referring now to the drawings , and more particularly to fig1 , there is shown an agricultural work system 10 that includes an agricultural work vehicle , such as tractor 12 that tows an agricultural implement 14 , which is depicted as a multi - row pivot transport seeder . seeder 14 can include a toolbar 16 with left and right marker assemblies 18 , 20 that are attached to left and right ends 22 , 24 of toolbar 16 , respectively . supports 25 can support marker assemblies 18 , 20 when in a folded position . seeder 14 can include other elements such as drawbar 26 for connection to tractor 12 , large storage tanks 28 , 29 which provide seeds to row or seed units 30 , and platform and gate assembly 32 for accessing and filling large seed hoppers 28 , 29 . row or planting units 30 can include a variety of elements for dispensing seed , fertilizer , pesticide , herbicide and other agricultural materials . such elements can include , but are not limited to , a furrow opening apparatus , gage wheels , a pair of lateral spaced , or staggered , furrow opener discs , a runner - type opener for providing a furrow in the ground , a pair of furrow closer discs , a seed meter , a press wheel arranged in fore - and - aft relationship relative to each other , and an agricultural chemical hopper . additionally , seeder 14 can have planting units 30 with individual seed boxes in addition to the large storage tanks 28 , 29 . as noted above , the seeder 14 has a pair of bulk fill storage tanks or hoppers 28 , 29 . bulk fill hopper 28 holds seed for the seed units 30 mounted to the left wing of frame 16 and bulk fill hopper 29 holds seed for the seed units 30 mounted to the right wing of frame 16 . the seed units 30 are flow coupled to its bulk fill hopper by supply hoses 34 . seed is metered from the bulk fill hopper 28 to the hoses by a seed metering assembly 36 , as known in the art . referring now to fig3 , as known in the art , each seed or row unit 30 includes a furrow opening apparatus 38 having furrow opening discs ( not shown ) and furrow closing discs 40 , 42 and a packer wheel 44 . the opening discs ( not shown ) cut a furrow into the planting surface and seed ( or fertilizer ) is deposited into the furrow . thereafter , the furrow closing discs 40 , 42 and trailing packer wheel 44 causes soil to fall back into the furrow to cover the seed and then packs the planting surface . each row unit 30 also includes an on - row hopper ( or mini - hopper ) 46 where seed is fed to the row unit 30 from the centralized storage tanks 28 or 29 is collected and stored . in a conventional manner , the seed is drawn from the on - row hopper 46 and is deposited into a furrow formed in the planting surface that is subsequently closed by discs 40 and 42 and packed by wheel 44 . referring now to fig4 and 5 , the on - row hopper 46 is generally comprised of a seed box 50 having an air / seed inlet 52 through which seed entrained in a forced air flow is fed to the seed box 50 . the seed box 50 also has a seed outlet ( not shown ) from which seed is drawn and deposited onto the planting surface . formed along the interior walls of the seed box 50 is a pair of flanges 54 , 56 that collectively define a channel or groove 58 . the groove 58 is sized to receive an outer edge of a flow restrictor member 60 that is mounted within the seed box 50 . the restrictor member 60 is designed to allow air to escape from the seed box 50 without letting seed escape . the flow restrictor 60 has a generally planar member 62 with a plurality of holes or orifices 64 formed therein . the orifices 64 are sized such that seed cannot pass through them but air is allowed to escape . thus , seed entrained in the forced air flow will effectively drop from the air flow as the air passes through the flow restrictor 60 . the air that passes through the restrictor 62 then passes through an air outlet ( designated by arrow 65 ) formed in the lower surface of the seed box 50 . in this regard , the flow restrictor 60 effectively divides the seed box into a seed collection portion and an air venting portion . as seed is collected in the seed box 50 , the orifices 64 of the flow restrictor 60 will become blocked . as the orifices become blocked , less air will be allowed to escape from the seed box 50 . as ( substantially ) all of the orifices 64 become blocked , a back pressure will develop in the supply hose to the seed box that will significantly decrease seed delivery to the seed box 50 . thus , when the seed box is ( substantially ) full , additional seed will not be fed to the seed box 50 . as seed is drawn from the seed box 50 and deposited onto the planting surface , the back pressure will reduce as air is allowed to escape , and more seed will be fed to the seed box . as shown in fig1 , the row units 30 are spaced laterally away from the storage tanks 28 , 29 . as a result , longer supply hoses are used to flow couple the seed boxes of the outer row units than those used for the inner row units . these differences in hose lengths can greatly impact seed distribution to the row units . in other words , as the air pressure at the seed metering system 36 is relatively fixed , air flow through the shorter hoses will be greater than the air flow through the longer hoses . that is , the back pressure in the shorter hoses is less than the back pressure in the longer hoses . this creates a flow differential that can lead to plugging of the shorter hoses or runs and insufficient seed delivery to those seed boxes associated with the longer hoses or runs . the inventors have found that this back pressure differential can be nullified , or exploited in a desired manner , through the judicious use of restrictors 60 having different flow characteristics . three exemplary restrictors are shown in fig5 . restrictor 60 ( a ) is similar to that shown in fig4 and includes a densely packed plurality of small orifices 64 ( a ) formed in a planar member 62 ( a ). restrictor 60 ( b ) is similar to restrictor 60 ( a ) as it includes a plurality of orifices 64 ( b ) formed in a planar member 62 ( b ). compared to restrictor 60 ( a ), orifices 64 ( b ) are spaced farther apart . while generally the same size as the orifices 64 ( a ) of restrictor 60 ( a ), the spacing of the orifices 64 ( b ) will cause less air to pass through restrictor 60 ( b ) compared to restrictor 60 ( a ). restrictor 60 ( c ), unlike the aforedescribed restrictors , is designed to greatly reduce , if not substantially eliminate , the exhaustion of air from the seed box 50 through the air outlet . the restrictor 60 ( c ) has a solid member 62 ( c ) and is therefore substantially free of any orifices or other openings that would otherwise allow air to escape the seed box . as known , the row units are not airtight assemblies . as a result , for a seed box outfitted with restrictor 60 ( c ), air would be prevented from being exhausted through the air outlet , but could be exhausted through various other escape points of the row unit . fig6 schematically illustrates a configuration in which the row units 30 are segmented into two sets : an inner set 30 ( a ) and an outer set 30 ( b ). in this configuration , each of the seed boxes for the inner set 30 ( a ) of row units is outfitted with a restrictor that substantially blocks air flow through the air outlet , such as restrictor 60 ( c ). each of the seed boxes for the outer set 30 ( b ) of row units is outfitted with a vented restrictor that allows air flow , such as restrictors 60 ( a ) and 60 ( b ). in another preferred embodiment , the row units are segmented into three sets based on their spacing from the centralized storage tanks 28 , 29 . the set farthest from the tanks could be outfitted with restrictors 60 ( a ) and the set closest to the tanks could be outfitted with the restrictors 60 ( c ). the set between those two sets could be outfitted with restrictors 60 ( b ). with such a configuration , the pressure differential described above could be lowered so that seed is fed to the plurality of row units in a more uniform manner . it is understood that the number , size , and shape of the openings could be different from those illustrated in the foregoing figures . it is also contemplated that the number of restrictors could be different from that described herein . that is , it is contemplated that each row unit could have a unique restrictor based on the length of the hose that flow couples the seed box for the row unit to the seed metering assembly . it will be appreciated that the present invention provides for balanced seed ( or other granular material ) distribution for agricultural planters having numerous distribution hoses or runs . moreover , the present invention may be used to retrofit existing seed boxes in a cost effective manner to provide for improved balancing . it is believed that the present invention provides operational advantages over other balancing techniques . for instance , it is believed that the present invention provides less air disturbance ( and hence less power requirements ), better control , and more reliability than other proposed solutions . many changes and modifications could be made to the invention without departing from the spirit thereof . the scope of these changes will become apparent from the appended claims .
the present invention provides a method and apparatus to improve seed distribution to a plurality of seed or row units of an agricultural planter . each row unit is fitted with a seed box having an air / seed inlet and an air outlet through which air is allowed to escape . the present invention effectively closes off or substantially reduces the flow of air out of one or more of the seed boxes to reduce the amount of seed that is fed to the seed boxes . through the use of restrictor plates , which may be vented to allow some air flow or solid to prevent air flow , the delivery of seed to the seed boxes can be equalized to provide more uniform seed distribution to the row units .