Micro-emitter

Abstract

A micro-emitter for pressure packages comprises an apertured member disposed across the nozzle opening through which a fluid product in the pressure package is expelled. The apertured member has at least one aperture which is from 0.5 to 15 .mu. in diameter. In one instance, propellant pressure is used to force the fluid through the aperture and break it into small drops. In a second instance a high velocity stream of vapor is used to assist the break up of the liquid either before the apertured member or after the fluid is forced through the apertures.

Description

BACKGROUND OF THE INVENTION

The present invention relates to aerosol containers and more particularly to a device for controlling discharge of a fluid product from a pressure package.

Numerous products which are normally marketed in pressurized containers could be more advantageously used if the product could be continuously expelled over a long period of time. For example, air sanitizers and fresheners, insecticides and medicinal products could be expelled into the atmosphere for extended periods thereby negating the necessity of concentrated exposures heretofore associated with aerosol sprays. An additional advantage obtained by controlled flow of the pressurized product is that the pressure package may be left unattended for long periods while maintaining a continuous discharge of the product.

Heretofore, devices have been used for allowing slow discharge of products by means of evaporation. For example, U.S. Pat. No. 2,826,453 relates to a seeper valve assembly utilizing a filter material pad in conjunction with a pressure package. The filter material, in this case, absorbs the liquid in the package and evaporates the liquid into the atmosphere. The product, therefore, goes from a liquid to a vapor state on the surface of the filter. In such case, the product to be discharged must have a high vapor pressure to evaporate, e.g., perfume. If the product has a low vapor pressure, it would simply pool on the surface of the filter. Moreover, any non-volatile solids dissolved in the product would tend to leave a crust on the filter. Accordingly, the device is severely limited as to products which may be used therewith.

SUMMARY OF THE INVENTION

In accordance with the present invention, a micro-emitter is provided which controls the flow of the fluid from the pressure package and influences the size of the drops exiting therefrom. The term microemitter, as used herein, designates the device of the present invention which controls and influences the discharge of a fluid product from a pressurized package. The above is accomplished by positioning an apertured substrate upstream from the exit orifice of an aerosol container. The apertured member may be filter or membrane material depending on the desired particle size of the expelled product. For example, extremely small drops, i.e., less than 5 microns, are required if the product is to remain airborne for long periods of time such as air fresheners and sanitizers and airborne residual insecticides and repellants. In such instances, a filter or membrane having pores or apertures of 5 microns would be appropriate. On the other hand, somewhat larger particles are required for insecticides which kill upon direct impaction; and the filter or membrane is chosen accordingly. The invention contemplates the use of a member having an aperture size between 0.5 to 15 microns. Any material having pores or apertures within the above-mentioned range are suitable for the present invention. For example, polycarbonate, glass, sintered silver, sintered stainless steel, sintered high density polyethylene, cellulose acetate, cellulose nitrate, etched stainless steel, etched copper and electrodeposited nickel, tin-lead alloy, rhodium, gold, copper, silver or iron are appropriate.

It is possible, then, to control the particle size from very small drops, e.g., less than 5 .mu. to large drops in the order of 30 .mu. simply by changing the diameter of the aperture in the substrate. In selecting the appropriate substrate, it should be noted that the flow rate through the aperture is influenced by pressure; viscosity, density and aperture diameter, tortuosity and length and the surface properties of the substrate.

It is to be noted that the filter or membrane of the present invention does not serve its usual known function, i.e., to remove or separate different sized material from a fluid stream or to absorb and permit evaporation of a fluid. On the contrary, the aperture or apertures in the filter or membrane serve to control the flow of the fluid and to assist drop formation. By controlling flow of the fluid, the discharge time for the product is significantly increased and continuous discharge may be obtained over a long period of time. Continuous discharge is also feasibly accomplished by drop formation of the product. By forming small drops, the product may be maintained in airborne condition for considerable time.

Basically, the present invention operates on the principle of atomization. The principle is discussed in a publication by W. R. Marshall Jr., Atomization and Spray Drying, Chemical Engineering Progress Monograph Series No. 2, 50, 1950, published by the American Institute of Chemical Engineers. As applied to the present invention, atomization is accomplished either hydraulically or pneumatically. In the hydraulic application, the pressure exerted on the fluid by the propellant forces the fluid from the apertures and breaks the fluid into small drops such as like a garden hose. In pneumatic atomization, a high velocity vapor stream is used to assist the break-up of the fluid. The vapor stream is preferably derived from the propellant in the pressure package and impacts the fluid either before or after the aperture and breaks it into small drops. To avoid any change in the composition of the liquid layer containing the actives within the pressure package, the vapor should come from a second liquid layer. The propellant, then, should be largely concentrated in one of two liquid layers.

