APPARATUS FOR NEBULIZING A LIQUID

Abstract: Apparatus for nebulizing a liquid, comprises a chamber (214) for the liquid to be nebulized; an ultra­ sonic generator (274) disposed within the chamber (214) to be submerged in a pool of the liquid to be nebulized and effective, when energized, to nebulize liquid in the pool; a sonic detector (200) located at a predetermined level of the chamber (214); and an electrical circuit con­ trolled by the sonic detector (200) for energizing the ultrasonic generator (274), but automatically de-energizing the ultrasonic generator (274) when the liquid in the pool is at a level below that of the sonic detector (200).

Description: The present invention relates to apparatus for nebulizing a liquid. The invention is particularly applicable to the apparatus described in EP-A-0 213 056 for use in producing a stream of heated vapor containing liquid droplets to be used for therapeutic purposes, and is therefore described below with respect to this application. EP-A-0 213 056 discloses apparatus for nebulizing a liquid comprising a chamber for the liquid to be nebulized, and an ultrasonic generator disposed within the chamber to be submerged in a pool of the liquid in the chamber. When the ultrasonic generator is energized, it produces a spout of intensely-agitated liquid spouting upwardly out of the surface of the liquid with an arcuate trajectory. In the described apparatus, the arcuate trajectory is produced by directing a jet of heated gas to impinge the spout at an angle to the spout axis and with sufficiently high velocity to deflect the upper portion of the spout laterally of its base at the liquid level. A delivery tube is connected to the chamber for outletting a confined stream of hot gas saturated with vapor and having a small quantity of liquid droplets mixed therein. As described in EP-A-0 213 056, the so-produced stream of heated vapor, when applied to the nasal passages, has been found to produce a beneficial therapeutic effect on persons suffering from a common cold or other similar ailment. US-A-3,469,785 also discloses an apparatus for nebulizing liquid comprising a chamber for the liquid to be nebulized, and an ultrasonic generator disposed within the chamber to be submerged in a pool of the liquid to be nebulized and effective, when energized, to nebulize liquid in the pool. However, in such apparatus the ultrasonic generator will be damaged if the water level is permitted go below that of the ultrasonic generator. US-A-3,469,785 does not provide any means for detecting the water lever in order to protect the ultrasonic generator should the level of the water drop below that of the ultrasonic generator. US-A-3,593,712 discloses an apparatus for nebulizing a liquid according to the precharacterizing portion of independent claim 1. The known apparatus has an optical level detector including an opaque float which blocks the light from a light source received by a photoconductive cell via a transparent housing when the water level drops too low. Such an optical system is highly sensitive to dirt on the transparent housing, requires frequent cleaning in order to keep the light passage dirt-free, and is inconvenient to change liquid levels because the positions of both the light source and cell must be changed while maintaining the two in precise alignment. To avoid these drawbacks, in accordance with the invention, the apparatus for nebulizing a liquid is characterized in that said level detector is a sonic detector. Such a sonic detector is considerably more trouble-free than an optical system type liquid level detector as in US-A-3,593,712, requires considerably less maintenance, and is much simpler initially to install or subsequently to change in order to protect the ultrasonic generator. In the drawings: Fig. 1 is a fragmentary view illustrating a portion of the nebulizing apparatus of EP-A-0 213 056 but equipped with a sonic detector for protecting the generator in the event the liquid drops below a predetermined level; Fig. 2 is a block diagram illustrating the circuit controlled by the sonic detector for protecting the ultrasonic generator; and Figs. 3 and 4 are fragmentary views illustrating an improved manner for minimizing the disturbance of the liquid to the formation of the spout produced in the nebulizing apparatus, Fig. 4 being a sectional view along lines a--a of Fig. 3. Fig. 1 illustrates only a portion of an ultrasonic-type nebulizing apparatus in which the invention may be used. A preferred such apparatus is that described in EP-A-0 213 056, but it will be appreciated that the invention could be advantageously used in other ultrasonic-type nebulizing apparatus. As shown in Fig. 1, the apparatus includes a sonic detector 200, such as a microphone, for protecting the ultrasonic generator 274 against damage should the water in the nebulizing chamber 214 drop below a predetermined level. Thus, as shown in Fig. 1, the sonic detector 200 is located on the outer face of a plastic side wall 202 of chamber 214 just below the normal level 222 of the water within the chamber. The spout 276 produced by ultrasonic generator 274 has an arcuate trajectory. As described above, this is preferably done by directing a confined stream or jet of gas to impinge the spout at an angle to the vertical axis of the spout and with sufficiently high velocity to deflect the upper portion of the spout laterally of its base, as shown at 272 in Fig. 3. Fig. 2 is a block diagram illustrating the circuit for energizing and de-energizing the ultrasonic generator 274. The circuit includes a power oscillator 204 driving ultrasonic generator 274 and controlled by a power-on reset capacitor 206 connecting the power oscillator to a power supply via a power switch 208. The power-on reset capacitor 206 maintains a predetermined voltage for a short interval when the power switch 206 is turned on. A threshold detector 210 is interposed between the power-on reset capacitor and the power oscillator 204. The juncture of the power-on reset capacitor 206 and threshold detector 210 is connected to a circuit including the ultrasonic detector 200, an amplifier-filter for amplifying and filtering the output of detector 200, and a rectifier for rectifying this output. Threshold detector 210 is effective to energize power oscillator 204 to drive the ultrasonic generator 274 only when a predetermined voltage is either present in the power-on reset capacitor 206, or is outputted by the sonic detector 200 via rectifier 214. The electrical circuit illustrated in Fig. 2 operates as follows: When power switch 208 is turned on by the user, the power-on reset capacitor 206 holds the output high to the threshold detector 210 for a sufficiently long period of time to energize the power oscillator 204 and to drive the ultrasonic generator 274. If the level 222 of the liquid within chamber 214 is above that of the sonic detector 200, the detector will output an electrical signal via the amplifier-filter 212 and rectifier 214 to hold the threshold detector 210 high and thereby to maintain the energization of the power oscillator driving the ultrasonic generator 274. However, if the level of the liquid is below that of sonic detector 200, the sonic detector will not generate the above electrical signal to the rectifier 214, so that as soon as the time interval expires during which the power-on reset capacitor 206 holds the high voltage applied to threshold detector 210, the latter will go low and will thereby energize power oscillator 204, terminating the energization of the ultrasonic generator 274. Preferably, capacitor 206 stores the voltage from the power supply for a period of 100-1,000 milliseconds when the power switch is turned on. In a preferred embodiment, this time period is 400 milliseconds, which is sufficient time for the sonic detector 200 to generate a signal for maintaining the energization of the sonic generator 274, but not sufficient to cause any damage to the ultrasonic generator if the water level is below the level of the sonic detector. If the ultrasonic generator is de-energized, it will remain de-energized until the user turns the unit off and then on, using the main power switch. Even then, the oscillator 204 will only remain on if the user has put water into chamber 214 to the level 222. Figs. 3 and 4 illustrate an improved arrangement, as compared to that illustrated in the above-cited patent application, for returning the water droplets from the spout 276 to the liquid surface in a manner minimizing the disturbance to the formation of the liquid spout. The arrangement illustrated in Figs. 3 and 4 includes a vertical wall section 216 laterally of the ultrasonic generator 274, and a horizontal wall section 216′ joined at one end to the vertical wall section 216 and formed at its opposite end with a U-shaped slot 216″ located so that the edges of the slot straddle the base of the spout 276 formed by the ultrasonic generator 274. Vertical wall section 216 is located so that its surface is not wetted by the water in the pool. Horizontal wall section 216′ is located at the water level 222 so that its lower surface is wetted by the water, whereas its upper surface preferably is not wetted by the water. As described above, a jet or confined stream of hot air is discharged from nozzle 272 at an angle to the axis of spout 276 and is of sufficiently high velocity to impart a curved trajectory to the spout as illustrated in Fig. 3, deflecting the upper portion of the spout to impinge the vertical wall section 216. The water flows down that section to the joined horizontal wall section 216′, and from there back into the water pool with a minimum of disturbance of the water pool to the formation of the spout. It will appreciated that while the invention has been described particularly with respect to a therapeutic instrument, the invention could advantageously be used in other applications involving the nebulization of a liquid by an ultrasonic generator. Many other variations, modifications and applications of the invention will be apparent.

Claims: Apparatus for nebulizing a liquid, comprising a chamber (214) for the liquid to be nebulized; an ultrasonic generator (274) disposed within said chamber (214) to be submerged in a pool of the liquid to be nebulized and effective, when energized, to nebulize liquid in said pool; a liquid level detector located at a predetermined level of the chamber (214); and an electrical circuit controlled by said level detector for energizing said ultrasonic generator (274), but automatically de-energizing said ultrasonic generator (274) when the liquid in said pool is at a level below that of said level detector, characterized in that said level detector is a sonic detector (200). Apparatus according to claim 1, characterized in that said electrical circuit includes a power oscillator (204) for driving said ultrasonic generator (274), an output detector for detecting an output from said sonic detector (200) when the liquid in the pool is above the level of the sonic detector (200), a power-on reset capacitor (206) for maintaining a predetermined voltage for a predetermined time interval when the power is turned on, and control means (208) for energizing said power oscillator (204) only when a predetermined voltage is either present in said power-on reset capacitor (206) or is outputted by said output detector. Apparatus according to claim 2, characterized in that said power-on capacitor (206) maintains said predetermined voltage for a period of 100-1,000 milliseconds when the power is turned on.

Inventors: VERITY, NIGEL
Applicants: RHINOTHERM NETZER SERENI LIMITED PARTNERSHIP
Application year: 1987
Main classification: B05B17
IPC codes: A61L9, B05B17, B05B7