Brush – broom – and mop making – Brush-making machines
Reexamination Certificate
2000-02-01
2003-02-25
Spisich, Mark (Department: 1744)
Brush, broom, and mop making
Brush-making machines
C300S021000, C264S243000, C425S123000, C425S805000
Reexamination Certificate
active
06523907
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to methods for producing brushware by injection molding, specifically methods of producing brushware by in-mold bristling techniques.
BACKGROUND OF THE INVENTION
The variety of brands, designs, and styles of toothbrushes available in the United States today is truly staggering. Brushes are available in sizes and styles appropriate for babies, adults, dentures, sensitive gums, and other specialized needs. Brushes can be had in every color of the rainbow and decorated with logos ranging from mermaids and cartoon characters to trade names of various kinds. Most brushes are produced via a two part technique. The handles are produced by injection molding, and the bristles are later inserted into a head portion of the handle. One common technique for inserting the bristles into the brushes is to staple them. Bristles are folded around a metal staple which is pushed into pre-molded holes in the brush. The staple cuts its way into the brush handle, which holds it and the bristles securely. However, rough use can easily remove the bristles from the handle, leading to shedding, or, in a worst case scenario, release of the metal staple inside the mouth.
Techniques wherein the bristles are fused with the handles can be used to produce brushes where the bristles are much harder to remove from the brush. Either the bristles or the brush head, or both, are heated, and the bristles are inserted into holes in the handle, where they are retained by the cooling plastic. Exemplary techniques for brush production by fusion, such as those disclosed in U.S. Pat. Nos. 4,609,228 and 4,646,381, produce brushes with high bristle retention strength but retain the economic disadvantage that the brush is produced in a two-part process on two different machines. That is, the handles are still produced on a different machine than the one on which the bristles are inserted into the handle. It is thus desirable to produce a toothbrush using techniques which minimize the apparatus used, and consequently, the amount of time and number of personnel required to produce the brushes.
In-mold bristling processes, wherein the handle of the brush is injection molded around the bristles, have been used to produce a variety of different brushes. For example, U.S. Pat. No. 4,635,313 (the '313 patent) to Fassler, describes an in-mold bristling process wherein the ends of the bristles are fused prior to the injection molding of the handle. The illustrative drawing on the front page of the patent shows a nail brush; however, the technique can also be used to produce toothbrushes. One concern in the production of brushes by this technique is the penetration (“flash”) of injection molded material through the bristle bundles into the face of the brush. This is not only unsightly but unhygienic because the excess material provides an excellent hiding place for bacteria and mold. To prevent this, the '313 patent describes a method of sealing the opening of the injection mold through which the bristles enter the mold with a melted fuse at the end of the bristle bundles. U.S. Pat. No. 5,045,267 (the '267 patent) to Weihrauch discloses a variation of the in-mold bristling technique described in the '313 patent. However, in the '267 patent, the fused ends of the bristle bundles are pulled against sleeves projecting from the end of the channels which lead into the mold. The tensile force holding the fuse against the sleeve further discourages injection molded material from penetrating the bristle bundles.
U.S. Pat. No. 5,143,424 to Boucherie also describes an in-mold bristling process. Bristles are loaded into one end of a two-ended magazine while, at the other end, the handle material is simultaneously injection molded into a previously loaded second end of the magazine. Each of the two ends of the magazine can hold the bristles for a single brush and mate with an injection mold to complete a mold cavity into which the handle is injection molded.
U.S. Pat. No. 5,823,633 to Weihrauch describes an in-mold bristling process similar to that described by the '267 patent. However, in this invention, the fuseballs are not brought into sealing contact with the sleeve. Instead, they are maintained at a finite distance, between 0.1 mm and 2.0 mm, from the opening of the channel, allowing air to escape from the mold cavity through the channel. The gap increases the depth of the fuses within the handle, reinforcing the length of bristle bundle material immediately adjacent to the fuse and increasing the force required to remove the bristle bundles from the brush handle. However, this technique also allows injection molded material to penetrate the bristle bundle and flash over the head of the brush.
U.S. Pat. Nos. 5,458,400 to Meyer and 5,474,366 to Strütt, et al., describe techniques wherein a first section of the brush, including a portion of the head and at least part of the handle is injection molded before the bristles are inserted into the mold. The bristle bundles are inserted into holes in the first brush section, after which the rest of the brush is injection molded.
U.S. Pat. No. 5,609,890 to Boucherie describes an in-mold bristling process wherein the handle comprises two materials instead of a single injection molded material. The invention utilizes a molding machine which comprises at least two injection molding stations and a tuft feeding station. At the feeding station, the bristles are fed into a magazine, following which the ends of the bristles are fused. The magazine, which includes part of a mold cavity, is mated with the rest of an injection mold, completing the mold cavity. The first section of the brush, including the head, is injection molded, following which the magazine, still carrying the first injection molded section of the brush, is transferred to a second injection mold, whereat the remainder of the brush is injection molded.
SUMMARY OF THE INVENTION
In one aspect, the invention is a method for manufacturing brushes. The method includes the steps of inserting a plurality of bristle bundles into a first mold cavity in a magazine, manipulating at least one end of the bristle bundles, mating the first mold cavity portion with a second injection mold cavity portion in an injection mold, and injection molding at least a portion of a brush handle. The first and second cavity portions define the shape of the portion of the brush handle. The bristles may be inserted into the magazine from an endless supply or a supply of pre-cut bristles.
Manipulating may comprise adjusting the relative heights of the bristle bundles with respect to one another before the first part of the brush handle is injection molded. Within the individual bristle bundles, the relative heights of a portion of the bristles may also be adjusted with respect to each other at this time. A non-use side of the bristle bundles may be trimmed to produce a level plane, and a portion of the bristle bundle may be end-rounded before or following the step of injection molding. Following the initial adjusting step, the relative height of the bristle bundles with respect to one another may be inverted in a further adjusting step. Alternatively, manipulating may include fusing a non-use end of each bristle bundle to form a region having a greater diameter than that of the remainder of the bristle bundle. The fusion may be accomplished thermally or chemically and may be followed by pressing the fused ends against a portion of the first mold cavity portion. Thermal fusion may be accomplished by a contact heater, a non-contact heater, or hot air. If the bristles are fused thermally, they may be partially flattened while the fused ends are still warm. A portion of the brush handle may comprise polypropylene, cellulose propionate acetate, polyethylene terephthalate, or a thermoplastic polymer.
The process may further comprise removing the completed portion of the brush handle from the second mold cavity portion, mating the magazine and the portion of the brush handle with a subsequent mold cav
Bible Kenan
Buckner Carroll
Collins James
Etter Lloyd
Harris David E.
Choate Hall & Stewart
Moll Industries, Inc.
Rosen Valarie B.
Spisich Mark
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