Abstract:
Reduction gear units are provided comprising a gearbox, a cam assembly, a bearing assembly, a first gear and a second gear. The first and second gears may engage one another and translate rotating movement from one axis to an axis perpendicular thereto. The second gear is disengagable from the first gear by action of the cam assembly, which is adapted to disengage the second gear from the first gear through eccentric rotation of the cam assembly. In one embodiment, a bearing assembly carried by the cam assembly is preloaded. The cam assembly is disposed so that the preloaded can be maintained during manufacture of the gearbox. In another embodiment, the gearbox case and cam assembly are disposed so as to minimize internal leakage from the case and enhance sealing of the gearbox.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a DIVISIONAL of U.S. patent application Ser. No. 12/434,429, filed on May 1, 2009, having the same Title, and hereby incorporated by references in its entirety. 
    
    
     BACKGROUND 
     The present invention relates generally to disengagable reduction gear units having bearings that are preloaded. Methods of use are also provided. 
     In the manufacture of disengagable reduction gearboxes, rotary bearings are utilized in the gearbox case to support input shafts and output shafts permitting rotation of the shafts. One particular type of bearing utilized in gearboxes is a thrust bearing, which is designed to support radial loads (thereby permitting rotation) and also high axial thrust loads. Thrust bearings may have a variety of configurations. One type of thrust bearing is a tapered roller bearing which consists of small tapered rollers disposed between a bearing cone and a bearing cup and arranged so that the axes of the rollers converge at a point on the axis of the bearing around which the cup and the cone are centered. One characteristic of thrust bearings is that they can be “pre-loaded” with an axial force when they are installed in an assembly. When a thrust bearing is pre-loaded, a certain amount of compressive force is applied to the cone as it seats in the cup of the bearing. The amount of pre-loading is determined by the particular use of the bearing. A significant pre-load generally makes the bearing harder to rotate, whereas minimal preloading leaves the bearing “loose.” Those skilled in the art with the benefit of this disclosure will appreciate that bearing pre-loading settings are often very precise and any variance or unintended change in the bearing pre-load that arises during the manufacturing process can hamper operation of the assembly in which they are utilized. Such variances or unintended changes in a pre-loaded bearing are often hard to prevent during the manufacturing process. This is particularly true of heavy equipment such as gearboxes where precision is often hard to maintain. Thus it would be desirable to provide a disengagable reduction gearbox in which thrust bearings utilized therein can be pre-loaded prior to assembly into the gearbox, and the desired pre-loaded can be maintained throughout the manufacturing process. 
     Likewise, in the manufacture of disengagable reduction gearboxes, the housing or case in which a shaft is supported must often be bored or otherwise machined to create a seat into which a movable bearing/shaft assembly is inserted. If the foregoing step is not performed with due care, o-ring seals between the bearing/shaft assembly and the gearbox housing are highly likely to leak oil or other lubricant contained within the gearbox. Moreover, such poor seals also enable the ingress of dirt or other debris into the gearbox case, thus potentially damaging the bearings, gears, or other internal components of the gearbox. Of course, those skilled in the art with the benefit of this disclosure will appreciate that the greater the precision used to machine such seats, the more expensive and time consuming the manufacturing process becomes. Thus, it would be desirable to provide a disengagable reduction gearbox with a sealing mechanism in which proper functioning is less dependent on the manufacturing process. It would also be desirable if such sealing mechanism not only inhibits leaks from within the gearbox, but also inhibits dirt or other debris from entering the interior of the gearbox. 
     SUMMARY 
     The present invention relates generally to disengagable reduction gear units having bearings that are preloaded. Methods of use are also provided. 
     An example of a gearset of the present invention comprises a gearbox; a cam assembly comprised of a first cam body having an outer surface disposed around a first cam axis and an inner bore disposed around a second cam axis, wherein the first and second cam axii are axially offset from one another, wherein a portion of said inner bore is threaded so as to form a threaded inner bore; a bearing assembly disposed within said threaded inner bore of said cam assembly; a threaded fastener engaging said threaded bore and abutting said bearing assembly so as to secure said bearing assembly within said cam assembly bore; a first gear within the gearbox mounted on a first shaft, said shaft defined along a first axis; a second gear within the gearbox and mounted on a second shaft, said second shaft defined along a second axis that is substantially perpendicular to the first axis of the first shaft, said second shaft supported by said bearing assembly so that the second axis of the second gear and the second cam axis are co-axial; and wherein said cam assembly is rotatably movable from a first position to a second position wherein said second gear engages said first gear when said cam assembly is in the first position and wherein said second gear and first gear are disengaged when said cam assembly is in the second position. 
