Toothbrush with injection-moulded bristles and method and apparatus for producing the same

This application is a broadening reissue of U.S. Pat. No. 10,835,025, issued Nov. 17, 2020.

The present invention relates to a toothbrush, to a method for producing a toothbrush and to an apparatus for producing a toothbrush.

Document WO 2008/135953 A1 makes known an oral hygiene implement, the head part of which has a base and a plurality of elastomer elements which protrude from the base. The elastomer elements can be produced using the injection molding method, the elastomer elements forming at least 250 edges and the tip radius of the elastomer elements being less than 0.006 inches.

In addition, document WO 03/079849 A1 discloses bristles for a bristle product, in particular a cleaning brush, a toothbrush or an application brush, the bristle having a lower root region by way of which it can be attached in or on a bristle carrier or is part of a bristle carrier and having a free length which is arranged outside the bristle carrier and is located above the root region. This is composed of a shaft region which adjoins the root region and a flex region which is arranged on top of the shaft region, the shaft region being composed of a lower shaft base portion which adjoins the root region and a shaft portion which lies above the shaft base portion. The flex region is composed of a lower acting and flex portion which adjoins the shaft region and a tip portion which lies above the acting and flex portion and forms the free end of the bristles. In the shaft base portion, the bristle has a continuous, recess-free lateral surface and in the flex region, at least in portions on the lateral surface, carries a profiling, which is formed by elevations and/or recesses and lies inside the enveloping surface of the bristle. The injection molding tool for producing the bristle consists of several mold plates which are layered transversely with respect to the longitudinal extension of the mold channel, each of which has a longitudinal section of the mold channel.

It is an object of the present invention to create a simply producible toothbrush with injection-molded bristles and a method as well as an apparatus for producing a toothbrush of this type.

The object is achieved with a toothbrush, a method and an apparatus as described below.

The further development of the toothbrush as claimed in the invention includes, along with the injection-molded bristles, further cleaning elements, in particular also inserted, previously extruded, conventional bristles and/or injection-molded (not with bristles) flexible massaging and cleaning elements.

The disclosure in conjunction with individual embodiments of the toothbrush as claimed in the invention and production methods with reference to injection-molded bristles, extruded conventional bristles and (bristle-free) injection-molded flexible massaging and cleaning elements are applicable in principle to all the embodiments, in particular to those according to.

A toothbrush as claimed in the invention has a bristle carrier, which is produced using the injection molding method and is provided with at least one distributing channel for bristle material. The injection-molded bristles, which are also produced using the injection molding method and have a bristle stem, protrude from the bristle carrier and are realized integrally, i.e. in one piece, with the bristle material in the distributing channel.

The injection-molded bristles are connected to the bristle carrier by means of material bonding and/or positive locking. The distributing channel serves for supplying the bristle material for the injection-molded bristles from an injection point. The injection point is provided in the injection molding tool by an injection nozzle and can usually be fixed on the toothbrush.

The toothbrush as claimed in the invention can be produced in a simple manner using the injection molding method, preferably using the one-component, two-component or multiple-component injection molding method.

The injection-molded bristles preferably have a conical form with a constant gradient (conical form) in the region of the bristle stem. A usage-side end region of the bristles, which is realized integrally with the bristle stem, preferably connects to the usage-side end of the bristle stem.

The end region is specially formed and preferably has a substantially spherical form, a bristle cap. In particular, it can be realized in a hemispherical manner, in a cone-shaped manner or flatly with a rounded transition to the lateral surface of the bristle stem. It is also possible for it to be divided into a number of tapered end bristles.

The form of the usage-side end region is different to that of the bristle stem.

It is possible to dispense with a specially formed usage-side end region, the usage-side end of the injection-molded bristles being formed by a flat termination of the bristle stem with a sharp-edged transition to the lateral surface of the bristle stem.

As an alternative to this, the injection-molded bristles can also have different gradients or shoulders as long as it is ensured that they can be removed from the mold in the direction of the bristle carrier.

In the case of a preferred embodiment of the toothbrush, the ratio between the diameter of injection-molded bristles produced using the injection molding method at the usage-side end of the bristle stem and the (exposed) length of the bristle stem is at least 1:35. In a preferred manner, the ratio is at least 1:40.

In a further preferred embodiment of the toothbrush as claimed in the invention, the above-mentioned ratio is a maximum of 1:90, in a preferred manner a maximum of 1:80.

In a preferred manner the above-mentioned ratio lies between 1:35 and 1:90, preferably between 1:40 and 1:80.

The selection of the ratio also influences the bristle hardness (elasticity). The reduction of the ratio thus leads to harder elastic bristles. A toothbrush can have injection-molded bristles where such ratios are different.

The distributing channel for the bristle material of the injection-molded bristles can be situated on the front side of the bristle carrier facing the exposed length of the injection-molded bristles. In a preferred manner, however, it is realized on the rear side of the bristle carrier facing away from the exposed length of the injection-molded bristles. In this case, the bristle carrier has passages for the bristle material which extend from the bottom of the distributing channel to the front side.

In a particularly preferred embodiment, one passage of the bristle carrier has associated therewith several injection-molded bristles, in particular between 2 and 15, preferably between 3 and 10 bristles form one bristle bundle which is associated with one passage.

In a particularly preferred manner, 4, 5, 6, 7, 8 or 9 bristles are associated with one bristle bundle. The named number of injection-molded bristles is preferably combined on one circular passage to form one bristle bundle. However, bundle sizes which are independent of the passages can also be formed.

The individual bristle bundles with injection-molded bristles are spaced apart by a minimum spacing. In this case, it has been shown that a minimum spacing of less than 2 mm, preferably a spacing of between 0.1 and 1.5 mm allows for an optimum cleaning action with excellent interdental penetration of the injection-molded bristles.

Preferably, between 20 and 50 bristle bundles are present on a toothbrush head. In a particularly preferred manner, between 25 and 45 bundles with injection-molded bristles are provided.

A toothbrush as claimed in the invention with injection-molded bristles includes between 100 and 500 injection-molded bristles for a good cleaning action. Preferably, there are between 150 and 300 injection-molded bristles.

The injection-molded bristles combined to form a bristle bundle preferably all converge slightly toward their usage-side end, i.e. the longitudinal center axes of the individual injection-molded bristles have a slight inclination toward the longitudinal center axis of their bristle bundle, apart from one centrally arranged bristle at most. The “moving closer together” of the ends of the injection-molded bristles influences the interdental cleaning in a very positive manner.

In the case of the embodiment of the toothbrush, where the distributing channel is realized on the rear side of the bristle carrier, the injection point for the bristle material, in a preferred manner, is offset with reference to the passages—also in a preferred manner in the longitudinal direction of the toothbrush—, i.e. the injection point is not situated directly opposite a passage.

In an even more preferred manner, the injection point is positioned in the vicinity of the edge of the bristle carrier, outside the zone with the passages.

The injection point, in a preferred manner, is designed such that the material, after exiting from the nozzle, initially contacts the plastics material of the bristle carrier or of a small carrier plate forming the bristle carrier and does not directly contact a passage. As a result, an even distribution of the bristle material in the cavity is achieved and more even pressure conditions in the bristle cavities (compared over all the bristle cavities) are created.

The cross section (width and depth) of the distributing channels is dependent on the number of passages, the spacing between the passages and the injection point or on the maximum spacing of a passage from the injection point and on the bristle material.

In a preferred embodiment of the toothbrush as claimed in the invention, the height of the distributing channel—measured from its bottom as far as up to the surface forming the rear side or front side of the bristle carrier—is at least 0.5 mm. The height is preferably between 0.5 and 2 mm, in particular between 0.7 and 1.5 mm.

The cross section of the distributing channel preferably corresponds to at least 35% of the cross section of the largest passage for the bristle material. In a further preferred manner, the cross section of the distributing channel corresponds to at least the area of the bristle bundle, a bristle base.

In a preferred further development, at least one bristle-free flexible massaging and cleaning element is injected on the bristle carrier. It protrudes on the same side of the bristle carrier as the injection-molded bristles. There can also be a bristle-free, flexible tongue cleaning element present. This latter is situated in a preferred manner on the side facing away from the bristles.

“Bristle-free” means that the flexible massaging and cleaning element or tongue cleaning element does not have any injection-molded bristles nor any extruded, conventional bristles.

The material for the bristle-free, flexible massaging and cleaning element (there can be several of them) can be distributed either by means of soft material distributing channels or in another manner. For example, a flat covering made of the material for the bristle-free, flexible massaging and cleaning element can be injected by means of the distributing channels which contain bristle material for the injection-molded bristles.

Thermoplastic polyurethane elastomers (TPE-U), thermoplastic styrene elastomers (TPE-S), such as, for example, a styrene-ethylene-butylene-styrene copolymer (SEBS) or a styrene-butadiene-styrene copolymer (SBS), thermoplastic polyamide elastomers (TPE-A), thermoplastic polyolefin elastomers (TPE-O) and thermoplastic polyester elastomers (TPE-E) are suitable as soft material for these types of bristle-free, flexible massaging and cleaning elements and for bristle-free tongue cleaning elements. In addition, thermoplastic polyethylene (PE) and polyurethane (PU) can be used as soft material; they can also be used as hard material. TPE-S is used in a preferred manner. The Shore A hardnesses of the soft materials are preferably less than 90 Shore A.

The Shore hardness of the soft material for the bristle-free, flexible massaging and cleaning element or elements is lower, in a preferred manner considerably lower than the Shore hardness of the bristle material for the injection-molded bristles.

The soft material for the bristle-free, flexible massaging and cleaning elements preferably has a Shore A hardness of less than 40.

If soft material is used in a handle part or neck part of a brush body of the toothbrush, it preferably has a Shore A hardness of less than 70 there. In general, when viewed over the entire toothbrush, the Shore A hardness of the soft materials is less than 90. Bristle-free, flexible massaging and cleaning elements can be in different forms. For example, these can be in a stem-shaped almost cylindrical, sail-like, wavy, spherical, conical, crescent-shaped, star-shaped or cup-shaped form.

Bristle-free, flexible massaging and cleaning elements are preferably shorter than injection-molded bristles; this means that they do not project as far beyond the bristle carrier as injection-molded bristles.

Bristle-free, flexible massaging and cleaning elements are typically considerably more voluminous than injection-molded bristles. For this reason, materials with a lower Shore hardness can also be used for bristle-free, flexible massaging and cleaning elements. The long, thin development gives the injection-molded bristles their flexibility.

The bristle carrier can have one, two or even more distributing channels for bristle material. In this case, it is possible that a different bristle material is used per distributing channel for bristle material. The bristle material can differ in the color, the Shore hardness and/or other characteristics which are generated by means of adding elements (antibacterial, surface changing, etc.) to the master batch.

In addition, the bristle carrier can have one (or several) soft material distributing channel(s) for the soft material for the flexible massaging and cleaning elements. If two or more soft material distributing channels are present, it is possible for a different material to be used per soft material distributing channel. The soft material for bristle-free, flexible massaging and cleaning elements can also differ in the color, the Shore hardness and/or other characteristics which are generated by means of adding elements (antibacterial, surface changing, etc.) to the master batch.

In a further preferred embodiment of the toothbrush as claimed in the invention, in the bristle carrier the soft material distributing channel is separated from the distributing channel for the bristle material. Consequently, in the embodiment there is no contact between the bristle material and the soft material.

The distributing channels for the different materials are preferably separated by the hard material of the bristle carrier. This means that, using the injection molding method, in a simple manner it is possible, by means of one single injection point for the soft material, simultaneously to produce, on the one hand, injection-molded bristles from bristle material and, on the other hand, a bristle-free, flexible massaging and cleaning element, where applicable together with a bristle-free tongue cleaning element. The bristle-free, flexible massaging and cleaning element—or several of them—and, where applicable, the bristle-free tongue cleaning element, are realized integrally, i.e. continuously, with the soft material in the soft material distributing channel.

In a particularly preferred embodiment of the toothbrush as claimed in the invention, the bristle carrier has a small carrier plate produced using the injection molding method (). The described characteristics for the bristle carrier are consequently also applicable in each case to the small carrier plate and vice versa. The distributing channel for the bristle material is realized on the small carrier plate as are, where applicable, the passages and the soft material distributing channel. The small carrier plate carrying the injection-molded bristles produced from the bristle material and, where applicable, the bristle-free, flexible massaging and cleaning elements is fastened on a brush body.

In a preferred manner, in a head region the brush body has a small carrier plate accommodating recess into which the assembled small carrier plate is inserted.

In a preferred manner, the small carrier plate on the brush body is fastened by means of ultrasound welding. Other types of fastening, however, are also possible such as bonding, snapping-in, latching or injecting around using the injection molding method. In the case of the latter, the small carrier plate with the injection-molded bristles and, where applicable, with the bristle-free, flexible massaging and cleaning elements, can be inserted once again into an injection molding tool; the connection can be formed by means of injecting over the brush body and the small carrier plate using a one-component, two-component or multiple-component injection molding method.

It is also possible to inject over the small carrier plate with the injection-molded bristles and, where applicable, with the bristle-free, flexible massaging and cleaning elements, once again inserted into the injection molding tool, and at the same time to form the brush body.