referring now to fig1 the grinder attachment mounted on the bowl of a food processor is referred to generally by the reference numeral 10 . this grinder attachment 10 is shown operatively positioned on a working bowl 12 having a handle 17 . this bowl is positioned on a base 14 , partially shown , of a food processor of the type described in the patents referred to above in the introduction . the bowl has a skirt 11 ( fig . 3 ) which seats down around a turret portion 15 on the base housing 14 . the base housing 14 contains . an electric motor drive 16 which is energized by an electric power cord 18 via a switch 20 having actuating means shown as a button 22 . extending vertically up from the base 14 is rotary tool drive means 24 in the form of a vertical tool drive shaft which is driven by the drive means 16 . this tool drive shaft 24 extends upward within an annular well 25 which is integral with the bottom 26 of the bowl . as is more fully explained in the aforesaid patents , a plurality of different kinds of food processing tools may be provided which may be selectively mounted on the drive shaft 24 for rotation within the bowl to perform a variety of food processing functions . in accordance with the present invention , grinding apparatus 30 comprising components of the attachment 10 are coupled to this drive shaft 24 and are driven thereby . thus , advantageously , the usage of this grinder attachment 10 does not require any modification of the existing base housing 14 , the motor drive 16 , the tool drive shaft 24 or the bowl 12 . formed on the side of the bowl 12 is a vertical semicylindrical boss 27 defining a guideway within which is carried a vertically movable actuating rod 28 which is normally urged upwardly by means of a spring 29 . when the bowl 12 is properly positioned upon the base housing 14 in operating position , then the actuating rod 28 becomes aligned with the actuating means 22 of the switch 20 , being separated therefrom by means of a flexible , fluid - tight membrane in the base 14 . the grinding attachment 10 , as seen in fig1 and 3 , includes the grinding apparatus 30 , a circular cylindrical hopper 32 positioned directly above this grinding apparatus and a downwardly and inwardly converging truncated conical bottom portion 33 of the hopper which serves as a funnel chute for gravity feeding of particulate food from the hopper down into the grinding apparatus 30 . encircling the hopper 32 , 33 is a mounting skirt 34 having a downwardly extending vertical cylindrical lip 36 ( fig . 3 ) which fits snuggly within the rim 35 of the bowl 12 and a radially extending horizontal flange 37 which seats on top of the bowl rim 35 . this mounting skirt 34 includes a rounded annular shoulder 38 which is formed integral with the wall of the hopper at the juncture 39 of its cylindrical and conical portions 32 and 33 , respectively . thus , the top of the working bowl 12 is effectively covered over by the hopper 32 , 33 and its mounting skirt 34 during operation , so that the user does not have direct access to the rotating parts to be described later which are located within the bowl . the peripheral mounting skirt 34 of the grinder attachment 10 is arranged to be engaged in locked relationship in its normal operating position on the bowl 12 whenever the grinding apparatus 30 is being driven by the motor drive 16 and its tool drive shaft 24 . for example , this mounting skirt 34 may be held in locked engagement on the bowl 12 by placing the mounting skirt 34 onto the rim 35 of the bowl and then partially rotating the whole attachment 10 to obtain a twist - lock effect . for this locking engagement , the mounting skirt 34 is shown to carry a plurality of circumferentially located depending lugs 40 ( fig1 ) which , upon slightly turning the attachment 10 , become engaged beneath cooperating radial ledges 41 on the bowl 12 near its rim 35 . it will be appreciate that the mounting skirt 34 may be secured in place in locking engagement on the rim of the bowl by any form of suitable manually engageable fastening means . the mounting skirt 34 includes a camming structure 42 which engages and pushes down the actuating rod 28 when the mounting skirt 34 has been positioned in its normal secured operating position on the bowl 12 . the camming structure 42 may be of the type more fully described in the aforesaid patents , and it may be of any type which pushes the actuating rod 28 downwardly , when the attachment 10 is appropriately mounted in secured operating position on the bowl 12 . the rod 28 in turn pushes down the actuating means 22 for closing the switch 20 , which