Abstract:
A right angle gear box includes a plurality of channels for carrying lubricating fluids to one or more upper bearing. Fluids in the gear box are naturally pumped through the channels by the rotation of gears in the gear box. The area between the shaft and the external housing is minimized to minimize fluid flow along the shaft encouraging flow through the channels instead. Lubrication of an upper bearing is therefore provided without the need for additional pumps, seals, or lubricants.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to lubricating gears and bearings in gearboxes and, more particularly, to a right angle gearbox with improved lubrication characteristics.  
         [0002]     Right angle or T-style gearboxes, which have input and output shafts that are perpendicular to each other, are widely used in industrial drive applications. These types of gearboxes can be operated in both a horizontal (with both shafts positioned horizontally) and a vertical (with one shaft positioned horizontally and the other vertically) configuration. Typically, the shafts are coupled to bearings, and oil or lubricants are provided in the gearbox to lubricate both the gears and the bearings. When used in a horizontal configuration, the input and output shafts are in substantially the same plane, and lubricants provided adjacent the gear can be easily spread or “splashed” onto the bearings and along the shaft as the gear rotates to lubricate the bearings and prevent overheating and premature wear.  
         [0003]     When the gearbox is operated vertically, however, the bearings are offset vertically from the gears and lubricants provided in the gearbox. One or more bearings, therefore, is offset at a height well above the first bearing and associated gears. Gravity, therefore, prevents lubricants in the gearbox from being splashed or splattered onto the bearing to lubricate the upper bearing. Typically, to provide sufficient lubrication, an oil seal is provided below the upper bearing or between the first and second bearings, and a resultant void is filled with grease. Alternatively, a grease fitting can be provided in the housing.  
         [0004]     While providing sufficient lubrication, traditional methods of retrofitting a gearbox for operation in the vertical position are time consuming, messy, and expensive. There remains a need, therefore, for a right angle gearbox which can be operated in a vertical position while providing sufficient lubrication to all of the gears and bearings.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In one aspect, the invention is a gearbox comprising a sealed housing for receiving a lubricant. A rotational shaft is provided in the housing, and is coupled to a gear drive which rotates the shaft. A bearing is further coupled to the first rotational shaft at a distance from the gear drive. At least one channel is provided in the housing, extending parallel to the length of the rotational shaft and extending to the bearing. A bottom of the channel is positioned adjacent the gear drive, and receives lubricating fluid rotated by the gear drive such that, as the gear rotates, fluids adjacent the gear are rotated due to friction characteristics of the fluid. The rotating lubricants pass into the channel and are carried by momentum to the bearing to lubricate the bearing. To improve the flow of fluids into the channel, a recess having a larger diameter than the channel is preferably provided at the bottom end of the channel to capture rotating fluids.  
         [0006]     The distance between the rotational shaft and the housing is preferably minimized to restrict the flow of fluid in the area between the housing and the rotational shaft and therefore to encourage circulation of fluids through the channel. A shoulder can be provided, for example, extending radially inward from an internal diameter of the housing. The internal diameter of the shoulder is selected such that the area between the shoulder and the shaft is restricted to the flow of fluid by viscosity of the lubricant, causing lubricants to instead flow through the channel.  
         [0007]     The rotational shaft can be vertical in use. Furthermore, the gearbox can be provided as a right angle gearbox, comprising a right angle rotational shaft provided in the housing at a substantially right angle to the rotational shaft, and coupled to the rotational shaft through the gear drive.  
         [0008]     The channels can be arranged so that fluids are directed to the upper bearing due to the fluid pressure on the lower side caused by the swirling fluid in the gear case. The fluid pressure on the lower side results in a pressure differential, with higher pressure on the lower side than the upper side. This differential results in fluid flow up to the upper bearing.  
         [0009]     To sufficiently lubricate the bearing or bearings, the gearbox preferably comprises a plurality of channels for carrying lubricating fluids. In one embodiment, four channels are spaced around a circumference of the housing surrounding the rotational shaft. The channels can be provided in a split case construction in which each half of the case, for example, includes one full channel and two half channels.  
         [0010]     These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]      FIG. 1  is a cross-sectional view of a gearbox constructed in accordance with the present invention, as viewed from the plane of both shaft axes;  
         [0012]      FIG. 2  is a fragmentary cross-sectional perspective view of one half of a split case version of the upper portion of the housing of  FIG. 1  illustrating channels for carrying lubricants to an upper bearing, looking up from below it; and  
         [0013]      FIG. 3  is a fragmentary perspective view looking up at the bottom of the upper portion of the housing of  FIG. 1  as partially assembled.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     Referring now to the Figures and more particularly to  FIG. 1 , a right angle gearbox  10  constructed in accordance with the present invention is shown. The gearbox  10  comprises a housing  34  containing a first shaft  12  and a second shaft  14 . A central axis of the first shaft  12  is provided at an angle substantially perpendicular to a central axis of the second shaft  14 . The angle between the two shafts could be any angle. First and second gears  16  and  17  couple the second shaft  14  to the first shaft  12 , wherein as the first shaft  12  is rotated, motion is translated to the second shaft  14  or vice versa. The housing  34  encloses the shafts  12  and  14  and associated gears, and can be constructed of a plurality of housing components including, at least, a lower housing component  33  for housing the shaft  14  and an upper housing or quill  28  for housing the shaft  12 . The shaft  12  is provided through the housing or quill  28  and extends through a first (lower) bearing  20  and second (upper) bearing  18  in the quill  28 , the bearing  20  being received in bearing seat  23  below shoulder  26  and the bearing  18  being received in bearing seat  19  above shoulder  26 . A first seal  30  is provided between the input shaft  12  and the quill  28 , while a second seal  32  is provided between the output shaft  14  and an associated housing  33 . The seals  30  and  32  enclose the housing  34  of the gearbox  10  such that lubricating fluids such as oils or other lubricants can be provided in the gearbox to lubricate the shafts  12  and  14 , gears  16  and  17 , and bearings  18  and  20 . The bearings  18  and  20  can be any of a number of different types of bearings, including tapered roller bearings as illustrated in  FIG. 1  having an outer race  21 , as shown without the other bearing components in  FIG. 3 .  
