referring to fig1 and 2 , an adjustable ratchet buckle in accordance with a preferred embodiment of the invention comprises a cover 10 , a base 20 , two arms 30 , a ratchet 40 , a spring 50 , and a strap 60 . each component is discussed in detail below . a housing is composed of the cover 10 and the base 20 . the ratchet 40 is provided in the housing . a front opening 11 is formed in the cover 10 for permitting the strap 60 to insert thereinto . two openings 12 are formed on opposite sides of the cover 10 for permitting the arms 30 to dispose therein . the rear end of the cover 10 is secured to an object such as mask , goggles , etc . the cover 10 is somewhat curve in shape . two holes 13 are provided on both sides of the front opening 11 . a strut 61 is secured between the holes 13 . a first stub 14 is formed on the bottom of the top surface of the cover 10 . a plurality of through apertures 15 are formed in the cover 10 . the base 20 comprises a plate member 22 , two opposite ears 23 proximate both sides of the plate member 22 , the ear 23 having a through hole 23 a , two pins 24 besides the ears 23 for pivotably mounting the arms 30 thereon , and a plurality of front and rear projections 21 . the arm 30 comprises a toothed trigger 31 on an outer surface , a rear protrusion 33 on an inner surface , the protrusion 33 having an inclined bottom plane 33 a , and a front protuberance 32 on the inner surface , the protuberance 32 having a longitudinal hole 32 a rotatably put on the pin 24 . hence , the arms 30 are adapted to pivot about the pins 24 . the rear end of the trigger 31 will be stopped by the rear end of the side opening 12 when the arms 30 pivot outwardly ( i . e ., releasing the arms 30 ). hence , the arms 30 are allowed to pivot in a limited angle as detailed later the ratchet 40 is somewhat curve at both ends . the ratchet 40 is provided in the housing consisting of the cover 10 and the base 20 . the ratchet 40 comprises two pins 41 in the midpoints of both sides , the pins 41 being rotatably inserted into the through holes 23 a ( i . e ., the pins 41 being served as fulcrum ), a front section 42 , an engagement tooth 44 on the front end of the front section 42 , the engagement tooth 44 having an inclined plane ( or a curved plane in other embodiments ) 44 a , a rear section 43 having two rounded top corners ( or inclined planes in other embodiments ) 43 a on both sides , and a second stub 45 on the top of the engagement tooth 42 aligned with the first stub 14 . the spring 50 has both ends put on the stubs 14 , 45 . that is , the spring 50 is biased between the ratchet 40 and the bottom of the top of the cover 10 . after mounting the ratchet 40 in the cover 10 by assembling with the base 20 , and mounting the arms 30 on the pins 24 , the projections 21 are matingly inserted into the through apertures 15 for assemble the cover 10 and the base 20 as a complete housing . note that the fastening of the cover 10 and the base 20 may be implemented in a fashion different from the one described above . hence , a lever - like ratchet 40 is mounted . note that the engagement tooth 44 may be replaced by a detent member having the same function as the engagement tooth 44 as detailed later . referring to fig3 , the strap 60 has a plurality of parallel rack teeth 62 on a portion of an upper surface , referring to fig3 to 6 , an operation of the invention will be described in detail below . in an inoperative position ( see fig3 and 5 ), the arms 30 are not pressed with the inclined bottom planes 33 a of the protrusions 33 being disengaged from the rounded top corners 43 a of the rear section 43 , the front section 42 being biased downward by the expanding spring 50 , and the engagement tooth 44 being lockingly engaged with one of the rack teeth 62 ( i . e ., the strap 60 being prevented from moving in a direction as indicated by arrow in fig3 ). hence , the strap 60 is fastened . as shown in fig4 and 6 , an individual may press the arms 30 toward each other to lower the inclined bottom planes 33 a of the protrusions 33 . hence , the rounded top corners 43 a of the rear section 43 are pressed down by the inclined bottom planes 33 a of the protrusions 33 . and in turn , the front section 42 pivots upward about the pins 41 . also , the ratchet 44 moves upward . hence , a gap between the ratchet 44 and the strut 61 increases to permit the strap 60 including its rack teeth 62 to freely pass ( i . e ., the strap 60 being unfastened for being ready to adjust its tension by pulling in a direction as indicated by the arrow shown in fig4 ). at the same time , the spring 50 is compressed to store elastic energy . the spring 50 will immediately release its stored energy to push the front section 42 downward after releasing the arms 30 after adjusting strap tension . as a result , the buckle returns to its inoperative position as shown in fig3 and 5 . at this position , the strap 60 is lockingly engaged with the ratchet 40 . in other words , it is possible of adjusting the buckle in discrete increments to tighten the strap 60 . as shown in fig3 and 4 , the rack teeth 62 are of triangular in cross - section ( i . e ., any tooth having an inclined plane and a flat shoulder abutting an immediately adjacent tooth ) and the engagement tooth 44 is shaped to complement any one of the rack teeth 62 . a pulling of the strap 60 is thus made possible with the engagement tooth 44 being disengaged from one of the rack teeth 62 after pressing the arms 30 ( see fig4 ). hence , an adjustment of the tension of the strap 60 can be made in discrete increments in order to tighten the strap 50 . to the contrary , the engagement tooth 44 engages with one of the rack teeth 62 due to the lowering of the front section 42 after releasing the arms 30 after adjusting strap tension . as an end , the strap 60 is locked in this position . in brief , pressing the arms 30 will unfasten the strap 60 for adjusting strap tension . releasing the arms 30 will fasten the strap 60 in its tightened , locked position . moreover , the lever - like ratchet 40 makes the strap tension adjustment operation more precise and reliable . while the invention herein disclosed has been described by means of specific embodiments , numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims .