Pump comprising a canned motor

A pump having a slotted tube motor, comprising:

• (a) a housing having a partition for defining a pump chamber and a motor chamber;
• (b) a can arranged in said housing for defining a rotor chamber and a stator chamber in said motor chamber, said can having a tubular wall and a bottom wall in which an opening is defined;
• (c) a pump shaft arranged in said pump and rotor chambers;
• (d) a rotor arranged in said rotor chamber and rigidly fixed to an intermediate portion of said pump shaft;
• (e) first and second bearing sleeves in which said pump shaft is rotatably mounted, said first bearing sleeve being arranged between said partition and said rotor, and said second bearing sleeve being arranged between said rotor and said opening in said bottom wall of said can;
• (f) an annular sealing means arranged between said second bearing sleeve and said bottom wall of said can, said sealing means defining an air duct;
• (g) a vent plug removably arranged in interlocking relationship with said sealing means whereby said air duct is closed;
• and
• (h) a connecting duct having an inlet adjacent to said bottom wall of said can and having an outlet connected at a point along a slot defined between said second bearing sleeve and said pump shaft, wherein in response to rotation of said pump shaft, a liquid medium is forced away from and a gaseous medium is forced toward said pump shaft, and wherein said connecting duct is arranged such that, in response to the opening of said air duct, said media pass from said rotor chamber to said open air duct by way of said slot exclusively, except that said liquid medium reaches said slot by way of said connecting duct, as a result of which said gaseous medium is ventilated and said liquid medium lubricates said slot, and wherein said gaseous medium is not ventilated when said air duct is closed.