Improved cap rudder, and boat

Abstract

An improved cap rudder and a vessel. The cap rudder (1) comprises a rudder shaft (10) and a cap plate (11) fixed to a lower end (104) of the rudder shaft. A rudder shaft sleeve (12) is positioned axially between the cap plate (11) and an upper end (101) of the rudder shaft. In a radial direction, the rudder shaft (10) is supported within the rudder shaft sleeve (12) via a first bearing arrangement. A pair of coaxially disposed transverse shafts (13) are arranged with their axis perpendicular to the axis of the rudder shaft (10). One end of the transverse shafts (13) is fixed to an outer wall of the rudder shaft sleeve (12), and the other end is a bearing connection end (132) connected to a second bearing (133). The transverse shafts and the rudder shaft sleeve form a cruciform structure, and the rudder shaft sleeve is rotatable about the transverse shafts, thereby changing the rudder angle of the cap rudder to enable adjustment and control of the longitudinal trim of the hull.

Description

TECHNICAL FIELD

[0001] The present invention relates to an improved marine cap rudder structure and to a vessel constructed using such an improved cap rudder, and more specifically, to an improved cap rudder and a vessel.BACKGROUND ART

[0002] Chinese Patent Application No. CN109050862A, entitled "Cap Rudder and Vessel," discloses a cap rudder structure. Compared to traditional plate rudders or nozzle rudders, the cap rudder offers the advantages of lower resistance and higher steering efficiency, and has demonstrated significant energy-saving performance over more than five years of practical vessel operation. However, there remains potential for further enhancing its energy-saving performance. According to general principles of hull design and navigation, the attitude offering minimum resistance during navigation is the "even keel" condition, i.e., a condition of zero trim (neither head trim nor stern trim). In practice, however, a vessel's longitudinal trim often changes due to factors such as varying speeds or uneven loading. For example, assuming other conditions remain constant, an increase in speed typically causes a change in attitude manifested as stern trim (bow-up), which generally increases navigation resistance and causes a sharp increase in energy consumption. Similarly, changes in trim following cargo loading or unloading inevitably lead to increased navigation resistance or reduced propulsion efficiency. The cap rudder has unique characteristics: like a plate rudder, it has a certain projected area on the centreline plane to enable steering (turning port or starboard); however, it also has a substantially larger projected area on the horizontal plane than a plate rudder. Furthermore, it is longitudinally positioned at the stem, at a considerable distance from the hull's longitudinal metacentre. Consequently, utilizing the cap rudder to actively control the hull's longitudinal trim in real-time can result in substantial energy savings. Additionally, trim changes during navigation, particularly stern trim, cause the elevated bow to obstruct the helmsman's forward view, creating a safety hazard.TECHNICAL PROBLEM

[0003] A prior art search reveals solutions capable of actively controlling hull trim during navigation under otherwise constant conditions. For instance, Chinese Utility Model CN219215352U, "A Biomimetic Robotic Fish Device Based on Dual-Axis Steering Actuator Control," employs two sets of steering actuators to separately control a caudal fin for turning to port and starboard, and pectoral fins for diving and surfacing, resulting in a relatively complex structure. Patent CN100348459C, "Cruciform Anti-Pitching Rudder," employs a cruciform plate rudder arrangement which effectively resists pitching but cannot actively control trim. On the other hand, Chinese Patent Application CN111792015A, "Rudder System Rotatable About Dual Axes and Vessel," discloses a system for a plate rudder that, in addition to the conventional vertical rudder shaft for horizontal rotation, includes a shaft for vertical rotation. Its design purpose, however, is to reduce the resistance of the plate rudder during straight-line navigation, and it is inherently incapable of altering the longitudinal trim of a vessel underway.TECHNICAL SOLUTION

[0004] The primary object of the present invention is to provide an improved cap rudder capable of adjusting the longitudinal trim of a vessel during navigation, thereby reducing energy consumption and improving the helmsman's field of view.

[0005] Another object of the present invention is to provide a vessel constructed using the improved cap rudder.

[0006] To achieve the primary object, the improved cap rudder provided by the present invention comprises a vertically oriented rudder shaft and a cap plate fixed to a lower end of the rudder shaft, an upper end of the rudder shaft constituting a connection end for connection to a tiller; and a rudder shaft sleeve. Axially, the rudder shaft sleeve is positioned between the cap plate and the connection end. Radially, the rudder shaft is disposed within the rudder shaft sleeve. The rudder shaft is supported within the rudder shaft sleeve by a first bearing arrangement, allowing the rudder shaft to rotate relative to the rudder shaft sleeve about its own axis. The cap rudder further comprises a pair of coaxially disposed transverse shafts, the axis of which is perpendicular to the axis of the rudder shaft. One end of the transverse shafts is fixed to an outer wall of the rudder shaft sleeve, and the other end constitutes a bearing connection end for connection to a second bearing.

[0007] In a further embodiment, the first bearing arrangement comprises a pair of bearings, specifically a ball bearing located at an upper portion of the rudder shaft sleeve and a copper bush bearing located at a lower portion of the rudder shaft sleeve. For large vessels, as the lower bearing is subjected to significant loads, the use of a copper bush bearing can effectively extend the service life of the bearing.

[0008] In another embodiment, the first bearing arrangement comprises a pair of bearings, specifically a ball bearing located at the upper portion of the rudder shaft sleeve and a ball bearing located at the lower portion. For small vessels, the load on the lower bearing typically does not exceed the compressive limit of a ball bearing. Therefore, a pair of ball bearings may be used, or a dual-bearing configuration may be adopted for the lower bearing to enhance radial load capacity. This solution offers the advantage of relatively lower cost.

[0009] In a still further embodiment, the rudder shaft features a radially recessed annular retaining groove. A snap ring is disposed within the annular retaining groove for axially constraining an inner ring of the upper ball bearing. A snap ring pressure plate and a sleeve cover plate are sequentially arranged above the snap ring in the axial direction. The snap ring pressure plate is fixedly connected to the snap ring via fasteners in the axial direction, and the sleeve cover plate is fixedly connected to the rudder shaft sleeve via fasteners in the axial direction. An axial gap is provided between the snap ring pressure plate and the sleeve cover plate. This arrangement axially constrains the rudder shaft of the cap rudder. Specifically, the snap ring prevents downward movement of the rudder shaft relative to the sleeve. Upward movement is prevented by the weight of the cap plate and rudder shaft, and is further constrained by the sleeve cover plate should any incidental upward displacement occur.

[0010] In yet another embodiment, an oil seal and an oil seal cover plate are provided at a lower end of the rudder shaft sleeve. This effectively prevents water from entering the internal cavity of the rudder shaft sleeve from below, thereby protecting the first bearing arrangement from corrosion.

[0011] To achieve the second object, the present invention provides a vessel comprising a hull and a cap rudder, wherein the cap rudder is the improved cap rudder according to any of the preceding solutions. The upper end of the rudder shaft is connected to a steering actuator via the tiller. The connection ends of the transverse shafts are connected to second bearings, the bearing seats of which are fixed to the hull. The pair of transverse shafts is arranged symmetrically with respect to the centreline plane of the hull. A second steering actuator is provided for driving rotation of the transverse shafts about their own axis.

[0012] In a further embodiment, one end of the steering actuator is connected to the hull via a ball joint, and the other end is connected to the tiller via a ball joint. This ensures that the steering actuator can effect steering smoothly regardless of the angular position of the cap rudder about the transverse shafts.

[0013] In another embodiment, a hinge base plate is fixed to the outer wall of the rudder shaft sleeve. The hinge base plate is situated on the centreline plane and at the upper end of the rudder shaft sleeve. One end of the second steering actuator is hinged to the hull, and the other end is hinged to the hinge base plate.

[0014] In a still further embodiment, two second steering actuators are provided, arranged on opposing sides of the rudder shaft sleeve, configured to drive the rotation of the improved cap rudder about the transverse shaft axis in a push-pull manner.

[0015] In a further embodiment, a cylindrical rudder trunk is provided at the location where the improved cap rudder passes through the hull to prevent water from entering the hull interior. The lower end of the rudder trunk is fixed to the bottom plate of the hull, the upper end is open, and the rear end is provided with a water outlet for discharging water that has entered the rudder trunk to outside the hull. This solution effectively addresses the drainage of water entering at the penetration point of the rudder shaft sleeve through the hull bottom.ADVANTAGEOUS EFFECTS

[0016] As evident from the above solutions, the present invention utilizes a rudder shaft sleeve disposed externally to the rudder shaft. This retains the steering capability of a cap rudder (i.e., turning port or starboard when the rudder shaft rotates relative to the sleeve). Additionally, the provision of the pair of transverse shafts forms a cruciform structural arrangement with the rudder shaft sleeve. When the rudder shaft sleeve rotates about the axis of the transverse shafts, the cap plate undergoes a pitching motion relative to the hull-regardless of whether the rudder is amidships or at a rudder angle. This action is analogous to the pitching action of flaps relative to a main wing, thereby enabling adjustment and control of the vessel's longitudinal trim.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a front view of a first embodiment of the improved cap rudder; FIG. 2 is an enlarged view of area A in FIG. 1; FIG. 3 is a left side view of FIG. 1; FIG. 4 is a front view of a first embodiment of the vessel, also constituting a longitudinal sectional view of the vessel; FIG. 5 is a top view of FIG. 4, also constituting a plan view of the steering actuator compartment; FIG. 6 is a sectional view taken along line B-B in FIG. 5, also constituting a view looking toward the bow; FIG. 7 is a schematic view illustrating the structure of the rudder trunk; FIG. 8 is a schematic view showing the state of the cap rudder relative to the hull when the vessel is in a design draught condition; FIG. 9 is a schematic view showing the depressed state of the cap rudder relative to the hull when the vessel experiences stern trim; FIG. 10 is a schematic view showing the raised state of the cap rudder relative to the hull when the vessel experiences head trim; FIG. 11 is a table comparing actual vessel test data of a vessel equipped with a cap rudder versus the improved cap rudder. Reference Numerals:

[0018] Improved cap rudder 1; Rudder shaft 10; Rudder shaft upper end 101; Annular retaining groove 102; Frustoconical section 103; Rudder shaft lower end 104; Snap ring 105; Snap ring pressure plate 106; Cap plate 11; Rudder shaft sleeve 12; Cylinder body 121; Sleeve cover plate 122; Sleeve upper bearing seat 123; Ball bearing 124; Copper bush bearing 125; Sleeve lower bearing seat 126; Oil seal 127; Oil seal cover plate 128; Transverse shaft 13; Fixed end 131; Bearing connection end 132; Second bearing 133; Steering actuator 14; Tiller 141; Ball joint 142; Ball joint 143; Second steering actuator 15; Hinge base plate 151; Hinge 152; Hinge 153; Rudder trunk 16; Rudder trunk water outlet pipe 161; Hull bottom plate 171; Stern transom plate 172.

[0019] The invention is described in detail below with reference to embodiments and the accompanying drawings.DETAILED DESCRIPTION OF THE EMBODIMENTS First Embodiment of the Improved Cap Rudder

[0020] Referring to FIGS. 1 and 2, the improved cap rudder 1 comprises a rudder shaft 10 having a vertical axis, and a cap plate 11 fixed to a lower end 104 of the rudder shaft. An upper end 101 of the rudder shaft is a prismatic portion having a rectangular cross-section, constituting a connection end for fixed attachment to a tiller. The rudder shaft 10 features a radially recessed annular retaining groove 102 and a frustoconical section 103. Axially, the annular retaining groove 102 is located between the rudder shaft upper end 101 and the frustoconical section 103, with the smaller diameter end of the frustoconical section 103 adjacent to the annular retaining groove 102. A rudder shaft sleeve 12 is positioned axially between the rudder shaft upper end 101 and the cap plate 11. Radially, the rudder shaft 10 (having a smaller diameter) is situated inside the rudder shaft sleeve 12 (having a larger diameter). The rudder shaft 10 is supported within the rudder shaft sleeve 12 by a first bearing arrangement comprising a ball bearing 124 and a copper bush bearing 125, thereby allowing the rudder shaft 10 to rotate relative to the rudder shaft sleeve 12 about the axis of the rudder shaft 10.

[0021] The rudder shaft sleeve 12 comprises a cylinder body 121 with a relatively thin wall, and a sleeve upper bearing seat 123 and a sleeve lower bearing seat 126 with thicker walls fixed to the upper and lower ends thereof, respectively. The copper bush bearing 125 is disposed within the sleeve lower bearing seat 126 with a radial interference fit. An oil seal 127 and an oil seal cover plate 128 are provided at the lower end of the sleeve lower bearing seat 126. The ball bearing 124 is disposed within the sleeve upper bearing seat 123 with a radial interference fit. A snap ring 105 is installed in the annular retaining groove 102 to axially constrain the inner ring of the ball bearing 105. A snap ring pressure plate 106 is fixedly connected to the snap ring via circumferentially distributed fasteners. Consequently, when the rudder shaft 10 rotates relative to the rudder shaft sleeve 12, both the snap ring 105 and the snap ring pressure plate 106 rotate together with the rudder shaft 10. A sleeve cover plate 122 is fixed to the upper end surface of the sleeve upper bearing seat 123 via circumferentially distributed fasteners, with an axial gap maintained between the sleeve cover plate 122 and the snap ring pressure plate 106. The smaller diameter end of the frustoconical section 103 abuts the lower end surface of the sleeve upper bearing seat 123. Thus, in the axial direction, the snap ring 105 restricts downward movement of the rudder shaft 10 relative to the sleeve 12, while the weight of the rudder shaft 10 and cap plate 11, combined with the sleeve cover plate 122, restricts upward movement. During assembly, the rudder shaft 10 is inserted into the sleeve 12 from bottom to top; once in position, the snap ring, which is composed of three circumferentially arranged segments, is installed, followed by the snap ring pressure plate 106 secured with fasteners, and finally the sleeve cover plate 122 is fixed.

[0022] Referring to FIG. 3, a fixed end 131 of a pair of coaxially disposed transverse shafts 13 is fixed to the outer wall of the rudder shaft sleeve 12. In this embodiment, it is fixed to the outer wall of the sleeve lower bearing seat 126, which has higher strength. The other end constitutes a free end, specifically a bearing connection end 132 for connection to a second bearing.Second Embodiment of the Improved Cap Rudder

[0023] This embodiment differs from the previous one in that the copper bush bearing 125 is replaced by a ball bearing; that is, a ball bearing capable of supporting axial loads is employed.Other Embodiments of the Improved Cap Rudder

[0024] Clearly, the rudder shaft upper end 101 may adopt various keyed configurations for connection with the tiller. Additionally, triangular reinforcing gussets may be circumferentially arranged at the connection between the fixed end 131 of the transverse shaft 13 and the sleeve lower bearing seat.First Embodiment of the Vessel

[0025] Referring to FIG. 4, which illustrates the stern region of the vessel in longitudinal section, a hull bottom plate 171 and a stern transom plate 172 (parts of the hull) form two walls of a steering actuator compartment. The lower end of the rudder shaft sleeve 12 passes through an aperture in the hull bottom plate 171. The size of this aperture must accommodate the required design angle for the rotation of the rudder shaft sleeve 12 about the transverse shafts 13. The method for managing water ingress through this aperture is described below. A second bearing 133 is secured to the hull bottom plate 171 via its bearing seat. Alternatively, it may be secured to the vessel's bottom truss via a bracket or fixed to the hull structure in other configurations.

[0026] The middle portion of a tiller 141 is fixed to the rudder shaft upper end 101. Both ends of the tiller 141 are connected to steering actuators 14 via ball joints 143.

[0027] A hinge base plate 151 is fixed to the outer wall of the rudder shaft sleeve 12, located on the centreline plane at the upper end of the sleeve 12. One end of a second steering actuator 15 is hinged to the hull bottom plate 171 (or bottom truss) via a hinge 152, and the other end is hinged to the hinge base plate 151 via a hinge 153.

[0028] Referring to FIG. 4 and FIG. 6 (FIG. 6 being a section along B-B of FIG. 5, equivalent to a transverse section through the axis of the rudder shaft 10 in FIG. 4): when the second steering actuator 15 extends, the cap plate 11 rotates anticlockwise about the transverse shafts 13; when it retracts, the cap plate 11 rotates clockwise.

[0029] Referring to FIG. 5, this embodiment employs dual steering actuators 14 arranged centrally symmetrically about the axis of the rudder shaft 10. When the dual steering actuators 14 extend synchronously, the cap plate 11 rotates anticlockwise about the axis of the rudder shaft 10; when they retract synchronously, the cap plate rotates clockwise. The connection ends of the transverse shafts 13 are connected to second bearings 133. The pair of transverse shafts is arranged symmetrically relative to the hull's centreline plane, with their axis perpendicular to that of the rudder shaft 10. One end is fixed to the outer wall of the rudder shaft sleeve 12 via the fixed end 131, and the other is connected to the second bearing 133 via the bearing connection end 132.

[0030] Referring to FIG. 7, the rudder trunk 16 is a cylindrical shell. Its lower end is fixed in a watertight manner to the hull bottom plate 171, its upper end is open, and its rear end features a water outlet for discharging water accumulated in the rudder trunk to outside the hull. The aperture in the hull bottom plate 171, through which the rudder shaft sleeve 12 passes, is enclosed within the rudder trunk 16. The vertical height of the rudder trunk should exceed the maximum stern draught line so that water entering through the aperture does not overflow the opening. A rudder trunk water outlet pipe 161 is provided in the middle of the rudder trunk, connecting the rear water outlet to the exterior of the stern transom plate 172. A watertight rubber bellows may optionally be arranged between the upper open end of the rudder trunk 16 and the rudder shaft sleeve 12. Thus, water entering the rudder trunk 16 discharges through the outlet pipe 161 without spilling into the hull.Second Embodiment of the Vessel

[0031] This embodiment differs from the previous one in that two second steering actuators 15 are used. As seen in FIG. 4, a second steering actuator 15 is also provided on the left side of the rudder shaft sleeve 12. The two second steering actuators 15 are symmetrical relative to the sleeve 12. To control the pitching motion of the cap plate 11, the two second steering actuators 15 drive the improved cap rudder 1 to rotate about the transverse shafts 13 in a push-pull manner.Controlling Vessel Trim with the Improved Cap Rudder

[0032] Referring to FIG. 8, in normal navigation without trim, the second steering actuator 15 holds the cap plate 11 in a substantially horizontal orientation. Even if water flow generates some vertical force component on the cap plate 11, it will not affect the vessel's trim, allowing the vessel to navigate at the design minimum resistance (even keel).

[0033] Referring to FIG. 9, when trim changes due to speed increases or uneven longitudinal cargo distribution-specifically stern trim (bow-up)-the second steering actuator 15 is extended. This rotates the cap plate 11 anticlockwise about the transverse shafts 13 by a given rudder angle. The resulting upward hydrodynamic force component on the cap plate creates a moment causing the hull to rotate clockwise about the longitudinal metacentre, thereby reducing the trim or restoring an even keel condition.

[0034] Referring to FIG. 10, similarly, if head trim (bow-down) occurs, the second steering actuator 15 is retracted. This rotates the cap plate 11 clockwise about the transverse shafts 13 by a given rudder angle. The resulting downward hydrodynamic force component on the cap plate 11 causes the hull to rotate anticlockwise about the longitudinal metacentre, reducing the longitudinal trim or restoring an even keel condition.

[0035] FIG. 11 presents a comparison table of measured data using a cap rudder versus the improved cap rudder on the same glass-reinforced plastic (GRP) high-speed diesel vessel, under unloaded and 1-ton load conditions, at a rated engine speed of 2300 rpm. Key parameters: Hull L×W×H = 13.8m × 2.7m × 1.25m; Engine: WP13FY1000-23E200; Gearbox: HCQ501; Propeller diameter: 0.84m; Pitch: 1130mm.

