Method for producing brushes with flexible bristles and brushes with stiff bristles

A method of permanently mounting bristles on a handle to form a brush, and a brush having bristles which extend preselected, irregular distances from the brush handle. First ends of bristles of substantially equal length are contacted against an insert element or a receiving body having a contour corresponding with the preselected, irregular distances. The insert element is heated to soften the bristle first ends or the receiving body, and then the insert element is cooled to harden the softened one of the bristle first ends and the receiving body, fastening the bristle first ends to the insert element. The insert element is fastened in a receptacle in the brush handle. As a result, the bristles extend from the brush handle with the corresponding contour. The several steps may be performed in various sequences.

FIELD OF THE INVENTION 
The present invention relates to a method for permanently mounting 
bristles, hairs, monofilaments, wires, and the like and/or tufts thereof 
in or on a handle. The present invention further relates to an application 
of the method to produce a brush with soft bristles or a brush with 
flexible bristles, including a brush with a specific shape. Additionally, 
the invention relates to a brush with flexible bristles or a brush with 
stiff bristles, the brush including a handle as well as hairs, bristles, 
monofilaments, or wires providing flexible bristles or stiff bristles held 
in or on the handle. 
BACKGROUND OF THE INVENTION 
The manufacture of brushes with stiff bristles, brushes with flexible 
bristles, toothbrushes, and the like is performed in a wide variety of 
ways. Thus, for example, to manufacture paint brushes or cleaning brushes, 
the tufts of bristles or hairs are retained by phenol or epoxy resin 
materials in a receiving box or a handle. 
In the case of smaller brushes, such as toothbrushes or precision cleaning 
brushes, as a rule monofilaments are held in a receptacle either by means 
of hot-melt materials or by so-called anchors. It is also known to 
introduce individual monofilaments or tufts thereof into receptacles in 
the shape of holes, and to weld shut the hole opening. 
The known methods are either partially objectionable from the physiological 
standpoint or are expensive, or they do not allow very small brushes to be 
manufactured. Thus it has been found especially in the manufacture of very 
small brushes for electrical cleaning devices, or of very fine cleaning 
brushes, for example for precision mechanics, that with very small wall 
thicknesses for the brush bodies, the known fastening methods are not 
suitable for retaining brush hairs, bristles, or monofilaments, etc. In 
addition, it is not possible with the known methods to shape the brush or 
to form the brush surface. 
Three U.S. Pat. Nos., 2,653,056, 2,664,316, and 2,397,471 describe the 
manufacture of brushes with stiff bristles, particularly toothbrushes, 
with the bristle tufts being fastened in the handle by metal inserts and 
inductive heating. 
EP-0,519,677 describes the manufacture of brushes with stiff bristles using 
ultrasonic welding. 
WO90/00359 describes a method of manufacturing small brushes with stiff 
bristles, with bristle structures disposed in practically any desired 
manner. It proposes that either a through opening be provided on a holder, 
and the bristle tuft be inserted into this opening, in order to pot it, 
glue it, or weld it from the other side of the holder, or alternatively a 
blind hole be made in the holder in order to use the remaining covering 
wall of the blind hole as a welding material after insertion of the tuft. 
Finally, EP-A-0,329,939 describes a method and a device for making devices 
for applying fluid media by means of bristles. 
The methods described in the prior art relate firstly to the manufacture of 
brushes with stiff bristles, with no adhesives or hot melt materials 
having to be used to secure the bristles or monofilaments that form the 
bristles, or relate to methods and devices for producing bristle 
structures or bristle tufts, either by applied heat or by adhesives. 
None of the publications known from the prior art is suitable for the 
manufacture of very delicate and/or very small brushes with stiff bristles 
or flexible bristles, in whose manufacture the shaping of the tufts is 
important, or in which special bristle structures are to be produced. 
SUMMARY OF THE INVENTION 
Hence, one goal of the present invention is to propose a method that does 
not suffer from the above disadvantages and which is especially suited for 
permitting the manufacture of very fine and/or very small brushes, and to 
facilitate the shaping process in the manufacture of brushes with flexible 
bristles and brushes with stiff bristles. 
In accordance with the present invention, in order to permanently mount 
bristles, hairs, or monofilaments or tufts thereof in or on a handle or in 
or on a receptacle, the bristles, hairs, monofilaments, or wires are 
placed in or on the receptacle or the handle and are connected to the 
receptacle or handle by welding. The welding is performed by means of wave 
or field lines applied and/or directed at the receptacle or handle. 
These waves or field lines applied or directed to the receptacle stimulate 
an insert element introduced onto or into the receptacle or the handle, 
and heat the latter to produce the welded connection. 
According to one embodiment of the method of the invention, initially at 
least one insert element is placed on or in the receptacle, then the 
hairs, bristles, monofilaments, or wires are supplied, and then a 
high-frequency field, which can be an electrical, electromagnetic, and/or 
a magnetic field, is produced in order to excite or heat the insert 
element so that the hairs, bristles, monofilaments, or wires in contact 
with the element, and/or the receptacle, are at least partially melted in 
order to produce the melted connection. 
According to another variation on the method according to the invention, 
initially an insert element is introduced into or onto the retaining 
element or the receptacle in order to be welded with it as it is excited 
by field or wave lines or in order to be joined mechanically or by 
adhesives. Then the hairs, bristles, monofilaments, or wires are 
introduced in the area of the insert element in or on the handle or 
receptacle, whereupon, by means of field or wave lines, the insert element 
is excited in order to trigger possible additional welding under 
temperature conditions that may be different from those of the first 
welding. 
This two-stage method is preferably used when the hairs, bristles, 
monofilaments, or wires exhibit a very different melting behavior from the 
receiving part or the handle. In the case of highly different melting 
temperatures, there is a danger in the single-stage method that either the 
hairs, bristles, monofilaments, or wires or the handle or the receptacle 
may be damaged by excessive heating. 
Another advantage of this two-stage method consists in the fact that 
initially the handle or the receptacle can be provided with an insert 
element, and then a supply of hairs, bristles, monofilaments, or wires can 
be added. The excitation of the insert element then takes place in this 
supply, whereupon only those hairs, bristles, monofilaments, or wires from 
the supply are welded to the insert element that are directly in contact 
with it. In this way the manufacture of a brush with stiff bristles or a 
brush with flexible bristles can be highly simplified. 
Another two-stage method according to the invention is similar, and it 
proposes that initially the hairs, bristles, monofilaments, or wires be 
placed in an insert element which is excited and heated by field or wave 
lines in order to at least soften or begin melting the added bristles, 
hairs, monofilaments, or wires to make a welded connection with the insert 
element. Then this insert element with the hairs, bristles, monofilaments, 
or wires welded to it is placed on or in a handle or a receptacle and 
connected with the latter mechanically by gluing or by welding once more. 
The methods defined according to the invention are especially suitable for 
producing a specific shape of a brush with stiff bristles or with flexible 
bristles, in which the insert element is adapted specially to the shape of 
the brush to be produced. The insert element, depending on the 
requirements, can be made convex, wavy, zigzag-shaped, conical, etc. 
whereby the ends of the hairs, bristles, or monofilaments projecting out 
of the receptacle form a contour that matches the insert element. 
The insert element however can also have gaps in the form of holes or 
slots, which means that the brush does not have any hairs, bristles, 
monofilaments, or wires at these gaps. 
By using the above-mentioned insert elements, comprising gaps in the form 
of holes or slots, it is also possible to make brushes that have areas in 
which the hairs, bristles, monofilaments, or wires have a reduced density. 
This can also be achieved by using a plurality of insert elements spaced 
apart from one another. In the spaces between the insert elements, zones 
can be created that have no hairs, bristles, monofilaments, or wires, or 
zones with reduced density. The advantage of creating such areas or zones 
of reduced density consists in the fact that the flexibility of a brush 
with flexible bristles or a brush with stiff bristles can be considerably 
increased as a result. 
Basically, the methods proposed according to the invention are generally 
suitable for manufacturing all kinds of brushes with flexible bristles or 
stiff bristles, for example paintbrushes, cleaning brushes, toothbrushes, 
precision cleaning brushes in mechanics, etc. 
