Abstract:
A rotary device having an inlet adapter for connecting the device to a pressurized fluid source, a turbine rotor, and an input passage. The input passage provides fluid communication between the input adapter and the turbine rotor, has a first end proximate the inlet adapter and an opening downstream from the first end, and has a generally constant cross sectional area between the first end and the opening.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to rotary tools. In particular, this invention relates to hand held or machine mounted pressurized fluid driven rotary tools. 
   SUMMARY OF THE INVENTION 
   In one embodiment, the present invention relates to a rotary device having an inlet adapter for connecting the device to a pressurized fluid source, a turbine rotor, and an input passage. The input passage provides fluid communication between the input adapter and the turbine rotor, has a first end proximate the inlet adapter and an opening downstream from the first end, and has a generally constant cross sectional area between the first end and the opening. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross-sectional view of a rotary tool according to the present invention. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , an exemplary rotary tool according to the present invention is shown generally at  10 . The exemplary tool described herein is a pneumatic tool having a turbine rotor powered by oil-free high pressure air, however, it will be understood that the concepts of the current invention could be used or adapted for use for any rotary tool having any type of fluid driven motor, such as a vane motor, and powered by any type of compressed fluid. 
   The rotary tool  10  generally has a housing  13 , formed by a front section  12  and a back section  14 , a rotor  16 , a rotatable shaft  18 , and a muffler housing  46 . 
   The front section  12  of the housing  13  comprises a long cylindrical forward part  24  and a short enlarged cylindrical rearward part  28 . The rearward part  28  comprises external threads that will engage internal threads on the back section  14 , as described in more detail below, to connect the front section  12  to the back section  14 . The forward part  24  comprises internal threads that will engage external threads on the holding nut  30 , as described in more detail below. 
   The back section  14  of the housing  13  has a fluid inlet portion  32 , a first flange  34  extending outwardly from one end of the fluid inlet portion  32 , and a second flange  36  extending forward from the outer edge of the first flange  34 . The inner surface of the second flange  36  is formed with internal threads which engage the external threads on the rearward part  28  of the front section  12 , forming a motor chamber  15  therein. The fluid inlet portion  32  has a bore  38  therethrough, which comprises internal threads in one end of the bore  38  that will engage external threads on the inlet adapter  40  and an enlarged counterbore at the opposite end of the bore  38 . The first flange  34  has a series of holes  45  that allow the exhaust fluid from the motor chamber  15  to flow through the first flange  34  and into the muffler housing  46 . A sealing ring  42  is fixed within the counterbore and has also has a bore  44  therethrough that is aligned with and in fluid communication with the bore  38  in the fluid inlet portion  32  of the back section  14 . Alternatively, the sealing ring  42  could also be formed as an integral part of the back section  14  of the housing  13 . 
   The muffler housing  46  comprises a back wall  47  and a side wall  48  extending outwardly from the back wall  47 , thereby forming a cavity therein. The back wall  47  has one or more holes  49 , each having a predetermined diameter, that allow the exhaust fluid from within the muffler housing  46  to exhaust to the atmosphere and a bore  51  through the center for receiving the inlet adapter  40 . The inlet adapter  40  extends through the back wall  47  and threads into the fluid inlet portion  32  of the back section  14  to hold the muffler housing  46  in place against the back section  14 . Inside of the cavity formed in the muffler housing  46  is muffling material  26 , which may be composed of a felt-like material and is adapted for muffling the noise caused by exhausted fluids. 
   The inlet adapter  40  is adapted to receive a hose from a high pressure air source and has a bore  41  to allow the flow of fluid therethrough. Alternatively, the inlet adapter  40  could be formed integrally as part of the fluid inlet portion  32  of the back section  14  and the muffler housing  46  could be secured to the back section through other means, such as by threading the muffler housing  46  directly to the back section  14  of the housing  13 . 
   A rotatable shaft  18  is rotatably mounted in the front section  12  of the housing  13  by a rear bearing assembly  20  and a front bearing assembly  21 . Each outer race of each bearing assembly  20 ,  21  is positioned in an annular counterbore in each end of the forward part  24  of the front section  12  while the inner race is positioned on the shaft  18 . The shaft  18  has a back end projecting into the motor chamber  15  and a coupler  70  affixed thereto. The forward end of the coupler  70  contacts the end of the inner race of the rear bearing assembly  20  to hold it in place. A holding nut  30  is threaded into the internal threads of the forward part  24  of the front section  12  and contacts the outer race of the front bearing assembly  21  to hold it in place. The shaft  18  has a forward end that projects forward of the holding nut  30  and is connected to a collet  22 , which is used to hold a tool (not shown), such as a grinding-type tool. Many other tool holding means well known in the art can also be used if desired. 
   The coupler  70  is formed as a cylindrical member having a first bore in the front end of the coupler  70  and a second bore  74  in the back end of the coupler. The first bore is adapted to fit over and receive the back end of the shaft  18 . The second bore is aligned with and in fluid communication with the bore  44  in the sealing ring  42  and has diametrically opposed radial openings  72  therethrough to the exterior of the coupler  70 . The rear of the coupler  70  has a rearwardly extending annular sealing flange around the second bore for sealing with the sealing ring  42 . This sealing arrangement provides for the flow of pressurized fluid through the fluid inlet portion  32  and sealing ring  42  and into the coupler  70  to the radial openings  72 . The coupler  70  is externally threaded from its rearward end to a place adjacent its front end where an annular shoulder  76  is formed. 
   The rotor  16  is mounted within the motor chamber  15  by threading it onto the external threads of the coupler  70  such that the rotor  16  can rotate therein. As described herein, the rotor  16  is a reaction turbine-type rotor, such as that described in U.S. Pat. No. 4,776,752 to Davis, which has a common assignee with the present invention, and the disclosure of which is hereby incorporated by reference. However, the present invention is not so limited and may be applied to rotary devices having other types of motors. 
   In operation, pressurized air enters the rotary tool through the inlet adapter  40 , flows through the fluid inlet portion  32  of the back section and the sealing ring  42  to the second bore  74  in the coupler  70 , and through the radial openings  72  into the rotor  16 . As the air enters the rotor  16  it enters a first annular chamber  50 , flows around a resilient valve ring  52  through radial holes  54  in annular wall  60  into a second annular chamber  56 , where it is directed through nozzles  58 , thereby imparting rotation to the rotor  16  and therefore the shaft  18 . The pressurized fluid is expelled from the rotor  16  through the nozzles  58  and passes into the motor chamber  15 , through the holes  45  in the back section  14  of the housing  13 , through the muffling material  26 , and exits the rotary tool  10  through the holes  49  in the muffler housing  46  to the atmosphere. 
   As the pressurized fluid is directed into the rotor  16 , rotation increases to a pre-selected maximum. Centrifugal forces acting on the resilient valve ring  52  tend to cause radial expansion of the resilient valve ring  52 , however, the inner surface of the annular wall  60  supports the resilient valve ring  52 , except at radial holes  54 . This enables the radial expansion of the resilient valve ring  52  to be directed into the holes  54  so as to cause a controlled elastic deformation of the resilient valve ring  52 . As the resilient valve ring  52  deforms it approaches the ends of radial holes  54 . As the distance narrows sufficiently, fluid flow through the radial holes  54  is restricted and rotating forces reduced. As drag forces acting on the system and rotating forces reach equilibrium, the forces acting on the resilient valve ring  52  will also be in equilibrium. This results in a constant rotary speed. If drag forces increase, the equilibrium would be disrupted, and the forces on the resilient valve ring  52  will retract the resilient valve ring  52  from its closest proximity to radial holes  54 , allowing additional fluid flow until another equilibrium is established. If for any reason the turbine should exceed the desired governed speed, the resilient valve ring  52  will move to restrict pressure fluid flow even further until sufficient overspeed will cause all flow to stop, thereby incorporating an overspeed safety. 
   The bore  38  through the back section  14  of the housing  13 , the bore  44  through the sealing ring  42 , and the second bore  74  through the coupler  70  define an input passage through the rotary tool  10  that allows the flow of fluid from the inlet adapter  40 , through the radial openings  72 , to the rotor  16 . The bores  38 ,  44 ,  74  have cross sectional areas that are approximately equal, thereby allowing the fluid that enters to rotary tool  10  to flow steadily through the tool  10  to the radial openings  72  without any contractions or expansions of the input passage. This increases the power of the rotary tool  10 . In the preferred embodiment of the invention, the bores  38 ,  44 ,  74  are cylindrical and have diameters of approximately 0.284 inches and therefore cross sectional areas of approximately 0.063 square inches. 
   The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The description was selected to best explain the principles of the invention and their practical application to enable other skills in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention not be limited by the specification, but be defined by the claims set forth below.