Toothbrush

Description

TECHNICAL FIELD

The invention relates to a toothbrush with a plastic brush head with at least one folded bristle bundle and at least one plastic anchor plate.

STATE OF THE ART

Conventionally, when producing a toothbrush, the bristle bundles are attached to the brush body with metal anchor plates. These anchor plates are, for example, 3/10 mm wider than the hole diameter. The anchor plates are stuffed together with folded bristle bundles into the bristle bundle holes, whereby they dig into the brush body material with opposite outer edges and are thus held.

Furthermore, it has already been proposed that in the case of a metal brush head, the bristle bundles are fixed by metal anchors. Holes are drilled in the brush head for the bristle bundles and small holes are made diametrically opposite each of these holes for inserting the metal anchors (JP 2009 125084 A, KAO CORP)

The known anchoring techniques are complex to produce and are not reliable enough in securing the bristle bundles.

DISCLOSURE OF THE INVENTION

The object of the invention is to create a toothbrush that can be more easily produced and ensures that the bristles are more reliably anchored, which belongs to the technical field mentioned at the beginning.

The solution to the object is defined by the characteristics of claim 1.

The toothbrush according to the invention has a plastic brush head, at least one folded bristle bundle and at least one plastic anchor plate. The brush head comprises a hole with a longitudinal axis and a hole cross-section with a basic shape for receiving the folded bristle bundle for the at least one bristle bundle. An anchor plate is fixed in the hole to anchor the respective bristle bundle in the free hole cross-section. In one wall of the hole, two grooves are held parallel to the longitudinal axis of the hole, which (viewed perpendicular to the longitudinal axis) extend beyond the base shape of the hole cross-section and which are formed by injection molding. The grooves form a U-shaped profile. The anchor plate is fixed in the two grooves in the U-shaped profile by welding. The grooves have a combination section with centering and tapering section adjacent to one entrance of the hole, which, when viewed in a direction perpendicular to the longitudinal axis, has a depth and a width that successively decrease with increasing distance from one entrance of the hole.

The invention is based on the finding that without the combination section according to the invention, it is not possible to anchor the plastic anchors sufficiently firmly (i.e. with a sufficiently high pull-out force) and sufficiently reliably (i.e. with sufficient consistency for each weld). The tests have shown that if the feed is not sufficiently symmetrical (e.g. due to a slight production-related offset between the grooves and the anchor plates) when the plates are inserted into the holes, either deformed and thus only partially welded, or that the welding only occurs at individual points because the contact between the edge of the anchor plate and three sides of the U-profile is insufficient at other points. In this context, it has also been shown that significantly higher pull-out forces are achieved for the bristles when the anchor plates are welded to all three sides of a U-shaped groove.

The tests also showed that it is important that the U-shaped grooves are embedded in the bulk material of the brush head. If the wall around the groove is not voluminous enough, the softened plastic material can yield, which significantly reduces stability.

Anchoring plates made of synthetic materials have the advantage over those made of steel that the toothbrush can be disposed of in an environmentally friendly manner, because it is not necessary to separate the materials (metal/synthetic material).

Preferably, the longitudinal axis of the hole is perpendicular to a surface of the brush head. In the brush head, several parallel rows of holes can be provided at a short distance from each other.

According to a particular embodiment, the hole (viewed transversely to its longitudinal axis) has a geometrically simple basic shape such as a circle, a rectangle or an ellipse.

The grooves are recessed into the wall of the hole, i.e. they extend beyond the basic shape of the hole cross-section and into the bulk material of the brush head. The grooves are already present in the hole when the bristles and anchor plates are inserted. They are applied by injection molding, i.e. when the brush head is produced by injection molding.

The wall is therefore preferably essentially the inner surface of a hollow cylinder or a rectangular or elliptical hollow profile defined by the hole. The wall is therefore essentially parallel to the longitudinal axis of the hole.

According to the invention, the grooves have a cross-section (viewed perpendicular to the longitudinal axis of the hole) that is U-shaped. Because the grooves are recessed in the wall and are not placed, for example, on a rib that extends into the (free) hole cross-section, the three wall sides of the U-profile are surrounded by the bulk material of the brush head. The unavoidable heating and softening of the material that occurs in the U-profile during welding cannot cause the plastic material to yield. The anchor plate is thus reliably fixed to both the front side (bottom of the U-profile) and the sides of the U-profile.

In order not to weaken the wall between closely spaced holes in a row and to ensure that there is sufficient distance between the grooves of adjacent holes, in a particular embodiment the basic shape of the holes is circular or elliptical and the alignment defined by the opposing grooves of a hole is offset by an angle greater than zero, in particular 30°-45°, to the direction of the row of holes (hole row direction of directly neighboring holes).

The fact that the basic shape is simple (circular, elliptical, rectangular or similar), that is, convex (i.e. has no indentations, such as ribs or inward projections), and the grooves are recessed into the wall, means that the hole cross-section can be optimally adapted to the tuft of bristles to be inserted.

At the entrance of the hole and thus at the entrance of the grooves, the combination section forms on the one hand a centering section of the U-shaped profile. This tapers, in relation to the longitudinal axis of the hole, radially the insertion area or insertion path for the anchor plate. On the one hand, the anchor plate is thus centered (e.g. with respect to the longitudinal axis of the hole) and on the other hand, the anchor plate is gradually inserted into the area (further below referred to as the “constant section), in which the anchor plate is finally fixed, whereby the anchor plate is welded there with the artificial section of the U-profile of the grooves over essentially the entire surface.

According to the invention, the grooves in the combination section each also have a tapering section, which, when viewed in the direction perpendicular to the longitudinal axis, has a width that successively decreases with increasing distance from the entrance of the hole. This ensures that the anchor plate is fed symmetrically onto the two side walls of the U-profile in the constant section.

The grooves have a constant section adjacent to the combination section, which, when viewed in the direction perpendicular to the longitudinal axis, has a width and a depth that are constant along the longitudinal axis. The width and depth of the U-profile in the constant section is adapted to the width and thickness of the anchor plate. Before the anchor plate is fixed by friction welding, the U-profile in the hole is slightly less wide than the edge of the anchor plate and the distance between the two base surfaces of the opposing grooves is slightly less than the width of the anchor plate.

According to the invention, the combination section is designed to serve simultaneously as a centering section and as a tapering section. This has the advantage that the centering and alignment of the anchor plate is achieved over the shortest possible distance.

According to the invention, the combination section is followed by the constant section.

In some embodiments, the depth decreases in two or more stages. For this purpose, the centering section can comprise two or more linear or curved subsections whose angle with the longitudinal axis successively decreases with increasing distance from an entrance to the hole.

In some embodiments, the width decreases in two or more stages. To this end, the tapering section can comprise two or more linear or curved sub-sections, the angle of which with the longitudinal axis decreases successively with increasing distance from an entrance to the hole.

In some embodiments, the width of the grooves at the entrance to the combination area can be greater than the thickness of the anchor plate, specifically by at least 5% and at most 100%. Such widening of the groove facilitates insertion and improves the symmetry of the load during friction welding in the constant section. The anchor plate is preferably rectangular. In particular, it can be advantageous if it has no bevels on the narrow sides.

The invention also relates to a method for producing a toothbrush with a brush head made of synthetic material and with at least one bristle bundle anchored in the brush head, with the steps:

• • a) providing a brush head with a hole for fixing the at least one bristle bundle, comprising a hole with a longitudinal axis and a hole cross-section with a basic shape for receiving the folded bristle bundle, wherein two grooves running parallel to the longitudinal axis and extending beyond the basic shape of the hole cross-section are grooves are formed by injection molding in a wall of the hole, the grooves having, adjacent to an entrance of the hole, a combination section with centering and tapering section, which, when viewed in a direction perpendicular to the longitudinal axis, has a depth (T) and a width (B) that successively decrease with increasing distance from an entrance of the hole.
  • b) providing a small anchor plate made of synthetic material for anchoring the respective folded bristle bundle in the hole,
  • c) Inserting the anchor plate with the folded bristle bundle into the hole, whereby the anchor plate is inserted into the combination section of the grooves and fixed in the u-profile using a friction welding process.

Preferably, each groove has a constant section which, when viewed in a direction perpendicular to the longitudinal axis, has a width and a depth that are each constant along the longitudinal axis.

The following detailed description and the entirety of the patent claims give rise to further advantageous embodiments and feature combinations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

To explain embodiments, the drawings show:

FIG. 1 a perspective view of several rows of holes in a brush head;

FIG. 2 a perspective view of several rows of holes with an anchor plate inserted;

FIG. 3 a schematic cross-section of a hole with an anchor plate that is able to insert a bristle bundle into the hole, and a centering section and a constant section of the grooves;

FIG. 4 a schematic view of the hole shown in FIG. 3;

FIG. 5 a schematic cross-section of the hole from FIGS. 3 and 4 with an anchor plate that has folded the bristle bundle and inserted it into the hole;

FIG. 6 a schematic view of the hole shown in FIG. 5;

FIG. 7 a schematic cross-sectional view of a hole comprising grooves having a taper section, a centering section and a constant section; and

FIG. 8 a schematic view of the hole shown in FIG. 7.

WAYS OF CARRYING OUT THE INVENTION

FIG. 1 shows a transparent brush head 1 of an embodiment of the toothbrush according to the invention. The embodiment comprises a plurality of circular cylindrical holes 5 in several rows. The basic shape of the hole in the longitudinal cross-section is thus a circle. Folded bristle bundles (not shown) and a corresponding plurality of anchor plates 3 made of synthetic material are inserted into the holes. The holes are preferably designed as blind holes in the one-piece brush head.

The brush head 1 further comprises a hole 5 with a longitudinal axis L1 for each bristle bundle. In the present example, all holes 5 are aligned in the same way with their longitudinal axis, namely perpendicular to the upper main surface of the brush head. The small anchor plate 3 is used to anchor the respective bristle bundle and is fixed in the hole 5. The longitudinal axis L1 is here exactly perpendicular to a surface 4 of the brush head.

According to a favorable embodiment, the hole 5 as such does not taper or widen, i.e. a cross-section of the wall 6 is constant along the longitudinal axis L1 of the hole 5. In other words, the wall is essentially parallel to the longitudinal axis L1.

Each hole now has two grooves 7 and 8, which are injection molded into the wall 6 of the hole 5, are aligned opposite each other and parallel to the longitudinal axis L1, and are designed to hold the anchor plate 3. The grooves extend from the entrance of the hole 5 or from the surface 4 of the brush head to a depth in the lower half of the hole 5.

In this embodiment, the alignment of the groove pair of a hole is not parallel to the row of holes, but is instead inclined at an angle of approximately 45° to the direction of the row of holes. This has the advantage that the grooves of adjacent holes are at a relatively large distance from one another.

FIG. 2 shows the view from FIG. 1, with the exemplary anchor plate 3 fixed here. The anchor plate is essentially rectangular. Preferably, it has no bevels on the sides. This allows the anchor plate to be welded over a large area in the constant section of the grooves.

When pushed in, the anchor plate 3 is clamped between the grooves 7 and 8, in that the corresponding dimension of the anchor plate 3 is higher by a certain amount than the distance between the bottoms of the grooves 7 and 8, at least in the end position of the anchor plate shown here. The anchor plate 3 is welded to the U-profiles of the grooves 7 and 8, e.g. by friction welding or by ultrasonic excitation of at least one of the components involved.

In an embodiment, which is shown in FIGS. 3 and 4, the two grooves 9 and 10 run continuously to the bottom of the hole 11. FIG. 4 is a view of the hole 12 and FIG. 3 is a section through the hole 12 in the plane S1. In the upper area, the groove has a centering section Z1, in which the groove base runs at an angle to the longitudinal axis L2. Subsequently, the groove has a constant section K1, in which the groove base is parallel to the longitudinal axis L2. In this way, the fact that a depth T of the grooves 9 and 10, viewed along the longitudinal axis L2 and starting from the surface 13 or the entrance of the hole 12 into the brush head 14, and that during insertion the anchor plate 15 is thereby guided symmetrically into the. In particular, the value of the depth T here ranges from the maximum T2 at the entrance of the hole to the minimum T1 at the end of the centering section Z1. In other words, the depth T of the groove is a distance value in a first plane S1/S2, which runs through the longitudinal axis L2 and perpendicularly through the two grooves. Accordingly, the width B1 is a distance value in a second plane, which runs perpendicular to the first plane.

FIGS. 3 to 6 now illustrate how the bristle bundle 2 is anchored by the anchor plate 15 in the hole 12. Inserting the anchor plate 15 into the grooves 9 and 10 folds the bristle bundle 2 so that, after the anchoring is complete, the bristles protrude upwards out of the hole 12, see FIGS. 5 and 6. Here, FIG. 5 is a view of the section S2 marked in FIG. 6. It can also be seen how the anchor plate 15 has jammed in the groove.

Both parts, bristle head 14 and anchor plate 15, are made of plastic, in particular of the same material, and both parts can be welded.

In this embodiment of FIGS. 3 to 6, there is also another optional aspect that can be used independently of other optional aspects in various embodiments: The width B1 in the combination section of the grooves is wider at the hole edge, in particular at least 5% (e.g. maximum 10%) than the thickness D of the anchor plate 15. Where the combination section meets the constant section, the width of the combination section is the same as the constant section.

If an even more precise and stable assembly is desired, the grooves can be modified according to the embodiment shown in FIGS. 7 and 8 by also providing a tapering section V. FIG. 7 is a view of the section S3 marked in FIG. 8. This embodiment is based on the embodiment shown in FIGS. 1 and 2. Viewed in the direction of S3, the depth decreases successively. Likewise, the width B of the grooves 16 and 17 decreases successively with increasing distance from the entrance of the hole 20 at the surface 18 of the brush head 19. This additional tapering has the effect that the anchor plate (not shown here) is loaded biaxially centered symmetrically when it is pushed into the grooves when it is inserted into the constant section by friction welding.

In addition, a further optional aspect is shown in the embodiment according to FIGS. 7 and 8, which can also be used independently of other optional aspects in various embodiments: The centering section Z2 and the tapering section V (only one of the two tapers would also be possible) are both designed in two stages, i.e. a first stage from the brush head surface 18 downwards tapers the groove at a first angle and a second stage, which follows on from the first stage, tapers the groove again, but at a second angle, which is smaller than the first angle. A third phase (constant section K2) up to the deposition of the grooves 16 and 17 is then parallel to the longitudinal axis L3, as shown, but could also be designed obliquely. In the embodiment according to FIGS. 3 to 6, the tapering of the depth of the groove could also be carried out in two or more stages.

While the invention has been explained in terms of its preferred embodiment(s), many other changes and variations can be made without going beyond the scope of the present invention. Therefore, it is intended that the enclosed claims cover changes and variations within the actual scope of the invention.