DISPOSABLE PUMP WITH SUCK-BACK MECHANISM
The present invention relates to a disposable pump (1) for a dispensing system for liquids, in particular for a dispensing system which comprises a compressible container (400), wherein the pump (1) comprises a chamber (110) in which the pressure may be varied for pumping liquid from the container (400) to the chamber (110), and further from the chamber (110) to a dispensing opening (120), the chamber (110) enclosing an inner valve (230) for regulating a flow of liquid between the container (400) and the chamber (110), and an outer valve (220) for regulating a flow of liquid between the chamber (110) and the dispensing opening (120), wherein the pump (1) may assume a closed position, in which a volume of liquid is drawn from the container (400) to the chamber (110) by means of a negative pressure created in the chamber (110), and a dispensing position, in which a volume of liquid is drawn from the chamber (110) to the dispensing opening (120). The pump is characterized in the inner valve (230) being a one-way valve, for opening for a flow of liquid in the dispensing direction at an inner valve opening pressure acting in the dispensing direction, and closing for any pressure acting in a direction opposite to the dispensing direction, the outer valve (220) being a two-way valve, for opening for a flow of liquid in the dispensing direction or in the direction opposite the dispensing direction at an outer valve opening pressure, depending on the direction of the outer valve opening pressure, such that, as the pump (1) transfers from the dispensing position to the closed position, and a negative pressure is created in the chamber (110), the pressure difference between the container (400) and the chamber (110) will cause the inner valve (230) to open so as to allow liquid to pass from the container (400) to the chamber (110), and the pressure difference between the dispensing opening (120) and the chamber (110) will cause the outer valve (220) to open to allow liquid to be sucked back from the dispensing opening (120) to the chamber (110).