Patent Publication Number: US-2020298355-A1

Title: Workpiece fixing jig

Description:
BACKGROUND OF THE INVENTION 
     This application claims the benefit of the Japanese Patent Application Number 2019-051533 filed on Mar. 19, 2019, the entirety of which is incorporated by reference. 
     FIELD OF THE INVENTION 
     The disclosure relates to a workpiece fixing jig used to fix a workpiece on a table and/or a pallet of a machine tool. 
     RELATED ART 
     To process a workpiece by a machine tool, the workpiece is fixed on a pallet and/or a table using a jig, such as an angle plate. For example, JP-A-2006-142419 discloses a mounting auxiliary base where a mounting tool body to which a workpiece is mounted using a fastening member, such as a damper, is coupled to a base body via a plurality of positioning members and the base body is configured to be mounted to a pallet with bolts. 
     However, a plurality of processes are required for a workpiece which has a complicated shape and needs multi-surface machining, since arrangement change, such as a change of a posture of a workpiece and a position of a jig, is required. The arrangement change leads to a mounting error of the workpiece or an extra time for arrangement change, which causes lowering production efficiency. JP-A-2018-62029 describes a clamp system in which a screw shaft portion disposed in a pillar-shaped support body is screwed with a lower surface of a workpiece to make the pillar-shaped support body be attracted and fixed to a magnetic fixing device. 
     The above-described conventional clamp system fixes the lower surface of the workpiece. Therefore, simultaneous multi-surface machining can be performed, and the mounting error and the time taken for arrangement change decrease. Thus improvement in production efficiency can be expected. However, the use of the magnetic fixing device causes increasing of a size of the device and its weight, resulting in a rise in cost. 
     An object of the disclosure is to provide a workpiece fixing jig that ensures achieving fixation of a workpiece which leads to improvement in production efficiency with a simple configuration at a low cost. 
     SUMMARY 
     In order to achieve the above-described object, a workpiece fixing jig for fixing a workpiece to a table or a pallet of a machine tool is provided. According to a first aspect of the disclosure, the workpiece fixing jig includes a base plate, a support block, a bolt, and a drop prevention unit. The base plate is clamped or unclamped to the table or the pallet. The support block is disposed upright on the base plate and has a placement surface for the workpiece on a top surface of the support block. The bolt is housed in the support block to be movable up and down and is projected from the placement surface to be screwable into a lower surface of the workpiece. The drop prevention means prevents the bolt from dropping from the inside of the support block. 
     A workpiece fixing jig according to a second aspect of the disclosure, which is in the first aspect of the disclosure, the drop prevention means includes a stopper plate and a nut. The stopper plate includes a penetrating portion where the bolt penetrates upward. The nut is screwed with the bolt above the stopper plate. 
     A workpiece fixing jig according to a third aspect of the disclosure, which is in the first aspect or the second aspect of the disclosure, a communication hole, which communicates with the inside of the support block and penetrates through the base plate, is formed under the bolt. A clamped portion for conveyance is provided on a side surface of the base plate. 
     According to the first aspect of the disclosure, the bolt is screwed into the lower surface of the workpiece without a risk of dropping to ensure fixing the workpiece. Accordingly, simultaneous multi-surface machining can be performed, and the fixation of the workpiece which leads to improvement in production efficiency can be achieved with a simple configuration at a low cost. 
     According to the second aspect of the disclosure, in addition to the effect of the first aspect, the drop prevention means is easily formed, because it includes the stopper plate and the nut. 
     According to the third aspect of the disclosure, in addition to the effects of the first aspect and the second aspect, the communication hole is formed to penetrate through the base plate under the bolt and the clamped portion for conveyance is provided on the side surface of the base plate. Therefore, with an industrial robot or the like, fixing the workpiece to the workpiece fixing jig, releasing the fixation, and conveying the workpiece to the table and/or the pallet can be automatically performed, and thus an application to an automatic machining line becomes possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a workpiece fixing jig. 
         FIG. 2A  illustrates a front surface of the workpiece fixing jig. 
         FIG. 2B  illustrates a planar surface of the workpiece fixing jig. 
         FIG. 2C  illustrates a side surface of the workpiece fixing jig. 
         FIG. 3  is an enlarged cross-sectional view of the workpiece fixing jig taken along the line A-A of  FIG. 2A . 
         FIG. 4  is a perspective view of the workpiece fixing jig to which a workpiece is fixed. 
         FIG. 5A  illustrates a front surface of the workpiece fixing jig. 
         FIG. 5B  illustrates a planar surface of the workpiece fixing jig. 
         FIG. 5C  illustrates a cross-sectional surface of the workpiece fixing jig taken along the line B-B. 
         FIG. 6  is a perspective view in a state where the workpiece fixing jig is placed on a temporary placement table. 
         FIG. 7  is a front view in a state where the workpiece fixing jig is placed on the temporary placement table. 
         FIG. 8  is a cross-sectional view taken along the line C-C of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     The following describes embodiments of the disclosure based on the drawings. 
