Abstract:
A cross-section of one of the strips in a frame is digitized in binary format by means of a scanner and graphically visualized; dimensions of the cross-section and points suitable for positioning a strip locking device are determined, together with points of application of the stapling elements and the number of the elements to be applied in each point. A frame assembling machine is then activate to perform the actual stapling of the strips.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method for controlling the assembly cycle of a frame assembling machine and to a machine for carrying out the method. 
     Frame assembling machines are known in which the manufacturing cycle is controlled by a system in which the necessary information is entered by an operator by means of an appropriately provided keyboard. This information varies according to the profile of the strips that compose the frame. 
     The information that the operator must enter in the system relate to the height and number of staples to be used for the corner jointing of the strips, to the positions in which the staples are to be inserted, particularly the distance from the outside and inside comers of the frame, and to the position of the means by way of which the frames are fixed to the worktable. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a method which allows to automatically control an assembling machine on the basis of parameters derived from the cross-section of the strips. 
     Within the scope of this aim, an object of the present invention is to provide an apparatus whose characteristics are defined in the appended claims. 
     This aim and this object are achieved with a method for controlling the assembly cycle of strips for forming frames in assembling machines, characterized in that it comprises the steps of: 
     reading, by means of a scanner, the cross-section of one of the strips that compose the frame in order to obtain a resulting image of said cross-section; 
     digitizing the resulting image in binary format; 
     graphically visualizing said cross-section; 
     calculating dimensions of the cross-section; 
     identifying points suitable for positioning strip locking means; 
     determining points of application of stapling elements and the number of said elements to be applied in each point; 
     activating the assembling machine to perform the stapling of the strips. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the method according to the present invention will become better apparent hereinafter on the basis of the accompanying drawings, wherein: 
     FIG. 1 is a schematic and non-limitative exemplifying view of a frame assembling machine which allows to carry out the method according to the present invention; 
     FIG. 2 is a flowchart of the operating sequence of the method; 
     FIGS. 3 and 4 are two flowcharts of two further embodiments of the method. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, the apparatus for performing the method comprises a footing  1  provided with a worktable  2  on which means are provided for arranging strips  3  for forming a frame. In the footing  1 , under the worktable  2 , there are fixed guides  4  for the sliding of a carriage  5  which can be positioned along the guides  4  by means of a reversible motor  6  which is fixed to the footing  1  and whose output shaft  7  is threaded so as to engage by screwing in a shoulder  8  of the carriage  5 . The shaft  7 , turned by the motor  6 , allows to move the carriage  5  in both directions A and B. 
     A conventional stapling head, generally designated by the reference numeral  9 , is rigidly arranged on the carriage  5 . The head  9  comprises a cylinder  10  which has a vertical axis and inside which a piston  12  is movable, said piston having a stem  13  which protrudes upward and ends with a striker punch  14  for expelling the stapling elements, particularly for the corner jointing of two strips that compose the frame. 
     The striker punch  14  is guided in a channel of a head  15  which protrudes from the worktable  2  through a slot which is parallel to the shaft  7 . 
     The elements for joining the strips, typically laminar staples, are contained in a magazine  16  and are conveyed into the channel of the head  15  through a lateral opening of the head. 
     A fluid-actuated actuator  17  is further installed below the worktable  2  and is composed of a cylinder  18  which is fixed below the worktable  2  and in which a piston  19  runs in the direction C. A column-shaped stem  20  is rigidly coupled to the piston  19 , protrudes above the worktable  2  and supports a strip locking device, generally designated by the reference numeral  21 , which is composed of an arm  22  which cantilevers out from the top of the column  20  to which it is fixed and includes guiding means for a pair of sliders  23  and  24 . 
     Two hydraulic jacks  25  and  26  are fitted on the sliders  23  and  24  and their stems  27  and  28  protrude downward below the arm  22  and support respective pads  29  and  30  at their lower end. 
     Respective threaded shafts  31  and  32  are engaged by screwing in the sliders  23  and  24  and can be actuated by a pair of motors  33  and  34  so as to allow the movement of the sliders  23  and  24  along the guides independently of each other. 
     According to the method of the invention, once the profile of the cross-section of the strips  3  has been detected, the motors  33  and  34  are actuated so as to place the pads  29  and  30  in the intended positions for locking the strips  3 . At the same time, the motor  6  is actuated so as to arrange the stapling head  9  on the points where the staples for joining the strips  3  are to be inserted. 
     According to the flowchart of FIG. 2, the method starts by reading, step  35 , the cross-section of the strips that compose the frame. This can occur by means of a scanner which faces a reference “slice” of the strip used. 
     The image obtained by the scanner is processed so as to provide the stapling machine with the necessary operating instructions. 
     This processing comprises the digitizing  36  of the image in binary format (black and white). 
     By using smoothing methods, the elimination  37  of the background noise from the image and the calculation and graphical visualization  38  on an appropriate display of the contour of the cross-section are performed. Such calculation and visualization can use electronic filters based on differentiation processes (gradient) and linear interpolation functions. 
     Depending on the resolution of the image and on the distance of the black and white pixels that define the contour, the calculation  39  of the dimensions of the frame is performed and the type of strip is identified. From the detected dimensions and the type (profile) of the identified strip, identification  40  of the points where the locking pads  29  and  30  are to be placed is performed. 
     The position  41  in which the staples must be driven into the strips and their number is determined depending on the type of stapling provided, i.e., on the characteristics of the staples used, on the sectional dimensions of the strips and on the frame to be provided, and on the engagement positions of the locking pads. 
     The stapling program thus set is sent to the stapling machine  42 , which performs it by initially placing the pads  29  and  30  and actuating them into the position for locking the strips and by then moving the carriage  5  along the guides  4  so that the stapling head  9  is arranged in a staple insertion point. Then, by means of the motor  6 , the head  9  is moved at the other positions for inserting the staples. 
     Conveniently, after determination  41  of the position of the staples and before transfer of the stapling program to the stapling machine  42 , it is possible to perform a verification  43  of the mechanical strength of the stapling according to the type of wood and staples used and a graphical visualization  44  on a display of the set stapling, so that the operator can perform optional variations of the stapling parameters. 
     The described method is susceptible of numerous modifications and variations, all of which are within the scope of the same inventive concept. FIG. 3 illustrates an embodiment in which, after calculation  39  of the dimensions of the frame and identification of the type of strip used, a search is conducted on a database  45  which contains programs for stapling a strip having the same characteristics as the visualized one. If the search leads to a positive decision  46 , the program is loaded  47  and visualized  44 . 
     On the other hand, if the decision  46  is negative, after identification  40  of the locking points, determination  41  of the stapling points and of the number of staples, verification  43  of mechanical strength is performed, with consequent automatic correction  48  of the stapling parameters or with visualization  44  of the stapling. 
     At this point it is possible to perform, or not perform, manual modifications  49  of the parameters of the stapling program. 
     In case of a negative decision regarding modifications, the program  51  is saved as new and transferred  52  to the stapling machine. 
     FIG. 4 illustrates another embodiment in which, if an operator does not wish to make changes  50  to the stapling program before it is saved and sent to the stapling machine, the newness or existence of applied modifications  53  is checked. 
     The disclosures in Italian Patent Application No. BO99A000601 from which this application claims priority are incorporated herein by reference.