Patent Publication Number: US-9903463-B2

Title: Gearbox with sight window

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/908,118, filed Oct. 20, 2010, now U.S. Pat. No. 8,601,868, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/253,932, filed Oct. 22, 2009, which is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     The present subject matter generally relates to oil level sight windows for gearboxes. 
     Description of Related Art 
     Engine-driven mechanisms require a minimum amount of a lubricant to ensure proper operation of the moving parts of the drive system. In some engine-driven mechanisms, such as agricultural equipment, the drive system includes a gearbox containing various gears, shafts, and other moving parts, as well as an amount of oil for lubricating the moving parts. 
     An exemplary prior art gearbox  10  is illustrated in  FIG. 1 . The gearbox  10  includes a gearbox housing  12  with opposing walls  14  and  16 . A pair of bearing bores  18  and  20  are defined in the opposing walls  14  and  16 , respectively. The bearing bores  18  and  20  are aligned with each other for mounting bearings (not illustrated) to support an input shaft (not illustrated) extending through the first bearing bore  18  and into the gearbox housing  12 . A metallic bore cap plug  22  is associated with the second bearing bore  20  to isolate the interior of the gearbox housing  12  from the outside environment. 
     To fill the gearbox housing  12  with oil, a fill plug  24  on the top of the gearbox housing  12  is removed to expose a fill hole  26 . Oil is poured into the gearbox housing  12  via the fill hole  26  and the fill plug  24  is replaced once the amount of oil in the gearbox housing  12  has reached the proper level. To ascertain the gearbox oil level, a side wall  28  of the gearbox housing  12  is provided with a small aperture  30  which receives a removable oil level plug  32 . The level of oil in the gearbox housing  12  is checked by removing the oil level plug  32  and looking inside. 
     It has been recognized that removing an oil level plug to check the gearbox oil level can be disadvantageous, so in some gearboxes, the oil level plug is either replaced by or supplemented with a sight window. The sight window typically comprises the combination of an aperture in the gearbox housing and a lens received by or otherwise associated with the aperture. Rather than having to remove a plug to check the gearbox oil level, one merely looks through the sight window to verify the oil level. 
     One problem with a typical sight window is that it can be labor-intensive to retrofit onto a gearbox having only an oil level plug. For example, in some cases, a large aperture must be machined in a wall of the gearbox housing to receive a lens. 
     To simplify installation of a sight window in retrofitting situations, it is known to replace the standard (i.e., opaque) oil level plug with a plug having a built-in lens, such as the GN 743 line of oil level indicators from Elesa S.p.A. of Monza, Italy. Such oil level indicators avoid the problem of adding a large bore to the gearbox housing, but can be disadvantageous in that they are small, which can make it difficult to accurately assess the gearbox oil level. 
     Accordingly, there remains the need for a larger oil level sight window which can be easily retrofitted onto a gearbox having only an oil level plug. 
     SUMMARY 
     There are several aspects of the present subject matter which may be embodied separately or together in the devices and systems described and claimed below. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to preclude the use of these aspects separately or the claiming of such aspects separately or in different combinations as set forth in the claims appended hereto. 
     In one aspect, a sight window is provided for a gearbox having a gearbox housing and a pair of bearing bores. The bearing bores are aligned with each other and defined in opposing walls of the gearbox housing. The sight window comprises one of the bearing bores and a generally transparent and/or translucent lens associated therewith. 
     In another aspect, a gearbox for an engine-driven mechanism comprises a gearbox housing having opposing walls. A first bearing bore is defined in one of the opposing walls and adapted for receiving a shaft. A sight window comprises a second bearing bore, which is defined in the other opposing wall and aligned with the first bearing bore, and a generally transparent and/or translucent lens associated with the second bearing bore. 
     In yet another aspect, a method of providing a gearbox of an engine-driven mechanism with a sight window comprises providing a gearbox and a generally transparent and/or translucent lens. The gearbox includes a gearbox housing having opposing walls, a first bearing bore defined in one of said opposing walls and adapted for receiving a shaft, and a second bearing bore defined in the other opposing wall and aligned with the first bearing bore. The lens is associated to the second bearing bore to provide a sight window as a feature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a known prior art gearbox having an oil level plug for checking the gearbox oil level; 
         FIG. 2  is a front perspective view of a gearbox incorporating a sight window according to one aspect of the present disclosure; 
         FIG. 2A  is an exploded perspective view of the gearbox of  FIG. 2 ; 
         FIG. 3  is an exploded perspective view of a gearbox incorporating an alternative sight window according to one aspect of the present disclosure; 
         FIG. 4  is a cross-sectional view of a gearbox incorporating yet another alternative sight window according to one aspect of the present disclosure; 
         FIG. 4A  is a detail cross-sectional view of the sight window of the gearbox of  FIG. 4 ; 
         FIG. 5  is a cross-sectional view of a gearbox incorporating another alternative sight window according to one aspect of the present disclosure; 
         FIG. 6  is a cross-sectional view of a ring member of the sight window of  FIG. 5 ; 
         FIG. 7  is a front elevational view of the ring member of  FIG. 6 , including a lens and other components of the sight window of  FIG. 5 ; 
         FIG. 7A  is a cross-sectional view of the ring member and associated components of  FIG. 7 , taken through the line A-A of  FIG. 7 ; 
         FIG. 8  is an exploded perspective view of a gearbox incorporating yet another alternative sight window according to one aspect of the present disclosure; 
         FIG. 9  is a perspective view of selected components of another embodiment of a sight window according to an aspect of the present disclosure; 
         FIG. 10  is a perspective view of a gearbox incorporating the sight window of  FIG. 9 ; and 
         FIG. 11  is a cross-sectional view of the gearbox of  FIG. 10 . 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The embodiments disclosed herein are for the purpose of providing the required description of the present subject matter. They are only exemplary, and may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting the subject matter as defined in the accompanying claims. 
       FIGS. 2 and 2A  show a gearbox  34  employing a sight window assembly  36  according to an aspect of the present disclosure. The gearbox  34  is identical to the gearbox  10  of  FIG. 1 , except that the bore cap plug  22  of  FIG. 1  has been eliminated and replaced with the sight window  36 . The sight window assembly  36  comprises the combination of the second bearing bore  20  and a generally transparent and/or translucent lens  38  associated therewith. As used herein, the term “lens” broadly refers to a generally transparent and/or translucent piece of material (typically glass, plastic, safety glass, or polycarbonate) and is not limited to a particular shape or configuration. 
     As shown in  FIG. 2A , the wall  16  includes four threaded holes  40  spaced around the second bearing bore  20 . The lens  38  includes four holes  41  adapted to align with the four threaded holes  40  when the lens  38  is placed against the wall  16 . Each hole  41  of the lens  38  receives a threaded fastener  42  which is mated with the corresponding threaded hole  40  of the wall  16  for securing the lens  38  to the wall  16 . Such a means for securing the lens  38  to the wall  16  is advantageous when the wall  16  is provided with threaded holes  40 , although other means for securing the lens  38  to the wall  16  may be employed without departing from the scope of the present disclosure. Each threaded fastener  42  may be used in combination with an associated washer  43  to protect the lens  38  when the threaded fasteners  42  are tightened. 
     The side of the lens  38  facing the wall  16  includes a groove, channel, or inset for accommodating a sealing member  44 , illustrated in  FIGS. 2 and 2A  as an annular o-ring. The sealing member  44  is positioned between the lens  38  and the wall  16 , such that it is tightly sandwiched between the lens  38  and the wall  16  when the lens  38  is secured to the wall  16 . The sealing member  44  surrounds the second bearing bore  20  and prevents leakage of oil  46  from the second bearing bore  20 . 
     The illustrated lens  38  is generally square or rectangular, but can be any shape, provided that it is sufficiently sized to overlay the second bearing bore  20 . As the bore cap plug  22  of  FIG. 1  is effectively replaced by the sight window  36 , the lens  38  itself provides the function of the bore cap plug, which is to isolate the interior of the gearbox housing  12  from the outside environment. 
     Once the lens  38  has been associated to the second bearing bore  20 , the resulting sight window assembly  36  may be used to monitor the interior of the gearbox housing  12 . As with known sight windows, sight windows according to the present disclosure may be used to monitor the level of oil  46  in the gearbox housing  12 , but positioning the sight window assembly  36  at the second bearing bore  20  is additionally advantageous because one can monitor the input shaft  48  and one of the bearings  50  from an end view ( FIG. 2 ). Such a perspective is useful for detecting and assessing a number of possible problems occurring in the gearbox without dismantling the gearbox. 
       FIG. 3  illustrates a gearbox  52  which has the same gearbox housing  12  of  FIGS. 2 and 2A , but employs a different sight window assembly  54  according to the present disclosure. In particular, the sight window assembly  54  of  FIG. 3  includes a lens  56  which is associated to the second bearing bore  20  by an assembly including a sealing member  58 , a locating member  60 , a cover member  62 , and fasteners  42 . In contrast to the lens  38  of  FIGS. 2 and 2A , the lens  56  of  FIG. 3  is substantially circular instead of being rectangular. Additionally, the lens  56  of  FIG. 3  omits holes for receiving the fasteners  42 , so it is not itself directly fastened to the wall  16  and the other elements of the sight window  54  provide means for positioning the lens  56  with respect to the second bearing bore  20  and securing it to the wall  16 . 
     In the illustrated embodiment, the sealing member  58  is an elastomeric gasket with a generally square or rectangular outer perimeter and a circular central opening  64  which is most advantageously at least as large as the second bearing bore  20 . Similar to the sealing member  44  of  FIGS. 2 and 2A , the sealing member  58  of  FIG. 3  is adapted to be positioned between the lens  56  and the wall  16  and tightly sandwiched therebetween when the lens  56  is secured to the wall  16 . Various gasket materials can be utilized, such as a natural rubber, a synthetic rubber, a resilient polymer, and so forth, preferably exhibiting elastomeric properties so as to provide a tight, leak-resistant and secure seal along the gasket. To facilitate the tight sandwiching aspect of the sealing member, it is most advantageous for the central opening  64  of the sealing member  58  to be smaller than the lens  56  so that, when the lens  56  is associated to the second bearing bore  20 , the perimeter of the lens  56  will press the sealing member  58  against the wall  16  to encircle the second bearing bore  20 . 
     As for the illustrated locating member  60 , it is provided as a relatively rigid bezel with a generally square or rectangular outer perimeter and a circular central opening  66 . The outer perimeter of the illustrated locating member  60  is substantially identical to the outer perimeter of the sealing member  58 , while the central opening  66  is substantially the same size as the lens  56 . The lens  56  is received within the central opening  66  of the locating member  60  to properly position the lens  56  with respect to the second bearing bore  20 . 
     The cover member  62  of  FIG. 3  is relatively rigid, with a generally square or rectangular outer perimeter and a circular central opening  68 . The outer perimeter of the illustrated cover member  62  is substantially identical to the outer perimeters of the sealing member  58  and the locating member  60 , while the central opening  68  is smaller than the central opening  66  of the locating member  60  to prevent the lens  56  from falling away from the gearbox housing  12 . Most advantageously, the central opening  68  of the cover member  62  is at least the same size as the second bearing bore  20  to maximize visibility into the gearbox housing  12 . 
     To assemble the components of the sight window assembly  54 , the lens  56  is seated within the central opening  66  of the locating member  60 , with the sealing member  58  being positioned between the locating member  60  and the wall  16  and the cover member  62  being positioned outwardly of the locating member  60 . Each of the illustrated sealing member  58 , locating member  60 , and cover member  62  is provided with four holes  70  that are each aligned with the corresponding holes  70  of the other members. Each hole  70  receives a threaded fastener  42  which is mated with the corresponding threaded hole  40  of the wall  16  for associating the lens  56  to the second bearing bore  20 . 
