Abstract:
A tool change device is applicable to a CNC machine center that includes a machining spindle and includes first and second tool change units. The first and second tool change units each include a tool magazine and a tool change arm having a gripper. As such, the tool change device of the CNC machine center is allowed to manage twice tools and the grippers are respectively mounted to different tool change arms for being simultaneously put into operation in an individually-moving and not interfering manner. When one of the grippers is operable to grip a tool-to-be-changed from the spindle, the other gripper is allowed to hold a new tool and located at a position close to the spindle for being ready for immediately change of tools. As such, the time required for a cycle of tool change is greatly reduced.

Description:
(a) TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a tool change device of a CNC (Computer Numerical Control) machine center, and more particularly to a tool change device of a CNC machine center that helps shorten the tool change time. 
       (b) DESCRIPTION OF THE PRIOR ART 
       [0002]    Referring to  FIG. 1 , a conventional CNC machine center  1  comprises a chassis  11 , a machining unit  12  that is slidably mounted to the chassis  11  and is reciprocally movable in a vertical direction, a too change unit  13  that is mounted on the chassis  11  and located at one side of the machining unit  12 , and a work table  14  that is movably mounted on the chassis  11  for receiving and retaining a work piece (not shown) thereon. The machining unit  12  comprises a spindle  121  to which a tool  10  is attachable and which is rotatable about a center axis thereof. The CNC machine center  1  has a computer system that controls, in response to instructions from a user, the operations of each of the machining unit  12 , the spindle  121 , and the work table  14 . As such, the tool  10  can be driven by the spindle  121  to rotate and to machine the work piece positioned on the work table  14 . 
         [0003]    When the work piece needs to be machined with another type of tool  10 , the tool change unit  13  is operated to change the tool for the spindle  121 . The tool change unit  13  comprises a tool magazine  131  that comprises a plurality of tools  10  arranged therein and a tool change arm  133  that is arranged between the tool magazine  131  and the spindle  121 . The tool change arm  133  is movable in the vertical direction and is also rotatable and comprises two tool grippers  134  that are respectively set at two opposite ends thereof. The computer system of the CNC machine center  1  is operable to respond to an instruction from the user to move a selected tool  10  to a tool exit port  132  of the tool magazine  133 . The tool grippers  134  are operable to respectively clamp and hold the tools  10  that are respective located on the spindle  121  and at the tool exit port  132  and then revolves 180 degrees to exchange the positions of the tool-to-be-changed  101  that is located on the spindle  121  and a new tool  102  that is supplied from the tool magazine  131 . As such, the process of tool change is completed. Details of the tool change process will be described as follows: 
         [0004]    Referring to  FIGS. 2 and 3 , to carry out tool change, the tool change arm  133  is controlled by the computer system and sets out from a home position between the tool exit port  132  of the tool magazine  131  and the spindle  121  and rotates 90 degrees to reach the position shown in  FIGS. 4 and 5 . Under this condition, the grippers  134  respectively oppose a center of the spindle  121  and the tool exit port  132  to grip a tool-to-be-changed  101  that is attached to the spindle  121  and a new tool  102  located at the tool exit port  132 . 
         [0005]    Referring to  FIGS. 6 and 7 , the tool change arm  133  slides downward to pull the tools  101 ,  102  gripped by the grippers  134  out of the spindle  121  and the tool exit port  132 . 
         [0006]    Referring to  FIGS. 8 and 9 , the tool change arm  133  rotates by 180 degrees to switch the tool-to-be-changed  101  removed from the spindle  121  to the position corresponding to the tool exit port  132  and the new tool  102  picked up from the tool magazine  131  to a position corresponding to the center of the spindle  121 . 
         [0007]    Referring to  FIGS. 10 and 11 , the tool change arm  133  slides upward again to have the new tool  102  attached to the spindle  121  and the tool-to-be-changed  101  placed in the tool exit port  132  to be stored back in the tool magazine  131 . Afterwards, the tool change arm  133  rotates 90 degrees to return to the home position shown in  FIGS. 2 and 3  to complete a tool change process with which the total rotation angle equals 360 degrees. 
