Variable-delivery external gear pump

A variable-delivery external gear pump, the pump comprising

• a) a casing having shell surface areas, a pump inlet port, and a pump outlet port,
• b) a plurality of axial sealing surface areas,
• c) at least one rotatively driven pair of gears comprising two intermeshing spur gears which form with said shell surface areas and said plurality of axial sealing surface areas a delivery space comprising a low-pressure side connected to said pump inlet port and a high-pressure side connected to said pump outlet port,
• d) a return element, and
• e) a piston, serving to rotatively mount one spur gear of said pair of gears, said piston being shifted axially relative to the other spur gear of said pair of gears so as to vary the delivery of said pump together with the one spur gear by charging said high-pressure side with fluid against the force of said return element, wherein,
• formed in at least one of said plurality of axial sealing surface areas adjoining a sealing land of said sealing surface area are a first pocket connecting a zone of deepest tooth engagement of said spur gears to said pump outlet port and a second pocket connecting said zone of deepest tooth engagement to said pump inlet port and wherein said first pocket has a first depth and said second pocket has a second depth less than said first depth.