         [0015]     Referring now to  FIGS. 1, 2 , and  3 , the quill  28  is preferably a cylindrical tubular housing sized to receive the input shaft  12 . The quill  28  includes a shoulder  26  which extends radially inward for a portion of the quill  28  centered about the approximate vertical center of the quill  28 . The shoulder  26  extends radially inward toward the horizontal center of the quill  28  to provide an inside diameter  31  which is slightly larger than the outside diameter of the shaft  12 . The inside diameter of the shoulder  26  is selected to allow clearance for the shaft  12 , but is small enough to be sealed to the shaft by the viscosity of lubricating fluids introduced into the gear box  10  as described below. The bearings  20  and  18  are positioned on opposing sides of the shoulder  26 , with the bearing  18  retained in seat  19  above a top edge of the shoulder  26  and the bearing  20  retained in seat  23  below a bottom edge of the shoulder  26 . The shoulder  26  provides extra axial support for the bearings  20  and  18  for when a thrust load is applied to the shaft  12 .  
         [0016]     Referring still to  FIGS. 1, 2 , and  3 , a plurality of grooves or channels  24  are also provided in the internal side walls of the quill  28 , through the shoulder  26 . As shown in  FIG. 3 , four channels  24  are spaced equidistantly (90° apart) around the circumference of the quill  28 . Any number of channels could be provided, equally spaced or not. The channels  24  each extend from a bottom section of the quill  28  adjacent the gear  17  and bearing  20  to a point above the top edge of the shoulder  26 , and therefore adjacent a bottom side of the upper bearing  18 . The channels  24  therefore extend between each of the first and second bearings  18  and  20 . At the end adjacent the gear  17 , each of the channels  24  widens into a recess  22  which opens in the direction of the rotating gear  17 . The recesses  22  provide an enlarged area at the bottom of the channels  24  for capturing lubricating fluids swirling in the gearbox  10 , as described below.  
         [0017]     The quill  28  can be provided as a single unitary piece, as shown in  FIG. 3 , or as a “split case” housing including both a first and a second half. Each half includes both a full channel  24  and one half of two additional channels  24  As shown in  FIG. 2 , the full channel  24  is provided centered at the back of the split case and half of a channel  24  is formed in each of the sides. The opposing half (not shown) is a mirror image of the half shown in  FIG. 2 . The two split case halves are cast separately, and coupled together with, for example, threaded or other fasteners provided through apertures  25  and  27  in each half of the split case.  
         [0018]     In operation, oil or other lubricating fluids are provided in the gearbox  10  to lubricate the gears  16  and  17 , input shafts  12  and  14 , and bearings  18  and  20 . As the gears  16  and  17  rotate, the lubricating fluids next to the gear are rotated due to the friction characteristic of the fluid provided inside the gearbox  10 , therefore causing the fluids to rotate or swirl. The swirling lubricating fluids are caught in the recesses  22  and the swirling motion causes a pressure differential, with higher pressure on a lower side and lower pressure on an upper side, such that the lubricating fluids are naturally circulated through the channels  24 , past the bearing  18  to the upper bearing  20  and back. The distance between the shoulder  26  and shaft  12  is selected such that the viscosity of the lubricating fluid restricts the opening between the shaft  12  and the shoulder  26  of the quill  28 , thereby providing a resistance to the flow of fluid back down into the gear case along the shaft and permitting a circulation of fluid through the channel  24 . As a result of the rotating motion of the gears  16  and  17 , both the lower bearing  20  and the upper bearing  18  can be easily lubricated without requiring any additional lubricating fluids, grease, seals, or pumps. Furthermore, when operated horizontally, lubricating fluids move easily through the channels  24  to lubricate the bearings  18  and  20 .  
         [0019]     Although the present invention has been described with reference to a right angle gear box, it will be apparent that the principles described can also be applied to other applications including a vertical shaft. Furthermore, although a specific housing has been described, variations in the construction of the housing will also be known.  
         [0020]     Additionally, although a construction including two bearings spaced along the rotating shaft has been shown, it will be apparent that one or any number of bearings could be provided.  
         [0021]     It should be understood that the methods and apparatuses described above are only exemplary and do not limit the scope of the invention, and that various modifications could be make by those skilled in the art that would fall under the scope of the invention. To apprise the public of the scope of this invention, the following claims are made: