GB2058951A

GB2058951A - Marine propeller shaft bearings

Info

Publication number: GB2058951A
Application number: GB8021535A
Authority: GB
Original assignee: SCATRA AB
Current assignee: SCATRA AB
Priority date: 1979-07-14
Filing date: 1980-07-01
Publication date: 1981-04-15
Also published as: IT8005166A0; SE8004961L; IT1136004B; JPS5614621A; GB2058951B; IT8006991V0; DE2928500A1; DE2928500C2

Abstract

A propeller shaft bearing for use in boats has an inner layer (10) made from a hard resilient material and a further concentric layer (11) made from a soft resilient material. The bearing may be water lubricated, and the further layer (11) may be provided with blind bores (17) which in use are continually deformed to assist in pumping water to the bearing surfaces. The two layers (10, 11) may be cased in a composite tubular member (12) comprising a metal/rubber/metal sandwich. The bearing provides adequate support for the propeller shaft (3) in addition to preventing or minimising transmission of vibrations and other noise from the propeller shaft to the ship's hull. <IMAGE>

Description

SPECIFICATION Propeller shaft bearings The present invention relates to a propeller shaft bearing for use in boats provided with a propelling unit connected to a propeller via the propeller shaft.

British Patent Specification No. 1,386,708 discloses an arrangement of mounting and enclosing an engine in a boats hull in which the entire propelling unit, including drive shaft and propeller shaft, is resiliently mounted.

The arrangement disclosed in the above mentioned Specification has the disadvaritage that, although the entire propelling unit and corresponding drive shaft is resiliently mounted, vibrations generated in the system as a whole must be damped in order that the vibrations are not transmitted to the ships hull which would result in undesired vibrations of the hull and excessive noise.

The method of arrangement of the installation also requires a substantial amount of space and since space is usually severely limited in a ship's hull the arrangement is not ideal.

It is an object of the present invention to provide a bearing for a ship's propeller shafts that reduces the amount of vibrations transmitted to a ship's hull from the propeller shaft.

According to the present invention we provide a bearing adapted to support a ship's propeller shaft relative to the ship's hull, said bearing comprising a tubular assembly including two coaxial layers of resilient material, said coaxial layers comprising an inner layer, further layer, the further layer being positioned radially outwardly of, and being softer than, the inner layer.

Preferably the bearing also comprises a tubular member or structure coaxial wih the inner layer and further layer and being located radially outwardly of both.

Preferably said inner layer and further layer are made from rubber, the inner layer being a hard rubber and the further layer a softer rubber.

The tubular member located outwardly of both inner and further layers may be of a composite construction and comprises a sandwich having inner and outer coaxial members of a relatively high specific weight and an intermediate member of a relatively low specific weight.

When the outer tubular structure is a composite construction the inner and outer member may be metal and the intermediate member may be rubber.

Such a bearing provides a satisfactory mount for the propeller shaft and it may comprise a water lubricated bearing.

The inner layer of relatively hard resilient material which is necessary for the support of the propeller shaft is now no longer directly in contact with the ship's hull but is mounted through the intermediary of at least a relatively soft resilient material thereby minimising the transmission of vibrations and noises associated with the propeller shaft to the ship's hull.

When the outer tubular structure is of composite construction comprising two metal tubes with an intermediate layer of rubber, the rubber may be relatively soft.

Such an arrangement gives an additional advantage since the two coaxial metal tubes have a relatively high specific weight the transmission of vibrations and noises from the inner tube to the outer tube is prevented or minimised because of the intermediate layer being material of low specific weight such as soft rubber.

The radial thickness of the further layer of soft resilient material may be greater than the thickness of the inner layer of hard resilient material and preferably the further layer of soft resilient material has at least twice the cross-sectional area of that of the inner layer of hard resilient material.

By appropriate dimensioning of the different parts of the bearing of the present invention the inner layer of relatively hard resilient material assumes the function of the bearing and the further layer of material, which is relatively soft compared with the inner layer, minimises or prevents the transmission of vibrations as well as absorbing other loads on the shaft.

The further layer of resilient material may be provided with blind bores distributing around the circumference, which blind bores may extend approximately over two thirds of its axial length.

The provision of such bores in the layer of relatively soft resilient material make this layer even more resilient and, in addition, the continual deformation of the shape of the bores during rotation of the propeller shaft provides a pumping effect which assists in circulating water around the bearing and propeller shaft to assist in lubrication thereof.

The blind bores may extend from either of the axial ends of the further layer of relatively soft resilient material or may extend from both ends.

The blind bores may extend alternately, taken in a circumferential direction, from opposite ends of the further layer.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings wherein: Figure 1 is a schematic illustration of a ship's hull with a propulsion unit and associated propeller shaft; Figure 2 is a sectional view of one embodiment of the bearing taken along the axis of the propeller shaft; Figures 3a, 3b and 3c are sectional views of different embodiments of bearing of the present invention taken at right angles to the longitudinal axis of the propeller shaft.

Referring first to Fig. 1 a ship's hull 1 is illustrated, the ship having an engine 2 which drives a propeller 4 via a propeller shaft 3.

The engine 2 is resiliently mounted to the ship's hull 1 by engine mountings 5. The engine can move relative to the ship's hull 1 and in order to allow for such relative movement a universal joint 6 is provided on the propeller shaft 3.

The propeller shaft 3 is provided with a water lubricated bearing 7 by means of which it is mounted to the ship's hull 1. The bearing 7 is made mainly from a resilient material, for example rubber, and prevents the transmission of noise and vibration to the ship's hull 1. Slight movements of the propeller shaft 3 relative to the ship's hull 1 is also compensated for by the resilient material of the bearing 7.

Referring now in addition to Fig. 2, a crosssection of the bearing 7 is illustrated in detail.

The propeller shaft 3 is illustrated having a propeller 4 at one end, the propeller shaft 3 being provided with a shaft seal 9 cooperating with sealing member 1 9 which serves to prevent water entering the boat along the surface of the propeller shaft. The seal 9 cooperates with a sleeve 8, the other end of which cooperates with a water lubricated bearing 7.

The water lubricated bearing 7 comprises an inner layer 10 of resilient material which in this case is a hard rubber and a further layer 11 of resilient material which is a soft rubber.

The two layers 10 and 11 may be joined to an intermediate metal tube 21, for example by vulcanisation.

The two layers 10 and 11 are arranged coaxially and in a tubular member 1 2 of composite construction having an outer member 1 3 and an inner member 14 made from a material of relatively high specific weight, in this case metal, an intermediate layer of soft rubber 1 5 being provided between the outer and inner members 1 3 and 14. The layer of soft rubber 1 5 may be vulcanised between the outer and inner members 1 3 and 14.

In use of the engine, vibrations and other noise associated with the propeller shaft 3 are transmitted through the layer of hard rubber 10 to the layer of soft rubber 11. The soft rubber 11 absorbs such vibrations and noise so that they are not transmitted to the ship's hull 1. The bearing 7 is affixed to the ship's hull via the outer casing member 1 3 of the tubular member 12.

Referring now to Figs. 3a, 3b and 3c, cross-sections of various embodiments of bearing of the present invention are shown which illustrate the arrangements of various layers of the bearing and also the configuration of blind bores which may be provided in the layer of relatively soft resilient material, which blind bores serve to make the layer of soft material more resilient and furthermore, on continued deformation of the shape of the bores due to vibration associated with the propeller shaft, perform the pumping action in order to enhance the water lubrication of the bearing surfaces between the propeller shaft 3 and the layer of relatively hard resilient material 10.

In the embodiments shown in Figs. 3a, 3b and 3c the layer of relatively soft resilient material 11 is received in a tubular member 1 2 of composite construction having an outer member 1 3 and an inner member 14 of a material of relatively high specific weight, for example metal, and a layer 1 5 of a material of low specific weight, for example rubber.

The layer of hard resilient material 10 is provided with grooves 1 6 to enable water to flow along the length of the bearing to provide adequate lubrication between the relative bearing surfaces of the propeller shaft 3 and hard resilient material 10.

During operation of the propeller shaft 3 water flows into a reservoir 18 provided between the bearing 7 and the shaft seal 9, the shaft seal 9 preventing water flowing further up the propeller shaft 3 and into the ship's hull.

The blind bores 1 7 render the layer of relatively soft rubber material 11 more resilient and assist in pumping water to and from the bearing during rotation of the shaft.

Claims

1. A bearing adapted to support a ship's propeller shaft relative to the ship's hull, said bearing comprising a tubular assembly including two coaxial layers of resilient material, said coaxial layers comprising an inner layer and a further layer, the further layer being positioned radially outwardly of, and being softer than the inner layer.

2. A bearing as claimed in Claim 1 wherein said bearing also comprises a tubular member or structure coaxial with the inner layer and further layer and being located radially outwardly of both.

3. A bearing as claimed in Claim 1 or Claim 2 wherein said inner layer and said further layer are made from rubber, the inner layer being a hard rubber and the further layer a softer rubber.

4. A bearing as claimed in Claim 3 wherein said inner layer and said further layer are joined to an inner surface and an outer surface respectively of a metal tube.

5. A bearing as claimed in Claim 2 wherein said tubular member is of composite construction comprising a sandwich having inner and outer coaxial members of a relatively high specific weight and an intermediate member of a relatively low specific weight.

6. A bearing as claimed in Claim 5 wherein said inner and outer members are made from metal and said intermediate member is made from rubber.

7. A bearing as claimed in any one of the preceding claims wherein the radial thickness of the further layer is greater than the radial thickness of the inner layer.

8. A bearing as claimed in any one of the preceding claims wherein the cross-sectional area of the further layer is greater than the cross-sectional area of the inner layer.

9. A bearing as claimed in Claim 7 wherein the cross-sectional area of the further layer is at least twice the cross-sectional area of that of the inner layer.

1 0. A bearing as claimed in any one of the preceding claims wherein the further layer is provided with a plurality of blind bores distributed around the circumference extending along the axial length of the further layer.

11. A bearing as claimed in Claim 10 wherein said blind bores extend approximately over two thirds the axial length of said further layer.

12. A bearing as claimed in Claim 10 or Claim 11 wherein the said blind bores extend alternatively, taken in a circumferential direction, from opposite ends of said further layer.

1 3. A bearing as claimed in any one of the preceding claims connected by a sleeve to a shaft seal, said sleeve in combination with said bearing and said shaft seal defining a reservoir into which water may flow, during use, to lubricate said bearing.

1 4. A bearing substantially as hereinbefore described with reference to and and as illustrated in Fig. 2 of the accompanying drawings.

1 5. A bearing substantially as hereinbefore described with reference to and as illustrated in Fig. 3a of the accompanying drawings.

1 6. A bearing substantially as hereinbefore described with reference to and as illustrated in Fig. 3b of the accompanying drawings.

1 7. A bearing substantially as hereinbefore described with reference to and as illustrated in Fig. 3c of the accompanying drawings.

1 8. A bearing including any novel feature or combination of features described herein and/or illustrated in the accompanying drawings.