BACKGROUND OF THE INVENTION

This invention relates to froth flotation cells, particularly froth flotation cells utilized for removing mineral values from ore slurries. This invention also relates to associated standpipes for froth flotation cells and to a method for retrofitting a froth flotation cell. The invention stabilizes a slurry vortex generated by a rotor inside a standpipe of a froth flotation cell and accordingly reduces surface instability at a pulp-froth interface inside the cell.

Froth flotation cells are used to separate mineral values from mineral wastes. An ore is finely ground and suspended as a water-based slurry or pulp in a flotation cell. An impeller or rotor is turned at a high speed in the slurry to suspend the mineral particulates and to distribute or disperse air bubbles into the slurry. The mineral values attach to the air bubbles. The bubbles with the entrained mineral values then rise to form a froth atop the pulp or slurry pool. The froth overflows a weir and is collected in a launder for further processing. Some examples of flotation cells are described in U.S. Pat. No. 5,611,917 to Degner; U.S. Pat. No. 4,737,272 to Szatkowski et al; U.S. Pat. No. 3,993,563 to Degner; U.S. Pat. No. 6,095,336 to Redden et al.; and U.S. Pat. No. 6,070,734 to Hunt et al.

Froth flotation cells of the above-described type include a vertical cylindrical standpipe or tube 2, depicted in FIGS. 1 and 2, which is concentric or coaxial with the rotor 4, and the longitudinal axes A and B, respectively, and mounted proximate an upper portion thereof. With reference to FIGS. 1 and 2, the general action of the rotor and standpipe assembly within the overall froth flotation cell results in air or other gas being sucked down along general direction 3, slurry or other mixture being sucked up along general direction 5, and a resulting bubbly jet stream being distributed in general direction 7, eventually helping to form a froth atop or proximate the pulp-froth interface 8. Furthermore, the rotor's action also usually generates, in the standpipe 2, a slurry vortex 6 that is unstable due to pressure fluctuation in the rotor region. The vortex jumps periodically, from a low level or height shown in FIG. 1 to a high level shown in FIG. 2. The instability of the vortex varies the degree of submergence of the rotor 4 and produces a fluctuating air- inflow rate. As a result, multi-phase jet characteristics such as void fraction and velocity become unstable. The unstable jet stream generates waves at the pulp-froth interface 8 and makes the interface sway periodically. This wave or swaying action makes it difficult to control the pulp level and to operate froth flotation cells in applications where the froth height is relatively low. If the level is adjusted too close to the pulp level, the pulp may splash into the launder and negatively impact machine performance. It is also desirable to be able to set a pulp level and control its location because this has an effect on the grade and recovery of the flotation device. When the surface is unstable, the level is at a variety of heights and, as a result, you are not as able to change or set this parameter.

SUMMARY OF THE INVENTION

An aim of the present invention is to provide an improved froth flotation cell where the vortex in the standpipe is stabilized. A related aim is to provide a standpipe for a froth flotation cell that may be used to retrofit existing cells.

A mixing apparatus of the froth-flotation-cell type comprises, in accordance with the present invention, a tank, a drive shaft rotatably disposed in the tank, a rotor connected to the drive shaft for imparting rotational energy to a fluidic material disposed in the tank, a standpipe mounted at least partially inside the tank proximate an upper end of the rotor, and at least one vortex stabilization structure connected to the standpipe and extending inwardly from an inner surface of said standpipe. The vortex stabilization structure generally exhibits a downwardly facing surface, more particularly a downwardly facing inclined surface. An outer edge of the structure radially removed from a longitudinal axis of the standpipe generally extends at an acute angle or pitch relative to a transverse plane oriented perpendicular to the axis.

In particular, the vortex stabilization structure is generally inclined in a circumferential direction relative to a horizontal plane. Thus, the vortex stabilization structure has an outer edge (radially removed or spaced from the longitudinal axis of the standpipe) that is oriented at an acute angle relative to the horizontal plane. During operation of a froth flotation cell in accordance with the present invention, the vortex stabilization structure exerts a downward force on liquid that moves outwardly from the vortex and flows against the downwardly facing inclined surface. This force generates a downwardly directed backflow that reduces the upward rising of the vortex and thereby stabilizes the vortex. The pitch angle of the vortex stabilization structure may vary depending on the rotor's rotational speed, the location of the structure along the standpipe, and/or the need for a steeper pitch angle to help clean out the structure. Furthermore, and as shown in laboratory tests and their results, the vortex stabilization structure is effective in reducing the vortex flow instability irrespective of the direction of rotation or spin of the vortex flow with respect and reference to the circumferential direction of inclination, and possibly also the radial direction of inclination, of the vortex stabilization structure.

Preferably, however, the vortex stabilization structure lies along a spiral curve and concomitantly the outer edge of the structure lies along a spiral path or locus about the axis of the standpipe. The vortex stabilization structure is generally disposed proximate a bottom end of the standpipe, within a vortex zone which is likewise generally disposed proximate a bottom end of the standpipe, and the structure may include a helical band, strip or web.

Furthermore, the vortex stabilization structure may be variously tilted upwardly or downwardly in along and from the radial direction with respect to the standpipe axis and thus the standpipe inner surface or wall; the structure may be made out of a variety of materials such as metal, plastic, rubber and/or mesh, or any combination thereof; and the structure may include various perforations, openings or holes at certain locations therein to help shed or wash particles therethrough and generally towards and out the bottom of the standpipe.

An associated standpipe for a froth flotation cell comprises, in accordance with the present invention, a cylindrical body member and at least one vortex stabilization structure extending inwardly from an inner surface of the cylindrical body member. The structure has a downwardly facing inclined surface, with an outer edge of the structure radially removed from a longitudinal axis of the body member extending at an acute angle relative to a plane that is perpendicular to the axis. In a preferred embodiment of the standpipe, the vortex stabilization structure takes the form of a helical band or strips that includes multiple windings or turns about the axis of the standpipe and defines a helical channel that likewise includes multiple windings or turns about the axis of the standpipe.

In general, and in view of the discussion above, the present invention comprises a vortex stabilization structure for use in and extending radially inwardly from a standpipe inner surface, said standpipe to be operationally mounted in a flotation cell and including a central longitudinal axis, said vortex stabilization structure being asymmetric when viewed with respect to any plane drawn through the central longitudinal axis of said standpipe.

A method for improving performance of a froth flotation cell, comprises, in accordance with the present invention, providing a vortex stabilization structure and installing the vortex stabilization structure in the flotation cell so that the vortex stabilization structure extends inwardly from an inner surface of a standpipe of the flotation cell, so that the vortex stabilization structure exhibits a downwardly facing inclined surface, and so that an outer edge of the vortex stabilization structure radially removed from a longitudinal axis of the standpipe extends at an acute angle relative to a plane that is perpendicular to the axis. This is a retrofit method for enhancing the operational efficiencies of froth flotation cells in the field.

Where the inclined surface of the vortex stabilization structure defines a channel inclined at the acute angle, the method further comprises operating the flotation cell so that a liquid vortex is formed inside the standpipe. The liquid in the vortex has a velocity that is inclined upwardly at an angle substantially opposed to the acute angle of the vortex-reduction channel. The method then further comprises capturing fluid from the vortex in the channel and directing the captured fluid downwardly along the channel. Where the channel is spiral or helical, the directing of the captured fluid downwardly along the channel includes directing the captured fluid along a downward spiral or helical path.

Furthermore, the method may include inclining the vortex stabilization structure along and with respect to a radial direction from the inner surface of the standpipe and/or include providing perforations within the vortex stabilization structure.

In yet another embodiment of the present invention, the vortex stabilization structure comprises a plurality of generally circular baffles extending radially inwardly from the inner surface of a standpipe, said standpipe to be mounted in a flotation cell, which baffles serve to inhibit the upward movement of the vortex formed on the inside of the standpipe. Such baffles could variously include certain appendages, perforations and/or permutations to improve their efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of a conventional standpipe or stand tube of a froth flotation cell, showing one possible condition of a liquid vortex inside the standpipe.

FIG. 2 is a schematic cross-sectional view similar to FIG. 1, showing another possible condition of a liquid vortex inside the standpipe. FIG. 3 is an elevational view, partially cut away and in section, of a froth flotation cell in accordance with the present invention, particularly including a standpipe with a spiral vortex stabilizer in accordance with the invention.

FIG. 4 is an elevational view, partially cut away and in section, of another froth flotation cell in accordance with the present invention, also including in particular a standpipe with a spiral vortex stabilizer in accordance with the invention.

FIG. 5 is a perspective view of a vortex-stabilizing spiral structure in accordance with the present invention.

FIG. 6 is a partial vertical cross-sectional view of the spiral structure of FIG. 5.

FIG. 7 is an enlarged partial cross-sectional view showing the profile of the spiral structure of

FIGS. 5 and 6 as sectional views of two adjacent turns of the spiral.

FIG. 8 is a view similar to FIGS. 1 and 2, showing the spiral structure of FIGS. 5 - 7 installed along an inner surface of the standpipe.

FIG. 9 is a diagram showing angles of inclination of a vortex stabilization structure and vortex liquid flow relative to transverse planes in a standpipe.

FIG. 10 is a schematic inside elevational view of a rolled-out flotation-cell standpipe, showing an alternative embodiment of a vortex stabilization structure in accordance with the present invention.

FIG. 11 is a top view of a flotation-cell standpipe, showing another embodiment of a vortex stabilization structure in accordance with the present invention.

FIG. 12 is a schematic inside elevational view of a vortex stabilization structure in accordance with the present invention.

FIG. 13 is a schematic inside elevational view of yet another vortex stabilization structure in accordance with the present invention. FIG. 14 is a schematic view of yet another vortex stabilization structure in accordance with the present invention.

DETAILED DESCRIPTION

As shown in FIG. 3, a froth flotation cell generally includes a liquid-holding tank 13 and a rotor- type mixing means 15 mounted centrally in the tank by a rigid stationary structure 17, for agitating the liquid in the tank. Tank 13 has a generally rectangular configuration and is defined by upstanding marginal sidewalls 20 - 23 and a bottom wall 24. Liquid to be mixed is introduced to the lower region of the tank, preferably via an appurtenant feed box 25 from which the influent liquid flows beneath the lower edge of the adjacent sidewall 21 into the tank 13 proper. At least one of the other sidewalls, e.g., wall 23, may be configured to serve as an overflow weir for removing froth and floating substances from the tank. Weir wall 23 may be adjustable in height so that the liquid overflow can be selectively varied. Processed liquid is usually removed from the tank via a conventional underflow weir, not shown. In certain applications, the flotation cell can also be sealingly enclosed by a removable cover 19 to contain vapors and fumes.

Mixing means 15 includes a drive unit 26, such as an electric motor, supported on mounting structure 17 and coupled to an upper end of a vertically arranged rotatable drive shaft 27. Drive shaft 27 is supportively journaled by a pair of bearing assemblies 28, extends downwardly therefrom into tank 13, and has an impeller or rotor 29 fixed to a distal end at a predetermined distance below the liquid surface 49. Rotor 29 includes a tubular hub 32 and a plurality of radially extending vanes 51 having long vertical outer edges. Vanes 51 can be flexible and their vertical edges can be thickened somewhat to increase the mixing action that occurs as rotor 29 turns with drive shaft 27.

A standpipe or stand tube 35 in the form of a hollow cylindrical conduit is fixedly suspended from the structure 17 to concentrically surround drive shaft 27 and to extend into the liquid to a location proximate rotor 29. Standpipe 35 has an interior diameter that substantially exceeds the diameter of drive shaft 27 and is preferably, but not necessarily, 1.3 to 2.0 times greater than the diameter of rotor 29. At its upper end, standpipe 35 is in communication with the atmosphere or with a source of gas via an inlet 37. In the case of an enclosed tank, inlet 37 could also extend from the side of standpipe 35 into the freeboard space 22.

As illustrated in FIG. 3, a stator assemblage is fixed to the lower end of standpipe 35 and includes a downwardly and outwardly flaring perforated hood 39 and a perforated cylindrical "disperser" member 40, both of which concentrically surround and are spaced from at least an upper portion of impeller or rotor 29. When the rotor 29 rotates, a liquid vortex is generated inside standpipe 35; the central core of the vortex is of reduced pressure and provides suction to draw gas downwardly through standpipe 35 for mixing with the liquid in tank 13.

