Hook structure and injection molded hook strap including the same

1. A hook, for an injection molded hook strap of a mechanical fastener, comprising:

a hook body having a base configured to be integrally formed with a substrate of the hook strap, at least one hook arm and a hook body side-curved portion corresponding to the at least one hook arm, the at least one hook arm including a hook end and a neck portion between the hook body and the hook end, the neck portion having an inner curved portion opposing to the hook body side-curve portion;

wherein the hook body side-curved portion is defined by a portion of a circumference of a first circle, the inner curved portion of the neck portion is defined by a portion of a circumference of a second circle and the hook end is defined by a portion of a circumference of a third circle, wherein the first, second and third circles satisfy following relationships:

a) the second circle inscribes the first circle at the interior of the first circle and the second circle contacts, without intersecting, the third circle at the exterior of the third circle;

b) an absolute value of a difference between a distance (Dl) measured from the center of the first circle (C 1 ) to a vertical central line (L) of the hook and a distance (D 2 ) measured from the center of the second circle (C 2 ) to the vertical central line (L) of the hook is less than 0.04 mm, i.e., <0.04 mm;

c) the radius (R 1 ) of the first circle (C 1 ) is no less than two times of the radius (R 2 ) of the second circle (C 2 ), i.e., R 1 ≧2R 2 ;

d) a distance (H 3 ) measured from the center of the third circle (C 3 ) to the substrate of the hook strap is less than a distance (H 2 ) measured from the center of the second circle (C 2 ) to the substrate of the hook strap, i.e., H 3 <H 2 ; and

e) an absolute value of a difference between the radius (R 2 ) of the second circle (C 2 ) and the radius (R 3 ) of the third circle (C 3 ) is less than 0.04 mm, i.e., <0.04 mm.

2. The hook according to claim 1 , wherein the at least one hook arm comprises a single hook arm extending in one direction.

3. The hook according to claim 1 , wherein the at least one hook arm comprises two hook arms extending in two different directions.

4. An injection molded hook strap of a mechanical fastener, comprising:

a substrate; and

a plurality of hooks according to claim 1 , 2 or 3 integrally formed on a surface of the substrate.