Technical Field

This invention concerns a magnetic mill designed to crush and mix materials by means of milling elements placed in a working chamber, said milling elements being moved by means of magnetic field.

Background Art

An electromagnetic mill known from US 4134557 patent specification comprises a cylindrical working chamber having electromagnets placed symmetrically on its circumference. Ferromagnetic crushing means as milling elements are placed inside the working chamber. These crushing means are rotated by alternating electromagnetic field. The rotational speed of the magnetic field, and by the same the speed with which milling elements are moved inside the working chamber, is regulated by changing the frequency of the magnetic field.

US 3869251 discloses a device for materials mixing in reaction vessels using ferromagnetic particles. This device comprises a coil creating variable electromagnetic field around a funnel into which a reaction vessel is introduced. The created alternating magnetic field moves ferromagnetic particles rotationally in order to intensively mix the material in its whole volume. Additional cyclic movements of the vessel caused by a driving unit comprising a connecting rod cause the greater complexity of the movement of ferromagnetic particles, and in effect the material is better mixed. From US3848363 patent specification there is also known a device intended for working objects having ferromagnetic elements driven by rotary magnetic field. This device comprises archwise windings, partially overlapping, powered by phase-shifted sources of electric current so that opposite electromagnets have opposite polarity. The created whirling electromagnetic field causes the whirling movement of ferromagnetic elements and their contact with workpieces.

From US4632315 patent specification a device for electromagnetic crushing and mixing is also known, said device comprising an annular working chamber with electromagnets placed opposite one to another on an outer and inner side of said ring. The greater variability of the magnetic field affecting ferromagnetic crushing elements is achieved by rotating an annular working chamber fastened rotatably in relation to fixed electromagnets.

Di sclosure o f Invent ion

A magnetic mill according to the invention has a cylindrical working chamber with ferromagnetic milling elements placed inside, and magnets placed in a body above an outer side surfaces of the cylindrical working chamber, said magnets being designed to create a magnetic field directed into the cylindrical working chamber interior. This solution is characterized in that between the magnets and an outer side surface of the cylindrical working chamber there is a rotatably embedded inner covering pipe rotated by means of a driving unit, said pipe being made of a material insulating the magnetic field. The inner covering pipe has on its circumference a longitudinal cut-outs directing the magnetic field inside the cylindrical working chamber. An additional covering pipe made of a material insulating the magnetic field, as well as having longitudinal cut-outs overlapping at least a part of longitudinal cut-outs made in the inner covering pipe, and is engaged with the inner covering pipe. Moreover, the additional covering pipe has an additional driving unit to move stepwise by an angle this additional covering pipe in relation to the inner covering pipe.

Advantageously, the inner covering pipe and additional covering pipe are driven by the same driving unit at the same time, whereas the additional covering pipe is driven by the driving unit through the inner covering pipe.

Advantageously, the inner covering pipe is supported rotatably on the cylindrical working chamber by means of bearings.

Advantageously, both covering pipes are made of the same magnetically insulating material. More advantageously, both covering pipes are made of different magnetically insulating materials .

Advantageously, the magnets are made as electromagnets with superconductive coils.

Advantageously, the magnets are made as permanent magnets, and more advantageously, they are made of neodymium.

Advantageously, the cylindrical working chamber has corrective inductors situated on its cylindrical surface.

When causing the rotary motion of the inner covering pipe made of a material insulating the magnetic field with cut-outs letting the magnetic field to path, an alternating magnetic field is created inside the working chamber, and consequently milling elements are accelerated what makes them collide with a material being ground. Moreover, achieving an alternating magnetic field variability in the working chamber by veiling and unveiling poles of magnets allows the magnetic field to be changed without causing losses related to magnetization and demagnetisation of electromagnets even when using very high currents. An additional protecting pipe made of a material insulating the magnetic field engaged with the inner protecting pipe allows to insulate the magnetic field better. However, the additional covering pipe engaging with additional driving unit allows, when it is needed, for quickly relative angular displacement of both covering pipes and to block immediately the magnetic field against penetrating into the working chamber.

The inductors placed on the outer surface of the cylindrical working chamber and connected with a sensor detecting a change in the magnetic field react when ferromagnetic milling elements are near the inner surface of the chamber, and as a result, they make it possible to initiate repulsive magnetic pulses to enable the protection of the working chamber against any damage.

An object of the invention is shown in its embodiment in a drawing, where;

Fig. 1 presents a magnetic mill in the side view with a local cut-out showing the interior of a cylindrical working chamber together with milling elements,

Fig. 2 presents the magnetic mill in the axial section, and Fig. 3 presents the main elements of the magnetic mill in an exploded view.

Description of Embodiments

A magnetic mill presented in its embodiment in Fig. 1 has its fixed body 1 shaped as a hexagonal prism having six magnets 2 placed on side walls 3. The suitable magnetic force has been achieved by using neodymium magnets. In an embodiment not shown in the drawing, as the magnets 2, the electromagnets having their superconductive coils chilled with liquid nitrogen have been used in order to create greater magnetic forces.

An immobile cylindrical working chamber 4 made of acid resistant austenitic steel X6CrNiTil8-10 according to DIN standard is fastened inside the body 1. Inside said chamber there are located cylindrical ferromagnetic milling elements 5. An inner covering pipe 6 made of magnetically insulating material (such as permalloy) comprising 80% Ni and 20% Fe is rotatably fixed between poles of the magnets 2 and an outer side surface of the cylindrical working chamber 4, said inner covering pipe 6 having on its circumference longitudinal cut-outs 7, throughout which the magnetic field from the poles of the magnets 2 is directed into the working chamber 4. The inner covering pipe 6 is engaged with an additional covering pipe 8 made of the same magnetically insulating material as the inner covering pipe 6 or of a material insulating the magnetic field, known as Mumetal, comprising 77% Ni, 16% Fe, 5% Cu, 2% Cr, and this pipe has longitudinal cut-outs 9 overlapping with the longitudinal cut ^¬ outs 7 made in the inner covering pipe 6. The inner covering pipe 6 is rotated by means of a driving unit 10. The inner covering pipe 6 is engaged with an additional covering pipe 8 in a position in which some of the longitudinal cut-outs 7, 9 of both pipes 6, 8 are located opposite each other, enabling directing the magnetic field into the cylindrical working chamber 4 interior.

The inner covering pipe 6 engaging with the additional covering pipe 8 enables them to be driven at the same direction by use of one drive unit 10. The inner covering pipe 6 engaging with the additional covering pipe 8 is made by a splined screw connection 11 made between these covering pipes 6, 8. Such the splined screw connection 11 when using an additional driving unit 12 makes it able to achieve the relative angular movement of the covering pipes 6, 8 in order to stop the magnetic field against getting inside the cylindrical working chamber 4.

The cylindrical working chamber 4 has corrective inductors 13 situated symmetrically on a circumference of its outer cylindrical surface, said corrective inductors 13 being connected with a sensor device (not shown in the drawing) sensing changes in the magnetic field. When a suitably high voltage is induced in any of the corrective inductors 13 because of a dangerously short distance between the ferromagnetic milling elements 5 and the inner surface of the cylindrical working chamber 4, the sensor device sensing changes in the magnetic field sends alternating electrical pulses to the chosen corrective inductors 13 in order to create a force pushing away a suitable group of ferromagnetic milling elements 5. Moreover the working chamber 4 is fastened on four supports 14. As it is shown in Fig. 2, the inner covering pipe 6 is moved by means of the driving unit 10 composed of an electric motor 15 and a belt gear 16. A driving wheel 17 of the belt gear 16 is fastened on the propeller shaft of the electric motor 15, and a driven wheel 18 is shaped on the outer surface of the inner covering pipe 6. The additional driving unit 12 comprises an electrical motor 19, a lead-screw 20 that is supported by means of bearings in a bracket 21 as well as a slider 22. In the slider 22 there is rotary fastened an outer ring 23 of an additional covering pipe 8, and thanks to such a connection and when the electrical motor 19 being started, the lead-screw 20 rotates, and covering pipes 6, 8 are moved axially and angularly one in relation to the other in order to close the path for a stream of the magnetic field directed into the cylindrical working chamber 4. On the outer surface of the working chamber 4 a rolling bearings 24 designed as a rotary support for the inner covering pipe 6 are fastened on both sides of the body 1.

As it is shown in Fig. 3, the slider 22 has a shaped cut-out 25 to be fastened with loose on the ring 23 of an additional covering pipe 8. Near a face of the inner covering pipe 6 there is shaped a driven wheel 18 of the belt-gear transmission 16, and between this wheel and the longitudinal cut-outs 7 there are made projections of a multi-pro ection screw connection 11, said projections being designed to co-operate with projections shaped on the inner surface of the additional covering pipe 8.