GB2413268A

GB2413268A - Toothbrush with pivotal force sensing mechanism

Info

Publication number: GB2413268A
Application number: GB0408901A
Authority: GB
Inventors: Igor Vasilev
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-04-21
Filing date: 2004-04-21
Publication date: 2005-10-26
Also published as: GB2413269A; GB0408901D0; GB0507922D0

Abstract

A toothbrush comprises a force sensing mechanism 4 that pivotally couples the head of the brush to the handle and which enables the head to move from an operative position to an inoperative position when a predetermined brushing force is exceeded. The force sensing mechanism comprises an inner part 6 housing two spring biased detent pins 8, and an outer part 5 having grooves into which pins 8 are biased. During normal brushing the grooves remain engaged with the pins 8 and allow the outer part to pivot slightly [Figure 12], however, should the brushing force exceed a predetermined maximum, the pins are forced to retract completely and allow the outer part 5 to pivot freely thus preventing further brushing. The head needs to be reset before the brush can be used again. The head may be replaceable.

Description

24 1 3268

TOOTHBRUSH WITH FORCE SENSING MECHANISM

The invention relates to a toothbrush that maintains the brushing force within recommended limit indicating the lowest force level, when brushing becomes most effective and suddenly 'snaps', changing shape if applied force exceeds recommended limit, making a further use uncomfortable if not impossible until the brush is reset.

Results of research conducted by Prof Peter Heasman and published in the Journal of Clinical Periodontology showed that the plaque removal improves when a user increases the brushing time as well as pressure, but once pressure or time goes beyond a certain point it could cause a permanent damage to their teeth, wearing enamel due to abrasion.

The gums are more sensitive therefore the impact of pressure on them is even more harmful. Also this report shows that it is virtually impossible to maintain a recommended force, which directly determines the pressure.

There are some designs oftoothbrushes with a flexible neck, where a head and a neck of the toothbrush flex back in relation to the handle. The greater the force applied, the greater flexing angle occurs. This type toothbrush is disclosed in US 2003/0208870, FR 053883 and US 5903949, where different types of connection between a head and a handle are used in order to modify the flexibility.

Other kind of toothbrushes with more sophisticated type of connections between a head and a handle are disclosed in WO 99/16332. The toothbrushes described in this application comprise separately made head end and handle end, which are connected by torsion element. In some ofthose elements an elastomeric material is used to create a torsion force that pushes the head ofthe toothbrush into its normal position, in other elements helical coil serves the same purpose.

In DE 3724476 disclosed another type of a toothbrush with a spiral spring fitted in the mechanism between a head and a handle as a part that creates reactive force and returns the head in normal position in relation to the handle.

A toothbrush disclosed in US patent No 6502272 comprises a head and a handle, which connected through elastomeric coupler. It allows the toothbrush to flex and returns the head into position it occupied before brushing.

All above mentioned designs have a common disadvantage that they use different types of elastic materials and mechanisms to force a head of a toothbrush into normal position when toothbrush is being used. This force added to the brushing force creates even greater pressure on user's teeth and gums.

All above mentioned toothbrushes have one common feature: although they make a toothbrush flexible and distribute brushing force more evenly they, however, do not limit it.

Application WO 2004/010822 discloses a toothbrush with leaf spring for ensuring the correct pressure. It comprises a head with bristles and a handle joined by a leaf spring, which allows the toothbrush to suddenly reduce the brushing pressure when excessive force is applied. The curved shape ofthe said leaf spring is a key feature that enables it to collapse and straighten out its curvature when a critical force is reached. However, apart from a force that acts in perpendicular direction relating to a longitudinal axis of the toothbrush there is another force, which is caused by friction ofthe bristles against teeth and gums and creates a torque, which twists the head and ultimately leaf spring that is connected directly to it around longitudinal axis. The said torque affects a leaf spring in a way that it can reduce or, in contrary, increase its resistance depending on a range of conditions, which is different with each stroke a brush makes. These conditions are: a variable angle with which bristles meet the gums, the viscosity oftoothpaste, flexibility of a user's wrist etc. The last mentioned factor is most complex taking under consideration that a toothbrush will be used by disabled and ill people, who's wrists are not as flexible as healthy people's and, of course, children, who's co-ordination is still developing. A torque should not be neglected especially at the moment when the bristles hit a gum that is far more sensitive than teeth. Because the head part is connected to the handle part directly through the spring there is no element in the design ofthe toothbrush that could neutralise the torque. The graph presented in the application clearly shows that the only force considered was the force that acts in perpendicular direction to the longitudinal axis ofthe toothbrush.

Apart from the disadvantages that are different in each above mentioned designs all they have one common disadvantage: they do not give a user an idea ofthe lowest force that makes brushing effective. This force is ofthe same importance as the maximum one because if plaque is not removed by brushing it accumulates on the teeth and causes dental diseases.

The object of this invention is to create a toothbrush with force sensing mechanism that indicates minimum level of applied force needed for effective brushing and makes the toothbrush unusable until it is reset protecting user's gums and teeth from damage if the force is too strong.

This is achieved with a toothbrush that consists a force sensing mechanism integrated in the joint between a head and a handle. The most important feature of the proposed toothbrush with the said mechanism is that it lets a user feel that he/she has reached the lowest force needed for effective brushing. The toothbrush gives rigid and solid feeling until the needed force is reached. After it happens the toothbrush becomes flexible and stays that way until maximum recommended force is reached. When it happens the toothbrush snaps and a head takes such a position in relation to a handle that brushing becomes difficult or even impossible. This makes users aware that they are brushing too hard. A need to reset the toothbrush prior to further use makes a mental note and helps them develop a sense of applied force, which is extremely important in childhood, when a lifelong routine is establishing. The most effective brushing takes place when the toothbrush gives the users that elastic bouncy feeling that is so recognizable and easy to feel and gauge.

The toothbrush is made of a rigid plastic material.

The invention now will be described with reference to drawings, where: FIGURE 1: shows a front view ofthe toothbrush combined with longitudinal section B-B ofthe force sensing mechanism; FIGURE 2: shows a side view in combination with longitudinal section A-A ofthe said mechanism; FIGURE 3: presents enlarged section C-C ofthe force sensing mechanism; FIGURE 4: shows a front view of a pin; FIGURE 5: shows section D-D of the pin; FIGURE 6: shows a front view of the toothbrush in the moment after it snapped. The head has taken the most uncomfortable for brushing position; FIGURE 7: shows a side view in combination with longitudinal section E-E ofthe said mechanism when the toothbrush has snapped. Also it shows the angle T that defines a position ofthe head and the neck against the handle ofthe toothbrush at the same moment; FIGURE 8: shows enlarged section F-F ofthe force sensing mechanism in the moment when brush snapped; FIGURE 9: shows a front view of the toothbrush when it is just about to snap; FIGURE 10: shows a side view of the toothbrush with the head in the position when it is just about to snap. Also it shows the angle U within which the toothbrush is in most effective mode. Combined with longitudinal section G-G of the force sensing mechanism; FIGURE 11: shows enlarged section H-H ofthe force sensing mechanism in the moment when the toothbrush is just about to snap; FIGURE 12: shows a section ofthe toothbrush along the longitudinal axis in the most effective mode. Also it shows a vector diagram of involved forces; FIGURE 13: shows a graph that represents a balance of involved forces; FIGURE 14: shows a front view of another embodiment ofthe toothbrush where a head is a replaceable component; FIGURE 15: shows a side view of the toothbrush with replaceable head combined with section I-l; FIGURE 16: shows an enlarged section J-J ofthe neck and the tail ofthe head.

It would be greatly appreciated if the drawings showing examples of possible embodiments will not be considered as a limitation ofthe invention.

Figure I shows one of possible embodiments ofthe toothbrush. It is combined with section B-B. According to the invention it consists a head l with the bristles, a neck 2 and a handle 3.

Figure 2 shows a side view of the toothbrush combined with section A-A. The force sensing mechanism 4 joins the handle 3 and the lower part of the neck 2 together and consists an outer part 5 and an inner part 6. The outer part 5 is a continuation of the neck and the inner part 6 is integrated with the upper part of the handle 3. Outer part 5 and inner part 6 can rotate relative to each other through restricted angle around axis X-X that is perpendicular to longitudinal axis Y-Y. The inner part 6 bares an integrated bar 7 of circular cross-section that serves as an axis of rotation for the head I and neck 2 when they rotate relatively to the handle 3. A cap 24 covers the mechanism and co-operates with the internal part 6 to retain the toothbrush together. For example such a connection may be achieved by snap fit co-operation when one or both of the connecting parts are resilient and assembling action forces a ramp surface of one part over and beyond a ramp surface of the other part. Therefore disconnecting the parts again requires some resistance to overcome.

The essential pieces of force sensitive mechanism pins 8, and spring 9 are shown on cross-section A-A, which is combined with a side view ofthe toothbrush and on figure 3, which shows cross section C-C and the same numbers define them. The said pins 8 are positioned in the holes 10 of the internal part 6 of the mechanism 4.

Figure 4 shows a front view of the pin 8.

Figure 5 shows section D-D of the pin 8. Both pins are identical and shaped as a cylinder, but their top end is sliced on angle R and that creates two flat surfaces 12. The pin has a very distinctive summit I I created by flat surfaces l 2 and projects into edge 13 shown on figure 4. The bottom part of the pins also sliced on angle S. which is not as sharp as angle R. Angle S should be bigger than angle R in order to minimise the size of the mechanism. The said bottom part of the pins also has a distinctive summit 14, which projects into edge 15 shown on figure 4. Edges 13 and 15 are parallel to each other. Edge has a semicircular groove 16 at the middle. This groove 16 protects spring 9 from displacement along axis X-X in relation to the pins 8. Spring 9 placed in the groove 17 of the internal part ofthe force sensing mechanism. If unstressed spring 9 has bigger diameter that the groove 17, thus during the assembly it has to be forced into the groove 17 and this stress creates a power that pushes the pins 8 out of the internal part 6 through the holes 10 into grooves 18 of external part 5. Due to the tension ofthe spring 9 the pins 8 hold the external part 5 in ready for use position in relation to the internal part 6 and, subsequently, handle 3. Simultaneously the same tension ofthe spring determines the lowest force needed for effective brushing, or first predetermined force.

Figure 6 shows a front view ofthe toothbrush in the position when an excessive force had been applied to it and the head I with the neck 2 has taken the most uncomfortable for brushing position in relation to the handle 3.

Figure 7 shows a side view of the toothbrush in the same condition as shown on figure 6.

It is combined with section E-E, which shows that spring 9 has been distorted in response to suppression by pins 8 that have been pushed into holes 10. It happened because excessive force had been applied to the handle 3, and as long as head 1 at that moment was pressed against the teeth a torque occurred. The torque forced the external part 5 of the force sensing mechanism 4 to rotate around internal part 6 and bar 7, which is integral piece of the external part 5. During this rotation the groove 18 of the external part 5 transferred the power to the flat surface 12 of the pin 8 and forced it into hole 10 compressing the spring 9. When the summit 1 1 of the pin 8 reached a cylindrical surface 19 (indicated on figure 8) ofthe external part 5 it started freely sliding along the said cylindrical surface and this allowed the toothbrush snap. As a result the neck 2 with the head 1 rotated in relation to the handle 3 through angle T. when brushing became unnatural and had to be stopped. At this moment the toothbrush has to be reset for the further use. In order to do so a user has to return the neck 2 with head 1 into position they occupied in relation to the handle 3 before use, rotating neck with head until pins 8 click into groove 18 ofthe external part 5 ofthe mechanism 4, i.e. operative position.

Figure 8 shows cross section F-F if the force sensing mechanism when the toothbrush has snapped and the pins 8 are forced into hole 10 and are in touch with cylindrical surface 19 of the external part 5.

Figure 9 shows a front view ofthe toothbrush when it is just about to snap.

Figure I O shows a side view of the toothbrush when it is about to snap combined with cross section G-G. The pins 8 are forced into holes 10 (shown on figure 1 1) and the summits 1 1 are on the edges ofthe grooves 18.

Figure 11 shows a cross section H-H of the force sensing mechanism when the toothbrush is about to snap.

Figure 12 shows cross section A-A of the toothbrush in the moment when applied brushing force is within recommended boundary and plaque removal is most effective with no damage to teeth and gums. Also it shows the forces that are occurring in the force sensing mechanism during brushing. Vector P represents the force of resistance ofthe spring, vector O represents the force that creates a torque that forces the external part 5 of the force sensing mechanism 4 to rotate around the internal part 6 of the said mechanism.

This force occurs when a user presses the head of the toothbrush against teeth. Vector N shows a force that neutralises force O (and the torque as a result) and returns the headl of the toothbrush into normal operative position in relation to the handle 3. Forces Q and R are the resulting forces of P+N and P+O respectively. Forces Q and R are very dynamic and keep changing during brushing. Presented force diagram shows that as long as force Q dominates over force R the toothbrush is in the most effective mode. When forces Q and R are equal the toothbrush is just about to snap. When force Q dominates over force R the toothbrush has snapped and has to be reset.

Figure 13 presents a graphical interpretation ofthe force diagram. Horizontal axis ofthe diagram shows a force applied to the toothbrush by user. Vertical axis presents a force that passed to the teeth and gums. A straight line between point O and point 44 shows that applied force (interval 0-40 on horizontal axis) is passed to the teeth and gums without any alteration (interval 0-42 on vertical axis). It happens when an applied force is under recommended limit and is not sufficient for plaque removal. Pins 8 do not compress the spring 9, force P dominates over all other forces and the toothbrush gives the user a rigid, stiff feeling, which means that applied force should be increased.

When an applied force reaches a certain point or first predetermined limit presented on the graph as point 40 in horizontal axis, forces O and N become more significant and torque that pushes the external part 5 to rotate around internal part 6 appears. During this rotation the groove 18 of external part 5 presses flat surface 12 of the pins and pushes them into holes 10. All this happens when an applied force lays between points 40 and 41 on horizontal axis, i.e. remains within first and second predetermined limits. As it clearly seen on the graph the line between points 44 and 45 becomes steeper that the line between points O and 44. It happens because force of compressed spring P creates force N that pushes external part 5 ofthe force sensing mechanism 4 trying to bring the head 1 with the neck 2 into normal operative position in relation to the handle 3. Within this interval the toothbrush gives a user that soft and bouncy feeling which means the applied force is right and plaque removal is most effective with no damage to the gums and teeth caused. The force that is passed to them lays within interval between points 42 and 43 on vertical axis, i.e. between first and second predetermined limits.

At the moment when applied force reaches its highest limit, or second predetermined force, above which brushing becomes harmful (point 41 on horizontal axis) the summit 11 ofthe pins 8 reaches the edge ofthe groove 18 beyond which lays cylindrical surface 19, where there is no more grip for the pins to hold the external part 5 with the head 1 and the neck 2 within angle U (operative position) and, if applied force rises, the toothbrush snaps. The head I with the neck 2 suddenly rotate around the bar 7 through angle T into inoperative position. At this point position of the head I with the neck 2 in relation to the handle 3 becomes very uncomfortable for brushing and, therefore, has to be stopped. As is seen on the graph the passed to the teeth and gums force drops suddenly from point 43 to point 46, which lays on the horizontal axis.

Figure 14 shows a front view ofthe toothbrush with replaceable head where head I with the neck 2 can be changed when needed.

Figure 15 shows a side view of the toothbrush with replaceable head. Combined with cross section I-l.

Figure 16 shows enlarged cross section J-J.

The following explains an embodiment ofthe toothbrush with replaceable head.

The neck 2 has a foot 20, which connects it to the external part 5 ofthe force sensing mechanism 4.though Y-shaped slide 21. The said slide fits onto Y-shaped slot 22 of the external part 5. The external part 5 has a stopper 23 that prevents the foot 20 from sliding backwards.

Claims

1. A toothbrush that comprises a handle part, a head part with bristles and a force sensing mechanism that connects both above mentioned parts together and enables the head part to move from an operative position to an inoperative position.

2. A toothbrush as claimed in Claim I that includes parts ofthe force sensing mechanism that designated to: a) engage the parts of the toothbrush in an operative position, preventing any movement of the parts of the toothbrush against each other until first predetermined force is applied to the head, b) return the head in an operative position when applied force stays within recommended limit, c) enable full movement to an inoperative position only when severe higher second predetermined force is applied to the head.

3. A toothbrush as claimed in Claiml and Claim 2 that indicates the sufficient and safe force required for most efficient plaque removal.

4. A toothbrush as claimed in Claim 1, Claim 2 and Claim 3 that protects teeth and gums from damage when excessive brushing force applied making brushing uncomfortable or impossible due to change of shape of the toothbrush.

5. A toothbrush as claimed in preceding Claims that has to be reset manually for further use after exceeding force was applied.

6. A toothbrush as described above and illustrated in the accompanied drawings. ) 1 s ) 1 > . , )

6. A toothbrush as herein described above that can have changeable head.

7. A toothbrush as claimed in any preceding Claims which is made from plastic or combination of different types of plastic.

8. A toothbrush as described above and illustrated in the accompanied drawings.

Amendments to the claims have been tiled as follows 1. A toothbrush that comprises a head connected to a handle via a force sensing mechanism, a first predetermined force corresponding to a minimum applied force needed for effective plaque removal wherein the force sensing mechanism is arranged to control movement of the head relative to the handle such that: when the force applied by a user reaches said first predetermined force, the movement of the head indicates to the user that the minimum force needed for effective brushing has been applied and has to be maintained in order to remove the plaque.

2. A toothbrush as claimed in claim 1 wherein the force sensing mechanism defining in the second predetermined force corresponding to a maximum applied force recommended for a harmless brushing and the said force sensing mechanism is arranged to control movement of the head relative to the handle such that: when the force applied by a user exceeds said second force, the head moves to an inoperative position relative to the handle.

3. A toothbrush as claimed in claim 1 and claim 2 wherein the force sensing mechanism is arranges such that: movement of the head relative to the handle is prevented until the applied force reaches said first predetermined force, the head is resiliently movable relative to the handle while applied force lays between said first predetermined force and second predetermined force, and the head moves to inoperative position relative to the handle when applied force exceeds the said second predetermined force.

4. A toothbrush as claimed in claim 1, claim 2 and claim 3 the head of which is resiliently movable relative to the handle due to implementation of pins that are pushed by the spring against the ramped surface and engage the head stationery relative to the handle if the applied force is lower than first predetermined force, resiliently retain the head ofthe toothbrush in operative position when the applied force lays between first predetermined force and second predetermined force, due to the tense of the said spring, enable a free rotation of the head through a certain angle relative to the handle when the applied force is higher than second predetermined force, releasing the said head into inoperative position.

5. A toothbrush as claimed in preceding claims that indicates the sufficient and safe force via incurring resilience when the applied force remains between the first predetermined force and the second predetermined force.