Abstract:
A rotor for pneumatic paddle motor is described, comprising a plurality of segments ( 50 ) separated by radial grooves ( 5 ) adapted to slidably house paddles ( 4 ). Each segment ( 50 ) includes a surface external edge ( 9, 9′ ) consisting of a convex portion ( 10 ) joined to at least one concave abutment ( 11, 11 ′).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Italian Patent Application MI2009A000988, filed Jun. 8, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a self-triggering rotor for pneumatic paddle motor which may be used on surface processing machines for example, such as surfacers, sanders, and polishers. 
       BACKGROUND OF THE INVENTION 
       [0003]    The rotor is eccentrically contained within a cylindrical housing of larger size than the rotor. The rotor is equipped with vertical radial grooves within which paddles slide in a radial direction. The paddles emerge due to the centrifugal force exerted by the rotor in the area where between the rotor and the housing, there is a spacing allowing the paddles to emerge and retract under the limiting action of the internal cylindrical walls of the rotor housing, in the area where rotor and housing are close to each other, due to the assembly eccentricity between rotor and housing. 
         [0004]    The rotor is rotated by a pressurized air flow acting on the rotor paddles. A suitable channelling of the compressed air consisting of radial and circumferential sections and placed in the rotor heads, manages the air from an inlet towards a first paddle by pushing it radially outwards, thus causing the supply chamber to close and triggering the rotation of the rotor. 
         [0005]    This solution has the drawback of requiring the heads to be milled for obtaining the triggering channelling, and at speed, of wasting a fraction of the compressed air “forced” to cross said channelling and therefore subject to load losses. 
       SUMMARY OF THE INVENTION 
       [0006]    It is the object of the present invention to provide a pneumatic paddle motor which is constructionally simple and capable of optimizing the activating air flow both in the triggering phase and at speed. 
         [0007]    In accordance with the invention such an object is achieved by a pneumatic motor as disclosed in claim  1 . 
         [0008]    These and other features of the present invention will become increasingly apparent from the following detailed description of a practical embodiment thereof; shown by way of non-limiting example in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows an exploded view of a machine with a rotor according to the known art; 
           [0010]      FIG. 2  shows a cross-section view of a machine with a rotor according to the known art; 
           [0011]      FIG. 3  shows an exploded view of a machine with a rotor according to the invention; 
           [0012]      FIG. 4  shows a cross-section view of a machine with a rotor according to the invention; 
           [0013]      FIG. 5  shows the enlarged circle A in  FIG. 4 ; 
           [0014]      FIG. 6  shows a perspective view of the rotor according to the invention; 
           [0015]      FIG. 7  shows a top plan view of the rotor in  FIG. 6 ; 
           [0016]      FIG. 8  shows a top plan view of the rotor according to a further embodiment; 
           [0017]      FIG. 9  shows a section view according to the line IX-IX in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    With reference to the accompanying drawings and in particular to  FIGS. 1 and 2 , a surfacer  100  is shown comprising a pneumatic paddle motor  20  belonging to the known art. Motor  20  is equipped with a rotor  10  with paddles  40 , eccentrically contained in a housing  60 , adapted to activate a shaft  170 . Motor  20  is described in the introduction of the present application. Hereinafter, a brief reminder of the activation of rotor  10  as depicted in  FIG. 2  is provided: the compressed air flow from an inlet  70  enters in a milled channel  400  in the upper  140  and lower  150  heads ( FIG. 1 ), thus triggering the rotation. 
         [0019]    Said channel  400  consists of a radial section  401  connected to inlet  70  and of a curved section  402  adapted to direct the air towards a housing  60  of a paddle  40 . 
         [0020]    The heads  140 ,  150  comprise bearings  200 . 
         [0021]    A self-triggering rotor  1  according to the present invention for a pneumatic paddle motor  2  is seen in  FIGS. 3-7 . In particular, in  FIG. 3  the self-triggering rotor  1  activating a shaft  17  is denoted, which comprises radial grooves  5  in which paddles  4  adapted to define rotor segments  50  are slidably housed. 
         [0022]    Rotor  1  is eccentrically contained in a closed cylindrical housing  6  which comprises an inlet  7  and a return  8  for a compressed air flow. 
         [0023]    Said rotor  1  is closed by heads  14 ,  15  comprising bearings  20 . 
         [0024]    The heads  14 ,  15  have no trigger channelling  400 . 
         [0025]    Said housing  6  is adapted to allow the paddles  4  to radially emerge and retract according to a predetermined, known program: given the assembly eccentricity between rotor  1  and housing  6 , as shown in  FIGS. 3-7 , the spacing between the periphery of rotor  1  and the internal wall of housing  6  varies, and upon the rotation of rotor  1 , the paddles  4  emerge due to the action of the centrifugal force when this spacing allows it, and they cyclically retract due to the lack of space, along their rotation. 
         [0026]    The inlet  7  directs the compressed air flow over the paddles  4  thus activating the rotation of rotor  1 . 
         [0027]    Instead of milling the heads  14 ,  15 , the present invention as operated in the known art suggests a particular external profile of rotor  1 . 
         [0028]    The edge  9  of each segment  50  of rotor  1  consists of a traditional convex portion  10  joined to a following concave abutment  11  ending in groove  5 . In the present embodiment, the concavity is radial while a right angle corner may be provided. 
         [0029]    The compressed air from inlet  7  functionally enters the housing  6  through a passageway  600 , directly interacting with the edge  9  of a first segment  50 . 
         [0030]    The rotation is then triggered. The rotation is triggered by the rotor itself, from which the definition “self-triggering”, 
         [0031]    The profile of said edge  9  described above determines an optimization of the air flow which determines the triggering and an optimal thrust on the paddles  4  due to the concave abutment  11  following the convexity  10 . 
         [0032]    By entering, the air from the inlet  7  hits the abutment  11  with a direct thrust on the segment  50  of rotor  1  by providing a localized acceleration which is translated into a greater thrust force adapted to trigger the rotation and the consequential emersion of the paddle  4  from groove  5  due to the centrifugal force. 
         [0033]    A rotor is shown in  FIG. 8 , where each segment  50  provides an edge  9 ′ with two concave abutments  11 ,  11 ′ joined to each other by the convex portion  10 . This constructional solution allows the assembly in housing  6  to be independent from the rotation direction of the rotor, an abutment  11 ,  11 ′ being provided however, for the self-triggering according to the invention. 
         [0034]    Moreover, the double abutment  11 ,  11 ′, combined with a double inlet  7  with a single discharge  8 , allows reversible motors with both right and left rotation directions to be manufactured. The two inlets  7  are placed so as to selectively activate the rotor in opposite directions.