Abstract:
A high-frequency induction hardening apparatus used for metal objects, including a heating coil holder ( 4 ) carrying a heating coil ( 40 ) for hardening a metal object ( 2 ), an eccentric rotor assemble housing a cam mechanism for allowing the heating coil to eccentrically rotate through the heating coil holder ( 4 ); and a pair of supporters ( 11 ), ( 12 ) for keeping the heating coil holder ( 4 ) in a desired position, the supporters ( 11 ), ( 12 ) limiting the movement of the heating coil holder ( 4 ) to a plane intersecting the axis ( 21 ) of the cam carried in an eccentric rotor mount ( 13 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a high-frequency induction hardening apparatus for metal objects such as metal cams, hereinafter referred to as “work”, and more particularly, to apparatus for inductively heating and hardening works. Hereinafter, the high-frequency induction hardening apparatus will be referred to as “hardening apparatus” or merely as “the apparatus”. 
     BACKGROUND ART 
     It is known that a work hardened to different depths will have a reduced strength. It is essential to harden works to an even depth over the entire surfaces. Many proposals have been made; two of the examples are disclosed in Japanese Patents No. 3,499,486 (Reference 1) and No. 3,522,636 (Reference 2). 
     The References (1) and (2) disclose an apparatus designed to harden a plurality of works, such as cams, mounted on a shaft at different angles, so as to harden their surfaces simultaneously. The apparatus disclosed there have the same structure which shares the feature of hardening works in that the oppositely located two heaters are eccentrically rotated by a single power source. Each heater is provided with a bearing having an eccentric cam, which is connected to the power source by means of a timing belt so as to effect the simultaneous heating. 
     However, a disadvantage is that the above-mentioned apparatus must require many component parts, which increase the production cost and a relatively large site for installation. 
     In order to solve the problems, the inventors of the present invention invented a hardening apparatus shown in  FIG. 1 , having a mount  50  including a heating coil  55 . The mount  50  is provided with two bearings  51  and  52  each having their own eccentric cams  53  and  54  driven by shafts  56  and  57 , respectively. The shafts  56  and  57  are synchronously rotated. By rotating the two shafts  56  and  57 , the heating coil  55  can eccentrically rotate in the same plane as a work  60 . While the heating coil  55  is in the eccentric rotation, the work  60  is heated and hardened. 
     The apparatus shown in  FIG. 1  has solved the problems of the known apparatus disclosed in the above-mentioned two literatures (1) and (2), but the difficulty is that the two shafts  56  and  57  are required to rotate in exact synchronism with each other. In order to achieve it, the cams must be made to high precision, thereby increasing the production cost and consuming time. In addition, it is difficult to continue to keep the two shafts  56  and  57  rotating in precise synchronism. Even if a small differentiation occurs between them, the heating coil fails to rotate eccentrically. 
     Therefore, it is an objective of the present invention to reduce the number of component parts and the area of the installation site, and also to ensure easy maintenance of the hardening apparatus. 
     SUMMARY OF THE INVENTION 
     To achieve the above-mentioned objective, a first version embodying the invention includes a heating coil holder for holding a heating coil for hardening a metal object, wherein the coil is held so as to be eccentrically rotative under a cam mechanism; and a supporter for keeping the heating coil in a desired position, the supporter limiting the movement of the heating coil to a plane intersecting the axis of the cam. 
     According to the first version, the heating coil holder is eccentrically rotated with respect to the work kept by limiting the movement of the heating coil holder to and along the plane by the supporter, thereby making it easy to synchronize the rotation of the cam with that of the work, with the result that the entire surface of the work is heated to an even depth. 
     A second version embodying the present invention includes a heating coil holder for holding a heating coil for hardening a metal object, wherein the coil is held so as to be eccentrically rotative under a cam mechanism; an eccentric rotor mount for supporting an eccentric rotor so as to enable the rotor to rotate eccentrically under a cam mechanism, wherein the eccentric rotor mount is integrally connected to the heating coil holder, and a supporter for keeping the eccentric rotor mount in a desired position, and urging it to rotate on and along a plane intersecting the axis of the cam mechanism. 
     According to the second version, the heating coil holder is eccentrically rotated in accordance with the eccentric rotation of the eccentric rotor with respect to the work, thereby ensuring that the entire surface of the work is heated to an even depth. 
