Supercharger with sun gear and planetary gears

A supercharger includes a supercharger housing, a primary rotor having a primary rotor shaft fixed to rotate therewith. A ring gear with internal teeth is attached to a transmission housing portion of the supercharger housing. A sun gear is fixed to the primary rotor shaft. A planetary gear carrier has a plurality of planetary gear shafts. A plurality of planetary gears rotate about corresponding planetary gear shafts and are meshingly engaged with the sun gear and the ring gear and are substantially equally spaced about the sun gear. A rotatable input shaft is connectable to the planetary gear carrier. The input shaft is connectable to receive rotational motion and power from an engine.

BACKGROUND

Superchargers may be used to increase or “boost” the air pressure in the intake manifold of an internal combustion (IC) engine to increase the horsepower output of the IC engine. The IC engine may thus have an increased horsepower output capability than would otherwise occur if the engine were normally aspirated (e.g., the piston would draw air into the cylinder during the intake stroke of the piston). A conventional supercharger is generally mechanically driven by the engine, and therefore, may represent a drain on engine horsepower whenever engine “boost” may not be required and/or desired. A selectively engageable clutch may be disposed in series between the supercharger input (e.g., a belt driven pulley) and the rotors of the supercharger. A transmission may be disposed in series between the clutch and the rotors of the supercharger.

SUMMARY

A supercharger includes a supercharger housing, and a primary rotor having a primary rotor shaft fixed to rotate therewith. A ring gear with internal teeth is attached to a transmission housing portion of the supercharger housing. A sun gear is fixed to the primary rotor shaft. A planetary gear carrier has a plurality of planetary gear shafts. A plurality of planetary gears rotate about corresponding planetary gear shafts and are meshingly engaged with the sun gear and the ring gear and are substantially equally spaced about the sun gear. A rotatable input shaft is connectable to the planetary gear carrier. The input shaft is connectable to receive rotational motion and power from an engine.

DETAILED DESCRIPTION

The present disclosure relates generally to superchargers.

Superchargers according to the present disclosure may be of various types. For example, a fixed displacement supercharger such as the Roots-type functions as a pump outputting a fixed volume of air per rotation. Compression of the air delivered by the Roots-type supercharger takes place downstream of the supercharger by increasing the mass of air in a fixed volume of the engine intake manifold. Another example of a supercharger is a compressor, such as a centrifugal-type supercharger that compresses the air as it passes through the supercharger. In the centrifugal-type supercharger, the pressure of air delivered to the engine is dependent on compressor speed.

Some engines, e.g., diesel engines, may have a relatively slow turning crankshaft and may have a relatively small diameter crankshaft pulley (e.g., about 152 mm, i.e., about 6 inches). In examples of the present disclosure, the supercharger may be driven by a belt connected from a crankshaft pulley to a drive-pulley connected to a pulley/input shaft of the supercharger. A transmission may be included in the supercharger to cause the supercharger rotors to turn at a step-up ratio of the pulley/input shaft speed. Examples of the planetary gear transmission of the present disclosure may allow higher step-up ratios in a more compact package than presently available supercharger transmissions.

With reference toFIG. 1, a supercharger may include a primary supercharger rotor shaft29as the output of a supercharger transmission54. The supercharger transmission54may have a gearing arrangement to step-up the speed of the primary supercharger rotor14and the secondary supercharger rotor14′ and thereby increase the airflow output of the supercharger12.

The supercharger12may be powered by a belt-driven drive pulley24. The drive pulley24may be driven by an engine crankshaft pulley (not shown) connected to the drive pulley24via a front end accessory drive (FEAD) belt (also not shown). In an example according to the present disclosure, the rotatable supercharger pulley driveshaft23may be driven in any suitable manner, for example by a chain drive (not shown). The drive pulley24may be fixed for rotation with a rotatable supercharger pulley driveshaft23. Therefore, the rotatable supercharger pulley driveshaft23may be connectable to receive rotational motion and power from a motor (not shown). The motor may be an internal combustion engine, an electric motor, or combinations thereof. It is to be understood that the motor that powers the supercharger12is not necessarily the same internal combustion engine that receives air driven by the supercharger12.