         [0008]    Referring to  FIGS. 1 ,  7 , and  9 , it can be easily found from the above described process of tool change that since the grippers  134  are respectively set at two ends of the same tool change arm  133 , after one of the grippers  134  removes the tool-to-be-changed  101  from the spindle  121 , the other one of the grippers  134  must make a rotation of 180 degrees to attach a new tool  102  to the spindle  121 . This takes about a half of the time period of a tool change cycle and also makes it impossible for the gripper  134  that carries a new tool  102  to get standby at a location close to the center of the spindle  121  in order to install the new tool  102  immediately after the tool-to-be-changed  101  is removed. Thus, increasing the efficiency of the tool change process is generally limited. 
         [0009]    It can be appreciated that if the grippers  134  are arranged at different tool change arms  133 , so that when one of the grippers  134  is at a position corresponding to the spindle  121 , the other one of the grippers  134  get, in advance, a new tool  102  and get ready for tool changing at a location close to the spindle  121 . After the gripper  134  that removes the tool-to-be-changed  101  from the spindle  121  is leaving away from the position corresponding to the center of the spindle  12 , the other gripper  134  may take the position and immediately install the new tool  102 , thereby greatly saving the time period necessary for a tool change cycle. 
         [0010]    Referring to  FIG. 12 , Taiwan Utility Model Application No. 102207866 discloses a CNC machining center  2 , which, beside a first tool change unit  21  that is traditionally used, comprises an additional second tool change unit  22  that is identical to the first tool change unit  21 . The tool change units  21 ,  22  each comprise a tool magazine  211 ,  221  and a tool change arm  212 ,  222  that has two ends each comprising a gripper  213 ,  223 . However, although an advantage that the number and type of the tools  20  that can be received in the tool magazines  211 ,  221  are both doubled due to the number of the tool magazines being double can be achieved, yet the second tool change unit  22  is simply provided as a backup means for the purposes of taking the place of the first tool change unit  21  when the later is malfunctioning without shutting down the entire device for maintenance. Further, the tool change arms  212 ,  222  that each comprise two grippers  213 ,  223  may interfere with each other, or may collide the spindle  23  of the CNC machine center  2 , if they are put into operations at the same time, so that it is general impossible to achieve an operation that a tool  20  is ready to immediately change through cooperative operations of the two tool change arms  212 ,  222 . 
       SUMMARY OF THE INVENTION 
       [0011]    Thus, an object of the present invention is to provide a tool change device of a CNC machine center that helps save the time for changing tools. 
         [0012]    The present invention provides a tool change device that is applicable to being mounted to a CNC machine center. The CNC machine center comprises a chassis unit and a machining unit that is mounted to the chassis unit and is reciprocally movable along a center axis. The machining unit comprises a spindle that is mounted along the center axis to receive a tool to be removably attached thereto. The tool change device of the CNC machine center comprises a first tool change unit, and a second tool change unit. 
         [0013]    The first tool change unit is arranged at a side of the center axis and comprises a first tool magazine that receives and holds therein a plurality of tools and has a tool exit port and a first tool change arm arranged between the spindle and the first tool magazine. The first tool change arm comprises a first fixed end and a first tool gripper that is distant from the first fixed end and selectively and releasable grips a tool. 
         [0014]    The second tool change unit is arranged at an opposite side of the center axis and comprises a second tool magazine that receives and holds a plurality of tools and has a tool exit port and a second tool change arm arranged between the spindle and the second tool magazine. The second tool change arm comprises a second fixed end and a second tool gripper that is distant from the second fixed end and selectively and releasably grips a tool. 
         [0015]    The first and second tool grippers are operable to rotate about the first and second fixed ends so as to each circulate between the spindle and the respective tool exit port to have a tool attached to the spindle and one of the tools of the first and second tool magazines exchange with each other in such a way that the first and second tool grippers do not contact each other during the rotation thereof. 
         [0016]    The efficacy of the present invention is that the tool change device of the CNC machine center comprises two grippers that are respectively arranged on different tool change arms so that the tool change arms are operable simultaneously to cooperate with each other for shortening the time required for a tool change process thereby achieving an advantage of greatly improving the performance of manufacturing. 
         [0017]    The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the following detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. Throughout the specification and drawings identical reference numerals refer to identical or similar parts. 
