GB2152459A

GB2152459A - Safety shielding of marine propulsion units

Info

Publication number: GB2152459A
Application number: GB08430642A
Authority: GB
Inventors: Robert Duncan Glen
Original assignee: Barrus EP Ltd; EP Barrus Ltd
Current assignee: Barrus EP Ltd; EP Barrus Ltd
Priority date: 1983-12-05
Filing date: 1984-12-05
Publication date: 1985-08-07
Also published as: GB8430642D0; GB2152459B; GB8332380D0

Abstract

An outboard motor with a skeg 1 and propeller 2 has a cage 7 bolted at 13 to flat bars 11 resting on the cavitation plate 6. The cage extends forward from collar 8 to rib 10 giving protection to the limbs of a swimming person in the vicinity of the propeller. In an alternative embodiment (not shown) which is easier to assemble the flat bars 11 have their flat faces vertical and the cage is held by clips pulled on the rearward edge of plate 6 by bolts, so that the cage grips the housing of the motor forwardly and the structure does not rest primarily on the cavitation plate. <IMAGE>

Description

SPECIFICATION Safety shielding of marine propulsion units This invention relates to the propulsion units of light marine craft. In particular, this invention relates to safety shielding of the propeller blades of such units, especially of outboard motor units as usual for inflatable craft.

Light marine craft driven by a more or less high speed propeller located in the water astern of the vessel (e.g. an outboard motor propeller, lying beneath the general contour ofthe hull of a fully inflatable dinghy or of a partly-inflatable inshorerescue or like craft) pose problems of safety or damage when used.

Frequently, they are used in shallow water or the surf zone, and the propeller blades can be damaged by impact with a rocky sea floor, or with floating objects. To guard against such damage, it is known to fit a protective tubular collar or shield around the blades.

However, such a tubular collar, designed to protech the blades without detrimentally affecting the propeller performance, is of only limited help against a second problem. Nor infrequently, craft of this nature are used in water with swimming or floating persons, e.g. as diver/frogman support vessel or as a rescue or like vessel. Known impact shields still leave a large enough aperture forward of the propeller for the arms or hands of a swimmerto enter (especially if drawn by the flow of water) with consequent serious injury.

The present invention sets out to overcome both these problems by providing a safety construction, ensuring protection against impact damage and also acting as a barrier, to limbs of a floating person, forward of the propeller blades without detrimentally affecting the propulsive characterisics of the blades.

In one aspect therefore the invention consists in a safety cage for the submerged portion of a propellerdriven light marine craft propulsion unit, comprising elongate metal bars, spaced apart by an amount to prevent passage of the limb of a swimmer, and extending forward from a circular collar coaxial with an spaced from the propeller.

Such a structure protects swimmers from accident and the propeller from floating debris and from damage by rock on the seabed without unacceptable loss of performance.

The cage can be generally forwardly convergent to deflect swimmers from the region of the propeller blades. The bar spacing is usually from 5 to 12 centimeters.

It is preferred if the cage is adapted for ready assembly to or disassembly from the propulsion unit e.g. by suitable bolts.

Thus in one preferred form the invention consists in a safety cage for attachment to the submersible portion of an outboard motor unit having a generally vertical fin or skeg; a propeller mounted rearwardly thereof and a horizontal cavitation plate extending above the propeller; said cage comprising elongate metal bars, spaced apart by an amount to prevent passage of a limb of a swimmer, and extending forward from a circular collar which is coaxial with and spaced from the propeller and interrupted to define two ends adapted to be attached to the said cavitation plate.

The ends of the collar, and the nature of the attachment to the motor unit, can vary, as described in more detail below.

In one form, the upper portion of the cage comprises two flat bars which when the cage is assembled lie on (and are usually bolted to) the top of the cavitation plate over at least part of their length, so as to assist in supporting the cage weight.

Preferably, moreover, the elongate bars converge forwardly to spaced locations upon a generally vertical rib.

In another form, each end of the collar is provided with a bolt extending longitudinally and at least one clip is associated with the bolts in such a way that when the bolts are tightened the clip is drawn on to the rearward edge of the cavitation plate, tightening the cage against at least the forward region of the motor. In such an instance, flat bars with their flat sides vertical can run to either side of the motor housing but above the cavitation plate. Thus, no boltholes need to be drilled in the cavitation plate.

The propulsion unit having one or other of such cages attached to its submersible portion is another aspect of the present invention.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 is a general view of an outboard motor fitted with a protective cage, and Figure 2 shows details of an alternative fitment.

The outboard motor unit shown in Figure 1 has a vertical rudder-like skeg 1, with the shaft of a propeller 2 mounted in a smooth bulbous housing portion 3 towards the skeg lower end 4, a suitable drive for this propeller shaft extending from a motor, not shown, and down inside the skeg. Rearward spur 5, above propeller 2, carries a horizontal cavitation plate 6 located above the propeller 2 and extending to both sides of the spur.

Cage 7 is attached to this known construction. The cage comprises a rearward collarS, a plurality of spaced shaped bars 9 (generally horizontally located) welded at their rearward ends 9a at intervals around the outside of the collar and attheirforward ends 9b to a vertical forward rib 10. The collar 8 is in this embodiment interrupted at the top to form two ends which are welded at 8a each to the rearward end of a port or starboard flat bar each referenced at 11. Each flat bar 11 itself is welded to the top of rib 10 at locations 11 a. Each flat bar 11 is moreover apertured at 12 to provide an attachment location for bolts 13 passing through holes in the caviation plate 6 above the propeller.

The exact number of bars 9, and their exact shape can vary in dependence upon the size and shape of the outboard motor unit. In the embodiment shown there are fifteen such bars, seven on each side and one along the bottom of the cage. As shown, the propeller 2 is located well inside the plane of the rearward edge of collar 8, as an additional safety feature, although the risk of impact or personal accident can more usually be expected from forward of the propeller. The angled shape shown for bars 9, defining ample undisturbed space for the propeller 2, and a forward impact face generally at F, is preferable. Usually radius of the inner periphery of collar 8 is from 1.1 to 2.0 times that of the propeller blades extremities; in the embodiment shown it is about 1.5.The spacing between at least the intermediate straight sections 9c of the bars 9 is adequate to prevent a limb of a swimmer being drawn on to the blades. From 5 to 12 centimeters is preferred; in the embodiment shown it is about 8 centimetres.

Depending on the exact shape of the skeg 1, the rib 10 can be angled generally to follow its forward contour. In general, in the embodiment of Figure 1, it is envisaged that the cage should usually be spaced by about 5-20 centimeters from the forward parts of this skeg.

Provision of the two-point bolt attachment 13 is of advantage since the cage can be assembled to or removed from the motor unit in a few minutes of unskilled work.

However, a simpler attachment is shown in Figure 2, which has the advantage that it does not necessitate the drilling of holes in the cavitation plate.

In Figure 2, in place of bolts, there is welded at each side a metal block 14 threaded at 15to hold an immobilised (orfree) bolt 16 in each instance, so as to protrude rearwardly. Atransverse retaining clip support 17 fits over the bolt and can be attached thereto by nuts 18 (wingnuts, not shown, could alternatively be used). When this is done the weldedon retaining clips 19fitsnuglyoverthe rearward edge of the cavitation plate, and the forward end 20 of the flat bars 21 (arranged fore-and-aft with flat sides vertical to form the top of the cage) is drawn on to grip the forward end of the motor housing. Figure 2 also shows that round-section bars can replace the flat-section bars of Figure 1. Moreover, although not shown in detail the relative bar spacing and configuration (e.g. using two relatively closely spaced parallel bars 23 joining front bar 22 to the sidebar at the base) can also be such as to retain the skeg.

The embodiment shown in Figure 2 is convenient since replacement of nuts or wing nuts 18 can readily take place in a few minutes unskilled work, whether at sea or on land.

Claims

1. A safety cage for attachment to the submersible portion of an outboard motor unit having a generally vertical fin orskeg; a propeller mounted rearwardly thereof and a horizontal cavitation plate extending above the propeller; said cage comprising elongate metal bars, spaced apart by an amount to prevent passage of a limb of a swimmer, and extending forward from a circular collar which is coaxial with and spaced from the propeller and interrupted to define two ends adapted to be attached to the said cavitation plate.

2. A safety cage as claimed in claim 1 in which the upper portion of the cage comprises two flat bars which when the cage is assembled lie on (and are usually bolted to) the top of the cavitation plate, over at least part of their length, so as to assist in supporting the cage weight.

3. A safety cage as claimed in claim 2 provided with bolts for holes drilled at the edge of the cavitation plate.

4. A safety cage as claimed in claim 2 or 3 in which the front of the cage is spaced from 5 to 20 cm from the forward edge of the skeg.

5. A safety cage as claimed in claim 1 in which each end of the collar is provided with a bolt extending longitudinally and at least one clip is associated with the bolts in such a way that when the bolts are tightened the clip is drawn on to the rearward edge of the cavitation plate, tightening the cage against at least the forward region of the motor.

6. A safety cage as claimed in claim 5 in which a transverse retaining-clip support bar is held by two bolts, one to either side of the cage, and carries two bent clips accommodating the rearward edge of the cavitation plate.

7. A safety cage as claimed in claim 5 or 6 in which flat bars with their flat sides vertical run to either side of the motor housing above the cavitation plate.

8. A safety cage as claimed in any of claims 5 to 7 further comprising two relatively closely spaced parallel bars joining the front of the cage to the base and for accommodating a forward edge of the sket between them.

9. A safety cage as claimed in any one preceding claim in which the radius of the collar internal periphery is from 1:1 to 2:0 times that of the propeller blade extremities.

10. A safety cage as claimed in any one preceding claim in which the maximum bar spacing is from Sto 12 cms.

11. A safety cage for the submerged portion of a propellor-driven light marine craft propulsion unit, comprising elongate metal bars, spaced apart by an amount to prevent passage of the limb of a swimmer, and extending forward from a circular collar coaxial with an spaced from the propeller.

12. A safety cage be claimed in claim 1 and substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawing.

13. An outboard motor having attached to its submersible portion a safety cage as claimed in any one preceding claim.