Abstract:
In a sliding door disposed in an opening of a cover surrounding a machine tool, 
     From among two adjacent door panels, at least one of sliding members of the door panel which is located closer to a door frame slides on a door frame guide track, whereas at least one of sliding members of the door panel which is located farther from the door frame slides on the door frame guide track, and at least one of the remaining sliding members slides on the door panel guide track. Thus, guide means can be prevented from projecting vertically.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a sliding door of a machine tool, and more particularly, to a guide structure of a sliding door. 
         [0003]    2. Description of the Related Art 
         [0004]    A machine tool has a machining space in which a workpiece is placed and machined. In machining the workpiece, a cover may sometimes be provided to protect the workpiece itself and prevent chips produced during the workpiece machining and a coolant from scattering to the surrounding area. 
         [0005]      FIG. 1  is a perspective view of an entire machine tool. The machine tool is provided therein with a machining space in which a workpiece (not shown) can be placed and its side surfaces are covered by a cover  50 . Further, first and second slide-type doors  10  and  20  for workpiece loading/unloading and the like are arranged on the front side of the machine tool. In this machine tool, a two-tiered sliding door is used in order to handle large workpieces. 
         [0006]    Japanese Patent Application Laid-Open No. 2006-205337 discloses a technique in which two sliding doors of a machine tool are arranged so that a second one of them is guided by a guide rail attached to the underside of a first one. Since guide means of the second door is located below that of the first door, according to this technique, the door may sometimes largely project downward from the lower end portion of its opening. Possibly, therefore, the door may interfere with an installation space for mechanism sections, such as a movable cover, saddle, etc., of the machine tool so that the opening width of the door cannot be increased. 
         [0007]    Further, Japanese Utility Model Application Laid-Open No. 62-127745 discloses a technique in which each of two sliding doors of a machine tool is guided by a rail disposed in its center. Since both of the doors are guided by their respective center rails, according to this technique, they may possibly interfere with each other or may increased in overall thickness. 
       SUMMARY OF THE INVENTION 
       [0008]    Accordingly, the object of the present invention is to provide a sliding door disposed in an opening of a cover surrounding a machine tool and configured for an increased door opening width. 
         [0009]    A sliding door according to the present invention is disposed in an opening of a cover surrounding a machine tool and comprises a door frame and at least two door panels (doors) disposed inside the machine tool with respect to the door frame. The door frame comprises a door frame guide track (rail). From among those door panels, one of the at least two adjacent door panels, which is located closer to the door frame, comprises a door panel guide track, one of the door panels, which adjoins the door frame, comprises at least one sliding member configured to slide on the door frame guide track, and the door panel which does not adjoin the door frame comprises at least two sliding members. And, from among the sliding members of the door panel which does not adjoin the door frame, at least one sliding member is configured to slide on the door frame guide track, and at least one of the remaining sliding members is configured to slide on the door panel guide track. 
         [0010]    According to the present invention, at least one of the sliding members of the door panel which is located farther from the door frame is configured to slide on the door panel guide track, not on the door frame guide track. Thus, every sliding member of the door panel which is located farther from the door frame can be prevented from projecting vertically by being slid on the door frame guide track. Consequently, a vertical space for the installation of the guide means can be reduced. 
         [0011]    The door frame guide track may be a single track configured to guide sliding members of a plurality of door panels. 
         [0012]    The sliding member configured to slide on the door frame guide track may be attached to a side end of an opening of the door panel. 
         [0013]    In this aspect, the sliding member configured to slide on the door frame guide track is disposed at the side end of the opening of the door panel so that the position where the sliding member of the door panel slides on the door frame guide track is located at the end of the opening. Thus, the opening width can be prevented from being reduced. 
         [0014]    The two door panels may be substantially equal in guide height. 
         [0015]    According to the present invention, there can be provided a sliding door of a machine tool configured for an increased door opening width. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other objects and features of the present invention will be obvious from the ensuing description of embodiments with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a perspective view of an entire machine tool; 
           [0018]      FIGS. 2A and 2B  are perspective views showing an example of a guide structure of one embodiment of a sliding door of a machine tool according to the present invention, in which  FIG. 2A  shows an open state of the sliding door and  FIG. 2B  shows a closed state of the door; 
           [0019]      FIGS. 3A to 3F  are views illustrating details of the guide structure of the sliding door shown in  FIGS. 2A and 2B , in which  FIG. 3A  is a front view,  FIG. 3B  is a sectional view,  FIG. 3C  is a sectional view taken along line A-A of  FIG. 3A  and from the right-hand side of  FIG. 3A ,  FIG. 3D  is a sectional view taken along line B-B of  FIG. 3A  and from the left-hand side of  FIG. 3A ,  FIG. 3E  is an enlarged view of a lower guide portion of  FIG. 3C , and  FIG. 3F  is an enlarged view of a lower guide portion of  FIG. 3D ; 
           [0020]      FIGS. 4A and 4B  are schematic views showing a prior art sliding door and its surroundings, in which  FIG. 4A  is a front view and  FIG. 4B  is a sectional view taken along line A-A of  FIG. 4A ; 
           [0021]      FIGS. 5A ,  5 B and  50  are views illustrating a guide structure of the prior art sliding door, in which  FIG. 5A  is a front view,  FIG. 5B  is a sectional view, and  FIG. 5C  is an enlarged view of a lower guide portion of  FIG. 5C ; and 
           [0022]      FIGS. 6A and 6B  are perspective views showing an example of the guide structure of the prior art sliding door, in which  FIG. 6A  shows an open state of the door and  FIG. 6B  shows a closed state of the door. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    A conventional technique related to a sliding door of a machine tool and its problems will be described first. 
         [0024]    An example of a guide structure of the sliding door of the machine tool according to the conventional technique will first be described with reference to  FIGS. 6A and 6B .  FIGS. 6A and 6B  show an open state and a closed state, respectively, of the door. 
         [0025]    As shown in  FIG. 6B , the sliding door comprises a first door  110  and a second door  120 , both of which are slidable. When the sliding door is in the open state, as shown in  FIG. 6A , the first and second doors  110  and  120  overlap each other to leave an opening  200  through which a workpiece (not shown) to be machined can be loaded into and unloaded from the machine tool. When the sliding door is in the closed state, in contrast, the first and second doors  110  and  120  hardly overlap each other so that the opening  200  is closed, as shown in  FIG. 6B . 
         [0026]    A structure in the vicinity of guide means of the prior art sliding door will now be described with reference to  FIGS. 4A and 4B . 
         [0027]    As is also shown in  FIGS. 6A and 6B , a front sliding door section comprises the first and second doors  110  and  120 . As shown in  FIG. 4B , moreover, a cover  150  and a saddle  160  are disposed at the lower part of the machine tool. The cover  150  is movable in the front-rear direction of the machine tool (i.e., horizontal direction in  FIG. 4B ). As shown in  FIG. 4B , a door guide portion  300  for the first and second doors  110  and  120  is configured so that a guide unit of the second door  120  is located below that of the first door  110 . The door guide portion  300  will be described in detail later. 
         [0028]    The guide structure of the sliding door according to the conventional technique will now be described with reference to  FIGS. 5A ,  5 B and  5 C. 
         [0029]    A door frame  140  is located on the front side (left-hand side of  FIG. 5B ) of the sliding door structure as viewed from its front. The first and second doors  110  and  120  are inwardly arranged from the side of the door frame  140  in the order named, as shown in  FIG. 5B . 
         [0030]    At the lower part of the sliding door structure, moreover, the door frame  140  is provided with first and second lower rails  112   a  and  112   b  that are arranged vertically in parallel relation to each other. On the other hand, the first and second doors  110  and  120  are provided with first and second lower door rollers  132   a  and  132   b , respectively. The first and second lower rails  112   a  and  112   b  guide the first and second lower door rollers  132   a  and  132   b , respectively. 
         [0031]    At the upper part of the sliding door structure, as in the case of the lower part, the door frame  140  is provided with first and second upper rails  114   a  and  114   b  that are arranged vertically in parallel relation to each other. On the other hand, the first and second doors  110  and  120  are provided with first and second upper door rollers  134   a  and  134   b , respectively. The first and second upper rails  114   a  and  114   b  guide the first and second upper door rollers  134   a  and  134   b , respectively. 
         [0032]    In the prior art sliding door constructed in this manner, as shown in  FIGS. 5B and 5C , the second lower rail  112   b  is located below the first lower rail  112   a , and the second lower door roller  132   b  is located below the first lower door roller  132   a , at the lower part of the sliding door structure. Possibly, therefore, the sliding door may largely project downward and interfere with mechanism sections, such as the cover  150  and the saddle  160  (see  FIG. 4B ). Thus, the opening width of the sliding door cannot be increased, in some cases. 
         [0033]    The present invention has been made to solve these problems. The following is a description of one embodiment of the sliding door of the machine tool according to the present invention. 
         [0034]    An example of a guide structure of the one embodiment of the sliding door of the machine tool according to the present invention will first be described with reference to  FIGS. 2A and 2B . 
         [0035]    Although the sliding door shown in  FIGS. 2A and 2B  is similar to the prior art sliding door shown in  FIGS. 6A and 6B , the guide structures of these two sliding doors are different from those shown in shown in  FIGS. 6A and 6B . 
         [0036]    The guide structure of the sliding door shown in  FIGS. 2A and 2B  will now be described in detail with reference to  FIGS. 3A to 3F . 
         [0037]    A door frame  40  is located on the front side (left-hand side of  FIG. 5B  or right-hand side of  FIG. 3D ) of the sliding door structure as viewed from its front. A first door  10  and a second door  20  are inwardly arranged from the side of the door frame  40  in the order named, as shown in  FIG. 3B . 
         [0038]    At the lower part of the sliding door structure, moreover, the door frame  40  is provided with a first lower rail  12  (single rail dissimilar to the two-tiered rail structure shown in  FIG. 5B ). The first door  10  is provided with a first lower door roller  32   a  as well as a second lower rail  22 . Further, the second door  20  is provided with a second lower door roller  32   b  on its left-hand side as viewed from its front. The first lower rail  12  of the door frame  40  guides the first lower door roller  32   a  of the first door  10 , while the second lower rail  22  of the first door  10  guides the second lower door roller  32   b  of the second door  20 . 
         [0039]    The second door  20  is further provided with a third lower door roller  32   c  on its right-hand side as viewed from its front, as shown in  FIGS. 3D and 3F . The first lower rail  12  of the door frame  40  guides the third lower door roller  32   c  of the second door  20 . The third lower door roller  32   c  is configured to form a side end of the opening of the sliding door. 
         [0040]    At the upper part of the sliding door structure, as in the case of the lower part, the door frame  40  is provided with a first upper rail  14 , as shown in  FIG. 3B . The first door  10  is provided with a first upper door roller  34   a  as well as a second upper rail  24 . Further, the second door  20  is provided with a second upper door roller  34   b  on its left-hand side as viewed from its front. The first upper rail  14  of the door frame  40  guides the first upper door roller  34   a  of the first door  10 , while the second upper rail  24  of the first door  10  guides the second upper door roller  34   b  of the second door  20 . 
         [0041]    The second door  20  is further provided with a third upper door roller  34   c  on its right-hand side as viewed from its front, as shown in  FIG. 3D . The first upper rail  14  of the door frame  40  guides the third upper door roller  34   c  of the second door  20 . The third upper door roller  34   c  is configured to form a side end of the opening of the sliding door. 
         [0042]    According to the configuration described above, the rails and door rollers that constitute guide members for guiding the first and second doors  10  and  20  are equal in height. Thus, large upward or downward projection of the sliding door, which may be caused by the presence of rails and door rollers arranged vertically in parallel relation, as in the conventional technique, is eliminated. Consequently, a vertical space for the installation of guide means and the like can be reduced. 
         [0043]    According to this configuration, the third lower and upper door rollers  32   c  and  34   c  on the right-hand side of the second door  20  are guided by the first lower and upper rails  12  and  14 , respectively, of the door frame  40 . Inevitably, therefore, the first lower and upper rails  12  and  14  interfere with the sliding range of the first door  10 . In some cases, therefore, the first and second doors  10  and  20  can not be opened until they entirely overlap each other, as a result, the opening width may be reduced. In case where a rubber cushion, knob, control arrangement, etc., are attached to any of the doors, however, the opening width has been already restricted for securing an installation space for them. Thus, the opening width cannot be particularly reduced despite the configuration of the present embodiment. 
         [0044]    In the present embodiment, the rails and door rollers are used as the members for guiding the doors. However, these members may be replaced with linear-motion guides (LM guides), such as slide packs, and their blocks. 
         [0045]    While the two doors are used in the configuration of the present embodiment described above, three or more doors may alternatively be used in a door configuration comprising a series of similar structures. In the case of a three-door configuration in which first, second, and third door panels are successively arranged with distance from the door frame, for example, one of door rollers of the second door panel slides on a rail attached to the door frame, while the other door roller slides on a rail attached to the first door panel. Further, one of door rollers of the third door panel is configured to slide on a rail attached to the door frame, and the other door roller to slide on a rail attached to the second door panel.