Abstract:
A mold clamping unit is provided. The mold clamping unit comprises a column mounted in a transfer means and moving in forward and backward directions; a mold clamping piston in which a clamping operation with the column and a clamping-releasing operation thereof are performed; a plurality of column teeth disposed on a surface of the column along an axial direction of the column, a space between the column teeth being defined as a column groove by the column teeth; a center bore provided in a central portion of the mold clamping piston so that the column can penetrate and can move the center bore when the column moves in forward and backward directions; a clamping tooth seating groove provided inside the mold clamping piston contacting the center bore in a ring shape along a circumference of the center bore; a plurality of clamping teeth seated in the clamping tooth seating groove in a circumferential direction; a rotating plate separated from the clamping teeth in the axial direction of the column; a plurality of clamping tooth guide grooves having a predetermined length provided on the rotating plate toward a center from an outer wall of the rotating plate; and a teeth rod positioned in each of the clamping tooth guide groove, wherein each teeth rod is connected to each clamping teeth so that, when the rotating plate makes a rotational motion, each teeth rod can move in the clamping teeth guide groove, each clamping tooth can move in a central or radial direction of the rotating plate and clamping of the clamping tooth and the column can proceed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Korean Patent Application No. 10-2005-81147, filed on Sep. 1, 2005, in the Korean Intellectual Property Office, the disclosure of which incorporated herein in its entirety by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a mold clamping unit, and more specially, to a mold clamping unit in which the amount of an operating oil required in mold clamping operations is minimized, processing facility and space efficiency are maximized when manufacture and stable mold opening and closing operations are guaranteed.  
         [0004]     2. Description of the Related Art  
         [0005]     Injection molding apparatuses largely include an injection unit and a mold clamping unit. The mold clamping unit basically controls an operation of opening and closing a mold, that is, a mold opening operation and a mold closing operation. A melting material is injected into the mold from the injection unit when the mold closing operations of the mold clamping unit are completed. In this case, the melting material with a high pressure is generally injected into the mold. Thus, the mold should be strongly clamped so that the mold cannot be opened by the high-pressure melting material.  
         [0006]     One of the most conventional mold clamping units are a direct pressure type clamping means. However, the clamping means is not suitable for a high-speed and accurate operation.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a mold clamping unit in which the amount of an operating oil required in mold clamping operations is minimized, processing facility and space efficiency are maximized when manufacture and stable mold opening and closing operations are guaranteed.  
         [0008]     According to an aspect of the present invention, there is provided a mold clamping unit, the mold clamping unit comprising: a column mounted in a transfer means and moving in forward and backward directions; a mold clamping piston in which a locking/unlocking operation with the column are performed; a plurality of column teeth disposed on a surface of the column along an axial direction of the column, a space between the column teeth being defined as a column groove by the column teeth; a center bore provided in a central portion of the mold clamping piston so that the column can penetrate through the center bore when the column moves in forward and backward directions; a clamping tooth seating groove provided inside the mold clamping piston contacting the center bore in a ring shape along a circumference of the center bore; a plurality of clamping teeth seated in the clamping tooth seating groove in a circumferential direction; a rotating plate separated from the clamping teeth in the axial direction of the column; a plurality of clamping tooth guide grooves having a predetermined length provided on the rotating plate toward a center from an outer wall of the rotating plate; and a teeth rod positioned in each of the clamping tooth guide groove, wherein each teeth rod is connected to each clamping teeth so that, when the rotating plate makes a rotational motion, each teeth rod can move in the clamping teeth guide groove, each clamping tooth can move in a central or radial direction of the rotating plate and engaging of the clamping tooth with the column can proceed.  
         [0009]     Each clamping tooth guide groove may include a groove starting point and a groove ending point and the groove ending point may be relatively close to a center of the rotating plate compared to the groove starting point.  
         [0010]     Each clamping tooth guide groove may have a predetermined curvature.  
         [0011]     The clamping tooth may include at least one clamping tooth protrusion in the axial direction of the column.  
         [0012]     A width of the column tooth groove and a width of the clamping tooth protrusion may correspond to a size of the column tooth of the column and a width of the column groove, respectively.  
         [0013]     A hydraulic piston may be provided at one side of the rotating plate to rotate the rotating plate.  
