Leaktight fitting for a shaft end

Details Leaktight fitting for a shaft end Leaktight fitting for a shaft end

1998-08-04

2001-06-12

Sandy, Robert J. (Department: 3626)

Seal for a joint or juncture

Seal between relatively movable parts

Diverse and distinct dynamic seals

C277S549000, C277S551000

Reexamination Certificate

active

06244600

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a leaktight fitting for a shaft end, particularly for a shaft end located in a housing and protected from the outside by a cap that can be removed when required.
2. Discussion of the Background
The advantages of this type of shaft end may be understood by studying
FIG. 1
which shows a gas turbine. Working from front to back along an annular gas circulation channel
1
, are fitted a blower
2
, a low pressure compressor
3
, a high pressure compressor
4
, a combustion chamber
5
, a high pressure turbine
6
and a low pressure turbine
7
. The channel
1
contains fixed, circular blade stages constructed as part of a housing
8
that delimits the outside of the channel and rotating blades connected to a rotor
9
that delimit the inside of the channel. The rotor
9
also comprises a line of low pressure shafts
10
that interconnect the blower
2
, the low pressure compressor
3
and the low pressure turbine
7
, as well as a line of high pressure shafts
11
that interconnect the high pressure compressor
4
and the high pressure turbine
6
. The lines of shafts
10
and
11
are coaxial and the line of high pressure shafts
11
surrounds the line of low pressure shafts
10
. The line of shafts ends at the front in a conical gear wheel that co-ordinates with a first conical gear wheel of a transmission shaft
12
radially positioned to form an angled gear
13
. Another angled gear
14
is formed at the opposite end of transmission shaft
12
between another conical gear wheel mounted on the shaft and a final conical gear wheel located at the rear end of shaft end
15
. Shaft end
15
lies parallel to the shaft lines
10
and
11
and next to the low pressure compressor
3
and the blower
2
. Its forward end finishes behind a plane surface
16
of housing
8
, opposite an aperture
17
that is closed by a cap
18
gripped by an elastic ring
19
clamped between the cap and aperture
17
. This ring
19
also ensures the leaktightness of aperture
17
.
The shaft end
15
allows individual inspection of the blades connected to the line of high pressure shafts
11
and particularly the blades of the high pressure compressor
4
. It is known that blades are relatively fragile structures that can be easily damaged, for example when a foreign body is introduced into the gas turbine. The method for inspecting the blades consists firstly in disassembling the gas turbine and opening a window of housing
8
facing one of the stages of the rotating blades to be inspected, usually the first of compressor
4
, and then rotating the line of high pressure shafts
11
in order that all the blades of the stage pass successively in front of the window. Movement is brought about using a key (not shown, but of standard design) which is inserted into an opening located at the front of shaft end
15
. The key is inserted through slot
17
once the cap
18
is removed and can be operated by hand or by a dedicated device. A drawback, however, of this construction is that the operator may forget to replace cap
18
, resulting in a large quantity of the oil contained in housing
8
draining from aperture
17
as soon as operation of the gas turbine is resumed, thus rapidly emptying the housing
8
. Despite seal
19
, cap
18
may also be accidentally dropped.
SUMMARY OF THE INVENTION
The present invention was designed to combat this risk. It consists in adding a leaktight seal between shaft end
15
and housing
8
in order to maintain leaktightness even when cap
18
is removed.
It should, however, be pointed out that the shaft end
15
rotates with the line of high pressure shafts
11
while the gas turbine is in use and is likely to cause rapid wear of the recently-added joint. The major contribution of the invention to the art therefore consists of the special construction of the added leaktight seal and of the cap designed to overcome this difficulty.
In its commonest form the invention therefore relates to a leaktight fitting for a shaft end fitted behind a movable cap on an aperture in the housing of the shaft end, characterized by the fact that it comprises a leaktight seal fastened to the housing, located between the housing and the shaft end and comprising an elastic lip tending to rest on the shaft end, and by the fact that the cap comprises a pusher component lying around the shaft end and pushing the elastic lip of the shaft end when the cap is placed on the aperture.


REFERENCES:
patent: 2405120 (1946-08-01), Evans
patent: 3788100 (1974-01-01), Pitner
patent: 4587749 (1986-05-01), Berlese
patent: 4664392 (1987-05-01), Hatch
patent: 5024449 (1991-06-01), Otto
patent: 5299811 (1994-04-01), Kershaw
patent: 5605337 (1997-02-01), Puri
patent: 5791658 (1998-08-01), Johnston
patent: 6050572 (2000-04-01), Balsells et al.
patent: 34 21 247 (1984-12-01), None
patent: 0 561 565 (1993-09-01), None

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