Zero resistance slow open and close check valve

The utility model relates to a zero resistance slow open and close check valve; the inside of a valve body is provided with a closed control cavity consisting of the connection of a valve cover 5 and a separator 4. a spring diaphragm 6 divides a control cavity into an independent upper control cavity 16 and an independent lower control cavity 17. The upper end of a central shaft 10 is connected with the spring diaphragm 6 via a floating shaft 9, and the lower end of the central shaft 10 is connected with a linkage rod 21. The linkage rod 21 is fixedly connected with a valve flap 2 at the same time, and the seat 24 of the linkage rod is fixedly connected with the valve body 1. the valve flap 2 is movably connected with the linkage rod 24 via the shaft 12 of the valve flap. An external connection control system thereof includes control ducts 22, 23, a needle valve 13, a manual ball valve 19, a normally-open type solenoid valve 15, a normally-close type solenoid valve 14. The utility model has the beneficial effects of that firstly, the utility model can slowly open during the starting of the water pump; secondly, water resistance doesn't happen under normal operation; thirdly, the utility model can quickly close 90% during the stop of the pump or improper power failure and then slowly close; fourthly, the utility model can conduct non return. The utility model can replace electric valves, check valves, and the receiving device of a water hammer designed in prior mode, and energy consumption can be lowered greatly; the space usage of the device can be reduced greatly, and the utility model can run stably.