The present invention relates to ^' an air pressure generator for generating pressure pulses for the treatment of ears, said pulses being intended to be transmitted to the interior of an ear, said generator comprising a housing, a membrane located in said housing and means for actuating said membrane.

The air pressure generator according to the invention is inter alia intended to influence the hydrodynamic system of the inner ear and is for instance very suitable for use in the method for treatment of Meniere's disease described in EP-A1-0266474.

Background to the invention

A device of the kind described above is disclosed in the published International Patent Application WO 83/02556. This prior art device thus comprises first means for generating a static pressure level in a reservoir and second means for varying the static pressure level. Said first means is a diaphragm pump comprising a membrane actuated by a piston rod and said second means comprises a valve for temporarily reducing the static pressure in the reservoir. It seems that the parameters are adapted to different treatments or to different patients solely by a manual adjustment of the mechanical parts of the device.

A similar device is disclosed in the International Patent Application WO 86/01399. This device comprises two rotary pumps. Each pump is connected to a respective three-way valve. Both valves are connected to an ear plug. The speeds of the pumps and the positions of the valves can be controlled in response to a program stored in a micro¬ computer and in response to a pressure transducer sensing the momentary pressure. The program in the microcomputer

is to contain all necessary data regarding the parameters for the series of pressure pulses. The pulses are intended to have a substantially sinusoidal modulation.

However, in some instances a continuously working pump building up a continuous superat ospheric pressure, irrespective of whether it is a membrane pump or a rotary pump, may produce high-frequency overtones which are undesirable when treating ears according to the method described above. Such undesirable overtones also can be produced by valves when such are used for generating the pressure variations. It also has proved to be important that the pressure pulses follow the desired softly shape.

Brief description of the inventive concept

The objects of the invention is to create an improved air pressure generator which avoids the undesirable high frequency overtones described above and which generates pressure pulses having a softly curved shape.

These and other objects are achieved in that an air pres¬ sure generator of the kind described introductorily is designed such that said membrane and said housing form a chamber connected by suitable connecting means to the ear, said chamber and said connecting means forming a closed system in the working position of the generator, said pressure pulses being generated by the direct action of the displacements of said membrane caused by said actuating means on the enclosed air in said closed system. In preferred embodiments said membrane is pre-tensioned and, if necessary, is moved to a pre-tensioned zero position by means of said actuating means when the generator is to be used and such that said actuating means comprises an elongate member which is attached to said membrane and which is driven by an electrical motor, said elongate member comprising a first and a second part being

provided with complementary threads being in engagement with each other, said parts being rotatable relative to each other by means of said electrical motor in response to signals from a control circuit, by which means said membrane can displaced, thus generating said air pressure pulses. These parts can be made in a very light-weight design and consequently there is no large inertia to be overcome when the rotational speed or direction of the motor is changed. This means that the air pressure generator can respond very fast to signals from the control circuit.

That the pressure is regulated directly at the source and without the use of any valves means that the high- frequency overtones discussed above can be avoided.

The fact that the membrane is pre-tensioned has two impor¬ tant advantages.

One advantage is that the membrane will not flutter in an uncontrolled way around the neutral, untensioned position, which would mean that it would be difficult to control the shape of the pulses. A pre-tensioned membrane will however generate pulses with the desired softly rounded shape.

Another advantage is that the mechanical parts of the actuating means will be spring-biased by the tension in the membrane which in turn means that any play between these mechanical parts will be taken up and that the actuating parts consequently also for this reason will respond immediately to a change in the driving force. This is important in view of the rapidity and the regularity desired in the sequence of pressure pulses in the above method.

Short description of the appended drawings

Fig 1 illustrates a relatively detailed section through a preferred embodiment of an air pressure generator according to the invention. The tubes connecting the generator to the ear and the electronic and electric circuits controlling the generator are only illustrated schematically.

Fig 2 illustrates an alternative driving system in an air pressure generator utilizing a friction wheel mechanism.

Fig 3 is a section III - III in Fig 2.

