a rotary knob, which has an upper end surface that is marked with a closing symbol indicating closing and timing digit symbols respectively indicating different intervals of time counting;

a gear-set main body, which is formed of a plurality of inter-meshed gears arranged in an interior thereof, and is provided with a rotation axle, arranged at a center thereof and is also provided, at a bottom thereof, with a cam having a notch, and is further provided, at one lateral side thereof, with a push bar, the rotation axle being linked up with the gears, the rotation axle having a top end that is mounted and fixed to the rotary knob, the rotation axle having a bottom end that is mounted and fixed to the cam, the push bar comprising a prop block linked up with the cam, wherein rotating the rotary knob causes the rotation axle and the cam to rotate simultaneously therewith to start a timing operation, wherein the prop block of the push bar is driven by the cam to drive the push bar to carry out a rotating movement;

a guide plate, which is mounted to and fixed to the lateral side of the gear-set main body to face toward the push bar and comprises at least one guide tube, the guide tube being formed, in an interior thereof, with a channel having two opposite ends penetrating to outside of the guide plate, one of the ends of the guide tube facing toward the push bar, an opposite end of the ends of the guide tube being connected to the guide plate;

an elastic element, which is arranged between the push bar and the guide plate and has one end supported on the push bar and an opposite end supported on the guide plate, so as to provide an elastic spring force that, after completion of the timing operation, drives the push bar, together with the prop block thereof, back to their original positions; and

a push axle, which is in the form of a cylinder and comprises a push axle first end and a push axle second end, and is pivotally received in the channel of the guide tube, the push axle first end being in contact engagement with the push bar, and being drivable by a force acting on the push axle first end or the push axle second end to move.