Self-cleaning grinding mill

Abstract

A self-cleaning grinding mill, especially for grain, has: a feeding assembly for feeding solid material into the mill; a grinding assembly having a stationary grinding head and a rotary grinding head located in a housing, the housing comprising a curved interior channel into which a ground product produced by the grinding heads flows during grinding; a discharge outlet that receives the flow of ground product from the channel, the channel and the discharge outlet connected by a curved surface where the ground product flows from the channel into the discharge outlet, the curved surface mitigating hang-up of the ground product in the channel; and, a subsampling orifice in a wall of the discharge outlet configured so that the channel directs the flow of the ground product into the discharge outlet directly toward the subsampling orifice with sufficient force to mitigate hang-up of the ground product in the subsampling orifice.

Description

[0001] SELF-CLEANING GRINDING MILL

[0002] Cross-reference to Related

[0003] This application claims the benefit of United States patent application USSN 63 / 688,053 filed August 28, 2024, the entire contents of which is herein incorporated by reference.

[0004] Field

[0005] This application relates to grinding mills, especially grinding mills for foodstuffs, in particular to such mills having subsampling capabilities for performing analytics on the ground product.

[0006] Background

[0007] In a grinding mill, avoidance of cross-contamination between different materials ground by the mill and the ability to conduct analytical testing of ground product to determine levels of contaminants are important features. To avoid cross-contamination, grinding mills are typically disassembled, at least partially, and cleaned between uses on different materials. Disassembly takes time and can lead to damage of the mill if the mill is disassembled or reassembled incorrectly. Analytical testing often involves including a subsampling port in the mill so that a portion of the ground product can be directed to analytical equipment for contaminant testing. The subsampling port also needs to be cleaned between the uses of the mill for grinding different materials to avoid crosscontamination. Examples of existing grinding subsampling mills that require cleaning between uses include US 5,553,792 issued September 10, 1996 and US 4,679,737 issued July 14, 1987.

[0008] There is a need for a grinding mill having both subsampling and self-cleaning capabilities.

[0009] A grinding mill comprises: a feeding assembly for receiving solid material, and feeding the solid material into the mill; a grinding assembly in solid material communication with the feeding assembly, the grinding assembly comprising a stationary grinding head and a rotary grinding head located in a housing, the grinding heads defining a grinding zone therebetween, the grinding zone receiving the solid material to be ground, the housing comprising a curved interior channel into which a ground product produced by the grinding heads flows during grinding; a discharge outlet that receives the flow of ground product from the channel and delivers the ground product to a location outside the mill, the channel and the discharge outlet connected by a curved surface where the ground product flows from the channel into the discharge outlet, the curved surface mitigating hang-up of the ground product in the channel; and, a subsampling orifice in a wall of the discharge outlet configured so that the channel directs the flow of the ground product into the discharge outlet directly toward the subsampling orifice with sufficient force to mitigate hang-up of the ground product in the subsampling orifice.

[0010] A grinding mill comprises: a feeding assembly for receiving solid material, and feeding the solid material into the mill; a grinding assembly in solid material communication with the feeding assembly, the grinding assembly comprising a stationary grinding disc and a rotary grinding disc located in a housing, the grinding discs defining a grinding zone therebetween, the grinding zone receiving the solid material to be ground; and, a discharge outlet that receives the flow of ground product from the grinding zone and delivers the ground product to a location outside the mill, wherein: the rotary grinding disc is mounted on a spindle that protrudes through the stationary disc, the spindle comprising a plurality of fins disposed around an external surface of the spindle, the fins oriented radially from and longitudinally along the external surface of the spindle; the rotary grinding disc comprises a series of cut-outs in a grinding face thereof, the cut-outs disposed annularly around the spindle and located between the fins; and, the grinding face of the rotary grinding disc and a grinding face of the stationary grinding disc comprise a plurality of teeth and radially oriented channels between the teeth configured in a two-way grinding pattern.

[0011] The grinding mill may be any type of grinding mill including disc mills, roll mills and the like. In some embodiments, the grinding mill is a disc mill, in which the grinding heads are discs. In some embodiments, each grinding disc has a grinding face and the grinding faces are mutually facing in the grinding assembly with the grinding zone located between the mutually facing grinding faces. The discs may therefore have flat or complementarily curved grinding faces opposed to each other across the grinding zone.

[0012] In some embodiments, one or both grinding faces comprise a plurality of teeth and radially oriented channels between the teeth configured in a two-way grinding pattern. In some embodiments, the two-way pattern comprises groups of parallel teeth and radially- extending channels, wherein the teeth and radially oriented channels of a first group form an angle with respect to the teeth and channels of a neighboring group. In some embodiments, the angle formed is in a range between 5° and 45°. In some embodiments, the angle formed is in a range between 15° and 35°.

[0013] In some embodiments, the grinding faces of the grinding heads comprise pluralities of cutouts. The cutouts communicate with central apertures of the grinding heads to draw the solid material into the grinding zone. In some embodiments, the plurality of cutouts in the rotary grinding head comprise larger and smaller cutouts. In some embodiments, the larger cutouts are elongated and arcuate in shape following an arc of an inner edge of the rotary grinding head around the central aperture of the rotary grinding disc head. The larger cutouts help with grinding solid material having a high moisture content, for example a moisture content in a range of 20-30% by weight, by preventing the high moisture solid material from piling up, which would cause the grinding mill 1 to surge and eventually jam. When grinding lower moisture solid material (e.g., in the range of 10-14% by weight of water) the larger cutouts accelerate the grinding process. Thus, the grinding mill can grind solid materials having moisture contents up to about 30 wt% water without jamming.

[0014] In some embodiments, the ground product follows a single flow path into the discharge outlet. In some embodiments, the channel opens into the discharge outlet at location across the discharge outlet from the subsampling orifice. In some embodiments, the flow path of the ground product entering the discharge outlet from the channel is on an axis that passes through the subsampling orifice. In some embodiments, a portion of the housing forms a wedge that blocks a portion of the discharge outlet above the subsampling orifice. In some embodiments, the wedge has a surface facing into the discharge outlet which further directs the flow of ground product from the channel through the discharge outlet to the subsampling orifice with enough force to further mitigate hangup of the ground product in the subsampling orifice. Mitigating hang-up of ground product in the subsampling orifice contributes to the self-cleaning functionality of the grinding mill.

[0015] In some embodiments, the subsampling orifice has an adjustable diameter. In some embodiments, the diameter of the subsampling orifice is controlled by a plate valve or an iris valve.

[0016] In some embodiments, the grinding mill comprises a single discharge outlet, which is preferred when the mill is used for grinding different kinds of grain and sampling of the ground product is performed to analyze for cross-contamination. In other embodiments, the grinding mill comprises two, three or more discharge outlets. In some embodiments, the grinding mill further comprises a solid particle cracker between the feeding assembly and the grinding assembly. The solid particle cracker is configured to preliminarily break outer surfaces of the solid material to facilitate complete grinding in the grinding zone. In some embodiments, the solid particle cracker comprises a stationary external roll having a series of ridges circumferentially disposed around an internal surface of the external roll, and a rotary internal roll situated inside the external roll, the internal roll having a series of fins disposed around an external surface of the internal roll. In some embodiments, the surfaces between tops of the ridges of the series of ridges are curved to mitigate hang-up of broken solid material in the solid particle cracker. In some embodiments, surfaces between the fins and a core of the internal roll are curved to further mitigate hang-up of the broken solid material in the solid particle cracker. Mitigating hang-up of broken solid material in the solid particle cracker contributes to the self-cleaning functionality of the grinding mill. In some embodiments, the internal toll comprises a spindle on which the rotary grinding head is mounted.

[0017] In some embodiments, the grinding mill further comprises a rotatable spindle. In some embodiments, the rotatable spindle has at least one radially-extending fan blade mounted thereon. In some embodiments, the at least one fan blade is situated in the housing, whereby rotation of the spindle causes the at least one fan blade to rotate arcuately in the housing thereby creating the flow of the ground product in the channel. In some embodiments, the at least one fan blade has as tip with an axially-oriented extension that extends across the channel toward a rear wall of the housing to further mitigate hang-up of the ground product in the channel. Mitigating hang-up of ground product in the channel contributes to the self-cleaning functionality of the grinding mill. In some embodiments, the at least one radially-extending fan blade is three radially- extending fan blades. In some embodiments, the spindle and the internal roll are the same structure.

[0018] In some embodiments, the grinding mill further comprises a motor operatively connected to the rotary grinding head to rotate the rotary grinding head. In some embodiments, the motor is also operatively connected to the rotary internal roll to rotate the rotary grinding head and the rotary internal roll together. In some embodiments, the motor is also operatively connected to the at least one fan blade roll to rotate the rotary grinding head and the at least one fan blade together. In some embodiments, the motor is operatively connected to the rotary grinding head, the rotary internal roll and the at least one fan blade so that all of those elements can be rotated together. In some embodiments, one or more of the surfaces in the grinding mill which encounter the solid material and / or the ground product are made of and / or coated with an anti-stick material.

[0019] The grinding mill is used to reduce the particle size of solid material for the purpose of material production (e.g., food production) and diagnostic testing. The grinding mill is useful for grinding any discrete solid material. The grinding mill is especially useful for grinding grains (e.g., cereals and legumes) and animal feed, especially grains. Grains include, for example, wheat, buckwheat, triticale, spelt, teff, oat, barley, finger millet, fonio, foxtail millet, Japanese millet, Job's tears, kodo millet, maize, corn, millet, pearl millet, proso millet, sorghum, barley, rice, rye, amaranth, chia, quinoa, kaniwa, chickpeas, common beans, common peas, fava beans, lentils, lima beans, lupins, mung beans, peanuts, pigeon peas, runner beans, soybeans, rapeseed, black mustard, India mustard, canola, sunflower seed, safflower, flax seed, hemp seed, poppy seed and the like. In some embodiments, the grinding mill is configured to grind corn.

[0020] In some embodiments, the grinding mill utilizes a two-phase milling system starting with a rotary screw (a spindle with fins) that cracks solid material in a preliminary solid material cracker and feeds the cracker solid material into two milling discs, one fixed the other rotating. The milling disc gap, which defines the grinding zone, can be adjusted (manually or automatically) by actuating a rotary knob to meet varying granulation specifications (for example, >95% ground product through a 20-mesh screen). The grinding mill has flow design innovations that allow the flow of solid material and ground product to self-clean during operation and clean-out, reducing cross-contamination between samples. The entire ground product flow exiting the discs is forcibly directed with rotary fan blades through a restricted channel towards a subsampling orifice that is varied by size according to subsample requirements. As the ground product is forced through the subsampling orifice the self-cleaning functionality is maintained. The entire milling process effectively reduces cross-contamination through self-cleaning design elements for reduction in product hang-up and forced channeling of ground product directly across to the subsampling mechanism. Further, by increasing grind size of a subsequent ground product sample, a scouring clean-out of the channel is an option to purge surfaces in the grinding mill. The grinding mill can also process a large sample size (e.g., 2 kg of corn) in a short time period (<2 minutes) and as new material is ground the self-cleaning functionality for subsampling effectively reduces the probability of cross-contamination due to product hang-up. Finally, should it be desired, the contact surfaces in the housing can be easily wiped clean with a cloth or vacuum nozzle with brush with very little effort. Further features will be described or will become apparent in the course of the following detailed description. It should be understood that each feature described herein may be utilized in any combination with any one or more of the other described features, and that each feature does not necessarily rely on the presence of another feature except where evident to one of skill in the art.

[0021] Brief Description of the Drawings

[0022] For clearer understanding, preferred embodiments will now be described in detail by way of example, with reference to the accompanying drawings, in which:

[0023] Fig. 1 A depicts a top perspective view of a grinding mill.

[0024] Fig. 1 B depicts a side perspective view of the grinding mill of Fig. 1 B.

[0025] Fig. 1 C depicts a front view of the grinding mill of Fig. 1A.

[0026] Fig. 2 depicts a side cross-sectional view taken through a longitudinal center line of the grinding mill of Fig. 1A.

[0027] Fig. 3A depicts a perspective view of an interior of the grinding mill of Fig. 1A.

[0028] Fig. 3B depicts a front view of Fig. 3A.

[0029] Fig. 4A depicts a perspective view of an interior of a seed cracker of the grinding mill of Fig. 1A.

[0030] Fig. 4B depicts a front view of Fig. 4A.

[0031] Fig. 5 depicts a rear perspective view of a spindle having a rotary grinding disc mounted thereon.

[0032] Detailed Description

[0033] With reference to the figures illustrating an embodiment of a grinding mill, the grinding mill 1 is a disc mill comprising a grinding assembly 10 having a housing 11 within which are disposed a stationary grinding disc 12 and a rotary grinding disc 14, the grinding discs 12, 14 each having a grinding face comprising a plurality of teeth and radially oriented channels between the teeth, the grinding faces mutually facing to define a grinding zone 15 therebetween where a ground product is produced from a solid material. The grinding discs 12, 14 are substantially circular and have complementary convex and concave grinding faces, each grinding disc having a central large aperture. The grinding discs 12, 14 are oriented so that cross-sections through edges of the grinding discs are substantially parallel to the gravitational field (i.e., substantially vertically oriented) and a rotational axis of the rotary grinding disc 14 points horizontally when the mill 1 is supported on a substantially horizontal surface. In the illustrated embodiment, a central axis of the stationary grinding disc 12 is coaxial with the rotational axis of the rotary grinding disc 14. A distance between the grinding discs 12, 14 can be varied to adjust the size of the grinding zone 15 depending on the nature of the solid material to be ground. The solid material ground between the grinding discs 12, 14 is eventually discharged downwardly under the influence of gravity through a downwardly oriented discharge outlet 30, which receives a flow of the ground product from the housing 11. A single discharge outlet 30 is illustrated, but the grinding mill 1 may comprise two or more discharge outlets in some embodiments. The discharge outlet 30 delivers the ground product through a terminal downward facing discharge opening 31 (see Fig. 2) to a location outside the mill 1 where a receptacle can be placed to collect the ground product. The housing 11 and the discharge outlet 30 are enclosed at a front of the mill 1 by a hinged door 35 secured in place by a latch 36. The door 35 can be opened to provide access to an inside of the mill 1 for maintenance. A subsampling port 32 is located at a side of the discharge outlet 30, the subsampling port 32 comprising an adjustable diameter subsampling orifice 33 through which samples of the ground product can be extracted from the flow of the ground product in the discharge outlet 30. To effect grinding of the solid material, the rotary grinding disc 14 is mounted on a drive shaft 71 of a motor 70, the motor 70 driving rotation of the rotary grinding disc 14 about a horizontal drive axis. The solid material in the grinding zone 15 is thereby ground into the ground product between the stationary grinding disc 12 and the rotary grinding disc 14. The drive shaft 71 is supported at a distal end thereof by a door plug 37 in an aperture in the door 35, the drive shaft 71 able to rotate in the door plug 37. The motor 70 is controlled from a control box 73 electrically connected to the motor 70.

[0034] The grinding mill 1 further comprises a feeding assembly 40 comprising a hopper 41 situated at a higher elevation than the grinding assembly 10 and a feeding chute 42 located at a bottom of the hopper 41 through which the solid material can flow under the influence of gravity further into the grinding mill 1. The flow of solid material through the feeding chute 42 is regulated by a hopper gate 43, which in the illustrated embodiment comprises a blocking plate that is insertable into the feeding chute 42 through a slot in a side of the feeding chute 42 in order to adjust an effective cross-sectional area of the feeding chute 42 by variably blocking the feeding chute 42 at the slot thereby regulating the amount of solid material passing out of the hopper 41 further into the grinding mill 1. With the hopper gate 43 fully inserted, the flow of solid material from the hopper 41 is stopped. In the illustrated embodiment, the solid material passes from the feeding chute 42 into a solid particle cracker 60 (e.g., a seed cracker) for preliminary breaking of outer surfaces of the solid material. In embodiments where a solid particle cracker is not used, the solid material can pass from the feeding chute directly into the grinding assembly. All the components of the grinding mill 1 are supported on a surface by a base 5.

[0035] The rotary grinding disc 14 is mounted on a spindle 16 with the spindle 16 mounted on the drive shaft 71 of the motor 70 so that the drive shaft 71 rotationally drives the spindle 16 and therefore rotationally drives the rotary grinding disc 14 in the housing 11. In the illustrated embodiment, the drive shaft 71, spindle 16 rotary grinding disc 14 and stationary grinding disc 12 are concentric and the motor 70 is mounted to a rear face of the solid particle cracker 60, although other configurations are possible. While the rotary grinding disc 14 is in the housing 11, a portion 17 of the spindle 16 extends through the central aperture of the rotary grinding disc 14 and into the solid particle cracker 60 through an aperture in a rear wall of the housing 11 and an aperture 61 in a front face 64 of the solid particle cracker 60.

[0036] The solid particle cracker 60 comprises a block 62 having an internal cavity 63 that acts as a stationary external roll of the solid particle cracker 60. In the illustrated embodiment (see Fig. 4A and Fig. 4B), the internal cavity 63 is frustoconical, although a cylindrical cavity is possible, and has a series of ridges 65 (only two labeled) circumferentially disposed around an internal surface 66 of the internal cavity 63. Surfaces 67 between tops of the ridges 65 are smoothly curved with no acute bends to mitigate hang-up of broken solid material in the solid particle cracker 60. The solid material enters the seed cracker 60 through an intake aperture 68 in a top surface of the block 62, the intake aperture 68 being in solid material communication with the feeding chute 42 of the feeding assembly 40, which is mounted on and above the solid particle cracker 60. The portion 17 of the spindle 16 that extends into the internal cavity 63 acts as a rotary internal roll situated inside the stationary external roll. The spindle 16 has a series of fins 18 disposed around an external surface of the spindle 16 (see Fig. 2 and Fig. 5). While three fins 18 are shown in the illustrated embodiment, two or more fins can be used, for example, two, three, four, five or six fins. The fins 18 are oriented radially from and longitudinally along the external surface of the spindle 16. Rotation of the spindle 16 causes the fins 18 to revolve inside the internal cavity 63 so that solid material in the internal cavity 63 is cracked between the fins 18 and the ridges 65. Surfaces 19 between the fins 18 and a core of the spindle 16 are smoothly curved with no acute bends to further mitigate hang-up of the broken solid material in the solid particle cracker 60.

[0037] The stationary grinding disc 12 is mounted inside the housing 11 at the rear wall of the housing 11 with the grinding face of the stationary grinding disc 12 facing forward in the housing 11 (see Fig. 3A and Fig. 3B) and the central aperture of the stationary grinding disc 12 aligned with the aperture in the rear wall of the housing 11 and the aperture 61 in the front face 64 of the solid particle cracker 60. The rotary grinding disc 14 is mounted on the spindle 16 with the grinding face of the rotary grinding disc 14 facing rearward (see Fig. 5). When assembled in the grinding mill 1 , the grinding faces of the two grinding discs 12, 14 are opposed to each other across the grinding zone 15 (see Fig. 2). The grinding face of the stationary grinding disc 12 comprises a plurality of radially- extending teeth 26 (only one labeled) and radially oriented channels 27 (only one labeled) between the teeth 26 configured in a two-way grinding pattern. Likewise, the grinding face of the rotary grinding disc 14 comprise a plurality of radially-extending teeth 28 (only one labeled) and radially oriented channels 29 (only one labeled) between the teeth 28 configured in the two-way grinding pattern. The two-way grinding pattern comprises neighboring groups of radially-extending channels, for example groups A and B on the grinding face of the stationary grinding disc 12 (Fig. 3A) and groups C and D on the grinding face of the rotary grinding disc 14 facing (Fig. 5), where the teeth and channels within a group are parallel to each other but the teeth and channels in one group form an angle with respect to the teeth and channels of the neighboring group. The angle formed is in a range between 5° and 45°, especially between 15° and 35°.

[0038] As seen in Fig. 3A and Fig. 5, the grinding faces of both the stationary grinding disc 12 and the rotary grinding disc 14 contain a plurality of first cutouts 51 (one of twelve labeled in Fig. 3A and two of twelve labeled in Fig. 5 annularly disposed around center points of the respective grinding disc 12, 14. More or fewer first cutouts can be provided. The first cutouts 51 open into the central apertures of their respective grinding disc 12, 14. The first cutouts 51 function to grab and pull cracked solid material from the spindle 16 and the solid material cracker 60 into the grinding zone 15. However, the first cutouts 51 are not sufficient to force cracked solid material having high moisture content into the grinding zone 15. High moisture solid materials contain about 20% or more water by weight, for example about 20-35% water by weight, or about 25-30%, water by weight. To extend the functionality of the grinding mill 1 to grinding high moisture solid material, the grinding face of the rotary grinding disc 14 is provided with a plurality of larger second cutouts 53 annularly disposed around the center point of the rotary grinding disc 14. The second cutouts 53 contain small portions of some of the first cutouts, for example a portion of first cutout 51a is contained in one of the second cutouts 53. The second cutouts 53 are elongated and arcuate in shape following an arc of an inner edge of the rotary grinding disc 14 around the central aperture of the rotary grinding disc 14 and are shallower than the first cutouts 51. Each of the second cutouts 53 are centered on one of the fins 18 of the spindle 16 to optimize withdrawing cracker solid material from around the spindle 16 into the grinding zone 15, which further mitigates hang-up of cracker solid material around the fins 18. In the illustrated embodiment, three second cutouts 53 are provided. The second cutouts 53 permit continuous flow of high moisture solid material within the grinding mill 1. Without the second cutouts, the cracked high moisture solid material piles onto the fins 18 causing the grinding mill 1 to surge and eventually jam. When grinding lower moisture solid material (e.g., in the range of 10-14% by weight of water) the second cutouts 53 function to accelerate the grinding process. The length of the second cutouts 53 is not as important as having the second cutouts 53 on both sides of each of the fins 18. Thus, the rotary grinding disc 14 comprises a series of second cutouts 53 in the grinding face, the second cutouts 53 disposed annularly around the spindle 16 and located radially outward of and straddling the fins 18. The two-way grinding pattern of the grinding discs 12, 14 together with the second cutouts 53 permit milling of high moisture content solid materials, such as high moisture grains (e.g., corn). Thus, the grinding mill 1 is capable of grinding grains having moisture contents up to about 30 wt% water without jamming.

[0039] The spindle 16 further comprises at least one radially-extending fan blade 21 mounted on a front face of the spindle 16. In the illustrated embodiment, the spindle 16 comprises three radially-extending fan blades 21 equally spaced around the front face of the spindle 16. One, two, three, four, five or more fan blades may be utilized depending to some extent on the radius of the housing, with more fan blades being useful when the radius of the housing is larger. The fan blades 21 are situated in an annular channel 23 inside the housing 11 whereby rotation of the spindle 16 causes the fan blades 21 to rotate arcuately in the housing 11 thereby creating a flow of the ground product in the annular channel 23, the annular channel 23 following a curved inner surface of the housing 11 (see Fig. 3A and Fig. 3B). The rear wall of the housing 11 and the inner wall of the door 35 form other walls of the annular channel 23. Each of the fan blades 21 has a tip with an axially-oriented extension 22 that extends across the annular channel toward a rear wall of the housing 11 to further mitigate hang-up of the ground product in the annular channel 23. In a grinding process, the solid material in the hopper 41 flows under the influence of gravity through the feeding chute 42 into the internal cavity 63 through the intake aperture 68 of the solid material cracker 60. In the internal cavity 63 of the solid material cracker 60, the solid material is preliminarily comminuted by the action of the fins 18 on the rotating spindle 16 and the ridges 65 on the internal surface 66 of the internal cavity 63 to produce the cracked solid material. The cracked solid material is forced out of the internal cavity 63 by more solid material entering the internal cavity 63 from the hopper 41, the cracked solid material being forced through the aperture 61 in the front face 64 of the solid particle cracker 60 and into the housing 11 through the aperture in the rear wall of the housing 11. In the housing 11 , the cracked solid material is forced into the central apertures of the two grinding discs 12, 14 where the cracked solid material is grabbed by the first cutouts 51 and the second cutouts 53 to be forced into the grinding zone 15 between the two grinding discs 12, 14. The cracked solid material in the grinding zone 15 is ground into ground product between the grinding faces of the grinding zone 15 by rotation of the rotary grinding disc 14 mounted on the rotating spindle 16. The ground product is propelled by centripetal force through the radially oriented channels 27 and 29 toward the perimeters of the two grinding discs 12, 14 where the ground product is ejected into the annular channel 23 in the housing 11. The housing 11 is cylindrical having a curved wall whose inner surface forms a floor of the annular channel 23. The radially-extending fan blades 21 mounted on the spindle 16 are rotating counterclockwise within the annular channel 23, as viewed in Fig. 3B, driving the ground product in the annular channel 23 toward a restricted exit channel 24.

[0040] A volume of the exit channel 24 is restricted by a lower curved transition surface 25 between the annular channel 23 and the discharge outlet 30 and an upper deflecting surface 81. The upper deflecting surface 81 is a lower curved surface of a wedge 82, the wedge 82 being a portion of the housing 11 that extends partially over the discharge outlet 30 above the subsampling orifice 33. An upper surface of the wedge 82 forms part of the floor of the annular channel 23. The upper deflecting surface 81 is a curved surface facing into the discharge outlet 30. The lower curved transition surface 25 and the curved upper deflecting surface 81 mitigate hang-up of the ground product in the annular channel 23 and the restricted exit channel 24. Ground product flowing through the restricted exit channel 24 follows a flow path axis FP, the flow path axis FP passing through the subsampling orifice 33 of the subsampling port 32. Thus, the ground product flowing out of the restricted exit channel 24 of the annular channel 23 is flowing into the discharge outlet 30 at location across the discharge outlet 30 from the subsampling orifice 33 and directly toward the subsampling orifice 33. Because the upper deflecting surface 81 restricts the volume of the exit channel 24 and extends from the floor of the annular channel 23 to the subsampling orifice 33, the upper deflecting surface 81 directs the flow of ground product from the exit channel 24 through the discharge outlet 30 directly to the subsampling orifice 33 with enough speed and force to mitigate hang-up of the ground product in the subsampling orifice 33, thereby providing a self-cleaning functionality for the subsampling port 32. Ground product that is not sampled falls through the discharge outlet 30 and out of the grinding mill 1 through the discharge opening 31.

[0041] The novel features will become apparent to those of skill in the art upon examination of the description. It should be understood, however, that the scope of the claims should not be limited by the embodiments but should be given the broadest interpretation consistent with the wording of the claims and the specification as a whole.

Claims

Claims:

1. A grinding mill comprising: a feeding assembly for receiving solid material, and feeding the solid material further into the mill; a grinding assembly in solid material communication with the feeding assembly, the grinding assembly comprising a stationary grinding head and a rotary grinding head located in a housing, the grinding heads defining a grinding zone therebetween, the grinding zone receiving the solid material to be ground, the housing comprising a curved interior channel into which a ground product produced by the grinding heads flows during grinding; a discharge outlet that receives the flow of ground product from the channel and delivers the ground product to a location outside the mill, the channel and the discharge outlet connected by a curved surface where the ground product flows from the channel into the discharge outlet, the curved surface mitigating hang-up of the ground product in the channel; and, a subsampling orifice in a wall of the discharge outlet configured so that the channel directs the flow of the ground product into the discharge outlet directly toward the subsampling orifice with sufficient force to mitigate hang-up of the ground product in the subsampling orifice.

2. The grinding mill of claim 1 , wherein a portion of the housing forms a wedge that blocks a portion of the discharge outlet above the subsampling orifice, the wedge having a surface facing into the discharge outlet which further directs the flow of ground product from the channel through the discharge outlet to the subsampling orifice with enough force to further mitigate hang-up of the ground product in the subsampling orifice.

3. The grinding mill of claim 1 or claim 2, wherein the channel opens into the discharge outlet at location across the discharge outlet from the subsampling orifice and a flow path of the ground product entering the discharge outlet from the channel is on an axis that passes through the subsampling orifice.

4. The grinding mill of any one of claims 1 to 3, wherein the discharge outlet is a single discharge outlet.

5. The grinding mill of any one of claims 1 to 4, further comprising a solid particle cracker between the feeding assembly and the grinding assembly, the solid particle cracker configured to break outer surfaces of the solid material.

6. The grinding mill of claim 5, wherein the solid particle cracker comprises: a stationary external roll having a series of ridges circumferentially disposed around an internal surface of the external roll; and, a rotary internal roll situated inside the external roll, the internal roll having a series of fins disposed around an external surface of the internal roll, wherein surfaces between tops of the ridges of the series of ridges are curved to mitigate hang-up of broken solid material in the solid particle cracker.

7. The grinding mill of claim 6, wherein surfaces between the fins and a core of the internal roll are curved to further mitigate hang-up of the broken solid material in the solid particle cracker.

8. The grinding mill of any one of claims 1 to 7, further comprising a motor operatively connected to the rotary grinding head to rotate the rotary grinding head.

9. The grinding mill of any one of claims 5 to 7, further comprising a motor operatively connected to the rotary grinding head and to the rotary internal roll to rotate the rotary grinding head and the rotary internal roll.

10. The grinding mill of any one of claims 1 to 9, further comprising a rotatable spindle having at least one radially-extending fan blade mounted thereon, the at least one fan blade situated in the housing, whereby rotation of the spindle causes the at least one fan blade to rotate arcuately in the housing thereby creating the flow of the ground product in the channel.

11. The grinding mill of claim 10, wherein the at least one fan blade has as tip with an axially-oriented extension that extends across the channel toward a rear wall of the housing to further mitigate hang-up of the ground product in the channel.

12. The grinding mill of claim 10 or claim 11 , wherein the at least one radially- extending fan blade is three radially-extending fan blades.

13. The grinding mill of any one of claims 1 to 12, wherein the subsampling orifice has an adjustable diameter.

14. The grinding mill of any one of claims 1 to 13, wherein the mill is a disc mill in which the grinding heads are discs, each disc having a grinding face opposed to each other across the grinding zone.

15. The grinding mill of any one of claims 1 to 14, wherein the solid material comprises a grain.

16. The grinding mill of claim 15, wherein the grain is corn.

17. A grinding mill comprising: a feeding assembly for receiving solid material, and feeding the solid material into the mill; a grinding assembly in solid material communication with the feeding assembly, the grinding assembly comprising a stationary grinding disc and a rotary grinding disc located in a housing, the grinding discs defining a grinding zone therebetween, the grinding zone receiving the solid material to be ground; and, a discharge outlet that receives the flow of ground product from the grinding zone and delivers the ground product to a location outside the mill, wherein: the rotary grinding disc is mounted on a spindle that protrudes through the stationary disc, the spindle comprising a plurality of fins disposed around an external surface of the spindle, the fins oriented radially from and longitudinally along the external surface of the spindle; the rotary grinding disc comprises a series of cutouts in a grinding face thereof, the cutouts disposed annularly around the spindle and located radially outward of and straddling the fins; and, the grinding face of the rotary grinding disc and a grinding face of the stationary grinding disc comprise a plurality of teeth and radially oriented channels between the teeth configured in a two-way grinding pattern.

18. The grinding mill of claim 17, wherein the two-way pattern comprises groups of parallel teeth and radially-extending channels, wherein the teeth and radially oriented channels of a first group form an angle with respect to the teeth and channels of a neighboring group, wherein the angle formed is in a range between 5° and 45°.

19. The grinding mill of claim 17 or claim 18, wherein the cutouts are elongated and arcuate in shape following an arc of an inner edge of the rotary grinding disc around a central aperture of the rotary grinding disc.

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