Abstract:
During a method for the production of a touch-and-close fastener ( 10 ), preferably of at least one plastic material, a backing ( 12 ) with a plurality of protruding stems ( 14 ) is connected to individual heads ( 16 ). For at least a part of the stems ( 14 ), their free ends ( 18 ) come into contiguous or embedded contact with a contact face ( 20 ) of each assignable head ( 16 ). The invention relates additionally to an apparatus for carrying out the method and to a fastener produced according to the method.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method for the production of an adhesive closure device or touch-and-close fastener, preferably of at least one plastic material. The invention relates furthermore to an apparatus for carrying out the method and an adhesive closure device produced according to the method and using the apparatus according to the invention. 
     BACKGROUND OF THE INVENTION 
     These touch fastener elements also include mechanical fastening elements, with touch fastener elements made in a complementary manner, form a fastener which can be repeatedly opened and closed. Hooks or mushroom-like fastener parts interacting with loop-like fastener elements of another touch fastener element with the formation of a touch or a touch-and-close fastener. Solutions are also known in which the same touch fastener elements of two different touch fastener elements interact with one another (hermaphroditic fastener). 
     DE 699 22 264 T2 discloses supplying a belt-like backing part with a plurality of projecting stem parts to a molding gap between heatable molding rolls. An extrusion means supplies an additional molding belt of plastic material into the gap as the actual molding tool with mold recesses shapes the hot stem ends of the stem parts into head parts to form a mushroom-like touch fastener element. Since the head parts in the known solution are formed from the plastic material of the stem parts, the head parts are of smaller dimension due to low material charging in the free and projecting head surface available for interlocking. This smaller dimension can adversely affect the required adhesion forces. 
     Conversely, U.S. Pat. No. 6,180,205 proposes a production method using a molding roll in which a belt-like backing part can be connected to a plurality of hook fastener elements dimensioned to be relatively large. For this purpose, the molding roll on its outer periphery has hook-shaped mold recesses into which plastic material is pressed to fill the mold a first extruder. Excess plastic material on the outer peripheral side of the molding roll is removed by cutting removal means, technically called a doctor blade. By a second extruder located downstream in the production direction, the backing part material is then applied and permanently connected to the hook-shaped fastener parts during the cooling process of the roll. A stripper roll then removes the finished fastener part from the molding means. Due to the hook geometry, difficulties can arise during the mold removal process. Furthermore, a relatively high proportion of plastic scrap is formed in the production process due to use of the doctor blade. 
     WO 2006/099000 A2 discloses spraying a belt-like conveyor device on its upper strand side with droplets of plastic material. The plastic material is molded based on its surface tension into hemispherical shell bodies which are then permanently connected on their arching top to a belt-like backing part, with the formation of a touch fastener element. In one development of this solution it is also possible, in the manner of thickened stem parts, to supply a belt-like backing part which on its top bears grain-shaped agglomerates as the stem parts onto which then the hemispherical head parts can be placed. The touch fastener element produced in this way and designed to be used in particular as a fastener for baby diapers or incontinence diapers is, however, made relatively stiff and leaves much to be desired with respect to the fastener characteristics. U.S. Patent Publication 2006/0220271 A1 discloses a comparable solution calling for a molding tool in the form of a molding roll with the corresponding mold recesses instead of a belt for production of hemispherical fastener elements. Production of stem parts between the head parts and backing part is not done with this known solution. 
     U.S. Pat. No. 5,785,784 discloses a production method for producing a belt-like backing part on which a plurality of projecting stem parts extend. In a downstream production step, the free stem ends are heated and then thicken as a result of the surface tension of the plastic material, in particular, into a hemispherical head part. If, in a continuation of the known solution, the head parts produced in this way are reshaped by a calander rolling method, widened head part geometries are formed which, with respect to the low material charge, are made relatively small and are widened only in the rolling direction. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved production system with low production costs making a reliable touch fastener adjustable in wide ranges in terms of its fastening behavior. 
     This object is basically achieved by a method, along with the apparatus and touch fastener element, to produce a touch fastener element, preferably of at least one plastic material, characterized in that a backing part with a plurality of projecting stem parts is connected to individual head parts such that at least for some of the indicated stem parts their free ends come into contiguous or embedded contact with the contact side of the respective head part. By subsequently placing separately produced head parts on the free end side of the respective stem parts, different material components of the stem parts can be combined with head parts in very wide ranges, and different geometries for head parts and/or stem parts can be defined. Based on the plurality of combination possibilities, a plurality of technical parameters can thus be set in a touch fastener element produced in this way. The method according to the invention is moreover reliable in application and can be economically implemented. 
     An apparatus proven to be especially economical for carrying out the method has for the individual head parts a molding tool with a plurality of mold recesses corresponding to the respective head geometry, and a supply device for the already finished or preformed backing part with the stem parts whose free ends can be inserted into the mold recesses by the supply device. 
     The touch fastener element is especially serviceable and mechanically durable if the stem parts and head parts are formed of plastic materials which are different from one another. In particular, the stem parts are formed from a thermoplastic, and the head parts are formed of acrylate material. The relatively hard acrylate material for the respective head part permits resistant hooking underneath for the loops of a corresponding touch fastener element so that a touch fastener structured in this way enables very high adhesive and peeling strength values. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure and which are schematic and not to scale: 
         FIG. 1  is a side elevational view of a part of the production apparatus according to an exemplary embodiment of the invention; 
         FIG. 2  is a side elevational view of a touch fastener element which can be produced, according to one embodiment of the invention; and 
         FIG. 3  is a side elevational view of a touch faster element which can be produced according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The method according to the invention is detailed below using the production apparatus as shown in  FIG. 1 . The method according to the invention is used to produce a touch or touch-and-close fastener element  10 . A belt-like backing part  12  is connected to a plurality of projecting stem parts  14  with individual head parts  16  such that at least for some of these stem parts  14  their free ends  18  come into contiguous or embedded contact with the contact side  20  of the respective head part  16 . When using the method according to the invention, the actual process of connecting the stem parts  14  to the respective head parts  16 , the head parts are still at least in the partially liquid or partially plasticized state. The head parts  16  are completely cured only after the connection. The free ends  18  of the stem parts  14  touch the still at least partially liquid contact sides  20  of the head parts  16  or preferably are embedded in the material of the head part to be able to ensure the connection in the subsequently cured state of the head part  16 . 
     For molding the individual head parts  16 , a molding tool  22  has a plurality of individual mold recesses  24  corresponding to the respective head geometry in terms of its configuration. The mold recesses  24  are a component of a molding belt  26  revolving in the manner of a transport belt. The mold recesses  24  of the upper strand are filled with plastic material. The lower strand guides essentially the empty mold recesses  24 . The mold recesses  24  are in turn repeatedly present in a regular or irregular distribution in the transverse and longitudinal direction of the molding belt  22 . 
     A supply device  28  supplies the already finished or preformed backing part  12  with the stem parts  14  whose free ends  18  can be inserted into the mold recesses  24  by the supply device  28 . For this purpose, the supply device  28  has a type of storage roll  30  from which the stem part-fastener material can be unwound. By corresponding deflection rolls  32  the belt material can be supplied to the molding tool  22 . The complete touch fastener product can be taken up on the end onto a transport roll  34  for further transport. For the sake of simpler depiction, individual transport and guide devices have been omitted. Likewise the heating and cooling devices for the production apparatus are not shown. The transport direction of the molding tool  22  and the supply device  28  is indicated with an arrow  36 . 
     As  FIG. 1  further shows, the mold recesses  24  are open to the outside. They are freely accessible from there, for filling the mold recesses  24  of the molding tool  22 . A filling device  38  is used which, without being specified in detail, can be a conventional extruder application device. Preferably, filling device  38  constitutes a droplet application apparatus that does not completely fill the mold recesses  24  as far as the free edge with plastic material without the mold recesses  24  overflowing. The filling device  38  can also be made as a doctor device for the plastic material with excess plastic material being removable from the top of the belt by a doctor blade device (not shown). 
     To produce the fixed connection between the stem parts  14  and the head parts  16 , in turn a curing device  40  (not detailed) is used and is located preferably at the end of the connecting process. Specifically, curing device  40  is at a short distance in front of the point before, viewed in the direction of the arrow  36 , the finished touch fastener element is removed from the molding tool  22  and carried away in the direction of the transport roll  34 . Depending on the plastic material used, the curing device  40  can be a conventional heat source, but also can be an UV emitter and the like. If acrylate material is used for the head parts  16 , the curing device  40  is preferably a UV emission source. 
     Touch fastener elements produced according to the illustrated method using the described apparatus, are shown enlarged in  FIGS. 2 and 3 . The head parts  16  as shown in  FIG. 2  are made essentially flat toward their free end side. This shape allows them to be made very narrow-lipped or thin-lipped relative to their surrounding edge, in contrast to the fastener solution as shown in  FIG. 3 , in which the top of the illustrated head part  16  is convexly curved so that this head part  16  toward the enclosing edge  42  extends with a thicker wall than the above described solution as shown in  FIG. 2 . It is common to both solutions that the head part  16  is formed of acrylate material, while the stem part consists preferably of a thermoplastic material, in particular of polyamide, polypropylene or polyethylene. Other material combinations are possible here. 
     It is surprising to one with average skill in the art in the field of fastener technology that for mushroom-head fastener systems any head parts  16  can be connected to any stem part material  14  in this way to be able to offer functional touch fasteners in a wide range of applications. As  FIG. 2  in particular shows, not all stem parts  14  need be provided with a head part  16 . In special applications it would also be possible to provide two and more stem parts  14  with only one head part  16  on the end side (not shown). Furthermore it would be possible, depending on the formation of the mold recesses  24 , to devise fastener systems, for example, combining the head geometries of the fastener elements of  FIGS. 2 and 3  according to predefinable patterns. Otherwise it has been shown that with the method according to the invention very smooth and hard head parts  16  can be obtained. This formation protects the fastener as a whole and leads to very long-lived touch fastener element systems. 
     Depending on the depth of the mold recesses  24  of the molding tool  22  used, different lengths for the stem parts  14  can also optionally be implemented so that then the head parts  16  end at different level heights relative to the belt-like backing part  12 . The backing part  12  itself can be a multiextrusion layer arrangement or can have be film-like and elastically stretchable. The head parts  16  viewed from overhead can form spherical shell bodies which are smooth to the outside. Implementations in polygonal form, in particular in a hexagonal shape, are also possible. By using acrylate material for the head parts  16  they also form a type of edge protection toward their surrounding edge  42 . This structure in turn benefits the service life of the overall fastener. 
     While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.