MARINE WAKE ADAPTED RUDDER ASSEMBLY

Abstract

A system for designing and assembling a ships rudder that allows for the manufacture of the rudder components, namely a rudder stock and rudder blade independently, and assembling them into a completed rudder using retaining bolts and injecting an epoxy like cement or grout in order achieve the required strength characteristics.

Claims

1. A marine rudder assembly comprising; a rudder blade forming an internal central cavity elongated along a vertical axis of the rudder blade, a rudder stock having an upper shaft portion and a lower insert portion, the lower insert portion shaped to fit into and closely conform with an inside surface of the internal central cavity, and an injectable filler material placed in a gap created between the inside surface of the internal cavity and the rudder stock lower insert portion.

2. The marine rudder assembly in accordance with claim 1, further comprising; the rudder blade forming a curved wake adapted outer surface forming a leading edge and a trailing edge, the trailing edge forming a curved edge shape.

3. The marine rudder assembly in accordance with claim 1, further comprising; the rudder stock lower insert portion forming a flattened and twisted configuration along the vertical axis and closely conforming with the inside surface of the central rudder blade cavity.

4. The marine rudder assembly in accordance with claim 1, further comprising; the rudder blade central rudder stock cavity forming an open upper end and a blind bottom end formed by a web.

5. The marine rudder assembly in accordance with claim 4, further comprising; the web forming apertures receiving threaded fasteners connecting a lower end of the rudder stock lower insert portion to the web.

6. The marine rudder assembly in accordance with claim 4, further comprising; the rudder blade central rudder stock cavity open end forms a shoulder providing an interference fit with the rudder stock lower insert portion.

7. The marine rudder assembly in accordance with claim 1, further comprising; the rudder blade is formed of a bronze alloy.

8. The marine rudder assembly in accordance with claim 1, further comprising; the rudder stock is formed of a high strength stainless steel alloy.

9. The marine rudder assembly in accordance with claim 1, further comprising; wherein the gap creates an internal volume between the lower insert portion and the inside surface of the internal central cavity and substantially the entirety of the internal volume is filled with the injectable filler material.

10. The marine rudder assembly in accordance with claim 1, further comprising; wherein the injectable filler material is an epoxy compound.

11. A method of forming a marine rudder assembly comprising the steps of; providing a rudder blade forming an internal central cavity elongated along a vertical axis of the rudder blade, providing a rudder stock having an upper shaft portion and a lower insert portion, the lower insert portion shaped to fit into and closely conform with an inside surface of the internal central cavity, locating the rudder stock lower insert portion into the rudder blade internal central cavity, and injecting a filler material into a gap created between the inside surface of the internal cavity and the rudder stock lower insert portion.

12. The method of forming a marine rudder assembly according to claim 11, further comprising the step of following the locating step and before the injecting step, structurally fastening the rudder stock to the rudder blade.

13. The method of forming a marine rudder assembly according to claim 11, further comprising, in the injecting step substantially fully filling the gap with the filler material.

14. The method of forming a marine rudder assembly according to claim 11, further comprising, the rudder blade central rudder stock cavity forming an upper end and a blind bottom end and the upper end forming a shoulder providing an interference fit with the rudder stock lower insert portion, and pressing the rudder stock lower insert portion into the upper end until the rudder stock lower insert portion contacts the blind bottom end.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is an elevational view of the rudder assembly in accordance with the present invention shown as a port side view.

[0020] FIG. 2 is an elevational view of the assembly of FIG. 1 shown in a front view.

[0021] FIG. 3 is an elevational view of the assembly of FIG. 1 shown in a rear view.

[0022] FIG. 4 is a detailed elevational view of the rudder blade showing internal features in phantom and showing certain components exploded from the assembly.

[0023] FIGS. 5 and 6 are elevational views of the rudder stock component shown respectively in rear and side views.

[0024] FIG. 7 is an elevational side view of the rudder blade.

[0025] FIG. 8 is a cross-sectional view through the rudder blade of FIG. 7 taken along lines 8-8 of FIG. 7.

[0026] FIG. 9 is a cross-sectional view through the rudder blade of FIG. 7 taken along lines 9-9 of FIG. 7.

[0027] FIG. 10 is a cross-sectional view through the rudder blade of FIG. 7 taken along lines 10-10 of FIG. 7.

[0028] FIG. 11 is a cross-sectional view through the lower portion of the rudder assembly showing the lower portion of the shaft, the rudder blade and the chocking material.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] With particular reference to FIGS. 1-3 rudder assembly 10 in accordance with an embodiment of the present invention is illustrated. Rudder assembly includes as principal components, rudder stock 12 and rudder blade 14.

[0030] Rudder stock 12 is shown in more detail in FIGS. 5 and 6. Rudder stock 12 is in the form of an elongated element having an upper shaft portion 16 and a lower insert portion 18. Upper shaft portion 16 has a generally cylindrical outer circumference and is adapted to provide a structural connection with a ship's steering system including associated torsional couplings which can engage features 19 formed at the top end of the shaft as shown in these figures. Of course various other designs for providing a mechanical connection for high torque force coupling can be employed for rudder stock 12. Upper shaft portion 16 also provides for mounting within suitable bearing elements for steering motion and further this portion is designed to restrain against the significant bending, vibration, cyclical, and shock loads applied to the rudder assembly during use.

[0031] Lower shaft portion 18 has a twisted blade-like configuration which is adapted for closely fitting within central cavity 30 of rudder blade 14, as will be described further in detail as follows. The lower end of lower insert portion 18 features, in one exemplary embodiment, a pair of threaded bores 20 having a function which will be described in more detail later.

[0032] FIGS. 7-10 show additional features of rudder blade 14 which features leading edge 22, trailing edge 24 and bottom surface 26. Rudder blade 14 is, in the illustrated embodiment, a cast structure having internal voids for reducing weight and material requirements. As evident from the cross-sectional views of FIGS. 8-10, the upper portion of the blade features three internal cavities including leading edge cavity 28, central rudder stock cavity 30, and trailing edge cavity 32. Central cavity 30 has an open upper end 33 and a blind (enclosed) bottom end 34. As explained previously, rudder blade 14 has a twisted configuration which provides improvements in propulsion efficiency as it cooperates with the thrust vortex created by the ships propeller (not shown) positioned immediately in front of rudder assembly 10. Rudder blade 14, in addition to having a twist along its vertical axis, is also tapered such that the leading edge cavity 28 in this embodiment grows smaller and disappears at the lower end of the blade.

[0033] FIG. 4 shows rudder stock lower insert portion 18 fit within central rudder stock cavity 30 of blade 14. The twisted blade-like configuration of the lower insert portion 18 follows the twisted contours of rudder stock cavity 30. Ideally, a small radial gap 56 of uniform dimension is formed around insert portion 18 and the inside surface of rudder stock cavity 30. For example, in one embodiment, this radial gap 56 or separation distance measures approximately 0.5 inches, although the design gap would be a function of many variables. A mechanical attachment is provided at the lower end of insert portion 18 featuring bores 20 mentioned previously. A structural connection between rudder stock insert portion 18 and rudder blade 14 is provided in the form of mechanical fasteners such as screws 38. In one design, at the bottom of rudder blade 14, bores are cast or machined into the rudder blade casting. Screws 38 pass through the bores to mesh with threaded bores 20. Once screws 38 are fully torqued in position, rudder stock insert portion 18 is clamped against the bottom of the rudder blade 24. This mechanical connection is provided for structural functions and further assembles the unit as a subassembly for subsequent fabrication steps. In another variation illustrated by the Figures and particularly FIG. 4, separate insert element 40 is provided having bores 21 which fits into a mating cavity 36 at rudder blade bottom surface 26. Screws 38 pass through shouldered bores 21 in insert element 40 and engage with threaded bores 20 of rudder stock 12. Additional fasteners may be provided to connect insert element 40 to rudder blade 14. Web 44 is provided between cavity 42 and rudder stock central cavity 30.

[0034] In a preferred embodiment shown in FIG. 11, the upper portion of central rudder stock cavity 30 features shoulder 48 which closely conforms to the outer surface of rudder stock 12. Alternatively, an interference fit can be provided at shoulder 48 with rudder stock lower insert portion 18 to properly locate and secure the components of the subassembly. Moreover, this close or interference fit at shoulder 48 provides a sealed internal volume formed by gap 56. FIG. 4 shows additional closure elements 50, 52 and 54 which enclose and seal internal cavities 28 and 32 within rudder blade 14.

[0035] The mechanical fixation of rudder stock 12 within blade 14 provided by the connection at the lower end of rudder stock 12 and the interference fit at the top of the rudder stock lower insert portion 18 and establishes gap 56. This subassembly can be handled for further processing while the parts are maintained as a securely connected subassembly.

[0036] In a further manufacturing process step, the subassembly of rudder stock 12 and rudder blade 14 is placed in a fixture and an injectable material, for example an epoxy compound such as Chockfast™ is injected to fill the void between rudder stock lower insert portion 18 and the inside surface of rudder stock cavity 30, shown as element number 58. Injection can be provided through injection hole 60 shown in FIG. 4. It is preferred that the entirety of the internal volume formed by gap 56 is filled with the injectable material 58. This produces an integrated composite structure. Higher levels of torque can be transferred between rudder blade 14 and rudder stock 12 aided by the twisted configuration of the lower portion of rudder stock insert 18 and its close conformance with the inside surface of rudder stock cavity 30. One or more of the Injection holes 60 may be provided to facilitate the introduction of the injectable filler material 58.

[0037] While the above description constitutes a preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims