Aerosol Valve For Low Delivery Rate

Abstract

A low delivery rate aerosol valve comprising a valve body extension having at least one additional restricted orifice to provide a plurality of restricted orifices disposed in series relative to each other and the valve body cavity such that product passes through the restricted orifices in succession and from there to the valve body cavity and valve stem discharge orifice and through the terminal orifice.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to aerosol valves and, in particular, to aerosol valves designed to deliver a fluid product at a reduced rate.

2. Description of the Prior Art

Aerosol dispensers usually consist of a container under superatmospheric pressure with a valve at the upper end thereof to control discharge of the product. The valve is generally manually operable and of the type which is biased to seal the discharge opening when the aerosol container is not in use. A dip tube is generally provided which extends downwardly into a liquid product to a point adjacent to the container bottom.

In such aerosol dispensers, a gaseous propellant normally occupies the space in the container at the top, around the valve. This space is commonly referred to in the trade as the head space. In the usual case, liquid product and liquid propellant are located beneath the head space. As the head space increases with use, the liquid propellant vaporizes, keeping the overall inside container pressure and thus the flow rate of product up the dip tube relatively constant. In some cases, compressed gases such as N.sub.2 O, CO.sub.2 and N.sub.2 are used as propellant. These will be discussed later in this application.

Several methods have been used to obtain a slow discharge rate in aerosol dispensers of the type described above. One method has been to use a capillary dip tub, that is, a dip tube with a very small inner diameter. This effectively slows the discharge rate of the liquid product. Another idea which has been used to slow the discharge rate has been to reduce the diameter of the discharge orifice. A third way has been to use a vapor tap, that is, to intentionally create a leak from the head space into the discharge stream in order to reduce the pressure drop across a valve body orifice thereby reducing the flow of liquid into the valve body and out the terminal orifice.

Each of these ideas for obtaining a low delivery rate in an aerosol valve has disadvantages in certain situations. In particular, difficulties arise when the fluid product to be dispensed has a high solids content, when the aerosol package will undergo "misuse" (that is, occasional use in positions other than an upright position), and/or when a particular type of discharge stream, namely a spray composed of relatively large particles, is desired.

In the case of a capillary dip tube, especially a flexible plastic capillary dip tube, it is very difficult to maintain proper orientation within the container. Because of the unreliable orientation of the dip tube, "misuse" may frequently occur. Misuse, of course, occurs any time the lower open end of the dip tube is exposed to vapor rather than to the product to be dispensed. Further, when the container is being misused, because of the limited dip tube capacity in a capillary dip tube, it would take only a brief period of time to exhaust the liquid contents of the dip tube before the misuse would become damaging, that is, before vapor would be exhausted from the container.

In the case of reducing the diameter in the discharge orifice as a method of obtaining a low flow rate valve, clogging can readily occur especially if such a valve is used with a product having a high solids content. Further, the use of such small reduced diameter orifices can result in large discharge rate fluctuations because proportionally large variations in cross-sectional area result from variations in the orifice diameter which are within normal production tolerances. Furthermore, there is a practical lower limit in the diameter of an orifice. These problems make the use of drastically reduced orifices undesirable or impossible in many situations.

A third known way of reducing the flow rate, namely the use of a vapor tap, may be out of the question when a product is to be dispensed in a spray having particles (or droplets) of a large size. The addition of the vapor in the product stream may have a tendency to agitate and break up the fluid product into small particles thus defeating the possibility of the desired large particles in the spray.

The valve of this invention overcomes all of these problems by providing a low delivery rate while at the same time avoiding the problems of misuse, clogging, and/or undersized particles in the spray.

Although the use of liquid propellants vaporizing into the head space to provide generally constant pressure as the contents of the container are exhausted in wide-spread and established in the aerosol industry, the use of compressed gases has been increasing for certain types of products. When using compressed gases, such as N.sub.2 O, CO.sub.2 and N.sub.2, the pressure decreases as the head space increases during product usage. Thus, to have a high enough pressure level when the product is nearly depleted, it is necessary to have a very high pressure initially, that is, when the head space is quite small. With such a high pressure and such changes in pressure, a low delivery rate is needed to avoid radical changes in spray characteristics. The valve of this invention is a superior way to achieve a low flow rate in high pressure aerosol products which use compressed gases as propellants.

The low delivery rate valve of this invention is characterized by an upstream valve body extension having at least one additional restrictive orifice to provide a plurality of restricted orifices within the valve disposed in series relative to each other and to the valve body cavity such that product passes through the restricted orifices in succession and from there to the valve body cavity, the valve stem discharge orifice and the terminal orifice. This valve is a superior device for obtaining a low delivery rate from an aerosol container. The problems of capillary dip tubes, extremely small orifices and vapor taps may be avoided Dip tubes having significant product capacity may be used, thus providing enough product in the dip tube that product will continue to be expelled for a period of time during which a container is being "misused." The plurality of restricting orifices may each be of size sufficient to avoid clogging and yet in combination provide a very low delivery rate. Gimmicks such as vapor taps, which are especially undesirable when a compressed gas is used as propellant or when a large particle spray is needed, are avoided.

The term "restricting" or "restricted" orifice refers to an orifice across which there is a significant pressure drop. A pressure drop of 5 percent would be an approximate minimum for a restricting orifice. A drop of about 10-30 percent would be accomplished across a preferred restricted orifice with about 20 percent being typical in this invention.

An object of this invention is to provide an aerosol valve overcoming the aforementioned problems.

Another object of this invention is to provide a low delivery rate valve overcoming the problems associated with capillary dip tubes, vapor taps, and extremely small orifices.

Another object of this invention is to provide a valve for low delivery rate which may be used in a product undergoing some "misuse" without sustaining the detriment associated with misuse when a small capacity dip tube, such as a capillary dip tube, is used.

Yet another object of this invention is to provide a low delivery rate valve which is not prone to clogging even with products having a high solids content.

Another object of this invention is to provide a low delivery rate valve the delivery rate of which may be readily varied by the use of piggyback valve extension members.

A still further object of this invention is to provide a low delivery rate valve which will allow a large particle spray.

Another object of this invention is to provide a low delivery rate valve which has superior functional characteristics when used in an aerosol product having a compressed gas propellant.

These and other important objects will become apparent from the following description and from the drawings showing preferred embodiments wherein:

FIG. 1 is a cross-sectional side view of one embodiment of this invention.

FIG. 2 is a cross-sectional side view of an alternative embodiment.

FIG. 3 is a cross-sectional side view of a third embodiment.

FIG. 4 is a cross-sectional side view of a fourth embodiment.

FIG. 5 is a fragmentary cross-sectional side view of a fifth embodiment of this invention.

Similar reference characters refer to similar parts throughout the several views of the drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, a typical aerosol dispenser upon which the invention may be used is illustrated, consisting of a container 10 having a mounting cup 12 attached thereto.

As also shown in FIG. 1, the device of the present invention comprises a valve generally indicated as 14. Valve 14 is contained within the customary central turret portion of the mounting cup 12 with a tubular valve stem 18 protruding through the central aperture 20 of mounting cup 12. Valve stem 18, including discharge orifice 22, is movably arranged within cavity 24 and spring biased in the sealed or closed position by valve spring 26. Spring 26 is compressed between the enlarged lower portion 27 of valve stem 18 and a shelf 28 in the interior of the valve body 29. A valve button 30, including terminal orifice 32, is affixed to the upper portion of the stem 18 protruding upwardly out of the container. Sealing means 16, a rubber ring, provides sealing engagement between the top of valve body 29 and the inside of mounting cup 12. Valve body 29 has an uppermost annular enlargement 25 snap fitted beyond annular head 23.

Valve body 29, which is substantially circular in any section cut normal to its axis, comprises an enlarged upper portion 34 which defines cavity 24. Extending downwardly from upper portion 34 is a lower portion 36 terminating in a restricted feed orifice 38. Affixed to lower portion 36 is a valve body extension 40 defining an expansion chamber 42 and terminating in a restricted feed orifice 44. A dip tube 50 affixed to the valve body extension 40 extends downwardly into the interior of the container 10.

The extension 40 defines an annular groove 46 which corresponds with an annular locking ring 48 to secure extension 40 to lower portion 36 of valve body 29. The groove and ring could be reversed. Extension 40 may be secured to valve body 16 in a variety of other ways. In some cases, extension 40 may be integrally formed with the valve body 29.

As shown in FIG. 2, the extension may comprise a dip tube 50 affixed to the lower portion 36 of valve body 29. Extension 40 defines a restrictive feed orifice 44 at its lower end, and dip tube 50 defines expansion chamber 42.

FIG. 3 shows another alternative embodiment of the present invention. Valve body extension 40 is connected to the reduced diameter lower portion 36 of valve body 29, which terminates in valve body restricted feed orifice 38. Valve body extension 40 defines a plurality of expansion chambers 52 set apart by a plurality of restricted feed orifices 54. Extension 40 may be secured to valve body 16 in a variety of other ways. In some cases, extension 40 may be integrally formed with the valve body 16.

As shown in FIG. 2, the extension may comprise a dip tube 50 affixed to the lower portion 36 of valve body 29. Extension 40 defines a restrictive feed orifice 44 at its lower end, and dip tube 50 defines expansion chamber 42.

FIG. 3 shows another alternative embodiment of the present invention. Valve body extension 40 is connected to the reduced diameter lower portion 36 of valve body 29, which terminates in valve body restricted feed orifice 38. Valve body extension 40 defines a plurality of expansion chambers 52 set apart by a plurality of restricted feed orifices 54. Extension 40 may be formed in a dip tube or may be a separate piece formed by molding or otherwise. If extension 40 is a separate piece, a dip tube may be attached to extension 40 and extend downwardly into the liquid contents of a container. Alternatively, the dip tube could be connected to the upper portion 56 of extension 40, which has a larger diameter and a larger capacity.

FIG. 4 shows still another embodiment comprising valve body 29, dip tube 50 and a plug 58 defining restricted feed orifice 60. Plug 58 may be force fitted into dip tube 50 or include an annular locking groove 62 which engages a corresponding ring 64 formed on the interior of the dip tube 50. Plug 58 may be placed at any desired location along the length of dip tube 50.

FIG. 5 shows another embodiment of this invention illustrating how a plurality of extension members 66, which are similar to valve body extension 40 shown in FIG. 1, may be piggy-backed to further restrict the flow rate within a valve. For each additional extension member 66, the valve has an additional restricted orifice and an additional expansion chamber. The dip tube 50 is attached to the extension member furthest upstream. Because of the variations possible in the number of extension members 66 and in the orifice sizes of such members a valving system which may be easily adjusted to obtain a desired low delivery rate is provided.

The valve body extensions of this invention are preferably made of plastic materials. The dip tubes which form the valve body extensions are preferably of flexible plastics while the extension shown in FIG. 1 and the extension members shown in FIGS. 3 and 5 are preferably formed of hard plastic materials. There are several methods presently known which may be used in forming valve body extensions.

With reference to FIG. 1, in operation, product is dispensed by depressing button actuator 30. As button actuator 30 is depressed, discharge orifice 22 is exposed to the interior of valve body cavity 24, having been axially displaced below seal 16. This allows product to flow from the interior of the container 10 through restricted feed orifice 44 into expansion chamber 42 and from there through valve body restricted feed orifice 38 and into valve body cavity 24. The product flows from valve body cavity 24 through discharge orifice 22 into discharge passage 19 defined in valve stem 18 and out the terminal orifice 32.

In the alternative embodiment of FIG. 2, product flows through restricted feed orifice 44, expansion chamber 42, restricted feed orifice 38 and into valve body cavity 24. The product is then dispensed in the manner previously described.

The low delivery rate valve of this invention, which has been described in detail, overcomes the problems associated with previously known low delivery rate valves. A precise low delivery rate may be obtained. Further, such a delivery rate may be obtained without problems of clogging, without a breakdown in particle size when large spray particles are desired, and without suffering the disadvantages normally accompanying occasional misuse of a pressurized container. It is further believed that there is an additional advantage relating to a low flow rate valve in a product in which large spray particles are desired. In such cases, when a vaporizing liquid propellant is used, it is believed that the upstream expansion chambers provided in this invention have the beneficial effect of allowing additional amounts of liquid propellant to be removed from a liquid state to a gaseous state prior to expulsion of the product from the terminal orifice. Thus, the liquid being expelled from the terminal orifice contains a smaller amount of liquid propellant, thereby reducing the expansion which breaks such product into minute particles. Theoretically, in some cases, it would be possible to remove nearly all of the liquid propellant from the liquid product prior to its passage through the terminal orifice. This would prevent "explosions" of droplets as they exit the terminal orifice and tend to promote large particle size in the spray.

While in the foregoing specification, this invention has been described in relation to certain preferred embodiments, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is suseptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

Claims

We claim:

1. A low delivery rate aerosol valve comprising a valve body including a valve body cavity and a valve body restricted feed orifice, a valve stem including at least one inlet orifice and a discharge passage, said valve stem movably mounted within said valve body cavity, a spray nozzle defining a terminal orifice in fluid communication with said valve stem, a biasing means to normally bias said valve stem to the closed position, and a valve body extension defining a plurality of expansion chambers, each of said expansion chambers interconnected to its adjacent expansion chamber by a restricted feed orifice, said expansion chambers communicating in series with the interior of said valve body cavity through said valve body restricted feed orifice such that upon actuation of the valve the contents of the dispenser pass in series through the restricted feed orifices and expansion chambers of said valve body extension, said valve body restricted feed orifice, said valve body cavity, said inlet orifice and discharge passage of said stem and said terminal orifice to the atmosphere, whereby the contents of the dispenser are delivered at a low rate.

2. In an aerosol valve of the type having a valve body defining a valve cavity and a restricted valve body orifice through which product enters said cavity from an associated container, a valve stem movably mounted within said cavity and defining an inlet orifice and a discharge passage, a spray nozzle attached to and in fluid communication with said stem and defining a terminal spray orifice, and means to bias said stem to a closed position, the improvement of additional means defining at least one expansion chamber positioned below said valve cavity and below said restricted valve body orifice, said additional means defining a second restricted feed orifice for product entry to said expansion chamber, whereby product is delivered by said valve at a reduced flow rate.

3. The valve of claim 2 wherein said valve body includes a valve body tail which defines said valve body restricted feed orifice, and said additional means comprising an extension member coupled to said tail such that said expansion chamber is adjacent said tail, said extension member further defining said second restricted feed orifice remote from said tail.

4. The valve of claim 2 wherein said additional means comprises an elongate dip tube attached to said valve body and having said second restricted feed orifice remote from said valve body.

5. The valve of claim 4 wherein said restricted feed orifice remote from said valve body is defined by a plug in said dip tube.

6. The valve of claim 2 wherein said additional means comprises at least one extension member which may be removably attached to said valve body.

7. The valve of claim 6 wherein said at least one extension member comprises a plurality of extension members removably attached together in piggy-back fashion.