In addition to the size of the apertures in the membrane or filter, the number thereof may also be controlled to give a desired discharge. The number of apertures may vary from 1 aperture to 3 .times. 10.sup.7 apertures depending on the specific application.

The present invention may be constructed integrally as a complete valve assembly or it may be constructed separately as a "top hat" which is readily affixed to the valve stem of a standard aerosol valve.

There has thus been outlined rather broadly the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures for carrying out the several purposes of the invention.

Specific embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawings, forming a part of the specification, in which like reference numerals designate like parts with like function, wherein;

FIG. 1 is an elevational view of a pressure package provided with a micro-emitter of the present invention;

FIG. 2 is an enlarged vertical cross-sectional view of the pressure package and micro-emitter of FIG. 1 with the valve in closed position;

FIG. 3 is a cross-sectional view similar to FIG. 2 with the valve open;

FIG. 4 is an enlarged vertical cross-sectional view of the micro-emitter of FIG. 1;

FIG. 5 is an enlarged vertical cross-sectional view of an alternative top hat for the valve of FIG. 1;

FIGS. 6-8 are enlarged vertical cross-sectional views of alternate embodiments of hydraulic type micro-emitters of the present invention;

FIG. 9 is an enlarged vertical cross-sectional view of a pneumatic type micro-emitter of the present invention;

FIG. 10 is an enlarged vertical cross-sectional view of the apertured substrate of the micro-emitter of FIG. 9; and

FIGS. 11-16 are enlarged vertical cross-sectional views of alternate embodiments of pneumatic type micro-emitters of the present invention.

With reference to FIG. 1, there is shown a typical pressurized aerosol container 10 well known in the art. The container is normally filled with a fluid product (not shown) which is to be discharged by opening a valve. Discharge pressure is obtained by a propellant which may be mixed with a product in a single or dual liquid phase system, or may be physically separated from the product in any well known manner. As shown in FIG. 2, a dip tube 12 and standard valve assembly 14 depend from the top of the container 10 and are mounted thereto by means of a cap 16. In this embodiment, the micro-emitter is adaptable to a standard depress actuated aerosol valve and comprises a top hat 18 and locking device generally indicated by the numeral 20. The conventional valve is of the type wherein downward pressure exerted on the valve stem 22 opens the valve (not shown) to allow the discharge of the fluid product. Secured between the dip tube 12 and the valve body 14 is a pre-filter 24 through which the product is filtered prior to entering the valve body. The prefilter material may be any well known filtering material which will separate solid particles which would tend to clog the valve parts.

Positioned on top of the valve stem 22 is a top hat 18 including a micro-emitter of the invention. The top hat 18 may be constructed of any suitable material and plastic is preferred. The top hat 18 is constructed so that its base will readily slide over the top of the valve stem and give a secure fit. Since valve stems are generally tubular, the top hat would also be tubular with an inside diameter approximately the same as the outside diameter of the valve stem. The top hat upwardly terminates in an exit orifice 26; and between the orifice 26 and top of the valve stem there is mounted an apertured member 28, seal 30, filter 32 and seal 34 in descending order. The apertured member 28 may be selected from any of the aforementioned materials depending on the number and size of apertures needed for the desired product and result. The apertured member 28 is preferably in the form of a thin sheet tightly secured between lip 36 and a first annular seal 30. The seal 30 may be any material which would not be degraded by the product or propellant; and flat rubber gaskets or plastic washers are preferred.

Since the apertures are very small, it is easy for foreign material to get into same causing them to be partly or completely plugged. It is necessary, then, to filter the fluid product before it reaches the apertures to remove all material that might occlude the apertures. Therefore, in addition to the pre-filter 24, a second filter 32 is secured immediately preceding the apertured member 28 in relation to fluid flow. As is shown in the drawings a filter sheet 32 is securely positioned between the first seal 30 and a second similar seal 34. In general, any filtering material which has the ability to remove material larger than the diameter of the apertures would be appropriate.

The second seal 34 also serves to provide a seal between the top hat and the top of the valve stem 22 to ensure that no fluid can leak therebetween.

The top hat also has an exterior annular flange 40 which is preferably moulded integrally therewith. The flange 40 coacts with an on-off feature, more fully described hereinafter, to actuate the valve.

The on-off feature or locking device 20 allows the operator to use the pressure package when he desires for the length of time that he desires. It is constructed so that it may be readily affixed to a standard valve cap 16. It comprises a cylinder shaped upstanding member 42 having exterior threads 44, an interior annular flange 46 positioned upwardly of the bottom of the cylinder and detent means such as annular bead 48 disposed inwardly at the bottom edge of the cylinder. The annular flange 46 engages the top of the valve cap 16 and the detent means 48 engages the lower lip of the valve cap 16 so that the cylinder 42 may be snapped onto the cap 16 and securely held thereto. Rotatably threaded onto the upstanding cylinder 42 is a cap 50 having a concave top 52. A central orifice 54 in the concave top 52 permits the top hat 18 to extend therethrough; and the edge of the orifice defines a shoulder 56 engageable with the annular flange 40 of the top hat 18.

When the locking device cap 50 is rotated, for example, in a clockwise direction to screw same in a downwardly direction, the shoulder 56 engages the annular flange 40 and depresses the top hat 18 and valve stem 22 to open the valve. The valve may then be left open for as long as needed and may thereafter be closed by simply unscrewing the locking cap 50 to release the pressure on the valve stem 22 to close the valve 14. It is to be noted that the continuous dispensing of the pressurized product is maintained as long as the locking cap is screwed downwardly as is shown in FIG. 3.

As shown in FIG. 4, the top hat 18 includes an apertured sheet 28 having a plurality of apertures 58, although it will be understood that a single aperture could be used. Among other names for the apertures 58 would be micro-orifice, pore or pin hole. When the valve is opened, the product fluid is forced up the dip tube 12 by the propellant, through a pre-filter 24 and through the depress type valve 14. The fluid product then is forced through the filter sheet 32 and then through the apertures 58 in the apertured sheet 28. As the fluid is forced out of the apertures 58, it is broken into small drops and expelled into the surrounding air as shown by the arrows.

An alternative top hat construction is shown in FIG. 5. In this construction, an interior shoulder 60 is formed to abut the top of a valve stem upon which the top hat is placed. An expanded chamber 62 houses a horizontally disposed filter sheet 32. The top hat then restricts into a nozzle canal 64 wherein the apertured member 28 is positioned immediately before the exit orifice 26. The apertured member 28 is secured within the canal 64 between lip 36 and seal 68. To prevent the filter sheet 32 from plugging the nozzle canal 64 under pressure from the product fluid, a spider 70 is positioned at the entrance to the canal 64.

In FIG. 6, a further embodiment of an hydraulic microemitter, according to the invention is shown which eliminates the depress type standard valve. In this embodiment, a dip tube 12 forms part of the valve and is equipped with a filter 32 suitably secured therein such as by seals 30 and 34. Between the filter 32 and the end of the tube 72, the interior thereof is restricted. An elongate cap 74 is positioned over the dip tube 12 and tightly secures an apertured member 28 therebetween so that the apertured member 28 covers the dip tube exit 76. In order to increase the surface area of the apertured member 28 through which the fluid product may pass, the portion thereof overlying the dip tube exit 76 may be slightly bowed as at 78. The dip tube 12 and cap 74 may be secured together in any well known fashion such as by gluing. The cap 74 has a centrally disposed conical exit orifice 26 which overlies the dip tube exit 76. As shown in FIG. 6, the conical exit orifice 26 may have its widest diameter at the base; however, as shown in FIG. 7, the opposite may also be the case. With respect to FIG. 6 and 7, the nozzle cap 74 has an annular flange 92 for securing same to a standard valve cap of a pressure package, such as by gluing.

A further embodiment of a hydraulic type micro-emitter is depicted in FIG. 8 wherein the dip tube 12 terminates as an annular flange 80 approximately the size of a standard valve cap 16. The disc 82 having a central exit orifice 26 is positioned over the flange 80 and apertured member 28 is secured therebetween. The disc 82, apertured member 28 and flange 80 are secured to the valve cap in any well known manner such as by a ring of glue 84. Additionally, a gasket 86 is secured between the disc 82 and valve cap 16 to ensure against any leakage of propellant or product.

In the embodiments depicted in FIG. 6, 7 and 8, it is to be noted that the micro-emitter is the valving member of the pressure package and the standard depress type valve 14 is eliminated. Thus, any means (not shown) may be used to close the nozzle and prevent discharge; typical would be a tape or plug.

Pneumatic atomization is accomplished by directing a stream of vapor to impact on the drops of fluid from the apertured member to further break-up the drops. As shown in FIG. 9, the dip tube 12 having a restrict end 88 abuts against an apertured member 28 suitably mounted to a nozzle cap 74. The apertured member 28 is secured to the interior of the nozzle cap 74 by means of a ring seal 30. The nozzle cap 74 and ring seal 30 have interior diameters larger than the external diameter of the dip tube 12 so that an annular vapor chamber 90 is formed therebetween. A centrally disposed exit orifice 26 communicates with the dip tube exit 76. The nozzle cap 74 has an external annular flange 92 for mounting same to a pressure package in any well known manner. In operation, propellant vapor enters the vapor chamber 90 and passes through the apertured member 28 as shown in FIG. 10. At the same time, fluid product is forced through the apertured member 28 by means of propellant force and exits same as small drops. As the vapor impacts the fluid drops it causes further break-up of the drops and enhances atomization. The very small drops then are discharged into the atmosphere. During storage, the exit orifice 26 may be blocked in any well known manner to prevent discharge.

A modification of a pneumatic micro-emitter is shown in FIG. 11 wherein the dip tube 12 is expanded at its upper end to form an enlarged chamber 96. The upper edge of the chamber forms a ledge 98 upon which is deposited an apertured member 28. This assembly is secured to a standard valve cap 16 which has an inwardly directed flange 100 defining an exit orifice 26. A floating disc 102 is positioned within the chamber 96 and is maintained in position by an annular shoulder 104 on the inside of the chamber 96. A lateral port 106 forms a vapor entrance in the chamber wall 108. When the valve is actuated such as by removing a blocking member from the exit orifice 26, the pressure from the vapor and product fluid causes the disc 102 to float off the shoulder 104 and approach the apertured member 28. Preferably, the disc 102 is maintained approximately 0.005 inch from the apertures by surface deformaties on the apertured member 28. In this embodiment, the vapor and fluid are in intimate contact before they exit, i.e., within the chamber, around the floating disc and through the apertures. The product fluid then exits through the exit orifice 26 as fine drops.

The vapor stream and fluid product may also approach the apertured member 28 at angles as is shown in FIG. 12. In this case, the dip tube 12 has a vapor channel 110 and a product channel 112 formed therein to respectively meet the apertured member at different angles. In such manner, the vapor impacts the fluid drops after exiting from the apertured member 28 to cause further break-up of the drops. A further modification of this arrangement is shown in FIG. 13 wherein two vapor channels 110 are formed in a block 114 surrounding the dip tube 12; and the apertured member 28 only covers the drip tube exit 76. Thus, as the product drops are forced out of the apertures, they are directly hit by two streams of vapor. It is preferred that the vapor channels 110 are positioned so that the angle at which the vapor contacts the drops above the apertured member 28 is 60.degree. from the plane of the apertures.

The vapor may also be directed to the fluid drops at angles after exiting the apertured member 28 as is shown in FIGS. 14 and 15. In FIG. 14, two vapor channels 110 direct the vapor to the apertured member 28 so that the vapor exits same at an angle of approximately 45.degree.. In FIG. 15, the vapor channel 110 terminates in a conical chamber 116 concentric with the exit orifice 26.

The vapor channel 110 may also be parallel to the dip tube exit 76 as is shown in FIG. 16. In this case, the vapor passes through the apertured member 28 and is then directed to the exit orifice 26 by means of a raised flange 118 on the valve cap 16.

In the above typical embodiments, liquid propellant may also be carried with the fluid product through the apertures. This results in flashing of the propellant which also enhances the break-up of the drops.

In the table I presented below are listed typical flow rates for conventional valves and for that achieved by the micro-emitter of this invention. Also listed is the length of time a 7 oz. can would operate if used continuously at the indicated flow rate.

Expulsion Operating VALVE Rate (g/min) Time for 7 OZ. Conventional 240 0.83 min. Conventional 60 3.3 min. Conventional 20 10 min. Micro-emitter 100 2 min. Micro-emitter 10 20 min. Micro-emitter 1 200 min. Micro-emitter 0.1 1.4 days Micro-emitter 0.02 7 days

As is evident from the above, the micro-emitter valve of this invention allows for discharge of the specific product for greatly extended periods. Since the valve has no moving parts, it is relatively inexpensive to produce, easy to construct and has minimal breakage. Moreover, the valve is readily adaptable to standard pressure packages.

