ES2973236T3 - Unit for grinding or polishing a sheet, in particular, a glass sheet, and a method for processing sheets using said unit - Google Patents

Abstract

A perimeter surface (5) of a glass sheet (2) is ground and polished using a grinding or polishing unit (30) having a slide (33) that can move in a rectilinear direction (K) and a grinding head. wheel (31) carried by the slide (33) and designed to carry a grinding wheel (22) or a polishing wheel (27); the slide (33) being moved by an electro-pneumatic drive assembly (35) that has an electric motor (50) coupled to the slide (33) by means of a reversible mechanical transmission (45) for positioning the grinding wheel (22) and a pneumatic thrust cylinder (39) that acts directly on the slide (33) to push the polishing wheel (27); a command and control unit (16) being provided to activate at least the pneumatic cylinder (39) when the polishing wheel (27) is mounted on the wheel head, and the electric motor (27) when an abrasive wheel is mounted. (22). in the same wheel head (31). (Automatic translation with Google Translate, without legal value)

Description

DESCRIPTION

Unit for grinding or polishing a sheet, in particular, a glass sheet, and a method for processing sheets using said unit

Cross reference with related requests

The present patent application claims priority over Italian Patent Application No. 102020000004819, filed on 06/03/2020.

Technical field

This invention relates to a unit for grinding or polishing a sheet, in particular a glass sheet, and to a method of processing sheets using such a unit. In particular, this invention relates to a unit for grinding or polishing a sheet, in general, and a glass sheet in particular, to which the following discussion explicitly refers, without any loss of generality thereby.

Background of the technique

In the field of glass sheet processing, it is known to use grinding or polishing units particularly, but not necessarily, to process perimeter surfaces, that is, those perimeter surfaces that extend transversely to the extended surfaces of the sheet itself. of glass.

There are two types of machines used to process the perimeter surfaces of a glass sheet. On the one hand, the so-called "bilateral" grinding machines belong to the first type. With these, the sheets are fed laterally and their opposite perimeter surfaces are simultaneously ground by two grinding-polishing groups, which are facing each other.

On the other hand, the so-called "straight-line" grinding machines belong to a second type. With these, the sheets are fed in a nearly vertical plane and ground by feeding the perimeter surfaces into an underlying grinding group.

Regardless of the type of machine used, each grinding-polishing group comprises a series of grinding units that are adjacent to each other and independent of each other to remove a given amount of material from the sheet, and a series of polishing units that are also independent of each other and arranged adjacent to each other, and following the grinding units in the direction of feeding the sheets to polish the surfaces rectified by the polishing units.

Each grinding unit comprises a corresponding grinding wheel, an electric motor for rotating the grinding wheel about its axis, and a device for placing the grinding wheel in a given operating position for removal. Each positioning device comprises, in turn, a slide to support the grinding wheel and its corresponding drive motor, and an electric motor to move and position this slide. Each polishing unit comprises a corresponding polishing disc, which is also rotated around its axis by a corresponding electric motor and is also mounted on a corresponding slide driven by a corresponding linear actuator designed to push the corresponding slide and consequently the disc. of corresponding polishing against the ground surface of the sheet. Depending on the application, the slides that carry the polishing discs are pushed by pneumatic cylinders or by mechanical springs with variable preload.

Known grinding machines of the type defined above are normally designed and manufactured on the basis of customer requirements and, in particular, according to the type of sheets to be processed, but, above all, according to the processing to be carried out and the degree of precision/finishing. surface required. To do this, a given number of grinding units and a predefined number of polishing units are planned and installed during the design stage.

Once done, it is normally no longer possible to vary the number of grinding and/or finishing units and therefore convert or customize the machine for a different processing, i.e. carry out a grinding and/or polishing programme. different or, again, obtain a different degree of polishing with the ground surfaces.

This rigidity makes it impossible to satisfy the emerging need among the users of these machines, which is to be able to have a basic machine, but, at the same time, to be able to reconfigure the basic machine in an extremely short time and in a simple and economical way without the need for specialized operators when production needs or the degree of finishing required changes.

From the Italian patent application No. 10201900002941 filed by the same applicant, the creation of a grinding machine provided with at least one configurable unit is known, that is, capable of using, according to needs, a grinding wheel or a polishing disc .

In the above configurable unit, any of the disks is mounted in a disk head arranged in a slide; in the case of the grinding wheel, it is brought to a predetermined grinding position by an electric displacement motor and maintained in that predetermined position by an irreversible screw-nut transmission with a metric screw rotated by the same electric motor.

On the other hand, when the polishing disc is mounted on the disc head, the slide is constantly pushed against the surface to be polished by a pneumatic actuator arranged in series with the electric motor. Note that the disc type on the slide, a pneumatic selection device interposed between the electric motor and the pneumatic actuator, connects the slide to the electric motor when there is a grinding wheel in the wheel head, keeping the pneumatic actuator deactivated, and activates the pneumatic actuator when the disc used is a polishing disc, isolating the electric motor.

Although appreciated by users, the known configurable unit defined above is relatively complex in terms of construction and therefore of relatively high cost, and requires careful control during the configuration stage. For these reasons, the above configurable unit does not find an immediate and satisfactory application in any type/range of grinding or polishing machines.

Additionally, a brake assembly is always connected to the above configurable unit to counteract the thrust of the pneumatic actuator during the transition from one surface to be ground to another and thus maintain the polishing disc in a predefined clamping position without deactivating the pneumatic actuator.

Each brake assembly has relatively large dimensions for the already crowded area in which it is located and, in any case, a cost that affects the total cost of the machine when considering that each polishing unit requires its own brake assembly.

Finally, in the known configurable unit of the type described above, controlling the wear of the polishing disc is particularly complicated and sometimes difficult and inaccurate since it is mainly done visually or using position sensors, while it is always necessary to act on the electric motor to position the slide to control the wear of the grinding wheel. The control, carried out mainly by detecting the variation in the current absorbed by the electric motor, is inaccurate due to the presence of the mechanical transmission driven by the electric motor itself, whose elastic failures can distort the detection of the instant at which the grinding wheel hits the expected fixed reference and thus the readjustment of the grinding wheel itself.

Units for grinding or polishing a sheet are disclosed, for example, in documents EP 1676671 A1, which forms the preamble of claim 1, WO 2007/015163 A1, EP 0865 970 A2, WO 2016/185374 A1 and US 2008/ 092594 A1.

Disclosure of the invention

The purpose of this invention is to provide a grinding or polishing unit, which solves, in a simple and economical way, the problems described above and, in particular, which is, compared to known solutions, simple and very fast to produce and configure/control and that is economical and compact in size. According to this invention, a grinding or polishing unit is defined as claimed in claim 1.

This invention also relates to a method of processing a sheet. According to this invention, there is provided a method of processing a sheet, according to claim 10.

Brief description of the drawings

The invention will now be described with reference to the attached drawings, which illustrate a non-limiting embodiment thereof, in which:

Figure 1 illustrates, schematically and mainly in blocks, a preferred embodiment of a glass sheet grinding or polishing machine according to this invention; and

Figures 2 and 3 illustrate, in perspective view and on an enlarged scale, two opposite side views of a grinding or polishing unit of the machine of Figure 1 produced according to the precepts of this invention;

Figure 4 is a perspective view, on an enlarged scale and with parts removed for clarity, of the unit in Figures 2 and 3; and

Figure 5 is similar to Figure 4 and illustrates, in cross section, some details of the unit in Figure 4.

Best way to carry out the invention

In Figure 1, the reference number 1 indicates, in its entirety, a glass sheet grinding and polishing machine 2: flat, rectangular glass sheets with two opposite, extended and flat surfaces, indicated with 3, and four consecutive surfaces, of flat perimeter or sides, one of which is indicated with the reference number 5, in the illustrated example.

Machine 1 can also be a bilateral machine, that is, with the sheets 2 fed flat, or a straight machine, that is, with the sheets 2 fed laterally. It comprises a rigid base 6 and a motorized sheet transport assembly 7, known per se and partially visible in Figure 1, for feeding a succession 8 of glass sheets 2 along a rectilinear path 9 and through a station. 13 to grind and polish the perimeter surfaces 5.

Group 7 is directed and controlled by an electronic command and control unit 16 for the entire machine 1. Again with reference to Figure 1, station 13 houses a row 18 of abrasive units that are independent of each other and are arranged one at a time. side by side in a direction parallel to path 9.

The row 18 of abrasive units comprises a group A of known grinding units 19 and a group B of polishing units 20, which are also known, and which polish the surfaces 5 ground by group A.

Each grinding unit 19 comprises a corresponding grinding wheel 22, which is rotated by a corresponding electric motor 23 driven by the electronic unit 16, and is transported by a corresponding slide 24.

The slider 24 is coupled to a guide 25 fixed to the base 6 and can slide orthogonally to the path 9 in opposite directions under the thrust of an electric motor 26, conveniently a servomotor controlled by the electronic unit 16.

Each polishing unit 20 comprises a corresponding polishing disc 27, which rotates about a corresponding axis by an electric motor 28 driven by the electronic unit 16 and is mounted on a slide 2 9 driven by its own actuator 29', e.g. a pneumatic cylinder controlled by a proportional solenoid valve which is, in turn, controlled by the electronic unit 16 to push the corresponding disc 27 against the surface 5 of the blades 2.

Still referring to Figure 1, the row 18 of abrasive units finally comprises one or more bifunctional abrasive units 30 arranged between groups A and B. Each bifunctional unit 30 can be controlled and adjusted by means of the unit 16 to perform a grinding operation or a polishing operation on the surfaces 5, as will be better described below.

According to a different configuration of the machine 1, the grinding assembly A comprises a single grinding unit 19, and the polishing assembly B comprises a single polishing unit 20.

Regardless of the number of abrasive units 19 and 20, each of the abrasive units 30 is independent of the other abrasive units, comprises a disc head 31, on which a grinding wheel 22 or a polishing disc 27 can be mounted.

An electric motor 32 driven by the electronic unit 16 rotates the disk head 31 about a corresponding axis 31A. The electric motor 32 and the disc head 31 are mounted on a slider 33 and move thereon. The slider 33 is coupled to a rectilinear guide 34 integral with the base 6 and is movable orthogonally to the path 9 in a direction K parallel to the axis 31A under the thrust of an electro-pneumatic assembly, indicated by 35. With reference to Figures 4 and 5, the electro-pneumatic assembly 35 comprises a pneumatic actuator device, indicated as a whole, with 36 and an electric actuator device 37.

The pneumatic device 36 comprises a double-acting pneumatic cylinder 39 connected to a source of compressed air and a control block 40 which is connected to and controlled by the unit 16.

The cylinder 39 comprises, in turn, a sleeve 41 stably connected to one end of the guide 34 by means of a support 42 and an output rod 43 having a free end stably connected to the slide 33 by means of of a support 44 (Figures 2 and 4).

Again referring to Figures 2, 4 and 5, the electrical actuating device 37 comprises a reversible or invertible mechanical transmission 45. The mechanical transmission 45 is, preferably, a recirculating ball screw-nut transmission and, for example, of the type identified by HIWIN identification codes: 1R16-5-FSI-231-0.052-C7 and TRM: SFNHR01605C1D+SSR01605X231L. The term reversible or invertible refers to a transmission that fails under load, that is, a transmission that cannot provide significant resistance to the axial thrust exerted by the discs 22, 27.

The transmission 45 comprises a screw 46 and a nut or nut screw 47. The screw 46 has its own shaft 46A which coincides with the shaft K and is coupled to the guide 34 rotatably and in an axially fixed position. The nut screw 47 is, however, stably connected to the slider 33 by means of a bracket 48.

The electric drive device 37 then comprises an electric motor 50, having a housing 51 stably connected to the guide 34 through a rigid structure 52 and a rotating output shaft 53 angularly and axially connected to one end of the screw. 46 through a joint 55.

The electric motor 50 is electrically connected to the unit 16.

Depending on the operations planned for the processing cycle, each of the units 30 is configured by mounting a grinding wheel 22 or a polishing disc 27 on its disc head, and the unit 16 informed accordingly.

When a grinding wheel 22 is mounted on the wheel head 31, the unit 16 discharges the pneumatic cylinder 36 and activates the electric motor 50. This motor 50 rotates the screw 46 and moves the slide 33 until the grinding wheel 22 is brought to a predefined grinding position. During its movement, the slider 33 drags the rod of the pneumatic cylinder 39 with it. Once the predefined position has been reached, the electric motor 50 is controlled in position to keep the grinding wheel 22 stationary in that position along the axis K for as long as necessary to grind the blade 2.

When, on the other hand, the polishing disc 27 is mounted on the disc head 31, again by means of the unit 16, the electric motor 50 is deactivated and the pneumatic cylinder 39 is activated, which, driving the screw of nut 47 with it, constantly push the polishing disc 27 against the surface 5 to be polished. Since the slider 33 drags the nut screw 47 with it and therefore rotates the screw 46, and with it the motor 50, using the encoder 50A connected to the motor 50, it is possible to determine the position of the slider 33 and the wear of the polishing disc 27 in real time.

Furthermore, by activating the motor 50 at the same time that the pneumatic cylinder 39 is activated and controlling it in a pair, it is possible to integrate or vary, in an extremely precise manner, the thrust action exerted on the slider 33 and, therefore, in the polishing disc 27.

Not only, but always by controlling the electric motor 50, in a pair, during the thrust exerted on the polishing disc 27 by the pneumatic cylinder 39, it is possible to exert on the slide 33 itself an action that counteracts or opposes that exerted by the pneumatic cylinder 39 and elevate this counteraction until keeping the slider stationary and in balance of forces along the direction K. Such a condition is advantageously used to implement the so-called "brake function", that is, to keep the slider 33 and, therefore, the polishing disc 27 is stationary during the change of blade, that is, in the transition from one blade 2 to another.

Finally, the pneumatic cylinder 39 can be used to move a grinding wheel 22 towards known fixed positioning stops, to determine the actual wear and the subsequent necessary repositioning of the grinding wheel 22 itself. In fact, the pneumatic cylinder is connected directly to the sliding, that is, without the interposition of transmissions that can yield elastically and differently depending on the conditions. The pneumatic cylinder solves this problem because the constancy of the thrust is ensured by the constancy of the pressure; Consequently, the elastic performances are always the same.

Additionally, it is impossible to reach a dangerous overload condition for the mechanical components and, therefore, the repositioning procedure is faster.

From the above, it is clear that the described grinding or polishing unit 30 has, with respect to known reconfigurable units, an obvious simplicity in construction and control, and smaller dimensions resulting from the elimination of the disc brake. polishing 27, since this function is performed by the electric motor 50.

In the unit 30 described, the reversibility of the transmission 45 makes it possible, then, to determine the wear of the polishing disc 27, in real time and through the encoder 50A, and to intervene quickly to always guarantee the same quality of the finished product. According to a variant, the wear of the polishing disc 27 is determined by detecting the position of the slider 33 along the axis K using, for example, a linear transducer interposed between the slider 33 and the corresponding guide 6.

The unit 30 can, furthermore, be easily controlled and, above all, controlled with extreme precision since the pneumatic cylinder 39 and the electric motor 50 are actuators arranged in parallel with respect to the slider 33, and are independent of each other. For this, the action of one of the two actuators can be integrated or reduced with the other actuator to obtain optimal working conditions.

From the above, it is clear that the machine 1 could comprise a single unit 30 or a number of units 30 different from those illustrated and that they can be chosen, at the design stage, to obtain sheets with perimeter surfaces with different shapes, independently of its thickness, and with different surface finishes of the perimeter surfaces themselves.

Similarly, the unit 30 described can find application in grinding/polishing machines other than those indicated, and, in particular, in all those machines in which grinding and subsequent polishing of the rectified sheet is required. Also included in the aforementioned machines are those in which the glass sheet is held stationary on a resting surface and the frame 6 of the unit 30 is movable in relation to the sheet itself.

Finally, it is clear that the described unit 30, regardless of the context in which it is used, may comprise a reversible transmission other than that described, for example, a belt transmission or a tooth transmission, or reversibility means, may be provided, interposed between the electric motor 50 and the slider 33.

Finally, as mentioned above, the unit 30 described can be used to grind and polish sheets other than glass sheets and, for example, sheets of stone material or sheets of agglomerate material or other material that can be processed by grinding wheels. and polished by polishing discs selected, case by case, according to the material to be processed.

Claims (15)

1. A unit for grinding or polishing (30) a sheet (2), in particular a glass sheet; the unit (30) comprising a fixed guide (34), a slide (33) coupled with said guide (43) to move in a rectilinear direction (K), a motorized head (31) connected to said slide (33) and configured to carry an abrasive wheel (22) or a polishing disc (27), and a configurable electro-pneumatic assembly (35) for the movement of said slide (33) in said rectilinear direction (K); comprising the electropneumatic assembly (35): - an electric motor (50); - a motion transmission (45) operated by said electric motor (50) and having a first mobile member (47); - a pneumatic actuator (39) having a second mobile member (43); and - command and control means (16) for activating said electric motor (50) at least when the grinding wheel (22) is mounted on the wheel head (31) or at least said pneumatic actuator when said polishing disc (27) is mounted on said disk head (31); wherein said pneumatic actuator (39) comprises a sleeve (41) fixed to one end of said fixed guide (34), wherein said first (47) and second moving member (43) are both stably connected to said slider ( 33) and where the reversible connection means (45) are interposed between said electric motor (50) and said first mobile member (47). 2. The unit according to claim 1, wherein said reversible connection means (45) constitute part of said transmission. 3. The unit according to claim 2, wherein said transmission comprises a reversible screw-nut transmission (45). 4. The unit according to claim 3, wherein said screw-nut transmission is a recirculating ball transmission. 5. The unit according to claim 3 or 4, wherein said reversible transmission (45) comprises a screw (46) that has its own axis (46A) that coincides with said rectilinear direction (K) and that rotates under the thrust of said electric motor (50). 6. The unit according to any one of the preceding claims, wherein it comprises position detection means configured to detect the position of said slide (33) along said rectilinear direction (K) with respect to said guide (34). 7. The unit according to claim 6, wherein said position detection means comprises an encoder associated with said electric motor (50). 8. The unit according to any one of the preceding claims, wherein said command and control means comprise detection means (50A) for continuously detecting wear on the grinding wheel (22) or the polishing disc (27); said wear detection means being arranged between said slider (33) and said fixed guide (34). 9. A machine (1) for grinding and polishing a sheet (2) to be processed, in particular, a glass sheet, the machine (1) comprising a conveyor (7) for advancing the sheet (2) to be processed. process and a set (A, B) for grinding and polishing said sheet (2), wherein said grinding and polishing set (A, B) comprises at least one grinding or polishing unit (30) according to claim 1. 10. A method for processing a sheet (2), in particular a glass sheet, using at least one grinding or polishing unit (30) according to claim 1; the method comprising a polishing operation; said polishing operation comprising the step of pushing said polishing disc (27) against the glass sheet (2) by moving a slide (33) that supports a polishing disc (27) controlling the thrust of at least one pneumatic cylinder (39). ), and a rest stage, where the slide (33) and the polishing disc (27) are kept stationary in the rectilinear direction, exerting on the slide (33) a braking action opposite to said pushing action, where Said braking action is carried out by controlling the torque of an electric motor (50) for positioning the slide (33) and when the slide (33) is supporting an abrasive wheel (22). 11. The method according to claim 10, wherein said polishing operation comprises a wear detection step for detecting wear on said polishing disc (27), said wear detection being carried out by controlling the position of a slider (33) that It carries the polishing disc (27) and moves in said longitudinal direction (K). 12. The method according to claim 11, wherein the wear detection of the polishing disc (27) is carried out by continuously detecting the variation of the rotation angle of the electric motor (50). 13. The method according to claim 12, wherein the variation of the angle of rotation is carried out using an encoder of the electric motor (10). 14. The method according to any one of claims 10 to 13, wherein said pushing step is carried out using the electric motor (50) in parallel with the pneumatic cylinder (39). 15. The method according to any one of claims 10 to 14, wherein it comprises a grinding operation; the grinding operation comprising the detection of wear on the grinding wheel (22); detecting wear on the grinding wheel (22) comprising the step of moving the grinding wheel (22) forward against a fixed stop by means of the pneumatic cylinder (39).