GB1563180A

GB1563180A - Boat propellor hub

Info

Publication number: GB1563180A
Application number: GB24766/78A
Authority: GB
Original assignee: Volvo Penta AB
Current assignee: Volvo Penta AB
Priority date: 1977-06-09
Filing date: 1978-05-31
Publication date: 1980-03-19
Also published as: AU523067B2; JPS5440494A; AU3689878A; CA1079582A; FR2393722A1; BR7803668A; SE7706728L; IT1105114B; FR2393722B1; SE410422B; DE2825256A1; JPS6220079B2; DE2825256C2; IT7849758A0

Description

(54) BOAT PROPELLER HUB (71) We, AB VOLVO PENTA, a Swedish Body Corporate, of Gropegardsgatan, S-417 15 Göteborg, Sweden, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a boat propeller hub, comprising an inner sleeve intended to be rigidly joined to a propeller shaft, an outer sleeve concentric with the inner sleeve and intended to carry propeller blades, and a bushing of elastic material disposed between the inner and outer sleeves.

Propeller hubs of this type are used primarily in recreational boats with powerful motors, to dampen shocks to the drive unit, for example when the boat bounces in the water while moving at high speed or when shifting rapidly between forward and reverse.

What is desired is low stiffness and high strength in order to achieve effective dampening in combination with long life.

For a long time now known propeller hubs of this type have been of right circular cylindrical shape with planar ends, i.e. the inner and outer sleeves as the bushings are made with right circular cylindrical shape with constant wall thickness. As the power of motors has increased and the hub has been subjected to heavier loads, hubs constructed in this way have proven to have an unacceptably short life, because the flexible rubber bushing is soon torn apart. Tests have shown that the rupture begins at the ends, close to the inner sleeve, and continues axially inwards towards the middle of the bushing.

The purpose of the present invention is to achieve a propeller hub which, for a given hub space in a propeller, will take greater stresses than said hubs used up to now.

This is achieved according to the invention by the bushing having a greater wall thickness at its end portions than in its middle portion.

With this new end construction it has been shown that the sheer stress can be reduced locally more than 20%, which means that the strength and life of the hub can be appreciably improved without having to change the outer dimensions of the hub. This, in turn, means that existing propellers and installations need not be modified in order to be able to be used together with the hub according to the invention.

The invention will now be described in more detail with reference to the accompanying drawing showing an example. The figure shows a longitudinal section through a propeller hub according to the invention shown in its actual size.

The hub shown consists generally of an inner sleeve 1 of metal, a bushing 2 of elastic material, preferably rubber, and an outer sleeve 3 of metal. The inner sleeve 1 is intended to be non-rotatably joined by means of splines 4 to a propeller shaft, while the outer sleeve 3 is intended to be inserted in a hub opening in a propeller and be cemented, for example, to the side of the opening.

The inner sleeve 1 has a main portion 5 with a constant external diameter and, on both sides thereof, portions 6 with successively decreasing external diameters. Furthermore, the inner sleeve 1 has at one end a flange 7 which extends radially to the outer sleeve 3 for radial control of the same.

In a corresponding manner the bushing 2 has a major portion 8 with constant inner diameter and, on both sides thereof, end portions 9 with successively decreasing inner diameters, so that the portions 9 of the bushing have a greater wall thickness than the other portion 8. The bushing 2 is vulcanized to the surfaces of the inner 1 and outer 3 sleeves except at the surface of the radial flange between the arrows a and b. At the right-hand end of the bushing in the figure, a protective casing 10 of stainless steel is cemented on.

The embodiment shown and described achieves a reduction of the stress at the sensitive end surfaces of the hub as compared with known hubs with right circular cylin drical rubber bushings and straight end surfaces. The greatest shear stress occurring in the inner sleeve is, where the bushing is thickest, more than 20% lower than where the bushing is thinnest in the embodiment shown.

The invention has been described in the preceding with reference to an example in which the inner diameter of the bushing has been varied to achieve a greater wall thickness at the ends of the bushing. This is preferable since a constant external diameter permits the use of existing propellers without modification.

However, it is also possible within the scope of the invention, if it should be desirable, to keep the inner diameter constant instead and vary the outer diameter or, alternatively, to vary both the outer and inner diameters to obtain a greater wall thickness towards the ends WHAT WE CLAIM IS: 1. Boat propeller hub, comprising an inner sleeve for rigid attachment to a propeller shaft, an outer sleeve disposed concentrically with the inner sleeve and arranged to carry propeller blades, and a bushing of elastic material disposed between the inner and the outer sleeves, characterized in that the bushing has a greater wall thickness at its end portions than at its middle portion.

2. Hub according to claim 1, characterized in that the bushing has a portion with constant wall thickness which passes towards the ends into portions with successively increasing wall thickness.

3. Hub according to claim 2, characterized in that the bushing has a constant outer diameter and an inner diameter which successively decreases towards the ends.

4. Hub according to any one of claims 1-3, characterized in that bushing consists of rubber which is vulcanized to the inner and outer sleeves.

5. Hub according to claim 4, characterized in that the inner sleeve is made at one end with an outwardly-directed flange abutting one end of the bushing without the bushing being vulcanized to the flange.

6. Boat propeller hub substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. drical rubber bushings and straight end surfaces. The greatest shear stress occurring in the inner sleeve is, where the bushing is thickest, more than 20% lower than where the bushing is thinnest in the embodiment shown. The invention has been described in the preceding with reference to an example in which the inner diameter of the bushing has been varied to achieve a greater wall thickness at the ends of the bushing. This is preferable since a constant external diameter permits the use of existing propellers without modification. However, it is also possible within the scope of the invention, if it should be desirable, to keep the inner diameter constant instead and vary the outer diameter or, alternatively, to vary both the outer and inner diameters to obtain a greater wall thickness towards the ends WHAT WE CLAIM IS:

1. Boat propeller hub, comprising an inner sleeve for rigid attachment to a propeller shaft, an outer sleeve disposed concentrically with the inner sleeve and arranged to carry propeller blades, and a bushing of elastic material disposed between the inner and the outer sleeves, characterized in that the bushing has a greater wall thickness at its end portions than at its middle portion.