The froth flotation cell of FIG. 3 also includes an optional open-ended draft tube 44 which is mounted concentrically below impeller or rotor 29 on a perforated "false bottom" plate 46 that is stationary and spaced somewhat above and parallel to a floor 24 of tank 13. A lower end of draft tube 44 is in direct communication with liquid in tank 13 below false bottom plate 46. When the unit is in operation, liquid is drawn upwardly through draft tube 44 and thence into rotor 29 and then is driven radially outward by the force of the rotor rotation.

As shown in FIG. 3, standpipe 35 is provided internally with a structure 48 for directing fluid from the vortex along a downward path. To that end, structure 48 defines a spiral channel 50 that at any given location is oriented at an angle, generally an acute angle, relative to the velocity vector of liquid in the vortex at the given location. Thus, where drive shaft 27 rotates clockwise (see arrow 52) and generates a liquid vortex with a velocity vector 54, structure 48 has an opposite inclination causing a liquid backflow 56. The structure 48 may comprise at least one spiral vane or web extending inwardly from an inner surface (not separately designated) of standpipe 35. Alternatively, structure 48 may comprise a plurality of mutually spaced vane sections generally aligned with one another in a spiraling configuration.

Structure 48 is therefore designed to exert a downward force on liquid that enters channel 50 from the vortex, discharging the dynamic potential energy in the vortex and reducing the accumulation of fluid along standpipe 35. In short, the fluid substance of the vortex, generally a liquid mixture or solution, will be transferred down along the channel 50 as it tries to spin up the wall or inner surface of the standpipe 35 and the amount of fluid piling up in the standpipe 35 is dramatically lessened. Thus the spiral structure 48 helps eliminate the conditions for vortex instability, ensures uniform rotor submergence over time and thus a more constant rate of air intake, stabilizes the multi-phase jet stream in a disperser region, and reduces any resulting surface instability or waves at the froth-pulp interface in the larger cell.

As illustrated in FIG. 4, a froth flotation cell comprises a rotor assembly 110 rotatably disposed in a generally cylindrical tank 112 for pumping a pulp phase or slurry together with air to thereby mix the air into the two-phase pulp, generating a froth or bubble mass which floats atop a pulp mass or slurry pool in the tank. Rotor assembly 110 includes a mixing structure in the form of a rotor or impeller 114 comprising a plurality of vertical vanes or propeller blades 116 disposed in a generally cylindrical configuration about a rotation axis 118 (a longitudinal axis of standpipe 152). A lower end of rotor 114 is juxtaposed to an upper end of a cylindrical draft tube extension or spacer element 125, which is coupled at a lower end to a conical draft tube 126. Draft tube 126 is spaced from a lower wall or panel 128 of tank 112 by a plurality of supports 130. Supports 130 define a plurality of openings 132 through which pulp or slurry moves is drawn into extension 126. An upper end of rotor 114 is surrounded by a fenestrated stationary disperser 134 which is coaxial with rotor 114 and acts to facilitate shearing of air bubbles and to reduce the energy after mixing of air and pulp. Positioned over and about disperser 134 is a perforated conical hood 136 for stabilizing the pulp surface. Rotor 114 is positioned near the top of the fluid volume and hood 136 functions to calm the turbulent fluid.

Rotor 114 is operatively connected to a motor 140 via a drive shaft 142, transmission belts 144 and sheaves 146 and 148. Motor 140 is supported on tank 112 via a mechanism stand 150 and a base plate and standpipe 152, while transmission belts 144 and sheaves 146 and 148 are covered by a belt guard 154. A bearing housing 156 surrounds drive shaft 142 along an upper portion thereof, a slide gate air control 158 being disposed at the lower end of bearing housing 156.

Flotation cell tank 112 is provided along an upper end thereof with a froth overflow weir or launder 160 which receives froth and channels it away from the flotation cell. A galvanized pipe 162 and nozzle element 164 are provided for spray washing froth in launder 160.

As shown in FIG. 4, standpipe 152 is mounted at least partially inside tank 112 proximate an upper end of the rotor 114 and provided internally with a spiral channel structure 166 for directing fluid from the rotor-generated vortex along a spiraling downward channel 168 that at any given location is oriented at an angle, generally an acute angle, relative to the velocity vector of liquid in the vortex at the given location. Thus, where drive shaft 142 rotates clockwise (see arrow 170) and generates a liquid vortex with a somewhat upward velocity vector 172, structure 166 has a generally opposite inclination causing a somewhat downward liquid backflow 174 during normal or forward operation of the froth flotation cell.

