Abstract:
In a method for the production of brushes consisting of a bristle support and bristles mounted thereon and combined to at least one group having a defined cross-section with at least two different types of bristles, the bristles of a bristle type are combined into a partial group and the partial groups forming a bristle group are combined into said bristle group and subsequently, the bristle group is mounted to the bristle support. The bristles of each partial group are formed in a surrounding guide of a shaping device into a cross-section corresponding to their partial cross-sections in the bristle group, and the partial groups are then combined while maintaining their partial cross-section in the guides to form the cross-section of the bristle group. A device for carrying out this method and brushes produced in this fashion are also described.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a method for the production of brushes, consisting of a bristle support and bristles of at least two different bristle types which are fastened thereto and combined to at least one group having a defined cross-section by uniting the bristles of one bristle type to form a partial group and the partial groups forming the bristle group are combined in converging guides to form the bristle group, wherein the bristle group is subsequently attached to the bristle support. The invention also concerns a device for carrying out the method. 
     Conventional brushes consist of a bristle support and bristles fastened thereon which are usually combined to form bristle groups, e.g. bundles. The bristle groups are mounted to the bristle support either mechanically, using the so-called punching method, or, if the bristles and bristle supports are made from plastic, more recently using a thermal process, in optional combination with a mechanical deformation method. Such recent methods include welding of the bristles onto the surface of the bristle support, inserting the bristle bundles into a bristle support surface which is melted to a greater or lesser extent or injection molding the bundle by melting the bristle ends at the bundle foot to form an enlargement and extruding bristle support material around this area. These thermal methods have been used, in particular, for tooth brushes, hygiene brushes etc. 
     The selection of bristles with regard to material, cross-section and length depends largely on the intended use of the brush. The arrangement and number of bristles in a bundle, the arrangement and shape of the bundles themselves or of the bristles which are combined into groups vary in dependence on the intended use. The term brushes also includes brush-like devices for applying media, wherein the bristles are generally disposed in one group only, i.e. a bundle, a package or the like. 
     As has been known in the art for some time, tooth brushes having a straight cut brush stock, i.e. with all bristle ends disposed in one plane, do not satisfy dental hygienic requirements, since the curved as well as uneven tooth surfaces and the interdental spaces are not adequately cleaned. For these reasons, tooth brushes were developed having bristle ends lying in envelope surfaces contoured to a greater or lesser degree, by e.g. providing the bristle stock with a wavy cut. There are also conventional brushes which have the ends of bristles of an individual bundle disposed on a conical surface. All these measures are intended to assure that the bristles reach into the interdental spaces. 
     Dental medical evaluations of such tooth brushes have, however, shown that the tips of individual bundles or the apex of a wavy cut are unacceptably aggressive on the smooth tooth surfaces and leave grinding traces on the enamel. They can also lead to injury of the gum and gingiva which causes discomfort, especially with sensitive gums. 
     These disadvantageous consequences can be alleviated, but not eliminated, by a conventional tooth brush (WO 96/16571). Its bristle stock consists of individual bundles whose ends lie in a conical surface having the above mentioned aggressive tip. Moreover, each bundle contains individual bristles which are longer than the other bristles in the bundles and whose ends are disposed in one single plane. These individual bristles thereby slightly protrude past the bundled bristles. This configuration is intended to improve cleaning of the interdental spaces, since the individual bristles can more easily access such areas compared to conical bundles. These brushes are difficult to manufacture, since the individual bristles have to be drawn into the bundles in a separate processing step. 
     Macroscopic studies have shown that the tooth surfaces have fine cracks into which conventional bristles, due to their diameter, cannot enter and which are therefore not cleaned. Thinner, fiber-like bristles (DE 94 08 268 U1) which are wrapped in an enclosed envelope, with only the ends protruding past the wrapping, were proposed for cleaning and gentle treatment of the gums. These thin fibers fold down outside the wrapping envelope and have almost no effect. In addition, the sharp envelope edge increases the danger of injury to the gums and gingiva as well as possible damage to the tooth surface due to grinding traces. This conventional tooth brush is also very difficult to manufacture. 
