Single lever keys
Introduction
A single-lever or single-lever is a type of tap for running water with a single control that regulates both the flow rate and the mixing of hot and cold water.
Currently, two main single-lever systems coexist to achieve regulation of the flow rate "Flow (fluid)") and the mixture: either by means of ceramic discs or by means of a metal sphere. In both systems, a simple drive reproduces the movement of the faucet handle, adjusting the position of the outlet holes with respect to the water supply holes (hot and cold), which is mixed inside the mechanism before exiting towards the mouth of the faucet.
History
The idea of the single-handle faucet dates back to 1937, when the American Alfred M. Moen was startled by a sudden jet of hot water when he went to wash his hands in his home in Seattle.[1] This problem associated with faucets with two independent drives (cold water and hot water) made him think of a system that would allow both flows to be regulated simultaneously with a single control (a concept from which the original English name "single-handle mixing faucet", translated, is derived). into Spanish as "single-lever faucet"). In early designs, a faucet controlled the flow rate, and a rotary knob regulated the temperature. It was not until 1947[1] when, under the impetus of Moen, the mixer acquired the appearance with which it is known today, with the characteristic handle whose inclination controls the flow and whose rotation regulates the temperature of the water.[1].
The next significant development was the design of standard "cartridges", which allow the faucet to be quickly repaired in the event of failure of the internal mechanism. This design was also devised by the Moen company.[2].
The system of flat ceramic discs that has subsequently been imposed and generalized in mixer taps due to its simplicity and robustness (almost completely displacing the more complex spherical or truncated conical valve systems), was patented in 1972[3] by the American company Wolverine Brass").[4].
As noted, the main advantage that has led to the widespread use of this type of ceramic disc faucets is that since they lack metal parts inside, they are practically immune to corrosion. In addition, its mechanism does not require the use of moving rubber gaskets. In this way, the dripping that inevitably occurs in the long term (due to the deformation of the rubber seals subjected to compression and decompression cycles) in the taps used by most other systems is avoided.