Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
RAZOR HEAD WITH IMPROVED GUARD BAR
Document Type and Number:
WIPO Patent Application WO/2015/067321
Kind Code:
A1
Abstract:
A razor head (1) comprising a main frame member (8), a blade member (5) mounted on the main frame member, having a blade edge (5a) extending along a transversal axis (X), and a guard bar (9) having a plurality of grooves (19) extending along a longitudinal axis (Y). Each groove comprises a deep section located next to the groove front end, a shallow section located next to the groove rear end and a sloped section connecting the deep section to the shallow section.

Inventors:
BOZIKIS IOANNIS (GR)
KONTOVAIOU ATHANASIA (GR)
Application Number:
PCT/EP2013/073432
Publication Date:
May 14, 2015
Filing Date:
November 08, 2013
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BIC VIOLEX SA (GR)
International Classes:
B26B21/40
Domestic Patent References:
WO2006108175A12006-10-12
WO2011062760A12011-05-26
Foreign References:
US20100058595A12010-03-11
Attorney, Agent or Firm:
CHATEAU, Marielle et al. (52 rue de la Victoire, Paris Cedex 09, FR)
Download PDF:
Claims:
CLAIMS

1. A razor head (1) comprising:

- a main frame member (8) extending along a transversal axis (X) ,

- at least one blade member (5) mounted on the main frame member, having a blade edge (5a) extending along the transversal axis (X) , and

- a guard bar (9) having a plurality of grooves (19), each groove having a bottom surface (20) that extends along a longitudinal axis (Y) perpendicular to the transversal axis from a groove front end (19a) up to a groove rear end (19b) in proximity of the blade edge,

wherein each groove comprises a deep section (21) located next to the groove front end, a shallow section (22) located next to the groove rear end and a sloped section (23) connecting the deep section to the shallow section .

2. Razor head according to claim 1, wherein the guard bar (9) is located forward of the blade edge (5a) .

3. Razor head according to claim 1 or 2, wherein the grooves (19) are separated one from the other by a plurality of ribs (24) having top surfaces (25), a rib defining a groove depth (D) measured along a vertical axis (Z), perpendicular to the longitudinal axis (Y) and to the transversal axis (X), between a bottom surface (20) of a groove and a top surface (25) of a rib.

4. Razor head according to claim 3, wherein the sloped section (23) of each groove (19) extends from a sloped section front end (23a) up to a sloped section rear end (23b),

the sloped section front end is connected to the deep section (21),

the sloped section rear end is connected to the shallow section (22), and a groove depth (D) decreases from the sloped section front end to the sloped section rear end.

5. Razor head according to claim 3 or 4, wherein a maximum angle of inclination (Max_A) between a bottom surface (20) and a top surface (25) of a sloped section (23) is smaller than forty-five degrees, preferably smaller than thirty-five degrees.

6. Razor head according to anyone of claims 3 to 5, wherein a minimum angle of inclination (Min_A) between a bottom surface (20) and a top surface (25) of a sloped section (23) is higher than ten degrees, preferably higher than twenty degrees.

7. Razor head according to anyone of claims 1 to 6, wherein a bottom transversal shape (28) of the bottom surface (20) of each groove (19) comprises a bottom rectilinear portion (28a) substantially parallel the transversal axis (X) ,

and wherein a bottom surface width (Wb) of said bottom rectilinear portion (28a), measured along the transversal axis (X) , is at least half of a groove width (Wg) , preferably at least seventy-five per cent of a groove width, more preferably at least ninety per cent of a groove width .

8. Razor head according to anyone of claims 1 to 7, wherein each groove (19) has two substantially parallel vertical walls (26, 27) extending along a vertical axis (Z) perpendicular to the longitudinal and transversal axis.

9. Razor head according to anyone of claims 3 to 8, wherein a top transversal shape (30) of the top surface (25) of each rib (24) comprises a top rectilinear portion (30a) parallel the transversal axis (X) ,

and wherein a top surface width (Wt) of said top rectilinear portion (30a) , measured along the transversal axis (X) , is less than ninety per cent of a rib width (Wr) , preferably less than seventy-five per cent of a rib width, more preferably less than half of a rib width.

10. Razor head according to anyone of claims 1 to 9, wherein a groove width (Wg) , measured along the transversal axis (X), is of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm.

