EP0652084A1 - Apparatus for cutting hair with a toothed cutter and process for manufacturing a cutter for such an apparatus - Google Patents

Abstract

The invention relates to an appliance (1) for cutting hair with a toothed cutting device (7) which exhibits a stationary cutter (10) with a series of cutting teeth (11) and a cutter (12) which can be driven back and forth and has a series of cutting teeth (13), the cutting teeth (11, 13) of at least one of the two cutters (10, 12) being of a rounded design at their free ends (31) apart from in the region of their running surfaces (15, 16). In the case of the appliance, the cutting teeth (11, 13) of the at least one cutter (10, 12) are additionally of a fully rounded design over the entire tooth depth as far as the tooth-root region (29), apart from in the region of their running surfaces (15, 16). <IMAGE>

Description

The invention relates to a device for cutting hair with a tooth cutting device, which has a stationary knife with at least one row of cutting teeth and a reciprocating knife with at least one row of cutting teeth, the cutting teeth having treads and the two knives at least with a part of the running surfaces of their cutting teeth abut each other and the cutting teeth of at least one of the two knives are rounded at their free ends except in the area of their running surfaces.

Furthermore, the invention relates to a method for producing a knife for a device according to the type mentioned in the first paragraph above.

A device according to the type mentioned in the first paragraph above is known for example from DE 28 09 345 A1. This known device is a thinning hair clipper for thinning, that is for thinning hair when cutting hair. In this known device, the cutting teeth of the reciprocable knife are rounded at their free ends and smoothed. Behind the roundings into the tooth root area, however, the cutting teeth of the knife which can be driven to and fro have sharp edges in the region of their side facing away from the running surfaces of the cutting teeth, as result from the stamping process used to manufacture this knife. These sharp edges can scratch the skin and irritate the skin when the cutting teeth move along the skin, which is uncomfortable and annoying to a user of the device and is therefore undesirable and disadvantageous.

The object of the invention is to avoid the difficulties mentioned above and to design a device for cutting hair in accordance with the type mentioned in the first paragraph in such a way that when the tooth cutting device of the device is moved along the skin there is no scratching of the skin and no irritation of the skin takes place. According to the invention, this object is achieved in that the cutting teeth of the at least one knife, which have rounded cutting teeth at their free ends except in the area of their treads, are also completely rounded over their entire tooth depth down to the tooth root area except in the area of their treads.

It is thereby achieved in a very simple way that the cutting teeth of the device according to the invention have no sharp edges at all, except in the area of their running surfaces, where the cutting edges of the cutting teeth are located, because the rounded cutting teeth, except in the area of their running surfaces, do not have any free edges Ends are completely rounded down into the tooth root area. As a result, scratching of the skin and irritation of the skin is not possible with the completely rounded cutting teeth of the tooth cutting device, so that a gentle cutting behavior is always achieved with a device for cutting hair according to the invention.

In the case of a device according to the invention, in which only one of the two knives can come into contact with the skin due to its design, it is sufficient to design only this knife with cutting teeth that are completely rounded according to the invention. However, it is very common for both knives of a tooth cutting device to come into contact with the skin. In this context, it has therefore proven to be advantageous if the cutting teeth of both knives are completely rounded over their entire tooth depth down to the tooth root area, except in the area of their running surfaces. This ensures that neither of the two knives can have a disruptive effect on the skin.

The manufacture of a knife with cutting teeth that are completely rounded according to the invention can be done, for example, in a metal casting process. Such a knife can also have been produced in such a way that a knife blank is first produced in a punching process, after which the completely rounded cutting teeth have been produced, for example, in an etching process or by laser processing. It has proven to be particularly advantageous if the two knives are formed by stamped metal parts and the rounded teeth are produced in one stamping process.

Knives of this type are particularly inexpensive because they have one simple stamping process and an equally simple subsequent stamping process can be produced.

A method for producing a knife for a device according to the invention for cutting hair is characterized according to the invention in that an unhardened steel band with a predetermined band thickness D is transported step by step to a subsequent step tool device and in a first subsequent step a pre-embossing of the steel band to produce pre-embossed first cutting tooth blanks of a knife, the pre-embossed first cutting tooth blanks remain connected via a steel band bridge embossed during pre-embossing with a bridge thickness d that is smaller in relation to the band thickness D, and that the steel band bridge connecting the pre-embossed first cutting tooth blanks is then cut away in a second step and at the same time second cutting tooth blanks of a knife are cut out of the first cutting tooth blanks and that after that a final stamping of the second is carried out in a third subsequent step Cutting tooth blanks for producing finished embossed third cutting tooth blanks of a knife are carried out, with this finishing embossing the third cutting tooth blanks being embossed in a completely rounded manner from their free ends over their entire tooth depth to the tooth root area, except in the area provided for forming the running surfaces of the cutting teeth. By pre-stamping the first cutting tooth blanks it is achieved that knives with cutting teeth with a cutting tooth width of, for example, only 0.4 mm can be produced from a relatively thick steel strip with a strip thickness D of, for example, 1.0 mm. The pre-stamping of the first cutting tooth blanks and the final stamping of the second cutting tooth blanks to produce the third cutting tooth blanks means that the shape of the cutting teeth, which is completely rounded from the free tooth ends down to the tooth root area, is produced in a stamping process in a very simple and inexpensive manner.

In such a method according to the invention, it has proven to be advantageous if a steel strip bridge with a bridge thickness d, which is at most 75% of the strip thickness D, is embossed during the pre-stamping in the first subsequent step. This is favorable in view of a good cutting out of the second cutting tooth blanks.

It has proven to be particularly advantageous if, during the pre-embossing in the first subsequent step, a steel belt bridge with a bridge thickness d of at most 30% of the strip thickness D is embossed. This is advantageous in view of a particularly good cutting out of the second cutting tooth blanks and the production of particularly fine cutting teeth.

It has also proven to be advantageous if, after the third subsequent step in the subsequent step tool device, the knife blank obtained here and its third cutting tooth blanks are hardened in a further working step.

In this way, particularly hard knives with very hard and wear-resistant cutting edges can be achieved. Hardening increases the elastic limit of the knife material, which prevents undesirable plastic deformation of the knife.

It has also proven to be very advantageous if, in a further work step, the third cutting tooth blanks of a knife are ground in the area provided for forming the running surfaces of the 5 cutting teeth to form defined running surfaces and sharp cutting edges. Such grinding of the treads is particularly inexpensive. The treads can also be lapped.

The invention is described below with reference to an embodiment shown in the drawings, but to which the invention is not intended to be limited. FIG. 1 shows an oblique view of a shaving device according to an embodiment of the invention, which has a short hair cutting device and a long hair cutting device. 2 shows schematically a long hair cutting device, as is provided in the device according to FIG. 1 and which is designed as a tooth cutting device with a tooth knife that can be driven back and forth and with a tooth knife that is stationary relative to the tooth knife that can be driven back and forth. 3 shows a top view on a larger scale than the natural size of a practical embodiment variant of a stationary tooth knife of a tooth cutting device according to FIG. 2. 4 shows a section along the line IV-IV of FIG. 3 the stationary tooth knife according to FIG. 3. 5 shows, on a much larger scale than in FIGS. 3 and 4, an oblique view of a single cutting tooth of the stationary tooth knife according to FIGS. 3 and 4. In FIGS. 6 to 13, a section along the line XIII-XIII in FIG. 3 which in a method according to the invention for Manufacture of a tooth knife according to FIGS. 3 and 4, products obtained successively in steps and partly the tools required for the manufacture of these products of a subsequent step tool device are shown schematically.

FIG. 1 shows a shaving device 1 for cutting hair. The shaving device 1 has a housing 2 on which a shaving head 3 is seated. The shaving head 3 comprises a shaving head frame 4 in which a short hair cutting device 5 is provided for cutting whiskers. The short hair cutting device 5 essentially consists of a curved shear foil 6 and a lamellar knife which is not visible in FIG. 1 and is resiliently pressed into the curvature of the shear foil 6. Furthermore, the razor 1 has a tooth cutting device 7 as a long hair cutting device for cutting long beard hair and head hair. The tooth cutting device 7 is held in the region of a side wall 8 of the housing 2 so that it can be moved back and forth in the longitudinal direction of the shaving apparatus 1 in order to be displaced between a rest position shown in FIG. 1 and an operating position not shown in FIG. 1 and closer to the short hair cutting device 5 to be able to. To move the tooth cutting device 7, the shaving device 1 has a sliding button 9.

FIG. 2 shows a schematic view of the tooth cutting device 7 of the shaving device 1 according to FIG. 1. The tooth cutting device 7 has a stationary first knife 10 which is designed as a tooth knife with a row of cutting teeth 11 and which is held stationary on a carrier (not shown) for the entire tooth cutting device 7. Furthermore, the tooth cutting device 7 has a second knife 12 which can be driven back and forth, which is also designed as a tooth knife with a row of cutting teeth 13 and which can be driven back and forth parallel to a drive direction indicated by an arrow 14. The cutting teeth 11 of the stationary tooth knife 10 have running surfaces 15, and the cutting teeth 13 of the tooth knife 12 which can be driven back and forth have running surfaces 16. The two knives 10 and 12 lie against one another at least with part of the running surfaces 15 and 16 of their cutting teeth 11 and 13. The stationary tooth knife 10 and the tooth knife 12 which can be driven back and forth are parallel to a pressing direction indicated by a further arrow 17 with the running surfaces 15 and 16 of their cutting teeth 11 and 13 held pressed together. The tooth cutter 12, which can be driven back and forth, is carried by a knife carrier 18, to which a compression spring 19 engages, which is supported on a stationary counter bearing 20 on the carrier for the entire tooth cutting device 7. The tooth pitches of the two rows of cutting teeth 11 and 13 of the tooth knives 10 and 12 are different.

In order to drive the tooth knife 12 which can be driven back and forth, a drive part 21 which can be driven back and forth is provided, which is formed, for example, by a pivotably mounted drive lever. Between the drive part 21 and the reciprocally drivable tooth knife 12 or the knife carrier 18 carrying the tooth knife 12, a joint device 22 is provided, via which a driving force from the drive part 21 to the reciprocally drivable tooth knife 12, essentially into the area of the point of application of the resultant of the frictional forces between the two knives 10 and 12. The joint device 22 has two webs 23 and 24 which are inclined in the opposite direction to the pressing direction 17 and which are connected to the drive part 21 via a joint 25 or 26 and to the knife carrier 18 via a joint 27 or 28.

The drive part 21 and the webs 23 and 24 and the knife carrier 18 are formed in one piece from plastic, the joints 25, 26, 27 and 28 being formed by film hinges. FIGS. 3 and 4 show a practical embodiment variant of a stationary tooth knife 10. As can be seen from FIGS. 3 and 4, this stationary tooth knife 10 is cranked both in the area of the row of cutting teeth 11, specifically in the tooth root area 29, and in the area 3 facing away from the row of cutting teeth 11.

3 and 4 of a tooth cutting device 7 according to FIG. 2, as is shown in detail in FIG. 5, the cutting teeth 11 are rounded at their free ends 31 except in the area of their running surfaces 15. In addition, however, the cutting teeth 11 are now also completely rounded over their entire tooth depth into the tooth root area 29, except in the area of their running surfaces 15. In other words, this means that the cutting teeth 11 are first rounded off along lines of curvature which lie in planes running parallel to the running surfaces 15 of the cutting teeth 11, as is indicated in FIG. 5 with the radius r1, and that the cutting teeth 11 secondly along lines of curvature are rounded, which lie in planes perpendicular to the running surfaces 15 and at the same time parallel to the tooth directions, as indicated in FIG. 5 with the radius r2, and that the cutting teeth 11 are thirdly rounded along lines of curvature which are perpendicular to the treads 15 and at the same time transverse to the tooth planes, as indicated in FIG. 5 with the radius r3.

Although this is shown in FIGS. 3, 4 and in particular 5 only for the cutting teeth 11 of the stationary tooth knife 10, it can be seen from FIG. 2 that the cutting teeth 13 of the tooth knife 12 which can be driven back and forth also have one of their free ends have a completely rounded design extending their entire tooth depth into the tooth root area, of course except in the area of the running surfaces 16 of the cutting teeth 13 of the reciprocating knife 12.

In a particularly advantageous manner, the two tooth knives 10 and 12 of the tooth cutting device 7 are formed by stamped metal parts and the rounding of the cutting teeth 11 and 13 of the two tooth knives 10 and 12 were produced in one stamping process.

An advantageous method for producing a tooth knife for a tooth cutting device of a device for cutting hair, that is to say for example for producing a stationary tooth knife 10 according to FIGS. 3 and 4, is described below with reference to FIGS. 6 to 13.

6 shows a cross section of an unhardened steel strip 32, the transverse direction of which is indicated in FIG. 6 by an arrow 33. The steel strip 32 has a predetermined strip thickness D, which is, for example, 1.0 mm. Such an unhardened steel strip 32 is transported step by step to a subsequent step tool device perpendicular to its transverse direction 33 and is transported further step by step in this subsequent step tool device while simultaneously performing step-by-step successive subsequent steps.

In a first subsequent step carried out in the subsequent step tool device, as is indicated schematically in FIG. 7, the steel strip 32 is pre-embossed in an embossing device 34, which has a lower tool part 35 and an upper tool part 36, in order to produce pre-embossed first cutting tooth blanks 37 of a tooth knife, being the pre-embossed first Cutting tooth blanks 37 remain connected via a steel band bridge 38 embossed during pre-embossing with a bridge thickness d that is smaller in relation to the band thickness D of the steel band 32. This pre-stamping process is shown schematically in FIG. The intermediate product 39 obtained in the pre-embossing process according to FIG. 7 is shown in FIG. As can be seen from FIGS. 7 and 8, in the described method during the pre-stamping in the first subsequent step, a steel band bridge 38 is embossed with a bridge thickness d that is approximately 30% of the band thickness D.

After the pre-embossing in accordance with the first subsequent step, in a second subsequent step with a cutting device 40, which consists of a cutting plate 41 and a cutting punch 42, the steel band bridge 38 connecting the pre-embossed cutting tooth blanks 37 is cut away and at the same time are removed from the first cutting tooth blanks 37 second cutting tooth blank 43 of a knife, as shown schematically in Fig.9. The intermediate product 44 obtained in the second subsequent step according to FIG. 9 is shown in FIG.

After the second subsequent step in the subsequent step tool device, in a third subsequent step in a further embossing device 45, which has a lower tool part 46 and an upper tool part 47, the second cutting tooth blanks 43 are finished embossed to produce finished embossed third cutting tooth blanks 48 of a knife. In this final embossing in accordance with the third subsequent step in the subsequent step tool device, the third cutting tooth blanks 48 are embossed in a completely rounded manner from their free ends over their entire tooth depth into the tooth root area, except in the area 49 provided for forming the running surfaces of the cutting teeth. This is achieved in a simple manner by a correspondingly rounded design of the embossing zones in the upper tool part 47 of the further embossing device 45. The intermediate product obtained in the final embossing process according to FIG. 11, that is to say the knife blank 50 obtained, is shown in FIG.

The knife blank 50 shown in FIG. 12 is then hardened together with its third cutting tooth blanks 48 in a further working step, which can be done by means of generally known technologies.

The hardened knife blank 50 is then fed to a grinding device, not shown, in which, in a further step, the third Cutting tooth blanks 48 of a knife are ground in the area provided for forming the running surfaces of the cutting teeth to form defined running surfaces 15 and sharp cutting edges 51. After this grinding process, the cutting teeth 11 of the tooth knife 10 produced are obtained which have a total height H which is somewhat less than the original band thickness D of the steel band 32. After the grinding process for grinding the treads 15, the method for producing the tooth knife 10 is essentially completed. Instead of a grinding process, a lapping process can also be used to produce the defined running surfaces 15.

In a tooth cutting device with completely rounded cutting teeth, as explained with reference to the exemplary embodiment described above, it is achieved in a very simple manner that the cutting teeth - apart from their sharp cutting edges - have no sharp edges at all, so that when a tooth cutting device is moved along with tooth knives with such perfectly rounded cutting teeth along the skin, scratching, injuring and irritating the skin is not possible. In this way, a gentle cutting behavior is always guaranteed.

A method for producing tooth knives with completely rounded cutting teeth, as explained above, offers the significant advantage that the completely rounded design of the cutting teeth is carried out in a particularly simple manner by pre-stamping and a final stamping of the cutting teeth that takes place after a cutting process has been carried out in the meantime. Such completely rounded cutting teeth can be produced in a particularly simple manner by an embossing process. Furthermore, such an embossing process is particularly advantageous because with such an embossing process it is possible to achieve cutting angles in a relatively large angular range in the region of the cutting edges of the cutting teeth.

The invention is not restricted to the exemplary embodiment described above. According to the described embodiment, the device for cutting hair is formed by a razor with a tooth cutting device. The measures according to the invention can also be advantageously used in other devices for cutting hair, for example in what are known as hair trimmers or beard trimmers have an essentially elongated rod-shaped housing, a tooth cutting device being provided at least in the head region of the housing. For example, such devices are disclosed in EP-A1-0 325 326 and US-A-5 054 199.

Claims (8)

Device for cutting hair with a tooth cutting device, which has a stationary knife with at least one row of cutting teeth and a reciprocating knife with at least one row of cutting teeth, the cutting teeth having treads and the two knives with at least part of the treads their cutting teeth abut each other and the cutting teeth of at least one of the two knives are rounded at their free ends except in the area of their treads, characterized in that the cutting teeth of the at least one knife which is rounded at their free ends except in the area of their treads Has cutting teeth, are also completely rounded over their entire tooth depth into the tooth root area except in the area of their running surfaces. Device according to claim 1, characterized in that the cutting teeth of both knives are completely rounded over their entire tooth depth down to the tooth root area except in the area of their running surfaces. Apparatus according to claim 1 or 2, characterized in that the two knives are formed by metal stamped parts and the rounding of the cutting teeth have been produced in one stamping process. Method for producing a knife for a tooth cutting device of a device according to one of claims 1 to 3, characterized in that an unhardened steel strip with a predetermined strip thickness D is transported step by step to a subsequent step tool device and that in a first subsequent step a pre-stamping of the steel strip to produce pre-stamped The first cutting tooth blanks of a knife take place, the pre-stamped first cutting tooth blanks remaining connected via a steel band bridge embossed during the pre-embossing with a bridge thickness d that is smaller in relation to the band thickness D, and that the steel band bridge connecting the pre-embossed first cutting tooth blanks is then cut away in a second step and hiebei at the same time second cutting tooth blanks of a knife are cut out of the first cutting tooth blanks and that after this, in a third subsequent step, the second cutting tooth blanks are finished-stamped to produce finished embossed third cutting tooth blanks of a knife, the third cutting tooth blanks being finished from their free ends over their entire tooth depth to this finished stamping into the tooth root area except in the area provided for the formation of the running surfaces of the cutting teeth. A method according to claim 4, characterized in that during the pre-embossing in the first subsequent step, a steel band bridge with a bridge thickness d, which is at most 75% of the band thickness D, is embossed. A method according to claim 5, characterized in that a steel strip bridge with a bridge thickness d, which is at most 30% of the strip thickness D, is stamped during the pre-stamping in the first subsequent step. Method according to claim 4, 5 or 6, characterized in that after the third subsequent step in the subsequent step tool device, the knife blank obtained here and its third cutting tooth blanks are hardened in a further working step. A method according to claim 4, 5, 6 or 7, characterized in that, in a further step, the third cutting tooth blanks of a knife are ground in the area provided for forming the running surfaces of the cutting teeth to form defined running surfaces and sharp cutting edges.

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