thereby enables the motor drive 16 to be energized upon manual operation of the controls ( not shown ) on the base housing 14 for rotating the vertical drive shaft 24 . the described actuation of the interlock switch 20 which occurs by means of the correct positioning of the bowl 12 and of the grinder attachment 10 on the bowl 12 is intended as a safety feature for preventing rotation of the tool drive shaft 24 unless the user has properly positioned the bowl and grinder attachment . the hopper 32 , 33 forms a passageway 44 ( fig3 ) for feeding particulate foods , which are to be ground , to the grinding apparatus 30 , as will be explained in detail later . there is a removable cover 46 which may be placed over the cylindrical portion 32 of the hopper . the hopper 32 , 33 contains a plurality of radial strengthening and support ribs 50 ( please see also fig2 ) for example four ribs in quadrature which extend from a central tubular support 52 to the truncated conical chute 33 . there are four openings 54 ( fig2 and 3 ) between these quadrature ribs 50 at the lower end of the conical chute 33 . these openings 54 are located below the lower end of the tubular central support 52 and serve to feed the particulate food down from the hopper chute 33 to the grinder apparatus 30 . the conical chute 33 is terminated at its lower end in an integral pedestal 56 ( fig3 ) which functions as the mounting to carry a stator member of the grinding apparatus 30 , as will now be explained . the grinding assembly apparatus 30 includes a stator grinding member 60 in the form of a hardened stationary annular grinder as is most clearly shown in fig4 and 6 . this stator grinding member 60 has a central throat opening 58 therein and has an upper mounting flange 62 thereon . on its lower surface , this stator member 60 has a flaired grinding surface 80 . as will best be seen in fig3 and 4 , the stator grinding element 60 is held on the pedestal 56 of the hopper chute 33 by a retaining ring collar 66 attached by a plurality of machine screws 68 which screw into threaded holes in the pedestal 56 . in order to secure the stator grinding member 60 firmly in place , its mounting flange 62 has a pair of diametrically opposed , parallel flattened regions 61 ( fig4 and 5 ). the pedestal 56 defines a socket 63 ( fig3 and 4 ) which receives the mounting flange 62 in tight fitting relationship , and this socket 63 has a pair of opposed , parallel flat regions ( as seen in fig4 ) which snuggly mate with the flats 61 for preventing the stator grinding member 60 from shifting position or from turning in its socket 63 . the retainer ring collar 66 has an upstanding ring 65 , as seen in fig3 which encircles the pedestal 56 so that this ring collar 66 defines a socket embracing the lower portion of the pedestal and also embracing the lower portion of the flange 62 of the stator grinding member . this retainer ring collar 66 has a cylindrical lower portion 67 which encircles the stator grinding member 60 in tight - fitting relationship for holding this stator grinding member securely in place accurately concentrically aligned with the vertical axis of rotation of a rotor grinding member 70 to be described in detail later . as seen most clearly in fig4 and 6 , the throat opening 58 in the stator member 60 is downwardly converging with its truncated conical serrated wall 72 slanting inwardly at a small acute angle &# 34 ; c &# 34 ;, for example at an angle &# 34 ; c &# 34 ; of about 15 ° to the vertical . this serrated wall 72 includes between 35 and 50 saw - tooth shaped serrations 74 , which cooperate with the rotor 70 , to be described later , for feeding the particulate food down , while shearing and cracking and commencing to grind it . in this illustrative embodiment there are 45 of these saw - tooth shape serration ridges 74 . shown by the arrow 75 in fig4 the rotor 70 turns in a counterclockwise direction as seen looking downwardly . the saw - tooth shaped ridges 74 each has an abrupt front face 76 ( fig4 ) facing toward the oncoming particulate food as driven by the impelling rotor 70 , i . e ., facing in the clockwise direction opposite to the rotation 75 . each abrupt face 76 is inclined at a small acute angle &# 34 ; b &# 34 ; ( fig4 ) to a radial line &# 34 ; r &# 34 ; extended from the vertical axis of rotation 78 of the rotor , for example at an angle &# 34 ; b &# 34 ; of about 15 °. also each abrupt face 76 slopes downward in the counterclockwise direction at a small acute angle &# 34 ; a &# 34 ; ( fig6 ) with respect to the vertical , for example at an angle &# 34 ; a &# 34 ; of about 5 °, for cooperating