Abstract:
A latch type solenoid switch including a frame, a permanent magnet providing magnetic force to the frame, a coil unit which offsets the magnetic force of a permanent magnet when power is supplied, and a moving part which adheres to and detaches from the frame depending on the power supply to the coil unit. Anti-corrosion coating is applied to the surface of the frame and the moving part. The plating thickness on the contact surfaces between the frame and the moving part is thinner than on the other surfaces of the two bodies.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims the benefit of Korean Patent Application No. 2003-3254, filed Jan. 17, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a solenoid switch, and more particularly, to a latch type solenoid switch plated with anti-corrosion material and a method of plating the solenoid switch.  
           [0004]    2. Description of the Related Art  
           [0005]    A solenoid switch operates by magnetic forces applied by a permanent magnet and an electromagnet. FIG. 1 illustrates the structure of a general latch type solenoid switch.  
           [0006]    Referring to FIG. 1, the solenoid switch includes a coil unit  10 , a frame  20 , a permanent magnet  30  and a moving part  40 . The coil unit  10  includes a coil  12  wound around a cylindrical bobbin  11 , and when current is supplied to the coil unit  10 , a magnetic field is generated in a direction opposite to a magnetic field of the permanent magnet  30 . A section of the moving part  40  is inserted into the bobbin  11 , and is elastically biased away from the permanent magnet  30  by a spring  50 .  
           [0007]    In the above structure, when current is not supplied to the coil unit  10 , the moving part  40  adheres to the frame  20  due to force acting thereon in the magnetic field of the permanent magnet  30 . When current is supplied to the coil unit  10 , a magnetic field opposite to that of the permanent magnet  30  is generated in the coil unit  10 , and the moving part  40  is detached from the frame  20  by the restoration force of the spring  50 . In this way, depending on the current supply to the coil unit  10 , the moving part  40  moves in the directions indicated by the arrow in FIG. 1.  
           [0008]    In general, the frame  20  and the moving part  40  are made of steel and are plated to prevent corrosion. The layer of plating has a thickness of about 3 μm, which is very thin. If the layer of plating is too thin, chemical resistance to salt in sweat from people&#39;s hands may be too weak. In order to increase resistance against corrosion, a sufficiently thick layer of plating is necessary, but if the layer is too thick, there is a possibility of reducing the adhesion force between the moving part  40  and the frame  20  by shielding the moving part  40  from the magnetic field of the permanent magnet  30 .  
         SUMMARY OF THE INVENTION  
         [0009]    Accordingly, it is an aspect of the present invention to provide an improved solenoid switch and a method of plating the switch to effectively prevent corrosion of a moving part and a frame, without shielding the magnetic field of a permanent magnet.  
           [0010]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
           [0011]    The foregoing and/or other aspects of the present invention may be achieved by providing a solenoid switch including a frame; a coil unit to selectively generate a magnetic field; and a moving part including a first surface selectively in contact with the frame based upon the magnetic field of the coil unit, a second surface not in contact with the frame, and an anti-corrosion material coating the first and second surfaces, a thickness of the anti-corrosion material being thinner on the first surface than on the second surface.  
           [0012]    The foregoing and/or other aspects of the present invention may also be achieved by providing a method of plating a solenoid switch including a frame having a contact surface, and a moving part including a contact surface selectively in contact with the contact surface of the frame, the method including plating the frame and the moving part with a first anti-corrosion material having a first thickness; removing the first anti-corrosion material from the contact surfaces of the frame and the moving part; and re-plating the frame and the moving part with a second anti-corrosion material having a second thickness.  
           [0013]    The foregoing and/or other aspects of the present invention may also be achieved by providing an apparatus to record and/or generate data to/from an optical medium, including a fixed frame; a tray; and a tray locking device, to selectively lock/unlock the tray to the fixed frame, including a locking post fixed on the fixed frame, a first lever, rotatably installed on the tray, including a locking portion selectively locked/unlocked to/from the locking post and a cam to selectively interfere with the locking post to turn the first lever in a direction which the locking portion can lock to the locking post, a first elastic member to bias the locking portion towards the locking post, a solenoid switch, provided on the tray, including a frame including a contact surface and a non-contact surface, a moving part including a contact surface to selectively contact the contact surface of the frame and a non-contact surface not in contact with the frame, a permanent magnet disposed within the frame to generate a magnetic force to attract the moving part, a coil to selectively generate a magnetic force to offset the magnetic force of the permanent magnet, and an anti-corrosion material coating the frame and the moving part, a second lever rotatably mounted to the tray and connected to the moving part and the first lever, and a second elastic member connected to the second lever to release the locking portion from the locking post when the moving part is detached from the frame, wherein a thickness of the anti-corrosion material is thinner at the contact surfaces than at the non-contact surfaces of the frame and the moving part. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiment, taken in conjunction with the accompanying drawings of which:  
         [0015]    [0015]FIG. 1 illustrates the structure of a general solenoid switch;  
         [0016]    [0016]FIG. 2 is an exploded view of a solenoid switch according to an embodiment of the present invention;  
         [0017]    [0017]FIGS. 3 through 5 illustrate operations of a method of plating the solenoid switch of FIG. 2, according to the embodiment of the present invention;  
         [0018]    [0018]FIGS. 6 and 7 illustrate an application of the solenoid switch of the embodiment of the present invention to a tray locking device of a slim optical disc drive; and  
         [0019]    [0019]FIGS. 8 and 9 respectively illustrate locked and unlocked states of the tray shown in FIG. 6 and FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0020]    Reference will now be made in detail to the embodiment of the present invention, an example of which is illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiment is described below to explain the present invention by referring to the figures.  
