Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2001-03-21
2003-11-18
Cole, Elizabeth M. (Department: 1771)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S163000, C156S164000, C156S229000, C156S250000, C156S252000, C156S253000, C156S268000, C156S269000, C442S327000, C442S328000
Reexamination Certificate
active
06649001
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a method and to an arrangement for producing basic starting material for the production of fastener tabs that are intended to fasten together the side portions of absorbent articles, such as diapers or like-articles that include a front part, a back part and an intermediate crotch part, so that the article will have a pants-like configuration. The invention also relates to such basic starting material and to a fastener tab produced from such material.
BACKGROUND OF THE INVENTION
Absorbent article fastener tabs used to fasten together the side portions of articles so that the article will have a pants-like configuration when worn are known in many different varieties. For instance, the tabs may be of a mechanical type that includes hooks of the touch-and-close fastener type or some like type, as described in EP-A1-0 235 014, for instance. Fastener tabs of this type, however, are expensive and difficult to apply at fast speeds in the manufacture of absorbent articles. Such tabs have therefore had limited use. WO-A1-95/05140 describes a fastener tab manufacturing method which is said to avoid these problems.
Other types of fastener devices that are more suited for application at high speeds are known to the art. For instance, it is known to provide a diaper with pressure-sensitive tape for fastening the diaper around the waist of a wearer, therewith fastening the front and back side of the diaper together to obtain a pants-like configuration. These tapes are often made of paper material and are therefore usually relatively rigid. These tapes are also often provided with some form of protective film that must be removed prior to use.
Elastic fastener devices are also known in the present context. For instance, U.S. Pat. No. 3,800,796 describes a disposable diaper that includes semi-elastic fastener tabs. The fastener tabs may comprise elastic material that forms an elastic zone surrounded by non-elastic material that forms two non-elastic zones, or may alternatively comprise solely elastic material that has been made non-elastic at its edge regions in some suitable manner. One of these non-elastic zones of the fastener tabs is fastened to the diaper and the other is provided with an adhesive substance, for instance.
TECHNICAL PROBLEMS
One problem resides in the ability of producing both left-hand and right-hand fastener tabs simultaneously, which is desirable since pairs of left-hand and right-hand fastener tabs are often fastened simultaneously to mutually sequential absorbent article blanks in the continuous manufacture of such articles. Furthermore, it shall be possible to produce absorbent articles provided with such fastener tabs at high production rates. Difficulties may be experienced in applying glue and other adhesive substances.
The fastener tabs must also be soft, partially air permeable and must not chafe the skin of the wearer.
Furthermore, it is desirable that elastic fastener devices will include a “stop function” that has a distinct stop which “informs” the user or the carer when the elastic part has been stretched to a maximum, i.e. includes casing material that prevents further stretching of the elastic sheets or layers. This can be achieved with stretched elastic fastened to a non-elastic casing material. Alternatively, the casing material can be pleated and fastened to a smooth elastic material, which may be either in a stretched or a relaxed state.
Against this background of the aforesaid problems, a preferred method has been a laminating method in which the elastic is stretched and the casing materials are smooth, and in which the casing materials are joined together, suitably by heat welding or ultrasound welding.
EP-A1-0 494 941 describes a method of producing an elastic material, by joining two sheets of non-stretchable material that enclose a stretched elastic sheet, through the medium of perforations in the elastic sheet. This document also discloses that zones of different elastic properties can be produced through the medium of different perforation patterns and that non-elastic zones can also be produced, wherein the non-elastic zones are parts that were originally elastic but that have been “killed” by intensive heat treatment or ultrasound welding. The resultant non-elastic zones are relatively dense, although they are air-permeable to some extent. Furthermore, the intensive treatment has a negative effect on the casing materials, which tend to become hard. The desired smooth surface is lost and the hard edges that are formed are very liable to chafe the wearer's skin when coming into contact therewith. Further examples of similar elastic material are found in WO-A1-92/15444, for instance.
It is difficult to pleat casing materials prior to being fastened to the elastic material, because of the high precision required. This difficulty is more pronounced at high manufacturing rates. The application of glue becomes difficult. When the materials are not thermally miscible, problems also occur in heat sealing processes.
There are thus problems which known technology has been unable to solve.
The above problems are essentially avoided completely by the present invention. The object of the invention is to provide a method and arrangement for producing basic starting material for the production of fastener tabs that have different degrees of stretchability in different directions and that are intended for fastening absorbent articles around the wearer's waist, and that can be produced in pairs at high production rates, and with which the use of adhesive agents can be limited. The fastener tabs shall also fulfil the requirement of softness, shall be air permeable and not cause chafing of the skin.
SUMMARY OF THE INVENTION
These objects are achieved in accordance with the invention with a method of producing basic starting material for the production of fastener tabs which are intended to join together the side-parts of the front and back portions of absorbent articles that include a front part, a back part and an intermediate crotch part so as to impart a pants-like configuration to said article, said method being characterised by the steps of
stretching a first sheet of elastic material in a first direction;
applying a second and a third sheet of material on respective opposite sides of the first sheet;
fastening the three sheets of material together in at least two mutually separate zones that extend parallel to each other in a second direction perpendicular to said first direction;
dividing the first sheet in each region between two zones along a line that lies between said zones, wherewith the first sheet in each region between two zones contracts to a non-stretched or relaxed state, and thereafter
fastening the three sheets of material together in each region between two zones.
In one preferred embodiment of the invention, the sheets of material are fastened together in each region between two zones in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state and with the first sheet stretched in said zones.
In one alternative, the first sheet of material may be caused to contract to an unstretched state prior to the sheets being fastened together in each region between two zones, in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state.
In one preferred embodiment of the invention, the first, second and third sheets of material are fastened together in two edge regions that extend in said second direction and that extend in said first direction outwardly of the nearest zone, in which the second and third sheets are fastened to the first sheet with said sheet in a stretched state subsequent to having caused said first sheet to contract to an unstretched state in the zones in which the second and third sheets have been fastened to the first sheet with said sheet in a stretched state.
Division of the first sheet in each region between two zones in which the second and third sheets are fastened to the
Heden Anna
Kling Robert
Mansisidor José-Maria
Nilsson Urban
Cole Elizabeth M.
SCA Hygiene Products AB
Young & Thompson
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