Description

Apparatus for feeding a fuel, in particular LPG, to an internal combustion engine

Technical Field

This invention relates to an apparatus for feeding a fuel, in particular LPG, to an internal combustion engine.

Background Art

The need to reduce pollution caused by emissions from internal combustion engines and to identify fuels other than petrol and diesel is leading many motor vehicle manufacturers to develop engines and vehicles that are powered by what have come to be known as "alternative" fuels. One of the most well-known alternative fuels for vehicles, appreciated for its low pollutant emissions, ready availability at worldwide level and cost effectiveness is undoubtedly LPG (liquefied petroleum gas) which is normally a mix of propane and butane. Other alternative fuels that are being adopted on an increasingly large scale for vehicles are LNG (liquefied natural gas), methanol and ethanol. Usage of these fuels in vehicles requires specific tanks/containers: for LPG, it is essential to use a tank/cylinder that keeps the gas under pressure in a liquid state, to prevent its gasification; for LNG, the tank/cylinder used must not only keep the gas under pressure but also keep it thermally insulated (the fuel is at - 163 ⁰ C); for methanol and ethanol, the use of hermetically sealed tanks is essential to prevent leakage of toxic fumes.

As mentioned, LPG is a gas which, in order to be transported and used in vehicles, must be placed in tanks under pressure (normally known as cylinders or bottles) which keep it under pressure in the liquid state. The pressure of the LPG inside the tank/cylinder may, depending on its temperature, vary anywhere from 0.5 to 22 bar. The maximum working pressure of the tanks is set by international standards at 27 bar. Suitable relief devices come into operation when the pressure exceeds this value.

For usage in vehicles, the LPG tanks that have been used for many years now, may be fitted with any of several types of valve or multivalve (which, as known, is a valve that combines different functions in one) for induction and

filling purposes and to detect the LPG level inside the tank and keep it within the filling limit of 80% of the total tank capacity in order to guarantee safety standards.

In most cases, these valves, or multivalves, used for fuel filling and induction purposes, have a feed pipe, with a non-return valve, for filling the fuel into the tank/cylinder, and an intake pipe for drawing LPG out of the tank in the liquid state, with a solenoid valve which shuts automatically when the vehicle engine stops. The supply of LPG from the tank/cylinder occurs through the multivalve's intake pipe immersed in the liquid phase, on account of the pressure in the tank/cylinder caused by the boiling of the LPG (the gas phase inside it, under pressure, expels the LPG in the liquid phase through the outlet of the intake pipe). The LPG in the liquid phase is pressurized "naturally" from the gas phase and usually feeds a reducer/vaporizer heated by the engine coolant, thus passing from the liquid phase to the gas phase and from there, through suitable devices (electronically controlled mixers or solenoid valves) supplies the engine.

Only recently have systems for injecting LPG in the liquid phase been developed in order to be able to supply the latest generation engines equipped with sophisticated phased sequential multipoint injection systems and with a view to supplying the latest direct petrol injection engines. These new systems do not necessitate reducer/vaporizers since they do not inject LPG in the gas phase but are fitted with an electric pump located inside the tank/cylinder which pressurizes the LPG to the liquid phase and pumps it through a suitable multivalve and pipe system to a common rail installed in the engine and equipped with specific injectors for LPG in the liquid phase which feed it in sequential and phased manner into the induction pipes of each cylinder.

In simpler terms, the liquid phase LPG injection system is very similar to petrol injection systems but with the major difference and complexity of having to control a fuel located in a totally sealed tank/cylinder subject to continuously variable pressure strongly influenced by ambient temperature or by the heated fuel returning from the injection system, the liquid fuel (i.e. LPG) being extremely volatile under certain conditions and being subject to the risk of boiling/evaporation.

