Hair cutting unit with hair entry slot having hair retaining structure

Abstract

A hair cutting unit (9a) comprises an outer cutting member (11a) and an inner cutting member (13a), the inner cutting member (13a) being rotatable relative to the outer cutting member about a central axis. The outer cutting member comprises a hair entry slot (35) having a slot angle (alpha) in the range of 0 DEG to 20 DEG in each radial position of the hair entry slot. The inner cutting member includes cutting elements (59a, 59b, 59c) each having a cutting edge (45a, 45b, 45c) having an edge angle (beta) in the range of 55 DEG to 85 DEG. The trailing edge (43) of each hair entry slot is provided with a hair retaining structure (47) having an array of hair abutment surfaces (53) extending transversely with respect to the trailing edge and facing the central axis (19).

Description

Technical Field

[0001] The present invention relates to a hair cutting unit comprising a central axis, an outer cutting member and an inner cutting member, the inner cutting member being covered by the outer cutting member and being rotatable relative to the outer cutting member about the central axis, wherein:

[0002] The outer cutting member comprises a plurality of hair entry slots, each of which extends from a radially inner slot end position to a longitudinal extension of the hair entry slot relative to the central axis.

[0003] radial outer groove end position;

[0004] - the inner cutting member comprises a plurality of cutting elements, each of the cutting elements having a cutting edge;

[0005] - when viewed in an axial direction parallel to the central axis, the slot angle of each hair entry slot is defined as the angle between the rear edge of the hair entry slot extending along the longitudinal extension of the hair entry slot relative to the rotation direction of the internal cutting member and the angle between the rear edge and the longitudinal extension of the hair entry slot;

[0006] The acute angle enclosed by the local radial direction with respect to the central axis; and

[0007] - When viewed in the axial direction, the edge angle of each cutting edge is defined as an acute angle enclosed by the cutting edge and a local radial direction at said cutting edge relative to the central axis, said edge angle being in the range of 55° to 85°.

[0008] The invention also relates to a shaving unit having at least one hair cutting unit as described above and also having a support structure configured to support the at least one hair cutting unit.

[0009] The present invention also relates to a shaving device having a main housing and a shaving unit as described above coupled to the main housing, wherein the main housing accommodates a drive system configured to drive the internal cutting member of each hair cutting unit of the shaving unit to rotate relative to the external cutting member. Background Art

[0010] As is well known, the hair cutting unit comprises an external cutting member and an internal cutting member, which is covered by the external cutting member and is rotatable around the central axis of the hair cutting unit relative to the external cutting member. Such a hair cutting unit can be a part of a shaving unit of an electric shaving device. The shaving unit can have two or more such hair cutting units supported by a supporting structure of the shaving unit. The shaving device can have a main housing for accommodating an electric motor. The shaving unit can be coupled to the main housing in a permanent manner or in a releasable manner. When the shaving unit is coupled to the main housing, the motor is coupled to the internal cutting member of the hair cutting unit via a transmission system to allow the motor to rotate the internal cutting member relative to the external cutting member. During the rotation of the internal cutting member, hair can penetrate into the external cutting member via the hair entry groove of the external cutting member, and can be cut by the interaction of the cutting edge of the cutting element of the rotating internal cutting member and the reverse cutting edge formed on the trailing edge of the hair entry groove of the external cutting member. The trailing edge of the hair entry groove of the external cutting member should be understood to be defined relative to the rotation direction of the internal cutting member associated with the external cutting member. That is, during rotation of the inner cutting member, the cutting edges of the cutting elements of the inner cutting member will first pass through the leading edge of the hair entry slot and will subsequently pass through the trailing edge of the hair entry slot.

[0011] The hair entry groove of the external cutting member usually extends from the radially inner groove end position to the radially outer groove end position along the longitudinal extension of the hair entry groove relative to the central axis. In the known hair cutting unit, the hair entry groove can be straight or curved, and can have a main extension direction in a radial direction relative to the central axis. The example of the hair cutting unit in which the hair entry groove has a V-shaped portion is also known. Usually, when observed in the axial direction parallel to the central axis, the groove angle of the hair entry groove in the predefined radial position at the hair entry groove place can be defined as an acute angle surrounded by the trailing edge of the hair entry groove and the local radial direction of the central axis at the hair entry groove place at the above-mentioned predefined radial position, and the trailing edge of the hair entry groove extends along the longitudinal extension of the hair entry groove. In the known hair cutting unit, the groove angle can be constant or can change in the whole extension range of the hair entry groove.

[0012] In known hair cutting units, the cutting elements of an internal cutting member can be arranged on the carrier of the internal cutting member with one or more annular arrays around the central axis, and the cutting edge of the cutting element can be straight or curved and can have a main extension direction in a radial direction. The example of a hair cutting unit in which the cutting edge of the internal cutting member has a V-shaped portion is also known. Usually, when observed in the axial direction, the cutting edge angle of the cutting edge of each cutting element in the predefined radial position at the cutting edge can be defined as an acute angle surrounded by the cutting edge and the local radial direction of the central axis at the above-mentioned predefined radial position at the cutting edge. In known hair cutting units, the cutting edge angle can be constant or can change within the radial extension range of the cutting edge of the internal cutting member.

[0013] A known problem of the hair cutting unit as described above is the so-called excessive skin bulging, that is, the skin of the user may protrude excessively into the hair entry groove of the external cutting member. Although a certain degree of skin bulging is necessary to achieve a sufficiently tight degree of the hair cutting process, excessive skin bulging may cause the skin to contact the rotating internal cutting member, which may cause skin irritation or skin damage. Excessive skin bulging may occur when the user places the shaving unit on the skin with excessive pressure. In order to reduce skin bulging and the resulting skin irritation, WO 2019 / 211128 proposes a hair cutting unit as described above, wherein the groove angle of the hair entry groove of the external cutting member is in the range of 35 ° to 60 °. Through this relatively large groove angle, it is observed that skin bulging is significantly reduced or even avoided. In order to fully prevent the cutting element of the rotating internal cutting member from displacing the hair entering the groove (hair manipulation) and achieving sufficient hair cutting performance, WO 2019 / 211128 proposes a relatively small shear angle between the reverse cutting edge on the trailing edge of the hair entering groove of the internal cutting member and the external cutting member in the range of 0° to 15° in combination with the above-mentioned relatively large groove angle. In the embodiment disclosed in WO 2019 / 211128, the cutting edge of the internal cutting member and the reverse cutting edge of the external cutting member are both straight, so that the shear angle between the cutting edge and the reverse cutting edge is constant over the entire extension range of the cutting edge and the reverse cutting edge. Although the hair cutting unit of WO 2019 / 211128 thus combines adequate hair cutting performance with relatively low skin irritation and hair manipulation, a disadvantage of this known hair cutting unit is that the relatively large groove angle of the hair entry groove reduces the hair capture performance of the hair cutting unit compared to a hair cutting unit in which the hair entry groove has a smaller groove angle and therefore has a larger radial extension relative to the central axis of the hair cutting unit. The hair capture performance is related to the ease with which hair can penetrate into the hair entry groove of the external cutting member during use. Summary of the invention

[0014] The object of the present invention is to provide a hair cutting unit as previously described in the "Technical Field" section, which provides a skin irritation level that is at least equivalent to or lower than the skin irritation level provided by the hair cutting unit of WO 2019 / 211128, and provides a hair cutting performance that is at least equivalent to or better than the hair cutting performance of the hair cutting unit of WO 19 / 211128, but its hair capturing performance is significantly better than the hair cutting unit of WO 2019 / 211138.

[0015] In order to achieve the above object, the present invention provides a hair cutting unit, which includes a central axis, an outer cutting member and an inner cutting member, the inner cutting member is covered by the outer cutting member and is rotatable around the central axis relative to the outer cutting member, wherein:

[0016] The outer cutting member comprises a plurality of hair entry slots, each of which extends from a radially inner slot end position to a longitudinal extension of the hair entry slot relative to the central axis.

[0017] radial outer groove end position;

[0018] - the inner cutting member comprises a plurality of cutting elements, each of the cutting elements having a cutting edge;

[0019] - a slot angle of each hair entry slot is defined as an acute angle enclosed by a trailing edge of the hair entry slot and a local radial direction relative to the central axis at the trailing edge when viewed in an axial direction parallel to the central axis, the trailing edge of the hair entry slot extending in a longitudinal direction of the hair entry slot relative to the rotational direction of the internal cutting member;

[0020] - When viewed in the axial direction, the edge angle of each cutting edge is defined as the area enclosed by the cutting edge and the local radial direction at the cutting edge relative to the central axis.

[0021] Angle, the cutting edge angle is in the range of 55° to 85°;

[0022] - in each radial position of the hair entry slot between the radially inner slot end position and the radially outer slot end position, each hair entry slot along the longitudinal extension of the hair entry slot

[0023] The groove angle of the groove is in the range of 0° to 20°; and

[0024] - The rear edge of each hair entry slot is provided with a hair retaining structure having an array of hair abutment surfaces arranged along the rear edge, each hair abutment surface extending transversely relative to the rear edge and facing the central axis.

[0025] Therefore, the hair cutting unit according to the present invention combines the relatively large edge angle of the cutting edge of the internal cutting member in the range of 55 ° to 85 ° with the relatively small groove angle of the hair entry groove of the external cutting member in the range of 0 ° to 20 °. This combination results in a relatively large angle surrounded by the trailing edge of the hair entry groove and the cutting edge of the internal cutting member. Compared with the hair cutting unit of WO 2019 / 211128, the relatively small groove angle of the hair entry groove in the range of 0 ° to 20 ° significantly improves the hair capture performance of the hair cutting unit.

[0026] Provide the hair holding structure with the hair abutment surface array arranged along the trailing edge of hair entry groove and produce the following technical effect.During operation, the hair that pierces the hair entry groove will be manipulated by the cutting element of rotating internal cutting member to the position that abuts with a hair abutment surface in the hair abutment surface of the hair holding structure that extends transversely relative to the trailing edge of hair entry groove.The hair abutment surface will prevent the cutting element from further manipulating the hair in the hair entry groove in the subsequent hair cutting process.Due to relatively large cutting edge angle, the cutting edge of the rotating internal cutting member will carry out slicing motion to hair in the hair cutting process, and wherein hair is maintained in a stationary position relative to the trailing edge by the hair abutment surface.Compared with the hair cutting unit, the above-mentioned slicing motion improves the hair cutting performance, wherein the cutting edge of the hair entry groove of the external cutting member and the internal cutting member both have the main extension direction in the radial direction relative to the central axis, and therefore, the cutting edge carries out the motion of cutting through the hair.The above-mentioned slicing motion further reduces the degree of wear of the cutting edge of the internal cutting member.

[0027] Another insight provided by the present invention is that, since the hair abutment surface extends in a direction transverse to the trailing edge of the hair entry groove, the trailing edge itself does not need to be equipped with a reverse cutting edge. The function of the hair abutment surface is only to maintain the hair in a static position in the hair entry groove during the hair cutting process, while the cutting edge of the internal cutting member is enough to effectively cut the hair through the slicing motion of the hair. The absence of any reverse cutting edge on the external cutting member simplifies the manufacturing process of the external cutting member.

[0028] The relatively large edge angle of the cutting edge of the inner cutting member also limits the degree of skin irritation, especially in combination with the presence of a hair retaining structure at the trailing edge of the hair entry slot. The above limited degree of skin irritation allows a relatively large degree of skin uplift into the hair entry slot. Therefore, the hair entry slot can have a relatively large width, which will further improve the hair capture performance of the outer cutting member.

[0029] It should be noted that although in the specification and claims, both the cutting edge angle and the groove angle are defined as having positive values ​​in the range of 55° to 85° and 0° to 20°, respectively, when viewed in the axial direction, the cutting edge angle and the groove angle can each have a positive or negative orientation relative to the local radial direction at the cutting edge and the trailing edge.

[0030] In one embodiment of the hair cutting unit according to the present invention, when observing in the axial direction, the shearing angle surrounded by the cutting edge of each cutting element in each hair abutment surface and the cutting element at the above-mentioned hair abutment surface is in the range of 0 ° to 15 °. When the above-mentioned shearing angle is within this range, in the hair cutting process, the hair abutment surface of the hair holding structure is maintained in the static position in the hair entry groove optimally. More preferably, the above-mentioned shearing angle is in the range of 0 ° to 5 °. Especially, when present at the hair abutment surface, the hair abutment surface can extend substantially parallel to each cutting edge in the cutting element separately.

[0031] In another embodiment of the hair cutting unit according to the invention, the cutting edge angle is in the range of 70° to 80°. When the cutting edge angle is in this range, a relatively small angle between 10° and 20° is enclosed by the cutting edge and the local movement direction of the cutting edge at the hair entry groove (tangent to the central axis). This results in a particularly low degree of skin irritation, while cutting hair by the slicing movement of the cutting edge through the hair is very effective.

[0032] In a preferred embodiment of the hair cutting unit according to the present invention, the groove angle is in the range of 0° to 5°. Since the groove angle is in this range, the hair catching performance of the hair cutting unit is further improved.

[0033] In the actual embodiment of the hair cutting unit according to the present invention, the hair holding structure comprises a toothed element array arranged along the trailing edge of at least one hair entry groove in the hair entry groove, wherein the hair abutment surface is formed by the first side edge surface of the corresponding toothed element in the toothed element facing the central axis.Therefore, the hair holding structure can have a comb-like structure arranged on the trailing edge.The hair that pierces the hair entry groove will be manipulated by the cutting element of the rotating internal cutting member to enter a space in the space between the continuous pairs of adjacent toothed elements, and will be cut by the cutting element when the above-mentioned first side edge surface of a toothed element in the toothed element defining the above-mentioned space abuts.By providing a relatively large amount of toothed elements along the trailing edge, the hair holding performance of the hair holding structure in the hair cutting process can be optimized.The second side edge surface of each corresponding toothed element facing away from the central axis can extend substantially parallel to the first side edge surface of the corresponding toothed element.This will optimize the hair catching performance of the hair holding structure provided along the trailing edge.

[0034] In the embodiment of the hair cutting unit according to the present invention, the leading edge of the direction of rotation of the hair entry groove relative to the internal cutting member extends to the radially outer groove end position from the radially inner groove end position as a straight line at a distance from the toothed element. In this embodiment, the hair entry groove has a first region and a second region, the first region extends to the radially inner groove end position from the radially outer groove end position as a continuous open groove region along the leading edge, and the second region extends along the trailing edge in which the toothed element array of the hair holding structure is arranged. In this embodiment, hair can be effectively captured in the above-mentioned first region of the hair entry groove at first, and can be efficiently manipulated by the cutting element of the internal cutting member of rotation to enter the above-mentioned second region of the hair entry groove subsequently, to be held in place by the toothed element of the hair holding structure.

[0035] In another embodiment of the hair cutting unit according to the present invention, the leading edge of the rotation direction of the hair entry groove relative to the internal cutting member comprises other hair holding structure, other hair holding structure has other toothed element array arranged along the leading edge, each other toothed element has other hair abutment surface, other hair abutment surface is formed by the side edge surface of other toothed element, and the side edge surface extends transversely relative to the leading edge and faces the central axis. In this embodiment, hair can also be cut while abutting with other hair abutment surfaces of other toothed elements of other hair holding structure arranged along the leading edge of the hair entry groove. Although the existence of other toothed elements in the hair entry groove may slightly reduce the overall hair capture performance of the hair entry groove, the overall hair capture performance of the hair entry groove in the hair cutting process is improved because of the existence of other hair capture structures. In this embodiment, the toothed elements of the hair holding structure at the trailing edge of the hair entry groove and the other toothed elements of the other hair holding structure at the leading edge of the hair entry groove can be arranged mutually in a staggered configuration, and when observed in the radial direction, can be arranged mutually in a partially overlapping configuration. As a result, the open groove area between the hair holding structure at the trailing edge and the other hair holding structure at the leading edge can extend in a zigzag shape from the radially outer groove end position to the radially inner groove end position. This will significantly improve the overall hair capture performance of the hair entry groove during the hair cutting process.

[0036] In a particular embodiment of the hair cutting unit according to the present invention, the ratio of the first radial distance between the radial inner groove end position and the central axis and the second radial distance between the radial outer groove end position and the central axis is between 0.4 and 0.8. In practice, the radial outer groove end position can be located at the periphery of the external cutting member or very close to the periphery. Therefore, in this particular embodiment, the hair enters the groove and can extend on a large part of the radius of the external cutting member (that is, between about 20% to about 60%). This will cause the hair to enter the groove and have a relatively high hair capture performance. The preferred range of the above ratio is between 0.5 and 0.6, which can represent in practice that the hair enters the groove and extends on the radial distance between about 40% to about 50% of the radius of the external cutting member.

[0037] It should be understood that the actual minimum value allowed of the ratio of the above-mentioned first radial distance and the above-mentioned second radial distance can depend on the cutting edge angle, particularly in a preferred embodiment of the hair cutting unit according to the present invention, wherein the cutting edge of each cutting element of the internal cutting member extends as a continuous curve from a radial position at or near the radial inner groove end position to a radial position at or near the radial outer groove end position. In particular, in this preferred embodiment, a relatively large cutting edge angle may result in a relatively high value for the above-mentioned ratio, i.e. a relatively short radial extension of the hair entering the groove, while a smaller value of the cutting edge angle may allow a smaller value of the above-mentioned ratio, i.e. a larger radial extension of the hair entering the groove. In this preferred embodiment, the number N of the cutting elements of the internal cutting member can be in the range of 2 to 6, preferably 3 or 4, and the cutting edge of each cutting element can extend within an angle of 360 ° / N around the central axis.

[0038] In another embodiment of the hair cutting unit according to the present invention, the cutting edge of the cutting element of the internal cutting member has a radial inner edge end position relative to the central axis respectively, and the radial inner edge end position is closer to the central axis than the radial inner groove end position of each hair entry groove in the hair entry groove. As a result, during the rotation of the internal cutting member, the skin of the user will not be exposed to the radial inner edge end position of the cutting edge via the hair entry groove, and these cutting edges are ahead of the cutting edge in the rotation direction of the internal cutting member. Especially, the radial inner edge end position of the cutting edge of the internal cutting member is always covered by the central skin contact surface of the external cutting member. Therefore, the skin irritation caused by contacting the front radial inner edge end position of the skin is prevented.

[0039] In order to further improve the hair catching performance of the hair entry slot, in another embodiment of the hair cutting unit according to the present invention, the hair entry slot is open in a radially outward direction at a radially outer slot end position.

[0040] The shaving unit according to the invention has at least one hair cutting unit as described above according to any embodiment and further has a support structure configured to support the at least one hair cutting unit.

[0041] As mentioned above, the shaving device according to the present invention has a main housing and a shaving unit according to the present invention, wherein the shaving unit is coupled to the main housing and the main housing accommodates a drive system, which is configured to drive the internal cutting member of each hair cutting unit of the shaving unit to rotate relative to the external cutting member.

[0042] The above and other aspects of the invention will become apparent and elucidated with reference to the following detailed description of embodiments of a hair cutting unit, a shaving unit and a shaving apparatus according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will be explained in more detail with reference to the accompanying drawings, in which the same or similar features are indicated by the same reference numerals, and in which:

[0044] Figure 1 An embodiment of a shaving apparatus according to the invention is shown;

[0045] Figure 2 Shows the composition Figure 1 an embodiment of a shaving unit according to the invention of a shaving device;

[0046] Figure 3 Shows the composition Figure 2 An embodiment of a hair cutting unit according to the invention of a shaving unit;

[0047] Figure 4 Shown with Figure 3 The hair cutting unit drives the engagement Figure 1 a drive shaft of a drive system of a shaving device;

[0048] Figure 5 Shows Figure 3 An outer cutting member of a hair cutting unit;

[0049] Figure 6 Shows Figure 3 an internal cutting member of a hair cutting unit;

[0050] Figure 7 Shows Figure 5 The hair-entry groove portion of the outer cutting member and Figure 6 a portion of a cutting element of an inner cutting member;

[0051] Figure 8 Shown in detail Figure 7 The cutting edge of the cutting element shown passes through the Figure 7The slicing motion of the hairs held in place by the hair holding structure of the hair entry slot shown; and

[0052] Fig. 9 shows an outer cutting member of a second embodiment of a hair cutting unit according to the invention; DETAILED DESCRIPTION

[0053] Figure 1 An embodiment of a shaving device 1 according to the invention is shown. The shaving device 1 comprises a main housing 3, which is designed to be held by a user's hand during operation. The shaving device 1 also comprises a shaving unit 5 according to the invention, which is coupled to the main housing 3. The shaving unit 5 comprises a supporting structure 7 and three hair cutting units 9a, 9b, 9c according to the invention. The supporting structure 7 is configured to support the three hair cutting units 9a, 9b, 9c. The supporting structure 7 may comprise a coupling structure, which is not shown in the figure and is of a type known to a person skilled in the art, by means of which the shaving unit 5 is releasably coupled to the main housing 3. Alternatively, the shaving unit 5 may be permanently connected to the main housing 3. It should be noted that the shaving unit according to the invention may comprise a different number of hair cutting units according to the invention, for example one, two or more than three hair cutting units.

[0054] Figure 2 1 shows a top view of a shaving unit 5. Three hair cutting units 9a, 9b, 9c are arranged in a triangular configuration and each comprises an outer cutting member 11a, 11b, 11c and an inner cutting member 13a, 13b, 13c which is covered by the outer cutting member 11a, 11b, 11c and thus Figure 2 In addition, the hair cutting units 9a, 9b, 9c each comprise a support member 15a, 15b, 15c, which is configured to support the respective outer cutting member 11a, 11b, 11c and the respective inner cutting member 13a, 13b, 13c, and which comprises a skin contact surface 17a, 17b, 17c around the respective outer cutting member 11a, 11b, 11c. The support members 15a, 15b, 15c can be pivoted relative to each other in a manner known to those skilled in the art, so that during use of the shaving device 1, the orientation of the outer cutting members 11a, 11b, 11c and the skin contact surfaces 17a, 17b, 17c of the support members 15a, 15b, 15c can be adjusted according to the local contour of the skin of the user.

[0055] Figure 3The outer cutting member 11a and the inner cutting member 13a of the hair cutting unit 9a are shown in more detail, wherein only half of the outer cutting member 11a is shown, so that the inner cutting member 13a (covered by the outer cutting member 11b) is visible to a greater extent. The hair cutting units 9b and 9c are the same as the hair cutting unit 9a. The hair cutting unit 9a includes a central axis 19, and the inner cutting member 13a is rotatable relative to the outer cutting member 11a around the central axis 19. For this reason, the outer cutting member 11a includes a cylindrical bearing pin 21, which is coaxially arranged on the inner side of the upper wall 23 of the outer cutting member 11a relative to the central axis 19. The inner cutting member 13a includes a bearing bushing 25, which receives the bearing pin 21 of the outer cutting member 11a. The outer cutting member 11a also includes a cylindrical wall 26, which is connected to the circumference of the upper wall 23. The upper wall 23 and the cylindrical wall 26 together cause the outer cutting member 11a to be cup-shaped and cover the inner cutting member 13a.

[0056] The shaving apparatus 1 comprises a drive system configured to drive the inner cutting member 13a, 13b, 13c of each hair cutting unit 9a, 9b, 9c of the shaving unit 5 in rotation relative to the corresponding outer cutting member 11a, 11b, 11c. Figure 1 , and may be of a type known to a person skilled in the art. In particular, the drive system may include an electric motor arranged in the main housing 3, three rotatable drive spindles arranged in the support structure 7 of the shaving unit 5 and each coupled to a corresponding internal cutting member 13a, 13b, 13c, and a transmission system arranged in the main housing 3 and in the support structure 7 of the shaving unit 5, via which the electric motor can drive the three drive spindles in rotation. Figure 4 One of the drive shafts 27 of the drive system is shown, which is drivingly engaged with the internal cutting member 13a of the hair cutting unit 9a. The drive shaft 27 includes a coupling head 29, which engages with a coupling cavity 31 of the internal cutting member 13a. The coupling cavity 31 is arranged on a carrier 33 of the internal cutting member 13a, which is centrally arranged on the internal cutting member 13a. The carrier 33 also includes the bearing bushing 25 of the internal cutting member 13a described above.

[0057] Figure 5The outer cutting member 11a of the hair cutting unit 9a is shown in a top view, i.e. viewed in an axial direction parallel to the central axis 19. The upper wall 23 of the outer cutting member 11a comprises a plurality of hair entry slots 35, each of which extends from a radially inner slot end position 37 to a radially outer slot end position 39 along the longitudinal extension of the hair entry slot relative to the central axis 19. The radially inner slot end position is the radially innermost point of the hair entry slot 35 relative to the central axis 19, while the radially outer slot end position is the radially outermost point of the hair entry slot 35 relative to the central axis 19 when viewed in the axial direction. Figure 5 In the embodiment shown, the outer cutting member 11a has 32 hair entry slots 35, which are arranged at equal mutual distances around the central axis 19. Alternatively, the outer cutting member may have a different number of hair entry slots, and the hair entry slots may be irregularly distributed around the central axis 19. Figure 5 In the illustrated embodiment, the inner groove end positions 37 of the hair entry grooves 35 are equidistant from the central axis 19, but alternatively, the distances of the inner groove end portions 37 from the central axis 19 may be different from each other. Figure 5 In the illustrated embodiment, the outer slot end positions 39 of the hair entry slots 35 are equidistant from the central axis 19, but alternatively, the outer slot end portions 39 may be at different distances from the central axis 19.

[0058] like Figure 5 As shown, both the leading edge 41 and the trailing edge 43 of each hair entry slot 35 extend along the longitudinal extension of the hair entry slot 35 and are defined relative to the rotational direction of the internal cutting member 13a, which is indicated by the arrow R. That is, when the internal cutting member 13a rotates in the rotational direction R, a specific portion of the internal cutting member 13b, in particular the cutting edge 45a of the internal cutting member 13a (to be described in more detail below) passes through the hair entry slot 35, and the above-mentioned specific portion will first pass through the leading edge 41 of the hair entry slot 35, and then will pass through the trailing edge 43 of the hair entry slot 35. Figure 5 As shown, the groove angle α of each hair entry groove 35 viewed in the axial direction is defined as an acute angle enclosed by the trailing edge 43 of the hair entry groove 35 and the local radial direction at the trailing edge 43 relative to the central axis 19. Figure 5In the embodiment of the present invention, the trailing edge 43 extends in the radial direction relative to the central axis 19, so the groove angle α of the hair entry groove 35 is 0°. According to the present invention, in each radial position of the hair entry groove 35 between the radial inner groove end position 37 and the radial outer groove end position 39, the groove angle α of each hair entry groove 35 along the longitudinal extension of the hair entry groove 35 is in the range of 0° to 20°. In each radial position of the hair entry groove 35, the groove angle α may be the same. Alternatively, in different radial positions of the hair entry groove 35, the groove angle α is different. The trailing edge 43 of the hair entry groove 35 may be straight, such as Figure 5 As shown in the embodiment of FIG. 4 , the trailing edge 43 may alternatively be slightly curved.

[0059] like Figure 5 As further shown, the rear edge 43 of each hair entry slot 35 of the outer cutting member 11a is provided with a hair retaining structure 47. Figure 5 In the illustrated embodiment, the hair retaining structure 47 includes an array of toothed elements 49 arranged along the trailing edge 43 of each hair entry slot 35. The first side edge surface 51 of each toothed element 49 facing the central axis 19 extends transversely relative to the trailing edge 43 and forms a hair abutment surface 53 of the hair retaining structure 47, the mode of operation of which will be described in detail below. Therefore, the hair retaining structure 47 includes an array of hair abutment surfaces 53 arranged along the trailing edge 43, wherein each hair abutment surface 53 extends transversely relative to the trailing edge 43 and faces the central axis 19. The second side edge surface 55 of each toothed element 49 of the hair retaining structure 47 faces away from the central axis 19 and extends substantially parallel to the first side edge surface 51. The leading edge 41 of each hair entry slot 35 extends as a straight line from the radially inner slot end position 37 to the radially outer slot end position 39 at a distance from the toothed element 49 of the hair retaining structure 47 at the trailing edge 43. In addition, as shown in FIG. Figure 3 As shown, the hair entry slot 35 opens in a radially outward direction at a radially outer slot end position 39 .

[0060] Figure 6 The inner cutting member 13a of the hair cutting unit 9a is shown in a top view, i.e. viewed in an axial direction parallel to the central axis 19. Figure 3 and Figure 6As shown, the internal cutting member 13a includes a cutter body 57, which is provided with three cutting elements 59a, 59b, 59c. The cutter body 57 is fixed to the carrier 33 of the internal cutting member 13a described previously, wherein the carrier 33 is arranged in the central opening 61 of the cutter body 57. The cutting elements 59a, 59b, 59c are each formed as a ridge 63a, 63b, 63c protruding relative to the upper surface 65 of the cutter body 57. The upper peripheral edge of each ridge 63a, 63b, 63c forms the cutting edge 45a, 45b, 45c of the corresponding cutting element 59a, 59b, 59c. Each of the cutting edges 45a, 45b, 45c extends as a continuous curve from the radial inner edge end position 67 to the radial outer edge end position 69 within an angle of 120° around the central axis 19. The radial inner edge end position 67 of the cutting edges 45a, 45b, 45c has a radial position relative to the central axis 19, which is at or close to the radial position of the radial inner groove end position 37 of the hair entry groove 35. The radial outer edge end position 69 of the cutting edges 45a, 45b, 45c has a radial position relative to the central axis 19, which is close to the radial position of the radial outer groove end position 39 of the hair entry groove 35. Figure 6 As shown, the edge angle β of each cutting edge 45a, 45b, 45c, viewed in the axial direction, is defined as an acute angle enclosed by the cutting edges 45a, 45b, 45c and a local radial direction 44 at the above-mentioned cutting edges 45a and 45b relative to the central axis 19. According to the present invention, in any position on the cutting edges 45a, 45b, 45c, the edge angle β is in the range of 55° to 85°.

