Abstract:
A diaphragm valve for opening or closing itself through making direct contact of or through breaking the direct contract of a metal diaphragm with a valve seat disposed inside a body provided with an inlet port and an outlet port, includes an elevating member which serves to make or break the direct contact of the metal diaphragm with the valve seat and which is fusion-bonded to the metal diaphragm.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a diaphragm valve of the so-called direct seal structure used as in a gas feeding system for the process of fabricating semiconductors or the process of producing liquid crystals and operated to open or close a fluid flow path by causing a valve body formed of a diaphragm to make or break direct contact with a valve seat.  
       DESCRIPTION OF THE PRIOR ART  
       [0002]     A diaphragm valve that is provided in the interior thereof with a seal structure formed of a metallic diaphragm and metallic seat packing has been prevailing to date. This diaphragm valve  1 , as illustrated in  FIG. 4 , forms a seal structure with a so-called domed diaphragm  2  having a swelled central part and seat packing  3 , disposes a vertically movable diaphragm-depressing member  4  above the diaphragm  2 , and enables the diaphragm  2  to be actuated by vertically moving the diaphragm-depressing member  4  with a stem  5 . At the time of closing the valve, by rotating a handle  6 , thereby moving the stem  5  downwardly and depressing the diaphragm-depressing member  4  in the direction of the diaphragm  2  as illustrated on the left side of the cross section, a polished surface  2   a  of this diaphragm  2  is enabled to seal the seat packing  3  and consequently block a flow path  7 . At the time of opening the valve, by rotating the handle  6  in the opposite direction to the direction used in closing the valve, thereby moving the stem  5  upwardly and raising the diaphragm-depressing member  4  upwardly as illustrated on the right side of the cross section, the diaphragm  2  is caused by its elastic force to restore the domed shape of keeping the valve opened and the flow path  7  is enabled to assume the opened state. The surface of the diaphragm-depressing member  4  for depressing the diaphragm  2  is formed in the shape of an arcuate face  4   a . By the contact of this arcuate surface  4   a , the diaphragm  2  is enabled to maintain the state from the time of closing the valve till the time of opening it. By the depression exerted by this arcuate surface  4   a  on the diaphragm  2 , the seat packing  3  is enabled to effect the sealing more positively and keep the flow path  7  in the closed state.  
         [0003]     Then, a diaphragm valve forming a diaphragm in an upwardly spherical shape, causing this diaphragm to form on the circumference slightly to the center an annularly projecting part of an arcuate cross section having the upper surface dented downwardly and the lower surface projected downwardly, forming a valve seat destined to be pressed by the leading terminal of the annular projecting part of the diaphragm in an annular shape having a flat upper surface, and hardening the upper surface of the annular valve seat by a treatment has been also known (refer, for example, to JP-B HEI 6-27551).  
         [0004]     A diaphragm valve having a diaphragm sealed and immobilized by causing an annular projection formed along the peripheral part of the diaphragm to be nipped on the outer peripheral side and the inner peripheral side thereof with the annular projection formed for retaining a main body or the diaphragm and an annular groove formed on the opposite side from the diaphragm at the position corresponding to the annular projection has been further known (refer, for example, to JP-A 2002-340203).  
         [0005]     Meanwhile, a diaphragm valve of a structure other than the direct seal structure resorting to a diaphragm that has a disc  12  disposed in a lower part than a diaphragm  11  and a sealing member  13  inserted in the lower part of this disc  12  as illustrated in  FIG. 5  has been known. This diaphragm valve  10  is enabled, by vertically moving a stem  14  as illustrated in the cross section, to bring the sealing member  13  into contact with a valve seat  15  and open or close a flow path  16 .  
         [0006]     The diaphragm valve  1  of the direct seal structure shown in  FIG. 4 , however, has the possibility that the operation of opening the valve will entail the phenomenon of causing the diaphragm  2  to be drawn toward the flow path  7  and resulting in decreasing the flow volume because it is adapted to retain the diaphragm  2  solely by virtue of the state of causing the diaphragm depressing member  4  to be kept in contact therewith. Particularly, when the diaphragm valve  1  happens to have a large diameter, the surface area of the diaphragm  2  exposed to the pressure of the fluid is proportionally increased. When the value of this large diameter is used in the state of vacuum, the load of negative pressure possibly causes the diaphragm  2  to sink as though it were copiously drawn in the direction of the seat packing  3  and induces the valve to be spontaneously closed besides decreasing the flow volume.  
