US 3520303 A
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D. D. ENDRES 3,520,303
DISPOSABLE DIAPER F led March 22, 1968 Juiy 14, 1970 United States Patent O1 3,520,303 Patented July 14, 1970 3,520,303 DISPOSABLE DIAPER Dan D. Endres, Neenah, Wis., assignor to Kimberly- Clark Corporation, Neenah, Wis., a corporation of Delaware Filed Mar. 22, 1968, Ser. No. 715,301 Int. Cl. A61f 13/16 U.S. Cl. 128-287 9 Claims ABSTRACT OF THE DISCLOSURE A disposable diaper with an improved construction designed to reduce leakage.
Each end of the diaper is provided with a leak preventing barrier comprising a thin flexible film disposed be tween the fluid pervious cover sheet and the absorbent core. The barrier comprises a narrow strip of thin film affixed between the cover sheet and backing sheet along a transverse heat seal line at each end of the diaper. One end of the film extends a short distance into the interior portion of the diaper, lying over the ends of the absorbent core and under the cover. This construction also lends itself to high speed machine production.
BACKGROUND OF THE INVENTION Important requisites for disposable diapers include such desiderata as high absorbency, comfort during wear, the use of non-irritating components, substantially leak-proof construction, and, of course, economical production costs. Of these, one of the most difficult to achieve has been a construction which reduces or prevents leakage sufficiently to insure that the outer clothing of the infant is not soiled during use.
In the customary methods for manufacturing disposable diapers, three continuous webs of material are fed through the processing machine. These webs comprise an upper fluid-pervious cover sheet of soft fibrous material, a lower fluid-impervious backing sheet which is usually a plastic film, and a central absorbent core of substantial thickness usually comprised of wood pulp fluff or piles of cellulose wadding. The outer edges of the cover sheet and backing sheet are continuously attached to each other by embossing; by overfolding and heat sealing; by adhesive attachment; or the like. Following some type of edge sealing operation, the continuous strip formed from the operation is cut into suitable diaper lengths and the ends either left unsealed with a raw cut edge, or sealed by embossing/ stamping, and/r heat sealing. In another type of operation, the absorbent core may be pre-cut into pads of a predetermined size and deposited at intervals on the backing or cover sheet before edge-sealing, with subsequent transverse cutting and sealing operations being timed to take place at the interval between pads. In either of the above operations, it is relatively easy to fold the longitudinal edges of the fluid-impervious backing sheet, in either overor under-lapping relationship to the cover sheet, whereby an edge channel or dam is provided along both edges of the diaper to prevent edge leakage of fluids from the absorbent core. However, it is a difficult and costly operation to perform a folding operation on the backing sheet, which operation is designed to fold the front and back ends of the sheet over the leading and traveling edge of the absorbent core, after the continuous assembly has been cut into diaper-size sections. As a result, while the side edges of commercial diapers now comprise folded over portions of the backing sheet to provide leakage inhibiting means along the edges, the front and back ends of the diapers are usually either merely pinched shut and heat-sealed, or left open. None of these arrangements provide positive end seals. Accordingly, serious leakage problems often exist at these ends.
In cases where the cover sheet and backing sheet are transversely heat sealed to each other, the fact that the cover sheet necessarily is pervious, permits fluid to flow over the ends when large quantities of urinary discharge occur. Since an infant spends the major part of its time in a reclining position, and the main force and primary direction of urinary flow is toward the diaper ends, these ends are particularly vulnerable to leakage.
In cases, where the ends are left open rather than pinched shut, or heat-sealed the absorbent core filler also tends to expand and shift out past the ends of the backing sheet to still further contribute to leakage.
It is the principal object of the present invention to overcome these disadvantages by providing a leakage reducing dam construction at the diaper ends.
It is an additional object to provide a diaper with a construction which reduces end leakage and which lends itself to economical high-speed machine production.
Still another object is to provide a diaper construction having end areas of increased strength.
Yet another object is to improve the strength of the heat seal itself thereby simplifying the end sealing process and allowing higher operating speeds.
SUMMARY OF THE INVENTION The improved diaper has the usual fluid-pervious coverv sheet, a fluid-impervious backing sheet, and a central core comprising a substantially rectangular batt of absorbent material. The longitudinal edge portions of the backing sheet are folded over the respective edge portions of the core and attached to the cover sheet along these edges in a narrow area substantially coextensive with the edges of the core. The ends of both the backing sheet and the cover sheet extend beyond the front and back edges of the absorbent core and have a thin strip of plastic film interposed between them. The plastic strip, cover sheet, and backing sheet are heat-sealed to each other along a line immediately adjacent the ends of the core. The edge of the thin plastic strip opposite from the heat-seal line extends inwardly beneath the cover and over the top of the absorbent core for a distance sufficient to overlie the core ends and form a fluid-retaining pocket around the ends. This constluction serves to hold sudden gushes of fluid within the pocket and substantially prevents end leakage as long as the absorbent core itself has some fluid capacity left.
In constructing the diaper on automatic machinery, the plastic strip can be fed onto the cover material at intervals timed to fall between spaced absorbent core sections. The dimension of the strip corresponding to the longitudinal dimension of the diaper, is twice as long as needed, and when cut in half transversely and heatsealed in the space between diapers, one-half of the strip provides an integral plastic dam at the trailing edge of the lead diaper while the other half provides a darn at the leading edge of the following diaper.
It has also been found that the introduction of the plastic strip between cover sheet and backing sheet greatly improves the heat seal attachment of cover sheet and backing sheet, resulting in an overall strength improvement in the end portion of the diaper, and more eflicient machine operation.
The foregoing and other advantages, objects, and features attendant the improved construction will become apparent by reference to the following specification and accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING In the drawing, wherein like numbers show like parts: I
FIG. 1 is a plan view with portions partially cut-away, showing a diaper of the improved construction as set forth in this invention.
FIG. 2 is a section taken along line 2-2 of FIG. 1.
FIG. 3 is a section taken along line 33 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in the drawing, the improved diaper 10, comprises an absorbent core 11, a fluid-pervious cover sheet 12, a fluid-impervious backing sheet 13, and a thin, flexible darn 14 of plastic film.
Longitudinal edge portions 13a of backing sheet 14 are folded back over core 11, and heat sealed or adhesively attached to cover sheet 12 at 15. The area of attachment 15 extends along the entire length of the diaper and is preferably confined to a narrow strip substantially coextensive with the edges of core 11.
Plastic strip 14 is interposed between cover sheet 12 and backing sheet 13 at both the front and back ends of the diaper, and the three elements are heat-sealed together along line 16 at each end. The opposite edge 14a of strip 14 extends inwardly a short distance over core 11 and is disposed immediately under cover sheet 12.
Fluids which strike cover sheet 12, most generally in the central area, are absorbed in core 11 and spread both laterally and longitudinally therein by gravity and capillary action. As the fluid flows to the ends of the diaper it is trapped in the pockets formed by impervious strips 14 and will not overflow until the central core area itself is substantially saturated. This construction permits the diaper to be used longer without leaking.
The arrangement of strip 14 and edges 13a under the cover sheet 12, as shown, also provides advantages with respect to comfort in that the soft fibrous cover material contacts the skin as opposed to prior art edge constructions, wherein a plastic backing sheet'is folded over the side edges of the diaper to seal the edges against leakage, and the film comes in contact with the skin during use.
The type of material used in the absorbent core is not critical. It may comprise a layer of cellulosic fluff from wood pulp, multiple layers of cellulose wadding, absorbent cotton or rayon fibers, or any similar material with suitable absorbent properties.
The cover sheet may consist of any fluid-pervious material and may consist of hydrophilic or hydrophobic components. The cover sheet should be soft and flexible and substantially non-adherent to the skin when either 'dry or wet. Non-woven webs are especially suitable and may comprise natural or synthetic fibers, or mixtures thereof. Thread-reinforced non-woven webs or cellulose wadding are also suitable. The prime characteristics necessary for the cover sheet is that it pass fluids rapidly while retaining substantially no fluid on the surface. As is well known, when such a sheet is placed in contiguous rerelationship to an underlying element having high absorptive capabilities, such as wood pulp flulf, the capillary attraction exerted by the latter is sufficient to rapidly draw fluid away from the surface of the cover sheet and keep the sheet relatively dry.
The underlying fluid-impervious backing may be of polyethylene sheet stock or other thin plastic films such as polypropylene, polyvinylchloride or the like, which in thin calipers are soft and flexible enough to conform to the body. Use of such material, of course, eliminates the need for supplementary rubber or plastic pants. Laminates of such films with a light weight tissue may also be used. A particularly useful material is a one mil thick, white-pigmented taffeta-embossed polyethylene.
The thin plastic film for the end dam is also preferably of a flexible sheet stock having the above properties. A particularly suitable film is a smooth clear polyethylene 1 mil thick. It is preferred that this element be as thin as possible and still perform its function. While thicker films provide greater strength, films as thin as /2 mil have proved satisfactory where a high degree of additional strength in the end of the diaper was not required.
The size of the diaper may vary according to needs. One suitable finished size is 12 /2" X 17 /2". Of the elements comprising the diaper, the cover sheet is 12 /2 x 18 /2"; the backing sheet is 15" x 17 /2", whereby each edge may be folded back over the top of the core a little more than 1"; the core is 12 /2" x 16" so that the cover and backing extend approximately /2" beyond each end to allow for heat sealing; and the plastic film insert is 12 /2 x 2 /2", extending across the entire width of the diaper and into the interior about 2".
In manufacturing the diaper, 5" strips of plastic are used as the base material for the dam. These strips are spaced to overlie the ends of two adjacent pads under a continuous cover sheet. When the continuous assembly is cut transversely between pads and simultaneously heat-sealed to form the individual diapers, the strip is also cut in half so that one half forms the dam for the rear of the leading diaper, While the other half forms the darn for the front of the next following diaper.
In addition to functioning as a leak-proofing element, the film strips also enable the heat-seal at each end to be much stronger and adds overall strength to the end portions of the diaper.
The resulting diaper may have adhesive tabs applied to one end for fastening purposes, or conventional pins may be used.
While only one specific embodiment of the improved diaper has been set forth above, it will be seen that numerous variations may be made without departing from the spirit or scope of the invention as defined by the appended claims.
What is claimed is:
1. An improved disposable diaper comprising a substantially rectangular absorbent core, a fluid-pervious cover sheet and a fluid-impervious backing sheet; the longitudinal edge portions of said backing sheet being folded over said core, extending inwardly a short distance over the top of said core, and being attached to said cover sheet along its entire length in a narrow area substantially coextensive with the side edges of said core; each of the ends of said backing sheet and said cover sheet extending beyond each of the ends of said core and having a thin sheet of flexible plastic interposed therebetween; said backing sheet, cover sheet and plastic sheet being bonded to each other transversely on a line adjacent the core ends; the edge portion of said plastic sheet opposite said bond line extending-inwardly above said core and being interposed between said core and said cover sheet.
2. The diaper of claim 1 in which said backing sheet is opaque polyethylene film.
3. The diaper of claim 1 in which said plastic sheet is clear polyethylene film.
4. The diaper of claim 3 in which said plastic sheet is not more than 1 mil thick.
5. The diaper of claim 1 in which the line of bond between backing sheet, cover sheet and plastic sheet is a heat seal.
6. The diaper of claim 1 in which the edges of said backing sheet which extend inwardly over said core are free of attachment.
7. The diaper of claim 1 in which said absorbent core comprises Wood pulp fluff.
8. The diaper of claim 1 in which said absorbent core comprises multiplies of cellulose wadding.
9. The diaper of claim 1 in which said absorbent core comprises a combination of wood pulp fluff and multi-plies of cellulose wadding.
References Cited UNITED STATES PATENTS Makela 128-290 Voigtman 128--287 Hrubecky 128-287 Wanberg 128-287 Sabee 128--287 Liloia et al. 128-2 87 10 CHARLES F. ROSENBAUM, Primary Examiner