The present invention proposes a cooking appliance (100) comprising a body (30), a control panel (40) provided on the body (30), a switch (50) for adjusting a power level of a heat source, the switch (50) comprising a shaft (60) extending through the control panel (40) and a control knob (70) connected to the shaft (60) for rotating the shaft, wherein said control knob (70) comprising an essentially hollow outer body (1) having an inner face, and an inner body (2) which is at least partly positioned inside the outer body (1) and wherein said outer body (1) is freely rotatable relative to the inner body (2) at a locked first position of the control knob (70). As an improvement, the inner body (2) being provided with a gear element (27) having a plurality of teeth (271), the inner face of the outer body (1) being provided with one or more coupling means (3) and each coupling means (3) is shaped and sized to engage with and be guided by corresponding gaps provided between adjacent teeth of the gear element (27) at an unlocked second position so that the outer body (1) and inner body (2) rotate together, when the outer body (1) is pushed and rotated at a potential engaging position.