Patent Application
20110303767
The present invention relates to atomizers for use with fluid spray devices and more particularly to atomizers suitable for producing relatively small particle size distributions.
Fluid atomizers are well known in the art. Fluid atomizers are used in sprayers to atomize a discrete quantity of liquid being dispensed. The liquid may be stored in bulk form in a reservoir 22. A manual pump or propellant charge may be used to provide motive force for drawing the liquid from the reservoir 22, to the atomizer and spraying through a nozzle. Once the liquid is sprayed through a nozzle is may be dispersed to the atmosphere, directed towards a target surface, etc. Common target surfaces include countertops, fabric, human skin, etc.
However, current atomizers do not always provide a sufficiently small particle size distribution, particularly at relatively low propellant pressures. Relatively low propellant pressures are desirable for safety and conservation of propellant material.
Attempts in the art include U.S. Pat. No. 1,259,582 issued Mar. 19, 1918; U.S. Pat. No. 3,692,245 issued Sep. 19, 1972; U.S. Pat. No. 5,513,798 issued May 7, 1996; US 2005/0001066 published Jan. 6, 2005; US 2008/0067265 published Mar. 20, 2008; SU 1389868 published Apr. 23, 1988; and SU 1176967 published Sep. 7, 1985. Each of these attempts shows a convergent flowpath provided by straight sidewalls.
The straight sidewalls correspond to conventional wisdom that the shorter flow path provided thereby results in less drag. For example see Lefebvre, Atomization and Sprays (copyright 1989), Hemisphere Publishing Company. Page 116 of Lefebvre shows three different nozzle designs. All three nozzles shave straight sidewalls. Lefebvre specifically teachers improving the quality of atomization by including the “minimum area of wetted surface to reduce frictional losses.” Id.
Lefebvre furthers recognizes the problem of trying to achieve desirable flow characteristics at relatively low flow rates, and the efforts to achieve flow at less than 7 MPa. Lefebvre further acknowledges that a major drawback of the simplex atomizer is that flow rate varies with only the square root of pressure differential. Thus doubling flow rate requires a four times increase in pressure. Id at pp. 116-117.
Another problem with atomizers found in the prior art is that to increase or decrease the cone angle of the spray pattern using an atomizer having the straight sidewalls of the prior art requires rebalancing various flow areas, (e.g. swirl chamber diameter, tangential flow area, exit orifice diameter or length/diameter ratio). Using the present invention, one of ordinary skill knowing the desired product delivery characteristics can easily rescale the helix cup to provide new spray characteristics and simply change out the helix cup to a new one. This process improves manufacturing flexibility and reduces cost relative to changing the entire cap, as occurs in the prior art.
It can be seen there is a need for a different approach, and one which allows for desirable spray characteristics at relatively low pressures.
The invention comprises a helix cup for use with a pressurized dispenser. The helix cup has a funnel wall which is not frustro-conical. This geometry provides a flow area defined as a convergent surface of revolution having a curvilinear funnel wall.
Referring to
The reservoir 22 of the aerosol dispenser 20 may be used for holding fluid product, propellant and/or combination thereof. The fluid product may comprise a gas, liquid, and/or suspension. The aerosol dispenser 20 may also have a dip tube, bag on valve or other valve arrangement to selectively control dispensing, as desired by the user and as are well known in the art.
The reservoir 22, cap 24 and/or other materials used for manufacture of the dispenser 20 may comprise plastic, steel aluminum or other materials known to be suitable for such applications. Additionally or alternatively, the materials may be bio-renewable, green friendly and comprise bamboo, starch-based polymers, bio-derived polyvinyl alcohol, bio-derived polymers, bio-derived fibers, non-virgin oil derived fibers, bio-derived polyolefinics, etc.
Referring to
Referring to
The helix cup 30 may be inserted into the cap 24, and particularly into the housing 36 thereof. The housing 36 may have a backstop 34. The backstop 34 limits insertion of the helix cup 30 into the housing 36 of the cap 24. The backstop 34 further forms a cutting plane 84 with the helix cup 30.
Upon depressing the button 25 to initiate dispensing, product, and optionally propellant mixed therewith, is released from the reservoir 22 and flows through a valve, as is well known in the art. The product enters a chamber 35 in the backstop 34 which chamber 35 is upstream of the cutting plane 84. The chamber 35 fills with the product to be dispensed. The chamber 35 may be annular in shape and circumscribe the axis of the nozzle 32.
Referring to
Referring to
The funnel wall 38 has an inlet radius 50 at the first end and an outlet 44 radius corresponding to the nozzle 32 exit. The axial distance 56 between the inlet radius 50 and outlet 44 is parallel to the longitudinal axis L-L, and cone length 54 is the distance along the sidewall taken in the axial direction.
The prior art teaches a flow path having a frustrum of a right circular cone. This flow path provides a surface area given by:
Area=Π×cone length×(inlet radius+outlet radius), (1)
wherein the inlet radius 50 is greater than the outlet 44 radius, cone length 54 is the distance between the inlet and outlet 44 taken along the sidewall skewed relative to the longitudinal axis L-L, and II is the known constant of approximately 3.14.
For the helix cup 30 of the present invention, the area of the flow path may be at least 10%, 20%, 30%, 40%, 50%, 75% or 100% greater than the area of a comparable frustrum of a right circular cone having the same inlet radius 50, outlet radius 52 and cone length 54.
The subtended volume is given by:
Π/3×h×[inlet radiuŝ2+outlet radiuŝ2+(inlet radius×outlet radius)], (2)
wherein h is the axial distance 56 between the inlet and outlet 44 taken parallel to the longitudinal axis L-L.
The frustrum flow path provides a convergent straight sidewall 60 shown in phantom, which would be predicted by one of ordinary skill to provide the least drag and flow resistance of all possible shapes. For example, in the aforementioned book Sprays and Atomization by Lefebvre, page 116, it is specifically taught that straight, convergent sidewalls are known and used in the art.
For the helix cup 30 of the present invention, the subtended volume of the flow path may be at least 10%, 20%, 30%, 40%, 50%, 75% or 100% greater than the subtended volume of a comparable frustrum of a right circular cone having the same inlet radius 50, outlet radius 52 and cone length 54. Likewise the helix cup 30 of the present invention, may have a subtended volume at least 10%, 20%, 30%, 40% or 50%, less than the subtended volume of a comparable frustrum of a cone.
Referring particularly to
Of course, the entire funnel wall 38 need not be arcuately shaped. As shown, the portion 64 of the funnel wall 38 juxtaposed with the orifice may be arcuate and the balance 66 of the funnel wall 38 may be straight. As used herein, straight refers to a line taken in the axial direction along the funnel wall 38 and may be thought of as the hypotenuse of a triangle disposed on the funnel wall 38, having one leg coincident the longitudinal axis L-L and having the other leg be a radius of the circle connected to the hypotenuse.
The funnel wall 38 of
Referring back to
The grooves 80 may be equally or unequally circumferentially spaced about the longitudinal axis L-L, may be of equal or unequal depth, equal or unequal length in the helical direction, equal or unequal width/taper, etc.
Referring to
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The flow area of the present invention may be conceptually divided into two flow paths. The first flow path is divided between four discrete grooves 80, and does not circumscribe the longitudinal axis L-L at any particular cross section. The second flow path, contiguous with the first, blends the flow to circumscribe the longitudinal axis L-L at all cross sections from the virtual plane to the nozzle 32. Contrary to the prior art, the projected length of the first flow path, may be less than the projected length of the second flow path, taken parallel to the longitudinal axis L-L.
