Abstract:
To provide a fully electric extrusion press to reduce power consumption, improve maintenability and operability, and eliminate an adverse effect on the environment. 
     An extrusion press ( 10 ) comprises an end platen ( 1 ), a fixed platen ( 2 ) arranged at the rear thereof, a tie rod ( 4 ) configured to link the end platen and the fixed platen, a die ( 20 ), a container ( 3 ) loaded with a billet ( 8 ), an extrusion stem ( 13 ) configured to press the billet, a crosshead ( 7 ) attached with the extrusion stem, and an extrusion drive configured to reciprocate the extrusion stem. The extrusion drive comprises a rotatable wire drum ( 31 ) driven by an electric extrusion main motor ( 39 ) and drives the extrusion stem to perform extrusion molding by winding the wire ( 30 ) by rotating the wire drum.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to an extrusion press and in particular, to an extrusion press device that molds an aluminum alloy, etc., by extrusion molding via a die and, in more particular, to an electrically driven extrusion press that applies the electrically driven system adopted in an injection molding machine of synthetic resin (or a die cast machine that die-casts an aluminum alloy). 
         [0003]    2. Background Art 
         [0004]    An extrusion press is used to mold a metal product, such as an aluminum sash, by extrusion molding. In the conventional extrusion press, a billet, which is a material, is loaded within a fixed container, extruded by a stem (or extrusion stem) driven by a ram cylinder, and passed through a die attached to the outlet of the container, and thereby, the billet is molded so as to have a predetermined cross-sectional shape. The billet loaded on such a molding machine is supplied by a billet loader. The billet loader is configured so as to grasp the billets one by one sent from a billet carrier arranged on the lateral side of the molding machine and move the billet to a billet load port of the container and then the billet is sent out by the stem and loaded on the container in a state where the billet and the load port are aligned and molded by being extruded under pressure. 
         [0005]    Many of the products molded by extrusion molding by the extrusion press are elongated, such as an aluminum sash, and in the case of an elongated product, the billet is extruded for a long time by the stem, and therefore, the ram cylinder that pushes the stem uses a hydraulic system capable of long strokes under high pressure. However, such a conventional extrusion press device uses hydraulic pressure as power (for example, see Patent Literature 1, Patent Literature 2), and therefore, there are problems with regard to the environment (noise, oil spill, etc.), energy saving (running cost), etc. In order to solve such problems, it is desired to realize an electric drive that is used in an injection molding machine of synthetic resin (or die cast machine that die-casts an aluminum alloy). In the case of an electric drive, in general, it is necessary to convert rotational motion of an electric motor, which is a drive in the first stage, into rectilinear motion or reciprocating rectilinear motion. 
         [0006]    However, such a mechanism (ball screw and ball nut etc.) that converts rotational motion into rectilinear motion in place of a conventional hydraulic cylinder device capable of continuously outputting a large output capacity required for the extrusion press, for example, 9,800 kN (1,000 tf), or a large output electric servomotor is not realized. Due to this, the electrically driven system is not applied to the extrusion press. 
         [0007]    Further, the extrusion press comprises various kinds of devices that move, such as an extrusion stem slide, shear device, die slide device (shear), die changer, and billet loader, and conventionally, these devices adopt the hydraulic system as the ram system does. 
         [0008]    The conventional extrusion press is a machine that produces extruded products by driving a plurality of hydraulic press devices by motors and pumps that consume electric power. Not only during the extrusion process but also during processes other than the extrusion process, for example, processes of, such as discard cutting and removal and insertion of the next billet, the same pump and motor are used as a drive source. The pump and motor and auxiliary pump and motor used for extrusion that utilize hydraulic equipment are always in the idling operation even when not necessary for the operation of the device directly, and therefore, power consumption loss occurs. 
         [0009]    Further, when a machine user uses a machine for many years, the user needs to perform maintenance and inspection inevitably in order to maintain and manage the machine and it is considered that the time required for maintenance is by far longer in the case where the drive source is a hydraulic source than in the case where only an electric motor is used. The reason is as follows. When the hydraulic equipment is used for many years, trouble, such as deterioration of the hydraulic oil, wear of valves, and oil spill from pipe connections, relates to many parts, such as pumps, valves, manifolds, and pipes, and therefore, it takes much time to troubleshoot the cause and take measures. 
         [0010]    Further, when the hydraulic source is used, the hydraulic oil flows out (leak, discharge, etc.) at the time of maintenance, etc., and therefore, the machine operability and working environment deteriorate and there is a risk of fire because containers and dies are used in a high-temperature environment. It is of course possible to use flame resistant hydraulic oil (water-glycol fluid etc.), however, ordinarily the hydraulic oil is used under high pressure in order to make the machine compact and the flame resistant hydraulic oil (water-glycol fluid etc.) is not suitable for use, and therefore, not normally used. 
         [0011]    As described above, as the drawbacks of the conventional hydraulic drive system, there are problems as follows. (1) The hydraulic oil is used as a medium, and therefore, it is difficult to realize accurate speeds and positions as in the case of the mechanical operation. (2) The amount of energy consumption is comparatively large and cooling water is required to prevent the oil temperature from rising, and therefore, the running cost is increased. (3) The number of components the circuit pressure of which is high is large and the noise during the operation is high. (4) Since hydraulic oil is used, there exit problems of maintenance, environment, and cost resulting from leak of the hydraulic oil and problems of environment and cost accompanying the disposal of the hydraulic oil. 
         [0012]    The extrusion presses are classified into the conventional system (conventional type: billets are supplied between the end surface of the container and the tip end surface of the stem, including the direct type and the indirect type) (for example, see Patent Literature 1), the short stroke system (including the front loading system (for example, see Patent Literature 2) and the rear loading system which are classified based on the position where billets are supplied), etc. The present invention can be applied to either type. In the front loading type, the container is moved to the stem side and billets are supplied in the gap between the end surface of the container and the die and the rear loading type differs from the front loading type in that the stem is moved in the horizontal or vertical direction and billets are supplied in the gap formed when the stem moves (between the container and the crosshead). 
       CITATION LIST  
     Patent Literature  
       [0013]    [PTL 1] Japanese Unexamined Patent Publication (Kokai) No. 8-206727 
         [0014]    [PTL 2] Japanese Unexamined Patent Publication (Kokai) No. 10-5853 
         [0015]    [PTL 3] Japanese Unexamined Patent Publication (Kokai) No. 2007-160335 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0016]    As described above, the conventional hydraulic extrusion press has problems of poor precision, inefficient energy consumption, adverse influence on the environment, etc., and therefore, the electric extrusion press that solves these problems is required. The present invention has been made in view of the circumstances described above and an object thereof is to improve precision, energy consumption, and maintenability/operability without adversely affecting the environment, and to reduce noise by providing an electric extrusion press. 
         [0017]    Another object of the present invention is to provide an extrusion press electrically powered in a perfect manner. 
       Solution of Problem 
       [0018]    In a first aspect of the present invention, in order to achieve the above-described objects, an extrusion press ( 10 ) comprises an end platen ( 1 ) arranged at the front end part in the lengthwise direction of the extrusion press ( 10 ), a fixed platen ( 2 ) arranged at the rear in the lengthwise direction in opposition to the end platen ( 1 ), a tie rod ( 4 ) that couples the end platen ( 1 ) and the fixed platen ( 2 ), a die ( 20 ) arranged so as to come into contact with the rear surface of the end platen ( 1 ), a container ( 3 ) arranged so as to oppose the die ( 20 ) and loaded with a billet ( 8 ), an extrusion stem ( 13 ) that presses the billet ( 8 ) loaded within the container ( 3 ), a crosshead ( 7 ) arranged at the front of the fixed platen ( 2 ) and to the front surface of which, the extrusion stem ( 13 ) is attached, and an extrusion drive that drives the crosshead ( 7 ) and the extrusion stem ( 13 ) attached to the crosshead ( 7 ) so as to reciprocate in the forward and backward directions. In the extrusion press ( 10 ), by pushing the extrusion stem ( 13 ) by an extrusion force of the extrusion drive, the billet ( 8 ) is put under pressure and extruded out via the die ( 20 ), and thus, a predetermined product is molded by extrusion molding. The extrusion drive comprises one or more wire drums ( 31 ) provided rotatably and one of the end parts of one or more wires ( 32 ) is fixed on the wire drum ( 31 ) and at the same time, the other end part of the wire ( 32 ) is connected mechanically to the crosshead ( 7 ) and by rotating the wire drum ( 31 ) to wind the wire ( 32 ), the crosshead ( 7 ) and the extrusion stem ( 13 ) are driven to move forward and the wire drum ( 31 ) is driven by an electric extrusion main motor ( 39 ). 
         [0019]    In a preferred aspect, the extrusion drive further comprises an extrusion mobile part ( 15 ) linked to the crosshead ( 7 ) at one of end parts thereof, and an extrusion part ( 16 ) attached to the other end part of the extrusion mobile part ( 15 ) and on which the other end part of the wire ( 32 ) is fixed. The extrusion press ( 10 ) further comprises a crosshead fast moving mechanism ( 40 ) capable of causing the extrusion mobile part ( 15 ) to reciprocate back and forth and a wire winding device ( 42 ) capable of winding and feeding the wire ( 32 ) to and from the wire drum ( 31 ) by rotating the wire drum ( 31 ) in the forward and reverse directions, separately from the extrusion drive. In the stage at the time of start of the extrusion molding process, in which the billet ( 8 ) has moved forward and come into contact with the die ( 20 ) but no load of extrusion molding acts on the extension stem ( 13 ), when moving back the extrusion stem ( 13 ) and causing the extrusion stem ( 13 ) to move forward and back at a high speed, the extrusion stem ( 13 ) is driven at a high speed via the extrusion mobile part ( 15 ) by the crosshead fast moving mechanism ( 40 ) and at the same time, the wire winding device ( 42 ) is operated to wind and feed the wire ( 32 ). 
         [0020]    At the time of the start of operation when driving the extrusion stem ( 13 ) at a high speed, it is preferable to operate the extrusion drive as well as the crosshead fast moving mechanism ( 40 ). 
         [0021]    It is preferable for the extrusion press ( 10 ) to further comprise a container operating device ( 14 ) using an electric motor as a drive source and capable of driving the container ( 3 ) in the forward and backward directions, a shear device ( 27 ) using an electric motor as a drive source and for cutting a discard, and a die slide device ( 21 ) using an electric motor as a drive source and capable of moving the die ( 20 ). It is preferable to connect the extrusion main motor ( 39 ) to the wire drum ( 31 ) via a clutch coupling ( 38 ) and a speed reducer ( 36 ). 
         [0022]    The extrusion press ( 10 ) further comprises a stem slider ( 11 ) using an electric motor as a drive source and capable of moving the extrusion stem ( 13 ) in order to provide a space for sending in the billet ( 8 ), between the crosshead ( 7 ) and the die ( 20 ). 
         [0023]    The symbols in the parenthesis  0  attached to each means described above indicate a correspondence with a specific means in the embodiments to be described later. 
       Advantageous Effects of Invention 
       [0024]    The extrusion press of the present invention adopts the electric motor driven system, and therefore, an idling operation necessary for the hydraulic system is not necessary and it is possible to operate the motor only when each individual elemental device needs to be operated, and therefore, the effect of reducing power can be expected. 
         [0025]    Since an electric motor is used as a drive source, it is only necessary to maintain the electric motor itself because the drive itself is the electric motor and the time and cost for maintenance and management are reduced because the number of parts to be maintained is smaller compared to that of a hydraulic source. 
         [0026]    The leak of hydraulic oil does not occur and noise can be reduced, and therefore, the improvement of working environment is realized and the risk of fire can be avoided. 
         [0027]    Further, controllability, such as positioning control, and operability are excellent. 
         [0028]    The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0029]      FIG. 1  is a side view showing an outline of the configuration of an extrusion press of a first embodiment. 
           [0030]      FIG. 2  is a plan view when the device in  FIG. 1  is viewed from above. 
           [0031]      FIG. 3  is a rear view when the device in  FIG. 1  is viewed from the rear thereof. 
           [0032]      FIG. 4  is a sectional view along A-A when the device in  FIG. 1  is viewed from ahead thereof 
           [0033]      FIG. 5  is a sectional view along B-B when the device in  FIG. 1  is viewed from the rear thereof 
           [0034]      FIG. 6  is a flowchart showing an operation process of the extrusion press of the first embodiment of present invention. 
           [0035]      FIG. 7  is a flowchart showing an operation process of an extrusion press of a second embodiment of present invention. 
           [0036]      FIG. 8  is a flowchart showing an operation process of an extrusion press of a third embodiment of present invention. 
           [0037]      FIG. 9  is an explanatory diagram of an operation of a die slide device. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0038]    An extrusion press of a first embodiment of the present invention is explained below in detail based on the drawings.  FIG. 1 ,  FIG. 2 ,  FIG. 3 , and  FIG. 4  diagrammatically show the first embodiment (stem slide system extrusion press) of the extrusion press according to the present invention, wherein  FIG. 1  is a side view showing an outline of the configuration of the extrusion press of the first embodiment,  FIG. 2  is a plan view of the device in  FIG. 1  when viewed from above,  FIG. 3  is a rear view of the device in  FIG. 1  when viewed from the rear thereof, and  FIG. 4  and  FIG. 5  each show a sectional view along A-A of the device in  FIG. 1  when viewed from ahead thereof and a sectional view along B-B when viewed from the rear thereof. The extrusion press of the present invention molds a predetermined product by extrusion molding via a die by pressing an extrusion stem (or a stem) by an extrusion force by an electric extrusion drive (mechanism) that converts rotational motion into rectilinear motion to apply pressure to a billet at about 400 to 500° C. generally. 
         [0039]    Referring to  FIG. 1  and  FIG. 2 , an extrusion press  10  of the first embodiment of the present invention comprises an end platen  1  located at the front end part and a fixed platen  2  located in the vicinity of the center of the device. At the center of the end platen  1 , a through hole  9  is provided through which a product is caused to pass, which product is molded by extruding a billet  8  into a predetermined shape via a die  20 . In the present embodiment, as can be seen clearly from  FIG. 4 , the end platen  1  and the fixed platen  2  are coupled by four tie rods  4  arranged in the four corners. Between the end platen  1  and the fixed platen  2 , in the vicinity of the end platen  1 , a container  3  to be loaded with the billet  8  is arranged so as to be supported by a container holder (not shown schematically) and on the side of the fixed platen  2 , a crosshead  7  is arranged so as to be supported by the four tie rods  4 . The tie rods  4  penetrate through the four corners of the crosshead  7 , respectively. Between the end platen  1  and the container  3 , the die  20  is arranged. The container  3  is driven by a container operating device  14  comprising a container operating motor  17  and moves back and forth. 
         [0040]    At the center on the side of the container of the crosshead  7 , an extrusion stem (or a stem)  13  is attached. The extrusion press  10  of the present embodiment adopts the stem slide system and the extrusion stem  13  is capable of moving vertically by a stem slider  11  comprising a stem slide motor  12 . In the present embodiment, the extrusion stem  13  is driven by the stem slide motor  12  and it is preferable for the stem slide motor  12  to be a speed-variable inverter motor or AC servomotor. 
         [0041]    To the side of the fixed platen of the crosshead  7 , an extrusion mobile part  15  in the shape of a hollow cylinder (may be in another shape, such as a polygon, and may be solid instead of hollow) is linked and the extrusion mobile part  15  is supported slidably by the fixed platen  2  while penetrating through the center of the fixed platen  2 . To the other end part of the extrusion mobile part  15 , an extrusion part  16  in the shape of a wing (may be in another shape) is attached as shown in  FIG. 1 . 
         [0042]    In the present embodiment, as shown in  FIG. 1  and  FIG. 2 , four wire drums (or drums)  31  rotatably arranged in the upper, lower, left, and right positions are arranged on the opposite side of the stem of the fixed platen  2 . To the wire drum  31 , a plurality (ten in the present embodiment) of wires  32  is fixed and wound on one of the end parts, respectively and the other end parts of the wires  32  are linked to the extrusion part  16 , respectively. In the present embodiment, when the plurality of the wires  32  is wound to the drum  31 , rotational motion is converted into rectilinear motion (the extrusion drive including the drum  31  etc. corresponds to the main cylinder part in the case of the hydraulic drive system). The wire drum  31  causes the extrusion stem  13  to move forward via the wire  32  and further, via the extrusion mobile part  15  and the crosshead  7 . It may also be possible to mount one or more wire drums  31  based on the capacity of the device (extrusion press  10 ) and the number of the wires  32  in each wire drum  31  may be one or more based on the capacity of the device. Each wire drum  31  is driven by an electric extrusion main motor  39 , which is preferably an AC servomotor, via a speed reducer  36  and a clutch coupling  38 . In the extrusion drive, the wire drum  31  is linked to the output shaft of the speed reducer  36  and the input shaft of the speed reducer  36  is connected to the output shaft of the extrusion main motor  39  via the clutch coupling  38 . The speed reducer  36  and the clutch coupling  38  may be other power transmitting components. 
         [0043]    The speed when moving the extrusion stem  13  by the wire drum  31  is low because the speed is reduced considerably by the speed reducer  36 . However, until the extrusion stem  13  comes into contact with the billet  8 , it is preferable to move at a high speed to reduce the operation time. Further, the movement direction of the extrusion stem  13  by the wire drum  31  is only the extrusion (forward) direction, and therefore, the movement in the pull-back (backward) direction of the extrusion stem  13  is also required. Due to this, a crosshead fast moving mechanism  40  is provided. In the present embodiment, the crosshead fast moving mechanism  40  comprises a crosshead fast moving motor  35 , which is preferably an AC servomotor or inverter motor, a ball nut  34 , a ball screw  33 , etc., and the ball screw  33  is linked to the crosshead fast moving motor  35  at one side and linked to the extrusion part  16  at the other side. In the present embodiment, the mechanism to convert the rotational motion of the crosshead fast moving motor  35  into linear motion uses the ball screw system, however, it may also be possible to use an already known mechanism, such as the rack/pinion system. In the present embodiment, as shown in  FIG. 2 , the crosshead fast moving mechanism  40  is fixed on and supported by the fixed platen  2  via four struts  41 , however, it may be supported by another supporting method. Further, when moving the extrusion stem  13  at a high speed by the crosshead fast moving mechanism  40 , the wire  32  loosens, and therefore, in order to prevent the wire  32  from loosening at this time, as shown in  FIG. 1 , a wire winding device  42  is provided to each wire drum  31  and a wire winding motor  43  of the wire winding device  42  is connected to the wire drum  31  via a chain, etc. The wire winding motor  43  is operated to drive the wire drum  31  so as to prevent the wire  32  from loosening at the same time as the crosshead fast moving motor  35  is operated. 
         [0044]    The extrusion press  10  comprises a machine base  6  and on the machine base  6 , the end platen  1 , the fixed platen  2 , the wire drum  31 , the speed reducer  36 , the extrusion main motor  39 , etc., are installed and fixed. In the center of the extrusion press  10 , a center axis line C extends in the lengthwise direction as shown in  FIG. 1  and  FIG. 2  and the extrusion press  10  has a configuration substantially bilaterally symmetric about the center axis line C. In the extrusion molding stage, the end platen  1 , the fixed platen  2 , the container  3 , the extrusion stem  13 , the crosshead  7 , and the extrusion mobile part  15  are arranged so that each center axis thereof agrees with the center axis line C. 
         [0045]    Further, the extrusion press comprises a billet loader (not shown schematically) configured to supply the billet  8  between the container  3  and the extrusion stem  13 , a shear device  27  (mounted on the end platen  1 ) configured to cut a discard, which is an unnecessary part at the end part of the product after extrusion molding of the billet  8 , a die slide device (shear)  21  configured to move a die, etc. 
         [0046]    The use and purpose of the die slide device (shear)  21  is to move the die ( 20 ) in the transverse direction perpendicular to the center axis line (C) and to cut and separate a product  60  extruded toward the rear of the end platen at the time of completion of extrusion from the die  20 . In the actual operation, by using a platen saw  51  installed ahead of the end platen on the front installation side, the product  60  is cut at the time of completion of extrusion (see  FIG. 9 ). After that, the product  60  is sent to the front table by the drive installed ahead thereof. At this time, a remaining material  53  of the product  60  remains within the end platen in the state of being molded by the die (see  FIG. 9 ). When moving the die slide  22  to the die replacement position by the die slide device  21  to replace the die  20  with another, a remaining material  54  of the product is cut and separated from a die stack  56  at the cutting surface of the front surface of the end platen and the front surface of the die slide  22  (see  FIG. 9 ). A remaining material  55  within the die stack  56  is cut and separated from the die  20  by another cutting device or manual operation after the die stack  56  is sent out of the machine. 
         [0047]    The container  3  is reciprocated (move forward and back) by the container operating motor  17 , which is preferably an inverter motor or AC servomotor, via the mechanism including the ball screw and the ball and configured to convert rotational motion into linear motion. In the case of the front loading system (second embodiment to be described below), on the opposite side of the extrusion stem of the fixed platen, the container operating device  14 , such as the container operating motor  17 , is provided. This is because the movement stroke of the container is large. In the shear device  27 , an electric motor is used as a power source and rotational motion is converted into rectilinear motion via the winding drive mechanism, such as a chain. The die slide device (shear)  21  uses an electric motor as a power source and converts rotational motion into rectilinear motion via the power transmission mechanism including the ball screw and the ball nut. The stem slider also uses an electric motor as a motor source and uses the mechanism configured to convert rotational motion into rectilinear motion via the power transmission mechanism including the ball screw and the ball nut. The die changer configured to change the die and the billet loader also use an electric motor as a power source. With this configuration, it is possible to operate the extrusion press only by electric power. 
         [0048]    The extrusion press  10  of the present embodiment is explained using a stem slide extrusion press belonging to the short stroke rear loading system as an example, however, it is clear that persons skilled in the art can easily understand that the present invention can be applied to the short stroke front loading system and the conventional system with no stem slider mounted. Further, the configuration of the present invention is explained using the direct extrusion press as an example, however, it is clear that persons skilled in the art can easily understand that the present invention can also be applied to the indirect extrusion press. 
         [0049]    Next, the operation of the stem slide (short stroke rear loading system) extrusion press  10  of the present embodiment is explained with reference to  FIG. 6 . 
         [0050]    The operation of the extrusion press  10  performs one cycle repeatedly and produces the mold product continuously. In the present embodiment, in step S 1  (S 1 ), the extrusion press  10  is in the stage in which one cycle of the extrusion molding process is completed and the container  3  has moved back and is in the state of being distant from the die  20 . In S 1 , the cycle of the next new extrusion molding process is started and first, the container operating motor  14  is operated and thereby the container  3  is moved forward and connected to the die  20 . Next, in step  2  (S 2 ), by lifting the stem slider  11  to lift the extrusion stem  13 , a sending-in space of the billet  8  is provided to send in the billet  8 . 
         [0051]    Next, in step  3  (S 3 ), by the billet loader (electric motor driven), the billet  8  is sent into the extrusion press center between the container  3  and the crosshead  7 . Next, in step  4  (S 4 ), the billet  8  held by the billet loader is inserted into the container  3  by the billet inserting device (electric motor driven) of the billet loader. Next, in step  5  (S 5 ), the billet loader is moved out of the extrusion press  10 . Next, in step  6  (S 6 ), by lowering the stem slider  11 , the extrusion stem  13  is arranged in the press center. The billet  8  within the container  3  and the extrusion stem  13  are aligned on the center axis line C. 
         [0052]    Next, in step  7  (S 7 ), the extrusion stem  13  is caused to move forward at a high speed and to substantially come into contact with the billet  8 . In this procedure, first, the load to move the extrusion stem  13  is heavy, and therefore, the crosshead fast moving motor  35  and the extrusion main motor  39  are operated to cause the extrusion stem  13  to start to move forward (with this configuration, it is possible to make small the capacity of the crosshead fast moving motor  35 ). When the extrusion mobile part  15  and the crosshead  7  start to move, the clutch of the clutch coupling  38  is disengaged and the extrusion main motor  39  is stopped. Then, the crosshead fast moving motor  35  and the wire winding motor  43  are driven continuously until the extrusion stem move-forward highest speed is reached and the extrusion stem  13  and the billet  8  move forward at constant speed until the billet  8  comes into contact with the die  20 . In the present embodiment, the state in which the die  20  comes into contact with the billet  8  is detected by the torque of the extrusion main motor  39 , however, it may also be possible to detect by another already known means, such as a stroke sensor and limit switch. 
         [0053]    Next, in step  8  (S 8 ), the initial speed extrusion is started by causing the extrusion main motor  39  to drive the drum  31 . The initial speed and the subsequent speed of extrusion are set in advance and in the present embodiment, the extrusion main motor  39  is an AC servomotor, and therefore, the speed adjustment is performed by controlling the rotating speed. Next in step  9  (S 9 ), when detecting that a predetermined advance stroke is reached, the rotating speed of the extrusion main motor  39  is controlled so that a predetermined extrusion speed is obtained. The predetermined stroke is detected by a stroke detector provided to the crosshead  7 , however, it may also be possible to detect the predetermined stroke by the rotating speed of the extrusion main motor  39  or the drum  31  and by another already known means, such as the limit switch. Next, in step  10  (S 10 ), the predetermined advance stroke is detected by the stroke detector and the rotating speed of the extrusion main motor  39  is controlled so that a predetermined extrusion final speed is obtained. Next, in step  11  (S 11 ), the state in which the predetermined advance stroke is reached is detected by the stroke detector, the extrusion main motor  39  and the crosshead fast moving motor  35  are stopped, and the extrusion is exited. 
         [0054]    Next, in step  12  (S 12 ), by operating the container moving motor  17  to move back the container and the discard (defective part at the rear end of the extrusion-molded product) is pushed out of the container  3 . Next, in step  13  (S 13 ), the extrusion stem  13  is moved back by operating the crosshead fast moving motor  35  up to the position where the next billet  13  can be sent in. At this time, the extrusion main motor  39  and the wire winding motor  43  are also operated at the same time, however, the extrusion main motor  39  is used only to initially move the drum  31  and when the speed of the crosshead fast moving motor  35  reaches the maximum rotating speed, the clutch coupling  38  is disengaged and the extrusion main motor  39  is stopped. After that, the crosshead  17  is continuously moved back at the highest speed by operating the crosshead fast moving motor  35  and the wire winding motor  43  and at the same time, the wire  32  wound to the drum  31  is extended. Until the stem moved-back slow position is detected by the stroke detector, the crosshead  7  is moved back at a constant speed and after the stem moved-back slow position is detected, the speed of the move-back is reduced. 
         [0055]    Next, in step  14  (S 14 ), the shear device  27  is operated and the discard is cut from the product and removed. It is preferable to drive the shear device  27  by an inverter motor or AC servomotor. The movement (downward) of the shear of the shear device  27  at the time of cutting is set so that the speed thereof is high until the shear comes into contact with the discard and after the contact (a predetermined position is detected by a shear position detector), the speed is reduced so as to keep the torque of the drive motor. It is preferable to lift the shear at a high speed. In step  14 , one cycle of the extrusion press is completed and the procedure returns to S 1  again. 
         [0056]    Referring to  FIG. 7 , an operation flow of an extrusion press of a second embodiment of the present invention is shown. The extrusion press  10  of the second embodiment of the present invention adopts the front loading system. In the front loading extrusion press, the space for loading the billet  8  between the die  20  and the container  3  is provided by moving the container  3  to the side of the extrusion stem  13  (in the stem slide system (rear loading system), the space is provided between the container  3  and the crosshead  7  by lifting the extrusion stem  13 ). In the front loading system also, the mechanism, etc., to extrude the extrusion stem  13  (or the crosshead  7 ) relating to the present invention is the same as that in the stem slide system, and therefore, explanation of the detailed configuration of the front loading extrusion press is omitted (see Patent Document 2). 
         [0057]    The operation flow of the present embodiment is explained below. 
         [0058]    In step  21  (S 21 ), which is the first step in the operation flow, the extrusion press  10  is in the stage in which one cycle of the extrusion molding process is completed and the stage in which the cycle of the next new extrusion molding process is started. Before the start of S 21 , the container  3  is moved back by the container operating motor  17  and the extrusion stem  13  is accommodated within the container  3 , and therefore, a space is already provided between the die  20  and the container  30 . In S 21 , the billet loader holding the billet  8  is moved into the machine in the vicinity of the extrusion press and the billet  8  held by the billet loader as if it were supported thereby is moved to the center of the extrusion press (press center) between the die  20  and the container  3 . The container is still in the state of being moved back and distant from the die  20 . 
