A gas-sealed shaft packing, comprises a rotary sealing ring which is adapted to be fixed to the shaft for rotation therewith and which has respective end surfaces which are spaced apart slightly from respective fixed sealing rings to define a sealing gap on respective sides of the rotary sealing ring. The fixed rings are biased toward the movable ring and gas conduits extend from a housing into each fixed ring and terminate in the gap between the fixed ring and the associated rotary sealing ring. The fixed rings are held by flange members which extend radially inwardly from the housing toward the shaft and resilient diaphragms are disposed between the flanges and the fixed rings or non-rotatable rings so as to urge them toward the rotatable sealing ring carried by the shaft. The biasing means also divides the housing to a space adjacent the shaft on one side of the diaphragms and a space adjacent the housing on the other side and gas is delivered into the gap through a conduit connected into each fixed ring and it escapes in both radial directions in respect to the shaft into the associated spaces on each side and then flows through an outlet conduit which may be advantageously regulated by a valve.

FIELD AND BACKGROUND OF THE INVENTION 
This invention relates in general to the construction of sealing devices 
for shafts and movable parts and, in particular, to a new and useful 
gas-sealed shaft which includes a non-rotatable sealing ring on each side 
of a rotary sealing ring carried by a shaft which is spaced apart from the 
shaft to define a sealing gap therebetween and which also includes means 
for directing a gas into the sealing gap through each fixed ring. 
DESCRIPTION OF THE PRIOR ART 
The present invention relates to a gas-sealed shaft packing comprising at 
least one fixed sealing ring and a rotary sealing ring which rotates with 
the shaft and is mounted axially adjacent the fixed ring, as well as 
resilient means which push the fixed sealing ring against the rotary 
sealing ring, and feed conduits which convey a sealing gas into the zone 
of the seal gap between the sealing rings. 
Known gas-sealed packings comprise a single sealing ring which is 
resiliently suspended from the housing by means of a gas-tight diaphragm 
by which it is pushed against another sealing ring rotating with the 
shaft. In operation, a gas stream, blown between the two sealing rings, 
separates the contact surfaces of the rings and forms a gas cushion which 
prevents a wearing of the rings. 
The axial pressure and the frictional heat produced by the sealing gas, 
with a unilateral arrangement of the radial sealing surface, results in 
irregular deformations of the rotary sealing ring. At high differential 
pressures and high speeds, the deformations may be of the order of 
magnitude of the seal gap height which is extremely small in this type of 
sealing, so that the rotary ring and the fixed ring may come into contact 
axially with the result of wearing of the sealing surfaces. 
In such cases, it is necessary to combine the sealing-gas packing with 
another conventional packing by which the high differential pressure is 
absorbed. However, with equal pressures on both sides of the seal, such a 
combination is needed if the sealing gas, compatible with the operational 
gas, is not compatible with the medium present in the space exterior to 
the sealing-gas packing, which is usually the surrounding air. 
While the use of conventional gas-tight packings, for example, labyrinth 
packings, considerable gas leakage to the outside is to be taken into 
account for the outer sealing, while, with an outer sealing in the form of 
a liquid packing, an expensive degasifying system for the sealing liquid 
would be required in cases where the sealing gas of the inner packing is 
explosive or toxic. In addition, liquid packings result in high mechanical 
frictional losses which may even prohibit the use of a sealing liquid at 
high speeds. 
SUMMARY OF THE INVENTION 
The present invention is directed to a gas-sealed shaft packing by which 
the operational space is sealed off hermetically, deformations at high 
differential pressures and circumferential speeds are avoided, and the use 
of a conventional outer sealing system is made unnecessary. 
It has been found that all of these problems can be solved by providing a 
gas-sealed packing in which the rotary sealing ring is disposed between 
two fixed sealing rings and a separate sealing-gas feed conduit is 
associated with each of the two fixed sealing rings, with the conduit 
being formed, at least partially, of bores, which extend within the 
sealing rings. 
By producing frictional heat simultaneously on both radial surfaces of the 
rotary sealing ring, the temperature is distributed more uniformly and the 
deformation of the rotary ring due to thermal influences is reduced. This 
is of particular importance at high speeds at which a greater amount of 
frictional heat is produced in the sealing gas in the seal gap. 
