The Balanced Vane Pump: Two Pumps Facing Each Other in One Ring

Vickers' drawings show a casing with "bilateral intake and exhaust passageways", a rotor carrying sliding vanes, and a **liner ring 5** which, in the patent's words, defines "the working chambers 6 and 7" at diametrically opposite portions. Sets of diametrically positioned ports in the flanges either side of the rotor register with those chambers, so each pair of inlets faces each other and so does each pair of outlets. Because "the rotor element … may centralize itself" between balanced intake and exhaust ports, the pressure forces on it cancel, and the patent claims the pump keeps its high volumetric and mechanical efficiency "over a much longer period of time".

Draw a cam ring 10 mm thick whose bore runs between a 26.5 mm minor radius and a 29 mm major radius, twice round — minor, rise, major, fall, minor, rise, major, fall — with smooth blends. Draw a 26 mm-radius rotor with ten radial slots 2.1 mm wide for 2 mm vanes, bored for an 8 mm shaft. Print both in PETG, and cut ten vanes from 2 mm acrylic sheet. Make the side plates from acrylic sheet: in the front plate cut two inlet ports, opposite each other, where the cells grow, and two outlet ports, opposite each other, where they shrink; join each pair to one hose barb. Seal with an O-ring round the ring. Drive the shaft with a cordless drill, inlet in a jug of water, outlet into a graduated cylinder. Count revolutions with a tachometer, compare the water per revolution with the notebook, and feel for the side load by hand at the shaft with the outlet squeezed: the balanced model runs true where a single-lobe one leans.

**Harry F. Vickers** of Detroit filed **US 1,989,900**, *Vane Type Pump*, on 15 January 1931; it was granted 5 February 1935. It is usually dated to his work of the mid-1920s. Balanced vane pumps with a replaceable cam ring are still made in the same pattern, and the double-lobe ring is the form the name 'balanced vane pump' refers to. **Honest limits.** Balancing removes the radial pressure load, not the other wear: vane tips still rub the ring, and a vane pump suits clean oil and moderate pressures. The notebook's bearing figures are illustrative, and a fixed double-lobe ring cannot vary its displacement — variable vane pumps go back to a single, movable ring and accept the side load.