| 摘要 |
<p>A magnetic device is formed from a permanent magnet (12, 14) generating magnetic flux, and an armature (10) which can occupy either a first air gap in which the flux is in one direction, or a second air gap in which the flux is in the opposite direction, with a region of flux cancellation between the two air gaps. At least one electromagnet winding (36, 38) may be provided to which current can be supplied which when energised produces a magnetic flux in one direction or the other, depending on the direction of the current, the flux from the winding increasing the flux density in one of the air gaps and reducing the flux density in the other air gap. This effectively shifts the flux cancellation region towards or into one of the two air gaps so as to produce a flux density gradient extending from one air gap to the other, which will cause the armature to move into (or remain in) the air gap having the higher flux density, and continue to remain in that air gap after the current flow ceases. The device can be incorporated into a fluid valve to act as a drive for opening and closing the valve. It may also serve as the drive for opening and closing electrical contacts. Monostable operation can be achieved by locating a magnetic flux shunt at one end of the armature travel. A holding solenoid may be incorporated. A plurality of such devices controlling the opening and closing of a plurality of orifices in a manifold containing fluid especially gas or air, under positive pressure, may be controlled by signals from a computer controlled signal generator to produce an air cushion for supporting and/or conveying articles, or a sound wave whose amplitude and frequency is controlled by the signal generator. Such a device may be incorporated into a pipeline to influence the flow of fluid therethrough or into the exhaust or inlet manifold of a turbine or engine, especially a jet engine, to interact with the gases flowing therethrough and introduce or reduce turbulence or otherwise alter the gas flow.</p> |
