Title of Invention

FUEL FILTER, IN PARTICULAR FOR DIESEL FUEL

Abstract

The present invention discloses a fuel filter, in particular for diesel fuel, comprising a first chamber (31) communicating with the fuel inlet of said fuel filter, a second chamber (32), downstream of the first chamber (31), into which the filtered fuel enters and which communicates with the outlet (12) of the fuel filter, a filter medium (20) for filtering off the impurities, which separates the second chamber (32) from the first chamber (31), and a third chamber (33) in which the fuel portion repelled by the filter medium (20) collects, characterised by a mesh surface (40) separating the second chamber (32) from the first chamber (31) and coated with a substance such as poly-tetra-fluoro-ethylene (PTFE) or silicone, said mesh surface having passage pores of diameter not greater than 200 microns to intercept the water parts present in the fuel.

Full Text

This invention relates to fuel filter, in particular for diesel fuel (generally known as gasoil) for diesel engines. 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. A technical problem which has not been totally solved 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 breakage thereof. For this problem, upstream of the cartridge there is inserted an inclined surface generally of frusto- conical shape, along which the entering fuel flow runs before reaching the filter cartridge. Because the water has a greater specific gravity than the fuel, it tends to move more towards the inclined surface, where its travel is decelerated, with the result that the water particles tend to unite to form relatively large water droplets, which then fall to the base of the filter, where they collect without passing through the filter cartridge. This solution is not however totally satisfactory, in that generally at least a fraction of the water is not separated and reaches the outlet to cause the described problems. An object of the present invention is therefore to provide a filter able to more effectively separate the water present in fuel, in particular in diesel fuel, and possibly to achieve complete separation. The present invention provides a fuel filter, in particular for diesel fuel, comprising: a first chamber communicating with the fuel inlet of said fuel filter, a second chamber, downstream of the first chamber, into which the filtered fuel enters and which communicates with the outlet of the fuel filter, a filter medium for filtering off the impurities, which separates the second chamber from the first chamber, and -1A- a third chamber in which the fuel portion repelled by the filter medium collects, characterised by a mesh surface separating the second chamber from the first chamber and coated with a substance such as poly-tetra-fluoro-ethylene (PTFE) or silicone, said mesh surface having passage pores of diameter not greater than 200 microns to intercept the water parts present in the fuel. The mesh surface is preferably formed from a single-thread fabric whose thread diameter varies from 0.02 to 0.2 mm. The mesh surface may be made of stainless steel, nylon or polyamide. The thickness of the coating substance on the mesh surface is preferably 2 to 8 microns. In one preferred embodiment, the fuel filter comprises first, second and third chambers provided in an outer container having a vertical axis and having an inlet and an outlet; said filter medium comprises a filter cartridge of cross-section in the form of a circular crown, substantially coaxial to the outer container and having its outer cylindrical surface spaced from the inner surface of the outer container and its lower surface spaced from the base of the outer container; said second chamber is connected to the outlet by means of a conduit; means are provided for closing the lower and upper ends of the cartridge, so that the only passageway between the first chamber and the second chamber is via the lateral surface of the cartridge; Said first chamber being defined by the region above and surrounding the cartridge, said second chamber being defined by the region within said cartridge and said third chamber being defined by the region below the cartridge and being arranged to intercept the entire flow which traverses the lateral surface of the cartridge. Preferably, above the lateral surface of the cartridge there is located an inclined surface along which the flow descends before passing through the cartridge, said surface carrying out an initial separation of the water part of the fuel. The mesh surface is preferably located to cover the outer lateral surface of the cartridge. -2- The invention is based on the idea of adding to the usual filter cartridge within a filter of known type a mesh surface through which the entire fuel flow passes. This mesh surface is coated with a substance such as poly-tetra-fluoro-ethylene (PTFE) or silicone or similar equivalent substances, and has passage pores of diameter not greater than about 200 microns, it having proved able to prevent passage of the water parts present in the fuel. Said mesh surface is positioned preferably (but not necessarily) downstream of an inclined surface for water pre-separation. The invention is described in detail hereinafter with the aid of the accompanying drawings, which illustrate a non-exclusive embodiment thereof. In these drawings, Figure 1 is a vertical elevation of the filter shown partly sectioned on an axial plane; Figure 2 is a section on the plane I-I of Figure 1; and Figure 3 is a section on the plane II-II of Figure 1. The filter comprises an outer container 10 having a vertical axis A, in particular being of substantially cylindrical shape with slight lower end dishing. 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 along a circumference with its centre on the axis A, the outlet being a single aperture with its centre on the axis A. -2A- f Within the container 10 there is a filter medium such as a filter cartridge 20 of known type, the cross-section of which is in the form of a circular crown, substantially coaxial with the container 10. The cartridge 20 defines the filter medium for filtering off the impurities present in the fuel. The outer diameter and height of the cartridge 20 are rather less than the corresponding dimensions of the container 10. Consequently the outer cylindrical surface of the cartridge 20 is spaced from the inner surface of the outer container 10. and its lower surface is spaced from the base 13 of the container 10. The region external to the cartridge, above and about its lateral surface, defines a first chamber 31 communicating with the fuel inlet ports 11. The region internal to the cartridge 20 defines a second chamber 32, which is separated from the chamber 31 by the cartridge itself. The region below the cartridge 20 defines a third chamber 33 which communicates with the first chamber 31. The upper end of the cartridge 20 and its lower end are closed respectively by an upper disc 21 and a lower disc 22 which are joined to the respective ends. To the inner lateral surface of the cartridge 20 there is fixed a perforated support tube 26. the ends of which are fixed to the upper disc 21 and lower disc 22 respectively. Between the upper disc 21 and the cover 14 there is positioned a conduit 24. which is joined to these latter and connects the inner chamber 32 to the outlet aperture 12. A spring 16 is inteiposed between the base 13 and the lower disc 22 to maintain the cartridge (with relative discs 21 and 22) urged against the conduit 24 and this latter urged against the cover 14. -3- - 4 - Passage between the first chamber 31 and the second chamber 32 takes place only via the lateral surface of the cartridge 20, in a substantially radial direction. The lower