Abstract:
A surgical instrument and a method according to which a vane is disposed in a rotor housing and is rotated by the impingement of air on the vane to drive a shaft to which a surgical tool is attached. The housing is fabricated of a relatively hard material to reduce the wear on it when compared to other materials.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a surgical instrument, and a method of operating same, for the purpose of cutting and dissecting bone and other tissue.  
       BACKGROUND  
       [0002]     Many conventional surgical instruments employ pneumatic motors to rotate a cutting element for performing surgical procedures, such as the dissection of bone or other tissue. These types of motors include a series of vanes that are rotated at a relatively high speed in a rotor housing in response to the passage of high pressure air through the housing, to drive a rotary shaft. A cutting or dissection tool, or the like, is coupled to the shaft for rotation with the shaft at the relatively high speed for use in the surgical procedure.  
         [0003]     The above-mentioned vanes seal against the inner wall of the housing which is often fabricated from a material, such as stainless steel or cast iron. As a result of the high-speed rotation, the vanes tend to wear down the inner diameter of the housing which, over time, compromises the seal and therefore the operation of the motor.  
         [0004]     In order to overcome this problem, the inner surface of the rotor housing has been coated with a relatively hard material. However, since the material below the surface of the coating is not as hard, the coating tends to score and flake off with use, which exacerbates the problem.  
         [0005]     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  
       [0006]     According to an embodiment of the invention, the wear resistance of the rotor housing of the pneumatic motor is increased significantly when compared to prior art designs, thus enabling a satisfactory seal between it and the vanes to be maintained over a relatively long period of time.  
         [0007]     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  
       [0008]      FIG. 1  is an isometric view of a surgical instrument according to an embodiment of the present invention.  
         [0009]      FIG. 2  is an enlarged exploded view of the instrument of  FIG. 1 .  
         [0010]      FIG. 3  is an enlarged, partial sectional view of the embodiment of  FIGS. 1 and 2  shown in an assembled condition.  
         [0011]      FIG. 4  is an end view of the components of the instrument of  FIG. 4 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]     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.  
         [0013]     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.  
         [0014]     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 . The rotor housing  20  is fabricated from a carbide material for reasons to be described.  
         [0015]     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.  
         [0016]     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.  
         [0017]     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.  
         [0018]     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.  
         [0019]     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.    
         [0020]     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.  
         [0021]     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.  
         [0022]     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 .  
         [0023]     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 .  
         [0024]     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 .  
         [0025]     In operation, a tool is coupled to the mounting flange  30   a  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 , thus establishing a seal between the outer surfaces of the vanes and the inner wall of the housing  20 . This also causes wear on the inner wall of the housing  20 , but this wear is minimized by the relatively hard, carbide rotor housing and is relatively low when compared to prior art designs utilizing housings of a different, less hard, material.  
         [0026]     It is understood that the motor  10 , including the interface between the vanes and the inner wall of the rotor housing  20 , can be lubricated in accordance with conventional techniques.  
         [0027]     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, as well as the structure for introducing air into the casing  12  and/or into the housing  20 , may be varied. Further, the shaft  30  can be used to drive any type of surgical tool. Moreover, the rotor housing can be self lubricating as disclosed in co-pending U.S. application Ser. No. ______ (attorneys docket P-21152.00), the disclosure of which is incorporated by reference. Also, the specific type of motor used is not limited to a pneumatic motor.  
         [0028]     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, but may find further applications in which high speed rotation of a relatively small motor is required.  
         [0029]     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.