Patent Grant
7712222
The present invention relates to utility blades, and more particularly, to composite utility blades wherein the outer cutting edge of the blade is made of a highly wear-resistant alloy, and a backing portion of the blade is made of an alloy selected for toughness, such as spring steel. The present invention also relates to methods of making such composite utility blades.
Conventional utility blades are made of carbon steel and define a back edge, a cutting edge located on an opposite side of the blade relative to the back edge, and two side edges located on opposite sides of the blade relative to each other and extending between the back and cutting edges of the blade. A pair of notches are typically formed in the back edge of the blade for engaging a locator in a blade holder. Typically, the back, cutting and side edges of the blade define an approximately trapezoidal peripheral configuration. However, prior art utility blades have been commercially available for many years in a variety of shapes other than trapezoidal, such as rectangular or hooked blades. In addition, prior art utility blades have been provided in snap-off configurations wherein a single blade includes axially spaced score lines and separable blades or blade segments therebetween.
Conventional utility blades are manufactured by providing a carbon steel strip, running the strip through a punch press to punch the notches at axially spaced locations on the strip, and stamping a brand name, logo or other identification thereon. Then, the strip is scored to form a plurality of axially spaced score lines, wherein each score line corresponds to a side edge of a respective blade and defines a preferred breaking line for later snapping the scored strip into a plurality of blades. The punched and scored strip is then wound again into a coil, and the coil is hardened and tempered. The hardening and tempering operations may be performed in a “pit-type” vacuum furnace wherein the coils are repeatedly heated and cooled therein. Alternatively, the hardening and tempering operations may be performed “in-line”, wherein the strip is unwound from the coil and successively driven through a series of furnaces and quenching stations to harden and temper the strip. The carbon steel strip is typically heat treated to a surface hardness of about 58 Rockwell “c” (“Rc”), and thus defines a relatively hard and brittle structure.
The heat treated strip is then ground, honed and stropped in a conventional manner to form the facets defining a straight cutting edge along one side of the strip. Then, the strip is snapped at each score line to, in turn, break the strip along the score lines and thereby form from the strip a plurality of trapezoidal or other shaped utility blades. Because the entire strip is relatively hard and brittle (about 58 Rc), the strip readily breaks at each score line to thereby form clean edges at the side of each blade.
One of the drawbacks associated with such conventional utility blades is that each blade is formed of a single material, typically carbon steel, which is heat treated to a relatively hard and brittle state, typically about 58 Rc. Thus, although such blades define a relatively hard, wear-resistant cutting edge, the entire blade is also relatively brittle, and therefore is subject to premature breaking or cracking in use. In addition, the cutting edges of such conventional blades are frequently not as wear resistant as might otherwise be desired. However, because the entire blade is made of the same material, any increase in hardness, and thus wear resistance of the cutting edge, would render the blade too brittle for practical use. As a result, such conventional utility blades are incapable of achieving both the desired wear resistance at the cutting edge, and overall toughness to prevent cracking or premature breakage during use. Another drawback of such conventional utility blades is that the carbon steel typically used to make such blades corrodes relatively easily, thus requiring premature disposal of the blades and/or costly coatings to prevent such premature corrosion.
Certain prior art patents teach composite utility blades defining sandwiched, laminated, or coated constructions. For example, U.S. Pat. No. 4,896,424 to Walker shows a utility knife having a composite cutting blade formed by a body section 16 made of titanium, and a cutting edge section 18 made of high carbon stainless steel and connected to the body section by a dovetail joint 25.
U.S. Pat. Nos. 3,279,283, 2,093,874, 3,681,846, and 6,105,261 relate generally to laminated knives or razor blades having cutting edges formed by a core layer made of a high carbon steel or other relatively hard material, and one or more outer layers made of relatively softer materials. Similarly, U.S. Pat. Nos. 3,911,579, 5,142,785, and 5,940,975 relate to knives or razor blades formed by applying a relatively hard carbon coating (or diamond like coating (“DLC”)) to a steel substrate. In addition, U.S. Pat. Nos. 5,317,938 and 5,842,387 relate to knives or razor blades made by etching a silicon substrate.
One of the drawbacks associated with these laminated, sandwiched and/or coated constructions, is that they are relatively expensive to manufacture, and therefore have not achieved widespread commercial use or acceptance in the utility blade field.
In stark contrast to the utility blade field, bi-metal band saw blades have been used in the saw industry for many years. For example, U.S. Reissue Pat. No. 26,676 shows a method of making bi-metal band saw blades wherein a steel backing strip and high speed steel wire are pre-treated by grinding and degreasing, and the wire is welded to the backing strip by electron beam welding. Then, the composite band stock is straightened and annealed. The sides of the annealed stock are then dressed, and the band saw blade teeth are formed in the high speed steel edge of the composite stock by milling. Then, the teeth are set and the resulting saw blade is heat treated. There are numerous methods known in the prior art for heat treating such band saw blades. For example, International Published Patent Application No. WO 98/38346 shows an apparatus and method for in-line hardening and tempering composite band saw blades wherein the blades are passed around rollers and driven repeatedly through the same tempering furnace and quenching zones. The heat treated composite band saw blades are then cleaned and packaged.
Although such bi-metal band saw blades have achieved widespread commercial use and acceptance over the past 30 years in the band saw blade industry, there is not believed to be any teaching or use in the prior art to manufacture utility blades defining a bi-metal or other composite construction as with bimetal band saw blades. In addition, there are numerous obstacles preventing the application of such band saw blade technology to the manufacture of utility blades. For example, as described above, conventional utility blades are manufactured by forming score lines on the carbon steel strip, and then snapping the strip along the score lines to break the strip into the trapezoidal or other shaped blades. However, the relatively tough, spring-like backing used, for example, to manufacture bi-metal band saw blades, can be relatively difficult to score and snap in comparison to conventional carbon steel utility blades. In addition, the heat treating applied to conventional utility blades could not be used to heat treat bimetal or other composite utility blades.
The high speed or tool steels used to manufacture wear-resistant cutting edges, such as the wear-resistant cutting edges in prior art band saw blades, are relatively expensive in comparison, for example, to the carbon steels used to manufacture conventional utility blades. In addition, the grinding and honing operations involved in forming wear-resistant cutting edges from high speed and tool steels can create significant amounts of scrap and/or waste of these expensive materials.
Accordingly, it is an object of the present invention to overcome one or more of the above-described drawbacks and disadvantages of prior art utility blades and/or methods of making such blades, and to provide a bi-metal or other composite utility blade defining a relatively hard, wear-resistant cutting edge, and a relatively tough, spring-like backing, and a method of making such utility blades.
One aspect of the present invention is directed to a composite utility blade comprising a back edge, a cutting edge located on an opposite side of the blade relative to the back edge, and two side edges located on opposite sides of the blade relative to each other and extending between the back and cutting edges of the blade. In one embodiment of the present invention, the back, cutting and side edges of the blade define an approximately trapezoidal peripheral configuration. However, the blades of the present invention may take any of numerous different shapes and configurations, including rectangular, hooked, and snap-off blades. The composite utility blade of the present invention further defines first and second metal portions, wherein the first metal portion extends between the back edge and the second metal portion, and further extends from approximately one side edge to the other side edge of the blade. The first metal portion is formed of an alloy steel heat treated to a first hardness that is preferably within the range of approximately 38 Rc to approximately 52 Rc. The second metal portion defines the cutting edge, and extends from approximately one side edge to the other side edge, and is formed of a high speed or tool steel heat treated to a second hardness that is greater than the first hardness, and preferably within the range of approximately 60 Rc to approximately 75 Rc. A weld region of the blade joins the first and second metal portions and extends from approximately one side edge to the other side edge of the blade.
Another aspect of the present invention is directed to a method of making composite utility blades. In accordance with one embodiment of the present invention, the method comprises the steps of providing an elongated wire formed of high speed or tool steel, and an elongated backing strip formed of an alloy steel and defining an approximately planar upper side, an approximately planar lower side, and opposing back and front edges extending between the upper and lower sides. The wire is butt joined to the front edge of the backing strip. Then, thermal energy is applied to the interface between the wire and backing strip to weld the wire to the backing strip and, in turn, form a composite strip defining a first metal portion formed by the steel backing strip, a second metal portion formed by the high speed steel wire, and a weld region joining the first and second metal portions. The composite strip is then annealed, and the annealed strip is straightened to eliminate any camber or other undesirable curvatures in the annealed composite strip. Then, a plurality of notches are formed, such as by punching, in axially spaced locations relative to each other along the back edge of the first metal portion and/or at other desired locations of the annealed composite strip. The annealed and punched composite strip is then hardened such that the first metal portion defines a first surface hardness that is preferably within the range of approximately 38 Rc to approximately 52 Rc, and the second metal portion defines a second surface hardness greater than the first surface hardness, and preferably within the range of approximately 60 Rc to approximately 75 Rc. The hardened strip is then subjected to at least one, and preferably two, tempering and quenching cycles. Then, facets are formed on the edge of the second metal portion, such as by grinding, honing and stropping, to in turn form an approximately straight, high speed or tool steel cutting edge along the side of the composite strip opposite the back edge of the first metal portion. The composite strip is then die cut, bent and/or snapped, or otherwise separated along shear or score lines axially spaced relative to each other to form a plurality of utility blades from the strip. In a currently preferred embodiment of the present invention, each utility blade defines an approximately trapezoidal peripheral configuration and at least one notch is formed in the back edge thereof. However, the blades of the present invention may take any of numerous different shapes and configurations, including rectangular, hooked, and snap-off blades.
In accordance with an alternative embodiment of the present invention, prior to hardening, the high speed or tool steel edge of the composite strip is cut to form notches, such as by punching, at the interface of each shear or score line and the second metal portion. The notches are formed to separate the high speed steel cutting edges of adjacent composite utility blades formed from the composite strip, to facilitate bending and snapping the blades from the composite strip, and/or to shape the corners of the cutting edges of the blades.
In accordance with another embodiment of the present invention, the composite strip is scored at axially spaced locations relative to each other to form a plurality of score lines, wherein each score line is oriented at an acute angle relative to the back edge of the first metal portion, and the plurality of score lines define a plurality of blade sections and scrap sections located between the blade sections. In the trapezoidal blade configuration, the scrap sections are approximately triangular and the blade sections are approximately trapezoidal. As described above, notches are preferably formed at the interface of each score line and the second metal portion to facilitate separation of the blades from the composite strip and to shape the corners of the cutting edges of the blades. In order to separate the blades from the composite strip, each scrap section is bent outwardly relative to a plane of the composite strip on one side of a respective score line. Upon bending each scrap section, the composite strip is pressed on an opposite side of the respective score line to, in turn, break the blade section away from the bent scrap section along the respective score line. This process is repeated at each score line, or is performed substantially simultaneously for each pair or other group of score lines defining each respective utility blade, to thereby form the plurality of blades from the composite strip.
In accordance with another aspect, the present invention is directed to a method of making a composite utility blade. The blade includes a first metal portion forming a backing, a second metal portion forming a cutting edge and defining a first predetermined cross-sectional shape, and a weld region joining the first and second metal portions. The method comprises the steps of:
(i) providing an elongated backing strip formed of steel, wherein the elongated backing strip includes a first side, a second side, and opposing edges extending between the first and second sides;
(ii) providing an elongated wire formed of wear-resistant steel and defining a second predetermined cross-sectional shape substantially corresponding to the first predetermined cross-sectional shape of the second metal portion of the blade;
(iii) placing the wire in contact with an edge of the backing strip;
(iv) applying thermal energy to the interface between the wire and backing strip to weld the wire to the backing strip and, in turn, forming a composite strip defining a first metal portion formed by the steel backing strip, a second metal portion formed by the wear-resistant steel wire having substantially the second predetermined cross-sectional shape, and a weld region joining the first and second metal portions;
(v) heat treating the composite strip; and
(vi) forming at least one facet on the second metal portion and, in turn, forming a wear-resistant steel cutting edge on the composite strip.
In one embodiment of the present invention, the step of providing an elongated wire includes providing a wire that defines an initial cross-sectional shape, and then shaping the wire into the second predetermined cross-sectional shape that is different than the initial cross-sectional shape. Preferably, the wire is shaped into the second predetermined cross-sectional shape prior to welding the wire to the backing strip. Also in one embodiment of the present invention, the initial cross-sectional shape of the wire is substantially round, and the second predetermined cross-sectional shape of the wire is multi-faceted. Preferably, the second predetermined cross-sectional shape of the wire is selected from the group including: (a) substantially rectangular; (b) substantially trapezoidal; (c) substantially triangular; (d) substantially parallelogram-shaped; and (d) a combination of substantially rectilinear and triangular. Also in currently preferred embodiments of the present invention, the step of shaping the wire into the second predetermined cross-sectional shape includes at least one of: (a) rolling the wire; (b) passing the wire through a Turks Head; and (c) passing the wire through a draw die.
In one embodiment of the present invention, the method further comprises the step of coating the wear-resistant cutting edge with at least one of TiN and AlTiN. In one such embodiment, the method further comprises the steps of coating the wear-resistant cutting edge with an inner layer of AlTiN and an outer layer of TiN. In one such embodiment, the method further comprises the step of applying the AlTiN coating in a gradient such that there is a lower concentration of aluminum at the inner side of the coating and a higher concentration of aluminum at the outer side of the coating.
In accordance with another aspect, the present invention is directed to a composite strip for forming therefrom at least one utility blade. The blade includes a first metal portion forming a backing, a second metal portion forming a cutting edge and defining a first predetermined cross-sectional shape, and a weld region joining the first and second metal portions. The composite strip comprises a first metal portion defined by an elongated backing strip formed of steel, wherein the elongated backing strip defines a first side, a second side, and opposing edges extending between the first and second sides. A second metal portion of the strip defines a second predetermined cross-sectional shape substantially corresponding to the first predetermined cross-sectional shape of the second metal portion of the blade, and is defined by an elongated wire formed of wear-resistant steel and having substantially the second predetermined cross-sectional shape. A weld region of the strip joins the first and second metal portions.
In one embodiment of the present invention, the second predetermined cross-sectional shape of the wire and the first predetermined cross-sectional shape of the second metal portion are selected from the group including: (a) substantially rectangular; (b) substantially trapezoidal; (c) substantially triangular; (d) substantially parallelogram-shaped; and (d) a combination of substantially rectilinear and triangular. In one such embodiment, the second predetermined cross-sectional shape of the wire is substantially the same as the first predetermined cross-sectional shape of the second metal portion of the blade.
In one embodiment of the present invention, the composite strip further comprises at least one of an AlTiN coating and a TiN coating. In one such embodiment, the composite strip comprises an inner AlTiN coating and an outer TiN coating. In one such embodiment, the coatings define a strip extending along opposite sides of the cutting edge relative to each other.
One advantage of the utility blades of the present invention, is that they provide an extremely hard, wear-resistant cutting edge, and an extremely tough, spring-like backing, particularly in comparison to the conventional utility blades as described above. Thus, the utility blades of the present invention provide significantly improved blade life, and cutting performance throughout the blade life, in comparison to conventional utility blades. In addition, the utility blades, and methods of making such blades, are relatively cost effective, particularly in comparison to the composite utility blades defining sandwiched, laminated and/or coated constructions, as also described above. As a result, the utility blades of the present invention provide a combination of wear resistance, toughness, cutting performance, and cost effectiveness heretofore believed to be commercially unavailable in utility blades.
Other objects and advantages of the present invention will become readily apparent in view of the following detailed description of preferred embodiments and accompanying drawings.
FIGS. 12A and 12D-12F are cross-sectional views of additional embodiments of the composite strip of the present invention formed by welding pre-shaped high speed steel wires to the spring steel backings.
In
The blade 10 further defines a first metal portion 20 and a second metal portion 22. As shown typically in
The first metal portion 20 defines a spring-like backing that is relatively pliable, tough, and thus highly resistant to fatigue and cracking. The second metal portion 22, on the other hand, is relatively hard and highly wear resistant, and thus defines an ideal, long-lasting cutting blade. As a result, the composite utility blades of the present invention define highly wear-resistant, long-lasting cutting edges, combined with virtually unbreakable or shatterproof backings (and thus shatter-proof blades). Thus, in stark contrast to the typical utility blades of the prior art, the composite utility blades of the present invention provide a cost-effective blade exhibiting both improved wear resistance and toughness heretofore commercially unavailable in such blades.
The first metal portion 20 of blade 10 is preferably made of any of numerous different grades of steel capable of being heat treated to a surface hardness within the preferred range of approximately 38 Rc to approximately 52 Rc, such as any of numerous different alloy steels or standard AISI grades, including without limitation 6135, 6150 and D6A. The second metal portion 22, on the other hand, is preferably made of any of numerous different types of wear-resistant steel capable of being heat treated to a surface hardness within the preferred range of approximately 60 Rc to approximately 75 Rc, including any of numerous different tool steels or high-speed steels, such as any of numerous different standard AISI grades, including, without limitation, M Series grades, such as M1, M2, M3, M42, etc., A Series grades, such as A2, A6, A7 A9, etc., H Series grades, such as H10, H11, H12, H13, etc., T Series grades, such as T1, T4, T8, etc., and W, S, O, D and P Series grades.
As may be recognized by those skilled in the pertinent art based on the teachings herein, the currently preferred materials used to construct the first and second metal portions 20 and 22 and disclosed herein are only exemplary, and numerous other types of metals that are currently or later become known for performing the functions of the first and/or second metal portions may be equally employed to form the composite utility blades of the present invention.
As further shown in
As also shown in
As further shown in
As also shown in
Turning to
At step 104 of
As shown at step 106 of
After annealing, the bi-metal strip 46 is then uncoiled, if necessary, as shown at step 110, and the strip is straightened, as shown at step 112. After welding and annealing, the bi-metal strip 46 may develop a significant camber or other undesirable curvatures, and therefore such curvatures must be removed prior to further processing. In the currently preferred embodiment of the present invention, the bimetal strip 46 is mechanically straightened by passing the strip through a series of pressurized rolls in a straightening apparatus of a type known to those of ordinary skill in the pertinent art, such as the Bruderer™ brand apparatus. However, as may be recognized by those skilled in the pertinent art based on the teachings herein, any of numerous straightening apparatus that are currently or later become known for performing the function of straightening metal articles like the bi-metal strip 46 may be equally employed. For example, as an alternative to the mechanical straightening apparatus, the bimetal strip 46 may be straightened by applying heat and tension thereto in a manner known to those of ordinary skill in the pertinent art.
As shown at step 114, the straightened bimetal strip 46 may be coiled again, if necessary, for transportation and further processing. As shown at step 116 of
In accordance with a currently preferred embodiment of the present invention, the depth of score is preferably within the range of about 40% to about 50% of the thickness of the blade, and most preferably within the range of about 45% to about 48% of the thickness of the blade. In the illustrated embodiment, the blade is approximately 0.6 mm thick, and the depth of score is preferably within the range of about 0.27 mm to about 0.29 mm. With the current blade design and materials of construction, a depth of score greater than about 50% of the blade thickness has tended to cause the bi-metal strip to pull apart at the score lines upon passage through the furnace. Also in accordance with the currently preferred embodiment of the present invention, each score line is approximately v-shaped, and the included angle of each v-shaped score line is preferably within the range of about 50° to about 60°. In the illustrated embodiment of the present invention, the included angle of each score line is about 55°. The greater the included angle of the score line, the greater is the pressure on the back side of the blade upon scoring, and thus the greater is the likelihood that the scoring tool will create a ripple effect on the back side of the blade. The smaller the included angle, on the other hand, the more rapid will be the scoring tool wear during use.
The apparatus 56 further includes a punch 66 defining a plurality of cutting surfaces 68, each corresponding in shape and position to a respective notch 24 and aperture 26. As shown in
As shown at step 120 of
At step 126, the tempered and quenched bi-metal strip 46 is coiled again, if necessary, for transportation to the next tempering station, and at step 128, the bi-metal strip is uncoiled for the second tempering cycle. As discussed above, these and other coiling and uncoiling steps can be eliminated by providing one or more in-line stations for processing the bi-metal strip. At step 130, the bi-metal strip is tempered again within a second tempering cycle at a temperature within the range of approximately 1000° F. to approximately 1200° F. for a tempering time within the range of about 3 to about 5 minutes. After the second tempering cycle, the bi-metal strip is quenched to room temperature. In the currently preferred embodiment, the quench is an air quench; however, as discussed above, this quench may take the form of any of numerous other types of quenching processes that are currently or later become known for articles of the type disclosed herein. Then, at step 132 the tempered and quenched bi-metal strip is coiled again either for temporary storage and/or transportation to the grinding, die cutting or bending and snapping stations.
At step 134, the annealed, hardened and tempered bi-metal strip 46 is uncoiled again, if necessary, and at 136, the bi-metal strip is subjected to grinding, honing, stropping, and die-cutting or bending and snapping steps. More specifically, the bi-metal strip 46 is ground, honed and stropped in a manner known to those of ordinary skill in the pertinent art to form the facets 30 and 32 of
As shown in
In accordance with an alternative embodiment of the present invention, and as shown typically in
The notches 98 of
Turning again to
Turning to
In
In the operation of the bending and snapping apparatus 142, the composite strip 46 is fed through the blade gap 184 of the apparatus in the direction of the arrow C of
As shown in
Turning to
In each case, the cross-sectional shape of the wire 244 more closely corresponds to the cross-sectional shape of the second metal portion of the blades to be formed from the composite strip than does a square cross-sectional shaped wire, for example. Preferably, the cross-sectional shape of the wire 244 substantially matches the cross-sectional shape of the second metal portion of the blade. For example, if the cross-sectional shape of the second metal portion is triangular, than the cross-sectional shape of the elongated wire is preferably also triangular. However, manufacturing limitations and/or other considerations may require that the cross-sectional shape of the wire not match the cross-sectional shape of the second metal portion of the blade. For example, although the second metal portion of the blade may define a triangular cross-sectional shape, the pre-shaped wire may define a trapezoidal cross-sectional shape as shown, for example, in
Accordingly, one advantage of pre-shaping the tool steel wire prior to forming the composite strip is that it reduces the amount of scrap generated during grinding and honing of the strip, and thus may enable a significant reduction in the amount of high speed or tool steel required to form the blades and, in turn, enable a decrease in the overall cost of the blades in comparison to blades formed from composite strips having, for example, round and/or square tool steel wires. For example, a conventional rectangular shaped high speed or tool steel wire, as described above, may define a width of about 0.04 inch and a height of about 0.025 inch. Thus, pre-shaping the wire in a triangular cross-sectional shape may reduce by about one half the amount of relatively expensive high speed or tool steel required to form the cutting edges of the blade in comparison to the same sized blades that employ rectangular wires. Although the trapezoidal shaped wires do not reduce by half the amount of high speed or tool steel in comparison to similarly sized rectangular wires, they nevertheless can significantly reduce the amount of high speed or tool steel required, and further, can reduce the amount of grinding required in comparison to blades that employ similarly sized rectangular wires. Accordingly, another advantage of employing pre-shaped wires is that they can significantly reduce the amount of grinding required and, in turn, increase the throughput of the manufacturing process, thus further enabling a decrease in overall cost of the blades.
As shown in
The wire 244 may be provided in round form. In this case, it may be necessary to draw the round stock through a drawing die or series of drawing dies in a manner known to those of ordinary skill in the pertinent art in order to reduce the diameter to that necessary or otherwise desired for further processing. Then, the drawn round wire is shaped into the desired predetermined shape that substantially corresponds to the shape of the second metal portion of the blade, as shown, for example, in
As shown in
The composite strip 246 is then processed in the same manner as any of the composite strips described above in order to form therefrom the composite utility blades. As indicated above, a significant advantage of the composite strip 246 is that it may use less high speed steel and/or increase the manufacturing throughput than otherwise might be achieved without pre-shaping the wire.
Turning to
In addition, many, if not all, of the coiling and uncoiling steps shown in
In some embodiments, a blade in accordance with any of the embodiments described hereinabove, is provided with one or more coatings. Such coating(s) may be provided for one or more of a number of reasons. For example, some types of coatings are purely decorative (i.e., non-functional or cosmetic). Some other types of coatings are purely functional (e.g., wear and/or corrosion resistance). Some other types of coatings may have decorative and functional aspects. Moreover, one or more coating(s) may be provided on top of one or more other coating(s). For example, in some embodiments, a functional coating is provided over a blade (or portion(s) thereof) and a decorative coating is provided over the functional coating (or portion(s) thereof). A coating may be provided over an entire blade or any portion thereof (e.g., the cutting edge 14 or portion(s) thereof).
As used herein, except where otherwise stated, the phrases “decorative” coating and “cosmetic” coating, mean at least primarily “decorative” and at least primarily “cosmetic”, respectively, so as not to preclude the possibility that a decorative coating or a cosmetic coating, respectively, provide some amount of wear and/or corrosion resistance (or some other non-decorative or non cosmetic property). For example, decorative coatings may provide some measure of wear and/or corrosion resistance. However, the amount of wear and/or corrosion resistance (or other property) provided by a decorative or cosmetic coating will generally be small compared to that of a purely functional coating of similar thickness and suitable composition.
Some examples of different types of coatings include carbide coatings, nitride coatings, and combinations thereof. Coatings intended to reduce the rate of wear of the blade may comprise, for example, any suitable material(s) including but not limited to titanium nitride (TiN), chrome nitride (CrN), titanium carbide (TiC), ceramic(s), titanium carbonitride (TiCN), Aluminum Titanium Nitride (AlTiN), Aluminum Titanium Carbonitride (AlTiCN), Zirconium Nitride (ZrN), Zirconium Carbonitride (ZrCN), and/or combinations thereof.
Some types of decorative coatings are used to make a blade (or portion(s) thereof, e.g., the cutting edge 14, or portion(s) thereof) having a colored appearance, e.g., gold, or any of numerous other colors. Some of such decorative coatings are comprised of titanium nitride (TiN). In some embodiments, a decorative coating is applied only to one or more of the first facets 30 (or portion(s) thereof), thereby defining colored strip(s) over the cutting edge 14.
Some methods for use in providing functional (e.g., wear or abrasion resistant coatings) on a blade include the step of heating the base material (e.g., carbon steel). Although such heating may cause a reduction in the hardness of the base material it also increases the ability of the base material to support the coating, which helps the coating hold up better against heat generated during cutting operations. For a base material formed of carbon steel, the temperature may be, but is not limited to, a temperature in the range of about 300° F. to about 400° F. For high speed steel, the temperature may be, but is not limited to, a temperature of about 1000° F. In some embodiments, the temperature may be greater than about 1000° F. One advantage of the bi-metal blades of the currently preferred embodiments of the present invention is that the high speed steels used to form the cutting edges can be heated to temperatures on the order at least about 1000° F. without damage thereto, and therefore such blades are uniquely suited for coatings that require high temperatures or that permit operation under high temperatures, such as AlTiN or other PVD coatings. Accordingly, if relatively high temperatures are generated at the cutting edges of the AlTiN coated blades of the present invention, the coating can better withstand the heat in comparison to prior art blades. If some conventional carbon steels, on the other hand, are heated to temperatures above between about 300° F. and about 400° F., the steel can lose its hardness and strength and, in turn, lose its ability to properly support some such coatings.
In at least some embodiments, one or more coating(s) are provided using physical vapor deposition (PVD). Physical vapor deposition may be carried out in any suitable manner including but not limited to using cathodic arc deposition, thermal/electron beam deposition, and/or sputter deposition. However coatings also may be provided by other methods. Indeed, coatings may be provided using any suitable manner including but not limited to painting, spraying, brushing, dipping, plating (electroplating or electro-less plating), physical and/or chemical vapor deposition, or any combination thereof. Powder coatings and e-coatings, and/or combinations of any of the above, also may be employed.
In accordance with currently preferred embodiments of the present invention, the utility blades are coated with either TiN or AlTiN, or with an inner layer of AlTiN and an outer layer of TiN for a gold-colored appearance. The coatings extend along the cutting edge, and along the sides of the blade adjacent to the cutting edge. The AlTiN coatings are applied to the pre-sharpened blades in a thickness within the range of about 3 micrometers to about 5 micrometers. In the embodiment employing an inner coating of AlTiN and out outer coating of TiN, the outer coater is thinner than the inner coating. Also in a currently preferred embodiment of the present invention, the AlTiN coating is applied so as to provide a gradient (linear or otherwise) such that the concentration of aluminum increases from about 32% (atomic percent) at the substrate surface to about 66% at the outer surface of the coating. One advantage of this configuration is that the higher concentration of titanium at the substrate/coating interface facilitates adhesion of the coating to the substrate.
The AlTiN and TiN coatings are applied to the blades in a commercially available cathodic arc deposition system, in which the coiled bi-metal strips (or separated blades if so desired) are processed through a multistage cleaning system to remove the bulk of surface contaminant soils. The PVD coating chamber is of a conventional type including gas lines for oxygen, nitrogen, argon, and methane/acetylene; a vacuum pump system coupled in fluid communication with the chamber for evacuating the chamber; a plurality of targets spaced relative to each other about the chamber; a water circulating unit that circulates hot and cold water via a closed loop system to the chamber; and a plurality of evaporators and evaporator power supplies.
Each bi-metal strip is preferably wound into a coil with a buffer strip interposed between the windings of the bi-metal strip. The buffer strip may be formed, for example, of stainless steel, and may define a plurality of axially spaced dimples projecting laterally therefrom to define a pre-determined spacing between adjacent windings of the bi-metal coil. The width of the buffer strip is preferably less than the width of the bi-metal strip. Thus, when the strips are wound together into a coil, the back edges of the strips are preferably aligned such that the cutting edge of the bi-metal strip extends beyond the corresponding edge of the buffer strip. The exposed portions of the bi-metal strip will be exposed to the targets, and thus will be coated with the AlTiN, TiN, AlTiN/TiN, or other PVD coating. Thus, the extent to which the bi-metal strip extends beyond the corresponding edge of the buffer strip defines the depth of coating on the bi-metal strip (or the width of the coating on opposing sides of the cutting edge).
A plurality of such coils are mounted on cross-shaped or other suitable fixtures for holding the coils in the coating chamber and allowing relative movement between the coils and targets for coating the cutting edges of the bi-metal strips. The exposed edges or cutting edges of the bi-metal coiled strips are preferably oriented in planes approximately parallel to the planes of the targets (i.e., the cutting edges are mounted to face the targets and to receive a substantially uniform PVD coating therefrom). The cross-shaped or other suitable fixtures for holding the coils are mounted on a planetary fixture that is received within the coating chamber and rotatably driven therein. The cross-shaped fixtures and coils mounted thereon are mounted on the planetary fixture such that they are axially and angularly spaced relative to each other. In one embodiment, the planetary fixture can hold about 8 coils, with a first set of four coils angularly spaced about 90° relative to each other, and a second set of four coils angularly spaced about 90° relative to each other and axially spaced relative to the first set of four coils. If desired, the two sets of coils can be angularly offset about 90° or otherwise relative to each other.
Once the coils are mounted within the coating chamber, the chamber is pumped down to insure a pure processing environment consisting of only the cleaned bi-metal strips to be coated and the solid material to be vaporized. Then, after the extremely low pressure or high vacuum pure environment is created, the coiled bi-metal strips are gently heated. Heating ensures out gassing of the bi-metal substrates and raises the core and surface temperatures of the bi-metal substrates to better match the thermodynamics of the coating cycle. One embodiment of the system uses PID controlled heaters to coat at a temperature within the range of about 100°-120° F. for a time period within the range of about 0-150 minutes.
The apparatus then performs etching by employing a combination of sputter etches at a high bias voltage and arc assisted argon etches at a high bias voltage (the apparatus may transition from sputter etch to arc assisted glow discharge etch in steps). Etch depth is controlled in a manner known to those of ordinary skill in the pertinent art. The sputter etch is a Ti ion bombard etch where the surface is heated up and conditioned by ramping the voltage in discrete steps as a precursor to an arc enhanced glow discharge. The arc enhanced glow discharge uses a Mod pulsar system for substrate conditioning. The shutter closes on the Ti/Cr targets and there is a generation of a glow (plasma) using bias voltage that gradually raises from 0 to about 400 V in steps with two targets running from 0 to about 85 V.
The next phase consists of Argon gas plasma cleaning (etching) of the substrates inside the vacuum chamber. The Argon back sputter ion cleaning is effective in atomically preparing the surface of the substrates by removing oxide layers and exposing native surfaces. One advantage of this feature is that it facilitates adhering the coating to the substrate and not to any oxides or other contaminants that otherwise could be located on the surface of the substrate.
The reactive coating process is performed at about 0-500 V bias and by turning on the evaporators from about 0-85 amps on the targets. Process gases are bled into the chamber and the coating material is vaporized and condensed or deposited on the exposed cutting edges and adjacent surfaces of the wound bi-metal substrates. The desired coating thickness is reached by allowing the vaporization to continue for a predetermined amount of time. Coating times may vary from about 30 minutes to about four hours. As described above, in currently preferred embodiments of the present invention, the coatings consist of either TiN or AlTiN, or an inner coating of AlTiN with an outer coating of TiN to achieve a gold-colored appearance. In a currently preferred embodiment of the present invention, the AlTiN coating is applied in a thickness within the range of about 3 micrometers to about 5 micrometers. In the embodiment including an inner AlTiN coating, and an outer TiN coating, the outer TiN coating is thinner than the inner AlTiN coating. The coating(s) preferably are applied in stripes or like narrow bands extending along opposite sides of the cutting edge relative to each other. In the currently preferred embodiments of the present invention, the width of each stripe is preferably within the range of about 0.005 inch through about 0.025 inch (for blades having a width of about 0.75 inch and a thickness of about 0.025 each). In one currently preferred embodiment of the present invention, the width of the stripe is about 0.125 inch. However, as may be recognized by those of ordinary skill in the pertinent art based on the teachings herein, the coatings may cover all and/or other portions of the blades, as may be applied in a format other than a stripe. Once the coating process is completed, the wound bi-metal strips are allowed to cool, the chamber is brought back to atmospheric pressure, and the coated bi-metal strips are removed and are ready for separating same into the individual blades as described above. Exemplary procedural steps involved in coating utility blades as described above are illustrated in Table 1 below.
Some types of coatings and methods for providing such coatings are described by Teer, D. G., et al., “Self Lubricating Coatings for the Protection of Cutting and Forming Tools and Mechanical Components”, Vacuum Technology & Coating, Society of Vacuum Coaters, October 2000, pp. 48-53, which is incorporated by reference herein. However, other types of coating(s) and method(s), or combinations thereof, also may be used.
Of course, as indicated above, the utility blades and processes of making such blades in accordance with the present invention do not require coating(s).
Accordingly, as may be recognized by those skilled in the pertinent art based on the teachings herein, numerous changes and modifications may be made to the above-described and other embodiments of the composite utility blades and the methods of making such blades of the present invention without departing from the scope of the invention as defined in the appended claims. This detailed description of preferred embodiments is to be taken in an illustrative, as opposed to a limiting sense.
This patent application claims the benefit of U.S. provisional patent application Ser. No. 60/451,985, filed Mar. 5, 2003, entitled “Composite Utility Knife Blade, And Method Of Making Such A Blade”. The foregoing patent application is assigned to the Assignee of the present invention and is hereby expressly incorporated by reference as part of the present disclosure.
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