Patent Publication Number: US-2015061238-A1

Title: Positioning board of chuck

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a machine tool, and more particularly to a positioning board of a chuck. 
     2. Description of Related Art 
     In the field of machine tool, a conventional electrode chuck usually has a first base and a second base. The first base is affixed to the machine tool, and the second base is designed to hole an object. Typically, the electrode chuck may hold different objects, so that there usually are a plurality of different second bases to hold different objects. These second bases are able to engage and disengage the first base. For repeated engagement and disengagement, the wearing between the first and second base will cause a loose engagement of the second base with the first base, and the loose engagement will decrease the precision of the machine tool. 
     Typically, a positioning board is provided between the first base and the second base to fix the problem of loose engagement.  FIG. 1  shows a conventional positioning board  1 , which has several bores  1   a  to engage posts  2   a  of a first base  2  and a plurality of elongated slots  1   b  to engage posts  3   a  of a second base  3 . The posts  3   a  of the second base  3  are flat, and a thickness thereof gradually reduces from a root to a tip thereof. With such posts  3   a  and the elongated slots  1   b , it may correct the position of the second base  3  in the engagement with the first base  2 . 
     In order to correct the position of the second base  3 , the positioning board must be a rigid board with a predetermined thickness. Such positioning board, however, will cause a friction between the posts  3   a  and sidewalls of the elongated slots  1   b . As a result, referring to  FIG. 2 , each post  3   a  only have a short potion received in the slot  1   b  that is insufficient for a stable engagement of the second base  3 . Besides, each post  3   a  only has a side contacting the sidewall of the slot  1   b  , and there is a gas G left between the other side of the post  3   a  and the other sidewall of the slot  1   b . The gaps are bad for the precise engagement as well. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above, the primary objective of the present invention is to provide a positioning board of a chuck, which provides precise engagement of the bases of the chuck. 
     In order to achieve the objective of the present invention, a positioning board for a chuck includes a board member with a positioning bore and a positioning slot. The positioning slot has a main slot and a first sub-slot connected to an end of the main slot, and the sub-slot is not parallel to the main slot. 
     The positioning slot of the positioning board provides a precise engagement of the first base with the second base. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which 
         FIG. 1  is a perspective view of the conventional chuck; 
         FIG. 2  is a sectional view of the conventional chuck, showing the engagement of the positioning board with the second base; 
         FIG. 3  is a perspective view of a first preferred embodiment of the present invention; 
         FIG. 4  is a sectional view of the first preferred embodiment of the present invention, showing the engagement of the positioning board with the second base; 
         FIG. 5  is a sectional view of a second preferred embodiment of the present invention, showing the engagement of the positioning board with the second base; 
         FIG. 6  is a sectional view of a third preferred embodiment of the present invention, showing the engagement of the positioning board with the second base; and 
         FIG. 7  is a perspective view of the third preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 3  shows a positioning board  100  of the first preferred embodiment of the present invention, which includes a board member  10  with a central bore  20 , a plurality of positioning bores  30 , and a plurality of positioning slots  40 . 
     The board member  10  is a rectangular rigid board with a predetermined thickness. The board member  10  has a first side  11  and a second side  12  opposite to the first side  11 . 
     The central bore  20  is a round though hole at a center of the board member  10 , and the positioning bores  30  are four round though holes at corners of the board member  10 . As shown in  FIG. 4 , the positioning board  100  is provided between a first base  2  and a second base  3  of a chuck. The first base  2  has several posts  2   a  for engagement with the positioning bores  30  of the positioning board  100  respectively to firmly affix the board member  10  to the first base  2 . 
     The positioning slots  40  are elongated through holes at a margin of the board member  10 . The positioning slots  40  are aligned with posts  3   a  of the second base  3  respectively. Each positioning slot  40  has a main slot  41 , a first sub-slot  42  and a second sub-slot  43 . The main slot  41  is designed for engaging the post  3   a . The main slot  41  has a first end  41   a  and a second end  41   b . The first sub-slot  42  is parallel to the second sub-slot  43 , and both of them are perpendicular to the main slot  41 . The first sub-slot  42  is connected to the first end  41   a  of the main slot  41 , and the second sub-slot  43  is connected to the second end  41   b . As shown in  FIG. 3 , the main slot  41  is connected to middle of the first and the second sub-slots  42 ,  43 , so that the positioning slots  40  are H-shaped slots, and two flexible tongues  13  are formed at opposite sides of the main slot  41 . Precisely, a width of the main slot  41  is W1, a length of the first sub-slot  42  is W2, and a length of the second sub-slot  43  is W3. W2 and W3 are equal to or greater than twice of W1. In an embodiment, W1 is 5 mm, and W2 and W3 are 10 mm. It provides the flexible tongues  13  a suitable flexibility. 
     As shown in  FIG. 4 , the posts  3   a  of the second base  3  are aligned with the main slots  41  of the positioning slots  40  and engage the main slots  41  respectively while the second base  3  is moved toward the first base  2 . At the same time, the post  3   a  bends the flexible tongues  13 , and is squeezed into the main slot  41 . The flexible tongues  13  provide no gap between the posts  3   a  and the sidewalls of the positioning slots  40  to give a precise engagement of the first base  2  with the second base  3 . 
       FIG. 5  shows a positioning board  100 A of the second preferred embodiment of the present invention, which is similar to the first preferred embodiment, except that a thickness of each flexible tongue  13 A on a board member  10 A gradually reduces from a root to a distal end thereof. In other words, the thickness of each flexible tongue  13 A is gradually thinner towards a main slot  41 A. Therefore, the flexible tongue  13 A has a high flexibility at the distal end and a high rigidity at the root. It may provide a precise and firm positioning function. 
       FIG. 6  shows a positioning board  100 B of the third preferred embodiment of the present invention, which is similar to the first and the second preferred embodiments, except that each flexible tongue  13 B on a board member  10 B has an even thickness and is thinner a thickness of the board member  10 B. The positioning board  100 B of the third preferred embodiment has the same function as above. 
       FIG. 7  shows a positioning board  100 C of the fourth preferred embodiment of the present invention, which is similar to the first preferred embodiment, except that a board member  10 C has a plurality of T-shaped positioning slots  40 C. Each positioning slot  40 C has a main slot  41 C and a sub-slot  42 C at an end of the main slot  41 C. The other end of the main slot  41 C extends to an edge of the board member  10 C, so that two flexible tongues  13 C are formed for each positioning slot  40 C. A width of the main slot  41  C is W1, and a length of the sub-slot  42 C is W2. W2 is greater than or equal to twice of W1. It provides the flexible tongues  13 C a predetermined flexibility for the same purpose as above. The flexible tongues  13 C may have a gradually reduced thickness or an even thickness as shown in  FIG. 5  and  FIG. 6 . 
     It must be pointed out that the embodiments described above are only some preferred embodiments of the present invention. All equivalent structures which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention.