Patent Grant
7186157
The present invention relates to a rotatable propeller drive for a boat. The propeller drive is provided with an exhaust duct for discharging exhaust gases from an internal combustion engine connected to the propeller drive. The propeller drive has an upper fixing plate for rotationally fixed attachment to the hull bottom of the boat, and a lower underwater housing on which at least one propeller is mounted. The underwater housing is mounted rotatably in the fixing plate, and the invention concerns in particular sealing between an upper duct section of the exhaust duct arranged in the fixing plate and a lower duct section of the exhaust duct arranged in the underwater housing, where the lower duct section is displaced in relation to the upper duct section when the propeller drive is rotated.
In propeller drives where an exhaust duct is divided into two duct sections as indicated above, a seal is required between the two duct sections in order to avoid exhaust gas leakage when the boat is driven, at least above a certain minimum speed. This minimum speed may be, for example, 3–5 knots and can also be said to correspond to a practical upper limit for driving the boat in a harbor area or in proximity to another mooring. If exhaust gases are allowed to leak out between the duct sections when the boat is driven above said minimum speed, exhaust gases may be drawn into the boat at the stern where a local negative pressure then prevails. This effect is sometimes called the wagon-back effect. An undesirable exhaust gas discharge between the duct sections when the boat is driven at a speed exceeding said minimum speed also leads to unfavorable hydrodynamic flow conditions arising in the transition region between the fixing plate and the underwater housing, which has a negative effect on the propulsion of the boat.
An obvious and generally well-known way of sealing exhaust ducts which are movable relative to one another is to arrange a sealing flexible exhaust bellows made of rubber or rubber-like material between the duct sections. A problem with such a solution in this case, however, is that the exhaust bellows is relatively bulky in the vertical direction, in particular when it has to cover a certain rotation range for the propeller drive.
The drawbacks described above are solved by virtue of the present invention's provision of a specially adaptation for a rotatable propeller drive of a boat. The propeller drive comprises (includes, but is not necessarily limited to) an upper fixing plate adapted for rotationally fixed attachment to the hull bottom of the boat. A lower underwater housing is provided and upon which at least one propeller is mounted and the housing is mounted rotatably in the fixing plate about an essentially vertical axis of rotation. An exhaust duct is provided with an exhaust exit located in the underwater housing.
The invention is characterized in particular in that the exhaust duct has an upper duct section which extends through the fixing plate and has an outlet opening located in proximity to an opposite inlet opening in a lower duct section which extends through the underwater housing. One of the outlet opening and inlet opening overlaps the other at least within a limited first rotation angle range for the propeller drive. Further, a sliding seal arrangement is provided that is adapted for sealing between the upper and lower duct sections, and in which the sliding seal arrangement comprises a sealing element accommodated in a seat around one of the outlet opening and inlet opening. The sealing element has a contact surface for sliding contact with an opposite sliding seal surface around the other of the outlet opening and inlet opening.
In one advantageous embodiment of the invention, the sliding seal surface is designed on a separate wear plate which is attached firmly either around the outlet opening in the upper duct section or around the inlet opening in the lower duct section and is provided with an opening which essentially coincides with that of said inlet opening or outlet opening around which the wear plate is attached.
In an embodiment which functions well, the sealing element is at least partly elastically deformable and has a radially inwardly facing side edge which is adapted so as, under the influence of an exhaust gas pressure in the exhaust duct, to be displaced radially outwardly fully or partly, while a radially outwardly facing side edge on the sealing element is adapted to bear against a fixed radially inwardly facing stay edge, the sealing element being adapted so as, by elastic deformation, to expand vertically in the direction of the sliding seal surface, as a result of which an increased sealing pressure against the sliding seal surface is obtained at increased exhaust gas pressure.
In a favorable embodiment of the invention, an inner sealing lip is designed in proximity to said radially inwardly facing side edge of the sealing element, which sealing lip bears against the seat in such a way that a hollow channel extending all around is defined radially outside said sealing lip between that edge of the sealing element facing the seat and the seat.
In one embodiment, the sealing element is divided into a lower elastically deformable part and an essentially rigid upper part, where the contact surface of the sealing element is located on the rigid part.
The elastically deformable part is suitably made wholly or partly from a rubber material or a material with rubber-like properties, while the rigid part is made wholly or partly from stainless steel or plastic.
The rigid part of the sealing element is preferably designed as a dimensionally stable frame with a U-shaped cross section, which frame partly accommodates the elastically deformable part of the sealing element.
In one embodiment, the radially inwardly facing stay edge mentioned above consists of an outer leg portion of the frame, while the radially outwardly facing side edge on the sealing element is defined on the elastically deformable part.
In an alternative embodiment, the radially inwardly facing stay edge consists of an outer delimiting edge for the seat.
In one embodiment, the rigid part constitutes a separate part in relation to the elastically deformable part.
In an alternative embodiment, the rigid part is attached to the elastically deformable part, for example by vulcanization.
In an advantageous embodiment, the wear plate is, at least at the sliding seal surface, made from a hard wearing low-friction material, such as, for example, polytetrafluoroethylene (PTFE).
The limited first rotation angle range preferably corresponds to a rotation of the propeller drive of between 10 and 15 degrees to starboard and port, respectively.
In a preferred embodiment, the propeller drive is adapted for at least one tractor propeller. A twin-propeller combination of a fore propeller and an aft propeller is especially advantageous.
The upper and lower duct sections of the exhaust duct are preferably located astern of the axis of rotation of the propeller drive.
The invention will be described in detail below with reference to accompanying drawings, in which:
In
A tractor propeller 10 is arranged on the underwater housing 6. Here, to be precise, the propeller consists of a twin propeller combination of a fore propeller 10a and an aft propeller 10b rotating in the opposite direction, both of which are illustrated diagrammatically in
In an exemplary embodiment, the fore propeller 10a is three-bladed (not shown in
The boat (not shown) can be equipped with a single propeller drive 1, or alternatively with a number of propeller drives 1, normally in a twinned mounting (not shown) arrangement in which two propeller drives 1 are mounted next to one another in order to achieve increased maneuverability.
As can also be seen from
An internal combustion engine (not shown) drives—via an input shaft 32 in a reversing gear mechanism 34—a vertical drive shaft 36, which, in the illustrative embodiment shown, coincides with the geometrical axis of rotation 8 (illustrated by dot/dash line), referred to in the introduction, of the propeller drive 1. Via a bevel gear 38, the vertical drive shaft 36 is coupled to two horizontal and concentric propeller shafts 40, 42, of which the propeller shaft 42 is a hollow shaft through which the propeller shaft 40 extends. In this connection, the propeller shaft 40 drives the fore propeller 10a, while the propeller shaft 42 drives the aft propeller 10b.
The rotation of the underwater housing 6 of the propeller drive 1 is brought about by a servomotor 44 via a gear rim 46 connected to the underwater housing 6.
An exhaust pipe 48 extends from the internal combustion engine (not shown) and on through an exhaust duct 50 in the propeller drive 1 to the exhaust exit 14 in the aft side 16 of the underwater housing 6. In
According to the invention, a sliding seal arrangement 58 is adapted for sealing between said upper and lower duct sections 54 and 56. For the sake of clarity, an enlarged part-section through the sliding seal arrangement 58 is shown in
The sliding seal arrangement 58 comprises an inlet opening 60 designed in the lower duct section 56, which inlet opening 60 overlaps an opposite outlet opening 62 in the upper duct section 54 at least within a limited first rotation angle range for the propeller drive 1. A sealing element 64 extending all around is accommodated in a seat 66 around the inlet opening 60 in the lower duct section 56. The sealing element 64 has an upper contact surface 68 for contact with an opposite, downwardly directed sliding seal surface 70 around the outlet opening 62 in the upper duct section 54. As can be seen clearly from
The sealing element 64 is designed to be at least partly elastically deformable and has a radially inwardly facing side edge 76. Under the influence of an exhaust gas pressure in the exhaust duct 50, the inwardly facing side edge 76 is displaced radially outward; that is to say, to the right in
In the illustrative embodiment shown, the fixed stay edge 80 is designed in an outer leg portion 82 of a dimensionally stable frame 84 with a downwardly directed, essentially rectangular U-shaped cross section. The frame 84 and its function will be described in greater detail later in this description.
By way of definition, the sealing element 64 can be said to be divided into a lower elastically deformable part and a rigid upper part. Here, the lower elastically deformable part is made wholly or partly from a rubber material or a material with rubber-like properties, while the rigid upper part, in the embodiment shown, consists of the U-shaped frame 84 described above. The frame 84 can suitably be made wholly or partly from stainless steel or plastic, but other materials suitable for the purpose can also be used.
The upper contact surface 68 of the sealing element 64 in contact with the downwardly directed sliding seal surface 70 on the wear plate 72 is, with such a definition, located on the rigid upper part; that is to say, on the frame 84. As can also be seen from
According to the invention, the frame 84 can either constitute a separate part in relation to the lower elastically deformable part of the sealing element 64, or the frame 84 can be attached to the lower elastically deformable part, for example by vulcanization. In the latter case, the stay edge 80 consists instead of an outer delimiting edge 86 for the seat 66 around the inlet opening 60 in the lower duct section 56. The outer delimiting edge 86 also serves as a positioning aid when the sealing element 64 is placed in the seat 66 in connection with mounting of the propeller drive 1.
As can also be seen from
In a suitable embodiment, the limited first rotation angle range corresponds to a rotation of the propeller drive 1; to be precise, of the underwater housing 6 of between 10 and 15 degrees to starboard and port, respectively. Full overlapping therefore takes place only within this limited first rotation angle range around the center position 96, which range easily covers typical maneuvers at normal cruising speed or speeds above this.
When rotation beyond the limited first rotation angle range takes place, however, the exhaust gases are blown in full or in part directly out of the outlet opening 62 of the upper duct section 54, as is shown by the representation in dashed lines of the underwater housing 6. Here, the underwater housing 6 is shown rotated to port (downward in the figure) by an angle β corresponding to roughly 30 degrees, which results in the inlet opening 60 in the lower duct section 56 being rotated in part past the opposite outlet opening 62 in the upper duct section 54. The exhaust gases are then discharged in part at the side of the inlet opening 60 in the lower duct section 56 on a level with the sealing device 64 directly below the hull bottom 2. This is acceptable at lower speeds—up to roughly 5 knots—for example when maneuvering in a harbor where large rotation angles may be required. This is because at these low speeds the same advantages of the exhaust gases being discharged on a level with the propeller shafts 40, 42, which therefore takes place at higher speeds and with a smaller rotation angle, are not achieved.
The outlet opening 62 in the upper duct section 54, like the opening 74 in the wear plate 72, has an essentially oblong triangular shape with the base facing the axis of rotation 8 and the top facing astern. As can also be seen from
The invention is not limited to the illustrative embodiments described above and shown in the accompanying drawings, but can be varied freely within the scope of the patent claims. For example, the design of the sliding seal arrangement 58 can be reversed compared with the embodiment shown in the figures. In such a reversed or inverted sliding seal arrangement 58, some of the references above to “upper” and “lower” consequently no longer apply, as the wear plate 72 is then instead attached firmly around the inlet opening 60 in the lower duct section 56, while the seat 66 is arranged around the outlet opening 62 in the upper duct section 54. The orientation of the sealing element 64 also is then reversed so that the frame 84 faces downward instead for contact with the wear plate 72. Here, the opening 74 in the wear plate 72 coincides instead with the inlet opening 62 in the lower duct section 56. To facilitate assembly in such a reversed embodiment, holder means (not shown) can be designed at the seat 66 or in the sealing element 64 for retaining the sealing element 64 during mounting of the underwater housing 6.
Furthermore, the frame 84 can be designed with a different cross-sectional shape, such as an L shape. Although the embodiment of the propeller drive 1 shown is intended for tractor propellers, the sliding seal arrangement can also be applied to a correspondingly designed propeller drive for pusher propellers (not shown). It is also conceivable, within the scope of the invention, for the rigid part and the elastically deformable part of the sealing element 64 to be produced by a process in which a common, originally homogeneous starting material is given locally different mechanical properties.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0302064 | Jul 2003 | SE | national |
The present application is a continuation patent application of International Application No. PCT/SE2004/000627 filed 23 Apr. 2004 now abandoned which is published in English pursuant to Article 21(2) of the Patent Cooperation Treaty, and which claims priority to Swedish Application No. 0302064-1 filed 11 Jul. 2003. Said applications are expressly incorporated herein by reference in their entireties.
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| 4911666 | Gage et al. | Mar 1990 | A |
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| Number | Date | Country | |
|---|---|---|---|
| 20060199452 A1 | Sep 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/SE04/00627 | Apr 2004 | US |
| Child | 11306796 | US |
