Abstract: A method and apparatus for supplying liquids by means of a pump combination comprising two single oscillating displacement pumps is provided, wherein a supply pressure of the pump supplying liquid into a user duct is used as a control value of a pressure controller, such that a pressure stroke movement of the other pump which is generating a pre-compression pressure, is discontinued when the pre-compression pressure equals the supply pressure, and the pre-compression pressure is maintained.

Abstract: A road marking machine comprising a spray gun and a combination of two displacement pumps for supplying the marking substance to the spray gun, wherein the combination is driven in proportion with the traveling speed and wherein the pumps, each after starting the positive displacement operation thereof, which starts during the supply operation of the corresponding other displacement pump, pre-compress the marking substance, then stops and continues the pressure stroke when the other displacement pump ends its supply, with hydraulic cylinders for driving the displacement pumps.