US20100043165A1

US20100043165A1 - Brush, particularly toohbrush and method for the manufacture thereof

Info

Publication number: US20100043165A1
Application number: US12/488,850
Authority: US
Inventors: Tim Juentgen; Erwin Buchholz; Juergen Weissenfels
Original assignee: M&C Schiffer GmbH
Current assignee: M&C Schiffer GmbH
Priority date: 2008-06-20
Filing date: 2009-06-22
Publication date: 2010-02-25
Also published as: EP2135526A1; DE102008029499A1; EP2135526B1

Abstract

Brush, particularly toothbrush and method for the manufacture thereof The present invention relates to a brush, particularly a toothbrush, comprising a brush head carrying bundles of bristles, and a handle with an injection-molded basic body which comprises a fastening section extending up to the brush head. To provide a brush that meets the hygienic standards as much as possible and can be manufactured in an easy way, it is suggested according to the invention that the bundles of bristles should be bonded to the basic body via a casting compound. Furthermore, the present invention provides a method for manufacturing a brush, particularly a toothbrush, comprising a brush head carrying bundles of bristles, and a handle, wherein the bundles of bristles are bonded to a basic body manufactured by injection molding from a thermoplastic after demolding of said basic body, and wherein the bond between the bundles of bristles and the basic body is formed by way of a casting compound that after its solidification is fastened to the basic body.