11. Razor head according to anyone of claims 3 to

10, wherein a groove depth (D) along the deep section (21) is of 0.1mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.7 mm.

12. Razor head according to anyone of claims 3 to

11, wherein a rib width (Wr) , measured along the transversal axis (X), is of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm.

13. Razor head according to anyone of claims 1 to

12, wherein the shallow section (22) is a zero depth section .

14. Razor head according to anyone of claims 1 to

13, wherein the guard bar (9) is integrally formed with the main frame member (8) .

15. Wet razor (100) comprising a handle (2) and a razor head (1) according to anyone of claim 1 to 14, said razor head (1) being borne by the handle (2) .

Description:
Razor head with improved guard bar .

FIELD OF THE INVENTION

The instant invention relates to wet razor with improved shaving properties. The invention particularly relates to a shaving razor head provided with an improved groove structure for improving the passage of the hairs to the blades.

BACKGROUND OF THE INVENTION

Razor heads having a guard with grooves are known, for instance from WO 2012/018892 which describes such a guard having a plurality of grooves extending perpendicular to the blade edges. However, such guard bars do not provide an even spreading of the shaving aid and a proper alignment of hairs during the shaving process and thus the shaving properties of such razor heads are not optimal.

One objective of the present invention is to improve the shaving properties of such a razor head.

SUMMARY OF THE INVENTION

To this aim, according to the invention, such a razor head comprises:

- a main frame member extending along a transversal axis ,

- at least one blade member mounted on the main frame member, having a blade edge extending along the transversal axis, and

- a guard having a plurality of grooves, each groove having a bottom surface that extends along a longitudinal axis perpendicular to the transversal axis from a groove front end up to a groove rear end in proximity of the blade edge,

wherein each groove comprises a deep section located next to the groove front end, a shallow section located next to the groove rear end and a sloped section connecting the deep section to the shallow section. In a specific embodiment, the guard bar is located forward of the blade edge.

In a specific embodiment, the grooves are separated one from the other by a plurality of ribs having top surfaces, a rib defining a groove depth measured along a vertical axis, perpendicular to the longitudinal and transversal axis, between a bottom surface of a groove and a top surface of a rib.

In a specific embodiment, the sloped section of each groove extends from a sloped section front end up to a sloped section rear end, the sloped section front end is connected to the deep section, the sloped section rear end is connected to the shallow section, and a groove depth decreases from the sloped section front end to the sloped section rear end.

In a specific embodiment, a maximum angle of inclination between a bottom surface and a top surface of a sloped section is smaller than forty-five degrees, preferably smaller than thirty-five degrees.

In a specific embodiment, a minimum angle of inclination between a bottom surface and a top surface of a sloped section is higher than ten degrees, preferably higher than twenty degrees.

In a specific embodiment, a groove depth is substantially constant along the shallow section.

In a specific embodiment, a groove depth is substantially constant along the deep section.

In a specific embodiment, a bottom transversal shape of the bottom surface of each groove comprises a bottom rectilinear portion substantially parallel the transversal axis.

In a specific embodiment, a bottom surface width of said bottom rectilinear portion, measured along the transversal axis, is at least half of a groove width, preferably at least seventy-five per cent of a groove width, more preferably at least ninety per cent of a groove width .

In a specific embodiment, the sloped section is respectively connected to the deep section and to the shallow section by two rounded portions.

In a specific embodiment, each groove has two substantially parallel vertical walls extending along a vertical axis perpendicular to the longitudinal and transversal axis.

In a specific embodiment, each rib defines two substantially parallel vertical walls extending along a vertical axis perpendicular to the longitudinal and transversal axis.

In a specific embodiment, the top surface of each rib comprises a top planar portion being substantially planar extending from a rib front end, located next to a groove front end, up to a rib rear end, located next to a groove rear end.

In a specific embodiment, a top transversal shape of the top surface of each rib comprises a top rectilinear portion parallel the transversal axis.

In a specific embodiment, a top surface width of said top rectilinear portion, measured along the transversal axis, is less than ninety per cent of a rib width, preferably less than seventy-five per cent of a rib width, more preferably less than half of a rib width.

In a specific embodiment, each groove extends from a front end of the guard bar up to a rear end of the guard bar .

In a specific embodiment, the guard bar comprises at least ten grooves, preferably at least fifteen grooves.

In a specific embodiment, a groove width, measured along the transversal axis, is of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm. In a specific embodiment, a groove pitch, measured along the transversal axis, is of 0.5 mm to 3 mm, preferably of 1 mm to 2 mm, more preferably of about 1.7 mm.

In a specific embodiment, a groove depth along the deep section is of 0.1mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.7 mm.

In a specific embodiment, a groove depth along the shallow section is of 0.1 mm to 1.5 mm, preferably of 0.1 mm to 0.5 mm, more preferably of about 0.3 mm.

In a specific embodiment, a rib width, measured along the transversal axis, is of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm.

In a specific embodiment, the shallow section is a zero depth section.

In a specific embodiment, a groove depth at a rear end of the sloped section is zero.

In a specific embodiment, the guard bar is integrally formed with the frame member.

In a specific embodiment, the guard bar is made of plastic .

In a specific embodiment, the guard bar is made of metal .

In a specific embodiment, the guard bar is made of thermoplastic elastomer.

Another object of the present invention is a wet razor comprising a handle and a razor head described above, said razor head being borne by the handle.

With these features, the shaving aid placed on the skin before shaving is being spread more evenly when the stroke occurs because of the shape of the grooves provided on the guard bar. The ribs of the guard bar help the user maintain the control of the strokes during shaving by grouping the hair and guiding them to the cutting edge of the blades thereby improving hair alignment and comb performance. The shaving process is also more controlled by the user, improving the comfort of the shaving. Due to the fact that the shaving aid is evenly distributed on the face, the friction forces are better distributed on the user's skin for a more consistent shave. Moreover, by avoiding bending the hair, the pulling of hair during cutting is reduced providing a more comfortable shave. The rinsability of the shaver is also increased due to the design of the sloped section of the grooves which facilitate the shaving aid flow thus leaving free space for water flow.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will readily appear from the following description of one of its embodiments, provided as a non- limitative example, and of the accompanying drawings.

On the drawings :

- Figure 1 shows a perspective view of a wet razor comprising a handle and a razor head according to the invention,

- Figure 2 is an exploded perspective view of the razor head of Figure 1,

- Figure 3 shows a schematic sectional view along the axis referenced III represented on Figure 2, of a razor head according to the invention,

- Figure 4A is a detailed schematic sectional along the axis referenced III represented on Figure 2, of a guard bar of a razor head according to a first embodiment of the invention,

- Figure 4B is another detailed schematic sectional along the axis referenced IV represented on Figure 2, of a guard bar of a razor head according to a first embodiment of the invention,

- Figure 5A is a detailed schematic sectional along the axis referenced III represented on Figure 2, of a guard bar of a razor head according to a second embodiment of the invention,

- Figure 5B is another detailed schematic sectional along the axis referenced IV represented on Figure 2, of a guard bar of a razor head according to a second embodiment of the invention,

- Figure 6 is a detailed schematic sectional along the axis referenced IV represented on Figure 2, of a guard bar of a razor head according to a third embodiment of the invention .

On the different Figures, the same reference signs designate like or similar elements.

DETAILED DESCRIPTION

Figure 1 shows a wet razor 100 comprising a razor head 1 and a handle 2.

The razor head 1 is intended to be borne by the handle 2 extending in a handle direction Ha between a proximal portion 2a and a distal portion 2b bearing the shaving head 1. The handle direction Ha may be curved or include one or several straight portions.

The razor head 1 includes a top face 3 defining a shaving window 4, and equipped with one or several blade members 5 and a bottom face 6 which is to be connected to the distal portion 2b of the handle 2 by a connection mechanism 7.

On the example shown on the Figures, there are three blade members 5. However, the razor head 1 may also use more or less blade members 5.

The blade members 5 have each a blade edge 5a extending along a transversal axis X.

The blade members 5 extend along the transversal axis X from a first transversal blade end 5b, to a second transversal blade end 5c. The transversal axis X further defines a longitudinal axis Y of the razor head 1 which is perpendicular to the transversal axis X, and a vertical axis Z of the razor head 1 which is perpendicular to the transversal axis X and to the longitudinal axis Y.

The longitudinal axis Y defines a front end la and a rear end lb of the razor head 1, the blade edges 5a being oriented toward the front end la of the razor head 1.

Unless it is expressly mentioned otherwise, the terms "front", "frontward", "rear" and "rearward" are thus to be understood as referring to the front and the back of the razor head 1, a rear-to-front direction, or direction of shaving, extending along the longitudinal axis Y, from the rear end lb of the razor head 1 toward the front end la of the razor head 1.

The connection mechanism 7 may enable the head 1 to pivot relative to a pivot axis X' which is substantially parallel to the transversal axis X. Said connection mechanism 7 may further enable to selectively release the razor head 1 for the purpose of exchanging razor heads.

One particular example of connection mechanism 7 usable in the present invention is described in document WO-A-2006/027018, which is hereby incorporated by reference in its entirety for all purposes.

As depicted on Figures 1, 2 and 3, the razor head 1 comprises a main frame member 8 connected to the handle 2 by the connection mechanism 7 and having:

- a guard bar 9 having a front end 9a and a rear end 9b, the guard bar 9 extending parallel to the transversal axis X from a first transversal end 9c to a second transversal end 9d,

- a blade receiving section 10 located rearward of the guard 9 in the direction of shaving,

- a rear portion 11 extending parallel to the pivot axis X' , from a first transversal end 11a to a second transversal end lib, located rearward of the blade receiving section 10 in the direction of shaving, and

- a first side portion 12 and a second side portion 13, the first side portion 12 joining the first transversal ends 9a, 11a of the guard bar 9 and of the rear portion 11 together, the second side portion 13 joining the second transversal ends 9b, lib of the guard bar 9 and of the rear portion 11 together.

The blade members 5 of such a wet shaver 100 are usually not driven by a motor relative to the main frame member 8.

Preferably, the main frame member 8 is in one- piece. The guard bar 9 may thus be integrally formed with the frame member 8. The guard bar 9 and the main frame member 8 can be made solely of synthetic materials or plastic, i.e. thermoplastic materials (polystyrene or ABS, for example) and elastomeric materials.

The razor head 1 may be produced by co-injection, in particular if the guard bar 9 is made in an elastomer, for instance a thermoplastic elastomer. The razor head 1 may be produced by single injection, in particular if the guard bar 9 is made in plastic.

In an alternate embodiment, the guard bar 9 may be separated from the frame member 8. The guard bar 9 and the frame member 8 may thus forms separate entities.

In this alternate embodiment, the guard bar 9 may be made in synthetic materials or plastic but may also be made in metal, wood or another material, in particular a material able to enhance the shaving properties of the guard bar. In this alternate embodiment, the razor head 1 may be produced by a process different from co-injection and single injection.

The blade members 5 may be made from bent sheet metal, or, preferably, they may be straight and supported by blade supports 14. The blade members 5 and/or the blade supports 14 are then accommodated in seats 15 provided in the side portions 12, 13.

Moreover, the blade members 5 may for instance be placed movably in the shaving head 1. The side portions 12,13 of the shaving head 1 may be provided with elastic fingers 16, extending towards the insides of the cartridge frame or frame member, in a direction parallel to the blade members 5, in particular substantially along the transversal axis X, and movably supporting the blade members 5.

The blade members 5 may be held in the blade receiving section 10 of the main frame member 8 by a pair of bent metal strips 17, which encircle the first and second transversal blade ends 5b, 5c and thus hold them in place .

On the rear portion 11, lying generally in a plane defined by the blade edges, a shaving aid 18 may be provided .

In other embodiments, the blade members 5 may be fixed .

As shown in figures 1, 2, 3, 4A and 4B, the guard bar 9 extends parallel to the transversal axis X. It comprises a plurality of grooves 19, each groove extending transverse to the transversal axis X, and thus substantially along the longitudinal direction Y.

In particular, the guard bar 9 may comprise at least ten grooves 19, preferably at least fifteen grooves Each groove 19 has a bottom surface 20 that extends longitudinally from a groove front end 19a to a groove rear end 19b close to the blade edge 5a.

Each groove 19 may extend from the front end 9a of the guard bar 9 up to the rear end 9b of the guard bar 9.

In another embodiment, each groove 19 may extend from the front end 9a of the guard bar 9 but not up to the rear end 9b of the guard bar 9. A spacing 19c may thus exist between the groove rear end 19b and the rear end 9b of the guard bar 9.

Each groove 19 comprises a deep section 21 located next to the groove front end 19a and a sloped section 23.

Each groove 19 may further comprise a shallow section 22 located next to the groove rear end 19b, the sloped section 23 connecting the deep section 21 to the shallow section 22.

The bottom surface 20 may thus comprises a deep section bottom surface 20a, a shallow section bottom surface 20b and a sloped section bottom surface 20c.

The sloped section 23 extends from a sloped section front end 23a up to a sloped section rear end 23b.

The sloped section front end 23a may be connected to the deep section 21 while the sloped section rear end 23b may be connected to the shallow section 22.

As represented in figures 2 and 4B, The grooves 19 may be separated one from the other by a plurality of ribs 24 defining top surfaces 25.

Each rib 24 may extend from the rib front end 24a up to the rib rear end 24b.

The rib front end 24a may be located next to a groove front end 19a.

The rib rear end 24b may further be located next to a rear groove rear end 19b. Each rib 24 may define a first vertical wall 26 and a second vertical wall 27.

The first vertical wall 26 and the second vertical wall 27 may be substantially parallel together.

The first vertical wall 26 and the second vertical wall 27 extend substantially along the longitudinal direction Y.

In the embodiments of figures 4B and 5B, the first vertical wall 26 and the second vertical wall 27 may extend along the vertical axis Z and substantially perpendicular to the transversal axis X.

In a third embodiment of the invention, illustrated on figure 6, the first vertical wall 26 and the second vertical wall 27 may show a wall angle Aw with the vertical axis Z. Said wall angle Aw may for instance be comprised between one and twenty five degrees.

In the third embodiment of figure 6, the first vertical wall 26 and the second vertical wall 27 may thus show a groove wall angle Ag between them. Said groove wall angle Ag may for instance be comprised between one and forty five degrees.

The term "vertical" in "first vertical wall" and "second vertical wall" should be understood as meaning that said "first vertical wall" and "second vertical wall" extend in particular along the vertical axis Z and may show a non-zero wall angle Aw with the vertical axis. In particular, the term "vertical" in "first vertical wall" and "second vertical wall" should not be understood as meaning that the "first vertical wall" and/or the "second vertical wall" are strictly vertical walls.

Figure 4B is a cross-section, perpendicular to the longitudinal axis Y, of the bottom surface 20 of each groove 19 showing

a bottom transversal shape 28, being a transversal shape of the bottom surface 20 of each groove 19,

a vertical transversal shape 29, being a transversal shape of the vertical walls 26, 27 of each groove 19, and

- a top transversal shape 30, being a transversal shape of the top surface 25 of each groove 24.

More precisely, each groove 19 thus comprises two substantially parallel vertical walls 26, 27. A first vertical wall 26 is defined by an adjacent rib 24 located next to said groove 19 in the direction of the first transversal end 9a of the guard bar 9 while a second vertical wall 27 is defined by another adjacent rib 24 located next to said groove 19 in the direction of the second transversal end 9b of the guard bar 9.

For each groove 19, said two vertical walls 26, 27 define a groove width Wg, said width being the distance separating said vertical walls 26, 27 as measured along the transversal axis X.

For each groove 19, the groove width Wg is substantially constant along the groove extension, i.e. along the longitudinal axis Y.

The groove width Wg may thus be of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm.

Similarly, each rib 24 has a first vertical wall 26 and a second vertical wall 27 and for each rib 24, the two vertical walls 26, 27 thus define a rib width Wr, said width being the distance separating said vertical walls 26, 27 as measured along the transversal axis X.

The rib width Wr may be of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.8 mm . A groove pitch Pg may be defined as the sum of the groove width Wg and the rib width Wr. Alternatively, the groove pitch Pg can be defined as the transversal periodicity of the grooves and ribs on the guard bar 9.

The groove pitch Pg may thus be of 0.5 mm to 3 mm, preferably of 1 mm to 2 mm, more preferably of about 1.7 mm .

The bottom transversal shape 28 of the bottom surface 20 of each groove 19 may further comprise a bottom rectilinear portion 28a parallel the transversal axis X.

A bottom surface width W of said bottom rectilinear portion 28a, measured along the transversal axis X, is at least half of the groove width Wg, preferably at least seventy-five per cent of the groove width Wg, more preferably at least ninety per cent of the groove width Wg.

The top transversal shape 30 of the top surface 25 of each rib 24 may also comprise a top rectilinear portion 30a parallel the transversal axis X.

A top surface width Wt of said top rectilinear portion 30a, measured along the transversal axis X, is less than ninety per cent of the rib width Wr, preferably less than seventy-five per cent of the rib width Wr, more preferably less than half of the rib width Wr.

As best seen on Figure 4A, for each groove 19, a groove depth D may also be defined, said depth being the distance separating the bottom surface 20 of a groove 19 from the top surface 25 of a rib 24 adjacent to said groove 19, as measured along the vertical axis Z.

In particular, the groove depth D may be the distance separating the bottom rectilinear portion 28a of the bottom transversal shape 28 of the bottom surface 20 of a groove 19 from the top rectilinear portion 30a of the top transversal shape 30 of the top surface 25 of a rib 24 adjacent to said groove 19, as measured along the vertical axis Z.

The groove depth D may be substantially constant along the deep section 21.

The groove depth D along the deep section 21 may be of 0.1 mm to 1.5 mm, preferably of 0.5 mm to 1 mm, more preferably of about 0.7 mm.

The groove depth D may also be substantially constant along the shallow section 22.

The groove depth D along the shallow section 22 may be of 0.1 mm to 1.5 mm, preferably of 0.1 mm to 0.5 mm, more preferably of about 0.3 mm.

Along the sloped section 23, the groove depth D may decrease from the sloped section front end 23a to the sloped section rear end 23b.

In particular, the groove depth D may decrease regularly from the sloped section front end 23a to the sloped section rear end 23b and in particular not show any increase going from the sloped section front end 23a to the sloped section rear end 23b.

In a second embodiment of the present invention illustrated on Figures 5A and 5B, the shallow section 22 may be a zero depth section.

In this embodiment, the bottom surface 20 of the shallow section 22 may thus be continuously connected with the top surfaces 25 of the ribs 24 adjacent to said groove 19.

In particular, the bottom surface 20 of the shallow section 22 and the top surfaces 25 of the ribs 24 adjacent to said groove 19 may be located in the same horizontal plane H, perpendicular to the vertical axis Z.

In this embodiment, the groove depth D at the sloped section rear end 23b may be equal to zero. The bottom surface 20 of each groove 19 may comprise a bottom planar portion 31 being a substantially planar portion of the bottom surface 20.

The bottom planar portion 31 may correspond to an extension along the longitudinal axis Y of the bottom rectilinear portion 28a of the bottom transversal shape 28 of the bottom surface 20 of each groove 19.

The bottom planar portion 31 may extend from the groove front end 19a up to the groove rear end 19b.

The top surface 25 of each rib 24 may comprise a top planar portion 32 being a substantially planar portion of the top surface 25.

The top planar portion 32 may correspond to an extension along the longitudinal axis Y of the top rectilinear portion 30a of the top transversal shape 30 of the top surface 25 of each rib 24.

The top planar portion 32 may extend from the rib front end 24a up to the rib rear end 24b.

As shown on figure 4A and 5a, an angle of inclination A can be defined, being an angle between the bottom surface 20, and in particular the sloped section bottom surface 20c, and the top surface 25 of the sloped section 20.

More precisely, the angle of inclination A may be an angle between the bottom planar portion 31 of the bottom surface 20 of a groove 19 and the top planar portion 32 of the top surface 25 of a rib 24 adjacent to said groove 19.

Alternatively, the angle of inclination A may be defined as an angle between the bottom surface 20, and in particular the sloped section bottom surface 20c, and an horizontal plane H perpendicular to the vertical axis Z.

A maximum angle of inclination Max_A being the highest value of the angle of inclination A along the sloped section 20 is smaller than eighty-five degrees, preferably smaller than forty-five degrees.

A minimum angle of inclination Min_A being the highest value of the angle of inclination A along the sloped section 20 is higher than six degrees, preferably higher than ten degrees.

In the embodiments of Figures 5A and 5B, the sloped section 23 is connected to the deep section 21 by a first rounded portion 33.

The sloped section 23 may also be connected to the shallow section 22 by a second rounded portion 34.

In particular, a maximum radius Max_R of the first rounded portion 33 and/or the second rounded portion 34 may be higher than the groove depth D along the deep section 21.