Abstract:
The present invention relates to a machine tool including a ram spindle and a tool holder, and provides a machine tool comprising: a tool holder including at least two inserts; and a ram spindle capable of fixing the tool holder in a clamped state or rotating the tool holder in order to change the position of the insert, such that the position of the insert can be quickly changed, thereby enabling an improvement in productivity and precision and a reduction in product costs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This present application is a national stage filing under 35 U.S.C § 371 of PCT application number PCT/KR2016/001281 filed on Feb. 5, 2016 which is based upon and claims the benefit of priority to Korean Patent Application No. 10-2015-0020324 filed on Feb. 10, 2015 in the Korean Intellectual Property Office. The disclosures of the above-listed applications are hereby incorporated by reference herein in their entirety. 
     
    
     FIELD OF DISCLOSURE 
       [0002]    The present invention relates to a machine tool which includes a ram spindle and a tool holder having improved structures, respectively. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    Machine tools refer to machines used for the purpose of machining metallic or non-metallic workpieces (hereinafter referred to as the “base materials”) into desired shapes and dimensions by means of appropriate tools by using various types of cutting or non-cutting methods. 
         [0004]    Furthermore, machine tools may be basically classified into turning centers configured to machine base materials by rotating the base materials and moving tools and machining centers configured to machine base materials by rotating tools and moving the base materials. 
         [0005]      FIG. 1  is a view showing a machine tool in which a conventional ram spindle is disposed, and  FIG. 2  is a perspective view showing the conventional ram spindle and a conventional tool holder which are coupled to each other. 
         [0006]    Referring to  FIG. 1 , in a conventional machine tool  10 , a turntable  2  is disposed, an auto tool changer (ATC) accommodated in an ATC accommodation part  6  and a column  8  are disposed on a base  1 , a cross rail  9  is disposed on the column  8 , and a ram carriage  5  is disposed on a side of the cross rail  9 . 
         [0007]    A base material (not shown) to be machined is fastened to and rotated on the turntable  2 , and the ram carriage  5  is movable in a direction parallel to a ground surface by means of the cross rail  9 . 
         [0008]    In this case, the ram carriage  5  is movable along a vertical transfer part  7  in a direction perpendicular to a ground surface. A ram spindle  4  is disposed at the distal end of the ram carriage  5 , and a head block  3  is disposed at the free end of the ram spindle  4 . 
         [0009]    In other words, the ram spindle  4  disposed on the ram carriage  5  is moved along the cross rail  9  in the x-axis direction and along the vertical transfer part  7  in the z-axis direction, and is thus disposed at a location where a tool can machine the rotating base material through turning. 
         [0010]    In this case, a tool holder  20  having a mounting depression  21  into which an insert (a tool) for machining a rotating base material is disposed may be mounted on the head block  3 . The tool holder  20  is mounted in or detached and replaced from the ATC inside the ATC accommodation part  6  depending on the machining path and shape of a base material. 
         [0011]    However, the method of replacing the tool holder  20  of the conventional machine tool  10  requires a long replacement time, and increases the number of required tool holders  20 , thereby increasing the costs of the machine tool  10 . 
         [0012]    Furthermore, the individual tool holders  20  have minute differences, and thus a problem with the reliability of the degree of precision may occur due to the differences in machining distance attributable to inserts mounted into the tool holders  20 . 
       SUMMARY 
       [0013]    The present invention has been conceived to overcome the above-described problems, and an object of the present invention is to provide a machine tool which includes a plurality of inserts, thereby reducing tool holder replacement time, performing rapid and precise machining, and increasing productivity and cost competitiveness. 
         [0014]    In order to accomplish the above object, the present invention provides a machine tool having a ram spindle and a tool holder, the machine tool including: a tool holder configured to include at least two inserts; and a ram spindle configured to fasten the tool holder in the state of clamping the tool holder and to rotate the tool holder in order to change the locations of the inserts. 
         [0015]    The ram spindle may include: a housing configured to have an open surface in the lower side surface thereof; a center part rotatably accommodated inside the housing; a first outer part disposed outside the center part, and configured to be co-rotated with the center part; a second outer part disposed between the housing and the first outer part, and fastened to the housing; and an actuator unit accommodated inside the housing, and configured to be selectively movable upward and downward through the open surfaces of the center part and the first outer part. 
