AN IMPROVED DOUBLE FILTERING OIL FILTER FOR INTERNAL COMBUSTION ENGINES OF MOTOR VEHICLES

Abstract: A double filtering filter for lubricating oil of internal combustion engines of motor vehicles comprises a cylindrical housing (1) containing a rough filtering cartridge (3) and a superimposed fine filtering cartridge (5), both in form of cylindrical crowns and fitted over a tube (8) extending within the rough filtering cartridge (3) from a cover (10) of said housing (1). A cover (10) is provided with a plurality of peripheral inlet holes (12) for the oil to be filtered, an axial hole (14) for the outlet of the roughly filtered lubricant, and an intermediate radial hole (13) for the outlet of the finely filtered lubricant. The filter further comprises an annular seal gasket (19) on the tube between said two cartridges, and a pair of annular seal gaskets (11, 15) on the cover, one gasket (11) being positioned outside said plurality of peripheral holes (12) for the innet of the lubricating oil, and the other gasket (15) being positioned between said eccentric outlet hole (13) and said axial outlet hole (14). The fine filtering cartridge (5) comprises a continuous strip of disks (40) of filter paper, each disk providing for a central hole (41) and radial lobes (42, 42′, 43, 43′, 44, 44′), said disks being accordion pleated with the lobes of a disk offset in respect of the lobes of an adjoining disk, and sandwiched between two rigid rings (46, 48) also provided with aligned central holes.

Description: This invention relates to an improved double cartridge filter for lubricating oil or lubricant of internal combustion engines of motor vehicles. IT-A-1 141 751 discloses a double cartridge filter of the type to be screwed, comprising a rough filter cartridge and a fine filter cartridge superimposed together, contained in a cylindrical housing closed by a cover, equipped with a central hole for the lubricating oil undergoing the rough filtering, and an eccentric hole for draining into the oil sump the lubricant undergoing the fine filtering, as well as inlet holes for the lubricant to be filtered. In the commercial construction of this known filter, the fine filtering cartridge is made up by cotton flock compressed in a box of punched plate shaped as a cylindrical hollow body or crown. Therefore, the manufacturing of such cartridge requires the forging of two strips of punched plate forming the inner and outer cylindrical surfaces of the box, their curving as a ring and the folded seam of the opposed ends, and thereafter the fitting of plate disks with central holes as a lower and an upper base of the cartridge, after the filling of the pressed cotton. This construction results to be expensive due to the installations required for the operation and to the necessary labor. The object of the present invention is therefore that of providing a filter of the above mentioned kind, equipped with a fine filtering cartridge having the same filtering quality of the already used pressed cotton cartridges, but with reduced manufacturing costs. Another object of the invention is that of proposing a few improvements of the filter general structure to render easier its manufacturing without prejudice for the performance thereof. The above and other objects and advantages of the invention, as will become evident from the following description, are achieved through a double cartridge filter for lubricating oil of internal combustion engines of motor vehicles, comprising a cylindrical housing containing a rough filtering cartridge with a superimposed fine filtering cartridge, both being in form of a cylindrical crown and being fitted over a tube extending within the rough filtering cartridge from a cover of said housing, said cover being provided with a plurality of peripheral inlet holes for the oil to be filtered, an axial hole for the outlet of the roughly filtered lubricant, and an intermediate radial hole for the outlet of the finely filtered lubricant, said filter further comprising an annular seal gasket on said tube between said two cartridges, and a pair of annular seal gaskets on said cover, one gasket being positioned outside said plurality of peripheral holes for the inlet of the lubricating oil, and the other gasket being positioned between said eccentric outlet hole and said axial outlet hole, characterized in that said fine filtering cartridge comprises a continuous strip of disks of filter paper, each disk providing for a central hole and radial lobes, said disks being accordion pleated with the lobes of a disk offset in respect of the lobes of an adjoining disk, and sandwiched between two rigid rings also provided with aligned central holes. A preferred embodiment of the invention will now be disclosed, as a non limiting example, with reference to the accompanying drawings, in which: Fig. 1 is an axial cross section view of a filter according to the invention; Fig. 2 is a plan top view of the filter in Fig.1; Fig. 3 is a plan top view of the detailed of the fine filtering cartridge in the extended (opened) configuration; and Fig. 4 is a side view of the detail of Fig. 3 partially pleated. With reference to Fig.s 1 and 2, there it is shown a double filtering filter incorporating the improvements according to the invention, the general construction of the filter being such as disclosed by the above mentioned Italian patent. For clarity of illustration, in the present description the basic components of such filter will be mentioned in general, since a detailed description thereof can be found in the above mentioned patent. Essentially, the filter is made up by a cylindrical housing 1 containing a rough filtering cartridge 3, i.e. adapted to retain particles larger than 15-20 µm, and a fine filtering cartridge 5, i.e. adapted to retain particles larger, for example, than 3-4 µm. The rough filtering cartridge 3 is built in a conventional manner, that is by means of a filter element of pleated paper, whereas the fine filtering cartridge according to the main improvement of the present invention will be described in detail later. Both cartridges are fitted over a tube 8 molded from synthetic resin, provided with a circular shoulder 9 sealingly abutting against the fine filtering cartridge 5 through the gasket 7. At its top the filter provides for a rugged metal cover 10 provided with a plurality of peripheral holes 12 for the admission of the lubricating oil to be filtered, a central hole formed in a threaded fitting or nipple, for the outlet of the roughly filtered lubricant , and an eccentric hole 13 which is in a radially intermediate position between the peripheral holes 12 and the central hole 14, for the purpose of draining into the sump the finely filtered lubricant. Above the cover 10 a ring 18 is located which is sealingly fastened to the housing 1 and provided with circular concentric grooves acting as seats for an outer seal gasket 11 and for an intermediate gasket 15 for realizing an outward seal and between the finely filtered lubricant and the incoming lubricant, respectively. The ring 18 is provided with holes corresponding to those provided on the cover 10, but that may not be coaxial with such holes. An annular gasket 19 having a circular cross section is located between the two cartridges 3 and 5 and the outer surface of the tube 8, so as to divide the roughly filtered lubricant -that passed through the cartridge 3 from outside inwards- from the finely filtered lubricant -that passed through the cartridge 5 from outside inwards. Between the circular shoulder 9 of tube 8 and the cover 10 it is positioned a yielding ring 20 of synthetic rubber or the like, adapted to cover with its peripheral portion the holes 12 for the lubricant inlet. Under the yielding ring 20 is coaxially mounted a rigid disk 22 against which reacts a helical spring 23 abutting against the fine filtering cartridge 5. According to the invention, the shoulder 9 of the tube 8 provides for a circular groove 28 in correspondence with the hole 29 for the outlet of the fine filtered lubricant. A complementary groove 30 is formed on the ring 20 in the face toward the circular shoulder 9. Further a hole 32 provides a communication between the groove 30 and the groove 33 formed on the opposite surface of the yielding ring 20, to convey the lubricant to the outlet hole in the cover. Such construction of the tube shoulder and of the yielding ring 20 allows for an easier assembling of the filter components in the manufacturing thereof, since it provides for a communication between holes 29, 32 and 13 without requiring their alignement, as on the contrary it is shown in the figure. Namely, the grooves 28, 30 and 33 ensure the oil passage from cartridge 5 to hole 13 of the cover for any arrangement, even offset, of the above mentioned holes. The invention further relates to the type of the double filtering cartridge employed. Instead of a cartridge made up by pressed cotton within a housing of punched plate, as disclosed in the above mentioned patent, or of a pleated paper cartridge having the same structure