Abstract:
A method and machine whereby a sheet of glass, held on a table of the machine, is first scored to form at least one score line, and is then broken along the score line by transmitting vibratory action to the sheet, about the score line.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit under 35 U.S.C. §119(a) of Italian Patent Application No. TO2008A 000497 filed Jun. 25, 2008, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of breaking sheet glass. 
         [0004]    2. Description of Related Art 
         [0005]    To break sheet glass, the sheet is first scored and then broken along the score line by applying pressure to curve the sheet locally along the score line. Pressure is exerted mechanically using break wheels forced against the sheet and rolled along the score line, or using break bars forced gradually onto the sheet. 
         [0006]    The above break methods provide for breaking sheets of various sizes, but does not guarantee the same quality in terms of surface finish or consistent shape, regardless of sheet thickness. 
         [0007]    That is, the above method necessarily involves mechanical deformation of the sheet and so produces stress in the glass, thus resulting in products with jagged edges or splinters. In some cases, the break may be out of square with the wide faces of the sheet and so require machining. 
         [0008]    In many cases, therefore, the broken sheets cannot be salvaged and must be rejected, thus resulting in production losses and unacceptably high end costs. 
         [0009]    Moreover, sheets of over six-eight millimetres in thickness call for considerable pressure, which means difficulty in controlling the break process and, above all, using special-purpose and, in particular, reinforced supporting structures and components to ensure the necessary dimensional stability. 
         [0010]    Finally, the above break method makes painstaking work of producing small-size pieces, and makes it extremely difficult to break the sheet along score lines close to the edge of the sheet. 
       SUMMARY OF THE INVENTION 
       [0011]    It is an object of the present invention to provide a method of breaking sheet glass along predetermined lines, designed to provide a straightforward, low-cost solution to the above problems. 
         [0012]    According to the present invention, there is provided a method of breaking sheet glass, the method comprising the steps of forming at least one score line on the sheet of glass, and breaking the sheet of glass along said score line; and being characterized in that said breaking comprises the step of stressing said sheet of glass by vibratory breaking action. 
         [0013]    The present invention also relates to a machine for breaking sheet glass. 
         [0014]    According to the present invention, there is provided a machine for breaking sheet glass, as claimed in the attached claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    A non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: 
           [0016]      FIG. 1  shows, schematically and substantially in block form, a machine for scoring and breaking sheet glass in accordance with the teachings of the present invention; 
           [0017]      FIGS. 2 to 5  show larger-scale details of the  FIG. 1  machine; 
           [0018]      FIG. 6  shows a variation of a detail in  FIGS. 4 and 5 ; 
           [0019]      FIG. 7  shows a variation of a detail in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Number  1  in  FIG. 1  indicates as a whole a machine for breaking a sheet  2  of glass along predetermined lines. 
         [0021]    Machine  1  comprises a frame  3 ; and a supporting structure  4  fitted to frame  3  and for supporting and retaining the work sheet  2  substantially horizontally. In the example described, structure  4  defines a table  5 , on which the sheet rests directly, as on conventional score and/or break tables, or with the interposition of elastomeric structures comprising spot or elongated projections distributed over table  5  to respectively form a spot mesh and a grille indicated as a whole by  6 . Alternatively, sheet  2  is retained by grippers connected to supporting structure  4  and engaging one or more edges of sheet  2  to retain sheet  2  in a break position, in which sheet  2  is at least partly raised off table  5  or at least partly forced against table  5 . 
         [0022]    Machine  1  also comprises a known powered cutting bridge  8  fitted in known manner to structure  4  to move back and forth longitudinally, and which is fitted integrally with a slideway  9  parallel to table  5  and along which a known powered carriage  10  slides axially back and forth. 
         [0023]    Carriage  10  supports a known score wheel  12  for forming a score line L on sheet  2 , and which is moved with respect to carriage  10  to and from sheet  2  by a linear actuator  13 ; and a break wheel  14  separate from and independent of score wheel  12 . 
         [0024]    Break wheel  14  is located in tandem with, i.e. behind or in front of, score wheel  12 , as shown in  FIGS. 1 and 3 , is fitted in sliding manner to carriage  10 , and is moved, independently of score wheel  12 , to and from table  5  and, hence, sheet  2  by a respective known linear actuator  15 . When positioned contacting sheet  2 , break wheel  14  is located at or over score line L, as shown in  FIG. 4 , or to one side of a plane P perpendicular to sheet  2  and through score line L, as shown in  FIG. 5 . 
         [0025]    Alternatively, in the  FIG. 6  variation, break wheel  14  is replaced by two coaxial, side by side break wheels  16 , which are positioned, in use, astride score line L and contacting intermediate portions of sheet  2  on opposite sides of plane P. 
         [0026]    In all the solutions described, a vibrating, e.g. electromagnetic vibrating, device  18  is located between carriage  10  and break wheel/s  14 ,  16 , to produce a pulsating or oscillating vibratory movement of break wheel/s  14 ,  16  with respect to sheet  2 , and with a law of motion, e.g. sinusoidal, pulsating or trapezoidal, that varies according to the characteristics and material of the sheets. 
         [0027]    In actual use, score line L is formed in known manner in sheet  2  by score wheel  12 . Once the sheet is scored, break wheel/s  14 ,  16  are moved onto sheet  2 , and vibrating device  18  is immediately activated to transmit vibratory breaking action to sheet  2  and in particular to the area of sheet  2  in which score line L is formed. If a single break wheel  14  is used, vibratory breaking action is exerted directly on or at score line L, as shown in  FIG. 4 , or on an area of sheet  2  alongside score line L and to one side of plane P, as shown in  FIG. 5 . If two break wheels  16  are used, vibratory breaking action is exerted simultaneously on both sides of plane P. 
         [0028]    Whatever the break wheel type or arrangement with respect to score line L, as the break wheel/s  14 ,  16  move along, vibratory action is transmitted to sheet  2  to gradually and simultaneously break sheet  2  along score line L. 
         [0029]    To achieve all-round scoring and breaking performance of machine  1 , i.e. to enable it to score and break sheets of any shape and thickness, device  18  also comprises an adjusting and/or calibrating module  20  which, given the geometry of the work sheet  2  and the pieces to be cut, and/or the constraints of sheet  2  on structure  4 , i.e. the way in which sheet  2  is supported on machine  1 , enables a specific vibratory action to be selected from a number of vibratory actions stored in a memory block  21  of device  18 . A further block  22  of device  18  provides for further modifying the selected vibratory action by modifying one or more parameters or characteristics, such as frequency, conveniently within a range of 5 to 3000 Hz. 
         [0030]    In a different operating mode, as score wheel  12  moves along, break wheel/s  14 ,  16  are lowered and vibrating device  18  is activated to break sheet  2  at the same time, or just after, the score line is formed. 
         [0031]    In the  FIG. 7  variation, machine  1 , shown partly, has no break wheels  14 ,  16 , and sheet  2  is broken using score wheel  12  itself. Accordingly, vibrating device  18 , formerly interposed between carriage  10  and break wheels  14 ,  16 , is now interposed between score wheel  12  and carriage  10 , so that vibratory breaking action is transmitted to sheet  2  by score wheel  12  and therefore simultaneously with the formation of score line L. 
         [0032]    In another variation, not shown, as opposed to being fitted to carriage  10 , break wheel/s  14 ,  16  together with actuators  15  and vibrating device  18  are fitted to a similar carriage, that also runs along a slideway parallel to the guide  9  and fitted to a bridge, in turn fitted to structure  4 , but underneath table  5 . The wheels underneath table  5 , and therefore sheet  2 , break the sheet in the same way as described above, but by transmitting vibratory action to the opposite face of the sheet to that in which score line L is formed. 
         [0033]    Machine  1  described therefore provides, on the one hand, for greatly reducing sheet breaking time and, on the other, for automatically cutting pieces of any shape and size, and particularly curved pieces, all of the same quality in terms of surface finish and consistent shape, regardless of the thickness and size of the work sheet and/or the pieces to be cut. 
         [0034]    This is substantially due to subjecting the work sheet to continuous or pulsating vibratory action, i.e. of a given frequency and amplitude, that breaks the sheet along the area weakened by the score line or an instantaneous break initiator, as in the case of simultaneous scoring-breaking. 
         [0035]    This is mainly due to the vibratory action transmitted to the sheet eliminating or drastically reducing flexing of the sheet—currently the basis of all known break methods—and so drastically reducing stress in the sheet, so that the break method is easily controllable. Moreover, by eliminating mechanical flexing, the structure of the machine is greatly simplified as compared with known solutions. 
         [0036]    From the operating standpoint, using vibratory action as a break “tool”, pieces of any, and in particular small, size can be produced, and, above all, the sheet can be broken easily even along score lines close to the edge of the work sheet. 
         [0037]    Clearly, changes may be made to the break method and machine  1  as described herein without, however, departing from the scope defined in the accompanying Claims. 
         [0038]    In particular, the vibratory stress transmitted to the work sheet, and the way in which the work sheet is supported on the machine, at least at the break stage, may differ from those described by way of example. That is, when transmitting vibratory action to the sheet, the sheet may be maintained at least partly raised off the table, or at least a portion of the sheet may be pushed against the table, e.g. by means of grippers or straightforward pushers or linear actuators. 
         [0039]    Finally, the machine described may have no score wheel, and only comprise the break wheel or other equivalent break member, such as a break bar, associated with the vibrating device to break sheets scored beforehand at a separate or adjacent scoring station. 
         [0040]    Clearly, the break method described of transmitting vibratory action to the sheet may also be implemented on vertical break machines, on which the work sheet is positioned substantially on edge, or even on twin-bridge machines for scoring and/or simply breaking multilayer sheets, i.e. sheets comprising two lateral sheets of glass with a sheet of synthetic material in between. In which case, the break method described is applied simultaneously or successively to each of the two lateral sheets of glass.