Abstract:
A check valve for a compressed gas system. The valve has a body with an internal passage extending through the body and a valve seat positioned in the passage. A poppet is movable between a closed position in which the poppet engages the seat to block flow of gas through the passage and an open position in which the poppet is spaced from the seat to permit flow of gas. A retainer mounts the poppet in the passage and guides movement of the poppet. A spring urges the poppet to the closed position such that the poppet is responsive to pressure of the gas exceeding a predetermined value to move the poppet away from the seat against the urging of the biasing member and to the open position.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to controlling flow of gas in a compressed gas system, and more particularly to a check valve for use in the delivery of air under pressure from an air compressor to a storage tank holding the air under pressure.  
           [0002]    Check valves are in widespread use for permitting pressurized gas to flow through a passage in one direction and preventing flow in the reverse direction. Most check valves have a movable poppet which is urged by a spring to engage a valve seat, thereby closing the valve. When force on the poppet due to air pressure exceeds the force of the spring, the poppet moves away from the seat, thereby opening the valve.  
           [0003]    One application is at a fitting on the storage tank, where a check valve receives a flow of air from a compressor for delivery to the tank, and then retains air in the tank when the compressor shuts off. That valve is exposed to a severe environment typical for a compressor discharge, including large air pressure fluctuations and turbulent flow. Consequently, the poppet and other parts of the valve are subject to substantial vibrations which can result in noise, damage, and/or failure. Some valves of the prior art include a guide mounted inside the valve for guiding movement of the poppet to prevent damage. Unfortunately, these guides are frequently located at a position within the valve where installation and replacement of a guide is difficult, or they are flexible in construction or otherwise ill-suited for the severe environment. Moreover, some guides or springs have configurations which obstruct a significant portion of the available flow area of the passage, thereby degrading air pressure as it flows through the valve and potentially causing additional vibration or failure.  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    Among the several objects of one or more embodiments of the invention may be noted the provision of a check valve which is adapted to reliably check escape of compressed air in association with a compressed air tank and air compressor which supplies the tank with compressed air; the provision of such a valve which can withstand the severe compressor discharge environment; the provision of such a valve which is easily assembled; the provision of such a valve which avoids substantial decrease in pressure of the air as it flows through the valve; the provision of such a valve which, in one embodiment, is adapted for relief of air pressure therein when the compressor shuts down; and the provision of such a valve which is of economical construction.  
           [0005]    In general, a check valve of the present invention comprises an elongate body having a passage extending therethrough from a first end constituting its end for entry of gas under pressure to flow through to a second end constituting its end for exit of the gas. The passage is formed with a valve seat intermediate its ends spaced from and directed toward the exit end. A retainer is fixed in the passage spaced downstream from the seat apertured for the exit of the gas. The retainer has a rigid construction with a substantially central sleeve extending therefrom toward the seat. A poppet is slidable in the sleeve biased for engagement with the seat for blocking flow through the passage and disengagement from the seat on pressurization above a predetermined value for flow in the space around the sleeve and through the retainer for exit from the passage.  
           [0006]    In another aspect, a check valve of the present invention is for a compressed gas system. The valve comprises a valve body adapted for connection to the compressed gas system, the body having opposite ends and an internal passage extending through the body between an entry at a first end of the body and an exit at a second end of the body. A valve seat is positioned between the entry and the exit. A poppet is movable between a closed position in which the poppet engages the seat to block flow of gas through the passage and an open position in which the poppet is spaced from the seat to permit flow of gas. A retainer is for mounting the poppet in the passage and for guiding movement of the poppet between the closed and open positions. A biasing member is for urging the poppet to the closed position such that the poppet is responsive to pressure of the gas exceeding a predetermined value to move the poppet away from the seat against the urging of the biasing member and to the open position. The valve body has an internal shoulder in the passage adjacent the exit end, the retainer being seated on the internal shoulder and held in place by the exit end of the body being crimped over on the retainer.  
