Abstract:
The invention relates to a method for production of panels for floor, wall or ceiling coverings, with the panels being cut from a large starting sheet and provided on their long sides ( 11, 12 ) with locking strips ( 15, 16 ). The starting sheet is hereby provided with parallel grooves ( 4, 5 ) along the topside and underside thereof, with the upper groove ( 4 ) and the lower groove ( 5 ) extending in the sheet plane (PE) at an offset in relation to one another at a distance (a), thereby forming a breaking web ( 6 ). The starting sheet ( 1 ) is then divided along the breaking web ( 6 ) such that projecting longitudinal strips remain along the long sides ( 11, 12 ) and are used for shaping the locking strips ( 15, 16 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method for production of panels for floors, wall or ceiling coverings. 
     Heretofore, coverings in the form of panels with various surface coatings as well as different décor and geometric configuration are oftentimes used as floor covering as well as wall or ceiling paneling. 
     Laminate floorings are widely used for example. A laminate floor panel includes a panel sheet of fiber material, mostly of highly compacted fiber board or fiber board of average compaction, with a decorative paper impregnated with resin being applied on its topside. The decorative paper is determinative for the look of the panel. The so-called overlay or the sealing forms a useful layer made of varnish and impregnated with special resin to thereby impart the floor panels the ability to withstand great surface strain. Applied to the underside of the panel sheet is a so-called counteracting layer which provides stable shape and a moisture barrier. Optionally, an impact sound insulation may further be provided on the underside. 
     The production of laminate floor panels as well as of panels for wall or ceiling paneling is realized by way of a continuous run-through process which applies on a large starting sheet of highly compacted fiber material or fiber material of average compaction the multiply layer structure with decorative paper, sealing as well as counteracting layer. Subsequently, the sheet is subdivided into panels. Thereafter, the edges of the panels are profiled to establish locking strips on their long sides and end sides. The locking strips are predominantly configured as groove and tongue on the confronting marginal sides of a panel. When the covering has been installed, the locking strips of neighboring panels engage one another. 
     Cutting the panels to size from the large starting sheet is implemented by a sawing cut. Thereafter, the edges are finished and profiled, as mentioned, to form the locking strips. The saw cut and the profiling works cause necessarily loss of material. Therefore, it is desired to streamline and optimize the production process. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object to provide a more efficient method of making panels, which saves material and is cost-efficient. 
     This object is solved according to the invention by a method for production of panels for floors, wall or ceiling coverings, with the panels being cut to size from a large starting sheet and provided with locking strips on their long sides, wherein the starting sheet is provided on its topside and on its underside with parallel grooves, with the upper groove and the lower groove extending at offset relationship in the sheet plane and with the starting sheet being divided so that projecting longitudinal strips remain along the long sides which are used for formation of the locking strips. 
     An essential feature of the invention is the measure to provide the starting sheet on its topside with an upper groove and on its underside with at least one lower groove, with the upper groove and the lower groove extending in parallel offset relationship. The starting sheet is then divided. As a result of the cut pattern of the groove, projecting longitudinal strips remain along the long sides and can be used for formation of the locking strips. 
     As the partition is implemented in a manner that the required cuts in the form of grooves are carried out in the regions which are trimmed when shaping the locking strips, waste caused by cutting is minimized when dividing the starting sheet. The need for a continuous saw cut is eliminated in accordance with the invention. As a consequence, the otherwise typical material loss, which is commensurate to at least the width of saw blade, can be omitted during each dividing step in length direction of the starting sheet. Overall, the process according to the invention results in a better utilization of the starting sheet by up to 8% depending on the panel width and profile of the locking strips. 
     The offset between the upper groove and the lower groove may basically correspond to the width of a saw blade so that the grooves meet on confronting cut edges, i.e. virtually run into one another. Longitudinal strips are then formed on the long sides of the panel boards in correspondence to the thickness of a saw blade. 
     According to a particularly advantageous configuration of the basic inventive idea, the upper groove and the lower groove are arranged offset to one another by a distance so as to establish a breaking web between the grooves, and the starting sheet is then divided along the breaking web. Preferably, the partition is carried out in horizontal direction parallel to the fiber material of the starting sheet. 
     As the individual panel portions are connected by the breaking webs even after providing the grooves, it is possible to transport the starting sheet as a whole and to transfer it to the shaping tool. This is beneficial as far as manufacture is concerned. The starting sheet is divided into individual panels only during or before shaping the longitudinal strips on the long sides. 
     Basically, different starting sheets with finished surface coat can be used. Known laminates or parquet as well as starting sheets with a surface coat of linoleum, cork, or a direct varnish as well as with a surface of a textile coating may be worked on with the method according to the invention in order to make panels for floor, wall or ceiling coverings. 
     In particular when starting sheets with a so-called aggressive surface are involved, i.e. a highly wear-resistant or non-abrasive coating, it may be suitable to trim areas of the surface in the region of the upper groove to be made beforehand. This is realized with a milling tool. The milling tool produces a broached groove and broaches the running surface of the starting sheet. The width of the broached groove is hereby sized to almost reach the respectively finished edge of the panels to be manufactured. The upper groove is then produced in the previously made broached groove. In this way, the milling or cutting tools used for producing the upper groove can reach a significantly longer service life as they have to work only on comparably softer material, for example MDF. This measure also positively affects the precision of the groove being produced. The upper groove may be so configured as to be guided in front of the end face of the later locking strip to be produced in a shaping operation, for example a tongue. 
     Within the scope of a further advantageous embodiment of the invention, a 1 st  lower groove and a 2 nd  lower groove is made on the underside of the starting sheet. This is realized at a horizontal distance to one another. The arrangement and configuration of the 1 st  lower groove and the 2 nd  lower groove is implemented in dependence on the shape of the longitudinal strips during the following operation. Basically, the 1 st  lower groove and the 2 nd  lower groove may be cut in a run-through process in parallel or staggered in time. The introduction of the 1 st  lower groove and the 2 nd  lower groove may be realized before or after partition of the panels. In reality, it is contemplated to first provide the upper groove and the 1 st  lower groove in the starting sheet, then to divide it, and subsequently to provide the 2 nd  lower groove before the shaping operation of the longitudinal strips. The inner  2 ″ d  lower groove serves in particular as guide groove for a shaping tool by which the longitudinal strips are worked on and the locking strips are produced. Primarily, the use of a so-called double-end profiler is here considered for use. 
     The 1 st  lower groove and the 2 nd  lower groove may be cut at different depth. This is undertaken in dependence on the shaping operation to be executed and the shape of the locking strips to be produced. 
     According to the another feature of the invention, the grooves have each a slanted groove base. It is advantageous for the partition procedure when the groove base of the upper groove and the groove base of the lower groove are slanted in the same direction. When the starting sheet is broken along the breaking web, a kind of desired breaking line is realized in the direction of the slants in the groove base. 
     According to another feature of the invention, the depth of one groove should correspond to a value which is 0.3 times to 0.6 times the thickness of a starting sheet. In practical tests, the upper and the lower grooves have been slitted by about half the thickness of the starting sheet and subsequently divided. This resulted in very good outcomes. The upper groove and the lower groove may also have different length. Placement and the depth of the grooves are implemented in dependence on the configuration of the locking strips to be produced. 
     The horizontal distance between the upper groove and the lower groove is dimensioned by a value which is between 0.5 times to 3 times the width of a groove. The distance between the grooves is dimensioned in dependence on the profile to be realized of the locking strips so as to attain a reliable partition along the breaking web. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will now be described with reference to the drawings. It is shown in: 
         FIGS. 1   a  to  1   c  a schematic representation of three different process steps involved in the operation for dividing a starting sheet; 
         FIG. 2  a vertical section of two adjacent panels with illustration of a portion of the long sides; 
         FIG. 3  the top view of a starting sheet; 
         FIGS. 4   a  to  4   e  various working steps showing the process for manufacture of panels from a starting sheet; 
         FIGS. 5   a  to  5   g  a further exemplary embodiment of the method according to the invention; 
         FIG. 6  a side view of a starting sheet during production of the upper and lower grooves; and 
         FIGS. 7   a  and  7   b  a summarizing illustration of the procedure during production of the grooves. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1   a  shows a portion of a large starting sheet  1 . The starting sheet  1  is made of a highly-compacted fiber material or fiber material of average compaction. Already applied onto the starting sheet  1  is the typical overlay and optionally also the counteracting layer. The starting sheet  1  is then divided in a run-through process first in length direction and then in transverse direction to there produce individual panels. 
     Dividing the starting sheet  1  in longitudinal direction involves, as shown in  FIG. 1   b , the provision of parallel grooves  4 ,  5  in the topside  2  and underside  3  of the starting sheet  1 , as viewed in the drawing plane. The upper groove  4  and the lower groove  5  are arranged at offset relationship at a distance a in the horizontal sheet plane PE so as to leave a breaking web  6  between the grooves  4 ,  5 . Thereafter, the starting sheet  1  is split and divided along the breaking web  6 , as shown in  FIG. 1   c . The emerging panels or panel boards are designated with  7  and  8 . 
     It can be seen that the grooves  4 ,  5  have each a slanted groove base  9 ,  10 , with the groove base  9  of the upper groove  4  and the groove base  10  of the lower groove  5  being slanted in the same direction. The depth t of the groove  4 ,  5  corresponds to about half the thickness d of the starting sheet  1 . The distance a between the upper groove  4  and the lower groove  5  corresponds to the width b of a groove  4 ,  5 . 
     In view of the offset cutting pattern of the grooves  4 ,  5 , projecting longitudinal strips  13 ,  14  remain on the panels or panel boards  7 ,  8  along the long sides  11 ,  12  once the starting sheet  1  has been divided. The long sides  11 ,  12  are profiled in a following processing step and locking strips  15 ,  16  are carved out from the material using the long sides  13 ,  14 , as shown in  FIG. 2 . The contours of the locking strips  15 ,  16  on the confronting long sides  11 ,  12  complement one another and engage one another when making a covering of neighboring panels. 
       FIG. 2  shows the profile of a panel or panel board  7  and  8  shaded on their long sides  11 ,  12 . The area shown in dashed lines between the panels  7 ,  8  has been trimmed during shaping of the locking strips  15 ,  16  after the starting sheet  1  has been divided. 
     Further shown are an upper saw blade  17  and a lower saw blade  18  for making the upper groove  4  and the lower groove  5 , respectively. The upper groove  4  and the lower groove  5  extend parallel and in horizontal sheet plane PE at distance a relative to one another. It can be seen that the grooves  4 ,  5  are introduced in the area of the starting sheet  1  that has not been shaded, i.e. in an area which is trimmed during production of the locking strips  15 ,  16 . In this way, material can be saved because of the absence of a continuous saw cut which would involve a partition of the starting sheet  1  across its entire thickness d. 
     It should further be noted that the underside of the panel boards, designated with  3  in  FIG. 2  analogous to  FIG. 1   b , forms the facing or topside of a finished panel  7  and  8 , respectively. 
       FIG. 3  shows a starting sheet  19  with finished coat and with a length l of 2,100 mm and a width b of 1,300 mm. The starting sheet  1  is divided in longitudinal direction into a total of five panels  20  which are profiled along their long sides  21 ,  22  and provided with locking strips  23 ,  24 , as is illustrated with reference to  FIGS. 4   a  to  4   e.    
     The topside  25  of the starting sheet  19  is first provided with broached grooves  27  in a run-through process with the aid of milling tools  26 . The hard topside  25  of the starting sheet  19  is hereby trimmed in the area of the broached grooves  27 . When viewed together with  FIG. 7   a , it becomes clear that the topside  25  is broached in the area of a broached groove  27  almost up to the finished edge  28  of a finished panel  20 . 
     Subsequently, the topside  25  of the starting sheet  19  is provided with an upper groove  29  and its underside  30  is provided with a lower groove  31 . The upper groove  29  is hereby established in the previously produced broached groove  27 . This takes place in the run-through process by means of diamond saw blades  32 ,  33 . 
     It can be seen that the upper groove  29  and the lower groove  30  extend parallel and in the horizontal sheet plane PE at distance a in relation to one another. Breaking webs  34  remain between the grooves  29 ,  30 , respectively, so that the starting sheet  19  remains still connected initially and thus can be transported as a unit. The starting sheet  19  is then transferred to a shaping station in which the long sides  21 ,  22  of the panels  20  are shaped and the locking strips  23 ,  24  are produced. The starting sheet  19  is hereby divided along the respective breaking webs  34  which define a desired breaking area, as shown in  FIGS. 4   c  and  4   d . It can be seen that the longitudinal strips  35 ,  36  remain along the long sides  21 ,  22  and are worked on by means of a shaping tool so that the locking strips  23 ,  24  are produced, using the material of the longitudinal strips  35 ,  36 , as can be seen in  FIG. 4   e.    
     Also in the process for the production of panels, as described with reference to  FIGS. 5   a  to  5   e  and  FIG. 6 , the topside  37  of a starting sheet  38  is first provided with a broached groove  39  and areas of the topside  37  are trimmed. An upper groove  40  is provided within the broached groove  39 . Parallel thereto, a 1 st  t lower groove  42  is produced on the underside  41  of the starting sheet  38 . 
     The upper groove  40  and the 1 st  lower groove  42  extend at a distance a in relation to one another and are still connected in this process state according to  FIG. 5   d  by a breaking web  43 . In the next step ( FIG. 5   e ), the starting sheet  38  is divided along the breaking webs  43  so that individual panels  44  are created that have long sides  45 ,  46  with projecting longitudinal strips  47 ,  48 . 
     Before the longitudinal strip  47  of a panel  44  is shaped, the underside  41  of the panel is provided with a 2 nd  lower groove  49 . The 2 nd  lower groove  49  extends at a horizontal distance a 1  to the 1 st  lower groove  42  so that a vertical web  50  is realized between 1 st  lower groove  42  and 2 nd  lower groove  49 . The 1 st  lower groove  42  is slightly cut deeper than the 2 nd  lower groove  49 . 
     The longitudinal strips  47  and  48  are then shaped so as to form locking strips  51 ,  52  on the long sides  45 ,  46  of the panels  44 . 
     The 2 nd  lower groove  49  forms a guide groove for a shaping tool, a so-called double-end profiler, during the shaping process. In addition, the 2 nd  lower groove  49  is used to produce an undercut on the locking strip  51  to form a locking recess  53  for a terminal locking web  54  on the corresponding bottom-side latching tab  55  of the locking strip  52 . 
     The dashed lines shown in  FIGS. 5   b  to  5   g  are intended as aid to illustrate the position or configuration of the longitudinal strips  47 ,  48  in relation to the later locking strips  51 ,  52 . 
       FIGS. 6  as well as  7   a  and  7   b  show an overview of the position of the milling and sawing tools in relation to the locking strips  51 ,  52  formed on the finished panels  44 . 
     The travel direction of the starting sheet  38  through the processing station for producing the broached groove  39  as well as the upper groove  40  and the lower grooves  42 ,  49  is labeled by the arrow LR in  FIG. 6 . 
     Looking at  FIG. 7   a  and  FIG. 5   b , it becomes clear that during production of the broached groove  39  the topside  37  of the starting sheet  38  is broached by means of the milling tool  56  almost up to the finished edge  28  of the panel  44 . The upper groove  40  is produced in the broached groove  39  by means of the upper saw blade  57 , with the saw blade  57  cutting hereby directly in front of the end surface  58  of the tongue  59  to be realized later on the locking strip  51 . The underside  41  of the starting sheet  38  is worked on by both saw blades  60  and  61  for producing the 1 st  lower groove  42  and the 2 nd  lower groove  49 . 
     Further shown in  FIG. 7   b  is the imaginary desired breaking line, labeled with SL and extending along the breaking web  43  which is formed between the upper groove  40  and the 1 st  lower groove  42 , as shown in  FIG. 5   c.