VOORHORST, Fokke, R. (AE Eindhoven, NL-5656, NL)
PRAGT, Johan (AE Eindhoven, NL-5656, NL)
DEKKER, Martijn, J. (AE Eindhoven, NL-5656, NL)
BOSMAN, Franciscus, J. (AE Eindhoven, NL-5656, NL)
QUINESSER, Albert (AE Eindhoven, NL-5656, NL)
DE WIT, Bastiaan, J. (AE Eindhoven, NL-5656, NL)
VOORHORST, Fokke, R. (AE Eindhoven, NL-5656, NL)
PRAGT, Johan (AE Eindhoven, NL-5656, NL)
DEKKER, Martijn, J. (AE Eindhoven, NL-5656, NL)
BOSMAN, Franciscus, J. (AE Eindhoven, NL-5656, NL)
QUINESSER, Albert (AE Eindhoven, NL-5656, NL)
| CLAIMS:
1. A shaving apparatus (1), comprising:
- two cutting members (4; 5) which are movably arranged with respect to each other, wherein a convergent cutting opening (9) for catching hair (13) is present between edges (10; 11, 12) of the cutting members (4; 5), and at least one of the cutting members (4; 5) comprises a cutting edge (10; 11) which is adapted to cutting through hair (13), and which extends between a first position on the edge (10; 11, 12) of the cutting member (4; 5) and a second position on the edge (10; 11, 12) of the cutting member (4; 5), as seen in a direction of convergence of the cutting opening (9); and
- means for varying a mutual position of the cutting members (4; 5), such that, in a first extreme mutual position of the cutting members (4; 5), the cutting opening (9) is smaller than in a second extreme mutual position of the cutting members (4; 5), yet still opened; characterized in that a ratio between a cutting distance in the first extreme mutual position of the cutting members (4; 5) and the cutting distance in the second extreme mutual position of the cutting members (4; 5) is at least 0.22, which cutting distance is defined as a variable distance between the edges (10; 11, 12) of the cutting members (4; 5) as measured along an imaginary line (15) extending in a direction in which the cutting members (4; 5), at the location of the cutting opening (9), are movable with respect to each other and intersecting the first position on the edge (10; 11, 12) of the cutting member (4; 5) having the cutting edge (10; 11).
2. A shaving apparatus according to claim 1, wherein the ratio between the cutting distance in the first extreme mutual position of the cutting members (4; 5) and the cutting distance in the second extreme mutual position of the cutting members (4; 5) is in a range of 0.22 to 0.6.
3. A shaving apparatus according to claim 2, wherein the ratio between the cutting distance in the first extreme mutual position of the cutting members (4; 5) and the cutting distance in the second extreme mutual position of the cutting members (4; 5) is in a range of 0.22 to 0.35.
4. A shaving apparatus (1) according to claim 1, comprising a drive train (16; 30; 37) for driving at least one of the cutting members (4; 5), wherein the drive train (16; 30; 37) comprises drive means for supplying a driving force, and coupling means for coupling the cutting member (4; 5) to the drive means, and a stiffness at a location where the cutting member (4, 5) and the drive train (16; 30; 37) are connected with each other being at least 3 * 10 4 N/m per mm functional length of the cutting member (4, 5).
5. A shaving apparatus (1) according to claim 4, wherein the drive means (17) comprise a rotatable output shaft (18), the coupling means comprise an excenter (19) which is mounted on the output shaft (18) of the drive means (17), a connection rod (20) which is coupled to the excenter (19), and a movably arranged element (22) for mounting one of the cutting members (4; 5), and the connection rod (20) and the mounting element (22) are coupled through a lever (23) which is tiltably arranged about a tilting point (25) at a position between ends of the lever (23).
6. A shaving apparatus (1) according to claim 4, comprising two elements (35; 38) which are biased towards each other, and actuation means (17, 18, 31; 40, 41) for driving the elements apart, wherein the actuation means comprise a wedging member (31; 41) which is arranged at a position between the elements (35; 38), and, on the basis of the shape of the wedging member (31; 41) of the actuation means, the extent to which the elements (35; 38) are driven apart during operation of the actuation means varies with a position of the wedging member (31; 41) of the actuation means with respect to the elements (35; 38).
7. A shaving apparatus (1) according to claim 6, comprising:
- two V-shaped elements (35) having stiffened portions (34), wherein ends of one the elements (35) are connected to ends of another of the elements (35); and - a rotatably arranged cam (31) having a non-circular cam surface (32), which is arranged at a central position between the elements (35).
8. A shaving apparatus (1) according to claim 6, wherein the actuation means comprise a combination of a piezo element (40) and a wedge (41).
9. A shaving apparatus (1) according to claim 1, comprising stopping means (46; 46a, 46b) for limiting a movement of at least one of the cutting members (4; 5) on the basis of a collision of an abutment member (45; 45a, 45b) associated with the cutting member (4; 5) and an area (47) of the stopping means (46; 46a, 46b).
10. A shaving apparatus (1) according to claim 9, comprising a pin (45), wherein one of the cutting members (4; 5) is fixedly connected to the pin (45), and another of the cutting members (4; 5) has a hole (46) for allowing the pin (45) to pass through with play in the direction in which the cutting members (4; 5) are movable with respect to each other.
11. A shaving apparatus (1) according to claim 9, comprising two pins (45a, 45b), wherein each cutting member (4; 5) has two holes (46a, 46b) for allowing a pin (45a, 45b) to pass through with play in the direction in which the cutting members (4; 5) are movable with respect to each other, and each pin (45 a, 45b) is coupled to another of the cutting members (4; 5) through resilient means (48a, 48b).
