Abstract:
The seed distribution tower of an air seeder has a distribution head that splits a single, primary stream of conveying air and seeds into a plurality of secondary streams for delivery to openers that deposit the seeds into the ground as the seeder advances. The outlets through which the secondary streams exit the head are constructed as modules that can be individually installed and replaced without disassembling the entire head. Shut-off valves and/or flow sensors may or may not be incorporated into certain or all of the modules to provide optimum user flexibility.

Description:
TECHNICAL FIELD 
     The present invention relates to seed distribution towers of the type used on air seeders to split a primary stream of air and seeds from a single source of supply into a plurality of secondary streams for conveyance to a corresponding plurality of separate openers that deposit the seeds into the ground as the seeder advances. More particularly, in some aspects it relates to improvements in a tower as disclosed and claimed in prior co-pending U.S. patent application Ser. No. 13/157,890, titled “Seed Distribution Tower for an Air Seeder”, and assigned to the assignee of the present invention. In other aspects it relates to modular construction concepts for a seed distribution tower that are not necessarily limited to use with the concepts disclosed in the &#39;890 application. 
     BACKGROUND AND SUMMARY 
     The tower as disclosed and claimed in the above-noted &#39;890 application has seed flow sensors for the secondary streams of air and seeds that are located at the distribution head of the tower, preferably within the head itself. Likewise, the tower of that application can be adapted for use in tram line farming practices wherein one or more of the hoses carrying secondary streams to the openers can be selectively shut off so that no seeds are planted for that particular row. As in the case of the sensors, a valve for the tram line hose is located at, and preferably within, the distribution head. In addition, a special housing immediately below the distribution head encloses and protects delicate wiring and sensitive connectors associated with the various sensors and valves of the tower. 
     A tower in accordance with the principles of the present invention carries forward with, and in some instances further refines, the above-noted aspects of the &#39;890 application. In addition, a tower in accordance with the principles of the present invention introduces a simplified, modular construction for the distribution head wherein discharge outlets for the secondary streams are presented by individual outlet modules that can be quickly and easily installed and removed from the distribution head on an individual basis. There is no need to disassemble the entire distribution head in order to replace a single outlet module. Among other things, this design facilitates manufacture, makes it easy for the farmer to remove, replace, and exchange individual modules, permits significant flexibility as to which, if any, of the discharge outlets will be devoted to a tram line, and provides the farmer with many choices as to which modules to install for carrying out different functions. The outlet modules may take a variety of different forms and carry out a variety of different functions in addition to their primary functions of serving as a means of directing secondary streams of seeds and air from the distribution tower. They need not include any flow sensors or shut-off valves at all. 
     In a preferred form of the invention a flow sensor for each secondary hose is incorporated into the outlet module itself so that the sensor forms a part of the distribution head. Likewise, at least certain of the outlet modules may have a shut-off valve incorporated into the body of the module so that the distribution head can be easily adapted for shutting off one or more of the secondary hoses by simply installing the appropriate valve-equipped module(s). An electrically operated motor can be provided for each valve as part of the module, and such motor can be selectively detached from the valve to permit manual valve actuation if desired. 
     The outlet modules are designed to be installed and removed without the use of tools. In a preferred embodiment a latch for releasably retaining a module in its seat within the distribution head includes a spring-loaded barb on the body of the module that cooperates with structure adjacent the seat to hold the module in place. By manually depressing the barb to a releasing position, the module may be easily withdrawn from the seat. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a left, front perspective view of a cultivation air seeder utilizing seed distribution towers in accordance with the principles of the present invention; 
         FIG. 2  is a left side elevational view of the seeder; 
         FIG. 3  is an enlarged left front perspective view of one of the distribution towers of the seeder with the secondary distribution hoses removed for clarity; 
         FIG. 4  is an enlarged, fragmentary bottom perspective view of the tower with parts broken away to reveal details of construction; 
         FIG. 5  is a fragmentary exploded view of the tower; 
         FIG. 6  is a top plan view of the tower with a portion of the distribution head broken away to reveal internal details of construction, including the plenum; 
         FIG. 7  is a fragmentary vertical cross-sectional view through the tower taken substantially along line  7 - 7  of  FIG. 6 ; 
         FIG. 8  is a fragmentary top perspective of the distribution head of the tower with the lid partially broken away to reveal internal details of construction, including the plenum; 
         FIG. 9  is an enlarged, cross-sectional perspective view of one embodiment of an outlet module of the tower, the shut-off valve of the module being shown in an open position; 
         FIG. 10  is an enlarged, cross-sectional perspective view of the module of  FIG. 9  with the shut-off valve shown in a closed position; 
         FIG. 11  is an exploded top perspective view of the module of  FIG. 9 ; 
         FIG. 12  is an exploded bottom perspective view of the module of  FIG. 9 ; 
         FIG. 13  is a side perspective view of the module of  FIG. 9  showing the manner in which the valve actuating motor may be detached from the valve; 
         FIG. 14  is a bottom perspective view of the module of  FIG. 9  showing the manner in which the valve actuating motor may be detached from the valve; 
         FIG. 15  is a fragmentary perspective view of the distribution head illustrating the manner in which the outlet module of  FIG. 9  may be installed into the support plate of the distribution head, the module being shown with its inboard end seated in place and its outboard end positioned to be pushed down into place; 
         FIG. 16  is a fragmentary bottom perspective view of the module in the partially installed position of  FIG. 15 ; 
         FIG. 17  is a fragmentary perspective view of the partially installed module with its outboard end further seated into the support plate such that retaining barbs on the module are flexed to accommodate such seating movement; 
         FIG. 18  is a fragmentary bottom perspective view of the partially installed module corresponding to the position of  FIG. 17 ; 
         FIG. 19  is a fragmentary perspective view of the module fully installed in its seat; 
         FIG. 20  is a fragmentary bottom perspective view of the fully installed module corresponding to the position of  FIG. 19 ; 
         FIG. 21  is a fragmentary side elevational view of the fully installed module corresponding to the position of  FIGS. 19 and 20 , the adjacent portions of the support plate of the distribution head being shown in cross-section for clarity; 
         FIG. 22  is an outboard end perspective view of an exemplary second embodiment of outlet module of a type adapted to receive and introduce an additional product into the secondary stream passing through the module; 
         FIG. 23  is an inboard end perspective view of the second embodiment of outlet module of  FIG. 22 ; 
         FIG. 24  is an inboard end perspective view of an exemplary third embodiment of outlet module of a type having a downward discharge of the secondary stream; and 
         FIG. 25  is an outboard end perspective view of the third embodiment of outlet module of  FIG. 24 . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is susceptible of embodiment in many different forms. While the drawings illustrate, and the specification describes, certain specific embodiments of the invention, it is to be understood that such disclosure is by way of example only. The principles of the present invention are not limited to the particular disclosed embodiments. 
     With initial reference to  FIGS. 1 and 2 , an exemplary air seeder that may incorporate a seed distribution tower in accordance with the present invention is broadly denoted by the numeral  10  and is provided with a mobile chassis or frame  12  having a tongue  14  and hitch structure  16  for connecting seeder  10  to a suitable towing tractor or other vehicle (not shown). A number of ground-engaging wheels  18  are disposed across the rear of frame  12  to support the frame for over-the-ground travel. In the exemplary disclosed embodiment, seeder  10  comprises a cultivation air seeder and is thus provided with a set of cultivation tools  20  on frame  12  ahead of wheels  18 . It will be appreciated, however, that the principles of the present invention may be readily employed on many different types of air seeders and are not limited to use with a cultivation air seeder. A row of openers  22  of any suitable construction well known to those skilled in the art is supported across the rear of frame  12  behind wheels  18 . In the illustrated embodiment, seeder  10  comprises a three-section machine, such that frame  12  has a main frame section  24  and pair of left and right wing frame sections  25 ,  26  respectively, although the number of frame sections is not of importance insofar as the principles of the present invention are concerned. When applied to various parts of the machine, the terms “left” and “right” are utilized as if the machine were being viewed from the rear, looking forwardly. 
     Seeder  10  further comprises a hopper  28  supported on main frame section  24  for holding a supply of seeds and/or fertilizer or other particulate materials to be distributed to openers  22 . Although the illustrated embodiment of the invention will be described in connection with the holding and distribution of seeds by hopper  28 , it will be appreciated that the principles of the present invention are not limited to seeds and may, in fact, be utilized in connection with many different kinds of particulate materials. 
