US 20050150911 A1
A system for dispensing exact quantities of fluid into containers without dripping or foaming can be made from the combination of a controllable pump, a tube (preferably hydrophobic), and a nozzle usually made of elastomeric material with an orifice or slit such a duck bill valves commercially available. Forward pressure causes the slit to open, while elastic force causes it to close when pumping stops. An alternative embodiment is to use slits backed by small diameter screen to achieve a back pressure.
1. A no-drip, anti-foaming fluid dispensing system comprising:
a fluid pump supplying a forward fluid pressure;
a delivery tube fluidly coupled to said pump for delivering said fluid into a fluid container;
an elastomeric tip on said delivery tube containing at least one exit orifice, said exit orifice expanding in response to said forward fluid pressure and contracting when said forward fluid pressure is removed.
2. The fluid dispensing system of
3. The fluid dispensing system of
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9. A no-drip, anti-foaming fluid dispensing system comprising:
a fluid pump supplying a forward fluid pressure;
a coupling tube fluidly coupled to said pump for delivering said fluid into a fluid container;
a dispensing tip on said coupling tube containing at least one exit orifice;
a screen covering said exit orifice, said polymer screen preventing drip through when said forward fluid pressure is removed.
10. The fluid dispensing system of
11. The fluid dispensing system of
12. The fluid dispensing system of
13. The fluid dispensing system of
14. The fluid dispensing system of
15. A method of dispensing a predetermined quantity of fluid into a container without drip or foaming comprising the steps of:
causing a fluid pump to move said predetermined quantity of fluid from a reservoir into a delivery tube, said delivery tube having at least one exit orifice, said exit orifice containing a means for causing backpressure on said flow, wherein a forward pressure from said pump overcomes this backpressure to allow said predetermined quantity of fluid to exit said orifice;
allowing said backpressure to keep any remaining fluid in said tube after said predetermined quantity of fluid has been dispensed.
16. The method of
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This application is related to and claims priority from U.S. Provisional patent application No. 60/532,307 filed Dec. 23, 2003. Application 60/532,307 is hereby incorporated by reference.
1. Field of the Invention
This invention relates generally to the field of precision fluid dispensing and more specifically to a fluid dispensing system the is prevents dripping and foaming.
2. Description of the Prior Art
Many applications in the field of bio-science and medicine require the precise dispensing of a quantity of fluid into a particular container. There is no tolerance for dripping. Also, some liquids tend to foam if dispensed too rapidly through a standard nozzle or through a tube with too small an inside diameter. For example, an application might require the precision dispensing of 125 ml of a particular liquid (like a salt solution) into a vessel holding exactly 125 ml. Usually such a fill needs to take place very rapidly (within a second or two). No liquid can be lost through dripping.
What is badly needed is a system and method for making fast fluid dispenses into containers designed to contain a precise amount of fluid without dripping or foaming.
The present invention relates to a non-drip, anti-foaming fluid dispensing system that can contain a fluid pump that supplies a forward fluid pressure, a coupling tube (preferably of hydrophobic material) that is coupled to the pump for delivering fluid into a fluid container, and an elastomeric tip on the coupling tube that can contain at least one exit orifice. The exit orifice can generally respond in response to the forward fluid pressure and contract when the forward fluid pressure is removed. This contraction prevents air from entering the delivery tube and causing dripping.
The fluid pump can be a positive displacement linear pump or a peristaltic pump or any other type of fluid pump causing a forward pressure on a fluid. In particular, the tip can be a duck bill valve with one or more openings or orifices. The pump can optionally supply a back pressure or suck-back after a predetermined amount of fluid has been dispensed.
Several drawings and illustrations have been presented to aid in the understanding of the present invention. The scope of the present invention is not limited to the figures.
The diameter of the tube usually must be chosen to match the required fill time against the volume of fluid being dispensed. For the example where a 125 ml container is to be filled with exactly 125 ml of fluid in 2 seconds or less, the tubing must have an ID of greater than ½ inch. The problem with large tubes such as this is that after the initial fill, residual fluid on the inside of the tube drips causing the fill volume to be exceeded. The surface tension on such large tubes is not sufficient to stop air from flowing up the tube, and the solution continuing to flow down the tube.
A small nozzle must generally be used on the end of the tube to stop this air flow and drip. An ideal nozzle is one made of an elastomeric material such as rubber or silicone with a small orifice 6. Such a material expands to expel the initial flow under forward pressure from the pump, but then contracts to prevent the entry of air and any subsequent drip. In addition, some pumps can be arranged to create a suck-back where the pump reverses direction and causes a negative pressure on the fluid. A positive displacement linear piston pump is particularly suited for this.
An ideal nozzle is a duck bill valve that can be purchased commercially.
The duck bill nozzle 5 shown in
An alternative embodiment of the present invention is shown in
A duck bill can be combined with the nozzle shown in
Several illustrations and descriptions have been provided to aid in understanding of the present invention. One skilled in the art will realize that many changes and variations are possible. These changes and variations are within the scope of the present invention.