Note: Descriptions are shown in the official language in which they were submitted.
216568(~
SE~L ARRANGEMENT FOR A SPINDLE PASSING IN AN AXIA~LY
MOVABLE M~NNER OUT OF A CASING
DESCRIPTION
The invention relates to a seal arrangement for a
spindle passing in an axially movable mAnner out of a
casing, a pressure line or the like, under the pressure
of an operating medium, according to the preamble to
Patent Claim 1.
Such a seal arrangement is known from DE 40 01 731 Al.
This known arrangement is characterised in that
operation of the casing or the like under pressure need
not be interrupted for servicing the external seal
arrangement, i.e. for replacement of the outer group of
annular seal members. The situation however is
different with the seal arrangement in the interior of
the casing. This may only be replaced after
interruption of operation.
In addition, in the known seal arrangement, as with all
other previous gland seals, the annular seal members
are placed from the exterior axially under such a
degree of initial tension that the innermost annular
seal members in the casing deform radially sufficiently
in order to achieve the necessary seal. This means
216~68~
that a large proportion of the axial force over the
length of the seal arrangement is converted into
unnecessarily high radial forces, which lead to
permanent deformation in the outer annular seal members
in the casing. In particular, high radial forces are
exerted over the entire length of the seal arrangement
on the spindle, with the result that the spindle
becomes relatively stiff. In addition, wear on the
annular seal members is unnecessarily increased.
The known gland seal arrangements are also
characterised by a relatively great constructive
length. Accordingly there is a risk that the seal
arrangement, and particularly the annular seal members
of the same, are exposed to additional stresses, which
are constrained by distortion or bending of the spindle
to the seal.
The known constructions also omit measures which would
guarantee sufficient seal of the spindle even when it
has a diameter changing over its length as a result of
temperature influences. The changing diameter, upon
axial movement of the spindle, causes a correspondingly
changing radial load and a deformation of the
individual annular seal members, which can lead to
leakage after protracted use.
The purpose underlying the present invention is to
provide a seal arrangement of the type already
3 21656~G
mentioned in which the annular seal members,
internally in the casing and primarily responsible for
the seal, are separately placed under initial tension,
so that the axially outward initial tension and the
overall constructive length of the arrangement can be
considerably reduced without loss of the desired seal
effect.
This purpose is fulfilled according to the invention in
that the annular seal members are initially axially
stressed from the interior of the casing by a pressure
transmission member under load by the operating medium.
By means of this measure the annular seal members in
the interior of the casing and primarily responsible
for the axially movable spindle undergo a separate
axial initial tension dependent on the pressure of the
operating medium. The annular seal members in the
interior of the casing are radially deformed to an
increased degree by the loading from the interior of
the casing, with a corresponding seal effect on the
spindle at the point essential for this, i.e. as close
as possible to the casing space which is under
pressure. ~he axially outward portion of the seal
arrangement is in this way relieved of stress to a
considera~le extent. Accordingly, the axial outer
initial tension on the annular seal members may also be
reduced. The same applies to the constructive length
of the seal arrangement, with the result that
distortion or bending of the spindle upon axial
4 216568G
movement of the same has hardly any further effect.
According to the invention, therefore, the m~ m
seal effect is achieved in the direct vicinity of the
operating medium under pressure. It is also of
importance that the axial initial tension on the
annular seal members inside the casing is load-
dependent, i.e. dependent on the pressure of the
operating medium in the interior of the casing. The
annular seal members are thus not unnecessarily heavily
loaded in dependence on the m~; mllm seal effect to be
achieved, but respectively only as is necessary for
operation. Thus the life-expectancy of the annular
seal members may be considerably increased.
The pressure transmission member provided according to
the invention preferably comprises a slide bush through
which the spindle passes, and which is connected in a
fluid-tight manner via a diaphragm within the inner
side of the casing, particularly by welding. Thus a
sufficiently large pressure transmission surface is
provided.
The constructive design according to Claims 3 and 4
- aids the transmissian of the pressure of the operating
medium to the s~ide bush through which the spindle
passes, and thus to the annular seal members which are
innermost in the casing.
216568(~
According to Claim 5, the wall thickness of the
diaphragm of the pressure transmission member decreases
radially in an outward direction, starting from the
slide bush, in particular continuously. In this way,
and in conjunction with one or a plurality of annular
shafts according to Claim 4, upon axial movement of the
slide bush, no bending movement is exerted thereon, or
the slide bush and the diaphragm are movable precisely
axially, i.e. parallel to the longitl~; n~l direction of
the spindle. The measures according to Claim 5 lead to
a particularly rigid design of the pressure
transmission member in the transitional area between
slide bush and diaphragm.
In a concrete embodiment of the seal arrangement
according to the invention, the slide bush of the
pressure transmission member projects through the
casing into the annular space accommodating the annular
seal members, there being arranged in the outer end,
or in the end of the slide bush projecting into the
annular space, a radially outwardly projecting stop
co-operating with the inner end or base of the annular
space, said stop being particularly in the form of a
stop ring which may be screwed on to the slide bush.
This stop ring limits the axial displacement of the
slide bush of the pressure transmission member in the
direction of the interior of the casing. In the
opposite direction, the axial mo~ement of the slide
bush is limited by the diaphragm connected thereto,
6 216558~i
particularly integrally formed as one piece, or by a
separate stop located on the outer periphery of the
slide bush and co-operating with the inner side of the
casing.
In order to enable replacement of the annular seal
members in any optional position of the spindle, the
measures according to Claims lO to 12 are provided. In
this case, contrary to the prior art already mentioned,
it is possible to replace all, i.e. even the ;nn~rmost
annular seal members in the casing during operation in
any optional spindle position or operational position.
The same also applies to other servicing operations on
the seal arrangement, e.g. replacement of the spacer or
the like. To this extent the seal arrangement
according to the invention represents considerable
progress compared to the previously known prior art.
The pressure medium chamber defined in more detail in
Claims 13 and 14 shows whether servicing of the seal
arrangement is necessary or not. Further, this
reliably avoids the penetration of operating medium in
an outward direction. This is above all important when
the operating medium involves gases and fluids which
are aggressive and injurious to health.
The measures according to Claims 15 et seq. are also of
particular importance; according to these the annular
seal members are radially movably mounted without this
7 2165681~
leading to any impairment in the seal effect.
Accordingly, distortions or bends in the spindle may be
compensated for without difficulty. The same applies
to the influence of an alteration in the diameter of
the spindle caused ~y temperature factors.
An embodiment of a seal arrangement according to the
invention will be explained in more detail in the
following with reference to the annexed drawing. This
shows one half of the abov~n~me~ embodiment in
longitudinal Section, the spindle passing in an axially
movable m~nner out of a casing 2 being identified ~y
the reference numeral I. The internal space of the
casing 2, under the pressure of an operating medium, is
indicated by reference numeral 40. The seal
arrangement shown comprises a so-called gland seal
which is located within an annular space 5 formed
between spindle 1 and casing 2. Seen from the exterior
inwards, the gland seal has the following elements
within the annular space 5:
- plate spring`s 29
- pressure ring 28
- axially and radially deformable annular seal member
27
- axial face disc 24
- annular seal member 23
- axial face disc 22
- annular seal member 21
2165686
- spacer 19 with radial opening 20
- annular seal member i8
- axial face disc 17
- annular seal member 16
5 - axial face disc 31
- stripper rings 14
- seal ring disc 13.
The spacer 19 subdivides the annular seal members,
10 located one after the other with an axial spacing, into
an axial inner group of annular seal mem.bers 16, 18 and
an axial outer group of annular seal me-m-bers 21, 23, 24
and 27. The spacer 19 is connected in terms of fluid
via a casing bore 32 with a closed, resiliently-
15 expandable, in this case bellows shaped, pressuremedium chamber 34. Between the casing bore 32 and the
pressure medium chamber 32 there is a connecting line
33. Axially outwardly, the annular space 5 is closed
by a casing lid 3 extending around the spindle 1. ~or
20 this purpose the casing lid 3 is screwed on to the
casing 2. The lid screw is indicated by reference
numeral 4. The plate springs 29 exert an axial
resilient initial tension on the annular seal members
or gland rings 27, 25, 23, 21, 18 and 16, the effect on
25 the annular seal members 16, 18 inside the casing still
being ml nl m~l. Accordingly, the axial initial tension
of the annular seal members 16, 17 in the interior of
the casing is exerted from the interior of the casing,
via a pressure transmission member 6, which is loaded
216S68~
by the operating medium. This pressure transmission
member comprises a slide bush 9, through which the
spindle 1 passes, and which is connected in fluid ter-ms
via a diaphragm 44 with the inner side o the casing 2,
i.e. by welding. The corresponding annular weld seam
is indicated by reference numeral 7. The diaphragm 44
is in annular disc form and has a portion 8 of
increased resilience extend; ng over the circumference.
This portion 8 extends close to the outer circumference
of the diaphragm 44 and is indicated by an annular
recess. Fur~her, it may be seen that the wall
thickness of the diaphragm 44, starting from the slide
bush 9, continuously decreases in a radial outward
direction, the wall thickness in the region of the
recess 8 being at a ml n;~llm, By means of this
construction, the transitional area between slide bush
9 and diaphragm 14 is sufficiently rigid. The
deformation of the soft resilient recess 18 enables it
to be ascertained that the slide bush with the
diaphragm is substantially free of bending moment, and
is axially movable in accordance with the pressure
loading exerted by the operating medium in the interior
of the casing 40. By means of the abo~enamed measures,
the ease of running on the spindle 1 is not impaired by
the slide bush 9, independently of its relative
position.
As the drawing further shows, the slide bush 9 of the
pressure transmission member 6 projects through the
lo 216568~
casing 2 into the annular space 5 receiving the annular
seal member 16 et seq., there being located at the
outer end, i.e. the end of the slide bush 9 projecting
into the annular space 5, radially outwardly projecting
stop co-operating with the inner end or base of the
annular space 5, said stop being in the form of a stop
ring 10 which may be screwed on to the slide bush 9.
This stop ring limits the axial movement of the slide
bush 9 in an inward direction, i.e. in the direction of
arrow E.
In the opposite direction, i.e. in the direction of the
~arrow D, the axial movement of the slide bush 9 is
limited by the membrane 44, which is integrally formed
thereon as one piece, in co-operation with the
associated inner side of the casing 2. It is also
feasible to provide on the outer circumference o~ the
slide bush 9 directly above the projection of the
membrane 44, a separate annular stop, which limits the
axial movement of the slide bush 9 from the outside
inwards, and in turn in co-operation with the inner
side of the casing 2 facing the diaphragm.
The space defined on the one hand by the pressure
transmission member 6 and by the associated inner side
of the casing 2 on the other side, in this case annular
space 42, is connected in fluid terms via a leakage
- hole 11 in the casing wall with the environment.
Accordingly, ambient pressure obtains in this space 42.
11 21656~
Accordingly, the pressure transmission member undergoes
a pressure loading acting axially outwards due to the
pressure of the operating medium obtaining in the
inside of the casing 40. In this way the axial initial
tension on the annular seal members 16, 18 on the
inside of the casing, is effected from the interior of
the casing, i.e. in the direction of arrow D.
A further important point is that on the inner or
pressure-loaded side of the pressure transmission
member 6, i.e. on the pressure-loaded side of the
diaphragm 44 of the same, there is located a further
diaphragm 36, extending around the spindle 1, and which
between itself, the spindle 1 and the diaphragm 44,
defines a space which commllnicates with the interior of
the casing 40 under pressure ~ia an annular slot ~8
between diaphragm 36 and spindle 1 on the one hand and
an opening located diametrically thereto, particularly
a bore 39, on the other hand, with the interior of the
casing 40. The diaphragm 36 is made of a heat-
resistant steel plate in the manner of a plate spring,
and is welded in a fluid-tight manner along its outer
peripheral edge to the diaphragm 44 of the pressure
- transmission member 6. The edge 37 of the diaphragm 36
2S exten~' ng about the spindle 1 is bent or curled
outwards, in adaptation to the radius of the facing
inner edge 45 of the slide bush 9, the outwardly bent
or curled edge 37 being at a spacing from the facing
inner edge 45 of the slide bush 9 under normal
12 216568~
operational conditions, as shown in the drawing, i.e.