         [0014]     A fine gear may be formed in the rotating plate, a pinion may be provided at one side of the rotation plate to be engaged with the fine gear and a driving motor for transmitting a driving force to the pinion may be provided so that the rotation plate can be rotated by driving the driving motor.  
         [0015]     According to features of the present invention, a plurality of clamping teeth are engaged with a column in a circumferential direction by a rotational motion of a rotating plate such that a clamping-associated device is simply configured, the inertia of the clamping tooth is not large, a high-speed operation is easily performed and a process of processing a column is simplified. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The above and other aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
         [0017]      FIG. 1  is a front cross-sectional view of a mold clamping unit according to an embodiment of the present invention;  
         [0018]      FIG. 2  is a perspective view of a column and a mold clamping piston of the mold clamping unit illustrated in  FIG. 1 ;  
         [0019]      FIG. 3  is a front cross-sectional view of a rotating means of a rotating plate according to another embodiment of the present invention;  
         [0020]      FIG. 4  is a cross-sectional view taken along line A-A′ of  FIG. 1 ;  
         [0021]      FIG. 5  is a front cross-sectional view showing the state where the column and a moving platen of the mold clamping unit illustrated in  FIG. 1  move;  
         [0022]      FIG. 6  is a perspective view of the column and the mold clamping piston in the state of  FIG. 5 ;  
         [0023]      FIG. 7  is a front cross-sectional view showing the case where the mold clamping piston and the column are engaged with each other by clamping teeth in the state of  FIG. 5 ;  
         [0024]      FIG. 8  is a perspective view of the column and the mold clamping piston in the state of  FIG. 5 ;  
         [0025]      FIG. 9  is a cross-sectional view taken along line B-B′ of  FIG. 7 ;  
         [0026]      FIG. 10  is a front cross-sectional view of clamping teeth according to another embodiment of the present invention; and  
         [0027]      FIG. 11  is a cross-sectional view taken along line C-C′ of  FIG. 10 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     Exemplary embodiments of the present invention will now be described in greater detail with reference to the accompanying drawings.  
         [0029]      FIG. 1  is a front cross-sectional view of a mold clamping unit according to an embodiment of the present invention. Referring to  FIG. 1 , a molding clamping unit  100  includes a first fixed platen  110 , a moving platen  120 , and a second stationary platen  130 .  
         [0030]     The first fixed platen  110 , the moving platen  120 , and the second fixed platen  130  are sequentially arranged and are connected by a tie bar  101  in a single unit. A first mold  111  and a second mold  121  are provided on opposed surfaces of the first fixed platen  110  and the moving platen  120 , respectively. For example, the convex-shaped first mold  111  may be provided on the first fixed platen  110  and the concave-shaped second mold  121  may be provided on the moving platen  120  that is opposite to the first fixed platen  110 .  
         [0031]     The moving platen  120  moves between the first fixed platen  110  and the second fixed platen  130  along the tie bar  101 . As such, mold clamping between the second mold  121  of the moving platen  120  and the first mold  111  of the first fixed platen  110  is determined. Here, moving of the moving platen  120  can be performed by a template transfer cylinder  102  provided at one side of the moving platen  120  and the first fixed platen  110  or machine frame respectively.  
         [0032]     A rod-shaped column  140  is provided at one side of the moving platen  120 , specifically, on the moving platen  120  that is opposite to a surface of the second mold  121 . A cross section of the column  140  may be circular, for example.  
         [0033]     A plurality of column teeth  141  having predetermined width and height are provided on the surface of the column  140  along an axial direction of the column  140  at regular intervals. A column groove  142  having a predetermined width is provided between the column teeth  141 . Here, the width of the column teeth  141  and the width of the column groove  142  may not have the same size.  
         [0034]     As described above, the second fixed platen  130  is basically connected to the first fixed platen  110  and the tie bar  101  and stably guides moving between the first fixed platen  110  of the moving platen  120  and the second fixed platen  130 .  
         [0035]     A mold clamping piston  150  is provided in an inner center of the second fixed platen  130 . A central portion of the mold clamping piston  150  is opened so that the column  140  can penetrate the mold clamping piston  150 . Here, a cross-sectional shape of a center bore  131  of the mold clamping piston  150  may correspond to a cross-sectional shape of the column  140 .  