     A third version of the invention includes a heating coil holder for holding a heating coil for hardening a metal object, wherein the coil is held so as to be eccentrically rotative under a cam mechanism; an eccentric rotor mount for supporting an eccentric rotor so as to enable the rotor to rotate eccentrically under a cam mechanism, wherein the eccentric rotor mount is integrally connected to the heating coil holder, and a supporter for supporting the eccentric rotor mount so as to move in two directions other than the axis of the cam mechanism. 
     According to the third version, as the heating coil holder can move in two directions other than the direction of the axis of the cam shaft, the heating coil heat a work to an even depth while it is in its eccentric rotation. 
     A fourth version is a modification to the second version or the third version, wherein the heating coil holder comprises a plurality of holders united as a unit, and the eccentric rotor mount comprises a plurality of mounts united as a unit, both units being integrally connected to each other. 
     According to the fourth version, a plurality of heating coils rotate in accordance with the eccentric rotation of the rotors of the mount, thereby eliminating the necessity of providing a number of eccentric rotors corresponding to that of the heating spots but ensuring that a smaller number of eccentric rotors can heat a greater number of spots on the work. 
     A fifth version is a modification to any of the first to the fourth versions, wherein the supporter comprises a first supporter and a second supporter, the first supporter moving either the heating coil holder or the eccentric rotor mount in a desired direction, and the second supporter moving the first supporter in different direction. 
     According to the fifth version, the heating coil holder and/or the eccentric rotor mount are eccentrically rotated in a plane specified by the two supporters. 
     A sixth version of the embodiment is a modification to the fifth version, wherein the direction in which either the heating coil holder or the eccentric rotor mount is moved by the first supporter intersects with the direction in which the first supporter is moved by the second supporter intersect with each other at right angle. 
     According to the sixth version, owing to the two moving directions intersecting each other at right angle, the heating coil holder and the eccentric rotor mount can be easily moved in the intersecting directions. 
     A seventh version is a modification to the fifth version or the sixth version, wherein the direction in which the heating coil holder or the eccentric rotor mount is moved by the first supporter, and the direction in which the first supporter is moved by the second supporter intersects with the axis of the cam mechanism. 
     According to the seventh version, the heating coil holder and the eccentric rotor mount can move in two directions intersecting each other, thereby causing the heating coils to rotate smoothly with little friction. 
     An eighth version is a modification to any of the first to seventh versions, wherein the cam mechanism comprises a plurality of cam members mounted on a single shaft. 
     According to the eighth version, the number of heating coils and eccentric rotors corresponding to that of the cams can be eccentrically rotated. 
     A ninth version is a modification to the eighth version, wherein each of the cam members is rotatively and integrally connected to the single shaft at a predetermined angular position. 
     According to the ninth version, the heating coil holder can be directed to the desired heating spot of the work: in other words, each cam is mounted on the same shaft, thereby causing the heating coil or the eccentric rotor to start its eccentric rotation from the predetermined angular position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a known hardening apparatus; 
         FIG. 2  is a perspective entire view of a hardening apparatus according to the present invention; 
         FIG. 3  is a perspective view of the hardening apparatus of  FIG. 2  in which the heating coils are in process of heating the work; 
         FIG. 4  is an exploded view of an eccentric rotor assembly and an eccentric rotor mount to show the relationship therebetween; 
         FIG. 5  is an exploded view of the eccentric rotor assembly and the eccentric rotor mount of  FIG. 4  when they are in operation; 
         FIG. 6  is a front view showing the relationship among a heating coil holder, an eccentric rotor assembly, and an eccentric rotor mount; 
         FIG. 7  is a front view of the same combination as that of  FIG. 6  wherein the shaft of the assembly is rotated at right angle; 
         FIG. 8  is a front view showing the same combination as that of  FIG. 7  wherein the shaft of the assembly is further rotated at right angle; 
         FIG. 9  is a front view showing the eccentric rotor mount shown in  FIG. 8  and the heating coil when the shaft of the assembly is further rotated at right angle; 
         FIG. 10A  is a front view of a modified version of the eccentric rotor assembly shown in  FIG. 6 ; 
         FIG. 10B  is a vector diagram showing the movement of the modified eccentric rotor assembly shown in  FIG. 10A ; 
         FIG. 11A  is a front view of another modified version of the eccentric rotor assembly shown in  FIG. 6 ; 
         FIG. 11B  is a vector diagram showing the movement of the modified eccentric rotor assembly shown in  FIG. 11A ; 
         FIG. 12A  is a front view of the eccentric rotor mount supported by springs; 
         FIG. 12B  is a front view showing another aspect of the eccentric rotor mount shown in  FIG. 12A ; 
         FIG. 13A  is a schematic front view showing a modified eccentric rotor assembly; and 
         FIG. 13B  is a schematic front view showing another modified eccentric rotor assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 2 ,  3  show a hardening apparatus  1  which has an eccentric rotor assembly  6  having eccentric rotors  6   a  to  6   f  respectively connected to heating coil holders  4   a  to  4   f  through bridging members  8   a  to  8   f  so that the eccentric rotations of the rotors  6   a  to  6   f  cause the heating coils  40  to rotate eccentrically. Herein, the eccentric rotor assembly  6  supports a plurality of eccentric rotor mounts  13  each of which has an eccentric rotor  6   a  to  6   f , respectively. The mount  13  is supported by a supporting frame  12  on a base  5 , the detail of which will be described by referring to  FIGS. 4 and 5 . In this way, it is ensured that the heating coil holders  4   a  to  4   f  and the eccentric rotors  6   a  to  6   f  constitute an interrelated entity. 
     In  FIGS. 2 and 3  each of the heating coil holders  4   a  to  4   f  is provided with a heating coil  40 . The bridging members  8   a  to  8   f  are located above the heating coil holders  4   a  to  4   f , each heating coil holder  4   a  to  4   f  accommodating transformers, inverters and power sources (all of them not shown for simplicity), so that the heating coils  40  are supplied with an electric current induced so as to heat the works. 
     The example shown in  FIGS. 2 and 3  uses a cam shaft  2  as a work to be hardened, which is loaded between supporting rods  9  and  10  while being passed through the coils  40  of the coil holders  4   a  to  4   f . It is difficult to harden a cam shaft to an even depth because of the various shapes of the cams. In order to achieve the equal hardening the heating coils are required to move in correspondence with the shape of the cams as the work. The cam shaft  2  can be reciprocally moved by moving the supporting rods  9  by means of servomotors  23  and  23   a , respectively. During the passage through the heating coils  40  each cam  3   a  to  3   f  of the cam shaft  2  is heated by the heating coils  40 . The number of the heating coil holders  4   a  to  4   f  (i.e. that of the heating coils  40 ) is decided as desired. 
     Either of servomotors  23  and  23   a  is operated so as to cause the cam shaft  2  rightward or leftward as it is required, or entirely withdrawn so as to avoid collision with the heating coils  40 . 
     The supporting rod  9  is rotatively supported at its one end by means of one bearing, and the supporting rod  10  is rotatively supported at its one end by another bearing, and both are moved in the same way by means of a motor  48 . The rotation of the supporting rod  10  causes the cam shaft  2  to rotate. The motor  48  reciprocally moves together with the supporting rod  10  in the latter&#39;s axial direction. 
     The supporting rods  9 ,  10  and the cam shaft  2  are coaxial, and cooling jackets  7  are held on the same axis. More specifically, the illustrated example has three cooling jackets  7  each of which has a bore  7   a  whose inside diameter is larger than the outside diameters of the supporting rod  9  and the cam shaft  2  so as to enable them to pass through the bore  7   a . The inside wall of the jacket  7  is provided with a number of pores (not shown) through which a coolant is sprayed onto the work passing through the bore  7   a . The coolant is supplied to the jacket  7  through a suitable duct (not shown). The coolant is sprayed toward and over the cam shaft  2  being processed at a given time intervals while the cooling jacket  7  is reciprocally moved along the axis of the supporting rods  9  and  10 . 
     After the cam shaft  2  is heated by the heating coil  40 , it is moved into the jacket  7  where the shaft  2  is quickly cooled by the coolant shower through the jackets  7 . 
     The eccentric rotors  6   a  to  6   f  will be described by referring to  FIGS. 4 and 5 : As described above, these rotors  6   a  to  6   f  are mounted on the eccentric rotor assembly  6 , which houses a seat  11 , a supporting frame  12  (hereinafter “frame”), eccentric rotor mounts  13 , and cams  14 . 
     The seat  11  is provided on a base  5 . In  FIG. 2  the seat  11  is omitted for explanatory convenience. The seat  11  is provided with a first guide  15  having a first guide groove  15   a  and a second guide  16  having a second guide groove  16   a . The guides  15  and  16  are straight. The frame  12  takes an L-form defined by a lower member  12   a  and an upright member  12   b  as best shown in  FIGS. 4 and 5 . The lower member  12   a  is provided with a rail  17  which is engaged with the guide grooves  15   a  and  16   a , thereby allowing the frame  12  to move leftward and rightward in  FIG. 4  with respect to the seat  11 . 
