Abstract:
A toothbrush having an elongated resilient handle has a brush head containing a plurality of tufts of bristles fabricated of polybutylene terephthalate. Each tuft has a multiplicity of short primary bristles and longer secondary bristles having tapered and pointed distal extremities. The effect of the secondary bristles is to function in a manner similar to dental floss to clean the spaces between the teeth.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention concerns toothbrushes, and more particularly relates to a toothbrush having a set of bristles for cleaning the teeth and a second set of bristles for cleaning the spaces between the teeth, and under the gumline. 
     2. Description of the Prior Art 
     The fundamental purpose of toothbrushes is to remove plaque and debris from the tooth surfaces, both along their outer surfaces and in the interproximal areas as well as provide gum and interdental stimulation. There is a continuing need to improve the interproximal cleaning effectiveness of toothbrushes, particularly because many consumers do not floss. 
     Currently marketed toothbrushes are classified into three categories: soft, medium and firm according to the degree of hardness or stiffness of the bristles. Firm toothbrushes, having stiff bristles, clean plaque well but irritate the gums. Soft toothbrushes are unable to provide adequate cleaning in the interproximal areas between the teeth. Medium toothbrushes cannot meet all three needs because some teeth need harder cleaning, others need minor cleaning, while the gums need just a massaging. 
     U.S. Pat. No. 6,021,541 to Mori et. al. describes a toothbrush intended to provide improved cleaning of interdental regions, and comprised of sheath/core bristles wherein the sheath is made from a polyester resin and the core is made from a polyamide resin. Bristles having tapered distal tip extremities are also disclosed. 
     U.S. Pat. No. 5,732,433 to Gocking et. al. discloses an interproximal brush for an electric toothbrush. The brush has bristles of two different heights, the longer length bristles providing interproximal cleaning function. 
     U.S. Pat. No. 5,398,367 to Lu concerns a toothbrush having both soft and hard bristles. The soft bristles are longer than the hard bristles, and provide a gum massaging effect. The variation in hardness of the bristles is accomplished by varying the diameter of the bristles. 
     U.S. Pat. No. 5,392,483 to Henizelman et. al. discloses a toothbrush for improved cleaning, gum stimulation and mouth feel, having varying bristle tuft heights, angling of the tufts, and critical positional arrangement of the tufts. 
     U.S. Pat. No. 5,511,275 to Volpenhein et. al. describes a toothbrush for achieving improved interproximal cleaning without increasing gum irritation. The ends of the bristles are rounded and have a critically selected stiffness. 
     U.S. Pat. No. 5,535,474 to Salazar concerns a toothbrush for cleaning teeth while simulating the gums, said toothbrush having polishing rods and stimulator rods that extend above surrounding bristles. 
     U.S. Pat. No. 5,926,897 to Volpenhein discloses a toothbrush for interdental stimulation comprised of a plurality of tufts having a multiplicity of primary and secondary bristles, said secondary bristles being stiffer than said primary bristles and extending above said primary bristles. 
     However, despite considerable prior effort, there still exists a need for a toothbrush having the ability to clean the teeth while providing the benefits of flossing. Some of the aforesaid prior toothbrushes, although having technical merit, would be expensive to manufacture. 
     It is accordingly a primary object of the present invention to provide a toothbrush which serves well in cleaning teeth and also provides the benefits of flossing. 
     It is another object of this invention to provide a toothbrush as in the foregoing object which will not irritate the gums. 
     It is a further object of the present invention to provide a toothbrush of the aforesaid nature which is easy to manipulate during the brushing activity. 
     It is a still further object of this invention to provide a toothbrush of the aforesaid nature of durable construction and amenable to low cost manufacture. 
     These objects and other objects and advantages of the invention will be apparent from the following description. 
     SUMMARY OF THE INVENTION 
     The above and other beneficial objects and advantages are accomplished in accordance with the present invention by a toothbrush comprising an elongated resilient handle extending between two ends and a brush head disposed at one of said ends, said brush head having a flat support surface and a plurality of tufts of bristles fabricated of polybutylene terephthalate, each tuft comprised of: 
     a) a multiplicity of primary bristles of uniform cross-sectional configuration having proximal ends embedded in said head and distal ends extending orthogonally outward from said support surface, and 
     b) a multiplicity of secondary bristles having proximal extremities embedded in said head and pointed distal extremities extending orthogonally outward from said support surface to an action zone beyond the distal ends of said primary bristles, said secondary bristles having a tapered cross-sectional configuration in said action zone that terminates in said pointed distal extremity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing forming a part of this specification and in which similar numerals of reference indicate corresponding parts in all the figures of the drawing: 
     FIG. 1 is a side view of a preferred embodiment of the toothbrush of the present invention. 
     FIG. 2 is an enlarged fragmentary side view showing the head extremity of the toothbrush of FIG.  1 . 
     FIG. 3 is a top view of the head extremity shown in FIG.  2 . 
     FIG. 4 is a further enlarged fragmentary side view of tufts of the toothbrush shown in FIG.  2 . 
     FIG. 5 is an enlarged sectional view of a single tuft of bristles of the toothbrush of FIG. 4 taken in the direction of the arrows upon the line  5 — 5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-5, an embodiment of the toothbrush  10  of the present invention is shown comprised of an elongated handle  11  extending between a brushing end  12  and holding end  13 , and a brush head  14  disposed upon said brushing end  12 . 
     Handle  11  is comprised of a contoured rigid gripping portion  15  extending upwardly from holding end  13  toward brush head  14 , and a narrowed resilient neck portion  18  extending between said gripping portion  15  and brush head  14 . Handle  11  is preferably a monolithic structure molded from a flexible thermoplastic polymer such as polyurethane, plasticized polyvinyl chloride, and product SM1300 available from the Dow Plastics Co., of Midland, Mich. Gripping portion  15  may be provided with protruding features  16  which prevent slipping in the user&#39;s hand, and further provided with a recess  17  for thumb placement. 
     Gripping portion  15  may have a thickness of 13 to 18 millimeters at its site of greatest thickness. Neck portion  18  has a contour which tapers to gradually diminished thickness in proceeding from gripping portion  15  toward brush head  14 . At its site of minimal thickness, adjacent said brush head, the thickness of the neck portion is preferably between about 4 and 6 millimeters. The resiliency of the neck portion may be characterized in terms of bending modulus. The preferred bending modulus is such that a force of one pound applied to brushing end  12  produces a deflection of said brush head between 3 and 8 millimeters, said deflection being produced by flexural movement in said neck portion. 
     Brush head  14  is comprised of a flat support surface  20  that secures bristles arranged in a plurality of tufts  21 . The number of tufts may range between about 35 and 40. The tufts are preferably symmetrically located with respect to a vertical plane of symmetry  22  that longitudinally bisects the toothbrush. The separation between contiguous tufts is preferably between about 0.5 and 2 millimeters. 
     Each tuft is comprised of a multiplicity of primary bristles  23  of equal length and uniform cross-sectional configuration, as having been produced by an extrusion operation. Said primary  15  bristles have proximal ends  24  which are embedded in said brush head, and distal ends  25  extending orthogonally outward from support surface  20  and terminating in a plane  30  parallel to support surface  20 . The length of said primary bristles extending above surface  20  may range from about 8 to 12 millimeters, and their distal ends are preferably rounded. 
     Also included within each tuft  21  is a multiplicity of secondary bristles  26  having proximal extremities  27  embedded in said brush head, and pointed distal extremities  28  extending orthogonally outward from said support surface to an action zone  29  located beyond the distal ends of said primary bristles. Said action zone extends between 2 and 4 millimeters above plane  30 . Within said action zone, said secondary bristles have a tapered cross-sectional configuration that terminates in said pointed distal extremity. 
     Within each tuft there may be, for example, about 21 primary bristles and  17  secondary bristles. The general ratio of primary to secondary bristles is preferably in the range of 1.1 to 1.4. If too many secondary bristles are employed, their penetrative ability will be diminished, and they will function more like the primary bristles. It has been found that, in order to achieve acceptable stiffness of the bristles without causing gum irritation, all bristles should be fabricated of polybutylene terephthalate. It has also been found preferable that the secondary bristles be of thinner cross-sectional contour than the cross-sectional contour of the primary bristles. 
     In the operation of the toothbrush of this invention, the secondary bristles in the action zone enter crevices between the teeth and thereby function in the manner of a flossing treatment. With somewhat greater pressure applied by the user, the distal ends of the primary bristles contact the outer surfaces of the teeth to provide a polishing action. 
     While particular examples of the present invention have been shown and described, it is apparent that changes and modifications may be made therein without departing from the invention in its broadest aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.