Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CONNECTING PIlECE WITH SEALING RING
This invention relates to connecting means, and
more particularly to a flange- or screw-type connecting
piece of the kind havin~ a bearing face including an
annular groove with a bottom which is either of arcuate
cross-section or flat, and a resiliently yielding sea-
ling rin~ disposed in the groove in such a way that .
about 20-35~ of the volume of the rin~ protrudes beyond
the bearing face.
A connecting piece of this kind is joined to
another connecting piece in order to obtain the fluid-
tight interconnection of apparatus, container~, or
other equipment either directly or by means of conduits,
or the sealing of apparatlls, containers, or other equip-
ment or conduits, whereby media of all ]kinds are pre-
vented from penetratin~ in or out.
The insertion of resiliently yield.ing sealing ringsbetween two connecting pieces i~ known. Previously
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proposed designs of such connections have various draw-
backs which may be classified in three groups.
In the first group, the resiliently yieldin~ seal-
ing rings are pressed into too small a space in the
annular grooves. The sealing material is thereby sub~
jected to excessive stress and ultimately destroyed.
Once the two connectinq pieces have been taken apart,
the sealing ring cannot be re-used. Designs of this
kind are disclosed in Swiss Patents Nos. 461,593 and
538,205; German Patents Nos. 1,640,968, 2,047,027 and
2,132,951; Austrian Patent No. 320,782, and V.S. Patents
Nos. 1,368,196 and 3,719,202.
In the second group, the resiliently yielding seal-
ing rinqs are accommodated in too large a space in
the annular grooves with a view to avoiding the draw-
backs of the first group. In this case, however, only
the cross section of the sealing ring is subjected
to deformation. The effort of the sealing material to
retain its original, undeformed shape insofar as
- 20 possible is frequently insufficient to prevent media
of all kinds from penetrating in or out. If, in such
cases~ the cross-sectional shape of the sealin~ ring
is deformed even slightly beyond the permissible extent,
the sealing effect is initially found to be satisfac-
tory, but later on premature aginq of the sealin~
ma~erial occurs, whereby its molecular structure is
destroyed. The filamentary molecules of the sealing
material become torn or the cross-linking points of
the filamentary molecules are ripped apart. The force
which strives to restore the undeformed cross-sectional
shape is thereby weakened, and the sealing effect is
thus jeopardized or even eliminated~ Designs of this
kind are disclosed in Swiss Patent No. 428,881, German
~tility Model No. 72 30680, and in U.S. Patents Nos.
3,499,670 and 4,090,02a.
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The third group comprises annular grooves in whicn
the space is unfavorably shaped for accommodating seal-
ing rings. The pounding and kneading motions which occur
during installation and deformation produce damage simi-
lar to that of the first and second groups, in additionto which the sealing rin~s are often further damaged
and destroyed by sharp edges and corners. Examples are
found in the international standard ISO/DI~ 6149 an~ in
German Patent No. 16 40 968.
Some previously proposed designs are even to be con-
sidered as combinations of these groups~
In the periodical Machine Design of 9 March 1967,
O-ring grooves having flat or rounded bottoms are des~
cribed. The O-ring inserted in a round-bottom groove
tightly enclosed by the wall of the groove because the
round-bottom groove has the same diameter as the actual
cross-section of the O-ring. The O-ring protrudQs 1/64
to 1/32 in. above the fa~e of the flange~ The groove for
receiving the O-ring is not U-shaped in cross section
because it tightly encloses the O-ring except for its
protruding portion. Hence there is no clearance bet-
ween the O-ring and the sections of the groove-walls
ending at ~he bearing ~ace of the flange. When pressure
is applied to the O~ring inserted in the groove, the
ring can be damaged by the edges of th~ groove~
In the periodical Product Engineering of 31 January
1966, a flange having a flat-bottom groove is described~
The optimum protrusion o~ the sealing ring above the
face of the flange is about 20% of the total volume of
the ring. Here, too, the sidewalls of the groove do not
run parallel toward the bearing face when viewed in
cross-section~ In this instance less than half of the
ring rather than the greatest part of it, is tightly
enclosed by the walls of 1:he groove. When pressure is
applied to the sealing ring, it is deformed only in
cross-section b~ the forces acting UpOIl it.
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In both of the foregoing cases, the deformation
of the sealing ring leads to its accelerated aging.
It is an object of this invention to provide a
connecting piece of the kind initially defined in
which the annular groove is designed in such a way
that the deforming forces acting upon the sealing
ring tencl rather to compact its molecular structure
than simply to deform its cross-section.
A further object of this invention is to provide
such a connecting piece in which the degree o compact-
ion of the sealing ring disposed in the annular groove
can be preselected by means of the shape given to the
groove.
To this end, in the connecting piece according to
the present invention, the diameter or width and the
depth of the groove are so dimensioned that the seal-
ing ring in its relaxed state is for the most part
tightly enclosed by the wall or walls of the groove
and that the two wall-sections of the groove ending
at the bearing face of the connecting piece are pa-
rallel to one another and space from the sealing ring.