Fig 4 illustrates another driving system utilizing a rack and pinion mechanism.

Fig 5 illustrates yet another driving system, utilizing a cogged belt.

Detailed description of a preferred embodiment of the invention.

In the description given below the terms "upper", "lower", "longitudinal" etc only are to be construed as terms of convenience relating to the specific, appended drawing and its orientation. As can be seen in Fig 1, the air pressure generator comprises a generally cylindrical main housing 1 with a central bore 2. The upper end of the housing 1 is closed by a mounting plate 3 attached to the housing by means of screws 4. The mounting plate 3 is provided with a central hole 5 for the shaft 6 of a reversible electrical DC motor 1 _r which is attached to the upper side of the mounting plate 3 by means of screws 8. The hole 5 is coaxial with the central bore 2 of the housing 1.

The motor may for instance be a DC-micromotor of the type 2842 006 C supplied by Minimotor SA in Switzerland. This motor has an angular acceleration exceeding the necessary

40 000 rad/sec ² . Of course any suitable similar motor may used, including step motors and motors provided with pulse counters.

The shaft 6 of the motor 7 is coupled to an actuating rod comprising two parts 9 and 10 by means of a coupling 11. The upper part of the first or upper part 9 of the ac¬ tuating rod is rotatably journalled in a bearing 12 loca¬ ted in the upper part of the central bore 2. The lower part of the part 9 is provided with threads. The second or lower part 10 of the actuating rod is tubular and is provided with internal threads. The second part 10 is non- rotatably but slideably supported in a slide bearing 48 located in the lower part of the central bore 2. When the the first part 9 is rotated by means of the motor 7, the lower part 10 will move upwards or downwards in dependance of the direction of rotation of the motor.

The lower end of the second part 10 of the actuating rod is located in a chamber 13 formed in the lower part of the housing 1 by a circumferential flange 14 and a lower mounting plate 15 attached to the housing 1 by means of screws 50. Two plates 19 and 20 are attached to the lower end of the second part 10 by means of a screw 21 threaded into the internal threads of the second part 10. One of the plates 19, 20 is provided with a circumferential groove clamping a complementary bead 17 on the inner rim of a ring-shaped, elastic membrane 16 which for instance may be made of rubber. The outer rim of the membrane 16 is also provided with a circumferential bead 18 clamped in a circumferential groove between the mounting plate 15 and the rim of the flange 14. A movement of the second part 10 upwards or downwards thus will result in a movement of the membrane 16.

The plates 19, 20, the membrane 16 and the lower mounting plate 15 form an air-tight chamber 24 in the chamber 13

having an outlet 22 for connection to an air tube or conduit 23. The lower mounting plate 15 also is provided with a check valve 29 allowing air to enter the air-tight chamber 24. One important function of the check valve 29 is to prevent any negative pressures in the chamber 24 when the membrane moves upwardly since such negative pressures may be harmful to the ear. The remaining part of the chamber 13 is vented to the ambient atmosphere by means of an opening 49.

The housing 1 further is provided with a relatively large opening 25 in its side which is intersected by a lon¬ gitudinal, excentric bore 26. The bore accommodates a longitudinal sensor rod 27 attached to the upper plate 19 and the opening 25 accommodates a plug 28 carrying two optical sensors 30,31 located a longitudinal distance from each other such that the sensor rod 27 will pass the sensors when moved longitudinally in the bore 26. The optical sensors thus can emit a signal each time the end of the sensor rod passes a sensor. The sensor rod 27 also will lock the plate 19, and thus also the second part 10, against rotation.

The air conduit 23 is connected to a pressure sensor or transducer 32 via a conduit 38 and to a pressure relief valve 33 via conduits 37 and 39. The conduit 37 also is connected to an ear plug 35 for connection to an ear 36 via a conduit 40, a restrictor valve 34 and a conduit 41.

The function of the pressure relief valve 33 is to prevent any harmful high pressures that may caused in the chamber 24 and the air conduits in case of a malfunction of the air pressure generator. The pressure relief valve 33 may for instance be set to open at a pressure of 35 cm H ₂ 0. The restrictor valve 34 serves to equalize and smoothen the pressure pulses in case the pulses for some reason should become deformed. A further important function of

the restrictor valve 34 is that may delay the build up of the pressure in the conduit 41 leading to the ear plug 35 if the pressure relief valve for some reason should be slow in responding.

A control unit 37 which comprises a power supply unit and a microprocessor is connected to the motor 7, to the pressure transducer 32 and to the optical sensors 30, 31 via leads 42, 43, 44, 45, 46 and 47. The control unit is arranged to vary, and, when necessary, to reverse the polarity of, the power supplied to the DC motor 7 in response to signals received from the optical sensors 30, 31 and the pressure transducer 32 in dependance of a program stored in the microcomputer. The program also contains parts controlling the optical sensors 30, 31 in such a way that they will serve as limit switches sensing and defining the upper and the lower position of the sensor rod 27 and thus also the upper and lower limits for the movement of the actuating rod and the membrane.

It should be noted that it is important that the system formed of the chamber 24, the conduits 23, 37, 40 and 41 and the ear plug 35 essentially is a closed system and that the membrane does not normally function as a pump even if smaller leaks in the system can be accommodated as described below in connection with the descripton of the function of the invention.

Function of the invention.

Before use, a program containing the desired momentary pressure expressed as a function of the time for a specific treatment (for instance sinusoidal functions of the kind described in the above-mentioned EP-A-0266474) is stored into the micro-computer as a reference. The program normally is adapted to a particular patient and/or to a particular treatment.

The parameters may for instance be chosen as follows:

Fix parameters.

Minimum pressure: 33% of the maximum pressure. Length of the pauses: 5 sec.

Variable parameters.

Maximum pressure: 10 - 30 cm H ₂ 0

Number of pulses: 1 - 18

Frequency: 1 - 10 Hz

Pulse length: 0.1 - 2.0 sec

The. number of pulses is of course limited in dependence of the chosen frequency. The active pulse-train should have a maximal duration of 2 seconds. The pulse length is however only relevant in single-pulse mode.

When the air pressure generator is switched on, the control unit 37, by means of the upper optical sensor 30, checks if the upper end of the sensor rod 27 is located at the optical sensor. If not, the control unit 37 will supply power to the electrical motor 7 until the end of the sensor rod 27 reaches the upper sensor 30. During this movement, air will enter the chamber 24 through the check valve 29. In this position the membrane 16 will be pre- tensioned and the chamber 24 will contain a defined volume of air. This air volume will be sealed from the ambient atmosphere when the ear plug 35 is inserted in the ear 36.

When the treatment is to begin, the ear plug is inserted into the ear and the air pressure generator is started, which results in that the control unit 37 energizes the motor 7 which starts to rotate, causing the second rod part 10 and the membrane 16 to move downwards. This raises the air pressure in the chamber 24 and in the conduits. The air pressure in the chamber 24 and in the air conduits

is continuously monitored by the control unit 37 by means of the pressure transducer 32 and is continuously compared with the desired pressure at this particular point of time as stored in the control unit. Any differences between the actual pressure and the desired pressure will immediately be transformed into a change in the electrical power supplied to the motor, which in turn results in a change in the speed or the direction of travel of the actuating rod and the membrane. In this way a train of pressure pulses can be generated which closely follows the ideal curve as stored in the control unit. It should be remem¬ bered that the check valve 29 will not open and admit air into the chamber 24 at the upward movements of the membrane as long as there is a εuperatmospheric pressure in the chamber.

Normally the curve has such a shape that the membrane oscillates around a point located somewhere in the upper half of the distance between the upper and the lower limit of travel depending on the desired maximum and minimum pressure. Should there however be a small air leak in the system, for instance at the ear plug, this will be compen¬ sated for in that the point of oscillation of the membrane will slowly be moved downwards concurrent with the loss of pressure until the sensor rod reaches the lower limit switch. A signal will then be sent to the control unit which will cause the actuating rod and the membrane to return to the original upper position during which movement air may be admitted through the check valve 29. The treatment then can continue if this is desired.