     Another example of a gearset comprises a gearbox; a cam assembly comprising a first cam body having an outer surface disposed around a first cam axis and an inner bore disposed around a second cam axis, a second cam body having an outer surface disposed around the first cam axis and an inner bore disposed around the second cam axis, and a crossbar joining said first and second cam bodies, wherein the first and second cam axii are axially offset from one another, wherein a portion of said inner bore is threaded; a bearing assembly disposed within said inner bore of said cam assembly; a threaded fastener engaging said threaded bore and abutting said bearing assembly so as to secure said bearing assembly within said cam assembly bore; a locking fastener securing said threaded fastener within said threaded bore; a first gear within the gearbox mounted on a first shaft, said shaft defined along a first axis; a second gear within the gearbox and mounted on a second shaft, said second shaft defined along a second axis that is substantially perpendicular to the first axis of the first shaft, said second shaft supported by said bearing assembly so that the second axis of the second gear and the second cam axis are co-axial; and wherein said cam assembly is rotatably movable from a first position in which said second gear engages said first gear to a second position in which said second gear and first gear are disengaged. 
     Another example a gearset comprises a gearbox; a first gear within the gearbox mounted on a first shaft, said shaft defined along a first axis; a second gear within the gearbox and mounted on a second shaft, said second shaft defined along a second axis that is substantially perpendicular to the first axis of the first shaft, said second shaft supported by said bearing assembly so that the second axis of the second gear and the second cam axis are co-axial; a cam assembly comprising a first cam body having an outer surface disposed around a first cam axis and an inner bore disposed around a second cam axis, wherein the first and second cam axii are axially offset from one another and an end cap extending from the first cam body, said end cap having an outer surface and axially aligned with said first cam axis and further including an aperture therein axially aligned with said second cam axis such that said second shaft extends through said aperture, said end cap further comprising at least one o-ring groove in the outer surface of said end cap; an o-ring disposed within said o-ring groove of said end cap; an end collar separable from said gearbox and in sealing engagement with said o-ring, said end collar attached to said gearbox so as to enclose said cam assembly within said gearbox; a bearing assembly disposed within said inner bore of said cam assembly and supporting said second shaft; and wherein said cam assembly is rotatably movable from a first position in which said second gear engages said first gear to a second position in which said second gear and first gear are disengaged. 
     One example of a method for manufacturing a disengagable reduction gearbox, said method comprises the steps of: providing a gearbox comprised of an upper portion and a lower portion; wherein the upper portion comprises a cam assembly comprised of a first cam body having an outer surface disposed around a first cam axis and an inner bore disposed around a second cam axis, wherein the first and second cam axii are axially offset from one another, wherein a portion of said inner bore is threaded so as to form a threaded inner bore; a bearing assembly disposed within said threaded inner bore of said cam assembly; a threaded fastener engaging said threaded bore and abutting said bearing assembly so as to secure said bearing assembly within said cam assembly bore; and a second gear within the gearbox mounted on a second shaft; wherein the lower portion comprises a first gear within the gearbox mounted on a first shaft, said shaft defined along a first axis; wherein said second shaft defined along a second axis that is substantially perpendicular to the first axis of the first shaft, said second shaft supported by said bearing assembly so that the second axis of the second gear and the second cam axis are co-axial, wherein said cam assembly is rotatably movable from a first position to a second position wherein said second gear engages said first gear when said cam assembly is in the first position and wherein said second gear and first gear are disengaged when said cam assembly is in the second position; preloading the bearing assembly; assembling the upper portion to the lower portion; and wherein the preloading is accomplished before the assembling. 
     The features and advantages of the present invention will be apparent to those skilled in the art with the benefit of this disclosure. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying figures, wherein: 
         FIGS. 1   a ,  1   b ,  1   c , and  1   d  illustrate perspective and side views of a disengagable gearbox in accordance with one embodiment of the present invention. 
         FIGS. 2   a  and  2   b  illustrate cross-sectional views of a disengagable gearbox in accordance with one embodiment of the present invention. 
         FIGS. 3   a ,  3   b ,  3   c ,  3   d , and  3   e  illustrate perspective, side, and cross-sectional views of a cam assembly in accordance with one embodiment of the present invention. 
         FIG. 4  is an exploded view of the gearbox of the invention. 
     
    
    
     While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the present invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention relates generally to disengagable reduction gear units having bearings that are preloaded. Methods of use are also provided. 
     Generally, the present invention provides a reduction gear units and systems having cam assemblies capable of disengaging a first gear from a second gear. In certain embodiments, a bearing assembly is provided for the second gear that is capable of being preloaded prior to certain assembly steps. Numerous other components, as detailed below, may form part of the system depending on the particular embodiment. 
     Advantages of the methods and devices of the present invention include, but are not limited to, the ability to preload the bearing assembly early in the gearset assembly process, improved sealing of certain components, and other advantages that will be apparent with the benefit of this disclosure. 
     To facilitate a better understanding of the present invention, the following examples of certain embodiments are given. In no way should the following examples be read to limit, or define, the scope of the present invention. 
       FIGS. 1   a ,  1   b ,  1   c  and  1   d  illustrate the disengagable gearbox  10  of the present invention, which gearbox  10  is generally comprised of a housing or case  12 , an input shaft  14 , an output shaft  16 , a hub mounted  18  mounted on output shaft  16  and a handle assembly  20 . Handle assembly  20  can be moved from a first position, shown in  FIG. 1   a , to a second position, shown in  FIG. 1   b , thereby permitting gears (not shown) in the gearbox  10  to be engaged or disengaged. 
     With reference to  FIGS. 2   a  and  2   b , case  12  is shown as having an upper portion  12   a  and a lower portion  12   b . Output shaft  16  is disposed in lower portion  12   b  of case  12 , supported by bearings  22 . An oil seal  24  is provided where shaft  16  protrudes from case  12 . 
     Mounted on shaft  16  is a gear  26 . In one preferred embodiment, gear  26  is a worm gear with teeth  28 . Gear  26  may be mounted on shaft  16  in any conventional manner. In one preferred embodiment, a key  30  may be provided on shaft  16  to engage a slot  32  in gear  26 , permitting gear  26  to be oriented and radially secured on shaft  16 . A fastener  34 , such as a retaining ring, may be further used to secure gear  26  on shaft  16 . To further ensure positioning of shaft  16  in case  12 , a spacer  36  may be disposed on shaft  16  between gear  26  and bearing  22 . 
     As shown in  2   a , shaft  16  is defined along an output shaft axial reference axis  38 . Reference axis  38  also passes through the hub  29  of gear  26  when gear  26  is aligned on shaft  16 . Gear  26  can likewise be characterized as having a radial reference axis  40  around which teeth  28  are symmetrically disposed. 
     Disposed in the upper portion  12   a  of case  12  is a cam assembly  42  which generally supports input shaft  14  so as to be substantially perpendicular to output shaft  16 . More specifically, input shaft  14  is supported by a bearing assembly  44  mounted in cam assembly  42 . The major axii of cam assembly  42  (as discussed below) are substantially perpendicular to output shaft axial reference axis  38 . Handle assembly  20  is attached to cam assembly  42 . 
     Bearing assembly  44  is comprised of one or more bearings  45 . In one embodiment of the present invention, bearings  45  are adjustable load bearings. More preferably, one or more of bearings  45  are thrust bearings, particularly of the cone and cup or tapered roller type. 
     Disposed on input shaft  14  is a gear  46 . In one preferred embodiment, gear  46  is a threaded worm shaft which threads  48  mesh with teeth  28  of gear  26  when gear  26  and gear  46  are engaged. 