     The upright member  12   b  is provided with a guide  18  having a guide groove  18   a  and a guide  19  having a guide groove  19   a . There is provided an eccentric rotor mount  13  having a rail  20  in its right side (in  FIGS. 4 and 5 ) which is engaged with the guide grooves  18   a  and  19   a , thereby allowing the eccentric rotor mount  13  to move vertically with respect to the frame  12 . 
     In the version illustrated in  FIG. 4  the seat  11  and the frame  12  are respectively provided with two guides  15 ,  16  and  18 ,  19  but the number of these guides can be selected as desired so long as the frame  12  and the eccentric rotor mount  13  are stably supported. 
     As diagrammatically shown in  FIG. 4 , the eccentric rotor mount  13  is provided with a bore in which bearing balls  24  are provided as schematically illustrated in  FIG. 4 , the bore having the bearing balls  24  being referred to as “bore  13   a ”. The tops of each ball  24  project inside. As shown in  FIG. 5 , the bore  13   a  has a cam  14  fitted in, wherein the cam  14  is subjected to a thrusting force of the balls  24 . In this state the cam  14  can rotate on the bearing balls  24 . 
     As shown in  FIG. 4 , the cam  14  is circular, having its own bore  14   a  which is eccentrically located with respect to the center of the circular cam  14 . The bore  14   a  is provided with a key-way  14   b . The cam  14  is a positive motion cam. 
     As shown in  FIG. 5 , a shaft  21  is passed through the bore  14   a . The inside diameter of the bore  14   a  is larger than the outside diameter of the shaft  21 , which has a key-way  21   a  located corresponding to the key-way  14   b  of the cam  14 . A key  22  is fitted in the key-way  21   a , and then the cam  14  is fitted onto the shaft  21 , thereby causing the cam  14  to move in the direction vertical to the paper of  FIG. 4 ; that is, in the axial direction of the shaft  21 , where the key  22  fits in the key-way so as to fasten the cam  14  to the shaft  21  in a non-rotative manner. Thus, the cam  14  can rotate together with the shaft  21  around the axis  21   b  by operating the motor. The shaft  21  rotates in synchronism with the supporting rod  10 , which functions as a power source for the cam shaft  2 . 
     The cam  21  is provided with a number of key-ways  21   a  corresponding to that of the cams  3   a  to  3   f  of the cam shaft  2 , wherein the plurality of key-ways  21   a  are located at intervals lengthwise of the axis of the shaft  21 , not on the diametrically opposite peripheral positions of the shaft  21 . In addition, their positions are displaced from one to another at a predetermined angle (in the illustrated embodiment, at  120   o ). The arrangement of the key-ways  21   a  corresponds to the eccentric positions of the cams  3   a  to  3   f  of the heating coil holders  4   a  to  4   f . In  FIGS. 3 to 8 , a single key-way  21   a  alone is shown for explanatory convenience. At any rate, these devices are conventional, so that a detailed description will be omitted. 
     In this way the cam  14  held by the shaft  21  is inserted into the bore  13   a  of the eccentric rotor mount  13 . The inside diameter of the bore  13   a  is slightly larger than the outside diameter of cam  14 . As the shaft  21  rotates, the peripheral surface of the cam  14  eccentrically presses the inside wall of the bore  13   a  while it is sliding thereon. 
     The illustrated version has six eccentric rotor mounts  13  each being mounted on the shaft  21  through the cams  14 , wherein the cams  14  are differently directed, thereby causing the eccentric rotor mounts  13  to take different positions. In this situation, each cam  14  rotates about the axis  21   b  of the shaft  21  while it presses its mating eccentric rotor mount  13  in the eccentric direction in the sliding motion. 
     Previously, the rail  20  of the eccentric rotor mount  13  engages in the guide groove  18   a  of the guide  18  of the frame  12  secured to the seat  11  and also in the guide groove  19   a  of the guide  19 . As a result, the shaft  21  securing the six eccentric rotor mounts  13  are caused to approach the frame  12  from above, until each eccentric rotor mount  13  engages its mating frame  12 . 
