Abstract:
A combined valve is constructed by integrating a manual valve operating as a safety mechanism and a pilot valve. When a handle of a knob of the manual valve is in a safety mechanism release position, a valve mechanism can be opened and closed depending on whether or not there is air supply to an operation port. When the handle is in the safety mechanism release position and the valve mechanism is even in a valve open state, the valve mechanism can be forcibly brought to a valve closed state by rotating the handle to a safety mechanism set position. Further, when the handle is in the safety mechanism set position, the valve mechanism can always be kept in the valve closed state irrespective of air supply to the operation port.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation application based upon and claims the benefit of the prior PCT International Patent Application No. PCT/JP2004/015058 filed on Oct. 13, 2004, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a combined valve for controlling the flow of fluid, integrally including a manual valve to be operated as a safety device and a pilot valve.  
       BACKGROUND ART  
       [0004]     2. Description of Related Art  
         [0005]     In conventional facilities having piping for flowing various kinds of gasses or the like, typically in a semiconductor manufacturing process, a safety device is required to prevent gas leakage resulting from malfunction of a pilot valve during various works needing demounting of the piping. As such conventional technique, Japanese unexamined patent application publication No. 11(1999)-51226 is explained below with reference to  FIG. 14 .  
         [0006]      FIG. 14  shows a structure of a process gas unit  200  in a first prior art to be used in a semiconductor manufacturing process. The process gas unit  200  includes a manual valve  201 , input air-operated valve  205 , mass flow controller  208 , output air-operated valve  210 , manual valve  211 , and others, which are connected in series. In this unit, process gas flows in along a left arrow GI and out along a right arrow GO toward a vacuum chamber or the like (not shown).  
         [0007]     During normal use, the manual valves  201  and  211  are held in a valve opening position, and the input air-operated valve  205  and the output air-operated valve  210  are operated by remote control to open and close for supply and stop of the process gas.  
         [0008]     During repair or maintenance of the process gas unit  200  by for example demounting of the mass flow controller  208 , the manual valves  201  and  211  are held in a valve closed state to stop gas supply regardless of the open/closed state of the air-operated valves  205  and  210 . Accordingly, gas supply can be started/stopped as needed while the manual valves  201  and  211  are open, whereas gas supply can surely be stopped while the manual valves  201  and  211  are closed.  
         [0009]     In case of emergency, even in supplying gas, gas supply can be stopped when the manual valves  201  and  211  are switched from the opening position to the closing position. In this piping arrangement that the manual valves and the air-operated valves are connected in series, the manual valves  201  and  211  serve as a safety device.  
         [0010]     For the semiconductor manufacturing line, the reduction in size and cost of devices has always been further demanded. Hence, it is conceivable that a manual valve and an air-operated valve are integrally arranged in one unit, forming a combined valve, as a measure of saving space of a process gas unit. Such combined valve is disclosed in for example Japanese unexamined patent application publication No. 2003-130249 relating to an air-operated valve combined with a manual operating lever valve into one unit. As one example of the air-operated valve with operating lever valve, a second prior art disclosed in the publication &#39;249 is explained below.  
         [0011]      FIG. 15  shows the air-operated valve with operating lever valve in the second prior art. This valve is arranged to control the flow of fluid by driving a valve element by means of a driving device provided in a valve casing and to inhibit the flow of fluid with the operating lever attached to the valve casing regardless of operation of the driving device.  
         [0012]     The structure shown in  FIG. 15  is described below. A main operation valve  101  includes a valve casing  103  provided therein with a flow passage  102  formed between an inlet and an outlet for process liquid. A valve seat  104  is formed near the center of the flow passage  102 . A valve element  105  is connected to an end of a valve rod  106 . The valve casing  103  is also provided with a holding part  107  in which the valve rod  106  is held movably toward and away from the valve seat  104 . This holding part  107  contains a piston  108  that is connected to the other end of the valve rod  106  and slidable within the holding part  107 . The piston  108  is normally urged by a compression coil spring  109  to bring the valve element  105  into contact with the valve seat  104 . When an electromagnetic valve not shown is activated, the piston  108  is caused to slide in a cylinder  116  by air pressure supplied through a through hole  115  against the urging force of the coil spring  109 . A pin-shaped pressing member  110  is urged by an extension spring not shown in an opposite direction to the piston  108 . The pressing member  110  has a round base end  110   a.  An operating lever  111  is disposed in contact with the base end  110   a  of the pressing member  110 . This lever  111  is provided with a handle  113  at one end and a contact end  114  abutting against the base end  110   a  at the other end with respect to an eccentric shaft  112 .  
         [0013]     When the handle  113  of the operating lever  111  is rotated up (in a direction indicated by an arrow A in  FIG. 15 ), the contact end  114  is rotated about the eccentric shaft  112 , pushing the pressing member  110  toward the piston  108  to bring the valve element  105  into contact with the valve seat  104 . In other words, the operating lever  111  may be switched between a first position for forcibly bringing the valve element  105  into contact with the valve seat  104  and a second position for bringing the valve element  105  out of contact with the valve seat  104 . As above, the valve element  105  is driven by the holding part  107  provided in the valve casing  103  to control the flow of process liquid and the pressing member  110  and the operating lever  111  provided in the valve casing  103  are operated to forcibly inhibit the flow of fluid regardless of the operating condition of the holding part  107 .  
         [0014]     The above conventional techniques involve the following problems.  
         [0015]     (1) In the first prior art, according to the piping arrangement in  FIG. 14 , the manual valves  201  and  211  function as a safety device. However, two types of valves, namely, the air-operated valves  205  and  210  and the manual valves  201  and  211  are needed, so that space for mounting the valves could not be saved.  
         [0016]     (2) The second prior art has the following disadvantages.  
         [0017]     As the action of toggle, it is possible to readily control the flow condition of process liquid by a toggle from the outside of the device. In the second prior art shown in  FIG. 15 , the operating lever  111  is adopted as the toggle and the air-operated valve with the operating lever valve is arranged.  
         [0018]     This arrangement may achieve an integral unit of the operating lever valve and the air-operated valve; however, this unit only could be closed manually and has no function to fixedly hold the operating lever  111  at a predetermined position. Thus, the valve closed state could not be ensured and it has no function as the safety device.  
         [0019]     In other words, the second prior art is merely arranged to manually perform temporal valve-closing. In case the piping is demounted for maintenance or the like, therefore, liquid may leak out due to malfunction of the air-operated valve.  
         [0020]     In the above publication &#39;249, it is disclosed that “this can combine two functions of a conventional toggle valve ( 13 ) and a safety valve ( 17 ), thus achieving a main operation valve ( 21 ) with reduced space for mounting”. However, this device has no function to reliably maintain the valve closed state and does not function as an original safety valve.  
         [0021]     (3) In case of a chemical liquid valve, chemical liquid to be used in the semiconductor manufacturing process is allowed to flow through the valve. Accordingly, a valve element has to be made of fluorocarbon resin having resistance to corrosion. The fluorocarbon resin is likely to creep. A long-term normal use as a pilot valve may therefore lead to plastic deformation of the valve seat, which shrinks in a loading direction.  
         [0022]     As such plastic deformation progresses, a sealing strength between the valve element and the valve seat will be decreased, causing leakage.  
         [0023]     (4) There is no mechanism to fixedly hold the operating lever  111  at the predetermined valve-opening position. Thus, the valve closed state could not be ensured and there is no function to maintain normal use as the pilot valve. Specifically, the second prior art is merely arranged to manually perform valve-opening. For example, when the piston  108  makes contact with a stopper (not shown) restricting a piston stroke, vibration is transmitted to the operating lever  111 , which may shift to the valve-closing position. Consequently, the pilot valve is closed irrespective of the intension of an operator, thus stopping the flow of liquid.  
         [0024]     (5) Further, when the operating lever  111  is to be operated to forcibly bring the valve element  105  into contact with the valve seat  104  if the cylinder  116  is supplied with air through the through hole  115 , a larger force than the air pressure on the piston  108  in the cylinder  116  is required to operate the operating lever  111 .  
       SUMMARY OF THE INVENTION  
       [0025]     The present invention has been made to solve the above problems and has a purpose to provide a combined valve integrally including a manual valve to be operated as a safety mechanism and a pilot valve.  
         [0026]     To be more concrete, to solve the above problems (1) to (3) of the prior arts mentioned above, an object of the present invention is to provide a combined valve which may be used as a chemical liquid valve arranged such that a pilot valve is allowed to open/close only when a manual valve operating as a safety mechanism is in a release position, the manual valve is switched to a valve closing position to shut off the flow of fluid even where the pilot valve is open, and the manual valve can be held in such position.  
         [0027]     To solve the above problem (4), another object of the present invention is to provide a combined valve allowing continuous normal use as a pilot valve by a mechanism for holding a manual valve in a valve opening position.  
         [0028]     To solve the above problem (5), further, another object of the present invention is to provide a combined valve including a manual valve easy for an operator to operate without applying large force.  
         [0029]     To achieve the above purpose, there is provided a combined valve comprising: a valve mechanism including a diaphragm valve element and a valve seat with which the diaphragm valve element is brought into and out of contact to control a flow of fluid; a pilot mechanism including an urging device that presses the diaphragm valve element against the valve seat, the pilot mechanism being operated to bring the diaphragm valve element out of contact with the valve seat by air pressure; and a manual mechanism arranged to act on operations of the pilot mechanism; wherein when the manual mechanism is operated to interrupt a supply passage of air to the pilot valve, the diaphragm valve element is axially moved from a valve open position to a valve closed position by means of the urging device, and the combined valve further comprises a manual-mechanism holding device for holding the manual mechanism in a predetermined position to hold the diaphragm valve element in the valve closed position.  
         [0030]     Accordingly, even in case of emergency where the valve operating mechanism has to be switched from a valve open state allowing air supply to a pilot mechanism to a valve closed state, an operator may react appropriately with the manual operating mechanism.  
         [0031]     Further, irrespective of air supply to the pilot mechanism, the valve operating mechanism is switched to the valve closed state by the manual operating mechanism. Even in the case where the air supply to the pilot mechanism is erroneously caused during maintenance, for example, the valve operating mechanism will not be switched to the valve open state. Accordingly, the operator may perform the maintenance work safely.  
         [0032]     According to another aspect of the present invention, there is provided a combined valve comprising: a valve mechanism including a diaphragm valve element and a valve seat with which the diaphragm valve element is brought into and out of contact to control a flow of fluid; a pilot mechanism including and an urging device that presses the diaphragm valve element against the valve seat, the pilot mechanism being operated to bring the diaphragm valve element out of contact with the valve seat by air pressure; and a manual mechanism arranged to act on operations of the pilot mechanism; wherein the manual mechanism is operated to axially move the diaphragm valve element from a valve open position to a valve closed position, and the manual mechanism is directly provided with a first manual-mechanism holding device for holding the diaphragm valve element in the valve closed position.  
         [0033]     According to the present invention, as described above, valve mounting space can be saved and further the pilot valve is allowed to open/close only when the manual valve is in a release state. Even where the pilot valve is in the open state, the flow of fluid can be stopped by switching the manual valve to a valve-closing position and the manual valve can be held in such position. Thus the manual valve has a function as a safety device and also can function as a safety valve. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0034]      FIG. 1  is a sectional view of a combined valve held in a valve closed state by a manual operating mechanism in a first preferred embodiment;  
         [0035]      FIG. 2  is a sectional view of the combined valve in a valve closed state;  
         [0036]      FIG. 3  is a sectional view of the combined valve in the valve open state;  
         [0037]      FIG. 4  is a partial view of the combined valve held in the valve closed state by the manual operating mechanism locked with a padlock;  
         [0038]      FIG. 5  is a sectional view of the combined valve used as a chemical liquid valve, showing a state of a valve seat plastic-deformed;  
         [0039]      FIG. 6  is a sectional view of the combined valve operated to cause a diaphragm valve element to follow the valve seat plastic-deformed shown in  FIG. 5 ;  
         [0040]      FIG. 7  is a sectional view of a combined valve held in a valve closed state by a manual operating mechanism in a second preferred embodiment;  
         [0041]      FIG. 8  is a sectional view of the combined valve in the valve closed state in the second embodiment;  
         [0042]      FIG. 9  is a sectional view of the combined valve in a valve open state in the second embodiment;  
         [0043]      FIG. 10  is a view of the combined valve in the second embodiment, in which the manual operating mechanism is rotated until a knob comes into contact with an adjusting rod at a curvature-changing point of the outer periphery of the knob to change the combined valve from the valve open state to the valve closed state by the manual operating mechanism,;  
         [0044]      FIG. 11  is a sectional view of a combined valve held in a valve closed state by a manual operating mechanism in a third preferred embodiment;  
         [0045]      FIG. 12  is a sectional view of the combined valve in the valve closed state in the third embodiment;  
         [0046]      FIG. 13  is a sectional view of the combined valve in the valve open state in the third embodiment;  
         [0047]      FIG. 14  is a view showing a structure of a process gas unit in a prior art;  
         [0048]      FIG. 15  is a view showing an air-operated valve with an operating lever valve in the prior art;  
         [0049]      FIG. 16  is a sectional view of a combined valve held in a valve closed state by a manual operating mechanism in a fourth preferred embodiment;  
         [0050]      FIG. 17  is a sectional view of the combined valve in the valve closed state in the fourth embodiment;  
         [0051]      FIG. 18  is a sectional view of the combined valve in a valve open state in the fourth embodiment;  
         [0052]      FIG. 19  is a view showing the position of a keyhole in a bracket and rotational play of a handle of the knob;  
         [0053]      FIG. 20  is a view showing a positional relation between the knob and the bracket;  
         [0054]      FIG. 21  is a sectional view of a combined valve in a valve open state in a fifth preferred embodiment;  
         [0055]      FIG. 22  is a top view of the combined valve in the fifth embodiment;  
         [0056]      FIG. 23  is an external view of an upper part of the combined valve in the fifth embodiment;  
         [0057]      FIG. 24  is a sectional view of a rod taken along a line A-A;  
         [0058]      FIG. 25  is a sectional view of the combined valve in a valve closed state in the fifth embodiment;  
         [0059]      FIG. 26  is a view of a packing in the fifth embodiment;  
         [0060]      FIG. 27  is an external view of the knob part;  
         [0061]      FIG. 28  is a view showing the relation between the knob, rod, and pin;  
         [0062]      FIG. 29  is a general view showing a technique to automatically slide by use of a return spring;  
         [0063]      FIG. 30  is a general view showing another technique to automatically slide by use of a return spring;  
         [0064]      FIG. 31  is a view showing another form of locking; and  
         [0065]      FIG. 32  is a view showing the shape of an end of a rod opposite to an end having the knob. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0066]     A detailed description of preferred embodiments of a combined valve embodying the present invention will now be given referring to FIGS.  1  to  13  and  16  to  32 .  
       First Embodiment  
       [0067]     A combined valve  1  in a first embodiment will be described with reference to FIGS.  1  to  6 .  
         [0068]     FIGS.  1  to  3  are sectional views of the combined valve  1  in the first embodiment of the present invention. As shown in  FIG. 3 , a body section of the combined valve  1  integrally includes a valve body  11 , cylinder  12 , and cover  13 . The combined valve  1  is structured of a pilot valve, a manual valve, and a valve-seat following mechanism. As for the combined valve  1 , “Upper” indicates a manual valve side and “Lower” indicates a pilot valve side.  
         [0069]     Firstly, the pilot valve of the combined valve  1  is explained. The pilot valve is further divided into a pilot mechanism and a valve operating mechanism. Here, the pilot mechanism includes the cylinder  12 , the cover  13 , a piston rod  21 , a spring  22 , and a spring  52 . These cylinder  12  and cover  13  constitute an airtight container, in which the piston rod  21  is slidably mounted. This piston rod  21  partitions the space defined by the cylinder  12  and the cover  13  into two chambers, upper and lower. The lower chamber is a pressure chamber  23 . This pressure chamber  23  is communicated with an operation port  24 . On the piston rod  21 , the springs  22  and  52  which urge the piston rod  21  downwards are mounted.  
         [0070]     The valve operating mechanism includes the valve body  11 , a valve seat  31 , a diaphragm valve element  32 , and ports  33  and  34 . In the valve body  11 , the ports  33  and  34  are communicated with each other through the valve seat  31  and a communicating area  35 . The diaphragm valve element  32  which will be brought into/out of contact with the valve seat  31  is partially sandwiched between the valve body  11  and the cylinder  12 . Accordingly, the valve body  11  and the cylinder  12  are airtightly partitioned by the diaphragm valve element  32 , preventing the fluid flowing in the communicating area  35  from leaking out to the cylinder  12  side. Slidably mounted in the cylinder  12  is the piston rod  21  coupled to the diaphragm valve element  32 . The diaphragm valve element  32  is arranged to come apart from the valve seat  31  when the piston rod  21  is not urged downwards, but come into contact with the valve seat  31  when the diaphragm valve element  32  is pressed downwards by the piston rod  21 .  
         [0071]     The manual valve of the combined valve  1  is explained below. The manual valve includes a rod  51 , a spring  52 , and a knob  53 . Above the rod  51 , the knob  53  is attached to be rotatable about an eccentric shaft  54 . The knob  53  is provided with a handle  55  and a keyhole  56 .  
         [0072]     The valve-seat following mechanism is described below. The valve-seat following mechanism includes a feed screw  71  formed with external threads, a holder  72  formed with internal threads which engage with the external threads of the feed screw  71 , an adjusting knob  73 , a setscrew  74 , and a lock nut  75 . The feed screw  71  is located in rotatable engagement with the holder  72  of the cover  13 . A rotation-locking pin  20  is provided between the feed screw  71  and the piston rod  21 . The lock nut  75  is placed on the holder  72 . The adjusting knob  73  and the setscrew  74  are arranged on the outer periphery of the holder  72 .  
         [0073]     The combined valve  1  having the above structure is operated as follows.  
         [0074]     A normal operation of the pilot valve will be described first.  FIG. 3  shows the combined valve  1  with the manual valve held in a valve opening position and the pilot valve opened to allow the flow of fluid.  FIG. 2  shows the combined valve  1  with the manual valve held in the valve opening position but the pilot valve closed to prevent the flow of fluid.  
         [0075]      FIG. 3  is first explained.  FIG. 3  shows the combined valve  1  with the pilot valve opened by supply of air pressure thereto by an electromagnetic valve not shown. Specifically, when air is supplied to the pressure chamber  23  through the operation port  24 , the air pressure in the pressure chamber  23  is increased. Under upward pressure, the piston rod  21  slides upwards in the cylinder  12  against the downward urging force of the springs  22  and  52 . In association with the upward sliding of the piston rod  21 , the diaphragm valve element  32 , which is not urged downwards, comes apart from the valve seat  31 . Accordingly, a passage space is generated between the valve seat  31  and the diaphragm valve element  32 , providing communication between the ports  33  and  34  through the communicating area  35 . The fluid supplied through the port  33  is thus allowed to flow out through the port  34 .  
         [0076]     Next,  FIG. 2  shows the combined valve  1  with the pilot valve brought into a closed state. Specifically, when air supply into the pressure chamber through the operation port  24  is stopped and the air pressure forcing the piston rod  21  upwards in the pressure chamber  23  is reduced, the piston rod  21  is pushed down by the urging force of the springs  22  and  52  mounted on the piton rod  21 . Accordingly, the piston rod  21  is urged downwards, bringing the diaphragm valve element  32  into contact with the valve seat  31 , thus closing the flow passage space between the valve seat  31  and the diaphragm valve element  32 . This interrupts the communication between the port  33 , the communicating area  35 , and the port  34  and thus the fluid supplied through the port  33  is not allowed to flow out through the port  34 .  
         [0077]     When the manual valve is located in the valve opening position, opening/closing operation of the pilot valve can be performed by the electromagnetic valve.  
         [0078]     An operation of the manual valve when used by an operator for example as a safety mechanism during maintenance or the like is explained referring to  FIG. 1 .  FIG. 1  shows the combined valve  1  with the manual valve in the valve closing position, which is switched from the valve opening position shown in  FIG. 2  or  3 .  
         [0079]     Firstly, explanation is made on the manual valve switched from the valve opening position shown in  FIG. 3  to the valve closing position.  
         [0080]     To be concrete, the operator rotates the handle  55  of the knob  53 , 180 degrees counterclockwise in front view, about the eccentric shaft  54  from the valve opening position (hereinafter, referred to as a safety mechanism release position R) to a position (hereinafter, referred to as a safety mechanism set position S). Then, the rod  51  comes into contact with the piston rod  21  which also receives the downward urging force of the springs  22  and  52 . The piston rod  21  is therefore urged downwards, bringing the diaphragm valve element  32  integral with the piston rod  21  into contact with the valve seat  31 . As a result, the fluid flowing in the port  33  is prevented from passing through the communicating area  35  closed by the diaphragm valve element  32  and flowing toward the port  34 .  
         [0081]     Secondly, explanation is made on the manual valve switched from the valve opening position shown in  FIG. 2  to the valve closing position.  
         [0082]     To be concrete, the operator rotates the manual valve from the safety mechanism release position R to the safety mechanism set position S. Then, the rod  51  comes into contact with the piston rod  21  which also receives the downward urging force of the springs  22  and  52 . The piston rod  21  is therefore urged downwards, holding the diaphragm valve element  32  integral with the piston rod  21  in contact with the valve seat  31 . As a result, the fluid flowing in the port  33  is prevented from passing through the communicating area  35  closed by the diaphragm valve element  32  and flowing toward the port  34 .  
         [0083]     As above, when the manual valve is rotated from the valve opening position in  FIGS. 2 and 3  to the valve closing position, the flow passage space between the diaphragm valve element  32  and the valve seat  31  is closed, thus interrupting the communication between the port  33 , the communicating area  35 , and the port  34 . Consequently, the fluid flowing in the port  33  is prevented from flowing out through the port  34 .  
         [0084]     In other words, even where the pilot valve is in a valve open state as shown in  FIG. 3 , the operator may rotate the handle  55  from the safety mechanism release position R to the safety mechanism set position S to forcibly switch the pilot valve from the valve open state to the valve closed state. Accordingly, in case of emergency where fluid discharge should be stopped immediately, the operator can react to the emergency case appropriately.  
         [0085]     Further, for example a padlock  57  may be inserted in the keyhole  56  of the knob  53  in the state of  FIG. 1  by the operator. In this case, the handle  55  is prevented from rotating from the safety mechanism set position S ( FIG. 4 ) even where air is supplied to the operation port  24 . The rod  51  and the piston rod  21  are thus held in contact relation, so that the rod  21  will not slide upwards. Thus, the pilot valve can be maintained in the valve closed state even if air is supplied through the operation port  24 .  
         [0086]     In other words, when the operator locks the manual valve in the valve closing position, the fluid will not flow out even if air is supplied through the operation port  24  due to malfunction. The operator is therefore allowed to safely work for maintenance or the like.  
         [0087]     Next,  FIGS. 5 and 6  are explained. Here,  FIGS. 5 and 6  are sectional views of the combined valve with the valve-seat following mechanism to prevent a decrease in the sealing strength of the valve operating mechanism when the combined valve  1  of the present invention is used as the chemical liquid valve.  
         [0088]     For use of the combined valve  1  as the chemical liquid valve, it is assumed that the valve seat  31  is made of a material having resistance to corrosion, such as fluorocarbon resin. At this time, when the valve is continuously used as the normal pilot valve shown in  FIGS. 2 and 3  for a long term, the valve seat  31  repeatedly receives stress from the diaphragm valve element  32  for the long term. Conceivably, the valve seat  31  may shrink downwards by plastic-deformation called a creep phenomenon. This may cause a clearance between the rod  51  and the piston rod  21  when the manual valve is placed in the safety mechanism set position S. Hence, if air is supplied through the operation port  24 , the piston rod  21  is caused to slide upwards by the clearance against the downward urging force of the springs  22  and  52 , leading to a decrease in downward urging force exerted on the diaphragm valve element  32  integral with the piston rod  21 . Consequently, the sealing strength between the diaphragm valve element  32  and the valve seat  31  may become insufficient.  
         [0089]     Even when air is not supplied through the operation port  24 , the diaphragm valve element  32  and the piston rod  21  may be moved to slide upwards by the pressure of chemical liquid flowing into the port  33 . This may leads to insufficient sealing strength between the diaphragm valve element  32  and the valve seat  31 .  
         [0090]     In other words, when the valve seat  31  shrinks downwards by plastic deformation, the sealing strength between the diaphragm valve element  32  and the valve seat  31  becomes insufficient, so that the port  33 , the communicating area  35 , and the port  34  are communicated with each other. Thus, the chemical liquid supplied to the port  33  might flow out through the port  34 .  
         [0091]     In  FIG. 6 , an operating state of the valve-seat following mechanism is illustrated. Specifically, when turned, the feed screw  71  is moved up/down, and the rod  51  inserted in the feed screw  71  is also moved up/down. Here, when the feed screw  71  is turned to move downwards, allowing the rod  51  to move down, thereby moving the piston rod  21  held in contact with the rod  51  downwards. Accordingly, the downward urging force on the diaphragm valve element  32  integral with the piston rod  21  is increased, thus providing sufficient sealing strength between the diaphragm valve element  32  and the valve seat  31 .  
         [0092]     In other words, by moving the feed screw  71  downwards, the sealing strength is enhanced between the diaphragm valve element  32  and the valve seat  31  to prevent the communication between the port  33 , the communicating area  35 , and the port  34 . It is therefore possible to prevent the chemical liquid supplied to the port  33  from flowing out through the port  34 .  
       Second Embodiment  
       [0093]     A combined valve  2  in a second embodiment will be explained with reference to  FIGS. 7 and 10 . As shown in  FIG. 9 , a body section of the combined valve  2  includes a valve body  311 , cylinder  312 , piston cylinder  314 , and cover  313 , which are integrally formed in one unit. The combined valve  2  is structured of a pilot valve and a manual valve. As for the combined valve  2 , “Upper” indicates a manual valve side and “Lower” indicates a pilot valve side.  
         [0094]     Firstly, the pilot valve of the combined valve  2  is explained. The pilot valve is further divided into a pilot mechanism and a valve operating mechanism. Here, the pilot mechanism includes the cylinder  312 , the cover  313 , a piston rod  321 , springs  322  and  352 , a piston  326 , and springs  327  and  328 .  
         [0095]     These cylinder  312 , cover  313 , and piston cylinder  314  constitute an airtight container. Mounted in the piston cylinder  314  are the piston  326  slidable therein, the spring  327  which urges the piston  326  upwards, and the spring  328  which urges the piston  326  downwards. The piston  326  partitions the space defined by the piston cylinder  314  and cover  313  into two chambers, upper and lower. The lower chamber is a pressure chamber  323  which is communicated with an operation port  324 .  
         [0096]     The shaft  325  is inserted in the piston  326  and integrally coupled to the rod  321 . Here, the spring  322  is located between the shaft  325  and the piston cylinder  314  to urge the shaft  325  downwards.  
         [0097]     The valve operating mechanism includes the valve body  311 , a diaphragm valve element  332 , and ports  333  and  334 . In the valve body  311 , the ports  333  and  334  are communicated with each other through a communicating area  335 . The diaphragm valve element  332  which will be brought into/out of contact with the valve body  311  is partially sandwiched between the valve body  311  and the cylinder  312 . Accordingly, the valve body  311  and the cylinder  312  are airtightly partitioned by the diaphragm valve element  32 , preventing the fluid flowing in the communicating area  335  from leaking out to the cylinder  312  side. The diaphragm valve element  332 , integrally coupled to the rod  321 , is arranged to be separated from the valve body  311  when the rod  321  is not urged downwards and to be brought into contact with the valve body  311  when the rod  332  is urged downwards.  
         [0098]     The manual valve of the combined valve  2  is explained below. The manual valve includes an adjusting rod  351 , the spring  328 , and a knob  353 . Above the adjusting rod  351 , the knob  353  is attached to be rotatable about an eccentric shaft  354 . The knob  353  is provided with a handle  355 , a keyhole  356 , and a notch  360 .  
         [0099]     The combined valve  2  having the above structure is operated as follows.  
         [0100]     A normal operation of the pilot valve will be described first.  FIG. 9  shows the combined valve  2  with the manual valve held in a valve opening position and the pilot valve opened to allow the flow of fluid.  FIG. 8  shows the combined valve  2  with the manual valve held in the valve opening position but the pilot valve closed to prevent the flow of fluid.  
         [0101]      FIG. 9  is first explained.  FIG. 9  shows the pilot valve opened by supply of air pressure thereto by an electromagnetic valve not shown. Specifically, when air is supplied to the pilot valve through the operation port  324 , the air is fed into the pressure chamber  323  via the air supply passage  315  of the piston cylinder  314 . Then, the air pressure in the pressure chamber  323  is increased. Under upward pressure in association with the increase in air pressure in the pressure chamber  323 , the piston  326  slides upwards in the piston cylinder  314  against the downward urging force of the spring  328 . In association with the upward sliding of the piston  326 , the shaft  325  whose flange portion bears on the piston  326  is simultaneously moved upwards against the downward urging force of the spring  322 . The rod  321  integral with the shaft  325  is also moved upwards. Accordingly, the diaphragm valve element  332  coupled to the rod  321  is not pressed downwards and is brought out of contact with the valve body  311 . Thus, a passage space is generated between the diaphragm valve element  332  and the valve body  311 , providing communication between the ports  333  and  334  through the communicating area  335 . The fluid supplied into the valve body  311  through the port  333  is then discharged out through the port  334 .  
         [0102]     Next,  FIG. 8  shows the pilot valve in the closed state. Specifically, when air supply into the pressure chamber  323  through the operation port  24  is stopped and the air pressure forcing the piston  326  upwards is reduced, the piston  326  is moved down by the urging force of the springs  327  and  328 . Then, the shaft  325  held in contact with the piston  326  is urged downwards by the spring  322  and then the diaphragm valve element  332  integral with the shaft  325  and the rod  321  is brought into contact with the valve body  311 .  
         [0103]     Accordingly, the flow passage space between the diaphragm valve element  332  and the valve body  311  is closed. This interrupts the communication between the ports  333  and  334  through the communicating area  335  and thus the fluid supplied through port  333  is not allowed to flow out through the port  334 .  
         [0104]     When the manual valve is located in the valve opening position, opening/closing operation of the pilot valve can be performed by the electromagnetic valve.  
         [0105]     Further, when the adjusting rod  351  is engaged in the notch  360  of the knob  353 , the manual valve is prevented from shifting to the valve closing position. This makes it possible to ensure the opening/closing operation of the pilot valve by the electromagnetic valve.  
         [0106]     Next, an operation of the manual valve when used by an operator for example as a safety mechanism during maintenance or the like is explained referring to  FIGS. 7 and 10 .  FIG. 7  shows the combined valve  2  with the manual valve in the valve closing position, which is switched from the valve opening position shown in  FIG. 8  or  9 .  
         [0107]     Firstly, explanation is made on the manual valve switched from the valve opening position shown in  FIG. 9  to the valve closing position. To be concrete, the operator rotates the handle  355  of the knob  353 , 180 degrees counterclockwise in front view, about the eccentric shaft  354  from the valve opening position (hereinafter, referred to as a safety mechanism release position R) to a predetermined position (hereinafter, referred to as a safety mechanism set position S). Here, the predetermined position represents the position where the outer tapered periphery of the knob  353  is in contact with the adjusting rod  351 . Then, as the rotating operation is started, the adjusting rod  351  receiving the downward load resulting from the rotation of the handle  355  of the knob  353  is moved down into contact with the piston  326  which is then slid downwards. Accordingly, the piston  326  is brought out of contact with the flange portion of the shaft  325 . The shaft  325  becomes movable up and down separately from the piston  326 . The shaft  325  is therefore urged downwards by the spring  322 . The shaft  325  and the diaphragm valve element  332  integral with the rod  321  are brought into contact with the valve body  311 .  
         [0108]     On the other hand, explanation is made on the manual valve switched from the valve opening position shown in  FIG. 8  to the valve closing position. To be concrete, the operator rotates the handle  355  of the knob  353  from the safety mechanism release position R to the safety mechanism set position S. Then, as the rotating operation is started, the adjusting rod  351  receiving the downward load resulting from the rotation of the handle  355  of the knob  353  is moved down into contact with the piston  326  which is then slid downwards. Accordingly, the piston  326  is brought out of contact with the flange portion of the shaft  325 . The shaft  325  becomes movable up and down separately from the piston  326 . However, the shaft  325  is urged downwards by the spring  322 . The shaft  325  and the diaphragm valve element  332  integral with the rod  321  are thus held in contact with the valve body  311 .  
         [0109]     As above, when the manual valve is rotated form the valve opening position shown in  FIGS. 8 and 9  to the valve closing position, the flow passage space between the diaphragm valve element  332  and the valve body  311  is closed, interrupting the communication between the ports  333  and  334  through the communicating area  335 . Thus, the fluid flowing in the port  333  is prevented from flowing out through the port  334 .  
         [0110]     In other words, even where the pilot valve is in a valve open state as shown in  FIG. 9 , the operator may rotate the handle  355  from the safety mechanism release position R to the safety mechanism set position S to forcibly switch the pilot valve from the valve open state to the valve closed state. Accordingly, in case of emergency where fluid discharge should be stopped immediately, the operator can react to the emergency case appropriately.  
         [0111]     Further, when the knob  353  is rotated to the position ( FIG. 7 ) where the outer tapered periphery of the knob  353  makes contact with the adjusting rod  351 , the handle  355  of the knob  353  can be locked in the safety mechanism set position S.  
         [0112]     Here, the reason why the handle  355  of the knob  353  can be locked in the safety mechanism set position S is as described below. Specifically, the distance (hereinafter, referred to as a “distance R 1 ”) from the center point of the eccentric shaft  354  of the knob  353  to an inflection point of the outer periphery of the knob  353  in  FIG. 10  is longer than the distance (hereinafter, referred to as a “distance R 2 ”) from the center point of the eccentric shaft  354  of the knob  353  to the outer tapered periphery of the knob  353 . Therefore the handle  355  of the knob  353  is held against rotation unless it receives a force pressing the adjusting rod  351  downwards by a distance corresponding to the difference between the distances R 1  and R 2  against the urging force of the spring  328 . The handle  355  can thus be locked in the state shown in  FIG. 7 .  
         [0113]     The pilot valve can be maintained in the valve open state even if air is supplied thereto through the operation port  324 .  
         [0114]     In other words, when the manual valve is placed in the valve closing position by the operator as shown in  FIG. 7 , the fluid is prevented from flowing out even when air is supplied through the operation port  324  due to malfunction. Accordingly, the operator is allowed to safely perform maintenance or the like.  
         [0115]     In addition, for example a padlock  357  may be inserted in the keyhole  356  of the knob  353  in the state of  FIG. 7  by the operator. This case is the same as in the combined valve  1  in the first embodiment and therefore the details are not repeated here.  
         [0116]     Further, when the handle  355  of the knob  353  in  FIG. 9  is rotated from the safety mechanism release position R to the safety mechanism set position S, as the rotating operation is started, the adjusting rod  351  receives the downward load resulting from the rotation of the handle  355  of the knob  353  and then is brought into contact with the piston  326  even where air is supplied to the operation port  324  by the electromagnetic valve not shown. The piston  326  is slid downwards, separating from the flange portion of the shaft  325 . Then, the air supplied through the operation port  324  and the air in the pressure chamber  323  are released through a gap generated between the piston  326  and the flange portion of the shaft  325  separated therefrom. Consequently, the air pressure in the enclosed space formed by the cover  313  placed above the piston  326 , the piston cylinder  314 , and the adjusting rod  351  becomes equal to the air pressure in the pressure chamber  323  under the piston  326 . As for the adjusting rod  351 , accordingly, upward thrust to the piston  326  resulting from the air pressure in the pressure chamber  323  is reduced. As a result, the upward thrust to the piston  326  resulting from the air pressure in the pressure chamber  323  is reduced. The handle  355  of the knob  353  can therefore be rotated when applied enough load against the upward urging force of the spring  327 .  
         [0117]     The operator is allowed to close the manual valve without applying a large force to counterbalance the air pressure.  
       Third Embodiment  
       [0118]     A combined valve  3  in a third embodiment is explained referring to FIGS.  11  to  13 .  
         [0119]     As shown in  FIG. 13 , a body section of the combined valve  3  includes a valve body  411 , cylinder  412 , piston cylinder  414 , and cover  413 , which are integrally formed in one unit. The combined valve  3  is structured of a pilot valve and a manual valve. As for the combined valve  3 , “Upper” indicates a manual valve side and “Lower” indicates a pilot valve side.  
         [0120]     Firstly, the pilot valve of the combined valve  3  is explained. The pilot valve is further divided into a pilot mechanism and a valve operating mechanism. Here, the pilot mechanism includes the cylinder  412 , the piston cylinder  414 , a rod  421 , a spring  422 , a shaft  425 , a piston  426 , and a spring  428 .  
         [0121]     The piston cylinder  414  and the adjusting rod  451  constitute an airtight container in which the piston  426  is slidably mounted. The spring  428  is placed to urge the adjusting rod  451  upwards and the piston  426  downwards. The piston  426  partitions the space defined by the piston cylinder  414  and the adjusting rod  451  into two chambers, upper and lower. The lower chamber is a pressure chamber  423  which is communicated with an operation port  429  through an air supply passage  415  of the piston cylinder  414  and an air supply passage  459  formed in the outer periphery of the adjusting rod  451 .  
         [0122]     Further, the shaft  425  is inserted in the piston  426  and coupled to the rod  421 . Here, the spring  422  is placed in contact with the shaft  425  to urge the shaft  425  and the rod  421  downwards.  
         [0123]     On the other hand, the valve operating mechanism includes the valve body  411 , a diaphragm valve element  432 , ports  433  and  434 . This structure is the same as in the combined valve  2  in the second embodiment and therefore the details thereof are not repeated here.  
         [0124]     Next, the manual valve of the combined valve  3  is explained. The manual valve includes the adjusting rod  451 , spring  428 , and knob  453 . The basic structure of the combined valve  3  except for the shape of the adjusting rod  451  is similar to that of the combined valve  2  in the second embodiment and its explanation is omitted here.  
         [0125]     The combined valve  3  having the above structure is operated as follows.  
         [0126]     A normal operation of the pilot valve will be described first.  FIG. 13  shows the combined valve  3  with the manual valve held in the valve opening position and the pilot valve opened to allow the flow of fluid.  FIG. 12  shows the combined valve  3  with the manual valve held in the valve opening position but the pilot valve closed to prevent the flow of fluid.  
         [0127]      FIG. 13  is first explained.  FIG. 13  shows the pilot valve opened by supply of air pressure thereto through an electromagnetic valve not shown. Specifically, when air is supplied to the pilot valve through the operation port  429 , the air is fed into the pressure chamber  423  via the air supply passage  459  formed on the outer periphery of the adjusting rod  451  and the air supply passage  415  of the cylinder  414 . Then, the air pressure in the pressure chamber  423  is increased. Under upward pressure in association with the increase in air pressure in the pressure chamber  423 , the piston  426  is allowed to slide upwards in the piston cylinder  414  against the downward urging force of the spring  428 . In association with the upward sliding of the piston  426 , the shaft  425  whose flange portion bears on the piston  426  is simultaneously moved upwards against the downward urging force of the spring  422 . The rod  421  coupled to the shaft  425  is also moved upwards. Accordingly, the diaphragm valve element  432  coupled to the rod  421  is not pressed downwards and is brought out of contact with the valve body  411 . Thus, a passage space is generated between the diaphragm valve element  432  and the valve body  411 , providing communication between the ports  433  and  434  through the communicating area  435 . The fluid supplied into the valve body  41  through the port  433  is then discharged out through the port  434 .  
         [0128]     Next,  FIG. 12  shows the pilot valve in a closed state. Specifically, air supply into the pressure chamber  423  through the operation port  429  is stopped and the air pressure forcing the piston  426  upwards is reduced. The subsequent operations are similar to those in the combined valve  2  in the second embodiment and therefore the details are not repeated here.  
         [0129]     Next, an operation of the manual valve when used by an operator for example as a safety mechanism during maintenance or the like is explained referring to  FIG. 11 .  FIG. 11  shows the combined valve  2  with the manual valve in the valve closing position, which is switched from the valve opening position shown in  FIG. 12  or  13 . This operation is similar to in the combined valve  2  in the second embodiment and therefore the details of switching of the manual valve from the valve opening position to the valve closing position are omitted here.  
         [0130]     Further, when the knob  453  is rotated to the position where the outer tapered portion of the knob  453  comes into contact with the adjusting rod  451 , as shown in  FIG. 11 , the handle  455  of the knob  453  can be locked in the safety mechanism set position S. The subsequent operations are similar to those in the combined valve  2  in the second embodiment and therefore the details thereof are not repeated here.  
         [0131]     In addition, for example a padlock  457  may be inserted in a keyhole  456  of the knob  453  in the state of  FIG. 11  by the operator. This case is the same as in the combined valve  1  in the first embodiment and the combined valve  2  in the second embodiment and therefore the details thereof are omitted here.  
         [0132]     Further, when the handle  455  of the knob  453  in  FIG. 13  is rotated from the safety mechanism release position R to the safety mechanism set position S, as the rotating operation is started, the communication between the air supply passage  459  of the adjusting rod  451  and the air supply passage  415  of the piston cylinder  414  is interrupted even where air is supplied to the operation port  429  by the electromagnetic valve not shown. The air is not supplied through the operation port  429 . Consequently, the handle  455  of the knob  453  is allowed to be rotated under no air pressure thereon.  
         [0133]     In other words, the operator is allowed to rotate the manual valve to the valve closing position without applying a large force to the manual valve.  
       Fourth Embodiment  
       [0134]     A combined valve  4  in a fourth embodiment is explained referring to FIGS.  16  to  20 .  
         [0135]     As shown in  FIG. 18 , a body section of the combination  4  includes a valve body  511 , piston cylinder  512 , spool cylinder  514 , and cover  513 , which are integrally formed in one unit. The combined valve  4  is structured of a pilot valve and a manual valve. As for the combined valve  4 , “Upper” indicates a manual valve side and “Lower” indicates a pilot valve side.  
         [0136]     Firstly, the pilot valve of the combined valve  4  is explained. The pilot valve is further divided into a pilot mechanism and a valve operating mechanism. Here, the pilot mechanism includes the cylinder  512 , the spool cylinder  514 , a spring  522 , and a piston  526 .  
         [0137]     The piston cylinder  512  and the spool cylinder  514  constitute an airtight container in which the piston  526  is slidably mounted. The spring  522  is located to urge the spool cylinder  514  upwards and the piston  526  downwards.  
         [0138]     The piston  526  partitions the space defined by the piston cylinder  512  and the spool cylinder  514  into two chambers, upper and lower. The lower chamber is a pressure chamber  523  which is communicated with an operation port  529  through an air supply passage  515  formed in the piston  526  and an air supply passage  559  formed in an adjusting rod  551  mentioned later. Alternatively, the pressure chamber  523  is communicated with an exhaust port  529  through the air supply passage  515  of the piston  526 .  
         [0139]     On the other hand, the valve operating mechanism includes the valve body  511 , a diaphragm valve element  532 , and ports  533  and  534 . This structure is the same as in the combined valve  2  in the second embodiment and the combined valve  3  in the third embodiment and therefore the details thereof are not repeated here.  
         [0140]     Next, the manual valve of the combined valve  4  is explained. The manual valve includes the adjusting rod  551 , the spring  528 , the knob  553 , and a bracket  558 . Attached above the adjusting rod  551  is a knob  553  rotatable about an eccentric shaft  554 . This knob  553  includes a handle  555  and a notch  560 . An air supply passage  559  is formed in the adjusting rod  551 , providing a simple passage structure easy to make. As shown in  FIG. 20 , furthermore, the bracket  558  is interposed between two arms of the forked handle of the knob  553 . The bracket  558  is formed with a keyhole  556 .  
         [0141]     The combined valve  4  having the above structure is operated as follows.  
         [0142]     A normal operation of the pilot valve will be described first.  FIG. 18  shows the combined valve  4  with the manual valve held in a valve opening position and the pilot valve opened to allow the flow of fluid.  FIG. 19  shows the combined valve  4  with the manual valve held in the valve opening position but the pilot valve closed to prevent the flow of fluid.  
         [0143]      FIG. 18  is first explained.  FIG. 18  shows the pilot valve opened by supply of air pressure thereto through an electromagnetic valve not shown. Specifically, when air is supplied to the pilot valve through the operation port  529 , the air is fed into the pressure chamber  523  via the air supply passage formed in the adjusting rod  551  and the air supply passage  515  of the piston  526 . Then, the air pressure in the pressure chamber  523  is increased. Under upward pressure in association with the increase in air pressure in the pressure chamber  523 , the piston  526  is allowed to slide upwards in the piston cylinder  512  against the downward urging force of the spring  522 . Accordingly, the diaphragm valve element  532  integral with the piston  526  is not pressed downwards and then is brought out of contact with the valve body  511 . Thus, a passage space is generated between the diaphragm valve element  532  and the valve body  511 , providing communication between the ports  533  and  534  through the communicating area  535 . The fluid supplied into the valve body  511  through the port  533  is then discharged out through the port  534 .  
         [0144]     Next,  FIG. 17  shows the pilot valve in a closed state. Specifically, air supply into the pressure chamber  523  through the operation port  529  is stopped and the air pressure forcing the piston  526  upwards is reduced. The subsequent operations are simply the reverse of the above mentioned operations for opening the pilot valve by supply of air pressure, and the details thereof are not repeated here.  
         [0145]     Next, an operation of the manual valve when used by an operator for example as a safety mechanism during maintenance or the like is explained referring to  FIG. 16 .  FIG. 16  shows the combined valve  4  with the manual valve in the valve closing position, which is switched from the valve opening position shown in  FIG. 17  or  18 .  
         [0146]     Firstly, explanation is made on the manual valve switched from the valve opening position shown in  FIG. 18  to the valve closing position. To be concrete, the operator rotates the handle  555  of the knob  553  clockwise in front view about the eccentric shaft  554  from the valve opening position (hereinafter, referred to as a safety mechanism release position R) to a predetermined position (hereinafter, referred to as a safety mechanism set position S). Then, a pressing force of the handle  555  of the knob  553  is decreased as the rotation thereof is started, thereby allowing the adjusting rod  551  to move upwards. In this state, the communication between the operation port  529  and the air supply passage  559  of the adjusting rod  551  is closed, whereas the pressure chamber  523  is brought into communication with the exhaust port  530 . Accordingly, the air in the pressure chamber  523  is exhausted through the exhaust port  530 , causing the downward sliding of the piston  526  by the urging force of the spring  522 . Then, the diaphragm valve element  532  integral with the piston  526  is moved downwards into contact with the valve body  511 . The combined valve  4  is thus placed in the valve closed state as shown in  FIG. 16 .  
