The present invention relates to sealing means for pressure carrying ele¬ ments, and pressure connection means employing such sealing means. The invention also relates to an application of the pressure connection means for the filtration of a fluid under low, medium, or high pressure in a filter system.

The use of O-rings of elastomeric material as fluid sealing means bet¬ ween two coupled components is well known in the art. The O-ring is normally placed in a groove or channel on the central element of the two elements to be joined. Due to machining tolerances, a small clear- ance gap exists between the members to be coupled. Under pressure the O-ring is deformed and partially leaves the O-ring channel and enters into the clearance or extrusion gap. This effect referred to as extrusion can lead to O-ring failure, for example in the form of peeling or nib¬ bling of the O-ring surface.

One method of avoiding failure is to provide an additional backup ring of higher hardness; which prevents the O-ring from entering into the extrusion gap.

There is an ever present need of developing new sealing arrangements, both for low, medium, and high pressure fluid systems, which substantially reduce the problem of O-ring failure. An object of the present invention is to provide a sealing means by which a clearance gap on the down¬ stream side ^" of the O-ring is substantially eliminated. A further object is to provide pressure connection means employing the sealing means, by

which a minimal number of connection elements is necessary. A further object of the invention is to provide a low, medium, or high pressure fluid filtration system making use of the pressure connection means.

In accordance with this invention, sealing means for pressure carrying coupling members are provided as defined in the claims. A first conical surface is arranged on one coupling member about a central axis there¬ of. The second coupling member has arranged thereon a second conical surface, which is brought into partial contact with the first surface. The cone angles of the surfaces measured from the central axis is such that the angle of the second surface is slightly larger, preferably 1 to 10° larger, most preferably about 5° larger, than the angle of the first surfa¬ ce.

By providing slightly different angles of the surfaces, the contact area of the two coupling members is formed in an annular region about the central axis. With this arrangement, no gap arises between the two coupling elements, which are in direct material contact.

The sealing means preferably also comprise an O-ring contacting the two coupling members, ^" where the contact area is displaced upstream from the high pressure side of the annular contact region of the two conical surfaces.

Pressure connection means are also provided in accordance with the invention as defined in the claims. The connection means comprise first and second coupling members each having interior chambers to provide a fluid passageway. The first coupling member has an outer threaded

portion which engages with an inner threaded portion of the second coupling member in the connected condition.

The threaded portions are preferably arranged on the coupling members axially displaced from the first and second conical surfaces such that contact is urged between the conical surfaces to form a tight material contact. The connection means has the advantage of comprising only two pieces joined by a screw connection. Preferably the threaded portions are located on the dry side of the seal which reduces the chance of possible contamination when the connection is assembled or disassembled.

Another advantage of the claimed sealing means and connection means is that with the conical surface contact seal, the tolerances in machining the two coupling members can be less severe. The cost of manufacturing the coupling elements can therefore be held down.

Further objects and advantages of the present invention will become clear in the following description of an embodiment in conjunction with the drawing.

Figure 1 shows an embodiment of the sealing means in accordance with the present invention.

Figure 2 shows an embodiment of the pressure connection means of the present invention, where one coupling member is a filter bowl.

Now referring to Figure 1, an embodiment of the sealing means 1 is shown arranged to provide a seal between the pressure carrying coupling members 10 and 11. Figure 1 shows an embodiment where a portion of

the first coupling member 10 with a central axis 20, is arranged coaxially within a portion of the second coupling member 11. The first coupling member 10 has a conical or frustocoπical surface 6, which extends about the central axis 20.

A second conical or frustoconical surface 9 is arranged on the second coupling member 11 and is in partial contact with the first surface 6. As can be seen in Figure 1, the cone angle of the second conical surface 9 with respect to the axis 20 is larger than the corresponding angle of the first conical surface 6.

The surfaces 6, 9 contact each other in a region 13 which extends annularly about the central axis 20. The radial extent of the contact region 13 will be less than the radial extent of either of the two conical surfaces. The radial distance of contact on the surfaces will also depend on the difference in cone angles of the two surfaces. In other words the smaller the difference, the larger the radial dimension of the annular contact region.

The cone angle of the first conical surface with respect to the axis 20 is preferably in the range of 3 and 45° and more preferably in the range of 15 to 20°. The angle of the second conical surface is nominally 1 to 10° greater than the cone angle of the first surface, preferably about 5° greater.

As can readily be seen from Figure 1, the two coupling members when engaged with one another form a material contact. Due to the arran¬ gement of tapered contact surfaces, the tolerances of machining the two coupling members, e.g. their diameters, can be relaxed or at least need

not be so stringent. A clearance gap or tolerance gap is eliminated in the contact region.

In a further embodiment, an O-ring in contact with the first and second coupling members is provided with a contact area displaced upstream of the high pressure side of the annular contact region. As shown in Figure 1, the high pressure side is indicated at (a) and the low pressure side at (b). The contact area of the O-ring 2 with the second coupling member 11 is preferably immediately adjacent to the annular contact region 13 of the two conical surfaces. In this manner, there is essentially no extrusion gap or clearance gap downstream of the O-ring 2. The O- ring 2 is preferably arranged in an annular channel 3 in an outer sur¬ face of the first coupling member 10. The channel 3 is preferably dis¬ placed adjacent in axial direction to the inside edge of the first conical surface 6.

An embodiment of the pressure connection means in accordance with the present invention is shown in Figure 2. The first coupling member 4 of this embodiment comprises an interior chamber 14, and the second coupling member 7 comprises an interior chamber 17. The two chambers communicate to form ' a fluid passageway. The first member 4 also comprises an outer threaded portion 5 which engages with an inner threaded portion 8 of the second coupling member 7.

The threaded portions 5, 8 are arranged on the coupling members axially displaced from the first and second conical surfaces of the sealing means 1 such that contact between the two surfaces is urged when screwed together. The two parts will materially butt each other and remain in

contact during service when the correct torque has been applied and is maintained.

As can also be seen in Figure 2, the threaded portions 5, 8 of the coupling members 4, 7 are arranged downstream or on the low pressure side of the sealing means 1. This corresponds to the low pressure side (b) of Figure 1. The threads are therefore not exposed to the pressur¬ ized medium passing the internal chambers 14 and 17.

The embodiment shown in Figure 2 illustrates the use of the pressure connection means in a high pressure fluid filtration system. The first coupling member 4 comprises a filter bowl into which a filter element (not shown) can be provided in the chamber 14. In this embodiment, the second coupling member 7 is a filter head which supplies the fluid to be filtered via the chamber 17.

The pressure connection means are particularly useful in this fluid filtration system. The means comprise only two parts to be screw connec¬ ted. The tolerances of the components as mentioned above need not be severe. In addition, the O-ring channel 3 can also be machined using normal tolerances. The ^' filter bowl and filter head material will normally be carbon steel, ductile iron castings or stainless steel.

Integrity tests in the form of fatigue tests have been made for the embodiment of the pressure connection means shown in Figure 2. The requirements for a rated fatigue pressure of 250 bar and for 400 bar have been demonstrated under the industry standard T2.6.1- 1974 of the National Fluid Power Association of the United Kingdom.

The embodiments shown in Figures 1 and 2 also illustrate the use of the sealing means 1 with coupling members fashioned from a polymeric or plastic material, such as polypropylene, poly-[tetrafluoroethylene/ perfluoro(alkylvinyl ether)] (PFA), or polyvinylidene difluoride (PVDF). It is frequently difficult to fashion plastic componentry with perfectly round features. For example, it may be difficult to fashion plastic coupling members 10, 11; 4, 7 with perfectly round exterior and interior circumferences. Even if the plastic coupling members are only slightly out-of-round, there may be clearance gaps in the region 13 where the conical surfaces 6, 9 initially contact one another. However, as the conical surfaces 6, 9 are axially forced together by the threaded portions 5, 8, the conical surfaces 6, 9 of the plastic coupling members 10, 11; 4, 7 conform to one another and completely engage one another in the generally annular region 13 around the central axis 20. This total annular engagement significantly enhances the seal provided by the sealing means 1.

The sealing means with plastic coupling members may be used in low, medium, or high pressure fluid systems. For example, it is particularly useful in fluid filtration systems with plastic coupling members such as plastic filter housings or plastic adapters for filter cartridges.