Brush – broom – and mop making – Processes
Reexamination Certificate
2002-04-17
2004-12-21
Till, Terrence R. (Department: 1744)
Brush, broom, and mop making
Processes
C015S167100, C015S187000
Reexamination Certificate
active
06832819
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a method for the manufacture of brushes with a plastic bristle carrier and a bristle configuration, fastened thereto and comprising individual or bundlewise-combined plastic bristles, in that the fastening side ends of the bristles or bundles are melted to a thickening, thickenings of adjacent bundles are interconnected by after shaping and displacement of the plastic mass and the connections are subsequently embedded in the plastics material of the bristle carrier. The invention is also directed at an apparatus for performing the method and to brushes manufactured according to the method.
The special features and problems described hereinafter using the example of toothbrushes apply equally to numerous hygiene brushes, as well as various other brushes for different uses. However, the prior art in connection with toothbrushes is the furthest advanced and consequently special reference is made thereto.
Modern dental medicine requires toothbrushes with a sensitive bristle action, the bristle configuration being adaptable to the greatest possible extent to the cleaning faces (teeth and interdental gaps) and massaging faces (gingiva), so as on the one hand to not only follow the spherical tooth surfaces on cleaning, but also to cover the desired interdental gaps and simultaneously avoiding injury during the desired massaging of the gingiva.
The requirement of reaching with the bristles the areas of the oral cavity to be cleaned and massaged on the one hand requires a certain length of the bristles, whilst on the other the complete overall height (bristle length plus overall height of the brush head) is to be kept low, so as to ensure an optimum bristle action even in the confined circumstances of the oral cavity. As exclusively the bristles decisive for the cleaning and massaging action and the bristle carrier makes no contribution thereto, the aim is to keep the overall height of the bristle carrier as small as possible. A limit is placed on this in that the bristles must have an adequate embedding length in order to offer the necessary resistance to pulling out oral extraction. Bristles or even bristle bundles which are released from the bristle configuration not only have an unpleasant effect in the oral cavity, but can even lead to health hazards in the gastrointestinal tract if swallowed. The in part opposing requirements for high extraction resistance and low overall height can only be fulfilled with difficulty.
At present brushware and in particular toothbrushes is still preponderantly made using conventional punching technology, i.e. the bundles are looped and fastened by anchoring in prepared bristle carrier holes. This procedure requires a bristle carrier overall height of at least 4 to 6 mm.
Toothbrushes produced by punching technology are only able to inadequately fulfil modern hygiene demands due to the existing gaps in the vicinity of the bristle fastening and the resulting inclusion of dirt and bacteria.
Substantially hygienically satisfactory toothbrushes can be produced by molding processes or thermoplastic joining processes, to which the method according to the independent claims relates. The fastening-side ends of the bristles are then provided with thickenings with which they are either pressed or shaped into the soft plastic mass of the bristle carrier or are placed in an injection mould, in which the bristle carrier molten mass is injection molded around the thickenings. This makes it possible to attain overall bristle carrier heights of 3.0 to 4.5. The limit is determined here again by the bristle embedding length offering the necessary extraction resistance. The requirement for a limited overall bristle carrier height is more particularly in conflict with the requirements of an adequate extraction resistance if account has to be taken of the further requirement in modern dentistry for a flexible behavior of the bristle configuration. This presupposes a corresponding flexibility of the bristle carrier and consequently a specific plastic choice and/or design measures. Through the flexibilizing of the bristle carrier the extraction resistance of the bristles is reduced, because the bristles are no longer held in a rigid environment. This more particularly applies if wholly or partly rubber-like materials, such as elastomers are used for the bristle carrier.
Purely constructional measures on the bristle carrier e.g. consist of a dividing up of the bristle carrier into areas in joint-like form (EP 577656, WO 92/17092). However, this generally leads to an increase in the overall height. The same applies in the case of toothbrushes in which the flexibilizing of the bristle configuration is achieved by means of elastomeric areas of the bristle carrier (WO 97/07707, WO 97/24048, WO 97/25899, WO 97/25900).
Attempts have already been made to resiliently mount the bristles in the bristle carrier (DE 19538569 A1) or to provide the bristle carrier with an elastomeric material and to weld the bristles to said material (DE 3628 722 A1, DE 19530057 A1). It is also known (WO 97/20484) to form the bristle carrier from a supporting skeleton of a relatively rigid plastic and fill the skeleton with an elastomer, the bristles being embedded in the skeleton material or in the elastomer. Here again no overall height reduction is obtained and the flexibility of the bristle configuration is restricted to the elastomeric marginal areas. It is also known (DE 19743556 A1) to subsequently separate the injection molded skeleton and then fill the same with elastomer.
In the case of rigid bristle carriers it is known (EP 405 204 B1, DE 19738256 A1) to introduce the bristle bundles into bores in a holding plate and melt same onto the back of the holding plate, whilst shaping the melt into corresponding depressions of the bores, so that all the bundles are connected at the back by means of a type of plate. This plate is then covered by the correspondingly recessed bristle carrier or it forms the bristle carrier together with the rigid holding plate. This construction in no way satisfies modern requirements regarding the flexibility of toothbrushes.
With toothbrushes having thermoplastically inserted or injection molded in bristle bundles with thickenings at the fastening-side end it is known (EP 150785 B1, EP 759711 B1) to after shape the thickenings on each bundle in order to widen same in plate-like manner and consequently increase the shear strength in the bristle carrier under the action of extraction forces, or also to shape the thickenings of adjacent bundles to form a cohesive thickening (EP 197384 B1, EP 326634 A1), exclusively strength aspects being in the foreground.
The problem of the invention is to propose a method for the manufacture of brushes which, in the case of an adequate bristle extraction resistance, allows a reduction of the overall height of the brush head. According to a further development a substantially controllable resilience of the bristle configuration is to be made possible.
SUMMARY OF THE INVENTION
According to the invention this problem is solved in that the thickenings are shaped by a mold to a clearly defined support structure of webs connecting adjacent thickenings and then the support structure and the bristles projecting over the same are embedded over a short length in the plastics material of the bristle carrier.
In the method according to the invention use is made of the plastics mass melted at the fastening-side end of the bristles or bundles in order to obtain a clearly defined support structure between the thickenings of the bundles or bristles introducing the tensile forces acting on the bristle bundles into the complete bristle carrier. It is no longer solely the shear strength of the bristle carrier material in the area of the thickenings which is decisive for the extraction resistance of the individual or bundlewise combined bristles, but larger areas of the bristle carrier significantly contribute thereto. If required, this makes it possible to reduce to a significant extent the bristle emb
Coronet-Werke GmbH
Till Terrence R.
Vincent Paul
LandOfFree
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