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Title:
POWER TAKE-OFF SYSTEM FOR AN INTERNAL COMBUSTION ENGINE
Document Type and Number:
WIPO Patent Application WO/2014/015035
Kind Code:
A1
Abstract:
A power take-off system (30) for an internal combustion engine (10) that has an engine crank gear (26) is described. The power take-off system includes a driver gear (60) driven by the crank gear and a housing (31) that includes an interior (37) and a flange (52) positioned under the driver gear. The flange has an upwardly facing surface (54) that extends from a location beneath the driver gear to an opening (56) of the interior of the housing. The upwardly facing surface is downwardly angled from the location beneath the driver gear to the opening of the interior of the housing. The power take-off system further includes a plurality of gears (70, 74, 80) that are positioned within the housing in gear-meshing engagement with each other, wherein a first (70) of the plurality of gears is co-rotatably coupled with the driver gear and a second (80) of the plurality of gears is coupleable with an auxiliary device (34).

Inventors:
HUANG, Cheng-Xiu (500 Jackson St, MC 60113Columbus, Indiana, 47201, US)
HE, Min (500 Jackson St, MC 60113Columbus, Indiana, 47201, US)
LEGGOTT, Paul A. (Cummins Engine Ltd, Yarm Road, Darlington Durham DL1 4PW, 4PW, GB)
Application Number:
US2013/050881
Publication Date:
January 23, 2014
Filing Date:
July 17, 2013
Export Citation:
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Assignee:
CUMMINS IP, INC. (1400-73rd Avenue NE, Minneapolis, Minnesota, 55432, US)
International Classes:
F02B61/06; F01M9/10; F02B67/04
Foreign References:
US20030015166A1
US20040108167A1
US6415758B1
Attorney, Agent or Firm:
MASSEY, Bryan J. et al. (8 East Broadway, Suite 600Salt Lake City, Utah, 84111, US)
Download PDF:
Claims:
CLAIMS

1. A power take-off system for an internal combustion engine having an engine crank gear, comprising:

a driver gear driven by the crank gear;

a housing comprising an interior and a flange positioned under the driver gear, the flange having an upwardly facing surface extending from a location beneath the driver gear to an opening of the interior of the housing, wherein the upwardly facing surface is downwardly angled from the location beneath the driver gear to the opening of the interior of the housing; and a plurality of gears positioned within the housing in gear-meshing engagement with each other, wherein a first of the plurality of gears is co-rotatably coupled with the driver gear and a second of the plurality of gears is coupleable with an auxiliary device.

2. The power take-off system of claim 1, further comprising a lubricant transfer path from the crank gear, along the upwardly facing surface, through the opening, and onto the plurality of gears.

3. The power take-off system of claim 1, wherein the upwardly facing surface is downwardly angled at an angle between about 5-degrees and about 45-degrees with respect to horizontal.

4. The power take-off system of claim 1, wherein the upwardly facing surface is downwardly angled at an angle between about 5-degrees and about 10-degrees with respect to horizontal.

5. The power take-off system of claim 1, wherein the upwardly facing surface is downwardly angled at an angle great than about 0-degrees and less than about 5-degrees with respect to horizontal.

6. The power take-off system of claim 1, wherein the engine crank gear is housed within a crankcase of the internal combustion engine, and wherein when coupled to the internal combustion engine, the driver gear is positioned within the crankcase.

7. The power take-off system of claim 1, wherein the plurality of gears comprises a first power transfer gear co-rotatably coupled to the driver gear.

8. The power take-off system of claim 7, wherein the plurality of gears comprises a second power transfer gear driven by the first power transfer gear.

9. The power take-off system of claim 8, further comprising at least one of (i) a first auxiliary device co-rotatably coupled to the first power transfer gear; or (ii) a second auxiliary device co-rotatably coupled to the second power transfer gear.

10. The power take-off system of claim 8, wherein the plurality of gears further comprises an idler gear driven by the first power transfer gear and driving the second power transfer gear.

11. The power take-off system of claim 1, further comprising a lubricant return line in lubricant receiving communication with a bottom portion of the interior of the housing.

12. An internal combustion engine system, comprising:

an engine crank gear housing comprising an interior and a crank gear positioned within the interior of the crank gear housing;

a lubrication supply line in lubrication supplying communication with the interior of the crank gear housing;

a power take-off housing coupled to the crank gear housing, the power take-off housing defining an interior and having an opening fluidly coupling the interior of the engine crank gear housing and the interior of the power take-off housing, wherein lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing via the opening; and

a gear train positioned within the interior of the power take-off housing, the gear train being driven by the crank gear.

13. The internal combustion engine system of claim 12, wherein the power take-off housing comprises a flange extending into the engine crank gear housing, the flange comprising a sloped surface that slopes downwardly toward the opening, and wherein lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing along the flange.

14. The internal combustion engine system of claim 13, wherein the sloped surface slopes downwardly at an angle of between about 0-degrees and about 45-degrees.

15. The internal combustion engine system of claim 13, wherein the gear train comprises a driver gear positioned within the interior of the engine crank gear housing, externally of the interior of the power take-off housing, and vertically above the flange, and wherein lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing via the driver gear.

16. The internal combustion engine system of claim 15, wherein the driver gear is positioned vertically above the crank gear.

17. The internal combustion engine system of claim 12, further comprising an engine block to which the engine crank gear housing is coupled, and further comprising a lubricant reservoir coupled to the engine block and a lubrication return line in lubrication receiving communication with a bottom portion of the power take-off housing and lubrication providing communication with the lubricant reservoir.

18. The internal combustion engine system of claim 12, further comprising first and second auxiliary devices coupled to the power take-off housing, the first auxiliary device being co-rotatably coupled to a first gear of the gear train and the second auxiliary device being co- rotatably coupled to a second gear of the gear train.

19. A method for lubricating a gear train within a power take-off system operably coupled to a lubricated crank gear within a crankcase of an internal combustion engine, the method comprising:

transferring lubrication from the crank gear to a first gear of the gear train;

collecting lubrication released from the first gear of the gear train;

directing the collected lubrication released from the first gear of the gear train along an angled surface and through an opening exposed to an interior of a housing coupled to the internal combustion engine externally of the crankcase; and

lubricating at least a second gear of the gear train with the lubrication directed through the opening, the second gear being positioned within the interior of the housing.

20. The method of claim 19, wherein the first gear of the gear train is positioned within the crankcase, and collecting lubrication released from the first gear of the gear train comprises receiving lubrication that drips down from the first gear of the gear train.

Description:
POWER TAKE-OFF SYSTEM FOR AN

INTERNAL COMBUSTION ENGINE FIELD

The present disclosure relates generally to a power take-off system of an internal combustion engine, and more particularly to the lubrication of a power take-off system.

BACKGROUND

Some internal combustion engines utilize power take-off systems for powering auxiliary components. Generally, power take-off systems harness a portion of the torque generated by an internal combustion engine and transfer the harnessed torque to one or more auxiliary systems using a gear train. Typically, the gears of the gear train are maintained in meshing engagement with each other within a housing. Desirably, an interior of the housing is supplied with oil to lubricate the gears, which reduces friction and wear between meshing gears. Conventional power take-off systems use several known methods for supplying oil to the housing. However, each known method of supplying oil has various shortcomings.

For example, some conventional power take-off systems employ an oil supply line and oil drain line for continuously recycling oil between an engine's oil pan and the interior of the housing. While such systems may adequately supply oil to and lubricate the gear train, the use of an oil supply line adds complexity and cost to the system.

Other conventional power take-off systems treat the housing as a dedicated oil bath. In other words, the housing includes an oil inlet through which the interior of the housing is filled with oil from a source external to the engine (e.g., an oil can or bottle). Because the oil in the housing is not continuously recycled through the housing, oil drain and supply lines to and from the engine's oil pan are not required. However, treating the housing as a dedicated oil bath requires a user to manually fill up the housing with oil as a separate step, which can be an undesirable approach for many users.

SUMMARY

The subject matter of the present application has been developed in response to the present state of the art, and in particular, in response to the problems and needs in power take-off system art that have not yet been fully solved by currently available power take-off systems. Accordingly, in certain embodiments, a power take-off system is disclosed herein that does not require a separate, stand-alone, oil supply line from the oil pan for lubrication and does not require manually filling up the system with oil in a separate step. In other words, the power take- off system described in the present disclosure overcomes many of the shortcomings of the prior art.

According to one embodiment, a power take-off system for an internal combustion engine having an engine crank gear is described. The power take-off system includes a driver gear driven by the crank gear and a housing that includes an interior and a flange positioned under the driver gear. The flange has an upwardly facing surface that extends from a location beneath the driver gear to an opening of the interior of the housing. The upwardly facing surface is downwardly angled from the location beneath the driver gear to the opening of the interior of the housing. The power take-off system further includes a plurality of gears that are positioned within the housing in gear-meshing engagement with each other, wherein a first of the plurality of gears is co-rotatably coupled with the driver gear and a second of the plurality of gears is coupleable with an auxiliary device.

In some implementations, the power take-off system includes a lubricant transfer path from the crank gear, along the upwardly facing surface, through the opening, and onto the plurality of gears. According to certain implementations, the upwardly facing surface is downwardly angled at an angle between about 5-degrees and about 45-degrees with respect to horizontal. In certain implementations, the upwardly facing surface is downwardly angled at an angle between about 5-degrees and about 10-degrees with respect to horizontal. In yet some implementations, the upwardly facing surface is downwardly angled at an angle great than about 0-degrees and less than about 5-degrees with respect to horizontal.

According to certain implementations of the power take-off system, the engine crank gear is housed within a crankcase of the internal combustion engine. When coupled to the internal combustion engine, the driver gear is positioned within the crankcase. The plurality of gears can include a first power transfer gear co-rotatably coupled to the driver gear. In some

implementations, the plurality of gears includes a second power transfer gear driven by the first power transfer gear. A first auxiliary device can be co-rotatably coupled to the first power transfer gear in some implementations. A second auxiliary device can be co-rotatably coupled to the second power transfer gear in some implementations. According to various implementations, the plurality of gears further includes an idler gear driven by the first power transfer gear and driving the second power transfer gear. The power take-off system may include a lubricant return line in lubricant receiving communication with a bottom portion of the interior of the housing.

In yet another embodiment, an internal combustion engine system includes an engine crank gear housing that includes an interior and a crank gear that is positioned within the interior of the crank gear housing. The internal combustion engine system also includes a lubrication supply line in lubrication supplying communication with the interior of the crank gear housing. The system also includes a power take-off housing that is coupled to the engine crank gear housing. The power take-off housing defines an interior and has an opening fluidly coupling the interior of the crank gear housing and the interior of the power take-off housing. Lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing via the opening. The internal combustion engine system also includes a gear train positioned within the interior of the power take-off housing. The gear train is driven by the crank gear.

According to some implementations of the internal combustion engine system, the power take-off housing includes a flange that extends into the engine crank gear housing. The flange includes a sloped surface that slopes downwardly toward the opening. Lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing along the flange. The sloped surface can slope downwardly at an angle of between about 0-degrees and about 45-degrees.

In certain implementations, the gear train includes a driver gear positioned within the interior of the engine crank gear housing, externally of the interior of the power take-off housing, and vertically above the flange. Lubrication within the interior of the engine crank gear housing is transferrable into the interior of the power take-off housing via the driver gear. The driver gear can be positioned vertically above the crank gear.

According to yet some implementations, the internal combustion engine system further includes an engine block to which the engine crank gear housing is coupled. The system may also include a lubricant reservoir that is coupled to the engine block and a lubrication return line in lubrication receiving communication with a bottom portion of the power take-off housing and lubrication providing communication with the lubricant reservoir. Additionally, in certain implementations, the system can include first and second auxiliary devices coupled to the power take-off housing. The first auxiliary device may be co-rotatably coupled to a first gear of the gear train and the second auxiliary device may be co-rotatably coupled to a second gear of the gear train.

In another embodiment, a method for lubricating a gear train within a power take-off system that is operably coupled to a lubricated crank gear within a crankcase of an internal combustion engine is described. The method includes transferring lubrication from the crank gear to a first gear of the gear train, and collecting lubrication released from the first gear of the gear train. Additionally, the method includes directing the collected lubrication released from the first gear of the gear train along an angled surface and through an opening exposed to an interior of a housing coupled to the internal combustion engine externally of the crankcase. The method further includes lubricating at least a second gear of the gear train with the lubrication directed through the opening. The at least second gear is positioned within the interior of the housing.