Description

The present invention relates to a brush, particularly a toothbrush, comprising a bristle head carrying bundles of bristles, and a handle with an injection-molded basic body which comprises a fastening section extending up to the brush head, through which the bundles of bristles are bonded to the basic body.
Such a toothbrush is known from EP 1 142 505. In this prior art, a bristle carrier in the form of a brush head platelet is first provided with bundles of bristles. The bundles of bristles are first fastened to the platelet-like bristle carrier, and the unit formed in this way is thereafter inserted into the brush head tray and fastened. As disclosed in EP 1 142 505, the fastening operation can be carried out by way of welding. The publication also discloses the gluing of the platelet to the brush head tray. To this end the contour of the platelet must exactly be matched to the contour of the brush head tray according to EP 1 142 505. Moreover, the inner circumference of the brush head tray and the peripheral rim of the platelet are made conical to achieve a contact that is as tight and secure as possible between the brush head and the platelet. This procedure is relatively complicated and cannot guarantee that dirt will not get caught between the platelet and the rim of the brush head tray. In an alternative variant, which is also known from EP 1 142 505, adhesive is applied to the upper side of the brush head to cover the rim of the platelet. It might be that this will lead to a complete sealing of the gap between the platelet and the brush head. However, this will result in an objectionable contouring on the surface of the brush, which also promotes the collection of dirt and bacteria and is moreover detrimental to the cleaning efficiency in specific brushes. Particularly in the case of toothbrushes attention must be paid that the surface penetrated by the bundles of bristles is made as smooth as possible.
The teaching imparted in EP 1 142 505, however, adopts an idea that should in principle be welcomed, i.e. first to manufacture the basic body by way of injection molding, which leaves the option to reproduce also complicated contours in an accurate way and at low costs, possibly in a multi-component injection-molding process to mount functional surfaces or advertising prints or ornamental supplements on the basic body. The manufacture of the basic body by applying relatively high internal mold pressures will be completed before the bundles of bristles are bonded to the basic body. It is only after the basic body has been removed from the injection mold that the bundles of bristles will be attached to the basic body. Nevertheless, it is not in the conventional way that the bundle of bristles is introduced into a recess provided on the brush head for this purpose and is equipped with a metallic anchor (conventional anchoring technique), but a relatively flat bristle carrier is first equipped with bundles of bristles and is then attached to the basic body. The bristle carrier can here be easily provided with bristle bundles of different sizes, which is rendered difficult in the conventional anchoring technique.
As has already been described above, the solution known from EP 1 142 505 is however not optimal under hygienic and usability aspects.
It is the object of the present invention to develop the prior-art brush in this respect. Moreover, the present invention wants to provide a method suited for manufacturing such a brush.
In consideration of the product-based problem the present invention provides a brush comprising a brush head carrying bundles of bristles, and a handle with an injection molded basic body having a fastening section extending up to the brush head through which the bundles of bristles are bonded to the basic body through a casting compound brush differs from the generic prior art in that the bundles of bristles are bonded to the basic body through a casting compound.
As compared with the prior-art adhesive, the casting compound is advantageous in terms of low viscosity so that possible free spaces between the basic body and the bundles of bristles or a basic body carrying said bundles of bristles are filled with the casting compound. This is true both for possible free spaces inside the brush head and for the filling of voids and small free spaces or slots on the phase boundaries of different elements of the brush head by the casting compound. Furthermore, the casting compound is preferably used with a volume that fills all free spaces inside the brush head, whereby hygienic standards are complied with in an improved way. The casting compound is here applied with a technique differing from injection molding onto, on or around the fastening section.
Owing to the low-viscosity characteristics of the casting compound it is further possible to form the contour of the brush head either completely or partly by way of the casting compound, i.e. also in cases where the exact molding of complex surfaces structures is required. Due to its low viscosity and its material constitution the casting compound can be processed at atmospheric pressure or at a relatively small overpressure, so that in contrast to the bonding of the bundles of bristles by way of injection molding less equipment is needed and there is also no danger that the casting compound will travel along the filaments of bundles of bristles beyond the outer surface of the brush head to be formed and will glue the filaments of the bundles of bristles.
According to a preferred development of the present invention it is suggested that the casting compound should be positioned at least at the height or level of the ends of the bundles of bristles at the fastening side. This development is governed by the idea that the basic body forms channels for passing the bundles of bristles therethrough that preferably project beyond the basic body with their ends at the fastening side and form thickened portions that are formed at the end of the channels particularly preferably by fusion and rest on the channels and can seal the same. The casting compound can be introduced for the manufacture of this preferred embodiment into a mold having surfaces that are copied by the casting compound, so that the casting compound forms the bottom surface of the brush head, i.e. the surface that in relation to the brush head surface penetrated by the bundles of bristles is provided opposite thereto.
In an alternative design the casting compound may also be bonded to the fastening section of the basic body and to a carrier shaped e.g. with the contour thereof and/or the contour of the brush head. This design yields a sandwich structure consisting of fastening section, casting compound and bristle carrier, with the ends of the bristle bundles at the fastening side being positioned inside the casting compound and preferably sealed or encapsulated by the same.
In a further alternative design, the casting compound forms the surface of the brush head penetrated by the bundles of bristles. In this design the casting compound is tightly placed around the bundles of bristles and seals the ends at the fastening side preferably on the phase boundary between the fastening section and the layer formed by the casting compound. The low viscosity of the casting compound yields a smooth surface penetrated by the bundles of bristles. Said bundles of bristles are kept in the manufacture of said development preferably in channels of a mold, which at any rate in a direction parallel to the bundles of bristles leaves some spacing between the fastening section and the mold surface. When said free space is filled with the casting compound, it need not be feared due to the processing of the casting compound at atmospheric pressure or at a just slightly raised internal pressure in the mold that the casting compound will enter into the channels and glue the filaments of bundles of bristles above the surface to one another.
In the above-mentioned development in which the layer formed of the casting compound is arranged between the fastening section and a bristle carrier, it is possible to provide just a relatively thin layer of casting compound. The brush head can be produced with a very small thickness. The casting compound is here provided between the fastening section and the bristle carrier just as a thin film. However, in this design the casting compound can also flow around the rim area of the fastening section and/or the bristle carrier. Said preferred design exploits the special material constitution of the casting compound after solidification, with the provision that said constitution differs from the material constitution of the injection-molded basic body. Thus cases are possible where the casting compound after solidification shows rubber-like or elastomeric characteristics by virtue of which a softer impact and/or cleaning surface can be created on the rim area of the brush head. Likewise, it is feasible to incorporate special ingredients into the casting compound before casting the latter, said ingredients being discharged during use of the brush. Cleaning additives are here above all envisaged that enhance the cleaning efficiency. In the case of a toothbrush, additives may also be added that exhibit a therapeutic effect in the oral cavity.
In contrast to the adhesive according to EP 1 142 505, which is just applied in the area of the contact surfaces between bristle carrier and basic body, the brush head tray is filled with a casting compound in the product according to the invention. Said compound solidifies substantially up to the rim of the brush head tray, preferably exactly at the same height with said rim. As for the aim to fill the casting compound “substantially” up to the rim of the brush head tray, this should be understood such that a small trough or a minor elevation is possibly provided in the area of the rim of the brush head tray. Said slight contour, however, is so insignificant that there will be no noticeable difference with respect to the cleaning properties and the hygienic demands as compared with a brush having an entirely flat continuous, e.g. materially identical, surface in the area of the brush head.
First of all, a volume of the casting compound may be introduced into the brush head tray that is smaller than the volume of the brush head tray. The casting compound may then be filled substantially up to the level of the rim in that the bundles of bristles are introduced with displacement of casting compound with their end at the fastening side into the casting compound. Optionally, said bundles of bristles may here also be fastened to a bristle carrier the insertion of which into the bristle head tray will displace casting compound, so that said compound solidifies approximately at the height of the rim of the brush head tray.
The casting compound preferably fills the whole brush head tray, whereby the hygienic properties are improved and also the attachment of the bundles of bristles to the basic body.
A hot melt adhesive may be used as the casting compound. Suitable hot melt adhesives show a very low viscosity at processing temperature, i.e. at a temperature below the melting point of the thermoplastic forming the basic body.
As an alternative, the casting compound may be formed by an oligomer system. Envisaged is here for instance a cyclic butylene terephthalate (CBT). Corresponding CBTs may be provided in powder-like or granular form. When heated, they will polymerize into thermoplastic PBT (polybutylene terephthalate). Likewise, the viscosity of such oligomer systems is relatively low. At the processing temperatures to be employed in this instance it is about at least ten times the viscosity of the thermoplastic forming the basic body.
Similar advantages are offered by casting compounds of the PUR system. Here, one-component or two-component systems may be used as casting compound. A casting compound of polyurethane can be adjusted in terms of processing time, color and hardness within wide limits and almost in any desired way. The viscosity during processing is about 10 to 100 times lower than that of the thermoplastic forming the basic body, which may e.g. be polypropylene.
