Patent Application
20160193575
The present invention relates generally to mixing impellers, and in particular to mixing impellers which are rotated by a motor-driven drive shaft for mixing a liquid material and being structured to fold about the motor-driven drive shaft for installation into and removal from a closed mixing vessel.
Mixing impellers are in wide use in industry. Examples of industrial mixing impellers include designs which have a central hub and two, three, four or more radially extending blade type structures. These blades may be flat, angled, and in some cases have a wing or propeller shape. Typically, the impellers extend radially outwardly from a motor-driven shaft and are submerged inside a material to be mixed. Oftentimes the impellers are in an at least partially liquid mix which is being confined in a vessel, which may be holding the material in a batch process or a continuous process.
Some mixing vessels are closed, and the impeller is moved into and out of the vessel through a small opening by folded the blades of the impeller around the drive shaft. Impellers having folding blades are known for being mounted at the end of the drive shaft. However, known designs for impellers having such folding blades tend to be for small impellers, and such known designs for small folding blade impellers tend to be inefficient and unsophisticated, and require a large opening to pass into and out of the closed vessel.
Some aspects of some embodiments of the invention provide a mixing impeller that can mitigate, at least to some extent, the effect of the development of “rags” or other collections adhering to the leading edge of the impeller, or to any edge of the impeller.
Accordingly, the present invention is a folding impeller formed around a central hub that has a cylindrical bore defining a center axis and a mechanism for rotationally and translationally fixing the impeller on an appropriate drive shaft. The folding impeller includes a plurality of impeller blades each being formed with a leading portion that is extended from a trailing portion, with the leading and trailing portions of the blade and forming an obtuse angle included therebetween. The trailing portion of each impeller blade is rotatably mounted for tangential rotation about the central hub between a folded state and a spread state, wherein in the folded state the axis of the hub lies within the angle included between the leading portion and the trailing portion of each of the impeller blades, and wherein in the spread state each of the impeller blades is tangentially extended from the center hub with the angle included between the leading portion and the trailing portion being arranged transverse of the axis of the hub, and wherein the trailing portion is arranged substantially parallel with the axis, and the leading portion is arranged an angle therewith.
According to another aspect of the invention, the blade design of the folding impeller is more efficient than known prior art designs. An angle of attack of the folding blades of the impeller is shallower or flatter and less perpendicular, to the center axis. Accordingly, the leading edge portion of each folding blade is more parallel to the axis and to the flow of the material in the vessel. The trailing edge portion of each blade is a steeper pitch relative to the center axis than known prior art devices. Therefore, the trailing edge portion of each blade is more perpendicular to the flow direction, which causes the flow to accelerate in the flow direction. This shallower or flatter and less perpendicular design of the leading edge portion, and the steeper pitched trailing edge portion of folding the blades is exactly opposite from the less sophisticated impellers of the prior art that fold the blade oppositely to fit around the drive shaft.
According to another aspect of the invention, the blade design of the folding impeller is a forward pitch blade design that actually folds the blades into the flow of the material in the vessel when the folding impeller is opening. Thus, this forward pitch blade of the folding impeller is a design that actually folds toward the flow direction in the vessel when opening the folding impeller is unfolding from the folded state into the spread state. Furthermore, this novel forward pitch design of the folding impeller permits the blades to be formed such that each blade wraps around the drive shaft when the impeller is folded, while providing an efficient blade design for operating in the mixing vessel. This action of the folding impeller of opening into the flow of the material is counter-intuitive, at least given the prior art designs, but centrifugal force generated by the drive shaft starts the unfolding movement of the impeller, and the blade pitch (the angle of attack) catches the flow and completes the opening action.
According to another aspect of the invention, the folding impeller has three impeller blades that are uniformly distributed around the central hub, which ensures balanced operation when the drive shaft is turning.
According to another aspect of the invention, the central hub of the folding impeller is formed with a cylindrical bore completely there through, which permits the impeller to be mounted anywhere on the drive shaft. In contrast, known folding impellers of the prior art only have socket-style hubs such that the impeller can only be mounted on the end of the drive shaft.
According to another aspect of the invention, the blades hang under gravity along the drive shaft when the folding impeller is in the folded state, which permits the pass-through opening in the mixing vessel to be smaller for inserting and removing the impeller than was possible for prior art impeller devices. Other folding impeller designs of the prior art hang the blades offset from the hub, and actually require the user to hold the blades together around the drive shaft when inserting the impeller into the vessel opening.
