EP3632614B1

EP3632614B1 - Rectilinear grinding machine

Info

Publication number: EP3632614B1
Application number: EP19201499.1A
Authority: EP
Inventors: Pierfranco Margaria
Original assignee: Bottero SpA
Current assignee: Bottero SpA
Priority date: 2018-10-05
Filing date: 2019-10-04
Publication date: 2021-04-07
Anticipated expiration: 2039-10-04
Also published as: IT201800009216A1; EP3632614A1

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102018000009216 filed on 05/10/2018.

TECHNICAL FIELD

This invention relates to a rectilinear grinding machine for grinding a glass sheet.

BACKGROUND ART

In the field of glass sheet-grinding, to which the following discussion will refer, without any loss of generality, it is well known to use grinding machines so-called "rectilinear", wherein the glass sheet to be ground, which is arranged vertically or edgeways, is fed along a rectilinear grinding path above a horizontal row of cup grinding wheels arranged along the rectilinear path. During the passage of the sheet over the row of cup grinding wheels, one of the lateral or perimetral surfaces of the sheet is progressively ground, specifically, the one facing downwards. During the passage of the sheet over the row of grinding wheels, the longitudinal edges arranged to the side of the above-mentioned lateral surface are also normally ground.
When the edges of the sheet also need to be ground, after all the lateral surfaces have been ground, the sheet is transferred to an edge-grinding station, is turned over, and arranged flat above a grinding unit.
It is difficult to turn the sheet over and reposition it on the grinding unit; it requires broad resting surfaces for the sheet and large manoeuvring spaces. In addition to this, turning over and repositioning the sheet take time, increasing the cycle time, but, above all, these operations are often the cause of both size and shape errors present on the sheet at the end of the grinding and which, in some cases, require the discarding of a sheet that has already been completely ground.
From the Italian patent application TO102018000003968 , on behalf of the same applicant, the use of a grinding plant, wherein the machining of the edges of the sheet is carried out by holding the sheet vertically, but always transferring the sheet to a grinding station outside the rectilinear machine, is known.
There are also known solutions wherein, after machining one of the lateral surfaces, the sheet passes through a grinding station, in which at least one grinding wheel is moved along two axes by means of pneumatic or mechanical actuator devices, such as cam-type devices. The use of pneumatic or mechanical actuator devices, on the one hand, does not allow the size and shape accuracy of the finished product to be improved, as they are difficult to control; on the other hand, their use does not enable the cycle time to be drastically reduced, since the speed of translation of the grinding wheel and the sheet to be machined cannot be raised above certain values. In fact, if you try to increase the feeding speed of the glass sheet to be machined, i.e. to increase the productivity of the machine, the risks of damaging the sheet, at least around the edges, are high due to the effect of sudden impacts between the sheet and the grinding wheel. If, on the other hand, you want to guarantee that you obtain high-accuracy ground edges and surface finishes, you need to drastically reduce the speed with the consequent loss of production.
Finally, at each production change or simple variation of the dimension/geometry of the edge to be made, manual adjustments of the actuators/mechanical devices are necessary and this increases the dead times limiting, in turn, the production.
A grinding machine for grinding lateral surfaces and a corners of a glass sheet according to the preamble of claim 1 is disclosed on EP 2 762 273 A1 .

DISCLOSURE OF INVENTION

The purpose of the present invention is to provide a rectilinear grinding machine for a glass sheet, which resolves, in a simple and inexpensive manner, the problems described above, and, in particular, which reduces grinding times with respect to the known methods and improves the quality of the size and shape of the ground sheets.
Another purpose of this invention is to provide a compact, reliable, and cost-effective grinding machine that does not require the intervention of the operator before or during the grinding phase.
According to the present invention, a rectilinear grinding machine for grinding a glass sheet is provided, as claimed in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanying drawings, which show a non-limiting embodiment thereof, wherein:

Figure 1 shows a front elevation view of a preferred embodiment of a rectilinear grinding machine produced according to the dictates of this invention;
Figure 2 is a view along the direction of the arrow A in Figure 1;
Figures 3 and 4 show, in perspective view greatly enlarged, a detail in Figures 1 and 2 in two different operating conditions; and
Figures 5 to 13 schematically show, and in block diagrams, a component of the machine in Figures 1 and 2 in different operating conditions.

