Abstract:
A cylinder to a vane motor is designed to include cylindrically shaped inlet and outlet holes, an axial passage that includes a blocked upstream portion that bypasses the upstream inlet holes, spaced circumferentially slots for leading a portion of the pressurized air into the inlet holes, discharging the portion of pressurized air from the axial passage into an annular cavity to bathe the bearing in the cooler pressurized air, and recirculating the portion of pressurized air through another axial passageway to flow into all of the inlet holes. The discharge holes are judiciously oriented in a particular pattern to assure that the edge of the vanes wear uniformly. The inlet holes are spaced from the pinch point of the spindle to cylinder to permit an increased volume of pressurized air to enter the vane motor and the outlet holes are spaced to maximize the power stroke of the vane motor. The pressurized air is introduced centrally in the motor housing and diverted to flow to the outer periphery of the cylinder.

Description:
This application claims the benefits under 35 U.S.C. § 119(e) of the U.S. provisional patent application 60/567,188 and 60/567,189 filed on Apr. 30, 2004 
   RELATED APPLICATIONS 
   This invention relates to the pneumatic motor entitled SURGICAL PNEUMATIC MOTOR and was invented by myself and co-inventor Douglas Perry and identified as Ser. No. 11/082,124 and SURGICAL PNEUMATIC MOTOR FOR USE WITH MRI invented by myself and identified as Ser. No. 11/074,821 both of which were recently filed as non-provisional applications and are incorporated herein by reference and are commonly assigned with this application to The Anspach Effort, Inc. 

   FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   TECHNICAL FIELD 
   This invention relates to the cylinder of a pneumatic vane motor of the type that converts fluid pressure to rotational movement and particularly to the design of the cylinder that results in an increase in efficiency, RPM and torque and reduce vibration and noise of the vane motor. The innovative cylinder also serves to increase the life of the vane and cool the vane motor and consequently, the size, temperature and life of the vane motor and the rotary machine incorporating the vane motor. 
   BACKGROUND OF THE INVENTION 
   Rotary machines typically utilize vane motors that are pneumatically powered to cause rotation of the output shaft. As is well known these machines comprise a cylinder, sometimes referred to as a casing and an eccentrically mounted spindle relative to the bore of the cylinder, sometimes referred to as a rotor. The cylinder is stationary and through apertures in the cylinder lead pressurized air to impinge on the working face of the reciprocating vanes mounted in slots formed in the spindle to cause the spindle to rotate and then exhaust the spent air through additional holes formed in the cylinder. The outer edge of the vanes is in contact with or in close proximity to the inner surface of the cylinder and the spindle during the power stroke of the vane motor transitions from close to the inner surface of the cylinder bore toward the furthest distance there from and during the exhaust portion of the stroke the spindle transitions from the furthest point away the inner surface of the cylinder toward the closest point thereto. Heretofore, the cylinder had apertures formed therein that were configured in the shape of slots. The pressurized air that is admitted to the spindle impinge on the working face of the vanes to cause them to rotate the spindle. 
   I have found that the vane motor can be enhanced by substituting cylindrical holes for the slots, providing a series of axially spaced holes defining the inlet to the vane motor, providing a pressurized air axial passageway in the cylinder to feed pressurized air to these inlet holes, by-passing the upstream portion of the inlet holes and providing circumferential slots in the cylinder that feed a portion of the pressurized air to the inlet holes, discharging that portion of the pressurized air to circulate over the bearings supporting the spindle and providing another axial passageway for returning the remaining pressurized air to the inlet holes and providing a plurality of judiciously located discharge cylindrical holes to discharge the spent air after performing work on the vanes. The routing of the pressurized air and spent air flowing into and out of the cylinder is done in such a way as to reduce both heat and noise that would otherwise be generated by the vane motor. Suffice it to say that this invention affords the following features that serve to enhance the vane motor and in certain medical instruments, such as a surgical drill, this invention reduces heat, vibration, noise and allows for a smaller envelope size that goes to the comfort and feel in the hands of a surgeon.
