EP1136017B1 - Method and device for melting ends of bristles - Google Patents

Description

The invention relates to a method for fusing the axial ends of bundled fibers made of thermoplastic, in which the fiber ends in contact with a heated surface of a stamp to be brought. The invention further relates to a device for Attachment of bristle tufts for brushes to carrier plates thermoplastic. The carrier plates with the attached Tufts of bristles are built into brush bodies, particularly for the production of toothbrushes.

Several methods are known for the production of brushes. in principle can brush bodies be provided with a perforated field, that corresponds to the desired bristle field. The bundles of bristles become then inserted and anchored in the holes of the brush body. Anchoring the tufts of bristles in the brush body using anchor plates or slings, however, requires very powerful and therefore elaborate machines.

According to an alternative brush manufacturing process, the bristle tufts attached to a carrier plate, which is then in a brush body is installed. The carrier plate can with the brush body can be connected by extrusion coating or welding. The carrier plate is provided with holes according to the desired hole pattern. The tufts of bristles are inserted into the holes, taking on a surface of the carrier, the use-side ends of the bristle tufts and on the opposite side those to be anchored in the brush The axial ends of the bristle tufts protrude slightly. Against this ends of the bristle tufts to be anchored in the brush body heated stamp pressed through the ends of the bristle tufts fused together and possibly formed into a thickening become. In the subsequent separation of the stamp from the fused fiber ends lead to the formation of pulling threads and smearing the tough plastic melt. Furthermore, since both the bristle ends as the carrier plate is heated, it is difficult on the one hand, the necessary for a perfect anchoring of the bristles To cause deformation thereof and on the other hand a to prevent undesired deformation of the carrier plate, especially as carrier plate and bristles usually made of different plastics consist.

In US-A-5,474,366 a generic method or a Generic device for producing a brush shown. According to the The process involves inserting tufts of bristles into the holes in a supporting body. The ends of the bristle tufts protruding on one side of the support body are by means of a heating plate with each other and with the support body merged.

EP-B-0 405 204 describes a method and an apparatus for manufacturing shown by bristle fields, in the bristle tufts in the holes one Holding plate can be introduced. The over the sides of the holding plate projecting ends of the bristle tufts are on one side by means of a heating or Melting station fused together.

The invention provides a method for fusing the axial Provided ends of bundled fibers of thermoplastic material, in which the fiber ends with a heated surface of a Be brought into contact with the stamp. In the process, the Stamp heated by controlled electrical current flow in its mass, which enables extremely fast and precisely controllable temperature changes of the stamp.

In a first variant of the method, the fiber ends are with a heated surface of a stamp, which then is suddenly cooled. Only after the surface has cooled down the fiber ends are separated from this. This allows the Detach the fused fiber ends from the heated surface and have a geometry determined by the shape of the surface. At this Variant, the use of a non-stick coating is advantageous.

In a second variant of the method, the fiber ends are first just like in the first variant with one on a first Brought into contact with the heated surface. Then will the area separated from the fiber ends, but the temperature the area remains unchanged. After that, the surface is on brought a second, higher temperature to adhere to the surface

Evaporate residues of the fiber material. In the last step the surface is cooled back to the first temperature. at this variant shows the adhesive properties of the heated surface the heated fiber material is not critical, so that there is a non-stick layer unnecessary.

Both variants of the process are particularly suitable for production of bristle fields for the production of brushes. Fibers for the Brush production mostly consists of a thermoplastic like poyamide ("nylon"). This material can be used with the specified Form the process well.

The invention also provides a device for fastening Bristle tufts on carrier plates for the production of brushes for Provided with the action of the stamp on the bristle ends done in a controlled and reproducible manner, so that the desired deformation of the bristle ends without undesired deformation of the carrier plate is guaranteed. In the case of the invention Device the stamp is heated by electrical current flow and cooled by a flowing cooling medium. The stamp leaves heat up very quickly and specifically through the flow of electrical current, especially if, according to the preferred embodiment, a has low heat capacity so that it quickly a temperature cycle can go through, in one phase of the cycle by the flowing cooling medium can be cooled quickly again. Because the bristle ends only heated for a very short time and then immediately again are cooled, smearing of the heated bristle material avoided on the carrier plate. Alternatively, the stamp by controlling the electric current alternately to a first one Temperature at which it is brought into contact with the fiber ends, and heated to a second, higher temperature at which the surface adhering fiber material evaporates. The carrier plate itself is only slightly heated because the stamp is powered by the electric Current flow only briefly to melt the bristle ends required temperature heated and then immediately cooled again becomes. By controlling the electrical current flow, in particular by Pulse duration modulation, strength and duration of the heating can be well control.

The stamp preferably has a body made of electrically conductive Material on which two electrical high-current connections in the form of angled contact shoes are formed. The body of the stamp has a thin-walled stamp plate that is angled by a Edge strips can be stiffened. Suitable materials for manufacturing of the stamp are metals that on the one hand have sufficient mechanical Have strength so that for rapid temperature changes desired low heat capacity is guaranteed, on the other hand but have only a moderately high specific resistance, thus the electrical heating power through an uncritically low electrical voltage can be provided. The necessary Heating currents are then a hundred amperes and more, for example two hundred amperes at 7 volts, but can be done in this way Control high currents well with available semiconductor devices. Due to the criteria mentioned are stainless steel, titanium and NiCr-containing alloys suitable materials for the production of the Stamp.

Compressed air is preferably used to cool the stamp. by virtue of the low heat capacity of the stamp can be directly Blowing with compressed air can be cooled again in a very short time, see above that cycle times in the range of one second are possible.

In the preferred embodiment of the device there are several stamps arranged in a group on a stamp carrier plate, and the the same number of carrier plates is placed opposite the stamps inserted into corresponding openings in a support plate. The Stamps are preferably electrically in on the stamp carrier plate Series connected so that the current of the heating current does not increase. This measure is particularly useful if the stamp carrier plate with the stamps relative to those in the support plate arranged carrier plate is moved back and forth, then the electrical supply lines for the heating current must be moved, so that large conductor cross sections would be unfavorable.

Fig. 1 bis 4

Skizzen zur Veranschaulichung einer ersten Variante des erfindungsgemäßen Verfahrens;

Fig. 5

eine schematische Perspektivansicht der Vorrichtung;

Fig. 6

eine vergrößerte Schnittansicht eines Teils der Vorrichtung;

Fig. 7

eine vergrößerte Perspektivansicht eines Teils der Vorrichtung;

Fig. 8

eine perspektivische Detailansicht eines Stempels der Vorrichtung;

Fig. 9

eine Schnittansicht, die eine Variante der in Fig. 2 gezeigten Anordnung zeigt; und

Fig. 10

schematisch eine weitere Ausführungsform.

Fig. 11 bis 15

Skizzen zur Veranschaulichung einer zweiten Variante des erfindungsgemäßen Verfahrens;

Further features and advantages of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. The drawings show:

1 to 4

Sketches to illustrate a first variant of the method according to the invention;

Fig. 5

a schematic perspective view of the device;

Fig. 6

an enlarged sectional view of part of the device;

Fig. 7

an enlarged perspective view of part of the device;

Fig. 8

a detailed perspective view of a stamp of the device;

Fig. 9

a sectional view showing a variant of the arrangement shown in Fig. 2; and

Fig. 10

schematically another embodiment.

11 to 15

Sketches to illustrate a second variant of the method according to the invention;

In the first variant shown schematically in FIGS. 1 to 4 The method fibers 1 are bundled from plastic, in particular e.g. a perforated plate 2, and placed on a stop 3. The stop 3 can be flat or a profiled shaped surface have and thus for profiling the bristles by means of axial displacement the bristles are used in a known manner. The free fiber ends are opposite to one through electric current flow heated stamp 4, of any shape, in particular with a shaped surface. The stamp 4 has a low heat capacity, so that it is by electrical resistance heating heated very quickly and by a flowing cooling medium can be cooled down just as quickly.

In a first step, the stamp 4 is heated to a temperature T ₁ . In a second step, the punch 4 is pressed against the fiber ends, as shown in FIGS. 1 and 2. The fiber ends are melted and reshaped. In a third step, Fig. 3, the stamp 4 is then rapidly cooled by targeted blowing with compressed air. Only then, in a fourth step, FIG. 4, is the stamp separated from the now fused and cleanly formed fiber ends.

In the described embodiment of the device, this is used for Manufacture of toothbrushes in which a tuft of bristles is provided Carrier plate inserted into a brush head and with it is welded. Details of such a device are, for example EP 0 972 464 A1 and EP 0 972 465 A1.

On a stand 10 (Fig. 5) is a stamp carrier plate 12 by means of Guide rods 14 arranged vertically back and forth, wherein the drive is ensured by a pneumatic cylinder 16. Four support bases 18 are attached to the underside of the carrier plate 12, each have a downward heatable stamp 20 wear. Under the stamp carrier plate 12 at a distance and parallel to this is a support plate 22 with four openings 24 in opposite relationship to the stamps 20. In each of these openings 24 is a Carrier plate 26 made of plastic can be used, with a perforated field is provided according to the desired bristle field.

Via a compressed air line branched on the stamp carrier plate 12 28 targeted compressed air blasts can be supplied to the device, which are aimed directly at the stamp 20. To the stamp carrier plate 12 also lead two flexible power cables 30, via the one controlled electrical current supplied by pulse duration modulation can.

6 shows details of the device in the area of an individual Stamp. This stamp 20, the design of which can be seen in more detail in FIG. 5 is consists of a metallic body, in particular stainless steel, with a thin-walled stamp plate 20a and two molded, angled high-current connections in the form of right-angled Contact shoes 20b, 20c. These contact shoes 20b, 20c serve at the same time for attaching the stamp 20 to the support bases 18, via which the electrical connection of the four stamps 20 is also carried out is. As can be seen from Fig. 6, the power cables 30 directly connected to a cable lug. The Support base 18 are provided with openings 18a through the stamp support plate 12 connected to the compressed air line 28 are and the compressed air flow directly against the stamp plate 20a judge.

As can also be seen from FIG. 6, the carrier plate 26 inserted into the opening 24 of the support plate 22 in such a way that its peripheral edge is supported on all sides by the edge of the opening 24 is. The tufts of bristles inserted into the holes in the carrier plates 32 protrude on the side of the stamp 20 by 2 to 3 millimeters out of the carrier plate 26 and are on the opposite Side supported on a bumper plate or stop 34. This The stop can either be designed flat or with a shaped surface be provided at the same time for profiling the tufts of bristles by axially moving the individual bristles within one Tuft is used. The stamp 20 is on the carrier plate facing surface provided with pointed projections 36, the Tips are directed against the area of the carrier plate, the surrounds the holes, and thus the tufts of bristles. Furthermore, the against the carrier plate facing surface of the stamp with a non-stick coating Provided.

As can be seen from FIG. 7, the four stamps 20 are on the stamp carrier plate 12 electrically connected in series. The interconnection the stamp can be by individual cable sections or by suitable Design of the support base 18 take place.

From the illustration in Fig. 8 it can be seen that the stamp is thin-walled component, which is formed by suitable curves Ribs, a curved peripheral edge and the angled contact shoes a high degree of dimensional stability is imparted.

As can also be seen from FIG. 7, at least one is the stamp 20, but preferably each stamp, assigned a temperature sensor 40. The or each temperature sensor 40 is equipped with a controller 42 connected, which drives an electrical power supply 44, at the Outputs the power cables 30 are connected. The power supply 44 works preferably with pulse duration modulation.

In a typical embodiment of the device, the body is made up each stamp 20 made of stainless steel. The wall thickness in the area of Stamp plate 20a is only a fraction of a millimeter. at a length of the stamp plate in the range of 20 millimeters and one Width of about 10 millimeters results in a heating output of about 1400 watts, corresponding to a current of 200 amps at 7 volts. The The body of the stamp has such a low heat capacity that the cycle of heating and cooling on the order of magnitude of a second. The rapid cooling takes place alone by a controlled blast of compressed air that hits the surface of the stamp plate is judged.

In the embodiment shown in Fig. 9, the carrier plate 26 in addition to the support plate 22 from a movable support ring 48 attacks. The support ring 48 has a passage opening provided for the passage of the stamp 20. The support ring 48 improved the support on the peripheral edge of the support plate 26 to one Deformation of the same by the action of the heated stamp 20 submissions. With this version of the device, one becomes special ensures good dimensional accuracy of the support plate 26, so that at the subsequent welding to the brush head a clean connection arises.

In the embodiment shown in Fig. 10, the through holes are expanded on the side of the fiber ends to be fused, in particular conical. When pressing the heated surface of the stamp plasticized mass of the fused fiber ends in these extensions indented, causing frusto-conical at the fused fiber ends Thickenings are formed, which are denoted by 5 in FIG. 10 are. Through these thickenings the "pull-out force", i.e. the tensile force in the direction "A" in Fig. 10, in which a tuft of the carrier plate 26 triggers, significantly enlarged. Another increase is achieved in that the plasticized mass of the fused At least fiber ends by pressing the heated stamp is reshaped in regions to form a continuous layer, such as indicated at 6 in Fig. 10. To insert the tufts of fibers 1 in to facilitate the through holes of the carrier plate 26, these are Through holes also on the opposite side of the carrier plate 26 extended, as indicated in Fig. 10 at 7.

The second variant of the shown schematically in FIGS. 11 to 15 The procedure is based on the same arrangement as the first variant the method (Fig. 1 to 4). The same parts are the same Reference numbers marked.

The first two steps of the second variant of the method correspond to the first two steps of the first variant. The punch 4 is heated to a first temperature T ₁ and pressed against the fiber ends, as shown in FIGS. 11 and 12. In a third step, the punch 4 is now lifted off the fiber ends, but its temperature is maintained unchanged (FIG. 13). After the stamp 4 has been lifted off at the temperature T ₁ , some fibrous material sometimes adheres to it. In order to eliminate this, in a fourth step the stamp 4 is heated to a second, higher temperature T2 (FIG. 14), which is chosen so high that the fiber material first breaks down into monomers by pyrolysis and then evaporates completely, so that the Stamp 4 is clean again and has no residues of the fiber material. In the last step, the stamp 4 is rapidly cooled to the temperature T ₁ by targeted blowing with compressed air (FIG. 15). When using polyamide fibers, the temperature T _{1 is} about 250 ° C to 300 ° C and the temperature T _{2 is} about 600 ° C to 700 ° C.

Claims (29)

1. A method of melting together the axial ends of bunched fibers (1) of thermoplastic material, in which the fiber ends are brought into contact with a heated surface of a stamp (4), characterized in that the bulk of the stamp (4) is heated by passing a controlled electric current through it.
2. The method according to claim 1, characterized in that the surface of the stamp (4) is cooled rapidly and the fiber ends are separated from the surface only after cooling of the surface is completed.
3. The method according to claim 2, characterized in that the surface is cooled by a flow of a cooling agent.
4. The method according to claim 1, characterized in that by controlling the electric current conduction the surface of the stamp (4) is heated alternately to a first temperature at which it is brought into contact with the fiber ends, and to a second, higher temperature at which fiber material adhering to the surface is vaporized.
5. The method according to any of the preceding claims, characterized in that tufts of fibers (1) for the fabrication of brushes are formed by melting together the fiber ends to be attached to the brush body.
6. The method according to claim 5, characterized in that a plurality of tuft ends is simultaneously brought into contact with the surface of the stamp (4).
7. The method according to claim 6, characterized in that the tufts are inserted into through holes of a carrier platelet (26) and are attached to it by melting their ends together.
8. The method according to claim 7, characterized in that the through holes are enlarged on the side of the fiber ends to be melted together and plasticized mass of the fiber ends already melted together is pressed into the enlargements of the through holes by pressing the heated surface against the mass.
9. The method according to claim 7 or 8, characterized in that at least part of the plasticized mass of the fiber ends melted together is shaped into a continuous layer by pressing the heated surface against it.
10. A device for attaching tufts of bristles intended for brushes to carrier platelets (26) of thermoplastic material provided with an array of holes corresponding to the array of bristles of the brush, comprising a heatable stamp (20) which can be pressed against the ends of the tufts of bristles protruding on one side of the carrier platelet (26) out of the holes of the array of holes, characterized in that the stamp (20) can be heated by passing a controlled electric current through it.
11. The device according to claim 10, characterized in that the stamp (20) can be cooled by a flow of a cooling agent.
12. The device according to claim 10 or 11, characterized in that the stamp (20) has a body made of an electrically conducting material having two electrical high-current terminals formed thereon.
13. The device according to claim 12, characterized in that the body of the stamp comprises a thin-walled stamp plate (20a) having two contact shoes (20b, 20c) formed thereon.
14. The device according to claim 13, characterized in that the stamp plate (20a) is strengthened by a bent-off edge strip.
15. The device according to claim 13 or 14, characterized in that the contact shoes (20b, 20c) are bent off.
16. The device according to any of claims 13 to 15, characterized in that the contact shoes (20b, 20c) at the same time form support brackets for the attachment of the stamp (20) to a stamp holder (12).
17. The device according to any of claims 10 to 16, characterized in that on its surface facing the carrier platelet (26) the stamp (20) is provided with projections having tips opposite to areas adjacent to and surrounding the holes of the carrier platelet (26).
18. The device according to any of claims 10 to 17, characterized in that on its surface facing the carrier platelet (26) the stamp (20) is provided with a non-stick coating.
19. The device according to any of claims 10 to 18, characterized in that the carrier platelet (26) can be inserted into an opening (24) of a supporting plate (22) having a rim which supports the peripheral edge of the carrier platelet (26) during the action of the stamp (20).
20. The device according to claim 19, characterized in that a movable supporting ring (48) provided with a through opening for the stamp (20) engages around the peripheral edge of the carrier platelet (26) inserted in the opening of the supporting plate (22).
21. The device according to any of claims 10 to 20, characterized in that the flow of the cooling agent is formed by compressed air directed immediately against the stamp (20).
22. The device according to any of claims 10 to 21, characterized in that a stamp carrier plate (12) is provided with a plurality of stamps (20) arranged in a group and an identical number of carrier platelets (26) are insertable into corresponding openings (24) of a supporting plate (22) opposite the stamps (20).
23. The device according to claim 22, characterized in that the stamp carrier plate (12) can be reciprocated in relation to the supporting plate (22).
24. The device according to claim 22 or 23, characterized in that the stamp carrier plate (12) is provided with flow channels for the cooling agent opening opposite the stamps (20).
25. The device according to any of claims 10 to 23, characterized in that the stamps (20) are electrically connected in series.
26. The device according to any of claims 12 to 25, characterized in that the body of the stamp (20) consists of a metal having a relatively high resistivity, such as stainless steel or titanium.
27. The device according to any of claims 10 to 26, characterized in that the electric power to heat the stamp (20) is supplied in the form of a high current pulse of several hundred amperes, in particular about 200 amperes for the fabrication of tooth brushes, at a voltage of a few volts.
28. The device according to any of claims 10 to 27, characterized in that at least one temperature probe (40) is associated with the stamp (20) and the electric heating power is controlled according to the temperature measured.
29. The device according to claim 28, characterized in that the electric heating power is closed-loop controlled using pulse width modulation.

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