METHOD FOR MOUNTING A STERN TUBE

Abstract: The present invention relates to a method for mounting and fixing stern tubes (1) in ships. The stern tube is adpated to enclose a propeller shaft (2) and comprises a tube with at least one interior bearing (3) supporting the propeller shaft. The method is distinguished by the stern tube (1) being arranged in an opening in a fixed part (4) of the ship, said opening having a size somewhat exceeding that of the stern tube transversely of the longitudinal direction of the tube; by arranging an expandable ring (7) between the opening and the stern tube, which ring is expanded so as to extend sealingly between the stern tube and the opening wall (4); and by introducing a curing material (6) from one of the opening ends to fill the space between the stern tube (1) and the opening wall (4) from said opening end to the expanded sealing ring (7), which material is cured and thus fixedly connects the stern tube to the opening wall.

Description: METHOD FOR MOUNTING A STERN TUBE Technical Field The present invention relates to a method for mounting and fixing stern tubes in ships. In this connection, the stern tube is adapted to enclose a propeller shaft and comprises a tube with at least one interior bearing supporting the propeller shaft. Background Stern tubes are used in large ships to enclose the propeller shaft which extends from a driving motor, through the ship hull and out to a propeller . The stern tube is intended to stabilise the propeller shaft, while providing a seal between the rotating propeller shaft and the fixed wall of the ship. When mounting and fixing stern tubes on the ship, use is, for instance, made of chemically curing epoxy or like material. One problem of this method of fixing stern tubes is that it is difficult to obtain an even distribution of the curing material before it cures. This results in non-satisfactory fixation, and if the worst comes to the worst the stern tube will be askew. Furthermore, in normal mounting of stern tubes it is necessary to perform operations both from the inside and the outside of the ship. Since it is difficult to alternate between these positions, this makes the work time-consuming and inefficient. Object of the Invention It is therefore an object of the present invention to provide a method for mounting stern tubes which is more efficient than prior-art methods. This object is achieved by means of the method according to the appended claims . Summary of the Invention The method according to the invention is characterised by the steps of: arranging the stern tube in an opening adapted thereto in a fixed part of the ship, said opening having a size somewhat exceeding that of the stern tube transversely of the longitudinal direction of the tube and having a wall surface facing the stern tube with at least some extension in the longitudinal direction of the tube; arranging an expandable ring between the opening and the stern tube; expanding the ring so that it extends sealingly around substantially the entire stern tube between the stern tube and the opening wall; introducing a curing material from one of the opening ends to fill the space between the stern tube and the opening wall from said opening end to the expanding sealing ring; and allowing the material to cure and thus fixedly connect the stern tube to the opening wall. By arranging an expanding ring in this manner, a seal is provided for the curing material, which makes it possible to introduce the material from one end, without having to check the filling degree and the like from the other. Advantageously, the expandable ring can also be arranged on the tube already before the introduction, which facilitates the work. The expandable ring also helps to place the tube in the desired position relative to the opening and to keep the tube in this position during the curing. Furthermore, the tube can advantageously be provided with a hole for supplying expansion material to expand the ring. In this manner, the step of expanding the ring can be performed from the inside of the stern tube, which inside is accessible from the outside as well as the inside before the positioning of the propeller shaft. Preferably, an overflow opening is also provided, the expandable ring being arranged on the side of the overflow opening which is opposite to the filling opening end. In this manner, the curing material can flow out of this hole when the space which is to be filled is full . This is desirable since this makes it easy to check if a sufficiently high filling level has been reached from the inside of the tube. Brief Description of the Drawings Below, the invention will be described in more detail for the purpose of exemplification by means of embodiments and with reference to the accompanying draw- ings, in which: Fig. 1 is a cross-sectional view of a stern tube having a propeller shaft arranged therein, the tube being mounted by means of the method according to the invention; Fig. 2 shows on a larger scale the portion marked II in Fig. 1; and Fig. 3 shows on a larger scale the portion marked III in Fig. 1. Description of Preferred Embodiments As shown in Fig. 1, and more clearly in Figs 2-3, a stern tube comprises a hollow-circular tube 1 adapted to enclose a propeller shaft 2. The propeller shaft has an end 2a which is adapted to be connected to a propeller and an opposite end 2b which is adapted to be connected to a driving motor. The tube may comprise several interconnected tube segments la-lc, and it also comprises at least one interior bearing 3 with a bearing surface supporting the propeller shaft. The stern tube is connected to fixed parts 4 of the ship, such as the hull, bulkheads or the like. This connection is preferably made, on the one hand, by means of bolt joints 5 or similar mechanical fixing means and, on the other, by means of a curing material 6, such as an epoxy. According to the invention, the stern tube is first positioned in an opening adapted thereto in the fixed part of the ship. The opening should be of dimen- sions somewhat exceeding that of the stern tube transversely of the longitudinal direction of the tube and be provided with a wall surface facing the stern tube with at least some extension m the longitudinal direction of the tube. Subsequently, the tube may be fixed mechanically by means of bolt joints 5 or the like, before the introduction of the curing material 6, so that the material fills at least part of the space between the stern tube and the opening wall . The material is then allowed to cure, which thus fixedly connects the stern tube 1 to the fixed part 4. To facilitate the introduction of the curing material, an expandable ring 7 is also arranged between the opening wall of the fixed part 4 and the stern tube 1. It is possible to position this ring after the introduction of the tube into the opening, but preferably it is positioned already before the tube is inserted. The ring can advantageously be arranged m a deepened groove 8 of the tube. When positioning the ring, it is in an unexpanded state. Subsequently, the ring is expanded so as to extend sealmgly around substantially the entire stern tube between the stern tube and the opening wall . The expanded ring then helps to keep the tube in place. Above all, it provides a sealing wall, which defines the space m which the curing material s to be introduced. As a result, the curing material can easily be introduced from one of the opening ends, the expanded ring preventing it from spreading more than desired. It is particularly preferable to perform essentially all the operations from the outside, i.e. from the propeller side. This means that the curing material is filled from the opening end facing the propeller and that the expandable ring is advantageously displaced towards the other opening end to provide a large attachment surface against which the curing material can act . The expandable ring may comprise a self -expanding material which is caused to expand by supplying liquid, heat or the like. However, the ring is preferably instead expanded by supplying an expansion material . The ring may, for instance, be an inflatable ring and the expansion material a gas, such as air. It is in particular preferable that the expansion material can be supplied from the inside of the stern tube via a hole 9 in the wall of the stern tube. As a result, also this operation can be performed from any side of the stern tube before the propeller shaft has been positioned. Preferably, an overflow opening 10 is also provided in the stern tube 1 in a part of its wall adapted to be arranged opposite to the opening wall 4. This opening is advantageously arranged on the side opposite to the filling opening end and thus allows curing material to flow out of this opening when the space which is to be filled is full. It is particularly convenient to arrange the overflow opening in a part of the stern tube which is located high up, and preferably in the topmost part, since this part is the last to be filled with the curing material. By this arrangement, it is possible to obtain, in a simple manner and from any end, a clear indication of when the space which is to be filled with curing material is full, which results in a good and even filling. The invention has now been described by means of an embodiment. It will, however, be appreciated that many variants of the invention are possible. It is, for instance, possible instead to introduce the curing material from the other, interior side, to use other types of curing material, to use other types of expandable rings, etc. These variants as well as other obvious variants must be considered to fall within the scope of the invention, such as defined by the appended claims..

Claims: CLAIMS 1. A method for mounting a stern tube (1) in a ship, said stern tube being adapted to enclose a propeller shaft (2) and comprising a tube with at least one interior bearing (3) supporting the propeller shaft, c h a r a c t e r i s e d by the steps of : arranging the stern tube (1) in an opening adapted thereto in a fixed part (4) of the ship, said opening having a size somewhat exceeding that of the stern tube transversely of the longitudinal direction of the tube and having a wall surface facing the stern tube with at least some extension in the longitudinal direction of the tube; arranging an expandable ring (7) between the opening and the stern tube; expanding the ring (7) so that it extends sealingly around substantially the entire stern tube (1) between the stern tube and the opening wall (4) ; introducing a curing material (6) from one of the opening ends to fill the space between the stern tube (1) and the opening wall (4) from said opening end to the expanded sealing ring (7) ; and allowing the material (6) to cure and thus fixedly connect the stern tube to the opening wall. 2. A method as claimed in claim 1, wherein the expandable ring (7) is expanded by supplying an expansion material . 3. A method as claimed in claim 2, wherein the ring is an inflatable ring and the expansion material is a gas, such as air. 4. A method as claimed in claim 2 or 3 , wherein the expansion material is supplied from the inside of the stern tube (1) via a hole (9) in the wall of the stern tube . 5. A method as claimed in claim 1, wherein the expandable ring (7) comprises a self-expanding material. 6. A method as claimed in any one of the preceding claims, wherein the curing material is introduced from the opening end which faces the part of the propeller shaft where the propeller is adapted to be arranged. 7. A method as claimed in any one of the preceding claims, comprising the further step of providing an overflow opening (10) in the stern tube (1) in a part adapted to be arranged opposite to the opening wall, the expandable ring (7) being arranged on the side of the overflow opening (10) which is opposite to the filling opening end. 8. A method as claimed in claim 7, wherein the over- flow opening end is arranged in a part of the stern tube (1) which is located high up, and preferably in the topmost part . 9. A method as claimed in any one of the preceding claims, further comprising the step of connecting the stern tube (1) to the fixed part (4) of the ship, before supplying the curing material (6) , with the aid of mechanical fixing means (5), such as bolt joints. 10. A method as claimed in any one of the preceding claims, wherein the curing material (6) is a chemically curing material, and preferably an epoxy.

Inventors: BOKEDAL NILS, BOKEDAL, NILS
Applicants: BOKEDAL NILS, SVENSKA BEARING AB, BOKEDAL, NILS
Application year: 2000
Main classification: B63H23
IPC codes: B63B9, B63H23, F16J15