Pipe joints or couplings – Deformed – Both members
Reexamination Certificate
1999-11-29
2001-07-17
Nicholson, Eric K. (Department: 3627)
Pipe joints or couplings
Deformed
Both members
C285S910000, C285S918000, C285S328000
Reexamination Certificate
active
06260891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a press fitting for producing a permanent or nondetachable tight connection of smooth-ended pipes.
2. Discussion of the Prior Art
It is known (see brochure: Mannesmann Pre&bgr;fitting GmbH, Release 8/1994) to produce a nondetachable tight connection of smooth-ended pipes with a fitting which engages around the smooth ends of the pipes and each of whose bead-shaped ends receives a sealing ring. The bead-shaped end and, at the same time, the adjacent cylindrical area of the fitting are deformed together with the pipe plastically and with the enclosed sealing ring elastically by means of an exchangeable holding device with articulated jaws which is connected with an actuating device. The sealing function of the connection is achieved in that the sealing ring is elastically deformed by the plastic deformation of the bead-shaped end of the press fitting and, along a defined portion of the cross-sectional circumference, linearly contacts the surrounding surface areas of the bead-shaped end of the fitting and of the pipe. In order to absorb the longitudinal forces occurring at a corresponding internal pressure, the cylindrical area of the fitting adjacent to the bead-shaped end is plastically deformed together with the pipe. Both the bead-shaped end and the adjacent cylindrical area are deformed simultaneously by means of the actuating device during pressing.
As a rule, a connection point that is not pressed leads to detectable leakage in the pressure test which must be carried out according to regulations following installation. However, in special cases, it may happen that the tolerance matching of the pipe and fitting is so unfavorable that, when the smooth-ended pipe is pushed in, the sealing ring undergoes a pre-deformation which, although only slight, is sufficient to withstand the pressure test during inspection of the installation. However, when the line breathes in subsequent operation, i.e., fast-switching valves lead to water hammers or pressure shocks, relative movements can come about depending on heating, so that, in the absence of axial securing when there is no pressing, the previously resulting slight pre-deformation of the sealing ring is not sufficient to further ensure the tightness of the connection point.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a press fitting for producing a nondetachable tight connection of smooth-ended pipes by which a location which is not pressed is detected as leaky, also in case of an unfavorable tolerance matching of pipe and fitting.
According to the invention, the sealing element has, in the circumferential direction, at least one portion which is provided with a cross section deviating from the starting cross section in that a bulge extends along the circumference and along the cross-sectional plane and a recess facing the pushed in pipe extends radially in the cross section of the sealing element. In order for the recess to be completely filled after pressing, the volume of the bulge compared with the starting cross section is at least equal to the volume of the recess lacking at the starting cross section. Before pressing, the recess of the sealing element forms a through-opening in the axial direction viewed in cross section. The sealing element is preferably constructed as a torus with a circular cross section. In order to prevent unwanted creasing and pinching of the sealing element during the pressing and displacement of the volume of the bulge into the negative volume of the recess, the portion with the diverging cross section passes continuously without interruptions into the starting cross section along a predetermined circumferential extension in both directions.
The sealing element preferably has three portions which are arranged so as to be symmetrically distributed along the circumference with a cross section diverging from the starting cross section. Viewed in cross section, the above-mentioned portion is pear-shaped, wherein, in the transitional area, the pear shape increasingly approximates the circular shape and the flattened portion below becomes steadily smaller. The suggested construction of the sealing element has the advantage that even in case of extreme tolerance matching of the pipe and fitting the slight pre-deformation of the sealing element is not sufficient to press the deliberately arranged recesses closed in a sealing manner. This means that when a connection of a sealing element of this type is not pressed, leaking will definitely result during the pressure test. A connection point of this kind can then be pressed subsequently and the pressure test can be repeated. The pear shape ensures that the absent volume in the recess is completely filled again by the pressing of the bulge, and the sealing element tightly contacts the contact face oriented toward the pipe and the magnitude of pretensioning is so selected that tightness is retained even after a long period of operation.
The construction of the sealing element according to the invention is described more fully in the drawing with reference to an example.
REFERENCES:
patent: 4880260 (1989-11-01), Gotoh et al.
patent: 5007667 (1991-04-01), Unewisse
patent: 5730476 (1998-03-01), Gouda
patent: 6049962 (2000-04-01), Pleiffer
patent: 1236874 (1967-03-01), None
patent: 1273280 (1968-07-01), None
patent: 1945362 (1970-03-01), None
patent: 2350265 (1974-05-01), None
patent: 2814700 (1979-10-01), None
patent: 92990 (1962-06-01), None
patent: 180398 (1990-07-01), None
Foering Herbert
Franzen Rainer
Gigowski Thomas
Cohen & Pontani, Lieberman & Pavane
Mannesmann AG
Nicholson Eric K.
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