disc 22 has apertures 22a in its periphery to provide free passage between the first chamber 31 and the third chamber 33. The chamber 31 is divided into an upper portion 31a positioned above the cartridge 20, and a lower portion 31b freely communicating with the portion 31a and positioned about the lateral surface of the cartridge 20. The upper portion 31a directly communicates with the inlet apertures 11. Within it there is provided a frusta-conical element 25 fixed to the conduit 24 and extending below the apertures 11, it being inclined outwards and downwards. Said element 25 defines an inclined surface along which the flow descends before passing through the cartridge 20, and serves to provide initial separation of the water part of the fuel. According to the invention, there is provided a mesh surface 40 which separates the first chamber 31 from the second chamber 32 and is coated with a substance such as poly-tetra-fluoro-ethylene (PTFS - usually known as teflonR) or siliccne or the like and has passage pores of diameter not exceeding about 200 microns, able to intercept the water parts present in the fuel. According to a preferred embodiment, said mesh surface 40 is positioned coaxial to the cartridge 20, in particular against and covering the lateral surface of the cartridge 20, and is arranged to intercept the entire flow which in passing from the first chamber 31 to the second chamber 32 traverses the cartridge 20. According to a preferred embodiment, the mesh surface 40 is formed from single-thread fabric, the thread diameter of which varies from 0.02 to 0.2 mm. - 5 - Preferably, the mesh surface is of stainless steel, or nylon, or polyamide. Preferably the coating thickness is 2-8 microns. In practice the PTFE is applied to both sides of the surface 40, or to one side only, by spraying followed by baking in an oven. Alternatively silicone is applied to one or both sides of the surface 40. In operation, the fuel firstly enters the upper portion 31a of the first chamber 31 via the aperture 11, and then runs along the surface of the frusta-conical element 25 to pass into the lower portion 31b. The element 25 (as is known) decelerates the travel of the water particles and tends to aggregate them into relatively large droplets which then tend to fail directly into the third chamber 33, the purpose of which is to collect the parts separated from the fuel. Those water parts which are not separated by the inclined surface are in any event halted by the mesh surface 40 according to the invention. In this respect it has bean experimentally found that the surface 40, having the aforesaid technical characteristics, substantially completely prevents or at least strongly limits water passage through it, whereas it provides no obstacle to the 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-coated mesh 40, break the bonds with the fuel molecules, then mutually agglomerate and are unable to pass through the mesh; and hence fall downwards into the collection - 6 - chamber 33, from which they are periodically extracted. Evidently the smaller the pore diameter of the surface 40, the greater is the interception action on the water particles. In practice, at around a diameter of 20 microns there is total interception of the water particles. Numerous modifications can be made to that part of the filter excluding the mesh surface 40. Numerous modifications of a practical and applicational nature can be made to the surface 40, without leaving the scope of the inventive idea as hereinafter claimed. We Claim : 1. A fuel filter, in particular for diesel fuel, comprising: a first chamber (31) communicating with the fuel inlet of said fuel filter, a second chamber (32), downstream of the first chamber (31), into which the filtered fuel enters and which communicates with the outlet (12) of the fuel filter, a filter medium (20) for filtering off the impurities,- which separates the second chamber (32) from the first chamber (31), and a third chamber (33) in which the fuel portion repelled by the filter medium (20) collects, characterised by a mesh surface (40) separating the second chamber (32) from the first chamber (31) and coated with a substance such as poly-tetra-fluoro-ethylene (PTFE) or silicone, said mesh surface having passage pores of diameter not greater than 200 microns to intercept the water parts present in the fuel. 2. A fuel filter as claimed in claim 1, wherein the mesh surface (40) is formed from single- thread fabric the thread diameter of which varies from 0.02 to 0.2 mm. 3. A fuel filter as claimed in claim 1, wherein the mesh surface (40) is made of stainless steel. 4. A fuel filter as claimed in claim 1, wherein the mesh surface (40) is made of nylon. 5. A fuel filter as claimed in claim 1,; wherein the mesh surface is made of polyamide. 6. A fuel filter as claimed in claim 1, wherein the thickness of the coating substance on the mesh surface is 2-8 microns. 7. A fuel filter as claimed in claim 1, wherein said first, second and third chambers are provided in an outer container (10) having a vertical axis and having an inlet (11) and an outlet (12); said filter medium comprises a filter cartridge (20) of cross-section in the form of a circular crown, substantially coaxial to the outer container (10) and having its outer cylindrical surface spaced from the inner surface of the outer container (10) and its lower surface spaced from the -7- base (13) of the outer container (10); said second chamber (32) is connected to the outlet (12) by means of a conduit (24); means comprising an upper disc (21) and a lower disc (22) are provided for closing the upper and lower ends of the cartridge (20), so that the only passageway between the first chamber (31) and the second chamber (32) is via the lateral surface of the cartridge (20); said first camber (31) being defined by the region above and surrounding the cartridge (20), said second chamber (32) being defined by the region within said cartridge (20) and said third chamber (33) being defined by the region below the cartridge (20), said mesh surface (40) being positioned coaxial to the cartridge (20) covering the lateral surface of the cartridge (20) and being arranged to intercept the entire flow which traverses the lateral surface of the cartridge (20). 8. A fuel filter as claimed in claim 7, wherein above the lateral surface of the cartridge (20) there is located an inclined surface (25) along which the flow descends before passing through the cartridge (20), said surface (25) carrying out an initial separation of the water part of the fuel. 9. A fuel filter as claimed in claim 7, the mesh surface (40) is located to cover the outer lateral surface of the cartridge (20). 10. A fuel filter, in particular for diesel fuel, substantially as herein described, particularly with reference to and as illustrated in the accompanying drawings. Dated this 9th day of June, 1997. -8- The present invention discloses a fuel filter, in particular for diesel fuel, comprising a first chamber (31) communicating with the fuel inlet of said fuel filter, a second chamber (32), downstream of the first chamber (31), into which the filtered fuel enters and which communicates with the outlet (12) of the fuel filter, a filter medium (20) for filtering off the impurities, which separates the second chamber (32) from the first chamber (31), and a third chamber (33) in which the fuel portion repelled by the filter medium (20) collects, characterised by a mesh surface (40) separating the second chamber (32) from the first chamber (31) and coated with a substance such as poly-tetra-fluoro-ethylene (PTFE) or silicone, said mesh surface having passage pores of diameter not greater than 200 microns to intercept the water parts present in the fuel.

Documents:

01084-cal-1997-abstract.pdf

01084-cal-1997-assignment.pdf

01084-cal-1997-claims.pdf

01084-cal-1997-correspondence.pdf

01084-cal-1997-description (complete).pdf

01084-cal-1997-drawings.pdf

01084-cal-1997-form-1.pdf

01084-cal-1997-form-13.pdf

01084-cal-1997-form-2.pdf

01084-cal-1997-form-3.pdf

01084-cal-1997-form-5.pdf

01084-cal-1997-gpa.pdf

01084-cal-1997-pa.pdf

01084-cal-1997-priority document others.pdf

01084-cal-1997-priority document.pdf

1084-CAL-1997-CORRESPONDENCE 1.1.pdf

1084-CAL-1997-FORM 27-1.1.pdf

1084-CAL-1997-FORM 27.pdf

1084-CAL-1997-FORM-27.pdf

1084-cal-1997-granted-abstract_.pdf

1084-cal-1997-granted-acceptance publication_.pdf

1084-cal-1997-granted-assignment_.pdf

1084-cal-1997-granted-claims_.pdf

1084-cal-1997-granted-correspondence_.pdf

1084-cal-1997-granted-description (complete)_.pdf

1084-cal-1997-granted-drawings_.pdf

1084-cal-1997-granted-form 13_.pdf

1084-cal-1997-granted-form 1_.pdf

1084-cal-1997-granted-form 2_.pdf

1084-cal-1997-granted-form 3_.pdf

1084-cal-1997-granted-form 5_.pdf

1084-cal-1997-granted-gpa_.pdf

1084-cal-1997-granted-letter patent_.pdf

1084-cal-1997-granted-pa_.pdf

1084-cal-1997-granted-priority document_.pdf

1084-cal-1997-granted-reply to examination report_.pdf

1084-cal-1997-granted-specification_.pdf

1084-cal-1997-granted-translated copy of priority document_.pdf