Abstract:
A workpiece transfer device for machine tools that easily achieves positional adjustment of the rack while suppressing increases in cost and therefore preventing occurrences of vibrations and noise is disclosed. The workpiece transfer device includes a frame member having a rectangular cross-section. The device extends from a workpiece machining position to a workpiece loading/unloading position. A support member is hung on the frame member so as to be movable via a linear guide and which has a workpiece holding mechanism mounted thereon. A drive mechanism for rotationally driving a pinion gear engaged with a rack is provided on the frame member so as to be parallel to the linear guide so that the support member is moved between the two positions. The linear guide is disposed on one wall of the frame member and the rack is disposed on another wall surface so as to have its position adjustable.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a workpiece transfer device for machine tools. The device is constructed so that a support member having a workpiece holding mechanism is mounted on a frame member and is extendable between a workpiece machining position and a workpiece loading/unloading position via a linear guide. The support member is moved in a reciprocating motion by a rack-and-pinion drive mechanism. 
   2. Discussion of the Related Art 
   In recent years, some machine tools are equipped with a workpiece transfer device that is designed to automatically and continuously perform such working processes as receiving an unprocessed workpiece from the workpiece stocker disposed at the workpiece loading/unloading position, loading the workpiece in a chuck of a spindle (which is at the workpiece machining position), receiving the processed workpiece from the chuck of the spindle, and unloading the workpiece at the workpiece stocker. 
     FIG. 8  shows a workpiece transfer device that has conventionally been provided. This device comprises a rectangular frame member  50  extending from a workpiece machining position to a workpiece loading/unloading position. The device also includes a support member  53  which is reciprocatably supported by two linear guides  51 ,  52  disposed on a top wall  50   a  and a side wall  50   b  of the frame member  50  and has a workpiece holding mechanism (not shown) mounted thereon. The device also includes a rack  54  disposed on the top wall  50   a  of the frame member  50  so as to extend along the linear guide  51 . The device also includes a drive motor  56  for rotationally driving a pinion gear  55  engaged with the rack  54  to thereby move the support member  53  in a reciprocating fashion. 
   In this prior-art transfer device, the transfer device adopts a structure that the support member  53  is supported by two costly linear guides  51 ,  52 . This causes a problem in that the cost for the whole device increases. Also, since the linear guides are disposed on two adjacent wall surfaces of the frame member, there is a need for ensuring the relative dimensional accuracy of the linear-guide fitting surfaces with the frame member surfaces. This accuracy also increases the cost of the transfer device. 
   Meanwhile, there is also a structure that allows the two linear guides to be reduced so that only one linear guide is used. In the transfer device shown in  FIG. 7 , one linear guide  61  is disposed on a top wall surface  60   a  of a frame member  60 . A rack  64  is disposed on a bottom wall surface  60   b  on the symmetrically opposite side from the top wall surface  60   a . The rack  64  has its right and left side faces pinched and held by a pair of cam followers  67 . Also, a drive motor  66  rotationally drives a pinion gear  65  engaged with the rack  64 . 
   In this structure, since one linear guide  61  can be used, cost increases can be reduced compared with the structure where two linear guides are used for support. 
   In this connection, general structural purpose steel tubes that have a relatively lower dimensional accuracy are adopted for the frame member  60 . When using a structure where the linear guide  61  is fit on the top wall surface  60   a  of the frame member  60  and the rack  64  is disposed on the bottom wall surface  60   b , there is difficulty in adjusting the vertical position of the rack  64  relative to the linear guide  61 . If the vertical position is not properly adjusted then vibrations and/or noise can occur. Performing a machining process on the wall surfaces of the frame member  60  could solve the above problem; however, doing so would lead to impractical increases in cost. 
   SUMMARY OF THE INVENTION 
   The present invention has been accomplished in view of these circumstances. An object of the present invention is to provide a workpiece transfer device for machine tools that is capable of easily achieving positional adjustment of the rack while suppressing increases in cost and preventing occurrences of vibrations and noise. 
   In a first aspect of the invention, there is provided a workpiece transfer device for machine tools, comprising: a frame member having a rectangular cross-sectional shape and extending at least from a workpiece machining position to a workpiece loading and unloading position; a support member movably disposed on the frame member so as to be movable via a linear guide and the support member has a workpiece holding mechanism mounted thereon; and a drive mechanism disposed on the support member and serving for rotationally driving a pinion gear engaged with a rack, the rack is disposed on the frame member and is parallel to the linear guide, the support member being reciprocatingly movable between the workpiece machining position and the workpiece loading and unloading position, wherein the linear guide is disposed on a first wall surface of the frame member, and the rack is adjustably disposed on a second wall surface of the frame member adjoining the first wall surface so that a position of the rack is adjustable relative to the linear guide. 
   In a second aspect of the invention, the workpiece transfer device also includes cam followers disposed on the support member for pinching and holding the rack, wherein the first wall surface is a top wall surface and the second wall surface is a side wall surface, and wherein the linear guide is disposed on a top wall surface of the frame member, and the rack is disposed on a side wall surface of the frame member. 
   In a third aspect of the invention, the workpiece transfer device includes the linear guide and the rack disposed on one wall surface of the frame member, and the rack is adjustable in its position relative to the linear guide. 
   In a fourth aspect of the invention, the workpiece transfer device includes cam followers disposed on the support member for pinching and holding the rack, and the linear guide and the rack are disposed on a side wall surface of the frame member. 
   With the workpiece transfer device according to the first aspect, since the linear guide is disposed on one wall surface of the frame member and the rack is disposed on another adjoining wall surface, positional adjustment of the rack relative to the linear guide can be fulfilled with ease. Moreover occurrence of vibrations or noise can be prevented while reducing the number of component parts. Also, since only one fitting surface for the linear guide can be used, the frame member may have a lower dimensional accuracy when compared with the cases where two linear-guide fitting surfaces are necessary. 
   Further, since the rack thickness can be increased without increasing the height of the support member, warping of the rack during the tooth-cutting process can be prevented. 
   With the workpiece transfer device according to another aspect of the invention, since the linear guide and the rack are disposed on one same wall surface of the frame member, positional adjustment of the rack relative to the linear guide can be fulfilled with ease. Moreover occurrence of vibrations or noise can be prevented while reducing the number of component parts so that the same benefits can be obtained. 
   Also, since the linear guide and the rack are disposed on the same wall surface, it is only necessary to perform planar machining on one side wall surface, thus allowing the machining costs to be reduced compared with the cases where two wall surfaces must be subjected to machining. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the present invention will be clearly understood from the following description with respect to the preferred embodiment thereof when considered in conjunction with the accompanying drawings and diagrams, in which: 
       FIG. 1  is a front view of a lathe equipped with a workpiece transfer device according to a first embodiment of the present invention; 
       FIG. 2  is a plan view of the lathe in  FIG. 1  according to an embodiment of the present invention; 
       FIG. 3  is a schematic perspective view of the workpiece transfer device according to an embodiment of the present invention; 
       FIG. 4  is a schematic perspective view of the workpiece transfer device according to an embodiment of the present invention; 
       FIG. 5  is a sectional view of the workpiece transfer device according to an embodiment of the present invention; 
       FIG. 6  is a sectional view explaining a workpiece transfer device according to a second embodiment of the present invention; 
       FIG. 7  is a sectional view of a common workpiece transfer device according to a prior art device; and 
       FIG. 8  is a sectional view of a workpiece transfer device according to a prior art device. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Hereinbelow, embodiments of the present invention are described with reference to the accompanying drawings. 
     FIGS. 1  to  5  are views explaining a workpiece transfer device for lathes and other machine tools according to a first embodiment of the invention.  FIGS. 1 and 2  show a front view and a plan view, respectively, of a lathe equipped with the workpiece transfer device.  FIGS. 3 and 4  are schematic perspective views of the workpiece transfer device. Further,  FIG. 5  is a sectional view of the workpiece transfer device. 
   Referring to the figures, a lathe  1  is equipped with a workpiece transfer device  2 . The lathe  1  is constructed so that a spindle  5  having a chuck  4  for holding a workpiece is rotatably supported by a headstock  3  provided on a fixed bed  1   a . A tool rest  6  loaded with a plurality of tools T is provided on the fixed bed la so as to be relatively movable in the X-axis, Y-axis and Z-axis directions. Then, the tool rest  6  is moved relative to the workpiece Wo. The chuck  4  holds the workpiece Wo so that the workpiece is machined using the tool T. 
   The workpiece transfer device  2  is disposed above the lathe  1 . The workpiece transfer device  2  comprises a frame member  10  extending from a workpiece loading/unloading position A to a workpiece machining position B. The workpiece transfer device  2  also includes a support member  11  supported by the frame member  10  so as to be movable in the Z-axis direction. A workpiece holding mechanism  12  is mounted on the support member  11  as shown in  FIGS. 1 and 2 . Also,  FIGS. 3 ,  5  and  6  show two different drive mechanisms  7 . 
   The frame member  10  is made of pipe steel having an oblong-shaped cross section. The frame member  10  is hung and supported by vertical column members  10   d  provided at the left and right end portions. 
   A workpiece stocker  15  is provided at the workpiece loading/unloading position A. This workpiece stocker  15  has a plurality of guide shafts  16  for supporting a plurality of unprocessed workpieces W 1  in a stacked state, and a transfer drive mechanism  17  for transferring the next-to-be-processed workpiece W 1 ′, from the unprocessed workpieces W 1 , to the workpiece takeout position. 
   The workpiece holding mechanism  12  has an up-and-down moving mechanism  20  placed and fixed on the support member  11 , a loader arm  21  to be driven up and down in the Y-axis direction by the up-and-down moving mechanism  20 , and a loader head  22  fitted at a lower end of the loader arm  21 . This loader head  22  is formed so as to be rotatable 90 degrees about a shaft  23  perpendicular to an axis of the loader arm  21  by a drive mechanism (not shown). 
   The loader head  22  has a pair of hands  24 ,  25  for holding a next-to-be-processed workpiece W 1 ′ and a processed workpiece W 0 . Each of these hands  24 ,  25  can be directed leftward in the Z-axis direction (see broken line in  FIG. 1 ) or downward in the Y-axis direction (see solid line in  FIG. 1 ) by rotating them 90 degrees. 
   The support member  11  has a lateral side portion  11   a  opposed to a top wall  10   a  of the frame member  10 . The support member  11  also has a longitudinal side portion  11   b  extending downwardly from a front end portion of the lateral side portion  11   a  and opposed to a front side wall  10   b  of the frame member  10 . The support member  11  also has a left-and-right pair of lower side portions  11   c  extending from a lower end portion of the longitudinal side portion  11   b  downwardly of a bottom wall  10   c  of the frame member  10 . The workpiece holding mechanism  12  is attached at the longitudinal side portion  11   b.    
   A linear guide  27  is provided between the top wall  10   a  of the frame member  10  and the lateral side portion  11   a  of the support member  11 . This linear guide  27  is constructed so that a pair of bearing blocks  27   b  disposed on the lateral side portion  11   a  of the support member  11 , so as to be fixedly spaced from each other, are slidably fitted to a guide rail  27   a  fixedly disposed on the top wall  10   a  so as to extend along the length of the top wall  10   a . As a result of this arrangement, the support member  11  is supported by the frame member  10  and is movable in the Z-axis direction via the linear guide  27 . 
   Further, a rack  30  is provided parallel to the guide rail  27   a  at a lower end portion of the front side wall  10   b  adjoining the top wall  10   a  of the frame member  10 . This rack  30  is formed into a vertically oblong bar-shaped body, as viewed in its cross section. The rack  30  is also fixedly disposed on the front side wall  10   b  so as to be adjustable in its vertical position relative to the linear guide  27 . More specifically, the rack  30  is fixed to the front side wall  10   b  of the frame member  10  with bolts  30   a  screwed into the front side wall  10   b  through bolt insertion holes  30   b  which are formed into vertically longer elongate holes. The fitting position of the rack  30  can be adjusted so that the distance to the linear guide  27  becomes constant over the entire length of the rack  30 . 
   A lower portion of the rack  30  protrudes downwardly of the bottom wall  10   c  of the frame member  10 , and a lower surface of the protruding portion has rack teeth that were formed by a tooth-cutting operation. 
   A pair of cam followers  31  are in rolling contact with the front side face and the rear side face of the rack  30 . The cam followers  31  are pivotally held on lower side portions of the support member  11 . The forward and backward movement of the lower side portions  11   c  is regulated by the cam followers  31 . 
   Further, a pinion gear  33  is engaged with the rack teeth of the rack  30 . The pinion gear  33  is mounted on a rotating shaft  34   a  of a drive motor  34 . This drive motor  34  is fixedly placed on the support member  11 . When the drive motor  34  drives the pinion gear  33  in rotation, the support member  11  reciprocates between the workpiece loading/unloading position A and the workpiece machining position B. 
   Next, additional benefits of this embodiment are described. 
   In the workpiece loading/unloading position A, the loader arm  21  moves down along the Y-axis direction, holding the next-to-be-processed workpiece W 1 ′ in one hand  24 . The loader arm  21  then moves up in the Y-axis direction to the upper end while holding the workpiece W 1 ′. Subsequently, the support member  11  moves along the frame member  10  to the spindle side in the Z-axis direction. 
   When machining on the workpiece held by the chuck  4  of the lathe  1  is completed, the tool rest  6  moves back, and stands by. Then, the hands  24 ,  25  turn so they face the chuck  4 , and the loader arm  21  moves down in the Y-axis direction, so that the empty hand  25  is positioned in the workpiece machining position B confronting the chuck  4 . 
   The hand  25  moves to the chuck side in the Z-axis direction, holding the processed workpiece W 0  held by the chuck  4 . The hand  25  then moves slightly back in the Z-axis direction pulling the processed workpiece W 0  off. In this state, the hand  25  moves down in the Y-axis direction, and the hand  24  is then positioned in the workpiece machining position B, moving forward in the Z-axis direction so that the next-to-be-processed workpiece W 1  is mounted and held on the chuck  4 . In this way, the processed workpiece W 0  and the next-to-be-processed workpiece W 1  are automatically exchanged therebetween. 
   Next, the loader arm  21  moves up in the Y-axis direction and then it moves to the workpiece stocker side in the Z-axis direction. The hands  24 ,  25  are then turned downward and moved down in the Y-axis direction, where the processed workpiece W 0  is placed on an empty guide shaft  16  and stored in the workpiece stocker  15 . 
   According to the workpiece transfer device  2  of this embodiment, since the linear guide  27  is disposed between the top wall  10   a  of the frame member  10  and the lateral side portion  11   a  of the support member  11  and since the rack  30  is disposed on the front side wall  10   b  adjoining the top wall  10   a , vertical positional adjustment of the rack  30  relative to the linear guide  27  can be fulfilled with ease by utilizing the bolt insertion hole  30   b . The bolt insertion hole  30   b  is an elongate hole and allows adjustment of the fitting position of this rack  30 . Moreover, the occurrence of vibrations or noise can be prevented while adopting relatively low dimensional accuracy square pipe steel for building use as the frame member  10 . 
   Further, since the vertical size of the rack  30  (rack thickness) can be increased without increasing the height of the support member  11 , warping of the rack  30  during the formation of the rack teeth at its lower surface by tooth-cutting can be prevented. 
   Furthermore, the front and rear side faces of the rack  30  can be pinched and easily held and secured by the cam followers  31 , so that back-and-forth vibrations of the support member  11  can be prevented notwithstanding the use of one linear guide. 
     FIG. 6  is a view for explaining a workpiece transfer device according to a second embodiment of the present invention. In this figure, the same reference numerals are used as those in  FIG. 5  to show the same or equivalent component members. 
   The workpiece transfer device  2  of this embodiment comprises a frame member  10  extending from a workpiece loading/unloading position A to a workpiece machining position B, a support member  11  supported by the frame member  10  so as to be movable in the Z-axis direction, a workpiece holding mechanism  12  mounted on the support member  11 , and a drive mechanism  7 . The basic construction of this workpiece transfer device  2  is similar to that of the first embodiment. 
   Further, a linear guide  27  and a rack  30  are disposed on a front side wall  10   b  of the frame member  10 . This linear guide  27  is fixedly placed at an upper end portion of the front side wall  10   b , and the rack  30  is disposed at a lower end portion of the front side wall  10   b  so its vertical position relative to the linear guide  27  is adjustable. 
   According to this embodiment, since the linear guide  27  and the rack  30  are disposed on the front side wall  10   b  of the frame member  10 , the vertical positional adjustment of the rack  30  relative to the linear guide  27  can be fulfilled with ease by utilizing the bolt insertion hole  30   b . This hole is an elongate hole and allows for adjustment of the fitting position of this rack  30  so that the same effects of the first embodiment can be obtained. 
   Furthermore, in this embodiment, since the linear guide  27  and the rack  30  are disposed on the same plane of the front side wall  10   b , only planar machining of the front side wall  10   b  is necessary. This allows the machining costs to be reduced compared to the cases where two wall surfaces are subjected to machining. 
   It is to be understood that although the present invention has been described with regard to preferred embodiments thereof, various other embodiments and variants may occur to those skilled in the art, which are within the scope and spirit of the invention, and such other embodiments and variants are intended to be covered by the following claims. 
   The text of Japanese priority application no. 2002-013022 filed Jan. 22, 2002 is hereby incorporated by reference.