AU5362000A - Propellor guard - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): EDWARD CHRISTOPHER ROBERTS Invention Title: PROPELLOR GUARD 0.

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The following statement is a full description of this invention, including the best method of performing it known to me/us: PROTECTIVE APPARATUS TECHNICAL FIELD This invention relates to protective apparatus.

In particular the protective apparatus is a guard for use around an object that spins or rotates at high speeds, such as a propeller, fan and so forth. It is envisaged that the protective apparatus will have greatest application as a propeller guard on boats to not only protect the propeller itself from damage that can result from striking hard objects or surfaces, but also as protection against injury for people in 1O the water in the vicinity of an operating propeller.

ooo$ The protective apparatus when used as a propeller guard is also configured to improve the operation and manoeuvrability of a boat to which the propeller guard is attached.

'Whilst the protecting apparatus is discussed in this application with 15 regard to its operation as a propeller guard, this invention may have application outside this field.

BACKGROUND ART Protective apparatus for use in the vicinity of the propeller of a boat is known in the prior art. It is accepted such guards are designed to prevent injury to persons is in the vicinity of the propeller of the boat from the cutting action of a propeller.

This is particularly relevant for people engaging in a number of sports such as water skiing, boat racing and so forth. In addition, it has P39318 particular application on surf-life saving boats designed to assist/rescue a person experiencing difficulty in the water. Such boats are typically launched off the shore and pass through stretches of water frequented by swimmers.

Material from which propellers are made, and their speed of rotation make them extremely hazardous to people in the water, who can be severely injured by them.

Unfortunately, the very nature of a propeller guard can affect the performance of the boat. For example, reduced performance of a motor by at least 20-25% may be experienced when a propeller guard is fitted. This arises because the propeller guard interferes with water flow around the propeller.

o In addition, if a boat is required to turn sharply, when propellers are *protected by propeller guards boats increased cavitation of the boat may occur accompanied by a corresponding drop in power. A similar affect is experienced when a boat is used in white water, where the air in the white water causes the boat motor to lose power.

Although a propeller guard is a recognisable safety attachment, the disadvantages of reduced motor power and boat performance may 20 make boat owners more reluctant to use such devices. Therefore, while such devices are an essential part of a surf-life saving boat, they may be less desired by boat owners who enjoy recreational boating such as water-skiing or boating in white water, and so forth.

It would therefore be an advantage to have a propeller guard that: P39318 a) Was designed to offer maximum protection in the vicinity of the boat propeller; and b) Did not contribute to the effect of turbulence in the vicinity of the propeller that in turn tends to contribute to substantial loss of power (of up to or more than 20% of motor power); and c) Minimised cavitation effects when the boat is sharply turned; d) Improved speed and handling performance of the boat; e) Offered the safety advantages not only in surf-life saving boats, but on standard boats where it is preferable to protect people in the water (adjacent to the boat), from injury from the boat propeller, such as when the boat is used for water skiing, racing, and tourism trips through white water rapids, and so forth.

It is an object of the present invention to address at least the foregoing problems or at least to provide the public with a useful choice.

"15 Further aspects and advantages of the present invention will become apparent from the ensuing description that is given by way of example only.

DISCLOSURE OF INVENTION According to one aspect of the present invention there is provided protective apparatus for a rotational device capable of generating flow of a fluid around the device during operation of the device, the protective apparatus including a body capable of encircling the rotational device; the body being attachable to a structural support P39318 adjacent the rotational device and the body including a substantially tapered portion and a substantially straight portion for directing the fluid through the body and around the rotational device, the trailing and leading edge of the body being substantially bevelled to streamline fluid flow through the body, and the body optionally including multiple fins extending across one end of the body.

For the purpose of this specification, the term rotational device shall specifically mean a propeller for use with boat motors. However, in other embodiments of this invention, where the protective apparatus is appropriately configured for use with other rotational devices, the term may be extended to include fan propellers, rotational blades for machinery and other vehicles, and so forth, without the term being seen as limited only to boat propellers.

Accordingly to another aspect of the present invention there is 1s provided protective apparatus substantially as described above wherein the body is substantially annular.

For the purpose of this specification, the term fin shall include any finlike projection or structure configured for use with the protective apparatus. The term may be applied to and describe any suitable 20 structure that may be used to provide added protectional features to the protective apparatus, but in a manner that minimises disturbance of the fluid directed passed the fins, whilst providing benefits where appropriate to steering, balancing, aerodynamic stability and so forth as may be required with the protective apparatus in its various possible embodiments.

P39318 Accordingly to another aspect of the present invention there is provided protective apparatus substantially as described above wherein each of the fins are substantially oval in cross-section such that the profile of the fin at the leading edge of the fin substantially equates to the profile of the trailing edge of the fin.

Accordingly to another aspect of the present invention there is provided protective apparatus substantially as described above wherein each of the fins are substantially oval in cross-section but that the profile of the fin at trailing edge of the fin is substantially tapered 1o compared to the profile of the leading edge of the fin.

For the purposes of this specification the term include should be *'"interpreted in the broadest possible sense. However, in jurisdictions where the term comprise has a broader definition, the term include as used in this specification should therefore be read as interchangeable 15 with the term comprise.

°For ease of reference the protective apparatus shall now be referred to as a propeller guard. It is envisaged this invention will be predominantly used in the vicinity of a boat propeller to reduce incidences of injury to people in the water from an operational 20 propeller. However, it should be appreciated that the invention may be adapted for use in other situations.

For example, the protective apparatus may be used in conjunction with any rotating or spinning device generating a flow of a fluid past or through the device to achieve a particular function, and particularly where the protective apparatus is attached to or encircles the device to P39318 minimise the likelihood of injury to individuals from contacting the particular device during its operation.

The fluid may be any liquid or gas (including air) and the device may include a propeller, a fan (for example as associated with air conditioning units) and so forth. Whilst it is desirable there be minimum impedance to the flow of the fluid over or past the device, the speed of operation of the device is such that it poses a hazard and can cause serious injury to an individual contacting the spinning or rotating portions of the device.

In addition, the protective apparatus also serves to minimise the likelihood of damage to the rotating device as a result of the rotating device contacting hard surfaces and so forth.

In preferred embodiments of the present invention, the body whilst *o preferably substantially annular is also substantially tapered along at least a portion of its length. Accordingly, the overall configuration may tend to a substantially conical shape with the body having a diameter suitable for encircling a boat propeller.

When the guard is used with small crafts, the body will preferably be about 115mm wide as necessary to surround the boat's propeller.

20 However, it can be appreciated that where the protective apparatus is used in other situations, the diameter of the body may vary accordingly, as well as the depth/width of the body.

In the preferred embodiment of the present invention, where the protective apparatus is a propeller guard, the tapered, substantially cone-shaped portion is configured to contribute to compressing the P39318 water and squeezing out any air in that water as the water passes through the guard. This is particularly useful when the boat is required to turn sharply. In normal situations, sharp turns can result in the boat cavitating badly. This cavitation arises as the air that is taken in passes the propeller. It is anticipated use of the present invention may result in a ten-fold improvement in the turning manoeuvrability of a boat.

Preferably, the cone-shaped portion of the body is substantially uniformly tapered. This configuration has been found to improve performance of a boat with which such a guard is used, by uniformly directing water across all contact surfaces of the blades of the propeller. However, it should be appreciated that whilst in one preferred embodiment of the invention the tapered portion of the body is substantially uniform and therefore contributes to the substantially annular configuration of the body, in other embodiments the body configuration may be substantially eccentric.

Towards the leading edge (at the wider diameter portion) of the cone portion of preferred embodiments the cone-shaped portion also includes a short, substantially straight section.

20 The body preferably includes a substantially short straight portion, whilst there is also a corresponding short substantially straight portion at one end of the cone-shaped portion. The short substantially straight section of the cone portion mirrors the configuration of the substantially straight portion of the body at the opposite distal end of the body. The straight leading portion of the body is configured to have a smaller diameter than the cone-shaped portion of the body.

P39318 Where the protective apparatus is a propeller guard the arrangement of the guard is such that the short substantially straight section of the cone portion is at the widest diameter portion of the cone and is also at the intake end of the propeller guard, but closest to the boat.

The substantially straight portion of the body is located at the opposite end of the body to the wide diameter intake of the cone portion. The straight section of the body is therefore substantially in line with the tapered section of the cone-shaped portion of the body.

The straight portion of the body is therefore located furthest from the boat and operates to direct the flow of water (that has been taken in and across the propeller) out from the propeller guard. The o.

substantially straight portion of the body is therefore located at the outlet end of the propeller guard.

Where the protective apparatus is a propeller guard, the straight portion of the body and the straight section of the cone-shaped portion have been found to improve the performance of the boat at lower speeds, as well as improving performance in white water and improving take off.

However, in other embodiments of the present invention the end of the outlet end of the annular body may instead of being only a substantially straight portion, may also include a flared section.

Preferably, once the guard is in position around the boat's propeller, the body is attached to either the boat's outboard motor itself or the actual boat, by appropriate attachment means.

P39318 A guarded ring is also an optional embodiment of this invention. In the guarded embodiment, the substantially annular body includes multiple streamlined fins running substantially horizontally around the intake end of the annular body. The fins are attached in that region to the body. A front rib may run the height of the propeller guard and serve to anchor the fins in their horizontal alignment as well as providing strengthening for the propeller guard and providing a means of attachment of the fins to the motor.

At least three fins are preferably included to contribute to maintenance of the cone structure, otherwise it may be necessary to make the annular ring/body and cone-shaped portion heavier, a heavier propeller guard may obviate against or impact on improved o boat performance.

i' Each fin has a preferred profile being substantially oval in cross- 5is section. In one preferred embodiment of the present invention, both the leading and trailing edge of the fin are configured substantially the **.same. In some embodiments it may be an advantage to have the sameedge profile for both the leading and trailing edge of the fin to ensure water (or fluid) is able to evenly pass over the fin. This is an advantage if the effects of either or both lift and drag are to be avoided, which can affect the performance of the boat. Depending on the profile of the fins lift and drag can be minimised.

The leading and trailing edges of the fins may be substantially rounded or tapered. Only one edge preferably may be substantially rounded. Whilst rounded edges on both the leading and trailing edges of the fins may be employed, having such a configuration on both sides P39318 of the fin tends to impact negatively on boat performance. Similarly, whilst tapering the front leading edge may improve the ability of the fin to cut into the water, it is the effect of the shape of the trailing edge that has greater impact. For example, it is important that turbulence of the water passing over the trailing edge is minimised. If there is significant turbulence, then the air content of the water is increased and the impact of this on poorer boat performance may be observed.

The profile of the fin(s) of this embodiment mirrors the profile on the leading and trailing edges of the body. Again, the profile of the leading and trailing edges of the body are designed to streamline the flow of water in and out of the (propeller) guard.

ooeo However, in other preferred embodiments, the leading and trailing edge of the fin may be otherwise configured. For example, the leading edge of the fin may be substantially rounded, whilst the trailing edge 15 of the fin may be substantially tapered.

Whilst the fins primarily function to protect the propeller from damage on rocks, and/or to minimise injury to persons unfortunate to be caught in the vicinity of a functioning propeller, the fins are configured to Soo# effect minimal disturbance to the water passing over them.

Having fins incorporated into the propeller guard does impact on the operational performance of the boat. However, having the leading and trailing edges of the fins and the edges of the body of the present invention configured as described above has been observed to reduce the amount of turbulence created as water (or fluid) passes over the leading and/or trailing edges of the fins/bevelled edges, compared with P39318 prior art systems where fins may simply be round bars with or without minimal tapering or rounding.

Minimising turbulence is advantageous, as turbulent fluid reduces the performance of the propeller and can contribute to a corresponding significant drop in motor power of between 20-25%. It is anticipated with the present invention that whilst there is still a drop in boat speed when compared to a boat operating without a propeller guard, the drop, whilst still occurring, is reduced to between rather than 20-25%.

10 A number of techniques may be used to achieve both the preferred 0. 0.

bevelled shaped edges of the body and the profiles of the fins, such as 0: 0:: die casting, press methods or grinding these portions to the required shape. However, the preferred method is an improved and/or adapted roll forming method, with which people skilled in the art will be 000015 familiar.

o 0 number of fins incorporated into the protective apparatus when 0o00 used as a propeller guard will be dependent on the particular boat and propeller with which guard will be used. Whilst specifically designed for use with surf-life saving boats, the propeller guard may also be used on standard boats. In boats such as a Thunder CatTM, the propeller guard may include four fins. However, the number of fins may vary depending upon the boat, the power required from the motor, the degree of control required when the boat is sharply turned, and the type of water in which the boat is typically used.

P39318 The arrangement of fins of a guard used on competition surf lifesaving boats may be spaced approximately 24mm apart and may include four or more fins. This spacing conforms to the spacing of fins as designated by self-regulatory bodies in some countries such as in Australia for example, where fin spacing is strictly adhered to.

However, to provide the preferred protection yet maintain reasonable boat performance such fins are preferably spaced at no less than approximately 15mm apart.

Typically surf lifesaving organisations have established their own rules regarding propeller guards, and as such guards for surf lifesaving boats typically include more fins than might a guard used by a private boat owner, where performance of the boat and available power may mean that fewer fins are preferred. For example, the average boat owner may require only a few fins (two or more) simply to protect the propeller from damage from striking rocks, to minimise the injury to swimmers and so forth.

Where the protective apparatus is used in conjunction with boats it is anticipated use of the guard will whilst effecting a drop in boat speed S-will nevertheless contribute to improved boat performance than may be the case with boats using alternative prior art guards. For example, improved boat performance in terms of the handling being more positive and the boat being easier to steer has been experienced in tests on fishing boats.

Further, it is anticipated the boat will be able to be raised out of the water, or get up to speed much more quickly than boats without the propeller guard of this invention. Further, it is anticipated differences P39318 in boat handling may be include improved turning ability because of improved flow of water over the propeller, reduction of turbulence with corresponding better handling in the overall performance of the boat.

The improved boat performance is attributable to the cone-shaped body that facilitates increased inflow of water across the propeller as the boat starts to move. The overall configuration of the propeller guard (by having a smaller diameter outlet of the body towards the back of the propeller as opposed to the greater diameter intake end) squeezes air out of the water (as a result of the tapering of the cone).

o The guard is further designed to improve water flow passed the propeller to effect a corresponding performance, handling and manoeuvrability of the boat to which the propeller guard is fitted.

In some preferred embodiments either or both the leading and trailing edges of the annular ring may be otherwise configured, such as to include crimping to improve overall performance of the boat by further minimising water turbulence and so forth.

Boats fitted with a crimped edged annular ring (crimped at the leading and/or trailing edges of the ring may demonstrate increased revs.

However, increasing the pitch on the propeller (resulting in a coarser propeller) can result in a slowing down of the revs resulting in an increase in the top end speed of the boat motor.

It should also be appreciated that varying performance, speed and control of the boat may be influenced by the extent to which the coneshaped portion of the guard is tapered.

P39318 Preferably the protective apparatus (including the fins) is made of stainless steel. Stainless steel is a suitable material as it is strong, durable and suitable for use in wet environments. However, some embodiments may also be made of aluminium as required. Yet, other materials may be used depending on the particular circumstances in which the protective apparatus is used. Accordingly, the guard may also be made of brass, thermoplastics materials, fibreglass, and so forth.

BRIEF DESCRIPTION OF DRAWINGS o* o 10 Further aspects of the present invention will become apparent from the following description that is given by way of example only and with reference to the accompanying drawings in which: S. Figure 1 is a diagrammatic end elevation or intake view of the S"protecting apparatus in accordance with one embodiment of the present invention; and ~Figure lb is a diagrammatic end elevation or outlet view of the protecting apparatus in accordance with another embodiment of the present invention; and Figure 2 is a diagrammatic side view of the protecting apparatus in accordance with the embodiment of Figure 1 of the present invention, and Figure 2b is a diagrammatic side view of the protecting apparatus in accordance with the embodiment of Figure lb of the present invention, and P39318 Figure 3 is a diagrammatic cross-sectional view of a fin profile, which also equates to the profile of the leading and trailing edge of the annular ring of the protecting apparatus in accordance with a preferred embodiment of the present invention; and Figure 3b is a diagrammatic cross-sectional view of a fin profile, in accordance with another preferred embodiment of the present invention; and Figure 4 is a diagrammatic view of the protective apparatus, as a propeller guard, attached round a propeller via attachment to the motor, in accordance with one preferred embodiment of the present invention; and Figure 5 is a diagrammatic side view of the protective apparatus, as a propeller guard, attached round a propeller via attachment to the motor, in accordance with one preferred embodiment of the present invention; and Figure 6 is a diagrammatic top plan view of the trailing edge of the annular ring of the protective apparatus showing a crimped configuration, in accordance with one preferred embodiment of the present invention; and Figure 7 is a diagrammatic side view of the annular ring of the protective apparatus showing a crimped configuration, in accordance with one preferred embodiment of the present invention.

P39318 BEST MODES FOR CARRYING OUT THE INVENTION With reference to the diagrams by way of example only, there is protective apparatus (indicated by arrow The protective apparatus in the embodiments shown in the diagrams is a propeller guard for use on boats (not shown) as illustrated in Figures 1 to 7.

In the form of a propeller guard the protective apparatus is designed to protect a propeller (17) of a boat motor (18) from being damaged when contacting hard objects or surfaces, as well as also protecting individuals in the vicinity of an operating boat propeller 10 from injury.

~The propeller guard as shown in Figures 1 to 2b includes a body The body is essentially in the form of an annular ring capable of surrounding a propeller (17) and being attached to an outboard motor (18) (as shown in Figures 4 and 5 respectively) or a boat directly (not shown).

The body includes a substantially tapered cone-shaped portion (4) .and a substantially straight portion The substantially straight portion of the body when the propeller guard is in situ is located in the vicinity of the outlet (12) end of the body as shown in Figures 2 and 2b.

Preferably the cone-shaped portion of the body is substantially evenly tapered. This configuration has been found to improve the performance of a boat to which the guard is attached. However, the tapered portion of the body may also be substantially eccentric.

P39318 Further, the intake end (11) of the cone-shaped portion includes a substantially straight section again as shown in Figures 2 and 2b.

When the protective apparatus is a propeller guard the straight portions and (10) of the body have been found to improve the performance of the boat motor in a number of areas. For example, improvement in performance is observable at lower speeds, as well as improvement in boat performance and boat handling when operating in white water, and improved take off speed. However, in some embodiments the straight section (10) of the tapered conical portion (4) lo may instead be flared.

The body is attachable at (13) and to a boat motor (18) as shown in Figure 4, or the boat itself, by appropriate attachment means.

In the embodiments shown in Figures 1 and 2 the wider diameter portion of the body corresponds to the cone-shaped portion and is oriented at the intake end of the guard .The smaller diameter of the body corresponding to the substantially *straight portion of the body is located in the vicinity of the outlet of the body The shape of the body having a greater diameter at the intake (11) end of the body compared with the narrower diameter at the outlet end (12) improves the inflow of water across the propeller.

This increased inflow of water across the propeller (17) as facilitated by the design, contributes to an increase in the velocity attainable by the motor when the boat starts to move.

P39318 Figures 1 to 5 illustrate the body of a guarded ring guard that includes multiple fins The fins are preferably aligned in a substantially horizontal plane in the vicinity of the intake portion (11) of the cone-shaped portion of the body As shown in Figures 3 and 3b, the fins are substantially oval in cross-section. The fin of the embodiment illustrated by Figure 3 is such that the profile of the fin at the leading edge equates to the profile of the trailing edge of the fin and is substantially tapered.

The same edge profile of both the leading and trailing edge of the fin ensures water (or fluid including gases depending on the oo use of the protective apparatus is able to evenly pass over the fin.

The fin of the embodiment illustrated by Figure 3b is such that the profile of the fin at the leading edge is substantially rounded when compared with the substantially tapered profile of the trailing 0O0* edge of the fin The same profiles may also be included on the leading edge (14) and trailing edge (15) of the body itself. Again the profile is designed to streamline the flow of water in and out of the body In some embodiments as illustrated in Figures 6 and 7 the leading edge (14) and/or the trailing edge (15) of the body may be otherwise configured to include crimping (19) to improve overall performance of the boat by further minimising water turbulence through the propeller guard and so forth.

A number of techniques may be used to achieve both the bevelled edges (14) and (15) of the body and the profiled edges and of P39318 the fins The preferred method is an improved and/or adapted roll forming method. However, die casting, pressing or grinding the bevelled edges (14) and (15) of the body and the fins or any other suitable method of manufacture may be employed.

Whilst both the body and the fins are preferably made of stainless steel, other materials may be used in other embodiments.

In the embodiments in Figures 1 and 5 up to approximately 12 fins (6) are incorporated into the propeller guard However, the number of fins will vary depending on the particular boat, propeller size, and 10 the use to which the boat is put. For example, the propeller guard (1) on a Thunder CatTM may include approximately four fins Whilst surf life-saving boats or competition boats may include a preferred number of fins, the average boat owner may require only a S: few fins (2 or more) simply to protect the propeller from damage in the event of striking hard objects.

Typically, the fins are optimally spaced approximately 22mm apart.

Although the distance between the fins may vary as required to effect the corresponding effectiveness of the fins in squeezing air out of the water passing around the propeller, and the effect of minimising turbulence. Changes in fin spacing may impact on the preferred operation of the propeller guard.

Either or both the number and spacing of fins incorporated into the propeller guard will ultimately affect the performance of the boat, in the power obtained from the motor, the degree of control required when a boat is turning sharply and so forth. The type of water in P39318 which the boat is used will also be a determining factor. For example, white water (foaming water) can impact severely on the operation of a propeller and the corresponding operation of the boat motor. However, with the inclusion of the fins and bevelled edges of the propeller guard, motor performance can be improved as the annular ring (particularly the cone portion) operates to squeeze air out of the water as it passes around the fins at the intake end (11) of the propeller guard This is particularly useful when the boat is required to turn sharply as the design and effect of the propeller guard also minimises the effects of boat cavitation.

~Both the leading and trailing edges and respectively of the fins and the leading and trailing edges (14) and (15) of the body (2) contribute to reducing the amount of turbulence created as water (or oany other fluid) passes over those edges of the fins and/or the bevelled oooo $ooo 5 edges of the body Where turbulence occurs, it can contribute to a significant drop in power of the motor between 20-25%. Inclusion of the bevelled edges on the fins and leading and trailing edges of the body is anticipated to contribute to a resultant drop in power of only 5-7%.

Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

P39318

Claims (39)

1. Protective apparatus for use with a rotational device, where operation of said device typically generates flow of a fluid around it, the protective apparatus including a body, the body being substantially annular and capable of encircling the rotational device, the body configured to include a substantially tapered portion and a substantially straight portion, and the body optionally including at least one fin in the region of fluid intake through the body, and 10 the protective apparatus characterised by the configuration of the body and optionally the fin(s) effecting change in either or both the physical characteristics of the fluid and streamlining of fluid flow through the body of the protective apparatus and around the rotational device to effect improved operation of the rotational device.

2. Protective apparatus as claimed in Claim 1 wherein the body is attachable to structural support(s) adjacent the rotational device.

3. Protective apparatus as claimed in Claim 1 wherein the protective apparatus is a propeller guard for encircling a boat propeller.

4. Protective apparatus as claimed in Claim 1 wherein the tapered portion of the body is substantially cone-shaped.

P39318 Protective apparatus as claimed in Claim 4 wherein the tapered, cone-shaped portion of the body is optionally evenly tapered or eccentric.

6. Protective apparatus as claimed in Claim 5 wherein the cone- shaped portion also includes a short, substantially straight section towards the wider diameter section of the cone shaped portion, corresponding to the leading edge of the body.

7. Protective apparatus as claimed in Claim 6 wherein the configuration of the cone-shaped portion of the body, when the 10 protective apparatus is used as a boat propeller guard, is located at the fluid intake end or leading edge of the body of the protective apparatus and operates to direct intake of water across the propeller.

Protective apparatus substantially as claimed in Claim 7 wherein the configuration of the cone-shaped portion of the body S.. contributes to compressing the water passing through the $o protective apparatus and squeezing out any air therein.

9. Protective apparatus as claimed in Claim 8 wherein the effect of the cone-shaped portion of the body on compressing the air content of the water passing therethrough further effects at least one of reduced cavitation, improved boat handling performance including turning manoeuverability.

Protective apparatus as claimed in Claim 1 wherein, when used as a propeller guard, the substantially straight portion of the body is located at the opposite distal end of the body closest to the P39318 boat and is the trailing edge or outlet end of the body of the protective apparatus.

11. Protective apparatus as claimed in Claim 10 wherein said straight portion of the body has a substantially smaller diameter than the cone-shaped portion of the body.

12. Protective apparatus as claimed in Claims 7 and 10 wherein the straight trailing edge portion of the body and the leading edge of the cone shaped portion of the body are substantially beveled. Oeee

13. Protective apparatus as claimed in Claims 11 and 12 wherein the substantially beveled trailing and leading edges of body, in 0. conjunction with the smaller diameter straight portion of the S.. body operate to streamline fluid flow through the protective S. apparatus. 0S o o$ see

14. Protective apparatus as claimed in Claim 13 wherein the 15 streamlined fluid flow across the beveled edges of straight portion of the body and the straight section of the cone-shaped portion contributes to at least one of an increase in the velocity of the Ce.. .i :motor, improved performance of the boat motor at lower speeds, improved motor performance in white water and improved take- off speed. Protective apparatus as claimed in Claim 10 wherein the trailing edge of the straight portion of the annular body is optionally substantially flared.

P39318

16. Protective apparatus as claimed in Claim 2 wherein the protective apparatus when used around a boat propeller is attached via the body of the protective apparatus to either the boat's outboard motor itself, or the actual boat, by attachment means.

17. Protective apparatus as claimed in Claim1 wherein the annular body includes one or more streamlined fins running substantially horizontally around the intake, substantially cone-shaped portion of the annular body and attached in that region to the body to 00 10 form a guarded version of the protective apparatus.

18. Protective apparatus as claimed in Claim 17 wherein each of the fins is substantially oval in cross-section, such that the profile of each fin at its leading edge substantially equates to the profile of the fin at its trailing edge.

19. Protective apparatus as claimed in Claim 17 wherein each fin is substantially tear-shaped in cross-section such that the leading edge is substantially rounded, whilst the trailing edge is substantially tapered.

Protective apparatus as claimed in Claim 18 wherein the same- edge profiles for both the leading and trailing edge of the fin ensures fluid passes evenly over the fin to minimise the effect of lift or drag, thereby improving the performance of the rotational device with which the protective apparatus is used.

21. Protective apparatus as claimed in Claim 12 wherein the leading and trailing edges of the body include a profile mirroring the P39318 profile of the fins, to improve streamline flow of fluid in and out of the protective apparatus.

22. Protective apparatus as claimed in Claim 21 wherein the profile of the leading and trailing edges of the fins and the leading and trailing edges of the body are beveled to reduce the amount of turbulence created as fluid passes over the leading and trailing edges of either or both the fins and body.

23. Protective apparatus as claimed in Claim 17 wherein the number of fins included in the protective apparatus is dependent on the 10 use to which the protective apparatus is directed.

24. Protective apparatus as claimed in Claim 23 wherein, when the protective apparatus is used as a propeller guard for a boat, the arrangement and number of fins will vary depending upon the 00•0 size and type of boat, the power required to be achieved from the 15 boat motor, the degree of control required when the boat is •...*sharply turned and the type of water in which the boat is typically used.

25. Protective apparatus as claimed in Claim 24 wherein, when the protective apparatus is used as a propeller guard on a surf life- saving boat, the protective apparatus will include at least four fins.

26. Protective apparatus as claimed in Claim 24 wherein the fins of protective apparatus used on a competitive surf lifesaving boat may include four or more fins spaced up to and including 24mm apart or as required to comply with regulated spacing. P39318

27. Protective apparatus as claimed in Claim 24 wherein two or more fins may be used with recreational boats to simply protect the propeller from damage from striking rocks, or to avoid injuring swimmers.

28. Protective apparatus as claimed in Claim 21 wherein the beveled profiled edges of the body and of the fins are obtained by a preferred roll-forming method.

29. Protective apparatus as claimed in Claim 1 wherein improved boat speed and performance is facilitated by improved water 10 quality and increased inflow of water directed through the body of the protective apparatus and across the propeller by virtue of the configuration of the body of the protective apparatus.

30. A method of manufacturing protective apparatus for use with a rotational device capable of generating flow of a fluid around the device during operation of the rotational device, the protective apparatus including a body, the body being substantially annular and capable of encircling the rotational device; and the body being configured to include a substantially tapered portion and a substantially straight portion for directing the fluid through the protective apparatus and around the rotational device, the body also including a trailing and leading edge, and the body optionally including at least one fin in the region of fluid intake through the body, said method including the steps of: P39318 a) manufacturing a body portion comprising an annular ring of the required diameter to encircle the preferred rotational device; and b) attaching thereto or integral therewith a substantially cone- shaped portion and a substantially straight portion; and c) optionally including at least one fin aligned in a substantially horizontal plane in the vicinity of the cone- shaped portion of the body; and d) said fin(s) being substantially oval in cross-sectional profile; 10 and e) the profile of the optional fin(s) having a leading edge and a trailing edge equating substantially to the profile of either or S.both the leading and trailing edge of the body; and S. f) said protective apparatus being attached to a support in the 15 vicinity of the rotational device so as to provide protection around the rotational apparatus when the rotational device is in use, the method characterised by the body and optionally the fin(s) being configured to improve operation of the rotational device with which the protective apparatus is used, by either or both effecting change in the physical characteristics of the fluid and streamlining fluid flow through the body and around the rotational device.

P39318

32. A method of manufacturing protective apparatus substantially as claimed in Claim 31 wherein the fins are manufactured by any one of an improved and/or adapted roll-forming method, die casting, pressing, grinding.

33. A method of manufacturing protective apparatus as claimed in Claim 31 wherein the fins attached to the protective apparatus vary in number and spacing dependent upon the propeller for which it provides a guard.

34. A method of manufacturing fins for use with a protective 10o apparatus for use with a rotational device, where operation of said device typically generates flow of a fluid around it, the protective apparatus including a body, the body of the protective apparatus being substantially annular and capable of encircling the rotational device, the body configured to include a substantially tapered portion and a substantially straight portion, and the body optionally including at least one fin in the region of fluid intake through the body, and wherein the fins are manufactured by an improved and/or adapted roll-forming method including the steps of: a) rolling the material from which the fins are made over onto itself to create a substantially hollow section; and b) configuring the fin to the preferred width and depth for attachment to a preferred protective apparatus; and P39318 c) effecting preferred rounding and/or tapering along either or both the leading and trailing longitudinal edges of the hollow section, said method characterised by the configuration of the trailing and leading edges of the fin(s) and the body effecting change in either or both the physical characteristics of the fluid and streamlining of fluid flow through the body of the protective apparatus and around the rotational device to effect improved operation of the rotational device. S" 10

35. A method of manufacturing fins for use with a protective apparatus as claimed in Claim 33 wherein the fins produced by the method are substantially lightweight, yet strong.

36. A method of manufacturing fins for use with a protective $oo. apparatus as claimed in Claim 34 wherein the method optionally includes the application of one or more of pressing, grinding and die casting to produce fins having the preferred configuration.

37. Protective apparatus substantially as described herein with reference to either or both the drawings and the examples contained herein.

38. A method of manufacturing protective apparatus substantially as described herein with reference to the accompanying examples and/or drawings. P39318

39. Fins for use with protective apparatus substantially as described herein with reference to the accompanying examples and/or drawings. A method of manufacturing fins for use with a protective apparatus substantially as described herein with reference to the accompanying examples and/or drawings Dated this 23rd day of August 2000 S: EDWARD CHRISTOPHER ROBERTS *15 By his Patent Attorneys S: GRIFFITH HACK 2 S. o* P39318