Patent Publication Number: US-2023150159-A1

Title: System and method for the shaped cutting of sanitary articles, namely of washable absorbent garments

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to sanitary articles and the like for the absorption and retention of liquids, and namely to washable and reusable absorbent garments comprising a back layer made of washable fabric. 
     More specifically the invention is directed to a system and to a method for the shaped cutting of the back layer of such washable absorbent garments, having a pant structure formed by rear and front waist sections and a crotch section intermediate between the rear and front waist sections. 
     PRIOR ART 
     In the production of washable absorbent garments, the fabric back layer is fed longitudinally along a travel direction to a cutting station including cutting tools movable transversally to said travel direction so as to cut each longitudinal side edge of the web, in combination with the displacement the web and, along curved profiles defining said crotch sections. 
     Each shaped cutting tool traditionally consists of a mechanical rotating blade (commonly defined as a roller knife), acting on a smooth contrast roller better defined as a counter knife or anvil. 
     Dimensions, limits of use and costs of such known cutting tools are essentially influenced by the type of raw material to be cut, by the process speed and, last but not least, by the type of steel used to produce the cutting blade, as well as clearly by the skill of the manufacturer. 
     The limitations regarding the aforementioned conventional technology essentially concern the lack of flexibility in the format changes, where at least the roller knife must be replaced. Therefore, it is necessary to always make at least two roller knives available in the warehouse for each format (one to be used when necessary and one as a spare). It goes without saying that considering the costs of all the knives and the downtime necessary for the integration of the format change unit into the machine, the known solution is of little advantage, especially in a context where frequent format change would be required. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a system and method for the shaped cutting of washable absorbent garments which overcome the above drawbacks of the prior art. 
     According to the present invention, this object is achieved by cutting system whose main features are set forth in claim  1  and by a cutting method as primarily defined in claims  10 . 
     The invention has been conceived to carry out, on a specific layer for instance made of fabric sheet, nonwoven, polyethylene film, etc., a shaped cutting with a continuous and/or discrete intermittent profile, the shape of which is obtained through the dynamic vectorial correlation between the instantaneous speed of the layer and the position of the sonic punch or the laser beam moved by scanners or fixed optical systems in a dynamic shape transversal direction with respect to that of the advancement of the layer under treatment, through the use of suitably proportioned motors or actuators. 
     In both cases, the cutting tools must act on an adequate support system, capable of guaranteeing adequate rigidity, inertia, and position of the treated material. 
     The system and method of the invention are released from any replacement of parts during the format change phase, as the latter can be achieved thanks to the loading on the electronic control unit of the cutting system of a different SW/Motion file specific to the cutting profile to be created. This dramatically reduces downtime and at the same time increases the flexibility of the cutting process. 
     The appended claims form an integral part of the disclosure provided here in relation to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in detail with reference to the attached drawings, given purely by way of non-limiting example, wherein: 
         FIG.  1    is a diagrammatic front elevational view of part of a cutting system according to a first embodiment the invention, 
         FIG.  2    is an enlarged view of part of  FIG.  1   , 
         FIG.  3    is a view same as  FIG.  2    showing a second embodiment of the invention, 
         FIG.  4    is a perspective enlarged view of an example of one cutting tool employed by the invention, 
         FIG.  5    is a perspective view of one example of washable absorbent garment for which the invention can be carried out, and 
         FIG.  6    is a plan view of  FIG.  5   . 
     
    
    
     It will be appreciated that the various figures may not be represented on the same scale. Some dimensions and dimensional ratios are being enlarged for the sake of better understanding. It will also be appreciated that in some figures certain elements or components may not be shown, also for a better understanding. 
     DETAILED DESCRIPTION 
     With reference initially to  FIGS.  5  and  6    the numeral reference  10  indicates an example of a washable absorbent garment for which the invention can be carried out to advantage. It is to be pointed out that such a garment is just exemplary since the invention can be equally employed with different washable garments having any shaped profile similar or comparable to the one disclosed hereinafter. 
     The washable absorbent garment  10  comprises a back layer  12  of washable fabric forming a pant structure. The back layer  12  has rear and front waist sections  14 ,  16  and a crotch section  18  intermediate between the rear and front waist sections  14 ,  16 . The rear and front waist sections  14 ,  16  are wider than the crotch section  18 , such that in the extended position of  FIGS.  5  and  6    the back layer  12  has substantially an hourglass shape. 
     The back layer  12  is a fabric formed by woven threads which is washable as ordinary textile garments, e.g. swimsuits, underwear, etc. The back layer  12  may be made of any natural or synthetic material used for producing textile articles, e.g. cotton, Lycra, nylon, polyester, polypropylene etc. and any mixture thereof. In possible embodiments, the back layer  12  may be an elastic fabric made of a mixture of polyamide and elastane or cotton and elastane, e.g. 80% cotton/polyamide and 20% elastane. The back layer  20  may have for instance a weight comprised between 100-200 g/m 2 . 
     The crotch section  18  of the back layer  12  has two curved side edges  22  shaped to conform to the legs of the user in the configuration in which the washable absorbent garment  10  is worn. The rear and front waist sections  14 ,  16  of the back layer  12  have respective side edges  24 ,  26  which are joined to each other such that the washable absorbent garment  10  is closed in a pant-like shape and has two leg openings on opposite sides of the crotch section  18 . 
     The side edges  24 ,  26  are joined to each other by ultrasonic welding or by glue. 
     The washable absorbent garment  10  also comprises a washable absorbent core  28  permanently fixed in the crotch section  18  of the back layer  12 . 
     Production of the washable absorbent garment  10  is carried out by unwinding the back layer  12  from a reel and advancing it continuously (or even intermittently) in generally horizontal machine direction. The individual absorbent cores  28  are provided on a parallel line and are permanently fixed onto the back layer in longitudinally spaced positions to form a continuous garment tape. 
     The continuous tape formed by the back layer  12  carrying the absorbent cores  28  is fed to a transversally movable cutting unit  30  configured for cutting the longitudinal side edges of the back layer  12 , as the continuous garment tape advances in the machine direction, along curved profiles shaped to conform to the legs of the user. The cutting tools are movable transversally to the travel direction of the continuous tape so as to cut each longitudinal side edge of the tape, in combination with the longitudinal displacement of the tape, along such curved profiles to provide the crotch sections  18  of the washable absorbent garments  10 . 
     Referring now to  FIG.  1   , the cutting unit  30  comprises a support frame  31  bearing a pair of juxtaposed cutting tools, operating jointly or even alternatively at the opposite sides of the back layer  12 , only one of which is depicted for the sake of simplicity in  FIGS.  1 - 3   . 
     It is to pointed out that the cutting unit  30  could be equipped with just one cutting tool in case the continuous layer of a sanitary article different from garment  10  is to be cut only along one of its longitudinal edges. 
     The cutting unit  30  is displaceable transversally, in the direction of arrows X, with respect to travel direction of the continuous tape formed by the back layer  12  carrying the absorbent cores  28 , which is advanced longitudinally by a motor-driven conveyor including for instance pairs of transverse superimposed rollers  32 ,  33 . Along the path aside the cutting unit  30  the support frame  31  can bear a backing plate or a flat anvil roller upon which cutting of the back layer  12  is performed, so as to provide the necessary rigidity and proper positioning of the material being cut. 
     According to the peculiar feature of the invention each cutting tool consists of either an ultrasonic cutter or a laser beam cutter, both generally well known per se in the art of cutting, and only the first one of which is shown in the drawings and is referenced as  34 . As shown in more detail in  FIG.  4    the ultrasonic cutter comprises a vertical sharpened sonotrode, in a fixed or rotatable configuration and for instance operated by a relatively low power at high frequency, which is displaced vertically and transversally to the back layer  12  for instance by a slide  35  in turn displaced over a guiding support  36  by means of an electric rotary motor  37  controlled electronically and of a conventional screw-and-nut transmission as shown in  FIGS.  1  and  2   . The slide  35  as well as energization of the sonotrode  34  are operated by a programmable electronic control unit in synchronism with the continuous (or intermittent) advancement of the layer, for instance by means of an encoder associated to one of the rollers  32 ,  33 . 
     In the alternative embodiment shown in  FIG.  3    displacement of the slide  35  carrying the sonotrode  34  is carried out by a cam system including a cam profile  38  for instance provided at least on the end face of the lower roller  32  facing the cutting unit  30 , and an adjustable cam follower  39  operatively connected to the slide  35 . The cam follower  39  is urged against the cam profile  38  for instance by a presser device comprising a pneumatic spring  40 . 
     The arrangement of the cutting system of the invention equipped with a laser cutter can be substantially same as the one disclosed in the above in connection with the ultrasonic cutter: in such a case a source is in a fixed position on the support  36  or  31  and the laser beam with a fixed optics or specific scanner if needed is displaced by the motor-driven slide  35  transversally to the travel direction of the substrate to be subjected to shaped cut of its longitudinal edges, or the slide  35  can be operated by the cam system  38 - 39 . As a further alternative the laser source can be kept stationary and an optical system can be provided to focus the laser beam onto the continuous tape formed by the back layer  12  carrying the absorbent cores  28 , along the desired curved trajectory defining the shaped cut. 
     The embodiment of the invention having the ultrasonic cutter is generally less expensive than the laser cutter: however, the latter is more precise while affording higher cutting speed, though being more expensive. 
     Of course, without prejudice to the principle of the invention, the details of construction and the embodiments can be widely varied with respect to those described and illustrated, without thereby departing from the scope of the invention as defined by the claims that follow. Namely, the washable absorbent garments disclosed in connection with the cutting system and method of the invention is to be considered as only one example of washable absorbent garments to which the invention can be applied.