Abstract:
The present invention provides a check valve in which correct sealing performance can be always ensured. In the check valve, a valve element  1  and a compression coil spring  2  which urges the valve element  1  in the valve closing direction are integrally molded by a synthetic resin material.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a check valve which is to be attached to a fluid apparatus such as a reciprocating pump to prevent fluid from reversely flowing, thereby allowing the fluid to flow only in one direction.  
           [0003]    2. Description of the Prior Art  
           [0004]    In a reciprocating pump which is used for circulating or transporting chemical cleaning liquids in a semiconductor producing apparatus, for example, a check valve for sucking or discharging the transported liquid is attached. Such check valves include a valve of the gravity type in which closure is attained only by the weight of a valve element itself, and that of the spring type in which a valve element and a compression coil spring for urging the valve element so that the valve element is closely contacted with a valve seat are incorporated into a valve casing. A valve of the spring type is mainly employed because it is superior in sealing property than that of the gravity type (for example, Japanese Patent Application Laying-Open No. 3-179184 and Japanese Patent Application Laying-Open No. 10-196521).  
           [0005]    In such a check valve of the spring type, the valve element and the compression coil spring are independently formed so as to be separable from each other, and, during operation of the valve, the center axis of the compression coil spring therefore easily deviates with respect to that of the valve element. In the worst case, the valve element and the compression coil spring are nearly disengaged from each other. Therefore, the urging force exerted by the compression coil spring cannot adequately act on the valve element, thereby often producing a problem in that correct sealing performance due to the valve element is lowered or lost.  
         SUMMARY OF THE INVENTION  
         [0006]    The invention has been conducted in order to solve the problem. It is an object of the invention to provide a check valve of the spring type in which correct sealing performance due to the valve element can be always ensured, and the work of incorporating the check valve into a fluid apparatus such as a reciprocating pump can be efficiently conducted.  
           [0007]    The check valve of the invention is configured by integrally forming a valve element and a compression coil spring which urges the valve element in a valve closing direction, by a metal or a synthetic resin.  
           [0008]    In the check valve of the invention, more specifically, the valve element is formed into a tapered truncated conical shape, the compression coil spring is formed into a cylindrical shape, and the valve element and the compression coil spring are integrally molded into a shape in which the valve element and the compression coil spring are connected to each other via a plurality of connecting rods that are integrally formed between a rear end portion of the valve element and a front end portion of the compression coil spring, so that center axes of the valve element and the compression coil spring coincide with each other. In this case, an outer diameter of the compression coil spring may be set to be larger than a maximum outer diameter of the valve element, or the maximum outer diameter of the valve element and the outer diameter of the compression coil spring may be set to be substantially equal to each other.  
           [0009]    In the thus configured check valve, the valve element and the compression coil spring which are formed integrally with each other are not positionally deviated or disengaged from each other. Therefore, the urging force exerted by the compression coil spring can always adequately act on the valve element, and it is possible to exert stable sealing performance in which a reverse flow and liquid leakage can be always surely prevented from occurring.  
           [0010]    As described above, the check valve of the invention can always exert stable sealing performance, and is advantageous from the view point of the work of incorporating the check valve into a fluid apparatus such as a reciprocating pump.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a side view of a check valve which is an embodiment of the invention;  
         [0012]    [0012]FIG. 2 is a front view of the check valve;  
         [0013]    [0013]FIG. 3 is a section view taken along the line A-A of FIG. 2;  
         [0014]    [0014]FIG. 4 is a side view of a check valve which is another embodiment; and  
         [0015]    [0015]FIG. 5 is a longitudinal section view of a reciprocating pump to which the check valve of FIG. 1 is attached.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    An embodiment of the invention will be described with reference to FIGS.  1  to  3 .  
         [0017]    A check valve  30  according to the invention is configured by integrally forming a valve element  1  and a compression coil spring  2  by a metal or a synthetic resin.  
         [0018]    In the case where the valve element  1  and the compression coil spring  2  are integrally molded by a synthetic resin, for example, a fluororesin which is excellent in heat resistance and chemical resistance, such as PTFE (polytetrafluoroethylen), or PFA (perfluoroalkoxy) is used as the molding material. When the integral molding is performed by the injection molding method, the valve can be economically mass-produced.  
         [0019]    The valve element  1  made of a synthetic resin is formed into a tapered truncated conical shape, and the compression coil spring  2  is formed into a cylindrical shape. The valve element  1  and the compression coil spring  2  are integrally molded into a shape in which the two members  1  and  2  are connected to each other via a plurality of connecting rods  3  that are integrally formed between a rear end portion of the valve element  1  and a front end portion of the compression coil spring  2 , so that center axes of the two members coincide with each other.  
         [0020]    As shown in FIG. 1, the outer diameter D 2  of the compression coil spring  2  may be arbitrarily set to be larger than the maximum outer diameter D 1  of the valve element  1 , or, as shown in FIG. 4, the maximum outer diameter D 1  of the valve element  1  and the outer diameter D 2  of the compression coil spring  2  may be arbitrarily set to be substantially equal to each other.  
         [0021]    [0021]FIG. 5 exemplarily shows a case where the thus configured check valve  30  is applied to a reciprocating pump  31  which is used for circulating or transporting chemical cleaning liquid in a semiconductor producing apparatus.  
         [0022]    The reciprocating pump  31  is configured in the following manner. A pair of bellows  14  which can extend and contract in the same direction are opposingly disposed in cylindrical casings  13 A and  13 B which are continuously fixed to the sides of a pump head wall  12  having liquid inflow and outflow paths  10  and  11 , respectively. Opening peripheral portions  14   a  of the paired bellows  14  are airtightly fixed to the pump head wall  12  via annular fixing plates  15 , whereby each of the inner spaces of the casings  13 A and  13 B is hermetically partitioned into a liquid chamber  16   a  and an air chamber  16   b,  so as to configure a pair of pumping portions  17 A and  17 B.  
         [0023]    The paired bellows  14  in the paired pumping portions  17 A and  17 B are interlockingly connected to each other via a plurality of connecting rods  18  which are passed through the pump head wall  12  and arranged in the circumferential direction, so that, when one of the bellows  14  contracts, the other bellow  14  extends. In the pump head wall  12 , suction ports  19  and discharge ports  20  which communicate with the inflow and outflow paths  10  and  11  are formed so as to be opened in the liquid chambers  16   a  in the pumping portions  17 A and  17 B. Suction and discharge valve casings  21  and  22  which are molded into a cylindrical shape by a resin material such as a fluororesin are screwingly coupled to the suction ports  19  and the discharge ports  20 , respectively. In this case, the check valve  30  configured as described above by the valve element  1  and the compression coil spring  2  which are integrated with each other is previously incorporated into each of the valve casings  21  and  22  so that the valve  1  is closely contacted with the corresponding valve seat  21   a  or  22   a.  Air holes  23  through which pressurized air is alternately supplied to the air chambers  16   b  are formed in bottom walls  13   a  and  13   b  of the casings  13 A and  13 B, respectively.  
         [0024]    According to this configuration, pressurized air which is fed from a pressurized air supplying device (not shown) such as a compressor is alternately supplied to the air chambers  16   b  through the air holes  23 , whereby the paired bellows  14  are driven via the connecting rods  18  to reversibly extend and contract, whereby the paired pumping portions  17 A and  17 B are caused to perform alternately sucking and discharging strokes. As a result, a pumping operation is conducted in which the liquid that flows from the inflow path  10  into the liquid chambers  16   a  via the check valves  30  in the suction valve casings  21  is discharged via the check valves  30  in the discharge valve casings  22 , into the outflow path  11  in a substantially continuous manner.  
         [0025]    As described above, in each of the check valves  30  incorporated into the reciprocating pump  31 , the valve element  1  and the compression coil spring  2  are formed integrally with each other. Consequently, the valve element  1  and the compression coil spring  2  are not positionally deviated or disengaged from each other in the corresponding valve casing  21  or  22 . Therefore, the urging force exerted by the compression coil spring  2  can always adequately act on the valve element  1 , so that it is always possible to surely prevent a reverse flow and liquid leakage from occurring, whereby the reliability of quantitative volume feeding can be improved.  
         [0026]    In each of the valve casings  21  and  22 , the work of incorporating the compression coil spring  2  can be conducted simultaneously with that of incorporating the valve element  1 . As compared with the case where these members are separately incorporated into a valve casing, therefore, they can be incorporated more efficiently.  
         [0027]    The entire disclosure of Japanese Patent Application No. 2000-60710 filed on Mar. 6, 2000 including specification, claims, drawings, and summary are incorporated herein by reference in its entirety.