PROCESS FOR GRINDING THE EDGES OF GLASS SHEETS

Abstract: Process for grinding the edges of glass sheets (15), (16), especially small sheets, whereby the processing movement is made, manually or mechanically, by the sheets (15), (16) instead of by the grinders (13), (14), said grinders being either linear and fixed with a constant, curved transversal cross section embracing the edge of the sheet (15), (16), or else discoid, moving freely around a geometrical axis placed at a certain distance from the sheet, non-perpendicular to the sliding plane of the sheet but perpendicular to its rectilinear edge.

Description: PROCESS FOR GRINDING THE EDGES OF GLASS SHEETS Machines for grinding the edges of sheets of glass are known to adopt wheels coated with diamond powder, said wheels be¬ ing made to rotate by electric motors and arbors, and trans- lating along the edges of the sheet. Translating is made on a sliding means moving along runners, on bridges or conveyor belts and the like supported by the bed of the machine. Bearing in mind on the one hand the presence of a mass of moving parts and, on the other, the need for highly accurate positioning to obtain good results, the systems hitherto in use are of considerable complexity and require continuous adjustment and maintenance. All this involving much expense, machining that is often imperfect and difficulties connected with preparation of the machine. The above invention not only avoids these drawbacks but pro¬ vides important advantages as well, here to be explained. Subject of the invention is a process for grinding the edges of sheets of glass, particularly small and very small sheets, in which the processing mo.ement is made by the sheet. The grinders are fixed or are freely rotating. Fixed grinders have one or more longitudinal grooves of a constant concave cross section, enclosing the edges of the sheet of glass, and are straight or curved according to whe- ther the sides of the sheet are straight or curved. Rotating grinders are disc shaped, grinding being done by their circular faces, and can freely rotate round an axis which is not perpendicular to the plane on which the sheet slides, but is perpendicular to the straight edges of said sheet at a certain distance from it. Due to friction a translation motion is set up on said circular face in the zone of contact between the sheet and the face of the grinder, said translation being the combined result of motion according to the direction of the sheet and motion perpendicular to said direction. The fixed rectilinear grinders can be made to translate around the geometrical axis of their longitudinal groove to reach the preferred position in relation to the edge of the sheet. The circular processing faces of freely rotating grinders are perpendicular or oblique to the sheet itself and are parallel to its direction of translation. Suitable devices are provided to adjust said position as desired. If necessary a clutch can be used with the grinders to re ¬ gulate pressure of abrasion. The processing movement is given to the sheet by hand or by mechanical means or even by vibrating means as the case may be. Contact relative to pressure between grinder and sheet is obtained by elastic means such as rubber pads and the like placed between the grinders and their supporting structures or other equivalent means. Grinders are preferably ' placed in pairs on one or other side of the sheet, or else there is a single grinder on one side of the sheet while a suitable type of fixed support is provided at the opposite edge, said support being suitably devised to allow the sheet to move freely. The distance between opposing grinders or between the single grinder and the above mentioned support may be varied as re ¬ quired to facilitate easy introduction of the sheet between the opposing parts and to allow accurate regulation of re¬ ciprocal pressure between grinders and sheet. In one type of execution the processing motion is given to the sheet by a ring-wise conveyor belt or similar means on whose surface the sheet is laid, said belt having raised ridges to press against the back edge of the sheet and push it forward. Characteristics and purposes of the invention will be made even clearer by the following examples of its execution il- lustrated by drawings. Fig. l. Perspective view of apparatus with fixed grinders. Fig.2. Detail of the device for adjusting a rectilinear grinder around the axis of its longitudinal groove. Fig.3. Perspective view of apparatus with freely rotating disc grinders. Fig. . Apparatus for grinding curved sheets. The apparatus ( 10) comprises the frame (11) for the pair of rectilinear grinders (13), (14) and the device (12) for mech¬ anized motion of sheets of glass like (15), (16). The frame (11) comprises the longitudinal and parallel side pieces (17), (18) fixed to the bed (32) On its support (21), the side piece ( 17) carries the recti¬ linear grinder (13) with semicircular groove (22) coated with diamond powder, with interposed rubber pad ( 19). By means of the horizontal, transversal rack rods (25), (26) the side piece (18) βupports the rectilinear block (23) in which the grinder (14) with diamond powder coated groove (24) is housed^t rubber pad (20) being interposed. Axial movement of rods (25), (26) is determined by pinions (27), (28) fixed to the rod (29) revolving freely on sup ¬ ports (30), (31) of the side piece (18) allowing the distance between the pair of grinders (13), (14) to be adjusted. Rotation of the rod (29) can be obtained by means of the handwheel (34) and the worm screw-cog wheel group (35). The worm screw is fixed to the handwheel while the cog wheel is fixed to the rod (29). The device (12) for translation of sheets of glass like (15) and (16) comprises the ring-type conveyor belt (40). Said belt is made with ribbing on its supper surface (43) to push forward the sheets and with teeth underneath (44) which fit into the grooves (45), (46) of the rollers (41) (42) supporting the belt at its two ends. The roller (41) is fixed to the shaft (33) with supports (36), turned by the ratiomotor (37). Roller (42) is fixed to the shaft (47) with support (48). Ttie supports (36), (48) are fixed to the bed (32). When the glass sheets are placed one after another on the conveyor belt pulled along by the ratiomotor, said sheets will be pushed forward oy the ribbings (43) so that one edge and the other slide between the two rectilinear grin- ders (13), (14). Fig. 2 shows a device (50) which, coupled to another simi¬ lar one, is suitable for rotating one of the two grinders (51) around the geometrical axis of its diamond powder coa¬ ted semicircular groove (52) to allow grinding to proceed over the various zones of the edge (54) of the sheet (53) of glass . Said rotation is obtained by maximum travel of the toothed arch (56) on the support (57), also arched, fixed to the side piece (58) . The rack (60) of the rod! (61) fixed to screw (62) gears in¬ to the teeth (59) on the toothed arch. Turning the handwheel (63) causes longitudinal transla¬ tion of racks like (60) and of the rod like (61) in the hole (64) in the bracket (65) mounted on the support (66) and therefore rotation of the rectilinear grinder (51) around its geometrical axis. Fig. 3 shows a variation of the grinding process with the processing movement still being made by the sheets (70), (71), consisting in the fact that the discoid grinders (72), (73) have a circular processing face (74), (75) and are free to rotate around their geometrical axis (76) set parallel to the translation plane of the sheets, at a certain distance from them, and perpendicular to the di¬ rection of their motion. Due to the effect of friction the zone of contact (80)be- tween the sheets and the face of the grinder present a mo¬ tion which is a component of the motion in the direction of the sheet and of the motion perpendicular to said direc_ tion. Due to the effect of this component motion, little by lit- tie the zone of contact between sheet and grinder covers the whole annular surface (81) of the grinder with a radius greater than the distance between said zone of contact and the axis of rotation, said surface therefore being entirely engaged in the process. Sheet movement is caused by the group (90) with annular con veyor belt (91), subs antially the same as that (12) already described, supported by columns (92), (93) on the bed (94). The ratiomotor (95) automatically draws the sheets forward. The grinders can revolve round the shaft (96) supported by columns (97) on the bed (94). To regulate friction between the edges of the sheets and - o — the grinders, and therefore the degree of abrasion, an adjustable clutch (98) is provided. By means of a device, not shown in the figures for sim¬ plicity, the position of the discoid grinders: in relation to the edges of the sheets can be adjusted both parallel one to the other and thus in relation to their distance from the sheets, and also their orientation in relation to the plane of translation of the sheets. Fig. shows a variant of the apparatus suitable for grind_ ing round pieces of glass. The frame (120) with bed (121) comprises the support(122) for the shaft rotating (123) by action of the belt trans¬ mission (124) and ratiomotor (125). The rotating shaft comprises the table (126) on which the round sheet (127) is placed. The sheet adheres to the plate by action of the rubber presser (130) subjected to action of the ball bearing (131) pressed against the sheet (127) by the fluodynamic piston(132) acting on the rod (133) guided and supported by the bracket (134) fixed to the frame (120), by means of lever (142). The semicircular grinders (135), (136) comprise the shoes (137) and rubber pads (138). The shoes are supported-, by means of the tabs (139) by the levers (140) pivoted in the intermediate points (141)round two pins supported by the frame (120). At the other end .(145)..said 'levers are connected to the hydraulic cylinders (144). Advantages Elimination of the ordinary diamond powder coated grinding wheels together with motors and arbors. Working speed much higher than at present. As the grinders are mounted on the fixed bed of the machine adjustments are much easier and simplier. Motion is straighter on the straight sheets and more even on round sheets any irregularities or bulges on the edges being eliminated prior ..to., beginning the movement. Elimination of cavities and imperfections on the edges of sheets caused by the ordinary moving round grinders. Higher precision in processing as there are none of the vibrations present with present types of rotating grinders; especially in the case of very thin sheets, breakages due to these vibrations are practically eliminated. In the case of thin mirrors splintering at the silver-backed edges is avoided as it becomes possible to use grinders having groove diameters approaching the thickness of the mirror whose edges are therefore closely embraced. In the case of manual equipment there are none of the mo¬ tors and movement mechanisms required for the present auto¬ matic and semi-automatic machines. There is no need for skilled operators as, once the sheet has been correctly placed in relation to the grinders as in the case of manual equipment, all that has to be done is to push the sheet of glass forward. A considerable reduction in equipment costs bearing in mind especially that many processes can be done manually, as well as in running costs, power consumption, maintenance, con¬ sumption of water.

Claims: CLAIMS 1. Process for grinding the edges of glass sheets, espe¬ cially small and very small sheets, characterized in that the processing movement is made by the sheet ( 15) , ( 16) , (53) , (70), (71), (127). 2. Process as in claim 1, characterized in that the grin¬ ders (13), (14), (51), (135), (136) are fixed and comprise a longitudinal groove (22), (24), (52) having a constant con¬ cave cross section, embracing the edge (54) of the sheet (15), (16), (53), (127), and are rectilinear or curved ac¬ cording to whether the edge of the sheet is rectilinear or curved. 3. Process as in claim 1, characterized in that the grin¬ ders (72), (73) are discoid with circular processing face (74), (75) and can rotate freely round an axis (76) non-per_ pendicular to the sliding plane of the sheet (70), (71) but perpendicular to its rectilinear edge, at a certain distance from said sheet (70), (71), the friction on the circular face (74), (75), of the grinder (72), (73) creating a move- ment of translation of the zone (80) of contact between the sheet (70), (71) and the face (74), (75) of the grinder(72), (73), said movement being the result of a combination be¬ tween a motion according to the direction of the sheet (70), (71) and a motion perpendicular to said direction. 4. Process as in claim 2, characterized in that the fixed rectilinear grinders (13), (14), (51) can be made to translate around the geometrical axis of their groove (22) , (2 ) , (52) to reach the preferred position in relation to the edge(54) of the sheet (15), (16), .(53). 5. Process as in claim 3, characterized in that the freely moving discoid grinders (72), (73) have their circular pr£ cessing face (74), (75) perpendicular or oblique to the plane of the sheet (70), (71) and parallel to its direction of ; translation, there being suitable devices to adjust such position as desired and said grinders (72), (73) being if necessary subjected to the action of a clutch(98) to regu¬ late abrasion pressure. 6. Process as in claim 1, characterized in that the pro¬ cessing movement of the sheet (15), (16), (53), (70), (71), ( 127) is brought about by manual or mechanical thrust or by vibrating devices, as the case may be. 7. Process as in claim 1, characterized in that the contact relative to pressure between the grinders (13), (14), (51), (135), (136) and the sheet (15), ( 16), (53), (127) is obtained by elastic means such as rubber pads (20), (138) and the like placed between the grinders (13), (14), (51), (135), (136) and the structures (21), (23), (137) supporting them, or other equivalent means . 8. Process as in claim 1, characterized in that the grinders (13), (14), (51), ( 135), (136) are placed in a pair at one and the other side of the sheet ( 15), ( 16), (53), (127), or else there is one grinder at one edge of the sheet ( 15), ( 16), (53), ( 127) while at the opposite edge there is an adequate fixed support provided with suitable means for allowing said sheet (15), (16), (53), ( 127) to move freely. 9. Process as in claim 8, characterized in that the distance between the opposing grinders ( 13) , ( 14 ) , ( 51 ) , ( 135) , ( 136 ) or between the grinders ( 13 ) , ( 14 ) , ( 51 ) , ( 135) , ( 136 ) and the sup¬ port on the opposite side can be varied as desired to allow easy introduction of the .sheet ( 15) , ( 16) , ( 53) , ( 127 ) between the opposing parts, and to secure precise adjustment of the reciprocal pressure between the grinders (13), (14), (51), (135), (136) and the sheet (15), (16), (53), (127). 10. Process as in claim 1, characterized in that the move_ ment for processing is given to the sheet (15), (16), (70), (71) by a ring-wise conveyor belt (40), (91) or similar means on the surface of which,where the sheet (15), (16), (70), (71) is laid, there may be raised ribbing (43) by means of which the necessary thrust can be applied to the sheet (15), ( 16), (70), (71) at its back edge.

Inventors: LANZETTA ALDO, LANZETTA, ALDO
Applicants: LANZETTA ALDO, LANZETTA, ALDO
Application year: 1987
Main classification: B24B9
IPC codes: B24B1, B24B9, B24D17