12. A shaving apparatus (1) according to claim 1, wherein, in every possible mutual position of the cutting members (4; 5), the cutting edge (10; 11) extending along the edge (10; 11, 12) of at least one of the cutting members (4; 5) is free from contact in the direction in which the cutting members (4; 5) are movable with respect to each other at the location of the cutting opening (9).
13. A shaving apparatus (1) according to claim 1, wherein at least one of the cutting members (4; 5) comprises a row of substantially V-shaped teeth (6; 7).
14. A shaving head (3) for use in a shaving apparatus (1) according to claim 1, comprising:
- two cutting members (4; 5) which are movably arranged with respect to each other, such that a convergent cutting opening (9) for catching hair (13) is present between edges (10; 11, 12) of the cutting members (4; 5), and at least one of the cutting members (4; 5) comprises a cutting edge (10; 11) which is adapted to cutting through hair (13), and which extends between a first position on the edge (10; 11, 12) of the cutting member (4; 5) and a second position on the edge (10; 11, 12) of the cutting member (4; 5), as seen in a direction of convergence of the cutting opening (9); and
- means for connecting the shaving head (3) to a body (2) of a shaving apparatus (1), in which body (2) a drive train (16; 30; 37) for driving at least one of the cutting members (4; 5) is accommodated; - wherein, in a first extreme mutual position of the cutting members (4; 5), the cutting opening (9) is smaller than in a second extreme mutual position of the cutting members (4; 5), yet still opened; characterized in that a ratio between a cutting distance in the first extreme mutual position of the cutting members (4; 5) and the cutting distance in the second extreme mutual position of the cutting members (4; 5) is at least 0.22, which cutting distance is defined as a variable distance between the edges (10; 11, 12) of the cutting members (4; 5) as measured along an imaginary line (15) extending in a direction in which the cutting members (4; 5), at the location of the cutting opening (9), are movable with respect to each other and intersecting the first position on the edge (10; 11, 12) of the cutting member (4; 5) having the cutting edge (10; 11). |
Shaving apparatus comprising two cutting members which are allowed limited movement with respect to each other
FIELD OF THE INVENTION
The present invention relates to a shaving apparatus comprising:
- two cutting members which are movably arranged with respect to each other, wherein a convergent cutting opening for catching hair is present between edges of the cutting members, and at least one of the cutting members comprises a cutting edge which is adapted to cutting through hair, and which extends between a first position on the edge of the cutting member and a second position on the edge of the cutting member, as seen in a direction of convergence of the cutting opening; and
- means for varying a mutual position of the cutting members, such that, in a first extreme mutual position of the cutting members, the cutting opening is smaller than in a second extreme mutual position of the cutting members, yet still opened.
The present invention further relates to a shaving head for use in a shaving apparatus, comprising:
- two cutting members (4; 5) which are movably arranged with respect to each other, such that a convergent cutting opening (9) for catching hair (13) is present between edges (10; 11, 12) of the cutting members (4; 5), and at least one of the cutting members (4; 5) comprises a cutting edge (10; 11) which is adapted to cutting through hair (13) and which extends between a first position on the edge (10; 11, 12) of the cutting member (4; 5) and a second position on the edge (10; 11, 12) of the cutting member (4; 5), as seen in a direction of convergence of the cutting opening (9); and
- means for connecting the shaving head (3) to a body (2) of a shaving apparatus (1), in which body(2) a drive train (16; 30; 37) for driving at least one of the cutting members (4; 5) is accommodated;
- wherein, in a first extreme mutual position of the cutting members (4; 5), the cutting opening (9) is smaller than in a second extreme mutual position of the cutting members (4; 5), yet still opened.
BACKGROUND OF THE INVENTION
A shaving apparatus and a shaving head as mentioned in the opening paragraphs are known from WO 2005/092579. The known shaving apparatus comprises a shaving head having a stationary cutting member and a movable, driven cutting member, wherein both cutting members comprise a row of substantially V-shaped teeth. A sloping tooth edge at one side of the teeth of the stationary cutting member comprises a cutting edge which is adapted to cutting through hair, and which extends along the entire length of the tooth edge. A sloping tooth edge at one side of the teeth of the movable cutting member comprises a cutting edge as well, but this cutting edge only extends along a part of the length of the tooth edge, at the side of a base of the teeth. The cutting members are arranged such that pairs of teeth comprising a tooth of the stationary cutting member and a tooth of the movable cutting member are obtained, and, in each pair, the side of the tooth of the stationary cutting member having the cutting edge faces the side of the tooth of the movable cutting member having the cutting edge. During operation of the shaving apparatus, the driven cutting member performs a reciprocating movement with respect to the stationary cutting member, so that the size of convergent cutting openings between the teeth of the pairs is continuously varied. In a shaving process, hair is caught in the cutting openings and is subjected to a cutting operation when the size of the cutting openings is decreased. Depending on the position of a hair to be cut in a cutting opening, the hair is cut only by means of the cutting edge of the stationary cutting member, or the hair is cut under the influence of the cooperation of the cutting edges of both cutting members, the latter taking place when the hair is positioned deeper in the cutting opening, i.e. closer to the base of the teeth.
A particular feature of the shaving apparatus known from WO 2005/092579 is the fact that during operation of the shaving apparatus, the cutting openings are never entirely closed. In a situation in which the cutting openings are smallest, which occurs when the movable cutting member is in one extreme position with respect to the stationary cutting member, portions of the tooth edges of the teeth at the side of a tip of the teeth are still at a distance with respect to each other. The reason for not entirely closing the cutting openings is the desire to minimize the risk of skin damage during shaving.