According to some implementations of the method, the first gear of the gear train is positioned within the crankcase. Collecting lubrication released from the first gear of the gear train may include receiving lubrication that drips down from the first gear of the gear train.

The described features, structures, advantages, and/or characteristics of the subject matter of the present disclosure may be combined in any suitable manner in one or more embodiments and/or implementations. In the following description, numerous specific details are provided to impart a thorough understanding of embodiments of the subject matter of the present disclosure. One skilled in the relevant art will recognize that the subject matter of the present disclosure may be practiced without one or more of the specific features, details, components, materials, and/or methods of a particular embodiment or implementation. In other instances, additional features and advantages may be recognized in certain embodiments and/or implementations that may not be present in all embodiments or implementations. Further, in some instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the subject matter of the present disclosure. The features and advantages of the subject matter of the present disclosure will become more fully apparent from the following description and appended claims, or may be learned by the practice of the subject matter as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which:

Figure 1 is a side elevation view of an internal combustion engine with a power take-off system according to one embodiment;

Figure 2 is a perspective view of a power take-off system coupled to an internal combustion engine according to one embodiment; Figure 3 is an end view a power take-off system coupled to an internal combustion engine according to one embodiment;

Figure 4 is a perspective view of a power take-off system coupled to an internal combustion engine according to one embodiment;

Figure 5 is a perspective view of a power take-off system according to one embodiment; and

Figure 6 is a cross-sectional side elevation view of a power take-off system according to one embodiment.

DETAILED DESCRIPTION

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. Similarly, the use of the term "implementation" means an implementation having a particular feature, structure, or characteristic described in connection with one or more embodiments of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more embodiments.

Referring to Figure 1, a side view of one embodiment of an internal combustion engine 10 is shown. The internal combustion engine 10 can be any of various types of engines known in the art. Generally, the engine 10 includes a block 12, a cylinder head 14 secured to an upper surface of the block, a valve cover 16 secured to the cylinder head, and a lubricant (e.g., oil) reservoir cover secured to a lower surface of the block. The reservoir cover defines an oil reserve or pan 18. The engine 10 also includes a crankcase or flywheel housing 20 that is configured to be coupled to a crankcase interface 22 formed in or coupled to the block 12 of the engine. The crankcase 20, or crank gear housing, at least partially houses a crank gear 26 (see, e.g., Figure 2) that is driven by a crankshaft or driveshaft 27 powered by the internal combustion engine 10. The crank gear 26 can be co-rotatably attached to a coupling component 24 of a transmission system (not shown) for transferring power generated by the engine into a motive force. Further, the crank gear 26 may be coupled to a cam gear that drives a cam shaft of the engine 10.

As shown in Figure 2, the crankcase interface 22 of the engine block 12 includes an aperture 21 for receiving an insert portion 50 of a housing 31 of a power take-off system 30. The housing 31 include two separately formed portions or halves coupled together via fasteners or other coupling techniques. Torque from the crank gear 26 is transferred to the power take-off system 30 via a gear-meshing connection between the engine crank gear and a driver gear 60 of the power take-off system. As shown, the driver gear 60 is positioned vertically above the crank gear 26, and in some implementations, positioned at least partially externally of the interior of the housing 31 and at least partially within the interior of the crankcase 20 (see, e.g., Figure 6). Accordingly, the insert portion 50 is configured to position the driver gear 60 in gear-meshing engagement with the crank gear 26. Torque transferred to the power take-off system 30 is further transmitted to at least one powered component or device. For example, in the illustrated embodiment of Figure 1, the power take-off system 30 facilitates the transfer of power from the crank gear 26 to a first device 36 and at least a second device 34. The power take-off system 30 can be a self-contained modular unit that may be easily attached to and removed from the engine 10 without modification to, deformation of, or destruction of the engine.

In some embodiments, the first device 36 is a mandatory auxiliary device required for operation of the engine 10. For example, in one implementation, the first device 36 is a fuel pump for supplying fuel from a fuel tank to the combustion chambers of the engine 10. In other implementations, the first device 36 can be any of various other mandatory or non-mandatory devices.

In some embodiments, the second device 34 is an auxiliary device or accessory not required for operation of the engine 10, but nonetheless is desirably powered by the engine. For example, in one implementation, the second device 34 is a hydraulic pump required for operation of an accessory coupled to the engine 10 or a vehicle in which the engine is housed. In other implementations, the second device 34 is a power steering pump or other auxiliary device associated with an accessory. The accessory can be any of various accessories known in the art, such as, for example, forklifts, backhoes, augers, diggers, drills, water pump, blower systems, winches, compactors, etc. In some implementations, the second device 34 is the drive shaft of torque -powered accessory, such as a combine or other farm equipment accessory or machine. The second device 34 may be an accessory that is installed by the end-user. For example, as shown in Figure 6, a plate 35 may be coupled to the housing 31 of the power take-off system 30 to prevent access to the system. An end user may remove the plate 35 from the housing 31 and attach the second device 34 to the housing in power transferring engagement with the system 30.

Generally, the power take-off system 30 can be usable in any of a number of

configurations without affecting the configuration of the underlying engine 10. For example, in one configuration, the power take-off system 30 simultaneously transfers power from the engine 10 to the first device 36 and a second device 34. In other configurations, perhaps only the first device 36 is mounted to the power take-off system 30. In these configurations, power is transferred to the first device 36 with a second device interface formed in the housing 31 of the power take-off system 30 going unused. Alternatively, only the second device 34 is mounted to the power take-off system 30, such that power is transferred only to the second device and a first device interface formed in the housing 31 is unused.

Power is transferred from the engine crank gear 26 (or an intermediate idle gear in some implementations) to the first or second devices 36, 34 via a gear train 55 at least partially housed by the housing 31 (see, e.g., Figure 6). The gear train 55 includes the driver gear 60, a first power transfer gear 70, an idler gear 74, and a second power transfer gear 80. Each of the first power transfer gear 70, idler gear 74, and second power transfer gear 80 is rotatably supported by a respective bearing or bearings 71, 73, 81. The first power transfer gear 70 is positioned within an upper section 42 of the housing 31 and is co-rotatably coupled with the driver gear 60 via a splined, off-round, or other connection type formed into the first power transfer gear at 62. The first power transfer gear 70 includes a receptacle 72 for engaging a portion of a first device or component (such as the device 36). The first power transfer gear 70 also drives the idler gear 74, which can be an annular gear that rotates about an idler gear spindle or shaft 76 retained within a middle section 44 of the housing 31. The idler gear 74 is maintained in place via bearing 73, which is supported by the idler gear spindle 76 and promotes low friction rotation of the idler gear. Further, the idler gear 74 in turn drives the second power transfer gear 80, which is located within a lower section 40 of the housing 31. The idler gear 74 facilitates a proper gear reduction between the first and second power transfer gears 79, 80.

The second power transfer gear 80 includes a splined channel 82 for engaging a portion of the second device 34. The splined channel 82 includes internal splines that form part of a central channel extending through the second power transfer gear 80, which can be maintained in place via bearings 81 that promote low friction rotation of the second power transfer gear. The engagement features or splines of the second power transfer gear 80 are engageable (e.g., in splined engagement) with corresponding engagement features (e.g., an externally splined input shaft) of the first device 36. When engaged with the engagement features of the first device 36, the engagement features of the second power transfer gear 80 facilitate co-rotation of the second power transfer gear and the input shaft of the first device. In this manner, the power take-off system 30 transfers torque or power from the engine 10 (e.g., drive shaft 27 of the engine) to the first and second devices 34, 36.

Although not shown, the engine 10 includes an oil supply line that directs oil or other lubricant from an oil reserve or pan 18 to the crank gear 26 for lubricating the crank gear and components of the engine positioned within the crankcase 20. The oil supply line may include one or more orifices positioned proximate the driveshaft 27 through which oil flows into the crankcase 20 for lubricating the crank gear 26.

