Patent Publication Number: US-2009238709-A1

Title: Magnetic vane ejection for a rotary vane air motor

Description:
FIELD OF THE DISCLOSURE  
     This disclosure relates to improved rotary vane pumps and, more specifically, to improved vane pump designs. Still more specifically, a rotary vane pump is disclosed wherein the vanes are biased away from the rotor and towards the inner wall of the casing by two magnets with opposite polarity, one magnet is disposed on an inner edge of the vane and the other disposed in the rotor body. The disclosed magnetic rotary vane pump designs are particularly useful in air motors but may be used in other applications where magnetic rotary vane pumps are employed. 
     BACKGROUND OF THE DISCLOSURE  
     Rotary vane pumps are positive-displacement pumps that consist of vanes mounted to a rotor that rotates inside of a cavity. In some cases, the vanes can vary in length or the outward force applied to the vanes can be varied to maintain good contact with the inside surface of the casing as the rotor of the pump rotates. The most simple vane pump is a circular rotor rotating inside of a larger circular cavity. The axes of the rotor and cavity are offset or are eccentric. The vanes are allowed to slide into and out of the rotor as they sealingly engage the inner surfaces of the cavity, thereby creating vane chambers that perform the compressing work as the rotor rotates. 
     On the intake side of the pump, the vane chambers are larger in volume due to the design of the cavity. These larger volume vane chambers are filled with fluid forced in by the inlet pressure. Often this inlet pressure is nothing more than atmospheric pressure. On the discharge side of the pump, the vane chambers are smaller in volume, forcing the fluid out of the pump. Rotary vane pumps are used in high and medium pressure applications. 
     One problem associated with rotary vane pumps or rotary vane pumps is the use of springs or pins for ejecting the vanes outward. The use of springs or pins for biasing vane movement requires lubrication, reduces maximum rotor speed and limits the time between service or maintenance because of the fatigue or failure rate of the pin and spring mechanisms. Also, using pins and springs to bias the vanes outward provides a relatively uncontrolled contact forced between the vanes and the internal surface of the cavity and places a limit on rotor speed. 
     Accordingly, there is a need for an improved rotary vane pump or pump that requires less lubrication or no lubrication, which is more reliable, which can operate at higher speeds and which has a longer operating life. 
     SUMMARY OF THE DISCLOSURE  
     In satisfaction of the aforenoted needs, an improved rotary vane pump is disclosed which comprises: a rotor disposed within a casing that comprises a cavity having an inlet and an outlet. The rotor includes at least one radial slot and at least one vane carried by the radial slot. The vane comprises an inner edge directed towards a central axis of the rotor and an outer edge directed towards the casing. The inner edge is permanently magnetized with a first polarity. The slot in the rotor comprises an inner wall that abuttingly engages or faces the inner edge of the vane when the vane is fully received within the slot. The inner wall of the slot is permanently magnetized with a second polarity opposite to the first polarity so that the inner edge of the vane and inner wall of the slot repel each other thereby biasing the vane radially outwards. 
     In a refinement, the inner edge of the vane comprises a first recess that receives a first magnet having first and second poles with the first pole facing the inner wall of the slot, and the inner wall of the slot comprises a second recess that receives a second magnet having first and second poles with the first pole facing the inner edge of the vane. 
     In a further refinement, the rotor comprises four radial slots, the pump comprises four vanes, each of which are received in one of the slots. Each vane comprises an inner edge directed toward an inner wall of its respective slot, and each inner edge and each inner wall are magnetized with opposite polarities. 
     Preferably, the inner edge of each vane includes a recess that receives a magnet and the inner wall of each slot includes a recess, aligned with the recess of its respective vane, and which receives a magnet. The magnets of the vanes and rotor recesses are arranged so that like poles of the magnets connected to the vanes face like poles of the magnets connected to the inner walls of the slots of the rotor. 
     A method for retrofitting a rotor and vane of a rotary vane pump is also disclosed. The method comprises: providing a rotor with at least one slot and a vane received in the slot, the vane comprising an inner edge directed towards a central axis of the rotor and an outer edge directed outwards away from the central axis of the rotor, the slot in the rotor comprising an inner wall that abuttingly engages or faces the inner edge of the vane when the vane is fully received within the slot; connecting the inner edge of the vane to a first magnet; connecting the inner wall of the slot a second magnet; wherein like poles of the first and second magnet are directed toward each other to generate a repelling force that biases the vane away from the inner wall of the slot. 
     In a refinement, the connecting of the first magnet to the inner edge the vane comprises forming a first recess in the inner edge of the vane and securing the first magnet in the first recess; and the connecting of the second magnet to the inner wall of the slot comprises forming a second recess in the inner wall of the slot and securing the second magnet in the second recess cell that like poles of the first and second magnets face each other. 
     In another refinement, the retrofitting is carried out on a rotor at that comprises four radial slots, each of which accommodates a vane. 
     In another refinement, the disclosed magnetic rotary vane pump is incorporated into an air motor. 
     Other advantages and features will be apparent from the following detailed description when read in conjunction with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
       One embodiment of a magnetic rotary vane pump made in accordance with this disclosure is illustrated more or less diagrammatically in the following figures, wherein: 
         FIG. 1  is a perspective view of a pump made in accordance with this disclosure; 
         FIG. 2  is a sectional view of the pump shown in  FIG. 1 ; 
         FIG. 3  is an exploded view of the pump shown in  FIGS. 1 and 2 ; 
         FIG. 4  is a sectional view of the pump casing shown in  FIGS. 1-3 ; 
         FIG. 5  is a plan view of one of the magnetized vanes shown in  FIGS. 2 and 3 ; 
         FIG. 6  is an exploded view of the rotor, vanes and magnets shown in  FIGS. 2 and 3 ; 
         FIG. 7  is an end view of the rotor shown in  FIG. 6 , particularly illustrating the placement of a magnet along and inside wall of one of the slots that receives one of the vanes; and 
         FIG. 8  is a partial sectional and exploded view of the rotor, one vane and two magnets associated therewith. 
     
    
    
     It should be understood that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated diagrammatically and in partial views. In certain instances, details which are not necessary for an understanding of the disclosed methods and apparatuses or which render other details difficult to perceive may have been omitted. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein. 
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
     Turning first to  FIG. 1 , a pump  10  made in accordance with this disclosure is shown in a perspective view. The pump  10  includes a rotor shaft  11  that passes through a seal  12  and mounting bracket  13 . The mounting bracket  13  is connected to a front plate  14  by a plurality of fasteners  15  as shown in  FIGS. 1-2 . A rotor casing  16  is sandwiched between the front plate  14  and a rear plate  17  as best seen in  FIG. 2 . The rear plate  17 , casing  16  and front plate  14  are held together by a plurality of fasteners, two of which are shown at  18  in  FIG. 2 , while three others are shown in  FIG. 3 . 
     As shown in  FIG. 3 , fasteners  19  may be used to secure the casing  16  to the front plate  14 . Referring to  FIGS. 1-3 , the rotor shaft  11  is supported by a front bearing  21  and a rear bearing  22 . An end cap  23  and O-ring seat  24  seals the rear end of the pump  10  while the rotor seal  12  seals the front end of the pump  10 . O-rings  25 ,  26  prevent fluid from leaking between the casing  16  and front and rear plates  14 ,  17 . 
     As shown in  FIG. 3 , the mounting bracket  13  may include a plurality of holes or apertures  27  for mounting the pump  10  to a motor housing (not shown). The front plate  14  includes a front hub section  28  for accommodating and supporting that he front bearing  21 . The rotor shaft  11  includes a slot  28  at the proximal end  29  of the shaft  11  for attachment to a rotor element of a motor (not shown) while the distal end  31  of the rotor shaft  11  passes through a rotor  32 , details of which are illustrated in greater detail in connection with  FIG. 6 . The rotor  32  shown includes four slots shown at  33 , each of which accommodates a vane  34 . As described in greater detail below, each vane  34  is attached to a magnet  35  and the inner wall  36  ( FIG. 6 ) of each slot  33  is connected to a magnet  37 . Finally,  FIG. 3  also shows the apertures  38  that pass through the rear plate  17  and the apertures  39  that pass through the casing  16  that accommodates the fasters  18 . FIG. three also illustrates the apertures  41  in the casing  16  that accommodates the fasters  19  that connect the casing  16  to the front plate  14 .  FIG. 3  also illustrates the apertures  42  that accommodate the fasteners  19 . 
     Turning to  FIG. 4 , the casing  16  includes input and output ports shown at  44 ,  45 . As the pump  10  is reversible, the ports  44 ,  45  can serve as either input or output ports, depending upon the rotational direction of the shaft  11  and rotor  32 . The casing  16  includes a circular bore  46  for accommodating the rotor  32 . The bore  46  is also connected to two recesses or slots  47 ,  48  for receiving the vanes  34  is the rotor  32  rotates within the casing  16 . This disclosure is directed primarily and an improved means for biasing the vanes  34  into the slots  47 ,  48  as the rotor  30  to rotates. 
     Specifically,  FIG. 5  illustrates a vane  34  with an inner edge  49 . The inner edge  49  of each vane  34  includes an aperture, slot, hole or recess  51  that accommodates a magnet  35 . Similarly, as shown in  FIGS. 6-8 , the inner wall  36  of each slot  33  includes an aperture, slot, hole or recess  52  that accommodates one of the magnets  37 . The magnets  35 ,  37  are arranged so that like poles are directed towards each other so that the magnets  35 ,  37  generate a repelling force that biases each vane  34  away from the inner wall  36  and out of its respective slot  33  and into one of the recesses  47 ,  48  as the rotor  32  rotates within the cavity  46  of the casing  16 . The disclosed design does not require a spring or pin or other mechanical feature that requires maintenance or replacement. Further, the disclosed design requires little or no lubrication and can operate at higher speeds than conventional vane pumps. 
     While only certain embodiments have been set forth, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.