FLUID FILTER WITH HIGH FILTERING CAPACITY

TECHNICAL FIELD The present invention relates to a filter for fluids, such as oil and diesel fuel, to be associated with motor vehicle internal combustion engines.

PRIOR ART

Modern fluid filters are known to consist of an outer casing containing a filter cartridge which divides the interior into two separate chambers to which an inlet conduit for the fluid to be filtered and an outlet conduit for the filtered fluid are connected respectively. The outer casing generally consists of a cup-shaped hollow body and a cover which closes it, while the filter cartridge comprises a tubular filtering baffle supported between a lower base and an upper stem which fixes it to said cover.

The performance of a fluid filter is also known to depend on its filtering capacity, i.e. the quantity of impurities which it is able to retain before becoming clogged, and hence before being replaced; this filtering capacity depending not only on the type and quality of the constituent material of the filtering baffle, but also on the size of the surface which this latter offers to the fluid flow to be filtered.

For this reason, for lubricating oil and diesel fuel filtration, filter cartridges are generally used comprising a perforated tubular support about which a pleated filtering baffle is wrapped, presenting a plurality of longitudinal pleats disposed radially about the support to provide a large filtering surface but with a relatively small overall volume; said filtering baffle being

known as a baffle of star geometry.

Notwithstanding the good results obtained from baffles of star geometry, it is apparent that to increase the filtering surface of a fluid filter of known type, the dimensions of the filter cartridge must in the final analysis be increased, with consequent increase in the filter dimensions. However this requirement is in contrast with the requirement in the automobile filtration field of producing fluid filters which provide continually increasing performance while maintaining overall space requirements constant, in order to adapt as far as possible to continuous technical developments in the automotive field.

DISCLOSURE OF THE INVENTION

The object of the present invention is therefore to provide a fluid filter which for the same overall volume has a higher filtering capacity than known filters, this being achieved within the framework of a simple, rational and low-cost solution.

This object is attained by a fluid filter for internal combustion engines, the interior of which is separated into two separate chambers to which an inlet conduit for the fluid to be filtered and an outlet conduit for the filtered fluid are connected respectively; said filter comprising a pair of tubular filtering baffles associated with each other and positioned one inside the other, such as to define, within the interspace between these latter, one of said chambers. By virtue of this solution, the two filtering baffles are traversed simultaneously by the fluid flow to be purified and, by working in parallel, provide a filtering surface equal to the sum of the filtering surfaces of each

of them.

Consequently, for the same overall volume, the same type of filtering baffle and the same constituent material, a filter according to the invention possesses a decidedly higher filtering capacity than a fluid filter of known type.

According to the invention, the fluid filter can be constructed in two different configurations which differ by the path taken by the fluid within the filter interior. More particularly, the chamber defined within the interspace between the two filtering baffles can be that connected to the inlet conduit, in which case the fluid passes through said filtering baffles from the inside to the outside; or it can be that connected to the outlet conduit, in which case the fluid passes through the filtering baffles from the outside to the inside. Finally, according to a preferred embodiment of the invention, the two filtering baffles of the filter are of star geometry, in order to advantageously maximize the filtering capacity of the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will be apparent on reading the ensuing description, provided by way of non-limiting example, with reference to the figures of the accompanying drawings, in which:

Figure 1 is a longitudinal section through a fluid filter according to the invention; Figure 2 is a section on the line H-Il indicated in Figure 1 ;

Figure 3 is a longitudinal section through a second embodiment of a fluid filter of the invention;

Figure 4 is a section on the line IV-IV indicated in Figure 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Figure 1 shows a fluid filter, indicated overall by 1 , comprising an outer casing 2 provided with an inlet conduit 3 for the fluid to be filtered and an outlet conduit 4 for the filtered fluid. The outer casing 2 is formed from a cup-shaped hollow body 20 tightly closed by an upper cover 21 into which said inlet conduit 3 and outlet conduit 4 open, the cover 21 being joined to the body 20 by usual fixing means such as welding, clinching or a threaded connection. The outer casing 2 contains a filter cartridge 5 which, associated with the cover 21 , divides the interior into two separate chambers 6 and 7, of which the first 6 communicates with the inlet conduit 3 for the fluid to be filtered, and the second 7 communicates with the outlet conduit 4 for the filtered fluid.

In detail, the filter cartridge 5 comprises an outer filtering baffle 50 of tubular form and an inner filtering baffle 51 , also of tubular form but of smaller diameter, to be positioned concentrically within the first to define an interspace representing said chamber 6 for the fluid to be filtered. In this manner, as can be seen in Figure 2, the filtered fluid chamber 7 is that portion of the interior of the casing 2 which remains defined on the outside of the outer baffle 50 and on the inside of the inner baffle 51. As visible in Figure 2, said filtering baffles 50 and 51 are both of star geometry, the outer filtering baffle 50 being contained within a first

perforated tubular support 52, while the inner filtering baffle 51 is wrapped about a second perforated tubular support 53, said first and second tubular support 52 and 53 being arranged to enable filtered fluid to pass to the chamber 7 while at the same time to retain the respective filtering baffles 50 and 51 in a radial direction.

With reference to Figure 1 , the filtering baffles 50, 51 and the perforated supports 52, 53 are assembled together and supported between a lower disc 54 and an upper disc 55, to which they are securely joined by fixing means, such as adhesive or welding. In detail, the lower disc 54 is provided with a central hole 540 connecting the space outside the filtering baffle 50 to the space inside the filtering baffle 51 , to enable all the filtered fluid to flow towards the outlet conduit 4. In contrast, the upper disc 55 is provided with a central hole 550 connecting the filtered fluid chamber 7 to the outlet conduit 4, and with a plurality of through holes or slots 551 connecting the inlet conduit 3 to the chamber 6 of the fluid to be filtered, this being situated within the interspace between the filtering baffles 50 and 51. The lower disc 54 and upper disc 55 are provided with circularly extending projecting ribs, 542 and 552 respectively, which face each other (see Figure 1) to maintain the filtering baffles 50 and 51 spaced apart.

The overall filter cartridge 5 is fixed to the upper cover 21 of the filter 1 by means of the upper disc 55, which comprises two concentric stems 553 and 554, of which the more inner stem 554 projects beyond the more outer 553. Said stems 553 and 554 engage as an exact fit, by way of usual interposed sealing members 8 (O-rings), with the interior of two corresponding cylindrical seats in the cover 21 , which are defined by two

circular concentric ribs 210 and 211 projecting from its lower surface. In detail (see Figure 1), the inner rib 211 surrounds the outlet conduit 4, while the outer rib 210 surrounds the inlet conduit 3, which therefore remains positioned between the two; in this manner, the engagement between the stems 553, 554 and the ribs 210, 211 results in the division of the interior of the filter 1 into the two separate chambers 6, 7, which are hermetically separated by the seal means 8.

In use, the fluid to be filtered is fed by a usual pumping unit into the filter 1 through the inlet conduit 3. By passing through the holes 551 in the upper disc 55, said fluid fills the chamber 6 and is urged by the pressure exerted by the pumping unit to pass through the filtering baffles 50 and 51 from the interior of the interspace to the outside, to undergo filtration and pass into the chamber 7. During this filtering stage the perforated supports 52 and 53 counteract the fluid thrusts which tend to urge the filtering baffles 50 and 51 apart, hence preventing these latter undergoing displacement or deformation. On reaching the chamber 7, that fluid part filtered by the outer baffle 50 mixes, by virtue of the hole 540 in the lower disc 54, with that fluid part filtered by the inner baffle 51 , to finally reach the outlet conduit 4 by passing through the aperture 550 in the upper disc 55. Figures 3 and 4 show an alternative embodiment of the invention, which differs from that already described by the path followed by the fluid within the filter 1. The basic constructional form of the filter 1 remains substantially the same, hence its structural components are indicated hereinafter, where possible, by the same reference numerals used for the first embodiment.

The inlet conduit of the filter 1 is now that indicated by 3', whereas the outlet conduit is that indicated by 4'.

In use, after passing through the conduit 3 ^J and the central hole 550 of the upper disc 55, the fluid to be filtered enters the interior of the chamber 7 where, because of the central hole 540 in the lower disc 54, it is able to simultaneously graze the inner lateral surface of the filtering baffle 51 and the outer lateral surface of the filtering baffle 50. Urged by the pressure exerted by the pumping unit upstream of the filter 1 , a first part of the fluid is filtered by the inner filtering baffle 51 , and a second part by the outer filtering baffle 50; the two filtered fluid fractions converge in the chamber 6 defined within the interspace between said filtering baffles 50 and 51 , to finally flow from the conduit 4' by passing through the holes 551 in the upper disc 55. From the constructional viewpoint, the filter 1 of this second embodiment differs from the preceding only with regard to the structure of the filter cartridge 5.

In this respect, as shown in Figures 3 and 4, said cartridge 5 no longer comprises two tubular perforated supports positioned outside the outer baffle 50 and inside the inner baffle 51 respectively, but comprises a single tubular perforated support 56 which is housed within the filtered fluid chamber 6, i.e. within the interspace between said filtering baffles 50 and 51.

In this second case, the fluid traverses the filtering baffles 50 and 51 from the outside to the inside, subjecting them to thrusts which tend to cause them to approach each other; consequently the function of the perforated support 56 is to allow fluid passage while at the same time retaining both

the filtering baffles, so preventing them from undergoing displacement or deformation. Moreover, as shown in Figure 4, in addition to being perforated, said support 56 is also shaped to leave defined within the chamber 6 a plurality of longitudinal conduits 560 which enable the filtered fluid to accumulate and then to flow towards the outlet conduit 4' via the holes 551.

An expert of the art can apply numerous modifications and variants to the described filter 1 to satisfy specific contingent requirements, all of which however are contained within the scope of protection of the invention, as defined by the following claims.