Automated control of razor blade colorization

Abstract

Methods of and systems for automated color control are provided. These methods and systems are suitable for use in various oxidation processes for the coloration of heat treated steel, for example razor blade steel. A feedback loop (closed loop control) is established, including the steps of measuring color, comparing the measured color to a target color and quantifying the difference there-between, and, if the difference exceeds a predetermined threshold, adjusting a color adjustment parameter, e.g., the airflow to the oxidation zone, so that the measured and target colors are equivalent or within a predetermined variance.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 750,962, filed Dec. 14, 2005.FIELD OF THE INVENTION [0002] This invention relates to the field of razor blades and processes for manufacturing razor blades and more particularly to automated control of razor blade color in such processes. BACKGROUND OF THE INVENTION [0003] Razor blades are typically formed of a suitable metallic sheet material such as stainless steel, which is slit to a desired width and heat-treated to harden the metal. The hardening operation utilizes a high temperature furnace, where the metal may be exposed to temperatures greater than 1100° C. for up to 10 seconds, followed by quenching. After hardening, a cutting edge is formed on the blade. The cutting edge typically has a wedge-shaped configuration with an ultimate tip having a radius less than about 1000 angstroms, e.g., about 200-300 angstroms. Various coatings may be applied to the cutt...

AI Technical Summary

Problems solved by technology

If the steel is over tempered it will lose its hardness and may not perform properly during use.

The hardening process results in martenization of the blade material.

If a thermal oxide coloration process were employed after the martensitic transformation, it would generally destroy the martensitic properties of the stainless steel strip.

The hardening process results in martenization of the blade material.

If a coloration process were employed after the martensitic transformation, it would either destroy the martensitic properties of the stainless steel strip, or would require extensive temperature control and special material handling.

Constructive interference occurs when the reflected light from one interface combines in phase with the reflected light from the other interface, producing brightness.

Destructive interference occurs when the reflected light from the interfaces combines out of phase, producing darkness.

Variation in the parameters associated with the hardening process, including temperature, gas flow rates, and gas leaks, result in color drift for the thermal oxidation color process.

Variation in the hardening process parameters as well as in the thickness or refractive index of the pre-hardened metal oxide / oxynitride film, if left uncompensated, will also lead to associated color drift in the hardened blade steel for the reduction / re-oxidation process.

In addition, abrupt changes in pre-deposited metal oxide film thickness can occur when slitted strips are welded together for continuous processing, thereby causing abrupt color changes in the final product.

However, manual adjustment increases production costs and does not allow sufficiently responsive compensation for color drift, increasing the amount of unacceptable blade material that is produced.

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