TOOTHBRUSH WITH LONGITUDINAL TO LATERAL MOTION CONVERSION

Abstract: A toothbrush (10) has a number of rotatable brush assemblies (18) mechanically linked so as to move together with a handle (16). Each rotatable brush assembly (18) includes a wheel (22), with radially projecting bristles (26), configured to rotate about an axis (24) which is roughly parallel to a plane of contact (20) with the teeth. The axis (24) of rotation is inclined relative to a primary direction of insertion (14) of the toothbrush (10), corresponding to an extensional direction (14) of the handle (16), by an angle of between about 15 DEG and about 75 DEG , and preferably closer to 45 DEG .

Description: TOOTHBRUSH WITH LONGITUDINAL TO LATERAL MOTION CONVERSION FIELD AND BACKGROUND OF THE INVENTION The present invention relates to toothbrushes and, in particular, it concerns a toothbrush with longitudinal to lateral motion conversion. It is known that best results are achieved by brushing teeth with an upwards and downwards action, thereby helping to remove food material stuck in the cracks between adjacent teeth. In practice, however, only a small proportion of users actually take the trouble to perform such a brushing action. Instead, most users revert to the much easier, but less effective, side-to-side brushing action. In power-driven toothbrushes, this problem is commonly addressed by causing vibration or rotation of brush elements perpendicular to the handle (which is generally parallel to the side-to-side primary direction of motion). Examples of power-driven toothbrushes which employ such an action may be found in U.S. Patents Nos. 2,583,886 to Schlegel, 2,665,675 to Grover, and 5,864,911 to Arnoux et al. In the field of manual toothbrushes, however, the problem is not so readily solved. A wide variety of toothbrush structures have been proposed in an attempt to produce a secondary up-down motion even when the user only actively moves the toothbrush in a side-to-side primary direction of motion. Many of these employ rotatable bristle-carrying elements deployed so as to rotate about an axis perpendicular to the primary direction of motion. Examples of such structures may be found in U.S. Patents Nos. 5,142,724 to Park, 5,186,627 to Amit et al., and 5,996,157 to Smith et al. None of these, however, has been found particularly effective. An alternative solution is suggested in U.S. Patent No. 1,643,217 to Lazarus. Here, a spiral arrangement of bristles extends along a rotatable shaft rotatably mounted parallel to the primary direction of motion. The description states that "the spiral arrangement of the bristle tufts tends to cause the bristle member, when rubbed against the teeth or the like, to rotate on the handle and so to bring a fresh surface continually into use." In practice, however, since the axis of rotation is parallel to the direction of motion, it is clear that little or no rotation would actually be induced. There is therefore a need for a manual toothbrush which would effectively produce a secondary up-down motion when the user only actively moves the toothbrush in a side-to-side primary direction of motion. It would also be highly advantageous to provide a method for brushing along a row of teeth so as to generate a brushing action perpendicular to a direction of motion. SUMMARY OF THE INVENTION The present invention is a toothbrush with longitudinal to lateral motion conversion. According to the teachings of the present invention there is provided, a toothbrush for brushing teeth within a mouth of a user, the toothbrush comprising: (a) a handle configured to define a primary direction of insertion of the toothbrush into the mouth; and (b) a plurality of rotatable brush assemblies mechanically linked so as to move together with the handle, the rotatable brash assemblies being deployed so as to define a plane of contact with the teeth, each of the rotatable brush assemblies including a wheel configured to be rotatable about an axis, the wheel having a plurality of bristles projecting substantially radially therefrom, wherein each of the rotatable brush assemblies is configured such that its aforementioned axis lies substantially parallel to the plane of contact and is inclined relative to the primary direction of insertion by an angle of between about 15° and about 75°. According to a further feature of the present invention, the axis of each of the rotatable brush assemblies is inclined relative to the primary direction of insertion by an angle of between about 30° and about 60°, and more preferably, between about 40° and about 50°. According to a further feature of the present invention, the plurality of rotatable brush assemblies includes a first group for which the axis of rotation is inclined in a first sense relative to the primary direction of insertion and a second group for which the axis of rotation is inclined in a second sense, opposite to the first sense, relative to the primary direction of insertion. According to a further feature of the present invention, the first group includes a plurality of the rotatable brush assemblies arrayed along a first line substantially parallel to the direction of insertion, and wherein the second group includes a plurality of the rotatable brush assemblies arrayed along a second line, parallel to but displaced from the first line. According to a further feature of the present invention, each of the rotatable brush assemblies includes at least one feature configured to inhibit rotation of the wheel in a given direction about the axis. According to a further feature of the present invention, each of the rotatable brush assemblies is mounted relative to the handle via a swivel mounting such that the rotatable brush assemblies can swivel about a swivel axis substantially perpendicular to the plane of contact, the swivel axis being offset relative to the axis of rotation of the wheel. According to a further feature of the present invention, there is also provided a toothbrush head portion integrally formed with the handle, the head portion including a recessed socket for each of the rotatable brash assemblies, a part of each rotatable brush assembly being received within a corresponding one of the recessed sockets. There is also provided according to the teachings of the present invention, a method for brushing along a row of teeth so as to generate a brushing action perpendicular to a direction of motion, the method comprising: (a) providing a toothbrush including at least one rotatable brush assembly including a wheel configured to be rotatable about an axis, the wheel having a plurality of bristles projecting substantially radially therefrom; (b) positioning the toothbrush with a number of the bristles in contact with a part of the row of teeth; and (c) moving the toothbrash along the row of teeth in a direction of motion, wherein the at least one rotatable brush assembly is oriented with its axis inclined at an angle of between about 15° and about 75° to the direction of motion such that rotation of the wheel caused by the movement generates a component of motion of the bristles substantially perpendicular to the direction of motion. According to a further feature of the present invention, the at least one rotatable brush assembly is oriented with its axis inclined at an angle of between about 30° and about 60°, and more preferably, between about 40° and about 50°, to the direction of motion. BRIEF DESCRIPTION OF THE DRAWINGS The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: FIG. 1A is a first schematic isometric view of a rotatable brush assembly being moved in a direction of motion to brush teeth according to the principles of the present invention; FIG. IB is a second isometric view taken along the direction of motion of Figure 1A; FIG. 2 is a schematic isometric view of a first embodiment of a toothbrush, constructed and operative according to the teachings of the present invention; FIGS. 3 A and 3B are schematic isometric views of a wheel assembly and a socket, respectfully, together forming a preferred implementation of a rotatable brush assembly of the toothbrush of Figure 2; FIG. 4 is a schematic cross-sectional view taken through the rotatable brush assembly of the toothbrush of Figure 2; FIG. 5A is a plan view of the toothbrash of Figure 2; FIG. 5B is a plan view of a first variant of the toothbrash of Figure 2, employing a staggered pattern of rotatable brash assemblies; FIG. 5C is a plan view of a second variant of the toothbrash of Figure 2, employing variable angle rotatable brush assemblies; FIG. 6 is a schematic cross-sectional view taken along line VI- VI of Figure 5C illustrating a preferred structure for the variable angle rotatable brash assembly; FIGS. 7 A and 7B are schematic isometric views of a wheel assembly and a socket, respectfully, together forming a first alternative construction of a rotatable brash assembly of the toothbrash of Figure 2; FIG. 8 is a schematic cross-sectional view showing a suspended rotatable brash assembly for use in a toothbrash constructed and operative according to the teachings of the present invention; FIG. 9 is a schematic cross-sectional view of an alternative suspended rotatable brash assembly for use in a toothbrash constracted and operative according to the teachings of the present invention; and FIG. 10 is a schematic cross-sectional view showing a suspended rotatable brash assembly configured for implementing the mode of operation of Figure 5C. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a toothbrash with longitudinal to lateral motion conversion. The principles and operation of toothbrushes according to the present invention may be better understood with reference to the drawings and the accompanying description. Referring now to the drawings, Figures 1A-5A illustrate a first embodiment of a toothbrash, generally designated 10, constracted and operative according to the teachings of the present invention, for brushing teeth 12 within a user's mouth. Toothbrash 10 is configured for use in a primary direction of motion 14 (Figure 1A) which corresponds to a primary direction of insertion into the mouth as defined by the extensional direction of a toothbrash handle 16 (Figure 2). Generally speaking, toothbrash 10 includes a plurality of rotatable brash assemblies 18, mechanically linked so as to move together with handle 16, the rotatable brash assemblies being deployed so as to define a plane of contact 20 with the teeth. Each rotatable brash assembly 18 includes a wheel 22 configured to be rotatable about an axis 24, and having a plurality of bristles 26 projecting substantially radially therefrom. Each rotatable brush assembly 18 is configured such that its axis 24 lies substantially parallel to the plane of contact 20 and is inclined relative to primary direction of motion 14 by an angle θ of between about 15° and about 75°, more preferably between about 30° and about 60°, and most preferably between about 40° and about 50°. Typically, an angle of approximately 45° is most preferred. As a result of this structure, when toothbrush 10 is inserted into the mouth, positioned with some of bristles 26 in contact with a part of the row of teeth 12 and moved in direction of motion 14, friction and/or mechanical engagement with the teeth causes rotation of rotatable brash assemblies 18. Due to the inclination of the axes 24 of rotatable brush assemblies 18 relative to the direction of motion 14, this rotation introduces a component of motion of the bristles 26 that are in contact with the teeth 12 in a direction perpendicular to direction of motion 14. As a result, the common side-to-side brushing action performed by most users inherently generates a significant secondary up-down brushing effect. Before addressing the features of the present invention in more detail, it will be useful to define certain terms as used herein in the specification and claims. Firstly, when defining the geometrical features of the present invention, reference is made variously to the "primary direction of motion 14", the "primary direction of insertion into the mouth" and "the extensional direction of a toothbrash handle 16". In a typical case, these are all assumed to be parallel. Conceptually, it is the geometry with respect to the direction of motion which is essential to proper operation of the present invention. The extensional direction of the handle is chosen as a structural feature which is related to the direction of motion. However, it will be noted that toothbrush handles are often designed to be non-parallel to the head of the toothbrush. For this reason, reference is made to "a primary direction of insertion of the toothbrash into the mouth" defined by the handle configuration. This direction is defined as the projection of the extensional direction of the handle onto plane 20. This geometrical construct corresponds to the direction of motion which will be performed by a typical user performing a side-to-side type brushing action. Axis 24 is described as "substantially parallel to plane of contact 20". This phrase is used to distinguish the configurations of the present invention from the numerous conventional structures where a bristle-supporting element is rotatable about an axis substantially perpendicular to the plane of contact. Such structures are clearly incapable of functioning according to the principles of the present invention. It should be noted that "substantially parallel" in this context should be interpreted broadly to encompass a considerable range of angles (up to as much as +30°) between axis 24 and plane 20 within which the principles of the present invention are still operative. With regard to the term "bristles", this is used herein generically to refer to any and all fibers suited for use in toothbrashes, including natural and synthetic bristles. Turning now to the features of toothbrush 10 in more detail, Figures 3 A, 3B and 4 illustrate a first preferred implementation of a rotatable brash assembly 18 for use in the present invention. This form is particularly preferred for its simplicity of production and assembly. Figure 3A shows wheel 22 with radially projecting bristles 26 prior to assembly. In this case, wheel 22 is formed with axial projections 28 to serve as an axle. This structure can be produced by a range of known manufacturing techniques used in the field. Examples include, but are not limited to, implantation of fiber bundles into softened plastic and injection molding around a prepared arrangement of fibers. Figure 3B shows the preferred form of a corresponding socket 30 formed in the surface of the head portion of toothbrash 10. Within, or adjacent to, socket 30 stand two spring brackets 40 which have recesses 42 configured to provide a permanent snap-fit engagement with projections 28 to define the axis of rotation of wheel 22 when assembled. The remainder of socket 30 is shaped to accommodate at least a proportion of bristles 26 in a manner to allow unimpeded rotation thereof of wheel 22. Optionally, wheel 22 may be formed with a slightly projecting hub 44 surrounding projection 28 so as to provide a well defined reduced-area contact surface with brackets 40, thereby reducing frictional opposition to rotation of the wheel. It will be appreciated that the entire body of toothbrash 10, including the head of the toothbrush formed with sockets 30 and the toothbrash handle, may conveniently be produced as a single integral element by a range of well known techniques such as plastic injection molding around suitable metallic brackets. Preferably, as may be seen in Figure 4, each socket 30 is additionally formed with a drainage channel 46 open to the rear of the toothbrash head to facilitate flushing out and cleaning of the assembly. It will be noted that a single rotatable brash assembly 18 of the structure described herein would have a tendency to creep laterally from the intended direction of motion. To counteract this tendency, toothbrash 10 preferably includes at least two groups of rotatable brash assemblies 18 inclined in opposite senses relative to the primary direction of insertion. By way of a preferred example, Figures 2, 5A and 5B show embodiments with two groups of rotatable brush assemblies 18 arrayed along two parallel lines with angles of inclination ±θ, respectively, relative to the primary direction of insertion. In this case, the arrays of rotatable brash assemblies 18 extend parallel to the direction of insertion. The implementations of Figures 2 and 5A differ only in that the sense of inclination of the two rows has been reversed. Although the rotatable brush assemblies 18 are preferably deployed in groups inclined in opposing senses for the reasons already mentioned, details of the deployment may clearly be varied considerably. Thus, depending upon the size of the elements, more than two rows may be provided. Optionally, the rows may be staggered, such as is shown in Figure 5B, to achieve effective close packing of the rotatable brash assemblies 18. In a first set of implementations of the present invention, rotatable brash assemblies 18 turns freely in both directions. As a result, in the configurations shown in Figures 5A and 5B, rotation of the assemblies causes an inwards brushing action, towards the center of the toothbrush head, when the toothbrash is advanced forward within the mouth, and an outward brushing action as it is withdrawn. Although this alternating direction is believed to be acceptable in many application, it is believed that superior results may sometimes be provided by modifying the assemblies to rotate exclusively in one direction, providing a ratchet-type functionality. This feature is preferably used to configure the rotatable assemblies to brash exclusively inwards, so that they do not turn during alternate strokes of the toothbrush. One preferred implementation of this optional feature is illustrated in Figure 4. Specifically, wheel 22 is shown here to have an axial dimension between hubs 44 slightly smaller than the spacing between brackets 40 so that it only one hub is in contact with its adjacent bracket at any time. One of hubs 44 is made smooth, while the other is enlarged and/or modified by addition of radial ribs 48 or other surface features configured to provide increased friction. The region of one bracket 40 opposite to the increased friction surface is preferably also roughened in a complementary manner. This structure provides a very simple and reliable, but yet effective, ratchet-type function. Specifically, when the toothbrush is advanced in a first direction, the forces on wheel 22 move it axially to a first position in which the smooth hub 44 contacts the corresponding bracket 40, thereby allowing wheel 22 to turn freely during operation as described above. When the direction of toothbrash motion is reversed, wheel 22 moves axially to contact the second bracket. In this position, the increased friction surfaces of the second hub and corresponding bracket are brought into contact, generating sufficient frictional resistance to substantially prevent rotation of wheel 22 during the reverse toothbrash stroke. According to a further optional feature, the rotating brash assemblies may be configured to operate during both stroke directions of the toothbrash exclusively inwards (or outwards) with respect to the toothbrush head. This may be achieved by use of a swivel-mounted rotatable brash assembly, as will now be described with reference to Figures 5C and 6. Specifically, in this example, each assembly 18 is configured to swivel about a swivel axis 50 substantially perpendicular to contact plane 20 so that its axis of rotation 24 can vary over a range of ±θ relative to direction of motion 14. Swivel axis 50 is preferably offset relative to the axis 24 of wheel 22 so that forces acting on wheel 22 from friction of bristles 26 with the teeth generate a turning moment about swivel axis 50 tending to swivel the assembly to the desired angle. Structurally, details of a preferred implementation are shown in Figure 6. Swivel axis 50 is here provided by a rotary sliding bearing 52 which is implanted within the base of an enlarges socket 30. Brackets 40 here extend upwards at an angle to provide the aforementioned offset between swivel axis 50 and the axis 24 of wheel 22. Turning now to Figures 7-10, it should be noted that the rotatable brash assembly 18 of Figures 3 and 4 is one preferred example chosen from a large number of possible implementations. By way of illustration, Figures 7-10 show a number of alternative implementations. Referring to Figures 7A and 7B, these show a structure generally similar to that of Figures 3 and 4, but wherein socket 30 features two shaped recesses 32 integrally formed on opposite sides of the socket to provide a snap-fit engagement with projections 28. In this case, just over half of each wheel 22 is housed within the head of the toothbrash when assembled. Optionally, socket 30 may have an increased width portion around its periphery, i.e., remote from recesses 32, to allow free rotation of the wheel even if bristles 26 become bent apart as a result of extensive use. Turning now to Figure 8, this shows an alternative implementation of rotatable brash assemblies 18 in which wheels 22 have hollow axial recesses or bores 34 which receive axle elements 36 which are supported above a surface of the toothbrash head by support posts 38. The result is a series of wheels rotatably mounted on a zigzag frame standing above the surface of the toothbrash head. Axle elements 36 may either be complete rods, or may be implemented as pairs of opposing projections which snap-fit into recesses or bores 34 on opposite sides of each wheel 22. Figure 9 shows a further alternative implementation in which each wheel 22 is formed from two parts which lock together to form a double wheel structure with a peripheral annular groove 54 which cooperates with a complementary slip ring 56. In this case, the two parts of wheel 22 are preferably snap-fitted or otherwise attached to each other during assembly of the toothbrush in position engaged with slip ring 56 as shown. Finally, with reference to Figure 10, it should be noted that the aforementioned swivel-mounted rotatable brash assembly may also be implemented in alternative forms. By way of example, Figure 10 shows a possible implementation in which a central, non-turning hub 60 of wheel 22 is mounted on a support bar 62 to provide a swivel joint offset from the center of central hub 60. The rotating portion of wheel 22 is implemented as an outer ring 64 deployed externally in sliding relation to central hub 60. It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the spirit and the scope of the present invention.

Claims: WHAT IS CLAIMED IS: 1. A toothbrash for brushing teeth within a mouth of a user, the toothbrash comprising: (i) a handle configured to define a primary direction of insertion of the toothbrash into the mouth; and (ii) a plurality of rotatable brush assemblies mechanically linked so as to move together with said handle, said rotatable brush assemblies being deployed so as to define a plane of contact with the teeth, each of said rotatable brush assemblies including a wheel configured to be rotatable about an axis, said wheel having a plurality of bristles projecting substantially radially therefrom, wherein each of said rotatable brush assemblies is configured such that its aforementioned axis lies substantially parallel to said plane of contact and is inclined relative to said primary direction of insertion by an angle of between about 15° and about 75°. 2. The toothbrash of claim 1, wherein said axis of each of said rotatable brash assemblies is inclined relative to said primary direction of insertion by an angle of between about 30° and about 60°. 3. The toothbrash of claim 1, wherein said axis of each of said rotatable brash assemblies is inclined relative to said primary direction of insertion by an angle of between about 40° and about 50°. 4. The toothbrush of claim 1, wherein said plurality of rotatable brash assemblies includes a first group for which the axis of rotation is inclined in a first sense relative to said primary direction of insertion and a second group for which the axis of rotation is inclined in a second sense, opposite to said first sense, relative to said primary direction of insertion. 5. The toothbrush of claim 4, wherein said first group includes a plurality of said rotatable brush assemblies arrayed along a first line substantially parallel to said direction of insertion, and wherein said second group includes a plurality of said rotatable brash assemblies arrayed along a second line, parallel to but displaced from said first line. 6. The toothbrush of claim 1, wherein each of said rotatable brash assemblies includes at least one feature configured to inhibit rotation of said wheel in a given direction about said axis. 7. The toothbrush of claim 1, wherein each of said rotatable brash assemblies is mounted relative to said handle via a swivel mounting such that said rotatable brash assemblies can swivel about a swivel axis substantially perpendicular to said plane of contact, said swivel axis being offset relative to said axis of rotation of said wheel. 8. The toothbrush of claim 1, further comprising a toothbrush head portion integrally formed with said handle, said head portion including a recessed socket for each of said rotatable brush assemblies, a part of each rotatable brush assembly being received within a corresponding one of said recessed sockets. 9. A method for brushing along a row of teeth so as to generate a brushing action perpendicular to a direction of motion, the method comprising: (i) providing a toothbrash including at least one rotatable brash assembly including a wheel configured to be rotatable about an axis, the wheel having a plurality of bristles projecting substantially radially therefrom; (ii) positioning the toothbrash with a number of the bristles in contact with a part of the row of teeth; and (iii) moving the toothbrush along the row of teeth in a direction of motion, wherein the at least one rotatable brush assembly is oriented with its axis inclined at an angle of between about 15° and about 75° to the direction of motion such that rotation of the wheel caused by the movement generates a component of motion of the bristles substantially perpendicular to the direction of motion. 10. The method of claim 9, wherein the at least one rotatable brash assembly is oriented with its axis inclined at an angle of between about 30° and about 60° to the direction of motion. 11. The method of claim 9, wherein the at least one rotatable brash assembly is oriented with its axis inclined at an angle of between about 40° and about 50° to the direction of motion.

Inventors: BEN-ARI TSAFRIR, BEN-ARI, TSAFRIR
Applicants: BEN ARI TSAFRIR, BEN-ARI, TSAFRIR
Application year: 2001
Main classification: A46B7
IPC codes: A46B7, A46B9, A46B15