Abstract:
A surgical instrument and a method of lubricating same according to which a vane is disposed in a chamber defined between a shaft and a lubricant-impregnated housing. When air is introduced into the chamber it impinges against the vane and rotates the shaft, and the lubricant weeps onto the inner wall of the housing to lubricate the wall.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to surgical instruments and in particular to surgical instruments for dissecting bone and other tissue.  
       BACKGROUND  
       [0002]     Many conventional surgical instruments employ motors to rotate a cutting element for the dissection of bone or other tissue. The motor usually includes a rotary shaft and a dissection tool coupled to the shaft and having a cutting or abrading element that is rotated at relatively high speeds by the motor.  
         [0003]     It can be appreciated that these instruments are relatively small yet the motor is required to drive the cutting element at relatively high speeds that generate heat. Thus, the motor must be lubricated, usually from an external source that is connected to the motor via a passage, conduit, or the like, which creates problems in the form of design challenges due to the small size of the instrument.  
         [0004]     All patents listed in Table 1 are hereby incorporated by reference herein in their respective entities. As those of ordinary skill in the art will appreciate readily upon reading the Summary of the Invention, Detailed Description of the Preferred Embodiments and claims set forth below, many of the devices and methods disclosed in the patents of Table 1 may be modified advantageously by using the teachings of the present invention.  
                       TABLE 1                       Patent/Publication No.   Patented/Published Date   Inventor                   4,068,987   Jan. 17, 1978   Crooks       4,197,061   Apr. 08, 1980   Hill       5,834,870   Nov. 10, 1998   Tokushima et al.       6,413,062   Jul. 02, 2002   Peters       2002/0151902 A1   Oct. 17, 2002   Riedel et al.       2003/0023256 A1   Jan. 30, 2003   Estes et al.       2003/0163134 A1   Aug. 28, 2003   Riedel et al.       6,626,577   Sep. 30, 2003   Horng, et al.       2003/0229351 A1   Dec. 11, 2003   Tidwell et al.                  
 
       SUMMARY  
       [0005]     The present invention eliminates the need for an external lubricant source and any passages, conduits, or the like, for the lubricant by providing a surgical instrument with a motor that is self-lubricating.  
         [0006]     Various embodiments of the invention discussed below may possess one or more of the above features and advantages, or provide one or more solutions to the above problems existing in the prior art. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIG. 1  is an isometric view of a surgical instrument according to an embodiment of the present invention.  
         [0008]      FIG. 2  is an enlarged exploded view of the instrument of  FIG. 1 .  
         [0009]      FIG. 3  is an enlarged, partial sectional view of the embodiment of  FIGS. 1 and 2  shown in an assembled condition.  
         [0010]      FIG. 4  is an end view of the components of the instrument of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0011]     Referring to  FIGS. 1 and 2  of the drawings, the reference  10  refers, in general, to a surgical instrument according to an embodiment of the invention which includes an outer casing  12  connected to a swivel assembly  14 , via a coupler  16 . One end of the coupler  16  is in threaded engagement with the rear end of the casing  12  and the other end is connected to one end of the assembly  14  by a conventional swivel connection which will not be disclosed in detail.  
         [0012]     An air inlet tube  18  has one end portion projecting from the other end of the assembly  14  for attachment to an air hose (not shown), so that air passes through the assembly  14  and the coupler  16  to the interior of the casing for use in a manner to be described. The front end of the casing  12  is open and is adapted to receive a cutting element (not shown), a portion of which would extend in the casing for connection to the instrument  10  in a manner to be described.  
         [0013]     Referring to  FIGS. 2 and 3 , a cylindrical rotor housing  20  is located in the casing  12  with the outer surface of the housing extending in a spaced relation to the inner surface of the casing  12  to define an air chamber  22 . Two annular flanges  24  and  26  are formed at the respective ends of the housing  20 , and a through opening  26   a  is formed in the flange  26  for reasons to be described.  
         [0014]     The outer diameter of the flanges correspond to the inner diameter of the casing  12  so that the outer surfaces of the flanges engage the inner wall of the casing with minimal clearance to support the rotor housing  20  in the casing. A series of five spaced, parallel arcuate air slots  20   a  are formed in the housing  20  for permitting the ingress of air into the interior of the housing under conditions to be described.  
         [0015]     A shaft  30  is supported in the casing  12  in a manner to be described, and a mounting flange  30   a  is formed at one end of the shaft  30  that projects from the corresponding end of the housing and is adapted to be engaged by the above-mentioned cutting element (not shown). A reduced-diameter portion  30   b  is formed at the other end of the shaft  30  and projects out from the other end of the housing  20  for reasons to be described.  
         [0016]     Three elongated vanes  32   a ,  32   b  and  32   c  are disposed in three angularly-spaced, longitudinal slots formed in the outer surface of the shaft  30 . Portions of the vanes project from the slots and the vanes are adapted for radial movement in the slots under conditions to be described.  
         [0017]     A bearing assembly  36  extends in the casing  12  and around the front end portion of the shaft  30 . The bearing assembly  36  is conventional and, as such, consists of a housing  36   a , a bearing  36   b  that extends in the housing, and a seal  36   c . As shown in  FIG. 2 , the bearing housing  36   a  and the bearing  36   b  are located between the front surface of the flange  24  and a shoulder formed in the interior of the casing  12 , and the seal  36   c  extends in a groove formed in the casing and engages the bearing  36   b.    
         [0018]     A bearing assembly  40  is also disposed in the casing  12  and extends around the reduced-diameter portion  30   b  of the shaft  30 . The bearing assembly  40  is conventional and, as such, consists of a housing  42  ( FIG. 3 ) and a bearing  44  that extends in the housing. A series of angularly spaced through openings  42   a  are provided through the housing  42 , for reasons to be described. A set screw  46  threadedly engages a threaded opening in the reduced-diameter portion  30   b  of the shaft  30 , with its head engaging the bearing  44  to maintain the assembly  40  in the above position.  
         [0019]     The shaft  30  is thus supported for rotation in the casing  12  by the bearing assemblies  36  and  40 , with the mounting flange  30   a  of the shaft  30  located in the interior of the front end portion of the casing  12  so that it can be coupled to a standard cutting tool (not shown) in a conventional manner. Thus, when the shaft  30  is rotated in a manner to be described, it drives the tool.  
         [0020]     An annular air distributor  50  is disposed in the casing  12  between the bearing assembly  40  and the rear end of the casing. A tube  52  ( FIG. 2 ) extends from the assembly  14  and through the coupler  16  into a central opening in the distributor  50 . Thus, air from the assembly  14  ( FIG. 1 ) is passed, via the tube  46 , to the distributor  50 .  
         [0021]     As shown in  FIG. 2 , an internal air passage  50   a  is provided in the distributor  50  that connects the air tube  46  to one of the openings  42   a  of the bearing housing  42 . The latter opening is in alignment with the opening  26   a  in the flange  26  of the housing  20  so that the air passes from the tube  46 , through the passage  50   a , the openings  42   a  and  26   a , and into the air chamber  22 .  
         [0022]     As shown in  FIGS. 2 and 4 , the shaft  30  is eccentrically disposed in the housing  20  to define an annular chamber  54  that varies in thickness, or cross section, in an angular direction around the shaft. Thus, as the vanes  32   a ,  32   b , and  32   c  rotate with the shaft  30  under conditions to be described, the vanes move radially in the above-mentioned slots in the shaft  30  depending on their angular position in the chamber  52 .  
         [0023]     The rotor housing  20  is manufactured from a lubricant-impregnated material, such as bronze, so that when subjected to relatively high temperatures, the lubricant will “weep” from the material, in a conventional manner. Examples of such a lubricant-impregnated material is a lubricant-impregnated sintered bronze material manufactured and marketed by Anchor Bronze and Metals, Inc. of Cleveland, Ohio, and by Bunting Bearings of Holland, Ohio. Applying this technology to the housing  20 , the housing would be manufactured of a bronze, or similar material as specified by these companies and, after forming, sintering and sizing, the material is vacuum-impregnated with a lubricant, such as oil, which flows, or weeps, from the material during the operation that will be described.  
         [0024]     In operation, a tool is coupled to the mounting flange  30  of the shaft  30  and an air hose is connected to the tube  18  of the assembly  14 . The air passes through the later assembly, through the tube  52 , the passage  50   a , the openings  42   a  and  26   a , and into the air chamber  22 . From the chamber  22 , the air passes through the slots  20   a  in the housing  20  and into the chamber  54  where it impinges against the vanes  32   a ,  32   b , and  32   c , causing rotation of the shaft  30  to drive the above-mentioned cutting tool. During this action, the vanes  32   a ,  32   b , and  32   c  are pushed, or forced, radially outwardly against the inner wall of the housing  20  as they rotate with the shaft  30 , creating heat and raising the temperature of the wall of the housing  20 . This causes the above-mentioned impregnated lubricant to weep from the material forming the housing  20  to the inner wall of the housing, and thus lubricate the interfaces between the housing and the vanes  32   a ,  32   b , and  32   c . As a result, adequate lubrication is provided without having to pass lubricant from an external source into the instrument  10 .  
         [0025]     It is understood that variations may be made in the above without departing from the scope of the invention. For example, the number of vanes and the type of lubricant impregnated into the wall of the housing  20  can be varied. Also, the type of element attached to the rotating shaft and the type of lubricant may be varied. Further, the structure for introducing air into the casing  12  and/or into the housing  20  may be varied. Still further, the shaft  30  can be used to drive any element that may be used in a surgical procedure. Moreover, the specific type of motor used is not limited to a pneumatic motor.  
         [0026]     The preceding specific embodiment is illustrative of the practice of the invention. It is to be understood that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the invention or the scope of the appended claims. For example, the present invention is not limited to surgical instruments employing a cutting element, but may find further applications in which high speed rotation of a relatively small motor is required.  
         [0027]     In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts a nail and a screw are equivalent structures.