Fuel cap of internal combustion device

A fuel cap of an internal combustion device, wherein the fuel cap is mounted on a fuel tank opening of a fuel tank, the fuel tank having a plurality of gaps provided around a periphery of the fuel tank opening, an outer projecting wall circumferentially provided outside the fuel tank opening, and a fuel cap receiving chamber located between the fuel tank opening and the outer projecting wall, the outer projecting wall having a top surface provided with at least a positioning notch, the fuel cap comprising:

• a fuel cap body having a main body portion extending along an axial direction;
• a turning knob portion provided on a top surface of the main body portion;
• an assembly cavity located between the main body portion and the turning knob portion, extending along a radial direction, and having an open configuration;
• a slide groove provided on a cavity wall of the assembly cavity;
• and a plurality of engaging blocks protrudingly provided on an outer periphery of a bottom portion of the main body portion;
• a restraining element having a slide block slidable along a longitudinal direction of the slide groove and a pushing plate retractable into the assembly cavity;
• a resilient element resiliently compressed between the pushing plate of the restraining element and the turning knob portion of the fuel cap body so as to urge the restraining element to slide outward when the restraining element is retracted, wherein the slide block of the restraining element is normally resiliently pressed by the resilient element and therefore protrudes from an outer periphery of the fuel cap body;
• and
• a positioning element fixed in the assembly cavity of the fuel cap body so as to cover the slide block of the restraining element and prevent the pushing plate from coming off the assembly cavity, there being a space between the positioning element and the turning knob portion, the pushing plate of the restraining element being movable in the space in the radial direction;
• wherein the fuel cap body can be inserted into the fuel tank upon alignment between the engaging blocks of the fuel cap body and the gaps of the fuel tank;
• then the fuel tank opening is tightly closed by the fuel cap upon alignment between the slide block of the restraining element and one of the at least a positioning notch;
• and when the pushing plate of the restraining element is pushed inward, the slide block of the restraining element is retracted into the slide groove to allow removal of the fuel cap body from the fuel tank opening.