Absorbent products such as diapers, training pants, adult incontinence garments, and the like generally are formed from a liquid pervious bodyside liner, a liquid impervious outer cover, and an absorbent assembly sandwiched between the bodyside liner and the outer cover. Typically, these garments include a pair of leg openings having elasticised portions which are designed to form a snug fit around a wearer's legs to prevent leakage from the garment.
Various different methods for attaching leg elastics to a moving web so as to provide elasticised leg openings on the web are known. For example, elastic ribbons may be applied along a straight line to a moving web by continuously running the elastic and the web at relatively high speeds while adhesive is applied to the elastic, and then bringing the elastic and the web together so that the elastic is bonded to the web to form elasticised portions on the web.
Although straight leg elastics improve the fit of leg openings in a garment, considerably better results can be obtained if the elastic is curved or contoured to follow the general curvature of the thigh or crotch area of a wearer. Methods for applying curved leg elastics to a moving web are also known. For example, in one method, an elastic ribbon is rolled directly into engagement with a moving web by a nip roll, and an oscillating roll is provided for oscillating the elastic ribbon so that the ribbon is applied to the nip roll in a curved line path for application to the moving web in the curved line path. In another method, a rotatable roll is moved in a direction transverse to the direction of a moving web, and the movement of the roll is imparted to an elastic ribbon which subsequently is adhered to the moving web.
A drawback with methods in which an elastic ribbon is applied continuously to a moving web is that the application of leg elastics is not limited to those regions of the web which are intended to form leg openings. As a result, various attempts have been made to apply discrete, curvilinear elastic strips to a moving web. In one method, elastic strips are adhered to flexible strip supports carried by transfer members on a rotatable support while the strip supports are in a linear configuration. The configuration of the strip supports and the elastic strips is then changed to a desired curvilinear configuration, and the transfer members are brought into transfer contact with the moving web to transfer the curvilinear elastic strips to the web. In another method, an elastic strip is stretched and wrapped about a curved side of a puck, and the puck is then rotated into alignment with a moving web to transfer the curved elastic strip, in a stretched condition, to the moving web, thereby forming a curved leg elastic on the web. The webs in these methods usually move at high linear speeds, often in excess of 600 feet per minute, and as the degree of curvature of the leg elastic increases, so the difficulty of holding and shaping the leg elastic, and of bonding the leg elastic at high speeds to the web, increases. Also, sharp direction changes of the applied strips tend to set up relatively high mechanical stresses in the moving web, and these stresses can damage the web material.
Accordingly, there remains a need in the art for a method which facilitates high-speed application of discrete, curved leg elastics or the like to curved leg openings on a moving web when forming elasticised leg openings on the web. There is also a need for a method of bonding discrete, curved leg elastics to a moving web without inducing relatively high mechanical stresses in the web.
USPTO Backgrounds
USPTO Backgrounds