the piston rod 171 the central channel communicates with the inclined channel of the hydraulic fluid discharge passage 15 the front end cap 101 is mounted on the front end of the cylindrical body 10 to close the hydraulic fluid reservoir 14 an air bladder 18 is mounted on the front end cap 101 inside the hydraulic fluid reservoir 14 the hydraulic fluid 141 in the hydraulic fluid reservoir 14 is outside the air bladder 18 the air bladder 18 communicates with the air discharge port 162 through a tube 19 and a joint not numbered on the front end cap 101 with reference to fig6 the air inlet 161 is opened when a second end of the pedal 11 is pivoted down to press the valve stem 166 and the air vent 163 is closed high pressure air flows into the air passage 16 and through the air port 164 into the piston chamber 13 and through the air discharge port 162 and the tube 19 into the air bladder 18 the high pressure air flowing into the piston chamber 13 causes the piston 17 to reciprocate the hydraulic fluid 141 in the hydraulic fluid reservoir 14 is pumped by the piston 17 into the hydraulic fluid discharge passage 15 and flows out from the hydraulic fluid discharge port 152 to the external hydraulic mechanism the air bladder 18 is inflated by the high pressure air through the tube 19 and the hydraulic fluid 141 in the hydraulic.