         [0016]    The tool holder may include: a coupling part configured such that one end thereof is mounted on the ram spindle; and a mounting part configured such that at least two inserts are coupled to the free end thereof, and disposed on the other end of the coupling part. 
         [0017]    Outer ribs protruding at equal intervals may be formed on the outer circumferential surface of the first outer part, a cavity may be formed in the other end of the coupling part, and inner ribs protruding to come into contact with an inner diameter of the first outer part or to be spaced apart at predetermined intervals may be formed on the inner circumferential surface of the cavity at equal intervals. 
         [0018]    The outer diameter of one end of the coupling part defined by the cavity may be formed to be equal to that of the second outer part, and the inner diameter of the one end of the coupling part may be formed to be equal to or larger than that of the second outer part. 
         [0019]    One or more protrusions may be formed on the first outer part; and depressions configured to be seated over the protrusions may be formed in the coupling part so as to correspond in number to the protrusions. 
         [0020]    The protrusions may be formed adjacent to the outer ribs; and the depressions may be formed adjacent to the inner ribs. 
         [0021]    A first protrusion and depression part and a second protrusion and depression part configured to be engaged with each other may be formed on the opposite surfaces of the second outer part and the coupling part, respectively, and may be engaged with each other when the center part and the first outer part are raised by the actuator unit. 
         [0022]    At least two protruding keys may be disposed on the outer circumferential surface of the center part; and key coupling depressions configured to be engaged with the keys may be formed on the first outer part. 
         [0023]    A guide protrusion formed to protrude may be disposed at the center of the cavity; and a guide depression corresponding to the guide protrusion may be formed in the center part. 
         [0024]    The actuator unit may be disposed inside the center part or first outer part. 
         [0025]    The actuator unit may include: a clamping passage configured to raise the center part; an unclamping passage spaced apart from the clamping passage, and configured to lower the center part; and a spring configured to provide restoring force in the direction in which the center part is raised. 
         [0026]    The machine tool may further include an auto tool changer (ATC) configured to store the tool holder unclamped from the ram spindle. 
         [0027]    The present invention can provide the machine tool which includes the ram spindle and the tool holder having the improved structures, respectively, so that the plurality of inserts is provided in the single tool holder and the locations of the inserts can be rapidly changed by changing whether to fasten the tool holder through the vertical movement of part of the ram spindle, thereby improving productivity and precision and also reducing the costs of products. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a view showing a machine tool in which a conventional ram spindle is disposed; 
           [0029]      FIG. 2  is a perspective view showing the conventional ram spindle and a conventional tool holder which are coupled to each other; 
           [0030]      FIG. 3  is a partial perspective view of a ram spindle according to an embodiment of the present invention; 
           [0031]      FIG. 4  is a perspective view of a tool holder according to an embodiment of the present invention; and 
           [0032]      FIG. 5A  and  FIG. 5B  show side sectional views schematically illustrating states in which an actuator unit according to an embodiment of the present invention moves a center part and a first outer part in upward and downward directions. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 
         [0034]    Unless specifically defined, all terms used herein have the general meanings that would be understood by those skilled in the art. If the meaning of a term used herein conflicts with the general meaning of the corresponding term, the definition made herein is used. 
         [0035]    However, the invention to be described below is intended merely to illustrate an embodiment of the present invention, and is not intended to limit the range of rights of the present invention. Throughout the specification, the same reference numerals designate the same components. 
         [0036]      FIG. 3  is a partial perspective view of a ram spindle according to an embodiment of the present invention,  FIG. 4  is a perspective view of a tool holder according to an embodiment of the present invention, and  FIG. 5A  and  FIG. 5B  show side sectional views schematically illustrating states in which an actuator unit according to an embodiment of the present invention moves a center part and a first outer part in upward and downward directions. 
         [0037]    Referring to  FIGS. 3 to 5A and 5B , a machine tool according to an embodiment of the present invention provides a ram spindle  100  and a tool holder  200  having improved structures, respectively. 
         [0038]    The machine tool according to the present embodiment implements a tool holder configured to include at least two inserts and a ram spindle configured to fasten the tool holder in the state of clamping the tool holder and to rotate the tool holder in order to change the locations of the inserts, thereby rapidly, accurately and stably machining a base material. 
         [0039]    More specifically, the ram spindle  100  may include a housing  110 , a center part  120 , a first outer part  130 , a second outer part  140 , and an actuator unit  150 . 
         [0040]    The housing  110  may have an open surface in the lower side surface thereof, and may form the appearance of the ram spindle  100 . In this case, the lower side surface is named based on the states shown in the drawings, and may be any one side surface of the housing  110 , such as the upper side surface, left side surface, or right side surface thereof, or the like, depending on a viewing direction. 
         [0041]    The center part  120  is accommodated inside the housing  110 , and is rotatably disposed. The center part  120  may be connected to an externally disposed motor via pulleys, or may be rotated by a directly connected motor disposed inside the housing  110 . 
         [0042]    Furthermore, at least two protruding keys  121  may be disposed on the outer circumferential surface of the center part  120 . These keys  121  may be integrated with the center part  120 , or may be coupled to the center part  120  by means of a well-known method, such as bolt coupling. 
         [0043]    Furthermore, a guide depression  122  corresponding to a guide protrusion  215  to be described later may be formed in the center part  120 . The tool holder  200  may be stably mounted on the ram spindle  100  by the guide depression  122  and the guide protrusion  215 . 
         [0044]    The first outer part  130  is disposed outside the center part  120 , and is co-rotated with the center part  120 . Outer ribs  131  protruding at equal intervals may be formed on the outer circumferential surface of the first outer part  130 . Although four outer ribs  131  may be formed along the end of the first outer part  130  at equal intervals, as shown in  FIG. 3 , the configuration of the outer ribs  131  is not limited thereto. 
         [0045]    In this case, the first outer part  130  and the center part  120  are components separate from each other, and thus key coupling depressions  132  coupled with the keys  121  may be formed in the first outer part  130  so as to receive rotation force when the center part  120  is rotated. 
         [0046]    Furthermore, one or more protrusions  133  formed adjacent to the outer rib  131  may be formed on the first outer part  130 . In other words, the protrusions  133  may be formed on the respective four outer ribs  131 , or a protrusion  133  may be formed on at least any one of the four outer ribs. Depressions  213  to be described later may be inserted over the protrusions  133 , and guide the tool holder  200  to an accurate fastening location with respect to the ram spindle  100 . 
         [0047]    The second outer part  140  may be disposed between the housing  110  and the first outer part  130 , and may be fastened to the housing  110 . In other words, the second outer part  140  supports the center part  120  and the first outer part  130 , surrounding the outer circumferential surface of the center part  120 , inside the housing  110 , and is also fastened to the housing  110 . Accordingly, the second outer part  140  is not rotated even when the center part  120  and the first outer part  130  are rotated. 
         [0048]    Accordingly, a bearing (not shown) may be disposed between the first outer part  130  and the second outer part  140 , and may promote the smooth rotation of the first outer part  130  inside the fastened second outer part  140 . 
         [0049]    Furthermore, a first protrusion and depression part  141  may be formed on the surface of the second outer part  140 , opposite to a coupling part  210  to be described later, so as to be engaged with a second protrusion and depression part  214  formed on the coupling part  210 . 
         [0050]    In other words, when the center part  120  and the first outer part  130  are raised by the actuator unit  150 , the tool holder  200  is firmly fastened to the ram spindle  100  through the engagement between the first protrusion and depression part  141  and the second protrusion and depression part  214 , thereby enabling a rotating base material to be precisely machined. 
         [0051]    The actuator unit  150  may be accommodated inside the housing  110 , may selectively move upward and downward through the open surfaces of the center part  120  and the first outer part  130 , and may be implemented as a pneumatic or hydraulic cylinder. 
         [0052]    Referring to  FIG. 5A  and  FIG. 5B , the actuator unit  150  includes a clamping passage  151  and an unclamping passage  152 , and may further include a spring  153  configured to provide restoring force. 
         [0053]    More specifically, the actuator unit  150  may be disposed inside the center part  120  or first outer part  130 . As shown in  FIG. 5A , a hydraulic or pneumatic medium enters into the clamping passage  151 , and raises the lower end of the center part  120 . This raising force may also raise the first outer part  130  coupled through the engagement between the keys  121  and the key depressions. 
         [0054]    In contrast, as shown in  FIG. 5B , a hydraulic or pneumatic medium enters into the unclamping passage  152 , and lowers the lower end of the center part  120 . This lowering force may also lower the first outer part  130  coupled through the engagement between the keys  121  and the key depressions. 
         [0055]    Furthermore, since the tool holder  200  needs to be firmly clamped to the ram spindle  100  in order to machine a base material, the spring  153  is preferably disposed to provide restoring force during a shift from an unclamping state to a clamping state. 
         [0056]    Meanwhile, the tool holder  200  may be divided into the coupling part  210  and a mounting part  220 , and the coupling part  210  and the mounting part  220  may be integrated with each other or disposed in a coupled form by using a bolting method. 
         [0057]    The ram spindle  100  is mounted at one end of the coupling part  210 , and the mounting part  220  to be described later is disposed at the other end thereof. 
         [0058]    More specifically, a cavity  211  may be formed at one end, i.e., upper side surface, of the coupling part  210 , and inner ribs  212  protruding to come into contact with the inner diameter of the first outer part  130  or to be spaced apart at predetermined intervals may be formed on the inner circumferential surface of the cavity  211  at equal intervals. 
         [0059]    In this case, the thickness of the upper end defined by the cavity  211  of the coupling part  210 , i.e., the length defined by the inner and outer circumferential surfaces of one end of the coupling part  210 , may be formed to be equal to or smaller than that of the second outer part  140 . 
         [0060]    However, when the coupling between the outer ribs  131  and the inner ribs  212  is taken into account, it is preferred that the outer diameter of the one end of the coupling part  210  is formed to be equal to that of the second outer part  140  and the inner diameter of the one end of the coupling part  210  is formed to be larger than that of the second outer part  140 . 
         [0061]    Furthermore, depressions  213  formed adjacent to the inner ribs  212  and configured to be seated over the protrusions  133  may be formed in the coupling part  210  so as to correspond in number to the protrusions  133 . 
         [0062]    In other words, the inner ribs  212  are made to be disposed at locations where the outer ribs  131  are not formed. When the tool holder  200  is raised and rotated in a clockwise or counterclockwise direction, the depressions  213  and the protrusions  133  are engaged with each other, and thus the accurate disposition location of the tool holder  200  can be determined. 
         [0063]    Furthermore, as described above, the second protrusion and depression part  214  is formed on the upper side surface of the coupling part  210 . When the center part  120  and the first outer part  130  are raised by the actuator unit  150 , the first protrusion and depression part  141  and the second protrusion and depression part  214  are engaged with each other, which enables the tool holder  200  to be firmly mounted on the ram spindle  100 . 
         [0064]    Furthermore, a guide protrusion  215  formed to protrude is formed at the center of the cavity  211 , and is engaged with the guide depression  122  of the center part  120 . Stable coupling is achieved by the guide depression  122  and the guide protrusion  215 . 
         [0065]    At least two inserts  230  may be coupled to the other side, i.e., free end, of the mounting part  220  other than one side of the mounting part  220  coupled to the coupling part  210 . Although a total of four heterogeneous inserts  230  are disposed along an overall region including the opposite side not shown in the drawing, the configuration of the inserts  230  is not limited thereto. 
         [0066]    The tool holder  200  according to the present embodiment may be unclamped from the ram spindle  100 , and may be stored in an auto tool changer (ATC) accommodated inside the ATC accommodation part  6  (see  FIG. 1 ). 
         [0067]    In summary, the present invention may be operated as follows. Once a base material is rotated by the turntable  2  (see  FIG. 1 ), an unclamping state in which the tool holder  200  is mounted on but not firmly fastened to the ram spindle  100 , as shown in  FIG. 5B , is entered in order to bring a programmed insert  230  into contact with the base material. 
         [0068]    Thereafter, the center part  120  is rotated to dispose the insert  230  suitable for an operation in the direction of the base material, and also the first outer part  130  is co-rotated by the center part  120 . The tool holder  200  may be also co-rotated by the rotation of the first outer part  130 . 
         [0069]    When the desired insert  230  is disposed in the direction of the base material, a clamping state is entered, as in the state of  FIG. 5A , and thus the first protrusion and depression part  141  and the second protrusion and depression part  214  are firmly engaged with each other, with the result that the tool holder according to the present embodiment is fastened to the ram spindle, thereby enabling a precise turning operation to be performed. 
         [0070]    From the foregoing description, it will be apparent to those skilled in the art that various alterations and modifications may be made without departing from the technical spirit of the present invention. The technical scope of the present invention is not limited to the details described in conjunction with the embodiments, but should be defined by the claims and the ranges equivalent to the claims.