- A mechanism with automatic timed locking for a tap, such as a shower, sink or urinal tap, said mechanism comprising: - a hollow cylindrical housing inside which a hollow control rod is able to slide axially, the upper end of the control rod being secured to a tap control button, the lower part of the control rod emerging from the hollow cylindrical housing and carrying a valve associated with a seat made up of the lower part of the hollow cylindrical housing, the return of the valve onto its seat being caused by a compression spring arranged between the hollow cylindrical housing and the tap control button, the hollow control rod having, downstream of the valve, at least two radial fluid inlet channels and at least one radial fluid outlet channel, a first lip seal being arranged between the hollow cylindrical housing and the control rod, said first lip seal being located downstream of the at least two fluid inlet channels and upstream of the at least one fluid outlet channel; - a timing box whose upper part is fitted on the lower part of the hollow cylindrical housing and fluidically connected thereto, a timing piston that carries a second lip seal whose lip presses on the inner lateral surface of the timing box being able to slide in the timing box, said timing box being configured to be connected to a fluid intake of the tap by means of at least one fluid inlet opening arranged in the timing box, the inner lateral surface of the timing box including a longitudinal streak to allow a calibrated fluid leak between the part of the timing box below the second lip seal and the part of the timing box above the second lip seal when the timing piston moves, the second lip seal carried by the timing piston including an upper part partially inserted into a groove located at the base of the upper part of the timing piston, - at least one fluid outlet opening arranged in the hollow cylindrical housing downstream of the first lip seal and allowing fluid to flow toward the fluid outlet of the tap; and - a flow adjustment screw arranged inside the hollow control rod, the median part of said flow adjustment screw including a conical part configured to adjust the passage of fluid in the lower part of the hollow control rod so as to limit the flow of fluid flowing through the at least one fluid outlet channel; characterized in that: the upper part of the timing piston is inserted into the lower part of the hollow control rod and has at least two locking elements fitted in the at least two fluid inlet channels of the control rod, and in that said upper part of the second lip seal comes into contact with the lower end of the control rod to tightly close the lower end of the control rod. - a hollow cylindrical housing inside which a hollow control rod is able to slide axially, the upper end of the control rod being secured to a tap control button, the lower part of the control rod emerging from the hollow cylindrical housing and carrying a valve associated with a seat made up of the lower part of the hollow cylindrical housing, the return of the valve onto its seat being caused by a compression spring arranged between the hollow cylindrical housing and the tap control button, the hollow control rod having, downstream of the valve, at least two radial fluid inlet channels and at least one radial fluid outlet channel, a first lip seal being arranged between the hollow cylindrical housing and the control rod, said first lip seal being located downstream of the at least two fluid inlet channels and upstream of the at least one fluid outlet channel; - a timing box whose upper part is fitted on the lower part of the hollow cylindrical housing and fluidically connected thereto, a timing piston that carries a second lip seal whose lip presses on the inner lateral surface of the timing box being able to slide in the timing box, said timing box being configured to be connected to a fluid intake of the tap by means of at least one fluid inlet opening arranged in the timing box, the inner lateral surface of the timing box including a longitudinal streak to allow a calibrated fluid leak between the part of the timing box below the second lip seal and the part of the timing box above the second lip seal when the timing piston moves, the second lip seal carried by the timing piston including an upper part partially inserted into a groove located at the base of the upper part of the timing piston, - at least one fluid outlet opening arranged in the hollow cylindrical housing downstream of the first lip seal and allowing fluid to flow toward the fluid outlet of the tap; and - a flow adjustment screw arranged inside the hollow control rod, the median part of said flow adjustment screw including a conical part configured to adjust the passage of fluid in the lower part of the hollow control rod so as to limit the flow of fluid flowing through the at least one fluid outlet channel; the upper part of the timing piston is inserted into the lower part of the hollow control rod and has at least two locking elements fitted in the at least two fluid inlet channels of the control rod, and in that said upper part of the second lip seal comes into contact with the lower end of the control rod to tightly close the lower end of the control rod.