Self-closing measuring valves, particularly as embodied in lavoratory faucets, have been known in the art for many years. This type faucet is generally characterized by having a manually depressable handle which, when depressed, initiates flow through the faucet. Unless the handle is held in this manually depressed condition, the operating mechanism of the faucet valve acts to slowly close the valve, returning the handle to its uppermost position in readiness for a succeeding manual actuation of the slow self-closing faucet.
Slow closing lavoratory faucets offer the advantage of assuring that the faucet valve is closed in a matter of a few seconds time so that thereby water usage is conserved and, more importantly, that in the absence of an intending user, the faucet is fully shut off against continued or indefinite water flow through the faucet if the last user intentionally or otherwise overlooked turning off the faucet. Slow closing lavoratory faucets are particularly valuable in conserving water when employed in public washrooms, large institutions and the like.
The art also has recognized the desirability in slow self-closing lavoratory faucets of having an adjustability capability for the faucet valve so that the time during which the slow closing operation takes effect after handle depression and manual release of the handle initiates water flow can be changed. In some applications for these slow closing lavoratory faucets, it may indeed be desirable to have a longer flow duration than in installations where a relatively brief flow duration occurs between handle depression and water shut-off.
Frequently, slow self-closing lavoratory faucets in the prior art have employed a dash-pot form of delay mechanism. This type delay mechanism usually finds it necessary to incorporate a restrictor valve which in effect meters or restricts the flow of fluid into the mechanism, thereby slowing the mechanism down to gain the desired slow closing of the faucet valve which is under control of this mechanism.
This sort of restrictor valve is frequently quite sensitive to the presence of dirt or foreign material such as rust particles which are invariably present in large, and particularly old, city water systems. This foreign material flowing through the water system into the restrictor valve of the slow self-closing lavoratory faucet tends to build up and eventually clog the restrictor valve. Thereupon difficult and expensive cleaning of the entire slow self-closing lavoratory faucet frequently becomes necessary.
Attempts to handle this clogging problem by the use of filters or other screening techniques have only transferred the clogging problem from the restrictor valve becoming clogged to the filter or screen leading to the restrictor valve becoming clogged. In either event the slow self-closing valve requires expensive and frequent cleaning.
Further, prior art solutions to obtaining an adjustability capability for varying flow duration have not been entirely satisfactory. The adjustable feature to gain this varying flow duration capability is too often inaccessible from the exterior of the slow closing valve faucet, thereby making it necessary to undertake major disassembly of the faucet simply to obtain variation in the duration of the water flow after the handle is manually depressed.