Abstract:
A set of dies for embossing or debossing is disclosed. The set has a female die ( 4, 80 ) and a male die ( 7, 67 ) each which has a steel backing plate ( 5, 47, 75 ). One of the dies is strongly magnetically attracted to a base plate ( 1, 68 ) which results in a weak magnetic attraction between the two dies ( 4, 7  or  67, 80 ). The weak magnetic attraction enables the set of dies to be substantially automatically self-aligning. Furthermore, such a set of dies can be used with a cutting and creasing die ( 50 ) to permit embossing or debossing simultaneously with cutting and/or folding during the same run.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a U.S. National Stage Application of PCT application Serial No. PCT/AU2010/000540, filed on 11 May 2010, which claims priority from Australian Patent Application Serial No. AU 2009902368, filed on 25 May 2009, and AU 2009905392, filed on 5 Nov. 2009, all of which are incorporated by reference in their entireties. 
     FIELD OF THE INVENTION 
     The present invention relates to embellishing processes including embossing and debossing. In particular, the invention relates to aligning dies used in such processes. 
     BACKGROUND ART 
     Debossing creates a depression in stock (such as sheets or paper) and the equivalent process in embossing creates an upstanding portion which is therefore in relief. Debossing is therefore a mirror image of embossing. With an embossing die, which is a female die, there is an equivalent male die termed a counter. The planar stock is passed between the two dies which are then subjected to pressure and thereby creates the raised image. 
     One type of female die used in these processes is a photopolymer die. Typically the photopolymers used have a high Shore hardness. The photopolymers are processed by means of photoresist. The non image area is washed away with water by soft nylon brushes. The photopolymer is adhered to a thin metal backing plate which is preferably steel. The photopolymer die is secured to a platen base by means of adhesive tape and recently by means of magnetic attraction between the backing plate and magnets positioned in the platen or cylinder bed. 
     Counters can be made in accordance with at least three known prior art methods. The first is that the counters are cut by hand from paper using the PRAGOPLAST (Registered Trade Mark) system which involves feathered paper with an adhesive backing. The second is the use of moulded counters which are fabricated from fiberglass, putty, and various other plastics which are moulded under both heat and/or pressure to form the male counter. The third type of counter is fabricated from photopolymer and has a film backing which is also of polymeric or other plastic material. The film backing normally is transparent or translucent and thus aids in the alignment of the two dies since the operator can visualize the intended mating. 
     It is necessary to align or position the counter on the platen of the stamping machine, or cylinder in the case of a rotary machine. For the first type of counters, the counter is hand cut in position after being secured to the platen or cylinder. For both moulded counters and film backed photopolymer counters, the counter is positioned by means of a “reverse” fit. That is to say, the male counter is positioned by hand over the female die until the male protrusions of the counter appear to mate with the recesses of the female die. Once a snug fit has been achieved, double sided adhesive tape is placed on the back of the counter (that is the surface of the counter away from the female die). Then the platen or cylinder is brought into contact with the adhesive tape in order to fasten the counter (or male die) to the platen or cylinder. 
     However, there is a danger that the counter can move out of its correct position or alignment in the process of fastening the counter to the platen or cylinder. There is also a risk that the male counter can be damaged in the securing process. 
     Die cutting involves the use of a die to cut and/or crease stock (such as paper sheets or thin sheets of plastic) so as to fabricate a blank for an article such as an envelope, a folder, or the like. The die normally has a base of inexpensive material such as timber, five ply, particle board, or the like. Mounted on the base, edge upper most, are thin strips of steel. In the case of a desired cut, the upper edge is sharp and constitutes a knife. In the case of a desired crease, the upper edge of the strip is rounded. Extending along either side of at least the knife strips is a strip of resilient material which in its uncompressed state has a surface higher than the upper edge of the knife. The two strips of resilient material function as an ejector mechanism to prevent the cut stock becoming jammed on the knife. 
     In general cutting stock to shape using die cutting is a separate function to that of embossing or debossing of the stock. Thus if a job calls for cutting, and embossing or debossing 1000 items, in general this requires 2×1000 or 2000 operations as the item must be separately embossed or debossed, and then die cut. 
     However, in recent times it has been known to combine both cutting and either embossing or debossing. This has been possible using an expensive magnesium (or other metal) die to carry out the embossing/debossing. Such metal dies require environmentally burdensome acids to etch away the die material or must be hand engraved or CNC machined. The embossing/debossing die is generally held on the cutting die by means of double sided adhesive tape or screwed or bolted into the cutting tool and must be painstakingly aligned with the cutting die and with any counter required. 
     GENESIS OF THE INVENTION 
     The genesis of the present invention is a desire to provide an alternative arrangement in which the above-mentioned disadvantages are at least ameliorated to some extent. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention there is disclosed a set of dies for use in embossing or debossing and comprising a male die and a mating female die, wherein each of said dies has a magnetic or magnetically permeable backing. 
     In accordance with a second aspect of the present invention there is disclosed a method of mutually aligning a male and a female die which are complementary, said method comprising the steps of: 
     (i) fabricating each die with at least a magnetic or magnetically permeable backing, and 
     (ii) in either order or substantially simultaneously, approximately aligning said dies and applying an attractive magnetic force between said dies; 
     whereby said magnetic force mates the male and female portions of said approximately aligned dies to accurately align same. 
     According to another aspect of the present invention there is provided a planar substrate of paper, cardboard or like printing stock embossed or debossed with dies aligned in accordance with the above-mentioned method or embossed or debossed with the above-mentioned set of dies. 
     The female die can take the form of a steel backed metal block (the metal being non-ferrous such as brass, copper, magnesium, zinc or aluminum) or a steel backed photopolymer block or any substrate that can laminated with a steel backing, all of which can enjoy the benefits of the abovementioned magnetic mounting and alignment. 
     Similarly the male die can be a steel block or a steel backed block fabricated from a material such as fiberglass, plastic, epoxy resin, photopolymer, non-ferrous metals or any substrate that can laminated with a steel backing and thus enjoy the benefits of the magnetic mounting and alignment 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: 
         FIG. 1  is an exploded perspective view of a set of embossing dies of a first embodiment, 
         FIG. 2  is a perspective view of a cutting and creasing die adapted to receive an embossing die, and 
         FIG. 3  is a perspective view of the male embossing die to be received by the die of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIG. 1 , a printing machine such as a foil stamping machine or a die cutting machine is provided with bed (conventional and not illustrated in  FIG. 1 ) and to the upper surface of which a base plate  1  is secured. The machine also has a conventional platen or cylinder drum  2 . Positioned above the base plate  1  is a female photopolymer die  4  having a backing plate  5 . Positioned above the female die  4  is a complementary male die  7  also fabricated from photopolymer and having a complementary male shape. In this connection it will be apparent that the female die  4  has two recesses  14  and  24  which are respectively triangular and quadrilateral in shape. The male die  7  has two protrusions or bosses  17  and  27  which are also respectively triangular and quadrilateral in shape. The male die  7  and the female die  4  are complementary in the sense that the bosses  17  and  27  mate with the recesses  14  and  24 . 
     In use the paper substrate, for example, is passed between the two dies  4  and  7 . The mating of the bosses  17 ,  27  with the recesses  14 ,  24  results in the substrate being embossed or debossed with the shape of the recesses  14 ,  24 . 
     As seen in  FIG. 1 , the male die  7  is provided with a photopolymer body  37  and a thin sheet steel backing plate  47 . The bosses  17 ,  27  project downwardly from the lower surface of the photopolymer body  37 . The upper surface of the backing plate  47  is provided with an array of adhesive strips  9  (the adhesive strips can be placed on the platen or cylinder  2 , or the backing plate  47  as illustrated, or both) which are provided with adhesive on both sides and thus are used to interconnect the male die  7  and the platen  2 . 
     However, before this interconnection takes place, the male die  7  must be correctly aligned with the female die  4 . 
     In accordance with the invention disclosed in International Patent Application No. WO2007/045037 (PCT/AU2007/001553), the contents of which are hereby incorporated herein for all purposes, the base plate  1  is provided with an embedded array of magnets (not illustrated in  FIG. 1 ). These magnets magnetically clamp the base plate  1  to the bed of the machine. The same magnets also secure the backing plate  5  of the female die  4  to the base plate  1  with a strong magnetic attraction. This strong magnetic attraction is sufficient to easily withstand vibration forces and other forces applied to the female die  4  during the processing. 
     However, fabricating the male die  7  so as to have a magnetically permeable backing plate  47  means that there is also a relatively weak magnetic attraction between the backing plate  47  and the magnets of the baseplate  1 . This force is weak relative to the strong magnetic forces between the bed and baseplate  1  and between the baseplate  1  and backing plate  5 , because the backing plate  47  is always spaced from the baseplate  1  by a substantial distance and because most of the magnetic flux generated by the baseplate magnets passes through the backing plate  5 . This weak magnetic force is approximately of the same strength as the magnetic force between a fridge magnet and the metal of a fridge door. 
     A consequence of the weak magnetic attraction between the male die  7  and the base plate  1  is that the male die  7  can be approximately correctly aligned with the female die  4  by hand and the weak magnetic attraction will guide the bosses  17 ,  27  into the recesses  14 ,  24  because this draws the backing plate  47  closer to the magnets in the base plate  1 . Consequently, the two dies  4 ,  7  when correctly aligned with the bosses  17 ,  27  mated with the recesses  14 ,  24  represent a lower energy state and thus are magnetically urged into that state. Thus the correct alignment is to some extent automatic. 
     In addition, some machines utilize an inverting bed which swings out and inverts the base upon which the dies reside. Thus normally in such a machine the male counter is located beneath the female die when the bed is swung outwardly. For such machines, the above described arrangement assists the operator in holding the dies securely before final fastening. 
     Once the correct alignment has been achieved, the adhesive strips  9  can be placed on the backing plate  47  and the platen  2  brought into contact with the adhesive strips  9 . Since the adhesion between the adhesive strips  9  and the platen or cylinder  2  is greater than the weak magnetic attraction between the backing plate  47  and the magnets in the base plate  1 , this means that the platen  2  with the adhered male die  7  can be raised out of contact with the female die  4  but the correct alignment between the two dies  4 ,  7  is maintained. 
     Turning now to  FIG. 2 , a substantially conventional cutting and creasing die  50  is illustrated having a base plate  51  fabricated from timber, 5 ply, particle board or some other such inexpensive material. Located on the base plate  51  are knives  53  and crease formers  54 . As seen in the right hand enlargement of  FIG. 2 , the crease former  53  takes the form of a thin strip of metal embedded edgewise into a groove cut into the base plate  51  and having an upper edge  56  which is rounded. 
     As seen in the left hand enlargement in  FIG. 2 , each knife  53  take the form of a very thin strip of metal again embedded edgewise into a groove cut into the base plate  51 . The upper edge of the knife  53  is sufficiently sharp to cut the stock, typically paper or cardboard. Extending along each side of the knife  53  is a corresponding ejector strip  58  which is slightly taller than the knife  53  and is fabricated from resilient material such as foamed plastics. 
     The cutting and creasing die  50  is conventionally used to cut and crease planar printing stock so as to create a blank, for example of an envelope. In the die  50  in  FIG. 2  the envelope outline has a front surface  60 , a rear surface  61  and two edge flaps  62  and  63 . In conventional fashion, when the stock is compressed between the base plate  51  and an overhead platen or cylinder (not illustrated), the knives  53  cut out the outline of the envelope blank. The resilient ejector strips push the cut stock away from the knives  53  and so prevent the cut or slit stock becoming jammed on the knife  53 . The stock is also bent over each crease former  54  and so creased to thereby form the location for corresponding folds in the cut stock. 
     The above description of the cutting and creasing die  50  is thus far conventional. The die  50  is modified in accordance with the second embodiment of the present invention by the cutting away, or routing, of the base plate  51  to form a cavity  59  which is preferably of a standard dimensional size eg. A6, A7, A8, etc. Located within the cavity  59  is a male embossing die  67 , a magnetic base plate  68  and a thin steel plate  72  as illustrated (to an enlarged vertical scale) in  FIG. 3 . The male embossing die  67  could be fabricated by etching a metal block such as a magnesium, brass, copper, zinc or steel block but this requires environmentally difficult acids. Where a metal other than steel is used the die  67  preferably includes a thin steel backing plate. Alternatively, the die  67  could be hand engraved or CNC machined. Instead the embossing die  67  is preferably formed from a photopolymer layer  74  and a steel backing plate  75 . Preferably the upper surface of the photopolymer layer  74  is shaped using photo resist techniques (which are water based and thus environmentally benign) so as to form a logo  70  or image such as the four interlinked rings of the AUDI Registered Trade Mark. 
     A magnetic base plate  68  (with its array of magnets  69 ) is located on the thin steel plate  72  within the cavity  59 . The thin steel plate  72  is preferably held in place by means of double sided adhesive tape (not illustrated in  FIGS. 2 and 3  but illustrated as  9  in  FIG. 1 ) or other such suitable strong adhesive. Thus, in this embodiment, the thin steel plate  72  always remains with the cutting tool die  50 . 
     There is a counter  80  (illustrated in phantom in  FIGS. 2 and 3 ) which has a reverse (ie female) image of the logo  70  and which can be magnetically guided into registration with the die  67  as described above in relation to  FIG. 1 . Once the counter  80  is in register with the die  67 , the counter  80  can be adhered by means of double sided adhesive tape to the platen (or cylinder) which is to compress the stock against the cutting and creasing die  50 . 
     As a result of the above describe arrangement, the stock is simultaneously compressed against the die  50  thus forming the shape of the desired blank, and also compressed between the counter  80  and the embossing die  67  thereby simultaneously embossing the logo  70  onto the front surface  60  of the envelope. Thus cutting the envelope and embossing same are achieved simultaneously by means of a single pass through the machine. 
     The magnetic base plate  68  can be removed from the cutting die  50  and used on other jobs. The magnetic base plate  68 , either with the embossing die  67  or a different embossing die, can be held on the thin steel plate  72  on another occasion when embossing or debossing is required. It is convenient for the thin steel plate  72  to remain with the die  50  and for the magnetic plate  68  to be transferred from job to job. 
     The foregoing describes only two embodiments of the present invention and modifications, obvious to those skilled in the printing arts, can be made thereto without departing from the scope of the present invention. 
     For example, the backing plate  47  can be fabricated from material which is magnetic, or magnetized, so as to create the desired weak magnetic attraction between the male die  7  and the platen  2 . Other magnetic and magnetically permeable arrangements, which contain ferric material, for example, will be apparent to those skilled in the magnetic arts. 
     Similarly, the die  67  can have a male representation of the logo  70 , and the counter  80  can have the female representation of the logo  70 , in which case the logo  70  is debossed onto the front  60  of the envelope rather than embossed. 
     Furthermore, some cutting tool dies have provision for multiple tools so that, say, eight envelopes are cut simultaneously. Under these circumstances such a die would have eight recesses  67  each with a thin steel plate  72  so that each of the eight envelopes can be simultaneously cut and embossed at the one time. 
     The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of”.