when there is sufficient seal~g of the annular seal
members 16 et seq.. Upon leakage or removal of the
annular seal members 16 et seq. the outwardly bent or
curled edge 37 of the diaphragm 36, deforming
resiliently, is forced into the slot between spindle 1
and associated inner edge 45 of the slide bush 9, in
such a way that a seal is produced between spindle 1
and slide bush 9 or pressure transmission member 6. As
already mentioned abo~e, upon incorporation of the
gland rings or annular seal members 16 et seq., the
axially outer plate springs 29 apply a m;n;ml1m axial
and deformation-constrained radial tension on the
annular seal member 16 et seq., which ensure a m;n;mllm
degree of seal of the spindle 1. Thus the gland seal
is tight towards the exterior. By means of this
procedure, the pressure transmission member ~ or its
slide bush 9 is displaced inwards, i.e. in the
direction of the arrow E, against the force of the
resilient portion 8 of the diaphragm 44. The axial
inward movement is limited by the stop ring 10. The
system is then in a pressure-free state of equilibrium,
as long as the stop ring 10 is ineffective. This means
that there are effective, on the axially outermost
annular seal member or gland ring 27, and on the
innermost stripper ring 14 inside the casing, the same
axial forces which are converted into radial tensions
in accordance with the coefficient of the material.
Upon an increase in the pressure in the interior 40 of
13 216568G
the casing 2, an axial force is exerted on the
diaphragm 44 of the pressure transmission member 6.
This axial force is transmitted via the slide bush 9
and its outer end face 41 to the stripper rings and
accordingly also to the annular seal members 16, 18
inside the casing. The pressure force arising at that
paint is proportional to the pressure differential to
be sealed off, always lying below the m; n;mllm pressure
force constrained by the plate springs 29. The
stripper rings 14 serve to ~eep solid components of the
medium to the outside upon movement of the spindle 1,
i.e in the direction of arrow D In the embodiment
shown, the annular seal member 16 et seq. and the
stripper rings 14 each have conical end faces. They
are aligned with one another by means of these surfaces
in such a way that, when under axial pressure, they are
alternatively forced radially outwards and inwards,
these radial movements being enabled by annular slots
46 or 46' between the gland ring seal members on the
one hand and the spindle 1 on the casing 2 on the other
hand (see Figure). Thus a good seal is achieved both
in relation to the spindle 1 and also to the casing or
annular space 5. Located between axially adjacent
annular seal members there is respectively an axial
face disc 15, 17, 22, 24, 26. The axial face discs 15,
etc. enable or facilitate , depending on their
inclination, a radial pressure dependent on direction
and the relative movement of annular seal members or
gland rings in the case of varying spindle diameters
14 216568~
and non-linearity of the flush alignment of the axes of
spindle 1 and of annular space 5. Should however a
leak occur in the region inside the casing of the seal
arrangement, the leakage arising is diverted through
the bore 20 in the spacer 19, casing bore 32 and pipe
33 into the already mentioned pressure medium chamber
34. Under normal conditions, the pressure medium
chamber 34 is under initial ~echanical tension, i.e. a
partial vacuum obtains in the chamber 34. Thus leakage
amounts need not cause high pressures in order to
expand the pressure medium chamber 34 in the direction
of arrow A. Upon a specific leakage amount, an
electrical contact 35 associated with the pressure
medium 34 is closed, triggering a corresponding signal.
~he pressure medium chamber 34 may then be again
pressurised, the leakage amount of the operating medium
being mechanically forced again back into the system.
The time intervals between two leak signals may be
interpreted as a measure of the flow of leakagei and
of the necessity for servicing o~ the seal arrangement.
