US 8,037,899 B2 · Backflow preventer

Abstract

A first check valve has a narrow flow path portion (68) formed between an arcuate portion (46) of the outer periphery (45) of a support member and a second enlarged-diameter portion (11) of a casing. The narrow flow path portion (first portion of an intermediate flow path) is in fluidic communication with a back-pressure chamber (50) defined in the support member at the rear of the top of a valving element through a communicating passage (67) including a gap (66) between the outer periphery of the valving element and the inner periphery of a large-diameter portion (38) and grooves (27) on the rear surface of the top of the valving element. Thus, a low static pressure of fluid flowing through the narrow flow path portion is introduced into the back-pressure chamber to move the valving element by a large differential pressure during the supply of fluid, thereby allowing the valve opening to become larger than in the conventional apparatus and enabling a reduction of pressure losses. An intermediate chamber has a pressure chamber (130) defined therein by using a rigid partition. A high-pressure chamber (131) of the pressure chamber is in communication with the upstream side of the first check valve, and a low-pressure chamber (132) thereof is in communication with the narrow flow path portion. Thus, a valving element (136) is acted upon by a force larger than the differential pressure between the upstream side and an internal flow path (106) of the intermediate chamber, thereby allowing a relief valve (135) to be surely kept closed.

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Claims19

Dependent claims

A pressure-reducing backflow preventer comprising:

a first check valve;
a second check valve;
an intermediate chamber provided between said first check valve and said second check valve;
a relief valve provided in said intermediate chamber;
said first check valve comprising:
a first casing having a first flow path formed therein and a first valve seat formed at an intermediate portion of said first flow path;
a first valving element disposed in said first flow path, said first valving element movably positioned, at least partially in said first flow path, to selectively seat on and unseat from said first valve seat at one end thereof;
a first urging member that urges said first valving element toward said first valve seat;
a back-pressure chamber that movably receives at one end thereof at least a portion of said first valving element;
a narrow flow path portion downstream of a position at which said first valving element abuts against said first valve seat, an upstream end of said narrow flow path portion being brought into and out of communication with an upstream side of said first flow path in response to said first valving element unseating from and seating on said first valve seat, a downstream end of said narrow flow path portion being constantly in communication with a downstream side of said first flow path;
and
a communicating passage providing fluidic communication between said narrow flow path portion and said back-pressure chamber
said relief valve comprising:
a discharge port formed in a casing of said intermediate chamber, said discharge port having a relief valve seat;
a relief valving element movable to selectively seat on and unseat from said relief valve seat;
a relief valve urging member that urges said relief valving element away from said relief valve seat;
and
a differential pressure applying mechanism that applies a differential pressure, determined by a pressure differential between a fluid pressure at an upstream side of said first check valve and a fluid pressure in said narrow flow path portion, to said relief valving element in a direction against said relief valve urging member,
wherein said differential pressure applying mechanism comprises:
a pressure chamber comprising a high-pressure chamber and a low-pressure chamber separated by a pressure-receiving movable member;
and
a coupling member that connects said pressure-receiving movable member and said relief valving element which move in interlocking relation to each other,
wherein said pressure chamber is part of said intermediate chamber, and;
said pressure-reducing backflow preventer further comprising:
a high-pressure side communicating conduit providing fluidic communication between said high-pressure chamber and the upstream side of said first check valve;
and
a low-pressure side communicating conduit providing fluidic communication between said low-pressure chamber and said narrow flow path portion.

24 more elements

A pressure-reducing backflow preventer comprising:

a primary flow path;
a secondary flow path;
an intermediate chamber provided between said primary flow path and said secondary flow path;
a first check valve provided between said primary flow path and said intermediate chamber;
a second check valve provided between said intermediate chamber and said secondary flow path;
a relief valve provided in said intermediate chamber;
said first check valve comprising:
a first casing having a first flow path formed therein and a first valve seat formed at an intermediate portion of said first flow path;
a first valving element disposed at the downstream side of the first valve seat in said first flow path, said first valving element movably positioned in said first flow path to selectively seat on and unseat from said first valve seat;
a first urging member that urges said first valving element toward said first valve seat;
said first check valve further comprising;
a substantially circular cylindrical first valving element support fixedly disposed centrally in said first flow path downstream of the first valve seat, said first valving element support movably supporting said first valving element, and
a first intermediate flow path which is annular in section formed between an outer periphery of said first valving element support and an inner periphery of said first casing,
wherein said first valving element comprises:
a head portion having a top portion for seating on and unseating from said first valve seat and a column portion extending in the downstream direction,
wherein said first valving element support comprises;
a recess movably receiving said column portion of the first valving element;
wherein said first intermediate flow path comprises a first narrow flow path portion extending from a position corresponding to a mouth of said recess toward the downstream side, said first narrow flow path portion being narrower than the rest of said first intermediate flow path in the flow path area,
said first check valve further comprising;
a first communicating passage formed between an inner periphery of said recess and an outer periphery of said column portion of the first valving element for connecting said first narrow flow path portion of said intermediate flow path to the inside of the recess on the rear side of said head of the first valving element;
and
said relief valve comprising:
a discharge port formed in a casing of said intermediate chamber, said discharge port having a relief valve seat;
a relief valving element movable to selectively seat on and unseat from said relief valve seat;
a relief valve urging member that urges said relief valving element away from said relief valve seat;
and
a differential pressure applying mechanism that applies a differential pressure, determined by a pressure differential between a fluid pressure at an upstream side of said first check valve and a fluid pressure in said first portion of the intermediate flow path, to said relief valving element in a direction against said relief valve urging member.

24 more elements

Dependencies are inferred from the claim text.

Description7,981 words

Summary1,928 words

#1. Technical Field

#The present invention relates to backflow preventers and, more particularly, to a backflow preventer in which check valves are provided at the upstream and downstream sides, respectively, and a relief valve is provided in an intermediate chamber formed between the two check valves.

#2. Background Art

Brief description of the drawings9 figures

#FIG. 1 is a front view showing the general structure of a pressure-reducing backflow preventer according to an embodiment of the present invention.

#FIG. 2 is a longitudinal sectional view showing a first check valve used in the backflow preventer of FIG. 1 that is in a water stop position.

#FIG. 3 is a longitudinal sectional view showing the first check valve used in the backflow preventer of FIG. 1 that is in a water supply position.

Detailed description5,844 words

#Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a front view showing the general structure of a pressure-reducing backflow preventer 1A (hereinafter referred to simply as “backflow preventer”) according to an embodiment of the present invention. The backflow preventer 1A comprises substantially three sections, i.e. a first check valve 1, an intermediate chamber 100, and a second check valve 200, which are located in the mentioned order from the upstream side when the backflow preventer 1A is actually used. In this embodiment, the first check valve 1, the intermediate chamber 100, and the second check valve 200 are constructed individually by using respective casings that are distinct from each other, and connected together by using joints 210 and 220 and connecting pipes 211 and 221. However, all the components of the backflow preventer 1A may be assembled into an integrated structure by using a single casing.

#The first check valve 1 will be explained below with reference to FIGS. 2 to 5B. FIGS. 2 and 3 are longitudinal sectional views showing the first check valve 1 in a closed position and in an open position, respectively. FIGS. 4A and 4B are a longitudinal sectional view and a right-hand side view, respectively, of a valving element 22 used in the first check valve 1. FIGS. 5A and 5B are a longitudinal sectional view and a right-hand side view, respectively, of a valving element support member 35 used in the first check valve 1.

#In FIGS. 2 and 3, a casing 2 comprises a casing body 3 and a retaining member 4 connected to the casing body 3 by thread engagement in this embodiment. The retaining member 4 is a member for installing a valving element assembly 21 (described later) inside the casing 2. The casing 2 is hollow throughout the body 3 and the retaining member 4 to form a through-hole 7. The through-hole 7 has openings at opposite ends thereof that are used as an inlet port 5 and an outlet port 6 when water flows in the forward direction (from left to right in FIG. 2). The terms “upstream” and “downstream” are used herein with reference to this “forward” flow direction.

Backflow preventer

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Backflow preventer

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Abstract

Drawings

Drawings

Claims19

Description7,981 words

Drawings

Classification9 codes

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Description7,981 words