FIELD OF INVENTION
The invention generally relates to field of marine propulsion systems and more particularly to power transmission arrangement in the marine propulsion systems.
BACKGROUND
A typical marine propulsion system includes a power generation source such as an engine or an electric motor or a combination of the engine and the electric motor that drives a propeller. The marine propulsion system includes a power transmission device connecting the power generation source and the propeller. The propeller generates thrust to move a marine vessel across water. Generally, the power source selection is based upon maximum continuous rating with 10% provided as a backup. In certain scenarios, when the marine propulsion system runs at slow speed, the engine runs at a lower efficiency. Even with hybrid propulsion system engine running at optimum efficiency, there are losses in power generation due to conversion of energy from one source to another source. Also space utilised on ship by battery for hybrid arrangement is pretty high due to required rating. It is advantageous to use multiple engines as a generator with a small rating of battery to utilise space as well as power efficiently. U.S. Pat. No. 7,207,852 discloses a ship propulsion arrangement in which a mechanical drive shaft extends through a hull of a ship to an external body and is driven by either a prime mover located within the ship or by an electric motor in a housing external to the ship through which the mechanical drive shaft extends. This arrangement includes the prime mover in the hull of the ship which occupies space in the ship.

Hence there is a need for a marine propulsion system that can overcome one or more of the problems as set forth above.
SUMMARY OF THE INVENTION
According to an exemplary embodiment of the invention, a propulsion system for a marine vessel is disclosed. The propulsion system may comprise of a pod, housing a first shaft. The first shaft may be arranged within the pod in a substantially horizontal position. According to an embodiment, the first shaft may be a propeller shaft. The propulsion system may further comprise of a second shaft. The second shaft may be arranged in a substantially vertical position. According to an embodiment, the second shaft may be a pinion shaft. The first shaft and the second shaft may be connected to each other through a gearing arrangement. The gearing arrangement may transmit power from the second shaft to the first shaft. According to an embodiment, the gearing arrangement may be a bevel gear arrangement. The propulsion system may comprise of at least two motors such that at least one motor selectively engages the first shaft and at least one motor selectively engages the second shaft. The selective engagement between the motors and the shaft may enable each motor to drive the propulsion system independently and simultaneously to the other motor.
BRIEF DESCRIPTION OF DRAWINGS
Other objects, features, and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:

Figure 1 illustrates a front cross section view of a propulsion system for a marine vessel according to an exemplary embodiment of the invention.
Figure 2 illustrates an isometric section view of a propulsion system according to an exemplary embodiment of the invention.
DETAILED DESCRIPTION OF DRAWINGS
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
Figure I and Figure 2 illustrates a front cross section view and an isometric section view respectively of a propulsion system 100 for a marine vessel according to an exemplary embodiment of the invention. The propulsion system 100 for a marine vessel may be a pod drive unit. According to an embodiment, the shape of the pod 102 of the propulsion system 100 may be similar to the shape of a gondola. The propulsion system 100 may be attached to a hull of the marine vessel. According to an embodiment, the attachment between the propulsion system 100 and the hull of the marine vessel may be such that the propulsion system 100 may be steerable from the surface of the marine vessel. The propulsion system 100 may comprise

of a first shaft 104. According to an embodiment, the first shaft 104 may be independently operated for small energy requirements. The first shaft 104 may be enclosed within the pod 102 of the propulsion system 100. According to an embodiment, the first shaft 104 may be in a substantially horizontal position such that the first shaft 104 may freely rotate along a substantially horizontal axis through a bearing arrangement 106a. The bearings 106a may be provided at multiple positions along the length of the first shaft 104.
According to an embodiment, the first shaft 104 may be a propeller shaft and may have one or more propellers 108 attached at one end. According to another embodiment, the first shaft 104 may have at least two propellers 108 attached at one end of the first shaft 104. According to yet another embodiment, the first shaft 104 may have at least one propeller 108 attached at each end of the first shaft 104. According to an embodiment, each propeller 108 may consist of at least two blades 110. The propeller 108 may be of any type such as, but not limited to, a fixed pitch propeller, controllable pitch propeller, highly skewed propeller, self-pitching propeller, balanced thrust propeller etc.
The propulsion system 100 for a marine vessel may further comprise of a second shaft 112. The second shaft 112 may be operated for moderate power requirements. According to an embodiment, the second shaft 112 may be in a substantially vertical position such that the second shaft 112 may freely rotate along a substantially vertical axis through a bearing arrangement 106b. The bearings 106b may be provided at multiple positions along the length of the second shaft 112. According to an embodiment, the second shaft 112 may be a pinion shaft. According to an embodiment, the first shaft 104 and the second shaft 112 are the power transmission shafts. The first shaft 104 may be connected to the second shaft 112 through a

gearing arrangement 114 such that the first shaft 104 and the second shaft 112 form a substantially orthogonal arrangement.
According to an embodiment, the propulsion system may further comprise of a third shaft 116 between the first shaft 104 and the second shaft 112. The third shaft 116 may be an intermediate shaft between the first shaft 104 and the second shaft 112. According to an embodiment, the third shaft 116 may be in a substantially horizontal position such that the third shaft 116 may freely rotate along the horizontal axis through the bearing arrangement 106c. The third shaft 116 may transmit the motion of the second shaft 112 to the first shaft 104 through the gearing arrangement 114. According to an embodiment, the gearing arrangement 114 may include a bevel gear 114a between the second shaft 112 and the third shaft 116 and a parallel gear 114b between the first shaft 104 and the third shaft 116. According to an embodiment, the bevel gear may be of any type such as, but not limited to, straight bevel gear, spiral bevel gear, zero bevel gear, hypOid bevel gear etc. According to an embodiment, the parallel gears may be of any type such as, but not limited to, spur gear, helical gear, planetary gear etc. The arrangement of the third shaft 116 in the propulsion system 100 may be such that the third shaft 116 may be parallel to the first shaft 104 and orthogonal to the second shaft 112.
According to another embodiment, the first shaft 104 may be directly connected to the second shaft 112 through a gearing arrangement 114. The gearing arrangement 114 may directly transmit the motion of the second shaft 112 to the first shaft 104. The gearing arrangement 114 may include a bevel gear. According to an embodiment, the bevel gear may be of any type such as, but not limited to, straight bevel gear, spiral bevel gear, zero bevel gear, hypoid bevel gear etc. The arrangement of the first shaft 104 and the second shaft 112 in this embodiment may be such that the first shaft 104 may be orthogonal to the second shaft 112.

According to an embodiment, the propulsion system 100 may further comprise of at least two motors such that at least one motor 118 selectively engages the first shaft 104 and at least one motor 120 selectively engages the second shaft 112. According to an embodiment, the motors 118, 120 may be permanent magnet induction motors. The motor 118 engaging the first shaft 104 may drive the first shaft 104 in a rotating motion. The motor 120 engaging the second shaft 112 may drive the second shaft in a rotating motion. According to an embodiment, the selective engagement and disengagement of the motor 118 to the first shaft 104 may be achieved by a clutch 122. According to an embodiment, the selective engagement and disengagement of the motor 120 to the second shaft 112 may be achieved by another clutch 124. According to an embodiment, the propulsion system 100 may be independently driven for small thrust requirements by engaging the running motor 118 on the first shaft 104. According to an embodiment, the propulsion system 100 may be independently driven for moderate thrust requirements by engaging the running motor 120 on the second shaft 112. According to an embodiment, the propulsion system 100 may be driven in combination for high thrust requirements by engaging both the running motors 118, 120 on the first shaft 104 and the second shaft 112 together. According to an embodiment, the propulsion system 100 may include an additional motor engaging the second shaft 112. The additional motor may engage the top part of the second shaft 112. The additional motor may be placed on the marine vessel surface. The additional motor may be operated to provide higher thrust requirements.
According to an embodiment, the clutches 122, 124 may be operated manually depending on the application. According to another embodiment, the clutches 122, 124 may be operated automatically based on the thrust requirement conditions. The marine propulsion system 100 may be stored with data to determine the operability of the motors 118, 120 as per the thrust

requirements. For small thrust requirements, only the motor 118 on the first shaft 104 may be engaged. For moderate thrust requirements, only the motor 120 on the second shaft 112 may be engaged. For high thrust requirements, the motor 118 on the first shaft 104 and the motor 120 on the second shaft 112 may be engaged together. According to an embodiment, the additional motor on the second shaft 112 may be further engaged along with other motors 118, 120 to provide much higher thrust requirements.
It is understood that the above description is intended to be illustrative, and not restrictive. It is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined in the appended claims. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms "including" and "in which" are used as the plain-English equivalents of the respective terms "comprising" and "wherein," respectively.

We claim:
1 - A propulsion system 100 for a marine vessel comprising:
a pod 102 housing a first shaft 104 in a substantially horizontal position;
a second shaft 112 in a substantially vertical position, the second shaft 112 is connected to the first shaft 104 through a gearing arrangement 114; and
at least two motors such that at least one motor 118 selectively engages the first shaft 104 and at least one motor 118 selectively engages the second shaft 112.
2. The propulsion system 100 for a marine vessel as claimed in claim 1, wherein the first shaft 104 is a propeller shaft.
3. The propulsion system 100 for a marine vessel as claimed in claim 1, wherein the second shaft 112 is a pinion shaft.
4. The propulsion system 100 for a marine vessel as claimed in claim 1, wherein the gearing arrangement 114 is a bevel gear arrangement.
5. The propulsion system 100 for a marine vessel as claimed in claim 1, wherein each motor 118, 120 selectively engages the shaft 104, 112 through a clutch 122,124.
6. The propulsion system for a marine vessel as claimed in claim 1, wherein the propulsion system further comprises of a third shaft 116.

7. The propulsion system 100 for a marine vessel as claimed in claim 6, wherein the third shaft 116 is an intermediary shaft between the first shaft and the second shaft.
8. The propulsion system 100 for a marine vessel as claimed in claim 7, wherein the third shaft 116 transmits the motion of the second shaft 112 to the first shaft 104 through a bevel gear 114a and a parallel gear 114b.