SUMMARY OF THE INVENTION
It is an objective of the present invention to further improve the shaving apparatus and shaving head known from WO 2005/092579. In particular, it is an objective of
the present invention to define an operation range of the shaving apparatus and the shaving head, such that it is ensured that the desired effect of avoiding skin damage is obtained.
According to the present invention, the objective is achieved by providing a shaving apparatus and a shaving head as defined in the opening paragraphs, which are characterized in that a ratio between a cutting distance in the first extreme mutual position of the cutting members and the cutting distance in the second extreme mutual position of the cutting members is at least 0.22, which cutting distance is defined as a variable distance between the edges of the cutting members as measured along an imaginary line extending in a direction in which the cutting members, at the location of the cutting opening, are movable with respect to each other and intersecting the first position on the edge of the cutting member having the cutting edge.
According to an important insight underlying the present invention, it is not sufficient to simply define a range in respect of the stroke of the movement of the cutting members with respect to each other, for example a range of 0.01 mm to 0.15 mm as mentioned in WO 2005/092579. Instead, a useful operation range is found by defining a minimum of a relation between a minimum value and a maximum value of a distance between the edges of the cutting members as measured along an imaginary line which extends in a direction in which the cutting members are movable with respect to each other, and which intersects the first position on the edge of the cutting member having the cutting edge, i.e. the position where hair may first encounter the cutting edge. In the following, the distance which is defined in this way will be referred to as cutting distance. The cutting distance depends on the mutual position of the cutting members, and accordingly is a variable distance.
Skin damage occurs in case a volume of skin domes in the cutting opening between the edges of the cutting members and gets compressed when the edges are moved towards each other, whereby the skin gets compressed to such an extent that a mechanical limit to compression of the skin is exceeded, so that plastic deformation of the skin takes place. According to the present invention, it is important to have a ratio of a minimum cutting distance and a maximum cutting distance which is at least 0.22, as it appears that in such a case, a situation in which the minimum cutting distance in relation to the maximum cutting distance gets so small that skin is plastically deformed does not occur.
In a preferred embodiment of the shaving apparatus according to the present invention, the ratio of a minimum cutting distance and a maximum cutting distance is in a range of 0.22 to 0.6. In a more preferred embodiment of the shaving apparatus according to
the present invention, the ratio of a minimum cutting distance and a maximum cutting distance is in a range of 0.22 to 0.35. Due to the fact that the ratio is at least 0.22, skin damage is avoided. By additionally keeping the ratio below a maximum value, it is possible to combine avoidance of skin damage with effective operation of the shaving apparatus. A stroke of the movement of the cutting members with respect to each other is in the micron range. For example, a suitable value in respect of the stroke is 0.1 mm (100 μm). In practice, there is a risk that a discrepancy between the theoretical value of the stroke and an actual value of the stroke occurs. In view of the fact that according to the present invention, it is important that a ratio of a minimum cutting distance and a maximum cutting distance is equal to or larger than 0.22 under all circumstances, and that it is also advantageous to prevent this ratio from exceeding a predetermined value, it is a further objective of the present invention to avoid a situation in which an unallowable discrepancy between theoretical and actual parameters of the movement of the cutting members with respect to each other is obtained. One way of reaching this objective involves ensuring that a stiffness at a location where a drive train for driving at least one of the cutting members and the cutting member are connected to each other is at least 3 * 10 4 N/m per mm functional length of the cutting member, i.e. length of the cutting member which is used in the process of cutting hair during operation of the shaving apparatus. In the following, this stiffness will be referred to as functional stiffness. In general, in a practical embodiment, the drive train of the shaving apparatus comprises drive means for supplying a driving force, and coupling means for coupling at least one of the cutting members to the drive means. When the functional stiffness is higher than or equal to 3 * 10 4 N/m per mm functional length of the cutting member, intended values of the stroke of the movement of the cutting members with respect to each other and the ratio of the minimum cutting distance and the maximum cutting distance are realized under all practical circumstances, so that negative consequences like skin damage or loss of effectiveness of the shaving apparatus are avoided under all practical circumstances.
Within the scope of the present invention, the desired functional stiffness may be obtained in any suitable way. According to the present invention, a number of advantageous possibilities are proposed.
In a first preferred embodiment of a drive train having a functional stiffness of at least 3 * 10 4 N/m per mm functional length of the cutting member, the drive means comprise a rotatable output shaft, and the coupling means comprise an excenter which is mounted on the output shaft of the drive means, a connection rod which is coupled to the
excenter, and a movably arranged element for mounting one of the cutting members, wherein the connection rod and the mounting element are coupled through a lever which is tiltably arranged about a tilting point at a position between ends of the lever. In this way, a robust drive train is realized, which may virtually be without play, for example in case flexures are applied. In order to avoid tilting of the mounting element, two flexures may be used for the purpose of supporting the mounting element.
In a second preferred embodiment of a drive train having a functional stiffness of at least 3 * 10 4 N/m per mm functional length of the cutting member, two elements which are biased towards each other, and actuation means for driving the elements apart are provided, wherein the actuation means comprise a wedging member which is arranged at a position between the elements, and, on the basis of the shape of the wedging member of the actuation means, the extent to which the elements are driven apart during operation of the actuation means varies with a position of the wedging member of the actuation means with respect to the elements. For example, the shaving apparatus may comprise two V-shaped elements having stiffened portions, wherein ends of one of the elements are connected to ends of another of the elements; and a rotatably arranged cam having a non-circular cam surface, which is arranged at a central position between the elements. In this embodiment of the drive train of the shaving apparatus, the drive force supplied by the motor is transmitted to the cutting members in a very efficient way, as there are no functional bending moments present in the elements. Furthermore, it is relatively easy to realize a larger drive ratio without loss of drive train stiffness.
In another drive train comprising elements which are biased towards each other and means for driving the elements apart, the means for driving the elements apart may comprise a combination of a piezo element and a wedge, for example, the piezo element being operated such as to exert pulsating forces on the wedge for pushing the wedge away.
Within the scope of the present invention, it is not necessary to have a stiff end portion of a drive train in order to realize a theoretically determined movement of the cutting members with respect to each other in practice, as long as extreme mutual positions of the cutting members are well-defined. An embodiment of the shaving apparatus according to the present invention in which this is the case comprises stopping means for limiting a movement of at least one of the cutting members on the basis of a collision of an abutment member associated with the cutting member and an area of the stopping means. For example, one of the cutting members is fixedly connected to a pin, and another of the cutting members has a hole for allowing the pin to pass through with play in the direction in which the cutting
members are movable with respect to each other. In that case, during operation of the shaving apparatus, the pin may be driven such as to perform a reciprocating movement, in a sideward direction, a stroke of the movement being determined by a size of the hole. The effect of limiting the movement of the cutting members with respect to each other may also be obtained by keeping the pin in a fixed position and driving the cutting member such as to perform a reciprocating movement. It is also possible for the shaving apparatus to comprise two pins, in which case each cutting member has two holes for allowing a pin to pass through with play in the direction in which the cutting members are movable with respect to each other, and each pin is coupled to another of the cutting members through resilient means. Preferably, measures are taken to ensure that in every possible mutual position of the cutting members, the cutting edge which extends along the edge of at least one of the cutting members is free from contact in the direction in which the cutting members are movable with respect to each other at the location of the cutting opening. In that case, a process of the cutting edge becoming blunt as a consequence of abutment of the cutting edge against a portion of the cutting member other than the cutting member of which the cutting edge is part is avoided. Moreover, there is no risk that the cutting edge runs up a sloping portion of the other cutting member, so that lifting of one cutting member with respect to the other cutting member, which may result in painful hair pulling during a shaving process, is avoided. Another advantageous effect of keeping the cutting edge free from contact in the direction as mentioned is limitation of noise emission from the shaving apparatus.
In a practical embodiment, like the shaving apparatus known from WO 2005/092579, the shaving apparatus according to the present invention comprises cutting members having a row of substantially V-shaped teeth.
The above-described and other aspects of the present invention will be elucidated with reference to a description of various embodiments of a shaving apparatus according to the present invention, which is given hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will now be explained in greater detail with reference to the Figures, in which equal or similar parts are indicated by the same reference signs, and in which:
Figure 1 shows a perspective view of a shaving apparatus according to the present invention;
Figure 2 shows a perspective view of portions of cutting members of the shaving apparatus as shown in Figure 1 ;
Figures 3a, 3b, 3c and 3d illustrate four steps of a process which leads to skin damage; Figure 4 diagrammatically shows a sectional view of a first preferred embodiment of a drive train for driving the cutting members of the shaving apparatus according to the present invention;
Figure 5 shows a perspective view of elements of a second preferred embodiment of a drive train for driving the cutting members of the shaving apparatus according to the present invention;
Figure 6 shows a top view of a rhomb-shaped element of the second preferred embodiment of a drive train for driving the cutting members of the shaving apparatus according to the present invention;
Figure 7 diagrammatically shows a top view of a third preferred embodiment of a drive train for driving the cutting members of the shaving apparatus according to the present invention;
Figure 8 illustrates an application of a pin extending through a hole in one of the cutting members of the shaving apparatus according to the present invention for the purpose of moving the cutting members with respect to each other; Figure 9 illustrates an application of two pins which each extend through holes in the cutting members of the shaving apparatus according to the present invention for the purpose of moving the cutting members with respect to each other; and
Figure 10 diagrammatically shows a perspective view of a portion of one cutting member of the shaving apparatus according to the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Figure 1 shows a shaving apparatus 1 according to the present invention, which comprises a body 2 and a shaving head 3, wherein the shaving head 3 is mounted on the body 2, and the shaving head 3 has two elongated cutting members 4, 5. For the purpose of performing a shaving action by means of the shaving apparatus 1, a user of the shaving apparatus 1 takes hold of the body 2 of the shaving apparatus 1 and moves the shaving head 3 across an area of skin where hair needs to be removed. During operation of the shaving apparatus, the cutting members 4, 5 are moved with respect to each other. In the shown example, one of the cutting members 4, 5 is a
stationary cutting member 4, and another of the cutting members 4, 5 is a movable, driven cutting member 5. That does not alter the fact that both cutting members 4, 5 may be arranged such as to be movable.
In Figure 2, portions of the cutting members 4, 5 of the shaving apparatus 1 are shown. Both cutting members 4, 5 comprise a row of substantially V-shaped teeth 6, 7. In the shaving head 3, the cutting members 4, 5 are mounted such that teeth 6, 7 of one of the cutting members 4, 5 are located in spaces between teeth 6, 7 of another of the cutting members 4, 5. Hence, in the shaving head 3, pairs 8 of teeth 6, 7 of the two cutting members 4, 5 may be discerned. Cutting openings 9 which are convergent in a direction towards bases of the teeth 6, 7 are present between the teeth 6, 7 of one pair 8.
During operation of the shaving apparatus 1, the driven cutting member 5 is driven such as to perform a reciprocating movement with respect to the stationary cutting member 4, in a direction in which the rows of teeth 6, 7 extend. Due to this movement, which is indicated by means of a double-headed arrow in Figure 2, the size of cutting openings 9 between the teeth 6, 7 is continuously varied. In one extreme position of the driven cutting member 5 with respect to the stationary cutting member 4, the cutting opening 9 is largest, whereas in another extreme position of the driven cutting member 5 with respect to the stationary cutting member 4, the cutting opening 9 is smallest, yet not entirely closed. A shaving action involves catching hair in the cutting openings 9, to which end the user of the shaving apparatus 1 needs to move the shaving head 3 across the skin, and decreasing the size of the cutting openings 9. By preventing the cutting openings 9 from getting entirely closed, a risk that skin damage is inflicted as a result of the shaving action is reduced, and may even be practically zero, as will be explained later.
The teeth 6, 7 of both cutting members 4, 5 are provided with cutting edges 10, 11 for the purpose of actually cutting through hair. In each pair 8 of teeth 6, 7, the cutting edges 10, 11 of the teeth 6, 7 face each other. In the shown example, the teeth 6 of the stationary cutting member 4 comprise a cutting edge 10 extending along the entire length of an edge of the teeth 6, and the teeth 7 of the driven cutting member 5 comprise a cutting edge 11 extending only along a portion of an edge of the teeth 7, which is located at the base of the teeth 7, the teeth 7 of the driven cutting member 5 also comprising a non-cutting edge 12.
When a shaving action is performed, a process of cutting through a hair 13 by means of a pair 8 of teeth 6, 7 comprises the following steps:
- making a notch in the hair 13 by pressing the hair 13 against the tooth 6 of the stationary cutting member 4 by means of the tooth 7 of the driven cutting member 5,
whereby the cutting edge 10 of the tooth 6 of the stationary cutting member 4 penetrates the hair 13 over a certain distance, while the hair 13 is being supported by the non-cutting edge 12 of the tooth 7 of the driven cutting member 5;
- releasing the pressure on the hair 13 by moving the tooth 7 of the driven cutting member 5 away from the hair 13;
- moving the shaving head 3 further, thereby causing the hair 13 to become located deeper in the cutting opening 9, such that the hair 13 is within reach of the cutting edge 11 of the tooth 7 of the driven cutting member 5; and
- making a through-cut in the hair 13 by moving the tooth 7 of the driven cutting member 5 towards the hair and pressing this tooth 7 against the hair 13, whereby the cutting edge 11 of the tooth 7 of the driven cutting member 5 penetrates the hair 13, and the cutting edge 10 of the tooth 6 of the stationary cutting member 4 penetrates the hair 13 over a further distance.
It is also possible that a process of shaving off a hair takes more steps than the steps described above. On the other hand, a relatively thin hair may be shaved off by means of only one encounter with at least one of the cutting edges 10, 11.
For the sake of completeness, it is noted that it is also possible that the teeth 6, 7 of only one of the cutting members 4, 5 comprise a cutting edge 10, 11. However, in order to realize an effective shaving action, it is preferred that at least portions of the teeth 6, 7 of both cutting members 4, 5 are suitable for penetrating hair. Furthermore, it is noted that within the context of the present invention, a cutting edge 10, 11 does not necessarily need to be a sharp edge of a component. For example, it is also possible that at least a portion of a side face of a component is used as a cutting edge 10, 11.
In general, when using a shaving apparatus comprising two cutting members having rows of teeth as described in the foregoing, despite of the fact that the cutting openings are never entirely closed, skin damage may occur as a result of a process which is explained hereinafter on the basis of Figures 3a, 3b, 3c and 3d. In these Figures, a portion of skin 14 and a pair 8 of teeth 6, 7 are diagrammatically shown, as seen at a position near tips of the teeth 6, 7. When the teeth 6, 7 are moved towards each other as a consequence of a movement of the driven cutting member 5 with respect to the stationary cutting member 4, due to contact of the teeth 6, 7 with the skin 14, pressure is exerted on a top layer of the skin 14, and a volume of skin 14 domes in the cutting opening 9 which is present between the teeth 6, 7. As the size of the cutting opening 9 decreases, the volume of skin 14 is
compressed. An initial situation is illustrated by Figure 3 a, whereas two steps in the process of compressing the doming volume of skin 14 are illustrated by Figures 3b and 3c. Skin damage occurs when the volume of skin 14 is compressed to such an extent that a mechanical limit of compression of skin 14 is exceeded, and plastic deformation of the volume of skin 14 takes place. This situation is illustrated by Figure 3d.
According to an important insight underlying the present invention, in a shaving apparatus 1 in which the cutting openings 9 are never entirely closed, it is dependent on a relation of a maximum size of the cutting opening 9 and a minimum size of a cutting opening 9 whether skin damage occurs or not. An explanation is found in the idea that in the case of a relatively large maximum size of the cutting opening 9, a relatively large volume of skin 14 is compressed between a pair 8 of teeth 6, 7, so that the minimum size of the cutting opening 9 needs to be relatively large as well in order to prevent a situation in which the compression leads to plastic deformation of the skin 14. In the case of a smaller maximum size of the cutting opening 9, the volume of skin 14 which is compressed is smaller, and the minimum size of the cutting opening 9 may be smaller as well.
It is noted that according to the present invention, the size of the cutting opening 9 is defined as a distance which is measured along an imaginary line which extends in the direction in which the cutting members 4, 5 are movable with respect to each other, and which intersects the teeth 6, 7 at a position where a hair 13 may first encounter a cutting edge 10, 11. Hence, in the example as shown in Figure 2, the imaginary line is intersecting a tip of the tooth 6 of the stationary cutting member 4. In Figure 2, the imaginary line is represented as a dashed line which is indicated by means of reference numeral 15. In the following, the distance which is measured along this line 15 will be referred to as cutting distance. According to the present invention, simply defining a range of the stroke of the movement of the cutting members 4, 5 with respect to each other, and keeping the stroke in that range in order to avoid skin damage, is not safe, as skin damage may still occur when a ratio of a minimum value of the cutting distance and a maximum value of the cutting distance is too small. According to the present invention, when a shaving apparatus like the shaving apparatus 1 as illustrated by Figures 1 and 2 is designed, it is important to take measures aimed at ensuring that the min/max ratio is equal to or larger than 0.22. In this way, skin damage as a consequence of a shaving action which is performed by means of the shaving apparatus is avoided. As, in practice, the movement of the cutting members 4, 5 with respect
to each other is influenced by, among other things, counteracting forces resulting from contact of the cutting members 4, 5 with hair, and the actual min/max ratio may deviate from a theoretical min/max ratio, and may even fall outside a predetermined range associated with absence of skin damage as well as convenient and effective use, it is important that measures are taken for ensuring that a discrepancy between theory and practice is as small as possible. These measures involve having well-defined extreme positions of the cutting members 4, 5 with respect to each other. In the following, on the basis of Figures 4-9, a number of examples of such measures will be explained.
Figure 4 shows a first preferred embodiment 16 of a drive train for driving the cutting members 4, 5 of the shaving apparatus 1.
The drive train 16 comprises a motor 17 having an output shaft 18 for supplying a drive force which is needed for driving one of the cutting members 4, 5. It is noted that in Figure 4 only a portion of the motor 17 is shown. The output shaft 18 supports an excenter 19. A connection rod 20 is coupled to the excenter 19, through a big end bearing 21. In this configuration, it is achieved that when the motor 17 is operated and the output shaft 18 is rotated, the connection rod 20 performs a reciprocating movement, in an axial direction.
The drive train 16 further comprises an element 22 for mounting the driven cutting member 5, which mounting element 22 is coupled to a short portion 23 a of a lever 23, through an intermediate element 24, which lever 23 is tiltably arranged about a tilting point 25. The connection rod 20 is coupled to a long portion 23b of the lever 23, so that, during operation of the motor 17, a reciprocating movement of the connection rod 20 is transmitted to the mounting element 22, through the lever 23 and the intermediate element 24. In the shown example, the lever 23 is adapted to give a drive ratio of 3 : 1. In this way, it is achieved that an influence of play present in the drive train 16 on the stroke of the reciprocating movement of the mounting element 22 is diminished. Furthermore, it is noted that the mounting element 22 is supported by two flexure elements 26, so that tilting of the mounting element 22 is prevented.
The whole of the mounting element 22, the lever 23, the intermediate element 24 and the flexure elements 26 is mounted on a support 27.
For the sake of completeness, it is noted that besides the element 22 for mounting the driven cutting member 5, an element 28 for mounting the stationary cutting member 4 is provided.
In practice, it is very well possible to achieve that a functional stiffness of the drive train 16, i.e. a stiffness at an end where the drive train 16 is connectable to the driven cutting member 5, is higher than or equal to 3 * 10 4 N/m per mm functional length of the cutting member 5. In this way, a stroke of the movement of the driven cutting member 5 with respect to the stationary cutting member 4 may actually be realized, even in case counteracting forces are exerted on the driven cutting member 5 during a shaving action.
Within the scope of the present invention, a simple and cheap variant of the drive train 16 is feasible, which does not comprise the intermediate element 24 and the flexure elements 26. In such a drive train, the connection rod 20 is elastically coupled to the lever 23, and an end of the lever 23 which is not connected to the connection rod 20 is pivotably connected to a pivot, and the element 22 for mounting the driven cutting member 5 is arranged at this end of the lever 23.
Figures 5 and 6 serve to illustrate a second preferred embodiment 30 of a drive train for driving the cutting members 4, 5 of the shaving apparatus 1. It is noted that a design of this drive train 30 is aimed at realizing a functional stiffness which is higher than or equal to 3 * 10 4 N/m per mm functional length of the cutting members 4, 5.
Like the first preferred embodiment 16 of the drive train, the second preferred embodiment 30 of the drive train comprises a motor 17 having an output shaft 18. Furthermore, the drive train 30 comprises a cam 31 having a non-circular cam surface 32, which is mounted on an end of the output shaft 18, and which is located in a centre of a rhomb-shaped element 33 comprising four stiffened flexure elements 34 which are configured according to a parallellogram. A top view of the rhomb-shaped element 33 is shown in Figure 6. In fact, the rhomb-shaped element 33 may be regarded as being composed of two V-shaped elements 35, wherein ends of one of these elements 35 are connected to ends of another of these elements 35. The V-shaped elements 35 are biased towards each other on the basis of the fact that the V-shaped elements 35 are driven apart by the cam 31. Therefore, contact of a central portion 36 of the V-shaped elements 35 with the cam surface 32 is guaranteed. Within the scope of the present invention, other ways of biasing the V- shaped elements 35 towards each other are feasible, wherein additional biasing means such as springs may be applied.
When the motor 17 is operated and the output shaft 18 is rotated, the cam 31 is also rotated. In the process, as the central portions 36 of the V-shaped elements 35 follow the non-circular cam surface 32, a distance between the central portions 36 is continuously varied. Due to the fact that the V-shaped elements 35 are connected to each other at their
ends, a distance between the ends of the V-shaped elements 35 is continuously varied as well. On the basis of these effects, the rhomb-shaped element 33 of which the V-shaped elements 35 are part is suitable to be used for the purpose of mounting and driving the cutting members 4, 5. It is noted that the cam surface 32 may be elliptical, for example. In such a case, it is achieved that a frequency of a reciprocating movement of the V-shaped elements 35 is twice a frequency at which the output shaft 18 of the motor 17 and the cam 31 are driven.
Figure 7 shows a third preferred embodiment 37 of a drive train for driving the cutting members 4, 5 of the shaving apparatus 1. It is noted that a design of this drive train 37 is aimed at realizing a functional stiffness which is higher than or equal to 3 * 10 4 N/m per mm functional length of the cutting members 4, 5.
The drive train 37 comprises two aluminium bars 38, which are biased towards each other by means of plate springs 39. The drive train 37 further comprises an elongated piezo element 40 and a wedge 41 which is positioned between the aluminium bars 38, at an end of the piezo element 40. During operation of the drive train 37, the piezo element 40 is activated such as to continuously exert pulsating forces on the wedge 41 for pushing the wedge 41 away. In the process, under the influence of ferees exerted by the wedge 41 on the one hand, and forces exerted by the plate springs 39 on the other hand, the aluminium bars 38 continuously move towards each other and away from each other. Hence, the aluminium bars 38 are suitable to be used for the purpose of mounting and driving the cutting members 4, 5.
Advantageously, for the purpose of adjusting the mutual positions of the aluminium bars 38, the piezo element 40 and the wedge 41, suitable means are provided. In Figure 7, an adjustment knob 42 for operating such means and a securing knob 43 for fixing the adjustment knob 42 are shown. Furthermore, in order to reduce an influence of heat, in particular heat emitted by the hand of a user of the shaving apparatus 1 with which the user is holding the shaving apparatus 1 during use, it is preferred if heat insulating elements 44 are provided.
Within the scope of the present invention, it is not necessary that an end portion of a drive train for driving at least one of the cutting members 4, 5 has a relatively high stiffness in order to have a well-defined movement of the cutting members 4, 5 with respect to each other. Figures 8 and 9 illustrate possibilities for driving the cutting members 4, 5, such as to move them with respect to each other with a relatively low stiffness, while the
extreme positions of the cutting members 4, 5 with respect to each other are still well- defined.
In particular, Figure 8 illustrates an application of a pin 45 for driving a movably arranged cutting member 5, wherein the pin 45 is attached to the movably arranged cutting member 5, and a stationary cutting member 4 comprises a slotted hole 46 for allowing passage of the pin 45. In a direction of movement of the movably arranged cutting member 5, a length of the hole 46 is larger than a diameter of the pin 45, whereas, in a direction perpendicular to the direction of movement of the movably arranged cutting member 5, a width of the hole 46 is substantially equal to the diameter of the pin 45, so that in this direction, the pin 45 is accommodated in the hole 46 without play.
During operation of the shaving apparatus 1 of which the cutting members 4, 5 are part, the pin 45 is moved in a sideward direction, the movement of the pin 45 being a reciprocating movement. Extreme positions of the movement are accurately defined, as these positions are the positions where the pin 45 collides with a wall 47 of the hole 46. This is all the more true when portions of the pin 45 which are intended for colliding with the wall 47 of the hole 46 have a well-defined shape, i.e. are accurately straight in an axial direction.
It is noted that it is not necessary that the pin 45 is moved and the cutting member 4 having the hole 46 is kept at a fixed position, but that it may also be the other way around in order to realize a desired movement of the cutting members 4, 5 with respect to each other. Furthermore, it is noted that, in practice, the pin 45 may also be realized as an integrated piece of the driven cutting member 5, i.e. as a bent portion of a plate from which the cutting member 5 is manufactured.
According to the possibility illustrated by Figure 9, two pins 45a, 45b are applied, and each of the cutting members 4, 5 has two slotted holes 46a, 46b for allowing passage of the pins 45a, 45b. One pin 45a is attached to one of the cutting members 4, 5 through resilient means, such as a coil spring 48a, and another pin 45b is attached to another of the cutting members 4, 5 through resilient means, such as a coil spring 48b, the resilient means being arranged such as to act in a direction of movement of the cutting members 4, 5 with respect to each other. The resilient means may be pre-stressed for the purpose of achieving that the cutting members 4, 5 are still capable of exerting sufficient forces on hairs to be shaved off.
Due to the fact that the pins 45 a, 45b are not fixedly connected to the cutting members 4, 5, but through resilient means, the stiffness at which the cutting members 4, 5 are driven when the pins 45 a, 45b perform a reciprocating movement in a sideward direction is
relatively low. Nevertheless, extreme positions of the cutting members 4, 5 with respect to each other are well-defined on the basis of the length of the holes 46a, 46b.
It is noted when two pins 45 a, 45b such as described in the foregoing are applied, it is also possible to keep the pins 45 a, 45b at fixed positions while the cutting members 4, 5 perform a reciprocating movement.
Advantageously, a movement of the driven cutting member 5 during which the teeth 6, 7 of the pairs 8 of teeth 6, 7 are moved towards each other is reversed at a moment that the cutting edge 10 of the tooth 6 of the stationary cutting member 4 is still free from contact with the non-cutting edge 12 of the tooth 7 of the driven cutting member 5, which serves for supporting a hair 13 which gets notched by means of the cutting edge 10 of the tooth 6 of the stationary cutting member 4. In this way, it is achieved that the cutting edge 10 of the teeth 6 of the stationary cutting member 4 is prevented from becoming blunt as a result of continuously hitting the non-cutting edge 12 of the teeth 7 of the driven cutting member 5, which would otherwise happen. As this advantageous effect of reversing the movement in time is beneficial to the lifespan of the shaving apparatus 1 of which the cutting members 4, 5 are part, it is important that the design of the shaving apparatus 1 and a drive train for driving the cutting members 4, 5 is such that contact of the cutting edge 10 of the teeth 6 of the stationary cutting member 4 with the non-cutting edge 12 of the teeth 7 of the driven cutting member 5 is avoided under all circumstances and during the entire operational life of the shaving apparatus 1.
Another reason why it is important to stop the movement of teeth 6, 7 of pairs 8 of teeth 6, 7 towards each other is now explained on the basis of Figure 10, in which a single tooth 7 of the driven cutting member 5 and a surrounding portion of the cutting member 5 is shown. At the position of the cutting edge 11, the tooth 7 is thinner than at the position of the non-cutting edge 12, and a relatively thin portion 49 is present near the base of the tooth 7. A transition area 50 of the relatively thin portion 49 to thicker portions of the tooth 7 and a supporting base 51 of the cutting member 5 has a certain radius. In view of this, it is important that abutment of the cutting edge 10 of a tooth 6 of the stationary cutting member 4 to surfaces 52, 53 of the tooth 7 of the driven cutting member 5 which are connected to the transition area 50 is prevented, as such abutment would lead to driving the teeth 6, 7 somewhat apart, due to the rounded shape of the transition area 50. As a result, painful hair pulling would occur, and as it is preferred to avoid this, it is important that the movement of the cutting members 4, 5 with respect to each other is reversed before any
portion of the teeth 7 of the driven cutting member 5 is capable of contacting the cutting edge 10 of the teeth 6 of the stationary cutting member 4.
Furthermore, it is noted that it is true that the smaller the number of collisions between components of the shaving apparatus 1 during operation, the less noise is emitted. It will be clear to a person skilled in the art that the scope of the present invention is not limited to the examples discussed in the foregoing, but that several amendments and modifications thereof are possible without deviating from the scope of the present invention as defined in the attached claims. While the present invention has been illustrated and described in detail in the Figures and the description, said illustration and description are to be considered illustrative or exemplary only, and not restrictive. The present invention is not limited to the disclosed embodiments.
For example, details of the geometry of the cutting members 4, 5 and the drive trains 16, 30, 37 as shown and described may be chosen to be different, while maintaining an equal functionality. Furthermore, drive trains other than the drive trains 16, 30, 37 as shown and described are feasible within the scope of the present invention.
Referring to Figure 2, it is also possible that the cutting member 4 comprising the teeth 6 having the cutting edge 10 extending along the entire length of the teeth 6 is a driven cutting member 4, and that the cutting member 5 comprising the teeth 7 having the cutting edge 11 and the non-cutting edge 12 is a stationary cutting member 5. It has already been noted that it is not necessary to have a stationary cutting member 4, and that the movement of the cutting members 4, 5 with respect to each other may also be realized by moving both cutting members 4, 5.
In case a drive train with a relatively high stiffness at its end which is intended for connection to at least one of the cutting members 4, 5 is applied in the shaving apparatus 1 according to the present invention, drive means, such as linear motors, with a relatively low stiffness can be realized by incorporating a sufficiently large drive ratio as compensation for the low stiffness of the motor. An example of such a drive ratio is 20:1.
Within the scope of the present invention, it is possible to apply suitable means for monitoring an actual stroke of the movement of the cutting members 4, 5 with respect to each other, and a feedback control loop for the purpose of compensating for any loss of stroke which might occur during a shaving action.
It is noted that a cross-section of the pins 45, 45 a, 45b as shown in Figures 8 and 9 may have any suitable shape. This cross-section may be shaped like a circle, but it is also very well possible that this cross-section is shaped like a rectangle or a square.
Other variations to the disclosed embodiments can be understood and effected by a person skilled in the art in practicing the claimed invention, from a study of the Figures, the description and the attached claims. In the claims, the word "comprising" does not exclude other steps or elements, 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 can not be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the present invention.
In the foregoing, a shaving apparatus 1 is disclosed, which comprises a stationary cutting member 4 having a row of substantially V-shaped teeth 6 and a movable, driven cutting member 5 having a row of substantially V-shaped teeth 7 as well. During operation of the shaving apparatus 1, the movable cutting member 5 is driven such as to perform a reciprocating movement. In the process, a size of convergent cutting openings 9 between teeth 6, 7 of pairs 8 of teeth 6, 7 of the two cutting members 4, 5 having cutting edges 10, 11 which face each other is continuously varied, so that hairs 13 which are caught in the cutting openings 9 are shaved off. In order to avoid skin irritation and skin damage, the cutting openings 9 are never entirely closed. Furthermore, a ratio of a minimum value of a size of the cutting openings 9 and a maximum value of the size of the cutting openings 9, in particular a ratio of a minimum value of a cutting distance and a maximum value of the cutting distance, the cutting distance being defined as a distance measured along an imaginary line 15 extending in a direction in which the cutting members 4, 5 are movable with respect to each other and intersecting the teeth 6, 7 at a position where a hair 13 may first encounter a cutting edge 10, 11, is at least 0.22.
Also, in the foregoing, examples of drive trains and assemblies of elements for driving at least one of the cutting members 4, 5 are disclosed. One way of ensuring that a desired ratio of a minimum value of the cutting distance and a maximum value of the cutting distance is actually realized in practice involves an application of a drive train 16, 30, 37 which is adapted to achieve that a stiffness at a location where the drive train 16, 30, 37 and at least one of the cutting members 4, 5 are connected to each other is at least 3 * 10 4 N/m per mm functional length of the cutting member. Another way of ensuring that a desired ratio of a minimum value of the cutting distance and a maximum value of the cutting distance is actually realized in practice involves an application of means for accurately defining extreme positions of the cutting members 4, 5 with respect to each other.