     A meter  30  at the bottom of hopper  28  may be utilized to dispense seeds at a metered rate into one or more conduits  32  that transport the metered seeds within an airstream toward the rear of the machine. One or more distribution towers  34  in accordance with the present invention are coupled with conduits  32  downstream from meter  30  for the purpose of dividing each primary stream of air and seeds into a multiplicity of secondary streams that flow to the openers  22  through hoses  35  (only a limited number being shown in the interest of clarity). A blower  36  adjacent the lower front end of hopper  28  supplies the transporting air for conduits  32  and the secondary hoses  35 . 
     Hopper  28  may be constructed in a variety of different shapes and sizes, and from a variety of different materials. In the illustrated embodiment, hopper  28  is constructed from sheet metal and is covered on three sides by an ornamental facing  29  of molded ABS plastic or the like, which is the subject of prior co-pending application Ser. No. 13/157,856 titled “Cultivation Air Seeder With Visually Enhanced Seed Hopper”, assigned to the assignee of the present invention. 
     Each of the towers  34  includes an upright pipe or conduit  38  fixed to frame  12  and connected at its lower end to the conduit  32  from hopper  28 . Conduit  38  may be provided with a multitude of exterior dimples  40  ( FIGS. 3 and 7  for example) that form corresponding interior projections disposed to be impinged by seeds in the moving primary stream to aid in scattering the seeds as they approach the upper end of conduit  38 . A generally flat, circular distribution head  42  is secured to the upper end of conduit  38  for splitting the primary stream into the secondary streams and transitioning the direction of seed flow from generally vertical to generally horizontal. 
     Broadly speaking, each distribution head  42  has an internal plenum chamber  44  ( FIGS. 6 ,  7  and  8 ) that receives the primary stream of air and seeds from the open top end of conduit  38  through a centrally disposed inlet  46  located in a floor  48  of plenum  44 . A top wall  50  of plenum is spaced above floor  48  and carries a centrally disposed, inverted transition cone  52  for causing the incoming primary stream of air and seeds to effectually transition from vertical to horizontal and split into a plurality of secondary streams that issue from distribution head  42  via a corresponding number of discharge outlets  52  arranged circularly about the central upright axis of tower  34 . Discharge outlets  52  are connected to the secondary hoses  35  that lead to openers  22 . 
     In accordance with the present invention, each of the discharge outlets  52  may take the form of an outlet module  54  that is independently installed on and removable from the tower  34  in a quick and easy manner. To this end, as particularly shown in FIGS.  5  and  15 - 20 , distribution head  42  includes a generally flat, annular support plate  56  that is fixedly secured to a mounting flange  58  on the upper end of conduit  38  in any suitable manner such as by a series of screws  60 . Support plate  56  has a central hole  62  defining the inlet  46  into plenum  44  and a plurality of specially configured seat openings  64  arranged in a circular series concentrically about hole  62 . Seat openings  64  are spaced radially outwardly from hole  62  to present an annular web surface  66  between hole  62  and seat openings  64  that defines the floor  48  of plenum  44 . The region of web surface  66  directly above flange  58  is horizontal, while the remainder of support plate  56  slopes slightly downwardly and outwardly to a radially outermost, circumferential, solid narrow margin  68  ( FIGS. 5 ,  7  and  15 - 20 ) immediately outboard of the seat openings  64 . 
     As illustrated particularly in FIGS.  5  and  15 - 20 , each seat opening  64  is generally rectangular and elongated in overall configuration, having a length in a radial direction that is somewhat greater than its width in a circumferential direction. Seat opening  64  has a pair of opposite side edges  70 , a radially innermost end edge  72 , and a radially outermost end edge  74 . Innermost end edge  72  is shaped to present a radially outwardly projecting tab  76 , while outermost edge  74  is straight and extends in perpendicular relationship to the radially extending, longitudinal axis of seat opening  64 . The outermost end of seat opening  64  has a somewhat T-headed configuration, presenting a pair of oppositely laterally extending, enlarged notches  78 . The inboard halves of side edges  70  taper toward one another as innermost end edge  72  is approached, while the outboard halves of side edges  70  extend parallel to one another out to the notches  78 . 
     Each outlet module  54  has an overall generally block-like configuration. As illustrated particularly in  FIGS. 11-21 , module  54  has an upper portion or half  54   a  that is slightly wider than its lower portion or half  54   b  so as to present an overhanging, downwardly facing shoulder  54   c  along both sides of module  54  at the intersection of upper half  54   a  and lower half  54   b . Lower half  54   b  is configured to be complementally received within seat opening  64  when module  54  is seated on support plate  56 , but upper half  54   a  is slightly wider than seat opening  64  such that overhanging shoulders  54   c  overlie and abut top surfaces of plate  56  adjacent seat opening  64  at that time, thus preventing module  54  from slipping completely downwardly through seat opening  64 . A recess  80  in the inboard end of lower half  54   b  is adapted to complementally receive tab  76  for locating and retaining purposes when module  54  is received in seat opening  64 , and a pair of spring-loaded, resilient barbs  82  on opposite sides of lower half  54   b  adjacent the outboard end of module  54  are complementally shaped with respect to notches  78 . Barbs  82  comprise a releasable latch  84  for securing module  54  to support plate  56  and present free upper ends that flare outwardly in their normal unrestrained state to a combined width that exceeds the width dimension of seat opening  64  across notches  78 . On the other hand, barbs  82  may be resiliently squeezed together at their upper ends to present a reduced combined width matching or less than the dimension across notches  78  to permit barbs  82  to pass through seat opening  64  during installation and removal of module  54 . The upper ends of barbs  82  are spaced below shoulder  54   c  a sufficient distance as to permit plate  56  to be trapped between the upper ends of barbs  82  and shoulder  54   c  when module  54  is fully seated in opening  64 , thereby latching module  54  in place. 
     Each outlet module  54  has a rectangular (preferably square) inboard inlet end  86  that communicates with plenum  44  and receives air and seeds therefrom. When all of the modules  54  are in place in the seat openings  64 , the inlet ends  86  of adjacent modules  54  abut one another in a lateral sense (see  FIGS. 6 and 8 ) to effectively form a circle that defines a radially outer wall of plenum  44 . The interengagement of inlet ends  86  with one another effectively seals those interfaces against the escape of air and seeds, leaving travel through the interior of the outlet modules  54  as the only means of exiting plenum  44 . Inlet ends  86  of modules  54  are lined up along the radially outer extremity of web surface  66  of plate  56 , as particularly shown in  FIGS. 6 and 8 . 
     Each module  54  has a flat top surface  88  that cooperates with the top surfaces of the other modules  54  in the circle to present an annular shelf that supports a circular, slightly domed lid  90  of distribution head  42 . Lid  90  has transition cone  51  secured to the underside thereof and forms the top wall  50  of plenum  44 . Four upright bolts  92  ( FIGS. 5 ,  8 ) at  90 E intervals about support plate  56  pass upwardly through lid  90  and threadably receive nutted hand knobs  94  for releasably securing lid  90  in place. A T-shaped handle  96  is attached to the center of lid  90  to facilitate handling thereof, the handle  96  also serving to threadably secure transition cone  51  to the underside of lid  90 . When lid  90  is secured down tightly against outlet modules  54 , it effectively retains modules  54  in place on the tower. Thus, although notches  78  and locating tabs  76  are preferred in addition to lid  90  for retaining modules  54  in place, notches  78  and tabs  76  are not necessarily required. 
     As detailed in  FIGS. 9-14 , each module  54  comprises a tubular body that includes a housing  98  containing a valve chamber  100  generally adjacent inlet end  86  and a sensor chamber  102  generally adjacent the opposite end of module  54 . An upright, cylindrical plug valve  104  is rotatably housed within valve chamber  100  for selective  90 E rotation about an upright axis between an open position as illustrated in  FIG. 9  and a closed position as illustrated in  FIG. 10 . A horizontal cylindrical bore  106  defines a passage through valve  104  that communicates with plenum  44  via inlet end  86  when valve  104  is in the open position and blocks such communication when valve  104  is in the closed position. A  90 E groove  107  around the bottom of valve  104  provides a track within which is received a fixed peg  108 . The opposite ends of groove  107  correspond to the open and closed positions respectively of valve  104 , and a pair of downwardly projecting, triangular detents  109  and  110  are provided within groove  107  a short distance from such respective opposite ends of groove  107  to yieldably retain peg  108  at one or the other of the opposite ends of the groove  107 . Detents  109 ,  110  can override peg  108  when valve  104  is rotated with force out of its open or closed position. The detents  109 ,  110  thus serve to yieldably retain valve  104  in its selected open or closed position. An arrow boss  112  on the bottom of valve  104  is shaped in the nature of an arrow boss to provide immediate visual recognition of whether valve  104  is in the open or closed position, the arrow boss  112  pointing in the outboard direction to indicate the open condition and pointing in a transverse direction to indicate a closed condition. 