         [0021]    [0021]FIG. 2 is an exploded perspective view of a latch type solenoid switch  100  according to an embodiment of the present invention.  
         [0022]    Referring to FIG. 2, a frame  120  and a moving part  130  are disposed at opposite sides of a coil section  110 . A permanent magnet  140  is connected to the frame  120 . The coil section  110  includes a coil  112  wound around twin, hollow, rectangular tubes of a bobbin  111 , and when current is supplied to the coil section  110 , a magnetic field is generated in a direction opposite to the magnetic field of the permanent magnet  140 . The frame  120  connected to the coil section  110  includes two parts: a first part  121  connects to the permanent magnet  140  and the second part includes projections  122  which are inserted a short distance into the hollow tubes of the bobbin  111 .  
         [0023]    The moving part  130  has two arms  131  which make contact with the projections  122  of the frame  120  due to attraction toward the permanent magnet  140  in the bobbin  111 . Although not shown in the drawings, the moving part  130  is elastically biased away from the permanent magnet  140  by an elastic member such as a spring.  
         [0024]    In the above structure, when no current is supplied to the coil section  110 , the moving part  130  makes contact with the frame  120  due to the attraction of the permanent magnet  140 . When current is supplied to the coil section  110 , the moving part experiences a magnetic force that counteracts that of the permanent magnet  140 . Then, the restoration force of the elastic member (not shown) causes the moving part  130  to detach from the frame  120 .  
         [0025]    The frame  120  and the moving part  130  are made of ordinary steel. Because steel is corroded by moisture or salt, the surface of the frame  120  and the moving part  130  are plated with anti-corrosion material to prevent corrosion. Anti-corrosion materials are nonferrous and have a diamagnetic composition such as nickel or copper and nickel.  
         [0026]    In order to provide effective prevention against corrosion, it is necessary for the plating to have a certain thickness. For example, if nickel or copper and nickel is used as the anti-corrosion material, the required thickness of the plating is more than 7 μm. However, in this case, the force of adhesion between the moving part  130  and the frame  120  can be decreased by the anti-corrosion material.  
         [0027]    A contact surface  132  of the moving part  130  accounts for only a very small portion of the total surface area of the moving part  130 , and likewise for a contact surface  123  of the frame  120 . Hence, it is unlikely for the contact surfaces  132  and  123  to be touched by hand during handling. Therefore, the contact surfaces  132  and  123  are less likely to corrode than other areas, even if the anti-corrosion plating is thinner on the contact surfaces  132  and  123 .  
         [0028]    According to these considerations, for the solenoid switch  100  according to the embodiment of the present invention, the contact surfaces  132  and  123  of the moving part  130  and frame  120  are plated thinner than the other surfaces of these elements. That is, the other surfaces except for the contact surfaces  132  and  123  are plated with a thickness of at least 7 μm in order to prevent corrosion, and the contact surfaces  132  and  123  are plated with anti-corrosion material to a thickness of about 3 μm to minimize reduction of the force of adhesion.  
         [0029]    The following is a detailed description of a method of plating of a solenoid switch according to the embodiment of the present invention.  
         [0030]    First, as illustrated in FIG. 3, a uniform plating layer P 1  is formed on the surface of the moving part  130  and the frame  120  with anti-corrosion material which may be nickel or copper and nickel. The thickness of the layer P 1  is about 5˜9 μm (the first thickness).  
         [0031]    Second, the plating layer P 1  on the contact surfaces  132  and  123  is removed either by grinding or by chemical means, so that all surfaces, except the contact surfaces  132  and  123 , are covered with a plating layer P 1  of about 5˜9 μm thickness (FIG. 4). In FIG. 4, the steel is exposed where needed at the contact surfaces  132  and  123 .  
         [0032]    Next, the plated surfaces of the moving part  130  and the frame  120  are re-plated with anti-corrosion material which is nickel or copper and nickel, and this forms a second plating layer P 2 . The thickness of the second plating layer P 2  is about 3 μm. Then, as illustrated in FIG. 5, the thickness of the plating is about 8˜12 μm on all surfaces except for the contact surfaces  132  and  123 , and is about 3 μm on the contact surfaces  132  and  123 .  
         [0033]    In the plating method of the present embodiment, the plating layer P 2  formed on the contact surfaces  132  and  123  is thin, so as to minimize the effect on the magnetic force of the permanent magnet  140 . However, the plating layer formed on the rest of the moving part  130  and the frame  120  P 1  and P 2  is of a reasonable thickness for the purpose of effectively preventing corrosion.  
         [0034]    This solenoid switch technology can be applied in various fields of industry. FIG. 6 shows an example of the application of the solenoid switch  100  to a tray locking device of a slim optical disc drive. FIG. 7 is an enlarged view of the tray locking device shown in FIG. 6. FIGS. 8 and 9 illustrate locking and unlocking of a tray  220 .  
         [0035]    Referring to FIGS. 6 and 7, the tray  220  is mounted on a fixed frame  210 , allowing the tray  220  to slide in and out. The tray includes a spindle motor  230  to turn a disc (not shown) and an optical pickup unit  240  which records and generates data on the disc as it slides over the surface of the disc in the directions indicated by arrows.  
         [0036]    A locking post  310  is installed on the fixed frame  210 . A first lever  320 , a first elastic body  330 , a second lever  340 , a second elastic body  350  and the solenoid switch  100  are mounted on the tray  220 .  
         [0037]    The first lever  320  rotates in both directions about a hinge unit  321  which is mounted on a hinge post  211  of the tray  220 . A working end of the first lever  320  includes a locking portion  322  which locks the tray  220  in connection with the locking post  310  when the tray  220  is loaded, while the other end of the first lever  320  includes a cam portion  325  which interferes with the locking post  310  when the tray  220  is unloaded. The locking portion  322  includes a stopper  323  to catch the locking post  310 , and a slanted protrusion  324  which turns the first lever  320  in the direction indicated by A in FIG. 7, interfering with the locking post  310  when the tray  220  is loaded. The cam portion  325  turns the first lever  320  in the direction indicated by B in FIG. 7, interfering with the locking post  310  when the locking post  310  and the locking portion  322  are uncoupled and when the tray  220  is unloaded.  
         [0038]    The first elastic body  330  provides an elastic force for the first lever  320  to enable docking between the locking post  310  and the stopper  323 , that is, to make the first lever  320  turn in the direction indicated by B in FIG. 7.  
         [0039]    The second lever  340  is rotatably mounted on the tray  220  and connected to the moving part  130  and the second elastic body  350 .  
         [0040]    The second lever  340  turns in the directions indicated by C and D in FIG. 7, interfering bilaterally with the first lever  320 . That is, the second lever  340  turns in the direction C by the elastic force of the second elastic body  350 , pushing the first lever  320  so that it turns in the direction indicated by A. However, when the first lever  320  turns in the direction indicated by B, it pushes the second lever  340  to turn in the direction indicated by D.  
         [0041]    The second elastic body  350  provides an elastic force to the second lever  340  to turn it in the direction indicated by C. The magnitude of the elastic force provided by the second elastic body  350  to the 2nd lever  340  is large enough to overcome the elastic force of the first elastic body  330  and turn the first lever  320  in direction A.  
         [0042]    In this model, the moving part  130  is in contact with the frame  120  while the tray  220  is loaded and locked to the fixed frame  210 , as indicated in FIG. 8. When current is supplied to the coil section  110 , the magnetic field of the permanent magnet  140  is offset by the magnetic field generated in the coil section  110 . Then, the elastic force of the second elastic body  350  turns the second lever  340  in direction C, detaching the moving part  130  from the frame  120 , as indicated in FIG. 9. The second lever  340  turns the first lever  320  in direction A, so that the stopper  323  is released from the locking post  310 . The tray  220  is now no longer locked. In this state, the tray  220  is unloaded.  
         [0043]    In order to maintain the tray  220  in a locked state on the fixed frame  210 , the force of adhesion between the moving part  130  and the frame  120  is stronger than the elastic force of the second elastic body  350 . As explained earlier, if the thickness of the anti-corrosion plating on the surface of the moving part  130  and on the frame  120  exceeds, for example, 7 μm, the magnetic field of the permanent magnet  140  could be blocked, thus weakening the force of adhesion between the moving part  130  and the frame  120 .  
         [0044]    In this case, one method to be considered is to employ a larger permanent magnet  140  to overcome the elastic force of the second elastic body  350 . However, the space available for the solenoid switch  100  is very limited in the slim-type optical drive, since it is designed for compact mobile computers. Therefore, the adoption of a larger permanent magnet  140  is not appropriate in this case.  
         [0045]    Another option is to reduce the elastic force of the second elastic body  350 . In this case, the locking force between the stopper  323  and the locking post  310  is weakened because it is necessary to reduce the elastic force of the first elastic body at the same time. As a result, the tray can be unlocked too easily, such as by a light impact.  
         [0046]    However, the problems described above can be solved by adopting the solenoid switch  100  of the embodiment of the present invention. The solution is for the thickness of anti-corrosion material plated on the contact surfaces  123  and  132  of the moving part  130  and the frame  120  to be, for example, as thin as about 3 μm, to minimize weakening adhesion, while the thickness of plating on other areas is about 7 μm, for example.  
         [0047]    By adopting the solenoid switch and the plating method described above, it is possible to prevent both corrosion and weakening of adhesion by plating the contact surfaces  123  and  132  more thinly than other surfaces.  
         [0048]    Although an embodiment of the present invention has been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.