         1. Smaller motor spherical ball bearing located at the fore end of the power cylinder provides a cavity within the housing to re-circulate the power cylinder&#39;s working compressed air which contributes to lowering the temperature of the bearing and affording improvements to the vibrations and heat characteristics.   2. Cylinder input holes are oriented relative to the spindle vanes so as to increase input airflow acting on the vane&#39;s working surface.   3. Slots in the cylinder formed adjacent to the inlet holes cool the cylinder before entering the vane motor.   4. A portion of the inlet air to the motor is diverted to flow to the front bearing and toward the aft end so as to air cool the front bearing housing and air cool the cylinder.   5. Additional increased power is obtained by the orientation of the exhaust holes in the vane motor relative to the inlet holes.   6. Minimizing vane wear by the uniform distribution of the vane&#39;s contact area with the cylinder.       

   SUMMARY OF THE INVENTION 
   An object of this invention is to provide for a vane motor an improved cylinder. 
   A feature of this invention is to provide cylindrical holes for the inlet and exit holes of the cylinder. 
   Another feature of this invention is to provide inlet air passages leading pressurized air to the outer periphery of the cylinder through an axial slot, allowing a portion the air to by-pass the inlet holes, a portion to flow through circumferential grooves formed in the cylinder to feed the inlet holes and to flow past the cylinder over the bearings and back into the cylinder and then through the inlet holes so as to power the spindle. 
   Another feature of this invention is to judiciously space the outlet holes of the cylinder so that the vanes uniformly contact the surface of the cylinder as it traverses each station of the cylinder to enhance the wear of the vane. 
   Another feature of this invention is to position the inlet of the vane motor relative to the vane to maximize the volume of air being admitted to the vane during the power stroke. 
   Another feature of this invention is to locate the inlet relative to the outlet of the vane motor to maximize the power stroke of the vane motor. 
   Another feature of this invention is to include cris cross discharge passages in the outlet circuit of the vane motor&#39;s spent air. 
   This invention provides a cylinder for a vane motor that is characterized as reducing heat, cooling the bearings, reducing vibrations and noise, being more efficient so as to increase the RPM and torque of the motor while at the same time reducing its size and extending its life. 
   The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial view partly in section and partly in elevation illustrating the cylinder and its associated parts of a vane motor enclosed in a rotary machine; 
       FIG. 2  is an enlarged exploded view in perspective of the vane motor of this invention; 
       FIG. 3  is an enlarged perspective view of one side of the cylinder opposite the side depicted in  FIG. 2  and illustrating the exhaust holes and passageway; 
       FIG. 4  is a sectional view of the vane motor illustrating the relationship of the inlet to the outlet in accordance with this invention; 
       FIG. 5  is a view in section illustrating the relationship of the inlet to the spindle of a prior art vane motor; 
       FIG. 5A  is a view in section illustrating the relationship of the inlet to the spindle of the present invention; and 
       FIG. 6  is a graphical representation illustrating the uniform contact of the vane as it traverses each station of the cylinder and the orientation of the cylinder discharge holes to achieve this result. 
   

   These figures merely serve to further clarify and illustrate the present invention and are not intended to limit the scope thereof. 
   DETAILED DESCRIPTION OF THE INVENTION 
   While this invention is being described in its preferred embodiment as the cylinders that are in the vane motors utilized in surgical pneumatic drills, as one skilled in the art will appreciate this improved cylinder and its appurtenances can be utilized for any type of pneumatic motor that is employed in any type of pneumatic surgical drill as well as any other pneumatic rotary machines that may or may not be utilized in the medical industry. 
   Referring next to all the Figs. the vane motor generally illustrated as reference numeral  10  is encased in a housing generally illustrated by reference numeral  12  and includes the cylinder  14  affixed to housing  12  in any suitable manner and the rotary spindle  16  and its vanes  18  supported in cylinder  14 . As is typical in vane motors the spindle includes stub shafts  20  and  22  suitably supported by bearings  24  and  26 , respectively, which in this instance are ball bearings. The partial view of the surgical drill depicted in  FIG. 1  includes a swivel connection  28  and suitable fittings to connect to a hose  29  for providing pressurized air to power the vane motor. The details of these components are well known and for the sake of simplicity and convenience are omitted here from. However, in accordance with this invention, the pressurized air used to power the vane motor is admitted into the central portion of the housing  12  and then to the outer periphery of the cylinder  14  of the vane motor via the inlet port  30  and the passage  32 , respectively and will be described in detail herein below. 
   In this rotary machine  12  and as mentioned above, the inlet air is admitted into a central opening or inlet port  30  formed in the end cap  34  which is located at the rear end of the motor housing  12  and is then directed toward the outer periphery via the passageway  32  also formed in the end cap  34 . Passageway  32  is in communication the axial groove  36  formed in the outer surface of cylinder  14  that serves to feed the inlet axially spaced cylindrical holes  38 . A portion of the pressurized air flows past the cylinder and then over the bearing  26  and then back into the cylinder  14 . Along the travel of the air toward the fore end a certain portion of the air is admitted into the vane motor while a portion serves to cool the cylinder  14  and the bearing  26  as described above and this air is then returned to the cylinder via the axial passage  40  where it then flows into the vane motor via the inlet axially spaced cylindrical holes  38 . 
   In accordance with one aspect of this invention, the pressurized air not only serves to cool the bearing it also serves to cool the cylinder. This is best illustrated in  FIGS. 2 and 3  illustrating that the pressurized air being admitted into the cylinder  14  flows via axial passageway  36  toward the forward end of the housing  12 . A portion of this air flows into inlet cylindrical holes  38  via the axially spaced slots  42  formed in cylinder  14 . As noted the slots  42  are located downstream of the blockage portion  44  formed on the outer diameter of cylinder  14  which serve to by-pass the inlet axially spaced cylindrical holes  38  located adjacent thereto. The purpose of the blocking portion  44  and the slots  42  is to dissipate the heat from the cylinder so as to cool the cylinder and the high speed spindle and vanes. The remaining portion of the pressurized air discharges from axial passageway  36  exiting cylinder  14  and flows over the bearing  26  and hence, cools the bearing  26 . This air that flows around the bearing  26  flows via the annular cavity  46 . Thereafter, the air after cooling the bearing is then re-admitted into the cylinder  14  via axial passageway  40  formed on the outer periphery of the cylinder  14 . Axial passageway  40  is in communication with the inlet axially spaced cylindrical holes  38  as best shown in  FIG. 2 . It will be appreciated that because of the innovations to the cylinder resulting in a more efficient vane motor, the ball bearing  26  can be made smaller than the heretofore designs. The reduced diameter of the bearing for a given envelope serves to create or define the annular cavity  46 . That portion of the air used for cooling bearing  26  re-circulates back to the cylinder via the annular cavity  46  is in communication with the axial passageway  40 . 
   It is apparent from the foregoing that the pressurized air from the source flows toward the forward end of the rotating machine and then reverses to flow toward the rear of the rotating machine. This allows a multiple use of the pressurized air before all of the air is admitted into the vane motor. The first portion of the pressurized air serves to cool the cylinder while a portion enters the inlet holes into the vane motor and the remaining portion of the pressurized air cools the bearing before it is admitted into the vane motor via axial passageway  40  and inlet holes  38 . Ultimately, all the pressurized air feeds into the vane motor to impinge on the vanes so as to power the spindle. The spent air exits the vane motor via the axial slot  48  and discharge holes  50  and then discharged from the motor housing  12 . 
   The next portion of this description will describe the inlet holes  38  which are another aspect of this invention. As mentioned above, the inlet holes  38  are contoured in a cylindrical shape for increasing the power of the vane motor. In addition, as noted from  FIGS. 5 and 5A  the inlet axially spaced cylindrical holes  38  are discretely located relative to the spindle  16  so as to increase the volume of air being admitted to impinge on the vane  18  during the power stroke. In the heretofore known vane motors the inlet apertures were located adjacent to the pinch point indicated by reference letter A which is the tangent point where the inner surface of the cylinder  14  contacts or nearly so the spindle  16  as best seem in  FIG. 5  and this defines the gap X. As seen in  FIG. 5A  the inlet axially spaced cylindrical hole  38  is positioned away from the pinch point A increasing the gap X and hence, allowing a sufficiently greater amount of air to enter the vane motor during the power stroke with an obvious increase in the vane motor&#39;s performance. This feature not only serves to increase the volume of air entering the vane motor but also positions the inlet axially spaced cylindrical hole  38  a further distance away from the outlet  50 . As can be seen in  FIG. 4 , the cylinder spindle  16  rotates about its central axes W and the axis Z of the bore  49  formed in cylinder  14  and hence placing the spindle eccentric to the center of the bore  49  and causing the spindle and vanes to advance in close proximity thereto during the power stroke and away therefrom during the exhaust stroke. By increasing this distance, namely the inlet axially spaced cylindrical hole  38  to the outlet  50  represented by reference letter Y, the power stroke is accordingly increased and hence, the power of the vane motor is enhanced. 
   In accordance with another aspect of this invention, not only is the circumferential distance between the inlet hole  38  and the exit hole  50  selected for increased power, the orientation of holes  50  are judiciously selected to avoid power losses and increase wear on the vane. Because of the arrangement of pattern these discharge holes in heretofore known surgical vane motors, there exhibited an unevenness of wear on the outer edge of the vanes. This invention addresses the problem of this unevenness and describes a solution to solve this problem as will be discussed herein below. 
   Attention is first directed to  FIG. 3  which illustrates the discharge holes  50  judiciously disposed in cylinder  16  in a circumferential and axial direction and serve as the exhaust outlet for vane motor. These holes are arranged so that the vane passing thereunder will virtually see an even contact of the cylinder surface so as to eliminate the uneven wearing of the vane&#39;s outer edge. As mentioned above, previous vane motors required early replacement of the vanes because the outer edges exhibited an unevenness of wear. It was recognized that this unevenness resulted in the placement of the discharge holes. This invention solved the problem by selecting a pattern of holes that proved to avoid this unevenness.  FIG. 6  is a showing of a portion of the inlet hole pattern where the column of holes  50  are identified as  50 A,  50 A 1 ,  50 B,  50 B 1 ,  50 C,  50 C 1 ,  50 D and  50 D 1 . For each repeat in the pattern of holes the relative location of holes A and B is such that a unit of measure U is established for one hole and used to position all the other holes. Referring to hole  50 A in  FIG. 3 , the cord H at the right hand side is selected and it equals the radius R. The distance between the center line of hole  50 A and this cord H establishes the unit U (the unit of measurement) which is used for the measurement to set the relative distance of all other cords within a column. Each space between cords (vertical lines) equals ½ the unit of measurement U. As is apparent from the foregoing, the holes are aligned in columns and rows, while the spacing of the rows is not critical however the adjacent hole in a given row cannot overlap its adjacent hole. The hole  50 B is established by aligning chords H of  50 B with chords H of  50 A and  50 A 1 . In the next row  50 C is established by aligning the chord G with the centerline F of  50 A. Row  50 C 1  is established by aligning centerline F of  50 C 1  with chord G of  50 A 1 . With this pattern of holes, each of the vanes  18  will displace uniformly over the surface of the cylinder  16 . 
   As is apparent from the foregoing one repeat of the hole pattern is described and it is to be understood that all repeats are identical. In this arrangement of holes, no holes in any row overlap each other. It will be noted that the displacement of the first two chords over the holes  50 A and  50 C is equal to F and G. The next displacement over the holes  50 A and  50 C is equal to G and F. The next displacement of vane  18  is over the holes in  50 A,  50 B and  50 C and this is equal to chords H, H and G. By following this pattern throughout the displacement of the vanes it will be noted that the total distance and hence, area that the edge of the vane is in contact with each of the holes of the cylinder is equal. It then follows that the total average area of contact that the edge of the vane makes relative to the surface of the cylinder is also equal. By designing the hole pattern of the cylinder in this manner, the vanes will wear evenly throughout its cycle and hence, will evidence a longer life. 
   What has been shown by this invention is an improved cylinder for a vane motor that minimizes vane wear that with respect to the discharge holes  50 , the contact area made by the vanes is even and the exhaust noise level is reduced; with respect to the input holes  39 , the input air flow is increased and the power stroke is expanded; with to the slots  42 , the heat transfer from the cylinder to the operating air flow is increased; by diverting the air flow from the cylinder, the front bearing is cooled, all of which contribute to the increase of power, the increase of torque, the reduction of vibrations, noise and heat. 
   Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the disclosed invention.