Deformations of the rotary ring due to pressure difference are largely 
avoided by the fact that the radial sealing surfaces of the rotary ring on 
both sides are exposed to axial forces which largely compensate each other 
so that no cambering of the ring in the axial direction occurs. In 
addition, the differential pressure between the operational gas and the 
outer air can be distributed between the two gas seals. By providing a 
sealing gas which is compatible with the outer air for the outer seal, the 
advantage is obtained that the consumption of sealing gas is minimized and 
the use of a liquid packing with an expensive degasifying system for the 
sealing liquid becomes unnecessary. 
The novel packing system may be designed so that, in practice, no deforming 
forces at all become effective on the rotary ring. This is obtained, in 
accordance with a development of the invention, by mounting the rotary 
ring between two elements which rotate with the shaft and which are 
yielding and, at the same time, seal but do not absorb any axial forces. 
The pressure forces which are exerted from both sides of the rotary ring on 
the radial seal surfaces and which depend on the axial range of the 
suspension system of the fixed sealing rings are automatically 
compensated, due to the fact that the rotary ring mounted on the shaft 
occupies an axial position in which these forces cancel each other. The 
absence of an axial loading of the rotary ring makes it possible to use 
narrow rings so that the out-of-balance forces are reduced and a much 
higher maximum admissible speed can be provided. 
A further feature of the invention is that the bores for feeding the 
sealing gas terminate in sickle-shaped recesses. 
Accordingly, it is an object of the invention to provide an improved shaft 
gas-sealed packing which includes a non-rotatable seal bearing on each end 
of a seal ring which is secured to the shaft for rotation therewith, the 
space between the fixed and the rotary seal rings defining sealing gaps, 
and wherein, a gas is directed into the sealing gaps on each end of the 
rotary seal ring by passages defined in the fixed rings. 
A further object of the invention is to provide a gas-sealed shaft packing 
which is simple in design, rugged in construction and economical to 
manufacture. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its uses, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings in particular, the invention embodied therein in 
FIGS. 1 and 2 comprises a gas-sealed shaft packing for a rotary shaft 4, 
for example, of a gas compressor, which extends from a housing 70 which is 
under excess pressure. The shaft packing provides a seal between the 
working space 52 and the outer air 54. A rotary sealing ring 3 is secured 
to shaft 4 for rotation therewith. 
The shaft is surrounded by a housing wall 10 in the zone of the shaft 
packing from which two housing flanges 5a and 5b project inwardly toward 
shaft 4. The housing flanges have a substantially L-shaped cross-section, 
with one leg of the L extending parallel to the inside surface of the 
housing and being gas-tightly connected to the housing wall, and the other 
leg of the L projecting freely inwardly. 
Sealing diaphragms 2a and 2b are connected between respective non-rotatable 
sealing rings 1a and 1b on respective sides of the seal ring 3 and the 
free legs of housing flanges 5a and 5b which are of symmetrical shape 
relative to the rotary sealing ring 3. The sealing diaphragms 2a and 2b 
are secured with two purposes. First, they constitute a seal between the 
annular space 20 adjacent the housing and the annular space 58 adjacent 
the shaft 4. Second, they embody a pair of accumulators of elastic force 
pushing the fixed sealing rings 1a and 1b against the rotary sealing ring 
3. The pressure surfaces 60 and 62 of rings 1a and 1b oppose respective 
sides of the sealing ring 3 and are spaced from each side by a small 
distance or seal gap 64 and 66, and the interspace thus formed is under 
gas pressure. The seal gaps 64 and 66 permit a motion of the sealing rings 
relative to each other without appreciable frictional losses. 
The sealing gas or gases are supplied through feed conduits, beginning with 
the first conduits 6 and 7 extending through the housing wall 10 and are 
connected to exterior supply lines outside the housing wall (not shown). 
The sealing gas is further directed through bores 11 and 12 extending in 
an angle through housing flanges 5a 5b. At the end of respective bores 11 
and 12, small bent tubes 13 and 14 are provided establishing communication 
between these bores and further respective bores 15 and 16 which are 
provided in the fixed sealing rings 1a, 1b. Bores 15 and 16 terminate in 
enlarged outlets 18 at the seal gaps 64 and 66. The enlargement of the 
outlets 18 may be of the configuration shown in FIG. 2. Here, 
sickle-shaped outlets 18 are designed for providing a better distribution 
of the sealing gases. 
The escaping gases pass from the seal gap between the sealing rings partly 
into the space 20 between the sealing rings and the housing wall and, 
therefrom, into a common discharge conduit 9. The other part passes into 
the space 58 between the shaft and the sealing rings and, therefrom, 
either to the outside or to the inside, into contact with the gases in the 
operational space of the respective machine in which the shaft packing is 
used. 
The function of the shaft packing may be learned from FIG. 1. For example, 
through the conduits of the packing stage at the inside, a sealing gas 
compatible with the operational gas is fed in. The packing stage at the 
outside is operated with an inert sealing gas which is allowed to escape 
to the outer air, because it is harmless. Due to the mixing of this inert 
sealing gas with the sealing gas which passes into the mixing space from 
the inside sealing ring and which might be explosive, dangerous chemical 
reactions are avoided. The mixture of sealing gases accumulating in space 
20 is discharged and rendered harmless. 
Pressure-regulating or throttle valves may be provided in the feed and 
discharge system of the sealing gases or sealing gas mixtures. It is 
possible, for example, to mount a throttle valve 21 at the end of bore 15 
within sealing ring 1b. A pressure-regulating valve 56 may also be 
provided at the end of conduit 9, whereby, the adjusted intermediate 
pressure between the operational pressure and the atmospheric pressure is 
kept constant. In this way, it is possible to provide a two-stage pressure 
buildup within the packing, while using two different sealing gases. An 
expensive liquid packing is saved and, additionally, a hermetic sealing 
with a minimized sealing-gas consumption is obtained. 
It is usual to provide more than two feed conduit arrangements which are 
distributed around the shaft. Pressure ratios, gap widths, and similar 
values and dimensions result from the requirements and experiences in the 
respective case of application. 
In another embodiment of the invention, as seen in FIG. 3, the shaft 
packing is designed so that each of the two fixed non-rotatable rings 5a 
and 5b is gas-tightly secured to the housing wall 10' by means of an 
elastic wall and the rotary sealing ring 3' is gas-tightly secured to the 
shaft 4, on both sides, by means of resilient sleeves. The spaces between 
the shaft and the fixed rings communicating with the operational space and 
with the outside, are made as small as possible. 
In FIG. 3, again, the operational space 52' is shown in the upper part and 
the ambient space 54' in the lower part. The rotary shaft 4' is connected 
to the rotary sealing ring 3'. 
Shaft 4' is surrounded by housing wall 10' in the zone of the shaft 
packing, from which the two housing flanges 5a' and 5b' project inwardly 
toward the shaft. The cross-section of the housing flanges is similar to 
that of the first embodiment shown in FIG. 1. The flanges are 
symmetrically arranged relative to rotary sealing ring 3'. Sealing 
diaphragms 2a', 2b' are secured between respective flanges 5a' and 5b' and 
rings 1a' and 1b' and they gas-tightly separate the annular space 20' 
adjacent the housing from the annular space 58 adjacent the shaft. The 
diaphragms 2a' and 2b' embody accumulators of resilient force by which the 
two symmetrically arranged fixed sealing rings 1a' and 1b' are pushed 
toward rotary sealing ring 3', with a small seal gap left between the 
presssure surfaces of sealing rings 1a', 1b', and 3', which gap is kept 
under gas pressure. 
The sealing gas or gases are supplied through similar conduits as already 
described in connection with FIG. 1. Bores 15' and 16' terminate in the 
zone of the seal gaps between the sealing rings. The escaping gases pass 
from the seal gap between the sealing rings partly into space 20'and from 
there into a common discharge conduit 9'. The other part of the gases 
passes into the space between the shaft and further resilient sleeves, 
particularly into space 50 described in the following. 
Resilient sleeves 40, which rotate with shaft 4', are secured to the shaft 
through fastening mechanisms 41. The rotary ring 3' is secured to the 
shaft through resilient sleeves 40 and is not directly connected to shaft 
4'. The rotary ring 3' can adjust its axial position on the shaft, 
depending on the pressure load to which it is exposed. 
A pressure balance is produced through passages 42 or 43 communicating with 
the operational space 52' and the outer air space 54', respectively, 
resulting in a force equilibrium. Consequently, the sealing elements of 
the packing are not deformed. 
Since the width of the gaps between the sealing rings can be adjuted 
automatically by means of the sealing gas provided separately for each 
individual seal, a contact-free function of the seal is ensured. The 
rotary sealing ring 3' is also mounted between resilient sleeves and is 
therefore axially displaceable. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.