The possibility of injecting LPG in the liquid phase instead of the gas phase has important advantages in terms of engine performance and environmental protection. Fuel under pressure and in the liquid phase can be injected with great

precision and speed and not only improves engine efficiency, allowing higher power and torque compared to normal petrol systems because the engine cylinders are filled better by the liquefied gas which is very cool and undergoing rapid expansion when injected, but also greatly reduces engine emissions. Also, controlling a system that injects LPG in the liquid phase greatly simplifies the electric/electronic interface with the engine's original petrol injection system. Injecting the LPG in the liquid phase means that the electric/electronic interface can be non-intrusive, basically using the original control of the petrol injection system and eliminating the risks of "electronic conflicts" with the many systems that modern vehicles are equipped with, such as, engine control, ABS, automatic gear change, ESP, traction control, air conditioning and, in particular, the on-board diagnostic system. This compares very favourably with current systems where the LPG is injected in the gas phase and which normally involve complex electric/electronic interfacing operations, requiring connections that intrude on the original system, and a specific and separate engine computer control system that must be programmed vehicle by vehicle, with the ever present risk of interference leading to malfunctions, in some cases very serious.

In short, a common rail system that injects LPG in the liquid phase enormously facilitates installation, does not create interface problems with the increasingly complex electronic control systems of modern vehicles, eliminates all conflicts with on-board diagnostics, improves engine performance and emissions, and considerably reduces conversion costs because of the less time required for installation. The indisputable advantages of injecting LPG in the liquid phase are, however, heavily counterbalanced by the poor reliability of the system due to the high failure rate of the electric injection pumps caused essentially by the contaminants of various kinds present in the LPG. As known, one of the most harmful contaminants for electric LPG injection pumps (where the fuel passes through the rotor and the electric motor contacts and serves as a coolant) is ferrous particulate, often present in significant quantities in LPG. The ferrous particulate is created by the oxide dust and other iron/steel waste particles, often smaller than 10 microns in size, from all the different tanks, pipes and containers the LPG comes into contact with from the time it is produced (refinery or natural gas separators) to the moment it reaches its destination at terminal storage points and

fuel stations after being transported by ship, train or truck. Ferrous particulate causes serious damage to electric pump contacts, short circuiting and may even lead to clogging of the injectors.

The need to replace the electric LPG pump located inside the pressurized tank/cylinder is a serious problem because it involves removing the tank/cylinder from the vehicle, the extremely complex task of emptying it, removing the multivalve and taking the pump out - a normally difficult job - dismantling the pump casing assembly, substituting the faulty component and, in most cases, also the filter. Once this has been done, the procedure must be repeated in reverse order to reassemble all the components, put the tank/cylinder back into the vehicle, fill it up and check it for leaks once it is under pressure again. The entire procedure requires many hours of painstaking work by highly skilled personnel using very expensive equipment that is not readily available and at a decidedly high cost. Moreover, some of the operations involved, such as transferring highly inflammable fuel under pressure, may be dangerous.

Disclosure of the Invention

This invention therefore provides an apparatus, as described in claim 1 appended hereto, for feeding a fuel, in particular an apparatus for feeding a fuel in the form of LPG (although the solution is also suitable for LNG and other fuels) to an internal combustion engine, the apparatus comprising an element (the element that contains the fuel pump) for delivering the fuel from the tank to the engine and mounted in a valve body, or more precisely in this case, a multivalve, but outside the fuel tank, and comprising also solutions which prevent the fuel from being delivered until the delivery element is inside the multivalve and which shut off fuel outflow when the delivery element is disconnected from the multivalve.

The invention proposes a solution whereby the fuel delivery element can be removed for maintenance or repairs in total safety without having to empty the tank, thus greatly facilitating work and saving a great deal of time. Preferably, the LPG feed system is built into a single device, with a fuel filtering element interposed between the charging point and the tank and, like the fuel delivery element, is characterized in that it is mounted inside the body of the multivalve but outside the tank and can therefore be removed for cleaning, maintenance and replacement of the filters inside it without having to empty the tank and in total safety, thus greatly facilitating work and saving a lot of time.

According to another advantageous aspect, the internal combustion engine fuel feed system built into a multivalve (multipurpose fuel filling and induction valve) for tanks with fuels under pressure, in particular LPG, is equipped with a feed pump and filtering elements located in independent and separable casings which allow maintenance and substitution without having to depressurize and hence empty the tank. This apparatus is called IMMISS (Integrated Multipurpose Multivalve for Injection System for Sealed tanks).

The main characteristic feature of the feed system is that it is built into a multivalve which allows the electric fuel pump, mounted outside the multivalve and thus outside the tank, to be removed for maintenance or substitution without requiring lengthy and complex procedures to empty the container (tank) which is under pressure and/or contains volatile and/or dangerous liquids, like LPG tanks for automotive use.

A further advantageous aspect of the fuel system of the feeding apparatus is that it incorporates a special filtering system, also inside the multivalve but outside the tank, capable of totally eliminating ferrous waste particulate material, thus preventing the problem of damage to and clogging of fuel pumps and injectors caused by the ferrous particles. This filtering system is also easy to remove for maintenance purposes without having to empty the tank and is fitted with two specific types of filter: a traditional filter which works by mechanical separation, and a high-efficiency magnetic separator fitted with extremely powerful permanent magnets capable of removing all traces of contamination by ferrous waste particulate material very often present in LPG.

The total elimination of ferrous waste particles, extremely harmful to the fuel pumps, significantly improves the reliability of brushed electric pumps but more importantly, allows new generation brushless pumps to be used. These brushless pumps would be difficult to use in the presence of contaminants sensitive to magnetic fields. The use of brushless pumps is a major breakthrough for engine injection systems because it provides a simple and economical means of controlling and very rapidly varying the pressure and flow rate of the fuel supply. These are fundamental characteristics when the fuel concerned, is subject, like LPG, to very high and rapidly changing pressure inside the tank. Another important characteristic of brushless pumps is that they can work without problems even in the presence of highly corrosive fluids such as soda, often found in LPG.

In particular, and without limiting the scope of the present feeding apparatus, this internal combustion engine injection apparatus built into a multivalve for tanks under pressure and/or sealed, for liquid and/or toxic fuels, with fuel pump and filters mounted inside the multivalve but outside the tank, allows dismantling for maintenance and substiution purposes without having to remove the multivalve from the tank, thus eliminating the need for complex and dangerous tank emptying operations.

For simplicity, the following specification describes the injection apparatus according to the invention as applied to LPG tanks, it being understood, however, that its characteristic features can be transferred and are equally applicable to cryogenic tanks for LNG and to sealed tanks containing methanol, ethanol or any other toxic liquid fuel.

Brief Description of the Drawings These and other characteristics of the apparatus are clearly described in the claims below and its advantages are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred embodiment of the invention provided merely by way of example without limiting the scope of the inventive concept, and in which: - Figure 1 is a schematic assembly view of the systems for feeding LPG in the liquid phase and petrol to an internal combustion engine of the type known as a bi-fuel engine, that is to say an engine that can be powered by either of these fuels, using a preferred embodiment of the apparatus for feeding LPG in the liquid phase according to the invention; the same solution, excluding the devices for supplying petrol, can be used for feeding an LPG only, or mono-fuel, internal combustion engine;

- Figure 2 is an exploded view, partly in cross section, of the preferred embodiment of the apparatus according to the invention and shows the body of the multivalve mounted on the LPG tank and housing the casing of the fuel delivery element and the casing of the filtering element;

- Figure 3 is a schematic view, partly in cross section, of the preferred embodiment of the apparatus according to the invention for feeding fuel to an internal combustion engine, and shows the casing of the fuel delivery element and the casing of the filtering element both seated and fixed in their housings inside the multivalve which is in turn mounted on the LPG tank;