       FIG. 1  is a perspective view illustrating one example of a workpiece fixing jig.  FIG. 2A  to  FIG. 2C  are respective explanatory views of the workpiece fixing jig.  FIG. 2A  illustrates a front surface,  FIG. 2B  illustrates a planar surface, and  FIG. 2C  illustrates a side surface. 
     A workpiece fixing jig  1  includes a base plate  2  and two supports blocks, which are a first support block  3  and a second support block  4 , fixed to a top surface of the base plate  2 . 
     The base plate  2  has a square shape in plan view whose corner portions are chamfered and includes a pair of parallel first side surfaces  5 ,  5 , and a pair of parallel second side surfaces  6 ,  6  perpendicular to the first side surfaces  5 ,  5 . A pair of conveyance holes  7 ,  7  are formed in the respective first side surfaces  5 ,  5 . Additionally, a pair of temporary placement holes  8 ,  8  are each formed to penetrate in an up-down direction in edges of the second side surfaces  6 ,  6  and are used for temporary placement to a temporary placement table  40  described later. Furthermore, a pair of positioning holes  9 ,  9  are formed to penetrate in the up-down direction in edges of first side surfaces  5 ,  5 . The holes are used for mounting the workpiece fixing jig to a base jig disposed in a pallet and a table. 
     The first support block  3  and the second support block  4  are arranged in a direction parallel to the second side surface  6  at a predetermined interval in a direction along the first side surface  5 . The first support block  3  and the second support block  4  have identical heights, and have respective placement surfaces  10  which are formed parallel to a top of surface of the base  2 . 
     As illustrated in  FIG. 3 , the first support block  3  includes a housing hollow portion  11  in the up-down direction with closed top opening to the second side surface  6  side. A stopper plate  12  is disposed slightly upward with respect to an intermediate portion of the first support block  3  to be incorporated parallel to the placement surface  10  to partition an inside of the housing hollow portion  11  divided into up and down. A U-shaped groove  13  opening to the second side surface  6  side is formed on the stopper plate  12  inside the housing hollow portion  11 . The housing hollow portion  11  is divided into up and down between which the stopper plate  12  is interposed and an upper hollow portion  14  and a lower hollow portion  15  has widths wider than that of the U-shaped groove  13  and each portion communicates with the U-shaped groove  13 . 
     A bolt  20  having a hexagonal hole at a head  21  is held in the housing hollow portion  11 . The bolt  20  includes a large-diameter first screw portion  22  at an intermediate portion and a small-diameter second screw portion  23  at a distal end, and a nut  24  is screwed with the first screw portion  22 . Here, with the nut  24  positioned in the upper hollow portion  14  and the head  21  and a washer  25  positioned in the lower hollow portion  15 , the first screw portion  22  is penetrated into the U-shaped groove  13 . The bolt  20  is held so as to be oriented upward in a state where the nut  24  abuts on the stopper plate  12  and thus a downward drop is prevented. A through-hole  26  opening to the placement surface  10  is formed in the first support block  3  on an extended line of the upper side of the second screw portion  23 . 
     Here, when the bolt  20  with the nut  24  is positioned at an upper side part of the first screw portion  22 , the second screw portion  23  is not projected upward from the through-hole  26  while the nut  24  contacts the stopper plate  12 . On the other hand, pressing up the bolt  20  until the washer  25  abuts on the stopper plate  12  makes the second screw portion  23  project upward from the through-hole  26 . A cover  27  to obstruct the housing hollow portion  11  is screwed to a side surface of the first support block  3 . 
     Similarly to the first support block  3 , the second support block  4  also includes the housing hollow portion  11  and the bolt  20  similarly to the first support block  3 , and here, the two sets are arranged side by side in a direction along the second side surface  6  and the covers  27 ,  27  are screwed corresponding to the respective housing hollow portions  11 ,  11 . 
     Accordingly, on the placement surfaces  10 ,  10  of the first support blocks  3  and the second support block  4 , the second screw portions  23  of the bolts  20  can appear at the three positions. 
     On the other hand, at the mounting positions for the first support block  3  and the second support block  4  in the base plate  2 , communication holes  16  communicating with the respective housing hollow portions  11  in the up-down direction and penetrating through the base plate are formed. 
     In the workpiece fixing jig  1  configured as described above, screw-holes  31  with which the second screw portions  23  can be screwed corresponding to the respective through-holes  26  in the first support block  3  and the second support block  4  are preliminarily formed in the lower surface of a workpiece  30  illustrated as  FIG. 4  and  FIG. 5A to 5C . The workpiece  30  is placed across the placement surfaces  10 ,  10  of the first support block  3  and the second support block  4  with the respective screw-holes  31  matched with the through-holes  26 . With the cover  27  removed, after a hexagonal wrench or the like is inserted into each housing hollow portion  11 , a rotating operation of the bolt  20  is performed, and the second screw portion  23  is screwed into each screw-hole  31  of the workpiece  30 . Then, as illustrated in  FIG. 4  and  FIG. 5A to 5C , the workpiece  30  is fixed on the first support block  3  and the second support block  4 . Since the front and rear, the right and left, and the top surface excluding the lower surface of the workpiece  30  are exposed in the state, by placing the base plate  2  on, for example, the pallet and by clamping the base plate  2 , the simultaneous multi-surface machining can be performed without arrangement change. 
