Note: Descriptions are shown in the official language in which they were submitted.
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Field of the Invention
This invention relates to clampiny ring for use in a
pipe joint, which ring has an inside surface formed with
peripherally extending indentations.
Description of the Prior Art
Clamping rings can be used in pipe join~s which are
adapted to take up axial loads applied to the pipes and which are
not only leakage-proof but will provide also a thrust-resisting
mechanical coupling. Such clamping rings have a conical outside
surface, which cooperates with a mating conical inside surface of
a pipe socket and by means of such socket can be forced on~o the
outside surface of a pipe. Such clamping rings have a serrated
inside surface, which is in pressure contact with the outside
surface of the pipe to hold the pipes against an axial
displacement. The known clamping rings are formed on their inside
surfaces with annular indentations so that the lands remaining
between the annular indentations will apply pressure to the
outside surface of ~he pipe and said outside surface will thus be
deformed to have annular peripheral grooves. Such a shape of the
pipe will result in a high stress concentration, which may cause
the pipe to crack under high load. Particularly pipes made of
plastic, such as polyvinylchloride and polyethylene, which are
increasingly used in underground pipelines owing to their
resistance ko corrosion, are highly susceptible to stress
concentration so that the use of the known clamping rings in
joints between such plastic pipes will give rise to difficulties.
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Summary of the Invention
According to the present invention there is provided in
a clamping ring for use in a pipe joint, which cla~piny ring has
an inside surface formed with a plurality of generally
peripherally extending, juxtaposed indentations and with pipe-
retaining riclges extending between adjacent ones of the
indentations, the improvement residing in that each of the
indentations extends only over a fraction of the peripheral extent
of the inside surface and is peripherally offset from a juxtaposed
one of the indentations.
The ridges may have different heights in a cross-
sectional plane of the clamping ring and may form a mesh pattern.
Preferably at least part of the ribs have an ed~e adjoining two
adjacent ones of the indentations.
The present invention also provides a clamping ring for
use in a pipe joint, comprising: an annular body having an
annular inner surface engageable with an outer surface of a pipe;
and a surface array of contiguous indentations in the inner
surface for gripping the outer surface of the pipe, the
~0 indentations being generally elongated and defined by arcuate
ridges, the indentations and ridges extending generally
peripherally of the inner surface with adjacent ridges and
indentations in a peripheral direction of the body overlapping one
another and adjacent indentations in a direction transverse to the
peripheral direction being peripherally offset from one another,
each of the indentations having a length which is only a fraction
of the peripheral extent of the inner surface whereby a
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multiplicity of the indentations lie in end-to-end rela-tionship
around the periphery of the lnner surface.
The following is a description by way of example of an
embodiment of the present invention.
Figure 1 is a developed view showing the inside surface
of a clamping ring according to the invention.
Figures 2, 3 and 4 are enlarged sectional views taken on
lines II-II, III-III and IV-IV, respectively, in Figure 1.
Figure 5 is a side elevation showiny apparatus for
shaping said inside surface.
Detailed Description of the Preferred Embodiment
The invention is illustrated by way of example on the
dra~?ing.
A thrust-resistant pipe joint which is not susceptible
to dangerous stress concentrations comprises a clamping ring 1,
which is formed in its inside surface 2 ~?ith a large number of
generally peripherally extending indentations 3, which are offset
from each other in the peripheral and axial directions and
overlap. Owing to these indentations the inside surface 2 is
formed with dense shingled serrations and adjacent indentations
are separated by arcuate ridges 4, which like the indentations 3
extend generally perlpherally and are also offset from
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each other and form a mesh pathern. In pressure contact
with the outside surface of a pipe, such an inside surface
2 will not deform said outside surface to form annular
indentations therein so that damage to the pipe due to
stress concentration need not be feared. Nevertheless, the
large number of indentations 3 and their shingled
arrangement result in a strong pressure contact between the
clamping ring 1 and the outside surface of the pipe so that
the pipe will be firmly held against axial displacement.
It is apparent from Figure 2 that the ridges 4
have different heights in a cross-sectional plane of the
clamping ring 1. This is due to the fact that adjacent
indentations 3 overlap.
As is apparent from Figure 5 a clamping ring 1
may be formed with such a serrated inside surface 2 by
means of a simple lathe 5, which comprises a rotatable
chuck 6, which is adapted to be driven, and a carriage 8,
which is axially movable by means of a lead screw 7 and
carries a milling unit 9. The clamping ring is fixed in
the chuck 6 and is shaped on the inside surface 2 of the
ring 1 by a radial cutter tooth 11, which is non-rotatably
secured to a cutter spindle 13 of the unit 9. As the
spindle 10 rotates, the cutter tooth tends to revolve on a
circular orbit and by means of the carriage 8 a straight
feed movement that is parallel to the axis of the clamping
ring is imparted to the cutter tooth 11. The clamping ring
1 is rotated by the chuck 6 at the same time. An upward
cut is provided in that the cutter spindle 10 and the chuck
6 are rotated in mutually opposite directions. Because the
rotation of the chuck and the movement of the carriage are
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~uperposed, the indentations successively cut into the
inside surface 2 of the clamping ring 1 will extend along a
helix. The pattern of the serrations Formed on the inside
surface 2 of the clamping ring 1 will be determined by the
ratio of the movements described hereinbefore, by the
number of revolutions per minute of the cutter tooth 11 and
by the radius of its orbit.
For a given diameter of the inside surface, the
shape of each indentation will be determined by the shape
of the cutter tooth 11 and by its depth of cut. If the
cutter spindle 10 is inclined relative to the axis of the
clamping ring, the indentations will be unsymmetrical in
cross-section so that the serrations on the inside surface
will have a sawtooth shape depending on the angle of
inclination.
The serrations formed in accordance with the
invention on the inside surFace 2 of the clamping ring
ensure that a pipe joint provided with such clamping ring
will resist high axial loads and will have optimum force-
transmitting properties without giving rise to dangerousstress concentrations. For this reason, clamping rings
having such inside surfaces are particularly suitable for
joints between plastic pipes or between joints made of
other materials which are susceptible to stress
concentrations.
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