Brush – broom – and mop making – Processes
Reexamination Certificate
2001-10-24
2004-08-10
Snider, Theresa T. (Department: 1744)
Brush, broom, and mop making
Processes
C300S017000
Reexamination Certificate
active
06773076
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a method for the treatment of bristles at least some of which are split by mechanical forces into several separate partial cross-sections, at least along part of their length. The invention also concerns brushes comprising such bristles.
Most bristles for brushes of any kind, e.g. brushes for body and tooth care, household brushes, technical brushes, paint brushes etc. are currently produced from polymers by extruding molten polymer into endless monofilaments with subsequent drawing thereof and, optionally, stabilization of the monofilaments. The bristles are then produced from the monofilaments by cutting them to a suitable length. In general, the monofilaments and the bristles have a circular cross-section. For particular applications, bristles having a different cross-section, e.g. an oval or polygonal cross-section have been used, wherein a monofilament of corresponding profile is extruded.
In particular applications, it is desirable to use bristles whose useful ends have a fibrous, in particular, fibrillar structure, especially e.g. for brushes for applying media onto surfaces or the like, e.g. paint brushes. Even if a fleecy structure is desired, the bristle must be fibrillar. Recent findings in dental medicine have established that conventional tooth brush bristles are insufficient for cleaning, since they slide across and do not penetrate into the fine fissures of the tooth surface. A similar cleaning problem obtains for the interdental spaces.
Bristles have been split using a rotating cutter for obtaining highly fibrous structures at the bristle end U.S. 2, 812,530, WO 98/48086). When the bristles are made from polymer mixtures, the following effects are utilized: during extrusion and subsequent drawing of the monofilament, the polymer molecules are oriented in the longitudinal direction of the monofilament. The primary binding forces acting in the longitudinal direction provide high tensile strength. This orientation of the molecules in the longitudinal direction also generates the desired bending flexibility. With monofilaments produced from one individual polymer, the so-called secondary binding forces, i.e. the forces transverse to the molecular extension, are sufficiently great to prevent fraying out or splitting of the monofilament or the bristle. With monofilaments made from two different mixed polymers, sliding zones, in which the secondary binding forces area reduced, are generated between the molecular chains of the polymers during drawing. A monofilament of this type or a bristle produced therefrom can be split by mechanical forces using cutters or cutting tools. The so-called flags produced in this fashion have a highly irregular shape, irregular cross-sections, and frayed outer surfaces. A large bundle of such bristles has a fleecy, well absorbing structure. However, the individual flags have poorly defined mechanical properties. They tear off, break off or fold over. Bristles frayed out in this manner are unsatisfactory and even unsuitable for many applications. Their use in tooth brushes is questionable for hygienic reasons.
Further problems arise with brushes comprising both bristles whose ends are split and divided into flags as well as unsplit bristles. During splitting of the bristles, the sharp blades of the rotating cutter also interact with the bristles which are not intended to be split and can damage or cut their outer sides. Production of a bristle field comprising both split and unsplit bristles requires special procedures, since the cutter must not act on the unsplit bristles. A possible solution to this problem would be to separate the bristles not to be split from the bristles to be split before treatment by separation and/or covering (DE 197 28 493 A1; EP 0 736 270 A1). This process, however, is difficult and expensive. If the ends of the bristles which are not split are to be further treated, e.g. rounded, further separation of the respective bristles and an additional processing step are required.
WO 98/38889 discloses disposing the ends of the bristles to be split in a plane above the ends of the bristles not to be split by combining the bristles to be split and the ones not to be split into corresponding bristle bundles of different respective length. This permits retroactive splitting of the protruding ends of the bundles of bristles to be split. However, the lower lying ends of the unsplit bristles can only be reached for subsequent rounding through separation, which makes production difficult and expensive. Since the protruding split bristles are relatively thin, the split bristle ends may form mop-like heads even following a short period of use to prohibit proper brushing. In particular, the very fine fissures in the chewing surfaces of the teeth and also the interdental spaces cannot be reached in this fashion.
The essential disadvantage of splitting the ends of bristles, made from polymer mixtures, using a circulating cutter is that defined division of the bristles into predetermined partial cross-sections is thereby not possible. In addition, splitting generates some flags of very thin cross-section which can break during use and can be swallowed by the user of a tooth brush, which is detrimental to health.
Bristles have been proposed, in particular for tooth brushes, which are made from a plurality of thin fibers having a cover, enclosing the fibers (WO 97/25902; DE 9 408 268 U1). The cover and fibers can also be co-extruded as filaments. After cutting to the desired bristle length, the cover at the useful end of the bristle is removed by mechanical treatment or cutting to expose a short length of the fibers. These bristles are difficult to produce and have limited applications. A substantial disadvantage is, in particular, the abrupt change of the bending behavior at the transition: region between the fibers and the cover. If such bristles are used in application devices, the treated surface can be damaged by this hard transition. Similar effects obtain for use of such bristles in tooth brushes with respect to their effect on the teeth and the gums. Furthermore, the fibers virtually do not bend and cannot penetrate sufficiently into deeper depressions, interdental spaces or the like. The fibers also tend to break easily at the cover edge after prolonged use.
DE 1 997 717 U1 and DE 196 40 863 A1 each disclose a bristle made from several plastic fibers, which are connected to one another. According to DE 1 997 717 U1, the fibers are oriented parallel to one another and are welded at their contacting lines, with the bristle ends remaining unwelded. This is difficult to achieve from a technical point of view. Moreover, capillary spaces remain between the fibers in which contaminants and bacteria can accumulate. According to DE 196 40 863 A1, a number of fibers are twisted together, connected by chemical means and spliced at their ends,.wherein hollow spaces are also produced between the individual fibers in which bacteria can accumulate. Neither of the two processes permits retroactive splitting or splicing of bristles.
It is the underlying purpose of the invention to provide a method for the treatment of bristles with which bristles can be easily split into defined partial cross-sections irrespective of their respective arrangement and design. The invention also concerns production of a brush comprising such bristles.
This object is achieved in accordance with the invention in that the mechanical forces for splitting the splittable bristles are applied from different directions, relative to the longitudinal axis of the bristles. The method in accordance with the invention is preferably used in bristle fields comprising splittable and also non-splittable bristles. The effect of external mechanical forces from various directions permits, within a relatively short time, complete separation of the splittable bristles, in particular at the bristle ends, into their partial cross-sections, i.e. into fingers. The mechanical forces are preferably applied by at least one blunt tool, e.g.
Pedex & Co. GmbH
Snider Theresa T.
Vincent Paul
LandOfFree
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