Lid having locking flap handles with improved elastic hinges for airtight containers

1. A lid (200) for an airtight container (100) having an upper open end, the lid comprising:

• a lid body having a rim part defining a sealing depression (230) for receiving and for sealing to the upper open end of the container, the rim part having an upper surface and an outer surface (202) connected to the upper surface to define a rim part corner with the upper surface, the lid body including a plurality of locking flap handles (210) each connected to the lid body at the rim part corner for rotation of each locking flap handle (210) between an open position and locked positions with respect to the container (100), each of the locking flap handles (210) having a locking protrusion (212) to be locked to a locking depression (110) formed in an outer surface of the upper open end of the container (100) when the locking flap handles are in the locked positions;
  
  the locking flap handles each including a film hinge (220) having an elastic hinge part (222) connecting each respective locking flap handle (210) to the rim part corner, and a connection part (224) connecting the elastic hinge part (222) to a remainder of the locking flap handle (210) that has the locking protrusion (212);
  
  the elastic hinge part (222), when the locking flap handle (210) is in the open position, having an outer surface that forms a smooth, continuous, curved, uninterrupted and following surface with the upper surface of the rim part without having a stepped portion, the outer surface of the elastic hinge part (222) with the following upper surface of the rim part together being curved outwards at a single predetermined curvature, the elastic hinge part (222) having thickness that is at a minimum at the rim part corner, with the thickness of the film hinge (220) smoothly increasing in the connection part (224) in a direction toward the locking protrusion (212);
  
  the connection part (224) for connecting the elastic hinge part (222) to the remainder of the locking flap handle (210), extending a predetermined length (L) to disperse an impact generated when the locking flap handle is locked to the container; and
  
  wherein, when the locking flap handle (210) is in the locked position to the container, the elastic hinge part (222) is folded around an inner corner (IC) of the elastic hinge part that is at the rim part corner, forming a boundary between the elastic hinge part and the lid body, and the elastic hinge part is elastically in contact with the outer surface (202) of the rim part of the lid body.