         [0018]    Many other advantages and features of the present invention will become manifest to those versed in the art upon making reference to the detailed description and the accompanying sheets of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a front view showing components of a conventional CNC machine center. 
           [0020]      FIG. 2  is a front view illustrating a tool change arm of the CNC machine center located at a home position and between a tool magazine and a spindle of the CNC machine center. 
           [0021]      FIG. 3  is a top view of  FIG. 2 . 
           [0022]      FIG. 4  is a front view illustrating the tool change arm rotating by 90 degrees and two grippers of the tool change arm respectively corresponding to a tool exit port of a tool magazine and a spindle center and each gripping a tool. 
           [0023]      FIG. 5  is a top view of  FIG. 4 . 
           [0024]      FIG. 6  is a front view illustrating the tool change arm sliding downward to pull the tools out of the tool exit port and the spindle. 
           [0025]      FIG. 7  is a top view of  FIG. 6 . 
           [0026]      FIG. 8  is a front view illustrating the tool change arm rotating by 180 degrees so that the grippers exchange the tools of the tool exit port and the spindle. 
           [0027]      FIG. 9  is a top view of  FIG. 8 . 
           [0028]      FIG. 10  is a front view illustrating the tool change unit sliding upward to have the tools respectively set to the tool magazine and the spindle. 
           [0029]      FIG. 11  is a top view of  FIG. 10 . 
           [0030]      FIG. 12  is a front view showing components of a conventional CNC machining center. 
           [0031]      FIG. 13  is a front view showing a tool change device according to a preferred embodiment of the present invention mounted to a CNC machine center. 
           [0032]      FIG. 14  is a front view illustrating a first tool gripper and a second tool gripper of the preferred embodiment of the tool change device, wherein the first and second tool grippers are respectively at a home position and a magazine position. 
           [0033]      FIG. 15  is a top view of  FIG. 14 . 
           [0034]      FIG. 16  is a front view illustrating the first tool gripper rotating 90 degrees to reach a spindle position to grip a tool-to-be-changed and the second tool gripper picking up a new tool from a second tool magazine of the preferred embodiment. 
           [0035]      FIG. 17  is a top view of  FIG. 16 . 
           [0036]      FIG. 18  is a front view illustrating the first tool gripper removing the tool-to-be-changed and the second tool gripper rotating to a location close to the spindle position for being ready for tool change. 
           [0037]      FIG. 19  is a top view of  FIG. 18 . 
           [0038]      FIG. 20  is a front view illustrating the first tool gripper leaving the spindle position and rotating to the magazine position and the second tool gripper taking the spindle position to install the new tool. 
           [0039]      FIG. 21  is a top view of  FIG. 20 . 
           [0040]      FIG. 22  is a front view illustrating the first tool gripper placing the tool-to-be-changed back into a first tool magazine of the preferred embodiment and the second tool gripper rotating 90 degrees back to           the home position. 
           [0041]      FIG. 23  is a top view of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    The following descriptions are exemplary embodiments only, and are not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention as set forth in the appended claims. 
         [0043]    Referring to  FIG. 13 , the present invention provides a tool change device for a CNC (Computer Numerical Control) machine center of which a preferred embodiment described herein is applicable to a CNC machine center  3  and comprises a first tool change unit  4  and a second tool change unit  5 . The CNC machine center  3  comprises a chassis unit  31 , a work table  32  that is movably mounted on the chassis unit  31  to receive a work piece (not shown) to be positioned and retained thereon, and a machining unit  33  that is mounted to the chassis unit  31  and is reciprocally movable along a center axis L 0 . The machining unit  33  comprises a spindle  331  that is mounted along the center axis L 0  to receive a tool  60  to be removably attached thereto. The spindle  331  is rotatable about the center axis L 0  to drive the tool  60  attached thereto to rotate. The work table  32 , the machining unit  33 , and the spindle  331  are controlled by a computer system of the CNC machine center  3  to carry out operations according to instructions from a user in order to proceed with operations of milling, drilling, or grinding on the work piece retained on the work table  32 . 
         [0044]    The instant embodiment is described with reference to a vertical CNC machine center  3  that is taken as an example for illustration. Thus, the machining unit  33  is set to reciprocally move in a vertical direction. However, the present invention is not limited to such an example and in a practical application, the present invention is equally applicable to a horizontal CNC machine center (not shown). 
         [0045]    When the work piece needs to be machined with other types of tools  6 , the first and second tool change units  4 ,  5  are operable to change tools for the spindle  331 . The first tool change unit  4  is mounted on the chassis unit  31  and is arranged at one side of the center axis L 0 . The second tool change unit  5  is mounted on the chassis unit  31  and is arranged at an opposite side of the center axis L 0 . Since the CNC machine center  3  is of a vertical configuration in the instant embodiment, the first and second tool change units  4 ,  5  are respectively set at the left hand side and the right hand side of the chassis unit  31  of the CNC machine center  3 . 
         [0046]    The first tool change unit  4  comprises a first tool magazine  41  that receives and holds therein a plurality of tools  60 , a first toothed cam drive mechanism  42  arranged between the spindle  331  and the first tool magazine  41 , and a first tool change arm  43  that is movably mounted to the first toothed cam drive mechanism  42 . The first tool magazine  41  comprises a plurality of tool holders  411  that is arranged in an annular configuration and a tool striking mechanism  412 . The first tool change arm  43  comprises a first fixed end  431  and a first tool gripper  432  that is distant from the first fixed end  431  and selectively and releasable grips a tool  60 . 
         [0047]    The tool holders  411  are provided for receiving and holding a set of tools  60  and are driven by the first toothed cam drive mechanism  42  to rotate. The computer system of the CNC machine center  3  is operable to have a selected one of the tools  60  and the tool holder  411  thereof to rotate to a lowermost position, where the tool  60  is forced out of the tool holder  411  by the tool striking mechanism  412 . As such, the tool  60  can be driven to extend out of the first tool magazine  41  via a tool exit port  413  to be gripped by the first tool change arm  43 . 
         [0048]    The second tool change unit  5  comprises a second tool magazine  51  that receives and holds therein a plurality of tools  60 , a second toothed cam drive mechanism  52  arranged between the spindle  331  and the second tool magazine  51 , and a second tool change arm  53  that is movably mounted to the second toothed cam drive mechanism  52 . The second tool magazine  51  comprises a plurality of tool holders  511  that is arranged in an annular configuration and a tool striking mechanism  512 . The second tool change arm  53  comprises a second fixed end  531  and a second tool gripper  532  that is distant from the second fixed end  531  and selectively and releasable grips a tool  60 . 
         [0049]    The second tool change unit  5  comprises components and the functions associated therewith that are substantially identical to those of the first tool change unit  4  so that repeated description will be omitted herein. The tool striking mechanism  512  of the second tool change unit  5  is similarly operable to force a selected one of the tools  60  out of a tool exit port  513  to be gripped by the second tool change arm  53 . 
         [0050]    The first and second tool grippers  432 ,  532  are respectively controlled by the computer system of the CNC machine center  3  and driven by the first and second toothed cam drive mechanisms  42 ,  52  to proceed with vertical movement and rotation with respect to the chassis unit  31 . To make movement, the first tool gripper  432  moves, reciprocally, along a first axis L 1  that extends through the first fixed end  431  and is parallel to the center axis L 0  and the second tool gripper  532  moves, reciprocally, along a second axis L 2  that extends through the second fixed end  531  and is parallel to the center axis L 0 . To make rotation, the first and second tool grippers  432 ,  532  respectively rotate about the first and second axes L 1 , L 2  to circulatively rotate between the spindle  331  and the respective tool exit port  413 ,  513 . 
         [0051]    As such, the first and second tool grippers  432 ,  532  each are circulatively rotatable among a home position, a spindle position, and a magazine position of its own. The spindle positions of the first and second tool grippers  432 ,  532  overlap each other. When located at the spindle position, the first and second tool grippers  432 ,  532  each oppose the spindle  331 , where the first and second tool grippers  432 ,  532  are each movable downward and remove a tool-to-be-changed  61  from the spindle  331  or movable upward to attach a tool  62  to the spindle  331 . When located at the magazine positions, the first and second tool grippers  432 ,  532  respectively oppose the tool exit ports  413 ,  513  and are movable upward to place the tools-to-be-changed  61  removed from the spindle  331  into the tool exit ports  413 ,  513  or movable downward to pick up news tool  62  from the tool exit ports  413 ,  513 . 
