FIELD OF THE INVENTION

The invention relates to the field of hair cutting devices, and more specially to a production method of a stationary cutting member of a cutting unit of a hair cutting device. BACKGROUND OF THE INVENTION

A hair cutting device is a device for cutting hair. It comprises a cutting unit and driving means for actuating the cutting unit.

Usually the cutting unit consists of two comb-like cutting members. One cutting member is a stationary cutting member, which is in contact with the skin of the user. The other cutting member is a moving cutting member, which is placed adjacent and in contact with the stationary cutting member. The moving cutting member is coupled to the driving means for driving movement relative to the stationary cutting member. The stationary cutting member may comprise rounded tips to avoid injury to the skin.

The driving means may be a pincer-like hand lever, an electric motor with eccentric or an oscillating armature drive. The driving means may be part of a handset and also occur in high-performance devices on joints or flexible shafts.

In common hair cutting devices for hair and beard trimming and also pet trimming the hair cutting devices have the problem with sharp feeling of cutting elements of the stationary cutting member, which are in contact with the skin while trimming hair.

In common hair cutting devices all cutting elements are grinded to provide a sharp cutting edge. The result is a cutting element of a cutting member with a planar surface. Even with the best minimized force, skin injuries and/or scratches are unavoidable. Usually laser melting is used to enlarge the tip area of the cutting element. However, this process is an expensive manufacturing process, and needs extra energy and it decreases the corrosion resistance of the cutting member.

SUMMARY OF THE INVENTION

Therefore, it is an object of this invention to provide a production method which is energy saving and increases the corrosion resistance of the cutting member and a cutting member, preferably a stationary cutting member, which provides a reduced risk of skin irritation.

This object is achieved by a production method for producing a cutting member of a hair cutting device, comprising the steps of: providing a cold formed blank of the stationary cutting member formed by a cold forming process, wherein the stationary cutting member comprises a plurality of cutting elements, wherein each cutting element comprises a proximal end connected to the base sheet and a distal end facing away from the base sheet, a first flank and a second flank each extending from the proximal end to the distal end, wherein each cutting element comprises a first section adjacent to the proximal end and a second section at the distal end; grinding of the first section of the cutting elements. The blank of the cutting member, preferably of the stationary cutting member, may comprise a comb like shape, wherein a plurality of cutting elements may be protruding from a base sheet. The blank may be produced by a cold forming process, for example by stamping. The grinding of the first section may be a grinding process wherein a coolant may be used to cool down heat which may be produced during the grinding process in order to increase the corrosion resistance of the cutting elements. The first section may be grinded in a direction perpendicular to the protruding direction of the cutting elements, wherein the cutting elements are protruding away from the base sheet. The first section may be grinded for example with a grinding wheel. The grinding wheel used for grinding the first section may use a coolant to cool down heat which may be produced during the grinding process. Thereby a first surface may be produced in the first section. Further, during the grinding process the blade edges may be grinded on the cutting elements. By using a cold forming process and a following grinding process an energy saving production method which does not impact material properties causing corrosion may be provided. The blade edges may be grinded on the first flanks and/or second flanks of the first section of the cutting elements, when the first sections are grinded by the grinding wheel. Furthermore, the guiding groove of the base sheet may also be grinded during the grinding process. By grinding only the first section, an additional height will be produced in the second section, whereby the additional height overtops the first surface of the first section. Further, it may be possible that the grinding wheel also deburr and/or round the additional height of the second section at the contact point of the first section and the second section. By using a grinding wheel a standard tool may be used which may reduce tooling costs. Thereby, an energy saving production method which does not impact material properties causing corrosion may be provided. According to an embodiment, the grinding of the first section may take place directly after the cold forming process of the blank. Thereby, a production method is provided which is energy saving and production time reducing, since it is possible to produce the cutting member directly after the cold forming process, and the produced parts need not to be transported to another production facility.

In one embodiment the blank may comprise a material with a yield stress in a range of about R _p o, ₂ = 250 N/mm ² to R _p o, ₂ = 300 N/mm ² and a tensile strength in a range of about R _m = 600 N/mm ² to R _m = 650 N/mm ² , wherein the material may be suitable for being used in a cold forming process. The cold forming process may be for example stamping. The sheet metal used for producing a cutting member may be for example a chrome steel, preferably a chrome steel 1.4028 (X30Crl3). The toughness and the ductility of the sheet metal are connected to each other. If the sheet metal may comprise a higher toughness it will comprise a lower ductility. If a sheet metal with higher toughness and lower ductility is used in a cold forming process, the machine for the cold forming process might get damaged or a higher pressure may be needed.

According to another embodiment the sheet metal may comprise a thickness of about 0.4 mm to 1 mm. Further, the width of the sheet metal may be in the range of about 42 mm to 8 cm. Thereby, cutting elements with different thicknesses and widths may be produced, which may be used in different types of hair cutting devices.

In one embodiment the pressure used for the cold forming process may be in the range of 4 MPa to 10 MPa, preferably in the range of 5 MPa to 7 MPa. Thereby, it may be possible to produce a cutting member out of a sheet metal in a cold forming process.

According to an embodiment, the cold forming process may take place in an environment with a room temperature, wherein the room temperature may be in a range of about 10 °C to 50°C, preferable in a range of about 18 °C to 30°C. By using the room temperature it is not necessary to heat up the sheet metal. Thereby, production costs may be reduced.

In a preferred embodiment the cold forming process comprises coining. The blank of the cutting member, preferably the cutting elements of the cutting member may be coined during the cold forming process. By coining the cutting member, preferably the cutting elements of the cutting member, a plastic flow of the material of the cutting member, preferably the cutting elements, may be induced. Thereby, the plastic flow reduces the grain size and work hardens the cutting member, preferably the cutting elements. Thereby, the cutting member does not need to be further heated up to be hardened. Thereby, an energy saving production method which does not impact material properties causing corrosion may be provided, since the energy for heating up may be saved, and it is not necessary anymore to wait until the cutting element is cooled down before it may be further processed.

According to another embodiment the production method may comprise the further step of brushing the second section, preferably with a diamond carbon brush. During the brushing the distal end and/or the additional height may be deburred and may be rounded to prevent the skin from getting injuries and/or scratches. The additional height, the distal end and the tip of the distal end may be round, smooth and may comprise a bigger area to protect the skin from injuries and/or scratches. Thereby, the distal end and/or the additional height form a rounded tip which protects the skin from injuries and/or scratches.

According to a further embodiment, the cutting member may be a stationary cutting member. By providing a stationary cutting member with an additional height at the second section of the cutting elements, a reduced risk of skin irritation may be provided.

The invention is further related to a cutting member for a hair cutting device, wherein the cutting member is formed by a production method as described above, comprising multiple cutting elements, wherein the multiple cutting elements are protruding from a base sheet, wherein each cutting element comprises a proximal end connected to the base sheet and a distal end facing away from the base sheet, a first flank and a second flank each extending from the proximal end to the distal end, and an essentially planar first surface for contacting a moving cutting member, wherein each cutting element comprises a first section adjacent to the proximal end and a second section at the distal end, wherein the first section comprises the first surface, wherein the second section comprises an additional height, wherein the additional height overtops the first surface of the first section. The cutting member comprise a comb-like shape, wherein a plurality of cutting elements may protrude from a base sheet of the cutting member, wherein each cutting element may be essential in a plane of the base sheet. Each cutting element comprises a proximal end connected to the base sheet and a distal end facing away from the base sheet. Furthermore, each cutting element may comprise a first flank and a second flank each extending from the proximal end to the distal end, wherein the first flank is arranged at the opposite side of the second flank. Further, each cutting element may comprise an essential planar first surface. The first surface may be the surface which may be in contact with a moving cutting member for cutting hair. The moving cutting member may also comprise a comb-like shape and may be placed on the first surface, so that the movable cutting member and the stationary cutting member are in contact with each other, wherein the first surface is adjacent to a contact surface of the movable cutting member. The moving cutting member may comprise blade pieces which may extend from the proximal end towards the distal end of the stationary cutting member. The cutting elements of the stationary cutting member and the blade pieces of the moving cutting member may be arranged in such a way that the blade pieces of the moving cutting member and the corresponding first flanks and/or the second flanks of the cutting elements of the stationary cutting member are adjacent to each other. Further, the base sheet of the stationary cutting member may comprise a guiding groove which may be in contact with a base sheet of the moving cutting member to guide the sideways movement of the moving cutting member. Each cutting element of the cutting member may be divided into a first section and a second section, wherein the first section may be adjacent to the proximal end and the second section may be at the distal end, wherein the second section may be adjacent to the first section and the distal end. The first surface may be located on the first section and the second section may comprise an additional height, which overtops the first section in direction of the surface for contacting the moving cutting member. By providing an additional height, the cutting member may provide a bigger surface to avoid scratches and injuries of the skin. From the physical point of view pressure is the quotient between force and area. p=F/A. Whereby p is the pressure, F is the force of the user and A is the area of cutting element on the skin of the user. The physically force by the use of hair cutting devices is not under control from the supplier of hair cutting devices. Even when the user reduces the force while trimming with common hair cutting devices, nevertheless skin injuries and/or scratches are unavoidable. To avoid scratches and/or injuries a larger tip area of the cutting element is needed. Further, the additional height may shield the skin against the blade pieces of the moving cutting member, since the blade pieces may extend from the proximal end towards the distal end of the stationary cutting member and therefore, the blade edges are not able to overlap the distal end of the stationary cutting member.

According to a further embodiment, the cutting member may be a stationary cutting member. By providing a stationary cutting member with an additional height at the second section of the cutting elements, a reduced risk of skin irritation may be provided.

According to one embodiment the distal end and/or the additional height may form a tip facing away from the proximal end, wherein the tip may comprise an essentially rounded shape. The tip may be arranged at the distal end, which may be connected to the additional height, to avoid sharp edges at the distal end to avoid injuries or scratches of the skin when the hair cutting device is used. The round shape of the tip at the distal end and/or additional height may provide a protection against scratches and/or injuries of the skin. In a preferred embodiment the first section may be shaped by a cold forming process preferably coining and grinding, and the second section may be shaped by a cold forming process preferably coining. The cutting member, preferably the moving cutting member, may be produced in two steps: in the first production step the cutting element, preferably the stationary cutting element may be produced by a cold form process, preferably by coining. Afterwards the cutting elements may be grinded by a grinding wheel in the first sections, preferably a grinding wheel which may be used with a coolant to cool down heat which may be produced during the grinding process in order to increase the corrosion resistance of the cutting element. The second sections may not be grinded by a grinding wheel. Further, the first section and the second section may be formed simultaneously in the same cold forming process, and afterwards the section may be grinded. By shaping the cutting member, preferably the stationary cutting member, in a cold form process an energy saving production may be provided, which does not impact material properties causing corrosion. Further, by not grinding the second section, the additional height of the second section may provide an enlarged tip at the distal end and/or additional height, which may protect the skin from injuries and/or scratches when the hair cutting device is used.

According to another embodiment the first flank and/or the second flank of the first section each may comprise a blade edge extending at least partially along the first flank and/or the second flank. The blade edges may be formed on the flanks during grinding the first section. The blade edges may face from the cutting elements towards an adjacent blade piece of the in moving direction adjacent blade pieces of the moving cutting member. By providing the cutting elements with blade edges, the cutting elements may be able to cut hair in combination with the blade pieces of the moving cutting member, when the moving cutting member is moving towards or over the in moving direction adjacent cutting elements.

According to a further embodiment the cutting elements may comprise at least one recess arranged in the first surface. The recess may stretch along the first surface from the proximal end towards the additional top, whereby the recess is directed in the opposite direction of a contact surface with the moving cutting member. Further, the recess may be positioned on the first flanks and/or second flanks of the cutting elements, whereby a bar shaped like blade edge may be formed in the middle between the first flanks and the second flanks. By providing a recess the cutting of the hair may be improved and the hair may not get jammed between the stationary cutting member and the moving cutting member during the hair cutting process. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 shows process steps of a production method for producing a cutting member;

Fig. 2 shows a sectional view of a cutting element of a cutting member produced by a production method as shown in Fig. 1;

Fig. 3 shows a detailed view of a cutting member produced by a production method as shown in Fig. 1;

Fig. 4 shows a detailed view of another cutting element of a cutting member produced by a production method as shown in Fig. 1.

DETAILED DESCRIPTION OF EMBODIMENTS

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Fig. 1 shows the steps of a production method for producing a cutting member

10, preferably a stationary cutting member, of a hair cutting device (not shown) by providing a cold formed blank (not shown) of the cutting member 10, preferably a stationary cutting member formed by a cold forming process, which comprises coining. Different cross sectional and detailed views of different cutting members 10, in particular stationary cutting members, which are produced according to the production method as shown in Fig. 1, are shown in the Figs. 2, 3 and 4. The references used for describing the production method as shown in Fig. 1 are taken from Fig. 3.

In the production method as shown in Fig. 1, the blank of the cutting member 10, preferably of the stationary cutting member, comprises a comb like shape, wherein a plurality of cutting elements 12 are protruding from a base sheet 14. As shown in Fig. 3, each cutting element 12 comprises a proximal end 16 which is connected to the base sheet 14 and a distal end 18 facing away from the base sheet 14, a first flank 30 and a second flank 32 each extending from the proximal end 16 to the distal end 18, wherein each cutting element 12 comprises a first section 22 adjacent to the proximal end 14 and a second section 24 at the distal end 16.

The blank provided for the production method as shown in Fig. 1 may be produced by a cold forming process, for example by stamping. The sheet metal used for producing the blank may be for example the chrome steel 1.4028 (X30Crl3). The sheet metal may comprise a thickness of about 0.4 to 1 mm, thereby different thicknesses of cutting elements may be produced, which may be used in different types of hair cutting devices. The pressure used for the cold forming process may be in the range of 4 to 10 MPa, preferably in the range of 5 to 7 MPa. The cold forming may take place in an environment with a room temperature, wherein the room temperature may be in a range of about 10 to 50°C, preferable in a range of about 18 to 30°C.

Further, the blank of the cutting member 10, preferably the cutting elements 12 of the cutting member 10 provided for the production method as shown in Fig. 1 may be coined and/or embossed during the cold forming process. By coining the cutting member 10, preferably the cutting elements 12 of the cutting member 10, a plastic flow of the material of the cutting member 10, preferably the cutting elements 12, may be induced. Thereby, the plastic flow reduces the grain size and work hardens the cutting element 10, preferably the cutting members 12. Thereby, the cutting element 10 does not need to be further heated up to be hardened. Thereby, an energy saving production method which does not impact material properties causing corrosion may be provided, since the costs for heating up can be saved, and it is not necessary anymore to wait until the cutting element 10 is cooled down before it may be further processed.

In the second step of the production method as shown in Fig. 1, the first section 22 of each cutting element 12 is grinded at least partially simultaneaously and/or sequentially, wherein a coolant may be used to cool down heat which may be produced during the grinding process in order to increase the corrosion resistance of the cutting elements 10. The first sections 22 are grinded in a direction essentially perpendicular to the protruding direction of the cutting elements 12, wherein the cutting elements 12 are protruding away from the base sheet 14. The first sections 22 may be grinded for example with a grinding wheel. By grinding the first section 22 of each cutting element 12, a first surface 20 will be produced in the first section 22 of each cutting element 12. Further, as shown in Fig. 2, since the second section 24 is not grinded an additional height 26 will be produced in the second section 24, which overtops the first surface 20 of the first section 22. Further, during the grinding process of the production method as shown in Fig 1 blade edges 34 may be grinded on the cutting elements 12. The blade edges 34 may be grinded on the first flanks 30 and/or second flanks 32 of the first section 22 of the cutting elements 12, when the first sections 22 are grinded by the grinding wheel. Furthermore, a guiding groove 38 of the base sheet 14 may also be grinded during the grinding process. Further, it may be possible that the grinding wheel also deburr and/or round the additional height 26 of the second section 24 at the contact point of the first section 22 and the second section 24. The grinding wheel may be shaped in order to provide a smooth changeover from the first surface 20 towards the additional height 26, for example with a radius. By using a grinding wheel a standard tool may be used which may reduce tooling costs. Further, by using a cold forming process and a following grinding process an energy saving production method which does not impact material properties causing corrosion may be provided.

Furthermore, the production method may comprise the further step (not shown) of brushing the second section 24, preferably with a diamond carbon brush. During the brushing the distal end 18 and/or the additional height 26 may be deburred and may be rounded to prevent the skin from getting injuries and/or scratches. The additional height 26, the distal end 18 and the tip of the distal end 18 may be round, smooth and may comprise a bigger area to protect the skin from injuries and/or scratches. Thereby, the distal end 18 and/or the additional height 26 form a rounded tip 28 which protects the skin from injuries and/or scratches.

Fig. 2 is showing a sectional view of a cutting element 12 of a cutting member 10, preferably a stationary cutting member, of a hair cutting device (not shown), which has been produced according to the production method as shown in Fig. 1. The cutting member 10, preferably the stationary cutting member, comprises a comb like shape, wherein a plurality of cutting elements 12 are protruding from a base sheet 14. Each cutting element 12 comprises a proximal end 16 connected to the base sheet 14 and a distal end 18 facing away from the base sheet 14. The base sheet 14 comprises adjacent to the proximal ends 16 a guiding groove 38 for guiding a moving cutting member (not shown), when the moving cutting member is moved sideways to cut the hair in combination with the in moving direction adjacent cutting elements 12. The moving cutting member may comprise a comb like shape and blade pieces which may extend from the proximal end 16 towards the distal end 18 of the stationary cutting member. Further, each cutting element comprises a first flank 30 and a second flank 32, which extend from the proximal end 16 towards the distal end 18. The first flank 30 and the second flank 32 are shown in Fig. 3.

The cutting elements 12 of the stationary cutting member and the blade pieces of the moving cutting member may be arranged in such a way that the blade pieces of the moving cutting member and the corresponding first flanks 30 and/or the second flanks 32 of the cutting elements 12 of the stationary cutting member may be adjacent to each other. Furthermore, the cutting element 12 comprises an essentially planar first surface 20 for contacting the moving cutting member. The cutting element 12 comprises a first section 22 adjacent to the proximal end 14 and a second section 24 at the distal end 18, wherein the second section 24 is adjacent to the first section 22 and the distal end 18. The first section 22 may comprise the first surface 20 and the second section 24 may comprise an additional height 26. The additional height 26 may overtop the first surface 20 in direction of the contact surface with the moving cutting member. The additional height 26 may be higher or the same height as the thickness of the blade pieces of the moving cutting member, thereby, the additional height 26 may be shielding the skin against the blade edges of the moving cutting member. The additional height 26 is rounded to prevent the skin from getting injuries and/or scratches when the hair cutting device is used to cut hair. Further the distal end 18 and/or the additional height may comprise a tip 28, wherein the tip 28 is facing away from the proximal end 16 and may comprise a rounded shape. Thereby, injuries and/or scratches of the skin may be prevented when the hair cutting device may be used.

The first section 22 of the cutting member 10, preferably the stationary cutting member, may be shaped by a cold forming process, preferably coining and grinding, and the second section 24 may be shaped by a cold forming process preferably coining. During the grinding of the first section 22 a coolant may be used to cool down heat which may occur during the grinding process. Thereby, a production method may be used, which is energy saving and does not impact material properties for example causing corrosion.

Fig. 3 shows a detailed view of a cutting member 10, preferably a stationary cutting member, which has been produced according to the production method as shown in Fig. 1. The first section 22 has been grinded and the second section 24 has not been grinded. Further, the tips 28 of the distal ends 18 and/or the additional heights 26 of the cutting elements 12 are rounded. The rounding of the tip 28 and/or the additional height 26 may be brushed, preferably with a diamond carbon brush, to become round to protect the skin from injuries and/or scratches. Further, the first sections 22 may comprise at least partially blade edges 34 on the first flanks 30 and/or second flanks 32 of the cutting elements 12. The base sheet 14 comprises the guiding groove 38 for guiding the moving cutting member in the sideways movement for cutting hair. The guiding rail 38 is adjacent to the proximal ends 16. The first surface 20 of the first section 22 is arranged next to the additional height 26, and the first surface 20 may merge with the surface of the additional height 26, preferably with a radius being formed in between the first surface 20 and the additional height 26.

Fig. 4 shows a detailed view of a cutting member 10, preferably a stationary cutting member, of another embodiment, which has been produced according to the method as shown in Fig. 1. The first section 22 may comprise at least one recess 36. The recess 36 may extend essential along the first surface 20 from the proximal end 16 towards the additional height 26. Further, the recess 36 may be positioned in the first surface 20 between the first flanks 30 and/or second flanks 32 of the cutting elements 12. The blade edges 22 may be formed onto the edges between the first surfaces 20 and the first flanks 30 and/or second flanks 32 during the grinding process of the first section 22 of the cutting member 10. By providing at least one recess 36 the cutting of the hair may be improved and the hair may not get jammed between the stationary cutting member and the moving cutting member during the hair cutting process.

REFERENCE SYMBOL LIST

10 cutting member

12 cutting element

14 base sheet

16 proximal end

18 distal end

20 first surface

22 first section

24 second section

26 additional height

28 tip

30 first flank

32 second flank

34 blade edge

36 recess

38 guiding groove