Retractable thruster, a swimming vessel and a method for retracting and ejecting a propeller of the retractable thruster

Abstract

A retractable thruster for a swimming vessel is provided, wherein the retractable thruster includes a propeller and a lifting and lowering arrangement which is configured to vertically move the propeller between a retracted position and an ejected position. In the retracted position the propeller is substantially inside a bottom well of the swimming vessel and in the ejected position the propeller is substantially outside the bottom well. The retractable thruster includes a water-permeable protective element configured to be located inside the bottom well above the propeller and configured to vertically move with the propeller. In the ejected position the water-permeable protective element is configured to substantially prevent loose ice from drifting inside the bottom well through the water-permeable protective element and when the propeller is moved from the retracted position to the ejected position, the water-permeable protective element is configured to push ice out of the bottom well.

1 . A retractable thruster for a swimming vessel, the retractable thruster comprising:
 a propeller;   a lifting and lowering arrangement configured to move the propeller in the vertical direction between a retracted position and an ejected position, wherein in the retracted position the propeller is substantially inside a bottom well of the swimming vessel and in the ejected position the propeller is substantially outside the bottom well; and   a water-permeable protective element configured to be located inside the bottom well above the propeller and configured to vertically move with the propeller, wherein in the ejected position the water-permeable protective element is configured to substantially prevent loose ice from passing through the water-permeable protective element to the inside of the bottom well and when the propeller is moved from the retracted position to the ejected position, the water-permeable protective element is configured to push ice out of the bottom well.   
     
     
         2 . The retractable thruster according to  claim 1 , wherein in the ejected position, the water-permeable protective element is in proximity to a lower end of the bottom well. 
     
     
         3 . The retractable thruster according to  claim 1 , wherein in the ejected position, the water-permeable protective element substantially covers a waterside opening of the bottom well. 
     
     
         4 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element comprises at least one perforated plate. 
     
     
         5 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element comprises mesh. 
     
     
         6 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element comprises a combination of a perforated plate and mesh. 
     
     
         7 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element comprises a combination of a pipe structure and mesh. 
     
     
         8 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element comprises a combination of a support structure and mesh. 
     
     
         9 . The retractable thruster according to  claim 1 , wherein the lifting and lowering arrangement comprises:
 a stationary support structure comprising a guiding element and a lead-through hole;   a non-pivoting tube configured through the lead-through hole, wherein a lower end of the non-pivoting tube is configured to be connected to the propeller enabling to slidably connect the propeller to the guiding element and enabling the propeller to be moved vertically; and   an actuator arrangement configured to be connected between the non-pivoting tube and the bottom well in such a way that when the propeller is moved to the retracted position, the actuator arrangement is configured to lift the propeller substantially inside the bottom well by sliding the non-pivoting tube inside the guiding element and correspondingly when the propeller is moved to the ejected position, the actuator arrangement is configured to lower the propeller substantially outside the bottom well by sliding the non-pivoting tube inside the guiding element.   
     
     
         10 . The retractable thruster according to  claim 9 , wherein the lifting and lowering arrangement comprises at least two hydraulic cylinders. 
     
     
         11 . The retractable thruster according to  claim 9 , wherein the actuator arrangement comprises at least two hydraulic cylinders. 
     
     
         12 . The retractable thruster according to  claim 10 , wherein each hydraulic cylinder comprises a piston which is hollow allowing a hydraulic fluid connection line connected to the at least two hydraulic cylinders to be placed to a location inside the bottom well, which is out of the reach of water. 
     
     
         13 . The retractable thruster according to  claim 10 , wherein the lifting and lowering arrangement comprises:
 a moving support structure fixed to the non-pivoting tube, wherein a piston of each hydraulic cylinder is configured to be connected to the non-pivoting tube via the moving support structure and cylinder housings of the hydraulic cylinders are configured to be connected to the bottom well.   
     
     
         14 . The retractable thruster according to  claim 1 , further comprising at least one stopper configured to stop movement of the propeller to the ejected position. 
     
     
         15 . The retractable thruster according to  claim 1 , wherein the water-permeable protective element is configured to prevent jamming of the lifting and lowering arrangement caused by freezing of loose ice. 
     
     
         16 . The retractable thruster according to  claim 1 , wherein the propeller is configured to be pivotable for 360 degrees around a vertical axis of the retractable thruster. 
     
     
         17 . The retractable thruster according to  claim 1 , wherein the retractable thruster is an azimuth thruster. 
     
     
         18 . A method for retracting and ejecting a propeller of a retractable thruster for a swimming vessel, wherein the method comprises:
 connecting a water-permeable protective element to the retractable thruster above the propeller inside a bottom well of the swimming vessel;   preventing, with the water-permeable protective element, loose ice from passing through the water-permeable protective element to the inside of the bottom well when the propeller is in an ejected position; and   pushing, with the water-permeable protective element, ice out of the bottom well when the propeller is moved from a retracted position to the ejected position.   
     
     
         19 . A swimming vessel comprising:
 a bottom well;   a retractable thruster according to  claim 1 ; and   a power pack for supplying power for moving a propeller of the retractable thruster in the vertical direction.