Brushing – scrubbing – and general cleaning – Machines – Brushing
Patent
1991-10-04
1993-06-01
Roberts, Edward L.
Brushing, scrubbing, and general cleaning
Machines
Brushing
15 23, 81467, 192 56R, 403351, A61C 1732
Patent
active
052148190
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a toothbrush of the type referred to in the preamble of the main claim. A toothbrush of this type is already known from a plurality of printed publications including, for example, EP-A2 0 173 150. Although, overall, these toothbrushes are well-proven and also established in practice, their handling is still capable of further improvement. One problem exists in protecting the user against the consequences of an improper handling of the toothbrush. Improper handling of the toothbrush is frequently involved if the user, in an attempt to accomplish an intensive cleaning effect, presses the toothbrush with too much pressure against the teeth and also the gums. Such manipulation may result in damage to the gums and may have other consequences adversely affecting the user.
To solve this problem, suggestions have already been made as represented, for example, in DE-C2 31 17 160. In the toothbrush of this specification, the contact pressure is sensed either by means of a pressure-responsive movement of the oscillating drive within the housing or by means of the amount of bending of the handle or the current consumption of the motor, and a visual indication is provided when the sensed value exceeds or drops below the optimum contact pressure. However, such solutions necessitate a high complexity of sensors and electrical means and, as it appears, have so far been unable to establish themselves in practice. In addition, the user may ignore the visual indication and continue improper manipulation of the toothbrush.
Moreover, these solutions fail to provide an indication of how the electric motor of the toothbrush is protected against overload. In view of the requirements for small dimensions and low weight of the toothbrush, the drive motors are correspondingly dimensioned, operating normally in the upper range of their capacity. Improper manipulation of the toothbrush caused, for example, by the application of an excessive contact pressure, may overload the motor and eventually cause a failure of the motor.
It is an object of the present invention to improve upon a toothbrush identified in the preamble in such a manner as to safeguard both the user and at the same time the toothbrush against the consequences of an improper manipulation of the toothbrush.
This object is accomplished by a toothbrush which incorporates the arrangement of a mechanical torque limiting device including a cam follower which is acted upon by a spring means between a drive shaft of the electric motor and the brush head that ensures that the mechanical torque limiting device takes effect in the event of the brush head exerting an excessive contact pressure on the teeth to be cleaned, the transmission of power between the electric motor and the brush head being thus interrupted. In the presence of an overload condition, the brush head remains motionless, while the electric motor rotates freely under a tolerable load which is adjustable by the mechanical torque limiting device. For one thing, the stoppage of brush head movement in case of overload prevents damage to the user's teeth and gums. At the same time, the user receives a clear signal to reduce the contact pressure. For another thing, the motor is protected against overload in that the transmission of power to the brush head is interrupted. Moreover, the use of any additional electrical means is avoided which is advantageous particularly under the prevailing operating conditions--humidity and contamination.
An application of force substantially radial to a pivot of the torque limiting device advantageously diminishes an axial load on the pivot bearings and reduces friction losses.
Because the torque limiting device includes a first and a second coupling half, with the first coupling half having associated to it at least one cam follower which is urged against an annular wall of a cup-shaped recess of the second coupling half, a low overall height of the torque limiting device is ensured in addition to a low amount of wear resulting from the omission of latching
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patent: 4420851 (1983-12-01), Wiener
patent: 4610340 (1986-09-01), Helmes et al.
patent: 4698869 (1987-10-01), Mierau et al.
Braun Aktiengesellschaft
Roberts Edward L.
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