A DRUM AND AN APPARATUS FOR THE SURFACE PROCESSING OF ROCK OR MOSAIC PIECES THROUGH ROTATION

FIELD OF THE INVENTION

The present invention is enclosed in the area of rock or mosaic processing, in particular the processing of rocks such as limestone, slate, marble, granite or kyanite, in pieces, to provide a smoothening or ultimately a change of shape of such pieces of rock or mosaic through the tumbling of such pieces of rock or mosaic inside a rotating drum. From such procedure may result rocks with a pebble-like look.

PRIOR ART

Solutions exist in the art where the inside of a rock or mosaic pieces processing drum is entirely covered with pieces of a type of rock which is expected to be harder than the rock or mosaic to be processed. When rocks or mosaic to be processed are placed inside the drum, the machine rotates the drum and the tumbling of the pieces under processing on the referred covered walls of the drum provides for the smoothening of corners, and results, after an amount of time, in entirely smooth pieces of rock/mosaic. These pieces may be more or less irregular, depending on their initial form and desired final form, as well as on the time which they have been tumbled in the drum and speed of rotation of the drum. Within the context of the present invention, terms rock and stone are used interchangeably.

Additionally, an abrasive substance may be added to the inside of the drum, to provide an additional abrasion and thereby smoothening of the rocks or mosaic under processing. Such is the case of patent application with publication number US5586925 A.

Yet, such solutions have two main issues: consumption of time/energy and low durability. Drums and machines following such methodology are considerably time consuming, which also results in a considerable amount of energy, required to tumble an overall mass of rocks (in case of rock processing) which may reach 11 typically during 6-10 h, to obtain a smooth pebble-like piece of rock.

On the other hand, and even though the rocks covering the inside of the tumbler are harder than those being processed, still a high abrasion occurs on such covering rocks, in due course leading to the loss of all or at least parts of the abrasion surface. Such loss increases the need for maintenance, in order to again provide a surface covered with the harder rocks.

The present solution innovatively overcomes such issues through a drum and apparatus comprising such drum which are simple and yet highly effective.

SUMMARY OF THE INVENTION

It is an object of the present invention a drum for the surface processing of rock or mosaic pieces through rotation which comprises:

- one or more longitudinal inner surfaces forming a tube and aligned with a rotation axis of the drum, and

- a plurality of plates, the plates: being adjacently provided on and connected to the one or more longitudinal inner surfaces, and having a surface with a hardness of at least 300 Brinell, each plate being so provided that such surface faces the interior of the drum, wherein each two adjacently provided plates are apart by a predefined distance in respective sides of the plates which are substantially aligned with the rotation axis of the drum, the predefined distance being substantially constant between two plates.

By comprising hard plates which are adjacently provided and yet apart by a predefined distance, the drum of the present invention provides that, upon rotation and thereby tumbling of rock or mosaic pieces provided inside the drum, a further abrasion is provided on the rock or mosaic pieces, not only by means of the plate having a hardness of at least 300 Brinell but also through the separation between plates, which creates a further element of tumbling and abrasion. Thus, the longitudinal inner surface of the drum does not need a full coverage as such not covered areas - formed by the separation between plates - provide for a higher efficiency. The hardness of the plates of the present invention (be it of 300 Brinell, 400 Brinell or higher) is a hardness as measured through EN ISO 6506-1:2005.

Thus, independently of the relevant parameters of the pieces of rock - such as hardness, initial form, desired final form - the solution of the present invention results in a decrease in the time spent for a smoothening process of 70-90 %, for a same rotating speed. The predefined distance is advantageously the same for every pair of adjacently provided plates.

It is also an object of the present invention an apparatus for the surface processing of rock or mosaic pieces through rotation which comprises the drum of the present invention, in any of its embodiments, and means for rotating the drum. Advantageously, the apparatus comprises control means configured to control the means for rotating the drum and thereby control the rotation of the drum, the control means being configured to provide the rotation of the drum with the adaptation of at least one operational parameter of the apparatus based on at least one physical property of the rock or mosaic pieces to be processed. Such solution allows to define programs for the processing of each type of rock (with a standard hardness), dependent of an initial form (e.g. round, elliptical, cubic, irregular) and desired final form (e.g. round, elliptical, cubic, irregular, depending of the initial form), thereby obtaining a rotation speed of the drum and/or the time of continuous rotation.

It is yet an object of the present invention a method for processing the surface of a plurality of rock or mosaic pieces which comprises the steps of:

- providing a plurality of rock or mosaic pieces inside the drum of the apparatus of the present invention, in any of its embodiments, and

- rotating the apparatus for an amount of time.

The rock pieces comprise may comprise limestone, slate, marble, granite or kyanite pieces.

DESCRIPTION OF FIGURES

Figure 1 - representation of an embodiment of the drum (1) of the present invention, in cross-section. In such case, the drum has a longitudinal inner surface (2) with a cylindrical shape, the cross-section thereby being circular. In the representation, also the plates (3) are presented apart by a predefined distance (d). Every two plates are apart in the same predefined distance (d).

Figure 2 - detailed representation of an embodiment of the plate (3) of the drum (1) of the present invention, in which case the plate is bent and formed by two bent sheets: a first sheet (31) and a second sheet (32). The first sheet has a hardness of at least 300 Brinell and is provided the surface with a hardness of at least 300 Brinell faces the interior of the drum. The bending allows for a better fitting to a cylindrical longitudinal inner surface (2). Figure 3 - representation of the drum of the present invention, making explicit the length (I) of the longitudinal inner surface (2).

DETAILED DESCRIPTION

The more general configurations of the present invention are described in the Summary of the invention. Such configurations are detailed below in accordance with other advantageous and/or preferred embodiments of implementation of the present invention.

In an aspect of the drum of the present invention, each plate is a bent plate, the bent being provided in a direction of the plate which is substantially aligned with the rotation axis of the drum, and substantially centred. Such allows for a better adaptation to non-planar sections, such as corners or rounded sections.

Preferably, each plate has a substantially rectangular shape. Such allows for an easiness of construction, in which rectangular plates are provided side by side (with the referred predefined distance / separation) and thereby cover the longitudinal inner surface of the drum.

Advantageously, each of the referred plates extends along a whole longitudinal section of the longitudinal inner surface. Such solution also provides an easiness of construction since a single plate extends through the whole length of the longitudinal inner surface of the drum.

The tubular longitudinal inner surface of the drum may have a cylindrical or polyhedric form. A cylindrical form results in a single tubular longitudinal inner surface with a circular cross-section. A polyhedric form results in a plurality of longitudinal inner surfaces forming a tube, the cross-section thereby being polygonal. When the form is polyhedric, the inner surface preferably forms a pentagonal, hexagonal, or higher order prism, the cross-section thereby being a pentagon or a hexagon or a higher order polygon.

Preferably, the referred surface with a hardness of at least 300 Brinell is a roughened surface. Rough meaning that such surface is rugged or, in other words, comprising irregular projections. It therefore provides an enhanced abrasion of the pieces of rock under process.

Several advantageous aspects of the plates of the drum are subsequently described.

In an embodiment, each plate comprises a first and a second sheet, the first sheet having the referred surface with a hardness of at least 300 Brinell and the second sheet being of a material suitable to weld the first sheet to the one or more longitudinal inner surfaces of the drum. It provides an enhanced connection between each plate and the longitudinal inner surface of the drum.

In an embodiment, the first sheet is metallic, having a hardness of at least 300 Brinell.

In an embodiment, the surface of each plate has a hardness of at least 400 Brinell, more preferably at least 500 Brinell, even more preferably at least 600 Brinell, at least 700 Brinell or at least 800 Brinell, in all cases determined according to EN ISO 6506.

In a specific embodiment, the first sheet is obtained by welding with tubular wire according to DIN 8555 together with metallic powder. ln an even more specific embodiment, the first sheet comprises overlapping weld beads obtained such that form of cracks during cooling. Preferably, the cracks are perpendicular to the surface of the first sheet.

In an embodiment, the second sheet comprises steel. More preferably the second sheet is made of an S235, S275 or S355 steel according to EN 10025, preferably S235.

In an embodiment, the predefined distance is 5-50 mm, preferably 20-40 mm, more preferably of 25 mm. Such is associated with the typical size of pieces of rock to be tumbled / processed.

In another embodiment, each longitudinal inner surface has a length of 1,000-3,000 mm, preferably 2,000-4,000 mm, more preferably of 2,000, 2,500, 3,000 or 4,000 mm.

In an embodiment, the plates are rectangular, having a length equal to the length of the longitudinal inner surface and a width of 225-325 mm, preferably 250- 300 mm, more preferably 275 mm.

Several embodiments of the apparatus of the present invention are subsequently described.

As previously referred, the apparatus comprises control means configured to control the means for rotating the drum and thereby control the rotation of the drum, the control means being configured to provide the rotation of the drum with the adaptation of at least one operational parameter of the apparatus based on at least one physical property of the rock or mosaic pieces to be processed. In an inventive aspect, the physical parameter comprises an average diameter of rocks prior to processing, a desired average diameter of rocks after processing, the form of rocks prior to processing, the desired form of rocks after processing and/or the average hardness of rocks to be processed.

In another inventive aspect, the operational parameter comprises the rotation speed of the drum and/or the time of continuous rotation.

In an embodiment, the apparatus is configured to provide a rotation speed of at least 5 rotations per minute (rpm), preferably from 10-20 rpm, more preferably of 10 or 15 rpm.

In an inventive aspect, the apparatus is configured to, in a continuous rotation of a plurality of rock or mosaic pieces, have two or more rotation speeds. Such allows to work with a lower rotation speed in a first stage of the processing / tumbling, when the pieces of rock are of higher dimension and more irregular, and a higher rotation speed in a second stage of the processing / tumbling, when the pieces of rock have been already abrased and are of lower dimension and more regular. Such procedure may be repeated, creating several different stages with several different rotation speeds and respective periods of time of duration. In an inventive aspect, is configured to, in a continuous rotation of a plurality of rock or mosaic pieces, change the rotation speed from a first rotation speed to a second rotation speed, thereby having to or more rotation speeds.

As will be clear to one skilled in the art, the present invention should not be limited to the embodiments described herein, and a number of changes are possible which remain within the scope of the present invention.

Of course, the preferred embodiments shown above are combinable, in the different possible forms, being herein avoided the repetition all such combinations.