       FIGS. 4 and 4A  show yet another gearbox  72  which has the same gearbox housing  12  of  FIGS. 1-3 , but employs a different sight window assembly  74  according to the present disclosure. Rather than securing a lens to the exterior of the wall  16  either directly (as in  FIG. 2 ) or indirectly (as in  FIG. 3 ), the sight window assembly  74  of  FIG. 4  has a lens  76  which is seated within the second bearing bore  20 . In particular, the sight window assembly  74  of  FIG. 4  includes a circular lens  76  with a perimeter which is received within an annular channel or groove  78  defined along the inner perimeter of an annular sealing or grommet member  80 . The sealing member  80  is at least partially formed of an elastomeric material (for example, rubber, synthetic rubber or a resilient polymer having elastomeric properties) and is configured to fit tightly within the second bearing bore  20  which, in this illustrated embodiment, has two circumferential portions  77  and  79 . Portion  77  is an outer circumferential portion sized to both receive and maintain the lens  76  in position and to also provide a seal between the second bearing bore  20  and the lens  76 . Portion  79  is an inner circumferential portion sized to receive, for example, shaft  48  and bearings  50  ( FIG. 2 ). It will be seen that the outer circumferential portion  77  has a diameter less than that of the inner circumferential portion  79 . The sight window assembly  74  of  FIG. 4  may be more advantageous than the embodiments of  FIGS. 2 and 3  when the wall of the gearbox housing adjacent the second bearing bore omits threaded holes or is otherwise unsuitable for easily securing a lens thereto. 
     Although the sight window assembly of each of  FIG. 2 ,  FIG. 3  and  FIG. 4  is shown in combination with the same gearbox housing, the principles described herein are not limited to the illustrated gearbox housing and may be employed with other gearbox housing configurations without departing from the scope of the present disclosure. For example,  FIG. 5  shows a gearbox  82  with a gearbox housing  84  which is similar to the gearbox  12  of  FIGS. 1-4A , but omits threaded holes surrounding the second bearing bore  86 . The gearbox  82  of  FIG. 5  includes a sight window assembly  88  which is similar to the sight window assembly  74  of  FIGS. 4 and 4A  in that it has a lens  90  which is seated within the second bearing bore  86  rather than being secured to the associated wall  92 . 
     More particularly, the sight window assembly  88  of  FIG. 5  includes an annular ring member  94 , which is shown in greater detail in  FIGS. 6-7A . The ring member  94  is relatively rigid, being formed of a metallic material in one embodiment, and has an inner surface which is adapted to seat the lens  90 . To that end, the inner surface of the illustrated ring member  94  is provided with a small annular shoulder  96  having a diameter suitably sized to orient the lens  90  and prevent it from falling into the interior of the gearbox housing  84 . 
     The inner perimeter of the ring member  94  further includes a pair of inner channels or grooves  98  and  100 . The first inner groove  98  is positioned closer to the interior of the gearbox housing  84  than the second inner groove  100  when the ring member  94  is received by the second bearing bore  86 , as shown in  FIG. 5 . 
     The first inner groove  98  is adapted to receive an inner sealing member  102 , which is illustrated as an annular o-ring. The shoulder  96  of the ring member  94  is adjacent to the first inner groove  98  and positions the lens  90  in line with the first inner groove  98 . With the inner sealing member  102  in place within the first inner groove  98 , the lens  90  is pressed into the ring member  94  until it abuts the shoulder  96 . So pressing the lens  90  into the ring member  94  presses the inner sealing member  102  against the first inner groove  98 , thereby providing a seal between the ring member  94  and lens  90 . 
     When the lens  90  has been pressed into the ring member  94 , a retaining member  104  is inserted into the second inner groove  100 . In the illustrated embodiment, the retaining member  104  is a typical snap ring with a diameter that can be temporarily decreased (e.g., using pliers) to position it within the second inner groove  100  and then returned to its original diameter to seat within the second inner groove  100 . As best shown in  FIGS. 5 and 7A , the diameter of the lens  90  is larger than at least the inner diameter of the retaining member  104 , so the retaining member  104  effectively prevents the lens  90  from falling away from the gearbox housing  84 . Hence, the lens  90  is trapped in place within the ring member  94  on opposite sides by the shoulder  96  and the retaining member  104  and on its outer perimeter by the inner sealing member  102 . 