- Figure 4 is a section view, of the fuel delivery element of the preferred embodiment of the apparatus according to the invention, seated and fixed in its housing inside the multivalve;

- Figure 5 is a section view, of the filtering element of the preferred embodiment of the apparatus according to the invention, seated and fixed in its housing inside the multivalve;

- Figure 6 is a schematic assembly view of the preferred embodiment of the apparatus according to the invention and shows the casing of the fuel delivery element and the casing of the filtering element while they are being removed from their housings in the multivalve and the detail of the fuel tank outlet shutoff devices when closed;

- Figure 7 is a schematic assembly section view of the preferred embodiment of the apparatus according to the invention and shows the fuel tank safety devices being inserted once the fuel delivery element and/or the filtering element have been removed;

- Figure 8 is a schematic assembly view of the preferred embodiment of the apparatus according to the invention and shows the fuel tank safety devices seated in their housing in the place of the fuel delivery element and of the filtering element.

Description of the Preferred Embodiments of the Invention Figure 1 diagrammatically represents a typical bi-fuel system, in this case petrol and LPG in the liquid phase, for an internal combustion engine, and schematically shows a cylinder block of the engine 44, with combustion chamber, piston, valves and spark plug.

The system for feeding LPG in the liquid phase comprises a tank 1, the multivalve 2 with the housing 14 for the delivery element and the delivery pipe 19, through which the LPG is sent under pressure to a common rail 32 having a plurality of injectors 33, suitably connected to the electronic control unit (ECU) 43, for feeding the fuel into a feed pipe leading into the combustion chamber 44.

The excess LPG sent to the common rail 32 is recycled back to the LPG tank 1 through the return pipe 34 and returns into the tank 1 through a customary nonreturn valve going one way only (towards the tank).

As illustrated, the engine is also powered by petrol, which is supplied through a respective injector 45, also located in the respective feed pipe leading to

the combustion chamber 44. The injector is fed through the petrol pipe 46 connected to the pump 47 immersed in the petrol, located inside the tank 48.

The ECU 43 processes the data detected by the devices (sensors) and according to the control and diagnostic software provided by the vehicle manufacturer and determines the amount of fuel, whether LPG in the liquid phase or petrol, that is injected into the combustion chamber 44. The fuel is selected using a specific switch 35 through which the ECU 43 activates either the petrol injectors 45 or the LPG injectors 33.

The ECU 43 also processes the signals it receives from the fuel level sensors on the bar 20 and uses these to stop filling when the tank 1 is 80% full and, in the case of a bi-fuel system, to switch automatically to petrol injection when LPG reaches the minimum level.

The numeral 10 denotes the LPG filler pipe running from the filler connector to the tank 1. Figure 2 shows a preferred embodiment of the invention, comprising a multivalve mounted on the LPG tank 1 to which it is fixed through a suitable flange Ia welded to, and forming an integral part of, the tank itself, both the delivery element 11 and the filtering element 4 being simply connectable to, and disconnectable from, this flange. As illustrated in Figure 2, the novel feature of the multivalve is that it has two cylindrical housings 7 and 14, which accommodate the filtering element 4 and the delivery element 11 like two syringes.

Described below is an embodiment of the multivalve 2, of the delivery element 11 and of the filtering element 4, to be considered as only one of the many technical solutions that might embody this invention, without excluding alternative technical solutions that might otherwise implement the invention.

As illustrated in Figure 2, the body of the multivalve 2 has a cylindrical housing 7 for the filtering element 4 and a cylindrical housing 14 for the delivery element 11, both securely attached to the body of the multivalve 2 itself: both the cylindrical housings 7 and 14 have attached to them respective sealing flanges 8 and 15 which, on the inside, comprise means for interfacing with the filtering element 4 and the delivery element 11, respectively. The interfacing means, which will be described in more detail below, together with the functions of the sealing flanges 8 and 15 and of the cylindrical housings 7 and 14, can keep the liquid inside the tank 1 isolated from the outside environment.

The filtering element 4 in turn comprises a cylindrical container, closed at the bottom by a flange 6, whose underside interfaces with the housing 7, and at the top by a sealing head 5 adapted to be inserted and fixed to the body of the multivalve 2, and has a fitting for connecting it to the filler pipe 10. As shown in more detail in Figure 5, the sealing head 5 of the filtering element, when seated in the retaining housing 3 a formed in the multivalve 2 and acting in conjunction with the O-ring 31, provides a tight seal with the body of the multivalve itself. The head 5 for sealing to the body of the multivalve 2 can be fixed by means of threading formed partly in the retaining housing 3 a or by other means such as a locking ring capable of providing the same safety levels.

The delivery element 11 in turn comprises a cylindrical container, closed at the bottom by a flange 13, whose underside interfaces with the delivery element housing 14, and at the top by an upper sealing head 12 adapted to be fixed to the body of the multivalve 2, and is equipped with a solenoid valve 17 for shutting off LPG delivery, with a manual valve 18 for shutting off LPG delivery and with a fitting for connecting it to the LPG delivery pipe 19.

As shown in more detail in Figure 4, the sealing head 12 of the delivery element, when seated in the retaining housing 3b formed in the multivalve 2 and acting in conjunction with the O-ring 31, provides a tight seal with the body of the multivalve itself. The head 12 for sealing to the body of the multivalve 2 can be fixed by means of threading formed partly in the retaining housing 3b or by other means such as a locking ring capable of providing the same safety levels.

Figure 3 shows the multivalve with the filtering element 4 seated in and fixed to its housing 7, and with the delivery element 11 seated in and fixed to its housing 14. The filtering element 4 is connected to the LPG filler pipe 10 and the delivery element 11 is connected to the LPG delivery 19 that feeds the common rail 32.

In particularly advantageous manner, means are provided for allowing the fuel to flow from the tank 1 to the delivery element 11 when the delivery element 11 is seated in its housing 14 and which are designed to shut off the fuel flow when the delivery element 11 is detached from its housing 14, as described in more detail below, with reference to Figures 4 and 6.

In particularly advantageous manner, means are provided for allowing the fuel to flow from the filler pipe 10 to the tank 1 through the filtering element 4 during refuelling when the filtering element 4 is seated in its housing 7 and which

are designed to shut off the fuel flow from the tank towards the outside when the filtering element 4 is detached from its housing 7, as described in more detail below, with reference to Figures 5 and 6.

Figure 3 shows other aspects of the present apparatus, such as the intake 5 pipe 16 which connects the tank 1 to the delivery element 11 and whose length must be such as to allow it to draw as much fuel as possible out of the tank. The infrared, minimum level sensor 20b must be suitably positioned relative to the inlet of the intake pipe 16, at a higher level than the inlet of the intake pipe 16 so that it will always indicate low fuel level before the level in the tank is too low for0 the intake pipe to draw fuel. The length of the intake pipe 16 and the position of the level sensor 20b are thus correlated to prevent the pump 27 in the delivery element 11 from running dry and hence to avoid the damage and premature breakage that would be caused by its running without fuel.

Figure 3 also shows another advantageous aspect of the preferred5 embodiment of the device. This is embodied by the 80% full level sensor 21 and by the solenoid valve 9 for shutting off fuel delivery during refuelling. The ECU 43 enables the solenoid valve 9 to open only when the level sensor 21 indicates that the LPG tank is less than 80% full: during refuelling, as soon as the LPG reaches the level of the sensor 21, indicating that the tank 1 is full to 80% of its o capacity, the ECU 43 shuts the solenoid valve 9 to prevent more LPG from being filled into the tank.

