Patent Publication Number: US-10774647-B2

Title: Rotor with sliding vane has a different width of vane slot extended from the longitudinal axis to the outer surface of the rotor body

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims benefit of priority to U.S. Provisional Application No. 62/525,252, filed Jun. 27, 2017 and hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention concerns rotors for compressors, pumps and rotary engines. 
     BACKGROUND 
     Rotors for devices such as compressors, pumps and rotary engines are finished to precise dimensions and tight tolerances. Rotors are thus among the more expensive and time consuming components in the manufacture of such devices. Rotors are furthermore complex parts because they receive one or more reciprocating vanes in slots that pass through the rotor body. It is a challenge to manufacture rotors economically and rapidly by conventional machining techniques, especially if it is desired that the rotor be formed from a single piece of metal. There is thus an opportunity to improve the design of rotors to promote their more efficient and rapid manufacture. 
     SUMMARY 
     The invention concerns a rotor. In one example embodiment the rotor comprises a first hub having a first hub radius. A second hub is coaxially aligned with the first hub. The second hub has a second hub radius. A vane housing is positioned between the first and second hubs. The vane housing comprises a cylindrical body having a longitudinal axis coaxially aligned with the first and second hubs. A slot extends through a diameter of the body and along the longitudinal axis. A first portion of the slot, extending radially from the longitudinal axis over a distance greater than both the first hub radius and the second hub radius, has a first width. A second portion of the slot, extending radially from the first portion to an outer surface of the body, has a second width less than the first width. A third portion of the slot, extending radially from the longitudinal axis over a distance greater than both the first hub radius and the second hub radius, hays a third width. Afourth portion of the slot, extending radially from the third portion to the outer surface of the body has a fourth width less than the third width. 
     In a particular example embodiment the first hub radius is equal to the second hub radius. Further by way of example the first width is equal to the third width. Again by way of example the second width is equal to the fourth width. 
     An example embodiment further comprises a shaft extending from the second hub. The shaft is coaxially aligned with the first and second hubs. Another example embodiment comprises a vane slidably positioned within the slot. The vane may be mounted on an eccentric cam such that rotation of the rotor about the longitudinal axis causes reciprocal motion of the vane within the slot. 
     The invention also encompasses a method of manufacturing a rotor. In one example embodiment the method comprises:
         integrally casting a first hub, a second hub and a vane housing between the first and second hubs, the first hub having a first hub radius, the second hub having a second hub radius, the vane housing comprising a cylindrical body having a longitudinal axis coaxially aligned with the first and second hubs;   using a mold core to cast a slot extending through a diameter of the body and along the longitudinal axis, a first portion of the slot, extending radially from the longitudinal axis over a distance greater than both the first hub radius and the second hub radius, having a first width, a second portion of the slot, extending radially from the first portion to an outer surface of the body having a second width less than the first width, a third portion of the slot, extending radially from the longitudinal axis over a distance greater than both the first hub radius and the second hub radius, having a third width, a fourth portion of the slot, extending radially from the third portion to the outer surface of the body having a fourth width less than the third width.       

     An example method according to the invention may further comprise integrally casting a shaft connected to the second hub. The shaft is coaxially aligned with the second hub. Further by way of example the method may comprise grinding the second and fourth slot portions to a desired final width. Another example method comprises grinding the second slot portion to a final width less than the first width. Another example method comprises grinding the fourth slot portion to a final width less than the third width. Additionally by way of example, the method may comprise turning the rotor to achieve final outer diameters of the first hub, the second hub, the shaft and the vane housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an isometric view of an example rotor according to the invention; 
         FIG. 2  is a cross sectional view taken at line  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a longitudinal sectional view taken at line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a partial sectional view showing an example rotor assembly according to the invention; and 
         FIG. 5  is an isometric view showing a step in an example manufacturing process of an example rotor according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an example embodiment of a rotor  10  according to the invention. Rotor  10  comprises a first hub  12  and a second hub  14  coaxially aligned with one another along an axis of rotation  16 . Hubs  12  and  14  may be received within bearings when the rotor is mounted within a device, such as a compressor, a pump, or a rotary engine (not shown). A vane housing  18  is positioned between the hubs  12  and  14 . Vane housing  18  comprises a cylindrical body  20  having a longitudinal axis  22 . Longitudinal axis  22  is coaxially aligned with the axis of rotation  16  of hubs  12  and  14 . A shaft  24  extends from the second hub  14 . Shaft  24  is coaxially aligned with the hubs  12  and  14  and the body  20 . 
     As shown in  FIGS. 1 and 2 , a slot  26  extends through a diameter of the body  20 . As shown in  FIGS. 1 and 3 , slot  26  also extends lengthwise along the body&#39;s longitudinal axis  22 . Slot  26  is formed of four portions. As shown in  FIGS. 1 and 2 , a first portion  28  of the slot  26  extends radially from axis  22  over a distance  30  greater than both the first and second hub radii  32  and  34 , the hub radii being measured from the axis of rotation  16 . A second portion  36  of slot  26  extends radially from the first portion  28  to the outer surface  38  of the body  20 . A third portion  40  of the slot  26  extends radially from axis  22  over a distance  42  greater than both the first and second hub radii  32  and  34 . A fourth portion  44  of slot  26  extends radially from the third portion  40  to the outer surface  38  of the body  20 . The third and fourth slot portions  40  and  44  are diametrically opposite to the first and second slot portions  28  and  36 . The first and third slot portions  28  and  36  extend respectively over the distances  30  and  42  which are greater than the radii  32  and  34  of the hubs  12  and  14  because this geometrical relationship allows the second and fourth slot portions  36  and  44  to be ground to a desired width using a grinding wheel without affecting the hubs as described below. Absent the separation between the second and fourth slot portions  36  and  34  and the hubs  12  and  14  a grinding wheel passing through the slot would also grind a channel through the hubs. Such a channel is to be avoided because it forms a leak path between high and low pressure areas of the device in which the rotor is used. For practical designs, as shown in the example rotor  10 , the hub radii  32  and  34  may be equal to one another. 
     The slot portions are distinguished from one another by their respective widths. First portion  28  of slot  26  has a first width  46 , and second portion  36  has a second width  48  less than width  46 . Third portion  40  of slot  26  has a third width  50 , and fourth portion  44  has a fourth width  52  less than the third width  50 . For practical designs, as shown in the example rotor  10 , the first width  46  is equal to the third width  50  and the second width  48  is equal to the fourth width  52 . 
     It is advantageous to control the second and fourth widths  48 ,  52  of slot  26  to precise dimensions and tight tolerances because these portions of the slot serve as guides for a vane  54  (see  FIG. 4 ) which reciprocates within the slot  26  during operation of the rotor in a device. Vane  54  is mounted on an eccentric cam arrangement  56  which causes the vane to undergo reciprocal sliding motion when the rotor rotates about axis  22 . 
     Rotor  10  is advantageously manufactured by integrally casting the hubs  12  and  14  with the body  20  and the shaft  24  in a cavity and core mold (not shown). A void space is created within the body  20  using a core which is shaped to the rough dimensions of the slot  26  including its four portions  28 ,  36 ,  40  and  44 . Once free of the mold and core, as shown in  FIG. 5 , the rotor casting  58  is subjected to turning and grinding operations. Shown is the use of a grinding wheel  60  which is run through the second and fourth slot portions  36  and  44  ( 36  shown) to establish the desired final width of these slot portions. Grinding is advantageous because it provides the needed precision and accuracy and is a faster and less expensive operation than other techniques, such as plasma cutting. The wheel  60  is able to finish the slot portions  36  and  44  to the desired final width without adversely affecting the hubs  12  and  14  because the first and third portions of the slot  26  extend outwardly beyond the radii of the hubs.