Abstract:
An air regulator comprises a housing, a shaft, a first air regulation member and an elastic ring. The shaft is rotationally fixed within the housing. The first air regulation member is coaxially coupled to the shaft and has a plurality of first air flow apertures positioned radially about the shaft. The elastic ring is configured and positioned to centrifugally deform and increasingly block the first air flow apertures.

Description:
PRIORITY INFORMATION 
     This patent application claims priority from PCT Application No. PCT/EP2007/000367 filed Jan. 17, 2007 and German Application No. 20 2006 005 899.0 filed Apr. 5, 2006, which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a compressed-air motor for rotationally driven tools, for example grinders, having a governor for limiting the rotational speed. 
     Compressed-air motors include turbines, vane motors and gear motors. Compressed-air drives having a governor are disclosed in German Patents DE 43 20 532 C1 and in DE 44 28 039 C1. 
     There is a need for a motor having a governor that reliably limits rotational speed. 
     SUMMARY OF THE INVENTION 
     An air regulator comprises a housing, a shaft, a first air regulation member and an elastic ring. The shaft is rotationally fixed within the housing. The first air regulation member is coaxially coupled to the shaft and has a plurality of first air flow apertures positioned radially about the shaft. The elastic ring is configured and positioned to centrifugally deform and increasingly block the first air flow apertures. 
     These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a sectional view of one example of a rotary tool; 
         FIG. 2A  illustrates an enlarged sectional view of the right-hand portion of the rotary tool in  FIG. 1 ; 
         FIG. 2B  illustrates a sectional view of an elastic ring in the rotary tool in  FIG. 1 ; 
         FIGS. 3A to 3B  illustrates a perspective view of a first half and a second half of a turbine rotor; 
         FIG. 3C  illustrates a perspective view of a bearing plate; 
         FIG. 3D  illustrates a perspective view of an air-guide plate; 
         FIGS. 3E-3F  illustrates a perspective view of a first and a second plate in a govenor; 
         FIG. 3G  illustrates a perspective view of the governor; and 
         FIG. 4  illustrates a sectional view of a turbine rotor along the arrow IV-IV in  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates an example of a rotary tool, for example a personal handheld grinder  200 , driven by a compressed-air motor. However, the application of compressed-air motors are not limited to grinders, but may be implemented in a variety of other devices, for example a tool spindle or a robot tool. 
     The grinder  200  comprises a first housing component  1 , a second housing component  2  and a cover  9 . In one example, the cover  9  is configured to screw onto the first housing  1  and the first housing  1  is configured to screw into the second housing  2 . A bearing plate  3 , clamped between the first and the second housings  1  and  2 , has a plurality of apertures  4  along its circumference, illustrated in  FIG. 3C , and is configured to hold a ball bearing  5 . A shaft  6  is rotatably supported by the ball bearings  5  in the bearing plate  3  and is configured to support a receptacle element  100 . The receptacle element  100  is configured to attached to an accessory, for example a grinding stone. 
     In one example, a governor  10 , shown in  FIG. 3G , comprises a first air regulation member, for example a first plate  11 , shown in  FIG. 3E , a second air regulation member, for example a second plate  12 , shown in  FIG. 3F , and an air-guiding plate  13 , shown in  FIG. 3D . The governor  10  is rigidly screwed to the shaft  6  through threads  7 . The second plate  12  comprises a hub  14  and a flange  16  having a plurality of apertures  17 . A circular elastic ring  15 , for example an O-ring, is seated on the hub  14  and defines a control element proper. The apertures  17  are configured and positioned in the plate  12  such that a stream of compressed air entering a space  25  through the apertures  17  is directed onto the ring  15  and deflected radially away from an axial center of the plate  12 . 
     The plate  11  comprises a plurality of apertures  18 , shown in  FIG. 3E , that are configured and positioned radially about the plate  11 . In the present example, the radius on which the apertures  18  lie is greater than the radius on which the apertures  17  lie. In one example, the aperatures  18 , fashioned into a pot shape, penetrate completely through the bottom  19  of the plate  11  and partially through a rim  20  of the plate  11 . A space  25  is defined by the bottom  9  and the rim  20  of the first plate  11  and the flange  16  of the second plate  12  such that a stream of air entering the space  25  through the apertures  17  may flow past the ring  15  and into the apertures  18 . A chamber  26  is defined by the bottom  9  of the first plate  11  and an air-guiding plate  13 , shown in  FIG. 3D , such that the stream of air may pass through the apertures  18  and into the chamber  26 . A plurality of radial channels  27 , for example three, are configured and positioned on the air-guiding plate  13  such that the air stream may flow from the chamber  26 , through the channels  27  and the apertures  28  and into a bore  30  in the shaft  6 . 
     An air inlet duct  40  positioned in the first housing  1  is coupled to, for example, a conically expanding chamber  35  defined by, for example, a conical partition shell  41  and the governor  10 . The partition shell  41  is clamped between the first housing  1  and the bearing plate  3 . 
     An aperture  45  is configured in the bore  30  such that a stream of air may pass from the bore  30  into a plurality of nozzles in a turbine rotor  50 . In one example, the turbine rotor  50  comprises a first half  51  and a second half  52 . The two halves, shown in  FIGS. 3A-3B , each comprise two air-guiding vanes  81 ,  82  or  83 ,  84  configured as mirror images. The vanes  81 ,  82 ,  83  and  84  are configured to define four nozzles  85 ,  86 ,  87  and  88  when the two halves  51  and  52  are joined at a 90° offset and held together by tightening the second plate  12  about the end of the shaft  6 , shown in  FIG. 2A . The nozzles  85 ,  86 ,  87  and  88  lie in a plane perpendicular to the shaft  6  such that the stream of air may exit from the nozzles tangentially to the circular shape of the turbine rotors and thus, through a reaction force, drive the shaft  6  and thereby a tool afixed to the receptacle element  100 . 
     When the stream of air flows from the chamber  35  through the apertures  17 , the chambers  25 , the apertures  18 , the chambers  26 , the channels  27  and the apertures  28  into the bore  30 , control of the rotational speed is effected by the centrifugal force acting on the elastic ring  15  causing the elastic ring to brace against the apertures  18  and the rim  20 . The elastic ring  15  may become flattened by the stream of air, thereby taking on an oval shape with the longer axis perpendicular to the shaft  6 , shown in  FIG. 2B . As the rotational speed increases, the elastic ring  15  blocks an increasingly larger portion of the apertures  18 . Therefore, the rotational speed of the compressed air motor is controlled/regulated at a value less than the maximum attainable rotational speed. Correspondingly, when the rotational speed decreases, the elastic ring permits more air into the apertures  18 . 
     A chamber  60 , defined by the turbine rotor  50  and the second housing  2 , and an annular chamber  61 , defined by the partition shell  41  and the first housing  1 , are configured such that a return stream of air may flow from the nozzles  85 ,  86 ,  87  and  88  in the rotor  50  and the apertures  4  in the bearing plate  3  through at least one exhaust duct  70  in the first housing  1  into at least one passage  71  between the cover  9  and the, for example, nipple-shaped end of the first housing  1 . 
     Reliable and simple rotational-speed limiting/regulation, for example to roughly 45,000 revolutions per minute (rpm), may be achieved in the range of optimal utilization of the energy contained in the air stream. The limiting/regulation depends particularly on the dimensions of the apertures  17 ,  18 , and the size and elasticity of the elastic ring  15 . The pressure available at industrial work stations where such implements are used and wherewith such grinders are driven is usually approximately 6-7 bar. 
     Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.