Abstract:
An abrasive device includes at least two abrasive tracks disposed on a support portion, the abrasive tracks having abrasive surfaces with abrasive elements. The abrasive device may be used to perform various abrasive processes either consecutively or in parallel by means of different abrasive surfaces.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
         [0001]    This application claims priority to German Patent Application No. DE 102 07 071.7, filed Feb. 20, 2002, which is incorporated herein by reference in its entirety.  
         TECHNICAL FIELD  
         [0002]    The invention relates to an abrasive device for finishing the ends of bristle filaments.  
         BACKGROUND  
         [0003]    U.S. Pat. No. 3,451,173 A discloses an abrasive device for preparing the ends of bristle filaments. The outer surface of an outwardly curved disc includes an abrasive surface, against which bristle tuft ends are pressed. As the disc rotates, the tufts move transversely to the disc, and the tuft ends are pressed against the abrasive surface. In this way, the tuft ends are worn down by contact with the roughness of the abrasive surface, or are finished by some other mechanical method. The various abrasive processes are executed by sequentially arranged abrasive units. This type of arrangement is awkward and expensive because after the initial rounding process, a transport means must transport each tuft to the next abrasion process. Such an apparatus also requires a great deal of space.  
           [0004]    German Patent No. DE 198 48 221 A1 discloses an abrasive device for finishing the ends of bristle filaments of toothbrushes, in which an abrasive surface is conformed to the outer peripheral surface of a drum. Two different abrasive surfaces are provided on the periphery of a lateral surface. The first abrasive surface forms a strip-like track extending in the direction of rotation. The second abrasive surface interrupts the first abrasive surface, and includes projections or ridges that run transversely to the first abrasive surface. As the first abrasive surface rounds the bristle ends, the second abrasive surface roughens the bristles&#39; directly adjacent lateral surfaces, thereby increasing the size of the active polishing surface. Thus, the bristles&#39; frontal extremities and lateral surfaces are finished alternatingly in a single abrasion process, and as frequently in a single revolution as there are protrusions and trace sections on the peripheral abrasion surface of the disc.  
         SUMMARY  
         [0005]    In one aspect, the invention features an abrasive device including a support portion and a disc portion. The disc portion has a first abrasive track with a first abrasive surface and a second abrasive track with a second abrasive surface. The abrasive surfaces include abrasive elements.  
           [0006]    In some embodiments, the individual abrasive surfaces are clearly differentiated from one another, such that the abrasive processes are clearly separated.  
           [0007]    In other embodiments, there is a gradation from one surface to the next. If the ends of the bristle filaments lie in one plane, then as the change is made from one abrasive surface to the other, the contact pressure of the bristle filament ends on the friction discs or bands is reduced or increased automatically in the second abrasion operation, according to the shape of the gradation. This change in contact pressure occurs because the distance between the ends of the bristle filaments and the second abrasive surface has either increased or decreased relative to the distance from the first abrasive surface. Thus, it is not necessary to employ expensive pressure maintenance devices for the bristle filaments. With a rotating disc, it is advantageous if the steps proceed radially towards the center of the disc.  
           [0008]    In some embodiments, the abrasive surface of at least one abrasive track is inclined or cambered or arched. Several abrasive surfaces may be inclined or cambered without a step being formed. Friction surfaces extending transversely to the bristle filaments may also be formed by the camber. If the bristles extend perpendicularly to the first abrasive surface, then the contact pressure decreases from the first abrasive surface to the second abrasive surface, if the second abrasive surface is inclined toward the bristle tufts. Such an arrangement may be advantageous in the subsequent polishing process.  
           [0009]    In some embodiments, the abrasive device has different abrasive surfaces on its various abrasive tracks because of different grain sizes, materials, or shapes. Different abrasive processes may be performed by the use of different abrasive elements. The different abrasive elements may be used either one after the other, or side-by-side.  
           [0010]    In some cases, an abrasive disc preferably has two abrasive tracks, so that two abrasive processes may be executed either synchronously or sequentially. In other cases, three, four, or even more abrasive tracks may be present on the abrasive disc, if a corresponding number of abrasive processes are to be executed and sufficient space is provided on the abrasive disc to accommodate the bristles and the tufts. The diameter of the abrasive disc is adapted to accommodate the abrasive tracks. As the diameter of the abrasive disc is increased, considerably higher friction speeds are engendered at the perimeter. Consequently, the bristle filaments may be finished considerably more effectively with coarser disc surfaces. Toward the center of the abrasive disc, where the diameters are relatively small, the lower friction speeds allow finer abrasive processes, such as polishing, to be performed. A round abrasive disc with circular and annular abrasive tracks has proven to be especially inexpensive to manufacture.  
           [0011]    In some embodiments, the abrasive disc is formed from a truncated cone or a cone surface. The different heights of the abrasive tracks enable varying contact pressures to be exerted on the bristle filaments. The inclination of the disc must be adapted to the abrasive surfaces, the friction speed, and the material of the bristle filaments.  
           [0012]    With regard to the abrading motion, the abrasive device does not have to rotate only about its own axis. The abrasive device may also perform tumbling rotations, so that the contact force of the disc against the bristle ends changes constantly, and both radial and tangential frictional forces are applied to the bristle ends. Such an arrangement improves the rounding of the bristle ends. The rotation of the abrasive disc may also be changed continuously from left rotation to right rotation, thereby contributing to better rounding. A combination of all of the properties described results in the optimal rounding technique.  
           [0013]    In some embodiments, the abrasive device includes a circulating band or circulating roller on which several abrasive tracks are disposed side-by-side. Because the diameter remains constant, the friction speeds are equal on all abrasive tracks. Where the circulating band or circulating roller is inclined toward the tuft axis as it passes, the contact pressure against the ends of the bristle filaments may also be varied.  
           [0014]    In some embodiments, the rotating speed changes with the change to another abrasive track. As a result, optimal abrasive processing on the bristle filament ends may be achieved.  
           [0015]    In another aspect, the invention features a method for finishing the ends of bristle tuft filaments. The method includes providing a rotating disc with at least two abrasive tracks having abrasive surfaces with different abrasive properties. Each abrasive surface includes corresponding abrasive elements. The method further includes contacting an end of a bristle tuft with the first abrasive track to perform a first finishing process; and then contacting the end of the bristle tuft with the second abrasive track to perform a second finishing process.  
           [0016]    In some embodiments, the abrasive tracks are disposed at different distances from the rotational center of the disc.  
           [0017]    Implementations of the invention may have one or more of the following advantages. Multiple abrasion processes may be executed easily and quickly, and by simple means. Rounding of complex bristle topographies may be adapted more precisely to an abrasive process. The abrasive device is simple and can save time and space. Furthermore, it may be relatively inexpensive.  
           [0018]    Another advantage resulting from an abrasive disc having several abrasive tracks is that it is possible to begin a second abrasive pass as soon as a first abrasive pass is completed. Either the bristle tufts undergo a minor displacement with respect to a first abrasive surface, or the abrasive disc is displaced with respect to the bristle tufts. Alternatively, both the bristle tufts and the abrasive disc may be displaced toward the second abrasive surface. The abrasive tracks are aligned so that they extend in the direction of movement of the abrasive disc and/or the bristle tuft ends.  
           [0019]    In this way, a simple device may economically effect multiple abrasive passes. For instance, the bristle tuft ends may be abraded coarsely in a first operation, more finely in a second operation, even more finely in a third operation, and polished in a fourth operation. To achieve this, four abrasive tracks would have to be conformed onto the disc and alternated in sequence once a previous abrasion operation was completed. It is also possible to pass over some abrasive tracks if, for example, the inner bristle tufts of a toothbrush do not have the same high surface area requirement as the peripheral bristle tufts.  
           [0020]    Some advantages of such an abrasive device are that it requires relatively little space and that it consumes a relatively small number of operating materials. Furthermore, the abrasion time per toothbrush is shorter, since the bristle tufts do not need to be worked with different abrasive discs for different abrasive processes. Thus, the cycle time of abrasive processes is reduced.  
           [0021]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
       
    
    
     DESCRIPTION OF DRAWINGS  
       [0022]    [0022]FIG. 1 is a reduced scale schematic plan view of one embodiment of an abrasive device.  
         [0023]    [0023]FIG. 2 is a cross-section taken through the middle of the abrasive device of FIG. 1, in which the abrasive surface is enlarged and the Support portion is only represented in part.  
         [0024]    [0024]FIG. 3 is a reduced scale schematic plan view of one embodiment of an abrasive device.  
         [0025]    [0025]FIG. 4 is a cross-section taken through the middle of the abrasive device of FIG. 3, in which the abrasive surface is enlarged and the support portion is only represented in part.  
         [0026]    [0026]FIG. 5 is a reduced scale schematic plan view of one embodiment of an abrasive device.  
         [0027]    [0027]FIG. 6 is a cross-section taken through the middle of the abrasive device of FIG. 5, in which the abrasive surface is enlarged and the support portion is only represented in part.  
         [0028]    [0028]FIG. 7 is a reduced scale schematic plan view of one embodiment of an abrasive device.  
         [0029]    [0029]FIG. 8 is a cross-section taken through the middle of the abrasive device of FIG. 7, in which the abrasive surface is enlarged and the support portion is only represented in part. 
     
    
     DETAILED DESCRIPTION  
       [0030]    Referring to FIGS.  1 - 8 , an abrasive device  1  includes a support portion  2  and a disc portion  3 . Disc portion  3  includes abrasive tracks  6  and  7 . Abrasive tracks  6  and  7  have abrasive surfaces  8  and  9 , which are adjacent along line  10 . Abrasive surfaces  8  and  9  include abrasive elements  4 . Abrasive surfaces  8  and  9  together form an abrasive coating  5 .  
         [0031]    [0031]FIGS. 1 and 2 show that abrasive surface  9  is in the shape of an enclosed circle surrounded by abrasive surface  8 . The transition from abrasive surface  9  to abrasive surface  8  at line  10  is practically seamless. Abrasive surfaces  8  and  9  lie in a single horizontal plane.  
         [0032]    In FIGS. 3 and 4, abrasive surface  8  has a half-moon shape in the middle of which, however, a semicircle is formed, so that the remainder of the overall circular abrasive coating  5  is occupied by abrasive surface  9 , in a half circle and ring. Abrasive surfaces  8  and  9  lie on the same horizontal plane.  
         [0033]    Referring to FIG. 5, abrasive surfaces  8  and  9  appear to have the same conformation as they do in FIG. 1. However, as shown in FIG. 6, abrasive surfaces  8  and  9  actually slope toward center  11 , so that their lateral surfaces form a uniform V-shaped surface.  
         [0034]    [0034]FIGS. 7 and 8 show abrasive surfaces  8  and  9 , with a step  12  at the transition from abrasive surface  8  to abrasive surface  9 . Thus, abrasive surface  9  is lower than abrasive surface  8 . However, it is also possible to reverse step  12  so that abrasive surface  9  is raised above abrasive surface  8 . Furthermore, it is possible to have a sloping ramp in the place of step  12 , so that the transition from abrasive surface  8  to abrasive surface  9  is gradual. Alternatively, step  12  may be formed by a continuous curve, so that the transition from abrasive surface  8  to abrasive surface  9  appears continuous.  
         [0035]    Referring now to FIG. 2, a bristle tuft  13  extends vertically to abrasive surface  8 . Bristle tuft  13  consists of individual bristle filaments  15  that all extend in the longitudinal direction of bristle tuft  13 . As soon as ends  14  of bristle tuft  13  have been sufficiently finished by abrasive surface  8 , bristle tuft  13  may be moved to contact second abrasive surface  9 . Alternatively, abrasive support  2  may be driven until ends  14  of bristle tuft  13  are located on surface  9 , and may thus be processed further. At the same time, the speed of rotation of abrasive device  1  may be increased or reduced to achieve the desired abrasive effect on the ends  14  of bristle tuft  13 .  
         [0036]    In FIGS. 3 and 4, abrasive device  1  is configured such that it must be rotated in an oscillating manner about its axis  11  (axis shown in FIG. 6) if bristle tufts  13  are to remain in contact with only one abrasive surface,  8  or  9 .  
         [0037]    [0037]FIGS. 5 and 6 show that bristle tufts  13  may be oriented to extend parallel to center  11 . In other words, ends  14  of bristle tufts  13  may be abraded obliquely, or rounded.  
         [0038]    Referring to FIGS. 7 and 8, abrasive device  1  enables contact pressure to be reduced when ends  14  of bristle tufts  13  are moved from outer abrasive surface  8  to inner abrasive surface  9 . Thus, ends  14  may be pressed against surface  9  with less contact pressure. In such cases, abrasive surface  9  may serve as a polishing surface.