Patent Publication Number: US-2022212905-A1

Title: Winche or hoist having a gearbox with high-contact ratio gears

Description:
BACKGROUND 
     Technical Field 
     The present disclosure relates generally to winches and hoists including gear boxes, and more particularly to winches and hoists including high-contact ratio gearing. 
     Description of the Related Art 
     Winches and hoists are typically driven by a motor, such as a hydraulic motor, and are often provided with gearboxes that change, e.g., increase or decrease, the speed at which the winch or hoist is driven relative to the speed of an output shaft of the motor. For example, a hydraulic motor can drive an output shaft thereof to rotate about its own central longitudinal axis at a first speed. The output shaft of the hydraulic motor can be rotationally coupled to an input shaft of a gearbox of a winch or hoist, and the gearbox can in turn drive a spool or a drum of the winch or hoist to rotate about its own central longitudinal axis at a second speed that is different than, e.g., greater than or less than, the first speed. Such gearboxes can also be used to increase or decrease the torque transferred to the spool or drum of the winch or hoist, which may in turn increase or decrease the total working capacity of the winch or hoist. 
     Traditional spur-type gearing creates more noise than desired in some particularly noise-sensitive applications, and is in some cases not suitable where noise, vibration, and harshness (NVH) are a major concern. A relatively standard solution in such cases is to use helical gearing, which generally creates less noise, vibration, and harshness, rather than spur-type gearing. Nevertheless, helical gearing has its own drawbacks, including the generation of thrust forces, that render it undesirable in certain applications. 
     Characteristic shapes of gear teeth are relatively standardized. Relevant information and standards have been published by the American Gear Manufacturers Association, such as in AGMA 933-B03, titled “Basic Gear Geometry,” in ANSI/AGMA B88, titled “Tooth Thickness Specification and Measurement,” in ISO 6336, and in other, related documents, such as counterpart Japanese and other national standards. Gears with teeth that do not conform to such standards have been used in certain applications. For example, gears with gear teeth shaped to provide a higher contact ratio than that specified in the AGMA and other relevant standards have been used in certain applications. Such gearing has significant disadvantages, however. For example, it requires significantly greater precision and is therefore more expensive to manufacture. 
     BRIEF SUMMARY 
     A winch or hoist may be summarized as comprising: an input shaft; a rotatable drum; and a gearbox including a plurality of high-contact ratio spur-type gears, the gearbox coupled to the input shaft and to the rotatable drum such that rotation of the input shaft at a first speed drives rotation of the rotatable drum at a second speed that is different than the first speed. The gearbox may be a planetary gearbox. The high-contact ratio spur-type gears may include internal gear teeth and external gear teeth. 
     The high-contact ratio spur-type gears may have a higher contact ratio than specified in ANSI/AGMA B88. The high-contact ratio spur-type gears may include gear teeth having longer addendums than specified in ANSI/AGMA B88. The high-contact ratio spur-type gears may include gear teeth having longer dedendums than specified in ANSI/AGMA B88. Each of the high-contact ratio spur-type gears may have a respective diametral pitch and include gear teeth having addendums greater than 1.00, 1.05, 1.10, 1.15, or 1.20 divided by the respective diametral pitch. Each of the high-contact ratio spur-type gears may have a respective diametral pitch and include gear teeth having dedendums greater than 1.25, 1.30, 1.35, or 1.40 divided by the respective diametral pitch. Each of the high-contact ratio spur-type gears may have a contact ratio greater than 1.60, 1.80, or 2.00. 
     A method of operating a winch or hoist or be summarized as comprising: coupling an input shaft of the winch or hoist to a motor; coupling a cable coupled to a rotatable drum of the winch or hoist to a load to be moved, wherein a gearbox including a plurality of high-contact ratio spur-type gears is coupled to the input shaft and to the rotatable drum such that rotation of the input shaft at a first speed drives rotation of the rotatable drum at a second speed that is different than the first speed; and actuating the motor to drive rotation of the input shaft at the first speed and rotation of the rotatable drum at the second speed, thereby moving the load. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  illustrates a perspective view of a winch including a gearbox having high-contact ratio gearing. 
         FIG. 2  illustrates another perspective view of the winch of  FIG. 1 . 
         FIG. 3  illustrates a perspective view of a drum of the winch of  FIGS. 1 and 2 . 
         FIG. 4  illustrates a perspective view of the winch of  FIGS. 1 and 2  with the drum of  FIG. 3  removed to illustrate other features. 
         FIG. 5  illustrates another perspective view of the winch of  FIGS. 1 and 2  with the drum of  FIG. 3  removed to illustrate other features. 
         FIG. 6  illustrates a perspective view of an input end portion of the winch of  FIGS. 1 and 2  with the drum of  FIG. 3  and other components removed to illustrate other features. 
         FIG. 7  illustrates a perspective view of an input end portion of the winch of  FIGS. 1 and 2  with the drum of  FIG. 3  and other components removed to illustrate other features, including an exterior of a planetary gearbox of the winch. 
         FIG. 8  illustrates a perspective view of a fixed ring gear of the planetary gearbox of  FIG. 7 . 
         FIG. 9  illustrates another perspective view of the fixed ring gear of  FIG. 8 . 
         FIG. 10  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9  removed to illustrate other features. 
         FIG. 11  illustrates another perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9  removed to illustrate other features. 
         FIG. 12  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9  and an input shaft removed to illustrate other features. 
         FIG. 13  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9 , an input shaft, and a first set of sun and planet gears removed to illustrate other features. 
         FIG. 14  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9 , an input shaft, a first set of sun and planet gears, and a first gear carrier removed to illustrate other features. 
         FIG. 15  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9 , an input shaft, a first set of sun and planet gears, a first gear carrier, and a second set of sun and planet gears removed to illustrate other features. 
         FIG. 16  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9 , an input shaft, a first set of sun and planet gears, a first gear carrier, a second set of sun and planet gears, and a second gear carrier removed to illustrate other features. 
         FIG. 17  illustrates a perspective view of the planetary gearbox of  FIG. 7  with the fixed ring gear of  FIGS. 8 and 9 , an input shaft, a first set of sun and planet gears, a first gear carrier, a second set of sun and planet gears, a second gear carrier, and a third set of sun and planetary gears removed to illustrate other features. 
         FIG. 18  illustrates a cross-sectional view of the winch of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures associated with the technology have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Also, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the context clearly dictates otherwise. 
     The use of ordinals such as first, second and third does not necessarily imply a ranked sense of order, but rather may only distinguish between multiple instances of an act or structure. Various examples of suitable dimensions of components and other numerical values are provided herein. Such dimensions are accurate to within standard manufacturing tolerances unless stated otherwise. 
       FIG. 1  illustrates a perspective view of a first end  102  of a winch  100  that has a central longitudinal axis  106 .  FIG. 2  illustrates a perspective view of a second end  104  of the winch  100 , which is opposite to the first end  102  illustrated in  FIG. 1  along the central longitudinal axis  106 .  FIG. 18  illustrates a cross-sectional view of the winch  100 . The winch  100  itself, as well as various components of the winch  100 , have cylindrical, generally cylindrical, rotationally symmetric, and/or generally rotationally symmetric shapes when viewed along the central longitudinal axis  106 . That is, the winch  100 , and each of a variety of components of the winch  100 , have respective central longitudinal axes, with each of those respective central longitudinal axes being coincident with one another, as illustrated by axis  106  in  FIGS. 1 and 2 . Some components of the winch  100  are also configured to rotate about the central longitudinal axis  106 , as described elsewhere herein. 
       FIG. 1  illustrates that the winch  100  includes a first mounting flange  108  at its first end  102 , which is oriented perpendicular to the central longitudinal axis  106  and includes a plurality of holes or apertures extending therethrough along respective axes parallel to the central longitudinal axis  106 . In use, the winch  100  can be mounted to another piece of machinery by mechanical fasteners such as bolts or screws that extend through the apertures in the first mounting flange  108  and through corresponding apertures in a mounting flange of the other piece of machinery. When the winch  100  is mounted to another piece of machinery in this way, the mounting first flange  108  is rigidly coupled to the other piece of machinery and remains stationary with respect to the other piece of machinery during use. 
       FIG. 2  illustrates that the winch  100  also includes a second mounting flange  110  at its second end  104 , which is oriented perpendicular to the central longitudinal axis  106  and parallel to the first mounting flange  108 , and includes a plurality of holes or apertures extending therethrough along respective axes parallel to the central longitudinal axis  106 . In use, the winch  100  can be mounted to the other piece of machinery by mechanical fasteners such as bolts or screws that extend through the apertures in the second mounting flange  110  and through corresponding apertures in a mounting flange of the other piece of machinery. When the winch  100  is mounted to another piece of machinery in this way, the second mounting flange  110  is rigidly coupled to the other piece of machinery and remains stationary with respect to the other piece of machinery during use. 
       FIGS. 1 and 2  illustrate that the winch  100  includes a spool or drum  112  that is rotatable about the central longitudinal axis  106  with respect to the mounting flanges  108  and  110 . In use, a cable, rope, wire, or chain having a first end and a second end opposite the first end may be fastened at the first end thereof to the drum  112 . The cable may be wound up about the drum  112 , and the second end of the cable may be coupled to a load to be pulled by the winch  100 . The winch  100  can be operated to drive rotation of the drum  112  about the central longitudinal axis  106  with respect to the mounting flanges  108  and  110  and with respect to the piece of machinery to which the winch  100  is mounted, such as to wind up the cable onto the drum  112  to pull the load toward the winch  100 . 
       FIG. 3  illustrates a perspective view of the drum  112  by itself, so that additional features of the drum  112  are visible. For example, as seen in  FIG. 3 , the drum  112  is hollow and has a cylindrical open internal space that extends along the central longitudinal axis  106 . The drum  112  also has a circular internal flange  114  that extends across its open internal space and is oriented perpendicular to the central longitudinal axis  106  at a location near the midpoint of the length of the drum  112  along the central longitudinal axis  106 . The internal flange  114  includes a plurality of holes or apertures extending therethrough along respective axes parallel to the central longitudinal axis  106 . In use, components of the winch  100  coupled to the first mounting flange  108 , including a ball bearing for rotatably mounting the drum  112  to the mounting flange  108 , can be positioned within the cylindrical open internal space within the drum  112  between the mounting flange  108  and the internal flange  114  of the drum  112 . Similarly, components of the winch  100  coupled to the second mounting flange  110 , including a ball bearing for rotatably mounting the drum  112  to the mounting flange  110 , can be positioned within the cylindrical open internal space within the drum  112  between the mounting flange  110  and the internal flange  114  of the drum  112 . 
       FIGS. 4 and 5  illustrate the winch  100  with the drum  112  removed so that internal components of the winch  100  are visible. As illustrated in  FIGS. 4 and 5 , the winch  100  includes a first ball bearing assembly  116  having an inner race rigidly coupled to the first mounting flange  108 , an outer race rigidly coupled to an inner surface of the drum  112 , and a plurality of balls seated within a groove formed in the inner race, within a groove formed in the outer race, and between the inner race and the outer race. The first ball bearing assembly  116  rotatably couples the drum  112  to the first mounting flange  108  such that the drum  112  can rotate about the central longitudinal axis  106  with respect to the first mounting flange  108 , but cannot translate in any direction with respect to the first mounting flange  108 . 
     As also illustrated in  FIGS. 4 and 5 , the winch  100  includes a second ball bearing assembly  118  having an inner race rigidly coupled to the second mounting flange  110 , an outer race rigidly coupled to an inner surface of the drum  112 , and a plurality of balls seated within a groove formed in the inner race, within a groove formed in the outer race, and between the inner race and the outer race. The second ball bearing assembly  118  rotatably couples the drum  112  to the second mounting flange  110  such that the drum  112  can rotate about the central longitudinal axis  106  with respect to the second mounting flange  110 , but cannot translate in any direction with respect to the second mounting flange  110 .  FIGS. 4 and 5  also illustrate a planetary gearbox  120  of the winch  100 , which is described in greater detail elsewhere herein. 
       FIG. 6  illustrates a larger perspective view of the second end  104  of the winch  100  with the drum  112  and other components removed so that other features are visible. As illustrated in  FIG. 6 , the winch  100  includes an input shaft coupler  122  to which an output shaft of a motor such as a hydraulic motor may be coupled to drive operation of the gearbox  120  and the drum  112 . As also illustrated in  FIG. 6 , the winch  100  includes a third ball bearing assembly  124 , which may include two ball bearings each having an inner race rigidly coupled to the input shaft coupler  122 , an outer race rigidly coupled to other components of the winch  100 , and a plurality of balls seated within a groove formed in the inner race, within a groove formed in the outer race, and between the inner race and the outer race. The third ball bearing assembly  124  rotatably couples the input shaft coupler  122  to the rest of the winch  100 , including the second mounting flange  110 , such that the input shaft coupler  122  can rotate about the central longitudinal axis  106  with respect to the second mounting flange  110 , but cannot translate in any direction with respect to the second mounting flange  110 . 
       FIG. 7  illustrates the same view as  FIG. 6  with additional components removed so that other features are visible. As illustrated in  FIG. 7 , the input shaft coupler  122  is a female-female coupler having a first, internal, input set of spline teeth at a first end thereof along the central longitudinal axis  106  that are configured to engage with complementary spline teeth of an output shaft of a motor, and a second, internal, output set of spline teeth at a second end thereof opposite to the first end thereof along the central longitudinal axis  106  that are configured to engage with complementary spline teeth of an input shaft  128  of the planetary gearbox  120 . Thus, the input shaft coupler  122  can transfer rotational motion and torque from the output shaft of the motor to the input shaft  128  of the planetary gearbox  120 . As also illustrated in  FIG. 7 , the input shaft coupler  122  has a first groove  126   a  and a second groove  126   b  formed in an outer surface thereof, within which the two ball bearings of the ball bearing assembly  124  can be seated and to which the inner races of the two ball bearings of the ball bearing assembly  124  can be rigidly coupled. 
       FIG. 7  illustrates that most of the planetary gearbox  120  is enclosed within or surrounded by a generally cylindrical outer ring gear  130  thereof.  FIG. 8  illustrates a perspective view of the cylindrical outer ring gear  130  by itself, so that additional features of the ring gear  130  are visible.  FIG. 9  illustrates another perspective view of the cylindrical outer ring gear  130  by itself, so that additional features of the ring gear  130  are visible. As illustrated in  FIGS. 8 and 9 , the ring gear  130  has an overall cylindrical shape that extends along the central longitudinal axis  106 , has a cylindrical open internal space that extends along the central longitudinal axis  106 , and has a relatively smooth outer surface. As also illustrated in  FIGS. 8 and 9 , the ring gear  130  has a first generally cylindrical internal surface  132  at a first end thereof along the central longitudinal axis  106 , a second generally cylindrical internal surface  134  at a second end thereof opposite the first end thereof along the central longitudinal axis  106 , and a third generally cylindrical internal surface  136  between the first generally cylindrical internal surface  132  and the second generally cylindrical internal surface  134  along the central longitudinal axis  106 . 
     As illustrated in  FIGS. 8 and 9 , the first internal surface  132  is closer to the second end  104  of the winch  100  than the second internal surface  134  is, and the second internal surface  134  is closer to the first end  102  of the winch  100  than the first internal surface  132  is, when the winch  100  is assembled. As also illustrated in  FIGS. 8 and 9 , the first internal surface  132  has a smaller diameter than the third internal surface  136  does, and the third internal surface  136  has a smaller internal diameter than the second internal surface  134  does, such that, when the ring gear  130  is assembled into and positioned within the winch  100 , the cylindrical open internal space within the ring gear  130  gets progressively wider, in a plurality of (e.g., three) steps in a direction extending from the second end  104  of the winch  100  to the first end  102  of the winch  100 . 
     As illustrated in  FIGS. 8 and 9 , the first internal surface  132  of the ring gear  130  includes a set of inward-facing inner spline teeth, the second internal surface  134  of the ring gear  130  includes a first set of inward-facing inner gear teeth having a first set of dimensions, and the third internal surface  136  of the ring gear  130  includes a second set of inward-facing inner gear teeth having a second set of dimensions. As illustrated in  FIG. 7 , the set of inner spline teeth of the first internal surface  132  do not mate with gears or gear teeth of the planetary gearbox  120 . Rather, the set of inner spline teeth of the first internal surface  132  engage complementary spline teeth that are rigidly coupled to the second mounting flange  110 . Such engagement can prevent or prohibit rotation of the ring gear  130  about the central longitudinal axis  106  and keep the entirety of the ring gear  130  stationary with respect to the second mounting flange  110 . Thus, in use, the ring gear  130  is stationary. The first and second sets of inner gear teeth of the ring gear  130  mate with and engage with other gears of the planetary gearbox  120  when the winch  100  is in use, as described elsewhere herein. 
       FIG. 10  illustrates a first perspective view, and  FIG. 11  illustrates a second perspective view, of the planetary gearbox  120  with the outer ring gear  130  thereof removed so that other features are visible. As illustrated in  FIGS. 10 and 11 , the planetary gearbox  120  includes, in addition to the input shaft  128  and the outer ring gear  130 , a first sun gear  138  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 , a first set of three planet gears  140  spaced equidistantly apart from one another about the first sun gear  138  and each having, and rotatable about, a respective central longitudinal axis parallel to the central longitudinal axis  106 , and a first gear carrier  142  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 . 
     As also illustrated in  FIGS. 10 and 11 , the planetary gearbox  120  further includes a second sun gear  144  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 , a second set of three planet gears  146  spaced equidistantly apart from one another about the second sun gear  144  and each having, and rotatable about, a respective central longitudinal axis parallel to the central longitudinal axis  106 , and a second gear carrier  148  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 . As also illustrated in  FIGS. 10 and 11 , the planetary gearbox  120  further includes a third sun gear  150  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 , a third set of three planet gears  152  spaced equidistantly apart from one another about the third sun gear  150  and each having, and rotatable about, a respective central longitudinal axis parallel to the central longitudinal axis  106 , and a third gear carrier  154  having, and rotatable about, a central longitudinal axis coincident with the central longitudinal axis  106 . 
     As illustrated in  FIG. 10  in particular, the third gear carrier  154  includes a generally cylindrical, disc-shaped main body having a central longitudinal axis coincident with the central longitudinal axis  106 , and five pegs, pins, or shafts that extend outward from a major surface of the main body along respective axes parallel to the central longitudinal axis  106  in a direction extending away from the planet gears  152 . In use, these shafts are positioned within and mated with the apertures extending through the internal flange  114  of the drum  112  illustrated in  FIG. 3  such that, as the third gear carrier  154  is driven to rotate about the central longitudinal axis  106 , the drum  112  is also driven to rotate about the central longitudinal axis  106 . 
     As illustrated in  FIGS. 10 and 11 , and as described further elsewhere herein, the planetary gearbox  120  includes a compound planetary gear system having a plurality of (e.g., two, three in the illustrated embodiment, four, five, six, or more) planetary gear sets or stages arranged in series with one another. In particular, the input shaft  128  drives operation and rotation of a first planetary gear stage including the first sun gear  138 , the first set of planet gears  140 , and the first gear carrier  142 , while operation and rotation of the first planetary gear stage (and an output thereof) in turn drives operation and rotation of a second planetary gear stage including the second sun gear  144 , the second set of planet gears  146 , and the second gear carrier  148 , and operation and rotation of the second planetary gear stage (and an output thereof) in turn drives operation and rotation of a third planetary gear stage including the third sun gear  150 , the third set of planet gears  152 , and the third gear carrier  154 . Such an arrangement can result in a larger transmission ratio and/or smaller-diameter system than alternative planetary gearing arrangements. In some alternative implementations, the planetary gearbox  120  is a single-stage planetary gearbox. In other alternative implementations, the gearbox  120  is a simple spur-type gear drive rather than a planetary gearbox. 
       FIG. 12  illustrates the planetary gearbox  120  with the outer ring gear  130  and input shaft  128  thereof removed so that other features are visible. In particular,  FIG. 12  illustrates that the first sun gear  138  is hollow and has a set of internal spline teeth meshed with external spline teeth formed in an end portion of the input shaft  128  engaged with the first sun gear  138 , such that rotation of the input shaft  128  about the central longitudinal axis  106  drives rotation of the first sun gear  138  about the central longitudinal axis  106  and such that torque can be transferred from the input shaft  128  to the first sun gear  138 .  FIG. 12  also illustrates that the first sun gear  138  has a set of external gear teeth meshed with external gear teeth of the first set of planet gears  140 , such that rotation of the sun gear  138  about the central longitudinal axis  106  drives rotation of the planet gears  140  about their own respective central longitudinal axes and such that torque can be transferred from the sun gear  138  to the planet gears  140 . 
     When the planetary gearbox  120  is assembled, the external gear teeth of the planet gears  140  are meshed with the internal gear teeth of the third internal surface  136  of the outer ring gear  130 . Thus, together, the first sun gear  138 , first set of planet gears  140 , the first gear carrier  142 , and the third generally cylindrical internal surface  136  of outer ring gear  130  that is meshed with the first set of planet gears  140  collectively form a first planetary gear set or first planetary gear stage. When the winch  100  is in use, the input shaft  128  drives operation of the planetary gearbox  120  by driving rotation of, or transferring torque to, the first sun gear  138 . The sun gear  138  in turn drives rotation of, or transfers torque to, the planet gears  140 . Because the planet gears  140  are meshed with the outer ring gear  130 , which is stationary, however, they are not freely rotatable about their own stationary central longitudinal axes. Thus, by driving rotation of, or transferring torque to, the planet gears  140 , the planet gears  140  are driven or urged to move circumferentially as a unit about the sun gear  138  such that their own central longitudinal axes move circumferentially as a unit about the sun gear  138  and about the central longitudinal axis  106  as they rotate about their own central longitudinal axes. 
       FIG. 13  illustrates the planetary gearbox  120  with the outer ring gear  130 , input shaft  128 , first sun gear  138 , and first planet gears  140  thereof removed so that other features are visible. In particular,  FIG. 13  illustrates that the first gear carrier  142  includes a generally cylindrical, disc-shaped, hollow main body having a central longitudinal axis coincident with the central longitudinal axis  106 , and three pegs, pins, or shafts that extend outward from a major surface of the main body along respective axes parallel to the central longitudinal axis  106  toward the planet gears  140 . 
     In use, the first planet gears  140  are rotatably mounted onto the shafts of the gear carrier  142  such that, as the planet gears  140  are driven to rotate circumferentially as a unit about the sun gear  138  and the central longitudinal axis  106 , the gear carrier  142  is also driven to rotate about the central longitudinal axis  106 . As also illustrated in  FIG. 13 , the hollow main body of the gear carrier  142  has a set of internal spline teeth meshed with external spline teeth of the second sun gear  144  such that rotation of the gear carrier  142  about the central longitudinal axis  106  drives rotation of the second sun gear  144  about the central longitudinal axis  106 . 
       FIG. 14  illustrates the planetary gearbox  120  with the outer ring gear  130 , input shaft  128 , first sun gear  138 , first planet gears  140 , and first gear carrier  142  thereof removed so that other features are visible. In particular,  FIG. 14  illustrates that the second sun gear  144  has a set of external spline teeth meshed with the internal spline teeth of the first gear carrier  142  engaged with the second sun gear  144 , such that rotation of the gear carrier  142  about the central longitudinal axis  106  drives rotation of the second sun gear  144  about the central longitudinal axis  106  and such that torque can be transferred from the gear carrier  142  to the second sun gear  144 .  FIG. 14  also illustrates that the second sun gear  144  has a set of external gear teeth meshed with external gear teeth of the second set of planet gears  146 , such that rotation of the sun gear  144  about the central longitudinal axis  106  drives rotation of the planet gears  146  about their own respective central longitudinal axes and such that torque can be transferred from the sun gear  144  to the planet gears  146 . 
     When the planetary gearbox  120  is assembled, the external gear teeth of the planet gears  146  are meshed with the internal gear teeth of a longitudinally inner portion of the second generally cylindrical internal surface  134  of the outer ring gear  130 . Thus, together, the second sun gear  144 , second set of planet gears  146 , the second gear carrier  148 , and the longitudinally inner portion of the second generally cylindrical internal surface  134  of outer ring gear  130  that is meshed with the second set of planet gears  146  collectively form a second planetary gear set or second planetary gear stage. When the winch  100  is in use, the first planetary gear stage drives further operation of the planetary gearbox  120  by driving rotation of, or transferring torque to, the second sun gear  144 . The sun gear  144  in turn drives rotation of, or transfers torque to, the planet gears  146 . Because the planet gears  146  are meshed with the outer ring gear  130 , which is stationary, however, they are not freely rotatable about their own stationary central longitudinal axes. Thus, by driving rotation of, or transferring torque to, the planet gears  146 , the planet gears  146  are driven or urged to move circumferentially as a unit about the sun gear  144  such that their own central longitudinal axes move circumferentially as a unit about the sun gear  144  and about the central longitudinal axis  106  as they rotate about their own central longitudinal axes. 
       FIG. 15  illustrates the planetary gearbox  120  with the outer ring gear  130 , input shaft  128 , first sun gear  138 , first planet gears  140 , first gear carrier  142 , second sun gear  144 , and second planet gears  146  thereof removed so that other features are visible. In particular,  FIG. 15  illustrates that the second gear carrier  148  includes a generally cylindrical, disc-shaped, hollow main body having a central longitudinal axis coincident with the central longitudinal axis  106 , and three pegs, pins, or shafts that extend outward from a major surface of the main body along respective axes parallel to the central longitudinal axis  106  toward the planet gears  146 . In use, the second planet gears  146  are rotatably mounted onto the shafts of the gear carrier  148  such that, as the planet gears  146  are driven to rotate circumferentially as a unit about the sun gear  144  and the central longitudinal axis  106 , the gear carrier  148  is also driven to rotate about the central longitudinal axis  106 . As also illustrated in  FIG. 15 , the hollow main body of the gear carrier  148  has a set of internal spline teeth meshed with external spline teeth of the third sun gear  150  such that rotation of the gear carrier  148  about the central longitudinal axis  106  drives rotation of the third sun gear  150  about the central longitudinal axis  106 . 
       FIG. 16  illustrates the planetary gearbox  120  with the outer ring gear  130 , input shaft  128 , first sun gear  138 , first planet gears  140 , first gear carrier  142 , second sun gear  144 , second planet gears  146 , and second gear carrier  148  thereof removed so that other features are visible. In particular,  FIG. 16  illustrates that the third sun gear  150  has a set of external spline teeth meshed with the internal spline teeth of the second gear carrier  148  engaged with the third sun gear  150 , such that rotation of the gear carrier  148  about the central longitudinal axis  106  drives rotation of the second sun gear  150  about the central longitudinal axis  106  and such that torque can be transferred from the gear carrier  148  to the third sun gear  150 .  FIG. 16  also illustrates that the third sun gear  150  has a set of external gear teeth meshed with external gear teeth of the third set of planet gears  152 , such that rotation of the sun gear  150  about the central longitudinal axis  106  drives rotation of the planet gears  152  about their own respective central longitudinal axes and such that torque can be transferred from the sun gear  150  to the planet gears  152 . 
     When the planetary gearbox  120  is assembled, the external gear teeth of the planet gears  152  are meshed with the internal gear teeth of a longitudinally outer portion of the second generally cylindrical internal surface  134  of the outer ring gear  130 . Thus, together, the third sun gear  150 , third set of planet gears  152 , the third gear carrier  154 , and the longitudinally outer portion of the second generally cylindrical internal surface  134  of outer ring gear  130  that is meshed with the third set of planet gears  152  collectively form a third planetary gear set or third planetary gear stage. When the winch  100  is in use, the second planetary gear stage drives further operation of the planetary gearbox  120  by driving rotation of, or transferring torque to, the third sun gear  150 . The sun gear  150  in turn drives rotation of, or transfers torque to, the planet gears  152 . Because the planet gears  152  are meshed with the outer ring gear  130 , which is stationary, however, they are not freely rotatable about their own stationary central longitudinal axes. Thus, by driving rotation of, or transferring torque to, the planet gears  152 , the planet gears  152  are driven or urged to move circumferentially as a unit about the sun gear  150  such that their own central longitudinal axes move circumferentially as a unit about the sun gear  150  and about the central longitudinal axis  106  as they rotate about their own central longitudinal axes. 
       FIG. 17  illustrates the planetary gearbox  120  with the outer ring gear  130 , input shaft  128 , first sun gear  138 , first planet gears  140 , first gear carrier  142 , second sun gear  144 , second planet gears  146 , second gear carrier  148 , third sun gear  150 , and third planet gears  152  thereof removed so that other features are visible. In particular,  FIG. 17  illustrates that the third gear carrier  154  includes a generally cylindrical, disc-shaped main body having a central longitudinal axis coincident with the central longitudinal axis  106 , and five pegs, pins, or shafts that extend outward from a major surface of the main body along respective axes parallel to the central longitudinal axis  106  toward the planet gears  152 . In use, the third planet gears  152  are rotatably mounted onto the shafts of the gear carrier  154  such that, as the planet gears  152  are driven to rotate circumferentially as a unit about the sun gear  150  and the central longitudinal axis  106 , the gear carrier  154  is also driven to rotate about the central longitudinal axis  106 . As described elsewhere herein, in use, the gear carrier  154  is mated with the flange  114  of the drum  112  such that, as the third gear carrier  154  is driven to rotate about the central longitudinal axis  106 , the drum  112  is also driven to rotate about the central longitudinal axis  106 . 
     As described elsewhere herein, each of the outer ring gear  130 , the first sun gear  138 , the first set of planet gears  140 , the second sun gear  144 , the second set of planet gears  146 , the third sun gear  150 , and the third set of planet gears  152  each have one or more sets of internal and/or external gear teeth meshed with corresponding gear teeth of other components of the planetary gearbox  120 . Such components are involute spur-type gears or related involute spur-type gearing components, and their respective sets of gear teeth are involute spur-type gear teeth. Further, such components may be high-contact ratio involute spur-type gears or related high-contact ratio involute spur-type gearing components, and their respective sets of gear teeth may be high-contact ratio involute spur-type gear teeth. 
     A spur-type gear has a pitch, which is the distance (e.g., an angular distance with respect to a center of the gear) between similar or corresponding points (e.g., sides or centers) of two adjacent teeth. As used herein, the term “contact ratio” may be used to mean the number of pitches a tooth rotates through while in constant contact with a corresponding tooth of a meshed gear. The contact ratio is also a measure of the average number of teeth in contact between two meshed gears while the gears are in use, where a higher contact ratio indicates that, on average, more teeth are engaged while the gears are in use and a lower contact ratio indicates that, on average, fewer teeth are engaged while the gears are in use. 
     As used herein, the term “high-contact ratio” may be used to mean a higher contact ratio than that specified in one or more standardized specifications for gear and gear tooth dimensions, such as may be promulgated by any of various generally recognized standards-setting organizations. For example, the term “high-contact ratio” may be used to mean a higher contact ratio than that specified in ANSI/AGMA B88, titled “Tooth Thickness Specification and Measurement.” Generally speaking, high-contact ratio gear teeth are longer than standard gear teeth such that high-contact ratio gearing provides a higher number of active teeth in mesh when in use than standard gearing. 
     A more detailed discussion of the geometry of the gears and gear teeth described herein follows. As used herein, geometrical terminology may be used in accordance with the explanations provided in AGMA 933-B03, titled “Basic Gear Geometry.” A spur-type gear has a central longitudinal axis and a gear center on the central longitudinal axis about which it rotates, and a plane of rotation perpendicular to the central longitudinal axis and including the gear center within which it rotates. A first spur-type gear may be meshed with a second spur-type gear such that the first and second spur-type gears have a common plane of rotation. The first spur-type gear can have a first pitch radius and the second spur-type gear can have a second pitch radius such that the sum of the first and second pitch radiuses is equal to the distance within the common plane of rotation from the gear center of the first spur-type gear to the gear center of the second spur-type gear, and such that a ratio of the first pitch radius to the second pitch radius is equal to the ratio of the number of gear teeth in the first spur-type gear to the number of gear teeth in the second spur-type gear. 
     Each of the first and second spur-type gears can have a respective pitch circle centered on its respective central longitudinal axis and gear center and lying within the common plane of rotation, and having a radius equal to its respective pitch radius. Each of the first and second spur-type gears can have a respective pitch diameter that is twice its pitch radius, such that its respective pitch circle has a diameter that is twice its radius. Each of the first and second spur-type gears can also have a respective diametral pitch, which is the ratio of the spur-type gear&#39;s number of teeth to the spur-type gear&#39;s pitch diameter. 
     A gear tooth of a gear can have an addendum, which is the radial length of the portion of the tooth that extends outward from the gear&#39;s pitch circle away from the gear center to the top of the tooth (which may be referred to as a tooth tip), and a dedendum, which is the radial length of the portion of the tooth that extends inward from the gear&#39;s pitch circle toward the gear center to the bottom of the space or gap between the gear tooth and an adjacent gear tooth (which may be referred to as a tooth root). In standard gears and gear teeth, such as those specified in relevant AGMA standards, the addendum is typically 1.00 divided by the diametral pitch, while the dedendum is typically 1.25 divided by the diametral pitch. Related metric standards, such as ISO 6336, are geometrically equivalent in this regard, but may refer to a “module” rather than a diametral pitch, where the “module” uses different units than, and is an inverse with respect to, the diametral pitch. In some cases, a high-contact ratio gear or a high-contact ratio gear tooth can therefore have a longer addendum and/or a longer dedendum than standard gears or gear teeth. As a result of having a longer addendum, the top of the tooth may be narrower and radiuses of curvatures thereof may be smaller. As a result of having a longer dedendum, the bottom of the tooth may be wider (and bottoms of the corresponding spaces or gaps between adjacent teeth may be narrower, and radiuses of curvature thereof may be smaller). 
     For example, a high-contact ratio gear may have high-contact ratio gear teeth, and high-contact ratio gear teeth may have an addendum greater than 1.00 divided by the respective diametral pitch, greater than or equal to 1.05 divided by the respective diametral pitch, greater than or equal to 1.10 divided by the respective diametral pitch, greater than or equal to 1.15 divided by the respective diametral pitch, greater than or equal to 1.20 divided by the respective diametral pitch, greater than or equal to 1.25 divided by the respective diametral pitch, greater than or equal to 1.30 divided by the respective diametral pitch, greater than or equal to 1.35 divided by the respective diametral pitch, greater than or equal to 1.40 divided by the respective diametral pitch, greater than or equal to 1.45 divided by the respective diametral pitch, greater than or equal to 1.50 divided by the respective diametral pitch, greater than or equal to 1.55 divided by the respective diametral pitch, or greater than or equal to 1.60 divided by the respective diametral pitch. 
     As another example, a high-contact ratio gear may have high-contact ratio gear teeth, and high-contact ratio gear teeth may have a dedendum greater than 1.25 divided by the respective diametral pitch, greater than or equal to 1.30 divided by the respective diametral pitch, greater than or equal to 1.35 divided by the respective diametral pitch, greater than or equal to 1.40 divided by the respective diametral pitch, greater than or equal to 1.45 divided by the respective diametral pitch, greater than or equal to 1.50 divided by the respective diametral pitch, greater than or equal to 1.55 divided by the respective diametral pitch, greater than or equal to 1.60 divided by the respective diametral pitch, greater than or equal to 1.65 divided by the respective diametral pitch, greater than or equal to 1.70 divided by the respective diametral pitch, greater than or equal to 1.75 divided by the respective diametral pitch, or greater than or equal to 1.80 divided by the respective diametral pitch. 
     In some cases, such addendum and dedendum lengths can result in a gear having a contact ratio that exceeds 1.60, or that exceeds 1.65, or that exceeds 1.70, or that exceeds 1.75, or that exceeds 1.80, or that exceeds 1.85, or that exceeds 1.90, or that exceeds 1.95, or that exceeds 2.00. 
     Addendum and dedendum dimensions of a gear tooth generally have upper limits determined by the involute curvatures and other related dimensions of the tooth. That is, due to the involute curvatures of the tooth, as the addendum is increased, the tooth tip becomes increasingly closer to forming a point where its two sides intersect, until the tooth tip forms a point where its two sides intersect and the addendum can no longer be increased. The dedendum of the gear tooth can have an upper limit determined in a similar manner. A gear tooth having a pointed tooth tip is typically fragile and difficult to manufacture relative to a gear tooth not having a pointed tooth tip. As a result, a pointed tooth tip may be avoided by providing a gear tooth with a tooth tip thickness that extends from a radially outermost end of a first one of its sides to a radially outermost end of a second one of its sides opposite to the first. 
     As understood in accordance with standard gear tooth dimensions and the description herein, a minimum gear tooth tip thickness (which may also be referred to in the industry as a top land thickness) may be 0.2 divided by the diametral pitch. The gears described herein may have gear teeth having gear tooth tip thicknesses greater than zero, or greater than or equal to 0.1 divided by the diametral pitch, 0.2 divided by the diametral pitch, 0.3 divided by the diametral pitch, or 0.4 divided by the diametral pitch. Maximum addendum and dedendum dimensions may be determined by specifying a gear tooth tip thickness or a minimum gear tooth tip thickness, and may be calculated based on such a specification and other known dimensions of the gear and its gear teeth. Resulting maximum addendum dimensions may be 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, or 1.80 divided by the respective diametral pitch. Resulting maximum dedendum dimensions may be 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75, 1.80, 1.85, 1.90, 1.95, or 2.00 divided by the respective diametral pitch. 
     The geometry discussed herein is primarily directed to gears having external gear teeth and such external gear teeth, such as the sun gears and the sets of planet gears. Nevertheless, the geometry discussed herein can be easily adapted for use in gears having internal gear teeth and such internal gear teeth, such as the outer ring gear. Such adaptation generally requires that the geometry of the gear teeth be turned “inside-out.” In such adaptations, the addendum becomes the radial length of the portion of the tooth that extends inward from the gear&#39;s pitch circle toward the gear center to the tooth tip, and the dedendum becomes the radial length of the portion of the tooth that extends outward from the gear&#39;s pitch circle away from the gear center to the tooth root. 
     In some implementations, all of the gears in the planetary gearbox  120  are high-contact ratio spur-type gears and all of the gear teeth in the planetary gearbox  120  are high-contact ratio spur-type gear teeth. All of, or any subset of, such gears and such gear teeth may have an addendum greater than 1.00 divided by the respective diametral pitch, or greater than or equal to 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, or 1.50 divided by the respective diametral pitch, as well as a dedendum greater than 1.25 divided by the respective diametral pitch, or greater than or equal to 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, or 1.75 divided by the respective diametral pitch, and a correspondingly high contact ratio resulting from such dimensions. 
     In some implementations, such a subset can be all of the gears and all of the gear teeth in the first planetary gear stage of the planetary gearbox  120  (e.g., the first sun gear  138  and its gear teeth, the first set of planet gears  140  and their gear teeth, and the third generally cylindrical internal surface  136  of outer ring gear  130  that is meshed with the first set of planet gears  140 , and its gear teeth). In some implementations, such a subset can be all of the gears and all of the gear teeth in the second planetary gear stage of the planetary gearbox  120  (e.g., the second sun gear  144  and its gear teeth, the second set of planet gears  146  and their gear teeth, and the longitudinally inner portion of the second generally cylindrical internal surface  134  of outer ring gear  130  that is meshed with the second set of planet gears  146 , and its gear teeth). In some implementations, such a subset can be all of the gears and all of the gear teeth in the third planetary gear stage of the planetary gearbox  120  (e.g., the third sun gear  150  and its gear teeth, the third set of planet gears  152  and their gear teeth, and the longitudinally outer portion of the second generally cylindrical internal surface  134  of outer ring gear  130  that is meshed with the third set of planet gears  152 , and its gear teeth). 
     In some implementations, such a subset can be all of the sun gears and their respective gear teeth (e.g., each of the first sun gear  138 , second sun gear  144 , and third sun gear  150 , and their respective gear teeth). In some implementations, such a subset can be all of the planet gears and their respective gear teeth (e.g., each of the first set of planet gears  140 , each of the second set of planet gears  146 , each of the third set of planet gears  152 , and their respective gear teeth). In some implementations, such a subset can be the outer ring gear  130 , its second generally cylindrical internal surface  134  and third generally cylindrical internal surface  136 , and the respective gear teeth thereof. 
     While the present disclosure has focused on high-contact ratio gearing in the winch  100 , the features described herein may be applied to other devices, such as hoists, track drives, wheel drives, or other drive systems including gearboxes. Such devices, including the winch  100 , can be mounted, such as in the manner described herein, to heavy equipment or machinery, such as cranes, mobile cranes, offshore (e.g., oil platform) cranes, utility vehicles such as bucket trucks, trucks, trailers, naval vessels, and tractor-type equipment such as bulldozers. 
     The gears described herein are high-contact ratio gears and include high-contact ratio gear teeth. As a result, in each meshed pair of gears described herein, a greater number of gear teeth are, on average, in contact with one another than would be in comparable standard, non-high-contact ratio gear systems. As a result, loads are distributed over a greater number of teeth, thereby increasing load carrying capacity and decreasing bending or flexure of the teeth, thereby reducing noise and other NVH-related issues. 
     The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.