Patent Abstract:
A robot hand having a suction holding unit on one face side holds a plate-shaped work by suction. An outer circumferential edge of the plate-shaped work is held, without contact with a surface of the plate-shaped work, by an outer circumference holding unit provided on the other face side. The robot hand can be used to hold the plate-shaped work yet to be worked by the suction holding unit, and to hold the plate-shaped work having been worked by the outer circumference holding unit. This prevents working debris from being deposited on the plate-shaped work yet to be worked and prevents defective working from occurring. In addition, since the plate-shaped work having been worked is held by the outer circumference holding unit, the robot hand does not make contact with surfaces of the worked plate-shaped work, and, accordingly, no contact marks are formed on the surfaces of the work.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a robot hand which can hold a plate-shaped work on a front face and a back face thereof. 
     2. Description of the Related Art 
     In a working system for working a plate-shaped work, conveying-in of the plate-shaped work onto a working table of the system and conveying-out of the plate-shaped work from the working table are conducted, for example, by use of a robot having a robot hand as described in Japanese Patent Laid-open No. 2005-260065. This robot hand is so configured that a wafer can be held and conveyed in the state of being accommodated in a recess formed on one face of a tray section formed in a plate-like shape. Examples of a working system on which a robot hand with such a configuration is mounted include a grinding machine. In the grinding machine, both a plate-shaped work yet to be ground and a plate-shaped work having been worked are conveyed by use of the robot hand. 
     SUMMARY OF THE INVENTION 
     However, there is a problem as follows. In the just-mentioned system, the conveyance before working and the conveyance after working are conducted using the same face of the same robot hand. Therefore, when working debris is deposited on the robot hand upon holding of the worked plate-shaped work, the subsequent holding of a plate-shaped work yet to be worked would cause the working debris deposited on the robot hand to be transferred onto the plate-shaped work yet to be worked. The working debris thus deposited on the plate-shaped work yet to be worked may cause defective working. 
     In addition, even if the worked plate-shaped work is cleaned by use of cleaning means provided on the working system before holding the worked plate-shaped work by the robot hand, the contact of the robot hand with a surface on one side of the plate-shaped work may leave a contact mark on the held surface of the plate-shaped work. 
     Accordingly, it is an object of the present invention to provide a robot hand which, when used for conveying a plate-shaped work yet to be worked and a plate-shaped work having been worked, ensures that no working debris will be deposited on the plate-shaped work yet to be worked and that no contact mark will be left on a surface of the plate-shaped work having been worked. 
     In accordance with an aspect of the present invention, there is provided a robot hand for holding a plate-shaped work, including: suction holding means for holding a plate-shaped work on one face side by suction; and outer circumference holding means for holding an outer circumferential edge of a plate-shaped work on the other face side. The outer circumference holding means includes an abutment section adapted to make contact with the outer circumferential edge of the plate-shaped work, a pressing unit having moving means disposed at a position opposite to the abutment section and adapted to move a pressing member toward and away from the abutment section, and a tentative receiving section disposed between the abutment section and the pressing unit and adapted to tentatively receive an outer circumferential portion of the plate-shaped work. The pressing member is moved toward the abutment section by the moving means, whereby the plate-shaped work tentatively received by the tentative receiving section is moved toward the abutment section, and the outer circumferential edge of the plate-shaped work is clamped and held by the abutment section and the pressing unit. 
     The robot hand according to the aspect of the present invention is thus configured so that the suction holding means provided on one face side holds the plate-shaped work by suction, whereas the outer circumference holding means provided on the other face side holds the outer circumferential edge of the plate-shaped work without touching a surface of the plate-shaped work. Therefore, by using the robot hand in a different way for each purpose, for example, holding the plate-shaped work yet to be worked by the suction holding means and holding the worked plate-shaped work by the outer circumference holding means, it is possible to prevent working debris from being deposited on the plate-shaped work yet to be worked, and to prevent defective working from occurring. In addition, since the plate-shaped work having been worked is held by the outer circumference holding means, the robot hand does not touch surfaces of the worked plate-shaped work, and, accordingly, no contact mark is formed on the surfaces of the plate-shaped work. 
     The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claim with reference to the attached drawings showing a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a front face side of a robot hand; 
         FIG. 2  is a perspective view showing the back face side of the robot hand; 
         FIG. 3  is a bottom view showing the front face side of the robot hand; 
         FIG. 4  is a front view showing a condition where a plate-shaped work is held by suction on the front face side of the robot hand; 
         FIG. 5  is a plan view showing a condition where a plate-shaped work is tentatively received on the back face side of the robot hand; 
         FIG. 6  is a plan view showing a condition where a plate-shaped work is clamped and held on the back face side of the robot hand; 
         FIG. 7  is a sectional view taken along line a-a of  FIG. 6 ; and 
         FIG. 8  is a sectional view taken along line b-b of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A robot hand  1  shown in  FIGS. 1 and 2  includes a flat plate section  2  formed in a plate-like shape, and a fork section  3  having two fingers  3   a  and  3   b  bifurcated along a direction from the flat plate section  2  toward the distal end of the robot hand  1 . The robot hand  1  has a function of holding a plate-shaped work, both on a front surface A, which is one side, and on a back surface B, which is the other side. The flat plate section  2  is supported, in such a manner that it can be advanced and retracted, by an advance/retraction driving unit  4  which advances and retracts the flat-plate section  2  and the fork section  3  along the longitudinal direction. 
     As shown in  FIG. 1 , suction holding means  5  for holding a plate-shaped work by suction is provided on the front surface A side of the flat plate section  2 . The suction holding means  5  includes a suction section  50  provided with a multiplicity of suction holes, a suction passage  51  formed inside the flat plate section  2  and the advance/retraction driving unit  4  as shown in  FIG. 3 , and an external suction source  52  communicating with the suction passage  51 . In addition, a detection unit  53  for detecting the presence or absence of a plate-shaped work to be held is embedded in the flat plate section  2  on the front surface A side. The detection unit  53  is composed, for example, of an electrostatic sensor. 
     As shown in  FIG. 2 , outer circumference holding means  6  for holding an outer circumferential edge of a plate-shaped work is provided on the back surface B. The outer circumference holding means  6  includes abutment sections  60  which are formed at the distal ends on the back surface B side of the fingers  3   a  and  3   b  and brought into contact with the outer circumferential edge of the plate-shaped work, a pressing unit  61  which is located at a position opposite to the abutment sections  60  and presses the plate-shaped work toward the abutment sections  60 , and tentative receiving sections  601  and  62  which are disposed between the abutment sections  60  and the pressing unit  61  and support the plate-shaped work from below. 
     The abutment sections  60  are formed to project from the back surface B in the thickness direction of the fingers  3   a  and  3   b , and are formed in conformity with the outer circumferential shape of the plate-shaped work to be mounted on the flat plate section  2  and the fork section  3 . In the embodiment shown in  FIG. 2 , a side surface  600  of an abutment section  60  is formed in a shape corresponding to an arc of the outer circumference of a circular plate-shaped work. 
     As shown in an enlarged form in  FIG. 4 , the side surface  600  of the abutment section  60  is erected substantially vertically. In addition, on the side closer to the pressing unit  61  than the abutment section  60 , there is formed a tentative receiving section  601  composed of a gently inclined surface which slopes down from the lower end of the side surface  600  toward the flat plate section  2  side. 
     As shown in  FIG. 2 , on the back surface B of the flat plate section  2 , two guide members  63  are provided at positions which are between the abutment sections  60  and the pressing unit  61  and which are nearer to the advance/retraction driving unit  4  than the center of the plate-shaped work, or the object to be held. Each of the guide members  63  is provided in a central area thereof with a projection  630  formed in a cylindrical shape. The projection  630  is formed on the radially outer side thereof with a tentative receiving section  62  composed of an inclined surface which gently slopes down radially outward from the base of the projection  630 . Incidentally, while two guide members  63  are provided in the embodiment shown, the guide members  63  may be provided in the number of three or more. 
     Besides, only one guide member  63  may be provided. In the embodiment shown, there are provided a total of four tentative receiving sections, consisting of the two tentative receiving sections  601  and the two tentative receiving sections  62 , thereby holding a plate-shaped work W before positioning. However, other configurations may also be adopted, for example, a configuration in which the plate-shaped work W is supported by at least three tentative receiving sections, which may consist of two tentative receiving sections  601  and one tentative receiving section  62 , or may consist of one tentative receiving section  601  and two tentative receiving sections  62 . Furthermore, each of the tentative receiving sections may be formed in a shape along the outer circumferential shape of the plate-shaped work. For example, in the case of a circular plate-shaped work as shown in the drawings, each tentative receiving section may be formed in a shape along an arc of the outer circumference of the work. 
     As shown in  FIGS. 2 and 4 , on the back surface B of the flat plate section  2 , a pair of pressing members  64  are provided at positions opposed to the abutment sections  60  in the longitudinal direction. A pressing member  64  is connected to a piston  66  through a connecting member  65 . The piston  66  is so supported that it can be advanced and retracted, by a cylinder  67 . When the pistons  66  are advanced or retracted, the pressing members  64  can also be advanced or retracted accordingly. The cylinders  67  and the pistons  66  function as moving means  68  for advancing and retracting the pressing members  64  in relation to the abutment sections  60 . In addition, the pressing members  64 , connecting members  65 , and moving means  68  make up the pressing unit  61 . 
     In the case of holding the plate-shaped work W on the front surface A of the robot hand  1 , the front surface A faced down is pressed against an upper surface Wa of the plate-shaped work W, as shown in  FIGS. 3 and 4 , and a suction force is exerted at the suction section  50  so that the plate-shaped work W is suction held by the suction holding means  5 . Then, in this condition, the robot hand  1  is raised, whereby the plate-shaped work W can be conveyed. 
     On the other hand, in the case of holding the plate-shaped work W on the back surface B of the robot hand  1 , the moving means  68  withdraw the pressing members  64  toward the advance/retraction driving unit  4  side (in a direction of arrow −X), as shown in  FIG. 5 , and, in this condition, press the plate-shaped work W against the back surface B. In this instance, it is ensured that an outer circumferential edge W 1  of the plate-shaped work W is located on the side nearer to the pressing unit  61  than the abutment sections  60  so that the outer circumferential edge W 1  does not make contact with the side surfaces  600  of the abutment sections  60 . 
     Next, the moving means  68  advance the pressing members  64  toward the side of the abutment sections  60  (in a direction of arrow +X), whereby the pressing members  64  are brought into contact with the outer circumferential edge W 1  of the plate-shaped work W, as shown in  FIG. 6 . Further, the pressing members  64  are moved in the +X direction, whereby the plate-shaped work W is moved progressively in the +X direction. As a result, as shown in  FIG. 6 , the outer circumferential edge W 1  of the plate-shaped work W comes into contact with the side surfaces  600  of the abutment sections  60 , and the plate-shaped work W is clamped and held between the abutment sections  60  and the pressing members  64 . 
     The process in which the plate-shaped work W is moved in the +X direction by being pressed by the moving means  68  is conducted as shown in  FIG. 7 . In this process, on the side of the abutment sections  60 , an outer circumferential portion W 2  of the plate-shaped work W tentatively received by the tentative receiving sections  601  is gradually moved upward while being guided by the tentative receiving sections  601 , and this movement is stopped when the outer circumferential edge W 1  of the plate-shaped work W is abutted on the abutment sections  60 . Incidentally, the term “tentative receiving” means a state in which the plate-shaped work W is supported in a tentative position before being positioned finally. 
     In addition, the process in which the plate-shaped work W is moved in the +X direction is conducted as shown in  FIG. 8 . As shown, on the side of the pressing members  64 , the plate-shaped work W is pressed in the +X direction with its outer circumferential edge W 1  making contact with side surfaces  640  of the pressing members  64 , whereby the outer circumferential portion W 2  of the plate-shaped work W tentatively received by the tentative receiving sections  62  is moved downward while being guided by the tentative receiving sections  62 . Then, this movement is stopped when the outer circumferential edge W 1  of the plate-shaped work W is abutted on the abutment sections  60 , as shown in  FIG. 7 . When the movement of the plate-shaped work W is stopped, the outer circumferential edge W 1  of the plate-shaped work W is clamped by the abutment sections  60  and the pressing unit  61 . 
     Thus, the outer circumferential portion W 2  of the plate-shaped work W is supported by the tentative receiving sections  601  and  62 , and the outer circumferential edge W 1  is supported from both ends. On the central side relative to the outer circumferential portion W 2 , surfaces of the plate-shaped work W do not make contact with any component part. When the plate-shaped work W is conveyed in such a held state, therefore, no contact mark will be formed on the surfaces of the plate-shaped work W. For example, in a case where the plate-shaped work W is a semiconductor wafer and the outer circumferential portion W 2  is a surplus region in which no device is formed, devices can be prevented from being damaged. 
     Besides, in the robot hand  1 , it is ensured that on one surface side, the plate-shaped work can be suction held by the suction holding means  5 , and, on the other surface side, the outer circumferential edge of the plate-shaped work can be held by the outer circumference holding means  6 . Therefore, by using the robot hand  1  in a different way for each purpose, for example, holding a to-be-worked plate-shaped work with no working debris deposited thereon by the suction holding means  5  and holding a worked plate-shaped work with working debris deposited thereon by the outer circumference holding means  6 , it is possible to prevent working debris from being deposited on a to-be-worked plate-shaped work, and to prevent defective working from occurring. 
     The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claim and all changes and modifications as fall within the equivalence of the scope of the claim are therefore to be embraced by the invention.

Technology Classification (CPC): 1