GB2201198A

GB2201198A - Marine propeller

Info

Publication number: GB2201198A
Application number: GB08621632A
Authority: GB
Inventors: Paul Stephen Tolley
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-03
Filing date: 1986-10-03
Publication date: 1988-08-24
Also published as: GB8621632D0

Abstract

A propeller 10 for an outboard motor has a hub 12 and a number of removable blades 14. The blades 14 are made from a plastics material in order to attenuate any shock loading imparted to the propeller drive and transmission. The individual blades are replaceable in the event of the propeller sustaining damage due to impact. The blade may be retained in the hub by way of the blade root 16 co-operating with hub slot 18. Alternatively, each blade root is part-annular in form so that roots of adjacent blades interlock to form the propeller hub (Figure 4). <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO MARINE PROPELLORS This invention relates to propellers for marine vessels and is particularly though not exclusively concerned with propellers for outboard motors. It is usual for most outboard propellers to be case as a complete unit in a non-corrodable metal such as bronze, which is relatively expensive material. If in use, the propeller strikes a hard underwater object, e.g. a rock, then usually a complete propeller replacement is required as it is quite difficult-to repair the individual blades. Also the shock loading transmitted to the propeller drive and gearbox as a result of impact puts considerable strain upon the propeller drive and associated seals.

The present invention seeks to provide a propeller having replaceable blades and having a degree of resilience to attenuate the shock loading imparted to the propeller drive should the propeller sustain an impact.

Accordingly, the present invention provides a marine propeller haing a hub, a plurality of removable blades and blade retaining means to retain the blades against axial and radial movement.

The blade retaining means can comprise slots on the hub and corresponding roots on the blade which can be of any appropriate form, for example, similar to those used on gas and steam turbines.

In an alternative arrangement, the blades can be secured to the hub by means of pins extending through the root of each blade and appropriate flanges of the hub.

The blade retaining means can also include a removable plate at one end of the hub and a plate at the other end of the hub which is removable or intergral with the hub.

The blades and/or the hubs can be formed from a plastics material such as polycarbonate and can be cast in a variety of colours and can also be made luminous if required.

In an alternative arrangement, each blade can have a root, partannular in form, the roots of adjacent blades interlocking with one another, and the roots of the blades together forming the propeller hub.

The present invention will now be more particularly described with reference to the accompanying drawings in which Fig. 1 shows an end elevation of one form of propeller according to the present invention, Fig. 2 shows a side elevation of the propeller shown in Fig. 1, and Fig. 3 shows an exploded view of the propeller shown in Fig. 1, Fig. 4 shows a alternative blade form for use in another embodiement of the present invention, and Fig. 5 shows another embodiement of the present invention using blades of the type shown in Fig. 4.

Referring to the drawings, a propeller 10 includes a hub 12 and three removable blades 14. Each blade 14 has a root 16 which fits within a respective slot 18 in the hub. In this example the roots and slots are of the tir tree form of the type found in gas and steam turbines. The blade rooots are a taper fit in the axial sense within the slots and the blades are retained axially on the hub by means of a removable plate 20 at one end of the hub and a further plate 22 at the other end of the hub which may be intergral with humor removable therefrom.

The hub has a central bore 24 to enable the propeller to be mounted on a shaft 26 (Fig. 2). The propeller is retained on the shaft 26 by a nut 28 and the nut is covered by a cone 30 held in place by a split pin 32 which passes through a hole 34 in the shaft.

Referring to Figs.4 and 5, each blade 36 has a part-annular root 38, and each root has a projection 40 and slot 42 arranged to engage corresponding features of the adjacent root. Thus the blade roots interlock with one another to form an annular hub 44.

The hub can be returned on the shaft 26 in a manner similar to that shown in Fig. 2.

As the blades are made of a relatively resilient material at least compared with metal blades, should the blades strike an underwater object, then the shock loading to the propeller drive will be attenuated thereby reducing the risk of damage to the tranmission, gearbox and associated seals of the propeller drive. Should the impact be of such force than one or more of the blades is broken then it is a relatively easy matter to remove the propeller from the shaft 26 and to slide out the damaged blades an to replace them with new blades. By this means a propeller can be repaired quickly and relatively inexpensively as compared with integrally cast propellers made from metals.

Also the ability to change blades rapidly means that a set or sets of blades of varying pitches can be made available so that the propeller can be easily modified to suit the intended conditions of use.

The blades can be made luminous if required an can be cast in a variety of colours for visual appeal.

The blades can be attached to the hub by a variety of means other than that shown for example, the root and slot shapes can be of the mortice an tenon form or similar to any of the types of root fixing found in gas and steam turbines, e.g. fir trees.

Alternatively the hub can include a flange at each end, each flange-being apertured to receive a pin and each blade can have root having an axially extending opening to receive a pin so that the blades can be retained on the hub by the pins passing through the flanges on the hub and through the root of each blade.

Claims

1. A marine propeller having a hub, plurality of removable blades and blade retaining means to retain the blades against axial an radical movement.

2. A propeller according to claim 1 in which the blade retaining means include a root on each blade and a corresponding shaped slot on the hub.

3. A propeller as claimed in claim 1 in which the blade retaining means for each blade includes a pin arranged to pass through part of the hub and through a root of the blade.

4. A propeller as claimed in claim 1 in which each blade had a part-annular root, and each root has at each end thereof, and interlocking feature arranged to co-operate with a corresponding feature of the adjacent root, the roots of the blades thereby forming an annular hub.

5. A propeller as claimed in claim 4 in which the interlocking features compirse a projection and a slot.

6. A propeller as claimed in claim 5 in which the projections and slots on the blade roots are fir tree in section.

7. A propeller as claimed in any one of the preceeding claims in which the blade retaining means included a removable plate located at one end of the hub, the plate being arranged to overlap at least a portion of each blade.

8. A propeller as claimed in any one of the preceeding claims in which at least the blades are formed from a plastics material such as polycarbonate.

9. A propeller as claimed in any one of the preceeding claims in which at least the blades include or are coated with a luminous material.

10. A propeller constructed and arranged for use in operations substantially as herein descrided and with reference to the accompanying drawings.

11. An outboard motor maring propeller kit including a hub and at least two sets of blades, the blades and the hub including blade retaining means to retain the blades on the hub against axial and radial movement, the pitch of the blades of each set being different to one another.