as the rough filtering cartridge but with finer holes as proposed by other manufacturers, the double cartridge filter according to the invention employs a paper cartridge having a special lobed structure, as shown in Fig.s 4 and 5. The cartridge comprises a continuous strip of adjacentely connected paper punched disks 40, 40a, 40b, 40c (and so on for the other not shown disks), each having a central hole 41, 41a, 41b, 41c and radial lobes such as 42, 42′, 43, 43′, 44, 44′ as shown for disk 40. The corresponding lobes on the other disks 41a, 41b and 41c have been marked with the same reference numerals with the addition of letter a, b or c, respectively. Each disk is positioned on the strip rotated with respect to the preceding one, and is preferably connected to the adjacent disk through at least one lobe, and preferably through two lobes. According to a preferred embodiment, each disk comprises two major lobes 42, 42′ and four minor lobes 43, 43′ and 44, 44′. The disks are accordion pleated as shown in Fig. 4, so that the offset lobes overlap each other in such a manner to form a three-dimension filtering maze which is highly effective, economically manufactured and of compact structure. To form the final cartridge 5 the pack of the stacked disks is sandwiched between two opposed reinforcing rings 46 and 48 as shown in Fig. 1. Preferably the employed paper incorporates wool fibers and is of the type known as "wool paper". In the operation of the filter most of the lubricating oil passes through the cartridge 3 and comes out through the axial hole 14, whereas a small amount passes through the fine filtering cartridge 5 and through the hole 13 is discharged to the sump where a pressure lower than that within the engine causes a pressure difference across the cartridge 5 enough for such oil fraction to overcome the greater hydraulic resistance offered by the cartridge 5. It is thus possible to carry out a rough filtering of almost all the flow of oil, and a fine filtering of a part thereof.

Claims: A double cartridge filter for lubricating oil of internal combustion engines of motor vehicles, comprising a cylindrical housing (1) containing a rough filtering cartridge (3) with a superimposed fine filtering cartridge (5), both being in form of a cylindrical crown and being fitted over a tube (8) extending within the rough filtering cartridge (3) from a cover (10) of said housing (1), said cover (10) being provided with a plurality of peripheral inlet holes (12) for the oil to be filtered, an axial hole (14) for the outlet of the roughly filtered lubricant, and an intermediate radial hole (13) for the outlet of the finely filtered lubricant, said filter further comprising an annular seal gasket (19) on said tube (8) between said two cartridges (3) and (5), and a pair of annular seal gaskets (11, 15) on said cover (10), one gasket (11) being positioned outside said plurality of peripheral holes (12) for the inlet of the lubricating oil, and the other gasket (15) being positioned between said eccentric outlet hole (13) and said axial outlet hole (14), characterized in that said fine filtering cartridge (5) comprises a continuous strip of disks (40) of filter paper, each disk providing for a central hole (41) and radial lobes (42, 42′, 43, 43′, 44, 44′), said disks being accordion pleated with the lobes of a disk offset in respect of the lobes of an adjoining disk, and sandwiched between two rigid rings (46, 48) also provided with aligned central holes. A double cartridge filter as claimed in claim 1, characterized in that said disks (40) of said fine filtering cartridge (5) comprises six lobes, two major lobes (42, 42′) and four minor lobes (43, 43′, 44, 44′), and are connected to each other at at least one of said lobes. A double cartridge filter as claimed in claim 1, further comprising a circular shoulder (9) integral with said tube (8) and a yielding ring (20) interposed between said tube shoulder and the cover (10) of the housing (1), characterized in that: a circular groove (28) is provided in said tube circular shoulder (9) where the discharge hole (29) of the finely filtered lubricant opens; in said yielding ring (20) a groove (30) is provided that is corresponding to and facing said shoulder groove (28), and communicating through a hole (32) with a groove (33) on the opposite face of the ring, in correspondence with the intermediate hole (13) of the cover (10).

Inventors: DRUSI, ALBERTO
Applicants: GILARDINI S.P.A.
Application year: 1989
Main classification: B01D27
IPC codes: B01D27