Abstract:
A check valve comprises: a pair of cylindrical body elements ( 1, 4 ) through which a fluid passes; a cylindrical valve element ( 7 ), which is disposed inside an upstream-side one ( 4 ) of the cylindrical body elements ( 1, 4 ), constantly subjected to a fluid pressure and biased toward its closed position under the influence of a resilient force exerted by a compression coil spring ( 10 ) coated with a tubular element; and, a stopper element ( 24 ) disposed in a downstream-side one ( 4 ) of the cylindrical body elements ( 1, 4 ). The check valve is characterized in that at least one of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is provided with a spiral seat portion ( 11 ) an axial spiral surface of which is brought into stable surface-contact with the compression coil spring ( 10 ) to support the compression coil spring ( 10 ) therein.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a check valve, and more particularly to a check valve provided with a spring seat portion which has its spiral seat surface brought into press-contact with at least one of opposite terminal turns of a compression coil spring to support the compression coil spring. 
   2. Description of the Related Art 
   In general, as viewed from  FIG. 3 , a conventional check valve has a single cylindrical body element  21 , slidably and coaxially mounted in an upstream-side portion of which body element  21  is a cylindrical valve element  23 . This cylindrical valve element  23  has its inner shoulder portion brought into press-contact with one of opposite open ends of a compression coil spring  22  and is therefore constantly biased leftward to its closed position by a biasing device such as the compression coil spring  22  in a longitudinal direction of the cylindrical body element  21 . Fixedly and coaxially mounted in a downstream-side bore portion of the cylindrical body element  21  is an annular stopper element  24  for receiving the other of the opposite open ends of the compression coil spring  22 . 
   In operation, when the cylindrical valve element  23  is subjected to a fluid pressure which is larger than a predetermined value, the cylindrical valve element  23  is forcibly moved rightward by the fluid pressure against the biasing force exerted by the compression coil spring  22 , so that a fluid passage of the check valve having been closed by the cylindrical valve element  23  is now opened. An O-ring  25  is fixedly mounted in an annular groove formed in an outer peripheral surface of a head portion of the cylindrical valve element  23  to ensure that the fluid passage of the check valve is fluid-tightly closed by the cylindrical valve element  23  when the fluid pressure is smaller than the predetermined value. 
   As for the biasing force exerted by the compression coil spring  22 , it is desirable to have such biasing force applied evenly to the entire circumferential area of the inner shoulder portion of the cylindrical valve element  23 . More specifically, when the biasing force is applied unevenly to the inner shoulder portion of the cylindrical valve element  23 , the cylindrical valve element  23  tends to incline inside the cylindrical body element  21 . Such inclination of the cylindrical valve element  23  inside the cylindrical body element  21  results in leakage of the fluid inside the cylindrical body element  21  in its closed configuration. In order to prevent such leakage of the fluid in the closed position of the cylindrical valve element  23 , it is necessary to have each of the opposite open ends of the compression coil spring  22  formed into a closed-end flat shape extending in a vertical plane perpendicular to the longitudinal direction of the cylindrical body element  21 , as viewed in FIG.  3 . The thus formed closed-end flat shape of each of the opposite ends of the compression coil spring  22  is capable of being brought into surface-contact with each of the cylindrical valve element  23  and the stopper element  24 , and therefore capable of having the biasing force of the compression coil spring  22  evenly applied to the entire circumferential area of the inner shoulder portion of each of the cylindrical valve element  23  and the stopper element  24 . 
   In the art of semiconductor fabrication in which the check valve is used in transferring a cleaning fluid, the compression coil spring  22  serving as a biasing device of the check valve is coated with a tubular element made of fluororesins to improve the compression coil spring  22  in chemical resistance. Due to the presence of such tubular element, in the art of semiconductor fabrication, it is impossible to form each of opposite open ends of the compression coil spring into a closed-end shape. 
   As is clear from the above description, the compression coil spring  22  tends to obliquely push the cylindrical valve element  23  inside the cylindrical body element  21 , which makes it impossible for the head portion of the cylindrical valve element  23  to be uniformly brought into press-contact with the O-ring  25 . This results in leakage of the fluid in the area of the O-ring  25  when the check valve is in its closed configuration, and also results in vibrations and issuance of noise of the cylindrical valve element  23  inside the cylindrical body element  21  due to misalignment in longitudinal axis between the cylindrical valve element and the cylindrical body element  21 . 
   SUMMARY OF THE INVENTION 
   Under such circumstances, the present invention was made. Consequently, it is an object of the present invention to provide a check valve free from any vibration and noise problems inherent in the conventional check valve. 
   The above object of the present invention is accomplished by providing: 
   A check valve comprising: a pair of body elements ( 1 ,  4 ) through which a fluid passes; a cylindrical valve element ( 7 ), which is disposed inside an upstream-side one ( 1 ) of the body elements ( 1 ,  4 ), constantly subjected to a fluid pressure and biased toward its closed position under the influence of a resilient force exerted by a compression coil spring ( 8 ) coated with a tubular element; and, a stopper element ( 24 ) disposed inside one ( 4 ) of the body elements ( 1 ,  4 ), CHARACTERIZED IN THAT: at least one of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is provided with a spiral seat portion ( 11 ) a spiral surface of which is brought into press-contact with the compression coil spring ( 10 ) to support the compression coil spring ( 10 ). 
   In the check valve having the above construction, preferably each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is provided with the spiral seat portion ( 11 ). 
   Further, preferably the spiral seat portion ( 11 ) of each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is integrally formed with each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ). 
   Still further, preferably the spiral seat portion ( 11 ) of each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is separated in construction from each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) to form a separate element. 
   Preferably, the spiral surface of the spiral seat portion ( 11 ) of each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) is brought into press-contact with one of opposite turns of the compression coil spring ( 10 ). 
   Further, preferably the spiral surface of the spiral seat portion ( 11 ) of each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) assumes a concave shape in cross section. 
   Still further, preferably the spiral surface of the spiral seat portion ( 11 ) of each of the cylindrical valve element ( 7 ) and the stopper element ( 24 ) assumes a semi-circular groove-like shape in cross section. 
   Preferably, an O-ring ( 8 ) is mounted in an innermost portion of one ( 1 ) of the body elements ( 1 ,  4 ) and brought into press-contact with a head portion of the cylindrical valve element ( 7 ) when the cylindrical valve element ( 7 ) is in its closed position to prevent the fluid from passing through an area between the O-ring ( 8 ) and the head portion of the cylindrical valve element ( 7 ). 
   Further, preferably the head portion of the cylindrical valve element ( 7 ) has its peripheral surface curved to form a curved peripheral surface portion which is brought into press-contact with the O-ring ( 8 ) when the cylindrical valve element ( 7 ) is in its closed position to prevent the fluid from passing through the area between the O-ring ( 8 ) and the head portion of the cylindrical valve element ( 7 ). 
   Preferably: the body elements ( 1 ,  4 ) comprise an upstream-side body element ( 1 ) and a downstream-side body element ( 4 ) a portion of which is threadably mounted in the upstream-side body element ( 1 ); and, the downstream-side body element ( 4 ) comprises the stopper element ( 24 ). 
   Further, preferably the tubular element of the compression coil spring ( 8 ) is made of fluororesins. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a longitudinal sectional view of an embodiment of the check valve of the present invention; 
       FIG. 2  is a perspective view of a spiral seat portion of each of the cylindrical valve element and the stopper element for supporting the biasing device such as a compression coil spring employed in the check valve of the present invention shown in  FIG. 1 ; and 
       FIG. 3  is a longitudinal sectional view of a conventional check valve. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The best modes for carrying out the present invention will be described in detail using embodiments of the present invention with reference to the accompanying drawings. 
   As shown in  FIG. 1 , an embodiment of a check valve of the present invention is provided with an upstream-side cylindrical body element  1  and a downstream-side cylindrical body element  4 . 
   The upstream-side cylindrical body element  1  is fluid-tightly connected with an upstream-side fluid conduit  3  through an upstream-side nut member  2 . On the other hand, the downstream-side cylindrical body element  4  has its upstream-side projection portion threadably engaged with a downstream-side bore portion of the upstream-side cylindrical body element  1 , so that, as viewed from  FIG. 1 , a left-hand axial end surface of a flange portion  5  of the downstream-side cylindrical body element  4  abuts against a right-hand axial end surface of the downstream-side portion of the upstream-side cylindrical body element  1  and is welded thereto by ultrasonic welding, whereby the upstream-side cylindrical body element  1  is fluid-tightly connected with the downstream-side cylindrical body element  4 . 
   As is clear from  FIG. 1 , an O-ring  8  is fixedly mounted in an annular groove formed in an inner peripheral wall of a bore portion of the upstream-side cylindrical body element  1 , and brought into press-contact with an outer peripheral surface of a head portion of a cylindrical valve element  7  when the check valve is in its closed configuration. 
   In operation, in order to facilitate flow of the fluid passing through the check valve when the check valve is opened and also to ensure that the outer peripheral surface of the head portion of the cylindrical valve element  7  is evenly brought into press-contact with the O-ring  8 , preferably the outer peripheral surface of the head portion of the cylindrical valve element  7  is curved. As is clear from  FIG. 1 , the head portion of the cylindrical valve element  7  is provided with a pair of diametrically opposed radial inlet openings  9  in its outer peripheral wall, through each of which openings  9  the fluid enters the interior of the cylindrical valve element  7 . 
   A biasing device such as a compression coil spring  10  is axially interposed between the cylindrical valve element  7  and the downstream-side cylindrical body element  4 . The compression coil spring  10  is constructed of a metal filament coated with a tubular element made of fluororesins. 
   Each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  is provided with an inner spiral shoulder portion in its innermost portion to support each of opposite turns of the compression coil spring  10 . More specifically, such inner spiral shoulder portion of the downstream-side cylindrical body element  4  serves as a stopper element  24  of a conventional check valve shown in FIG.  3 . Due to this, for convenience in description, the inner spiral shoulder portion of the downstream-side cylindrical body element  4  is hereinafter also referred to as the stopper element  24 . 
   The inner shoulder portion of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  forms a spiral seat portion  11  provided with a spiral axial surface. Such spiral axial surface of the seat portion  11  of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  is capable of being evenly brought into press-contact with each of opposite turns of the compression coil spring  10 . As viewed from  FIG. 2 , the spiral seat portion  11  of the cylindrical valve element  7  has its left-hand axial surface  11   a  formed into a flat surface extending in a vertical plane perpendicular to the longitudinal axis of the cylindrical valve element  7 , and brought into press-contact with the innermost axial surface of the cylindrical valve element  7 . In the embodiment shown in  FIG. 1 , the spiral seat portion  11  is shown as if it were integrally formed with the cylindrical valve element  7 . On the other hand, a right-hand inner axial surface of the cylindrical valve element  7  is formed into a spiral shape to serve as a spring seat  12 . This spring seat  12  of the cylindrical valve element  7  is capable of receiving approximately one terminal turn of the compression coil spring  10 , and assumes, for example, a semi-circular concave shape in cross section to receive therein a left-hand half of the cross sectional area of the metal filament of the compression coil spring  10 . 
   The spiral seat portion  11  of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  shown in  FIG. 2  maybe separated from each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  to form a separate element. Such separate element may be fixedly mounted in (or integrally formed with) an innermost portion of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  to serve as the spiral seat portion  11  of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4 . 
   Since the check valve of the present invention has the above construction, it is possible for the biasing device such as the compression coil spring  10  to have its resilient force directly exerted on the spring seat portion  11  of each of the cylindrical valve element  7  and the downstream-side cylindrical body element  4  in the longitudinal direction of the check valve. More specifically, as viewed from  FIG. 2 , the compression coil spring  10  has its leftmost turn entirely brought into press-contact with the right-hand axial spiral surface of the spring seat portion  11  of the cylindrical valve element  7 , and is therefore capable of directly applying its resilient force to the spring seat portion  11  of the cylindrical valve element  7  in the longitudinal direction of the check valve. As for the rightmost turn of the compression coil spring  10  shown in  FIG. 2 , such rightmost turn of the compression coil spring  10  is entirely brought into press-contact with the left-hand inner axial spiral surface of the downstream-side cylindrical body element  4 , as viewed from FIG.  1 . Due to the above construction, the check valve of the present invention is free from a fear that the longitudinal axis of the cylindrical valve element  7  is inclined inside the axial bore of the downstream-side cylindrical body element  4  under the influence of the axial resilient force exerted by the compression coil spring  10 . Since the cylindrical valve element  7  is prevented from inclining inside the axial bore of the downstream-side cylindrical body element  4  as described above, the check valve of the present invention is free from a fear that the fluid leaks from the area of the O-ring  8  of the check valve in its closed configuration. Due to this, the check valve of the present invention is substantially free from any vibration and noise problem caused by such inclination of the longitudinal axis of the cylindrical valve element  7  inside the downstream-side cylindrical body element  4 . 
   Further, in the check valve of the present invention, as is clear from  FIG. 1 , the O-ring  8  is not mounted on the outer peripheral surface of the head portion of the cylindrical valve element  7 , but is fitted in the annular groove formed in an inner peripheral wall of the innermost portion of the upstream-side cylindrical body element  1 . Due to this construction, there is no fear that the O-ring  8  drops out of the annular groove formed in the, inner peripheral wall of the upstream-side cylindrical body element  1  when the cylindrical valve element  7  is axially moved relative to the upstream-side cylindrical body element  1  in valve-opening operation. 
   The effects of the present invention will be now described. Since the check valve of the present invention has the above construction, the compression coil spring  10  is capable of exerting its resilient force evenly on the cylindrical valve element  7  in the longitudinal direction of the valve element  7  without fail. Due to this, in the check valve of the present invention, there is no fear that the fluid leaks from the area of the O-ring  8  when the cylindrical valve element  7  is in its closed position. This makes it possible to prevent the check valve of the present invention from vibrating and therefore from issuing any noise in operation. Due to this, the check valve of the present invention is capable of functioning properly for a long period of its service time without fail and without any cumbersome maintenance service.