Abstract:
A method for forming shaped fibrous articles. The method involves introducing at least a portion of a fibrous element into a shaping tool and subjecting the fibrous element in the shaping tool to ultrasonic energy. This imparts the shape of the shaping tool to the surface of the fibrous element. The apparatus has a guide-holder to receive and removably retain a fibrous element and an ultrasonic shaping tool which can be applied to the fibrous element. The shaping tool has a recess corresponding to a predetermined shape for the article. Preferably, the shaping tool and guide-holder are reciprocally moveable with respect to one another.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a method and device for forming shaped fibrous articles or the like, especially of tampons. In particular, it relates to ultrasonic shaping of fibrous articles. 
     Fibrous articles, for example, tampons, ear plugs or the like, are formed having a specific shape. Moreover, these fibrous products can be formed of a single type of fiber or of mixed fibers (natural or synthetic). These fibrous products are brought to the desired shape either by rolling or by applying a shaping tool. Thus, for example, a shaping tool having a recess is applied to the tip of a tampon, the recess having the shape to be imparted to the tampon tip. An example of this is shown in Brien et al., U.S. Pat. No. 3,738,364. 
     An additional prior art shape-forming apparatus is illustrated in FIG.  3 . In a conventional shaping device, a tampon  1  having an essentially circular cross-section is held in a guide-holder  2 . By means of this guide-holder  2 , the tip  3  of the tampon  1  projects beyond the guide-holder  2  and is introduced into a recess  4  of a heated shaping tool  5 . The recess  4  has the shape of the desired tampon tip to be produced. The tampon  1  is introduced under pressure into this recess  4 , with the result that the fibers in the tip region are compacted. on account of the continuously decreasing cross-section, the friction of the tampon fibers on the surface of the recess  4  increases and the individual tampon fibers are compressed in the tip region, so that the internal friction also rises sharply. It has been shown that the outermost tampon tip is shaped only insufficiently or, as shown in FIG. 3, not at all. 
     SUMMARY OF THE INVENTION 
     The object on which the invention is based is to provide a method for forming shaped fibrous articles, for example, tampons, ear plugs, and the like, and an apparatus for forming these articles. The method involves introducing at least a portion of a fibrous element into a shaping tool and subjecting the fibrous element in the shaping tool to ultrasonic energy. This imparts the shape of the shaping tool to the surface of the fibrous element. 
     The apparatus has a guide-holder to receive and removably retain a fibrous element and an ultrasonic shaping tool which can be applied to the fibrous element. The shaping tool has a recess corresponding to a predetermined shape for the article. The recess has a periphery and an axis orthogonal to the periphery. Preferably, the shaping tool and guide-holder are reciprocally moveable with respect to one another along the orthogonal axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows an ultrasonic shaping apparatus according to the present invention; 
     FIG. 2 shows a shaped fibrous article formed in the ultrasonic apparatus of FIG. 1; and 
     FIG. 3 shows a device for the shaping of fibrous articles according to the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention is described below with reference to a tampon, although the invention is not to be restricted to this example of use, but is to embrace all fibrous or fibrous-like products. According to the invention, the tampon region to be shaped is shaped ultrasonically. This provides the following advantageous effects: (1) by virtue of the action of ultrasound and, if appropriate, simultaneously of a pressing force on the tip of the tampon, heat is generated in this region; (2) moreover, the ultrasonic vibrations cause the individual fibers of the tampon to move more easily past one another to improve shape-forming; (3) furthermore, the ultrasonic vibrations reduce the friction between the wall of the tool and the tampon tip located in the tool; and (4) the heat generated by the ultrasonic vibration gives rise to an ironing or smoothing effect. Due to the improved “flow behavior” of the individual fibers, the present invention provides for much more severe shaping of fibers, for example an elongated, parabolic tampon tip. 
     According to a preferred feature of the invention, thermal energy in the form of heating or cooling may be supplied to the tampon before, during and/or after the ultrasonic processing to maintain a preferred operating environment. Thus, if sufficient heat to smooth and/or set the fibers is not generated as a result of the pressure and ultrasonic energy, additional thermal energy can be supplied. In contrast, if too much heat is generated by pressure and ultrasonic energy which may damage the fibrous product, the excess heat can be removed by cooling the system. However, additional thermal energy is not always necessary, because an appropriate level of heat may be generated by the application of pressure and ultrasonic energy. 
     The ultrasonic energy may be applied in any direction to the shaping tool. However, it is preferred that the ultrasonic energy be applied orthogonal to the receiving orifice of the shaping tool. In the case of a tampon, this would be in the axial direction of the tampon. 
     The preferred embodiment comprises a device which has a guide-holder, for receiving the shank of the tampon, and a shaping tool which is capable of receiving the tip of the tampon. The shaping tool is designed to deliver ultrasonic energy to the fibrous product via at least one recess corresponding to the desired shapes of the fibrous product. Thus, the tampon can be shaped into the finished product in one operation. Of course, the fibrous product may be preformed to bring it into a cylindrical or approximately cylindrical shape. Advantageously, in this case, at least one of the guide-holder and ultrasonic shaping tool is movable relative to the other. 
     In one embodiment, there is provision for equipping the guide-holder with a sliding means which displaces the tampon in the guide-holder. Via this sliding means, the tampon can additionally be pressed into the ultrasonic shaping tool, for example while the ultrasonic energy is supplied. This may provide pressure on the tampon and therefore on the tampon tip in addition to the ultrasonic energy. It is also possible, however, to push in the tampon further via the sliding means and put it under pressure only after the ultrasonic processing, so that the fibers located on the surface of the tampon tip are compressed. 
     In a preferred embodiment, an element absorbing ultrasonic vibrations is provided between the free end face of the ultrasonic shaping tool and that end face of the guide-holder which faces the ultrasonic shaping tool. During the ultrasonic processing, this element allows a guide-holder to exert pressure over its entire area on the ultrasonic shaping tool, without the vibrations of the ultrasonic shaping tool being transmitted to the guide-holder. In a preferred embodiment, the ultrasonic shaping tool has a vibration frequency of up to about 35 kHz and/or an amplitude of about 50 to about 100 microns, more preferably about 80 microns. 
     For the simultaneous processing of a plurality of tampons, the ultrasonic shaping tool may have a plurality of recesses. In this case, the ultrasonic shaping tool is designed so that the introduction of energy into the individual tampons is distributed uniformly. In addition, a more complex, single fibrous product may be formed using an ultrasonic shaping tool having a plurality of recesses, or complex recesses. 
     Further advantage, features and particulars of the invention emerge from the following description which, with reference to the drawing, represents in detail an especially preferred embodiment. At the same time, the features in the drawing and mentioned in the claims of the description can be essential to the invention each individually in themselves or in any combination. 
     Referring to FIG. 1, the present invention includes a shaping device, designated as a whole by  10 , which has a guide-holder  12  for the tampon  11  to be shaped. This guide-holder  12  is operatively connected to an ultrasonic shaping tool  13 . The ultrasonic shaping tool  13  is transmits ultrasonic energy supplied by a converter  14  through a transformer  15 . Moreover, the guide-holder  12  has a sliding means  16  which is arranged displaceably in the orifice  17  of the guide-holder  12 . 
     The tampon  11  to be shaped is inserted into this orifice  17 , so that its tip  18  to be shaped projects beyond the guide-holder  12 . Subsequently, at least one of the guide-holder  12  and the ultrasonic shaping tool  13  are moved with respect to the other to introduce the tip  18  a recess  19  of the ultrasonic shaping tool  13 . The ultrasonic shaping tool  13  is then set in vibration, an indicated by the double arrow  20 . At the same time, the surface friction between the recess  19  and fibers of the tampon  11  and the mutual friction of the individual fibers are greatly reduced, so that the tip  18  Of the tampon  11  adapts to the shape of the recess  19  and assumes this shape. Simultaneously, heat is supplied to the tampon tip  18  via the ultrasonic shaping tool  13 . 
     Either this heat can be introduced externally (applied thermal energy) or it is generated during the ultrasonic processing (ultrasonic energy). Furthermore, during the ultrasonic processing, the tampon  11  can be further compressed by moving the sliding means  16  as indicated by arrows  21 . Thus, the tampon tip  18  can be better forced into the recess  19 . The sliding means  16  can be actuated during ultrasonic processing and/or also after the conclusion of ultrasonic processing, which lasts from between about 0.2 and about 5 seconds, preferably about 0.5 seconds. An element  22  absorbing ultrasonic vibrations is located between the guide-holder  12  and the ultrasonic shaping tool  13 , so that, even during ultrasonic processing the guide-holder  12  can touch the ultrasonic shaping tool  13  and nevertheless substantially all of the ultrasonic energy is introduced into the tampon  11  or its tip  18 . The pressing of the fibers of the tampon tip  18  onto the hot surface of the recess  19  gives rise to an ironing effect and to a compression of fibers. 
     As shown in FIG. 2, the apparatus and method can produce tampons  11  which have, for example, a parabolic tip. In contrast to a conventional hemispherical tip, this parabolic tip  18  has a cross-section which changes over a much longer length. Thus, conventional shaping methods may be unsuitable.