A fuel filter equipped with a quick fastening cover for an internal combustion engine

Abstract: The filter comprises a case (1; 1') for a fuel filter element (2) and a cover (3; 3') that can be built according to two embodiments: with holes (19, 20) allowing the screwing of the filter onto a threaded fix or connection of the fuel supply line, or with elbow-ducts (32, 33) projecting from the cover and integrally formed therewith. Both the cover and the case are of plastic material. The fastening of the cover to the case is obtained by means of a quick screwing and a subsequent blocking thanks to the presence of oblique teeth both in the case (1; 1') and in the cover acting as a ratchet gear arrangement for preventing the unscrewing. A settlement chamber (10) is formed at the bottom of the case (1; 1') having radial projections (5) reinforcing the structure thereof.

Description: The present invention relates to a fuel filter for an internal combustion engine, equipped with a quick fastening cover. There are known several fuel filters, particularly filters for feeding gas oil to internal combustion engines, mainly of motor vehicles. Since these devices are to be mass-produced, both for the original equipment of motor vehicles and as spare parts, it is important to reconcile the product reliability and quality with a low manufacturing cost thereof. A fuel filter for internal combustion engines is disclosed in the Italian Utility Model Application No.53316-B/88 in the name of the present Applicant. In such a type of filter a paper filter element is housed within a plastic cylindrical case to be screwed onto a suitably threaded connection provided in the engine. The case is closed by a cover having a number of holes for the fuel passage and suitable seals. The cover is fastened to the case upper lip by means of a welding and in order to allow this latter corresponding grooves are formed in the case and in the cover to collect the so produced swarf material. This solution has some drawbacks both for what concerns the product quality and the manufacturing cost thereof. The object of the present invention is that of overcoming or at least reducing the drawbacks of the known filters, by providing a fuel filter for an internal combustion engine wherein the cover can be fastened to the case through a simple and easy operation, without thermal treatments. Another object of the invention is that of providing a fuel filter adapted to be made in two alternative embodiments, one of the type to be screwed onto a suitable fix or connection (spin-on), and the other of the type connectible to the fuel supply line through ducts, both embodiments incorporating a common main structure. The above and other objects and advantages of the invention as will be clear from the rest of the description, are achieved by a fuel filter for an internal combustion engine comprising a plastic material cylindrical case housing a filter element above a settlement chamber defined at the case bottom, and a cover also of plastic material for closing said case, provided with fuel inlet openings and fuel outlet openings, characterized in that said case terminates with an upper collar provided with helical screwing means adapted to cooperate with complementary helical screwing means on the collar of the cover, and in that said screwing means are both associated with clamping oblique teeth for the permanent blocking of said cover to said case. An additional characteristic of the filter according to the invention is that the case bottom wherein a settlement chamber for the fuel is formed is provided with a series of radial projections that stiffen the structure and are integrally formed with the case, defining upwardly a rest plane for said filter element. A preferred embodiment of the invention will now be described with reference to the attached drawings, in which: Fig. 1 is an axial cross section view of a first embodiment of the filter according to the invention; Fig. 2 is a top plan view of the filter of Fig. 1 with the cover taken away; Fig. 3 is a part section top plan view of the filter cover of Fig. 1; Fig. 4 is an axial cross section of the cover according to an embodiment of the screwing system; Fig. 5 is a partial view of the case according to an embodiment of the screwing system of Fig. 4; Fig. 6 is a part section top plan view of a second embodiment of the filter cover of Fig. 3; Fig. 7 is a cross section view along line VII-VII of the cover of Fig. 6; Fig. 8 is a part section top plan view of a third embodiment of the filter cover of Fig. 3; Fig. 9 is an axial part section view of the cover of Fig. 8; Fig. 1⊘ is a part section top plan view of a fourth embodiment of the filter cover of Fig. 3; and Fig. 11 is an axial part section view of the cover of Fig. 1⊘. With reference to Fig. 1, there is shown a first embodiment of a fuel filter for engines of vehicles according to the invention. The filter substantially comprises a cylindrical case 1 housing a filter element 2 and closed by a cover 3. Both the case 1 and the cover 3 are of a plastic material having suitable characteristics, in case filled with glass fibers or other substances adapted to increase the mechanical and thermal resistance to the values desired for a specific application. The case and the cover can therefore be inexpensively manufactured by moulding. The filter element 2 is formed by crepe paper wrapped around a central tube 4 as it is known in the art. As shown in Figures 1 and 2, the bottom of the case 1 is provided with a series of projections 5 raising from the case bottom that extend radially but terminate before the center of the case. Such radial projections stiffen the lower portion of the case structure which is bound to be stressed by compression either manually or by means of a tool when the filter is screwed onto the engine. Since all the projections have the same height, the projections 5 provide a flat resting surface for the filter element 2. To this aim each of the projections 5 comprise an upper rib 7 shaped as a circle arc at the inner end of the projections: the whole of the ribs 7 forms a centering sleeve onto which the filter element 2 is fitted through the axial hole of the tube 4. Thus a settlement chamber 1⊘ is defined below the filter element 2, at the bottom of which a drain hole 12 is provided that is closed by a screw plug 13. The case 1 terminates upwards with an inwardly tapered collar 14 adapted to engage a circular groove 21 with a conical cross section in the cover 3, and provided on its outer surface of helical projections 15 that are relatively short and inclined. In correspondence with the the end portion of each projection 15 an array of oblique teeth 17 directed upward is moulded on the rest projection 16, the oblique teeth extending between each helical projection 15. The case 1 is watertight sealed by a cup shaped cover 3 provided with inlet and outlet openings for the fuel to be filtered. In the embodiment of Figures 1, 3 and 4, the cover 3 is of the type allowing for the filter to be screwed onto a threaded fix or connection projecting from the engine or from that portion (not shown) of the fuel supply line to which the filter is to be applied. Therefore the cover is equipped with a central threaded hole 19 also acting as an outlet opening of the filtered fuel. The cover is further provided with a series of openings 2⊘ located on a circle having a diameter that is about one half the cover diameter, acting as inlet openings of the fuel to be filtered. On the outer face of the cover there are provided two annular seal gaskets 22 and 23, the former being outside the holes 2⊘ and the latter being located between the holes 2⊘ and the central hole 19. The gaskets 22 and 23 are forcibly received in circular grooves 24 and 25 ensuring the correct positioning of the gaskets when the filter is screwed onto the threaded fix or connection. Preferably the cross section of the grooves 24 and 25 is trapeziform. As indicated, the cover 3 is of the cup shaped type, with the concavity towards the case. Within the cover, along the side wall thereof, there are provided helical grooves 27 having the same inclination as the threads or helical projections 15 of the case 1. On the collar of the case 1 there is formed an array of downwardly directed oblique teeth 28, whose direction of inclination (slant) is the same as that of teeth 17 of the case 1. Such construction allows for the cover 3 to be screwed onto the the case 1 by means of a quick movement thanks to the inclination of the projections 15 and the grooves 27 and to the fact that both are relatively short, so that the cover is brought from a starting position to a final position of complete screwing through a fraction of turn. After the screwing has been completed, by imparting a further torsion to the cover, the teeth 28 are driven to move over the back of the teeth 17 of the case, which is possible due to the fact that they both are inclined the same way. After this operation, the fastening of the cover has become irreversible, that is permanent, since the unscrewing thereof is prevented by the ratchet and gear engagement between the two arrays of teeth 17 and the teeth 28 with each tooth 17 acting as a ratchet or pawl with respect to the teeth 28 on the cover so that this latter can no longer be turned in a direction opposed to the one that caused the screwing thereof. This way it becomes possible to assemble together the case and the cover by means of a simple and quick mechanical operation. When the cover has been fastened, the sleeve 29 defining the axial hole 19 is fitted into the tube 4 (Fig. 1) and thanks to its slightly frusto-conical external configuration, it ensures the seal between the incoming fuel flow through the holes 2⊘ and the outlet fuel flow through the hole 19. Figures 4 and 5 show an embodiment of the screwing system of the cover to the case obtained by means of helical grooves 15' on the collar 14' of the case 1' below which are located the clamping teeth 17' outwardly directed and by means of relatively short projections 27' and inclined inwardly of the collar of the case under which projections are provided the teeth 28' turned inwardly of the cover and correspondingly oblique with respect to the teeth 17' on the collar of the case. The operation of the above illustrated filter is well known: the fuel to be filtered, usually gas oil, penetrates the filter through the holes 2⊘ and flows through the filter element 2 reaching the settlement chamber 1⊘. Here the water and other settled impurities to be periodically drained through the hole 12 are collected, then the filter fuel flows upwardly through the axial hole 8 from the tube 4 and comes out through the central hole 19 in the cover 3. Figures 6 and 7 show another embodiment of the filter cover according to the invention, generally designated with 3⊘. Such cover can be fastened the same way as shown above for the cover 3 to the case 1 since the portion to be mated with the case is the same in both embodiments. The difference between the cover 3⊘ and the cover 3 is that the cover 3⊘ is provided with elbow ducts 32 and 33 integrally formed with the cover body by moulding, for the fuel inlet into and the fuel outlet from the filter, respectively. Duct 32 opens into the filter chamber 34 over the filter element, whereas duct 33 is located at an axial position aligned with the tube 4 that has already been discussed with reference to the case 1. An air venting hole 35 is further provided for in the cover which is normally closed by a screw 36. A frusto-conical collar or sleeve 39 projecting within the cover is provided for the seal connection between the tube 4 and the case 1. By assembling together the cover 3⊘ and the case 1 one obtains a filter that needs no longer to be screwed for the connection to the fuel supply line, but rather one that is to be directly connected to the line through the ducts 32 and 33. The connection is achieved by fitting the end portions of the ducts 32 and 33 into the pipes of the fuel supply line and blocking them together by means of hose clamps. Figures 8 and 9 show a third embodiment of the cover generally designated at 4⊘. The cover 4⊘ is different from the previous illustrated embodiments in that the ducts 41 and 42 are of the quick connection type. They are provided with portions 43 and 44 adapted to sealingly fitting corresponding portions provided at the ends of the fuel supply pipes (not shown). Such portions include one or more seal gaskets and allow for the pipe fastening by simply press fitting of the portions 43 and 44 of the ducts 41 and 42. Several types of quick coupling devices are commercially available. Figures 1⊘ and 11 show a fourth embodiment of the cover that is on the whole designate at 5⊘. In this embodiment the ducts 51 and 52 are no longer integrally formed with the cover, but rather separately built and then rotatably mounted on the cover. The cover therefore is provided with two holes having a proper diameter to receive the ducts 51 and 52. In the axial hole into which the outlet duct 52 is fitted there is provided a gasket 54 formed by two sealing ribs held in the proper position by a rigid insert 55 that in turn is equipped with a rib 56 binding the axial position thereof. The lower portion of the duct is slightly conical and is formed with a tooth 58 so as to allow the insertion into the hole and prevent the later extraction thereof. The inlet duct 51 is fitted into the peripheral hole formed in a portion of the cover having a reduced thickness with respect to the central portion. Consequently the gasket 59 is a simple seal ring, e.g. an O ring, again held in position by an insert 6⊘ equipped with a fastening rib 61. The ducts 51 and 52 can be formed with quick coupling connections 63 and 64, or being terminated by conventional components requiring hose clamps for the fastening of the gas oil supply pipes, as shown in Figures 6 and 7. Thanks to the embodiment shown in Figures 1⊘ and 11 the elbow ducts 51 and 52 can be radially oriented as desired in order to select the optimum position for mounting the filter in the gas oil supply line to the engine.