Referring to
The flow in the continuous film of the helix cup 30 circumscribes the longitudinal axis. Further the flow converges in the axial direction, as the nozzle 32 is approached. The flow in the helix cup 30 radially converges in the axial direction. Such radial convergence may be about a concave wall 64, a convex wall or a combination thereof.
The converging wall may have some portions 66 which are straight, but the entirety of the wall, from the one or more inlet port(s) to the nozzle 32 is not. By straight, it is meant that a line on the wall from an inlet port 92 to the nozzle 32, forms the hypotenuse of a triangle. As noted above, the triangle has one leg coincident the longitudinal axis and the other leg a radius of the circle connected to the hypotenuse.
In the helix cup 30, flow can intermix and circumscribe the longitudinal axis. As the flow approaches the discharge nozzle 32, the flow may converge. Such convergence increases the density of the flow, creating a low pressure zone. Further, the radius of the flow decreases throughout much of the longitudinal direction, although a portion of constant radius may be included proximate the discharge nozzle 32.
Referring to
Referring to
One of skill will recognize that hybrid geometries are also feasible and within the scope of the claimed invention. In a hybrid embodiment, a portion of the funnel wall 38 may be convex, another portion may be concave, and optionally, yet another portion may be linear. Again, in such a geometry, the funnel wall 38 may have a surface area and subtended volume which do not correspond to the equalities set forth in equations (1) and (2) above.
The embodiments of
More particularly, in the upper portion of
In the lower portion of
Referring to
Referring particularly to
In another embodiment, the helix cup 30 may be used with a trigger pump sprayer or a push button 25 finger sprayer, as are known in the art. In pump sprayers, the differential pressure is created by the hydraulic pressure resulting from piston displacement in response to the pumping action.
Once the piston is charged with product, it is ultimately disposed into the helix cup 30 under pressure, using any suitable flow path, as is known in the art. Upon dispensing from the helix cup 30, the aforementioned benefits may be achieved.
The present invention may be used with aerosol dispensers 20 having a gage pressure less than about 1.9, 1.5, 1.1, 1.0, 0.9, 0.7, 0.5, 0.4 or 0.2 MPa. The present invention unexpectedly provides for improved particle size distribution without undue increase in the gage pressure.
As in the case of the aerosol dispenser 20, relatively lower pressures may be used than with prior art trigger sprayers or push button 25 sprayers, while benefiting from a relatively tighter particle size distribution. The relatively lower pressure provides the benefit that tighter seals are not necessary for the pump piston and less manual force to actuate the pump using the finger or hand is required. The benefit to not requiring relatively tighter seals is that manufacturing tolerances become easier to achieve. As the force to actuate the pump dispenser decreases, the user encounters less fatigue from manual actuation. As fatigue decreases, the user is more likely to manually dispense an efficacious amount of the product from the trigger sprayer or push button 25 sprayer. Furthermore, as gage pressure decreases, the wall thickness of the reservoir 22 may proportionately decrease. Such decrease in wall thickness conserves material usage and improves disposability.
Three different spray systems were tested. The first sample 100 utilized the helix cup 30 of
The second sample 200 is a commercially available Kosmos spray actuator sold by Precision Valve Co. having an orifice diameter of 0.18 mm.
The third sample 300 is a helix cup 30 having the same groove 80 geometry, outlet 40 diameter of 0.18 mm, same flow area ratio of approximately 7.5:1, and the same included angle of approximately 64 degrees. But the third sample had the frustro-conical funnel wall 38, discussed by Lefebvre. The funnel wall 38 of sample 300 was approximately 20 percent greater than the corresponding area of the funnel wall 38 of sample 100.
Each sample 100, 200, 300 was loaded with 50 ml of deodorant spray product and charged with propellant to approximately 850 KPa. Each sample was then sprayed, and various measurements were made.
Referring to
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All percentages stated herein are by weight unless otherwise specified. It should be understood that every maximum numerical limitation given throughout this specification will include every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this specification will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this specification will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