     With the lens  90  secured in place within the ring member  94 , the ring member  94  may be inserted within the second bearing bore  86  of the gearbox housing  84  to form the sight window assembly  88 . The ring member  94  is configured to fit snugly within the second bearing bore  86  ( FIG. 5 ), but there may be slight dimensional differences therebetween, creating a small gap. To avoid oil leakage, the outer surface of the ring member  94  may be provided with an outer channel or groove  106  for receiving an outer sealing member  108 , illustrated as an annular o-ring. The outer sealing member  108  is positioned between the ring member  94  and the second bearing bore  86  to eliminate any gap therebetween. 
       FIG. 8  illustrates another gearbox  110  incorporating a sight window  112  which may be advantageous for use in combination with a gearbox housing lacking threaded holes or other means for affixing a lens to the wall  114  associated with the second bearing bore  116 . In the embodiment of  FIG. 8 , the sight window  112  includes a lens  118  and a modified bore cap plug  120 . The modified bore cap plug  120  of  FIG. 8  is similar to the bore cap plug  22  of  FIG. 1 , but includes an opening  122  machined or otherwise formed in its center. The central opening  122  is illustrated in  FIG. 8  as being circular, but may be any shape without departing from the scope of the present disclosure. Most advantageously, the central opening  122  is relatively large to increase visibility through the sight window  112  and into the interior of the gearbox housing  124 . 
     As per the design which is conventional of known bore cap plugs, the modified bore cap plug  120  includes a skirt or rim  126  extending in one direction from its outer perimeter. The lens  118  is adapted to be received within the skirt  126  to ensure that the lens  118  does not interfere with the association of the second bearing bore  116  and the modified bore cap plug  120  (via the skirt  126 , per conventional design). In addition to being adapted to seat within the skirt  126 , it is also advantageous for the lens  118  to be sized and configured to completely overlay the central opening  122  to prevent leakage of oil when the combination of the modified bore cap plug  120  and the lens  118  are associated to the second bearing bore  116 . In the illustrated embodiment, the lens  118  is substantially circular, with a diameter greater than the diameter of the circular central opening  122  and less than the diameter of the skirt  126 . In other embodiments, the central opening  122  and the lens  118  may be provided in non-circular shapes without departing from the scope of the present disclosure, provided that the lens  118  overlays the central opening  122  when seated within the skirt  126 . 
     The lens  118  is affixed to the modified bore cap plug  120  to prevent it from becoming dislodged during use of the gearbox  110 . The lens  118  may be affixed by any one of a variety of means such as, but not limited to, an adhesive that will not degrade upon prolonged exposure to oil or whatever other lubricant is used in the gearbox  110 . When the lens  118  has been affixed to the modified bore cap plug  120 , the combination is secured within the second bearing bore  116  in the same way as a conventional bore cap plug (such as the bore cap plug  22  of  FIG. 1 ) to provide a sight window  112 . 
       FIGS. 9-11  show another alternative sight window assembly  128 , which can be incorporated into the gearbox housing  84  of  FIG. 5 , as shown in  FIGS. 10 and 11 . Similar to the embodiment of  FIGS. 4 and 4A , the sight window assembly  128  has a lens  130  which is seated within the second bearing bore  86 , the second bearing bore having an outside edge with an outside edge perimeter The outside edge is visible at the end of lead line for 86 in  FIG. 11 . In particular, the sight window assembly  128  of  FIG. 9  includes a circular lens  130  with a perimeter which is received snugly within a first annular channel or groove  132  defined along the inner perimeter of an annular grommet member  134 . Lens  130  has an outer planar face or surface (at the end of lead line  130  in  FIG. 11 ) with a lens peripheral ring spaced inwardly from the lens&#39; circular outer edge. First annular channel  132  has a circular surface of a first perimeter size and a front ring surface (located at the end of lead line  132  in  FIG. 11 ) that engages or that overlies the lens peripheral ring. 
