WO2005005029A1

WO2005005029A1 - Apparatus for the mixing of particulate materials

Info

Publication number: WO2005005029A1
Application number: PCT/IB2004/002251
Authority: WO
Inventors: Charl Marais; Christian George Frederick Richter
Original assignee: Charl Marais; Richter Christian George Frede
Priority date: 2003-07-11
Filing date: 2004-07-12
Publication date: 2005-01-20
Also published as: ZA200509710B

Abstract

The invention provides a mixing apparatus (10) for mixing particulate materials in a desired ratio. The mixing apparatus (10) includes a mixing chamber (12), a main feeding arrangement (24) and a supplement feeding arrangement (36). The mixing chamber (12) mixes a main particulate material such as mealie meal with a particulate supplement material such as a powdery vitamin supplement. The supplement feeding arrangement (36) has a feed outlet through which the particulate supplement material is fed to the mixing chamber (12) at an adjustable selected rate. The supplement feeding arrangement (36) includes a rotary feed member, having a circumferentially extending series of axially extending feed chambers, such that operative rotation of the feed member successively delivers particulate supplement material from the respective feed chambers into the mixing chamber (12).

Description

APPARATUS FOR THE MIXING OF PARTICULATE MATERIALS

THE INVENTION relates to the mixing together of particulate materials. In particular, the invention provides a mixing apparatus for mixing two particulate materials, such as a particulate foodstuff and a particulate supplement material, in a desired ratio. The invention also relates to a particulate material feed device.

Although the invention relates to the mixing together of particulate materials in general, the invention is particularly applicable to the mixing together of fine particulate substances, more particularly powdery substances such as mealie meal, corn meal, fish meal, vitamin powder, or the like. However, the invention can also be applied to the mixing together of less fine particulate substances.

The invention provides a mixing apparatus for mixing particulate materials in a desired ratio, which apparatus includes: a mixing chamber for mixing together a main particulate material and a particulate supplement material; a main feeding arrangement for feeding the main particulate material to the mixing chamber at an adjustable selected rate; a supplement feeding arrangement for feeding the particulate supplement material to the mixing chamber at an adjustable selected rate, the supplement feeding arrangement including a feed outlet which is in communication with the mixing chamber for transportation of the particulate supplement material to the mixing chamber, the supplement feeding arrangement further including a rotary feed member which is mounted for rotation about an axis of rotation, the rotary feed member having a plurality of feed chambers such that operative rotation of the feed member successively brings the feed chambers into register with the feed outlet for successive discharge of particulate supplement material from the respective feed chambers into the mixing chamber via the feed outlet.

It will be appreciated that the volume of one of the particulate materials in the mixture will typically be substantially greater than that of the other particulate material, for instance when a vitamin supplement is added to a foodstuff material. The respective materials are thus referred to as a main particulate and a supplement particulate material to distinguish between the materials. This distinction is for ease of description only, and is not intended to limit the relative volumes of the materials.

It should also be appreciated that the apparatus can be configured for mixing together more than two particulate materials, for instance being for mixing a plurality of supplements into a particulate foodstuff.

The feed chambers may be angularly spaced about the axis of rotation, each feed chamber extending axially through the feed member. In one embodiment of the invention, each feed chamber is an axially extending channel in a radially outer cylindrical surface of the feed member, each feed chamber thus being open in a radially outward direction, the rotary feed member being located in a complementary cylindrical cavity in a stationary housing, such that there is no more than a radial working clearance between the radially outer surface of the feed member and a peripheral wall of the complementary cavity. Each feed chamber is thus defined partly by peripheral walls provided by the rotary feed member, and partly by a registering part of the radially inwardly directed peripheral wall of the cavity. It will be appreciated that the rotary member, in use, rotates relative to the stationary housing.

The axis of rotation of the feed member preferably extends operatively upwardly, the feed member being located superjacent the feed outlet, so that discharge of particulate supplement material from the respective feed chambers into the feed outlet, when the feed chambers are successively brought into register with the feed outlet, is by gravity flow. The feed outlet may be provided in a stationary base member, the feed member being mounted above the base member and being in frictional abutment therewith.

The supplement feeding arrangement may include a feed chamber discharging arrangement for inhibiting bridging of particulate supplement material in the respective feed chambers when the feed chambers are brought into register with the feed outlet. The discharging arrangement may comprise a synchronised tapping mechanism which is arranged successively to tap the feed member as the respective feed chambers are brought into register with the feed outlet. In other embodiments of the invention, the feed chamber discharge arrangement may be arranged to deliver a jet of air to the respective feed chambers as they are successively brought into register with the feed outlet, successively to puff a charge of particulate supplement material from the respective feed chambers. The tapping mechanism may include a strike member or tapper mounted for reciprocating movement relative to the feed member, repeatedly to strike the feed member adjacent the feed outlet. The tapping mechanism may be arranged for movement of a head of the strike member in a radial direction, the head of the strike member being in axial register with the feed outlet. Typically, the strike member is mounted for reciprocating pivotal displacement about a pivot axis which is more or less parallel to the axis of rotation of the feed member.

The supplement feeding arrangement may include a supplement hopper which has a hopper chamber for housing particulate supplement material, the hopper chamber being located above the rotary feed member for gravity feed of particulate supplement material to the feed member, the supplement feeding arrangement further including a delivery mechanism for delivering particulate supplement material from the hopper chamber to the feed member such that the feed member is not directly exposed to the weight of particulate supplement material in the hopper chamber.

Typically, the delivery mechanism includes a cover member superjacent the feed member, to cover upper ends of some of the feed chambers of the feed member, thus preventing flow of particulate supplement material into those feed chambers, and to support particulate supplement material on the cover member, the cover member having a delivery opening therethrough such that, upon rotation of the feed member, the feed chambers are successively brought into register with the delivery opening, to permit successive filling of the feed chambers with particulate supplement material resting on the cover member. The delivery mechanism preferably includes a primary agitator for agitating particulate supplement material supported on the cover member, to promote movement of supplement material through the delivery opening in the cover member into the respective feed chambers under gravity. The primary agitator may be mounted for rotation about a rotational axis co-axial with the axis of rotation of the feed member, the primary agitator extending more or less radially for rotation in a plane superjacent the cover member. The primary agitator may conveniently be shaped and arranged for displacing particulate supplement material supported on the cover member towards the delivery opening in response to rotation of the primary agitator.

In addition, the delivery mechanism may include a floor member which provides a floor of the hopper chamber, the floor member being spaced above the cover member, so that an ante-chamber is defined between the cover member and the floor member, spacing particulate supplement material in the hopper chamber from the cover member, the floor member having at least one discharge opening therethrough for permitting the passage of particulate supplement material into the ante-chamber under gravity.

The delivery mechanism may additionally include a secondary agitator for agitating particulate supplement material in the hopper chamber to promote passage of particulate supplement material in the hopper chamber through each discharge opening in the floor member into the ante-chamber. The secondary agitator is typically mounted for rotation about a rotational axis co-axial with the axis of rotation of the feed member, the secondary agitator extending more or less radially for rotation in a plane superjacent the floor member and being shaped and arranged for displacing particulate supplement material supported on the floor member towards the discharge opening in the floor member in response to rotation of the secondary agitator.

Preferably, the delivery opening in the cover member is radially and/or circumferentially spaced from each discharge opening in the floor member. In one embodiment of the invention, the floor member and the cover member are generally circular in outline when viewed in an axial direction, each opening in the floor member being located adjacent a radially outer periphery of the floor member, while the delivery opening in the cover member is spaced radially inwardly from the openings in the floor member, being located adjacent the centre of the cover member. In such case, the secondary agitator will be arranged to push particulate supplement material radially outwardly towards the opening or openings in the floor member upon rotation thereof, while the primary agitator will be arranged to draw particulate material radially inwardly towards the delivery opening in response to rotation thereof. The respective agitators thus serve both as agitators and impellers.

The main feeding arrangement typically comprises a main hopper for holding main particulate material, the main feeding arrangement including a rotary valve adjacent an outlet of the main hopper for delivering discrete batches of main particulate material to the mixing chamber. In one embodiment of the invention, the rotary valve is a star feeder which is mounted in the outlet of the main hopper at or adjacent a lower end thereof, the star feeder being rotatable about an operatively more or less horizontally extending axis. The rotary valve thus comprises a rotary valve member having a circumferentially extending series of compartments which respectively open radially outwardly, such that rotation of the valve member brings the compartments successively into communication with the main hopper for filling of the respective compartments with main particulate material under gravity, such rotation also successively bringing the compartments into communication with the mixing chamber for discharge of main particulate material from each compartment under gravity, when the compartments are directed downwardly.

The apparatus may include a control system for controlling the speed of rotation of the feed member and the rotary valve respectively, permitting a user to determine the ratio of particulate supplement material to main particulate material in the resultant mixture by operation of the control system. It will be appreciated that the ratio of the volume of the main particulate material to the particulate supplement material in the resultant mixture is determined by the relationship of the speed of rotation of the feed member of the supplement feeding arrangement to the speed of rotation of the rotary valve of the main feeding arrangement. The apparatus thus preferably includes a drive arrangement for driving the feed member and the rotary valve.

The mixing chamber may be an elongated conduit which has an impelling mechanism for transporting particulate material along the conduit and for mixing together main particulate material and particulate supplement material while it is transported along the conduit. The invention also provides a feed device for feeding a fine particulate material at an adjustable selected rate, which device includes: a feed outlet for the delivery of particulate material from the feeding device; a rotary feed member mounted superjacent the feed outlet for rotation about an axis of rotation to feed particulate material to the feed outlet in discrete batches; and a particulate material holder for holding particulate material and for feeding the particulate material to the rotary feed member, the feed member being provided with a series of angularly spaced feed chambers for receiving particulate material from the holder, each feed chamber extending through the rotary feed member in an axial direction, such that operative rotation of the feed member about its axis of rotation successively brings the feed chambers into register with the feed outlet for successive discharge of particulate material from the respective feed chambers through the feed outlet.

The feed device may be similar to the supplement feeding arrangement defined above with reference to the mixing apparatus in accordance to the invention.

Each feed chamber may thus be an axially extending channel in a radially outer cylindrical surface of the feed member, each feed chamber thus being open in a radially outward direction, the rotary feed member being located in a complementary cylindrical cavity in a stationary housing, such that there is no more than a radial working clearance between the radially outer surface of the feed member and a peripheral wall of the complementary cavity. The feed device may include a feed chamber discharging arrangement for inhibiting bridging of particulate material in the respective feed chambers when the feed chambers are brought into register with the feed outlet, typically being provided by a synchronised tapping mechanism which is arranged successively to tap the feed member as the respective feed chambers are brought into register with the feed outlet.

The feed device may further include a cover member superjacent the feed member, to cover upper ends of some of the feed chambers of the feed member and to support particulate material thereon, the cover member having a delivery opening therethrough such that, upon rotation of the feed member, the feed chambers are successively brought into register with the delivery opening, to permit successive filling of the feed chambers with particulate material resting on the cover member.

Typically, the feed device includes a primary agitator for agitating particulate material supported on the cover member, to promote movement of supplement material through the delivery opening in the cover member into the respective feed chambers under gravity.

A floor member may be provided in the holder to separate an interior of the holder into a hopper chamber and an ante-chamber, the floor member being spaced above the cover member to provide a floor of the hopper chamber, so that an antechamber is defined between the cover member and the floor member, spacing particulate material in the hopper chamber from the cover member, the floor member having at least one discharge opening therethrough for permitting the passage of particulate material into the ante-chamber under gravity. The feed device may additionally include a secondary agitator for agitating particulate material in the hopper chamber to promote passage of particulate material in the hopper chamber through each discharge opening in the floor member into the ante-chamber. The feed member, the primary agitator, and the secondary agitator conveniently be mounted for rotation about a common rotational axis, typically being mounted on a common shaft.

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic three-dimensional view of an apparatus for mixing a particulate foodstuff and particulate supplement material in accordance with the invention; Figure 2 is a sectional side view of a main feeding arrangement forming part of the apparatus of Figure 1 ; Figure 3 is a sectional side view of the main feeding arrangement of Figure 2, taken along line Ill-Ill in Figure 2; Figure 4 is a schematic sectional side view of the apparatus of Figure 1 ; Figure 5 is, on an enlarged scale, a partly sectioned schematic three-dimensional view of a supplement feeding arrangement forming part of apparatus of Figure 1 ; Figure 6 is a schematic side view of the supplement feeding mechanism of Figure 5; Figure 7 is, on an enlarged scale, a sectional plan view of the feeding mechanism of Figure 6, taken along line VII-VII in Figure 6; Figure 8 is a view corresponding to Figure 7, taken along line VIII-VIII in Figure 6; and Figure 9 is a view corresponding to Figures 7 and 8, taken along line IX-IX in Figure 6.

In the drawings, reference numeral 10 generally indicates a mixing apparatus for mixing together a main particulate material and a particulate supplement material in accordance with the invention. In this example, the main particulate material is a particulate foodstuff in the form of mealie meal, and the supplement material is a powdery vitamin supplement.

The apparatus 10 includes a mixing chamber 12 for mixing together the mealie meal and the vitamin powder, the mixing chamber 12 being provided by a horizontally extending conduit in the form of a pipe 14, so that the mixing chamber 12 is elongated (Figure 4). An impeller mechanism is mounted in the pipe 14 for transporting powdery material along the pipe 14 from an inlet 16 at one end of the pipe 14 to an outlet 18 at the other end of the pipe 14, and for simultaneously mixing together the powdery materials as they are transported along the pipe 14. In this example, the impeller mechanism is provided by a shaft 20 which is rotatably mounted in the pipe 14, being longitudinally aligned therewith. A series of radially extending vanes 22 is mounted on the shaft 20, the series of vanes 22 extending along the length of the shaft 20 (Figure 4). Although not shown clearly on the drawings, each vane 22 has a radially extending impelling surface which is at an angle to the lengthwise direction of the shaft 20, so that rotation of the shaft 20 results in propeller-fashion movement of the material along the pipe 14. The inlet 16 of the pipe 14 is upwardly open, to permit flow of mealie meal and vitamin powder into the pipe 14 under gravity, while the outlet 18 is downwardly open for the discharge of a resultant mixture from the pipe 14. The apparatus 10 further includes a main feeding arrangement 24 (Figures 2 and 3) for feeding mealie meal in discrete batches into the pipe 14 through its inlet 16. The main feeding arrangement 24 includes a foodstuff hopper 26 for holding mealie meal in bulk, the hopper 26 having a rotary valve in the form of a star valve or star feeder 28 mounted in an outlet 30 at the bottom of the hopper 26.

In conventional fashion, the star feeder 28 is mounted for rotation about an operatively horizontal axis of rotation 32, the feeder 28 having a circumferentially extending series of radially outwardly open compartments 34. Thus, operative rotation of the star feeder 28 about its axis 32 results in the compartments 34 being successively brought into communication with the interior of the foodstuff hopper 26, thus filling with mealie meal, the compartments 34 thereafter being successively brought into communication with the inlet 16 of the pipe 14, so that the compartments 34 successively empty or discharge their contents into the pipe 14.

The apparatus 10 further includes a particulate material feed device 36 which provides a supplement feeding arrangement for feeding vitamin powder to the pipe 14. As can best be seen in Figures 5 - 9, the supplement feeding arrangement 36 includes a supplement hopper 38 having a hopper chamber 40 for holding vitamin powder in bulk. The supplement feeding arrangement 36 further includes a rotary feed member 42 connected in-line between the mixing chamber 12 provided by the pipe 14 and the hopper chamber 40, for feeding discrete batches of vitamin powder to the inlet 16 of the pipe 14. The supplement hopper 28 has a circular-cylindrical sleeve or wall 44 which extends vertically, the hopper chamber 40 being bordered by an upper part of the interior of the cylindrical wall 44. The hopper chamber 40 is bordered on a lower side thereof by a floor member in the form of a floor plate 46 which extends horizontally.

The floor plate 46 is complementary in outline to the peripheral wall 44 of the hopper chamber 40, being peripherally connected to the wall 44. The floor plate 46 has two openings 48 therethrough, said openings 48 being located on a radially outer periphery of the floor plate 46, against the wall 44, and being diametrically opposed. A secondary agitator 50 is mounted on the floor plate 46, immediately above the floor plate 46, for rotation in the direction of arrow 52 about an axis of rotation 54 which is coaxial with the longitudinal or polar axis of the cylindrical wall 44. The secondary agitator 50 extends more or less radially, being swept backwards in a circumferential direction relative to the direction of rotation 52. Thus, operative rotation of the secondary agitator 50 about its axis 54 in the direction of arrow 52 pushes vitamin powder radially outwardly towards the openings 48, so that the vitamin powder in the hopper chamber 40 falls through the openings 48 under gravity.

The supplement feeding arrangement 36 further includes a cover member in the form of a cover plate 56 which is parallel to and axially spaced below the floor plate 46, so that an ante-chamber 58 is formed between the cover plate 56 and the floor plate 46, the ante-chamber 58 being bordered peripherally by the cylindrical wall 44.

As can best be seen in Figure 5 of the drawings, the feeding arrangement also includes a base member in the form of a circular base plate 60 which is parallel to and axially spaced below the cover plate 56, a stationary housing in the form housing plate 62 being sandwiched between the base plate 60 and the cover plate 56. The housing plate 62 has an axially extending circular-cylindrical mounting opening or cavity 64 therethrough, in which cavity 64 the feed member 42 is rotatably mounted. The feed member 42, which is generally circular-cylindrical in shape, is thus mounted in the complementary mounting cavity 64 such that a radially outer cylindrical surface of the feed member 42 is spaced by no more than a radial working clearance from a radially inwardly directed peripheral wall of the cavity 64. The feed member 42 is bordered on its upper and lower end faces by the cover plate 56 and the base plate 60 respectively with no more than a working clearance, preferably being in sliding frictional abutment.

As can be seen in Figures 5 and 8, the cover plate 56 has a delivery opening 66 therethrough, the delivery opening 66 being located adjacent the centre of the cover plate 56, but off-set to one side thereof. A generally star-shaped primary agitator 68 is mounted immediately above the cover plate 56 for rotation about a common axis of rotation 54, thus rotating in a plane superjacent the cover plate 56. The primary agitator 68 has a main blade 70 which extends generally radially outwardly into close spacing from the peripheral wall 44, the main blade 70 being curved, sweeping forward in a circumferential direction in the direction of arrow 52. Operative rotation of the primary agitator 68 about the axis 54 in the direction of arrow 52 thus draws vitamin powder supported on the cover plate 56 radially inwardly towards the delivery opening 66.

The base plate 60 has a feed opening 72 (shown only in broken lines in Figure 9) which is located adjacent the centre of the base plate 60, being off-set to one side of the centre of the base plate 60, out of register with the delivery opening 66 of the cover plate 56. The feed member 42 is circular in outline, having a circumferentially extending series of eight cylindrical feed chambers 74 which respectively extend axially through the feed member 42. The shape and positioning of the feed chambers 74, on the one hand, and the shape and positioning of the delivery opening 66 in the cover plate 56 and the feed opening 72 in the base plate 60, on the other hand, are respectively such that rotation of the feed member 42 successively brings the feed chambers 74 into register with the delivery opening 66 and successively brings the feed chambers 74 into register with the feed opening 72 in the base plate 60.

The feed opening 72 in the base plate 60 is in gravity flow communication with a chute or slide 76 (Figure 1) which connects the supplement feeding arrangement 36 with the inlet 16 of the pipe 14 for gravity flow of vitamin powder from the feed opening 72 to the mixing chamber 12, via the chute 76.

Each feed chamber 74 is in the form of a slot or channel which extends axially along a radially outer periphery of the feed member 42. Each chamber 74 is thus partly bordered by peripheral walls provided by the feed member 42 and is partly bordered by a registering part of the radially inwardly directed wall of the mounting cavity 64 in the housing plate 62. During rotation of the feed member 42, vitamin powder in the respective chambers 74 is supported on the base plate 60, until the chambers 74 are successively brought into register with the feed outlet 72.

The supplement feeding arrangement 36 includes a feed chamber discharging arrangement in the form of a striking or tapping mechanism 78 (Figure 9) for promoting emptying of the feed chambers 74 and inhibiting bridging of material in the feed chambers 74. which comprises a tapper or strike member 80 which is mounted on a frame of the apparatus 10 for reciprocating pivotal displacement about a vertical pivot axis .82, so that a head 84 of the strike member 80 moves radially inwardly and outwardly in reciprocating fashion towards and away from the radially outwardly directed periphery of the feed member 42. Movement of the strike member 80 is synchronised with rotation of the feed member 42, such that the head 84 of the strike member 80 strikes or taps against the feed member 42 every time a feed chamber 74 is brought into register with the feed opening 72. As can be seen in Figure 9, the tapper head 84 moves along a radially extending passage 86 provided therefor in the housing plate 62.

Although omitted from Figure 5 of the drawings for ease of illustration, the primary agitator 68, the secondary agitator 50, and the feed member 42 are mounted on a common vertically extending shaft 88 (Figure 1) for synchronised rotation about the axis of rotation 54. This common shaft 88 is connected to a drive mechanism in the form of an electric motor 90 which is also connected by a mechanical linkage (not shown) to the tapping mechanism 78 for synchronised movement of the strike member 80. A similar electric motor 92 is connected to the star feeder 28.

The motors 90, 92 form part of a control system which permits adjustment of the speeds of rotation of the feed member 42 and the star feeder. A user can thus select the rates of feeding of the mealie meal and the vitamin supplement to the mixing chamber 12, so that the ratio of vitamin powder to mealie meal in the resultant mixture can be controlled by controlling the respective speeds of rotation of the star feeder 28 and the feed member 42. In use, mealie meal in the foodstuff hopper 26 is fed to the inlet 16 of the pipe 14 by rotation of the star feeder 28. The compartments 34 of the star feeder 28 are successively brought into communication with the interior of the foodstuff hopper 26, successively filling with mealie meal, and the compartments 34 are successively rotated to open downwardly, emptying the mealie meal contained therein into the mixing chamber 12 provided by the pipe 14. Mealie meal is thus fed into the mixing chamber 12 in discrete batches at a predetermined, controllable rate. At the same time, vitamin powder is fed from the foodstuff hopper 26 to the inlet 16 of the pipe 14 in discrete batches or packets at a controllable predetermined rate, by rotation of the feed member 42.

Rotation of the secondary agitator 50 about the axis of rotation 54 ensures that vitamin powder in the supplement hopper chamber 40 falls through the openings 48 in the floor plate 46. It will be appreciated that the fine particulate vitamin powder is prone to bridging, inhibiting the flow of powder through the openings 48, 66. The operation of the agitators 50, 68 combats such bridging and promotes controlled flow of vitamin powder through the openings 48, 66.

Vitamin powder that falls through the openings 66 lands on the cover plate 56 near the radially outer periphery of the cover plate 56, and is drawn radially inwardly towards the delivery opening 66 by operation of the curved main blade 70 of the primary agitator 68. The feed member 42 is continuously rotated, the feed chambers 74 being successively brought into register with the delivery opening 66, so that the feed chambers 74 successively fill with vitamin powder which falls through the delivery opening 66 and into the respective chambers 74.

The filled feed chambers 74 are successively brought into register with the feed opening 72 in the base plate 60, so that vitamin powder in the respective feed chambers 74 is successively emptied or discharged through the feed opening 72 along the chute 76 and into the inlet 16 of the mixing chamber 12. Proper successive discharge of the respective feed chambers 74 is promoted by operation of the tapping mechanism 78. As each feed chamber 74 is brought into register with the feed opening 72 by rotation of the feed member 42, the strike member 80 delivers a tap or strike to the feed member 42 adjacent said feed chamber 74. This tap serves to destabilize and thus dislodge vitamin powder from the feed chamber 74 by hindering or inhibiting bridging of vitamin powder in the feed chamber 74.

Mealie meal and vitamin powder are thus delivered to the mixing chamber 12 in a desired ratio per volume, the mealie meal and vitamin powder being mixed by propeller-fashion transportation thereof along the pipe 14 because of rotation of the vaned shaft 20. A resultant foodstuff mixture is discharged from the outlet 18 of the pipe 14. To alter the ratio of the respective materials in the mixture, the speeds of rotation of the feed member 42 and the star feeder 28 can be varied by use of the control system.

It is an advantage of the apparatus 10 as described with reference to the drawings that it permits the mixing together of fine particulate materials, especially powdery materials in a reliable and controllable ratio. Difficulties presented by bridging or resistance to flow of particularly vitamin powder are ameliorated by the supplement feeding arrangement 36, which is configured specifically to promote proper flow of vitamin powder therethrough.

Claims

CLAIMS:

1. A mixing apparatus for mixing particulate materials in a desired ratio, which apparatus includes: a mixing chamber for mixing together a main particulate material and a particulate supplement material; a main feeding arrangement for feeding the main particulate material to the mixing chamber at an adjustable selected rate; a supplement feeding arrangement for feeding the particulate supplement material to the mixing chamber at an adjustable selected rate, the supplement feeding arrangement including a feed outlet which is in communication with the mixing chamber for transportation of the particulate supplement material to the mixing chamber, the supplement feeding arrangement further including a rotary feed member which is mounted for rotation about an axis of rotation, the rotary feed member having a plurality of feed chambers such that operative rotation of the feed member successively brings the feed chambers into register with the feed outlet for successive discharge of particulate supplement material from the respective feed chambers into the mixing chamber via the feed outlet.

2. A mixing apparatus as claimed in claim 1 , in which the feed chambers are angularly spaced about the axis of rotation, each feed chamber extending axially through the feed member.

3. A mixing apparatus as claimed in claim 2, in which each feed chamber is an axially extending channel in a radially outer cylindrical surface of the feed member, each feed chamber thus being open in a radially outward direction, the rotary feed member being located in a complementary cylindrical cavity in a stationary housing, such that there is no more than a radial working clearance between the radially outer surface of the feed member and a peripheral wall of the complementary cavity.

4. A mixing apparatus as claimed in claim 2 or claim 3, in which the axis of rotation of the feed member extends operatively upwardly, the feed member being located superjacent the feed outlet, so that discharge of particulate supplement material from the respective feed chambers into the feed outlet, when the feed chambers are successively brought into register with the feed outlet, is by gravity flow.

5. A mixing apparatus as claimed in claim 4, in which the feed outlet is provided in a stationary base member, the feed member being mounted above the base member and being in frictional abutment therewith.

6. A mixing apparatus as claimed in claim 4 or claim 5, in which the supplement feeding arrangement includes a feed chamber discharging arrangement for inhibiting bridging of particulate supplement material in the respective feed chambers when the feed chambers are brought into register with the feed outlet.

7. A mixing apparatus as claimed in claim 6, in which the feed chamber discharging arrangement comprises a synchronised tapping mechanism which is arranged successively to tap the feed member as the respective feed chambers are brought into register with the feed outlet.

8. A mixing apparatus as claimed in claim 7, in which the tapping mechanism includes a strike member mounted for reciprocating movement relative to the feed member, repeatedly to strike the feed member adjacent the feed outlet.

9. A mixing apparatus as claimed in claim 8, in which the strike member is mounted for reciprocating pivotal displacement about a pivot axis which is more or less parallel to the axis of rotation of the feed member.

10. A mixing apparatus as claimed in any one of claims 4 to 9 inclusive, in which the supplement feeding arrangement includes a supplement hopper which has a hopper chamber for housing particulate supplement material, the hopper chamber being located above the rotary feed member for gravity feed of particulate supplement material to the feed member, the supplement feeding arrangement further including a delivery mechanism for delivering particulate supplement material from the hopper chamber to the feed member such that the feed member is not directly exposed to the weight of particulate supplement material in the hopper chamber.

11. A mixing apparatus as claimed in claim 10, in which the delivery mechanism includes a cover member superjacent the feed member, to cover upper ends of some of the feed chambers of the feed member and to support particulate supplement material thereon, the cover member having a delivery opening therethrough such that, upon rotation of the feed member, the feed chambers are successively brought into register with the delivery opening, to permit successive filling of the feed chambers with particulate supplement material resting on the cover member.

12. A mixing apparatus as claimed in claim 11 , in which the delivery mechanism includes a primary agitator for agitating particulate supplement material supported on the cover member, to promote movement of supplement material through the delivery opening in the cover member into the respective feed chambers under gravity.

13. A mixing apparatus as claimed in claim 12, in which the primary agitator is mounted for rotation about a rotational axis co-axial with the axis of rotation of the feed member, the primary agitator extending more or less radially for rotation in a plane superjacent the cover member.

14. A mixing apparatus as claimed in claim 13, in which the primary agitator is shaped and arranged for displacing particulate supplement material supported on the cover member towards the delivery opening in response to rotation of the primary agitator.

15. A mixing apparatus as claimed in any one of claims 11 to 14 inclusive, in which the delivery mechanism includes a floor member which provides a floor of the hopper chamber, the floor member being spaced above the cover member, so that an ante-chamber is defined between the cover member and the floor member, spacing particulate supplement material in the hopper chamber from the cover member, the floor member having at least one discharge opening therethrough for permitting the passage of particulate supplement material into the ante-chamber under gravity.

16. A mixing apparatus as claimed in claim 15, in which the delivery mechanism includes a secondary agitator for agitating particulate supplement material in the hopper chamber to promote passage of particulate supplement material in the hopper chamber through each discharge opening in the floor member into the antechamber.

17. A mixing apparatus as claimed in claim 16, in which the secondary agitator is mounted for rotation about a rotational axis co-axial with the axis of rotation of the feed member, the secondary agitator extending more or less radially for rotation in a plane superjacent the floor member and being shaped and arranged for displacing particulate supplement material supported on the floor member towards the discharge opening in the floor member in response to rotation of the secondary agitator. .

18. A mixing apparatus as claimed in any one of claims 15 to 17 inclusive, in which the delivery opening in the cover member is radially and/or circumferentially spaced from each discharge opening in the floor member.

19. A mixing apparatus as claimed in any one of the preceding claims, in which the main feeding arrangement comprises a main hopper for holding main particulate material, the main feeding arrangement including a rotary valve adjacent an outlet of the main hopper for delivering discrete batches of main particulate material to the mixing chamber.

20. A mixing apparatus as claimed in claim 19, in which the rotary valve is a star feeder which is mounted in the outlet of the main hopper at or adjacent a lower end thereof, the star feeder being rotatable about an operatively more or less horizontally extending axis.

21. A mixing apparatus as claimed in claim 19 or claim 20, which includes a control system for controlling the speed of rotation of the feed member and the rotary valve respectively, permitting a user to determine the ratio of particulate supplement material to main particulate material in the resultant mixture by operation of the control system.

22. A mixing apparatus as claimed in any one of the preceding claims, in which the mixing chamber is an elongated conduit which has an impelling mechanism for transporting particulate material along the conduit and for mixing together main particulate material and particulate supplement material while it is transported along the conduit.

23. A feed device for feeding a fine particulate material at an adjustable selected rate, which device includes: a feed outlet for the delivery of particulate material from the feeding device; a rotary feed member mounted superjacent the feed outlet for rotation about an axis of rotation to feed particulate material to the feed outlet in discrete batches; and a particulate material holder for holding particulate material, and for feeding the particulate material to the rotary feed member,. the feed member being provided with a series of angularly spaced feed chambers for receiving particulate material from the holder, each feed chamber extending through the rotary feed member in an axial direction, such that operative rotation of the feed member about its axis of rotation successively brings the feed chambers into register with the feed outlet for successive discharge of particulate material from the respective feed chambers through the feed outlet.

24. A feed device as claimed in claim 23, in which each feed chamber is an axially extending channel in a radially outer cylindrical surface of the feed member, each feed chamber thus being open in a radially outward direction, the rotary feed member being located in a complementary cylindrical cavity in a stationary housing, such that there is no more than a radial working clearance between the radially outer surface of the feed member and a peripheral wall of the complementary cavity.

25. A feed device as claimed in claim 23 or claim 24, in which the feed device includes a feed chamber discharging arrangement for inhibiting bridging of particulate material in the respective feed chambers when the feed chambers are brought into register with the feed outlet.

26. A feed device as claimed in claim 25, in which the feed chamber discharging arrangement comprises a synchronised tapping mechanism which is arranged successively to tap the feed member as the respective feed chambers are brought into register with the feed outlet.

27. A feed device as claimed in any one of claims 23 to 26 inclusive, which includes a cover member superjacent the feed member, to cover upper ends of some of the feed chambers of the feed member and to support particulate material thereon, the cover member having a. delivery opening therethrough such that, upon rotation of the feed member, the feed chambers are successively brought into register with the delivery opening, to permit successive filling of the feed chambers with particulate material resting on the cover member.

28. A feed device as claimed in claim 27, which includes a primary agitator for agitating particulate material supported on the cover member, to promote movement of supplement material through the delivery opening in the cover member into the respective feed chambers under gravity.

29. A feed device as claimed in claim 28, which includes a floor member in the holder to separate an interior of the holder into a hopper chamber and an ante-chamber, the floor member being spaced above the cover member to provide a floor of the hopper chamber, so that an ante-chamber is defined between the cover member and the floor member, spacing particulate material in the hopper chamber from the cover member, the floor member having at least one discharge opening therethrough for permitting the passage of particulate material into the ante-chamber under gravity.

30. A feed device as claimed in claim 29, which includes a secondary agitator for agitating particulate material in the hopper chamber to promote passage of particulate material in the hopper chamber through each discharge opening in the floor member into the ante-chamber.

31. A feed device as claimed in claim 30, in which the feed member, the primary agitator, and the secondary agitator are mounted for rotation about a common rotational axis.