From the crank gear 26, some of the oil is transferred to the driver gear 60 for lubricating the driver gear via the geared engagement between the crank gear and driver gear. Referring to Figures 2-6, oil from the driver gear 60 follows an oil transfer path defined by the power take-off system 30. More specifically, oil is transferred from (e.g., drips off of) the driver gear onto a flange or baffle 52 of an insert portion 50 of the housing 30 as indicated by directional arrow 90 (see, e.g., Figure 6). The flange 52 is an extension of the insert portion 50 that extends through the aperture 21 in the engine block 12 as described above. The flange 52 partially surrounds the driver gear 60 at a location underneath the driver gear as shown in Figure 6. In this manner, oil from the driver gear 60 is transferred onto or collects on the flange 52 or oil sump during use.

An inner surface 54 of the flange 52 (e.g., a surface facing the driver gear 60) is downwardly angled with respect to horizontal (e.g., a line parallel to the central axes of the driver gear 60, first power transfer gear 70, idler gear 74, and second power transfer gear 80) at an angle Θ. In other words, the inner surface 54 of the flange 52 slopes downwardly in a direction away from the driver gear 60 toward an interior 37 of the housing 30. In this manner, oil that collects on the inner surface 54 (e.g., upwardly facing surface) of the flange 52 is funneled via gravitation forces along the inner surface and into the interior 37 of the housing 30 as indicated by directional arrow 92. The angle Θ can be any of various angles. In one implementation, the angle Θ is greater than 0-degrees and less than about 90-degrees. In another implementation, the angle Θ is between about 5-degrees and about 45-degrees. According to yet some implementations, the angle Θ is between about 5-degrees and about 10-degrees, and in certain implementations, the angle Θ is between 0-degrees and 5-degrees. In some

implementations, the angle Θ is limited according to the amount of space available within the engine system and other physical constraints of the system.

As shown in Figures 4-6, the insert portion 50 of the housing 30 may have an opening 56 through which oil passes in order to enter the housing. The oil entering the housing through the opening 56 contacts and lubricates the first power transfer gear 70, idler gear 74, and second power transfer gear 80 as it percolates downwardly through the interior of the housing 30.

Accordingly, the power take-off system 30 facilitates an oil transfer path from within the crankcase 20 (e.g., from the crank gear to the driver gear 60), from the driver gear 60 to the angled or slopped inner surface 54 of the flange 52, along the inner surface, through the opening 56, and onto the gears of the gear train 55 within the gear train housing 31. After lubricating the gears in the gear train 55, the oil collects within a collection volume 33 at a bottom of the interior 37 of the housing 31. Oil collected in the collection volume 33 is transferred back to the oil pan 18 via an oil return line 38.

Although not necessary, in the illustrated embodiment, the oil return line 38 is positioned vertically offset relative to the bottom-dead center of the interior 37 such that a portion of the collected oil remains within the housing 31 in contact with the second power transfer gear. In this manner, should the engine 10 and power take-off system 30 be angled relative to horizontal such that oil 92 does not flow into the housing 31 along the angled surface 54 (e.g., the tilting of the engine and power take-off system negates the downward angle of the surface 54), at least some oil remains within the housing for lubricating the gears 70, 76, 80 of the gear train 55. In some implementations, the housing 31 may also include a back-up oil supply interface, such as an oil inlet opening and associated oil cap or plug 39, for the exceptional situation where oil must be manually supplied to supplement or replace a deficiency or lack of oil dripping into the housing via the inner surface 54 and opening 56 from the crank gear 26.

In the above description, certain terms may be used such as "up," "down," "upper,"

"lower," "horizontal," "vertical," "left," "right," "over," "under" and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an "upper" surface can become a "lower" surface simply by turning the object over. Nevertheless, it is still the same object. Further, the terms "including," "comprising," "having," and variations thereof mean "including but not limited to" unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. The terms "a," "an," and "the" also refer to "one or more" unless expressly specified otherwise. Further, the term "plurality" can be defined as "at least two."

Additionally, instances in this specification where one element is "coupled" to another element can include direct and indirect coupling. Direct coupling can be defined as one element coupled to and in some contact with another element. Indirect coupling can be defined as coupling between two elements not in direct contact with each other, but having one or more additional elements between the coupled elements. Further, as used herein, securing one element to another element can include direct securing and indirect securing. Additionally, as used herein, "adjacent" does not necessarily denote contact. For example, one element can be adjacent another element without being in contact with that element. As used herein, the phrase "at least one of, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, "at least one of means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

The present subject matter may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.