[0061] Figure 7 1 shows a portion of the hair entry slot 35 of the outer cutting member 11a and a portion of the cutting element 59b of the inner cutting member 13a as the cutting edge 45a of the cutting element 59a passes through the hair entry slot 35 during operation of the shaving apparatus 1. Figure 7 As shown, when viewed in the axial direction parallel to the central axis 19, Figure 7 In the embodiment shown, when present at the above-mentioned hair abutment surface 53, the shear angle γ enclosed by the hair abutment surface 53 and the cutting edge 45a of the toothed element 49 of the hair holding structure 47 is 0°. In other words, Figure 7 As shown, the hair abutment surface 53 extends parallel to the cutting edge 45a at the location of the toothed element 49. According to the invention, the above-mentioned shearing angle γ is in the range of 0° to 15°.

[0062] During operation of the shaving device 1, the internal cutting members 13a, 13b, 13c rotate relative to the external cutting members 11a, 11b, 11c. In the following, the operation of the shaving device 1 will be described with reference to the hair cutting unit 9a having the external cutting member 11a and the internal cutting member 13a. The operation of the hair cutting units 9b and 9c is similar. In operation, the cutting edges 45a, 45b, 45c slide along the inside of the angled portion of the upper wall 23 of the external cutting member 11a in which the hair entry groove 35 is arranged. Because the cutting edges 45a, 45b, 45c are arranged on narrow ridges 63a, 63b, 63c protruding relative to the upper surface 65 of the cutter body 57, an optimal sliding contact is achieved between the cutting edges 45a, 45b, 45c and the inside of the above-mentioned angled portion of the upper wall 23 of the external cutting member 11a.

[0063] During operation, hair on the user's skin will penetrate into the hair entry slot 35 of the outer cutting member 11a. The relatively small slot angle α of the hair entry slot 35 in the range of 0° to 20° improves the hair capture performance of the hair cutting unit 9a, that is, improves the ability of the hair entry slot 35 to receive hair. With regard to the above-mentioned hair capture performance, the preferred range of the slot angle α of the hair entry slot 35 is 0° to 5°. Figure 3 As shown, since the hair entry groove 35 opens in the radially outward direction at the radially outer groove end position 39, the hair capturing performance is further improved.

[0064] The hair that pierces a hair entry groove 35 in the hair entry groove 35 will be manipulated by a cutting element 59a, 59b, 59c of the rotating internal cutting member 13a, to enter a space 71 in the space 71 between the pairs of adjacent toothed elements 49 of the hair holding structure 47 present in the trailing edge 43 of the hair entry groove 35. This hair manipulation is due to the cutting element 59a, 59b, 59c moving from the leading edge 41 of the hair entry groove 35 to the trailing edge 43, plus the cutting edge angle β of the cutting edge 45a, 45b, 45c is less than 85 °. After being manipulated to enter a space 71 in the space 71 of the hair holding structure 47, the hair will be manipulated to the position of abutting the hair abutment surface 53 of the toothed element 49 that defines the space 71. The hair abutment surface 53 will prevent the cutting elements 59a, 59b, 59c from further manipulating the hairs into the groove 35 during subsequent hair cutting processes, in particular due to friction between the hairs and the hair abutment surface 53.

[0065] like Figure 5 and Figure 7As shown, the hair entry slot 35 has a first region 73 and a second region 75, the first region 73 extending from the radially outer slot end position 39 to the radially inner slot end position 37 as a continuous open slot region along the leading edge 41, and the second region 75 extending along the trailing edge 43, in which the array of toothed elements 49 of the hair holding structure 47 is arranged. In this embodiment, hairs can initially be effectively captured in the above-mentioned first region 73 of the hair entry slot 35, and can then be efficiently manipulated by the cutting elements 59a, 59b, 59c of the rotating internal cutting member 13a to enter the above-mentioned second region 75 of the hair entry slot 35 and abut against the hair abutment surface 53 of the hair holding structure 47.

[0066] Due to the relatively large edge angle β of the cutting edges 45a, 45b, 45c, the cutting edges 45a, 45b, 45c of the rotating inner cutting member 13a will perform a slicing motion on the hair during the hair cutting process, wherein the hair is held in a stationary position abutting against the hair abutment surface 53 of the hair holding structure 47. The above slicing motion Figure 7 As schematically shown in Figure 7 The cutting edge 45a and the hair 77 are shown, the hair 77 is held in place by the hair holding structure 47 and is partially cut by the cutting edge 45a. The slicing motion of the cutting edge 45a through the hair 77 is shown in FIG. Figure 8 The local movement direction of the cutting edge 45a through the hair 77 is Figure 7 and Figure 8 , which is tangential to the central axis 19. The acute angle δ enclosed by the cutting edge 45a and the arrow M at the location of the hair 77 is equal to 90°-β. Since the angle δ is relatively small, the local velocity of the cutting edge 45a passing through the hair 77 in a direction parallel to the cutting edge 45a (i.e., Figure 8 The slice motion speed V shown SM ) is much greater than the local velocity of the cutting edge 45a passing through the hair 77 in a direction perpendicular to the cutting edge 45a (i.e., Figure 8 The haircut motion speed V shown CM ). Compared with the hair cutting unit, the relatively high slicing motion speed V of the cutting edge 45a through the hair 77 is SM Improved hair cutting performance, wherein the hair entry groove of the outer cutting member and the cutting edge of the inner cutting member both have a radial main extension direction relative to the central axis, and therefore, the cutting edge basically only performs a hair-cutting motion through the hair. In addition, due to the above-mentioned slicing motion of the cutting edge 45a, 45b, 45c through the hair, the cutting process of a single hair is performed by a relatively large part of the cutting edge 45a, 45b, 45c. This will result in a relatively low degree of wear of the cutting edge 45a, 45b, 45c.

[0067] As mentioned above, the function of the hair abutment surface 53 of the hair holding structure 47 is only to maintain the hair in the static position in the hair entry groove 35 during the hair cutting process. For this reason, in the embodiment described above, the shearing angle γ surrounded by each hair abutment surface 53 and the cutting edges 45a, 45b, 45c when present at the above-mentioned hair abutment surface 53 is 0 °, that is, the hair abutment surface 53 extends substantially parallel to the cutting edges 45a, 45b, 45c when present at the hair abutment surface 53. Usually, in order to best maintain the hair in the static position in the hair entry groove 35 by the hair abutment surface 53 of the hair holding structure 47 during the hair cutting process, the shearing angle γ should be in the range of 0 ° to 15 °. More preferably, the shearing angle γ is in the range of 0 ° to 5 °. Because as mentioned above, hair can be effectively cut only by the slicing movement of the cutting edges 45a, 45b, 45c through the hair, the rear edge 43, the toothed element 49, and in particular the hair abutment surface 53 of the hair holding structure 47 do not need to be equipped with a counter-cutting edge. The absence of any counter-cutting edge on the external cutting member 11a, 11b, 11c simplifies the manufacturing process of the hair cutting unit 9a, 9b, 9c.

[0068] The relatively large edge angle β of the cutting edges 45a, 45b, 45c of the internal cutting members 13a, 13b, 13c limits the degree of skin irritation, particularly in combination with the presence of the hair retaining structure 47 at the trailing edge 43 of the hair entry groove 35. The limited degree of skin irritation allows a relatively large degree of skin bulging into the hair entry groove 35. Therefore, the hair entry groove 35 can have a relatively large width. In particular, the first region 73 of the hair entry groove 35 can have a relatively large width in a direction perpendicular to the radial direction. This will further improve the hair capture performance of the external cutting members 11a, 11b, 11c.

