Inhaling Apparatus

TECHNICAL FIELD

This invention relates to an inhaling apparatus. More particularly, it relates to an inhaling apparatus for ejecting droplets of a medical agent, an aromatic, nicotine or some other savory substance and causes the user to inhale them.

BACKGROUND ART

Our society is aging because of the prolonged mean life that is realized by the advancement of medicine and science in recent years. On the other hand, new diseases and infectious diseases have been found due to the changes in the living environment and the eating habits, the environmental pollution and new strains of viruses and microbes to make people anxious about their health. Particularly, in the so-called advanced countries, the increasing number of medical patients suffering from life-style related diseases, including diabetes and hypertension imposes a serious problem on the society.

For example, diabetic patients have to be dosed with insulin. Conventionally, it is a general practice to inject insulin to a diabetic patient after each meal. Dosing insulin by means of a syringe forces pain on the part of the patient. To solve this problem, dosing a medicine by way of the respiratory system of the patient has been discussed. Generally three techniques of dosing a medicine are known to date. They include the use of a metered dose inhaler, the use of a dry powder inhaler and the use of an atomizer.

Metered does inhalers (MDIs) are being widely used to treat asthma. An MDI is provided with a valve for ejecting a dose of aerosol in operation. The apparatus main body can be downsized for the convenience of portability, although each dose can vary to a considerable extent. Additionally, the user of an MDI is required to operate the valve and inhale the dose in a considerably synchronized manner. and many users feels the synchronized operation of the MDI difficult and cumbersome.

The user of a dry powder inhaler (DPI) is required to inhale a large volume of air in order to effectively apply dry powder to the inside of the bronchus system of the user with a sufficient degree of fluidity. While dry powder inhalers may be free from the above-described problem of synchronizing the valve operation and the inhalation of the dose, it is a considerable burden for the user of a dry powder inhaler to inhale a large volume of air. Additionally, patients who are sensitive to moisture and also to the inhaled powder cannot use a DPI because the patient can burst into a fit of asthma. Additionally, since the power for inhaling air varies from person to person, the dose can vary also from person to person.

An atomizer is adapted to generate aerosol by atomizing liquid by means of a carrier gas flow. It requires a gas compressor that operates continuously or a large volume of compressed gas for its operation. Generally, the size of aerosol droplets is a function of the pressure and the velocity of carrier gas and hence it is not easy to independently change the concentration of the medical agent, in a gas flow. Additionally, as the patient inhales the atomized liquid, the pressure in the nozzle of the atomizer falls. In other words, the dose and the particle size of the medical agent are affected by the period and the strength of each breathing action.

Thus, the above-described known apparatus are accompanied by the problem of a low degree of precision of applying a right dose of a medical agent of right particle size to a right position of the patient body. In other words, they can be used only for medical agents that show a large tolerance in terms of dose. In any case, currently, it simply relies on the technique of the user for applying a right dose to a right position.

On the other hand, there is a demand for improved medicinal administration systems that can be used to optimally cure diseases of the nose and those of the lung by means of a medical agent that works only locally. Additionally, it has been proved as a result of the advancement of medicine in recent years that application of a medical agent such as protein, peptide or an analgesic to the lungs is advantageous if compared with conventional administration techniques such as oral administration and injection. However, known inhalers cannot be used for such applications because they are accompanied by the problem of variable particle size and that of variable dose.

These problems will be described in greater detail by way of examples. Of the current diabetic patients, whose number is increasing, those suffering from insulin dependent diabetes mellitus, which is also referred to as type I diabetes mellitus, do not secrete insulin from the pancreas and hence insulin has to be administered periodically to them.

Currently, administration of insulin is realized by means of subcutaneous injection to impose a great physical and mental burden on the patient. Pen-type syringes designed to use a very thin needle have been developed to significantly reduce the pain on the part of the patient. However, many patients suffering from type I diabetes mellitus are working like healthy people unless insulin has to be administered periodically to them and it will be mentally difficult for such a patient to inject insulin to him- or herself by means of a syringe while he or she is exposed to the public if the syringe is of the pen-type.

Thus, there is a demand for an easy method of administering a medical agent by the patient him- or herself that does not involve the use of a syringe but can eject the medical agent in the form of droplets and drive them to reliably reach the lungs.

Recently, there have been proposed methods for ejecting a physiologically effective medical agent by a predetermined number of droplets of proper size from a discharge orifice into an airflow to be inhaled through a mouthpiece or the like under the effect of a bubble jet or a piezoelectric element arranged in an ejection head section (ejecting section) (see International Publication WO95/01137 and International Publication WO02/04043).

DISCLOSURE OF THE INVENTION

The proposed apparatus make it possible to eject droplets of uniform size. However, since the ejection head section of the apparatus is directly subjected to negative pressure that is produced by the atmospheric pressure as pressure difference at the time of inhalation, liquid can leak from the orifice also at the time of inhalation. When liquid leaks, it is not turned into droplets of proper size and liquid is no longer ejected from the clogged orifice. Then, it is no longer possible to eject droplets by a predetermined quantity. Additionally, the ejection head section is directly subjected to negative pressure to curtail the service life of the ejection head section. Thus, the proposed apparatus can hardly find practical applications.

In view of the above-identified problems, it is therefore the object of the present invention to provide an inhaling apparatus to be used by a user to inhale a liquid medical agent from an inhalation port thereof, the apparatus comprising: a liquid medical agent ejecting section having an ejection port for ejecting a liquid medical agent as droplets; and a pressure detecting section for detecting the negative pressure produced by the atmospheric pressure as pressure difference at the time of inhalation of the user for the purpose of controlling the ejection of droplets from the ejection port; the ejection port of the liquid medical agent ejecting section being arranged at a position producing a pressure difference smaller than the pressure difference with the atmospheric pressure as detected by the pressure detecting section at the time of inhalation.

In another aspect of the present invention, there is provided a mouthpiece to be removably fitted to an inhaling apparatus according to the invention to form a flow path for an airflow between an inhalation port and an external air intake port, the mouthpiece comprising: pressure alleviating means arranged on the halfway of the flow path to alleviate the negative pressure of the ejecting section; a part (e.g., a communication hole communicating with a negative pressure sensor, which will be described hereinafter) for receiving the pressure detecting section to be arranged therein, the part being arranged closer to the inhalation port than the pressure alleviating means; and a part (e.g., a liquid medical agent intake port, which will be described hereinafter) for receiving the ejection port of the liquid medical agent ejecting section to be arranged therein, the part being arranged closer to the external air intake port side than the pressure alleviating means.

In still another aspect of the present invention, there is provided an inhaling apparatus to be used by a user to inhale a liquid medical agent from an inhalation port thereof, the apparatus comprising: a flow path for forming an airflow by means of an inhaling action of a user, the flow path having the inhalation port at an end thereof; a liquid medical agent ejecting section having an ejection port arranged in the flow path to eject the liquid medical agent as droplets; and a pressure detecting section arranged in the flow path for detecting the negative pressure produced by the atmospheric pressure as pressure difference at the time of an inhaling action of the user; the ejection port of the liquid medical agent ejecting section being arranged at a position adapted to produce a pressure difference smaller than the pressure difference with the atmospheric pressure as detected by the pressure detecting section at the time of the inhaling action.

Thus, according to the present invention, since the ejection port of the liquid medical agent ejecting section is arranged at a position where the pressure difference with the atmospheric pressure is smaller than the pressure difference detected by the pressure detecting section at the time of inhalation, the risk of liquid leakage from the ejecting section is minimized to by turn minimize the adverse effect of leaking liquid on the service life of the ejecting section.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of an example of inhaler or inhaling apparatus according to the present invention;

FIG. 2 is a schematic perspective view of the inhaling apparatus of FIG. 1 in a state where the access cover is opened;

FIG. 3 is a schematic perspective view of an example of the CRG unit;

FIG. 4 is a schematic cross sectional view of an example of mouthpiece taken along a lateral surface thereof;