Figure 4 shows in more detail how the pump 27 is positioned inside the delivery element 11 and its connection to the head 12, with the fuel outlet pipe 29 inserted into the housing made in the head 12 and the delivery element 11 fixed to5 the inside of the cylindrical housing 14, forming part of the multivalve body 2. hi particularly advantageous manner, a member 28 for filtering the fuel flowing out of the tank 1 and into the pump 27 is located inside the delivery element 11 before the pump 27.

Advantageously, the filtering member for the fuel flowing out of the tank 1 0 is located upstream of the fuel pump 27 and downstream of the non-return valve

26.

Advantageously, the filtering member 28 is in the form of an element for retaining ferromagnetic waste, in particular ferrous particulate.

Advantageously, the filtering member 28 is in the form of a magnetic 5 retaining element equipped with high-efficiency permanent magnets.

For this purpose, a magnetic separator 28 of any kind might be used, such as, for example, a filtration system like the one described in the United States patent 6,743,365. For brevity, therefore, the filter 28 is not described in detail.

It should be noticed that the shutter of the non-return valve 26, overcoming

5 the force of the valve spring, opens to allow the fuel to flow from the tank 1 to the pump 27, the shutter 26 being directly acted upon by a push-open element 25 inserted into the connector fitting and forming part of the sealing flange 13 of the delivery element 11. The shutter of the non-return valve 26 is opened only when the delivery element 11 is secured to its housing 14 by tightening the upper sealing0 head 12 of the delivery element 11 into the retaining housing 3b of the multivalve

2 by screwing it in directly or by fastening a locking ring.

Once the delivery element 11 has been secured in its housing 14, the LPG contained in the tank 1 can flow freely into the intake pipe 16, to the non-return valve 26 opened by the shutter 25, through the magnetic filter separator 28 to5 reach the pump 27 which pressurizes it and pumps it through the pipe 29 to the LPG delivery pipe 19 and from there to the LPG injector rail 32, the flow being enabled by the ECU 43 which opens the solenoid valve 17. According to this solution, the intrinsic safety of the system is guaranteed because it depends on the operation of the ECU 43, which is connected to all the vehicle's dynamic sensors - o including the inertia switch - and which, in the event of an accident, interrupts the supply of fuel to the injectors, to the fuel pump 27 and to the LPG delivery shutoff valve 17, normally closed, thus interrupting the supply of LPG to the delivery pipe 19. Another safety component is the manual valve 18, which can be used to manually shut off fuel supply from the tank 1 to the delivery pipe 19 or to the5 injector rail 32, overriding the ECU 43, so as to allow maintenance to be carried out on the supply pipes 19 and 34 .

Figure 5 shows in more detail how the filtering devices 22 and 23 are positioned inside the cylindrical filtering element 4 and how the latter is fixed to the inside of the cylindrical housing 7, forming part of the multivalve body 2. As o shown in the drawing, it should be noticed that a particularly advantageous nonreturn valve 24 is provided whose shutter, normally closed, is held closed not only by its own spring but also by the pressure inside the tank 1. The solenoid valve 9, also normally closed, is positioned downstream of this non-return valve to allow fuel to flow from the filer pipe 10 to the tank 1 solely and exclusively when the5 80% full level sensor 21 gives the signal for the ECU 43 to enable fuel to be filled

into the tank. After receiving the enable signal from the level sensor 21, the ECU 43 causes the solenoid valve 9 to open and, as a result, as illustrated in Figure 5, the higher pressure from the filler pump opens the shutter of the non-return valve 24 to allow LPG to flow into the tank 1. Fuel will be filled into the tank until it reaches the 80% full level, detected by the sensor 21 which sends a signal for the ECU 43 to close the solenoid valve 9 to stop fuel from continuing to be filled into the tank 1. When the filtering element 4 has to be removed from the body of the multivalve 2, the small quantity of LPG present in the filler pipe 10 and in the filtering element 4 can be discharged through the filler valve and the head 5 of the filtering element 4 very simply disconnected from the body of the multivalve 2 without any risk of the LPG escaping from the tank since it is sealed off by the shutter of the non-return valve 24 which is kept shut not only by the pushing action of its own spring but also by the pressure inside the tank 1.

