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[0001]    This patent application is a continuation-in-part of Ser. No. 14/726,790 filed on Jun. 14, 2015, currently pending. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a manufacturing method of an attraction plate for electromagnetic door locks, particularly to one that manufactures an attraction plate with two convex-curve surfaces to form a curved internal stress for door locks. 
         [0004]    2. Description of the Related Art 
         [0005]      FIG. 1  is an armature for electromagnetic locks in U.S. Pat. No. 4,957,316 disclosed by Frolov. Frolov disclosed an electromagnetic lock having an electromagnet mounted to a door frame and having an armature  22  mounted to a door  10  for attraction to the electromagnet to lock the door  10 . The armature  22  has a strike plate  29  and a back plate  30 . The strike plate  29  further has a recess for engagement with an end of a bolt  25 , and the back plate  30  is disposed between the strike plate  29  and the door  10  and is penetrated through by the bolt  25  to be mounted to the door  10 . In addition, the armature  22  has a surface  39  at the reverse side of the side with the recess, and the center of the armature  22  is slightly bowed toward the surface  39  thereof within a range of 0.004-0.005 inches. Such structure allows the back plate  30  of the armature  22  to attach to the strike plate  29  in operation; however, the range of bowing between 0.004-0.005 inches does not applied to attraction plates with a different thickness other than the seven and three-eights inches suggested in Frolov&#39;s patent. According to experiments conducted by the inventor, when Frolov&#39;s invention is applied to attraction plates with different thickness, the results may not be satisfying. In other words, the thickness of attraction plates in electromagnetic locks has essential relation with bowing of armatures. 
         [0006]      FIG. 2  is an improved attraction plate structure for electromagnetic door locks disclosed by the present inventor in U.S. Ser. No. 14/149,166 filed on Jan. 7, 2014. It has an attraction plate  30  disposed on a mounted body  40  by a positioning assembly. The attraction plate  30  has a recessed portion  32  arranged on an attraction surface  31  at a central region thereof, and the recessed portion  32  further extends towards both ends  34  to form a concave-arc surface  33  on the attraction plate  30 . The concave-arc surface  33  is arranged to be lower than a horizontal plane within a range of 0.06-0.26 mm to achieve strong tensile force for applications. This application has exactly an opposite structure to the present invention; nevertheless, it can also achieve a satisfying tensile value. The application has already received a Notice of Allowability and is currently in procedure for patent issuance. 
         [0007]    In fact, apart from different designs of the attraction plate, thickness of the attraction plate also has something to do with the tensile values in such structure. Without proper numbers of the thickness, the tensile values would not achieve the best numbers in operation. Therefore, thickness of the attraction plate shall be further disclosed in accordance with a height arranged at a center of the attraction plate to obtain stronger tensile values. 
       SUMMARY OF THE INVENTION 
       [0008]    A primary object of the present invention is to provide a manufacturing method of an attraction plate for electromagnetic door locks that is able to increase a tensile value of a door lock by at least 10%, in order to achieve purposes of energy-saving and ensuring safety. 
         [0009]    To achieve the object mentioned above, the present invention comprises steps as following: a) providing an electric magnet in a long shape; b) providing a mounted body disposed at a corresponding side to the electric magnet with a positioning hole arranged in the middle thereof; c) providing an attraction plate with a thickness between 10-16 mm and a length in correspondence to the length of the electric magnet, said attraction plate including an attraction surface at a side facing the electric magnet; d) deciding a thickness of the attraction plate to determine a height of an arch portion arranged at the center on the attraction surface, the thickness of the attraction plate being inversely proportional to the height of the arch portion and the height being between 0.04-0.27 mm with the thickness of the attraction plate being between 10-16 mm; e) manufacturing the attraction plate according to pre-determined numbers of thickness and height in step d, the attraction plate having two corresponding convex-curve surfaces extending from the arch portion to both ends of the attraction plate, defining the arch portion a higher central region than both ends of the attraction plate; f) providing the attraction plate manufactured in steps c-e, which has an engaging hole correspondingly arranged to the positioning hole; and g) providing a bolt to fixedly screw the engaging hole to the positioning hole for placement of the attraction plate on the mounted body with the attraction surface thereof facing upward, defining both ends thereof as free ends. Among the steps, c)-f) are processed in advance. 
         [0010]    With structures disclosed above, the present invention has the arch design to increase a tensile value of the electric magnet for door locks instead of the conventional method of increasing electric currents or attraction area of an attraction plate and an electric magnet. Such design also has features of energy-saving and efficient functioning for better safety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram of a mounted body of a conventional electromagnetic door lock; 
           [0012]      FIG. 2  is another schematic diagram of a mounted body of a conventional electromagnetic door lock; 
           [0013]      FIG. 3  is an exploded view of the present invention in a preferred embodiment; 
           [0014]      FIG. 4  is a perspective view of the present invention in a preferred embodiment; 
           [0015]      FIG. 5  is a sectional view of the present invention in a preferred embodiment; 
           [0016]      FIG. 6  is a sectional view of the present invention in a preferred embodiment illustrating a magnet thereof in attraction with an attraction plate thereof; 
           [0017]      FIG. 7A  is a sectional view of an attraction plate structure in the present invention; 
           [0018]      FIG. 7B  is a partially enlarged view of area  7 B in  FIG. 7A ; 
           [0019]      FIG. 8A  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 10 mm; 
           [0020]      FIG. 8B  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 11 mm; 
           [0021]      FIG. 8C  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 12 mm; 
           [0022]      FIG. 8D  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 13 mm; 
           [0023]      FIG. 8E  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 14 mm; 
           [0024]      FIG. 8F  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 15 mm; 
           [0025]      FIG. 8G  is a spline chart illustrating a relationship between a height of the arch portion thereof and a thickness of the attraction plate with the attraction plate being 16 mm; and 
           [0026]      FIG. 9  is a chart concluding a preferable range of a height of the arch portion thereof with a thickness of the attraction plate ranging from 10 mm to 16 mm in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0027]    Referring to  FIGS. 3-9 , in a preferred embodiment, the present invention comprises the following steps. 
         [0028]    Step a: providing an electric magnet  20  in a long shape to be fixed to a door fame  15 . 
         [0029]    Step b: providing a mounted body  40  disposed at a corresponding side to the electric magnet  20  with a positioning hole  41  arranged in the middle thereof. The mounted body  40  can be in different design to be installed on a door plate  14 . In this embodiment, it can be a box-shaped body, a U-shaped body, a L-shaped body, a flat body; or it can be made in one piece together with the door plate  14  for attraction engagement. 
         [0030]    Step c: providing an attraction plate  30  with a thickness T between 10-16 mm and a length in correspondence to the length of the electric magnet  20 . The attraction plate  30  also has an attraction surface  31  at a side facing the electric magnet  20 . 
         [0031]    Step d: deciding a thickness T of the attraction plate  30  to determine a height h of an arch portion  32  arranged at the center on the attraction surface  31 . The thickness T of the attraction plate  30  is inversely proportional to the height h of the arch portion  32 . With the thickness T of the attraction plate  30  being between 10-16 mm, the height h is arranged between 0.04-0.27 mm. 
         [0032]    Step e: manufacturing the attraction plate  30  according to pre-determined numbers of thickness T and height h in step d. The attraction plate  30  further has two corresponding convex-curve surfaces  33  extending from the arch portion  32  to both ends  34 , defining the arch portion  32  a higher central region than both ends  34 . With reference to  FIGS. 7A and 7B , the convex-curve surfaces  33  are higher than a bottom plane L. The bottom plane L is a virtual plane formed along the lowest point of the ends  34 , and the height h of the arch portion  32  is the height from the lower bottom from the center of the arch portion  32  to the bottom plane L. With the inversely proportional relationship, the thinner the attraction plate  30  is within the 10-16 mm, the curve of the convex-curve surfaces  33  has a higher convex. The convex-curve surfaces  33  can be made by bending, stamping, shaping, or all known manufacturing method. 
         [0033]    Step f: providing the attraction plate  30  manufactured in steps c-e with an engaging hole  35  arranged thereon correspondingly to the positioning hole  41  and a pad  42  arranged between the attraction plate  30  and the mounted body  40 . 
         [0034]    Step g: providing a bolt  50  to fixedly screw the engaging hole  35  to the positioning hole  41  for placement of the attraction plate  30  on the mounted body  40  with the attraction surface  31  thereof facing upward, defining both ends  34  thereof as free ends. In this embodiment, the pad  42  is the fulcrum for both ends  34  of the attraction plate  30  being free ends on the mounted body  40 . 
         [0035]    Thereby when the attraction plate  30  contacts the electric magnet  20 , the attraction plate  30  with internal stress would be attracted, deformed and attached to the electric magnet  20  as shown in  FIG. 6 . Additionally, the steps c)-f) are processed in advance. 
         [0036]    To further illustrate the essential relationship between the thickness T of the attraction plate  30  and the height h of the arch portion  32  thereof for better tensile values, an experiment is conducted and concluded in a table below. In the table, the thickness T has a length of 185 mm, a width of 60 mm and different thickness T of 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, and 16 mm. The voltage is 12V and the electric magnet 20 has a 500 mA electric current passing through. 
         [0000]    
       
