Abstract:
A toothbrush including a brush head, bristle clusters protruding from a cleaning surface of the brush head and a depression disposed in the surface and surrounding at least one bristle cluster, the depression having a bottom into which the bristle cluster penetrates and in which the bristle cluster is fixed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage of PCT application Ser. No. PCT/EP2004/006022, filed Jun. 4, 2004, which claims priority to German Patent Application No. 103 31 369.9, filed Jul. 11, 2003. 
     TECHNICAL FIELD 
     The disclosure pertains to toothbrushes having a brush head including a plurality of bristle clusters protruding from a surface of the brush head and having variable free bending lengths. 
     BACKGROUND 
     German Utility Model 77 15 006 discloses a toothbrush having a slotted or perforated plate, through the slots or perforations of which bristle clusters protrude upward. The slotted or perforated plate is provided with a manually actuated adjusting device that makes it possible to vary the distance between the slotted or perforated plate and the surface, from which the bristle clusters protrude, namely in such a way that the free length of the bristle clusters can be respectively extended or shortened. This makes it possible to respectively decrease or increase the hardness of the toothbrush. One less advantageous aspect of this arrangement can be seen in that—leaving aside the already costly construction—only the freely protruding length of all bristle clusters arranged on the brush head is varied with a single adjustable slotted or perforated plate, respectively. 
     U.S. Pat. No. 2,274,042 discloses a manually operated toothbrush, in which bristle clusters of identical dimensions protrude from the toothbrush head, namely from surfaces thereof that are arranged at different heights. The quality as well as the length and the thickness of all bristle clusters are identical such that the flexural strength of all bristle clusters is also identical. Although the brushing ends of a few bristle clusters protrude from the brushing plane such that they respectively lie above or below the brushing ends of other bristle clusters, all bristle clusters have the same flexural strength because they protrude by the same length. 
     A manually operated toothbrush is also known from U.S. Pat. No. 6,553,604, wherein bristle clusters of different cross sections protrude from a surface of the brush head of this toothbrush. In this case, bristle clusters situated on the edge are arranged in openings that are larger than the cross section of the individual bristle clusters such that they are flexible in the longitudinal direction of the manually operated toothbrush. This enables these bristle clusters to better penetrate into the interdental spaces when the toothbrush is moved back and forth while brushing the teeth. The bristle clusters are supported in the recesses by means of barrel-shaped thickenings arranged on their ends. Although a toothbrush of this type functions well, its manufacture and assembly are more costly than those of conventional toothbrushes. 
     SUMMARY 
     According to one aspect, a toothbrush includes a brush head having bristle clusters protruding from the surface of the brush head which are configured to make it easier or more difficult for individual bristle clusters of the brush head to move back and forth than other bristle clusters of the brush head. This implementation also aims to improve the cleaning result, particularly in the region of the interdental spaces, and also offers a simple design which can be inexpensively manufactured with simple manufacturing techniques. 
     According to another aspect, the arrangement of an annular depression around an individual bristle cluster results in this bristle cluster having a different flexural strength than adjacent bristle clusters that are not arranged in such an annular depression, wherein this comparison naturally is based on the individual bristle clusters having the same quality and the same dimensions. The variation of the free bending length—at otherwise unchanged tuft parameters such as filament diameter, filament material and filament quantity—causes the bristles of this tuft or this bristle cluster to become freely movable and therefore promotes the cleaning effect of the toothbrush similarly well as it is the case with U.S. Pat. No. 6,553,604. 
     The annular depression or the depression extending around a bristle cluster can be manufactured in a particularly simple fashion if—in contrast to fixing the bristle clusters in bore holes of the brush head by means of anchors—a plastic mass is injection-moulded around the free ends of the bristle clusters in order to fix the bristle clusters on the brush head that is formed by the thusly moulded plastic mass in this case. The injection-moulding tool used for moulding the brush head merely needs to be provided with corresponding elevations that produce the annular depressions on the brush head during the injection-moulding process. Since only an annular depression needs to be realized around individual bristle clusters, it is possible to position such a depression around any bristle cluster of the brush head without a significant technical expenditure, namely in dependence on the positions of the brush head, at which harder or softer bristle clusters should be arranged. This makes it possible to realize a superior flexural strength of individual bristle clusters and therefore a superior flexural strength of the entire bristle section. The brush head is suitable for use in connection with manually operated toothbrushes as well as electric toothbrushes with an oscillating round brush head, for example, according to EP 1 138 222 A2 or EP 0 765 642 A2. 
     In some embodiments, the shape of the annular depression is adapted to the cross section of a bristle cluster protruding from the bottom of the annular depression. This has the advantage that the base of the bristle cluster is essentially always spaced apart from the edge of the annular depression by the same distance and therefore occupies the least space possible on the brush head. 
     In some embodiments, a bristle cluster of essentially rectangular cross section having rounded corners includes peripheral depression of essentially rectangular cross section with rounded corners, i.e., an annular depression, the walls of which extend parallel to and are slightly spaced apart from the outer walls of a bristle cluster. However, when a bristle cluster is used that has, for example, a round or oval cross section, the annular depression can also have a round or oval cross section. When using a bristle cluster of star-shaped or other cross section, the shape of the annular depression can also be correspondingly adapted to this cross section. 
     In some embodiments, the longer cross-sectional sides of the bristle clusters extend transverse to the longitudinal direction of the brush head. This cross-sectional shape has a relatively low flexural strength in the longitudinal direction of the toothbrush head and a relatively high flexural strength in the direction extending transverse thereto. When the toothbrush is moved transverse to the longitudinal direction of the teeth, the corresponding bristles can easily penetrate into the interdental spaces due to their relatively low flexural strength. However, when the toothbrush is moved in the longitudinal direction of the teeth, i.e., in the direction in which the bristle clusters have a higher flexural strength and therefore are relatively stiff, they are not significantly bent and therefore can be guided through the interdental spaces quite well while very effectively removing particles therefrom. This results in a very good cleaning effect on the surface of the teeth, as well as in the interdental spaces. The toothbrush may consist of a manually operated toothbrush, in which case the hand needs to mechanically carry out all brushing movements, or of an electric toothbrush that carries out a reciprocating brushing movement or even a vibratory oscillating movement. 
     In some embodiments, the depressions are arranged on the edge of the brush head. With such a configuration, the bristle clusters protruding from the annular depressions are particularly effective in cleaning the teeth because they are able to penetrate particularly well into the interdental spaces when the brush head is customarily turned slightly about its longitudinal axis. In this case, the bristle clusters situated on the edge are used more intensely than the centrally arranged bristle clusters. 
     In some embodiments, the annular depressions are laterally tapered off, i.e., they are not outwardly enclosed by a wall. This has the advantage that particles deposited in the annular depressions can be easily washed out laterally when the brush head is cleaned. The annular depressions can be easily rinsed out in this fashion. 
     In some embodiments, several annular depressions with bristle clusters protruding therefrom are provided on the lateral edges of the brush head in order to achieve a superior interdental cleaning effect, in particular, in the edge region. Additional bristle clusters are arranged between the individual bristle clusters protruding from the annular depressions, wherein these additional bristle clusters are not surrounded by annular depressions and, assuming they have the same cross-section, consist of the same bristle material and end in the same brushing plane of the brush head, have a higher flexural strength than the bristle clusters surrounded by the depressions because their base is embedded to a higher elevation. 
     In some embodiments, the bristle clusters are arranged at a higher elevation and also have a thicker cross section and a shorter length than the bristle clusters provided with the annular depressions. The bristle clusters protruding from the annular depressions are activated better and more intensely while brushing the teeth and therefore have a significantly improved interdental cleaning effect. This is achieved, in particular, in that the shorter bristle clusters of thicker cross section that also lie at a higher elevation do not become effective in cleaning the teeth until the free ends of the bristle clusters of smaller cross section that protrude from the annular depressions are deformed by the teeth, pushed sideward and penetrate into the individual gaps. 
