Abstract:
An automatic machine for grinding the borders of glass panes, particularly the edges, arranged preferably vertically but applicable to any other arrangement, comprising devices which allow the machining of glass panes, which are notoriously fragile and have an irregularly cut or even contoured perimeter by means of a rigid tool, such as a diamond grinding wheel, by acting simultaneously on the two edges along the perimeter of the pane. In particular, the machine comprises a feeler element and feedback circuits for symmetrically edging the glasspane and, advantageously, for keeping unchanged the perimetric profile of the pane.

Description:
[0001]    The present invention relates to an automatic machine for grinding the borders of glass panes.  
         BACKGROUND OF THE INVENTION  
         [0002]    Methods for grinding (“edging”, in the jargon) the borders of glass panes as they result after they have been cut into the final formats for use are currently known. In principle, the grinding operation can be applied to any step of the working of the glass pane, for example before toughening.  
           [0003]    Edging is performed for two reasons: the first reason relates to safety in handling said panes, the edges of which would be dangerously sharp if they were not ground. The second reason relates to eliminating the border defects of panes, typically so-called microcracks, which may trigger breakage of the pane in subsequent working steps (particularly during toughening) as well as in subsequent use.  
           [0004]    In order to better understand the configuration of the glass pane, not so much in its possible separate use but especially in its use in combination with other components in order to constitute a so-called double-glazing unit, some concepts related to the intermediate component, i.e. the glass pane, and the final product, i.e. the double-glazing unit, are summarized hereafter. The subsequent use of the double-glazing unit, i.e. as a component of doors and windows, is known to the person skilled in the art and is not discussed here in detail.  
           [0005]    With reference to FIG. 1, the double-glazing unit is typically constituted by two or more glass panes  1001 ,  1002 , which are mutually separated by one or more spacer frames  1003 , which are internally hollow and are provided with microperforations on the side directed toward the inside of the unit.  
           [0006]    The spacer frames  1003  usually contain, in their hollow part, hygroscopic material, which is not shown in the figure. The chamber (or chambers)  1006  delimited by the glass panes  1001  and  1002  and by the frame  1003  may contain air or gas or mixtures of gases injected therein, which give the double-glazing unit particular properties, for example thermal insulation and/or soundproofing properties. The glass panes and the frame are mutually joined by means of two levels of seal: the first seal  1004  is adapted to provide a hermetic closure and affects the lateral surfaces of the frame  1003  and the portion adjacent thereto of the glass panes  1001 ,  1002 ; the second seal  1005  affects the compartment constituted by the outer surface of the frame and by the faces of the glass panes up to their borders and is adapted to provide cohesion between the components and to maintain the mechanical strength of the coupling between them.  
           [0007]    [0007]FIG. 1 illustrates five possible sectional views of configurations of the double-glazing unit  1 A,  1 B,  1 C,  1 D,  1 E, only the first of which has been described. However, it is straightforward to extend the considerations made above to the configurations  1 B- 1 E, in which a plurality of frames or of panes are provided, said panes being optionally laminated. In the figure, the sun schematically represents the outside environment of a building in which the double-glazing units are installed, and the inside of the building is represented schematically by a radiator.  
           [0008]    The glass panes used in the composition of the double-glazing unit may have different configurations depending on their use: for example, the outer pane  1001  (with respect to the building) may be normal or reflective in order to limit the input of heat during summer months, or can be laminated/armored ( 1 D) for intrusion/vandalism prevention functions, or can be laminated/toughened (for security functions) or combined, for example reflective and laminated.  
           [0009]    The internal pane  1002  (with respect to the building) may be normal or of the low-emissivity type, in order to limit heat loss during winter months, or laminated/toughened (for security functions) or combined ( 1 E), for example of the low-emissivity type and laminated.  
           [0010]    The brief summary provided above already makes it evident that a production line, in order to obtain the double-glazing unit, requires many operations in sequence and that both the intermediate components (i.e. the glass panes) and the finished product (i.e. the double-glazing unit) have the edges of the glass panes that are accessible for contact with the hands of the operators and users. It is therefore important to increase safety by beveling the peripheral borders of the glass panes. If the finished product, which in any case has a considerable added value with respect to the individual pane, had sharp pane borders or sharp-edged panes, it would be degraded in terms of quality and commercial value.  
           [0011]    The processes for producing the double-glazing unit are typically numerous, and each one requires a corresponding particular machine to be arranged in series with respect to the other complementary ones. Some processes or operations, cited by way of non-limiting example and at the same time not all necessary, are the following:  
           [0012]    REMOVAL, on the peripheral face of the pane, of any coatings in order to allow and maintain over time the bonding of the sealants;  
           [0013]    WASHING of the individual panes, alternating an inner pane with an outer pane (the orientation being the one defined above);  
           [0014]    APPLICATION OF THE SPACER FRAME: the previously manufactured frame, filled with hygroscopic material and coated on its lateral faces with an adhesive sealant, which has a sealing function, is applied to one of the panes that constitute the double-glazing unit in a specifically provided station of the double-glazing unit production line;  
           [0015]    COUPLING AND PRESSING of the assembly constituted by the panes and the frame or frames;  
           [0016]    FILLING WITH GAS of the chamber or chambers thus obtained;  
           [0017]    SECOND SEALING.  
           [0018]    The processes listed above may be performed by the respective machine automatically or semiautomatically, but in any case entail contact of the intermediate components and of the finished products with the operator, for example during loading and unloading of the line and in subsequent steps for storage, transport, assembly and installation of the double-glazing units.  
           [0019]    In known manual processes, the glass panes, rested on supporting surfaces, are placed in contact with belt grinders, which are arranged sequentially and are angularly staggered so as to bevel both edges of the side of the pane (methods of this type are disclosed for example in DE-A 44 19 963). The main drawbacks that arise from the known methods described above relate to the considerable bulk and cost of the machines, to the complex operations for process maintenance (such as replacement of the abrasive belts), the less than optimum quality of the grinding operation, the abnormal behavior of the belt in interaction with the pane when its width does not overlap the pane completely (i.e. at the end of the side of the pane), and finally the excessively long production times.  
           [0020]    EP-A 0 920 954 discloses an apparatus for beveling panes of cut glass that uses two belt grinders.  
         SUMMARY OF THE INVENTION  
         [0021]    The aim of the present invention is to solve the above-noted problems, eliminating all the drawbacks of the known prior art, by providing a machine that allows to grind the borders of glass panes safely and cheaply, obtaining a better qualitative result than the background art.  
           [0022]    Within this aim, an object of the present invention is to automate the grinding operation, minimizing interventions of operators.  
           [0023]    Another object is to avoid altering the structure of the production line by exploiting the modularity that typically characterizes it.  
           [0024]    Another object is to ensure symmetrical beveling of the edges, regardless of the surface irregularity of the border of the pane or panes of laminated glass.  
           [0025]    A further object is to perform grinding in a manner that is substantially independent of the perimetric profile of the glass pane.  
           [0026]    A still further object is to eliminate the surface irregularities that typically characterize the lateral surface of glass panes.  
           [0027]    This aim and these and other objects that will become better apparent hereinafter are achieved by an automatic machine for grinding the borders of substantially flat glass panes, characterized in that it comprises a machine body and at least one machining head, which is suitable to make contact with the borders of the pane and can move along the perimeter of the pane, said at least one machining head comprising a tool body that is movable substantially transversely to the plane of the pane, the tool body comprising an abrasive tool for grinding and at least one feeler element arranged upstream of the machining area of the abrasive tool with respect to the direction of relative advancement of the tool with respect to the pane, so as to make contact with the border of the pane being machined before the abrasive tool, the tool body further comprising sensors suitable to detect a relative movement between the feeler element and the abrasive tool caused by local misalignment between the border of the pane being machined and the abrasive tool, the machine further comprising a controller for receiving feedback signals from the sensors and actuation means that are operated by the controller in response to the feedback signals, in order to regulate the mutual position of the abrasive tool and of the border of the pane being machined.  
           [0028]    Advantageously, the tool body comprises at least two sensors, a first sensor being suitable to detect transverse misalignment of the abrasive tool with respect to the plane of the pane by means of the feeler head and a second sensor being suitable to detect, by means of the feeler head, the tangent relationship of the machining region of the abrasive tool with respect to the pane border being machined.  
           [0029]    Preferably, the feeler head comprises a wheel that substantially has the same profile as the abrasive tool and is rotatably pivoted on a laminar arm, which in turn is pivoted to the tool body. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]    Further characteristics and advantages of the present invention will become better apparent from the following detailed description of particular embodiments of the invention, illustrated merely by way of non-limiting example in the accompanying drawings, wherein:  
         [0031]    [0031]FIG. 1 is a partial sectional view of a plurality of typical configurations of a double-glazing unit;  
         [0032]    [0032]FIG. 2 is a general front view of a machine that incorporates the invention;  
         [0033]    [0033]FIG. 3 is a general side view of the core of the machine that incorporates the invention;  
         [0034]    [0034]FIG. 4 is a general rear view of the machine that incorporates the invention;  
         [0035]    [0035]FIG. 5 a  is a schematic front view of the internal components of the machine according to the invention;  
         [0036]    [0036]FIGS. 5 b  and  5   c  are lateral views, taken respectively along the direction indicated by the arrows A-A and along the direction indicated by the arrows B-B, of the grinding section of the machine according to FIG. 5 a,  in which the washing section has been removed;  
         [0037]    [0037]FIG. 5 d  is a perspective view of the grinding section of FIG. 5 a;    
         [0038]    [0038]FIG. 6 is a perspective view of the upper machining head of the machine according to the invention;  
         [0039]    [0039]FIG. 7 is a perspective view of the tool body of the upper machining head of FIG. 6;  
         [0040]    [0040]FIGS. 8 a  and  8   b  are respectively a front view and a top view of the assembly that comprises the upper machining head;  
         [0041]    [0041]FIG. 9 is a perspective view of a detail of the lower machining head;  
         [0042]    [0042]FIGS. 10 a  and  10   b  are respectively a front view and a top view of the lower machining head of the machine according to the invention;  
         [0043]    [0043]FIGS. 11 a  and  11   b  are views of the mutual arrangement of the grinding wheel and of an individual glass pane, respectively when there is no machining tool position regulation and when said regulation is present;  
         [0044]    [0044]FIGS. 12 a  and  12   b  are views of the mutual arrangement of the grinding wheel and of a laminated glass pane, respectively when there is no machining tool position regulation and when said regulation is present;  
         [0045]    [0045]FIG. 13 is a perspective view of a grinding wheel used in a machine according to a particular embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]    As described earlier, FIG. 1 schematically illustrates the peripheral portion of the double-glazing unit according to an exemplifying series of possible combinations: normal configuration ( 1 A), triple-glazing unit ( 1 B), staggered glass panes ( 1 C), laminated outer pane and low-emissivity inner pane ( 1 D), toughened reflective outer pane and laminated low-emissivity inner pane ( 1 E). The two types of sealant used are illustrated: the butyl sealant  1004 , which has a sealing function (first seal) and is applied between the lateral surfaces of the frame and the glass panes, and the polysulfide or polyurethane or silicone sealant  1005 , which is adapted to provide mechanical strength (second seal) and is applied between the outer surface of the frame and the inner faces of the glass panes up to their border.  
         [0047]    [0047]FIG. 1 shows that, even after the second seal is applied, the double-glazing unit has two outer perimeters that are particularly dangerous due to the sharpness of the edges of the glass panes. It is in fact known that the border of the glass pane obtained by mechanical cutting (scoring with diamond tool and subsequent breaking by localized flexing) has borders that can cut like a sharp blade. It is also known that the border of cut glass panes is never perfectly perpendicular to the plane of the panes but is typically inclined, as shown by way of example in FIGS. 11 a,    11   b,    12   a  and  12   b.    
         [0048]    With reference to the figures, single-digit numerals designate the main units of the machine so as to have an overview thereof, while the constructive mechanisms and details are designated by three-digit numerals, the first digit of which being the digit of the main unit to which they belong.  
         [0049]    The reference numeral  1  designates the “single” glass pane, in which the sides being machined (in the case of two machining heads) are respectively the front side  1   a,  the longitudinal sides  1   b  and  1   c  (which are machined simultaneously), and the rear side  1   d.    
         [0050]    With reference to FIG. 2, the machine according to the preferred embodiment comprises a main body  2 , which is cascade-connected between two conveyors  6   a  and  6   b,  which are arranged respectively upstream and downstream of the machine body  2 . The machine body  2  comprises a grinding or beveling section  7   a  and preferably a washing section  7   b  in order to clean the glass panes after grinding.  
         [0051]    For safety reasons, the sections of the machine body can be delimited by protective barriers  8 , shown by way of example in FIG. 2, which can comprise the enclosure itself of the machine. As an alternative, the barriers may be of an optical (or laser) type or can comprise electrically sensitive mats. Such barriers allow to prevent injuries caused by reckless access to the inside of the machine on the part of an operator.  
         [0052]    With reference to FIG. 3, at the rear of the machine an electrical/electronic panel  9  is provided for managing the operating steps of said machine, which are described hereinafter. An optional control post  10  is connected to the machine in order to change process parameters manually.  
         [0053]    The optional washing station  7   b  comprises a hydraulic pump  701 , which draws water from a recirculation tank  702 , in order to direct a stream of water toward the washing nozzles of the section  7   b  and/or toward the grinding tools of the section  7   a,  so as to clean the pane and cool the machining area of the tools.  
         [0054]    With reference to FIGS. 5 a,    5   b  and  5   c,  the grinding section  7   a  comprises a lower machining head  3 , an upper machining head  4 , and a set of vertical traction rollers  5 ; said set comprises two pairs of front rollers  504   a,    504   b  and two pairs of rear rollers  502   a,    502   b,  respectively upstream and downstream of the section of the machine in which the machining heads work.  
         [0055]    When the term “vertical” is used hereinafter with reference to the machine, an orientation is intended which is slightly inclined with respect to the direction that is perpendicular to the surface on which the machine rests. The pane is in fact typically carried on conveyors, the supporting surface of which is inclined by approximately 6 degrees with respect to the true vertical plane. Accordingly, the lower conveyance rollers provided on said conveyors (for example the conveyors  6   a  and  6   b ) also have an axis that is inclined by about 6 degrees with respect to the horizontal axis.  
         [0056]    With reference to FIG. 5 a,  the machine according to one embodiment of the invention comprises the input conveyor  6   a,  the grinding section  7   a,  the output conveyor  6   b,  which are arranged sequentially. The optional washing section  7   b  is comprised between the grinding section  7   a  and the output conveyor  6   b.    
         [0057]    The input conveyor  6   a  can be connected to, or is comprised in, an upstream machining section, for example the section for cutting the glass into panes. As an alternative, the glass pane to be beveled can also be loaded manually onto the input conveyor independently of the production line.  
         [0058]    The output conveyor  6   b  can instead be connected to, or is comprised in, a downstream machining section, for example the section where manufacturing of double-glazing units is provided. Both conveyors, as well as the central machine body, keep the pane at an inclination of approximately 6 degrees with respect to the vertical; however, for the sake of clarity, the view of FIG. 5 a  is taken along an axis that is perpendicular to the plane of the pane being machined, and the views of FIGS. 5 b  and  5   c  are likewise taken from the viewpoint of the front of the pane being machined.  
         [0059]    The input conveyor  6   a  comprises a base  603  for supporting the lower border of the glass pane, on which a series of supporting and conveyance rollers  602  is arranged. The conveyor further comprises a supporting surface  601 , on which the glass pane is rested in a substantially vertical position in the sense described above.  
         [0060]    The conveyors are widely known and therefore are not described here in detail. It is therefore straightforward to understand that the output conveyor  6   b  is substantially similar to the input conveyor.  
         [0061]    The input conveyor preferably comprises a thickness detector  203  of a known type for measuring the thickness of the glass pane to be machined before it enters the grinding section  7   a  and for producing an initial centering signal of the machining tools with respect to the border of the glass pane.  
         [0062]    The grinding section  7   a  internally comprises a series of free rollers  501   a  and  501   b  for supporting the base of the glass panes during machining.  
         [0063]    As mentioned above, the section  7   a  further comprises a first pair  504   a  of consecutive input traction rollers, which face a second pair  502   a  of consecutive input traction rollers; said rollers are arranged vertically so that a glass pane that enters the machine body is accommodated and retained between the first and second pairs of rollers.  
         [0064]    In output from the grinding section there are two other pairs  504   b  and  502   b  of vertical rollers, which are fully similar respectively to the vertical input rollers  504   a  and  502   a  both from the structural and the operating standpoint, as described hereinafter.  
         [0065]    In FIG. 5 b,  the vertical input rollers, as well as all the components that actuate them, are hidden, since FIG. 5 b  is a view of the machine body taken from the viewpoint indicated by the arrows A-A.  
         [0066]    The input components are designated by the letter “a” at the end of the corresponding reference numeral, and the letter “b” designates the output components, which have substantially the same structural and functional characteristics.  
         [0067]    With reference to FIGS. 5 b  and  5   d,  the rollers  504   a,    504   b  can slide in a transverse direction on respective guides  505   a,    505   b  and can move by means of an actuation system of the screw-and-nut type  506   a,    506   b,  which is actuated by pulleys  507   a,    507   b  and by a respective belt  508   a,    508   b.  The belt closes onto a pneumatic through rod cylinder  509   a,    509   b,  in order to move said belt as a consequence of appropriate commands of the controller of the machine, actuated by means of an electric valve.  
         [0068]    In particular, the movement of the sliding vertical rollers  504   a  and  504   b  away from the fixed rollers  502   a  and  502   b  caused by the action of the cylinders  509   a,    509   b,  respectively, is controlled by the controller of the machine and by means of known transit sensors (not shown in the figure), which are mounted on the machine directly upstream of the vertical input and/or output rollers and are adapted to produce an activation signal toward the controller as soon as the forward edge  1   a  of the glass pane passes beyond them.  
         [0069]    The grinding section  7   a  further comprises a motor  510 , which is connected by means of a reduction unit  511  to a transmission mechanism that comprises a belt  512  and a pinion  513 , by means of which the vertical input rollers are made to rotate in order to produce the advancement of the glass pane. The motor  510  is also connected to the controller of the machine so as to actuate the vertical rollers in response to a command of the controller.  
         [0070]    The machine preferably comprises similar (if not the same) mechanisms for moving the vertical output traction rollers.  
         [0071]    The glass pane  1  that arrives from the previous treatment machine (or that is loaded manually or by means of a loading unit onto the input conveyor  6   a  of the machine) is made to advance, carried by the supporting and conveyance rollers  602  of the conveyor  6   a  and by the supporting rollers  501   a  of the grinding section  7   a,  until it makes contact with the first rear vertical traction roller  502   a.  When the transit sensor is activated, the front vertical traction rollers  504   a  adapt their distance from the opposite rear rollers  502   a  according to the thickness of the glass pane  1  and produce a mutual force against the rear rollers  502   a.    
         [0072]    The mutually opposite forces that act against the glass pane  1  are proportional to the force applied by the pneumatic cylinder  509   a  that acts on the belt  508   a,  the pressure of which is indeed adjusted by the controller of the machine according to the reading of the thickness of the pane  1  or to the kind of the pane.  
         [0073]    According to the mechanism described above, the glass pane is thus conveyed to the section where the machining heads  3  and  4  described hereinafter are active. Once the machining heads  3  and  4  have been passed, the other pairs of rollers  502   b,    504   b  interact with the glass pane  1  by means of similar mechanisms  505   b,    506   b,    507   b,    508   b  and  509   b,  which are not described in detail here because they are substantially identical to the mechanisms described above. In this manner, the glass pane has a valid support provided by the series of horizontal rollers  602 ,  501   a,    501   b  and a coordinated and synchronized traction produced by the rear vertical rollers  502   a  and  502   b  and front vertical rollers  504   a  and  504   b.  Said control of the position of the glass pane  1  is important for the correct operation of the process performed by the machining heads  3  and  4 , as it will become apparent from the continuation of this description, and if the glass panes to be machined are non-rectangular, it is important also for the coordination of the horizontal movement of the glass pane and of the vertical movement of the machining head  4 , required in order to ensure that the grinding tool is always mated with the perimeter of the non-rectangular glass pane  1 .  
         [0074]    Once the vertical border  1   a  of the glass pane  1 , synchronized thanks to the actuation of the above cited vertical rollers, arrives at the machining head  4 , the traction movement of the rollers is stopped (due to the action of other transit sensors, which are not shown).  
         [0075]    With reference to FIGS. 6 and 7, the machining head  4  comprises an abrasive tool  401 , typically in the form of a diamond grinding wheel with a V-shaped profile, by means of which edging is performed on both of the perimetric edges of the glass pane  1 . The grinding wheel  401  is connected to a coaxial motor  402 , which provides it with a rotary motion.  
         [0076]    The machining head  4  comprises a first supporting frame  431 , on which a motor  408 , for moving the tool substantially transversely to the plane of the glass pane, and a motor  419 , for rotating the tool body  400  about an axis that is substantially perpendicular to the plane of the glass pane, are mounted.  
         [0077]    The supporting frame  431  is connected to a ballscrew  403 , which in turn is connected, by means of a reduction unit  405 , to a motor  404  mounted on the machine body  2 , for movement in the vertical direction (in the sense described above) of the movable machining head  4 . The vertical movement is guided by means of the sliding of ballscrew sliders  406   a,    406   b,    406   c,    406   d  provided on the frame  431  along guides  433  appropriately provided on the rear part of the machine body  2 .  
         [0078]    A second frame  432  is mounted on the supporting frame  431 , can slide substantially at right angles to the plane of the glass pane, and comprises sliders  436   a,    436   b,    436   c  and  436   d  for sliding on respective guides (for example the guide  437 ) provided on the supporting frame  431 . The second frame  432  is connected to the motor  408  by means of a ballscrew  407  and a reduction unit  409 , so that the sliding of the frame  432  with respect to the supporting frame  431  is actuated by the motor  408 .  
         [0079]    A rotating turret  418  is further mounted on the second frame  432  and is connected to the motor  419  by means of a reduction unit  420 , a pinion  421  and a ring  422 . The motor  402  and the tool  401  are mounted on the rotating turret  418  so as to allow the rotation of the tool body  400  about an axis that is perpendicular to the plane of the glass pane.  
         [0080]    The tool body  400  further comprises a feeler element or probe  410 , which is mounted on a laminar arm  411 , which in turn is pivoted to the tool unit by means of a pivot  412  and is further connected to the tool unit by means of a piston  423 . The feeler head is preferably a wheel that substantially reproduces the same shape and thickness as the grinder  401  although having a smaller diameter than that of the grinder.  
         [0081]    Therefore, the feeler head  410  preferably has the same profile as the grinder  401 , i.e. it has a biconical profile (as shown in the figures).  
         [0082]    The piston  423 , connected to the controller of the machine, is used substantially to keep the feeler head  410  pressed against the edges of the glass pane being machined, as described hereinafter.  
         [0083]    The flexibility of the lamina  411  allows to have mobility thereof substantially at right angles to the plane of the glass pane, while the pivot  412  allows a partial rotation of the lamina  411 . In this manner, the feeler element  410  can move both due to the rotation about the pivot  412 , and therefore on a plane that is parallel to the glass pane  1 , and due to the flexibility of the lamina  411  itself, and therefore at right angles to the glass pane  1 .  
         [0084]    In order to detect the movement of the probe  410  substantially transversely to the plane of the glass pane  1 , the lamina  411  is coupled by means of a sensor  414  with a corresponding plate  414 ′ to the fixed part of the machining head  4 , which is rigidly coupled to the turret  418 . Advantageously, a second sensor  413  with a corresponding plate  413 ′ is provided between the lamina  411  and the tool body  400 , so as to detect the rotation of the lamina  411  with respect to the inactive or zero position.  
         [0085]    The sensors  413 - 413 ′ and  414 - 414 ′ are connected to the controller of the machine in order to continuously transmit the displacement of the position of the feeler element  410  with respect to the inactive or zero position during grinding, in order to adjust the mutual position of the tool  401  with respect to the border of the pane  1  being machined.  
         [0086]    With reference to FIGS. 7 and 8 b,  the machining head  4  comprises advantageously a support for adjusting the inclination of the tool  401  with respect to the plane of the glass pane. In particular, it is preferred to adjust this inclination so as to form linear contacts instead of point-like contacts between the tool  401  (of the biconical or pseudo-biconical type) and the borders of the glass pane, with a consequent improved cutting action of the tool and reduced tool wear. Tool adjustment is performed for example by interaction between screws  416  and slots  417  with reference to the axis  415  shown in FIG. 7.  
         [0087]    The main components of the upper machining head  4  are also provided in the lower machining head  3  of the machine. In particular, with reference to FIGS. 9, 10 a  and  10   b  the machining head  3  comprises a tool  301 , which is actuated by a coaxial motor, and a feeler head or probe  310 . The tool body composed of these three elements is mounted on a fixed plane  318 , which is fixed at the footing of the machine or, in an alternative embodiment, is mounted on a lifting device that is similar to the one provided for the movement of the upper machining head  4  in a vertical direction (FIGS. 10 a  and  10   b ). In this second case, the lifting device is used to allow complete machining on the part of the machining head  4  on the sides  1   a  and  1   d  of the pane.  
         [0088]    The probe  310  is preferably a wheel, which is mounted on a flexible lamina  311 , which in turn is pivoted to the support  318  along an axis  312 . The rotation of the lamina about the axis  312  and its movement substantially transversely to the plane of the glass pane are detected by suitable sensor-plate pairs  314 - 314 ′ and  313 - 313 ′.  
         [0089]    While the fixed lower machining head  3  works with the side  1   b  of the glass pane  1 , the movable upper machining head  4  works in progression with the sides  1   a,    1   c  and  1   d  of the glass pane  1  and therefore with a continuous change of the active quadrant of said head. For this reason, in the case of substantially rectangular glass panes, the turret is actuated so as to perform finite phase rotations through 90°, while in the case of contoured glass panes the turret is moved continuously by means of the actuation of the motor  419 , which therefore operates in synchronous tie with the drives of the motors  404  and  510 , which in turn are mutually in synchronous tie.  
         [0090]    The machine body  7   a,  the internal tools  301  and  401  of which work in a water stream, is adjacent to the nearby post-washing section  7   b,  which removes, by means of sprayers, the abrasive particles and the glass particles from the panes  1 . The water stream is directed to the tools  301 ,  401  and to the washing section  7   b,  and is obtained by means of the pump  701 , which draws water from the recirculation tank  702  and sends it through the filter  703  to the spray nozzles  704 . This last washing system belongs to the background art.  
         [0091]    The operation of the machine is as follows. The grinding step begins as soon as the front border  1   a  of the glass pane is moved at the machining heads  3  and  4 .  
         [0092]    The feeler at least partially makes contact with the border  1   a  of the glass pane  1 , for example at the edge formed by the sides  1   a  and  1   b.  The shape of the feeler produces a movement of the lamina  411 , which is detected at least by the sensor  414 , if the border of the glass pane is not completely included within the groove of the wheel of the feeler.  
         [0093]    Depending on the signal detected by the sensor  414  and optionally by the sensor  413 , the controller of the machine (not shown in the figures), operates the axial movement of the tool in a direction that is substantially perpendicular to the plane of the glass pane by means of the motor  408 .  
         [0094]    At this point, the machining head is moved in a vertical direction by means of the controller and the motor  404 , so as to perform grinding along the entire side  1   a  of the glass pane. Grinding occurs advantageously symmetrically on both edges of the border  1   a,  as shown in FIGS. 11 b  and  12   b,  since the feeler tends to adapt to the border of the pane, slipping perpendicularly to the plane of the pane due to the pressure applied by the piston  423  so that both edges of the border of the pane are in contact with the internal surface of the feeler head. This advantageously avoids the asymmetric beveling effect that would occur if the groove of the tool were perfectly centered with respect to the centerline of the border of the glass pane, as shown in FIGS. 11 a  and  12   a.    
         [0095]    The displacement signals of the lamina  411  are continuously detected and fed back to the motor  408  by means of the PID controller of the machine, so as to follow any less than perfect flatness of the pane.  
         [0096]    Moreover, the signals of the sensor  413 , by means of the PID control system, provide feedback to the motor  510 , repositioning the pane so that even if its vertical side  1   a  or  1   d  is not perfectly perpendicular with respect to the base  1   b  of the pane, its point of contact with the grinder  401  is instantaneously located in the position of the vertical line that passes through the tangent with respect to the grinder.  
         [0097]    For example, the movements about the axis of the pivot  412  indicate a profile of the pane that is not perfectly rectangular but is for example trapezoidal. Accordingly, the feedback toward the motor  510  is useful in order to produce (i) the further advancement of the pane through the vertical rollers  502   a  and  504   a  if the angle between the sides  1   a  and  1   b  is acute, and (ii) the backward movement of the pane if said angle is obtuse, thus keeping unchanged the perimetric profile of the pane.  
         [0098]    Likewise, the feedback of the signal sent by the feeler toward the motor  408  allows to move the tool  401  in a direction that is perpendicular to the plane of the pane  1 , as described above.  
         [0099]    As it is known, PID control allows optimum regulation of the process, since if x is the displacement of the value to be controlled (in the specific case, the distance between the sensor, for example,  413  and the plate  413 ′) that one wishes to return to the set value (in the specific case, zero), the motorized actuation means that restore the set situation act with a power that is proportional to:  
         [0100]    the linear value x (displacement),  
         [0101]    its derivative over time (speed),  
         [0102]    its integral over time, allowing to attenuate the minimal off-sets that were not eliminated completely with the two preceding actions.  
         [0103]    Moreover, the proportionality bands can be set to appropriate ranges.  
         [0104]    This control system can be provided with the functions made available by the programmable logic of the controller, advantageously of the PLC type, and is particularly necessary in order to avoid instability, resonance, vibration and drift phenomena that tend to be triggered autonomously if the contact between the abrasive tool and the glass pane combined with the cutting and feeding motions of the tool  301 ,  401  itself is not properly and dynamically controlled in terms of physical value.  
         [0105]    The description provided above refers to a grinding machine in which the source machine (edging machine) is arranged to the left and the destination machine (washer) is arranged to the right of said grinding machine; it is easy to imagine a description and corresponding figures in the case of mirror-symmetrical or otherwise different arrangements.  
         [0106]    All the movements related to the steps of the cycle are of course mutually interlocked, by virtue of a parallel but always active logic system, in order to avoid, during the process, conditions of mutual interference between the actuation elements, the tools and the material being machined.  
         [0107]    It is evident that the industrial application is a sure success, since machines for edging glass are currently not widely used. Moreover, the double-glazing unit market is growing continuously, since in recent years it has been increased by all those configurations that require the use of special glass panes such as the ones described in the introduction (and particularly toughened glass panes, which require arrissing as a preparatory step for toughening) and therefore border beveling is a very important added value that qualifies the product. Moreover, the spread of non-rectangular shapes, for example polygonal or curved or mixed shapes, further enhances the importance of the present invention, in contrast with the limitation of conventional machines, which can work only on rectangular shapes.  
         [0108]    Moreover, one sector that is growing every day and also requires grinding of the edges and of the entire perimetric borders of glass panes  1  is constituted by glass toughening. For this application, the machine can assume either a vertical position or a horizontal position.  
         [0109]    It has thus been shown that the machine according to the invention achieves the intended aim and objects. The invention is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Thus, for example, the mechanical solutions for the motions for feeding the tools, for supporting and moving the glass pane, and the actuation means may be electrical, electrical-electronic, pneumatic, hydraulic and/or combined, and the control means may be electronic or fluidic and/or combined means.  
         [0110]    Another embodiment of the invention is constituted by the logic combination of the actuations respectively for translational motion of the glass pane, for movement of the machining heads and for synchronization of the inclination of the tool so as to allow machining of shaped glass panes, i.e., non-rectangular glass panes. To achieve this, as described previously, the electronic actuation systems of the three motors  404 ,  510  and  419  are concatenated by means of a synchronous tie with numeric control.  
         [0111]    The tools  301  and  401  may also have a shape (other than biconical) or be distributed in such a quantity so as to act not only on the edges of the glass pane but also on the entire face of the perimeter in order to grind not only the sharp edges but also the flat strip region between them, so as to eliminate defects, dust, contamination, et cetera. For example, the diamond grinder may have a profile that is different from the V-shaped or biconical one. In particular, it is straightforward to understand that if a cylindrical grinder is used, the same machine described so far can perform grinding operations on the profile of said pane in order to eliminate any defects or microcracks produced by the previous cutting operation to which said pane has been subjected.  
         [0112]    The tool body may of course mount interchangeable tools for this purpose. The grinder may have a profile that comprises two adjacent sections, the first section  801  having a frustum or V-shaped profile and the second section  802  having a cylindrical shape, as shown in FIG. 13. In this case, it is possible to bevel the edges of the borders and to grind the surface comprised between said edges simply by moving transversely the grinder with respect to the pane  1  so as to use the portion having the V-shaped profile or having the cylindrical profile, respectively.  
         [0113]    Moreover, in the light of the above description it is straightforward to understand that by using cylindrical grinders in the grinding operations it is possible to bevel the edges that connect the two sides of the pane.  
         [0114]    The constructive details may be replaced with other technically equivalent ones. The materials and the dimensions may be any according to requirements, in particular as derived from the dimensions (base and height) of the glass panes  1 .  
         [0115]    The disclosures in Italian Patent Application No. TV2003A000091 from which this application claims priority are incorporated herein by reference.