METHOD AND APPARATUS FOR END ROUNDING BRISTLES

Abstract

A method for end rounding bristles of a brush section includes providing a focused laser beam propagating along a geometrical main propagation direction and having a main irradiation spot, providing a relative motion between an end of each bristle and the main irradiation spot of the focused laser beam such that the end of each bristle is moved through the main irradiation spot in a path having a main component transverse to a longitudinal extension of the bristle, wherein the focused laser beam is directed such that the geometrical main propagation direction has a main component transverse to the longitudinal extension of respective bristle having its end at the main irradiation spot, whereby a rounding of the end is provided by the focused laser beam heating the end and causing it to partly melt and form a rounded end, and providing a relative motion between the main irradiation spot and the brush section along a direction having a main component being transverse to the path, thereby subjecting in sequence the ends of the plurality of bristles to the focused laser beam thereby providing a brush section having end rounded bristles. The disclosure also relates to an apparatus.

Claims

1. Method for end rounding bristles of a brush section comprising a plurality of bristles, the method comprising providing a focused laser beam propagating along a geometrical main propagation direction and having a main irradiation spot, providing a relative motion between an end of each bristle and the main irradiation spot of the focused laser beam such that the end of each bristle is moved through the main irradiation spot in a path having a main component transverse to a longitudinal extension of the bristle, wherein the focused laser beam is directed such that the geometrical main propagation direction has a main component transverse to the longitudinal extension of respective bristle having its end at the main irradiation spot, whereby a rounding of the end is provided by the focused laser beam heating the end and causing it to partly melt and form a rounded end, providing a relative motion between the main irradiation spot and the brush section along a direction having a main component being transverse to the path, thereby subjecting in sequence the ends of the plurality of bristles to the focused laser beam thereby providing a brush section having end rounded bristles.

2. Method according to claim 1, the method further comprising end cutting respective bristle by a mechanical cutter before rounding of the end.

3. Method according to claim 1, the method further comprising end cutting respective bristle by means of a focused laser beam before rounding of the end.

4. Method according to claim 1, the method further comprising end cutting respective bristle by means of a focused laser beam while the end is heated to be rounded.

5. Method according to any one of claim 2, the method further comprising positioning the brush section in a first fixture and keeping the brush section in the first fixture during both the end cutting and the end rounding of the ends.

6. Method according to claim 1, wherein the brush section is an interdental brush section, the method further comprising: providing the interdental brush section comprising a brush stem extending along a longitudinal axis and a plurality of bristles supported by the stem and extending from the stem in a mainly radial direction, wherein the step of providing a relative motion between an end of each bristle and the main irradiation spot of the focused laser beam, comprises rotating the interdental brush section about the longitudinal axis such that an end of each bristle sweeps around the longitudinal axis whereby the path in which the end of each bristle is moved through the main irradiation spot becomes a circular path in which circular path the end passes the main irradiation spot, wherein the step of providing a relative motion between the main irradiation spot and the brush section, comprises providing a relative motion of the main irradiation spot along the longitudinal axis thereby subjecting the ends of the plurality of bristles to the focused laser beam in sequence thereby providing a brush section having end rounded bristles.

7. Method according to claim 6, the method further comprising directing the focused laser beam such that the geometrical main propagation direction forms an angle of up to 45 relative to a tangent of the circular path in the main irradiation spot.

8. Method according to claim 6, the method further comprising end cutting respective bristle by means of a focused laser beam by providing a relative motion of the focused laser beam along the longitudinal axis thereby end cutting the plurality of bristles before providing a relative motion of the focused laser beam along the longitudinal axis for rounding of the ends.

9. Method according to claim 1, wherein the focused laser beam has a maximum intensity of 10-20000 W/mm.sup.2 at the geometrical focus spot.

10. Method according to claim 1, the method further comprising focusing the focused laser beam to a geometrical focus spot having an area of 0.01 to 1.0 mm.sup.2.

11. Method according to claim 1, the method further comprising focusing the focused laser beam to a geometrical focus spot having a maximum width being less than two times a width in a direction orthogonal to the maximum width.

12. Method according to claim 1, further comprising focusing the focused laser beam to a focus depth of between 100 to 10000 m.

13. Method according to claim 1, further comprising subjecting respective bristle end to the focused laser beam for a time period being between 100-100000 s, thereby heating the end and causing it to partly melt.

14. Apparatus for end rounding bristles of a brush section comprising a plurality of bristles, the apparatus comprising: a laser comprising a laser beam source and optics configured to provide a focused laser beam propagating along a geometrical main propagation direction and having a main irradiation spot, a fixture for holding a brush section comprising a plurality of bristles, wherein the fixture is configured to provide a relative motion between an end of each bristle and the main irradiation spot of the focused laser beam such that the end of each bristle is moved through the focused laser beam at the main irradiation spot in a path having a main component transverse to a longitudinal extension of the bristle, wherein the focused laser beam is directed such that the geometrical main propagation direction has a main component transverse to the longitudinal extension of respective bristle having its end at the main irradiation spot, whereby a rounding of the end is provided by the focused laser beam heating the end and causing it to partly melt and form a rounded end, wherein the apparatus is configured to provide a relative motion between the main irradiation spot and the brush section along a direction having a main component being transverse to the path, thereby subjecting the ends of the plurality of bristles to the focused laser beam in sequence thereby providing a brush section having end rounded bristles.

15. Apparatus according to claim 14, wherein the fixture is configured to rotate the brush section about a longitudinal axis such that an end of each bristle sweeps around the longitudinal axis in a circular path, wherein the laser is oriented relative to the fixture such that the focused laser beam becomes directed towards the bristles of a brush section in the fixture such that an end of respective bristle sweeping in the circular path passes the main irradiation spot, and wherein the apparatus is configured to provide a relative motion between the fixture and the main irradiation spot along the longitudinal axis such that the focused laser beam becomes directed towards the respective end of the plurality of bristles in sequence.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The invention will by way of example be described in more detail with reference to the appended schematic drawings, which shows a presently preferred embodiment of the invention.

[0063] FIG. 1a is a plan view of an interdental brush.

[0064] FIG. 1b is a plan view of an interdental brush according to another embodiment in which the bristle ends have different lengths such that the geometrical circular envelope surface has a curved profile along the longitudinal direction.

[0065] FIG. 1c is a plan view of a brush section.

[0066] FIG. 2 is a side view of a laser irradiating a bristle end.

[0067] FIG. 3 is an enlargement of FIG. 2.

[0068] FIG. 4 is a second side view of the set-up in FIG. 2.

[0069] FIG. 5 is a plan view of an apparatus including the set-up of FIGS. 2-4.

[0070] FIG. 6 is a set-up providing after-heating.

[0071] FIG. 7 is a set-up providing pre-heating.

[0072] FIG. 8 is a diagram of a method for end rounding bristles of a brush section.

[0073] FIG. 9 is a schematic drawing of an end rounded bristle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0074] The method and apparatus for end rounding bristles are especially configured for end rounding of bristles of a brush section for an interdental brush

[0075] In FIG. 1a and FIG. 1b, there is shown a typical interdental brush 1 according to a first and a second embodiment. The interdental brush 1 comprises a handle 2, from which a brush stem 3 extends along a longitudinal axis L. The brush stem 3 may be formed of a twisted metal wire, which preferably is coated with a protective polymer coating. The brush stem 3 supports a plurality of bristles 4. The respective bristle 4 extends from the stem in a mainly radial direction R. This may also be said that the elongate bristles 4 extend with their longitudinal extension LE in the radial direction R. The stem 3 extends into the interior of the handle 2 and is attached to the handle 2. This is indicated by the dashed line extending from the visible part of the stem 3 into the handle 2. The attachment may e.g. be accomplished by the stem 3 being clamped between two halves of the handle 2 or by the handle 2 being moulded with the stem 3 inserted into the moulding cavity defining the handle 2. The stem 3 with the bristles 4 may be referred to as a brush section 1 as shown in FIG. 1c. The stem 3 may be twisted along its complete length, only along the distance where it supports the bristles 4, or it may, as is indicated in FIG. 1c, be twisted a distance slightly longer than the part the supports the bristles 4 and then the final inner most part of the stem 3 is not twisted and the two strands of the stem 3 extends in parallel with each other.

[0076] The ends of the bristles 4 are end rounded. This is in accordance with a preferred embodiment accomplished by a method which in short with reference to FIG. 8 may be said to include

[0077] providing 110 a brush section, such as an interdental brush section,

[0078] fixing 120 the brush section 1, such as in a first fixture 21,

[0079] rotating 130 the brush section,

[0080] end cutting 140 the bristles,

[0081] end rounding 150 the bristle ends, and

[0082] moving 160 a main irradiation spot of a laser 10 along the longitudinal direction L.

[0083] It may be noted that it is preferred that the end rounding is performed on a brush section 1 basically being formed of the stem 3 and the bristles 4. However, the method is equally applicable to a finished brush 1 or to any intermediate state between a brush section 1 being formed of a stem 3 and bristles 4 and a finished brush 1.

[0084] The end rounding is performed using a focused laser beam 11 propagating along a geometrical main propagation direction PD and having a main irradiation spot 12 as shown in FIG. 2 and the enlargement in FIG. 3.

[0085] By rotating 130 the brush section 1 about the longitudinal axis L there is provided a relative motion between an end of each bristle 4 and the main irradiation spot 12 of the focused laser beam 11. The rotation 130 will cause an end of each bristle 4 sweeping around the longitudinal axis L in a circular path P in which circular path P the end passes the main irradiation spot 12. It may be noted that this will result in that the end of each bristle 4 is moved through the main irradiation spot 12 in a path P having a main component transverse to a longitudinal extension LE of the bristle 4.

[0086] As shown in FIGS. 2 and 3, the focused laser beam 11 is directed such that the geometrical main propagation direction PD has a main component transverse to the longitudinal extension LE of respective bristle 4 having its end at the main irradiation spot 12. In the embodiment shown in FIGS. 2 and 3, the geometrical main propagation direction PD is orthogonal to the longitudinal extension LE of respective bristle 4 having its end at the main irradiation spot 12. In FIGS. 6 and 7, the focused laser beam 11 is oriented with its geometrical main propagation direction PD at different angles, not being orthogonal, but still having a main component transverse to the longitudinal extension LE of respective bristle 4 having its end at the main irradiation spot 12. A rounding 150 of the end is provided by the focused laser beam 11 heating the end and causing it to partly melt and form a rounded end

[0087] As shown in FIG. 4, the focused laser beam 11 is configured to move 160 the main irradiation spot 12 along the longitudinal axis L of the brush section 1, thereby providing a relative motion between the main irradiation spot 12 and the brush section 1 and thereby subjecting the ends of the plurality of bristles 4 to the focused laser beam 4 in sequence. It may be noted that the focused laser beam 11 is directed such that it does not hit the upper part of the brush section but instead shoots past the brush section with the main irradiation spot 12 positioned in a plane in front of the brush section 1 or in a plane behind the brush section 1 as shown in e.g. FIG. 2. Once the sequence 160 has been completed there is provided a brush section 1 having end rounded bristles 4. It may be noted that the relative motion 160 between the main irradiation spot 12 and the brush section 1 will be along a direction having a main component being transverse to the path P. In the shown embodiment, the relative motion 160 will be orthogonal to the path P.

[0088] In accordance with one embodiment the method further comprises end cutting 140 respective bristle 4 by a mechanical cutter 40 before rounding 150 of the end of respective bristle 4. This cutting may e.g. be performed by rotating the brush section 1 about the longitudinal direction L with the bristles 4 sweeping against a knife edge 40, such as a razor blade 40. This is shown in FIG. 5. The knife edge may e.g. be movable between an active position where it cuts the bristles (shown in solid lines) and a non-active position (shown in dashed lines). After the bristles 4 has been cut by the cutter 40, the laser 10 is activated and the bristles 4 are end rounded 150.

[0089] In accordance with one embodiment the method comprises end cutting 140 respective bristle 4 by means of a focused laser beam 11 before rounding 150 of the end. This may e.g. be performed by a separate laser. However, if the end cutting is performed using a laser it is currently preferred that the method comprises using the same laser 10 for end cutting 140 and end rounding 150 whereby there is provided a relative motion of the focused laser beam 11 along the longitudinal axis L also for the end cutting operation 140 such that the plurality of bristles 4 are cut before there is provided a relative motion of the focused laser beam 11 along the longitudinal axis L for rounding of the ends of the bristles 4. This may e.g. be performed by a complete sweep along all the bristles 4 for the end cutting operation 140 followed by a complete sweep along all the bristles 4 for the end rounding operation 150. Alternatively, the end cutting 140 and end rounding 150 may be divided into portions such that initially a first portion including the bristles 4 along a portion of the longitudinal axis are cut 140 and then end rounded 150 where after the bristles 4 of a second portion are cut 140 and end rounded 150. Such a stepwise process may e.g. be useful if the relative motion is provided as a combination of a redirection of the focused laser beam 11 and a translational motion.

[0090] In accordance with one embodiment, the method further comprises end cutting 140 respective bristle 4 by means of a focused laser beam 11 while the end is heated to be rounded 150. This may e.g. be accomplished by using the laser 10 to both end cut 140 and end round 150 the end of the respective bristle 4. This simultaneous end cutting 140 and end rounding 150 is indicated by the dashed bracket in FIG. 8.

[0091] As shown in FIG. 5, the method further comprises positioning the brush section 1 in a first fixture 21 comprising a first part 21a and a second part 21b and keeping the brush section 1 in the first fixture 21a, 21b during both the end cutting 140 and the end rounding 150 of the end of respective bristle 4. This fixture 21, with its parts 21a, 21b, is also used to perform the twisting of the stem 3. The fixture part 21a grabs the two strands of the stem 3 and the fixture part 21b grabs the folded end. A relative rotation of the fixture parts 21a and 21b will cause the part of the stem 3 between the fixture parts 21a, 21b to be twisted.

[0092] It may however be noted that in accordance with an alternative, the brush section 1 may be gripped by a first fixture 21 during end cutting and then be transferred to another fixture 21 holding the brush section 1 in place during the end rounding 150.

[0093] In FIGS. 2 and 3, the main propagation direction PD of the focused laser beam 11 is directed such that it is parallel to but in the opposite direction of a tangent P of the circular path P in the main irradiation spot 12. In FIG. 4, it is shown how the angle of the main propagation direction PD is altered from a first angle 1 of slightly less than 45 on a first side to a second angle 2 of slightly less than 45 on a second side of the tangent P of the path P, with the angles measured between the tangent P of the path P in the main irradiation spot 12 and the main propagation direction PD. It may be noted that in FIG. 4, the angle is used to provide a sweep of the focused laser beam 11. It is also conceivable that the laser beam 11 is provided at a fixed angle and that the brush section 1 and/or the laser source 10 is moved along the longitudinal axis L. It is also conceivable to use a combination of a sweeping of the focused laser beam 11 as shown in FIG. 2 and a relative translational motion. The angle is measured in a plane defined by the longitudinal axis L and the tangent P of the circular path P in the main irradiation spot 12.

[0094] In FIGS. 6 and 7, there is shown how the main propagation direction PD of the focused laser beam 11 is directed such that it forms an angle in a defined by the circular path P relative to the tangent P of the circular path P in the main irradiation spot 12. In FIGS. 6 and 7, the plane defined by the circular path P is parallel to the plane of the paper. Both angles 1 and 2 are less than 45 and preferably less than 30.

[0095] It may be noted that the focused laser beam 11 may be inclined as discussed above with both an angle and an angle . One or both angles may be fixed and/or one or both angles may be actively changed during the end rounding.

[0096] It may be noted that it is also conceivable that the focused laser beam 11 may be directed such that the main propagation direction PD and the tangent P of the circular path P in the main irradiation spot 12 are directed in the same direction.

[0097] Thus it is preferred that the focused laser beam 11 is directed relative to the tangent P of the circular path P in the main irradiation spot 12 basically within an hour glass shaped double cone with the side surfaces forming an angle of up to 45 relative to the centre line formed by the tangent P of the circular path P in the main irradiation spot 12.

[0098] The focused laser beam 11 has a maximum intensity of 10-20000 W/mm.sup.2 at the geometrical focus spot.

[0099] The focused laser beam 11 has a focus spot having an area of 0.01 to 1 mm.sup.2.

[0100] The focused laser beam 11 has preferably a circular focus spot or a focus spot at least having a maximum width being less than 2 times a width in a direction orthogonal to the maximum width.

[0101] The focused laser beam 11 has a wavelength of 300 to 11000 nm.

[0102] The focused laser beam 11 has a focus depth of between 100 to 10000 m. The focus depth being defined as a distance measured along the propagation direction between two spots 12 and 12, one on either side of the geometrical focus spot along the propagation direction, at which spots 12, 12 the intensity per surface area is 95% of the intensity per surface area at the geometrical focus spot. In FIG. 3, there is shown a focus spot 12 with an alternative geometry. The focus spot 12 has a maximum width w1 being slightly less than two times the minimum width w2.

[0103] When performing the end rounding, the respective bristle end is subjected to the focused laser beam for a time period being between 100-100000 s, preferably between 100 and 10000 s, thereby heating the end and causing it to partly melt. This may e.g. be accomplished by rotating the bristle section 1 about the longitudinal axis at a rotational speed of between about 100 and about 10000 revolutions per minute and with the main irradiation sport 12 being a distance R being between about 0.5 mm to 10 mm from the rotational axis L, thereby giving the end of the bristle 4 a tangential speed of between about 0.01 to 10 m/s along the tangent P of the path P.

[0104] It may be noted that when the focused laser beam 11 is directed relative to the tangent P and relative to the direction of rotation as shown in FIG. 6, a smaller amount of energy from the laser beam 11 is applied to the bristle 4 before the bristle 4 reaches the main irradiation spot 12 than the amount of energy applied to the bristle 4 after the bristle 4 has passed the main irradiation spot 12. This may be referred to as an after-heating the bristle ends.

[0105] It may be noted that when the focused laser beam 11 is directed relative to the tangent P and relative to the direction of rotation as shown in FIG. 7, a greater amount of energy from the laser beam 11 is applied to the bristle 4 before the bristle 4 reaches the main irradiation spot 12 than the amount of energy applied to the bristle 4 after the bristle 4 has passed the main irradiation spot 12. This may be referred to as a pre-heating the bristle ends.

[0106] In FIG. 9, there is schematically shown a bristle 4 with an end being end rounded in accordance with the method and apparatus disclosed above.

[0107] As noted in FIG. 9, the end rounding will basically result in a drop-like shape being formed at the end of the bristle 4. The drop-like shape of the rounded end has a maximum extension D along a radial direction of the bristle extending between 1.1 and 2 times, preferably between 1.1 and 1.5 times, the maximum extension d of an unaffected part of the bristle 4. The unaffected part of the bristle 4 is typically circular in cross-section and the maximum extension is basically a diameter d. The drop-like shape is typically circular in cross-section and the maximum extension is basically a diameter D.

[0108] The drop-like shape of the rounded end has an extension H along the longitudinal extension LE the bristle 4 being between 1.1 and 2 times, preferably between 1.1 and 1.5 times, the maximum extension d of an unaffected part of the bristle 4.

[0109] The bristles 4 are preferably made of polyamide or polyester. The respective bristle 4 has preferably a diameter between about 0.03 to 0.2 mm.

[0110] It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.