[0069] In the embodiment described above, the cutting edge angle β is 75 °. It will be clear to those skilled in the art that when the cutting edge angle β increases, the extent to which the motion of the cutting edge 45a, 45b, 45c through the hair is a slicing motion will increase. However, for a cutting edge angle approaching 90 °, the motion component of the cutting edge 45a, 45b, 45c perpendicular to the cutting edge 45a, 45b, 45c is too small for an effective hair cutting process. Therefore, according to the present invention, the upper limit of the scope of the cutting edge angle β is 85 °. According to the present invention, the lower limit of the scope of the cutting edge angle β is 55 °. For the cutting edge angle β of 55 °, the slicing motion component (that is, the motion component parallel to the cutting edge 45a, 45b, 45c) of the cutting edge 45a, 45b, 45c through the hair is still large enough to realize an effective hair cutting process, without the need for the reverse cutting edge at the external cutting member 11a, 11b, 11c. The preferred range of the cutting edge angle β is 70 ° to 80 °. When the cutting edge angle β is within this range, a particularly low degree of skin irritation can be achieved, while at the same time the hair cutting by the slicing movement of the cutting edge through the hair is very effective.

[0070] Due to the existence of toothed elements 49, the hair holding structure 47 that is provided with along the trailing edge 43 of hair entry groove 35 in the embodiment described before has comb-like structure.The comb-like structure causes the cutting elements 59a, 59b, 59c of the internal cutting member 13a, 13b, 13c that rotate effectively to be manipulated into a space 71 that enters in the space 71 that is present between the continuous pairs of adjacent toothed elements 49.By arranging a relatively large amount of toothed elements 49 along the trailing edge 43, the hair holding performance of hair holding structure 47 in the hair cutting process can be improved.The second side edge surface 55 of each toothed element 49 back to the central axis 19 can extend substantially parallel to the first side edge surface 51, as in the embodiment described before, or can extend not parallel to the first side edge surface 51.

[0071] Fig. 9 With Figure 5 A similar top view in 100 shows an external cutting member 111 of a second embodiment of a hair cutting unit according to the invention. In this second embodiment, the hair cutting unit comprises an internal cutting member similar to the internal cutting member 13a of the hair cutting unit 9a according to the previously described embodiment. Fig. 9 The inner cutting member, which is not visible in the drawing, is covered by the outer cutting member 111 and is rotatable relative to the outer cutting member 111 around the central axis 119 of the hair cutting unit. The outer cutting member 111 comprises a plurality of hair entry slots 135, each of which extends from a radially inner slot end position 137 to a radially outer slot end position 139 along the longitudinal extension of the hair entry slot 135 relative to the central axis 119.

[0072] and Figure 5 Similar to the embodiment of the external cutting member 11a of the hair cutting unit, the leading edge 141 and the trailing edge 143 of each hair entry slot 135 of the external cutting member 111 of the second embodiment of the hair cutting unit each extend as a straight line along the longitudinal extension of the hair entry slot 135, and its main extension direction is in the radial direction relative to the central axis 119. However, unlike the embodiment of the external cutting member 11a, the leading edge 141 and the trailing edge 143 of the external cutting member 111 do not extend precisely in the radial direction. Therefore, as Fig. 9 As shown, the hair entry slots 135 each have a non-zero slot angle α, which is bounded by the trailing edge 143 of the hair entry slot 135 and a local radial direction 144 at the trailing edge 143 relative to the central axis 119. Since the trailing edge 143 extends as a non-radial straight line, the slot angle α is different in different positions along the trailing edge 143 (i.e., along the longitudinal extension of the hair entry slot 135). In particular, the slot angle α increases from a minimum value at the radially outer slot end position 139 to a maximum value at the radially inner slot end position 137, wherein according to the present invention, in each radial position of the hair entry slot 135 between the radially inner slot end position 137 and the radially outer slot end position 139, the slot angle α along the longitudinal extension of the hair entry slot 135 is at most 20°.

[0073] and Figure 5 The embodiment of the external cutting member 11a of the hair cutting unit is similar, the rear edge 143 of the hair entry groove 135 of the external cutting member 111 of the second embodiment of the hair cutting unit is respectively provided with a hair holding structure 147, which has an array of toothed elements 149 arranged along the rear edge 143. The first side edge surface 151 facing the central axis 119 of each toothed element 149 extends transversely relative to the rear edge 143, and forms a hair abutment surface 153 of the hair holding structure 147. Therefore, the hair holding structure 147 at the rear edge 143 includes an array of hair abutment surfaces 153 arranged along the rear edge 143, wherein each hair abutment surface 153 extends transversely relative to the rear edge 143 and faces the central axis 119. The second side edge surface 155 of each toothed element 149 of the hair holding structure 147 at the rear edge 143 is opposite to the central axis 119, and extends obliquely to the first side edge surface 151.

[0074] and Figure 5Unlike the embodiment of the external cutting member 11a of the second embodiment of the hair cutting unit, in the external cutting member 111 of the second embodiment of the hair cutting unit, the front edge 141 of the hair entry slot 135 is also each provided with an additional hair holding structure 181, which has an additional array of toothed elements 183 arranged along the front edge 141. Each additional toothed element 183 has a first side edge surface 185 facing the central axis 119, extends transversely relative to the front edge 141, and forms an additional hair abutment surface 187 of the additional hair holding structure 181. Therefore, the additional hair holding structure 181 arranged at the front edge 141 includes an additional array of hair abutment surfaces 187 arranged along the front edge 141, wherein each additional hair abutment surface 187 extends transversely relative to the front edge 141 and faces the central axis 119. At the leading edge 141 , the second side edge surface 189 of each further toothed element 183 of the further hair retaining structure 181 runs away from the centre axis 119 and obliquely to the first side edge surface 185 .

[0075] like Fig. 9 As shown, the toothed elements 149 of the hair retaining structure 147 arranged along the rear edge 143 of the hair entry slot 135 and the additional toothed elements 183 of the additional hair retaining structure 181 arranged along the front edge 141 of the hair entry slot 135 are arranged in a staggered configuration and, when viewed in the radial direction, in a partially overlapping configuration.

[0076] In the external cutting member 111 of the second embodiment of the hair cutting unit, hair can also be cut while abutting against the additional hair abutment surface 187 of the additional toothed element 183 of the additional hair holding structure 181 arranged along the front edge 141 of the hair entry slot 135. Although the presence of the additional toothed element 183 in the hair entry slot 135 may slightly reduce the overall hair capture performance of the hair entry slot 135 compared to the hair entry slot 35 of the external cutting member 11a described previously, the overall hair holding performance of the hair entry slot 135 during hair cutting is improved due to the presence of the additional hair holding structure 181 compared to the hair entry slot 35 of the external cutting member 11a. Due to the mutual arrangement of the toothed elements 149 of the hair holding structure 147 at the trailing edge 143 and the other toothed elements 183 of the other hair holding structure 181 at the leading edge 141 in a staggered configuration and in a partially overlapping configuration when viewed in the radial direction, the open groove area between the hair holding structure 147 at the trailing edge and the other hair holding structure 181 at the leading edge 141 extends in a zigzag shape from the radially outer groove end position 139 to the radially inner groove end position 137. This zigzag extension of the above-mentioned open groove area will significantly improve the overall hair holding performance of the hair entry groove 135 during the hair cutting process. In order to achieve the best hair holding performance during the hair cutting process, the shear angle surrounded by the cutting edge of each cutting element of each hair abutment surface 153 of the hair holding structure 147 and the internal cutting member should be in the range of 0 ° to 15 °, preferably in the range of 0 ° to 5 °. Likewise, the other shearing angle surrounded by the cutting edge of each cutting element of each other hair abutment surface 187 of other hair holding structure 181 and inner cutting member should be in the scope of 0 ° to 15 °, preferably in the scope of 0 ° to 5 °. In the embodiment shown in Figure 11, both the above-mentioned shearing angle and the above-mentioned other shearing angle are 0 °.

[0077] exist Figure 5 In the embodiment of the outer cutting member 11a shown, the hair entry slot 35 has the same hair retaining structure 47 arranged at its rear edge 43, while in Fig. 9 In the embodiment of the external cutting member 111 shown, the hair entry slot 135 has the same hair retention structure 147 arranged at its rear edge 143 and the same additional hair retention structure 181 arranged at its leading edge 141. Note that the present invention also covers hair cutting units in which the hair entry slot of the external cutting member has mutually different hair retention structures arranged at different rear edges and, when present, mutually different additional hair retention structures arranged at different leading edges. An example of such an alternative external cutting member has the same Figure 5 The hair entry groove 35 of the outer cutting member 11a shown is similar to the hair entry groove 35 of the outer cutting member 11a. Fig. 9 The hair entry groove 135 of the outer cutting member 111 shown in the figure is similar to the hair entry groove 135. In any embodiment, the hair holding structure at the trailing edge and the additional hair holding structure at the leading edge (when present) have an array of hair abutment surfaces arranged along the trailing edge and the leading edge, respectively, wherein each hair abutment surface extends laterally relative to the trailing edge and the leading edge, respectively, and faces the central axis. However, the hair abutment surfaces can also be arranged in the hair holding structure in a different manner, rather than as Figure 5 and Fig. 9 As in the illustrated embodiment, it is formed as a side edge surface arranged on the toothed elements of the comb-like structure.

[0078] exist Figure 5 In FIG. 1 , D1 indicates a first radial distance between the radially inner groove end position 37 of the hair-entering groove 35 and the central axis 19, and D2 indicates a second radial distance between the radially outer groove end position 39 of the hair-entering groove 35 and the central axis 19. Figure 5 In the embodiment of the present invention, the ratio D1 / D2 is 0.5. Because the radial outer groove end position 39 of the hair entry groove 35 is very close to the outer periphery of the outer cutting member 11a, in this embodiment, the hair entry groove 35 extends over a large part (i.e., about 50%) of the radius of the outer cutting member 11a. This will result in the hair entry groove 35 having a relatively high hair capture performance.

[0079] In the embodiment of the hair cutting unit 9a, wherein the cutting edge 45a, 45b, 45c of the internal cutting member 13a extends from the radial inner edge end position 67 near the radial inner groove end position 37 to the radial outer edge end position 69 near the radial outer groove end position 39 as a continuous curve, the actual minimum allowable value of the ratio D1 / D2 depends on the value of the cutting edge angle β of the cutting edge 45a, 45b, 45c. In particular, a relatively large cutting edge angle β will result in a relatively short radial extension of the cutting edge of the internal cutting member, and thereby result in a relatively large first radial distance D1 and a relatively high value of the ratio D1 / D2. A relatively small cutting edge angle β will allow a relatively long radial extension of the cutting edge of the internal cutting member, and therefore, will allow a relatively small first radial distance D1 and a relatively low value of the ratio D1 / D2. Typically, for an embodiment of the hair cutting unit in which the cutting edge of the inner cutting member extends as a continuous line as described above with respect to the inner cutting member 13a, the ratio D1 / D2 may be between 0.4 and 0.8, preferably between 0.5 and 0.6. This ratio indicates that the hair entry slot 35 extends over a radial distance between about 20% and about 60% of the radius of the outer cutting member 13a, and preferably extends over a radial distance between about 40% and about 50% of the radius of the outer cutting member 13a.

[0080] The radially inner edge end positions 67 of the cutting edges 45a, 45b, 45c have a radial position closer to the central axis 19 relative to the central axis 19 than the radially inner groove end positions 37 of the hair entry groove 35 of the external cutting member 11a. As a result, the radially inner edge end positions 67 of the cutting edges 45a, 45b, 45c of the internal cutting member 13a are always covered by the central closed portion of the upper wall 23 of the external cutting member 11a. Therefore, during the rotation of the internal cutting member 13a, the user's skin is not exposed to the radially inner edge end positions 67 of the cutting edges 45a, 45b, 45c at the radially inner groove end positions 37 of the hair entry groove 35. Because these radially inner edge end positions 67 are ahead of the cutting edges 45a, 45b, 45c in the rotation direction R of the internal cutting member 13a, if the skin is exposed to these radially inner edge end positions 67, they may damage the skin. Because, as described above and as Figure 6 As shown, each of the cutting edges 45a, 45b, 45c of the inner cutting member 13a extends as a continuous curve from the radially inner edge end position 67 to the radially outer edge end position 69, so the skin is not exposed to any leading edge end point of any of the cutting edges 45a, 45b, 45c. Therefore, skin irritation or skin damage caused by contact between the skin and the rotating cutting edges 45a, 45b, 45c is minimized, especially due to the relatively large edge angle β.

[0081] As mentioned above and Figure 6 As shown, each of the three cutting edges 45a, 45b, 45c of the inner cutting member 13a extends within an angle of 120° around the central axis 19. It should be noted that the inner cutting member may have a different number of cutting elements. Figure 6 As shown, in an embodiment in which each cutting edge extends from a radially inner edge end position to a radially outer edge end position as a continuous curve, the number N of cutting elements may depend on the edge angle β of the cutting edge, in particular when the cutting edges do not overlap each other in a tangential direction around the central axis of the hair cutting unit. In particular, if the edge angle β is relatively small, the number N of cutting elements may be relatively large. In this embodiment, typically, the number N of cutting elements of the inner cutting member may be in the range of 2 to 6, preferably 3 or 4. The cutting edge of each cutting element may extend within an angle of 360° / N around the central axis, as shown. Figure 6 Alternatively, the cutting edges may extend at mutually different angles around the central axis, and therefore, if the cutting edges have similar edge angles β, the cutting edges may have mutually different radial extensions. In embodiments in which the cutting edges overlap each other in a tangential direction around the central axis of the hair cutting unit, the number N of cutting edges may be increased compared to embodiments in which the cutting edges do not overlap each other in a tangential direction around the central axis.

[0082] It should be noted that in Figure 6 In the embodiment of the internal cutting member 13a shown, the edge angle β of each cutting edge in the cutting edges 45a, 45b, 45c is equal at all positions between the radial inner edge end position 67 and the radial outer edge end position 69. This will require the cutting edges 45a, 45b, 45c to have a specific curved shape between the radial inner edge end position 67 and the radial outer edge end position 69, which can be directly designed by a person skilled in the art. Alternatively, the edge angle β of the cutting edges 45a, 45b, 45c can vary along the cutting edges 45a, 45b, 45c. In this case, according to the present invention, in each position on the cutting edge between the radial inner edge end position and the radial outer edge end position, the value of the edge angle β should be in the range of 55° to 85°.

[0083] exist Figure 5 In the embodiment of the present invention, a plurality of hair entry slots 35 arranged annularly around the central axis 19 can be regarded as forming a single so-called shaving track of the hair cutting unit 9a. Fig. 9 111. The embodiment of the hair cutting unit with external cutting member 111 has a single shaving track. It should be noted that the present invention also encompasses embodiments in which the hair cutting unit has two or more shaving tracks. In such embodiments, the external cutting member comprises two or more annular arrays of hair entry grooves arranged concentrically around the central axis, and the internal cutting member comprises two or more annular arrays of cutting elements with cutting edges arranged coaxially around the central axis. In such embodiments, the number of cutting elements in each individual shaving track can be greater than the number of cutting elements in the embodiment with a single shaving track, particularly when the edge angle β in all embodiments is similar.

[0084] The cutting edges 45a, 45b, 45c of the inner cutting member 13a described hereinbefore have a wedge angle θ of approximately 90°. Figure 3 As shown, the wedge angle θ is the angle enclosed by the upper surface 60 and the front surface 62 of the cutting elements 59a, 59b, 59c at the location of the cutting edges 45a, 45b, 45c. By reducing the wedge angle θ to a value less than 90°, the cutting force required for cutting the hair can be reduced. This can be achieved by locally providing an inclined portion on the front surface 62 at the location of the cutting edges 45a, 45b, 45c. Alternatively, the entire front surface 62 can be arranged obliquely relative to the upper surface 60.

[0085] It will be clear to those skilled in the art that the scope of the present invention is not limited to the above examples, and that several corrections and modifications may be made thereto without departing from the scope of the present invention as defined in the appended claims. The present invention is intended to be interpreted as including all such corrections and modifications as long as they are within the scope of the claims or their equivalents. Although the present invention is shown and described in detail in the drawings and the specification, such illustration and description are to be regarded as illustrative or exemplary only and not restrictive. The present invention is not limited to the disclosed embodiments. The accompanying drawings are schematic, in which details not necessary for understanding the present invention may be omitted, and the drawings are not necessarily drawn to scale.

[0086] Variations to the disclosed embodiments may be understood and effected by those skilled in the art in practicing the claimed invention by studying the drawings, the description, and the appended 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. Any reference signs in the claims should not be construed as limiting the scope of the invention.

[0087] Unless expressly stated otherwise, elements and aspects discussed for or relating to a particular embodiment may be appropriately combined with elements and aspects of other embodiments. Thus, the 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.

[0088] Those skilled in the art will understand that the terms "comprise" and "include" used in this text encompass the term "consist of". Thus, with respect to one embodiment, the term "comprise" or "include" may mean "consist of", but in another embodiment, may mean "at least comprising / having / equipped with the defined species and optionally one or more other species".

Claims

1. A hair cutting unit (9a) comprising a central axis (19), an outer cutting member (11a) and an inner cutting member (13a), the inner cutting member being covered by the outer cutting member and being rotatable relative to the outer cutting member about the central axis, wherein: - the outer cutting member comprises a plurality of hair entry slots (35), each of which extends from a radially inner slot end position (37) to a radially outer slot end position (39) along a longitudinal extension of the hair entry slot relative to the central axis; - the inner cutting member comprises a plurality of cutting elements (59a, 59b, 59c), each of the cutting elements having a cutting edge (45a, 45b, 45c); - a slot angle (α) of each hair entry slot is defined as an acute angle enclosed by a trailing edge (43) of the hair entry slot and a local radial direction (144) relative to the central axis at the trailing edge when viewed in an axial direction parallel to the central axis, the trailing edge (43) of the hair entry slot extending relative to the rotational direction (R) of the internal cutting member and along the longitudinal extension of the hair entry slot; and - a cutting edge angle (β) of each cutting edge, when viewed in the axial direction, defined as an acute angle enclosed by the cutting edge and a local radial direction (44) at the cutting edge relative to the central axis, the cutting edge angle being in the range of 55° to 85°; Features: - in each radial position of the hair entry slot between the radial inner slot end position (37) and the radial outer slot end position (39), the slot angle (α) of each hair entry slot (35) along the longitudinal extension of the hair entry slot is in the range of 0° to 20°; and - the rear edge (43) of each hair entry slot is provided with a hair retaining structure (47) having an array of hair abutment surfaces (53) arranged along the rear edge, each hair abutment surface extending transversely relative to the rear edge and facing the central axis (19).

2. A hair cutting unit (9a) according to claim 1, wherein when viewed in the axial direction, the shear angle (γ) enclosed by each hair abutment surface (53) and the cutting edge (45a, 45b, 45c) of each cutting element in the cutting elements (59a, 59b, 59c) at the hair abutment surface is in the range of 0° to 15°, preferably in the range of 0° to 5°.

3. The hair cutting unit (9a) according to claim 1 or 2, wherein the cutting edge angle (β) is in the range of 70° to 80°.

4. The hair cutting unit (9a) according to any one of claims 1 to 3, wherein the groove angle (α) is in the range of 0° to 5°.

5. A hair cutting unit (9a) according to any one of claims 1 to 4, wherein the hair retaining structure (47) comprises an array of toothed elements (49) arranged along the rear edge (43) of at least one of the hair entry grooves (35), wherein the hair abutment surfaces (53) are each formed by a first side edge surface (51) of a corresponding toothed element among the toothed elements facing the central axis (19).

6. The hair cutting unit (9a) according to claim 5, wherein the second side edge surface (55) of each respective toothed element (49) facing away from the central axis (19) extends substantially parallel to the first side edge surface (51) of the respective toothed element.

7. A hair cutting unit (9a) according to claim 6, wherein a leading edge (41) of the hair entry groove (35) relative to the rotation direction (R) of the internal cutting member (13a) extends as a straight line from the radially inner groove end position (37) to the radially outer groove end position (39) at a certain distance from the toothed element (49).

8. A hair cutting unit according to claim 5, wherein the leading edge (141) of the hair entry groove (135) relative to the rotation direction (R) of the internal cutting member includes an additional hair retaining structure (181), the additional hair retaining structure having an array of additional toothed elements (183) arranged along the leading edge, each additional toothed element having an additional hair abutment surface (187), the additional hair abutment surface being formed by a side edge surface (185) of the additional toothed element, the side edge surface extending laterally relative to the leading edge and facing the center axis (119).

9. A hair cutting unit according to claim 8, wherein the toothed element (149) of the hair retaining structure (147) of the trailing edge (143) of the hair entry slot (135) and the further toothed element (183) of the further hair retaining structure (181) of the leading edge (141) of the hair entry slot (135) are arranged with respect to each other in a staggered configuration and, when viewed in the radial direction, in a partially overlapping configuration.

10. The hair cutting unit (9a) according to any one of claims 1 to 9, wherein a ratio of a first radial distance (D1) between the radial inner groove end position (37) and the central axis (19) and a second radial distance (D2) between the radial outer groove end position (39) and the central axis (19) is between 0.4 and 0.8, preferably between 0.5 and 0.

6.

11. A hair cutting unit (9a) according to any one of claims 1 to 10, wherein the cutting edge (45a, 45b, 45c) of each cutting element (59a, 59b, 59c) of the internal cutting member (13a) extends as a continuous curve from a radial position at or near the radial inner groove end position (37) of each hair entry groove (35) to a radial position at or near the radial outer groove end position (39) of each hair entry groove (35), and wherein the number of the cutting elements of the internal cutting member is in the range of 2 to 6, preferably 3 or 4.

12. A hair cutting unit (9a) according to claim 11, wherein the cutting edge (45a, 45b, 45c) of each cutting element (59a, 59b, 59c) of the internal cutting member (13a) extends around the central axis (19) within an angle of 360° / N, wherein N is the number of the cutting elements of the internal cutting member.

13. A hair cutting unit (9a) according to any one of claims 1 to 12, wherein the cutting edges (45a, 45b, 45c) of the cutting elements (59a, 59b, 59c) of the internal cutting member (13a) each have a radial inner edge end position (67) relative to the central axis (19), and the radial inner edge end position is closer to the central axis than the radial inner groove end position (37) of each hair entry groove in the hair entry groove (35).

14. The hair cutting unit (9a) according to any one of claims 1 to 13, wherein the hair entry slot (35) opens in a radially outward direction at the radially outer slot end position (39).

15. A shaving unit (5) having at least one hair cutting unit (9a, 9b, 9c) according to any one of claims 1 to 14, and further having a support structure (7) configured to support the at least one hair cutting unit.

16. A shaving device (1) comprising a main housing (3) and a shaving unit (5) according to claim 15, wherein the shaving unit is coupled to the main housing and the main housing accommodates a drive system, which is configured to drive the internal cutting member (13a, 13b, 13c) of each hair cutting unit (9a, 9b, 9c) of the shaving unit to rotate relative to the external cutting member (13a, 13b, 13c).

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