GB2069626A - Bearing and method of mounting bearing - Google Patents

Abstract

A system for mounting a stern bearing 11 in a bore 25 in the stern frame boss 24 of a ship comprises mounting an arcuate bar 29 on the bearing and inserting the sub-assembly into the bore. The bar permits pivoting of the bearing about two mutually perpendicular transverse axes so that the bearing can be set at the desired alignment. The ends of the clearance space 33 are closed by seals 27 and 28 and the space 33 is then filled with a hardenable grout to set the bearing in position. <IMAGE>

Description

SPECIFICATION Bearing and method of mounting bearing The present invention relates to bearings and methods of mounting bearings. It is especially concerned with the stern bearings of ships.

In the construction of a ship, one operation that is critical in determining the completion date of the ship is the operation of boring out the stern frame boss to match the shafting alignment. This operation must be left until after all the structural welding of the hull is completed. Furthermore, the operation of boring out the stern frame boss must be made on site using a portable boring bar and adjustable bearing plates for supporting and guiding the boring bar. The bearing plates must be set on the effective line of sight of the shafting which is obtained by calculation. It is a matter requiring a great deal of skill and application which must be maintained under extreme pressure from management to complete the operation-the last and most critical-in the completion of the ship.

According to the present invention in one aspect, a method of mounting a bearing in a structure comprises mounting the bearing in a bore in the structure so as to permit limited pivoting movement of the bearing relative to the structure about a transverse axis, aligning the bearing, closing the ends of a clearance space between the sleeve and the bore, injecting a hardenable grout into the clearance space, and allowing the grout to set.

When applied to the mounting of stern bearing in a ship the invention may eliminate boring the stern frame boss on site and to facilitate fitting work. In practice something approaching two weeks and much accompanying anxiety may be saved. The stern frame can be delivered to the shipyard complete with the stern bearing installed, pivoted to be self-aligning to the propeller tailshaft which it will support. To align the bearing to the deflected form which the tailshaft will take when it is supporting the weight of the propeller three alternative methods may be used.

In the first method, the sections of the ships shafting are bolted together to a calculated shafting alignment. The propeller is fitted and the ship is launched. The stern bearing, being pivotally mounted in the stern frame bore, automatically adjusts its alignment to the tailshaft deflection. The bearing is then permanently secured in the stern frame boss by the grout injection. This is the preferred method and will be used where the ambient temperature of the sea creates no problems regarding the setting time for the grout. For low temperature work a heating wire may be incorporated in a two-start thread machined on the periphery of the bearing sleeve.

The second method is a pre-launch technique, where, as is common practice, the alignment is carried out with the ship on the slipway but the shores, in way of the stern are knocked out to simulate the floating alignment of the hull. To simulate the easily calculable bending deflection of the hull, the shaft, without the propeller fitted, is tilted upwards at the after-peak bulkhead and the grout injected to secure the bearing. The actual deflected form of the bearing is known from gap measurements between bearing periphery and the bore of the stern frame boss (see reference numeral 38 in Fig. 2).

The third method is also a pre-launch technique, but made either with the propeller fitted or alternatively, the propeller weight applied by a hydraulic jack pressing vertically downwards onto the outboard end of the tailshaft, the upward reaction being taken by the stern frame arch. Suitable hardwood spreaders attached to steel pads must be provided to spread the load.

According to the present invention in a second aspect a bearing assembly comprises a bearing sleeve, located in a bore in a supporting structure, means for pivotally mounting the sleeve in the bore, and means for closing the ends of a clearance space between the bore and the sleeve, the clearance space being filled with a hardened grouting composition.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 shows a longitudinal section through the stern of a ship showing a bearing assembly in accordance with the invention; Figure 2 shows a longitudinal section of the bearing assembly of Fig. 1 on an enlarged scale; Figure 3 shows a longitudinal section through the bearing bush of Fig. 1; Figure 4 shows a longitudinal section through a bearing sub-assembly of Fig. 1; Figure 5 shows a transverse section of the bush of Fig. 3; and Figure 6 shows a transverse section of the sub-assembly of Fig. 4.

Referring to the drawings, a standard commercially available (Glacier Metal Co) cast iron bearing bush 11 modified as described below, is used. The bush has the standard white metal lining 12, internal and external oil distribution grooves 1 3 and 14 interconnected by oil holes 1 5. Alternatively the white-metal lined bearing bush can be replaced by a Railko-type bush that is a bush of bonded asbestos which requires no cast iron carrier sleeve. A Railko (Registered Trade Mark) bush would require an increased running clearance to allow for the additional contraction of the bore when force fitted in the sleeve, as will be described below.

The cast iron bush 11 is modified as follows: (a) The external periphery of the bush is given a 1 /30 taper.

(b) A 8mm thick mild steel sleeve 16 is rolled to a 1/30 taper, wrapped around the bush and butt welded at 1 7 along the longitudinal seam. The exterior of the sleeve 1 6 is roughened. The bush 11 is then force fitted into the sleeve 16 with a force of 50 to 1 50 tons (depending on the size) in a press. Eight dowels 1 8, 20mm in diameter and screwed at one end with a metric 22mm outside diameter screw thead of 2mm pitch, are fitted in eight radially drilled holes 1 9, of 20mm diameter which are tapered with a matching screw thread from the base outwards for half their length.These dowels 18 which are finally secured with an adhesive such as is sold under the Trade Mark "Locktite", serve to secure the bush firmly in the sleeve. In the event of serious bearing damage, the bush can be jacked out of the sleeve (using for example hydraulic nut) after unscrewing the dowels 18. After the bush has been remetalled it can be jacked into position and relocked as before.

(c) The sleeve 1 6 has a pivot bar 20 of 20mm thick by 30mm wide mild steel attached at mid length by welding. The pivot bar is divided in two arcuate halves, with a central gap 21, 20mm wide for the injection of the grouting composition.

(d) Two 20mm wide axially extending slots 22 are provided in the outer periphery of the cast iron bush to take the void space drain and air tubes where an oil gland seal as is described in our patent application 53704/76, 647/77 and 4438/78 (cognate).

(e) In one of these slots 22 a cable with temperature sensing thermocouple will be provided to show the temperature of the bearing at about 1 /6L from aft. A copper conductor in copper tube with a mineral insulation between, such as is sold under the Trade Mark Pyrotenax is particularly suitable for the cable.

Fig. 3 shows the assembly of the bearing bush 11 in the stern frame boss 24 of a ship.

The stern frame boss 24 has a bore 25 which has a larger diameter throughout its forward half than its aft half. An annular shoulder 26 is thus provided half way along the bore 25. The bearing sub-assembly consisting of the sleeve 1 6 and the bush 11 is inserted into the bore 25 from the forward end so that the pivot bar 20 abuts the shoulder 26. The radial thickness of the pivot bar 20 is such as to place the bearing subassembly centrally in the bore 25 whilst permitting the sub-assembly to pivot or rock about transverse axes relative to the bore.

The bearing bush is aligned by one of the methods described above.

Inflatable oil seals 27 and 28 formed by hollow annular tubes, one towards each end of the bush 11, are let into grooves 29 and 30 turned in the bore 25 of the boss. Inlet stems 31 and air bleed stems 32 are used to fill tiie seals with oil and pressurize them to approx. 1 50 psi to form a seal between the sleeve 1 6 and the bore 25. The void space 33 trapped between the seals 27 and 28, the bore 25 of the boss and the outer periphery of the sleeve 16, is finally filled with a suitable grout such as an expoxy resin composition, after testing for tightness with solvent such as carbon tetrachloride (pressurised 100 psi) which will be blown down and devaporised. The grout is injected through the inlet bore 34 while air is bled out through the bores 35.

The change in the vertical and transverse gap readings from line of sight alignment will be a true measure of the final alignment.

The bore of the stern frame boss is stepped to provide a positive step against which the pivot bar locates the bush axially, yet allowing the bush to pivot on the bar. The maximum angle of declivity ' is such as to provide for a transverse malalignment up to + 50mm at the tailshaft coupling. This is many times the practical malalignment which could be found in practice.

Claims (11)

1. A method of mounting a bearing in a structure comprising mounting the bearing in a bore in the structure so as to permit limited pivoting movement of the bearing relative to the structure about a transverse axis, aligning the bearing, closing the ends of a clearance space between the sleeve and the bore, injecting a hardenable grout into the clearance space, and allowing the grout to set.

2. A method according to claim 1 in which the bearing is pivotable about two mutually perpendicular transverse axes prior to the injection of said grout.

3. A method according to claim 2 in which the bearing is pivotable on an arcuate projection.

4. A method according to claim 3 in which the bore has a shoulder which abuts the projection to axially locate the bearing in the bore.

5. A method according to claim 1, 2, 3 or 4 in which the grout is an epoxy resin composition.

6. A bearing assembly comprising a bearing sleeve, located in a bore in a supporting structure, means for pivotally mounting the sleeve in the bore, and means for enclosing the ends of a clearance space between the bore and the sleeve, the clearance space being filled with a hardened grouting composition.

7. A bearing asssembly according to claim 6 in which the bearing is pivotable about two mutually perpendicular axes prior to injection of the grout.

8. A bearing assembly according to claim 7 in which the pivotally mounting means comprises an arcuate projection on the outside of the bearing which supports the bearing in the bore prior to the injection of grout.

9. A bearing assembly according to claim 8 in which the projection is substantially half way along the bearing.

10. A bearing assembly according to claim 8 or 9 in which the bore comprises two portions of different diameter with a shoulder between them, the projection abutting the shoulder.

11. A bearing assembly according to claim 6, 7, 8, 9 or 10 in which the means for closing the clearance space comprise hollow annular tubes which are filled with hydraulic fluid prior to the injection of the grouting composition in the clearance space.

1 2. A bearing assembly according to any of claims 6 to 11 in which the hardenable grouting composition is an epoxy resin composition.

1 3. A bearing assembly substantially as hereinbefore described with reference to the accompanying drawings.

1 4. A method of mounting a bearing in a structure substantially as hereinbefore described with reference to the accompanying drawings.