System and method of coating products

Systems and methods are provided for coating interior surfaces of products with coating material. The systems and methods can include at least one plug to selectively close an opening of the product, wherein the plug is movable relative to the opening between a first position in which the plug is retracted from the opening and a second position in which the plug is engaged with the opening to seal the opening. When the plug is in the second position, a pump delivers coating material to the cavity of the product via a fluid line and a port in the plug. The coating material can fill the cavity, and an electrode can be energized to coat the interior surface of the product with an electrophoretic deposition process. Other coating processes can also be used in a similar manner.

BACKGROUND

Embodiments of the invention relate to coating systems and methods, and methods of coating the inside of pipes and other products having interior surfaces.

Electrophoretic deposition (or EPD) is a method of applying a material, such as paint, to an electrically conductive surface. For example, EPD 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. Some forms of electrophoretic deposition include electrocoating, e-coating, cathodic electrodeposition, anodic electrodeposition, aqueous electrophoretic deposition, and electrophoretic coating, or electrophoretic painting.

The EPD process involves preparing the product for coating, coating the product with the main coating, and the curing the coating on the product. During the preparation stage, the product is typically cleaned and coated with a pre-coat, such as an inorganic phosphate coating, silane coating, zirconium, or any other conversion coating. When applying the main coat, the product is submerged in a reservoir filled with a solution of polymers that often includes of a mixture of the coating and water. The coating is applied by directing an electrical current through the reservoir using electrodes. The product being coated is considered one of the electrodes, and a set of “counter-electrodes” is used to complete the circuit. Typical voltages can be anywhere from 25-400 volts of direct current. Depending at least in part on the material of the product being coated, higher and lower voltages are possible.

When the voltage is applied to the system, the molecules in the coating attach to the surface of the product, which acts as one of the electrodes. More specifically, the polymer molecules carrying a certain charge will attach to the product, which carries the opposite charge as the polymers. For example, if an anodic EPD process is used, the polymers will carry a negative charge, and will be deposited on a positively charged product. In this case, the counter-electrodes act as cathodes and the product acts as the anode. On the other hand, if a cathodic EPD process is used, the polymers will carry a positive charge, and will be deposited on a negatively charged product. In this case, the counter-electrodes act as anodes, and the product acts as the cathode.

After the coating is applied to the product, excess solution is then rinsed off of the product. Finally, the coating is fixed, or cured, to the product.

EPD processes have a number of advantages that make the process appealing. For example, the applied coatings generally have a very uniform thickness. Objects with complex shapes can be easily coated. The process is fairly high speed and can apply to a wide range of materials, such as metals, ceramics, and polymers. One limitation of EPD is that it is difficult to use to use EPD to coat the inside of products having interior surfaces, such as pipes, and other products having internal cavities where the electric current cannot travel easily. Accordingly, many product manufacturers coat the inside of products with materials that are less than optimal primarily because EPD and other product coating processes are not available. By way of example, many large pipe manufacturers coat the inside surfaces of the pipes with asphalt using an alternative method, rather than EPD.

SUMMARY

Some embodiments of the present disclosure provide a product coating system for coating a product with a coating material, wherein the product includes an exterior surface, a cavity defined by an interior surface, and an opening extending between the exterior surface and the interior surface, and wherein the product coating system comprises a plug sized and shaped to selectively close the opening, the plug movable relative to the opening between a first position in which the plug is retracted from the opening, and a second position in which the plug is engaged with the opening to close the opening; a port defined in the plug and through which the coating material passes to enter the cavity; a pump; and a fluid line establishing fluid communication between the pump and the port; the system having a first configuration in which the plug is in the first position and coating material delivery to the cavity is stopped, and a second configuration in which the plug is in the second position and in which the pump delivers coating material to the cavity of the product via the fluid line and port.

In some embodiments, a method of coating a product with coating material is provided, wherein the product includes an exterior surface, a cavity defined by an interior surface, and an opening extending between the exterior surface and the interior surface, and wherein the method comprises moving a plug from a first position disengaged with respect to the opening to a second position in which the plug is engaged with the opening of the product; closing the opening of the product by moving the plug to the second position; pumping coating material through the plug and into the cavity while the plug is in the second position; coating the interior surface of the product with the coating material pumped into the cavity while the plug is in the second position; and draining excess coating material from the cavity.

