Backflow Preventer

Abstract

A reduced pressure zone backflow preventer comprising a body 12 entirely made of plastic material, formed with an inlet port ( 14 ) accommodating an inlet check valve assembly 120 and an outlet port accommodating an outlet check valve assembly 122 . The check valve assemblies extend along a coaxial axis coinciding with a longitudinal axis of the body. A central space 60 formed between the check valves is accessible through a service opening in the body. A relief valve assembly 70 is received within the central space and a drain port extends from the space. The relief assembly is responsive to pressure differential between the inlet port and the space by a flow passage extending between the inlet port and an upper side of a pressure diaphragm of the relief valve assembly.

1 . A reduced pressure zone backflow preventer comprising a body formed with an inlet port accommodating an inlet check valve assembly and an outlet port accommodating an outlet check valve assembly, said check valve assemblies extending along a coaxial axis coinciding with a longitudinal axis of the body, a central space formed between said check valves accessible through a service opening in the body, a relief valve assembly received within the central space and a drain port extending from said space; said relief assembly is responsive to pressure differential between the inlet port and the space by a flow passage extending between the inlet port and an upper side of a pressure diaphragm of the relief valve assembly; and wherein the entire body is made of plastic material.  
   
   
       2 . A backflow preventer according to  claim 1 , wherein the space accommodates a retention member fixedly receivable within the space and extending between the check valve assemblies so as to bear axial loads applied by said check valves, though without transferring axial loads between said check valve assemblies.  
   
   
       3 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly, the outlet check valve assembly, the relief valve assembly and a retention member are slidingly introduced through the service opening.  
   
   
       4 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly, the outlet check valve assembly, the relief valve assembly and a retention member are made of plastic material.  
   
   
       5 . A backflow preventer according to  claim 1 , wherein the body is made of reinforced composite plastic material.  
   
   
       6 . A backflow preventer according to  claim 1 , wherein the central space within the body has a longitudinal axis intersecting the longitudinal axis of the body at an essentially right angle.  
   
   
       7 . A backflow preventer according to  claim 1 , wherein the body assumes a shape of two cylindrical bodies intersecting at a right angle.  
   
   
       8 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly are replaceable modular elements.  
   
   
       9 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly are designed for foolproof assembly so as to prevent reverse assembly thereof within the body.  
   
   
       10 . A backflow preventer according to  claim 1 , wherein one or more test cocks are fitted to the body, each of which being in flow communication with a respective zone of the preventer and being selectively opened.  
   
   
       11 . A backflow preventer according to  claim 2 , wherein the retention member can be removed withdrawn for servicing the preventer even if a piston stem of the inlet check assembly is arrested at a position projecting into the central space.  
   
   
       12 . A backflow preventer according to  claim 2 , wherein the retention member is biased in its location within the central space by a spring of the relief valve assembly, whilst the retention member supports the spring and provide guidance for axial displacement of a stem member.  
   
   
       13 . A backflow preventer according to  claim 2 , wherein one of the retention member and the body is formed with at least one radially projecting rib, asymmetrically extending along the longitudinal axis thereof, for engagement with a corresponding groove formed in the other one of the retention member and the body.  
   
   
       14 . A backflow preventer according to  claim 1 , wherein the central space is fitted with a pair of parallel side walls.  
   
   
       15 . A backflow preventer according to  claim 14 , wherein the side walls are interconnected at their bottom ends via an arced surface.  
   
   
       16 . A backflow preventer according to  claim 14 , wherein the side walls constitute a double walled portion within the central space said parallel walls slidingly receive a retention member and reinforce the body.  
   
   
       17 . A backflow preventer according to  claim 1 , wherein a cylindrical portion within the body receiving the inlet check valve assembly has a first diameter at a portion adjacent the central space which is slightly larger in diameter than an end portion thereof adjacent an inlet end.  
   
   
       18 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly differ from one another in the shape of their distinguishable outer casing.  
   
   
       19 . A backflow preventer according to  claim 1 , wherein the central space is formed with a normally open discharge outlet, sealable by the relief valve assembly under liquid flow through the preventer.  
   
   
       20 . A backflow preventer according to  claim 19 , wherein a plastic spout is attachable to the discharge outlet.  
   
   
       21 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly are each fitted with a retraction tab or grove to facilitate extraction thereof from the body.  
   
   
       22 . A backflow preventer according to  claim 1 , wherein an inlet end and an outlet end of the body are fittable with a replaceable connecting member made of plastic material.  
   
   
       23 . A backflow preventer according to  claim 22 , wherein the connecting member is fixable to the respective inlet end and an outlet end of the body by a bracing coupler clampingly bracing a flanged rim portion of the connecting member to the body.  
   
   
       24 . A backflow-preventer according to  claim 1 , wherein the body is formed with a flow passage communicating between the inlet port and a control chamber of the relief valve assembly.  
   
   
       25 . A backflow preventer according to  claim 24 , wherein the flow passage is in flow communication with a test cock of the preventer.  
   
   
       26 . A backflow preventer according to  claim 24 , wherein the flow passage is formed by a bore extending from a flanged rim portion at an inlet end of the body, an opening of said bore being blocked by a plug.  
   
   
       27 . A backflow preventer according to  claim 26 , wherein the plug is retained in place by forehead portion of a connecting member fixedly coupled to the body.  
   
   
       28 . A backflow preventer according to  claim 1 , wherein all components of the preventer are fittable through the central space.  
   
   
       29 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly are modular assemblies each comprising a cylindrical capsule slidingly accommodate a sphere-like piston body fitted with a stem member supporting a coiled spring biasing the piston member into sealing engagement against a sealing seat surface thereof.  
   
   
       30 . A backflow preventer according to  claim 29 , wherein the inlet check valve assembly and the outlet check valve assembly are packed by a cover member snappingly engaged to the cylindrical capsule.  
   
   
       31 . A backflow preventer according to  claim 1 , wherein each of the body, the inlet check valve assembly, the outlet check valve assembly, and a retention member are formed with indicia corresponding to correct assembly and flow direction of the preventer.  
   
   
       32 . A backflow preventer according to  claim 1 , wherein the relief valve assembly comprises a resilient diaphragm supported by rigid plastic disc with a stem member downwardly extending and supporting at its bottom end a sealing ring sealingly engageable with a discharge outlet of the body.  
   
   
       33 . A backflow preventer according to  claim 32 , wherein sealing ring extends above a guiding portion sized so as to ensure smooth sliding within a tubular section at the discharge outlet.  
   
   
       34 . A backflow preventer according to  claim 32 , wherein a coiled spring of the relief valve assembly bears at one end thereof against the rigid plastic disc and at an opposed end thereof against a seat of a retention member of the preventer.  
   
   
       35 . A backflow preventer according to  claim 1 , wherein the inlet check valve assembly and the outlet check valve assembly comprise a piston body fitted with a sealing ring received in a circumferential grove of the piston body and retained by sealing ribs projecting between the seal ring and side walls of the groove in a watertight fashion.  
   
   
       36 . A backflow preventer according to  claim 35 , wherein the sealing ribs are integral with the sealing ring.  
   
   
       37 . A backflow preventer according to  claim 35 , wherein the sealing ribs are integral with walls of the groove.  
   
   
       38 . A backflow preventer according to  claim 1 , devoid of any metal components apart for springs and screws.