Electrophoretic deposition system

Abstract

An electrophoretic disposition system for simultaneously coating the exterior and interior of metal parts having an exterior portion and an interior portion comprising an emersion tank having four side walls and a bottom, at least one vertical anode for conducting current through the paint positioned along one of the walls, and at least one retractable remote anode positioned adjacent the at least one vertical anode. Once a part to be coated is submerged into the emersion tank, the at least one remote anode is extended into the interior of the part. Once in place, a current is passed through both the anodes. The at least one vertical anode creates a current path on the exterior of the part and the at least one horizontal anode creates a current path on the interior of the part.

Description

RELATED UNITED STATES PROVISIONAL PATENT APPLICATION

[0001] This application claims the priority of provisional patent application Ser. No. 60/787,916, filed Mar. 31, 2006.

I. TECHNICAL FIELD

[0002] The present invention relates to electrophoretic disposition systems and, more particularly, to an electrophoretic disposition system which evenly and simultaneously coats the interior and exterior surfaces of hollow apparatus.

II. BACKGROUND OF THE INVENTION AND PRIOR ART

[0003] Electrophoretic deposition (EPD) covers a broad range of material coating processes which have as a characteristic feature colloidal particles suspended in a liquid medium that migrate under the influence of an electric field (electrophoresis) and are deposited onto an electrode. Non-limiting examples of EPD processes include electrocoating, electrophoretic coating, and electrophoretic painting.

[0004] In general, any colloidal particle that can be used to form a stable suspension and that can carry a charge can be used in electrophoretic deposition. Non-limiting examples of suitable materials include polymers, pigments, dyes, ceramics and metals.

[0005] EPD is useful for applying materials to any electrically conductive surface and is used industrially for applying coatings to metal fabricated products. It has been widely used to coat automobile bodies and parts, tractors and heavy equipment, electrical switch gear, appliances, metal furniture, beverage containers, fasteners, and many other industrial products.

[0006] During the EPD process itself, direct current is applied to a solution of polymers with ionizable groups or a colloidal suspension of polymers with ionizable groups which may also incorporate solid materials such a pigments and fillers. The ionizable groups incorporated into the polymer are formed by the reaction of an acid and a base to form a salt. The particular charge, positive or negative, which is imparted to the polymer depends on the chemical nature of the ionizable group. If the ionizable groups on the polymer are acids, the polymer will carry a negative charge when salted with a base. If the ionizable groups on the polymer are bases, the polymer will carry a positive charge when salted with an acid.

[0007] There are two types of EPD processes, anodic and cathodic. In the anodic process, negatively charged material is deposited on the positively charged electrode, or anode. In the cathodic process, positively charged material is deposited on the negatively charged electrode, or cathode.

[0008] When an electric field is applied, all of the charged species migrate by the process of electrophoresis towards the electrode with the opposite charge. In anodic deposition, the material being deposited will have salts of an acid as the charge bearing group. These negatively charged anions react with the positively charged hydrogen ions (protons) which are being produced at the anode by the electrolysis of water to reform the original acid. The fully protonated acid carries no charge (charge destruction) and is less soluble in water, and may precipitate out of the water onto the anode.

[0009] The analogous situation occurs in cathodic deposition except that the material being deposited will have salts of a base as the charge bearing group. If the salt of the base has been formed by protonation of the base, the protonated base will react with the hydroxyl ions being formed by electrolysis of water to yield the neutral charged base (again charge destruction) and water. The uncharged polymer is less soluble in water than it was when was charged, and precipation onto the cathode occurs.

[0010] The cathodic process results in considerably more gas being trapped within the film than the anodic process. Since the gas has a higher electrical resistance than either depositing film or the bath itself, the amount of gas has a significant effect on the current at a given applied voltage. This is why cathodic processes are often able to be operated at significantly higher voltages than the corresponding anodic processes.

[0011] The ability for the EPD coating to coat interior recesses of a part is called the "throwpower." In many applications, it is desirable to use coating materials with a high throwpower. The throwpower of a coating is dependent on a number of variables, but generally speaking the higher the coating voltage, the further a given coating will "throw" into recesses. High throwpower electrophoretic paints typically use application voltages in excess of 300 volts DC.

[0012] However, prior art systems often fail in the complete coating of interior surfaces as the ability to completely coat the interior surface of a part using EPD is limited. This can occur for many reasons, including but not limited to the to-be-coated-part size, insufficient voltage capibilities, colloid insufficiency, insufficient coating time, and systems directed at a general coating scheme as opposed to site specific coatring. This is a significant shortcoming when working in environments in which it is important that all surfaces of the treated object are coated, leaving no uncovered areas such as a truck bed or utility box. Uncoated areas require hand coating. This, in turn, results in increased cost due to having to have an employees inspect and coat the uncoated surfaces, increased production time in having to do the hand work, and the increased probability that the part may be ruined to inadequate hand coating work.

[0013] There is need, therefore, for a system to coat parts having an interior surface that must be completely coated, leaving no uncovered areas. The present invention provides such a solution.

III. OBJECTS AND ADVANTAGES OF THE PRESENT INVENTION

[0014] It is an object of the present invention to provide an electrophoretic disposition system which evenly coats the exterior and interior surfaces of a part.

[0015] It is a further object of the present invention to provide an electrophoretic disposition system which coats the exterior and interior surfaces of a part in a continuous process.

[0016] It is yet a further object of the present invention to provide an electrophoretic disposition system which decreases manufacturing time.

[0017] It is yet a further object of the present invention to provide an electrophoretic disposition system which decreases manufacturing cost.

[0018] The advantages offered by the present invention include but are not limited to providing parts having an interior surface being less susceptible to corrosion, and to further decrease the time and cost involved in manufacturing the coated parts.

IV. SUMMARY OF THE INVENTION

[0019] The present invention comprises an emersion tank having four side walls and a bottom, at least one vertical anode for conducting current through the paint positioned along one of the walls, and at least one retractable remote anode positioned adjacent the at least one vertical anode.

[0020] Once a part to be coated is submerged into the emersion tank, which contains a material to be applied to the part, the at least one remote anode is extended into the interior of the part. Once in place, a current is passed through both the at least one vertical anode and the remote anode. The at least one vertical anode creates a current path on the exterior of the part and the at least one horizontal anode creates a current path on the interior of the part. The current, in turn, results in both the exterior of the part and the interior of the part to be coated in a single continuous process which results in a coating of the exterior and interior surfaces.

[0021] There has been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and that will form the subject matter of the invention.

[0022] As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions in so far as they do not depart from the spirit and scope of the present invention.

[0023] Further, the purpose of the abstract is to enable the US patent and trademark office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with the patent or legal terms or phraseology, to determine quickly from what cursory inspection the nature and essence of the technical disclosure of the application. The abstract is neither intended to define the invention of the application, which is measured by the claims, nor is it intended to be limiting as to the scope of the present invention in any way.

[0024] These together with other objects of the present invention, along with the various features of novelty which characterize the present invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the present invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the present invention.

[0025] Before explaining the preferred embodiment of the present invention in detail, it is to be understood that the present invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 depicts a top perspective view of the inventive device from the anode end of the emersion tank.

[0027] FIG. 2 depicts a top perspective view of the inventive device from the rectifier end.

[0028] FIG. 3 depicts a cross section perspective view of the remote anode.

[0029] FIG. 4 depicts a side cross sectional view of the remote anode.

V. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] Before explaining the preferred embodiment of the present invention in detail, it is to be understood that the present invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.

[0031] Turning to FIG. 1, electrophoretic disposition system 20 is seen. Emersion tank 22 comprises four walls, A, B, C, and D and a bottom. Emersion tank 20 holds the solution which is to be coated to metal part E. For non-limiting example, emersion tank 20 can hold paint for coating a metal part E, such as a utility truck bed as depicted in FIGS. 1 and 2. Emersion tank 22 can be constructed of any suitable material. The inventors have found that a steel construction with the interior of the tank coated in fiberglass works best.

[0032] Attached to the interior of at least one of the walls, are vertical anodes 24 (FIG. 2). There may a single vertical anode or a plurality of vertical anodes. The number only depends on the needs of the user and the type and size of the part to be coated. In this non-limiting example, there are a plurality of anodes surrounding the interior of the emersion tank 22 and affixed adjacent to Wall A, B, C, and D. Vertical anodes 24 comprise stainless steel rod connected in electrical series via wire F and conduct current through the emersion tank to coat the exterior of the metal part.

[0033] Returning to FIG. 1, affixed to and extending through, in this example, Wall C is remote anode 26. Remote anode 26 further extends generally perpendicular to wall C and horizontal to the bottom of emersion tank 22. Remote anode 26 is placed generally adjacent to vertical anode 22, however, as those skilled in the arts will quickly understand, the placement of remote anode 26 is flexible and limited only by the configuration of the system 20.

[0034] Turning to FIG. 3, it is seen that remote anode 26 further comprises and external sheath which affixes to and extends through wall C at point F. Housed within sheath 28 is found anode 30 and piston 32. Anode 30 is sized lightly smaller than sheath and designed to move freely within sheath 28.

[0035] Located on the exterior of sheath 28 and extending through it are found extension valve 34 and retraction valve 36. Return to FIG. 1, connected to Extension valve 34 is first fluid line 38 which in turn is connected to first hydraulic tank 40. Connected to retraction valve 36 is second fluid line 42 which in turn is connected to second hydraulic tank 44. First fluid line 38 supply deionized water to the piston end of remote anode 26 and second fluid line 42 supply deionized water to the anode end of remote anode 26 to retract anode 30. The deionized water entering the piston end and anode end of sheath 28 are kept separated by divider 46 (FIG. 3).

[0036] System 20 is used simultaneously coat the exterior and interior of a metal part having an interior portion. In use, a metal part E is submerged into a solution found within emersion tank 22. Force is supplied to first hydraulic tank 40 which pushes deionized water through first line 38, through extension valve 34, causing piston 32 to move forward, thereby causing anode 30 to move within sheath 28 and extend into emersion tank 22 and into part E (FIG. 2).

[0037] Power is then applied to system 20 via rectifier 50. Rectifier 50 can be any suitable power source capable of supplying sufficient current to the anodes. The inventors have found that an 800 amp rectifier works best. Current is then passed through the anodes, both vertical and remote, causing the electrophoretic disposition of both the exterior of the part E via the vertical anodes and the interior of part E via the remote anode.

[0038] Applying a current to the solution through the at least one vertical anode and the at least one remote anode draws the solution to the metal part.

[0039] Once the electrophoretic disposition process is complete, force is applied to second tank 44, thereby pushing fluid through second fluid line 42, thereby causing anode 30 to retract into sheath 28. Remote anode 26 can include a safety solenoid which enables power to be supplied to anode 30 only when anode 30 is extended. Applying retraction force to the piston withdraws the at least one remote anode from the interior of the metal part and from the tank once the metal part is sufficiently coated.

[0040] It is to be understood, however, that even though numerous characteristics and advantages of the preferred and alternative embodiments have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only.

[0041] Such variations should be considered to be within the scope and spirit of the invention which is meant to cover an electrophoretic disposition system for simultaneously coating the exterior and interior of parts having an interior portion. Changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1) A system for the electrophoretic disposition of the exterior and interior of parts comprising: An emersion tank having a first wall, a second wall, a third wall, a fourth wall, and a bottom; At least one vertical anode positioned along the first wall of the emersion tank; At least one retractable remote anode positioned adjacent the at least one vertical anode; and, An electrical current supply for providing current to the anodes.

2) The system for the electrophoretic disposition of the exterior and interior of parts of claim 1 wherein the at least one retractable remote anode further comprises an outer generally cylindrical sheath having a tank end and a distal end, a generally cylindrical anode of a diameter smaller than the sheath and having a current end and a piston end housed within the sheath at the tank end, a piston positioned at the piston end of the anode, an inlet valve for supplying piston extension force, and an outlet valve for supplying piston retraction force.

3) A system for system for simultaneously applying a coating to the exterior and interior of a metal surface comprising: An emersion tank having a first wall, a second wall, a third wall, a fourth wall, and a bottom; At least one vertical anode positioned along the first wall of the emersion tank; At least one retractable remote anode positioned adjacent the at least one vertical anode, the at least one retractable remote anode further comprises an outer generally cylindrical sheath having a tank end and a distal end, a generally cylindrical anode of a diameter smaller than the sheath and having a current end and a piston end housed within the sheath at the tank end, a piston positioned at the piston end of the anode, an inlet valve for supplying piston extension force, and an outlet valve for supplying piston retraction force.

4) The system for simultaneously applying a coating to the exterior and interior of a metal surface of claim 3 further comprising a hydraulic system for extending and retracting the remote anode.

5) A method for simultaneously applying a coating to the exterior and interior of a metal part through electrophoretic disposition comprising the steps of: submerging a metal part into a solution found within an emersion tank, the emersion tank having a first wall, a second wall, a third wall, a fourth wall, and a bottom, at least one vertical anode positioned along the first wall of the emersion tank, and at least one retractable remote anode positioned adjacent the at least one vertical anode, the at least one retractable remote anode further comprises an outer generally cylindrical sheath having a tank end and a distal end, a generally cylindrical anode of a diameter smaller than the sheath and having a current end and a piston end housed within the sheath at the tank end, a piston positioned at the piston end of the anode, an inlet valve for supplying piston extension force, and an outlet valve for supplying piston retraction force; applying force to the piston, thereby activating the piston which in turn extends the at least one remote anode into the tank and into the interior of the metal part; applying a current to the solution through the at least one vertical anode and the at least one remote anode, thereby drawing the solution to the metal part.

6) The method of claim 5 comprising the further step of applying retraction force to the piston, thereby withdrawing the at least one remote anode from the interior of the metal part and from the tank once the metal part is adequately coated.