         [0052]    As such, the first and second tool grippers  432 ,  532  are operable to exchange the tools-to-be-changed  61  that are attached to the spindle  331  and the new tools  62  that extend out of the first and second tool magazines  41 ,  51  with each other and the first and second tool grippers  432 ,  532 , when in rotation, do not contact each other. The tool change operations of the first and second tool grippers  432 ,  532  will be described as follows: 
         [0053]    Referring to  FIGS. 14 and 15 , the first tool gripper  432  starts from the home position. When the first tool gripper  432  is located at the home position, the second tool gripper  532  is located at the magazine position and corresponds to the tool exit port  513  of the second tool magazine  51  to grip a new tool  62  extending out of the tool exit port  513 . 
         [0054]    Referring to  FIGS. 16 and 17 , the first tool gripper  432  rotates 90 degrees and reaches the spindle position to correspond to the spindle  331  and grip a tool-to-be-changed  61  attached to the spindle  331 . At the same time, the second tool gripper  532  moves downward to pick up the new tool  62  from the second tool magazine  51 . 
         [0055]    Referring to  FIGS. 18 and 19 , the first tool gripper  432  that is located at the spindle position moves downward to remove the tool-to-be-changed  61  from the spindle  331 . At the same time, the second tool gripper  532  rotates from the magazine position to a location adjacent to the spindle position to get ready for changing the tool and under this condition, the rotation angle for the second tool gripper  532  to reach the spindle position is less than 90 degrees. 
         [0056]    Referring to  FIGS. 20 and 21 , the first tool gripper  432  leaves from the spindle position and moves toward the magazine position. Due to the rotation angle thereof away from the spindle position being relatively small, the second tool gripper  532  can immediately occupy the spindle position that just got vacant when the first tool gripper  432  left and moves upward to attach the new tool  62  to the spindle  331 . 
         [0057]    Referring to  FIGS. 13 ,  22 , and  23 , the first tool gripper  432  reaches the magazine position and moves upward to place the tool-to-be-changed  61  that is removed from the spindle  331  through the tool exit port  413  back into the first tool magazine  41  and then picks up a tool  60  necessary for the next machining operation. The second tool gripper  532 , after having the new tool  62  attached, leaves the spindle position and rotates 90 degrees to reach the home position. Under this condition, the first and second tool grippers  432 ,  532  are both away from the spindle position, so that the spindle  331  is allowed to descend to proceed with machining of the work piece retained on the work table  32  with the new tool  62 . To this point, the ending positioning of the first and second tool grippers  432 ,  532  are exactly opposite to the starting points shown in  FIGS. 16 and 17 . It can be readily appreciated that in the next cycle, the operations of the first and second tool grippers  432 ,  532  will be switched and go through the processes illustrated from  FIGS. 16 and 17  to  FIGS. 22 and 23  and repeatedly cyclically to allow the first and second tool grippers  432 ,  532  to work in combination with each other to complete all the necessary processes of tool changes for the spindle  331 . 
         [0058]    In summary, the present invention has an advantages of possessing two sets of tool magazines of a conventional CNC machine center and can realize storage and management of a great number of diversified tools. Further, when one of the first and second tool grippers  432 ,  532  is set at the spindle position for removing the tool-to-be-changed  61  from the spindle  331 , the other one is holding a new tool  62  at a location between the magazine position and the spindle position, preferably at a position between the home position and the spindle position so that a rotation angle to reach the spindle position is made extremely small. Thus, when the former leaves the spindle position, the later may take the position immediately without any undesired rotation of 180 degrees of the tool change arms as that required by the conventional CNC machine center that completes the tool change process with a waste of around half of the time of a cycle. Thus, the present invention can effectively reduce the time required for each tool change operation and greatly increases the speed of tool change, so that the present invention can meet the need for machining of work pieces of highly complicated shapes and is suitable for long-term machining operations. 
         [0059]    It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
         [0060]    While certain novel features of this invention have been shown and described and are pointed out in the annexed claim, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention.