Abstract:
A valve assembly comprising a body member forming a channel having first and second ends, forming a seat surface within and at the first end of the channel about an orifice that faces in the direction of the second end, the channel forming a first coupler at the second end, a closure member forming a closing surface and an oppositely facing bearing surface, the closing surface configured to be received on the seat surface to close the orifice, the closing member received within the channel with the closing surface facing the seat surface, a spring member having first and second ends and received within the channel with the first end of the spring member contacting the bearing surface and an adjustment member having first and second ends and forming a second coupler at the first end of the adjustment member that cooperates with the first coupler to mechanically link the adjustment member within the channel in various relative juxtapositions, one of the adjustment member and the body member forming an outlet passage from the channel, whereby, the adjustment member position within the channel is adjustable to alter the degree of spring compression and also the pressure on the closure member.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable. 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   This invention relates generally to variable flow valve assemblies and more specifically to an adjustable flow rate valve assembly for use with a liquid fertilizer sprayer implement. 
   This section of this document is intended to introduce various aspects of art that may be related to various aspects of the present invention described and/or claimed below. This section provides background information to facilitate a better understanding of the various aspects of the present invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
   When agricultural liquids are applied to crops it is typically desirable to apply an ideal amount of liquid to each crop. Thus, for instance, when liquid fertilizer is applied to crops, to ensure that the crops grow at the same rate and are harvestable at the same time, it is desirable that the same amount of liquid fertilizer be applied to each crop. One way to apply an agricultural liquid to crops is by towing a liquid dispensing assembly behind a tractor through a field where the implement includes a wheel supported liquid container/tank, a manifold, a pump and valves. Here, the manifold typically includes an elongated member that forms a channel that is generally perpendicular to the trajectory of tractor travel through the field. In some cases the manifold will be 16 or even 32 crop row units wide and will form separate outlet apertures that generally reside above each of the rows that the manifold passes over during transport. 
   Valves are positioned at each of the openings and hence above each of the crop rows. Each valve includes a spring loaded needle member having a closure surface that is biased against a seat surface to close the valve. The valve is juxtaposed with respect to the manifold such that pressure within the manifold is applied to the closure surface. The pump pumps liquid from the container to the manifold and, when manifold pressure exceeds a cracking pressure, the manifold pressure forces the needle member into an open position and hence liquid is dispensed through the valve. 
   The rate of liquid dispensation must be controllable in most agricultural applications for two reasons. First, some crops may require more of the dispensed liquid than other crops and, indeed, even within a single field the same type of crop may require different amounts of the dispensed liquid in different sections of the field. Second, even where each section of a field requires the same amount of liquid, where tractor speed is varied, to deliver the same amount of liquid to crops, the rate of dispensing must be modified. For instance, where a tractor moves at five miles an hour and a first rate of dispensing occurs, if the tractor speed is increased to ten miles an hour, to dispense the same amount of liquid per meter within the field, the rate of dispensing likewise must be increased by 100%. 
   In the system described above rate of dispensing is generally controllable by controlling the pressure within the manifold. To this end, after a valve cracking pressure is exceeded, the size of the gap between a valve seat surface and closure surface changes as a function of the pressure within the manifold. Thus, as pressure within the manifold increases, the rate of liquid dispensed through a valve likewise increases. 
   One problem that has occurred with liquid delivery systems like the one described above is that it is expensive to manufacture valve springs that have identical loading characteristics. Where less expensive and less uniform springs are employed, the cracking pressures of the valves used on a single assembly may be very different and, indeed, the pressures that result in uniform opening of the valves may be different. Thus, as the manifold pressure is constant throughout the manifold, the end result when non-uniform springs are used within a valve is that the rate of dispensing with systems like the one described may be different for each of the valves on a system. 
   Thus, it would be advantageous to have a liquid dispensing assembly where valve construction enables a valve user to modify relative juxtapositions of valve components to compensate for different spring loading characteristics. 
   BRIEF SUMMARY OF THE INVENTION 
   Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
   It has been recognized that a simple adjustment member may be provided that alters the location of an anchoring end of a valve spring thereby increasing or decreasing the pressure applied by the valve spring on a closure member and against the force of pressure within the manifold. When such an adjustment member is provided, valves can be tested to determine if valve flow rate with respect to manifold pressure is acceptable and, where the pressure to flow characteristics are not acceptable, the adjustment member can be adjusted to alter the characteristics. In some cases the valve characteristics will be set after assembly and prior to shipping the valves and in other cases end users will be able to modify valve operating characteristics via the adjustment members. 
   Consistent with the above comments, at least some embodiments of the present invention include a valve assembly comprising a body member forming a channel having first and second ends, forming a seat surface within and at the first end of the channel about an orifice that faces in the direction of the second end, the channel forming a first coupler at the second end, a closure member forming a closing surface and an oppositely facing bearing surface, the closing surface configured to be received on the seat surface to close the orifice, the closing member received within the channel with the closing surface facing the seat surface, a spring member having first and second ends and received within the channel with the first end of the spring member contacting the bearing surface and an adjustment member having first and second ends and forming a second coupler at the first end of the adjustment member that cooperates with the first coupler to mechanically link the adjustment member within the channel in various relative juxtapositions, one of the adjustment member and the body member forming an outlet passage from the channel, whereby, the adjustment member position within the channel is adjustable to alter the degree of spring compression and also the pressure on the closure member. 
   In at least some cases the adjustment member forms the outlet passageway between the adjustment member first and second ends. In addition, in some cases the first coupler includes a threaded second end of the channel and the second coupler includes a threaded first end of the adjustment member. 
   Some embodiments include a valve assembly comprising a body member forming an annular channel having first and second ends, forming an annular seat surface within and at the first end of the channel about an orifice that faces in the direction of the second end, the channel threaded at the second end, a closure member forming a closing surface and an oppositely facing bearing surface, the closing surface configured to be received on the seat surface to close the orifice, the closing member received within the channel with the closing surface facing the seat surface, a helical spring having first and second ends and received within the channel with the first end of the spring contacting the bearing surface and an adjustment member forming an annular outlet channel between first and second adjustment member ends, the adjustment member threaded at the first end of the adjustment member, the first end of the adjustment member threadably received within the body member channel and contacting the second end of the spring thereby at least partially compressing the spring and placing pressure on the closure member. 
   Moreover, some embodiments include a flow divider apparatus comprising a header member forming a header channel, at least one inlet and at least two outlets, a liquid source linked to the header channel inlet, a separate valve assembly for each of the header member outlets, each valve assembly including: a body member forming a body member channel having first and second ends, forming a seat surface within and at the first end of the body member channel about an orifice that faces in the direction of the second end, the body member channel threaded at the second end, the first end of the body member linked to one of the header member outlets, a closure member forming a closing surface and an oppositely facing bearing surface, the closing surface configured to be received on the seat surface to close the orifice, the closing member received within the channel with the closing surface facing the seat surface, a spring member having first and second ends and received within the channel with the first end of the spring member contacting the bearing surface and an adjustment member forming an annular outlet channel between first and second adjustment member ends, the adjustment member threaded at the first end of the adjustment member, the first end of the adjustment member threadably received within the body member channel and contacting the second end of the spring member thereby at least partially compressing the spring and placing pressure on the closure member. These and other objects, advantages and aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
       FIG. 1  is a side perspective view of a tractor pulling an agricultural implement according to at least one aspect of the present invention; 
       FIG. 2A  is a schematic diagram illustrating the liquid delivery assembly of  FIG. 1  in greater detail; 
       FIG. 2B  is a side perspective view of a coupling mechanism extending from a manifold of  FIG. 2A ; 
       FIG. 3  is an exploded side elevational view of one of the valve assemblies of  FIG. 2 ; 
       FIG. 4  is a side elevational view of the valve assembly of  FIG. 3 , albeit in an assembled state; 
       FIG. 5  is a cross-sectional view taken along the line  5 - 5  in  FIG. 3 ; 
       FIG. 6  is a top plan view of the closure member of  FIG. 3 ; 
       FIG. 7  is an enlarged view of the closure member of  FIG. 3 ; 
       FIG. 8  is a partial cross-sectional view taken along the line  8 - 8  in  FIG. 4  with the valve assembly in a closed state; 
       FIG. 9  is similar to  FIG. 8 , albeit illustrating the assembly in one open state; 
       FIG. 10  is similar to  FIG. 9 , albeit illustrating the assembly in a second open state; 
       FIG. 11  is similar to  FIG. 8 , albeit illustrating the assembly in a closed state with the adjustment member in a second adjusted position that is different than the position illustrated in  FIG. 8 ; 
       FIG. 12  is similar to  FIG. 9 , albeit illustrating another embodiment of the present invention; and 
       FIG. 13  is a plan view of a manifold coupling member of the valve assembly of  FIG. 3 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   One or more specific embodiments of the present invention will be described below. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
   Turning now to the drawings where like reference numbers correspond to similar elements throughout the several views and, more specifically, referring to  FIG. 1 , the present invention will be described in the context of an exemplary agricultural assembly  40  shown attached to a tractor  10 , including an operator control cab  12 . Tractor  10  includes an engine compartment  14 , the engine of which is coupled to a drive train  16  and  18  to the rear and front wheels  22  and  20 , respectively, of the tractor  10 . Tractor  10  may be coupled by a three point hitch  24  or by means of a standard draw bar  26  to a frame  38  of implement  40  for towing implement  40  across agricultural fields. Implement  40 , as illustrated in  FIG. 1 , includes ground support wheels  44  connected to the frame  38  which in turn supports a plurality of row planters, in the illustrated instance  16  (not separately illustrated), in spaced apart relation across frame  38 . 
   Several components are mounted to frame  38  and other supporting structure appended thereto including a controller  230 , a liquid (e.g., fertilizer, herbicide, insecticide, etc.) distribution assembly  30  and a seeding assembly  50 . Hereinafter, unless indicated otherwise, assembly  50  will be referred to as a fertilizer assembly although other fluid dispersing assemblies are contemplated. Fertilizer assembly  30  includes a fertilizer bin or container  45  and seeding assembly  50  includes one or more seed hoppers  75  for storing fertilizer and seed during transport. Generally, referring still to  FIG. 1 , fertilizer is supplied to the ground through a metering device which controls the flow of the fertilizer and keeps it moving from container  75  to the ground as implement  40  is moved over a field. The fertilizer precedes the seed, and is deposited via fertilizer tubes (see  121  in  FIG. 1 ) adjacent (e.g., two inches to the side of) each seed furrow to be subsequently formed. To this end, a separate disk  96  associated with each row unit opens a furrow and fertilizer is deposited into the furrow. Second, furrow openers  97 , associated with each of the row units form additional furrows to the sides of the first furrows for depositing seed at predetermined intervals. A furrow closer  98  closes the loose soil over the deposited seeds. A furrow packing wheel  99  gently rolls over the closed furrow and tamps the soil to insure the seed remains within the soil. 
   Here, it should be appreciated that while fertilizer assembly  30  is illustrated as being located in front of seeding assembly  50  and is described as depositing fertilizer to the side of the seed furrows, other embodiments are contemplated wherein the fertilizer assembly may deposit fertilizer subsequent to seed application and, in some cases, directly into the furrows receiving the seed or, in some cases, onto the packed soil that covers the applied seed. Moreover, in some cases the liquid fertilizer assembly  30  may be used with other fertilizer assemblies such as dry fertilizer assemblies or, in some cases, may be used as part of a fertilizer implement that does not include a seeding assembly. 
   Seeding assembly  50  includes a well known drum or barrel type dispenser  120  which is fed seed or the like from hopper  75  and, due to air pressure provided by a blower  122 , maintains seed in peripheral, spaced apart, row-like apertures  124  circumscribing the barrel  120  of the seed applicator. Seed pick-up tubes  126 , disposed within barrel  120  conduct air and single seeds at a time to the row units and thereby to the ground or soil there below. The amount of seed output through the tubes per unit of time (i.e. the rate of seed deposition), such as by tube  127 , is dependent upon the speed of rotation of barrel  120 . Barrel  120  is rotated by a drive means  130  under control of local controller  230 . 
   The amount or dosage of farming material to be applied for each portion of a field is calculated by a processing located within tractor cab  12 . The dosage to be applied is converted to the amount of actuator or applicator motion per distance of the planter traveled and sent by way of a bus  200  to implement controller  230 . Controller  230  is equipped with a ground speed sensor (not illustrated) and uses signals therefrom to determine the proper amount or dosage of farming material, whether it be seed or fertilizer (or, in some cases, herbicide or insecticide), to deposit at any time. Once proper dose is determined, processor  230  controls the seeding assembly drum  120  speed to affect desired seed dispensation. In addition, controller  230  controls fertilizer dispensing assembly  30  as described below to deliver the required amount of fertilizer via tubes  121 . 
   Referring now to  FIGS. 1 and 2A , in addition to container  45 , fertilizer assembly  30  includes a pump  64 , a manifold  70 , a plurality of valve assemblies, three of which are identified collectively by numeral  68  and distribution tubes  60  and  62 . Tube  60  connects the bottom of container  45  to the inlet of pump  62  while tube  62  connects the outlet of pump  64  to the inlet of manifold  70 . Controller  230  is linked to pump  64  via a control line and, as its label implies, controls pump operations including turning pump  64  on and off and controlling the speed of the pump impeller (not separately illustrated). 
   Manifold  70  may take any of several different forms. In the illustrated example manifold  70  is an elongated and rigid pipe member having an inlet end  71  and a distal capped end  73  opposite the inlet end  71 . Manifold  70  forms a generally open manifold channel (not illustrated) along its length. Member  70  forms a series of generally downward facing openings, one of which is identified by numeral  79 , one opening  79  for each of the row units included in implement  40 . Thus, in the present example, member  70  includes sixteen separate openings that are generally equispaced along its length, one opening for each of the sixteen separate row units included on implement  40 . 
   Surrounding each opening  79  manifold  70 , in at least some embodiments, includes some type of coupling mechanism that cooperates with another coupling mechanism on one of the valve assemblies  68  to secure the valve assembly to manifold  70 . For example, referring to  FIG. 2B , an exemplary coupling mechanism  300  is illustrated. Mechanism  300  includes a rigid cylindrical nipple member  302  that surrounds an associated manifold opening (see again  79  in  FIG. 2A ) and that extends to an open distal end that forms a flat annular sealing surface  304 . Thus, nipple member  302  forms a channel  306  from the inside of manifold  70  that opens at a distal end. Two locking members  308  extend laterally from opposite sides of nipple member  302  that cooperate with other structures to be described below to secure a valve assembly  68  to nipple member  302 . Other mechanical coupling configurations are contemplated. Here it must suffice to say that the coupling mechanism must be robust and must form a hermetic seal between the manifold and the valve assembly  68 . 
   Referring still to  FIG. 2A , each of valve assemblies  68  has a similar configuration and operates in a similar manner and therefore, in the interest of simplifying this explanation, only one of valve assemblies  68  will be described here in detail. To this end, referring also to  FIG. 3 , exemplary valve assembly  68  includes a manifold coupling member  72 , a body member  74 , a closure member  76 , a spring member  78  and an adjustment member  80 . Manifold coupling member  72  has top and bottom ends  88  and  86 , respectively and forms an internal channel  83  that extends, generally, from the top end  88  through to the bottom end  86 . In at least some embodiments, some type of coupling mechanism is provided proximate top end  88  which may be configured to cooperate with coupling mechanism  300  on manifold  70  (see again  FIG. 2B ) to couple coupling member  72  to manifold  70  such that one of the openings  79  in manifold  70  opens into channel  83  and is hermetically sealed therewith. To this end, referring still to  FIG. 3 , member  72  generally includes three integral sections including a first coupling section  310 , a sealing section  312  and a second coupling section  314 . 
