Abstract:
A process for forming a tampon having a relatively high density, compressed core and a plurality of lower density longitudinal ribs is disclosed. The longitudinal ribs have a softer fiber structure and a coarser capillary structure and extend radially from the core. The process includes forming a fibrous tampon blank, radially pressing a circumferential surface of the blank over spaced apart longitudinally extending portions to form spaced apart ribs, exposing the longitudinal ribs to a radially applied second pressure to form a tampon having a relatively high density, compressed core and a plurality of lower density longitudinal ribs extending therefrom. The longitudinal ribs are separated one from another by outwardly open longitudinal grooves, at least where they extend from the core, and they form a soft, essentially smoothly cylindrical outer surface of the tampon.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a divisional application of prior application Ser. No. 08/427,468, filed Apr. 24, 1995, now US Pat. No. 6,310,269, which is a continuation of application Ser. No. 08/124,374 filed Sep. 20, 1993 now abandoned, which is a continuation of application Ser. No. 07/929,844 now abandoned filed Aug. 13, 1992, which is continuation application Ser. No. 07/799,922 now abandoned, filed Nov. 26, 1991, which is a continuation application of Ser. No. 07/596,454, filed Oct. 12, 1990 now abandoned, which are hereby incorporated by reference and all abandoned. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention relates to a tampon, especially for feminine hygiene, having a relatively high density compressed core and a plurality of lower density longitudinal ribs, as well as, to a process and an apparatus for producing the tampon.  
           [0003]    A tampon of the abovementioned generic type is known from German Auslegeschrift 1,491,161. This tampon has proved appropriate in practice because of its high absorption capacity, fluid retention capacity, rate of absorption, stability and buckling strength. For this, the tampon has longitudinal grooves which are caused by pointed press jaws and on each of the two sides of which occur longitudinal ribs which are pressed to the approximately cylindrical final form of the tampon during a subsequent pressing operation by means of press jaws with partially cylindrical press faces.  
         SUMMARY OF THE INVENTION  
         [0004]    The object on which the invention is based is to improve the tampon of the abovementioned generic type in such a way that the absorption capacity and rate of absorption of the tampon appertaining to the two are essentially maintained, but the specific absorption capacity of the tampon is increased.  
           [0005]    This and other objects are achieved by the tampon disclosed that makes it possible to obtain an appreciable increase in the specific absorption capacity (ml/g), whilst preserving the hitherto obtained absorption capacity and rate of absorption, with a surprisingly smaller amount of fibre material being used. This effect is attributable to a coarser capillary structure of the fibre material in the outer layer of the tampon.  
           [0006]    Thus, it was found that a tampon according to the invention consisting of 100% rayon fibres with a weight of 2.4 g without the withdrawal string can have a specific absorption capacity of 4.8 ml/g with a rate of absorption of 1.9 ml/s. The absorption capacity of such a tampon at a static counterpressure of 20 mbars is 11.3 ml. In a test with a pulsating counterpressure of 20 to 110 mbars approximating extremely closely to the practical conditions of use, the absorption capacity of the tampon according to the invention can amount to 8.0 ml and the specific absorption capacity to 3.4 ml/g.  
           [0007]    The diameter of the tampon is set at between 13 and 15 mm according to the customary physiological conditions, and the central fibre core can preferably have a diameter of 4 to 8 mm. A high buckling strength of the tampon can thus be achieved, whilst at the same time the soft surface of the tampon guarantees a pleasant handling of the tampon.  
           [0008]    The invention relates, furthermore, to a process for producing this tampon. A process of this type is known from German Auslegeschrift 1,491,161 already mentioned.  
           [0009]    According to the invention, this process for producing the tampon according to the invention is improved by means of pressing only narrow strip-shaped portions of the surface of the blank. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The invention is explained in more detail below by means of the diagrammatic drawing of an exemplary embodiment of a tampon and of an apparatus for producing this. In the drawing:  
         [0011]    [0011]FIG. 1 shows the tampon according to the invention in a middle longitudinal section along the sectional line I-I in FIG. 2,  
         [0012]    [0012]FIG. 2 shows a cross-section along sectional line II-II shown in FIG. 1, showing the tampon of the current invention having outwardly open grooves,  
         [0013]    [0013]FIG. 3 shows a cross-section through the preform along the line III-III in FIG. 10,  
         [0014]    [0014]FIG. 4 shows a cross-section of the tampon of the invention, having closed grooves  
         [0015]    [0015]FIG. 5 shows a diagrammatic view of a preforming press in the opened state with a winding blank arranged in it,  
         [0016]    [0016]FIGS. 6 and 7 show a separate closing movement of the pressing dies, wherein  
         [0017]    [0017]FIG. 6 illustrates a first pressing face of the preforming press with closed press segments, whilst a second, final press face of the preforming press is illustrated in  
         [0018]    [0018]FIG. 7 showing the sliding plates in the closed position, wherein all press dies enclose the preform arranged in it, and  
         [0019]    [0019]FIGS. 8 and 9 show an alternative sequence of movements of the press dies, wherein the press segments and the sliding plates are simultaneously moved into the closed position;  
         [0020]    [0020]FIG. 8 shows an intermediate phase of the pressing procedure and  
         [0021]    [0021]FIG. 9 the press dies completely closed with the preform arranged in it, and  
         [0022]    [0022]FIG. 10 shows a partially sectional side view of the apparatus for producing the tampon with the preforming press and with the following forming die. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    [0023]FIGS. 1 and 2 show a tampon  10  for feminine hygiene formed from an approximately cylindrical blank  11  which is shaped by winding up a portion of length of nonwoven material, needled if appropriate. The nonwoven can consist of natural or synthetic fibres or of a mixture of such fibres. Natural fibres coming under consideration are preferably those of cotton. Rayon or other synthetic fibres are also highly suitable. The circumferential surface of this winding blank is pressed in a way known per se radially relative to the longitudinal mid-axis of the winding blank over an even number of at least six, preferably eight portions mutually adjacent in the circumferential direction of the winding blank  11 .  
         [0024]    According to the invention, these circumferential portions of the winding blank  11  are exclusively narrowstrip-shaped portions  12 ,  13  of the circumferential surface  14  of the winding blank  11  which are arranged at equal angular distances from one another and which are pressed to produce a preform  15  in FIGS. 3, 7 and  9 . As seen in cross-section, the preform  15  consists of a central approximately circular fibre core  16  of high compression and stability or buckling strength and of longitudinal ribs  17  extending radially outwards from the fibre core  16  and of a fibre structure softer than that of the fibre core and of correspondingly coarser capillary structure (FIG. 3). The longitudinal ribs  17  are separated from one another by outwardly open longitudinal grooves  18 . Only the soft longitudinal ribs  17  of the preform  15  are exposed to a low uniform radial pressure during manufacture relative to the longitudinal mid-axis  19  of the preform  15 , in such a way that the radially outer ends  20  of the longitudinal ribs  17  form a soft essentially smoothly cylindrical surface of smaller diameter corresponding to the final form of the tampon  10 .  
         [0025]    It was found that the tampon according to the invention has a stability 100% higher than that of the known tampon. It was shown, furthermore, that approximately 10% of the fibres used for the tampon can be saved, without any appreciable impairment, if any, of the absorption capacity. In contrast, the rate of absorption is in the upper range of known tampons, whilst the specific absorption capacity is increased appreciably in relation to known tampons.  
         [0026]    The following table illustrates a comparative test of the tampon according to the invention consisting of a needled nonwoven composed of 100% of rayon fibres from Hoechst AG, and a tampon obtainable in the trade under the commercial designation “Standard o.b.®”:l  
                                             TABLE                                   Tampon according   “Standard           to the invention   o.b. ®” Tampon                                    1.   Weight (g) without   2.4    2.7           the withdrawal           string       2.   Absorption capacity   11.3   11.5-12.5       3.   Specific absorption   4.8    4.2-4.5           capacity (ml/g)       4.   Rate of absorption   1.9    1.5-2.0       5.   Absorption capacity   8.0    8.6       6.   Specific absorption   3.4    3.1           capacity (ml/g) in           ABTS test unit                  
 
         [0027]    The absorption capacity values indicated in line 2 of the Table were determined in a test unit, in which the tampon is surrounded by an elastic diaphragm which exerts a static counterpressure on the tampon, whilst one end of the tampon is sprinkled with water. This resulted in the specific fluid absorption capacity in ml/g of fibre material of the tampon evident from line 3 of the Table.  
         [0028]    The rate of absorption emerging from line 4 was determined in this test arrangement. The values show that, at a weight of the tampon according to the invention reduced by approximately 10%, the absorption capacity of the tampon is not essentially reduced in relation to the known tampon, the rate of absorption is of the upper limit of that of the known tampon, and the specific absorption capacity is appreciably higher than in the known tampon. Since the specific absorption capacity is evidence of a better utilization of the absorbency of the fibre material per unit weight, it is clear that the tampon according to the invention can be produced more cheaply as a result of the lower weight of material.  
         [0029]    Lines 5 and 6 of the Table give values for the absorption capacity and the specific absorption capacity determined in a test arrangement allowing test conditions such as actually occur when the tampon is being worn.  
         [0030]    The system designated as ABTS, corresponding to Absorptive Behaviour Test System, is computer-assisted and serves for the acquisition and processing of measurement data regarding the absorption behaviour of absorbent products and for controlling the test cycle.  
         [0031]    The test of the tampon is conducted under the following conditions which, as mentioned, occur approximately in vivo:  
         [0032]    chemical/physical compositions of the test fluid  
         [0033]    spacial arrangement of the product, for example inclination  
         [0034]    positioning of the product in the measuring cell  
         [0035]    strength of the flow  
         [0036]    interruption (start/stop) of the flow  
         [0037]    pressure variant.  
         [0038]    The test cycle is software-controlled automatically and allows a dialogue between the operator and system. The measurement data are required automatically, their evaluation taking place according to statistical factors. The test cycle for each random sample can be tracked on a video screen by means of a measurement curve and, if appropriate, printed out automatically. Furthermore, the fluid distribution in the product is represented qualitatively and quantitatively. Moreover, the leakage behaviour of the tampon can be checked. By leakage is meant. the phenomenon in which menstrual fluid can escape between the body wall and tampon. The feed of test fluid to the tampon is carried out exclusively without pressure, since the fluid level is at the height of the test tampon. The fluid is therefore sucked up into the tampon solely as a result of the wetting of the tampon and the wick effect caused by the capillary forces of the latter, and by means of the pulsating counterpressure on the tampon which is felt in practice.  
         [0039]    The values determined with this ABTS test device illustrate, in lines 5 and 6 of the Table, that, at the pulsating counterpressure indicated, the absorption capacity of the tampon is only slightly lower than in the reference tampon, but here too the specific absorption capacity of the tampon according to the invention per gram of fibre material is approximately 10% higher than in the reference tampon.  
         [0040]    The diameter of the tampon according to the invention is between 13 and 15 mm in its final form. The central fibre core  16  has a diameter of approximately 4 to 8 mm.  
         [0041]    [0041]FIG. 4 shows an enlarged cross-sectional representation of the fibre structure of the tampon according to the invention. It is possible to see clearly the central fibre core  16 , from which extend outwards eight longitudinal ribs  17  touching one another at their outer ends  20 . The tampon cross-section shows, moreover, that the loose fibre structure with its coarser capillary structure of the longitudinal ribs  17  is preserved, despite the concentric pressure to which these longitudinal ribs are exposed during the production of the final form of the tampon. In contrast, the fibre core  16  having a high fibre compression guarantees a stability or buckling strength which is twice as high as that of the reference tampon and which is of great importance when the tampon is used as a digital tampon.  
         [0042]    The figures illustrate an apparatus according to the invention for producing the tampon. According to FIGS.  5  to  7 , this apparatus consists of two groups of altogether eight press dies arranged in a plane perpendicular to the press axis  21 , the first group of press dies forming press segments  22  and the second group of press dies forming sliding plates  24 . In the closing position shown in FIG. 6, the side flanks  23  of these four press segments  22  form respectively for each of the four press dies of the second group guide surfaces which are designed as sliding plates  24 . At the same time, the press segments  22  and the sliding plates  24  serve, as a preforming press, for pressing the winding blank  11  to produce the preform  15  in FIG. 7. Exclusively press cutters  27  projecting from the end faces  25  and  26  of the press segments  22  and of the sliding plates  24  serve for pressing the blank. It is evident from FIGS.  5  to  7  that the press cutters project from the end faces  25  and  26  of the press segments  22  and sliding plates  24  at equal angular distances and over the same length. The shape and dimensions of all the press cutters are identical. The press cutters are therefore also equipped at their front end with the same pressing faces  28  which, in the exemplary embodiment illustrated, each extend parallel to the press axis and are curved outwards in the manner of a semi-cylinder.  
         [0043]    In the exemplary embodiment, the length and width of the press cutters  27  radial relative to the press axis  21  amount to 10 mm and 2 mm respectively. In the closed state of the preforming press, the pressing faces  26  of the press cutters  27  assume a clear distance of 2 to 4 mm from the press axis  21  (FIG. 10).  
         [0044]    In contrast with FIGS. 6 and 7, FIGS. 8 and 9 show a synchronous closing movement of the press segments  22  and sliding plates  24  in the radial direction. FIG. 8 shows an intermediate phase of this closing movement of the press dies, whilst the final closing position of these press dies is shown in FIG. 9. The position of the dies shown in FIG. 9 corresponds to the final dimension of the preform  15 . The simultaneous pressing movement of the press segments  22  and the sliding plates  24  has the advantage, that the geometrical uniformity of the circumferential strip-shaped portions  12  and  13  of the preform  15  will be enhanced. If the tampon is wetted by a fluid the tampon will expand to a more circular shape than in case of the sequential movement of the press dies as shown in FIGS. 6 and 7.  
         [0045]    If appropriate, however, the press faces can also have a mutually differing shape. If appropriate, the sliding plates can also be designed differently, for example made angular, arrow-shaped or drop-shaped. It is essential that they load and press only a narrow circumferential portion of the blank corresponding approximately to a generatrix. Furthermore, the cycle of movement of the two groups of press dies can, where appropriate, also take place simultaneously or interruptedly in the preforming and post forming and alternately between these two movement actions. Thus, it can be important, according to the process of German Auslegeschrift 1,491,161, first to close all the press dies simultaneously only up to the circumference of the blank  11 , in order to centre the blank as exact as possible in relation to the press axis  21 , before commencing the actual pressing operation, so as to ensure that the central fibre core  16  comes to rest exactly in the middle of the tampon  10 . This is desirable to obtain the highest possible buckling strength or stability of the tampon, above all when the latter is to be used as a digital tampon.  
         [0046]    According to FIG. 10, the preforming press described is followed by a stationary conical forming die  29 . This forming die  29  is arranged coaxially relative to the press axis  21 . The entry orifice  30  of the forming die has a diameter of 20 mm which corresponds approximately to the orifice of the preforming press in the closed state of its press dies which is shown in FIG. 7. The inner face  31  is narrowed towards the cylindrical exit orifice  32  according to an obtuse-angled circular cone, the exit orifice  32  has a diameter of 13 mm and its cross-section corresponds to the final cross-section of the finished tampon  10 . Arranged on the input side of the preforming press is a ram  33  which serves for introducing the winding blank  11  into the preforming press and for ejecting the preform  15  through the forming die  29 . For this purpose, the ram  33  is arranged movably to and fro coaxially in relation to the press axis  21 . Rams of this type are known in the art, and therefore there is no need to represent the driving elements for the ram.  
         [0047]    The production of the tampon according to the invention by means of the above-described apparatus is carried out according to the following process: the essentially cylindrical winding blank  11  is pressed solely on the narrow strip-shaped portions  12  and  13 , arranged at equal angular distances from one another, of the circumferential surface of the winding blank, to produce the preform  15  which, as seen in cross-section, consists of the central approximately circular fibre core  16  of high compression and buckling strength or stability and of longitudinal ribs  17  of softer fibre structure extending radially outwards from the fibre core  16 . At the same time, the longitudinal ribs  17  are separated from one another by the outwardly open longitudinal grooves  18 . Thereafter, only the soft longitudinal ribs  17  of the preform  15  are exposed to a low uniform pressure radial relative to the longitudinal mid-axis of the preform, until the outer ends of the longitudinal ribs have produced a soft essentially smoothly cylindrical surface of smaller diameter corresponding to the final form of the tampon  10 . As mentioned, preferably before the actual pressing, the winding blank  11  is centred relative to the press axis  21  of the preforming press as a result of the simultaneous concentric closing of the press segments  22  and sliding plate  24  approximately as far as the circumference of the winding blank.  
         [0048]    After the pressing of the preform, the latter is ejected through the forming die  29  by means of the ram  33  and thereby brought to the final dimension of the tampon which is determined by the exit orifice  32  of the forming die  29 .