Fluid handling – With cleaner – lubrication added to fluid or liquid sealing... – Cleaning or steam sterilizing
Reexamination Certificate
1999-08-18
2001-07-03
Shaver, Kevin (Department: 3759)
Fluid handling
With cleaner, lubrication added to fluid or liquid sealing...
Cleaning or steam sterilizing
C251S026000, C251S030010
Reexamination Certificate
active
06253784
ABSTRACT:
The invention relates to a monostable valve for progressively charging, then controlling the sudden discharge of a gas contained in an enclosure.
To facilitate the flow of granular material and/or to prevent the formation of concretions, for example, in cement-producing kilns, devices known as air guns are used.
This device comprises an enclosure in which a volume of air is accumulated under pressure, then periodically released suddenly, for example through a nozzle, so that the blast produced removes the concretions.
In order to allow, first of all, the accumulation of the air in the enclosure, and secondly, this sudden discharge, a monostable valve disposed between the enclosure and the nozzle controls the passage of the air from a source inside the enclosure, and from the enclosure to the nozzle or another means.
Typically, this monostable valve comprises:
a body delimiting a chamber having an inlet conduit connected to the enclosure and a so-called discharge opening to an outlet conduit,
a piston housed in the above-mentioned chamber that moves between a so-called closed position in which the front surface of this piston closes the discharge opening and a so-called open position in which this front surface is separated from the discharge opening so that the air in the enclosure can be discharged suddenly through the outlet conduit, which piston:
has a flange that divides the chamber into a front chamber and a rear chamber, whose so-called “front surface” facing the front of the piston and the discharge opening is subjected to the pressure of the air trapped in the enclosure, which pressure generates a so-called opening force that tends to push the piston back and bring it into the open position, and
delimits, between its rear surface and the body of the valve, said rear chamber in which a pressure is exerted that generates on the back of the piston a so-called closing force, pushing the piston into its closed position, which closing force has a modulus that is approximately identical to that of the opening force, but in the opposite direction, and
a means for suddenly reducing the pressure in the rear chamber, thus causing the sudden backward movement of the piston.
The efficiency of these air guns is, of course, particularly dependent on the volume of the enclosure and on the pressure of the air contained in it, but is equally dependent on the speed with which the enclosure is connected to the outlet conduit and on the head loss.
For example, there is a known valve (FR-A-2.660.395) whose piston is bowl-shaped, thus making it possible to reduce the weight, and therefore the inertia, of the piston, which makes it possible to substantially improve the backward speed of said piston.
The concavity of the bowl also makes it possible for it to house a plunger of small cross section forming the means for guiding the piston, thus making it possible to reduce the length of the piston as compared to a conventional piston.
In order to suddenly reduce the pressure in the rear chamber, the air in this chamber must be discharged rapidly.
In an attempt to achieve this, a known valve (FR-A-2.712.639) comprises:
disposed in a discharge conduit connecting the rear chamber to the outlet conduit, a shutoff element called the main shutoff, which is movable between a so-called closed position and a so-called discharge position, this shutoff being stressed:
toward its so-called discharge position by the prevailing pressure in the above-mentioned rear chamber, which exerts on the front surface of this shutoff a so-called discharge force, and
toward its closed position by the pressure of a gas contained in a so-called control chamber, which exerts on the rear surface of the shutoff a so-called closing force which pushes the shutoff into its seat, and
means for returning the piston and the main shutoff to their respective closed positions.
A source of gas under pressure is connected to this valve and feeds the control chamber, which feeds the rear chamber through a so-called feed duct of small cross section, and this rear chamber feeds the enclosure via a controlled leak.
Thus, during the filling of the enclosure, it is the feed pressure that keeps the piston and the shutoff pressed into their respective seats.
A distributor is placed between the source of gas under pressure and the valve.
In order to produce the movement of the piston, the supply of pressurized gas is cut off, then the control chamber is connected at least indirectly to the atmosphere via the above-mentioned distributor, so that the pressure is rapidly reduced, and the shutoff opens to allow the gas contained in the rear chamber to escape.
This pressure reduction in the rear chamber allows the piston to move back, so as to establish the connection between the enclosure and the outlet conduit.
This series of steps makes it possible, with a relatively low control pressure, to release a large volume of air.
The path through which the gas escapes is sinuous, and unfortunately causes a substantial head loss.
In the example (FR-A-2.660.395), the inlet conduit that connects the enclosure to the valve has a constant diameter that is slightly smaller than the length of the piston, which inlet conduit opens into the lateral wall of this piston.
This constancy of the diameter reduces the head loss in the fluid that flows from the enclosure to the outlet conduit.
There is also a known valve (U.S. Pat. No. 4,201,362) whose opening is controlled by the movement of two shutoff elements:
Thus, the valve comprises:
in a so-called control conduit connecting the control chamber at least indirectly to the atmosphere, a second shutoff called a control shutoff that is movable between a so-called closed position in which the gas contained in the control chamber cannot escape and a so-called discharge position in which the gas contained in the control chamber can escape,
a drive means for rapidly moving the control shutoff into its discharge position, and
a means for respectively returning the control shutoff to its closed position.
In this multistage control system, the backward speed of the piston could be further improved, thereby producing better efficiency.
To this end, the subject of the invention is a valve of the above-mentioned type, characterized in that:
the area defined by the cross section of the discharge conduit is at least constant, or even increasing from the rear chamber toward the outlet conduit, in order to limit head loss and
the main shutoff has a low inertia.
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Bastianelli John
Feeney William L.
Kondracki Edward J.
Miles & Stockbridge P.C.
Shaver Kevin
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