This invention relates to a method and apparatus for producing waistband-equipped disposable diapers and, more particularly, to a method and apparatus wherein the usual processing steps performed or normal features added without having to go to extraordinary lengths to maintain the waistbands in their original tensioned condition. This has been a problem especially in diapers of the adult brief variety where the waistbands are much larger and stronger than in the infant variety.
Waistband application in disposable diapers has been addressed in a number of prior art patents. Co-owned U.S. Pat. No. 4,523,969 proved successful in commercially producing adult diapers but with complicated machinery and processing. In the '969 patent and in U.S. Pat. No. 4,925,520 there were vacuum drums which were expensive to maintain.
Another prior art approach is seen in co-owned U.S. Pat. No. 5,000,806. This featured the diapers of the adult brief variety and which include a novel waistband construction and method of providing the same.
The prior art relating to waistbands can be seen in co-owned U.S. Pat. No. 5,000,806. This featured the application of an elastic strand manufactured by E. I. Du Pont de Nemours and Company marketed under the trademark Lycra. As Lycra can be stretched to levels exceeding 400%, it was difficult to obtain accurate placement of tapes or diecutting symmetry. This is overcome by the instant invention. Another prior art use of elastic waistbands is in U.S. Pat. No. 5,004,466 which employed a tape transfer step prior to adhesion to the poly-nonwoven substrates. The drawbacks of this method were high cost, unattractive tails visible through the material and the inability to control the placement.
Still further, the prior art procedure was the use of a single strand elastic aligned on a drum-type former system. This left red lines due to concentrated elastic force to the wearer and the diaper had to be held in vacuum to remain aligned which resulted in a costly method as well as the elastic having to be rotated before application.
The shortcomings of the prior art are overcome by the instant invention which employs a center position nonwoven web to sandwich waistband material between the bottom moisture impervious sheet and the center nonwoven material. More particularly, the invention provides for applying spaced-apart longitudinally-extending webs of non-woven, performing the usual processing steps such as leg cutout and tape tab application, and then applying the waistbands. Other objects and advantages of the invention may be seen in the details of the ensuing specification.