     Turning to  FIGS. 3   a - 3   e , cam assembly  42  is illustrated. In one preferred embodiment illustrated in  FIGS. 3   c  and  3   e , cam assembly  42  is comprised of a single cam body  50 . In this embodiment, cam body  50  is generally cylindrical in shape and is characterized by an outer wall  53  and an inner bore  54 . Outer wall  53  has an outer surface  56 . As best seen in  FIG. 3   c , outer wall  53  varies in thickness, i.e., tapers, around its circumference. As such, outer surface  56  can be characterized as being centered around a first axis  58 , while bore  54  can be characterized as being centered around a second axis  60  which is radially offset from axis  58 . Axial rotation of cam body  50  thus results in an eccentric movement of cam body  50 . The taper of wall  53  creates eccentric movement of cam assembly  42  as it is rotated from a first position to a second position, so as to permit gears  46  and  26  to engage and disengage. 
     As best seen in  FIG. 3   e , cam body  50  also includes an end cap  62  extending therefrom so as to form a shoulder  64 . End cap  62  can also be characterized as having an outer surface  66  which is centered around first axis  58 . An aperture  68  is disposed in end cap  62  which aperture is centered around second axis  60 , thus appearing “off center” with respect to outer surface  66 , as best illustrated in  FIG. 3   a . End cap  62  has at least one, and preferably at least two, o-ring grooves  70  disposed in outer surface  66 . End cap  62  may also be disposed for receipt of a fastener, such as is shown at  67 , to permit handle assembly  20  to be secured thereto. 
     Bore  54  is disposed for receipt of a bearing that comprises bearing assembly  44 . 
     In another preferred embodiment, cam assembly  42  is comprised of cam body  50  and cam body  52 , joined by a crossbar or arm  54 . In this embodiment, cam bodies  50 ,  52  and arm  54  may be integrally formed as a single component of one piece construction. Cam body  52  is similarly formed with respect to cam body  50 , being generally cylindrical in shape and characterized by an outer wall  52  and an inner bore  54 . Outer wall  53  has an outer surface  56 . The thickness of outer wall  53  tapers around its periphery and outer surface  56  can be characterized as being centered around first axis  58 , while bore  54  can be characterized as being centered around second axis  60  which is radially offset from axis  58 . As such, bore  54  of cam body  52  and bore  54  of cam body  50  are aligned. 
     The foregoing cam assembly  42  having two eccentric bore bosses or cam bodies is desirable, because the cam bodies, being disposed adjacent opposite ends of gear  48 , permit a uniform rotational/translational force to be applied to gear  48  as it moves along its eccentric path, which has the effect of increasing worm gear mesh life. Likewise, the load on any one bearing  45  is reduced, which is particularly desirable when cam assembly  42  is moved between its first and second positions, i.e., the point where thrust or axial forces on bearings  45  are likely to be maximized. Again, this is likely to have the effect of lengthening the operational life of the bearings. Furthermore, the arrangement permits larger bearings to be utilized in association with cam assembly  42 , which in turn permits a smaller or “shorter” gear case  12 . Although the angular rotation of cam assembly  42  from the first position to the second position can be of any degree that permits the respective gears to be disengaged, in one preferred embodiment, the angular rotation is approximately 60° while in another preferred embodiment the angular rotation is approximately 90°. 
     Bore  54  of cam body  52  is also disposed for receipt of a bearing. A portion of bore  54  is threaded, as shown at  72 , for receipt of a threaded bearing fastener  74  (shown in  FIG. 2   b ) provided to constrain bearing  45  in bore  54 . Additionally, cam body  52  is disposed at  75  for receipt of a second fastener  76  (shown in  FIG. 2   b ), which is provided to secure bearing fastener  74  in place. The foregoing arrangement represents one novel aspect of the present invention since it permits bearing  45  to be pre-loaded to desired specifications before the bearing is assembled into gearbox  10  and then ensures that the selected bearing pre-load is maintained during assembly. More specifically, as threaded bearing fastener  74  is screwed into the threaded portion of bore  54 , it applies an axial force on bearing  45  as it is seated in bore  54 . This axial force, which is the pre-load force, can be precisely adjusted due to the threaded nature of bearing fastener  74 . Once the precise adjustment is achieved, second fastener  76 , such as a set screw, is used to “lock” bearing fastener  74  into place, thereby insuring that the position of bearing fastener  74 , and hence the “pre-load” force, is not inadvertently altered as the cam assembly  42  is inserted into case  12  during assembly of gearbox  10 . In another embodiment, second fastener  76  may simply be another threaded fastener  74  that is screwed into bore  54  so as to lock the threaded bearing fastener  74  that abuts against bearing  45  into place. 