     In some embodiments, four annular depressions with one respective bristle cluster protruding therefrom are respectively provided to both sides of the brush head. This number of annular depressions proved advantageous for manually operated toothbrushes designed for adults, namely because a sufficient distance in the longitudinal direction lies between the individual bristle clusters in this case such that they are able to bend sufficiently while brushing the teeth without interfering with one another. However, if the bristle clusters protruding from the depressions as well as the shorter bristle clusters arranged in between have a smaller cross section, it would be possible to arrange more than four annular depressions with bristle clusters protruding therefrom in the longitudinal direction. Smaller brush heads can also be provided with less than four annular depressions with bristle clusters protruding therefrom, e.g., three or two annular depressions. 
     When brushing the teeth, these longer bristle clusters come in contact with the surface of the teeth first and therefore are also subjected first to a force in the longitudinal direction or transverse thereto, respectively. Consequently, these longer bristle clusters are able to better penetrate into the interdental spaces before the shorter bristle clusters arranged in between come in contact with the surface of the teeth. The shorter bristle clusters begin to clean the surface of the teeth as additional pressure is exerted upon the toothbrush. 
     In some embodiments, bristle cluster protruding from the annular depressions have a greater length than adjacent bristle clusters such that the penetration of the bristle clusters protruding from the annular depressions into the interdental spaces is additionally simplified. 
     In some embodiments, enable the left side to move independently of the right side of the brush head such that the bristles become more resilient and even more elastic. Therefore, they are also able to better follow the contour of the teeth and to penetrate into many uneven areas on the tooth surface. 
     Any of the aforementioned embodiments can be implemented with a round brush head of an electric toothbrush that is driven by an electric drive such that it carries out an oscillating rotational movement, wherein the longer side of the rectangle of the annular depression essentially extends in the circumferential direction of the round brush head in this case. This arrangement ensures that the bristle clusters protruding from the annular depressions can be deformed more easily in the circumferential direction than transverse to the moving direction of the drive segment of the electric toothbrush due to their lower flexural strength. An improved penetration into the interdental spaces is also achieved in this case. However, these bristle clusters have a higher flexural strength when the round toothbrush head is moved in the longitudinal direction of the interdental space(s) and therefore are able to better transport particles out of the interdental spaces. 
     The characteristics of claims  14 - 18  reflect the characteristics of a manually operated toothbrush according to claims  5 - 8  and  11 , but pertain to a round toothbrush head. In order to prevent unnecessary repetitions, we refer to the above-discussed advantages that consequently can be realized analogously with a round toothbrush head. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from drawing and descriptions, and from the claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1 , a bottom view of a toothbrush, wherein the handle is drawn with broken lines and only its front end is shown; 
         FIG. 2 , a perspective representation of the rear side of the brush head of the toothbrush according to  FIG. 1 , however, without an illustration of the handle; 
         FIG. 3 , a side view of the brush head according to  FIG. 2 ; 
         FIG. 4 , a perspective representation of the brush head according to  FIG. 3 , and 
         FIG. 5 , a representation of the brush head that is almost identical to that shown in  FIG. 4 , however, on an enlarged scale. 
         FIG. 6 , a top view of a round brush head configured for oscillating rotational movement. 
     
    
    
     DETAILED DESCRIPTION 
     The toothbrush  1  consists of a brush head  2  and a handle  3  that is only partially illustrated with broken lines in  FIG. 1  and not shown at all in  FIGS. 2-5 . In  FIGS. 1-5 , the brush head  2  consists of two brush head halves  5 ,  6  that are divided in the longitudinal direction  4  of the toothbrush  1  and separated from one another by a centrally extending S-shaped slot  7 . The slot  7  begins a short distance behind the handle  3 , namely on the neck  8  that forms the transition to the brush head  2  as clearly illustrated in  FIG. 1 . Behind the neck  8 , the brush head  2  abruptly widens in the direction toward the point  30  until the widest points  31  are reached. The edges  26  are then continuously tapered toward the point  30  from these widest points. The edges  26  are smoothly connected to one another at the point  30  with a radius R. 