Vortex stabilization structure 166 may comprise at least one spiral vane or web (not separately labeled) extending inwardly from an inner surface (not separately designated) of standpipe 152. Alternatively, vortex stabilization structure 166 may comprise a plurality of mutually spaced vane sections generally aligned with one another in a spiraling configuration. In general, standpipes 35 and 152 are provided with internal structures that exhibit downwardly facing inclined surfaces having an angle of inclination, relative to a horizontal plane, that is opposed to the angle of inclination of the vortex velocity. Liquid that drifts outward from the vortex is captured in the channels 50 and 168 and directed downwardly, opposite to the upward drift of the vortex. The inner edges of the vortex stabilization structures 48 and 166 thus define outer peripheries of the respective vortices. The higher the vortices attempt to climb, the more liquid is drawn into the channels 50 and 168, thereby reducing vortex height increases and stabilizing the vortices.

FIGS. 5-8 show a particular embodiment of a vortex stabilization spiral structure 200 installable along an inner surface 202 of a standpipe 204. Spiral structure 200 includes a helical web or strip 206 and, along a circumferential outer edge thereof, an enlarged band or flange 208 that is connected to the inner surface of standpipe 204. Of course, the web or strip 206 could also comprise any different cross- sectional geometry, e.g. it could simply be rectangular. Furthermore, and as described hereinafter with respect to FIGS. 12 and 13, the web or strip 206 does not necessarily need to be mounted perpendicular to the standpipe 204 inner surface 202. For example, the web or strip 206 could be variously inclined upwardly or downwardly in along and from a radial direction with respect to the standpipe 204 inner surface 202, to, for example, help keep the vortex stabilization structure 200 flowing smoothly and help clean out any accumulated solids or other debris therein.

In addition, the web or strip 206 could be made of a variety of materials such as metal, plastic, rubber or mesh, or any combination thereof; the web or strip 206 may include various perforations, openings, or holes 214 at certain locations therein to help shed or wash particles therethrough and generally towards and out the bottom of the standpipe; and the web or strip 206 may be made of a variously solid and/or flexible material.

Web or strip 206 has a downwardly facing surface 210 that is inclined, as discussed hereinafter with reference to FIG. 9, so as to exert a downward force on liquid that moves outwardly from a vortex to enter a spiral or helical channel 212 between adjacent turns of spiral structure 200. Web or strip 206 has a width sufficiently large to draw off an effective volume of liquid in a rising vortex, at least impeding if not arresting an increase in height of the vortex. Web or strip 206 is not wide enough as to completely block the vortex.

Vortex stabilization spiral structures 48, 166, and 200 may be affixed to the respective standpipes 35, 152 and 204 by welding. Vortex stabilization spiral structures 48, 166, and 200 may be installed in a retrofit operation, wherein the spiral structures are inserted into extant standpipes 35, 152 and 204 on site. Alternatively, spiral structures 48, 166, and 200 may be mounted to replacement standpipes at the factory or other off- site facility, and the replacement standpipes installed in existing froth flotation cells in retrofit operations.

As depicted in FIG. 9, a vortex stabilization structure 220 as described hereinabove is inclined relative to a transverse plane 222, i.e., a plane oriented perpendicularly to a longitudinal or rotation axis 224 of a standpipe. More particularly, vortex stabilization structure 220 has an outer edge 225 (radially removed or spaced from axis 224) oriented at an angle al relative to transverse plane 222. Vortex stabilization structure 220 is thus inclined in a circumferential direction so that an intersection between vortex stabilization structure 220 and a cylinder coaxial with axis 224 is oriented at an acute angle relative to a horizontal or transverse plane 222. In addition, vortex stabilization structure 220 may or may not be inclined in a radial direction. With a radial inclination, an intersection of vortex stabilization structure 220 and a radial plane through axis 222 would be a section having an acute angle relative to a horizontal or transverse plane 222. During operation of a froth flotation cell containing vortex stabilization structure 220, vortex liquid moves with a velocity vector 226 that is inclined at an angle a2 relative to transverse plane 222, while vortex stabilization structure 220 creates a downward backflow 227 that reduces upward rising of the vortex and thereby stabilizes the vortex.

As illustrated in FIG. 10, a vortex stabilization structure 228 for a froth flotation cell comprises a plurality of mutually spaced vanes 230 projecting inwardly from an inner surface 232 of a standpipe or stand tube 234. Vanes 230 have outer edges 236, flush along the inner surface 232 of the standpipe 234, that are inclined as discussed above with reference to FIG. 9.

As illustrated in FIG. 11, a vortex stabilization structure 238 comprises a plurality of mutually spaced rectangular vanes 240 attached to an inner surface 242 of a standpipe or stand tube 244 via spacers 246. Vanes 240 have outer edges 248, juxtaposed to but spaced from inner surface 242 of standpipe 244, that are inclined as discussed above with reference to FIG. 9. In this embodiment liquid in the vortex may move upwardly in a layer along the inner surface of standpipe 244 while additional vortex fluid moves upwardly along the inner side of the vortex stabilization structure 238, with the vortex stabilization structure 238 impelling a generally opposing, downward movement of the vortex fluid collected therein. Vanes 240 may be disposed along a spiral path or locus about a longitudinal axis of standpipe 244.

As discussed above, and also as illustrated schematically in FIGS. 12 and 13, the vortex stabilization structure 250 may be variously inclined, or directly perpendicular to, in along and from a radial direction with respect to the stand pipe 252 inner surface 254. Such a radial vortex stabilization structure inclination may be used with a particular slurry and also in order to help prevent the accumulation of solids or particles within said structure. Furthermore, the structure 250 could also be made somewhat flexible for certain specific applications for similar purposes. Described in yet another way, in general, and in view of the discussion and various of the figures discussed above, the present invention comprises a vortex stabilization structure for use in a standpipe and extending radially inwardly from the standpipe' s inner surface, said standpipe to be mounted in a flotation cell and including a central longitudinal axis (axes C-L as shown in FIGS. 3-6, 8, 9, and 11-14), said vortex stabilization structure being asymmetric when viewed with respect to any plane drawn through the central longitudinal axis of said standpipe.

A vortex stabilization structure as described herein generally defines a channel that spirals generally downwardly. Such a vortex stabilization structure transfers the substance of the vortex down along the channel as the vortex spins, discharging the dynamic potential energy of the vortex.

Consequently, the piling up of fluids along the standpipe is reduced dramatically. Stabilization of the vortex also stabilizes the rotor submergence condition and the air intake rate. Accordingly, the multiphase jet stream in the disperser region is stabilized and the fluid surface of the flotation cell calms down.

With respect to FIG. 14, yet another embodiment of the present invention is shown where a plurality (i.e. two or more) of generally circular baffles, 302, 304 and 306, is shown. Such a plurality of baffles would form the vortex stabilization structure 300 in the present embodiment and these baffles would generally be installed along the inner surface of a standpipe, not specifically shown in FIG. 14 but generally as shown and discussed with respect to the various other embodiments herein, wherein the baffles' lower surfaces, 314, 316 and 318, would act to inhibit the upward movement of a liquid/slurry vortex formed inside the standpipe when installed and operating inside a flotation cell. In short, the FIG. 14 vortex stabilization structure 300 would be for use in a standpipe and extending inwardly from the standpipe' s inner surface, said standpipe to be operationally mounted in a flotation cell, said vortex stabilization structure 300 comprising a plurality of baffles extending inwardly from the inner surface of the standpipe.

Furthermore, and as shown in FIG. 14, any of the plurality of baffles, e.g., 302, 304 and 306, could be simply circular and flat, oblong or otherwise varied in geometric shape, and/or include various appendages 320 (e.g., tabs, wings, and/or inclinations, possibly formed and/or mounted at a general angle b to the plane of the baffle(s)) and/or perforations 322 to improve a baffle's efficiency and performance with respect to particular vortex, flow and/or slurry conditions encountered. Of course, said baffles could likewise be variously mounted within the standpipe, both in terms of mounting methods such as welding or with fasteners, but also in geometric terms such as generally horizontally, at a kilter, and/or at various angles to the horizontal plane cross-secting the structure and the standpipe and in view of the central longitudinal axis L of the vortex stabilization structure 300 and of the

accompanying standpipe.

Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.