As may be noticed, the invention especially advantageously contemplates the provision of a double filtration system for the fuel filled into the tank 1. The first filtration system encountered by the fuel flowing through the filler pipe 10 is a mechanical filter of substantially known type consisting of a cartridge 22 with a glass fibre filtering element that prevents solid particles up to 6-3 microns in size from passing through it. The ingoing fuel filtration means advantageously further comprise a second filtering member 23, located downstream of the first mechanical cartridge filter 22, said second filtering member 23 for the fuel filled into the tank 1 being in the form of a magnetic retaining member designed to separate out metallic particles less than a micron in size and is of substantially the same type as that forming part of the filtration means described above with reference to Figure 4 and is not therefore be described in detail again.

Figure 6 shows how the casing of the delivery element 11 and the casing of the filtering element 4 are of a type that can be quickly, easily and safely removed from their housings 14 and 7. Once the LPG delivery pipe 19 and the LPG filler pipe 10 have been disconnected, it is sufficient to release the delivery element 11 and the filtering element 4, whether they are held in place by screw or locking ring fastening systems, to remove both these devices from the fuel tank 1 for any maintenance or repairs to be easily carried out.

Under these conditions, the non-return valves 26 and 24 are closed and the fuel inside the tank 1 is thus sealed in. The shutter of the non-return valve 26, once disengaged from the push-open

element 25 forming part of the delivery element 11 when the latter is removed from its housing 14, is kept in the closed position by the pressure of its own spring and by the pressure inside the tank; the shutter of the non-return valve 26 is held in the normally closed position not only by the pressure of its own spring but also by the pressure inside the tank.

In practice, when work has to be done on the delivery means 11, it is sufficient to disconnect the head 12 from the delivery pipe 19 and take the delivery element 11 out of its housing 14.

When work has to be done on the filtering element 4, on the other hand, it is sufficient to disconnect the head 5 from the LPG filler pipe 10 and take the filtering element 4 out of its housing 7.

Advantageously, the retaining housing 3b of the delivery element has a pressure relief hole 30 for discharging any LPG from the non-return valve 26 in the housing 14 when the delivery element 11 is removed from the housing 14. The relief hole 30 is designed to enable LPG to be released gradually and safely from the system so that the delivery element 11 can be removed without risk.

The pressure relief hole 30 comes into operation when the head 12 of the delivery element 11 is disengaged from the retaining housing 3b but before the head 12 is completely released from its fastening system, whether screw threading or locking ring, and enables LPG pressure to be slowly and safely relieved as long as the OR seal 31 remains in place in the retaining housing 3b in the head 12.

Figure 7 shows the two fuel tank safety devices 36 and 37 which, upon removal of the filtering element 4 or delivery element 11, or both, for maintenance on the apparatus, stop gas from leaking out of the tank 1 through the non-return valves 24 and 26, should fuel be escaping from the tank 1 on account of impurities or debris on the contact surfaces of the valve shutters.

As may be inferred from Figure 8, the safety devices 36 and 37, are rapidly positioned in the place of either the filtering element 4 or of the delivery element 11, when the head 39 is placed in the retaining housing 3a and 3b (see Figure 7), in the body of the multivalve 2 and by positioning the sealing element fitted with closing means or a seal 38 which seals the pipe that communicates with the shutter of the non-return valve 24 in one case, or the pipe that communicates with the shutter of the non-return valve 26 in the other case. The safety devices 36 and 37 are fitted with manual relief valves 40, which must be opened before the body of the multivalve 2 is disengaged in order to discharge any gas that may be in the

housings: any gas present, even in small quantities, may be discharged through the relief hole 42 and the outlet 41.

The safety devices 36 and 37 must be used during maintenance or repairs to the apparatus.

The invention described above is susceptible of industrial application and may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements.