United States Patent 3775285

A method and apparatus for placing extremely thin finish coatings on previously sharpened coils of band or ribbon type razor blade material prior to cutting such strips into shorter lengths for eventual inclusion in magazine fed ribbon blade safety razors. The method includes winding a relatively great length of ribbon blade into a helix or coil with an open center, fitting the coil within a special fixture, and placing the coil and fixture within an evacuable chamber wherein one or more coating materials are sputtered onto the blade edge in extremely thin layers under carefully controlled conditions. The chamber, in addition to conventional vacuum system components, includes at least one, and sometimes plural electrodes, each adapted to receive thereover a target plate containing a coating of the material to be sputtered therefrom and onto the blade edge. A shutter arrangement is provided to shield the blade edge against contamination during the time the target is being cleaned in vacuo prior to coating, and to protect the target from contamination when the blade edge is being sputter etched in order to clean it before coating. Means are provided for indexing the shutter to desired positions for these operations and for rotating the fixture so as to cause portions of the blade coil to be passed successively adjacent the target in facing relation thereto when the shutter is indexed so as to provide a generally perpendicular line of sight between the target and the portion of the blade coil facing the target. The fixture is preferably in the form of a disc with an annular groove therein for receiving the blade coil and for providing controlled exposure of the edge portion thereof, while the shutter preferably is in the form of one or more rotatably mounted apertured plates. The sputtering process includes the formation of a plasma within the evacuated chamber by the ionization of an otherwise inert or non-reactive gas; the coating materials may be metals or alloys as well as dielectric materials such as organic plastics applied to the edge for imparting lubricity thereto. Coating thicknesses range from about 50 Angstroms or less up to several hundred Angstroms or more, but, in any case, are insufficiently thick to dull the previously sharpened blade edge.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
204/298.08, 204/298.15, 204/298.28
International Classes:
C23C14/35; (IPC1-7): C23C15/00
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US Patent References:

Primary Examiner:
Mack, John H.
Assistant Examiner:
Valentine D. R.
I claim

1. An apparatus for applying a coating material to an edge portion of strip material rolled in a coil, said apparatus comprising, in combination, an evacuatable chamber, means within said chamber including an annular recess for holding said coil of strip material arranged in said recess with said edge portion upwardly exposed and concentrically aligned about a vertical axis of said holding means, at least one electrode within said chamber, means for maintaining target means containing the coating material disposed in closely overlying relation to said electrode, said target means being radially spaced from said axis and disposed in oppositely facing relation to a sector of said recess, means for establishing a voltage gradient between said target and said coil of material, means for admitting minute amounts of an ionizable gas into said chamber under controlled conditions to establish a plasma in said chamber for sputtering the coating material from said target means to said edge portion, and means for rotating said holding means about said axis during sputtering.

2. An apparatus as in claim 1 wherein said holding means is in the form of a generally flat disc.

3. An apparatus as in claim 1 wherein said means for establishing a voltage gradient includes a radio frequency alternating voltage supply source.

4. An apparatus as in claim 1 wherein means is interposed between said electrode and said recess to allow sputter removal of material from both said electrode and said coil without deposition of said sputtered material on said electrode or said coil in the form of an apertured shutter disposed in generally facing relation to said holding means, with said aperture being spaced radially from the center of said coil and overlying a portion of said coil within only a narrow sector thereof.

5. An apparatus as in claim 5 wherein aid interposable means is in the form of a shutter mounted coaxially with said holding means, said shutter being rotatably mounted for indexing of an aperture therein into and out of aligned relation with said target means, said aperture being in said aligned relation with said target means when said sputtered target material is to be deposited on said coil and wherein said means is interposed when the surface of said target and said coil are to be sputter cleaned.

6. An apparatus as in claim 1 wherein said at least one electrode comprises a pair of electrodes, and wherein said target means includes a target plate for each electrode for sequentially sputtering different target materials.


The present invention relates generally to methods and apparatus for coating the edge portions of cutting instruments. More particularly, the invention is directed to applying extremely thin coatings of materials over the edges of razor blades and the like in order to increase the longevity of the blades or to impart other desirable characteristics thereto. In particular, the present invention is directed to coating extremely long, continuous strips of sharpened material from which shorter lengths of ribbon type razor blades are subsequently cut for loading into magazine type razors.