   First section  310  is cylindrical and forms two apertures (one shown as  82  in  FIG. 3 ) in opposite sides thereof that are formed to tightly receive the locking members  308  that extend from one of the nipple members  302  (see again  FIG. 2B ). In addition, referring also to  FIG. 13 , the internal surface of channel  83  forms passageways  316  that are sized and juxtaposed to pass locking members  308 . Each of passageways  316  open at lower ends thereof into one of apertures  82 . To couple member  72  to one of nipple members  302 , locking members  308  are aligned with passageways  314 , member  72  is slid over nipple member  302  and then member  72  is rotated until locking members  308  are jammed into the restricted portions of apertures  82 . To help rotate coupling members  72  during installation, two arm members  84  are provided on each member  72  that extend from opposite sides of the external. 
   Referring still to  FIGS. 3 and 13 , within sealing section  312  the internal surface of channel  83  forms an annular sealing surface  320  dimensioned to receive the annular sealing surface  304  formed at the distal end of nipple member  302 . An elastomeric O-ring may be positioned between surfaces  320  and  304  to affect a hermetic seal. Within second coupling section  314  the internal surface of channel  83  is threaded. 
   Referring still to  FIG. 3  and also to  FIG. 8 , body member  74  is an elongated, rigid and generally cylindrical member having first and second ends  142  and  144 , respectively, and forming a body member channel  173  that extends from the first end  142  through to the second end  144 . The external surface of member  74  at first end  142  is threaded (see  90  in  FIG. 3 ) with a thread that matches the pitch of the thread formed by channel surface  83  of coupling member  72  at the lower end  86  of member  72  so that first end  142  is threadably receivable within the lower end of channel  83 . In addition, three ribs  140  are formed on the external surface of member  74  near second end  144 . Ribs  140  are provided so that a tube  121  (see again  FIG. 1 ) for delivering liquid fertilizer or the like can be securely mounted thereto by press-fitting the tube over members  140 . If desirable, an additional mechanical clamping mechanism (not illustrated) may be provided to hold a tube  121  on to second end  144 . 
   Referring still to  FIG. 8 , proximate first end  142  the internal surface of channel  173  is restricted and forms a reduced diameter orifice  260 . In addition, referring also to  FIG. 9 , below orifice  260  channel surface  173  forms a valve seat surface  262  that generally faces downwardly and has a frusto-conical shape. While member  74  may be formed of any sufficiently rigid material, in at least some embodiments, member  74  is formed of steel and, most preferably, is formed of stainless steel. 
   Referring still to  FIG. 3  and also to  FIGS. 6 and 7 , closure member  76  is a rigid and, in some embodiments, stainless steel member including first and second ends  180  and  182 , respectively, and an external surface  172  that defines various features of member  76  that are important to proper operation of the illustrated embodiment. More specifically, external surface  172  forms a conical closure surface  184  at first end  180  that has an apex  174  that faces away from second end  182 . Conical surface  184  is configured and dimensioned such that it is snuggly receivable against seat surface  262  (see again  FIG. 8 ) formed by body member  74  so that, when surface  184  is received against surface  262 , no liquid passes therebetween. 
   Referring still to  FIGS. 3 and 7 , external surface  272  forms a bearing surface  186  at second end  182  of member  76  where bearing surface  186  generally extends in the direction opposite first end  180 . Bearing surface  186  has specific dimensions which, as best illustrated in  FIG. 8 , enable at least a portion of surface  186  to be received within one end of helical spring  78  so that spring  78  is centered on surface  186  and with respect to member  76 . 
   Between surfaces  184  and  186 , external surface  172  is generally a cylindrical member having sections or channels of the external surface removed such that passageways are formed therealong generally along the length of member  76  between ends  180  and  182 . For example, referring also to  FIG. 6 , in at least one embodiment of the present invention, portions of the external surface  172  are removed such that three generally equispaced channels  170   a ,  170   b  and  170   c  are formed along the length of member  76  between the first and second ends  180  and  182 , respectively. Between each two passageways (e.g.,  170   a  and  170   b ) a lateral guide member (e.g.,  171   a ,  171   b ,  171   c ) is formed. The radius R of member  76  (see again  FIG. 6 ) is slightly less than the radius formed by channel  173  within body member  74  (see again  FIG. 8 ). Member  76  may be formed of any rigid material and, in at least some embodiments, will be formed of stainless steel. 
   Referring once again to  FIG. 3 , spring member  78  is, in at least the illustrated embodiment, a helical spring having first and second ends  146  and  148 , respectively. Spring  78  is configured and dimensioned such that bearing surface  186  is at least partially receivable within first end  146  as described above. In addition, member  78  is dimensioned such that member  78  is receivable within channel  173  formed by body member  74 . 
   Referring once again to  FIG. 3 , adjustment member  80  is a rigid cylindrical member having first and second ends  149  and  150 , respectively. Referring also to  FIG. 8 , member  80  is threaded on its external surface (see  87  in  FIG. 8 ) with a pitch that matches the pitch of the thread formed at the second end of body member  74  (see again  147  in  FIG. 8 ) such that first end  149  of member  80  is threadably receivable within second end  144  of body member  74 . As best seen in  FIG. 8 , in at least some embodiments, adjustment member  80  forms an internal channel  274  that extends between first and second ends  149  and  150 , respectively. At first end  149 , channel  274  is wider so that a rib or rim  270  is formed therein that faces out first end  149 . Channel  274  is dimensioned such that second end  148  of spring member  78  is receivable within the wider portion of channel  274  formed at first end  149  and on rim  270  as illustrated. 
   To assemble valve assembly  68 , referring to  FIGS. 3 and 8 , first end  142  of body member  74  is aligned with the threaded lower end of channel  83  and is threadably attached thereto. Next, first end  180  of closure member  76  is aligned with second end  144  of body member  74  and, more specifically, with the second end of channel  173 , and is slid there into until closure surface  184  rests against seat surface  262 . Continuing, spring  78  is aligned with channel  173  and is inserted into channel  173  until first end  146  contacts bearing surface  186 . Next, first end  149  of adjustment member  80  is aligned with the threaded second end  144  of member  74  and is threadably attached thereto. Eventually, as member  80  is further threadably attached to the second end of member  74 , rim  270  (see again  FIG. 8 ) contacts second end  148  of spring member  78  and forces spring member  78  and closure member  76  against seat surface  262 . Further rotation of member  80  causes additional pressure to be applied via spring  78  and member  76  between seat surface  262  and closure surface  184 . 
   After the valve assemblies  68  have been assembled as described above, referring once again to  FIG. 2 , ach of the valve assemblies  68  is mounted with respect to a separate one of openings  79  to operate as an outlet for liquid fertilizer pumped into manifold  70 . 
   In operation, referring still to  FIG. 2A  and also to  FIGS. 8 and 9 , with adjustment member  80  set to a specific relative location with respect to orifice  260 , when pump  64  is turned on, the pressure within manifold  70  increases. If the speed of pump  64  is sufficient, the pressure within manifold  70  will increase to the point where the pressure forces each of valves  68  from a closed state into an open state. To this end, referring to  FIG. 9 , when a cracking pressure is achieved within manifold  70 , the pressure above orifice  260  forces closure surface  184  off seat surface  262 . Once an opening is formed between surfaces  184  and  262 , liquid fertilizer passes along the trajectories indicated by arrows  250  from within the portion of channel  173  above orifice  260 , through closure member channels (e.g.,  170   a ), through spring member  78  and then through adjustment member channel  274 . For any manifold pressure above the cracking pressure, the closure member  76  and spring member  78  will reach a steady-state orientation wherein the space defined by surfaces  184  and  262  remains steady. When pressure within manifold  70  is altered, the steady-state relationship between surfaces  184  and  262  changes. For example, referring also to  FIG. 10 , assuming a greater pressure within manifold  70  at least some of that pressure is relieved by spring  78  becoming further compressed and the space between surfaces  184  and  262  increasing as illustrated. 
   It should be appreciated that the cracking pressure of each valve assembly  68  may be adjusted by simply rotating adjustment member  80  in the clockwise or counter-clockwise direction to increase or decrease the pressure or force placed on closure member  76  by spring member  78 . To this end, when member  80  is rotated such that member  80  is further received within channel  173 , spring  78  is preloaded to a greater degree and therefore the cracking pressure for the assembly is increased appreciably. Similarly, by rotating member  80  in the opposite direction so that member  80  is received to a lesser degree within channel  173 , spring member  78  loading is reduced and hence the cracking pressure of the valve assembly is also reduced. To this end,  FIG. 11  illustrates the assembly of  FIG. 9 , albeit with adjustment member  80  further received within channel  173  such that spring member  78  is compressed to a greater degree in  FIG. 11  than in  FIG. 9 . As described above, the cracking pressure for the valve assembly as adjusted in  FIG. 11  would be greater than the cracking pressure for the valve assembly as adjusted in  FIG. 9 . 
   In at some embodiments of the present invention it is contemplated that the valve assemblies  68  may be configured so that they are adjustable by an ultimate end user (e.g., a farmer). In other cases, it is contemplated that the valve assembly  68  would be pre adjusted at a manufacturing facility prior to shipping for use. In either case, a jamming nut (not illustrated) or the like may be provided that is threadably receivable on the second end  150  (see again  FIG. 8 ) of adjustment member  80  and that can be threadably jammed against second end  144  of body member  74  to lock the relative positions of body member  74  and adjustment member  80  unless affirmatively unjammed. 
   In at least some cases spring member  78  is selected and adjustment member  80  is set and locked with respect to body member  74  such that the pressure within manifold  70  ranges between 10 and 100 pounds per square inch (psi) for liquid fertilizer flow rates between 0.05 and 0.50 gallons per minute (gpm). In other cases, the pressure range will be between 15 to 50 psi for flow rates between 0.7 and 0.43 gpm. 
   Referring now to  FIG. 12 , one additional embodiment  68 ′ of the present invention is illustrated. In  FIG. 12 , many of the components described above are identical and, therefore, in the interest of simplifying this explanation, will not be described again here in detail. Here, it should suffice to say that elements that are identical to the elements described above are identified by the same numerals and, elements or features that are similar but have some distinguishing characteristics are identified by the same numerals used above followed by a “′”  . Moreover, new features of the embodiment illustrated in  FIG. 12  are identified with new numerals. 
   Valve assembly  68 ′ in  FIG. 12  is generally different than the embodiment described above in that, adjustment member  80 ′ does not form a channel but rather blocks flow out the second end of body member  74 ′ and, body member  74 ′ includes a lateral nipple  290  that extends laterally about mid-way along its length between its first and second ends and forms an outlet channel  292  that opens from body member channel  173 ′. In this case, as illustrated, when closure surface  184  is separated from seat surface  262 ′, liquid passes between the space formed by surfaces  184  and  262 ′, through the channels (e.g.,  170   a ) formed by closure member  76  and out of channel  173 ′ through lateral channel  292 . In this case, delivery tubes, like tube  121  in  FIG. 1  would be secured about nipple  290  in some suitable fashion to deliver liquid to the soil there below. 
   While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. For example, while threaded mating surfaces  173  and  87  are used above to adjustably couple adjustment member  80  to body member  74 , other types of mechanical couplers are contemplated. Thus, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. 
   To apprise the public of the scope of this invention, the following claims are made: