Fluid handling – Control by change of position or inertia of system – With second control
Reexamination Certificate
1999-05-12
2001-05-15
Hepperle, Stephen M. (Department: 3753)
Fluid handling
Control by change of position or inertia of system
With second control
C137S043000
Reexamination Certificate
active
06230732
ABSTRACT:
The present invention relates to a safety valve for venting a liquid tank.
Liquid tanks, when they are liable to be moved along with the liquid they contain, have to be equipped with a ventilating system which is reliable as far as the environment is concerned while the tank is subjected to various influences: movements in all directions and of all amplitudes, thermal stresses, depressions and overpressures.
This requirement is encountered in the case of fuel tanks, particularly when they are mounted on motor vehicles, and it is essential that liquid fuel should be prevented from getting out and that significant changes in pressure and volume of gas during filling and throughout storage in the tank be controlled.
For many years, solutions to these problems have been provided by the use of special gas-release circuits combined with vent valves. In certain devices, the functions of allowing gas to escape during filling and of ventilating in the event of a depression are provided by a complex valve which incorporates a second spring-loaded valve arranged in series with a first main float valve, like in the valve described in U.S. Pat. No. 5,518,018.
These valves do, however, have the drawback of being difficult to manufacture because of their complexity and because numerous springs made of an elastic material made of a different substance than the rest of the valve are mounted inside them. Furthermore, they are generally relatively bulky, tricky to operate, and expensive.
The invention aims to provide a single valve capable of fulfilling all the safety functions described above but which is simple to manufacture, reliable, and inexpensive.
To this end, the invention relates to a safety valve for venting a liquid tank, comprising means for:
a) ventilating the tank, including when the latter is inclined with respect to the initial position for which it was designed,
b) preventing liquid from being ejected from the tank if the latter is inclined or if waves of liquid are produced inside the tank,
c) automatically closing the tank if the latter is inverted,
d) adjusting the useful volume of the tank and preventing the tank from being filled beyond a predetermined level,
e) allowing gas to escape from the tank during filling thereof, which is characterized in that it comprises a valve element equipped with at least one flexible seal.
The tanks on which the valve according to the invention is mounted are closed chambers of varying shapes, generally sealed against the outside, which may be equipped with various internal accessories or accessories which pass through the wall of the chamber. In particular, they are fuel tanks for motor vehicles.
Examples of internal accessories or accessories that pass through the wall are, without implying any limitation, baffles for the liquid, gauges and temperature or pressure sensors, vent valves, filling nozzles, the pipes for withdrawing the liquid, and the withdrawing pumps.
The term “safety valve” is intended to denote a valve which plays a part in keeping the object on which it is mounted in a condition that is safe for the user, that is to say protected from any hazardous situation, particularly the risks of explosion, implosion, combustion or contamination of any kind, while at the same time preserving the external environment from any undesirable leak of liquid or emanation of gas.
In an attempt at being forearmed against such risks, the role of the safety valve mounted on a tank is to vent the tank, in other words to allow its programmed opening so as to fulfill the two distinct functions of allowing gas to escape when filling the tank and to ventilate the tank as its contents are used and consumed.
The operation of filling a tank with a liquid is necessarily accompanied by an increase in the pressure inside the tank. When the tank has a gas release circuit, the slight overpressure caused by the liquid freshly introduced into the tank tends to be cancelled out by the escape of a similar volume of the gas which occupied the tank. In the case of volatile liquids, the gas which escapes will be a somewhat homogeneous mixture of the gas present in the tank before filling and of vapours originating from the partial vaporization of the liquid introduced.
Furthermore, in normal use of the liquid contained in the tank, the volume thereof decreases as somewhat regular and/or continuous withdrawals are made. It is therefore necessary to provide and equip tanks with devices allowing air in so as to compensate for the loss of liquid during operation and thus prevent there being a depression in the tank and the dangers inherent to this situation.
The valve according to the invention is intended to equip the tanks which can contain any liquid which can be stored in a closed chamber under usual conditions.
It is well suited to the storage of volatile liquids at ambient temperature and pressure. Examples of such liquids are the organic liquids which give off a strong smell like the various solvents such as halogenated solvents, alcohols and esters and fuels such as kerosene, lamp oil, oil for oil-fired heating, petrol or diesel fuel, as well as heavy fuel. In particular, the valve according to the invention is advantageously used in tanks for storing liquid fuels such as petrol or diesel fuel in motor vehicles. It is most particularly suited to the tanks for storing diesel fuel in diesel-engine vehicles.
A first important function of the valve according to the invention is that of ventilating the tank when it is placed in the position for which it was designed, or when it is inclined with respect to this position.
The term “inclined” denotes the condition of the tank when it is subjected to small-amplitude movements resulting from the use of the tank and of the liquid contained which are compatible with the absence of flow of liquid by gravity from the tank via the valve.
In order to fulfill this function, the valve according to the invention must comprise means for performing this ventilation. All the means that allow this function to be fulfilled under conditions that are favourable to user safety may be suitable.
As examples of such means, mention may be made of the float valve, in which the float is secured to a valve element communicating with the outside, and the valve element of which remains in the open position under normal conditions of use. The dimensions of the float and of the attached element bearing the valve element are designed to allow ventilation under normal conditions, that is to say whether the tank is inclined or not and when the level of liquid prior to inclination does not exceed a certain threshold within the tank and when any angle of inclination does not exceed a critical angle.
One means that has given good results is the one employing a float valve secured to a valve element which remains in the open position when the valve is in the vertical or inclined position.
A second important function of the safety valve according to the invention is that of preventing liquid from being ejected from the tank when the tank is inclined as described above or when waves of liquid are produced inside it. The term “prevent” also comprises, in the case of the valve according to the invention, partial prevention as well as limiting the free flow of liquid from the tank.
Waves of liquid are the hydrodynamic movements which arise at the surface of the liquid and may be propagated throughout its mass in the tank when the tank is subjected to movements in various directions as a result of its use.
The safety valve according to the invention comprises means for preventing liquid from being ejected in the event of excessive inclination of the tank or in the event of waves of liquid of excessive amplitude being produced within it.
All effective means of blocking the orifices through which liquid passes towards the outside in the event of excessive inclination or excessive waves in the tank may be suitable.
An example of such means is the float valve secured to a shut-off valve element. The float slides in a barrel which may, as an alternative, extend u
Denis Alain
Ganachaud Patrick
Hepperle Stephen M.
Schneller Marina V.
Solvay S.A.
Venable
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