1. Field of the Invention
The present invention relates to consumer product packages which incorporate spray devices; and more particularly, to such consumer product packages with spray devices which utilize air to aid small particle spray formation.
2. Description of the Prior Art
It has long been desirable to provide consumer product packages with spray devices which produce excellent spray qualities. Characteristics of spray quality include mean droplet size (e.g., as measured by the Sauter mean diameter); droplet size distribution width; spray velocity and clean starting and stopping (i.e., no spitting or dripping). Historically, aerosol spray packages have utilized partially dissolved propellants to pressurize the package. Atomization is primarily driven by the propellant dissolved in the product "boiling off" upon exiting the spray device. Unfortunately, traditional dissolved propellants have been the subject of environmental concerns for many years now.
Spray devices have also utilized vapor tap valves which mix propellant vapor with the liquid. This improves atomization quality. It is believed that the vapor provides bubbles which function as nucleation sites for the dissolved propellant. Exemplary vapor tap valves are disclosed in U.S. Pat. No. 2,746,796 issued to St. Germain on Aug. 5, 1953; U.S. Pat. No. 3,544,258 issued on Aug. 19, 1963 to Presant et. al.; U.S. Pat. No. 4,227,631 issued on Oct. 14, 1980 to Schneider; and U.S. Pat. No. 4,417,674 issued to Giuffredi on Nov. 29, 1983. One disadvantage of vapor taps is they utilize, and therefore, release even more of the propellants of environmental concern.
Spray devices have also included passages which pass the liquid through a swirl chamber immediately prior to its exiting the discharge orifice. The swirl chamber causes the liquid to exit the discharge orifice in a thin walled-expanding cone configuration which aids atomization. Swirl chambers are often found on standard aerosol packages and are usually found on mechanical pumps. Disadvantages of swirl chambers include manufacturing complexities; the requirement of relatively high pressures due to the energy losses caused by the small channels of the swirl chamber; and difficulties atomizing relatively viscous fluids.
Several spray device designs combine more than one atomization mechanism. For example, many spray devices combine the vapor tap approach and the swirl chamber approach. Exemplary combination designs include U.S. Pat. No. 4,247,025 which issued to Gailitis on Jan. 27, 1981; U.S. Pat. No. 4,260,110 which issued on Apr. 7, 1981 to Werding; and U.S. Pat. No. 4,396,152 which issued on Aug. 2, 1983 to Abplanalp. Of course, these combination designs have the disadvantages of each of the features they incorporate.
One other approach which has been tried with consumer product packages involves mixing air with the liquid in such a manner as to reduce the velocity at which choke flow occurs. Then the two phase (i.e., air and liquid) mixture is passed through one or more restrictions such that choke flow occurs, thereby providing a shock wave to help atomize the liquid. One such example is illustrated in a PCT patent application published under number WO 90/05580 on May 31, 1990. One major disadvantage to utilization of the choked flow phenomenon is the large amount of energy required. This means the driving pressure in the package must be relatively high for flow rates applicable to consumer product packages.
Outside the area of consumer packages, air has been utilized (sometimes in conjunction with swirl or turbulence generating geometries) at great velocity and/or in great quantities to provide kinetic energy to the liquid to aid in atomization. Examples include the devices disclosed in U.S. Pat. No. 3,130,914 issued to Catkin et. al. on Apr. 28, 1964; U.S. Pat. No. 3,764,069 issued on Oct. 9, 1973 to Runstadler, Jr. et al.; U.S. Pat. No. 4,284,239 issued to Ikeuchi on Aug. 18, 1981; and U.S. Pat. No. 4,632,314 issued to Smith et al. on Dec. 30, 1986. However, the relatively high pressures necessary to provide high velocity air and/or the relatively large quantities of air necessary, inhibit utilization of these techniques in consumer product packages; particularly when low container pressure and/or low air-to-liquid ratio is desired.
Additional work has also been performed outside the area of consumer product packages with spray devices which mix air and liquid prior to the final exit orifice. Much of this work, for example, has been done by the faculty and students of Purdue University. This work was typically performed at much higher pressures, flow rates and at air-to-liquid ratios greater than those desirable for consumer product applications. In fact, most of this work was done at combinations of such high flow rates and air-to-liquid ratios that choked flow occurred resulting in shock waves. Although some of this work was done at either low pressure or low air-to-liquid ratios, none of the work was done here both were simultaneously low and consumer product flow rates were utilized.
None of the spray devices discussed above provide all of the advantages of the present invention. For example, consumer product spray packages of the present invention does not depend upon mechanisms like swirl chambers and choked flow. Consequently, excellent spray qualities are provided at consumer product flow rates while simultaneously maintaining relatively low air-to-liquid ratios and relatively low pressures.
In conjunction with the advantages discussed above, the spray device of the present invention offers significant environmental advantages. The product being sprayed with the spray device of the present invention does not have propellant dissolved therein. Consequently, the viscosity of the propellantless liquid are typically higher and the spray device of the present invention produces excellent spray qualities with higher viscosity liquids; e.g., above about 10 cP. Furthermore, products are typically formulated to include volatile solvents to reduce the viscosity of the product. Like the propellants discussed above, these volatile solvents are of concern from environmental and safety standpoints. The present invention permits at least partial replacement of these volatile solvents with water to reduce viscosity. One reason water has not been utilized extensively in the past to reduce viscosity is because it typically increases the surface tension of the product which is generally thought to produce poorer spray qualities. However, spray devices of the present invention actually produce better spray qualities with higher surface tension liquids.