         [0007]     Further, since in the diaphragm valve  1  the diaphragm  2  is adapted to form the domed shape by dint of its restoring force during the operation of opening the valve, it is required to be attached to the diaphragm-depressing member  4  in such a manner as to ensure formation of the domed shape. The diaphragm  2  is attached as adjusted for enabling exclusively the neighborhood of a top part  4   b  to contact the diaphragm-depressing member  4  during the operation of opening the valve.  
         [0008]     When the diaphragm-depressing member  4  is moved downward through the motion of the stem  5 , the diaphragm  2  carries out a stroking motion while it is deformed along the arcuate surface  4   a  from the top part  4   b  of the diaphragm-depressing member  4 . At this time, the stem stroke L 1  of the stem  5  in the vertical direction is converted to the valve stroke L 2  which is the distance from the position which the top part  4   b  assumes when the valve begins to open to the position at which the seat packing  3  is sealed and the stroke (not shown) in the vertical direction of the amount of deformation produced by the diaphragm  2  along the arcuate surface  4   a . Consequently, the valve stroke L 2  of the diaphragm  2  to the seat packing  3  is shorter than the stem stroke L 1  of the stem  5 . When the stem stroke L 1  of the stem  5  happens to be 1.8 mm in the diagram of  FIG. 4 , for example, the valve stroke L 2  of the diaphragm  2  measures 1.0 mm. The valve stroke L 2 , therefore, is shorter than the stem stroke L 1 .  
         [0009]     Thus, the diaphragm valve  1  has not been efficient because the valve stroke L 2  acquired thereby is not equal in size to the stem stroke L 1  and the flow volume acquired thereby is small for the size of the stem stroke L 1 . Further, the diaphragm valve  1  is required during the course of manufacture to have the stem stroke L 1  set in advance at a prescribed magnitude for the purpose of obtaining the same magnitude as the valve stroke L 2 .  
         [0010]     Further, an effort to increase the flow volume by giving the diaphragm valve  1  a large diameter and enlarging the area for passing the fluid has resulted in suffering the amount of deformation of the diaphragm  2  relative to the arcuate surface  4   a  to increase further proportionately to the size of the area for passage in addition to entailing the aforementioned problem of the diaphragm  2  being drawn in the direction of the seat packing  3 . As a result, the proportion of the valve stroke L 2  to the stem stroke L 1  is decreased and the proportion of the flow volume consequently obtained is decreased in accordance as the area for passing the fluid (seat diameter of the seat packing  3 ) is increased.  
         [0011]     The diaphragm valve of JP-B HEI 6-27551 is aimed at increasing the Cv value which is the coefficient of flow volume by preventing the diaphragm from ruffling (furrowing) when the diaphragm is being sealed and by enlarging the stroke of the diaphragm, thereby widening the gap between the lower surface of the diaphragm and the upper surface of the annular valve seat during the operation of opening the valve. Since this diaphragm valve is not different from the countertype of  FIG. 4  in possessing the structure of opening or closing the flow path by vertically moving the stem which is in the state of keeping contact with the upper side of the diaphragm in the doped shape, it cannot prevent the phenomenon of the diaphragm being drawn in the direction of the seat packing and cannot easily overcome the problem, such as the decrease of the flow volume.  
         [0012]     As regards the diaphragm valve of JP-A 2002-340203, it is aimed at providing the diaphragm with a prescribed restoring force and consequently stabilizing the ability of the valve to open or close the flow path by having the inner and outer peripheral surfaces of the projection excluding the annular projection nipped and sealed through the diaphragm. The idea of causing the valve to assume an opened state by dint of the restoring force of the diaphragm, similarly to the invention of JP-B HEI 6-27551, falls short of preventing the decrease of the flow volume during the operation of opening the valve.  
         [0013]     The diaphragm valve  10  which opens or closes the flow path by dint of the seal member  13  of the disc  12  as shown in  FIG. 5  has the stroke of the stem  14  form as it is the valve stroke L 3  of the disc  12  and is allowed to increase the flow volume during the operation of opening the valve because this valve stroke L 3  can be increased. This structure of having the diaphragm  11  attached as nipped on the upper side of the disc  12  by helical attachment of the disc  12 , however, induces the occurrence of a gap between the disc  12  and the diaphragm  11  and consequently entails the problem that the disc  12  and the diaphragm  11  will rub against each other and give rise to particles.  
         [0014]     This invention has been initiated in view of the conventional problems and has for an object thereof the provision of a diaphragm valve of the direct seal structure capable of increasing the flow volume during the operation of opening the valve, namely a diaphragm valve that is capable of infallibly suppressing the generation of particles.  
       SUMMARY OF THE INVENTION  
       [0015]     A first aspect of the present invention provides a diaphragm valve for opening or closing a fluid flow path through making direct contact of or through breaking the direct contract of a metal diaphragm with a valve seat disposed inside a body provided with an inlet port and an outlet port, comprising an elevating member which serves to make or break the direct contact of the metal diaphragm with the valve seat and which is fusion-bonded to the metal diaphragm.  
         [0016]     In a second aspect that includes the first aspect of the invention, the metal diaphragm has a perforation approximately at a central position thereof and the metal diaphragm and the elevating member are welded together at the position of this perforation.  
         [0017]     In a third aspect that includes the first aspect of the invention, the elevating member comprises a manually or automatically driven stem or a manually or automatically driven stem and a diaphragm piece interlocked with the stem.  
         [0018]     In a fourth aspect that includes the first aspect of the invention, the metal diaphragm is a metal having a high degree of hardness including a Ni—Co alloy, and the valve seat is disposed integrally with or separately from the body and is a metal including SUS 316L having a lower degree of hardness than the metal diaphragm.  
         [0019]     In a fifth aspect that includes the first aspect of the invention, the valve seat is a heat-resistant nonmetallic member of PTFE, PI, PCTFE or PFA and the metal diaphragm is a metal including Ni—Co alloy, SUS, inconel and hastelloy.  
         [0020]     In a sixth aspect that includes the third aspect of the invention, the stem has a depressing part at a lower end thereof, the depressing part or the diaphragm piece and the metal diaphragm are so disposed as to contact each other always at a sealing position of the valve seat.  
         [0021]     In a seventh aspect that includes the first aspect of the invention, the valve seat is set in position at a level lower by a valve stroke than an outer peripheral part of a seal of the metal diaphragm.  
         [0022]     In an eighth aspect that includes the seventh aspect of the invention, the valve seat is set in position at a level lower by about ½ of the valve stroke.  
         [0023]     The first aspect of the invention provides a diaphragm valve that enables the flow volume during the operation of opening the valve to be increased because the metal diaphragm is not drawn in the direction of the flow path and because the stroke during the course of operation can be substantially equalized with the stroke of the metal diaphragm. The diaphragm valve further can infallibly suppress the generation of particles during the operation of the valve body and infallibly retain the prescribed flow volume during the course of service in a vacuum state without the possibility of blocking the valve body.  
         [0024]     The second aspect of the invention concerns a diaphragm valve that is capable of enhancing the durability of the valve body because the central portion of the valve body is vertically moved so that the valve body may be displaced to positions above and below the position of the outer diameter of the seal during the course of the operation of the valve body. It is also capable of opening or closing the valve body infallibly and, at the same time, permitting the structure of infallibly operating the valve body to be easily disposed, and simplifying the valve interior owing to this internal structure. It is further capable of preventing the generation of particles more infallibly.  
         [0025]     The third aspect of the invention provides a diaphragm valve that enables the valve body to be infallibly operated during either a manual operation or an automatic operation using an electric actuator and enables fine adjustment of the flow volume to be infallibly effected by directly operating the valve body.  
         [0026]     The fourth aspect of the invention provides a diaphragm valve that is capable of retaining highly accurate adjustment of the flow volume through repeated opening and closing operations without the possibility of inflicting damage to the valve body. This diaphragm valve, even when the sealing property thereof is deteriorated, is still capable of permitting easy maintenance and retaining high sealing property constantly.  
         [0027]     The fifth aspect of the invention provides a diaphragm valve that is capable of successfully handling even a fluid of high temperature and manifesting a high sealing property infallibly. This diaphragm valve is also capable of avoiding infliction of damage on the valve body.  
