Pumps – Three or more cylinders arranged in parallel – radial – or...
Reexamination Certificate
1999-09-30
2001-09-18
Thorpe, Timothy S. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
C417S222100, C092S071000, C277S565000
Reexamination Certificate
active
06290470
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a shaft sealing assembly. More specifically, the present invention pertains to a shaft sealing assembly that prevents fluid such as refrigerant and lubricant from leaking from a compressor.
A typical shaft sealing assembly
50
is structured as follows. As shown in
FIGS. 4 and 4A
, the sealing assembly
50
is located between a drive shaft
61
and a compressor housing to prevent leakage of fluid from the inside to the outside of the compressor. A first lip ring
51
, which is made of synthetic rubber, includes a lip
51
a
. The lip
51
a
is formed at the radially inner area of the first lip ring
51
. A retainer ring
52
, which is made of metal, retains the position of the lip
51
a
to contact a drive shaft
61
. A second lip ring
53
, which is made of fluororesin, includes a lip
53
a
. The lip
53
a
is formed at the radially inner area of the second lip ring
53
and is curved toward the inside of the compressor (right side in FIG.
4
). A spiral pump slit
53
b
is formed in the lip
53
a
about the axis of the second lip ring
53
. A third lip ring
54
, which is made of synthetic rubber, includes a lip
54
a
. The first lip ring
51
, the retainer ring
52
, the second lip ring
53
, and the third lip ring
54
are arranged in this order from the inside to the outside of the compressor as shown in FIG.
4
.
The rings
51
-
54
are tightly held together in a cylindrical case
55
. Accordingly, the first and the second lip rings
52
,
53
contact the retainer ring
52
and the case
55
.
When the drive shaft
61
is rotating, or when the compressor is operating, high pressure gas in the compressor is applied to the lip
53
a
of the second lip ring
53
. Accordingly, the lip
53
a
is pressed against the drive shaft
61
by a predetermined force, which prevents leakage of fluid from the compressor. In this state, the pump slit
53
b
of the lip
53
a
has a spiral pumping effect and positively sends fluid back between the lip
53
a
and the drive shaft
16
. This also improves the fluid-sealing performance of the second lip ring
53
.
When the drive shaft
61
is not rotating, or when the compressor is not operating, the lip
51
a
of the first lip ring
51
resiliently contacts the drive shaft
61
. This prevents leakage of fluid from the compressor. When the drive shaft
61
is not rotating, the pressure in the compressor is relatively low and the lip
53
a
of the second lip ring
53
is pressed against the rotational shaft
61
by a relatively small force. Accordingly, the shaft sealing assembly includes the first lip ring
51
to compensate for the weak sealing ability of the second lip ring
51
.
When the drive shaft
61
is rotating, the lip
51
a
of the first lip ring
51
allows fluid in the compressor to flow toward the second lip ring
53
. The position of the lip
51
a
with respect to the drive shaft
61
is retained by the retainer ring
52
when high pressure is applied to the inside of the first lip ring
51
.
The fluid (mainly lubricant) that leaks by the lip
51
a
of the first lip ring
51
lubricates and cools the lips
51
a
,
53
a
of the first and second lip rings
51
,
53
. Accordingly, the lips
51
a
,
53
a
are not worn by friction. This extends the life of the first and second lip rings
51
,
53
.
The lip
54
a
of the third lip ring
54
resiliently contacts the drive shaft
61
and prevents foreign particles from entering. Accordingly, foreign particles do not enter between the lip
53
a
and the drive shaft
61
, which prevents the performance of the second lip ring
53
from deteriorating. When the rotation of the drive shaft
61
is stopped, the third lip ring
54
prevents leakage of fluid that remains between the first lip ring
51
and the second lip ring
53
.
However, the first lip ring
51
permits leakage of fluid (refrigerant gas) during the rotation of the drive shaft
61
. The seal formed between the second lip ring
53
and the retainer ring
52
and between the second lip ring
53
and the case
55
has a lower sealing performance compared to the contact area seal formed between the first lip ring
51
and the retainer ring
52
and between the first lip ring
51
and the case
55
. Accordingly, as shown by
FIG. 4A
, the refrigerant gas that leaks past the first lip ring
51
is likely to enter between the second lip ring
53
and the retainer ring and between the second lip ring
53
and the case
55
.
When the rotation of the drive shaft
61
is stopped, the third lip ring
54
prevents leakage of the fluid remaining between the first lip ring
51
and the second lip ring
53
. In other words, the fluid (especially refrigerant gas) between the second lip ring
53
and the retainer ring
52
and between the second lip ring
53
and the case
55
does not flow out of the compressor after the drive shaft
61
is stopped. When the drive shaft
61
is stopped for a relatively long period, the refrigerant gas between the second lip ring
53
and the retainer ring
52
and between the second lip ring
53
and the case
55
can be liquefied by cooler temperatures.
If the drive shaft
61
rotates in this state, the temperature around the shaft sealing assembly
50
increases. Then, the liquidized refrigerant between the second lip ring
53
and the case
55
vaporizes, which moves the second lip ring
53
radially inward. This may release the second lip ring
53
from the case
55
. Since the second lip ring
53
and the retainer ring
52
are held together in the case
55
by friction and compression, the release of the second lip ring
53
also releases the retainer ring
52
from the case
55
. Accordingly, the retainer ring
52
cannot retain the initial position of the lip
51
a
of the first lip ring
51
with respect to the drive shaft
61
. As a result, the first lip ring
51
may not leak fluid, which causes the first and the second lip rings
51
,
53
to wear prematurely.
On the other hand, the released second lip ring
53
may lift the first lip ring
51
, through the retainer ring
52
, from the drive shaft
61
. Thus, when the drive shaft
61
rotates, the first lip ring
51
may leak too much fluid that for the second lip ring
53
and the third lip ring
54
to stop.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a shaft sealing assembly for compressors that prevents fluid from entering between the periphery of the second lip ring and the case.
To achieve the above objective, the present invention provides a shaft sealing assembly for a rotary shaft extending through and supported by a housing. The shaft sealing assembly includes a first lip ring placed around the shaft. The first ring has a first peripheral portion, which extends in a substantially radial direction with respect to the shaft. The first lip ring also has a first lip portion that contacts the surface of the shaft. The first lip portion resiliently contacts the surface of the shaft. The first lip ring has a predetermined shape that prevents leakage of fluids from the inside of the housing when the shaft is stopped and allows leakage of fluids from the inside of the housing when the shaft rotates. A retainer ring is placed adjacent to the first lip ring around the shaft. The retainer ring has a second peripheral portion that extends in a substantially radial direction with respect to the shaft. The retainer ring supports the first lip ring so that the first ring substantially retains its shape. A second lip ring is also placed around the shaft and adjacent to the retainer ring on the opposite side of the retainer ring from the first lip ring. The second lip ring has a third peripheral portion that extends in a substantially radial direction with respect to the shaft and a second lip portion that extends substantially along the surface of the shaft. The second lip portion resiliently contacts the surface of the shaft to substantially prevent leakage of fluids from the inside of the housing. Further, a case is included for holding the rings together by gripp
Chiba Keiichi
Kawaguchi Masahiro
Morishita Atsuyuki
Okuno Takuya
Sonobe Masanori
Gray Michael K.
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Thorpe Timothy S.
LandOfFree
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