Patent Publication Number: US-2007096858-A1

Title: Electromagnetic coil

Description:
RELATED U.S. APPLICATIONS  
      Not applicable.  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not applicable.  
     REFERENCE TO MICROFICHE APPENDIX  
      Not applicable.  
     FIELD OF THE INVENTION  
      The present invention is related to an electromagnetic coil, more specifically to an electromagnetic coil with a high intensity magnetic field.  
     BACKGROUND OF THE INVENTION  
      According to electromagnetic theory, when a current flows through a solenoid, a magnetic field will be generated in the spiral coils and stretch outward. The direction of the magnetic field is dependent upon the direction of the current (Ampere&#39;s Law). Given a larger current or more spiral coils, the generated magnetic field will be larger, and the magnetic density is directly proportional to the number of the spiral coils.  
      As shown in  FIG. 1 , the magnetic field can be enhanced by increasing the number of spiral coils. A copper wire  11  spirals upward and then downward with a view to increasing the number of the spiral coils, thereby forming a coil  10 . The current flowing through the coil  10  is dependent on applying voltages to the electrodes  12  connected to the two ends of the copper wire  111  and the load of copper wire  11  itself. The increase of spiral coils results in a higher resistance of copper wire  11 , i.e., the increase of the so-called load, and as a result the current flowing therein will decrease. Accordingly, although the increase of the spiral coils would increase the magnetic density, the intensity of the magnetic field is not significantly beneficial.  
      Referring to  FIG. 2 , an electromagnetic coil  20  is formed by spiraling a plate-like wire  21 , and the two ends of the plate-like wire  21  are equipped with electrodes  22 . The plate-like wire  21  bends on the short side in terms of the cross-sectional view, and the cross-sectional area increases significantly in comparison with that of a traditional copper wire. Consequently, the load of the wire  21  is relatively low, so that the intensity of the magnetic field will increase. However, because the inner and outer radiuses are differentiated a lot, the wire  21  needs a large force to bend it, so the manufacturing will be more difficult. Moreover, the inner rim and outer rim of the plate-like wire  21  need to withstand large residual stresses in compression and tension, respectively, so that the wire  21  may be broken on condition that the force exceeds the yielding point of the material.  
      The plate-like wire can also be made by casting. However, the manufacturing for a mold is costly and the mold design is limited due to the consideration of size and mold flow, therefore a large plate-like electromagnetic coil is hard to make.  
      Obviously, it is important to produce a large electromagnetic coil with low load for the application of large motors or other appliances.  
     BRIEF SUMMARY OF THE INVENTION  
      The objective of the present invention is to provide an electromagnetic coil with low load, whereby the intensity of the magnetic field can be increased so as to comply with the requirements of making a large electromagnetic coil.  
      In order to achieve the above objective, an electromagnetic coil formed by spiraling a plate-like wire cluster is disclosed. The plate-like wire cluster is constituted of a plurality of conductive lines, and the normal direction of the plane constituted of the long sides of the plate-like wire cluster on the cross-sectional view is approximately parallel to the forward direction of the spiral plate-like wire cluster, i.e., the axial direction of the spiral plate-like wire cluster. In other words, the normal direction of the wider surface of the plate-like wire cluster is approximately parallel to the forward direction of the spiral plate-like wire cluster.  
      The plurality of conductive lines could be disposed in a row to form the plate-like wire cluster. If the cross-section of the conductive line is rectangular, the long sides of the cross-sections of every pair of adjoining conductive lines are contacted to form the plate-like wire cluster.  
      When the plate-like wire cluster spirals, the discrepancy of the inner and outer radiuses of each conductive line is slight. In addition, each conductive line is substantially independent, so that even in the circumstance of bending with a large angle, some offsets between two adjoining conductive lines are allowed, thereby making the manufacturing easier.  
      In comparison with the traditional electromagnetic coil, the plate-like wire is replaced with the plate-like wire cluster and the cross-sectional area of the plate-like wire cluster is substantially equivalent to that of the plate-like wire; thus, the plate-like wire cluster can also provide a large current.  
      Moreover, to avoid the high heat generated due to the large current, the conductive lines can be replaced by hollow conductive tubes in which cooler flows inside, so as to achieve superior heat dissipation efficiency.  