[0036] The cap plate length is 1.35m. The cap plate is a semi-circular arc plate with a diameter 1.1 times the propeller diameter.INDUSTRIAL APPLICABILITY

[0037] The actual vessel test data as shown in the table in FIG. 11, regarding speed: in the unloaded condition, the improved cap rudder increased speed by 2.5% over the cap rudder; under a 1-ton load, speed increased by 5%. Regarding stern trim adjustment: in the unloaded condition, stern trim was reduced by 13 degrees; under a 1-ton load, stern trim was reduced by 9.2 degrees.

Claims

1. An improved cap rudder, comprising a vertically oriented rudder shaft and a cap plate fixed to a lower end of the rudder shaft, an upper end of the rudder shaft constituting a connection end for connection to a tiller; characterised by further comprising: a rudder shaft sleeve, wherein axially, the rudder shaft sleeve is positioned between the cap plate and the connection end, and radially, the rudder shaft is disposed within the rudder shaft sleeve, the rudder shaft being supported within the rudder shaft sleeve by a first bearing arrangement such that the rudder shaft is rotatable relative to the rudder shaft sleeve about an axis of the rudder shaft; and a pair of coaxially disposed transverse shafts, wherein an axis of the transverse shafts is perpendicular to the axis of the rudder shaft, one end of the transverse shafts is fixed to an outer wall of the rudder shaft sleeve, and the other end is a bearing connection end for connection to a second bearing.

2. The improved cap rudder according to claim 1, wherein the first bearing arrangement comprises a pair of bearings, specifically a ball bearing located at an upper portion of the rudder shaft sleeve and a copper bush bearing located at a lower portion of the rudder shaft sleeve.

3. The improved cap rudder according to claim 1, wherein the first bearing arrangement comprises a pair of bearings, specifically a ball bearing located at an upper portion of the rudder shaft sleeve and a ball bearing located at a lower portion thereof.

4. The improved cap rudder according to claim 2 or 3, wherein the rudder shaft comprises a radially recessed annular retaining groove, and a snap ring for axially constraining an inner ring of the ball bearing at the upper portion of the rudder shaft sleeve is disposed within the annular retaining groove; a snap ring pressure plate and a sleeve cover plate are sequentially arranged above the snap ring in the axial direction, wherein the snap ring pressure plate is fixedly connected to the snap ring via fasteners in the axial direction, and the sleeve cover plate is fixedly connected to the rudder shaft sleeve via fasteners in the axial direction; and an axial gap exists between the snap ring pressure plate and the sleeve cover plate.

5. The improved cap rudder according to any one of claims 1 to 3, wherein an oil seal and an oil seal cover plate are provided at a lower end of the rudder shaft sleeve.

6. A vessel, comprising a hull and a cap rudder, the cap rudder being the improved cap rudder according to any one of claims 1 to 5, the upper end of the rudder shaft being connected to a steering actuator via the tiller; characterised in that: the bearing connection ends of the transverse shafts are connected to second bearings, bearing seats of the second bearings are fixed to the hull, and the pair of transverse shafts is arranged symmetrically with respect to a centreline plane; and a second steering actuator is provided for driving the transverse shafts to rotate about their own axis.

7. The vessel according to claim 6, wherein one end of the steering actuator is connected to the hull via a ball joint, and the other end of the steering actuator is connected to the tiller via a ball joint.

8. The vessel according to claim 6, wherein a hinge base plate is fixed to the outer wall of the rudder shaft sleeve, the hinge base plate being located on the centreline plane and at an upper end of the rudder shaft sleeve; one end of the second steering actuator is hinged to the hull, and the other end of the second steering actuator is hinged to the hinge base plate.

9. The vessel according to claim 8, wherein two second steering actuators are provided, arranged on opposing sides of the rudder shaft sleeve, configured to drive the rotation of the improved cap rudder about the axis of the transverse shafts in a push-pull manner.

10. The vessel according to any one of claims 6 to 9, wherein a cylindrical rudder trunk for preventing water from entering a hull interior is arranged at a location where the improved cap rudder passes through the hull, a lower end of the rudder trunk being fixed to a bottom plate of the hull, an upper end being open, and a rear end being provided with a water outlet for discharging water that has entered the rudder trunk to outside the hull.

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