     The grommet member  134  of  FIGS. 9-11  is comparable to the sealing member  80  of  FIG. 4  (e.g., being at least partially formed of an elastomeric material, such as rubber, synthetic rubber, or a resilient polymer having elastomeric properties). The grommet member  134  may be embossed or otherwise molded or designed to include various markings and information such as, for example, a company name, a part number, etc. In contrast to the sealing member  80  of  FIG. 4 , the grommet member  134  of  FIG. 9  has an outer diameter less than that of the second bearing bore  86 . Accordingly, the grommet member  134  forms a seal around the lens  130 , but does not form a secondary seal against the second bearing bore  86 . Instead, the sight window assembly  128  is provided with a generally annular sealing ring  136  which serves to provide a seal between the grommet member  134  and the second bearing bore  86 , as shown in  FIGS. 10 and 11 . 
     As best illustrated in  FIG. 11 , the sealing ring  136  has a generally L-shaped cross-section, with a first leg or surface  138  and a second leg or surface  140  which are generally or substantially perpendicular to each other. In an embodiment, an elastomeric member or layer is over at least the second leg or surface of the annular sealing ring, and at least a portion of the elastomeric member or layer is between the second leg of the annular sealing ring and the second bearing bore. At least an outer end of the first surface  138  is received within a second annular channel or groove  142  defined in the outer perimeter of the grommet member  134 . Second annular channel  142  has an external surface of a second perimeter size. As evident from  FIG. 11 , the first perimeter size is less than this second perimeter size, which is less than the outside edge perimeter size of the second bearing bore  86  and greater than the lens perimeter, and the first surface  138  extends in a generally or substantially radial direction to span the gap between the outer perimeter of the grommet member  134  and the second bearing bore  86 . The seated sight window assembly  128  or annular sealing ring is of a perimeter size not greater than the outside edge perimeter size of the second bearing bore. The second surface  140  has a curvature matching that of the second bearing bore  86  and forms a friction fit therein when the sealing ring  136  is pressed into or seated within the second bearing bore  86  creating a friction-fit seal. Being a friction-fit seal within the second bearing bore, this seal alone is sufficient to secure the seated sight window assembly to the second bearing bore. Further, the annular sealing ring, the first annular channel, the second annular channel and the lens are in straight line alignment with each other as shown in  FIG. 11 , and force resulting from the friction-fit seal transmits in ordered sequence through the annular sealing ring, the second annular channel, the annular grommet member and the first annular channel to the lens, assisting in securing the lens in place. 
     The sealing ring  136  is a composite component, being comprised of a relatively rigid base  144  (formed of a metallic material in a preferred embodiment) and a softer coating layer  146  (formed of an elastomeric or rubber material in a preferred embodiment). The base  144  and coating layer  146  may be joined by any suitable means, including known means for applying an elastomeric coating to a metallic piece of material. 
     In the illustrated embodiment, the coating layer  146  covers substantially the entire outer side of the base  144  (i.e, the portion of the first surface  138  which faces away from the gearbox housing and the portion of the second surface  140  which abuts the second bearing bore  86  when the sealing ring  136  is installed within the second bearing bore  86 ). However, in other embodiments, the coating layer  146  may cover only a portion of the outer side of the base  146  and/or some or all of the inner side of the base  144  (i.e., the portion of the first surface  138  which faces toward the interior of the gearbox housing and the portion of the second surface  140  which faces the central axis of the second bearing bore  86  when the sealing ring  136  is installed within the second bearing bore  86 ). In an embodiment, an elastomeric layer covers substantially all outwardly facing surfaces of the rigid base ( 144  and  146 ). By such a composite configuration, the sealing ring  136  is sufficiently rigid to hold the grommet member  134  in place within the second bearing bore  86  (in the orientation of  FIGS. 10 and 11 ), while being sufficiently soft at the location(s) of the coating layer  146  to provide a fluid-tight sealing surface. 
     Although the sight window assembly of  FIGS. 9-11  is shown in combination with the gearbox housing of  FIG. 5 , it should be understood that it may be used in combination with other gearbox housings (including the gearbox housing  12  of  FIG. 1 ) without departing from the scope of the present disclosure. 
     It will be understood that the embodiments described above are illustrative of some of the applications of the principles of the present subject matter. Numerous modifications may be made by those skilled in the art without departing from the spirit and scope of the claimed subject matter, including those combinations of features that are individually disclosed or claimed herein. For these reasons, the scope hereof is not limited to the above description but is as set forth in the following claims.