         [0059]    Next, in step  22  (S 22 ), the extrusion stem  13  is moved forward at a high speed and the extrusion stem  13  is caused to substantially come into contact with the billet  8  and further, the billet  8  in the state of being supported by the billet loader is pushed until it comes into contact with the die  20  and sandwiched by the die  20  and the extrusion stem  13  and thus held. In this procedure, first, the load to start movement is heavy, and therefore, the crosshead fast moving motor  35  and the extrusion main motor  39  are operated to start forward movement (with this configuration, it is possible to reduce the capacity of the crosshead fast moving motor  35 ). When the extrusion mobile part  15  and the crosshead  17  start to move and the speed of the extrusion main motor  39  reaches the maximum rotating speed, the clutch of the clutch coupling  38  is disengaged and the extrusion main motor  39  is stopped. Then, the crosshead fast moving motor  35  and the wire winding motor  43  are driven continuously until the extrusion stem move-forward highest speed is reached and the extrusion stem  13  and the billet  8  are moved forward at constant speed until the billet  8  comes into contact with the die  20 . In the present embodiment, the state in which the billet  8  comes into contact with the die  20  is detected by the torque of the extrusion main motor  39 , however, it may also be possible to detect the contact by another already known means, such as the stroke sensor, limit switch, and extrusion stem load sensor. 
         [0060]    Next, in step  23  (S 23 ), the billet loader is moved out of the extrusion press  10 . Next, in step  24  (S 24 ), the container moving motor  14  is operated and the container  3  is moved forward and connected to the die  20 . The state at this time is the state when S 7  is completed in the first embodiment. 
         [0061]    After that, steps  25 ,  26 ,  27 , and  28  are carried out sequentially. The contents of these procedures (steps) are the same as those in S 8 ,  9 ,  10 , and  11  in the first embodiment. That is, in step  25  (S 25 ), the extrusion main motor  39  is caused to drive the drum  31  and the initial extrusion is started. In step  26  (S 26 ), that the predetermined advance stroke is reached is detected and the rotating speed of the extrusion main motor  39  is controlled so that a predetermined extrusion speed is obtained. In step  27  (S 27 ), the predetermined advance stroke is detected by the stroke detector and the rotating speed of the extrusion main motor  39  is controlled so that a predetermined extrusion final speed is obtained. In step  28  (S 28 ), that the predetermined advance stroke is reached is detected by the stroke detector and the extrusion main motor  39  and the crosshead fast moving motor  35  are stopped and then the extrusion is exited. The contents of S 25  to S 28  are the same as those of S 8  to S 12  in the first embodiment, and therefore, detailed explanation is omitted to avoid duplication. Next, in step  29  (S 29 ), the container moving motor  17  is operated to move back the container  3  and then the discard (defective part at the rear end of the extrusion molded product) is pushed out of the container  3 . 
         [0062]    Next, in step  30  (S 30 ), the container  3  and the extrusion stem  13  are moved back. In S 31 , the crosshead fast moving motor  35  is operated up to the position where the next billet  8  can be sent in and the extrusion stem  13  is moved back. At this time, the extrusion main motor  39  and the wire winding motor  43  are also operated at the same time, however, the extrusion main motor  39  is used only to start to move the drum  31  and when the speed of the crosshead fast moving motor  35  reaches the maximum rotating speed, the clutch coupling  38  is disengaged and the extrusion main motor  39  is stopped. After that, the crosshead fast moving motor  35  and the wire winding motor  43  are operated and the crosshead  7  is moved back continuously at the highest speed and at the same time, the wire  32  wound to the drum  31  is extended. Until the stem moved-back slow position is detected by the stroke detector, the crosshead  7  is moved back at a constant speed and after the stem moved-back slow position is detected, the move-back speed is reduced. The procedure to operate the extrusion main motor  39 , etc., of step S 31  is similar to that of S 13  in the first embodiment. The container  3  is moved back by using the container moving motor  17  in such a manner that the move-back speed is in harmony with that of the extrusion stem  13 . 
         [0063]    Next, in step  31  (S 31 ), the shear device  27  is operated and the discard is cut from the product and removed. The contents of S 31  are the same as those of S 14  in the first embodiment, and therefore, details are omitted to avoid duplication. In step  31 , one cycle of the extrusion press in the present embodiment is completed and the procedure returns to S 21  again. 
         [0064]    Referring to  FIG. 8 , an operation flow of an extrusion press of a third embodiment of the present invention is shown. The extrusion press of the third embodiment of the present invention adopts the conventional system. The configuration of the conventional extrusion press is such that between the extrusion stem  13  and the container  3 , a sufficient space for sending in the billet  8  exists and it is not necessary to move the extrusion stem  13  or the container  3  to another place. Consequently, in the conventional system, the device is increased in length. On the contrary, the stem slide extrusion press and the front loading extrusion press are devised to reduce the length of the conventional system. Consequently, the operation of the conventional system is basically the same as that of the stem slide system. The configuration of the conventional extrusion press is such that the stem slider  11  is removed in the stem slide extrusion press  10 . That is, in the conventional extrusion press, the extrusion stem  13  is fixed on the crosshead  7 . 
         [0065]    The operation flow of the present embodiment is explained below. 
         [0066]    Step  41  (S 41 ) is the same as step  1  (S 41 ) in the stem slide system and the step of starting one cycle of the new extrusion molding process, in which the container operating motor  14  is operated and the container  3  is moved forward and connected to the die  20 . Next, in step  42  (S 42 ), by the billet loader (electric motor driven), the billet  8  is sent into the extrusion press center between the container  3  and the crosshead  7  (or the extrusion stem  13 ) (step  2  in the stem slide system is no longer necessary). 
         [0067]    Next, in step  43  (S 43 ), the extrusion stem  13  is moved forward at a high speed, the extrusion step  13  is caused to substantially come into contact with the billet  8 , and further, the billet  8  in the state of being supported by the billet loader is pushed until the billet  8  comes into contact with the die  20  and the billet  8  is sandwiched by the die  20  and the extrusion stem  13  and thus held. S 43  is the same as step  22  (S 22 ) in the front loading system and step  7  (S 7 ) in the stem slide system, and therefore, detailed explanation is omitted. Next, in step  44  (S 44 ), the billet loader is moved out of the extrusion press. 
         [0068]    After that, steps  45 ,  46 ,  47 ,  48 , and  49  are performed sequentially. The contents of these procedures (steps) are the same as the procedures (steps) of S 8 ,  9 ,  10 ,  11 , and  12  in the first embodiment (and S 25 ,  26 ,  27 ,  28 , and  29  in the second embodiment). That is, in step  45  (S 45 ), the drum  31  is driven by the extrusion main motor  39  to start the initial speed extrusion. In step  46  (S 46 ), that the predetermined advance stroke is reached is detected and the rotating speed of the extrusion main motor  39  is controlled so that the predetermined extrusion speed is obtained. In step  47  (S 47 ), the predetermined advance stroke is detected by the stroke detector and the rotating speed of the extrusion main motor  39  is controlled so that the predetermined extrusion final speed is obtained. In step  48  (S 48 ), that the predetermined advance stroke is reached is detected by the stroke detector, the extrusion main motor  39  and the crosshead fast moving motor  35  are stopped, and the extrusion is exited. In step  49  (S 49 ), the container moving motor  17  is operated to move back the container and the discard (defective part at the rear end of the extrusion-molded product) is pushed out from the container  3 . The contents of S 45  to S 49  are the same as those of S 8  to S 12  in the first embodiment, and therefore, a detailed explanation is omitted to avoid duplication. 
         [0069]    Next, in step  50  (S 50 ), the container  3  and the extrusion stem  13  are moved back. S 50  is the same as step  30  in the second embodiment, and therefore, detailed explanation is omitted to avoid duplication. Next, in step  51  (S 51 ), the shear device  27  is operated and the discard is cut from the product and removed. The contents of S 51  are the same as those of S 14  in the first embodiment and those of S 31  in the second embodiment, and therefore, detailed explanation is omitted to avoid duplication. In step  51 , one cycle of the operation process of the extrusion press in the present embodiment is completed and the procedure returns to S 41  again. 
         [0070]    In the second and third embodiments, the same as or similar component to the component in the first embodiment is specified by the same reference symbol. 
         [0071]    The effects and workings of the embodiments described above are explained. 
         [0072]    By the extrusion press in the first embodiment of the present invention, the following effects can be expected. 
         [0073]    The extrusion press includes a number of mobile elemental devices and is operated by operating each elemental device in a variety of ways, and in the present invention, each elemental device is driven by the electric motor, and therefore, it is possible to operate the motor only when each elemental device needs to be operated. Due to this, the effect of reducing electric power can be expected (in the hydraulic system, in general, the idling is necessary even when the operation is not required). 
         [0074]    Since the electric motor is used as a drive source, the drive itself is the electric motor, and therefore, it is only necessary to maintain the electric motor itself and the time and cost for maintenance and management are reduced because the number of parts to be maintained is small compared to that of the hydraulic source. 
         [0075]    Spill of hydraulic oil does not occur and noise can be reduced, and therefore, the working environment is improved and the risk of fire can be avoided. 
         [0076]    By the use of the AC servomotor, etc., precise positional control, etc., is excellent and operability is improved. 
         [0077]    By the extrusion press in the second and third embodiments of the present invention, the same effects as those in the first embodiment can be expected. 
         [0078]    In the explanation described above, the extrusion press of the present invention is explained using an example of the direct extrusion press, however, the present invention may be applied to an indirect extrusion press. 
         [0079]    The embodiments described above are mere examples of the present invention and the present invention is not limited by the embodiments but specified only by claims and embodiments other than those described above can be embodied. 
         [0080]    While the invention has been described by reference to specific embodiments chosen for the purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art without departing from the basic concept and scope of the invention.