Electric toothbrush reduction gearbox

[0001] The present invention relates to an electric toothbrush having a reduction gearbox. More particularly, although not exclusively, the invention relates to an electric toothbrush having a motor driving an oscillating bristle head via a drive shaft and a reduction gearbox.

[0002] Known electric toothbrushes have a handle within which there is situated a battery or batteries, an electric motor receiving power from the batteries via a switch, and a drive shaft extending through a neck of the toothbrush to an oscillating bristle head. As the motor's output is at relatively high RPM compared to the desired oscillation frequency of the bristle head, it would be desirable to reduce the output speed of the motor to drive the drive shaft at lower speed. Electric toothbrushes having a reduction gearbox have been proposed, however, they are of complex design requiring many parts. They have also been mounted to the handle independently of the motor, thereby requiring special attachment to the housing to counteract the motor's output torque.

[0003] It is an object of the present invention to overcome or substantially ameliorate at least one of the above disadvantages and/or more generally to provide an electric toothbrush having a motor and a reduction gearbox fitted directly to the motor to counteract the motor's output torque.

[0004] It is a further object of the present invention to provide an improved electric toothbrush having a reduction gearbox.

[0005] There is disclosed herein an electric toothbrush comprising:

• • [0006] a handle,
  • [0007] a bristle head,
  • [0008] a neck extending from the handle to the bristle head,
  • [0009] a drive shaft extending through the neck to the bristle head,
  • [0010] a motor situated within the handle and having a pair of spaced apart recesses and an output shaft situated between the recesses,
  • [0011] a reduction gearbox receiving torque from the output shaft of the motor and transmitting it to the drive shaft at a reduced speed, the gearbox comprising a base plate having a pair of projections extending into the recesses of the motor, a cover plate fixed to the base plate and at least one gear set between the base plate and the cover plate and transmitting torque from the motor to the drive shaft.

[0012] Preferably a first driving gear is mounted upon the output shaft of the motor.

[0013] Preferably the base plate has extending therefrom a pin upon which a first driven gear is rotatably mounted.

[0014] Preferably the first driven gear has fixedly associated therewith a second driving gear.

[0015] Preferably the cover plate has a pair of bridges by which the cover plate is fixed to the base plate.

[0016] Preferably the cover plate has a pin upon which a second driven gear is rotatably mounted.

[0017] Preferably the second driven gear has extending therefrom an output member received by an end of the drive shaft.

[0018] Preferably the output member passes through a retaining plate that is affixed to the cover plate.

[0025] In the accompanying drawings there is schematically depicted an electric toothbrush having a plastics-moulded housing that comprises a handle H and a neck N formed integrally with the handle. Within the handle there is situated a pair of batteries 2. These batteries might be of the disposable or rechargeable type. As an alternative, a single battery might be provided. In the depicted embodiment, there are two batteries connecting series at the base by a coil spring and conductive plate arrangement 1. At the upper end of the batteries, one is connected at 3 to a positive terminal whereas the other is connected 4 to a negative terminal. Positive terminal 3 is connected via a switch wire 7 to a switch 8 that has an ON/OFF button 10. The switch 8 is connected to an electric motor 6 via a switch-motor wire 9. The positive terminal 4 is connected directly to the motor 6 via a battery-motor wire 5. The motor has in its upper surface a pair of recesses 28, between which there is situated an output shaft 29. Mounted directly to the motor 6 is a gearbox base plate 12. Base plate 12 is typically formed of moulded plastic material and has a pair of projections 27 that extended downwardly and into the respective recesses 28. Fixed to the output shaft 29 is a first driving gear 11. The base plate 12 has an outstanding pin 31 onto which a first driven gear 13 is rotatably mounted. The first driven gear 13 meshes with the first driving gear 11. Formed integrally with the first driven gear 13 is a second driving gear 14.

[0026] A gearbox cover plate 15 is fixed to the base plate 12 by a pair of bridges 30. That is, the first driving gear 11 and the first driven gear 13 are sandwiched between the base plate 12 and the cover plate 15. This maintains a meshing inter-engagement between the gears 11 and 13.

[0027] The cover plate 15 includes a pin 32 upon which there is rotatably mounted a second driven gear 16. This gear is maintained in position upon the pin 32 by a retaining plate 17, typically formed of stainless steel. The plates 12 and 15 are typically formed of moulded plastic materials such as nylon for example. The gears 11, 13, 14 and 16 are typically formed of metal or hard-wearing plastics material such as nylon.

[0028] A pair of fixing lugs 34 secures the retaining plate 17 to the cover plate 15. The fixing lugs are formed integrally with the cover plate. These include narrowed top portions that pass through corresponding apertures in the retaining plate and are typically moulded or plastics-welded thereover.

[0029] The retaining plate 17 maintains inter-engagement between the second driving gear 14 and the second driven gear 16.

[0030] Formed integrally with the second driven gear 16 is an output member 35. Output member 35 might be in the form of an externally tapered or straight spline or a short shaft with a key-way. The output member 35 is received within a coupling 26 that is affixed at an input end of a drive shaft 19 that extends through the neck N of the toothbrush. The drive shaft 19 is mounted in bushings 22 and 24. These bushings maintain the drive shaft 19 within the neck N. A pair of O-ring seals 23 and 25 are also positioned around the drive shaft. These prevent the ingress of liquid downwardly along the shaft toward the gearbox and motor in use. The driveshaft 19 has a dogleg portion 33 that is received within a slot of the bristle head 18. Bristle head 18 is mounted upon a positioning shaft 20 having a positioning sleeve 21. The positioning shaft 20 defines an axis of rotation of the bristle head.

[0031] In use, the ON/OFF button 10 is depressed to provide electric current to the motor 6 so as to turn the first driving gear 11. The rotational speed of the motor's output shaft 19 is reduced through the gearbox such that the output member 35 turns at a lower speed. This results in reduced speed and increased torque delivered to the drive shaft 19.