Reduced-pressure type backflow preventer

Abstract

The invention discloses a reduced-pressure type backflow preventer which comprises a valve body, two check valves with the same structure and a drain valve, wherein a cavity is formed in the valve body, and a water inlet, a water outlet and a drain opening are formed in the valve wall of the valve body; the two check valves are fixedly mounted in the valve body through support pieces and are located at the water inlet and the water outlet respectively; the drain valve is mounted outside the valve body and located at the drain opening; each check valve comprises a valve seat, a valve clack, a rocker and a twins torsional spring; one side of each valve clack is hinged to the upper end of the corresponding valve seat, and rollers are mounted on the other sides of the valve clacks; the rockers are connected with the lower ends of the valve seats through pin shafts; the rollers are propped against the rockers and slide on the rockers; the pin shafts are sleeved with the twins torsional springs; and the spring forces of the twins torsional springs act on the rockers to keep the valve clacks in a normally-closed state, and the rollers on the valve clacks are enabled to roll on the rockers by external forces to realize the opening of the valve clacks. Owing to the twins torsional spring-rocker structures of the check valves, the reduced-pressure type backflow preventer achieves a better flow prevention effect.

Description

technical field [0001] The invention relates to the technical field of pipeline valves, in particular to a decompression type backflow preventer. Background technique [0002] The backflow preventer is used in pipelines such as sewage treatment to prevent backflow pollution caused by the backflow of liquid in the flow direction. The backflow preventer is a valve device composed of two separated check valves and a safety drain valve. The structure of the existing check valve is too simple, and the resistance to the water flow is very obvious. The resistance of the check valve to water flow increases linearly with the increase of the opening of the disc, and when the pressure chambers of the backflow preventer produce small pressure fluctuations, the safety drain valve frequently discharges water. [0003] In addition, the valve seats of domestic check valves are basically made of metal, and the fixed connection between parts must adopt traditional mechanical connections, su...

AI Technical Summary

Problems solved by technology

[0003] In addition, the valve seats of domestic check valves are basically made of metal, and the fixed connection between parts must adopt traditional mechanical connections, such as threaded connections. The valve seat must be drilled and tapped, and then Each component is fixedly installed in the valve seat through threaded connection, which consumes time and materials

Moreover, during the opening and closing process of the check valve, the components and the valve seat vibrate repeatedly, and the components are prone to loosening

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