Pump for liquids

A pump, for liquids, comprising a rotor having therein a plurality of radially extending bores each slidably receiving a piston, the pistons being coupled at their outer ends to means constraining the pistons, when rotating with the rotor, to rotate about an axis spaced from but parallel to the axis of rotation of the rotor whereby the pistons reciprocate in their respective bores so that the radially innermost ends of the pistons cooperating with liquid inlet and outlet means within the rotor effect a pumping action, the rotor being mounted on a hollow shaft for rotation relative thereto about a first axis, the outer surface of said shaft being formed with recesses which, with the rotor, define inlet and outlet chambers communicating with said bores of the rotor as the rotor rotates, a spindle is rotatable in said hollow shaft about a second axis parallel to but spaced from said first axis, and said means constraining said pistons includes a member engaged with each piston for movement relative thereto in a direction transverse to the length of the piston, said member being rotatably mounted on said spindle for rotation relative thereto about a third axis parallel to and spaced from said second axis and said member being constrained to rotate with the rotor but about said third axis whereby the spacing between the first and third axes effects reciprocation of the pistons as the rotor rotates, said spacing of the first and third axes determining the stroke of the pistons and thus the displacement of the pump and being variable by rotation of the spindle about said second axis relative to said shaft.