Patent Grant
8840192
The present invention relates to a method for producing a toothbrush and to a toothbrush.
A method and a toothbrush of this type are known from publication WO 03/086140 A1. A carrier plate provided with bristles, and, if necessary, other cleaning elements, is inserted into a mount molded integrally on a head part of a toothbrush body, said carrier plate being fixed to the head part by means of ultrasonic welding. To test this fixation, a force is applied either directly or indirectly to the head region or to the carrier plate at the end of the tufting process once the body has cooled after the welding process, or the head part of the toothbrush body is bent slightly.
In particular with the use of transparent plastics for the toothbrush body, a risk of brittle fractures in areas subject to high mechanical load was determined, in particular in the end region of the head part facing the neck part and in the region of transition from the head part into the neck part. Brittle fractures are dangerous if they occur during use of the toothbrush, that is to say when teeth are being cleaned. The surface of the fracture may have sharp edges and corners, which have the potential to injure the user.
It was also determined that inaccuracies with regard to the fit in the region between the mount recess and the carrier plate, for example if the carrier plate is too large and the recess in the head of the toothbrush body is too small, may also have a negative influence on fracture behavior. Toothbrushes which are produced from hard materials which are conventional nowadays, such as polypropylene, are also affected by this.
The object of the present invention is to develop a generic method for the production of a toothbrush, in such a way that the risk of brittle fractures is practically eliminated, and to create a toothbrush produced by this method.
This object is achieved by a method having the features of a toothbrush body (12) having at least one head part (14) and a neck part (32) connected to the head part (14) and carrying it is produced, the head part (14) is provided with a carrier plate (20) carrying bristles (22) and the carrier plate (20) is fixed to the head part (14) by means of welding, and a force is then exerted on the toothbrush body (12), characterized in that the neck part (32) and the head part (14) are bent relative to one another from the original shape by a predetermined angle (α), still in the hot state of the weld zone (51), by means of the force, and the force is removed after the bending process so as to allow the toothbrush body (12) to bend back into its original shape, and by a toothbrush having the features of a mount (16), formed integrally on the head part (14), for a carrier plate (20) and a carrier plate (20) provided with bristles (22) and inserted into the mount (16), said carrier plate being fixed to the head part (14) by means of welding, in particular ultrasonic welding, wherein either a gap (30), preferably of 0.03 mm to 0.35 mm, is provided between an outer surface (26) of the mount (16) and a lateral surface (28) of the carrier plate (20, or welding is substantially prevented.
In accordance with the invention, the neck part and the head part are bent relative to one another from the original shape thereof by a predetermined angle in the hot state in the weld zone between the toothbrush body and the carrier plate and the zone close to the weld. The bending process is carried out immediately after the welding process so that the weld zone and the zone close to the weld are still hot during said bending process.
After the bending process, the force is removed so that the toothbrush body can move back into the original shape thereof due to the resilient properties of the material thereof. By bending the neck part relative to the head part, the material of the toothbrush body and in particular of the weld zone between the toothbrush body and the carrier plate, and also partly of the zone close to the weld, is stretched in the region subject to high mechanical load, that is to say in the end portion of the carrier plate, relative to the neck part, which leads to orientation of the molecules and thus to improved fracture behavior in this zone.
For maximum effect, the resilient region of the toothbrush body, of the carrier plate and of the weld zone is preferably utilized practically fully during the bending process. Generally, no plastic deformation of these elements is caused by the described stretching process, this process being a resilient bending process, that is to say a reversible bending process.
The method according to the invention presupposes a connection process between the carrier plate and the toothbrush body, and therefore at least some of the material of the carrier plate and/or of the toothbrush body is melted, thus producing a weld zone by means of material connection.
In addition to ultrasonic welding, which is known in general, other welding or connection methods may also be considered in this instance. For example, a weld can be obtained by means of selective heating or friction. However, a weld can also be produced by means of injection molding, in which the plastic forming the toothbrush body is sprayed over the carrier plate. The material of the carrier plate is also melted locally by the encapsulating material, and a material connection is produced.
In the case of the welding methods described here, like or compatible materials are preferably used in the carrier plate and toothbrush body, at least in the relevant portions, so that a material connection can also be produced during the welding process, two hard materials preferably being welded.
Ultrasonic welding will be discussed hereinafter by way of example, although it is known that the fracture behavior can also be improved for other welding or connection methods by means of the method according to the invention.
The method according to the invention can also be used at other points of a toothbrush. For example, if the weld zone is not provided in the head part, but in the neck part or grip part of the toothbrush, the method according to the invention can be used in the relevant weld zone and zone close to the weld.
Tests have proven that the known risk of a brittle fracture is reduced considerably, if not prevented completely, by the method according to the invention, even with the use of opaque and in particular transparent plastics for the production of the toothbrush body.
The neck part is preferably deflected relative to the head part by an angle of 5° to 45°, in particular by 15° to 25°.
The deflection is further preferably maintained for a predetermined period of time before the force is removed. This period of time preferably lasts for approximately 0.3 seconds to 5 seconds, and in particular is selected between 0.5 seconds and 1.2 seconds.
It has been determined on the basis of tests that there is an increased risk of brittle fractures in particular if a carrier plate provided with bristles and/or rubbery-elastic massaging and cleaning elements has been inserted into a mount of the head part and if said carrier plate has been fixed to the head part by means of ultrasonic welding. As a result of the ultrasonic welding, the toothbrush body is heated in the weld zone and in the zone close to the weld due to vibrations, in particular in the head region and in an end portion of the neck region adjacent to the head region. The force for bending the neck part relative to the head part is particularly preferably applied immediately after the ultrasonic welding process whilst the toothbrush body is still hot in the weld zone and in the zone close to the weld as a result of the welding process.
In addition, the risk of fracture can also be prevented by providing a defined gap, which is open towards the front face, between an outer surface of the mount in the head part and a lateral surface of the carrier plate opposite thereto. This gap preferably measures 0.03 mm to 0.35 mm, in particular 0.05 mm and 0.18 mm.
This gap may have a different width over its length. The greatest width of the gap is preferably selected in an end portion of the mount facing the neck part.
Similarly, the risk of fractures can also be prevented by preventing welding of the carrier plate to the head part in a region between the outer surface of the mount and the lateral surface of the carrier plate by means of an adhesion reducer or an adhesion suppressor, preferably at least in the end portion of the mount facing the neck part.
The head part is preferably held in a receiving element whilst the force is applied to the neck part. The head part is more preferably supported in the receiving element over its lower face, facing away from the tufted upper face, along a peripheral edge portion, wherein the region of transition from the head region to the neck region is released.
For example, a sonotrode, by means of which the ultrasonic welding was carried out beforehand, or another element of the welding apparatus can be used to fix the head part in the receiving element. Furthermore, it is also possible to use another auxiliary device to fix the head part in the receiving element.
It is accordingly also possible to fix the neck part in an end region remote from the head part by means of a corresponding receiving element, and to apply the force to the head part so as to deflect said head part relative to the neck part by bending. If the toothbrush body has a grip part, the grip part is preferably held by means of the receiving element in the present case.
The toothbrush body and the carrier plate can be produced by conventional injection molding from a hard component. However, they can also be produced by two-component injection molding or by multi-component injection molding from one hard component and one or more soft components, or from two or more hard components and possibly one soft component. The hard component or hard components form the bearing part of the toothbrush body and of the carrier plate.
Different plastics can be used to implement the invention. Exemplary options from the field of thermoplastics include:
Examples from the field of thermoplastic elastomers (TPEs) include:
In the case of a non-transparent brush, PP is preferably used as a hard component, and PP having a modulus of elasticity of 1000 to 2400 N/mm2, preferably 1300 to 1800 N/mm2, is most preferred. Polyesters such as the aforementioned BR003, CAP, PA, PMMA, SAN or ABS, are preferably used as a hard component to form a transparent brush.
A TPE-S is preferably used as a soft component. The Shore-A hardnesses of the soft plastic are preferably below 90 Shore A.
The invention will be explained in greater detail on the basis of an exemplary embodiment illustrated in the drawing.
In the drawing, in purely schematic form:
As can be inferred from
Connecting to the head part 14, the toothbrush body 12 has a neck part 32 connecting integrally to said head part and of which only a portion facing the head part 14 is shown in
The bristles 22 of the bristle field 24 protrude from the carrier plate 20 on the front face 36 of the toothbrush body 12. The exposed surface of the carrier plate 20 is aligned with the corresponding surface of the toothbrush body 12.
In the embodiment shown in the figures, the head part 14 of the toothbrush body 12 is equipped with a tongue cleaner 40 on the rear face 38, facing away from the front face 36. Embodiments without a tongue cleaner 40 are also possible.
In the embodiment shown, the toothbrush body 12 consists in the neck part 32 and head part 14 of a hard component. It is also possible, however, for the tongue cleaner 40 made of a soft component to be injected integrally onto the hard component by two-component or multi-component injection molding, or for the soft component to be removed from relatively large surface portions of the surface of the toothbrush body 12, in particular including the head part 14, for decorative purposes.
A fracture point region 42 is also indicated in
The mount 16 is formed by a stepped recess 44 in the head part 14, said recess being open towards the front face 36 and the base 46 thereof being closed towards the rear face 38 by a wall of the toothbrush body 12.
The oval recess 44 in view from the front face 36 is defined from the front face 36 of the toothbrush body 12 as far as a step 48 by the outer surface 26, which in the present example extends in the head part 14 at right angles to the surface of the front face of the toothbrush body 12. The step 48 reducing the recess 44 extends in a plane parallel to the front face 36 of the head part 14, and a weld bead 50 acting as an energy concentrator/energy director protrudes from said step at a radially inward edge in the direction towards the front face 36. The cross-section of the weld bead 50, which is preferably completely peripheral and closed, is preferably triangular.
The weld bead 50 may also be formed differently, however. For example, the width (preferably not the height) may vary over the periphery. Furthermore, the weld bead 50 may have a shape which is interrupted in the peripheral direction, for example by successive individual weld points or by successive individual weld edges, wherein the distances and lengths of the elements may vary in both cases. For example, weld points may be pyramidal or conical. The height of the weld bead 50 is between 0.05 mm and 0.8 mm, preferably between 0.15 mm and 0.4 mm.
Adjacent to the weld bead 50, the recess 44 is defined by a lower, second outer surface 52, which preferably likewise extends at right angles to the front face 36 of the head part 14 or tapers slightly conically towards the base 46.
In the exemplary embodiment shown, the base 46 further has a peripheral, groove-like depression 54 in an edge region adjacent to the second outer surface 52.
It can also be inferred from
The step 48, measured from the base 46 to the front face 36 of the head part 14, is arranged at most at 70%, preferably at most at 66%, of the overall height, wherein 50% or less is also conceivable. The weld bead 50 and the weld zone 51 produced later are therefore positioned as close to the base 46 as possible.
The depth of the recess 44, that is to say the distance from the front face 36 to the base 46, is 1.8 mm to 2.6 mm, preferably 2.1 mm to 2.3 mm. The groove-like depression 54 has a depth, measured from the front face 36, of 2.5 mm to 3.5 mm, preferably of 2.8 mm to 3.2 mm. The height of the step 48, measured from the front face 36, is between 0.6 mm and 2 mm, preferably between 1 mm and 1.2 mm.
The carrier plate 20, which is flat over the front face 36 in the exemplary embodiment shown, is shaped in such a way that its peripheral lateral surface 28, in the assembled state, extends at least approximately parallel to the outer wall 26 and at a distance therefrom, thus forming the gap 30. This means that the shape of the recess 44 is adapted to the shape of the carrier plate 20 and of the bristle carrier element 18. The two may consequently also have shapes which differ geometrically, but which in any case have to be matched to one another.
A stepped, flat counter-surface 56 corresponding to the step 48 is also formed on the carrier plate 20 and is defined radially inwardly by a centering wall 58, which protrudes from the carrier plate 20 on the rear face thereof. The radially outer surface of the centering wall 58 mirrors the second outer surface 52 and the mount 16 and centers the bristle carrier element 18 in the toothbrush body 12.
So that the width of the gap 30 can also always be maintained in practice, it is necessary to tolerate accordingly the tools used to produce the toothbrush body 12 and the recess 44 and the carrier plate 20. To this end, the tolerances of the carrier plate 20 and of the recess 44 in the toothbrush body 12 have to be matched to one another in the region of the mount 16 so that the carrier plate 20 when formed with maximum size, in combination with the recess 44 in the toothbrush head when formed with minimum size, still form the gap 30 with the given dimension. This means that the tolerances of the centering wall 58, the inner edge and outer edge of the counter-surface 56, and the tolerance of the lateral surface 28 have to be matched to one another and to the recess 44 and mount 16 in the toothbrush body 12 on the side of the carrier plate 20. In the toothbrush body 12, the tolerances of the inner and outer edges of the step 48 and of the outer surface 26 have to be matched to one another and to the aforementioned tolerances of the carrier plate 20.
With regard to the peripheral centering wall 58, the carrier plate 20 has bristle-receiving openings 60 arranged radially inwardly and penetrating from the front face of the carrier plate 20 to the rear face thereof.
As is generally known from the AFT (anchor free tufting) method, the bristle carrier element 18, for example the carrier plate 20, is produced by injection molding, in the present case preferably from a hard component. Cleaning and massaging elements 22′ made of a soft component can also be injected integrally onto the carrier plate 20. The bristles 20 forming the bristle field 24 are guided through the bristle-receiving openings 60 in the carrier plate 20 and are aligned so as to form the tooth cleaning geometry. The bristles 20 are then melted in their end region projecting beyond the rear face of the carrier plate 20, for example by means of a punch, whereby a melt film 62 of molten bristle material is formed on the rear face of the carrier plate 20 and within the region defined by the centering wall 58. The tufted bristle carrier element 18 is thus formed by means of the bristles 22.
The tufted bristle carrier element 18 is then inserted into the mount 16 of the toothbrush body 12 from the front face 36, until the counter-surface 56 of the carrier plate 20 comes to rest against the weld bead 50 of the mount 16 of the head part 14. Centering occurs by cooperation of the centering wall 58 with the second outer surface 52 or the edge thereof terminating in the direction of the front face 36. When melting the bristles 22 in practice to form the melt film 62, the centering wall 58 is thus inclined radially inwardly due to the effect of the heat. The result of this change in geometry caused by the process is that the centering wall 58 forms a quasi run-in bevel towards its starting point, and the terminal edge in the region of the counter-surface 56 is thus used for the centering process.
As can be seen in particular from
Once the tufted bristle carrier element 18 has been inserted into the mount 16 of the head part 14, the carrier plate 20 is connected rigidly in a known manner to the toothbrush body 12 by means of ultrasonic welding. The weld bead 50 on the toothbrush body 12 is used as an energy concentrator/energy director. It is liquefied during the process of ultrasonic welding and produces a welded connection together with the material of the carrier plate 20 in the region of the counter-surface 56 thereof, thus forming a weld zone 51. The melt may spread in the region of the step 48 and may also melt regions close to the weld bead 50, wherein penetration into the gap 30 is preferably prevented. The process of ultrasonic welding is preferably carried out between two compatible hard components which allow a material connection, preferably between two same hard components.
As is clear in particular from
With regard to the weld zone 51 shown in
So as to ensure, in particular in an end region, facing the neck part 32, of the recess 44 or of the mount 16, that the gap 30 remains free from weld melt as far as the step 48, the step 48 is wider in this region and the distance between the outer wall 26 and the weld bead 50 is preferably greater than in the other regions; to this end see
If the toothbrush is formed without a tongue cleaner, the shape of the receiving depression 66 may follow the geometry of the rear face of the toothbrush head, release being possible, but not absolutely necessary. In the vertical direction, the receiving depression 66 supports the head part 14 of the toothbrush at a height of 40% to 70% of the overall height of the toothbrush body 12 in the head part 14.
As can be seen in comparison with
As can also be inferred from
The end of the release depression 70 is preferably adapted in such a way that the step 48 and the weld bead 50 lie in line with the support portion 68, at least at right angles to the front face 36, the release depression 70 preferably lying directly against the support portion 68. It is thus ensured that the mount 16 or the weld bead 50 is supported during the process of ultrasonic welding in the region at right angles to the front face 36, thus enabling optimal welding and yet not impairing the bending process.
In addition to the release depression 70, the lateral release region 70′ is also illustrated in
At the earliest, the lateral release 70′ is implemented from a region 75% the length of the carrier plate 20, measured from the free end of the bristle field 24. So that the welding process is carried out in an optimal manner and so that a possibility for material displacement is also provided on the front face 36 of the toothbrush body 12, a sonotrode 76 may be formed in such a way that it is easily released at the end located in the direction of the toothbrush body 12, towards the support portion.
The toothbrush 10 is shown with the head part 14 inserted into the receiving depression 66, with the rear face 38 inserted first, whilst the neck part 32 and the grip part 34 connecting thereto are free. It should be mentioned at this juncture that the grip part 34 may have, for example, a thumb rest 72 and an index finger rest 74 made of a soft component. It should also be mentioned that regions of the neck part 32 and/or of the head part 14 and/or of the grip part 34 may also be equipped in a known manner with a soft component.
The sonotrode 76, with which the bristle carrier element 18 provided with bristles 22 and the head part 14 or the toothbrush body 12 are welded together in a welding station of the toothbrush production device, can also be seen in
The sonotrode 76 is annular, at least in its end region facing the receiving element 64, that is to say it is formed with a cavity inside for the bristle field 24. This is indicated in
The bending process is indicated in
The welding station is also assigned a stretching device 80, which is intended to bend the neck part 32 relative to the head part 14, from the original shape shown in
The direction of movement of the roll 84 extends orthogonal to a plane defined by the front face 36 of the carrier plate 20 and of the head part 14. The stretching device 80 is also arranged in such a way that the roll 84 comes to rest against the front face in an end region 32′ of the neck part 32 remote from the head part 14 and arranged at the grip part 34. Due to the extension of the cylinder/piston assembly 82, the roll 84 presses onto the surface of the toothbrush body 12, rolls over it and deflects the body by the angle α.
If, by rotating the round table 64′, a receiving element 64 fitted with a toothbrush body 12 provided with a bristle carrier element 18 reaches the welding station, the sonotrode 76 is lowered onto the carrier plate 20 of the bristle carrier element 18, and the ultrasonic welding process is carried out between the carrier plate 20 and the head part 14 in a known manner by excitation of the sonotrode 76. Once the time necessary for the welding process has elapsed, the sonotrode 76 (in an unexcited state) remains in contact with the bristle carrier element 18 so as to hold the head part 14 during the subsequent stretching process. To stretch as a result of bending, the roll 84 is contacted against the end region 32′ of the neck part 32 in the manner of a ram by control of the cylinder/piston assembly 82 and is then lowered further by a predetermined stroke so as to bend the neck part 32 relative to the head part 14 by the angle α. After a predetermined period of time, during which the roll 84 is held in the lowered position, the roll 84 is withdrawn again into the starting position by means of the cylinder/piston assembly 82 so that the toothbrush body 12, due to its resilience, can bend back again into the original shape.
The surface of the roll is concave so that it guides the neck part 32 of the toothbrush body 12 in an optimal manner and the deflection occurs in a direction perpendicular to the bristle field 24. It is thus ensured as a result of the shape of the roll that the toothbrush body 12 does not turn.
It should be mentioned at this juncture that it is also conceivable to provide a second ram to assist the return movement of the toothbrush body 12 into the original shape thereof. The design of the second ram for the return movement is determined by two factors: the speed of the return movement and the effective position after the return movement. If the speed of the return movement is too slow, the cycle of the machine will be slowed, which means that the cycle time will be greater, thus leading to poorer efficiency with weaker ejection. By contrast, the second factor (the position after the return movement) plays a role in that the support is again brought into the original position after the stretching process. If, at this moment, the toothbrush is not in the same position as originally, this may lead to disturbances in the machine and may thus affect the consistency of the process.
It is also possible to design the roll in a manner other than that described. Systems which are not rotatable and which rest against the surface of the toothbrush body 12, preferably with low friction, are also conceivable. Geometrically, plates having rounded edges are thus also conceivable as a pressing element, similarly to the roll. However, it is preferable for these alternative elements to be provided with a layer having low frictional resistance.
The neck part 32 is bent relative to the head part 14 immediately once the welding process is complete so that the toothbrush body 12 is still hot, at least in the head part 14 and in an end portion of the neck part 32 connecting thereto, that is to say in the zone close to the weld and in particular in the weld zone 51. The exact temperature cannot be specified, since there is a distribution of temperature over the toothbrush body in the region of the weld. Temperatures around the melting point of the material are thus reached at the moment of welding in the region of the weld bead 50. This heat irradiates into the surrounding environment and thus also heats regions of the body not affected directly.
The angle α is selected between 5° and 45°, and preferably lies in the range of 15° to 25°. The angle α is defined by the virtual line from the bending axis to the free end 90 of the grip part 34, more specifically as an angle between the original state and the deflected state. The release depression 70 and an opening or a depression 86 in the round table 64′ (see
The resilience of the toothbrush body 12 is disregarded when considering, the angle, that is to say it is assumed that the toothbrush body behaves rigidly beyond the bending zone; no correction factor is introduced for the resilience. In principle however, the resilience is less if the stretching device is effective closer to the point at which the head part 14 is clamped.
The bending axis extending at least approximately parallel to the front face 36 of the head part 14 and at right angles to the longitudinal axis of the toothbrush body 12 and about which the toothbrush body 12 bends as a result of the force exerted thereon by means of the stretching device 80 lies at least approximately at the transition from the head region to the neck region, that is to say approximately in the region denoted in
The distance between the last bristles 22 over the longitudinal central axis of the bristle field 24 and the point at which the stretching device 80 acts on the toothbrush body 12 is 20 mm to 60 mm, preferably 30 mm to 50 mm. The point at which the stretching device 80 acts on the toothbrush body 12 preferably lies in front of the thumb support 72.
The speed with which the stretching device 80 acts on the toothbrush body 12 so as to bend it by the angle α is controlled by a throttle on the cylinder/piston assembly 82 or in the supply thereof and is selected in accordance With the conditions.
The start of the stretching process is preferably controlled by the position of the sonotrode 76. Between 0.1 seconds and 0.8 seconds, preferably 0.2 seconds, after the sonotrode 76 has reached its end position in the welding process, the welding process still taking place however, the stretching process is begun as the support is moved away and the ram is subsequently extended.
The toothbrush body 12 is held for 0.3 seconds to 2 seconds, preferably between 0.5 seconds and 1.2 seconds, in the deflected position (stretching position). The entire additional process, that is to say from the moment at which the vibration of the sonotrode 76 is stopped until the moment at which the sonotrode is raised, is referred to as the holding period. In an integrated stretching process, this holding period lasts between 0.8 seconds and 2 seconds, preferably 1 second. No losses in efficiency therefore have to be endured during the stretching process, and the machine therefore does not have to endure any extension of the cycle time. However, the holding period used in the invention is greater than the holding period in the “normal” process, in this case it lies specifically in the range of 0.1 seconds to 0.8 seconds, preferably 0.2 seconds to 0.5 seconds.
Generally, the cycle time for the welding and stretching processes should be quicker than the cycle time for tufting a carrier plate 20 (machine cycle time) in the case of in-line production.
The width of the gap 30 between the head part 14 and the carrier plate 20, that is to say between the lateral surface 28 of the carrier plate 20 and the outer surface 26 of the mount 16, is selected between 0.03 mm and 0.35 mm, preferably between 0.08 mm and 0.18 mm. The gap 30 is preferably wider in its end portion facing the neck part 32 than in the lateral portions and in the end portion facing the free end of the head part 14. The width of the gap 30 is preferably 0.1 mm to 0.2 mm in the end portion facing the neck part 32, is 0.09 mm to 0.19 mm in the end portion facing the free end, and is 0.03 mm to 0.35 mm, preferably 0.05 mm to 0.18 mm, in between in the lateral portions. The gap width preferably changes continuously. However, it is also conceivable to form a gap 30, which has a constant peripheral width in the range between 0.03 mm and 0.35 mm, preferably between 0.08 mm and 0.18 mm.
According to the general flow diagram of
It should be mentioned at this juncture that the stretching process is provided immediately after the welding process due to the fact that the zone close to the weld and the weld zone 51 are still hot, but can also be carried out elsewhere. In other words, the above-described embodiment by means of a stretching process at the welding station is understood to be exemplary.
The flow diagram of
The toothbrush body 12 is supplied to the round table 64′ and is placed in the receiving depression 66 of a receiving element 64 on the round table 64′ (see
The bristle carrier element 18 inserted into the toothbrush body 12 can be fixed in the mount 16 by means of a “primary holding mechanism”. The round table 64′ is rotated further, for example again through 90°, whilst the bristle carrier element is fixed in this manner. At the same time, the clamping mechanism, which clamps the toothbrush body 12 onto the support, is mechanically released a little and stabilized, so that it exerts merely a light pressure onto the toothbrush body 10, said pressure not increasing further. It is thus ensured, in this position of the round table 64′, that the clamping mechanism has no further influence on the process.
A re-clamping process may then be carried out, in which a “secondary holding mechanism” for holding the bristle carrier element 18 is moved theretowards and then the primary holding mechanism is moved away therefrom. In addition to holding the bristle carrier element 18, the secondary holding mechanism is also used to press the bristles 22 over the bristle field 24 in the direction of the center of the bristle carrier element 18. Space is then created so that the sonotrode 76 (see
The welding process is then carried out for a predetermined period of time, for example from 0.03 seconds to 0.8 seconds, preferably from 0.05 seconds to 0.2 seconds, in particular 0.08 seconds, as a result of the known corresponding excitation of the sonotrode 76. Up until this moment, the grip part 34 is preferably supported by means of a support (not shown in the figures). If this was the case, this support is moved away at this point so that the grip part 34 is released. Since the clamping mechanism has been released, the toothbrush body 12 is no longer loaded once the support has been moved away.
In the method step of “stretching the toothbrush body”, the neck part 32 is bent relative to the head part 14 by the angle α by corresponding control of the cylinder/piston assembly 82, as described further above, is held in this deflected position for the period mentioned and is then released again. The toothbrush body 12 can move back into its original shape automatically due to its resilience. This process of moving back can be assisted, however, by delivery of the previously mentioned support to the grip part 34 or by other aids. For the stretching process, the sonotrode 76 may be raised from the welding position by 0.1 mm to 0.5 mm, preferably 0.2 mm to 0.3 mm. Space can thus be created so that the toothbrush body 12 can expand during the stretching process at the corresponding points. The position preferably is not changed, however, and the sonotrode 76 remains in the position in which the welding process was concluded. If necessary, the position can be changed by forces, which act on the sonotrode 76 from the stretching process and through, the toothbrush body 12.
The sonotrode 76 is then moved away from its position in contact with the bristle carrier element 18, for example by being raised, and the round table 64′ is rotated, for example through a further 90°. The clamping mechanism is released again, either in parallel with the onset of the rotational movement or just before, so that it again holds the toothbrush body 12 on the receiving element 64 and the support under full pressure, inter alia even during rotation of the round table 64′. Only at a removal station is the clamping mechanism released and the toothbrush released. The finished, tufted and stretched toothbrush 10 is then removed from the receiving element 64 and from the support and is supplied to the further process steps, for example by means of a robot or manipulator.
If the bristles 22 have not been rounded beforehand, a further process step consists for example in rounding the ends of the bristles 22 in a known manner. Another further process step may consist in inscribing or printing or embossing the toothbrush body 12. A further process step may consist in packing the toothbrush 10.
With regard to the force/path measurement, it should also be noted that the force required for deflection, that is to say for the stretching process, does not play any role and is not considered. Merely the angle α reached is of importance.
The illustration in
It is also possible to attach the bristles to the carrier plate 20 by the IMT (in mold tufting) method and to then assemble said carrier plate in the mount 16 of the head part 14 and to weld it thereto, in particular by means of ultrasonic welding. It is also possible to produce toothbrushes 10 completely by the IMT method and to improve the fracture properties thereof by stretching them whilst they are still hot from the injection molding process. In this case, the hot state is generally caused by injection molding and not by a welding process.
A further tufting method, which can be applied in conjunction with the present invention, is the IAP (integrated anchorless production) method. In this case, too, the brush is stretched whilst still hot.
The variant shown, in which the receiving element 64 is arranged together with the further required devices about a round table 64′, is to be considered as an example. It is also possible to arrange the receiving element 64 in a peripheral chain, an endless conveyor or another suitably adapted transport means and to thus implement the invention in the production method.
It is also possible to attach part of the bristle field 24 to the head part 14 itself, and to attach the other part to the bristle carrier element 18. This may also apply in the case of rubbery-elastic cleaning elements.
The production method according to the invention is not only suitable for manual toothbrushes, but also for the production of sonic toothbrushes and electric toothbrushes having rotating and/or pivoting head parts 14.
Furthermore, other types of cosmetic, body care or oral hygiene products, for example tongue cleaners or interdental cleaners, can also be produced by the method according to the invention.
Reference sign 22′ in
The method according to the invention is suitable in particular if the toothbrush body 12 has been heated by means of an ultrasonic effect in the region of the head part 14 and/or the neck part 32.
So as to prevent connection of the outer surface 26 and the lateral surface 28, alternative variants are also possible besides the discussed variant of the gap 30. For example, adhesion reducers or adhesion suppressors may thus be printed, painted or sprayed onto the outer surface 26 and/or the lateral surface 28. Furthermore, the carrier plate 20 could be provided laterally with a soft component, which, similarly to the manner in which a seal acts, cannot be welded (due to the material properties), fills the gap 30 and thus prevents lateral welding.
Furthermore, the counter-surface 48 on the carrier plate 20 and/or the step 48 can be geometrically adapted to prevent lateral connection of the outer surface 26 and the lateral surface 28. Due to the provision of a reservoir/bunker/buffer in this surface, this element may collect some of the melt produced during ultrasonic welding so that the melt does not infiltrate the gap 30 and thus have a detrimental effect on fracture behavior.
It should also be mentioned that other arrangements of the weld bead 50 are also possible in order to provide the interface between the carrier plate 20 and the toothbrush body 12, which inter alia involves the mount 16. For example, the weld bead 50 may also be arranged at the free end of the centering wall 58. The accordingly adapted elements (base 46 and groove-like depression 54) contribute to the fact that the carrier plate 20 and the toothbrush body 12 are welded in the region of the base. Furthermore, the position of the weld bead 50 may also be varied with respect to the distance from the base 46 and to the front face 36 of the toothbrush body 12. As already described previously, the position is more likely deeper than illustrated. Other possibilities not discussed for the arrangement and geometric adaptation of the elements are not ruled out by the invention.
The ultrasonic welding process is defined by means of different parameters. The weld path, that is to say the path covered by the sonotrode 76 during the welding process, is thus between 0.05 mm and 0.4 mm, preferably 0.15 mm to 0.2 mm. The sonotrode 76 is excited by ultrasound with a frequency of 25,000 Hz to 45,000 Hz, preferably of 35,000 Hz to 40,000 Hz, at an amplitude of 0.02 mm to 0.12 mm, preferably 0.05 mm to 0.09 mm. An energy of 5 Ws to 35 Ws is thus expended, preferably 15 Ws to 25 Ws. With this parameter constellation and the previously described geometry, the welding process lasts from 0.03 seconds to 0.8 seconds, preferably from 0.05 seconds to 0.2 seconds, in particular 0.08 seconds.
Of course, the variants shown in this document are exemplary and the individual characteristics and elements of these variants can be combined with other variants without departing from the scope of this invention.
For the sake of completeness, it should be mentioned that it is possible to determine from the toothbrush 10 itself, for example by means of polarization microscopy, whether or not the toothbrush body 12 has been stretched. This is the case in particular with the use of transparent or opaque material for the toothbrush body 12.
The descriptions given for specific figures can of course also be transferred to other figures showing like or similar characteristics and in which the characteristics have not been described to the same level of detail.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10000699 | Jan 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/007797 | 12/20/2010 | WO | 00 | 7/25/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/091835 | 8/4/2011 | WO | A |
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| Number | Date | Country |
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| 200 06 311 | Aug 2001 | DE |
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| Entry |
|---|
| International Search Report issued in International Patent Application No. PCT/EP2010/007797 dated Mar. 16, 2011 (with translation). |
| Aug. 7, 2012 English translation of International Preliminary Report on Patentability issued in International Patent Application No. PCT/EP2010/007797. |
| Number | Date | Country | |
|---|---|---|---|
| 20120284945 A1 | Nov 2012 | US |
