AND TOOTHBRUSHES PRODUCED BY THE PROCESS,

The present invention relates to a process for producing a toothbrush having a toothbrush head which is provided with a first and a second bristle- supporting head portion, where the head portions in a finished condition have a concavely curved contour or have the main plane extending at an angle a of less than 180 to each other, bristles of the head portions being directed obliquely inwards towards each other at an angle b = 80-180°. Tooth brushes are known the toothbrush head of which is provided with a first and a second bristle- supporting head portion, which permits that two or more surfaces (outside, inside and masticating sur¬ faces) on a tooth in a series of teeth can be simul- taneously brushed. From French Patent Specification 1,230,365 it is known to allow the bristle end planes to form an angle of between 40 and 80°. In Austrian Patent Specification 352,260 bristle end planes are proposed and illustrated which form an angle substantially below 40 . In United States Patent Specification 4,115,894 several different designs of toothbrush heads are proposed with diffe¬ rent angles for the head portions and with different angles for the bristle end planes. In order to achieve the best possible effect of brushing teeth with two obliquely impacting groups of bristles provision has been made for the bristles in each group to have the shortest bristle innermost and the longest bristle outermost, reckoned from the point of

the bristle end planes impacting in V form. However such a bristle design involves significant manufac¬ turing problems, since is has been difficult with simple means and in a simple way to cut and polish the bristle end plane of the two head portions simultaneously. As a consequence of said manufac¬ turing problems toothbrushes of the afore-mentioned kind, even if they exhibit significantly useful advan¬ tages, have not been competitive from a price point of view relative to conventional toothbrushes having a simple toothbrush head.

According to United States Patent Specification 4,449,266 it has been proposed to install the bristles in the two head portions, while these are present in a flush position to each other, after which the bristles - while the head portions still occupy the same mutually flush position - are cut and polished and the head portions are finally bent into a finished position. The problem with such a mode of manufacture is that the bristle end planes are cut and polished at an angle relative to each other. Both the cutting equipment and the polishing equip¬ ment must necessarily be of complicated design if one is to be able to effect the cutting operation and the polishing operation in an accurate manner. Special problems involve the polishing device being mainly able to rotate in a specific position with¬ out substantial -sideways movement, as is otherwise customary in the polishing of the bristle end sur- face of a toothbrush. The toothbrush materials must thereby be worked singly to a large extent.

With the present invention the aim is to avoid the afore-mentioned problems, conventional cutting equipment and polishing equipment being able to be employed according to the invention and this equip¬ ment being able to be moved in a conventional manner in one and the same plane along the bristle end

planes. In this way there is the possibility of simul¬ taneously finishing a large group of toothbrush materials with associated bristles in a common cutting operation and thereafter in a common polishing ope- ration, in a conventional manner.

The process according to the invention is characterised in that the bristles, after they are installed in their respective head portions approxi¬ mately at right angles (80-100°) to the main plane of the head portion, are cut and polished at the ends jointly in a position where the head portions form a convex arc or where the main planes of the head portions form an angle d greater than 180 with each other, after which the head portions are bent into a concavely curved contour or into a position where the main planes of the head portions extend at said angle a. to each other.

By providing according to the invention a con¬ vex arc or a "negative" bending angle for the head portion, while cutting and polishing is effected, there is the possibility of utilising conventional equipment for mass production in a simple and uncom¬ plicated manner, so that there is achieved a precisely defined cutting and polishing having a high degree of quality on the two groups of bristles of the toothbrush material, which thereafter are bent towards each other into a finished condition.

In order to ensure an accurate establishment of the intended angle between the bristle end planes the bending operation can be controlled to finished position with the aid of simple means. In this connection it is preferred that the process accor¬ ding to the invention is characterised by using a toothbrush material which, at any rate at the tooth- brush head and if desired over the whole length of the toothbrush material, is provided with one or more mutually parallel, hinge—forming attenuation

line(s), formed by V-shaped grooves, the side surfaces of the V-shaped groove after bending into the position of finished design form support abutments against each other and said side surfaces in said position of finished design being glued or welded into permanent connection with each other.

The invention also relates to a toothbrush pro¬ duced by the process according to the invention, where the head of the toothbrush is provided with mutually angled head portions having rows of bristle groups directed obliquely towards each other.

The toothbrush is characterised in that outer edges of the toothbrush head converge in a direction forwards towards the longitudinal central plane of the toothbrush, and that the groups of bristles are arranged in equivalent forwardly converging rows.