      In the case of the use of conductive tubes, it is better to spiral in circles so the possible strain caused by the stress of spiraling is accounted for.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a perspective view illustrating a known electromagnetic coil.  
       FIG. 2  is a perspective view illustrating another known electromagnetic coil.  
       FIGS. 3 and 4  are perspective views illustrating the electromagnetic coil of the first embodiment in accordance with the present invention.  
       FIG. 5  is a cross-sectional view of the electromagnetic coil in accordance with the present invention.  
       FIG. 6  is another cross-sectional view of the electromagnetic coil in accordance with the present invention.  
       FIG. 7  is a perspective view illustrating the electromagnetic coil of the second embodiment in accordance with the present invention.  
       FIG. 8  is the cross-sectional view along line  2 - 2  in  FIG. 7 .  
       FIG. 9  is another perspective view illustrating the electromagnetic coil of the third embodiment in accordance with the present invention.  
       FIG. 10  is the cross-sectional view along line  3 - 3  in  FIG. 9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 3 and 4  illustrate the exploded view and assembly diagram of the electromagnetic coil in accordance with the present invention. An electromagnetic coil  30  is formed by spiraling a plate-like wire cluster  31 , and the plate-like wire cluster  31  including a plurality of conductive lines  33  spirals upward and bends on the short side in terms of the cross-section thereof. The adjoining conductive lines  33  can be either soldered or tightly pressed to make electrical conduction therebetween. The two ends of the plate-like wire cluster  31  are connected to two electrodes  32  in order to connect to an electrical power source. The electromagnetic coil  30  generates a magnetic field approximately parallel to the forward direction of the spiral plate-like wire cluster  31  as the dotted lines shown in  FIG. 4 .  
       FIG. 5  illustrates the cross-sectional view of line  1 - 1  in  FIG. 4  to show the constitution of the plate-like wire cluster  31 . The cross-section of the plate-like wire cluster  31  is rectangular; the normal direction of the plane of the long side  320  is approximately parallel to the spirally forward direction of the plate-like wire cluster  31 , i.e., parallel to the direction of the magnetic field generated by the electromagnetic coil  30 . The short side  321  of the rectangular cross-section is approximately perpendicular to the long side  320 , so that the normal direction of the plane of the short side is approximately perpendicular to the spirally forward direction of the plate-like wire cluster, i.e., perpendicular to the direction of the magnetic field generated by the electromagnetic coil  30 .  
      The plate-like wire cluster  31  can be constituted of seven copper wires  311 , i.e., conductive lines  33 , connected in a row along the long side direction of the cross-section of the plate-like wire cluster  31 . In practice, five to fifteen copper wires  311  are preferable. For each copper wire  311 , the cross-section is approximately square, so that the manufacturing difficulty caused by a large discrepancy between inner and outer radiuses of the copper wire  311  will not occur.  
      In manufacturing, one end of the seven copper wires  311  can be first soldered to one of the electrodes  32 , and the other end is soldered to the other electrode  32  after the seven copper wires  311  are spiraled. As a result, the lengths of the copper wires  311  are adjustable so as to comply with the requirements of the longer outer spiral copper wire  311  and shorter inner spiral copper wire  311 , and especially for the case of a large number of the copper wires  311 . In contrast, if only few copper wires  311  are in use, or the lengths of the inner and outer copper wires are not much different, the two ends of the copper wires  311  can be soldered to the two electrodes  32  first before the wires  311  spiral.  
       FIG. 6  illustrates the cross-sectional view of another embodiment of the plate-like wire cluster  31 . The plate-like wire cluster  31  comprises seven rectangular copper wires  411  disposed in a row, and the copper wires  411  are positioned vertically. Consequently, the long sides  422  of cross-sections of the copper wires  411  are parallel to a short side  421  of the cross-section of the plate-like wire cluster  31 , and the short sides  423  of the seven copper wires  411  constitute a long side  420  of the plate-like wire cluster  31 . As a result, the difference between the inner and outer radiuses of the plate-like wire cluster  31  while spiraling is minimized, thereby making manufacturing easier and decreasing residual stress as well. In this embodiment, the long side  422  of the copper wire  411  is between 4 to 6 millimeters (mm) whereas the short side  423  thereof is between 1 to 3 mm.  
      The copper wires  311  and  411  can be replaced by other conductive lines made of other metals or conductive materials, and the number of the wires depends on what is desired.  
      Referring to  FIG. 4  again, the plate-like wire cluster  31  can be spiraled as a rectangle to form the electromagnetic coil  30 . In such design, an over-current can be avoided as a result of the increase of the impedance resulting from the bending parts of the wire cluster  31 , so that it is more applicable in practice.  
      When the plate-like wire cluster  31  spirals completely, it can be wrapped by an insulation tape (not shown), and only the electrodes  32  are exposed for connection to a power source. Therefore, the plate-like wire cluster  31  is insulated and constrained to avoid deformation.  
      The comparison of the electromagnetic coil of the present invention and the two known electromagnetic coils is summarized in Table 1. The electromagnetic coil of the present invention has a high intensity magnetic field and is easily manufactured, and a mold is not needed to manufacture the electromagnetic coil in accordance with the present invention, so the cost can be reduced and a large electromagnetic coil can be fabricated.  
                                   TABLE 1                                           The intensity of               Load   Current   magnetic field   Manufacture                                                        Copper wire   Large   Small   Small   Easy       spiral upward       and downward       Plate wire   Small   Large   Large   Difficult                  
 
      Although the above-mentioned electromagnetic coil has the advantages of easy manufacturing and large current loading, if used in a high temperature environment or a place of inferior heat dissipation, heat dissipation may be an issue.  
       FIG. 7  illustrates the electromagnetic coil of another embodiment of the present invention, and  FIG. 8  is the cross-sectional view of line  2 - 2 . This kind of electromagnetic coil has superior heat dissipation efficiency and therefore is suitable to be used in high temperature or inferior heat dissipation environments. An electromagnetic coil  70  is formed by spiraling a plate-like wire cluster  71 , and the plate-like wire cluster  71  comprises a plurality of conductive tubes  73  spiraling upwards, wherein the plurality of conductive tubes  73  can be soldered or pressed to make the electrical conduction. The two ends of the plate-like wire cluster  71  are connected to two cooler connectors  72  to allow cooler to flow through the hollow interior  732  of the conductive tube  73  for cooling the plate-like wire cluster  71 . Furthermore, the two ends of the plate-like wire cluster  71  are connected to two electrodes  74  in order to connect to an electrical power source. The conductive tube  73  can be made of copper, which has the advantages of material availability and low cost. The electromagnetic coil  70  generates a magnetic field approximately parallel to the spirally forward direction of the plate-like wire cluster  71  as the dotted line shown in  FIG. 7 . Because the conductive tubes  73  are hollow, if the conductive tubes  73  spiral in the form of a rectangle as shown in  FIG. 4 , the conductive tubes  73  may not be as strong as a solid conductive line, and the bending portions of the conductive tubes  73  may be deformed owing to uneven stresses on the inside and the outside of the tubes  73 . Therefore, the wire cluster  71  spiraling as a circle can avoid deformation and allow the cooler to flow steadily and freely so as to increase the cooling efficiency.  
      The cross-section of the conductive tube is not limited to a round shape; a rectangular cross-section can be employed as well. As shown in  FIGS. 9 and 10 ,  FIG. 10  is the cross-sectional view of line  3 - 3  in  FIG. 9 , an electromagnetic coil  90  is formed by spiraling a plate-like wire cluster  91 , and the plate-like wire cluster  91  comprises a plurality of conductive tubes  93  spiraling upwards. The two ends of the plate-like wire cluster  91  are connected to two cooler connectors  92  to allow cooler to flow through the hollow interior  932  of the conductive tube  93  for cooling the plate-like wire cluster  91 . Furthermore, the two ends of the plate-like wire cluster  91  are connected to two electrodes  94  in order to connect to an electrical power source. As compared to  FIG. 8 , the conductive tube  93  is rectangular in the cross-sectional view, and spirals as a circle to avoid deformation or internal stress.  
      The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by those skilled in the art without departing from the scope of the following claims.