During this procedure, in any case, the external
portion of the gland seal arrangement is still fluid-
tight, so that no operating medium emerges into the
environment in an uncontrolled m~nner. Exchange of
defective annular seal members 16 and 18 inside the
casing, or of strippers 14, may be carried out in any
position on the spindle 1, with the aid of the already
mentioned further diaphragm 36. Under normal
operational conditions an annular slot 38 is formed
216~6~G
between the diaphragm 36 and the spindle 1. Close to
the outer circumferential edge, the diaphragm 36 has a
bore 39, whose cross-section is less than the free
cross-section of the slot 38. When leakage amounts
flow in the direction of the arrow D through the slot
38, solid matter is carried into the space 43 between
diaphragm 36 and pressure transmission member 5 or its
diaphragm 44, and is there separated. These solid
materials or solid particles can however leave the
space 43 again through the bore 39. If the leakage
amounts are greater, the bore 39 is partially or
entirely closed by the solid particles carried along,
so that a pressure differential arises between the
inner space of the casing 40 and the said diaphragm
space 43. This causes an outward movement of the
diaphragm 36, i.e. in the direction of arrow D. Thus
the annular slot 38 reduces to an increasing degree,
with the consequence that the said pressure
differential is correspondingly increased. Finally,
the outwardly bent or curled edge 37 of the diaphragm
36, in contact with the associated inner edge 45 of the
slide bush 9, is forced into the slot between spindle 1
and the said inner edge 45. Thus a metallic seal of
spindle 1 is achieved. In this position of the
diaphragm 36, all annular seal members or gland rings
16 etc., together with stripper rings, spacer, etc.,
may be removed from the annular space 5 and replaced by
new seal members. In this case operation of the
arrangement need not be interrupted. The diaphragm 36
16 216568~
.,,
is preferably so designed that it has two stable
conditions, i.e. on the one hand the condition shown in
the drawing with annular slot 38, and on the other hand
the condition of purely metallic seal. In both
conditions, the diaphragm 36 remains unaffected by
external forces. From the last named condition, i.e.
the condition of metallic seal, the diaphragm 36 may be
loosened axially inwardly, i.e. in the direction of
arrow E, by movement of the spindle 1. Alternatively,
1~ the diaphragm 36 may also be pressure-loaded via the
casing bore 32 and spacer 19. The corresponding design
of the diaphragm 36 ~internal tension in the pressure-
free condition), achievement of the two stable
conditions is not a continuous process. In this
lS embodiment the diaphragm 36 is bistable, i.e. held
stable either in the open or in the sealing position.
This has the advantage that the two diaphragm positions
are clearly defined.
All the features disclosed in the Application Documents
are claimed as essential to the invention, insofar as
they are new in comparison to prior art, individually
or in combination.
17 21 6568g
LIST OF REFERENCE N~MER~LS
1 Spindle
2 Casing
3 Lid
4 Connecting screw
Annular space
6 Pressure transmission member
7 Annular weld seam
8 Resilient portion
9 Slide bush
Stop ring
11 Leakage bore
12 Thread for screwing on stop ring 10
13 Annular seal disc
14 Stripper ring
Axial face disc
16 Annular gland seal member
17 Axial face disc
18 Annular gland seal member
19 Spacer member
Bore
21 Annular gland seal member
22 Axial face disc
23 Annular gland seal member
24 Axial face disc
Annular gland seal member
18 21 6s6~6
26 Axial face disc
27 Annular gland seal member
28 Pressure ring
29 Plate springs
Slot
31 Slot
32 Leakage bore
33 Fluid pipe
34 Pressure medium chamber
Contact signal emitter
36 Diaphragm
37 Inner edge of diaphragm 36
38 Annular slot
39 Bore
Inner space in casing
41 Outer end face of slide bush 9
42 Annular space
43 Space
44 Diaphragm of the pressure transmission member 6
Inner edge of the pressure transmission member or .
of the slide bush 9
46 Annular slot between annular gland seal member and
spindle
46' Annular slot between annular gland seal member and
casing