A toothbrush is preferred, where the groups of bristles at the inner front edge portion of the toothbrush head are significantly shorter than the groups of bristles at the outer rear edge portion of the toothbrush head.

The toothbrush is characterised in that a smaller number of groups of bristles are arranged at the front edge of each of the head portions of the toothbrush head than at the rear edge of said head portions, and that between inner edges of the head portions facing towards each other there is cut out a forwardly opening V-shaped groove, while corre¬ spondingly between inner rows of groups of bristles of the head portions there is fashioned a similar forwardly opening V-shaped groove at outer portions of the bristles, at least between the groups of bristles at front inner edges of the head portions. Further features of the invention will be evident from the following description having regard to the accompanying drawings, in which:

Fig. 1-3 show in section a preliminary operation

known per se for installing bristles in two head portions of a toothbrush blank.

Fig. 4 and 5 show the step of heating and a first bending with a "negative" angle. Fig. 6 and 7 show respectively the cutting operation and the polishing operation with the head portions bent in a "negative" angle.

Fig. 8 shows the head portions with associated bristles in a finished condition. Fig. 9 shows a toothbrush blank according to the invention illustrated from the back side.

Fig. 10 shows a toothbrush blank according to the invention according to an alternative construc¬ tion, illustrated from the back side, correspondingly as in Fig. 9.

Fig. 11-18 show in section production steps as shown correspondingly in Fig. 1-8 and based on a toothbrush blank in accordance with Fig. 10.

Fig. 19 shows in plan a part of a toothbrush blank in a third embodiment.

Fig. 20 shows the toothbrush blank according to Fig. 19 with associated bristles during cutting, seen from the side.

Fig. 21 shows in part the toothbrush head accor- ding to the embodiment of Fig. 19, after completing bending into the ready for use condition, illustrated in perspective from the front.

In Fig. 1 and 9 there are shown two head por¬ tions 20 and 21 which are supported by a common handle 22 (Fig. 9), and which together constitute a toothbrush blank. The head portions 20 and 21 have the main planes as indicated by chain lines 20a and 21a extending in alignment with each other, that is to say they form an intermediate angle of 180 with each other.

In Fig. 2 the head portions 20 and 21 are shown after they have been fashioned with a series of bores

or with precast holes 23, and in Fig. 3 there are shown fastened-in groups of bristles 24 received in the bores or the holes 23 in the head portions 20 and 21. In Fig. 4 the head part of the toothbrush blank is subjected to heating shown by arrows 25a locally along an attentuation line 25 (Fig. 9) as indicated by a first obtuse, U-shaped cavity on the under side and a certain, V-shaped angle on the upper side of the transition portion between the head portions 20 and 21.

In Fig. 5 the main plane 20a and 21a of the head portions are bent to an intermediate "negative" angle d of 210 . In Fig. 6 a cutting operation is ^' shown illustrated by a broken straight line 26 which shows that all the bristles are cut with a common cut in one and the same plane. Correspondingly there is shown schematically in Fig. 7 a polishing operation illustrated by arrows 27, the polishing equipment being able to be moved in a pattern of movement parallel to the line 26 on Fig. 6. After the polishing operation is effected, a new heating of the hinge-forming transition portion between the head portions 20, 21 is undertaken, after which the head portions 20, 21 are pivoted back an angle d - a = 110 and the main planes 20a and 21a of the head portions assume an intermediate angle a equal to 100 . This angle can be guaranteed in an accurately established manner by allowing the side surfaces along the V- shaped groove of the attentuation line 25 to form a supporting abutment against each other. Finally the head portions 20, 21 are connected in rigid combi¬ nation with each other in that said side surfaces are glued, welded or jointed together in another manner into a permanent and rigid union with each other. In the position which is shown in Fig. 8 the bristles in the first head portion 20 and the bristles in the

second head portion 21 assume an angle b = a relative to each other, that is to say an angle b_ = 100 . As a consequence of the cutting to the "negative" angle d as shown in Fig. 5, that is to say an angle d = 210 , the bristle end planes 20b and 21b of the bristles of the two head portions 20 and 21 will form an angle £ with each other, that is to say an angle c = 75 .

Instead of effecting the bending from the position of Fig. 4 to the position of Fig. 5 the brush heads can if desired be produced in the position which is illustrated in Fig. 5, the bristles being able to be installed directly into the brush head in the position shown in Fig. 5.

