Brush – broom – and mop making – Brush-making machines
Reexamination Certificate
2000-04-28
2003-06-17
Spisich, Mark (Department: 1744)
Brush, broom, and mop making
Brush-making machines
C300S017000, C300S021000
Reexamination Certificate
active
06578927
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method and a device for producing brush products, such as brushes, brooms, artists' brushes and the like, using endless cords of bristles, whose brush bodies are injection molded from plastic, and the bristle sheaves are simultaneously cast integrally in the form of tips of the endless cords of bristles introduced into the mold interior through bores in the bottom plate.
Since the introduction of plastic bristles in the manufacture of brush products, technological solutions for producing these products using endless cords of bristles have been sought.
The so-called “anchor method”, which is to be the point of departure as an example below and that continues as before to be employed predominantly in brush production, in which bristle sheaves are stuffed into prefabricated/predrilled brush bodies with the aid of a bristle stuffing machine and are secured to the bottom of the hole with wire or tiny plate anchors, has many disadvantages.
Not only the very high equipment costs but in particular also questions of quality of the finished products have led to the search for alternative solutions. In mechanically stuffing the bristle sheaves into prepared bores of the brush bodies, for instance, tiny interstices and gaps between the walls of the drilled holes and the filaments of the bristle sheaves, as well as between the filaments of the bristle sheaves themselves, are unavoidable. These interstices and gaps are then favored sites for mildew and the like and promote soiling.
To solve the technological and quality problems, various fundamentally different courses have been taken, such as connecting the ends of the bristles and the corresponding bores in the brush body by fusing or melting, or, in a particularly rational solution, directly embedding the ends of the bristles in the plastic brush body at the same time the brush body is made in an injection mold.
It has also been proposed that the tips of bristle cords be passed through bores in the bottom plates of an injection molding tool into the mold interior for the brush body and jointly sheathed in this brush body in a single operation in the injection molding.
The most difficult, and until now practically unsolved, problem in embedding the bristle ends in the course of the injection molding of the brush body is the reliable avoidance of overshooting as a result of the bores in the bottom plate of the injection mold that are needed for introducing the cords of bristles into the mold interior.
By a known method disclosed in East German Patent Disclosure DD 293 718 A5, bristle sheaves of endless bristle cords of plastic are used for brush goods, in that the tips of the cords are passed through bores in the bottom plates of the injection molding tool into the mold interiors and simultaneously jointly injected into the brush body without further machining in the injection molding of the brush body.
These method proposals state that overshooting of the composition could be avoided with the aid of conical bores, tapering toward the mold interior, in the bottom plate that terminate cylindrically, allowing a slight pressure of the cords of bristles to be attained. Many practical tests, however, have shown that this cannot effectively, in terms of equipment and/or process technology, counteract the tendency of the injection molding composition, as a function of the injection pressure and the degree of the temperature-dependent viscosity, to escape to the outside during the injection molding process between the filaments of the cords of bristles and between the cords of bristles and the walls of the bores. Furthermore, even the slightest escapes of the composition in the case of conically shaped bores leads to the immediate formation of plastic plugs in these bores, which quite effectively prevent the cords of bristles from being pulled through the bores in the bottom plate in the final molding, and as a rule this causes interruptions in production with sometimes severe underinjections on the bottom plates of the injection molding tools. With the provisions proposed in these methods, the problems of reliable avoidance of overshooting during the injection molding process cannot be solved.
One method for producing brush bodies with a bristle field for toothbrushes, the brush bodies being formed in some regions of at least two plastic components, is known from German Patent Disclosure DE 44 39 431 A1. In this method, bristle sheaves already cut to the proper length and assembled into bristle fields and located in a bristle mount are injected jointly with the production of the brush body in a first operation. In other words, the use of endless cords of bristles is not the point of departure. Nor does this reference show how the bristle sheaves are introduced with frictional engagement into the bristle mount, whose assembly is supposed to be done outside the tool in separate operations. In particular, it does not show how the intrusion of injection molding composition into the bores of the bristle mount, which could occur despite the frictionally engaged packing of the bristle sheaves, should be prevented. For the reasons given, this method is again unable to solve the problems described.
A further major problem in producing brush products using endless cords of bristles is severing the cords of bristles after the conclusion of the injection molding process in conjunction with furnishing the requisite bristle lengths for the next injection molding operation, inside an automated, continuous production sequence.
In DD 293 718 A5, the severing of the finished brush products from the cords of bristles that remain in the bores of the bottom plate of the injection molding tool is done in the open. To that end, after the brush bodies have cooled down, the upper part and a framelike middle part of the injection molding tool is lifted, along with the hardened brush body, from the bottom plate and in the process the cords of bristles are pulled to the required lengths through the bores in the bottom plate. The brush body is lifted from the bottom plate with the aid of an intermediate plate. Further details on the manner and function of the severing device and on the creation of further required cutting conditions for severing the bristle cords in the open without a supporting cutting edge are not disclosed in this proposal, however.
So far, attempts to sever the cords of bristles under the aforementioned preconditions, whether with rotating knives or reciprocating knives, without a supporting cutting edge have failed. Many filaments of the cords of bristles to be severed are pulled through the bore of the bottom plate during the severing process, resulting in unstable cutting conditions. The method presented cannot solve the existing problems, for the reasons given.
From German Patent DE-PS 845 933, the severing of toothbrushes with the injection molding tool open, using a rotating severing disk, is known; during the severing process, the toothbrushes are not firmly held stably, for instance by means of an intermediate plate or some other holding device. Severing the finished brush products from the bristle fields without establishing a stable position of the brush body, as proposed in this reference, is extremely difficult because of the actual events that occur in such severing processes. The lack of a stable position of the brush bodies during the severing process makes the possibility of a severing cut over the entire bristle field highly doubtful. Furthermore, during the severing operation, the brush bodies can be torn by force out of their positioning and tumbled about in the tool, making stable production sequences in fact impossible.
Serving by means of a rotating severing disk is problematic for two reasons in particular, without addressing the aforementioned inadequacies at all. First, a cut in the same direction results in persistent forces of friction and tension in its direction of motion. These forces are transmitted by the rotary motion of the severing disk to the cords of bristle
Hoeft Bernd
Ruediger Udo
Stiawa Paul
Schlesinger Maschinenbau GmbH
Spisich Mark
Striker Michael J.
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