.  So as to drive the heater disposed in the casing upon the coupling between the juice extractor body and the oil expeller, further, the plug of the power supply cord connected to the heater has to be inconveniently connected to the socket of the juice extractor body.