Toothbrush

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.

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.

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.

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:

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.

shows a transparent brush headof an embodiment of the toothbrush according to the invention. The embodiment comprises a plurality of circular cylindrical holesin 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 platesmade of synthetic material are inserted into the holes. The holes are preferably designed as blind holes in the one-piece brush head.

The brush headfurther comprises a holewith a longitudinal axis Lfor each bristle bundle. In the present example, all holesare aligned in the same way with their longitudinal axis, namely perpendicular to the upper main surface of the brush head. The small anchor plateis used to anchor the respective bristle bundle and is fixed in the hole. The longitudinal axis Lis here exactly perpendicular to a surfaceof the brush head.

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

Each hole now has two groovesand, which are injection molded into the wallof the hole, are aligned opposite each other and parallel to the longitudinal axis L, and are designed to hold the anchor plate. The grooves extend from the entrance of the holeor from the surfaceof the brush head to a depth in the lower half of the hole.

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.

shows the view from, with the exemplary anchor platefixed 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 plateis clamped between the groovesand, in that the corresponding dimension of the anchor plateis higher by a certain amount than the distance between the bottoms of the groovesand, at least in the end position of the anchor plate shown here. The anchor plateis welded to the U-profiles of the groovesand, e.g. by friction welding or by ultrasonic excitation of at least one of the components involved.

In an embodiment, which is shown in, the two groovesandrun continuously to the bottom of the hole.is a view of the holeandis a section through the holein the plane S. In the upper area, the groove has a centering section Z, in which the groove base runs at an angle to the longitudinal axis L. Subsequently, the groove has a constant section K, in which the groove base is parallel to the longitudinal axis L. In this way, the fact that a depth T of the groovesand, viewed along the longitudinal axis Land starting from the surfaceor the entrance of the holeinto the brush head, and that during insertion the anchor plateis thereby guided symmetrically into the. In particular, the value of the depth T here ranges from the maximum Tat the entrance of the hole to the minimum Tat the end of the centering section Z. In other words, the depth T of the groove is a distance value in a first plane S/S, which runs through the longitudinal axis Land perpendicularly through the two grooves. Accordingly, the width Bis a distance value in a second plane, which runs perpendicular to the first plane.

now illustrate how the bristle bundleis anchored by the anchor platein the hole. Inserting the anchor plateinto the groovesandfolds the bristle bundleso that, after the anchoring is complete, the bristles protrude upwards out of the hole, see. Here,is a view of the section Smarked in. It can also be seen how the anchor platehas jammed in the groove.

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

In this embodiment of, there is also another optional aspect that can be used independently of other optional aspects in various embodiments: The width Bin 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. 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 inby also providing a tapering section V.is a view of the section Smarked in. This embodiment is based on the embodiment shown in. Viewed in the direction of S, the depth decreases successively. Likewise, the width B of the groovesanddecreases successively with increasing distance from the entrance of the holeat the surfaceof the brush head. 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, which can also be used independently of other optional aspects in various embodiments: The centering section Zand 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 surfacedownwards 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 K) up to the deposition of the groovesandis then parallel to the longitudinal axis L, as shown, but could also be designed obliquely. In the embodiment according to, 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.