Claims

What is claimed is:

1. A device for continuously dispensing fluid from a pressurized container which has a discharge conduit defining a channel extending from the liquid reservoir to the atmosphere, said conduit comprising:

-- a dip tube having one end positioned to be in said fluid; and

-- a nozzle means having its innermost end attached to the other end of said dip tube, said nozzle means having an apertured member positioned therein to be the last element for forming droplets of the discharged spray, said apertured member defining at least one aperture of diameter of from 0.5 to 15.mu..

2. The device of claim 1 wherein said apertured member is selected from the group consisting of polycarbonate, glass, sintered silver, sintered stainless steel, sintered high density polyethylene, cellulose acetate, cellulose nitrate, etched stainless steel, etched copper and electrodeposited nickel, tin-lead alloy, rhodium, gold, copper, silver or iron.

3. The device of claim 1 which further includes filtering means secured within said channel.

4. In an aerosol container having a depress type valve, a dip tube depending from said valve into said container and a valve stem extending upwardly from said valve, a continuous dispensing device which comprises:

a top hat positioned over the end of said valve stem and defining a discharge channel and having an outermost discharge exit;

an apertured member mounted within said channel and interposed between said valve stem and said discharge exit, said apertured member having at least one aperture having a diameter of from 0.5 to 15.mu., said apertured member being the last element for forming droplets of the discharged spray;

filter means mounted within said top hat between said apertured member and said valve stem, said filter means being capable of filtering out solid particles of a size at least as large as the smallest of said at least one aperture;

sealing means within said top hat to prevent leakage of fluid normally flowing from said valve stem through said top hat; and

locking means engaging said top hat and adapted to depress said top hat and valve stem to open said valve and to maintain said valves in open position.

5. The device of claim 4, wherein pre-filtering means is interposed between said dip tube and said depress valve.

6. The device of claim 4, wherein said locking means comprises:

an upstanding cylinder shaped member mountable to said valve cap; and

a rotatable cap threadably engaging said cylinder member and defining a central orifice through which said discharge exit extends, the rim of said orifice being engageable with said top hat whereby, rotation of said cap downward depresses said top hat and actuates said depress valve.

7. The device of claim 4, wherein a spider is interposed between said filter means and said apertured member to prevent said filter from stopping fluid flow.

8. A device for continuously dispensing fluid from a pressurized container which comprises:

a dip tube;

nozzle means positioned over one end of said dip tube;

an apertured member secured within said nozzle means positioned to be the last element for forming droplets of the discharged spray, said apertured member defining at least one aperture having a diameter of from 0.5 to 15.mu.; and

means defining at least one vapor channel directing vapor from within said container to said nozzle to impact upon droplets of said fluid after such droplets are forced through said apertured member.

9. The device of claim 8, wherein said means defining at least one vapor channel is a solid member surrounding said dip tube having at least one vapor channel communicating said nozzle with the interior of said container.

10. The device of claim 8, wherein said vapor channel terminates exteriorly of said apertured member.

11. The device of claim 8 wherein said apertured member defines a multiplicity of apertures and wherein said apertured member extends across said vapor channel whereby said vapor passes therethrough at a position adjacent to that portion of said apertured member through which a liquid is passing.

12. The device of claim 8, wherein said vapor channel terminates in a conical channel concentric with said dip tube.

13. The device of claim 8, wherein said vapor channel is parallel to said dip tube and said device further includes a raised flange positioned exteriorly of said apertured member to direct vapor to said nozzle means.

14. The device of claim 8, wherein said dip tube includes an expanded chamber preceding said apertured member, said chamber having an annular shoulder, said means defining at least one vapor channel comprises a lateral port through the side of said chamber, and said device further includes a floating disc positioned between said shoulder and said apertured member.

15. A device for continuously dispensing a fluid from a pressurized container which comprises:

a dip tube;

an elongate tubular member positioned over an end of said dip tube, said member having a centrally disposed orifice communicating with said dip tube, said nozzle member and said central orifice having an interior diameter greater than the exterior diameter of said dip tube to form an annular vapor canal therebetween;

an apertured member positioned between said central orifice and said dip tube in a position to be the last element forming droplets of the discharged spray, said apertured member defining a multiplicity of apertures having diameters of from 0.5 to 15.mu., some of said apertures being within said vapor canal and at least one being over said dip tube; and

annular sealing means positioned to secure said apertured member to said nozzle member.