Some embodiments of the present disclosure provide a product coating system for coating an interior surface of a cavity of a product with a coating liquid, wherein the product includes an exterior surface, a first opening extending between the exterior surface and the interior surface, and a second opening extending between the exterior surface and the interior surface, and wherein the product coating system comprises first and second plugs sized and shaped to selectively seal the first and second openings, respectively, each of the first and second plugs movable relative to the respective first and second openings between respective first positions in which the first and second plugs are retracted from the first and second openings, and respective second positions in which the first and second plugs seal the first and second openings; a pump; a first fluid line extending between the pump and the first plug for directing coating liquid from the pump toward the first plug; a second fluid line extending between the pump and the second plug for directing coating liquid from the second plug back to the pump; and an electrode removably insertable into the cavity of the product to a position in which the electrode is inside the cavity and out of contact with the interior surface of the cavity while the first and second plugs are in the respective second positions; wherein coating liquid pumped to the first plug enters the cavity through the first plug and fills the cavity; and wherein coating liquid is drained from the cavity through the second plug and into the second fluid line.

DETAILED DESCRIPTION

FIG. 1illustrates a system and method10of coating a product14. Specifically, the method includes coating an interior surface18defining a cavity16of the product14. An exterior surface22of the product14may be coated as well, and may be coated using the same or a different method as is used to coat the interior surface18of the cavity16. For example, the interior surface18of a pipe14can be coated with an e-coat paint using electrophoretic deposition (EPD), and the exterior surface22of the pipe14can be coated with a dry powder paint, such as acrylic powder. In another embodiment by way of example, both the interior surface18and the exterior surface of the product may be coated using a powder paint.

It should be noted that while the below description is made with respect to pipes14, the method10can be used to coat any product14having an internal cavity16that is difficult or impossible to effectively and economically coat using conventional methods. Likewise, while the below description is made with respect to coating the interior surface18of the product with an EPD method, other types of coating applications may be used for the interior surfaces18. For example, the interior surface18of the product14may be coated using powder coating, auto deposition, and other product coating systems and methods.

With reference toFIGS. 1 and 2, the illustrated system and method10involves a three phase process including an internal coating phase26, an exterior coating phase30, and a curing phase34.FIG. 1illustrates a top view of the three phases26,30,34of the system10, andFIG. 2illustrates a side view of the three phases26,30,34of the system10. During the internal coating phase26, pipes14are moved along a load conveyor38(from left to right as shown inFIG. 1) and loaded into a pretreatment stage42. The illustrated conveyor38is a chain-on edge conveyor38whereby a chain is positioned under each end of the pipes14. The pipes14are rolled onto the chain and thereafter mechanically stopped at each step. In other embodiments, different types of conveyor38systems can be used to move the pipes14through the system.

As shown inFIG. 3, during the pretreatment stage42, the conveyor38moves each pipe14through a series of reservoirs46containing various pretreatment solutions. Here, the pipes14are cleaned and coated with a pretreatment coating. Specifically, each pipe14is carried along the conveyor38from reservoir46to reservoir46. The conveyor38lowers the pipes14into each of the reservoirs46where the pipes14are immersed in each of the pretreatment solutions for a predetermined period. In the illustrated embodiment, the pretreatment stage42includes a series of eight reservoirs46. However, the number and type of reservoirs46can vary.

Once the pipes14are cleaned and prepared with a pretreatment coating during the pretreatment stage42, the pipes14enter the first treatment stage50. During the first treatment stage50of the illustrated EPD process, the pipes14are pre-rinsed (step54), internally coated (step58), and post-rinsed (step62). Depending at least in part upon the type of other product coating processes used as described above, either or both of the pre-rinse and post-rinse steps54,62can be different or can be eliminated, and more pre- or post-coating steps can be added as desired. The conveyor38moves the pipes14through each of these steps54,58,62. Similar to the pretreatment stage42, a reservoir46is associated with each of these steps54,58,62in the illustrated embodiment. However, in the illustrated embodiment, the conveyor38moves the pipes14from reservoir46without lowering the pipes14into each reservoir46. The reservoirs46are used to catch excess solution that falls during the steps54,58,62described herein.

In the illustrated embodiment, a reverse osmosis rinse is used as the pre-rinse54. In other embodiments, other types of rinses can be used as a pre-rinse54. A sealing device66can be used to seal the interior18of the pipe14during the pre-rinse54. Once the pipes14are pre-rinsed, the interior18of the pipes14are coated using a type of electrophoretic deposition in the illustrated embodiment.

With reference toFIGS. 4-7, the internal coating is applied using one or more applicators70. In the illustrated embodiment, an applicator70is inserted into each end of the pipe14. Specifically, the applicators70are each inserted through an opening68that extends between the interior surface18and the exterior surface22of the pipe14. In other embodiments, a single applicator70may be used to apply the coating material. In the illustrated embodiment, the applicator70is primarily made of a metal, such as steel, and has an elongated body86(seeFIG. 7). The elongated body86can have a cylindrical shape as shown in the illustrated embodiment, with a first end90and a second end94. The first end90of the illustrated body86is tapered to form a pointed end. The diameter of the actuator70is less than the diameter of the pipe14such that it can be inserted into the pipe14. In the illustrated embodiment, the applicators70each include an electrode74to apply coating material to the interior surface18of the pipe14using an EPD method. In other embodiments, different types of applicators70may be used to apply coating material depending on the type of coating process used. For example, the applicator may include a spray or misting head.

With combined reference toFIGS. 5A, 5B and 7, the second end94of the applicator70extends from a plug78that is used to seal the opening68of the pipe14. Prior to coating the internal surface18of the pipe14, the plug78closes the opening68, and in some cases seals the opening68in a liquid-tight or air-tight manner. In the illustrated embodiment, and as shown inFIGS. 4A and 4B, a plug78is inserted into the opening68on each end of the pipe14to seal the cavity16of the pipe14during the coating process. In other embodiments, only one plug78is used, leaving one of the openings68open during the coating process. In other embodiments, the product14may have only one opening68, in which case a single plug78can be used.

As shown inFIGS. 6A-C, in some embodiments the plug78is flared to form a conical projection98. The diameter of the largest portion of the conical projection98is greater than the diameter of the pipe14, and is used to prohibit the applicator70from being inserted further into the pipe14after the plug78has been brought into contact with the pipe14. When the applicator70is inserted into the pipe14, the conical projection98engages with an edge102of the opening68to close (and in some cases, seal) the opening68and prevent the applicator70from being inserted further into the pipe14. In addition, the plug78can be shaped to maintain the position of the applicator70in an orientation that is parallel to the pipe14, such as the conical shape of the plug as shown in the illustrated embodiment. This can ensure that the applicator70does not contact or engage the interior18of the pipe14. In other embodiments, the plug78may have different shapes and sizes that are sufficient to close, and in some cases seal, the opening68.

In some embodiments, the plug78is coated with a rubberized or otherwise elastomeric material. The elastomeric material on the plug78softens the engagement of the plug78and the pipe14, and helps to seal the end of the pipe14. In some embodiments, the pipe14is only engaged with the applicator70on the rubberized surface of the plug78, and does not engage directly with a metal surface of the applicator70.

With reference now toFIGS. 4A and 4B, in the illustrated embodiment an actuator104(not shown) is actuatable to move the plug78between a first position in which the plug78is retracted from the pipe14and in which the applicator70is withdrawn therefrom, and a second position in which the plug78is engaged with the pipe14to selectively seal the cavity16and in which the applicator70is received within the pipe14. In the second position (FIGS. 4B, 5B, and 6B), the plug78engages the opening68and seals the cavity16. Specifically, the conical projection98of the plug78engages with the edge102of the opening68, as shown inFIGS. 5B and 6B. In addition, when the plug78is in the second position, the applicator70extends into the cavity16in order to coat the interior surface18of the cavity16. In the first position (FIGS. 4A, 5A, and 6A), the plug78is disengaged from the opening68and the cavity16is no longer sealed. In addition, the applicator70is removed from the cavity16in the first position.

Accordingly, prior to coating the pipes14, the actuator104moves the plug78into the second position to seal the opening68of the cavity16. Once the pipe14is sealed off by the plugs78, the applicators70are used to distribute coating material into the cavity16of the pipe14. The coating material is guided into and removed from the cavity16of the pipe14through one or more ports77in each plug78(shown only inFIGS. 4A and 4B). The ports77of each plug78are in fluid communication with an internal chamber or manifold (not shown) at the base of each plug78, which is itself in fluid communication with a fluid line72as shown inFIGS. 4A and 4B. In this manner, a fluid passageway leading to the port(s)77is defined through the plug78through which coating fluid can be introduced into the pipe14and through which coating fluid can be removed from the pipe14.

With continued reference toFIGS. 4A and 4Bof the illustrated embodiment, coating fluid is supplied to the internal cavity16of the pipe14through the ports77of the plug78at the right side ofFIGS. 4A and 4B, exits the internal cavity16via ports77of the plug78at the left side ofFIGS. 4A and 4B, is received in the reservoir46(which can be a tank or other structure capable of holding an amount of the coating fluid, such as in a location beneath the pipe14as shown inFIGS. 4A and 4B), is drawn from the reservoir46by a pump76that delivers the fluid via the fluid line72back to the plug78at the right side ofFIGS. 4A and 4B, and again enters the cavity16of the pipe14via the ports77of the plug78on the right side ofFIGS. 4A and 4B. In those embodiments in which the reservoir46is located beneath the pipe14, such as in the illustrated embodiment, any coating fluid that escapes the pipe14or plugs78can simply fall to the reservoir46to re-enter the fluid cycle just described. Also, although the pump76of the illustrated embodiment is described as being downstream of the reservoir46, in other embodiments the flow of coating fluid can be reversed so that coating fluid enters the pump76, is supplied to the reservoir46and then to the plug76on the left side ofFIGS. 4A and 4B, and exits the pipe14via the plug76on the right side ofFIGS. 4A and 4B. In these and other embodiments, the pump76, reservoir46, and fluid lines72can all be plumbed in a closed fluid system allowing fluid to be forced to the plug78at the left side ofFIGS. 4A and 4B. Also, in some embodiments the reservoir46is not used. In embodiments in which a reservoir46is used, any type of reservoir (e.g., closed or open tank, well, accumulator, and the like) can be used as desired.

Although in the illustrated embodiment coating fluid enters and exits the internal cavity16of the pipe14via ports77in the plugs78as described above, in other embodiments the applicator70is in fluid communication with an internal chamber or manifold at the base of each plug78or applicator70, and can be provided with one or more internal passages extending axially along any portion or all of the length of the applicator70to one or more exit ports positioned at any desired location(s) along the applicator70. By way of example only, an alternative fluid exit or entry location in the illustrated embodiment is one or more (e.g., ring) of exit ports82on the body of the applicator70, in which case ports77in the plugs78need not exist. In the illustrated embodiment, the applicator70and the plug78are defined as a single integral unit. However, in other embodiments, the applicator70and the plug78are separable pieces.

In some embodiments, fewer or greater numbers of plugs78or fluid passageways may be used. For example, a single plug78may include two passageways and respective ports77. In such embodiments, one passageway and port77may be used to inject coating fluid into the cavity16, whereas the other passageway and port77may be used to remove the coating fluid from the cavity16. In other embodiments, the same passageway and port(s)77may be used to both inject and remove coating fluid into and out of the cavity16.

As described above, in the illustrated embodiment the pump76pumps coating fluid from the reservoir46to the end of the pipe14on the right side ofFIGS. 4A and 4Bvia fluid line72, and into the internal cavity16of the pipe14via the ports77of the plug78. In some embodiments, the coating fluid fills the internal cavity of16of the pipe14. The pipe14can be oriented at a slight upward angle so that that coating material must travel uphill to fill the pipe14. In other words, one end of the pipe14is gravitationally higher than the other end. The upward angle of the pipe14reduces the number of bubbles in the pipe as the coating material is injected into the pipe14, and can allow bubbles that do form to dissipate more readily.

With the pipe14filled with coating fluid, the applicator70is used to apply the coating material to the interior surface18of the cavity16. In the illustrated embodiment, electrical current is driven through the pipe14in an EPD process. Specifically, the applicator70includes an electrode74, which is used as either an anode or a cathode to help conduct electrical current through the pipe14during the EPD process. The electric current is driven through the pipe14, from one applicator70to another. The applicators70act as counter-electrodes74, and the pipe14acts as an electrode74. The pipe14can either be used as a cathode or an anode depending on whether an anode EPD method is used or a cathode EPD method is used. Driving electrical current through the pipe14causes the e-coating to attach to the interior surface18of the pipe14.

After the coating process is complete, the actuators104retract the plugs78into the respective first positions so that the plugs78are disengaged from the openings68and the applicators70are removed from the cavity16. The pipe14is drained of the coating fluid via the fluid line72on the left side ofFIGS. 4A and 4Band/or by retraction of either or both plugs77from the pipe14via the actuators104as described above. The drained coating fluid then collects in the reservoir46, and can be re-used by being drawn by the pump76as described above. In other embodiments, the drained coating is instead discharged to waste.

As described above, other surface coating methods (other than EPD coating) can be used to coat the interior surface18of the cavities16of the pipes14. In such alternative embodiments, the plugs78and/or applicators70can have different shapes and sizes. By way of example only, in some embodiments the applicator delivers a spray of powder to the interior of the pipes14, in which case the powder can be discharged from a plurality of spray ports along the length and circumference of the applicators70. As other examples, in some types of coating systems coating fluid (e.g., as a liquid or powder) is introduced into the pipe14through the plugs78without the use of applicators70. In such cases, the plugs78can appear as shown inFIG. 6A, which can be the same as those plugs78used in the pre-rinse and post-rinse steps54,62described above.

After being coated as described above, the pipe14is moved to the post-rinse process62. In the illustrated embodiment, each pipe14goes through two post-rinse processes62. However, in other embodiments, only a single post-rinse process62is used. The post-rinse process62marks the end of the first treatment stage50.

The conveyor38moves the pipes14from the first treatment stage50to a drying stage106, where the pipes14are dehydrated (step110) for a predetermined period and then cooled (step114) for a predetermined period. In the illustrated embodiment, the dehydration period110lasts for approximately 14 minutes and the cooling114period lasts for approximately 14 minutes. The drying stage106partially dries the interior18coating of the pipes14, but does not fully cure the interior18coating. The drying stage106is the last stage of the interior coating phase26.

The pipes14move from the interior coating phase26to the exterior coating phase30. In some embodiments, the pipes14are moved from one conveyor38to another conveyor38between these phases26,30. During the exterior coating phase30, the pipes undergo a second treatment stage118. During the second treatment stage118, the exterior surfaces22of the pipes14are powered coated. The pipes14are moved through a powder coating machine122where power coating is misted onto the exterior surface22of the pipes14until the coating becomes thick. In other embodiments, the exterior surface22of the pipes14is coated in other manners, such as by electrophoretic deposition, auto deposition, powder coating, and painting, by way of example only.

Following the exterior coating phase30, the pipes14are moved to the curing phase34where both the interior coating and exterior coating are cured to the pipe14. The curing phase34consists of several stages of heating and cooling. During the first curing stage126, the pipes14are heated in a melt zone oven for a short period of time at a relatively lower temperature. For example, the pipes14are heated for approximately 14 minutes at 300 degrees Fahrenheit. During the second curing stage130, the pipes14are heated in a melt zone oven for a relatively longer period of time at a higher temperature. For example, the pipes14are heated for approximately 60 minutes at 400 degrees. Finally, the pipes14enter the third stage of curing134where the pipes14are cooled and unloaded by an unload conveyor38. In one embodiment, the pipes14are cooled for approximately 24 minutes.

Although the invention has been described with reference to certain preferred embodiments, variations and modifications exit within the spirit and scope of the present invention.