FIELD OF THE INVENTION

The invention relates to a personal care device comprising at least one hair cutting module provided with a cutting member being rotatable about an axis of rotation, with a longitudinal hair-entry opening extending parallel to the axis of rotation and with a stationary blade comprising a longitudinal side surface extending parallel to the axis of rotation and forming a side surface of the hair-entry opening, said longitudinal side surface being provided with a counter cutting edge extending parallel to the axis of rotation and cooperating with at least one cutting edge of the cutting member during rotation of the cutting member, and said longitudinal side surface having a height in a direction

perpendicular to the counter cutting edge.

BACKGROUND OF THE INVENTION

WO 99/36233 discloses a razor for shaving hair from the skin. The razor comprises cutting blades which are mounted in a cartridge. The cartridge is mounted in a roller which is rotatably mounted in a stationary housing having upper openings via which the cartridge comes in contact with the skin during operation. The razor comprises a drive mechansim to rotate the roller. The cartridge comprises a guide element associated with the cutting blade. The cutting blade and the associated guide element are configured to form a safety blade such that, when the cutting blade rotates in direct contact with the skin, the cutting blade shaves hair from the skin without cutting the skin. Preferably, the razor includes two similar blade assemblies rotated by the drive mechanism in opposite directions so as to apply a stretching tension to the skin.

WO2011086474A1 discloses a shaving apparatus comprising a rotary cutter being rotatable about an axis and a fixed blade having a counter cutting edge. The fixed blade is mounted adjacent to the rotary cutter. The counter cutting edge is formed along an edge of an elongated hair-entry opening.

When the shaving apparatus is moved over the skin of a user, hairs of the user will enter the hair-entry opening and will be sheared between the counter cutting edge of the fixed blade and cutting edges of the rotating rotary cutter. For good shaving results, hair must be cut very close to the skin. This means that near the counter cutting edge the fixed blade needs to be very thin. To prevent cutting of the skin by such a very thin, fixed blade, the width of the hair-entry opening in a direction perpendicular to the counter cutting edge needs to be relatively small. However, in the case of a relatively narrow hair-entry opening, many of the hairs being longer than the width of the hair-entry opening will not be able to enter the hair-entry opening and thus will not be sheared between the counter cutting edge of the fixed blade and cutting edges of the rotary cutter, so that poor shaving results will be obtained.

If the hair-entry opening is wide enough to be able to catch relatively long hairs, the fixed blade needs to be relatively thick to avoid cutting of the skin, as a result of which the remaining length of the sheared hairs will be relatively long and hence the shaving results are not good either.

SUMMARY OF THE INVENTION

In view of the above, a general object of the present invention is to provide a personal care device wherein good cutting results can be obtained when cutting relatively long hairs.

According to a first aspect, the invention provides a personal care device of the type mentioned in the opening paragraph, further comprising at least two of said hair cutting modules, wherein the cutting members of the at least two hair cutting modules are rotatable in a same direction about parallel-extending axes of rotation, and wherein the height of the longitudinal side surface of the stationary blade of a first of the at least two hair cutting modules is greater than the height of the longitudinal side surface of the stationary blade of a second of the at least two hair cutting modules, whilst in a direction perpendicular to the side surface of the stationary blade the longitudinal hair-entry opening of the first hair cutting module is wider than the longitudinal hair-entry opening of the second hair cutting module.

When the cutting modules are moved over the skin of a user, hairs are pressed flat against the skin. In the hair-entry opening the hairs erect and are cut between the cutting edge of the cutting member and the counter cutting edge of the rotating cutting member. If a hair is pressed against the skin in a direction perpendicular to the counter cutting edge and is longer than the width of the hair-entry opening, the hair will not be able to erect over its full length in the hair-entry opening.

Due to the relatively wide hair-entry opening of the first hair cutting module, the first hair cutting module is suitable for cutting comparatively long hairs of up to for example 1.5 millimetre, wherein cutting of the skin is prevented due to the relatively high side surface of the blade. The length of the hairs after being cut by the first module is shorter than the original length of the relatively long hairs, but is still too long, for example 300 microns. Since the hair-entry opening of the second hair cutting module is narrower than the hair-entry opening of the first hair cutting module, the second hair cutting module is suitable for cutting hairs with a shorter length, for example hairs already shortened by the first hair cutting module. As the height of the side surface of the blade of the second hair cutting module is smaller than the height of the side surface of the blade of the first hair cutting module, the hair will be cut closer to the skin and a hair with a relatively short length, for example 500 micron, can be cut practically to skin level (0-100 micron). By first reducing the length of relatively long hairs by the first hair cutting module, the shortened hairs and other relatively short hairs can be cut to the desired length by the second hair cutting module, whereby good cutting results are obtained.

