1. Field of the Invention
The present invention relates in general to an ultrasonic nebulizer apparatus. More particularly, the present invention relates to a portable ultrasonic nebulizer apparatus and a method for automatically adjusting an operating frequency and checking an operating state of the apparatus.
2. Description of the Related Art
Medical nebulizers that nebulize a fluid into a fine spray or aerosol for inhalation by a patient are well-known devices commonly used for the treatment of certain conditions and diseases. Persons requiring treatment of certain kinds of respiratory conditions frequently need to have medications delivered directly to the lungs. Since the lungs are close to the heart and the blood circulatory system of the body, drug administration by inhalation provides an effective delivery system to all organs of the body. Further, nebulizers have applications for conscious, spontaneously-breathing patients and for controlled, ventilated patients.
Effective and economical nebulizer therapy includes the ability to quickly generate a large amount of aerosol within a predetermined particle size range. There are several other considerations that relate to the effectiveness of nebulizer therapies. For example, it has been suggested that nebulization therapy is more effective when the generation of aerosol particles is relatively uniform.
In the recent years, the percentage of the chronic patients is increasing such that multiple therapies are required in home care, and therefore, portable ultrasonic nebulizers maybe available for such patients with time. In an ultrasonic nebulizer, the fine spray is produced by ultrasonic vibration of the liquid, as by a piezoelectric element. The liquid is dropped on, or otherwise applied to, the piezoelectric element. In addition, a specific characteristic of ultrasonic nebulizers is that the mechanical movement of the piezoelectric element may be tens or hundreds times higher at a mechanical resonance frequency compared with mechanical movement beyond the mechanical resonance frequency. It is a nonlinear mechanical movement of the piezoelectric element against the electrical signal frequency driving it. At the mechanical resonance frequency, and therefore, it is much more efficient to produce the vibrations to nebulize liquid.
Base on the above reason, conventional nebulizers set a constant frequency corresponding to a mechanical resonance frequency at that time when manufactured. However, many factors, such as variable environment temperature, usable in a period of time or changeable a part element of the nebulizer, will cause the mechanical resonance frequency displacement and alteration. As a result, the real time mechanical resonance frequency is changed timely dependent on the variable factors and will not maintain in a constant value so as to cause the mechanical movement of the piezoelectric element outside of the maximum movement. Conventional solving method is to send the nebulizer to the original manufactory or call a maintenance worker coming in a period of time for calibration and adjusting the operation frequency corresponding to the mechanical resonance frequency. There is a checking table for maintenance worker to detect and adjust some factors which will influence the operation frequency and then the worker will send the nebulizer back to owners. It wastes time and is so inconvenient for sending to and fro of the nebulizer or calling the maintenance worker coming.
Besides, if the liquid received in the nebulizer is insufficient or will be completely sprayed, the conventional nebulizer will not detect this situation and keep going for vibrating. Furthermore, at another abnormal situation, for example, a cover for protecting the liquid is removed, a part element of the apparatus is not connecting finely or a short circuit is occurred will not be detected. It means that when the conventional nebulizer is in an erroneous state, the nebulizer will not turn off itself. Further, a power saving of a portable apparatus is an important issue and then how to solve this problem is worth considering. Thus, a need exists for improved nebulizer.