US Patent 7799074 Rotary displacement pump with smaller radial dimensions

According to the invention the rotary pump consists of an external gear (13) with internal teeth (16) in the form of a squirrel cage, and an internal gear (9), housed in an off-centre manner in the interior of said external gear (13) and fitted with external teeth (9D) intermeshing with said internal teeth (16) and consisting of a number of inferior teeth of a unit with the number of teeth of the later. The rotation means of said external teeth (13) comprise at least a bearing (11, 12) centrally laid out in a flange end (14,15) of said aforementioned external gear (13) and the aforementioned external gear (13) is at least partly dismantled in order to introduce said internal gear (9).