Method for controlling a propeller drive assembly

Abstract

A method of controlling a propeller drive assembly attachable to a hull of a marine vessel, said propeller drive assembly comprising a propeller drive unit and a housing for attachment to a hull of the marine vessel on an inside of the hull. The housing defines an inner space and an opening through which at least a portion of the propeller drive unit is movable into and out of the inner space. The propeller drive assembly comprises a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is adapted to move the propeller drive unit between a stowed position and a deployed position. The method comprises a first step comprising triggering rotation of each propeller shaft such that the respective propeller shaft reaches a respective predetermined rotational position and stops at the respective predetermined rotational position, and a second step comprising triggering movement of the suspension mechanism from the deployed position to the stowed position. Each propeller shaft is provided with a respective propeller, and wherein the respective predetermined position of each propeller shaft is such that each respective propeller is at least partly confined within the inner space of the housing when the propeller drive unit is in the stowed position.

1 . A method of controlling a propeller drive assembly attachable to a hull of a marine vessel, said propeller drive assembly comprising a propeller drive unit carrying at least one propeller shaft for carrying a respective propeller for rotation about a first rotational axis,
 wherein the propeller drive assembly comprises a housing for attachment to a hull of the marine vessel on an inside of the hull such that the housing surrounds a first opening of the hull and seals to the hull, wherein the housing defines an inner space and wherein the housing is provided with a second opening through which at least a portion of the propeller drive unit is movable into and out of the inner space, and   wherein the propeller drive assembly comprises a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is movable along a first longitudinal axis of the housing between a stowed position, in which the propeller drive unit is positioned inside the inner space of the housing, and a deployed position in which at least a portion of the propeller drive unit protrudes outside the housing through the second opening,   wherein the method comprises:   a first step comprising triggering rotation of each propeller shaft such that the respective propeller shaft reaches a respective predetermined rotational position and stops at the respective predetermined rotational position, and   a second step comprising triggering movement of the suspension mechanism from the deployed position to the stowed position, wherein each propeller shaft is provided with a respective propeller, and wherein the respective predetermined position of each propeller shaft is such that each respective propeller is at least partly, such as fully, confined within the inner space of the housing when the propeller drive unit is in the stowed position.   
     
     
         2 . A method according to  claim 1 , wherein the propeller drive assembly further comprises at least one electric drive means configured to control a rotational position of each propeller shaft about said first rotational axis and wherein the first step comprises triggering the electric drive means to perform the rotation(s) of the respective propeller shaft(s) to the respective predetermined rotational position(s). 
     
     
         3 . A method according to  claim 1 , wherein said propeller drive unit comprises two propeller shafts each carrying one propeller wherein the propellers are rotatable relatively each other about the first rotational axis such that that a joint projected driving area provided by the propellers in a plane perpendicular to the first rotational axis varies in response to a relative rotation between a maximum joint projected driving area and a minimum joint projected driving area together defining a joint projected driving area range, and wherein the predetermined positions are such that the joint projected driving area when the propeller shafts are in their respective predetermined positions is within a lower 10% of the joint projected driving area range or within a lower 5% of the joint projected driving area range, or is the minimum joint projected driving area. 
     
     
         4 . A method according to  claim 3 , wherein the propellers have a same number of blades. 
     
     
         5 . A method according to  claim 1 , wherein said second step is performed after, and/or simultaneously with said first step. 
     
     
         6 . A method according to  claim 1 , wherein said propeller drive unit comprises two propeller shafts each carrying one propeller wherein the propellers are rotatable relatively each other about the first rotational axis such that that a joint projected driving area provided by the propellers in a plane perpendicular to the first rotational axis varies in response to a relative rotation between a maximum joint projected driving area and a minimum joint projected driving area together defining a joint projected driving area range, and wherein the predetermined positions are such that the joint projected driving area when the propeller shafts are in their respective predetermined positions is within a higher 20% of the joint projected driving area range or within a higher 10% of the joint projected driving area range, or is the maximum joint projected driving area. 
     
     
         7 . A control unit for controlling a propeller drive assembly attachable to a hull of a marine vessel, said control unit being configured to perform the method according to  claim 1 . 
     
     
         8 . A propeller drive system comprising a propeller drive assembly and a control unit, said propeller drive assembly comprising a propeller drive unit carrying at least one propeller shaft for carrying a respective propeller for rotation about a first rotational axis, said propeller drive assembly further comprising a housing for attachment to a hull of the marine vessel on an inside of the hull such that the housing surrounds a first opening of the hull and seals to the hull, wherein the housing defines an inner space and wherein the housing is provided with a second opening through which at least a portion of the propeller drive unit is movable into and out of the inner space, and
 wherein the propeller drive assembly comprises a suspension mechanism attached to the housing and configured to suspend the propeller drive unit, wherein the suspension mechanism is movable along a first longitudinal axis of the housing between a stowed position, in which the propeller drive unit is positioned inside the inner space of the housing, and a deployed position in which at least a portion of the propeller drive unit protrudes outside the housing through the second opening,   wherein each propeller shaft is provided with a respective propeller, and,   wherein the control unit is configured to trigger rotation of each propeller shaft such that the respective propeller shaft reaches a respective predetermined rotational position and stops at the respective predetermined rotational position,   wherein the control unit is further configured to trigger movement of the suspension mechanism from the deployed position to the stowed position, and   wherein the respective predetermined position of each propeller shaft is such that each respective propeller is at least partly, such as fully, confined within the inner space of the housing when the propeller drive unit is in the stowed position.   
     
     
         9 . A propeller drive system according to  claim 8 , further comprising at least one electric drive means configured to control a rotational position of each propeller shaft about said first rotational axis, wherein the control unit is configured to trigger the electric drive means to perform the rotation(s) of the propeller shaft(s) to the respective predetermined rotational position(s). 
     
     
         10 . A propeller drive system according to  claim 8 , wherein said propeller drive unit comprises two propeller shafts each carrying one propeller, wherein the propellers are rotatable relatively each other about the first rotational axis such that that a joint projected driving area provided by the propellers in a plane perpendicular to the first rotational axis varies in response to a relative rotation between a maximum joint projected driving area and a minimum joint projected driving area together defining a joint projected driving area range, and wherein the predetermined positions are such that the joint projected driving area when the propeller shafts are in their respective predetermined positions is within a lower 10% of the joint projected driving area range or within a lower 5% of the joint projected driving area range, or is the minimum joint projected driving area. 
     
     
         11 . A propeller drive system according to  claim 8 , wherein the control unit is configured to trigger movement of the suspension mechanism from the deployed position to the stowed position after, and/or simultaneously with said triggering of rotation of each propeller shaft such that the respective propeller shaft reaches a respective predetermined rotational position and stops at the respective predetermined rotational position. 
     
     
         12 . A marine vessel comprising a propeller drive system according to  claim 8 . 
     
     
         13 . A computer program comprising program code means for performing the method of  claim 1  when said program is run on a control unit.