Devices for measuring hair characteristics

Abstract

The present invention provides a device for measuring hair properties, comprising a first part (I) and a second part (II), between which a hair (H) is guided. The first part (I) comprises a measuring probe (MP), and the second part (II) is arranged to deform the hair (H) against the measuring probe (MP). When the device is moved along the hair (H), the measuring probe (MP) is subjected to a friction force generated by the hair (H) being guided along the measuring probe (MP) and a deformation force (DF) generated by the hair (H) being deformed by the second part (II) against the measuring probe (MP). Advantageously, the second part (II) comprises a pressure element (PB, S) for pressing the hair (H) against the measuring probe (MP) to compress the hair (H). In an alternative embodiment, the second part (II) comprises: an alignment element (AE) located on opposite sides of the measuring probe (MP) for bending the hair (H) on the measuring probe (MP), and a guiding element (G) for reducing the influence of the angle at which the device is applied to the hair (H) on the friction force and / or the deformation force, while the measuring probe (MP) is mounted on a load cell module (LC‑X, LC‑Y) for measuring the load in two-dimensional space to measure the friction force and deformation force respectively.

Description

Technical Field

[0001] The present invention relates to a device for measuring hair characteristics. Background Art

[0002] US 2009 / 0071228 A1 discloses a method for measuring the surface smoothness of hair using a handheld friction sensor comprising a clamping member and a load cell. A key indicator of the overall condition of hair is friction. Load cells are well known in the art of measuring friction and can be easily incorporated into various devices. A tuft of hair is placed between the clamping member and the load cell, and the clamping member is closed, which produces a substantially constant normal force on the hair sample and the load cell. The device is pulled across the hair tuft in a root-to-tip direction at a substantially constant rate, and the coefficient of friction of the material generates a voltage in the load cell that is correlated with the hair smoothness value based on the measured coefficient of friction.

[0003] DE 2719482 A1 discloses a professional hairstylist's comb that incorporates a strain gauge that can be used to quantitatively assess the effectiveness of various hair treatments by measuring the resistance to combing the hair before and after the treatment. The steel comb has a strain gauge mounted approximately between the teeth and the handle, with a cable and plug fitting. As the hair is combed, readings are obtained from a circuit connected to the strain gauge, which measures the deflection of the comb and the resistance to combing the hair.

[0004] FR2442607 A1 discloses a flexible plastic comb with a metal plate riveted to the comb and supporting a sensor consisting of four strain gauges connected in a bridge arrangement. The bridge is powered by a battery connected to one of its diagonals. A cable allows the battery to be located in a counter circuit and also allows the bridge output to be applied to a voltage-to-frequency converter. The output is used in a pulse counter with a digital readout. The counter reading is proportional to the force required to detangle the hair. This arrangement allows the relative performance of different shampoos to be compared.

[0005] US4167869 A discloses a device for measuring the increasing combing force applied to a tress of hair during combing and providing an instantaneous readout of this force. The device comprises a comb or brush with strain gauges attached thereto that change resistance when mechanically deformed. The change in resistance is measured electrically to provide an indication of the increasing combing force. A continuous monitor is connected to the resulting electrical signal to provide an instantaneous indication of the increasing combing force.

[0006] US2010147323 A1 provides a hair styling device with two arms. Each arm has a styling section that cooperates with a styling section on the other arm to perform a hair styling operation. At least one of the styling sections is designed to heat hair inserted into a hair shaping gap between the styling sections. A pressure measuring device is included in one of the two arms. The pressure measuring device detects the pressure applied to the hair between the styling sections when the hair styling gap is closed, or a value representing this pressure. The hair styling device also includes a display device for displaying the pressure or pressure value detected thereby.

[0007] EP1958531 A1 discloses an ultrasonic hair styling device comprising a main frame, an ultrasonic vibration generating component disposed on the main frame and generating ultrasonic vibrations, and a burn prevention component that prevents parts of the human body other than hair from contacting the vibrating surface of the ultrasonic vibration generating component. Embodiments further include a pressing component having a pressing surface for pressing hair against the vibrating surface; a pressure detection sensor for detecting pressure applied to the pressing surface; and a drive circuit for driving the ultrasonic vibration generating component to generate ultrasonic vibrations only when the pressure detected by the pressure detection sensor is equal to or greater than a predetermined pressure. Summary of the Invention

[0008] It is an object of the present invention, inter alia, to provide an improved device for measuring hair properties. The invention is defined by the independent claims. Advantageous embodiments are defined in the dependent claims.

[0009] Embodiments of the present invention provide a device for measuring hair characteristics. The device comprises a first portion and a second portion, between which hair is guided. The first portion includes a measurement probe, and the second portion is configured to deform (e.g., squeeze or bend) the hair against the measurement probe. When the device is moved along the hair, the measurement probe is subjected to frictional forces generated by the hair being guided along the measurement probe, and deformation forces generated by the hair being deformed by the second portion against the measurement probe.

[0010] The second portion may include a pressure element for pressing the hair against the measurement probe, thereby compressing the hair. Preferably, when the hair is guided between the pressure element and the measurement probe, this compression occurs by pushing the pressure element in the direction of the measurement probe, while the hair is not compressed before being guided between the pressure element and the measurement probe. One of the pressure element and the measurement probe may include a pin, while the other may include a hole for accommodating the pin. A spacer may be applied between the first and second portions to provide a minimum gap between the measurement probe and the pressure element. The minimum gap may have a width of approximately 0.2 mm.

[0011] In an alternative embodiment, the second part includes: alignment elements located on opposite sides of the measuring probe, for bending the hair against the measuring probe, and guiding elements for reducing the influence of the angle at which the device is applied to the hair on the friction and / or deformation force, while the measuring probe is mounted on a load cell module for measuring the load in two-dimensional space to measure the friction and deformation force respectively.

[0012] The hair measurement can be embedded in a hair styling device having a treatment plate. If so, the measurement probe is preferably positioned along the treatment plate, and advantageously, the length of the measurement probe is substantially matched to the length of the treatment plate.

[0013] Preferably, the measuring device further comprises an arrangement for compensating for the weight of the measuring probe. The arrangement advantageously comprises an accelerometer for measuring the force of gravity in the measuring direction of the measuring probe.

[0014] These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A shows an embodiment of a device for measuring hair properties embedded in a hair styling device;

[0016] Figure 2 An embodiment of a first mode of implementing the present invention is illustrated;

[0017] Figure 3 An embodiment of a stand-alone device for measuring hair characteristics is shown;

[0018] Figures 4A to 4D The diagram illustrates the principle of an embodiment of a first mode of implementing the present invention;

[0019] Figure 5 A second embodiment of an apparatus for measuring hair characteristics according to the first mode of carrying out the invention is shown;

[0020] Figure 6 A third embodiment of an apparatus for measuring hair characteristics according to the first mode of carrying out the present invention is shown;

[0021] Figure 7 An embodiment of an embodiment of a second mode of carrying out the invention is shown;

[0022] Figure 8 Shown for Figure 7 The load cell module of the embodiment;

[0023] Figures 9A to 9B An embodiment of a stand-alone hair characteristic measuring device according to a second mode of implementing the present invention is shown;

[0024] 10A to 10D An embodiment of the measuring device as part of the top side of the brush is illustrated;

[0025] Figures 11A to 11C Another embodiment of the measuring device of the present invention is shown; and

[0026] 12A to 12E An embodiment of a brush is shown which has a measuring device on the side where the bristles are located. DETAILED DESCRIPTION

[0027] In the field of hair care, it is desirable to analyze and assess hair condition and / or hair health. Women tend to judge their hair by running their fingers through it and combing it. One embodiment provides a product in which the principle determining "hair feel" (i.e., a combination of the surface roughness of the hair and the ease with which a lock of hair deforms) is measured outside of a laboratory environment using a separate analyzer and converted into an indication of hair health.

[0028] A first set of embodiments of the present invention can determine and quantify hair characteristics by using a single sensor to measure a combination of surface friction and squeezeability of a strand of hair. This combination of friction and squeezeability is closely related to how human fingers assess hair. The sensor can include a measuring probe (e.g., a load cell, e.g., cylindrical in shape) and a counterpart that presses the strand of hair against the measuring probe with a constant force. By pulling the strand of hair between the measuring probe and a pressure bar, the reaction force is measured by the load cell. By filtering and processing the measured values, the hair characteristics are derived. The device quantifies "hair feel" by measuring a combination of surface friction and squeezeability, while being small enough to fit into a hair styling device or other handheld device, requiring no special handling for operation, and integrating into the styling process. "Hair feel" is best described as a combination of the surface roughness of the hair and the ease with which a strand of hair can be deformed (squeezability). To this end, embodiments of the measuring device include the following key features:

[0029] • Measurement of the combination of friction and hair strand deformation using only two contact elements.

[0030] • Hair strands are trapped simply by the opening and closing action.

[0031] A sensor measures a combination of friction and deformation, where the ratio of the contributions of friction and deformation can be controlled by varying the geometry of the two contact elements. One of the contact elements is also used to measure the force (e.g. via a measuring probe).

[0032] In an embodiment, the sensor is incorporated into a styling device, such as a hair straightener, but the sensor could alternatively be incorporated into other devices having on / off functionality or into a standalone device.

[0033] Figure 1 An embodiment of a device for measuring hair properties is shown, embedded in a hair styling device HS having a treatment plate HP. The treatment plate HP may be a conventional heating plate of a hair iron, or, in the case of hair styling using light radiation, a transparent plate. A measuring probe MP is located next to the treatment plate HP on the lower leg I of the hair styling device HS. Figure 1 The arrow in A indicates the direction of hair movement.

[0034] Figure 2 The figure shows an embodiment of the first mode of implementing the present invention. Figure 2 In the embodiment of the present invention, in the upper leg II of the hair styling tool HS there is a pressure element formed by a pressure rod PB pushed downwards by a spring S. In the lower leg I of the hair styling tool HS, below the measuring probe MP, there is a load cell LC.

[0035] Figure 2 The embodiment has the following 4 key components:

[0036] Measurement probe MP: A cylindrical element (but not necessarily cylindrical) with a certain diameter (e.g., 5 mm, but not limited to this dimension), a certain length (e.g., 90 mm, but can be any length of at least 5 mm), and a certain roughness. Roughness is a very important parameter for the measurement results, but is preferably low to minimize the effects of contamination. Roughness and cylinder diameter will affect the ratio of the contributions of surface friction and deformation forces. Preferably, if the measurement probe MP is embedded in a hair straightener HS, the length of the measurement probe MP is equal to the length of the treatment plate HP to prevent hair from being easily squeezed out of the measurement system. The length of the measurement probe MP generates momentum in the load cell LC that measures friction and deformation (e.g., squeezing) forces, resulting in a sensor signal that depends on the position at which the hair strand H contacts the measurement probe MP. This problem can be solved simply by using a parallel hinge structure, as can also be seen in load cells used in scales.

[0037] Load cell LC: In an embodiment, this may be a standard shear-type strain gauge sensor with a maximum load of 1 N. It is mounted on the measurement probe MP in such a way that the measuring direction is perpendicular to the clamping direction. The sensor is not limited to this type of sensor but can be any type of force measurement system. For example, a piezoelectric load cell can be used.

[0038] Pressure bar PB: This element forces the hair strand to rub against the probe, making it possible to measure the reaction force. In the example, the element has a flat surface, but the geometry strongly influences the ratio of the contribution of the surface friction and the deformation forces.

[0039] Pressure spring S: When the device is closed, this element presses the pressure rod PB against the measuring probe MP with a defined force. Therefore, when a hair is between the pressure rod PB and the measuring probe MP, it is compressed with a defined force. In this example, the spring preload is 0.75 N. Lower forces produce lower signal amplitudes. Higher forces produce a better signal but also pull the hairs more against the head. The force also affects the ratio of friction to deformation force.

[0040] Figure 3 An embodiment of a stand-alone device for measuring hair characteristics is shown. Figure 3 Only the measuring probe MP is shown, but in the upper part II of the device there is a pressure rod PB pushed downwards by a spring S, and in the lower part I of the device there is a pressure rod PB pushed downwards by a spring S. Figure 2 As in , there is a load cell LC where it is attached to the measurement probe MP.

[0041] Figures 4A to 4D The diagram illustrates the principles of embodiments of the present invention belonging to the first group of embodiments. Figure 4A A lock of hair H is shown falling from a person's head. Figure 4B The diagram shows that, on one side, the measuring probe MP is placed against the hair strand H. When the hair styling device HS is closed, the pressure bar PB is pressed against the opposite side of the measuring probe MP, with the hair strand H trapped between them. The pressure spring S ensures a constant force. By moving the device in the downward direction, the hair strand H is pulled through the system. Figure 4C As shown, the reaction force RF on the sensor occurs in two ways (measurement direction consistent with the arrow in the figure):

[0042] • Due to the normal force NF of the pressure bar PB, on the opposite side of the measuring probe MP the pure surface friction force F of the hair lock H will be measured.

[0043] Due to the squeezing action which generates the deforming force DF, the hair lock H will push against the lower part of the measuring probe MP, generating a reaction force RF. The amplitude of this force depends largely on how easy it is to squeeze the hair lock H and therefore on the properties of the hair.

[0044] Figure 4DAn example of how the ratio between the surface friction force and the deformation force DF can be varied is shown. The hair bending element HB on the pressure bar PB pushes the hair strand H, making it harder to squeeze, thereby generating a greater reaction force on the lower part of the measuring probe MP. However, many different implementations are conceivable.

[0045] An important aspect of hair characteristics is the degree of entanglement of hair strands. It is difficult to determine this entanglement based solely on surface friction and deformation. Figure 5 In the embodiment shown, a pin EP is mounted on the measuring probe MP, and a hole HL is formed in the pressure bar PB. By combing the hair strands together, it is possible to determine if the hair strands are tangled. One embodiment is shown in the figure, while another embodiment is one in which the pin can be easily attached and detached.

[0046] Although the results of the above-described measurement system are satisfactory, the signal can be contaminated by pulling on a few hairs. As long as there are enough hairs between the measuring probe MP and the pressure bar PB, the contact pressure is relatively low. When there are only a few hairs in the system, which usually happens at the end of a hair strand, the pressure increases sharply, causing the hair to deform (Hertzian contact pressure) and thus to clamp. Not only will the output of the sensor be contaminated with unrealistic values, but the user will also feel pain on his head. For this purpose, in Figure 6 In an embodiment of the present invention, a spacer is applied between the first part I and the second part II to provide a guaranteed gap between the measuring probe MP and the pressure bar PB. It is sufficient to provide a guaranteed opening of about 0.2 mm between the measuring probe MP and the pressure bar PB. This size is based on the maximum thickness of the hair. In order to reduce the chances of hair being trapped, the element used to create the gap should be narrow. One possible way to meet these two requirements is to apply a wire with a diameter of 0.2 mm around the pressure bar PB or the measuring probe MP. In another implementation, a narrow element with a height of about 0.2 mm can be fixed to the measuring probe MP or the pressure bar PB. Figure 6 In the embodiment shown, a 0.2 mm thick wire W is provided on the measuring probe MP to provide a 0.2 mm gap G. In yet another embodiment, narrow elements can be stamped into the measuring probe MP or the pressure bar PB. The width of the spacer is limited by the fact that the high pressure of the spacer on the opposing element should not exceed the maximum permissible contact pressure.

[0047] By using a single sensor to measure the combined surface friction and squeeze of a lock of hair, the above-described embodiments of the present invention are able to determine and quantify hair characteristics. The sensor is intended for use in an uncontrolled user environment and should be able to measure subtle differences in the forces acting on the hair. Preferred embodiments of the present invention are based on the recognition that changes in the orientation of the device due to user manipulation of the device can result in significant errors caused by the weight of the measurement probe. By measuring the contribution of the weight in the measurement direction, the effect of the weight of the measurement probe can be compensated. Advantageous embodiments use a unidirectional accelerometer to provide compensation for the weight.

[0048] The hair styler can be used in all possible orientations. Friction and deformation forces are measured using a measurement probe with a certain weight. In an embodiment, this weight is added to the friction signal according to the orientation of the styler and based on the direction of the gravity vector. Because the weight of the measurement probe can be significant in the signal, the contribution of the weight is advantageously eliminated from the force sensor reading. The main element of this embodiment is to know the instantaneous contribution of the measurement probe weight to the signal of the deformation force sensor. To this end, the embodiment uses:

[0049] a unidirectional absolute accelerometer (or another unidirectional sensor that determines the contribution of gravity in the measurement direction of the deformation force sensor) located along the direction of the measurement direction, and

[0050] • Known weights of measurement probes.

[0051] The resulting output is not affected by the weights:

[0052] Friction and deformation force [N]

[0053] = sensor output [N] - (accelerometer output [m / s 2 ]*weight[g])

[0054] In an embodiment, compensation involves:

[0055] A sensor that measures the force of gravity in the same direction as the deformation force sensor. In the example, this is implemented using a standard accelerometer (such as those used in smartphones). Another implementation could be a second force sensor with a mass located in the same direction as the deformation force sensor with the measurement probe. This second force sensor is able to measure the contribution of gravity to the measurement signal. In practice, to meet the requirement of measuring in the same direction for both systems, the deformation force sensor and the accelerometer are mounted on the same structure in the measurement device.

[0056] • Knowledge of the weights of measurement probes.

[0057] Most likely (but not necessarily) a microcontroller subtracts the accelerometer compensation data from the deformation force sensor signal to obtain the "true" force signal. Another implementation might be analog subtraction circuitry when an analog sensor is used to derive the gravity contribution. There might even be no circuitry at all when the same sensor is used for both force and gravity sensing, where the mass attached to the gravity sensor is equal to the mass of the measurement probe. In this case, the signals can be directly subtracted from each other to produce the compensated force signal.

[0058] If the orientation of the deformation force sensor is at an angle to the z-axis of the world coordinate system due to the user's handling of the device Where the z-axis is in the negative direction of the earth's gravity, the output of the force sensor during use will be:

[0059]

[0060] Because the orientation of the accelerometer is mechanically coupled to the orientation of the deformation force sensor, the output of the accelerometer will be:

[0061]

[0062] Together with the known weight of the measurement probe, the microcontroller can calculate the compensation by multiplying the accelerometer output with this known weight:

[0063] Calculated compensation

[0064]

[0065] If, when measuring the deformation force, the compensation is added to the signal, only the required friction force is determined by the measuring system:

[0066]

[0067] In order to ensure that the contribution of acceleration due to movement is lower than the gravity, the weight of the measuring probe is preferably as low as possible.

[0068] A second way of implementing the invention provides a hair health analyzer that is able to determine and quantify hair characteristics by determining the relative friction coefficient using two sensors (which can again be implemented as load cells). The basic principle of an embodiment of the second way of implementing the invention is to use the bending stiffness of the hair to apply a deformation force formed by a normal force to a surface to measure the dynamic friction coefficient of the hair strand and along the length of the hair strand. One sensor (load cell LC-Y in the Y direction) measures the surface friction between the hair and the measuring probe, and the other sensor (load cell LC-X in the X direction) measures the dynamic bending stiffness of a strand of hair (which is the normal force applied to the surface of the measuring probe). The sensor combination is installed in a hair analyzing device or a hair styling device, such as Figure 1 As shown. Using the hair health analyzer, a lock of hair is clamped between two pins and a measuring probe, and the hair health analyzer is pulled from the tip to the root. The relative friction coefficient can be calculated using the output of the two sensors through a hair health algorithm.

[0069] An embodiment of the device uses the combined output of two sensors to quantify "hair feel" by determining the coefficient of friction. Simultaneously, the sensors separately measure two forces: one associated with the motion of the two surfaces interacting, and the other perpendicular to the axis of pull, namely friction and normal force. The normal force is generated by forcing the hair to bend over the measurement probe. While small enough to fit into a separate analyzer, the two sensor outputs are used to determine the coefficient of friction over time, which limits the need for special handling for operation and can be easily used by consumers and outside of controlled laboratory environments.

[0070] An embodiment provides a measurement device wherein the friction and deformation forces (here: bending forces) of the hair are determined using the following key features:

[0071] Use the 3-point bending stiffness tester for:

[0072] Deformation measurement of a hair strand by measuring the deformation force (here: bending force) perpendicular to the direction in which the hair strand is pulled.

[0073] A normal force is applied to the sensor surface, and the bending force of the hairs is used to detect friction.

[0074] The hair strands are trapped simply by the opening and closing motion.

[0075] Two sensors are used to measure the dynamic bending force (X direction) and friction force (Y direction) along the length of the hair strand simultaneously, and the ratio of friction force to bending force can be adjusted by changing the three components of the test system (i.e., two supports and a measuring probe (see Figure 7 The dynamic relative coefficient of friction along a hair strand can be determined using two sensors.

[0076] The embodiment shown in Figure 7 includes four key components:

[0077] 1. Measurement probe MP: A cylindrical element (but not necessarily cylindrical) with a certain diameter (here, 6 mm, but not limited to this size), a certain length (here, 12 mm, but can have any length), and a certain roughness (here, Ra of ~0.3, but can have any surface roughness). The friction between two surfaces is a function of the surface roughness and the contact surface area. Roughness and surface contact area are expected to affect the ratio of the friction coefficients, due to an increase or decrease in surface friction.

[0078] 2. Load cell module (see Figure 8 ): In this case, standard shear type strain gauge sensors with a maximum load of 1N (Y direction) and 7.8N (X direction). They are mounted in such a configuration that both sensors measure in the desired direction without affecting each other. The sensor is not limited to this type of sensor, but can be any kind of force measurement system. The load cell module includes a first load cell LC-Y connected to the measuring probe MP in the Y direction, a connecting piece CP and a second load cell LC-X in the X direction. The second load cell LC-X has a surface RW connected to the real world.

[0079] 3. An alignment element AE, formed by a support (e.g., a support pin), is positioned adjacent to the measurement probe MP (in an embodiment with a 2.7 mm measurement probe radius, within a 6.35 mm support span). It has a constant overlap, length, diameter, and material. In this case, it has a 4 mm overlap or deflection, a 20 mm length, a 4 mm diameter, and is made of stainless steel, but can have any dimensions, length, diameter, and material. The overlap D determines the contribution of the force in the X direction (normal force) to the coefficient of friction, which is a function of the volume of the hair strand and the bending stiffness of the individual hairs. The alignment element AE can be static, but can also be dynamic by using rollers to reduce tension or incorporating a velocity sensor. The alignment element AE is used to bend the hair H and uses the hair's bending stiffness to apply a normal force to the measurement probe MP. The radius of curvature can be adjusted by moving (deflecting) the alignment element (support pin) AE toward the measurement probe MP or by moving it in the X direction (support span SS). Differences in the X and Y directions increase or decrease the normal force on the system.

[0080] 4. Guide elements G, formed by elements that help eliminate the tension in the system caused by the holding angle. These elements have a certain diameter and material (here, 4 mm and stainless steel), but can be of any diameter and material. Guide elements G can be static, but can also be dynamic by using rollers to reduce tension or incorporating speed sensors.

[0081] exist Figure 7In the embodiment, the left-side guide element G, measurement probe MP, and load cell module belong to one device part I, while the right-side guide element G and alignment element AE belong to another device part II, with the hair being guided between these two parts. The alignment element AE and guide element G absorb the tensile forces required to remove additional forces from the sensor system, ensuring clean friction measurement in the Y direction, regardless of speed. The tip (distal end) of the hair is free to move in all directions, while the top (proximal) end of the hair remains attached to the scalp.

[0082] The alignment element AE and the guide element G offer another advantage. With handheld devices, it's difficult to use the same angle, speed, and volume of hair strands during each measurement or each individual measurement. One factor is the angle of the incoming hair strand relative to the device, which can change as the end user uses the device. The positioning of the guide pins G and support pins AE provides the same configuration between the hair strand H and the measurement probe MP for each measurement. By default, the selected design ensures a constant angle in the area where hair friction is measured. Specifically, the guide element G ensures that the hair enters the test area at the same angle, regardless of the angle at which the user applies the device to the hair H.

[0083] Figures 9A to 9B A standalone hair properties measuring device according to a second way of implementing the present invention is shown, wherein the measurement probe MP and half of the guide element G are located in the main body I, which also houses the load cell module, while the alignment element AE and the other half of the guide element G are located in the cover part II of the measuring device. The guide elements G are preferably oriented so that hairs enter the measurement unit (holder and measurement probe MP) straight, and for that purpose they may have hinged surfaces.

[0084] In an embodiment, the measurement is performed as follows:

[0085] 1. The system is switched on or off by default before a hair lock H is introduced into the system and can be switched on or off, for example, by pressing a button or in another suitable way.

[0086] 2. Introducing the hair lock H into the system between the measurement probe MP and the alignment element (eg support rod) AE.

[0087] 3. Close the system to clamp the hair bundle H between the alignment element (support rod) AE and the measurement probe MP. The guide elements G have a small gap between them of, for example, 2 mm (but can have any gap size), and the pull of the analyzer is determined by the user and the number of hairs in the system.

[0088] 4. Pull the analyzer down to the tip of the hair strand H. During this downward movement, the friction is determined between the surface of the measurement probe MP and the hair strand H, and at the same time, the normal force is calculated over time or along the length of the hair strand. This is a function of the bending stiffness of the hair strand H between the alignment element AE and the measurement probe MP.

[0089] 5. Receive data from both sensors and use the following equation to determine the coefficient of friction over time:

[0090]

[0091] Here, various concepts have the following meanings:

[0092] symbol definition <![CDATA[μ Friction hair tress ]]> Coefficient of friction of the total hair strand <![CDATA[F Friction hair tress ]]> Measured friction <![CDATA[F flexural stiffness hair tress ]]> Measured normal force (deformation force) n The number of recorded data samples

[0093] The coefficient of friction is used as a parameter to determine the "hair feel" to the user.

