Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to a sealing ring for place-
ment in an axially open groove in a first rotor part of a centri-
fugal separator of the type having a second rotor part, which is
axially movable relative to the first rotor part and arranged to
be moved into and out of abutment against said sealing ring placed
in the groove via an annular projection, which is narrower than
said groove in the first rotor part.
A sealing ring of this type is subjected to heavy compres-
sion between the two rotor parts, which are axially movable rela-
tive to each other. As a result of this the sealing ring is rather
quickly impressed, i.e. plastically deformed by the annular pro-
jection of the second rotor part. After some operation time, dur-
ing which the rotor parts have been axially moved a number of
times relative to each other into and out of sealing engagement
via the sealing ring, the impression of the sealing ring has become
so extensive that the sealing ring has to be replaced.
The present invention provides an arrangement by means of
which the problem of impression of sealing rings of the above desc-
ribed kind is considerably reduced.
According to the present invention there is provided a
sealing ring for placement in an axially open groove in a first
rotor part of a centrifugal separator of the type having a second
rotor part which is axially movable relative to the first rotor
part into and out of abutment against said sealing ring placed
in said groove via an annular projection, which is narrower than
said groove, the edges of the sealing riny on each side of the
surface with which the sealing ring abuts the projection of
the second rotor part, are bevelled to such a degree that the
annular surface of the projection, adjacent the sealing ring, has
a radial extension at least as large as that of the sealing ring
surface between the bevels.
Thus, according to the invention, by only a minor change
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of the design of the sealing ring, namely such than the edges of
the sealing ring on each side of the surface, by which the sealing
ring abuts the projection of the second rotor part, are bevelled
.o such a degree that the annular surface of the projection, loca-
ted nearest the sealing ring, has a radial extension which is at
least as large as that of the sealing ring surface between the
bevels. The bevel is preferably such that the annular surface of
the projection has a larger radial extension than the sealing ring
surface remaining between the bevels.
By designing sealing rings in this way an essentially
d^uble life-time has been verified by tests for the sealing rings.
In one case, for instance, it has been possible to prolong the
operational time of a centrifugal separator from 1000 to 2000 hours
before replacement of the sealing ring has been necessary.
The present invention will be further described more in
detail below with reference to the accompanying drawing, in which:-
Figure 1 is a section through part of a centrifugalseparator with a sealing ring;
Figure 2 are sections through a sealing ring designed
in a conventional manner, before and after impression; and
Figure 3 is a section of a sealing ring according to
one embodiment of the present invention.
Figure 1 shows a part of a centrifugal separator compris-
ing a lower rotor part 1 and an upper rotor par$ 2, which are
axially joined by a lock ring 3. The axis of the rotor is denoted
by a dash-dot line 4. In a downwardly open annular groove in the upper
rotor part 2 there is disposed a sealing ring 5. Abutting sealing
rings is an annular projection 6 o~ a slide member 7, which is
axially mQvable relative to the ro~or parts 1 and 2. Bet~een the slide
member 7 and the upper rotor part 2 there is a separation chamber
8, in which a set of conical separation plates 9 is arranged. The
separation chamber 8 has an inlet 10 for a mixture of liquid and
7~
sludge to be separated. ~etween the slide member 7 and the lower
rotor part 1 there is a chamber 11, which during operation of the
rotor is charged and kept filled with liquia, usually water. By
the rotation of the rotor a liquid pressure is created in the
chamber 11, which forces the slide member 7 into sealing contact
wi~h the sealing ring 5 against the pressure from the mixture of
sludge and liquid present in the separation chamber 8. Sludge 12
is separated in the separation chamber 8.
Liquid freed from sludge 12 leaves the separation chamber
8 through an outlet (not shown) radially inside the set of plates
9. I~hen desired, the supply of liquid to the chamber 11 is tempor-
arily cut off, the chamber 11 being drained via a plurality of
throttled peripheral outlets 13. The slide member 7, thereby,
will be forced downwards by the pressure of the contents of the
separation chamber 8, and the separated sludge will be thrown out
through a plurality of peripheral outlets 14. Dependi ng on the
length of the time period, during which the supply of liquid to
the chamber 11 is cut off, more or less of the contents of the
separation chamber 8 will be thrown out through the outlets 14.
In Figure 2 at a there is shown a sealing ring 5 of con-
ventional design as it appears in a newly manufactured condition.
After some operation time of a centrifuge rotor according to Figure
1 a sealing ring of this kind has assumed a shape as that illustra-
ted at b. This is because it has been impressed, i.e. plastically
deformed, by the projection 6 of the slide member 7, lips 15 having
been formed therein. If such an impression is allowed to proceed
too far, the sealing ability of the sealing ring 5 may be los-t by
a piece of a lip 15 being bent inwardly and being squeezed between
the sealing surfaces of the ring 5 and the projection 6, respect-
ively, in connection with sludge discharge through the outlets 14.
There is also a risk -than an insufficient gap would be provided
between the sealing ring 5 and the projection 6 for separated sludge
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to leave the separation chamber 8.
To avoid this and to ~rolong the life-time of the sealing
ring the sealing ring may be as shown in Figure 3. ~ere a seal-
ing ring 5a is disposed in the aforesaid groove in the rotor part
2. The size of the flat surface 16 of the sealing ring facing
away from the groove has, in this embodiment, been reduced by
bevelling of the sealing ring edges at 17. The bevels 17 are such
that the flat surface 16 has a somewhat smaller radial extension
than the flat surface 18 of the projection 6 facing the sealing
ring 5a. As shown, the surface 16 of the sealing ring 5a is loca-
ted at a level somewhat axially outside the groove in the rotor
part 2, so that a sufficient gap can be created for unobstructed
passage of sludge between the rotor part 2 and the projection 6 even
after a certain plastic deformation of the sealing ring 5a has
occurred.
After some operation time a sealing ring 5a according to
Figure 3, has assumed substantially the same form as a sealing ring
5 of conventional design according to Figure 2a. After some fur-
ther time the sealing ring 5a will have the same form as illustrated
in Figure 2b. The total time of operation, during which a sealing
ring 5a according to the invention can be used, is approximately
twice as long as the corresponding time of operation for a sealing
ring of conventional design.
The present invention has been defined to mean bevelling
of the sealing ring edges on each side of the surface 16, with which
the sealing ring abuts the projection 6. By the expression bevell-
ing in this connection it shall be understood any recessing action
giving as a result that the recess i.s filled up with material from
the sealing ring, when the sealing ring is plastically deformed by
compression between the rotor parts 2 and 7 during the operation of
the centrifugal separator.
