Abstract:
In a pallet exchange apparatus according to the prior art, it has been necessary to raise two pallets to be exchanged and therefore, a load sufficient to raise the weight of the two pallets has been necessary. To raise and turn a heavy pallet, it is necessary to raise the pallet to a certain degree of height when flexure is taken into account. However, to raise the weighty pallet to that height, a considerably great load has been required. To solve this problem, the present invention provides an apparatus provided with turn driving means rotatable about an axis perpendicular to the plane of a pallet and also movable in the direction of the axis, sliding means disposed on only the lower side of the pallet, and push-up means having a first guide portion for causing the pallet normally separate from the sliding means to abut against the sliding means and further, guiding the direction of movement of the pallet, wherein during pallet exchange, the turn driving means turns the pallet on the sliding means and exchanges the pallet.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to a pallet exchange apparatus for exchanging the pallets of a machining side and a work exchange side in a machining apparatus such as a machining center.  
           [0003]    2. Related Background Art  
           [0004]    In a machining apparatus such as a machining center, there is known a pallet exchange apparatus having a pallet on each of a machining side and a work exchange side, and turning and exchanging these pallets by a turn driving apparatus in conformity with the requirement of the machining process. In such a machine, conventionally, a machining side pallet is installed on an XY table freely moved horizontally in the surface direction of that table to thereby effect machining. Heretofore, as the pallet exchange apparatus provided with such turn driving apparatus, there has been an apparatus of a type in which during machining, pallets are fixed so as not to move and during exchange, the pallets are raised by a turning apparatus and thereafter are turned and exchanged by the turn driving apparatus, or an apparatus of a type in which a sliding device such as bearings for exchanging pallets is arranged on not only areas beneath the pallets but also areas below the pallets, and the pallets are moved along the sliding devices and the pallets are exchanged.  
           [0005]    Such apparatuses according to the prior art have suffered from the following problems.  
           [0006]    (1) Since it is necessary to raise two pallets to be exchanged, a load sufficient to raise the weight of the two pallets has been necessary. To raise and turn the pallets, it is necessary to raise the pallets to a certain degree of height, but a considerably great load has been required to raise the pallets which are weight goods to that position.  
           [0007]    (2) Further, oil pressure driving is generally used to raise the pallets, but a great quantity of oil has been required because the quantity to be raised is great.  
           [0008]    (3) Since the XY table for machining is moved at random in a horizontal direction during machining, a pallet is disposed at a certain distance from a pallet to be exchanged. Therefore, in the pallet exchange apparatus of the type using the sliding devices such as bearings, it is necessary that the pallet be also moved by the sliding devices over this distance. Thus, the bearings or the like have unavoidably been disposed not only on the lower areas of the pallets but also on the outside areas of the pallets. Therefore, cut powder has been caught into the bearings or the like to hinder smooth movement.  
           [0009]    (4) Particularly, the turn driving portion is disposed at a location on which the cut powder always falls, and this has led to the problem that the turn driving portion catches the cut powder into its mechanism.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention provides a pallet exchange apparatus comprising turn driving means rotatable about an axis perpendicular to the plane of a pallet and also movable in the direction of the axis, sliding means disposed only on the lower side of the pallet, and push-up means having sliding means and contacting the sliding means to the pallet being off sliding means, and further guiding the direction of movement of the pallet, and during the exchange of the pallet, the turn driving means turns the pallet on the sliding means and exchanges the pallet, whereby the turning of the pallet can be made possible only by raising the pallet to a slight height and the problem of the load becoming great can be solved. Thereby, further, the quantity of oil may be small in the oil pressure driving for raising the pallet. Also, the necessary load becomes small, whereby it becomes possible to substitute an air oil booster for the oil pressure driving.  
           [0011]    The pallet exchange apparatus of the present invention is further characterized in that the sliding means is provided on moving means movable in the direction of the plane of the pallet, and during the exchange of the pallet, the moving means approaches turning means and therefore, the sliding means can be disposed on only the lower side of the pallet. Thereby, the problem that cut powder falls on and is absorbed in the bearings can be solved.  
           [0012]    The pallet exchange apparatus of the present invention is further provided with a cover having on the upper portion of the turn driving portion an inclined surface descending from the central portion thereof toward around it, and is characterized in that an insertion bar to transmit rotation force has an inclined surface coinciding with the plane of the cover during descent, and protrudes from the cover during ascent and therefore, the cut powder falling on the turn driving portion does not accumulate but can be dropped. Thereby, the cut powder can be prevented from being absorbed into the turn driving portion and hindering the driving.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a top plan view of a pallet exchange apparatus in a state in which pallet exchange is not effected.  
