strap connecting element application_number US 67902403 A description as shown in fig1 and 3 a buckle 9 for straps according to a preferred embodiment of the present invention comprises an upper first shell unit 1 and a lower second shell unit 2 as well as a locking element 3 a moving element 4 and a pushing element 5 which are interposed between the first shell unit 1 and the second shell unit 2 the first shell unit 1 includes a cap 11 a releasing piece 12 mounted to the cap 11 and a first elastic member 13 interposed between the cap 11 and the releasing piece 12 the cap 11 has a stepped first snick at the front end thereof a perforation 112 shown in fig5 at the middle portion thereof a second snick 113 at the rear end thereof in addition the cap 11 in the interior also has two longitudinal ribs 114 parallel to each other and a first slot 115 adjacent to the second snick 113 and between the two ribs 114 the releasing piece 12 at the exterior has a ring of flange 121 and recess 122 defined by the flange 121 in the interior the releasing piece 12 also has a longitudinal second slot 123 at the central portion two triangular guiding tabs 124 respectively extended from two sides of the releasing piece 12 and two protrusions 125 respectively protruding outwardly from the distal ends of the guiding tabs 124 the assembly of the first shell unit 1 is completed by first putting the first elastic member 13 with one end thereof into the first slot 115 of the cap.