Marine propulsion – Screw propeller – Shafting
Patent
1996-05-29
1998-04-07
Swinehart, Edward L.
Marine propulsion
Screw propeller
Shafting
440 75, B63H 512
Patent
active
057357188
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a drive unit for boats, comprising an internal combustion engine with a flywheel fixed on a crank shaft and surrounded by a flywheel casing, and a propeller drive with a housing connected to said flywheel casing and an input shaft driven by said crank shaft.
In drive units of this type, for example outboard drive units, it is common to make parts of the drive unit, for example the rig, the propellers, the lower transmission housing of aluminum. Since these components are submerged in the water, it is important to see to it that measures are taken to prevent i.a. galvanic corrosion from shortening the useful life, should the parts be electrically connected to another submerged component of a metal which is more electro-positive, for example a keel of iron with stainless steel bolts which are grounded together with the engine block in a single-pole electric system. The parts of the drive unit submerged under water can be protected by known methods, i.e. by mounting a sacrificial anode on the drive, or by painting with protective paint, or by a combination of these two measures.
Another known method of avoiding galvanic corrosion on the propeller drive, e.g. a sailboat drive unit in a sailboat with an iron keel with stainless steel keel bolts, is to equip the boat with a two-pole electrical system, i.e. a system in which each electrical power consumer, such as the starting motor, the generator, the oil pressure sensor etc, is connected to the battery, via a positive and a negative conductor. The advantage of a two-pole electrical system is that the drive unit will be insulated from the rest of the electrical system and no attention must be paid to replacing the sacrificial anode or repainting with protective paint.
However, it is important that the boat owner, when installing additional equipment for example, does not modify the engine electrical system so that the engine drive units are grounded.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a drive unit of the type described by way of introduction, which permits connecting the engine block to ground and where the electrical power consumers can thus be coupled to the battery via a single pole electrical system without risk that the submerged components of the drive will be subjected to galvanic corrosion.
This is achieved according to the invention in a drive unit in which the drive lacks electrically conducting connection to the engine.
In a preferred embodiment of the invention applied to known inboard and outboard drives with a metal transition housing, which has a flange screwed securely to a flange on the flywheel casing of the engine, and in which the input shaft of the drive can be drivingly connected to the flywheel via an elastic coupling, the screws are mounted in bushings of insulating material. Spacer elements of insulating material are arranged between the flanges and between the bolt heads and the flange of the drive housing. The flywheel is joined to the input shaft of the drive via an elastic coupling which has coupling halves which are electrically insulated from each other.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail with reference to examples shown in the accompanying drawings, where FIG. 1 shows a schematic sideview of a drive unit according to the invention in a schematically indicated sailboat hull, and FIG. 2 shows a longitudinal section through the encircled area in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The numeral 1 in FIG. 1 indicates a sailboat hull with a keel 2a and a rudder 2b spaced from each other. The keel can be made of iron or lead and have stainless steel keel bolts 3 cast therein, which are screwed fast to the inside of the hull by means of nuts 4. A drive unit consisting of an internal combustion engine 5, preferably a diesel engine, and a propeller drive 6 is bolted securely to an engine bed (not shown). The drive 6 is a so-called S-drive and has a rig leg 7 which extends o
REFERENCES:
patent: 2051442 (1936-08-01), Geyer
patent: 3136281 (1964-06-01), Kiekhaefer et al.
patent: 4583953 (1986-04-01), Nakase
patent: 4634391 (1987-01-01), Entringer et al.
patent: 5009619 (1991-04-01), Meier
patent: 5465678 (1995-11-01), Ekman
AB Volvo Penta
Swinehart Edward L.
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