Abstract:
The injection apparatus is provided with a high speed step cylinder, a pressure accumulation part and a coupling mechanism. The high speed step cylinder has a rod and an operating chamber. The coupling mechanism is capable of switching between a coupled state in which the movement of the rod is restricted, and a non-coupled state in which the coupled state is released so as to enable the rod to move due to the operating pressure. The coupling mechanism includes a first coupling member, a second coupling member and a drive source. The coupling mechanism is kept in the coupled state in which the second coupling member is rotated to less than 90°. When the second coupling member is forced to rotate in the coupled state, the first coupling member rotates such that a first contact surface is in contact with a second contact surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a National Stage of International Application No. PCT/JP2012/075525 filed Oct. 2, 2012, claiming priority based on Japanese Patent Application No. 2011-230015 filed Oct. 19, 2011, the contents of all of which are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to an injection apparatus that performs a low speed operation, a high speed operation, and a pressurizing operation to inject and fill molding material into a mold. 
       BACKGROUND ART 
       [0003]    Generally, an injection apparatus for a molding machine moves an injection plunger forward in a sleeve with an injection cylinder and forces molding material (e.g., molten material) out of the sleeve into a cavity formed between molds (mold unit) to inject and fill the molding material into the cavity. The injecting and filling operation includes a low speed operation, a high speed operation, and a pressurizing operation. 
         [0004]    The injection apparatus performs the high speed operation by, for example, supplying hydraulic oil, which is accumulated in an accumulator, to the injection cylinder, and moving a rod (piston) of the injection cylinder at a high speed. Generally, in the high speed operation, a control valve controls an open degree of an oil passage connected to the accumulator to restrict movement of the rod and control the movement speed of the rod. 
         [0005]    In the high speed operation, it is desirable that the injection time be further shortened. The response in the movement of the rod needs to be increased to shorten the injection time. To improve the response in the movement of the rod, the hydraulic pressure and the flow rate of the hydraulic oil acting on the piston need to be increased. The control valve, however, gradually opens the oil passage, and the hydraulic pressure acting on the piston is gradually increased. Thus, there is a limit to increasing the response in the movement of the rod. 
         [0006]    The rod may be mechanically coupled to restrict movement of the rod when the hydraulic pressure of the hydraulic oil is acting on the piston. Under this situation, the mechanical coupling may be released to move the piston with the maximum hydraulic pressure. To implement such a structure, a connection mechanism that may be mechanically connected to and disconnected from the rod is required. 
         [0007]    Patent document 1 describes a hydraulic clamp as an example of such a connection mechanism. As shown in  FIG. 8 , in the hydraulic clamp  80  of patent document 1, a hydraulic cylinder  81  includes a lower portion that accommodates a piston  82 , which is movable in the vertical direction. A clamp hydraulic oil chamber  83  is defined at the lower side of the piston  82 . In the hydraulic cylinder  81 , an oil supply/discharge port  81   a  is formed below the clamp hydraulic oil chamber  83 . Hydraulic oil from a hydraulic source  84  is supplied to and discharged from the oil supply/discharge port  81   a  through an electromagnetic supply/discharge valve  83  and a supply/discharge oil passage  86 . 
         [0008]    In the hydraulic cylinder  81 , a clamp tool  87 , which is formed by combining a plurality of clamp jaws  87   a,  is set on the upper surface of the piston  82 . A retraction means (not shown) urges the clamp jaws  87   a  in directions enlarging the diameter. A tubular advancing inclination cam  88  is arranged at the upper side of the clamp tool  87 . In an upper portion of the hydraulic cylinder  81 , a pneumatic cylinder  90  is arranged above the clamp tool  87 , and a pneumatic piston  91  of the pneumatic cylinder  90  surrounds the clamp tool  87 . 
         [0009]    A pneumatic operation chamber  92  is formed in the lower side of the pneumatic piston  91 . A piston recovery spring  93  is arranged inside the pneumatic piston  91 . The advancing inclination cam  88  is inserted into a piston rod  91   a  extending from the pneumatic piston  91  toward the clamp tool  87 . An unclamp piston  99 , movable in the vertical direction, is accommodated in the pneumatic operation chamber  92 . 
         [0010]    The hydraulic cylinder  81  includes a compressed air supply/discharge port  81   b,  which is in communication with the pneumatic operation chamber  92 . Compressed air from a pneumatic source  94  is supplied to and discharged from the compressed air supply/discharge port  81   b  through an electromagnetic pneumatic supply/discharge valve  95  and a supply/discharge air passage  96 . 
         [0011]    The hydraulic clamp  80  sets the hydraulic cylinder  81  onto the clamp rod  97  from above and clamps the clamp rod  97  clamped with the clamp tool  87  to mechanically connect the hydraulic clamp  80  and the clamp rod  97 . The clamp rod  97  includes a distal end defining a passive portion  97   a  that engages with the clamp tool  87 . 
         [0012]    To clamp the clamp rod  97  with the hydraulic clamp  80 , the electromagnetic pneumatic supply/discharge valve  95  is controlled to discharge compressed air out of the pneumatic operation chamber  92 . This moves the pneumatic piston  91  toward the advancing inclination cam  88  with the spring force of the piston recovery spring  93 . This moves the advancing inclination cam  88  downward and reduces the diameter of the clamp tool  87  so that the clamp tool  87  is arranged facing the lower surface in the passive portion  97   a  of the clamp rod  97 . When the hydraulic oil from the hydraulic source  84  is supplied to the oil supply/discharge port  81   a,  the clamp tool  87  moves upward as the piston  82  moves upward, and the distal end of the clamp tool  87  is pushed against the lower surface of the passive portion  97   a.  As a result, the clamp rod  97  is clamped by the hydraulic clamp  80 , and the clamp rod  97  and the hydraulic clamp  80  are mechanically connected. 
         [0013]    When the pressure oil is discharged from the oil supply/discharge port  81   a  and the compressed air is supplied to the pneumatic operation chamber  92 , the piston  82  is moved downward by the unclamp piston  99 . Further, the pneumatic piston  91  moves upward. Thus, the clamp tool  87  unclamps the clamp rod  97 . That is, the clamp rod  97  and the hydraulic clamp  80  are mechanically disconnected. 
         [0014]    The use of the hydraulic clamp  80  in the injection cylinder allows for the rod to be mechanically connected to and disconnected from the hydraulic clamp  80 . This improves the response for moving the rod of the injection cylinder and allows for an increase in the injection speed during the high speed operation. 
       PRIOR ART DOCUMENT 
     Patent Document 
       [0015]    Patent Document 1: Japanese Laid-Open Patent Publication No. 3-287336 
       SUMMARY OF THE INVENTION 
       [0016]    However, a hydraulic circuit and a pneumatic circuit are both needed to clamp the clamp rod  97  with the clamp tool  87  in the hydraulic clamp  80  disclosed in patent document 1. Thus, even though the use of the hydraulic clamp  80  allows for an increase in the injection speed during the high speed operation, the structure of the connection mechanism is extremely complicated. This increases the manufacturing cost of the injection apparatus. 
         [0017]    It is an object of the present invention to provide an injection apparatus having a simple and inexpensive structure that allows for an increase in the injection speed during a high speed operation. 
         [0018]    To achieve the above object, one aspect of the present invention is an injection apparatus that performs a low speed operation, a high speed operation, and a pressurizing operation to inject and fill a molding material into a mold. The injection apparatus includes a high speed operation cylinder, an accumulating unit, and a connection mechanism. The high speed operation cylinder is operated during the high speed operation and includes a rod and an operation chamber. The accumulating unit is connected to the operation chamber to supply operational pressure to the operation chamber and move the rod. The connection mechanism is switchable between a connected state, in which the connection mechanism restricts movement of the rod caused by the operational pressure of the accumulating unit, and a disconnected state, in which the connection mechanism cancels the connected state so that the rod is movable by the operational pressure. The connection mechanism includes a first connection member, a second connection member, and a drive source. The first connection member is rotatably supported by the rod and includes a first abutment surface and a first rotation axis extending in a direction substantially orthogonal to an axis of the rod. The second connection member includes a second abutment surface that comes into planar contact with the first abutment surface to form a joined surface with the first abutment surface. The drive source rotates the second connection member about a second rotation axis. A hypothetical axis is defined by an axis lying on and orthogonal to the axis of the rod and parallel to the first rotation axis. A hypothetical plane is defined by a plane set by the axis of the rod and the hypothetical axis. A referential connection state is defined by a situation in which at least a portion of the joined surface extends at a right angle relative to the hypothetical plane, a normal direction extending toward the second connection member in the first abutment surface conforms with a direction in which the rod is moved by the operational pressure of the accumulating unit, and the first rotation axis substantially conforms to the second rotation axis. The connection mechanism remains in the connected state until the second connection member is rotated by the drive source from the referential connection state by less than 90 degrees in either one of a forward direction and a reverse direction. When the second connection member is rotated by the drive source in the connected state, the first connection member is rotated with the first abutment surface in planar contact with the second abutment surface. 
         [0019]    In the structure described above, the rod is movable toward the mold by the hydraulic pressure of the accumulating unit. However, the movement of the rod is restricted by the connection mechanism in the connected state. When movement of the rod is restricted, the rod is stands by so as to be immediately movable by the hydraulic pressure. When the connection mechanism is in the connected state, the movement of the first connection member is restricted with a simple structure in which the first abutment surface comes into planar contact with the second abutment surface. Further, when the drive source is driven to shift the connection mechanism to the disconnected state and cancel the planar contact between the first abutment surface and the second abutment surface, the rod in the standby state is moved by the hydraulic pressure. In this case, the hydraulic pressure from the accumulating unit has already been entirely acting on the rod. Thus, the rod may be immediately moved by the hydraulic pressure. This improves the response of the movement of the rod compared to, for example, when opening a valve so that hydraulic oil from the accumulating unit acts on the rod. Accordingly, in the present invention, the movement of the rod may be restricted (obtain the connected state) with a simple structure in which the first abutment surface of the first connection member comes into planar contact with the first abutment surface of the second connection member. Moreover, the planar contact may be released (shift to the disconnected state) with just one single drive source. Thus, the response of the movement of the rod in the high speed operation may be improved with a simple and inexpensive structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a schematic diagram of an injection apparatus according to an embodiment of the present invention. 
           [0021]      FIG. 2  is a graph showing changes in the injection pressure and the injection speed of the injection apparatus of  FIG. 1 . 
           [0022]      FIG. 3A  is a cross-sectional view showing a connection mechanism of  FIG. 1  in a connected state,  FIG. 3B  is a cross-sectional view showing a first abutment surface and a second abutment surface in the connected state,  FIG. 3C  is a perspective view showing a first connection member of  FIG. 3A , and  FIG. 3D  is a perspective view showing a second connection member of  FIG. 3A . 
           [0023]      FIG. 4  is a schematic view showing the injection apparatus of  FIG. 1  during a low speed operation. 
           [0024]      FIG. 5  is a schematic view showing the injection apparatus of  FIG. 1  during a high speed operation. 
           [0025]      FIG. 6A  is a view showing the connection mechanism of  FIG. 1  in a disconnected state,  FIG. 6B  is a cross-sectional view taken along line  6   b - 6   b  in  FIG. 6A  showing the first connection member in the disconnected state,  FIG. 6C  is a view showing the first connection member and the second connection member of  FIG. 6A  in the disconnected state. 
           [0026]      FIG. 7  is a schematic view showing the injection apparatus of  FIG. 1  during pressurizing operation. 
           [0027]      FIG. 8  is a diagram showing the prior art. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    One embodiment of the present invention will now be described with reference to  FIGS. 1 to 7 . 
         [0029]    As shown in  FIG. 1 , a mold K includes a fixed mold  12  and a movable mold  13 . A mold fastening device (not shown) opens and closes the mold K and fastens the fixed mold  12  and the movable mold  13 . The injection apparatus  11  injects and fills a metal material serving as the molding material into a cavity  14  formed in the mold K. The metal material, which is injected into the mold K, is solidified and then removed from the mold K to obtain a desired molded product. 
         [0030]    The fixed mold  12  includes an injection sleeve  15 , which is in communication with the cavity  14 , and an injection plunger  16 , which is arranged in the injection sleeve  15  in a movable manner. When the injection sleeve  15  is supplied with metal material through a supply port (not shown) formed in the injection sleeve  15 , the injection plunger  16  is moved in the injection sleeve  15  toward the cavity  14  to inject and fill the metal material into the cavity  14 . 
         [0031]    A connection member  17  connects the injection plunger  16  to a distal end of a rod  18   c  of a pressurizing operation cylinder  18 . In the pressurizing operation cylinder  18 , a cylinder tube  18   a  accommodates a movable piston  18   b,  which is integrated with the rod  18   c.  The piston  18   b  divides the interior of the cylinder tube  18   a  into a rod side chamber  18   e,  from which the rod  18   c  extends, and an opposite head side chamber  18   d.    
         [0032]    The rod side chamber  18   e  opens to the atmosphere through a supply/discharge port (not shown) formed in the cylinder tube  18   a.  An amplification oil passage  19  connects the head side chamber  18   d  to an operation cylinder  20 . The operation cylinder  20  has a smaller cylinder diameter than the pressurizing operation cylinder  18 . The operation cylinder  20 , which has a smaller diameter than the pressurizing operation cylinder  18 , and the amplification oil passage  19 , which connects the operation cylinder  20  to the pressurizing operation cylinder  18 , form an amplification circuit that amplifies the thrust of the rod  18   c  in the pressurizing operation cylinder  18 . 
         [0033]    The operation cylinder  20  includes a cylinder tube  20   a  that accommodates a piston  20   b.  A rod  20   c  is formed integrally with the piston  20   b.  The piston  20   b  divides the interior of the cylinder tube  20   a  of the operation cylinder  20  into a rod side chamber  20   e,  from which the rod  20   c  extends, and an opposite head side chamber  20   d.  The amplification oil passage  19  connects the head side chamber  20   d  of the operation cylinder  20  and the head side chamber  18   d  of the pressurizing operation cylinder  18 . Hydraulic oil serving as an incompressible fluid is sealed in the two head side chambers  18   d  and  20   d.    
         [0034]    An operation ball screw/nut mechanism BN 1  that moves the rod  20   c  forward and rearward is connected to the rod  20   c.  In detail, an operation nut N 1  is connected to the distal end of the rod  20   c,  and the operation nut N 1  is fastened to an operation ball screw B 1 , which is rotated by an operation motor M 1 . The operation ball screw B 1  is rotated so that the operation nut N 1  moves forward or rearward in the axial direction of the operation ball screw B 1 . In this manner, the operation ball screw/nut mechanism BN 1  includes the operation nut N 1 , the operation ball screw B 1 , and the operation motor M 1 . 
         [0035]    In the present embodiment, the pressurizing operation cylinder  18 , the amplification oil passage  19 , the operation cylinder  20 , and the operation ball screw/nut mechanism BN 1  form a pressurizing operation unit U 1 . 
         [0036]    In the pressurizing operation unit U 1 , the side opposite to the mold K is mechanically connected to a rod  30   c  of a low speed operation cylinder  30  in a low speed operation unit U 2 . The low speed operation cylinder  30  includes a cylinder tube  30   a  that accommodates a movable piston  30   b,  which is formed integrally with the rod  30   c.  The piston  30   b  divides the interior of the cylinder tube  30   a  into a rod side chamber  30   e,  from which the rod  30   c  extends, and an opposite head side chamber  30   d.    
         [0037]    A low speed operation ball screw/nut mechanism BN 2  that moves the rod  30   c  forward and rearward is connected to the rod  30   c.  In detail, a low speed operation nut N 2  is connected to the rod  30   c,  and the low speed operation nut N 2  is fastened to a low speed operation ball screw B 2 . The low speed operation ball screw B 2  is rotated by a low speed operation motor M 2 . 
         [0038]    The low speed operation motor M 2  rotates the low speed operation ball screw B 2  to move the low speed operation nut N 2  forward or rearward in the axial direction of the low speed operation ball screw B 2 . The low speed operation nut N 2 , the low speed operation ball screw B 2 , and the low speed operation motor M 2  form a low speed operation ball screw/nut mechanism BN 2 . 
         [0039]    The rod side chamber  30   e  of the low speed operation cylinder  30  is connected to one end of a low speed operation oil passage  31 . The head side chamber  30   d  is connected to the other end of the low speed operation oil passage  31 . In other words, the rod side chamber  30   e  and the head side chamber  30   d  form a closed circuit with the low speed operation oil passage  31 . Further, a low speed operation electromagnetic switch valve  32  is arranged in the low speed operation oil passage  31 . The low speed operation electromagnetic switch valve  32  may be switched between a first position  32   a,  which disconnects the head side chamber  30   d  and the rod side chamber  30   e,  and a second position  32   b,  which allows hydraulic oil to flow between the head side chamber  30   d  and the rod side chamber  30   e.    
         [0040]    The low speed operation oil passage  31  includes a bypass oil passage  33  that bypasses the low speed operation electromagnetic switch valve  32 . A check valve  34  is arranged in the bypass oil passage  33 . When the low speed operation electromagnetic switch valve  32  is at the first position  32   a,  the check valve  34  inhibits the flow of hydraulic oil from the head side chamber  30   d  to the rod side chamber  30   e  and permits the flow of hydraulic oil from the rod side chamber  30   e  to the head side chamber  30   d.    
         [0041]    When the low speed operation electromagnetic switch valve  32  is at the first position  32   a,  even if back pressure force from the mold K acts on the rod  30   c  such that the rod  30   c  pushes the piston  30   b  toward the head side chamber  30   d,  the discharge of hydraulic oil from the head side chamber  30   d  to the rod side chamber  30   e  is inhibited by the check valve  34 , and the back pressure force is received by the hydraulic oil. In the present embodiment, the low speed operation unit U 2  is formed by the low speed operation cylinder  30 , the low speed operation ball screw/nut mechanism BN 2 , and a back pressure receiving portion. 
         [0042]    In the low speed operation unit U 2 , the side opposite to the pressurizing operation unit U 1  is mechanically connected to a first rod  40   c  of a high speed operation cylinder  40  in a high speed operation unit U 3 . The high speed operation cylinder  40  is a double rod cylinder and includes a cylinder tube  40   a,  which accommodates a movable piston  40   b  formed integrally with the first rod  40   c,  and a second rod  40   f  is formed integrally with the side of the first rod  40   c  opposite to the piston  40   b.  The piston  40   b  divides the interior of the cylinder tube  40   a  into a first chamber  40   e,  serving as an operation chamber at the side of the first rod  40   c,  and a second chamber  40   d,  serving as an operation chamber at the opposite side from which the second rod  40   f  extends. 
         [0043]    A supply/discharge mechanism T is connected to the first chamber  40   e.  The supply/discharge mechanism T supplies hydraulic oil to the first chamber  40   e  and discharges hydraulic oil from the first chamber  40   e.  The supply/discharge mechanism T includes an oil tank  43 , a pump  44  that draws hydraulic oil from the oil tank  43 , and an electromagnetic switch valve  45  arranged in a supply/discharge oil passage  47 . The electromagnetic switch valve  45  may be switched to a first position  45   a,  at which the electromagnetic switch valve  45  supplies the hydraulic oil drawn from the oil tank  43  by the pump  44  to the first chamber  40   e,  and a second position  45   b,  at which the electromagnetic switch valve  45  discharges the hydraulic oil from the first chamber  40   e  into the oil tank  43 . An accumulator  46  serving as an accumulating unit is connected to the second chamber  40   d  of the high speed operation cylinder  40 . Hydraulic oil is accumulated in the accumulator  46 . The hydraulic oil from the accumulator  46  is supplied to the second chamber  40   d.  Hydraulic pressure (operational pressure) directed toward the low speed operation unit U 2  acts on the piston  40   b,  and the hydraulic pressure moves the first rod  40   c  and the second rod  40   f  toward the low speed operation unit U 2 . The hydraulic pressure and the flow rate acting on the piston  40   b  are adjusted to realize the desired injection speed in the high speed operation. 
         [0044]    A connection mechanism R arranged in the high speed operation cylinder  40  will now be described. 
         [0045]    As shown in  FIGS. 3A to 3C , a cylindrical first support member  50  is fixed to the distal end of the second rod  40   f  of the high speed operation cylinder  40 . The first support member  50  is fixed to the second rod  40   f  so that its axis L 1  extends in the radial direction of the second rod  40   f  (orthogonal to the axis L of the second rod  40   f ). The inner circumferential surface of the first support member  50  supports a first bearing  51 , which rotatably supports a first connection member  52 . The first connection member  52  is formed from a rod to have a predetermined shape, and is supported by the first bearing  51  to rotate about the axis of the first connection member  52  that serves as a first rotation axis G 1 . The first rotation axis G 1  extends at a substantially right angle relative to the axis L of the second rod  40   f.  Here, to be a substantially right angle, the first rotation axis G 1  only needs to be rotatable relative to the second rod  40   f  and does not have to be a perfect right angle. 
         [0046]    The two sides of the first connection member  52  in the direction in which the first rotation axis G 1  extends (hereinafter referred to as axial direction), that is, the two sides of which reference is the second rod  40   f  are semi-cylindrical, and a planar portion extending in the radial direction of the first connection member  52  defines a first abutment surface  52   a.  A line that lies on the axis L of the second rod  40   f  and is orthogonal to the axis L and parallel to the first rotation axis G 1  is referred to as a hypothetical axis N. As shown in  FIG. 3C , a plane lying on the hypothetical axis N and the axis L is referred to as a hypothetical plane D. When the first connection member  52  is rotated, the angle of the first abutment surface  52   a  changes relative to the hypothetical plane D. In  FIGS. 3A to 3C , the first abutment surface  52   a  is arranged at a right angle relative to the hypothetical plane D. 
         [0047]    As shown in  FIGS. 3A and 3D , a second connection member  53  is arranged on each of two axial outer sides of the first connection member  52 . A second support member  54  rotatably supports the second connection member  53  with a second bearing  55 . The second connection member  53  is formed from a rod to have a predetermined shape and is supported by the second bearing  55  so as to rotate about the axis of the second connection member  53  serving as a second rotation axis  2 . The second connection member  53  is rotated by a motor M 3  serving as a drive source. 
         [0048]    The second connection member  53  at the side of the first connection member  52  is formed to be semi-cylindrical and includes a planar portion extending in the radial direction of the second connection member  53  that defines a second abutment surface  53   a.  The second abutment surface  53   a  has the same shape as the first abutment surface  52   a  of the first connection member  52  and may be in planar contact with the first abutment surface  52   a.  When the second connection member  53  is rotated, the angle of the second abutment surface  53   a  changes relative to the hypothetical plane D. As shown in  FIG. 3B , the second abutment surface  53   a  and the first abutment surface  52   a  of the first connection member  52  are in abutment thus forming a joined surface when the angle of the second abutment surface  53   a  relative to the hypothetical plane D is within a predetermined angle range. 
         [0049]    As shown in  FIGS. 3A and 3B , when the first abutment surface  52   a  and the second abutment surface  53   a  are in abutment and thus form the joined surface and the portion forming the semi-cylindrical form of the second connection member  53  is arranged closer to the accumulator  46  than the portion forming the semi-cylindrical form of the first connection member  52 , the second connection member  53  restricts movement of the first connection member  52  toward the accumulator  46 . In detail, movement of the first connection member  52  and the second connection member  53  toward the accumulator  46  is restricted when in a referential connection state. Accordingly, in the referential connection state, movement of the second rod  40   f  is restricted even if the hydraulic pressure from the accumulator  46  is acting on the piston  40   b.  When movement of the second rod  40   f  is restricted, the second rod  40   f  stands by so as to be immediately movable by the hydraulic pressure from the accumulator  46 . 
         [0050]    The referential connection state is a state in which at least a portion of the joined surface of the abutment surfaces  52   a  and  53   a  intersects the hypothetical plane D at a right angle, and a normal direction H extending toward the second abutment surface  53   a  in the first abutment surface  52   a  conforms with the direction in which the second rod  40   f  is moved by the hydraulic pressure from the accumulator  46 . In this state, the first and second rotation axes G 1  and G 2  are substantially coaxial. Here, to be substantially coaxial, the first and second rotation axes G 1  and G 2  only need to be in a relationship in which the rotation of the second connection member  53  rotates the first connection member  52  and does not have to be perfectly coaxial. 
         [0051]    In the connection mechanism R, when the second connection member  53  is rotated by less than 90 degrees in both directions from the referential connection state by the motor M 3 , the first abutment surface  52   a  and the second abutment surface  53   a  remain in abutment, and movement of the first connection member  52  toward the accumulator  46  is restricted. Thus, the first connection member  52  and the second connection member  53  are in the connected state from the referential connection state to where they are rotated by less than 90 degrees in both forward and reverse directions. 
         [0052]    As shown in  FIG. 6 , in the connection mechanism R, when the motor M 3  rotates the second connection member  53  by 90 degrees, the second abutment surface  53   a  rotates the first connection member  52  by 90 degrees. Consequently, the second connection member  53  is no longer located in the direction in which the first connection member  52  and the second rod  40   f  are moved by the hydraulic pressure of the accumulator  46 . Accordingly, the first connection member  52  is movable toward the accumulator  46  with the second rod  40   f,  and the connected state is cancelled. Thus, in the present embodiment, the high speed operation unit U 3  is formed by the connection mechanism R, the high speed operation cylinder  40 , the supply/discharge mechanism T, and the accumulator  46 . 
         [0053]    In the present embodiment, the rod  18   c  of the pressurizing operation unit U 1  is mechanically connected to the mold K, and the rod  30   c  of the low speed operation unit U 2  is mechanically connected to the pressurizing operation unit U 1 . Further, the rod  40   c  of the high speed operation unit U 3  is mechanically connected to the low speed operation unit U 2 . The rods  18   c,    30   c,  and  40   c  are arranged along the same axis, and the pressurizing operation cylinder  18 , the low speed operation cylinder  30 , and the high speed operation cylinder  40  are arranged in series. 
         [0054]    The operation pattern (ejection pattern) when the injection apparatus  11  performs injection will now be described with reference to  FIG. 2 . 
         [0055]    The injection apparatus  11  performs three operations, the low speed operation, the high speed operation, and the pressurizing operation. The low speed operation is performed in the initial stage of injection and operates the injection plunger  16  in the low speed operation unit U 2  when extruding metal material from the injection sleeve  15  to the cavity  14 . 
         [0056]    The high speed operation follows the low speed operation and operates the injection plunger  16  at a higher speed than the low speed operation. The high speed operation operates the injection plunger  16  in the high speed operation unit U 3 . 
         [0057]    The pressurizing operation, which follows the high speed operation and which is the final stage of injection performed, pressurizes the metal material in the cavity  14  with the force generated when the injection plunger  16  moves forward and toward the mold K. The pressurizing operation operates the injection plunger  16  in the pressurizing operation unit U 1 . 
         [0058]    In each of these operations, the injection apparatus  11  is operated in different patterns, as shown in  FIG. 2 . More specifically, in the high speed operation, the injection plunger  16  needs to be operated at a higher speed than the low speed operation. However, speed is not necessary in the pressurizing operation. Further, the injection plunger  16  needs to be operated to apply a higher pressure than the low speed operation and the high speed operation in the pressurizing operation but does not have to be operated to apply as much pressure as the pressurizing operation in the low speed operation and the high speed operation,. 
         [0059]    The operation of the injection apparatus  11  in the present embodiment will now be described. 
         [0060]    First, the low speed operation will be described with reference to  FIGS. 1 and 4 . 
         [0061]    Before starting the low speed operation, the injection plunger  16  of the injection sleeve  15 , the rod  18   c  of the pressurizing operation cylinder  18 , the rod  20   c  of the operation cylinder  20 , the rod  30   c  of the low speed operation cylinder  30 , and the two rods  40   c  and  40   f  of the high speed operation cylinder  40  are located at predetermined initial positions as shown in  FIG. 1 . The rods  18   c,    20   c,    30   c,    40   c,  and  40   f  located at the initial positions do not apply injection pressure to the metal material supplied to the injection sleeve  15  (time T 1  in  FIG. 2 ). 
         [0062]    The low speed operation electromagnetic switch valve  32  of the low speed operation unit U 2  is switched to the first position  32   a  during molding to disconnect the rod side chamber  30   e  and the head side chamber  30   d.  Further, the electromagnetic switch valve  45  of the supply/discharge mechanism T of the high speed operation unit U 3  is switched to the first position  45   a  so that the hydraulic oil of the first chamber  40   e  in the high speed operation cylinder  40  does not return to the oil tank  43 . 
         [0063]    After completing molding preparations such as the fastening of the fixed mold  12  and the movable mold  13  and the supply of metal material to the injection sleeve  15 , the low speed operation unit U 2  starts the low speed operation. In the low speed operation, the rod  30   c  of the low speed operation cylinder  30  has the injection velocity V 1  shown in  FIG. 2 . The low speed operation motor M 2  is driven to rotate the low speed operation ball screw B 2  and move forward the low speed operation nut N 2 , which is fastened to the low speed operation ball screw B 2 . As a result, referring to  FIG. 4 , the low speed operation nut N 2  applies drive force to the rod  30   c  of the low speed operation cylinder  30  and moves the rod  30   c  forward. The forward movement of the rod  30   c  entirely pushes the pressurizing operation unit U 1  toward the mold K. 
         [0064]    When the pressurizing operation unit U 1  moves forward, the pressurizing operation cylinder  18  moves forward. The injection plunger  16 , which is connected to the rod  18   c  of the pressurizing operation cylinder  18 , is also moved forward. The forward movement of the injection plunger  16  injects the metal material from the injection sleeve  15  to the cavity  14 . 
         [0065]    When the rod  30   c  of the low speed operation cylinder  30  reaches a terminal position in the low speed operation (time T 2  of  FIG. 2 ), the low speed operation is shifted to the high speed operation. 
         [0066]    The high speed operation will now be described with reference to  FIGS. 5 and 6 . 
         [0067]    In the high speed operation, the injection plunger  16  accumulates the hydraulic oil in the accumulator  46  and drives the motor M 3  at a predetermined timing to rotate the second connection member  53  by 90 degrees and obtain the injection velocity V 2  shown in  FIG. 2 . Here, the electromagnetic switch valve  45  needs to be switched to the second position  45   b.    
         [0068]    Then, as shown in  FIG. 6A , the rotation of the second connection member  53  rotates the first connection member  52  by 90 degrees with the second abutment surface  53   a.  As shown in  FIGS. 6B and 6C , when the joined surface of the first abutment surface  52   a  and the second abutment surface  53   a  is located on the hypothetical plane D and extends in the horizontal direction, the movement restriction of the first connection member  52  imposed by the second connection member  53  is cancelled. That is, the connection state of the first connection member  52  and the second connection member  53  is cancelled (disconnected state). Then, the piston  40   b,  to which the hydraulic pressure from the accumulator  46  acts and which is in a standby state to be immediately movable, is immediately moved toward the first chamber  40   e  by the hydraulic pressure. Further, hydraulic oil is discharged from the first chamber  40   e  to the oil tank  43  through the electromagnetic switch valve  45 . As a result, the piston  40   b  of the high speed operation cylinder  40  is moved forward at a high speed toward the first chamber  40   e,  and the first rod  40   c  is also moved forward at a high speed. Then, the first rod  40   c  pushes and moves forward the pressurizing operation unit U 1  toward the mold K with the low speed operation unit U 2  by the first rod  40   c.    
         [0069]    As shown in  FIG. 5 , when the low speed operation unit U 2  moves the pressurizing operation unit U 1  forward at the injection speed V 2 , the pressurizing operation cylinder  18  moves forward. This moves forward the injection plunger  16 , which is connected to the rod  18   c  of the pressurizing operation cylinder  18 , at the injection speed V 2  and injects the metal material from the injection sleeve  15  into the cavity  14 . During the high speed operation, the pressurizing operation unit U 1  and the low speed operation unit U 2  are operated at higher speeds compared to the low speed operation. 
         [0070]    During the high speed operation, the pressurizing operation unit U 1  applies back pressure force from the mold K to the low speed operation cylinder  30  of the low speed operation unit U 2 . However, in the low speed operation cylinder  30 , the check valve  34  inhibits the flow of the hydraulic oil from the head side chamber  30   d  to the rod side chamber  30   e.  This inhibits the rearward movement of the rod  30   c  toward the head side chamber  30   d  caused by the back pressure force. As a result, rotation is inhibited in the low speed operation ball screw B 2  caused by the low speed operation nut N 2 , which is fastened to the rod  30   c,  and the low speed operation motor M 2 . 
         [0071]    The pressurizing operation will now be described with reference to  FIG. 7 . 
         [0072]    In the pressurizing operation, the pressure applied by the rod  18   c  of the pressurizing operation cylinder  18  produces the injection pressure P shown in  FIG. 2 . The rotation produced by the operation motor M 1  moves forward the operation nut N 1 , which is fastened to the operation ball screw B 1 , and the operation nut N 1  applies drive force that moves the rod  20   c  of the operation cylinder  20  forward. 
         [0073]    When the rod  20   c  of the operation cylinder  20  moves forward, the hydraulic oil of the head side chamber  20   d  is supplied to the head side chamber  18   d  of the pressurizing operation cylinder  18  through the amplification oil passage  19 . In the present embodiment, when the hydraulic oil is supplied from the operation cylinder  20  to the head side chamber  18   d  of the pressurizing operation cylinder  18 , the pressure in the head side chamber  18   d  increases, and the pressure received by the injection plunger  16  from the pressurizing operation cylinder  18  increases in accordance with the Pascal&#39;s principle. As a result, the force of the injection plunger  16  that pressurizes the metal material in the cavity  14  increases. 
         [0074]    During the pressurizing operation, the back pressure force from the mold K also acts on the low speed operation cylinder  30  of the low speed operation unit U 2  through the pressurizing operation unit U 1 . However, in the low speed operation cylinder  30 , the flow of hydraulic oil from the head side chamber  30   d  to the rod side chamber  30   e  is inhibited by the check valve  34 . Thus, the back pressure does not move the rod  30   c  rearward toward the head side chamber  30   d.  This inhibits the rotation of the low speed operation ball screw B 2  and the low speed operation motor M 2  through the low speed operation nut N 2  fastened to the rod  30   c.    
         [0075]    Then, when the metal material in the cavity  14  is solidified, the operation motor M 1  produces rotation in a direction reversed from the pressurizing operation. The operation motor M 1  moves the operation nut N 1 , which is fastened to the operation ball screw B 1 , rearward. This applies drive force to the rod  20   c  of the operation cylinder  20  with the operation nut N 1 . When the rod  20   c  of the operation cylinder  20  moves rearward, hydraulic oil is drawn from the head side chamber  18   d  of the pressurizing operation cylinder  18  into the head side chamber  20   d  of the operation cylinder  20  through the amplification oil passage  19 . This moves the rod  18   c  of the pressurizing operation cylinder  18  rearward. As a result, the injection plunger  16  moves rearward in the injection sleeve  15 . 
         [0076]    Subsequently, the low speed operation electromagnetic switch valve  32  in the low speed operation unit U 2  is switched to the second position  32   b  to allow the flow of hydraulic oil from the head side chamber  30   d  to the rod side chamber  30   e.  The low speed operation motor M 2  produces rotation reversed from the low speed operation. The low speed operation motor M 2  moves the low speed operation nut N 2 , which is fastened to the low speed operation ball screw B 2 , rearward. This applies drive force to the rod  30   c  of the low speed operation cylinder  30  with the low speed operation nut N 2 . When the rod  30   c  of the low speed operation cylinder  30  moves rearward, hydraulic oil is drawn from the head side chamber  30   d  of the low speed operation cylinder  30  into the rod side chamber  30   e  through the low speed operation oil passage  31  and the low speed operation electromagnetic switch valve  32 . As a result, the rod  30   c  moves rearward, and the pressurizing operation unit U 1 , to which the rod  30   c  is connected, moves rearward. This move the injection plunger  16  rearward in the injection sleeve  15 . 
         [0077]    Then, in the high speed operation unit U 3 , the electromagnetic switch valve  45  is controlled and switched to the first position  45   a.  The pump  44  is driven to supply hydraulic oil from the oil tank  43  to the first chamber  40   e.  The piston  40   b  is then moved rearward toward the second chamber  40   d,  and the hydraulic oil of the second chamber  40   d  is accumulated in the accumulator  46 . At the same time, the piston  40   b  moves rearward. This moves the first rod  40   c  and the second rod  40   f  rearward by applying drive force and moves the low speed operation unit U 2 , to which the first rod  40   c  is connected, rearward. The pressurizing operation unit U 1 , to which the rod  30   c  of the low speed operation unit U 2  is connected, is also moved rearward. As a result, the injection plunger  16  moves rearward in the injection sleeve  15 . 
         [0078]    When the second rod  40   f  moves rearward and the first abutment surface  52   a  of the first connection member  52  is in planar contact with the second abutment surface  53   a  of the second connection member  53  thus forming the joined surface, the motor M 3  produces a 90-degrees rotation so that the first connection member  52  and the second connection member  53  shift to the referential connection state. This restricts forward movement of the piston  40   b.    
         [0079]    Accordingly, the injection plunger  16  of the injection sleeve  15 , the rod  18   c  of the pressurizing operation cylinder  18 , the rod  20   c  of the operation cylinder  20 , the rod  30   c  of the low speed operation cylinder  30 , and the two rods  40   c  and  40   f  of the high speed operation cylinder  40  are located at the initial positions shown in  FIG. 1 . Then, the fixed mold  12  and the movable mold  13  are separated to remove the molded product from the mold. 
         [0080]    The embodiment described above has the following advantages. 
         [0081]    (1) When the motor M 3  is driven to rotate the second connection member  53  and shift the connection mechanism R to the disconnected state, the planar contact (mechanical connection) of the first abutment surface  52   a  and the second abutment surface  53   a  is cancelled. This allows the second rod  40   f  to be moved by the hydraulic pressure. Under this situation, the hydraulic pressure from the accumulator  46  entirely acts on the piston  40   b.  Thus, the hydraulic pressure immediately moves the second rod  40   f.  This improves the response of the movement of the second rod  40   f  compared to when opening a valve so that the hydraulic oil from the accumulator  46  acts on the piston  40   b.  Thus, the use of the connection mechanism R enabling mechanical connection and disconnection of the second rod  40   f  improves the response of the movement of the second rod  40   f  in the high speed operation with a simple and inexpensive structure. 
         [0082]    (2) The accumulator  46  is connected to the second chamber  40   d  of the high speed operation cylinder  40 , and the hydraulic pressure from the accumulator  46  entirely acts on the piston  40   b  so that the second rod  40   f  is in a standby state and immediately movable toward the mold K. Further, the connection mechanism R is in the connected state to restrict movement of the second rod  40   f.  When the connection mechanism R is in the connected state, the first abutment surface  52   a  of the first connection member  52  and the second abutment surface  53   a  of the second connection member  53  are in planar contact to restrict movement of the first connection member  52  and thereby restrict movement of the second rod  40   f.  Accordingly, there is no need for a complicated structure including a hydraulic circuit and a pneumatic circuit, and the movement of the second rod  40   f  is restricted with a simple structure in which the first abutment surface  52   a  and the second abutment surface  53   a  come into planar contact. 
         [0083]    (3) The first abutment surface  52   a  and the second abutment surface  53   a  are each flat. Thus, compared to when, for example, the first abutment surface  52   a  and the second abutment surface  53   a  engage each other using a recess and a projection in the connected state, the first abutment surface  52   a  and the second abutment surface  53   a  come into planar contact and shift to the connected state more easily. 
         [0084]    (4) The first rotation axis G 1  of the first connection member  52  is located on the axis L of the second rod  40   f.  For example, when the first rotation axis G 1  of the first connection member  52  is separated from the axis L of the second rod  40   f  and the first connection member  52  is supported beside the second rod  40   f,  the second rod  40   f  tends to move in the direction in which the hydraulic pressure acts in the connected state. Thus, forces act in opposite directions on an axis that differs from that of the second rod  40   f  and the first connection member  52 . This may damage the portion connecting the second rod  40   f  and the first connection member  52 . However, by arranging the first rotation axis G 1  on the axis L of the second rod  40   f,  the first connection member  52  is supported on the axis L of the second rod  40   f,  and forces act in opposite directions on the same line in a connected portion. Thus, the connected portion is not easily damaged. 
         [0085]    (5) The first abutment surfaces  52   a  of the first connection member  52  is arranged on both sides of the first connection member  52  using the axis L of the second rod  40   f  as a reference. Thus, the first abutment surfaces  52   a  come into planar contact at two locations. Compared to when the planar contact occurs at only one location, the area of contact may be increased between the first abutment surfaces  52   a  and the second abutment surfaces  53   a.  This stabilizes the connected state stably restricts movement of the second rod  40   f.  Further, since there are two locations of planar contact, the first connection member  52  is supported at two portions by the two second connection members  53 . This prevents tilting of the first connection member  52  and tilting of the second rod  40   f.    
         [0086]    (6) The first connection member  52  includes the first abutment surfaces  52   a  formed on two sides of a cylindrical member. The second connection member  53  includes the second abutment surface  53   a  formed on one side of a cylindrical member. Thus, the abutment surfaces  52   a  and  53   a  are easily formed on cylindrical members. This reduces manufacturing costs of the first connection member  52  and the second connection member  53 . 
         [0087]    The embodiment described above may be modified as follows. 
         [0088]    At least one of the first connection member  52  and the second connection member  53  may not be a non-cylindrical member as long as it is rotatable. 
         [0089]    The first abutment surface  52   a  may be formed by fixing a discrete member to the first connection member  52 , and the second abutment surface  53   a  may be formed by fixing a discrete member to the second connection member  53 . 
         [0090]    In the first connection member  52 , the first abutment surface  52   a  may be formed only on one side in the axial direction (radial direction of the second rod  40   f ). In this case, only one second connection member  53  is arranged at a location corresponding to the first abutment surface  52   a.    
         [0091]    In the embodiment, the first connection member  52  is arranged in the second rod  40   f  so that the first rotation axis G 1  of the first connection member  52  is located on the axis L of the second rod  40   f.  However, the first connection member  52  may be arranged in the second rod  40   f  so that the first rotation axis G 1  is separated from the axis L of the second rod  40   f.    
         [0092]    In the embodiment, the first abutment surface  52   a  and the second abutment surface  53   a  are each flat. However, for example, the first abutment surface  52   a  may be formed to be a projection and the second abutment surface  53   a  may be formed to be a recess that is engaged with the first abutment surface  52   a  can engage. Alternatively, the first abutment surface  52   a  may be formed to be outwardly curved, and the second abutment surface  53   a  may be formed to be inwardly curved. In this manner, the shapes of the first abutment surface  52   a  and the second abutment surface  53   a  may be changed as long as planar contact is possible. 
         [0093]    The injection apparatus  11  may be applied to an injection apparatus that injects a resin material into the cavity  14  to manufacture a resin molded product.