Preferred embodiments of the invention will now
be described in detail with reference to the accom-
i panying clrawinqs~ in which:
Figure 1 is a cross--section through a flange-
-type connecting piece having an annular groove
machined in the bearing face thereof and an O-ring
i~ undeformed state inserted in the groove,
Figure 2 is a cross--section through a flange-
-type connecting piece having an annular groove made
in the bearinq face thereof and a sealing ring of
polygonal cross-section in undeformed state inserted
in the groove and
Figure 3 is a cross-section through a screw-type
connecting piece havinq an annular groove in the bearing
face thereof and an O-rinq in underformed state inserted
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in the groove.
The connecting piece 1 shown in Figure 1 includes
a bearing face 2 into which a continuous annular
groove 3 of substantially U-shaped cross-section has
S been machined. The bottom 6 of groove 3 is arcuater
the two parallel flanks merging tangentially without
transition into bottom 6. The radius of arcuate groove
bottom 6 is exactly the same as that of an O-ring 4
inserted in groove 3. The diameter or width of groove 3
is such that O-ring 4, in its relaxed state, is for
the most part tightly enclosed by the wall 5 of
groove 3. ~he segment of O-rin~ 4 protruding from
groove 3 beyond face 2 represents about 25-30% of the
total volume of O-ring 4. Two clearance spaces are
formed between O-ring 4 and the respective flanks
of groove 3 adjoining face 2.
By tightening a screw 7 in a threaded bore 8a
of a second connecting piece 8 to be joined to the
first connecting piece 1 piec~s 1 an 8 are caused
- 20 to approach one another, whereupon the protruding
segment of O-ring 4 is partially deformed, a small
portion of this segment being forced into the two
clearance spaces. As screw 7 is further tightened
until pieces 1 and 8 bear snugly against one another t
the molecular structure of the material of which
O-ring 4 is made becomes compacted. This step prevents
any displacement of the sealing material in an undesired
direction in which it would be destroyed~
W~en the molecular structure of the sealing mate
rial is thus compacted, better and more reliable seal-
ing effects are achieved than when the cross~sectional
shape of the sealing material is deformed. Since the
filamentary molecules have shorter distances to cover
when being crowded together~ there is but a very
slight risk of cross-linking points being parted or
of the rilamentary molecu]es themselves being torn;
~9 ~
it is thus apparent that the sealing effect will not
be jeopardized by premature aging of the sealing ma-
terial.
When screw 7 is beinq tightened, a perceivable
resistance is encountered as soon as the faces of
connecting pieces 1 and 8 are fast against one another,
so that proper assembly is ensured. The snug fit be-
tween pieces 1 and 8 makes it impossible for the seal-
ing material to be compressed beyond the preselected
degree of compaction.
The embodiment illustrated in Figure 2 has the
same function and the same effect as that of Figure 1.
This embodiment differs only in that the cross
-section of an annular groove 3a is polygonal to con-
orm to that of a sealing ring 4a inserted therein.The groove bottom 6a is flat, corresponding to the
shape of sealing ring 4a. Here, too, ring 4a of poly-
gonal cross-section is for the most part tightly
enclosed by groove walls 5a. The sides of ring 4a
running toward bearing face 2 are inclined toward
one another so that two clearance spaces are created
in this region between sealing ring 4a and the re-
spective groove walls 5a. The portion of ring 4a
protruding beyond face 2 may represent 20-35% of
the total volume of ring 4a.
The depth of annular groove 3 or 3a is to be so
chosen that the portion of ring 4 or 4a protruding
beyond bearing face 2 corresponds to the optimum
degree of compaction of the sealing material being
used. For sealiny rinqs of ordinary quality as are
customari:Ly available in commerce, the volume of
the portion protruding beyond face 2 will constitute
about 25-33% of the total volume of the sealing ring;
thus, a faultless, reliab e, and fluid tight connection
is obtained.
Instead of insertinq a conventional sealinq ring
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in the annular groove, a sealing ring of plasticized
sealing materials can be injected into the annular
qroove by means of an injection tool designed for this
purpose.
The steps described above are also applicable in
the case of screw-type connecting pieces~
The sealing ring disposed in the above-described annular
groove guarantees reliable sealing of the connection
aqainst media of all kinds penetratinq in our out. The
sealing ring is fixed in the groove designPd in this way
and is not subjected to any change of position during
storager assembly, and disassembly. Any shifting of
part of the sealing ring is also made impossible, so
that no damage or premature aging occurs. Because
the forces of deformation are necessarily directed
largely to the molecular compaction of the material r
the connected parts can, in case of need, be disassem-
bled and re-assembled without having to replace the
sealing rin~. The compaction of the sealing ring can
be controlled by means of the preselected depth and
shape of the annular groove. Through the choice of the
materials in injection molding processes, greater
demands may be made on the sealing effect be~ause
harder sealing materials are available than in the case
of loose sealing rings, which are also extensible.
