Dispensing – With filter – With discharge assistant
Reexamination Certificate
2000-02-24
2001-10-30
Derakshan, Philippe (Department: 3754)
Dispensing
With filter
With discharge assistant
C222S153140, C222S190000, C222S564000
Reexamination Certificate
active
06308866
ABSTRACT:
FIELD OF INVENTION
The present invention is generally related to liquid dispensing devices, and more particularly to a dispenser that forms a foam from the liquid being dispensed.
BACKGROUND
In the field of dispensable liquid cleaning and disinfecting substances, a wide range of liquids are used. Many of these liquids evolved from the use of soap and detergent bars for handwashing. Bar soaps are economical, long-lasting and an effective way to dispense small quantities of a sparingly soluble material soap, for handwashing. Unfortunately, bar soaps, even when they contain an antimicrobial agent are also excellent vehicles for transmission of microorganisms from one user to another.
One of the earliest widespread uses of liquid handwashing compounds was in hospital scrub environments. These handwashing compounds incorporated a variety of antibacterial agents for use in surgical scrub protocols and hospital infection control procedures. The surfactant component of the compound serves to disperse the antimicrobial agents on the practitioner's skin with the water used for washing and to facilitate the removal by the wash water of materials on the skin surface that could harbor microorganisms.
In the surgical scrub application, the liquid handwashing products serve primarily as a delivery system for delivery of antimicrobial agents onto the practitioner's skin so that microorganisms are removed or rendered non-viable. Many of these liquid antimicrobial agents are not particularly water soluble. Thus if a large droplet of a not particularly easily dispersible handwashing liquid is dispensed, considerable effort is required to distribute the agent over the practitioner's skin. To facilitate the practitioner's use of these antimicrobial handwashing compounds, dispensing devices that form a foam from the liquids were developed. When foamed, most of these handwashing compounds are significantly more easily dispersed in manual handwashing than the same compound in the liquid, unfoamed, state, because by being foamed, the surface area of the material is greatly increased. There are other benefits of foamed compounds: a) since the compound is readily dispersed, practitioners tend to use significantly less of the product while accomplishing the same desired effect of the surgical scrub procedure; and less water is needed to disperse the compounds the effective concentration of the antimicrobial compounds on the skin is likely higher than with the same liquid in a non-foamed state. A variety of different antimicrobial handwashing compounds are now available with many different types of antimicrobial agents. The physical attributes of these antimicrobial handwashing compounds vary from materials with viscosities not much higher than water, i.e. about five to about thirty-five centipoise (cps). to viscosities similar to motor oil or hand lotions, i.e. up to about one hundred cps, and up to about one thousand six hundred cps, similar to a cream.
U.S. Pat. No. 4,957,218 to Ford discloses a foam dispenser that utilizes manually created negative air pressure to fill a pump from a larger container with a foamable liquid and manually created positive air pressure to displace the liquid into a mixing chamber where a foam is formed from mixing the air and the liquid. The device disclosed in this patent is effective with low viscosity (ca. five to about thirty-five cps) liquids as a substrate, but with more viscous liquids (ca. about fifty to about one hundred cps), the foam produced is low density, i.e. high air content, and perceived as “dry” by users.
Another U.S. Pat. No. 5,411,177 to Blake discloses a foam dispensing apparatus that includes a liquid container and a foam generating device. The foam generating device has a plurality of passages through which pressurized gas flows simultaneously with foamable liquid into the foam generating chamber past a flow restricter. Again, the device disclosed in this patent produces acceptable foam with low viscosity liquids. Liquids having a viscosity greater than about twenty cps are not well dispensed by the device described in this patent.
U.S. Pat. No. 6,053,369, discloses a foam dispensing device capable of forming acceptable foam with handwashing antimicrobial liquids over a range of viscosities. The device included a filter disposed in the delivery line between the pressure source and the reservoir. The filter disclosed in U.S. Pat. No. 6,053,369 is adequate to prevent introduction of foreign matter and microorganisms into the reservoir. However, the filter in this patent application may not prevent fluid which may back up from the reservoir, flow along the delivery line, and into the pressure source. Such fluid flow can cause contaminants that have been trapped in the filter to dislodge from the filter travel into the pressure source. If the solution is stagnant in the pressure source, microorganisms may grow and contaminate the entire system. It would be advantageous to provide a device which prevents fluid flow along the delivery line and into the pressure source. It would also be advantageous to provide a filter capable of being placed in the delivery line that could control the air flow into the bottle by smoothing out pressure spikes generated by activation of the pressure source.
SUMMARY OF THE INVENTION
A foam dispensing apparatus of the present invention includes a reservoir containing a foamable liquid, with a closed headspace above a surface of the liquid. The apparatus also includes a source of a gas disposed to impose a gas pressure higher than ambient atmospheric pressure into said closed headspace. There is a mixing chamber having an inside diameter, an inlet and an outlet open to the ambient atmosphere with a flow restricter having a plurality of openings therein in gaseous communication with the closed headspace. The flow restricter is positioned at the inlet of the mixing chamber and an elongate delivery tube with an open passageway therethrough that defines a longitudinal axis extending from the inlet of the mixing chamber to below the surface of the foamable liquid disposed so that an application of the gas having higher pressure than atmospheric pressure to the headspace causes the foamable liquid to flow through the tube past the flow restricter, to mix with the headspace gas having higher pressure than atmospheric pressure that flows from the openings in the flow restricter and then to expand to atmospheric pressure in the mixing chamber thereby to form a foam from the foamable liquid and discharge the foam from the outlet.
The foam dispensing apparatus of the invention further includes an in-line air filter to prevent contamination by microorganisms and back flow into the source of gas, which may be a foot pump. The filter is preferably a hydrophobic air filter that allows air to pass through the filter is capable of trapping particulate matter, and prevents liquid from flowing from the reservoir, along the delivery line and to the pressure source.
The foam dispensing apparatus of the invention is capable of forming acceptable foam from foamable liquids with viscosities ranging from about five to about one hundred cps. The device is simple to manufacture and easy to use.
REFERENCES:
patent: 3631654 (1972-01-01), Riely
patent: 4235677 (1980-11-01), Karamian
patent: 5054688 (1991-10-01), Grindley
patent: 5222633 (1993-06-01), Blake
patent: 5411177 (1995-05-01), Blake, III
patent: 5490938 (1996-02-01), Swan et al.
patent: 6053369 (2000-04-01), Hoang et al.
Becton Dickinson E-Z SCRUB Antimicrobial Foam Dispenser System Brochure-dated Mar. 1999.
Pall Medical Air and Gas Barrier Filters Brochure-Undated.
Burkholz Jonathan Karl
Hoang Minh Quang
Hunt Donald Edward
Becton Dickinson and Company
Derakshan Philippe
Lee Eric M.
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