Abstract:
A toothbrush with a flexible head is disclosed. At least the head of the toothbrush may be manufactured by in-molded technology. A blend of thermoplastic elastomer and polypropylene is used to impart added flexibility to the head. That flexibility is further enhanced by the tapered profile of the head. Cleaning elements may be secured in place during manufacture using in-molded techniques or staples.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a continuation of International Application PCT/US03/34589, filed Oct. 30, 2003, which claims priority from U.S. Application 60/423,254, filed Nov. 1, 2002, both of which are incorporated by reference herein in their entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention is directed to a toothbrush, either manual or powered, which includes a handle and a head. Cleaning elements are mounted to the head such as tufts of bristles and/or elastomeric wipers. When toothpaste is applied to the cleaning elements the user inserts the head into the mouth and brushes the teeth in a known manner.  
         [0003]     The head of a conventional toothbrush usually has a flat or slightly altered surface to which cleaning elements are attached. Usually the cleaning elements are strands of plastic material(s) formed into tufts, bundles or other groupings. A goal of many toothbrushes is to accommodate the cleaning element profile to that of the teeth being cleaned. Achieving that goal is complicated by the difficulty in matching a toothbrush profile to the complex surface of a typical set of human teeth. The latter generally lie in a “C” shaped curve which presents the need for a brush to address a convex outer curve and a concave inner curve. In addition, the toothbrush should be capable of cleaning irregularities on the tooth surface as well as the interproximal area between teeth.  
         [0004]     Various approaches have been taken in the prior art to accommodate the complex shape of the human mouth and the attendant difficulties in cleaning teeth and gums within the mouth. One approach to this problem is provision of a flexible toothbrush head.  
         [0005]     Blakeman U.S. Pat. No. 2,706,825 issued Apr. 26, 1955 discloses a replaceable bristle head for a toothbrush. The flexible head undulates in a manner so that rows of bristles move in a direction aligned with the axis of the toothbrush handle.  
         [0006]     U.S. Pat. No. 5,651,158 issued Jul. 29, 1997 to Hans Halm discloses a toothbrush handle with a segmented head wherein adjoining segments are linked by an elastomeric material. The segments are primarily oriented transverse to the longitudinal axis of the toothbrush but may also be oriented parallel to that axis.  
         [0007]     U.S. Pat. No. 6,408,476 discloses another form of segmented toothbrush head with transverse grooves and an elastomeric portion joining the segments. A method of manufacturing this head is also disclosed.  
         [0008]     The use of elastomeric material within folds of a toothbrush handle is the subject of U.S. Pat. No. 5,903,949.  
         [0009]     International Publication Number WO96/02165 dated Feb. 1, 1996 discloses a resiliently flexible bristle-bearing toothbrush head containing bristles with a generally concave surface. The head, being flexible, can flex under the action of tooth brushing to accommodate the varying profiles of users&#39; teeth. Grooves transverse or parallel to the longitudinal axis of the toothbrush which are filled with elastomeric material permit flexure along the length or across the breath of the head (pages 4-5).  
         [0010]     A tip region of a toothbrush head is flexibly mounted to the rigid balance of the head in the disclosure of International Publication Number WO 97/07707 dated Mar. 6, 1997. A flexible plastic material forms the link (hinge) which connects the two parts of the head (pages 2-3). In use, the tip region of the head can fold backwards toward the rigid balance of the head, thereby enabling the head to better accommodate itself to the curved shape of the user&#39;s teeth.  
         [0011]     Another flexible toothbrush head is disclosed n European Patent Specification No. EP 0577 656 B1 published May 4, 1997.  
       SUMMARY OF THE INVENTION  
       [0012]     A common theme among the aforementioned approaches to providing a flexible head is the use of different materials throughout the head to achieve the desired flexibility. Most of the above cited art use elastomeric materials at joints in the head structure to provide that flexibility. This invention proposes to achieve flexibility while using a homogeneous material for the head, rather than separate portions of the head with varying physical properties. This approach offers considerable simplification of a flexible toothbrush head assembly.  
         [0013]     The preferred material for forming the head has sufficient rigidity to maintain the structure of the head and retain the cleaning elements in place within the head while still offering the desired flexibility. This desired mix of properties can be achieved by blending two or more materials prior to molding. A preferred blend uses a large percentage (up to about 50%) of a thermoplastic elastomer (TPE) with polypropylene. The percentages of the respective components would be governed by the geometry of the head, with a thinner head generally needing less TPE for flexibility.  
         [0014]     Because a softer material is used in the head, retention of cleaning elements in the head may require special attention. Therefore, special care should be taken in staple insertion to properly anchor the cleaning elements. Alternatively, groups or tufts of cleaning elements can be secured in the flexible head of this invention using the injection molding technique (IMT) for placement and securement of toothbrush bristles. In the IMT process, the bristles are preferably attached during formation of the toothbrush handle, or at least during formation of the head. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a fragmental top plan view of a toothbrush head showing placement of a group of bristles (tufts) and staples holding the bristles in the head.  
         [0016]      FIG. 2  is a schematic fragmental top plan view of a single tuft of bristles placed in the hole of the flexible head of this toothbrush.  
         [0017]      FIG. 3  is a fragmental side elevational view, partially broken away to show flexible encasement of bristles in the toothbrush head.  
         [0018]      FIG. 4  is a cross sectional end view taken along line  4 - 4  of  FIG. 3  with phantom outline of the bristles movement with the flexible head.  
         [0019]      FIG. 5  is a fragmental side elevational view of a power toothbrush having a removable flexible head. 
     
    
     DETAILED DESCRIPTION  
       [0020]     The toothbrush  10  of this invention includes handle  12  and head  14 . Head  14  is preferably formed of a flexible plastic material, comprising a blend of thermoplastic elastomers such as those sold under the KRATON® trademark, and polypropylene. This blend, and those similar to it, provide a unique combination of flexibility and structural integrity for the toothbrush head.  
         [0021]     The desired flexibility of head  14  is also a function of its shape and thickness. Thus, as shown in  FIG. 3 , the thickness of head  14  may be gradually reduced or tapered toward the distal end of the toothbrush  10  to improve the flexibility of the head  14 .  
         [0022]     While it is an object of this invention to provide a flexible head  14 , the handle  12  typically should be more rigid so that the user can control the force of the toothbrush  10  on the user&#39;s teeth. To accomplish that goal, it is desirable to include a more rigid plastic in at least a portion of the handle  12  of toothbrush  10 . To achieve this marriage of a flexible head and relatively rigid handle, several approaches can be taken. The flexible blend of KRATON® and polypropylene can be used as a core material  16  for the handle surrounded by a more rigid plastic shell  18 . Conversely, the core  16  can be formed of a more rigid material and the shell  18  formed from the TPE and polypropylene blend. As shown in  FIG. 3 , the latter embodiment provides a soft “feel” to the handle and is thus a desirable feature in most applications.  
         [0023]     The use of the more flexible blend material for head  14  does present some special issues regarding placement and retention of cleaning elements  20  in head  14 . During flexure of flexible head  14 , the holes  22  in head  14  which hold the cleaning elements  20  may be widened or expanded as illustrated in  FIG. 2 . More specifically, one dimension of the hole  22  may be enlarged as represented by the distances shown in  FIG. 2 . That enlargement of hole  22  could loosen the hold on the tufted end  24  of cleaning elements  20  inserted in head  14 . To minimize the chance that any group of cleaning elements  20  might pull out of hole  22  in head  14 , it is desirable to carefully orient staples  26  used to secure the tufted end of cleaning elements  20  in hole  22 . Thus, as shown in  FIG. 1 , if head  14  flexes along a line perpendicular to the longitudinal axis of toothbrush  10  as shown by the arrows in the Figure, the staples  26  are preferably similarly aligned with the flex axis. Thereby, there is minimal movement of the staples during flexure.  
         [0024]     An alternative means for improving retention of cleaning elements  20  in the flexible head  14  is use of the IMT process. Descriptions of that process used for the manufacture of toothbrushes are found in U.S. Pat. Nos. 5,390,984; 5,533,791 and 5,609,890, the disclosures of which are incorporated herein by reference.  
         [0025]     In the IMT process, the tufted ends  24  of cleaning units  20  are held in place as the head  14  is formed. The rounded ends  24  assume a mushroom shape (See  FIGS. 3 and 4 ) which is essentially surrounded by the TPE/polypropylene blend used to form head  14 . This mushroom shape helps to hold the tufted ends  24  of cleaning elements  20  in place, even when one axis of the head  14  is stretched. To further improve retention of cleaning elements  20  in head  14 , the IMT process can be operated with localized heating to partially melt the tufted ends  24  of cleaning elements  20  so that a bridge  25  is formed between ends  24 . As illustrated in  FIG. 4 , this bridge  25  integrates the various groupings of cleaning elements  20  at the ends  24 . The flexible head  14  is then molded around the bridge  25 . This substantially improves retention of cleaning elements  20  in head  14 . This bridging is particularly effective in holding cleaning elements  20  in place where the head  14  is flexed in a direction where the cleaning elements move laterally relative to the longitudinal axis of the toothbrush  10 , as illustrated in  FIG. 4 .  
         [0026]     Any suitable form of cleaning elements may be used as the cleaning elements  20  in the broad practice of this invention. The term “cleaning elements” is intended to be used in a generic sense which could include conventional fiber bristles or massage elements or other forms of cleaning elements such as elastomeric fingers or walls arranged in a circular cross-sectional shape or any type of desired shape including straight portions or sinusoidal portions.  
         [0027]     It is to be understood that the specific illustration of the cleaning elements is merely for exemplary purposes. The invention can be practiced with various combinations of the same or different cleaning element configurations (such as stapled or in-molded technology bristles, etc.) and/or with the same bristle or cleaning element materials (such as nylon bristles, spiral bristles, rubber bristles, etc.) Similarly, while  FIGS. 3-4  illustrate the cleaning elements to be generally perpendicular to head  14 , some or all of the cleaning elements may be angled at various angles with respect to the outer surface of head  14 . It is thereby possible to select the combination of cleaning element configurations, materials and orientations to achieve specific intended results to deliver additional oral health benefits, like enhanced cleaning, tooth polishing, tooth whitening and/or massaging of the gums.  
         [0028]     This invention may also be practiced where the head  14  includes one or more power or electrically operated movable sections carrying cleaning elements.  
         [0029]      FIG. 5  illustrates a toothbrush  10 A which includes a power driven movable disc or section  40  having cleaning elements. The movable section  40  could be oscillated rotationally such as by using the type of drive mechanism shown in U.S. Pat. No. 5,625,916, or could move in and out using the type of drive mechanism shown in U.S. Pat. No. Re35,941; all of the details of both patents are incorporated herein by reference thereto. Alternatively, the other types of drives referred to above could move section  40  in other manners and directions. Although  FIG. 5  shows movable section  40  to be at one end of the head, the movable section(s) could be located at any desired location on the head.