If desired, more than two hair cutting modules can be used, wherein each further hair cutting module is suitable for cutting hairs with a shorter length than the previous hair cutting module to a length that is shorter than the length of the hairs after being cut by the previous hair cutting module.

In an embodiment of a personal care device according to the invention, in use, at a position of the counter cutting edges, a circumferential direction of motion of the cutting members is opposite to a direction of movement of the hair cutting modules over askin of a user and, seen in said direction of movement, the first hair cutting module is located in front of the second hair cutting module.

By placing the first hair cutting module in front of the second hair cutting module, a relatively long hair will be reduced in length by the first hair cutting module. When the personal care device is moved further in the direction of movement of the hair cutting modules over the skin of the user, the shortened hair will immediately be cut to the desired length.

If the second hair cutting module is located in front of the first hair cutting module, the personal care device needs to be moved twice over the same part of the skin, whereby, during the first time, a relatively long hair will be reduced in length by the first hair cutting module, whilst, during the second time, the shortened hair will be cut to the desired length.

In a further embodiment of a personal care device according to the invention, a width of the longitudinal hair-entry opening of at least one of the hair cutting modules is at least three times the height of the longitudinal side surface of the stationary blade of said at least one of the hair cutting modules.

At such a ratio, the width of the hair-entry opening is as large as possible to allow hairs with a length similar to the width of the hair-entry opening to enter the hair-entry opening, whilst due to the height of the side surface of the blade, cutting of the skin is prevented.

In a further embodiment of a personal care device according to the invention, a ratio between the height of the longitudinal side surface of the stationary blade of the first hair cutting module and the width of the longitudinal hair-entry opening of the second hair cutting module is in a range between 0.15: 1 and 1.5: 1.

At such a ratio, hairs can be shortened to a desired length of about 0-100 micron in two steps, wherein each hair cutting module can be optimized for hair with a specific length.

In a further embodiment of a personal care device according to the invention, a ratio between the width of the longitudinal hair-entry opening of the first hair cutting module and the width of the longitudinal hair-entry opening of the second hair cutting module is in a range between 2 : 1 and 5: 1.

At such a ratio between the width of the longitudinal hair-entry openings, the maximum length of the hairs that can be cut by the different hair cutting modules differs by about the same ratio, so that each hair cutting module can be optimized for hair with a specific length.

In a further embodiment of a personal care device according to the invention, the cutting edge of the cutting member of the second hair cutting module is located at a same or smaller distance from the axis of rotation than the cutting edge of the cutting member of the first hair cutting module.

By having cutting members with a same radius, the distances will be the same and an elegant and compact design is obtained. By having different radii, each radius can, for example, be equal to at least the length of the hair to be cut, to optimize the cutting function of each hair cutting module. Since the second hair cutting module cuts hairs that have already been shortened by the first hair cutting module, the radius of the second hair cutting module can be smaller.

In a further embodiment of a personal care device according to the invention, at least one of the cutting members comprises a number of cutting edges extending spirally about the axis of rotation. During each complete rotation of the cutting member, the cutting edges, one after the other, will cooperate with the counter cutting edge, so that a number of cutting actions will take place during one revolution of the cutting member. By having the cutting edge extend spirally about the axis of rotation, the forces applied to the cutting edge during cutting will be spread over time during rotation of the cutting member through a certain angle.

In a further embodiment of a personal care device according to the invention, said at least one of the cutting members comprises passages extending between the cutting edges and through the axis of rotation.

The passages form openings in which the hairs located in a hair-entry opening may extend.

BRIEF DESCRIPTION OF THE DRAWINGS

The personal care device according to the invention will be further explained with reference to the drawings, wherein,

Figure 1 is a perspective schematic view of a personal care device according to the invention,

Figures 2A and 2B are perspective views, respectively, from below and behind a hair cutting module of the personal care device as shown in figure 1 ,

Figure 3 is a perspective view of a cutting member of the personal care device as shown in figure 1 ,

Figure 4 is a cross section of the personal care device as shown in figure 1. In the drawings, like reference numerals refer to like elements.

DESCRIPTION OF PREFERRED EMBODIMENTS

Figures 1-4 show a personal care device 1 according to the invention, comprising a handle 2 and a shaving unit 3 located at an end of the handle 2. The personal care device 1 comprises a motor (not visible) located in the handle 2 which is coupled to a first gear wheel 4 being rotatable about an axis 5. The first gear wheel 4 is coupled to a second gear wheel 6 being rotatable about an axis 7. The diameter of the second gear wheel 6 is much larger than the diameter of the first gear wheel 4. The second gear wheel 6 is coupled to two identical third gear wheels 8 of a first and a second cutting module 9, 10. The diameter of the third gear wheels 8 is about the same as the diameter of the first gear wheel 4.

As can be seen in figures 2A and 2B, each hair cutting module 9, 10 is provided with a cutting member 11 being rotatable about an axis of rotation 12, and with a longitudinal hair-entry opening 13 extending parallel to the axis of rotation 12, and with a blade 14 comprising a longitudinal side surface 15 forming a side surface of the hair-entry opening 13. The axis of rotation 12 also constitutes the axis of rotation of the third gear wheel 8. The axes of rotation 5, 7 and 12 extend parallel to each other. The longitudinal side surface 15 is provided with a counter cutting edge 115 extending parallel to the axis of rotation 12 and cooperating with the cutting member 11. The blade 14 forms part of a housing 16 of the cutting member 11. The longitudinal hair-entry opening 13 is located between the

longitudinal side surface 15 and an edge 17 of the housing 16 extending parallel to the counter cutting edge 115. The housing 16 is provided with outlet openings 18 for cut hair, which outlet openings 18 are located on a rear side 19 of the housing 16. The hair cutting module 9, 10 is provided with a leaf spring 20 a first end 21 of which is connected to the housing 16 and a second end 22 of which rests on the cutting member 11 to push the cutting member 11 towards the blade 14 by means of spring force. The leaf spring 20 may be bolted, glued or welded to the housing 16. By driving the motor accommodated in the handle 2, the gear wheels 4, 6, 8 and thus the cutter members 11 will be rotated.

Figure 3 shows a perspective view of the cutting member 11 provided near its ends with axles 23, 24 and four blades 25 extending spirally between the axles 23, 24. The blades 25 are equally spaced from each other. Each blade 25 comprises a cutting edge 26 along its length. Between the axles 23, 24, the blades 25 are connected to each other by bridges 27. Passages 28 between the cutting edges 26 of the blades 25 extend through the axis of rotation 12, and provide the cutting member 11 with an open structure into which hairs can easily enter and from which they can easily be removed.

The housing 16 can be produced by means of wire spark erosion and/or milling, the cutting member 11 can be produced by a combination of turning and milling, the leaf spring 20 can be produced by metal stamping, laser cutting etc. For low-cost production, the housing 16 may be made by combining injection moulded parts with extruded or cold- formed metal parts, and the cutting member 11 may be made by a combination of extrusion, grinding and cold forming.

Figure 4 shows a schematic cross section of the personal care device 1 as shown in figure 1, wherein the two hair cutting modules 9, 10 are shown, positioned on the skin 30 of a user. The skin 30 is provided with hairs 31 which need to be cut.

The hair cutting module 9 forms a first hair cutting module, having a width Wl of the longitudinal hair-entry opening 13 in a direction perpendicular to the side surface 15. PI indicates a direction in which the shaving unit 3 of the personal care device 1 is to be moved over the skin 30 of a user. The direction PI extends perpendicularly to the axis of rotation 12. The longitudinal side surface 15 of the blade 14 of the first hair cutting module 9 has a height HI . The cutting edges 26 of the cutting member 11 of the first hair cutting module 9 are located at a radius Rl from the axis of rotation 12.

The hair cutting module 10 forms a second hair cutting module having a width

W2 of the longitudinal hair-entry opening 13. The longitudinal side surface 15 of the blade 14 of the second hair cutting module 10 has a height H2. The cutting edges 26 of the cutting member 11 of the second hair cutting module 10 are located at a radius R2 from the axis of rotation 12.

The diameters 2*R1, 2*R2 of the cutting members 11 are preferably between

2 and 6 millimetres, wherein the diameter 2*R1 is preferably between 3 and 6 millimetres whilst the diameter 2*R2 is preferably between 2 and 4 millimetres. Due to the small diameters 2*R1, 2*R2, the blade 14 can curve upwards fast enough to allow a sufficient thickness increase of the blade 14 directly behind the longitudinal side surface 15 to ensure sufficient strength and rigidity of the blade 14. The length L of the cutting members 11, the length of the hair-entry openings 13 and the length of the longitudinal side surfaces 15 is preferably between 30 and 40 millimetres.

The width Wl, the height HI and the radius Rl of the first hair cutting module 9 are larger than the width W2, the height H2 and the radius R2 of the second hair cutting module 10. The ratio between the width Wl, W2 and the height HI, H2 is preferably

W1/H1=W2/H2=3, wherein HI is in the range of 0.15-1.5 times W2.

With the first hair cutting module 9, hairs 31 with a length of 1,5 millimetre can be cut to a length of 300 micron.

With the second hair cutting module 10, hairs 31 with a length of 500 micron can be cut to a length of 0- 100 micron.

At a position of the counter cutting edges 115, a circumferential direction of motion of respectively the cutting member 11 of the first hair cutting module 9 and the cutting member 11 of the second hair cutting module 10, associated with the rotational directions Dl and D2 of the respective cutting members 11, is opposite to the movement of hair cutting modules 9, 10 in the direction PI over the skin of a user. Seen in the direction PI, the first hair cutting module 9 is located in front of the second hair cutting module 10.

The cutting members 11 may rotate at about 6000-12000 rpm. As there are four cutting edges 26 on each cutting member 11 , this results in a value between

6000(60*4)=400 Hertz and 12000(60*4)=800 Hertz. At a minimum width W2 of the hair- entry opening of 0.25 millimetre and a shaving stroke speed s in the direction PI of 50 millimetres per second, the maximum cutting opportunity time t=W2/s= 0.25/50 seconds = 5 ms. A cutting frequency of 400 Hertz or 800 Hertz means that a cutting edge 26 passes every 2.5 ms or 1.25 ms. So, during the 2.5 or 5 ms of the cutting opportunity time t, there are 2 or 4 cutting opportunities for a hair to be cut.

Driving of the cutting members 11 can take place via "direct drive", but also via a gearbox at one of the sides of the housing 16.

In another embodiment, the driving members (motor, handle, battery) of the personal care device can be in line with the axis of rotation of the cutting members 11.

It is also possible to have more than one longitudinal hair-entry opening in each hair cutting module 9, 10, wherein the longitudinal hair-entry openings are located in line with each other.

It is also possible that the edge 17 bounding the hair-entry opening 13 opposite the longitudinal side surface 15 is provided with comb teeth or fingers extending transversely to the longitudinal hair-entry opening 13 and to the counter cutting edge 115. The distance between the comb teeth or fingers and the length of the comb teeth or fingers can be in the range of 0.5 - 3 millimetres. The distance between tips of the fingers and the longitudinal side surface 15 is for example 0.3 millimetre. By using comb teeth or fingers, longer hairs can be captured in the hair-entry opening 13, whilst still having a minimum width W of the hair- entry opening 13 between the longitudinal side surface 15 and the ends of the comb teeth or fingers and a height H of the longitudinal side surface 15 in a ratio W/H in the order of 10: 1- 25: 1.

If desired, more than two hair cutting modules can be used and located behind each other, wherein each subsequent hair cutting module is suitable for cutting shorter hairs to a shorter length.

The personal care device can also be a vibratory shaver, a trimmer, a grooming device or other kind of cutting device.

The person skilled in the art will realize that the present invention is by no means limited to the preferred embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Any reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS

1 personal care device

2 handle

3 shaving unit

4 gear wheel

5 axis

6 gear wheel

7 axis

8 gear wheel

9 hair cutting module

10 hair cutting module

11 cutting member

12 axis of rotation

13 longitudinal hair-entry opening

14 blade

15 longitudinal side surface

16 housing

17 edge

18 outlet opening

19 rear side

20 leaf spring

21 first end

22 second end

23 axle

24 axle

25 blade

26 cutting edge

27 bridge

28 passage 30 skin

31 hair

1 15 counter cutting edge

Dl direction of rotation

D2 direction of rotation

HI height

H2 height

L length

PI direction

Rl radius

R2 radius

Wl width

W2 width