         [0028]     The six aspect of the invention provides a diaphragm valve that is capable of allowing the stroke of the valve body to be increased and the flow volume to be increased and, while the fluid is flowing, enabling the flow volume to be retained at a fixed level constantly.  
         [0029]     The seventh and eighth aspects of the invention provide a diaphragm valve that is capable of allowing the flow volume to be increased by widening the gap between the valve body and the surface of the valve seat during the operation of opening the valve and, during the course of the operation of closing the valve, maintaining the sealing property infallibly.  
         [0030]     The above and other objects, characteristic features and advantages of the present invention will become apparent to those skilled in the art from the description given herein below with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a halved cross section illustrating one embodiment of the diaphragm valve according to the present invention.  
         [0032]      FIG. 2  is a halved cross section illustrating the diaphragm valve of  FIG. 1  in a state of keeping the valve closed.  
         [0033]      FIG. 3  is a partly magnified cross section illustrating the diaphragm valve of this invention in the states of opening and closing the valve.  
         [0034]      FIG. 4  is a halved cross section illustrating a conventional diaphragm valve.  
         [0035]      FIG. 5  is a halved cross section illustrating another conventional diaphragm valve. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0036]     One preferred embodiment of the diaphragm valve contemplated by this invention will be described below with reference to the accompanying drawings.  
         [0037]     A diaphragm valve main body  20  illustrated in  FIG. 1  through  FIG. 3  comprises as principal components a body  21 , a metal diaphragm  22 , an elevating member  24  and a valve seat  25 . The valve has a structure such that it is opened or closed by causing the metal diaphragm  22  to directly contact the valve seat  25  disposed inside the body  21 .  
         [0038]     The body  21  is formed of a metal, such as stainless steel. Inside this body  21 , a primary side approximately L-shaped inflow port  21   a , a secondary side approximately L-shaped outflow port  21   b , and a valve chamber  21   c  so formed as to pass along the upper sides thereof. Below the valve chamber  21   c , a fitting groove  21   d  is formed.  
         [0039]     The metal diaphragm  22  is formed, approximately in the shape of a dome, of an extremely hard metal, such as Ni—Co alloy, SUS, inconel, hastelloy or other such metallic material. The valve seat  25  is formed of a metal, such as SUS 310 having a lower hardness than the metal diaphragm  22  and disposed integrally with or separately from the body  21 . This valve seat  25  may be made of a heat-resistant nonmetallic material, such as PTFE, PI, PCTFE or PFA.  
         [0040]     The elevating member  24  comprises a manually or automatically driven stem  28  or a combination of such a stem  28  and a diaphragm piece  23  that is driven as interlocked with the stem  28 . In the present embodiment, the diaphragm piece  23  is used as the elevating member  24  and the metal diaphragm  22  is welded to the diaphragm piece  23  so that the metal diaphragm  22  may be enabled by the diaphragm piece  23  to make or break contact with the valve seat  25 . Specifically, the metal diaphragm  22  is provided approximately at the central position thereof with a through hole  22   a  and the metal diaphragm  22  and the diaphragm piece  23  are integrally fusion-bonded by being welded with a welding part P at the position of this through hole  22   a.    
         [0041]     When the stem  28  is used as the elevating member  24 , it suffices to form the stem  28  in a shape for opening or closing the metal diaphragm  22  and welding the metal diaphragm  22  directly to the stem  28 . In any event, an unshown depressing part at the lower end of the stem  28  or the diaphragm piece  23  is so disposed as to contact the valve seat  25  always at the seal position. To be specific, the metal diaphragm  22  is adapted to assume a constantly deformed state at the plane of contact with an arcuate surface part  23   d  ( FIG. 3 ) of the diaphragm piece  23  or an arcuate surface part formed on an unshown steam, no matter whether the valve is in an opened state or a closed state.  
         [0042]     At the time of assembling the diaphragm valve main body  20 , the metal diaphragm  22  welded to the diaphragm piece  23  has its peripheral edge portion mounted on a stepped part  21   e  formed inside the body  21  and a roughly annular diaphragm retainer  26  is mounted from above and immobilized thereon to have the metal diaphragm  22  inserted airtightly between the stepped part  21   e  and the retainer  26 . In the diaphragm retainer  26 , a retaining part  23   a  formed as radially diverged on the leading end side of the diaphragm piece  23  is fitted in so as to be inserted into an inserting hole  26   a . At this time, the diaphragm piece  23  is fitted in a state prevented from rotating by causing more than one projecting parts  23   b  formed on the depressing part  23   a  of the diaphragm piece  23  to be loosely inserted into grooved parts  26   b  formed at the corresponding positions of the inserting hole  26   a.    
         [0043]     A cylindrical part  27  made of a metal is inserted from above so as to depress the diaphragm retainer  26  while a male thread  27   a  formed on the outer side thereof is managed to be helically attached to a female thread  21   f  formed at the corresponding position of the body  21 , with the result that the metal diaphragm  22  will be nipped and immobilized between the diaphragm retainer  26  and the stepped part  21   e . The stem  28  is fitted so as to attach helically a male thread  28   a  to a female thread  27   b  formed inside the cylindrical member  27 . The stem  28  has a female thread  28   b  formed therein. A male thread  23   c  formed on the diaphragm piece  23  is helically attached to the female thread  28   b.    
         [0044]     The male thread  28   a  of the stem  28  and the female thread  27   b  of the cylindrical member  27 , and the male thread  23   c  of the diaphragm piece  23  and the female thread  28   b  of the stem  28  are formed each by the combination of prescribed pitches to form a mechanism adapted to decrease the amount of motion of the diaphragm piece  23  relative to the amount of vertical motion of the stem  28  and enable the diaphragm piece to be vertically moved in a minute amount at a time.  
         [0045]     A drive means  30 , such as a manual handle, is fixed with a pin  31  on the stem  28  in a state of preventing rotation and it is so disposed that the rotation of this drive means  30  may rotate the stem  28  relative to the cylindrical member  27  and impart a vertical motion to the diaphragm piece  23 . The drive means  30  may be any of various devices operated electrically, pneumatically and electromagnetically besides the manual handle.  
         [0046]     When the drive means  30  is set rotating from the state of  FIG. 1  and consequently made to depress the diaphragm piece  23  toward the depressing part  23   a , the metal diaphragm  22  is depressed by the diaphragm piece  23  toward of the valve seat  25  and the metal diaphragm  22  is made to collide against and seal the valve seat  25  as illustrated in  FIG. 2 , with the result that the fluid flowing inside the body  21  is blocked. The valve seat  25  is so adapted as to lower at this time the position of the valve seat  25  by less than the valve stroke S from the stepped part  21   e  which is the outer peripheral sealing part of the metal diaphragm  22 . Further, the height H from the valve seat surface  25   a  to the stepped part  21   e  is set at approximately ½ of the stroke S and the position of the valve seat  25  is lowered by less than the valve stroke S as illustrated in  FIG. 3 . The height H may be properly varied with the diameter of the diaphragm piece  23  or the valve seat surface  25   a  and the ratio thereof to the stroke S may be also varied.  
         [0047]     Now, the function of the embodiment in the diaphragm valve of this invention will be described below.  
         [0048]     Since the diaphragm valve of this invention has the elevating member  24  for causing the metal diaphragm  22  to make or break contact with the valve seat  25  welded to the metal diaphragm  22 , the metal diaphragm  22  can be forcibly set to motion when the derive means  30  is operated to impart a vertical motion to the elevating member  24  (diaphragm piece  23 ). As a result, the metal diaphragm  22  is not drawn toward the inflow port  21   a  or the outflow port  21   b  during the operation of opening the valve and this metal diaphragm  22  is consequently enabled to retain the domed shape thereof intact and maintain the flow volume of the fluid infallibly without being spontaneously blocked.  
         [0049]     Furthermore, since the stroke S of the diaphragm piece  23  equals the stroke of the metal diaphragm  22 , the flow volume which conforms to this stroke S can be obtained as it is and, even when the flow volume is increased by forming the diaphragm valve in a large diameter, the flow volume can be efficiently retained relative to the stroke S. Since the metal diaphragm  22  and the diaphragm piece  23  are fixed, no component part is suffered to generate friction or give rise to particles.  
         [0050]     This invention is ideal for diaphragm valves in the gas supply system and the gas discharge system in the process for fabricating semiconductors or the process for producing liquid crystals and it can be extensively applied to other various fields.