Abstract:
A gripper which is structurally simple and can reliably and quickly grip small articles of various different shapes. The gripper has a base including a fixed portion and a movable portion movable longitudinally toward and away from the fixed portion, a first gripper portion provided on the fixed portion, a second gripper portion provided on the movable portion, and a moving/fixing mechanism for gripping a small article of an indefinite shape by moving the second gripper portion toward the first gripper portion.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for gripping articles having various shapes. 
     In order to grip articles having triangular, semicircular, trapezoidal, L and other shapes, particularly small ones, it was necessary to machine gripping surfaces according to the contour of an article to be gripped, or use V-blocks and liners in combination. 
     But conventional methods are low in versatility and workability. Also, it was extremely difficult to fix a small article to be gripped in a parallel or vertical position with respect to an X-Y table of a machine tool. 
     An object of the present invention is to provide a gripper which is structurally simple and can reliably and quickly grip small articles of different shapes. 
     SUMMARY OF THE INVENTION 
     According to the present invention, there is provided a gripper for gripping an article having an irregular shape, comprising a base, a fixed member mounted on the base, a movable member mounted on the base so as to be movable in a first direction toward and away from the fixed member, a first gripper portion provided on the fixed member and having a first gripper groove having a V shape in plan view, a second gripper portion provided on the movable member and having a second gripper groove having a V shape in plan view and arranged opposite the first gripper groove, and a moving/fixing means for moving the second gripper portion toward the first gripper portion together with the movable member so that an article K will be gripped firmly between the first and second gripping portions. The second gripper portion is slidable in a second direction perpendicular to the first direction relative to the first gripper portion. Each of the first and second gripper portions comprises a plurality of plates arranged in vertical tiers like a comb and adapted to be inserted in spaces defined by the plates of the other gripper portion. 
     According to the present invention, there is also provided a gripper for gripping an article having an irregular shape, comprising a base, a fixed member mounted on the base, a movable member mounted on the base so as to be movable in a first direction toward and away from the fixed member, a first gripper portion provided on the fixed member and having a first gripper groove having a V shape in plan view, a second gripper portion provided on the movable member and having a second gripper groove having a V shape in plan view and arranged opposite the first gripper groove, and a moving/fixing means for moving the second gripper portion toward the first gripper portion together with the movable member so that an article K will be gripped firmly between the first and second gripping portions. The first gripper portion is slidable in a second direction perpendicular to the first direction relative to the second gripper portion. Each of the first and second gripper portions comprises a plurality of plates arranged in vertical tiers like a comb and adapted to be inserted in spaces defined by the plates of the other gripper portion. 
     Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a gripper embodying the present invention; 
     FIG. 2 is a partial sectional view of a base of the gripper; 
     FIG. 3 is a partially sectional, partial plan view of first and second gripper portions when they are moved close to each other; 
     FIG. 4 is a partially sectional, partial plan view showing a state in which a small article is about to be gripped; 
     FIG. 5 is a partially sectional, partial plan view showing a small article gripped; 
     FIG. 6 is a perspective view of another embodiment; 
     FIG. 7 is a side view in section of a first gripper portion of the FIG. 6 embodiment; 
     FIG. 8 is a side view in section of a second gripper portion of the FIG. 6 embodiment; 
     FIG. 9 is a sectional view showing how a moving/fixing means engage; and 
     FIG. 10 is a partially sectional, partial plan view showing how an article is gripped. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is now described in detail with reference to the drawings showing embodiments of the invention. 
     FIG. 1 shows a gripper for gripping small articles with various irregular shapes, embodying the present invention. This gripper comprises a base  1 , a first and a second gripper unit  2  and  3  provided on the base  1 , and a moving/fixing unit  4  for moving the second gripper unit  3  toward and away from the first gripper unit  2  and fixing it in a desired position. 
     To be more specific, as shown in FIGS. 1-3, the base  1  comprises a guide portion  6  having a longitudinal guide slit  5 , fixed blocks  7  and  8  provided at the front and rear ends of the guide portion  6 , and a movable block  9  mounted so as to be movable along the guide portion  6  between the blocks  7  and  8 . 
     The movable block  9  has on its bottom a rib  9   a  slidably received in the guide slit  5  of the guide portion  6  so as to be slidable between the fixed blocks  7  and  8 . In the illustrated embodiment (FIG.  2 ), the guide slit  5  has a uniform width but may be dimensioned such that its width gradually increases downwardly like a dovetail. In this case, the rib  9   a  of the movable portion  9  is also formed like a dovetail complementary to the dovetail-shaped slit  5 . 
     The first gripper portion  2  comprises plate members  10  protruding rearwardly from the fixed block  7  at the front end of the base  1  in a plurality of (three in the embodiment) vertical tiers. Each plate member  10  has along a rear edge thereof a V-shaped (in plan) first gripping groove  11  vertically aligned with the grooves  11  of the other plates  10 . 
     The second gripper portion  3  comprises a vertical wall  14  having a rib  15  engaged in a dovetail groove  13  formed in the front surface  12  of the movable block  9 , and plate members  16  protruding from the vertical wall  14  toward the first gripper portion  2  in a plurality of (two in the embodiment) vertical tiers. Each plate  16  has along its front edge a V-shaped (in plan view) second gripper groove  17  opposite the first gripper grooves  11  of the first gripper portion  2 . 
     The plates  16  of the second gripper portion  3  are inserted into the spaces defined between the plates  10  of the first gripper portion  2 . When the plates  16  are inserted most deeply into the spaces between the plates  10 , the corners  17   a  of the second gripper grooves  17  substantially align with the corners  11   a  of the first gripper grooves  11  (FIG.  3 ). 
     The moving/fixing unit  4  comprises a threaded hole  18  formed in the fixed block  8  at the rear end of the base  1 , and a bolt  20  having threads  19  threaded into the threaded hole  18  and into the movable block  9 . By turning the bolt  20 , the movable block advances and retracts relative to the fixed block  8  to move the second gripper portion  3  together with the movable block  9 . 
     The gripper according to the present invention further includes a stopper  21  for restricting transverse sliding movement of the second gripper portion  3 . The stopper  21  comprises a transverse groove  22  formed in the rib  15  of the second gripper portion  3 , and a stopper pin  23  extending through the movable block  9  and having its tip received in the groove  22 . For example, the stopper pin  23  may be a threaded pin threaded into a threaded hole formed in the movable block  9 . The stopper  21  prevents the second gripper portion  3  from unduly coming off the movable block  9 . 
     As shown in FIGS. 4 and 5, in order to grip a small article K for machining, with the article K pressed against the corners  11   a  of the first gripper grooves  11  of the first gripper portion  2 , the bolt  20  of the moving/fixing unit  4  is turned to advance the second gripper portion  3  toward the first gripper portion  2  together with the movable block  9  until the inclined surfaces of the second gripper grooves  17  abut part P (protruding toward the second gripper portion  3 ) of the article K. When the second gripper portion  3  is further advanced from this position, it will slide in the direction of the arrow A until the corners  17   a  of the second gripper grooves  17  are pressed against part P of the article K. By tightening the bolt  20  in this state, the article K is firmly gripped by the first and second gripper portions  2  and  3 . 
     FIG. 6 shows another gripper embodying the present invention. This gripper comprises a base  1  having a fixed block  7  at the front end and a movable block  9  movable longitudinally toward and away from the fixed block  7 , a first gripper portion  2  provided on the fixed block  7 , a second gripper portion  3  provided on the movable block  9 , and a moving/fixing unit  4  for moving the second gripper portion  3  toward and away from the first gripper portion  2  together with the movable block  9 . 
     Specifically, as shown in FIGS. 6-9, the base  1  has a guide portion having longitudinal cutout guide grooves  24  formed along side edges thereof, and a longitudinal slit  25  provided between the guide grooves  24 . The fixed block  7  is provided at the front end of the guide portion  6 . The movable block  9  is slidable along the guide grooves  24  of the guide portion  6 . 
     Under the slit  25 , the guide portion  6  has a wide hole  25   a  having a corrugated ceiling  28  (FIG.  9 ). The movable block  9  has a chamfered surface  26  at its rear end, and is formed with a hole  27  extending forwardly and downwardly from the chamfered surface  26 . The diameter of the hole  27  increases downwardly. 
     The first gripper portion  2  comprises a block  33  having three plates  10  protruding rearwardly from the block  33  in vertical tiers like a comb as seen from one side (FIG.  7 ), and is transversely slidable along the fixed block  7  of the base  1 . A linear guide bearing  29  is provided between the block  33  of the first gripper portion  2  and the fixed block  7  (FIG.  6 ). 
     The second gripper portion  3  comprises two plates  16  integrally formed on the front face  12  of the movable block  9  in vertical tiers. The plates  10  and  16  of the first and second gripper portions  2  and  3  mesh together when the gripper portions  2 ,  3  move toward each other. 
     The moving/fixing unit  4  comprises a bolt  30  inserted in the hole  27  of the movable block  9 , a polygonal nut  32  (FIG. 9) threaded onto male threads  30   a  at the tip of the bolt  30  and having protrusions  31  on both sides thereof, and the corrugated ceiling  28  formed on the guide portion  6  and adapted to engage the protrusions  31  at a predetermined longitudinal position. The nut member  32  has substantially the same width as the width of the slit  25  of the guide portion  6  at its upper portion. 
     By turning the exposed head of the bolt  30 , the polygonal nut  32  moves up and down relative to the threads  30   a , so that the protrusions  31  engage and disengage from the corrugated ceiling  28 . 
     As shown in FIG. 10, the gripper further includes a stopper  21  for restricting transverse movement of the first gripper portion  2 . The stopper  21  comprises a narrow transverse groove  22  formed in the front face of the block  33  of the first gripper portion  2 , and a stopper pin  23  extending through the fixed block  7  and having its tip received in the groove  22 . The stopper  21  prevents the first gripper portion  2  from unduly coming off the fixed block  7 . 
     In order to grip a small article K for machining, with the article K pressed against the corners  11   a  of the first gripper grooves  11  of the first gripper portion  2 , the second gripper portion  3  is slid toward the first gripper portion  2  together with the movable block  9 , and then, as shown in FIG. 10, the first gripper portion  2  is slid in the direction of arrow B until the corners  17   a  of the second gripper grooves  17  are pressed against part P (protruding toward the second gripper portion  3 ) of the article K. 
     With the article K gripped by the first and second gripper grooves  11 ,  17 , the bolt  30  of the moving/fixing unit  4  is tightened. When it is tightened, the nut  32  is raised as shown in FIG. 9, so that the protrusions  31  engage the corrugations  28 . When the bolt  30  is tightened further firmly, it pivots counterclockwise (in FIG. 8) about the protrusion  31  in a space around the bolt in the hole  27  formed in the movable block  9 , so that the movable block  9  and the second gripper portion  3  advance a little. The article K is thus gripped further firmly between the first and second gripper grooves  11 ,  17 . 
     The present invention is not limited to the above embodiments. For example, the gripper of FIGS. 1 and 2 may be modified such that the first gripper portion  2  is slidable transversely, and the second gripper portion  3  is integral with the movable block  9 . Also, the gripper of FIGS. 6 and 7 may be modified such that the first gripper portion  2  is integral with the fixed block  7  and the second gripper portion  3  is transversely slidable. 
     According to the invention, a small article K having an irregular shape can be gripped easily and reliably without the need to work the chucking surfaces or use V-blocks and liners. It is possible to grip the article K with its reference surface arranged perpendicularly to or in the moving direction of an X-Y table of a machine tool. Thus, the gripper of the invention can handle articles having various shapes and thus is versatile. Also, the gripper of the invention is relatively simple in structure and easy to manufacture. 
     According to the invention, the stopper prevents the first or second gripper portion from unduly coming off.