This invention is related generally to the field of aerosolization of liquids, and in particular to the aerosolization of liquids using an aerosol generator that operates at ultrasonic vibrational frequencies. More specifically, the invention relates to techniques for vibrationally isolating an aerosol generator that is connected to another structure, such as the housing of an aerosolization device, when aerosolizing a liquid.
Aerosolization of liquids is an important aspect of many businesses. For example, liquids are commonly aerosolized in connection with drug delivery, air humidification, deodorant or insecticide delivery, and the like. One exemplary way to aerosolize liquids is by supplying liquid to a vibratable member having a plurality of apertures and vibrating the vibratable member at ultrasonic frequencies. One way to vibrate the vibratable member is by use of a piezoelectric transducer. Such techniques are described in, for example, U.S. Pat. Nos. 5,164,740; 5,938,117; 5,586,550; 5,758,637 and 6,085,740, the complete disclosures of which are herein incorporated by reference.
When vibrating such vibratable members at ultrasonic frequencies, there is a need to ensure that a maximum amount of the vibrational energy is transferred from the piezoelectric transducer to the vibratable member, rather than to some surrounding structure. Otherwise, performance losses or performance variations may occur because of the forces that are transmitted through the material which couples the aerosol generator to surrounding structures, such as the housing of an aerosolization device.
Hence, this invention is related to ways to maximize the amount of vibrational energy transferred to the vibratable member, thereby maximizing the efficiency of the aerosol generator. In this way, the repeatability and performance of the aerosol generator are enhanced, irrespective of the devices into which the aerosol generators are integrated.
The invention provides for the vibrational isolation of an aerosol generator from surrounding structures. In one embodiment, this is accomplished by the design of an aerosol generator that comprises a vibratable member having a front, a rear, an outer periphery and a plurality of apertures extending between the front and the rear. A support element is disposed about the outer periphery of the vibratable member. A vibratable element is coupled to the support element and is configured to vibrate the vibratable member at ultrasonic frequencies. An isolating structure is coupled to the support element and is configured to couple the aerosol generator to a support structure, such as the housing of an aerosolization device. The isolating structure has a vibrational mechanical impedance that is sufficient to substantially vibrationally isolate the aerosol generator from the support structure. In this way, the aerosol generator may be operated at increased efficiencies and in a repeatable manner when coupled to surrounding structures.
Conveniently, the isolating structure and the support element may be integrated into a single component, thereby facilitating its manufacture. In one aspect, the isolating structure may comprise a plurality of arms that extend from the support element. These arms may have a wide variety of shapes and contours. For example, the arms may be bent, crimped, curved, or the like to facilitate vibrational isolation.
In another aspect, the isolating structure may comprise one or more elastomeric or plastic members. For example, the isolating structure may be constructed of an elastomeric or plastic washer. Conveniently, the washer may be coupled to the support element by forming tabs in the support element and inserting the washer between the tabs. As another example, the isolating structure may be constructed of a plurality of discrete elastomeric members or bellows that extend from the support element.
To facilitate vibrational isolation, the isolating structure may be configured so that it has a resonant frequency that is outside the operating range of the aerosol generator. Such an operating range for the aerosol generator may be about 50 kHz to about 250 kHz.
In a further aspect, the vibratable member may be dome shaped and include tapered apertures. Examples of such vibratable members are described in U.S. Pat. Nos. 5,586,550, 5,758,637 and 6,085,740, previously incorporated by reference.
The invention further provides an exemplary method for aerosolizing liquids. Such a method utilizes an aerosol generator having a vibratable member with apertures and a vibratable element to vibrate the vibratable member. According to the method, liquid is supplied to the vibratable member and the vibratable element is used to vibrate the vibratable member at an ultrasonic frequency to eject liquid droplets through the apertures. During vibration, an isolating structure is used to substantially vibrationally isolate the aerosol generator to enhance the operating performance of the aerosol generator. Further, the vibratable member may be vibrated at a frequency that is different from a fundamental frequency of the isolating structure to enhance the efficiency of the aerosol generator. As previously mentioned, a variety of isolating structures may be used to vibrationally isolate the aerosol generator from any surrounding structures. Such isolating structures also have resonant frequencies outside of the operating range of the aerosol generator.
In a further embodiment, the invention provides a method for forming an aerosol generator. According to the method, an isolating structure is stamped or coined out of a sheet of material. A vibratable member having a plurality of apertures is coupled to the isolating structure, and a vibratable element, such as a piezoelectric transducer, is coupled to the isolating structure or the vibratable member. The vibratable element is used to vibrate the vibratable member at ultrasonic frequencies while the isolating structure is used to vibrationally isolate the aerosol generator from surrounding structures. By forming the isolating structure in this way, the cost of producing the aerosol generator may be greatly reduced and the aerosol generator may be produced in higher volumes.
In one aspect, the isolating structure comprises an annular member and a plurality of arms extending from the annular member. In another aspect, the arms are bent or crimped after the isolating structure has been stamped. In a further aspect, the vibratable member is coupled across a central opening of the annular member, and the vibratable element comprises an annular piezoelectric element that is coupled to the annular member.
Another method for forming an aerosol generator uses a support element having an outer periphery. A plurality of tabs are formed in the outer periphery of the support element. This may be accomplished by making a pair of cuts in the support element and then bending the material between the cuts away from the support element. A vibratable member having a plurality of apertures is coupled to the support element, and a vibratable element is coupled to the support element or the vibratable member and is vibratable at ultrasonic frequencies. A gasket is coupled about the support element, with the gasket being received into the tabs. The gasket has a mechanical vibrational impedance that is sufficient to substantially vibrationally isolate the aerosol generator. Such a process is useful in producing an isolated aerosol generator in a time and cost efficient manner.