Gear pump with transmission gearwheel adjustment

A gear pump comprising a casing, intermeshing pumping gears carried in said casing, said pumping gears having a contact ratio of less than one, and gear transmission means connected to the respective pumping gears for rotating said pumping gears in synchronised relation with each other, said gear transmission means including intermeshed auxiliary gears, a first shaft having one of said auxiliary gears mounted thereon by an interference fit fixing the gear on the shaft by friction, said first shaft also having one of said pumping gears fixed thereon and axially spaced from said one auxiliary gear, a second shaft having the other one of said auxiliary gears fixed thereon, and also having the other said pumping gear secured thereon in axially spaced relation from the other one of said auxiliary gears, bearing means rotatably supporting said shafts in said casing, said bearing means for at least said first shaft comprising axially spaced rotary bearing elements and said one of said auxiliary gears being mounted on said first shafts between said bearing elements, an interface between said one auxiliary gear and said shaft having an annular space extending circumferentially about said shaft for pressure hydraulic fluid, and a passage through said shaft communicating with said space to convey hydraulic fluid under pressure therethrough to said annular space to cause hydraulic expansion of said one auxiliary gear to allow relative angular adjustment between said one auxiliary gear and said first shaft.