Girondi, Giorgio (Le Sun Tower, Monaco, 98003, MC)
| 1. | A fuel filter, in particular for diesel engines, comprising a first chamber (31) of vertical axis and, positioned in the first chamber (31), a filtering means (15) traversed by the fuel in a substantially axial direction and having a lower surface (15') from which the fluid leaves in a substantially vertical direction after passing through the filtering means (15), characterised by comprising ; a water separator means (20), positioned below the lower surface (15') of the filtering means (15) and comprising, facing said lower surface (15') and forming an angle to the vertical, a downwardly inclined flow surface (22) along which the fluid flows and which deviates the fuel stream, to aggregate and separate the water parts present in the fuel; and a lower chamber (33) positioned below the separator means (20), to collect the water parts separated from the fuel. |
| 2. | A filter as claimed in claim 1, comprising a filter exit chamber (32) coaxial to the filtering means and communicating, at its lower end, with the lower chamber (33), characterised in that the filtering means (15) comprises a flow deviator member (21) having an upwardly converging upper frustoconical surface (22) virtually completely occupying the projection of the lower surface 15'of the filtering means 15, to define said flow surface, the deviator member (21) being lowerly hollow and having a central passage port (24) positioned at the lower end of the exit chamber (32). |
| 3. | A filter as claimed in claim 2, characterised in that the separator means (20) comprises a filtering mesh (25) coated with a substance such as polytetrafluoroethylene (PTFE) or silicone or the like, and having passage pores of diameter not exceeding about 200 micron, to intercept the water parts present in the fuel, said filtering mesh (25) being positioned on the lower end of the deviator member (22) to cover the cavity therein. |
| 4. | A filter as claimed in claim 2, characterised by comprising, rigid with the outer casing (10) of the filter, a central tubular duct (35) which bounds said exit chamber (32), the deviator member (21) being fixed to the lower end of said central duct (35). |
| 5. | A filter as claimed in claim 4, characterised in that the deviator member (21) comprises a plurality of radial support elements (26) projecting upwards from the flow surface (22), to act as a support for the lower surface (15') of the filtering means (15). |
| 6. | A filter as claimed in claim 4, characterised in that the deviator member (21) comprises one or more projecting ridges (27) situated on the flow surface (22), to define spiral paths starting from the vertex of the surface (22), to increase the length of the fluid travel. |
Technical field This invention relates to the filtration of fuel, in particular of diesel engine fuel (generally known as gasoil).
Background art In this sector the sophistication of injection equipment requires the most careful filtration to prevent the impurities present in the fuel causing damage to and malfunction of the delicate injection equipment.
Filters are known using a filtering means of the type formed from paper rolled about a central axis and traversed by the fuel stream in an axial direction. These filters have a useful filtering surface which is much greater than the more traditional filters of pleated paper.
A technical problem which has not been totally solved, and also exists with the said filters with rolled paper, is caused by the presence of water parts in the fuel, which are not intercepted by the usual filter cartridges (designed to intercept more solid parts) and hence reach the downstream mechanical members, resulting in oxidation problems and damage to these members. This problem is felt particularly in injection feed equipment.
An object of this invention is to provide a filter using a filtering means which is traversed by the fuel stream in an axial direction, in particular a filtering means with rolled paper, and is able to effect a very high degree of water separation.
Disclosure of the invention This and further objects are attained by the invention as characterised in the claims.
The invention is based on the fact of comprising a water separator means positioned below the lower surface of the filtering means, and comprising, facing said lower surface and forming an angle to
the vertical, a downwardly inclined flow surface along which the fluid flows and which deviates the fuel stream, to aggregate and separate the water parts present in the fuel; and further comprising a lower chamber positioned below the separator means, to collect the water parts separated from the fuel.
The invention is described in detail hereinafter with the aid of the accompanying figures which illustrate one embodiment thereof by way of non-limiting example.
Figure 1 is an axial section through the filter of the invention.
Figure 2 is an enlarged detail of Figure 1.
Figure 3 is a section on the plane III-III of Figure 2.
Figure 4 is an enlarged detail, as Figure 2, of a second embodiment of the separator means 20.
Figure 5 is a section on the plane V-V of Figure 4.
The filter comprises an outer casing 10, in particular of substantially cylindrical shape with slight dishing, having a vertical axis A.
The fuel inlet and outlet are located on the upper cover 14 of the container 10.
Specifically, the inlet is defined by various apertures 11 regularly distributed at a constant distance from the axis A, the outlet being defined by a single aperture with its centre on the axis A.
Within the container 10 there is defined a first chamber 31 of vertical axis, communicating with the inlet apertures 11, and an exit chamber 32, communicating with the outlet 12 and substantially coaxial with the first chamber 31.
The two chambers 31 and 32 are, at least partly, separated from each other by a central tubular duct 35, rigid with the outer casing 10 of the filter and fixed to the upper cover 14, which bounds said exit chamber 32.
Within the casing 10 below the separator means, there is positioned a lower chamber 33 to collect those water parts which are separated from the fuel. The exit chamber 32 is positioned along the axis of the filtering means 15 and communicates, at its lower end, with the lower chamber 33.
A filtering means 15, in particular of the type formed from an overall cylindrical roll of paper wrapped about its axis, is positioned in the first chamber 31; the filtering means 15 is disposed coaxially to the chamber 31 and to the chamber 32, and occupies in cross-section the entire section of the chamber 31, whereas in the axial direction it occupies the chamber 31 virtually completely, except for the top portion 31a of the chamber 31 which communicates with the inlet apertures 11, this remaining free. The filtering means 15 is traversed by the fuel stream in a substantially axial direction (ie parallel to the generators of the paper roll), and possesses a substantially horizontal lower surface 15'from which the fluid leaves in a substantially vertical direction after passing through the filtering means.
A water separator means 20 is provided below the lower surface 15' of the filtering means 15, and comprises a flow deviator member 21 having an upwardly converging upper frusto-conical surface 22 virtually completely occupying the projection of the lower surface 15'of the filtering means 15; this upper surface 22, which is downwardly inclined and forms an angle to the vertical, defines a flow surface along which the fluid flows and which deviates the fuel stream, to aggregate and separate the water parts present in the fuel.
The member 21 separates the first chamber 31 from the lower chamber 33 and has, in plan view, a circular shape of extension slightly less than the cross-section through the inner surface of the casing 10; between the peripheral edge of the member 21 and the inner surface of the casing 10 there is therefore defined a narrow annular passage 17 through which the flow passes from the chamber 31 to the chamber 33.
The deviator member 21 is lowerly hollow and has a central passage port 24 positioned at the lower end of the exit chamber 32, in particular fixed to the lower end of the central duct 35.
The separator means 20 comprises a filtering mesh 25 positioned on the lower end of the deviator member 22 to cover the cavity in this latter and the access to the port 24. The filtering mesh 25
is coated with a substance such as poly-tetra-fluoro-ethylene (PTFE-usually known as TeflonR) or silicone or the like, and has passage pores of diameter not exceeding about 200 micron, to intercept the water parts present in the fuel.
In a preferred embodiment, the filtering mesh 25 is formed of single-thread fabric with thread diameter varying from 0.02 to 0.2 mm and a weft spacing varying from 25 to 200 micron. The filtering mesh 25 is preferably of stainless steel, nylon or polyamide.
The coating thickness is preferably 2-8 micron.
In practice, the PTFE is applied either to both sides or only to one side of the filtering mesh 25, by spraying followed by baking in an oven.
In operation, the fuel firstly enters via the aperture 11 into the upper portion 31a of the chamber 31, and from there descends axially along the filtering means 15, flowing along the mutually adhering surfaces of the rolled paper sheet, where the more solid foreign particles are retained, whereas the water particles are not retained.
On leaving the filtering means 15, the fuel stream encounters the deviator member 21 which deviates its path and compels it to flow along the upper surface 22. Being heavier than the fuel, the water particles tend to maintain their exit direction from the lower surface 15'of the filtering means 15 more than the fuel, hence tending to deposit on the surface 22; a further factor favouring deposition of the water particles on the surface 22 is that in flowing along the surface 22, these particles are slowed down more than the fuel. The overall result is that the water particles tend to sediment on the surface 22 where they accumulate and aggregate, to then, as their mass increases, fall onto the bottom of the lower chamber 33 where they form an accumulated mass M, which is periodically bled through a lower outlet 36.
The fuel stream which has entered the lower chamber 33 then rises upwards through the exit chamber 32.
However, before entering the chamber 32, the stream encounters the filtering mesh 25 which retains those water particles which were
not separated by the surface 22.
In this respect, it has been found that the filtering mesh 25, having the aforedescribed technical characteristics, prevents passage of water through it to a substantially complete or at least considerable extent, while not posing any obstacle to passage of the actual fuel.
Presumably, this favourable phenomenon is caused by a different surface tension of the water particles, which, in the presence of the teflon or silicon covered mesh 25, break the bonds with the fuel molecules, agglomerate with each other and are unable to pass through the mesh; and then fall downwards onto the bottom of the collection chamber 33.
Obviously the smaller the diameter of the pores of the filtering mesh 25, the greater their intercepting action on the water particles. In practice, with a diameter of close to 20 microns there is already virtually total interception of the water particles.
Using the invention it has been found experimentally possible to achieve very high levels of water separation, close to total separation.
In the embodiment shown in Figures 2 and 3, the deviator member 21 is also arranged to support the filtering means 15. For this purpose the deviator member 21 comprises a plurality of radial elements 26 projecting upwards from the flow surface 22, to act as a support for the lower surface 15'of the filtering means 15.
In the embodiment shown in Figures 4 and 5, the deviator member 21 comprises one or more projecting ridges 27 situated on the flow surface 22, to define spiral paths starting from the vertex of the surface 22. The ridges 27 increase the length of the fluid travel along the surface 22, to hence facilitate sedimentation of the water particles on the surface 22.
The filtering means 15 is supported on a perforated horizontal baffle 28 rigid with the member 21 and positioned above the surface 22.
Numerous modifications of a practical and applicational nature can be made to the invention, but without deviating from the inventive idea as claimed below.
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