| 摘要 |
<p>In a fluid control valve, a force acting on the spool is produced by the inevitable inclination of the fluid flow into the spool chamber, and the force tends to be balanced by the fluid flowing over first and second surfaces of the spool, the inclination of the fluid flow as it leaves the spool chamber to a return port being less than, and of opposite sense to, the inclination of its entry. The fluid is received from the spool chamber by a chamber associated with the return port, the return port chamber being shaped to divert a portion of the fluid. In a known valve construction, the portion of the fluid is diverted to re-enter the spool chamber, to enhance the balancing force. In accordance with the present invention, however, the return port chamber is modified so that a portion of the fluid flow is directed to form a stable vortex, the effect of the vortex ensuring that the whole of the fluid flow leaves the spool chamber at substantially the required inclination, increasing the balancing force in this manner. A second stable vortex may be formed to ensure the integrity of the fluid flow as it enters the spool chamber; and to enhance the stability of the first vortex.</p> |
