Note: Descriptions are shown in the official language in which they were submitted.
CA 02325451 2000-09-22
Pipe connection
Description
The invention relates to a pipe connection comprising
a press fitting and a conduit, which is inserted in said
press fitting and connected in a non-releasable manner
thereto, according to the preamble of patent claim 1.
A pipe connection with a fitting which encloses the
smooth pipe ends and of which the ends, which are of bead-
like design, each accommodate a sealing ring, it being the
case that an exchangeable retaining device which is connected
to an actuating device and has articulated jaws is used to
deform the bead-like end and, at the same time, the adjacent
cylindrical region of the fitting together with the pipe
plastically and the enclosed sealing ring elastically, is
known (see extract from the "Mannesmann Pressfitting GmbH"
brochure, issue 8/1994). The sealing function of the
connection is achieved in that, by virtue of plastic
deformation of the bead-like end, the sealing ring is
deformed elastically and, over a certain part of the cross-
sectional circumference, comes into abutment linearly against
the enclosing surface regions of the bead-like end of the
fitting and of the pipe. For the purpose of absorbing the
longitudinal forces which occur with corresponding internal
pressure, that cylindrical region of the fitting which is
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adjacent to the bead-like end, together with the pipe, is
deformed plastically. During the pressing operation, the
bead-like end and the adjacent cylindrical region are
deformed at the same time by means of the actuating device.
It is pointed out on pages 13 and 14 of the brochure that,
for a reliable press connection, the correct insertion length
for the conduit is extremely important. In this case "correct
insertion length" is intended to mean that, before the
pressing operation, the conduit is intended to be inserted
axially, with a slight rotary action and simultaneous
pressing action, as far as the stop produced by the bead-like
depression of the press fitting. A previously provided
marking on the conduit serves as a control means here.
However, in order to achieve a practical sequence of
operations, a conduit is not always laid, on site, step by
step, i.e. measuring, cutting to size, deburing, marking,
inserting and pressing; rather, a plurality of conduit
sections which are to be connected are simultaneously
measured and inserted and, finally, all the connecting
locations are subjected to a pressing action. With this
method of operation, however, it is not possible to rule out
the situation where the measuring, in particular in narrow-
angled space conditions, was not exact and the conduit, which
may possibly have been cut to too short a size, cannot any
longer be inserted fully into one or even two press fittings
or, following alignment of the line at one location, the
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already inserted conduit is drawn some way out of the press
fitting again. Since it is not always possible to see this
rearward displacement from the outside, if, for example, the
necessary insertion length is not marked correctly or the
marking was incomplete (non-visible rear side), the pressing
operation nevertheless takes place. Depending on the degree
of rearward displacement, such a defective pressing location,
as a result of the movement of the line, may subsequently
lead to leakages, and possibly also to the connection being
released.
Another pipe connection is known from JP 55-88939.
This pipe connection comprises a press fitting which has at
least one section which receives a sealing ring in a cross-
sectionally bead-like manner and an adjoining, first
cylindrically designed section, which is directed toward the
insertion side. Provided on the other side of the annular
bead is a second cylindrically designed section, which is of
smaller internal diameter, with the result that it forms a
stop. The transition from the annular bead to the second
cylindrically designed section takes place via a step which
merges with rounded shaping into the two adjacent regions. In
this case, the step serves as a guide for the inserted
conduit. The smooth end region of the conduit which is to be
connected comes into abutment, following insertion, against
the stop of the second cylindrically designed section. By
means of a pressing tool, which encloses the press fitting
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and has two or more pressing jaws, a non-releasable, sealed
pipe connection is formed following the closure of the
pressing jaws, it being the case that, during the pressing
operation, the pressing jaws act both on the annular bead,
including the sealing ring positioned therein, and on the
first cylindrically designed section of the press fitting.
The problem concerning the correct insertion length
is the same as has already been described in detail above.
For this reason, this pipe connection has the same
disadvantages as the first-mentioned pipe connection.
The object of the invention is to specify a pipe
connection that comprises a press fitting and a conduit,
which is inserted therein, and, following the pressing
operation, allows compensation in length within a fixed limit
without any risk of sealing being lost.
This object is achieved, taking the preamble as the
departure point, in conjunction with the defining features of
patent claim 1. Advantageous developments form the subject
matter of the subclaims.
The invention proposes to arrange in the region of
the cylindrically designed section which is directed away
from the insertion side a means which allows the inserted
conduit to be moved back axially only within a fixed limit,
it being the case that the inside width of said means, in the
non-loaded state, is smaller than the smallest tolerance-
induced external diameter of the inserted conduit. Said means
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is preferably a ring produced from an elastic material. For
example, said ring may be a sheet-metal ring which is bent in
the form of a U, as seen in cross section, and of which the
legs are located in the insertion direction of the conduit.
In order to achieve a certain claw action, the leg which
rests on the conduit has a curved end region directed toward
the conduit. Alternatively, the ring may have at least one
inwardly extending nose which is inclined slightly in the
insertion direction of the conduit. The means may be produced
from a metallic material or from plastic or from a
metal/plastic composite material.
The advantage of the proposed pipe connection can be
seen in that, although the means allows a rearward movement,
this rearward movement becomes increasingly difficult, until
the means comes into abutment against the sealing ring or
against a stop, with the result that further rearward
movement is prevented. In this position, the production of a
sealed pipe connection is ensured since there is still a
sufficient length of the rearwardly moved conduit located in
front of the sealing ring. The axial length of the means is
as short as possible and is selected, in relation to the
length of the second cylindrically designed section, which is
directed away from the insertion side, or that of the
intermediate section, such that a sufficient compensating
length of a number of millimeters remains.
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The pipe connection designed according to the
invention will be explained in more detail, with reference to
a number of exemplary embodiments, in the drawing, in which:
Figure 1 shows a longitudinal section of half a pipe
connection designed according to the invention,
Figure 2 shows the same as Figure 1, but with the capacity
for rearward movement being illustrated,
Figure 3 shows a longitudinal section of half of a second
embodiment of a pipe connection designed according
to the invention,
Figure 4 shows the same as Figure 3, but with the capacity
for rearward movement being illustrated,
Figure 5 shows a variation of the embodiment illustrated in
Figure 3, and
Figure 6 shows the same as Figure 5, but with the capacity
for rearward movement being illustrated.
Figure 1 illustrates a longitudinal section of half a
pipe connection designed according to the invention. Said
pipe connection comprises a press fitting 1 with an outwardly
extending section 2, which is of bead-like design, and a
sealing ring 3, which is positioned in said section, and a
conduit 4, which is pushed into the press fitting 1. The
bead-like section 2 merges in a known manner, via a flank 5,
into a first cylindrically designed section 6 located in the
insertion direction. The insertion direction is marked by an
arrow 7. On the other side of the bead-like section 2, the
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flank 8 merges, according to the invention, into a second
cylindrically designed section 9. Said section 9 has a larger
internal diameter 10 than the internal diameter 11 of the
first cylindrically designed section 6. The second
cylindrically designed section 9 merges into a third
cylindrically designed section 12, forming a stop for the
inserted conduit 4 in the process, the internal diameter 13
of said last-mentioned section being smaller than the
internal diameter 11 of the first cylindrically designed
section 6. This means that a stop is formed for the inserted
conduit 4. Arranged, according to the invention, in the
region of the second cylindrically designed section 9 is a
means which inhibits the rearward movement of the inserted
conduit 4, the means in this exemplary embodiment being a
sheet-metal ring 14 which is bent in the form of a U and of
which the legs 15, 16 are located in the insertion direction
7. In order to achieve a certain claw action, the leg 16,
which is directed toward the conduit 4, is provided with a
curved end region 17, which is directed toward the conduit 4.
The sheet-metal ring 14 is placed in position, together with
the sealing ring 3, during the production of the press
fitting 1. In this non-loaded state, the inside width of the
sheet-metal ring 14 is smaller than the smallest tolerance-
induced external diameter 18 of the inserted conduit 4, with
the result that the sheet-metal ring 14 is compressed
elastically following the insertion of the conduit 4.
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Figure 2 shows the capacity for rearward movement of
the inserted conduit 4 in order for it to be possible to
cover, for example, a certain compensation in length of the
previously laid line. As a result of the friction, the
rearward movement becomes increasingly difficult, until the
sheet-metal ring 14 comes into abutment against the sealing
ring 3. If a pressing operation takes place in this position,
sealing is ensured since there is a sufficient length of the
end region of the inserted conduit 4 located in front of the
sealing ring 3.
Figure 3 illustrates a longitudinal section of half
of a second embodiment of a pipe connection designed
according to the invention, the same designations having been
selected for the same elements. This pipe connection
comprises a press fitting 20 with a section 2 which extends
outward in a bead-like manner and a sealing ring 3, which is
positioned in said section, and a conduit 4, which is pushed
into the press fitting 20. The bead-like section 2 merges in
a known manner, along a flank 8, into a first cylindrically
designed section 9 located counter to the insertion
direction. The insertion direction is marked by an arrow 7.
At the end of the extent of the first cylindrically designed
section 9, the latter merges into a second cylindrically
designed section 12, forming in the process a stop for the
conduit 4 which is to be pushed in. The internal diameter 13
of said second cylindrically designed section 12 is in the
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region of the internal diameter 19 of the inserted conduit 4
and is smaller than the internal diameter 10 of the first
cylindrically designed section 9. Arranged, according to the
invention, in the region of the first cylindrically designed
section 9 is a means which inhibits the rearward movement of
the inserted conduit 4. In this exemplary embodiment, said
means is a ring 21 with an inwardly extending nose 22. The
nose 22 is inclined, to be precise in the insertion direction
7. The ring 21 is placed in position, together with the
sealing ring 3, during the production of the press fitting
20. In this non-loaded state, the inside width of the ring 21
is smaller than the smallest tolerance-induced external
diameter 18 of the inserted conduit 4, with the result that
the ring 21, following the insertion of the conduit 4, is
compressed elastically.
Figure 4 shows the capacity for rearward movement of
the inserted conduit 4. As a result of the friction, the
rearward movement becomes increasingly difficult, until the
ring 21 comes into abutment against the sealing ring 3. If a
pressing operation takes place in this position, sealing is
ensured since there is a sufficient length of the inserted
conduit 4 located in front of the sealing ring 3. In order
that the sealing ring 3 is not damaged by the ring 21 during
the rearward movement, the ring 21 has a rounded section 23
at the end region directed toward the sealing ring 3.
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Figure 5 shows a variant of the embodiment
illustrated in Figure 3. In contrast to the latter, there is
provided in the first cylindrically designed section 9 of the
press fitting 24 a cylindrically designed intermediate
section 25, of which the internal diameter 26 is larger than
that of the first cylindrically designed section 9. At the
end of the extent, the intermediate section 25 merges into
the second cylindrically designed section 12, forming a stop
for the inserted conduit 4 in the process, the internal
diameter 13 of said last-mentioned section being in the
region of the internal diameter 19 of the inserted conduit 4.
Arranged, according to the invention, in the region of the
intermediate section 25 is a means which inhibits the
rearward movement of the inserted conduit 4. Said means is
designed, as illustrated in Figure 3, as a ring 21 with a
nose 22 located in the insertion direction 7. However, it
would equally be possible for the sheet-metal ring 14
illustrated in Figure 1 to be used as the means which
inhibits the rearward movement.
Figure 6 shows that, in contrast to Figure 4, the
capacity for rearward movement of the inserted conduit 4 is
bounded by the shoulder 27 of the intermediate section 25
rather than by the sealing ring 3. The resulting maximum
possible compensating length 28 is indicated by arrows.
