| 摘要 |
A system for maintaining a predetermined average liquid level in a pool comprises a pilot valve responsive to a float in the pool and a main valve controlled by the pilot valve to unblock a normally blocked supply conduit when the liquid in the pool drops below that level. The pilot valve, when opened by the float, lets incoming liquid under pressure-branched off the supply conduit at a point upstream of the main valve-enter a compartment under a membrane in the body of the main valve, that membrane carrying a control rod connected with a movable plate which coacts with a stationary plate obstructing the supply conduit inside the valve body; the two plates have apertures which are normally offset from each other but register upon pressurization of the membrane to give passage to the incoming liquid. The control rod passes with small annular clearance through a calibrated bushing in a bore communicating with the compartment under the membrane, that clearance forming a bleeder hole through which pressure liquid in that compartment can leak off to the downstream side of the supply conduit at least as long as the movable plate is in its unblocking position. The pilot valve may be provided with a similar pair of relatively slidable plates and a control rod which is coupled with a float-supporting lever by a double-jointed link.
|
