Backflow preventing device with low opening pressure, low flow resistance and reliable check

Abstract

The invention discloses a backflow preventing device with low opening pressure, low flow resistance and reliable check. The backflow preventing device comprises a water inlet check valve, a water outlet check valve and a discharge valve, wherein the water inlet check valve and the water outlet check valve divide the backflow preventing device into a water inlet cavity, a middle cavity and a water outlet cavity; a first rubber diaphragm movably covers a first valve port between the water inlet cavity and the middle cavity through a water inlet spring, and isolates the water inlet cavity and the middle cavity; and in the state that an acting force F1 which is generated by multiplying an area S1 of the first rubber diaphragm in the outer ring water inlet cavity of the first valve port by water inlet pressure intensity P1 is larger than an acting force F3 of the water inlet spring on the first rubber diaphragm, the first rubber diaphragm is away from the first valve port, the water inlet cavity is communicated with the middle cavity, and the valve port of the water inlet check valve is open. The backflow preventing device has the characteristics of low opening pressure, low flow resistance and reliable check, the influence on water pressure of a terminal user is extremely small, water pressure of a specified outdoor fire hydrant outlet is met, and easily-damaged parts can be convenient to replace.

Description

technical field

[0001] The invention relates to a hydraulic control device for controlling fluid in a pipeline to flow only in one direction, in particular to a backflow preventer with low cracking pressure, low flow resistance and reliable non-return used on a tap water pipeline. Background technique

[0002] In foreign countries, backflow preventers must be installed on the water pipes to the end users, strictly restricting the water in the pipes to flow in one direction only, so as to prevent the backflow pollution of the pipes, and cities in our country are also implementing it one after another. The backflow preventer is a special device to protect the water quality of the main tap water pipeline. It is installed in front of the end user on the tap water pipeline. If the end user's water pressure is higher than the inlet water pressure, it can prevent the end user's water from flowing back into the main pipe.

[0003] There are two types of backflow preventers: decompre...

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