with the rotor 70 in providing a downward component of force on the particulate food in the converging throat feeding - shearing - cracking - grinding zone 58 . the saw - tooth shaped ridges 74 each have a more gradually sloping rear surface 79 facing away from the oncoming particulate food , that is , the rear face 76 faces generally in the counterclockwise direction 75 . each ridge 74 has a sharp v - shaped apex between its front and rear faces 76 and 79 , respectively , and each ridge also has a sharp v - shaped groove between its front face 76 and the rear face 79 of the preceding adjacent ridge . each v - shaped groove forms an acute angle &# 34 ; d &# 34 ; as seen in fig4 at the top surface of the stator grinding member 60 , for example , angle &# 34 ; d &# 34 ; in the range from about 60 ° to about 80 °, with the preferred value being about 75 °. when the angle of these grooves is less than about 60 ° they become unduly deep in the radial direction , thereby forming channels tending to protect the particulate food from the desired shearing / cracking and grinding action between stator 60 and rotor 70 . conversely , when the angle &# 34 ; d &# 34 ; of these grooves is greater than about 80 °, they become unduly shallow in the radial direction , and consequently each saw - tooth shaped ridge 74 has insufficient frontal area 76 &# 34 ; bite &# 34 ; for producing the desired shearing / cracking action on the particulate food between stator 60 and rotor 70 . this stator 60 is made of stainless steel which is machined and then heat treated to produce a high degree of hardness . the inner surface of the funnel chute 33 ( fig3 and 7 ) is directly contiguous with the bottom of each groove between the saw - tooth shaped ridges 74 for rapidly feeding particulate food into the feeding - shearing / cracking - grinding zone 58 between stator 60 and rotor 70 . the stator 60 includes a downwardly facing flared grinding surface 80 extending radially outwardly and sloping downwardly which includes numerous grinding serrations 82 each having a saw - tooth shaped ridge configuration extending generally radially outwardly for providing a second grinding zone 81 ( fig3 ). for example , this grinding surface 80 slopes downwardly at an angle &# 34 ; e &# 34 ; to the horizontal in the range from about 5 ° to about 40 °, with the presently preferred value for &# 34 ; e &# 34 ; being about 10 ° to about 15 °. these saw - tooth shaped grinding ridges 82 are similar in shape to those ridges 74 previously described , having abrupt front faces and more gradually sloping rear surfaces except that ridges 82 are considerably smaller and more numerous , for example there are between twice and three times as many of the ridges 82 . in this illustrative embodiment there are 120 of these grinding ridges 82 . as seen in fig5 looking upward , the direction of rotation 75 of the rotor about its vertical axis 78 is clockwise . the grinding ridges 82 are inclined outward in the clockwise direction as seen looking upwardly in fig5 at a small acute angle &# 34 ; f &# 34 ; with respect to a radial line &# 34 ; r &# 34 ; extended from the axis of rotation 78 , for example angle &# 34 ; f &# 34 ; is in the range from about 10 ° to about 30 °, preferably being about 15 °, to cooperate with the rotor in providing a component of force acting outwardly away from the axis 78 on the particulate food being ground . in order to feed the particulate food down into the first zone 58 there is a downwardly and outwardly sloping truncated conical shape feeder and grinder section 85 ( fig3 ) of the rotor 70 made of hardened stainless steel like that from which the stator 60 is made . this rotor 70 includes a plurality of serrations , for example four , helical flutes 84 as seen most clearly in fig7 and 8 , which have a right hand screw twist as seen from above for feeding the particulate food downwardly . for example , these helical flutes 84 are inclined at a screw pitch angle &# 34 ; g &# 34 ; ( fig7 ) of less than about 40 ° and more than about 15 ° to the horizontal , preferably angle &# 34 ; g &# 34 ; being about 30 °. these helical flutes 84 each have an abrupt radially extending somewhat cupped front surface 86 ( fig8 ) in order to catch onto and claw into the particulate food for pushing / feeding the particulate food downwardly in the first shearing / cracking and grinding zone 58 . for its mounting , the rotor 70 has a bore 88 ( fig . 8 ) in positive drive relationship with a shaft 90 ( fig3 ) rotatably mounted in a pair of axially spaced ball bearing units 91 and 92 seated in an adjustable tubular housing 94 . this shaft 90 has a head 96 ( fig3 ) engaging an internal shoulder in the bore of the rotor 70 . above this head 96 there is a hexagonal section of the shaft 90 mating with the hexagonal portion 88 ( fig8 ) of the bore of the rotor 70 . then , above this hexagonal section , the shaft 90 has a screw thread section 97 engaged by a shouldered retainer nut 98 which is screwed down tightly onto the rotor 70 for securely holding the rotor down against the shaft head 96 . in addition to the feeding and cracking and grinding section 85 ( fig3 ) of the rotor 70 , this rotor also includes a second grinding section 95 which flares outwardly like a skirt and has an upwardly facing truncated conical rotor grinding surface 100 ( fig3 and 7 ) positioned in opposition to the downwardly facing truncated conical stator grinding surface 80 , thereby defining the second grinding zone 81 between these opposed grinding surfaces 100 and 80 . this rotor grinding surface 100 extends radially outwardly and slopes downwardly at about the same angle &# 34 ; e &# 34 ; as the stator grinding surface 80 thus being effectively parallel thereto , and includes about the same number of grinding serrations 102 of about the same saw - tooth shape ridge configuration as the serration 82 . in other words , these saw - tooth shape grinding ridges 102 have abrupt front faces and more gradually sloping rear surfaces . in order to cooperate with the stator ridges 82 for providing a component of force acting outwardly away from the axis of rotation 78 , these rotor ridges 102 are inclined outward in the counterclockwise direction as seen looking upward in fig5 at an angle &# 34 ; h &# 34 ; with respect to a radial line &# 34 ; r &# 34 ; in the range from about 20 ° to about 50 °, preferably being about 30 °. thus , the sum of grinding serration angles &# 34 ; f &# 34 ; and &# 34 ; h &# 34 ; of the opposed ridges 82 and 102 is in the range from about 35 ° to about 50 °, preferably being about 45 °. if the clockwise radial inclination &# 34 ; f &# 34 ; of the grinding ridges 82 is decreased , then the counterclockwise radial inclination &# 34 ; h &# 34 ; of the grinding ridges 102 is increased for keeping their sum in the range from about 35 ° to about 50 ° and preferably at about 45 °, which i have found to work to advantage in rapidly and uniformly grinding a wide variety of particulate foods as described in the introduction . although the rotor 70 is shown as a one - piece high hardness , stainless steel unit , its feeder - shearer / cracker - grinder section 85 and its second grinder section 95 may be fabricated as two separate highly hardened stainless steel pieces having a mating joint 104 between them as shown dashed in fig3 . they then rotate the same as an integral unit , because they are coupled together in positive drive relationship by the hexagonal section of the shaft 90 and by their mating joint 104 . in order to drive the rotor 70 by means of the tool drive shaft 24 ( fig3 ) the rotor includes a downwardly projecting socket portion 106 which extends down into the annular well 25 and has a socket 108 concentric with its axis 78 and which removably engages the shaft 24 in positive drive relationship . for example , this socket 108 may be keyed or splined to the tool drive shaft 24 , for example there are a pair of opposed flats 110 ( only one is seen in fig3 ) on the tool drive shaft which mate with a corresponding pair of opposed flats 112 ( only one is seen ) in the socket 108 . for clarity of illustration of the socket 108 , the upper end of the tool drive shaft 24 is shown broken away in fig3 it being understood that this shaft 110 actually extends well up into socket 108 , for example almost up to the head 96 of the rotor mounting shaft 90 . the support arrangement of a seal and of the ball bearing units 91 and 92 for the rotor mounting shaft 90 will now be described . the shouldered retainer nut 98 carries an annular seal 116 ( fig3 and 7 ) on its upwardly facing shoulder , and this seal 116 fits into the lower end of the tubular bearing housing 94 with sufficient clearance for allowing the shaft 90 and nut 98 to rotate , while the tubular housing 94 remains stationary . in order to apply axial preloading on the bearing units 91 and 92 , there is a boss 118 on the retainer nut 98 which thrusts upwardly against the inner race of the ball bearing unit 92 , while the outer race of this bearing unit 92 is thrust downwardly by seating up against an annular shoulder 120 within the tubular housing 94 . an axial thrust wave washer 122 is sandwiched between the annular shoulder 120 and the outer race of the upper bearing unit 91 . a washer 124 is held by a pair of lock nuts 126 screwed onto the threaded top end 128 of the shaft 90 . this washer 124 is thrust downwardly by the lock nuts 126 against the inner race of the upper bearing unit 91 , while the wave washer 122 thrusts upwardly against its outer race . thus , these two bearing units 91 and 92 run smoothly without chatter at the normal operating speed of about 1725 to 1750 rpm of the food processor tool drive shaft 24 by virtue of the axial pre - loading in opposite directions of their respective inner and outer races provided by this bearing mounting arrangement just described . for controlling the fineness of the ground food products , the grinding clearance spacing is adjustable between the opposed grinding surfaces 80 and 100 in the second grinding zone 81 . the tubular housing 94 is conveniently manually axially adjusted in position relative to the tubular support 52 . this housing 94 has an externally screw - threaded section at 114 engaging a corresponding internally screw - threaded section within the tubular bearing support 52 . the upper end of this tubular bearing housing 94 has a knob handle 130 which is keyed to the bore of the housing 94 by a plurality of splines 132 . this handle knob 130 carries a seal 134 attached by a threaded stud 136 to its lower surface . it will be understood that this knob 130 is removed during assembly of the bearing mounting arrangement for the rotatable shaft 90 , and it may be cemented in place , if desired , after assembly . the seals 116 and 136 protect the ball bearing units 91 and 92 from entry of foreign substances , and they retain lubrication within the tubular housing 94 for these bearings . the user turns the handle knob 130 for turning the housing 94 relative to its tubular support 52 for axially adjusting the housing 94 for adjusting the grinding clearance in the second zone 81 for regulating the fineness of the ground food particles or flour being produced . an external shoulder stop 138 on the housing 94 abuts against the lower end of the tubular support 52 , as shown in fig3 for establishing the minimum grinding clearance adjustment in the zone 81 for assuring that the opposed grinding surfaces 100 and 80 do not clash against each other when the user adjusts for minimum clearance to produce fine flour . in fig7 the housing 94 has been adjusted downwardly by turning the knob 130 , and thus the shoulder stop 138 is now spaced from the lower end of tubular support 52 , and consequently there is more clearance between the opposed grinding surfaces 80 and 100 in the zone 81 . the ground food product will be less fine than with the minimum setting in fig3 . in order to lock firmly the adjusted position of the housing 94 , there is a hand - turned locking member 140 including a wheel - shaped handle 142 having a rim 144 . this locking member 140 has a tubular bottom portion 146 which is screw - threaded at 148 onto the upper portion of the threaded section 114 of the housing 94 . the user turns this locking handle 140 in the manner of a large lock nut for jamming its tubular bottom portion 146 down tightly against the upper end 150 of the tubular support 52 thus locking the housing 94 against moving away from its adjusted position . the user loosens the locking handle 140 before turning the adjustment knob 130 . after the desired fineness of grinding adjustment has been made by turning the knob 130 , then the locking handle 140 is again tightened down for locking and holding the new adjustment . during such axial adjustment , the socket 108 slides upwardly or downwardly along the tool drive shaft 24 for accommodating the slight change in axial position of the rotor grinding member 70 . the hopper 32 , 33 , the radial support ribs 50 , the tubular support 52 , the ring retainer collar 66 , and the tubular bearing housing 94 are preferably made of clear , transparent , strong , rugged , rigid plastic material , for example such as polycarbonate . the hand knobs 130 and 140 are preferably made from transluscent , milky plastic for example , such as nylon polyamide or delrin acetal resin . cleaning of the whole attachment 10 is convenient by removing it from the bowl 12 and flushing water down through the hopper bottom openings 54 . it is to be noted that in defining the first grinding zone 58 the stator surface 72 slopes downardly and inwardly and the opposed coaxial inner surface 85 slopes downwardly and outwardly , thus defining substantially a vertical path for maximizing the downward feeding effect of gravity for aiding the helical flutes in propelling the particulate food downwardly through this first zone 58 . conversely , the second grinding zone 81 defines generally a more horizontal rather than vertical path . this more generally horizontal zone 81 flares outwardly at more than an angular difference of 50 ° from the first vertical zone 58 for enabling relatively small adjustments in the relative axial position of the stator and rotor grinding means to effect significant changes in the clearance between the opposed grinding surfaces 80 and 100 in said second grinding zone . advantageously , the rotor grinding surfaces 85 and 100 are both wholly positioned closer to the vertical axis of rotation 78 than an overall horizontal width &# 34 ; w &# 34 ; ( fig7 ) of 1 . 8 inches for keeping the relative speed between the opposed grinding surfaces 85 and 72 , 100 and 80 within reasonable speed limits for avoiding undue heating effects . it will be appreciated that the larger the horizontal width &# 34 ; w &# 34 ; of the rotor 70 , the greater will be its peripheral speed , and consequently the greater will be the grinding power being applied to the particulate food being ground at the normal rotational operating speed ( about 1725 to 1750 rpm ) of the tool drive means 24 of the food processor , and thus the greater will be the heating effect on the ground food product . these dimensions as specified provide a quick and effective and uniform grinding action while avoiding undue heating . in operation grain , kernels , coffee beans , condiments or other dry particulate food which is to be ground is easily fed down into the hopper 32 after removing the cover 46 . the particulate food passes by gravity down through the passageway 44 into the truncated conical chute 33 which directs the material to be ground down through the arcuate openings 54 into the first feeding - shearing / cracking - grinding zone 58 . the partially ground product is then fed into the second grinding zone 81 above the rotating flared grinder section 95 by which the finished ground product or flour is distributed around uniformly into the bowl 12 . the operation is clean , efficient and quick . for example , a full cup of hard durum wheat is ground into fine wheat flour in approximately 15 seconds . accordingly , with the grinding attachment 70 of the present invention the user may adapt a food processor at home for the preparation of a wide variety of food items , for example such as whole wheat flour for making bread or pancakes , etc . employing the grinding attachment in the form shown utilizes the bowl , motor drive and toolshaft and base of a food processor , requiring no modifications thereof , which makes this attachment considerably less costly than providing an individual complete appliance for performing the described adjustable grinding operations . since other changes and modifications varied to fit particular operating requirements and environments will become recognized by those skilled in the art , the invention is not considered limited to the examples chosen for purposes of illustration , and includes all changes and modifications which do not constitute a departure from the true spirit and scope of this invention as claimed in the following claims and equivalents of the claimed elements .
method and apparatus for quickly and effectively grinding kernels of grain , such as wheat or corn , coffee beans , and the like , in a food processor producing a finely divided or flour - like consistency food product or condiment . nutritious home - ground whole - grain flour can be conveniently and quickly made . the kernels , grains , beans , or other food products to be ground are introduced into a hopper positioned above the bowl of the food processor and located above a grinder assembly including a downwardly converging then diverging stator grinding member which encircles a rapidly rotating rotor grinding member having a vertical axis of rotation and being positioned within the stator member . this rotor grinding member is coupled to the vertical tool shaft of the food processor which extends up into the bowl . the separation between stator and rotor grinding members is manually adjustable and settable by a hand knob located above the grinder assembly for controlling the consistency and fineness of the ground product , which is deposited from the grinder assembly into the bowl . the illustrated grinder attachment for a food processor may be conveniently operated , adjusted , controlled and cleaned in a safe , efficient manner utilizing without alteration the basic components of the food processor , namely the motor drive , safety interlock system , as well as the bowl .