Recently, the advantages of applying extremely thin coatings of various materials to the cutting edges of instruments such as razor blades has become a common commercial practice, in view of the improved properties which may be imparted to such blade edges by placing thereover a strongly adherent coating of materials in extremely thin layers after the finished processing has otherwise been completed, or has been completed except for the addition of a lubricating coating.

Thus, it has recently been made possible to place a replicate coating of a corrosion-resistant material such as metallic chromium, over blade edges in thicknesses of 50 to 200 Angstroms by a sputtering process. These coatings are far too thin to affect the sharpness of a previously sharpened blade but quite surprisingly are thick enough to be extremely tenacious and to provide excellent rust and corrosion resistance to the edges. Methods such as those described in U.S. application Ser. No. 680,926, now U.S. Pat. No. 3,632,494, have proved able to provide blades of superior performance under extremely reliable and economical conditions of manufacture with the result that millions of razor blades are manufactured every day using techniques which are the same or similar to those described in this application.

Following the discovery that individual single and double edge blades may advantageously be coated by such methods, a demand arose for a suitable method of coating those continuous strips of ribbon type razor blade material from which shorter lengths are subsequently cut for assembly and incorporation into magazine type razors, since razors of this type are also currently in common use. However, the forms of apparatus used for individual blades or groups of blades have not been readily adaptable to the economical mass production of extreme lengths of continuous blade stock. Accordingly, while there has been a need for ribbon type blades containing coatings of the type obtainable by these processes, the requirement for producing the vacuums necessary for production of sputtered coatings has seemed incompatible with the requirements that such blades be formed, sharpened and treated in continuous lengths of considerable extent in order to obtain satisfactory quality and economy.

In other words, whereas ribbon type blades are necessarily handled in long strips, vacuum coating operations must be carried out, on a practical basis, in small areas or volumes, and such regions are, in a manner of speaking, spatially inconsistent with existing processing equipment which produces ribbon blade material and which occupies extensive floor space. Although the continuous strips of blade are eventually subdivided into shorter lengths for inspection and assembly, it is not desirable to cut the blades in this manner immediately after sharpening and honing, since it is customary to place a lubricous coating (such as "Teflon") on the blades after finishing, and existing equipment and technology is based on performing this operation on extended rather than shortened lengths of blade material. Consequently, where it is desired to place an anti-corrosion coating on the edge, such as a chromium or alloy coating, this step will normally be followed by the application of the fluoropolymer coating, which is advantageously carried out in the continuous, extended lengths. Therefore, the anti-corrosion coating should be applied to the extended, rather than subdivided, lengths of blade to fit properly into this operational sequence and thereby to avoid the necessity of obtaining new equipment or extensively modifying existing equipment.

Accordingly, it is an object of the present invention to provide methods and apparatus for applying thin surface coatings to the edges of continuous lengths of ribbon razor blade stock.

Another object is to provide an improved apparatus and method adapted for use in manipulating continuous lengths of razor blade and like material within an evacuated region.

A further object is to provide an apparatus which includes means for cleaning a substantial length of ribbon razor blade stock, cleaning the surface of the target containing the material which is to be applied to the blade, and thereafter placing one or more thin coatings uniformly on the blade edges, all without removing the blades from the evacuated region within which they are disposed for treatment.

A still further object is to provide a blade treating apparatus wherein the blade stock is retained in a special rotatable fixture in a predetermined position in relation to a target, and wherein the fixture is capable of undergoing a predetermined motion sequence to insure uniform application of a layer of coating material, such as a metal, metal alloy or organic coating, for example, to the edge portion of the blade material.

Another object is to provide an apparatus having at least one generally planar holder for a continuous coil of blade, an electrode and an associated target disposed in generally facing relation to one sector of the holder, an apertured, rotatable shutter disposed between the target and the holder, and lying in a generally coplanar relation to the holder, with the shutter being rotatable co-axially with the holder so as to obscure or expose the target upon shutter rotation, with the holder being rotatable so as to permit passage of the blade beneath or otherwise in facing relation to the target when the aperture in the shutter is indexed into a position of registry with the target.

Another object is to provide an apparatus such as that referred to in the immediately foregoing object, but which includes plural electrodes, targets and shutters so that the operations described above may be repeated in respect to plural targets.

Another object is to provide a fixture or holder for a continuous coil of blade wherein the blade is entirely received within an annular groove in the holder with the annular groove being spaced apart from the center and the outer edge portions of the holder by margins of substantial extent.

A further object is to provide a method of coating continuous strips of ribbon razor blade material which method includes forming a strip of blade material of extended length into a continuous coil having an opening of substantial diameter in the center thereof, placing the coil within an evacuated region which includes an energizable electrode and an operatively associated target, positioning the target in a generally facing relation to one sector of the blade coil, and thereafter applying electrical energy to the target in the presence of a minute amount of an inert gas to create a plasma within the evacuated region and to cause the ions thus formed to strike the target and sputter the coating material disposed thereon from the target and onto the blade edges under carefully controlled conditions.

Another object is to provide a clean vacuum system for the sputter deposition of films.

Another object is to provide a method as generally set forth above which further includes the steps of protecting the target and the blade respectively during cleaning operations carried out prior to coating and thereafter applying a coating of material from a cleaned target surface to the cleaned edge portion of the continuous coil of ribbon blade material, all without removing the coil of blade material from the evacuated region.

A further object is to carry out a coating method within a vacuum which includes manipulating a protective shutter and coil of blade in such a manner as to facilitate cleaning of the target and electrode while protecting them against contamination and thereafter manipulating the shutter and the blade coil in such a way as to advance successive portions of the blade coil past the target in generally facing relation thereto.

Another object is to provide an apparatus which includes plural targets and associated electrodes, at least one generally disc-like, apertured shutter plate lying parallel to the plane of the target, a generally disc-like blade coil holder having a groove therein for receiving a coil of blade, means for evacuating the region in which these elements are disposed, means for applying electrical energy to each of the electrodes and means for rotating the shutter and rotating a holder in desired motion sequences to provide for cleaning of the blade edges and the target and thereafter for applying the coating material by a sputtering operation directly from the target to the blade edge portion of the continuous coil of blade.

These and other objects of the invention are accomplished by providing an apparatus having means for receiving a continuous coil of blade, electrode means and an associated target, and protective means which may be removably interposed between generally facing portions of the target and a portion of the blade coil holder. The objects are also carried out by providing a method wherein the coil of blade is disposed within an evacuated region, and protected against contamination during cleaning, wherein the target associated with at least one electrode is cleaned while the blades are protected, and wherein the blade is thereafter manipulated in relation to the target so as to pass successive portions thereof adjacent the target in generally facing relation thereto under controlled conditions.

The manner in which the foregoing and other objects are achieved may be more clearly understood when reference is made to the accompanying detailed description of the preferred embodiments of the invention and when reference is made to the accompanying drawings, wherein like reference numerals indicate corresponding parts throughout.


FIG. 1 is a vertical sectional view, partly diagrammatic in nature, showing the principal elements of one form of the apparatus of the invention;

FIG. 2 is a horizontal sectional view of the apparatus of FIG. 1 taken along lines 2--2 thereof;

FIG. 3 is a diagrammatic view of the electrical connections to be made for providing a typical operating sequence undergone by the apparatus of FIGS. 1 and 2 in carrying out the method of the invention;

FIG. 4 is a greatly enlarged, fragmentary view of the portion of the apparatus of FIGS. 1 and 2; and,

FIG. 5 is a schematic view of one form of electronic circuitry which is useful with the invention.


Although it will be understood that the principles of the invention may be carried into practice in various manners and embodied in a number of different forms of apparatus, the invention will be described with respect to an embodiment wherein one or more electrodes and targets within a single vacuum chamber are used to apply single or plural coatings to a single continuous length of blade in coil form without breaking the vacuum in the apparatus.

Referring now to FIG. 1, one form of the invention is shown to be embodied in an apparatus shown generally at 4 and including an evacuable chamber 6 with an interior 8 and generally defined by a continuous cylindrical side wall portion 28 extending between a top wall portion 29 and a bottom wall portion 30. Disposed within the interior 8 are a pair of electrode and target assemblies 26, 27 with targets 24, 25 overlying the face of each electrode 17, 18 and with a shutter 21 being provided for operative association with one electrode assembly 26 and another shutter 22 being provided for association with the other electrode and target assembly 27. Disposed beneath the shutters 21, 22 is a means in the form of a holder 23 for receiving a tightly wound coil 36 of ribbon blade which, as shown, is of a substantial radial extent so as to include an extended continuous length of blade, but which also has a relatively large opening in the center thereof. Referring again to FIG. 1, it will be noted that the apparatus 4 also includes a coil rotation and shutter indexing assembly 19 which, in the embodiment shown, comprises three generally cylindrical drive shafts 20, 20a, and 20b, arranged in concentric relation. The drive shaft 20 terminates adjacent its lower end in a fixed connection with the coil holder 23, the intermediate drive shaft 20a terminates adjacent its lower end in a fixed connection to the shutter 22, and the outermost sleeve or drive shaft 20b, being similarly associated in operation with the shutter 21, is attached thereto adjacent the lower end of the shaft 20b. Accordingly, rotation of each of the shafts 20, 20a, 20b will bring about a corresponding rotation of the part associated with it and lying within the evacuated region 8.

Means for producing the desired motion sequence of the holder 23 and the shutters 21, 22 are provided in the form of a mechanical drive assembly 31, which is only schematically represented, further detailed description being omitted since the drive assembly 31 may be of a known, conventional type forming no part of the invention which is necessarily novel per se. It will also be understood that appropriate seals of a known type may be provided to permit relative mechanical motion of the drive shafts 20, 20a, 20b, and that seals of a known type are also provided for insuring that electrical contact may be established and maintained with various elements lying within the chamber.

Although further detailed reference will be made herein to the electrical connections, it may be seen generally in FIG. 1 that one electrode and target assembly 26 is operatively associated with line 13 which terminates at the base portion of the electrode 17, that a similar line 14 is joined to a portion of the electrode 18, and that lines 15 and 16 terminate in the vicinity of the coil rotation and shutter indexing assembly 19. Opposite ends of the line 13-16 terminate at the switch and matching control assembly 12, details of which will be described in greater detail herein. FIG. 1 also shows that this assembly 12 permits connections to be made between the appropriate energy sources, or such as the radio frequency generator 10, a ground potential point, and various elements disposed within the chamber 6. This assembly 12 is adapted for matching the impedance of the target circuit generally with that of the output circuit of the radio frequency generator 10 which is shown to be associated with the control assembly 12 by line 11.

The chamber unit 6 is also shown in FIG. 1 to have associated therewith a number of more or less conventional auxiliary elements which are commonly used in sputtering and the like high vacuum operations. For example, a coolant source 32 is provided for ensuring that excessively high temperatures are not developed in the electrode and target assemblies 26, 27. A nitrogen vent 33 is provided for purging air or other relatively reactive gases from the interior 8 of the chamber 6 prior to and during evacuating thereof and introducing nitrogen gas prior to opening of the chamber 6. Liquid nitrogen is thus also available for use in a cold trap associated with the vacuum system schematically indicated at 34.

Although the type of vacuum system does not form a necessary part of the invention, it is well known to be advantageous to use a mechanical forepump or "roughing" pump for preliminary chamber evacuation, and a so-called turbomolecular, multi-stage, axial-flow, turbine type high vacuum pump in series therewith and lying upstream thereof. Oil diffusion pumps may also be used. Process requirements for deposition of certain films may require complete absence of hydrocarbon contaminants common to even higher developed diffusion pump systems. The use of molecular sieve cryopumping followed by the use of an ion pump combined with titanium sublimation provides the necessary "clean" vacuum. This novel pumping arrangement has proven of exceptional merit in sputter depositing films of a critical nature on razor blade edges and has reached pressure levels of approximately 10-10 Torr. Inasmuch as sputtering will take place in the presence of a plasma wherein elecron flow ionizes a minute amount of inert gas admitted to an otherwise highly evacuated interior 8 of the chamber 6, a gas supply 35 is schematically shown, it being also understood that this unit may include a precision leak valve, and may have an ionization gauge or the like associated therewith for determining the exact vacuum level within the chamber and the amount of inert gas supplied to the chamber. The gases used include argon and other known gases.

Referring now to the interior 8 of the chamber 6, and specifically to the holder 23, it will also be noted that a generally annular groove 37 is provided therein for receiving the coil 36 of blade. As shown, it is preferred that only the edge portion of the coil 36 project upwardly of the top surface 38 of the holder 23.

Referring now to FIG. 2, the generally concentric relation of the parts shown may be appreciated, and it may also be seen that the opening 21a in the shutter 22 may be of a circular configuration and that it is in a directly overlying relation to one sector of the coil 36 of blade disposed or passing therebeneath. FIG. 2 also illustrates that there is a center section 40 and an outer margin 41 of the holder 23 which define therebetween the groove 37 in which the coil 36 of blade material is received. Accordingly, it will be appreciated that upon rotation of the disc 23 at a selected angular velocity V, successive portions of the blade coil are passed beneath the opening or aperture 22a in the shutter 22, and beneath a fixed target assembly, such as target assembly 26, which lies above and in facing relation to the coil 36 in the holder 23.

Thus, assuming that the aperture 22a is indexed to a position directly beneath the electrode and target assembly 26, the portion of the coil 36 passing beneath the electrode and target assembly 26 and in facing relation thereto will be exposed to any material sputtered from the target plate 24, whereas, if the shutter 22 is indexed to a position wherein the aperture 22a is out of registry with the electrode and target assembly 26, any material sputtered from the face of the target plate 24 will be deposited on the upper surface of the shutter 22 which lies between and generally parallel to the target plate 24 and the holder 23.

A similar mode of operation exists in respect to the electrode and target assembly 27 and the shutter 21 having the aperture 21a therein. That is, as long as the opening 21a is in registry with the electrode and target assembly 27, material sputtered generally perpendicularly from the surface of the target plate 25 will pass directly downwardly through the aperture 21 and onto that portion of the coil 36 lying therebeneath. On the other hand, when the opening or aperture 21a is moved out of registry with the assembly 27, any material sputtered from the target plate 25 will fall on an upwardly directed surface of the shutter 21. It will also be appreciated that, if two or more electrode and target assemblies such as the assemblies 26 and 27 are present, and if more than one shutter, such as the shutters 21 and 22 are present, both apertures 21a, 22a, must be registered with each electrode in order to permit flow of the sputtered material from either of the targets 24, 25 onto the edges of the blade coil 36 lying therebeneath and in oppositely facing relation thereto.

Referring now to FIG. 4, an enlarged view is shown of some of the elements within the chamber 6 and their relation. By reference to FIG. 4, it may be seen that the individual segments or turns 42 of the blade are in tightly packed relation with the adjacent sides thereof abutting one another. It will also be noted that the edge portions 43 lie only a slight distance above the upper surface 38 of the holder 23, this dimension being shown at A in FIG. 4. The importance of this feature will be set forth elsewhere herein. FIG. 4, also shows the overall radius of the holder 23 to be indicated by dimension B, and that the inner and outer walls forming the groove 37 are shown to fall on radii having dimensions C and D respectively. It will also be noted that the aperture 21a in the shutter 21 is indexed so as to fall beneath the target plate 24 which overlies electrode 17.

In a preferred form of the invention, the radius (C) of the center section 40 of the holder 23 may be approximately 7 inches, the width of the coil (dimension D minus dimension C) is preferably about 2 inches, and the width of the margin 41 lying radially outwardly thereof is at least 1 inch. In such an embodiment, bearing in mind that the thickness of the typical stock comprising the coil 36 of the blade is only about 0.0015 inches, it will be appreciated that about 1,200 to 1,400 turns of blade per inch of coil thickness are provided, and that, accordingly, a blade coil about 2 inches thick, and having a mean diameter of 15 inches would contain about 10,000 feet of blade stock, that is, about two miles thereof. Preferably, the edges 43 rise above the surface 38 of the holder 23 only about 0.005 inches. In this connection, it will be realized that the sizes and shapes of the individual turns 42 of the blade coil 36 are not shown to scale, but are shown greatly enlarged for clarity of illustration.

Referring now to FIG. 5, a simplified schematic drawing of certain portions of the switch and matching control unit 12 is shown. Inasmuch as an object of the invention is the provision of an apparatus 4 capable of use in various modes, FIG. 5 shows a blade etching circuit 44 and a sputtering circuit 45 for use in the sputter etch or blade etching a cleaning mode, it will be assumed that line 16 is connected within the unit 12 to a source of radio frequency energy, and that switches 46 and 47, which are ganged for simultaneous operation, are in the position shown in solid lines in FIG. 5. In this mode, radio frequency energy present in line 16 will also appear in line 48, which includes a divider 50 having one line 52 thereof forming a part of a tunable, inductance-capacitance circuit. A second line 56 extends from the divider 50 to an inductance-resistance circuit having one terminal 58 thereof at ground potential.

In the illustrated form, tunable capacitor 60 is placed in series with the principal inductor 62, which has the other terminal 64 thereof connected to switch 47 and to a second tunable capacitor 66 which is disposed parallel to the switch 47 and which has one terminal 54 thereof at ground potential. Accordingly, the signal in line 52 may be tuned for the desired resonant condition by adjustment of the capacitors 60 and 66, it being generally desirable, as will be pointed out herein, to obtain a certain forward power and a certain reflected power within the evacuated chamber 8 in order to provide the desired sputtering rate. The second line 56, which is parallel to the tunable portion of the circuit 44, includes an inductance of fixed value 68, a series resistor 70, and parallel resistors 72, 74 each having a ground potential terminal and having the opposite terminals thereof connected to each other and to the series resistor 70 by a diode 76. The resistance 74 is preferably in the form of the potentiometer shown to permit adjustment of this portion of the circuit. In use, the switches 44, 46 being in the position shown, the radio frequency current will be supplied to the blades, causing the blades to serve as the target in the sense that the surfaces thereof will be bombarded by the ions created in the plasma, thus bringing about a slight surface etching thereof. In this mode, the shutters 21, 22 are placed at the R.F. ground potential.

Moving the ganged switches 46, 47 to the other position shown in FIG. 5, associates line 13 to the circuit 45, which is functionally similar to circuit 44 but which differs therefrom in detail only.

Thus, this circuit 45 also includes a tuning capacitor 84, a principal inductor 86 and a tunable capacitance circuit 88 parallel with line 82. However, in this instance, capacitance circuit 88 includes two fixed capacitors 90, 92 and one adjustable capacitor 94 to bring about fine tuning. Similarly, line 78 is analogous to line 56, except that in addition to the grounded, divided resistance network 96, and the inductor 98 and resistor 100 in series relation, an additional inductor 102 and grounded capacitor 104 are provided as shown. In use, the circuit 45 operates such that the signal in line 13 is supplied to the electrode and target assembly 26, which receives a correctly matched signal. Sputtering therefore takes place in respect to target 24, which has the R.F. signal applied thereto. Accordingly, in this mode, once the plasma is formed by the admission of a minor amount of inert gas into the evacuated area 8, sputtering will commence as long as the plasma is maintained.

It will be understood, in connection with the foregoing illustrative description, that the elements of circuits 44 and 45 were described merely for purposes of indicating a typical form of circuit and that the illustrated circuit does not form a necessary part of the invention. Although it is conventional and well known to form the switch and matching networks in a number of different ways, it is preferred that, for most effective operation, a matching box circuit should possess the ability to be tuned so as to closely match the impedances of the output circuit and the target load portion of the circuit.

Referring now to FIG. 3, it is diagrammatically shown that three cycles or operational modes are typically able to be provided by the apparatus 4, and that the connections made within the switch unit 12 between the leads 13-16 and the R.F. generator 10 will determine the mode of operation.

Thus, since it is customary first to etch the blade edges, the switch and matching control unit 12 is manipulated so as to establish an operation connection between line 16 and the R.F. energy source, thereby furnishing radio frequency energy to the holder 23 and the coil 36 of blades associated therewith. Line 15 is then operatively associated with the radio frequency ground, and accordingly, one or both shutters 21, 22 assume a ground potential with respect to the holder 23, it being understood that the shutters 21, 22 and the holder 23 are all electrically isolated from each other. Accordingly, the ionized atoms will be attracted within the plasma to the exposed edges 43 of the individual blade segments 42 and the lower surfaces of the shutters 21, 22 will receive a coating of whatever small amount of material is sputter etched or removed from the edge 43. For this operation, the shutters 21, 22 are indexed so as to avoid direct exposure of either target plate 24, 25 to the coil 36. Thereafter, the blade edges having been cleaned, any surface contamination is next removed from the targets 24, 25 by operation of the apparatus in the target etch mode or cycle. In this mode, the line 15 is operatively associated with the radio frequency ground, thereby again grounding the shutters 21, 22. Depending upon which electrode 17 or 18 is to be activated for etching of its associated target 24, 25, the appropriate line 13 or 14 is connected to the R.F. energy source. In this mode, the surface of the target is etched or cleaned by a sputtering operation, but deposition of material from the targets 24, 25 onto the edges 43 of the blade coil 36 is prevented by assuring that the shutters 21, 22 remain indexed in positions such that their apertures 21a, 22a are out of registry with the electrode and target assemblies 26, 27. Furthermore, since the shutters 21, 22 are at R.F. ground potential, the upper surfaces thereof serve to collect the material sputtered from the surfaces of the targets 24, 25.

After the target has been etched to insure presentation of a totally clean surface thereof, the shutters 21, 22 are indexed to the proper positions so that the apertures 21a, 22a therein lie beneath the assembly which will be energized and from which it is desired to remove the material for deposition onto the coil 36, and the apparatus is then operated in the ordinary sputter coating mode. In this mode, the radio frequency energy is again supplied to either electrode and target assembly 26, 27, while line 16 is connected to a radio frequency sound, thereby grounding the coil 36 of blades and causing the sputtered material to be attracted to the edges 43 of the blade coil 36.

In a typical operation of the apparatus 4, the holder 23 is loaded with a coil 36 of blade material and sputter etching thereof is carried out by reducing the vacuum level to an approximate order of 5 × 10-6 Torr, and, while maintaining this background pressure, leaking argon into the chamber interior 8 from source 35 until the plasma starts, and thereafter quickly reducing the leak rate thereof. Preferably, the pressure of the system is maintained at about 2.5 × 10-3 Torr. A 1,000 volt direct current bias between the blades and a ground potential point is allowed to build up, and a forward power setting of about 750 watts is maintained with a reflected power level of 250 watts or less. The frequency preferred is 13.56 MHz operating the apparatus for about 5 minutes at an angular velocity V of one to three revolutions of the holder per minute, will serve to clean the blades effectively. Thereafter, the argon or other inert gas inflow is stopped, and the argon supply is discontinued and the background pressure is reduced to 5 × 10-6 Torr. Thereupon, with the shutters 21, 22 remaining in the same position, the controls may be actuated to etch the target, which is carried out in a similar manner, a pressure of 5 × 10-3 Torr being common, for example, the DC bias between the shutters and the target may be 2 KV in this mode, while power settings remain approximately the same. After this operation, the shutters 21, 22 may be indexed to the desired position, that is, with their apertures disposed directly beneath the target to which the R.F. energy is supplied. With a target-to-blade bias of about 2 KV and with 750 watts forward bias and a reflected power rating of less than 250 watts, the holder 23 may again be rotated in a similar manner. Approximately 6 minutes of sputtering will ordinarily serve to coat a material such as chromium onto the blade edges in a desired thickness, that is, a thickness of from about 25 to 50 Angstroms up to about 200 or more Anstroms.

In any case, a coating of this thickness is a substantially replicate coating of great tenacity and uniformity, and has proved to increase greatly the durability of the blades in use without in any respect dulling them. After coating with the metallic material such as a chromium, or an alloy such as an alloy of chromium and platinum or a composite material such as iron carbide, chromium oxide, or the like, the coil 36 may be removed from the fixture 23 for continued processing on conventional equipment. On the other hand, it may be desired to coat the lubricous material onto the coil 36 while allowing the coil 36 to remain in the chamber 6. In such a case, the second target 25 may have disposed thereon a coating of a lubricous material such as a polymer of tetrafluoroethylene or the like. Sputtering of this material from the target 25 may be carried out as described in U.S. application Ser. No. 680,794, now U.S. Pat. No. 3,635,811.

The illustrated embodiment of the apparatus of the invention contains two targets 24 and 25, and a pair of shutters 21 and 22. It will be appreciated, however, that only a single electrode and target assembly need be provided to obtain most or all of the advantages of the invention, and that it is possible to carry out the invention using only a single shutter even though two targets are used. It is also within the scope of the invention to arrange shutters and targets so that sputtering could take place simultaneously from two targets, if this were desired for some reason. Other variations will also be apparent to those skilled in the art, it being understood that the description herein was made for the purpose of illustrating an embodiment suitable for the solution of a particular problem in a particular environment.

Referring now to one feature of the invention, although the reason therefor is not clearly understood, it has been discovered that significantly improved coatings may be placed on the coil of blade material when the edge portion 43 thereof is either planar with surface 41 or projects only slightly above the surface, in any case less than 0.2 inches. Accordingly, it is preferred that the depth of the groove 37 be only a few thousandths of an inch shallower than the total height of the blade stock.

It will thus be seen that the present invention provides a new and improved coating apparatus and method for coating the edges of a coil of blade material, and that this method provides a number of advantages and characteristics including those expressly pointed out herein and others which are inherent in the invention. Since it is believed that a number of modifications and variations of the apparatus and method disclosed in detail herein will occur to those skilled in the art, it is anticipated that such changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.