     With tooth brushes and also with other brushes, such as paint brushes and the like, the bristle groups must be arranged in defined geometrical shapes and different types of bristles must be inserted into the bristle stock or individual bristle groups forming same to achieve the effects required for the respective application. DE 16 04 673 discloses bundles having differing cross-sectional shapes and DE 35 05 972 discloses combining the bristle stock of differently shaped bundles. These different bundle shapes are generated by rolling endless monofilaments to form a cord, wherein each cord consists of a number of monofilaments corresponding to the number of bristles in a bundle. The monofilament cord is pulled or pushed through a shaping device which forms the cord, of irregular cross-sectional shape, into the desired cross-sectional shape. Downstream of the shaping device, the bundles are cut to the desired length and fastened to the bristle support. This only allows variation of the bundle shape. 
     DE 196 16 309 suggests the production of bundles of bristles of different types by winding together endless monofilaments of various types to form a cord, from which individual bundles are cut. In this case, different types of bristles are present within the bundle in a static, uniform distribution. The various bristles are not distributed and arranged in dependence on the application. EP-A1-0 716 821 discloses tooth and body care brushes with which the bristles are collected into groups containing different kinds of bristles. 
     In conventional brushes having injection molded bundles (U.S. Pat. No. 5,728,408) the bristles, cut to bundle length, are removed from a magazine using punching tubes and inserted in bundle channels of an injection molding form and into the mold cavity. Several bundles of circular cross-section can thereby be combined via converging channels, next to one another, into stripe-shaped bristle groups having a width corresponding to the bundle diameter. Neighboring bundles may comprise various bristles disposed next to one another in the stripe-shaped bristle group. The various types of bristles thereby disadvantageously mix in the transition area between neighboring bundles and are not effective in this area. Since bristles of various types are adjacent to one another in the stripe-shaped bristle group and are used in the same manner during brushing, both types of brushes display differing signs of premature wear. 
     It is the underlying purpose of the invention to further develop the conventional method of U.S. Pat. No. 5,728,408 according to the preamble of claim 1 in such a manner that brushes can be produced in any form and in dependence on the intended use which have bristle groups consisting of partial groups of various cross-sections, with bristles of different types and different numbers in the partial groups. 
     SUMMARY OF THE INVENTION 
     This object is achieved in accordance with the invention in that the bristles of each partial group are shaped in a surrounding shaping device guide to obtain a cross-section corresponding to their partial cross-section in the bristle group and the partial groups are then combined in the guides to obtain the cross-sectional shape of the bristle group. Preferably, the bristle group is then transferred to a holding means to transport the bristle group for fastening to the bristle support. The finished bristle group can also be attached to the bristle support directly after shaping. 
     The method according to the invention permits production of a bristle group of defined cross-section from partial groups of various bristle types also having defined partial cross-sections such that the various types of bristles are present within the bristle group in a defined geometrical shape optimally adapted to the respective use of the brush. With this geometrical shape generated by the shaping device, the bristle groups or the partial groups forming same may be subsequently fixed in the holding means and fastened to the bristle support using conventional mechanical or thermal methods while maintaining this geometrical shape. The inventive method can generate bristle groups of arbitrary cross-section within which the partial groups of arbitrary cross-section are arranged to always optimize the respective intended use. The partial groups may thereby be arranged e.g. concentrically, in the form of segments, sectors or stripes. The invention permits different numbers of bristles to be used in each partial group. 
     Preferably, the bristles of each partial group are compressed during shaping into close proximity to one another and support each other within the partial group. This dense packaging of bristles is particularly advantageous for thermal fastening of the bristle group on the bristle support, since the softened plastic mass of the bristle support cannot enter between the bristles. 
     With the method in accordance with the invention, all groups of bristles in the bristle stock of the brush can be simultaneously or sequentially formed in the shaping device. In either event, they can be passed on to a holding means accepting all bristle groups for attaching the complete bristle stock to the bristle support. 
     In a preferred embodiment, the partial groups, after being combined to form a bristle group, are transferred, with different lengths, to the holding means and are cut flat at a location between the shaping device and the holding means. 
     This allows the useful ends of the partial groups forming the bristle groups to be disposed in different planes such that their different characteristics can be simultaneously effective during brushing. 
     The bristle groups are preferably clamped in the holding means to fix the geometrical shape generated by the shaping device. 
     This allows, in particular, the useful ends of the bristles of the bristle groups clamped in the holding means to be mechanically treated, e.g. rounded, and also facilitates preparation of their opposite ends for mounting to the bristle support: e.g. to melt them into a bundle foot, to shape them, or to size them. 
     In the unclamped state, the holding means also permit axial displacement of the bristles therein relative to one another to bring the useful ends of each partial group into different envelope surfaces. These surfaces may be curved in a smooth or non-smooth manner. 
     The method according to the invention permits the partial groups to be in close proximity to each other during formation of a bristle group and to be tightly packed together to form a bristle group with defined, bordering surfaces always being located between the partial groups. 
     In a preferred embodiment, the bristles of the partial groups are made from endless monofilaments by accommodating bristles of the same type, in the form of endless monofilament cords, on separate spools, removing the cords of bristles from the spools and introducing them into the guides to form one partial group each, wherein the bristles of all partial groups forming a bristle group are simultaneously supplied to the guides. The cords forming the partial groups may have different amounts of endless monofilaments. 
     The partial groups may also be made from short-cut bristles of appropriate length. 
     The invention further concerns a device for carrying out the method according to the invention. A device of this type forms a bristle group comprising at least two partial groups of different type bristles, by providing at least one spool with a cord of monofilaments having the same type of bristle, for each partial group, and with at least one drawing device, disposed downstream of the spool, with one guiding channel for each cord and, downstream of the drawing device, a stationary shaping device having a corresponding number of shaping channels whose openings facing the drawing devices are aligned with the guiding channels, wherein the opening thereof has a cross-sectional shape that varies into the partial cross-section of the partial group and simultaneously converges towards an envelope cross-section corresponding to the cross-section of the bristle group. A moveable holding means for the bristle group is advantageously disposed downstream of the shaping device having holding channels whose shape and arrangement correspond to those of the guiding channels of the drawing device facing same, wherein the cords can be removed from the spools by the linearly moveable drawing device, and can be pushed through the shaping device and optionally transferred to the downstream holding means, and further comprising a cutting device, disposed between the shaping device and the holding means, for cutting the bristle group, located in the holding means, to a desired length, wherein, the holding means with the bristle group can be moved for mounting the bristle group to the bristle support. 
     The device according to the invention cyclically produces the bristle groups, or the entire bristle stock, from several bristle groups which are then fastened to the bristle support or transported by the holding means to be fastened thereto. 
     The shaping channels of the shaping device can simultaneously taper in the direction of their cross-sectional variation such that the bristles of the partial group are simultaneously compressed during shaping. 
     In a preferred embodiment, at least two separately movable drawing devices are disposed one after the other, which, either individually or collectively, cooperate with the cords forming the partial groups to insert the partial groups into the holding means to the same or differing extents. 
     In this manner, partial groups of differing lengths can be easily made within one bristle group. 
     The drawing device and the holding means preferably comprise parallel layered plates, one of which is a clamping plate which can be moved transverse to the guiding or holding channels. 
     With the inventive device, the holding means with the clamped bristle group can be transported to a processing device and/or a device for treatment of the useful bristle ends and/or of the bristle ends which are to be mounted, before the bristle group or the bristle stock, consisting of several bristle groups, is fastened to the bristle support. 
     The method and device in accordance with the invention facilitate production of brushes having a bristle stock formed from bristle groups of defined cross-sectional shapes and having at least two partial groups of bristles of various types with complementary cross-sectional shape, wherein flat or curved bordering surfaces are formed between the at least two partial groups of a bristle group. Undefined mixing of the various bristle types is prevented and the partial groups are disposed within each bristle group in defined geometrical shape. 
     The at least one partial group of a bristle group may thereby surround the other partial group, e.g. two partial groups can be disposed concentric to one another. Several partial groups of a bristle group can also surround a central partial group in a concentric fashion. 
     The at least two partial groups of a bristle group can consist of bristles of various cross-sections, various cross-sectional shapes, various materials, various material compositions or material characteristics, various surface conditions or various colors. 
     A preferred embodiment provides that the partial group within a bristle group consists of bristles having a lower flexural strength that that of the bristles in the partial group(s) surrounding this partial group. In this way the inner, softer, e.g. thinner bristles are supported from all sides along at least part of their length. 
     In each bristle group of this embodiment, the partial group of the bristles having the lower flexural strength can protrude past the ends of the surrounding bristles having the higher flexural strength. 
     Bach bristle group can have the ends of partial group bristles disposed in flat, optionally differing envelope surfaces or in curved envelope surfaces and, optionally, in envelope surfaces of various curvatures. 
     The ends of the bristles of all partial groups of a bristle group are preferably disposed in a smoothly curved envelope surface which, in a further advantageous embodiment, is symmetric with respect to an axis extending parallel to the bristles of the bristle group. 
     The invention is described below with embodiments shown in the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 shows a schematic side view of the device for carrying out the method; 
     FIG. 2 shows a first section of the device of FIG. 1; 
     FIG. 3 shows a second section of the device of FIG. 1; 
     FIG. 4 shows a third section of the device of FIG. 1; 
     FIG. 5 shows a fourth section of the device of FIG. 1; 
     FIG. 6 shows a fifth section of the device of FIG. 1; 
     FIG. 7 shows the device of FIG. 1 in a first stage of the method; 
     FIG. 8 shows the device of FIG. 1 in a second stage of the method; 
     FIG. 9 shows the device of FIG. 1 in a third stage of the method; 
     FIG. 10 shows the device of FIG. 1 in a fourth stage of the method; 
     FIG. 11 shows the device of FIG. 1 in a fifth stage of the method; 
     FIG. 12 shows the device of FIG. 1 in a sixth stage of the method; 
     FIG. 13 shows a first view of a further embodiment of a device for carrying out the method; 
     FIG. 14 shows a second view of the further embodiment; 
     FIG. 15 shows a third view of the further embodiment; 
     FIG. 16 shows a fourth view of the further embodiment; 
     FIG. 17 shows a fifth view of the further embodiment; 
     FIG. 18 shows a schematic side view of a longitudinal section of a first embodiment of a bristle group; 
     FIG. 19 shows a schematic side view of a longitudinal section of a second embodiment of a bristle group; 
     FIG. 20 shows a schematic side view of a longitudinal section of a third embodiment of a bristle group; 
     FIG. 21 shows a schematic side view of a longitudinal section of a fourth embodiment of a bristle group; 
     FIG. 22 shows a top view of a bristle group comprising a first partial group; 
     FIG. 23 shows a top view of a bristle group comprising a second partial group; 
     FIG. 24 shows a top view of a bristle group comprising a third partial group; 
     FIG. 25 shows a top view of a bristle group comprising a fourth partial group; 
     FIG. 26 shows a top view of a bristle group comprising a fifth partial group; 
     FIG. 27 shows a top view of a bristle group comprising a sixth partial group; 
     FIG. 28 shows a top view of a bristle group comprising a seventh partial group; 
     FIG. 29 shows a top view of a bristle group comprising an eighth partial group; 
     FIG. 30 shows a top view of a bristle group comprising a ninth partial group; 
     FIG. 31 shows a top view of a bristle group comprising a tenth partial group; 
     FIG. 32 shows a side view of a bristle group comprising two partial groups; 
     FIG. 33 shows a top view of the bristle group of FIG. 32; 
     FIG. 34 shows a side view of a bristle group with two partial groups in a different embodiment; 
     FIG. 35 shows a top view of the embodiment according to FIG. 34; 
     FIG. 36 shows a perspective partial view of a tooth brush head; 
     FIG. 37 shows a perspective partial view of a different embodiment of a tooth brush head; 
     FIG. 38 shows a side view of FIG. 37; 
     FIG. 39 shows a top view of FIG. 37; 
     FIG. 40 shows a perspective partial view of a tooth brush head in a modified embodiment; 
     FIG. 41 shows a partial longitudinal section through the tooth brush head according to FIG. 40; 
     FIG. 42 shows a perspective partial view of a tooth brush head for an electric tooth brush; 
     FIG. 43 shows a perspective view of a replaceable head for an electric tooth brush,; 
     FIG. 44 a  shows a view of a first embodiment of an application brush; 
     FIG. 44 b  shows a top view of the first embodiment of an application brush; 
     FIG. 45 a  shows a view of a second embodiment of an application brush; 
     FIG. 45 b  shows a top view of the second embodiment of an application brush; 
     FIG. 46 a  shows a view of a third embodiment of an application brush; 
     FIG. 46 b  shows a top view of the third embodiment of an application brush; 
     FIG. 47 shows a partial view of a brush; 
     FIG. 48 shows a top view of the brush according to FIG. 43; and 
     FIG. 49 shows a view of the brushes according to FIG. 47, rotated through 90°. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The device shown in FIG. 1 serves for the production of bristle groups from partial groups of various types of bristles, wherein the bristles of each partial group are combined from endless monofilaments into a cord and e.g. disposed on spools from which they are removed by the device according to FIG.  1  and processed into bristle groups. The device in the embodiment shown comprises two drawing devices  1 , 2 , disposed one after the other, a shaping device  3  disposed downstream of the drawing device  2  and a holding means  4  disposed downstream of the shaping device  3 . The drawing devices  1  and  2  can be linearly displaced in the direction of the double arrows  5  and  6 , respectively, whereas the shaping device  3  is stationary. The holding means  4  can be moved in accordance with the double arrow  7 . The embodiment shown also comprises a cutting device  8  downstream of the shaping device  3 . 
     The device according to FIG. 1 serves for the production of a bristle group comprising a central partial group and six partial groups enclosing same (see FIG.  5 ). Each drawing device  1  comprises two outer plates  9  with a total of seven guiding channels  10 , each for an external cord  11 , and a central cord  12 . The external cords  11  consist of one single bristle type, e.g. of bristles having a relatively large cross-section, whereas the central cord  12  consists of endless monofilaments of a smaller cross-section. The cords  11 ,  12  are guided with play in the guiding channels  10  of the two outer plates  9 . The drawing device  1  comprises a clamping plate  13  between the two plates  9  which can be displaced transversely to the cords  11 ,  12 , as shown by the double arrow. 
     The drawing device  2  likewise comprises external plates  9 ,  9  with guiding channels  10  and a central clamping plate  17 . The clamping plate  13  has channels  18  of larger cross-section which are aligned with the guiding channels  10 , and a central guiding channel  19  of smaller cross-section (FIG.  3 ). The clamping plate  17  has channels  20  aligned with the guiding channels  10 , for the cords  11  of identical cross-section, and a central channel  21  of larger cross-section (FIG.  4 ). 
     The shaping device  3  has a number of shaping channels  15 ,  16  which corresponds with the number of guiding channels of the drawing device  1 ,  2 . The shaping channel  16  is aligned with the central channel of the drawing devices  1 ,  2 , and the openings in the peripheral shaping channels  15  facing the drawing device  2  are aligned with the guiding channels  10 . The shaping channels  15  converge towards the central shaping channel  16  at the opposing side openings. Shaping channel  16  has a constant circular cross-section. The cross-sections of the peripheral shaping channels  15  vary in the direction of their conversion from a circular cross-section at the inlet opening to a circular sector shaped cross-section at the opposing opening. 
     The holding means  4  is structured as a clamping device. It comprises two external plates  22 ,  23  and a central clamping plate  24  which can be displaced in the direction of the double arrow  25 . The holding means  4  comprises a central holding channel  25  which is closely surrounded by peripheral holding channels  26  which are disposed with respect to one another in the same manner as the shaping channels  15  and  16  at the opening facing the holding means  4 . As shown in FIG. 6, narrow braces  14  are disposed between the peripheral holding channels  26  and between these channels and the central holding channel  25 . 
     FIGS. 7 to  12  describe operation of the device. At the start of operation, the cords  11  and  12  are inserted at the drawing devices  1  and  2  into the shaping device  3  with the clamping plates  13 ,  17  open. This shapes the leading ends of the cords  11 ,  12  in the shaping device to achieve the corresponding partial cross-sections of the partial groups. During the first operating cycle, the clamping plate  17  is closed, thus clamping the outer cords  11 . The clamping plate  13  remains in its open position. The drawing devices  1  and  2  then move towards the right (FIG. 8) until the cords  11  have been pushed through the holding means  4 , the clamping plate  24  of which is also in the open position, such that the cords  11  protrude past the holding means  4 . The drawing device  2  thereby abuts against shaping device  3 . 
     The clamping plate  17  of the drawing device  2  is then opened and the clamping plate  13  of the drawing device  1  is closed and drawing device  1  is moved towards drawing device  2  (FIG.  9 ). The drawing device  1  carries only the central cord  12  for the central partial group of the bristle group and pushes it through the shaping device  3  and the holding means  4  until its leading end protrudes past the cords  11  already disposed in the holding means. The clamping plates  13 ,  17  are then opened to release the cords in the drawing devices  1  and  2 . The holding means  4  is moved away from the shaping device  3  with the clamping plate  24  closed and thereby pulls the cords  11 ,  12  through the shaping device  3  (FIG.  10 ). The cutting device  8  is then lowered in front of the shaping device  3  to cut the cords clamped within the holding means  4  at the shaping device  3  (FIG.  11 ). The holding means  4  fixes a bristle group (FIG. 12) consisting of outer partial groups  27  and a central partial group  28  whose cross-section and correlation with respect to one another is shown in FIG. 5. A new holding means  4  is then disposed in front of the shaping device  3  (FIG.  12 ), the drawing devices  1  and  2  are withdrawn and a new working cycle starts as delineated with reference to FIG.  7 . 
     The holding means  4  can then be transported to processing stations to e.g. treat the useful ends  29  of the partial group  28  and the useful ends  30  of the partial group  27  (e.g. round them off). The partial groups may also be displaced axially with respect to one another after releasing the clamping plate  24  to dispose the useful ends  29 , 30  in any desired envelope surface. The opposing ends  32  of the entire bristle group  31  may also be processed for mounting to the bristle support. For example, the ends may be melted together, shaped or sized. 
     The device according to FIGS. 1 to  12  processes endless monofilaments. The device of FIGS. 13 to  17  processes so-called short cuts, wherein the partial groups forming the bristle group are already cut to the required length. This latter device comprises a guiding block  33  having guiding channels  34  followed by a shaping device  35  with converging shaping channels  36  and a central shaping channel  37 . The shaping channels  36  have cross-sectional shapes which change in the direction of conversion. The shaping device  35  is followed by a holding means  38  comprising a central clamping plate  39 . The holding means  38  has peripheral holding channels  40  and a central holding channel  41  which are aligned with the openings of the shaping channels  36  and  37  facing the holding means. The short cuts  42 , each constituting one peripheral partial group within the bristle group, are inserted into the guiding channels  34  of the guiding block  33  and displaced into the shaping channels  36  of the shaping device  35  via punches inserted into the channels  34  until they finally pass through and protrude past the front of the holding means  38  (FIG.  14 ). The guiding block  33  is then removed and a guiding block  44  with a central guiding channel  45  is disposed in front of the shaping device  38  for a short cut  46  forming the central partial group (FIG.  15 ). The short cut  46  is displaced by a punch  47  through the shaping device into the holding means  38  until the short cut  46  forming the central partial group protrudes past the short cuts  42  forming the peripheral partial groups (FIG.  16 ). The holding means  38  is then removed from the shaping device  35  with the clamping plate  39  closed, and the short cuts  42 ,  46  are removed from the shaping device  35  (FIG.  17 ). 
     The devices according to FIGS. 1 to  12  and  13  to  17 , respectively, can produce bristle groups of differing geometrical shapes. Some embodiments are described below. 
     FIG. 18 shows a side view of a bristle group  47  consisting of partial groups as shown in FIG. 5 or only of one central partial group  48  and one surrounding partial group  49  enclosing the complete circumference thereof as shown e.g. in FIG.  22 . In this embodiment, the partial group  48  consists of small diameter bristles and the surrounding bristle group  49  comprises bristles of a larger diameter. The ends  50  of the central partial group  48  and the ends  51  of the central partial group  48  and the ends  51  of the surrounding partial group  49  lie in one plane. FIG. 19 shows a bristle group  52  of a central partial group  53  and an outer partial group  54  which surrounds same concentrically, wherein the ends  55  of the partial group  53  and also the ends  56  of the partial group  54  lie in flat envelope surfaces disposed at different heights. 
     The bristle group  56  according to FIG. 20 differs from the one shown in FIG. 19 in that the ends. 59  of the central partial group  60  are disposed on a conical surface while the ends  58  of the surrounding partial group  57  are again disposed in a plane. Finally, FIG. 21 shows a bristle group  61 , wherein the ends  62  of the surrounding bristle group and the ends  63  of the central bristle group are disposed on a common conical surface. 
     FIG. 22 has already been discussed in connection with FIG.  18 . In the embodiment of FIG. 23, the circumference of a central partial group  64  having bristles of smaller diameter is completely enclosed by a bristle group  65  having bristles of larger diameter, wherein both partial groups have a square cross-section. The embodiment according to FIG. 24 differs in that the central partial group  66  has a triangular cross-section and the partial group  67  surrounding it also has a triangular shape. FIG. 25 shows an embodiment having a central partial group  68  of approximately oval cross-section which can optionally also be formed of several partial groups and comprises bristles of smaller cross-section, whereas the outer partial group  69  surrounding same, which can also consist of several partial groups, comprises bristles of a larger cross-section. 
     FIG. 26 shows a bristle group comprising a central partial group  70  of only a few bristles of large diameter and a partial group  71  surrounding same, which can also be formed from several partial groups, containing bristles of smaller diameter. The bristle group according to FIG. 27 differs in shape from the circular cross-section of the bristle group according to FIG. 26 in that the central partial group  72  is again approximately circular, whereas the outer partial group  73  is square. 
     FIG. 28 shows a bristle group  74  consisting of three partial groups  75 ,  76  and  77  comprising partial cross-sections having a circular sector shape which are complementary to form a circular cross-section of the bristle group  74 , wherein the groups are separated from one another by planar bordering surfaces  78 . The partial group  75  comprises bristles of smaller diameter than the partial groups  76  and  77 . FIG. 29 shows a bristle group  79  consisting of a central partial group  80  with approximately rhombus-shaped cross-section and four surrounding partial groups  81  of lens-shaped cross-section. The central partial group  80  comprises bristles of smaller diameter and the surrounding lens-shaped partial group  81  contains bristles of the same and larger diameters. Curved bordering surfaces  82  are disposed between the central partial group  80  and the outer partial groups  81 . 
     FIG. 30 shows a bristle group  83  having a central partial group  84  with circular cross-section and six surrounding partial groups  85  of sector-shaped cross-section. The production of this bristle group  83  has been explained with reference to FIGS. 1 to  5 . 
     The bristle group  86  according to FIG. 31 consists of a central partial group  87  and neighboring partial groups  88  of essentially square cross-section, wherein the central partial group  87  comprises bristles of larger diameter. Partial groups  89  having an essentially semi-circular cross-section and containing e.g. bristles of the same diameter as the central partial group  87  are outwardly adjacent to the two partial groups  88 . 
     FIGS. 32 and 33 show a bristle group  90  having an inner partial group  91  and a surrounding partial group  92  of circular cross-section, wherein the inner partial group  91  consists of extremely thin bristles and the outer partial group  92  consists of bristles of a larger cross-section which support the bristles of the inner partial group  91  at all sides. The embodiment according to FIGS. 34 and 35 differs from the one shown in FIGS. 32 and 33 in that the outer partial group  93  and the inner partial group  94  each have a square cross-section and the thin bristles of the inner partial group  94  protrude upwardly past the bristles of the outer partial group  93 . 
     The embodiment of FIG. 36 shows how a bristle stock may be configured, e.g. for a tooth brush. Only the head  100  and part of the neck  101  are shown. A field of bristle stock comprising individual standing bristles  102  is mounted to a relatively large surface of the head  100 , proximate the neck  101 . The front area of the brush head  100  is provided with individual bristle groups  103  having an essentially circular cross-section. Each bristle group  103  consists of an inner partial group  104  and an outer partial group  105  which are arranged concentrically, wherein the ends of the bristles of the two partial groups  104  and  105  are disposed on a conical envelope surface. 
     FIGS. 37 to  39  show the head  100  and part of the neck  101  of a tooth brush. The head  100  is provided with bristle groups of essentially triangular cross-section, but with differing triangular shapes. The bristle group  106 , disposed at the front end of the brush head, has an equilateral triangular cross-section. The bristle group consists of several partial groups, wherein the bristle ends of the partial groups are disposed on an envelope surface  110  of equilateral pyramid shape. The next two bristle groups  107  differ therefrom in that their cross-section is a triangle with differing side lengths. The next bristle groups  108  again have equilateral triangular cross-sections. The bristle groups  109  proximate the neck  101  have a cross-section corresponding to an extremely acute-angled triangle. The bristle ends of all partial groups are disposed on an envelope surface, as shown in FIG. 38, of equilateral or non-equilateral pyramid shape. 
     FIG. 40 shows a tooth brush head  100  whose bristle stock proximate the neck  101 , consists of cylindrical bristle groups  111  and whose front area consists of a large volume bristle group  112 . The cylindrical bristle groups  111  can be made from one single type of bristle or from two or more partial groups of different bristles. The bristle group  112  at the front end of the brush head  100  consists of three partial groups  113 ,  114  and  115  which are arranged in an essentially concentric manner with respect to one another and which expand in a cupped manner towards the bristle ends. The ends of the individual partial groups  113 ,  114 ,  115  lie on a convex envelope surface  116  (see FIG.  41 ). 
     The embodiment according to FIG. 42 shows an exchangeable head for an electric tooth brush. The head  116  comprises a pin  117  for mounting to the driving part of the electric tooth brush. The head  116  has bristle groups  118  to  122 . The bristle group  118  extends in a zigzag shaped manner and has bristle ends protruding past the ends of the bristle groups  119  to  122 . The bristles of the bristle group  118  and those of the groups  119  to  122  preferably consist of various types of bristles. The bristle group  118  can optionally be composed of several partial groups with bristles of the same or differing types. 
     FIG. 43 also shows an exchangeable head  123  for an electric tooth brush which is mounted to the driving part of the electric tooth brush via a pin  124 . The bristle stock consists of one single bristle group  125  composed of two partial groups  126  and  127 , wherein the partial group  126  protrudes upwardly past the partial group  127  and its bristle ends lie on a spiral. The partial groups  126  and  127  can be composed of several partial groups of the same type of bristles. 
     FIGS. 44 to  46  show various embodiments of a small application brush. In the embodiment according to FIG. 44, a bristle group  129  is mounted to a brush handle  128  and consists of two concentric partial groups  130  and  131  (FIG. 44 b ), wherein the central partial group  131  comprises shorter bristles to create a storage region  132  for the application means. The embodiment according to FIG. 46 differs from the one of FIG. 44 in that the central partial group  131  is somewhat shorter to create a larger storage region  133 . In the embodiment of FIG. 46, the bristle group  134  consists of concentrically disposed partial groups  135  and  136 , wherein the central partial group  136  consists of wavy bristles  137  (FIG. 46 a ) for additional storage of media which are likewise shorter than the bristles of the surrounding partial group  135 . 
     FIG. 47 shows a flat brush whose handle  138  supports a bristle group having a central partial group  139 , surrounded in a circular manner by a partial group  140 . The bristles of the central partial group  139  create intermediate, narrow capillaries for receiving paint or lacquer while the bristles of the outer partial group  140  are closely adjacent to one another and prevent lateral escape of the medium to be applied. A flat brush is thereby produced with which the medium can be applied in precise stripes.