           [0007]    Other objects and features will be in part apparent and in part pointed out hereinafter.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective of a check valve of this invention;  
         [0009]    [0009]FIG. 2 is a top end view of the check valve of FIG. 1 with certain parts removed to illustrate a valve body;  
         [0010]    [0010]FIG. 3 is a view generally in section on line  3 - 3  of FIG. 2 and showing the valve at a closed position;  
         [0011]    [0011]FIG. 4 is a view similar to FIG. 3 showing the valve at an open position;  
         [0012]    [0012]FIG. 5 is a perspective of a poppet of the check valve;  
         [0013]    [0013]FIG. 6 is an elevation of the poppet of FIG. 5;  
         [0014]    [0014]FIG. 7 is a bottom end view of the poppet of FIG. 6;  
         [0015]    [0015]FIG. 8 is a perspective of a retainer of the check valve;  
         [0016]    [0016]FIG. 9 is a top end view of the retainer of FIG. 8;  
         [0017]    [0017]FIG. 10 is a section in the plane of line  10 - 10  in FIG. 9; and  
         [0018]    [0018]FIG. 11 is a view similar to FIG. 3 showing a modified check valve having a threaded lateral port for relieving air pressure in the valve. 
     
    
       [0019]    Corresponding reference characters indicate corresponding parts throughout the views of the drawings.  
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]    Referring now to the drawings and in particular to FIGS.  1 - 4 , a check valve of this invention, designated  10  in its entirety, is shown to comprise an elongate body  12 , a movable poppet  14 , a valve retainer  16 , and a spring  18 .  
         [0021]    The valve body  12  has upper and lower cylindric ends  20  and  22  which are externally threaded for connecting the valve  10  a compressed gas system, such as to a storage tank  24 . An intermediate polygonal section  26  is suitable for engagement by a wrench. In one embodiment, section  26  is hexagonal in shape with a nominal size of 0.875 inches across external flats, but it will be understood that the section can have other shapes and sizes. The elongate body  12  (formed of brass, for example) has a passage  28  extending therethrough from a first end  30  constituting its end for entry of gas (air) under pressure to flow through to a second end  32 , constituting its end for exit of the gas. Passage  28  is formed with a tapered valve seat  34  intermediate its ends, more particularly at the upper end of the intermediate section  26  (the upper end of an intermediate section  36  of the passage  28 ), the seat being spaced from and directed toward the exit end  32 . The body  12  has an internal shoulder  38  in the passage  28  adjacent the exit end  32 . Other forms of the valve body  12 , including configurations assembled from two or more parts, other sizes, and valve seat arrangements do not depart from the scope of the invention. The body  12  is shown in FIG. 2 with the poppet  14 , retainer  16 , and spring  18  removed for illustration.  
         [0022]    The poppet  14  is movable between a closed position (FIG. 3) in which the poppet engages the seat  34  to block flow of gas through the passage  28  and an open position (FIG. 4) in which the poppet is spaced from the seat to permit flow of gas through the valve  10 . The poppet  14  is slidable in the retainer  16  and biased by the spring  18  to the closed position. When air supplied to the entry end  30  has a pressure above a predetermined value such that a force applied to the poppet  14  by the air exceeds an opposing force applied by the spring  18 , the poppet disengages from the seat  34  and moves to the open position.  
         [0023]    The poppet  14  (FIGS.  5 - 7 ) comprises a generally cylindric stem  40  configured for being slidably received in the retainer  16  and a head  42  for sealing engagement with the seat  34 . The head  42  comprises, in one embodiment, a toroid shaped seal which is mounted on the stem  40 . The stem  40  has two spaced flanges  44  thereon, with the head  42  being captured between the two flanges  44 . The head  42  is mounted on the stem  40  with an interference fit to ensure it is tight and reliably secured. In the preferred embodiment, the head  42  has a nominal inside diameter of about 0.177 in., and the stem  40  has a diameter of about 0.193 in. Thus the head  42  must stretch to be inserted on the stem  40 , and it remains tightly in position when exposed to turbulent flow of air. Other types of connections or fits between the head and stem, or one integral part, do not depart from the scope of this invention.  
         [0024]    The stem  40  is formed of a suitable material which is strong, rigid, thermally stable, and resistant to corrosion and wear. In the preferred embodiment, the stem  40  is formed of a thermoplastic resin such as RYTON thermoplastic (RYTON is a federally registered trademark of the Chevron Phillips Chemical Company LP of Houston, Tex.). The head  42  is sized for mounting on the stem  40  and configured to sealingly engage the seat  34 . It is formed of a suitable material which is resilient, strong, thermally stable, and resistant to corrosion and wear. In the preferred embodiment, the head  42  is formed of a synthetic rubber such as VITON fluoroelastomer (VITON is a federally registered trademark of DuPont Dow Elastomers L.L.C. of Wilmington, Del.). Other shapes and materials may be used for the stem and head without departing from the scope of this invention.  
         [0025]    The valve retainer  16  (FIGS.  8 - 10 ) mounts the poppet  14  in the passage  28  and guides movement of the poppet between its closed and open positions, preventing any change to the orientation of the poppet which could result in failure of the valve  10 . The retainer  16  comprises a substantially central sleeve  46  and an annular outer rim  48  spaced from the sleeve and sized to engage the valve body  12 . The sleeve  46 , which extends from the retainer  16  toward the seat  34  (FIG. 3), receives the poppet  14  and defines a linear path of movement between the closed and open positions. The sleeve  46  is mounted in alignment with the body  12  (i.e., coaxial with the passage  28 ) such that the path of movement of the poppet  14  is aligned with the body and generally along its center.  
         [0026]    In order to ensure good alignment, a radial clearance between the stem  40  and an inner surface of the sleeve  46  is small. In the preferred embodiment, the clearance is in a range of 0.006 to 0.014 in., and more preferably about 0.010 in. (i.e., the stem  40  has an outer diameter of about 0.195 in. and the sleeve  46  has an inner diameter of about 0.205 in.). Further for maintaining alignment, the sleeve  46  preferably has an axial length L (FIG. 10) extending a distance greater than the outer diameter of the stem 40 (1.8 times in the preferred embodiment), and also preferably extending at least the distance traveled by the poppet  14  in moving between open and closed positions. In the preferred embodiment, the sleeve  46  has a length L (FIG. 10) of about 0.350 in.; the poppet  14  has a total length L2 (FIG. 6) of about 0.815 in.; the portion of the stem  40  downstream of the shoulder  40  slidable in the sleeve  46  has a length L3 of about 0.570 in.; and the distance traveled by the poppet  14  in moving between open and closed positions is about 0.125 in. Other dimensions and dimension ratios do not depart from the scope of this invention.  
         [0027]    In the embodiment shown in FIG. 9, three circumferentially spaced arms  50  extend generally radially between the rim  48  and the sleeve  46  for supporting the sleeve in the passage  28 . The arms  50  define three arcuate apertures  52  in the retainer  16  between the rim  48  and the sleeve  46 , the apertures permitting exit of the flow of gas therethrough. The apertures  52  are on a circle centered in the retainer  16 , the apertures being spaced at 120 degrees around the circle. The arms  50  provide adequate support to the sleeve  46  while minimizing blockage of the flow area through the apertures  52 .  
         [0028]    The retainer  16  is formed of a suitable material which is strong, rigid, thermally stable, and resistant to corrosion and wear, such as RYTON thermoplastic. Unlike some prior art poppet guides which are flexible, the rigid retainer  16  makes it particularly effective for use in a compressor discharge environment. Preferably, the sleeve  46 , outer rim  48 , and arms  50  are integrally formed, although it is understood that a retainer formed of several separate parts does not depart from the scope of this invention. Further, the number, size, and configuration of the arms and apertures may vary so long as the sleeve is rigidly supported and the gas is able to flow freely through the retainer.  
         [0029]    As seen in FIG. 3, the retainer  16  is fixed in the passage  28 , spaced downstream from the valve seat  34 . The outer rim  48  is seated on the internal shoulder  38  in the passage at the exit end  32  of the passage and body and held in place by the exit end being crimped over on the retainer  16 . Significantly, the position of the retainer  16  at the exit end  32  beneficially provides for straightforward assembly, good accessibility, and avoids the difficulty of trying to maneuver the retainer for attachment at a location deep inside the passage  28 . Crimping provides a simple attachment and precludes fasteners or more complex retainers which are integral with the body. However, it is understood that the attachment can be done in other ways without departing from the scope of this invention.  
         [0030]    The spring  18  (FIG. 3) comprises a helical compression spring extending between the retainer  16  and one of the flanges  44  on the poppet  14 . That flange  44  has a raised shoulder  54  engageable by the spring  18  for seating the spring and preventing lateral shifting of the spring. Therefore, the spring  18  is guided and constrained from lateral shifting on both of its ends (i.e, by both the retainer  16  and the poppet  14 ) so that it will remain secure as the poppet moves and when exposed to turbulent flow of air. Springs  18  of varying spring constant may be selected appropriate to the expected air pressure and/or size of the valve  10  to select the predetermined value of air pressure which moves the poppet  14  from the closed to the open position. In the preferred embodiment, the spring  18  is formed of stainless steel. It is understood that other types of springs or biasing members and other materials do not depart from the scope of this invention.  
         [0031]    Significantly, the spring  18  is configured to remain out of the path of air as it flows through the passage  28  to prevent flow turbulence, loss of air pressure, and vibratory motion of the spring. The spring  18  has turns of uniform diameter which are configured to remain generally adjacent to the retainer  16  and the poppet  14  along an entire length of the spring, such that when the poppet is at the open position, flow of air through the passage  28  is not obstructed by any part of the spring. A radial clearance between the spring  18  and sleeve  46  (and between the spring and the shoulder  54 ) is within a range of about 0.003 to 0.031 in., and more preferably about 0.017 in. In the preferred embodiment, the sleeve has an outside diameter of about 0.300 in. and the spring  18  has an inside diameter of about 0.317 in. Other dimensions and dimension ratios do not depart from the scope of this invention.  
         [0032]    The passage  28  and the poppet  14  are sized for providing adequate flow areas as air passes through the valve  10  to avoid causing a decrease in either pressure or mass flow. The intermediate section  36  defines a minimum area, or “throat” of the valve  10 . When the poppet  14  is open, the flow area in the passage  28  increases as the air moves from the intermediate section  36  past the conical seat  34 . Preferably, the flow area downstream of the conical seat is in a range from about 125% to 225% of the flow area at the intermediate section  36 , and more preferably about 175%. In the preferred embodiment, for example, the intermediate section  36  has a flow diameter of about 0.312 in., providing a cross sectional flow area of 0.076 square in. Downstream of the conical valve seat  34 , the cross sectional flow area of passage  28  at location  58  (see FIG. 4) is annular in shape and is about 0.132 square in. (174% of the minimum flow area).  
         [0033]    Referring to FIG. 11, a modification  60  of the check valve has a conventional lateral outlet  62  from the passage  28  between the entry end  30  of the body and the valve seat  34  for relieving pressure from the passage upstream from the valve seat. As known to those skilled in the art, the outlet  62  is commonly used as a threaded “unloader port” for connection of an electrical pressure switch, for example, operable to release air trapped between the compressor and the valve, subsequent to the compressor shutting off, in order to facilitate proper re-start of the compressor.  
         [0034]    The valve  10  of the present invention is compact in size and has a small number of component parts to minimize cost. The valve is reliable in operation in the severe environment typical for a compressor discharge. At the open position, the valve provides good internal flow characteristics with generally restriction-free flow areas, minimal turning (i.e., the flow proceeds generally straight through the valve) and with the only obstructions being the three arms  50 . Therefore, the valve avoids producing a substantial decrease in pressure as air flows through the valve. Assembly of the valve  10  is facilitated by the convenient position of the retainer  16  at the exit end  32  and its attachment by crimping the end.  
         [0035]    In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results obtained.  
         [0036]    When introducing elements of the present invention or the preferred embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.  
         [0037]    As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.