Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
2000-08-21
2002-07-30
Noori, Max (Department: 2855)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
Reexamination Certificate
active
06425295
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to a force sensing system for toothbrushes, and more specifically concerns such a system which uses three spaced sensors to determine force in three dimensions.
BACKGROUND OF THE INVENTION
It is generally well accepted that the use of excessive force (force=pressure×area) against the teeth with a toothbrush during brushing over an extended period of time can cause wear on gum tissues and eventually the teeth enamel. The problem of excessive brush force is known to be widespread. Although excessive force can be applied by both manual and power toothbrushes, a power toothbrush will typically substantially increase the effects of excessive force. It is thus desirable that a user have a reliable indication when excessive force is being applied to the teeth, so that the force can be quickly reduced by the user.
Very few, if any, commercial toothbrushes include a force indicator. Since the tendency of individual users is to exert too much force against the teeth, and since the effects of excessive force are certainly detrimental, it is desirable to develop a reliable, accurate force sensor, one which is simple to use and yet is economical to include on a toothbrush.
Various pressure and force sensors are known which measure brushing force in different ways, including both mechanical and electrical sensors. Some sensors measure pressure while others measure actual force. Force sensors are generally desirable over pressure sensors because pressure sensors are sensitive to the size of the loaded member (the brushhead) pushing against the sensor and/or the relative positions of the loaded member and the sensor. Pressure sensors can, however, be converted to force sensors by including a shaped protrusion (bump) of a selected area on the sensor to significantly reduce, if not eliminate, the sensitivity of the sensing system to size, shape and/or position of the loaded member (which can in fact be flat).
Some sensors use a piezoelectric device to measure the rate of deflection of the sensor and provide velocity information concerning movement of the member, rather than force or pressure information. Still other sensors use strain gauges, some of which incorporate temperature compensation elements.
In addition, there are sensors which make use of particular materials which include a characteristic, such as electrical resistance, which changes upon application of pressure or force over a given range. Information from these pressure or force elements is then compared against a threshold to provide an indication of when a threshold value of excessive pressure or force is exceeded.
SUMMARY OF THE INVENTION
Accordingly, the present invention is a three point force sensing system for a toothbrush, comprising: a toothbrush body; three spaced sensor members responsive to force thereon, positioned in the toothbrush body beneath a brushhead which is mounted in such a manner that the brushhead moves relative to the sensor members in response to force thereon against the teeth of a user, the sensor members having a selected characteristic which changes upon application of force on the sensor members; sensor member connectors which extend from the three sensor members and which are connectable to a processor for calculating force on the brushhead in response to changes in said characteristic of the three sensor members, and three raised bump-like portions on the bottom surface of the brushhead which contact the three sensor members, such that change in force on the brushhead changes the force on the sensor members through the three raised portions, thereby producing an identifiable change in the selected characteristic of the sensor members, so that force of the bristles/tips of the brushhead against the teeth of a user can be determined.
REFERENCES:
patent: 4476604 (1984-10-01), White et al.
patent: 4680825 (1987-07-01), White
patent: 5355544 (1994-10-01), Driksing
patent: 5784742 (1998-07-01), Giuliani et al.
patent: 5876207 (1999-03-01), Sundius et al.
patent: 5974615 (1999-11-01), Schwarz-Hartmann et al.
Jensen & Puntigam P.S.
Koninklijke Philips Electronics , N.V.
Noori Max
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