Patent Publication Number: US-6659000-B1

Title: Rotary embossing machine

Description:
Rotary embossing machines of this type are known e.g. from the following documents: U.S. Pat. No. 5,486,254, WO 98 12 051 A1, DE 196 25 064 A1, DE 37 13 666 A1, EP 0 718 099 A2, EP 0 437 794 A2, DE 37 18 048 A1, DE 90 04 865 U1. 
    
    
     The invention concerns a rotary embossing machine in accordance with the features of the indepenent claim. 
     BACKGROUND OF THE INVENTION 
     These rotary embossing machines are used to apply embossing sheet sections onto an endless material web. The embossing sheet sections are sections of a heat-sealing sheet having structured or smooth surfaces and can also have a hologram and a thermally activatable fusion adhesive on the rear side. During application thereof, the embossing sheet section is transferred from the sheet web and glued onto the material web or the remaining sheet backing is removed from the glued section. During or after gluing, a pattern can be embossed into the surface of the sheet. These machines can also be used to apply holograms onto material webs wherein, in particular, the temperature of the embossing tool and of the embossing sheet should be precisely regulated and the tension of the embossing sheet must be exactly controlled to prevent destruction of the hologram. 
     The embossing sheet advance, which is usually also an endless sheet, must be exactly controlled for exact positioning of the embossing sheet sections and for minimizing embossing sheet waste. The embossing sheet advance is usually less than the transport speed of the material web. The location where the embossing sheet section is applied must correspond to the imprint in the material web. Finally, for holograms, the section of the embossing sheet to be embossed must be precisely oriented relative to the embossing stamp to prevent destruction of the hologram, to transfer it into the correct position, and to fix it on the material web. 
     Conventional rotary embossing machines have the associated problem that the transport speed of the embossing sheet is adjusted in order to minimize waste. This is associated with a relatively large degree of effort. 
     It is therefore the underlying purpose of the invention to provide a rotary embossing machine with which the embossing sheet and also the material web are treated with great care, wherein the transport speed of the embossing sheet can be adjusted in a simple fashion. 
     SUMMARY OF THE INVENTION 
     This object is achieved with a rotary embossing machine having the features of the independent claim. Advantageous further developments can be extracted from the dependent claims. 
     The inventive rotary embossing machine ensures that the material web and also the embossing sheet provided as an endless web are transported only in one direction and do not exert any back and forth motion, i.e. the transport direction does not change. The embossing device, which rotates in a direction opposite to that of the counter pressure cylinder, contains at least one embossing unit with each embossing unit having its own complete supply of embossing sheet for that embossing unit. The embossing sheet is transported by a transport means provided in the embossing unit such that a new embossing sheet section is continuously supplied while minimizing sheet waste. This can be effected in a gentle fashion through slow advance. 
     The rotary motion of the embossing device imparts a speed to the embossing sheet section which corresponds to that of the material web such that the section can be easily transferred from the embossing tool to the material web. Directly after transfer of the embossing sheet section, the embossing sheet is gently further transported and a new embossing sheet section is provided. It is important that the embossing device precisely matches the speed of the embossing sheet to the speed of the material web. The embossing sheet itself is at rest in the embossing device during the embossing process. 
    
    
     Further advantages, features and details of the invention can be extracted from the following detailed description of three particularly preferred embodiments with reference to the drawing. The features shown in the drawing and disclosed in the description and the claims may be essential to the invention either individually or in any arbitrary combination. 
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a side view of the inventive rotary embossing machine; 
     FIG. 2 shows a section II—II in accordance with FIG. 1, of a first embodiment of an embossing device; 
     FIG. 3 shows a section II—II in accordance with FIG. 1 of a second embodiment of an embossing device; and 
     FIG. 4 shows a section II—II in accordance with FIG. 1 of a third embodiment of an embossing device. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a rotary embossing machine, referred to in its entirety with  10 , comprising a machine tool table  12  supporting a rotatably disposed drive shaft  14  for two embossing devices  16 , and with a counter pressure cylinder  18 . The drive shaft  14  is coupled to a transmission  20  and a drive  22 . The other end of the drive shaft  14 , which is hollow, is provided with a suctioning device  24  for suctioning e.g. a waste sheet (described in more detail below). The drive  22  of the embossing device  16  may be discontinuous. 
     FIG. 2 shows a section II—II in accordance with FIG. 1 of a first embodiment of the embossing device  16  which rotates in the direction of arrow  68 . The embossing device  16  comprises a disc-shaped support  26  with a total of four embossing units  28 . The embossing units  28  are mutually offset by angles of  900  and uniformly distributed about the periphery. Each embossing unit  28  has a supply roller  30  for an embossing sheet  32  which is stored as an endless web on this supply roller  30 . The embossing sheet  32  is removed from the supply roller  30  by a first transport means  34  and is transported in the direction of a take-up roller  36 . A further transport means  38  is provided before the take-up roller  36  which ensures easy transport of the embossing sheet  32  about an embossing tool  40 . 
     The embossing tool  40  is an embossing stamp  42  which is disposed for displacement towards and away from the counter pressure cylinder  18 . The two transport means  34  and  38  each have a traction station  44  formed by two rollers and a device  46  for keeping the tension on the embossing sheet  32  constant. This device  46  comprises e.g. spring-loaded rollers which apply a constant tension on the embossing sheet  32 . 
     A heating shoe  48  is located between the transport means  34  and the embossing stamp  42  and heats the embossing sheet  32  to a temperature of e.g. between 80° and 120° C. Moreover, a sensor  50  is located in the region of the heating shoe  48  or generally before the embossing stamp  42  which scans a registration mark of the embossing sheet  32  in an optical, electronic, magnetic or contacting fashion and which controls the transport means  34  and optionally the transport means  38 . 
     The embossing stamp  42  can also be heatable and the counter pressure cylinder  18  can be heatable or coolable. The transport direction of the material web  52  is indicated by arrow  54 . The counter pressure cylinder  18  rotates correspondingly in the direction of the arrow  56 . The transport direction of the embossing sheet  32  is therefore opposite to the transport direction  54  of the material web  52 . 
     The embossing devices  16  can be displaced and adjusted on the drive shaft  14  in the longitudinal direction thereof. This permits processing of different material webs  52  or of different locations on material webs  52 . Moreover, the drive shaft  14  can be easily provided with additional embossing devices  16  which are also fixed thereon for secure mutual rotation therewith. 
     The material web  52  passes a printer controller (indicated with arrow  70 ) upstream of the embossing stamp  42 . This printer mark control  70  or embossing control detects registration marks on the material web  52  and controls the embossing stamp  42  and optionally the transport means  34  and  38 . 
     In the embodiment of FIG. 3, a central disposal means  58  is provided instead of a take-up roller  36  into which the waste sheet  60  of each embossing unit  28  is suctioned and removed via the hollow drive shaft  14  and the suction device  24 . This embodiment advantageously reduces the mass of the embossing device  16  and the embossing units  28  can be provided with larger supply rollers  30 . 
     In the embodiment of FIG. 4 of an embossing device  16  which also has four embossing units  28 , the drive of the embossing sheet  32  is realized via a transport band  62 , in particular a vacuum transport band with the vacuum being provided by vacuum chambers  64  and  66 . Moreover, vacuum chamber  64  has a heating means for pre-heating the embossing sheet  32 . The waste sheet  60  is also centrally suctioned. 
     Transfer of electrical energy and of data to the embossing devices  16  is effected either through slip rings or contract-free through a telemetry transfer means e.g. from the machine tool table  12  to the drive shaft  14 .