Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-03-08
2001-01-30
Chambers, A. Michael (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S115160, C137S115180, C137S115210
Reexamination Certificate
active
06178998
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a reverse flow prevention apparatus for use mainly in a directly-connected water distribution system.
2. Description of the Related Art
As a conventional apparatus of this type, there is cited a pressure-reduction type reverse flow prevention apparatus a as shown in FIG.
10
. The pressure-reduction type reverse flow prevention apparatus a is provided with first and second check valves d, e, which are installed upstream and downstream, respectively, in a flow path c formed inside a casing b thereof and which operate independently from each other, and is further provided with an intermediate chamber g equipped with a pressure regulator mechanism f between the first and second check valves d, e.
The pressure regulator mechanism f is provided with a bypass h linking the intermediate chamber g with a portion of the flow path c, on the upstream side thereof, and is capable of adjusting a pressure inside the intermediate chamber g so as to be always lower than a pressure on the upstream side and higher than that on the downstream side by blocking up the bypass h with a diaphragm i, and linking an escape valve k for opening and closing a drain outlet j of the intermediate chamber g with the diaphragm i through the intermediary of a valve bar m.
However, the pressure-reduction type reverse flow prevention apparatus a described above has a problem that it becomes large in size and heavy in weight because it is provided with the pressure regulator mechanism f which is mechanically independent, that is, the bypass h, the escape valve k, and so forth.
Further, the pressure-reduction type reverse flow prevention apparatus a has another problem in that pressure loss therein is very large because the same is constructed such that a pressure inside the intermediate chamber g is lessened to a level lower than that on the upstream side thereof due to magnitude of a spring load of a first check valve spring n of the first check valve d, that is, because a condition is set such that a resistance at which the first check valve d is opened by flow of water is rendered large, and a pressure inside the pressure-reduction type reverse flow prevention apparatus a is caused to fall gradually from the upstream of the flow path c towards the downstream thereof.
SUMMARY OF THE INVENTION
In order to solve these problems described above, a reverse flow prevention apparatus according to the invention comprises an outer box provided with a flow path formed coaxially therewith between an inlet and an outlet, and also provided with a drain outlet in a midstream region of the flow path, a diaphragm provided on the inner periphery of the outer box for partitioning the interior thereof into an upstream region of the flow path, and the downstream of the midstream region, an inner cylindrical body slidably fitted into the upstream region of the outer box, an escape valve provided on a face of an open end of the inner cylindrical body, on the downstream side, so as to be freely attachable to and detachable from a valve seat provided around a valve port formed between the midstream region and a downstream region, and energized in the direction of valve opening by the urging of an escape valve spring, and first and second check valves provided inside the inner cylindrical body and the downstream region of the outer box, respectively, such that reverse flow of a fluid from the downstream side can be prevented, so that by setting an effective diameter of the diaphragm and a diameter of the valve seat of the escape valve substantially at an equal value so as to maintain a pressure balance between a pressure acting on the escape valve for valve closing and a pressure acting on the escape valve for valve opening while setting a spring load of a first check valve spring urging the first check valve in the direction of valve closing and that of the escape valve spring such that a pressure of the midstream region is maintained always lower by a predetermined value than a pressure on the upstream side, the pressure in the midstream region can be controlled without installing an independent pressure regulator mechanism as in the case of a conventional reverse flow prevention apparatus, thereby solving the problems as described above while drastically lessening pressure loss in comparison with that for the conventional reverse flow prevention apparatus.
REFERENCES:
patent: 2503424 (1950-04-01), Snyder
patent: 2706488 (1955-04-01), Harrington
patent: 2892464 (1959-06-01), Glass
patent: 4190071 (1980-02-01), Dean et al.
patent: 4232704 (1980-11-01), Becker et al.
Katou Makoto
Matsuura Nobuyuki
Ochiai Masaru
Chambers A. Michael
Flynn ,Thiel, Boutell & Tanis, P.C.
Kane Kougyou Co., Ltd.
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