a hopper and feed apparatus for the introduction of coke , ferrosilicon , ferromanganese , aluminum , silicon metal , silicon carbide , silica sand and other material inputs to a vertical shaft furnace and more specifically a cupola will be utilized in the present description . it is recognized that a prime requisite will be the introduction of materials which are smaller than the tuyere inner diameter , and preferably less than one - third the diameter of the tuyere inner diameter to avoid potential blockage of the tuyere . in fig4 the basic outline of a vertical shaft furnace and more specifically cupola 10 with bustle pipe 12 is shown . cupola 10 is noted as discontinuous at its top 14 but it is basically open and may have a raw - material charge opening ( not shown ) in its sidewall 16 in proximity to top 14 . cupola 10 may slightly resemble a cylinder tapering at its lower extremity 15 to a different diameter from top 14 . there is a well or hearth region 18 for retention of molten slag and iron . iron is tapped from well 18 through tap hole 20 . tuyeres 22 in fig4 are connected to downcomer pipes 24 and bustle pipe 12 , and extend through sidewall 16 into melting zone or well 18 . in this configuration , blast gasses at a pressure above atmospheric pressure and at a high flow rate are communicated from bustle pipe 12 to melting zone 18 for combustion of the coke in the burden . coke combustion produces heat and results in the evolution of gaseous materials and ash , which is fluxed from the iron by the slag - forming limestone in the burden . coke also provides carbon for retention in the molten metal . although only two tuyeres 22 are shown for purposes of illustration , there are generally a plurality of tuyeres 22 positioned around the well diameter of a furnace or cupola 10 . in the configuration of fig4 additive material feed system 25 has feeder 28 positioned above tuyere 22 and bustle pipe 12 to receive raw material charges for communication to tuyere 22 through conduits 30 , 32 and 34 , and into tuyere passage 37 for blast media entrainment into melting zone 18 and the burden . as shown , there are no extraneous couplings to hopper 28 , conduits 30 , 32 , 34 or tuyere 22 for any of mechanical , pneumatic or hydraulic transfer of raw material charges to the burden . in the preferred embodiment of feed system 25 , feeder 28 is positioned in transfer bin 38 , as shown in fig1 . chamber 39 of bin 38 has upper port 40 in bin top 41 with seal plate 42 operable to close port 40 , which is sealable against open communication with the atmosphere . a tapered or conical funnel 44 extends from port 40 to feeder 28 for transfer of raw materials to feeder 28 from a feed chute or other apparatus ( not shown ). discharge port 46 at bin lower surface 48 in fig5 is operably coupled to conduit 30 for communication of raw materials from chamber 39 to tuyeres 22 . feeder 28 in fig1 and 2 is positioned and rotatable in chamber 39 . feeder 28 is a generally cylindrical shell with working volume 29 , outer wall 50 , upper rim 52 and lower rim 54 . feed - control apparatus 56 has skirt 58 positioned and operable around bin lower rim 54 . skirt 58 has upper segment 60 , which may be an annulus secured to bin outer wall 50 . flange 62 radially outwardly extends from upper segment 60 and wall 50 , which flange 62 has a plurality of bolt holes therethrough . plate 64 is a generally flat circular plate with a diameter greater than the cross - sectional area of the bin cylinder or working volume 29 , which plate 64 is mounted below lower rim 54 in chamber 39 and separated therefrom . second skirt segment 68 is a cylindrical section with a second flange 70 radially extending from its upper edge 72 . in fig1 second skirt segment 68 is slidable along outer wall 50 of feeder 28 to vary gap distance 66 between plate upper surface 76 and second - skirt - segment lower edge 74 to vary the discharge rate of raw material from working volume 29 to chamber 39 and discharge port 46 . in fig2 plows 78 of feed - control apparatus 56 are secured to bin 38 in chamber 39 and extend through gap 66 into feeder working volume 29 . plow 78 is shown in an enlarged plan view in fig3 which plow 78 may be a rigid material , such as hot - rolled steel plate with a wall thickness of about three - quarter ( 3 / 4 ) inch . plow 78 is illustrated as generally rectangular with first and mounting edge 80 at an acute angle to the two parallel sides 82 and 84 of the rectangle . plow leading edge 86 is a rounded projection with tapered surface 88 extending from parallel side 82 . in the apparatus of fig1 two plows 78 are noted as positioned and operable in feed - control apparatus 56 , although the number of plows 78 and their position are variable by the operator to accommodate the desired feed rate . this feed rate may be dependent upon the rate of operation of cupola 10 , the particular additive material and the rate of rotation of feeder 28 . top bearing support 90 with a central bore 92 extends across chamber 39 and is anchored to bin 38 in fig1 . drive shaft 94 is coupled to drive means , such as a motor 96 , sprocket 98 and drive chain 100 , and extends through passage 102 of bin lower wall 48 . drive shaft first end 104 is secured in rotatable bearing assembly 106 , and second shaft end 108 is secured in central bore 92 of support 90 . stirring rods 110 radially extend from shaft 94 in volume 29 and , as shown in fig6 are located at both the upper and lower level of volume 29 . conical member 112 with its larger diameter end 114 mounted on plate 64 extends into working volume 29 , and shaft 94 projects generally through the center of cone 112 . in fig2 bracing members 1 . 16 extend diametrically across volume 29 , and in this figure two of members 116 are noted at right angles to each other . in operation , feeder 28 is filled with the additive raw materials through port 40 and rotated in sealed bin 38 by drive means 96 , 98 , 100 , which is coupled to shaft 94 . lower skirt 68 is raised a predetermined distance above upper surface 76 of plate 64 to provide desired gap distance 66 , which may be based upon density of the raw material , its diameter or size , desired feed rate into cupola 10 or any other parameter of the user , as the particular condition utilized to set the feed rate is not a limitation . the material in working volume 29 is transferred through gap 66 by the rotation of feeder 28 and the contact of the fixed plows 78 . it is known that plows 78 may be adjusted radially inward or outward to increase or decrease the rate of feed through slot 66 at the same rotational speed of feeder 28 . as the material is displaced from feeder 28 to lower wall 48 of chamber 39 , it is transferred through discharge port 46 to conduits 30 , 32 and 34 at the opening of valve 120 for transfer to tuyere passage 37 and entrainment in the air blast to cupola volume 18 and the burden . the precise location of the addition may vary as there is a constant draft of air in cupola 10 , and it has been observed that at least some of the larger or more dense materials contact the burden before being melted , oxidized or otherwise consumed in the melt . no particular mechanism is presently attributed to the interaction of the added materials for the consequent chemical relations noted in the cast iron materials . as noted above , materials are transferred to feeder 28 and chamber 39 is sealed by seal 42 to allow chamber 39 to operate at the same relative pressure as cupola volume 18 . the balanced pressure between chamber 39 and cupola volume 18 is attained by closing valve 120 during raw material charging to working volume 29 and closing seal 42 prior to opening valve 120 . this balancing of the pressures between chamber 39 and cupola well 18 , although cupola pressures in the melting zone are usually not more than 80 inches of water above atmospheric pressure , allows for a free transfer of materials through conduits 30 , 32 , 34 with no inhibiting backpressures from furnace 10 , which might inhibit gravitational feeding of these materials . potential pressure leaks at the chamber seals may be compensated for by external pressurization , such as through a pipe and valve arrangement 26 coupled to a source 27 of air at a pressure above atmospheric pressure . as an example , during brief trials of the feed mechanism on a single tuyere 22 , carbon in the form of screened and undersized coke was utilized as the additive raw material , which screened coke was from the coke to be added to the top of cupola 10 , and is about less than one and three - quarters inches in size . this undersized coke addition had a relatively high moisture content from outdoor storage , which moisture is generally considered to have a detrimental impact on the operation of smelting furnaces . the results of the tests to date have indicated that the theoretical carbon recovery for carbon ( coke ) added at tuyere 22 was greater than eighty percent ( 80 %) versus a normal carbon recovery of about fifty percent ( 50 %) for normal carbon additions through the cupola top . this recovery allows for a higher carbon content in the molten iron at the tap hole , which avoids or reduces external carbon additions in the ladle or holding vessel to attain the requisite carbon level in the molten metal . in addition , utilization of the normally rejected materials avoids the loss of the expensive purchased metallurgical coke , while attaining higher recovery rates than is presently experienced with the larger sized materials preferred for the top charging to the burden . a similar test with ferrosilicon noted that the recovery of silicon from ferrosilicon additions through tuyere 22 provided as much as ninety - five percent ( 95 %) recovery of the silicon in the as - tapped molten iron , which significantly reduces the additions of silicon to the molten metal to attain the requisite silicon specification level . it is considered that other alloy additions can be provided to furnace 10 with other alloying or additive components such as ferromanganese , magnesium , aluminum and silicon metal , and that these additions will positively enhance furnace practices , such as desulfurization , although specific examples of the levels of attainment of these practices are not presently available . as noted , tests to date have shown no negative impact on furnace operation or as - tapped molten metal temperature , and have produced positive impacts on metal chemistry . a precise chemical and thermodynamic balance for any individual cupola furnace is the consideration of the operator . however , the ability to provide the alloying additions to molten metal at tuyere 22 instead of to furnace top 14 has been shown to improve chemical additive recovery utilizing presently available materials and providing access to other currently discardable or limited value materials . exemplary of the materials perceived as potential candidates for use as carbon alloying additions at tuyere 22 are comminuted vehicle tires . also , silica sand addition to the melting zone is presently considered a potential source of silicon for the metal . although the precise size of material additions utilized to date have been noted above , the acceptable size of additives for transfer through conduits is considered to be additives having a particle size one - third or less than the inner diameter of the transferring conduit , that is tuyere passage 37 . as an example , in a six - inch tuyere , it is expected that the materials must be less than two inches in diameter . further , the optimum feed rate in a vertical shaft furnace is determined by the volumetric rate of the air blast , as an excessive feed rate would not be an acceptable practice in view of the potential to block free passage through tuyere 22 . there is also the potential to add an excessive amount of cold mass charge to the furnace and the potential to cause large variations in molten metal chemistry and temperature , which acts are to be avoided . in an alternative embodiment of the transfer apparatus 56 , intermittent charging may be provided by the use of a dual - valve structure as illustrated in fig4 . in this figure , first valve 120 is located in the sequence of conduits 30 , 32 , 34 , and second valve 122 is operable positioned between conduits 30 and 32 . as a reference condition , first valve 120 is closed when second valve 122 is opened . feeder 28 is coupled to first conduit 30 for transfer of material to conduit 30 through discharge port 46 . with first valve 120 closed , material is communicated from feeder 28 , by opening second valve 122 , which permits material to flow from feeder 28 and conduit 30 into conduit 32 between first and second valves 120 and 122 . thereafter , second valve 122 is closed and first valve 120 is opened to provide material transfer from conduit 32 to conduit 34 , tuyere passage 37 and the furnace burden . the rate of opening and closing transfer valves 120 , 122 is dependent upon the rate of material flow from feeder 28 and conduit 30 to the respective conduits 32 and 34 , as it is known that fast - response valves may be utilized for this function . valves 120 , 122 may be coupled to a control apparatus 124 , such as a computer controlled device , which may include reception of sensed signals from line sensors 130 , 132 , which are respectively connected to said control device by lines 134 and 136 , to note both the full and empty positions of any of conduits 30 , 32 , 34 and safety sensors ( not shown ) indicating closed and open positions of valves 120 , 122 , as known in the art . valves 120 and 122 are noted as coupled to controller 124 by lines 126 and 128 , respectively . it is known that valves 120 , 122 are rapidly operable to provide an almost continuous flow of material to tuyeres 22 . although only one bin 38 and feeder 28 system has been shown in the figures , it is apparent that a similar feed system may be coupled to each tuyere 22 to provide multiple raw material feed operations , or that a single feeder 28 and bin 38 could be coupled to more than one tuyere 22 . while only specific embodiments of the invention have been described and claimed herein , it is apparent that various modifications and alterations of the invention may be made . it is , therefore , the intention in the appended claims to cover all such modifications and alterations as may fall within the true spirit and scope of the invention .