BACKGROUND ART Internal combustion engines are known to generally comprise a lubrication system with which a disposable filter cartridge is associated contained in a cup, which it is not necessary to describe in detail.

Said cartridge is intended to be removably coupled, generally by a threaded system and by way of suitable interposed seal means, to a base provided on the engine structure and comprising a suitable seat.

The base of said cartridge is provided with apertures for the entry of the oil to be filtered and for the exit of the filtered oil, said seat presenting corresponding arrival and departure channels for the oil to be filtered and for the filtered oil respectively.

Engines exist in which the cartridge carrying seat generally faces downwards, and others in which it generally faces upwards.

Sunken regions which fill with oil during engine operation are generally present at the mutually facing surfaces of said seat and said cartridge.

When the cartridge is to be removed, for example for its replacement, at least a part of the oil present in said regions is no longer retained, hence is free to pour out of the base.

If the cartridge carrying seat generally faces downwards, the loss of said oil fraction is generally not a problem because the oil is retained by the cup of the cartridge.

However if the cartridge carrying seat faces generally upwards, the loss of said oil fraction can be a problem for at least one of the following reasons: soiling of engine parts and accessories reaching high temperature, oil seepage into electrical and/or electronic equipment, dirtying of the engine compartment and panels, and contamination of the workplace floor.

The main object of the present invention is to provide a base for a filter cartridge able to overcome the aforesaid problem.

A further object of the invention is to attain said object within the context of a simple, rational, reliable and economical construction.

DISCLOSURE OF THE INVENTION Said objects are attained by a base presenting the characteristic elements indicated in the claims.

In a totally general sense it comprises an upwardly facing engagement seat for receiving a filter cartridge contained in a cup-shaped sealed casing and provided with apertures for the entry of the oil to be filtered and for the exit of the filtered oil. According to the invention, there is peripheral associated with said seat a salient enveloping element with which it forms a sort of bowl, from the base of which there branches a recovery conduit extending to a suitable collection site, such as the engine oil sump, and intercepted by a check valve, described in detail hereinafter, the closed or open state of which depends on whether the cartridge and base are mutually engaged or disengaged respectively.

All the objects of the invention are attained by virtue of the aforesaid means.

In this respect, when in its closed state, i. e. with the cartridge mounted, said valve enables the oil to undergo normal filtration, whereas when in its closed state, i. e. with the cartridge removed and with the aid of said enveloping element, it allows automatic recovery of the oil which would otherwise spill out of the base.

Preferably the valve is closed and opened automatically, for example by elastic thrust means interposed between the valve and the base, and loaded by the action of the cartridge during its mounting.

The characteristics and the constructional merits of the invention will be apparent from the ensuing detailed description given with reference to the figures of the accompanying drawings, which illustrate a preferred embodiment thereof given by way of non-limiting example.

Figure 1 is an axial section through the invention with the cartridge shown mounted.

Figure 2 is a perspective view of the check valve of the invention.

Figure 3 is a partial schematic view showing the cartridge during an intermediate stage of its unscrewing from its seat.

Figure 4 is a view similar to the preceding showing the cartridge removed.

Said figures, and in particular Figures 1,3 and 4, show the base 1 on which a seat 2 is provided for mounting a lubricating oil filtration cartridge, of the disposable type.

In the illustrated example said seat 2 lies horizontally and is open upwards, but could equally be slightly inclined.

The seat 2 is provided with a central conduit 4 for exit of the filtered oil, and with a concentric annular groove 5 for feeding the oil to be filtered to the cartridge 3.

A usual arrival conduit for the oil to be fed, not shown for simplicity, and a recovery conduit 6 of different cross-sections, described hereinafter, open into said groove 5.

As can be seen, into said central conduit 4 there is screwed a hollow stem 7 which extends beyond the seat 2 with a threaded portion provided for fixing the overlying cartridge 3.

Said cartridge 3, of known type, comprises a cup-shaped outer casing 8, to the mouth of which there is seam-joined an annular ring 9 carrying an underlying gasket 10 for sealing along the outer annular edge of the seat 23 (Figure 1).

Proceeding in the figure from the bottom upwards, said cup 8 internally contains a centrally holed disc 11, a lip-shaped annular retention gasket 12, a hollow cylindrical filtering body 13, and a thrust spring 14 positioned between the base of the cup 8 and the upper cover 130 of the filtering body 13, to elastically clamp the assembly together.

A central anti-emptying tube 15 is also provided, coupled to the perforated lower cover of the filtering body 13.

The central hole of said disc 11 has a thread to be screwed onto the hollow stem 7, about said hole said disc 11 presenting a circumferential series of holes 110 facing the lip gasket 121, which acts as a valve. Said gasket 12 closes and opens automatically when the engine is stopped and started respectively.

In this respect, during engine operation the oil to be filtered, which is under pressure, enters the chamber defined by the groove 5, passes through the holes 110 and into the cartridge by raising the gasket, then passes through the filtering body 13 and finally reaches the exit conduit 4 via the tube 15 and the stem 4.

According to the invention, the base 1 comprises an enveloping element 33, said recovery conduit 6 being intercepted by a check valve, or valving element, indicated by 66.

Said enclosing element 33 consists of a relatively thin enclosing wall projecting upwards from the base and having its inner surface suitably spaced from the outer surface of the bottom end of the cartridge 3.

In the illustrated example said wall is integral with the base 1, but could also be constructed separately of metal or other suitable material, and then suitably secured to the base 1.

The valving element 66 comprises a cylindrical rod 16 presenting at its bottom an annular gasket 17, in an intermediate position two diametrically opposing longitudinal ribs 18 provided lowerly with an elastically deformable anti-withdrawal tooth 19, and at its top a widened head 20 beyond which there is a coaxial threaded pin 21.

The widened head 20 and the pin 21 are received in the groove 5.

The holed arm of a right-angled appendix 23 is engaged with said pin 21 and fixed thereto by the nut 22, the other arm passing beyond the seat 2 to rest against the ring 9 of the cartridge 3 with a sliding engagement.

Said other arm is shaped to maintain the valve 66 closed when the cartridge 3 is mounted, and to prevent the valve from rotating when the cartridge 3 is screwed in or out.

With reference to the recovery conduit 6, this connects the groove 5 to a convenient collection point, for example the engine oil sump. It comprises (see Figures 1,3 and 4) a lower smaller diameter portion with which it sealedly engages the gasket 17, and an upper larger diameter portion presenting an intermediate circumferential ledge 24.

This latter acts as an abutment for the underlying teeth 19, and as a support for an overlying thrust spring 25 mounted about the upper part of the rod 16, below the head 20.

When the cartridge 3 is removed, for example to be replaced, the region between the groove 5 of the base 1 and the lip gasket 12 is filled with filtered oil.

As the unscrewing of the cartridge 3 proceeds, it rises from the seat 2 and is followed by the valving element 66 by the effect of the thrust of the spring 25.

When there is no longer a seat between the cartridge 3 and seat 2, the oil contained between this latter and the lip gasket 12 seeps to the outside of the cartridge 3 and is distributed uniformly on the flat surface bounded by the wall 33 (see Figure 3).

When the cartridge 3 has been completely unscrewed it can be removed (see Figure 4), the oil lying above the seat 2, within the groove 5, and in the top of the recovery conduit 6 then discharging into the engine oil sump.