Pipe joints or couplings – Nonmetal to metal – Internal member
Reexamination Certificate
2001-08-14
2004-02-24
Bochna, David (Department: 3679)
Pipe joints or couplings
Nonmetal to metal
Internal member
C285S245000
Reexamination Certificate
active
06695355
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a pipe fitting element, particularly for plastic pipes, comprising a tubular fit-in sleeve or the like, which can be fitted into an end of a pipe section to be connected, and a clamping ring nut, coaxial to the sleeve and having an internal thread, for cooperating with a matching external thread on at least one part of the sleeve, both the ring nut and the tubular sleeve having facing surfaces for tightly clamping the pipe and for mechanically restraining the pipe onto the tubular sleeve; the clamping surface provided on the tubular sleeve being in contact with the inner wall of the pipe, and the clamping surface provided inside the ring nut being in contact with the outer wall of the pipe, when the pipe fitting element is in the mounted condition; and said threads being such that the pipe is clamped by tightening and further translating the ring nut towards the end of the tubular sleeve inside the pipe and by simultaneously drawing the two clamping surfaces mutually closer.
Pipe fitting elements of the above described type are known, which find application in the connection or union of pipes, lines, devices or components of hydraulic or pneumatic systems. Particularly, these well-known pipe fitting elements find application in plastic pipe connection for irrigation systems or the like.
In these known pipe fitting elements, the mutually facing clamping surfaces provided on the outer surface of the sleeve and on the inner surface of the ring nut generally have each an annular step. This step typically consists of an annular cylindrical narrowing of the outside diameter of the sleeve, usually situated immediately upstream, with respect to the tightening direction, of a pipe lead-in section at the sleeve end turned towards the pipe to be connected, and of a corresponding widening of the inside diameter of the ring nut end turned towards the pipe. During the clamping operation, after inserting the sleeve into the pipe end, by tightening the ring nut, the latter is translated towards the pipe, the two clamping surfaces are drawn mutually closer and the pipe is tightly secured, also due to the gripping action exerted by the two steps on the inner and outer surfaces of the pipe to be connected.
Although these known pipe fitting elements can effectively achieve their purpose, they have a few serious drawbacks. Typically, the steps provided on the clamping surfaces of the ring nut and of the sleeve have a considerable radial projection, whereby the pipe is strongly deformed upon clamping. Hence, said pipe must be made from a highly deformable material to prevent fluid tightness problems or even ruptures of the pipe. Tightness is a critical problem, and the operator can run the risk of excessively tightening the ring nut and of damaging the pipe. Further, these known pipe fitting elements have a very poor adaptability to different pipe thicknesses, hence a pipe fitting element with specific dimensional features must be provided for each pipe wall thickness and for each pipe diameter.
SUMMARY OF THE INVENTION
Therefore, the invention has the object to allow, by simple and inexpensive means, the provision of a pipe fitting element of the above described type, allowing a tight, non-unthreadable connection, with an end of a pipe to be connected, having at least equal, or even better characteristics than prior art pipe fitting elements, and further allowing effective clamping of the pipe, while avoiding an excessive deformation thereof. A further object is to allow the provision of a so-called “multifit” pipe fitting element, i.e. able to be used, with no ring nut or sleeve replacement, for connection of pipes having different thicknesses, without requiring, like prior art ones, a joint with different characteristics based on the thickness of the pipe in use.
The invention achieves the above purposes thanks to a pipe fitting element of the above described type wherein said clamping surfaces consist of progressive widenings of the outside diameter of the fit-in tubular sleeve and of the inside diameter of the ring nut end turned towards the pipe to be connected.
These widenings of the outside diameter of the tubular sleeve and of the inside diameter of said ring nut end may be progressive in the ring nut tightening direction.
Hence, the pipe may be clamped between two annular surfaces, one in the ring nut and the other in the tubular sleeve at said progressive diameter widenings.
These progressive widenings of the tubular sleeve and of the inner surface of the ring nut may have such a progression as to form clamping surfaces having a substantially conical shape or similar. In other words, these clamping surfaces, regardless of their conformation, may have substantially conical enveloping surfaces.
The clamping surfaces provided on the tubular sleeve and inside the ring nut may be tapered in the same direction, i.e. widening towards the end of the pipe.
Advantageously, the clamping surfaces may have different tapering directions.
Further, they may have diverging tapering directions, i.e. the clamping surface provided inside the ring nut may be less steep than the clamping surface provided on the tubular sleeve. By this arrangement, as the thickness of the pipe to be connected increases, clamping between the ring nut and the sleeve may occur at decreasing diameters of the two clamping surfaces, hence different portions both of the ring nut and of the sleeve adhere to the pipe.
At least one of the two clamping surfaces may consist of a succession of step-like widenings, but considerable advantages are obtained if both clamping surfaces of the tubular sleeve and of the clamping ring nut consist of step-like widenings. These steps provide an effective grip on the pipe walls and effectively prevent unthreading thereof. Further, the progression of the step-like widenings ensures a progressive clamping of the pipe, which is thus gradually, but firmly secured, while avoiding the excessive deformations that occur when using prior art pipe fitting elements having a single step with a considerable radial projection.
These steps may be equal or different in number along the same axial length, in radial projection and in radial length.
According to a preferred embodiment of the invention, the step-like widenings provided on the two clamping surfaces consist of a plurality of annular surfaces having the shape of cylinders or of truncated cones, with equal or different taperings.
In accordance with a preferred embodiment, the clamping surface provided on the tubular fit-in sleeve may consist of a plurality of annular surfaces having the shape of cylinders or of truncated cones with equal axial lengths and steepness, whereas the clamping surface provided inside the ring nut may consist of a plurality of annular surfaces having the shape of cylinders or of truncated cones with equal axial lengths and, at least partially, with a decreasing steepness in the tightening direction. Thanks to the above characteristics the clamping surface inside the ring nut is less steep than the clamping surface provided outside the sleeve, as desired.
The end portion of the ring nut turned towards the tightening direction may have a widening flare to facilitate the insertion of the end of the pipe to be connected into the ring nut. This ring nut may have, on the pipe insertion end, a diameter substantially identical to the outside diameter of the pipe threaded on the tubular sleeve and/or slightly greater than said outside diameter of the pipe.
The maximum diameter of the tubular sleeve may be slightly smaller than the minimum diameter of the clamping ring nut, so as to allow insertion of the ring nut on the tubular sleeve from the end of the tubular sleeve turned towards the pipe to be connected. According to an advantageous variant, the maximum diameter of the tubular sleeve is not smaller than the minimum diameter of the ring nut, but slightly greater, within the limits the material has for the passage of the ring nut over the widening of the sleeve. Depending on the materi
Bochna David
Irritec S.r.l.
Narasimhan Meera P.
Way James Creighton
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