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(11) | EP 2 591 849 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Mixing apparatus |
| (57) A microsphere mixing apparatus that comprises a container (1) provided with a removable
cover (2), inside said container (1) a mixing chamber (C) is defined intended for
receiving internally said microspheres and a watery suspension of a powder material
to be treated, inside said chamber (C) a stirring device (5) is arranged that is rotated
by a motor (3) through a motor shaft (4), said stirring device (5) comprising a plurality
of stirring elements (6) arranged radially with respect to said motor shaft (4), with
a substantially constant angular pitch.
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[0001] The present invention relates to a mixing apparatus of the so-called microsphere mill type, i.e. an apparatus for homogenising powder materials such as, for example, silk-screen printing glazes and pastes for the ceramic industry, and reducing the granulometry thereof.
[0002] Microsphere mills known from the state of the art comprise a tank containing a powder material to be homogenised, in a water suspension, together with microspheres in a material with elevated hardness, such as, for example, alumina, or vitreous material. Under the tank a homogenising chamber is provided, in which the microspheres and the material to be homogenised are rotated by an impeller consisting of a ring to which stirring elements are fixed peripherally. By driving the impeller an interaction is obtained between the powder material and the microspheres that causes a homogenisation and a reduction in the granulometry of the material. Nevertheless, in known microsphere mills, the granulometry of the material is reduced very slowly inasmuch because only a fraction of the powder material interacts with the microspheres, which requires very long treatment time if said granulometry has to be reduced significantly. Further, the capacity of the homogenising chamber is much less than the capacity of the tank, so that numerous treatment cycles are required to be able to homogenise all the material contained in the tank, which requires a significantly long time to be able to homogenise all the material contained in the tank.
[0003] An object of the present invention is to provide a microsphere mixing apparatus that enables not only good homogenisation of the material treated therein but also a significant rapid reduction of the granulometry of said material and a significant reduction of the total treatment time of all the material loaded into the mixing apparatus. The object of the present invention is achieved with a mixing apparatus according to claim 1.
[0004] Owing to the invention, is possible to obtain effective homogenisation of the treated material and significant reduction of the granulometry thereof in a short time. Further, the apparatus according to the invention is easy to make and extremely reliable.
[0005] An embodiment of the invention is illustrated, purely by way of non-limiting example, in the three tables of drawings attached, in which:
Figure 1 is a raised sectioned view of the mixing apparatus according to the invention;
Figure 2 from the right of Figure 1;
Figure 3 is the section III-III of Figure 1.
[0006] With reference to the figures, the microsphere mixing apparatus according to the invention comprises a container 1 inside which a treatment chamber C is defined, in which homogenisation and reduction of the granulometry of the powder material to be treated is made, for example a ceramic glaze, or a silk-screen printing paste.
[0007] Both the microspheres and a water suspension of the powder material to be treated are delivered to the chamber C.
[0008] The internal surface of the chamber C is provided with a coating made of wear and contamination resistant material, to prevent the surface of the chamber C being able to be damaged by the microspheres and being able to contaminate the material subjected to treatment.
[0009] The container 1 is provided with a cover 2, suitable for coupling with the container 1 in such a manner as to make a sealed closure thereof. To the cover 2 a motor 3 is fixed, for example an electric motor, that drives, through a motor shaft 4, a stirring device 5, consisting of a hub M, fixed to the motor shaft 4, and of a plurality of stirring elements 6, which are fixed to the hub M and extend radially therefrom. The stirring elements 6 can each be blade-shaped, for example rectangular, and are arranged around the hub M with a substantially constant angular pitch. In the figures a stirring device 5 is shown that is provided with three stirring elements 6 arranged at an angular pitch of about 120°. It is intended that the number of stirring elements 6 can be more or less than 3, without thereby falling outside the scope of the present invention.
[0010] The stirring elements 6 are provided, on at least on face, with a coating 14 of wear-resistant material.
[0011] The container 1 is provided with an interspace 15 in which a cooling liquid can be circulated that is supplied by a cooling device 13, to eliminate the heat generated during treatment of the material in the chamber C of the container 1. The cooling device 13 is hydraulically connected to the interspace 15.
[0012] The mixing apparatus according to the invention can be provided with a lifting/lowering device 16 for lifting/lowering the cover 2 of the container 1, to automate opening and closing of the container 1.
[0013] The lifting/lowering device 16 comprises a substantially horizontal arm 8 fixed to a first end 7a, to a slide 9 moved along a vertical guide 11 by a second motor 10.
[0014] To a second end 7b of the arm 8, opposite said first end 7a, a pair of rods 17 is fixed, that extend vertically downwards. The lower end 18 of each rod 17 is made in such a manner as to couple with hooking elements (that are not shown) provided on the cover 2, in such a manner as to hook therewith. In order to open the container 1, it is sufficient to lower the arm 8 by means of the slide 9, until the ends 18 of the rods 17 hook the coupling elements of the cover 2. After the rods 17 have hooked the cover 2, lifting the arm 8 the cover 2 is also lifted, thus making the chamber C of the container 1 accessible.
[0015] In order to reclose the container 1, the arm 8 are lowered until the cover 2 rests on the upper edge of the container 1 and the rods 17 are released from the cover 2.
[0016] The container 1 is provided with seal closing elements to lock the cover 2 in a closed position, after the cover 2 has been rested on the edge of the container 1.
[0017] Obviously, when the cover 2 has to be raised, seal closing elements have to be released beforehand.
[0018] In the lower part of the container 1 an opening 22 is provided, communicating with the chamber C and with the environment outside the container 1, provided with a closing element 23. Through the opening 22 the chamber C can be emptied at the end of treatment of the material, removing the closing element 23. The chamber C can also be emptied by a pump, which is not shown, connected to the opening 22. In this case the closing element 23 is not present and with the opening 22 a filter is associated to retain the microspheres during emptying of the chamber C.
[0019] All the components of the apparatus 1 according to the invention can be arranged inside a protection structure 19 provided with a platform 12 to which the components of the apparatus according to the invention can be fixed and with a safety cage 20, provided with an access door 21 with an automatic safety lock, which automatically locks the access door 21 in a closed position when the mixing apparatus is operating. The safety cage 19 prevents an operator being able to access the mixing apparatus according to the invention when the latter is operating.
[0020] The protection structure 19 can be provided with wheels 24 to enable the protection structure 19 to be easily moved.
[0021] The mixing apparatus according to the invention operates as follows:
- first, the microspheres are delivered into the chamber C until a first level L1 is reached, for example equal to about a quarter of the height of the chamber C;
- then a watery suspension of the material to be treated is delivered until a second level L2 is reached, equal, for example, to about 3/4 of the height of the chamber C. The proportion of material to water in said suspension depends on the nature of the material to be treated;
- then the cover 2 is lowered, with the motor 3 and the stirring device 5, until the cover 2 rests on the container 1 and is fixed thereto;
- the motor 3 is then driven that rotates the stirring device 5, the blades 6 of which stir the water suspension vigorously that has been delivered to the tank and the microspheres, making the microspheres interact with the suspended material;
- lastly, when the desired degree of homogenisation and granulometry of the material has been reached, the watery suspension is discharged from the chamber C of the container 1.
[0022] It should be known that the radial arrangement of the blades 6 and the substantially rectangular shape thereof enables it to be obtained that the microspheres substantially interact with the entire mass of suspended material, unlike what happens in microsphere mills of known type, in which only a small part of the material interacts with the microspheres. This enables rapid homogenisation of the material and a rapid diminution of the granulometry thereof to be obtained, substantially reducing treatment time.
[0023] Further, unlike known microsphere mills, all the material delivered to the apparatus according to the invention is treated simultaneously, which further reduces treatment time. At the end of treatment of the material, after water suspension has been discharged, if necessary, the chamber C can be washed by a washing device (not shown).
1. Microsphere mixing apparatus comprising a container (1) provided with a removable
cover (2), inside said container (1) a treatment chamber being defined (C) intended
for receiving internally said microspheres and a watery suspension of a powder material
to be treated, inside said chamber (C) a stirring device (5) being arranged that is
rotated by a motor (3) through a motor shaft (4), said stirring device (5) comprising
a plurality of blade-shaped stirring elements (6) arranged radially with respect to
said motor shaft (4), with a substantially constant angular pitch, characterised in that each of said stirring elements (6) is provided, on at least one face, with a coating
(14) of wear-resistant material.
2. Mixing apparatus according to claim 1, wherein each of said stirring elements (6)
is fixed to a hub (M) connected to said motor shaft (4).
3. Mixing apparatus according to any preceding claim, wherein said motor (4) is fixed
to said cover (2).
4. Mixing apparatus according to any preceding claim, wherein an internal surface of
said chamber (C) is provided with a wear-resistant coating (22).
5. Mixing apparatus according to any preceding claim, wherein said container (1) is provided
with an interspace (15) inside which a cooling fluid can be circulated.
6. Mixing apparatus according to any preceding claim, wherein in the lower part of said
container (1) an opening (22) is provided, communicating with said chamber (C) and
with the environment outside the container (1), said opening (22) being provided with
a removable closing element (23).
7. Mixing apparatus according to any one of claims 1 to 5, wherein in the lower part
of said container (1) an opening (22) is provided, communicating with said chamber
(C) and with the environment outside the container (1), said opening (22) being provided
with a filter suitable for retaining said microspheres.
8. Mixing apparatus according to any preceding claim, characterised in that it comprises a lifting/lowering device (16) suitable for being connected to said
cover (2), to lift or lower said cover (2).
9. Mixing apparatus according to claim 8, wherein said lifting/lowering device (16) comprises
a substantially horizontal arm (8) fixed, at a first end (7a), to a slide (9) moved
along a vertical guide (11) by a second motor (10), to a second end (7b) of said arm
(8), opposite said first end (7a), a pair of rods (17) being fixed, that extend vertically
downwards, a lower end (18) of each rod (17) being made in such a manner as to couple
with hooking elements provided on said cover (2), in such a manner as to hook therewith.
10. Mixing apparatus according to any one of claims 5 to 9, further comprising a cooling
device (13) suitable for supplying said cooling fluid to said interspace (15), said
cooling device (13) being hydraulically connected to said interspace (15).
11. Mixing apparatus according to any preceding claim, further comprising a protection
structure (19) inside which said mixing apparatus is provided, said protection structure
(19) comprising a safety cage (20) provided with an access door (21) with an automatic
safety lock that is suitable for automatically locking said access door (21) in a
closed position when the mixing apparatus is operating.
12. Mixing apparatus according to claim 11, wherein said protection structure (19) is
provided with platform (12) that is suitable for supporting the components of said
mixing apparatus, said platform (12) being able to be provided with wheels (24).
13. Mixing apparatus according to any preceding claim, further comprising a washing device
for washing said chamber (C).