The methods according to the invention are especially suitable for making 
toothbrushes, both ordinary toothbrushes and those designed for use with 
an electrical tooth cleaning device. 
The brushes with flexible bristles or brushes with stiff bristles 
manufactured according to the invention thus comprise a handle or 
receiving part or a receptacle, as well as hairs, bristles, monofilaments, 
or wires which form flexible bristles or stiff bristles that are held in 
the handle or receiving part, whereby at least one insert element is 
provided which is located in or on the receiving part or handle, and which 
is located adjacent to the hairs, bristles, monofilaments, or wires held 
in the handle or receiving part, and with the hairs, bristles, 
monofilaments, or wires being held in or on the handle or receiving part 
by a welded connection. 
It makes no difference in this respect whether the hairs, bristles, 
monofilaments, or wires are of animal or plant origin or whether they are 
monofilaments made of polymer materials, like those manufactured for 
example from a synthetic polymer.

DETAILED DESCRIPTION 
In FIGS. 1a to 1c, a method according to the invention is shown 
schematically to indicate how the hairs, bristles, monofilaments, and the 
like, or tufts thereof, of brushes with stiff bristles or with flexible 
bristles are permanently mounted in a receptacle. 
A body 1 of a brush with stiff or flexible bristles comprises a receptacle 
5 that is delimited laterally by walls 3 and has a bottom 7. An insert 
element 9 is provided for insertion into this receptacle 5, the element 
preferably being made in the form of a disk, foil, lattice, wire, ring, or 
plate, or as a molded body. Hairs, bristles, monofilaments, or wires 11 
are also provided for insertion and permanent mounting. 
In FIG. 1b, both insert element 9 and the hairs or bristles or 
monofilaments 11 are shown inserted into receptacle 5. The body 1 of the 
brush is inserted into a wire coil 21, the coil being located in the 
vicinity of insert element 9. It is important to note in this regard that 
coil 21 should be located as close as possible to the external contour of 
body 1 of the brush with flexible bristles or brush with stiff bristles. 
By applying a current, such as an alternating current for example, through 
wire coil 21, a magnetic field is generated that changes its direction 
synchronously with the frequency of the alternating current. 
If insert element 9 is an electrically conducting material, for example an 
electrically conducting metal such as iron or copper, an alternating 
voltage will be induced in the insert element, or eddy currents will be 
produced in the insert element, so that insert element 9 is heated. As a 
result of the strong heating of insert element 9, firstly the ends of the 
hairs, bristles, monofilaments, or wires inserted into receptacle 5 will 
be at least softened or slightly melted, as will bottom 7 of the 
receptacle. This produces a welded connection, and the hairs, bristles, 
monofilaments, or wires are thus held firmly in receptacle 5. 
In FIG. 1c, the brush with stiff or flexible bristles that is eventually 
obtained according to the invention is shown, with the idea according to 
the invention being indicated schematically by the fact that, above insert 
element 9, a welded layer 10 is formed. Of course a welded connection 14 
can be produced between the insert element and brush body 1 as well. 
In the method using inductive heating that is described with reference to 
FIGS. 1a to 1c, this is of course only an example that can be supplemented 
by additional suitable methods. 
Thus it is possible for example to insert an insert element 9 that does not 
conduct, or conducts only slightly, and to heat it by using so-called 
dielectric or capacitive heating. Then insert element 9 together with two 
plate electrodes forms the lossy dielectric of a capacitor powered with 
high frequency. The dielectric losses cause insert element 9 to be heated 
uniformly. 
Another possibility is to use a material that has mostly polar compounds as 
insert element 9. In this case the heating can be produced by microwaves. 
However the use of ultrasound or other suitable high-frequency waves or 
electrical, electromagnetic, or magnetic fields is possible, by means of 
which suitable materials can be excited in order to heat them in this 
manner. Although inductive heating is described with reference to FIGS. 1a 
to 1c, the present invention is not limited in any way to this type of 
heating. 
If neither the receiving part nor the brush hairs, bristles, monofilaments, 
or wires consist of a material that can be softened or melted, or if they 
have a melting point that is too high, it is also possible to introduce a 
so-called intermediate support into the receptacle that rests directly 
above the insert element for example. This intermediate support then 
consists of a material that can be melted slightly by heating the insert 
element in order in this way to produce the welded connection of the 
hairs, bristles, monofilaments, or wires inserted into the receptacle, 
with the receptacle itself. 
Another possibility consists in making the method according to the 
invention in two stages in which initially insert element 9 and the hairs, 
bristles, monofilaments, or wires 11 are welded outside receptacle 5. Then 
insert element 9 together with the hairs, bristles, monofilaments, or 
wires welded to it is introduced into receptacle 5 in order again to be 
secured in the latter by welding, or by means of conventional adhesives, 
or by using mechanical retainers. Thus it is possible for example to 
provide insert element 9 with lateral clamping elements which secure 
insert element 9 in the receptacle. 
Yet another possibility consists in performing the method in two stages, 
but in which insert element 9 is initially connected with receptacle 5. 
This connection again can be made by welding, gluing, or mechanically. In 
a second step, the hairs, bristles, monofilaments, or wires are then 
introduced in order to be welded into the receptacle by using the method 
described in connection with FIGS. 1a to 1c. By means of this latter 
two-stage method it is then possible to take the receptacle together with 
the insert element to a supply of hairs, bristles, monofilaments, or 
wires, to apply the supply, and then to fasten the necessary number by 
means of the welding method according to the invention. Then the 
receptacle with the insert element can be taken away from the supply once 
more and the required hairs, bristles, monofilaments, or wires are 
accordingly removed from the supply. 
In regard to the method to be used for heating the insert element, it 
should also be noted that it basically involves methods that are known 
from the prior art. It is in the final analysis a question of optimization 
as to which method and which process conditions are selected. In the case 
of inductive heating, it should be added that the heating of the insert 
element is dependent upon firstly the distance of the wire coil from the 
insert element, the number of turns, the wire material selected, the 
applied field strength or current density, and the time during which the 
insert element is heated. Heating of the insert element however can be 
also controlled by the selected form of insert element, since the weight, 
size, and selected material play an important role for example. Thus for 
example an annular insert element can be heated readily, while a ring that 
is interrupted at one point is practically impossible to heat. 
However these factors also make it possible to control the heating of the 
insert element or to establish a temperature range to which the insert 
element is to be heated. In addition, reference should be made to the 
prior art from which the above-mentioned methods and procedures are best 
known. 
FIG. 2a shows a brush 1' with flexible bristles 11' which has been produced 
according to the invention, comprising a handle 2' as well as a 
thin-walled receptacle 3' into which the hairs 11' are inserted. The 
melted layer 10 by means of which the hairs 11' are held in the brush can 
be seen above insert element 9. 
FIG. 2b shows a toothbrush 1" manufactured according to the invention that 
has a specially shaped handle 2", suitable for example for use of this 
toothbrush on an electrical tooth cleaning device. Once again the 
individual bristles or monofilaments 11" are held by a welded connection 
10, 14 on insert element 9. These monofilaments for example can be 
polyamides or another polymer material that is usually used for 
manufacturing toothbrushes. 
As described above, the method according to the invention is suitable for 
giving brushes with stiff bristles and brushes with flexible bristles a 
specific contour. 
As is clearly evident from FIG. 2b, a plurality of receptacles 5" is formed 
in toothbrush 1" into each of which an insert element 9 is fitted. Thus 
so-called gaps 4 are produced between the various receptacles 5" and have 
no insert element. In this way it is basically possible to make brushes 
that have a plurality of bristle tufts with gaps between them. It is also 
possible to make a toothbrush with gaps 4 so that the flexibility of the 
individual bristle tufts 11" is increased considerably, which is 
especially desirable in toothbrushes. 
FIG. 3 shows in a cross section how a brush 1c with stiff bristles or with 
flexible bristles can be made convex or projecting. Insert element 9 used 
in FIG. 3 is likewise made convex or projecting, so that when hairs, 
bristles or monofilaments of the same length are used an external contour 
12 that is convex or projecting can be produced. The manufacture of such a 
brush with flexible bristles or a brush with stiff bristles of this kind 
is performed by analogy with the method described for example with 
reference to FIGS. 1a to 1c. 
Similarly in FIG. 4 an insert element 9 of a different design is employed, 
having a zigzag shape, for example, whereby brush 1d in FIG. 4 has three 
receptacles 5. Again the outer contour 12' of the individual elements of 
the brush with stiff or flexible bristles is made zigzag shaped. 
The great advantage of providing this contour by means of an insert element 
consists in the fact that after the brush with stiff or flexible bristles 
is produced, the individual hairs, bristles, or monofilaments do not have 
to be cut in order to produce the desired external contour 12. Especially 
in the case of monofilaments it has been found that during cutting, the 
ends that project out of the receptacle are indented or frayed, which is 
undesirable especially in the case of toothbrushes, since the gums can be 
injured by damaged bristles. In this case it is necessary after cutting to 
use a special grinding or melting method to round off the ends of the 
hairs, bristles, monofilaments, or wires projecting out of the receptacle, 
said method being relatively costly and cumbersome. According to the 
invention, there is no need for this additional step. 
With the manufacturing method in use today for making brushes with flexible 
bristles and brushes with stiff bristles, in producing brushes with 
flexible and stiff bristles with special shapes, it is necessary as a rule 
to cut and grind the hairs, bristles, monofilaments, or wires before 
making the brush, which is cumbersome. Brush shapes, like those shown in 
FIG. 4, cannot be made with conventional methods. 
In FIGS. 5 and 6, an insert element 9 is employed that has a hole or gap 13 
in the middle. Insert element 9 in FIG. 5 also has an indentation or 
groove 15. Accordingly, gap 13 is located centrally in contour 12 of the 
brush manufactured according to the invention, since no welding of the 
inserted hairs, bristles, or monofilaments can take place in the middle of 
hole 13. After the brush with flexible or stiff bristles according to the 
invention has been manufactured, the hairs, bristles, or monofilaments 
that are inserted into gap 13 automatically fall out again. Moreover, 
external contour 12 has a matching groove or indentation 16 in the 
vicinity of indentation or groove 15. 
Similarly in brushes with stiff bristles and brushes with flexible 
bristles, areas can also be produced with a lower hair, bristle or 
monofilament density. In this way, as already mentioned in connection with 
FIG. 2b, the flexibility of a brush with stiff bristles or a brush with 
flexible bristles can be increased. 
FIGS. 5 and 6 however again show the advantage of the method according to 
the invention as mentioned with reference to FIG. 4 when it comes to 
creating contours or brush shapes without the necessity of cutting and 
grinding hairs, bristles, monofilaments, wires, or the like before or 
after the brush with flexible or stiff bristles is manufactured. 
FIGS. 7a and 7b show a brush with stiff bristles or a brush with flexible 
bristles which are provided in individual tufts 17. If as shown in FIG. 7a 
a wire coil 21 is placed around body 1 of the brush with flexible or stiff 
bristles or the outside wall 3, the peripheral tufts 17 of hair or 
monofilament of the brush with flexible bristles would be melted to a 
greater degree at the inserted ends, since the peripheral insert elements 
would also be heated to a greater degree. However, there would be a danger 
in the middle tufts that no real melting would take place so that the 
hairs, bristles, or monofilaments of such tufts would fall out again when 
manufacture was complete. 
For this reason it is advantageous as shown in FIG. 7b to rotate the coil 
21 through approximately 90.degree., compared with the diagram in FIG. 7a 
and to insert brush 1 with stiff bristles in the horizontal direction into 
coil 21. This in turn ensures that all the insert elements 9 are arranged 
equally spaced relative to coil 21. As a result the insert elements 9 will 
also be heated uniformly. 
In FIG. 8 another possibility is shown of how an insert element for the 
welding of the ends of the hairs, bristles, or monofilaments inserted in 
the receptacle of the brush with flexible or stiff bristles can be 
achieved. In FIG. 8, hole-shaped contact points 24 to which electrodes or 
terminals 25 can be connected are provided in the lateral receptacle walls 
3. If an electrical current is applied to the electrodes or terminals 25, 
insert element 9 acts as a form of resistance element and is heated as a 
result. Welding of the hairs, bristles or monofilaments 11 takes place 
once more in known fashion and as described with reference to FIGS. 1a to 
1c. 
FIGS. 9 and 10 show two additional examples of a brush with flexible 
bristles or a brush with stiff bristles manufactured according to the 
invention, whereby no actual receptacle 5 is provided on handle 1, but 
where insert element 9 is mounted directly on a flat surface on the handle 
or the brush or hair body. Thus, no walls 3 are provided laterally with 
respect to insert element 9, as in the brushes shown in FIGS. 1 to 8. In 
FIG. 9 the insert element is made plate-shaped in a single stage, while 
insert element 9 in FIG. 10 is made in two layers, with the lower part 
being provided in order to be fitted into the handle or body 1 while the 
upper part is provided to hold hairs, bristles, monofilaments, or wires. 
Again it is possible to join insert element 9 with the handle or body 1 by 
gluing, mechanically, or by welding, while the hairs, bristles, 
monofilaments, or wires of the brush with flexible bristles or brush with 
stiff bristles are joined with insert element 9 by welding. Once again 
welding layers 10 and 14, which are shown schematically, can be produced 
by means of the above-mentioned intermediate support, if welding of the 
hairs, bristles, monofilaments, or wires is not possible. Metal wires are 
mentioned as an example of this, which as a rule cannot be melted or 
softened by the method according to the invention. In this case it is 
definitely advantageous to use an intermediate support, for example 
consisting of a hot-melt material that can be readily melted or softened. 
In FIGS. 11 and 12 in a schematic top view, a head 1" of a toothbrush 2" is 
shown, comprising bristle tufts 11" that have a specific concrete shape 
12". In the case of FIG. 11, it is a company name so that the toothbrush 
shown can be used for example for advertising purposes. In the case of 
FIG. 12, bristle tuft 11" has the shape of comic figures so that the 
toothbrush 1" shown in FIG. 12 is suitable for children for example. 
FIGS. 13a to 13d show various heating elements 9 that can be used to 
produce special shapes. 
Finally, with reference to FIGS. 14a to 14e, the manufacture of a 
toothbrush or a toothbrush head, shown schematically, will be described in 
order for example to give the brush head a shape similar to the brush head 
shown in FIG. 11. 
The process begins with a basic toothbrush body 21", having at one end a 
head receptacle 5", as shown in FIG. 14a. The heating element 9 shown in 
FIG. 14b is inserted into receptacle 5", with the bottom of receptacle 5" 
matching the corrugated shape of heating element 9. A receiving body 3", 
shown in FIG. 14c, is placed on heating element 9. This receiving body 3" 
has gaps or openings for insertion of toothbrush bristles 11" shown in 
FIG. 14d. Originally the toothbrush bristles 11" are of the same length, 
whereupon the insertion of bristles 11" through receiving body 3" into 
receptacle 5" produces shape 12" as shown in FIG. 14d. Finally the heating 
of heating element 9 according to the invention produces the toothbrush 
head or toothbrush 1" as shown in FIG. 14e. 
In the manufacturing method and designs of brushes with stiff bristles or 
brushes with flexible bristles according to the invention as shown in 
FIGS. 1 to 14, only examples are involved and of course they can be 
supplemented or modified or changed in some way. Thus of course it makes 
no difference whether the hairs, bristles, monofilaments, and the like are 
of animal or plant origin or are synthetic polymers or materials. Examples 
include sisal, ramie, hog bristles, hairs of whatever kind, monofilaments 
made of metal, glass, polyamide, polyethylene, polyester, polypropylene, 
PVC, polystyrene, etc., or wires, threads, cables, strings, made of any 
synthetic or natural materials. 
The inductive heating of the insert element is likewise only one possible 
example, and other examples such as dielectric heating, heating using 
microwaves, ultrasound, etc. are possible variations for working the 
method according to the invention. 
In the designs shown in FIGS. 3 to 6 as well as 11, 12, and 14, once again 
only examples are involved and any shapes or contours can be produced by 
appropriately shaping the insert element. 
It is important that the fastening of the hairs, bristles, monofilaments, 
and the like in or on the receptacle or the handle of the brush be 
performed by welding, with the welding being performed by applying wave or 
field lines onto or into the receptacle or handle.