Patent Publication Number: US-2003235509-A1

Title: High aspiration valve design for piston pumps or compressors

Description:
BACKGROUND OF THE INVENTION  
       [0001] I. Field of the Invention  
       [0002] The invention relates generally to a high aspiration compound valve for controlling the flow of fluids to and from a pumping chamber in a piston or diaphragm pump. More particularly, it relates to a compound valve which is part of a positive displacement pump assembly and creates easy suction without great concern for the discharge of fluid forced by the piston. The valve of the invention provides a unique design having a generous area of opening which allow for capable operation of a pump at high speeds when at large displacements or when pumping viscous fluids.  
       [0003] II. Discussion of the Prior Art  
       [0004] Typically, positive displacement piston and diaphragm pumps are designed with one of two valve arrangements. These arrangements are either plate porting or valves.  
       [0005] Plate porting is commonly used in hydraulic pumps having a swash plate drive and operates when the bores in a piston barrel rotate over holes in a precision mounted aperture plate to allow the entry and exit of fluid from the piston. This porting arrangement is only practical for very clean fluids with good lubricating qualities such as highly filtered hydraulic oils.  
       [0006] Valves are used in piston/plunger and diaphragm pumps having a non-rotating cylinder block. Typically, spring loaded check valves which use balls, disks, or small pistons to enable the opening and closing of a valve are used. For each multi-cylinder piston on a piston pump, two separate valves are used, one for fluid entry, and one for fluid discharge. There are two major problems with traditional valves of this type. First, they pose major restrictions in the entry fluid path to the pump cylinders on the suction stroke. Second, the valve is not mounted directly over a piston bore and is usually on a passage offset from the piston. This mounting position causes further restriction to the entrance of fluid into the piston and cylinder during the suction phase. Additionally, the valve return spring adds to the force required to open the valves.  
       [0007] In compressors requiring check type valves, similar comments can be made regarding traditional valves. If the gas being compressed is restricted when entering the piston chamber for compression, then the efficiency of the device is compromised.  
       [0008] Over the years, a wide variety of valve structures, including unitary inlet and outlet valves have been used to control fluid flow. There are several prior art arrangements in which unitary inlet and outlet valves with alternating pressure strokes are utilized.  
       [0009] Prior art also exists teaching a direct, in-line, suction and discharge poppet valves. The Pareja U.S. Pat. No. 4,032,263 describes a valve device that is somewhat similar to the present invention, but its construction and operational features are quite different from the present invention. A central difference results from the selection of which component becomes the suction valve and which becomes the discharge valve. In U.S. Pat. No. 4,032,263, the suction valve is the central poppet and the discharge valve is the annular poppet surrounding the central poppet. In the present invention, the situation is reversed. The suction poppet is the annular ring and the discharge poppet is centrally disposed. By making this reversal, the suction characteristics of the new valve design are greatly improved. Generally, the new valve is designed to achieve a larger open area for fluid flow with less restrictions, especially in the suction valve. It is also designed to minimize the valve travel to limit backflow during the reverse of the stroke of the pump having alternating suction and pressure cycles. This permits the pump to operate at higher speeds and increased flow rates.  
       SUMMARY OF THE INVENTION  
       [0010] The present invention provides for a high aspiration compound valve for regulating fluid flow to and from a chamber by coordinated interaction between a piston and the compound valve. The compound valve is generally made up of a cylindrical housing into which the piston fits, a valve body which remains stationary within the housing, a discharge valve centrally located, a suction valve annularly located outside the discharge valve, a suction valve return spring, and a discharge valve return spring. The stationary valve body provides two different sets of seats that cooperate with the suction and discharge poppet to seal at least one of either the discharge valve or the suction valve, depending upon the movement of the piston in its reciprocating travel within the cylindrical housing. The above-listed components work together in conjunction with the aid of the discharge valve return spring and suction valve return spring to enable an improved valve design for transferring gas or liquid from the suction inlet of the housing to the discharge outlet. It provides very smooth, relatively turbulent free flow from the pump and is capable of operating at high speeds when at very large displacements or when pumping viscous fluids.  
