Method and Apparatus for Making Diapers With Elastic Bands

The present invention relates to method and apparatus for making a diaper and a new diaper construction. U.S. Pat. No. 3,860,003 discloses a diaper construction with elastic strips adhesively secured to the backing sheet of a diaper to provide a close fit of the diaper to the baby's legs. The elastic ribbon provides elastically contractable leg openings. U.S. Pat. No. 4,081,301 discloses apparatus for making diapers of the type disclosed in U.S. Pat. No. 3,860,003. In a diaper construction of the type exemplified by U.S. Pat. No. 3,860,003, it is desirable that the elastic be only in the leg-contacting diaper portions rather than in the waistband portions. Accordingly, the elastic band is only adhered to the facing or backing sheet in the leg-contacting zone of the diaper. To accomplish this result, glue is intermittently applied to the continuously fed elastic band so that it will adhere to the desired leg-contacting portion of the diaper but not the waistband portions of the diaper. Inasmuch as the elastic bands are superimposed on the backing as a continuous ribbon, the bands extend to the ends of the diaper. When the diapers are cut from the web, the tension on the non-glued portions of the elastic bands adjacent the cuts is relaxed and the ends of the bands contract. The non-adhering portions of the elastic ribbon provide or serve no useful function in the completed diaper and constitute considerable waste of ribbon. The wasted portion of the ribbon can constitute as much as 40% of the total length of ribbon used per diaper.

The invention provides method and apparatus for pre-applying two elastic ribbons or bands to either the moisture impervious backing or the moisture pervious top sheet in advance of assembly of the absorbent material top sheet and backing at the assembly station where the diaper is formed. More specifically, the elastic ribbon and web to which the ribbons will be affixed are continuously fed to an elastic band applying station. Adhesive is supplied to the entire lengths of elastic ribbon prior to superimposing the ribbon on the web. The web is folded at spaced intervals by forming festoons to prevent portions of the elasticized band from contacting the adhesive bearing elastic band. The folds in the web which do not have an adhesively adhered portion of elastic ribbon later become the non-elasticized waistband portions of the diapers. The festoons or folds are formed by feeding the web top sheet or backing sheet to a conveyor which carries spaced web support plates carried by chains which form a substantially planar and continuous surface when the chains are making an upper horizontal run. However, as the chain winds around the end sprockets just prior to the horizontal run, the plates separate slightly to form a break in the web-supporting surface. As the support plates approach the horizontal supporting run and come into contact with the incoming web, spaced tucker bars carried by an offset chain continuously and successively push the web downwardly between the spaced web supporting plates.

Thus a series of festoons or folds in the web are continuously and sequentially formed at spaced intervals by the tucker bars in gaps between plates. As the support plates move along the horizontal supporting run, the plates come together with only a minor gap separating the adjacent ends. The loops or folds of the facing sheet are confined within the gap and wrapped around the ends of the tucker bars. Two spaced elastic bands or ribbons under tension and with adhesive applied are fed into the system and superimposed on the facing sheet over the gaps above the folds or festoons. Continued movement of the facing sheet and elastic bands takes the facing sheet and bands under a hold-down belt with a pressure plate which sets the adhesive. the elastic bands are severed in the gaps between the support plates by a rotary cut-off knife or the like which moves in sequence and cuts the elastic band. Inasmuch as the elastic band is cut by the knife in a gap where the web is folded, with the bight of the fold substantially below the ribbon, the web itself is not cut, only the elastic ribbon.

The foregoing method and apparatus result in minimal waste of elastic ribbon and provide a method for pre-application of ribbon to the backing sheet which can be stored for later use or immediately delivered to the diaper assembly station.

Further objects, advantages and features of the invention will become apparent from the disclosure.

FIG. 1 is a diagrammatic side elevational view of apparatus for performing the method of the invention.

FIG. 2 is an enlarged view of a portion of FIG. 1.

FIG. 3 is a fragmentary plan view of apparatus shown in FIG. 2.

FIG. 4 is a perspective view of the web with elastic ribbons applied in accordance with the invention.

FIG. 5 is a perspective view of a single diaper.

FIG. 6 is a fragmentary enlarged plan view of the apparatus illustrated in FIG. 1.

FIG. 7 is a diagrammatic side elevational view of an elastic ribbon applying station and a diaper forming station.

FIG. 8 is a modified embodiment of apparatus to practice the invention.

FIG. 9 is a view along line 9--9 of FIG. 8.

FIG. 10 is an enlarged view of the cut-off knife shown in FIG. 1.

Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structure. The scope of the invention is defined in the claims appended hereto.

The illustrated apparatus will be described relative to a process for forming disposable diapers. However, the apparatus and method disclosed herein are suitable for applying ribbons of elastic to a web for other garments or products. As disclosed, a parent or supply roll 10 supplies a web 12 which can be either the facing sheet which is absorbent or a non-absorbent or impervious backing sheet for a diaper. Feed rolls 14 provide a velocity V-1 higher than the velocity of the web in the elastic ribbon applying station, as subsequently described. This provides slack which is used to form fold or festoons. Dancer rolls 16 control the slack.

The web 12 is fed to a ribbon applying or combining station 20. At the ribbon combining station 20, two ribbons or bands 22, 23 of elastic material are super-imposed on the web 12 while in a stretched condition under tension. The stretched elastic bands 22, 23 are applied continuously to the web 12 and over the gaps where festoons or folds are formed.

In this regard, the combining station 20 includes upper and lower conveyor chain pairs 26 and 28 which are laterally offset as shown in FIG. 6. Chains 28 are arranged around sprockets 36, with the spaced chains 28 carrying a plurality of web support plates 40 which are connected to the chains by brackets 42 having suitable chain connectors 43 (not described in detail). The support plates 40 are arranged and spaced on the chains 28 so that they form a substantially continuous supporting surface when in the upper run position 30 (FIG. 1), with the support plates 40 separated by small gaps 44. However, as the chain 28 traverses the radius of the sprockets 36, the plates 40 spread and form larger gaps 48 (FIG. 1). It is through the gaps 48 that folds, festoons or tucks 50 are formed as presently described.

As illustrated in FIGS. 1 and 6, chain pair 26 is laterally offset from chain pair 28 and carries a plurality of tucker bar supports 51 which carry tucker bars 54. The tucker bars project laterally to register with the gaps 48 between the support plates 40 and push the web 12 into the gaps 48 to form folds 50 in sequence. Each tucker bar 54 is provided with a longitudinally extending fin 57 or anvil bar which cooperates with the ribbon cut-off knife 78 as presently described.

The elastic ribbons 22, 23 are applied in a stretched condition under tension to the web 12 at 66 (FIG. 2). Adhesive is continuously supplied to the ribbons 22, 23 by a glue applicator 64 prior to contact of the ribbons 22, 23 with the web 12. A hold-down belt 70 with a pressure plate 72 firmly applies the ribbons to the web 12 and maintains the contact of the elastic ribbons 22, 23 and web 12 until the adhesive sets.

As illustrated in FIG. 10 the elastic ribbons 22, 23 are severed in the small gaps 44 between the support plates 40 by a rotary cut-off knife 78 which is timed to apply the cutting edge 80 to the ribbons within the small gaps 44 above the bights of the folds or festoons so that the web 12 is not also severed. An anvil back-up or support roller 81 can be provided.

Draw rolls 86 withdraw the web 12 and superimposed elastic strips 88 from the combining unit 20 and the festoons or folds 50 are removed as the slack in the web is taken out by the dancer rolls 87 to result in gaps 90 on the web 12 between adjacent ends of the elastic band or ribbon. The web 12 (FIG. 4) with the spaced and stretched elastic leg band portions can then be stored or fed to a station for combining the web and absorbent pad and top or backing sheet to form a diaper. The draw rolls 86 increase the velocity of the web 12 to a velocity greater than that in the combining unit to remove the folds or festoons. Inasmuch as the elastic bands are assembled and maintained under tension, upon release of the tension when a diaper is cut from the diaper chain, the relaxed elastic bands will cause the diaper to bunch up as shown in FIG. 5.

The composite 101 of elastic ribbons and web 12 include portions 90 which form the waistband portion of the diaper and which are free of elastic band. Thus there is no waste of unused elastic band material as there is in the prior art diapers such as that disclosed in the U.S. Pat. No. 3,860,003, hence reducing the cost of the diaper. The width of the waistband portions 90 which is non-elasticized is determined by the depth of the festoons or folds 50 and the radius of the tucker bar 54. The length of the stretched ribbon is equal to the distance between festoons. The size of the festoons or folds can be varied for the particular application. Small festoons will provide a greater percent of elasticized length, with large festoons resulting in a smaller percentage of elasticized length. Hence, varying the festoon size determines the length of the attached elastic band.

The web in FIG. 4 can be delivered immediately to a diaper assembly station 102 shown in FIG. 7. At the diaper forming station 102, a second web 104 which comprises either a backing sheet or facing sheet, depending on the character of web 90, carries spaced apart absorbent pad elements 106 which are assembled in a lamina with sheet 101 which contains the elastic bands 22, 23. The assembly is synchronized so that the gaps 112 between the ends of the bands are centered between the pads so that there is no elastic in the waistband portions 90 (FIG. 5) of the diapers. The lamina of web 101 and web 104 can be glued by equipment 118 to form a chain of diapers which are separated in the waistband portions by a cut-off knife 122 after being secured by a press bar 117.

In the embodiments of the apparatus shown in FIGS. 1 and 2, an adhesive is applied to secure the ribbon to the web. Alternatively, the adhesive can be a hot melt adhesive with a heater and cooling unit to process the adhesive. The ribbons 22, 23 can be heat sealed to the web by a heat seal unit rather than by the use of adhesive.

FIGS. 8 and 9 show a modified embodiment of the apparatus of the invention. In the modified embodiment, the folds are formed on a grooved roller 150 which has equally spaced grooves 152. Festoon, tucker or fold forming bars 154 having anvil surfaces or anvil blocks 156 are carried by spaced chains 167 about a tortuous circuit.

The web 160 of facing or backing material for diapers is drawn from a parent roll 162 and controlled by dancer rolls 164. The web is fed to the roll 150 at a velocity V.sub.1 higher than the velocity V.sub.2 of the peripheral surface of the roll 150. The tucker bars register with the grooves 152 and push the web 160 into the groove 152 to form a fold or festoon 166.

Spaced elastic bands 170 are delivered to the backing or facing sheet web 160 after glue is applied by glue applicator 172. A vacuum or friction roll 173 can be employed to stretch the ribbons after adhesive is applied. The adhesive applicator can be operated by a cam 175 or other timing device so that adhesive is not applied in the ribbon severing zones, thus reducing the quantity of adhesive required. One or more hold-down belts 174 retain the stretched elastic bands 170 against the web 160 until the adhesive sets. The elastic bands 170 are severed in the folds with or by rotary cut-off knives 178 which cooperate with the anvil 156 of each tucker bar. As the web 160 leaves the roll 150, the web is accelerated from velocity V.sub.2 to velocity V.sub.1 to remove the folds. The web leaves dancer rolls 180 and travels to the diaper assembly station (not shown).

The chains carrying the tucker bars 154 are arranged around sprockets 184, 186, 188, 190 and 192. The sprockets are arranged to maintain the tucker bars in position with the grooves 152 in the roll 150 for a major portion of the periphery of the rolls, as illustrated, to accomplish the application and cutting of the elastic bands or ribbon 170.

It is apparent that additional cost savings can be obtained if the adhesive is applied intermittently to the elastic ribbon, such as in the form of spaced dots rather than continuously. The length and extent of the adhesive application can be varied and adhesive need not be applied in ribbon severing zones as pointed out above.

The unit length of the web for one diaper or article to which the ribbon is applied is always longer than the unit length of the applied ribbon under tension for one diaper or article because of the tucks or folds in the web.