     In this situation a greater part of the weight of the eccentric rotor mounts  13  is supported by the shaft  21  through the bore  13   a , and the eccentric rotor mounts  13  are held by the seat  11  and the frame  12  so as to be motionless or not rotative. 
     The shaft  21  is rotated by the servomotor  23  shown in  FIG. 2 . As is stated above, each eccentric rotor  6   a  to  6   f  is located at different angular position from each other, but each moves in the same manner, except when they position differently as the shaft  21  starts its own rotation. For illustration purpose, in  FIGS. 6 to 9 , one of the eccentric rotors  6   a  to  6   f  alone is shown to show the different eccentric positions taken by them during the rotation of the shaft  21 . 
     Suppose that in  FIG. 6  the shaft  21  is rotated anti-clockwise at right angle. As a result, the state shown in  FIG. 7  is reached, where each of the eccentric rotor mounts  13  (the bore  13   a ) is pressed by the cam  14 , and slightly moved upward by a distance Y 1  against the frame  12  which, in turn, moves rightward ( FIG. 7 ) by a distance X 1 . As a result, the eccentric rotor mount  13  moves upward by a distance Y 1 , and rightward by a distance X 1 . The dotted line in  FIG. 7  shows a position of the eccentric rotor mount  13  of  FIG. 6 . 
     As shown in  FIG. 8 , when the shaft  21  is further rotated anti-clockwise at right angle, the eccentric rotor mount  13  pressed by the cam  14  is moved upward by a distance Y 1  and leftward by a distance X 1  each from the position shown in  FIG. 7 . As a result, the eccentric rotor is moved upward by a distance Y 2  (Y 2 =Y 1 +Y 1 ) and neither rightward nor leftward. The dotted line in  FIG. 8  shows the position of the eccentric rotor mount  13  of  FIG. 6 . 
     When the shaft  21  is rotated anti-clockwise at right angle from the position shown in  FIG. 8 , the eccentric rotor mount  13  is moved downward by a distance Y 1  and leftward by a distance X 1  from the position shown in  FIG. 8 . In this way, the state shown in  FIG. 9  is reached. As a result, the eccentric rotor mount  13  is moved upward by a distance Y 1  and leftward by a distance X 1  from the position shown in  FIG. 6   
     When the shaft  21  is rotated anti-clockwise at right angle from the state shown in  FIG. 9 , the state shown in  FIG. 6  is regained. 
     As is evident from the foregoing description, the rotation of the shaft  21  causes the frame  12  of the eccentric rotor assembly  6  to move rightward or leftward with respect to the seat  11 , and also causes the eccentric rotor mount  13  to move upward and downward with respect to the frame  12 , and causes the eccentric rotor mount  13  to rotate smoothly in an eccentric manner. 
     In the illustrated embodiment six eccentric rotor assemblies  6   a  to  6   f  are secured to the shaft  21  at different angular positions (the eccentric positions) previously determined for each of the works  3   a  to  3   f  to be hardened. 
     The heating coil holders  4   a  to  4   f  are respectively held by their own mating eccentric rotors  6   a  to  6   f  through the bridging members  8   a  to  8   f ; more specifically, the coil holder  4   a  is held by the assembly  6   a  through the bridging member  8   a , and so on. As a result, by rotating the shaft  21  each heating coil holder  4   a  to  4   f  rotates along the profile of the works  3   a  to  3   f.    
       FIG. 4  shows a version where the lower part  12   a  of the frame  12  intersects with the side part  12   b  thereof at right angle but the 90° angular intersection is not always required. It can be an acute angle or an obtuse angle. 
     Referring to  FIGS. 10A and 10B , an instance of performing at an obtuse angle will be described: 
       FIG. 10A  is a front view showing the eccentric rotor mount where the lower part and the side part of the frame intersect with each other at an obtuse angle.  FIG. 10B  is a vector diagram showing a vertical component and a horizontal component of the direction in which the eccentric rotor moves along the frame  12 . 
     When the shaft  21  rotates and the eccentric rotor mount  13  vertically moves, the eccentric rotor mount  13  also moves horizontally by a vector  27  ( FIG. 10B ) against a vector  26 . Therefore, by making the quantity of horizontal movement of the frame  12  for the seat  11  equal to a distance obtained by reducing an equivalent to the vector  27  from the distance X 1  shown in  FIG. 6 , the eccentric rotor mount  13  can eccentrically rotate for each of the works  3   a  to  3   f  to be hardened. 
     Referring to  FIGS. 11A and 11B , an instance of performing at an acute angle will be described: 
       FIG. 11A  is a front view showing the eccentric rotor mount  13  where the lower part and the side part of the frame  12  intersect with each other at an acute angle.  FIG. 11B  is a vector diagram showing a vertical component and a horizontal component of the direction in which the eccentric rotor mount  13  moves along the frame  12 . 
     When the shaft  21  rotates and the eccentric rotor mount  13  vertically moves, the latter also moves horizontally by a vector  29  ( FIG. 11B ) against a vector  28 . Therefore, by making the quantity of horizontal movement of the frame  12  for the seat  11  equal to a distance obtained by adding an equivalent to the vector  29  from the distance X 1  shown in  FIG. 7 , the eccentric rotor mount  13  can eccentrically rotate for each of the works  3   a  to  3   f  to be hardened. 
     In  FIGS. 6 to 9 , the eccentric quantities of the cam  14  (the distances X 1 , Y 1 , Y 2 ) are exaggeratingly shown as compared with those of the cams  14  so as to clearly illustrate the structure of the eccentric rotor mount. In fact, the eccentric quantity of the cam  14  is equal to that of the cam  3 . 
     The hardening apparatus  1  is operated as follows: 
     First, the cam shaft  2  (the work) is loaded between the supporting rods  9  and  10  of the apparatus  1 . The supporting rods  9  and  10  can slide in their axial direction by means of the servomotors  23  and  23   a , thereby allowing the cam shaft  2  to stay between the supporting rods  9  and  10  with no heating coil  40  or any other obstructing the work  2  from being placed therebetween, wherein the supporting rod  10  passes through the heating coil holders  4   a  to  4   f . The power source is not limited to the servomotors; for example, a pneumatic cylinder may be used. 
     Before the cam shaft  2  is loaded, the cooling jacket  7  is desirably withdrawn so as to give way to the cam shaft  2 . The cooling jacket  7  also can slide along the supporting rods  9  and  10 . 
     When the cam shaft  2  has been loaded between the supporting rods  9  and  10 , they are moved so as to cause the works (cams)  3   a  to  3   f  to locate near the heating coil holders  4   a  to  4   f.    
     The cams  3   a  to  3   f  are arranged along the length of the cam shaft  2 , and the neighboring two cams  3   a  and  3   b  are paired. The angles at which the cams  3   a  and  3   b  are secured to the cam shaft  2  are different at 120° from each other, where, however, the adjacent two cams (for example, the cams  3   b  and  3   c ) are secured to the shaft  2  at the same angle. 
     Each heating coil holder  4   a  to  4   f  is eccentrically located at a position corresponding to that of its mating cam  3   a  to  3   f , so that the cams  3   a  to  3   f  are hardened to an even depth. 
     While the cam shaft  2  (the supporting rod  10 ) and the shaft  21  are synchronously rotated, the cam shaft  2  is thermally hardened. At this stage, the cooling jacket  7  is shifted to above the tray  25 . 
     When the cam shaft  2  has been heated, the cam shaft  2  is quickly shifted to the cooling jacket  7 , and the jacket  7  is caused to spray cooling liquid over the cam shaft  2 . 
     When the cam shaft  2  has been cooled the hardening process is finished. The cooling jacket  7  is withdrawn, and the supporting rods  9  and  10  are released from holding the cam shaft  2 , thereby unloading the cam shaft  2  from the apparatus  1 . Then, the sequence advances to where the next cam shaft is loaded between the supporting rods  9  and  10 . This procedure is repeated. 
     The members inter-located between the cam shaft  2  and the frame  12  can be removed from the apparatus  1 . The number, size and shape of the works to be loaded on the apparatus  1  are different as the case may be. Accordingly, the shaft  21  and the cam  14  are appropriately selected, thereby constituting the effective eccentric rotor assembly  6 . The synchronous rotations of the cam shaft  2  and the shaft  21  ensure that the distance between each cam  3   a  to  3   f  to be processed and the mating heating coil holders  4   a  to  4   f  are constant, thereby enabling the work to be hardened to an even depth. 
