BE1021713B1 - DEVICE AND METHOD FOR MANUFACTURING BRUSH BODIES OR PARTIAL BRUSH BODIES - Google Patents

Abstract

A device for making brush bodies or partial brush bodies provided with tufts of bristles (5), comprising a mold (1) which has a mold cavity (10) and at least two mold halves (2, 3) a first mold half (2) of which is designed to receive the tufts of bristles (5) and in which the mold (1) opens out a supply channel for the injection molding material, has a second mold half (3) or a guided mold part movable in a second mold half (3) intended to receive a covering body (8) opposite to the region for receiving tufts of bristles of the first mold half (2). The second mold half (3) or the mold part can be moved between a shaping position and an injection position set back from it, enlarging the mold cavity (10).

Description

The invention relates to a device for producing brush bodies or partial brush bodies provided with tufts of injection-molded bristles, comprising a mold which has a mold cavity and comprises at least two mold halves of which a first half is adapted to receive the tufts of bristles and wherein a feed channel for the injection molding material issues. The invention also relates to a method for producing brush bodies or partial brush bodies having tufts of injection-molded bristles, wherein the injection molding material is injected into a cavity of a mold in which the tufts of bristles protruding with their ends on the link side.

The problem with these known devices and associated methods is that the free flow path for the injection molding material is reduced in the region of the tuft of bristles projecting into the mold cavity and that all regions around the fastening ends of the tufts of bristles may not be filled with the injection molding material. To ensure complete filling of the mold cavity, the injection pressure can be selected accordingly. The injection molding material, however, may be pressed outwardly through the pile filaments of the pile tufts, which is unattractive and may render the brush unusable.

DE 10 2009 052 867 A1 discloses a device and an associated method in which a movable mold part is guided movably in a mold half and can be moved between a forming position and a recessing position enlarging the cavity of mold. The injection molding material is introduced into the mold cavity through the supply channel, the injection pressure being in this case sufficiently large to fill the mold cavity but not so large that the injection molding material is pressed outwardly through the tufts of bristles. After injecting the injection molding material into the mold cavity, the moving mold part is moved into its forming position. The injection molding material in the mold is compressed by so-called injection-compression, with the result that, on the one hand, contractions of the injection molding material are compensated during cooling and that on the other hand, the injection molding material is further pressed into the regions between the tufts fixing ends so that any remaining free regions are reliably filled with the injection molding material.

For brushes with interchangeable heads or brushes for electric toothbrushes in particular, it is necessary to provide on the side opposite the useful ends of the bristles a connection region where they can be connected to a drive or a handle. In this region, the brushes are subjected to increased mechanical loads. The plastic material, most often polypropylene (PP), generally used for the coating of tufts of hair does not generally meet these mechanical stresses. If, on the other hand, a high-quality, more durable injection molding material were used to coat the tufts of hair by injection, it would be necessary to work with a higher injection pressure which would again have the consequence that Injection molding could penetrate into the receiving holes for tufts of bristles and also between the individual filaments of the bristles and thus render the brush unusable.

Therefore, the object is to provide a device and a method of the type mentioned at the beginning with which it is possible to manufacture brush bodies or partial brush bodies which have on the one hand a precise connection part, mechanically soliicitable, and on the other hand a bristle area which has tufts of bristles with a properly delineated brush body material without overmolding.

This object is achieved with respect to the device by the fact that a second mold half or movable guided mold part in a second mold half is designed to receive a cover body opposite to the tufts receiving region. of the first mold half and the second mold half or mold part can be moved between a forming position and a recessed injection position with respect thereto, enlarging the mold cavity.

The cover body may be injection molded in a pre-work step from suitable solid material, for example polyoxymethylene (POM). This cover body forms, when the (partial) brush body is finished, the connection region, for example for a drive or a handle. To coat the tufts of the bristles, more flexible injection molding material, particularly PP, can be used to work with a lower injection pressure and the injection molding material is not pressed through the holes for receiving tufts of hair or outward through the filaments of bristles. As soon as the injection molding material has cooled somewhat but not yet solidified, the second mold half or mold part guided therewith with the cover body is brought into the forming position, which allows, on the one hand, to distribute the injection molding material around the tufting region of the bristles and, on the other hand, to connect the cover body with the injection molding material. The tufts of bristles can be melted in their binding region in particular to give mushroom heads, the melt occurring before the insertion of the tufts of bristles into the mold.

It is thus possible to coat the tufts of bristles in one operation and in a treatment station, to obtain complete encirclement of the ends of the tufts by the injection molding material and to connect the support part of the tufts of bristles thus injection molded with the cover body.

A preferred embodiment provides for the second mold half or mold part to be a part of an additional injection molding device for injection molding the cover body and for the second mold half or mold part to be provided. be transferred between the additional injection molding device and the mold. Thus, it is not necessary, after the injection molding of the cover body to completely demold it from its mold and transfer it to another mold part for the (partial) brush body, which simplifies the process. handling and simplifies the design complexity of the device, since fewer mold parts are needed.

It is appropriate that the additional injection molding device used to injection mold a cover body is designed with an outer edge portion protruding beyond the opening side of the second mold half or the mold part. and that the first half of the mold has a receiving region for the edge portion of the cover body.

The edge portion makes it easy to seal the mold cavity to the outside and yet be able to bring the second mold half or the mold part closer to the first mold half. The edge portion serves as a mold wall for the plastic material to be injected for the tufted bristle support portion.

It is further appropriate that the injection molding device has at least one mold portion to form an undercut in the cover body. During the injection of the material for the support part of the tufts of hair, it fills this undercut. This prevents, when the (partial) brush body is completed, that the cover body can be removed from the bristle support portion or inadvertently dislodged. In the case of circular (partial) brush bodies, the undercut may be interrupted to prevent rotational movement between the tufted bristle support portion and the cover body.

To meet the requirements of differently arranged hair areas, the first mold half may have tufts receiving holes for receiving the tufts of bristles that are arranged, oriented and profiled according to the desired bristle area. It is thus possible to create hair areas with tufts of hair obliquely, tufts of hair of different length or different profiling.

It is advantageous that a stop plate for the free ends of the tufts is associated with the first half of the mold intended to receive the tufts of bristles. The free ends of the tufts are thereby supported during injection and optionally maintained in their profiled position, which surely prevents inadvertently bypassing the tufts of bristles from their set position.

To increase the speed of production, the mold may be a multi-cavity mold for simultaneously molding several brush bodies or partial brush bodies simultaneously.

Insofar as one or more open passages are provided on the cover body, the second mold half or the mold part may also have at least one recess which opens into the mold cavity and in which a punch is guided by movably between a forming position encroaching on the mold cavity and an injection position leaving the mold cavity. The punch can be guided through the cover body and actuated so that the pressure for the compression injection is directly exerted from the punch on the plastic material injected into the mold cavity.

With regard to the method, the invention is characterized in that firstly in a first operation, a cover body is injection molded, in that in another operation, a tufts support part is injection molded and the tufts of bristles protruding into the mold cavity for the tufted bristle support portion are coated and in that the cover body is disposed in the region of the mold cavity opposite to the tuft of bristles when injection molding of the tufted bristle support portion and is pressed toward the tuft of bristles after injection of the injection molding material into the mold cavity. This results in the advantages already mentioned in the description of the device according to the invention.

An embodiment of the device according to the invention will be explained in more detail below on the basis of the drawings.

It is shown schematically in FIG. 1 a first mold half with tufts of bristles contained therein, FIG. 2 a second mold half with a cover body, FIG. 3 the joined mold halves of FIGS. 1 and 2, and FIG. 4 the arrangement according to Figure 3 with the second mold half moved to the forming position.

The figures show a device for producing brush bodies or partial brush bodies only a mold 1 which has two mold halves 2, 3. A first mold half 2 shown in FIG. 1 has tufts receiving holes 4 for receiving tufts of bristles. The tufts of bristles 5 are respectively melted at their fixing end to give a mushroom head 6. The free ends of the tufts of bristles 5 rest against a stop plate 7.

A cover body 8 is retained in a second mold half 3 (FIG. 2). The cover body 8 may in particular be injection molded into an additional injection molding device, not shown, from a loadable material, for example polyoxymethylene (POM). In the completed brush body, the cover body 8 serves, for example, as a connecting part for a handle or a drive.

The second mold half 8 may in particular be part of the additional injection molding device so that after the injection molding of the cover body 8, the second mold half 3 with the cover body 8 contained therein can be fed to the first half mold 2 (Figure 3) and forms the mold 1 with it. A transfer of the cover body 8 from one mold part to another is not necessary.

As can be seen in particular in Figure 2, the cover body 8 has an edge portion 9 projecting beyond the opening side of the second mold half 3. This edge portion 9 can be placed in the opening region of the first form mold half 2 according to FIG. 3 so that the two mold halves 2, 3 together with the cover body 9 define the cavity 10 mold for the injection molding material to be injected. As a result, the second mold half 3 can first be positioned in its injection position at a distance from the first mold half 2. However, the injection molding material can not pass out through the remaining slot 11 between the mold halves 2, 3. In the forming position according to Figure 3, the slot 11 has a width Ы.

Injection molding material, in particular polypropylene (PP) is injected into the mold cavity 10 via a not shown feed channel. This can be done with a comparatively small injection pressure so that the injection molding material can not penetrate the tufts receiving holes 4 or between the filaments of the tuft of bristles 5. After injection of the material in the mold cavity 10, the pressure is exerted (arrow Pf) according to FIG. 4 on the second mold half 3 so that the latter is moved into its machined position close to the first mold half 2. In doing so, the slot width is reduced to the measure b2. The injection molding material in the mold cavity 10 is reliably pressed around the mushroom heads 6 of the bristle tufts 5, thereby ensuring that the bristle tying regions 5 are completely surrounded by the molding material. by injection and that the tufts of bristles 5 are securely retained in the tufted bristle support portion 12 formed by the injection molding material. Since the injection molding material is already somewhat cooled during the application of pressure and is thus more viscous, it is surely prevented that the injection molding material can penetrate the tufts receiving holes 4. . In addition, the cover body 8 is connected to the support portion 12 of tufts of bristles by compression. The connection between the cover body 8 and the tuft bristle support portion 12 is further enhanced by the undercut 13 on the cover body 8. The injection molding material for the tuft support portion 12 of the tuft bristles penetrate this undercut 13, which prevents pulling the bristle support portion 12 from the cover body 8 after solidification of the injection molding material.

The measurement h (FIG. 4) describes the total height of the brush body or the part of the brush body carrying the tufts of bristles 5 and which is formed of the cover body 8 and the bristle support part 12. . The region of the cover body 8 extending beyond is for example the connecting region for connecting the brush body to the drive portion of an electric toothbrush.

Claims (9)

Apparatus for producing brush bodies or partial brush bodies having tufts of bristles (5) molded by injection, comprising a mold (1) having a mold cavity (10) and at least two halves (2, 3) of which a first mold half (2) is adapted to receive the tufts of bristles (5) and wherein the mold (1) opens a feed channel for the injection molding material, characterized in that a second mold half (3) or movable guided mold part in a second mold half (3) is adapted to receive a cover body (8) opposite to the first half of the tufted pile receiving region ( 2) and that the second mold half (3) or the mold part can be moved between a forming position and a recessed injection position with respect thereto, enlarging the cavity (10) by mold. 2. Device according to claim 1, characterized in that the second mold half (3) or the mold part is a part of an additional injection molding device for injection molding the cover body (8) and the second mold half (3) or the mold part can be transferred between the additional injection molding device and the mold (1). Device according to claim 2, characterized in that the additional injection molding device is adapted to injection mold a cover body (8) with an outer edge portion (9) protruding beyond the side of opening the second half (3) of the mold or the mold part and in that the first half (2) of the mold (1) has a region receiving the edge portion (9) of the cover body (8). 4. Device according to claim 2 or 3, characterized in that the additional injection molding device has at least one mold part to form an undercut in the cover body (8). 5. Device according to any one of claims 1 to 4, characterized in that the first half (2) of the mold has receiving holes (4) of tuft of bristles for receiving the tufts of bristles (5) which are arranged, oriented and profiled according to the desired hair area. 6. Device according to any one of claims 1 to 5, characterized in that a stop plate (7) for the free ends of the tufts is associated with the first half (2) of mold for receiving the tufts of hair (5). 7. Device according to any one of claims 1 to 6, characterized in that the mold (1) is a mold with multiple impressions for simultaneously molding by injection several brush bodies or partial brush body. 8. Device according to any one of claims 1 to 7, characterized in that the second half (3) of the mold or the mold part has at least one recess opening into the cavity (10) of the mold (1) in which a punch is movably guided between a forming position encroaching on the mold cavity (10) and an injection position extending from the mold cavity (10). A method for producing brush bodies or partial brush bodies having tufts of bristles (5) injection-molded, the injection molding material being injected into a cavity (10) of a mold (1) in which the tufts of bristles (5) project with their end on the connection side, characterized in that firstly, in a first operation, a cover body (8) is injection molded, in that in another operation, a tufted bristle support portion (12) is injection molded and the tufted bristles (5) protruding into the mold cavity (10) for the tufted bristle support portion (12) are coated and that the cover body (8) is disposed in the region of the mold cavity (10) opposite the tuft of bristles (5) during injection molding of the tufted bristle support portion (12) and is pressed into direction of hair tufts (5) after injection molding material by injection into the mold cavity (10).