BRPI0619916A2 - automated shaving or shaving blade coloring control - Google Patents

Abstract

<UM> AUTOMATED CONTROL OF COLORING OF SHAVING OR DEPILING BLADES <MV>. These are methods and systems for automated color control. These methods and systems are suitable for use in various oxidation processes for the coloring of heat treated steel, for example razor or shaving steel blade. A feedback circuit (with closed-loop control> is established, including the steps of measuring the color, comparing the measured color with a final color and quantifying the difference between them and, if the difference exceeds a predetermined limit, regulation of the parameters of color adjustment, for example, the air flow in the oxidation zone, so that the measured and final color are equivalent or are within a predetermined variance.

Description

AUTOMATED COLORING CONTROL OF SHAVING OR SHAVING BLADES

FIELD OF INVENTION

This invention relates to the field of razor or shaving razors and processes for manufacturing razor or shaving razors and more specifically to automated shaving or shaving blade colorization control in such a process.

BACKGROUND OF THE INVENTION

The epilating blades are typically formed of a suitable metallic laminar material, such as stainless steel, which is slotted to the desired width and heat treated to quench the metal. The hardening operation uses a high temperature furnace in which the metal can be exposed to temperatures above 1,100 ° C for up to 10 seconds and then subjected to sudden cooling. After the hardening process, a sharp edge is formed on the blade. The cutting edge typically has a wedge-shaped configuration with an end having a radius of less than about 1000 angons, for example, about 200 to 300 angles. Various coatings can be applied to the cutting edge. For example, hard coatings such as diamond, amorphous diamond, diamond like carbon (DLC), nitrides, carbides, oxides or ceramics are often applied to the cutting edge or edge to improve stiffness, corrosion resistance and the ability to shave or shave. Intermediate layers of niobium or chromium-containing materials can help improve the bond between the substrate, typically stainless steel, and hard coatings. An outer layer of polytetrafluoroethylene (PTFE) may be used to provide friction reduction.

It is important that these coatings are applied, and any other post-hardening processing steps performed, under sufficiently low temperature conditions so that the hardened and sharpened steel is not significantly quenched. If the steel becomes too tempered, it will lose its stiffness and may not perform properly during use.

Examples of shaving or razor blade cutting structures and processes for their manufacture are described in US Patent Nos. 5,295,305, 5,232,568, 4,933,058, 5,032,243, 5,497,550, 5,940,975, No. 5,669,144, EP 0591334 and PCT 92/03330, which are incorporated herein by reference.

Shaving or shaving blades may include a colored coating, i.e. a coating containing a different color from the color of the underlying blade material. The term "colored" for use in the present invention includes all colors, including black and white. The colored coating provides a desirable aesthetic effect without adversely affecting blade performance or physical properties. The color of shaving or shaving blades can be coordinated with the carcass color of a shaving cartridge, the handle or other components of a shaving or shaving system. In some preferred embodiments, the coating substantially covers the entire blade surface, accentuating the aesthetic effect and simplifying production. The coatings are durable, exhibit excellent adhesion to the blade material and can be produced consistently and relatively inexpensively.

Shaving or shaving blades may be colored during the steel hardening process through the use of techniques such as thermal oxidation of the steel blade or controlled reduction and re-oxidation of a rigid metal oxide surface coating, eg titanium dioxide. , applied to the steel blade. To reduce costs, reduce scrap and achieve quality and color control, these two techniques require machining and an automated color control process.

Thermal oxidation technique includes subjecting the blade material to a hardening process and, during the hardening process, exposing the blade material to pure dry air to form an oxide layer on its surface. The method also includes quenching the blade material after the oxidation step to initiate martensitic transformation of the blade material and giving the hardened material the shape of the depilatory blade, in which the oxide layer provides a surface colored to the hair removal blade. Preferred methods do not adversely affect the final properties of the slide. The process of staining the slide by controlled reduction and oxidation of a rigid metal oxide surface coating involves the application of a layer of a rigid metal oxide and / or metal oxynitride, for example titanium oxide and / or other transition metals including zirconium, aluminum, silicon, tungsten, tantalum, niobium, iron, and mixtures thereof, to a soft sheet steel for blades, for example by physical vapor deposition (PVD), chemical vapor deposition Enhanced Plasma (PECVD), or other deposition technique, in a layer of uniform thickness. For this staining process, the hardening operation includes subjecting the metal oxide coated sheet material to a hardening process and, during the hardening process, reducing the oxygen content of the present metal oxide or oxynitride coating and then re-oxidizing the oxide by exposing the coating to a controlled amount of pure dry air in proportion to the desired final coating color. This method also includes abrupt cooling of the blade material after the re-oxidation step to initiate martensitic transformation of the blade material and the transformation of the hardened blade material into a shaving or shaving blade. Preferred methods do not adversely affect the final properties of the slide.

Thermal oxidation technique includes passing the blade material through a two zone tunnel oven. The first zone is used to austenize the steel blade and to remove any native oxide coating. This first zone contains mainly hydrogen and nitrogen. A second zone of the tunnel-shaped furnace, called the oxidation zone, which follows directly from the first zone, is used to oxidize the surface of the stainless steel strip. The first zone has temperatures close to 1,100 ° C for almost its entire length. Temperatures near the exit of the first zone just prior to the oxidation zone reduce the temperature of the blade material from almost 1,100 ° C during austenization to below about 800 ° C as it enters the second zone. Oxygen available in the tunnel oven oxidation zone can be controlled by controlling the amount of dry air and nitrogen injected into this zone. By controlling the available oxygen from the oxidation zone, the color of the oxide film formed can be defined and controlled. After the oxidized steel passes through the oxidation zone of the tunnel furnace through water-cooled rough cooling blocks, martensitic quenching is initiated. The hardening process results in martensitization of the blade material.

The oxide-thermal slide staining processes described above allow a decorative oxide film to be produced on a steel sheet during the hardening process, after austenization and before martensitic transformation. If instead the steel blade were colored using an oxide-thermal staining process prior to the hardening process, the color would generally be degraded during the conventional hardening process. If a thermal oxide colorization process is employed after martensitic transformation, this will generally destroy the martensitic properties of the stainless steel strip. The processes described above generally produce highly adhesive protective oxides while allowing excellent color control without negatively impacting the metallurgical properties of hardened stainless steel strip strips.

The technique of hardening and staining the blade by controlled reduction and re-oxidation of a rigid metal oxide surface coating includes the passage of the blade material through a two zone tunnel oven. The first zone is used to austenize the steel blade and to reduce the oxide coating. This first zone contains mainly hydrogen and nitrogen. A second tunnel oven zone, located immediately after the first zone, is used to re-oxidize the coating. Oxygen partial pressure in the second tunnel furnace zone can be controlled regardless of the ambient conditions in the first tunnel furnace zone. By controlling the partial oxygen pressure in the second zone of the tunnel furnace, the desired color of the oxide film can be defined and controlled. After the coated steel passes through the second tunnel furnace zone by means of water-cooled rough cooling blocks, martensitic cooling is initiated. The hardening process results in martensitization of the blade material. The reduction and re-oxidation blade staining processes described above allow a transition metal oxide decorative film to be specially modified (colored) during the hardening process of a martensitic stainless steel. If a transition metal oxide decorative film is colored prior to the hardening process, it will usually be degraded during the conventional hardening process. If a coloring process were employed after the martensitic transformation, it would either destroy the martensitic properties of the stainless steel strip, or would require intense temperature control and special material handling. The processes described above generally produce highly adhesive protective oxides while allowing excellent color control without negatively impacting the metallurgical properties of hardened stainless steel strip strips.

In both of the above described methods of producing colored sheets, both in the thermal oxidation of the steel sheet and in the controlled reduction and re-oxidation of a rigid metal oxide surface coating, color arises from the thin film interference between the reflectance. light at the air / oxide interface and the light reflectance at the oxide / steel interface. Constructive interference occurs when reflected light from one interface has the same phase as reflected light from another interface, producing brightness. Destructive interference occurs when reflected lights from interfaces are out of phase, producing darkness. The optical phase difference between the reflected light of each interface depends on the optical path length (OPL) through the thin oxide film. The OPL is given by:

<formula> formula see original document page 9 </formula>

on what:

nf = thin film refractive index d = thin film thickness

θ = angle between incident and normal light of the thin film surface.

Factor 2 considers the double passage through the film due to reflection.

In the case of thermal oxidation of an uncovered steel sheet, the oxide refractive index is considered to be almost constant and the color is primarily due to the final oxide thickness, d. When there is a re-oxidation of a rigid metal oxide film on a steel sheet, the thickness of the rigid metal oxide is considered to be almost constant and color is primarily a function of the degree of reoxidation, which correlates with an increase. associated with the refractive index.

Variations in the parameters associated with the hardening process, including temperature, gas flow rates and gas leaks, result in the color change for the thermal oxidation staining process. Variations in the hardening process parameters as well as the thickness or refractive index of the metal oxide / pre-hardened oxynitride film, if left unbalanced, will also lead to color change in the hardened steel blade associated with the reduction / re -oxidation. In addition, abrupt changes in pre-deposited metal oxide film thickness can occur when cracked strips are welded together for continuous processing, thereby causing abrupt color changes in the final product.

For the blade staining processes discussed, variations can be compensated, and thus a final color can be achieved by observing the color of the hardened steel blade followed by an adjustment of the pure dry air flow during oxidation processes. re-oxidation. However, manual adjustments increase production costs and do not allow compensations fast enough for color change, increasing the amount of unacceptable blade material that is produced.

The present invention intervenes to provide an improvement in automated color control. Such methods and systems are described below. These methods and systems are suitable for use in various oxidation processes for staining steel razor blades. A feedback loop (with closed loop control) is established, including the steps of color measurement, comparison of the measured color with a final color value, and quantification of the difference between them and, if the difference exceeds a predetermined limit, adjusting a color adjustment parameter, for example, the oxidation zone air flow, so that the measured and final color are equivalent or within a predetermined variance.

SUMMARY OF THE INVENTION

The present invention relates to a process for manufacturing razor or shaving razors comprising: an automated feedback circuit, measuring a color parameter of a blade steel strip exiting a coloring process, comparing the measured color to a final color and quantifying the difference between them and, if the difference exceeds a predetermined limit, by adjusting a color adjustment parameter so that the measured and final color are equivalent or within a predetermined variance.

In another embodiment, the invention relates to a system for automated shaving or shaving blade color control comprising:

a spectrometer configured to measure a reflection spectrum of the steel blade as it leaves the colorization process,

a controller configured to adjust a parameter of the colorization process, a processor configured to determine a parameter associated with the measured reflection spectrum, calculate the difference between the measured parameter and a predetermined end value, and if the difference is above a predetermined limit, send a voltage to the mass flow controller, and a hardening furnace equipped with an oxidation zone.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a flowchart showing the steps in a process for manufacturing a razor blade or shaving blade including blade staining by thermal oxidation according to one embodiment of the invention.

Figure 2 is a temperature profile for a hardening furnace.

Figure 3A is a diagrammatic side view of an oxidation zone.

Figure 3B is a diagrammatic cross-sectional view of a sprinkler taken along line A-A in Figure 3A.

Figure 3C is a front view of an outlet opening through the oxidation zone shown in Figure 3A.

Figure 4 is a flowchart showing the steps in a process for shaving or shaving the blade including blade staining through controlled reduction and re-oxidation according to one embodiment of the invention.

Figure 5 is a graph of the reflection spectra for rigid metal oxide steel sheets in their pre-hardening condition and various post-hardening conditions (with hardening having been conducted through different airflow rates in the oxidation zone). ). The graph also shows the correlation between the minimum spectrum value, Xmin, and the approximate blade color. Figure 6 is a diagram showing an automated color control supply circuit consisting of a spectrometer, a processor, a mass flow controller and a hardening furnace equipped with an oxidation zone.

Figure 7 is a flowchart depicting the color control feedback process.

Figure 8 is a graph showing the Xmn of a rigid metal oxide film on a pre-hardened steel sheet, Xmin of a rigid metal oxide film on a post-hardened steel sheet within a feedback control as well as the minimum target wavelength λT.

Similar reference symbols in the various drawings indicate similar elements.

DETAILED DESCRIPTION OF THE INVENTION

A suitable oxide-thermal process for colored oxide layer formation and shaving or shaving razor fabrication is shown diagrammatically in Figure 1. First, a steel blade plate is split into strips. The strips are then welded together and then drilled for ease of handling during subsequent processing.

When the desired sequence of pre-hardening steps is completed, the blade material is subjected to a hardening process, which includes austenizing stainless steel. A typical temperature profile for the quenching process, which is conducted in a tunnel furnace, is shown in Figure 2. The material is rapidly raised to a high temperature, for example, approximately 1160 ° C and held at that temperature for a while. , in which the austenization of stainless steel occurs, and then allowed to cool. A forming gas (eg including hydrogen and nitrogen) flows through a high temperature zone of the furnace during austenization. The composition and flow rate of the forming gas are controlled so that no oxidation occurs and any native oxide is reduced. In one embodiment, the forming gas includes hydrogen to prevent oxidation and reduce any native oxide, and nitrogen as an inert gas used to dilute the overall hydrogen concentration. For example, in some implementations the formation gas may include about 75% hydrogen and about 25% nitrogen, and may be released at a flow rate of about 7 to 38 L / min.

After austenization, the strips pass through an oxidation zone, in which the colored oxide layer is accumulated on the surface of the steel sheet. Forming gas flows from the hardening furnace into the oxidation zone. An oxidizing gas (for example including oxygen) is introduced to the forming gas to a desired point in the oxidation zone (until the strips have reached a suitable oxidation temperature) and guides the oxidation process. Oxygen may be supplied as pure dry air. Oxidation zone and oxidation conditions (eg hydrogen to oxygen ratio) will be discussed in detail below. After the material leaves the oxidation zone, it is rapidly cooled, resulting in a martensitic transformation of stainless steel. Sudden cooling (quenching) does not adversely affect the color of the oxide layer.

The processes described herein can be added to existing blade steel hardening processes, often with minimal changes to the existing process. For example, an existing blade steel hardening process utilizes a high temperature furnace (greater than about 1,100 ° C) containing a forming gas outlet. Two parallel and continuous strips of stainless steel blade are pulled through this high temperature furnace at 36.6 m / min (120 ft / min) each. This high temperature treatment is used to austenitize stainless steel strips. Near the outlet of the high temperature furnace is a water-cooled jacketed tube (also referred to as a water-cooled tubular muffle). This section is used to begin the cooling process of stainless steel blade strips. Immediately after the water-cooled zone, the stainless steel blade strips are pulled through a set of rough water-cooled cooling blocks. The rough cooling blocks begin the martensitic transformation of steel. This existing process can be modified to form a colored oxide layer by replacing the water-cooled tubular muffle between the high temperature furnace and the rough cooling blocks with the above oxidation zone. In certain instances, the temperature profile of the furnace may be modified so that the strips exit the furnace at a temperature of less than about 800 ° C, or about 400 to 750 ° C, or even about 600-700 ° C. ° C.

A suitable oxidation zone is shown diagrammatically in Figure 3A. The oxidation zone may be, for example, an Inconel pipe attached to the pipe used in the tempering line high temperature furnace. In one embodiment, a gas sprinkler system 200 is installed about 2.9 cm from the inlet of tube 202 and sized to extend to about 5.1 cm along the tube. In this case, the sprinkler has a total of 16 gas inlets (not shown), and is designed so that the gas injected through the sprinkler (arrows in Figure 3A) acts evenly on the stainless steel strips. Gas is introduced into the sprinkler through a pair of inlet tubes 201 and 203. A gas deflector 204 may be included such that two stainless steel strips of blade material are separated from each other so that the gas composition in each side of the deflector can be controlled partially independently from the other side. Deflector 204 may define two chambers 210, 212 as shown: in Figure 3B. In this case, the gas deflector may, for example, start about 0.3 cm from the oxidation zone inlet and extend along the pipe to about 10.2 cm. If desired, gas deflector 204 may extend along the entire length of the oxidation zone so that no gas flow mixtures of inlet tubes 201 and 203 occur, allowing independent control of both sides of the deflector. inside the tube (210 and 212). The gas sprinkler is designed to allow dual control of gas flow, allowing two strips to be processed at the same time using the same furnace. Gas flow rates can be controlled by gas flow meters. The outlet of each chamber of the oxidation zone may be equipped with a flange and two steel parts 218 which define a slot 219 and thus act as an outlet port 220 (Figure 3C). For example, the slot may be from about 0.1 to about 0.2 cm wide. This outlet port prevents any reflux of ambient air into the oxidation zone and encourages better mixing of gases in the air. interior of said zone. As discussed above, immediately after the oxidation zone, the stainless steel blade strips are pulled through a set of water-cooled rough block 206. The rough cool block initiates martensitic transformation of the steel.

The desired color is generally obtained by controlling the thickness and composition of the oxide layer. The thickness and composition of the colored oxide layer will depend on several variables. For example, the thickness of the oxide layer will depend on the temperature of the stainless steel strip when the oxidizing gas is introduced, and the ratio of hydrogen to oxygen of the formation gas and oxidation gas mixture in the oxidation zone. . The composition or stoichiometry of the oxide layer will depend on these same factors and also on the surface composition and strip morphology. Generally, lower temperatures and flow rates produce golden colors and higher temperatures and flow rates produce color from the violet to blue spectrum. In some implementations the ratio of hydrogen to oxygen is from about 100: 1 to 500: 1. For a particular type of slide material, with the ratio of hydrogen to oxygen around the midpoint of this range, an aesthetic dark blue oxide is obtained. Increasing the relative amount of oxygen will tend to produce light blue and light blue-green colors, while reducing the relative amount of oxygen will tend to produce violet colors and then golden colors.

The speed at which material travels through the oxidation zone and the length of the oxidation zone will also affect colorization. Suitable speeds may be, for example, in the range of from about 15 to about 40 m / min.

In some cases, it may be necessary to adjust the quench process and / or oxidation process parameters in order to obtain a consistent end product. The temperature of the strip upon entering the oxidation zone may be controlled by adjusting the temperature of the last zones in the quenching furnace and / or by using heating elements in the oxidation zone. Increasing the temperature of the strip upon entering the oxidation zone will increase the thickness of the oxide produced in the oxidation zone. When the process is performed using the most conventional furnaces, the temperature of the strip upon entering the oxidation zone can only be adjusted in the initial process setting. Since the oxidizing gas composition of the oxidation zone can be quickly adjusted; This is the parameter that is generally used to compensate for variations in the material strip and to precisely adjust the oxidized color. The exact temperature setting of the last hardening furnace zones and the exact composition of the oxidizing gas are selected based on the desired color, size, shape, composition and speed of the steel strip, among other factors.

A suitable process for applying colored coating through a shaving / shaving and shaving or shaving blade process is shown diagrammatically in Figure 4. As shown in Figure 4, the oxide or oxynitride layer is preferably applied; to the laminar material from which the blade is formed, prior to slitting the laminar material to a desired width, which is typically significantly wider than the width of the final blade. Performing the coating step at this stage simplifies production as a large surface area can be coated at one time. The oxide coating is applied to a soft sheet steel for blades, for example by physical vapor deposition (PVD), plasma enhanced chemical vapor deposition (PECVD), or other deposition technique, in a uniformly thick layer. The layer is typically from about 400 to about 10,000 angstrons, for example from about 500 to about 800 angstrons.

When the desired sequence of pre-hardening steps has been completed, the blade material undergoes a hardening process which results in martensitic transformation of stainless steel. A typical temperature profile for the quenching process, which is conducted in a tunnel furnace, is shown in Figure 2. This temperature profile inside the furnace involves rapid elevation. from the temperature of the material to a high temperature, for example approximately 1,160 ° C, the material being held at that temperature for a period of time during which austenization of stainless steel occurs. After the material comes out of the oven, it is rapidly cooled, which causes the martensitization of stainless steel,

During the hardening process, the oxide coating is "colored", that is, the coloring of the oxide coating is intensified and / or altered. Staining may result in a color accentuation, for example a brighter hue or appearance, and / or may result in a change of coating color to a different color such as bluish gray to violet, gold or blue, or opaque green to greenish yellow, dark green, or bluish green. Such colorization results from a change in the refractive index of the coating which in turn results from a change in the composition, stoichiometric composition and / or crystal structure of the oxide coating. The degree of change in the evident refractive index of the film will control the color of the colored film.

The composition and crystalline structure of the coating after staining, and therefore the final color of said coating, will depend on several variables. For example, the composition or stoichiometry of the coating will depend on the gases present in the furnace during the hardening process. The introduction of nitrogen only into the furnace usually changes a titanium oxide coating, the color of which is initially grayish blue to bright blue or bluish violet. This color change is due to a reduction in the oxygen content of the titanium oxide coating. If air and / or moisture is introduced into the furnace, the reduction in oxygen content in the titanium oxide coating is much smaller, and the resulting refractive index is higher.

Other variables that affect coloration are the initial thickness and composition of the oxide coating, the temperature profile of the hardening furnace, and the speed at which the material passes through the furnace. Should the thickness and / or composition of the coating vary along the length of the material, it may be necessary to adjust the hardening process parameters to obtain a consistent ifinal product. Because it is difficult to quickly adjust the temperature and ambient conditions in large tunnel-shaped furnaces that are typically used for hardening, it may be desirable to provide a shorter separate furnace that is more quickly adjustable (referred to below as "the oxidation zone"). . Thus, the conventional and larger tunnel furnace can be used for the high temperature step of the hardening operation and to slightly reduce the oxide coating (which may also increase the uniformity of its composition), and the furnace. Additional and shorter can be used for oxidation / coloring, providing an oxidation zone where the gas composition can be adjusted relatively quickly to compensate for variations in material. The temperature of the strip in this oxidation zone, and consequently the ambient coloring responsiveness, can be adjusted more or less by adjusting the setpoint of the last zones of the high temperature furnace. The composition and / or flow rate of the gas (s) introduced into the oxidation zone may then be altered based on the appearance of the material as it leaves the oxidation zone and cooling area.

The oxidation zone may be similar to that described for oxide-thermal slide staining above, and as previously shown in Figure 3A. The oxidation zone, when used, is situated between the high temperature furnace and the first set of water-cooled rough block, and replaces the water-cooled tubular muffle used in a standard hardening line. The temperature profile of the furnace may be modified such that the coated stainless steel strip strips emerge from the hardening furnace and enter the oxidation zone at a temperature close to or below about 1,160 ° C. The addition of heating elements to the oxidation zone may also be employed to optimize process stability, for example during its initiation. Oxidation gas, for example a mixture of oxygen and nitrogen introduced as dry air and nitrogen, can be used to control the coloring process, in which case it is added directly to the gas stream from the high temperature furnace.

The inventors have developed automated color control methods and systems that are suitable but not limited to use in any of the staining processes described above. A feedback loop (with closed loop control) is established including the steps of color measurement, comparison of the measured color with a final color and quantification of the difference between them and, if the difference exceeds a predetermined limit, the adjustment of the Color adjustment parameters, for example, of the air flow in the oxidation zone, will cause the measured color and the final color to be equivalent or within a predetermined variance. Preferred systems and methods substantially reduce the long-term detectable color change or change.

In one aspect, the invention features systems for automated shaving or shaving blade coloring that include a spectrometer, a processor, a mass flow controller (MFC), and a hardening furnace equipped with an oxidation zone. The spectrometer measures the reflection spectrum of the steel sheet as it exits the colorization process (for example, the metal oxide coated hardened and re-oxidized steel sheet or the thermally oxidized steel sheet). Reflection spectrum is the percentage of reflected light that returns to the spectrometer in contrast to the wavelength of the reflected light. The processor determines a parameter associated with the measured reflection spectrum, for example, the minimum wavelength of the reflected light (λmin), and calculates the difference between the measured parameter and a predetermined target value. If the difference is above a predetermined limit, the processor then sends a voltage to the mass flow controller to either increase or decrease the flow of fresh dry air in the oxidation zone so that the target value is approximated. In some implementations, the parameter is the maximum wavelength of the reflected light, λmax.

Color measurement can be very subjective and complicated due to the variety of measurement settings, patterns, and methods and the degrees of freedom that comprise "color space". The International Lighting Committee (CIE) has developed standards where definite numbers are used to represent a color. According to CIE standards, color is typically defined by 3 parameters. Advantageously, when using a single parameter, for example, λmin or λmax, as a designation for color, the three-dimensional color space is represented by a single number. This single number can then easily be used as the color control parameter to adjust a single color adjustment parameter (eg air flow) in a real time feedback loop.

With respect to the present invention, the first step in obtaining automated color control is to measure and define color. The reflection spectra of a metal oxide or rigid oxide film on a steel sheet follow the thin film interference ratio given by the following equation which may be derived from equation (1) above.

2nfd = (m-1/2) ʎmin (2)

where nf = the refractive index of a metal oxide film

d = the thickness of the metal oxide film

m = an integer representing the order of interference

ʎmin = the minimum wavelength of reflectance, and

θ = 0 for normal incidence of light in the oxide film.

In equation (2), nf> nS, where ns is the refractive index of the substrate (steel blade). When nf <ns, the ratio for thin film interference is modified as shown below:

2nfd = min (3).

Each of the spectra has a minimum value, ʎmin, which is proportional to the film thickness, d, and refractive index, nf.

Figure 5 is a graph of the refractive spectrum (reflected light in contrast to wavelength) of a pre- and post-hardened titanium dioxide coated steel sheet, measured with a fiber optic spectrometer. Each curve corresponds to the same film thickness but to different refractive indices. The pre-hardened film is represented by a spectral curve 1 with a λmin 2 of about 720 nm. Being subjected to the hardening process, the oxide in the film is reduced, which also decreases the nf and changes the Xmin spectrum associated with shorter wavelengths. The remaining spectral curves represent post-hardened titanium dioxide films that have gone through different amounts of airflow in the oxidation zone. For example, the post hardening reflectance curve 3 exhibits a λ min 4 of about 480 nm. This material was produced without air flow in the oxidation zone. Adjacent curves, with increasing Xmin, represent post-hardened titanium dioxide films with increasing airflow in the oxidation zone. Since the amount of re-oxidation increases the air flow well, the refractive index increases as well. This changes the spectra and the λ min associated with longer wavelengths. The air flow rates used for post-hardened titanium dioxide films in Figure 5 were in the range (but not limited to) 0-200 mL / min for the associated set of conditions. Each spectrum and associated Xmin correlates to a distinct color as seen on the color scale at the top of the chart (the color scale is reproduced in black and white. - The original scale will start with pink at the left end, darkening to violet, bluish violet , and dark blue in the center, then fading to light blue at the far right). Following marker 5 from the minimum wavelength 2 of the hardened material spectral curve 1 to the color scale at the top of the graph indicates that a 720 nm λmin would have a light blue visual appearance. 6. Following marker 7 from the minimum wavelength 4 from the spectral curve of post-hardened material 3 to the color scale at the top of the graph indicates that a λ min of 480 nm would have a violet visual appearance 8. Therefore, using λ min as a designation for Film color allows the representation of three-dimensional color space through a single parameter.

The second step in achieving color control is to develop a feedback circuit that allows a final color to be maintained regardless of changes in thickness and refractive index of the rigid metal oxide film, or changes in parameters associated with the oxide staining process. - thermal (eg temperature, gas concentration, etc.). Figure 6 represents an automated color control power circuit consisting of a spectrometer system 9, a processor 13, a mass flow controller 14, and a hardening furnace equipped with an oxidation zone-15. The software inside the processor communicates with and controls the spectrometer, analyzes the reflection spectra, and communicates with and controls the mass flow controller. The spectrometer system 9 consists of a light source 10, for example a tungsten light source, a spectrometer 11, and a fiber optic reflection / retrodispersion probe 12. Light from light source 10 is joined to a beam of six lighting fibers 17. These six lighting fibers surround a centrally located reading fiber 18 which is attached to the spectrometer 11. Light emitted from the lighting fibers 17 is directed to the sample 16.

The reflected light from the sample is then collected by the central reading fiber 18, and attached to the spectrometer 11. Within the spectrometer 11, the light is collimated and scattered from a diffraction reticle in a set of detectors whose pixels are spatially calibrated to correlate the linear position along the set to a particular wavelength. A processor 13 shows the intensity of light reflected at each wavelength. Fiber core diameters are typically (but not limited to) in the range 100-400 microns. A smaller fiber core diameter allows for a smaller sample area diameter at the expense of lower fiber optic bonding efficiency, resulting in less light available for measurement. The processor determines the wavelength with the minimum reflected light, and then sends a calculated VN + 1 19 voltage control to a mass flow controller 14 'which controls the amount of air flow in the oxidation zone 15, completing thus the feedback circuit. The calculated voltage control is related to the difference between the minimum reflectance final wavelength, λ T, and the minimum reflectance measured wavelength, λmin. Voltage control calculation can use traditional proportional integral and derivative (PID) feedback based on color difference and / or incorporate a variety of continuous feed and adaptive modeling techniques to reduce the color variation also attributed to interference. An example of an algorithm used to determine the mass flow controller (MFC) voltage control required to reach (λT - λmin) <limit would be as follows:

<formula> formula see original document page 29 </formula>

on what

Vn + 1: The New MFC Voltage Control in Voltage Units

Vn: The Old MFC Voltage Control in Voltage Units

∆V: the changes required in voltage control so that (λT - λmin) <limit, in volts λT: the minimum final wavelength in units of nm

λmin = the minimum wavelength measured in units of nm

G: the feedback loop gain setting, without unit

Mcor: The angular color coefficient in units of (nm-min) / mL

MMFC: the angular coefficient of the mass flow controller in units of mL / (min-volt) In equation 4 above, the new MFC adjustment voltage, Vn + 1, required to make (λT - λmin) less than some predetermined limit, T, is equal to the existing voltage setting, Vn, plus some voltage setting, AV. The experimentally determined angular color coefficient, Mcor, is the angular coefficient of Xmin in contrast to the air flow rate curve for a specific steel oxide coated steel sheet material and hardening furnace parameters. The angular coefficient of the MFC, Mmfc, is the equation describing the relationship between the voltage applied to the MFC and the associated flow rate. For example, if the MFC flow range is 0-200 mL / min for a corresponding 0-5 volts control voltage, the angular coefficient would be 40 mL / (min-volt). The T limit can be set too low for compact color control, or even set to zero. A flowchart depicting the color control feedback process is shown in Figure 7.

A graph showing the performance of the feedback circuit is shown in Figure 8. The triangular data points 100 at the top of the graph represent minimum wavelength (AR Xmin) as received (pre-hardened), measured from the reflection spectrum of the titanium dioxide film on the steel blade. The average value is 760.4 nm, with a standard deviation of 2.8 nm. To simulate a large differential between the Xmin of a rigid metal oxide film on the pre-hardened steel sheet and the final minimum wavelength λτ, and to demonstrate the color control range, setpoint, or final color, λτ has been incrementally modified as seen on the dashed line scale 101, 102, ..., 108. The lozenges, 109, 110 ..., 116, surrounding the dashed lines, represent a minimum measure of wavelength after hardening, AH Xmin, on a feedback control. The measured Xmin follows a setpoint λτ with a standard deviation of about 3.3 nm. Average spectral sweeps can be used to optimize the signal to interference ratio and reduce measurement error over a longer time interval between updates.

To optimize the responsiveness of the feedback loop, the response time of the mass flow controller should be as fast as possible, and the volume of space comprising the oxidation zone and associated piping carrying pure dry air. For oxidation zone: to be minimized. In addition, as the steel blade travels through the hardening furnace and oxidation zone at relatively high speeds (eg 60.9 cm / s (24 in./second)), it is important to position the spectrometer (or other measuring instrument) fiber optic probe as close as possible to the oxidation output port.

As the film thickness increases, the reflectance spectra may exhibit multiple highs and lows corresponding to successive orders of interference, m. If multiple minimum reflectances exist within the wavelength limit of the spectrometer, the processor software program may use a window function to limit Xmin's search for a specific portion of that wavelength limit to isolate the minimum spectral. corresponding to a specific interference order. More complex software can use the number and location of multiple highs and lows to reflect and control the color of the strip.

Several embodiments of the invention have been described. However, it should be understood that various modifications may be made without departing from the spirit and scope of the invention.

For example, in addition to using a reflection spectrum characteristic measured with a spectrometer as the feedback control parameter, other types of measurement systems with their own characteristics may be used to specify a control parameter for the feedback loop. . For example, a differentiator sensor of three "RGB" color light sources may represent color using the red, green and blue light ratios reflected from the sample material compared to the ratios of these colors from a single color material. specific end color. Sensor output is a percentage representing how close the color of the sample material is to the color of the final material. The sensor output can be used as the control parameter of the feedback circuit.

In addition, as noted above, the maximum reflectance Xmax / can be used as a color designation more than Xmin, and follows a similar ratio for thin film interference.

Accordingly, other embodiments are within the scope of the claims set forth below. The dimensions and values set forth in the present invention should not be construed as being strictly limited to the exact numerical values mentioned. Instead, unless otherwise specified, each of these dimensions is intended to mean both the mentioned value and a functionally equivalent range of values around that value. For example, a dimension displayed as "40 mm" is intended to mean "about 40 mm".

All documents cited in the Detailed Description of the Invention are, in their relevant part, incorporated herein by reference, and the citation of any document should not be construed as an admission that it represents prior art with respect to the present invention. In the event that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it should be apparent to those skilled in the art that various other changes and modifications may be made without departing from the character and scope of the invention. Therefore, it is intended to cover in the appended claims all such changes and modifications that fall within the scope of the present invention.

Claims (11)

Process for the manufacture of a razor or razor blade comprising: an automated feedback circuit, the measurement of a color parameter of a steel strip of the blade exiting a coloring process, color comparison measured with a final color and quantifying the difference between them and, if the difference exceeds a predetermined limit, adjusting a color adjustment parameter so that the measured color and the final color are equivalent or within a predetermined variance . Process according to Claim 1, characterized in that the coloring process includes the passage of the steel strip through an oxidation zone, and the color adjustment parameter comprises an air flow rate in the zone. Oxidation Process according to Claim 1, characterized in that the measuring step comprises measuring the reflection spectrum of the steel blade. Process according to Claim 3, characterized in that the color parameter is the maximum or minimum value of the reflection spectrum. Process according to Claim 3, characterized in that the measurement step is performed using a spectrometer. Process according to claim 2, characterized in that the adjustment step comprises the use of a mass flow controller to adjust the air flow. Process according to Claim 1, characterized in that the coloring process comprises a thermal oxidation process or a reduction / re-oxidation process. Process according to Claim 7, characterized in that the thermal oxidation process or the reduction / re-oxidation process is part of the steel hardening process. Process according to claim 1, characterized in that the quantification of the difference is performed by a processor. 10. Shaving or shaving blade automated color control system comprising: a spectrometer configured to measure the reflection spectrum of the steel blade as it exits the colorization process, a controller configured to adjust a process parameter A processor configured to determine a parameter associated with the measured reflection spectrum, calculate the difference between the measured parameter and a predetermined end value and, if the difference is above a predetermined limit, send a voltage to the mass flow controller. , and a hardening furnace equipped with an oxidation zone. System according to Claim 10, characterized in that the parameter is the wavelength of the minimum reflected light (Xmin) or the maximum reflected light Xmax) of the reflection spectrum or higher order minimums or maximums.