Abstract:
A flow divider, particularly for use in uniformly dividing a single incoming stream of liquid fertilizer into multiple outlet streams. The flow divider features a housing having a bore therein; a distribution sleeve which fits within the bore; and a distribution needle which slides within the distribution sleeve to evenly divide the incoming flow. Flow enters a distribution chamber formed between a tip portion of the distribution needle and the distribution sleeve, preferably flowing over a series of circumferential ribs located on the tip portion, and accelerates through a narrowing, flow-accelerating region between the distribution needle and the distribution sleeve. The flow is then discharged through a series of orifices in the distribution sleeve and out through a series of flow passageways radially arranged around the flow divider. When fluid flow supply is terminated, no pressure is developed and the distribution needle automatically returns to a closed position in which the inlet orifice in the distribution sleeve is closed by the tip portion of the distribution needle, and the outlet flow orifices in the distribution sleeve are closed by means of the body portion of the distribution needle.

Description:
FIELD OF THE INVENTION 
     The invention relates to fluid flow dividers or distributors and, in particular, to a fluid flow divider for use with liquid agricultural fertilizer. 
     BACKGROUND OF THE INVENTION 
     In large-scale agricultural production (i.e., farming), it is common practice to fertilize the soil with a liquid fertilizer. 
     Often, this is done using a knife or disc opener on an applicator or planter, as well known in the art, with a plurality of distribution lines from the flow divider—preferably one associated with each knife or disc opener—used to distribute the liquid fertilizer. A supply of the liquid fertilizer typically is contained in a large tank which is supported on or pulled by the agricultural machinery, and the liquid fertilizer is pumped from the supply tank through a conduit to a flow divider distributor which divides the flow of fertilizer into a plurality of streams, with one stream flowing to each point of placement behind the knife or disc opener. 
     In general, it is important for the flow of fertilizer to be divided uniformly among the several flow streams. Otherwise, some areas of the ground will receive more fertilizer than is required or can be used (hence wasting fertilizer) and other areas will receive less fertilizer than required (hence causing poor crop growth in those areas). 
     Previously, it has been known to use a standard “manifold” system to distribute the liquid fertilizer. Such a manifold system has a single inlet and multiple outlet ports receiving flow from a central manifold plenum or chamber. In order for such a manifold system to distribute flow accurately, an appropriately sized orifice is provided in the flow path of each outlet port, thereby creating a minimum pressure and promoting even distribution between the various ports. Unfortunately, these orifices typically are each sized for a specific, generally narrow flow range. Therefore, variation in fertilizer flow rate, e.g., due to variation in application speed or rate, requires the operator to suspend the fertilizer application and manually change the external orifices to match the new required flow rate. Furthermore, these orifices are subject to clogging. 
     Alternatively, automatically adjusting flow dividers, which operate over a wider range of fertilizer flow rates, have also been used. These previously known, automatically adjusting flow dividers utilize separate needle valves each regulating the flow through a respective exit flow port, and each needing to be calibrated independently. All of the valve needles are linked to a central rod; the central rod, in turn, is held against a spring and diaphragm to control its axial movement and hence the axial positioning of each of the individual port needles. This design has proven to be somewhat cumbersome, and therefore inefficient because the relatively large number of parts and the required calibration of each of those parts increases the cost of the divider and decreases its serviceability—particularly when in the field. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an automatically adjusting flow divider which avoids these limitations of the prior art. 
     A flow divider according to the invention is composed basically of: a housing having a central bore, an inlet port for receiving the input stream of fluid, the inlet port selectively being in fluid communication with the central bore, and a plurality of radially oriented outlet passageways spaced equiangularly around the central bore; and a distribution needle which slides coaxially within the central bore, is biased toward a closed position in which the distribution needle interrupts communication between the inlet port and the central bore and communication between the central bore and the outlet passageways, and, in response to fluid pressure at the inlet port, slides axially in the bore so as to open fluid communication between the inlet port and the central bore and fluid communication between the central bore and the outlet passageways, whereby fluid is distributed generally uniformly to provide the plurality of separate output streams. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The invention will now be described in greater detail in connection with the drawings, in which: 
     FIG. 1 is a perspective view of a flow divider according to the invention; 
     FIG. 2 is an assembly view of the flow divider shown in FIG. 1; 
     FIG. 3 is a section view of the flow divider of the invention taken along lines  3 — 3  in FIG. 1 with no fluid flow through it; 
     FIG. 4 is a cross-sectional view to a larger scale showing the circled portion of FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A flow divider  10  according to the invention is shown in FIGS. 1-3. The flow divider includes a two-piece housing constructed from  316  stainless steel or other suitable corrosion resisting material and consisting of a lower, distribution unit  12  and a cap member  14 ; a removable, universal distribution sleeve  16  constructed from  316  stainless steel or other suitable corrosion resistant material; and a preferably two-component distribution needle  18 , constructed as described in more detail below. The flow divider  10  according to the invention preferably is axially symmetric and formed as a body of revolution, e.g., round in cross-section anywhere along the central axis  19  (FIG.  3 ). 
     The distribution unit  12  has a stem-like, unitary inlet portion  20  and a wheel-like outlet portion  22 . A central bore  24  extends from cap member seating surface  26  through both the outlet portion  22  and the inlet portion  20  and is configured to receive the universal distribution sleeve  16  therein, as described in greater detail below. The central bore  24  extends all the way through the stem-like inlet portion  20  so as to provide a single inlet port  28  at the end thereof, which inlet port  28  preferably is threaded—either internally as shown or externally—so as to connect a conduit (not shown) between the flow divider and a pump which draws liquid fertilizer from a supply tank. A plurality of radially oriented outlet passageways  30  extend all the way from the central bore  24  through the outlet portion  22  of the distribution unit  12  to the exterior surface  32  thereof, with the longitudinal axes arranged perpendicular to axis  14 . The outlet passageways  30  preferably are internally threaded at their outermost ends such that the individual delivery conduits (not shown) can be connected to the flow divider. 
     The outlet ends of the delivery conduits may be connected to row knives or may be positioned behind a disc opener for fertilizer placement in a row without requiring use of any orifice devices. Outlet portion  22  of distribution unit  12  may be provided with between 2 and 20 passageways  30 , models presently under development being provided with either  12  or  20  passageways. 
     Removable universal distribution sleeve  16  is a generally tubular member which fits coaxially within the central bore  24 . Distribution sleeve  16  has an end wall  39  and a side wall (not separately numbered) provided with a plurality of outlet flow orifices  34  extending radially through the side wall of the sleeve so as to provide fluid communication between the cavity  36  of the sleeve and the exterior of the sleeve. The outlet flow orifices  34  are axially or longitudinally positioned along the distribution sleeve  16  such that when the sleeve is inserted completely into the central bore  24  (at which point the bottom end  38  of the sleeve will abut internal shoulder  40  formed within the bore  24 ), the outlet flow orifices  34  will be aligned with the outlet passageways  30  extending through the outlet portion  22  of the distribution unit  12 . 
     If it is desired to distribute liquid to fewer than all outlet passageways  30 , a selected number of those passageways can be blocked by screwing a plug into their outlet ends. Preferably, the passageways to be left open, or the passageways to be plugged, are selected to be uniformly distributed around central axis  19 . For example, if outlet portion  22  has twelve passageways  30  and eight passageways are to be used, every third passageway would be plugged. 
     As shown most clearly in FIG. 2, sleeve  16  has an outer diameter which is reduced slightly over a region below a line  140 . This diameter reduction minimizes the length of the close tolerance fit between sleeve  16  and central bore  24  that prevents fluid from flowing between outlet passageways  30 . 
     A seating flange  42  extends circumferentially around the distribution sleeve  16  near the upper portion thereof and sits within a slightly enlarged, “counterbored” portion  44  formed at the upper end of the central bore  24 , against a shoulder surface  46  of outlet portion  22 . This feature, in connection with the abutment of the bottom end  38  of the distribution sleeve  16  against the internal shoulder  40 , properly positions sleeve  16  longitudinally or axially within the central bore  24 . Furthermore, a small notch  50  formed in the seating flange  42  registers with a small rib  52  extending from the shoulder surface  46  so as to ensure proper angular or rotational positioning of the distribution sleeve  16  within the distribution unit  12 . 
     Distribution needle  18  fits within the cavity  36  of the distribution sleeve  16  and is sized so as to be able to slide axially within the cavity. As noted above, the distribution needle  18  preferably has a two-component design. In particular, the distribution needle  18  has a core needle body member  56  and a sheath-like needle tip member  58 , which is press-fitted onto a needle body extension  60  and securely held thereon, e.g., by small barbs  62  as shown in FIG.  4 . Preferably, needle body member  56  is made from  316  stainless steel or other suitable corrosion resistant material, and the needle tip member  58  is made capable of providing a suitable sealing surface with radial seal  106 , to be described below, from corrosion resistant material such as PFTE, nylon, polypropylene, etc. having good corrosion resistance and a low coefficient of friction. The benefit derived from constructing the distribution needle from two different components is that the material of body member  56  is resistant to wear and corrosion, thereby assuring accurate positioning of needle  18 , and the material of needle tip member  58  minimizes friction between distribution needle  18  and sleeve  16  (described below) or other bearing surfaces (such as between the tip portion of the distribution needle and the needle-receiving inlet flow orifice  72 , as described below). This, in turn, enhances smooth, accurate axial positioning of the distribution needle within the assembly. 
     The lowermost end  66  of the tip portion  68  of distribution needle  18  (i.e., the lowermost end of the needle tip member  58 ) is conically shaped, and the remainder of the tip portion is generally cylindrically shaped. The distribution needle  18  has a series of ribs  70  extending circumferentially around approximately the upper two-thirds of the tip portion  68 , while approximately the lower one-third of the tip portion  68  is smooth-walled so as to fit through and slide easily within needle-receiving inlet flow orifice  72  formed in the end wall  39  of the distribution sleeve  16 . The number of ribs  70  may be between four and six and would depend on needle length. 
     The distribution needle  18  increases in diameter over the length of the frustroconical, flow-accelerating, throat-forming portion  74  to have essentially the same diameter as the cavity  36 , i.e., so that a cylindrical body portion  76  formed partly by body member  56  and partly by needle tip member  58  makes sliding engagement along its length and its periphery with the walls of the cavity  36 . 
     Ribs  70  create a spiraling turbulence in the liquid flow to help distribute the liquid uniformly to the outlet passageways  30 , while the tapered port above ribs  70  converts the turbulent flow to a laminar flow. 
     As shown most clearly in FIG. 3, the distribution needle  18 , and more specifically needle body portion  76 , extends axially or longitudinally beyond the upper surface  80  of distribution sleeve  16 . Cap member  14  is configured to fit down over the portion of the sleeve/needle assembly extending above the cap member seating surface  26  of outlet portion  22 , and cap member  14  is provided with a bore  84  having a diameter through lower portion  86  of the cap member that is approximately the same as the outer diameter of distribution sleeve  16  and a diameter through upper portion  88  of the cap member that is approximately the same as the outer diameter of the body portion  76  of the distribution needle. The cap member  14  fits over the distribution needle/distribution sleeve assembly, as shown most clearly in FIGS. 3 and 4, and is secured against cap member seating surface  26  using, e.g., bolts  90 , which are screwed into corresponding bolt holes  92 , and lock washers  94 . As noted above, the distribution sleeve  16  is removable, and configuring the cap member as a removable item (with the distribution sleeve being securely positioned and held within that portion of the central bore that extends through the distribution unit  12 ) permits easy servicing of all components of the flow divider (e.g., to change to a differently configured distribution sleeve) without needing to remove or disconnect the flow divider from the various inlet or outlet conduits. 
     Compression spring  96  is disposed within the cap bore  84  and bears against end wall  98  of the cap member so as to bias the distributor needle downward against the end wall  39  of the distribution sleeve, with the lowermost one of the circumferential ribs  70  bearing against the inner surface of the end wall  39  of the distribution sleeve so as to limit downward movement of the distribution needle. The stiffness of spring  96  (i.e., the spring constant) is based upon the fluid pressure to which the needle assembly will be subjected in operation. 
     Vent plug  100  is screwed into threaded aperture  102  formed in end wall  98  of cap member  14 . The vent plug  100  allows air to enter and be expelled from the cavity formed within the cap member (i.e., the cap bore  84 ) as distribution needle  18  reciprocates within the bore, thereby permitting free sliding movement of the needle while at the same time keeping environmental debris (e.g., dust) out of the flow divider and preventing contamination. 
     If the flow divider is used for distributing certain types of liquid, such as anhydrous ammonia, vent plug  100  may usefully be replaced by a conduit which would, in the event of seal failure, transport liquid which escapes past the seal to a safe location for containment or re-use. 
     Finally, with respect to the construction of the flow divider  10  according to the invention, a number of seals are provided for proper leak-proof operation. (The seals also help stabilize the position of the distribution sleeve within the assembly.) In particular, a circumferential seal  106  surrounds the upper portion of the body portion  76  of the distribution needle and is positioned so as to sit against the upper surface  80  of the distribution sleeve  16 . It is radially bounded by the wall of the cap bore  84 , and it is longitudinally or axially restrained against the upper surface  80  of the distribution sleeve by means of circumferential shoulder surface  108  formed in the cap member  14 . 
     Seal  106  may be a component referred to as a “V” packing, one form of which is marketed under the name Polyseal™. The “V” packing is oriented so that the open end of the V is exposed to the pressure region to be sealed. Therefore, as pressure increases, the V opens to form a tighter seal. This expansion also imposes a greater resistance to movement on needle  18 . However, expansion occurs at higher pressure levels which allow the increased frictional resistance to be overcome. Such a “V” packing provides greater stability than a conventional O-ring. Seal  106  may be made of a material comparable to Viton®, which offers a good combination of chemical compatibility, coefficient of drag and sealing qualities. For distribution of certain liquids, a material such as Buna-N may be preferable. A seal made of one the materials mentioned above forms a relatively corrosion-resistant seal against the distributor needle while allowing it to move axially substantially without impediment due to the low level of friction between the material from which the lip seal is made and the material ( 316  stainless steel) from which the needle body member  56  is made. 
     O-ring seal  110  fits within circumferential groove  112  formed on the outer surface of the distribution sleeve  16 , near the upper end thereof, and forms a seal between the upper end of the distribution sleeve and the interior surface of the cap member. Similarly, O-ring seal  116  fits within circumferential groove  118  formed in the exterior surface of the distribution sleeve  16  and forms a seal between the distribution sleeve  16  and the outlet portion of the distribution unit  12 , above the outlet passageways  30 ; and O-ring seal  122  fits within circumferential groove  124  formed in the outer surface of the distribution sleeve  16  near the bottom end  38  and forms a seal between the lower end of the distribution sleeve and the interior surface of the inlet portion of the distribution unit. The O-ring seals may be made of the same materials as seal  106 . 
     The seal  106  prevents liquid fertilizer flowing through the flow divider (as described in greater detail below) from flowing between the distribution needle and the distribution sleeve and leaking out of the top of the flow divider. The O-ring seal  116 , along with O-ring seal  110 , prevents fluid from leaking from the flow passageways  30  along the exterior of the distribution sleeve  16  and out of the flow divider through the cap member. O-ring seal  122  prevents fluid being introduced into the flow divider through inlet port  28  from bypassing the needle/sleeve assembly and flowing along the exterior of the distribution sleeve, into the outlet passageways  30  without being regulated. 
     The flow divider according to the invention automatically provides four process stages to distribute the flow of fertilizer substantially equally to all distribution ports. In particular, as liquid fertilizer (or other fluid which the flow divider might be used to distribute) is pumped into the flow divider through the inlet port, the distribution needle is forced to rise within the distribution sleeve against the biasing force of the compression spring such that an annular, flow-through gap is formed between the conical, lowermost end  66  of the distribution needle  18  and needle-receiving inlet flow orifice  72  formed in the bottom end of the distribution sleeve, as shown in FIG.  4 . As the distribution needle rises within the distribution sleeve and the annular flow-through gap opens, the liquid fertilizer flows over the axially symmetric, conical surface of the lowermost end  66  of the distribution needle. The axial symmetry promotes uniform circumferential distribution of the flow past the tip portion  68  of the distribution needle. 
     As the fertilizer (or other fluid) enters the flow distribution chamber  130  defined between the lower portion of the outer surface of the distribution needle and the walls of the cavity  36  of the distribution sleeve  16 , it flows over the series of circumferential ribs  70 . This further helps to distribute the fluid uniformly around the flow distribution chamber and helps to eliminate non-uniformity in the fluid flow which results from the initial distribution around the conical lowermost end  66  of the distribution needle as the fluid enters the flow distribution chamber  130 . 
     As the distribution needle rises within the distribution sleeve, the juncture edge  132  between the cylindrical body portion  76  and the conical surface of the throat-forming portion  74  moves at least partially past the outlet flow orifices  34  in the wall of the distribution sleeve, thereby at least partially opening the outlet flow orifices  34  so as to permit fluid flow through them. As the fluid flows beyond the flow distribution chamber  130 , it is caused to accelerate in a flow-accelerating region  131  by virtue of the narrowing of the flow passageway, which narrowing is attributable to the outward taper (from bottom to top) of the throat-forming portion of the distribution needle is constructed to prevent liquid separation from the walls delimiting the flow passageway and greater control at the variable orifice outlets. 
     The flow area associated with each outlet passageway  30  increases abruptly at the inlet end of each outlet flow orifice  34 . The narrowing passage which defines flow-accelerating region  131  constitutes a venturi which combines with each outlet passageway for form a flow nozzle. At the outlet side of each flow nozzle, i.e., in each orifice  34 , there is a sudden pressure drop due to the increased flow area, offset by the pressure developed in chamber  130 . 
     Device  10  functions in the manner of an orifice meter and has an automatic self-equalizing operation in that the pressure within chamber  130  is balanced against the return force of spring  96 . Therefore, as the rate at which liquid is delivered to chamber  130  increases, the pressure in chamber  130  increases and needle  18  is displaced to increase the area of the narrowest point in each liquid flow path. 
     Because of this adjustment in the area at the narrowest point in each flow path, the flow resistance within device  10  decreases with increasing flow rate. As a result, the outlet pressure experienced by the pump increases at a relatively low rate as flow rate increases. In contrast, with a fixed flow resistance, pump outlet pressure would increase at a higher rate, as a quadratic function of flow rate. In the case of a positive displacement pump, the results would be that the outlet pressure would reach the limit of the pump after only a small change in flow rate. 
     This four-stage process occurs automatically as a result of the design of the flow divider of the invention and results in highly evenly distributed flow from the single inlet to the multiple outlets. 
     Preferably, the flow divider is supplied from a positive displacement pump having a variable pumping rate. As liquid is pumped, the resulting pressure displaces distribution needle through a distance which varies with the flow rate. Therefore, the cross section of the passage at each flow orifice  34  increases with flow rate. As a result, the pressure as seen at the pump outlet increases more gradually and the pumping rate can be varied over a wider range than a distribution having outlet passages of fixed cross section. Thus, uniform flow distribution is maintained across a relatively wide range of fertilizer application rates (as compared to prior art, orifice-based systems), and such variation in fertilizer application rates will promote self-equalizing adjustments, with minimal change in system pressure, within flow divider  10  to accommodate changes in application, or flow, rate. 
     When the supply pressure drops to zero (i.e., when the supply pump is stopped), the compression spring  96  forces the distribution needle back to its original, closed position, with the tip portion of the distribution needle closing off the needle-receiving inlet flow orifice  72  and the juncture edge  132  sliding back past the outlet flow orifices  34  such that they are covered by the body portion of the distribution needle and flow through the divider is sealed off, preventing back flow siphoning between passageways  30 . 
     It will occur to those having skill in the art that other configurations and embodiments beyond those shown in the preceding disclosure are possible. For example, although the flow divider  10  is shown as being axially symmetric with all components having round cross-sections, i.e., the flow divider is formed as a body of revolution, the components do not need to be so limited in their configuration. For example, a square bore, sleeve, and pin configuration are envisioned. Such modifications to and departures from the embodiments described above are deemed to be within the scope of the following claims.