Liquid dispensing device having a pre-compression outlet valve
Provided is a liquid dispensing device that includes: a piston chamber; a piston that is moveable within the piston chamber to pressurize a liquid to be dispensed; a nozzle with a defined throughput for dispensing the liquid; an outlet valve having a defined minimum opening pressure arranged between the piston chamber and the nozzle; and a prime valve for priming the device, where the prime valve may be mechanically operable and may be arranged on or in the piston.
1. A liquid dispensing device comprising:
a piston chamber;
a piston that is moveable within the piston chamber to pressurize a liquid to be dispensed, the piston having an upper seal and a lower seal;
a nozzle with a defined throughput for dispensing the liquid;
an outlet valve having a defined minimum opening pressure arranged between the piston chamber and the nozzle; and
a prime valve for priming the device;
wherein:
the prime valve is mechanically operable and is arranged on or in the piston;
the liquid dispensing device further comprises an operating member in the piston chamber which is arranged to move the prime valve from a closed position to an open position when the piston is near or at an end of a piston stroke, wherein the operating member protrudes from an end wall of the piston chamber; and
the prime valve comprises:
a sealing part arranged radially inward of the piston upper and lower seals and closing off an orifice in the piston, said orifice opening onto a peripheral sidewall of the piston; and
an actuating part connected to the sealing part and arranged to cooperate with the operating member.
2. The liquid dispensing device of claim 1 , wherein the operating member comprises a plurality of operating members.
3. The liquid dispensing device of claim 1 , wherein the sealing part is deformable together with the actuating part when the actuating part is engaged by the operating member.
4. The liquid dispensing device of claim 1 , wherein an end wall of the piston chamber and/or the piston comprises an air flow path leading to the prime valve.
5. The liquid dispensing device of claim 1 , wherein the prime valve is arranged to be biased towards an open position when a pressure in the piston chamber exceeds a predetermined value.
6. The liquid dispensing device of claim 5 , wherein the sealing part is oriented away from an end wall of the piston chamber.
7. The liquid dispensing device of claim 1 , wherein the prime valve is arranged to be biased towards a closed position by a pressure in the piston chamber.
8. The liquid dispensing device of claim 7 , wherein the sealing part is oriented towards an end wall of the piston chamber.
9. The liquid dispensing device of claim 1 , wherein the piston chamber is cylindrical, the piston has a circular circumference and the prime valve is annular, the sealing part of the prime valve being formed by an outer peripheral edge portion thereof.
10. The liquid dispensing device of claim 9 , wherein the actuating part comprises an annular rim that is concentric with the sealing part and has a smaller diameter than the sealing part.
11. The liquid dispensing device of claim 1 , wherein the sealing part and the actuating part have substantially parallel orientations.
12. The liquid dispensing device of claim 1 , wherein the sealing part and the actuating part have substantially opposite orientations.
13. The liquid dispensing device of claim 1 , further comprising a return opening in a side wall of the piston chamber, wherein the piston lower seal is configured for sealing a part of the piston chamber between the piston and a piston chamber end wall and the piston upper seal is spaced apart from the piston lower seal, such that when the piston is at or near an end of the piston stroke the return opening is located between the piston upper and lower seals.
14. The liquid dispensing device of claim 13 , further comprising a vent opening in the side wall of the piston chamber, wherein when the piston is at or near an end of the piston stroke the piston upper and lower seals are located between the vent opening and the piston chamber end wall.
15. The liquid dispensing device of claim 1 , wherein the outlet valve is configured to minimize a difference between a valve opening pressure and its closing pressure.
16. The liquid dispensing device of claim 15 , wherein the outlet valve comprises a dome and wherein the dome has a stiffness which varies in a radial direction.
17. The liquid dispensing device of claim 16 , wherein the outlet valve has an inner flexible portion surrounding a center of the outlet valve and an outer stiffer portion.
18. The liquid dispensing device of claim 17 , wherein the outlet valve is thinnest in the inner flexible portion, having a radius R 1 , and gets thicker as the radius increases beyond R 1 .
19. The liquid dispensing device of claim 1 , further comprising a buffer arranged between the piston chamber and the outlet valve.
20. The liquid dispensing device of claim 1 , further comprising a container for the liquid to be dispensed, the container being in fluid communication with the piston chamber through an inlet valve.