Patent Publication Number: US-2016236309-A1

Title: Rotary table

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 104202515, filed on Feb. 13, 2015. 
     FIELD 
     The disclosure relates to a rotary table, more particularly to a rotary table adapted for use in a computer numerical control machine. 
     BACKGROUND 
     Rotary table is a main component of a computer numerical control machine, and is a positioning device used when performing machining operation, such as drilling, milling, circular or linear cutting, etc., on a work piece. Rotary table can be used with index plates so as to position the work piece at a precise angle relative to the CNC machine or enable rotation of the work piece at desired time interval. For example, Taiwanese Utility Model Patent No. M492217 discloses a conventional rotary table, which includes a mounting seat defining a space, a driving shaft mounted to the mounting seat, an indexing plate fixedly connected to an end of the driving shaft and holding a work piece in place, a worm disposed in the space and connected to the driving shaft, a worm gear disposed in the space and meshing with the worm, and a driving motor mounted to the mounting seat. The driving motor is operable to rotate of the worm so as to drive rotation of the indexing plate via the worm gear. However, wear of the worm and the worm gear due to frequent or long-term usage may lead to backlash, which may adversely affect rotation of the indexing plate and may affect precision in indexing. Furthermore, dimensional tolerances of the worm and the worm gear may also affect the precision in indexing. 
     Taiwanese Utility Model Patent Publication No. 200930495 discloses another conventional rotary table that includes an indexing plate and a direct drive motor co-axially and directly connected to the indexing plate so as to directly drive rotation of the indexing plate. The direct drive motor includes an electromagnetic coil and a magnetic component. Since a fixture used with the conventional rotary table may be relatively large and heavy, a sufficient number of turns of the electromagnetic coil and a relatively strong magnetic field produced by the magnetic component are required to supply an adequate amount of torque to the fixture, thereby undesirably increasing the size and complexity of such conventional rotary table. Such conventional rotary table has higher manufacturing costs, is relatively difficult to perform maintenance and repair operations, and may interfere with the machining operation of the work piece. Moreover, since rotational speed of the fixture decreases with an increase in torque delivered to the fixture in a case where the same power output of the driving motor is transmitted, a relatively high rotational speed may be hard to achieve or maintain. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a rotary table that can alleviate at least one of the aforesaid drawbacks of the prior arts. 
     According to one aspect of the disclosure, the rotary table is adapted for use in a computer numerical control machine that includes a fixture to drive rotation of the fixture. The fixture has opposite first and second ends. The rotary table includes a first mounting seat, a first spindle, a second mounting seat, a second spindle and a motor unit. 
     The first mounting seat defines a first space. The first spindle is disposed in the first space, is rotatable about an axis, and is securely connected to the first end of the fixture. The second mounting seat is spaced apart from the first mounting seat along the axis and defines a second space. The second spindle is disposed in the second space, is rotatable about the axis, and is securely connected to the second end of the fixture. The motor unit includes a main driving motor that is directly connected to the first spindle so as to directly drive rotation of the first spindle, and an auxiliary driving motor that is for driving rotation of the second spindle. 
     The motor unit is operable in a first mode, where the main driving motor drives rotation of the first spindle and the auxiliary driving motor does not drive rotation of the second spindle, and in a second mode, where the auxiliary driving motor cooperates with the main driving motor to drive rotation of the first and second spindles so as to deliver a torque which is larger than that delivered in the first mode to the fixture to drive rotation of the fixture. 
     According to another aspect of the disclosure, the rotary table is adapted for use in a computer numerical control machine that includes a fixture. The rotary table includes a mounting seat, a spindle and a motor unit. 
     The mounting seat defines a space. The spindle is disposed in the space, is rotatable about an axis, and is adapted to be securely connected to an end of the fixture. The motor unit includes a main driving motor that is directly connected to the spindle so as to directly drive rotation of the spindle, and an auxiliary driving motor that is for driving rotation of the spindle. 
     The motor unit is operable in a first mode, where the main driving motor drives rotation of the spindle and the auxiliary driving motor does not drive rotation of the spindle, and in a second mode, where the auxiliary driving motor cooperates with the main driving motor to drive rotation of the spindle so as to deliver a torque which is larger than that delivered in the first mode to the fixture to drive rotation of the fixture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the exemplary embodiments with reference to the accompanying drawings, of which: 
         FIG. 1  is a perspective view of a CNC machine including a fixture and a first exemplary embodiment of a rotary table according to the disclosure; 
         FIG. 2  is a partly sectional view illustrating the fixture and the first exemplary embodiment; 
         FIG. 3  is a schematic view illustrating a motor unit of the first exemplary embodiment of the rotary table being driven by a control system; 
         FIG. 4  is a perspective view of the CNC machine including a modified fixture and the first exemplary embodiment; 
         FIG. 5  is a partly sectional view illustrating the modified fixture and the first exemplary embodiment; 
         FIG. 6  is a perspective view of a CNC machine including a fixture and a second exemplary embodiment of the rotary table according to the disclosure; and 
         FIG. 7  is a partly sectional view illustrating the fixture and the second exemplary embodiment; 
         FIG. 8  is a perspective view of a CNC machine including a third exemplary embodiment of the rotary table according to the disclosure; and 
         FIG. 9  is a partly sectional top view illustrating the third exemplary embodiment and a tailstock. 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail, it should be noted that like elements are denoted by the same reference numerals throughout the disclosure. 
     Referring to  FIGS. 1 to 2 , a first exemplary embodiment of a rotary table  6  according to the disclosure is adapted for use in a computer numerical control (CNC) machine  1  that includes a fixture  4 . The rotary table  6  is adapted to drive rotation of the fixture  4 , which has opposite first and second ends  401 ,  402  and on which a plurality of work pieces  100  are mounted. The CNC rotary machine  1  includes a bed  11 , a support post  13  extends upwardly from the bed  11 , a slidable stage  14  mounted on the support post  13  and slidable in a vertical direction, a processing tool  15  mounted to the slidable stage  14 , and a worktable  12 , which is disposed on the bed  11 , which is movable in a horizontal direction, and on which the rotary table  6  is disposed. 
     The rotary table  6  of the first exemplary embodiment includes a base  60 , a first mounting seat  61 , a second mounting seat  62 , a first spindle  63 , a second spindle  64 , a motor unit  600 , a gear set  67 , a brake unit  68  and two bearings  69 . The base  60  is securely mounted on the worktable  12 . 
     The first mounting seat  61  is fixedly disposed on the base  60  and defines a first space  610 . The second mounting seat  62  is fixedly disposed on the base  60 , is spaced apart from the first mounting seat  61  along an axis (X), and defines a second space  620 . The first spindle  63  is disposed in the first space  610 , is rotatable about the axis (X), and is securely connected to the first end  401  of the fixture  4  . The second spindle  64  is disposed in the second space  620 , is rotatable about the axis (X), and is securely connected to the second end  402  of the fixture  4 . In this embodiment, the second spindle  64  is formed with a through hole  641  that extends along the axis (X) and that is adapted for an electrical cable  41  of the fixture  4  to extend therethrough. 
     Each of the first and second spindles  63 ,  64  has a stepped-shaped longitudinal section (see  FIG. 2 ). The first and second spindles  63 ,  64  are securely and respectively disposed in the first and second mounting seats  61 ,  62  by virtue of the respective bearings  69 . 
     The motor unit  600  includes a main driving motor  65  and an auxiliary driving motor  66 . The main driving motor  65  is mounted to the first mounting seat  61 , and includes a first output shaft  651  co-axially and directly connected to the first spindle  63  so as to directly drive rotation of the first spindle  63 . The auxiliary driving motor  66  is mounted to the second mounting seat  62 , and includes a second output shaft  661  parallel to and spaced apart from the second spindle  64  in a horizontal direction perpendicular to the axis (X). 
     The gear set  67  is disposed in the second space  620 , and includes a first gear  671  and a second gear  672 . The first gear  671  is securely connected to and co-rotatable with the second spindle  64 . The second gear  672  meshes with the first gear  671 , is connected to and co-rotatable with the second output shaft  661 , and is driven by the auxiliary driving motor  66  to enable rotation of the second spindle  64  via the first gear  671 . In this embodiment, the speed ratio of the second gear  672  to the first gear  671  is 1:1 so as to permit the first and second spindles  63 ,  64  to rotate at the same rotational speed. 
     The brake unit  68  includes a plurality of first and second braking members  681 ,  682 . The first braking members  681  are disposed in the first mounting seat  61 , are angularly spaced apart and surround the first spindle  63 , and are operable to press against an outer surface of the first spindle  63  so as to arrest rotation of the first spindle  63 . The second braking members  682  are disposed in the second mounting seat  62 , are angularly spaced apart and surround the second spindle  64 , and are operable to press against an outer surface of the second spindle  64  so as to arrest rotation of the second spindle  64 . Since operation of the brake unit  68  is not the main feature of the disclosure, further details of the same will not be provided herein for the sake of brevity. 
     Referring to  FIGS. 2 and 3 , the first and second output shafts  651 ,  661  are controlled and driven by a control system  3  that includes a motion controller  31 , a servo driver  32  and two optical encoders  33 . The motion controller  31  and the servo driver  32  control rotation of the first and second output shafts  651 ,  661 . The optical encoders  33  are respectively connected to the first and second output shafts  651 ,  661  to obtain real-time position signals indicative of exact rotation angles of the first and second output shafts  651 ,  661  and output the position signals to the motion controller  31 . In response to reception of the position signals, the motion controller  31  modifies a command that includes rotation parameters for controlling rotation of the first and second output shafts  651 ,  661 , and that is sent to the servo driver  32 , so that the servo driver  32  drives rotation of the first and second output shafts  651 ,  661  based on the command. As such, the rotation angles of the first and second output shafts  651 ,  661  are precisely controlled. 
     The motor unit  600  is operable in a first mode, where the main driving motor  65  drives rotation of the first spindle  63  to rotate the fixture  4 , and the auxiliary driving motor  66  does not drive rotation of the second spindle  64 , and in a second mode, where the auxiliary driving motor  66  cooperates with the main driving motor  65  to drive rotation of the first and second spindles  63 ,  64  so as to deliver a torque which is larger than that delivered in the first mode to the fixture  4  to drive rotation of the fixture  4 . 
     In this embodiment, the main driving motor  65  directly drives rotation of the first output shaft  651  in the first mode. When a relatively large amount of torque is required to drive the rotation of the fixture  4 , the auxiliary driving motor  66  is actuated to drive rotation of the second spindle  64  via the gear set  67  so that a relatively large torque is delivered to the fixture  4  in the second mode. 
     It should be noted that the configuration of the fixture  4  used is not restricted to that shown in  FIGS. 1 and 2 . For example, as shown in  FIGS. 4 and 5 , the fixture  4  may be configured as a jig  7  that includes a main body  71  having two opposite ends  701 ,  702  respectively connected to the first and second spindles  63 ,  64 , and a rotatable disc  72 , which is mounted on the center of the main body  71  and on which a work piece (not shown) is mounted. The work piece can be rotated in two directions as indicated by the arrows in  FIG. 5 . 
     To sum up, a precise positioning or indexing operation of the CNC machine can be ensured since rotation of the fixture  4  is mainly and directly driven by the main driving motor  65 . Additionally, the auxiliary driving motor  66  delivers additional torque to the fixture  4  when a relatively large torque is needed for driving rotation of the fixture  4 . Moreover, servo motors that are commercially available in market can be used as the main driving motor  65  and the auxiliary driving motor  66 . As a result, the rotary table  6  of the disclosure has relatively low manufacturing costs, and is relatively easy to assemble and repair as compared with the conventional rotary table disclosed in Taiwanese Utility Model Patent Publication No. 200930495. 
     Referring to  FIGS. 6 and 7 , a second exemplary embodiment of the rotary table  6  according to the disclosure is similar to the first exemplary embodiment. The difference between the first and second exemplary embodiments resides in that the gear set  67  (see  FIG. 2 ) of the first exemplary embodiment is omitted in the second exemplary embodiment, and the auxiliary driving motor  66  is directly connected to the second spindle  64  so as to directly drive rotation of the second spindle  64 . 
     Referring to  FIGS. 8 and 9 , a third exemplary embodiment of the rotary table  6  according to the disclosure is similar to the first exemplary embodiment. The difference between the first and third exemplary embodiments resides in that the rotary table  6  of the third exemplary embodiment includes only one mounting seat  21  and one spindle  22 . The mounting seat  21  defines a space  210  that accommodates the spindle  22 . The main driving motor  65  is also mounted to the mounting seat  21  and is directly connected to the spindle  22 . The auxiliary driving motor  66  and the main driving motor  65  are disposed side by side. The first and second output shafts  651 ,  661  are parallel to and spaced apart from each other in the horizontal direction, and permit the first and second gears  671 ,  672  to be mounted thereon, respectively. As such, the auxiliary driving motor  66  drives rotation of the spindle  22  via the gear set  67 . 
     In this embodiment, a fixture  29  is securely connected to the spindle  22  and stably holds one end of the work piece  100  (see  FIG. 9 ). The CNC machine  1  is provided with a tailstock  27  that is spaced apart from the spindle  22  along the axis (X). The tailstock  27  includes a body  271  and a center  272  that is aligned with the axis (X) and that is movable back and forth along the axis (X) such that the center  272  can abut against the other end of the work piece  100  for securely holding the work piece  100  in place. 
     While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments 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.