Domed compressed tampons

Details Domed compressed tampons Domed compressed tampons

1999-08-06

2001-10-09

Vo, Peter (Department: 3721)

Manufacturing container or tube from paper; or other manufacturi

Bending

Crushing or crumpling

C053S436000, C604S904000, C028S118000

Reexamination Certificate

active

06299573

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention concerns apparatus and methods for providing dimensionally stable absorbent bodies which comprise cellulose fibers and, in particular, concerns providing such bodies compressed into cylindrical tampons having a rounded or domed tip. Specifically, this invention provides methods and apparatus for manufacturing dimensionally stabilized tampons with a domed tip having a smooth surface.
Absorbent, cylindrical tampons are now widely used for a number of absorbent purposes in the medical and dental field but are primarily used in the field of feminine hygiene as catamenial tampons. In this latter field, there are two basic types: digitally inserted tampons, inserted with the fingers, and applicator tampons inserted with the aid of an applicator. Both types are usually made by folding or rolling a loosely associated, generally rectangular strip of absorbent material, usually fibrous and cellulosic in nature, into a blank and then compressing the blank into a cylindrically shaped product. In the case of digital tampons, the product is then wrapped and packaged and, in the case applicator tampons, the product is first inserted into the applicator and then wrapped and packaged.
In both instances it is highly desirable that the tampon maintains its final compressed shape and presents a smooth outer surface at the dome whereby both the removal from the applicator and/or packaging and the insertion into the vagina are facilitated. To this end, the art has provided various suggestions for attaining shape stability and surface smoothness of the dome tip. In U.S. Pat. No. 4,081,884 for example, it has been suggested that a tampon blank be first radially compressed and then axially compressed and, while in the axially compressed state, heated to impart a set to the compressed body. The axial compression is applied to the extent that the axially compressed tampon is about 90 to about 98% of the desired length of the tampon in its final state. Owing to the heat setting technique described therein, the tampon is said to “grow” only moderately i.e. 2-10%, based on the final length. While this technique does indeed produce a relatively dimensionally stable tampon, unfortunately the required heating step entails expensive equipment and is particularly difficult to carry out at the high production speeds (of up to fifteen hundred tampons per minute) required for practical commercialization.
The art has also made suggestions with respect to presenting a smooth forward or insertion end for the tampon and, in particular for presenting a tapered, domed, or hemispherical end for a tampon to facilitate insertion. Such a suggestion may be found in U.S. Pat. No. 3,738,364 wherein a ram having a recess designed to impart a tapered shaped to a tampon blank is described. Most recently, in European Patent Application 94/102244.4 filed on Feb. 14, 1994, there is described a tampon blank which is axially compressed in a cylinder between two rams with the insertion end ram having a cup like recess to impart a hemispherical shape to the insertion end of a tampon. Such a system is found to work well for a moderate degree of axial compression. On the other hand, as will be described in greater detail herein drawbacks are inherent in such systems. This is particularly true in seeking to obtain dimensional stability without resorting to a heat setting step and at the same time attempting to dome the insertion end of the tampon.
SUMMARY OF THE INVENTION
This invention therefore concerns providing an improved apparatus and method for compressing a cylindrical blank into a tampon which is dimensionally stable and is provided with a domed insertion end. Specifically, the invention comprises introducing a cylindrical blank into a cylindrical axial compression chamber having an insertion end, an opposed withdrawal end and cylindrical side walls therebetween. The withdrawal end of the chamber is open and adapted for the introducing the cylindrical blank into the chamber and for accepting a reciprocating compression ram. The compression ram is adapted to axially reciprocate into the chamber and exert axial compression force against the withdrawal end of the so introduced cylindrical blank. The insertion end of the chamber presents an immovable closed insertion end wall to the cylindrical blank when it is introduced into the chamber. Upon introducing the blank into the chamber and urging the axial compression ram toward the insertion end to axially compress the blank therebetween, the insertion end of the blank is forced against the closed inner surface of the insertion end of the chamber and takes the shape of this inner surface; preferably, a smooth surfaced dome, e.g., a hemispherical shape.
In accordance with this invention, shape stability is achieved, not as in the prior art by slight overcompression and recovery in conjunction with heat setting, but instead, by an extreme axial overcompression step. In the axial compression step of an embodiment of this invention the blank is pressed from its original length to a length ranging from about 15-30% of its original length. Blank is then allowed to recover to a finished compressed tampon with the recovery length ranging from about 50-80% of the original blank length. Blank length is chosen to produce a finished tampon which has the desired finished length, e.g., about 45 millimeters.
The high degree of axial overcompression has been found to result in a dimensionally stable tampon without the need for heat setting. While the precise reasons for the remarkable stability of the tampon is not entirely known, it is believed to be the result of circular pleats forming on the cylindrical surface of the blank during the compression step. These pleats tend to fold over the cylindrical surface. When constrained from opening, as when the finished tampon is packaged and/or placed in an applicator, the pleats retard axial growth. It has been discovered however that the high degree of compression in combination with conventional doming techniques and apparatus, does not result in a smooth surfaced domed insertion end. Accordingly, the closed insertion end of the compression chamber is, in accordance with this invention, uniquely designed to insure such smooth surface. Specifically, the closed end wall of the chamber comprises a bore therethrough. The bore is generally coaxial with the chamber and has a periphery, at the insertion end wall, having a smaller diameter than that of the cylindrical compression chamber. The bore is adapted to accept a reciprocating ejection ram having a ram surface facing into the chamber. The ram may be seated, in a first position, with the ram surface contiguous with the insertion end wall. Further, the ram may be axially reciprocated out of such first position, through the bore and through the compression chamber to eject the axially compressed blank. When the ram is seated in the first position, the ram surface and the insertion end wall of the compression chamber together form a smooth doming surface for imparting a smooth surfaced dome to the insertion end of the blank when the blank is compressed by the action of the compression ram. The smooth doming surface may be accomplished as a result of having the ram closely fitted to the bore at the periphery so as to present essentially no gap between the bore periphery and the ram surface. The dome shape may be imparted by machining the insertion end wall with the seated ram in place, thereby obtaining a continuous smooth doming surface. Because the ram is closely fitted within the bore, no ridges are formed on the insertion end of the tampon, notwithstanding the high degree of axially compression. Notwithstanding the tight fit of the ram within the bore, because the bore periphery is of a smaller diameter than the chamber and hence radially spaced from the side walls of the chamber, the ram has sufficient clearance to move through the chamber and eject the tampon without interference from the walls of the chamber.


REFERENCES:
patent: 2798260 (1957-07-01), Niepmann

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