Abstract:
A method for electroplating small workpieces includes the steps of: (A) providing a rotatable barrel which has an axis of rotation and a plurality of spaced-apart partition plates disposed one above the other; (B) mounting the barrel in a plating tank with the axis of rotation being inclined with respect to a horizontal line; (C) feeding a batch of the workpieces into the barrel; and (D) allowing the workpieces to fall down by gravity from one of the partition plates to the other one of the partition plates by rotating the barrel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method and an apparatus for electroplating small workpieces. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional barrel  1  used in an electroplating process is immersed in a plating solution  22  of a plating tank  21 . The barrel  1  is formed with a plurality of perforations  14  to permit flowing of the plating solution  22  there through, and includes a conductive piece  13  at the center of the barrel  1 , a top opening  15 , and a cover plate  16  to openably close the top opening  15 . Two transmission gears  12  (only one is shown) are respectively provided on two opposite sides of the barrel  1 . 
     During electroplating, small workpieces  3 , such as screws, are put into the barrel  1  via the opening  15 , after which the opening  15  is closed by the cover plate  16 . The barrel  1  is then immersed in the plating solution  22  of the plating tank  21 . The transmission gears  12  are subsequently activated so as to rotate the barrel  1  about a horizontal axis, thereby plating the workpieces  3 . 
     However, loading and unloading of the workpieces  3  from the barrel  1  are time-consuming. In particular, the barrel  1  must be removed from the plating tank  21  and uncovered to unload the electroplated workpieces  3 . After unloading, the barrel  1  is loaded with a new batch of workpieces  3  and is then re-immersed in the plating tank  21  to proceed with electroplating. Hence, the efficiency of the aforementioned conventional electroplating process is not high. 
       FIG. 2  shows another conventional barrel  4  that extends in a plating solution  22  (shown in phantom lines) Through a driving unit  23 , the barrel  4  can be activated to rotate along a horizontal axis. The barrel  4  includes a helical partition plate  44  extending along an inner wall face of the barrel  4 . 
     After the workpieces  3  are put into the barrel  4 , the barrel  4  is rotated by the driving unit  23 , such that the workpieces  3  move forwardly along the lower side of the inner wall face of the barrel  4  and are immersed in the plating solution  22 . The electroplating process continues until the electroplated workpieces  3  are moved out of the barrel  4 . Although the workpieces  3  can be loaded into or unloaded from the barrel  4  without the need to stop rotation of the barrel  4 , since the workpieces  3  are moved along the inner wall face of the barrel  4  through the helical partition plate  44 , the tumbling movement of the workpieces  3  is limited so that the platings formed on the workpieces  3  are thin and not uniform. 
     SUMMARY OF THE INVENTION 
     Therefore, the object of the present invention is to provide a method and an apparatus for electroplating small workpieces that are capable of overcoming the aforementioned prior art drawbacks. 
     According to one aspect of this invention, a method for electroplating small workpieces comprises the steps of: (A) providing a rotatable barrel which has an axis of rotation and a plurality of spaced-apart partition plates disposed one above the other; (B) mounting the barrel in a plating tank with the axis of rotation being inclined with respect to a horizontal line; (C) feeding a batch of the workpieces into the barrel; and (D) allowing the workpieces to fall down by gravity from one of the partition plates to the other one of the partition plates by rotating the barrel. 
     According to another aspect of this invention, an apparatus for electroplating small workpieces comprises a plating tank, a barrel, and a barrel support. The barrel includes a surrounding wall, a top wall with a top inlet opening, a bottom wall with a bottom outlet opening, and a plurality of spaced-apart partition plates disposed one above the other between the top and bottom walls and spanning the surrounding wall. Each of the partition plates has a passage hole proximate to an inner side of the surrounding wall. The passage hole in each of the partition plates is staggered with the passage hole in an immediately adjacent one of the partition plates. The barrel support holds the barrel in the plating tank in an inclined position so that the partition plates are inclined with respect to a horizontal line. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a sectional view of a conventional barrel immersed in a plating solution of a plating tank; 
         FIG. 2  is a schematic side view of another conventional barrel; 
         FIG. 3  is a sectional side view of the preferred embodiment of an apparatus for electroplating small workpieces according to the present invention; 
         FIG. 4  is a sectional side view taken along line IV-IV of  FIG. 3 , illustrating one configuration of a passage hole of a partition plate; 
         FIG. 5  is a view similar to  FIG. 5 , but illustrating another configuration of the passage hole of the partition plate; and 
         FIG. 6  is an enlarged fragmentary sectional view of the preferred embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 3 to 6 , the preferred embodiment of an apparatus  5  for electroplating small workpieces  7  according to the present invention is shown to comprise a barrel support  51 , a plating tank  52  containing a plating solution  50 , a barrel  53 , a drive unit  54 , and a conveying unit  55 . 
     The barrel support  51  is provided in the plating tank  52  to support the barrel  53 , and includes a lower inclined support member  511  disposed inside the plating tank  52 , and an upper inclined support member  512  disposed above the lower inclined support member  511 . However, the present invention need not be limited to the construction of the barrel support  51  shown in  FIG. 3  and may employ any other suitable support that can rotatably and inclinedly hold the barrel  53  in the plating tank  52 . 
     The barrel  53  has an axis of rotation (L), and includes a surrounding wall  531  having a plurality of perforations  536  to permit flowing of the plating solution  50  therethrough, top and bottom walls  532 ,  533  connected respectively to top and bottom ends of the surrounding wall  531 , a top inlet opening  534  formed in the top wall  532 , a bottom outlet opening  535  formed in the bottom wall  533 , and three spaced-apart partition plates  537  disposed one above the other between the top and bottom walls  532 ,  533  and spanning the surrounding wall  531 . The barrel  53  is supported in the plating tank  52  with the axis of rotation (L) being inclined with respect to a horizontal line by the barrel support  51  so that the partition plates  537  are also inclined with respect to the horizontal line. The top wall  532  is supported rotatably by the upper inclined support member  512 , while the bottom wall  533  is supported rotatably by the lower inclined support member  511 . 
     The partition plates  537  cooperate with the surrounding wall  531  and the top and bottom walls  532 ,  533  to define first, second, third, and fourth receiving spaces ( 530   a ,  530   b ,  530   c ,  530   d ). The first receiving space ( 530   a ) is in spatial communication with the top inlet opening  534 . The fourth receiving space ( 530   d ) is in spatial communication with the bottom outlet opening  535 . Each partition plate  537  has a passage hole  539  proximate to an inner side of the surrounding wall  531 . The passage hole  539  in each partition plate  537  is staggered in an axial direction with the passage hole  539  in an immediately adjacent one of the partition plates  537 . Preferably, the passage hole  539  in each partition plate  537  is diametrically opposite to the passage hole  539  in the immediately adjacent one of the partition plates  537 . The top inlet opening  534  is staggered with the passage hole  539  in an uppermost one of the partition plates  537 , and the bottom outlet opening  535  is staggered with the passage hole  539  in a lowermost one of the partition plates  537 . 
     The passage hole  539  in each partition plate  537  may be sector-shaped, as shown in  FIG. 4 , or rectangular, as shown in  FIG. 5 . The size and shape of the passage holes  539  are not limited. As long as the size of each passage hole  539  is not too large to reduce significantly the retention time of the workpieces  7  in each receiving space ( 530   a ,  530   b ,  530   c ,  530   d ) and to decrease the effect of plating the workpieces  7 , any size and shape of the passage hole  539  may be suitably used. Preferably, the size of each passage hole  539  is smaller than one-half the area of the corresponding partition plate  537 . 
     The drive unit  54  is mounted on the upper inclined support member  512  to rotate the barrel  53  about an axis (L). 
     The conveying unit  55  includes a conveying belt  551  disposed proximate to the bottom outlet opening  535  to receive the plated workpieces  7  that fall out from the barrel  53  by virtue of gravity. The conveying unit  55  may be any conventional conveyor that can convey the workpieces  7  falling from the barrel  53 . 
     A method for electroplating the small workpieces  7  using the apparatus  5  will now be described with reference to  FIGS. 3 and 6 . 
     The barrel  53  is first placed in the plating tank  52  with the axis of rotation (L) being inclined with respect to the horizontal line by mounting the barrel  53  on the barrel support  51  so that the partition plates  537  are also inclined with respect to the horizontal line. The plating solution  50  may be varied as needed. For example, to electroplate screws, a chrome solution is generally used to form a chromium metal film layer on each screw. 
     Next, the barrel  53  is rotated at a predetermined speed about the axis of rotation (L) so that each partition plate  537  rotates to move the corresponding passage hole  539  upward and downward alternately between topmost and bottommost positions. Each partition plate  537  retains the workpieces  7  when the corresponding passage hole  539  is at the topmost position, and delivers the workpieces  7  to a lower one of the receiving spaces ( 530   a ,  530   b ,  530   c ,  530   d ) when the corresponding passage hole  539  is at the bottommost position. 
     A batch of the workpieces  7  is fed into the first receiving space ( 530   a ) via the top inlet opening  534 . Hence, the workpieces  7  are retained on the uppermost one of the partition plates  537  which has its passage hole  539  moved to the topmost position. As the barrel  53  continues to rotate, the workpieces  7  fall downward into the second receiving space ( 530   b ) and onto the adjacent partition plate  537  by virtue of gravity. This is made possible by the passage hole  539  in the uppermost one of the partition plates  537  being moved to the bottommost position and the passage hole  539  in the immediately adjacent partition plate  537  being moved to the topmost position. 
     A new batch of the workpieces  7  is fed into the first receiving space ( 530   a ) via the top inlet opening  534  after the previous batch of the workpieces  7  has fallen from the uppermost one of the partition plates  537  to the partition plate  537  immediately therebelow. Generally, whenever the barrel  53  completes one cycle of rotation, a new batch of the workpieces  7  can be fed into the barrel  53 . Hence, continuous feeding of the workpieces  7  can be performed with the apparatus  5 . There is no need to stop rotation of the barrel  53  when the workpieces  7  are loaded into the barrel  53  so that electroplating can be conducted in a highly productive manner. 
     Continued rotation of the barrel  53  causes the workpieces  7  to fall downward from the partition plates  537  one after the other and eventually from the bottom wall  533  to the conveying unit  55 . 
     Through the continuous rotation of the barrel  53 , the passage hole  539  in each partition plate  537  can move alternately at a fixed speed between the topmost and bottommost positions. Therefore, each batch of the workpieces  7  can be retained in each receiving space ( 530   a ,  530   b ,  530   c ,  530   d ) for a period of time to permit the workpieces  7  to thoroughly make contact with the plating solution  50 . As a result, the workpieces  7  can be plated gradually and uniformly layer by layer. To ensure that surfaces of the workpieces  7  are completely plated and to increase the plating thickness of the metal film layers, the time the workpieces  7  stay in each receiving space ( 530   a ,  530   b ,  530   c ,  530   d ) can be extended. In the present invention, additional partition plates  537  may be provided to increase the number of the receiving spaces ( 530   a ,  530   b ,  530   c ,  530   d ) in the barrel  53 . As such, each batch of the workpieces  7  may undergo plating for a prolonged time to achieve better surface-covering and plating thickness results. If a thick metal film layer is not desired, on the other hand, the number of the partition plates  537  can be reduced so as to shorten the plating time. 
     The description below will permit further understanding of the operation of the present invention. If it is assumed that the rotational speed of the barrel  53  is one cycle per minute, and that there are three partition plates  537  in the barrel  53  defining four receiving spaces ( 530   a ,  530   b ,  530   c ,  530   d ), for each batch of the workpieces  7  fed into the barrel  53 , the total time required to pass through the four receiving spaces ( 530   a ,  530   b ,  530   c ,  530   d ) and the bottom outlet opening  535  is 4 minutes. Because subsequent batches of the workpieces  7  can be fed respectively for each turn of the barrel  53 , when one batch of the workpieces  7  is moved out of the barrel  53 , the barrel  53  still has four batches of the workpieces  7  therein, so that in the next 4 minutes, four batches of the workpieces  7  can fall consecutively out of the bottom outlet opening  535 . It is apparent, then, that following the initial 4 minutes, electroplating may be performed at a steady rate and in a highly productive manner. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.