     Another novel aspect of the present invention is found in the manner in which cam assembly  42  is mounted and “sealed” within case  12 . As shown in  FIG. 2   b , when cam assembly  42  is inserted into case  12 , end cap  62  protrudes from the upper portion  12   a  of case  12 . End collar  78  having a bore  80  there through is seated on end cap  62  to abut shoulder  64  so that the inner surface of collar  78  is disposed adjacent o-ring grooves  70 . Bore  80  is sized so as to create a tight seal between end collar  78  and end cap  62  when an o-ring  82  is disposed within o-ring groove  70 . End collar  78  is then fastened to case  12  by any standard means, such as fasteners (not shown). Those skilled in the art with the benefit of this disclosure will appreciate that the foregoing is preferable over the prior art, because rather than precisely machining an entire bore in case  12  (which is large and bulky) in order to effectuate a seal between cam assembly  42  and case  12 , only the inner surface of collar  78  need be precisely machined. Machining this small surface on a small piece (collar  78 ) is much easier than machining the much larger surface area of case  12 . Thus, a much better gearbox seal can be achieved much more easily utilizing the configuration of the present invention. 
     While such a seal can be achieved with a single o-ring  82 , it is preferable that the seal have at least two o-rings  82 . Additionally, an o-ring  84  may be provided at shoulder  64  to provide an additional seal between cam assembly  42 , case  12  and end collar  78 . 
     The foregoing gearbox sealing arrangement is also desirable, because it permits a single lubricant disposed within case  12  to be utilized to lubricate both gearset  48  and bearing assembly  44 , rather than utilizing separate lubrication systems. 
     As described above, handle assembly  20  attaches to cam assembly  42 , and more specifically, end cap  62 , to permit cam assembly  42  to be moved between engagement and disengagement positions between gears  16  and  26 . With reference to  FIGS. 1   a ,  1   b ,  1   c  and  2   b , handle assembly  20  is comprised of handle  86  and shield plate  88 . Preferably, handle  86  and shield plate  88  are integrally formed. Disposed in shield plate  88  is an aperture  90  through which input shaft  14  passes, as shown in  FIG. 2   b . Inner side  88   a  of shield plate  88  abuts end cap  62 . In one preferred embodiment, o-ring  92  may be provided between inner side  88   a  of shield plate  88  and end cap  62 , forming an “external” seal, which is useful in preventing dirt or other debris from migrating into gearbox  12 . Handle  86  may also include sleeve  94  or similar aperture to permit a lever (not shown) to utilize handle assembly  20 . 
     An exploded view of the gearbox of the invention is illustrated in  FIG. 4 , wherein gearbox  100  is comprised of a housing  110 , a output cap  112 , an output oil seal  113 , an output bearing cup  114 , an output bearing cone  115 , a flanged output shaft  116 , an output spacer  117 , a worm gear  118 , a output key,  119 , a retaining ring  210 , an output shim  211  for the inboard bearing, an output shim  212  for the cap, output cap fasteners  213 , output cap lock washers  214 , a worm shaft  215 , an input bearing cup  216 , an input bearing cone  217 , an input end cap  218 , o-rings  219 , an input oil seal  220 , an input cap shim  221 , an input cap fastener  222 , a diaphragm  223 , an expansion chamber  224 , fasteners  225 , lock washers  226 , a flange pipe plug  228  and o-ring  229 , studs  229 , wheel nuts  230 , a right hand cam  231 , bearing cup nut  232 , set screws  233 , thrust washers  234 , a right hand side end cap  235 , a right hand shield  236 , a right hand handle  237 , cap screws  238 , a handle lock pin  239 , a hitch pin  240  and a wire rope strap  241 . 
     Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.