Systems and methods for electroprocessing a gun barrel using a moving electrode

A guide system for use in electro-processing a bore of a gun barrel includes a non-conductive external bore guide and a non-conductive internal bore guide. The external bore guide is an adapter that is configured to removably engage the outside of the gun barrel and includes a conduit formed therein. The conduit is disposed such that it is axially aligned with a bore of the gun barrel when the external bore guide is engaged with the gun barrel. The internal bore guide is elongated and includes an axial recess that is sized to seat an electro-processing electrode (an anode). A method for uniformly plating the bore includes moving an anode through the gun barrel at one or more rate(s) of travel to uniformly plate the bore is also disclosed. The plating is sufficiently uniform to conform to military specifications. The systems, methods, support structures, etc. described herein are particularly well-suited to plating small-bore gun barrels.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to electrochemical processing and, more particularly, to electrochemically processing small-bore gun barrels. Even more particularly, the invention relates to systems and methods for electroplating a small-bore gun barrel using a moving anode and guide system.

Description of the Background Art

Electroplating the bores of small-bore gun barrels is known. For example, applying a thin layer of chromium (chrome) to the bore of a barrel is desirable, because chrome is very hard. The chrome plating improves wear resistance of the bore and, thus, increases the number of projectiles that the gun barrel can discharge in its lifetime. Chrome plating also has the advantage of adding a corrosion-resistant coating to the bore, which increases the life of the barrel, especially in humid environments. Small-bore gun barrels are considered to be those having bores of approximately 50 caliber (0.500 inch diameter) and less.

One known method for plating the bore of a small-bore gun barrel includes placing a long anode wire through the entire length of the bore. Chromium electrolyte solution is then pumped through the bore while voltages are applied to the anode and gun barrel, respectively. Current flowing from the anode to the bore via the electrolyte causes a thin chrome layer to be deposited on the bore's surface.

A significant drawback of known plating methods is that they are incapable of reliably depositing a layer of material on the surface of a bore that is sufficiently uniform in thickness and quality to meet strict military specifications (e.g., MIL-STD-171F, Finish No. 1.2.2 for chrome) or other plating specifications associated with high-accuracy barrels. Because plating is done after barrel rifling is formed, non-uniformities in the plating's thickness and/or quality (e.g., waviness, pits, lumps, cracks, etc.) readily cause projectile inaccuracy. Thus, existing plating techniques yield an unacceptably large percentage (commonly 20-25%) of barrels that do not meet plating specifications and must be reworked, which significantly increases production costs. Accordingly, it is often the case that small-bore barrels remain unplated so that they shoot more accurately. Unfortunately, they also wear out faster and must be replaced more often.

SUMMARY OF THE INVENTION

The present invention overcomes the problems associated with the prior art by providing systems and methods for uniformly plating small-bore gun barrels. Because the plating is more uniform in thickness and quality, the accuracy of the barrel is maintained and the plating conforms to military standards. Accordingly, the number of barrels that must be rejected and/or reworked is significantly reduced. Additionally, the invention facilitates customized plating to be readily implemented.

A system for electro-processing a bore of a gun barrel according to an exemplary embodiment of the present invention includes an electrode (e.g., an anode) having a length less than a length of the bore, a lead electrically coupled to the electrode, a barrel end adapter, and an actuator. The barrel end adapter is configured to removably engage a first end of the gun barrel. The barrel end adapter also defines a conduit therethrough that is axially aligned with the bore when the barrel end adapter is engaged with the gun barrel. The actuator is coupled to the lead and is operative to move the electrode through the bore and the conduit by moving the lead during electro-processing.

A barrel end adapter according to an exemplary embodiment of the present invention includes a non-conductive body, a conduit formed in the non-conductive body and defining an axis through the body, and a barrel interface. The barrel interface is configured to removably engage a distal end of a gun barrel to temporarily affix the barrel end adapter to the gun barrel. Additionally, the conduit is axially aligned with a bore when the barrel interface is engaged with the distal end of the gun barrel. A bore guide according to an exemplary embodiment of the present invention includes an elongated, non-conductive body and a passage formed axially through the non-conductive body. The body has a top surface, a bottom surface, and a plurality of sides between the top and the bottom surfaces. The passage is formed through the elongated body from an opening defined by the top surface to an opening defined by the bottom surface. Additionally, the passage is sized to closely accept an electro-processing electrode therein through at least one of the opening defined by the top and the bottom surfaces. A remainder of the passage is sized to pass an electrical lead coupled to the electro-processing electrode.

An exemplary method for electro-processing a bore of a gun barrel includes steps of providing a gun barrel having a bore defining an axis, providing an electrode having a lead electrically coupled thereto, providing a barrel end adapter defining a conduit therethrough, temporarily affixing the barrel end adapter to a first end of the gun barrel such that the conduit is axially aligned with the bore, positioning the electrode within the bore, positioning the gun barrel in electro-processing solution, moving the electrode within at least one of the bore and the conduit, and applying process current via the electrode during the step of moving the electrode to cause electro-processing of the bore. The length of the lead is shorter than the length of the bore.

A guide system for use in electro-processing a gun barrel according to an exemplary embodiment of the invention includes a non-conductive external bore guide and a non-conductive internal bore guide. The external bore guide is an adapter that is configured to removably engage the outside of the gun barrel and includes a conduit formed therein. The conduit is disposed such that it is axially aligned with a bore of the gun barrel when the external bore guide is engaged with the gun barrel. The internal bore is elongated and includes an axial recess that is sized to seat an electro-processing electrode (an anode). Utilizing the external and internal bore guides, the anode can be pulled through the gun barrel at one or more rate(s) that provide uniform plating of the bore. The plating is sufficiently uniform to conform to military specification.

DETAILED DESCRIPTION

Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously employ the present invention. In other instances, details of well-known components and manufacturing practices (e.g., molding, 3D printing, metal fabrication and assembly, actuator control, regulator control, etc.) have been omitted so as to avoid unnecessarily obscuring the present invention.

FIG. 1is a block diagram showing an electro-processing system100according to an exemplary embodiment of the present invention. Here, electro-processing system100is being used to electroplate a small-bore gun barrel102. Barrel102is for a model M16 rifle in this embodiment and, therefore, includes a barrel extension104attached thereto as is well-known. Barrels for other guns might not include a barrel extension.

System100includes a barrel end adapter110, a moving electrode (anode)assembly112having a conductive lead114electrically coupled thereto, an electrode mover (actuator)116, a power supply118, a process controller120, and a support structure122. Support structure122includes a clamping member124, which secures barrel102to support structure122when fastener(s)126are engaged therewith. Support structure122holds barrel102substantially vertically, but submerged, within a tank (vat)128of electrolyte solution130(e.g., hexavalent chromium solution, etc.) so that the electrolyte fills the bore (not shown inFIG. 1) of barrel102. Support structure122is shown generally representationally here and it should be understood that other support structures122can be employed.

Barrel end adapter110functions as an external (to barrel102) electrode guide that is temporarily affixed to the muzzle end of barrel102. Lead114is positioned through a conduit (FIGS. 5A-5D) formed in barrel end adapter110and through the bore of barrel102so as to move (e.g., pull) anode assembly112therethrough. Electrode mover116comprises an actuator (e.g., a linear actuator, servo motor, rack and gear, etc.) that is coupled to lead114and functions to move lead116, and thus anode assembly112, through gun barrel102under the control of process controller120in the directions of the arrow shown. In this embodiment, actuator116draws anode assembly112through barrel102, beginning at its chamber end132, and continuing up barrel102through barrel end adapter110during electroplating. Process controller120is electrically coupled to actuator116and controls the rate at which actuator116moves lead114. Actuator116, in turn, moves anode assembly112by pulling lead114at rate(s) specified by process controller120. In other embodiments, electroplating can start at the muzzle end and proceed to the chamber end, etc.

Power supply118provides process current for electro-processing system100. Power supply118includes a first power supply terminal134, a second power supply terminal136, and an optional control input set138. First power supply terminal134is electrically coupled to conductive lead114and is operative to assert first (e.g., positive) voltage(s) on anode assembly112. Second power supply terminal136is electrically coupled to support structure122via a second lead140and associated connecting mechanism(s) (e.g., a terminal post, clamp, etc.) such that power supply118can assert second (e.g., negative) voltage(s) on gun barrel102via support structure122. Accordingly, during electroplating, current flows from anode assembly112to barrel102via electrolyte130causing plating material to be deposited on the surface of the bore of barrel102as anode assembly112moves therethrough.

In the present embodiment, power supply118comprises a rectifier capable of providing an amount of current sufficient to maintain a predetermined current density during electroplating. Control input set138thus enables process controller120to specify a desired current (or current density) for power supply118to maintain. In an alternative mode of operation, power supply118can be configured to maintain predetermined voltages on terminals134and136. In still other embodiments, a human operator can set the operational parameters of power supply118directly.

Process controller120provides overall control of the electro-plating process of gun barrel102. For example, process controller120can, via control input set138, instruct power supply118to provide process power with the desired characteristics. Process controller120can also instructs actuator116, via a control path142, to lengthen or retract lead114to position anode assembly112relative to barrel102, to pull lead114at a specified rate, etc. Process controller120further includes a user input/output (I/O)144so the user can specify process current/voltages, anode draw rate(s), the type/length of barrel102, start and/or stop processing commands, etc. Processor controller120is shown to further include a timer146, which provides time information/signals and enables process controller120to control the rate of travel of anode assembly112via actuator116, to determine regional and/or aggregate plating time(s), etc. Process controller120can be implemented in hardware (e.g., in an integrated circuit, firmware, EEPROM, etc.), in software (e.g., stored or running in memory of a computer), etc. or some combination thereof. In a particular embodiment, process controller120comprises a STAC6-Si programmable driver by Applied Motion Products.

The inventors have determined that the non-uniformity of prior art chrome plating is caused by several factors. First, with respect to the prior art system discussed, the voltage on the anode varies significantly along its length, and this voltage variation induces a corresponding variation in the thickness of the chrome layer along the length of the bore. Second, bubbles (e.g., evolved hydrogen gas, etc.) are generated in the electrolyte as a by-product of the electro-processing. Such bubbles reduce contact between the electrolyte and the bore surface and interfere with current flowing between the anode and barrel, which in turn, causes thickness and quality variation of the plating. Third, even small variations in the prior machining (e.g., rifling formation, etc.) and cleaning of barrel102in preparation for plating can affect how the plating is deposited and can render the applied plating out of specification.

The electro-processing systems of the present invention overcome these drawbacks, because the rate(s) at which anode assembly112moves through the bore of gun barrel102is controlled by actuator116and process controller120. As a result, chrome plating is deposited on the portions of bore adjacent to the anode for a time that yields a desired thickness of chrome plating (e.g., 0.0005 to 0.001 inches, etc.) plus or minus a predetermined tolerance (e.g., +/−5%, etc.) that maintains plating with specifications for accuracy, etc. Additionally, because bubbles are only generated near the plating length of the anode assembly112, which is small relative to the overall length of the bore, the amount of bubbles within the bore are reduced and flow readily upward out of the plating area. Moreover, because the plating time can be adjusted within different regions of barrel102, the present invention enables the plating process to be easily adapted to any changes in barrel production. As a result, the present invention enables a layer of chrome plating with the desired thickness and high quality (e.g., reduced or eliminated waviness, pits, lumps, cracking, etc.) to be applied to the bore of barrel102. Even more advantageously, the chrome plating meets military specification such that significantly fewer barrels require reworking.

FIG. 2is a cross-sectional view of a portion of barrel102taken along line A-A inFIG. 1. Barrel102includes a body202and a generally-cylindrical bore204formed axially through body202along an axis206. Barrel102also includes a chamber208, which receives a cartridge therein (not shown) so as to position the cartridge's projectile relative to bore204. Bore204includes rifling210(lands and grooves) formed thereon as is well known. Rifled bore204may thus be described by both a land diameter and a groove diameter. The land diameter is often referred to by those skilled in the art as the “bore” diameter and corresponds to the diameter across the lands (high points) in the rifling. The groove diameter, by contrast, corresponds to the diameter across the grooves (low points) in the rifling and is, therefore, slightly larger than the land diameter. Therefore, unless otherwise stated, references to the “diameter” of bore204made herein can mean the land diameter, the groove diameter, or both as the case may be.

Barrel extension104is attached to barrel102using well-known means (e.g., threads, pin, etc.; not shown), and forms a distal end of chamber208. When a barrel extension104is used, as in the case of M16 barrels, it can be desirable for plating not to be applied to areas within the barrel extension104(e.g., so as to not interfere with operation of the bolt carrier group, etc.) Accordingly, an extension shield212is provided and covers the interior portions of barrel extension104to which plating is not to be applied. Here, barrel extension104comprises a generally-cylindrical sidewall214and a plurality of chamfered ribs216extending radially-inward therefrom. Extension shield212covers the inside of cylindrical sidewall214and is retained by ribs216.

FIG. 2also shows anode assembly112in greater detail to include an electrode220and a non-conductive bore guide222coupled to electrode220. Electrode220is also electrically coupled to conductive lead114. As anode assembly112is drawn through bore204, bore guide222prevents electrode220from contacting the sides of bore204and chamber208, including the portion of chamber208formed by barrel extension104. During electroplating, current provided by lead114flows through the plating length of anode220(the portion protruding from bore guide222) to bore204via the intermediate electrolyte.

FIG. 3is a cross-sectional view showing taken along line A-A (FIG. 1) showing anode assembly112in greater detail still. In particular, electrode220includes an elongated, cylindrical body224having an axial bore226formed therein. Lead114is coated in an insulating material228along its length, but includes a stripped end230that is secured (e.g., with conductive adhesive, interference fit, etc.) within bore226of electrode220such that electrode220can be electrified. Bore guide222also defines an axial passage232, which closely accepts the electrode220therein and passes lead114therethrough to actuator116. Bore guide222can be affixed to electrode220via an adhesive, interference fit, etc. between the outside of electrode220and axial passage232. Notably, the combination of bore guide222and electrode220creates a rigid, elongate assembly that resists bending. This maintains the electrode-bore spacing throughout electro-processing, including when electrode assembly passes between bore204and the conduit510(FIG. 5B) of barrel end adapter110.

In a particular embodiment, electrode220comprises a metal (e.g., copper, titanium, etc.) core that is coated (clad) in platinum. Such coated anode cores are commercially available from, for example, Anomet Products. Such commercially available anodes can be machined to form bore226therein. In another particular embodiment, the electrode body224has a diameter of 3.0 mm, which yields a muzzle standoff of around 1.27 mm to 1.35 mm (0.050 to 0.053 inches) and a chamber standoff of around 3.02 mm (0.119 inches) in the case of an M16 barrel. (Standoff indicates radial clearance between electrode220and bore204or chamber208).

It should further be noted that the length of electrode220is much less than the length of bore204. For example, in some embodiments, the length of electrode220is less than half the length of bore204. In other embodiments, the length of electrode is less than 25% the length of bore204. In the particular embodiment shown, the total length of electrode220is around 4 inches, and the active plating length (the portion that protrudes from bore guide222) is around 3 inches, which means that the total length of anode220is approximately equal to 20% of the length of an M16 barrel (20 inches or 508 mm), and the active plating length of anode220around 15% of the length of an M16 barrel. Indeed, the active plating length of anode220can be made even shorter. A shorter anode220advantageously reduces bubble production, which increases plating uniformity.

Now with reference toFIGS. 1-3, it should be noted that the rate at which plating material is deposited by anode assembly112onto the surface of the bore of gun barrel102can be determined experimentally for a predetermined current density provided by power supply118and relative to other established electro-processing parameters such as electrolyte solution composition and temperature, anode geometry, etc. Once a deposition rate is obtained, axial draw rate(s) for anode assembly112can be determined to ensure that desired thickness(es) of chrome plating is/are applied to bore204as anode220moves therethrough. In one implementation for plating an M16 barrel, an anode assembly112with electrode220having a plating length of 7.62 cm (3.0 in) and a diameter of 3.0 mm was operated to yield a current density of 19.3 A/dm2(the area of the adjacent M16 bore adjacent is 0.065 dm2(2.1 in2)). Based on these parameters, it was determined that an effective draw rate was around 3 inches per hour, resulting in a total plating time of around 7 hours. These values are only exemplary however and can be expected to change depending on the particular implementation.

It should also be noted that the land and/or groove diameter(s) of bore204can be measured prior to plating using an air gage. (An air gage is an instrument that uses streams of air to accurately measure bore diameter.) Depending on the measured diameter, a desired amount of plating to apply can be determined (e.g., the difference between a target diameter and a measured diameter). A draw rate of anode assembly112can then be calculated based on the plating deposition rate of anode assembly112and the amount of plating that needs to be applied to yield the target diameter. Indeed, a series of diameter measurements can be taken at a plurality of locations (or even continuously) along the length of bore102. Accordingly, in some embodiments, process controller120can control actuator116to vary the rate at which anode assembly112is pulled through barrel102depending on the axial position of anode assembly112within bore204. This enables plating to be applied at different thicknesses along the length of bore204. Furthermore, given a starting position of anode assembly112relative to barrel102and a length of bore204, process controller120can also determine the axial position of anode assembly112during processing based on the implemented draw rate(s) and associated time(s) spent at those draw rate(s). Process controller120can thus know when to adjust the draw rate, stop processing, etc.

FIGS. 4A and 4Bshow top and perspective views of bore guide222, respectively. Bore guide222includes an elongated, non-conductive body250having a top surface252, a bottom surface254, and a plurality of sidewalls256(four in this embodiment) between top and bottom surfaces252and254. Passage232is formed axially through elongated body250from an opening256defined by top surface252to an opening258(FIG. 3) defined by bottom surface254. Passage232is sized to closely accept electrode220therein through at least one of openings256and258. A remainder of passage232, and at least one of openings256and258, are sized to pass lead114therethrough. Bore guide222can be formed from a non-conductive resin (e.g., ABS-M30, polyvinyl chloride (PVC), etc.) by 3-D printing, molding, milling, etc.

A beneficial aspect of bore guide222is that at least some of its sidewalls256are shaped to facilitate the passage of bubbles upward past bore guide222. Here, each of sidewalls256is concave, and their inward arcuate shapes define a plurality of gaps260between bore guide222and bore204(shown representationally in dash) that permit bubbles passed. Meanwhile, a maximum width (W) of bore guide222in this embodiment is across a diagonal of top surface252and is slightly smaller (e.g., 0.0005-0.001 inches) than a land diameter of bore204.

Accordingly, bore guide222also keeps anode assembly112well-centered in bore204and prevents electrode220from significant tipping toward or away from bore204. Because bore guide222readily passes bubbles upward past anode assembly112and maintains electrode220in a centered position, the uniformity of the deposited chrome layer is improved, particularly in the rifling210, and projectile accuracy is improved.

FIG. 5Ais a perspective view showing barrel end adapter110in greater detail. Barrel end adapter110includes a non-conductive, generally-prismatic body502having a top surface504, a bottom surface506, and a plurality (e.g., four) of sidewalls508therebetween. Body502further includes a conduit510and barrel interface512(FIG. 5B) formed therein, which define an axis515through body502. In this embodiment, barrel end adapter110is formed from a non-conductive material, such as PVC, by 3-D printing, molding, milling, tapping, or some combination thereof. In a particular embodiment for an M16 rifle, barrel end adapter110has exterior dimensions of around 2×2×6 inches, and conduit510has a diameter of 0.224 to 0.225 inches.

FIG. 5Bis a front plan view showing barrel end adapter110and barrel102in greater detail. In particular, barrel interface512is generally cylindrical and formed through bottom surface506of body502. Barrel interface512is configured to removably engage a muzzle end514of gun barrel102such that barrel end adapter110can be temporarily affixed to barrel102with conduit510in axial alignment with bore204. In this embodiment, barrel interface512comprises a thread set516for screwing onto a complementary thread set518formed on muzzle end514of barrel102. After plating and removal of barrel end adapter110, complementary thread set518can be used to mount a flash suppressor or other accessory (not shown) to barrel102. In this embodiment, barrel interface512includes an optional countersunk seat520that engages a ledge522of barrel102below thread set518.

FIG. 5Cis a cross-sectional view taken along line B-B ofFIG. 1showing barrel end adapter110screwed onto muzzle end514of barrel102, but with lead114and anode assembly112removed. Conduit510is axially aligned with bore204on axis206. Note that thread set516is slightly deeper than thread set518, which leaves a small gap530between the ends of bore204and conduit510due to seat520contacting ledge522. In other embodiments, thread sets516and518are configured such that no gap530exists.

FIG. 5Dis another cross-sectional view taken along line B-B that illustrates how barrel end adapter110guides anode assembly112as it is being drawn through the muzzle end514of barrel510. In particular, as anode assembly112is drawn out bore204at muzzle end514, the leading end of bore guide222enters conduit510of adapter110. Conduit510thereafter functions to maintain electrode220in axial alignment with bore204as electrode220is drawn the remainder of the way through bore204and electroplating is completed on barrel102. Because conduit510is sized to closely accept bore guide222therein, electrode220does not tilt as it is being pulled through the muzzle end514barrel102, which maintains the uniformity of the plating near muzzle end514.

FIG. 6Ais a bottom view of barrel extension104showing sidewall214and ribs216in greater detail.FIG. 6Bis a perspective view of extension shield212, which in this embodiment comprises a cylindrical tubular element made of a flexible insulating material (e.g., rubber, etc.). The flexibility enables extension shield212to be temporarily deformed to facilitate insertion past ribs216and into position against the inner surface of sidewall214of barrel extension104. In a particular embodiment, barrel shield212is made of rubber, has a 0.810 inch outer diameter, a 0.620 inch inner diameter, and is 0.285 inches tall. Other shapes and sizes of extension shields can be provided depending on the shapes of the surfaces to be covered.

As will be apparent from the foregoing description, the present disclosure describes a bore guide system for use in electro-processing (e.g., chrome plating, etc.) a gun barrel, which includes an external bore guide (e.g., barrel end adapter110) and an internal bore guide (e.g., bore guide222), both of which are non-conductive. The external bore guide is configured to removably engage the outside of the gun barrel and includes a conduit formed therein, which axially aligns with the bore of the barrel when the external bore guide is engaged therewith. In contrast, the internal bore guide is sized to facilitate movement of the internal bore guide within the bore of the barrel and within the conduit of the external bore guide. The internal bore guide includes an axial recess formed therein that is configured to seat an electro-processing electrode (e.g., an anode). Optionally, the bore guide system can also include one or more processing shield(s) (e.g., extension shield212) to prevent portions of the barrel from being electro-processed.

While particular embodiments have been described above, it should be recognized that alterations and modifications can be made without departing from the spirit and scope of the invention. For example, a bore guide having a triangular cross-section, with or without concave sidewalls, can be used. Additionally, the dimensions and parameters provided above are only exemplary and can be altered as desired. Electrode220can also take other forms and can be affixed to bore guide in other ways (e.g., by a snap-in channel, etc.). Barrel end adapter110can also be modified, for example, such that it can be temporarily affixed to the outside of a barrel by interference fit, clamping, etc. Such an alternative is useful where the barrel does not have a threaded muzzle end. Like bore guide, the shape and dimensions of barrel end adapter110can also be modified as desired. These and other modifications will become apparent in view of the present disclosure.

FIG. 7is a perspective view showing an exemplary embodiment of a support structure (fixture)700for supporting a plurality of gun barrels102to be electro-processed according to the present invention within a tank701of chroming solution (e.g., a solution of chromic and sulfuric acids, etc.). The electrolyte is omitted fromFIG. 7and subsequent figures so as not to unnecessarily obscure other elements.

Support structure700includes a plurality of risers702(1-2), a frame704, an actuator mount706, a plurality of guides708(1-2), a lead puller710, and a barrel mount712. The elements of support structure700cooperate to hold a plurality of barrels102vertically within tank701and facilitate movement of anode assemblies112therethrough. In particular, each of risers702(1-2) is affixed (e.g., by clamps, fasteners, etc.) to the upper perimeter of tank701and includes a receiver714that removably receives an associated portion of frame704therein. Frame704is generally rectangular and provides a structure on which to mount actuator116, guides708(1-2), carrier710, and barrel mount712. When the lateral sides of frame704are positioned in receivers714, frame704stands vertically over the open top of tank701.

Actuator mount706includes a support plate716affixed to frame704and a bracket718affixed to support plate716. Support plate716is shown affixed to frame by fasteners720but alternatively could be welded, etc. Bracket718can be similarly affixed to support plate716by fasteners, welding, etc. Actuator116is a linear actuator in this example (e.g., a Nook™ In-Line ACME Screw Drive Programmable Actuator, etc.), so bracket718mounts (e.g., clamps, etc.) actuator116in a vertical orientation with its shaft720directed vertically toward lead puller710. Support plate716is affixed near the top of frame704to accommodate the stroke of shaft720but can be readily repositioned to accommodate other actuator mechanisms (e.g., a rotational actuator, pulleys, gears, racks, etc.).

Guides708(1-2) comprise guide rails coupled longitudinally to frame on either side of shaft720. Lead puller710is mounted transversely so as to slide vertically within guide rails708(1-2). The distal end of actuator shaft720is affixed to lead puller710such that lead puller710moves up and down as shaft720retracts and extends, respectively. Lead puller710also includes a plurality of attachment mechanisms (FIG. 8), which selectively affix leads114to puller710. Barrel mount712removably affixes a plurality of barrels102and positions them in tank701for electro-processing. Thus, when shaft720extends, lead puller710moves the leads114and associated anode assemblies112coupled thereto downward (e.g., further into barrels102). When shaft720retracts, lead puller710moves upward, thereby pulling leads114and the anode assemblies112attached thereto upward toward the muzzle ends of barrels102.

FIG. 8is a front perspective view showing a portion of support structure700in greater detail.FIG. 8shows that frame704is fabricated from square tubing that is, for example, welded together at the corners where the tube sections abut. Frame704is also shown to include a plurality of intermediate cross-members730(1-2) that extend between the lateral sides of frame704to support other elements. Guide rail supports732(1-2) comprise rectangular plates mounted (e.g., welded) to the front of frame704. Each of guide rails708(1-2) is mounted on a respective one of guide rail supports732(1-2) via a riser734and a plurality of fasteners736. Fasteners736pass through apertures formed in guide rails708(1-2) and risers734to secure guide rails708(1-2) to supports732(1-2). Thus assembled, guide rails708(1-2) and risers734define opposing gibs, where risers734define gaps between supports732(1-2) and guide rails708(1-2) in which the lateral ends738(1-2) of lead puller710ride. The lateral ends738(1-2) are also notched to maintain lead puller710generally-orthogonal to guide rails708(1-2) during vertical travel. In the present example, the vertical lengths of guide rails708(1-2) and supports732(1-2) are selected based on the travel of shaft720of actuator116.

Puller710is also shown in greater detail to includes a shaft bracket740affixed thereto by threaded fasteners742(e.g., bolts and nuts, etc.). Shaft720is coupled to shaft bracket740via a pin744passing through bracket740and shaft720. Accordingly, movement of actuator shaft720causes corresponding movement of puller710. Puller710also includes a plurality of lead couplers746, which are secured to puller710via threaded fasteners748in this example. Fasteners748comprise wing nuts for rapid removal and reinstallation. When leads114(1-2) are clamped between lead couplers746(1-2) and puller710, respectively, vertical movement of shaft720causes corresponding vertical movement of leads114(1-2) and their attached anode assemblies112(1-2).

FIG. 8also shows that barrel mount712is affixed to a bottom plate750of frame704via pairs of threaded fasteners752. Plate750itself can be affixed to frame704by welding, fasteners, etc. Barrel mount712holds a plurality of barrels102(1-2) vertically such that leads114(1-2) are axially aligned with their respective bores204. Lead couplers746permit lateral adjustment of leads114(1-2) relative to the bores204of each barrel102(1-2). When installed, leads114(1-2) pass between respective lead couplers746(1-2) and puller710, through respective barrel end adapters110, through respective bores204of barrels102(1-2) to electrically couple with respective anode assemblies112(1-2). From this position, upward movement of puller710caused by actuator116retracting shaft720pulls anode assemblies112(1-2) vertically through barrels102. Leads114(1-2) are truncated inFIG. 8so as not to obscure other elements. However, it should be understood that leads114(1-2) will be coupled to receive electric power from one or more power source(s) (e.g., power supply(ies)118) during electro-processing.

FIG. 9is a front perspective view showing barrel mount712in larger detail. Barrel mount712includes a plurality of drop arms760(1-2), which are affixed to bottom plate750of frame704via fasteners752. Drop arms760(1-2) extend below the bottom of frame704and enable barrels102(1-2) and barrel end adapters110(1-2) to be submerged in electrolyte in tank701. Barrel mount712also includes a cross member762, which is affixed to drop arms760(1-2). Buttresses764(1-2) further connect cross member762and drop arms760(1-2). Cross member762defines a plurality of notches766(1-2), which receive respective barrels102(1-2) therein. Each notch766(1-2) is selectively closed by a clamp768(1-2), which can be rotated into or out of position over notches766(1-2) by loosening fasteners770(1-2), respectively. When clamps768(1-2) are securely positioned over notches766(1-2), the barrels102(1-2) are further secured within notches722(1-2) by tightening set bolts772(1-2) against the outside of barrels102(1-2), respectively. This prevents the barrels102(1-2) from moving (e.g., due to electrolyte agitation, etc.) during electroplating.

InFIG. 9, barrels102(1-2) have been prepared for electro-processing by undergoing prior cleaning and have barrel end adapters110(1-2) and extension shields (not shown) installed. Anode assemblies112(1-2) and leads114(1-2) can now be installed through the conduits510of barrel end adapters110(1-2) and through bores204of barrels102(1-2), respectively, until the electrodes220of anode assemblies112(1-2) are in their desired start positions for electroplating. Once leads114(1-2) are secured to puller710, leads114(1-2) and anode assemblies112(1-2) can be electrified and pulled through barrels102(1-2) at a desired rate(s) of travel to apply plating at one or more desired thickness(es) to bores204.

FIG. 10is a front perspective view showing support structure700at the beginning of an electroplating process. Here two barrels102(1-2) are secured to barrel mount712and are submerged in electrolyte (not shown) in tank701. Shaft720of actuator116is extended to position puller710at or near the bottom of its range of travel. Anode assemblies112(1-2) (not shown) and leads114(1-2) are positioned axially through barrel adapters110(1-2) and barrels102(1-2), respectively, and are secured within lead coupler746(1-2) so that puller710can draw anode assemblies112(1-2) vertically when actuator116retracts shaft720.FIG. 10also shows that risers702(1-2) are fabricated from tubular and plate metal components and are secured to the top of tank701via fasteners1002. Here, front and rear complementary vertical members1004(e.g., plates, etc.) define a receiver714with a gap1006that receives frame704vertically therein.

FIG. 11is a front perspective view showing frame704similar toFIG. 10after the electroplating process of the bores204of barrels102(1-2) has been completed. As shown, actuator116has moved puller710to near the top of its stroke, thereby drawing anode assemblies112through bores204of barrels102(1-2) and through conduits510of barrel end adapters110(1-2). Accordingly, the powered anode assemblies112will have uniformly plated bores204of barrels102(1-2) as they were drawn through bores204. Barrels102(1-2) can now be removed from barrel mount712and rinsed.

WhileFIGS. 7-11describe a particular embodiment of a support structure700for use with electro-processing system100, it should be understood that other support structures can be employed. For example, support structure700can be modified to provide an actuator for each barrel102, such that the actuators can be operated to provide different draw rates.

FIG. 12is a block diagram illustrating another system1200for electroplating a plurality of small-bore gun barrels1202(1-n) according to another embodiment of the invention. System1200includes a plurality of anode assemblies1212(1-n) electrically coupled to respective ones of a plurality of conductive leads1214(1-n), a plurality of actuators1216(1-x), one or more power supplies1218(one in this example), a process controller1220, and a user input/output (I/O)1244. Anode assemblies1212(1-n) and leads1214(1-n) can be similar to those anode assemblies and leads described above or different. Similarly, actuators1216(1-x) can be linear actuators as described above, rotational actuators, rack-and-gear drive actuators, etc. or some combination thereof. In the embodiment shown, there is one actuator1216per anode assembly1212such that (x) equals (n). However, in other embodiments the number of actuators1216can be different (e.g., less than) the number of anode assemblies1212, for example, where one actuator1216moves multiple anode assemblies1212.

Support structure(s) holding barrels1202(1-n) in a tank of electrolyte is/are omitted fromFIG. 12. However, such support structure(s) can be implemented employing design considerations and features discussed above. The design of such support structures will also take into consideration the type(s) of actuator(s)116employed, the size and shape of the electrolyte tank, the space around such tank, etc.

Power supply1218includes a plurality of first (e.g., positive) power supply terminals1234(1-n), a common (e.g., negative) power supply terminal1236, and a control input set1238. Each of first power supply terminals1234(1-n) is electrically coupled to a respective one of leads1214(1-n) and is operative to supply process current to a respective one of anode assemblies1212(1-n). Common power supply terminal1236is electrically coupled to each of barrels1212(1-n), for example, via the support structure(s) holding barrels1202(1-n) in the electrolyte. Alternatively, a power supply terminal1236can be provided for each barrel1202(1-n). Power supply1218is also coupled to receive control signals from process controller1220(or directly from a user) via a control input set1238. Responsive to the control signals received, power supply1218is operative to assert process current to carry out electroplating of barrels1202(1-n).

Process controller1220includes a plurality of actuator control sets1242(1-x), one or more power supply control set(s)1248(one in the present example), one or more user input/output(s)1244, and one or more timers1246. Process controller1220can be implemented in hardware (e.g., in an integrated circuit, firmware, etc.), in software (e.g., stored or running in memory of a computer), etc. or some combination thereof. Process controller1220is operative to assert control signals on each of actuators1216(1-x) via respective actuator control sets1242(1-x) to control the rate at which each of actuators1216(1-x) moves each of anode assemblies1212(1-n). Accordingly, process controller1220enables each of anode assemblies1212(1-n) to be moved independently (in the case that x equals n) or in predetermined groups (where x is less than n). Timer1246provides time information/signal(s) and enables process controller1220to adjust the rate of travel of each of anode assemblies1212(1-n) during the electroplating process to yield a desired plating thickness. Additionally, given known barrel length(s) and the initial positions of anode assemblies1212(1-n) relative to barrels1202(1-n), respectively, process controller1220can determine the position of each anode assembly1212throughout the plating process depending on their respective anode draw rate(s) and the time period(s) at those draw rates. Process controller1220can also controls power supply1218via control set1248to selectively power ones of power supply terminals1234(1-n) and common power supply terminal1236.

System1200has the advantage that the electroplating process can be controlled for each barrel1202(1-n) (or groups of barrels where x is less than n) independently. For example, process controller1220can slow the movement of an anode assembly1212through a barrel1202whose bore needs thicker plating. Conversely, process controller1220can increase the rate of travel of an anode assembly1212through a barrel1202whose bore needs thinner plating. Moreover, process controller1220can vary the rate of travel of each individual anode assembly1212through the bore of its associated barrel1202to apply different plating thicknesses to different regions of the bore. Thicker plating can thus be applied in desirable regions of the bore (e.g., near the muzzle end, in the throat, etc.) of a barrel1202by process controller1220slowing the draw rate of the anode assembly1202in those regions. Similarly, the draw rates implemented for a barrel1202can be varied to “even-out” variations in a diameter of the bore along the length of the barrel. Bore diameter(s) can be determined for each barrel, for example, by air-gaging as discussed above.

FIG. 13is a front plan view showing a barrel end adapter1310according another exemplary embodiment of the present invention. Like barrel end adapter510, barrel end adapter1310includes a non-conductive, generally-prismatic body502having a top surface504, a bottom surface506, and a plurality (e.g., four) of sidewalls508therebetween. Body502further includes a conduit510and barrel interface512formed therein along an axis515. Like barrel end adapter110, body502of barrel end adapter1310is formed from a non-conductive material, such as PVC, by 3-D printing, molding, milling, tapping, or some combination thereof.

Unlike adapter510, however, barrel end adapter1310further comprises a detector device1312having a conduit1314formed therethrough and a flange1316. Detector device1312is coupled to top surface504of body502via a plurality of fasteners1318(e.g., two, four, etc.) passed through flange1316and into top surface504. In this embodiment, detector device1312includes a wire coil1320wound about axis515and having a plurality of control leads1322and1324configured to electrically couple coil1320with a process controller (e.g., process controller120, process controller1220, etc.; see e.g.,FIG. 12).

Detector device1312enables the process controller to detect the passage of an anode assembly (e.g., anode assembly112, etc.) through detector device1312by providing a detection signal via first and second control leads1322and1324. In particular, as a lead (e.g., lead114, etc.) is pulled through conduit1314during electro-processing, lead114induces a voltage on the coil1320, causing amperage feedback to the process controller. Based on such feedback, the process controller can determine when the anode assembly112has exited barrel end adapter1310and thus the barrel.

In this embodiment, detector device1312is ruggedized (e.g., sealed against liquid intrusion, etc.) to withstand the harsh environment of the chemical bath. Additionally, during electro-processing, the barrel end adapter1310can be submerged up to flange1316to prevent corrosion and/or inadvertent shorting of wire coil1320.

FIG. 14is a perspective view showing a rotary electro-processing assembly1400according to another embodiment of the present invention. Assembly1400includes a rotary electrode assembly1412, a lead1414, and a rotary coupling1416including a power terminal1418. Electrode assembly1412includes a fluted bore guide1422coupled to an electrode1420. As above, electrode1420will be referred to as an anode herein, but in other cases could function as a cathode.

Rotary electro-processing assembly1400facilitates rotation of anode assembly1412as anode assembly1412is drawn through the bore204of a gun barrel102during electro-processing (elecro-plating in this example). Rotary coupling1416includes a lower portion1424that rotates relative to an upper portion1426having power terminal1418electrically coupled thereto. Upper portion1426is configured to be mounted to a lead puller of an associated fixture (e.g., lead puller710of fixture700, etc.) such that power terminal1418can be electrically coupled to a power supply (e.g., power supply118, power supply1218, etc.). Upper portion1426can be insulated to prevent shorting power terminal1418to the fixture. In a particular embodiment, rotary coupling1416comprises a Mercotac110-T electrical slip ring.

Lead1414is similar to lead114, except that lead1414is electrically coupled between lower portion1424of rotary coupling1416and anode1420. Anode1420is substantially similar to anode220discussed previously. Here, however, anode1420is coupled to fluted bore guide1422, which rotates as it is drawn through the rifled bore204of gun barrel102as will be discussed below.

FIG. 15is a perspective view showing fluted bore guide1422in greater detail. Bore guide1422includes an elongated, non-conductive body1450having a top surface1452, a bottom surface1454, and a plurality of helical flutes1456formed therebetween about axis1458. A passage1460is formed axially through top surface1452, through elongated body1450, and through bottom surface1454. Passage1460is sized to closely accept anode1420therein through the opening in bottom surface1454. In a particular embodiment, fluted bore guide1422is approximately 1.5″ in length, and is configured to seat approximately one inch of anode1420therein. A remainder of passage1460and the opening in top surface1452are sized to pass lead1414therethrough. Bore guide1422can be formed from a non-conductive resin (e.g., ABS-M30, polyvinyl chloride (PVC), etc.) by 3-D printing, molding, milling, etc.

A beneficial aspect of bore guide1422is that the ridges1462between adjacent flutes1456are configured to engage the grooves of rifling210formed on bore204of barrel102. This engagement causes bore guide1422to rotate about axis1458as it is pulled through bore204, which in turn, causes anode1420, lead1414, and lower portion1424of rotary coupling1416to rotate as well. The rotating bore guide1422, thus, advantageously acts as a pump to move gases and chrome solution away from anode1420via the helical flutes1456. Additionally, the rotation of anode1420assists in evening out the application of chrome to bore204, thereby creating a more consistent and evenly applied thickness of chrome.

As mentioned above, the form of flutes1456are complementary to the rifling210of bore204. In a particular embodiment, the number of flute ridges1462is equal to the number of grooves in the rifling210. Additionally, the inches per turn (along axis1458) of flutes1456can be the same as rifling210. In other embodiments, however, the number of flute ridges1462and/or inches-per-turn of the flutes of bore guide1422can be different from rifling210. For example, rifling210can have a number of grooves that is an integer multiple of the number of ridges1462(e.g., six rifling grooves to 2 ridges1462, etc.). As mentioned previously, inconsistent application of chrome to a rifled bore has historically been a detriment to the accuracy of rifle barrels. These features associated with bore guide1422, and others of the invention described herein, improve the quality of the chrome plating, thereby producing a barrel that yields accuracy approaching that of an unlined barrel, but with superior resistance to projectile wear.

Exemplary methods of the present invention will now be described with reference toFIGS. 16 and 17. For the sake of clear explanation, these methods might be described with reference to particular elements or modules of the foregoing description. However, it should be noted that other elements or modules, whether explicitly described herein or created in view of the present disclosure, can be substituted for those referenced without departing from the scope of the present invention. Accordingly, the methods of the present invention are not limited to any particular element(s) that perform(s) any particular functions. Furthermore, the steps of the methods presented herein need not necessarily occur in the order shown and/or some steps might occur simultaneously. These and other variations of the disclosed methods will be readily apparent in view of this disclosure and are considered to be within the scope of the invention.

FIG. 16is a flowchart summarizing an exemplary method1600for electro-processing a bore of a gun barrel according to the present invention. In a first step1602, a gun barrel having a bore defining an axis is provided. Prior to electro-processing, the bore of the barrel can be electro-cleaned (electro-polished), rinsed with clean water, and dried. In a second step1604, an electrode having a lead electrically coupled thereto is provided, where the length of the electrode is less than the length of the bore. In a third step1606, a barrel end adapter defining a conduit therethrough is provided, and in a fourth step1608the barrel end adapter is temporarily affixed to a first end of the gun barrel such that the conduit is axially aligned with the bore. In a fifth step1610, the electrode is positioned within the bore of the gun barrel, and in a sixth step1612, the gun barrel is positioned in an electro-processing solution (e.g., a chromium electrolyte, etc.). In a seventh step1614, the electrode is moved within at least one of the bore of the gun barrel and the conduit of the barrel end adapter. In an eighth step1616, process current is applied via the electrode during the step of moving the electrode to cause the bore to be electro-processed (e.g., electroplated). In an optional ninth step1618, the rate of travel of the electrode through the bore can be varied to adjust the amount of electro-processing applied to the bore.

FIG. 17is a flowchart summarizing another exemplary method1700for electro-processing (plating here) a bore of a gun barrel according to the present invention. In a first step1702, an actuator of an electro-plating fixture is extended. In a second step1704, the fixture is raised above the plating tank to facilitate barrel loading. In a third step1706, a barrel end adapter is temporarily affixed to an end of the barrel, and in a fourth step1708, the barrel is temporarily mounted to the fixture. Prior to mounting the barrel end adapter and mounting the barrel, the bore of the barrel can be electro-cleaned (electro-polished), rinsed with clean water, and dried. In a fifth step1710, an anode assembly attached to a lead is threaded through the bore of the barrel and barrel end adapter, and the lead is secured to a portion of the fixture that is movable by the actuator. In a sixth step1712, the fixture is lowered such that the barrel is submerged in the plating solution in the plating tank. In a seventh step1714, the anode assembly and barrel are electrically coupled to a power supply. In an eighth step1716, the bore of the barrel is electro-plated by supplying process current to the anode assembly as the anode assembly is drawn through the bore by movement of the actuator. When plating is complete, in a ninth step1718, the barrel is removed from the fixture (e.g., by raising the fixture again) and the bore is checked (e.g., via air gauge measurement, etc.) to determine if the plating conforms to predetermined specifications for thickness and uniformity. If it conforms, then method1700ends. However, if the plating is not within specifications (e.g., military standards, etc.), then in a tenth step1720, the plating is removed from the barrel and the barrel is plated again. In view of the various features of the invention discussed herein, however, the occurrence of plating that does not conform to such specifications is significantly reduced.

As will be apparent in view of the foregoing disclosure, the electro-processing systems and methods described herein are very versatile. While the foregoing figures have been described with respect to electro-plating, it should be understood that the systems and method described herein can also be used to electropolish the bores of gun barrels (e.g., as a pre-cleaning process prior to chrome plating, etc.) wherein material is ablated from the surface of bore204. As yet another example, the electroplating processes and systems disclosed herein can be used to plate other materials than chromium.

The present invention is particularly advantageous in electroplating small-bore gun barrels because the rate of plating adjacent the anode assembly can be controlled by varying the rate at which the anode assembly is pulled through the bore204. The uniformly applied plating preserves the rifling profile through the bore, ensures an accurate barrel102, and produces a finish to military specification, which significantly reduces the number of barrels that need to be reworked. However, it should be understood that the systems and methods disclosed herein can be used to electro-process other tubes having small inner diameters.