         [0014]    [0014]FIG. 2 is a side view of the exchange apparatus taken along the line  2 - 2  of FIG. 1.  
         [0015]    [0015]FIGS. 3A and 3B are enlarged views of the cover portion of a mechanical driving portion, FIG. 3A showing a state in which a sliding portion has descended, and FIG. 3B showing a state in which the sliding portion has ascended.  
         [0016]    [0016]FIG. 4 is an enlarged view of the clamp plate bearing portion of a machining side portion.  
         [0017]    [0017]FIG. 5 is a top plan view of the pallet exchange apparatus in a state in which the machining side portion and a work exchange side portion have become close to each other to effect pallet exchange.  
         [0018]    [0018]FIG. 6 is a side view of the exchange apparatus taken along the line  6 - 6  of FIG. 5.  
         [0019]    [0019]FIG. 7 is a conceptual view of the pallet exchange apparatus, when the present invention is applied, wherein the exchange of numerous pallets is to be effected.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     EMBODIMENT 1  
       [0020]    A first embodiment of the present invention will hereinafter be described with reference to FIGS.  1  to  6 . FIGS. 1 and 2 show a machining apparatus provided with the pallet exchange apparatus of the present invention, and more particularly, FIG. 1 is a top plan view thereof, and FIG. 2 is a side view taken along the line  2 - 2  in FIG. 1.  
         [0021]    The pallet exchange apparatus of the machining apparatus comprises a turn driving portion  1 , a machining side portion  2  and a work exchange side portion  3 .  
         [0022]    The turn driving portion  1  in turn comprises a sliding portion  11 , a driving shaft  12  for turning pallets, an inclined cover  13 , a round pin  14  and a partition cover  16 .  
         [0023]    The driving shaft  12  for turning pallets is rotatable about its axis and also is vertically movable. The sliding portion  11  is mounted on the upper end of the driving shaft  12  for turning pallets and is vertically movable in accordance with the driving shaft  12  for turning pallets. Driving gears  15   a,    15   b  and  15   c  for turning are in meshing engagement with the lower end of the driving shaft  12  for turning pallets.  
         [0024]    The inclined cover  13 , as shown in FIG. 3, is mounted on the upper end portion of the turn driving portion and contains the sliding portion  11  therein. The inclined cover  13  has a surface of which the central portion is perpendicular to the driving shaft  12  for turning pallets, and has an inclined portion  13   a  extending therefrom toward the periphery thereof.  
         [0025]    The round pin  14  is provided on the upper surface of the sliding portion  11 , and is set so that the tip end of the round pin  14  may become flush with the surface of the inclined cover  13  when as shown in FIG. 3A, the sliding portion  11  is positioned at the lowermost end. Also, design is made such that when the sliding portion  11  ascends as shown in FIG. 3B, the round pin  14  protrudes outwardly from the surface of the inclined cover  13  in conformity therewith. While in the present embodiment, two round pins  14  are utilized for the respective pallets of the machining side portion  2  and the work exchange side portion  3 , the cross section of the pins may be made polygonal. By changing the cross-sectional shape of the pins, it is also possible to improve the strength of the pins and decrease the number of the pins.  
         [0026]    The partition cover  16  is also mounted on the upper surface of the sliding portion  11 , and protrudes out of the central gap portion of the inclined cover  13 . Accordingly, as the sliding portion  11  ascends or descends, the partition cover  16  also ascends or descends.  
         [0027]    The machining side portion  2  comprises a pallet base  21 , a saddle  22 , a bed  23 , a pallet clamp driving portion  24 , a clamp plate  25  and pallet positioning pins  26 .  
         [0028]    The pallet clamp driving portion  24  is a driver disposed at the center of the machining side portion  2 . The clamp plate  25  is mounted on the upper end of the movable portion of the pallet clamp driving portion  24 . The pallet clamp driving portion  24  drives the clamp plate  25  so as to ascend and descend. Bearings  27  are embedded in the side of the clamp plate  25 . The bearings  27  are mounted so that the rotary shafts thereof may be parallel to a plane perpendicular to the driving shaft  12  for turning pallets. FIG. 4 is an enlarged view of the clamp plate  25 , and as shown in FIG. 4, the bearing  27  of the clamp plate  25  is disposed so that the rotation center portion thereof may be eccentric somewhat upwardly from the center axis in the direction of thickness of the clamp plate  25 . Accordingly, as will be described later, in a case where a pallet  4   a  is disposed on the upper surface side of the clamp plate  25 , when the clamp plate  25  is made to ascend, only the bearing  27  touches the inner surface of the pallet.  
         [0029]    On the other hand, when the clamp plate  25  is made to descend, the bearing  27  does not touch the pallet, while the bearing  27  presses down the lower surface  6   a  of the pallet to fix the pallet by a holding-down portion  28 .  
         [0030]    On the other hand, the work exchange side portion  3  comprises a base portion  31 , a pallet holding stand  32  provided on the base portion  31 , and bearings  33  mounted on the pallet holding stand  32 . The bearings  33 , like the bearings  27  of the machining side portion, are mounted so that the rotary shafts thereof may be parallel to the plane perpendicular to the driving shaft  12  for turning pallets.  
         [0031]    A machining side pallet  4   a  is placed on the upper portion of the saddle  22  of the machining side portion  2 . A space portion  5   a  capable of containing the clamp plate  25  therein and a hold-down edge  6   a  are provided inside the machining side pallet  4   a.  The machining side pallet  4   a  is mounted so that the clamp plate  25  may be contained in this space. On the other hand, a work exchange side pallet  4   b  is a standby pallet to be exchanged, the work exchange side pallet being placed on the bearings  33  of the pallet holding stand  32  of the work exchange side portion  3 . A space portion  5   b  capable of containing the pallet holding stand  32  and a hold-down edge  6   b  are also provided inside the work exchange side pallet  4   b.  The work exchange side pallet  4   b  is placed so that the holding stand  32  may be contained in the space portion  5   b.  The machining side pallet  4   a  and the work exchange side pallet  4   b  have interchangeability therebetween, and it is possible to place the work exchange side pallet  4   b  on the machining side portion  2  in the same fashion as the machining side pallet  4   a,  and on the other hand, it is also possible to place the machining side pallet  4   a  on the work exchange side portion  3  in the same fashion as the work exchange side pallet  4   b.    
         [0032]    Further, the plane formed by the bearings  27  of the machining side portion  2  is usually at a position lower than the plane formed by the bearings  33  of the work exchange side  3 , and the levels of the planes formed by both of the bearings  27  and  33  are set so as to just coincide with each other when the clamp plate  25  has ascended. Also, the turning orbit of the machining side pallet  4   a  constituted by the row of the bearings of the machining side portion  2  and the turning orbit of the work exchange side pallet  4   b  constituted by the row of the bearings of the work exchange side portion  3  are designed to coincide with each other when the machining side pallet  4   a  completes to approach a predetermined position for pallet exchange which will be described later. Accordingly, when the clamp plate  25  has ascended, the machining side pallet  4   a  and the work exchange side pallet  4   b  can change their positions by the bearings  27  and  33  thereof.  
         [0033]    The operation and effect of the present embodiment will now be described. During machining, the machining side portion  2  and the work exchange side portion  3  are spaced apart from each other as shown in FIGS. 1 and 2. At this time, the clamp plate  25  is in its lowered state, and the machining side pallet  4   a  is firmly pushed against the pallet base  21  by the pallet holding-down portion  28  of this clamp plate  25 . Thereby, the machining side pallet  4   a  is fixed to the machining side portion  2 . In order to accurately position the machining side pallet  4   a  relative to the saddle, the pallet positioning pins  26  are inserted in the positioning pin holes  8   a  of the machining side pallet  4   a.  Pallet fixing pins  34  are inserted in positioning pin holes  8   b  so that the work exchange side pallet  4   b  may not move on the pallet holding stand  32 .  
         [0034]    The machining side portion  2  is designed such that the saddle  22  is horizontally moved on the bed  23  in conformity with machining. Accordingly, a sufficient distance is kept between the machining side portion  2  and the work exchange side portion  3  so that they may not interfere with each other even if the saddle  22  is horizontally moved. However, since the distance is kept, it would occur to mind that cut powder produced by machining falls from the machining side pallet  4   a  onto the turn driving portion  1  and is lodged among the sliding portion  11 , the driving shaft  12  for turning pallets, the round pins  14 , etc. to thereby hinder driving, but in the present embodiment, the inclined portion  13   a  of the inclined cover  13  mounted on the turn driving portion  1  prevents the adherence of the cut powder to the driving portion  1  and the entry of the cut powder into the interior to thereby solve this problem. Particularly the upper ends of the round pins  14  are also inclined in conformity with the inclined portion  13   a  so that the cut powder may not remain thereon. Further, the partition cover  16  prevents the entry of the cut powder into the work exchange side portion  3 .  