BEST MODE FOR CARRYING OUT THE INVENTION

In Figure 1, the number 1 denotes, as a whole, a rectilinear grinding machine for the perimetric grinding of a glass sheet 2 arranged edgeways. Here and in what follows, the term "grinding" means any operation that is carried out on board the machine on the external periphery of the sheet 2 using rotary grinding or polishing tools arranged on board the machine 1.
In the example described, the sheet 2 is rectangular and has two opposing, extended flat surfaces, indicated with 3 and 4, four consecutive flat perimetric or lateral surfaces to be ground, indicated with 5, 6, 7 and 8 respectively, and four edges 9 with a right angle, each delimited by a relative pair of the above-mentioned perimetric surfaces 5, 6, 7 and 8.
Again with reference to Figure 1, the machine 1 comprises a base 10, in turn, comprising a rigid rectilinear structure 11 stretched along a rectilinear longitudinal path or direction 12 for feeding the sheet 2 to be ground. The structure 11 is raised by a floor 13 on which the base 10 rests by means of uprights M constituting part of the base 10.
From the structure 11 a resting back or frame 14 extends upwards, in a way known in itself, defining, in a known way, a resting surface for the sheets 2 fed edgeways in the direction 12. Here and in what follows, the term "edgeways" means a sheet arranged vertically or in a position, which is slightly inclined, for example, by 5-7 degrees, to ensure its stability when it rests on the back 14.
The machine 1 further comprises an assembly 15 for conveying sheets, known in itself and partially visible in Figures 1-4. In this specific case, the assembly 15 comprises an input section 16 for the sheet to be ground, an output section 18 for the ground sheet, and an intermediate motorised conveyor 19 for keeping and feeding sheets in a grinding position. The conveyor 19 is arranged inside a grinding station 20 for grinding the perimetric surfaces 5-8 and the edges 9.
The conveyor 19 comprises two closed ring conveyor belts and their respective delivery branches that face each other and are designed to clamp together in packs the sheets 2 to be fed. The conveyor 19 is driven and controlled by an electronic drive and control unit 21A for feeding the sheets 2 arranged edgeways at a constant speed, generally variable between 0.8 and 20 meters per minute, in the rectilinear direction 12 and above a virtual resting surface that is horizontal or orthogonal to the placement plane of the sheet 2 on the back 14, the track of which is indicated with the letter P in Figures 1 and 5.
Below the conveyor 19, the station 20 houses a horizontal row of cup grinding wheels 21 and 22, known in themselves. In use, the grinding wheels 21 machine the lateral surfaces 5-8 while the grinding wheels 22 machine the longitudinal lateral edges of the sheet 2 extending parallel to direction 12.
The grinding station 20 houses, in addition, an edge-grinding assembly 25 for the edges 9. The grinding assembly 25 is, preferably, arranged at one end of the row 21 and is, conveniently, arranged alongside the last grinding wheel of the row 21 in the feeding direction of the sheet 2.
With reference to Figures 3 and 4, the assembly 25 is hung on the structure 11 and comprises a slide 26 arranged below the plane P and coupled to the rigid rectilinear structure 11 by means of a guide and slide assembly 27. The assembly 27 enables the slide 26 to move in opposite directions in one direction 28 that is parallel to direction 12. According to a variant not shown, the assembly 25 rests on the floor or is connected to the base 10 at a different point from the crossbeam 11.
The slide 26 is mobile in direction 28 in opposite directions between two extreme, end-stop longitudinal positions, indicated with the letters A and B in Figure 5, under the thrust of a linear actuator 30, preferably a pneumatic actuator, which is driven and controlled by the unit 21.
According to a variant not shown, the linear actuator 30 comprises an electric motor. The motor can be of the rotative type coupled to the slide 26 by means of a device for converting the rotary motion to linear motion, or an electric linear motor. However the linear actuator 30 is produced, it must always be of the type configured to be controlled by a numeric-control block of the unit 21. Whatever the production mode of the linear actuator 30, it is always numerically driven and controlled in the position of the unit 21.
The grinding assembly 25 then comprises a slide 32, which is coupled to another slide 26 in a vertically sliding manner by means of a guide and slide assembly 33 (Figure 4). The slide 32 is mobile in a direction 34 substantially vertical and orthogonal to the directions 12 and 28 and parallel to the placement plane of the sheet 2 under the thrust of a linear actuator 35 controlled by a numeric-control block 36 of the unit 21. The linear actuator 35 comprises an electric linear motor. Alternatively, the linear actuator 35 comprises a rotary electric motor coupled to the slide 32 by means of an assembly for converting rotary to linear motion.
The slide 32 has a grinding head 37 stably connected to it, in turn, comprising a cylindrical grinding wheel 38. The grinding wheel 38 is fitted to an end portion 39 of a drive shaft 40. It has its own axis 41 orthogonal to the direction 12, parallel to the plane P and orthogonal to the placement plane of the sheet 2 when clamped in packs between the two closed ring conveyor belts of the conveyor 19.
The shaft 40 is coupled to the slide 32 in an axially fixed position and rotates under the thrust of a gear motor device 43. The gear motor device 43 preferably comprises a rotative motor 44 and a belt-drive transmission 45 with a pulley fitted to one end of the shaft opposite to the end 39 on which the grinding wheel 38 is fitted.
Again with reference to Figures 3 and 4, the grinding wheel 38 is surmounted by a section 47 of an abutment 48 that is fixed with respect to the axis 41 and stably connected to the slide 32. The abutment 48 is preferably made of plastic material, or consists of a rigid core covered with a layer of soft material, or portions of soft material, so as not to scratch the sheet 2 and to enable a gentle resting of the sheet 2.
Along direction 12, the section 47 is delimited by two fixed and opposing axial surfaces, indicated with the numbers 50 and 51. The surfaces 50 and 51 are flat surfaces parallel to each other and orthogonal to direction 12. The section 47 is then delimited above by a flat surface 49 orthogonal to the surfaces and parallel to the plane P.
The operation of the machine 1 will now be described with reference to Figures 5 to 13, and starting from the condition shown in Figure 5. In Figure 5, the front end of the sheet 2 has crossed the row 21 of grinding wheels and is being fed on the plane P towards the assembly 25; one slide 26 is arranged in its rearward end-stop position A wherein the axis 41 of the grinding wheel intersects the point A; and another slide 32 is arranged in its lowered end-stop position wherein it holds the surface 49 of the block 48 on a zero plane, indicated with P0.
As soon as the sheet 2 is intercepted by the presence sensor 55 (Figure 5), which is connected to the unit 21 and communicates with the unit 21 itself in a known way, the unit 21, knowing, at this point, the exact position of the surfaces 6 and 8 and, therefore, of the respective edges 9, activates the linear actuator 35 and raises the slide 32 until the surface 49 of the block 48 is brought onto a waiting plane, indicated with PA, and is raised with respect to the plane P by two to five millimetres (Figure 6). The block 48 is held in this position until the sheet 2 abuts against the surface 50 of the block 48, as shown in Figure 7. At this point, the unit 21 activates the actuator 30, which progressively translates the slide 26 in the direction 12 towards its forward end-stop position B so as to hold the sheet 2 against the block 48, i.e. in a condition where the relative speed of the sheet 2 with respect to the block 48 is zero. During the feeding of the slide 26 towards its position B, the unit 21 drives the actuator 35 again, which further raises the block 48 to bring the surface 49 of the block 48 itself to a machining surface indicated by PV. During this last raising of the block 48, the grinding wheel 38 machines the edge 9A, as shown in Figure 8. Once the edge 9A has been ground and before the slide 26 reaches its forward end-stop position B, the unit 21 drives the linear actuator 35 again and returns the surface 49 to the plane P0, as shown in Figure 9. The unit 21 holds the block 48 in this position as long as the sheet 2 has passed through position B, i.e. as long as the edge 9B has moved beyond a vertical placement plane of the surface 51, indicated by K in Figure 10. At the same time, the unit 21 drives the actuator 30 and responds to the slide 26 in its rearward end-stop position A. At this point, the unit 21 drives the actuator 35 by raising the block 48 and bringing the surface 49 to the plane PA, as shown in Figure 11, after which, the unit 21 again drives the actuator 30 and moves the block 48 at a higher speed than that of the sheet 2 until the surface 51 of the block 48 abuts against the surface 6 of the sheet 2 in Figure 12. As before, when the grinding wheel 38 and the sheet 2 translate at the same speed, the unit 21 drives the actuator 35 until its surface is brought onto the plane PV. During this movement, the grinding wheel 38 machines the edge 9B, as shown in Figure 13. Once the grinding is complete, the unit 21 lowers the slide and brings the surface 49 of the block 48 back to the plane PA, translates the slide 26 to its rearward position A and waits for the next sheet 2 to reach the block 48 and then repeats the same positioning and grinding steps described above.
From the above, it is clear that in the machine 1 described, the sheet 2 can be fed at "high" speed along the direction 12 without running the risk of chipping the sheet 2 itself because the first object with which it comes into contact is not the grinding wheel 38 but is an element of plastic material that has a flat resting surface parallel to a front or back surface of the sheet 2.
From a functional point of view, the fact that the linear actuator 35 is electric but, above all, a numerically controlled motor in terms of position and speed enables, first of all, a "fast" raising of the grinding wheel 38 towards the sheet 2 to bring it to the machining position and, then, a second raising at a "slow" speed to carry out the grinding gently and accurately.
The use of the electric linear actuator 35 enables, in addition, the simple setting - directly from the control panel of the unit 21 of the machine 1, or remotely - of the size and/or the geometry of the edge 9 to be machined, without having to intervene manually on mechanical stops or to carry out complicated adjustments on board the machine that stop the production for long periods of time.
Experimentally, it was found that, even with the numerical control of the electric actuator 35 alone, it is possible to obtain high-accuracy edge-machining at high sheet-feeding speeds in direction 12 and thus to increase productivity while maintaining quality.
If the linear actuator 30 is also a numerically controlled electric actuator, it is possible to accurately interpolate the two actuators and move the grinding wheel 38 with respect to the sheet 2 along any grinding path, the circular paths comprised, while maintaining high production and excellent quality.
From the above, it is also clear that the grinding wheel 38 can be flanked by grinding wheels of different abrasive grains and, in particular, polishing wheels. In this case, the shaft 40 is coupled to the slide 32 so as to translate parallel to its axis 41, for example under the thrust of its own dedicated actuator. The considerations made for the grinding wheel 38 apply to any other grinding wheel fitted to the shaft 40.
The fact that the assembly 25 is housed in the same grinding station enables extremely compact rectilinear machines to be obtained that can also be easily inspected because the grinding assembly 25 is placed alongside other grinding wheels and hung from the structure 11 or, in any case, is coupled to the base 10 and, therefore, in a position that is easy to reach both for maintenance and replacement.

Claims

A rectilinear grinding machine (1) for grinding a glass sheet (2), comprising a base (10); feeding means 15 for feeding the sheet (2) to be ground along a longitudinal rectilinear path (12) and in contact with a horizontal virtual plane parallel to said rectilinear path (12), a row of grinding wheels (21) for grinding a lateral surface of said glass sheet, and an assembly (25) for machining an edge (9) of the glass sheet (2) comprising at least one rotary motor-driven grinding wheel (38); said machining assembly (25) being arranged below said virtual plane (P), and said motor-driven grinding wheel (38) being rotated about an axis (41) parallel to said virtual plane (P) and orthogonal to said path (12); characterized in that said machining assembly (25) further comprising a longitudinal abutment element (48) for said glass sheet (2), which is raised with respect to said motor-driven grinding wheel (38), first actuator means (30) for translating said grinding wheel and the abutment element (48) in opposite directions parallel to said rectilinear path (12), and second electric actuator means (35) for translating said grinding wheel (38) and the abutment element (48) in a substantially vertical direction orthogonal to said direction (12) and to said virtual plane (P) ; driving and control means (21) being provided for controlling said first (30) and second actuator means (35) and said means (15) for feeding the glass sheet (2) and comprising at least one numeric-control block for controlling at least said second actuator means (35).
The machine according to Claim 1, characterized in that said first actuator means (30) comprise at least one pneumatic actuator controlled by said driving and control means (21).
The machine according to Claim 1, characterized in that said second actuator means (35) comprise an electric actuator controlled by a further numeric-control block.
The machine according to any one of the preceding claims, characterized in that said abutment element (48) is held in a fixed position with respect to a rotation axis (41) of said grinding wheel (38).
The machine according to any one of the preceding claims, characterized in that said base (10) comprises a rectilinear structure (11) raised with respect to a resting surface of said base (10); said grinding assembly (25) being arranged below, or hanging from, said rectilinear structure (11) .
The machine according to any one of the preceding claims, characterized in that it comprises an intermediate grinding station (20) arranged along said rectilinear path (12), means (16) for input of the sheet (2) to be ground arranged edgeways in said grinding station (20), and means (18) for output of said ground sheet (2) from said grinding station (20); said grinding station (20) housing said row of grinding wheels (21) and said edge-grinding assembly (25).
The machine according to Claim 6, characterized in that said grinding assembly (25) is arranged alongside the last grinding wheel (21) of said row of grinding wheels.
The machine according to any one of the preceding claims, characterized in that said grinding assembly (25) comprises a first slide (26) mobile with respect to said base (10) under the thrust of said first actuator means (30), and a second slide (32) carried by said first slide (26) and is mobile under the thrust of said second actuator means (35) and carries said grinding wheel (38); said abutment (48) element being stably connected to said second slide (32) .