Claims: A fuel filter for an internal combustion engine comprising a plastic material cylindrical case (1; 1') housing a filter element (2) above a settlement chamber (1⊘) defined at the case bottom, and a cover (3; 3'; 3⊘) also of plastic material for closing said case (1), provided with fuel inlet openings (2⊘; 32) and fuel outlet openings (19; 33), characterized in that said case (1; 1') terminates with an upper collar (14; 14') provided with helical screwing means (15; 15') adapted to cooperate with complementary helical screwing means (27; 27') on the collar of the cover (3; 3'; 3⊘), and in that said screwing means (15; 15' and 27; 27') are both associated with clamping oblique teeth (17; 17') for the permanent blocking of said cover (3; 3', 3⊘) to said case (1; 1'). A filter as claimed in claim 1, characterized in that said case (1) has a tapered collar (14) and in that the cover (3) has a circular groove (21) with a conical cross section adapted to receive the tapered collar (14) of the case. A filter as claimed in claims 1 and 2, characterized in that the helical screwing means on the collar of the case (1) and those on the collar of the cover (3) are made up by relatively short helical projections and inclined (15) and helical grooves (27), respectively, and in that the oblique teeth (17) associated to the projections (15) and those (28) associated to the grooves (27) are located on the rest projection (16) of the collar (14) of the case (1) as an upwardly directed array and on the collar of the cover (3) as a downwardly directed array, respectively, said oblique teeth being adapted to prevent the unscrewing of the cover (3) from the case (1). A filter as claimed in claim 1, characterized in that the helical screwing means on the collar (14') of the case (1') and on the collar of the cover (3') are made up by helical grooves (15') and relatively short and inclined helical projections (27'), respectively, and in that the oblique teeth (17') associated to the helical grooves (15') and those (28') associated to the helical projections (27') are both located as an array below the grooves (15') of the case (1) and below the projections (27') of the cover (3'), respectively, said oblique teeth (17') and (28') being adapted to prevent the unscrewing of the cover (3') from the case (1') A filter as claimed in claim 1, characterized in that the bottom of said settlement chamber (1⊘) of the case (1; 1') is provided with radially extending projections (5) that terminate before the center of the case and upwardly define a flat rest surface for said filter element (2). A filter as claimed in claim 1, characterized in that said cover (3; 3') is provided with eccentric holes (2⊘) for the fuel inlet and with an axial threaded hole (19) for the fuel outlet and the filter fastening, and with a pair of ring-shaped seal gaskets (22, 23) forcibly received in seats (24, 25) one (25) of which being located between said threaded axial hole (19) and said eccentric holes (2⊘), and the other (24) of which being located outside said eccentric holes (2⊘). A filter as claimed in claim 6, characterized in that said threaded axial hole (19) is defined in a sleeve terminating downwardly with a frusto-conical portion (29) for the coupling with a tube (4) of the filter element (2). A filter as claimed in claim 1, characterized in that said cover (3⊘) is provided with fuel inlet ducts (32) and outlet ducts (33) that are integrally formed with said cover and are elbow-bended outside it. A filter as claimed in claim 8, characterized in that said inlet ducts are equipped with quick connection fixes or connections (43, 44) for the connection to the fuel supply line. A filter as claimed in claim 1, characterized in that said cover (5⊘) is equipped with fuel inlet ducts (51) and fuel outlet ducts (52) separately formed from the cover (5⊘) and rotatably mounted into holes in said cover. A filter as claimed in claim 1⊘, characterized in that between said elbow ducts (51, 52) and said cover holes there are interposed a seal gasket (59; 54) and an insert (6⊘; 53) for the fastening of said gasket.

Inventors: BARACCHI FABRIZIO, CASALICCHIO SILVANO, GALLINO MAURO, TARDITI LUIGI, BARACCHI, FABRIZIO, CASALICCHIO, SILVANO, GALLINO, MAURO, TARDITI, LUIGI
Applicants: GILARDINI SPA, GILARDINI S.P.A.
Application year: 1991
Main classification: F02M37
IPC codes: B01D35, B01D36, F02M37