Grinder for engraving glass, mirrors and the like

Abstract

 Grinder for engraving glass, mirrors and the like comprising a supporting frame (2,3;4;5,6), a beam (12) movably mounted on the frame, a slide or carriage (30) slidably mounted on the beam (12) in a transverse direction with respect to the direction of motion of the beam, a plurality of motorized grinding wheels (15 to 18) mounted aligned on the slide or carriage (30), means (27) for selective lifting or lowering of each grinding wheel, and a sheet-bearing table (32) rotatably arranged below the beam (12).

Description

[0001] The present invention relates to a grinder for engraving sheet material such as glass, mirrors and the like.

[0002] Grinders for engraving sheet materials which to perform curved or elliptical engravings on said sheet materials must use appropriate templates are known in the art. Such grinders, however, require long idle times, with consequent decrease in productivity and great ability on the part of the operator.

[0003] An object of the present invention is to provide a grinder for engraving sheet materials to obtain engravings of fillets, both continuous and discontinuous and either rectilinear or curved, according to various configurations, without using a template.

[0004] Another object of the present invention is that said grinder operates with high precision, reliability and productivity.

[0005] These and other objects, which will better appear hereinafter are achieved by a grinder for engraving sheet materials, according to the invention, comprising a support frame, a sheet-bearing table, a grinding head movably carried above the sheet-bearing table, and a beam carrying the grinding head and mounted on the frame so as to be able to move backwards and forwards in a direction parallel to the laying of the sheet-bearing table, the said sheet-­bearing table being rotatable about an axis normal to the direction of movement of both the beam and the grinding head.

[0006] Further features and advantages of the present invention will become more apparent from the following detailed description of a preferred, but not-exclusive, embodiment thereof, given by way of non-limitative example with reference to the accompanying drawings wherein:

Figure 1 is a front elevation view of a grinder according to the invention;

Figure 2 is a top view of the sheet-bearing table of the grinder of Figure 1;

Figure 3 is a diagrammatic view of the control mechanisms of the grinding head; and

Figure 4 is a cross-section view on an enlarged-scale of a twin-wheel grinding head.

[0007] With reference to the above described figures, it will be noted that a grinder 1 for sheet products has a support frame including four uprights (one pair 2 on the left side and one 3 on the right side in Figure 1) and intermediate stiffening crosspieces 4 mutually connecting the uprights 2 and 3. Each pair of uprights 2 and 3 is bridge-like connected at its top by a respective horizontal stringer 5, 6 on each of which a slide 9, 10 is slidably mounted, e.g. on guides 7 and/or rollers 8. Each slide 9, 10 supports one end of a beam 12 which can thus move back and forth along the stringers 5 and 6 on a horizontal plane. On the beam 9 there is slideably mounted on longitudinal guides 13 a grinding head 14 comprising four grinding wheels 15, 16, 17 and 18 arranged one after the other aligned in the direction of the beam 12. Each grinding wheel, similarly to the grinding wheel 15 shown in Figure 3, is rotatably mounted about its own axis 19 and is operatively connected, e.g. by means of a toothed belt 20, to a geared motor 21. Moreover, each grinding wheel is carried on a structure 23 which is, in turn, mounted vertically slideable against the action of one or two springs 24 on two guides supported, in turn, by a bracket 26. The latter can perform lifting/lowering movements under the control of a respective fluid-operated jack 27 fixed to a supporting structure 28 which is, in turn, adjustable in height by means of one or two lifting/lowering screws 29 (that can be motor-driven) with respect to a carriage or slide 30 movable along the guides 13 along the beam 12.

[0008] Both the slides 9 and 10 and the carriage or slide 30 can move back and forth along their guide supports, e.g. by means of a respective rack-and-pinion assembly, not shown in the drawings where a motor 31 for actuating the slide 30 is shown in Figure 1.

[0009] Owing to the possibility of movement of the beam 12 along the stringers 5 and 6 and the slide 30 along the beam 12, the head 14 can move to any position within the range of movement of the beam.

[0010] Below the beam 12 and between the uprights 2 and 3 there is arranged a sheet-bearing table 32, which is mounted for rotation about a horizontal axis x-x which is perpendicular to the directions of motion of both the carriage or slide 30 and the slides 9 and 10. The table 32 can be controllably rotated by a control unit 34, e.g. a reversible geared motor, which also actuates a center plate (not shown) rigid with the table 32.

[0011] The table 32 has a workplane 35 where a plurality of recesses 36 are provided whose bottom wall in formed with a hole 37 in communication with a suction and compression unit (not shown) arranged to suck air while a sheet or plate 33 is laid on the workplane, whereby each recess 36 acts as suction cup for holding down the sheet, and to feed compressed air after the same sheet has been ground to ensure its removal from the work and support plane 35.

[0012] Advantageously, on the workplane 35 there can be provided a graduated positioning bar or ruler 38, which is slidably mounted on two parallel guides 39 each arranged on a respective opposite side of the table 32, and can be controlled by means of two fluid-operated jacks 40.

[0013] The operation of the above described grinder is as follows. Once a sheet or plate 33 to be machined has been placed on the worktable 32, it is held and retained in position by the suction cups or cavities 36. Before the grinding wheels 15-18 are set in rotation, the operator must make sure, if necessary, by acting on the raising-­lowering screws 29, that the same are arranged slightly (a few millimeters) above the sheet, then the grinding head 14 is moved so as to move the grinding wheel 15 at the beginning of the engraving to be made. If a rectilinear engraving is to be obtained, the grinding wheel 15 is set in rotation and is simultaneously lowered by its respective jack 27 onto the sheet or plate 33 to start the machining operation. At the same time, the slide or carriage 30 starts to advance along the beam 12 from right to left (when viewing Figure 1) to ensure the feed motion. As soon as the slide or carriage 30 has advanced a length equal to the distance between the grinding wheels 15 and 16, the grinding wheel 18 is set in rotation and lowered onto the sheet, and thus it will start working precisely at the beginning of the engraving produced by the grinding wheel 15. The same applies to the other grinding wheels 17 and 18, which thus perform a total of four passes (one for each grinding wheel) for each engraving. At the end of each engraving pass, the respective grinding wheel is lifted away from the sheet 33 and comes to a standstill in reverse sequence with respect to the start.

[0014] If a curved engraving is to be obtained on the sheet or plate 33, the grinding wheel 15 must first be moved to starting point of the curved pass to be made, the unit 34 is then energized and at the same time the grinding wheel 15 is set in rotation and performs the first pass along a curved path on the sheet or plate on the table 32. Such a path is determined and will have a configuration depending on the mutual position and the relative movement of the head 14 with respect to the table 32. The second pass is performed by the grinding wheel 16, but during the return rotation movement of the table 32 and, possibly, during the return stroke of the head 14; the third pass is performed by the grinding wheel 17 which operates likewise the grinding wheel 15, by causing a new advancement of the head-­table 32; then the fourth pass by the grinding wheel 18 occurs likewise the second pass of the grinding wheel 16.

[0015] By combining the relative motion of the table 32 (which performs circular movements) with respect to the head 14 (which performs rectilinear movements along the beam 12 but can also perform composite movements owing to the movement of the beam along the stringers 5 and 6), one can obtain various shapes and configurations of curved engravings formed in the sheets.

[0016] Operational and functional control of the various movements of the carriage 30, the slides 9 and 10, the grinding wheels 15 to 18 and the table 32 is advantageously performed by a central unit (not shown) controlled by a computer, and thus the grinder 1 requires minimum supervision by a single operator.

[0017] A grinder for engraving sheet products such as that described above is susceptible to numerous modifications and variations within the scope of the inventive concept as defined by the appended claims. Thus for example the grinding wheels 15 to 18 may be mounted on a respective axis or mandrel 19 in pairs 18A and 18B as shown in Figure 4.

[0018] Furthermore, even when the grinding tool 18 comprises a single grinding wheel designed to perform the last pass, the same is advantageously mounted (Figure 4) between two springs 40 and 41 mounted on the mandrel 19 to allow small axial movements in a horizontal direction for the grinding wheel or wheels 18 to compensate for any small defects in alignment between, and differences in wear among, the grinding wheels thereby obtaining engravings with perfectly machined sides.

[0019] It will be appreciated by a person skilled in the art that the grinding machine can be provided with a whole range of accessories, e.g. a system for feeding water under each grinding wheel during an engraving operation. Above the beam 12 a millimeter-graduated bar 44 can be provided on which reference lugs 45 are slideably arranged which have the function of stroke start or end for the working head 14, for example because they are arranged to abut against switches 46, one for each grinding wheel, adapted to send a specific control impulse to the central control unit.

[0020] The central unit may also be programmed to perform discontinuous interrupted engravings, in which case the grinding wheels 15-18 rise and lower in sequence at each engraved section owing to the action of a respective jack 27.

[0021] If desired, it is possible to provide a grinding wheel dresser removably fixed to the table 32 and against which the grinding wheels 15-18 can act in sequence, e.g. to give them a desired face angle or to true them.

[0022] A grinder according to the invention is particularly suitable for obtaining engravings on glass sheets, mirrors and the like, although it can be used for machining a large number of sheet or plate products, including stone slabs, tiles and the like.

[0023] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

1. A grinding machine for sheet or plate materials, having a support frame (2,3;4;5,6), a sheet-bearing table (32) and a grinding head (14) movably carried above the sheet-bearing table (32), characterized in that it comprises a beam (12) carrying the grinding head (14) and mounted on the frame (2,3;4;5,6) to perform backward and forward movements in a direction parallel to the laying of the sheet-bearing table (32), and in that said sheet-bearing table (32) is mounted for rotation about an axis normal to the direction of movement both of the beam (12) and the grinding head (14).

2. A machine according to claim 1, characterized in that the said grinding head (14) comprises a plurality of grinding wheels (15 to 18) arranged aligned along the direction of movement of the grinding head (14) along the beam (12).

A machine according to claim 2, characterized in that for each grinding wheel (15-18) the said head (14) comprises a support structure (23) slideably mounted so that it can move towards and away from the sheet-bearing table (32), and actuation means (27) for the said structure (23).

4. A machine according to claim 3, characterized in that each support structure (23) comprises a support (19) on which a respective grinding wheel is rotatably mounted, guiding means (25) and resilient return means (24) for said support (19).

5. A machine according to claim 3 or 4, characterized in that said actuation means (27) of each support structure (23) comprises at least one fluid-operated jack (27).

6. A machine according to any claim 3 to 5, characterized in that it comprises a computerized central unit for sequentially controlling the actuation means (27) of each support structure (23) to obtain discontinuous engraving on sheet or plate materials.

7. A machine according to any of claim 2 to 6, characterized in that said grinding head (14) comprises a slide or carriage (30) having guiding means (29) for the said support structure (23) whereby adjustably setting the distance between grinding wheels (15 to 18) and said sheet-­bearing table (32).

8. A machine according to any preceding claim, characterized in that said sheet-bearing table (32) has a workplane formed with a plurality of recesses (36) in fluid communication with air suction and compression means, whereby each recess (36) acts as a suction sup for a sheet or plate being machined and as an expeller for it after having been machined.

9. A machine according to claim 8, characterized in that the sheet-bearing table (32) comprises a millimeter-­graduated reference ruler (38) and actuation means (40) for automatically positioning it on the table (32).

10. A machine according to any one of the preceding claim, characterized in that it comprises a millimeter-­graduated reference bar (44) along the beam (12), a plurality of abutments (45) arranged along the said bar (44) for actuating limit switches (46) for said head (14) and a refacing device which can be removably fixed to the sheet-bearing table (32) for refacing or chamfering the grinding wheels (15 to 18) on the grinding head (14).

Drawing