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A valve can varied in operating pressure and stopped in opening and closing by an efficiently movable actuator due to feeding of electric power without malfunction due to disturbance of magnetism, impact or temperature. A variable pressure valve is provided with a shape memory alloy spring. The shap

A valve can varied in operating pressure and stopped in opening and closing by an efficiently movable actuator due to feeding of electric power without malfunction due to disturbance of magnetism, impact or temperature. A variable pressure valve is provided with a shape memory alloy spring. The shape memory alloy spring is raised in temperature and varied in length by a secondary coil that is electromagnetically given power from a primary coil of a control probe. When the shape memory alloy spring varies in length, a feed ratchet performs linear movement to rotate a cam wheel. The cam wheel has a cam with which an urge spring and a rectifying lever at its one end is engaged. The urge spring and rectifying lever at their other ends engage a ball valve to vary an urge force on the ball valve due to rotation of the cam wheel.

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A valve can varied in operating pressure and stopped in opening and closing by an efficiently movable actuator due to feeding of electric power without malfunction due to disturbance of magnetism, impact or temperature. A variable pressure valve is provided with a shape memory alloy spring. The shap

A valve can varied in operating pressure and stopped in opening and closing by an efficiently movable actuator due to feeding of electric power without malfunction due to disturbance of magnetism, impact or temperature. A variable pressure valve is provided with a shape memory alloy spring. The shape memory alloy spring is raised in temperature and varied in length by a secondary coil that is electromagnetically given power from a primary coil of a control probe. When the shape memory alloy spring varies in length, a feed ratchet performs linear movement to rotate a cam wheel. The cam wheel has a cam with which an urge spring and a rectifying lever at its one end is engaged. The urge spring and rectifying lever at their other ends engage a ball valve to vary an urge force on the ball valve due to rotation of the cam wheel. low activated switch for coupling a voltage generating means across the first and second electrodes. 5. An inhaler according to claim 3, wherein the air flow activated switch comprises a closure member and spring biassing means normally biassing the closure member into a position closing off the supply of air into the housing through the air inlet, the closure member being movable against the spring biassing to a position allowing air to flow into the housing through the air inlet in response to the air flow. 6. An inhaler according to claim 1, wherein the housing is arranged to enable a user to create the air flow by breathing in through the housing outlet. 7. An inhaler according to claim 1, further comprising a pump for creating the air flow. 8. An inhaler according to claim 1, wherein the electric field creating means comprises: first and second spaced apart electrodes with the first electrode being provided at or adjacent the outlet of the liquid supplying means; and user-operable voltage supplying means for providing a potential difference between the first and second electrodes to create the electric field for causing comminution of liquid issuing from the liquid supplying means outlet to produce a stream of electrically charged comminuted matter, the first and second electrodes being spaced from the housing outlet and being arranged so as to provide, when a potential difference is applied across them by the voltage supplying means, and electric field which reduces rapidly in the direction of liquid flow from the liquid supplying means and the housing having an air flow path to the housing outlet for causing liquid comminuted by the electric field to be entrained by the air flow for supply via the housing outlet to the nasal passages of a user. 9. An inhaler according to claim 3, wherein the first and second spaced apart electrodes are spaced apart in a direction perpendicular to a flow of liquid from the liquid supplying means. 10. An inhaler according to claim 3, wherein the second electrode is located downstream of the liquid outlet. 11. An inhaler according to claim 1, wherein the electric field creating means comprises: first and second spaced apart electrodes with the first electrode being provided at or adjacent the outlet of the liquid supplying means; and user-operable voltage supplying means for providing a potential difference between the first and second electrodes to create the electric field for causing comminution of liquid issuing from the liquid supplying means outlet to produce a stream of electrically charged comminuted matter for supply via the housing outlet to the nasal passages of a user, wherein current-limiting means are provided for limiting the supply of current by the voltage supplying means. 12. An inhaler according to claim 11, wherein current-limiting means is coupled to one of the first and second electrodes. 13. An inhaler according to claim 11, wherein the current-limiting means comprises a dielectric or semi-insulating coating or sleeve provided on said one of the first and second electrodes. 14. An inhaler according to claim 8, wherein the voltage supplying means comprises an air flow activated switch for coupling a voltage generating means across the first and second spaced apart electrodes. 15. An inhaler according to claim 14, wherein the air flow activated switch comprises a closure member and spring biassing means normally biassing the closure member into a position closing off the supply of air into the housing through the air inlet, the closure member being movable against the spring biassing to a position allowing air to flow into the housing through the air inlet in response to a user breathing in through the housing outlet or in response to an air supply to the air inlet. 16. An inhaler according to claim 3, wherein the voltage supplying means comprises a further electrode positioned adjacent the second electrode and resistive means coupling the second electrode to earth, th