         [0036]      FIG. 2  is a perspective view of a column and a mold clamping piston of the mold clamping unit illustrated in  FIG. 1 . Referring to  FIG. 2 , a clamping tooth seating groove  151  in which a clamping tooth  152  is seated is provided in a predetermined inner portion of the mold clamping piston  150 . The clamping tooth seating groove  151  contacts the center bore  131  of the mold clamping piston  150  and may be formed in a ring shape along the center bore  131 . The clamping tooth  152  is seated in the clamping tooth seating groove  151 . A plurality of clamping teeth  152  may be provided in an axial direction of the column  140 . Here, the width of the clamping tooth  152  may have the size corresponding to the width of the claming groove  142  placed between the column teeth  141 .  
         [0037]     A rotating plate  160  is provided in a position that is separated from the clamping tooth  152  in an axial direction of the column  140  by a predetermined distance. The rotating plate  160  can be rotated by a predetermined driving means. Specifically, the rotating plate  160  can be rotated by connecting a hydraulic piston  170  to one side of the rotating plate  160 , as illustrated in  FIG. 1 . Alternatively, the rotating plate  160  can be rotated by a predetermined driving motor (not shown) when a fine gear  162  is formed around the rotating plate  160  and a pinion  180  is provided to be engaged with the fine gear  162 , as illustrated in  FIG. 3 .  
         [0038]     Referring to  FIG. 2 , a clamping tooth guide groove  161  having a predetermined length is formed on the rotating plate  160 . A teeth rod  153  is positioned in the clamping tooth guide groove  161  so that the teeth rod  153  can move in the space of the clamping tooth guide groove  161 . A moving operation of the teeth rod  153  will be described later.  
         [0039]     The teeth rod  153  is fixed and supported at one side of each clamping tooth  152 . That is, the number of the teeth rod  153  corresponds to the number of the clamping teeth  152 . In addition, the clamping tooth guide groove  161  in which one end of each teeth rod  153  is positioned and which has the number corresponding to the number of the clamping teeth  152  is also provided on the rotating plate  160 . As each clamping tooth guide groove  161  provided on the rotating plate  160  has a predetermined length, each clamping tooth guide groove  161  includes a groove starting point  161   a  and a groove ending point  161   b . The groove ending point  161   b  is relatively close to the center of the rotating plate  160  compared to the groove starting point  161   a . In addition, each clamping tooth guide groove  161  may have a predetermined curvature.  
         [0040]     The rotating plate  160  can be rotated by a predetermined driving means, as described above. By rotation of the rotating plate  160 , each teeth rod  153  can move in the clamping tooth guide groove  161 , that is, between the groove starting point  161   a  and the groove ending point  161   b . In addition, as each teeth rod  153  is connected to each of the clamping tooth  152  and is fixed therein, the clamping tooth  152  also move when each teeth rod  153  moves.  
         [0041]     At this time, as the clamping tooth guide groove  161  is formed so that its groove starting point  161   a  and its groove ending point  161   b  are not positioned at the same distance from the center of the rotating plate  160 , when the teeth rod  153  moves in the clamping tooth guide groove  161 , the clamping tooth  152  moves in a direction that is close to or distant from the rotating plate  160 . Specifically, when the teeth rod  153  moves to the groove ending point  161   b  from the groove starting point  161   a , the clamping tooth  152  moves in a direction that is close to the center of the rotating plate  160  when its motion in a circumferential direction is confined by the clamping tooth seating groove  151  in the mold clamping piston  150 . On the other hand, when the teeth rod  153  moves to the groove starting point  161   a  from the groove ending point  160 , the clamping tooth  152  moves in a direction that is distant from the center of the rotating plate  160 . Here, when the clamping tooth  152  moves in the direction that is close to the center of the rotating plate  160 , the clamping tooth  152  is inserted into the column groove  142  of the column  140  so that the column  140  and the mold clamping piston  150  can be engaged.  
         [0042]     As the teeth rod  153  moves by rotation of the rotating plate  160 , a space in which the teeth rod  153  can move should be provided inside the mold clamping piston  150 . For reference, the rotating plate  160  may be provided inside or outside the mold clamping piston  150 . When the rotating plate  160  is provided inside the mold clamping piston  150 , a space (not shown) corresponding to the rotating plate  160  is provided inside the mold clamping piston  150 .  
         [0043]     The clamping tooth  152  can be modified and implemented in various shapes. According to an embodiment of the present invention, as illustrated in  FIGS. 10 and 11 , a clamping tooth  152 ′ may be implemented so that a plurality of clamping tooth protrusions  152   a  can be provided in an axial direction of the column  140 . Here,  FIG. 11  is a cross-sectional view taken along line C-C of  FIG. 10 . As illustrated in  FIG. 11 , a plurality of clamping teeth  152 ′ can be installed in a circumferential direction. For reference, a space between the clamping tooth protrusions  152   a  can be defined as a column tooth groove  152   b.    
         [0044]     The clamping tooth  152 ′ in which the column tooth  141  of the column  140  can be accommodated can be provided. When the column tooth groove  152   b  is provided, the clamping tooth  152 ′ includes at least one column tooth groove  152   b  and at least one clamping tooth protrusion  152   a  and has an uneven shape. Here, the width of the column tooth groove  152   b  and the width of the clamping tooth protrusion  152   b  correspond to the width of the column tooth  141  and the width of the column groove  142 , respectively.  
         [0045]     Referring to  FIG. 1 , a first oil chamber  154  and a second oil chamber  155  are provided at one side of the mold clamping piston  150 . The first oil chamber  154  is a space to which a high-pressure operating oil is supplied. If the operating oil is supplied to the first oil chamber  154 , the mold clamping piston  150  and the column  140  can be securely clamped by the pressure of the operating oil. On the other hand, the second oil chamber  155  is a space to which operating oil is supplied. If the operating oil is supplied to the second oil chamber  155 , a rear motion of the mold clamping piston  150  is possible.  
         [0046]     An operation of the mold clamping unit having the above structure according to the present invention will now be described.  FIGS. 1, 5 , and  7  illustrate a procedure in which the column  140  and the moving platen  120  move according to the operation of the mold clamping unit according to the present invention.  FIGS. 2, 6 , and  8  are reference diagrams illustrating a procedure in which a column and a mold clamping piston are engaged, illustrated in  FIGS. 1, 5 , and  7 , respectively.  FIGS. 4 and 9  are cross-sectional views taken along line A-A′ of  FIG. 1  and B-B′ of  FIG. 7 , respectively.  
         [0047]     The operation of the mold clamping unit according to the present invention is largely classified into a mold opening operation in which mold clamping is released, and a mold closing operation in which a mold is clamped. First, the mold opening operation is a state in which mold clamping is released, as described above. As illustrated in  FIG. 1 , the first mold  111  of the first fixed platen  110  and the second mold  121  of the moving platen  120  are separated from each other. In addition, the moving platen  120  is relatively close to the second fixed platen  130  and a portion of the column  140  provided on the moving platen  120  penetrates the center bore  131  of the second fixed platen  130  and is protruded. A correlation between the column  140  and the mold clamping piston  150  is illustrated in  FIGS. 2 and 4 .  
         [0048]     The mold closing operation is performed in the mold opening state. The mold closing operation can be classified into a high-speed moving operation, a locking operation, and a clamping operation.  
         [0049]     First, the high-speed moving operation is a procedure in which the moving platen  120  moves to the first fixed platen  110  along the tie bar  101  by the template transfer cylinder  102  provided at one side of the moving platen  120  and the first fixed platen  110  or machine frame, respectively, in the mold opening state. Through the high-speed transfer operation, the second mold  121  of the moving platen  120  and the first mold  111  of the first fixed platen  110  are close to each other or do not contact each other, as illustrated in  FIG. 5 . That is, in order to prevent mold damages caused by rapid mold clamping, the second mold  121  of the moving platen  120  and the first mold  111  of the first fixed platen  110  are separated from each other at a predetermined small distance d. At this time, as the high-speed transfer operation is performed, the column  140  also moves toward the first fixed platen  110  together with the moving platen  120  so that the column tooth  141  of the column  140  can be positioned in the center bore  131  of the mold clamping piston  150 .  
         [0050]     When the high-speed moving operation is completed, as illustrated in  FIG. 6 , the clamping tooth  152  is positioned in the clamping tooth seating groove  151  of the mold clamping piston  150 . In addition, the teeth rod  153  connected to the clamping tooth  152  is positioned in the groove starting point  161   a  of the clamping tooth guide groove  161 .  
         [0051]     The locking operation proceeds when the high-speed moving operation is completed. The locking operation is a procedure in which the column  140  and the mold clamping piston  150  are engaged. To this end, first, the rotating plate  160  is rotated using a predetermined driving means. Specifically, the hydraulic piston  170  is connected to one side of the rotating plate  160  so that the rotating plate  160  can be rotated (see  FIG. 1 ). Alternatively, the rotating plate  160  can be rotated by a predetermined driving motor in the state where the fine gear  162  is formed around the rotating plate  160  and the pinion  180  is provided to be engaged with the fine gear  162  (see  FIG. 3 ).  
         [0052]     By rotation of the rotating plate  160 , each teeth rod  153  moves toward the groove ending point  161   b  from the groove starting point  161   a  of the clamping tooth guide groove  161 , as illustrated in  FIGS. 7, 8 , and  9 . At this time, as described above, the groove ending point  161   b  of the clamping tooth guide groove  161  is relatively close to the center of the rotating plate  160  compared to the groove starting point  161   a . Thus, the teeth rod  153  moves toward the center from an outer wall of the rotating plate  160 . As such, each clamping tooth  152  connected to each teeth rod  153  moves toward the center of the column  140  and is finally seated in the column groove  142  of the column  140 .  
         [0053]     Since the clamping tooth  152  is seated in the column groove  142  of the column  140 , an operation of locking the column  140  and the mold clamping piston  150  is completed. For reference, when the clamping tooth  152  includes at least one column tooth groove  152   b  and at least one clamping tooth protrusion  152   a , by rotation of the rotating plate  160 , each clamping tooth  152  connected to each teeth rod  153  moves toward the center of the column  140 . Finally, the clamping tooth protrusion  152   a  is seated in the column groove  142  of the column  140  and the column tooth  141  of the column  140  is seated in the column tooth groove  152   b  so that the column  140  and the mold clamping piston  150  can be locked.  
         [0054]     When the locking operation, that is, engaging the column  140  with the clamping piston  150 , is completed, the boosting operation is performed. First, if a high-pressure operating oil is supplied to the first oil chamber provided at one side of the mold clamping piston  150 , clamping force caused by an oil pressure of the operating oil is applied to the mold clamping piston  150 . At this time, since the mold clamping piston  150  and the column  140  are engaged, the force applied to the mold clamping piston  150  is also transferred to the column  140 .  
         [0055]     In addition, since the column  140  is connected to the moving platen  120 , the load caused by the operating oil is finally transferred to the second mold  121  of the moving platen  120 . As such, the first mold  111  of the first fixed platen  110  and the second mold  121  of the moving platen  120  are clamped. For reference, since the high-pressure operating oil flows into the first oil chamber  154 , the column  140  and the moving platen  120  can move in a forward direction at a small distance.  
         [0056]     By the above-described operations, that is, the high-speed moving operation, the locking operation and the clamping opreation the mold closing operation is completed. Meanwhile, the mold opening operation after the mold closing operation proceeds in a reverse order of the mold closing operation. Specifically, after the operating oil of the first oil chamber  154  is discharged, the rotating plate  160  is rotated so that the engaging state between the clamping tooth  152  and the column  140  can be released, and subsequently, the operating oil is supplied to the second oil chamber  155  so that the mold clamping piston  150  can move in a backward direction. At this time, when clamping between the clamping tooth  152  and the column  140  is released, the teeth rod  153  moves to the groove starting point  153  to the groove ending point  161   b  of the clamping tooth guide groove  161 . As such, the clamping tooth  152  moves to the clamping tooth seating groove  151  of the mold clamping piston  150 .  
         [0057]     The mold clamping unit according to the present invention is applied to an injection molding apparatus but the present invention is not limited thereto. The mold clamping unit can also be applied to all industrial devices requiring mold clamping.  
         [0058]     The mold clamping unit according to the present invention has the following effects. First, since a plurality of clamping teeth are engaged in a column by a rotational motion of a rotating plate such that a clamping-associated device can be simply configured and the inertia of the clamping tooth is not large, a high-speed operation can be easily performed and a process of processing a column can be simplified. In addition, as the clamping operation is performed using a small amount of operating oil, an energy efficiency is high and the size of an oil chamber storing an operating oil and the size a mold clamping piston are reduced such that an area for installing the device is reduced.  
         [0059]     Furthermore, as a high-speed moving operation and the clamping operation are separately performed, a moving speed for mold opening and closing is fast and a uniform mold clamping force can be applied to the entire surface of the mold such that work reliability is improved.  
         [0060]     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims.