Patent Application
20180105246
The field of the disclosure relates generally to propulsion systems and, more particularly, to retaining composite marine propellers.
At least some known 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, marine propeller assembly includes a plurality of circumferentially-spaced blades that each includes a dovetail having a radially inner surface. The marine propeller assembly also includes a hub including a plurality of circumferentially-spaced dovetail receiving portions configured to receive a corresponding dovetail of the plurality of blades. At least one gap is formed between the radially inner surface and at least a portion of the dovetail receiving portion.
In another aspect, a hub for use with a marine propeller assembly includes a plurality circumferentially-spaced wedge receiving portions configured to receive a corresponding wedge of a plurality of wedges and a plurality of circumferentially-spaced dovetail receiving portions configured to receive a corresponding blade of a plurality of blades. Each blade includes a dovetail including a radially inner surface. The wedge receiving portions are alternatingly circumferentially-spaced with the dovetail receiving portions, and at least one gap is formed between the radially inner surface and at least a portion of the dovetail receiving portion.
In yet another aspect, a marine propulsion system includes a rotatable propulsive shaft extending away from a hull of a water craft and a plurality of circumferentially-spaced blades. Each blade includes a dovetail having a radially inner surface. The marine propulsion system also includes a hub including a plurality of circumferentially-spaced dovetail receiving portions configured to receive a corresponding dovetail of the plurality of blades. At least one gap is formed between the radially inner surface and at least a portion of the dovetail receiving portion.
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 shell with 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 propulsive 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. The blades are retained axially 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, the marine propeller assembly includes the plurality of circumferentially-spaced blades that each include a dovetail having a radially inner surface. The hub includes a plurality of circumferentially-spaced dovetail receiving portions configured to receive a corresponding dovetail of the plurality of blades. At least one gap is formed between the radially inner surface and at least a portion of the dovetail receiving portion. In addition to providing axial and radial retention of the separable blades in the hub, the gaps formed between the blade dovetail and the hub facilitate reducing stress concentrations located at the intersection of the dovetail inner surface and the opposing dovetail sidewalls among other performance benefits of the propeller assembly. Such performance improvement may relate to: (a) creation of a direct load path through the propeller blades, the hub, and the drive shaft; (b) reduction of stress concentrations where the blades couple to the hub; and (c) reduction in cost of parts and labor due to an extended operational service time of the blades.
Hub 102 includes a first face 108, a second face 110 (not shown in
In the exemplary implementation, dovetail 127 also includes a first circumferential end 410, an opposing second circumferential end 412, and a radially inner surface 414 extending therebetween for a first length L1. Furthermore, groove 126 of hub 102 includes a dovetail receiving portion 416 and an adjacent wedge receiving portion 418. Dovetail receiving portion 416 is configured to receive a corresponding dovetail 127 of blades 106 and wedge receiving portion 418 is configured to receive a corresponding wedge 104. More specifically, hub 102 includes a plurality of circumferentially-spaced dovetail receiving portions 416 that are alternatingly circumferentially-spaced with the plurality of wedge receiving portions 418.
In the exemplary embodiment, each dovetail 127 includes a first edge 411 at the intersection of sidewall 201 and inner surface 414 at first circumferential end 410. Furthermore, each dovetail 127 includes a second edge 413 at the intersection of sidewall 404 and inner surface 414 at second circumferential end 412. Edges 411 and 413 extend the full axial length of dovetail 127 and include a relief cut to facilitate relieving stresses concentrated at the intersection of sidewalls 401 and 404 and inner surface 414. In the exemplary embodiment, edges 411 and 413 are chamfered along their length. In another embodiment, edges 411 and 413 are rounded. Generally, edges 411 and 413 are modified in any manner that reduces stress as described herein and that facilitates operation of blades 106.
As shown in
In the exemplary embodiment, radially inner surface 414 of dovetail 127 is spaced away from dovetail receiving portion 416 of groove 126 such that a gap 428 is formed therebetween. More specifically, a first gap 428 is formed at first circumferential end 410 of dovetail 127 between radially inner surface 414 and dovetail receiving portion 416. Similarly, a second gap 430 is formed at second circumferential end 412 of dovetail 127 between radially inner surface 414 and dovetail receiving portion 416. Gaps 428 and 430 extend circumferentially toward each other from respective circumferential ends 410 and 412 and extend axially from hub forward face 108 to hub aft face 110.
More specifically, dovetail receiving portion 416 includes a radially inner surface 432 that at least partially forms gaps 428 and 430. In the exemplary embodiment, dovetail receiving portion 416 also includes a platform 434 extending radially outward from radially inner surface 432. Platform 434 includes a dovetail receiving surface 436 that couples to dovetail inner surface 414 such that gaps 428 and 430 are defined between dovetail inner surface 414 and radially inner surface 432. Platform 434 includes a first circumferential end 438 and an opposing second circumferential end 440 that define a platform length L2 therebetween that is shorter than the length L1 of dovetail inner surface 414. In the exemplary embodiment, first gap 428 is positioned adjacent first circumferential end 438 and second gap 430 is positioned adjacent second circumferential end 440. More specifically, platform 434 extends perpendicularly from surface 432 and is substantially centered along dovetail inner surface 414 such that gaps 428 and 430 are substantially similar in circumferential length and radial depth. Alternatively, gaps 428 and 430 include different circumferential lengths and/or radial depths. First gap 428 is defined by dovetail inner surface 414, receiving portion inner surface 432, and platform first end 438. Second gap 430 is defined at least in part by wedge 104 and, more specifically, by platform second end 440, dovetail inner surface 414, receiving portion inner surface 432, and first wedge sidewall 402. In such a configuration, platform 434 is defined by forming grooves in surface 436 to form surface 432, which defines gaps 428 and 430 when dovetail 127 is coupled within slot 126.
In operation, blades 106 are preloaded into hub 102 to create a direct load path from the blade/media interface to hub 102 to a drive shaft (not shown in
Dovetail 520 also includes a first circumferential end 540, an opposing second circumferential end 542. Similar to marine propeller assembly 400 (shown in
An exemplary technical effect of the methods, systems, and apparatus described herein includes at least one of: (a) creation of a direct load path through the propeller blades, the hub, and the drive shaft; (b) reduction of stress concentrations where the blades couple to the hub; and (c) reduction in cost of parts and labor due to an extended operational service time of the blades.
The above-described embodiments of an apparatus and system of retaining a separable composite marine propeller assembly on a propulsive 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 forming gaps between a portion of the blade dovetails and the hub to reduce the level of stress concentrations that may occur at the intersection thereof. 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.
