Fluid handling – Liquid level responsive or maintaining systems – By float controlled valve
Reexamination Certificate
1999-04-06
2001-07-24
Rivell, John (Department: 3753)
Fluid handling
Liquid level responsive or maintaining systems
By float controlled valve
C137S423000, C137S492000, C137S501000
Reexamination Certificate
active
06263905
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an automatic regulating valve apparatus to be installed in a fluid conducting line. More specifically, the present invention relates to an automatic regulating valve apparatus with a pilot valve unit based on a novel technical idea, capable of being easily formed in large size or high-pressure type, and of exercising excellent automatic control functions including a constant-flow control function, an emergency shutoff function, a liquid level control function and an upstream pressure control function, having a perfect sealing function and a clogging preventing function achieved by a self-cleaning operation, and convenient for application.
In this description, the terms “water” and “liquid” are used as general designations of fluids.
BACKGROUND ART
Various kinds of automatic regulating valve devices have been proposed. A lift valve apparatus disclosed in JP-B No. 2-46818 is a direct-acting constant-flow valve not provided with any pilot valve.
As shown in
FIG. 23
, this prior art lift valve apparatus has a valve casing
101
having an internal space divided into three passages, i.e., an inlet passage a an intermediate chamber u and an outlet passage c arranged in that order from an upstream side toward the downstream side, by a flow rate setting valve element
103
and an automatic restriction control valve element
104
. The respective pressure receiving areas of the valve element
103
and the automatic valve element
104
are substantially equal. A sealed chamber e defined by a sealing member
104
s attached to the automatic valve element
104
, and a valve top
102
is connected to the inlet passage a by a connecting passage t. The automatic valve element
104
is biased for automatic restriction control function by a balancing spring
105
. The automatic valve element
104
moves automatically in opposite directions according to the position of the valve element
103
corresponding to a set opening to maintain a constant flow rate.
This direct-acting constant-flow valve is used prevalently. However, the direct-acting constant-flow valve has unsolved problems in forming the same in large size and high-pressure type. The size of the balancing spring
105
increases inevitably as the size and the pressure capacity of the direct-acting constant-flow valve are increased, entailing difficulties in assembling, designing and manufacturing the direct-acting constant-flow valve. It is not easy to select a balancing spring
105
capable of properly controlling flow rate in a conduit in which pressure varies frequently.
Pilot-operated automatic regulating valve apparatuss provided with a main valve driving piston or diaphragm operated by a pilot valve, which adjusts flow rate with a fixed restriction passage such as a needle valve, are also used prevalently instead of the direct-acting constant-flow valve. A liquid level control valve provided with a float valve as a pilot is one of those valve apparatuses.
Referring to
FIG. 24
, this liquid level regulating or control valve apparatus has a main valve unit controlled by the opening and closing actions of a piloting float valve
230
. The main valve unit has a main valve casing
201
, a main valve element
205
disposed in the main valve casing
201
, and a main valve driving member
206
having a pressure receiving area greater than that of the main valve element
205
and combined with the main valve element
205
. A restricted passage is formed between the main valve element
205
and a main valve seat
204
. The main valve driving member
206
is fitted slidably in a space defined by a cylindrical wall
203
formed inside the main valve casing to form a main valve driving pressure chamber d between the cylindrical wall
203
and a valve top
202
. The float valve
230
closes when the liquid level on the downstream side of the main valve unit rises above a predetermined level and opens when the same drops below the predetermined level. The main valve driving pressure chamber d is connected to an inlet passage in an upstream end of the main valve unit by a connecting passage t provided with a fixed restricting valve
220
and is connected through the float valve
230
to the downstream side of the main valve unit. The pressure in the main valve driving pressure chamber d drops to the pressure in a passage on the downstream side of the main valve unit when the float valve
230
opens, and the main valve element
205
is moved in a valve opening direction to start supplying the liquid. In the meantime, the float valve
230
closes when the liquid level on the downstream side of the main valve unit rises above the predetermined level, the pressure in the main valve driving pressure chamber d rises to the pressure on the upstream side of the main valve unit, and the main valve element
205
is moved so that a sealing member
205
s
comes into close contact with the main valve seat
204
to stop supplying the liquid.
This prior art pilot-operated automatic regulating valve apparatus, however, needs troublesome maintenance and management work and has many problems in durability. The following are examples of those problems.
(1) Most of various sealing means for use as a sealing member
206
s
put on the main valve driving member
206
in contact with the cylindrical wall
203
are required to achieve perfect sealing not permitting leakage when the main valve unit is closed, and a bellows and a diaphragm have been employed as the sealing member
206
s
to solve the problem. When the pilot-operated automatic regulating valve apparatus is of a large size and a large pressure capacity, difficulties arise in the durability and machining accuracy of the sealing arrangement, and troublesome maintenance and management work is necessary; that is, the fluid is liable to leak downstream.
(2) The main valve unit must gradually be driven to prevent undesirable operations, such as chattering and hunting, due to pressure pulsation resulting from the change of flow. Therefore, the prior art pilot-operated automatic regulating valve apparatus needs the fixed restricting valve
220
forming a restricted passage, such as a needle valve, in the connecting passage t through which the fluid of the upstream pressure flows. This small restricted passage is clogged with sand and dust to cause troubles and hence a strainer or the like is necessary. Thus, it is difficult to use this prior art pilot-operated automatic regulating valve apparatus in fluid passages other than a fluid passage for a clean liquid.
The present invention employs a pilot valve unit based on a novel technical idea to realize a valve capable of being formed in a large size and a large pressure capacity, which could not have been realized by the prior art direct-acting constant-flow valve. Also, it is an object of the present invention to provide a pilot-operated automatic regulating valve apparatus capable of exercising excellent automatic control functions including a constant-flow control function, an emergency shutoff function, a liquid level control function and an upstream pressure control function, having a perfect sealing function, provided with a pilot valve unit not having any fixed restricting passage, such as a needle valve, and capable of exercising a clogging preventing function achieved by self-cleaning operation, capable of operating quickly without entailing chattering and hunting, and convenient for application.
DISCLOSURE OF THE INVENTION
With the foregoing object in view, the present invention provides an automatic regulating valve apparatus comprising a main valve unit and a pilot valve unit operatively connected to the main valve unit to control the main valve unit, wherein the main valve unit comprises a main valve casing, a main valve element disposed in the main valve casing, and a main valve driving member disposed in the main valve casing together with the main valve element and having a pressure receiving area greater than that of the main valve element, the main valve element is disposed on an upstream side of a va
Yokota Hiroshi
Yokota Shingo
Kabushiki Kaisha Yokota Seisakusho
Ladas & Parry
Rivell John
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