Spray arm, and water pumping mechanism and cleaning machine thereof

A spray arm, comprising:

• a body (1;1′) having a top surface (1a;1a′), a bottom surface (1b) and a side wall (1c;1c′) between the top surface (1a;1a′) and the bottom surface (1b);
• a top plate (2;2′) disposed above the body (1;1′);
• wherein,
• the body (1;1′) has a flow channel (11) extending along a length of the body (1;1′);
• the body (1;1′) has a water inlet (12) in communication with the flow channel (11) arranged on the bottom surface (1b) of the body (1;1′);
• the body (1;1′) has a plurality of water spray holes (13) arranged on the top surface (1a;1a′) and/or the sidewall (1c;1c′) of the body (1;1′);
• an air collection chamber (20;20′) for storing air is defined between the top plate (2;2′) and the top surface (1a;1a′) of the body (1;1′), the positions of the water spray holes (13) are distributed corresponding to the air collection chamber (20;20′);
• the top plate (2;2′) has a plurality of spray openings (21) each corresponding to one water spray hole (13), and a gap (100) where negative pressure is generated during water flow spraying is formed between a top end of each water spray hole (13) and a bottom end of the corresponding spray opening (21);
• and an air inlet (154) in communication with the air collection chamber (20;20′) is arranged on the top plate (2;2′) and/or the side wall (1c;1c′) of the body (1;1′);
• the body (1;1′) has two ends and a central portion, the top surface (1a;1a′) of the body (1;1′) has a recessed area sinking downward which is defined as a drainage area (15;15′), a water outlet (151;151′) for draining water is arranged at an edge of the drainage area (15;15′).