Patent Application
20110314678
The present invention relates to razor cartridges and blades in general and, more particularly, to razor blade cartridges having one or more razor blades with a bent portion and a method for manufacturing the same.
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 1145° C., followed by quenching. After hardening, a cutting edge is formed on an elongated edge of 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.
The razor blades are generally mounted on a plastic housing (e.g., a cartridge for a shaving razor) or on a bent metal support that is attached to a housing. The razor blade assembly may include a planar blade attached (e.g., welded) to a bent metal support. The blade may include a tapered region that terminates in a sharpened cutting edge. This type of assembly is secured to shaving razors (e.g., to cartridges for shaving razors) to enable users to cut hair (e.g., facial hair) with the cutting edge. The bent metal support may provide the relatively delicate blade with sufficient support to withstand forces applied to blade during the shaving process. Examples of razor cartridges having supported blades are shown in U.S. Pat. No. 4,378,634 and in U.S. patent application Ser. No. 10/798,525, filed Mar. 11, 2004, which are incorporated by reference herein.
The performance and commercial success of a razor cartridge is a balance of many factors and characteristics that include rinsability (i.e., the ability of the user to be able to easily rinse cut hair and skin particles and other shaving debris from the razor cartridge and especially from between adjacent razor blades or razor blade structures). The distance between consecutive cutting edges or so-called “span” is theorized to affect the shaving process in several ways. The span between cutting edges may control the degree to which skin will bulge between blades, with smaller spans resulting in less skin bulge and more skin comfort during shaving, but may also increase opportunities for double engagement. Larger spans may reduce opportunities for double engagements, but may result in more skin bulge between cutting edges and less skin comfort. The span between cutting edges and, thus between blades, may affect rinsing of shave preparations and shave debris after a shaving stroke, with larger spans easing or quickening rinsing and smaller spans slowing or making rinsing more difficult. A razor cartridge including a razor blade having a bent portion can have certain advantages, such as decreased manufacturing costs and improved rinsability.
The manufacture of commercially acceptable razor cartridges having one or more bent blades present issues such as failure of the blade during manufacturing or even during shaving. Various bent blade designs have been suggested in the literature; however, these designs often result in failure in certain types of steel (e.g., the blades crack or fracture during bending). Accordingly, the geometry of the blade is usually compromised to prevent failure (e.g., bent portion has a larger radius). In multi-bladed systems bent blades having a larger radius result in decreased rinsability. Alternatively, a softer steel may be used to achieve the desired bend radius; however, this also has drawbacks. Blades manufactured from softer steels often do not have the necessary edge strength for a close and comfortable shave.
In one aspect, the invention features, in general, a process for manufacturing a razor blade in which a strip of blade steel is cut into discrete blanks each having an elongated edge and an elongated support portion extending between a pair of lateral end faces that are generally transverse to the elongated edge. The elongated edges are sharpened to form a cutting edge. The discrete blanks are deformed to form a bent portion. The pair of lateral end faces of the discrete blacks is treated to remove cracks. The manufacturing process may optionally include grinding the lateral end faces to an average roughness of about 0.45 um to about 1.0 um at a distance of about 1.0 mm to about 2.5 mm from elongated edge.
In another aspect, the invention features, in general, a razor cartridge having a housing with a guard and a cap. A bent blade is mounted to the housing between the guard and the cap. The bent blade has a cutting edge extending parallel to the cap and the guard, an elongated support portion, a bent portion between the cutting edge and the base portion, and a pair of lateral end faces generally transverse to the cutting edge. The lateral end faces have an average roughness of about 0.45 to about 1.0 um.
Referring to
The blades 18 may be mounted to the housing 16 and secured in at least one direction by at least one clip 24. The blades 18 may be rigidly fixed to the housing such that the blades 18 do not move relative to the housing 16 during a shaving stroke. Alternatively, the blades 18 may be spring loaded within the housing 16 such that the blades 18 are pushed up against the clips 24 in a neutral or rest position. The blades 18 may move slightly away from the clips 24 during a shaving stroke. As shown in
The housing 16 and the handle 14 may be injection molded from a semi-rigid polymeric material. In certain embodiments, the housing 16 and/or the handle 14 may be molded from Noryl™ (a blend of polyphenylene oxide (PPO) and polystyrene developed by General Electric Plastics, now SABIC Innovative Plastics). The housing 16 and/or the handle 14 may be molded from other semi-rigid polymers having a Shore A hardness of about 60 to 140, including, but not limited to acrylonitrile butadiene styrene (ABS), acetal, polypropylene, high impact polystyrene, or any combinations thereof. The guard 20 may be molded from the same material as the housing 16 or a softer material. For example, the guard 20 may be molded from materials having a shore A hardness of about 20 to about 70, such as thermoplastic elastomers (TPEs) or rubbers. The cap 22 may also be molded from the same material as the housing 16. In certain embodiments, the cap 22 may have an elongated strip containing a shaving aid to provide lubrication to the surface of the skin during shaving.
Referring to
In certain embodiments, the bent blade 18 (e.g., the elongated support portion 26) may have a hardness of about 540 HV to about 750 HV (e.g., about 540 HV to about 620 HV). In some embodiments, the bent portion 32 may have a hardness that is less than the hardness of the elongated support portion 26. The bent portion 32 may, for example, have a hardness of about 540 HV to about 620 HV. The hardness of the bent blade 18 may be measured by ASTM E92-82—Standard Test Method for Vickers Hardness of Metallic Materials. In certain embodiments, the bent blade 18 may have a substantially uniform hardness. In other embodiments, the cutting edge 30 may harder than the other portions of the bent blade 18. The cutting edge 30 may have a hardness of about 550 HV, 600 HV, or 650 HV to about 700 HV, 725 HV, or 750 HV.
Referring to
In some embodiments, the tapered portion 28 and/or the elongated support portion 26 have minimal levels of bow and sweep. Bow is a term used to describe an arching normal to the plane in which the portion of the cutting member is intended to lie. Sweep, also commonly referred to as camber, is a term used to describe an arching within the plane in which the portion of the cutting member lies (e.g., an arching of the longitudinal edges of the portion of the cutting member). In some embodiments, the tapered portion 28 has a bow of about +0.0004 to about −0.002 inch (+0.01 to −0.05 millimeter) or less across the length of the blade portion. In certain embodiments, the tapered portion 28 has a sweep of about ±0.0027 inch (±0.07 millimeter) or less across the length of the tapered portion 28. The elongated support portion 26 can have a bow of about ±0.0024 inch (±0.060 millimeter) or less across the length of the base portion. By reducing the levels of bow and/or sweep in the tapered portion 28 and/or the elongated support portion 26, the comfort of the user and/or the cutting performance of bent blade 18 can be improved.
The blades 18 must have a sufficient bend radius R to achieve the desired shaving geometry (e.g., interblade span, which is the distance between adjacent cutting edges 30 within the cartridge 12) for rinsing and overall shaving performance. Generally, softer materials may be bent to a sufficient bend radius; however these materials are difficult to sharpen such that the cutting edge 30 has sufficient strength and sharpness for close and comfortable shave. Generally, stiffer materials may be sharpened such that the cutting edge 30 has sufficient strength and sharpness; however the blades 18 often break during bending because the blade material is more brittle. Accordingly, the bend radius must often be decreased to avoid failure of the bent blade 18 which may compromise shaving performance.
Every part's surface (e.g., the lateral end faces 36 of the bent blade 18) is made up of texture and roughness which varies due to manufacturing techniques and the part structure itself. The average roughness (Ra value) of blade may be measured using a white-light 3D surface profiler (e.g., ZYGO, NV5000 Corporation, Middlefield, Conn.). The average roughness Ra is the computed average of all deviations of the roughness profile from the median line over the defined length. The white-light 3D surface profiler (WLS) provides fast, non-destructive, quantitative surface characterization of step heights, texture, roughness, and other surface topography parameters. This measurement technique is non-contact, three-dimensional, scanning white light and optical phase-shifting interferometry. Scanning white-light interferometry is a traditional technique that uses fringe contrast to yield surface information. A pattern of bright and dark lines (fringes) result from an optical path difference between a reference and a sample beam. Incoming light is split inside an interferometer, one beam going to an internal reference surface and the other to the sample. After reflection, the beams recombine inside the interferometer, undergoing constructive and destructive interference and producing the light and dark fringe pattern. WLS combines the power of modern high-speed computers with the vast amount of surface information produced by white-light interferometry. This permits WLS-based systems to measure surface features far more accurately than those measurable with conventional phase-measuring interferometry techniques. The most accurate of these systems, when operated in ideal environment have a repeatable accuracy of 0.0000025 inches or 0.0635 microns.
As shown in
Referring to
The continuous strip of blade steel 350 may be conveyed (e.g., pulled by a rotating roll from a roll of blade steel to a heat-treating device 310 (which may comprise multiple heat-treating devices), where strip 350 is heat-treated with a heat treating device (e.g., a furnace or oven) to increase the hardness and/or increase the ductility of discrete regions of the blade strip. Strip 350 is then re-coiled into a roll of hardened blade steel, and subsequently unwound and conveyed to a sharpening device 315, where an elongated edge region 317 (e.g., tapered portion 28 of
The strip 350 may then be conveyed to a segmenting device 335. The segmenting device 335 can be any device capable of separating the regions of the strip 350 between the slots 355 from the remainder of the strip 350 to form a plurality of discrete blanks 100. In some embodiments, the separating device 335 may be a punch press. The progression of the strip 350 can be periodically paused to allow the punch press to accurately separate the regions of the strip 350 between the slots 355 from the remainder of the strip 350 to form the discrete blanks 100. The cutting and/or segmenting process often produce discrete blanks 100 having a pair of rough lateral end faces 36. The rough lateral end faces may have micro-cracks and/or macro-cracks that can propagate during subsequent processing steps, such as bending. The lateral end faces of blades are typically not treated because they do not form part of the cutting edge and treating the lateral end faces would be an unnecessary and costly step. Furthermore, the lateral end faces of the blades are typically hidden away within the blade cartridge and not seen by the consumer. Prior to a bending process, the blade segments may go through a finishing device 359 to remove cracks (micro-cracks and/or macro-cracks) from the pair of lateral end faces 36. Examples of finishing processes may include, but are not limited to, grinding and electro-polishing. The finishing device 359 may produce discrete blanks 100 having a pair of lateral end faces 36 with a surface finish of about 0.45 um to about 1.0 um.
After the finishing step, the discrete blanks 100 may be then conveyed to a bending device 330 that creates a longitudinal bend 360 (e.g., bent portion 32 of
To form bent region 360 of strip 350, the discrete blanks 100 may be positioned between the punch 365 and die 370, as shown in
Use of the disclosed method increases the choices of stainless steel materials (and other materials) and blade geometries for a bent blade. Furthermore, the disclosed method of bending may avoid the necessity to provide a local secondary heat treatment or scoring process to a portion of the blade body to enhance ductility and minimize macro-cracks in the bent portion of the blade. For example, U.S. Patent application publications 2007/0124939 and 2007/0234577 disclose methods of locally heat treating a portion of a hardened razor blade body to enhance ductility and thus facilitate formation of a bent portion. However, a localized heat treatment or scoring processes can be used with the present method if desired.
While certain embodiments have been described, other embodiments are possible. For example, the localized heat-treating processes described above can be used to heat treat blades other than the bent blades described above. For instance, a localized heat-treating process can be used to locally harden the edge of a blade. Moreover, the order of many of the process steps discussed above can be altered. The process steps can be ordered in any of various different combinations. As another example, while heat-treating device 310 has been described as being configured to treat an edge region of strip 350, heat treating device 310 can alternatively or additionally be arranged to treat additional regions of strip 350 (e.g., regions of strip 350 that are not intended to be sharpened by sharpening device 315). In some embodiments, for example the entire strip 350 is hardened by heat-treating device 310.
As a further example, while increasing the ductility of a region of strip 350 that is to be bent has been described above, additional or other regions of strip 350 (e.g., regions of strip 350 that are not intended to be bent by bending device 330) may be heat-treated to increase ductility. In certain embodiments, for example, substantially the entire strip 350 is heat-treated to increase its ductility. In some embodiments, as noted above, strip 350 is conveyed through a heat treating device to harden substantially the entire strip. After initially hardening substantially the entire strip an edge region of strip 350 is sharpened as described above. Then, strip 350 is subjected to heat treating to increase the ductility of substantially the entire strip, which can help to improve the bending of strip 350. Strip 350 can then be further processed as discussed above.
As another example, while the embodiments above describe heat-treating a discrete region of strip 350 to increase the ductility of that region, in certain embodiments, the cutting member forming process can be carried out without this heat-treating step. In such embodiments, strip 350 can be formed of a relatively ductile material. Strip 350 can be conveyed through heat-treating device 310 to locally harden an edge region of strip 350 so that the edge region can be sharpened. After being sharpened, strip 350 can be cut and bent without first heat-treating the bend region. The material from which strip 350 is formed, for example, can be sufficiently ductile so that the second heat-treating step is not required to prevent damage to the strip as a result of the bending process. After bending strip 350, the remainder of the process can be carried out in accordance with the description herein.
As an additional example, in some embodiments, a heating device is configured to apply heat to both longitudinal edges of strip 350. For example, one of the longitudinal edges can be heat-treated, as discussed above, in order to harden the region for sharpening, and the opposing longitudinal edge can be heat treated to reduce (e.g., to prevent) sweep within strip 350. For example, the opposing longitudinal edge can be heat-treated to substantially the same temperature as edge 352. In some embodiments, the regions that are heat-treated are symmetrical with respect to a center line of strip 350. Various types of hard carbon coatings such as amorphous diamond, diamond-like-carbon (DLC) and combinations with the above can be applied. An outer coating of a fluoropolymer material, preferably PTFE is applied.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.”
Every document cited herein, including any cross referenced or related patent or application, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent 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 would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
