CA1243627A - Constant voltage anode system - Google Patents
Constant voltage anode systemInfo
- Publication number
- CA1243627A CA1243627A CA000529030A CA529030A CA1243627A CA 1243627 A CA1243627 A CA 1243627A CA 000529030 A CA000529030 A CA 000529030A CA 529030 A CA529030 A CA 529030A CA 1243627 A CA1243627 A CA 1243627A
- Authority
- CA
- Canada
- Prior art keywords
- anode
- housing
- sea water
- voltage
- constant voltage
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Prevention Of Electric Corrosion (AREA)
Abstract
ABSTRACT
A marine propulsion unit having a housing exposed to sea water and subject to attack by the sea water is provided with a permanent type anode housing substantially constant surface characteristics mounted on the housing and supplied with constant voltage. Holes under the anode through the housing to an interior passage permits the current on the anode to influence and protect the passage.
A marine propulsion unit having a housing exposed to sea water and subject to attack by the sea water is provided with a permanent type anode housing substantially constant surface characteristics mounted on the housing and supplied with constant voltage. Holes under the anode through the housing to an interior passage permits the current on the anode to influence and protect the passage.
Description
~LZ~3G'~7 CONSTANT VOLTAGE ANODE SYSTEM
RE~ATED APPLICATION
This application is a division of application Serial No. 456,440 filed June 13, 1984.
FIELD OF THE INVENTION
This invention relates to cathooic protection systems for marine propulsion systems.
BACKGROUND OF THE INVENTION
Aluminum marine propulsion systems have been protected by sacrificial anodes (zinc, magnesium or certain alloys) which are dissolved in the course of time. They have also been protected by impressed current systems supplied by the boat battery. The latter systems use "permanent" anodes which are subject to surface passivation layers which radically alter the impedance of the anode surface to the sea waterO This can result in the anode potential going above 1200 millivolts which leads to chemical attack of the aluminum. Therefore, a feedback circuit including a referenca electrode, normally silver-silver chlQride, is desireable.
The anode is normally mounted on tne outside of the housing. Interior cavities in the lower housing of the motor have been unprotected.
Attention is directed to U.S. Patent No. 3,477,931 which relates generaLly to a voltage control with various anode materials. It does not;
~ ~ tea~h how to protect interior cavities.
:; : ~ ~ ;: ,^ ;
RE~ATED APPLICATION
This application is a division of application Serial No. 456,440 filed June 13, 1984.
FIELD OF THE INVENTION
This invention relates to cathooic protection systems for marine propulsion systems.
BACKGROUND OF THE INVENTION
Aluminum marine propulsion systems have been protected by sacrificial anodes (zinc, magnesium or certain alloys) which are dissolved in the course of time. They have also been protected by impressed current systems supplied by the boat battery. The latter systems use "permanent" anodes which are subject to surface passivation layers which radically alter the impedance of the anode surface to the sea waterO This can result in the anode potential going above 1200 millivolts which leads to chemical attack of the aluminum. Therefore, a feedback circuit including a referenca electrode, normally silver-silver chlQride, is desireable.
The anode is normally mounted on tne outside of the housing. Interior cavities in the lower housing of the motor have been unprotected.
Attention is directed to U.S. Patent No. 3,477,931 which relates generaLly to a voltage control with various anode materials. It does not;
~ ~ tea~h how to protect interior cavities.
:; : ~ ~ ;: ,^ ;
-2-SUMMARY OF THE INVENTION
The invention provides a marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housin~i and means for impressing a constant voltage on the anode.
In one embodiment of the invention, the housing has an internal passage and the anode is mounted on and insulated from the housing in a position outside the passage, which housing is apertured so the internal passage is exposed to the anode.
The invention also provides a marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housing, and means for impressing~a voltage on the anode, which voltage impeessing means includes regulator means for maintaining substantially constant the impressed voltage.
An important feature of this invention is sllpplying a constant voltage to a permanent type of anode naving substantially constant surface characteristlcs to protect an aluminum marine propulsion system.
This invention i~s not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is , : :: ~ :
capable of other embodiments~and of be~ng practiced and carried out in various way~s. Also, it is to be ~ -understood that the phraseology;and terminology lZ436Z~
employed herein is for the purpose of description and should not be regarded as limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmentary side elevation of the lower portion of an outboard motor.
Fig. 2 is a section taken as indicated by line 2-2 in Fig. 1.
Fig. 3 is a schematic ~block) diagram of one type of constant voltage circuit for the anode.
Fig. 4 is a schematic (block) diagram of another constant voltage circuit.
DETAILED DESCRIPTION OF THE DRAWINGS
Fig. 1 shows the lower portion of an outboard motor (or stern drive or other marine propulsion device). The propeller 10 projects from the lower gearcase 12 below the faired housing 14 and the anti-cavitation plate 16. The housing 14 encloses the drive shaft 18, a cooling water passage 20 and an exhaust passage 22.
Typically, the housing 14 and gearcase are made of aluminum alloy which is subject to corrosion in sea water. To protect the aluminum a carbon anode 24 is fixed to the housing with an insulator 26 between the housing and the anode to electrically insulate the anode from the housing.
The anode and insulator may be glued or bolted to the housing. If bolted, the bolts must be insulated.
The anode covers an aperture 28 to tne cooling water~
passage and an aperture 30 to the exhaust passage.
When the boat is at rest, sea water will rise above the anode in the passages. Therefore, the anode is , :
~2436~7 a ferrite sprayed on titanium or niobium which is satisfactory. A11 these anodes can be operated at constant voltage, they will last the life of the marine peopulsion system and, with the holes under the anode, will protect inside as well as outside.
:
: ::
.
:
~L2~3~27 effective to protect the aluminum walls of the ,~
passages as well as the outside of the lower unit.
The carbon anode is a permanent type ano~e which is not subject to surface passi~ation layers which, in turn, require a ~eedback circuit including a half-cell to prevent the protection level from becoming too high. Instead, the carbon anode has a surface not pasivated or polarized permanently. Its surface impedance to the water remain~ very constant and predictable. Therefore, the anod~ can be operated from a constant voltage source without a half-cell reference electrode.
The constant voltage circuit of Fig. 3 can be used to provide a regulated voltage V~ to the anode. The boat battery 32 supplies 12V to the voltage regulator 34 which supplies a regulated voltage VA (somewhat less tnan 12V) to the anode 24. The holes 28, 30 allow the anode current to be effec~ive in the cavitie-~ 20, ~2.
In Fig. 4 the battery supplies 12V to the power converter/voltage regulator 36 to supply considerably less voltage ~ to the anode. Since the converter/regulator is a power converter, the current IA supplied to the anode is higher than the current KB drawn from the battery. This arrangement greatly prolongs the battery life between charging. Further details of such a circuit may be seen in my copending Canadian application Serial No.
456,360, filed June 12, 1984 and entitled "Cathodic Protection System". For the present invention it is sufficient to realize this is another constant voltage circuit which can be used.
Other anode materials can be used.
There is a ferrite material availabls from TDE
Corporation and magnetite can also be used. There i 8 :
.
:
The invention provides a marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housin~i and means for impressing a constant voltage on the anode.
In one embodiment of the invention, the housing has an internal passage and the anode is mounted on and insulated from the housing in a position outside the passage, which housing is apertured so the internal passage is exposed to the anode.
The invention also provides a marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housing, and means for impressing~a voltage on the anode, which voltage impeessing means includes regulator means for maintaining substantially constant the impressed voltage.
An important feature of this invention is sllpplying a constant voltage to a permanent type of anode naving substantially constant surface characteristlcs to protect an aluminum marine propulsion system.
This invention i~s not limited to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is , : :: ~ :
capable of other embodiments~and of be~ng practiced and carried out in various way~s. Also, it is to be ~ -understood that the phraseology;and terminology lZ436Z~
employed herein is for the purpose of description and should not be regarded as limiting.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmentary side elevation of the lower portion of an outboard motor.
Fig. 2 is a section taken as indicated by line 2-2 in Fig. 1.
Fig. 3 is a schematic ~block) diagram of one type of constant voltage circuit for the anode.
Fig. 4 is a schematic (block) diagram of another constant voltage circuit.
DETAILED DESCRIPTION OF THE DRAWINGS
Fig. 1 shows the lower portion of an outboard motor (or stern drive or other marine propulsion device). The propeller 10 projects from the lower gearcase 12 below the faired housing 14 and the anti-cavitation plate 16. The housing 14 encloses the drive shaft 18, a cooling water passage 20 and an exhaust passage 22.
Typically, the housing 14 and gearcase are made of aluminum alloy which is subject to corrosion in sea water. To protect the aluminum a carbon anode 24 is fixed to the housing with an insulator 26 between the housing and the anode to electrically insulate the anode from the housing.
The anode and insulator may be glued or bolted to the housing. If bolted, the bolts must be insulated.
The anode covers an aperture 28 to tne cooling water~
passage and an aperture 30 to the exhaust passage.
When the boat is at rest, sea water will rise above the anode in the passages. Therefore, the anode is , :
~2436~7 a ferrite sprayed on titanium or niobium which is satisfactory. A11 these anodes can be operated at constant voltage, they will last the life of the marine peopulsion system and, with the holes under the anode, will protect inside as well as outside.
:
: ::
.
:
~L2~3~27 effective to protect the aluminum walls of the ,~
passages as well as the outside of the lower unit.
The carbon anode is a permanent type ano~e which is not subject to surface passi~ation layers which, in turn, require a ~eedback circuit including a half-cell to prevent the protection level from becoming too high. Instead, the carbon anode has a surface not pasivated or polarized permanently. Its surface impedance to the water remain~ very constant and predictable. Therefore, the anod~ can be operated from a constant voltage source without a half-cell reference electrode.
The constant voltage circuit of Fig. 3 can be used to provide a regulated voltage V~ to the anode. The boat battery 32 supplies 12V to the voltage regulator 34 which supplies a regulated voltage VA (somewhat less tnan 12V) to the anode 24. The holes 28, 30 allow the anode current to be effec~ive in the cavitie-~ 20, ~2.
In Fig. 4 the battery supplies 12V to the power converter/voltage regulator 36 to supply considerably less voltage ~ to the anode. Since the converter/regulator is a power converter, the current IA supplied to the anode is higher than the current KB drawn from the battery. This arrangement greatly prolongs the battery life between charging. Further details of such a circuit may be seen in my copending Canadian application Serial No.
456,360, filed June 12, 1984 and entitled "Cathodic Protection System". For the present invention it is sufficient to realize this is another constant voltage circuit which can be used.
Other anode materials can be used.
There is a ferrite material availabls from TDE
Corporation and magnetite can also be used. There i 8 :
.
:
Claims (3)
1. A marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housing, and means for impressing a constant voltage on said anode.
2. The structure set forth in Claim 1 in which the housing has an internal passage and the anode is mounted on and insulated from the housing in a position outside said passage, said housing being apertured so said internal passage is exposed to said anode.
3. A marine drive unit having a housing exposed to sea water and subject to attack by the sea water, a permanent type anode having substantially constant surface characteristics mounted on the housing, and means for impressing a voltage on said anode, said voltage impressing means including regulator means for maintaining substantially constant the impressed voltage.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000529030A CA1243627A (en) | 1983-09-12 | 1987-02-04 | Constant voltage anode system |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US531,462 | 1983-09-12 | ||
| US06/531,462 US4559017A (en) | 1983-09-12 | 1983-09-12 | Constant voltage anode system |
| CA000456440A CA1224745A (en) | 1983-09-12 | 1984-06-13 | Constant voltage anode system |
| CA000529030A CA1243627A (en) | 1983-09-12 | 1987-02-04 | Constant voltage anode system |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000456440A Division CA1224745A (en) | 1983-09-12 | 1984-06-13 | Constant voltage anode system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1243627A true CA1243627A (en) | 1988-10-25 |
Family
ID=25670411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000529030A Expired CA1243627A (en) | 1983-09-12 | 1987-02-04 | Constant voltage anode system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1243627A (en) |
-
1987
- 1987-02-04 CA CA000529030A patent/CA1243627A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |