Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-10-16
2002-05-21
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C428S370000
Reexamination Certificate
active
06391445
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a bristle comprising a core of a comparatively rigid, bending-elastic plastic and at least one layer of a rubber-elastic plastic. The invention also relates to a process for the production of such bristles and to implements equipped with such bristles.
Independently of the intended use of a brush, certain fundamental demands are made on the bristles. These more particularly include the bending elasticity, flexural strength and resistance to wear. Further and often very differing requirements result from the intended use of the brush. Thus, e.g. brushes for oral and body hygiene must be sufficiently soft to avoid injury, whereas abrasively acting, industrial brushes must have hard and rough bristles. Other technical brushes, such as car wash brushes, must once again be smooth and pliable. This also applies in the case of polishing brushes. Brushes or paintbrushes used for the application of media, must have relatively closely juxtaposed, standing bristles for storing the medium, whereas in other applications individual standing bristles or bristle bundles are desired.
The action of a bristle on the surface of the object to be treated or worked is decisively dependent on the surface characteristics thereof and the bristle material. Generally bristles are produced from extruded plastic monofilaments. As a result of the choice of the plastic it is essentially only possible to influence the bending and wear resistance, but only to a very limited extent the surface characteristics and the effectiveness of the surface, apart from simple longitudinal profiles. Thus, numerous attempts have been made in the prior art to modify the surface characteristics or the effectiveness of the surface of bristles by additional measures in order to better meet the requirements of each intended use.
Prior art documents describe bristles with incorporated, abrasively acting particles for different uses. It is in each case a question of giving the bristle a hard, abrading action.
Another development referred to in prior art is to profile in different ways the jacket of a bristle formed from a plastic monofilament. It is in each case a question of forming more or less sharp edges and this extends to frayed structures.
All the aforementioned solutions with particle-filled or profiled, monofilament bristles suffer from the decisive disadvantage that the strength characteristics, particularly the bending elasticity, flexural strength and also the resistance to wear are significantly reduced, so that use must once again be made of larger bristle diameters and/or higher quality plastics. However, this is often impossible for use reasons and also leads to undesired higher costs.
Other known proposals aim at producing the bristle from two plastic components, namely a plastic core and a coating applied thereto either in the form of a jacket enveloping the core or in the form of fibers applied to the core. In these known solutions the strength characteristics of the bristle remain substantially controlled. To the extent that the core has a smooth-walled jacket, the bristle action can only be insignificantly modified. If only the hard core is profiled and a profile-following, rubber-elastic coating is applied the latter is rapidly worn away at the profile humps and the hard core is exposed. To the extent that the core is flocked with fibers, the bristle can only be used for specific purposes and is also complicated and expensive to manufacture.
Prior art has proposed a bristle comprising an extruded, relatively stiff core of PA (polyamide) or high density PE (polyethylene) and a soft, thermoplastic coating of natural or artificial rubber. This known bristle is designed for toothbrushes, where the soft, rubber-elastic coating is mainly intended to ensure a careful treatment of the teeth and gums, whilst the stiff core ensures the necessary strength characteristics for the bristle. However, such a bristle does not satisfy the demands made during cleaning, because its surface is too smooth. It is also unsuitable for applying media to an object.
On the basis of this prior art, the problem of the invention is to provide a bristle which, whilst maintaining the necessary strength characteristics in the case of a soft surface also provides a good cleaning action and absorptivity for media.
On the basis of a bristle comprising a core of a comparatively rigid, bending-elastic plastic and at least one layer of a rubber-elastic plastic, the invention solves this problem in that the rubber-elastic layer is profiled by stamping against the core, preferably by hot stamping.
SUMMARY OF THE INVENTION
The invention is based on the surprising finding that a rubber-elastic plastic, e.g. a thermoplastic elastomer, even with a very limited thickness, which necessarily arises in the case of bristles and with toothbrushes is only a few tenths of a millimeter, can be profiled by stamping or embossing, without there being any shape recovery of the rubber-elastic plastic. A decisive part is played by the relatively rigid core against which the stamping or embossing forces can be applied. It is possible to implement fine to coarse structures with any random shaping. Small profile depths are in particular chosen in the case of bristles for oral and body hygiene, whereas greater profile depths are used for cleaning or coating brushes for in the first case receiving dirt and in the second application media.
The rubber-elastic layer can surround the core in jacket-like manner or also only zonally and the profiling resulting from stamping can be provided over the entire length of the bristle or only over partial lengths thereof.
In the case of the bristle constructed according to the invention the core is made from a plastics material defining the bending and flexural strength of the bristle and the rubber-elastic layer with its profiling from a plastics material defining the surface action of the bristle on the object and the resistance to wear. Through the choice of the two plastics and the nature of the profiling, the bristle can be readily adapted to random requirements.
In a preferred embodiment the core is made from a plastics material having a Shore hardness D>45 and the rubber-elastic layer from a plastics material with a Shore hardness D<35. In a particularly preferred embodiment the Shore hardness of the core plastic is D>65 and that of the rubber-elastic layer 20<D<35. Materials fulfilling the aforementioned requirements are e.g. in the case of the core PE (polyethylene), PP (polypropylene) or PA (polyamide) and for the rubber-elastic layer thermoplastic elastomers.
The profiling of the rubber-elastic layer can be formed by locally defined depressions distributed over the circumference. Instead of this the profiling can also run in the bristle extension direction, e.g. along generatrixes or in helical manner. Finally, the profiling can also be preponderantly oriented transversely to the bristle extension direction.
According to a further feature of the invention, to the profiled, rubber-elastic layer is applied a film-like coating of a soft plastic clinging to its profile. As a result a certain smoothing effect can be obtained on the profiling without removing the surface action therefrom.
The core can be formed from one or more monofilaments. The first-mentioned form is recommended for toothbrushes and body brushes, whereas the second is better for industrial brushes and in particular car wash brushes. In this particular application the bristles must be bending-soft, so as to be applied in optimum manner to the contour of the surface to be cleaned and also so as to carefully clean the surface. These bristles are subject to very rapid wear from the free end. This means in the case of the bristle according the invention, that the rubber-elastic layer is firstly worn away at the bristle ends. In the variant according to the invention with several core monofilaments they are exposed in the form of fibers, which then still ensure a careful action compared with a single,
Edwards N.
Pedex & Co. GmbH
Vincent Paul
LandOfFree
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