EP2768638B1 - Cutting system for a hairclipper - Google Patents

Description

Object of the invention

The present invention relates to a cutting system for a hair trimmer. It relates more particularly to a movable blade having a plurality of teeth of different height and angle of attack.

State of the art

Hair clippers are now used by both hairdressers and the general public. Lawnmowers for hairdressing professionals are nevertheless more powerful because they are either directly connected to the 230 V sector, or equipped with powerful batteries allowing the use of knives producing a quasi perpendicular cut of the hair. This type of mower has movable blades with deep (long) teeth that do not suffer any limitation in terms of the angle of attack of the hair because very powerful torques of force are available.

The mowers are much less powerful and must reconcile the angle of attack of the hair (angle of opening of the teeth), and thus the mowing capacity and the power available. This compromise is reflected in particular by the configuration of the teeth on the movable blade, whose geometric shape must be adjusted to this constraint. To obtain a good cutting capacity, one must open (enlarge) the angle of opening of the teeth but to keep a sufficient number of teeth, the hollows must be shallow which does not allow to cut a lot of hair in few time.

In addition, manufacturers are looking for optimized manufacturing methods to be able to offer a lower cost product to the general public. Among these methods, etching, or "etching" in English, has a considerable advantage provided that the blade to be treated is sufficiently thin.

The "etching" method consists in printing a layer of polymer or protective wax on a steel strip and then treating it with an acid to create recesses in unprotected areas. Unaffected areas will be the blade teeth.

We are therefore faced with two constraints, the first being the limited power of a "general public" lawnmower and the second being the relatively limited thickness of the mobile blade to be able to practice chemical erosion ("etching"). By limited thickness, we mean a dimension less than mm, and preferably less than 0.5 mm.

The low blade thicknesses and the limited power thus impose not only a rather large angle of attack of the "guillotine" type of hair, but also a relatively short tooth, since a fine and long tooth would tend to break because of the small thickness. of the blade.

On the other hand, it is necessary to have a certain depth (length) of tooth to not hinder the mowing ability.

The problem of optimizing cutting systems of lawnmowers has been studied in the prior art. The documents FR 2 398 584 , US 2006/0156549 , GB 2,435,845 and DE 10 2009 035 232 A1 are particularly representative of this type of study, although they are not dedicated to the optimization of a cutting system of a mower "general public" as we evoke in this patent application.

Goals of the invention

The present invention aims to provide an optimized cutting system for a mower "general public". This optimization concerns both the cutting performance with the handicap of a relatively limited power and the reduction in manufacturing cost by using a thin blade that can be manufactured by "etching".

More particularly, the present invention aims to establish a practicable geometry on a thin blade for a mower "general public" and for a mode particular of the invention, a relationship between the geometry of the teeth of the movable blade and the force available for mowing.

Main characteristic elements of the invention

• le rapport x/y est compris entre 1,33 et 6 ;
• le rapport β/α est compris entre 1,2 et 3,55 ;

avec

• α compris entre 9° et 15° ;
• β compris entre 18° et 32°.

The present invention discloses a cutting system for a hair clipper having a movable blade and a fixed blade, said movable blade moving, in use, in a back and forth motion with a force F, characterized in that said moving blade comprises a number of teeth N of two different lengths (x) and (y) and having two angles of attack α and β, the relationship between the two lengths and the angles of attack being defined as follows:

• the ratio x / y is between 1.33 and 6;
• the ratio β / α is between 1.2 and 3.55;

with

• α between 9 ° and 15 °;
• β between 18 ° and 32 °.

• De préférence la relation entre les deux longueurs et les angles d'attaque est:
  • le rapport x/y est compris entre 1,5 et 3 ;
  • le rapport β/α est compris entre 1,42 et 2,8 ;
  avec
  • α compris entre 10° et 14° ;
  • β compris entre 20° et 28°.
• De préférence la relation entre les deux longueurs et les angles d'attaque est:
  • le rapport x/y est compris entre 1,54 et 2,6 ;
  • le rapport β/α est compris entre 1,61 et 2,36 ;
  avec
  • α compris entre 11° et 13° ;
  • β compris entre 20° et 24°.
• Les variables (x, y) et α, β sont ajustées de telle manière que le nombre de dents N sur une lame mobile donnée reste constant.
• La longueur (x) est constante et que les seules variables sont la longueur (y) et les angles α et β.
• De préférence la somme α + β est constante.
• De préférence (x) est compris entre 2mm et 4mm, de préférence entre 2 et 3mm, et que (y) est compris entre 0,3mm et 2mm, de préférence entre 0,5 et 1,5mm.
• De préférence F est inférieur à 16 N et de préférence inférieur à 13 N
• De préférence les lames ont une épaisseur inférieure à 1 mm, de préférence inférieure à 0,8mm, de manière particulièrement préférée inférieure à 0,6 mm.