     To use the workpiece fixing jig  1  for an automatic machining line, the temporary placement table  40  as illustrated in  FIG. 6  to  FIG. 8  is used. The temporary placement table  40  has a top board  42  on a top of a square-box-shaped frame  41 . Positioning members  43 ,  43 , and so on are abutted on the first side surfaces  5  and the second side surfaces  6  of the base plate  2  of the workpiece fixing jig, and are disposed upright on the top board  42 . Positioning bolts  44  corresponding to the temporary placement holes  8 ,  8  of the base plate  2  are disposed to protrude upward. An opening  45  to open the communication hole  16  is formed underneath the communication hole  16  in the top board  42 . 
     Accordingly, to fix the workpiece  30  to the workpiece fixing jig  1 , the base plate  2  is positioned on the top board  42  of the temporary placement table  40  with the positioning members  43  and the positioning bolts  44 . With the workpiece  30  placed on the first support block  3  and the second support block  4 , using robot hands to which nutrunners  50  are mounted, socket bits mounted to the nutrunners  50  are moved upward from the lower portion of the top board  42 . The socket bits are caused to enter the housing hollow portions  11  in the first support block  3  and the second support block  4  in order via the opening  45  and the bolts  20  are fastened to ensure fixing the workpiece  30 . The nutrunner  50  has a torque value management function which enables it to fasten the bolt  20  with an appropriate torque and to determine whether the fastening is completed. 
     With the workpiece fixing jig  1  to which the workpiece  30  is fixed, a pair of conveyance pins disposed in the respective robot hands are inserted into and locked to the pair of conveyance holes  7 ,  7 , which are disposed in the respective first side surfaces  5  of the base plate  2 , using an industrial robot to which a pair of robot hands are mounted. Thus, the base plate  2  is clamped and can be conveyed to a machining station without further processes. At the machining station, all surface excluding the lower surface of the workpiece  30  are exposed by placing the base plate  2  on the pallet and/or the table and clamping the base plate  2 , thus the simultaneous multi-surface machining can be performed. After terminating the machining, the workpiece fixing jig  1  is removed by using the robot hands similarly and is set to the temporary placement table  40 , which allows the nutrunners  50  to remove the workpiece. 
     The workpiece fixing jig  1  with the above-described configuration includes the base plate  2 , the first support block  3  and the second support block  4 , the bolts  20 , and the stopper plates  12  and the nuts  24  (drop prevention means). The base plate  2  is clamped or unclamped to the table or the pallet. The first support block  3  and the second support block  4  are disposed upright on the base plate  2  and have the placement surfaces  10  for the workpiece  30  on the top surfaces. The bolts  20  are housed in the first support block  3  and the second support block  4  to be movable up and down. The bolts  20  are projected from the placement surfaces  10  to be screwable into the lower surface of the workpiece  30 . The stopper plates  12  and the nuts  24  prevent the bolts  20  from dropping from the insides of the first support block  3  and the second support block  4 . Thus, the bolts  20  are screwed into the lower surface of the workpiece  30  without a risk of dropping to ensure fixing the workpiece  30 . Accordingly, the simultaneous multi-surface machining can be performed, and the fixation of the workpiece  30  leading to improvement in production efficiency can be achieved with a simple configuration at a low cost. 
     Especially here, the drop prevention means includes the stopper plate  12  and the nut  24 . The stopper plate  12  includes the U-shaped groove  13  (penetrating portion) where the bolt  20  penetrates upward and the nut  24  is screwed with the bolt  20  above the stopper plate  12 . Accordingly, the drop prevention means can be easily formed. 
     Moreover, the communication holes  16 , which communicates with the insides of the first support blocks  3  and the second support blocks  4  and penetrates through the base plate  2 , are formed under the bolts  20 . The conveyance holes  7  (clamped portions) for conveyance are provided on the side surfaces of the base plate  2 . Therefore, using with an industrial robot or the like, fixing the workpiece  30  to the workpiece fixing jig  1 , releasing the fixation, and conveying the workpiece  30  to the table and/or the pallet can be automatically performed, and thus an application to an automatic machining line becomes possible. 
     The number of support blocks and the structure of the support blocks are not limited to the above-described configurations, one support block may be disposed with a plurality of bolts, or three or more support blocks may be disposed with a bolt provided in each block. Depending on the shape of the workpiece, a plurality of support blocks having different heights can be used. 
     Additionally, when the penetrating portion disposed in the stopper plate is configured as the U-shaped groove in the drop prevention means, the bolt can be removed from and entered into the side surface of the support block and working efficiency to fix the workpiece is more improved. However, the penetrating portion is not limited to the groove and may be a through-hole where the bolt penetrates. The retention to the stopper plate needs not be the nut, and other members, such as a circlip or a pin, may be used. The housing hollow portion may be opened to another surface. 
     Furthermore, the clamped portion is not limited to the conveyance hole with the above-described configuration and appropriately changeable depending on a structure of the conveyance means side, such as the industrial robot. 
     It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.