Fluid handling – Control by change of position or inertia of system – Vent opening or closing on tipping container
Reexamination Certificate
2000-01-18
2002-01-08
Buiz, Michael Powell (Department: 3753)
Fluid handling
Control by change of position or inertia of system
Vent opening or closing on tipping container
C137S039000, C137S202000
Reexamination Certificate
active
06336466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for the venting of a liquid tank.
2. Description of the Related Art
The present invention relates to a system for the venting of a liquid tank.
Liquid tanks, when liable to be displaced together with the liquid which they contain, are usually equipped with a ventilation system ensuring environmental safety when the tank is subjected to various stresses: movements in all directions and of any amplitude, thermal stresses, pressure drops or excess pressures.
This requirement is applicable to fuel tanks, particularly when they are mounted on motor vehicles, and when it is essential to prevent liquid fuel from escaping and to control the pronounced changes in gas pressure and volume during filling and for the entire duration of storage in the tank.
Solutions for solving these problems have been developed, making use of safety valves which are submerged in the tank and the upper part of which passes through a wall of the latter. These valves usually open onto a pipe leading to a housing or canister containing a material capable of trapping the liquid vapours present in the gases coming from the tank. It is not uncommon, however, for systems of this type still to present difficulties because, due to the special circumstances occurring during use, such as sudden movements or excessive inclination of the vehicle, liquid coming from the tank may nevertheless pass through the barrier of the safety valve and be present in the pipe leading to the canister, even reach the latter and disturb the free passage of the vapours.
To remedy this accidental entrainment of liquid out of the tank, attempts have been made to retain the liquid, which would escape through the pipe leading to the canister, by inserting into this pipe a dead volume intended to act as a capacity for collecting the liquid and allowing the vapours to pass freely.
Moreover, when it is not possible for them to be integrated into the safety valve itself, safety devices ensuring the prevention of overfilling of the tank (an “ISR” device wherein ISR stands for the French “Intediction de Sur—Remplissage”) and for the automatic closing of the latter in the event of overturning (“ROV” device or roll-over valve) also have to be mounted on the tank or in its immediate surroundings. Multiple pipelines then connect the valve, the ISR and ROV devices and the canister to one another. These pipelines and the numerous connections which they require are often the source of microleaks which are unacceptable in view of the EURO 2000 programme and aims for the drastic reduction of emissions. It is also not uncommon for these multiple pipelines to have low points and siphons, in which small quantities of liquid accumulate and form as many obstacles to the free passage of the gases.
It is known, from British patent application GB-A-2,269,375, to use a capacity which has leaktight walls and is integrated within a fuel tank and in which a safety valve is housed (see FIG.
2
). A calibrated orifice
14
made at the top of the capacity allows the liquid to enter in the event of excessive inclinations or excessively violent movements of the tank. A duckbill-shaped non-return valve
12
makes it possible to empty the capacity
11
when the level of the liquid has fallen.
In this system, however, there are still problems associated with the inopportune closing of the valve and with the increase in pressure in the tank which may disturb the smooth operation of the engine. Moreover, when liquid droplets of small size are entrained via the orifice
14
, they may, because of their low weight, be entrained directly towards the venting line
7
by the gas stream, without falling into the capacity
11
. Furthermore, the ISR and ROV devices must still be connected to the valve with the aid of lines external to the tank.
SUMMARY OF THE INVENTION
The object of the invention is to overcome the disadvantages of the known ventilation systems by providing a system which avoids a capacity being placed on the lines external to the tank, makes it possible to empty out the liquid retained in the capacity in the event of a fall in the liquid level in the tank, conforms to the most stringent environmental standards and does not bring about any excess pressure inside the tank.
For this purpose, the invention relates to a system for the venting of a liquid tank, comprising, on the one hand, a float valve arranged in the tank, in communication with a venting pipe, and, on the other hand, a closed volume internal to the tank and provided with an emptying device, the said volume acting as a capacity intended for collecting and retaining any possible entrainments of liquid coming from the tank, according to which this float valve is located outside the volume of the capacity and is connected to the latter by means of the pipe of the venting circuit.
Preferably, the venting pipe in communication with the valve forms one end of a venting circuit. There may be a single venting circuit or, on the contrary, a plurality of these. Even more preferably, this pipe forms the end of the single venting circuit.
The liquid tank is a closed containment, of various shapes, which is generally leaktight relative to the outside and which may be equipped with various internal accessories or accessories passing through the wall of the containment. The tank may contain any type of organic or inorganic liquid or any mixture of such liquids. In particular, it is a fuel tank for motor vehicles. All the types of fuel used by motor vehicles may be stored in the liquid tank, in particular petrol and gas oil.
The system for the venting of a liquid tank, which is the subject of the invention, is a device comprising a plurality of elements, the overall function of which is to make it possible to degas a tank during the filling of the latter and to ventilate it during the period of use and consumption of the liquid which it contains, whilst keeping its external surroundings protected from any leak or emanation of undesirable gases.
The venting system according to the invention comprises a float valve, that is to say a device making it possible to open the tank with the aid of a valve controlled by the displacement of a float driven by the liquid level present in the tank.
According to the invention, the float valve is arranged completely within the tank.
Alternatively, the float valve may also be arranged in the tank and have an upper part which passes through a wall of this tank. The passage of the upper part of the valve through the wall of the tank is carried out under leaktight conditions by means of any suitable technique which is well-known per se. As an example of a leaktightness technique which may be used, mention may be made in a non-limiting way of the welding of the upper part of the valve to the cut-out wall of the tank, leaktight clamping or the use of a gasket designed for the type of liquid contained.
In the venting system according to the invention, the valve upper part emerging from the wall of the tank is in communication with a pipe which forms one end of a venting circuit. In other words, the gases emerging from the tank or entering the latter circulate in this pipe which, on one side, is connected in a leaktight manner to the valve upper part opening onto the valve actuated by the float and, on the other side, communicates with a circuit terminating in the outside atmosphere.
According to the invention, the venting system also comprises a closed volume internal to the tank. The term “closed volume” is intended to designate a volume of any desired shape delimited by walls tight to liquids and to gases. This volume is arranged inside the tank and communicates with the valve by means of the venting pipe, one end of which is connected to the valve. The function of this volume is to form a capacity capable of connecting and retaining any possible entrainments of liquid coming from the tank which would have passed through the barrier of the valve.
The size of the volume of this capacity is selected
Ganachaud Patrick
Percebois Serge
Buiz Michael Powell
Krishnamurthy Ramesh
Larson & Taylor PLC
Solvay
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