Possible modifications of the invention

The invention of course can be modified in many ways within the scope of the appended claims.

For instance, the limit switches have been illustrated as comprising optical sensors, but may of course comprise any kind of remotely-sensing devices, such as magnetical sensors. Although it for instance is conceivable to use mechanical micro-switches, it is preferable to use limit devices not touching the movable mechanical parts.

In the preferred embodiment the second part 10 of the actuating rod is locked against rotation by means of the sensor rod 27. This of course can be achieved in any other suitable way, for instance by means of splines or similar. It may also be possible to sense the movement of the second part directly without using a separate sensor rod.

As illustrated in Figs 2 and 3, the actuating means may comprise a friction wheel 260 frictionally engaging an actuating rod 209 located in a longitudinal bore 202 in a housing 201 and attached to the membrane 216 in the same way as the actuating rod in the preferred embodiment described above. Although not shown here, the air pressre generator comprises control systems and connections identical or similar to the systems described above in connection with the preferred embodiment. The friction wheel 260 is attached to the shaft of the electrical motor 207 and in the embodiment depicted is provided with two flanges 265 so that the wheel will partly embrace the actuating rod, which in this case is partly circular in section. The actuating rod is supported by two supporting wheels 264, 265 opposite to the friction wheel and the rod is clamped between the friction wheel and the supporting wheels with a predetermined force. This force may for instance be obtained by adjusting the relative positions of the motor and the supporting wheels accordingly or by spring-biasing the the friction wheels against the supporting wheels or vice versa. One possibility is to design the friction wheel as comprising two beveled discs, their beveled sides facing each other, which are spring-

loaded against each other and which consequently form the flanges. It should be noted that the friction wheel may be shaped in many different ways as long as there is an frictional engagement between wheel and rod. This frictional engagement will ensure that the rod moves in dependence of the rotations of the electric motor in response to signals from the control system.

Two limit switches 231 and 232 detect the movements of the actuating rod 209.

The actuating means may also for instance comprise a rack driven directly by a pinion mounted on the shaft of the electrical motor as illustrated in Fig 4.

The embodiment shown in this drawing also is assumed to be provided with the control systems and connections desribed above. In this embodiment the actuating rod 109 is located in a longitudinal bore in a housing 101. The rod is provided with a longitudinal row of teeth or serrations

166 on one side which are in engagement with teeth or cogs 163 on the periphery of a pinion 160 mounted on the shaft of an electric motor 107. Although no supporting wheels are shown opposite to the pinion, their provision is of course envisaged. It should perhaps also be noted that, in all the embodiments utilizing a reversible, longitudinal movement of the rod, the supporting wheels are not always necessary and that the rod also could slide on the wall, either directly or on rolls or similar. The rod 109 is attached to a lηembrane 116 in the same way as the rods in the embodiments described above. Limit switches 131 and 132 detect the movements of the end of the rod. The engagement between pinion and wheel will ensure that the rod moves in dependence of the rotations of the motor 107.

In a variant of the embodiment in Fig 4, shown in Fig 5, the cogs or teeth on the rod 309 in the bore 302 in the

housing 301 have been exchanged against cogs or teeth 367 on a cogged endless belt 365 attached to the rod by means of a screw 364 and carried on a pinion or cog wheel 366 on the shaft of an electrical motor 307 and on a supporting wheel 361. The rod is supported opposite the wheels 360 and 361 by means of supporting wheels 362 and 363. In a variant, the belt of course could be attached to the pinion and be provided with cogs or teeth cooperating with cogs or teeth on the rod. Alternatively, it is conceivable to have cogs or teeth on both sides of the belt cooperating with cogs or teeth on both the pinion and the rod.

An important advantage in these three alternative embodiments is that that the actuating rod does not need to be locked against rotation and, as mentioned above, the limit switches easily can be designed and placed to detect the movements of the end of the actuating rod. This may simplify the construction.