AUTOMATIC SMOOTHING AND POLISHING SYSTEM FOR PLATES AND BLOCKS MADE OF MARBLE, GRANITE AND STONE IN GENERAL

Abstract: Automatic smoothing and polishing system for plates and blocks, generally of large sizes, made of marble, granite and plate in general, wherein during the translation of plates or blocks arranged along a conveyor belt (2), at least two rows of tool-holder heads (18) are made simultaneously interact so that the plates are worked along longitudinal portions to the advancement motion thereof. The tool-holder heads (8) arranged at the same height with respect to the plate advancement direction are provided with the same abrasive grain; moreover, the heads are made reciprocally integral by means of a carriage (6) provided with oscillating motion that is independent and transverse with respect to the advancement motion of the plates to be abraded.

Description: AUTOMATIC SMOOTHING AND POLISHING SYSTEM FOR PLATES AND BLOCKS MADE OF MARBLE, GRANITE AND STONE IN GENERAL The present invention refers to an automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general, that operates for the optimisation of the overall sizes and the increase of production and quality requirements. It is known that smoothing and polishing operations of stony materials at least for the last ten years has been performed, suitably controlled, in a completely automatic way. The stony material extracted from the quarry in the shape of a block, is transformed in big- sized plates, long and narrow plates, blocks whose sizes and shape are rather variable and with a surface roughness that is as high as the impact effect is high with respect to the abrasion, both embedded into the particular cutting process. The automatic smoothing and polishing system arranged to work the surface of the above semifinished product is particularly sophisticated, being provided with a control logic for major cycle variables - tool speed, different approach motions between material to be worked and tool, particular semi-finished product geometry, etc. The interaction between both smoothing and polishing tools and stony plate surface occurs by means of the surface roughness reduction when the plate passes below a row of tool-holder heads arranged longitudinally with respect to the advancement direction of the plate itself. These heads are provided with abrasive tools whose roughness is more and more decreasing along the plate advancement direction; moreover, each tool- holder head is characterised by a motion along the vertical approach direction towards the plate, adapted to avoid dangerous tool interactions with the etching edge of the semi-finished product to be abraded, that due to its nature is not prone to impacts . A system of this type fully guarantees smoothing and polishing of disho ogeneous stony material with variable geometry; it also has the following inconveniences, whose solution is the object of the present invention: the system size is as large as the layer to be smoothed is thick and as high the desired gloss degree is; this implies the problem of the placement of a smoothing and polishing system inside a shed that is not always easy; the transverse oscillation of the bridge, integral with tool-holder heads, creates large alignment and "leeway making" problems with the following wear of mechanical parts that are already strongly stressed next to inversion points; the amount of forces due to mutual interaction between tool and plate is dishomogeneous along the bridge: the forces produced by smoothing heads disturb the finishing heads integral thereto through the bridge, and generate the breakage of thin plates and composite plates, being these latter ones characterised by small thicknesses of stony material - of the order of 5 mm - with respect to the polyurethane support and stiffening layer, aluminium honeycomb, etc. The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a system as claimed in Claim 1. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims. Tool-holder heads belonging to contiguous rows and arranged at the same height with respect to the plate advancement direction are provided with an abrasive tool having the same grain; moreover these heads are made mutually integral by means of a carriage possessing an independent oscillating motion with respect to the support carriage motion of the tool-holder heads with different grain. The surface portion interacting with a row of tool-holder heads is worked by means of the carriage oscillating motion, this motion being transverse to the advancement motion of the plates to be abraded and with a width equal to the global width ratio of the conveyor belt and the number of these rows of tool-holder heads; moreover, the heads belonging to a single carriage and arranged at the same height with respect to the plate advancement direction are arranged at prefixed relative distances: this in order to guarantee the necessary "covering" next to the area shared by heads of contiguous rows. The present invention will be better described by some preferred embodiments thereof, given as a non-limiting example, with reference to the enclosed drawings, in which: Figures 1 and 1A are respectively a front and a side view of the system in the preferred embodiment of the present invention; Figure 2 is a plan view pointing out the carriages in the extreme transverse translation points; Figure 3 points out the covering area in a plan view; and Figure 4 shows the main constructive parts of the system. The system shown in Figure 1 is composed of a fixed carrier structure 1, a conveyor belt 2 along which plates or blocks are laid in succession and are subjected to a smooth advancement motion through the actuator 3 and the belt winding cylinders 4. The carrier structure 1 includes the seats for sliding guides 5 of carriages 6 provided with transverse motion by means of the respective actuators 7 not shown in the drawings . The tool-holder heads 8 integral with each carriage 6 are provided with tools having the same grain next to the respective surface portion to be abraded, this latter one being increased by a "covering" factor, computed from the surface portion interacting with the contiguous heads. Each carriage 6 performs an alternate excursion X, generally according to the harmonic law: X = (h/ (2*n) -kD) *sin( (2*PI*N/60) *n*t) where: h is the plate sliding belt width; n is the number of rows of heads, provided with tools having the same grain, housed on the carriage 6; D is the tool-holder head diameter; k is the above-mentioned "covering" factor; PI=3.141592; N is the optimum oscillating frequency of a traditional system; t is the time variable. Proceeding with an example referred to a traditional system with a row of heads defined by: h = 2 m; k = 0.3; D = 0.460 m; N = 80 revs/min, it follows that: n = 1 Xmax = ± 1 m; N = 80 strokes/min; Max ace. = ± 60.5 m/sec 2 . For the corresponding system with two rows of heads, we obtain: n = 2 Xmax = ± 0.5 m; N = 160 strokes/min; Max ace. = ± 101.6 m/sec 2 . A traditional system composed of 18 heads assembled on a single bridge finds its corresponding system, according to the present invention, in a system with two similar rows of heads arranged on 9 oscillating carriages with an oscillation frequency that is equal to twice the optimum frequency with respect to a traditional system, guaranteeing an unchanged production. The main advantage of the system of the present invention is having obtained a very interesting reduction of the overall sizes; in fact, a smoothing and polishing system with 18 heads, arranged in succession on a single bridge, whose overall sizes are around 14 meters * 3.0 meters (42.0 m ) has its corresponding system in a system with two rows of heads, whose overall sizes are around 6.6 meters * 3.7 meters (24.42 m 2 ) . Another clear advantage is given by the chance of abrading blocks up to 200 mm thick without modifying the conveyor belt features, the traction tension induced on the conveyor belt itself due to the total mass of material laid along the belt itself, having remained roughly unchanged. Moreover, the system is adapted to be conceived as a set of modules, each one implying a carriage oscillating along guides that are integral with an independent casing. The system is capable of a high flexibility both in the choice of the type of heads - thickness calibration rather than constant pressure calibration - and in the definition of relative motions among the heads belonging to a single carriage . A system variation, included in Figure 4, in fact takes into account the chance of keeping the two rows of heads independent. The advantage offered by this configuration is obtained in working plates whose minimum width is 600 mm: the plate is worked by the single row of heads, while the contiguous row remains disabled. The carrier structure is in this example a monolithic electro-welded structure subjected to stress relieving; the carriage actuator is of the brushless type; the carriage is connected to the carrier structure by means of sliding guides that are sized and chosen as function of the real load conditions that are imposed upon the carriage whether the operation is smoothing or polishing; in fact, the system object of the present invention allows discriminating design variables by optimising the design of the single smoothing carriage - characterised by the presence of high shear forces with low cohesion between plate and tool - rather than the smoothing carriage - high cohesion between abrasive surface and plate, susceptibility to impacts, etc. The choice of the sliding guides depends on pre-load and accuracy, in addition to the nature of the load that can be more or less concentrated and subjected to quick displacements and sudden variations: these are elements that can be kept in due consideration depending on the requirements for each carriage. Adjustment screws are further present to adjust the coupling; these are guides that are able to solve some of the problems of roller guides, like irregular rolling at high speeds, leeway making, and the phenomenon of load concentration. Another characteristic aspect of these guides is the capability of absorbing support structure errors without the need of interposing elastic parts.

Claims: CLAIMS 1. Automatic smoothing and polishing system for plates and blocks, generally of large sizes, made of marble, granite and stone in general, said system being adapted to perform: the translation of plates or blocks arranged on a conveyor belt; the motion of tools due to rotation of a main spindle of each head; characterised in that: at least two identical rows of tool-holder heads (8) interact with respective surfaces to be abraded and with a surface portion that is shared by respective contiguous rows of heads according to a "covering" factor. 2. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to Claim 1, characterised in that: the tool-holder heads (8), arranged at the same height with respect to the plate advancement direction and next to the respective portion of a surface to be abraded, are provided with tools having the same grain. 3. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to Claim 2, characterised in that: the tool-holder heads (8), having the same abrasive grain, are made mutually integral by means of an independent carriage (6) . 4. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to Claim 3, characterised in that: each carriage (6) is provided with an oscillating motion having a transverse direction to the advancement motion of the plates to be abraded and whose width is equal to the ratio between the global conveyor belt width and the number of said rows of tool-holder heads (8) . 5. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to any one of Claims 1 to 3, characterised in that: the carrier structure (1) includes the seats of sliding guides (5) of carriages (6) provided with transverse motion by means of the respective actuators ( 7 ) . 6. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to Claim 5, characterised in that: the sliding guides (5) are aligned by means of adjustment screws to adjust the coupling. 7. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to any one of Claims 1 to 3, characterised in that: the tool-holder heads (8) belonging to a single carriage (6) are mutually independent. 8. Automatic smoothing and polishing system for plates and blocks made of marble, granite and stone in general according to Claim 7, characterised in that: the tool-holder heads (8) belonging to a row are disabled by system control.

Inventors: GALIMBERTI ROMOLO, GALIMBERTI, ROMOLO
Applicants: GALIMBERTI ROMOLO, GALIMBERTI ROMOLO S P A, GALIMBERTI ROMOLO S.P.A., GALIMBERTI, ROMOLO
Application year: 2000
Main classification: B24B7
IPC codes: B24B7