Seal for a joint or juncture – Seal between relatively movable parts – Diverse and distinct dynamic seals
Reexamination Certificate
1999-03-30
2001-12-04
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Diverse and distinct dynamic seals
C277S408000
Reexamination Certificate
active
06325378
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to and claims the early filing date of Japanese Patent Applications No. 10-089045, filed Apr. 1, 1998 and No. 10-092101, filed Apr. 3, 1998.
FIELD OF THE INVENTION
This invention relates to a shaft seal apparatus. The shaft seal apparatus of the present invention is employed in rotary equipment such as stirrers and mixers that are intended for use in the manufacture of pharmaceuticals, foodstuffs, and the like.
BACKGROUND OF THE INVENTION
A vertical type stirrer or agitator
101
as shown in
FIG. 5
is used in the production of fermented products such as, for instance, fermented drinks. This stirrer
101
has a motor-supporting frame
103
set up on a tank shell
102
forming a fermentation tank, a motor (with a reducer, etc.)
104
mounted on the top of the motor-supporting frame
103
, and a rotary shaft or stirrer shaft
106
connected to the motor
104
. Shaft
104
is supported in a free-rotating state by motor-supporting frame
103
by means of a bearing
105
. Shaft
104
extends down inside tank shell
102
and is held vertically in the fermentation tank inner space
107
. Shaft
104
is constituted so that agitation propellers
108
,
108
mounted at the lower end thereof agitate a treatment material to enhance fermentation in tank inner space
107
.
This type of fermentation stirrer
101
is designed so as to prevent fermentation gases generated in tank
107
from leaking out by providing an appropriate shaft seal apparatus
109
between rotary shaft
106
and a rotary shaft penetrating portion
102
a
of tank shell
102
.
Some known types of shaft seal apparatus
109
installed on this type of stirrer
101
are equipped with a single or double end-face contact mechanical seal while others are provided with grand-packings.
The type of shaft seal apparatus equipped with a single mechanical seal (hereinafter referred to as “the first prior art apparatus”) has a seal case in the rotary shaft penetrating portion
102
a
in which a stationary seal ring on the seal case is pressed against a rotary seal ring on the rotary shaft
5
. Thus, in the first prior art apparatus, tank inner space
107
is sealed by a sliding contact between the two seal rings rotating relative to one another.
The end-face contact type shaft seal apparatus provided with a double mechanical seal (hereinafter called “the second prior art apparatus”) has a pair of mechanical seals, of the same type of the first prior art apparatus, arranged side by side. A sealing fluid region is thus formed between the pair of mechanical seals and keeps the tank inner space
107
air-tight. The sealing fluids used in this type of apparatus include oils and liquids that would cause no problems if they leak into the tank. The type of shaft seal apparatus using oil as sealing fluid is additionally provided with an oil unit where the oil is circulated so as to keep the oil from leaking into the tank inner space from the seal region. This type of shaft seal apparatus is also designed so that the pressure of the oils and liquids (that would cause no problems if they leak into the tank) can be held higher than that inside the tank, to prevent the gas inside the tank (i.e., the fermentation gas) from leaking out into the seal region.
The type of apparatus using a grand-packing (hereinafter name “the third prior art apparatus”) has a stuffing box installed in the rotary shaft penetrating position
102
a
and a number of grand packings, generally braided packings, are arranged side by side in the space between the stuffing box and the rotary shaft
106
to seal the tank inner space
107
. Also, a lantern ring is usually provided in the middle of the group of grand-packings, where nitrogen gas is fed.
Rotary equipment such as the aforesaid fermentation stirrers
101
, when used with pharmaceuticals, foodstuffs, raw materials to be processed into pharmaceuticals and foodstuffs, and other such materials, require strict hygienic control. They are subjected to sterilization treatment periodically or as necessary by the injection of a sterilization gas, usually high-temperature steam, into the tank inner space
107
. In this sterilization treatment, parts of the shaft seal apparatus that face the tank inner space
107
cannot be cleaned well by the sterilization gas which is jetted into the tank alone. Therefore, the same gas is directly jetted onto those parts of the shaft seal apparatus.
In the first and second prior art apparatuses, however, the seal end faces on both sides which are in contact with each other cannot be well sterilized by the jetting of the sterilization gas. Especially in the second prior art apparatus, which is of complicated construction, the sterilization gas cannot reach many parts of the apparatus, which results in grossly insufficient sterilization. Another problem is that since those prior art apparatuses are based on end-face contact type mechanical seals, dust will arise from the contact wearing of the two end faces in operation, which can fall into the tank inner space
107
. It is difficult, therefore, to achieve sufficient hygienic control in the tank. The problem with the first prior art apparatus is that the gas in the tank cannot be shut out completely. Toxic or odiferous gases in the tank could contaminate or otherwise damage the environment.
The third prior art apparatus also presents the following problems. The grand-packings cannot be cleaned enough even by jetting a sterilization gas directly at them. Furthermore, the grand-packings produce dust from contact with the rotary shaft
106
in operation, and that dust can fall into the tank inner space
107
. For those reasons, sufficient hygienic control in the tank inner space
107
is difficult to effect, as with the first and second prior art apparatuses.
As set forth above, the first through third prior art apparatuses cannot be well-sterilized by hygienic procedures including treatment by jetting sterilization gas. They are accordingly not suitable for use in rotary equipment where strict sanitation is required. The industry would benefit if those problems were addressed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a shaft seal apparatus which can completely seal off fermentation gas in a fermentation tank without causing dusting (such as from wearing) and which is fully sterilizable by sterilization gas. A shaft seal apparatus having these attributes is quite suitable for use in rotary equipment where vigorous hygienic control must be exercised.
It is another object of the present invention to provide a shaft seal apparatus the construction of which is simplified to the maximum possible extent by using gas feeding passages formed in a seal case and a stationary seal ring not only as means for generating static pressure by seal gas but also as means for sterilizing a tank by sterilization gas.
It is a further object of the present invention to provide a shaft seal apparatus which affords excellent sealing even in rotary equipment in which a seal case is difficult to mount with precision or in which the shaft vibrates because of the construction or function of the machine.
These objects are achieved by a shaft seal apparatus which comprises a seal case mounted in a rotary shaft penetrating portion of a tank shell of rotary equipment, a rotary seal ring fixed to the rotary shaft of the rotary equipment, a stationary seal ring held in the seal case opposite to the rotary seal ring and movable in the direction of the shaft axis, a thrusting member mounted between the seal case and the stationary seal ring and thrusting the stationary seal ring against the rotary seal ring, a gas feeding channel comprising a series of gas passages running through the seal case and the stationary seal ring and opening between two opposing seal end faces of the two seal rings, and a gas jetting mechanism to jet seal gas or sterilization gas selectively to between the seal end faces from the gas feeding channel.
In normal operation, the shaft seal apparatus function
Fujiwara Satoshi
Fuse Toshihiko
Okumachi Eiji
Griffin & Szipl, P.C.
Knight Anthony
Nippon Pillar Packing Co. Ltd.
Patel Vishal
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