Abstract:
The pressing method includes the first step of displacing a sub-piston provided within a sub-cylinder from its initial position to press working fluid such that the working fluid is introduced via a check valve into a main cylinder to displace a main piston provided therein, and the second step of causing the sub-piston to return to the initial position such that the working fluid is supplied to the sub-cylinder. The first and second steps are repeated successively until the working fluid in the main cylinder attains a prescribed pressure level. With this method, variation in the way of pressing an object is alleviated, contamination due to the working fluid is prevented, and downsizing of the pressing mechanism is enabled.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a pressing method, a pressing mechanism and a resin molding device that utilize pressure of working fluid. 
   2. Description of the Background Art 
   A pressing mechanism conventionally used in a resin sealing device, which introduces molten resin into a cavity to resin-seal an electronic component in a chip form in a substrate, or in other resin molding devices is of the type that has a base freely movable up and down. The base is provided with a cylindrical hole through which a piston is inserted via a spring, and the entire base is moved up and down by hydraulic pressure. In the case of the resin molding device, a plunger that is attached to an end of the piston is pushed up to press molten resin to make it enter the cavity, where the molten resin is hardened for resin molding. 
   The conventional pressing mechanism, however, poses the following problems. First, the hydraulic pressing mechanism requires piping for hydraulic oil. The oil may leak out of the piping, contaminating the surrounding area. Such contamination becomes a serious problem especially in the assembly process of electronic components like semiconductor devices. 
   In addition, to use a spring to transmit the movement of the base to the piston, the spring should have a large diameter to receive the pressure. This makes it difficult to downsize the pressing mechanism. Usually such a problem is fatal in the resin molding device employing a plurality of plungers, as it becomes difficult to downsize the device itself. 
   Further, variation in spring characteristics is likely to cause variation in the way of pushing up the piston by the pressing mechanism. In the resin molding device employing a plurality of plungers, such variation is usually accompanied by variation in fluidity of the molten resin, making it difficult to push up the pistons in a uniform manner. This may create void or surface sink in a molded article, thereby degrading the quality thereof. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a pressing method, a pressing mechanism and a resin molding device employing the mechanism, which lessen variation in the way of pressing an object, prevent contamination due to working fluid, and permit downsizing of the pressing mechanism and the resin molding device. 
   According to one aspect, the pressing method of the present invention for accomplishing the object above is a method for pressing an object with a main piston placed in a main cylinder by means of applying a prescribed pressure to the main piston with working fluid, wherein the working fluid is compressed to the prescribed pressure by supplying the working fluid to the main cylinder with driving power of a piezoelectric element. 
   More specifically, a prescribed voltage is applied to the piezoelectric element repeatedly until the pressure of the working fluid reaches to the prescribed pressure. 
   According to the present method, the piezoelectric elements each having an accurate displacement are displaced for repeatedly supplying the working fluid to the main cylinder and pressing it to displace the main piston in a stepped manner. Accordingly, the variation in the way of pressing the object by the main piston can further be alleviated. 
   According to another aspect, the pressing method of the present invention relates to a method for pressing an object with a main piston, utilizing working fluid to which a prescribed pressure is applied through a piping system. The piping system includes a main cylinder, a supply line and a discharge line of the working fluid with respect to the main cylinder, a check valve preventing reverse flow of the working fluid from the main cylinder to the supply line, and a sub-cylinder provided in the supply line. The method includes: a first step of displacing a sub-piston provided within the sub-cylinder from its initial position to press the working fluid, and introducing the working fluid via the check valve into the main cylinder to displace the main piston provided within the main cylinder; and a second step of causing the sub-piston to return to the initial state to supply the working fluid to the sub cylinder. The first and second steps are repeated successively until the working fluid in the main cylinder attains a prescribed pressure level. 
   More specifically, the first step is performed in the state where a discharge control valve provided in the discharge line and a supply control valve provided in the supply line are closed. The second step is performed in the state where the discharge control valve and the check valve are closed and the supply control valve is open. 
   According to the pressing method, the main piston provided with the main cylinder is displaced in a stepped manner by repeating the step of supplying the working fluid to the sub-cylinder and the step of pressing the fluid. Accordingly, compared to the conventional pressing method in which the movement of the base is transmitted to the piston via the spring, the variation in the way of pressing the object by the main piston can be alleviated. 
   In the pressing method of the present invention, a piezoelectric element as driving means is preferably attached to each of the supply control valve, the discharge control valve and the sub-piston. These piezoelectric elements serve to open and close the supply control valve and the discharge control valve, and to displace the sub-piston from its initial position. 
   With such a step, the piezoelectric elements each having an accurate displacement are displaced for repeatedly supplying the working fluid to the sub-cylinder and pressing it to displace the main piston in a stepped manner. Accordingly, the variation in the way of pressing the object by the main piston can further be alleviated. 
   In a preferred embodiment of the pressing method of the present invention, in the pressing method described above, a detector provided in the main cylinder detects the pressure of the working fluid, and when the detector detects the prescribed pressure level, the displacement of the sub-piston is terminated. 
   With such a structure, it is possible to detect the pressure of the working fluid pressing the main piston and thus to detect the position of the main piston with accuracy. The main piston can be stopped when it reaches a prescribed position. 
   The pressing mechanism of the present invention for accomplishing the object above is a pressing mechanism that presses an object using pressure of working fluid supplied from a working fluid source to a piping system with a prescribed pressure. The pressing mechanism includes: a main piston for pressing the object; a main cylinder having the main piston placed therein and supplied with the working fluid for displacement of the main piston; a check valve preventing reverse flow of the working fluid supplied to the main cylinder; a sub-cylinder linked to the main cylinder and having the working fluid reserved therein for supply to the main cylinder; a sub-piston placed within the sub-cylinder; a supply line for supplying the working fluid from the working fluid source to the sub-cylinder; a supply control valve provided in the supply line; a discharge line for discharging the working fluid from the main cylinder to the working fluid source; a discharge control valve provided in the discharge line; a first driving mechanism for driving the sub-piston; a second driving mechanism for driving the supply control valve; and a third driving mechanism for driving the discharge control valve. 
   With this mechanism, the working fluid supplied to the sub-cylinder is pressed to push up the main piston, and the main piston presses the object. 
   Preferably, in the pressing mechanism of the present invention, the first, second and third driving mechanisms each include a piezoelectric element, and the piezoelectric elements drive the sub-piston, the supply control valve and the discharge control valve, respectively. 
   With such a mechanism, the piezoelectric elements each having an accurate displacement are used for repeatedly supplying the working fluid to the sub-cylinder and pressing it to displace the main piston in a stepped manner. Accordingly, the variation in the way of pressing the object by the main piston can be alleviated. 
   In a preferred embodiment of the pressing mechanism of the present invention, of the first, second and third driving mechanisms, at least the first driving mechanism is provided with a displacement enlarging portion that enlarges the displacement of the sub-piston for transmission to the main piston. 
   With such a mechanism, even a minute displacement of the first driving mechanism causes the working fluid to be pressed, and the main piston is displaced by the working fluid. Accordingly, it becomes possible to downsize the first driving mechanism and hence the entire pressing mechanism. 
   In the pressing mechanism of the present invention, the piping system through which the working fluid flows may be built in the pressing mechanism. This can prevent the working fluid from leaking outside the pressing mechanism. 
   The resin molding device of the present invention uses the pressing mechanism described above. The resin molding device includes: a reservoir in which molten resin is reserved; a plunger that is pressed by the main piston to press the molten resin; and a cavity into which the pressed molten resin is introduced. The molten resin introduced into the cavity is hardened for resin molding. 
   With such a structure, the main piston is pushed up as the working fluid supplied to the sub-cylinder is pressed. The main piston then presses the plunger, and the plunger in turn presses the molten resin, so that the molten resin is introduced into the cavity. 
   The pressing method, the pressing mechanism and the resin molding device of the present invention described above provide the following effects. 
   First, as the step of supplying the working fluid to the sub-cylinder and the step of pressing it to displace the main piston in a stepped manner are repeated, variation in the way of pressing the object by the main piston can be lessened. As the piezoelectric element having an accurate displacement is displaced, the variation in the way of pressing the object by the main piston can further be alleviated. 
   Further, by using the piezoelectric element, instead of a spring, as the driving means, downsizing of the pressing mechanism itself and hence the resin molding device itself is enabled. 
   Still further, the piping system is built in the pressing mechanism, so that the leakage of the working fluid outside the pressing mechanism can be prevented. 
   Accordingly, the present invention is practically very advantageous in that it provides the pressing method, the pressing mechanism and the resin molding device using the same that can reduce the variation in the way of pressing the object, prevent contamination due to the working fluid, and permit downsizing of the pressing mechanism and the resin molding device. 
   The above pressing method and mechanism can effectively be applied to a method and a mechanism for driving plungers of a resin molding device, whereby the plungers can be controlled independently from each other with high accuracy. Accordingly, respective plungers press the molten resin evenly, so that the molten resin can be introduced into corresponding cavities with a uniform pressure. This prevents generation of voids or surface sinks in the molded articles. 
   The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional view showing a structure of the pressing mechanism according to a first embodiment of the present invention. 
       FIG. 2  is a cross sectional view of the pressing mechanism of  FIG. 1 , illustrating how the main piston is pushed up. 
       FIG. 3  is a cross sectional view of the pressing mechanism of  FIG. 1 , illustrating how a preparation is made for the main piston having been pushed up to be further pushed up. 
       FIG. 4  is a cross sectional view of the pressing mechanism of  FIG. 1 , illustrating how the main piston is lowered to return to its initial position. 
       FIG. 5  is a cross sectional view showing a structure of a variation of the pressing mechanism shown in FIG.  1 . 
       FIG. 6  is a cross sectional view showing portions of the pressing mechanism and a resin molding device using the same according to a second embodiment of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   A pressing mechanism and a pressing method according to the first embodiment will be described with reference to  FIGS. 1-4 .  FIG. 1  shows in cross section the structure of the pressing mechanism of the present embodiment. 
   Referring to  FIG. 1 , a supply line  3  links a hydraulic oil source  2  in which hydraulic oil  1  as the working fluid is reserved to a first sub-cylinder  4  and to a main cylinder  6  via a check valve  5 . A discharge line  7  also links main cylinder  6  to hydraulic oil source  2 . Gas  8  and a bottom plate  9  apply a prescribed pressure to hydraulic oil  1  reserved in hydraulic oil source  2 . Accordingly, the hydraulic oil  1  is kept at a prescribed pressure through the entire piping system from hydraulic oil source  2 , via supply line  3 , first sub-cylinder  4 , main cylinder  6 , discharge line  7 , back to hydraulic oil source  2 . 
   Hydraulic oil  1  within first sub-cylinder  4  is pressed by a first sub-piston  10 . First sub-piston  10  is pressed via a pressure plate  11  by hydraulic oil reserved in a second sub-cylinder  13 . When the hydraulic oil stops pressing, pressure plate  11  is pushed down by a compression spring  12 . The hydraulic oil reserved within second sub-cylinder  13  is pressed by a second sub-piston  15  via a leaf spring provided within second sub-cylinder  13 . Second sub-piston  15  is attached to an end of a first piezoelectric element  16  that drives the sub-piston  15 . First sub-cylinder  4 , first sub-piston  10 , pressure plate  11 , compression spring  12 , second sub-cylinder  13 , leaf spring  14 , and second sub-piston  15  in all constitute a displacement enlarging portion  17 . 
   Check valve  5  allows the hydraulic oil  1  pressed in supply line  3  to flow into main cylinder  6 , while it prevents reverse flow of hydraulic oil  1  from main cylinder  6  to supply line  3 . A main piston  18  is provided within main cylinder  6 , which ascends as hydraulic oil  1  flows via check valve  5  into main cylinder  6 , and descends as hydraulic oil  1  flows out of main cylinder  6  to discharge line  7 . When hydraulic oil  1  is discharged from main cylinder  6  to discharge line  7 , a compression spring  19  ensures that main piston  18  is sufficiently pressed down. A pressure sensor  20  is provided on a wall surface of main cylinder  6 , which detects a pressure of the working fluid in main cylinder  6 , i.e., the hydraulic pressure of hydraulic oil  1 . It generates an electrical signal corresponding to the hydraulic pressure, and outputs the signal to a control portion (not shown). Check valve  5 , main cylinder  6 , main piston  18 , compression spring  19 , and pressure sensor  20  in all constitute a pressing portion  21  that is a main portion of the pressing mechanism. 
   A supply control valve  22  is provided in supply line  3 , which is driven via hydraulic oil by a valve piston  23  to open/close supply line  3 . Valve piston  23  is attached to an end of a second piezoelectric element  24  that drives the piston  23 . 
   Similarly, a discharge control valve  25  is provided in discharge line  7 , which is driven via hydraulic oil by a valve piston  26 , to open/close discharge line  7 . Valve piston  26  is attached to an end of a third piezoelectric element  27  by which it is driven. 
   Supply control valve  22  and discharge control valve  25  are each provided with a leaf spring (not shown), as in second sub-cylinder  13 , in a portion where the hydraulic oil is reserved. 
   Hereinafter, the pressing method using the pressing mechanism shown in  FIG. 1  will be described with reference to  FIGS. 2-4 .  FIG. 2  shows in cross section how the pressing mechanism of  FIG. 1  performs a pushing up operation of the main piston. 
   Initially, gas  8  and bottom plate  9  keep hydraulic oil  1  at a prescribed pressure through the piping system, i.e., from hydraulic oil source  2 , via supply line  3 , first sub-cylinder  4 , main cylinder  6 , discharge line  7 , and back to hydraulic oil source  2 . 
   In this state, a prescribed voltage is applied to each of second and third piezoelectric elements  24 ,  27  to make their ends slightly protrude, so that valve pistons  23 ,  26  attached to the ends of second and third piezoelectric elements  24 ,  27 , respectively, are displaced upward in the drawing. Such displacements are enlarged by means of the hydraulic oil, and thus, supply control valve  22  closes supply line  3 , and discharge control valve  25  closes discharge line  7 . 
   Next, a prescribed voltage is applied to first piezoelectric element  16  to cause its end to protrude slightly, so that second sub-piston  15  attached to the end of first piezoelectric element  16  is displaced upward in the drawing. Thus, the hydraulic oil within second sub-cylinder  13  presses pressure plate  11 , which in turn presses first sub-piston  10 , which in turn presses hydraulic oil  1  within first sub-cylinder  4 . The pressed hydraulic oil  1  flows via check valve  5  into main cylinder  6 , so that main piston  18  is pushed up. 
   Here, second sub-cylinder  13  is configured to have a cross section sufficiently larger than that of a portion of pressure plate  11  receiving a pressure of the hydraulic oil from second sub-cylinder  13 . This enables the minute displacement of the end of first piezoelectric element  16  to be enlarged and transmitted to first sub-piston  10 , and the enlarged displacement to be further transmitted via hydraulic oil  1  to main piston  18 . In other words, displacement enlarging portion  17  enlarges minute protrusion of the end of first piezoelectric element  16  for transmission to main piston  18  to push it up. 
   Next, as shown in  FIG. 3 , a preparation is made to further push up main piston  18 .  FIG. 3  shows in cross section how the pressing mechanism of  FIG. 1 , whose main piston has been pushed up, prepares for a succeeding pushing up operation of the main piston. 
   Here, hydraulic oil  1  is introduced into first sub-cylinder  4 , with main piston  18  being maintained in its position. More specifically, the voltage having been applied to second piezoelectric element  24  is shut down to let its end return to the initial position. This lowers valve piston  23 , which in turn lowers supply control valve  22  by means of the hydraulic oil, so that supply control valve  22  opens supply line  3 . Further, the voltage having been applied to first piezoelectric element  16  is shut down to make its end return to the initial position. This lowers second sub-piston  15 , which in turn lowers first sub-piston  10  by means of the hydraulic oil within second sub-cylinder  13  and of pressure plate  11 . Through a series of these operations, displacement enlarging portion  17  works as a pump to let hydraulic oil  1  flow from hydraulic oil source  2  to first sub-cylinder  4 . During this process, check valve  5  is closed to prevent reverse flow of hydraulic oil  1  within main cylinder  6  to supply line  3 , and discharge control valve  25  is closed to prevent discharge of the oil to discharge line  7 . Accordingly, main piston  18  is maintained in place. 
   Next, the operation described in conjunction with  FIG. 2  is repeated. Specifically, a prescribed voltage is applied to second piezoelectric element  24  to let its end slightly protrude, so that valve piston  23  attached to the end is displaced upward. The displacement is enlarged by means of the hydraulic oil, and thus, supply control valve  22  closes supply line  3 . 
   Further, a prescribed voltage is applied to first piezoelectric element  16 , so that the end of first piezoelectric element  16  is slightly protruded or displaced upward. Displacement enlarging portion  17  enlarges this minute displacement, and transmits the enlarged displacement to main piston  18  to further push up main piston  18 . 
   Repeating the operations of pushing up main piston  18  and of introducing hydraulic oil  1  into first sub-cylinder  4  causes main piston  18  to ascend in a stepped manner. Pressure sensor  20  detects the hydraulic pressure within main cylinder  6 , and outputs an electrical signal corresponding to the detected hydraulic pressure to a control portion (not shown). 
   Main piston  18  is configured to ascend up to a preset position. When the hydraulic pressure within main cylinder  6  attains a prescribed pressure level corresponding to the position, i.e., when the control portion receives an electrical signal of a prescribed value, the control portion stops applying the voltage to first piezoelectric element  16 . Thus, the end of first piezoelectric element  16  stops displacement and returns to its initial position, and second sub-piston  15  also stops displacement. Accordingly, main piston  18  is stopped at the preset position. 
   When main piston  18  is no longer necessary to stay at the preset position, main piston  18  is lowered to return to its initial position, as shown in FIG.  4 .  FIG. 4  shows in cross section how the pressing mechanism of  FIG. 1  causes the main piston to descend to its initial position. 
   Here, in the state where supply line  3  is closed by supply control valve  22 , the voltage having been applied to third piezoelectric element  27  is shut down to cause its end to return to the initial position. This lowers valve piston  26 , which in turn lowers discharge control valve  25  by means of the hydraulic oil, so that discharge control valve  25  opens the discharge line  7 . Main piston  18  descends as compression spring  19  pushes it downward. With check valve  5  being closed, reverse flow of hydraulic oil  1  within main cylinder  6  to supply line  3  is prevented. Hydraulic oil  1  flows back to hydraulic oil source  2 , so that bottom plate  9  is pressed down. With these operations, main piston  18  returns to its initial position. 
   As explained above, according to the present embodiment, the piping for hydraulic oil  1  is placed within the body of the pressing mechanism, which prevents contamination of the surrounding area due to leakage of hydraulic oil  1 . Further, first piezoelectric element  16  is used, whose minute displacement is enlarged by displacement enlarging portion  17  for transmission to main piston  18 . Thus, unlike the case where the ascent of the base is transmitted to the main piston by means of the spring, a spring with a large diameter is unnecessary, allowing downsizing of the pressing mechanism. To drive a plurality of main pistons  18 , a plurality of pressing mechanisms can be provided corresponding thereto, so that each piston  18  can be controlled individually using relevant first piezoelectric element  16 . Accordingly, it becomes possible to push up respective main pistons  18  evenly, with high accuracy. 
   A variation of the pressing mechanism of the present embodiment will now be described with reference to  FIG. 5  showing the structure thereof. 
   In the pressing mechanism shown in  FIG. 1 , supply control valve  22  and discharge control valve  25  have both been located close to main cylinder  6  in supply line  3  and discharge line  7 , respectively. Instead, in  FIG. 5 , they both are located close to hydraulic oil source  2 . Alternatively, supply control valve  22  and discharge control valve  25  may be located in any other places in supply line  3  and discharge line  7 , respectively. 
   As explained above, according to the present embodiment, a high degree of freedom is ensured for placement of supply control valve  22  and discharge control valve  25 . Accordingly, it becomes possible to provide a pressing mechanism of a desired shape, e.g., of an elongated shape, or of a shape low in height and large in base area. 
   In the present embodiment, two stages of sub-cylinders, first and second sub-cylinders  4 ,  13 , have been provided for first piezoelectric element  16 . Not limited thereto, just one stage of sub-cylinder may be provided, as long as one displacement of first piezoelectric element  16  can realize a displacement required for main piston  18 . In this case, a sub-cylinder and a sub-piston of large area may be utilized to increase the displacement of main piston  18  corresponding to one displacement of first piezoelectric element  16 . 