FIG. 5 is a schematic cross sectional view of the mouthpiece of FIG. 4 taken along the front surface thereof;

FIG. 6 is a schematic cross sectional view of the mouthpiece of FIG. 4, illustrating the position relation with the negative pressure sensor and the ejection head section of the CRG unit;

FIG. 7 is a schematic cross sectional view of the inhaler or inhaling apparatus of FIG. 1, showing the entire apparatus;

FIG. 8 is a graph illustrating an inhaling operation of the inhaler or inhaling apparatus of FIG. 1;

FIG. 9 is a flow chart of the overall operation of the inhaler or inhaling apparatus of FIG. 1;

FIG. 10 is a schematic cross sectional view of Embodiment 2 of the present invention, which is a parallel flow paths type, showing the configuration of the mouthpiece and its vicinity; and

FIGS. 11A and 11B are schematic cross sectional view of Embodiment 3 of the present invention comprising a valve, illustrating its operation.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be described. An embodiment of inhaling apparatus or inhaler according to the invention is designed to be carried by the user. It comprises a memory means for storing personal information of the user, including information on the medical chart and the medical prescription of the user. It is designed to eject micro-droplets of a liquid medical agent by a predetermined amount so as to have the user inhale the agent. The micro-droplets are highly uniform in terms of their sizes. With this embodiment, the user can put a mouthpiece, which has an inhalation port by way of which the user can inhale the liquid medical agent, and an ejection head cartridge (CRG) unit to an inhaler main body. The ejection head cartridge unit includes a tank containing the agent and is adapted to eject the agent supplied from the tank as micro-droplets. Thus, the user can efficiently and hygienically inhale the liquid medical agent according to the information provided by the prescription.

The flow path for establishing an airflow in the entire inhaler is formed only by the mouthpiece. The mouthpiece is provided on the halfway thereof with a narrowed section that operates as a pressure alleviating means. A pressure detecting section is arranged at a position closer to the user than the narrowed section (at the side close to the inhalation port) to detect the pressure there and the ejecting section of the CRG unit is arranged at a position closer to the external air intake port than the narrowed section. The liquid medical agent can flow out through the ejection port to clog the ejection port when negative pressure higher than a predetermined level (e.g., higher than −0.3 KPa (or greater than an absolute value of 0.3)) is applied to the ejection head section. Then, the liquid medical agent will not be ejected properly thereafter. However, the narrowed section prevents the ejection head section from being directly subjected to the negative pressure generated when the user inhales the liquid medical agent so that micro-droplets are continuously and smoothly ejected from the ejection port of the ejection head section. In other words, the ejection port of the ejecting section is arranged at a position where the pressure difference from the atmospheric pressure that is produced at the time of inhalation is such that the liquid medical agent would not be ejected naturally from the ejection port by the negative pressure produced by the atmospheric pressure so that micro-droplets of the agent are ejected smoothly. Micro-droplets of the liquid medical agent may be ejected in any mode of operation so long as they are ejected through an orifice. For example, thermal energy, piezoelectric energy or energy produced by pressurizing liquid may be utilized to eject micro-droplets through an orifice. However, the use of an ink-jet system, which may be a bubble jet system or a piezo jet system, is preferable. When an ink-jet system is used, liquid is supplied from a tank that is exposed to the atmosphere by the capillary force of a nozzle so that environmental pressure needs to be found within a range that allows the negative pressure produced by the tank and the meniscus of the ejection port to be well balanced with each other. From this point of view, the use of the arrangement of the present invention is very effective.

As shown in FIG. 8, an ejecting operation from the ejection port starts when the pressure detecting section detects negative pressure of a predetermined level. However, the lowest negative pressure that the pressure detecting section detects needs to be defined appropriately because the negative pressure produced in the pressure detecting section as a result of inhalation can vary from person to person and generally relates to the breathing capacity of the lungs. Considering about children and senior persons having a relatively small breathing capacity, the cross sectional area of the narrowed section is preferably defined to be about 10 mm²so that the negative pressure may be higher than −0.5 Kpa (or greater than an absolute value of 0.5). Then, it is possible for the pressure detecting section to accurately observe changes in the negative pressure produced as a result of inhalation (inhalation curve as shown in FIG. 8).

Since the flow path for establishing an airflow in the entire inhaler is formed only by the mouthpiece, the airflow section is contaminated by the liquid medical agent only in the flow path of the mouthpiece. In other words, the inside of the inhaler is held safe and hygienic only by washing the mouthpiece.

The efficiency of inhalation can be improved when more liquid medical agent is brought into the lungs of the user by changing some or all of the parameters (ejection speed, ejection time, etc.) relating to the ejection of the liquid medical agent typically according to the inhaled quantity (in other words depending on the change of the inhalation curve as shown in FIG. 8 that is detected by the pressure detecting section). When an inhaler according to the invention is equipped with an ejection control means that is adapted to change some or all of the parameters relating to the ejection of the liquid medical agent depending on to the change in the flow rate for inhalation (the change in the negative pressure) as detected by the negative pressure sensor within a predetermined time period for which the user inhales the liquid medical agent, it may additionally provided with a notification means that operates when the user could not inhale a predetermined quantity of the liquid medical agent within the predetermined time period so as to notify the user that he or she needs to inhale the liquid medical agent once again. Such an embodiment is easy to use because it minimizes cumbersome operations that have to be carried out by the user. Thus, such an embodiment can be used by anyone at anywhere.

An inhaling apparatus according to the invention may alternatively be configured in a manner as described below.

A valve that constantly and substantially closes the flow path of an airflow except when the apparatus is operated for inhalation may be used for the pressure alleviating means. Then, the pressure detecting section is arranged at a position closer to the inhalation port than the valve and the ejection port of the ejecting section is arranged at the opposite side of the valve. As the apparatus is operated for inhalation, the valve that has been closed starts opening. Then, the negative pressure is alleviated before it gets to the ejection port of the ejecting section located at the side opposite to the inhalation port at a slightly delayed timing so that the valve operates as a pressure alleviating means.

Still alternatively, the pressure detecting section and the ejection port of the ejecting section may be so arranged as to face respective flow paths coming from the inhalation port. With this arrangement, one flow path has its exit at the inhalation port, which inhalation port is formed around the exit of the flow path to show a profile similar to that of the mouth of human being and have a part forming another flow path. The pressure detecting section (with a communication hole communicating with the negative pressure sensor) is arranged as facing the another flow path.

Still alternatively, an inhaler according to the invention may be provided with a means for monitoring the inhaled quantity, utilizing the negative pressure sensor, (in other words, monitoring the inhalation curve as shown in FIG. 8) and notifying the user if the inhaled quantity is appropriate or not by flashing an LED or by changing the mode of vibration of a vibratory motor. Further, the inhaler comprises a means for notifying the user of the inhalation time period from the start of inhalation and when the inhalation should be stopped. As for the means for notifying the inhalation time period, a means that uses the vibration of the vibratory motor can be used.

Thus, an inhaling apparatus according to the invention having any of the above-described configurations can alleviate the physical and mental burden imposed on the patient (user) and allow the patient to inhale the (liquid) medical agent with ease. Therefore, an inhaling apparatus according to the invention can accurately control the patient's action of inhaling the medical agent according to the prescription and feed a greater amount of medical agent to the lungs than ever to improve the efficiency of inhalation so as to efficiently administer the medical agent by changing the drive parameters relating to the ejection of the liquid medical agent according to the quantity of the medical agent inhaled by the patient.

Now, the present invention will be described in greater detail by referring to the accompanying drawings that illustrate preferred embodiments of the invention.

