EP0313524A1

EP0313524A1 - Method of treatment for natural and artificial lapideous materials and the like by means of abrasives

Info

Publication number: EP0313524A1
Application number: EP88830387A
Authority: EP
Inventors: Gianfranco Bertoletti
Original assignee: TOFREN MACCHINE SpA
Current assignee: TOFREN MACCHINE SpA
Priority date: 1987-10-01
Filing date: 1988-09-22
Publication date: 1989-04-26
Also published as: IT8705230A0; IT1220078B; JPH01135461A

Abstract

A method of treatment for natural or artificial lapideous materials by using appliances subjected to elastic vibration and/or high frequency oscillation acting on incoherent abrasives in order to supply the abrasive material with a high dynamic percussive power to move, mix and compact it, in order to achieve its exchange on the relevant surface and to quickly discharge the removed material.

Description

The invention relates to a method of treatment for natural and artificial lapideous materials and the like, here under indicated by the term "materials" and comprising, for instance, marble, granite and other natural stones, agglomerates obtained with said materials and any kind of binding agents, concretes, plastic materials, etc.
The term "abrasives" indicates any kind of granulate and/or powder which, provided it is suitably controlled, is able to remove particles of the above mentioned materials. Said abrasives may be either loose or glued on a carrier to form a regularly shaped solid featuring the necessary mechanical strength. If the abrasive is loose it may also be bonded with a liquid containing a bonding medium like, for instance, water lime.
Loose abrasives act on materials by means of a moving metallic or ceramic tool like, for instance, a saw blade, a wire rope, a disk, etc.
If bonded in the form of a solid body abrasives exert their action by means of a rotary and/or translatory motion of said body on the materials to be treated.
In both cases the tool taking the abrasive into contact with the material will just be indicated by the term "tool".

Operating mode of abrasives on materials

The abrasive elements, even if they are very small, moved or blasted by the tool along or against the surface of material, will disintegrate and progressively detach some particles of the material, as it happens, e.g., in the case of granite.
Granite is an intrusive rock of magmatic origin featuring a crystalline structure mainly (but not wholly) composed of quartz and feldspar crystals in very variable percentages. Its crystals are fixed to one another owing to a crystallization or recrystallization process under very high pressures. The abrasive particles, moved or blasted by the tool, penetrate into the feldspar bed and "pull out" the quartz crystals.
More in general, it is quite obvious that the effect of the abrasive on the treated material is actually depending on the number of active parts of the abrasive elements passing on the surface of the material in the unit of time as well as on the energy developd by each element. Active parts have been mentioned because each abrasive element, no matter how small it is, always comprises some more "aggressive" parts bent to loose their efficacy once they have performed their abrasive action.
It is therefore evident that to achieve its maximal efficiency it must not only contact the material but must also possess a maximum dynamic energy and be moved about and replaced as quickly as possible.
This applies to any kind of abrasive selected considering the kind of material to be treated.

Present methodology

According to prior art abrasives are brought into contact with the material by a regular and continual motion of the tool.
In consequence, the following factors which, as mentioned above, are determining for the efficacy of the abrasive action are subject of some limits, like:
- energy of the single abrasive elements:
- quantity of abrasive elements acting on the surface to be treated;
- probability of a contact between the material and the active parts of the abrasive elements;
- removal of exploited abrasive elements and their replacement by a new one;
- removal of the materials resulting from the abrasion.
In addition, the conventional system, by its regular and continouos motion combining a rotary and translatory motion, does not allow a thorough action of the abrasive on uneven and complex surface, save the use of expensive appliances and a high consumption of abrasive.

Principle of the invention

The invention is based on the principle to keep the tool subjected to an intensive vibration or to a high frequency and small amplitude oscillation to which the regular and continouos motion of the conventional system may be added.
Vibration exerts the following effects on the abrasive, which can be either incoherent or glued on a tool:
- an energy increasing the percussion power of the abrasive elements on the material to disintegrate;
- a local and repeated compaction in the areas which are usually out of reach for the incoherent abrasive and thus a more thorough action on the whole surface as it is treated;
- an increased speed of the moving abrasive elements and thus their enhanced efficiency;
- a continouos and forced turnover of all abrasive elements and thus an increased probability that the more aggressive particles will reach the material;
- a faster removal of the exploited elements which are immediately replaced by fresh and effective elements;
- a faster movement of grits and thus their quick removal from the treated surface;
- the possibility to concentrate the abrasive action within small areas which cannot be defined or circumscribed by the regular and continouos motion of conventional systems.

Examples of application

- Sawing of granite - At present, thin granite slabs are obtained by means of two parallel metallic blades fixed on a frame controlled by a crank-and-rocker mechanism, the circulating abrasive being usually a metallic grit bonded with limewash. According to the present invention said blades are subjected to an intensive vibration at a frequency of 6000 cycles p.m. approx. and with an amplitude of a few tenths of millimeter. At the same time the blades may be slowly driven on according to the conventional system.
- Sawing of marble - Marble is usually sawn by means of frame saws like those used for granite, but their blades are coated with abrasive, thus eliminating the circulation of abrasive powder.
Also in this case the saw blades are subjected to intensive vibration according to the above stated principle and may be slowly driven on according to conventional systems.
- Carving on surfaces of lapideous materials or the like is usually carried out either by grit blasting or by means of a tool, which may be coated or not with an abrasive and moved by hand or by a copying attachment.
Basing on the above stated principle the tool to be used shall bear a relief reproducing the pattern to be carved. The tool is then vibrated on the surface to be carved through a thin and continouos layer of abrasive. A more or less deep carving will thus be achieved depending on the time of application and the intensity of the vibration.
- Polishing of ground surfaces is now obtained by grit blasting or flaming. To improve the results of this operation a kind of plate coated with an abrasive is vibrated of the surface to be decorated through a thin and continouos layer of abrasive. For the same purpose a set of vibrating needles may replace said plate.
- Linear incisions on lapideous materials and the like can be worked into the surface covered with a layer of abrasive by means of a vibrating wire rotating on its axis or slowly moving along same.

Claims

1.) Method of treatment for natural and artificial lapideous materials and the like characterized in that it uses a tool subjected to elastical vibrations and/or high frequency oscillations acting on incoherent abrasives and in that said tool induces said abrasive to develop a high percussive energy so as to move, mix and compact it, as well as its rapid replacement within the treated area and the fast disposal of any kind of grit.

2.) Method of treatment for natural and artificial lapideous materials and the like according to Clain 1), characterized in that the abrasive is incorporated in the tool.

3.) Method of treatment for natural and artificial lapideous materials and the like,according to which the tool subjected to an elastic vibration and/or a high frequency oscillation is also regularly and continouosly driven.

4.) Method of treatment for natural and artificial lapideous materials and the like according to Clains 1), 2) and 3) characterized in that abrasives are replaced and grits are discharged also by gravity.