   To further increase the displacement of main piston  18  corresponding to one displacement of first piezoelectric element  16 , first piezoelectric element  16  may also be provided with more than two stages of sub-cylinders. 
   Second Embodiment 
   A pressing mechanism and a resin molding device using the same according to the second embodiment of the present invention will now be described with reference to  FIG. 6  showing respective portions thereof. 
   Referring to  FIG. 6 , the pressing portion  21  is provided separately from the portion where the hydraulic oil source (not shown) of the pressing mechanism is provided. A supplying pipe  28  as supply line  3  from the hydraulic oil source and a discharging pipe  29  as discharge line  7  to the hydraulic oil source are connected to pressing portion  21 . Preferably, supplying pipe  28  and discharging pipe  29  are each formed of a flexible pipe. 
   As shown in  FIG. 6 , the resin molding device of the present embodiment is provided with a lower mold  30  and an upper mold  31  facing each other. Lower mold  30  has a space of a cylindrical shape, in which a plunger  32  secured at an end of the axis integrated with main piston  18  is inserted. Of the space of the cylindrical shape, a portion above the plunger  32  forms a pot  33 , in which a resin tablet (not shown) of a columnar shape made of thermosetting resin, for example, is placed. 
   Upper mold  31  includes: a cull portion  34  for distributing the resin tablet molten by heat, or molten resin; a cavity  35  as a space into which the molten resin is introduced for hardening; and a gate portion  36  as an opening through which the molten resin is provided via cull portion  34  to cavity  35 . 
   In the present embodiment, pressing portion  21  is provided in a block  37  constituting a portion of the body of the resin molding device. 
   The resin molding device shown in  FIG. 6  is of the type in which a substrate with an electronic component in a chip form mounted therein is rested on a die-matching plane (indicated as P. L. in FIG.  6 ), and molten resin is introduced into cavity  35  and hardened to resin-seal the substrate. Referring to  FIG. 6 , hydraulic oil  1  being provided via supplying pipe  28  to main cylinder  6  causes main piston  18  to ascend, and thus, plunger  32  presses molten resin (not shown), which is introduced via cull portion  34 , gate portion  36  into cavity  35 . After the molten resin is hardened to cured resin, lower mold  30  and upper mold  31  are separated, and the substrate integrated with the cured resin is taken out. 
   As explained above, according to the pressing mechanism of the present embodiment, as in the first embodiment, downsizing of the pressing mechanism is enabled, and if a plurality of main pistons  18  are provided, they can be pushed up evenly, with high accuracy. In addition, since supplying pipe  28  and discharging pipe  29  are used for supply and discharge of hydraulic oil  1  between the hydraulic oil source and pressing portion  21 , it becomes possible to place the hydraulic oil source and pressing portion  21  separately from each other. This increases the degree of freedom of design when designing a device using the pressing mechanism. 
   Further, according to the resin molding device of the present embodiment, the degree of freedom in designing the resin molding device is increased, and downsizing of the resin molding device is allowed. In the case where there are a plurality of plungers  32 , they can be controlled independently from each other with high accuracy. Accordingly, respective plungers  32  press the molten resin evenly, so that the molten resin can be introduced into corresponding cavities  35  with a uniform pressure. This prevents generation of voids or surface sinks in the molded articles. 
   In the present embodiment, the pressing mechanism having the hydraulic oil source and pressing portion  21  provided separately from each other has been used. However, the pressing mechanism shown in  FIG. 1  may be used alternatively, in which case contamination due to the hydraulic oil can further be prevented. 
   In the respective embodiments described above, first, second and third piezoelectric elements  16 ,  24  and  27  have been used to drive first sub-piston  10 , supply control valve  22  and discharge control valve  25 , respectively. Alternatively, electrical actuators like solenoids or air cylinders may be employed. 
   Further, as the working fluid, instead of hydraulic oil  1 , any fluid working in a similar manner may be employed. 
   Although bottom plate  9  has been held by gas  8  in  FIG. 1 , a compression spring may be employed instead of gas  8 , or a combination of the compression spring and the gas may be employed. Further, compression spring  19  used in pressing portion  21  may be replaced with gas, or a combination of compression spring  19  and the gas may be employed. 
   The resin molding device using the pressing mechanism has been described above. However, the pressing mechanism of the present invention is of course applicable to other devices. 
   Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.