| 摘要 |
A magnetic flux-shifting or magnetic latch valve includes a first flux path including a first permanent magnet having a large coercive force so that its polarity cannot readily be altered. It further includes a second flux path including a second permanent magnet having a small coercive force so that its polarity can be altered. A valve according to this invention further includes a d-c source and a winding energized by said d-c source for altering the polarity of said second magnet. The fluid valve includes a valve element and a valve seat cooperating with the valve element. The valve has two limit positions, i.e. fully open and fully closed. In the fully closed position the pole surfaces of magnetic flux paths have the same magnetic polarity and hence do not attract each other permitting gravity, spring or hydrostatic means to form a gap therebetween. However, in the fully open position the pole surfaces of the magnetic flux paths have opposite magnetic polarities and hence attract each other, closing the aforementioned gap. To put it in other words, in the fully open position of the valve, the two magnets of the valve establish two parallel flux paths, while in the closed position of the valve the magnetic flux paths of both magnets are in series. The above structure makes it possible to operate the valve by mere d-c pulses, thus distinguishing from flux-shift valves that require sustained currents for maintaining the valve in one of its limit positions.
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