         [0035]    During pallet exchange, the saddle  22  of the machining side portion  2  spaced apart from the work exchange side portion  3  as shown in FIGS. 1 and 2 is horizontally moved and approaches a predetermined position. This predetermined position is a position in which as shown in FIGS. 5 and 6, the horizontal positions of the round pins and the round pin holes coincide with each other so that the round pins  14  of the turn driving portion  1  can be inserted into the round pin holes  7   a  of the machining side pallet  4   a.  After or prior to the movement of the machining side portion  2  to the above-mentioned predetermined position, the clamp plate  25  of the machining side portion  2  raises the machining side pallet  4   a  until the plane of the bearings  27  comes to the same level as that of the plane of the bearings  33 . The distance to which the clamp plate  25  raises the machining side pallet  4   a  can be freely set, but may be a distance wherein the machining side pallet  4   a  separates from the pallet base and therefore, a distance of about 1 mm is enough to achieve the purpose. With the ascent of the clamp plate  25 , the pallet positioning pins  26  which have so far positioned the machining side pallet  4   a  descend and come out of the positioning pin holes  8   a.  On the other hand, the pallet fixing pins  34  which have so far positioned the work exchange side pallet  4   b  descend and come out of the positioning pin holes  8   b.    
         [0036]    In timed relationship with these series of operations, the sliding portion  11  of the turn driving portion  1  ascends with the driving shaft  12  for turning pallets. With this ascent, the tip ends of the round pins  14  protrude from the plane of the inclined cover  13  and are inserted into round pin holes  7   a  and  7   b  formed in the machining side pallet  4   a  and the work exchange side pallet  4   b,  respectively.  
         [0037]    At this stage, the machining side pallet  4   a  and the work exchange side pallet  4   b  are both designed to be movable on and along the tracks formed by the rows of the bearings  27  and  33 . Accordingly, when the driving shaft  12  for turning pallets is rotated, the round pins  14  transmit the turning force thereof to the machining side pallet  4   a  and the work exchange side pallet  4   b,  and in accordance therewith, the machining side pallet  4   a  and the work exchange side pallet  4   b  are turned about the driving shaft  12  for turning pallets on the bearings  27  and  33 .  
         [0038]    The driving shaft  12  for turning pallets is turned by 180° and the machining side pallet  4   a  and the work exchange side pallet  4   b  change their places with each other, whereafter the pallet positioning pins  26  are caused to ascend and are inserted into the pallet positioning pin holes  8   b  of the work exchange side pallet  4   b  moved to the machining side portion  2 , while on the other hand, the pallet fixing pins  34  of the work exchange side portion  3  are inserted into the pallet positioning pin holes  8   a  of the machining side pallet  4   a  moved to the work exchange side portion  3 . By these series of operations, the machining side pallet  4   a  and the work exchange side pallet  4   b  can be exchanged with each other.  
         [0039]    Further, by adopting as a second embodiment construction pallets having portions of a circular pallet circumferentially equally divided as construction units as shown in FIG. 7, these pallets can be exchanged with one another as in the first embodiment. For example, work exchange side pallets  44   b,    44   c,    44   d,    44   e,    44   f,    44   g  and  44   h  of the same shape as a machining side pallet  44   a  are prepared, and the pallet  44   a  is moved in the direction of arrow in FIG. 7 to thereby exchange the pallets by a turn driving apparatus  41 .  
         [0040]    As described above, unlike the prior art, not a driving shaft for turning but a clamp plate is used as means for raising pallets to exchange the pallets, whereby it has become possible to support the weight of the pallets by a large area. Thereby, a design rich in structural strength becomes possible. Accordingly, the driving shaft for turning can have a load necessary for the pallets to be turned on the bearings and therefore, the driving shaft for turning can also be made light in weight and compact.  
         [0041]    Further, the clamp plate can be caused to ascend by only an amount corresponding to a slight height and therefore, the load and the quantity of oil necessary for oil pressure driving can both be reduced as compared with the prior art. Furthermore, not an oil pressure unit but an air oil booster may be used.  
         [0042]    Further, inclinations are provided to the inclined cover  13  of the turn driving potrion  1  and the tip ends of the round pins  14  and therefore, it is difficult for the cut powder to adhere.  
         [0043]    Further, utilization is made of a contrivance in which in case of pallet exchange, the pallets are turned and exchanged after the machining side portion has approached the work exchange side portion and therefore, it is not necessary to dispose bearings on the other portions than the lower side of the pallets. Therefore, it never happens that the cut powder enters the bearings and hinders rotation.