Patent Publication Number: US-8118574-B1

Title: Radial suction valve assembly for a compressor

Description:
This application claims the benefit of co-pending provisional application Ser. No. 61/102,637 filed Oct. 3, 2008. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to valves for reciprocating gas compressors, and in particular to a radial suction valve assembly designed to increase efficiency by creating a vortex effect which increases flow through the valve assembly and keeps at least some valve members of the valve assembly open past bottom dead center of the compressor piston. 
     2. Description of the Related Art 
     Reciprocating gas compressors act to move gas from a suction line to a discharge line at increased pressure. These compressors include a piston slidably moveable in a cylinder. Flow from the suction line into the cylinder is controlled by a suction valve assembly and flow from the cylinder into the discharge line is controlled by a discharge valve assembly. 
     Suction valve assemblies generally include valve members which open and close in response to pressure differentials within the compressor. When the compressor piston is at top dead center (TDC), the suction valve members are closed. As the piston moves away from TDC, pressure within the cylinder decreases. When the cylinder pressure drops below the pressure in the suction line, the valve members open to allow flow from the suction line into the cylinder. The valve members remain open until the piston reaches bottom dead center (BDC), at which point the cylinder pressure is equalized with the suction line pressure and the valve members close. 
     The efficiency of a reciprocating compressor can be increased by reducing the obstructions to flow across the suction valve and by increasing flow rate through the suction valve assembly. It is therefore desirable to produce a suction valve which has the least possible restriction. It would also be desirable to increase the flow rate or to continue flow past Bottom Dead Center without allowing gas to flow backward from the cylinder into the suction line. 
     SUMMARY OF THE INVENTION 
     The present invention is a suction valve assembly which comprises a hollow cylindrical valve seat having radially extending suction ports formed therethrough. The outside of the valve seat is in fluid communication with the suction line, and the inside of the valve seat is in fluid communication with the cylinder. The inside of the valve seat, is covered by a layer of resilient material, such as spring steel, which has a plurality of generally C-shaped cuts formed therein to create flaps which cover the suction ports and serve as sealing members to selectively close the suction ports. 
     As the piston of the compressor moves downwardly, away from Top Dead Center, gas is pulled from the suction line of the compressor through the suction ports and into the inside of the valve seat. The flaps open in response to pressure differentials to allow the gas to flow into the cylinder. The flaps are all oriented in the same circumferential direction, such that as the flaps open and the gas is pulled through the valve assembly, the gas will swirl, creating a vortex effect. This vortex effect will produce increased flow both by creating suction which pulls more gas in through the suction ports near the cylinder, and by causing the flaps furthest from the cylinder to be delayed in closing, allowing flow to continue past the point of the piston reaching Bottom Dead Center. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary cross sectional view of a reciprocating gas compressor showing a radial suction valve according to the present invention installed in a suction pocket thereof. 
         FIG. 2  is a side elevational view of the radial suction valve. 
         FIG. 3  is a perspective view of the radial suction valve. 
         FIG. 4  is a cross sectional view of the suction valve taken generally along line  4 - 4  in  FIG. 3 . 
         FIG. 5  is a cross sectional view of the suction valve taken generally along line  5 - 5  in  FIG. 2  and showing valve members thereof in an open position. 
         FIG. 6  is a fragment of a cross sectional view similar to  FIG. 5  showing an alternative embodiment of the suction valve assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
     Certain terminology will be used in the following description for convenience in reference only and will not be limiting. For example, the words “upwardly,” “downwardly,” “rightwardly,” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the embodiment being described and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof and words of a similar import. 
     Referring to the drawings in more detail, and in particular to  FIG. 1 , the reference number  1  generally designates a radial suction valve assembly according to the present invention. The suction valve assembly  1  is for use on a reciprocating compressor  3  including a cylinder  5  slidably receiving a piston  7  connected to a crankshaft (not shown). The suction valve assembly  1  is mounted in a suction valve pocket  10  of the compressor  3  and selectively communicates the cylinder  5  with a suction line  11 . The suction valve  1  is retained in the pocket  10  by a valve cap  12 . Similarly, a discharge valve assembly  13  selectively communicates the cylinder  5  with a discharge line  15 . The compressor  3  generally operates to move gas from the suction line  11  to the discharge line  15  at increased pressure. 
     Referring to  FIGS. 2-5 , the suction valve assembly  1  generally comprises a hollow cylindrical valve seat  17  having an inner surface  19  and an outer surface  20 . The assembly  1  may also include first and second annular spacer rings  21  and  22 , respectively positioned on opposite ends of the valve seat  17 . The inner surface  19  of the valve seat  17  defines an axial passageway  23  which extends between the opposite ends of the valve seat  17 . The axial passageway  23  is closed at one end by the valve cap  12  and is open to the cylinder  5  at the opposite end. A plurality of radial ports  25  are formed through the valve seat  17  and extend between the axial passageway  23  and the outer surface  20 . The ports  25  are shown as being arranged in a plurality of axially spaced rings  27 , designated herein as rings  27   a  through  27   d , with ring  27   a  being positioned closest to the valve cap  12  and ring  27   d  being nearest the cylinder  5 . It should be noted that the ports  25  can be arranged in patterns other than parallel rings if so desired. 
     Positioned inside the valve seat  17 , against the inner surface  19 , is a layer of resilient material  28 , such as spring steel, having a plurality of generally C-shaped cuts  29  formed therein. The layer of resilient material  28  may be fastened to the valve seat  17  using mechanical fasteners or the like, including machine screws, bolts or rivets (not shown). Each cut  29  in the resilient material  28  defines a flap  31 . The flaps  31  are each associated with a respective one of the ports  25  and are positioned in covering relation with the respective port  25 . Each flap  31  is moveable between opened and closed positions by flexion of the resilient material. The flaps  31  are cut somewhat larger than the ports  25  such that outer portions of each flap  31  bear against the inner surface  19  of the valve seat  17  when the flap  31  is in the closed position. Each of the cuts  28  is oriented such that the flaps  31  open in the same circumferential direction. 
     In use, the valve assembly  1  controls flow between the suction line  11  and the cylinder  5 . When the piston  7  is at top dead center, the flaps  31  are closed and sealed against the inner surface  19  of the valve seat  17 . As the piston  7  moves away from top dead center, pressure in the cylinder  5  decreases until it drops below the pressure in the suction line  11 , at which point the flaps  31  open by flexion of the resilient material of which they are formed. As gas moves through the suction ports  25  and into the axial passageway  23 , the flaps  31  act as vanes to cause a swirling motion in the gas, creating a vortex effect, as indicated by the arrows in  FIG. 5 . The vortex effect creates suction which increases the flow rate through the suction ports, particularly in those suction ports closest to the cylinder, and thereby increases the efficiency of the compressor. Furthermore, the suction from the vortex effect exerts a force on the flaps  31  which tends to hold the flaps  31  open. This second result is particularly important as the piston reaches bottom dead center since the vortex effect can keep some of the flaps, particularly those flaps furthest from the cylinder and closest to the end cap, open past bottom dead center and thereby allow gas to continue to flow into the cylinder for a brief time after bottom dead center is reached. This continued flow after bottom dead center also increases the efficiency of the compressor. 
     The suction valve assembly  1  provides very little obstruction to flow, since there are no moving parts except for the flaps  31 , and the flaps open easily once the proper pressure differentials are achieved. It is believed that the gas flowing through each suction port  25  will act as a stop or cushion for the flap  31  associated with the adjacent port  25  and, in this manner, the flaps  31  will be prevented from opening too far. The lack of any mechanical stops for the flaps  31 , also helps provide a unobstructed flow path for the gas passing through the suction valve assembly  1 . 
     It is also believed that the suction valve assembly  1  of the present invention can act as a venturi and that additional gas will therefore be pulled through the assembly  1  as the result the Bernoulli Effect. This is because the combined area of the ports  25  is greater than the area of the passageway  23 , and as gas flows from the ports  25  and through the passageway  23 , the flow becomes constricted proximate the ring of ports  27   d  nearest the piston  7  and furthest from the valve cap  12 , forming the throat of a venturi. In the area of the throat, the velocity of the flow is increased and the static pressure is decreased. This decrease in pressure will act to pull more gas through the ports  25  in ring  27   d  than would otherwise be possible. 
       FIG. 6  shows an alternative embodiment of the suction valve assembly  1 , denominated as valve assembly  1   a , which includes ports  25   a  (one shown) arranged in the same manner described above. The ports  25   a  are similar to the ports  25 , except that a first wall  33  thereof is angled inwardly toward the hinged side of the respective flap  31 . The angle of the wall  33  allows the gas to flow in a more direct path, and contributes to the vortex effect that is produced by the flaps  31  all pointing the same direction. While not essential to the operation of the suction valve assembly, this feature gives the gas a smoother flow path, as it flows through the valve seat  17  along the angled wall  33  and then through the flap  31  without having to make a substantial change in direction. 
     It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown. For example, it is foreseen that the flaps  31  could be attached to the valve seat  17  by hinges or the like and need not necessarily be formed as cut-outs in a layer of resilient material or rely on flexion of such a material for their ability to move between open and closed positions. If hinges were used to mount the flaps  31  biasing means, such as springs, could be used to bias the flaps toward their closed positions. 
     As used in the claims, identification of an element with an indefinite article “a” or “an” or the phrase “at least one” is intended to cover any device assembly including one or more of the elements at issue. Similarly, references to first and second elements is not intended to limit the claims to such assemblies including only two of the elements, but rather is intended to cover two or more of the elements at issue. Only where limiting language such as “a single” or “only one” with reference to an element, is the language intended to be limited to one of the elements specified, or any other similarly limited number of elements.