     A modified version of the present invention will be described by referring to  FIGS. 12A and 12B : 
     As shown in  FIG. 12A , there is provided an eccentric rotor assembly  30  having an eccentric rotor mount  31 , a cam  14 , springs  32  to  35 , and a supporting frame  41 . The eccentric rotor assembly  30  is different from the eccentric rotor assembly  6  ( FIG. 6 ) in that the behavior of the eccentric rotors are regulated in a plane, and that they are differently shaped, but both are the same in that the eccentric rotors are rotated by the cam  14 . More specifically, the eccentric rotor mount  13  employs the springs  32  to  35  as elastic members in place of the seat  11  and the frame  12 , and the shape of the eccentric rotor mount  31  is different from that of the eccentric rotor mount  13 . 
     As shown in  FIGS. 12A and 12B , the L-shaped supporting frame  41  includes a lower side  41   a  and an erect side  41   b . The frame  41  is secured to a base  5 . The eccentric rotor mount  31  is secured to the frame  41  through the springs  32  to  35  which are secured to bases  36   a ,  36   b , and sides  37   a ,  37   b  between the rotor mount  31  and the lower side  41   a  of the frame  41 , and to the bases  38   a  and  38   b ,  39   a  and  39   b  between the rotor mount  31  and the erect side  41   b  of the frame  41 . The springs  32  to  35  elastically support the rotor mount  31 . 
     Most of the weight of the eccentric rotor mount  31  is supported by the shaft  21 , and the rotor mount  31  is provided with guides (not shown) located in front and behind with respect to the paper of  FIG. 12A . Therefore, the rotation of the shaft  21  causes the rotor mount  31  to rotate eccentrically in the position shown in  FIG. 12A . 
       FIG. 12B  shows a state reached when the shaft  21  is rotated anti-clockwise at right angle from the state shown in  FIG. 12A . As shown in  FIG. 12B , the eccentric rotor mount  31  eccentrically rotates with no declines from the position indicated in dotted line to the position indicated in solid line. 
     At this stage, the springs  32  and  33  expand right upward, whereas the springs  34  and  35  contract right upward. When the shaft  21  further rotates, each spring  32  to  35  expands and contracts as required, so as to prevent the eccentric rotor mount  31  from becoming declined. 
     Another modified version will be described by referring to  13 A and  13 B: 
     An eccentric rotor mount  46  is accommodated in an eccentric rotor assembly  42  and driven by the cam  14  of the shaft  21  in the same manner as the eccentric rotor mount  13  of  FIG. 6  is. There is provided a four-joint linkwork  45  on the eccentric rotor mount  46  with its lower link being connected thereto. The upper link of the linkwork  45  is connected to a ceiling  43  by means of a spring balancer  44 . 
     The eccentric rotor mount  46  moves leftward and rightward by the linkwork  45 , and can vertically move by the spring balancer  44 . In this way, the rotation of the shaft  21  causes the eccentric rotor mount  46  to rotate smoothly with no decline. The eccentric rotor mount  46  is secured to the heating coil holder  4  by the bridging member  47 . Therefore, the eccentric rotation of the eccentric rotor mount  46  causes the heating coils  40  of the heating coil holder  4  to rotate eccentrically. 
     An eccentric rotor mount  46  of the eccentric rotor assembly  60  shown in  FIG. 13B  is driven by the cam  14  held by the shaft  21 , just like the eccentric rotor mount  13  shown  FIG. 6 . There is provided a pantograph-like member  62  connected to the upper part of the eccentric rotor mount  46 . Its upper part is connected to the supporting member  63  which is provided with a wheel  64 . The wheel  64  runs on a rail  61  horizontally held. The pantograph-like member  62  allows the eccentric rotor mount  46  to move vertically, and the wheel  64  allows it to move leftward and rightward 
     As a result, the eccentric rotor mount  46  eccentrically rotates in accordance with the rotation of the shaft  21 . Accordingly, the heating coils  40  of the heating coil holder  4  secured to the bridging member  47  can eccentrically rotate together. 
     In the foregoing description of the eccentric rotor assembly  6  and  30 , they are so arranged to ensure that even when the cam shaft  2  (the work to be hardened) rotates, the distances between the heating coils  40  and the peripheral surface of each cam  3   a  to  3   f  (the work) are kept constant. 
     In an alternative embodiment, it is possible to arrange so that those distances change in accordance with the rotation of the cam shaft  2  (the work), wherein an inverter (not shown) is employed to adjust the output of power, thereby ensuring that the works are hardened to an even depth. The output of power is adjusted in accordance with the change in the distances between the work and the heating coil; more specifically, when the distance is shortened, the output is decreased, and when it is widened, the output is increased, so as to harden the works to an even depth.