Abstract:
A fixture used for supporting and protecting a rotor during the magnetization process comprising features enabling it to properly support and protect a delicate rotor is described herein. Generally, the fixture is prevented from rolling on a horizontal surface, may seal the delicate rotor assembly therein, maintains the rotor assembly by its opposed longitudinal ends and/or allows the magnetization process results to be tested while the rotor remains sealed inside.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to fixtures. More specifically, the present invention is concerned with a rotor assembly fixture to be used during the magnetization of the magnet of a rotor assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     Rotors are used in numerous fields and, with the rise of miniaturization, rotors find themselves employed even in more applications. For instance, in the medical field, small cardiac pumps which can be inserted inside a heart&#39;s ventricle, are now designed with small rotors. For the making of such delicate rotors, special attention and equipments have to be considered.  
         [0003]     For instance, since the shape of small rotors is often critical, the rotors are first machined before being magnetized. Because of their small size, such machined rotors tend to be very fragile and delicate to handle during the magnetization process. Some of the encountered challenges include: 
    1) keeping the integrity of the surfaces of the rotor assembly during the magnetization process;     2) providing solid and sound support for the rotor assembly in order to avoid any deformation, movement and unstability;     3) providing means for measurements, control and monitoring while or shortly after the rotor assembly is being magnetized;     4) providing sealing means in order to isolate the rotor assembly from any foreign particles during and after the magnetization process; and     5) protecting the rotor assembly during transportation.    
 
         [0009]     It would be therefore very interesting to have an equipment made for such a specific application of rotors, which can meet all the needs mentioned above.  
       OBJECTS OF THE INVENTION  
       [0010]     An object of the present invention is therefore to provide a rotor assembly fixture for magnet magnetization.  
       SUMMARY OF THE INVENTION  
       [0011]     More specifically, in accordance with the present invention, there is provided a fixture for supporting a rotor assembly during magnetization, the fixture comprising: a body defining a chamber and comprising first and second ends and at least one flat external surface, the first end defining an opening; and a cover so mountable to the body as to selectively close the opening; wherein the chamber receives the rotor assembly and the flat external surface enables the fixture to rest on a generally horizontal surface in a substantially stable manner.  
         [0012]     In accordance with another aspect of the present invention, there is provided a fixture for supporting a rotor assembly during magnetization, the fixture comprising: a body defining a chamber and comprising first and second ends and at least one cut-out therein, the first end defining an opening to the chamber; and a cover so mountable to the body as to selectively close the opening; wherein the cut-out provides for a gauss meter to measure the magnetic strength of the magnetized rotor while the rotor assembly stays inside the chamber.  
         [0013]     In accordance with a further aspect of the present invention, there is provided a fixture for supporting a rotor assembly during magnetization, the rotor assembly being provided with longitudinally opposed ends, the fixture comprising: a body defining a chamber and a longitudinal axis and comprising first and second ends, the first end defining an opening, the second end being closed and comprising a first rotor end supporting element; and a cover so mountable to the body as to selectively close the opening and comprising a second rotor end supporting element; wherein the first and second rotor end supporting elements provide support for opposed ends of the rotor assembly resting inside the chamber and allow the rotor assembly to rotate about the longitudinal axis.  
         [0014]     Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     In the appended drawings:  
         [0016]      FIG. 1  is a perspective view of a fixture for supporting a rotor assembly during magnetization of the magnet of the rotor assembly, according to an embodiment of the present invention;  
         [0017]      FIG. 2  is a sectional exploded side elevation view showing a rotor assembly fitting into the fixture of  FIG. 1 ;  
         [0018]      FIG. 3  is a sectional side elevation view of the fixture of  FIG. 1  with its cover not mounted; and  
         [0019]      FIG. 4  is a sectional side elevation view of the fixture of  FIG. 1  with its cover mounted. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Generally stated, the present invention relates to a fixture for supporting a rotor assembly during the magnetization of the rotor&#39;s magnet.  
         [0021]     An embodiment of the present invention introduces a fixture  10  having a body  12  and a cover  14 , as illustrated in  FIG. 1 . The fixture  10  defines a longitudinal axis  15 .  
         [0022]     As can be better seen from  FIG. 2 , the body  12  defines a chamber  16  having two ends, one end defining an opening  18  and the other end defining a generally cross-shaped closed end  20 . The chamber  16  is so configured and sized as to receive a rotor assembly  40  and is divided into two cylindrical sections  22  and  24  with different diameters to accommodate the particular shape of the rotor assembly  40 .  
         [0023]     More specifically, a smaller cylindrical section  22  extends from the cross-shaped closed end  20  to the larger cylindrical section  24  and is surrounded by four reinforcement plates  30 . The larger cylindrical section  24  extends from the smaller cylindrical section  22  and ends with the square edges  26  (see  FIG. 1 ) surrounding the circular opening  18 . The square edges  26  have rounded inside edges  27  and rounded corners  29  (see  FIG. 1 ). They also have a sufficient thickness to provide enough weight and flat surface for the fixture  10  to be positioned upright and to have balance.  
         [0024]     Returning to  FIG. 1 , the cross-shaped closed end  20  has a flat surface, having a sufficient thickness, enabling the fixture  10  to be positioned upright (position not shown) with stability. Furthermore, together with the square edges  26 , the cross-shaped end  20  allows the fixture  10  to rest horizontally on a generally horizontal surface in a stable manner and prevents the fixture  10  to roll during handling. The cross-shaped end  20  and the square edges  26  have approximately the same size. The cross-shaped end  20  has round corners  21 . From the four corners of the flat surface of the cross-shaped end  20 , four reinforcement plates  30  are provided to strengthen the structure of the fixture  10 . Finally, the cross-shaped end  20  is provided with a recess  28  (see  FIG. 2 ), in which one of the ends of a rotor assembly  40  can be placed.  
