GB2526302A

GB2526302A - Propeller with detachable blades

Info

Publication number: GB2526302A
Application number: GB1408918.9A
Authority: GB
Inventors: David Alexander Duncan
Original assignee: TEIGNBRIDGE PROPELLERS INTERNAT Ltd
Current assignee: TEIGNBRIDGE PROPELLERS INTERNAT Ltd
Priority date: 2014-05-20
Filing date: 2014-05-20
Publication date: 2015-11-25
Anticipated expiration: 2034-05-20
Also published as: GB2526302B; GB201408918D0

Abstract

A propeller assembly includes a hub 1 secured to a shaft 2 and a plurality of radially-extending propeller blades 3 each having a mounting flange 4 seated on the hub. The blades are held to the hub by first and second axially-spaced clamping rings 9 and 10 that may have axially-extending collars 11 and 12 which co-operate with inclined shoulders on the mounting flanges to position and hold the flanges to the hub. The longitudinal edges of the mounting flanges (18 and 19, Fig 3) may abut each other. The first clamping ring 9 may be located relative to the hub by an annular abutment 8 and the second ring 10 may be urged axially by a propeller nut 24, which may include a plurality of individually-adjustable thrust elements 25.

Description

PROPELLER WITH DETACHABLE BLADES

TECHNICAL FIELD OF THE INVENTION

This invention relates to propellers with detachable blades, particularly (but not exclusively) marine propellers.

BACKGROUND

Monobloc propellers (formed in a single piece) have known characteristics so that they have an assured optimum performance and efficiency. Nevertheless, manufacture of large monobloc propellers requires expensive machinery, and the delivery of such large propellers also presents transportation problems.

Propellers having blades bolted onto a hub are known, see DE 483 317 C for example, but it is difficult to ensure that the blades are correctly positioned when they are simply bolted on. Very minor variations in position at the root of the blade can produce very significant changes to the propeller characteristics.

GB 1 455 504 describes another marine propeller with detachable blades in which the blades are secured by stud bolts inserted from inside a hollow hub. Dowels are used to locate the blades in a precise pitch position before the stud bolts are tightened. A variation on this design allows adjustment of the blade position from inside the hub. However, making adjustments and tightening bolts inside a hollow hub presents practical difficulties and also requires considerable skill and knowledge to achieve precise propeller characteristics.

The present invention seeks to provide a new and inventive form of propeller with detachable blades which is easy to assemble whilst being capable of achieving precise and accurately reproduced blade characteristics.

SUMMARY OF THE INVENTION

The present invention proposes a propeller assembly comprising a hub secured to a shaft and a plurality of radially-extending propeller blades each having a mounting flange seated on an external surface of the hub, in which the blades are held to the hub by first and second axially-spaced clamping rings.

The invention also provides a propeller assembly which includes a hub and first and second axially-spaced clamping rings and at least one of the clamping rings is movable relative to the hub.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and includes clamping rings which engage opposite ends of the mounting flanges.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and a clamping ring having an axially-extending portion which engages a co-operating outer bearing surface of the mounting flanges.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and clamping rings having an axially-extending portion which engages a co-operating outer bearing surface of the mounting flanges, and the axially-extending portions of the clamping rings and/or the co-operating outer bearing surfaces of the mounting flanges are inclined towards the hub in opposite directions.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and axially-extending edge faces of the mounting flanges abut each other.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and axially-extending edge faces of the mounting flanges extend substantially radially of the propeller shaft.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and a clamping ring is axially located against an abutment surface on the hub.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and a second clamping ring is urged towards a first clamping ring by a propeller nut.

The invention also provides a propeller assembly which has blades secured to a hub by mounting flanges and clamping rings and a propeller nut screw-threaded onto a portion of the hub or a propeller shaft.

The invention also provides a propeller assembly with a propeller nut which has a plurality of circumferentially-spaced thrust elements which can be individually adjusted.

The invention also provides a propeller assembly with a propeller nut which has a plurality of circumferentially-spaced thrust elements screwed into co-operatively screw-threaded holes in the propeller nut.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Figure 1 is an axial section through a marine propeller assembly in accordance with the invention; Figure 2 is an end view of the propeller hub together with one of the blades; Figure 3 is a general view of the propeller hub together with one of the propeller blades; and Figure 4 is a general side elevation of the assembled propeller, shown transparent for clarity.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring firstly to Fig. 1, the marine propeller assembly includes a hub 1 secured to a shaft 2 and a plurality of radially-extending propeller blades 3 each having a mounting flange 4 seated on an external surface of the hub.

The hub 1 may be secured to the shaft 2 in various ways. It would be possible for the hub to be integrally formed with the shaft, or the hub and shaft may be splined or similarly keyed to each other.

In the present example the hub 1 has a tapered bore, the shaft 2 has a corresponding external taper, and the hub is hydraulically fitted to the shaft. As can be seen in Fig. 2, the external surface of the hub 1 has five flat facets S matching the number of blades, but the number of blades which a propeller has may vary.

Referring back to Fig. 1, the free end of the shaft 2 is stepped inwardly to form a short cylindrical section 6 which projects from the hub 1 ending in a screw-threaded end section 7. The hub has an external annular abutment 8 for axially locating a first clamping ring 9 received on the hub. At the opposite end of the hub the projecting cylindrical section 6 receives a second clamping ring 10.

The clamping rings 9 and 10 are provided with opposing axially-extending retaining collars 11 and 12 having inclined undersurfaces 13 and 14 respectively.

Referring to Fig. 3, the mounting flange 4 at the root of each propeller blade 3 is of generally rectangular shape, corresponding to the external profile of one external facet 5 of the hub 1. The bottom face 16 of the flange 4 is flat, the opposing top face 17 is part-cylindrical, and the two longitudinal edges 18 and 19 extend substantially radially of the propeller shaft (see Fig. 2 also). The opposite ends of the mounting flange 4 are provided with part-circular external recesses 20 and 21 which, as seen in Fig. 1, form sloping shoulders for co-operation with the inclined undersurfaces 13 and 14 of the clamping rings 9 and 10. The sloping surfaces of the two shoulders are inclined towards the hub in opposite directions.

To assist in the assembly of the propeller the mounting flanges 4 may be provided with one or more holes 22 (Fig. 1) through which retaining screws 23 may be inserted to hold the blades in position on the hub 1. (See Fig.s 2 and 3 also.) It should however be noted that the retaining screws do not accurately position the blades and they do not increase the strength of the propeller.

Assembly of the propeller commences with the hub 1 hydraulically fitted onto the propeller shaft 2 and the first clamping ring 9 located on the hub against the abutment 8. A first propeller blade 3 is placed against the hub 2 so that the flat bottom face 16 of the flange 4 lies against one of the facets 5. The blade is centralised and slid along the facet until the sloping shoulder formed by recess 20 engages beneath the sloping underside of collar 11 on the clamping ring 9. At this point the retaining screws 23 may be inserted to hold the blade onto the hub. The remaining blades are mounted on the hub in a similar manner, following which the second clamping ring 10 is placed onto the shaft so that the retaining collar 12 engages over the sloping shoulders formed by the recesses 21 at the adjacent end of the blade mounting flanges.

Referring again to Fig. 1, a propeller nut 24 is then screwed onto the threaded end 7 of shaft 2 and tightened against the second clamping ring 10 urging the clamping ring towards the first ring 9.

The inclined surfaces of the collars 11 and 12 and the recesses 20 and 21 of the mounting flange co-operate to firmly hold the mounting flanges 4 against the hub 1 and axially locate the mounting flanges between the clamping rings. Mutual contact between the adjacent radial edges 18 and 19 of the mounting flanges also helps to ensure that a precise blade pitch is achieved.

Thus, the hub, blades and clamping rings are locked securely together using the propeller nut, with the blades firmly held in precisely defined positions.

The propeller nut 24 will generally be tightened to a recommended torque using a suitable torque wrench. The propeller nut may, however, be provided with a plurality of circumferentially-spaced thrust screws 25, or similar thrust elements, which are inserted through threaded holes in the nut. By tightening the thrust screws against the second clamping ring 10 the screws individually apply a proportion of the total clamping torque to the clamping ring, enabling maximum clamping torque to be applied with a relatively small torque wrench.

The assembly of the propeller may be completed as shown in Fig. 4 by attaching a nose cone 26 using a bolt 27 inserted into a threaded hole in the end of the propeller shaft 2.

The performance and characteristics of the assembled propeller at least equals that of a monobloc propeller with all the advantages of a built-up propeller. The propeller also has additional advantages over known detachable blade propellers since the hub can be smaller resulting in less frictional drag and increased performance and efficiency. The longer blade base also allows a longer cord length at the blade root, which again reduces frictional drag and reduces the likelihood of root section cavitation.

It should be noted that both of the clamping rings could be movable relative to the hub and that the collar and the mounting flanges do not necessarily both need to have inclined faces.

Furthermore, since the hub and shaft may form a single unit the propeller nut could be screw-threaded onto a portion of the hub or the shaft.

Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art.

* * * * * * * *

Claims

-10 -CLAIMS1. A propeller assembly comprising a hub secured to a shaft and a plurality of radially-extending propeller blades each having a mounting flange seated on an external surface of the hub, in which the blades are held to the hub by first and second axially-spaced clamping rings.
2. A propeller assembly according to Claim 1 in which at least one of the clamping rings is movable relative to the hub.
3. A propeller assembly according to Claim 1 or 2 in which the clamping rings engage opposite ends of the mounting flanges.
4. A propeller assembly according to any preceding claim in which at least one of the clamping rings has an axially-extending portion which engages a co-operating outer bearing surface of the mounting flanges.
5. A propeller assembly according to any preceding claim in which both of the clamping rings have an axially-extending portion which engages a co-operating outer bearing surface of the mounting flanges
6. A propeller assembly according to Claim 5 in which the axially-extending portions of the clamping rings and/or the co-operating outer bearing surfaces of the mounting flanges are -11 -inclined towards the hub in opposite directions.
7. A propeller assembly according to any preceding claim in which axially-extending edge faces of the mounting flanges abut each other.
8. A propeller assembly according to Claim 7 in which the axially-extending edge faces of the mounting flanges extend substantially radially of the propeller shaft.
9. A propeller assembly according to any preceding claim in which the first clamping ring is axially located against an abutment surface on the hub.
10. A propeller assembly according to any preceding claim in which the second clamping ring is urged towards the first clamping ring by a propeller nut.
11. A propeller assembly according to Claim 10 in which the propeller nut is screw-threaded onto a portion of the hub or the shaft.
12. A propeller assembly according to Claim 10 or 11 in which the propeller nut has a plurality of circumferentially-spaced thrust elements which can be individually adjusted to apply axial pressure to the second clamping ring.
13. A propeller assembly according to Claim 12 in which the -12 -thrust elements are screwed into co-operatively screw-threaded holes in the propeller nut.
14. A propeller assembly substantially as described with reference to the drawings.* * * * * * * *