Abstract:
Disclosed is a hot-pressing apparatus capable of quenching a workpiece at a sufficient cooling rate. The hot-pressing apparatus performs a hot-press forming of a workpiece using a lower die and an upper die, in which a cooling channel and a cooling channel, and a plurality of gas-introduction paths and a plurality of gas-introduction paths through which heat-conducting gas flows are provided in the lower die and the upper die. The plurality of gas-introduction paths penetrate through the dies. The hot-press forming is performed while the heat-conducting gas is supplied to the areas between the dies and the workpiece from the plurality of gas-introduction paths opening on the forming surfaces of the dies.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a hot-pressing apparatus which presses and cools a heated workpiece at the same time. 
       BACKGROUND ART 
       [0002]    Conventionally, a hot-pressing apparatus is widely known which causes a die to press a workpiece, such as a steel plate, heated to above a temperature at which an austenite structure appears, and at the same time, quenches the workpiece by bring the die into contact with the workpiece. 
         [0003]    A technique on the hot-pressing apparatus is publicly known which enables the die to suitably cool the workpiece during the quenching by providing water channels through which cooling water to cool the die flows in the die (for example, see Patent Literature 1). 
         [0004]    However, since the pressed workpiece deforms because of spring back, uneven thickness thereof and the like, a gap is formed between the workpiece and the die during the quenching. Consequently, a contact area between the surface of the workpiece and the forming surface of the die decreases during the quenching, which causes a problem that some parts in the workpiece are not cooled at a sufficient cooling rate (e.g. 30 [° C./sec] and above), and hardness of some parts in the workpiece is smaller than a predetermined value. 
       CITATION LIST 
     Patent Literature 
       [0005]    Patent Literature 1: JP 2006-326620 A 
       SUMMARY OF INVENTION 
     Problem to Be Solved By the Invention 
       [0006]    The objective of the present invention is to provide a hot-pressing apparatus capable of quenching a workpiece at a sufficient cooling rate. 
       Means for Solving the Problem 
       [0007]    The first embodiment of the present invention is a hot-pressing apparatus including a lower die having a lower forming surface, and an upper die having an upper forming surface facing the lower forming surface, which performs a hot-press forming in which the lower die and the upper die press a heated workpiece arranged therebetween, and at the same time, the forming surfaces of the lower die and the upper die are kept in contact with a surface of the workpiece to cool the workpiece. The lower die and/or the upper die includes a cooling channel through which a cooling medium flows, and a plurality of gas-introduction paths through which heat-conducting gas flows. The plurality of gas-introduction paths penetrate through the lower die and/or the upper die from the forming surface thereof to a surface other than that forming surface. The hot-press forming is performed while the heat-conducting gas is supplied to an area between the workpiece and the lower die and/or the upper die from the plurality of gas-introduction paths opening on the forming surface of the lower die and/or the upper die. 
         [0008]    Advantageously, the plurality of gas-introduction paths are formed to run in the vicinity of the cooling channel. 
         [0009]    Preferably, the plurality of gas-introduction paths open on the forming surface of the lower die and/or the upper die so as to coincide in position with gaps formed by deformation of the pressed workpiece between the workpiece and the lower die and/or the upper die where the plurality of gas-introduction paths are formed. 
       Effects of the Invention 
       [0010]    The present invention makes it possible to quench a workpiece at a sufficient cooling rate, and to prevent hardness of some parts in the workpiece from being smaller than a predetermined value. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  illustrates a hot-pressing apparatus according to an embodiment of the present invention. 
           [0012]      FIG. 2  illustrates the hot-pressing apparatus in which an upper die moves to the bottom dead center when pressing a workpiece. 
           [0013]      FIG. 3  illustrates the hot-pressing apparatus in which the upper die is at the bottom dead center when pressing the workpiece. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0014]    With reference to  FIGS. 1 to 3 , described below is a hot-pressing apparatus  1  as an embodiment of a hot-pressing apparatus according to the present invention. 
         [0015]    The hot-pressing apparatus  1  performs hot-press forming of a workpiece W. 
         [0016]    The workpiece W is a steel plate to be pressed by the hot-pressing apparatus  1 , and is heated to above a temperature at which an austenite structure appears by ohmic heating and the like. 
         [0017]    For convenience, a top-bottom direction in  FIG. 1  is defined as a top-bottom direction of the hot-pressing apparatus  1 , and a right-left direction in  FIG. 1  is defined as a right-left direction of the hot-pressing apparatus  1 . In addition, this side in  FIG. 1  is defined as a front side of the hot-pressing apparatus  1 , and the far side in  FIG. 1  is defined as a rear side of the hot-pressing apparatus  1 , thereby a front-rear direction of the hot-pressing apparatus  1  being defined. 
         [0018]    As shown in  FIG. 1 , the hot-pressing apparatus  1  includes a lower die  10 , an upper die  20 , two lateral gas-feeders  30 , a lower gas-feeder  40 , and an upper gas-feeder  50 . 
         [0019]    The lower die  10  and the upper die  20  are arranged so that the forming surfaces thereof are opposed to each other. The upper die  20  is brought close to the lower die  10  by a hydraulic cylinder and the like to move to the bottom dead center. Thereby, the lower die  10  and the upper die  20  press the workpiece W arranged therebetween to form the workpiece W into what is called a hat shape. At the same time, the lower die  10  and the upper die  20  keep the forming surfaces thereof in contact with the surface of the workpiece W to cool the workpiece W. Consequently, the workpiece W as a product is produced. 
         [0020]    The lower die  10  corresponds to the upper die  20 . The lower die  10  has a protrusion  11  which protrudes upward from the forming surface (the upper surface) thereof. 
         [0021]    The protrusion  11  protrudes upward from the forming surface of the lower die  10 . The protrusion  11  is continuously formed in the front-rear direction in the intermediate part (the substantially middle part), in the right-left direction, of the forming surface of the lower die  10 . 
         [0022]    The lower die  10  has a top surface  10   a  extending in the right-left direction at the uppermost part of the protrusion  11 , two lateral surfaces  10   b  extending downward from both the ends of the top surface  10   a  in the right-left direction, and two base surfaces  10   c  extending outward in the right-left direction from the bottom ends of the lateral surfaces  10   b,  and these surfaces act as what is called a hat-shaped forming surface of the lower die  10 . 
         [0023]    The lower die  10  has a cooling channel  12 , a plurality of gas-introduction paths  13 , a plurality of gas-introduction paths  14 , and a plurality of gas-introduction paths  15  which are provided inside the lower die  10 . 
         [0024]    The cooling channel  12  is a channel through which a cooling medium such as water flows, and is provided in the lower die  10  to cool the forming surface of the lower die  10 . The cooling channel  12  is configured so that the cooling medium flows into the lower die  10  through the lower surface of the right part of the lower die  10 , and then flows to the outside of the lower die  10  through the lower surface of the left part of the lower die  10  after flowing inside the lower die  10  in the front-rear direction and the right-left direction (see the white-painted arrows in  FIG. 1 ). Note that a predetermined pump (not shown) enables the cooling medium to flow in the lower die  10 . After the cooling medium cools the forming surface of the lower die  10  and flows to the outside of the lower die  10 , the cooling medium is cooled and flows into the lower die  10  again. Thus, the cooling medium constantly circulates in the lower die  10 . 
         [0025]    The gas-introduction path  13 , the gas-introduction path  14  and the gas-introduction path  15  are paths through which helium gas flows which is inert gas (hereinafter referred to as “heat-conducting gas”) with thermal conductivity extremely higher than that of air. The gas-introduction path  13 , the gas-introduction path  14  and the gas-introduction path  15  are bored through the lower die  10  in the top-bottom direction from the forming surface to the lower surface of the lower die  10 , and are formed to run the vicinity of the cooling channel  12 . The gas-introduction path  13 , the gas-introduction path  14  and the gas-introduction path  15  open on the middle of the top surface  10   a  in the right-left direction, on the part of the left base surface  10   c  in the vicinity of the left lateral surface  10   b,  and on the part of the right base surface  10   c  in the vicinity of the right lateral surface  10   b,  respectively. Note that, although not shown, each of the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed in the lower die  10  at predetermined intervals in the front-rear direction. 
         [0026]    As mentioned above, in the lower die  10 , the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed on three places in total: the middle of the top surface  10   a  in the right-left direction, and the parts of the base surfaces  10   c  in the vicinities of the lateral surfaces  10   b.    
         [0027]    Note that each of the openings, which open on the forming surface of the lower die  10 , of the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  formed in the lower die  10  has such an inner diameter that the openings have no negative influence on the press working of the workpiece W (that the press working of the workpiece W is performed similarly to a conventional press working thereof). 
         [0028]    The upper die  20  corresponds to the lower die  10 . The upper die  20  has a recess  21  in which the forming surface (the lower surface) of the upper die  20  dents upward along the shape of the protrusion  11 . 
         [0029]    The recess  21  is formed so that the forming surface of the upper die  20  dents upward. The recess  21  is continuously formed in the front-rear direction in the intermediate part (the substantially middle part), in the right-left direction, of the forming surface of the upper die  20 . 
         [0030]    The upper die  20  has a bottom surface  20   a  extending in the right-left direction at the uppermost part of the recess  21 , two lateral surfaces  20   b  extending downward from both the ends of the bottom surface  20   a  in the right-left direction, and two base surfaces  20   c  extending outward in the right-left direction from the bottom ends of the lateral surfaces  20   b,  and these surfaces act as what is called a hat-shaped forming surface of the upper die  20 . 
         [0031]    The upper die  20  has a cooling channel  22 , a plurality of gas-introduction paths  23 , a plurality of gas-introduction paths  24 , a plurality of gas-introduction paths  25 , and a plurality of gas-introduction paths  26  which are arranged inside the upper die  20 . 
         [0032]    The cooling channel  22  is a channel through which the cooling medium such as water flows, and is provided in the upper die  20  to cool the forming surface of the upper die  20 . The cooling channel  22  is configured so that the cooling medium flows into the upper die  20  through the upper surface of the right part of the upper die  20 , and then flows to the outside of the upper die  20  through the upper surface of the left part of the upper die  20  after flowing inside the upper die  20  in the front-rear direction and the right-left direction (see the white-painted arrows in  FIG. 1 ). Note that a predetermined pump (not shown) enables the cooling medium to flow in the upper die  20 . After the cooling medium cools the forming surface of the upper die  20  and flows to the outside of the upper die  20 , the cooling medium is cooled and flows into the upper die  20  again. Thus, the cooling medium constantly circulates in the upper die  20 . 
         [0033]    The gas-introduction path  23 , the gas-introduction path  24 , the gas-introduction path  25  and the gas-introduction path  26  are paths through which the helium gas as the heat-conducting gas flows. The gas-introduction path  23 , the gas-introduction path  24 , the gas-introduction path  25  and the gas-introduction path  26  are bored through the upper die  20  in the top-bottom direction from the forming surface to the upper surface of the upper die  20 , and are formed to run the vicinity of the cooling channel  22 . The gas-introduction path  23 , the gas-introduction path  24 , the gas-introduction path  25  and the gas-introduction path  26  open on the part of the bottom surface  20   a  in the vicinity of the left lateral surface  20   b,  on the part of the bottom surface  20   a  in the vicinity of the right lateral surface  20   b,  the part of the left base surface  20   c  in the vicinity of the left lateral surface  20   b,  and the part of the right base surface  20   c  in the vicinity of the right lateral surface  20   b,  respectively. Note that, although not shown, each of the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed in the upper die  20  at predetermined intervals in the front-rear direction. 
         [0034]    As mentioned above, in the upper die  20 , the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed on four places in total: the parts of the bottom surface  20   a  in the vicinities of the lateral surfaces  20   b,  and the parts of the base surfaces  20   c  in the vicinities of the lateral surfaces  20   b.    
         [0035]    Note that each of the openings, which open on the forming surface of the upper die  20 , of the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  formed in the upper die  20  has such an inner diameter that the openings have no negative influence on the press working of the workpiece W (that the press working of the workpiece W is performed similarly to a conventional press working thereof). 
         [0036]    The lateral gas-feeders  30  are devices for feeding the helium gas as the heat-conducting gas to an area between the lower die  10  and the upper die  20  (to an area between the workpiece W and the lower die  10 , and an area between the workpiece W and the upper die  20 ). The lateral gas-feeders  30  discharge the helium gas as the heat-conducting gas stored in a predetermined container (not shown) into the area between the lower die  10  and the upper die  20 . The lateral gas-feeders  30  are arranged to the left and the right of the lower die  10  in the vicinities of the base surfaces  10   c  of the lower die  10  so as to discharge the helium gas as the heat-conducting gas into the space between the lower die  10  and the upper die  20  from the outside of the lower die  10  and the upper die  20  when the upper die  20  arrives at the bottom dead center (see  FIG. 3 ). Note that, although not shown, each of the lateral gas-feeders  30  has a plurality of nozzles from which the helium gas as the heat-conducting gas discharges, and the plurality of nozzles are arranged at predetermined intervals in the front-rear direction. 
         [0037]    The lower gas-feeder  40  is a device for feeding the helium gas as the heat-conducting gas to an area between the workpiece W and the lower die  10 . Specifically, the lower gas-feeder  40  causes the helium gas as the heat-conducting gas stored in a predetermined container (not shown) to flow into the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  formed in the lower die  10  from the openings on the lower surface of the lower die  10 , and to spout from the openings on the forming surface of the lower die  10 . 
         [0038]    The upper gas-feeder  50  is a device for feeding the helium gas as the heat-conducting gas to an area between the workpiece W and the upper die  20 . Specifically, the upper gas-feeder  50  causes the helium gas as the heat-conducting gas stored in a predetermined container (not shown) to flow into the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  formed in the upper die  20  from the openings on the upper surface of the upper die  20 , and to spout from the openings on the forming surface of the upper die  20 . 
         [0039]    Described below is behavior of the hot-pressing apparatus  1  configured as mentioned above during the hot-press forming of the workpiece W. 
         [0040]    As shown in  FIG. 2 , the upper die  20  moves toward the lower die  10  to press the workpiece W. Then, before the upper die  20  arrives at the bottom dead center, the lateral gas-feeders  30  feed the helium gas as the heat-conducting gas to the area between the lower die  10  and the upper die  20 , the lower gas-feeder  40  feeds the helium gas as the heat-conducting gas to the area between the workpiece W and the lower die  10 , and the upper gas-feeder  50  feeds the helium gas as the heat-conducting gas to the area between the workpiece W and the upper die  20 . 
         [0041]    Note that black-painted arrows in  FIG. 2  show directions in which the helium gas as the heat-conducting gas discharges. 
         [0042]    As shown in  FIG. 3 , until the upper die  20  arrives at the bottom dead center, the lateral gas-feeders  30 , the lower gas-feeder  40  and the upper gas-feeder  50  continue to feed the helium gas as the heat-conducting gas. Thus, the upper die  20  is kept at the bottom dead center in the state where the helium gas as the heat-conducting gas fills the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20 . 
         [0043]    Note that timing when the lateral gas-feeders  30 , the lower gas-feeder  40  and the upper gas-feeder  50  feed the helium gas as the heat-conducting gas is not limited as long as the helium gas as the heat-conducting gas fills the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20  when the upper die  20  is kept at the bottom dead center. 
         [0044]    Since the pressed workpiece W slightly deforms because of spring back and the like, gaps are formed between the lower die  10  and the upper die  20 . 
         [0045]    However, when the lower die  10  and the upper die  20  cool the workpiece W, the helium gas with thermal conductivity extremely higher than that of air fills the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20 . This makes it possible to quench even a part of the workpiece W separate from the forming surface of the lower die  10  or the forming surface of the upper die  20  at a sufficient cooling rate (e.g. 30 [° C./sec] and above). 
         [0046]    Therefore, it is possible to prevent hardness of some parts in the workpiece W from being smaller than a predetermined value. 
         [0047]    Moreover, it is possible to control oxidation of the lower die  10  and the upper die  20  to a minimum because the helium gas is inert gas difficult to undergo chemical reactions. 
         [0048]    Hydrogen gas with thermal conductivity comparable to that of the helium gas may be given as the heat-conducting gas according to the present invention in addition to the helium gas. However, it is preferable that the helium gas which is inert gas is adopted because the hydrogen gas is easy to undergo chemical reactions. 
         [0049]    On the other hand, nitrogen gas, argon gas and the like may be given as inert gas. However, these gases are excluded because each of these gases has thermal conductivity comparable to that of air. 
         [0050]    As mentioned previously, the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed in the lower die  10 , and the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed in the upper die  20 . 
         [0051]    Thus, when the helium gas as the heat-conducting gas discharged from the lower gas-feeder  40  flows through the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15 , the lower die  10  cooled by the cooling channel  12  cools the helium gas. In addition, when the helium gas as the heat-conducting gas discharged from the upper gas-feeder  50  flows through the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26 , the upper die  20  cooled by the cooling channel  22  cools the helium gas. 
         [0052]    Therefore, the helium gas as the heat-conducting gas can be cooled without using a device for cooling the helium gas as the heat-conducting gas, and the helium gas as the heat-conducting gas can quickly remove heat of the workpiece W when the workpiece W is quenched. 
         [0053]    The plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed to run the vicinity of the cooling channel  12 , and the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed to run the vicinity of the cooling channel  22 . 
         [0054]    Thus, when the helium gas as the heat-conducting gas discharged from the lower gas-feeder  40  flows through the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15 , the helium gas is cooled by the cooling channel  12 . In addition, when the helium gas as the heat-conducting gas discharged from the upper gas-feeder  50  flows through the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26 , the helium gas is cooled by the cooling channel  22 . 
         [0055]    Therefore, the helium gas as the heat-conducting gas can more quickly remove heat of the workpiece W when the workpiece W is quenched. 
         [0056]    It is desirable that the gas-introduction path  13 , the gas-introduction path  14  and the gas-introduction path  15  are formed so as to have as many parts in the vicinity of the cooling channel  12  as possible. In addition, it is desirable that the gas-introduction path  23 , the gas-introduction path  24 , the gas-introduction path  25  and the gas-introduction path  26  are formed so as to have as many parts in the vicinity of the cooling channel  22  as possible. 
         [0057]    The plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed to open on the forming surface of the lower die  10 , and the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed to open on the forming surface of the upper die  20 . 
         [0058]    Thus, the helium gas as the heat-conducting gas discharged from the lower gas-feeder  40  can spout from the openings on the forming surface of the lower die  10 , and the helium gas as the heat-conducting gas discharged from the upper gas-feeder  50  can spout from the openings on the forming surface of the upper die  20 . 
         [0059]    Therefore, the helium gas as the heat-conducting gas can efficiently be supplied to the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20  without the helium gas diffusing to the atmosphere, compared with the case where the helium gas is supplied from a place, for example, situated sideward of the workpiece W. 
         [0060]    The plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  are formed on the middle of the top surface  10   a  in the right-left direction, and on the parts of the base surfaces  10   c  in the vicinities of the lateral surfaces  10   b.  In addition, the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  are formed on the parts of the bottom surface  20   a  in the vicinities of the lateral surfaces  20   b,  and on the parts of the base surfaces  20   c  in the vicinities of the lateral surfaces  20   b.  In other words, as shown in  FIG. 3 , the plurality of gas-introduction paths  13 , the plurality of gas-introduction paths  14  and the plurality of gas-introduction paths  15  open on the forming surface of the lower die  10  so as to coincide in position with the gaps between the pressed workpiece W and the lower die  10 . In addition, the plurality of gas-introduction paths  23 , the plurality of gas-introduction paths  24 , the plurality of gas-introduction paths  25  and the plurality of gas-introduction paths  26  open on the forming surface of the upper die  20  so as to coincide in position with the gaps between the pressed workpiece W and the upper die  20 . 
         [0061]    This makes it possible to efficiently supply the helium gas as the heat-conducting gas to the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20 , and to fill the area between the workpiece W and the lower die  10 , and the area between the workpiece W and the upper die  20  with the helium gas in a small mount. 
         [0062]    Therefore, it is possible to control consumption of the helium gas as the heat-conducting gas to a minimum, and to reduce costs. 
         [0063]    Note that positions of the gaps between the workpiece W and the lower die  10 , and the gaps between the workpiece W and the upper die  20  can be grasped in advance because deformation characteristics of the pressed workpiece W can be acquired through experiment and the like. 
         [0064]    In the present embodiment, each of the lower die  10  and the upper die  20  is provided with a cooling channel and a plurality of gas-introduction paths, but one of the lower die  10  and the upper die  20  may be provided with the cooling channel and the plurality of gas-introduction paths. 
         [0065]    Moreover, in the present embodiment, the lower die  10  and the upper die  20  have shapes to form the workpiece W into the hat shape, but the shapes thereof are not limited thereto. The present invention may be applied to a hot-pressing apparatus including a lower die and an upper die with other shapes. 
         [0066]    In the present embodiment, a gas-feeder according to the present invention consists of the lateral gas-feeders  30 , the lower gas-feeder  40  and the upper gas-feeder  50 , but these may be configured as one gas-feeder. 
       INDUSTRIAL APPLICABILITY 
       [0067]    The present invention is applied to a hot-pressing apparatus which presses and cools a heated workpiece at the same time. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : hot-pressing apparatus 
           10 : lower die 
           12 : cooling channel 
           13 ,  14 ,  15 : gas-introduction path 
           20 : upper die 
           22 : cooling channel 
           23 ,  24 ,  25 ,  26 : gas-introduction path 
           30 : lateral gas-feeder 
           40 : lower gas-feeder 
           50 : upper gas-feeder