         [0025]     As illustrated in  FIG. 1 , the four reinforcement plates  30  surrounding the smaller cylindrical section  22  are trapezoidal-shaped, extending from the cross-shaped closed end  20  to the larger cylindrical section  24 . They are evenly spread around and attached to the smaller cylindrical section  22 . A cutout  32  is located in each plate  30 , enabling a gauss meter or other types of meters (not shown) to be positioned therein to measure the magnetic strength of the magnetized rotor assembly, resting inside the chamber  16 , for control or monitoring purposes without removing the rotor assembly  40  from the fixture  10 . In this embodiment of the present invention illustrated in  FIG. 3 , the cutouts  32  are trapezoidal-shaped.  
         [0026]     A cover  14 , as better shown in  FIGS. 2 and 3 , comprises a flat and square portion  34 , from which a cylindrically shaped shoulder  36  extends. The shoulder  36  has such a diameter and length that it snugly fits into the opening  18 , thus making the fixture  10  adequately sealed. The shoulder  36  includes a beveled edge  37  facilitating the insertion of the cover  14  into the body  12 . The dimensions, length and thickness of the square portion  34  are generally the same as the square edges  26  of the opening  18 . Moreover, the cover  14  is provided with a recess  38  in the flat and square portion  34 , the recess  38  acting as a support element for the other end of the rotor assembly  40 .  
         [0027]     A person skilled in the art will understand that the recesses  28  and  38  provide support for the ends of a rotor assembly  40  during the magnetization process. Indeed, once the rotor assembly  40  enters the chamber  16 , as illustrated in  FIG. 4 , its ends are placed inside the recesses  28  and  38  for stability, free rotation and pole alignment. The recesses  28  and  38  are aligned on the same longitudinal axis  15  on opposed ends of the fixture  10 . It should also be understood that the thickness of the flat surface of both the cover  14  and the cross-shaped closed end  20  are so designed and sized as to provide enough depth and strength to the recesses in order for them to support the ends of the rotor assembly  40 .  
         [0028]     In order to prevent foreign particles from contaminating the rotor assembly  40 , resting in the chamber  16 , sealing features are provided by the fixture  10  to isolate the rotor assembly  40  from the external world during the magnetization process. As an example, the fixture  10  can be sealed by closing the cover  14  and blocking the recesses  28  and  38 , as seen in  FIG. 4 , by the ends of the rotor assembly. It will be understood that the recesses could be designed as to be closed at all times. By doing so, not only are the rotor assembly surfaces free of scratches and uncorrupted but also they stay clean.  
         [0029]     As illustrated in  FIGS. 2 and 4 , an example of a rotor assembly  40  entering the fixture  10  is given. The rotor assembly is made of titanium 6AL4V and is provided with two conical ends  42 ,  43  which can respectively be placed into the recess  38  of the cover  14  and the recess  28  of the cross-shaped closed end  20 . The rotor assembly has two portions  44  and  46 . The smaller portion  44  enters the smaller cylindrical section  22  of the chamber  16  of the fixture  10  and the larger portion  46  enters the larger cylindrical section  24  of the chamber  16 . The rotor assembly is so positioned and supported by the recesses  38  and  28 , that it rests comfortably and in a stable manner inside the chamber  16 . The dimensions of the two cylindrical sections  22  and  24  of the chamber  16  are so designed as to adequately receive the portions  44  and  46  of the rotor assembly respectively and to enable the rotor assembly  40  to rotate freely inside the fixture  10 . The larger portion  46  of the rotor assembly  40  is provided with an impeller  48 .  
         [0030]     It should be noted that such a rotor assembly  40  is only an example of rotor assemblies fitting into the fixture  10 . Of course, many other rotor assemblies, properly configured and sized can use the present embodiment of the fixture  10  during their magnetization process. It is also possible to design a fixture to fit other rotor topologies not shown herein.  
         [0031]     For instance, to magnetize a small rotor used in a cardiac pump inserted inside a heart&#39;s ventricle, the fixture  10  is provided with the following specifications and dimensions. The fixture  10  is made with a white stereo-lithographic material and has a length of 67.1 mm. Typically, the diameter of the smaller cylindrical section  22  is 8.5 mm and the diameter of the larger cylindrical section  24  is 20.5 mm. The thickness of the flat and square portion  34  of the cover  14  measures 4.6 mm. The recess  28  has a diameter of 2.8 mm and the recess  38  has a diameter of 3.2 mm. The cutouts  32  are located about 1.0 mm away from the external surface of the smaller cylindrical section  20  and in the middle of the plates  30 . As an indication, each side of the flat and square portion  34  measures 25.4 mm. It should be noted that all the specifications and dimensions of the fixture  10  provided above can be changed and modified depending on the configuration and size of rotors that need to be magnetized.  
         [0032]     Although an embodiment illustrating the present invention has been described, it should be kept in mind that many aspects can be modified without departing from the spirit of the present invention. For example, the number and the shape of the cut-outs can be different than what has been described in this document, the square and cross shapes of the cover and the closed end of the chamber can be modified, and different means, beside recesses, can be used to provide support for the rotor assembly during the magnetization process and sealing of the fixture. The dimensions and configuration of the fixture depend on the rotor assembly to be magnetized. Finally, the square portion can be replaced by other flat surfaces enabling the fixture to rest on a horizontal surface.  
         [0033]     Although the present invention has been described in the foregoing specification by means of a non-restrictive illustrative embodiment, this illustrative embodiment can be modified at will within the scope, spirit and nature of the subject invention.