     Different groups of bristle clusters  11 ,  12 ,  13 ,  14 ,  15 ,  16  and  17  protrude from the entire surface  10  of the brush head  2  that lies opposite of the rear side  9 , wherein said bristle clusters consist of many individual fine bristles or filaments (individual bristles are not illustrated) that respectively have the same length within a cluster. The bristle clusters  11 ,  12 ,  13 ,  14 ,  15 ,  16  and  17  have different cross sections, different lengths and different qualities. 
     The bristle clusters  11  according to  FIG. 5  have an essentially rectangular cross section with slightly rounded corners  20 . The cross section of the bristle clusters  11  is defined by the longitudinal side e and the broadside f. The rectangular cross section of the bristle clusters  11  may also be slightly oval, i.e., the broadside f may be formed, for example, by an outwardly curved radius that seamlessly connects the two longer side walls  23 ,  24  to one another rather than a straight line. The surface  10  extends essentially parallel to the rear side  9  that is slightly curved outward and flattened toward the edges such that the thickness of the brush head  2  slightly decreases toward the edge. Depending on how the bristle clusters  11 ,  12 ,  13 ,  14 ,  15 ,  16  and  17  are arranged relative to the surface  10  and the longitudinal axis  4  of the handle  3  in order to achieve the best cleaning result, the surface  10  may, however, also extend horizontally or at an incline referred to the longitudinal axis  4  of the handle  3 . 
     The surface  10  shown in  FIGS. 1-5  contains annular depressions  21  that are arranged in the edge region  18  of the brush head  2  and respectively defined by the bottom  22 , the longer side walls  23 ,  24  and a shorter side wall  25 . The annular depressions  21  provided on both brush head halves  5 ,  6  extend as far as the nearest edge  26 , where they are tapered off such that shorter side walls analogous to those on the opposite side are not formed at these locations. The longer side walls  23 ,  24  extend transverse to the longitudinal direction  4  of the manually operated toothbrush  1 . The bottoms  22  essentially extend perpendicular to the bristle clusters  11 , and the side walls  23 - 25  extend essentially parallel to the bristle clusters. The transition from the side walls  23 - 25  to the bottom  22  is realized with small radii such that sharp edges are prevented and rounded edges  27  are formed in these regions. If viewed in the form of a top view, the annular depressions  21  have an essentially rectangular cross section analogous to the cross section of the bristle clusters  11 . Their long side b has a length between 3 and 4 mm, preferably 3.5 mm. Their broadside a has a length between 2 and 3 mm, preferably 2.5 mm. The depth t measured from the surface  10  to the bottom  22  of the annular depression lies between 1 and 2 mm, preferably at 1.4 mm. 
     The bristle clusters  11  protrude upward from the bottoms  22  of the individual annular depressions  21 . The free length L 1  measured from the bottom  22  to the free end  20  of the bristle cluster  11  lies between 12 and 14 mm, preferably at 13 mm ( FIG. 3 ). The longitudinal side e of the bristle clusters  11  has a length between 2.1 and 2.4 mm, preferably 2.3 mm, and the broadside f of the bristle clusters  11  has a length between 0.7 and 0.8 mm, preferably 0.75 mm. The longitudinal side e extends transverse to the longitudinal direction  4  of the manually operated toothbrush  1 , i.e., the bristle clusters  11  have a lower flexural strength in the brushing direction X than in the brushing direction Y. 
     According to  FIG. 3 , the height of the brush head is composed of the dimensions d 2  and t and therefore amounts to 3.5-5 mm, preferably 4.1 mm. Naturally, these “preferred” dimensions may also be shorter or longer. In  FIG. 3 , the thickness d 2  measured from the bottom  22  of the annular depression  21  to the underside  9  of the brush head  2  lies between 2.5 and 3 mm, preferably at 2.7 mm. 
       FIGS. 2-5  show that the bristle clusters  11  are arranged in the form of a successive row in the edge region  18  and centrally protrude upward from the annular depressions. Bristle clusters  12  protrude upward from the surface  10  between the annular depressions  21 , wherein these bristle clusters have a larger cross section than the bristle clusters  11 , but their longitudinal sides d also extend essentially transverse to the longitudinal axis  4  of the manually operated toothbrush  1 . The longitudinal side d of a bristle cluster  12  has a length between 2.2 and 2.8 mm, preferably 2.5 mm, and the broadside c has a length between 1.6 and 2 mm, preferably 1.8 mm. Their length measured from the surface  10  to the free ends  29  lies between 9 and 10 mm, preferably at 9.5 mm. Another bristle cluster  12  is arranged adjacent to the bristle cluster  11  situated nearest the neck  8  such that four bristle clusters  11  and 4 bristle clusters  12  are alternately arranged in a row in the edge region  18 . Since in some embodiments, the bristle clusters  11 ,  12  need to have a constant distance from the edge  26  but this edge is slightly curved outward, the row of bristle clusters  11 ,  12  also has a slight outward curvature. According to  FIG. 5 , four bristle clusters  11  are respectively arranged successively in a row along the lateral edges  18  and spaced apart by a distance g, wherein this distance g lies between 3 and 3.5 mm, preferably at 3.2 mm. The distance h between the rearmost and the foremost bristle cluster  11  lies between 18 mm and 21 mm, preferably at 19.6 mm. 
     The bristle clusters  11  have a different color such that they can be distinguished from the bristle clusters  12 - 17 , wherein this is indicated in  FIGS. 2-5  by the darker manner of representation. 
     The cross sections of the bristle clusters  12  are also rounded on the corners  19  in order to prevent sharp edges and to realize a simple manufacture. 
     Additional bristle clusters  13 ,  14 ,  15  and  17 , all of which protrude upward from the surface  10 , are arranged within the bristle clusters  11 ,  12  situated in the edge region  18 . These additional bristle clusters may also extend perpendicular to the surface  10  or have a slight forward or rearward or sideward incline. The bristle clusters  13 ,  14  also have an essentially rectangular or slightly oval cross section. With respect to the rectangular cross section, the shorter sides can once again be formed by outwardly curved radii in this case. The front region is provided with a bristle cluster  17  of round cross section, the free end of which is inclined toward the handle  3  and in the direction of the surface  10 . 
     The free ends  33 ,  34 ,  35  of the bristle clusters  11 ,  12 ,  13  extend essentially parallel to the surface  10  of the brush head  2 , but may also be slightly inclined forward or rearward if this improves the cleaning result. The free ends  33  of the bristle clusters  11  protrude upward beyond the free ends  34  of the bristle clusters  12  by a short distance in order to achieve a superior penetration into the interdental spaces. 
     The front region of the brush head  2 , i.e., the region situated in front of the first bristle cluster  11  and the bristle cluster  17 , merely contains two essentially lunulate bristle clusters  15 ,  16  that are inclined toward the front and the surfaces of which are inclined rearward in the direction of the handle  4  and in the direction of the surface  10  on their free ends  36 ,  37 . The bristle clusters  15 ,  16  are divided into two halves by the slot  7 . These bristle clusters are designed, in particular, for cleaning the rear molar region while brushing the teeth. 
     The bristle clusters  11 ,  12  consist of many individual bristles or filaments (that are not illustrated in the figures). The bristles of the bristle clusters  11  preferably have a thickness of 0.008 inch, and the bristles of the bristle clusters  12  have a thickness of 0.006 inch. Due to the greater thickness of the filaments that form the bristle clusters  11 , these filaments also have a superior durability, i.e., the thickness and the quality of the individual filaments, as well as the number of the individual filaments in a bristle cluster  11 , are chosen such that these bristle clusters do not wear out faster than the bristle clusters  12 - 17  and the state of wear of all bristle clusters of a toothbrush  1  appears to be approximately identical. 
     The manually operated toothbrush shown in  FIGS. 1-5  functions as described below: 
     When using the toothbrush such that the free ends  32 - 37  of the bristle clusters  11 - 17  move in the direction X, i.e., transverse to the teeth in the mouth while being essentially arranged perpendicular thereto, the free ends  33  of the bristle clusters  11  are pressed against the surface of the teeth first. This causes these bristle clusters to deflect or bend opposite to the moving direction X until the free ends  33  of the bristle clusters  11  slide into the interdental spaces. During this process, these bristle clusters press particles out of the interdental spaces. The free ends  34  of the bristle clusters  12  simultaneously come in contact with and clean the front surfaces of the teeth. The bristle clusters  11  can be deformed much easier in the direction X than the bristle clusters  12  because they have a smaller cross section and a greater protruding length than the bristle clusters  12 . The superior elastic bending properties of the bristle clusters  11 , as well as their slender cross section, promotes the penetration of their free ends  33  into the interdental spaces while brushing the teeth such that the cleaning result is improved. 
     If the toothbrush  1  is moved back and forth in the direction Y as shown in  FIG. 1 , the free ends  32  of the bristle clusters  11  initially penetrate into the interdental spaces and press particles out of these interdental spaces because the flexural strength is greater in the direction Y than in the direction X, i.e., the interdental spaces can be cleaned particularly well by moving the toothbrush in the direction Y. The width f of the bristle clusters  11  is chosen such that the free ends  32  are able to penetrate well into the interdental spaces. At least some of the bristle clusters  11  penetrate into the interdental spaces even if the interdental spaces are very small. In this respect, it is also advantageous that the individual bristles have a larger diameter than those of the bristle clusters  12  because this enables the bristles of the bristle clusters  11  to offer greater resistance to particles lodged in the interdental spaces. 
     When brushing the teeth, the toothbrush  1  is moved in the X-direction as well as in the Y-direction. This mixed movement results in a combination of the above-described advantages such that very good cleaning results are achieved. Adequate cleaning results can also be achieved with an electric toothbrush with a round oscillating brush head, for example, according to EP 1 138 222 A2 or EP 0 765 642 A2. In such a (not-shown) round brush head in which the bristle clusters are annularly arranged on the brush head surface, bristle clusters  11  and bristle clusters  12  according to  FIGS. 1-5  are arranged on the outer edge and the annular depressions as well as the bristle clusters that protrude upward from these depressions extend concentric to the round toothbrush on its edge region. The free length L 1  of the bristle clusters  11  is also longer in this case because they protrude upward from the bottom  22  of the annular depressions  21  rather than the surface  10  as shown in  FIGS. 1-5 . Additional figures of this embodiment are not provided because the annular depressions analogously extend along the edge in a round toothbrush. 
       FIG. 6  depicts a top view of an oscillating round brush head  50  configured for oscillating rotational movement. Brush head  50  includes a plurality of depressions  51  extending a short distance from an outer edge of the brush head. The depressions  51  are tapered off outwardly along a radial direction. Brush head  50  includes bristle clusters  53  protruding from depressions  51  and brustle clusters  55  not surrounded by the depressions and protruding between two adjacent depressions. The bristle clusters  53  and  55  have a rectangular cross section and define a pair of side walls of major and minor extent. The walls of major extent are disposed in a circumferential direction of the brush head and are each at the same distance from the edge. The bristle clusters  53  protruding from the depressions have a greater length than those of the adjacent bristle clusters  55 .