MXPA96003331A - Brush and method for your manufacture - Google Patents

Abstract

The present invention relates to a brush with a one-piece plastic brush body produced by injection molding consisting of a head covered with bristles and a dimensionally stable handle with a cross-section greater than the head, the body of the brush being manufactured from an elastomer mixed with a foaming agent and foamed or expanded in the area of the handle, while being solid in the area of the smallest cross-section of the head. Such a brush is produced by injection molding in a two-part mold which, to form the head, has smaller cross-sections than to form the handle, the elastomer with the foaming agent is used and the cross-sections molded for the head they are manufactured in a way that they are smaller compared to those for the handle so that the elastomer is formed only in the area of the handle

Description

BRUSH AND METHOD FOR ITS MANUFACTURE DESCRIPTION OF THE INVENTION The invention relates to a brush having a one-piece plastic brush body produced by injection molding and comprising a head covered with bristles and a dimensionally stable handle or handle having a cross section greater than the head. Currently, the brushes, and in particular the toothbrushes or dentifrices are made entirely of plastic. Due to the different profile of requirement, the brushes are constituted mainly of high-grade polyamide, processed by extrusion to thin fibers, which are then stretched and thermally stabilized. This makes it possible to obtain the desired properties, specifically high flexibility with a good ability to re-erect or straighten, high limits to fatigue, good resistance to abrasion and chemical stability. However, the brush body is usually made from a less expensive plastic produced by injection molding. The area of the head of the brush body must be dimensioned as a function of the nature of the bristles, which finally, which are optionally combined in REF: 22915 beams or groups, which are fixed firmly. However, the head should be tempered as much as possible so that it requires little space in the oral cavity so that it is capable of using the existing space with substantially extended bristles. The handle must be dimensionally stable and rigid. It is also desirable for the head to be flexible to some extent with respect to the handle in order to dampen the pressing force during cleaning of the teeth or to control the pressure. Therefore, a neck portion in smaller cross section is provided between the head and the handle which provides the brush body with some flexibility. The construction resulting from the neck also satisfies an ergonomic function, in order to allow guiding the toothbrush in the desired cleaning movements with the mouth closed. Thermoplastics used mainly for toothbrushes inadequately satisfy these conflicting requirements. This applies more particularly to the desired flexibility between the head and the handle and also to the desired small cross section in the head and neck. Therefore, the cross section in the neck area should be relatively large, so that it does not arrive at the point of rupture during use or in any other extraordinary tension process. The same applies with respect to the head, because the latter is weakened in its cross-section due to suggestion measures for the groups of bristles, particularly if, as is the normal case, the groups are fixed mechanically or thermally, or injected into holes in the head. Furthermore, when the groups are welded on the head material, a weakening occurs, because the molecular structure of the surface on the head is modified in a non-advantageous manner. To obtain the necessary flexibility of the head in comparison with the handle, use is made of brushes of multiple components, which have in the area of the neck inserted springs (DE 38 40 136, WO 93/15 627) or bodies of elastic rubber inserted (DE 39 23 495, EP 0 613 636). There are also proposals to fix the flexibility of the neck area (DE 3640 898), but these proposals leave open the question of how much of this can be obtained in both construction and technology. The object of the invention is to propose a brush and a process for its production, which allows the use of simple and inexpensive plastic materials, which allows adequate flexibility in the area of the head and between the latter and the handle, and same time, which provides a rigid construction of the handle and which, in particular in the case of toothbrushes, satisfy the requirement usage profile. Based on the brush mentioned initially, this objective is obtained insofar as the body of the brush is made of an elastomer mixed with a foaming agent and is foamed in the handle area, while being substantially solid in the area of the section smaller cross section of the head. The elastomers have the advantage of being relatively soft, that is, they mainly exclude the risk of damage when used in oral and body hygiene. They have the ergonomic advantage of a relatively flat surface and therefore a good grip. Its obvious features also include good bending or bending capacity with high breaking strength. Thus, although the material is obviously usable for brush bodies, the bending capacity is disadvantageous, because the brush body must be oversized to a large extent in the region of the handle in order to obtain a rigid handle. This in turn affects the use of the corresponding material in the case of a cross-sectional design that is not ergonomically optimal. The invention solves the problem to the extent that the elastomer is mixed with a foaming agent which, during injection molding, produces swelling or melt expansion in the areas having a larger cross section, but in areas with narrower cross sections, the foaming agent does not expand or only does so to an insignificant degree. This produces a brush body which has a solid construction in the area of the head, so that the elastomer presents or retains its favorable bending characteristics, while in the area of the handle, due to the pore volume, the capacity of Bent is eliminated to a large extent. Therefore, standard cross sections can be obtained in the handle region. As a function of the degree of foaming, the material requirement in the foamed area is 20 to 50% less than with a solid construction, and the weight of the brush is reduced. This is particularly advantageous in that the benefits obtainable to date can only be obtained in multi-component constructions, and can now be obtained with a single elastomer with the same material or a simpler material. As a result of the solid construction of the head, the bristles or groups can be anchored from any conventional random attachment method to the head. The principle of the invention mentioned in the above can be implemented in any brush, but preferably in toothbrushes, in which the handle is connected to the head by means of a neck and only the handle is foamed, and therefore both is dimensionally stable, while the elastic neck that can be bent allows a deflection of the head and the head can also be curved in a convex or concave manner. In the case of toothbrushes, the invention also proposes that between the head or the neck and the handle there is a transition area with a constantly increasing cross section, and the pore volume of the foamed elastomer in the handle area is increased constantly in the area of transition to the neck. This ensures that there is a properly stable area between the neck and the handle in which the pore volume decreases constantly from the handle to the neck, so that in the transition regions there are no excessive cracking stresses which can lead to rupture . In another advantageous construction, the body of the brush in the area of the head and / or the neck has a smooth, ultra-glossy surface, while the body of the brush may have, in the area of the handle, a rough or structured surface. The smooth, ultra-bright surface in the regions of the head and neck leads to the desired sliding capacity in the oral cavity. It also satisfies the hygienic requirements very well and favors the resistance in the areas of small cross sections. A good grip or grip is improved by a rough or structured structure in the region of the handle. For the production of such brush, the invention makes use of the known injection molding processes, in which a mold of at least two parts is used, which to form the head or the neck has smaller cross-sections molded than to form the handle. According to the invention, this process is characterized in that the plastic material is constituted by an elastomer with a foaming agent, and the cross sections molded for the head or neck are much smaller in comparison with those for the handle, so that the plastic is only foamed in the area of the handle. Practical tests have been carried out which show that this requirement can be completely satisfied with standard head and handle cross sections. As a function of the shape of the brush body, an adequate arrangement of the injection points can support the desired result. In the case of a toothbrush, whose brush body comprises a head, a neck, a handle and a transition area between them, the molded cross-sections of the head, neck, transition area and handle are chosen from Since the plastic is foamed essentially only in the area of the handle and the transition area, the pore volume gradually decreases from the handle to the transition area. According to the invention, another possibility for producing the brush comprises providing in the mold at least two injection channels, in which the first is supplied in the head or neck and the second in the molding area that forms the handle, and that the plastic material is constituted by an elastomer which is supplied to the first injection channel in pure form and to the second injection channel mixed with a foaming agent. This process, which can also be known as a back pressure process, can also be controlled so that the pure elastomer only fills the molded cavity for the head or neck, while the foamed elastomer only fills the molded cavity for the handle and the transition area between the neck and the handle takes place a mixture. A variety of this process is characterized in that the brush body is molded in an injection mold with highly polished molding surfaces in the head and / or neck area, while the body of the brush is molded in the handle area by means of rough surfaces or molded structures. This allows to obtain a brush whose surface satisfies the different requirements of the different areas, specifically displaceable capacity on one side and good grip on the other. The process according to the invention offers the possibility as a result of the solid construction of the head, the fixing of bristles, which can be combined in groups or bundles, using standard clamping or fixation methods. Therefore, the bristles, for example, in channels of one or two parts of the mold by injection can be introduced projecting in the quality of the mold and the injection molding compound that forms the body of the brush can be injected around them. . In connection with injection molding, holes may be made in the head of the brush body to receive the bristles or groups of bristles and the bristles or groups are fixed mechanically or thermally thereto. As a function of the fastening method, it is advantageous if the bristles or groups of bristles melt on the fastening side to the head with which they are fixed on the body of the brush. This offers particularly advantages when the brush body is injected around the groups, as is known per se. Instead of these bristles or groups being able to be provided with a head having a cross section greater than the narrowest cross-section of the holes in the head and occurring in the holes accompanied by pressure parallel to the bristlesMa. , the elastic characteristics of the elastomer can be used, which provides a way of coupling under pressure and subsequently firmly surrounding the groups at the head. Optionally, holes with cuts can be provided for this purpose. The invention is described in greater detail in the following in relation to the embodiment and the accompanying drawings, in which: Figure 1 shows a longitudinal section through the toothbrush. Figures 2 to 5 show cross sections II-II to VV according to figure 1. The toothbrush shown in figure 1 is constituted by a handle 1, a head 2 and an intermediate neck 3, which passes towards the handle via the transition area 5. The toothbrush is also covered with individual vertical bristles or groups 4 in the area of the head 2.

The body of the bristles is constituted by an elastomer, which is solid in the area of the head 2 and the neck 3, while it is foamed by means of a foaming agent in the area of the handle, so that the elastomer can be fold more easily. In the transition area 5 between the neck 3 and the handle 1, the foaming agent only has a partial action, so that there is a volume portion that increases toward the handle. The cross-sectional path over the length of the brush body is apparent from FIGS. 2 to 5. In the area of the head (FIG. 2), a flat area is desired, but relatively wide in its cross-section, and in FIG. the area of the neck 3 (figure 3) passes towards the cross section of the narrowest brush body. In the transition area (figure 4), the cross section gradually increases again until it assumes the maximum cross section in the area of the handle 1. While the elastomer is in solid form in the region of the head 2 and the neck 3 , in the transition area 5, as the cross section increases, there is an increase in the pore volume, which reaches its highest value in the area of the handle 1. This is shown in figure 1, by shading with separation in increase, and in figures 4 and 5, compared with figures 2 and 3, by the corresponding cavities. The bristles or groups (bunches) 4 can be inserted mechanically or thermally into pre-injected holes of the head 2 or the molding around them can take place directly in the injection molding. These methods of fixation are known and consequently do not require additional description herein. It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (15)

REIVINPATION

1. A brush with a one piece plastic brush body produced by injection molding comprising a head covered with bristles and a dimensionally stable handle with a larger cross section compared to the head, the brush is characterized in that the brush body is manufactured of a mixed elastomer, with a foaming agent and is foamed in the area of the handle, while being substantially solid in the area of the smallest cross section of the head.

2. A brush, particularly a toothbrush or toothbrush with a one-piece plastic brush body produced by injection molding, comprising a head covered with bristles and a dimensionally stable handle with a cross-section greater than the head and a neck that connects the head and the handle, the brush is characterized in that the body of the brush is made of an elastomer mixed with a foaming agent and is foamed in the area of the handle, while being substantially solid in the area of the smallest cross-section of head and neck.

3. The brush according to claim 1 or 2, characterized in that between the head of the neck and the handle there is provided a transition area with a constantly increasing cross section and that the pore volume of the foamed plastic in the area of the handle decreases constantly in the area of transition to the neck.

4. The brush according to claim 2, characterized in that the body of the brush has a super-bright smooth surface in the area of the head and neck.

5. The brush according to claim 1 or 2, characterized in that the body of the brush has a rough or structured surface in the vicinity of the handle.

6. A process for the production of a plastic brush according to claim 1 or 2 by injection molding in at least one two-part mold, which, to form the head or the neck, has smaller cross-sections than to form the handle, the process is characterized in that the plastic material is an elastomer with a foaming agent and the cross-sections molded to the head or neck are manufactured so that they are much smaller compared to the sections of the handle, so that the Plastic is foamed substantially only in the area of the handle.

7. The process according to claim 6, for producing a toothbrush according to claim 3, characterized in that the molded cross-sections of the head, neck, transition area and handle are chosen so that the plastic is essentially foamed only in the area of the mango, and in the transition area and the neck, the pore volume gradually decreases from the mango in the transition area.

8. The process for the production of a plastics brush according to claim 1 or 2 by injection molding in at least one two-part mold, which, to form the head or the neck, has smaller cross-sections molded to form the handle, the process is characterized in that the mold is provided with at least two injection channels, wherein the first is in the mold that forms the head or neck, and the second in the molding area that forms the handle, and the plastic is an elastomer, which is supplied to the first injection channel in pure form and the second injection channel mixed with a foaming agent.

9. The process according to claim 6 or 8 for producing a brush according to claim 4, characterized in that the body of the brush is molded in an injection mold with highly polished molded surfaces in the area forming the head and neck.

10. The process according to claim 6 or 8 for producing a brush according to claim 5, characterized in that the body of the brush is molded in an injection mold with rough or structured surfaces in the area of the handle.

11. The process according to claim 6 or 8, characterized in that the bristles, optionally in groups, in channels of one of two parts of the mold by injection are inserted projecting into the cavity of the mold and the elastomer forming the body of the brush is injected around them.

12. The process according to claims 6 or 8 characterized in that in relation to the injection molding, the holes for receiving the bristles or groups of bristles, are formed in the head of the body of the brush.

13. The process according to claim 12, characterized in that the bristles are fixed mechanically or thermally in the holes in the head.

1 . The process according to claim 12, characterized in that the bristles or groups are provided with a head having a cross section greater than the narrowest cross section of the holes and pressed into the holes under pressure parallel to the bristles.

15. The process according to claims 6 or 8 characterized in that the bristles or groups of bristles melt at the end of their clamping side to form a head which is then fixed to the head of the body of the brush.