Patent Publication Number: US-2012045975-A1

Title: Lens-processing device

Description:
TECHNICAL FIELD 
     The present invention relates to a highly versatile lens-processing device that can polish, cut, or otherwise process a lens surface using a variety of processing methods. 
     BACKGROUND ART 
     Well-known conventional methods for processing lens surfaces include Oscar-type, inclined-axis-type, spherical-oscillation-type, and planetary-oscillation-type methods. The optimal processing method is chosen from among these processing methods according to the shape, material, and other properties of the lens; and the lens surface is processed using a lens-processing device that is specialized for processing using the selected processing method. Conventionally, lens-processing devices of various formats must therefore be separately prepared, and problems are accordingly presented in that equipment costs and installation space increase, which presents economic drawbacks. 
     In Patent Document 1 (Japanese Patent No. 3981326), the present applicants proposed a lens-processing device that can precisely move a plate-shaped or cup-shaped lens-processing tool along a desired trajectory without using a cam mechanism, and that can process a lens surface using a variety of processing formats. In this lens-processing device, the downward-oriented processing surface of a lens-processing tool is pressed against the lens to be processed from below, and processing is performed. The lens is held horizontally by suction on a downward-oriented lens-holding surface of a lens holder and is held from above with respect to the processing surface of the upward-oriented lens-processing tool. The movement of the lens-processing tool in a Z-axis direction (vertical direction), the movement in an X-axis direction (horizontal direction), and swiveling about a θ-axis that is perpendicular to the Z-axis and the X-axis are controlled, whereby the lens surface can be processed using a variety of lens-processing methods. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         [Patent Document 1] Japanese Patent No. 3981326 
       
    
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     In Oscar-type, inclined-axis-type, and planetary-oscillation-type lens-processing devices that are conventionally used for processing curved lens surfaces, the lens cannot be maintained in a horizontal state when the axis of rotation of the lens-processing tool and the lens holder shaft are inclined at a predetermined angle. During processing, the lens moves in a rotary fashion following the rotation of the lens-processing tool, and a force for returning the lens to the horizontal state is always in effect due to the inertial force resulting from the rotation. The pressing stress that is generated between the lens and the lens-processing tool is therefore not uniform, and the processing precision of the lens-processing surface is reduced. 
     During replacement of the lens, when the axis of rotation of the lens-processing tool and the lens holder shaft are inclined, the lens may fall from the processing surface of the lens-processing tool and break when pressure on the lens holder shaft is released, and the pressing force of the lens on the lens-processing tool is removed. 
     If the orientation of the lens at the completion of processing is not fixed, difficulties will be encountered in attaching or detaching the lens using automatic conveying devices, and the lens will inevitably have to be replaced by hand. Automating lens replacement and increasing the efficiency of the operation is therefore impossible. 
     In light of the above, it is an object of the present invention to allow a curved lens surface to be processed using a variety of processing formats while always maintaining the lens in a horizontal state in a lens-processing device in which the lens is held by suction on a lens holder that is supported so as to allow rotation and oscillation interposed by a pivot bearing on a distal end of the lens holder shaft, and in which the lens and a lens-processing tool are made to move relative to each other; and the curved lens surface is processed in a state in which the lens-processing tool is pressed against the lens. 
     Means Used to Solve the Above-Mentioned Problems 
     In order to solve the aforementioned problems, a lens-processing device of the present invention is characterized in comprising: 
     a lens-holder shaft extending in a vertical direction; 
     a lens holder capable of rotating and oscillating about a pivot bearing, the lens holder being attached coaxially and in a downward orientation to a lower end of the lens-holder shaft interposed by the pivot bearing; 
     a Z-axis movement mechanism for moving the lens-holder shaft in a Z-axis direction, the Z-axis direction being the vertical direction; 
     an X-axis movement mechanism for moving the lens-holder shaft in an X-axis direction, the X-axis direction being a horizontal direction; 
     a lens-processing tool having a convex or concave circular-arc shaped processing surface positioned in an upward orientation for processing a lens held by the lens holder; 
     a θ-axis-swiveling mechanism for causing the lens-processing tool to swivel about a θ-axis, the θ-axis extending in a horizontal direction perpendicular to the X-axis; 
     a lens-processing-tool-rotating mechanism of the lens-processing tool for causing the lens-processing tool to rotate about a center axis, the center axis passing through the θ-axis; 
     drive-control means for controlling driving of the X-axis movement mechanism, the Z-axis movement mechanism, and the θ-axis-swiveling mechanism; and controlling movement in the X-axis direction of the lens holder attached to the lens-holder shaft, movement of the lens holder in the Z-axis direction, and swiveling of the lens-processing tool about the θ-axis, whereby a plurality of types of lens-processing modes are executed. 