In Fig. 10 there is shown a toothbrush blank 30-33 consisting of a first head portion 30 and a second head portion 31 together with an intermediate head portion 32 which forms a planar extension of the handle 33.

As shown in Fig. 10 and 11, each of the head portions 30, 31 are connected to the intermediate head portion 32 via attentuation lines 34 and 35 shown in the form of a V-shaped groove on one side of the toothbrush blank. The side surfaces which define said grooves form in a manner corresponding to that shown in Fig. 8 stop-forming support abutments against each other and cooperating joint surfaces between the head portions, such as illustrated in Fig. 18, the pro¬ duction taking place in Fig. 11-18 in an equivalent manner to that shown and descibed in connection with Fig. 1-8 according to the first embodiment.

In the illustrated embodiments there are shown head parts which are adapted to be angled with narrow angles relative to each other along one or two hinge- forming attentuation lines. If desired two or three such attentuation lines can be employed. By employing said attentuation lines short heating times can be employed, at the same time as reliable control of the

bending operation can be obtained. Alternatively one can effect, instead of narrow angled bends, bending froma convex to a concave arcuate shape, by under¬ taking heating of the whole of the head parts and fashioning the latter by means of an extra moulding surface or extra moulding means.

By employing said arcuate shape of the head part there is the possibility of fashioning the head portion in an easy manner into different variants as required, that is to say with different shapes of the bristles in one and the same group or with diffe¬ rent shapes of the groups of bristles.

While there is shown herein only two head portions with their respective group of bristles three or more head parts can be alternatively employed, each with its respective group of bristles. In the con¬ struction which is illustrated in Fig. 10, 18 the central main part can for example be provided with a separate group of bristles which can be received between the groups of bristles of the two remaining head parts.

In Fig. 19-21 there is shown a third embodiment according to the invention. The toothbrush blank 40 as shown in Fig. 19 is provided with a handle portion 41 which via a Y-shaped transition portion 42 branches into two mutually separate head parts 43 and 44. Each of the two head parts is shown provided with five rows of holes 45, that is to say rearmost at the transition portion 41 with two rows each with four holes and three rows each with three holes, for the reception of their respective group of bristles in the conven¬ tionally known manner. The two head parts 43 and 44 are each provided with a tapered shape in a forward direction and the rows of holes are arranged in each head part in an equivalent tapered shape. The head parts 43, 44 are mutually separated via an inter¬ mediate, forwardly opening gap 46.

In Fig. 19 the blank 40 is shown with the head parts arranged in a mutually aligned position (as shown correspondingly in Fig. 4 and 14) for installing the groups of brushes at right angles to the head parts. Alternatively the groups of brushes can be in¬ stalled at larger or smaller oblique angles relative to the plane of the head parts. After the groups of brushes are mounted in position the head parts are bent to a negative angle corresponding to that shown in Fig. 5 and 15 for cutting as is shown in Fig. 6 and 16. In the present embodiment the section surface 5 is disposed in addition obliquely inclined from the front edge to the rear edge, as is shown in Fig. 20. Thereafter final working is effected in a correspon- ding position, as illustrated correspondingly in Fig. 7 and 17, before head parts 43 and 44 of the blank are bent with a positive angle as shown correspondingly in Fig. 8 and 18. In Fig. 21 there is indicated in a per¬ spective view the brush head parts 43, 44 in a finished bent form. It should be evident from this that the foremost groups of bristles have smaller height than the rearmost groups of bristles and that at the outer edges the groups of bristles have a greater height than at the inner edges of the groups of bristles, that is to say at the edges of the head parts facing each other. Furthermore it is evident that at the front edge of the head of the toothbrush there is formed a V-shaped gap 47 between the groups of bristles at said inner edges. According to the third embodiment there is achieved with the tapered head parts and equivalent tapered rows of groups of bristles a possibility for effective penetration of the toothbrush into the oral cavity in a relatively gentle manner and a simul- taneous possibility for effective treatment of even the rearmost molars in the oral cavity. By means of the gap 47 between the groups of bristles of the two

head parts there can be ensured an effective control of the head of the toothbrush along top edges of the rows of teeth with an oblique positioning against the rearmost molar. In addition there can be ensured with the relatively short groups of bristles at the front edge of the head of the toothbrush an especially effective brushing effect, mainly for brushing chewing surfaces and top parts of the teeth, and with the relatively long groups of bristles at the back parts of the toothbrush a gentle sweeping of the neck portions of the teeth and adjacent gum portions of the teeth is ensured.-