Patent Application
20180080539
The present disclosure relates to a variable speed drive mechanism.
Current variable speed drives typically include a fixed sheave and a movable sheave which is coupled by splines to a drive shaft. This splined connection must be routinely maintained with a lubricant such as oil or grease. The translational movement of the parts requires seals to contain the lubricant along the splined interface. When the lubricant leaks through the seals the loss of lubricant causes premature spline wear. Further, leaking lubricant often contacts one or more V-belts causing premature belt wear.
Other variable speed fan drives utilize drive fingers in one of the sheaves and corresponding recesses in the other sheave to rotatably couple the fixed sheave to the movable sheave. The drive fingers have a wear member positioned between the drive finger and the recess.
Variable speed fan drives implementing either the lubricated splines or the wear members require maintenance and monitoring to ensure that the fixed sheave and the movable sheave properly engage one another or the drive shaft.
One embodiment of the present disclosure is a variable speed drive having a rotatable drive shaft, a fixed sheave fixed relative to the drive shaft and mounted for rotation with the drive shaft, a movable sheave mounted for axial movement relative to the drive shaft, a plurality of drive fingers projecting axially from one of the sheaves, each drive finger defining a finger contact, and a plurality of recesses in the other sheave, each drive finger being movably received by a corresponding one of the recesses, and each recess defining a recess contact that slidably engages the corresponding finger contact.
Another embodiment is a variable drive having a rotatable drive shaft, a fixed sheave fixed axially relative to the drive shaft and mounted for rotation with the drive shaft, a movable sheave mounted for axial movement relative to the drive shaft, a plurality of drive fingers projecting from one of the sheaves, each finger defining a finger contact, and a plurality of recesses in the other sheave, each recess defining a recess contact. Wherein each drive finger is movably received by a corresponding one of the recesses, and the finger contact slidably engages the corresponding recess contact. Further wherein at least one of the finger contact or the recess contact is hardened through a surface treatment.
Another embodiment is a method of manufacturing a fixed sheave and a movable sheave for a variable speed drive including forming a first sheave by shaping a first material to define a first belt engaging flange and at least one drive finger defining a finger contact, forming a second sheave by shaping a second material to define a second belt engaging flange and at least one recess defining a recess contact, hardening the first or second material of the respective finger contact or recess contact through a surface treatment, fixing one of the sheaves to a drive shaft and positioning the other of the sheaves about the drive shaft, and positioning at least a portion of the drive finger within the recess where the finger contact slidably engages the recess contact.
The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein:
Corresponding reference numerals are used to indicate corresponding parts throughout the several views.
The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure.
Referring to
Referring now to
The movable sheave 20 includes a hollow axially extending central hub 30 and a belt-engaging flange 32 which surrounds the hub 30. The hub 30 forms a first and second bearing member 34 and 36 which receive the shaft 14. The hub 30 also includes a plurality of spaced apart recesses 38. The recesses 38 are open in a direction facing the fixed sheave 16, and extend axially into the hub 30 and away from the fixed sheave 26.
Each drive finger 28 is movably received by a corresponding one of the recesses 38. More specifically, the fixed sheave 16 may be fixedly coupled to the drive shaft 14 through the one or more bolts 18. In this configuration, as the drive shaft 14 rotates, the fixed sheave 16 may also rotate because it is fixedly coupled thereto.
In one embodiment, a prime mover may apply a torque to the drive gear 54. The drive gear 54 may be splined or otherwise coupled to the drive shaft 14 and transfer the applied torque from the prime mover through the drive shaft 14 and into the fixed sheave 16. The fixed sheave 16 may transfer the torque to the movable sheave 20 through contact between the drive fingers 28 and the recesses 38.
One aspect of the present disclosure is the ability of the movable sheave 20 to slide axially along the drive shaft 14 relative to the fixed sheave 16 while rotating therewith. In other words, the movable sheave 20 may be axially spaced from the fixed sheave 16 several different distances along the drive shaft 14 while still allowing sufficient torque transfer through the drive fingers 28 and recesses 38 to rotate the movable sheave 20 with the fixed sheave 16. In this embodiment, the drive fingers 28 may engage the recesses 38 at a finger contact 56 (see
The central hub 30 may also have a first seal 58 and a second seal 60 positioned on each end of the central hub 30. The first and second seal 58, 60 may substantially restrict debris from entering the space between the drive shaft 14 and the central hub 30. More specifically, the respective seal 58, 60 may extend from the central hub 30 or other portion of the movable sheave 20 and contact the outer surface of the drive shaft 14. In this configuration, as the movable sheave 20 moves along the drive shaft 14, the respective seals 58, 60 slide along the outer surface of the drive shaft 14, thereby removing any debris that may be positioned thereon. In one aspect of the present embodiment, the seals 58, 60 may substantially restrict debris from becoming positioned between the respective bearing members 36, 40.
While the embodiment shown herein displays the first and second seals 58, 60 coupled to the central hub 30, this disclosure is not limited to having any seals at all. More specifically, the movable hub 20 may not have the first and second bearing members 34, 36 at all. Rather, the central hub 30 may have an inner diameter that is larger than an outer diameter of the drive shaft 14. In this configuration, there may be a space between the outer surface of the drive shaft 14 and the inner surface of the central hub 30. The spacing between the drive shaft 14 and the central hub 30 may be sufficient to allow debris to be positioned therebetween without substantially affecting the axial movement of the movable sheave 20 relative to the fixed sheave 16.
Referring now to
Now referring to
Referring now to
While an arc-shaped leading edge profile 72 has been shown and described above, this disclosure is not limited to such an embodiment. Further, while the arc-shaped leading edge profile 72 has been compared to a straight leading edge profile 72, one embodiment of the present disclosure may utilize a straight leading edge profile 72 instead of the arc-shaped leading edge profile 72 shown in
The trailing edge 64 of the drive finger 28 may be slanted relative to a base portion 76 of the fixed sheave 16. In one embodiment, the drive finger 28 may have a top width 78 that is less than a bottom width 80. The leading edge 64 may be substantially perpendicular to the base portion 76 while the slanted trailing edge 64 extends a height 82 of the drive finger 28 between the base width 80 and the top width 78. The slanted trailing edge 66 and the overall dimensions of the drive finger 28 may be sufficiently sized to transfer torque from the fixed sheave 16 to the movable sheave 20 without shearing or otherwise deforming the drive finger 28. Accordingly, while the trailing edge 66 has been shown and described as slanted, such a configuration is not limiting. In other embodiments the trailing edge 66 may be perpendicular to the base portion 76. Accordingly, many different orientations for the trailing edge 66 are considered and no specific orientation is limiting.
Referring now to
The radial spacing of the recesses 38 may be substantially similar to the radial spacing of the drive fingers 28 as illustrated in
A side profile section view of the recess 38 is shown in
Referring now to
The portion of the outer surface of the drive shaft 14 positioned adjacent to the respective first and second bearing members 34, 36 may vary depending on the axial location of the movable sheave 20 relative to the fixed sheave 20. Accordingly, the first and second shaft contacts 90, 92 may have an axial width greater than a width of the first and second bearing members 34, 36 to ensure that the first and second bearing members 34, 36 are positioned proximate to the respective first and second shaft contacts 90, 92 regardless of the axial position of the movable sheave 20 relative to the fixed sheave 16.
In one embodiment, the first and second bearing members 34, 36 and the corresponding first and second shaft contact 90, 92 may substantially contact one another. In this configuration, as the movable sheave 20 slides axially along the drive shaft 14, the first and second bearing members 34, 36 slide along the outer surface of the drive shaft 14 along the first and second shaft contact 90, 92.
However, in a different embodiment the bearing members 34, 36 may not substantially contact the drive shaft 14 regardless of the axial position of the movable sheave 20 relative to the fixed sheave 16. In this embodiment, the bearing members 34, 36 may be spaced from the outer surface of the drive shaft 14 and thereby not directly contact the drive shaft 14. In this configuration, there may be no bearing members 34, 36 defined in the movable sheave 20 at all. Further, the drive shaft 14 may not have the first and second shaft contact 90, 92 positioned thereon. In other words, in an embodiment where the movable sheave 20 does not substantially directly contact the drive shaft 14, the bearing members 34, 36 and shaft contacts 90, 92 may not be necessary.
In one aspect of the present disclosure, the material positioned along the finger contact 56 and the recess contact 88 may be configured to engage one another and transfer torque from the fixed sheave 16 to the movable sheave 20 without requiring additional lubricants or other material. More specifically, in one embodiment the fixed sheave 16 and the movable sheave 20 may be made from a material that can be hardened. In one embodiment, a surface treatment may be performed on at least the finger contact 56 and the recess contact 88 to harden the respective surfaces. Any form of surface treatment, such as heat treatment or case-hardening, may be used at the finger contact 56 and the recess contact 88 to improve the wear life of the respective surfaces 56, 88 during use. In one embodiment, the finger contact 56 and the recess contact 88 may be formed of austempered ductile iron. In this embodiment, the austempering of the finger contact 56 and the recess contact 88 may form a surface that has increased wear resistance. By hardening the finger contact 56 and the recess contact 88, wear life of the respective contacts 56, 88 may be improved without requiring additional maintenance steps such as adding grease or other lubricants to the contacts 56, 88.
While austempering ductile iron has been described as a surface treatment method for hardening the finger contact 56 and the recess contact 88, this disclosure is not limited to such a method. Any form of heat treating, case or surface hardening, laser hardening, or the like may be used on the finger contact 56 and the recess contact 88.
Similarly, in the embodiment where the first and second bearing members 34, 36 contact or are positioned proximate to the first and second shaft contacts 90, 92, a hardening surface treatment may be performed on the bearing members 34, 36 and the shaft contacts 90, 92. By hardening the surface of the bearing member 34, 36 and the shaft contacts 90, 92, those surfaces may not require grease or other lubricants while still resisting wear.
In one embodiment, the fixed sheave 16 and the movable sheave 20 may be cast parts. In this embodiment, after the fixed sheave 16 and movable sheave 20 are cast, a machining process may execute additional forming steps to the fixed sheave 16 and movable sheave 20. After the fixed sheave 16 and movable sheave 20 are in the proper form, a hardening process may be performed to the finger contact 56 and the recess contact 88. Alternatively, in another embodiment the hardening process may be performed to the entire fixed sheave 16 and movable sheave 20. The hardening process may be at least any of the hardening processes described above but is not limited to only those hardening processes. Any process known to a person having skill in the relevant art is considered for generating a harder surface of the finger contact 56 and the recess contact 88 and this disclosure is not limited to any particular hardening process.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