     The arrow boss  112  on the bottom of each valve  104  is adapted to be manually gripped to permit manual turning of valve  104 , if desired. Alternatively, mechanical drive is provided for by a splined bore  115  in arrow boss  112  that facilitates the connection of a suitable drive motor or the like to valve  104 . In this respect, as illustrated particularly in  FIGS. 13 and 14 , an electrically energized actuating motor  114  may be removably secured to housing  98  by screws  118  and a mounting plate  116  fixed to motor  114 . The output shaft of motor  114  has a spur gear  120  fixed thereto that is adapted to be drivingly received within bore  115  to provide motorized operation of valve  104 . A conductor wire  122  for supplying electrical power to motor  114  leads away from motor  114  toward a source of such power. Thus, if the user desires motorized operation of valve  104 , he attaches motor  114  to valve  104 . If only manual actuation is desired, motor  114  is removed by simply unscrewing mounting plate  116  from housing  98 . 
     Each outlet module  54  further includes a sensor  126  disposed within sensor chamber  102  for detecting the movement or non-movement of seeds through module  54 . In the exemplary embodiment, sensor  126  includes a tube  128  having a central passage  130  that communicates with plenum  44  via bore  106  in valve  104  when valve  104  is open. The opposite outboard end of passage  130  communicates with a corresponding secondary hose  35  via an elbow fitting  132  on the outboard end of tube  128 . 
     In the illustrated embodiment, sensor  126  is an optical sensor, although a variety of other types of sensors could be utilized, such, for example, an audio sensor, a pressure sensor, or an impact sensor. As an optical sensor, each sensor  126  includes a pair of photo cells  134 ,  136  carried by tube  128  in diametrically opposed locations for transmitting a light beam across passage  130 . One of the cells is a sender and the other is a receiver. Breaking of the light beam by seeds moving in passage  130  is used to confirm the fact that seeds are indeed being dispensed through the module. A clear lens  138  in the wall of tube  128  covers cell  134 , while another clear lens  140  covers cell  136 . A pair of circuit boards  142 ,  144  are embedded within potting material  146  surrounding tube  128  within sensor chamber  102 , such circuit boards  142 ,  144  being electrically connected to the cells  134  and  136  respectively. Suitable boards that may serve as circuit boards  142 ,  144  are available from DICKEY-john Corporation of Auburn, Ill. as the VIGILENSE brand blockage sensor. An electrical conductor  148  connected to boards  142 ,  144  has a quick connector  150  at its distal end for connecting sensor  126  with an appropriate control system of the machine. 
     As seen in  FIGS. 4 and 7 , the conductors  148  associated with sensors  126  of all of the outlet modules  54  of distribution head  42  exit from the lower halves  54   b  of modules  54  below support plate  56 . They then lead generally radially inwardly from modules  54  toward upright conduit  38  and pass over the upper edge of a bowl-shaped housing  152  that is spaced a short distance below support plate  56 . The free ends of sensor conductors  148  having connectors  150  thereon are enclosed within housing  152  where they may be joined with leads  154  from the control system of the seeder. Thus, housing  152  provides a protective compartment  156  within which sensor conductors  148 , connectors  150 , and leads  154  may be contained. One or more holes  158  may be provided in the bottom of housing  152  through which leads  154  may be trained. 
     Housing  152  is retained on conduit  38  by any suitable means, such as, for example, a ring  158  ( FIGS. 4 and 7 ) fixed to conduit  38  below a larger diameter opening  160  in the bottom of housing  152  and a removable spring clip  162  that embraces conduit  38  above ring  158  and below the bottom of housing  152 . A petal-shaped plate  164  (see also  FIG. 5 ) of larger diameter than opening  160  may be fixed to conduit  38  a short distance above ring  158  to overlie and engage the top side of the housing bottom and serve as an upper limit to housing  152  when it is installed on conduit  38  by lifting it up into place from the bottom end of conduit  38 . 
     Only a few of the outlet modules  54 , if any, on each distribution tower  34  are likely to be used as tram lines. Thus, it is within the purview of the present invention for only a few of the outlet modules  54  on each tower  34 , or none at all, to be provided with shut-off valves  104 . Similarly, even if all of the outlet modules  54  on a particular tower  34  are provided with valves  104 , it is within the purview of the present invention to have only a few of them, or none at all, provided with actuating motors  114 . The conductors  122  associated with any motors  114  that are utilized on a head  42  may conveniently be trained up and over the upper edge of housing and into the protective compartment  156 , where their connectors  124  may be connected with appropriate ones of the leads  154  from the control system of the seeder. 
     It should be apparent from the foregoing detailed description of the construction of distribution tower  34  that the modular nature of tower  34  permits rapid assembly and disassembly of the tower, as well has quick and easy replacement of individual ones of the outlet modules  54 . For example, as illustrated in  FIGS. 15-21  installation of a module  54  onto support plate  56  is accomplished by simply properly orienting the module with respect to the selected seat opening  64 , inserting the inboard end of the module&#39;s bottom half  54   b  on an incline down into seat opening  64  to cause tab  76  to enter recess  80 , and then pushing the outboard end of module  54  downwardly until the module&#39;s bottom half  54   b  snaps securely in place within opening  64 .  FIGS. 15 and 16  illustrate the start of this sequence wherein tab  76  is received within recess  80  but barbs  82  are up out of opening  64 ;  FIGS. 17 and 18  illustrate the midpoint of the sequence wherein barbs  82  are received within notches  78  of opening  64  and are being flexed inwardly to permit continued downward movement of the module&#39;s bottom half  54   b  into opening  64 ; and  FIGS. 19 and 20  illustrate the module&#39;s bottom half  54   b  fully in place within opening  64  with barbs  82  snapped resiliently back out to their normal positions to underlie adjacent surface areas of support plate  56  so as to latch module  54  against upward movement.  FIG. 21  also shows module  54  fully latched in place. 
     To remove a module from support plate  56 , it is only necessary for the user to squeeze barbs  82  toward one another a sufficient extent that their upper ends become aligned with notches  78  and then, while maintaining the barbs  82  squeezed inwardly, thrust the outboard end of the module upwardly to dislodge the module from the seat opening. The dislodged module can then be lifted completely off support plate  56  for service or replacement as may be necessary or desirable. 
     ALTERNATIVE EMBODIMENTS 
     It is to be appreciated that the modules which provide outlets  52  for distribution head  42  may embody a variety of different designs and perform different and/or additional functions. Yet, all are provided with those common features that render the outlet truly modular in nature. 
     For example,  FIGS. 22 and 23  show an alternative embodiment wherein outlet module  200  has an extra inlet  202  by which additional products such as dry or liquid fertilizer, other types of seeds, or other substances could be added to the secondary stream exiting the plenum of distribution head  42 . Module  200  may or may not have an internal shut-off valve, and may or may not be provided with a flow sensor. Nonetheless, module  200  still has a body that is configured the same as the module  54  with respect to the way it seats within seat opening  64 . It will be noted in this respect that the bottom half  200   b  of module  200  is the same configuration as the bottom half  54   b  of module  54 , barbs  204  are the same configuration as barbs  82  of module  54 , and recess  206  is the same configuration as recess  80  of module  54 . The overall size of module  200  is the same as module  54  such that a distribution head may contain a mixture of different types of the modules if desired. 
       FIGS. 24 and 25  illustrate another alternative embodiment wherein an outlet module  300  does not have the usual type of horizontal discharge tube for the secondary stream leaving the module but instead is provided with a downwardly projecting discharge tube  302 . Once again, module  300  may or may not have a shut-off valve and may or may not have a flow sensor. But with respect to its modular mounting aspects, it is the same as modules  200  and  54 . Note in this respect that the bottom half  300   b  of module  300  is the same configuration as the bottom half  54   b  of module  54  and the bottom half  200   b  of module  200 , barbs  304  are the same configuration as barbs  82  of module  54  and barbs  204  of module  200 , and recess  306  is the same configuration as recess  80  of module  54  and recess  206  of module  200 . The overall size of module  300  is the same as module  54  and module  200  such that a distribution head may contain a mixture of different types of the modules if desired. 
     The inventors hereby state their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of the present invention as it pertains to any apparatus not materially departing from but outside the literal scope of the invention as set forth in the following claims.