Particular embodiments of the invention have at least one or a suitable combination of the following features:

• Preferably the relationship between the two lengths and the angles of attack is:
  • the ratio x / y is between 1.5 and 3;
  • the ratio β / α is between 1.42 and 2.8;
  with
  • α between 10 ° and 14 °;
  • β between 20 ° and 28 °.
• Preferably the relationship between the two lengths and the angles of attack is:
  • the ratio x / y is between 1.54 and 2.6;
  • the ratio β / α is between 1.61 and 2.36;
  with
  • α between 11 ° and 13 °;
  • β between 20 ° and 24 °.
• The variables (x, y) and α, β are adjusted in such a way that the number of teeth N on a given moving blade remains constant.
• The length (x) is constant and the only variables are the length (y) and the angles α and β.
• Preferably the sum α + β is constant.
• Preferably (x) is between 2mm and 4mm, preferably between 2 and 3mm, and (y) is between 0.3mm and 2mm, preferably between 0.5 and 1.5mm.
• Preferably F is less than 16 N and preferably less than 13 N
• Preferably the blades have a thickness of less than 1 mm, preferably less than 0.8 mm, particularly preferably less than 0.6 mm.

Brief description of the figures

The figure 1 and 2 represent a plan view of a movable blade of the prior art provided for a high power mower with a large tooth length.

The figure 3 and 4 represent a plan view of a movable blade of the prior art provided for a "general public" mower with a shorter tooth length.

The figure 5 to 10 represent plan views of a series of possible configurations of a moving blade portion according to the invention, wherein the parameters (y) have been varied between 0.5 and 1.8 mm, and α between 9 ° and 15 ° and β between 18 ° and 30 °. Other configurations were tested where, in addition to the previous parameters, the parameter (x) was varied. For reasons of economy of figures, however, they have not been represented.

The figure 11 represents the method of measuring the force exerted by the movable blade, in use, during its back-and-forth movement.

The figure 12 represents a detail view in 3 D of the head of the mower provided with the movable blade according to the invention.

Detailed description of the invention

The performance of a hair clipper depends on many factors that can be all the more limiting as the power available is low.

Without pretending to be exhaustive, mention may be made of the geometry of the movable blade and the fixed blade, and in particular the length and the angles of opening of the teeth, the sharpening angles and the number of teeth, the lubrication facilitating the back-and-forth motion, and the speed of this movement, the pressure of the moving blade on the fixed blade, & c.

Optimizing the cutting system of a hair trimmer is therefore a multifactorial problem. The present patent application has deliberately chosen to approach this problem by one of its preponderant parameters, which is the geometry of the teeth on the moving blade. This geometry is conditioned by the opening angles combined with the length of the teeth.

The present invention does not take into account a possible adaptation of the geometry of the teeth of the fixed blade to the teeth of the movable blade. It is therefore considered that the fixed blade invariably has regular teeth of generally triangular shape and whose length slightly exceeds that of the movable blade to avoid possible injury to the scalp. Nevertheless the following discussion could also apply to the fixed blade.

In order to find the best compromise between the available force torque and the opening angle of the teeth, the tooth of the movable blade has been configured to obtain a fairly long tooth with a closed opening angle. It has a shape that is in a way the synthesis between the narrow long teeth generally present on high power mowers (see Fig. 1 ) and the short teeth used so far on low-power "consumer" mowers (see Fig. 1 and 2 ).

The process of manufacturing blades by "etching" allows only the realization of very thin blades with a very sharp profile. Nevertheless, in this case, the longer the tooth, the more fragile it is. To overcome this fragility, we cut the tip of the tooth and dig it to obtain a double tip with different angles (α, β - see Fig. 3.4 and 5 ).

The variables studied in this patent application are the lengths x and y and the angles α and β (see figures). The influence of the sharpening angles of the moving and stationary blades has been deliberately ignored. We consider here simply that a Optimal sharpening has been practiced to focus on the other parameters mentioned above.

The force F exerted by the movable blade was measured with a dynamometer. The scheme of this measure is shown in figure 8 .

Tests were carried out with mowers of different power which made it possible to delimit the parameters F, x and y and the angles α and β. For values of α less than 9 ° and values β less than 18 °, the number of teeth N per unit length is relatively high if the x / y ratios are low, for example less than 1.33. This case is close to the blades provided for professional mowers and requires high power. On the other hand, the relatively long teeth need a relatively large blade thickness and run counter to the use of "etching" technology for this type of blade.

For values of α greater than 15 ° and values β greater than 32 °, the number of teeth N per unit length is relatively small if the x / y ratios are high, for example greater than 6. This case does not occur. does not require high power and allows the use of etching technology for this type of blade. The mowing capacity of this type of blade is however relatively limited.

Between the two extremes described above, a whole series of configurations are of course possible. However, it has been determined experimentally that for a blade having a thickness of less than 0.6 mm, values of x greater than 5 mm, preferably greater than 4 mm, are difficult to practice for issues of fragility of the blade. Furthermore, the values of x less than 1 mm, preferably less than 2 mm, are not really useful in practice because they limit too much the cutting capacity.

In that the object of the present invention was to provide a blade for a "general public" mower, we conducted the tests with lawn mowers of this type. These are not able to deliver forces on the moving blade exceeding about 20 N, they are generally even less than 15 N.

The most conclusive tests have been shown in the table below. They are merely illustrative, and in no way intended to limit the scope of the present invention. These tests nevertheless made it possible to delimit approximately the ranges of the lengths and ratios of the length of the teeth as well as the practicable angles on a relatively thin movable blade. The table below shows that a powerful mower can be obtained with a judicious combination of opening angles and tooth lengths, even for a force delivered to the blade of less than 16 N. Trial X (mm) Y (mm) x / y α ° β ° β / α F (N) Evaluation section 1 2 1.5 1.33 9 18 2 15 satisfactory 2 2.5 1 2.5 13 25 1.92 15 good 3 3 0.5 6 15 32 2.13 15 satisfactory 4 2 1.5 1.33 9 32 3.55 15 satisfactory 5 3 0.5 6 15 18 1.2 15 satisfactory 6 2.5 1.5 1.33 11 20 1.81 15 good 7 2.5 1 2.5 12 24 2 15 Very good 8 2.5 1 2.5 12 24 2 12 good 9 2.5 1 2.5 11 22 2 12 good 10 2.6 1.1 2.36 12 22 1.83 12 Very good 11 2.6 1.8 1.44 9 18 2 12 satisfactory 12 2.6 0.5 5.2 15 30 2 12 satisfactory 13 2.35 1.31 1.79 12.5 22 1.76 12 Very good

Claims (11)

1. A cutting system for a hair clipper comprising a moving blade and a stationary blade, said moving blade moving, during use, in a back-and-forth movement with a force F, characterized in that said moving blade comprises a number of teeth N with two different lengths (x) and (y) and having two angles of attack α and β, the relationship between the two lengths and the angles of attack being defined as follows:

   - the ratio x/y is comprised between 1.33 and 6;

   - the ratio β/α is comprised between 1.2 and 3.55;

   with

   - α comprised between 9° and 15°;

   - β comprised between 18° and 32°.
2. The cutting system according to claim 1, characterized in that the relationship between the two lengths and the angles of attack is such that:

   - the ratio x/y is comprised between 1.5 and 3;

   - the ratio β/α is comprised between 1.42 and 2.8;

   with

   - α comprised between 10° and 14°;

   - β comprised between 20° and 28°.
3. The cutting system according to claims 1 or 2, characterized in that the relationship between the two lengths and the angles of attack is such that:

   - the ratio x/y is comprised between 1.54 and 2.6;

   - the ratio β/α is comprised between 1.61 and 2.36;

   with

   - α comprised between 11° and 13°;

   - β comprised between 20° and 24°.
4. The cutting system according to any one of the preceding claims, characterized in that the variables (x, y) and α, β are adjusted such that the number of teeth N on a given moving blade remains constant.
5. The cutting system according to any one of the preceding claims, characterized in that the length (x) is constant and the only variables are the length (y) and the angles α and β.
6. The cutting system according to any one of the preceding claims, characterized in that the sum α + β is constant.
7. The cutting system according to any one of the preceding claims, characterized in that (x) is comprised between 2 mm and 4 mm, preferably between 2 and 3 mm, and (y) is comprised between 0.3 mm and 2 mm, preferably between 0.5 mm and 1.5 mm.
8. The cutting system according to any one of the preceding claims, characterized in that said force F is less than 16 N.
9. The cutting system according to any one of the preceding claims, characterized in that said force F is less than 13 N.
10. The cutting system according to any one of the preceding claims, characterized in that said blades have a thickness smaller than 1 mm, preferably smaller than 0.8 mm, particularly preferably smaller than 0.6 mm.
11. A hair clipper comprising a cutting system according to any one of the preceding claims.

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