Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Reexamination Certificate
2000-08-21
2002-11-19
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
C277S408000, C277S559000, C277S563000, C277S927000, C440S112000
Reexamination Certificate
active
06481720
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a stern tube sealing apparatus for a vessel.
Conventionally, a stern tube sealing apparatus with a seal ring made of an elastic material has been used for a vessel. However, since a draft pressure is increased in accordance with the vessel getting larger in size, a pressure applied to the seal ring is increased and many troubles that the seal ring is damaged are caused, so that a seawater enters into the vessel and a disadvantage is generated on maintaining the vessel. Accordingly, conventionally as a countermeasure therefor, it has been intended that the entering of the seawater is sealed and a durability of the seal ring is improved by supplying a pressurized air having a pressure slightly higher than the draft pressure to an aftermost annular space formed by a first seal ring and a second seal ring and always discharging the air from the annular space to the sea side.
In this case, when the air is fed out to the sea as mentioned above, a load of the first seal ring is reduced, however, the first seal ring becomes dry by the air, so that a sliding contact surface may be abraded. When the abrasion is generated in the first seal ring, a little amount of seawater enters, water is evaporated within a rearmost chamber and salt is crystallized, so that the salt is attached to the seal ring and a liner so as to be solidified, whereby there are generated disadvantages that the abrasion of both elements is promoted or that a drain line is clogged. Further, a foreign substance such as a marine growth, mud or the like attached to the first seal ring on the seawater side enters into the rearmost chamber, thereby further abrading the seal ring and the liner.
SUMMARY OF THE INVENTION
The present invention is made on the basis of the matters mentioned above, and an object of the present invention is to provide a stern tube sealing apparatus which prevents an abrasion by cooling and lubricating a sliding contact surface of a first seal ring, prevents a foreign substance and a seawater from entering so as to further improve a durability of a seal ring and a liner, intends to make the sealing apparatus compact and reduce a cost by using no pressurizing apparatus, and has a high reliability of a seal system.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a stern tube sealing apparatus comprising a plurality of seal rings slidably brought into contact with a liner of a propeller shaft, wherein piping communicating with one of a liquid reservoir tank and a pressure control valve connected to a liquid supply source is provided in a stern annular space defined by a first seal ring arranged on a stern side and a second seal ring adjacent to the first seal ring, and feeding means for forcibly feeding the liquid in the stern annular space to an outside of a vessel having a higher pressure than that in the stern annular space at a time of shaft rotation is provided on at least one of a sliding contact surface of the first seal ring and an opposing sliding contact surface with which the first seal ring is slidably contact.
The feeding means in this case includes all of means for feeding out a liquid from a low pressure side of the seal ring to a high pressure seawater side thereof to be sealed due to a pumping effect by a seal ring at a time of the shaft rotation (including a time of regular rotation and a time of reverse rotation of the propeller). Further, the seal ring corresponds to an idea including a lip type seal ring, a face type seal ring and a mechanical seal. In the case of the lip type seal ring, the seal ring provided with the feeding means is not required to always have a feature that the lip is directed to the seawater side, for example, it is sufficient that a contact angle with respect to the liner on the seawater side is greater than that on the vessel interior side.
When the structure is made in the manner mentioned above, it is possible to keep a pressure within the stern annular space lower than a pressure on the seawater side, it is possible to feed the liquid to the seawater side and it is possible to simultaneously cool and lubricate the sliding surface of the first seal ring, whereby it is Possible to prevent the foreign substance and the seawater from entering and the sliding load of the second seal ring with respect to the liner is reduced under a low pressure.
In this case, the feeding means for feeding the liquid from the low pressure side of the seal ring to the high pressure seawater side to be sealed is not required to be always provided on the seal ring, and when the feeding means is provided on the opposing sliding contact surface with which the first seal ring is slidably contact, the same functions and effects as those in the case that the feeding means is provided on the first seal ring can be obtained. Further, the feeding means may be provided on each of the sliding contact surfaces of the first seal ring and the opposing element. In the case of the lip type seal ring, the opposing element with which the seal ring is slidably brought into contact is a liner.
Further, in accordance with the present invention, there is provided a stern tube sealing apparatus as recited in the first aspect mentioned above, wherein a branch pipe with a pressure control valve and a flow control valve connecting to the liquid supply source is provided, via a first change-over valve, in the middle of the piping communicating with the liquid reservoir tank and the aftermost annular space, and a constant flow amount valve making it possible to flow out a constant flow amount of liquid from the stern annular space to the outside of the vessel in accordance with a change-over operation of the first change-over valve is interposed in the branch pipe.
In the case that the structure is made in the manner mentioned above, the constant flow amount valve is operated due to changing over the flow passage by means of the first change-over valve so as to flow the constant flow amount of liquid from the first seal ring to the outside of the vessel even when the feeding means does not effectively function, whereby the cooling and lubricating state of the sliding contact surface in the first seal ring can be maintained, and further it is possible to prevent the foreign substance and the seawater from entering.
Further, the first seal ring is generally arranged at the rearmost position (a position closest to the seawater), however, at least one auxiliary seal ring may be further arranged on the seawater side and the feeding means is provided in at least one of the auxiliary seal ring and an opposing element on a sliding contact surface between the auxiliary seal ring and the opposing element. In the case that the auxiliary seal ring is the lip type seal ring, the opposing element is a liner. When the structure is made in this manner, it is possible to further improve a reliability of the feeding effect.
In this case, as mentioned above, the feeding means for feeding out the liquid with a pumping action, or pump-in-action from the low pressure side of the seal ring to the seawater side corresponding to the high pressure side to be sealed is not particularly limited, however, the structure may be made such that a fine unevenness or a fine screw groove is formed on the seal ring and/or the opposing element in the seal ring and the opposing sliding contact surface. A shape of the unevenness is not limited to a circular shape, an angular shape or the like. Here, with respect to a magnitude of the “fine” evenness, the unevenness can be realized in a range of height between some microns and some hundreds microns, however, in order to achieve an effective feeding function, some tens microns is desirable. Further, a magnitude of the “fine” screw groove is set to be wide since a desirable value changes in accordance with an angle and a depth of the screw or the like, however, a width and a depth of the screw groove are set to a range between some microns and some hundreds microns.
Takayasu Minoru
Yoshida Hisashi
Arent Fox Kintner Plotkin & Kahn
Japan Marine Technologies Ltd.
Knight Anthony
Pickard Alison K.
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