         [0147]     In the above operation, only the adjusting rod  551  is moved by the knob  553  and the piston  526  is not pressed. Accordingly, the piston  526  receives no force resulting from the rotation of the knob  553 , and the valve body  511  receives only the urging force of the spring  522  through the piston  526  and the diaphragm valve element  532 . No creep will therefore be caused, so that the sealing strength of the valve operating mechanism can be ensured.  
         [0148]     Further, for example a padlock  557  may be inserted in the keyhole  556  of the bracket  558  in the state of  FIG. 16  by the operator. In this case, the handle  555  is prevented from rotating even where air is supplied to the operation port  529 , so that the pilot valve can be maintained in the valve closed state ( FIG. 20 ). Referring to  FIG. 19 , the keyhole  556  of the bracket  558  is designed to have sufficient play or clearance to hold the adjusting rod  551  against movement even if the handle  555  wobbles when the padlock  557  is inserted in the keyhole  556 . In other words, the keyhole  556  has play enough to prevent the knob  553  from making contact with the adjusting rod  551  even when the knob  553  is rotated and the handle  555  touches a shackle of the padlock  557 . The adjusting rod  551  is therefore held against movement even when the operator erroneously touches the handle  555 . Thus, no air will be supplied into the pressure chamber  523  through the operation port  529 . In  FIG. 19 , an arrow X indicates a moving range of the handle  555  where the adjusting rod  51  is held against movement. As an alternative, the bracket  558  may be formed to have a reduced thickness. In this case, a padlock  557  with a shackle having a curved end smaller in radius may be used as shown in  FIG. 20 .  
         [0149]     Further, when the handle  555  of the knob  553  in  FIG. 18  is rotated from the safety mechanism release position R to the safety mechanism set position S, as the rotation of the handle  555  is started, the communication between the air supply passage  559  of the adjusting rod  551  and the operation port  529  is interrupted even where air is supplied to the operation port  529  by an electromagnetic valve not shown. Consequently, no air is supplied through the operation port  529  and the handle  555  of the knob  553  is thus allowed to be rotated without the air pressure thereon. In the combined valve  4  in the fourth embodiment, particularly, the diameter of the adjusting rod  551  is small and therefore the upward air pressure exerted on the adjusting rod  551  is low. Even at the beginning of rotation of the handle  555  of the knob  553 , the operator does not have to apply strong force to rotate the handle  555 .  
         [0150]     In other words, the above structure enables the operator to readily rotate the manual valve to the valve closing position.  
         [0151]     In the combined valve  4 , moreover, the air supply passage  515  is formed in the piston  526  and the spring  528  is located inside the spring  522  in a height direction as shown in FIGS.  16  to  18 . Accordingly, the combined valve  4  is of a smaller height as compared with the combined valves in the above embodiments. Here, a component urging the adjusting rod  551 , namely, the spring  528  in the present embodiment corresponds to the springs  328  and  428  in the combined valves  2  and  3  in the second and third embodiment respectively. If particularly paying attention to the positional relation of those springs, it is to be understood that the combined valve  4  is shorter in height than the combined valves  2  and  3  in the second and third embodiments.  
       Fifth Embodiment  
       [0152]     A combined valve  5  in a fifth embodiment is explained referring to FIGS.  21  to  32 .  
         [0153]      FIG. 21  is a sectional view of the combined valve  5  in a valve open state.  FIG. 22  is a top view of the combined valve  5 .  FIG. 23  is an external view of an upper part of the combined valve  5 .  
         [0154]     As shown in  FIG. 21 , a body section of the combined valve  5  includes a valve body  611 , cylinder  612 , and housing  613 . The combined valve  5  is also structured of a pilot valve and a manual valve. As for the combined valve  3 , “Upper” indicates a manual valve side and “Lower” indicates a pilot valve side.  
         [0155]     Firstly, the pilot valve of the combined valve  5  is explained. The pilot valve is further divided into a pilot mechanism and a valve operating mechanism. Here, the pilot mechanism includes the cylinder  612 , the housing  613 , a spring  622 , and a piston  626 .  
         [0156]     The cylinder  612  and the housing  613  constitute an airtight container in which the piston  626  is slidably mounted. The spring  622  is located on the piston  626  to urge the housing  613  upwards and the piston  626  downwards.  
         [0157]     The piston  626  partitions the space defined by the cylinder  612  and the housing  613  into two chambers, upper and lower. The lower chamber is a pressure chamber  623  which is communicated with an air supply port  659  mentioned later through an air supply passage  615  formed in the piston  626 .  
         [0158]     As shown in FIGS.  21  to  23 , the housing  613  is formed with an operation port  629 , exhaust port  630 , and air supply port  659 , which constitute a 3-port valve shown in  FIGS. 24A  to  24 C in combination with a rod  651  mentioned later.  FIGS. 24A  to  24 C are sectional views of a part of the combined valve  5  taken along a line A-A of  FIG. 25 .  FIG. 24A  shows the manual valve placed in a valve opening position;  FIG. 24C  shows the manual valve in a valve closed position; and  FIG. 24B  shows the manual valve in an intermediate position between those in  FIG. 24A and 24 .  
         [0159]     On the other hand, the valve operating mechanism includes the valve body  611 , a diaphragm valve element  632 , and ports  633  and  634 . This structure is the same as in the combined valves  2  to  4  in the second to fourth embodiments and therefore the details thereof are not repeated here.  
         [0160]     Next, the manual valve of the combined valve  5  is explained. The manual valve includes a rod  651 , knob  653 , gaskets  661 ,  662 , and  663 , and slide plate  665 . The rod  651  is fit in a through hole  667  formed in the housing  613 . The knob  653  is rotatably attached to one end of the rod  651 . The knob  653  is provided with a handle  655 . The rod  651  is formed with a pin  664  placed in a hole of the knob  653 . The gasket  661  having the shape shown in  FIG. 26  is located on the outer periphery of the rod  651  at its center area in an axial direction. The gaskets  662  and  663  are located surrounding the rod  651  at both sides of the gasket  61  in the axial direction. The slide plate  665  is placed above the rod  651 .  FIG. 26A  is a top view of the gasket  661  and  FIG. 26B  is a sectional view of the gasket  661  taken along a line A-A of  FIG. 26A .  
         [0161]     The combined valve  5  having the above structure is operated as follows.  
         [0162]     A normal operation of the pilot valve will be described first.  FIG. 21  shows the combined valve  5  with the manual valve held in the valve opening position and the pilot valve opened to allow the flow of fluid.  FIG. 25  shows the combined valve  5  with the manual valve held in the valve opening position but the pilot valve closed to prevent the flow of fluid.  
         [0163]      FIG. 21  is first explained.  FIG. 21  shows the pilot valve opened by supply of air pressure thereto through an electromagnetic valve not shown. Specifically, when air is supplied to the pilot valve through the operation port  629 , the air passes through the space formed between the outer periphery of the rod  651  and the through nole  667  and the air supply passage  659  and then the air is fed into the pressure chamber  623  through the air supply passage  615  in the piston  626 . Accordingly, the air pressure in the pressure chamber  623  is increased. Under upward pressure in association with the increase in air pressure in the pressure chamber  623 , the piston  626  is allowed to slide upwards in the cylinder  612  against the downward urging force of the spring  622 . Then, the diaphragm valve element  632  integral with the piston  626  is not pressed downwards and is brought out of contact with the valve body  611 . A passage space is accordingly generated between the diaphragm valve element  632  and the valve body  611 , providing communication between the ports  633  and  634  through the communicating area  635 . The fluid supplied into the valve body  611  through the port  633  is then discharged out through the port  634 .  
         [0164]     Next,  FIG. 25  shows the pilot valve in the closed state. Specifically, air supply into the pressure chamber  623  through the operation port  629  is stopped and the air pressure forcing the piston  626  upwards is reduced. The subsequent operations are simply the reverse of the above mentioned operations and the details thereof are not repeated here.  
         [0165]     Next, an operation of the manual valve when used by an operator for example as a safety mechanism during maintenance or the like is explained referring to  FIGS. 27 and 28 .  FIG. 27  is a sectional view of the knob  653  taken along a line B-B of  FIG. 25 .  FIGS. 28A  to  28 C are explanatory views showing a relation between the knob  653 , rod  651 , and pin  664 .  
         [0166]     Explanation is made on the manual valve switched from the valve opening position to the valve closing position. To be concrete, the operator rotates the handle  655  of the knob  653  couterclockwise in front view in  FIG. 27  from the valve opening position (hereinafter, referred to as a safety mechanism release position R) to a predetermined position (hereinafter, referred to as a safety mechanism set position S). When the handle  655  is rotated by a predetermined angle from a state of  FIG. 28A  to a different state of  FIG. 28B , the rotation of the knob  653  is transmitted to the rod  651  through the pin  664 , causing the rod  651  to rotate. When the handle  655  has completely been rotated to the safety mechanism set position S, the knob  653  is positioned as shown in  FIG. 28C .  
         [0167]     The knob  653  is provided as shown in  FIG. 28  with a predetermined amount of play to provide a delay until the rotating of the knob  653  is transmitted to the rod  651  through the pin  664 . In other words, backlash is provided for the rotating amount of the rod  651  with respect to the rotating amount of the knob  653 . The rotating amount with backlash is set in a range from 90 degrees to 110 degrees. Accordingly, the rotating amount of the knob  653  is 180 degrees, whereas the actual rotating amount of the rod  651  is in a range from 70 degrees to 90 degrees.  
         [0168]     When the manual valve is rotated to the safety mechanism set position S, the communication between the operation port  629  and the air supply port  659  is interrupted with the gasket  661 , while the exhaust port  630  is communicated with the air supply port  659  and hence with the pressure chamber  623 . Accordingly, air is exhausted through the exhaust port  630 , reducing the air pressure in the pressure chamber  623 . The piston  626  is slid downwards by the urging force of the spring  622 . The diaphragm valve element  632  coupled to the piston  626  is also then moved downwards into contact with the valve body  611 , bringing the combined valve  5  to the valve closed state.  
         [0169]     Further, the slide plate  665  is slid from the above position toward the knob  653  until an end of the slide plate  665  protrudes as shown in  FIGS. 21 and 23 . A padlock  657  for example is inserted and locked in a key hole  665   a  formed in the end of the slide plate  665 . In this state, the knob  653  is prevented from rotating and therefore the combined valve  5  can be held in the valve closed state.  
         [0170]     The slide plate  665  may be slid by;  
         [0171]     (1) Pushing a lug  665 b of the slide plate  665  with fingers; or  
         [0172]     (2) Utilizing a return spring placed between the slide plate  665  and the housing  613  for automatic sliding.  
         [0173]     To be concrete, the above manner (2) that utilizes the return spring for automatic sliding may include the following techniques A and B.  
         [0174]      FIGS. 29A  to  29 D are schematic views of the manual valve to explain the technique A; specifically,  FIG. 29A  is a side view of the manual valve in the valve opening position,  FIG. 29B  is a sectional view of the same,  FIG. 29C  is a side view of the manual valve in the valve closing position, and  FIG. 29D  is a sectional view of the same.  
         [0175]     In the technique A, the slide plate  665  is provided with the lug  665   b  and a hook  665   c  as shown  FIGS. 29A  to  29 D, and a return spring  666  is located between the slide plate  665  and the housing  613 . While the manual valve is in the valve opening position, the hook  665   c  is engaged with a flange  651   a  of the rod  651  as shown in  FIG. 29A and 29B , thereby holding the slide plate  665  against sliding. In this state, tension is exerted on the return spring  666 .  
         [0176]     The flange  651   a  of the rod  651  includes a notch formed along the periphery thereof. When the knob  653  is rotated to bring the manual valve to the valve closing position, the notch will be adjusted to face to the hook  665   c  of the slide plate  665  as shown in  FIGS. 29C and 29D . The hook  665   c  of the slide plate  665  is then disengaged from the flange  651   a  of the rod  651 . Accordingly, the tension exerted on the return spring  666  is eliminated, allowing automatic sliding the slide plate  665 .  
         [0177]      FIGS. 30A and 30B  are schematic views of the manual valve to explain the technique B; specifically,  FIG. 30A  is a sectional view of the manual valve in the valve opening position and  FIG. 30B  is a sectional view of the same in the valve closing position.  
         [0178]     In the technique B, the slide plate  665  is similarly provided with the lug  665   b  and a return spring  666  is located between the slide plate  665  and the housing  613 . This technique B adopts the reverse operation of the return spring  666  to that in the technique A. To be concrete, while the lug  665   b  of the slide plate  665  is not pressed with fingers, the return spring  666  is held in a natural length, generating no spring force. The slide plate  665  is therefore held in a non-sliding state. To slide the slide plate  665 , the lug  665   b  is pushed with fingers, thereby compressing the return spring  666 .  
         [0179]     Another configuration using a padlock  657  may be adopted as shown in  FIGS. 31 and 32 . In this combined valve  5 , the rod  651  is provided with a flange  651   a  at an end opposite to the knob  653  side. This flange  651   a  has a shape shown in  FIG. 32 . In particular, the flange  651   a  is oriented as shown by a solid line in  FIG. 32  when the manual valve is in the valve opening position. On the other hand, the flange  651   a  is oriented as shown by a double-dashed line in  FIG. 32  when the manual valve is in the valve closing position. When the manual valve is in the valve closing position, accordingly, the keyhole  651   b  is placed vertically above the housing  613 . In this position, the padlock  657  or the like is engaged for locking.  
         [0180]     In the above operation, only the rod  651  is moved by the knob  653  and the piston  626  is not pressed. Accordingly, the piston  626  receives no force resulting from the rotation of the knob  653 , and the valve body  611  receives only the urging force of the spring  622  through the diaphragm valve element  632 . No creep will therefore be caused, so that the sealing strength of the valve operating mechanism can continuously be ensured.  
         [0181]     Further, when the handle  655  of the knob  653  in  FIG. 21  is rotated from the safety mechanism release position R to the safety mechanism set position S, as the rotation of the handle  655  is started, the communication between the air supply passage  659  and the operation port  629  is interrupted by the gasket  661  of the rod  651  even when air is supplied to the operation port  629  by an electromagnetic valve not shown. Consequently, no air is supplied through the operation port  629  and the handle  655  of the knob  653  is thus allowed to be rotated under no air pressure thereon.  
         [0182]     The above structure enables the operator to readily rotate the manual valve to the valve closing position without applying a large force to the manual valve.  
         [0183]     In the combined valve  5 , moreover, the rod  651  is placed in a lateral direction perpendicular to a vertical (height) direction of the combined valve  5  and also the knob  653  is provided on the side of the combined valve  5 . Accordingly, the combined valve  5  is shorter in height than the combined valves  1  to  4  in the first to fourth embodiment where the valve mechanisms are arranged vertically and coaxially.  
         [0184]     According to the above embodiments of the present invention, the above combined valves include a mechanism for preventing or covering a decrease in sealing strength of the valve operating function due to creep phenomenon which may occur in the valve seats. If the valve seats are made of fluorocarbon resin having resistance to corrosion, therefore, those combined valves may also be applied to a chemical liquid valve used in a semiconductor manufacturing process.