A fishing net preventing structure for a marine stern shaft

Abstract

The utility model discloses a kind of ship propeller shaft anti-fishing net structures, including propeller shaft, the rope cover of being sleeved on propeller shaft, the propeller of being installed on propeller shaft and being located the rear end of rope cover, and the net cutter of being installed on rope cover, it is characterized by: the rope cover is designed as the front section and rear section of being connected, the front section is the reducing section of gradually reducing diameter, rear section is equal diameter section, and the outer diameter of equal diameter section is not less than the outer diameter of propeller boss, one end of multiple the net cutter is respectively fixed in the circumferential surface of equal diameter section, another end is axially across the gap between equal diameter section and boss until boss outer wall top;The tail end of the equal diameter section is also provided with first sealing cover, and the front end of propeller boss is also provided with second sealing cover, and first sealing cover and second sealing cover are staggered and matched to form the labyrinth seal of anti-fishing net. The structure can effectively play a role to the protection of propeller shaft, realize zero leakage. In addition, the structure is simple, convenient for optimizing modification to existing ship.

Description

Technical Field

[0001] This utility model relates to stern shaft protection technology, and more particularly to a ship stern shaft anti-fishing net structure. Background Technology

[0002] Traditional anti-rope guards often have an axial gap of 8–18 mm between themselves and the propeller hub. Under the centripetal force generated by the rotating propeller, fishing nets can easily enter the guard through this gap and become entangled in the stern shaft seal. Statistics show that approximately 50% of emergency dry-docking repairs are caused by fishing net entanglement. Entanglement can lead to anything from minor lubricant emulsification to severe lubricant leakage, polluting the ocean, or seawater leaking into the lubricant system, causing the sealing rings to burn out, necessitating an emergency dry-docking.

[0003] At the same time, countries around the world attach great importance to marine environmental pollution. Once lubricating oil leaks and pollute the ocean, they will face huge fines. For example, the IMO's International Convention for the Prevention of Pollution from Ships (MARPOL) has stricter penalties for oil spills, and the Port State Control (PSC) considers stern shaft leaks as a depositable defect (Item 30).

[0004] like Figure 1 Currently, a common method for preventing fishing net entanglement involves welding multiple net-cutting blades 2 to the circumferential surface of the stern of the rope guard 1. While this design can cut the fishing net to some extent using the blades 2, the rope guard 1 is a funnel shape with a diameter that gradually decreases from front to back. Therefore, the net-cutting blades 2 on its circumferential surface are all angled towards the axis, resulting in a certain gap 5 between the tip of the blades 2 and the tip of the propeller hub 4 of the propeller 3. This gap 5, which cannot be effectively reduced, still allows the fishing net to easily enter the gap 5 without being cut. Therefore, there is an urgent need for a stern shaft protection design that can both prevent fishing net entanglement and achieve zero leakage, in order to avoid dry-docking maintenance and hefty fines caused by fishing net entanglement. Utility Model Content

[0005] To address the aforementioned problems in the prior art, this utility model provides a ship stern shaft anti-fishing net structure that can reduce the gap and effectively prevent fishing nets from entering the stern shaft.

[0006] A ship stern shaft anti-fishing net structure includes a stern shaft, an anti-rope cover sleeved on the stern shaft, a propeller mounted on the stern shaft and located at the rear end of the anti-rope cover, and net cutters mounted on the anti-rope cover. The anti-rope cover is characterized by: a front section and a rear section connected together; the front section is a variable diameter section with a gradually decreasing diameter, and the rear section is a constant diameter section, with the outer diameter of the constant diameter section not less than the outer diameter of the propeller hub; one end of each of the net cutters is fixed to the circumferential surface of the constant diameter section, and the other end axially crosses the gap between the constant diameter section and the propeller hub to the top of the outer wall of the propeller hub; a first sealing cover is also provided at the rear end of the constant diameter section, and a second sealing cover is also provided at the front end of the propeller hub, with the first and second sealing covers interlocking to form a labyrinth seal for the anti-fishing net.

[0007] The first sealing cover includes a first annular plate extending radially inward from the tail end of a section of equal diameter, and a first cylinder extending axially forward from the inner edge of the first annular plate; the second sealing cover includes a second cylinder extending axially forward from the front end of the propeller hub, a second annular plate extending radially outward from the front end of the second cylinder, and a third cylinder extending axially backward from the outer edge of the second annular plate; the inner diameter of the first cylinder is larger than the outer diameter of the second cylinder, the front end of the second cylinder extends beyond the front end of the first cylinder, and the inner diameter of the third cylinder is larger than the outer diameter of the first cylinder, such that the first cylinder and the third cylinder respectively extend into the three-sided enclosure structure of the second sealing cover and the first sealing cover.

[0008] The gap is controlled to be no more than 3mm.

[0009] The outer diameter of the constant diameter section is 3-5 mm larger than the outer diameter of the propeller hub.

[0010] This invention discloses a ship stern shaft anti-fishing net structure. By designing the anti-rope cover in two sections, with the rear section being of equal diameter, the net cutter can be installed axially. This allows the net cutter to cover the gap between the anti-rope cover and the propeller hub, extending to above the outer edge of the propeller hub, forming the first layer of protection. Simultaneously, it effectively reduces the gap, achieving a second layer of protection. Furthermore, intersecting L-shaped labyrinth seals are installed at the tail end of the equal-diameter section and the front end of the propeller hub. Even if fishing nets enter the gap, the labyrinth seal provides a third layer of protection, preventing them from entering the stern shaft, thus achieving effective protection and zero leakage. In addition, this structure is simple and facilitates optimization and modification of existing vessels. Attached Figure Description

[0011] Figure 1 This is a structural diagram of an existing rope guard and wire cutter.

[0012] Figure 2 This is a schematic diagram of the anti-fishing net structure of this utility model;

[0013] Figure 3 This is a cross-sectional schematic diagram of the anti-fishing net structure of this utility model;

[0014] Figure 4 yes Figure 3 An enlarged schematic diagram of the labyrinth seal. Detailed Implementation

[0015] The following is a further description of a ship stern shaft anti-fishing net structure according to this utility model.

[0016] The ship stern shaft anti-fishing net structure of this utility model is as follows: Figure 2-3 As shown, it is similar to existing technology in that it also includes a stern shaft 6, a rope guard 1 sleeved on the stern shaft 6, a propeller 3 mounted on the stern shaft 6 and located at the rear end of the rope guard 1, and multiple wire cutters 2 mounted on the rope guard 1. The difference is that the rope guard 1 is designed as a connected front and rear section. The front section is a variable diameter section 11 with a gradually decreasing diameter, and the rear section is a constant diameter section 12. The outer diameter of the constant diameter section 12 can be the same as the rear end of the variable diameter section 11, but not smaller than the outer diameter of the propeller hub 4 of the propeller 3. Preferably, the outer diameter of the constant diameter section 12 is 3-5 mm larger than the outer diameter of the propeller hub 3. Thus, one end of each of the 3-8 wire cutters 2 is fixed to the circumferential surface of the constant diameter section 12, and the other end axially crosses the gap between the constant diameter section 12 and the propeller hub 4 until it reaches above the outer wall of the propeller hub 4. Since the axial installation of the wire cutter 2 does not affect the gap 5 between the rope guard 1 and the paddle hub 4, the gap 5 can be reduced to the maximum extent. Through repeated design and testing, it can be controlled to be no more than 3mm.

[0017] Furthermore, a first sealing cover 7 is provided at the tail end of the equal diameter section 12, and a second sealing cover 8 is provided at the front end of the propeller hub 4. The first sealing cover 7 and the second sealing cover 8 are interlocked to form a labyrinth seal for preventing fishing nets.

[0018] Please combine Figure 4As shown, through multiple actual tests, the following structure was found to be the most effective at preventing fishing nets in the labyrinth seal. Specifically, the first sealing cover 7 comprises a first annular plate 71 extending radially inward from the tail end of the equal-diameter section 12, and a first cylinder 72 extending axially forward from the inner edge of the first annular plate 71, forming an L-shape. The second sealing cover 8 comprises a second cylinder 81 extending axially forward from the front end of the propeller hub 4, a second annular plate 82 extending radially outward from the front end of the second cylinder 81, and a third cylinder 83 extending axially backward from the outer edge of the second annular plate 82, with the second annular plate 82 and the third cylinder 83 forming corresponding inverted L-shapes. The first cylinder 7... The inner diameter of cylinder 2 is greater than the outer diameter of cylinder 81, the inner diameter of cylinder 81 is greater than the outer diameter of stern shaft 6, the front end of cylinder 81 extends beyond the front end of cylinder 72, and the inner diameter of cylinder 83 is greater than the outer diameter of cylinder 72, so that cylinder 72 extends into the three-sided enclosing structure formed by cylinder 81, second annular plate 82 and cylinder 83, while cylinder 83 also extends into the three-sided enclosing structure formed by equal diameter section 12, first annular plate 71 and cylinder 72, thereby forming a labyrinth seal with two L-shaped interlocking parts.

[0019] The anti-fishing net structure of this utility model employs three layers of protection from the outside in: a net-cutting blade 2 that covers the axial gap 5, a reduced gap 5, and a labyrinth seal. These three layers effectively protect the stern shaft 6, achieving zero leakage. Actual trials have shown excellent results. Furthermore, due to its simple structure and ease of manufacture, it is convenient for retrofitting existing vessels. Only a portion of the rear section of the original anti-rope cover 1 needs to be cut off, and the corresponding equal-diameter section 12, labyrinth seal, and net-cutting blade 2 need to be welded on. It is easy to process, the installation accuracy is easy to control, and the cost increase is limited, making it economical and practical.

[0020] However, those skilled in the art should recognize that the above embodiments are only used to illustrate the present utility model and are not intended to limit the present utility model. Any changes or modifications to the above embodiments within the scope of the essential spirit of the present utility model will fall within the scope of the claims of the present utility model.

Claims

1. A ship stern shaft anti-fishing net structure, comprising a stern shaft, a rope-proof cover sleeved on the stern shaft, a propeller mounted on the stern shaft and located at the rear end of the rope-proof cover, and a net-cutting knife mounted on the rope-proof cover, characterized in that: The anti-rope cover is designed as a connected front section and a rear section. The front section is a variable diameter section with a gradually decreasing diameter, and the rear section is a constant diameter section. The outer diameter of the constant diameter section is not less than the outer diameter of the propeller hub. One end of each of the multiple net-cutting blades is fixed to the circumferential surface of the constant diameter section, and the other end axially crosses the gap between the constant diameter section and the propeller hub and extends to the top of the outer wall of the propeller hub. The tail end of the constant diameter section is also provided with a first sealing cover, and the front end of the propeller hub is also provided with a second sealing cover. The first sealing cover and the second sealing cover are staggered to form a labyrinth seal against the fishing net.

2. The anti-fishing net structure for a ship's stern shaft as described in claim 1, characterized in that: The first sealing cover includes a first annular plate extending radially inward from the tail end of a section of equal diameter, and a first cylinder extending axially forward from the inner edge of the first annular plate; the second sealing cover includes a second cylinder extending axially forward from the front end of the propeller hub, a second annular plate extending radially outward from the front end of the second cylinder, and a third cylinder extending axially backward from the outer edge of the second annular plate; the inner diameter of the first cylinder is larger than the outer diameter of the second cylinder, the front end of the second cylinder extends beyond the front end of the first cylinder, and the inner diameter of the third cylinder is larger than the outer diameter of the first cylinder, such that the first cylinder and the third cylinder respectively extend into the three-sided enclosure structure of the second sealing cover and the first sealing cover.

3. The anti-fishing net structure for a ship's stern shaft as described in claim 1, characterized in that: The gap is controlled to be no more than 3mm.

4. The anti-fishing net structure for a ship's stern shaft as described in claim 1, characterized in that: The outer diameter of the constant diameter section is 3-5 mm larger than the outer diameter of the propeller hub.

Images