[0094] Advantageously, the friction coefficient calculated based on the friction and deformation forces measured by the respective load cells LC-X and LC-Y is not affected by volume changes, which can be caused, for example, by damaged hair or by the hair H being cut into layers, so that the volume of the hair strand is not constant over the length of the hair strand. If only the normal force or the friction force were measured, the result would be a system that is highly influenced by the number of hairs placed in the system by the user. 10A to 10D The brush is shown with the sensing module on the back. The hair is manually inserted into the slot that accommodates the measurement probe. The measuring device can thus be part of the top side of the brush B, with the bristles Bt mounted on the bottom side of the brush B. Figure 10A The top of brush B is shown, Figure 10B Shown in Figure 10A The cross section along the horizontal line in the middle, Figure 10C The reference symbol II shows the Figure 10A The cross section of the vertical line in Figure 10D Some sketches of the measuring probe MP and the guiding and holding part GHP for this brush B are shown.

[0095] like Figure 10A and Figure 10B As shown, the top side of the brush B is provided with slits S, in which the hairs can be guided. 10A to 10D The second part of the measuring equipment II is fixed, while Figures 9A to 9B In the embodiment of the present invention, it is hinged. The top of the second part II of the measuring device is at the same level as the top of the brush B, while the first part I of the measuring device is located in the cavity at the top of the brush B. Figure 10CA cross section is shown with the same elements discussed previously: the measuring probe MP and the alignment element AE. In order to allow the hair to enter the measuring device easily, the measuring probe MP is moved downwards when a strand of hair enters, after which it is moved upwards to ensure that the second part II deforms the hair H against the measuring probe MP while the hair H is guided between the first part I and the second part II. Figure 10D In the embodiment shown, the guide and holding part GHP, which is located before the measuring probe MP in the direction of hair entry, is Figure 10D The hair is in a downward position as shown in the upper half of the drawing and in an upward position to prevent the hair from escaping to the side (i.e., in a direction perpendicular to the hair H) when the hair is guided between the first part I and the second part II.

[0096] Figures 11A to 11C A further embodiment of the measuring device of the invention is shown. Figure 11A shows a front view, and Figure 11B Shown by Figure 11A The section along line AA in . Figure 11C Three possible variants of the measuring probe MP and the alignment element AE are shown, as Figure 11B An alternative to the enclosed part. Figures 11A to 11C The measuring device has a base Bs on top of which are placed three teeth, which respectively form two alignment elements AE and a measuring probe MP. The measuring probe MP comprises a sensor module SM on top of which are placed sensor teeth ST. The sensor module SM can be located within the base Bs. The teeth AE, ST can be completely rigid or flexible on the bending line BL to prevent excessive hair pulling in the event of hair entanglement. 10A to 10D Same as the example, Figures 11A to 11C The embodiment has no moving parts I and II.

[0097] like Figure 11C As shown, the alignment elements AE and / or sensor teeth ST preferably have angled tips above the bend line BL, which facilitates insertion of hairs into the measuring device. To ensure that hairs do not escape the device at the top (i.e., perpendicular to the hairs H) as the device moves through them, the alignment elements AE and / or sensor teeth ST may be equipped with a hair-blocking element (not shown) located above the bend line BL. This hair-blocking element can be manually or automatically operated. Once a defined number of hairs have entered the sensing area, this hair-blocking element can also be used to prevent further hair from entering the sensing area. For example, this hair-blocking element can be activated once the force sensor exceeds a certain threshold and deactivated if the sensor output appears stable.

[0098] 12A to 12EAn embodiment of a brush B is shown with a measuring device on the side where the bristles Bt are located. The device has the same elements as discussed in the previous embodiment: measuring probe MP, alignment element AE and guide element G. 10A to 10D and Figures 11A to 11C As in the embodiment, the first part I and the second part II are mounted in a fixed relationship; various components can be assigned to the first part I and the second part II, as in Figure 7 The same as in the embodiment.

[0099] Figure 12A The embodiment is based on Figure 7 Measuring device. The basic procedure is that, when combing the hair, the hair H is guided along the alignment element AE and the measuring probe MP. By pulling the brush through the hair, a friction force is generated in load cell Y (LC-Y) and a bending force is generated in load cell X (LC-X).

[0100] Figures 12B to 12E The embodiments are intended to increase the number of hairs captured in the system, thereby obtaining a stronger measurement signal.

[0101] Figure 12B An example is Figure 12A Improved version. The alignment element AE and the top of the measuring probe MP are curved in such a way that when combing hair, more hair is captured in the opening of the measuring system, resulting in a larger measurement signal. An additional guide pin G has been added to reduce the dependence on the holding angle of the device.

[0102] exist Figure 12C In this embodiment, the entire measurement probe MP is positioned at a shallow angle. Due to the shallow angle, hairs are captured and retained in the system, requiring only minimal force. Consequently, the bending force is no longer constant over the length of the measurement system. Because the coefficient of friction is the only parameter used, tests have shown that the system is unaffected by skewness.

[0103] exist Figure 12D In the embodiment of , not only the measurement probe MP is angled, but also the alignment element AE. Thus, even more hairs are captured in the system, resulting in a larger measurement signal.

[0104] Figure 12E The embodiment solves the problem of erroneous measurement signals when the brush is not positioned perpendicular to the direction of hair on the head, but rather guides the hairs at an angle to the wrong side of the measurement probe MP. To prevent hairs from ending up on the wrong side of the measurement probe MP, the two alignment elements AE and the two guide elements G are interconnected. Hairs now only face the intended side of the measurement probe MP.

[0105] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. Figure 7 In an embodiment, the dimensions of the measurement probe radius, deflection D, and support span SS can be sized according to the area of ​​the measurement probe surface in contact with the hair H. The guiding element G can be positioned closer to the alignment element AE rather than at the outer perimeter of the measurement device. Hair guidance can be accomplished by a single body containing both guiding features, or by two separate guiding features. The spacer can also be placed in another area of ​​the structure to prevent it from being a hinged implementation. In the claims, any reference numerals placed between parentheses should not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention can be implemented by hardware comprising several different elements and / or by a suitably programmed processor to analyze signals from the measurement probe MP. In a device claim enumerating several components, several of these components may be embodied as one and the same item of hardware. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A device for measuring a property of hair (H), comprising: The first part (I) comprises a measuring probe (MP) and is characterized in that The second part (II) is arranged to bend the hair (H) against the measuring probe (MP) when the hair (H) is guided along the measuring probe (MP) between the first part (I) and the second part (II), wherein the second part (II) includes alignment elements (AE) located on opposite sides of the measuring probe (MP) in a plane parallel to the boundary between the first part (I) and the second part (II) for bending the hair (H) against the measuring probe (MP).

2. A device according to claim 1, wherein when the device moves past the hair, the measuring probe is subjected to friction forces and deformation forces, the friction forces being generated because the hair is guided along the measuring probe, and the deformation forces being generated because the hair is bent by the second part against the measuring probe.

3. A device according to claim 1 or 2, wherein the device is arranged to subject the measuring probe (MP) to a friction force and a deformation force (DF), wherein the friction force is generated because the hair (H) is guided along the measuring probe (MP) and the deformation force is generated because the hair is bent by the second part (II) against the measuring probe (MP).

4. A device according to claim 1, wherein the measuring probe is subjected to friction and deformation forces when the device moves through the hair, and the device also includes a guiding element (G) arranged to reduce the influence of the angle at which the device is applied to the hair (H) on the friction and / or deformation forces.

5. Apparatus according to claim 4, wherein the alignment elements (AE) are coupled to one another and the guide elements (G) are coupled to one another.

6. Apparatus according to claim 1 or 2, wherein the measuring probe (MP) is mounted to a load cell module (LC-X, LC-Y) arranged to measure loads in two dimensions to measure friction and deformation forces, respectively.

7. Apparatus according to any of claims 1-2, further comprising means arranged for compensating for the weight of the measurement probe (MP).

8. The device according to any of claims 1-2, further comprising an accelerometer arranged for measuring the force of gravity in a measuring direction of the measurement probe (MP).

9. Apparatus according to any of claims 1-2, wherein the measuring probe (MP) is at least partially flexible or tiltable.

10. Apparatus according to any one of claims 1-2, wherein the elements of the second portion (II) are at least partially flexible or inclined.

11. The device according to any one of claims 1-2, embedded in a brush (B) having a plurality of bristles (Bt).

12. The device according to any of claims 1-2, wherein the measurement probe (MP) is movable to allow a hair (H) to enter the device.

13. Device according to any of claims 1-2, further comprising a portion (GHP) arranged to prevent the hair (H) from leaving the device in a direction perpendicular to the hair (H).

14. Device according to any of claims 1-2, embedded in a hair styling device (HS) having a treatment plate (HP), along which the measuring probe (MP) is positioned.

15. Apparatus according to claim 14, wherein the length of the measurement probe (MP) substantially matches the length of the processing plate (HP).

Images