         
               
             
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Tensile values with different thickness (T) and height (h) 
               
             
          
           
               
                   
                 Thickness (T) 
               
             
          
           
               
                   
                   
                   
                 12 
                   
                   
                   
                 16 
               
               
                 Height (h) 
                 10 mm 
                 11 mm 
                 mm 
                 13 mm 
                 14 mm 
                 15 mm 
                 mm 
               
               
                   
               
             
          
           
               
                 0.00 
                 976 
                 1060 
                 1080 
                 1190 
                 1213 
                 1245 
                 1249 
               
               
                 0.01 
                 980 
                 1085 
                 1142 
                 1252 
                 1235 
                 1240 
                 1258 
               
               
                 0.02 
                 1000 
                 1102 
                 1150 
                 1252 
                 1245 
                 1248 
                 1284 
               
               
                 0.03 
                 1010 
                 1113 
                 1169 
                 1257 
                 1252 
                 1256 
                 1325 
               
               
                 0.04 
                 1044 
                 1143 
                 1201 
                 1268 
                 1274 
                 1278 
                 1394 
               
               
                 0.05 
                 1060 
                 1158 
                 1216 
                 1280 
                 1290 
                 1301 
                 1392 
               
               
                 0.06 
                 1065 
                 1181 
                 1222 
                 1287 
                 1304 
                 1387 
                 1381 
               
               
                 0.07 
                 1103 
                 1188 
                 1239 
                 1298 
                 1320 
                 1385 
                 1252 
               
               
                 0.08 
                 1117 
                 1216 
                 1269 
                 1302 
                 1376 
                 1335 
                 1248 
               
               
                 0.09 
                 1138 
                 1226 
                 1273 
                 1310 
                 1380 
                 1215 
                 1236 
               
               
                 0.10 
                 1150 
                 1227 
                 1280 
                 1359 
                 1330 
                 1145 
                 1115 
               
               
                 0.11 
                 1168 
                 1250 
                 1294 
                 1364 
                 1217 
                 1110 
                 1041 
               
               
                 0.12 
                 1184 
                 1262 
                 1315 
                 1346 
                 1187 
                 1026 
                 961 
               
               
                 0.13 
                 1197 
                 1281 
                 1330 
                 1212 
                 1145 
                 943 
               
               
                 0.14 
                 1212 
                 1290 
                 1337 
                 1152 
                 1064 
               
               
                 0.15 
                 1216 
                 1298 
                 1347 
                 1105 
                 937 
               
               
                 0.16 
                 1233 
                 1299 
                 1358 
                 1035 
               
               
                 0.17 
                 1263 
                 1314 
                 1361 
                 953 
               
               
                 0.18 
                 1276 
                 1325 
                 1298 
                 938 
               
               
                 0.19 
                 1279 
                 1343 
                 1275 
               
               
                 0.20 
                 1281 
                 1345 
                 1270 
               
               
                 0.21 
                 1285 
                 1348 
                 1241 
               
               
                 0.22 
                 1303 
                 1313 
               
               
                 0.23 
                 1318 
                 1265 
               
               
                 0.24 
                 1319 
                 1116 
               
               
                 0.25 
                 1324 
                 964 
               
               
                 0.26 
                 1344 
               
               
                 0.27 
                 1323 
               
               
                 0.28 
                 1270 
               
               
                 0.29 
                 1070 
               
               
                 0.30 
                 916 
               
               
                   
               
             
          
         
       
     
         [0037]    The values in the table are average numbers divided by 3 experiments for each combination of thickness T and height h. From the numbers we can learn that the tensile values have different results with different thickness T and height h. However, it can be further concluded as following with reference to  FIGS. 8A to 8G . 
         [0038]    The arch portion  32  has a height h between 0.22-0.27 mm when the attraction plate  30  has a thickness T of 10 mm to obtain a preferable range of strong tensile values. 
         [0039]    The arch portion  32  has a height h between 0.17-0.22 mm when the attraction plate  30  has a thickness T of 11 mm to obtain a preferable range of strong tensile values. 
         [0040]    The arch portion  32  has a height h between 0.12-0.17 mm when the attraction plate  30  has a thickness T of 12 mm to obtain a preferable range of strong tensile values. 
         [0041]    The arch portion  32  has a height h between 0.10-0.12 mm when the attraction plate  30  has a thickness T of 13 mm to obtain a preferable range of strong tensile values. 
         [0042]    The arch portion  32  has a height h between 0.08-0.10 mm when the attraction plate  30  has a thickness T of 14 mm to obtain a preferable range of strong tensile values. 
         [0043]    The arch portion  32  has a height h between 0.06-0.08 mm when the attraction plate  30  has a thickness T of 15 mm to obtain a preferable range of strong tensile values. 
         [0044]    The arch portion  32  has a height h between 0.04-0.06 mm when the attraction plate  30  has a thickness T of 16 mm to obtain a preferable range of strong tensile values. 
         [0045]    Although numbers of the tensile values would be different due to different sizes of the attraction plate  30 , the increase percentages and curves of spline charts would still remain in the same tendency since attraction plates in the markets usually have a length ranging from 180 mm to 200 mm.  FIG. 9  is a further conclusion from  FIGS. 8A to 8G  illustrating the preferable ranges of heights h of the arch portion  32  with the thickness T of the attraction plate  30  ranging from 10-16 mm. 
         [0046]    In conclusion, the present invention has the attraction plate  30  being able to increase at least 10% of tensile values with the same number of electric currents passing through the electric magnet  20  by the specific numbers obtained from experiments, so as to be applied to door locks with better safety and energy-saving features. 
         [0047]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

Summary:
A manufacturing method of an attraction plate for electromagnetic door locks has an attraction plate positioned on a mounted body with a positioning hole at the center thereof. The attraction plate further has an arch portion at the center thereof which is reversely proportional to a thickness thereof and the thickness thereof is pre-determined for manufacturing a different height of the arch portion thereof for better effects. With an internal stress from the curved design, a tensile value of a door lock is increased for better operation of a door lock.