     The lens-processing device of the present invention is characterized in that the lens-processing modes of the drive-control means includes a lens-processing mode for controlling driving of the X-axis movement mechanism, the Z-axis movement mechanism, and the θ-axis-swiveling mechanism so that the lens to be processed is pressed from above in a horizontal state onto the circular-arc-shaped processing surface of the lens-processing tool, the lens being held on a lens-holding surface of the lens holder, and the lens-processing tool swiveling about the θ-axis. 
     In the lens-processing device of the present invention, an operation for feeding the lens holder in two perpendicular directions (the Z-axis and X-axis directions) can be used to move a lens to be processed along a desired trajectory on a vertical plane that includes the Z-axis and the X-axis. The lens is held by suction on the lens holder. The circular-arc-shaped processing surface of the lens-processing tool can also be made to swivel along a circular trajectory about the θ-axis on the vertical plane. Lens-processing modes can therefore be implemented in which the lens surface is processed while the lens is maintained pressing from above in a horizontal state on the circular-arc-shaped processing surface of the lens-processing tool. 
     The lens-processing device of the present invention preferably comprises a Y-axis movement mechanism for moving the lens-processing tool in a direction of a Y-axis, the Y-axis being parallel to the θ-axis. 
     The Y-axis movement mechanism is used to hold the lens-processing tool in a desired position in the Y-axis direction. The lens holder is moved back and forth in the X-axis direction by the X-axis movement mechanism at this position, whereby the lens surface can be processed using a lens-processing mode that corresponds to a conventional Oscar format. Separately controlling the X-axis movement mechanism, the Z-axis movement mechanism, and the θ-axis-swiveling mechanism, and moving and immobilizing the lens holder and the lens-processing tool at predetermined positions allows the lens surface to be processed using a lens-processing mode that corresponds to a conventional inclined-axis-type. 
     Effect of the Invention 
     According to the lens-processing device of the present invention, lens processing can be performed using lens-processing modes in which the lens surface is processed such that the lens is always maintained in a horizontal state. In these lens-processing modes, the pressing stress of the lens on the circular-arc-shaped processing surface of the lens-processing tool is uniform on all the portions of the lens surface. When the pressing force on the lens holder shaft is removed, and the lens that is held by suction on the lens holder that is supported on the end thereof is released, the lens does not fall and break along the circular-arc-shaped processing surface of the lens-processing tool. The position of the lens is always horizontal at the completion of processing, and therefore the work of replacing the lens on the lens holder can be efficiently performed using an automated conveying device. 
     The lens-processing device of the present invention allows processing using Oscar-type, inclined-axis-type, planetary-oscillation-type, and a variety of other types of lens-processing modes using a single machine. The lens-processing device is therefore highly versatile. Lens-processing devices of various formats therefore need not be separately prepared; therefore, equipment costs and installation space can be planned for in an extremely economical fashion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a mechanistic diagram of a lens-processing device in which the present invention is applied; 
         FIG. 2  is a descriptive diagram that shows a lens-processing mode in which the lens is maintained in a horizontal state according to the lens-processing device of  FIG. 1 ; and 
         FIG. 3  is a descriptive diagram that shows a different lens-processing mode according to the lens-processing device of  FIG. 1 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Embodiments of a lens-processing device in which the present invention is applied will be described below with reference to the drawings. 
     As described in  FIGS. 1 and 2 , a lens-processing device  1  according to the present embodiment has an upper axial unit  10 , a lower axial unit  30  that is positioned directly below the upper axial unit  10 , a conveyor unit  50  that is positioned at a height between the upper axial unit  10  and the lower axial unit  30 , and a drive control unit  70  that governs drive control of the various parts. 
     The upper axial unit  10  holds a lens holder  12  in a downward-oriented state, where the purpose of the lens holder is to hold a lens  11  to be processed. The lower axial unit  30  holds a lens-processing tool  31  in an upward-oriented state, where the lens-processing tool is used for processing the lens surface. The conveyor unit  50  supplies the lens  11  to be processed to the lens holder  12  and retrieves the lens  11  from the lens holder  12  after the completion of processing. 
     The upper axial unit  10  is provided with a lens-holder shaft  13  that is positioned in the vertical direction. The lens holder  12  is attached in a downward-oriented state to a lower end of the lens-holder shaft  13  interposed by a pivot-shaft-bearing mechanism  14 . The lens  11  to be processed can be, e.g., held by suction on a downward-oriented lens-holding surface  12   a  of the lens holder  12  using a vacuum. 
     The upper axial unit  10  is provided with an X-axis movement mechanism  15  for feeding the lens-holder shaft  13  along an X-axis direction that extends in a horizontal direction, and a Z-axis movement mechanism  19  for feeding the lens-holder shaft  13  along a Z-axis direction that extends in a vertical direction. In the present example, the X-axis movement mechanism  15  is provided with an X-axis guide  16  that extends in the horizontal direction; an X-axis table  16   a  that can slide in the X-axis direction along the X-axis guide  16 ; an X-axis feed screw  17  for feeding the X-axis table  16   a  in the X-axis direction; and an X-axis servo motor  18  that serves as a drive source. The Z-axis movement mechanism  19  is provided with a Z-axis guide  20  that extends in the vertical direction perpendicular to the X-axis and that attaches to the front surface of the X-axis table  16   a ; a Z-axis table  20   a  that can freely slide in the Z-axis direction along the Z-axis guide  20 ; a Z-axis feed screw  21  for feeding the Z-axis table  20   a  in the Z-axis direction; and a Z-axis servo motor  22  that serves as a drive source. 
     A holder-shaft base  23  is fixed on the Z-axis table  20   a  of the Z-axis movement mechanism. The holder-shaft base  23  rotatably supports the lens-holder shaft  13  in a vertical state. The lens-holder shaft  13  is always urged downward by a holder-pressing spring  24 . The pressing force of the holder-pressing spring  24  can be adjusted using a pressure-adjusting bolt  25 . Besides a spring, the method of pressing may also employ a weight, a pneumatic cylinder, or a hydraulic cylinder. The lens-holder shaft  13  can also be made to rotate about a center axis line  13   a  thereof using a holder-shaft-driving motor  26  that is mounted on the holder-shaft base  23 . 
     Various types of structures can be employed as the pivot-shaft-bearing mechanism  14  between the lens-holder shaft  13  and the lens holder  12 . The lens holder  12  should be attached in a state that allows oscillation about a back-surface position  12   b  that is supported by the lens-holder shaft  13  and that allows rotation about the center axis line  13   a . When the lens  11  is held on the lens-holding surface  12   a  of the lens holder  12  by suction using a vacuum, the vacuum-suction line for applying vacuum suction to the lens  11  must be formed to pass through the lens-holder shaft  13  and the pivot-shaft-bearing mechanism  14  and open on the lens-holding surface  12   a  of the lens holder  12 . The pivot-shaft-bearing mechanism  14  that is employed should be appropriate for forming such a vacuum-suction line. 
     The lower axial unit  30  is provided with a θ-axis swiveling mechanism  33  for causing the lens-processing tool  31  to swivel about a θ-axis  32  that extends horizontally in a forward-and-backward direction that is perpendicular to both the X-axis and the Z-axis; and a Y-axis movement mechanism  36  for causing the lens-processing tool  31  to move in a horizontal direction that is parallel to the θ-axis  32 . The θ-axis swiveling mechanism  33  is provided with a θ-axis servo motor  34  that is provided with a rotating shaft  34   a  that rotates about the central axis line of the θ-axis  32 ; and an L-shaped θ-bracket  35  attached to a distal end of the rotating shaft  34   a . The Y-axis movement mechanism  36  is provided with a spindle case  37  and a Y-axis microhead  38 , which defines the position of the spindle case  37  in the Y-axis direction. The spindle case  37  is mounted on the θ-bracket  35  in a state that allows movement in the Y-axis direction. 
     A spindle  39  is rotatably supported in the spindle case  37 . The spindle  39  is rotationally driven using a spindle-driving motor  40 . The lens-processing tool  31  is coaxially attached in an upward orientation to the upper end of the spindle  39 . A rotational mechanism  41  of the lens-processing tool  31  is configured from the spindle case  37 , the spindle  39 , and the spindle-driving motor  40 . 
     The conveyor unit  50  is provided with a conveyor  52  for conveying lens cases  51 , and a conveyor-driving motor  53  for rotationally driving the conveyor  52 . A conveyor-advancing/retracting cylinder  54  allows the conveyor  52  and the conveyor-driving motor  53  to be moved between a position between the upper axial unit  10  and the lower axial unit  30 , and a position withdrawn therefrom on the Y-axis. 
     An example of an operation for conveying lenses using the conveyor  52  will be described. At the withdrawn position, the conveyor  52  conveys the lens cases  51 , replaces the lens case  51  containing a processed lens with the lens case  51  containing an unprocessed lens, transfers the lens case  51  that has reached the end of the conveyor  52  to a conveyor of the next stage, and receives the lens case  51  ejected by a conveyor of the previous stage. 
     The conveyor  52  then moves forward, causes the lens case  51  to be positioned below the upper axial unit  10 , supplies the lens  11  to the lens holder  12  or receives the processed lens  11  from the lens holder  12 , and moves to a rearward position. 
     The upper axial unit  10  positions the lens holder  12  directly above the lens case  51  that is loaded on the conveyor  52  that has moved forward, uses, e.g., a vacuum to suction the lens of the lens case  51  onto the lens holder  12 , and temporarily withdraws. After the lens case  51  has moved to the rear along with the conveyor  52 , the lens  11  that is held on the lens holder  12  is moved into position for processing by the plate-shaped or cup-shaped lens-processing tool  31 . 
     After processing by the plate-shaped or cup-shaped lens-processing tool  31  has completed, the lens holder  12  causes the lens  11  to be moved back from the lens-processing tool  31 . The lens holder  12  waits until the conveyor  52  moves forward and the lens case  51  is positioned below, then, e.g., removes the suction when directly above the lens case  51 , and drops the lens  11  into the lens case  51 , in which the lens is stored. The lens holder  12  is then withdrawn. 
     (Example of Operation) 
     An example of the operation of the lens-processing device  1  having this configuration will be described.  FIG. 2  is a descriptive diagram that shows a lens-processing mode in which the lens  11  is processed while being maintained in a horizontal state. A processing radius r (m), a left movement amount L (m), and a right movement amount R (m) are set as movement conditions. A processing surface  31   a  of the lens-processing tool  31  has a convex circular-arc shape. The lens-processing tool  31  is attached to an upper end of the spindle  39  so that an apex  31   b  of the processing surface  31   a  is positioned on the θ-axis  32 . In the initial position, the center axis line  13   a  of the lens-holder shaft  13  and a rotational center line  31   c  of the lens-processing tool  31  are aligned. 
     In the initial position shown by the broken line in  FIG. 2 , the coordinate positions of the upper axial unit  10  are Xo (m) in the X-axis direction and Zo (m) in the Z-axis direction, and the swivel angle of the lower axial unit  30  is θo (degrees). A feed amount Zd in the Z-axis direction and a swivel amount θd about the θ-axis in this instance are set according to a feed amount Xd in the X-axis direction as shown below so that a lens surface  11   a  of the lens  11  and the circular-arc-shaped processing surface  31   a  of the lens-processing tool  31  slide past each other in a state in which the lens  11  is pressed against the circular-arc-shaped processing surface  31   a  while being maintained in a horizontal state. 
     X=Xd (m) 
     θd=sin −1 (Xd/r) (degrees) 
     Zd=r(1−cos θd) (m) 
     The feed amount Xd in the X-axis direction is gradually increased, and a movement is made from the initial position Xo to L (m). The feed amount Zd (m) and the swivel amount θd (degrees) are calculated according to the feed amount Xd, and the operations for propulsion in the Z-axis direction and swiveling about the θ-axis are performed to synchronize with the propulsion in the X-axis direction. After the feed amount Xd has reached L (m), the feed amount Xd is reversed and gradually reduced, and negative movement is made from the initial position Xo to R (m). The operations for feeding in the Z-axis direction and swiveling about the θ-axis are also performed in concert with propulsion in the X-axis direction at this point. The lens surface  11   a  can thereby be processed while the lens  11  is maintained in a horizontal state. 
     During the operation for processing the lens surface, the rotational mechanism  41  of the lens-processing tool causes the lens-processing tool  31  to rotate about the rotational center line  31   c . The lens surface  11   a  of the lens  11  is pressed on the processing surface  31   a  of the lens-processing tool  31  from above, and therefore the lens  11  rotates following the rotation of the lens-processing tool  31 . The processing operation is performed in a state in which the lens  11  is vacuum-suctioned on the lens-holding surface  12   a  of the lens holder  12  or in a state in which the vacuum suction has been removed. 
     When the movement stroke of the lens-holder shaft  13  in the Z-axis direction is greater than the maximum value of the feed amount in the Z-axis direction, the calculation of Zd and the drive control for the Z-axis movement mechanism can be omitted. 
     Providing a positive value to the processing radius r allows the lens surface  11   a  that has a convex surface to be processed, as shown in  FIG. 2 . Providing a negative value allows concave lenses to be processed. 
     If the processing radius r is taken to be infinite, only lateral movement (propulsion in the X-axis direction) is produced, and therefore an Oscar-type lens-processing mode can be implemented if the movement is made in conjunction with movement in the Y-axis direction. An inclined-axis-type lens-processing mode can be implemented if movement in the direction of the X-axis, Z-axis, and Y-axis is prevented; swiveling about the θ-axis is prevented; the lens  11  and the lens-processing tool  31  are immobilized at desired positions and angles; and processing is performed. 
     The lens surface  11   a  can also be processed as shown in  FIG. 3 , where the lens-processing tool  31  is immobilized in a vertical state and made to rotate in this state by the rotational mechanism  41  of the lens-processing tool, the Z-axis movement mechanism  19  and the X-axis movement mechanism  15  are driven, and the lens  11  is made to slide along the processing surface  31   a  of the lens-processing tool  31 . 
     OTHER EMBODIMENTS 
     When a small number of work pieces (lenses) are present, the outside diameter is large, or in order to establish simple and inexpensive manufacturing means, a turntable that is made to rotate by electrical power, air indexing, or other means may be put in place of the conveyor unit  50 ; and the work pieces provided and retrieved thereby. It shall also be apparent that the work pieces may be attached and detached by manual labor without using a device for replacing the work pieces. 
     The Y-axis microhead  38  of the lower axial unit  30  can also be replaced by a Y-axis movement mechanism composed of a feed screw and a servo motor. Simultaneously driving the Y-axis movement mechanism and the X-axis movement mechanism in such instances allows planetary-format lens processing to be implemented. 
     KEY 
     
         
           1  Lens-processing device 
           10  Upper axial unit 
           11  Lens 
           11   a  Lens surface 
           12  Lens holder 
           13  Lens-holder shaft 
           13   a  Center axis line 
           14  Pivot-shaft-bearing mechanism 
           15  X-axis movement mechanism 
           16  X-axis guide 
           16   a  X-axis table 
           17  X-axis feeding screw 
           18  X-axis servo motor 
           19  Z-axis movement mechanism 
           20  Z-axis guide 
           20   a  Z-axis table 
           21  Z-axis feed screw 
           22  Z-axis servo motor 
           23  Holder-shaft base 
           24  Holder-pressing spring 
           25  Pressure-adjusting bolt 
           30  Lower axial unit 
           31  Lens-processing tool 
           31   a  Processing surface 
           31   b  Apex 
           31   c  Rotational center line 
           32  θ-axis 
           33  θ-axis swiveling mechanism 
           34  θ-axis servo motor 
           34   a  Rotating shaft 
           35  θ-bracket 
           37  Spindle case 
           38  Y-axis microhead 
           39  Spindle 
           40  Spindle-driving motor 
           41  Rotational mechanism of lens-processing tool 
           50  Conveyor unit 
           51  Lens case 
           52  Conveyor 
           53  Conveyor-driving motor 
           70  Drive control unit