The alternatives presented above with respect to the material constitution of the casting compound show the common feature of a considerably reduced viscosity under processing conditions. Thus, while being filled into a mold for bonding the bristle bundle to the basic body, the casting compounds can fill all of the free spaces and can also seal minor gaps to the outside that are e.g. exposed between the outer circumference of the bristle carrier and the inner circumference of the brush head tray and/or within a grid-like bristle carrier and, without the penetration of the casting compound, would provide cavities in which dirt or germs might accumulate. Low viscosities within the meaning of the present invention are particularly viscosities of between 0.5 mPa·s and 10⁶mPa·s, preferably between 10²mPa·s and 10⁴mPa·s at processing temperature. The processing temperature may be room temperature. At elevated temperatures the processing temperature is below the melting point of the thermoplastic forming the basic body. The thermoplastic forming the wall of the brush head tray is of relevance in the case of basic bodies which are injection-molded from several components.
For the solution of the method aspect according to the present invention, the present invention provides a method for manufacturing a brush, particularly a toothbrush, comprising a brush head carrying bundles of bristles, and a handle, wherein the bundles of bristles are bonded to a basic body manufactured by injection molding from a thermoplastic after demolding of the basic body, which method differs from the previously indicated generic prior art in that the bond between the bundles of bristles and the basic body is established through a casting compound that after its solidification is fastened to the basic body.
In this procedure the casting compound after solidification will preferably fill all cavities in the area of the brush head. The casting compound can shape the brush head partly or however also predominantly. In the method according to the invention the casting compound is possibly cast into an upwardly open mold accommodating the fastening section, in which it solidifies. As an alternative, the mold for forming the brush head may also be substantially closed with inclusion of the fastening section. Such a closed mold will particularly be used whenever the casting compound is to form a substantial portion of the surface of the brush head, or even the whole surface of the brush head. While being processed the casting compound shows a relatively low viscosity, particularly within the above-mentioned parameter limits. At atmospheric pressure or at a low internal pressure at the most, the casting compound is introduced into the mold and is solidified therein. Thus the casting compound can first be introduced into the mold under atmospheric conditions.
A mold within the above meaning may also be one formed by the fastening section itself. Said section may e.g. be shaped in the form of a brush head tray which is introduced into the casting compound. When the ends of the bristle bundles at the fastening side are introduced into such a brush head tray, the casting compound will rise, namely preferably up to the rim of the brush head tray. This creates a brush in which the surface penetrated by the bristle bundles is entirely even and smooth. In matching the volume of the brush head tray with the displacement volume of the introduced bundles of bristles optionally of the bristle carrier carrying the bundles of bristles, the volume of the casting compound to be filled in can here be determined such that it solidifies at the same level with the rim of the brush head tray also in the areas between the bundles of bristles. Such solidification also between the bundles of bristles will also occur in the case of a bristle carrier on condition that said carrier has an individual grid structure connecting the bristle bundles to one another. The casting compound will flow through this open grid, which is sealed in the casting compound for the attachment of the bundles of bristles.
If the bristle carrier is shaped as a platelet with a closed surface penetrated by the bristle bundles, the casting compound will exclusively pass into a gap between the bristle carrier and the basic body and will be moved by displacement approximately up to the height of the rim of the brush head tray, with the casting compound preferably solidifying after a short period of time.
While in the above-described procedure the brush head tray is not completely closed in the manufacturing process, an alternative configuration yields a cavity that is first closed and into which the casting compound is introduced. To this end the bundles of bristles are first arranged in holes of a hole field plate, the hole field of which is predetermined by the bristle attachment of the brush to be formed. This hole field plate is sealingly applied to the rim of the brush head tray. The cavity created thereby is filled with the casting compound. At the back side of the brush head tray oriented away from the bundles of bristles, a filling hole may be formed for the casting compound. A venting hole may possibly be provided at said place as well, through which venting hole the air displaced out of the cavity can escape. However, the air can just as well exit through the holes of the hole field plate. The internal pressure inside the cavity is thereby controlled such that the casting compound during solidification inside the cavity molds the surface of the hole field plate without, however, penetrating into the holes to a considerable extent. Such a procedure is possible owing to the relatively low viscosity and due to the application of only relatively low internal pressures in the cavity. As a result of such a procedure, a smooth surface penetrated by the bundles of bristles is obtained on the finished brush. After solidification the casting compound may show a certain residual elasticity, so that the ends of the bristle bundles at the fastening side are elastically supported within limits. Filling and sealing of the brush head tray does not require any complicated injection mold, as is needed in the procedure according to U.S. Pat. No. 5,350,219.
The brush produced according to the method can thus be manufactured in an economic way, it meets the hygienic demands to be e.g. made in the case of toothbrushes and has a brush head surface which could be called even and defect-free and which is penetrated by the bundles of bristles.

Advantages and details of the invention become apparent from the following description of embodiments in combination with the drawing, in which drawing:

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention in the form of a toothbrush;

FIG. 2 is a longitudinal sectional view of a second embodiment of the present invention in the form of a toothbrush; and

FIG. 3 is a longitudinal sectional view of a third embodiment of the present invention in the form of a toothbrush.

FIG. 1 shows a basic body 1 which in the area of the brush head 2 forms a brush head tray 3 that is open towards the upper side of the brush and is defined by a surrounding rim 4.
FIG. 1 shows the basic body schematically at a time when a brush head platelet 6 carrying a bundle of bristles 5 and forming a bristle carrier is not yet bonded to the basic body 1. The brush head platelet 6 comprises channels through which the individual bundles of bristles 5 are inserted. At the ends at the fastening side the bundles of bristles 5 are provided with a thickening 7 that is produced by fusion of the bundles of bristles 5. The thickening 7 rests on the bottom side of the brush head platelet 6, thereby closing the channels. A casting compound 8 is applied to the surface formed in part by the thickening 7 and in part by the bottom side of the brush head platelet. The brush head platelet 6 prepared in this way is inserted together with the bundles of bristles 5 into the brush head tray 3. The casting compound 8 is here flowing inside the brush head tray 3, filling all cavities, and finally penetrates into a gap between the circumferential surface of the brush head platelet 6 and the basic body 1, until the casting compound 8 is approximately at the same height as the rim 4 and the surface of the brush head platelet 6. The casting compound 8 is solidifying at said place.
FIG. 2 shows an alternative embodiment in which the basic body forms a substantially flat fastening section 9 which forms channels for holding bundles of bristles 5. These bundles of bristles 5 are also fused at their ends at the fastening side for forming thickenings 7. The basic body 1 prepared in this way is subjected, projecting with the bundles of bristles 5 downwards from the basic body 1, to a further treatment step in which the casting compound 8 is applied to the bottom side of the basic body and partly to the thickenings 7. After the casting compound 8 has solidified, a shoulder-free surface is obtained on the bottom side of the brush. The bottom side formed by the basic body 1 passes without any shoulders into the bottom side formed by the casting compound 8. A corresponding structure is obtained at the face end of the brush.
In the alternative embodiment shown in FIG. 3, a hole field plate 10 is first equipped with bundles of bristles 5 that at their ends at the fastening side are provided with a thickening 7 by way of fusion. The hole field plate 10 prepared in this way is mounted on the brush head tray 3 so that the hole field plate 10 rests on the rim 4 and seals a cavity 11 predetermined by the brush head tray 3. The hole field plate 10 is here sealing the brush head tray 3 on its rim. The casting compound 8 is introduced into the cavity 11 through an introduction opening 12 recessed on the bottom side of the basic body 1. The casting compound 8 solidifies inside the cavity 11 with inclusion of the ends of the bundles of bristles 5 at the fastening side and particularly of the thickenings 7. The casting compound thereby seals the ends of the bundles of bristles 5 at the fastening side, with the ends projecting into the brush head tray 3. After solidification a shoulder-free even surface that is penetrated by the bundles of bristles 5 is obtained on the brush head 2, the surface being partly formed by the material of the casting compound 8 and partly by the plastic component of the basic body 1. The solidified casting compound 8 solidifies while molding the surface of the hole field plate 10.

LIST OF REFERENCE NUMERALS

1 Basic body
2 Brush head
3 Brush head tray
4 Rim
5 Bundles of bristles
6 Brush head platelet
7 Thickening
8 Casting compound
9 Fastening section
10 Hole field plate
11 Cavity
12 Introduction opening

Claims

1. A brush comprising a brush head carrying bundles of bristles, and a handle with an injection-molded basic body; the handle comprising a fastening section extending up to the brush head, through which the bundles of bristles are bonded to the basic body, with a casting compound (8).

2. The brush according to claim 1, wherein the casting compound is positioned at least at the height of the ends of the bundles of bristles at the fastening side.

3. The brush according to claim 2, wherein the casting compound seals the ends of the bundles of bristles at the fastening side.

4. The brush according to claim 1, wherein the casting compound forms a surface of the brush head which is penetrated by the bundles of bristles.

5. The brush according to claim 1, wherein the casting compound forms the bottom surface of the brush head which faces away from the surface penetrated by the bundles of bristles.

6. The brush according to claim 1, wherein the casting compound is provided between a bristle carrier carrying the bundles of bristles and the basic body.

7. The brush according to claim 1, wherein the casting compound forms the outer surface, preferably the rim area of the brush head, at least in part.

8. The brush according to claim 1, wherein the fastening section is formed in the manner of a brush head tray, and that the bundles of bristles are bonded to the basic body by way of the casting compound filled into the brush head tray.

9. The brush according to claim 8, wherein the casting compound is filled substantially up to the rim of the brush head tray.

10. The brush according to claim 1, wherein the casting compound is member selected from the group consisting of a hot melt adhesive, an oligomer system, a PUR system.

11. The brush according to claim 8, wherein a plurality of bundles of bristles are fastened to a bristle carrier having a surface which is penetrated by the bundles of bristles and is arranged substantially flush with the rim of the brush head tray.

12. The brush according to claim 11, wherein the bristle carrier is configured as a plate-shaped component the contour of which is matched to the contour of the rim of the brush head tray.

13. The brush according to claim 4, wherein the ends of the bundles of bristles at the fastening side are held in the casting compound and the casting compound forms the surface of the bristle head that is penetrated by the bundles of bristles.

14. The brush according to claim 6, wherein the casting compound has solidified flush with the surface of the bristle carrier penetrated by the bundles of bristles.

15. The brush according to claim 8, wherein the brush head tray is completely filled with the casting compound.

16. A method for manufacturing a brush having a brush head carrying bundles of bristles, and a handle, in which the bundles of bristles are bonded to a basic body manufactured by injection molding from a thermoplastic after demolding of said basic body, which comprises forming the bond between the bundles of bristles and the basic body with a casting compound that is fastened to the basic body after solidification of the casting compound.

17. The method according to claim 16, which comprises injection molding the basic body with a brush head tray for accommodating the bundles of bristles, introducing the bundles of bristles with their ends at the fastening side into the brush head tray, filling the brush head tray with the casting compound and sealing the ends of the bundles of bristles at the fastening side.

18. The method according to claim 17, which comprises introducing the casting compound into the brush head tray, and introducing the bundles of bristles at the end side of the brush head tray with displacement of the casting compound up to about the height of the rim of the brush head tray.

19. The method according to claim 17, which comprises fastening the bundles of bristles to a bristle carrier penetrated by the bundles of bristles, and introducing the bristle carrier into the brush head tray to such an extent that the casting compound is displaced into a gap between the bristle carrier and the basic body approximately up to the height of the rim of the brush head tray.

20. The method according to claim 18, which comprises fastening the bundles of bristles to a bristle carrier penetrated by the bundles of bristles, and introducing the bristle carrier into the brush head tray to such an extent that the casting compound is displaced into a gap between the bristle carrier and the basic body up to about the height of the rim of the brush head tray.

21. The method according to claim 17, which comprises arranging the individual bundles of bristles in holes of a hole field plate containing a hole field that predetermines the bristle attachment to be formed, sealingly placing the hole field plate on the rim of the brush head tray, and introducing the casting compound into the cavity closed by the hole field plate such that the ends of the bundles of bristles at the fastening side that project into the brush head tray are sealed in the casting compound, and the casting compound solidifies with molding of the surface of the hole field plate.

22. The method according to claim 18, which comprises arranging individual bundles of bristles in holes of a hole field plate having a hole field which predetermines the bristle attachment to be formed, sealingly placing the hole field plate on the rim of the brush head tray, and introducing the casting compound into the cavity closed by the hole field plate such that the ends of the bundles of bristles at the fastening side that project into the brush head tray are sealed in the casting compound, and the casting compound solidifies with molding of the surface of the hole field plate.

23. The method of claim 18 wherein the brush comprises a toothbrush.

24. The brush of claim 1 comprising a toothbrush.