       [0011] The combination valve operates by first drawing fluid in the housing during the piston&#39;s down stroke when the suction valves are open. Next, when the piston completes travel to the bottom of its down stroke and begins the discharge stroke it rapidly closes due to the combination of the suction valve spring expanding and the flow direction of the fluid in the cylinder reversing. This limits backflow to a minimum, and improves the pump&#39;s volumetric efficiency. As the piston/plunger continues upwards motion, the discharge valve is forced open permitting the fluid to flow out of the discharge port. After the piston reaches the top of its stroke and reverses direction to initiate the suction stroke, the combination of the discharge valve return spring expanding and the reversal in direction of the fluid flow rapidly closes the discharge valve. The piston/plunger will continue the downward stroke and the entire cycle is repeated.  
       [0012] These and other objects, features, and advantages of the present invention will become readily apparent to those skilled in the art through a review of the following detailed description in conjunction with the claims and accompanying drawings in which like numerals in several views refer to the same corresponding parts. 
     
    
    
     DESCRIPTION OF THE DRAWINGS  
     [0013]FIG. 1 is a longitudinal sectional view of the valve assembly in a pump or compressor;  
     [0014]FIG. 2 is a perspective exploded isometric view showing the basic valve parts;  
     [0015]FIG. 3 is a sectional view of the valve assembly during the suction stroke;  
     [0016]FIG. 4 is a sectional view of the valve assembly at the bottom of the suction stroke;  
     [0017]FIG. 5 is a sectional view of the valve assembly during the discharge stroke;  
     [0018]FIG. 6 is a sectional view of the valve assembly at the top of the discharge stroke.  
     [0019]FIG. 7 is a sectional view of an alternative embodiment of the valve assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0020] The present invention represents broadly applicable improvements for valve design in positive displacement pumps. The embodiments herein are intended to be taken as representative of those in which the invention may be incorporated and are not intended to be limiting.  
     [0021] Referring first to FIG. 1, there is shown in cross-section a valve assembly  8  comprised of a valve housing  10  having a cylinder bore  11 , a pump or compressor piston  12 , compound valve body  14 , suction or fluid inlet port  16 , fluid outlet or discharge port  18 , suction valve  20 , suction valve return spring  22 , discharge valve  24 , and discharge valve return spring  26 . The piston/plunger  12  is reciprocally driven in the cylinder bore  11  by a suitable pump drive assembly (not shown). Those wishing further information on a complete pump design in which the valve arrangement of the present invention are referred to the Maki et al application Ser. No. ______, filed ______, and entitled “Variable Displacement Positive Displacement Pump”, the teachings of which are hereby incorporated by reference.  
     [0022] Referring next to FIG. 2, there is shown a perspective exploded isometric view of the basic valve parts. It is observed that all elements of the compound valve are aligned concentrically around a central axis  27 . The valve body  14  has its largest diameter ring segment  34  near its center. In general, the valve body  14  is of a cylindrical shape, containing three ring segments  33 ,  34 , and  36  of differing diameters.  
     [0023] The individual elements comprising the preferred embodiment will be analyzed more closely, beginning with the suction return valve spring  22  shown in the lower left-hand corner of the drawing of FIG. 2 and, moving diagonally upward and to the right.  
     [0024] The suction valve return spring  22  is a cylindrical, metal, compression spring which is coiled into approximately five convolutions of constant diameter. The spring&#39;s outer diameter is slightly less than the inner diameter of the annular suction poppet  20 , allowing it to fit within the confines of the annular poppet  20 . The diameter of spring  22  is also large enough so that the piston  12  can reciprocate within it during its pumping action without the spring contacting the piston. It is a resilient structure and is fairly resistant to deformation.  
     [0025] Suction poppet  20  is the element to which the suction valve return spring  22  is joined. The suction poppet  20  is an annular, substantially cylindrical member. One of the distinctive features on the valve includes a lip  28  on the diagonally upward facing end in FIG. 2. This lip  28 , extends in an inward concentric manner about three times the depth of the outer wall diameter of the suction poppet  20 . The lip  28  also extends downward slightly so as to form an annular pocket  30  within the suction poppet  20  inner diameter. This pocket  30  is the abutment point for the suction valve return spring  22 . The valve lip also has two concentric, tapered valve seats  29  and  31  for sealing the suction valve  20  along its outermost edges when it closes against a complementary surface of ring segment  32  of valve body  14 . The outside and inside valve seats  29  and  31  form a cone-like section on poppet  20  which narrows toward its center and is able to be matched to an opposing seat  33  on the valve body  14  at the proper time in the piston stroke cycle. This is an adaptation of a feature generally known as a conical seat valve. It provides the conical seal on the outside of a ring completely around the annular opening defined by ring segment  32 .  
     [0026] Referring once more to FIG. 2, the valve body  14  is made up of three cylindrical rings which are formed into one structure but mounted concentrically and in axially spaced relation by integrally molded ribs or spokes. The basic rings include a lower ring  32 , an outer ring  34 , and an inner ring  36  that are linked together by a plurality or radial ribs as at  37 . As mentioned, the lower ring  32  has a frustoconical tapered seat  33  comprising the suction valve seat. There is also an annular passageway  38  defined by these seats, through which fluid is suctioned in when the valve body seat  33  is not engaged against the suction poppet seats  29  and  31  as shown by the flow arrows in FIG. 3.  
     [0027] The outside ring  34  of the valve body  14  provides the base for the outside dome-shaped cylindrical wall of the upper discharge chamber  35  of the valve. Concentric with this wall is another cylindrical segment forming inner ring  36 , which is co-axially mounted to the walls of outside ring  34  by ribs  37 . Inner ring  36  is used to house the discharge poppet  24  and the discharge valve return spring  26 . The fluid pumped into valve body  14  will pass between the walls of the outside ring  34  and the walls of the inner ring  36  between the ribs  37 . The valve body  14  also contains a valve seat  39  (FIG. 3) which mates with the valve seat on the discharge poppet  24 . The seat surface of the valve seat  39  tapers concentrically inward from the outer portion of the valve body  14  at the same angle as the taper on the discharge poppet  24 .  
     [0028] Discharge poppet  24  is a cylindrical cup-shaped segment which has a seat surface  41  which is angled inward to form a conical seat. It is capable of sealing against the opposing seat  39  on the valve body  14  when the piston is in the suction stroke of its cycle. Poppet  24  has a relatively thin cylindrical wall thickness with an inner diameter slightly greater than the diameter of the discharge valve return spring  26 . As such, the return spring is contained within the cup-shaped discharge valve  24 .  
     [0029] The discharge valve return spring  26  may preferably be a metal spring of a slightly smaller diameter than the suction valve return spring  22 . This spring  26  has approximately four convolutions, a constant outer diameter, and, as stated, fits within the inner concentric cylinder of discharge poppet  24 . The spring is stationed against the retaining cap  40  and retracts and compresses against it when the piston is in the discharge stroke of the pump cycle.  
     [0030] The retaining cap  40  is annular and fits tightly against the top of the inner cylinder  36  of the valve body, and contains two grooved surfaces around its outer rim.  
     [0031] FIGS.  3 - 6  illustrate the disposition of the valve parts during the intake and discharge strokes of the pump&#39;s piston. In FIG. 3, fluid is being drawn in suction port  16  during the down stroke of the piston  12 . The fluid is drawn into the lower chamber cavity  42  through an open suction valve  20 . Discharge valve  24  remains seated at this point in the cycle.  
     [0032] The valve housing  10  can also be observed in FIG. 3. The lower portion of the housing shown is a cylindrical shape and contains a bore slightly larger than the piston diameter, allowing reciprocating movement of the piston/plunger therein. Moving upward, the interior bore widens to a width wide enough to house the suction valve return spring  22 . After only a short distance, the bore in the valve housing widens again to accommodate the outer dimensions of suction poppet  20 . In this segment of the bore, the outer diameter of the housing  10  widens outward in a somewhat funnel shape. The interior width of the bore continues for a distance equal to the height of the suction poppet  20  before yet another wider bore is needed to accommodate the bottom of the valve body  14 . At an elevation near the completion of this bore diameter, the outer diameter of the housing  10  regains a vertical cylindrical shape. The interior bore widens to a substantial cavity surrounding the valve body  14 . This opening is contained within the housing  10  except for a suction port  16  which is seen on the left-hand side of the figure. The interior bore narrows again above the cavity to a width appropriate for the upper section of the housing. This bore diameter continues until the completion of the lower section of the housing. The housing is then topped by its second section  35  which is roughly a dome shape and has lower diameter wall which partially slides into the bore diameter. In the top of the second section  35  is a discharge port  18 .  
     [0033]FIG. 4 shows the valve when the piston  12  has reached the bottom of its stroke. When the suction force of the downwardly moving piston drops to zero at the bottom of the stroke, the suction valve return spring  22  is able to expand to force the suction poppet  20  to close against the valve body  14 . The suction poppet  20  and the valve body  14  have mating angled valve seats  44  and  46 , respectively. When seated to one another, they provide a good seal for fluid on either side of the chamber cavity.  
     [0034]FIG. 5 demonstrates a next step in the operating sequence in which the piston  12  moves upward in a discharge stroke. This upward motion causes fluid to push against the discharge poppet  24  and to compress the discharge return spring  26 . These actions cause the discharge valve  24  to be forced open and fluid is forced to flow into the upper chamber  48  and out the discharge opening  18  of the housing  10 . The suction valve is forced closed by its spring  22  and by fluid pressure.  
     [0035]FIG. 6 illustrates the last step in the operation sequence of the valve. Here, the piston  12  has reached the top of its stroke. At this point, the fluid pressure is such as to allow the discharge valve return spring  26  to again expand and close the discharge poppet  24 . This sealed condition is reached when the angled discharge valve seal seat  50  mates with the conical upper seat  52  on the valve body  14 . The valve operation sequence repeats once the piston again starts its downward suction stroke (FIG. 3).  
     [0036] The foregoing is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purposes of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention claimed or the equivalents thereof.  
     Alternative Embodiment  
     [0037]FIG. 7 contains an alternative embodiment of the present invention. This figure generally shows a compound valve assembly for enabling controlled fluid flow. The main components of the device are the valve housing  110  having a cylinder bore  111 , pump or compressor piston  112 , compound valve body  114 , suction or fluid inlet port  116 , fluid outlet or discharge port  118 , suction valve poppet  120 , suction valve return spring  122 , discharge valve poppet  124 , and discharge valve return spring  126 . The piston/plunger  112  is reciprocally driven in the cylinder bore  111  by a suitable pump drive assembly such as that in the aforereference&#39;s Maki et al application.  
     [0038] The valve housing  110  is largely responsible for the overall shape of the valve assembly and contains the main elements within it. The lower portion of the housing is a cylindrical shape and contains a bore lined with an insert  154  whose inside diameter is slightly larger than the piston outside diameter, allowing reciprocating movement of the piston/plunger therein. Moving upward, the interior bore widens to a diameter wide enough to house the suction valve return spring  122  within insert  154 . This diameter continues until the upper end of insert  154  is reached where the interior cavity widens for a small segment just below the lower end of the valve body  114 . Attached above the valve body  114  is a discharge manifold  119 . This portion caps the valve body opening and contains the discharge port  118  through which fluid is expelled under pressure. The outside of the valve housing, generally, is cylindrical and increases in diameter in moving from the bottom of FIG. 7 upward. There is also an additional outwardly protruding ring  121  approximately one quarter the distance up the side of the housing.  
     [0039] The suction valve return spring  122  is a cylindrical, metal, compression spring which is coiled into convolutions of constant diameter. The number of convolutions of this spring is a function of the spring rate and how far one wishes to allow the suction poppet  120  to move, being careful to balance suction spring tension in a way to prevent causing too great of a restriction to the ability of the poppet  120  to open. This is particularly important in applications requiring suction lift. The spring&#39;s outer diameter is slightly less than the outer diameter of the annular suction poppet  120  and fits up against it. The diameter of spring  122  is also large enough so that the piston  112  can reciprocate within it during its pumping action without the spring contacting the piston. It is a resilient structure and is fairly resistant to deformation.  
