1. Field of the Invention
Our invention relates to an insert for dispensing a compressed gas product, a system that includes such an insert, and a method of dispensing a compressed gas product. More generally, our invention relates to apparatuses, systems, and methods for dispensing compressed gas products with a relatively constant flow rate and with a relatively constant particle size.
2. Related Art
In general, aerosol dispensers provide low cost, easy to use methods of dispensing products, typically, as an airborne mist. Thus, aerosol dispensers have been commonly used to dispense personal, household, industrial, and medical products. The airborne mist provided by an aerosol dispenser itself may provide a desired effect, as is the case with air freshening fragrances. Alternatively, the mist may be used to form a thin coating on surfaces, such as with furniture polishes.
Typically, aerosol dispensing systems include a container that holds a product with liquid and gas parts. Examples of liquid compositions included in aerosol systems are air and fabric fresheners, soaps, insecticides, paints, deodorants, disinfectants, and the like. The gas included with the liquid product acts as a propellant to discharge the liquid product from the container. The propellant pressurizes the container holding the liquid composition, and provides a force to expel the liquid composition from the container when a user actuates the aerosol dispenser by pressing an actuator button or trigger.
There are two main types of propellants used in aerosol systems: (1) liquefied gas propellants, such as hydrocarbon and hydrofluorocarbon (HFC) propellants, and (2) compressed gas propellants, such as carbon dioxide and nitrogen. In the past, chlorofluorocarbon propellants (CFCs) were used as propellants in aerosol systems. The use of CFCs, however, has essentially been phased out due to the potentially harmful effects of CFCs on the environment.
In an aerosol system that uses a liquefied petroleum gas-type propellant (LPG), the container is loaded with liquid composition and LPG propellant to a pressure approximately equal to the vapor pressure of the LPG. After being filled, the container has a certain amount of space that is not occupied by liquid. This space is referred to as the headspace. Since the container is pressurized to approximately the vapor pressure of the LPG propellant, some of the LPG is dissolved or emulsified in the liquid product. The remainder of the LPG remains in the vapor phase and fills the headspace. As the product is dispensed, the pressure in the container remains approximately constant because liquid LPG moves from the liquid to the vapor in the headspace, thereby replenishing discharged LPG propellant vapor.
In contrast, compressed gas propellants in aerosol systems largely remain in the vapor phase. That is, only a relatively small portion of a compressed gas propellant is contained in the liquid composition. Hence, a “compressed gas product” includes a liquid composition and a compressed gas propellant. As a result, the pressure within a compressed gas aerosol dispenser assembly decreases as the product is dispensed. While this aspect of using compressed gas propellants is, in some ways, disadvantageous, the use of compressed gas propellants has gained favor as compressed gas propellants do not usually contain volatile organic compounds (VOCs). On the other hand, LPGs are considered to be VOCs, thereby making their use subject to various regulations.
From a consumer satisfaction standpoint, an important aspect of an aerosol system is that the system provides a consistent fragrance experience provided by a consistent flow rate and a consistent particle size. A consistent flow rate and a consistent particle size ensures that a relatively consistent effect is achieved as the product is dispensed from the container. For example, in the case of air freshening products, the fragrance experience is a function of the amount of fragrance in the air, which in turn is related to both the flow rate and particle size of product dispensed by the related system. Thus, it is important that the flow rate and particle size of product that is dispensed when the container is relatively full be as close as possible to the flow rate and particle size of product that is dispensed when the container is relatively empty so that the user can achieve the same levels of air freshening with equal lengths of application, regardless of the amount of product remaining in the container.
Ideally, in an aerosol system configured to dispense an air freshener, the system dispenses a product with a flow rate and a particle size such that a sufficient amount of fragrance experience is achieved soon after the dispensing, but also such that there is longevity in the fragrance experience. The higher the flow rate of product from the system, the more fragrance that will be available with a given length of application. Too high of flow rate, however, may lead to an overwhelming fragrance experience. With respect to particle size, larger particles provide a smaller total surface area for evaporation of the fragrance as compared to an equivalent volume of smaller particles. The smaller surface area for evaporation of fragrance in larger particles provides for less of an initial fragrance experience compared to an equivalent volume of smaller particles. However, the smaller surface area for evaporation of fragrance in larger particles provides for a longer fragrance experience compared to an equivalent volume of smaller particles, i.e., the fragrance evaporates more slowly from the larger particles. Still other factors are taken into account when considering the particle size for an air freshener. Smaller particles may be more easily carried away with air flow, which also reduces the longevity of the fragrance experience. On the other hand, there is a greater tendency for larger particles to fall out of the air and onto surfaces. Such fall out behavior of larger particles is often undesirable because of the resulting accumulation on a surface.
Ideally, an aerosol system is configured to provide a flow rate and particle size that balances these considerations. That is, the aerosol system provides a flow rate and particle size such that a sufficient amount of fragrance is available quickly after dispensing the product, with the product particle sizes providing longevity to the fragrance experience, but not so large to present substantial fall out. With compressed gas propellants, however, there is a tendency for the spray rate to decrease as the product is dispensed from a container. Further, there is a tendency for the particle size to increase as the product is dispensed from the container. In prior art dispensing systems, the flow rate may decrease by more than 40% as the product in the container is used up. In the same prior art systems, the particle size may increase by more than 50% as the product in the container is used up. Accordingly, the desired effects of the dispensed product achieved by having a consistent flow rate and a consistent particle size are not found in prior art compressed gas aerosol systems. Further, even if the initial flow rate and initial particle size can provide an air freshener with a good fragrance experience, the changes in the flow rate and particle size may degrade the fragrance experience.