Pump with variant strokes

A pump with variant strokes comprising:

• a body having
• a housing defined in a center of the body;
• an inlet cavity and an outlet cavity respectively defined in the body adjacent to two sides of the housing;
• two check valves mounted respectively at sidewalls of the inlet cavity to allow liquid flowing out of the inlet cavity;
• two check valves mounted respectively at sidewalls of the outlet cavity to allow liquid flowing into the outlet cavity;
• an entrance defined in the body and communicating with the inlet cavity;
• an exit defined in the body and communicating with the outlet cavity;
• and
• a communication hole defined in the body and communicating with the housing;
• a piston assembly mounted in the housing and having
• a piston seat having
• a first piston mounted in and extending out of the housing and having a first notch defined radially in an inside surface of the first piston;
• a second piston mounted in and extending out of the housing and having a second notch defined radially in an inside surface of the second piston;
• and
• two bars mounted between and connecting to the first piston and the second piston;
• and
• two elastic members mounted respectively between two ends of the piston seat and the body;
• a driving bearing having a central hole and engaging the first notch of the first piston and the second notch of the second piston wherein a holder is mounted in the central hole of the driving bearing, at least two openings are defined separately in the holder and distances between each one of the at least two openings and a center of the holder are different;
• a decelerating member mounted in the housing and connecting to one of the at least two openings of the holder.