MECHANICAL TOOTHBRUSH

Abstract: A mechanical toothbrush (20) including a rotating drive shaft (26) and a plurality of bristles (38), having inner ends eccentrically coupled to be driven by the drive shaft and outer ends for contacting a tooth surface, such that the outer ends move in a cyclical two-dimensional path in a plane generally perpendicular to the shaft axis (28).

Description: MECHANICAL TOOTHBRUSH FIELD OF THE INVENTION The present invention relates in general to toothbrushes, and specifically to powered mechanical toothbrushes BACKGROUND OF THE INVENTION Mechanical, and especially electromechanical, toothbrushes are well known m the art. Most of these mechanical or electromechanical toothbrushes rotate or oscillate in some manner so as to improve the cleaning of the teeth compared to a simple manual toothbrush. U.S. patent 5,120,225, to Amit, which is incorporated herein by reference, describes a manual toothbrush wherein a rack and pinion within the toothbrush head converts longitudinal reciprocation of the handle to oscillatory rotation of the rotatable bristle tufts. U.S. patent 4,974,278, to Homrtiann, which is incorporated herein by reference, describes an electric toothbrush comprising a shaft mounted in the toothbrush casing so as to be rotatably and longitudinally movable, so that brush elements attached to the shaft perform a circular movement over the surface of the teeth. The shaft and brush elements move in a plane containing the shaft axis, parallel to the brush handle. The brush elements do not give a scraping action when the handle is moved with a typical up and down or side-tc-side motion relative to the teeth, and the mechanism is very complicated. U.S. patent 5,259,083, to Stansbury, which is incorporated herein bv reference, describes an blocks of bristles are driven by a six-lobed camshaft. In a portion of the cristle motion the general direction of the bristles is perpendicular to and towards the tooth surface. When the bristle ends contact the tooth, the bristles are deflected by the tooth so the bristle motion becomes a chiseling action. U.S. patent 5,504,958, to Herzog, which is also incorporated herein by reference, describes an electromechanical toothbrush wherein six separate tuft blocks of bristles are driven by six separate cams, so that a portion of the motion of some of the bristles is a chiseling action. In general the mechanisms for the electric toothbrushes providing chiseling action are relatively complicated. SUMMARY OF THE INVENTION It is an object of some aspects of the present invention to provide an improved mechanical toothbrush with a simple mechanism. It is a further object of some aspects of the present invention to provide a mechanical toothbrush that cleans teeth more thoroughly than conventional toothbrushes . In preferred embodiments of the present invention, a mechanical toothbrush comprises a rotating eccentric drive shaft and bristles, which are coupled at inner ends thereof to the drive shaft, preferably via one or more bearings, and protrude radially outward therefrom. The eccentric rotation of the drive shaft causes the bristles' inner ends to revolve accordingly about an axis parallel to the shaft. The bristles are laterally constrained at a fulcrum, intermediate the bristles' inner and outer ends, so that as the inner ends rotate, the outer ends cyclically describe a two-dimensional closed path, preferably a reentrant oval pattern, in a plane generally perpendicular to the drive shaft. When the bristles are brought into contact with a tooth, they are thus driven together across and against the tooth surface, providing a scraping action that cleans teeth more thoroughly than manual or mechanical toothbrushes known in the art. The drive shaft is preferably driven by a motor, although other means of rotational propulsion may also be used, as are known in the art. The motor and drive shaft are enclosed by a housing. In some preferred embodiments of the present invention, the inner ends of the bristles are held by a bristle holder, which mates with the eccentric drive shaft. Preferably, the bristles are rigidly connected to the holder. Lateral constraint of the bristles is provided by first and second linear jaws which grip the bristle holder, and which are equidistantly offset from and substantially parallel to the drive shaft. In other preferred embodiments of tne present invention, a plurality of eccentric drive shafts mate with respective bristle holders. Each of the bristle holders holds a respective group of bristles, so that different groups of bristles can move in different directions and/or m different phases of rotation. Preferably the bristle holder and first and second jaws are constructed from a hard self-lubricatmg plastic such as nylon, and most preferably the first and second aws and the housing are constructed as one piece by injection molding. There is therefore provided, in accordance with a preferred embodiment of the present invention, a mechanical toothbrush including: a rotating drive shaft; and a plurality of bristles, having inner ends eccentrically coupled to the drive shaft and outer ends for contacting a tooth surface, such that the outer ends move in a cyclical two-dimensional path m a plane generally perpendicular to the shaft axis. Preferably, the plurality of bristles are constrained laterally at a fulcrum intermediate the inner and outer ends thereof. Preferably, the drive shaft includes an eccentric end portion, to which the plurality of oristles are coupled. Preferably, the bristles are coupled to the drive shaft by a oeaπng, which is preferably self-lubricatmg. Preferably, the fulcrum s formed of first and second opposing linear jaws substantially parallel to and equidistantly offset from the drive shaft, and a housing including tne jaws encloses the drive snaft. Preferably, the jaws grip a bristle holder holding the plurality of bristles, and the contact between the jaws and the bristle holder is self-lubricating. Preferably, the fulcrum constrains the bristle outer ends to move in a generally lateral direction when the drive shaft motion is substantially parallel to the plane containing the jaws, and in a generally radial direction when the drive shaft motion is substantially perpendicular to the plane containing the jaws. Preferably, the drive shaft is rotated by a motor. Alternatively, the drive shaft is rotated by a turbine . Preferably, the two-dimensional path comprises a reentrant oval . There is further provided, in accordance with a preferred embodiment of the present invention, a method for producing a mechanical toothbrush including: providing a rotating drive shaft and a plurality of bristles having outer ends for cleaning a tooth surface; coupling the plurality of bristles eccentrically to the drive shaft at respective inner ends thereof; and constraining the lateral motion of the bristles so that the outer ends move in a cyclical two-dimensional path whose plane is generally perpendicular to the shaft axis. Preferably, constraining the lateral motion of the bristles includes providing a fulcrum intermediate the inner and outer ends thereof. Preferably, providing the drive shaft includes providing an eccentric end thereof, to which the plurality of bristles are coupled. Preferably, providing the fulcrum includes forming first and second opposing linear jaws substantially parallel tc and equidistantly offset from the drive shaft. Preferably, forming the jaws includes gripping a bristle holder holding the plurality of bristles by the jaws . Preferably, constraining the lateral motion of the bristles includes constraining the bristles so that the outer ends move in a generally reentrant oval. The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a schematic, sectional view of a toothbrush, in accordance with a preferred embodiment of the present invention; Fig. IB is a schematic cross-sectional view of the toothbrush of Fig. 1A, taken along line IB-IB; Fig. 1C is a schematic cross-sectional view of the toothbrush of Fig. 1A, taken along line IC-IC; Figs. 2A - 2D are schematic cross-sectional views of the toothbrush as shown in Fig. IB, illustrating motion thereof, in accordance with a preferred embodiment of the present invention; Fig. 3 is a diagram showing a path followed by the bristle ends, when the toothbrush moves as shown in Figs. 2A - 2D; Fig. 4A is a schematic, cross-sectional view of a toothbrush, in accordance with another preferred embodiment of the present invention; Fig. 4B is a schematic cross-sectional view of the toothbrush of Fig. 4A, taken along line IVB-IVB; Fig. 4C is a schematic cross-sectional view of the toothbrush of Fig. 4A, illustrating motion thereof; Fig. 4D is a schematic cross-sectional view of the toothbrush of Fig. 43, taken along line IVD-IVD, illustrating a drive mechanism; and Fig. 4E is a schematic cross-sectional enlarged view of the toothbrush of Fig. 4D, taken along line IVE-IVE, illustrating a gear train. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to Fig. 1A, which shows a schematic sectional view of a toothbrush 20, in accordance with a preferred embodiment of the present invention. Toothbrush 20 comprises a drive shaft 26 which is rotated about an axis 28 by a motor 30. Motor 30, generally but not necessarily a DC electric motor, rotates drive shaft 26 at a rate of the order of 120 - 600 revolutions per minute. Optionally, motor 30 is connected to a switch 31, used to set the direction of rotation of motor 30, as described below. Drive shaft 26 has an eccentric rod 32 rigidly coupled to it, with an offset of the order of 3/64", so that the shaft and the rod rotate as one unit. Rod 32 has a pin 33 coupled to it. Preferably shaft 26, rod 32, and pin 33 are constructed from 3/32" diameter reinforced Zytel, and most preferably shaft 26, rod 32, and pin 33 are melded together. Drive shaft 26 is supported by a bearing 42, and pin 33 is supported by a bearing 43. Preferably bearing 42 and bearing 43 are constructed of Zytel or similar plastic, so as to form a self-lubricating bearing. Most preferably, .bearing 42 and bearing 43 are formed as a part of a housing 40, which contains motor 30, shaft 26, rod 32, pin 33 and a bristle holder 36. Rod 32 mates with a bore 34 in bristle holder 36. Bristle holder 36 is preferably in the form of a six- sided right rectangular parallelepiped. Bristle holder 36 is preferably constructed from a nylon material, such as Zytel or other similar hard plastic, by injection molding, so that rod 32 and bore 34 form a self- lubricated bearing. Bristle holder 36 grips sets of bristles 38. The sets of bristles are inserted into bristle holder 36, for example in a 4 by 6 rectangular array, preferably during injection molding of the bristle holder. Reference is now made to F g. IB and Fig. 1C. Fig. IB is a scnematic cross-sectional view of brush 20 taken along line I3-IB in Fig. 1A and orthogonal to axis 28 of the brusn. Fig. 1C is a schematic cross-sectional view of brush 20 taken along line IC-IC in Fig. 1A. Bristle holder 36 is constrained on the two sides parallel to axis 28 and orthogonal to the plane of Fig. 1C by V- shaped jaws 44, and on the two sides orthogonal to axis 28 by plane jaws 46. Preferably jaws 44 and jaws 46 are constructed from a nylon material, such as Zytel, or other similar hard plastic, so as to form a self- lubricatmg contact with the bristle holder. Most preferably jaws 44 and jaws 46 are formed as part of housing 40. Figs. 2A - 2D show schematically different cross- sectional views of toothbrush 20 in the plane of Fig. IB, as drive shaft 26 rotates, so that eccentric rod 32 revolves sequentially in a counterclockwise circle 50 about axis 28. Arrows 52, 58, 60, 62, 64, and 66 are schematic representations of velocity vectors, drawn rougnly to scale. Fig. 2A shows eccentric rod 32 revolving to the right, with a velocity represented by arrow 52. It will be appreciated that jaws 44 and jaws 46 constrain bristle holder 36 to turn generally aoout a fulcrum line 54 parallel to axis 28 and between jaws 44. Fulcrum line 54 causes bristle ends 56 to move laterally at a velocity represented by arrow 58. Fig. 23 snows eccentric rod 32 revolving vertically upward, witn a velocity represented by arrow 60. Jaws 44 and jaws 46 constrain bristle holder 36 to move radially outward, with substantially the same velocity as rod 32, so that πstle ends 36 move at a velocity represented by arrow 60. Fig. 2 shows eccentric rod 32 revolving to the left, with a velocity represented by arrow 62. Jaws 44 and aws 46 constrain bristle holder 36 to turn substantially about fulcrum line 54, so that bristle ends 56 move laterally at a velocity represented by arrow 58. Fig. 2D shows eccentric rod 32 revolving vertically downward, with a velocity represented by arrow 66. Jaws 44 and jaws 46 constrain bristle holder 36 to move racially inward, at substantially the same velocity as roc 32, so that bristle ends 36 move with a velocity represented by arrow 66. It will be appreciated that Fig. 2A and Fig. 2C illustrate situations which the bristle holder is constrained by jaws 44 to a lever-like motion in a lateral direction around fulcrum line 54. Fig. 2B and Fig. 2D illustrate situations m which the bristle holder is constrained by jaws 44 to a piston-like motion a radial direction, orthogonal to a plane connecting jaws 44. Fig. 3 is a schematic representation of a path 80 followed by bristle ends 36, relative to a tooth 90, as eccentric rod 32 rotates. Positions 82, 84, 86, and 88 correspond to Figs. 2A, 2B, 2C, and 2D respectively. Arrows 58, 60, 64, and 66 represent the velocities of the bristle ends corresponding to F gs. 2A, 2B, 2C, and 2D respectively. It will be apparent from Fig. 3 that the oristle end motion cyclically descnr.es a two-dimensional figure, which is generally a reentrant oval, a plane perpendicular to tne surface of tooth 90. During the motion from position 84 to position 86, and from position 88 to position 82, there will be a component of bristle end motion towards tooth 90, and this component /ill induce the bristle ends to move w th a scraping action during the aforementioned motion when tne bristles contact the tooth surface. This scraping action is believed to provide thorough cleaning of tne tooth surface and to be useful m penetrating into crevices and spaces between the teeth. As described above, the purpose of switch 31 is to set the direction of movement of bristles 38 according to the orientation of toothbrush 20, so that the bristles are made to brush against the teeth in a preferred direction, generally up-to-down, regardless of the orientation. Preferably, switch 31 comprises a gravity- actuated mercury switch 31, although a manually-actuated switch may also be used. The downward motion of the bristles against the tooth surface, together with the scraping motion described above, is believed to provide further improved cleaning of the tooth surface. Reference is now made to Fig. 4A and Fig. 4B, which are schematic, sectional views of a toothbrush head 100 in accordance with another preferred embodiment of the present invention. Toothbrush head 100 comprises first and second bristle holders 102 and 104, held respectively by first and second pairs of jaws 106 and 108. The bristle holders grip single linear sets of bristles 118 and 120. Bristle holders 102 and 104 are driven by rods 110 and 112 respectively, such that the circular paths 114 and 116 followed by the rods are clockwise and counterclockwise respectively. Housing 122 grips a dual set of linear bristles 124, which are fixed relative to the housing. Preferably, the inner rows of bristles 124 protrude less than the outer rows of bristles 113 and 120, so that in use the inner rows brace the head against the tooth while the outer rows move against the teeth, generally as illustrated in Fig. 3. Fig. 4C shows schematically a cross-sectional view of toothbrush head 100 after rods 110 and 112 have revolved 90 degrees clockwise and counterclockwise respectively from the position shown in Fig. 4A. The respective paths 126 and 128 followed by the bristle ends are shown. It will be apparent that when the toothbrush is held so that bristles contact the teeth, one set of moving bristles will always be moving downward over a tooth surface. Fig. 4D is a schematic cross-sectional view of toothbrush nead 100 taken along line IVD-IVD, illustrating how bristles 118 and 120 are driven. Fig. 4E is a schematic cross-sectional enlarged view taken along line IVE-IVE, illustrating a gear tra the toothbrush head. Drive shaft 130 is coupled to a gear 132. Gear 132 mesnes witn gear 134, upon which rod 110 is mounted eccentrically. Gear 132 also meshes with a transmission gear 136, wmch m turn mesnes with a gear 140 upon wnich rod 112 is mounted eccentrically. Rods 110 and 112 are supported at their distal ends by respective discs 142 and 144. Preferaoiy the aforementioned gears and discs are constructed from self-lubricatmg material, such as Delrm or Kevlar-remforced nylon, so that meshing surfaces and bearing surfaces in contact with housing 122 are lubricated. When shaft 130 rotates, rod 112 will revolve in the same direction, and rod 110 will revolve m the opposite direction. The combination of clockwise and counterclockwise rotations m toothbrush head 100 reduces the vibration inherent in the toothbrush. Furthermore, regardless of tne orientation of the nead, there will be an upper row of bristles moving against the tooth with the desired combination of downward and scraping actions independent of the orientation of the toothbrush. It will be appreciated that toothbrushes may be produced m accordance with the principles of the present invention having different nuir-oers and configurations of rows of bristles. For example, another preferred embodiment of the present invention, not shown the figures, two rows of bristles may move togetner a clocK ise direction, and tne otner two rows may move m a counterclockwise direction. While the preferred embodiments of the present invention are described using an electric motor, it will be appreciated that other means known in the art for rotating drive shafts may be used, including hydraulic, fluid, or manual drives. Thus, as the above-described preferred embodiments demonstrate, toothbrushes in accordance with the principles of the present invention provide optimal cleaning of tooth surfaces, and are also simple and inexpensive to manufacture. The preferred embodiments described above are cited by way of example, and the full scope of the invention is limited only by the claims.

Claims: CLAIMS 1. A mechanical toothbrush comprising: a rotating drive shaft; and a plurality of bristles, having inner ends eccentrically coupled to be driven by the drive shaft and outer ends for contacting a tooth surface, such that the outer ends move m a cyclical two-dimensional path m a plane generally perpendicular to the shaft axis. 2. A toothbrush according to claim 1, wherein the drive shaft comprises an eccentric end portion, to which the plurality of bristles are coupled. 3. A toothbrush according to claim 1 or 2, wherein the bristles are coupled to the drive shaft by a oearmg. 4. A toothbrush according to claim 3, wherein the bearing is self-lubricatmg. 5. A toothbrush according to any of the preceding claims, wnere the plurality of bristles are constrained laterally at a fulcrum intermediate the inner and outer ends thereof. 6. A toothbrush according to claim 5, wherein the fulcrum is formed of first and second opposing linear jaws suostantially parallel to and equidistantly offset from the drive shaft. 7. A toothbrush according to claim 6, wherein a housing comprising the jaws encloses the drive shaft. 8. A toothbrush according to claim 6 or 7, and comprising a bristle holder which holds the plurality of bristles and which is engaged by the jaws. 9. A toothorush according to claim 8, wnerem the contact between the jaws and the bristle holder is self- lubricatmg. 10. A tootnbrusn according to any of claims 6-9, wnerem the fulcrum constrains the bristles sucn that the outer ends thereof move in a generally lateral direction relative to tne shaft when the inner ends of the bristles move a direction substantially parallel to a plane containing the jaws, and in a generally radial direction when the inner ends move m a direction substantially perpendicular to the plane containing the aws. 11. A toothbrush according to any of the preceding claims, and comprising a motor, coupled to rotate the drive shaft. 12. A toothbrush according to claim 11, and comprising a switch coupled to the motor for reversing the direction of rotation thereof. 13. A toothbrush according to claim 12, wherein the switch is gravity-actuated. 14. A toothbrush according to any of the preceding claims, and comprising a turbine, coupled to rotate the drive shaft. 15. A toothbrush according to any of the preceding claims, wherein the drive shaft rotates m response to a force applied manually to the toothbrush. 16. A tootnbrush according to any of the preceding claims, wherein the two-dimensional path describes a reentrant oval shape. 17. A toothbrush according to any of the preceding claims, wherein the plurality of bristles comprises first and second rows of bristles, separately coupled to the drive snaft, such that the outer ends of the bristles in the first row move against the tooth surface in a first direction and the outer ends of the bristles m the second row move in a second direction, generally opposite the first direction. 18. A toothbrush according to claim 17, and comprising first anc second rods, driven oy the drive shaft in opposite directions to respectively drive the first and second rows of bristles. 19. A toothbrush according to any of tne preceding claims, and comprising additional stationary bristles whicn are not coupled to be driven by tne drive shaft. 20. A tootncrush according to claim 19, wnerem the stationary bristles bear against the tooth surface wnile the plurality of bristles driven by the drive shaft move against the tooth surface.. 21. A method for producing a mechanical tootncrush comprising: providing a rotating drive shaft and a plurality of onstles having outer ends for cleaning a tootn surface; coupling the plurality of bristles eccentrically at respective inner ends of the bristles to be driven by the drive shaft; and constraining a lateral motion of the onstles so that the outer ends move in a cyclical two-dimensional path wnose plane is generally perpendicular to the snaft axis. 22. A method according to claim 21, wherein providing the drive snaft comprises providing an eccentric end thereof, to which the plurality of bristles are coup_ed. 23. A method according to claim 21 or 22, wnerem constraining the lateral motion of the bristles comprises providing a fulcrum intermediate the inner and outer ends thereof. 24. A method according to claim 23, wherein providing the fulcrum comprises forming first and second opposing linear jaws substantially parallel to and equidistantly offset from the drive shaft. 25. A method according to claim 24, wherein providing the fulcrum comprises engaging a bristle holder homing the plurality of bristles between the jaws. 26. A method according to any of claims 21-25, wherein constraining the lateral motion of the bristles comprises constraining the bristles so that the outer ends move in a generally reentrant oval. 27. A method according to any of claims 21-26, wherein coupling the plurality of bristles eccentrically to the drive shaft comprises eccentrically coupling first and second rows of bristles respectively to first and second rods, such that the direction of motion of the first row is generally opposite the direction of motion of the second row. 28. A method according to any of claims 21-27, and comprising providing additional stationary bristles which bear against the tooth surface while the plurality of bristles coupled to the drive shaft move against the surface .

Inventors: RAMON EFI, RAMON, EFI
Applicants: RAMON EFI, RAMON, EFI
Application year: 1998
Main classification: A61C17
IPC codes: A61C17