Seal for a rotating shaft

A seal for a rotating shaft is disclosed which seals the shaft as it passes through a stationary partition wall. The seal has a segmented graphite sealing ring extending around the shaft located in an annular recess of a casing attached to the partition wall. A retaining ring having axial projections extending into radial grooves defined by the sealing ring is attached to the casing and a retaining washer extends circumferentially between the graphite segments and the retaining ring to prevent any relative axial movement between the elements. Relative rotation and axial movement between the retaining ring and the casing is prevented by stop pegs and a stop ring.

BACKGROUND OF THE INVENTION 
The present invention relates to a seal for a rotating shaft, more 
specifically an integrated seal for a gas turbine engine shaft. 
Frequently in gas turbine engines, it is necessary to pass a rotating shaft 
through a stationary partition wall forming part of an enclosure, one of 
which contains air and oil on one side of the partition and the other of 
which holds air on the opposite side of the partition which must be kept 
free of oil. It has proven difficult to provide a seal around the shaft 
passing through the partition which will effectively prevent the 
intermixing of the elements on opposite sides of the partition wall. 
European patent application 0 110 804 discloses a rotating seal arrangement 
wherein a circular shaped seal element is fixedly secured to a rotating 
shaft and is used in combination with a valve element to prevent the 
escape of oil from the lubricated seal. 
French Patent 2,120,656 discloses, in FIG. 2, a carbon ring held around a 
shaft by means of a circumferential spring extending around the carbon 
ring. The ring is placed within a cage wherein it is positioned relative 
to a retaining ring by a spring means. 
Other solutions to this problem have involved the mounting of a case with a 
de-oiling coil near where the shaft passes through the partition. These 
solutions may or may not include a segmented ring which is directly 
mounted and preassembled on the case. While these solutions had made the 
implementation easier, they entail the drawback of increased weight and 
higher costs. 
SUMMARY OF THE INVENTION 
A seal for a rotating shaft is disclosed which seals the shaft as it passes 
through a stationary partition wall to prevent oil from contaminating the 
elements on either side of the partition wall. The seal has casing 
attached to the partition wall which extends around the shaft and defines 
an annular recess. A de-oiling coil extends from the casing and surrounds 
the outer surface of the rotating shaft. 
A segmented graphite sealing ring extends around the shaft and is located 
in the annular recess of the casing. Each of the graphite segments defines 
a circumferential groove and a radial groove. 
A retaining ring having axial projections extending into each of the radial 
grooves is attached to the casing and a retaining washer extends 
circumferentially between the graphite segments and the retaining ring to 
prevent any relative axial movement between these elements. Springs are 
interposed between the retaining ring and the graphite segments to urge a 
surface of each of the graphite segments into contact with a surface of 
the casing. 
Relative rotation between the retaining ring and the casing is prevented by 
stop pegs extending from the casing and engaging grooves formed in the 
retaining ring. A stop ring disposed in a circumferential groove in the 
casing and contacting a portion of the retaining ring prevents relative 
axial movement. 
The seal according to the present invention averts the various drawbacks of 
the known seals, while at the same time assure the impermeability of the 
partition crossed by the shaft, one of which may hold air while the other 
holds oil.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
As illustrated in the FIGURE, a shaft 1 is rotationally supported by a 
sealing bearing such that it may rotate with respect to stationary 
partition wall 3. Partition wall 3 separates two adjacent enclosures, an 
air enclosure 4 on one side of the partition wall 3 and an oil enclosure 5 
on an opposite side of the partition wall 3. A casing 2 is attached to the 
partition wall 3 and extends around the rotating shaft 1. A collar 7 
extends axially from the casing 2 and defines a de-oiling coil 6 adjacent 
to the surface of the rotating shaft 1. 
The casing 2 defines a generally annular recess 8 adapted to receive a 
seal, generally indicated at 9. 
The seal 9 comprises a sealing ring 10 extending circumferentially around 
the rotating shaft and comprising a plurality of graphite ring segments. A 
first side 10a of each of the graphite sealing ring 10 bears against side 
8a of the casing 2 which defines a portion of the annular recess 8 while a 
second side slidingly contacts the surface of the shaft. Each of the 
graphite ring segments define a circumferentially extending groove 11 
which is adapted to receive a resilient retaining washer 12. The retaining 
washer 12 extends through all of the segments to connect them together to 
form the sealing ring. Side 10b of the sealing ring 10, located opposite 
of the aforementioned side 10a defines at least one generally radially 
extending groove 13. 
Retaining ring 14 is located on the side of the sealing ring opposite the 
side 10a and has a plurality of axial projections 14b located such that 
each projection extends into one of the radially extending grooves 13 on 
each of the ring segments. Springs 15 are located in the axial projections 
14b and bear against side 10b of the sealing ring and the retaining ring 
14. 
Retaining ring 14 also has a generally axially extending arm portion 16 
that defines an inwardly opening, circumferential groove 17. Groove 17 is 
adapted to accommodate a portion of the retaining washer 12 so as to 
prevent any relative axial movement between the retaining ring 14 and the 
sealing ring 10. 
A circumferential spring 18 extends around the outer periphery of the 
sealing ring segments thereby urging them into contact with the rotating 
shaft 1 and to increase the rigidity of the sealing ring. 
Locking means are operatively interposed between the retaining ring 14 and 
the casing 2 in order to prevent any relative rotation and any relative 
axial movement between these elements. The anti-rotation locking means may 
comprise a stop peg 19 having a portion extending into opening 20 formed 
in the casing 2 and a portion extending into a generally axially extending 
groove 21 formed in the outer surface of the retaining ring 14. The 
contact between the anti-rotational peg 19 and the groove 21 prevents any 
relative rotation between the locking ring 14 and the casing 2. 
A stop ring 22 extending from circumferential groove 23 formed in casing 2 
bears against a surface of the retaining ring 14 to prevent any axial 
movement between the retaining ring and the casing. In order to facilitate 
the disassembly of the seal structure, side 14a of the retaining ring 14 
defines a hole 24 to receive rivet 25 which holds the spring 15 within the 
axial projection 14b such that it bears against side 10b of the sealing 
ring 10. 
The seal assembly according to the invention may be assembled by the 
following steps: 
a) the retaining ring 14 is interfitted with the graphite ring segments 
held together via circumferential spring 18 such that the projections 14b 
enter the grooves 13 and spring 15 bears against surface 10b; 
b) the resilient retaining washer 12 is radially compressed such that it 
may be moved into alignment with the groove 17 formed in the retaining 
ring 14 and subsequently expanded to hold these elements together; 
c) stop peg 19 is placed in hole 20 on casing 2 and the assembly of the 
retaining ring and the sealing ring segments is placed into the annular 
recess 8 such that a portion of the stop peg engages the groove 21 on the 
retaining ring; and 
d) the stop ring 22 is resiliently compressed such that it may enter the 
groove 23 in the casing and bear against the surface 14a of the retaining 
ring 14. 
The disassembly of the seal structure is also easily carried out by 
compressing and withdrawing the stop ring 22 and withdrawing the entire 
seal assembly from the annular recess 8. Upon withdrawal, the elastic 
retaining washer 12 is radially compressed to be disengaged from the 
groove 17. This may be achieved by inserting a tool into small holes 16a 
defined in the axially extending portion 16 of the retaining ring 14 in 
alignment with the groove 17. This disconnects the retaining ring 14 from 
the graphite ring 10. 
The foregoing is provided for illustrative purposes only and should not be 
construed as in any way limiting this invention, the scope of which is 
defined solely by the appended claims.