Engaging and securing structure of flip-up eyeglasses

An engaging and securing structure of flip-up eyeglasses, comprising:

• a first lens provided with a first pivotal connection portion, wherein the first pivotal connection portion has two lateral sides each provided with a pivot block, the two pivot blocks face each other and are each formed with a pivot hole, the two pivot holes face each other, an engaging portion is provided between the two pivot blocks, the engaging portion is provided therein with a first engaging groove and a second engaging groove, and the first engaging groove and the second engaging groove are adjacent to each other and in a front-and-rear relationship;
• and
• a second lens provided with a second pivotal connection portion, wherein the second pivotal connection portion is pivotally connected to the first pivotal connection portion, the second pivotal connection portion has two lateral sides each provided with a pivot shaft, each said pivot shaft corresponds to and is engaged in one of the two pivot holes, the second pivotal connection portion is further provided with an engaging block between the two pivot shafts, the engaging block corresponds in position to the engaging portion, the engaging block has a non-circular cross section and forms a plurality of contact surfaces with respect to the engaging portion, each two adjacent said contact surfaces form a corner defined as an engaging corner, and any of the contact surfaces is selectable to lie flat on the engaging portion, or any of the engaging corners is selectable to be engaged in the first engaging groove or the second engaging groove, such that the second lens is able to be secured at a plurality of angular positions with respect to the first lens.