A machine for sizing and squaring slabs of materials such as glass, stone and marble, ceramic tiles and the like

Abstract: The invention relates to a machine and process for sizing and squaring slabs of materials such as glass, stone and marble, ceramic tiles and the like. At least one workpiece-bearing device (2) is provided, upon which a tile (3) or a stack thereof can be placed and blocked. The workpiece-bearing device (2) is revolvable and can be positioned at any angle about a fixed axis. At least one drive head (4) is fitted with at least one rotating grinding wheel (40), which operates on one side of the tile (3) or on same sides of tiles (3) forming the stack. The workpiece-bearing device (2) and the drive head (4) are constrained to a fixed frame (1) in such a way that a plane of work motion of the at least one grinding wheel (40) is disposed parallel to an axis of rotation of the workpiece-bearing device (2).

Description: The invention relates to a machine for sizing and squaring slabs of various materials. The invention finds wide application since it is adaptable for sizing and squaring slabs of different kinds of material, such as glass, stone, ceramic material and the like. Preferably but not exclusively, the invention can be used for sizing and squaring ceramic tiles made of materials, such as porcelain stoneware, that after firing have to be taken on to finishing operations, such as grinding. The prior art teaches sizing and squaring machines for such operations, which are structurally complex and expensive; setting and adjustment is also problematic and complex in these machines, with a resultant qualitative inconsistency in results obtained, especially after prolonged use. In the above machines, the slab to be sized and squared moves along a line during which it is ground, by a plurality of opposed grinding wheels, on two opposite edges thereof that are parallel to its direction of advancement. The grinding wheels are located in facing and opposite pairs along the line. The distances between the two opposing grinding wheels of each pair are set according to the slab sizing required, the distances therebetween being graduated along the line diminishingly until a final pair thereof achieves a final desired workpiece size. The workpiece is drawn by a conveyor to which it is pressed by means of rollers or belts (speed-synchronized with the conveyor) acting as pressors. Prior art realizations characterized by an ability to carry out both sizing and squaring phases are equipped with a first series of grinding wheels, as described above, and thereafter include a rotating device which rotates the piece, usually by 90°. The rotating device is provided with simple means for introducing and transferring the piece to a second sizing unit, almost identical to the first, which sizes the two remaining unground opposite sides. The above mentioned known machines, apart from being complicated and expensive, are not capable of offering satisfactory results either in terms of sizing or squaring. Furthermore, the said prior art machines require scrupulous and accurate adjustment and setting up, and have to be tried out several times before perfect setting is achieved, and even then there is no guarantee of results of consistent and acceptable quality. For this reason, even in optimal working conditions, it is not possible to obtain a constant sizing regularity, which results in the need to classify and store the tiles according to the different sizes obtained. The prior art document DE-U-1826154 discloses a machine for sizing and squaring slabs of material such as glass, stone and marble, ceramic tiles and the like, including a first frame (1,9), one workpiece bearing device (8) onto which one tile can be placed, one drive head (15, 16, 19, 21, 22, 23) bearing one rotating grinding wheel (19) destined to work on at least one side of said tile (13); said workpiece bearing device and said drive head being constrained to said frame (1, 9) in such a way as to enable a relative notion thereof in at least one plane which is not parallel to a lie plane of said tile. The technical effect is to be able to present various surfaces of the tile to the grinding wheel, so as to grind them, and to hold the workpiece fast. DE-C-38548 discloses several revolvable workpiece-bearing devices able to present different faces of a stonelike plate to a grinding wheel, see descriptions of S2, S3, S4, also claim 5. Of these, S2 and S3 explicitely allow for precise positioning, S3 with a division (see page 2, column 2, last paragraph) S2 with precise indexing with notches (same column, second paragraph). The present invention, as defined in claim 1, aims to resolve problems in the prior art by providing a machine which comprises: at least one workpiece-bearing device, onto which a workpiece or a stack thereof can be placed and blocked; said device being revolvable and positionable at various angles about a fixed axis thereof; at least one chuckhead fitted with a rotating tool, for the present purpose a grinding wheel, which grinding tool operates on one edge of the workpieces or the stack of workpieces; the chuckhead bearing the grinding wheel being provided with a back-and-forth movement that is parallel to an axis of the workpiece-bearing device. One advantage of the present invention is that it is constructionally simple. A further advantage is represented by its structural configuration which makes it suitable for lengthy and continuous operations in a particularly hostile environment characterized by the presence of fine powders of extremely abrasive materials highly damaging to all kinds of mechanical coupling. A still further advantage of the present invention is that it can be readily incorporated into a production line. Yet another advantage of the present invention lies in the simplicity with which it can be adapted to various types of workpiece shapes. Further advantages and characteristics of the present invention will emerge from the detailed description that follows, made with reference to the accompanying drawings, which represent some preferred but not exclusive embodiments of the invention, and examples of apparatus of the same general type, not embodying the invention but shown to facilitate its understanding. Figure 1 shows a schematic front view in vertical elevation of an apparatus of the same general type, not embodying the invention. figure 2 shows a schematic view from above of figure 1; figure 3 shows a schematic front view in vertical elevation of a first preferred embodiment of the invention; figure 4 shows a schematic view from above of figure 3; figure 5 shows in enlarged scale a part of a front view in vertical elevation of a further embodiment of the invention; figure 6 shows, in enlarged scale, a detail common to the examples and embodiments represented in figures 1, 3, and 5. With reference to these figures, 1 denotes in its entirety a fixed frame 1 to which a rotating platform 5, capable of rotating about a vertical axis, is fixed. On the rotating platform 5 two identical workpiece-bearing devices 2 are located in diametrically opposite positions. Each workpiece-bearing device 2 comprises a horizontal support surface 20 designed to accommodate a face of a slab, in the present case constituted by a ceramic tile 3. Pneumatically activated means for blocking 21, operating above the support surface 20, are inferiorly equipped with a small plate 23. The means for blocking 21 are preferably constituted by pneumatic cylinders whose cylinder end is solidly fixed to an arm 50 of the platform 5 while the cylinder stem is hinged by an end thereof to the small plate 23 in such a way that the small plate 23 can rotate with respect to the stem. The small plate 23 is arranged vertically dead above the support surface 20 so that a single tile or a stack of tiles can be gripped therebetween. The support surface 20 is mounted on an indexing device 22 of known type having a function of enabling precise, angularly predetermined rotations to be made about the vertical axis of rotation thereof. The example shown in figures 1 and 2 exhibits a drive head 4 fixed to a mobile frame 10 which is hinged about a horizontal axis thereof to the fixed frame 1, said horizontal axis being also perpendicular to the axis of rotation of the platform 5 and to the axis of each single workpiece-bearing device 2. The drive head 4 is fixed to the mobile frame 10 in such a way that its position can be set in a parallel direction to the axis about which the mobile frame 10 is pivoted to the frame 1. A cutting tool constituted by a frontal grinding wheel 40 is mounted on the drive head 4. Because of its position, the frontal grinding wheel 40 operates along a vertical plane which is parallel to the axes of rotation of the workpiece-bearing devices 2. The advancing motion towards the drive head 4 and consequently to the grinding wheel 40 is caused by a double acting cylinder 6 connecting the mobile frame 10 to the fixed frame 1. The platform 5 can also be set in predetermined positions and can rotate through 180° so as to alternatively place the workpiece-bearing devices into the positions indicated in the figures by the letters A and B. Position A represents the working position whilst position B represents the loading and unloading position. The drive head 4 is mounted on the mobile frame 10 in such a way as enable adjustment of the drive head position in a perpendicular direction to median line X-X containing both axes of the rotating platform 5 as well as the axes of rotation of each workpiece-bearing device 2 when the latter are in positions A and B. The setting of the drive head 4 position and thus the distance between the frontal grinding wheel 40 and line X-X makes it possible to carry out the tile sizing operation to the specifications desired. According to the operative working cycle of the machine, a single tile 3 or -more frequently- a stack of tiles is placed onto a workpiece-bearing device 2 in position B. Means for positioning, not shown in the accompanying drawings, enable the positioning of a stack of tiles 3 so that two opposite sides thereof are parallel to line X-X. The stack of tiles 3 is held fast on the workpiece-bearing structure 2 through use of means for gripping 21 which operate on the stack of tiles by means of the small plate 23. The workpiece-bearing device 2 loaded with the stack of tiles 3 can be moved from position B to position A by a rotation of 180°. After the said rotation the two opposite edges of the tiles 3 in the stack are still parallel to line X-X. The platform 5 is now blocked. The drive head 4can be moved foreward by action of the cylinder 6 which causes the grinding wheel 40 to interact with one edge of all the tiles 3 in the stack placed on the same side, and consequently one side of the stack of tiles 3 on the workpiece-bearing device 2 is levelled off. Once the levelling off of one side of the tiles has been carried out and the grinding wheel has returned to a position of non-interference with the stack, the stack can be rotated by 90° or 180° using the indexing device 22 to bring adjacent or opposite sides of the tiles 3 into a workable position. By repeating this operation of the frontal grinding wheel 40 on the sides of the tiles 3, the sizing operation thereon is complete in one direction. The size of the tiles when completely levelled off is twice the distance between the frontal grinding wheel 40 and line X-X. The same operation can be repeated for the remaining two sides of the stack of tiles 3 to complete the sizing operation. The use of the indexing head 22 allows for precise angular positioning of the stack of tiles 3 which are tightly gripped on the workpiece-bearing device 2. Thanks to the use of the indexing head 22, the sizing and squaring of the stack of tiles 3 are carried out simultaneously. Once the operation has been completed, the platform rotates by 180° and carries the stack of finished tiles to position B, and a new stack of tiles to be worked into position A. Obviously, it is also possible to size and square non-square tiles, such as rectangular-shaped ones, by adjusting the distance between the drive head 4 and line X-X. In the first embodiment, two opposite drive heads 4 are mounted on the mobile frame 10 by adjustable couplings. In this case, the size which will obtain is represented by the distance between the two opposite grinding wheels 40 keyed on the two drive heads 4. Compared to the example of figs. 1 and 2, the first embodiment offers the possibility of working simultaneously on two opposite sides of the stack of tiles 3 tightly blocked on the workpiece-bearing device 2. Once a pair of opposite sides have been worked, it is sufficient to rotate the workpiece-bearing device 2 by 90°in order to size the remaining two sides of the tiles 3. Here too, the sizing and squaring operations are carried out rapidly and efficiently thanks to the structure of the machine incorporating the indexing head 22. Exact sizing of the stack of tiles 3 is made possible by the fact that it is the same pair of opposite grinding wheels 40, mounted on the drive heads 4 which are both fixed on the same frame 10, that operate on opposite sides of the stack of tiles 3. To check that sizing is constantly accurate, it is sufficient periodically to check the distance between the two opposite grinding wheels 40 and to adjust the position of the heads 4 accordingly. A second embodiment differs from the second in that it is equipped with drive heads on which edge-working grinding wheels 41 are mounted. Naturally, in this case the axis of rotation of the grinding wheels 41 has to be situated in a plane parallel to that of line X-X. The machine described, in all the above-described first and second embodiments, is structured in such a way as to permit sizing and squaring of tiles. To sum up, the machine carries out the following operations: positioning and blocking of at least one tile 3 on a workpiece-bearing device 2 which can be precisely positioned at any angle about an axis thereof; working of one side of a tile 3 by means of rotating grinding wheels 40, 41 positioned opposite each other at a predetermined distance one from another and operating on a plane which is parallel to the axis of rotation of the said workpiece-bearing device 2; rotation of the workpiece-bearing device 2 through a predetermined angle and its blocking in said position; working of other edges of the tile 3 by means of grinding wheels 40 and 41 operating on planes which are parallel to the axis of rotation of the workpiece-bearing device 2. To square the tiles 3, the angle of rotation of the workpiece-bearing device 2 between one work phase and a next is 90°. The workpiece-bearing device 2 is so shaped and realized as to permit positioning and gripping of an orderly stack of matching tiles. With this invention it is possible to carry out the sizing and squaring of the tiles with geometrical precision thanks to the possibility of working the stacked tiles simultaneously. A further consequence is an increase in production speed. For this reason, the present invention can be easily incorporated into a tile production line. A further advantage of the invention is its versatility thanks to which the machine can be used to work tiles or other slabs which are neither square nor rectangular. Yet another advantage of the invention is its structural resistance to wear on mechanical couplings and components which is due to the presence of very fine particles of very hard materials which develop during the working of the machine.

Claims: A machine for sizing and squaring slabs of materials such as glass, stone and marble, ceramic tiles and the like, comprising: a fixed frame (1); at least one workpiece-bearing device (2) onto which at least one tile (3) can be placed; at least one drive head (4) bearing at least one rotating grinding wheel (40, 41) destined to work on at least one side of said tile (3); said workpiece-bearing device (2) and said drive head (4) being constrained to said fixed frame (1) in such a way as to enable a relative motion thereof in at least one plane which is not parallel to a lie plane of said tile (3), characterized in that said workpiece-bearing device (2), being revolvable and precisely positionable about at least one axis thereof at various angles with respect to said fixed frame (1), permits to hold the tile fast and in that it comprises two of said drive heads (4), situated reciprocally opposite one another and bearing grinding wheels arranged such as to be able to operate on two opposite sides of said tiles (3); said two drive heads (4) being constrained to a mobile frame (10) which is hinged to said fixed frame (1) about a fixed axis and being fixed to the mobile frame (10) by means of adjustable couplings allowing for setting a desired distance between the grinding wheels mounted on the drive heads (4). The machine of claim 1, characterized in that said workpiece-bearing device (2) comprises a support surface (20) on which one face of said tile (3) can be placed; above said support surface (20) operate means for blocking (21) which upon being activated press said tile (3) against the support surface (20) such that said tile (3) is held fast there-between. The machine of claim 2, characterized in that said support surface (20) and said means for blocking (21) are shaped in such a way as to interact with central areas of the faces of said tile (3). The machine of claim 2, characterized in that said workpiece-bearing device (2) and said means for blocking (21) are arranged and shaped in such a way as to accommodate a stack of tiles (3) on said support surface (20). The machine of claim 1 or 4, characterized in that it comprises two of said workpiece-bearing devices (2) arranged in reciprocally opposite positions on a rotating platform (5); said rotating platform (5) being able to rotate at least in such a way as to bring either of said two workpiece-bearing devices (2) precisely into a position previously occupied by another of either of said two workpiece-bearing devices (2). The machine of claim 1, characterized in that said drive heads (4) are mounted on a mobile frame (10) which is hinged to said fixed frame (1) about a fixed axis. The machine of claim 1, characterized in that said mobile frame (10) is hinged to said fixed frame (1) about an axis which is perpendicular to an axis about which said workpiece-bearing device (2) can be rotated. The machine of claims 1, characterized in that said grinding wheels are constituted by frontally-acting grinding wheels (40). The machine of claim 1, characterized in that said grinding wheels are constituted by peripherally-acting grinding wheels (41). The machine of claim 1 or 8 or 9, characterized in that said grinding wheels (40, 41) mounted on said drive heads (4) are positioned reciprocally opposite in such a way as to give rise to two working areas which are parallel to the axis of rotation about which said workpiece-bearing device (2) can be angularly revolved by means of an indexing device (22).

Inventors: CUOGHI PAOLO, CUOGHI, PAOLO
Applicants: ONIX S R L, ONIX S.R.L.
Application year: 1995
Main classification: B24B7
IPC codes: B24B7, B24B9