Pipe joints or couplings – Deformed – Both members
Patent
1985-03-18
1986-07-08
Callaghan, Thomas F.
Pipe joints or couplings
Deformed
Both members
29508, 29520, 285397, F16L 1314
Patent
active
045989389
DESCRIPTION:
BRIEF SUMMARY
Coupling devices for making a permanent pipe connection, in which the pipe end part is pressed, as a result of cold-forming in zones, by means of a press ring to be displaced axially, to form a positive leak-proof connection with a connection piece of a pipe fitting, are known in many embodiments, for example from U.S. Pat. Nos. 3,149,860, 3,375,026, 3,498,648, 3,528,689 and 4,061,367.
By means of a coupling device of this type, a pipe connection with good physical properties, such as high mechanical strength and a high degree of leak-proofing, can be made in a simple way and with a relatively low outlay in terms of time and material.
However, it has been shown, in practice, that, in pipe connections of this type, in certain uses the quality of the physical properties mentioned is not maintained in the long term, but on the contrary can diminish to an inadmissible extent within a relatively short operating time as a result of the influences of corrosion and erosion, as a result of which the pipe connection is broken.
If the pipe end part is located within the connection piece, such as, for example, in the pipe connections according to U.S. Pat. Nos. 3,375,026 (FIG. 3) and 4,061,367 (FIG. 5), then, when a liquid medium flows through the pipeline at high speed, turbulence arises on the end face of the pipe end part or at the junction point of two pipe ends as a result of shoulders or gaps. This turbulence leads to erosion effects on the inner wall of the connection piece, that is to say material is removed from the connection piece (and from the pipe end part), until the connection piece finally fractures. Although this defect can be largely eliminated if the coupling parts are constructed in a suitable way and the pipe connection is made accurately, it is nevertheless important, above all, to ensure that the pipe end is cut to size precisely. However, in all uses in which the pipe connection is not made at the factory, for example on building sites, there is no guarantee that the high precision required will be maintained.
Fewer problems arise in this respect in pipe connections with a pipe end part located outside the connection piece, for example according to U.S. Pat. Nos. 3,528,689 (FIG. 3) and 4,061,367 (FIG. 10). In these embodiments, there are no discontinuities in the course of the axial cross-section on the inner wall of the pipe fitting with the connection piece or pieces. In contrast, here, the connection zone at the end of the connection piece is endangered, since crevice corrosion can occur as a result of the capillary penetration of line liquid into the gap between the connection piece and the pipe wall surrounding the latter with a sliding fit, and the pipe is attacked from inside and gradually destroyed. Moreover, a discontinuous change in the throughflow cross-section at the end of the connection piece can also result in turbulence and consequently in erosion in this connection zone.
The invention is intended to provide a coupling device of the type described in the introduction, in which the disadvantages described above can be avoided, in order to obtain a longer service life for the pipe connection.
The gap between the connection piece and the pipe end part and consequently the danger of crevice corrosion can be avoided by means of a press connection of these parts which takes effect at the end of the connection piece. Accordingly, in the invention, the press ring has at its rear end an annular inner bead which, when the press ring is pressed onto the sleeve, displaces the sleeve material radially inwards at the rear sleeve end, and the length of the connection piece in relation to the length of the press ring and consequently to the axial position of the annular recess occurring at the rear sleeve end and located in the pipe end part is selected so that the free end of the connection piece does not project beyond the lowest point of this recess.
In this way, when the pipe connection is made properly, it is guaranteed that a press connection is obtained at the end of the connection piece
REFERENCES:
patent: 3149860 (1964-09-01), Hallesy
patent: 3375026 (1968-03-01), Szohatzky
patent: 3498648 (1970-03-01), Hallesy
patent: 3528689 (1970-09-01), Roe
patent: 3893718 (1975-07-01), Powell
patent: 4061367 (1977-12-01), Moebius
Boss Hans
Pfister, administrator by Lisa
Pfister, deceased Jurg
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