Pipe joints or couplings – End to side or plate – Bolt or hook in flow
Patent
1994-11-30
1996-10-15
Nicholson, Eric K.
Pipe joints or couplings
End to side or plate
Bolt or hook in flow
55505, 55523, 285206, B01D 3920
Patent
active
055647553
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process for fixing a fitting on a sintered metallic filtering element and to the product thus obtained.
Metallic filtering elements are generally produced by sintering a metal powder, for example of 316 type stainless steel according to the AISI nomenclature, by adjusting the porosity to obtain the desired filtering effect while having the slightest possible loss of charge for a given flow rate; they are generally in the form of a cylindrical tube which is closed at one end and comprises, at the other end, a fitting producing the connection to a load-bearing structure such as a plate perforated by orifices. This unit is frequently called a "candle filter". According to the prior art, the fitting is either welded to the porous tube or is metallurgically fixed thereon during sintering.
The first solution has the following drawbacks: generally more fragile generally leading to poor filtration and, in certain cases, to mechanical breakages, particularly if the weld is located close to the fixing, that is to say in a region where the bending moment (due to vibrations for example) is high.
In the second solution, a solid metallic fitting is positioned at one end of the cold compression mould (for example by isostatic pressure) before introduction of the powder into the annular space delimited by a central mandrel and the external flexible casing of plastics material. After compression, the unit is sintered, producing a metallurgical connection between the fitting and the tube.
However, this method has the following drawbacks: detachment or fissuring in the region of the connecting interface therefore subject to variations tube tube.
SUMMARY OF THE INVENTION
The method according to the invention allows the aforementioned drawbacks to be overcome.
It involves: of which the connecting end has excess thickness delimited by a circular internal truncated cone and having a half angle at the vertex .alpha.=0 has an external thread, is equipped with a truncated cone-shaped end and has the same half angle at the vertex .alpha. as the sintered tube normal stress between the two aforementioned coupled elements is greater than twice the mean normal stress imposed by the mounting of the candle on its support.
More specifically, the method involves: of which the connecting end has an excess thickness delimited by a circular internal truncated cone and having a half angle at the vertex .alpha. of between 4.degree. and 7.degree. over a height (h) of between 20 and 80 mm externally threaded, is equipped with a truncated cone-shaped end and has the same half angle at the vertex as the sintered tube over a height h' which is smaller than h, of which the small diameter (d) is greater than the orifice of the tube (t) and of which the large diameter (D) is smaller than the internal diameter of the tube (Ti). normal stress between the two aforementioned coupled elements is greater than twice the mean normal stress imposed by the mounting of the candle on its support (and remains greater than 2 MPa).
In a preferred embodiment, the lateral surface of the truncated cone is equipped with one (or more) annular ribs having any cross-sectional profile, but preferably polygonal (for example triangular) with sharp corners which impress themselves in the porous tube during the force fitting operation.
If the candle is mounted directly on its support, the widened end of the sintered tube has an annular housing for a seal (for example an O ring).
The candle may also be mounted on its support with an intermediate member which is a screw nut having an annular housing for a seal on its free face. In this case, it is preferable for this nut to carry, on its surface in contact with the widened end of the filtering tube, one (or more) annular rib(s) similar to those of the conical fitting which also impresses itself in the porous tube when installed. This nut may have the form of a tubular sleeve equipped with two end flanges if a filtering zone at the head of the porous tube is to be el
REFERENCES:
patent: 2348490 (1944-05-01), Newman et al.
patent: 3722186 (1973-03-01), Parker et al.
patent: 4731184 (1988-03-01), Ostreicher et al.
patent: 4735638 (1988-04-01), Ciliberti et al.
patent: 4968467 (1990-11-01), Zievers
patent: 5098454 (1992-03-01), Carpentier et al.
patent: 5249882 (1993-10-01), Nagoshi et al.
Ackermann Luc
Gueydan Henri
Montfollet Thierry
Tollar Michel
Nicholson Eric K.
Sintertech
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