Submersible diaphragm pump with multi-stage speed reducing mechanism

The submersible diaphragm pump comprises a submersible motor, a first-stage speed reduction reversing mechanism, the multi-stage speed reduction mechanism, a crank connecting rod mechanism, a plunger and a diaphragm, the multi-stage speed reduction mechanism comprises a plurality of gear pairs, and a small gear of each gear pair is connected with an output shaft of the upper-stage gear pair; a pinion of the gear pair located at the input end is connected with a primary speed reduction transmission shaft; the crank connecting rod mechanism comprises a crank; an eccentric shaft of the crank is fixedly connected with one end of a connecting rod; the rotation center of the crank is fixedly connected with a large gear of a gear pair, located at the output end, of the multi-stage speed reduction mechanism. The plunger is fixedly connected with the other end of the connecting rod; the plunger is movably arranged in the cylinder sleeve; the diaphragm is fixedly arranged in the working cavity and divides the working c