Other aspects of the invention are detailed herein.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
A detailed illustrative embodiment of the present mixing impeller device is disclosed herein. However, techniques, systems and operating structures in accordance with the present mixing impeller device may be embodied in a wide variety of forms and modes, some of which may be quite different from those in the disclosed embodiment. Consequently, the specific structural and functional details disclosed herein are merely representative, yet in that regard, they are deemed to afford the best embodiment for purposes of disclosure and to provide a basis for the claims herein which define the scope of the present mixing impeller device. The following presents a detailed description of an illustrative embodiment of the present mixing impeller device.
In the Figures, like numerals indicate like elements.
Folding impeller 10 includes a plurality (three shown) of impeller blades 18 uniformly distributed around central hub 12 in such manner as to ensure balanced operation when drive shaft S is turning. Each impeller blade 18 has a leading edge portion 20 extended along a bend 21 thereof from a trailing edge portion 22 and forming an obtuse angle 24 included therebetween. As shown in
Folding mixing impeller 10 is collapsible into it's folded state (phantom lines) about hub 12 to a size small enough to fit through an opening into a closed vat. Flats 32 also permit impeller blades 18 collapse within a smaller footprint 34 (shown in dashed lines) than would result without flats 32 being present. For example, in
Accordingly, proximal end portion 28 of each trailing portion 22 of each impeller blade 18 is rotatably mounted by hinge member 26 to one of flats 32 on exterior wall 30 of central hub 12 for tangential rotation thereabout.
In
Impeller blades 18 are rotated (arrow 37) about hinge members 26 for being tangentially extended from respective flats 32 on exterior wall 30 of center hub 12. In the spread state (solid lines) of impeller 10, angle 24 included between leading portion 20 and trailing portion 22 of each impeller blade 18 is arranged substantially transverse of axis 16 of center hub 12. Accordingly, trailing portion 22 of each impeller blade 18 is arranged substantially parallel with axis 16, and leading portion 20 is arranged at an angle-of-attack 36 from the perpendicular thereto when impeller 10 rotates in a direction (arrows 38) according to drive shaft S and positive relative to a plane of rotation 39 through which impeller hub 12 rotates on drive shaft S, as illustrated in
Folding impeller 10 is a design aimed at smaller sizes, e.g., less than twenty (20) inch diameter, but the design could be expanded upwards from there as well without undue experimentation.
One unique feature of folding impeller 10 is a blade design that is more efficient than known prior art designs. Angle of attack 36 of folding blades 18 of impeller 10 is shallower or flatter and less perpendicular, to axis 16. Accordingly, leading edge portion 20 of each folding blade 18 is more parallel to axis 16 and to the flow (arrow 40) of the material in the vessel. Trailing edge portion 22 of each blade 18 is a steeper pitch relative to axis 16 than known prior art devices. Therefore, trailing edge portion 22 of each blade 18 is more perpendicular to the flow direction, which causes the flow to accelerate in the flow direction. This shallower or flatter and less perpendicular design of leading edge portion 20, and steeper pitched trailing edge portion 22 of folding blades 18 is exactly opposite from the less sophisticated impellers of the prior art that fold the blade oppositely to fit around the drive shaft S.
Another unique feature of folding impeller 10 is a forward pitch blade design that actually folds blades 18 into the flow of the material in the vessel when folding impeller 10 is opening. Thus, this forward pitch blade 18 of folding impeller 10 is a design that actually folds toward the flow direction in the vessel when opening folding impeller 10 is unfolding from the folded state into the spread state. Furthermore, as illustrated in
Most known folding impellers of the prior art only have two blades, which causes the impellers to be both less efficient and less stable in operation, than the three impeller blades 18 of folding impeller 10 that are uniformly distributed around central hub 12, which ensures balanced operation when drive shaft S is turning.
Central hub 12 of folding impeller 10 is formed with cylindrical bore 14 completely there through, which permits impeller 10 to be mounted anywhere on drive shaft S. In contrast, known folding impellers of the prior art only have socket-style hubs such that the impeller can only be mounted on the end of drive shaft S.
Also, blades 18 of folding impeller 10 hang along drive shaft S when in the folded state, which permits the pass-through opening in the vessel to be smaller for inserting and removing impeller 10 than was possible for prior art impeller devices. Other folding impeller designs of the prior art hang the blades offset from the hub, and actually require the user to hold the blades together around drive shaft S when inserting the impeller into the vessel opening.
While the preferred and additional alternative embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. Therefore, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. Accordingly, the inventor makes the following claims.
