TW201729722A - Method for mechanically sharpening bristles and grinding device - Google Patents

Abstract

The invention relates to a method for mechanically sharpening bristles for brushes, in particular toothbrushes, by grinding, comprising the following steps: a) holding bristle clusters (12) in a cluster holder (18) such that the ratio (L/l) of the exposed length (L) of the bristle cluster, measured from the holder to exposed end to be sharpened, to the length (l) of the conical point of the bristles that is to be created is greater than or equal to 3, and b) grinding the bristle ends (24) on the first exposed end. The invention further relates to a grinding device for mechanically sharpening bristles for brushes, wherein the cluster holder is designed to have a holding unit which enables a holding, in particular a clamping, of at least one bristle cluster at different locations of the bristle cluster over the length thereof, and a displacing of the bristle cluster into a non-holding, in particular non-clamping, position of the cluster holder, relative to the cluster holder.

Description

Method for mechanically sharpening bristles and grinding equipment

The invention relates to a method for mechanically sharpening bristles and a grinding device for mechanically sharpening bristles.

The sharpened bristles are applied in different brushes, in particular toothbrushes, since these bristles can have a beneficial effect on the cleaning properties of the brush.

In order to sharpen the bristles, on the one hand, a method is known in which the bristles are clamped as tufts of bristles in the bristle bundle holding member and are mechanically sharpened by a grinding device. This method has the disadvantage that, with the prior art, it is not possible to sharpen the bristles to the extent that "satisfying the cleaning characteristics of the brush" is required.

On the other hand, a chemical method for sharpening bristles is known, by which the performance of the bristles can be improved. Here, the ends of the bristles are immersed in a strongly alkaline or strongly acidic solution and taken out of the solution over a period of about 30 minutes. At the point where the bristles are in contact with the solution, the surface of the bristles dissolves thereby causing the diameter of the ends of the bristles to gradually decrease, thereby causing the ends of the bristles to be sharpened.

A disadvantage of the chemical method is that the solution used has environmentally destructive properties. Therefore, not only the staff and the environment are harmed by the solution, but also the production equipment is damaged, for example, due to corrosion. This results in a shortened service life of the machine and tool, which is not economical.

It is an object of the present invention to provide a method and apparatus for sharpening bristles that ensure high performance of the bristles of the bristles without the application of environmentally damaging chemical solvents.

According to the invention, the above object is achieved in a method by means of grinding mechanically sharpening the bristles for a brush, in particular a toothbrush, the method having the following steps: a) holding the tuft of bristles (12) in the bristles In the bundle holding member (18), in the bristle bundle, "the free length (L) measured from the holding portion to the free end portion to be sharpened" and the length of the tapered tip portion to be produced in the bristles (l) The ratio (L/l) is greater than or equal to 3; and b) grinding the ends of the bristles at the first free end.

The invention proposes a completely different specification with respect to the prior art at the time of treatment: in the case where the bristles should have a tip of a predetermined length, in which the tip portion tapers conically, the bristle bundle should be relative to the holding portion How much distance is extended. For example, if the bristles are ground such that each brist has or should have a sharpened length of 4 mm, the bundle of bristles is clamped into the bristle bundle retaining member such that the free length of the tuft of bristles is at least 12 at the beginning of the grinding process Mm. Here, the following portion of the bristle bundle holding member is understood to be a holding portion which is closest to the just-polished end of the bristle bundle and which is in contact with the bristle bundle.

This large free length of bristles facilitates the exceptional performance of the bristles during the grinding process. In the prior art, the tufts of bristles are always clamped such that the free length of the tufts of bristles is significantly lower than this ratio. Preferably, the free length of the bristle bundle to be ground which is clamped in the prior art is even less than half of the total length. In the prior art, a relatively short free length is considered to improve the positional stability of the bristles and the predictability of the grinding process, and is considered advantageous. However, the present invention is directed to sharpening the tuft of bristles at a smaller angle and significantly more accurately by the extreme elasticity of the bristles that are largely extended. The bristles are tapered to taper.

In the same way as in the case of a tuft of bristles which are fastened via a peg or a wire loop, the method is also suitable for brushes having bristles which are not bolted, wherein the unsharpened ends of the unidirectionally sharpened bristles are fixed, in particular Adhesive or welded in the brush head.

According to an embodiment of the invention, the previously mentioned ratio L/l is at least 4 and/or less than or equal to 7, in particular less than or equal to 6.5.

In order to grind the other end of the tuft of bristles and to sharpen the bristles after grinding the first end, the invention proposes the following steps: c) changing the position of the bristles in the bristles holding member so that they have not been ground The free end is set to the same ratio as that set for the sharpened end; and d) the bristle end is ground on the second free end.

A further embodiment of the method according to the invention proposes in the aforementioned step a) that the tuft of bristles is clamped into the bristle bundle holding member such that the tuft of the tufts from the holding portion to the first free end to be sharpened The free length of the portion is at least 12 mm and/or greater than 40% of the total length of the unbrushed bristle bundle.

In a preferred embodiment, the detailed method comprises the following further steps after step b): e) changing the position of the tuft of bristles in the bristle bundle holding member such that the bristle bundles from the retaining portion to the bristles The free end of the opposite free ends of the bundle has a minimum length of 12 mm and/or is greater than 40% of the total length of the unpolished bristle bundle, and f) grinding the bristle ends on the second free end.

Thereby, the bristles are sharpened on the ends of the two bristles, wherein by changing the position of the bristles in the bristle bundle holding member, the large free length required for the bristles to ensure the superior performance of the bristles of the bristles is achieved.

The method for sharpening the bristles from both sides is particularly suitable for brushes in which the bristles are folded and secured in the brush head by metal pegs or wire loops.

Preferably, the bristles are used in small brushes, especially toothbrushes, the bristles of which extend approximately 10 mm to 15 mm from the head.

It is proposed in this method that the bristle bundle holding member is rotated by 180° about the axis perpendicular to the longitudinal direction of the clamped bristles after step b) and before step d) so as to be on the other side of the bristle bundle holding member The ends of the bristles are brought into position for processing.

Preferably, the unbrinded bristle bundle has a length of from 26 mm to 32 mm, and based on such characteristics, it is desirable for a toothbrush having folded bristles.

In a further solution, the invention also relates to a method for mechanically sharpening a bristles for a brush, in particular a toothbrush, by grinding a bundle of bristles on a grinding surface of a rotating tool. It is characterized in that the bristle bundle is gradually advanced in the direction of the grinding surface of the tool side during the continuous grinding step, and here the relative speed between the grinding surface and the bristle bundle is getting lower and lower. This solution can of course also be combined with the above solution.

The idea here is to first sharpen the tip of the bristles at a high grinding speed. Next, the bristles are gradually advanced in the direction of the grinding surface so that the gradually enlarged portion of the bristle ends can come into contact with the grinding surface. Therefore, the portion where the end portion of the bristle is gradually enlarged in the axial direction is further ground. However, the grinding speed (the relative speed between the bristle bundle and the grinding surface) is also lower and lower, in which the "progression of the bristle bundle to the grinding surface" and the "reduction of the grinding" can be continuously performed. speed". As can be seen from the large-scale experimental series, the quality of the grinding can be greatly improved. Furthermore, by the method of the present invention, materials which have hitherto been suitable for non-mechanical sharpening, such as bristles composed of nylon or PBT, can be mechanically ground. This can be achieved by lowering the grinding speed when the bristles are placed on the grinding surface over a relatively large length and the friction is increased. This produces less frictional heat. The bristles are no longer close to the critical melting temperature. In addition, it is inherently necessary to remove the material to the greatest extent at the ends of the bristles, and from the beginning of the grinding process, this portion has removed most of the material that needs to be removed. In the method according to the invention, the grinding surface is relatively moved in space. The bristle bundle is rotated during grinding by rotating the bristle bundle holding member as well.

In a preferred embodiment, one or more grinding rolls are used for grinding, the grinding rolls preferably having a cylindrical or tapered side on which the grinding step is performed. The curved surface of the grinding roller here has a beneficial effect on the performance of the bristle tip. The grinding roller can of course also form a rotationally symmetrical side with any shape, which is not limited to a cylindrical or conical shape.

The bristle bundle retaining member is rotatable about a rotational axis during grinding, the rotational axis being parallel to the longitudinal direction of the clamped bristles, and the rotational axis forms an angle of at least 80° with respect to the rotational axis of the grinding roller. This relative movement facilitates sharpening of the ends of the bristles.

Preferably, the tuft retaining member moves substantially along the longitudinal direction during the grinding step. Here, the direction of movement of the bristle bundle holding member is in particular not parallel to the axis of rotation of the grinding roller. Additionally or alternatively, the spacing of the bristle bundle retaining members from the side and/or axis of rotation may be made smaller during movement. This arrangement of the bristles relative to the grinding roller also has a favourable effect on the sharpened bristle ends, since the bristle ends are sharpened over ever larger lengths.

In a preferred embodiment, the ratio of the radius of the grinding roller to the distance between the clamped bristle bundle and the axis of rotation that is furthest from the axis of rotation of the tuft holding member is (R/r), In particular, from 1 to 3, all of the bristle bundles of the bristle bundle holding members are located within the outer edge of the side boundary as viewed in the direction of the axis of rotation of the bristle bundle holding member. Here, this ratio has a favorable influence on the performance of the bristle tip.

Preferably, the bristle bundle holding member is so close to the surface of the grinding wheel that the farthest bristles abut against the grinding wheel over its entire rotational orbit. When the bristle length is from 26 mm to 32 mm, the minimum distance between the holding portion and the grinding surface in the bristle bundle holding member is particularly in the range of 5 mm to 12 mm. Here, make sure that all bristles are in contact with the grinding wheel and are sharpened. However, it is of course also possible for the "each bristles to overlap vertically and not all of the bristles are in contact with the grinding wheel without interruption".

According to the present invention, in order to achieve the above object, a grinding apparatus is also proposed. The grinding apparatus for mechanically sharpening a brush, in particular a bristles of a toothbrush, comprises: at least one bristle bundle holding member having at least one receiving portion for a tuft of bristles; and at least one grinding wheel, The grinding wheel has a ground surface. Here, the bristle bundle holding member has a holding unit that can clamp at least one bristle bundle at different portions in the longitudinal direction of the bristle bundle, and can be in the "non-clamped state of the bristle bundle holding member", At least one bristle bundle moves relative to the bristle bundle holding member. The bristle bundle retaining member acts as a tool and does not thereafter form part of the finished brush head. The bristle bundle holding member achieves a setting of the free length of the bristles by means of a holding unit of the bristle bundle holding member, which free length is necessary for achieving a particularly good performance of the bristle tip. Furthermore, the bristle bundle holding member allows grinding on the two free ends, since the tufts of bristles must be enclosed for this purpose, and the large bundle of tufts causes the bristle bundle holding members to not simply pivot. Therefore, the free length of the bristle bundle that has not been ground is unlikely to reach the minimum free length according to the invention.

Preferably, the free length of the bristles from the retaining portion to the first free end to be sharpened is at least 12 mm and/or greater than 40% of the total length of the unpolished bristle bundle. This ensures the free length required for the high performance of the bristle tip.

In a preferred embodiment, the bristle bundle retaining member has a plurality of receptacles for a plurality of tufts of bristles that can be sharpened together in this manner.

The retaining unit preferably comprises a pressing element and at least one resilient element disposed between the pressing elements. Here, the elastic element surrounds the receiving opening for the tuft of bristles and the cross section of the receiving opening can be reduced by compression in order to retain the tuft of bristles in the receiving portion. This configuration enables a simple control of the holding unit as well as a compact design. Here, the elastic element can be designed, for example, in the shape of an O-ring or as a layer having a plurality of through openings. If an O-ring is provided, an O-ring must be present on each of the receiving portions.

To sharpen the two opposite bristle ends, the tuft retaining member can be rotated 180[deg.] about an axis perpendicular to the longitudinal direction of the clamped bristles to sharpen the ends.

In a preferred embodiment, the grinding wheel is a grinding roller having a side formed as a grinding surface, which is preferably cylindrical or conical. Here, the curved surface of the grinding roller has a beneficial effect on the performance of the bristle tip.

The bristle bundle retaining member is rotatable about the axis of rotation during grinding, the axis of rotation being more parallel to the longitudinal direction of the clamped bristles, and the axis of rotation forms an angle of at least 80° with respect to the axis of rotation of the grinding roller. The bristle ends are advantageously sharpened by this relative movement.

Preferably, the bristle bundle holding member is mounted in a manner that is movable along the side substantially in the longitudinal direction. Here, the moving direction of the bristle bundle holding member is particularly not parallel to the rotation axis of the grinding roller and/or the distance between the bristle bundle holding member and the side surface and/or the rotation axis is gradually reduced during the movement. The advantage of the above aspect is that the portion where the bristles are in contact with the grinding wheel increases as the moving distance increases, thereby gradually increasing the processing width of the bristles, which also has the advantageous effect of grinding the bristles.

According to a preferred embodiment, the ratio of the radius of the grinding roller to the distance from the axis of rotation of the clamped bristle bundle which is furthest from the axis of rotation of the tuft holding member (R/r) is approximately 1 and 4. Between, especially between 1 and 3. Here, as viewed in the direction of the rotational axis of the bristle bundle holding member, in the plan view, all of the bristle bundles in the bristle bundle holding member are located within the outer edge of the side boundary. With this design, it is ensured that all the bristle ends are processed uniformly and correspondingly well sharpened after the grinding process.

The method of sharpening the brush, in particular the bristles of the toothbrush, from both sides with the grinding device 10 is shown in five steps in FIG.

In a first step, the tufts of bristles 12 are extracted from the storage area 16 by the tufts of bristles 14, the tufts of bristles are positioned above the bristle bundle holding members 18, and pushed into the bristle bundle holding members 18 by the sliders 20.

In the second step, the bristle bundle 12 clamped in the bristle bundle holding member 18 is moved over the grinding wheel 22 and sharpened on the side of the bristle bundle that is in contact with the grinding wheel 22.

In the next third step, the bristle bundle holding member 18 is rotated by 180°.

In the fourth step, a grinding step is carried out analogously to the second step, wherein this time the opposite bristle ends 24 are sharpened.

In the fifth and at the same time the final step, the bristle bundle 12 sharpened from both sides is evacuated from the bristle bundle holding member 18 into the bristle container 26.

A perspective view of the first step in Fig. 1 is illustrated in Fig. 2. A tuft of bristles 12 having a length of about 26 mm to 32 mm (corresponding to the length of the bristles) and having a diameter of about 1.5 mm to 3 mm is extracted from the storage region 16 by the bristle bundle separator 14 to position the tuft of bristles above the bristle bundle holding member 18, and The slider 20 is pushed into the accommodating portion 28 of the bristle bundle holding member 18. Here, the bristle bundle 12 is arranged such that the bristle bundle has a relatively large free length L at the end to be machined in a subsequent step, the free length being closest from the holding portion, more precisely from the holding portion The holding portion of the sharpened end (refer to Figure 10b) is measured. At the time of grinding (refer to Fig. 7), a tapered tapered tip is produced on each of the bristles, the tip having a length l. This length l is specified structurally. The bristle bundles 12 are now set such that the free ends to be machined project correspondingly far apart relative to the holder in order to achieve a ratio L/l of greater than or equal to 3, in particular greater than or equal to 4.

It is also possible to selectively provide an upper limit of 7, for example, less than or equal to 7, especially less than or equal to 6.5.

One option is to clamp the tuft of bristles 12 such that the free length of the end to be machined is at least 12 mm or greater than 40% of the total length of the unwound bristle bundle 12 with respect to the retaining portion.

Figures 3 and 4 illustrate perspective views of the second step in Figure 1. The tufts 12 held, for example clamped in the bristle bundle holding member 18, are moved over a rotating grinding wheel 22, which in the present embodiment is a grinding roller, on the cylindrical or tapered side 30 of the grinding roller ( Grinding steps are performed on the grinding surface). During this movement, the bristle bundle holding member 18 additionally rotates about an axis of rotation A which is parallel to the longitudinal direction of the clamped bristle bundle 12. The bristle bundle holding member is along a straight track B which is parallel to or coincides with the axis of rotation X of the grinding roller in plan view. In the side view, reference is made to Fig. 4, however it can be seen that the track B extends slightly obliquely towards the grinding surface, i.e. the side surface 30, i.e. at an angle α of 2°-10°. That is, during the grinding step and the movement of the bristle bundle holding member 18 along the grinding surface, the bristle bundle holding member 18 and the bristle bundle are gradually advanced in the direction of the rotation axis X or in other words toward the side surface 30. Therefore, the axial portion where the bristles are gradually enlarged is ground. Since in the embodiment according to Fig. 4 the grinding wheel has a cylindrical side 30, the angle α also exists between the side 30 and the axis of rotation X.

Here, the minimum distance a between the holding portion and the grinding surface in the bristle bundle holding member 18 is in the range of 5 mm to 10 mm.

Alternatively or additionally, the distance between the bristle bundle holding member 18 and the grinding wheel 22 can also be reduced by forming the grinding wheel 22 into a tapered shape as in FIG. 5 such that the bristle bundle holding member The spacing between 18 and the surface of the grinding wheel 22 is reduced.

In the present embodiment, the ratio of the radius of the grinding roller to the distance from the rotation axis A of the bristle bundle holding member 18 that is the farthest from the rotation axis A of the bristle bundle holding member 18 (R/r) is 1 and 4 It can also be between 1 and 3.

Viewed in the direction of the axis of rotation A of the bristle bundle holding member 18, all of the bristle bundles 12 of the bristle bundle holding members 18 are additionally located within the linear outer edge 40 of the grinding roller which is bounded to the side in plan view.

Also in the present embodiment, the taper angle β of the grinding wheel 22 is also shown.

The grinding is started on the following portion of the grinding wheel 22 by the bristle bundle holding member 18 moving from the end portion of the grinding wheel 22 having the larger diameter R to the end portion having the smaller diameter during the linear movement along the rail B. The cutting step has a greater peripheral velocity on the upper side of the portion than on the end having a smaller diameter.

As can be clearly seen in Fig. 5, only the ends of the bristles are first ground, wherein the grinding step is carried out at a high grinding speed. The distance between the bristle bundle holding member 18 and the grinding surface is then getting smaller and smaller, that is, the bristle bundle is gradually advanced toward the grinding surface. However, the peripheral speed of the grinding wheel 22 is simultaneously lowered. Therefore, the amount of heat introduced into the bristles by friction is lowered.

However, the idea that the individual bristles are progressively advanced towards the grinding surface during the grinding process, but at the same time reducing the grinding speed, can also be achieved in other ways, as illustrated in Figure 6.

Fig. 6 illustrates five bristle bundle holding members 18 arranged side by side with each other, which accommodate a large number of bristle bundles 12 and rotate around the axis A of the bristle bundle holding members. In the first step illustrated in the upper portion of Fig. 6, the distance T3 of the bristle bundle holding member 18 from the rotation axis R is still relatively large, so that only the axial end portions of the bristles are ground. However, the grinding speed is here relatively high because the grinding wheel 22 rotates rapidly at the speed n1. The rotational speed and rotational speed are gradually or continuously reduced from n2 to n1 and at the same time the distance between the bristle bundle holding member 18 and the rotational axis R is reduced to T1 via T2.

In the embodiment according to Fig. 6, the bristle bundle holding member 18 does not move along the rail B extending transversely to the rotational axis A, but only rotates and advances in the direction of the rotational axis A of the bristle bundle holding member 18, thus The axis of rotation A is the track B. Of course, the roller can also be advanced in the direction of the tuft holding member.

Figure 7 illustrates how many different portions of the subsequently formed bristle tip are produced at a high rotational speed and at a large spacing.

Figure 8 depicts the different course progressions of the change in speed and the change in pitch along which the grinding step is performed. Figures 4 and 5 illustrate bristles that have been sharpened on one side, the bristles being sharpened at the second end. Here, the gradual sharpening of the bristle bundle is symbolically illustrated. In fact, the tufts of bristles are as shown in the enlarged view at the lower left in Fig. 9, in which the individual bristles themselves become sharpened.

A side view of the third step in Fig. 1 is illustrated in Fig. 9. The bristle bundle retaining member 18 is rotated 180° about an axis perpendicular to the longitudinal direction of the clamped bristle bundle 12 in order to grind the other bristle ends 24. Additionally, after the bristle bundle holding member 18 enters a non-retained, for example unclamped state (Fig. 10a) from a held, for example clamped, state (Fig. 10b), the bristle bundle 12 is held in the bristle bundle The inside of the member 18 moves axially (refer to the arrow in Fig. 9), for example, by the slider 20 moving in the axial direction. Thereby, the bristle bundle 12 has a free length L of at least 12 mm or greater than 40% of the total length of the unpolished bristle bundle 12 at the end where the bristle bundle 12 has not been ground.

More generally, the ratio L/l of the free length L to the length l of the tapered taper to be produced is greater than or equal to 3, in particular greater than or equal to 4. That is, the corresponding ratio L/l is also set when the second end of the bristle bundle 12 is being grounded, so that the two ends have the same tip shape and tip length on their bristles.

As the upper limit of the ratio L/l, it is preferably 6 or 5.

FIGS. 10a and 10b illustrate a bristle bundle holding member 18 having two receiving portions 28 and holding units 32 respectively provided in the housing portions 28, by which the bristle bundles 12 can be placed on the tufts 12 The length is fixed at different locations and the bristle bundle 12 can be moved relative to the bristle bundle holding member 18 in the unclamped state of the bristle bundle holding member 18.

Here, Fig. 10a illustrates the open position of the holding unit 32, wherein the two plate-like pressing members 34 are located in an open position away from each other, and are disposed between the pressing members in the form of an O-ring. The resilient element 36 is in a non-clamped position.

The blocking position of the holding unit 32 is illustrated in Fig. 10b, wherein the two pressing elements 34 are in a closed position close to each other, and the elastic element 36 disposed between the pressing elements is in a clamped, squeezed position position. In this position, the receiving opening surrounding the bristle bundle 12 is reduced in cross section by the compression elastic member 36, thereby clamping the bristle bundle 12 in the receiving portion 28.

In order to perform the method according to the present invention, when the other end portion should be sharpened, the bristle bundle must be moved, that is, exchanged, over a long distance in the bristle bundle holding member, as shown in Figs. 9 and 10, but is not limited thereto. this. It is also possible to grind both ends in the same clamping manner.

In the case of unfolded tufts of bristles, i.e., bundles of bristles that are not retained by the pegs in the brush body, only one end of the bristles must be sharpened. Because the bristles are extremely short, the bristles are not mechanically sharpened by cutting. The solution to this problem is to use extra-long bristles that are sharpened at both ends as described above and then separated from the middle.

10‧‧‧grinding equipment
12‧‧‧Brushing
14‧‧‧Brushing beam separator
16‧‧‧ storage area
18‧‧‧Brushing bundle retaining member
20‧‧‧ Slider
22‧‧‧ grinding wheel
24‧‧‧breast ends
26‧‧‧Brush container
28‧‧‧ 收纳 department
30‧‧‧ side
32‧‧‧Holding unit
34‧‧‧Compression element
36‧‧‧Flexible components
40‧‧‧ outer edge

Further advantages and features are further described below in conjunction with the drawings. In the schema:

- Figure 1 illustrates a side view of a process according to the invention for the step of sharpening bristles from both sides in a grinding apparatus according to the invention;

- Figure 2 illustrates a perspective view of filling the bristle bundle retaining member with a tuft of bristles from the storage area;

- Figure 3 is a perspective view showing the grinding process of the bristle bundle of the bristle bundle holding member on the grinding roller;

- Figure 4 illustrates a side view of the grinding process in Figure 3;

- Figure 5 shows a side view of a variant of the grinding device according to the invention with a tapered grinding wheel;

- Figure 6 illustrates three different steps in grinding a large number of tufts;

- Figure 7 illustrates the bristles, the sharpened end of the bristles being divided into a plurality of different portions;

- Figure 8 shows a chart showing the relationship between the depth of advance and the speed of the grinding wheel;

- Figure 9 illustrates a side view of the tuft of bristles clamped in the bristle bundle holding member;

- Figs. 10a and 10b are cross-sectional views showing the accommodating portion of the bristle bundle holding member in an open state or a closed state.

(Please change the page separately) No

10‧‧‧grinding equipment

12‧‧‧Brushing

14‧‧‧Brushing beam separator

16‧‧‧ storage area

18‧‧‧Brushing bundle retaining member

20‧‧‧ Slider

22‧‧‧ grinding wheel

24‧‧‧breast ends

26‧‧‧Brush container

Claims (27)

A method for mechanically sharpening a bristles for a brush, in particular a toothbrush, by grinding, characterized by the steps of: a) holding a tuft of bristles (12) in a tuft holding member (18) In the bristle bundle, the ratio of the free length (L) measured from the holding portion to the free end portion to be sharpened and the length (1) of the tapered tip portion to be generated in the bristles ( L/l) is greater than or equal to 3; and b) grinding the bristle ends (24) on the first free end. The method of claim 1, wherein the ratio (L/l) is greater than or equal to 4 and/or the ratio (L/l) is less than or equal to 7, especially less than or equal to 6.5. The method of claim 1 or 2, wherein the method further comprises the step of: c) changing the position of the bristle bundle (12) in the bristle bundle holding member (18) after step b); The second free end portion being ground is set to the same ratio (L/l) as that set for the sharpened end; and d) the bristle ends are ground on the second free end (24) ). The method of claim 1 or 2, wherein in the step b), the free length (L) measured from the holding portion to the first free end to be sharpened in the bristle bundle (12) ) is at least 12 mm and/or greater than 40% of the total length of the bristle bundle (12) that is not ground. The method of claim 4, wherein the method further comprises the step of: a) changing a position of the bristle bundle (12) in the bristle bundle holding member (18) such that the bristle bundle ( In 12), the free length (L) from the retaining portion to the opposite free end of the bristle bundle (12) is at least 12 mm and/or greater than the total length of the bristle bundle (12) that is not ground. 40% of the degree, and b) grinding the bristle ends (24) on the second free end. The method of claim 3, wherein the bristle bundle holding member (18) is rotated 180 about an axis perpendicular to the longitudinal direction of the clamped tuft (12) after step b) and before step d) °. The method of claim 1 or 2, wherein the tuft of bristles (12) that are not ground has a length of from 26 mm to 32 mm. A method as claimed in claim 1 or 2, for mechanically sharpening the bristles for a brush, in particular a toothbrush, by grinding a bundle of bristles on a grinding surface of a rotating tool Characterized in that the tuft of bristles (12) is progressively directed in the direction of the grinding surface on the tool side during the grinding step, and here the relative speed between the grinding surface and the bristle bundle (12) lower and lower. The method of claim 1 or 2, wherein one or more grinding rolls are used for grinding, the grinding rolls having a preferably cylindrical or tapered side (30) on which the grinding is performed Cutting steps. The method of claim 9, wherein the bristle bundle holding member (18) rotates about an axis of rotation (A) during grinding. The method of claim 10, wherein the axis is parallel to the longitudinal direction of the clamped tuft (12) and the axis forms an angle of at least 80 with respect to the axis of rotation (X) of the grinding roller (α) ). The method of claim 9, wherein the bristle bundle holding member (18) moves along the side (30) substantially longitudinally during the grinding step. The method of claim 1 or 2, wherein the moving direction of the bristle bundle holding member (18) is not parallel to the rotation axis (X) of the grinding roller and/or the bristle bundle holding member (18) is The spacing (a) of the sides (30) is getting smaller during this movement. The method of claim 9, wherein the radius of the grinding roller is proportional to the distance of the clamped bundle of the bristle bundles (12) that is furthest from the rotational axis (A) of the bristle bundle holding member (18) (R/r) is X to Y. The method of claim 1 or 2, wherein one or more grinding rolls are used for grinding, the grinding roll having a side (30) on which the grinding step is performed and along the bristles Viewed in the direction of the axis of rotation (A) of the bundle holding member (18), all of the tufts (12) of the bristle bundle holding member (18) are located within the outer edge of the side of the grinding roller that is bounded by the side. The method of claim 1 or 2, wherein the bristle bundle holding member (18) is brought close to the surface of the grinding wheel (22) until the farthest bristles are attached to the grinding wheel (22) over its entire rotating orbit . The method of claim 16, wherein the minimum distance (a) between the retaining portion in the bristle bundle holding member (18) and the grinding surface is 5 mm when the bristle bundle length is 26 mm to 32 mm In the range of 12 mm. A grinding device (10) for mechanically sharpening bristles for a brush, in particular a toothbrush, the grinding device having: at least one bristle bundle holding member (18), the tuft holder holding member having at least one a accommodating portion (28) of a tuft of bristles (12); and at least one grinding wheel (22) having a grinding surface, characterized in that the bristles holding member (18) has a holding unit (32), the holding The unit may hold, in particular clamp, the at least one bristle bundle (12) at different locations over the length of the bristle bundle (12); and may not hold, in particular non-clip, the bristle bundle holding member (18) In the tight state, the bristle bundle (12) is moved relative to the bristle bundle holding member (18). The grinding apparatus (10) of claim 18, wherein in the tuft of bristles (12), the free length (L) from the retaining portion to the first free end to be sharpened is at least 12 mm and (or ) is greater than 40% of the total length of the bristle bundle (12) that is not ground. A grinding apparatus (10) according to claim 18 or 19, wherein the bristle bundle holding member (18) has a plurality of receiving portions (28) for a plurality of bristle bundles (12) that are collectively sharpened. A grinding apparatus (10) according to claim 18 or 19, wherein the holding unit (32) comprises a pressing element (34) and at least one elastic element (36) disposed between the pressing elements (34) Wherein the elastic member (36) surrounds a receiving opening for the tuft of bristles (12), and by compressing the elastic member (36), the cross section of the receiving opening can be reduced to bundle the bristle bundle ( 12) held or clamped in the accommodating portion (28). The grinding apparatus (10) of claim 18 or 19, wherein the tuft holding member (18) is capable of surrounding the bristles that are clamped perpendicularly in order to sharpen the two opposite bristle ends (24) The longitudinal axis of the bundle (12) is rotated by 180°. A grinding apparatus (10) according to claim 18 or 19, wherein the grinding wheel (22) is a grinding roller having a side surface (30) constituting a grinding surface, the side surface preferably being cylindrical or tapered . A grinding apparatus (10) according to claim 18 or 19, wherein the bristle bundle holding member (18) rotates about an axis of rotation (A) during grinding. A grinding apparatus (10) according to claim 24, wherein the axis of rotation (A) is parallel to the longitudinal direction of the bristles being clamped, and the axis of rotation (A) is relative to the axis of rotation of the grinding roller (X) ) forming an angle (α) of at least 80°. A grinding apparatus (10) according to claim 18 or 19, wherein the bristle bundle holding member (18) is mounted in such a manner as to be movable substantially longitudinally along the side (30). A grinding apparatus (10) according to claim 26, wherein the moving direction of the bristle bundle holding member (18) is not parallel to the rotation axis (X) of the grinding roller and/or the bristle bundle holding member (or) 18) The spacing (a) from the side (30) is getting smaller during this movement.