Patent Application
20180105243
The field of the disclosure relates generally to propulsion systems and, more particularly, to retaining propellers in a propeller hub.
At least some known propulsion systems, such as, marine propulsion systems, rely on a rotating propeller assembly including a central hub and propeller blades extending from the central hub. During operation, fluid generally flows across surfaces of the propeller assembly and through gaps defined between blades of the propeller assembly. Performance of the propeller assembly is highly dependent on the shape of the propeller assembly surfaces including those of the blades, central hub, and blade retaining members. As a result, propeller assemblies in which the shape of propeller assembly components are limited by construction methods, material limitations, component sizes, and the like, may result in sub-optimal flow characteristics, decreasing the efficiency of the propeller assembly and requiring more powerful drive systems to achieve required propulsion.
In one aspect, a forward retention member that may be used with propeller assembly includes a planar base, a drive shaft engagement end opposite the planar base, and a conic body extending therebetween along a centerline normal to the planar base. The forward retention member also includes at least one protuberance extending radially away from a surface of the conic body, the protuberance extending axially from the planar base arcuately convergent to a predetermined point between the planar base and the drive shaft engagement end.
In another aspect, a marine propeller assembly includes a hub including a forward face, an aft face, and a hub body extending therebetween, the hub configured to couple to a rotatable drive shaft, the hub further configured to receive a plurality of propeller blades spaced circumferentially around the hub. The marine propeller assembly also includes a forward retention member configured to couple to the forward face. The forward retention member includes a planar base, a drive shaft engagement end opposite the planar base, and a truncated conic body extending therebetween along a centerline normal to the planar base. The forward retention member further includes a central bore configured to receive a drive shaft and at least one protuberance extending radially away from a surface of the conic body, the protuberance extending axially from the planar base arcuately convergent to a predetermined point between the planar base and the drive shaft engagement end.
In yet another aspect, a marine propulsion system includes a rotatable drive shaft extending away from a hull of a water craft, a hub including a forward face, an aft face, and a hub body extending therebetween, the hub body formed of at least one of a metal material and a composite material, the hub body coupled to the drive shaft, the hub including a plurality of circumferentially-spaced composite propeller blades. The marine propulsion system also includes a forward retention member configured to couple to the forward face. The forward retention member includes a planar base, a drive shaft engagement end opposite the planar base, and a conic body extending therebetween along a centerline normal to the planar base. The marine propulsion system further includes at least one protuberance extending radially away from a surface of the conic body, the protuberance extending axially from the planar base arcuately convergent to a predetermined point between the planar base and the drive shaft engagement end.
These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Unless otherwise indicated, the drawings provided herein are meant to illustrate features of embodiments of this disclosure. These features are believed to be applicable in a wide variety of systems comprising one or more embodiments of this disclosure. As such, the drawings are not meant to include all conventional features known by those of ordinary skill in the art to be required for the practice of the embodiments disclosed herein.
In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise.
As used herein, the terms “axial” and “axially” refer to directions and orientations that extend substantially parallel to a centerline of the propulsion shaft or propeller hub. Moreover, the terms “radial” and “radially” refer to directions and orientations that extend substantially perpendicular to the centerline of the propulsion shaft or propeller hub. In addition, as used herein, the terms “circumferential” and “circumferentially” refer to directions and orientations that extend arcuately about the centerline of the propulsion shaft or propeller hub.
Embodiments of the marine propeller assemblies and systems described herein provide a cost-effective method for reducing the weight of marine propellers as compared to those that are currently available. The marine propeller assemblies and systems also provide hydrodynamics efficiencies not found in current propeller assemblies. As opposed to monolithic cast and machined propeller assemblies, some embodiments of the marine propeller assemblies described herein are formed of a composite material laid over an internal structural frame and/or a filler material, such as, but not limited to a structural foam filler. The blades are formed individually and coupled to a metallic hub coupled to a drive shaft of a marine vessel. The separable blades provide a manageable weight and size for maintenance of the propeller system. The separable blades are retained in a dovetail groove configured to receive a dovetail of each blade. Axially, the blades are retained by an axial retention member couplable to the hub and configured to abut an end face of a dovetail associated with each blade. The axial tension or force used to secure each dovetail axially may be adjustable based on an axial bias member formed either in the end face of the dovetail or in the surface of the axial retention member adjacent the dovetail end face. The blades are retained radially and circumferentially using wedges configured to engage a dovetail sidewall and be coupled to the hub using fasteners.
In one embodiment, a forward retention member is coupled to a forward end of the hub system, which is formed in a three-dimensional (3-D) truncated conic shape and also provides axial retention for the separable blades. The conic shape is truncated because the apex of the conic shape and portion of the length of forward retention member is removed to permit fitting the forward side of the forward retention member onto the drive shaft of the marine propeller assembly. In addition to providing axial retention of the separable blades in the hub, the forward retention member also provides hydrodynamic benefits and improves performance of the propeller assembly. The forward retention member includes contours or protuberances that transition the conic shape of the body of the forward retention member into the airfoil shape of the blade to promote efficient hydrodynamic flow through the marine propeller assembly. Such performance improvement may relate to (i) an amount of cavitation during operation; (ii) generated thrust; (iii) open water efficiency; (iv) hull efficiency; (v) relative rotative efficiency; (vi) mechanical efficiency; (vii) a quasi-drive coefficient; and (viii) acoustic efficiency.
Because the blades may be retained in a spiral or arcuate groove in the hub and the root of the blade may include a twist in its root, the transitional contour or protuberances also extends these characteristics from the blade in diminishing fashion to the surface of the forward retention member. In various embodiments, the forward retention member is formed of metal and in some other embodiments, the forward retention member is formed of composite material with or without an internal structural frame.
Hub 102 includes a first or forward face 108, a second or aft face 110 (not shown in
In various embodiments, propeller blades 106 are formed of a composite structure that includes dovetail 127 (shown in
An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) forward axial retention for separable marine propeller blades, (b) a hydrodynamically efficient and streamlined conic shape, (c) 3D contours of the forward axial retention member transition the shape of the forward axial retention member to the shape of the associated propeller blade, and a 3D spiral introduction to the blade shape.
The above-described embodiments of an apparatus and system of retaining a separable composite marine propeller assembly on a propulsive or drive shaft of a watercraft provides a cost-effective and reliable means for operating and maintaining the marine propeller assembly. More specifically, the apparatus and system described herein facilitate maintaining an axial position of the marine propeller assembly on the shaft while providing a hydrodynamically streamlined flow path for water over the marine propeller assembly. As a result, the apparatus and system described herein facilitate operating a large commercial water craft in a cost-effective and reliable manner.
Although specific features of various embodiments of the disclosure may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the disclosure, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.
This written description uses examples to disclose the embodiments, including the best mode, and also to enable any person skilled in the art to practice the embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