The drive pulley24is connected to the rotatable supercharger pulley driveshaft23of the supercharger12. The rotatable supercharger pulley driveshaft23may be connected to a carrier driveshaft25to rotate a planetary gear carrier51. A clutch assembly10may be disposed between the rotatable supercharger pulley driveshaft23and the carrier driveshaft25. The clutch assembly10may selectively connect the rotatable supercharger pulley driveshaft23to the carrier driveshaft25for rotation therewith.

In examples of the present disclosure, the pulley driveshaft may rotate at a range of speeds up to about 10,000 RPM (revolutions per minute). When an internal combustion (IC) engine turns, the rotatable supercharger pulley driveshaft23may turn at a speed that depends on a ratio of the diameters of the crankshaft pulley (not shown) and the drive pulley24. In an example, if the IC engine turns at about 1000 RPM, and the ratio of the crankshaft pulley diameter to the drive pulley diameter is about 2.5, then the rotatable supercharger pulley driveshaft23will turn at about 2500 RPM.

It may be desirable to turn the supercharger rotors14,14′ at over 10,000 RPM to boost the power of the IC engine at low IC engine speeds. IC engines may turn over a wide range of speeds. For example, some captive two-stroke low speed diesel engines operate in a range from 100-200 RPM. Other diesel engines may operate in a range from about 500 RPM to about 2500 RPM. Some IC engines may operate from about 500 RPM to over 10,000 RPM.

In the example depicted inFIG. 1, the rotatable supercharger pulley driveshaft23is supported for rotation, at least in part, by an outer shaft bearing38. In an example, the outer shaft bearing38may be a greased double-row ball bearing (e.g., not requiring access to a common sump of lubricant from within the supercharger housing15, and, in some cases, lubed for the service life of the greased double-row ball bearing). The outer shaft bearing38may be disposed in a bore of the supercharger housing15near the drive pulley24. In an example, the drive pulley24may surround a portion of the outer shaft bearing38. An oil seal76may be disposed in the transmission housing20around the carrier driveshaft25on a portion of the carrier driveshaft25near an interface between the transmission housing20and the clutch housing11. The oil seal76may be, for example, a double lip shaft seal, or a single lip shaft seal that allows the carrier driveshaft25to turn while substantially preventing oil from flowing between the interface of the carrier driveshaft and the oil seal76. The oil seal76may retain lubricant substantially within the transmission housing20to allow for a common sump of lubrication for various internal components of the supercharger12and may provide a barrier to keep external contaminants outside of the common sump.

As depicted inFIG. 1, the rotatable supercharger pulley driveshaft23may also be supported by a deep-groove ball bearing21. In an example of the present disclosure, the deep-groove ball bearing21and the outer shaft bearing38may be separated as much as possible along the rotatable supercharger pulley driveshaft23. The deep-groove ball bearing21may be pressed on the rotatable supercharger pulley driveshaft23and disposed within the clutch housing11to float within a bearing bore66adjacent to clutch assembly10. The bearing bore66may be sized to have a slip fit with the deep-groove ball bearing21. A spring33may be disposed surrounding the rotatable supercharger pulley driveshaft23and between the clutch housing11and the deep-groove ball bearing21to place a light axial load on an outer race37″ of the deep-groove ball bearing21and prevent the outer race37″ from spinning in the bearing bore66. The spring33may include, for example, a helical spring, a wave spring, a Belleville washer, an O-ring, and combinations thereof.

An example of an assembly method for the rotatable supercharger pulley driveshaft23according to the present disclosure includes the following: 1) pressing the deep-groove ball bearing21onto the rotatable supercharger pulley driveshaft23; 2) pressing the outer shaft bearing38into the supercharger housing15; 3) inserting spring33into the supercharger housing15; and 4) pressing the rotatable supercharger pulley driveshaft23(with the deep-groove ball bearing installed thereon) into the outer shaft bearing38while supporting the inner race (not shown) of the outer shaft bearing38. The foregoing disclosed method may reduce bearing damage during assembly.

The clutch assembly10may selectively connect the rotatable supercharger pulley driveshaft23to the carrier driveshaft25for rotation therewith. It is to be understood that the clutch assembly10may allow the rotatable supercharger pulley driveshaft23and the carrier driveshaft25to be selectively rotationally disconnected. Further, the clutch assembly10may allow rotational slippage between the rotatable supercharger pulley driveshaft23and the carrier driveshaft25for a time during engagement of the clutch10before the clutch10reaches full engagement. When the clutch10is fully engaged, the rotatable supercharger pulley driveshaft23and the carrier driveshaft25substantially rotate together without rotational slippage.

The clutch assembly10may include any type of clutch. For example, the clutch assembly10may be pneumatically actuated (not shown), hydraulically actuated (not shown), or electrically actuated (FIG. 1). The clutch assembly10may include a single plate friction clutch (FIG. 1), multiple plate friction clutch (not shown), or a dog clutch (not shown), etc. In an example, the clutch assembly10may include an electromagnetically actuated friction clutch27having an electromagnetic coil31, a clutch armature26, and a clutch rotor28. The clutch rotor28may be attached to the rotatable supercharger pulley driveshaft23to rotate therewith. The clutch armature26may be attached to the carrier driveshaft25to rotate therewith. In another example (not shown) the clutch rotor28may be attached to the carrier driveshaft25to rotate therewith, and the clutch armature26may be attached to the pulley driveshaft. This example (not shown) may reduce the rotating inertia of the portion of the supercharger that is not arranged to be decoupled from the rotatable supercharger pulley driveshaft23.

In the example depicted inFIG. 1, the electromagnetically actuated friction clutch27is biased to a normally disengaged configuration. Normally disengaged, as used herein, means that the clutch rotor28and the clutch armature26are in contact to rotate together when the electromagnetic coil31is energized by passing electric current through the electromagnetic coil31. Otherwise, when no electric current passes through the electromagnetic coil31, the clutch rotor28and the clutch armature26are not in contact and do not rotate together. Actuation of the electromagnetically actuated friction clutch27is caused by energizing the electromagnetic coil31to cause engagement or disengagement of opposing friction surfaces in the clutch mechanism (for example on opposed surfaces of the clutch rotor28and the clutch armature26).

In the example depicted inFIG. 1, the clutch armature26may be magnetically attracted to the clutch rotor28when the electromagnetic coil31is energized, and the clutch armature26may be normally biased away from the clutch rotor28by a spring (not shown). For example, a plurality of leaf springs within the clutch armature26may be disposed to return the clutch armature26to a disengaged position when the electromagnetic coil31is not energized.

As depicted inFIG. 1, the carrier driveshaft25may be supported by a carrier shaft bearing40. The carrier shaft bearing40may be located within the transmission housing20adjacent to the planetary gear carrier51(discussed further below). The carrier shaft bearing40may have an inner bearing end41proximate the planetary gear carrier51and an outer bearing end42distal to the planetary gear carrier51. The carrier shaft bearing40may be disposed on the carrier driveshaft25against a shoulder39formed on the carrier driveshaft25to act as an axial stop for axially retaining the outer bearing end42. A resilient annular element35may be disposed surrounding the carrier driveshaft25and between the outer bearing end42of an outer race37of carrier shaft bearing40and the oil seal76to provide a small amount of axial force to prevent the outer race37of the carrier shaft bearing40from rotating relative to the transmission housing20. It is believed that by using the resilient annular element35as disclosed herein, damage to the carrier shaft bearing40may be avoided. The resilient annular element35may be, for example, a helical spring, a wave spring, a Belleville washer, O-rings, etc.

The resilient annular element35and carrier shaft bearing40arrangement disclosed above may improve durability of the carrier shaft bearing40in at least two ways: 1) compensating for the ratio of thermal expansion between an aluminum housing and the steel shaft contained within; and 2) avoiding pressing loads across the bearing that may cause brinelling of the bearing race. The thermal expansion ratio difference between the shaft and bearings and the aluminum housing in which they are contained may generate axial loads under thermal cycling that may reduce bearing life if both ends of the shaft are constrained by having both inner and outer bearing races installed by pressing.

In an example of the present disclosure, the carrier driveshaft25may be connectable to a planetary gearset50. The planetary gearset50serves to turn the supercharger rotors14,14′ at a step-up ratio applied to the speed of the carrier driveshaft25. The planetary gearset50includes a plurality of planetary gears53, a sun gear55, and a ring gear57. The ring gear57has internal teeth59and surrounds the planetary gears53in meshing engagement with each of the planetary gears53simultaneously. The sun gear55is in meshing engagement with each of the planetary gears53simultaneously, and the sun gear55is fixed to the primary supercharger rotor shaft29for rotation therewith.

The planetary gears53are substantially equally spaced about the sun gear55. In examples of the present disclosure, the plurality of planetary gears53may include3planetary gears53or5planetary gears53. In other examples, the planetary gears may include any number of planetary gears53, for example 4 or 6 planetary gears53. The planetary gears53are configured to revolve around the axis43of the sun gear55with the planetary gear carrier51via a plurality of planetary gear shafts61disposed thereon. The planetary gear shafts61each are substantially parallel to a carrier primary axis of rotation63which is substantially coincident with an axis of rotation of the carrier driveshaft25and the axis43of the sun gear55. The planetary gears53include a plurality of gear bores65axially defined respectively within the plurality of planetary gears53. Further, there may be a plurality of planetary roller bearings49respectively disposed within the plurality of planetary gear bores65for the planetary roller bearings49to support the plurality of planetary gear shafts61. In other words, each gear bore65has a corresponding planetary roller bearing49for a respective corresponding planetary gear shaft61. As such, each of the plurality of planetary gears53may rotate about a corresponding planetary gear shaft61of the plurality of planetary gear shafts.

It is to be understood that the gears of the planetary gearset50, including the ring gear57, sun gear55, and planetary gears53, may be sized according to particular application loading conditions. For example, the ring gear57may maximize the strength density of the transmission package volume by substantially matching the outer diameter of the clutch. In an example, the ring gear57may have an outer diameter of about 100 mm. In examples of the present disclosure, the planetary gears may have 24 teeth, on a diameter of 60 mm centers, and a pitch diameter of about 30 mm. In an example, the internal teeth59of the ring gear57may be helical gear teeth, and the sun gear55and the plurality of planetary gears53each have helical teeth to engage the internal teeth59of the ring gear57. In an example of the present disclosure, the planetary gears53may be plastic, steel or combinations thereof.

The planetary gearset50may include a plurality of spacers67(seeFIGS. 2 and 3) respectively disposed on the plurality of planetary gear shafts61between the plurality of planetary roller bearings49and the planetary gear carrier51. The spacers67may improve interchangeability between parts. The spacers67may establish the value of the relative distance between the planetary gear53and the planetary gear carrier51. Each of the planetary gear shafts61includes an annular bearing retention groove69on a bearing end45of each of the planetary gear shafts61and an annular carrier retention groove71defined on a carrier end47of each of the planetary gear shafts61. The carrier end47of each planetary gear shaft61is distal to the bearing end45. A first clip ring74may be disposed in the annular bearing retention groove69and a second clip ring75may be disposed in the annular carrier retention groove71. At least one of the first clip ring74and the second clip ring75may be a bevel clip ring88. (SeeFIG. 4A and 4B.)

It is to be understood that the supercharger housing15may include a rotor housing16that is separable from a transmission housing20. The supercharger housing15may be joined together with bolts or other fasteners. A resilient gasket or other form of sealer may be disposed between portions of the supercharger housing to form a seal. For example, the primary supercharger rotor14may be disposed within the supercharger housing15. The primary supercharger rotor14may be substantially, if not entirely, contained within the rotor housing16(i.e., the rotor may extend beyond the rotor housing16into the transmission housing20portion of the supercharger housing15).

In an example, the transmission housing20may define an annular shaft clearance groove73for accommodating travel of the plurality of planetary gear shafts61.

The ring gear57may be fixedly attached to the supercharger housing15. In an example, the ring gear57may be clamped in series or parallel with a resilient ring77disposed between the rotor housing16and the transmission housing20. The resilient ring77may provide a substantially liquid-tight seal between the ring gear57and the rotor housing16. Clamping the ring gear57between the rotor housing16and the transmission housing20substantially prevents motion between the ring gear57and the supercharger housing15. The resilient ring77provides a substantially uniform clamping load on the ring gear57. The uniformity of the clamping load may reduce noise from cyclical inconsistencies of the planetary gears53engaging with the ring gear57. The resilience of the resilient ring77further serves to damp vibration.

As shown inFIG. 1andFIG. 2, the transmission housing20may have a piloting diameter79for the ring gear57.

In an example, the ring gear57is not clamped to the transmission housing20and is free to rotate relative to the supercharger housing15(not shown). In such an example, the ring gear57may be driven by an alternate power device (e.g., electric drive motors) to provide further modification of the gear ratios in the transmission by increasing or decreasing the relative speed of the ring gear57. Examples of the present disclosure with a moving ring gear57may generate a range of ratios from about 20:1 to about 0.5:1. In this way, the supercharger may have a variable step-up ratio.

In an example of the present disclosure, the primary supercharger rotor14is fixed to a primary supercharger rotor shaft29for rotation therewith. The primary supercharger rotor14and a secondary supercharger rotor14′ are cooperatively driven through a pair of timing gears58,60, discussed more fully below. The primary supercharger rotor shaft29is fixed for rotation with the primary supercharger rotor14and a primary timing gear58. The primary timing gear58is meshingly engaged with a secondary timing gear60. The secondary timing gear60is fixed for rotation with a secondary rotor shaft18. The secondary rotor shaft18is also fixed for rotation with the secondary rotor14′. The secondary rotor14′ cooperatively rotates with a controlled position relative to the primary supercharger rotor14with substantially no contact therebetween. An abradeable powdercoat on the rotors14,14′ may compensate for manufacturing tolerances. The timing gears58,60may include an equal number of gear teeth spaced at a relatively high tooth pitch. For example, the timing gears58,60may each have30teeth for meshing engagement with one another, therefore the timing gears58,60rotate with a substantially equal angular speed. As such, the timing gears58,60substantially synchronize the rotors14,14′, thereby substantially preventing contact between the lobes of the rotors14,14′. A small amount of flank-to-flank lash may be split between rotors to compensate for thermal and pressure induced distortion of rotor size, shape, and position.

FIG. 2is a semi-schematic cross-section view of a portion of an example of a supercharger12′ with a planetary gearset50similar to the supercharger12ofFIG. 1without a clutch assembly between the drive pulley24and the planetary gearset50according to the present disclosure. Many of the elements of the supercharger12′ depicted inFIG. 2are the same as the elements inFIG. 1. InFIG. 2, however, a rotatable input shaft22is a combination of the rotatable supercharger pulley driveshaft23and the carrier driveshaft25depicted inFIG. 1.

In the example depicted inFIG. 2, the rotatable input shaft22is supported for rotation, at least in part, by an outer shaft bearing38similar to the outer shaft bearing38inFIG. 1. An oil seal76may be disposed in the transmission housing20around the rotatable input shaft22on a portion of the rotatable input shaft22near the outer shaft bearing38. The oil seal76may be, for example, a double lip shaft seal, or a single lip shaft seal that allows the rotatable input shaft22to turn while substantially preventing oil from flowing between the interface of the rotatable input shaft22and the oil seal76. The oil seal76may retain lubricant substantially within the transmission housing20to allow for a common sump of lubrication for various internal components of the supercharger12′ and may provide a barrier to keep external contaminants outside of the common sump.

As depicted inFIG. 2, the rotatable input shaft22may be supported by a carrier shaft bearing40′. The carrier shaft bearing40′ may be located within the transmission housing20adjacent to the planetary gear carrier51. The carrier shaft bearing40′ may have an inner bearing end41′ proximate the planetary gear carrier51and an outer bearing end42′ distal to the planetary gear carrier51. The carrier shaft bearing40′ may be disposed on the rotatable input shaft22against a shoulder39′ formed on the rotatable input shaft22to act as an axial stop for axially retaining the outer bearing end42′.

A resilient annular element35may be disposed surrounding the rotatable input shaft22and between the outer bearing end42′ of an outer race37′ of carrier shaft bearing40′ and the oil seal76to provide a small amount of axial force to prevent the outer race37′ of the carrier shaft bearing40′ from rotating relative to the transmission housing20. It is believed that by using the resilient annular element35as disclosed herein, damage to the carrier shaft bearing40′ (such as brinelling that could occur from pressing the bearing into the transmission housing20by applying a pressing force to the rotatable input shaft22) may be avoided. Further, the disclosed arrangement may reduce side loading of the bearing during thermal expansion of the aluminum housing and steel rotatable input shaft22. Without the arrangement including the resilient annular element35, the difference between the thermal expansion rates may cause excessive translation of the related bearing race positions. For example, if the bearing were pressed on both the inner and outer races, the housing could expand in diameter thereby reducing retention force on the bearing. The housing could also expand in length—enabling the bearing to shift in position in the thermally expanded bore. Subsequently, the housing may cool and re-retain the bearing in an incorrect position. The resilient annular element35may be, for example, a helical spring, a wave spring, a Belleville washer, O-rings, etc.

FIG. 3is a semi-schematic cross-section view of a portion of an example of a supercharger12″ with a planetary gearset50similar to the supercharger12′ ofFIG. 2without the carrier shaft bearing40′ depicted inFIG. 2. In the example depicted inFIG. 3, the rotatable input shaft22is supported near a pulley end19of the rotatable input shaft22by the outer shaft bearing38disposed in a bore85of the transmission housing20, and the rotatable input shaft22is supported on a planetary end17of the rotatable input shaft22distal to the pulley end19by the planetary gear carrier51without a bearing supporting the rotatable input shaft22between the planetary gear carrier51and the outer shaft bearing38. Thus, the planetary gearset50may function as a bearing support for the rotatable input shaft22. In this way, the rotatable input shaft22receives sufficient support from the planetary gears53through the planetary gear shafts61in order to omit the carrier shaft bearing40′ that was included in the example depicted inFIG. 2. As such, in the example depicted inFIG. 3, the outer shaft bearing38is the only bearing directly on the rotatable input shaft22. It is to be understood that oil seal76substantially does not contribute to support of the rotatable input shaft22because of the flexibility of the resilient portions90. As such, an oil seal76with resilient portions90that are the only contact between the oil seal76and the rotatable input shaft22is not to be considered a bearing as used herein. The supercharger12″ may weigh less, and have a shorter length than the supercharger12′ because the carrier shaft bearing40′ depicted inFIG. 2has been removed from the supercharger12″ depicted inFIG. 3.

FIG. 4Ais a cross-section view of an example of a bevel clip ring88according to the present disclosure. The bevel clip ring88is distinguished from other clip rings by the beveled inner diameter89. The beveled inner diameter89cooperates with the annular bearing retention groove69and/or the annular carrier retention groove71to reduce axial motion of the planetary gears53along the planetary gear shaft61. A thickness91of the bevel clip ring88may be larger than the annular bearing/carrier retention groove69/71. As such, the beveled inner diameter89may act as a wedge, eliminating play between the bevel clip ring88and the planetary gear shaft61.

A range of transmission gear ratios, i.e., step-up gear ratios, from about 2:1 to about 6:1 may be used in examples of the present disclosure. As shown inFIG. 5, a two-gear step-up drive81may be used in addition to the planetary gearset50as described above to provide a combination transmission83for the supercharger. In this way, the output of the planetary gearset50drives one of the gears of the two-gear step-up drive81to provide a cumulative gear ratio. The drive ratio of combination transmission83provides a rotational speed differential between a step-up input shaft86and a step-up output shaft87. For example, if using a 2:1 step-up gear ratio, when the step-up input shaft86spins at 1,000 revolutions per minute (RPM), the primary supercharger rotor14may spin at 2,000 RPM because the primary supercharger rotor14rotates with the step-up output shaft87. The step-up output shaft87may be the primary supercharger rotor shaft29. The combination transmission83also allows for packaging flexibility by allowing the input shaft centerline to be located in any angular position about the pitch diameter interface of the step-up gears—even if a 1:1 ratio is selected.

It is to be understood that the terms “connect/connected/connection” and/or the like are broadly defined herein to encompass a variety of divergent connected arrangements and assembly techniques. These arrangements and techniques include, but are not limited to (1) the direct communication between one component and another component with no intervening components therebetween; and (2) the communication of one component and another component with one or more components therebetween, provided that the one component being “connected to” the other component is somehow in operative communication with the other component (notwithstanding the presence of one or more additional components therebetween).

It is to be understood that the ranges provided herein include the stated range and any value or sub-range within the stated range. For example, a range from about 500 RPM to about 2500 RPM should be interpreted to include not only the explicitly recited limits of about 500 RPM to about 2500 RPM, but also to include individual values, such as 550 RPM, 820 RPM, 1200 RPM etc., and sub-ranges, such as from about 750 RPM to about 1000 RPM, etc. Furthermore, when “about” is utilized to describe a value, this is meant to encompass minor variations (up to +/−10%) from the stated value.

Furthermore, the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Reference throughout the specification to “one example”, “another example”, “an example”, and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the example is included in at least one example described herein, and may or may not be present in other examples. In addition, it is to be understood that the described elements for any example may be combined in any suitable manner in the various examples unless the context clearly dictates otherwise.

While several examples have been described in detail, it will be apparent to those skilled in the art that the disclosed examples may be modified. Therefore, the foregoing description is to be considered non-limiting.