     [0040] Suction poppet  120  is the element with which the suction valve return spring  122  coacts. Suction poppet  120 , in the embodiment of FIG. 7, is a flat disc containing a circular opening at its center. It is capable of sealing the outer concentric, annular inlet port  116  when in the upper closed position. A flat suction poppet of this type has the advantage of easy manufacture and no concentricity issues. Other types of poppets which could be applied to this design are inwardly tapered poppets and outwardly tapered poppet valves. The suction poppet  120  is limited in its downward travel by a stop provided by insert  154 , positioned around the interior bore of the housing  110 . The stop limits the suction travel of the poppet  120  and the tension placed on spring  122  to minimize the force needed to open the poppet, particularly in applications requiring suction lift.  
     [0041] The valve body  114  is made up of three cylindrical rings which are formed into one structure but mounted concentrically and in axially spaced relation by integrally molded ribs or spokes. There is also an annular passageway  138 , through which fluid is suctioned in when the suction poppet  120  is not sealed against the lower end of the valve body  114 . The outside ring of the valve body  114  provides the base for the upper segment  119  of the valve assembly.  
     [0042] Valve body  114  surrounds the discharge poppet  124  and the discharge valve return spring  126 . The fluid pumped into valve body  114  from annular passageway  138  force the discharge poppet  124  open and will pass over and around the discharge poppet  124  and discharge valve return spring  126 . The valve body  114  contains a valve seat  127  which mates with the tapered periphery forming the valve seat on the discharge poppet  124 . The seat surface of the valve seat tapers concentrically inward from the outer portion of the valve body  114  at the same angle as the taper on the discharge poppet  124 .  
     [0043] Discharge poppet  124  has a head portion which has a tapered seat surface which is angled inward to form a conical seat. It is capable of sealing against the opposing seat on the valve body  114  when the piston  112  is in the suction stroke of its cycle. Extending from the head of the discharge poppet, opposite the conical seat, is a concentrically located stem of small diameter. This stem fits inside the discharge valve return spring  126  and slides along a guide bore  156  within the discharge manifold  119 . This guide bore  156  restricts and gives direction to the discharge poppet  124 . It could be replaced with a cage to serve a similar function.  
     [0044] The discharge valve return spring  126  surrounding the stem of the discharge poppet  124  may preferably be a metal spring of a smaller diameter than the suction valve return spring  122 . This spring  126  has a constant outer diameter. It is compressed between the discharge manifold  119  and the head of the discharge poppet  124  when the piston is in the discharge stroke of the pump cycle.  
     [0045] The operation of this device occurs in a series of steps governed by the reciprocating movement of piston  112 . In the first step, fluid is drawn in suction port  116  during the down stroke of the piston  112 . This fluid is drawn into the housing bore, above the piston  112 , through a now open suction poppet  120 . Discharge poppet  124  remains seated at this point in the cycle by action of its associated spring  126 .  
     [0046] Once fluid has been suctioned into the housing cavity and the piston has reached the bottom of its stroke, the suction force of the downwardly moving piston drops to zero and the suction valve return spring  122  is able to expand to force the suction poppet  120  to close against the seat in the valve body  114 .  
     [0047] The piston  112  then begins to move upward in a discharge stroke. This upward motion causes fluid to push against the discharge poppet  124  and to compress the discharge return spring  126 . These actions cause the discharge valve  124  to be forced open and fluid to be forced into the discharge manifold  119  and out the discharge opening  118 . At this time, the suction valve is forced closed by its spring  122  and by fluid pressure acting on the poppet  120 .  
     [0048] The last step in the operation sequence of the valves occurs when the piston has reached the top of its stroke. At this point, the fluid pressure is such as to allow the discharge valve return spring  126  to again expand and close the discharge poppet  124 . This sealed condition is reached when the angled surface of discharge poppet  124  mates with the seat on the valve body  114 . The operation sequence repeats once the piston again starts its downward suction stroke.