and corresponding to the light transmitting portion 120 of fig1 a cover 230 is hinge coupled to the cut out portion 12 and a seal 234 is disposed on an inner surface of the cover 230 in correspondence to the introduction opening 204 the seal 234 is attached to a protrusion 232 having a shape corresponding to the orifice portion 206 referring to fig5 a floating member 260 is installed in the reservoir 200 and the floating member 260 includes a coupling portion 262 hinge coupled to the floating member 260 at a lower side and an arm 264 extending from the coupling portion 262 an outer circumferential surface of the coupling portion 262 is partially exposed out through the light transmitting slot 220 and calibrations are formed on the outer circumferential surface of the coupling portion 262 with a constant interval therebetween the calibrations are exposed out of the cover plate 202 through the light transmitting slot 220 thereby allowing the user to check the remaining amount of the liquid on the outer circumferential surface of the coupling portion 262 not only the calibrations but also substantial numeric values or a plurality of regions having different colors may be displayed so as to directly display the remaining amount of the liquid a through hole 266 is formed near the end of the arm 264 like the through hole 166 of fig1 the through hole 266 is formed at a position overlapping the introduction opening 204 when the arm 264 is rotated to a maximum degree accordingly the liquid being injected into the introduction opening 204 is prevented from being dispersed out with colliding with the surface.