Embodiment 1

FIG. 1 is a schematic perspective view showing the outer appearance of an inhaler according to the present invention. Referring to FIG. 1, there are shown an inhaler main body 1, an access cover 2 and a front cover 3, which constitute the housing of the inhaler. In FIG. 1, reference symbol 5 denotes a lock lever urged by a spring and having a claw-like part at the front end thereof that engages with a projecting section 2a arranged at the front end of the access cover 2 in order to prevent the access cover 2 from opening in operation. As the lock lever is driven to slide downward, the access cover 2 is turned around a hinge pivot (not shown) to become open by the resilience of the access cover returning spring (not shown) that urges the access cover 2. In FIG. 1, reference symbol 101 denotes a power supply switch and reference symbol 102 denotes a display LED which indicates that an ejection head cartridge (CRG) unit or a mouthpiece, which will be described in greater detail hereinafter, is not mounted in the housing or that the tank of the CRG unit is empty and no liquid medical agent is contained therein.

FIG. 2 is a schematic perspective view of the inhaler of FIG. 1 in a state where the access cover 2 is opened. As the access cover 2 is opened, the CRG unit 6 and the mouthpiece 4 that are mounted in the housing along a CRG guide 20 are exposed. The mouthpiece 4 is located under the CRG unit 6. They are mounted so as to be transversal relative to each other. FIG. 3 is a schematic perspective view of the entire CRG unit 6. The CRG unit 6 comprises a tank 7 for containing a liquid medical agent, a head section (ejecting section) 8 for ejecting the liquid medical agent, a part (electrically connecting section) 9 having an electric connection surface for supplying electric power from battery 10 (see FIG. 7) to cause the heater arranged in the head section 8 to generate thermal energy and so on. The battery 10 is rechargeable and operates as secondary cell for storing electric power in the inside of the inhaler in order to cause the heater to generate thermal energy. The front surface section of the CRG unit 6 can be opened around a hinge section 24 to allow access to the tank 7. A projection is typically formed on the rear surface of the front surface section so that the projection forcibly moves into the tank 7 and slightly applies pressure to the liquid medical agent in the tank 7 to refresh the ejection port of the head section 8 at the moment that the front surface section is closed.

FIGS. 4 and 5 are schematic cross sectional views of the mouthpiece 4. The mouthpiece 4 alone forms an airflow path and is provided at a part located close to its air intake port 11 with a window (liquid medical agent intake port) 12 for taking the liquid medical agent from the ejection port of the head section 8 of the CRG unit 6 into the inside of the mouthpiece 4. A narrowed section 4a is formed on the halfway of the mouthpiece 4 so as to gradually reduce the cross sectional area. As shown in FIG. 6 in detail, an air hole 13 is bored at a part of the flow path where the cross sectional area increases from that of the narrowed section 4a so as to make the flow path communicate with the measuring hole of a negative pressure sensor 19 for detecting the rate of inhalation or the inhaled quantity that is the value of the integral of the rate of inhalation by detecting the negative pressure there. The negative pressure sensor 19 is arranged on a control substrate 21 (see FIGS. 6 and 7). An expanded space 22 is arranged on the halfway of the flow path between the air hole 13 and the negative pressure sensor 19. The expanded space 22 operates as pool for storing dirt, dust, water drops and the liquid medical agent in order to prevent them from entering through the air hole 13 and adhering to the surface of the negative pressure sensor 19 so that the inhaler may not operate improperly.

A mouthpiece exit (inhalation port) 15 is formed at the end of the mouthpiece 4 opposite to the air intake port 11 so as to show a profile adapted to be held in the mouth of the user. The mouthpiece exit 15 shows an elliptic cross section that matches the profile of the mouth of human being. The inside of the mouthpiece 4 has a dual structure and a flow path exit 14 is formed to allow the liquid medical agent to pass through the inside. The flow path exit 14 is so formed as to show a profile that makes its cross sectional area gradually increase because, if the exit increases its cross sectional area suddenly, the mixed fluid of air and the liquid medical agent can be expanded abruptly to adhere to some of the teeth of the user who is holding the mouthpiece exit in his or her mouth. Thus, the user is suggested to allow the end of the flow path exit 14 to slightly pass through his or her teeth when holding the mouthpiece exit 15 in the mouth. The end of the flow path exit 14 may be so formed as to slightly extend outward beyond the end of the mouthpiece exit 15 so that the user can allow the end of the flow path exit 14 to pass through the teeth with ease. As shown in FIGS. 1 and 2, the airflow path of the mouthpiece 4 shows a rectangular cross section so that the mouthpiece 4 can be mounted in the housing with the air intake port 11 reliably directed upward.

FIG. 7 is a schematic cross sectional view of this embodiment of inhaling apparatus, showing the entire apparatus. A control substrate 21 for controlling the inhaler is arranged below the battery 10. The control substrate 21 is connected to a probe substrate 16 by way of a cable or a connector (a connector 25 is used in FIG. 7), which probe substrate 16 is arranged below the CRG unit 6. A contact probe 17 is also arranged to connect the probe substrate 16 and the electrically connecting section 9 of the CRG unit 6 and electrically energize the head section 8 of the CRG unit 6 for the purpose of emission of heat. A vibration motor 18 is arranged in contact with the control substrate 21 in the space between the battery 10 and the mouthpiece 4.

Now, the operation of inhalation of this embodiment having the above-described configuration will be described by referring to FIG. 8.

As the user starts inhalation and the negative pressure (relating to the rate of inhalation or the flow rate) detected by the negative pressure sensor 19 reaches a level that allows ejection of the liquid medical agent to take place, the inhaler starts ejecting the liquid medical agent from the head section 8 of the CRG unit 6 under the control of the control substrate 21 and the vibration motor 18 starts vibrating at the same time to notify the user that the inhaler start ejecting the liquid medical agent. After the end of ejection of a predetermined quantity from the head section 8, the vibration motor 18 keeps on vibrating for a supplementary inhalation time that is determined on the basis of the rate of inhalation and the continuous inhalation time as computed from the negative pressure value of the negative pressure sensor 19 for the purpose of encouraging the user to inhale a quantity for supplementary inhalation and so that the ejected liquid medical agent may completely reach the lungs. As the vibration motor 18 stops vibrating, the user, or the patient, stops inhaling the liquid medical agent. With this arrangement, the process of ejecting the liquid medical agent and that of inhalation are interlocked with each other so that the liquid medical agent is reliably fed into the lungs to avoid a failure of insufficient inhalation.

As the result of the inhaling action of the user, air is fed into the mouthpiece 4 from the air intake port 11 to produce a mixed fluid of air and the liquid medical agent ejected from the ejection port arranged in the head section 8 of the CRG unit 6. The mixed fluid is then led to the mouthpiece exit 15 having a profile adapted to be held in the mouth of the user. The mouthpiece exit 15 is adapted to prevent the mixed fluid from leaking through the lateral ends of the mouth, minimizing the waste of the mixed fluid, and cause the mixed fluid to hardly collide with the obstacles in the mouth such as teeth so that the liquid medical agent may be efficiently inhaled into the body of the user.

This embodiment is provided with the vibration motor 18 because the user may not want to be known about his or her use of the inhaler and vibrations may be more preferable than sounds to the user as notification means. Thus, with this arrangement, the embodiment can be used by anyone at anywhere.

An example of overall operation of the inhaling apparatus will be described below by referring to the flow chart of FIG. 9. As the power supply switch 101 is turned on, the open or closed state of the access cover 2 is detected (S801). If the access cover 2 is open, the user is warned about it typically by means of the display LED 102. If it is closed, it is then detected if a CRG unit 6 is mounted or not (S802). In the example, if a CRG unit 6 is not mounted, a Bluetooth communication is started (S803) to exchange data with the user, including data on the quantity to be administered to the user (S804). The operation ends when the communication is completed (S805). This mode of operation may be utilized mainly by the doctor of the user.

If, on the other hand, a CRG unit 6 is mounted, the operation proceeds in a manner as described below. This mode of operation may be utilized mainly by the patient, or the user. As the user starts inhalation (S806) and the inhalation is detected, negative pressure is detected by the negative pressure sensor 19 when it reaches a predetermined level (S807). Then, the ejection head section 8 starts ejecting the liquid medical agent (S808). If it is not detected that negative pressure reaches a predetermined level, a warning for prompting the user to inhale harder may be issued.

The liquid medical agent is ejected for a predetermined time period after the start of ejection so that a predetermined quantity of the liquid medical agent may be ejected. The quantity is determined on the basis of the data read in by the inhaling apparatus. Subsequently, the negative pressure sensor 19 monitors the change with time of negative pressure due to inhalation and the inhaling apparatus detects if the predetermined quantity has been inhaled or not on the basis of the value of the integral of the change with time (S809). The time for starting the integral may be selected appropriately. Since the integrated value relates to the inhaled quantity of the mixed fluid of air and the liquid medical agent, it corresponds to detecting if the liquid medical agent has been inhaled by the predetermined quantity. The operation ends when the liquid medical agent has been inhaled by the predetermined quantity. Then, the vibration motor 18 stops vibrating. If it is not detected that the liquid medical agent has been inhaled by the predetermined quantity after the elapse of a predetermined time period, a warning is issued to the user typically by means of a change in the mode of vibration of the vibration motor 18 in order to prompt the user to inhale the liquid medical agent again (S806). In such a case, the quantity short of the quantity to be inhaled is computed (S810) and the quantity of the liquid medical agent to be ejected from the ejection head section 8, the inhalation time period (or the vibration time period of the vibration motor 18) and other necessary values are computationally determined accordingly.

Since the ejection port of the liquid medical agent ejecting section is arranged reliably at a position where the pressure difference with the atmospheric pressure is smaller than the pressure difference detected by the pressure detecting section at the time of inhalation in the above described embodiment, the risk of liquid leakage from the ejecting section is minimized to by turn minimize the adverse effect of leaking liquid on the service life of the ejecting section. Furthermore, the liquid medical agent is reliably and efficiently administered to the user by a predetermined quantity by way of a simple operation.

Embodiment 2

FIG. 10 is a schematic cross sectional view of Embodiment 2 of the present invention, which differs from Embodiment 1 only in terms of the configuration of the flow path to the pressure detecting section (the communication hole 13 communicating with the negative pressure sensor 19). In Embodiment 2, the communication hole 13 is arranged to the outside of the flow path exit 14 of the mouthpiece exit 15 located at the front end of the mouthpiece 4. With this arrangement, a negative pressure detecting flow path led to the negative pressure sensor 19 is completely separated from and arranged in parallel with the airflow path of the mouthpiece 4. When the mouthpiece 4 is mounted in the apparatus from the upper and front surface thereof, the mounting direction agrees with the direction in which the communication hole 13 comes tightly close to the negative pressure detecting flow path led to the negative pressure sensor 19. Thus, this arrangement is advantageous for preventing air from leaking. Then, negative pressure is reliably detected. Additionally, since the negative pressure detecting flow path led to the negative pressure sensor 19 and the liquid medical agent flow path are completely separated from each other, the negative pressure detecting flow path is minimally contaminated by the liquid medical agent to ensure a highly accurate detection of negative pressure. Otherwise, Embodiment 2 is identical with Embodiment 1.

Embodiment 3

FIG. 11A and 11B show Embodiment 3 comprising a pressure alleviating means that is different from the narrowed flow path of Embodiment 1. A valve 30 having a size substantially same as the cross sectional area of the flow path of the mouthpiece 4 is rotatably arranged between the communication hole 13 led to the negative pressure sensor 19 and the liquid medical agent intake port 12 receiving the ejection head section 8 in the flow path of the mouthpiece 4. The valve 30 is constantly held to state where it substantially closes the flow path as it is made to abut a valve stopper 31 as illustrated in FIG. 11A. The valve 30 is opened as shown in FIG. 11B when the user starts an inhaling operation. While relatively strong negative pressure is generated in the flow path space at the side of the negative pressure sensor 19 at this time, such strong negative pressure is not generated in the flow path space at the side of the ejection head section 8. Thus, the net results will be same as those of Embodiment 1. Otherwise, Embodiment 3 is identical with Embodiment 1.

The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.

This application claims priority from Japanese Patent Application No. 2004-225510 filed on Aug. 2, 2004, which is hereby incorporated by reference herein.

Inhaling Apparatus

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